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Sample records for carbon stabilized expanded

  1. Lattice expansion of carbon-stabilized expanded austenite

    DEFF Research Database (Denmark)

    Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.

    2010-01-01

    The lattice parameter of expanded austenite was determined as a function of the content of interstitially dissolved carbon in homogeneous, carburized thin stainless steel foils. For the first time this expansion of the face-centered cubic lattice is determined on unstrained austenite. It is found...

  2. Extended X-Ray Absorption Fine Structure Investigation of Carbon Stabilized Expanded Austenite and Carbides in Stainless Steel AISI 316

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny;

    2011-01-01

    Low temperature carburized AISI 316 stainless steel - carbon expanded austenite - was investigated with EXAFS and synchrotron diffraction together with synthesized carbides of the type M3C2, M7C3 and M23C6. It was found that the chemical environment of carbon expanded austenite is not associated...... with any of the investigated carbides, that carbon has a strong affinity for chromium, i.e. short range order, and that carbon is in solid solution....

  3. Stress and Composition of Carbon Stabilized Expanded Austenite on Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2009-01-01

    Low-temperature gaseous carburizing of stainless steel is associated with a colossal supersaturation of the fcc lattice with carbon, without the development of carbides. This article addresses the simultaneous determination of stress and composition profiles in layers of carbon xpanded austenite...

  4. Stability of non compact steady and expanding gradient Ricci solitons

    OpenAIRE

    Deruelle, Alix

    2014-01-01

    We study the stability of non compact steady and expanding gradient Ricci solitons. We first show that strict linear stability implies dynamical stability. Then we give various sufficient geometric conditions ensuring the strict linear stability of such gradient Ricci solitons.

  5. Propagation and stability of expanding spherical flames

    Science.gov (United States)

    Jomaas, Grunde

    High-fidelity experiments were conducted to determine the laminar flame speeds of various fuels, to define the transition boundaries of both cellular and spiral flame front instabilities that develop over the flame surface, and to determine the cellular flame acceleration constants for outwardly propagating spherical flames in a near-constant pressure environment up to 60 atmospheres. The flame front movement was monitored using schlieren cinematography and recorded with a high-speed digital camera. Experiments were conducted for a wide range of pressures and equivalence ratios to yield flame speed data for acetylene, ethylene, ethane, propylene, propane, dimethyl ether, and hydrogen/carbon monoxide in air. These data were post-processed in order to account for stretch effects, yielding laminar, unstretched flame speeds and Markstein lengths. The results were compared with existing chemical kinetics mechanisms and used to suggest improvements. The instant of transition to cellularity was experimentally determined for various fuels and fuel mixtures and subsequently interpreted on the basis of hydrodynamic and diffusional-thermal instabilities. Experimental results show that the transition Peclet number, Pec = Rc/ℓL, assumes an almost constant value for the near-equidiffusive acetylene and ethylene flames with wide ranges in the mixture stoichiometry, oxygen concentration, and pressure, where Rc is the flame radius at transition and ℓL the laminar flame thickness. However, for the non-equidiffusive hydrogen and propane flames, Pec respectively increases and decreases somewhat linearly with the mixture equivalence ratio. Evaluation of Pec using the theory of Bechtold and Matalon show complete qualitative agreement and satisfactory quantitative agreement, demonstrating the insensitivity of Pec to all system parameters for equidiffusive mixtures, and the dominance of the Markstein number, Ze(Le-1), in destabilization for non-equidiffusive mixtures, where Ze is the

  6. Stability of stagnation via an expanding accretion shock wave

    Science.gov (United States)

    Velikovich, A. L.; Murakami, M.; Taylor, B. D.; Giuliani, J. L.; Zalesak, S. T.; Iwamoto, Y.

    2016-05-01

    Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case, the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. This conclusion has been supported by our simulations done both on a Cartesian grid and on a curvilinear grid in spherical coordinates. Dispersion equation determining the eigenvalues of the problem and explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented, making it possible to use the theory for hydrocode verification in two and three dimensions.

  7. Stability of stagnation via an expanding accretion shock wave

    CERN Document Server

    Velikovich, A L; Taylor, B D; Giuliani, J L; Zalesak, S T; Iwamoto, Y

    2016-01-01

    Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Y. Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [H. Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); M. Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic...

  8. Stability of expanded granular sludge bed process for terylene artificial silk printing and dyeing wastewater treatment

    Institute of Scientific and Technical Information of China (English)

    GUAN Bao-hong

    2005-01-01

    Terylene artificial silk printing and dyeing wastewater(TPD wastewater), containing averaged 710 mg/L terephthalic acid(TA) as the main carbon source and the character pollutant, was subjected to expanded granular sludge bed(EGSB) process. The stability of theEGSB process was firstly conducted by laboratory experiment. TA ionization was the predominated factor influencing the acid-base balance of the system. High concentration of TA in wastewater resulted in sufficient buffering capacity to neutralize the volatile fatty acids(VFA)generated from substrate degradation and provided strong base for anaerobic system to resist the pH decrease below 6.5. VFA and UFA caused almost no inhibition on the anaerobic process and biogas production except that pH was below 6.35 and VFA was at its maximum value. Along with the granulating of the activated sludge, the efficiency of organic removal and production rate of biogas increased gradually and became more stable. After start-up, the efficiency of COD removal increased to 57%-64%, pH stabilized in a range of 7.99-8.04, and production rate of biogas was relatively high and stable. Sludge granulating, suitable influent of pH and loading were responsible for the EGSB stability. The variation of VFA concentration only resulted in neglectable rebound of pH, and the inhibition from VFA could be ignored in EGSB. The EGSB reactor was stable for TPD wastewater treatment.

  9. Dynamic characteristics and seismic stability of expanded polystyrene geofoam embankments

    Science.gov (United States)

    Amini, Zahra A.

    Expanded Polystyrene (EPS) geofoam has become a preferred material in various construction applications due to its light weight. Application of EPS accelerates the projects particularly on soft soils. The focus of this research is on the application of the EPS in embankments and its behavior mainly under harmonic vibration. The goal of this study was to investigate dynamic characteristics of freestanding vertical EPS geofoam embankment and address potential seismic issues that result from the distinguished dynamic behavior of such systems due to the layered and discrete block structure. A series of experimental studies on EPS 19 and a commercially available adhesive was conducted. Two-dimensional numerical analyses were performed to replicate the response of EPS geofoam embankment to horizontal and vertical harmonic motions. The results of the analyses have shown that for some acceleration amplitude levels interlayer sliding is expected to occur in EPS geofoam embankments almost immediately after the start of the base excitation; however, as a highly efficient energy dissipation mechanism sliding ceases rapidly. Shear keys and adhesive may be used to prevent interlayer sliding if they cover the proper extent of area of the embankment. EPS blocks placed in the corners of the embankment and at the edges of the segment prohibited from sliding may experience high stress concentrations. The embankment may show horizontal sway and rocking once sliding is prevented.

  10. Stability of a Bubble Expanding and Translating Through an Inviscid Liquid

    Indian Academy of Sciences (India)

    Dinesh Khattar; B B Chakraborty

    2002-05-01

    A bubble expands adiabatically and translates in an incompressible and inviscid liquid. We investigate the number of equilibrium points of the bubble and the nature of stability of the bubble at these points. We find that there is only one equilibrium point and the bubble is stable there.

  11. Extended x-ray absorption fine structure investigation of annealed carbon expanded austenite

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas L.; Somers, Marcel A. J.;

    2012-01-01

    Carbon expanded austenite synthesized through carburizing of austenitic stainless steel powder at 380°C was annealed at 470°C and investigated with extended X-ray absorption fine structure (EXAFS) and synchrotron powder diffraction (SPD). SPD showed that the samples consisted of carbon expanded......-carburized in a temperature regime around 470°C. The surface zone is converted into carbon expanded austenite; the high interstitial content of carbon dissolved in the surface results in highly favorable materials properties. In the present article the local atomic environment of (annealed) carbon expanded austenite...... was investigated with EXAFS. Copyright © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim....

  12. The Photochemical Stability of Carbonates on Mars

    Science.gov (United States)

    Quinn, Richard; Zent, Aaron P.; McKay, Christopher P.

    2006-08-01

    Carbonates, predominately MgCO3, have been spectroscopically identified at a level of 2-5% in martian dust. However, in spite of this observation, and a large number of climate studies that suggest 1 to several bars of CO2 should be sequestered in carbonate rocks, no outcropscale exposures of carbonate have been detected anywhere on Mars to date. To address one hypothesis for this long-standing puzzle, the effect of ultraviolet (UV) light on the stability of calcium carbonate in a simulated martian atmosphere was experimentally investigated. Using 13C-labeled calcite, we found no experimental evidence of the UV photodecomposition of calcium carbonate in a simulated martian atmosphere. Extrapolating the lower limit of detection of our experimental system to an upper limit of carbonate decomposition on Mars yields a quantum efficiency of 3.5 × 10-8 molecules/photon over the wavelength interval of 190-390 nm and a maximum UV photodecomposition rate of 1.2 × 10-13 kg m-2 s-1 from a calcite surface. The maximum loss of bulk calcite due to this process would be 2.5 nm year-1 (Mars year). However, calcite is expected to be thermodynamically stable on the surface of Mars, and potential UV photodecomposition reaction mechanisms indicate that, though calcium carbonate may decompose under vacuum, it would be stable in a CO2 atmosphere. Given the expected stability of carbonate on Mars and our inability to detect carbonate decomposition, we conclude that it is unlikely that the apparent absence of extensive carbonate deposits on the martian surface is due to UV photodecomposition in the current environment.

  13. Impacts of Soil Organic Stability on Carbon Storage in Coastal Wetlands

    Science.gov (United States)

    Williams, E. K.; Rosenheim, B. E.

    2015-12-01

    Coastal wetlands store vast amounts of organic carbon, globally, and are becoming increasingly vulnerable to the effects of anthropogenic sea level rise. Recently, we used ramped pyrolysis/oxidation decomposition characteristics as proxies for soil organic carbon (SOC) stability to understand the fate of carbon storage in coastal wetlands (fresh, brackish, and salt marshes) comprising the Mississippi River deltaic plain, undergoing rapid rates of local sea level rise. At equivalent soil depths, we observed that fresh marsh SOC was more thermochemically stable than brackish and salt marsh SOC. The differences in stability imply stronger carbon sequestration potential of fresh marsh soil carbon, compared to that of salt and brackish marshes. Here, we expand upon these results of differential organic carbon stability/reactivity and model how projected changes in salinity due to sea-level rise and other environmental changes will impact carbon storage in this region with implications globally.

  14. Expanding the coordination chemistry of donor-stabilized group-14 metalenes

    OpenAIRE

    Cabeza de Marco, Javier Ángel; García Álvarez, Pablo; Polo Coca, Diego

    2013-01-01

    The transformation of an amidinate germylene, equipped with just one accessible lone pair of electrons on the Ge atom, into a bidentate 4-electron donor κ(2)Ge,N-ligand, has been achieved for the first time, opening new doors to the non-carbene-like coordination chemistry of heavier carbene analogues. [Available from: http://www.researchgate.net/publication/233537999_Expanding_the_coordination_chemistry_of_donor-stabilized_group-14_metalenes [accessed Jul 13, 2015].

  15. Fabrication of porous carbon composite material from leaves waste as lightweight expanded carbon aggregate (LECA)

    Science.gov (United States)

    Sulhadi, Rosita, N.; Susanto, Nisa', K.; Wiguna, P. A.; Marwoto, P.; Aji, M. P.

    2016-04-01

    Leaves waste has been used as Lightweight Expanded Carbon Aggregates (LECA) because of its high carbon material. LECA can be used as a water storage media. LECA is low in density so thatits massis very light. Due to its use as a water storage medium, it is important to find out the absorption which occurs in LECA.The LECA's absorption and evaporation rate is affected by the pores. The pores serves to increase water storage ability from LECA. LECA with PEG (pore-forming agent) mass percent variation of 5%, 10%, 15%, 20% and 25% is the focus of this study. LECA fabrication was conducted by mixing the carbon resulting from leaves waste pyrolysis and PEG and PVAc. The characterization of LECA was found out by calculating the porosity, the pore size distribution, absorption rate and evaporation rate. The result of the calculation shows that the higher PEG mass percentage, the higher LECA's porosity, the pore size distribution, absorption rate and evaporation rate. However, the porosity, the pore size distributionand absorption rate will be saturated by 25% PEG mass percent addition.

  16. Carbon stabilization mechanisms in Ecuadorian Andosols

    Science.gov (United States)

    Jansen, Boris; Tonneijck, Femke; Nierop, Klaas; Verstraten, Koos

    2010-05-01

    Volcanic ash soils contain very large stocks of soil organic matter (SOM) per unit area. Consequently, they constitute potential sources or sinks of the greenhouse gas CO2. Whether soils become a net carbon source or sink upon climate and/or land-use change depends on the stability of SOM against decomposition, which is influenced by stabilisation mechanisms in the soil. To clarify the role of chemical and physical carbon stabilisation mechanisms in volcanic ash soils, we applied selective extraction techniques, performed X-ray diffraction analyses of the clay fraction and estimated pore size distributions at various depths in the top- and subsoil along an altitudinal transect in the Ecuadorian Andes. The transect encompassed a sequence of paleosols under natural upper montane forest as well as grassland (páramo). From several soils SOM was further characterized at a molecular level using GC/MS analyses of extractable lipids and Pyrolysis-GC/MS analyses of bulk organic matter. Our results show that organic carbon stocks under forest as well as páramo vegetation roughly doubled global averages for volcanic ash soils. The carbon stabilization mechanisms involved are: i) direct stabilization of SOM in organo-metallic (Al-OM) complexes; ii) indirect protection of SOM through low soil pH and toxic levels of Al; and iii) physical protection of SOM due to a very high microporosity. When examining the organic carbon at a molecular level, interestingly we found extensive degradation of lignin while extractable lipids were preferentially preserved, hinting at fungal degradation in the face of inhibited bacterial decomposition. Both vegetation types contributed to soil acidification, thus increasing SOM accumulation and inducing positive feedbacks. Most types of land-use change will result in immediate and substantial carbon loss to the atmosphere. Our results stress the urgent need to protect the Tropical Andes 'hotspot' from destructive land-use change, not only for the

  17. Extended X-ray absorption fine structure investigation of nitrogen stabilized expanded austenite

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny;

    2010-01-01

    the N atoms remaining in the solid state after H2-reduction are trapped by Cr atoms. Quantitative interpretation in terms of the local distortions around Cr atoms and their N coordination number reveals that no Cr–N clusters or CrN platelets are present.......As-delivered austenitic stainless steel and nitrogen stabilized expanded austenite, both fully nitrided and denitrided (in H2), were investigated with Cr, Fe and Ni extended X-ray absorption fine structure. The data shows pronounced short-range ordering of Cr and N. For the denitrided specimen...

  18. Dynamic Stability Study of Static Gas Bearing for Small Cryogenic Turbo-Expander

    International Nuclear Information System (INIS)

    An experimental method is presented to analyze the dynamic stability of the gas bearing for small cryogenic turbo-expanders. The rotation imbalance response and the shape of the rotor orbit were obtained for different speeds up to 110,000 rpm, and the critical speed of the rotor-bearing system was determined by a Bode diagram. An FFT signal analytical method was applied to identify the resonance frequency, and the waterfall plot was presented. During the whole process of speeding up to the designed speed of 110,000 rpm, the rotor-bearing works stably with no whirl instability, which is validated in a waterfall plot. Also, the tested rotor-bearing model was analyzed theoretically. It was proved that the experimental results were highly consistent with those of theoretical calculations. Thus the experimental method proposed here to analyze the dynamic stability of the gas bearing is feasible. (fusion engineering)

  19. Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets

    CERN Document Server

    Yang, Jun; Abbot, Dorian S

    2013-01-01

    The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phen...

  20. Configuration Consideration for Expander in Transcritical Carbon Dioxide Two-Stage Compression Cycle

    Institute of Scientific and Technical Information of China (English)

    MA Yitai; YANG Junlan; GUAN Haiqing; LI Minxia

    2005-01-01

    To investigate the configuration consideration of expander in transcritical carbon dioxide two-stage compression cycle, the best place in the cycle should be searched for to reinvest the recovery work so as to improve the system efficiency. The expander and the compressor are connected to the same shaft and integrated into one unit, with the latter being driven by the former, thus the transfer loss and leakage loss can be decreased greatly. In these systems, the expander can be either connected with the first stage compressor (shortened as DCDL cycle) or the second stage compressor (shortened as DCDH cycle), but the two configuration ways can get different performances. By setting up theoretical model for two kinds of expander configuration ways in the transcritical carbon dioxide two-stage compression cycle, the first and the second laws of thermodynamics are used to analyze the coefficient of performance, exergy efficiency, inter-stage pressure, discharge temperature and exergy losses of each component for the two cycles. From the model results, the performance of DCDH cycle is better than that of DCDL cycle. The analysis results are indispensable to providing a theoretical basis for practical design and operating.

  1. The Fuzzy Logic Model for the Prediction of Marshall Stability of Lightweight Asphalt Concretes Fabricated using Expanded Clay Aggregate

    Directory of Open Access Journals (Sweden)

    Sercan SERİN

    2014-07-01

    Full Text Available In the study, predictability of Marshall Stability (MS of light asphalt concrete that fabricated using expanded clay and had varied mix properties with Fuzzy Logic (FL were researched. With this aim, asphalt concrete samples that added expanded clay aggregate (EC in accordance with gradation determined in Highway Technical Specification, had different percentage of bitumen (POB (4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5% and unit weight (UW (1,75–1,87 (gr/cm3 were prepared and determined Marshall stabilities with Marshall test

  2. Effect of an Internal Heat Exchanger on Performance of the Transcritical Carbon Dioxide Refrigeration Cycle with an Expander

    OpenAIRE

    Zhenying Zhang; Lili Tian; Yanhua Chen; Lirui Tong

    2014-01-01

    The effect of the internal heat exchanger (IHE) on the performance of the transcritical carbon dioxide refrigeration cycle with an expander is analyzed theoretically on the basis of the first and second laws of thermodynamics. The possible parameters affecting system efficiency such as heat rejection pressure, gas cooler outlet temperature, evaporating temperature, expander isentropic efficiency and IHE effectiveness are investigated. It is found that the IHE addition in the carbon dioxide re...

  3. Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite

    DEFF Research Database (Denmark)

    Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.

    2008-01-01

    Abstract. In the present paper various experimental procedures to experimentally determine the concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. To this end thermogravimetric carburization was simulated for various experimental conditions and the evaluated...... composition dependent diffusivity of carbon derived from the simulated experiments was compared with the input data. The most promising procedure for an accurate determination is shown to be stepwise gaseous carburizing of thin foils in a gaseous atmosphere; the finer the stepsize, the more accurate...... the approximation of the diffusivity. Thermogravimetry was applied to continuously monitor the weight change of thin foils of AISI 316 during carburizing in CO-H2 gas mixtures for one of the simulated experimental procedures....

  4. Plasma species dynamics in a laser produced carbon plasma expanding in low pressure neutral gas background

    Science.gov (United States)

    Ruiz, H. M.; Guzmán, F.; Favre, M.; Bhuyan, H.; Chuaqui, H.; Wyndham, E.

    2012-06-01

    We present time and space resolved spectroscopic observations of a laser produced carbon plasma, in an argon background. An Nd:YAG laser pulse, 370 mJ, 3.5 ns, at 1.06 μm, with a fluence of 6.8 J/cm2, is used to produce a plasma from a solid graphite target, at a base pressure of 0.5 mTorr, and with 80 mTorr Argon background. The spectral emission in the visible is recorded with 15 ns time resolution. 20 ns time resolution plasma imagining, filtered at characteristic carbon species emission wavelengths, is used to study the dynamics of the expanding plasma. Two different fronts with ionic or molecular compositions are seen to detach from de laser target plasma.

  5. Nanocasting Process to Pore-Expanded Ordered Mesoporous Carbons with 2D Hexagonal Mesostructure

    Directory of Open Access Journals (Sweden)

    Chongwen Jiang

    2014-01-01

    Full Text Available Pore-expanded ordered mesoporous carbons with 2D hexagonal mesostructure were synthesized by a simple nanocasting process. We adopted sucrose as carbon precursors, mesoporous silica materials SBA-15 as the hard templates, and hexane as micelle swelling agents. The pore size distribution of OMCs was narrow and centered at 5.4 nm, which is larger than the upper limit of pore diameters typically reported for CMK-3. The BET surface area and mesopore volume of PE-CMK-3 can reach to 1213.47 m2/g and 1.56 cm3/g, respectively, indicating that choosing large pore size materials as template is good for preparation of high performance of OMCs.

  6. Structure Stability of Ⅰ-Type Carbon Nanotube Junctions

    Institute of Scientific and Technical Information of China (English)

    夏丹; 袁喆; 李家明

    2002-01-01

    Carbon nanotubes with junctions may play an important role in future ‘nanoelectronics' and future ‘nano devices'.In particular, junctions constructed with metal and semiconducting nanotubes have potential applications. Basedon the orthogonal tight-binding molecular dynamics method, we present our study of the structure stability ofI-type carbon nanotube junctions.

  7. Effect of an Internal Heat Exchanger on Performance of the Transcritical Carbon Dioxide Refrigeration Cycle with an Expander

    Directory of Open Access Journals (Sweden)

    Zhenying Zhang

    2014-11-01

    Full Text Available The effect of the internal heat exchanger (IHE on the performance of the transcritical carbon dioxide refrigeration cycle with an expander is analyzed theoretically on the basis of the first and second laws of thermodynamics. The possible parameters affecting system efficiency such as heat rejection pressure, gas cooler outlet temperature, evaporating temperature, expander isentropic efficiency and IHE effectiveness are investigated. It is found that the IHE addition in the carbon dioxide refrigeration cycle with an expander increases the specific cooling capacity and compression work, and decreases the optimum heat rejection pressure and the expander output power. An IHE addition does not always improve the system performance in the refrigeration cycle with an expander. The throttle valve cycle with IHE provides a 5.6% to 17% increase in maximum COP compared to that of the basic cycle. For the ideal expander cycle with IHE, the maximum COP is approximately 12.3% to 16.1% lower than the maximum COP of the cycle without IHE. Whether the energy efficiency of the cycle by IHE can be improved depends on the isentropic efficiency level of the expander. The use of IHE is only applicable in the cases of lower expander isentropic efficiencies or higher gas cooler exit temperatures for the refrigeration cycle with an expander from the view of energy efficiency.

  8. Enhanced Mechanical Stability of Gold Nanotips through Carbon Nanocone Encapsulation

    Science.gov (United States)

    Cano-Marquez, Abraham G.; Schmidt, Wesller G.; Ribeiro-Soares, Jenaina; Gustavo Cançado, Luiz; Rodrigues, Wagner N.; Santos, Adelina P.; Furtado, Clascidia A.; Autreto, Pedro A. S.; Paupitz, Ricardo; Galvão, Douglas S.; Jorio, Ado

    2015-06-01

    Gold is a noble metal that, in comparison with silver and copper, has the advantage of corrosion resistance. Despite its high conductivity, chemical stability and biocompatibility, gold exhibits high plasticity, which limits its applications in some nanodevices. Here, we report an experimental and theoretical study on how to attain enhanced mechanical stability of gold nanotips. The gold tips were fabricated by chemical etching and further encapsulated with carbon nanocones via nanomanipulation. Atomic force microscopy experiments were carried out to test their mechanical stability. Molecular dynamics simulations show that the encapsulated nanocone changes the strain release mechanisms at the nanoscale by blocking gold atomic sliding, redistributing the strain along the whole nanostructure. The carbon nanocones are conducting and can induce magnetism, thus opening new avenues on the exploitation of transport, mechanical and magnetic properties of gold covered by sp2 carbon at the nanoscale.

  9. On the Carbon Solubility in Expanded Austenite and Formation of Hägg Carbide in AISI 316 Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas L.; Ståhl, Kenny; Brink, Bastian K.;

    2016-01-01

    –420 °C and 465–470 °C, respectively. Hägg carbide (x-M5C2)develops when the carbon content in the expanded austenite exceeds the metastable solubility limit; the transformation of carbon expanded austenite into Hägg carbide occurs irrespective of carburizing temperature in the investigated temperature...... range (380–470 °C). The maximum solubility of carbon in expanded austenite (380 °C) is found to correspond to an occupancy (yC) of 0.220 of the interstitial octahedral sites of the austenite lattice (i.e., 4.74wt%C). Decomposition of Hägg carbide into M7C3 occurs upon prolonged carburizing treatment...

  10. Inhibition of surface bound carbonate stabilization of tetragonal zirconia

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; Lelieveld, A. van

    2011-01-01

    and water in order to increase the transformation rate in the zirconia crystals. It was found possible to limit the reaction by reacting the surface carbonates with alcohols, a thiol and a primary amide prior to reaction with water. It was also concluded that di- and trialcohols are able to stabilize...

  11. Earthworms facilitate carbon sequestration through unequal amplification of carbon stabilization compared with mineralization

    Science.gov (United States)

    A recent review concluded that earthworm presence increases CO2 emissions by 33% but does not affect soil organic carbon stocks. However, the findings are controversial and raise new questions. Here we hypothesize that neither an increase in CO2 emission nor in stabilized carbon...

  12. Stabilization of ultrafine metal nanocatalysts on thin carbon sheets

    Science.gov (United States)

    Liu, Xiaofang; Cui, Xinrui; Liu, Yiding; Yin, Yadong

    2015-10-01

    A novel strategy was proposed to anchor ultrafine metal nanoparticles (NPs) on thin carbon sheets for highly stable and efficient heterogeneous catalysts. In this facile approach, a dense monolayer of ultrafine AuNPs was sandwiched between a silica core and a resin shell, followed by carbonization of the shell at a high temperature and then selective removal of the silica core. The shrinkage of the shells during carbonization facilitates partial embedment of the AuNPs on the carbon shell surface and provides superior stability against particle sintering during high temperature/mechanical post-treatments and catalytic reactions. It was also found that diffusion of reactants to the surface of AuNPs could be maximized by reducing the thickness of the hollow shells or simply by cracking the shells into thin carbon sheets, both significantly benefiting the catalytic efficiency. The advantages of this ultra-stable architecture together with the densely dispersed catalytic sites were demonstrated by their high stability and superior catalytic activity in reducing hydrophilic 4-nitrophenol and hydrophobic nitrobenzene.A novel strategy was proposed to anchor ultrafine metal nanoparticles (NPs) on thin carbon sheets for highly stable and efficient heterogeneous catalysts. In this facile approach, a dense monolayer of ultrafine AuNPs was sandwiched between a silica core and a resin shell, followed by carbonization of the shell at a high temperature and then selective removal of the silica core. The shrinkage of the shells during carbonization facilitates partial embedment of the AuNPs on the carbon shell surface and provides superior stability against particle sintering during high temperature/mechanical post-treatments and catalytic reactions. It was also found that diffusion of reactants to the surface of AuNPs could be maximized by reducing the thickness of the hollow shells or simply by cracking the shells into thin carbon sheets, both significantly benefiting the

  13. Nitrogen-enriched carbon sheets derived from egg white by using expanded perlite template and its high-performance supercapacitors

    Science.gov (United States)

    Chen, Jiucun; Liu, Yinqin; Li, Wenjun; Xu, Liqun; Yang, Huan; Li, Chang Ming

    2015-08-01

    Nitrogen-enriched carbon sheets were synthesized using egg white as a unique carbon source and expanded perlite as a novel template. The as-prepared material was further used as an electrode material for supercapacitor applications, demonstrating excellent supercapacitance with a maximum gravimetric specific capacitance of 302 F g-1 at 0.5 A g-1 in a 3-electrode setup for a sample carbonized at 850 °C and activated for 6 h. Moreover, the carbon sheet-based capacitor with 2-symmetric electrodes showed an excellent cycle life (2% loss at 0.1 A g-1 after 10 000 cycles). The excellent performance may be attributed to the combination of the 3D carbon structure and the highly concentrated doped nitrogen component from the natural egg source for superior pseudocapacitance.

  14. Remarkable crystallization morphologies of poly(4-vinylpyridine on single-walled carbon nanotubes in CO2-expanded liquids

    Directory of Open Access Journals (Sweden)

    Y. N. Wei

    2011-12-01

    Full Text Available Poly(4-vinylpyridine (P4VP is a widely studied polymer for applications in catalysis, humidity sensitive and antimicrobial materials due to its pyridine group exhibiting coordinative reactivity with transition metals. In this work, the non-covalent functionalization of single-walled carbon nanotubes (SWCNTs with P4VP in CO2-expanded liquids (CXLs is reported. It is found that P4VP stabilized SWCNTs show good dispersion in both organic solvent and aqueous solution (pH = 2. The ability to manipulate the dispersion state of CNTs in water with P4VP will likely benefit many biological applications, such as drug delivery and optical sensors. Furthermore, the structure and morphology of P4VP/SWCNTs composite are examined, with the focus on molecular weight of P4VP (MW-P4VP, the pressure of CXLs and the concentration of P4VP. It is amazing that the P4VP15470 wrapping patterns undergo a notable morphological evolution from dotlike crystals to bottle brush-like, then to compact kebab-like, and then to widely-spaced dotted kebab patterns by facile pressure tuning in the higher polymer concentration series. In other words, the CXLs method enables superior control of the P4VP crystallization patterns on SWCNTs. Meanwhile, the CXL-assisted P4VP crystal growth mechanism on SWCNT is investigated, and the dominating growth mechanism is attributed to ‘size dependent soft epitaxy’ in P4VP15470/SWCNTs composites. We believe these studies would r

  15. Evaluating Stability of Aqueous Multiwalled Carbon Nanotube Nanofluids by Using Different Stabilizers

    Directory of Open Access Journals (Sweden)

    Tun-Ping Teng

    2014-01-01

    Full Text Available The 0.5 wt.% multiwalled carbon nanotubes/water nanofluids (MWNFs were produced by using a two-step synthetic method with different types and concentrations of stabilizers. The static position method, centrifugal sedimentation method, zeta potential measurements, and rheological experiments were used to assess the stability of the MWNFs and to determine the optimal type and fixed MWCNTs-stabilizer concentration of stabilizer. Finally, MWNFs with different concentrations of MWCNTs were produced using the optimal type and fixed concentration ratio of stabilizer, and their stability, thermal conductivity, and pH were measured to assess the feasibility of using them in heat transfer applications. MWNFs containing SDS and SDBS with MWCNTs-stabilizer concentration ratio were 5 : 2 and 5 : 4, respectively, showed excellent stability when they were evaluated by static position, centrifugal sedimentation, zeta potential, and rheological experiments at the same time. The thermal conductivity of the MWNFs indicated that the most suitable dispersing MWNF contained SDBS. MWNFs with MWCNTs concentrations of 0.25, 0.5, and 1.0 wt.% were fabricated using an aqueous SDBS solution. In addition, the thermal conductivity of the MWNFs was found to have increased, and the thermal conductivity values were greater than that of water at 25°C by 3.20%, 8.46%, and 12.49%.

  16. EXPANDED IRON UTA SPECTRA-PROBING THE THERMAL STABILITY LIMITS IN AGN CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Ferland, G. J.; Lykins, M. L. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Kisielius, R.; Jonauskas, V. [Institute of Theoretical Physics and Astronomy, Vilnius University, A. Gostauto 12, LT-01108 (Lithuania); Keenan, F. P. [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Van Hoof, P. A. M. [Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussel (Belgium); Porter, R. L. [Department of Physics, University of Georgia, Athens, GA 30602 (United States); Williams, R. J. R., E-mail: gary@pa.uky.edu [AWE plc, Aldermaston, Reading RG7 4PR (United Kingdom)

    2013-04-20

    The Fe unresolved transition arrays (UTAs) produce prominent features in the {approx}15-17 A wavelength range in the spectra of active galactic nuclei (AGNs). Here, we present new calculations of the energies and oscillator strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These are crucial ions since they are dominant at inflection points in the gas thermal stability curve, and UTA excitation followed by autoionization is an important ionization mechanism for these species. We incorporate these, and data reported in previous papers, into the plasma simulation code Cloudy. This updated physics is subsequently employed to reconsider the thermally stable phases in absorbing media in AGNs. We show how the absorption profile of the Fe XIV UTA depends on density, due to the changing populations of levels within the ground configuration.

  17. Flexible all-carbon photovoltaics with improved thermal stability

    International Nuclear Information System (INIS)

    The structurally robust nature of nanocarbon allotropes, e.g., semiconducting single-walled carbon nanotubes (SWCNTs) and C60s, makes them tantalizing candidates for thermally stable and mechanically flexible photovoltaic applications. However, C60s rapidly dissociate away from the basal of SWCNTs under thermal stimuli as a result of weak intermolecular forces that “lock up” the binary assemblies. Here, we explore use of graphene nanoribbons (GNRs) as geometrically tailored protecting layers to suppress the unwanted dissociation of C60s. The underlying mechanisms are explained using a combination of molecular dynamics simulations and transition state theory, revealing the temperature dependent disassociation of C60s from the SWCNT basal plane. Our strategy provides fundamental guidelines for integrating all-carbon based nano-p/n junctions with optimized structural and thermal stability. External quantum efficiency and output current–voltage characteristics are used to experimentally quantify the effectiveness of GNR membranes under high temperature annealing. Further, the resulting C60:SWCNT:GNR ternary composites display excellent mechanical stability, even after iterative bending tests. - Graphical abstract: The incorporation of solvent resistant, mechanically flexible and electrically addressable 2-D soft graphene nanoribbons facilitates the assembly of photoconductive carbon nano-p/n junctions for thermally stable and flexible photovoltaic cells.

  18. Flexible all-carbon photovoltaics with improved thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Chun; Ishihara, Hidetaka; Sodhi, Jaskiranjeet; Chen, Yen-Chang; Siordia, Andrew; Martini, Ashlie; Tung, Vincent C., E-mail: ctung@ucmerced.edu

    2015-04-15

    The structurally robust nature of nanocarbon allotropes, e.g., semiconducting single-walled carbon nanotubes (SWCNTs) and C{sub 60}s, makes them tantalizing candidates for thermally stable and mechanically flexible photovoltaic applications. However, C{sub 60}s rapidly dissociate away from the basal of SWCNTs under thermal stimuli as a result of weak intermolecular forces that “lock up” the binary assemblies. Here, we explore use of graphene nanoribbons (GNRs) as geometrically tailored protecting layers to suppress the unwanted dissociation of C{sub 60}s. The underlying mechanisms are explained using a combination of molecular dynamics simulations and transition state theory, revealing the temperature dependent disassociation of C{sub 60}s from the SWCNT basal plane. Our strategy provides fundamental guidelines for integrating all-carbon based nano-p/n junctions with optimized structural and thermal stability. External quantum efficiency and output current–voltage characteristics are used to experimentally quantify the effectiveness of GNR membranes under high temperature annealing. Further, the resulting C{sub 60}:SWCNT:GNR ternary composites display excellent mechanical stability, even after iterative bending tests. - Graphical abstract: The incorporation of solvent resistant, mechanically flexible and electrically addressable 2-D soft graphene nanoribbons facilitates the assembly of photoconductive carbon nano-p/n junctions for thermally stable and flexible photovoltaic cells.

  19. Phase Behavior of Dilute Carbon Black Suspensions and Carbon Black Stabilized Emulsions

    Science.gov (United States)

    Godfrin, Michael; Tiwari, Ayush; Bose, Arijit; Tripathi, Anubhav

    2014-11-01

    We use para-amino benzoic acid terminated carbon black (CB) as a tunable model particulate material to study the effect of inter-particle interactions on phase behavior and steady shear stresses in suspensions and particle-stabilized emulsions. We modulate inter-particle interactions by adding NaCl to the suspension, thus salting surface carboxylate groups. Surprisingly, yield stress behavior emerged at a volume fraction of CB as low as ϕCB = 0.008, and gel behavior was observed at ϕCB >0.05, well below the percolation threshold for non-interacting particles. The yield stress was found to grow rapidly with carbon black concentration suggesting that salt-induced hydrophobicity leads to strong inter-particle interactions and the formation of a network at low particle concentrations. The yield stresses of CB-stabilized emulsions also grows rapidly with carbon black concentrations, implying that inter-droplet interactions can be induced through the tuning of carbon black concentration in emulsion systems. Emulsions stabilized by ionic surfactants show no inter-droplet interactions. In contrast, oil droplets in the CB-stabilized emulsion move collectively or are immobilized because of an interconnected CB network in the aqueous phase.

  20. Removal of dispersant-stabilized carbon nanotubes by regular coagulants

    Institute of Scientific and Technical Information of China (English)

    Ni Liu; Changli Liu; Jing Zhang; Daohui Lin

    2012-01-01

    Coagulation followed by sedimentation,as a conventional technique in the water treatment plant,can be the first line of defense against exposures of carbon nanotubes(CNTs)to aquatic organisms and human beings,which has been rarely documented.This study investigated the removal of dispersant-stabilized CNT suspensions by poly aluminum chloride(PAC1)and KAI(SO4)2·12H2O (alum),with a focus on the effects of dispersant type,coagulant type and dosage.PAC1 performed better than alum in the removal of tannic acid-,humic acid-,and sodium dodecyl benzenesulfonate-stabilized CNTs,but worse for polyethylene glycol octylphenyl ether(TX100)-stabilized CNTs.Neither coagulant could effectively precipitate cetyltrimethyl ammonium bromide-stabilized CNTs.The removal by PAC1 first increased up to a plateau and then decreased with the continued increase of coagulant dosage.However,the removal rates leveled off but did not decrease after achieving their highest level with the continued addition of alum.The coagulation and flocculation of the CNT suspensions by PAC1 could be regulated mainly by the mechanism of adsorption charge neutralization,whereas the coagulation by alum mainly involved electrical double-layer compression.

  1. Carbon stabilization mechanisms in soils in the Andes

    Science.gov (United States)

    Jansen, Boris; Cammeraat, Erik

    2015-04-01

    The volcanic ash soils of the Andes contain very large stocks of soil organic matter (SOM) per unit area. Consequently, they constitute significant potential sources or sinks of the greenhouse gas CO2. Climate and/or land use change potentially have a strong effect on these large SOM stocks. To clarify the role of chemical and physical stabilisation mechanisms in volcanic ash soils in the montane tropics, we investigated carbon stocks and stabilization mechanisms in the top- and subsoil along an altitudinal transect in the Ecuadorian Andes. The transect encompassed a sequence of paleosols under forest and grassland (páramo), including a site where vegetation cover changed in the last century. We applied selective extraction techniques, performed X-ray diffraction analyses of the clay fraction and estimated pore size distributions at various depths in the top- and subsoil along the transect. In addition, from several soils the molecular composition of SOM was further characterized with depth in the current soil as well as the entire first and the top of the second paleosol using GC/MS analyses of extractable lipids and Pyrolysis-GC/MS analyses of bulk organic matter. Our results show that organic carbon stocks in the mineral soil under forest a páramo vegetation were roughly twice as large as global averages for volcanic ash soils, regardless of whether the first 30cm, 100cm or 200cm were considered. We found the carbon stabilization mechanisms involved to be: i) direct stabilization of SOM in organo-metallic (Al-OM) complexes; ii) indirect protection of SOM through low soil pH and toxic levels of Al; and iii) physical protection of SOM due to a very high microporosity of the soil (Tonneijck et al., 2010; Jansen et al. 2011). When examining the organic carbon at a molecular level, interestingly we found extensive degradation of lignin in the topsoil while extractable lipids were preferentially preserved in the subsoil (Nierop and Jansen, 2009). Both vegetation

  2. Wellbore stability analysis in carbonate reservoir considering anisotropic behaviour

    Science.gov (United States)

    Alves, José; Guevara, Nestor; Coelho, Lucia; Baud, Patrick

    2010-05-01

    Carbonate reservoirs represent a major part of the world oil and gas reserves. In particular, recent discoveries in the pre-salt offshore Brazil place big challenges to exploration and production under high temperatures and pressures (HTHP). During production, the extraction of hydrocarbons reduces pore pressure and thus causes an increase in the effective stress and mechanical compaction in the reservoir. The compactive deformation and failure may be spatially extensive or localized to the vicinity of the wellbore, but in either case the consequences can be economically severe involving surface subsidence, well failure and various production problems. The analysis of wellbore stability and more generally of deformation and failure in carbonate environments hinges upon a relevant constitutive modeling of carbonate rocks over a wide range of porosities, in particular, observed microstructure of samples suggests anisotropic behaviour. In this study, we performed a wellbore stability analysis for a lateral wellbore junction in three dimensions. The complex geometry for the wellbore junction was modeled with tetrahedral finite elements considering a rate independent elastic-plastic isotropic material that presented linear behavior during elastic strain and associated flow rule. A finite element model simulating drilling and production phases were done for field conditions from a deep water reservoir in Campos basin, offshore Brazil. In this context, several scenarios were studied considering true 3D orientation for both in situ stresses and geometry of the wellbore junction itself. We discussed the impact of constitutive modeling, considering anisotropic ductile damage and pressure sensitiveness on the wellbore stability. Parameter values for the analysis were based based on experimental data on two micritic porous carbonates. Series of conventional triaxial experiments were performed at room temperature in dry and wet conditions on samples of Comiso and Tavel

  3. Forestry and the carbon market response to stabilize climate

    International Nuclear Information System (INIS)

    This paper investigates the potential contribution of forestry management in meeting a CO2 stabilization policy of 550 ppmv by 2100. In order to assess the optimal response of the carbon market to forest sequestration, we couple two global models. An energy-economy-climate model for the study of climate policies is linked with a detailed forestry model through an iterative procedure to provide the optimal abatement strategy. Results show that forestry is a determinant abatement option and could lead to significantly lower policy costs if included. Linking forestry management to the carbon market has the potential to alleviate the policy burden of 50 ppmv or equivalently of 1/4 deg. C, and to significantly decrease the price of carbon. Biological sequestration will mostly come from avoided deforestation in tropical-forest-rich countries. The inclusion of this mitigation option is demonstrated to crowd out some of the traditional abatement in the energy sector and to lessen induced technological change in clean technologies

  4. Lignin-based carbon fibers: Carbon nanotube decoration and superior thermal stability

    KAUST Repository

    Xu, Xuezhu

    2014-08-23

    Lignin-based carbon fibers (CFs) decorated with carbon nanotubes (CNTs) were synthesized and their structure, thermal stability and wettability were systematically studied. The carbon fiber precursors were produced by electrospinning lignin/polyacrylonitrile solutions. CFs were obtained by pyrolyzing the precursors and CNTs were subsequently grown on the CFs to eventually achieve a CF–CNT hybrid structure. The processes of pyrolysis and CNT growth were conducted in a tube furnace using different conditions and the properties of the resultant products were studied and compared. The CF–CNT hybrid structure produced at 850 °C using a palladium catalyst showed the highest thermal stability, i.e., 98.3% residual weight at 950 °C. A mechanism for such superior thermal stability was postulated based on the results from X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and electron energy loss spectroscopy analyses. The dense CNT decoration was found to increase the hydrophobicity of the CFs.

  5. Synthesis and CO{sub 2} adsorption study of modified MOF-5 with multi-wall carbon nanotubes and expandable graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ullah, Sami, E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Bustam, M. A., E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Shariff, A. M., E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Elkhalifah, Ali E. I., E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Murshid, G., E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Riaz, Nadia, E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com [Research Center for Carbon Dioxide Capture, Dept. of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Sri Iskandar, Tronoh 31750 Perak (Malaysia)

    2014-10-24

    MOF-5 was synthesized by solvothermal method and its reactivation under anhydrous conditions. This research is conducted to investigate the effect of MOF-5 and MOF-5 modified with multi-wall carbon nanotubes (MWCNTs) and expandable graphite (EG) on the performance of CO{sub 2} adsorption. The synthesized MOFs were characterized using Field emission scanning electron microscopy (FESEM) for surface morphology, Thermogravimetric analysis (TGA) for thermal stability, X-ray diffraction (XRD) for crystals plane, Brunauer-Emmet-Teller (BET) for surface area and CO{sub 2} adsorption. The result had showed that the modified MOF-5 enhanced the CO{sub 2} adsorption compared to the pure MOF-5. The increment in the CO{sub 2} uptake capacities of MOF materials was attributed to the decrease in the pore size and enhancement of micropore volume of MOF-5 by multi-walled carbon nanotube and EG incorporation. The BET surface area of the synthesized MOF-5@MWCNTs is more than MOF-5. The CO{sub 2} sorption capacities of MOF-5 and MOF-5@MWCNTs were observed to increase from 0.00008 to 0.00048 mol g-1 at 298 K and 1 bar. The modified MOF-5@MWCNTs resulted in the highest CO{sub 2} adsorption followed by the modified MOF-5@ EG and lastly, MOF-5.

  6. Photodissociation and stability of carbon clusters; Photodissociation et stabilite d`agregats de carbone

    Energy Technology Data Exchange (ETDEWEB)

    Bouyer, R.

    1995-04-01

    This work is devoted to the study of the dissociation of ionised carbon clusters (containing 16 to 36 atoms) after photoexcitation by a UV-visible laser pulse. It contributes to experimental studies on formation mechanisms of carbon clusters, and particularly fullerenes. Its first aim is the knowledge of the internal energy of the clusters before dissociation. In the first part, a general overview summarizes the theoretical and experimental studies devoted to energetics (structure, stability, dissociation) of carbon clusters containing less than 60 atoms. In the second part, two techniques for producing mass-selected carbon clusters are described. The particular characteristics for such a production in a direct vaporization source are compared to those in a collisional-cooled source. The question of stability of intermediate-size clusters is asked. We study the photoabsorption spectroscopy of carbon clusters in the third part. A model for sequential absorption of several photons is developed, and used to analyze cluster dissociation versus the photoexcitation laser fluence. The absolute photoabsorption cross sections, and the number of absorbed photons are deduced. For some cluster sizes, laser wavelength scanning leads to evidence for existence of several clusters structures (or so-called isomers). The last part deals with photo dissociation mechanisms. Dissociation is found to occur after single-photon absorption, or after vibrational heating of the clusters. In that latter case, a statistical model including restricted intramolecular vibrational energy redistribution is used to calculate dissociation energies from measured fragmentation times of well-defined internal energy states. These energies, which are characteristic of cyclic structures, are then used to a better understanding of carbon cluster formation in a direct vaporization source. (Author). 76 refs., 63 figs., 23 tabs.

  7. Carbon Stabilization in Wet Tropical Forest Volcanic Soils

    Science.gov (United States)

    Marin-Spiotta, E.; Chadwick, O.; Kramer, M.

    2008-12-01

    Volcanic soils, particularly Andisols, have high carbon storage capacities due to the accumulation of highly reactive, non-crystalline minerals. Previous research along a pedogenic chronosequence on volcanic lava in Hawai'i found that soils in the intermediate weathering stage, dominated by allophane, contained the largest soil C stocks with slowest turnover rates. Potential mechanisms for long-term soil C stabilization include an accumulation of chemically recalcitrant C, microenvironmental conditions unfavorable for decomposition, and strong sorption of soluble and otherwise labile C to mineral and/or metals. In well-drained soils in wet climates, dissolved organic matter (DOM) is a likely main pathway for the transport of C from the zones of highest microbial activity to deeper mineral horizons. To address the production, transformation, and fate of dissolved organic matter (DOM), we have installed tension and zero tension lysimeters throughout sequentially deeper organic and mineral horizons in an intermediate aged soil (ca. 350k years) under wet (ca. 3000 mm mean annual rainfall) native tropical forest in Hawai'i. The soils are characterized by thick O horizons and Bh horizons 20-30 cm deep, followed by mineral horizons showing redoximorphic features. Bulk soil carbon to nitrogen ratios increase with soil depth, matching that of DOM in the surface organic horizons at 40-50 cm depth. Low pH does not seem to explain this accumulation of C-rich, N-depleted OM, as soils become less acidic with depth. Soil C:N are positively correlated with alumina, oxalate-extractable Al, and dithionite citrate-extractable Al. The greatest source of DOC is the forest floor (Oie), followed by the Oa horizon, and concentrations decrease significantly in the mineral horizons. DOC concentrations increase with total dissolved Al and Fe in the Oie horizon, and with total Fe in solution in the Bg horizon. In the Bh horizon, DOM C:N are negatively correlated with total Al and Fe in

  8. Harvesting Carbon from Eastern US Forests: Opportunities and Impacts of an Expanding Bioenergy Industry

    Directory of Open Access Journals (Sweden)

    Sarah C. Davis

    2012-06-01

    Full Text Available Eastern forests of the US are valued both as a carbon sink and a wood resource. The amount of biomass that can be harvested sustainably from this biome for bioenergy without compromising the carbon sink is uncertain. Using past literature and previously validated models, we assessed four scenarios of biomass harvest in the eastern US: partial harvests of mixed hardwood forests, pine plantation management, short-rotation woody cropping systems, and forest residue removal. We also estimated the amount and location of abandoned agricultural lands in the eastern US that could be used for biomass production. Greater carbon storage was estimated to result from partial harvests and residue removals than from plantation management and short-rotation cropping. If woody feedstocks were cultivated with a combination of intensive management on abandoned lands and partial harvests of standing forest, we estimate that roughly 176 Tg biomass y−1 (~330,000 GWh or ~16 billion gallons of ethanol could be produced sustainably from the temperate forest biome of the eastern US. This biomass could offset up to ~63 Tg C y−1 that are emitted from fossil fuels used for heat and power generation while maintaining a terrestrial C sink of ~8 Tg C y−1.

  9. Stability and aggregation of silver and titanium dioxide nanoparticles in seawater: role of salinity and dissolved organic carbon.

    Science.gov (United States)

    Wang, Huanhua; Burgess, Robert M; Cantwell, Mark G; Portis, Lisa M; Perron, Monique M; Wu, Fengchang; Ho, Kay T

    2014-05-01

    The behavior and fate of nanoparticles (NPs) in the marine environment are largely unknown and potentially have important environmental and human health implications. The aggregation and fate of NPs in the marine environment are greatly influenced by their interactions with seawater and dissolved organic carbon (DOC). In the present study, the stability and aggregation of 30-nm-diameter silver nanoparticles (AgNPs) capped with citrate and polyvinylpyrrolidone (PVP; AgNP-citrate and AgNP-PVP) and 21-nm-diameter titanium dioxide (TiO(2)) NPs as affected by seawater salinity and DOC were investigated by measuring hydrodynamic diameters and zeta potentials. The added DOC (in humic acid form) stabilized the 3 types of NPs when the seawater salinities were ≤5 parts per thousand (ppt), but the stabilizing effect of DOC was reduced by a higher salinity (e.g., 30 ppt). In addition, AgNP-PVP was more stable than AgNP-citrate in seawater, indicating that surface capping agents and stabilization mechanisms govern the stability and aggregation of NPs. Statistical analysis showed that salinity is the most dominant influence on the stability and aggregation of AgNPs and TiO(2) NPs, followed by DOC. These findings expand our knowledge on the behavior of AgNPs and TiO2 NPs in seawater and indicate that the fate of these NPs will be primarily to aggregate in the water column, precipitate, and accumulate in sediments following release into the marine environment.

  10. Stabilization of STEP electrolyses in lithium-free molten carbonates

    OpenAIRE

    Licht, Stuart

    2012-01-01

    This communication reports on effective electrolyses in lithium-free molten carbonates. Processes that utilize solar thermal energy to drive efficient electrolyses are termed Solar Thermal Electrochemical Processes (STEP). Lithium-free molten carbonates, such as a sodium-potassium carbonate eutectic using an iridium anode, or a calcium-sodium-potassium carbonate eutectic using a nickel anode, can provide an effective medium for STEP electrolyses. Such electrolyses are useful in STEP carbon ca...

  11. Stabilization of STEP electrolyses in lithium-free molten carbonates

    CERN Document Server

    Licht, Stuart

    2012-01-01

    This communication reports on effective electrolyses in lithium-free molten carbonates. Processes that utilize solar thermal energy to drive efficient electrolyses are termed Solar Thermal Electrochemical Processes (STEP). Lithium-free molten carbonates, such as a sodium-potassium carbonate eutectic using an iridium anode, or a calcium-sodium-potassium carbonate eutectic using a nickel anode, can provide an effective medium for STEP electrolyses. Such electrolyses are useful in STEP carbon capture, and the production of staples including STEP fuel, iron, and cement.

  12. Carbon Fibers from UV-Assisted Stabilization of Lignin-Based Precursors

    Directory of Open Access Journals (Sweden)

    Meng Zhang

    2015-06-01

    Full Text Available Production of high strength carbon fibers from bio-derived precursors is of topical interest. Recently, we reported on dry-spinning of a partially acetylated softwood kraft lignin to produce carbon fibers with superior properties, but the thermo-oxidative stabilization step required a long time due to a slow heating rate needed to prevent the fibers from being heated too rapidly and sticking to each other. Here we report a rapid strategy of dual UV-thermoxidative stabilization (crosslinking of dry-spun lignin fibers that significantly reduces the stabilization time. The fibers undergo reaction close to the surface such that they can be subsequently thermally stabilized at a rapid heating rate without fibers fusing together, which reduces the total stabilization time significantly from 40 to 4 h. Consequently, the glass transition temperature of UV irradiated fibers was about 15 °C higher than that of fibers without UV treatment. Stabilized fibers were successfully carbonized at 1000 °C and resulting carbon fibers displayed a tensile strength of 900 ± 100 MPa, which is amongst the highest reported for carbon fibers derived from softwood lignin-based precursors. These results establish that UV irradiation is a rapid step that can effectively shorten the total stabilization time for production of lignin-derived carbon fibers.

  13. Phase stability of iron-carbon nanocarbides and implications for the growth of carbon nanotubes

    Science.gov (United States)

    Awasthi, Neha

    Catalyst nanoparticles play a crucial role in the synthesis of single-walled carbon nanotubes by chemical vapor deposition technique. Understanding the thermal behavior of the nano-catalysts, their interaction with Carbon and stability of nanocarbides can give better insight into the growth mechanism and control over selective, yield of nanotubes. In this work, we present results using first-principle calculations and classical molecular dynamics simulations to understand the thermodynamics of free and Al2O3 supported Fe-C nanoparticles. We observe that the substrate plays an important role during the growth reaction by increasing the melting temperatures of small and medium size Fe nanoparticles. We investigate Fe-C phase diagrams for small Fe nanoparticles (d˜2nm) and discover that as the size of the Fe nanoparticle is reduced, the eutectic point shifted significantly toward lower temperatures, as expected from the Gibbs-Thomson law, and also toward lower concentrations of C. We devise a simple model based on the Young-Laplace pressure-radius relation, to predict the behavior of the phases competing for stability in Fe-C nanoclusters at low temperature. We identify ranges of nanoparticle sizes which are compatible for steady state-, limited- and no-growth of SWCNTs corresponding to unaffected, reduced and no solubility of C in the Fe nanoparticles. We also calculate Fe-Mo-C ternary phase diagrams to investigate the behavior of bimetallic Fe:Mo catalyst nanoparticles. Our results show that addition of Mo (upto small concentrations) lowers the minimum radius when stable carbides nucleate and poison the catalyst, which enables a larger range of catalyst nanoparticles sizes to nucleate nanotubes. We also find that pure Fe has the highest surface concentration in Fe:Mo nanoparticles and is likely to be the active nucleation site for nanotubes.

  14. Crystalline polymer decoration on multiwalled carbon nanotubes: MWCNT-induced P4VP periodic crystallization in CO2-expanded liquids

    Directory of Open Access Journals (Sweden)

    2011-01-01

    Full Text Available This work reports the functionalization of multi-walled carbon nanotubes (MWCNTs with crystalline poly(4- vinylpyridine (P4VP in CO2-expanded liquids (CXLs. The structure and morphology of MWCNT-induced polymer crystallization are examined, with the focus on molecular weight of P4VP (MW-P4VP, the pressure of CXLs and the concentration of P4VP. First, it is observed that the crystallization morphologies for the P4VP/MWCNTs composite with a low molecular weight P4VP (LMW-P4VP matrix could be finely controlled in CXLs, and it is surprising to find that the P4VP8700 wrapping patterns undergo a morphological evolution from dot crystals to dotted helical wrappings, and then to dense helical patterns by facile pressure tuning under lower polymer concentration. In other words, the CXLs method enables superior control of the P4VP crystallization patternings on MWCNTs, particularly efficient for LMW-P4VP at lower polymer concentration. Meanwhile, the CXL-assisted P4VP crystal growth mechanism on MWCNT is investigated, and the dominating growth mechanism is attributed to 'normal epitaxy' at lower P4VP concentration rather than 'soft epitaxy' at higher concentration. We believe that this work reports a new crystalline polymer wrapping approach in CXLs to noncovalent engineering of MWCNTs surfaces.

  15. Stability of Soil Carbon Fractions - Aggregation Versus Mineral Association

    Science.gov (United States)

    Mueller, C. W.; Koegel-Knabner, I.

    2007-12-01

    Models that seek to describe the dynamics of soil organic C typically distinguish between two or more C fractions according to differences of biochemical and microbial degradation. The rates are a consequence of recalcitrance, accessibility and interactions. Soil aggregation is an important mechanism controlling the accessibility of substrates by microbes and enzymes and thus the dynamics of minerals bound C are interacting with soil aggregate dynamics. In this study we focused on C fractions isolated by particle size fractionation. The main objective of our study was to differentiate between C stabilization of soil fractions due to accessibility/aggregation or to association with minerals. For a detailed understanding of these processes and the sources of respired soil CO2 we combined the measurement of heterotrophic respiration, CO2-13C analyses and radiocarbon dating of the respired CO2 in a long-term laboratory mineralization experiment. For the experiment we took soil material from the A horizon of an Albic Luvisol under Norway spruce forest (Picea abies) in southern Germany. The air dried bulk soil ( 63 µm to 2000 µm - sand, > 6.3 µm to 63 µm - silt and silt/clay fraction NMR spectroscopy was used to analyze the composition of bulk soil and fractions. The incubation of the three fractions and the bulk soil was done for 250 days in triplicate at 20 degree Celsius and 70% of maximal water holding capacity. A relative enrichment of alkyl C and an increase of the alkyl / O/N-alkyl C ratios in the order of sand NMR. On a long term the sand fraction and the bulk soil showed a sustained C bioavailability. For the silt and clay fraction similar respiration rates and a low C bioavailability were detected. The recombined fractions (by calculation) showed 35% higher amounts of respired CO2-C than the bulk soil. This difference accounts for the absence of restricted accessibility due to soil aggregation. Because of the high amounts of mineral bound C the main source

  16. Synthesis, model and stability of helically coiled carbon nanotubes

    DEFF Research Database (Denmark)

    Fejes, Dora; Raffai, Manuella; Hernadi, Klara;

    2013-01-01

    Structural model of helically coiled carbon nanotubes is proposed. It is constructed by means of topological coordinate method. Relaxation and cohesive energy calculation are performed by molecular mechanics, using second-generation bond order potential for hydrocarbons introduced by D. W. Brenner....... Our experiments focused on the production and development of catalysts for the synthesis of helically coiled CNTs (carbon nanotubes). The catalysts were tested in the decomposition of acetylene by CCVD (Catalytic Chemical Vapor Deposition) method. The carbon deposit was imaged by TEM (Transmission...

  17. Influence of different carbon nanostructures on the electrocatalytic activity and stability of Pt supported electrocatalysts

    DEFF Research Database (Denmark)

    Stamatin, Serban Nicolae; Borghei, Maryam; Andersen, Shuang Ma;

    2014-01-01

    Commercially available graphitized carbon nanofibers and multi-walled carbon nanotubes, two carbon materials with very different structure, have been functionalized in a nitric–sulfuric acid mixture. Further on, the materials have been platinized by a microwave assisted polyol method. The relativ...... that the functionalization improves the stability for multi-walled carbon nanotubes, at the cost of decreased activity.......Commercially available graphitized carbon nanofibers and multi-walled carbon nanotubes, two carbon materials with very different structure, have been functionalized in a nitric–sulfuric acid mixture. Further on, the materials have been platinized by a microwave assisted polyol method. The relative....../F-MWCNT. Transmission electron microscopy showed that the Pt particle size is around 3 nm for all samples, which was similar to the crystallite size obtained by X-ray diffraction. The activity towards electrochemical reduction of oxygen has been quantified using the thin-film rotating disk electrode, which has shown...

  18. Synergistic effects of expandable graphite and dimethyl methyl phosphonate on the mechanical properties, fire behavior, and thermal stability of a polyisocyanurate-polyurethane foam

    Institute of Scientific and Technical Information of China (English)

    Hu Xiangming; Wang Deming; Wang Shuailing

    2013-01-01

    In this study,a series of flame-retardant polyisocyanurate-polyurethane (PIR-PUR) foams were prepared using various concentrations (0-25% by weight) of expandable graphite (EG) and dimethyl methyl phosphonate (DMMP) (0-7% by weight).The effect of these additives on the properties of the PIR-PUR foams,including physico-mechanical,morphological,flame retardancy,and thermal stability,was studied.Increasing amounts of EG in the PIR-PUR foam caused a significant drop in the compression strength.However,DMMP caused the mechanical properties of PIR-PUR foam to improve compared to foam filled with EG alone.The flame retardancy of PIR-PUR foams containing both EG and DMMP was enhanced significantly compared to EG filled foams.Thermogravimetric analysis (TGA) indicated that EG enhances the thermal stability of PIR-PUR foams but that DMMP decreased it.The morphology of the residual char provided conclusive evidence for the weak thermal stability of foams filled with DMMP.

  19. Carbonate leaching of uranium and hydrogen peroxide stabilizer therefor

    International Nuclear Information System (INIS)

    In the carbonate leaching process for the solution mining of subterranean uranium containing formations in which an injection well is drilled and completed within the uranium formation; alkaline carbonate uranium leaching solution and sufficient hydrogen peroxide are injected through the injection wells into the formation whereby uranium values are produced from production wells, characterized by providing in the leaching solution a mixture of 1-hydroxyethylidene-1,1-diphosphonic acid and an alkali metal pyrophosphate in a weight ratio of from 1 to 10 to 10 to 1, the amount of said mixture being sufficient to inhibit decomposition of the hydrogen peroxide in said leaching solution

  20. Effect of oxidation treatment on the adsorption and the stability of mercury on activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Hu, C.X.; Zhou, J.S.; Luo, Z.Y.; He, S.; Wang, G.K.; Cen, K.F. [Zhejiang University, Hangzhou (China)

    2006-07-01

    Oxidation treatment on the adsorption and the stability of Hg on activated carbon (AC) was investigated. Both MnO{sub 2}-AC and FeCl{sub 3}-AC were produced during oxidation treatment. The measurement of modified AC's mercury adsorption capacity was conducted in a simulated coal-fired flue gas by adsorbing test apparatus. TCLP and column leaching methods were used to test the stability of mercury adsorbed on ACs. The results indicate that the oxidation treatment changed the pore structure of the AC and modified the carbon surface by creating chemical components such as MnO{sub 4}{sup -}, Mn{sup 4+}, NO{sub 3}{sup -}, Fe{sup 3+} Cl{sup -}, etc. The Hg sorption capacity on MnO{sub 2}-AC or FeCl3-AC was about three times higher than that of untreated carbon. In addition, the mercury control cost of each of the formers was about the half cost of the untreated carbon. The stability of Hg absorption was studied. It was found that mercury adsorbed on the oxidation treated AC was not better than that of untreated carbon. It could be concluded that the insoluble form of Hg is very important to the stability of mercury adsorbed on AC. This study suggests that the FeCl3-AC is the best absorbent for Hg with high adsorption capacity, better Hg adsorption stability in leaching environment, and lower cost among the three ACs tested.

  1. Effect of oxidation treatment on the adsorption and the stability of mercury on activated carbon

    Institute of Scientific and Technical Information of China (English)

    HU Chang-xing; ZHOU Jin-song; LUO Zhong-yang; HE Sheng; WANG Guang-kai; CEN Ke-fa

    2006-01-01

    Oxidation treatment on the adsorption and the stability of Hg on activated carbon (AC) was inrestigated. Both MnO2-AC and FeCl3-AC were produced during oxidation treatment. The measurement of modified AC's mercury adsorption capacity was conducted in a simulated coal-fired flue gas by adsorbing test apparatus. TCLP and column leaching methods were used to test the stability of mercury adsorbed on ACs. The results indicate that the oxidation treatment changed the pore structure of the AC and modified the carbon surface by creating chemical components such as MnO4-, Mn4+, O, NO3-, Fe3+, Cl-, etc. The Hg sorption capacity on MnO2-AC or FeCl3-AC was about three times higher than that of untreated carbon. In addition, the mercury control cost of each of the formers was about the half cost of the untreated carbon. The stability of Hg absorption was studied, it found that mercury adsorbed on the oxidation treated AC was not better than that of untreated carbon. It could concluded that the insoluble form of Hg is very important to the stability of mercury adsorbed on AC. This study suggests that the FeCl3-AC is the best absorbent for Hg with high adsorption capacity, better Hg adsorption stability in leaching environment, and lower cost among the three ACs tested.

  2. Stability of singlet and triplet trions in carbon nanotubes

    DEFF Research Database (Denmark)

    Rønnow, Troels Frimodt; Pedersen, Thomas Garm; Cornean, Horia

    2009-01-01

    We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.5% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band...

  3. Stability of singlet and triplet trions in carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ronnow, Troels F. [Department of Physics and Nanotechnology, Skjernvej 4C, 9220 Aalborg Ost (Denmark)], E-mail: tfr@nanophysics.dk; Pedersen, Thomas G. [Department of Physics and Nanotechnology, Skjernvej 4C, 9220 Aalborg Ost (Denmark)], E-mail: tgp@nano.aau.dk; Cornean, Horia D. [Department of Mathematical Sciences, Frederik Bajers Vej 7G, 9220 Aalborg Ost (Denmark)], E-mail: cornean@math.aau.dk

    2009-04-06

    We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.6% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band gap energy.

  4. Stability of singlet and triplet trions in carbon nanotubes

    International Nuclear Information System (INIS)

    We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.6% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band gap energy.

  5. Flame retardancy and thermal stability of polyurethane foam composites containing carbon additives

    Science.gov (United States)

    Lee, Pyoung-Chan; Kim, Bo-Ram; Jeoung, Sun Kyoung; Lee, Geesoo; Han, San Wook; Kim, Hyunchul; Lee, Ki-Dong; Han, Joo-Kwon

    2016-03-01

    Polyurethane (PU) is an important class of polymers that have wide application in a number of different industrial sectors. The goal of this work was the synthesis of flame-retarded PU foam with expandable graphite (EG) or commercial graphene. The flame retardancy and thermal stability of the foams has been studied through cone calorimeter analysis, the limited oxygen index and thermal conductivity. The presence of expandable graphite brings an improvement in fire behavior. In particular, the limited oxygen index increases in a linear way and the highest limited oxygen index values are obtained for EG-PU foams. The results from the cone calorimeter are in agreement with those of oxygen index; EG filled foams show a considerable decrease of maximum-heat release rate (M-HRR) with respect to unfilled foams. The results of thermal conductivity show that an increase in expandable graphite amount in PU foams lead to an increased conductivity.

  6. Annealing effect and stability of carbon nanotubes in hydrogen flame

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Annealing of carbon nanotubes (CNTs) by the hydrogen flame in air was investigated in this study. Raman spectroscopy and scanning electron microscopy were used to characterize the products. The peak width of Raman spectra decreased with the increase in the annealing time. The CNTs were not stable in the hydrogen flame and the etching rate of the CNTs by hydrogen flame was very high. The hydrogen flame annealing had some effects on improving the crystallinity of CNTs.

  7. Polyethylene-Based Carbon Fibers by the Use of Sulphonation for Stabilization

    Directory of Open Access Journals (Sweden)

    Gisa Wortberg

    2015-09-01

    Full Text Available Polyethylene has great potential as an alternative material for carbon fiber production. Polyethylene can be processed in the economic melt spinning process. These precursors are prepared for the subsequent process step of carbonization by using chemical stabilization (sulphonation. The strategy is to adjust these precursor properties by the melt spinning process, thus resulting in a precursor, which can be stabilized sufficiently by sulphonation. The objective is to find the correlation between precursor properties and the results of the sulphonation. In this paper, the chemical stabilization is described and the results of the chemical stabilization are discussed. The novelty in this paper is that the results of the sulphonation are brought in correlation with the precursor properties. It can be shown that the filament diameter and the polymer structure (e.g., the crystallinity of the precursor have an influence on the sulphonation process.

  8. Phosphorus-assisted biomass thermal conversion: reducing carbon loss and improving biochar stability.

    Science.gov (United States)

    Zhao, Ling; Cao, Xinde; Zheng, Wei; Kan, Yue

    2014-01-01

    There is often over 50% carbon loss during the thermal conversion of biomass into biochar, leading to it controversy for the biochar formation as a carbon sequestration strategy. Sometimes the biochar also seems not to be stable enough due to physical, chemical, and biological reactions in soils. In this study, three phosphorus-bearing materials, H3PO4, phosphate rock tailing (PRT), and triple superphosphate (TSP), were used as additives to wheat straw with a ratio of 1: 0.4-0.8 for biochar production at 500°C, aiming to alleviate carbon loss during pyrolysis and to increase biochar-C stabilization. All these additives remarkably increased the biochar yield from 31.7% (unmodified biochar) to 46.9%-56.9% (modified biochars). Carbon loss during pyrolysis was reduced from 51.7% to 35.5%-47.7%. Thermogravimetric analysis curves showed that the additives had no effect on thermal stability of biochar but did enhance its oxidative stability. Microbial mineralization was obviously reduced in the modified biochar, especially in the TSP-BC, in which the total CO2 emission during 60-d incubation was reduced by 67.8%, compared to the unmodified biochar. Enhancement of carbon retention and biochar stability was probably due to the formation of meta-phosphate or C-O-PO3, which could either form a physical layer to hinder the contact of C with O2 and bacteria, or occupy the active sites of the C band. Our results indicate that pre-treating biomass with phosphors-bearing materials is effective for reducing carbon loss during pyrolysis and for increasing biochar stabilization, which provides a novel method by which biochar can be designed to improve the carbon sequestration capacity. PMID:25531111

  9. Limits to soil carbon stability; Deep, ancient soil carbon decomposition stimulated by new labile organic inputs

    Science.gov (United States)

    Soil carbon (C) pools store about one-third of the total terrestrial organic carbon. Deep soil C pools (below 1 m) are thought to be stable due to their low biodegradability, but little is known about soil microbial processes and carbon dynamics below the soil surface, or how global change might aff...

  10. Influence of oxidation inhibitor on carbon-carbon composites : 3. Effect of molybdenum disilicide on thermal stability of the composites

    Energy Technology Data Exchange (ETDEWEB)

    Park, S.J.; Cho, M.S.; Lee, J.R. [Korea Research Institute of Chemical Technology, Taejon (Korea, Republic of)

    1999-03-01

    PAN-based carbon fibers, impregnated with phenolic resin used as a precursor of carbonized matrix, was modified by the addition of molybdenum disilicide (MoSi{sub 2}) in different concentrations. i.e., 0, 4, 12 and 20% by weight. Thus, the unidirectional carbon fiber-reinforced phenolic matrix composites were manufactured by prepreg method, and were submitted to carbonization (heat treated to 1100 {sup o} C) and graphitization (to 2300 {sup o} C). The influence of MoSi{sub 2} concentrations having oxidation inhibition and brittle-to-ductile transition (BDT) properties at high temperatures on the thermal stability of the composites was investigated by using thermogravimetric analysis (TGA0 in air atmosphere. Thermal stabilities of the composites were characterized by the integral procedural decomposition temperature (IPDT) obtained from the analytical method of Doyle and the activation energy derived from the integral method of Horowitz-Metzger. It was found that the thermal stabilities increased with increasing the final heat treatment temperature (HTT) and the concentration of MoSi{sub 2} in C/C composites. This seems to be a consequence of the improvement in physical adhesion between fiber-matrix-MoSi{sub 2} of the composites, due to the BDT at high temperatures. 17 refs., 4 figs.

  11. Aggregate structure and stability linked to carbon dynamics in a south Chilean Andisol

    OpenAIRE

    C. Oyarzún; Godoy, R.; O. Van Cleemput; P. Boeckx; Huygens, D.

    2005-01-01

    International audience The extreme vulnerability of soil organic carbon to climate and land use change emphasizes the need for further research in different terrestrial ecosystems. We have studied the aggregate stability and carbon dynamics in a chronosequence of three different land uses in a south Chilean Andisols: a second growth Nothofagus obliqua forest (SGFOR), a grassland (GRASS) and a Pinus radiata plantation (PINUS). The aim of this study was to investigate the role of Al as soil ...

  12. Thermodynamic stabilities of carbon-and nitrogen-centered radicals

    Institute of Scientific and Technical Information of China (English)

    程津培; 赵永昱; 还振威

    1995-01-01

    The gas-phase homolytic C-H and N-H bond dissociation energies(BDE)of the substi-tuted phenoacetonitrile families,aromatic amines,and semicarbazone derivatives were systematically investigatedor reinvestigated based on a cycle utilizing the thermodynamic quantities determined in DMSO solution.Theexperimental evidence collected in.this work dearly indicates that the radicals derived from the above familiesare of the‘Class O’type,i.e.to be stabilized by a remote electron-donating substituent but destabilized by anelectron-withdrawing substituent.

  13. Stability and signatures of biexcitons in carbon nanotubes

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Pedersen, Kjeld; Cornean, Horia Decebal;

    2005-01-01

    The linear optical properties of semiconducting carbon nanotubes are dominated by quasi-one-dimensional excitons formed by single electron-hole pairs. Hence, the nonlinear response at high pump levels most likely leads to the formation of exciton complexes involving several electron-hole pairs....... Such complexes would threfore play an important role in e.g. lasing applications. We demonstrate here that the biexciton complex is surprisingly stable for nanotubes in a wide diameter range. Theoretical predictions for the signature of such states in pump-probe spectroscopy are presented....

  14. Hydrated salts/expanded graphite composite with high thermal conductivity as a shape-stabilized phase change material for thermal energy storage

    International Nuclear Information System (INIS)

    Highlights: • Hydrated salts were prepared into shape-stabilized phase change materials. • Phase segregation of the hydrated salts was inhibited. • Thermal conductivity of hydrated salts/EG composite was higher than others. - Abstract: A novel shape-stabilized phase change material (PCM) was developed by impregnation of hydrated salts into expanded graphite (EG) and further coated with paraffin wax. It was displayed by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR) measurements that the hydrated salts were filled into pores or adhered onto the flakes of EG by physical interactions, including capillary forces and surface tension. It was revealed from differential scanning calorimetry (DSC) analysis that phase segregation was inhibited and subcooling weakened in the coated composite PCM. The melting and freezing enthalpy of the coated composite PCM can reach 172.3 kJ/kg at 32.05 °C and 140.8 kJ/kg at 17.11 °C, respectively. Also, the results of thermal gravimetric analysis (TG) suggested that the coated composite PCM had good thermal stability in the working temperature range from 25 to 50 °C. Furthermore, the enthalpy loss of melting and freezing was negligible after 100 cycles, indicating its good thermal reliabilities. The thermal conductivity of the coated composite PCM can be as high as 3.643 W/(m K). According to the obtained results, the coated hydrated salts/EG composite PCM enjoys high latent heat, good thermal reliability and high thermal conductivity. Apart from its favorable thermal properties, the cost of the coated hydrated salts/EG composite PCM was quite low, making it promising for low temperature thermal energy storage applications

  15. High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

    KAUST Repository

    Stoltz, Brian

    2010-06-14

    The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

  16. Thermal Stability of Zirconia-coated Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    R. Manivannan

    2010-04-01

    Full Text Available Sol-gel method has been used to coat multiwalled carbon nanotubes (MWCNTs with zirconia at room temperature and the coated tubes were sintered at high temperature. The samples were characterised by Raman spectroscopy, x-ray diffraction, environmental scanning electron microscope, transmission electron microscopy, and energy-dispersive x-ray analyses. The performance of the coated-MWCNTs was investigated as a function of temperature. The TGA studies indicated that sintering of coated-MWCNTs has improved its oxidation resistance and this improvement is related to the proper selection of sintering temperature.Defence Science Journal, 2010, 60(3, pp.337-342, DOI:http://dx.doi.org/10.14429/dsj.60.362

  17. Citrate effects on amorphous calcium carbonate (ACC) structure, stability, and crystallization

    DEFF Research Database (Denmark)

    Tobler, Dominique Jeanette; Rodriguez Blanco, Juan Diego; Dideriksen, Knud;

    2015-01-01

    Understanding the role of citrate in the crystallization kinetics of amorphous calcium carbonate (ACC) is essential to explain the formation mechanisms, stabilities, surface properties, and morphologies of CaCO3 biominerals. It also contributes to deeper insight into fluid-mineral inte...

  18. Soil and plant responses to pyrogenic organic matter: carbon stability and symbiotic patterns

    NARCIS (Netherlands)

    Sagrilo, E.

    2014-01-01

    Soil and plant responses to pyrogenic organic matter: carbon stability and symbiotic patterns Edvaldo Sagrilo Summary Pyrogenic organic matter (PyOM), also known as biochar, is the product of biomass combustion under low oxygen concentration. There

  19. Thermal stability of catalytically grown multi-walled carbon nanotubes observed in transmission electron microscopy

    DEFF Research Database (Denmark)

    Wang, Cheng-Yu; Liu, Chuan-Pu; Boothroyd, Chris

    2009-01-01

    The thermal stability of multi-walled carbon nanotubes (MWCNTs) was assessed in situ by transmission electron microscopy. Upon heating, Ni catalysts in MWC-NTs containing bamboo structures shrank from the tail due to evaporation, leading to additional bamboo formation and tube elongation at 800...

  20. Temperature and Microbial Activity Effects on Soil Carbon Stabilization

    Science.gov (United States)

    Fissore, C.; van Diepen, L.; Wixon, D.; Marin-Spiotta, E.; Giardina, C. P.

    2014-12-01

    Uncertainties on the importance of environmental controls on soil C stabilization and turnover limit accurate predictions of the rate and magnitude of the response of soils to climate change. Here we report results from a study of interactions among vegetation and soil microbial communities in North American forests across a highly constrained, 22OC gradient mean annual temperature (MAT) as a proxy for understanding changes with climate. Previous work indicated that turnover and amount of labile SOC responded negatively to MAT, whereas stable SOC was insensitive to temperature variation. Hardwood forests stored a larger amount of stable SOC, but with shorter mean residence times than paired pine forests. Our findings suggest that the interaction between vegetation composition and microbial communities may affect SOC accumulation and stabilization responses to rising temperature. To investigate these relationships, we characterized the microbial communities with Phospholipid Fatty Acid (PLFA) analysis. PLFA analyses indicate complex microbial responses to increased MAT and vegetation composition. Microbial biomass declined with MAT in conifer forests and increased in hardwood forests. Relative abundance of actinomycetes increased with MAT for both forest types, and was correlated with amount and turnover of active SOC. The relative abundance of fungi decreased with increasing MAT, while gram+ bacteria increased, such that fungi:bacteria ratio decreased with MAT, with this trend being more pronounced for hardwood cover type. These results are consistent with a long-term warming experiment in a hardwood forest at the Harvard Forest LTER site, where after 12 years of warming the relative abundance of gram positive bacteria and actinomycetes increased, while fungal biomass decreased. In contrast, relationships between microbial groups and the stable fraction of SOC along the gradient were only observed in conifers. Increases in mean residence time of stable SOC were

  1. Electrochemical stability of carbon nanofibers in proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, Garbine [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Alcaide, Francisco, E-mail: falcaide@cidetec.es [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Miguel, Oscar [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Cabot, Pere L. [Laboratori d' Electroquimica de Materials i del Medi Ambient, Dept. Quimica Fisica, Universitat de Barcelona, Marti i Franques, 1-11, 08028 Barcelona (Spain); Martinez-Huerta, M.V.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica (CSIC), Marie Curie 2, Cantoblanco, 28049 Madrid (Spain)

    2011-10-30

    This fundamental study deals with the electrochemical stability of several non-conventional carbon based catalyst supports, intended for low temperature proton exchange membrane fuel cell (PEMFC) cathodes. Electrochemical surface oxidation of raw and functionalized carbon nanofibers, and carbon black for comparison, was studied following a potential step treatment at 25.0 deg. C in acid electrolyte, which mimics the operating conditions of low temperature PEMFCs. Surface oxidation was characterized using cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Cyclic voltammograms clearly showed the presence of the hydroquinone/quinone couple. Furthermore, identification of carbonyl, ether, hydroxyl and carboxyl surface functional groups were made by deconvolution of the XPS spectra. The relative increase in surface oxides on carbon nanofibers during the electrochemical oxidation treatment is significantly smaller than that on carbon black. This suggests that carbon nanofibers are more resistant to the electrochemical corrosion than carbon black under the experimental conditions used in this work. This behaviour could be attributed to the differences found in the microstructure of both kinds of carbons. According to these results, carbon nanofibers possess a high potential as catalyst support to increase the durability of catalysts used in low temperature PEMFC applications.

  2. Activity and stability studies of platinized multi-walled carbon nanotubes as fuel cell electrocatalysts

    DEFF Research Database (Denmark)

    Stamatin, Serban Nicolae; Borghei, Maryam; Dhiman, Rajnish;

    2015-01-01

    A non-covalent functionalization for multi-walled carbon nanotubes has been used as an alternative to the damaging acid treatment. Platinum nanoparticles with similar particle size distribution have been deposited on the surface modified multi-walled carbon nanotubes. The interaction between...... platinum nanoparticles and multi-walled carbon nanotubes functionalized with 1-pyrenecarboxylic acid is studied and its electrochemical stability investigated. This study reveals the existence of a platinum-support interaction and leads to three main conclusions. First, the addition of 1-pyrenecarboxylic...... acid is improving the dispersion of platinum nanoparticles, leading to an improved electrochemical activity towards oxygen reduction reaction. Second, the investigations regarding the electrochemical stability showed that the platinum-support interaction plays an important role in improving the long...

  3. Role of carbonates in soil organic matter stabilization in agricultural Mediterranean soils

    Science.gov (United States)

    Apesteguía, Marcos; Virto, Iñigo; Plante, Alain

    2016-04-01

    Carbonated soils are present in many semiarid areas, where lithogenic and secondary carbonates are important constituents of the soil mineral matrix. The presence of CaCO3 in calcareous soils has been described as an organic matter stabilization agent mainly due to chemical stabilization mechanisms. In two recent studies in the north of Spain the importance of CaCO3 on soil physical characteristics was highlighted, as they were observed to be acting as macroaggregates stabilization agents. A third study was carried out on the same experimental site, with the hypothesis that the observed differences in aggregation may favor organic matter stabilization in carbonate-containing soils. With that aim we studied the soil physical characteristics (water retention and porosity) and the bioavailability of soil organic matter (SOM) in the two contrasting soils in that site, one Typic Calcixerept (CALC) and one Calcic Haploxerept (DECALC). Bioavailability was evaluated trough the measurement of mineralization rates in a 30 days soil incubations. Intact and disaggregated samples were incubated to evaluate the effect of physical protection on SOM bioavailability in whole soil and macroaggregates 2-5 mm samples. Therefore, four fractions of each soil were studied: intact whole soil organic carbon content was greater in CALC and had smaller mineralization rates during incubation, indicating a smaller organic matter bioavailability for microbial decomposition. However, the greater increment of mineralization observed in DECALC after disaggregation, together with the scarce differences observed in physical characteristics among both soils, indicate that physical protection was not responsible of greater SOM stability in CALC soil. New hypotheses are needed to explain the observed better protection of organic matter in carbonate-rich Mediterranean soils.

  4. Aggregate structure and stability linked to carbon dynamics in a south Chilean Andisol

    Directory of Open Access Journals (Sweden)

    C. Oyarzún

    2005-02-01

    Full Text Available The extreme vulnerability of soil organic carbon to climate and land use change emphasizes the need for further research in different terrestrial ecosystems. We have studied the aggregate stability and carbon dynamics in a chronosequence of three different land uses in a south Chilean Andisols: a second growth Nothofagus obliqua forest (SGFOR, a grassland (GRASS and a Pinus radiata plantation (PINUS. The aim of this study was to investigate the role of Al as soil organic matter stabilizing agent in this Andisol. In a case study, we linked differences in carbon dynamics between the three land use treatments to physical protection and recalcitrance of the soil organic matter (SOM. In this study, C aggregate stability and dynamics were studied using size and density fractionation experiments of the SOM, δ13C and total carbon analysis of the different SOM fractions, and mineralization measurements. The results showed that electrostatic attractions between and among Al-oxides and clay minerals are mainly responsible for the stabilization of soil aggregates and the physical protection of the enclosed soil organic carbon. Whole soil C mineralization rate constants were highest for SGFOR and PINUS, followed by GRASS. In contrast, incubation experiments of isolated macro organic matter fractions showed that the recalcitrance of the SOM decreased in another order: PINUS > SGFOR > GRASS. We concluded that physical protection of soil aggregates was the main process determining whole soil C mineralization. Land use changes affected soil organic carbon dynamics in this south Chilean Andisol by altering soil pH and consequently available Al.

  5. Yttria stabilized zirconia membrane stability in molten fluoride fluxes for low-carbon magnesium production by the SOM process

    Directory of Open Access Journals (Sweden)

    Milshtein J.

    2013-01-01

    Full Text Available The Solid Oxide Membrane (SOM process for magnesium production involves the direct electrolysis of magnesium oxide for energy efficient and low-carbon magnesium production. In the SOM process, magnesium oxide is dissolved in a molten oxy-fluoride flux. An oxygen-ion-conducting SOM tube, made from yttria stabilized zirconia (YSZ, is submerged in the flux. The operating life of the electrolytic cell can be improved by understanding degradation processes in the YSZ, and one way the YSZ degrades is by yttria diffusion out of the YSZ. By adding small amounts of YF3 to the flux, yttria diffusion can be controlled. The diffusion of yttria into the flux was quantified by determining the yttria concentration profile as a function of immersion time in the flux and distance from the flux-YSZ interface. Yttria concentrations were determined using x-ray spectroscopy. The diffusion process was modeled using a numerical approach with an analytic solution to Fick’s second law. These modeling and experimental methods allowed for the determination of the optimum YF3 concentration in the flux to minimize yttria diffusion and improve membrane stability. Furthermore, the effects of common impurities in magnesium ores, such as calcium oxide, silica, and sodium oxide/sodium peroxide, on YSZ stability are being investigated.

  6. Nucleation and stabilization of carbon-rich structures in interstellar media

    CERN Document Server

    Patra, N; Sadeghpour, H R

    2014-01-01

    We study conditions under which carbon clusters of different sizes form and stabilize. {We describe an approach to equilibrium by simulating tenuous carbon gas dynamics to long times.} First, we use reactive molecular dynamics simulations to describe the nucleation of long chains, large clusters, and complex cage structures in carbon and hydrogen rich interstellar gas phases. We study how temperature, particle density, presence of hydrogen, and carbon inflow affect the nucleation of molecular moieties with different characteristics, in accordance with astrophysical conditions. We extend the simulations to densities which are orders of magnitude lower than current laboratory densities, to temperatures relevant to circumstellar environments of planetary nebulae, and to longtime (microsecond) formation timescales. We correlate cluster size distributions from dynamical simulations with thermodynamic equilibrium intuitions, where at low temperatures and gas densities, entropy plays a significant role.

  7. Aqueous solutions of acidic ionic liquids for enhanced stability of polyoxometalate-carbon supercapacitor electrodes

    Science.gov (United States)

    Hu, Chenchen; Zhao, Enbo; Nitta, Naoki; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2016-09-01

    Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s-1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.

  8. Organic Carbon Stabilization of Soils Formed on Acidic and Calcareous Bedrocks in Neotropical Alpine Grassland, Peru

    Science.gov (United States)

    Yang, Songyu; Cammeraat, Erik; Jansen, Boris; Cerli, Chiara; Kalbitz, Karsten

    2016-04-01

    Increasing evidence shows that Neotropical alpine ecosystems are vulnerable to global change. Since soils in the alpine grasslands of the Peruvian Andean region have large soil organic carbon (SOC) stocks, profound understanding of soil organic matter (OM) stabilization mechanisms will improve the prediction of the feedback between SOC stocks and global change. It is well documented that poor-crystalline minerals and organo-metallic complexes significantly contribute to the OM stabilization in volcanic ash soils, including those in the Andean region. However, limited research has focused on non-ash soils that also express significant SOC accumulation. A pilot study of Peruvian Andean grassland soils suggests that lithology is a prominent factor for such carbon accumulation. As a consequence of contrasting mineral composition and pedogenic processes in soils formed on different non-volcanic parent materials, differences in OM stabilization mechanisms may be profound and consequently may respond differently to global change. Therefore, our study aims at a further understanding of carbon stocks and OM stabilization mechanisms in soils formed on contrasting bedrocks in the Peruvian Andes. The main objective is to identify and compare the roles that organo-mineral associations and aggregations play in OM stabilization, by a combination of selective extraction methods and fractionations based on density, particle size and aggregates size. Soil samples were collected from igneous acidic and calcareous sedimentary bedrocks in alpine grassland near Cajamarca, Peru (7.17°S, 78.63°W), at around 3700m altitude. Samples were taken from 3 plots per bedrock type by sampling distinguishable horizons until the C horizons were reached. Outcomes confirmed that both types of soil accumulate large amounts of carbon: 405.3±41.7 t/ha of calcareous bedrock soil and 226.0±5.6 t/ha of acidic bedrock soil respectively. In addition, extremely high carbon contents exceeding 90g carbon per

  9. Powder metallurgical nanostructured medium carbon bainitic steel: Kinetics, structure, and in situ thermal stability studies

    Energy Technology Data Exchange (ETDEWEB)

    Lonardelli, I., E-mail: il244@cam.ac.uk [University of Cambridge, Materials Science and Metallurgy, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); University of Trento, Materials Engineering and Industrial Technologies, via Mesiano 77, 38123 Trento (Italy); Bortolotti, M. [Fondazione Bruno Kessler, via Sommarive 18, 38123 Trento (Italy); Beek, W. van [Swiss-Norwegian Beamlines, ESRF, BP 220, 38043 Grenoble Cedex (France); Girardini, L.; Zadra, M. [K4-Sint, via Dante 300, 38057 Pergine Valsugana (Italy); Bhadeshia, H.K.D.H. [University of Cambridge, Materials Science and Metallurgy, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2012-10-15

    It has been possible to produce incredibly fine plates of bainitic ferrite separated by a percolating network of retained austenite in a medium carbon steel produced by mechanical alloying followed by spark plasma sintering and isothermal heat treatment. This is because the sintering process limits the growth of the austenite grains to such an extent that the martensite-start temperature is suppressed in spite of the medium carbon concentration. Furthermore, the fine austenite grain size accelerates the bainite transformation, which can therefore be suppressed to low temperatures to obtain a nanostructure. Microscopy and in situ synchrotron X-ray diffraction were used to investigate the morphology and the thermal stability of the retained austenite during continuous heating. These latter experiments revealed a gradient of carbon concentration in the retained austenite and a reduced thermal stability in high carbon film-austenite. It was also possible to correlate the evolution of defect density and carbon depletion in both retained austenite and bainitic ferrite during tempering.

  10. Powder metallurgical nanostructured medium carbon bainitic steel: Kinetics, structure, and in situ thermal stability studies

    International Nuclear Information System (INIS)

    It has been possible to produce incredibly fine plates of bainitic ferrite separated by a percolating network of retained austenite in a medium carbon steel produced by mechanical alloying followed by spark plasma sintering and isothermal heat treatment. This is because the sintering process limits the growth of the austenite grains to such an extent that the martensite-start temperature is suppressed in spite of the medium carbon concentration. Furthermore, the fine austenite grain size accelerates the bainite transformation, which can therefore be suppressed to low temperatures to obtain a nanostructure. Microscopy and in situ synchrotron X-ray diffraction were used to investigate the morphology and the thermal stability of the retained austenite during continuous heating. These latter experiments revealed a gradient of carbon concentration in the retained austenite and a reduced thermal stability in high carbon film-austenite. It was also possible to correlate the evolution of defect density and carbon depletion in both retained austenite and bainitic ferrite during tempering.

  11. Expanding Universe

    Science.gov (United States)

    Murdin, P.

    2000-11-01

    A universe that expands with time. Although the possibility had been raised earlier through theoretical work carried out by Willem de Sitter (1872-1934), Aleksandr Friedmann (1888-1925), and the Abbé Georges Lemaître (1894-1966), that our universe is expanding was first demonstrated observationally in 1929 by Edwin P Hubble (1889-1953), through his measurements of the redshifts in the spectra of ...

  12. The oxidative stability of carbon fibre reinforced glass-matrix composites

    Science.gov (United States)

    Prewo, K. M.; Batt, J. A.

    1988-01-01

    The environmental stability of carbon fibre reinforced glass-matrix composites is assessed. Loss of composite strength due to oxidative exposure at elevated temperatures under no load, static load and cyclic fatigue as well as due to thermal cycling are all examined. It is determined that strength loss is gradual and predictable based on the oxidation of carbon fibres. The glass matrix was not found to prevent this degradation but simply to limit it to a gradual process progressing from the composite surfaces inward.

  13. Surface morphology stabilization by chemical sputtering in carbon nitride film growth

    Energy Technology Data Exchange (ETDEWEB)

    Buijnsters, J G [Institute for Molecules and Materials (IMM), Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen (Netherlands); Vazquez, L [Instituto de Ciencia de Materiales de Madrid (CSIC), C/Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)

    2008-01-07

    We have studied the influence of chemical sputtering effects on the morphology of carbon nitride films grown on silicon substrates by electron cyclotron resonance chemical vapour deposition. This study has been performed by comparing the evolution of their morphology with that of hydrogenated amorphous carbon films grown under similar conditions, where these effects are not present. When chemical sputtering effects operate we observe a film surface stabilization for length scales in the 60-750 nm range after a threshold roughness of about 3-4 nm has been developed. This stabilization is explained on the basis of the re-emission of nitrogen etching species, which is confirmed by growth experiments on microstructured substrates. (fast track communication)

  14. Li-ion capacitors with carbon cathode and hard carbon/stabilized lithium metal powder anode electrodes

    Science.gov (United States)

    Cao, W. J.; Zheng, J. P.

    2012-09-01

    A lithium-ion capacitor was developed using a mixture of stabilized lithium metal powder and hard carbon as the anode electrode, while activated carbon was used as the cathode. A specific energy of approximately 82 Wh kg-1 was obtained based on the weight of electrode materials; however, when the electrolyte, separator, and current collectors were included, the specific energy of an assembled Li-ion capacitor was about 25 Wh kg-1. The capacitor was able to deliver over 60% of the maximum energy at a discharge C-rate of 44C. Through continuous galvanostatic charge/discharge cycling, the capacitance of the Li-ion capacitor degraded less than 3% over 600 cycles.

  15. Assessment of Soil Organic Carbon Stability in Agricultural Systems by Using Natural Abundance Signals of Stable Carbon and Nitrogen Isotopes

    International Nuclear Information System (INIS)

    Information on the stability and age of soil organic matter (SOM) pools is of vital importance for assessing the impact of soil management and environmental factors on SOM, an important part of the global carbon (C) cycle. The terrestrial soil organic C pool, up to a depth of 1 m, contains about 1500 Pg C (Batjes, 1996). This is about 2.5 times more organic C than the vegetation (650 Pg C) and about twice as much as in the atmosphere (750 Pg C) (Batjes, 1998), but the assessment of the stability and age of SOM using 14C radio carbon technique are expensive. Conen et al. (2008) developed a model to estimate the SOM stability based on the isotopic discrimination of 15N natural abundance by soil micro-organisms and the change in C/N ratio during organic matter decomposition, for steady state, Alpine and permanent grasslands. In the framework of the IAEA funded coordinated research project (CRP) on Soil Quality and Nutrient Management for Sustainable Food Production in Mulch based Cropping Systems in sub-Saharan Africa, research was initiated to use this model in agricultural systems for developing a cost effective and affordable technique for Member States to determine the stability of SOM. As part of this research, soil samples were taken and analysed in four long term field experiments, established on soils with low and high SOM, in Austria and Belgium. The participating institutions are the Austrian Agency for Health and Food Safety (AGES), the University of Natural Resources and Life Sciences in Vienna (BOKU), the University of Leuven (KUL), the Soil Service of Belgium (BDB) and the Centre Wallon de Recherches Agronomiques (CRA-W)

  16. Improved stability of redox enzyme layers on glassy carbon electrodes via covalent grafting

    Energy Technology Data Exchange (ETDEWEB)

    Pellissier, Marie; Barriere, Frederic [Universite de Rennes 1, CNRS UMR no. 6226, Sciences Chimiques de Rennes, Equipe MaCSE (France); Downard, Alison J. [MacDiarmid Institute for Advanced Materials and Nanotechnology, Department of Chemistry, University of Canterbury, Christchurch (New Zealand); Leech, Donal [School of Chemistry, National University of Ireland, Galway (Ireland)

    2008-06-15

    One of the challenges in the field of enzymatic biofuel cells is to significantly improve their current limited lifetime. In the present work, we report the covalent immobilization of enzyme layers on glassy carbon electrodes, functionalized via electrochemical reduction of in situ generated aryldiazonium salts bearing carboxylic acid groups. We present the performance and the stability over time of the modified electrodes. For glucose oxidase - modified electrodes, stable catalytic activity is observed for a minimum of 6 weeks. (author)

  17. Integrating plant-microbe interactions to understand soil C stabilization with the MIcrobial-MIneral Carbon Stabilization model (MIMICS)

    Science.gov (United States)

    Grandy, Stuart; Wieder, Will; Kallenbach, Cynthia; Tiemann, Lisa

    2014-05-01

    If soil organic matter is predominantly microbial biomass, plant inputs that build biomass should also increase SOM. This seems obvious, but the implications fundamentally change how we think about the relationships between plants, microbes and SOM. Plant residues that build microbial biomass are typically characterized by low C/N ratios and high lignin contents. However, plants with high lignin contents and high C/N ratios are believed to increase SOM, an entrenched idea that still strongly motivates agricultural soil management practices. Here we use a combination of meta-analysis with a new microbial-explicit soil biogeochemistry model to explore the relationships between plant litter chemistry, microbial communities, and SOM stabilization in different soil types. We use the MIcrobial-MIneral Carbon Stabilization (MIMICS) model, newly built upon the Community Land Model (CLM) platform, to enhance our understanding of biology in earth system processes. The turnover of litter and SOM in MIMICS are governed by the activity of r- and k-selected microbial groups and temperature sensitive Michaelis-Menten kinetics. Plant and microbial residues are stabilized short-term by chemical recalcitrance or long-term by physical protection. Fast-turnover litter inputs increase SOM by >10% depending on temperature in clay soils, and it's only in sandy soils devoid of physical protection mechanisms that recalcitrant inputs build SOM. These results challenge centuries of lay knowledge as well as conventional ideas of SOM formation, but are they realistic? To test this, we conducted a meta-analysis of the relationships between the chemistry of plant liter inputs and SOM concentrations. We find globally that the highest SOM concentrations are associated with plant inputs containing low C/N ratios. These results are confirmed by individual tracer studies pointing to greater stabilization of low C/N ratio inputs, particularly in clay soils. Our model and meta-analysis results suggest

  18. Effects of three different biochars on aggregate stability, organic carbon mobility and micronutrient bioavailability.

    Science.gov (United States)

    Hartley, William; Riby, Philip; Waterson, James

    2016-10-01

    Previous studies have demonstrated both beneficial and detrimental effects on soil properties from biochar incorporation. Several biochars, with different feedstock origins, were evaluated for their effectiveness at improving soil quality of a sandy agricultural soil. A pot trial was used to investigate aggregate stability and microbial activity, pore water trace element mobility and micronutrient concentrations in grain of spring wheat after incorporation of three biochars. The feedstocks for biochar production were selected because they were established UK waste products, namely oversize woody material from green waste composting facilities, and rhododendron and soft wood material from forest clearance operations. Biochars were incorporated into the soil at a rate of 5% v/v. Aggregate stability was improved following addition of oversize biochar whilst microbial activity increased in all treatments. Dissolved organic carbon (DOC) concentrations in soil pore water from biochar-treated soils were raised, whilst micronutrient concentrations in wheat grain grown in the treated soils were significantly reduced. It was concluded that incorporation of biochar to temperate agricultural soils requires caution as it may result in reductions of essential grain micronutrients required for human health, whilst the effect on aggregate stability may be linked to organic carbon functional groups on biochar surfaces and labile carbon released from the char into the soil system. PMID:27444723

  19. Improvement of luminescent stability from carbon nanotube field emission display based on printed CNT film

    Institute of Scientific and Technical Information of China (English)

    ZENG; Fanguang; ZHU; Changchun; LIU; Xinghui

    2006-01-01

    Aiming at the influences of poor contact at carbon nanotube (CNT)/electrode interface on luminescence stability in printed CNT film, a new co-sintering process for cathode fabrication was presented to improve the luminescent stability of fully printed CNT-FED. By co-sintering the printed silver and CNT layers, CNTs geometrically matched with Ag surface and/or embedded into Ag layer at the bottom of the co-sintered film, large CNTs block and bulk silver nested each other at the top of the co-sintered film. All these structures increased the contact area at CNT/Ag interface, which could increase the probability of forming ohmic contact at CNT/Ag interface. The luminescent stability of printed CNT-FED with co-sintered cathode could be improved as 5.6 times high as that of common devices.

  20. Nanoscale analysis of the morphology and surface stability of calcium carbonate polymorphs

    Science.gov (United States)

    Sekkal, W.; Zaoui, A.

    2013-04-01

    Under earth surface conditions, in ocean and natural water, calcium carbonate is ubiquitous, forming anhydrous and hydrous minerals. These hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. Atomistic simulation techniques have been employed here to perform a comprehensive and quantitative study of the structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. Results show that the dry forms are prone to ductility; while hydrous phases are found to be brittle. The (001) surface of monohydrocalcite appears to be the most stable (0.99 J/m2) whereas for the ikaite phase, the (001) surface is the most stable. The corresponding value is 0.2 J/m2, i.e. even lower than the surface energy of the Beautiful computed morphology pictures are obtained with Xiao's model and are very similar to the observed SEM images.

  1. Transport and deposition of carbon at catchment scale: stabilization mechanisms approach

    Science.gov (United States)

    Martínez-Mena, María; Almagro, María; Díaz-Pereira, Elvira; García-Franco, Noelia; Boix-Fayos, Carolina

    2016-04-01

    Terrestrial sedimentation buries large amounts of organic carbon (OC) annually, contributing to the terrestrial carbon sink. The temporal significance of this sink will strongly depend on the attributes of the depositional environment, but also on the characteristics of the OC reaching these sites and its stability upon deposition. The fate of the redistributed OC will ultimately depend on the mechanisms of its physical and chemical protection against decomposition, its turnover rates and the conditions under which the OC is stored in sedimentary settings. This framework is more complex in Mediterranean river basins where sediments are often redistributed under a range of environmental conditions in ephemeral, intermittent and perennial fluvial courses, sometimes within the same catchment. The OC stabilization mechanisms and their relations with aggregation at different transport and sedimentary deposits is under those conditions highly uncertain. The main objective of this work was to characterize the stabilization and mineralization of OC in sediments in transit (suspended load), at a range of depositional settings (alluvial bars, reservoir sediments) and soils from the source areas in a sub-catchment (111 km2) at the headwaters of the Segura catchment in South East Spain. In order to obtain a deeper knowledge on the predominant stabilization mechanism corresponding to each erosional phase, the following organic carbon fractionation method was carried out: Four aggregate size classes were distinguished by sieving (large and small macroaggregates, free microaggregates, and free silt plus clay fraction), and the microaggregates occluded within macroaggregates (SMm) were isolated. As a further step, an oxidation of the OC occluded in silt plus clay fraction and that of the free silt plus clay fraction was performed to estimate the oxidant resistant OC pool. Measured OC in these fractions can be related to three functional pools: active (free particulate organic

  2. Field-Scale Partitioning of Ecosystem Respiration Components Suggests Carbon Stabilization in a Bioenergy Grass Ecosystem

    Science.gov (United States)

    Black, C. K.; Miller, J. N.; Masters, M. D.; Bernacchi, C.; DeLucia, E. H.

    2014-12-01

    Annually-harvested agroecosystems have the potential to be net carbon sinks only if their root systems allocate sufficient carbon belowground and if this carbon is then retained as stable soil organic matter. Soil respiration measurements are the most common approach to evaluate the stability of soil carbon at experimental time scales, but valid inferences require the partitioning of soil respiration into root-derived (current-year C) and heterotrophic (older C) components. This partitioning is challenging at the field scale because roots and soil are intricately mixed and physical separation in impossible without disturbing the fluxes to be measured. To partition soil flux and estimate the C sink potential of bioenergy crops, we used the carbon isotope difference between C3 and C4 plant species to quantify respiration from roots of three C4 grasses (maize, Miscanthus, and switchgrass) grown in a site with a mixed cropping history where respiration from the breakdown of old soil carbon has a mixed C3-C4 signature. We used a Keeling plot approach to partition fluxes both at the soil surface using soil chambers and from the whole field using continuous flow sampling of air within and above the canopy. Although soil respiration rates from perennial grasses were higher than those from maize, the isotopic signature of respired carbon indicated that the fraction of soil CO2 flux attributable to current-year vegetation was 1.5 (switchgrass) to 2 (Miscanthus) times greater in perennials than that from maize, indicating that soil CO2 flux came mostly from roots and turnover of soil organic matter was reduced in the perennial crops. This reduction in soil heterotrophic respiration, combined with the much greater quantities of C allocated belowground by perennial grasses compared to maize, suggests that perennial grasses grown as bioenergy crops may be able to provide an additional climate benefit by acting as carbon sinks in addition to reducing fossil fuel consumption.

  3. Stabilization/solidification of an alkyd paint waste by carbonation of waste-lime based formulations.

    Science.gov (United States)

    Arce, R; Galán, B; Coz, A; Andrés, A; Viguri, J R

    2010-05-15

    The application of solvent-based paints by spraying in paint booths is extensively used in a wide range of industrial activities for the surface treatment of a vast array of products. The wastes generated as overspray represent an important environmental and managerial problem mainly due to the hazardous characteristics of the organic solvent, rendering it necessary to appropriately manage this waste. In this paper a solidification/stabilization (S/S) process based on accelerated carbonation was investigated as an immobilization pre-treatment prior to the disposal, via landfill, of an alkyd solvent-based paint waste coming from the automotive industry; the purpose of this S/S process was to immobilize the contaminants and reduce their release into the environment. Different formulations of paint waste with lime, lime-coal fly-ash and lime-Portland cement were carbonated to study the effect of the water/solid ratio and carbonation time on the characteristics of the final product. To assess the efficiency of the studied S/S process, metals, anions and dissolved organic carbon (DOC) were analyzed in the leachates obtained from a battery of compliance and characterization leaching tests. Regarding the carbonation of paint waste-lime formulations, a mathematical expression has been proposed to predict the results of the leachability of DOC from carbonated mixtures working at water/solid ratios from 0.2 to 0.6. However, lower DOC concentrations in leachates (400mg/kg DOC in L/S=10 batch leaching test) were obtained when carbonation of paint waste-lime-fly-ash mixtures was used at 10h carbonation and water to solid ratio of 0.2. The flammability characteristics, the total contents of contaminants and the contaminant release rate in compliance leaching tests provide evidence for a final product suitable for deposition in non-hazardous landfills. The characterization of this carbonated sample using a dynamic column leaching test shows a high stabilization of metals, partial

  4. Expanding subjectivities

    DEFF Research Database (Denmark)

    Lundgaard Andersen, Linda; Soldz, Stephen

    2012-01-01

    A major theme in recent psychoanalytic thinking concerns the use of therapist subjectivity, especially “countertransference,” in understanding patients. This thinking converges with and expands developments in qualitative research regarding the use of researcher subjectivity as a tool to understa...

  5. Co-composting solid biowastes with alkaline materials to enhance carbon stabilization and revegetation potential.

    Science.gov (United States)

    Chowdhury, Saikat; Bolan, Nanthi S; Seshadri, Balaji; Kunhikrishnan, Anitha; Wijesekara, Hasintha; Xu, Yilu; Yang, Jianjun; Kim, Geon-Ha; Sparks, Donald; Rumpel, Cornelia

    2016-04-01

    Co-composting biowastes such as manures and biosolids can be used to stabilize carbon (C) without impacting the quality of these biowastes. This study investigated the effect of co-composting biowastes with alkaline materials on C stabilization and monitored the fertilization and revegetation values of these co-composts. The stabilization of C in biowastes (poultry manure and biosolids) was examined by their composting in the presence of various alkaline amendments (lime, fluidized bed boiler ash, flue gas desulphurization gypsum, and red mud) for 6 months in a controlled environment. The effects of co-composting on the biowastes' properties were assessed for different physical C fractions, microbial biomass C, priming effect, potentially mineralizable nitrogen, bioavailable phosphorus, and revegetation of an urban landfill soil. Co-composting biowastes with alkaline materials increased C stabilization, attributed to interaction with alkaline materials, thereby protecting it from microbial decomposition. The co-composted biowastes also increased the fertility of the landfill soil, thereby enhancing its revegetation potential. Stabilization of biowastes using alkaline materials through co-composting maintains their fertilization value in terms of improving plant growth. The co-composted biowastes also contribute to long-term soil C sequestration and reduction of bioavailability of heavy metals. PMID:26381784

  6. Mechanochemically Activated, Calcium Oxide-Based, Magnesium Oxide-Stabilized Carbon Dioxide Sorbents.

    Science.gov (United States)

    Kurlov, Alexey; Broda, Marcin; Hosseini, Davood; Mitchell, Sharon J; Pérez-Ramírez, Javier; Müller, Christoph R

    2016-09-01

    Carbon dioxide capture and storage (CCS) is a promising approach to reduce anthropogenic CO2 emissions and mitigate climate change. However, the costs associated with the capture of CO2 using the currently available technology, that is, amine scrubbing, are considered prohibitive. In this context, the so-called calcium looping process, which relies on the reversible carbonation of CaO, is an attractive alternative. The main disadvantage of naturally occurring CaO-based CO2 sorbents, such as limestone, is their rapid deactivation caused by thermal sintering. Here, we report a scalable route based on wet mechanochemical activation to prepare MgO-stabilized, CaO-based CO2 sorbents. We optimized the synthesis conditions through a fundamental understanding of the underlying stabilization mechanism, and the quantity of MgO required to stabilize CaO could be reduced to as little as 15 wt %. This allowed the preparation of CO2 sorbents that exceed the CO2 uptake of the reference limestone by 200 %.

  7. Mechanochemically Activated, Calcium Oxide-Based, Magnesium Oxide-Stabilized Carbon Dioxide Sorbents.

    Science.gov (United States)

    Kurlov, Alexey; Broda, Marcin; Hosseini, Davood; Mitchell, Sharon J; Pérez-Ramírez, Javier; Müller, Christoph R

    2016-09-01

    Carbon dioxide capture and storage (CCS) is a promising approach to reduce anthropogenic CO2 emissions and mitigate climate change. However, the costs associated with the capture of CO2 using the currently available technology, that is, amine scrubbing, are considered prohibitive. In this context, the so-called calcium looping process, which relies on the reversible carbonation of CaO, is an attractive alternative. The main disadvantage of naturally occurring CaO-based CO2 sorbents, such as limestone, is their rapid deactivation caused by thermal sintering. Here, we report a scalable route based on wet mechanochemical activation to prepare MgO-stabilized, CaO-based CO2 sorbents. We optimized the synthesis conditions through a fundamental understanding of the underlying stabilization mechanism, and the quantity of MgO required to stabilize CaO could be reduced to as little as 15 wt %. This allowed the preparation of CO2 sorbents that exceed the CO2 uptake of the reference limestone by 200 %. PMID:27529608

  8. Molecular dynamics study of the stability of a carbon nanotube atop a catalytic nanoparticle

    CERN Document Server

    Verkhovtsev, Alexey V; Solov'yov, Andrey V

    2014-01-01

    The stability of a single-walled carbon nanotube placed on top of a catalytic nickel nanoparticle is investigated by means of molecular dynamics simulations. As a case study, we consider the $(12,0)$ nanotube consisting of 720 carbon atoms and the icosahedral Ni$_{309}$ cluster. An explicit set of constant-temperature simulations is performed in order to cover a broad temperature range from 400 to 1200 K, at which a successful growth of carbon nanotubes has been achieved experimentally by means of chemical vapor deposition. The stability of the system depending on parameters of the involved interatomic interactions is analyzed. It is demonstrated that different scenarios of the nanotube dynamics atop the nanoparticle are possible depending on the parameters of the Ni-C potential. When the interaction is weak the nanotube is stable and resembles its highly symmetric structure, while an increase of the interaction energy leads to the abrupt collapse of the nanotube in the initial stage of simulation. In order t...

  9. Expanding Universe

    Science.gov (United States)

    Schrödinger, E.

    2011-02-01

    Preface; Part I. The de Sitter Universe: 1. Synthetic construction; 2. The reduced model: geodesics; 3. The elliptic interpretation; 4. The static frame; 5. The determination of parallaxes; 6. The Lemaître-Robertson frame; Part II. The Theory of Geodesics: 7. On null geodesics; i. Determination of the parameter for null lines in special cases; ii. Frequency shift; 8. Free particles and light rays in general expanding spaces, flat or hyperspherical; i. Flat spaces; ii. Spherical spaces; iii. The red shift for spherical spaces; Part III. Waves in General Riemannian Space-Time: 9. The nature of our approximation; 10. The Hamilton-Jacobi theory in a gravitational field; 11. Procuring approximate solutions of the Hamilton-Jacobi equation from wave theory; Part IV. Waves in an Expanding Universe: 12. General considerations; 13. Proper vibrations and wave parcels; Bibliography.

  10. Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

    Directory of Open Access Journals (Sweden)

    Phei Li Lau

    2013-12-01

    Full Text Available The palladium metal catalysed Heck reaction of 4-iodoanisole with styrene or methyl acrylate has been studied in a continuous plug flow reactor (PFR using supercritical carbon dioxide (scCO2 as the solvent, with THF and methanol as modifiers. The catalyst was 2% palladium on silica and the base was diisopropylethylamine due to its solubility in the reaction solvent. No phosphine co-catalysts were used so the work-up procedure was simplified and the green credentials of the reaction were enhanced. The reactions were studied as a function of temperature, pressure and flow rate and in the case of the reaction with styrene compared against a standard, stirred autoclave reaction. Conversion was determined and, in the case of the reaction with styrene, the isomeric product distribution was monitored by GC. In the case of the reaction with methyl acrylate the reactor was scaled from a 1.0 mm to 3.9 mm internal diameter and the conversion and turnover frequency determined. The results show that the Heck reaction can be effectively performed in scCO2 under continuous flow conditions with a palladium metal, phosphine-free catalyst, but care must be taken when selecting the reaction temperature in order to ensure the appropriate isomer distribution is achieved. Higher reaction temperatures were found to enhance formation of the branched terminal alkene isomer as opposed to the linear trans-isomer.

  11. Low temperature superplasticity and thermal stability of a nanostructured low-carbon microalloyed steel

    Science.gov (United States)

    Hu, J.; Du, L.-X.; Sun, G.-S.; Xie, H.; Misra, R. D. K.

    2015-12-01

    We describe here for the first time the low temperature superplasticity of nanostructured low carbon steel (microalloyed with V, N, Mn, Al, Si, and Ni). Low carbon nanograined/ultrafine-grained (NG/UFG) bulk steel was processed using a combination of cold-rolling and annealing of martensite. The complex microstructure of NG/UFG ferrite and 50-80 nm cementite exhibited high thermal stability at 500 °C with low temperature elongation exceeding 100% (at less than 0.5 of the absolute melting point) as compared to the conventional fine-grained (FG) counterpart. The low temperature superplasticity is adequate to form complex components. Moreover, the low strength during hot processing is favorable for decreasing the spring back and minimize die loss.

  12. Effects of prenatal exposure to nanoparticles titanium dioxide and carbon black on female germline DNA stability

    DEFF Research Database (Denmark)

    Boisen, Anne Mette Zenner

    are needed. Expanded simple tandem repeat (ESTR) loci in mice are sensitive markers of mutagenic effects resulting from environmental exposures; Studies on adult mice have revealed that while particulate air pollution induced ESTR mutations in premeiotic sperm cells, the female germline was not affected...... are actively dividing. The aim of this PhD study was to determine if two widely used nanoparticles titanium dioxide UV-Titan and carbon black Printex 90 induce ESTR mutations in the germ cells of prenatally exposed females. Pregnant generation P mice were exposed to ~42 mg UV-Titan/m3/1 h/d during gestation...... grown to maturity and mated with unexposed males. The ESTR mutation rate in F2 offspring was estimated from full pedigrees (mother, father, offspring). ESTR mutation rates of 0.029/0.0025 (maternal allele) and 0.047/0.053 (paternal allele) in UV-Titan/Printex 90-exposed F2 offspring were...

  13. Fluoride enhances transfection activity of carbonate apatite by increasing cytoplasmic stability of plasmid DNA

    International Nuclear Information System (INIS)

    Highlights: → Cytoplasmic stability of plasmid DNA is enhanced by fluoride incorporation into carbonate apatite carrier. → Fluoridated carbonate apatite promotes a robust increase in transgene expression. → Controlled dissolution of fluoridated carbonate apatite in endosomal acidic environment might buffer the endosomes and prevent degradation of the released DNA. -- Abstract: Intracellular delivery of a functional gene or a nucleic acid sequence to specifically knockdown a harmful gene is a potential approach to precisely treat a critical human disease. The intensive efforts in the last few decades led to the development of a number of viral and non-viral synthetic vectors. However, an ideal delivery tool in terms of the safety and efficacy has yet to be established. Recently, we have developed pH-sensing inorganic nanocrystals of carbonate apatite for efficient and cell-targeted delivery of gene and gene-silencing RNA. Here we show that addition of very low level of fluoride to the particle-forming medium facilitates a robust increase in transgene expression following post-incubation of the particles with HeLa cells. Confocal microscopic observation and Southern blotting prove the cytoplasmic existence of plasmid DNA delivered by likely formed fluoridated carbonate apatite particles while degradation of plasmid DNA presumably by cytoplasmic nucleases was noticed following delivery with apatite particles alone. The beneficial role of fluoride in enhancing carbonate apatite-mediated gene expression might be due to the buffering potential of generated fluoridated apatite in endosomal acidic environment, thereby increasing the half-life of delivered plasmid DNA.

  14. Radial stability and configuration transition of carbon nanotubes regulated by enclosed cores

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Yonggang; He, Haitang; Ye, Hongfei, E-mail: yehf@dlut.edu.cn [State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024 (China)

    2015-05-15

    The radial stability and configuration transition of carbon nanotubes (CNTs) with enclosed cores have been studied in this paper by using atomistic simulations. We found that an abnormal transition of CNTs from open to collapse can be regulated by enclosing deformable and rigid cores. The energy barrier for the configuration transition can be reduced by nearly one order of magnitude due to the presence of these cores, i.e., from ∼0.3 eV/Å to ∼0.03 eV/Å. These findings may provide guidance for the design of controllable CNT-based carrier systems for the delivery of drug, gene and fluid.

  15. Influence of methyl functional groups on the stability of cubane carbon cage

    Science.gov (United States)

    Katin, Konstantin P.; Prudkovskiy, Vladimir S.; Maslov, Mikhail M.

    2016-07-01

    We present a quantum-chemical study to elucidate the structure, energetics and stability of isolated polymethylcubane molecules C8H8-q(CH3)q. The results obtained by means of originally developed nonorthogonal tight-binding approach are in good agreement with the existed experimental data for solid octamethylcubane C8(CH3)8. The isomerization mechanisms for polymethylcubane family are studied in detail and the minimum energy barriers' heights preventing the decomposition are calculated. The temperature dependence of octamethylcubane molecule lifetime to the decomposition moment was determined by direct molecular dynamics simulation. It is shown that methyl groups destabilize the cubic carbon cage, but less than nitro groups.

  16. A carbon nanotube field emission cathode with high current density and long-term stability

    Energy Technology Data Exchange (ETDEWEB)

    Calderon-Colon, Xiomara; Zhou, Otto [Curriculum in Applied Science and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Geng Huaizhi; Gao Bo [Xintek, Incorporated, 7020 Kit Creek Road, Research Triangle Park, NC (United States); An Lei; Cao Guohua [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States)

    2009-08-12

    Carbon nanotube (CNT) field emitters are now being evaluated for a wide range of vacuum electronic applications. However, problems including short lifetime at high current density, instability under high voltage, poor emission uniformity, and pixel-to-pixel inconsistency are still major obstacles for device applications. We developed an electrophoretic process to fabricate composite CNT films with controlled nanotube orientation and surface density, and enhanced adhesion. The cathodes have significantly enhanced macroscopic field emission current density and long-term stability under high operating voltages. The application of this CNT electron source for high-resolution x-ray imaging is demonstrated.

  17. Theoretical studies of "stabilizing" behavior about carbon nanotubes under the electrostatic force.

    Science.gov (United States)

    Zhao, Hong-Wei; Hu, Li-Chun; Chang, Chun-Rui

    2013-04-01

    We study the dispersion and stability of carbon nanotube (CNT) suspensions under the electrostatic interactions. The potential energies of van der Waals (vdW) attractions between the CNT themselves are obtained on the continuum Lennard-Jones (LJ) model. The potential energies of electrostatic repulsions are based upon the Yukawa-segment model. We explore the overall interactions mediated by the vdW force and the electrostatic force between two identical, parallel CNTs. Consequently, we preliminarily confirm the accuracy and reliability of the electrostatic model. PMID:23763212

  18. Aromaticity as stabilizing element in the bidentate activation for the catalytic reduction of carbon dioxide.

    Science.gov (United States)

    Lu, Zhenpin; Hausmann, Heike; Becker, Sabine; Wegner, Hermann A

    2015-04-29

    A new transition-metal-free mode for the catalytic reduction of carbon dioxide via bidentate interaction has been developed. In the presence of Li2[1,2-C6H4(BH3)2], CO2 can be selectively transformed to either methane or methanol, depending on the reducing agent. The bidentate nature of binding is supported by X-ray analysis of an intermediate analogue, which experiences special stabilization due to aromatic character in the bidentate interaction. Kinetic studies revealed a first-order reaction rate. The transformation can be conducted without any solvent. PMID:25871326

  19. Stability, defect and electronic properties of graphane-like carbon-halogen compounds

    Institute of Scientific and Technical Information of China (English)

    Lu Di; Yang Yu-Rong; Xiao Yang; Zhang Xiao-Yu

    2011-01-01

    We perform first-principles total energy calculations to investigate the stabilities and the electronic structures of graphane-like structures of carbon-halogen compounds,where the hydrogen atoms in the graphane are substituted by halogen atoms.Three halogen elements,fluorine (F),chlorine (Cl) and bromine (Br),are considered,and the graphanelike structures are named as CF,CCl and CBr,respectively.It is found that for the single-atom adsorption,only the F adatom can be chemically adsorbed on the graphene.However,the stable graphane-like structures of CF,CCl and CBr can form due to the interaction between the halogen atoms.The carbon atoms in the stable CF,CCl and CBr compounds are in the sp3 hybridization,forming a hexagonal network similar to the graphane.The electronic band calculations show that CF and CCl are semiconductors with band gaps of 3.28 eV and 1.66 eV,respectively,while CBr is a metal.Moreover,the molecular dynamics simulation is employed to clarify the stabilities of CF and CCl.Those two compounds are stable at room temperature.A high temperature (≥ 1200 K) is needed to damage CF,while CCl is destroyed at 700 K.Furthermore,the effects of a vacancy on the structure and the electronic property of CF are discussed.

  20. Modified carbon paste electrode as a tool for the evaluation of oxidative stability of rapeseed oil

    Directory of Open Access Journals (Sweden)

    Simona Žabčíková

    2015-10-01

    Full Text Available Carbon paste electrode was used for evaluation of oxidative stability of rapeseed oil samples using cyclic voltammetry in 0.1 mol.L-1 HCl as a supporting electrolyte. Rapeseed oil samples were exposed to daylight and oxygen in open glass baker at the laboratory condition in order to obtain oils with accelerated primary and secondary products of oxidation. The oxidation status was determinated by peroxide value and p-anisidine value. Total oxidative stability was expressed as TOTOX index. The edible oils were used for preparation (modification of the carbon paste composite material followed by the cyclic voltammetric measurement. Peroxide values significantly increased whereas p-anisinde value rather fluctuated during 40 days of storage in all the samples. Cyclic voltammograms showed anodic current peaks at 575 - 600 mV and cathodic current peaks at 400 - 425 mV. The oxidation and reduction waves diminished at pH ≥3.0 suggesting not only phenolic compounds contributed to the electrochemical characteristic of oil samples. The peroxide value or p-anisidine value did not correlate with oxidation or reduction peak currents at the potential 575 - 600 mV and 400 - 425 mV, respectively. Both cathodic and anodic currents increased with increasing TOTOX index exhibiting positive correlation with high Spearman correlation coefficient (r = 0.894 and r = 0.914 for anodic and cathodic current, respectively. Linear relationship was found for each sample individually. A caution has to be done when interpreting results since the correlation seems to be of oil sample specific. Nevertheless, the modified carbon paste electrode with rapeseed oil represents a suitable and alternative tool for determination of the oxidative state of edible oils without use of organic solvents.

  1. Stability, carbon resistance, and reactivity toward autothermal reforming of nickel on ceria-based supports

    International Nuclear Information System (INIS)

    'Full text:' Solid Oxide Fuel Cell (SOFC) normally requires a reformer unit, where the fuel such as natural gas, methane, methanol, or ethanol can be reformed to hydrogen before introducing to the main part of fuel cell. Nickel on commercial supports such as Al2O3, MgO, ZrO2 has been widely reported to be used as the reforming catalyst commercially. Carbon formation and catalyst deactivation are always the main problems of using this type of catalyst. It is well established that CeO2 and CeO2-ZrO2 have been applied as the catalysts in a wide variety of reactions involving oxidation or partial oxidation of hydrocarbons (e.g. automotive catalysis). In order to quantify the performance of nickel on CeO2 and CeO2-ZrO2 supports for reformer application, the stabilities toward methane steam reforming and the carbon formation resistance were studied. After 18 hours, nickel on CeO2-ZrO2 with the Ce/Zr ratio of 3/1 presented the best performance in term of stability and activity. It also provided excellent resistance toward carbon formation compared to commercial Ni/Al2O3. The autothermal reforming of methane over Ni catalyst on CeO2 and CeO2-ZrO2 supports were also investigated. Ni/Ce-ZrO2 with the Ce/ Zr ratio of 3/1 also showed the best performance. The kinetics of this reaction was also studied. In the temperature range of 750-900C, the reaction order in methane was always closed to 1. The catalyst showed a slight positive effect of hydrogen and a negative effect of steam on the steam reforming rate. The addition of oxygen increased the steam reforming rate. However, the productions of CO and H2 decreased with increasing oxygen partial pressure. (author)

  2. Enhancement of Electrochemical Stability about Silicon/Carbon Composite Anode Materials for Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Wei Xiao

    2015-01-01

    Full Text Available Silicon/carbon (Si/C composite anode materials are successfully synthesized by mechanical ball milling followed by pyrolysis method. The structure and morphology of the composite are characterized by X-ray diffraction and scanning electron microscopy and transmission electron microscope, respectively. The results show that the composite is composed of Si, flake graphite, and phenolic resin-pyrolyzed carbon, and Si and flake graphite are enwrapped by phenolic resin-pyrolyzed carbon, which can provide not only a good buffering matrix but also a conductive network. The Si/C composite also shows good electrochemical stability, in which the composite anode material exhibits a high initial charge capacity of 805.3 mAh g−1 at 100 mA g−1 and it can still deliver a high charge capacity of 791.7 mAh g−1 when the current density increases to 500 mA g−1. The results indicate that it could be used as a promising anode material for lithium ion batteries.

  3. CONSIDERATIONS REGARDING THE INFLUENCE OF METALIC IONS OF THE STABILITY OF CARBONATES FROM SOILS

    Directory of Open Access Journals (Sweden)

    D. Bulgariu

    2005-10-01

    Full Text Available The distribution of minor elements in heterogeneous mineral / aqueous solutions systems represent one of important problem, with many applications in environmental geochemistry field. Ours studies was focus on the metal ions distribution in carbonate (CaCO3 / solution systems, from applicability point of view to the estimation of formation conditions and of carbonates stability from soils. On the base of our results obtained by sequential solid / liquid extraction for 17 soil samples and theoretical modeling of CaCO3 / solution systems, and the results from literature we try to develop the McIntire prognosis models and the free Gibbs enthalpy linear correlation model, by the inclusion in calculus relations of distribution coefficients a higher number of factors which effective influenced the thermodynamics and kinetics of interphase distribution processes of metal ions. The established correlations has been used to the estimation of time evolution of carbonate / solution equilibrium under the influence of some metal ions (Cd, Zn, Cu, Pb, Bi, which appear usual as pollutants in soils. The prognosis realized on the base of the established correlations are in agreement with the theoretical modelling results and studies of case for different types of polluted soils with heavy metals.

  4. Polypropylene/Expanded Graphite/Carbon Fiber Thermal Conductive Composite%聚丙烯/膨胀石墨/碳纤维导热复合材料

    Institute of Scientific and Technical Information of China (English)

    徐睿杰; 雷彩红; 杨志广; 廖敦锃; 刘舜莉

    2012-01-01

    The thermal conductivity, mechanical properties and processing property of polypropylene ( PP)/expanded graphite (EG)/carbon fiber(CF) composite were studied. The results showed that the thermal conductivity of the composite with 20 % content of EC was 2 times that of pure PP,but its melt flow rate was decreased. The PE wax at the weight fraction of 1 % could improve the melt flow rate. When the content of carbon fiber was 5 % , the thermal conductivity reached 0.91 W ? M-1K-1 and was five times of pure PP. The melt flow rate was 1.72 g/10 min and the mechanical properties were good.%研究了聚丙烯(PP)/膨胀石墨(EG)/碳纤维(CF)复合材料的导热、力学以及加工性能.研究发现:当膨胀石墨的质量含量达到20%时,热导率是纯聚丙烯的2倍,但熔体流动性能有所下降;添加1%的聚乙烯蜡可以明显改善体系的熔体流动性能;将膨胀石墨与5%的碳纤维杂化使用,热导率达0.91 W·m-1K-1,是纯聚丙烯的5倍,熔体指数达到1.72 g/10 min,同时该复合材料具有较好的力学性能.

  5. Thermal stability of alkyl carbonate mixed-solvent electrolytes for lithium ion cells

    Science.gov (United States)

    Kawamura, Tetsuya; Kimura, Arihisa; Egashira, Minato; Okada, Shigeto; Yamaki, Jun-Ichi

    The thermal stability of some mixed-solvent electrolytes used in lithium cells was measured by differential scanning calorimetry (DSC) using airtight containers. The electrolytes used were ethylene carbonate ( EC)+ diethyl carbonate ( DEC) , EC+ dimethyl carbonate ( DMC) , propylene carbonate (PC)+DEC, and PC+DMC in which was dissolved 1 M LiPF 6 or 1 M LiClO 4. The influence of water addition and lithium metal addition on the thermal behavior of these electrolytes was also investigated. The exothermic peak of LiPF 6 electrolytes containing DEC was found at 255 °C, and the peak temperature of the electrolytes containing DEC was 15-20 °C lower than that of LiPF 6 electrolytes containing DMC. This effect was also observed in the electrolytes including LiClO 4. DMC was found to be more reactive than DEC. The thermal behavior of various kinds of LiPF 6 electrolytes with lithium metal was measured by DSC. The exothermic reaction of 1 M LiPF 6/EC+DEC, 1 M LiPF 6/EC+DMC, and 1 M LiPF 6/PC+DMC with lithium metal began at the melting point of lithium metal because of the break down of the solid electrolyte interface (SEI). The temperature was approximately 180 °C, whereas the self-heating of 1 M LiPF 6/PC+DEC occurred before the melting point of lithium metal. The temperature at which the self-exothermal reaction began was 140 °C. Therefore, the lithium metal in this electrolyte was found to be thermally unstable. When water was added to the above electrolytes with lithium metal, the exothermic reaction began at less than 130 °C, probably due to a collapse of SEI in response to the HF that was a product of the reaction between LiPF 6 and the added water.

  6. Dynamics of Soil Organic Carbon and Aggregate Stability with Grazing Exclusion in the Inner Mongolian Grasslands.

    Directory of Open Access Journals (Sweden)

    Ding Wen

    Full Text Available Grazing exclusion (GE has been deemed as an important approach to enhance the soil carbon storage of semiarid grasslands in China; however, it remains unclear how different organic carbon (OC components in soils vary with the duration of GE. Here, we observed the changing trends of different OC components in soils with increased GE duration in five grassland succession series plots, ranging from free grazing to 31-year GE. Specifically, we measured microbial biomass carbon (MBC, easily oxidizable OC (EOC, water-soluble OC (WSOC, and OC in water stable aggregates (macroaggregates [250-2000 μm], microaggregates [53-250 μm], and mineral fraction [< 53 μm] at 0-20 cm soil depths. The results showed that GE significantly enhanced EOC and WSOC contents in soils, but caused a decline of MBC at the three decade scale. Macroaggregate content (F = 425.8, P < 0.001, OC stored in macroaggregates (F = 84.1, P < 0.001, and the mean weight diameter (MWD of soil aggregates (F = 371.3, P < 0.001 increased linearly with increasing GE duration. These findings indicate that OC stored in soil increases under three-decade GE with soil organic matter (SOM stability improving to some extent. Long-term GE practices enhance the formation of soil aggregates through higher SOM input and an exclusion of animal trampling. Therefore, the practice of GE may be further encouraged to realize the soil carbon sequestration potential of semi-arid grasslands, China.

  7. Dynamics of Soil Organic Carbon and Aggregate Stability with Grazing Exclusion in the Inner Mongolian Grasslands.

    Science.gov (United States)

    Wen, Ding; He, Nianpeng; Zhang, Jinjing

    2016-01-01

    Grazing exclusion (GE) has been deemed as an important approach to enhance the soil carbon storage of semiarid grasslands in China; however, it remains unclear how different organic carbon (OC) components in soils vary with the duration of GE. Here, we observed the changing trends of different OC components in soils with increased GE duration in five grassland succession series plots, ranging from free grazing to 31-year GE. Specifically, we measured microbial biomass carbon (MBC), easily oxidizable OC (EOC), water-soluble OC (WSOC), and OC in water stable aggregates (macroaggregates [250-2000 μm], microaggregates [53-250 μm], and mineral fraction [< 53 μm]) at 0-20 cm soil depths. The results showed that GE significantly enhanced EOC and WSOC contents in soils, but caused a decline of MBC at the three decade scale. Macroaggregate content (F = 425.8, P < 0.001), OC stored in macroaggregates (F = 84.1, P < 0.001), and the mean weight diameter (MWD) of soil aggregates (F = 371.3, P < 0.001) increased linearly with increasing GE duration. These findings indicate that OC stored in soil increases under three-decade GE with soil organic matter (SOM) stability improving to some extent. Long-term GE practices enhance the formation of soil aggregates through higher SOM input and an exclusion of animal trampling. Therefore, the practice of GE may be further encouraged to realize the soil carbon sequestration potential of semi-arid grasslands, China. PMID:26751370

  8. Spherical nano-SnSb/MCMB/carbon core–shell composite for high stability lithium ion battery anodes

    International Nuclear Information System (INIS)

    A novel multi-step design of spherical nano-SnSb/MCMB/carbon core–shell composite for high stability and long life lithium battery electrodes has been introduced. The core–shell composite was successfully synthesized via co-precipitation and subsequent pyrolysis. The resultant composite sphere consisted of nanosized SnSb alloy and mesophase carbon microbeads (MCMB, 10 μm) embedded in a carbon matrix pyrolyzed from glucose and petroleum pitch, in which the MCMB was treated to be the inner core to offer mechanical support and efficient electron conducting pathway. The composite material exhibited a unique stability with a retention discharge capacity rate of 83.52% with reversible capacity of 422.5 mAh g−1 after 100 cycles and a high initial coulombic efficiency of 83.53%. The enhanced electrochemical performance is attributed to the structural stability of the composite sphere during the charging–discharging process

  9. Relative stability of soil carbon revealed by shifts in δ15N and C:N ratio

    Directory of Open Access Journals (Sweden)

    C. Alewell

    2008-02-01

    Full Text Available Life on earth drives a continuous exchange of carbon between soils and the atmosphere. Some forms of soil carbon, or organic matter, are more stable and have a longer residence time in soil than others. Relative differences in stability have often been derived from shifts in δ13C (which is bound to a vegetation change from C3 to C4 type or through 14C-dating (which is bound to small sample numbers because of high measurement costs. Here, we propose a new concept based on the increase in δ15N and the decrease in C:N ratio with increasing stability. We tested the concept on grasslands at different elevations in the Swiss Alps. Depending on elevation and soil depth, it predicted mineral-associated organic carbon to be 3 to 73 times more stable than particulate organic carbon. Analysis of 14C-ages generally endorsed these predictions.

  10. Relative stability of soil carbon revealed by shifts in δ15N and C:N ratio

    Directory of Open Access Journals (Sweden)

    C. Alewell

    2007-08-01

    Full Text Available Life on earth drives a continuous exchange of carbon between soils and the atmosphere. Some forms of soil carbon, or organic matter, are more stable and have a longer residence time in soil than others. Relative differences in stability have often been derived from shifts in δ13C (which is bound to a vegetation change from C3 to C4 type or through 14C-dating (which is bound to small sample numbers because of high measurement costs. Here, we propose a new concept based on the increase in δ15N and the decrease in C:N ratio with increasing stability. We tested the concept on grasslands at different elevations in the Swiss Alps. Depending on elevation and soil depth, it predicted mineral-associated organic carbon to be 3 to 73 times more stable than particulate organic carbon. Analysis of 14C-ages generally endorsed these predictions.

  11. Low density polycarbonate-graphene nanocomposite foams produced by supercritical carbon dioxide two-step foaming. Thermal stability

    OpenAIRE

    Gedler, Gabriel; Antunes, Marcelo de Sousa Pais; Velasco Perero, José Ignacio

    2016-01-01

    The thermal stability of low density polycarbonate-graphene nanocomposite foams prepared by supercritical carbon dioxide two-step foaming was investigated. Unfilled polycarbonate foams showed improved thermal stabilities when compared to the unfoamed polycarbonate, as the cellular structure of foams effectively slowed down the heat transfer process. Comparatively, polycarbonate foams with larger cells exhibited the highest delays in the early stage of thermal decomposition. Low density polyca...

  12. Grazing incidence beam expander

    Energy Technology Data Exchange (ETDEWEB)

    Akkapeddi, P.R.; Glenn, P.; Fuschetto, A.; Appert, Q.; Viswanathan, V.K.

    1985-01-01

    A Grazing Incidence Beam Expander (GIBE) telescope is being designed and fabricated to be used as an equivalent end mirror in a long laser resonator cavity. The design requirements for this GIBE flow down from a generic Free Electron Laser (FEL) resonator. The nature of the FEL gain volume (a thin, pencil-like, on-axis region) dictates that the output beam be very small. Such a thin beam with the high power levels characteristic of FELs would have to travel perhaps hundreds of meters or more before expanding enough to allow reflection from cooled mirrors. A GIBE, on the other hand, would allow placing these optics closer to the gain region and thus reduces the cavity lengths substantially. Results are presented relating to optical and mechanical design, alignment sensitivity analysis, radius of curvature analysis, laser cavity stability analysis of a linear stable concentric laser cavity with a GIBE. Fabrication details of the GIBE are also given.

  13. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties

    Science.gov (United States)

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-05-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ~4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (~60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications.Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability

  14. Plant stimulation of soil microbial community succession: how sequential expression mediates soil carbon stabilization and turnover

    Energy Technology Data Exchange (ETDEWEB)

    Firestone, Mary [Univ. of California, Berkeley, CA (United States)

    2015-03-31

    It is now understood that most plant C is utilized or transformed by soil microorganisms en route to stabilization. Hence the composition of microbial communities that mediate decomposition and transformation of root C is critical, as are the metabolic capabilities of these communities. The change in composition and function of the C-transforming microbial communities over time in effect defines the biological component of soil C stabilization. Our research was designed to test 2 general hypotheses; the first two hypotheses are discussed first; H1: Root-exudate interactions with soil microbial populations results in the expression of enzymatic capacities for macromolecular, complex carbon decomposition; and H2: Microbial communities surrounding roots undergo taxonomic succession linked to functional gene activities as roots grow, mature, and decompose in soil. Over the term of the project we made significant progress in 1) quantifying the temporal pattern of root interactions with the soil decomposing community and 2) characterizing the role of root exudates in mediating these interactions.

  15. Surfactant-assisted dispersion of carbon nanotubes: mechanism of stabilization and biocompatibility of the surfactant

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Raman Preet, E-mail: ramanpreetsingh@hotmail.com [Evalueserve SEZ (Gurgaon) Pvt. Ltd. (India); Jain, Sanyog [National Institute of Pharmaceutical Education and Research, Centre for Pharmaceutical Nanotechnology, Department of Pharmaceutics (India); Ramarao, Poduri, E-mail: ramaraop@yahoo.com [Central University of Punjab, School of Basic and Applied Sciences (India)

    2013-10-15

    Nanoparticles (NPs) are thermodynamically unstable system and tend to aggregate to reduce free energy. The aggregation property of NPs results in inhomogeneous exposure of cells to NPs resulting in variable cellular responses. Several types of surfactants are used to stabilize NP dispersions and obtain homogenous dispersions. However, the effects of these surfactants, per se, on cellular responses are not completely known. The present study investigated the application of Pluronic F68 (PF68) for obtaining stable dispersion of NPs using carbon nanotubes as model NPs. PF68-stabilized NP suspensions are stable for long durations and do not show signs of aggregation or settling during storage or after autoclaving. The polyethylene oxide blocks in PF68 provide steric hindrance between adjacent NPs leading to stable NP dispersions. Further, PF68 is biocompatible in nature and does not affect integrity of mitochondria, lysosomes, DNA, and nuclei. Also, PF68 neither induce free radical or cytokine production nor does it interfere with cellular uptake mechanisms. The results of the present study suggest that PF68-assisted dispersion of NPs produced suspensions, which are stable after autoclaving. Further, PF68 does not interfere with normal physiological functions suggesting its application in nanomedicine and nanotoxicity evaluation.

  16. Effect of graphitic order on field emission stability of carbon nanotubes

    International Nuclear Information System (INIS)

    We observed current density (J) dependent degradation in field emission current from multiwalled carbon nanotubes (MWCNTs). These degradations are recoverable and can be explained by emission current-induced dislocations along the MWCNTs. MWCNTs grown by thermal chemical vapour deposition (CVD) can emit stable current continuously for at least 1200 min with upper current density limits of ∼0.5 mA cm-2. In contrast, this upper limit is-2 for nanotubes grown by plasma-enhanced CVD (PECVD), although higher J is possible with relatively shorter stability duration. High-resolution transmission electron microscopy and Raman spectroscopy indicate higher graphitic order of the thermal CVD grown MWCNTs as compared to PECVD grown MWCNTs. Our study suggests that graphitic order affects their upper performance limits of long-term emission stability, although the effects from adsorbates cannot be completely ignored. These results indicate that field emission cannot be considered as an ideal quantum tunnelling process. The effect of electron transport along CNTs before electron tunnelling must be considered

  17. Aqueous stabilization of carbon nanotubes: effects of surface oxidization and solution chemistry.

    Science.gov (United States)

    Bai, Yingchen; Wu, Fengchang; Lin, Daohui; Xing, Baoshan

    2014-03-01

    Surface oxygen functional groups can affect the morphological characteristics, aggregation kinetics, and adsorption capacity of multi-walled carbon nanotubes (MWCNTs). However, little is known about the quantitative relationship between oxygen content and the dispersion stability of MWCNTs. To investigate the effects of surface oxidization, MWCNTs were oxidized using concentrated H2SO4/HNO3 acids for 0, 1, 2, 4, and 8 h, respectively. Experimental results showed that the oxygen content of MWCNTs increased with surface oxidization time. Linear correlations were found to exist between the oxygen content, critical coagulation concentration (CCC) for NaCl, and critical coagulation pH values of MWCNTs detected by optical density at 800 nm. The CCC values for CaCl2 increased with oxygen contents for unmodified MWCNTs and lowly oxidized MWCNTs, while which decreased after further increasing the surface oxidization. CCC ratios in the presence of Ca(2+) to Na(+) were consistent with the empirical Schulze-Hardy rule for unmodified MWCNTs and lowly oxidized MWCNTs; however, which were much lower than the expected values for highly oxidized MWCNTs. Fulvic acid can clearly increase the stability of MWCNT suspension with unmodified MWCNTs and lowly oxidized MWCNTs, while it cannot affect the dispersion of highly oxidized MWCNTs. This study implied that the oxidation and presence of fulvic acid will possibly increase the mobility, exposure, bioavailability, and toxicity of MWCNTs. PMID:24323322

  18. Surfactant-assisted dispersion of carbon nanotubes: mechanism of stabilization and biocompatibility of the surfactant

    International Nuclear Information System (INIS)

    Nanoparticles (NPs) are thermodynamically unstable system and tend to aggregate to reduce free energy. The aggregation property of NPs results in inhomogeneous exposure of cells to NPs resulting in variable cellular responses. Several types of surfactants are used to stabilize NP dispersions and obtain homogenous dispersions. However, the effects of these surfactants, per se, on cellular responses are not completely known. The present study investigated the application of Pluronic F68 (PF68) for obtaining stable dispersion of NPs using carbon nanotubes as model NPs. PF68-stabilized NP suspensions are stable for long durations and do not show signs of aggregation or settling during storage or after autoclaving. The polyethylene oxide blocks in PF68 provide steric hindrance between adjacent NPs leading to stable NP dispersions. Further, PF68 is biocompatible in nature and does not affect integrity of mitochondria, lysosomes, DNA, and nuclei. Also, PF68 neither induce free radical or cytokine production nor does it interfere with cellular uptake mechanisms. The results of the present study suggest that PF68-assisted dispersion of NPs produced suspensions, which are stable after autoclaving. Further, PF68 does not interfere with normal physiological functions suggesting its application in nanomedicine and nanotoxicity evaluation

  19. Longitudinal vibration and stability analysis of carbon nanotubes conveying viscous fluid

    Science.gov (United States)

    Oveissi, Soheil; Toghraie, Davood; Eftekhari, Seyyed Ali

    2016-09-01

    Nowadays, carbon nanotubes (CNT) play an important role in practical applications in fluidic devices. To this end, researchers have studied various aspects of vibration analysis of a behavior of CNT conveying fluid. In this paper, based on nonlocal elasticity theory, single-walled carbon nanotube (SWCNT) is simulated. To investigate and analyze the effect of internal fluid flow on the longitudinal vibration and stability of SWCNT, the equation of motion for longitudinal vibration is obtained by using Navier-Stokes equations. In the governing equation of motion, the interaction of fluid-structure, dynamic and fluid flow velocity along the axial coordinate of the nanotube and the nano-scale effect of the structure are considered. To solve the nonlocal longitudinal vibration equation, the approximate Galerkin method is employed and appropriate simply supported boundary conditions are applied. The results show that the axial vibrations of the nanotubesstrongly depend on the small-size effect. In addition, the fluid flowing in nanotube causes a decrease in the natural frequency of the system. It is obvious that the system natural frequencies reach zero at lower critical flow velocities as the wave number increases. Moreover, the critical flow velocity decreases as the nonlocal parameter increases.

  20. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  1. Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

    NARCIS (Netherlands)

    Haasterecht, van T.; Ludding, C.C.I.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 ¿, autogenous pressure, batch reactor). The initial surface-specific activities

  2. Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

    NARCIS (Netherlands)

    van Haasterecht, T.; Ludding, C.C.I.; de Jong, K.P.; Bitter, J.H.

    2013-01-01

    Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 ◦C, autogenous pressure, batch reactor). The initial surface-specific activities

  3. High temperature stability of onion-like carbon vs highly oriented pyrolytic graphite.

    Directory of Open Access Journals (Sweden)

    Alessandro Latini

    Full Text Available The thermodynamic stability of onion-like carbon (OLC nanostructures with respect to highly oriented pyrolytic graphite (HOPG was determined in the interval 765-1030 K by the electromotive force (emf measurements of solid electrolyte galvanic cell: (Low Pt|Cr3C2,CrF2,OLC|CaF2s.c.|Cr3C2,CrF2,HOPG|Pt (High. The free energy change of transformation HOPG = OLC was found positive below 920.6 K crossing the zero value at this temperature. Its trend with temperature was well described by a 3rd degree polynomial. The unexpected too high values of [Formula: see text] jointly to the HR-TEM, STEM and EELS evidences that showed OLC completely embedded in rigid cages made of a Cr3C2/CrF2 matrix, suggested that carbon in the electrodes experienced different internal pressures. This was confirmed by the evaluation under constant volume of [dP/dT by the α/κ ratio for OLC (0.5 MPa K(-1 and HOPG (8 Pa K(-1 where α and κ are the isobaric thermal expansion and isothermal compressibility coefficients, respectively. The temperature dependency of the pressure was derived and utilized to calculate the enthalpy and entropy changes as function of temperature and pressure. The highest value of the internal pressure experienced by OLC was calculated to be about 7 GPa at the highest temperature. At 920.6 K, ΔrH and ΔrS values are 95.8 kJ mol(-1 and 104.1 JK(-1 mol(-1, respectively. The surface contributions to the energetic of the system were evaluated and they were found negligible compared with the bulk terms. As a consequence of the high internal pressure, the values of the enthalpy and entropy changes were mainly attributed to the formation of carbon defects in OLC considered as multishell fullerenes. The change of the carbon defect fraction is reported as a function of temperature.

  4. Effects of a carbon implant on thermal stability of Ni0.95(Pt0.05)Si

    International Nuclear Information System (INIS)

    The effects of a carbon implant on thermal stability of Ni0.95(Pt0.05)Si films are investigated by implanting carbon of different doses into Si substrates before silicidation with two steps of rapid thermal annealing. Compared with the Ni0.95(Pt0.05)Si films without carbon implanting, the thermal stability of Ni0.95(Pt0.05)Si films with two carbon implant doses are improved 100 °C (1 × 1015 cm−2) and 150 °C (3 × 1015 cm−2), respectively. Through sheet resistance measurement, X-ray diffraction and scanning electron microscopy, we conclude that carbon atoms precipitated at Ni(Pt0.05)Si grain boundaries and Ni0.95(Pt0.05)Si/Si interface account for the improved thermal stability of Ni0.95(Pt0.05)Si films. Furthermore, the presence of C in Ni0.95(Pt0.05)Si films changes the preferred orientation of polycrystalline NiSi which will benefit the practical application of this material. (paper)

  5. Stability of retained austenite in high carbon steel under compressive stress: an investigation from macro to nano scale

    Science.gov (United States)

    Hossain, R.; Pahlevani, F.; Quadir, M. Z.; Sahajwalla, V.

    2016-10-01

    Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels’ performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.

  6. Increase of uncertainty in transient climate response to cumulative carbon emissions after stabilization of atmospheric CO2 concentration

    International Nuclear Information System (INIS)

    We analyzed a dataset from an experiment of an earth system model of intermediate complexity, focusing on the change in transient climate response to cumulative carbon emissions (TCRE) after atmospheric CO2 concentration was stabilized in the Representative Concentration Pathway (RCP) 4.5. We estimated the TCRE in 2005 at 0.3–2.4 K/TtC for an unconstrained case and 1.1–1.7 K/TtC when constrained with historical and present-day observational data, the latter result being consistent with other studies. The range of TCRE increased when the increase of CO2 concentration was moderated and then stabilized. This is because the larger (smaller) TCRE members yield even greater (less) TCRE. An additional experiment to assess the equilibrium state revealed significant changes in temperature and cumulative carbon emissions after 2300. We also found that variation of land carbon uptake is significant to the total allowable carbon emissions and subsequent change of the TCRE. Additionally, in our experiment, we revealed that equilibrium climate sensitivity (ECS), one of the 12 parameters perturbed in the ensemble experiment, has a strong positive relationship with the TCRE at the beginning of the stabilization and its subsequent change. We confirmed that for participant models in the Coupled Model Intercomparison Project Phase 5, ECS has a strong positive relationship with TCRE. For models using similar experimental settings, there is a positive relationship with TCRE for the start of the period of stabilization in CO2 concentration, and rate of change after stabilization. The results of this study are influential regarding the total allowable carbon emissions calculated from the TCRE and the temperature increase set as the mitigation target. (letter)

  7. Enhanced cycle stability of micro-sized Si/C anode material with low carbon content fabricated via spray drying and in situ carbonization

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dingsheng; Gao, Mingxia, E-mail: gaomx@zju.edu.cn; Pan, Hongge; Liu, Yongfeng; Wang, Junhua; Li, Shouquan; Ge, Hongwei

    2014-08-01

    Highlights: • Micro-sized Si/C composites were fabricated via. spray drying and carbonization. • Multi-morphology carbon was formed in the Si/C composites. • Si/C composite with 5.6 wt.% C provides significant improved cycling stability. • Multi-morphology carbon plays effective role in improving the electrochemical property. • The method provides potential for mass production of superior Si-based anode materials. - Abstract: Micro-sized Si/C composites with in situ introduced carbon of multi-morphology were fabricated via spray drying a suspension of commercial micro-sized Si and citric acid followed by a carbonization. Different ratios of Si to citric acid were used to optimize the composition and structure of the composites and thus the electrochemical performance. Carbon flakes including crooked and flat ones were well dispersed in between the Si particles, forming Si/C composites. Floc-like carbon layers and carbon fragments were also found to cover partially the Si particles. The Si/C composite with a low carbon content of 5.6 wt.% provides an initial reversible capacity of 2700 mA h/g and a capacity of 1860 mA h/g after 60 cycles at a current density of 100 mA/g as anode material for lithium-ion batteries (LIBs), which are much higher than those of pristine Si and the Si/C composites with higher carbon content. The mechanism of the enhancement of electrochemical performance of the micro-sized Si/C composite is discussed. The fabrication method and the structure design of the composites offer valuable potential in developing adaptable Si-based anode materials for industrial applications.

  8. Metal organic frameworks/macroporous carbon composites with enhanced stability properties and good electrocatalytic ability for ascorbic acid and hemoglobin.

    Science.gov (United States)

    Zhang, Yufan; Nsabimana, Anaclet; Zhu, Liande; Bo, Xiangjie; Han, Ce; Li, Mian; Guo, Liping

    2014-11-01

    The thermal, water and electrochemical stability of Cu-based metal organic frameworks (Cu-MOFs) confined in macroporous carbon (MPC) hybrids has been investigated. Thermogravimetric analyses, X-Ray diffraction, scanning electron microscopy, and cyclic voltammetry were employed to confirm the stability of pure Cu-MOFs, MPC, and Cu-MOFs-MPC. As compared to pure Cu-MOFs, the porous composite materials of MPC and Cu-MOFs interact and seem to form new materials having homogenous structure and chemistry, which show structural stability in aqueous media and electrochemical stability in phosphate buffer solution (PBS pH 7.4). The detection of ascorbic acid and hemoglobin is performed as an electrochemical probe, indicating Cu-MOFs-MPC holds great promise for the design of electrochemical sensors.

  9. Economic Stability to Papua New Guinea by Contribution in Reducing Carbon Emissions through Support of DC

    Directory of Open Access Journals (Sweden)

    Eshan Ahuja,

    2014-07-01

    Full Text Available Papua New Guinea is said to be PNG which is one of the most adversely affected small country by the impacts of climate change. Climate Change is one of the biggest challenges facing by them today, its devastation is widespread and intense. This issue has been discussed to evolve a method to support the nation in achieving the goal of emission reduction. The affects include those on Agriculture, Fisheries, Forestry and Tourism which have major contribution towards GDP of the PNG. PNG has a very low economic growth rate according to several economic and social indicators, the performance of the PNG economy since independence has been disappointing. Thus, there is need of taking special attention & responsibilities by giving cooperation by the nations. This is to be done by especially developed ones so as to support the small island nations in adaptation to the impacts of climate change through financial support. Through this act, the Least Developed Countries will achieve economic stability as well as imparting in reduction of carbon emissions. This paper discusses to find a path and sort out the issue. The paper also discusses various negotiating points so as to achieve the said goal mutually and amicably.

  10. Performance and Stability of Supercapacitor Modules based on Porous Carbon Electrodes in Hybrid Powertrain

    Institute of Scientific and Technical Information of China (English)

    GONG Xuan; XIE Changjun; ZOU Yaohui; QUAN Shuhai; PIOTR Bujlo; SHEN Di

    2014-01-01

    Hybrid power sources have attracted much attention in the electric vehicle area. Particularly, electric-electric hybrid powertrain system consisting of supercapacitor modules and lithium-ion batteries has been widely applied because of the high power density of supercapacitors. In this study, we design a hybrid powertrain system containing two porous carbon electrode-based supercapacitor modules in parallel and one lithium ion battery pack. With the construction of the testing station, the performance and stability of the used supercapacitor modules are investigated in correlation with the structure of the supercapacitor and the nature of the electrode materials applied. It has been shown that the responding time for voltage vibration from 20 V to 48.5 V during charging or discharging process decreases from about 490 s to 94 s with the increase in applied current from 20 A to 100 A. The capacitance of the capacitor modules is nearly independent on the applied current. With the designed setup, the energy efficiency can reach as high as 0.99. The results described here provide a guidance for material selection of supercapacitors and optimized controlling strategy for hybrid power system applied in electric vehicles.

  11. Biochar affects carbon composition and stability in soil: a combined spectroscopy-microscopy study

    Science.gov (United States)

    Hernandez-Soriano, Maria C.; Kerré, Bart; Kopittke, Peter M.; Horemans, Benjamin; Smolders, Erik

    2016-04-01

    The use of biochar can contribute to carbon (C) storage in soil. Upon addition of biochar, there is a spatial reorganization of C within soil particles, but the mechanisms remain unclear. Here, we used Fourier transformed infrared-microscopy and confocal laser scanning microscopy to examine this reorganization. A silty-loam soil was amended with three different organic residues and with the biochar produced from these residues and incubated for 237 d. Soil respiration was lower in biochar-amended soils than in residue-amended soils. Fluorescence analysis of the dissolved organic matter revealed that biochar application increased a humic-like fluorescent component, likely associated with biochar-C in solution. The combined spectroscopy-microscopy approach revealed the accumulation of aromatic-C in discrete spots in the solid-phase of microaggregates and its co-localization with clay minerals for soil amended with raw residue or biochar.The co-localization of aromatic-C:polysaccharides-C was consistently reduced upon biochar application. We conclude that reduced C metabolism is an important mechanism for C stabilization in biochar-amended soils.

  12. Activity and stability of immobilized carbonic anhydrase for promoting CO2 absorption into a carbonate solution for post-combustion CO2 capture

    Science.gov (United States)

    Zhang, S.; Zhang, Z.; Lu, Y.; Rostam-Abadi, M.; Jones, A.

    2011-01-01

    An Integrated Vacuum Carbonate Absorption Process (IVCAP) currently under development could significantly reduce the energy consumed when capturing CO2 from the flue gases of coal-fired power plants. The biocatalyst carbonic anhydrase (CA) has been found to effectively promote the absorption of CO2 into the potassium carbonate solution that would be used in the IVCAP. Two CA enzymes were immobilized onto three selected support materials having different pore structures. The thermal stability of the immobilized CA enzymes was significantly greater than their free counterparts. For example, the immobilized enzymes retained at least 60% of their initial activities after 90days at 50??C compared to about 30% for their free counterparts under the same conditions. The immobilized CA also had significantly improved resistance to concentrations of sulfate (0.4M), nitrate (0.05M) and chloride (0.3M) typically found in flue gas scrubbing liquids than their free counterparts. ?? 2011 Elsevier Ltd.

  13. Dynamic Relationship Between Biologically Active Soil Organic Carbon and Aggregate Stability in Long-Term Organically Fertilized Soils

    Institute of Scientific and Technical Information of China (English)

    LI Cheng-Liang; XU Jiang-Bing; HE Yuan-Qiu; LIU Yan-Li; FAN Jian-Bo

    2012-01-01

    Biologically active soil organic carbon (BASOC) is an important fraction of soil organic carbon (SOC),but our understanding of the correlation between BASOC and soil aggregate stability is limited.At an ecological experimental station (28° 04′-28° 37′ N,116°41′-117° 09′ E) in Yujiang County,Jiangxi Province,China,we analyzed the dynamic relationship between soil aggregate stability and BASOC content over time in the red soil (Udic Ferrosols) fertilized with a nitrogen-phosphorus-potassium chemical fertilizer (NPK)without manure or with NPK plus livestock manure or green manure.The dynamics of BASOC was evaluated using CO2 efflux,and soil aggregates were separated according to size using a wet-sieving technique.The soils fertilized with NPK plus livestock manure had a significantly higher content of BASOC and an improved aggregate stability compared to the soils fertilized with NPK plus green manure or NPK alone The BASOC contents in all fertilized soils decreased over time The contents of large aggregates (800-2000μm) dramatically decreased over the first 7 d of incubation,but the contents of small aggregates (< 800.μm) either remained the same or increased,depending on the incubation time and specific aggregate sizes.The aggregate stability did not differ significantly at the beginning and end of incubation,but the lowest stability inall fertilized soils occurred in the middle of the incubation,which implied that the soils had a strong resilience for aggregate stability.The change in BASOC content was only correlated with aggregate stability during the first 27 d of incubation.

  14. Stabilizing of the Transitory Species (TiO2)2 by Encapsulation Into Carbon Nanotubes.

    Science.gov (United States)

    Dargouthi, Sarra; Boughdiri, Salima; Tangour, Bahoueddine

    2015-01-01

    The aim of this paper is studying the encapsulation effect of carbon nanotubes (CNTs ) on the stabilizing process of titanium dioxide molecule dimers (TiO2)2. First, a theoretical study was performed concerning the guest species that are various titanium dioxide dimers. Five structures were treated as following: i) Cis (C) or ii)Trans (T) relatively to a square shaped fragment Ti2O2, iii) a mixed Tetrahedral/Pyramidal (T/P) disposition while two titanium atoms are sharing three oxygen atoms, and finally not bonded dimers in iv) parallel (P) and v) orthogonal (O) positions respectively. Only the (T), (C) and (T/P) isomers may be considered as stable compounds. The structure of the T-dimer is more stable than the Cis one by only 6.5 kcal mol-1. Typically, intra and extracyclic Ti-O bond lengths are 1.84Å and 1.61Å respectively. (T/P) dimer can be described as a metastable structure since its energy is higher than (T) one by 19 kcal mol-1. NBO analysis highlights the participation of dative bonding between oxygen lone pair and vacant titanium 3d orbitals. (P) and (O) structures represent transitory species that transform into the more stable structure which is the T-dimer. The second and principal part of this work concerns the re-optimization of the studied structures placed inside the CNT (12,0). Only (T), (C) and (P) dimers are stabilized by encapsulation through the establishment of strong interactions with the CNT wall. The (T / P) and (O) isomers which are converted into (T) and (P) dimers respectively, are leaving the nanotube while they still interacting with its edge. These favorable results are indicating in one hand the possibly detection of (T) and (C) isomers, and in another hand that the process of polymerization of the TiO2 molecule which is leading to nanostructured materials could be controlled by encapsulation within the CNTs. PMID:26085429

  15. Soil Organic Matter Stability and Soil Carbon Storage with Changes in Land Use Intensity in Uganda

    Science.gov (United States)

    Tiemann, L. K.; Grandy, S.; Hartter, J.

    2014-12-01

    As the foundation of soil fertility, soil organic matter (SOM) formation and break-down is a critical factor of agroecosystem sustainability. In tropical systems where soils are quickly weathered, the link between SOM and soil fertility is particularly strong; however, the mechanisms controlling the stabilization and destabilization of SOM are not well characterized in tropical soils. In western Uganda, we collected soil samples under different levels of land use intensity including maize fields, banana plantations and inside an un-cultivated native tropical forest, Kibale National Park (KNP). To better understand the link between land use intensity and SOM stability we measured total soil C and N, and respiration rates during a 369 d soil incubation. In addition, we separated soils into particle size fractions, and mineral adsorbed SOM in the silt (2-50 μm ) and clay (chemically characterized via pyrolysis-GC/MS. Cultivated soil C and N have declined by 22 and 48%, respectively, in comparison to uncultivated KNP soils. Incubation data indicate that over the last decade, relatively accessible and labile soil organic carbon (SOC) pools have been depleted by 55-59% in cultivated soils. As a result of this depletion, the chemical composition of SOM has been altered such that clay and silt associated SOM differed significantly between agricultural fields and KNP. In particular, nitrogen containing compounds were in lower abundance in agricultural compared to KNP soils. This suggests that N depletion due to agriculture has advanced to pools of mineral associated organic N that are typically protected from break-down. In areas where land use intensity is relatively greater, increases in polysaccharides and lipids in maize fields compared to KNP indicate increases in microbial residues and decomposition by-products as microbes mine SOM for organic N. Chemical characterization of post-incubation SOM will help us better understand how microbes preferentially break-down SOM

  16. Noncovalent functionalization of carbon nanotubes and graphene with tetraphenylporphyrins: Stability and optical properties from ab-initio calculations

    OpenAIRE

    Orellana, Walter; Correa, J. D.

    2015-01-01

    The stability, electronic and optical properties of single-walled carbon nanotubes (CNTs) and graphene noncovalently functionalized with free-base tetraphenylporphyrin (TPP) molecules is addressed by density functional theory calculations, including corrections to dispersive interactions. We study the TPP physisorption on 42 CNT species, particularly those with chiral indices ($n$,$m$), where $5 \\leq n \\leq 12$ and $0\\leq m\\leq n$. Our results show a quite strong $\\pi$-$\\pi$ interaction betwe...

  17. Population Evolution of Oxide Inclusions in Ti-stabilized Ultra-low Carbon Steels after Deoxidation

    Institute of Scientific and Technical Information of China (English)

    Wen YANG; Ying ZHANG; Li-feng ZHANG; Hao-jian DUAN; Li WANG

    2015-01-01

    Population density function (PDF),which can eliminate the arbitrariness caused by the choice of the num-ber and the size of bins compared to the well-used histograms,was introduced to analyze the amount of inclusions. The population evolution of oxide inclusions in forms of PDF in Ti-stabilized ultra-low carbon steels after deoxidation during industrial RH refining and continuous casting processes was analyzed using an automated SEM-EDS system. It was found that after deoxidation till the early stage of casting,the alumina inclusions exhibited a lognormal PDF distribution,and three factors including the existence of a large amount of alumina clusters,the generation of alumi-na from the reduction of Al-Ti-O inclusions and the reoxidation of molten steel were estimated as the reasons.The shape parameterσwas high after deoxidation and then decreased after Ti treatment,indicating that in a short period after deoxidation,the size of alumina inclusions was widely distributed.After Ti treatment,the distribution of inclu-sion size was more concentrated.The scale parameter m decreased with time during the whole refining process,indi-cating that the proportion of large inclusions decreased during refining.Contrarily,the Al-Ti-O inclusions presented a fractal PDF distribution except at the end of casting with fractal dimension D of 4.3,and the constant of propor-tionality C decreased with time during RH refining and increased during casting process.The reoxidation of steel by slag entrapped from ladle was considered as the reason for the lognormal PDF behavior of Al-Ti-O inclusions at the end of casting.

  18. Electrochemical behaviour of ceramic yttria stabilized zirconia on carbon steel synthesized via sol-gel process

    International Nuclear Information System (INIS)

    Chromate conversion coatings have been widely applied for the corrosion of different metallic substrates. However, the waste containing Cr6+ has many limitations due to the environmental consideration and health hazards. An interesting alternative seems to be the deposition on metallic surface of thin layers of yttria or zirconia or both by the sol-gel process. In this study, Ytttria and Yttria stabilized zirconia (YSZ, 8% Y2O3) thin films were used for coating commercial carbon steel substrates by sol-gel method and the dip-coating process. The evolution of organic compounds up to crystallization process as a function of heat treatments was study by FT-IR spectroscopy. The structure and morphology of the coatings were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The anticorrosion performance of the coatings has been evaluated by using electrochemical techniques in an aggressive media (3.5 wt.% NaCl). The corrosion behaviour of sol-gel method was compared with traditional chromate conversion coatings. Differences in the electrochemical behaviour of YSZ coatings are related to the development of microcracks during the sintering process and to the presence of organic compounds during growth film. Electrochemical results showed that sol-gel YSZ and Y2O3 coatings can act as protective barriers against wet corrosion; however yttria films displayed low adhesion to substrate. The corrosion parameters provide an explanation of the role of each film and show a considerable increase in the corrosion resistance for coated samples in comparison to the bare steel samples.

  19. Electrochemical behaviour of ceramic yttria stabilized zirconia on carbon steel synthesized via sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Crespo, M.A. Dominguez, E-mail: mdominguezc@ipn.m [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Murillo, A. Garcia; Torres-Huerta, A.M. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Yanez-Zamora, C. [Estudiante del postgrado en Tecnologia Avanzada del CICATA-IPN, Unidad Altamira, km 14.5, Carr. Tampico-Puerto Industrial. C.P. 89600, Altamira, Tamaulipas (Mexico); Carrillo-Romo, F. de J [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico)

    2009-08-26

    Chromate conversion coatings have been widely applied for the corrosion of different metallic substrates. However, the waste containing Cr{sup 6+} has many limitations due to the environmental consideration and health hazards. An interesting alternative seems to be the deposition on metallic surface of thin layers of yttria or zirconia or both by the sol-gel process. In this study, Ytttria and Yttria stabilized zirconia (YSZ, 8% Y{sub 2}O{sub 3}) thin films were used for coating commercial carbon steel substrates by sol-gel method and the dip-coating process. The evolution of organic compounds up to crystallization process as a function of heat treatments was study by FT-IR spectroscopy. The structure and morphology of the coatings were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The anticorrosion performance of the coatings has been evaluated by using electrochemical techniques in an aggressive media (3.5 wt.% NaCl). The corrosion behaviour of sol-gel method was compared with traditional chromate conversion coatings. Differences in the electrochemical behaviour of YSZ coatings are related to the development of microcracks during the sintering process and to the presence of organic compounds during growth film. Electrochemical results showed that sol-gel YSZ and Y{sub 2}O{sub 3} coatings can act as protective barriers against wet corrosion; however yttria films displayed low adhesion to substrate. The corrosion parameters provide an explanation of the role of each film and show a considerable increase in the corrosion resistance for coated samples in comparison to the bare steel samples.

  20. Effect of carbon nanospheres on shape stabilization and thermal behavior of phase change materials for thermal energy storage

    International Nuclear Information System (INIS)

    Highlights: • Introducing novel form-stable PCM of stearic acid (SA)/carbon nanospheres (CNSs). • The highest stabilized SA content is 83 wt% in the SA/CNS composites. • Increasing thermal conductivity of composite phase change material with high amount of latent heat. - Abstract: Stearic acid (SA) is one of the main phase change materials (PCMs) for medium temperature thermal energy storage systems. In order to stabilize the shape and enhance the thermal conductivity of SA, the effects of adding carbon nanospheres (CNSs) as a carbon nanofiller were examined experimentally. The maximum mass fraction of SA retained in CNSs was found as 80 wt% without the leakage of SA in a melted state, even when it was heated over the melting point of SA. The dropping point test shows that there was clearly no liquid leakage through the phase change process at the operating temperature range of the composite PCMs. The thermal stability and thermal properties of composite PCMs were investigated with a thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC), respectively. The thermal conductivity of the SA/CNS composite was determined by the laser flash method. The thermal conductivity at 35 °C increased about 105% for the highest loading of CNS (50 wt%). The thermal cycling test proved that form-stable composite PCMs had good thermal reliability and chemical durability after 1000 cycles of melting and freezing, which is advantageous for latent heat thermal energy storage (LHTES)

  1. Octahedral core–shell cuprous oxide/carbon with enhanced electrochemical activity and stability as anode for lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Jiayuan, E-mail: xjyzju@aliyun.com [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Chen, Zhewei [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Hangzhou No. 2 High School, Hangzhou 310053 (China); Wang, Jianming [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China)

    2015-10-15

    Highlights: • Core–shell octahedral Cu{sub 2}O/C is prepared by a one-step method. • Carbon shell is amorphous and uniformly decorated at the Cu{sub 2}O octahedral core. • Core–shell Cu{sub 2}O/C exhibits markedly enhanced capability and reversibility. • Carbon shell provides fast ion/electron transfer channel. • Core–shell structure is stable during cycling. - Abstract: Core–shell Cu{sub 2}O/C octahedrons are synthesized by a simple hydrothermal method with the help of carbonization of glucose, which reduces Cu(II) to Cu(I) at low temperature and further forms carbon shell coating at high temperature. SEM and TEM images indicate that the carbon shell is amorphous with thickness of ∼20 nm wrapping the Cu{sub 2}O octahedral core perfectly. As anode of lithium ion batteries, the core–shell Cu{sub 2}O/C composite exhibits high and stable columbic efficiency (98%) as well as a reversible capacity of 400 mAh g{sup −1} after 80 cycles. The improved electrochemical performance is attributed to the novel core–shell structure, in which the carbon shell reduces the electrode polarization and promotes the charge transfer at active material/electrolyte interface, and also acts as a stabilizer to keep the octahedral structure integrity during discharge–charge processes.

  2. Oxygen vacancy induced carbon deposition at the triple phase boundary of the nickel/yttrium-stabilized zirconia (YSZ) interface

    Science.gov (United States)

    Zhang, Yanxing; Fu, Zhaoming; Wang, Mingyang; Yang, Zongxian

    2014-09-01

    The carbon deposition at the Triple Phase Boundary (TPB) of the Nickel/Yttrium-Stabilized Zirconia (YSZ) interface is studied using the first-principles method based on density functional theory, with consideration of the interface oxygen vacancy. It is found that the CH fragment (the most stable dissociation products of CH4 on Ni catalyst) can easily diffuse and be trapped at the O vacancy. The trapped CH can dissociate to C and H with a much lower dissociation barrier (0.74 eV) as compared with that (1.39 eV) on the pure Ni (111) surface. Therefore, we propose that the carbon deposition may form easily at the interface oxygen vacancy of TPB as compared with that on the pure Ni (111) surface, which offers new understanding on the carbon deposition of the Ni/YSZ anode of solid oxide fuel cell.

  3. Experimental investigation of the stability of Fe-rich carbonates in the lower mantle

    Science.gov (United States)

    Boulard, E.; Menguy, N.; Auzende, A.; Benzerara, K.; Bureau, H.; Antonangeli, D.; Corgne, A.; Morard, G.; Siebert, J.; Perrillat, J.; Guyot, F. J.; Fiquet, G.

    2011-12-01

    Carbonates are the main C-bearing minerals that are transported deep in the Earth's mantle via subduction of the oceanic lithosphere [1]. The fate of carbonates at mantle conditions plays a key role in the deep carbon cycle. Decarbonation, melting or reduction of carbonates will affect the extent and the way carbon is recycled into the deep Earth. To clarify the fate of carbonates in the deep mantle, high-pressure high-temperature experiments were carried out up to 105 GPa and 2850 K on oxide assemblages of (Mg,Fe)O + CO2. The presence of Fe(II) in starting materials induces redox reactions from which Fe(II) is oxidized and a part of the carbon is reduced. This leads to an assemblage of magnetite, diamonds, and carbonates or, pressure depending, their newly discovered Fe(III)-bearing high-pressure polymorphs based on a silicate-like chemistry with tetrahedrally coordinated carbon [2]. Our results show the possibility for carbon to be recycled in the lowermost mantle and provide evidence of a possible coexistence of reduced and oxidized carbon at lower mantle conditions. [1] Sleep, N. H., and K. Zahnle (2001) J. Geophys. Res.-Planets 106(E1), 1373-1399. [2] Boulard et al. (2011) PNAS, 108, 5184-5187.

  4. DFT study of Fe-Ni core-shell nanoparticles: Stability, catalytic activity, and interaction with carbon atom for single-walled carbon nanotube growth

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhimin; Wang, Qiang, E-mail: wangqiang@njtech.edu.cn; Shan, Xiaoye; Zhu, Hongjun, E-mail: zhuhj@njtech.edu.cn [Department of Applied Chemistry, College of Science, Nanjing Tech University, Nanjing 211816 (China); Li, Wei-qi [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Chen, Guang-hui [Department of Chemistry, Shantou University, Shantou, Guangdong 515063 (China)

    2015-02-21

    Metal catalysts play an important role in the nucleation and growth of single-walled carbon nanotubes (SWCNTs). It is essential for probing the nucleation and growth mechanism of SWCNTs to fundamentally understand the properties of the metal catalysts and their interaction with carbon species. In this study, we systematically studied the stability of 13- and 55-atom Fe and Fe-Ni core-shell particles as well as these particles interaction with the carbon atoms using the density functional theory calculations. Icosahedral 13- and 55-atom Fe-Ni core-shell bimetallic particles have higher stability than the corresponding monometallic Fe and Ni particles. Opposite charge transfer (or distribution) in these particles leads to the Fe surface-shell displays a positive charge, while the Ni surface-shell exhibits a negative charge. The opposite charge transfer would induce different chemical activities. Compared with the monometallic Fe and Ni particles, the core-shell bimetallic particles have weaker interaction with C atoms. More importantly, C atoms only prefer staying on the surface of the bimetallic particles. In contrast, C atoms prefer locating into the subsurface of the monometallic particles, which is more likely to form stable metal carbides. The difference of the mono- and bimetallic particles on this issue may result in different nucleation and growth mechanism of SWCNTs. Our findings provide useful insights for the design of bimetallic catalysts and a better understanding nucleation and growth mechanism of SWCNTs.

  5. Comparing measured and modelled soil carbon: which site-specific variables are linked to high stability?

    Science.gov (United States)

    Robertson, Andy; Schipanski, Meagan; Ma, Liwang; Ahuja, Lajpat; McNamara, Niall; Smith, Pete; Davies, Christian

    2016-04-01

    Changes in soil carbon (C) stocks have been studied in depth over the last two decades, as net greenhouse gas (GHG) sinks are highlighted to be a partial solution to the causes of climate change. However, the stability of this soil C is often overlooked when measuring these changes. Ultimately a net sequestration in soils is far less beneficial if labile C is replacing more stable forms. To date there is no accepted framework for measuring soil C stability, and as a result there is considerable uncertainty associated with the simulated impacts of land management and land use change when using process-based systems models. However, a recent effort to equate measurable soil C fractions to model pools has generated data that help to assess the impacts of land management, and can ultimately help to reduce the uncertainty of model predictions. Our research compiles this existing fractionation data along with site metadata to create a simplistic statistical model able to quantify the relative importance of different site-specific conditions. Data was mined from 23 published studies and combined with original data to generate a dataset of 100+ land use change sites across Europe. For sites to be included they required soil C fractions isolated using the Zimmermann et al. (2007) method and specific site metadata (mean annual precipitation, MAP; mean annual temperature, MAT; soil pH; land use; altitude). Of the sites, 75% were used to develop a generalized linear mixed model (GLMM) to create coefficients where site parameters can be used to predict influence on the measured soil fraction C stocks. The remaining 25% of sites were used to evaluate uncertainty and validate this empirical model. Further, four of the aforementioned sites were used to simulate soil C dynamics using the RothC, DayCent and RZWQM2 models. A sensitivity analysis (4096 model runs for each variable applying Latin hypercube random sampling techniques) was then used to observe whether these models place

  6. Application of δ13C and δ15N isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms

    OpenAIRE

    Kayler, Z.E.; Kaiser, M; Gessler, A.; Ellerbrock, R. H.; M. Sommer

    2011-01-01

    Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. Analysis of δ13C and δ15N isotopic signatures of stabilized OM fractions along with soil mineral characteristics may yield important information about OM-mineral associations and their processing history. We anlayzed the δ13C and δ15N isotopic signatures from two organic matter (OM) fractio...

  7. Enhancement of Electrochemical Stability about Silicon/Carbon Composite Anode Materials for Lithium Ion Batteries

    OpenAIRE

    Wei Xiao; Chang Miao; Xuemin Yan; Qing Sun; Ping Mei

    2015-01-01

    Silicon/carbon (Si/C) composite anode materials are successfully synthesized by mechanical ball milling followed by pyrolysis method. The structure and morphology of the composite are characterized by X-ray diffraction and scanning electron microscopy and transmission electron microscope, respectively. The results show that the composite is composed of Si, flake graphite, and phenolic resin-pyrolyzed carbon, and Si and flake graphite are enwrapped by phenolic resin-pyrolyzed carbon, which can...

  8. Soil redistribution and weathering controlling the fate of geochemical and physical carbon stabilization mechanisms in soils of an eroding landscape

    Directory of Open Access Journals (Sweden)

    S. Doetterl

    2014-11-01

    Full Text Available It has been suggested that eroding landscapes can form C sinks or sources, but the underlying mechanisms are not fully understood. Our analysis aims to clarify the effects of soil redistribution on physical and biogeochemical soil organic carbon (SOC stabilization mechanisms along a hillslope transect. The observed mineralogical differences seem partly responsible for the effectiveness of geochemical and physical SOC stabilization mechanisms as the mineral environment along the transect is highly variable and dynamic. The abundance of primary and secondary minerals and the weathering status of the investigated soils differ drastically along this transect. Extractable iron and aluminum components are largely abundant in aggregates, but show no strong correlation to SOC, indicating their importance for aggregate stability but not for SOC retention. We further show that pyrophosphate extractable soil components, especially manganese, play a role in stabilizing SOC within non-aggregated mineral fractions. The abundance of microbial residues and measured 14C ages for aggregated and non-aggregated SOC fractions demonstrate the importance of the combined effect of geochemical and physical protection to stabilize SOC after burial at the depositional site. Mineral alteration and the breakdown of aggregates limit the protection of C by minerals and within aggregates temporally. The 14C ages of buried soil indicate that C in aggregated fractions seem to be preserved more efficiently while C in non-aggregated fractions is released, allowing a re-sequestration of younger C with this fraction. Old 14C ages and at the same time high contents of microbial residues in aggregates suggest that microorganisms either feed on old carbon to build up microbial biomass, or that these environments consisting of considerable amounts of old C are proper habitats for microorganisms and preserve their residues. Due to continuous soil weathering and, hence, weakening of

  9. Interactive control of minerals, wildfire, and erosion on soil carbon stabilization in conifer ecosystems of the western U.S.

    Science.gov (United States)

    Rasmussen, C.

    2014-12-01

    Answering the question of what controls the fate and stabilization of organic carbon in forest soils is central to understanding the role of western US ecosystems in mitigating climate change, optimizing forest management, and quantifying local and regional terrestrial carbon budgets. Over half of forest soil C is stored belowground, stabilized by a number of separate, but interacting physical, chemical and biological mechanisms. Here we synthesize data from a series of field and laboratory studies focused on identifying mineral, physical, and landscape position controls on belowground C stabilization mechanisms in western U.S. conifer ecosystems. Results from these studies demonstrate an important for role for short-range-order Fe- and Al-oxyhydroxides and Al-humus complexes in C stabilization, and that the soil mineral assemblage moderates C cycling via control on partitioning of C into physical fractions ("free", "occluded", "mineral") with varying MRT and chemistry. Measures of occluded fraction chemical composition by 13C-NMR indicate this fraction is 2-5 times more enriched in pyrogenic C than the bulk soil and that this fraction is on the order of ~25 to 65% charred materials. Radiocarbon analyses of a large set of conifer soil samples from California and Arizona further indicate the occluded fraction is generally older than either the free light or mineral fraction. In particular, soil C in convergent, water and sediment gathering portions of the landscape are enriched in long MRT charred materials. These results indicate an important role for the interaction of soil mineral assemblage, wildfire, and erosion in controlling belowground C storage and stabilization in western conifer forests. Drought and wildfire are expected to increase with climate change and thus may exert significant control on belowground C storage directly through biochemical and physical changes in aboveground biomass, production of charred materials, and indirectly via post

  10. Thermodynamic Stability of LiFeO2 in Molten Carbonate Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    LiFeO2, as one of candidate cathode materials or additive for molten carbonate fuel cell, has been found to be thermodynamically unstable in CO2 atmosphere at 650℃ (the condition of molten carbonate fuel cell) both by computation and experimental confirmation.

  11. Chemical Characterization of Stabilized and Carbonized Polyacrylonitrile (PAN Fibers Treated with Oleic Acid.

    Directory of Open Access Journals (Sweden)

    Salleh Shahrul Nizam Md

    2014-07-01

    Full Text Available Polyacrylonitrile (PAN fiber is the best precursor for carbon fibers due to high carbon content after heat treatment. After the polymer was spun into fibers, the fibers will undergo pretreatment process with chemical solution known as post spinning treatment. Post spinning will directly affect conversion of PAN fiber to carbon fiber. Oleic acid was used as post spinning treatment chemical solution to PAN fibers. The pretreated PAN fiber will be heated at 250°C and 800°C. The fibers were studied using Fourier Transform Infra-Red (FTIR, X-ray Photoelectron Spectroscopy (XPS and DSC to study the chemical change during heat treatment. PAN fibers treated with oleic acid have reduced the cyclization energy and increase oxygen and carbon content leading to high performance carbon fibers.

  12. Interannual stability of organic to inorganic carbon production on a coral atoll

    Science.gov (United States)

    Kwiatkowski, Lester; Albright, Rebecca; Hosfelt, Jessica; Nebuchina, Yana; Ninokawa, Aaron; Rivlin, Tanya; Sesboüé, Marine; Wolfe, Kennedy; Caldeira, Ken

    2016-04-01

    Ocean acidification has the potential to adversely affect marine calcifying organisms, with substantial ocean ecosystem impacts projected over the 21st century. Characterizing the in situ sensitivity of calcifying ecosystems to natural variability in carbonate chemistry may improve our understanding of the long-term impacts of ocean acidification. We explore the potential for intensive temporal sampling to isolate the influence of carbonate chemistry on community calcification rates of a coral reef and compare the ratio of organic to inorganic carbon production to previous studies at the same location. Even with intensive temporal sampling, community calcification displays only a weak dependence on carbonate chemistry variability. However, across three years of sampling, the ratio of organic to inorganic carbon production is highly consistent. Although further work is required to quantify the spatial variability associated with such ratios, this suggests that these measurements have the potential to indicate the response of coral reefs to ongoing disturbance, ocean acidification, and climate change.

  13. Restoring forest structure and process stabilizes forest carbon in wildfire-prone southwestern ponderosa pine forests.

    Science.gov (United States)

    Hurteau, Matthew D; Liang, Shuang; Martin, Katherine L; North, Malcolm P; Koch, George W; Hungate, Bruce A

    2016-03-01

    Changing climate and a legacy of fire-exclusion have increased the probability of high-severity wildfire, leading to an increased risk of forest carbon loss in ponderosa pine forests in the southwestern USA. Efforts to reduce high-severity fire risk through forest thinning and prescribed burning require both the removal and emission of carbon from these forests, and any potential carbon benefits from treatment may depend on the occurrence of wildfire. We sought to determine how forest treatments alter the effects of stochastic wildfire events on the forest carbon balance. We modeled three treatments (control, thin-only, and thin and burn) with and without the occurrence of wildfire. We evaluated how two different probabilities of wildfire occurrence, 1% and 2% per year, might alter the carbon balance of treatments. In the absence of wildfire, we found that thinning and burning treatments initially reduced total ecosystem carbon (TEC) and increased net ecosystem carbon balance (NECB). In the presence of wildfire, the thin and burn treatment TEC surpassed that of the control in year 40 at 2%/yr wildfire probability, and in year 51 at 1%/yr wildfire probability. NECB in the presence of wildfire showed a similar response to the no-wildfire scenarios: both thin-only and thin and burn treatments increased the C sink. Treatments increased TEC by reducing both mean wildfire severity and its variability. While the carbon balance of treatments may differ in more productive forest types, the carbon balance benefits from restoring forest structure and fire in southwestern ponderosa pine forests are clear.

  14. Restoring forest structure and process stabilizes forest carbon in wildfire-prone southwestern ponderosa pine forests.

    Science.gov (United States)

    Hurteau, Matthew D; Liang, Shuang; Martin, Katherine L; North, Malcolm P; Koch, George W; Hungate, Bruce A

    2016-03-01

    Changing climate and a legacy of fire-exclusion have increased the probability of high-severity wildfire, leading to an increased risk of forest carbon loss in ponderosa pine forests in the southwestern USA. Efforts to reduce high-severity fire risk through forest thinning and prescribed burning require both the removal and emission of carbon from these forests, and any potential carbon benefits from treatment may depend on the occurrence of wildfire. We sought to determine how forest treatments alter the effects of stochastic wildfire events on the forest carbon balance. We modeled three treatments (control, thin-only, and thin and burn) with and without the occurrence of wildfire. We evaluated how two different probabilities of wildfire occurrence, 1% and 2% per year, might alter the carbon balance of treatments. In the absence of wildfire, we found that thinning and burning treatments initially reduced total ecosystem carbon (TEC) and increased net ecosystem carbon balance (NECB). In the presence of wildfire, the thin and burn treatment TEC surpassed that of the control in year 40 at 2%/yr wildfire probability, and in year 51 at 1%/yr wildfire probability. NECB in the presence of wildfire showed a similar response to the no-wildfire scenarios: both thin-only and thin and burn treatments increased the C sink. Treatments increased TEC by reducing both mean wildfire severity and its variability. While the carbon balance of treatments may differ in more productive forest types, the carbon balance benefits from restoring forest structure and fire in southwestern ponderosa pine forests are clear. PMID:27209781

  15. Size and Promoter Effects on Stability of Carbon-Nanofiber-Supported Iron-Based Fischer–Tropsch Catalysts

    Science.gov (United States)

    2016-01-01

    The Fischer–Tropsch Synthesis converts synthesis gas from alternative carbon resources, including natural gas, coal, and biomass, to hydrocarbons used as fuels or chemicals. In particular, iron-based catalysts at elevated temperatures favor the selective production of C2–C4 olefins, which are important building blocks for the chemical industry. Bulk iron catalysts (with promoters) were conventionally used, but these deactivate due to either phase transformation or carbon deposition resulting in disintegration of the catalyst particles. For supported iron catalysts, iron particle growth may result in loss of catalytic activity over time. In this work, the effects of promoters and particle size on the stability of supported iron nanoparticles (initial sizes of 3–9 nm) were investigated at industrially relevant conditions (340 °C, 20 bar, H2/CO = 1). Upon addition of sodium and sulfur promoters to iron nanoparticles supported on carbon nanofibers, initial catalytic activities were high, but substantial deactivation was observed over a period of 100 h. In situ Mössbauer spectroscopy revealed that after 20 h time-on-stream, promoted catalysts attained 100% carbidization, whereas for unpromoted catalysts, this was around 25%. In situ carbon deposition studies were carried out using a tapered element oscillating microbalance (TEOM). No carbon laydown was detected for the unpromoted catalysts, whereas for promoted catalysts, carbon deposition occurred mainly over the first 4 h and thus did not play a pivotal role in deactivation over 100 h. Instead, the loss of catalytic activity coincided with the increase in Fe particle size to 20–50 nm, thereby supporting the proposal that the loss of active Fe surface area was the main cause of deactivation. PMID:27330847

  16. Structural stability of hydrogenated amorphous carbon overcoats used in heat-assisted magnetic recording investigated by rapid thermal annealing

    KAUST Repository

    Wang, N.

    2013-01-01

    Ultrathin amorphous carbon (a-C) films are extensively used as protective overcoats of magnetic recording media. Increasing demands for even higher storage densities have necessitated the development of new storage technologies, such as heat-assisted magnetic recording (HAMR), which uses laser-assisted heating to record data on high-stability media that can store single bits in extremely small areas (∼1 Tbit/in.2). Because HAMR relies on locally changing the coercivity of the magnetic medium by raising the temperature above the Curie temperature for data to be stored by the magnetic write field, it raises a concern about the structural stability of the ultrathin a-C film. In this study, rapid thermal annealing (RTA) experiments were performed to examine the thermal stability of ultrathin hydrogenated amorphous carbon (a-C:H) films deposited by plasma-enhanced chemical vapor deposition. Structural changes in the a-C:H films caused by RTA were investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, x-ray reflectivity, and conductive atomic force microscopy. The results show that the films exhibit thermal stability up to a maximum temperature in the range of 400-450 °C. Heating above this critical temperature leads to hydrogen depletion and sp 2 clustering. The critical temperature determined by the results of this study represents an upper bound of the temperature rise due to laser heating in HAMR hard-disk drives and the Curie temperature of magnetic materials used in HAMR hard disks. © 2013 American Institute of Physics.

  17. Treatment of coke-oven wastewater with the powdered activated carbon-contact stabilization activated sludge process. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Suidan, M.T.; Deady, M.A.; Gee, C.S.

    1983-11-01

    The objective of the study was to determine optimum parameters for the operation of an innovative process train used in the treatment of coke-over wastewater. The treatment process train consisted of a contact-stabilization activated sludge system with powdered activated carbon (PAC) addition, followed by activated sludge nitrification, followed by denitrification in an anoxic filter. The control and operating parameters evaluated during the study were: (a) the average mixed-liquor PAC concentration maintained in the contact-stabilization system, (b) the solids retention time practiced in the contact-stabilization system, and (c) the hydraulic detention time maintained in the contact aeration tank. Three identical treatement process trains were constructed and employed in this study. The coke-oven wastewater used for this investigation was fed to the treatment units at 30% strength. The first part of the study was devoted to determining the interactions between the mixed liquor PAC concentration and the solids retention time in the contact-stabilization tanks. Results showed that optimum overall system performance is attainable when the highest sludge age (30 day) and highest mixed liquor PAC concentration were practiced. During the second phase of the study, all three systems were operated at a 30 day solids retention time while different detention times of 1, 2/3 and 1/3 day were evaluated in the contact tank. PAC addition rates were maintained at the former levels and, consequently, reduced contact times entailed higher mixed liquor carbon concentrations. Once again, the system receiving the highest PAC addition rate of PAC exhibited the best overall performance. This system exhibited no deterioration in process performance as a result of decreased contact detention time. 72 references, 41 figures, 24 tables.

  18. Oxidative Treatment to Improve Coating and Electrochemical Stability of Carbon Fiber Paper with Niobium Doped Titanium Dioxide Sols for Potential Applications in Fuel Cells

    International Nuclear Information System (INIS)

    Highlights: • Solution coating of metal oxide layer directly onto carbon paper. • Most uniform Metal oxide coating on functionalized carbon paper. • Highest electrochemical stability for metal oxide coated functionalized carbon paper. - Abstract: Regular hydrophobized carbon paper cannot be used for unitized regenerative fuel cell applications as it corrodes at high potentials on the oxygen electrode side. Reported here are the oxidative treatment and dip-coating of carbon paper (Spectracarb™ 2050A-0850) with Nb-doped TiO2 sols (anatase phase) to increase the corrosion resistance of the carbon paper at the interface between catalyst layer and gas diffusion backing layer. Coating of carbon paper with Nb-doped TiO2 sols generates a reasonably uniform layer of TiO2 and covers the individual carbon fibers well only if the carbon paper is oxidatively functionalized prior to coating. This can be reasoned with a better wetting of the functionalized carbon paper by the sol-gel and the formation of covalent bonds between Ti and the large number of functional groups on the surface of oxidized carbon paper, which is in good agreement with previous observation for carbon nanotubes. The resistance towards oxidation of coated and uncoated samples of untreated and functionalized carbon paper was probed by cyclic voltammetry in 0.5 M aqueous H2SO4 at 1.2 V versus Ag/AgCl for up to 72 hours to mimic the conditions in a unitized regenerative fuel cell. Among these four cases studied here, functionalized carbon paper coated with a layer of Nb-doped TiO2 shows the highest stability towards electrochemical oxidation while uncoated functionalized carbon paper is the least stable due to the large number of available oxidation sites. These results clearly demonstrate that a coating of carbon fibers with TiO2 generates a lasting protection against oxidation under conditions encountered at the oxygen electrode side of unitized regenerative fuel cells

  19. Activated carbon derived from peat soil as a framework for the preparation of shape-stabilized phase change material

    International Nuclear Information System (INIS)

    This work focuses on the preparation of AC (activated carbon) through a physical activation method using peat soil as a precursor, followed by the use of the AC as an inorganic framework for the preparation of SPCM (shape-stabilized phase change material). The SPCM, composed of n-octadecane as the core and AC pores as a framework, was fabricated by a simple impregnation method, with the mass fraction of n-octadecane varying from 10 to 90 wt.%. The AC has a specific surface area of 893 m2 g−1 and an average pore size of 22 Å. The field emission scanning electron microscope images and nitrogen gas adsorption-desorption isotherms shows that the n-octadecane was actually encapsulated into the AC pores. The melting and freezing temperatures of the composite PCM (phase change material) were 30.9 °C and 24.1 °C, respectively, and its corresponding latent heat values were 95.4 Jg−1 and 99.6 Jg−1, respectively. The composite shows a good thermal reliability, even after 1000 melting/freezing cycles. The present research provided a new SPCM material for thermal energy storage as well as some new insights into the design of composite PCM by tailoring the pore structure of AC derived from peat soil, a natural resource. - Highlights: • Activated carbon from peat soil was used as framework. • n-Octadecane/activated carbon composite was fabricated by impregnation method. • The thermal property could be tailor by adjusting pore size of activated carbon. • The shape-stabilized PCM (phase change material) have the potential to be used for thermal energy storage

  20. Stabilization of unstable CGC+ triplex DNA by single-walled carbon nanotubes under physiological conditions

    OpenAIRE

    Song, Yujun; Feng, Lingyan; Ren, Jinsong; Qu, Xiaogang

    2011-01-01

    Triplex formation is a promising strategy for realizing artificially controlling of gene expression, reversible assembly of nanomaterials and DNA nanomachine and single-walled nanotubes (SWNTs) have been widely used as gene and drug delivery vector or as ‘building blocks’ in nano-/microelectronic devices. CGC+ triplex is not as stable as TAT triplex. The poor stability of CGC+ triplex limits its use in vitro and in vivo. There is no ligand that has been reported to selectively stabilize CGC+ ...

  1. Climate, soil texture, and soil types affect the contributions of fine-fraction-stabilized carbon to total soil organic carbon in different land uses across China.

    Science.gov (United States)

    Cai, Andong; Feng, Wenting; Zhang, Wenju; Xu, Minggang

    2016-05-01

    Mineral-associated organic carbon (MOC), that is stabilized by fine soil particles (i.e., silt plus clay, organic carbon (SOC) persistence and sequestration, due to its large contribution to total SOC (TSOC) and long turnover time. Our objectives were to investigate how climate, soil type, soil texture, and agricultural managements affect MOC contributions to TSOC in China. We created a dataset from 103 published papers, including 1106 data points pairing MOC and TSOC across three major land use types: cropland, grassland, and forest. Overall, the MOC/TSOC ratio ranged from 0.27 to 0.80 and varied significantly among soil groups in cropland, grassland, and forest. Croplands and forest exhibited significantly higher median MOC/TSOC ratios than in grassland. Moreover, forest and grassland soils in temperate regions had higher MOC/TSOC ratios than in subtropical regions. Furthermore, the MOC/TSOC ratio was much higher in ultisol, compared with the other soil types. Both the MOC content and MOC/TSOC ratio were positively correlated with the amount of fine fraction (silt plus clay) in soil, highlighting the importance of soil texture in stabilizing organic carbon across various climate zones. In cropland, different fertilization practices and land uses (e.g., upland, paddy, and upland-paddy rotation) significantly altered MOC/TSOC ratios, but not in cropping systems (e.g., mono- and double-cropping) characterized by climatic differences. This study demonstrates that the MOC/TSOC ratio is mainly driven by soil texture, soil types, and related climate and land uses, and thus the variations in MOC/TSOC ratios should be taken into account when quantitatively estimating soil C sequestration potential of silt plus clay particles on a large scale. PMID:26905446

  2. Climate, soil texture, and soil types affect the contributions of fine-fraction-stabilized carbon to total soil organic carbon in different land uses across China.

    Science.gov (United States)

    Cai, Andong; Feng, Wenting; Zhang, Wenju; Xu, Minggang

    2016-05-01

    Mineral-associated organic carbon (MOC), that is stabilized by fine soil particles (i.e., silt plus clay, organic carbon (SOC) persistence and sequestration, due to its large contribution to total SOC (TSOC) and long turnover time. Our objectives were to investigate how climate, soil type, soil texture, and agricultural managements affect MOC contributions to TSOC in China. We created a dataset from 103 published papers, including 1106 data points pairing MOC and TSOC across three major land use types: cropland, grassland, and forest. Overall, the MOC/TSOC ratio ranged from 0.27 to 0.80 and varied significantly among soil groups in cropland, grassland, and forest. Croplands and forest exhibited significantly higher median MOC/TSOC ratios than in grassland. Moreover, forest and grassland soils in temperate regions had higher MOC/TSOC ratios than in subtropical regions. Furthermore, the MOC/TSOC ratio was much higher in ultisol, compared with the other soil types. Both the MOC content and MOC/TSOC ratio were positively correlated with the amount of fine fraction (silt plus clay) in soil, highlighting the importance of soil texture in stabilizing organic carbon across various climate zones. In cropland, different fertilization practices and land uses (e.g., upland, paddy, and upland-paddy rotation) significantly altered MOC/TSOC ratios, but not in cropping systems (e.g., mono- and double-cropping) characterized by climatic differences. This study demonstrates that the MOC/TSOC ratio is mainly driven by soil texture, soil types, and related climate and land uses, and thus the variations in MOC/TSOC ratios should be taken into account when quantitatively estimating soil C sequestration potential of silt plus clay particles on a large scale.

  3. One-step facile synthesis of carbon-supported PdAu nanoparticles and their electrochemical property and stability

    International Nuclear Information System (INIS)

    Graphical abstract: Well-crystallized PdAu alloy nanoparticles with the average size of 2–5 nm supported on Ketjen Black (KB) were successfully fabricated from the metal wire electrodes via a one-step solution plasma process in water at atmospheric pressure. Multi-scan cyclic voltammetry showed they have better electrochemical stability in alkaline than in acidic solution. - Highlights: • Carbon-supported PdAu nanoparticles were fabricated by a solution plasma technique. • As-obtained PdAu nanoparticles were confirmed to be alloy. • PdAu nanoparticles have good electrochemical activities and stabilities. • PdAu nanoparticles in alkaline have better stability than that in acidic solution. - Abstract: Well-crystallized PdAu nanoparticles supported on Ketjen Black (KB) were successfully fabricated when both Pd and Au wires were served as the electrode pair by a solution plasma technique at atmospheric pressure. The synthesis of PdAu nanoparticles was almost simultaneous with their dispersion on KB. As-obtained PdAu nanoparticles were confirmed to be alloy by ultraviolet–visible spectrophotometer, transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX) of each particle. PdAu nanoparticles with the average diameter of 2–5 nm were equably distributed on KB. PdAu nanoparticles showed good electrocatalytic activity both in acidic and alkaline solution corresponding to their obvious oxidation and reduction features. PdAu nanoparticles have improved electrochemical stability compared with the electrochemical properties of Pd and Au nanoparticles mixture after long time multi-scan cyclic voltammetry. Multi-scan cyclic voltammetry also presented the PdAu nanoparticles in alkaline solution have better stability than that in acidic solution. Thus as-obtained PdAu alloy nanoparticles would become a promising electrocatalysts for fuel cells or Li-air batteries. This novel process showed its potential applications in designing optimization of

  4. Utilize Cementitious High Carbon Fly Ash (CHCFA) to Stabilize Cold In-Place Recycled (CIR) Asphalt Pavement as Base Coarse

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Haifang; Li, Xiaojun; Edil, Tuncer; O' Donnell, Jonathan; Danda, Swapna

    2011-02-05

    The purpose of this study was to evaluate the performance of cementitious high carbon fly ash (CHCFA) stabilized recycled asphalt pavement as a base course material in a real world setting. Three test road cells were built at MnROAD facility in Minnesota. These cells have the same asphalt surface layers, subbases, and subgrades, but three different base courses: conventional crushed aggregates, untreated recycled pavement materials (RPM), and CHCFA stabilized RPM materials. During and after the construction of the three cells, laboratory and field tests were carried out to characterize the material properties. The test results were used in the mechanistic-empirical pavement design guide (MEPDG) to predict the pavement performance. Based on the performance prediction, the life cycle analyses of cost, energy consumption, and greenhouse gasses were performed. The leaching impacts of these three types of base materials were compared. The laboratory and field tests showed that fly ash stabilized RPM had higher modulus than crushed aggregate and RPM did. Based on the MEPDG performance prediction, the service life of the Cell 79 containing fly ash stabilized RPM, is 23.5 years, which is about twice the service life (11 years) of the Cell 77 with RPM base, and about three times the service life (7.5 years) of the Cell 78 with crushed aggregate base. The life cycle analysis indicated that the usage of the fly ash stabilized RPM as the base of the flexible pavement can significantly reduce the life cycle cost, the energy consumption, the greenhouse gases emission. Concentrations of many trace elements, particularly those with relatively low water quality standards, diminish over time as water flows through the pavement profile. For many elements, concentrations below US water drinking water quality standards are attained at the bottom of the pavement profile within 2-4 pore volumes of flow.

  5. One-step facile synthesis of carbon-supported PdAu nanoparticles and their electrochemical property and stability

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xiulan, E-mail: whoxiulan@163.com [College of Materials Science and Engineering, Nanjing Tech University (China); Shi, Junjun; Zhang, Jianbo [College of Materials Science and Engineering, Nanjing Tech University (China); Tang, Weiping [Shanghai Institute of Space Power Sources, Shanghai (China); Zhu, Haikui; Shen, Xiaodong [College of Materials Science and Engineering, Nanjing Tech University (China); Saito, Nagahiro [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University (Japan)

    2015-01-15

    Graphical abstract: Well-crystallized PdAu alloy nanoparticles with the average size of 2–5 nm supported on Ketjen Black (KB) were successfully fabricated from the metal wire electrodes via a one-step solution plasma process in water at atmospheric pressure. Multi-scan cyclic voltammetry showed they have better electrochemical stability in alkaline than in acidic solution. - Highlights: • Carbon-supported PdAu nanoparticles were fabricated by a solution plasma technique. • As-obtained PdAu nanoparticles were confirmed to be alloy. • PdAu nanoparticles have good electrochemical activities and stabilities. • PdAu nanoparticles in alkaline have better stability than that in acidic solution. - Abstract: Well-crystallized PdAu nanoparticles supported on Ketjen Black (KB) were successfully fabricated when both Pd and Au wires were served as the electrode pair by a solution plasma technique at atmospheric pressure. The synthesis of PdAu nanoparticles was almost simultaneous with their dispersion on KB. As-obtained PdAu nanoparticles were confirmed to be alloy by ultraviolet–visible spectrophotometer, transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX) of each particle. PdAu nanoparticles with the average diameter of 2–5 nm were equably distributed on KB. PdAu nanoparticles showed good electrocatalytic activity both in acidic and alkaline solution corresponding to their obvious oxidation and reduction features. PdAu nanoparticles have improved electrochemical stability compared with the electrochemical properties of Pd and Au nanoparticles mixture after long time multi-scan cyclic voltammetry. Multi-scan cyclic voltammetry also presented the PdAu nanoparticles in alkaline solution have better stability than that in acidic solution. Thus as-obtained PdAu alloy nanoparticles would become a promising electrocatalysts for fuel cells or Li-air batteries. This novel process showed its potential applications in designing optimization of

  6. Hard carbon nanoparticles as high-capacity, high-stability anodic materials for Na-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Lifen; Cao, Yuliang; Henderson, Wesley A.; Sushko, Maria L.; Shao, Yuyan; Xiao, Jie; Wang, Wei; Engelhard, Mark H.; Nie, Zimin; Liu, Jun

    2016-01-01

    Hard carbon nanoparticles (HCNP) were synthesized by the pyrolysis of a polyaniline precursor. The measured Na+ cation diffusion coefficient (10-13-10-15cm2s-1) in the HCNP obtained at 1150 °C is two orders of magnitude lower than that of Li+ in graphite (10-10-13-15cm2s-1), indicating that reducing the carbon particle size is very important for improving electrochemical performance. These measurements also enable a clear visualization of the stepwise reaction phases and rate changes which occur throughout the insertion/extraction processes in HCNP, The electrochemical measurements also show that the nano-sized HCNP obtained at 1150 °C exhibited higher practical capacity at voltages lower than 1.2 V (vs. Na/Na⁺), as well as a prolonged cycling stability, which is attributed to an optimum spacing of 0.366 nm between the graphitic layers and the nano particular size resulting in a low-barrier Na+ cation insertion. These results suggest that HCNP is a very promising high-capacity/stability anode for low cost sodium-ion batteries (SIBs).

  7. Assessing the temporal stability of surface functional groups introduced by plasma treatments on the outer shells of carbon nanotubes

    Science.gov (United States)

    Merenda, Andrea; Ligneris, Elise des; Sears, Kallista; Chaffraix, Thomas; Magniez, Kevin; Cornu, David; Schütz, Jürg A.; Dumée, Ludovic F.

    2016-01-01

    Plasma treatments are emerging as superior efficiency treatment for high surface to volume ratio materials to tune functional group densities and alter crystallinity due to their ability to interact with matter at the nanoscale. The purpose of this study is to assess for the first time the long term stability of surface functional groups introduced across the surface of carbon nanotube materials for a series of oxidative, reductive and neutral plasma treatment conditions. Both plasma duration dose matrix based exposures and time decay experiments, whereby the surface energy of the materials was evaluated periodically over a one-month period, were carried out. Although only few morphological changes across the graphitic planes of the carbon nanotubes were found under the uniform plasma treatment conditions, the time dependence of pertinent work functions, supported by Raman analysis, suggested that the density of polar groups decreased non-linearly over time prior to reaching saturation from 7 days post treatment. This work provides critical considerations on the understanding of the stability of functional groups introduced across high specific surface area nano-materials used for the design of nano-composites, adsorptive or separation systems, or sensing materials and where interfacial interactions are key to the final materials performance. PMID:27507621

  8. Assessing the temporal stability of surface functional groups introduced by plasma treatments on the outer shells of carbon nanotubes

    Science.gov (United States)

    Merenda, Andrea; Ligneris, Elise Des; Sears, Kallista; Chaffraix, Thomas; Magniez, Kevin; Cornu, David; Schütz, Jürg A.; Dumée, Ludovic F.

    2016-08-01

    Plasma treatments are emerging as superior efficiency treatment for high surface to volume ratio materials to tune functional group densities and alter crystallinity due to their ability to interact with matter at the nanoscale. The purpose of this study is to assess for the first time the long term stability of surface functional groups introduced across the surface of carbon nanotube materials for a series of oxidative, reductive and neutral plasma treatment conditions. Both plasma duration dose matrix based exposures and time decay experiments, whereby the surface energy of the materials was evaluated periodically over a one-month period, were carried out. Although only few morphological changes across the graphitic planes of the carbon nanotubes were found under the uniform plasma treatment conditions, the time dependence of pertinent work functions, supported by Raman analysis, suggested that the density of polar groups decreased non-linearly over time prior to reaching saturation from 7 days post treatment. This work provides critical considerations on the understanding of the stability of functional groups introduced across high specific surface area nano-materials used for the design of nano-composites, adsorptive or separation systems, or sensing materials and where interfacial interactions are key to the final materials performance.

  9. Synthesis, characterization, and stability of Fe-MCM-41 for production of carbon nanotubes by acetylene pyrolysis.

    Science.gov (United States)

    Amama, Placidus B; Lim, Sangyun; Ciuparu, Dragos; Yang, Yanhui; Pfefferle, Lisa; Haller, Gary L

    2005-02-24

    Fe-substituted MCM-41 molecular sieves with ca. 1, 2, and 3 wt % Fe were synthesized hydrothermally using different sources of colloidal silica (HiSil and Cab-O-Sil) and characterized by ICP, XRD, N2 physisorption, UV-vis, EPR, TPR, and X-ray absorption. Catalysts synthesized from Cab-O-Sil showed higher structural order and stability than those from HiSil. The local environment of Fe in the mesoporous material as studied by UV-vis reveals the dominance of framework Fe in all the as-synthesized Fe-MCM-41 samples. Dislodgement of some Fe species to extraframework location occurs upon calcination, and this effect is more severe for Fe-MCM-41 (2 wt %) and Fe-MCM-41 (3 wt %), as confirmed by EPR and X-ray absorption. These materials have been used as catalytic templates for the production of carbon nanotubes (CNTs) by acetylene pyrolysis at atmospheric pressure. A relationship between the Fe loading in MCM-41 and the carbon species produced during this reaction has been established. Using our optimized conditions for this system, Fe-MCM-41 with ca. 2 wt % Fe showed the best results with particularly high selectivity for single-wall carbon nanotube (SWNT) production. This catalyst was selective for carbon nanotubes with a low amount of amorphous carbon for a narrow range of temperatures from 1073 to 1123 K. To account for the different selectivity of these catalysts for CNTs production, the local environment and chemical state of Fe in the used catalyst was further probed by X-band EPR. PMID:16851270

  10. Stability and chirality effect on twist formation of collapsed double wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    XIAO Jian-liang; LIU Bin; HUANG Yong-gang; HWANG Ke-zhi; YU Min-feng

    2006-01-01

    This study is to reveal the effect of interlayer lattice registry on the formation of collapsed double wall carbon nanotubes (DWCNTs). It is found that collapsed carbon nanotubes can be energetically unstable,metastable or stable,depending mainly on the diameter of the CNT. A fully collapsed DWCNT can adopt different structural morphologies,such as a straight ribbon,a warping ribbon or a twisted ribbon,depending on the chirality of the CNT,which is similar to single wall carbon nanotubes (SWCNTs). Different from SWCNTs,this study also shows some unique phenomena in the formation of collapsed DWCNTs. A fully collapsed DWCNT can have different combinations of the interlayer lattice registry effect within the inner and outer tube,thus the outer tube can influence the formation of the collapsed CNT via lattice registry effect,sometimes even dominates the twist of the CNT.

  11. A MERGE model with endogenous technological change and the cost of carbon stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Kypreos, Socrates [Laboratory of Energy Systems Analysis, The Energy Departments, Energy Economics Group, Paul Scherrer Institute, CH-5232, Villigen PSI (Switzerland)

    2007-11-15

    Two stylized backstop systems with endogenous technological learning (ETL) are introduced in the ''model for evaluating regional and global effects'' (MERGE): one for the electric and the other for the non-electric markets. Then the model is applied to analyze the impacts of ETL on carbon-mitigation policy, contrasting the resulting impacts with the situation without ETL. We model research and development (R and D) spending and learning subsidies for the demonstration and deployment stage as control variables, and we investigate the ability of this extra spending to create path-dependent experience and knowledge to aid in the implementation of carbon-free technologies. Based on model estimations and sensitivity analyses, we conclude that increased commitments for the development of new technologies to advance along their learning curves has a potential for substantial reductions in the cost of mitigating climate change and thereby helping to reach safe concentrations of carbon in the atmosphere. (author)

  12. Structures and stability of calcium and magnesium carbonates at mantle pressures

    OpenAIRE

    Pickard, Chris J.; Needs, Richard J.

    2014-01-01

    Ab initio random structure searching (AIRSS) and density functional theory methods are used to predict structures of calcium and magnesium carbonate (CaCO$_3$ and MgCO$_3$) at high pressures. We find a previously unknown CaCO$_3$ structure which is more stable than the aragonite and "post aragonite" phases in the range 32--48 GPa. At pressures from 67 GPa to well over 100 GPa the most stable phase is a previously unknown CaCO$_3$ structure of the pyroxene type with fourfold coordinated carbon...

  13. A high-porosity carbon molybdenum sulphide composite with enhanced electrochemical hydrogen evolution and stability

    DEFF Research Database (Denmark)

    Laursen, Anders B.; Vesborg, Peter C. K.; Chorkendorff, Ib

    2013-01-01

    This work describes a highly active and stable acid activated carbon fibre and amorphous MoSx composite hydrogen evolution catalyst. The increased electrochemical-surface area is demonstrated to cause increased catalyst electrodeposition and activity. These composite electrodes also show an impro......This work describes a highly active and stable acid activated carbon fibre and amorphous MoSx composite hydrogen evolution catalyst. The increased electrochemical-surface area is demonstrated to cause increased catalyst electrodeposition and activity. These composite electrodes also show...

  14. Organic Matter Quality and its Influence on Carbon Turnover and Stabilization in Northern Peatlands

    Science.gov (United States)

    Turetsky, M. R.; Wieder, R. K.

    2002-12-01

    Peatlands cover 3-5 % of the world's ice-free land area, but store about 33 % of global terrestrial soil carbon. Peat accumulation in northern regions generally is controlled by slow decomposition, which may be limited by cold temperatures and water-logging. Poor organic matter quality also may limit decay, and microbial activity in peatlands likely is regulated by the availability of labile carbon and/or nutrients. Conversely, carbon in recalcitrant soil structures may be chemically protected from microbial decay, particularly in peatlands where carbon can be buried in anaerobic soils. Soil organic matter quality is controlled by plant litter chemical composition and the susceptibility of organic compounds to decomposition through time. There are a number of techniques available for characterizing organic quality, ranging from chemical proximate or elemental analysis to more qualitative methods such as nuclear magenetic resonance, pyrolysis/mass spectroscopy, and Fourier transform infrared spectroscopy. We generally have relied on proximate analysis for quantitative determination of several organic fractions (i.e., water-soluble carbohydrates, soluble nonpolars, water-soluble phenolics, holocellulose, and acid insoluble material). Our approaches to studying organic matter quality in relation to C turnover in peatlands include 1) 14C labelling of peatland vegetation along a latitudinal gradient in North America, allowing us to follow the fate of 14C tracer in belowground organic fractions under varying climates, 2) litter bag studies focusing on the role of individual moss species in litter quality and organic matter decomposition, and 3) laboratory incubations of peat to explore relationships between organic matter quality and decay. These studies suggest that proximate organic fractions vary in lability, but that turnover of organic matter is influenced both by plant species and climate. Across boreal peatlands, measures of soil recalcitrance such as acid

  15. Stability of soil organic carbon changes in successive rotations of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian; WANG Silong; FENG Zongwei; WANG Qingkui

    2009-01-01

    The importance of soil organic carbon (SOC) under forests in the global carbon cycle depends on the stability of the soil carbon and its availability to soil microbial biomass. We investigated the effects of successive rotations of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations on the stability of SOC and its availability to microbes by adopting the two-step hydrolysis with H2SO4 and density fractionation. The results showed that successive rotations of Chinese fir decreased the quantity of total SOC, recalcitrant fraction, and carbohydrates in Labile Pool I (LPI), and microbial properties evidently, especially at 0-10 cm horizon. However, cellulose included in Labile Pool II (LP II) and the cellulose/total carbohydrates ratio increased in successive rotations of Chinese fir. The non-cellulose of carbohydrates included in LPI maybe highly available to soil microbial biomass. Hence the availability of SOC to microbial biomass declined over the successive rotations. Although there was no significant change in recalcitrance of SOC over the successive rotations of Chinese fir, the percentage of heavy fraction to total SOC increased, suggesting that the degree of physical protection for SOC increased and SOC became more stable over the successive rotations. The degradation of SOC quality in successive rotation soils may be attributed to worse environmental conditions resulted from disturbance that related to "slash and burn" site preparation. Being highly correlated with soil microbial properties, the cellulose/total carbohydrates ratio as an effective indicator of changes in availability of SOC to microbial biomass brought by management practices in forest soils.

  16. Carbon stabilization and microbial growth in acidic mine soils after addition of different amendments for soil reclamation

    Science.gov (United States)

    Zornoza, Raúl; Acosta, Jose; Ángeles Muñoz, María; Martínez-Martínez, Silvia; Faz, Ángel; Bååth, Erland

    2016-04-01

    The extreme soil conditions in metalliferous mine soils have a negative influence on soil biological activity and therefore on soil carbon estabilization. Therefore, amendments are used to increase organic carbon content and activate microbial communities. In order to elucidate some of the factors controlling soil organic carbon stabilization in reclaimed acidic mine soils and its interrelationship with microbial growth and community structure, we performed an incubation experiment with four amendments: pig slurry (PS), pig manure (PM) and biochar (BC), applied with and without marble waste (MW; CaCO3). Results showed that PM and BC (alone or together with MW) contributed to an important increment in recalcitrant organic C, C/N ratio and aggregate stability. Bacterial and fungal growths were highly dependent on pH and labile organic C. PS supported the highest microbial growth; applied alone it stimulated fungal growth, and applied with MW it stimulated bacterial growth. BC promoted the lowest microbial growth, especially for fungi, with no significant increase in fungal biomass. MW+BC increased bacterial growth up to values similar to PM and MW+PM, suggesting that part of the biochar was degraded, at least in short-term mainly by bacteria rather than fungi. PM, MW+PS and MW+PM supported the highest microbial biomass and a similar community structure, related with the presence of high organic C and high pH, with immobilization of metals and increased soil quality. BC contributed to improved soil structure, increased recalcitrant organic C, and decreased metal mobility, with low stimulation of microbial growth.

  17. Evaluation of metal oxide and carbonate nanoparticle stability in soybean oil: Implications for controlled release of alkalinity during subsurface remediation

    Science.gov (United States)

    Ramsburg, C. A.; Leach, O. I.; Sebik, J.; Muller, K.

    2011-12-01

    Traditional methods for adjusting groundwater pH rely on injection of aqueous solutes and therefore, amendment distribution is reliant upon aqueous phase flow and transport. This reliance can limit mixing and sustention of amendments within the treatment zone. Oil-in-water emulsions offer an alternative for amendment delivery - one that has potential to enhance control of the distribution and release of buffering agents within the subsurface. Focus here is placed on using metal oxide and carbonate nanoparticles to release alkalinity from soybean oil, a common dispersed phase within emulsions designed to support remediation activities. Batch reactor systems were employed to examine the influence of dispersed phase composition on particle stability and solubility. The stability of uncoated MgO and CaCO3 particles in unmodified soybean oil was explored in a series of sedimentation studies conducted at solid loadings of 0.05, 0.1, and 0.2% mass. Three nominal sizes of MgO particles were examined (20, 50, and 100 nm) and one CaCO3 particle size (60 nm). Results from sedimentation studies conducted over four hours suggest that the viscosity of the soybean oil imparts a kinetic stability, for all sizes of the uncoated MgO and CaCO3 nanoparticles, which is sufficient time for particle encapsulation within oil-in-water emulsions. Based upon these results, the sedimentation of the 50 nm and 100 nm MgO, and 60 nm CaCO3 particles was assessed over longer durations (≥72 hr). Results from these stability tests suggest that the 50 nm and 100 nm MgO particles have greater kinetic stability than the 60 nm CaCO3. Batch studies were also used to assess the influence of n-butanol, a co-solvent hypothesized to aid in controlling the rate of alkalinity release, on phase behavior and metal (Mg2+ and Ca2+) solubility. Phase behavior studies suggest that n-butanol has a limited region of miscibility within the soybean oil-water system. Use of n-butanol and water within this region of

  18. Effects of multiple polyaniline layers immobilized on carbon nanotube and glutaraldehyde on performance and stability of biofuel cell

    Science.gov (United States)

    Christwardana, Marcelinus; Kwon, Yongchai

    2015-12-01

    Enzymatic biofuel cell (EBC) employing new catalyst for anode electrode is fabricated. The new catalyst consists of glucose oxidase (GOx), polyaniline (PANI) and carbon nanotube (CNT) that are multiply stacked together and finally the stack layer is surrounded by glutaraldehyde (GA) (GA/[GOx/PANI/CNT]n). To evaluate how the GA/[GOx/PANI/CNT]n layer affects EBC performance and stability, electrochemical characterizations are implemented. Regarding optimization, GA/[GOx/PANI/CNT]3 is determined. For elucidating reaction mechanism between glucose and flavin adenine dinucleotide (FAD) of GA/[GOx/PANI/CNT]3, associated investigations are performed. In the evaluations, drop in reduction current peak of FAD is observed with provisions of glucose and O2, while glucose does not influence FAD reaction without O2, confirming O2 makes mediator role. When the GA/[GOx/PANI/CNT]3 layer is adopted, superior catalytic activity and EBC performance are gained (electron transfer rate constant of 5.1 s-1, glucose sensitivity of 150 ìA mM-1 cm-2, and EBC maximum power density (MPD) of 0.29 mW cm-2). Regarding EBC stability, MPD of EBC adopting GA/[GOx/PANI/CNT]3 maintains up to 93% of their initial value even after four weeks. Although GA is little effective for improving EBC performance, EBC stability is helped by GA due to its adhesion promotion capability with [GOx/PANI/CNT]n layer.

  19. Preparation, melting behavior and thermal stability of poly(lactic acid)/poly(propylene carbonate) blends processed by vane extruder

    Science.gov (United States)

    Zou, Wei; Chen, Rongyuan; Zhang, Haichen; Qu, Jinping

    2016-03-01

    Poly (lactic acid) (PLA)/Poly (propylene carbonate) (PPC) blends were prepared by vane extruder which is a type of novel polymer processing extruder based on elongation force field. Scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric (TG) were used respectively to analyze the compatibility, the melting behavior and thermal stability properties of PLA/PPC blends affected by the different content of PPC. The results showed that with the increase of the PPC content, the glass transition temperature of PLA was reduced, and the glass transition temperature of PPC was increased, which indicated that PLA and PPC had partial compatibility. The cold crystallization temperature of PLA increased with the increase of the PPC content, which showed that PPC hindered the cold crystallization process of PLA. The addition of PPC had little impact on the melting process of PLA, and the melting temperature of PLA was almost kept the same value. Thermogravimetric analysis showed that the thermal stability of PPC was worse than that of PLA, the addition of PPC reduced the thermal stability of PLA.

  20. Formate stability and carbonate hydrogenation on strained Cu overlayers on Pt(111)

    DEFF Research Database (Denmark)

    Schumacher, Nana Maria Pii; Andersson, Klas Jerker; Nerlov, Jesper;

    2008-01-01

    . This is a significantly lower decomposition temperature than obtained earlier on pristine Cu(111) (460 K), as well as for thicker Cu layers where we assign an observed decomposition peak at 440 ± 5 K to relaxed, but defect-rich Cu(111). However, the thermal stability of formate on strained and defect-rich Cu is similar...

  1. Effect of Wrapped Carbon Nanotubes on Optical Properties, Morphology, and Thermal Stability of Electrospun Poly(vinyl alcohol Composite Nanofibers

    Directory of Open Access Journals (Sweden)

    Naoual Diouri

    2013-01-01

    Full Text Available Electrospinning was used to elaborate poly(vinyl alcohol (PVA nanofibers in the presence of embedded multiwall carbon nanotubes (MWCNTs in surfactant and polymer. MWCNTs were dispersed in aqueous solution using both sodium dodecyl sulfate (SDS as surfactant and Poly(vinyl pyrrolidone (PVP. Changing the surfactant and polymer concentration reveals that the maximum dispersion achievable is corresponding to the mass ratios MWCNTs : SDS—1 : 5 and MWCNTs : SDS : PVP—1 : 5 : 0.6 in the presence of the PVP. After the optimization of the dispersion process, the SEM image of the PVA/PVP/SDS/MWCNTs electrospun fibers presents high stability of the fibers with diameter around 224 nm. Infrared spectroscopy and thermal gravimetric analysis elucidate the type of interaction between the PVA and the coated carbon nanotube. The presence of PVP wrapped carbon nanotubes reduced slightly the onset of the degradation temperature of the electrospun nanofibers.

  2. STRUCTURE, MECHANICAL PROPERTIES AND THERMAL STABILITY OF DIAMOND-LIKE CARBON FILMS PREPARED BY ARC ION PLATING

    Institute of Scientific and Technical Information of China (English)

    Y.S. Zou; J.D. Zheng; J. Gong; C. Sun; R.F. Huang; L.S. Wen

    2005-01-01

    Diamond-like Carbon (DLC) films have been prepared on Si(100) substrates by arc ion plating in conjunction with pulse bias voltage under H2 atmosphere. The deposited films have been characterized by scanning electron microscopy and atomic force microscopy. The results show that the surface of the film is smooth and dense without any cracks, and the surface roughness is low. The bonding characteristic of the films has been studied by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It shows the sp3 bond content of the film deposited at -200V is 26.7%. The hardness and elastic modulus of the film determined by nanoindentation technique are 30.8 and 250.1GPa, respectively. The tribological characteristic of the films reveals that they have low friction coefficient and good wear-resistance. After deposition, the films have been annealed in the range of 350-700℃ for 1h in vacuum to investigate the thermal stability. Raman spectra indicate that the ID/IG ratio and G peak position have few detectable changes below 500℃. Further increasing the annealing temperature, the hydrogen can be released, the structure rearranges, and the phase transition of sp3 configured carbon to sp2 configured carbon appears.

  3. Probing the Interfacial Interaction in Layered-Carbon-Stabilized Iron Oxide Nanostructures: A Soft X-ray Spectroscopic Study.

    Science.gov (United States)

    Zhang, Hui; Liu, Jinyin; Zhao, Guanqi; Gao, Yongjun; Tyliszczak, Tolek; Glans, Per-Anders; Guo, Jinghua; Ma, Ding; Sun, Xu-Hui; Zhong, Jun

    2015-04-22

    We have stabilized the iron oxide nanoparticles (NPs) of various sizes on layered carbon materials (Fe-oxide/C) that show excellent catalytic performance. From the characterization of X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), scanning transmission X-ray microscopy (STXM) and X-ray magnetic circular dichroism spectroscopy (XMCD), a strong interfacial interaction in the Fe-oxide/C hybrids has been observed between the small iron oxide NPs and layered carbon in contrast to the weak interaction in the large iron oxide NPs. The interfacial interaction between the NPs and layered carbon is found to link with the improved catalytic performance. In addition, the Fe L-edge XMCD spectra show that the large iron oxide NPs are mainly γ-Fe2O3 with a strong ferromagnetic property, whereas the small iron oxide NPs with strong interfacial interaction are mainly α-Fe2O3 or amorphous Fe2O3 with a nonmagnetic property. The results strongly suggest that the interfacial interaction plays a key role for the catalytic performance, and the experimental findings may provide guidance toward rational design of high-performance catalysts. PMID:25839786

  4. Probing the Interfacial Interaction in Layered-Carbon-Stabilized Iron Oxide Nanostructures: A Soft X-ray Spectroscopic Study.

    Science.gov (United States)

    Zhang, Hui; Liu, Jinyin; Zhao, Guanqi; Gao, Yongjun; Tyliszczak, Tolek; Glans, Per-Anders; Guo, Jinghua; Ma, Ding; Sun, Xu-Hui; Zhong, Jun

    2015-04-22

    We have stabilized the iron oxide nanoparticles (NPs) of various sizes on layered carbon materials (Fe-oxide/C) that show excellent catalytic performance. From the characterization of X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), scanning transmission X-ray microscopy (STXM) and X-ray magnetic circular dichroism spectroscopy (XMCD), a strong interfacial interaction in the Fe-oxide/C hybrids has been observed between the small iron oxide NPs and layered carbon in contrast to the weak interaction in the large iron oxide NPs. The interfacial interaction between the NPs and layered carbon is found to link with the improved catalytic performance. In addition, the Fe L-edge XMCD spectra show that the large iron oxide NPs are mainly γ-Fe2O3 with a strong ferromagnetic property, whereas the small iron oxide NPs with strong interfacial interaction are mainly α-Fe2O3 or amorphous Fe2O3 with a nonmagnetic property. The results strongly suggest that the interfacial interaction plays a key role for the catalytic performance, and the experimental findings may provide guidance toward rational design of high-performance catalysts.

  5. What Expands in an Expanding Universe?

    Science.gov (United States)

    Pacheco, José A De Freitas

    2015-01-01

    In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative) of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM) all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

  6. What Expands in an Expanding Universe?

    Directory of Open Access Journals (Sweden)

    JOSÉ A. DE FREITAS PACHECO

    2015-12-01

    Full Text Available ABSTRACT In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

  7. Carbon replacement and stability changes in short-term silvo-pastoralo experiments in Colombian Amazonia

    NARCIS (Netherlands)

    Mosquera Vidal, O.; Buurman, P.; Ramirez, B.L.; Amezquita, M.C.

    2012-01-01

    There is little information on the effects of land use change on soil Carbon stocks in Colombian Amazonia. Such information would be needed to assess the impact of this area on the global C cycle and the sustainability of agricultural systems that are replacing native forest. The aim of this study w

  8. Soil aggregation and the stabilization of organic carbon as affected by erosion and deposition

    NARCIS (Netherlands)

    X. Wang; E.L.H. Cammeraat; C. Cerli; K. Kalbitz

    2014-01-01

    The importance of soil aggregation in determining the dynamics of soil organic carbon (SOC) during erosion, transportation and deposition is poorly understood. Particularly, we do not know how aggregation contributes to the often-observed accumulation of SOC at depositional sites. Our objective was

  9. Colloidal stability of (functionalised) fullerenes in the presence of dissolved organic carbon and electrolytes

    NARCIS (Netherlands)

    J.J.H. Haftka; P.S. Bäuerlein; E. Emke; N. Lammertse; D. Belokhovstova; B Hilvering; P. de Voogt; T.L. ter Laak

    2015-01-01

    Carbon-based nanoparticles such as fullerenes have been widely applied in personal care products, drug delivery systems, and solar cells. The properties of nanoparticles have been increasingly studied because of their applications and their potential risks to the environment and human health. Many s

  10. The Stability of Peatland Carbon Stores to Global Change: Evidence for Enhanced Methane and Carbon Dioxide Production

    Science.gov (United States)

    Chanton, J.; Wilson, R.; Tfaily, M. M.; Sebestyen, S. D.; Medvedeff, C.; McFarlane, K. J.; Kolka, R. K.; Kostka, J. E.; Keller, J.; Hanson, P. J.; Guilderson, T. P.; de La Cruz, F.; Cooper, W. T.; Bridgham, S. D.; Barlaz, M.

    2015-12-01

    Peatlands sequester large stores of carbon in sedimentary sequences that can be meters thick. Peatlands can be separated into two main layers: the acrotelm, which is exposed to the atmosphere and dominated by living plants, and the catotelm, which tends to be anoxic and is where the majority of organic matter is stored. In response to warming climate, to what extent will peatland organic matter be activated to form additional CH4 and CO2 relative to current production rates? To predict the answer to this question the SPRUCE (Spruce and Peatland Responses Under Climatic and Environmental Change) project is being conducted in a bog ecosystem in northern Minnesota. The study is designed to improve predictive skill in peat and wetland-methane models by defining quantitative relationships among decomposition indices, microbial communities, and CO2 and CH4 production rates. The manipulation is being conducted in a staged approach, and deep warming through the entire ~2 m peat profile was initiated in June of 2014 at +0, +2.2, +4.5, +6.8 and +9C. Starting in summer 2015, the project will enhance both above and belowground temperature and CO2 levels. Following months of temperature enhancement there is no evidence of an effect on catotelm peat. In bog pre-treatment, control and treatment plots, microbial respiration and CO2 and CH4 production in the deep peat is driven primarily by recent plant production and to date, this trend continues in the catolem following treatment. Methane d13C and fractionation factors are invariant across the treatments, as are gas concentrations at depth. Surface CH4 emission, however, has shown a positive correlation with peat temperature, and measurements of CH4 production in incubations across the depth profile suggest that surface peat is more responsive to increases in soil temperature, apparently driving the emission response. Shifts in the composition and metabolic potential of microbial communities are being examined using next

  11. Adsorption behavior of perfluorinated sulfonic acid ionomer on highly graphitized carbon nanofibers and their thermal stabilities

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma; Borghei, Maryam; Dhiman, Rajnish;

    2014-01-01

    isotherm), the ionomer has varying affinities for CNFs (Keq. = between 5 and 22) as compared to Vulcan (Keq. = 18), depending on surface treatments. However, the interactions are most likely governed by different adsorption mechanisms depending on hydrophilicity / hydrophobicity of the adsorbent carbon......A systematic adsorption study of perfluorinated sulfonic acid Nafion® ionomer on ribbon type highly graphitized carbon nanofibers (CNFs) was carried out using 19 fluorine nuclear magnetic resonance spectroscopy. Based on the values obtained for the equilibrium constant (Keq., derived from Langmuir....... The ionomer is probably adsorbed via the polar sulfonic group on hydrophilic Vulcan, whereas, it is adsorbed primarily via hydrophobic -CF2- backbone on the highly hydrophobic pristine CNFs. Ionomer adsorption behavior is gradually altered from apolar to polar group adsorption for the acid modified CNFs...

  12. Stability of carbonated magmas at the base of the Earth's upper mantle

    Science.gov (United States)

    Ghosh, Sujoy; Ohtani, Eiji; Litasov, Konstantin; Suzuki, Akio; Sakamaki, Tatsuya

    2007-11-01

    We measured the density of carbonated basaltic melt containing 5.0 wt.% CO2 at 2573 K and in the pressure range from 16.0 to 20.0 GPa by using the sink/float method with single crystal diamond as a density marker. We observed sinking of diamond at 19.0 GPa and flotation of diamond at 20.0 GPa and 2573 K. Using the third order Birch-Murnaghan equation of state, the calculated isothermal bulk modulus (K T ) of the carbonated basaltic melt (5.0 wt.% CO2) and its pressure derivative (K') are 16.0 +/- 1.0 GPa and 5.2 +/- 0.2, respectively. Our result implies that magmas can contain up to 3.0-4.0 wt.% CO2 to be denser than the surrounding mantle at the top of the 410 km discontinuity.

  13. Effect of charge on the stability of single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    LUO Ji; WU Jinlei

    2004-01-01

    By using density-functional-theory based DMol3 code, the structure optimizations are performed on a short charged single-walled carbon nanotube. Results show that the total energy of the nanotube exhibits a parabolic variation with respect to the amount of extra charge, and one negatively charged nanotube has the lowest total energy; thus the carbon nanotube has a positive electron affinity. When the charge is small, the variation of the atomic structure of the nanotube is also small, and neglecting the atomic structure variation leads to the qualitatively correct properties of the total energy and the energy of the highest occupied molecular orbital. When the extra charge is large, the end structure of the nanotube will be first affected and form into a trumpet shape. With the increasing of the extra charge, the nanotube end gradually becomes unstable, and this may lead to the ultimate destruction of the nanotube.

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

    Science.gov (United States)

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

    2014-01-01

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

  15. Colloidal stability of (functionalised) fullerenes in the presence of dissolved organic carbon and electrolytes

    OpenAIRE

    Haftka, J.J.H.; Bäuerlein, P.S.; Emke, E.; Lammertse, N.; Belokhovstova, D.; Hilvering, B; Voogt, de, P.; Laak, ter, E.A.

    2015-01-01

    Carbon-based nanoparticles such as fullerenes have been widely applied in personal care products, drug delivery systems, and solar cells. The properties of nanoparticles have been increasingly studied because of their applications and their potential risks to the environment and human health. Many studies have focused on the environmental fate and properties of C60. However, there is limited information available on the environmental properties of functionalised fullerenes. This study focuses...

  16. Flow induced vibration and stability analysis of multi wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Kyung Jae [Agency for Defense Development, Daejeon (Korea, Republic of); Choi, Jong Woon [Korean Intellectual Property Office, Daejeon (Korea, Republic of); Kim, Sung Kyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Song, Oh Seop [Chungnam National Univ., Daejeon (Korea, Republic of)

    2012-12-15

    The free vibration and flow induced flutter instability of cantilever multi wall carbon nanotubes conveying fluid are investigated and the nanotubes are modeled as thin-walled beams. The non-classical effects of the transverse shear, rotary inertia, warping inhibition, and van der Waals forces between two walls are incorporated into the structural model. The governing equations and associated boundary conditions are derived using Hamilton's principle. A numerical analysis is carried out by using the extended Galerkin method, which enables us to obtain more accurate solutions compared to the conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for a flow velocity below a certain critical value. However, beyond this critical flow velocity, flutter instability may occur. The variations in the critical flow velocity with respect to both the radius ratio and length of the carbon nanotubes are investigated and pertinent conclusions are outlined. The differences in the vibration and instability characteristics between the Timoshenko beam theory and Euler beam theory are revealed. A comparative analysis of the natural frequencies and flutter characteristics of MWCNTs and SWCNTs is also performed.

  17. Electrical resistance stability of high content carbon fiber reinforced cement composite

    Institute of Scientific and Technical Information of China (English)

    YANG Zai-fu; TANG Zu-quan; LI Zhuo-qiu; QIAN Jue-shi

    2005-01-01

    The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50℃C, increases relatively by 4% when ambient temperature decreases from 15℃ to-20℃, and decreases relatively by 13% with temperature increasing by 88℃. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.

  18. Evaluation of the retained austenite mechanical stability in the medium-carbon TRIP steel

    Directory of Open Access Journals (Sweden)

    A. Kokosza

    2012-12-01

    Full Text Available Purpose: The aim of this study was to evaluate the inclination to mechanical destabilization of retained austenite in the microstructure of the TRIP steel containing 0.4% C, 1.5% Mn and 1.2% Si.Design/methodology/approach: The new, simple method for evaluating the mechanical stability of retained austenite was proposed, which is based on the bending test and the measurement of volume fraction of retained austenite by X-ray quantitative phase analysis. The relationship between stress and local strain as well as local volume fraction of this phase in selected locations on the surface of the bending sample were revealed.Findings: The applied heat treatment, modified with respect to the classic one, allowed remain approximately 25 vol.% of the retained austenite in the microstructure of the investigated TRIP steel. It was pointed that retained austenite has high mechanical stability if stress is low. Under influence of the higher stress a partial destabilization this phase occurred. It was found that in the examined steel such mechanical destabilization of retained austenite has two - or three-stage nature.Research limitations/implications: Results of this study indicate a significant stability of retained austenite in the investigated TRIP steel. It is advisable to check how will change the stability of this phase when the stress or strain will be higher than those that occurred in this research.Practical implications: The new method of the evaluation of the retained austenite mechanical stability provides the possibility of an easy and effective estimation of this phase tendency to mechanical destabilisation and to martensite transformation in the steel. In addition, this method allows analysing the influence of the stress as well as the strain on changes in this phase volume fraction, which occur during three-point bending.Originality/value: The proposed method may be used for evaluation of susceptibility of retained austenite on transformation

  19. Laboratory Investigations in Support of Carbon Dioxide-in-Water Emulsions Stabilized by Fine Particles for Ocean and Geologic Sequestration of Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Dan Golomb; David Ryan; Eugene Barry

    2007-01-08

    Since the submission of our last Semi-annual Report, dated September 2006, the research objectives of this Co-operative Agreement shifted toward geologic sequestration of carbon dioxide. In the period September 2006-February 2007, experiments were conducted in a High-Pressure Batch Reactor (HPBR) for creating emulsions of liquid carbon dioxide (/CO{sub 2})-in-water stabilized by fine particles for geologic sequestration of CO{sub 2}. Also, emulsions were created in water of a binary mixture of liquid carbon dioxide and liquid hydrogen sulfide (/H{sub 2}S), called Acid Gas (AG). This leads to the possibility of safe disposal of AG in deep geologic formations, such as saline aquifers. The stabilizing particles included pulverized limestone (CaCO{sub 3}), unprocessed flyash, collected by an electrostatic precipitator at a local coal-fired power plant, and pulverized siderite (FeCO{sub 3}). Particle size ranged from submicron to a few micrometers. The first important finding is that /CO{sub 2} and /H{sub 2}S freely mix as a binary liquid without phase separation. The next finding is that the mixture of /CO{sub 2} and /H{sub 2}S can be emulsified in water using fine particles as emulsifying agents. Such emulsions are stable over prolonged periods, so it should not be a problem to inject an emulsion into subterranean formations. The advantage of injecting an emulsion into subterranean formations is that it is denser than the pure liquid, therefore it is likely to disperse in the bottom of the geologic formation, rather than buoying upward (called fingering). In such a fashion, the risk of the liquids escaping from the formation, and possibly re-emerging into the atmosphere, is minimized. This is especially important for H{sub 2}S, because it is a highly toxic gas. Furthermore, the emulsion may interact with the surrounding minerals, causing mineral trapping. This may lead to longer sequestration periods than injecting the pure liquids alone.

  20. Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals

    Directory of Open Access Journals (Sweden)

    M. Schrumpf

    2013-03-01

    Full Text Available Conceptual models suggest that stability of organic carbon (OC in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Density fractionation is a useful tool to study the relevance of OC stabilization in aggregates and in association with minerals, but it has rarely been applied to full soil profiles. We aim to determine factors shaping the depth profiles of physically unprotected and mineral associated OC and test their relevance for OC stability across a range of European soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions – fLF, occluded light fractions – oLF, heavy fractions – HF were analysed for OC, total nitrogen (TN, δ14C, and Δ14C. Bulk samples were also incubated to determine CO2 evolution per g OC in the samples (specific mineralization rates as an indicator for OC stability. Depth profiles of OC in the light fraction (LF-OC matched those of roots for undisturbed grassland and forest sites, suggesting that roots are shaping the depth distribution of LF-OC. Organic C in the HF declined less with soil depth than LF-OC and roots, especially at grassland sites. The decrease in Δ14C (increase in age of HF-OC with soil depth was related to soil pH as well as to dissolved OC fluxes. This indicates that dissolved OC translocation contributes to the formation of subsoil HF-OC and shapes the Δ14C profiles. The LF at three sites were rather depleted in 14C, indicating the presence of fossil material such as coal and lignite, probably inherited from the parent material. At the other sites, modern Δ14C signatures and positive correlations between specific mineralization rates and fLF-OC indicate the fLF is a potentially available energy and

  1. Combining Old and New Stable Isotope Techniques to Evaluate the Impact of Conservation Tillage on Soil Organic Carbon Dynamics and Stability

    International Nuclear Information System (INIS)

    Soil organic matter (SOM) is a major carbon pool. It is a crucial factor for soil quality including several soil physical properties and a major nutrient source for crops. It also plays a significant role in the global carbon cycle. Soils can act as a carbon sink or source depending on land use and agricultural management practices. Some practices such as conservation tillage or no-tillage could increase SOM stocks, particularly in the topsoil, but in the long term it remains to be seen if and how this SOM is stabilized (De Clercq et al., 2015; Govaerts et al., 2009). In order to evaluate the sustainability and efficiency of soil carbon sequestration measures and the impact of different management and environmental factors, information on SOM stability and mean residence time (MRT) is required. However, this information on SOM stability and MRT is expensive to determine via radiocarbon dating, precluding a wide spread use of stability measurements in soil science. But alternative methods based on stable carbon and nitrogen isotopes, can provide this information at a fraction of the cost

  2. Comparative study of ageing, heat treatment and accelerated carbonation for stabilization of municipal solid waste incineration bottom ash in view of reducing regulated heavy metal/metalloid leaching

    OpenAIRE

    Santos, Rafael; Mertens, Gilles; Salman, Muhammad; Cizer, Özlem; Gerven, Tom Van

    2013-01-01

    This study compared the performance of four different approaches for stabilization of regulated heavy metal and metalloid leaching from municipal solid waste incineration bottom ash (MSWI-BA): (i) short term (three months) heap ageing, (ii) heat treatment, (iii) accelerated moist carbonation, and (iv) accelerated pressurized slurry carbonation. Two distinct types of MSWI-BA were tested in this study: one originating from a moving-grate furnace incineration operation treating exclusively house...

  3. Functional Stability of a Mixed Microbial Consortium Producing PHA From Waste Carbon Sources

    Energy Technology Data Exchange (ETDEWEB)

    David N. Thompson; Erik R. Coats; William A. Smith; Frank J. Loge; Michael P. Wolcott

    2006-04-01

    Polyhydroxyalkanoates (PHAs) represent an environmentally-effective alternative to synthetic thermoplastics; however, current production practices are not sustainable. In this study, PHA production was accomplished in sequencing batch bioreactors utilizing real wastewaters and mixed microbial consortia from municipal activated sludge as inoculum. Polymer production reached 85%, 53%, and 10% of the cell dry weight from methanol-enriched pulp-and-paper mill foul condensate, fermented municipal primary solids, and biodiesel wastewater, respectively. Employing denaturing gradient gel electrophoresis of 16S-rDNA from PCR-amplified DNA extracts, distinctly different communities were observed between and within wastewaters following enrichment. Most importantly, functional stability was maintained despite differing and contrasting microbial populations.

  4. Carbon doped molybdenum disulfide nanosheets stabilized on graphene for the hydrogen evolution reaction with high electrocatalytic ability

    Science.gov (United States)

    Li, Yong; Wang, Jiao; Tian, Xike; Ma, Longlong; Dai, Chu; Yang, Chao; Zhou, Zhaoxin

    2016-01-01

    Fabricating a cost effective hydrogen evolution reaction catalyst without using precious metal elements is in crucial demand for environmentally-benign energy production. In this work, the thin and edge-rich molybdenum disulfide nanosheets, with carbon doped in the interlayers and decorated on graphene, were developed by a facile solvothermal process. The as-synthesized nanohybrids exhibited high catalytic ability for the hydrogen evolution electrochemical reaction with an onset overpotential of 0.165 mV and a Tafel slope of 46 mV dec-1. Furthermore, the prepared nanohybrids also showed better durability and stability. Our work may lead to a potential method for in situ production of metal carbide-sulphur hybrid nanomaterials with promising applications for the hydrogen evolution reaction.Fabricating a cost effective hydrogen evolution reaction catalyst without using precious metal elements is in crucial demand for environmentally-benign energy production. In this work, the thin and edge-rich molybdenum disulfide nanosheets, with carbon doped in the interlayers and decorated on graphene, were developed by a facile solvothermal process. The as-synthesized nanohybrids exhibited high catalytic ability for the hydrogen evolution electrochemical reaction with an onset overpotential of 0.165 mV and a Tafel slope of 46 mV dec-1. Furthermore, the prepared nanohybrids also showed better durability and stability. Our work may lead to a potential method for in situ production of metal carbide-sulphur hybrid nanomaterials with promising applications for the hydrogen evolution reaction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07370g

  5. Functional Stability Of A Mixed Microbial Consortia Producing PHA From Waste Carbon Sources

    Energy Technology Data Exchange (ETDEWEB)

    David N. Thompson; Erik R. Coats; William A. Smith; Frank J. Loge; Michael P. Wolcott

    2006-04-01

    Polyhydroxyalkanoates (PHAs), naturally-occurring biological polyesters that are microbially synthesized from a myriad of carbon sources, can be utilized as biodegradable substitutes for petroleum-derived thermoplastics. However, current PHA commercialization schemes are limited by high feedstock costs, the requirement for aseptic reactors, and high separation and purification costs. Bacteria indigenous to municipal waste streams can accumulate large quantities of PHA under environmentally controlled conditions; hence, a potentially more environmentally-effective method of production would utilize these consortia to produce PHAs from inexpensive waste carbon sources. In this study, PHA production was accomplished in sequencing batch bioreactors utilizing mixed microbial consortia from municipal activated sludge as inoculum, in cultures grown on real wastewaters. PHA production averaged 85%, 53%, and 10% of the cell dry weight from methanol-enriched pulp-and-paper mill foul condensate, fermented municipal primary solids, and biodiesel wastewater, respectively. The PHA-producing microbial consortia were examined to explore the microbial community changes that occurred during reactor operations, employing denaturing gradient gel electrophoresis (DGGE) of 16S-rDNA from PCR-amplified DNA extracts. Distinctly different communities were observed both between and within wastewaters following enrichment. More importantly, stable functions were maintained despite the differing and contrasting microbial populations.

  6. Structural stability of transparent conducting films assembled from length purified single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    J. M. Harris; G. R. S. Iyer; D. O. Simien; J. A. Fagan; J. Y. Huh; J. Y. Chung; S. D. Hudson; J. Obrzut; J. F. Douglas; C. M. Stafford; E. K. Hobbie

    2011-01-01

    Single-wall carbon nanotube (SWCNT) films show significant promise for transparent electronics applications that demand mechanical flexibility, but durability remains an outstanding issue. In this work, thin membranes of length purified single-wall carbon nanotubes (SWCNTs) are uniaxially and isotropically compressed by depositing them on prestrained polymer substrates. Upon release of the strain, the topography, microstructure, and conductivity of the films are characterized using a combination of optical/fluorescence microscopy, light scattering, force microscopy, electron microscopy, and impedance spectroscopy. Above a critical surface mass density, films assembled from nanotubes of well-defined length exhibit a strongly nonlinear mechanical response. The measured strain dependence reveals a dramatic softening that occurs through an alignment of the SWCNTs normal to the direction of prestrain, which at small strains is also apparent as an anisotropic increase in sheet resistance along the same direction. At higher strains, the membrane conductivities increase due to a compression-induced restoration of conductive pathways. Our measurements reveal the fundamental mode of elasto-plastic deformation in these films and suggest how it might be suppressed.

  7. Polyaniline-Coated Carbon Nanotube Ultrafiltration Membranes: Enhanced Anodic Stability for In Situ Cleaning and Electro-Oxidation Processes.

    Science.gov (United States)

    Duan, Wenyan; Ronen, Avner; Walker, Sharon; Jassby, David

    2016-08-31

    Electrically conducting membranes (ECMs) have been reported to be efficient in fouling prevention and destruction of aqueous chemical compounds. In the current study, highly conductive and anodically stable composite polyaniline-carbon nanotube (PANI-CNT) ultrafiltration (UF) ECMs were fabricated through a process of electropolymerization of aniline on a CNT substrate under acidic conditions. The resulting PANI-CNT UF ECMs were characterized by scanning electron microscopy, atomic force microscopy, a four-point conductivity probe, cyclic voltammetry, and contact angle goniometry. The utilization of the PANI-CNT material led to significant advantages, including: (1) increased electrical conductivity by nearly an order of magnitude; (2) increased surface hydrophilicity while not impacting membrane selectivity or permeability; and (3) greatly improved stability under anodic conditions. The membrane's anodic stability was evaluated in a pH-controlled aqueous environment under a wide range of anodic potentials using a three-electrode cell. Results indicate a significantly reduced degradation rate in comparison to a CNT-poly(vinyl alcohol) ECM under high anodic potentials. Fouling experiments conducted with bovine serum albumin demonstrated the capacity of the PANI-CNT ECMs for in situ oxidative cleaning, with membrane flux restored to its initial value under an applied potential of 3 V. Additionally, a model organic compound (methylene blue) was electrochemically transformed at high efficiency (90%) in a single pass through the anodically charged ECM. PMID:27525344

  8. Ferricyanide-backfilled cylindrical carbon fiber microelectrodes for in vivo analysis with high stability and low polarized potential.

    Science.gov (United States)

    Zhong, Peipei; Yu, Ping; Wang, Kai; Hao, Jie; Fei, Junjie; Mao, Lanqun

    2015-11-01

    The development of stable and reproducible methods for in vivo electrochemical monitoring of neurochemicals is of great physiological importance. In this study, we demonstrate ferricyanide-filled cylindrical carbon fiber microelectrodes (CFEs) of high stability and low polarized potential for in vivo electrochemical analysis. We first studied the voltammetric behavior of cylindrical CFEs by using a model system consisting of two separated cells each containing potassium ferricyanide (K3Fe(CN)6) or potassium ferrocyanide (K4Fe(CN)6). We observed that E1/2 values of the system were dependent on the ratio of the lengths of the cylindrical CFEs and of the concentrations of the redox species on both poles. Based on this property, we prepared the ferricyanide-backfilled cylindrical CFEs, and found that this kind of electrode exhibits a more stable current response and a lower polarized potential than the CFEs backfilled with KCl or Ru(NH3)6Cl3. Animal experiments with the ferricyanide-backfilled cylindrical CFEs demonstrate that this kind of electrode could be used for in vivo monitoring of neurochemical release with a high stability under some physiological conditions. PMID:26378690

  9. Activity, short-term stability (poisoning tolerance) and durability of carbon supported Pt-Pr catalysts for ethanol oxidation

    Science.gov (United States)

    Corradini, Patricia G.; Antolini, Ermete; Perez, Joelma

    2014-04-01

    Pt-Pr/C electrocatalysts were prepared by a modified formic acid method, and their activity for carbon monoxide and ethanol oxidation, their short term stability and durability were compared to that of commercial Pt/C and Pt-Sn/C (3:1) catalysts. By derivative voltammetry (DV) it was found that ethanol electro-oxidation takes place by two main pathways at different potentials. It was observed that, in the presence of Pr, ethanol electro-oxidation takes place mostly through the pathway at lower potential, which is the most interesting for fuel cell application. The Pt-Pr/C catalysts were less tolerant to poisoning by ethanol oxidation intermediate species than Pt/C. Durability test by a repetitive potential cycling under Ar atmosphere revealed a good structural stability of Pt-Pr/C catalysts. A repetitive potential cycling under CO atmosphere carried out on the Pt-Pr/C (1:1) catalyst, instead, indicated a structural change, likely by formation of a core-shell structure.

  10. Crystallization behavior and thermal stability of poly(butylene succinate)/poly(propylene carbonate) blends prepared by novel vane extruder

    Science.gov (United States)

    Chen, Rongyuan; Zou, Wei; Zhang, Haichen; Zhang, Guizhen; Qu, Jinping

    2016-03-01

    This work focused on the study of crystallization behavior and thermal stability of degradable poly(butylene succinate) (PBS) and poly(propylene carbonate) (PPC) blends prepared by vane extruder based on elongation force field, which is novel equipment for polymer processing. Dicumyl peroxide (DCP) was applied in this work as compatibilizer for PBS/PPC blend. Crystallization behavior and melting behavior of the blends were investigated by differential scanning calorimetry (DSC) testing. Thermal stability of the blends was studied by thermogravimetric (TG) testing. Furthermore, the melt flow indices (MFI) of the blends were examined by a MFI instrument. The results showed that the crystallization temperature of PBS decreased with the addition of PPC and DCP. The glass transition temperature of PPC increased and the melting temperature of the blend increased with the addition of PPC and DCP, which indicated that the entanglement between the molecular chains of PBS and PPC was enhanced. Thermogravimetric analysis showed that a two-step decomposition process of the blend occurred due to the different thermal resistance of PBS and PPC, and the addition of PBS reduced the decomposition rate of PPC. Moreover, the addition of PBS improved the melt flow property of PPC.

  11. The Ferrocyanide/Stabilized Carbon System, a New Class of High Rate, Long Cycle Life, Aqueous Electrolyte Batteries

    KAUST Repository

    Huggins, R. A.

    2013-02-21

    Transient energy sources, such as wind and solar systems are getting increased attention. Their integration with the energy distribution grid requires methods for energy storage. The required characteristics of this type of storage are quite different from those for energy storage in portable devices. Size and weight are not so important. Instead, matters such as power, cost, calendar life, cycle life, and safety become paramount. A new family of hexacyanoferrate materials with the same open framework crystal structure as Prussian Blue has been recently developed with characteristics ideally suited for this type of application. Several monovalent cations can be rapidly and reversibly inserted into these materials, with very little crystallographic distortion, leading to high rates and long cycle lives. In addition, a new type of composite negative electrode material has been developed that has the rapid kinetics typical of carbon electrodes, but with a potential that varies little with the state of charge. The result is the development of a new battery system, the ferrocyanide/stabilized carbon, MHCF-SC, system. © 2013 The Electrochemical Society.

  12. Enhanced methanol oxidation activity and stability of Pt particles anchored on carbon-doped TiO2 nanocoating support

    Science.gov (United States)

    Qin, Yuan-Hang; Li, Yunfeng; Lv, Ren-Liang; Wang, Tie-Lin; Wang, Wei-Guo; Wang, Cun-Wen

    2015-03-01

    In this work, carbon-doped TiO2 nanocoating (TiO2-C) was prepared by a sol-gel process and employed as the support of Pt nanoparticles for methanol oxidation reaction (MOR). The obtained Pt/TiO2-C catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. XRD characterization shows that the average crystallite sizes of Pt particles and TiO2-C support are 2.7 and 6.5 nm, respectively. TEM characterizations show that Pt particles are highly dispersed on TiO2 nanocoating, which preserves its nanoscale structure without no apparent sintering after carbon doping. XPS characterization shows that the Pt particles anchored on TiO2-C exhibit positively shifted binding energies of Pt 4f. Cyclic voltammetry (CV) and chronoamperometry (CA) characterizations show that TiO2-C has a greatly enhanced electrical conductivity and Pt/TiO2-C catalyst has better electrocatalytic activity and stability than Pt/C catalyst for MOR, which could be attributed to the high dispersion of Pt particles on TiO2-C support, the strong metal-support interactions between Pt particles and TiO2-C support, and the rich active -OH species on TiO2-C support.

  13. Integrating microbial physiology and physiochemical principles in soils with the MIcrobial-MIneral Carbon Stabilization (MIMICS model

    Directory of Open Access Journals (Sweden)

    W. R. Wieder

    2014-01-01

    Full Text Available Previous modeling efforts document divergent responses of microbial explicit soil biogeochemistry models when compared to traditional models that implicitly simulate microbial activity, particularly following environmental perturbations. However, microbial models are needed that capture current soil biogeochemical theories emphasizing the relationships between litter quality, functional differences in microbial physiology, and the physical protection of microbial byproducts in forming stable soil organic matter (SOM. To address these limitations we introduce the MIcrobial-MIneral Carbon Stabilization (MIMICS model. In MIMICS, the turnover of litter and SOM pools are governed by temperature sensitive Michaelis–Menten kinetics and the activity of two physiologically distinct microbial functional types. The production of microbial residues through microbial turnover provides inputs to SOM pools that are considered physically or chemically protected. Soil clay content determines the physical protection of SOM in different soil environments. MIMICS adequately simulates the mean rate of leaf litter decomposition observed at a temperate and boreal forest sites, and captures observed effects of litter quality on decomposition rates. Initial results from MIMICS suggest that soil C storage can be maximized in sandy soils with low-quality litter inputs, whereas high-quality litter inputs may maximize SOM accumulation in finely textured soils that physically stabilize microbial products. Assumptions in MIMICS about the degree to which microbial functional types differ in the production, turnover, and stabilization of microbial residues provides a~mechanism by which microbial communities may influence SOM dynamics in mineral soils. Although further analyses are needed to validate model results, MIMICS allows us to begin exploring theoretical interactions between substrate quality, microbial community abundance, and the formation of stable SOM.

  14. Ductile flow in sub-volcanic carbonate basement as the main control for edifice stability: New experimental insights

    Science.gov (United States)

    Bakker, Richard R.; Violay, Marie E. S.; Benson, Philip M.; Vinciguerra, Sergio C.

    2015-11-01

    Limestone in volcanic basements has been identified as a hazard in terms of edifice stability due to the propensity of calcite to decompose into lime and CO2 at high temperatures (>600 °C), causing a decrease in mechanical strength. To date, such hypotheses have been tested by experiments performed at ambient pressure. The present work determines the mechanical strength of limestone under sub-volcanic conditions of pressure and temperature and evaluates the effect of calcite decomposition. To this end, we use Mt. Etna as a case study, deforming sub-Etnean carbonate samples under triaxial compression using a Paterson deformation apparatus. We evaluate the effect of thermal decomposition of calcite on sample strength by comparing closed and open systems and measuring the permeability evolution under static conditions. Mechanical and micro-structural observations at a constant strain rate of 10-5 s-1 and at a confining pressure of 50 MPa indicate that the rocks are brittle up to and including 300 °C. At higher temperatures the deformation becomes macroscopically ductile, i.e., deformation is distributed throughout the sample. The brittle to ductile transition is accompanied by an irreversible permeability decrease from ∼10-17 to ∼10-19 m2 between 200 and 600 °C. We present new evidence that permanent change in permeability is due to ductile processes closing the initial pore space. Samples deformed at temperatures up to 900 °C do not contain any decarbonation products. At these temperatures, permeability is sufficiently low to permit CO2 pore pressures to increase, thereby increasing local CO2 fugacity, which in turn strongly limits the decarbonation reaction. We note that, for non-pure calcite rocks, permeability might be sufficient to allow decarbonation reactions to occur. As such, variability in lithologies may slightly influence the efficiency of decarbonation reactions. We conclude that, in a closed system, the instability of Mt. Etna is related to high

  15. Initial characterization of processes of soil carbon stabilization using forest stand-level radiocarbon enrichment

    Energy Technology Data Exchange (ETDEWEB)

    Swanston, C W; Torn, M S; Hanson, P J; Southon, J R; Garten, C T; Hanlon, E M; Ganio, L

    2004-01-15

    Although the rates and mechanisms of soil organic matter (SOM) stabilization are difficult to observe directly, radiocarbon has proven an effective tracer of soil C dynamics, particularly when coupled with practical fractionation schemes. To explore the rates of C cycling in temperate forest soils, we took advantage of a unique opportunity in the form of an inadvertent stand-level {sup 14}C-labeling originating from a local industrial release. A simple density fractionation scheme separated SOM into inter-aggregate particulate organic matter (free light fraction, free LF), particulate organic matter occluded within aggregates (occluded LF), and organic matter that is complexed with minerals to form a dense fraction (dense fraction, DF). Minimal agitation and density separation was used to isolate the free LF. The remaining dense sediment was subjected to physical disruption and sonication followed by density separation to separate it into occluded LF and DF. The occluded LF had higher C concentrations and C:N ratios than the free LF, and the C concentration in both light fractions was ten times that of the DF. As a result, the light fractions together accounted for less than 4% of the soil by weight, but contained 40% of the soil C in the 0-15 cm soil increment. Likewise, the light fractions were less than 1% weight of the 15-30 cm increment, but contained more than 35% of the soil C. The degree of SOM protection in the fractions, as indicated by {Delta}{sup 14}C, was different. In all cases the free LF had the shortest mean residence times. A significant depth by fraction interaction for {sup 14}C indicates that the relative importance of aggregation versus organo-mineral interactions for overall C stabilization changes with depth. The rapid incorporation of {sup 14}C label into the otherwise depleted DF shows that this organo-mineral fraction comprises highly stable material as well as more recent inputs.

  16. Organic carbon, water repellency and soil stability to slaking at aggregate and intra-aggregate scales

    Science.gov (United States)

    Jordán López, Antonio; García-Moreno, Jorge; Gordillo-Rivero, Ángel J.; Zavala, Lorena M.; Cerdà, Artemi; Alanís, Nancy; Jiménez-Compán, Elizabeth

    2015-04-01

    Water repellency (WR) is a property of some soils that inhibits or delays water infiltration between a few seconds and days or weeks. Inhibited or delayed infiltration contributes to ponding and increases runoff flow generation, often increasing soil erosion risk. In water-repellent soils, water infiltrates preferentially through cracks or macropores, causing irregular soil wetting patterns, the development of preferential flow paths and accelerated leaching of nutrients. Although low inputs of hydrophobic organic substances and high mineralization rates lead to low degrees of WR in cropped soils, it has been reported that conservative agricultural practices may induce soil WR. Although there are many studies at catchment, slope or plot scales very few studies have been carried out at particle or aggregate scale. Intra-aggregate heterogeneity of physical, biological and chemical properties conditions the transport of substances, microbial activity and biochemical processes, including changes in the amount, distribution and chemical properties of organic matter. Some authors have reported positive relationships between soil WR and aggregate stability, since it may delay the entry of water into aggregates, increase structural stability and contribute to reduce soil erosion risk. Organic C (OC) content, aggregate stability and WR are therefore strongly related parameters. In the case of agricultural soils, where both the type of management as crops can influence all these parameters, it is important to evaluate the interactions among them and their consequences. Studies focused on the intra-aggregate distribution of OC and WR are necessary to shed light on the soil processes at a detailed scale. It is extremely important to understand how the spatial distribution of OC in soil aggregates can protect against rapid water entry and help stabilize larger structural units or lead to preferential flow. The objectives of this research are to study [i] the OC content and the

  17. Reforestation with native mixed-species plantings in a temperate continental climate effectively sequesters and stabilizes carbon within decades.

    Science.gov (United States)

    Cunningham, Shaun C; Cavagnaro, Timothy R; Mac Nally, Ralph; Paul, Keryn I; Baker, Patrick J; Beringer, Jason; Thomson, James R; Thompson, Ross M

    2015-04-01

    Reforestation has large potential for mitigating climate change through carbon sequestration. Native mixed-species plantings have a higher potential to reverse biodiversity loss than do plantations of production species, but there are few data on their capacity to store carbon. A chronosequence (5-45 years) of 36 native mixed-species plantings, paired with adjacent pastures, was measured to investigate changes to stocks among C pools following reforestation of agricultural land in the medium rainfall zone (400-800 mm yr(-1)) of temperate Australia. These mixed-species plantings accumulated 3.09 ± 0.85 t C ha(-1) yr(-1) in aboveground biomass and 0.18 ± 0.05 t C ha(-1) yr(-1) in plant litter, reaching amounts comparable to those measured in remnant woodlands by 20 years and 36 years after reforestation respectively. Soil C was slower to increase, with increases seen only after 45 years, at which time stocks had not reached the amounts found in remnant woodlands. The amount of trees (tree density and basal area) was positively associated with the accumulation of carbon in aboveground biomass and litter. In contrast, changes to soil C were most strongly related to the productivity of the location (a forest productivity index and soil N content in the adjacent pasture). At 30 years, native mixed-species plantings had increased the stability of soil C stocks, with higher amounts of recalcitrant C and higher C:N ratios than their adjacent pastures. Reforestation with native mixed-species plantings did not significantly change the availability of macronutrients (N, K, Ca, Mg, P, and S) or micronutrients (Fe, B, Mn, Zn, and Cu), content of plant toxins (Al, Si), acidity, or salinity (Na, electrical conductivity) in the soil. In this medium rainfall area, native mixed-species plantings provided comparable rates of C sequestration to local production species, with the probable additional benefit of providing better quality habitat for native biota. These results

  18. Study of the stabilization of uranium dioxide fuel with carbon dioxide gas

    International Nuclear Information System (INIS)

    Stabilization of the UO2 is an important step in the manufacturing process of fuel powder. After the reduction the UO2 powder is made chemically passive by slight oxidation to quite a large extent fixed by specifications that allow to storage powder till the sintering process is performed. In this work the UO2 powder is oxidized with a versatile automated physisorption/chemisorption analyzer as to generate adsorption isotherms with different pressures and temperatures of gaseous CO2 sequentially added to the samples. The reduction process is carried out in the same device as to obtain the same fluorite structure UO2.00 to perform control oxidation experiences so to get 2.04 and 2.06 UO2 powder. To check the extend of oxidation of UO2 powder, samples are characterized for O/U ratio analyses. The advantage of using CO2 is the possibility of high temperature controlled oxidative step which definitely is very beneficial for fuel manufacturing from an economic point of view. (author)

  19. Limestone-particle-stabilized macroemulsion of liquid and supercritical carbon dioxide in water for ocean sequestration.

    Science.gov (United States)

    Golomb, D; Barry, E; Ryan, D; Lawton, C; Swett, P

    2004-08-15

    When liquid or supercritical CO2 is mixed with an aqueous slurry of finely pulverized (1-20 microm) limestone (CaCO3) in a high-pressure reactor, a macroemulsion is formed consisting of droplets of CO2 coated with a sheath of CaCO3 particles dispersed in water. The coated droplets are called globules. Depending on the globule diameter and the CaCO3 sheath thickness, the globules sink to the bottom of the water column, are neutrally buoyant, or float on top of the water. The CaCO3 particles are lodged at the CO2/ H2O interface, preventing the coalescence of the CO2 droplets, and thus stabilizing the CO2-in-water emulsion. We describe the expected behavior of a CO2/H2O/CaCO3 emulsion plume released in the deep ocean for sequestration of CO2 in the ocean to ameliorate global warming. Depending on the amount of CO2 injected, the dense plume will descend a few hundred meters while entraining ambient seawater until it acquires neutral buoyancy in the stratified ocean. After equilibration, the globules will rain out from the plume toward the ocean bottom. This mode of CO2 release will prevent acidification of the seawater around the release point, which is a major environmental drawback of ocean sequestration of liquid, unemulsified CO2. PMID:15382876

  20. Carotenoids, Fatty Acid Composition and Heat Stability of Supercritical Carbon Dioxide-Extracted-Oleoresins

    Directory of Open Access Journals (Sweden)

    Antonella Leone

    2012-03-01

    Full Text Available The risk of chronic diseases has been shown to be inversely related to tomato intake and the lycopene levels in serum and tissue. Cis-isomers represent approximately 50%–80% of serum lycopene, while dietary lycopene maintains the isomeric ratio present in the plant sources with about 95% of all-trans-lycopene. Supercritical CO2 extraction (S-CO2 has been extensively developed to extract lycopene from tomato and tomato processing wastes, for food or pharmaceutical industries, also by using additional plant sources as co-matrices. We compared two S-CO2-extracted oleoresins (from tomato and tomato/hazelnut matrices, which showed an oil-solid bi-phasic appearance, a higher cis-lycopene content, and enhanced antioxidant ability compared with the traditional solvent extracts. Heat-treating, in the range of 60–100 °C, led to changes in the lycopene isomeric composition and to enhanced antioxidant activity in both types of oleoresins. The greater stability has been related to peculiar lycopene isomer composition and to the lipid environment. The results indicate these oleoresins are a good source of potentially healthful lycopene.

  1. Functionalization of Metal-Organic Frameworks for Enhanced Stability under Humid Carbon Dioxide Capture Conditions.

    Science.gov (United States)

    Andirova, Dinara; Lei, Yu; Zhao, Xiaodan; Choi, Sunho

    2015-10-26

    Metal-organic frameworks (MOFs) have been highlighted recently as promising materials for CO2 capture. However, in practical CO2 capture processes, such as capture from flue gas or ambient air, the adsorption properties of MOFs tend to be harmed by the presence of moisture possibly because of the hydrophilic nature of the coordinatively unsaturated sites (CUSs) within their framework. In this work, the CUSs of the MOF framework are functionalized with amine-containing molecules to prevent structural degradation in a humid environment. Specifically, the framework of the magnesium dioxybenzenedicarboxylate (Mg/DOBDC) MOF was functionalized with ethylenediamine (ED) molecules to make the overall structure less hydrophilic. Structural analysis after exposure to high-temperature steam showed that the ED-functionalized Mg/DOBDC (ED-Mg/DOBDC) is more stable under humid conditions, than Mg/DOBDC, which underwent drastic structural changes. ED-Mg/DOBDC recovered its CO2 adsorption capacity and initial adsorption rate quite well as opposed to the original Mg/DOBDC, which revealed a significant reduction in its capture capacity and kinetics. These results suggest that the amine-functionalization of the CUSs is an effective way to enhance the structural stability of MOFs as well as their capture of humid CO2 . PMID:26367016

  2. Plasma oxidation and stabilization of electrospun polyacrylonitrile nanofiber for carbon nanofiber formation

    Science.gov (United States)

    Hamideh Mortazavi, S.; Pilehvar, Soheil; Ghoranneviss, Mahmood; Hosseinnejad, M. T.; Zargham, Shamim; Mirarefi, Ali A.; Mirarefi, Amir Y.

    2013-11-01

    The effect of plasma treatment on the stabilization of copolymer P(AN-MA) containing 6.1 mol% methyl acrylate (MA) prepared by an electrospinning technique has been investigated at various oxygen contents (10 %, 20 % and 30 %) and different exposure times. The morphology and chemical structural evolution of electrospun and oxidized nanofibers were studied using field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). FT-IR analysis indicated that the treated nanofibers were effectively oxidized under different contents of oxygen and prolonged plasma exposure times by increasing the peak intensities of polar groups at 1730 and 3400 cm-1 corresponding to C=O stretching band and OH stretching vibration mode, respectively. Additionally, a reduction in the extent of the cyclization reaction is observed with further increase in exposure times and contents of oxygen, which implies lower conversion of C≡N bands into C=N ones in the copolymer chain. According to the FE-SEM studies, the surfaces of the treated nanofibers were completely etched after 15 min of treatment due to the existence of strong ion bombardment and a reduction in the average fiber diameters was observed.

  3. Functionalization of Metal-Organic Frameworks for Enhanced Stability under Humid Carbon Dioxide Capture Conditions.

    Science.gov (United States)

    Andirova, Dinara; Lei, Yu; Zhao, Xiaodan; Choi, Sunho

    2015-10-26

    Metal-organic frameworks (MOFs) have been highlighted recently as promising materials for CO2 capture. However, in practical CO2 capture processes, such as capture from flue gas or ambient air, the adsorption properties of MOFs tend to be harmed by the presence of moisture possibly because of the hydrophilic nature of the coordinatively unsaturated sites (CUSs) within their framework. In this work, the CUSs of the MOF framework are functionalized with amine-containing molecules to prevent structural degradation in a humid environment. Specifically, the framework of the magnesium dioxybenzenedicarboxylate (Mg/DOBDC) MOF was functionalized with ethylenediamine (ED) molecules to make the overall structure less hydrophilic. Structural analysis after exposure to high-temperature steam showed that the ED-functionalized Mg/DOBDC (ED-Mg/DOBDC) is more stable under humid conditions, than Mg/DOBDC, which underwent drastic structural changes. ED-Mg/DOBDC recovered its CO2 adsorption capacity and initial adsorption rate quite well as opposed to the original Mg/DOBDC, which revealed a significant reduction in its capture capacity and kinetics. These results suggest that the amine-functionalization of the CUSs is an effective way to enhance the structural stability of MOFs as well as their capture of humid CO2 .

  4. Ultrafine-Grained Structure and its Thermal Stability in Low-Carbon Steel

    Science.gov (United States)

    Korznikov, A. V.; Safarov, I. M.; Galeyev, R. M.; Sergeev, S. N.; Potekaev, A. I.

    2015-11-01

    The influence of annealing temperature on ultrafine-grained structure (UFG) of low-carbon steel 05G2MFB, produced by multiple isothermal forging (MIF) and warm rolling is investigated. Following 1-hour annealing (from 20 to 550°C), the fibrous UFG-structure formed as a result of rolling remains virtually the same. The equiaxial UFG-structure is found to be stable as the annealing temperature is increased up to 600°C. An examination of the resulting UFG-states by the method of electron backscatter diffraction (EBSD) provided a way to identify the differences in softening processes for a number of structure types. When the temperature of annealing treatment of as-rolled steel specimens is increased to 600°C, the fraction of low-angle boundaries (LAB) is found to remain at about 56%, while the average grain/subgrain size in the rod cross-section increases from 0.4 to 0.9 μm. In the MIF-processed specimens, an increase in the annealing temperature up to 625°C gives rise to a gradual decrease in the fraction of LAGBs from 53 to 30%, with the average grain/subgrain size increasing from 0.4 to 0.6 μm.

  5. Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals

    Directory of Open Access Journals (Sweden)

    M. Schrumpf

    2012-09-01

    Full Text Available Conceptual models suggest that stability and age of organic carbon (OC in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Various tools like density fractionation, mineralization experiments, and radiocarbon analyses have been used to study the importance of these mechanisms. We systematically apply them to a range of European soils to test whether general controls emerge even for soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled in 10 cm depth intervals to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions – fLF, occluded light fractions – oLF, heavy fractions – HF were analysed for OC, total nitrogen (TN, δ13C, and Δ14C. Bulk samples were also incubated to determine mineralizable OC.

    Declining OC-normalized CO2 release and increasing age with soil depth confirm greater stability of OC in subsoils across sites. Depth profiles of LF-OC matched those of roots, which in turn reflect plant functional types in soil profiles not subject to ploughing. Modern Δ14C signatures and positive correlation between mineralizable C and fLF-OC indicate the fLF is an easily available energy and nutrient source for subsurface microbes. Fossil C derived from the geogenic parent material affected the age of OC especially in the LF at three study sites. The overall importance of OC stabilization by binding to minerals was demonstrated by declining OC-normalized CO2 release rates with increasing contributions of HF-OC to bulk soil OC and the low Δ14C values of HF-OC. The stability of HF-OC was greater in subsoils than in topsoils; nevertheless, a portion of HF-OC was active throughout the profile. The decrease in Δ14C (increase

  6. Effect of sustainable land management practices on soil aggregation and stabilization of organic carbon in semiarid mediterranean ecosystems

    Science.gov (United States)

    Garcia-Franco, Noelia; Albaladejo, Juan; Almagro, María; Wiesmeier, Martin; Martínez-Mena, María

    2016-04-01

    Arid and semiarid regions represent about 47% of the total land area of the world (UNEP, 1992). At present, there is a priority interest for carbon (C) sequestration in drylands. These areas are considered as very fragile ecosystems with low organic carbon (OC) saturation, and potentially, high capacity for soil OC sequestration. In addition, the restoration of these areas is one of the major challenges for scientists, who will be able to identify and recommended the best land uses and sustainable land management (SLM) practices for soil conservation and mitigation of climate change in these environments. In this regard, in semiarid Mediterranean ecosystems there is an urgent need for the implementation of SLM practices regardless of land-use type (forest, agricultural and shrubland) to maintain acceptable levels of soil organic matter (SOM) and the physico-chemical protection of the OC. Long- and short-term effects of SLM practices on soil aggregation and SOC stabilization were studied in two land uses. The long-term experiment was conducted in a reforestation area with Pinus halepensis Mill., where two afforestation techniques were implemented 20 years ago: a) mechanical terracing with a single application of organic waste of urban soil refuse, and b) mechanical terracing without organic amendment. An adjacent shrubland was considered as the reference plot. The short-term experiment was conducted in a rain-fed almond (Prunus dulcis Mill., var. Ferragnes) orchard where two SLM practices were introduced 4 years ago: a) reduced tillage plus green manure, and b) no tillage. Reduced tillage was considered as the reference plot given that it is the habitual management practice. Four aggregate size classes were differentiated by sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, different organic C fractions corresponding with active

  7. Structural and elastic properties and stability characteristics of oxygenated carbon nanotubes under physical adsorption of polymers

    Energy Technology Data Exchange (ETDEWEB)

    Ansari, R., E-mail: r_ansari@guilan.ac.ir [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Ajori, S. [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Rouhi, S. [Department of Mechanical Engineering, Langroud Branch, Islamic Azad University, Langroud (Iran, Islamic Republic of)

    2015-03-30

    Highlights: • Buckling of functionalized CNTs under physical adsorption of polymer is studied. • Molecular dynamics simulations are employed for the study. • Values of the critical buckling load and critical strain are shown to increase. • Values of Young's modulus and their variations are dependent on adsorbed polymer type. - Abstract: The importance of covalent and non-covalent functionalization approaches for modification the properties of carbon nanotubes is being more widely recognized. To this end, elastic properties and buckling behavior of oxygenated CNT with atomic oxygen and hydroxyl under physical adsorption of PE (Polyethylene) and PEO (Poly (ethylene oxide)) are determined through employing the molecular dynamics (MD) simulations. The results demonstrate that non-covalent bonding of polymer on the surface of oxygenated CNT causes reductions in the variations of critical buckling load and critical strain compared to oxygenated CNTs. Critical buckling load and critical strain of oxygenated CNT/polymer are higher than those of oxygenated CNT. Also, it is demonstrated that critical buckling load and critical strain values in the case of oxygenated CNT/polymer are independent of polymer type unlike the value of Young's modulus. It is shown that variations of Young's modulus decrease as PE adsorbed on the surface of oxygenated CNT. Moreover, the presence of oxygen atom on PEO chain leads to bigger variations of Young's modulus with weight percentage of chemisorbed component, i.e. atomic oxygen and hydroxyl. It is also demonstrated that Young's modulus reduces more considerably in the presence of PEO chain compared to PE one.

  8. Study on expanded graphite/phenolic resin carbon composite bipolar plate%膨胀石墨/酚醛树脂复合材料双极板研究

    Institute of Scientific and Technical Information of China (English)

    陈惠; 刘洪波; 涂文懋; 杨荔; 杨丽; 何月德

    2011-01-01

    Expanded graphite/phenolic resin composite bipolar plates used for polymer electrolyte membrane fuel cells (PEMFC) were prepared through a compression molding process. The conductivity and flexural strength of the composite bipolar plate were measured with four-point probe method and three point bending technique respectively. The influences of resin content, molding pressure, additive content and adding manner of additive on the performance of the composite bipolar plate were investigated. The results show that resin content, molding pressure, additive content and adding manner of additive have a grate influence on the performance of the composite bipolar plate. Resin content of 20%-30% and molding pressure of 10-12 Mpa are appropriate. Influences of carbon black on the properities of composite bipolar plate are complicated. In the range of carbon black used in experiment, the conductivity increases and flexural strength increases firstly and then decreases with the increase of the carbon black. When carbon black is added to resin, the properities of composite bipolar plate are better.%以膨胀石墨为导电骨料、炭黑为添加剂、酚醛树脂为黏结剂,采用模压成形工艺制备质子交换膜燃料电池用膨胀石墨/酚醛树脂复合材料双极板.考察树脂含量、成形压力、添加剂用量及添加剂加入方式对复合材料双极板性能的影响.研究结果表明:上述因素对复合材料双极板的性能影响较大,黏结剂的加入量(质量分数)为20%-30%、压力在10~12 MPa较为合适;炭黑对复合材料双极板的性能影响比较复杂,在实验用炭黑范围内,随着炭黑用量的增加,电导率增大较快,抗折强度先增大后减小;在复合材料的混料过程中,将炭黑添加在树脂中,制备的复合材料双极板性能比炭黑添加在膨胀石墨性能好.

  9. On Interlayer Stability and High-Cycle Simulator Performance of Diamond-Like Carbon Layers for Articulating Joint Replacements

    Directory of Open Access Journals (Sweden)

    Kerstin Thorwarth

    2014-06-01

    Full Text Available Diamond like carbon (DLC coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and −3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES and cross section scanning electron microscopy (SEM analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen, limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD. It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs

  10. Organo-mineral interactions promote greater soil organic carbon stability under aspen in semi-arid montane forests in Utah

    Science.gov (United States)

    Van Miegroet, H.; Roman Dobarco, M.

    2014-12-01

    Forest species influence soil organic carbon (SOC) storage through litter input, which in interaction with soil microclimate, texture and mineralogy, lead to different SOC stabilization and storage patterns. We sampled mineral soil (0-15 cm) across the ecotone between aspen (Populus tremuloides) and mixed conifers stands (Abies lasiocarpa and Pseudotsuga menziesii) in semi-arid montane forests from Utah, to investigate the influence of vegetation vs. site characteristics on SOC stabilization, storage and chemistry. SOC was divided into light fraction (LF), mineral-associated SOC in the silt and clay fraction (MoM), and a dense subfraction > 53 μm (SMoM) using wet sieving and electrostatic attraction. SOC decomposability and solubility was derived from long term laboratory incubations and hot water extractions (HWE). Fourier transform infrared spectroscopy (FTIR) was used to study differences in chemical functional groups in LF and MoM. Vegetation cover did not affect SOC storage (47.0 ± 16.5 Mg C ha-1), SOC decomposability (cumulative CO2-C release of 93.2 ± 65.4 g C g-1 C), or SOC solubility (9.8 ± 7.2 mg C g-1 C), but MoM content increased with presence of aspen [pure aspen (31.2 ± 15.1 Mg C ha-1) > mixed (25.7 ± 8.8 Mg C ha-1) > conifer (22.8 ± 9.0 Mg C ha-1)]. Organo-mineral complexes reduced biological availability of SOC, indicated by the negative correlation between silt+clay (%) and decomposable SOC per gram of C (r = -0.48, p = 0.001) or soluble SOC (r = -0.59, p plant or microbial origin. FTIR spectra clustered by sites with similar parent material rather than by vegetation cover. This suggests that initial differences in litter chemistry between aspen and conifers converged into similar MoM chemistry within sites.

  11. Enhancement of electron emission and long-term stability of tip-type carbon nanotube field emitters via lithium coating

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong-Pil [Health and Medical Equipment R and D Team, Samsung Electronics, Suwon, Gyeonggi-do 443-742 (Korea, Republic of); Chang, Han-Beet; Kim, Bu-Jong [Dept. of Electronic Systems Engineering, Hanyang University, Ansan, Gyeonggi-do 426-791 (Korea, Republic of); Park, Jin-Seok, E-mail: jinsp@hanyang.ac.kr [Dept. of Electronic Systems Engineering, Hanyang University, Ansan, Gyeonggi-do 426-791 (Korea, Republic of)

    2013-01-01

    Carbon nanotubes (CNTs) were deposited on conical tip-type substrates via electrophoresis and coated with lithium (Li) thin films with diverse thicknesses via electroplating. For the as-deposited (i.e., without Li coating) CNT, the turn-on (or triggering) electric field was 0.92 V/μm, and the emission current, which was generated at an applied field of 1.2 V/μm was 56 μA. In the case of the 4.7 nm-thick Li-coated CNT, the turn-on field decreased to 0.65 V/μm and the emission current at the same applied field increased more than ten times to 618 μA. The analysis based on the Kelvin probe measurement and Fowler–Nordheim theory indicated that the coating of Li caused a loss in the structural-aspect-ratio of the CNTs and it reduced their effective work functions from 5.36 eV to 4.90 eV, which led to a great improvement of their electron emission characteristics. The results obtained in this study also showed that the long-term emission stability could be enhanced by the coating of thin Li films on CNTs. - Highlights: ► CNTs are deposited via electrophoretic deposition (EPD). ► Thin films of Li are coated on CNTs via electroplating, without plasma damage. ► Li coating enhanced field emission properties and emission stability of CNTs. ► The effective work functions and field enhancement factors of CNTs are evaluated.

  12. Soil Organic Carbon Storage and Stability in the Aspen-Conifer Ecotone in Montane Forests in Utah, USA

    Directory of Open Access Journals (Sweden)

    Mercedes Román Dobarco

    2014-04-01

    Full Text Available To assess the potential impact of conifer encroachment on soil organic carbon (SOC dynamics and storage in montane aspen-conifer forests from the interior western US, we sampled mineral soils (0–15 cm across the aspen-conifer ecotones in southern and northern Utah and quantified total SOC stocks, stable SOC (i.e., mineral-associated SOC (MoM, labile SOC (i.e., light fraction (LF, decomposable (CO2 release during long-term aerobic incubations and soluble SOC (hot water extractable organic carbon (HWEOC. Total SOC storage (47.0 ± 16.5 Mg C ha−1 and labile SOC as LF (14.0 ± 7.10 Mg C ha−1, SOC decomposability (cumulative released CO2-C of 5.6 ± 3.8 g C g−1 soil or HWEOC (0.6 ± 0.6 mg C g−1 soil did not differ substantially with vegetation type, although a slight increase in HWEOC was observed with increasing conifer in the overstory. There were statistically significant differences (p = 0.035 in stable MoM storage, which was higher under aspen (31.2 ± 15.1 Mg C ha−1 than under conifer (22.8 ± 9.0 Mg C ha−1, with intermediate values under mixed (25.7 ± 8.8 Mg C ha−1. Texture had the greatest impact on SOC distribution among labile and stable fractions, with increasing stabilization in MoM and decreasing bio-availability of SOC with increasing silt + clay content. Only at lower silt + clay contents (40%–70% could we discern the influence of vegetation on MoM content. This highlights the importance of chemical protection mechanisms for long-term C sequestration.

  13. Application of δ13C and δ15N isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms

    Directory of Open Access Journals (Sweden)

    M. Sommer

    2011-10-01

    Full Text Available Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. Analysis of δ13C and δ15N isotopic signatures of stabilized OM fractions along with soil mineral characteristics may yield important information about OM-mineral associations and their processing history. We anlayzed the δ13C and δ15N isotopic signatures from two organic matter (OM fractions along with soil mineral proxies to identify the likely binding mechanisms involved. We analyzed OM fractions hypothesized to contain carbon stabilized through organo-mineral complexes: (1 OM separated chemically with sodium pyrophosphate (OM(PY and (2 OM occluded in micro-structures found in the chemical extraction residue (OM(ER. Because the OM fractions were separated from five different soils with paired forest and arable land use histories, we could address the impact of land use change on carbon binding and processing mechanisms. We used partial least squares regression to analyze patterns in the isotopic signature of OM with established mineral and chemical proxies indicative for certain binding mechanisms. We found different mechanisms predominate in each land use type. For arable soils, the formation of OM(PY-Ca-mineral associations was identified as an important OM binding mechanism. Therefore, we hypothesize an increased stabilization of microbial processed OM(PY through Ca2+ interactions. In general, we found the forest soils to contain on average 10% more stabilized carbon relative to total carbon stocks, than the agricultural counter part. In forest soils, we found a positive relationship between isotopic signatures of OM(PY and the ratio of soil organic carbon content to soil surface area (SOC/SSA. This indicates that the OM(PY fractions of forest soils represent layers of slower exchange not directly attached to mineral surfaces. From the isotopic composition

  14. Long-term leaching behavior of phenol in cement/activated-carbon solidified/stabilized hazardous waste.

    Science.gov (United States)

    Liu, Jianguo; Nie, Xiaoqin; Zeng, Xianwei; Su, Zhaoji

    2013-01-30

    The long-term leaching behavior of phenol in solidified/stabilized (S/S) hazardous wastes cured for 28 d with different amounts of activated carbon (AC) was investigated using synthetic inorganic acid (H(2)SO(4):HNO(3) = 2:1, pH = 3.2), acetic acid buffer (HAc/NaAc, pH = 4.93), and deionized water as leachants to simulate the leaching of phenol in three exposure scenarios: acid-precipitation, co-disposal, and neutral-precipitation. Phenol immobilization was enhanced by AC adsorption and impaired by the growth of micropores with increasing amount of AC; thus the optimal added amount of AC to be to added S/S wastes was 2%. The leaching behavior of phenol in co-disposal scenario was unpredictable due to inadequate ionization of HAc in the HAc-NaAc buffer solution. The findings indicated that S/S products should be disposed of in hazardous waste landfills rather than municipal solid waste landfills.

  15. Long-term stability of organic carbon-stimulated chromatereduction in contaminated soils, and its relation to manganese redoxstatus

    Energy Technology Data Exchange (ETDEWEB)

    Tokunaga, Tetsu K.; Wan, Jiamin; Lanzirotti, Antonio; Sutton,Steve R.; Newville, Matthew; Rao, William

    2007-03-13

    In-situ reduction of toxic Cr(V1) to less hazardous Cr(II1)is becoming a popular strategy for remediating contaminated soils.However, the long term stability of reduced Cr remains to be understood,especially given the common presence of MnfIIIJV) oxides that reoxidizeCr(II1). This 4.6 year laboratory study tracked Cr and Mn redoxtransformations in soils contaminated with Cr(V1) which were then treatedwith different amounts of organic carbon (OC). Changes in Cr and Mnoxidation states within soils were directly and nondestructively measuredusing micro X-ray absorption near edge structure spectroscopy. Chromatereduction was roughly lst-order, and the extent of reduction was enhancedwith higher OC additions. However, significant Cr(||1) reoxidationoccurred in soils exposed to the highest Cr(V1) concentrations (2,560 mgkg"'). Transient Cr(II1) reoxidation up to 420 mg kg1 was measured at 1.1years after OC treatment, followed by further reduction. Chromateconcentrations increased by 220 mg kgm1a t the end of the study (4.6years) in one soil. The causal role that Mn oxidation state had inreoxidizing Cr was supported by trends in Mn K-edge energies. Theseresults provide strong evidence for longterm dependence of soil Croxidation states on balances between OC availability and Mn redoxstatus.

  16. Silicon microfabricated beam expander

    Energy Technology Data Exchange (ETDEWEB)

    Othman, A., E-mail: aliman@ppinang.uitm.edu.my; Ibrahim, M. N.; Hamzah, I. H.; Sulaiman, A. A. [Faculty of Electrical Engineering, Universiti Teknologi MARA Malaysia, 40450, Shah Alam, Selangor (Malaysia); Ain, M. F. [School of Electrical and Electronic Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300,Nibong Tebal, Pulau Pinang (Malaysia)

    2015-03-30

    The feasibility design and development methods of silicon microfabricated beam expander are described. Silicon bulk micromachining fabrication technology is used in producing features of the structure. A high-precision complex 3-D shape of the expander can be formed by exploiting the predictable anisotropic wet etching characteristics of single-crystal silicon in aqueous Potassium-Hydroxide (KOH) solution. The beam-expander consist of two elements, a micromachined silicon reflector chamber and micro-Fresnel zone plate. The micro-Fresnel element is patterned using lithographic methods. The reflector chamber element has a depth of 40 µm, a diameter of 15 mm and gold-coated surfaces. The impact on the depth, diameter of the chamber and absorption for improved performance are discussed.

  17. Laboratory Investigations in Support of Carbon Dioxide-in-Water Emulsions Stabilized by Fine Particles for Ocean and Geologic Sequestration of Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Dan Golomb; Eugene Barry; David Ryan

    2006-07-08

    C/W emulsion, the total cost of preparing the emulsion on site is about $8.5 per ton of liquid CO{sub 2}, not including the cost of the emulsion mixer. Currently, the cost estimates of capturing and liquefying CO{sub 2} at a coal-fired power plant range from $15 to 75/t CO{sub 2}. Thus, the preparation of C/W emulsions stabilized by pulverized limestone particles would add about 10 to 50% to the capture cost of CO{sub 2}. At this juncture the primary research objectives of this Co-operative Agreement are shifting toward geologic sequestration of carbon dioxide. Experiments are underway to create micro-emulsions of CO{sub 2}-in-Water (C/W) and Water-in-CO{sub 2} (W/C) stabilized by ultrafine particles ranging from sub-micrometer to a few micrometer in size. Such microemulsions are expected to readily penetrate deep geologic formations, such as porous sedimentary layers, including saline aquifers and semi-depleted oil and gas fields. Injections of (C/W) and (W/C) type micro-emulsions may prove to be less prone to leakage from the formations compared to injections of neat liquid or supercritical CO{sub 2}.

  18. SnO2 nanocrystals deposited on multiwalled carbon nanotubes with superior stability as anode material for Li-ion batteries

    Science.gov (United States)

    Ren, Jianguo; Yang, Junbing; Abouimrane, Ali; Wang, Dapeng; Amine, Khalil

    2011-10-01

    We report a novel ethylene glycol-mediated solvothermal-polyol route for synthesis of SnO2-CNT nanocomposites, which consist of highly dispersed 3-5 nm SnO2 nanocrystals on the surface of multiwalled carbon nanotubes (CNTs). As anode materials for Li-ion batteries, the nanocomposites showed high rate capability and superior cycling stability with specific capacity of 500 mAh g-1 for up to 300 cycles. The CNTs served as electron conductors and volume buffers in the nanocomposites. This strategy could be extended to synthesize other metal oxides composites with other carbon materials.

  19. Expanding mediation theory

    NARCIS (Netherlands)

    Verbeek, P.P.C.C.

    2012-01-01

    In his article In Between Us, Yoni van den Eede expands existing theories of mediation into the realm of the social and the political, focusing on the notions of opacity and transparency. His approach is rich and promising, but two pitfalls should be avoided. First, his concept of ‘in-between’ runs

  20. Expanding Student Assessment Opportunities.

    Science.gov (United States)

    Bartscher, Beth; Carter, Andrea; Lawlor, Anna; McKelvey, Barbara

    This paper describes an approach for expanding assessment opportunities for students to demonstrate their understanding of content. The targeted population consisted of elementary and junior high school students in two schools in a growing middle-class community in north central Illinois. The elementary school enrolled 467 students and the junior…

  1. Carbon-rich icosahedral boron carbides beyond B4C and their thermodynamic stabilities at high temperature and pressure from first principles

    Science.gov (United States)

    Ektarawong, A.; Simak, S. I.; Alling, B.

    2016-08-01

    We investigate the thermodynamic stability of carbon-rich icosahedral boron carbide at different compositions, ranging from B4C to B2C , using first-principles calculations. Apart from B4C , generally addressed in the literature, B2.5C , represented by B10C2p (C-C), where Cp and (C-C) denote a carbon atom occupying the polar site of the icosahedral cluster and a diatomic carbon chain, respectively, is predicted to be thermodynamically stable under high pressures with respect to B4C as well as pure boron and carbon phases. The thermodynamic stability of B2.5C is determined by the Gibbs free energy G as a function of pressure p and temperature T , in which the contributions from the lattice vibrations and the configurational disorder are obtained within the quasiharmonic and the mean-field approximations, respectively. The stability range of B2.5C is then illustrated through the p -T phase diagrams. Depending on the temperatures, the stability range of B2.5C is predicted to be within the range between 40 and 67 GPa. At T ≳ 500 K, the icosahedral Cp atoms in B2.5C configurationally disorder at the polar sites. By investigating the properties of B2.5C , e.g., elastic constants and phonon and electronic density of states, we demonstrate that B2.5C is both mechanically and dynamically stable at zero pressure, and is an electrical semiconductor. Furthermore, based on the sketched phase diagrams, a possible route for experimental synthesis of B2.5C as well as a fingerprint for its characterization from the simulations of x-ray powder diffraction pattern are suggested.

  2. Effects of Land Use Practices on the Organic Carbon Content, Cation Exchange Capacity and Aggregate Stability of Soils in the Catchment Zones

    OpenAIRE

    Mosayeb Heshmati; Arifin Abdu; Shamshuddin Jusop; Nik M. Majid

    2011-01-01

    Problem statement: Land use practice leads to changes in the physico-chemical properties of soils, such as Soil Organic Carbon (SOC), Cation Exchange Capacity (CEC) and Soil Aggregate Stability (SAS) that cause soil erosion. Approach: Merek catchment, Iran suffers from land degradation due to poor land use practice. A study was carried out with the objectives: (i) to determine soil nutrient status in different agro-ecological zones in Merek catchment; and (ii) to evaluate the influence of lan...

  3. Strong stabilization of liquid amorphous calcium carbonate by ovalbumin: gaining insight into the mechanism of ‘polymer-induced liquid precursor’ processes

    Science.gov (United States)

    Leiterer, Jork; Pipich, Vitaliy; Barrea, Raul; Tremel, Wolfgang

    2011-01-01

    The impact of the ovo-proteins ovalbumin and lysozyme—present in the first stage of egg shell formation—on the homogeneous formation of the liquid-amorphous calcium carbonate (LACC) precursor, was studied by a combination of complementing methods: in situ WAXS, SANS, XANES, TEM, and immunogold labeling. Lysozyme (pI = 9.3) destabilizes the LACC emulsion whereas the glycoprotein ovalbumin (pI = 4.7) extends the lifespan of the emulsified state remarkably. In the light of the presented data: (a) Ovalbumin is shown to behave commensurable to the ‘polymer-induced liquid precursor’ (PILP) process proposed by Gower et al. Ovalbumin can be assumed to take a key role during eggshell formation where it serves as an effective stabilization agent for transient precursors and prevents undirected mineralization of the eggshell. (b) It is further shown that the emulsified LACC carries a negative surface charge and is electrostatically stabilized. (c) We propose that the liquid amorphous calcium carbonate is affected by polymers by depletion stabilization and de-emulsification rather than ‘induced’ by acidic proteins and polymers during a polymer-induced liquid-precursor process. The original PILP coating effect, first reported by Gower et al., appears to be a result of a de-emulsification process of a stabilized LACC phase. The behavior of the liquid amorphous carbonate phase and the polymer-induced liquid-precursor phase itself can be well described by colloid chemical terms: electrostatic and depletion stabilization and de-emulsification by depletion destabilization. PMID:21736300

  4. Strong stabilization of amorphous calcium carbonate emulsion by ovalbumin: gaining insight into the mechanism of 'polymer-induced liquid precursor' processes.

    Science.gov (United States)

    Wolf, Stephan E; Leiterer, Jork; Pipich, Vitaliy; Barrea, Raul; Emmerling, Franziska; Tremel, Wolfgang

    2011-08-17

    The impact of the ovo proteins ovalbumin and lysozyme--present in the first stage of egg shell formation--on the homogeneous formation of the liquid amorphous calcium carbonate (LACC) precursor, was studied by a combination of complementing methods: in situ WAXS, SANS, XANES, TEM, and immunogold labeling. Lysozyme (pI = 9.3) destabilizes the LACC emulsion whereas the glycoprotein ovalbumin (pI = 4.7) extends the lifespan of the emulsified state remarkably. In the light of the presented data: (a) Ovalbumin is shown to behave commensurable to the 'polymer-induced liquid precursor' (PILP) process proposed by Gower et al. Ovalbumin can be assumed to take a key role during eggshell formation where it serves as an effective stabilization agent for transient precursors and prevents undirected mineralization of the eggshell. (b) It is further shown that the emulsified LACC carries a negative surface charge and is electrostatically stabilized. (c) We propose that the liquid amorphous calcium carbonate is affected by polymers by depletion stabilization and de-emulsification rather than 'induced' by acidic proteins and polymers during a so-called polymer-induced liquid-precursor process. The original PILP coating effect, first reported by Gower et al., appears to be a result of a de-emulsification process of a stabilized LACC phase. The behavior of the liquid amorphous carbonate phase and the polymer-induced liquid-precursor phase itself can be well described by colloid chemical terms: electrostatic and depletion stabilization and de-emulsification by depletion destabilization. PMID:21736300

  5. Application of δ13C and δ15N isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms

    Directory of Open Access Journals (Sweden)

    M. Sommer

    2011-03-01

    Full Text Available Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. We used the δ13C and δ15N isotopic signatures from two organic matter (OM fractions from soil to identify the likely binding mechanisms involved. We used OM fractions hypothesized to contain carbon stabilized through organo-mineral complexes: (1 OM separated chemically with sodium pyrophosphate (OM(PY and (2 OM stabilized in microstructures found in the chemical extraction residue (OM(ER. Furthermore, because the OM fractions were separated from five different soils with paired forest and arable land use histories, we could address the impact of land use change on carbon binding and processing mechanisms within these soils. We used partial least squares regression to analyze patterns in the isotopic signature of OM with established proxies of different binding mechanisms. Parsing soil OM into different fractions is a systematic method of dissection, however, we are primarily interested in how OM is bound in soil as a whole, requiring a means of re-assembly. Thus, we implemented the recent zonal framework described by Kleber et al. (2007 to relate our findings to undisturbed soil. The δ15N signature of OM fractions served as a reliable indicator for microbial processed carbon in both arable and forest land use types. The δ13C signature of OM fractions in arable sites did not correlate well with proxies of soil mineral properties while a consistent pattern of enrichment was seen in the δ13C of OM fractions in the forest sites. We found a significant difference in δ13C of pooled OM fractions between the forest and arable land use type although it was relatively small (<1‰. We found different binding mechanisms predominate in each land use type. The isotopic signatures of OM fractions from arable soils were highly related to the clay and silt size particles

  6. Application of δ13C and δ15N isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms

    Science.gov (United States)

    Kayler, Z. E.; Kaiser, M.; Gessler, A.; Ellerbrock, R. H.; Sommer, M.

    2011-03-01

    Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. We used the δ13C and δ15N isotopic signatures from two organic matter (OM) fractions from soil to identify the likely binding mechanisms involved. We used OM fractions hypothesized to contain carbon stabilized through organo-mineral complexes: (1) OM separated chemically with sodium pyrophosphate (OM(PY)) and (2) OM stabilized in microstructures found in the chemical extraction residue (OM(ER)). Furthermore, because the OM fractions were separated from five different soils with paired forest and arable land use histories, we could address the impact of land use change on carbon binding and processing mechanisms within these soils. We used partial least squares regression to analyze patterns in the isotopic signature of OM with established proxies of different binding mechanisms. Parsing soil OM into different fractions is a systematic method of dissection, however, we are primarily interested in how OM is bound in soil as a whole, requiring a means of re-assembly. Thus, we implemented the recent zonal framework described by Kleber et al. (2007) to relate our findings to undisturbed soil. The δ15N signature of OM fractions served as a reliable indicator for microbial processed carbon in both arable and forest land use types. The δ13C signature of OM fractions in arable sites did not correlate well with proxies of soil mineral properties while a consistent pattern of enrichment was seen in the δ13C of OM fractions in the forest sites. We found a significant difference in δ13C of pooled OM fractions between the forest and arable land use type although it was relatively small (<1‰). We found different binding mechanisms predominate in each land use type. The isotopic signatures of OM fractions from arable soils were highly related to the clay and silt size particles amount while

  7. Thermal stability and structural study of the poly(3-hexyl thiophene)/HiPCO single walled carbon nanotubes (P3HT/SWCNT) nanocomposites

    Science.gov (United States)

    Bakour, Anass; Baitoul, Mimouna; Faulques, Eric; Wery-Venturini, Jany

    2016-05-01

    In this work we present the effect of HiPCO single walled carbon nanotubes (SWCNT) introduction into the conjugated polymer matrix poly(3-hexyl thiophene) (P3HT) on the structural and thermal stability of these nanocomposites. The P3HT/SWCNT nanocomposite films were prepared using chloroform and chlorobenzene as solvents and optimised ultrasonication duration. The prepared samples were analyzed by thermogravimetric analysis (TGA), X-ray diffraction and transmission electron microscopy (TEM) to study the effect of carbon nanotubes on the thermal stability and structure of the polymer matrix. The measurements carried out for different SWCNT loadings show that the thermal stability was enhanced for a 0.5 wt.%, but exhibits a decrease with increasing the SWCNT content. Our results prove the structural enhancement which is in favor of a better organisation for both P3HT chains and carbon nanotubes due to their interaction. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  8. Stability of a carbon gel electrode when used for the electro-assisted removal of ions from brackish water

    OpenAIRE

    Haro Remón, Marta; Rasines, Gloria; Macías, C.; Ovín Ania, María Concepción

    2011-01-01

    [EN] A porous carbon gel obtained from the poly-condensation of resorcinol and formaldehyde was synthesized and used as an electrode material for the capacitive deionization (CDI) of synthetic brackish water. The desalting capacity of this material was evaluated in terms of applied voltage and zero-voltage regeneration over a number of cycles, and compared to that of commercially available carbon materials (powdered activated carbon and activated carbon cloth). Due to an adequate combination ...

  9. Expandable LED array interconnect

    Science.gov (United States)

    Yuan, Thomas Cheng-Hsin; Keller, Bernd

    2011-03-01

    A light emitting device that can function as an array element in an expandable array of such devices. The light emitting device comprises a substrate that has a top surface and a plurality of edges. Input and output terminals are mounted to the top surface of the substrate. Both terminals comprise a plurality of contact pads disposed proximate to the edges of the substrate, allowing for easy access to both terminals from multiple edges of the substrate. A lighting element is mounted to the top surface of the substrate. The lighting element is connected between the input and output terminals. The contact pads provide multiple access points to the terminals which allow for greater flexibility in design when the devices are used as array elements in an expandable array.

  10. The enhanced electrocatalytic activity and stability of supported Pt nanopartciles for methanol electro-oxidation through the optimized oxidation degree of carbon nanotubes

    Science.gov (United States)

    Xiao, Meiling; Zhu, Jianbing; Ge, Junjie; Liu, Changpeng; Xing, Wei

    2015-05-01

    Carbon nanotubes (CNTs) with different oxidation degrees are synthesized by the modified Hummer's method and used as the support materials for platinum (Pt) catalysts. The effect of their oxidation degree on the catalytic activity and stability of the supported Pt catalysts for methanol electrooxidation is investigated for the first time. The electrocatalytic activity for methanol oxidation reaction increases with increasing the oxidation degree due to more oxygen-containing species introduced to CNTs, which improves the dispersion of Pt nanoparticles and also modifies the electronic structure of Pt catalysts. However, under more severe oxidation condition, the stability of Pt catalysts decreases due to the destruction of graphitic structure of CNTs. Therefore, the optimized treatment condition for the CNTs is mild oxidation, which provides the supported Pt catalysts with both excellent catalytic activity and stability.

  11. OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING

    Energy Technology Data Exchange (ETDEWEB)

    Hector Colonmer; Prabhu Ganesan; Nalini Subramanian; Dr. Bala Haran; Dr. Ralph E. White; Dr. Branko N. Popov

    2002-09-01

    This project focused on addressing the two main problems associated with state of art Molten Carbonate Fuel Cells, namely loss of cathode active material and stainless steel current collector deterioration due to corrosion. We followed a dual approach where in the first case we developed novel materials to replace the cathode and current collector currently used in molten carbonate fuel cells. In the second case we improved the performance of conventional cathode and current collectors through surface modification. States of art NiO cathode in MCFC undergo dissolution in the cathode melt thereby limiting the lifetime of the cell. To prevent this we deposited cobalt using an electroless deposition process. We also coated perovskite (La{sub 0.8}Sr{sub 0.2}CoO{sub 3}) in NiO thorough a sol-gel process. The electrochemical oxidation behavior of Co and perovskites coated electrodes is similar to that of the bare NiO cathode. Co and perovskite coatings on the surface decrease the dissolution of Ni into the melt and thereby stabilize the cathode. Both, cobalt and provskites coated nickel oxide, show a higher polarization compared to that of nickel oxide, which could be due to the reduced surface area. Cobalt substituted lithium nickel oxide (LiNi{sub 0.8}Co{sub 0.2}O{sub 2}) and lithium cobalt oxide were also studied. LiNi{sub x}Co{sub 1-x}O{sub 2} was synthesized by solid-state reaction procedure using lithium nitrate, nickel hydroxide and cobalt oxalate precursor. LiNi{sub x}Co{sub 1-x}O{sub 2} showed smaller dissolution of nickel than state of art nickel oxide cathode. The performance was comparable to that of nickel oxide. The corrosion of the current collector in the cathode side was also studied. The corrosion characteristics of both SS304 and SS304 coated with Co-Ni alloy were studied. This study confirms that surface modification of SS304 leads to the formation of complex scales with better barrier properties and better electronic conductivity at 650 C. A three

  12. Expanding the HAWC Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Johanna [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-17

    The High Altitude Water Cherenkov Gamma-Ray Observatory is expanding its current array of 300 water tanks to include 350 outrigger tanks to increase sensitivity to gamma rays above 10 TeV. This involves creating and testing hardware with which to build the new tanks, including photomultiplier tubes, high voltage supply units, and flash analog to digital converters. My responsibilities this summer included preparing, testing and calibrating that equipment.

  13. Sulfur-doped ordered mesoporous carbons: A stability-improving sulfur host for lithium-sulfur battery cathodes

    Science.gov (United States)

    Nitze, Florian; Fossum, Kjell; Xiong, Shizhao; Matic, Aleksandar; Palmqvist, Anders E. C.

    2016-06-01

    We report on sulfur-functionalized ordered mesoporous carbons aimed for lithium-sulfur battery electrode applications with improved charge capacity retention. The carbons were obtained by a hard-template strategy using a mixture of furfuryl alcohol and furfuryl mercaptan. For the application as electrode material in lithium-sulfur batteries, the carbons were additionally loaded with sulfur following a traditional melt-diffusion approach. It was found that the sulfur interacts stronger with the sulfur-functionalized carbon matrix than with the non-functionalized material. Electrodes showed very high capacity in the second discharge-charge cycle amounting to approximately 1500, 1200 and 1400 mAh/g (sulfur) for carbon materials with no, medium and high degrees of sulfur functionalization, respectively. More importantly, the sulfur-functionalization of the carbon was found to increase the capacity retention after 50 discharge-charge cycles by 8 and 5% for the carbons with medium and high degrees of sulfur-functionalization, respectively, compared to carbon with no sulfur-functionalization. We attribute this significant improvement to the presence of covalently bound sulfur groups at the internal surface of the functionalized carbon providing efficient anchoring sites for catenation to the sulfur loaded into the pores of the carbons and provide experimental support for this in the form of results from cyclic voltammetry and X-ray photoelectron spectroscopy.

  14. The Radical Stabilization Energy of a Substituted Carbon-centered Free Radical Depends both on the Functionality of the Substituent and the Ordinality of the Radical

    Energy Technology Data Exchange (ETDEWEB)

    Poutsma, Marvin L [ORNL

    2011-01-01

    Chemical intuition suggests that the stabilization of a carbon-centered free radical by a substituent X would be the greatest for a prim and least for a more stable tert radical because of saturation. However, analysis of a comprehensive recent set of bond dissociation energies computed by Coote and coworkers (Phys. Chem. Chem. Phys. 2010 12 9597) and transformed into radical stabilization energies (RSE) suggests that this supposition is often violated. The RSE for a given X depends not only on the nature of X but also on the ordinality (i.e., prim, sec, or tert) of the radical onto which it is substituted. For substituents that stabilize by electron delocalization but also contain electron-withdrawing centers, such as the carbonyl function, the stabilization of XCMe2 compared with HCMe2 is greater than for XCH2 compared with HCH2 . However, for substituents that stabilize by lone-pair electron donation, such as N or O centers, the order is strongly reversed. This contrast can be qualitatively rationalized by considering charge-separated VB contributors to the radical structure (R2C+ X- and R2C- X+ ) and the contrasting effects of methyl substituents on them. This conclusion is not dependent on the particular definition used for RSE.

  15. The expanding universe

    CERN Document Server

    Lew, Kristi

    2011-01-01

    People have always been fascinated with the stars above and the universe that contains them. Over the years, astronomers have developed numerous theories to explain how the universe began, how it works, and what its ultimate fate will be. But all of the scientists' questions are far from answered. The Expanding Universe goes beyond the creation of the universe to explain how scientists think the universe works, grows, and changes, including what great thinkers Isaac Newton and Albert Einstein had to say about its fate. Readers will also learn about how researchers are slowly shedding light on

  16. Expanding Your Horizon 2015

    CERN Multimedia

    Kaltenhauser, Kristin

    2015-01-01

    Expanding your horizons is a bi-annual “Science Day” for girls aged 11 to 14, held at the University of Geneva on 14 November. The girls had the opportunity to take part in hands-on workshops held by local professional women in the field of science, mathematics, engineering and technology. For the fourth time, CERN was part of this event, offering three workshops as well as a booth at the Discovery Fair, including Higgnite, an interactive visualization of the Higgs Field.

  17. Changes in Marsh Vegetation, Stability and Dissolved Organic Carbon in Barataria Bay Marshes Following the Deepwater Horizon Oil Spill

    Science.gov (United States)

    Holloway, J. M.; Aiken, G.; Kokaly, R. F.; Heckman, D.; Butler, K.; Mills, C. T.; Hoefen, T. M.; Piazza, S.

    2010-12-01

    Coastal wetlands in Southern Louisiana were contaminated by the release of record volumes of oil between April and July 2010. Barataria Bay was extensively impacted, resulting in the oiling and dieback of marsh grasses along a discontinuous margin up to 30m into the marshes. Shoreline stability and biogeochemistry have been monitored over three site visits between between July 10 and August 25, 2010. Initial observations in early July were that grasses, dominantly shape Spartina alterniflora and shape Juncus roemerianus, were bent over under the weight of a thick oil coating. The bent-over grasses were broken off along some reaches, leaving a stubbled shoreline more susceptible to erosion. Repeated site visits in mid and late August found visible erosion along some of the effected shorelines. Water samples were collected from the shoreline marsh remnants and from visibly unaffected marshes to characterize dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). In spite of visible oil sheens in unfiltered water from contaminated shorelines and no visible sign of impact on vegetation in the “control” sites with no visible oil on vegetation, DOC concentrations were similar in impacted and visibly unimpacted sites in Barataria Bay. Subsequent samples in mid- and late-August had increased DOC concentrations relative to previous sample events regardless of whether the site was visibly impacted. There was a general increase in specific UV absorbance (SUVA), an index of aromaticity, with increasing DOC concentrations, either due to seasonal effects or continued dissolution of petroleum compounds. Further chemical characterization using fluorescence and gas chromatography will be used to confirm the presence of petroleum compounds. The ratio of DOC to TDN also increased over time, which may have implications for vegetation regrowth and plant community structure, including the shift of grass species dominating effected marshes. These initial findings suggest

  18. Thermal stability and oxidizing properties of mixed alkaline earth-alkali molten carbonates: A focus on the lithium-sodium carbonate eutectic system with magnesium additions

    International Nuclear Information System (INIS)

    Highlights: • TG/DSC analysis was conducted on magnesium-containing eutectic Li/Na eutectic carbonates. • Magnesium influence on the oxygen solubility properties of carbonate was also experimentally determined at 600 °C and 650 °C. • A reproducible partial decarbonation process in premelting region caused formation of magnesium oxycarbonate-like phases. • The acidobase buffering action of magnesium oxycarbonate species could explain the high basic/oxidizing properties of such carbonate melts. • A general correlation between thermal instability in premelting region and basic/oxidizing melt properties was established. - Abstract: A comparative study on thermal behavior and oxygen solubility properties of eutectic 52/48 lithium/sodium carbonate salt containing minor additions of magnesium up to 10 mol% has been made in order to determine whether a general correlation between these two properties can be found or not. Consecutive TG/DSC heating/cooling thermal cycles carried out under alternating CO2 and N2 gas flows allowed to assign thermal events observed in the premelting region to a partial decarbonation process of the magnesium-alkali mixed carbonates. The observed decarbonation process at 460 °C is believed to come from initial stage of thermal decomposition of magnesium carbonate resulting in the metastable formation of magnesium oxycarbonate-like phases MgO·2MgCO3, in a similar manner as previously reported for lanthanum. Reversible formation and decomposition of the magnesium carbonate phase has been observed under a CO2 gas atmosphere. The intensity of the decomposition process shows a maximum for a 3 mol% MgO addition that gives also the highest oxygen solubility, suggesting therefore that instability thermal analysis in the premelting region can be considered as providing an effective measure of the basicity/oxidizing properties of alkali carbonate melts with magnesium or, in more general terms, with cations that are strong modifiers of the

  19. Adsorption of Carbon Dioxide on Unsaturated Metal Sites in M2 (dobpdc) Frameworks with Exceptional Structural Stability and Relation between Lewis Acidity and Adsorption Enthalpy.

    Science.gov (United States)

    Yoo, Ga Young; Lee, Woo Ram; Jo, Hyuna; Park, Joonho; Song, Jeong Hwa; Lim, Kwang Soo; Moon, Dohyun; Jung, Hyun; Lim, Juhyung; Han, Sang Soo; Jung, Yousung; Hong, Chang Seop

    2016-05-23

    A series of metal-organic frameworks (MOFs) M2 (dobpdc) (M=Mn, Co, Ni, Zn; H4 dobpdc=4,4'-dihydroxy-1,1'-biphenyl-3,3'-dicarboxylic acid), with a highly dense arrangement of open metal sites along hexagonal channels were prepared by microwave-assisted or simple solvothermal reactions. The activated materials were structurally expanded when guest molecules including CO2 were introduced into the pores. The Lewis acidity of the open metal sites varied in the order MnZn, as confirmed by C=O stretching bands in the IR spectra, which are related to the CO2 adsorption enthalpy. DFT calculations revealed that the high CO2 binding affinity of transition-metal-based M2 (dobpdc) is primarily attributable to the favorable charge transfer from CO2 (oxygen lone pair acting as a Lewis base) to the open metal sites (Lewis acid), while electrostatic effects, the underlying factor responsible for the particular order of binding strength observed across different transition metals, also play a role. The framework stability against water coincides with the order of Lewis acidity. In this series of MOFs, the structural stability of Ni2 (dobpdc) is exceptional; it endured in water vapor, liquid water, and in refluxing water for one month, and the solid remained intact on exposure to solutions of pH 2-13. The DFT calculations also support the experimental finding that Ni2 (dobpdc) has higher chemical stability than the other frameworks. PMID:27105924

  20. Adsorption of Carbon Dioxide on Unsaturated Metal Sites in M2 (dobpdc) Frameworks with Exceptional Structural Stability and Relation between Lewis Acidity and Adsorption Enthalpy.

    Science.gov (United States)

    Yoo, Ga Young; Lee, Woo Ram; Jo, Hyuna; Park, Joonho; Song, Jeong Hwa; Lim, Kwang Soo; Moon, Dohyun; Jung, Hyun; Lim, Juhyung; Han, Sang Soo; Jung, Yousung; Hong, Chang Seop

    2016-05-23

    A series of metal-organic frameworks (MOFs) M2 (dobpdc) (M=Mn, Co, Ni, Zn; H4 dobpdc=4,4'-dihydroxy-1,1'-biphenyl-3,3'-dicarboxylic acid), with a highly dense arrangement of open metal sites along hexagonal channels were prepared by microwave-assisted or simple solvothermal reactions. The activated materials were structurally expanded when guest molecules including CO2 were introduced into the pores. The Lewis acidity of the open metal sites varied in the order MnZn, as confirmed by C=O stretching bands in the IR spectra, which are related to the CO2 adsorption enthalpy. DFT calculations revealed that the high CO2 binding affinity of transition-metal-based M2 (dobpdc) is primarily attributable to the favorable charge transfer from CO2 (oxygen lone pair acting as a Lewis base) to the open metal sites (Lewis acid), while electrostatic effects, the underlying factor responsible for the particular order of binding strength observed across different transition metals, also play a role. The framework stability against water coincides with the order of Lewis acidity. In this series of MOFs, the structural stability of Ni2 (dobpdc) is exceptional; it endured in water vapor, liquid water, and in refluxing water for one month, and the solid remained intact on exposure to solutions of pH 2-13. The DFT calculations also support the experimental finding that Ni2 (dobpdc) has higher chemical stability than the other frameworks.

  1. Application of accelerated carbonation with a combination of Na2CO3 and CO2 in cement-based solidification/stabilization of heavy metal-bearing sediment.

    Science.gov (United States)

    Chen, Quanyuan; Ke, Yujuan; Zhang, Lina; Tyrer, Mark; Hills, Colin D; Xue, Gang

    2009-07-15

    The efficient remediation of heavy metal-bearing sediment has been one of top priorities of ecosystem protection. Cement-based solidification/stabilization (s/s) is an option for reducing the mobility of heavy metals in the sediment and the subsequent hazard for human beings and animals. This work uses sodium carbonate as an internal carbon source of accelerated carbonation and gaseous CO(2) as an external carbon source to overcome deleterious effects of heavy metals on strength development and improve the effectiveness of s/s of heavy metal-bearing sediment. In addition to the compressive strength and porosity measurements, leaching tests followed the Chinese solid waste extraction procedure for leaching toxicity - sulfuric acid and nitric acid method (HJ/T299-2007), German leaching procedure (DIN38414-S4) and US toxicity characteristic leaching procedures (TCLP) have been conducted. The experimental results indicated that the solidified sediment by accelerated carbonation was capable of reaching all performance criteria for the disposal at a Portland cement dosage of 10 wt.% and a solid/water ratio of 1:1. The concentrations of mercury and other heavy metals in the leachates were below 0.10mg/L and 5mg/L, respectively, complying with Chinese regulatory level (GB5085-2007). Compared to the hydration, accelerated carbonation improved the compressive strength of the solidified sediment by more than 100% and reduced leaching concentrations of heavy metals significantly. It is considered that accelerated carbonation technology with a combination of Na(2)CO(3) and CO(2) may practically apply to cement-based s/s of heavy metal-bearing sediment. PMID:19128876

  2. Frictional properties and slip stability of active faults within carbonate-evaporite sequences: The role of dolomite and anhydrite

    NARCIS (Netherlands)

    Scuderi, M.M.; Niemeijer, A.R.; Collettini, C.; Marone, C.

    2013-01-01

    Seismological observations show that many destructive earthquakes nucleate within, or propagate through, thick sequences of carbonates and evaporites. For example, along the Apennines range (Italy) carbonate and evaporite sequences are present at hypocentral depths for recent major earthquakes (5.0<

  3. Expandable pattern casting research

    Science.gov (United States)

    1993-09-01

    The Expandable Pattern Casting (EPC) Process is a developing foundry technology that allows designers the opportunity to consolidate parts, reduce machining, and minimize assembly operations. An air gauging system was developed for measuring foam patterns; exact shrinkage depended on type and density of the foam. Compaction studies showed that maximum sand densities in cavities and under overhangs are achieved with vibrational amplitudes 0.001-0.004 in., and that sand moved most freely within a few inches of the top free surface. Key to complete mold filling while minimizing casting defects lies in removing the foam decomposition products. The most precise iron castings were made by EPC in four commercial EPC foundries, with attention paid to molding and compaction. EP cast 60-45-12 ductile iron had yield strengths, ultimate strengths, and elastic modulus similar to conventionally cast ductile iron cast from the same ladle.

  4. The effects of ordered carbon vacancies on stability and thermo-mechanical properties of V8C7 compared with VC

    Science.gov (United States)

    Chong, XiaoYu; Jiang, YeHua; Zhou, Rong; Feng, Jing

    2016-01-01

    The ordered non-stoichiometric V8C7 can form in the VCy carbides by the disorder–order phase transformation. The intrusion of ordered carbon vacancies can affect their stability, mechanical, thermal and electronic properties. The relatively thermodynamic stability and mechanical properties at high temperature for the ordered stoichiometric VC and non-stoichiometric V8C7 are investigated in this paper by first-principle calculations combined with the quasi-harmonic approximation. The difference between the properties of VC and V8C7 can be obtained. We find that the V8C7 is thermodynamic more stable than VC, but has weaker elastic heat resistance than VC. Moreover, the minimum thermal conductivity of VC is a little larger than V8C7 and a simple way is proposed to characterize the anisotropy of lattice thermal conductivity based on the Cahill’s model. PMID:27659072

  5. Thermal stability and oxidizing properties of mixed alkaline earth-alkali molten carbonates: A focus on the lithium-sodium carbonate eutectic system with magnesium additions

    Energy Technology Data Exchange (ETDEWEB)

    Frangini, Stefano, E-mail: stefano.frangini@enea.it [Hydrogen and Fuel Cell Laboratory (UTRINN-IFC), ENEA CR Casaccia, Via Anguillarese 301, I-00123 Rome (Italy); Scaccia, Silvera [Sustainable Combustion Laboratory (UTTEI-COMSO), ENEA CR Casaccia, Via Anguillarese 301, I-00123 Rome (Italy)

    2013-12-20

    Highlights: • TG/DSC analysis was conducted on magnesium-containing eutectic Li/Na eutectic carbonates. • Magnesium influence on the oxygen solubility properties of carbonate was also experimentally determined at 600 °C and 650 °C. • A reproducible partial decarbonation process in premelting region caused formation of magnesium oxycarbonate-like phases. • The acidobase buffering action of magnesium oxycarbonate species could explain the high basic/oxidizing properties of such carbonate melts. • A general correlation between thermal instability in premelting region and basic/oxidizing melt properties was established. - Abstract: A comparative study on thermal behavior and oxygen solubility properties of eutectic 52/48 lithium/sodium carbonate salt containing minor additions of magnesium up to 10 mol% has been made in order to determine whether a general correlation between these two properties can be found or not. Consecutive TG/DSC heating/cooling thermal cycles carried out under alternating CO{sub 2} and N{sub 2} gas flows allowed to assign thermal events observed in the premelting region to a partial decarbonation process of the magnesium-alkali mixed carbonates. The observed decarbonation process at 460 °C is believed to come from initial stage of thermal decomposition of magnesium carbonate resulting in the metastable formation of magnesium oxycarbonate-like phases MgO·2MgCO{sub 3}, in a similar manner as previously reported for lanthanum. Reversible formation and decomposition of the magnesium carbonate phase has been observed under a CO{sub 2} gas atmosphere. The intensity of the decomposition process shows a maximum for a 3 mol% MgO addition that gives also the highest oxygen solubility, suggesting therefore that instability thermal analysis in the premelting region can be considered as providing an effective measure of the basicity/oxidizing properties of alkali carbonate melts with magnesium or, in more general terms, with cations that are

  6. Investigation of heavy metal (Cu, Pb, Cd, and Cr) stabilization in river sediment by nano-zero-valent iron/activated carbon composite.

    Science.gov (United States)

    Chen, Wei-fang; Zhang, Jinghui; Zhang, Xiaomao; Wang, Weiya; Li, Yuxiang

    2016-01-01

    Nano-zero-valent iron/activated carbon (nZVI/AC) composite was evaluated for its effectiveness in the stabilization of Cu, Pb, Cd, and Cr in dredged river sediment. Synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP) were adopted to compare the effects of nZVI/AC dosage, particle size, time duration, and temperature on heavy metal leachability. The results show that leachability dropped considerably with the addition of nZVI/AC and powdered particles in the size of 0.075-0.18 mm was more effective in stabilization than granular ones. Stabilization effect was stable in long-term and robust against changes in temperature. Tessier sequential extraction revealed that heavy metals were associated with solid particle, inorganic or organic matters in sediment. The addition of nZVI/AC was able to convert relatively weakly bound heavy metals into more strongly bound species and thus reduce the bioavailability and toxicity. Also, the standard potential of heavy metals may decide the mechanism of stabilization process. PMID:26370818

  7. Thermal stability and formation barrier of a high-energetic material N8 polymer nitrogen encapsulated in (5,5) carbon nanotube

    Science.gov (United States)

    Ji, Wei; Timoshevskii, V.; Guo, H.; Abou-Rachid, Hakima; Lussier, Louis-Simon

    2009-07-01

    We report the density functional theory total energy calculations of thermal stability and formation barrier of polymer nitrogen confined in carbon nanotubes (CNT). The analysis suggests that N8 polymer nitrogen encapsulated in (5,5) carbon nanotube [N8@CNT(5,5)] is thermally (meta)stable at a finite temperature up to energy scale of at least 5000 K, similar to nitrogen molecule gas phase confined in CNT [N2@CNT(5,5)]. The energetic difference between these two phases of N does not significantly change with temperature. A barrier of 1.07 eV was found for the formation of N8@CNT(5,5) from N2@CNT(5,5), while the dissociation barrier was found to be 0.2 eV. Snapshots of the reaction pathway show that the transition state is composed by a N2 and a N6 inside a CNT(5,5).

  8. Study of calcium forms and their effect in carbon stabilization in fertile soils by FTIR and XPS

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, J.R.; Assis, K.L.S.; Calil, V.L.; Souza, K.R.; Beltrao, M.S.S.; Sena, L.A.; Archanjo, B.S.; Achete, C.A., E-mail: jraraujo@inmetro.gov.br [Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Duque de Caxias, RJ (Brazil). Divisao de Materiais e Metrologia

    2013-07-01

    Organic matter or black carbon atoms of Terra Preta de Indio (Amazonian Dark Earth) soils are composed of oxidized carbon groups as phenols, epoxide, carbonyl and carboxyl groups in their surface. At the pH of soil, carboxylate groups are deprotonated generating carboxylate anions leaving the surface of these soils with negative charges. Calcium cations can interact with oxidized carbon groups by chemisorption interactions lowering the total system energy. In this work, Terra Preta de Indio was examined by X-ray photoelectron spectroscopy and Infrared spectroscopy in order to correlate its organic fraction rich in calcium with calcium containing samples. (author)

  9. Development of a cheap and accessible carbon fibers-in-poly(ether ether ketone) tube with high stability for online in-tube solid-phase microextraction.

    Science.gov (United States)

    Feng, Juanjuan; Sun, Min; Bu, Yanan; Luo, Chuannan

    2016-02-01

    Carbon fibers (CFs) are one kind of important industrial materials that can be obtained commercially at low price. Based on the high extraction efficiency of carbon sorbents, a cheap and accessible carbon fibers-in-poly(ether ether ketone) (PEEK) tube was developed for online in-tube solid-phase microextraction (SPME) method. Coupled to high performance liquid chromatography (HPLC), the CFs-in-tube SPME was applied to analyze eight polycyclic aromatic hydrocarbons (PAHs) in environmental aqueous samples. Extraction conditions (sampling rate, extraction time, methanol content) and desorption time were investigated for optimization of conditions. Under the optimum conditions, the CFs-in-tube SPME-HPLC method provided high extraction efficiency with enrichment factors up to 1748. Good linearity (0.05-50 μg L(-1), 0.5-50 μg L(-1)) and low detection limits (0.01-0.1 μg L(-1)) were also obtained. The online analysis method was finally applied to determine several model PAHs analytes in real environmental aqueous samples. Some target analytes were detected and relative recoveries were in the range of 92.3-111%. Due to natural chemical stability of carbon fibers and PEEK tube, the CFs-in-tube device exhibited high resistance to organic solvent, acid and alkaline conditions. PMID:26653455

  10. Energetics, relative stabilities, and size-dependent properties of nanosized carbon clusters of different families: fullerenes, bucky-diamond, icosahedral, and bulk-truncated structures.

    Science.gov (United States)

    Yu, M; Chaudhuri, I; Leahy, C; Wu, S Y; Jayanthi, C S

    2009-05-14

    Structures and relative stabilities of carbon clusters belonging to different families have been investigated for diameters d simulation. Carbon clusters studied include fullerenes and fullerene-derived structures (e.g., cages and onions), icosahedral structures, bucky-diamond structures, and clusters cut from the bulk diamond with spherical and facetted truncations. The reason for using a semiempirical MD is partly due to the large number of different cases (or carbon allotropes) investigated and partly due to the size of the clusters investigated in this work. The particular flavor of the semiempirical MD scheme is based on a self-consistent and environment-dependent Hamiltonian developed in the framework of linear combination of atomic orbitals. We find that (i) among the families of carbon clusters investigated, fullerene structures have the lowest energy with the relative energy ordering being E(fullerene) structures is likely at d approximately 8 nm, (iii) the highest occupied molecular orbital-lowest unoccupied molecular orbital gap as a function of the diameter for the case of fullerenes shows an oscillatory behavior with the gap ranging from 2 eV to 6 meV, and the gap approaching that of gapless graphite for d > 3.5 nm, and (iv) there can be three types of phase transformations depending on the manner of heating and cooling in our simulated annealing studies: (a) a bucky-diamond structure --> an onionlike structure, (b) an onionlike --> a cage structure, and (c) a bucky-diamond --> a cage structure.

  11. The Artful Universe Expanded

    International Nuclear Information System (INIS)

    The cosmos is an awfully big place and there is no better guide to its vast expanse and fascinating nooks and crannies than John Barrow. A professor of mathematical sciences at Cambridge University, Barrow embodies that rare combination of highly polished writer and expert scientist. His deft touch brings together the disparate threads of human knowledge and weaves them into a tapestry as rich and interesting for the expert as it is for the layperson. The Artful Universe Expanded is an updated edition of this popular book first published in 1995. It explores the deeply profound manner in which natural law and the nature of the cosmos have moulded and shaped us, our cultures and the very form of our arts and music-a new type of 'cosmic' anthropology. The main themes Barrow chooses for revealing this new anthropology are the subjects of evolution, the size of things, the heavens and the nature of music. The book is a large, eclectic repository of knowledge often unavailable to the layperson, hidden in esoteric libraries around the world. It rivals The Da Vinci Code for entertainment value and insights, but this time it is Nature's code that is revealed. It is rare indeed to find common threads drawn through topics as diverse as The Beetles, Bach and Beethoven or between Jackson Pollock, the Aztecs, Kant, Picasso, Byzantine mosaics, uranium-235 and the helix nebula. Barrow unerringly binds them together, presenting them in a stimulating, conversational style that belies the amount of time that must have gone into researching this book. Dip into it at random, or read it from cover to cover, but do read it. The Artful Universe Expanded is an entertaining antidote to the oft-lamented pressures to know more and more about less and less and the apparently inexorable march of specialization. On reading this book one can, for a short time at least, hold in one's mind a vision that unifies science, art and culture and glimpse a universal tapestry of great beauty. (book review)

  12. The Artful Universe Expanded

    Energy Technology Data Exchange (ETDEWEB)

    Bassett, B A [Institute of Cosmology and Gravitation, University of Portsmouth (United Kingdom)

    2005-07-29

    The cosmos is an awfully big place and there is no better guide to its vast expanse and fascinating nooks and crannies than John Barrow. A professor of mathematical sciences at Cambridge University, Barrow embodies that rare combination of highly polished writer and expert scientist. His deft touch brings together the disparate threads of human knowledge and weaves them into a tapestry as rich and interesting for the expert as it is for the layperson. The Artful Universe Expanded is an updated edition of this popular book first published in 1995. It explores the deeply profound manner in which natural law and the nature of the cosmos have moulded and shaped us, our cultures and the very form of our arts and music-a new type of 'cosmic' anthropology. The main themes Barrow chooses for revealing this new anthropology are the subjects of evolution, the size of things, the heavens and the nature of music. The book is a large, eclectic repository of knowledge often unavailable to the layperson, hidden in esoteric libraries around the world. It rivals The Da Vinci Code for entertainment value and insights, but this time it is Nature's code that is revealed. It is rare indeed to find common threads drawn through topics as diverse as The Beetles, Bach and Beethoven or between Jackson Pollock, the Aztecs, Kant, Picasso, Byzantine mosaics, uranium-235 and the helix nebula. Barrow unerringly binds them together, presenting them in a stimulating, conversational style that belies the amount of time that must have gone into researching this book. Dip into it at random, or read it from cover to cover, but do read it. The Artful Universe Expanded is an entertaining antidote to the oft-lamented pressures to know more and more about less and less and the apparently inexorable march of specialization. On reading this book one can, for a short time at least, hold in one's mind a vision that unifies science, art and culture and glimpse a universal tapestry of great

  13. Influence of expander components on the processes at the negative plates of lead-acid cells on high-rate partial-state-of-charge cycling. Part II. Effect of carbon additives on the processes of charge and discharge of negative plates

    Energy Technology Data Exchange (ETDEWEB)

    Pavlov, D.; Nikolov, P.; Rogachev, T. [Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences, Acad. Georgi Bonchev Street, bl. 10, Sofia 1113 (Bulgaria)

    2010-07-15

    Lead-acid batteries operated in the high-rate partial-state-of-charge (HRPSoC) duty rapidly lose capacity on cycling, because of sulfation of the negative plates. As the battery operates from a partially discharged state, the small PbSO{sub 4} crystals dissolve and precipitate onto the bigger crystals. The latter have low solubility and hence PbSO{sub 4} accumulates progressively in the negative plates causing capacity loss. In order to suppress this process, the rate of the charge process should be increased. In a previous publication of ours we have established that reduction of Pb{sup 2+} ions to Pb may proceed on the surface of both Pb and carbon black particles. Hence, the reversibility of the charge-discharge processes improves, which leads to improved cycle life performance of the batteries in the HRPSoC mode. However, not all carbon forms accelerate the charge processes. The present paper discusses the electrochemical properties of two groups of carbon blacks: Printex and active carbons. The influence of Vaniseprse A and BaSO{sub 4} (the other two components of the expander added to the negative plates) on the reversibility of the charge-discharge processes on the negative plates is also considered. It has been established that lignosulfonates are adsorbed onto the lead surface and retard charging of the battery. BaSO{sub 4} has the opposite effect, which improves the reversibility of the processes on cycling and hence prolongs battery life in the HRPSoC duty. It has been established that the cycle life of lead-acid cells depends on the type of carbon black or active carbon added to the negative plates. When the carbon particles are of nano-sizes (<180 nm), the HRPSoC cycle life is between 10,000 and 20,000 cycles. Lignosulfonates suppress this beneficial effect of carbon black and activated carbon additives to about 10,000 cycles. Cells with active carbons have the longest cycle life when they contain also BaSO{sub 4} but no lignosulfonate. A summary of

  14. Steady state and stability characteristics of natural circulation loops operating with carbon dioxide at supercritical pressures for open and closed loop boundary conditions

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Natural circulation experiments conducted with supercritical carbon dioxide. • The instability observed in the pseudo-critical temperature range of operation. • Instability is found for small power range bounded by upper and lower stable zones. • NOLSTA code predicts very large unstable zone compared to experimental data. • Thermal capacitance model included in NOLSTA code to simulate experimental data. - Abstract: Experiments were conducted in a closed supercritical pressure natural circulation loop (SPNCL) with carbon dioxide as working fluid. Instability was observed in a narrow window of power with the loop operating in the pseudo-critical temperature range (heater inlet temperature in the range of 27–31 °C and heater outlet temperature oscillating from 29 to 45 °C). Only horizontal heater horizontal cooler orientation exhibited instability and that too at low secondary side chilled water mass flow rate, i.e. 10–15 lpm. A computer code NOLSTA has been developed to carry out steady state and stability analysis of open and closed loop natural circulation at supercritical conditions. The code adequately predicts steady state natural circulation performance for both open and closed loop boundary conditions. However, code predicts very large unstable zone for SPNCL, hence pipe wall thermal capacitance models were incorporated in NOLSTA code to simulate the experimental results. The stability predictions by NOLSTA code (with pipe wall thermal capacitance model) have been compared with experimental data available in open literature and experiments conducted in SPNCL

  15. Thermal conductivity and stability of a three-phase blend of carbon nanotubes, conductive polymer, and silver nanoparticles incorporated into polycarbonate nanocomposites

    KAUST Repository

    Patole, Archana

    2015-04-16

    Metallic and non-metallic nanofillers can be used together in the design of polycarbonate (PC) nanocomposites with improved electrical properties. Here, the preparation of three-phase blend (carbon nanotubes (CNT), silver nanoparticles, and conductive polymer) in a two-step process before incorporation in the PC is reported. First, ethylene diamine functionalized multiwall carbon nanotubes (MWCNT-EDA) were decorated with Ag nanoparticles. Next, the Ag-decorated CNTs were coated with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Due to the high thermal conductivity instrinsic to both metallic and non-metallic phases, it is expected that the thermal properties of the resulting nanocomposite would largely differ from those of pristine PC. We thus investigated in detail how this hybrid conductive blend affected properties such as the glass transition temperature, the thermal stability, and the thermal conductivity of the nanocomposite. It was found that this strategy results in improved thermal conductivity and thermal stability of the material. © 2015 Wiley Periodicals, Inc.

  16. A stability comparison of redox-active layers produced by chemical coupling of an osmium redox complex to pre-functionalized gold and carbon electrodes

    International Nuclear Information System (INIS)

    The production of stable redox active layers on electrode surfaces is a key factor for the development of practical electronic and electrochemical devices. Here, we report on a comparison of the stability of redox layers formed by covalently coupling an osmium redox complex to pre-functionalized gold and graphite electrode surfaces. Pre-treatment of gold and graphite electrodes to provide surface carboxylic acid groups is achieved via classical thiolate self-assembled monolayer formation on gold surfaces and the electro-reduction of an in situ generated aryldiazonium salt from 4-aminobenzoic acid on gold, glassy carbon and graphite surfaces. These surfaces have been characterized by AFM and electrochemical blocking studies. The surface carboxylate is then used to tether an osmium complex, [Os(2,2'-bipyridyl)2(4-aminomethylpyridine)Cl]PF6, to provide a covalently bound redox active layer, E0'' of 0.29 V (vs. Ag/AgCl in phosphate buffer, pH 7.4), on the pre-treated electrodes. The aryldiazonium salt-treated carbon-based surfaces showed the greatest stability, represented by a decrease of <5% in the peak current for the Os(II/III) redox transition of the immobilized complex over a 3-day period, compared to a decrease of 19% and 14% for the aryldiazonium salt treated and thiolate treated gold surfaces, respectively, over the same period

  17. A stability comparison of redox-active layers produced by chemical coupling of an osmium redox complex to pre-functionalized gold and carbon electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Boland, Susan; Foster, Kevin [School of Chemistry, National University of Ireland, Galway (Ireland); Leech, Donal [School of Chemistry, National University of Ireland, Galway (Ireland)], E-mail: donal.leech@nuigalway.ie

    2009-02-28

    The production of stable redox active layers on electrode surfaces is a key factor for the development of practical electronic and electrochemical devices. Here, we report on a comparison of the stability of redox layers formed by covalently coupling an osmium redox complex to pre-functionalized gold and graphite electrode surfaces. Pre-treatment of gold and graphite electrodes to provide surface carboxylic acid groups is achieved via classical thiolate self-assembled monolayer formation on gold surfaces and the electro-reduction of an in situ generated aryldiazonium salt from 4-aminobenzoic acid on gold, glassy carbon and graphite surfaces. These surfaces have been characterized by AFM and electrochemical blocking studies. The surface carboxylate is then used to tether an osmium complex, [Os(2,2'-bipyridyl){sub 2}(4-aminomethylpyridine)Cl]PF{sub 6}, to provide a covalently bound redox active layer, E{sup 0}'' of 0.29 V (vs. Ag/AgCl in phosphate buffer, pH 7.4), on the pre-treated electrodes. The aryldiazonium salt-treated carbon-based surfaces showed the greatest stability, represented by a decrease of <5% in the peak current for the Os(II/III) redox transition of the immobilized complex over a 3-day period, compared to a decrease of 19% and 14% for the aryldiazonium salt treated and thiolate treated gold surfaces, respectively, over the same period.

  18. The Artful Universe Expanded

    Science.gov (United States)

    Barrow, John D.

    2005-07-01

    Our love of art, writes John Barrow, is the end product of millions of years of evolution. How we react to a beautiful painting or symphony draws upon instincts laid down long before humans existed. Now, in this enhanced edition of the highly popular The Artful Universe , Barrow further explores the close ties between our aesthetic appreciation and the basic nature of the Universe. Barrow argues that the laws of the Universe have imprinted themselves upon our thoughts and actions in subtle and unexpected ways. Why do we like certain types of art or music? What games and puzzles do we find challenging? Why do so many myths and legends have common elements? In this eclectic and entertaining survey, Barrow answers these questions and more as he explains how the landscape of the Universe has influenced the development of philosophy and mythology, and how millions of years of evolutionary history have fashioned our attraction to certain patterns of sound and color. Barrow casts the story of human creativity and thought in a fascinating light, considering such diverse topics as our instinct for language, the origins and uses of color in nature, why we divide time into intervals as we do, the sources of our appreciation of landscape painting, and whether computer-generated fractal art is really art. Drawing on a wide variety of examples, from the theological questions raised by St. Augustine and C.S. Lewis to the relationship between the pure math of Pythagoras and the music of the Beatles, The Artful Universe Expanded covers new ground and enters a wide-ranging debate about the meaning and significance of the links between art and science.

  19. Demands of Expanding Populations and Development Planning

    Science.gov (United States)

    Lim, Bo

    2010-04-01

    This book is a practical resource for development planners, demographers, and organizations involved with development projects related to improving the well-being and welfare of expanding human populations. Demands of Expanding Populations and Development Planning essentially is a treatment on sustainability and includes a heavy emphasis on major issues of environmental pollution over the last 3 decades. The book's coverage of ecosystems, atmospheric chemistry, water availability and quality, and soils is comprehensive. The author's extensive teaching experience makes this somewhat of an authoritative book on air quality and emissions from natural and anthropogenic sources, volatile heavy metals, carbon monoxide, radon, and nuclear waste. Most of the book focuses on the atmospheric chemistry of air pollution, whether the pollution source is from energy, industrial production, and manufacturing processes or from the treatment of waste products from such processes.

  20. Decomposition kinetics of expanded austenite with high nitrogen contents

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2006-01-01

    This paper addresses the decomposition kinetics of synthesized homogeneous expanded austenite formed by gaseous nitriding of stainless steel AISI 304L and AISI 316L with nitrogen contents up to 38 at.% nitrogen. Isochronal annealing experiments were carried out in both inert (N2) and reducing (H2......, respectively. Isothermal stability plots for expanded austenite developed from AISI 304L and AISI 316 were obtained....

  1. Kinetics stabilized doping: computational optimization of carbon-doped anatase TiO2 for visible-light driven water splitting.

    Science.gov (United States)

    Sun, Yi-Yang; Zhang, Shengbai

    2016-01-28

    Using density functional theory calculation we investigate the carbon doping of anatase TiO2, a technique widely studied for visible-light driven water splitting. By a detailed analysis of the thermodynamics of C defects in TiO2, we show that any significant concentration of C dopants in the TiO2 lattice must be a result of non-equilibrium doping, which emphasizes the importance of kinetics stabilized C defects. Based on the band gaps calculated using hybrid density functionals, we exclude the possibility of C occupying Ti lattice sites or interstitial sites to enhance visible-light absorption of TiO2, as extensively discussed in the literature. Also, the recently proposed defect with a CO species occupying two O sites yields a too small band gap for water splitting. Two defects that can effectively reduce the band gap for the water splitting application are identified to be: (1) the CO-VO complex, i.e., a C substituting for O (CO) paired with an O vacancy (VO) and (2) the (C2)2O complex with a C dimer (C2) occupying two neighboring O vacancies. Compared with the CO-VO complex, (C2)2O exhibits strong binding (greater than 2.5 eV) between the two C atoms, which could significantly enhance its kinetic stability to survive from high temperature annealing. With a reduced band gap of about 1.4 eV, carbon dimers could be ideal for kinetic doping of anatase TiO2 to enhance its visible-light activity in photocatalytic reactions. Molecular doping using C2H2 or C2H4 as C precursors has been proposed to introduce the carbon dimers into TiO2. PMID:26725589

  2. Ionic Liquid-Organic Carbonate Electrolyte Blends To Stabilize Silicon Electrodes for Extending Lithium Ion Battery Operability to 100 °C.

    Science.gov (United States)

    Ababtain, Khalid; Babu, Ganguli; Lin, Xinrong; Rodrigues, Marco-Tulio F; Gullapalli, Hemtej; Ajayan, Pulickel M; Grinstaff, Mark W; Arava, Leela Mohana Reddy

    2016-06-22

    Fabrication of lithium-ion batteries that operate from room temperature to elevated temperatures entails development and subsequent identification of electrolytes and electrodes. Room temperature ionic liquids (RTILs) can address the thermal stability issues, but their poor ionic conductivity at room temperature and compatibility with traditional graphite anodes limit their practical application. To address these challenges, we evaluated novel high energy density three-dimensional nano-silicon electrodes paired with 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide (Pip) ionic liquid/propylene carbonate (PC)/LiTFSI electrolytes. We observed that addition of PC had no detrimental effects on the thermal stability and flammability of the reported electrolytes, while largely improving the transport properties at lower temperatures. Detailed investigation of the electrochemical properties of silicon half-cells as a function of PC content, temperature, and current rates reveal that capacity increases with PC content and temperature and decreases with increased current rates. For example, addition of 20% PC led to a drastic improvement in capacity as observed for the Si electrodes at 25 °C, with stability over 100 charge/discharge cycles. At 100 °C, the capacity further increases by 3-4 times to 0.52 mA h cm(-2) (2230 mA h g(-1)) with minimal loss during cycling. PMID:27237138

  3. Effects of earthworms on soil aggregate stability and carbon and nitrogen storage in a legume cover crop agroecosystem.

    NARCIS (Netherlands)

    Ketterings, Q.M.; Blair, J.M.; Marinissen, J.C.Y.

    1997-01-01

    We investigated the effects of earthworms on soil aggregate size-distribution, water-stability, and the distribution of total C and N among aggregates of different sizes. Earthworm populations were experimentally manipulated (reduced, unaltered or increased) in field enclosures cropped to soybean (G

  4. Crystallization degree change of expanded graphite by milling and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Tang Qunwei [Key Laboratory for Functional Materials of Fujian Higher Education, Institute of Material Physical Chemistry, Huaqiao University, Quanzhou 362021 (China); Wu Jihuai [Key Laboratory for Functional Materials of Fujian Higher Education, Institute of Material Physical Chemistry, Huaqiao University, Quanzhou 362021 (China)], E-mail: jhwu@hqu.edu.cn; Sun Hui; Fang Shijun [Key Laboratory for Functional Materials of Fujian Higher Education, Institute of Material Physical Chemistry, Huaqiao University, Quanzhou 362021 (China)

    2009-05-05

    Expanded graphite was ball milled with a planetary mill in air atmosphere, and subsequently thermal annealed. The samples were characterized by using X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). It was found that in the milling initial stage (less than 12 h), the crystallization degree of the expanded graphite declined gradually, but after milling more than 16 h, a recrystallization of the expanded graphite toke place, and ordered nanoscale expanded graphite was formed gradually. In the annealing initial stage, the non-crystallization of the graphite occurred, but, beyond an annealing time, recrystallizations of the graphite arise. Higher annealing temperature supported the recrystallization. The milled and annealed expanded graphite still preserved the crystalline structure as raw material and hold high thermal stability.

  5. Size and Promoter Effects on Stability of Carbon-Nanofiber-Supported Iron-Based Fischer-Tropsch Catalysts

    NARCIS (Netherlands)

    Xie, Jingxiu; Torres Galvis, Hirsa; Koeken, Ard C J; Kirilin, Alexey; Dugulan, A Iulian; Ruitenbeek, Matthijs; de Jong, Krijn P

    2016-01-01

    The Fischer-Tropsch Synthesis converts synthesis gas from alternative carbon resources, including natural gas, coal, and biomass, to hydrocarbons used as fuels or chemicals. In particular, iron-based catalysts at elevated temperatures favor the selective production of C2-C4 olefins, which are import

  6. A comparative study on effects of heterotrophic microbial activity on the stability of bivalve and coral carbonate during early diagenesis.

    Science.gov (United States)

    Lange, Skadi M.; Krause, Stefan; Immenhauser, Adrian; Ritter, Ann-Christin; Gorb, Stanislav N.; Kleinteich, Thomas; Treude, Tina

    2016-04-01

    Following deposition and shallow burial, marine biogenic carbonates are exposed to an environment that is geochemically affected by a manifold of bacterial metabolic redox processes. To allow for comparison of potential microbe-mediated alteration effects on carbonates, we used aragonitic bivalve shell samples and porous aragonitic coral fragments for incubation experiments in oxic- and anoxic seawater media. The media contained marine sediment slurries or bacterial cultures to mimic the natural processes in vitro. The results for anoxic experimental media containing bivalve shell samples or coral fragments displayed considerable changes in carbonate-system parameters (pH, AT, CA, DIC) and divalent-cation ratios (Mg/Ca, Mg/Sr, Sr/Ca) over time. Furthermore, incubated bivalve shell samples were altered in morphology, elemental composition and isotopic signature. Coral-fragment bearing oxic incubations were run at two temperature regimes and divalent-cation ratios of the high-temperature bacterial medium displayed withdrawal of Ca2+ and Sr2+ from the medium, thus indicating microbe-induced secondary aragonite precipitation. Analyses of coral fragments include electron-microprobe mapping and X-ray microtomography to resolve elemental sample composition and pore-space alteration features, respectively. Up to this point our results indicate that heterotrophic bacterial activity has the potential to affect surficial or open pore space in carbonate archives by increasing rates of alteration relative to sterile environments.

  7. Temporal change in soil carbon stability at a paired old-growth douglas-fir forest/clear-cut site

    Science.gov (United States)

    Forest ecosystems are estimated to contain one-half of the total terrestrial carbon (C) pool (1146 Pg), with two-thirds of this C (787 Pg) residing in forest soils. Given the magnitude of this C pool, it is critical to understand the effects of forest management practices on soil...

  8. Impact of short-lived non-CO2 mitigation on carbon budgets for stabilizing global warming

    NARCIS (Netherlands)

    Rogelj, Joeri; Meinshausen, M.; Schaeffer, M.; Knutti, R.; Riahi, Keywan

    2015-01-01

    Limiting global warming to any level requires limiting the total amount of CO2 emissions, or staying within a CO2 budget. Here we assess how emissions from short-lived non-CO2 species like methane, hydrofluorocarbons (HFCs), black-carbon, and sulphates influence these CO2 budgets. Our default case,

  9. Interseismic re-strengthening and stabilization of carbonate faults by "non-Dieterich" healing under hydrothermal conditions

    NARCIS (Netherlands)

    Chen, Jianye; Verberne, Berend A.; Spiers, Christopher J.

    2015-01-01

    Friction experiments, consisting of a "velocity stepping" stage, a "slide-hold-slide" (SHS) stage and a second "velocity stepping" stage, have been performed to study the frictional healing behavior of carbonate fault gouge, and the effects of healing on the velocity dependence of friction, at 20-14

  10. Effect of heat treatment on the activity and stability of carbon supported PtMo alloy electrocatalysts for hydrogen oxidation in proton exchange membrane fuel cells

    Science.gov (United States)

    Hassan, Ayaz; Carreras, Alejo; Trincavelli, Jorge; Ticianelli, Edson Antonio

    2014-02-01

    The effect of heat treatment on the activity, stability and CO tolerance of PtMo/C catalysts was studied, due to their applicability in the anode of proton exchange membrane fuel cells (PEMFCs). To this purpose, a carbon supported PtMo (60:40) alloy electrocatalyst was synthesized by the formic acid reduction method, and samples of this catalyst were heat-treated at various temperatures ranging between 400 and 700 °C. The samples were characterized by temperature programmed reduction (TPR), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), cyclic voltammetry (CV), scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDS). Cyclic voltammetry was used to study the stability, and polarization curves were used to investigate the performance of all materials as CO tolerant anode on a PEM single cell text fixture. The catalyst treated at 600 °C, for which the average crystallite size was 16.7 nm, showed the highest hydrogen oxidation activity in the presence of CO, giving an overpotential induced by CO contamination of 100 mV at 1 Acm-2. This catalyst also showed a better stability up to 5000 potential cycles of cyclic voltammetry, as compared to the untreated catalyst. CV, SEM and WDS results indicated that a partial dissolution of Mo and its migration/diffusion from the anode to the cathode occurs during the single cell cycling. Polarization results showed that the catalytic activity and the stability can be improved by a heat treatment, in spite of a growth of the catalyst particles.

  11. Improving the stability and ethanol electro-oxidation activity of Pt catalysts by selectively anchoring Pt particles on carbon-nanotubes-supported-SnO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Li, J.J.; Wang, J.S.; Zhao, J.H.; Song, C.Y.; Wang, L.C. [School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou (China); Guo, X. [Department of Chemistry, Tsinghua University, Beijing (China)

    2012-10-15

    To improve the stability and activity of Pt catalysts for ethanol electro-oxidation, Pt nanoparticles were selectively deposited on carbon-nanotubes (CNTs)-supported-SnO{sub 2} to prepare Pt/SnO{sub 2}/CNTs and Pt/CNTs was prepared by impregnation method for reference study. X-ray diffraction (XRD) was used to confirm the crystalline structures of Pt/SnO{sub 2}/CNTs and Pt/CNTs. The stabilities of Pt/SnO{sub 2}/CNTs and Pt/CNTs were compared by analyzing the Pt size increase amplitude using transmission electron microscopy (TEM) images recorded before and after cyclic voltammetry (CV) sweeping. The results showed that the Pt size increase amplitude is evidently smaller for Pt/SnO{sub 2}/CNTs, indicating the higher stability of Pt/SnO{sub 2}/CNTs. Although both catalysts exhibit degradation of electrochemical active surface area (EAS) after CV sweeping, the EAS degradation for the former is lower, further confirming the higher stability of Pt/SnO{sub 2}/CNTs. CV and potentiostatic current-time curves were recorded for ethanol electro-oxidation on both catalysts before and after CV sweeping and the results showed that the mass specific activity of Pt/CNTs increases more than that of Pt/SnO{sub 2}/CNTs, indicating that Pt/CNTs experiences more severe evolution and is less stable. The calculated area specific activity of Pt/SnO{sub 2}/CNTs is larger than that of Pt/CNTs, indicating SnO{sub 2} can co-catalyze Pt due to plenty of interfaces between SnO{sub 2} and Pt. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Synergistically enhanced stability of highly flexible silver nanowire/carbon nanotube hybrid transparent electrodes by plasmonic welding.

    Science.gov (United States)

    Lee, Jongsoo; Woo, Ju Yeon; Kim, Ju Tae; Lee, Byung Yang; Han, Chang-Soo

    2014-07-23

    Here, we report highly transparent and flexible AgNW/SWCNT hybrid networks on PET substrates combined with plasmonic welding for securing ultrahigh stability in mechanical and electrical properties under severe bending. Plasmonic welding produces local heating and welding at the junction of AgNWs and leads strong adhesion between AgNW and SWCNT as well as between hybrid structure and substrate. The initial sheet resistance of plasmon treated AgNW/SWCNT hybrid film was 26 Ω sq(-1), with >90% optical transmittance over the wavelength range 400-2700 nm. Following 200 cycles of convex/concave bending with a bending radius of 5 mm, the sheet resistance changed from 26 to 29 Ω sq(-1). This hybrid structure combined with the plasmonic welding process provided excellent stability, low resistance, and high transparency, and is suitable for highly flexible electronics applications, including touch panels, solar cells, and OLEDs. PMID:24972024

  13. Nanoscale stabilization of zintl compounds: 1D ionic Li-P double helix confined inside a carbon nanotube.

    Science.gov (United States)

    Ivanov, Alexander S; Kar, Tapas; Boldyrev, Alexander I

    2016-02-14

    One-dimensional (1D) ionic nanowires are extremely rare materials due to the difficulty in stabilizing 1D chains of ions under ambient conditions. We demonstrate here a theoretical prediction of a novel hybrid material, a nanotube encapsulated 1D ionic lithium monophosphide (LiP) chain, featuring a unique double-helix structure, which is very unusual in inorganic chemistry. This nanocomposite has been investigated with density functional theory, including molecular dynamics simulations and electronic structure calculations. We find that the formation of the LiP double-helical nanowire is facilitated by strong interactions between LiP and CNTs resulting in a charge transfer. This work suggests that nanostructured confinement may be used to stabilize other polyphosphide 1D chains, thus opening new ways to study the chemistry of zintl compounds at the nanoscale.

  14. Effects of carbon on the stability and chemical performance of transition metal carbides: A density functional study

    Science.gov (United States)

    Liu, Ping; Rodriguez, José A.

    2004-03-01

    Density functional theory was employed to study the stabilities and chemical activities of transition metal carbides. Here we take the well-known Mo carbides and Ti carbides as an example. Different kinds of structures including the bulk surfaces [Mo2C(001), MoC(001), and TiC(001)] and metcars [Mo8C12 and Ti8C12] are taken into consideration. Systematic studies show that by raising the C coordination number of the metal atoms in the carbides, in general the stability of the carbides increases (metcars are an exception since they include both high-coordinated and low-coordinated metal atoms.); at the same time, the chemical activities of the carbides decrease due to a downshift of the metal d-band center (ligand effect). Considering the better catalysts those that combine high stability and moderate chemical activity, our results suggest that the catalytic potential of Mo carbide systems should decrease in the following sequence: Mo8C12>Mo2C(001) or MoC(001)>pure Mo(110). In spite of having the largest C/Mo ratio, the metcar appears as the most attractive system. Our studies also indicate that the "magic" behavior of metcars is not unique for Mo carbides. Similar behavior is also observed for Ti carbides. This implies that nanoparticles like metcar species could exhibit better performances than the corresponding bulk metal carbides as catalysts.

  15. Enhanced dispersion stability and mobility of carboxyl-functionalized carbon nanotubes in aqueous solutions through strong hydrogen bonds

    Energy Technology Data Exchange (ETDEWEB)

    Bahk, Yeon Kyoung; He, Xu; Gitsis, Emmanouil; Kuo, Yu-Ying [ETH Zurich, Institute of Environmental Engineering (Switzerland); Kim, Nayoung [EMPA, Building Energy Materials and Components (Switzerland); Wang, Jing, E-mail: jing.wang@ifu.baug.ethz.ch [ETH Zurich, Institute of Environmental Engineering (Switzerland)

    2015-10-15

    Dispersion of carbon nanotubes has been heavily studied due to its importance for their technical applications, toxic effects, and environmental impacts. Common electrolytes, such as sodium chloride and potassium chloride, promote agglomeration of nanoparticles in aqueous solutions. On the contrary, we discovered that acetic electrolytes enhanced the dispersion of multi-walled carbon nanotubes (MWCNTs) with carboxyl functional group through the strong hydrogen bond, which was confirmed by UV–Vis spectrometry, dispersion observations and aerosolization-quantification method. When concentrations of acetate electrolytes such as ammonium acetate (CH{sub 3}CO{sub 2}NH{sub 4}) and sodium acetate (CH{sub 3}CO{sub 2}Na) were lower than 0.03 mol per liter, MWCNT suspensions showed better dispersion and had higher mobility in porous media. The effects by the acetic environment are also applicable to other nanoparticles with the carboxyl functional group, which was demonstrated with polystyrene latex particles as an example.

  16. Enhanced dispersion stability and mobility of carboxyl-functionalized carbon nanotubes in aqueous solutions through strong hydrogen bonds

    International Nuclear Information System (INIS)

    Dispersion of carbon nanotubes has been heavily studied due to its importance for their technical applications, toxic effects, and environmental impacts. Common electrolytes, such as sodium chloride and potassium chloride, promote agglomeration of nanoparticles in aqueous solutions. On the contrary, we discovered that acetic electrolytes enhanced the dispersion of multi-walled carbon nanotubes (MWCNTs) with carboxyl functional group through the strong hydrogen bond, which was confirmed by UV–Vis spectrometry, dispersion observations and aerosolization-quantification method. When concentrations of acetate electrolytes such as ammonium acetate (CH3CO2NH4) and sodium acetate (CH3CO2Na) were lower than 0.03 mol per liter, MWCNT suspensions showed better dispersion and had higher mobility in porous media. The effects by the acetic environment are also applicable to other nanoparticles with the carboxyl functional group, which was demonstrated with polystyrene latex particles as an example

  17. On the stability of carbon nanotube and titania nanowire based catalyst materials:from synthesis to applications

    OpenAIRE

    Rautio, A.-R. (Anne-Riikka)

    2016-01-01

    Abstract Degradation of the support and sintering of catalyst nanoparticles inherently leads to a loss of functionality of catalyst materials in converters and sensors. Malfunction in such devices may lead to serious economic and environmental damage. The quest for novel and sustainable catalyst materials with better durability is thus ongoing. In this thesis, one-dimensional nanomaterials such as carbon nanotubes and titanium dioxide nanowires are studied and compared to their convention...

  18. The Strontium Isotope Record of Zavkhan Terrane Carbonates: Strontium Isotope Stability Through the Ediacaran-Cambrian Transition

    OpenAIRE

    Petach, Tanya N.

    2015-01-01

    First order trends in the strontium isotopic (87Sr/86Sr) composition of seawater are controlled by radiogenic inputs from the continent and non-radiogenic inputs from exchange at mid-ocean ridges. Carbonates precipitated in seawater preserve trace amounts of strontium that record this isotope ratio and therefore record the relative importance of mid-ocean ridge and weathering chemical inputs to sea water composition. It has been proposed that environmental changes during the Ediacaran-Cambria...

  19. Technology, innovation and the economic costs of ambitious atmospheric stabilization: A modeler's view of the global carbon problem

    Science.gov (United States)

    Mignone, B. K.

    2007-12-01

    Policies designed to avoid "dangerous anthropogenic interference" with the climate system often focus on targets for atmospheric carbon dioxide between 450 and 550 ppm. At the same time, economic analyses of policies designed to achieve these outcomes yield conflicting results, with the variability in global cost estimates in some recent comparisons spanning more than an order of magnitude. In this talk, I revisit the mitigation cost question in one well-documented integrated assessment model (MERGE), focusing on the sensitivity to the rate of energy efficiency improvements and the availability of future carbon-free energy supply technologies. By considering these effects in isolation, I control for many of the factors that prohibit mechanistic attribution in larger inter-model comparison studies. The results can be interpreted in one of two ways: as uncertainty analysis in which different combinations of parameters represent different possible future worlds outside the control of policy, or alternatively, as policy assessment, in which different collections of assumptions represent the endpoints of deliberate policy intervention. I discuss the latter interpretation in the context of recent political developments and highlight the implications of these results for the design of effective carbon control regimes.

  20. Synergistic effects from graphene and carbon nanotubes endow ordered hierarchical structure foams with a combination of compressibility, super-elasticity and stability and potential application as pressure sensors

    Science.gov (United States)

    Kuang, Jun; Dai, Zhaohe; Liu, Luqi; Yang, Zhou; Jin, Ming; Zhang, Zhong

    2015-05-01

    Nanostructured carbon material based three-dimensional porous architectures have been increasingly developed for various applications, e.g. sensors, elastomer conductors, and energy storage devices. Maintaining architectures with good mechanical performance, including elasticity, load-bearing capacity, fatigue resistance and mechanical stability, is prerequisite for realizing these functions. Though graphene and CNT offer opportunities as nanoscale building blocks, it still remains a great challenge to achieve good mechanical performance in their microarchitectures because of the need to precisely control the structure at different scales. Herein, we fabricate a hierarchical honeycomb-like structured hybrid foam based on both graphene and CNT. The resulting materials possess excellent properties of combined high specific strength, elasticity and mechanical stability, which cannot be achieved in neat CNT and graphene foams. The improved mechanical properties are attributed to the synergistic-effect-induced highly organized, multi-scaled hierarchical architectures. Moreover, with their excellent electrical conductivity, we demonstrated that the hybrid foams could be used as pressure sensors in the fields related to artificial skin.Nanostructured carbon material based three-dimensional porous architectures have been increasingly developed for various applications, e.g. sensors, elastomer conductors, and energy storage devices. Maintaining architectures with good mechanical performance, including elasticity, load-bearing capacity, fatigue resistance and mechanical stability, is prerequisite for realizing these functions. Though graphene and CNT offer opportunities as nanoscale building blocks, it still remains a great challenge to achieve good mechanical performance in their microarchitectures because of the need to precisely control the structure at different scales. Herein, we fabricate a hierarchical honeycomb-like structured hybrid foam based on both graphene and

  1. Most Blood Biomarkers Related to Vitamin Status, One-Carbon Metabolism, and the Kynurenine Pathway Show Adequate Preanalytical Stability and Within-Person Reproducibility to Allow Assessment of Exposure or Nutritional Status in Healthy Women and Cardiovascular Patients123

    OpenAIRE

    Midttun, Øivind; Townsend, Mary K.; Nygård, Ottar; Tworoger, Shelley S.; Brennan, Paul; Johansson, Mattias; Ueland, Per Magne

    2014-01-01

    Knowledge of stability during sample transportation and changes in biomarker concentrations within person over time are paramount for proper design and interpretation of epidemiologic studies based on a single measurement of biomarker status. Therefore, we investigated stability and intraindividual vs. interindividual variation in blood concentrations of biomarkers related to vitamin status, one-carbon metabolism, and the kynurenine pathway. Whole blood (EDTA and heparin, n = 12) was stored w...

  2. Effect of C–O Bonding on the Stability and Energetics of High-Energy Nitrogen-Carbon Molecules N10C2 and N16C2

    Directory of Open Access Journals (Sweden)

    Douglas L. Strout

    2014-01-01

    Full Text Available Molecules consisting of nitrogen have been the subject of much attention due to their potential as high-energy materials. Complex molecules consisting entirely of nitrogen can be subject to rapid decomposition, and therefore other atoms are incorporated into the structure to enhance stability. Previous studies have explored the incorporation of carbon atoms into otherwise all-nitrogen cages molecules. The current study involves two such cages, N10C2 and N16C2, whose structures are derived from N12 and N18, respectively. The N10C2 and N16C2 cages in this study are modified by bonding groups O3 and CO3 to determine the effect on the relative energies between the isomers and on the thermodynamic energy release properties. Energetic trends for N10C2 and N16C2 are calculated and discussed.

  3. The Evolution of Multicomponent Systems at High Pressures: VI. The Thermodynamic Stability of the Hydrogen-Carbon System: The Genesis of Hydrocarbons and the Origin of Petroleum

    CERN Document Server

    Kenney, J F; Bendeliani, N A; Alekseev, V A; Kutcherov, Vladimir G.; Bendeliani, Nikolai A.; Alekseev, Vladimir A.

    2002-01-01

    The spontaneous genesis of hydrocarbons which comprise natural petroleum have been analyzed by chemical thermodynamic stability theory. The constraints imposed upon chemical evolution by the second law of thermodynamics are briefly reviewed; and the effective prohibition of transformation, in the regime of temperatures and pressures characteristic of the near-surface crust of the Earth, of biological molecules into hydrocarbon molecules heavier than methane is recognized. A general, first-principles equation of state has been developed by extending scaled particle theory (SPT) and by using the technique of the factored partition function of the Simplified Perturbed Hard Chain Theory (SPHCT). The chemical potentials, and the respective thermodynamic Affinity, have been calculated for typical components of the hydrogen-carbon (H-C) system over a range pressures between 1-100 kbar, and at temperatures consistent with those of the depths of the Earth at such pressures. The theoretical analyses establish that the ...

  4. Active packaged lamb with oxygen scavenger/carbon dioxide emitter sachet: physical-chemical and microbiological stability during refrigerated storage

    Directory of Open Access Journals (Sweden)

    Marco Antonio Trindade

    2013-09-01

    Full Text Available Lamb meat has been commercialized in Brazil almost exclusively as a frozen product due to the longer shelf life provided by freezing when compared to refrigeration. However, as a result of the current trend of increased demand for convenience products, a need has emerged for further studies to facilitate the marketing of refrigerated lamb cuts. The aim of the present study was to evaluate the contribution of active packaging technology in extending the shelf life of lamb loins (Longissimus lumborum stored under refrigeration (1±1 ° C when compared to the traditional vacuum packaging. For this purpose, two kinds of sachets were employed: oxygen scavenger sachet and oxygen scavenger/carbon dioxide emitter sachet. Experiments were conducted in three treatments: 1 Vacuum (Control, 2 Vacuum + oxygen scavenger sachet and 3 Vacuum + oxygen scavenger/carbon dioxide emitter sachet. Microbiological (counts of anaerobic psychrotrophs, coliform at 45 ° C, coagulase-positive staphylococci, Salmonella and lactic acid bacteria and physical-chemical (thiobarbituric acid reactive substances, objective color, pH value, water loss from cooking and shear force analyses were carried out weekly for a total storage period of 28 days. The experiment was performed three times for all treatments. Results showed that the lamb meat remained stable with respect to the majority of the evaluated physical and chemical indexes and remained within the standards established by Brazilian legislation for pathogenic microorganisms throughout the storage period in all three packaging systems. However, all treatments presented elevated counts of anaerobic psychrotrophic microorganisms and lactic acid bacteria, reaching values above 10(7 CFU/g at 28 days of storage. Thus, under the conditions tested, neither the oxygen scavenger sachet nor the dual function sachet (oxygen scavenger/carbon dioxide emitter were able to extend the shelf life of refrigerated lamb loin when added to this

  5. Impact of short-lived non-CO2 mitigation on carbon budgets for stabilizing global warming

    International Nuclear Information System (INIS)

    Limiting global warming to any level requires limiting the total amount of CO2 emissions, or staying within a CO2 budget. Here we assess how emissions from short-lived non-CO2 species like methane, hydrofluorocarbons (HFCs), black-carbon, and sulphates influence these CO2 budgets. Our default case, which assumes mitigation in all sectors and of all gases, results in a CO2 budget between 2011–2100 of 340 PgC for a >66% chance of staying below 2°C, consistent with the assessment of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Extreme variations of air-pollutant emissions from black-carbon and sulphates influence this budget by about ±5%. In the hypothetical case of no methane or HFCs mitigation—which is unlikely when CO2 is stringently reduced—the budgets would be much smaller (40% or up to 60%, respectively). However, assuming very stringent CH4 mitigation as a sensitivity case, CO2 budgets could be 25% higher. A limit on cumulative CO2 emissions remains critical for temperature targets. Even a 25% higher CO2 budget still means peaking global emissions in the next two decades, and achieving net zero CO2 emissions during the third quarter of the 21st century. The leverage we have to affect the CO2 budget by targeting non-CO2 diminishes strongly along with CO2 mitigation, because these are partly linked through economic and technological factors. (letter)

  6. Endohedral confinement of a DNA dodecamer onto pristine carbon nanotubes and the stability of the canonical B form

    CERN Document Server

    Cruz, Fernando J A L; Mota, José P B

    2016-01-01

    Although carbon nanotubes are potential candidates for DNA encapsulation and subsequent delivery of biological payloads to living cells, the thermodynamical spontaneity of DNA encapsulation under physiological conditions is still a matter of debate. Using enhanced sampling techniques, we show for the first time that, given a sufficiently large carbon nanotube, the confinement of a double-stranded DNA segment, 5'-D(*CP*GP*CP*GP*AP*AP*TP*TP*CP*GP*CP*G)-3', is thermodynamically favourable under physiological environments (134 mM, 310 K, 1 bar), leading to DNA-nanotube hybrids with lower free energy than the unconfined biomolecule. A diameter threshold of 3 nm is established below which encapsulation is inhibited. The confined DNA segment maintains its translational mobility and exhibits the main geometrical features of the canonical B form. To accommodate itself within the nanopore, the DNA end-to-end length increases from 3.85 nm up to approximately 4.1 nm, due to a 0.3 nm elastic expansion of the strand termin...

  7. Application of Stabilized Silver Nanoparticles as Thin Films as Corrosion Inhibitors for Carbon Steel Alloy in 1 M Hydrochloric Acid

    Directory of Open Access Journals (Sweden)

    Ayman M. Atta

    2013-01-01

    Full Text Available Nanometer scaled materials have attracted tremendous interest as corrosion protective films due to their high ability to form self-assembled films on the metal surfaces. It is well known that the silver nanoparticles have higher reactivity towards aqueous acidic solution. The present work aims to prepare coated silver nanoparticles to protect carbon steel alloys from aqueous acidic corrosive media. In this respect, Ag nanoparticles colloid solutions were produced through reducing AgNO3 separately with trisodium citrate in an aqueous solution or in the presence of stabilizer such as poly(ethylene glycol thiol and poly(vinyl pyrrolidone. The morphology of the modified silver nanoparticles was investigated by TEM and DLS. UV-Vis absorption spectrum was used to study the effect of HCl on the stability of the dispersed silver nanoparticles. The corrosion inhibition efficiency of the poly (ethylene glycolthiol, the self-assembled monolayers of Ag nanoparticles, was determined by polarization method and electrochemical impedance spectroscopy (EIS. Polarization curves indicated that the coated silver poly (ethylene glycolthiol acted as a mixed type inhibitor. The data of inhibition efficiencies obtained measured by polarization measurements are in good agreement with those obtained with electrochemical impedance.

  8. Volterra系统全局稳定、扇形稳定及关联稳定的一些新判据%Some New Criterions for Overall Situation Stability, Sector Stability and Connection Stability of Volterra Systems

    Institute of Scientific and Technical Information of China (English)

    刘锋; 葛照强

    2007-01-01

    Stability of Volterra systems are discusses by subpositive definite matrix, and some new criterions for Volterra systems on overall situation stability, sector stability and connection stability are acquired. These results expand or improve some existing criterions.

  9. High kinetic stability of Zn(II) coordinated by the tris(histidine) unit of carbonic anhydrase towards solvolytic dissociation studied by affinity capillary electrophoresis.

    Science.gov (United States)

    Sato, Yosuke; Hoshino, Hitoshi; Iki, Nobuhiko

    2016-08-01

    Solvolytic dissociation rate constants (kd) of bovine carbonic anhydrase II (CA) and its metallovariants (M-CAs, M=Co(II), Ni(II), Cu(II), Zn(II), and Cd(II)) were estimated by a ligand substitution reaction, which was monitored by affinity capillary electrophoresis to selectively detect the undissociated CAs in the reaction mixture. Using EDTA as the competing ligand for Zn-CA, the dissociation followed the unimolecular nucleophilic substitution (SN1) mechanism with kd=1.0×10(-7)s(-1) (pH7.4, 25°C). The corresponding solvolysis half-life (t1/2) was 80days, showing the exceptionally high kinetic stability of t Zn-CA, in contrast to the highly labile [Zn(II)(H2O)6](2+), where the water exchange rate (kex) is high. This behavior is attributed to the tetrahedral coordination geometry supported by the tris(histidine) unit (His3) of CA. In the case of Co-CA, it showed a somewhat larger kd value (5.7×10(-7)s(-1), pH7.4, 25°C) even though it shares the same tetrahedral coordination environment with Zn-CA, suggesting that the d(7) electronic configuration of Co(II) in the transition state of the dissociation is stabilized by the ligand field. Among M-CAs, only Ni-CA showed a bimolecular nucleophilic substitution (SN2) reaction path in its reaction with EDTA, implying that the large coordination number (6) of Ni(II) in Ni-CA allows EDTA to form an EDTA-Ni-CA intermediate. Overall, kd values roughly correlated with kex values among M-CAs, with the kd value of Zn-CA deviating strongly from the trend and highlighting the exceptionally high kinetic stabilization of Zn-CA by the His3 unit. PMID:27235274

  10. Trivalent expanders and hyperbolic surfaces

    CERN Document Server

    Ivrissimtzis, Ioannis; Vdovina, Alina

    2012-01-01

    We introduce a family of trivalent expanders which tessellate compact hyperbolic surfaces with large isometry groups. We compare this family with Platonic graphs and modifications of them and prove topological and spectral properties of these families.

  11. DEX: self-healing expanders

    OpenAIRE

    Pandurangan, Gopal; Robinson, Peter,; Trehan, Amitabh

    2015-01-01

    We present a fully-distributed self-healing algorithm DEX, that maintains a constant degree expander network in a dynamic setting. To the best of our knowledge, our algorithm provides the first efficient distributed construction of expanders --- whose expansion properties hold {\\em deterministically} --- that works even under an all-powerful adaptive adversary that controls the dynamic changes to the network (the adversary has unlimited computational power and knowledge of the entire network ...

  12. Cyclic hydrogenation stability of γ-hydrides for Ti{sub 25}V{sub 35}Cr{sub 40} alloys doped with carbon

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Chia-Chieh, E-mail: ccshen@saturn.yzu.edu.tw [Department of Mechanical Engineering, Yuan Ze University, Chungli 32003, Taiwan (China); Graduate School of Renewable Energy and Engineering, Yuan Ze University, Chungli 32003, Taiwan (China); Fuel Cell Center, Yuan Ze University, Chungli 32003, Taiwan (China); Li, Hsueh-Chih [Graduate School of Renewable Energy and Engineering, Yuan Ze University, Chungli 32003, Taiwan (China)

    2015-11-05

    An automatic Sievert's apparatus equipped with a temperature-programmed desorption spectrometer was constructed to study the stability of annealed Ti{sub 25}V{sub 35}Cr{sub 40}C{sub x} (x = 0 and 0.1) alloy under cyclic hydrogenation at 6 N H{sub 2}. The specimens were tested at 30 °C with a hydrogen loading of around 1.00 H/M, which enabled the phase transformation from β-to γ-hydrides. After 500 cycles, 83% and 90% of the initial hydrogen capacities were preserved for Ti{sub 25}V{sub 35}Cr{sub 40} and Ti{sub 25}V{sub 35}Cr{sub 40}C{sub 0.1}, respectively. Therefore, a small amount of C doping was effective in reducing the hydrogenation degradation of Ti{sub 25}V{sub 35}Cr{sub 40}. The hydrogenation degradation of Ti{sub 25}V{sub 35}Cr{sub 40} was examined by measuring the P–C isotherms, temperature-programmed desorption spectra, and X-ray diffraction patterns. The degradation was ascribed to intrinsic disproportionation, i.e., Ti{sub 0.25}V{sub 0.35}Cr{sub 0.40} + 0.88H{sub 2} → yTiH{sub 2} + Ti{sub 0.25−y}V{sub 0.35}Cr{sub 0.40}H{sub 1.76–2y}, where the coefficient y indicates the amount of Ti-rich precipitate. The better cyclic hydrogenation stability of Ti{sub 25}V{sub 35}Cr{sub 40}C{sub 0.1} was related to the suppression of intrinsic disproportionation by the presence of carbon atoms in the body-centered-cubic lattice. - Highlights: • The stability of γ-hydride for Ti{sub 25}V{sub 35}Cr{sub 40} alloys was examined for 500 cycles. • The γ-hydride of Ti{sub 25}V{sub 35}Cr{sub 40} alloy degraded by intrinsic disproportionation. • The disproportionation of γ-hydride can be suppressed through carbon inclusion.

  13. Dissolved Organic Matter as a Mechanism for Carbon Stabilization at Depth in Wet Tropical Forest Volcanic Soils

    Science.gov (United States)

    Marin-Spiotta, E.; Kramer, M. G.; Chadwick, O. A.

    2007-12-01

    Dissolved organic matter (DOM) plays an important role in many biological and chemical processes in soils. Our understanding of the types of plant and microbially-derived organic matter that accumulate in soils and the mechanisms responsible for their transformation and stabilization is still limited. In particular, we know very little about how microbial activity and water movement contribute to the production of DOM and the formation of stable C in soils. In well-drained soils under wet climates, DOM is potentially a primary pathway for the transport of C from the surface litter layers and the zones of highest microbial activity to deeper horizons in the soil profile where the potential for long-term storage increases. The mechanisms for long-term stabilization of organic C in deep mineral horizons include an accumulation of chemically recalcitrant C, strong sorption of soluble and otherwise labile C to mineral and/or metals making them inaccessible to decomposers, and microenvironmental conditions (low pH, low O2) which result in incomplete decomposition and persistence of labile C. Although most work to date has focused on the role of dissolved organic C and N (DOC and DON) in the C and N cycles of temperate forests, DOM fluxes may be even more important in forests in the wet tropics, where high rainfall and high primary productivity could lead to greater DOM production. In order to address the role of DOC in the transport and stabilization of C in mineral horizons, we are studying DOC production, transformation, and loss pathways in volcanic soils dominated by highly reactive, non-crystalline minerals (allophane). We are quantifying flux and solute concentrations (C, N, cations, anions) in rainwater, throughfall, and in soil water. We have installed tension and zero tension lysimeters throughout sequentially deeper organic and mineral horizons in an intermediate aged soil (ca. 350k years) under wet (ca. 3000 mm mean annual rainfall) native tropical forest

  14. Stability constants important to the understanding of plutonium in environmental waters, hydroxy and carbonate complexation of PuO2+

    International Nuclear Information System (INIS)

    The formation constants for the reactions PuO2+ + H2O = PuO2(OH) + H+ and PuO2+ + CO32 = PuO2(CO3)- were determined in aqueous sodium perchlorate solutions by laser-induced photoacoustic spectroscopy. The molar absorptivity of the PuO2+ band at 569 nm decreased with increasing hydroxide concentration. Similarly, spectral changes occurred between 540 and 580 nm as the carbonate concentration was increased. The absorption data were analyzed by the non-linear least-squares program SQUAD to yield complexation constants. Using the specific ion interaction theory, both complexation constants were extrapolated to zero ionic strength. These thermodynamic complexation constants were combined with the oxidation-reduction potentials of Pu to obtain Eh versus pH diagrams. 120 refs., 35 figs., 12 tabs

  15. Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost

    Science.gov (United States)

    Euskirchen, Eugenie S; Edgar, C.W.; Turetsky, M.R.; Waldrop, Mark P.; Harden, Jennifer W.

    2016-01-01

    Changes in vegetation and soil properties following permafrost degradation and thermokarst development in peatlands may cause changes in net carbon storage. To better understand these dynamics, we established three sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, an internal collapse scar bog formed as a result of thermokarst, and a rich fen without permafrost. Measurements include year-round eddy covariance estimates of carbon dioxide (CO2), water, and energy fluxes, associated environmental variables, and methane (CH4) fluxes at the collapse scar bog. The ecosystems all acted as net sinks of CO2 in 2011 and 2012, when air temperature and precipitation remained near long-term means. In 2013, under a late snowmelt and late leaf out followed by a hot, dry summer, the permafrost forest and collapse scar bog were sources of CO2. In this same year, CO2 uptake in the fen increased, largely because summer inundation from groundwater inputs suppressed ecosystem respiration. CO2 exchange in the permafrost forest and collapse scar bog was sensitive to warm air temperatures, with 0.5 g C m−2 lost each day when maximum air temperature was very warm (≥29°C). The bog lost 4981 ± 300 mg CH4 m−2 between April and September 2013, indicating that this ecosystem acted as a significant source of both CO2 and CH4 to the atmosphere in 2013. These results suggest that boreal peatland responses to warming and drying, both of which are expected to occur in a changing climate, will depend on permafrost regime.

  16. Spatial Prediction of Soil Aggregate Stability and Aggregate-Associated Organic Carbon Content at the Catchment Scale Using Geostatistical Techniques

    Institute of Scientific and Technical Information of China (English)

    J.MOHAMMADI; M.H.MOTAGHIAN

    2011-01-01

    The association of organic carbon with secondary parzicles (aggregates) results in its storage and retention in soil. A study was carried out at a catchment covering about 92 km2 to predict spatial variability of soil water-stable aggregates (WSA), mean weight diameter (MWD) of aggregates and organic carbon (OC) content in macro- (> 2 mm), meso- (1-2 mm), and micro-aggregate (< 1 mm) fractions, using geostatistical methods. One hundred and eleven soil samples were c(o)llected at the 0-10 cm depth and fractionated into macro-, meso-, and micro-aggregates by wet sieving. The OC content was determined for each fraction. A greater percentage of water-stable aggregates was found for micro-aggregates, followed by meso-aggregates. Aggregate OC content was greatest in meso-aggregates (9 g kg-1), followed by micro-aggregates (7 g kg-1), while the least OC content was found in macro-aggregates (3 g kg-1). Although a significart effect (P = 0.000) of aggregate size on aggregate OC content was found, however, our findings did not support the model of aggregate hierarchy.Land use had a significant effect (P = 0.073) on aggregate OC content. The coefficients of variation (CVs) for OC contents associated with each aggregate fraction indicated macro-aggregates as the most variable (CV = 71%). Among the aggregate fractions, the micro-aggregate fraction had a lower CV value of 27%. The mean content of WSA ranged from 15% for macro-aggregates to 84% for micro-aggregates. Geostatistical analysis showed that the measured soil variables exhibited differences in their spatial patterns in both magnitude and space at each aggregate size fraction. The relative nugget variance for most aggregate-associated properties was lower than 45%. The range value for the variogram of water-stable aggregates was almost similar (about 3 km) for the three studied aggregate size classes. The range value for the variogram of aggregate-associated OC contents ranged from about 3 km for macro

  17. Soil Aggregate Stability and Aggregate-Associated Carbon Under Different Tillage Systems in the North China Plain

    Institute of Scientific and Technical Information of China (English)

    DU Zhang-liu; REN Tu-sheng; HU Chun-sheng; ZHANG Qing-zhong; Humberto Blanco-Canqui

    2013-01-01

    The inlfuences of tillage systems on soil carbon (C) stocks have been studied extensively, but the distribution of soil C within aggregate fractions is not well understood. The objective of this study was to determine the inlfuences of various tillage systems on soil aggregation and aggregate-associated C under wheat (Triticum aestivum L.) and corn (Zea mays L.) double cropping systems in the North China Plain. The experiment was established in 2001, including four treatments:moldboard plow (MP) with residue (MP+R) and without residue (MP-R), rotary tillage with residue (RT), and no-till with residue (NT). In 2007 soil samples were collected from the 0-5, 5-10, and 10-20 cm depths, and were separated into four aggregate-size classes (>2 000, 250-2 000, 53-250, and2 000 and 250-2 000 µm) compared with the MP-R and MP+R treatments. Averaged across all depths, mean weight diameters of aggregates (MWD) in NT and RT were 47 and 20% higher than that in MP+R. The concentration of bulk soil organic C was positively correlated with MWD (r=0.98; P=0.024) and macroaggregate fraction (r=0.96; P=0.036) in the 0-5 cm depth. In the 0-20 cm depth, comparing with MP+R, total C occluded in the>2 000 µm fraction was increased by 9 and 6%under NT and RT, respectively. We conclude that adoption of conservation tillage system, especially no-till, can increase soil macro-aggregation and total C accumulation in macroaggregates, which may improve soil C sequestration in the intensive agricultural region of the North China Plain.

  18. Carbon and hydrogen isotopic reversals in deep basin gas: Evidence for limits to the stability of hydrocarbons

    Science.gov (United States)

    Burruss, R.C.; Laughrey, C.D.

    2010-01-01

    During studies of unconventional natural gas reservoirs of Silurian and Ordovician age in the northern Appalachian basin we observed complete reversal of the normal trend of carbon isotopic composition, such that ??13C methane (C1) >??13C ethane (C2) >??13C propane (C3). In addition, we have observed isotopic reversals in the ??2H in the deepest samples. Isotopic reversals cannot be explained by current models of hydrocarbon gas generation. Previous observations of partial isotopic reversals have been explained by mixing between gases from different sources and thermal maturities. We have constructed a model which, in addition to mixing, requires Rayleigh fractionation of C2 and C3 to cause enrichment in 13C and create reversals. In the deepest samples, the normal trend of increasing enrichment of 13C and 2H in methane with increasing depth reverses and 2H becomes depleted as 13C becomes enriched. We propose that the reactions that drive Rayleigh fractionation of C2 and C3 involve redox reactions with transition metals and water at late stages of catagenesis at temperatures on the order of 250-300??C. Published ab initio calculated fractionation factors for C-C bond breaking in ethane at these temperatures are consistent with our observations. The reversed trend in ??2H in methane appears to be caused by isotopic exchange with formation water at the same temperatures. Our interpretation that Rayleigh fractionation during redox reactions is causing isotopic reversals has important implications for natural gas resources in deeply buried sedimentary basins. ?? 2010.

  19. Changes in soil organic carbon and aggregate stability after conversion to conservation tillage for seven years in the Huang-Huai-Hai Plain of China

    Institute of Scientific and Technical Information of China (English)

    SHU Xin; ZHU An-ning; ZHANG Jia-bao; YANG Wen-liang; XIN Xiu-li; ZHANG Xian-feng

    2015-01-01

    Soil aggregate stability and organic carbon (OC) are regarded as effective indicators of soil structure and quality. A long-term ifeld experiment was established in 2006 to examine the inlfuence of til age systems on soil aggregation and OC in a sandy loam soil in the Huang-Huai-Hai Plain of China. The study involved eight treatments:plowing every year with (TS) and without residue (T), plowing every 2 years with (2TS) and without residue (2T), plowing every 4 years with (4TS) and without residue (4T), and no plowing with (NTS) and without residue (NT). In 2013, soil samples were col ected at depths of 0–5, 5–10 and 10–20 cm, and separated into three aggregate-size classes:macroaggregates (>250μm), microaggregates (53–250μm) and the silt+clay fraction (microaggregates>silt+clay fraction. In the 0–5 cm soil layer, concentrations of macroaggregate-associated OC in 2TS, 4TS and NTS were 14, 56 and 83%higher than for T, whereas T had the greatest concentration of OC associated with the silt+clay fraction in the 10–20 cm layer. Soil OC concentrations under 4TS and NTS were signiifcantly higher (P<0.05) than that of T in the 0–10 cm layer. Residue retention promoted formation of macroaggregates, increased macroaggregate-associated OC concentrations and thus increased total soil OC stock. The macroaggregate-associated OC was positively correlated (R2=0.96) with soil OC concentration, while the silt+clay fraction-associated OC was negatively correlated (R2=0.82) with soil OC concentration. The concentration of soil OC was positively correlated with MWD (R2=0.94) and GMD (R2=0.92). We concluded that increasing til age intensity led to a loss of carbon (C)-rich macroaggregates and an increase of C-depleted silt+clay fraction. The conservation til age system, especial y NTS and 4TS, increased soil aggregate stability and promoted OC accumulation in macroaggregates, provided the potential to improve soil C sequestration and soil structure in the Huang

  20. Federal government expands compliance initiatives.

    Science.gov (United States)

    Dugan, J K

    1997-09-01

    In 1995, the Federal government initiated Operation Restore Trust to increase enforcement of fraud and abuse regulations in Medicare and Medicaid programs. With the success of the original initiative, the government is expanding the project to additional states and program areas. The initial scrutiny of home health agencies, nursing homes, hospice care, and durable medical equipment is being expanded to managed care plans and acute care hospitals with an eye toward DRG creep. To manage this increased enforcement activity, healthcare organizations should institute comprehensive corporate compliance programs. Such programs should provide a framework that delineates responsibilities and provides a systematic means to resolve issues in a timely manner.

  1. Stearic-acid/carbon-nanotube composites with tailored shape-stabilized phase transitions and light–heat conversion for thermal energy storage

    International Nuclear Information System (INIS)

    Highlights: • A facile preparation of shape-stabilized composite PCMs for thermal energy storage. • The composite PCMs present tunable phase change temperatures and enthalpy. • Sunlight-driven phase change for photothermal conversion and storage. - Abstract: The development of functional materials with both light–heat conversion and thermal energy storage properties is of crucial importance for efficient utilization of sunlight to meet the growing demand for sustainable energy. In this work, the shape-stabilized phase change composites were designed and prepared by integration of stearic acid (SA) and acid-treated carbon nanotubes (a-CNTs). The a-CNTs not only acted as a flexible matrix but also endowed the composites high light–heat conversion ability. The reversible phase transitions shifted from high temperatures (Tm = 74 °C, Tf = 57 °C) of pure SA to near room temperature (Tm = ∼30 °C, Tf = ∼22 °C) of SA/a-CNTs composites, probably resulting from the strong interface confinement effect. The phase change enthalpy of the SA/a-CNTs composite could also be tailored by changing the mass ratio of SA and a-CNTs. The composites containing SA of 54.2 wt.%, 67.8 wt.% and 79.5 wt.% presented the melting enthalpy of 76.3 J/g, 98.8 J/g and 111.8 J/g, respectively. Moreover, the phase transition of SA/a-CNTs composite could be driven by sunlight for the energy storage/release. Therefore, this research provides a new platform for improving solar utilization, and understanding the phase transition behaviors of organic PCMs in dimensionally confined environments as well

  2. Single-walled carbon nanotubes dispersed in aqueous media via non-covalent functionalization: effect of dispersant on the stability, cytotoxicity, and epigenetic toxicity of nanotube suspensions.

    Science.gov (United States)

    Alpatova, Alla L; Shan, Wenqian; Babica, Pavel; Upham, Brad L; Rogensues, Adam R; Masten, Susan J; Drown, Edward; Mohanty, Amar K; Alocilja, Evangelyn C; Tarabara, Volodymyr V

    2010-01-01

    As the range of applications for carbon nanotubes (CNTs) rapidly expands, understanding the effect of CNTs on prokaryotic and eukaryotic cell systems has become an important research priority, especially in light of recent reports of the facile dispersion of CNTs in a variety of aqueous systems including natural water. In this study, single-walled carbon nanotubes (SWCNTs) were dispersed in water using a range of natural (gum arabic, amylose, Suwannee River natural organic matter) and synthetic (polyvinyl pyrrolidone, Triton X-100) dispersing agents (dispersants) that attach to the CNT surface non-covalently via different physiosorption mechanisms. The charge and the average effective hydrodynamic diameter of suspended SWCNTs as well as the concentration of exfoliated SWCNTs in the dispersion were found to remain relatively stable over a period of 4 weeks. The cytotoxicity of suspended SWCNTs was assessed as a function of dispersant type and exposure time (up to 48 h) using general viability bioassay with Escherichia coli and using neutral red dye uptake (NDU) bioassay with WB-F344 rat liver epithelia cells. In the E. coli viability bioassays, three types of growth media with different organic loadings and salt contents were evaluated. When the dispersant itself was non-toxic, no losses of E. coli and WB-F344 viability were observed. The cell viability was affected only by SWCNTs dispersed using Triton X-100, which was cytotoxic in SWCNT-free (control) solution. The epigenetic toxicity of dispersed CNTs was evaluated using gap junction intercellular communication (GJIC) bioassay applied to WB-F344 rat liver epithelial cells. With all SWCNT suspensions except those where SWCNTs were dispersed using Triton X-100 (wherein GJIC could not be measured because the sample was cytotoxic), no inhibition of GJIC in the presence of SWCNTs was observed. These results suggest a strong dependence of the toxicity of SWCNT suspensions on the toxicity of the dispersant and point to

  3. Ocean sequestration of carbon dioxide: modeling the deep ocean release of a dense emulsion of liquid Co2-in-water stabilized by pulverized limestone particles.

    Science.gov (United States)

    Golomb, D; Pennell, S; Ryan, D; Barry, E; Swett, P

    2007-07-01

    The release into the deep ocean of an emulsion of liquid carbon dioxide-in-seawater stabilized by fine particles of pulverized limestone (CaCO3) is modeled. The emulsion is denser than seawater, hence, it will sink deeper from the injection point, increasing the sequestration period. Also, the presence of CaCO3 will partially buffer the carbonic acid that results when the emulsion eventually disintegrates. The distance that the plume sinks depends on the density stratification of the ocean, the amount of the released emulsion, and the entrainment factor. When released into the open ocean, a plume containing the CO2 output of a 1000 MW(el) coal-fired power plant will typically sink hundreds of meters below the injection point. When released from a pipe into a valley on the continental shelf, the plume will sink about twice as far because of the limited entrainment of ambient seawater when the plume flows along the valley. A practical system is described involving a static mixer for the in situ creation of the CO2/seawater/pulverized limestone emulsion. The creation of the emulsion requires significant amounts of pulverized limestone, on the order of 0.5 tons per ton of liquid CO2. That increases the cost of ocean sequestration by about $13/ ton of CO2 sequestered. However, the additional cost may be compensated by the savings in transportation costs to greater depth, and because the release of an emulsion will not acidify the seawater around the release point. PMID:17695916

  4. Land use Effects on Storage, Stability and Structure of Organic Carbon in Soil Density Fractions Revealed by 13C Natural Abundance and CPMAS 13C NMR

    Science.gov (United States)

    Flessa, H.; Helfrich, M.; John, B.; Yamashita, T.; Ludwig, B.

    2004-12-01

    The type of land use and soil cultivation are important factors controlling organic carbon storage (SOC) in soils and they can also influence the relative importance, the structure, and the stability of different SOC pools. The objectives of our study were: i) to quantify the SOC stocks in different density fractions (mineral-associated soil organic matter > 2 g cm-3 (Mineral-SOM), free particulate organic matter soils under different land use (spruce forest, grassland, maize, wheat), ii) to determine the structure of these SOC fractions by CPMAS 13C NMR spectroscopy, and iii) to analyse the stability of these SOC fractions in the maize soil on the basis of the stable isotope composition of SOC. The SOC concentration in the A horizon increased in the order wheat (12.7 g kg-1) soil, the particulate organic matter accounted for 52% of the total SOC content. The chemical structure of the soil organic matter (SOM) was influenced by litter quality, the intensity of litter decomposition and the related production and storage of microbially-derived substances. SOM of the acid forest soil was characterized by large amounts of POM with a high content of spruce litter-derived alkyl C. In the biologically more active grassland and maize soil, litter-derived POM was decomposed more rapidly and SOC stocks were dominated by mineral-associated SOM which contained greater proportions of aryl and carbonyl C. The cultivation of the grassland soil induced enhanced mineralization of POM and in particular of mineral-associated SOM. The faster SOC turnover was associated with a relative accumulation of aromatic and carbonyl C structures in the mineral-bound SOM. In all soils, the free particulate organic matter had a smaller proportion of alkyl C and a larger proportion of O-alkyl C than the particulate organic matter occluded in aggregates. The mean age of the SOM in the density fractions of the maize soil increased with increasing aromaticity in the order free POM (22 yr) humification

  5. Heptaphyrins: Expanded porphyrins with seven heterocyclic rings

    Indian Academy of Sciences (India)

    Venkataramanarao G Anand; Simi K Pushpan; Sundararaman Venkatraman; Tavarekere K Chandrashekar

    2003-10-01

    Expanded porphyrins containing seven pyrrole/heterocyclic rings linked in a cyclic fashion are termed heptaphyrins. The number of -electrons in heptaphyrins depends on the number of meso carbon bridges used to link the heterocyclic rings, accordingly heptaphyrins with 28-electrons and 30 -electrons are reported to date. Both condensation reactions of the appropriate precursors and acid-catalysed oxidative coupling reactions have been utilized to synthesise the heptaphyrins. The 30 heptaphyrins exhibit rich structural diversity where some of the heterocyclic rings in the macrocycle undergo a 180° ring flipping. An overview of the synthetic methods employed for the synthesis of heptaphyrins, their spectroscopic properties, structural behaviour and aromatic properties are highlighted in this paper.

  6. Applying a new procedure to assess the controls on aggregate stability - including soil parent material and soil organic carbon concentrations - at the landscape scale

    Science.gov (United States)

    Turner, Gren; Rawlins, Barry; Wragg, Joanna; Lark, Murray

    2014-05-01

    Aggregate stability is an important physical indicator of soil quality and influences the potential for erosive losses from the landscape, so methods are required to measure it rapidly and cost-effectively. Previously we demonstrated a novel method for quantifying the stability of soil aggregates using a laser granulometer (Rawlins et al., 2012). We have developed our method further to mimic field conditions more closely by incorporating a procedure for pre-wetting aggregates (for 30 minutes on a filter paper) prior to applying the test. The first measurement of particle-size distribution is made on the water stable aggregates after these have been added to circulating water (aggregate size range 1000 to 2000 µm). The second measurement is made on the disaggregated material after the circulating aggregates have been disrupted with ultrasound (sonication). We then compute the difference between the mean weight diameters (MWD) of these two size distributions; we refer to this value as the disaggregation reduction (DR; µm). Soils with more stable aggregates, which are resistant to both slaking and mechanical breakdown by the hydrodynamic forces during circulation, have larger values of DR. We made repeated analyses of DR using an aggregate reference material (RM; a paleosol with well-characterised disaggregation properties) and used this throughout our analyses to demonstrate our approach was reproducible. We applied our modified technique - and also the previous technique in which dry aggregates were used - to a set of 60 topsoil samples (depth 0-15 cm) from cultivated land across a large region (10 000 km2) of eastern England. We wished to investigate: (i) any differences in aggregate stability (DR measurements) using dry or pre-wet aggregates, and (ii) the dominant controls on the stability of aggregates in water using wet aggregates, including variations in mineralogy and soil organic carbon (SOC) content, and any interaction between them. The sixty soil

  7. Expanding the eukaryotic genetic code

    Science.gov (United States)

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2013-01-22

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  8. Expanding the eukaryotic genetic code

    Energy Technology Data Exchange (ETDEWEB)

    Chin, Jason W; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G

    2015-02-03

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  9. ERBU, Expanding Rubber Band Universe

    CERN Document Server

    Soares, Domingos

    2015-01-01

    I put forward a simple unidimensional mechanical analogue of the three-dimensional universe models of modern relativistic cosmology. The main goal of the proposal is the appropriate appreciation of the intrinsic relationship between Hubble's law and the homogeneity of expanding relativistic models.

  10. Carbon dioxide-expanded ethanol-assisted synthesis of carbon-based metal composites and their catalytic and electrochemical performance in lithium-ion batteries%二氧化碳膨胀乙醇体系中碳基金属复合物的合成及其催化和电化学性能

    Institute of Scientific and Technical Information of China (English)

    王凌燕; 禚林海; 赵凤玉

    2016-01-01

    Highly dispersed metals, metal oxides and their composites on substrates have received considera‐ble interest in catalysis and lithium‐ion batteries, because of their superior properties compared with their single‐component counterparts. In this review, we introduce the properties of super‐critical carbon dioxide (scCO2) expanded ethanol, such as low viscosity, near‐zero surface tension and high diffusivity. We discuss the deposition procedure and formation mechanism of car‐bon‐based composites in scCO2‐expanded ethanol. This method has been used to fabricate several carbon‐based composites, such as metal and metal oxide composites deposited on zero‐dimensional colloidal carbon, one‐dimensional carbon nanotubes, two‐dimensional graphene, and three‐dimensional hierarchical porous carbon. These materials and their performance as anodic materials for lithium‐ion batteries will also be reviewed.%与块体材料相比,功能复合材料表现了更加优异的性能,而且比其中任何单一组分的性能都好,因此在催化、锂离子电池等领域得以广泛研究。通常情况下,在复合材料的制备中金属或金属氧化物粒子要求能够以足够小的粒径在基底上均匀分散,并实现活性组分负载量的可控。据报道,很多方法可以将金属(或氧化物)活性组分引入到载体之中,比如水热/溶剂热、水解、热分解、化学气相沉积等,但这些方法均存在如下缺点。第一,为了获得满意的负载量和可控包覆,碳基底需要预氧化处理使其表面含有丰富的含氧官能团。例如,由于碳纳米管自身的相容性和加工性较差,需要硝酸预氧化处理;石墨烯也需要预处理为石墨烯氧化物然后再进行第二组分的负载。但是,剧烈的氧化处理条件不可避免地造成对碳sp2结构和电子特性的破坏,并且增加了繁杂的后续处理过程。第二,金属组分前驱体在基底上

  11. Structure, stability, and nature of bonding in carbon monoxide bound EX3+ complexes (E = group 14 element; X = H, F, Cl, Br, I).

    Science.gov (United States)

    Ghara, Manas; Pan, Sudip; Kumar, Anand; Merino, Gabriel; Chattaraj, Pratim K

    2016-09-15

    A density functional theory study is performed to predict the structures and stability of carbon monoxide (CO) bound EX3+ (E = C, Si, Ge, Sn, Pb; X = H, F, Cl, Br, I) complexes. The possibility of bonding through both C- and O-sides of CO is considered. Thermochemical analysis reveals that all the dissociation processes producing CO and EX3+ are endothermic in nature whereas most of the dissociation reactions are endergonic in nature at room temperature. The nature of bonding in EC/O bonds is analyzed via Wiberg bond index, natural population analysis, electron density, and energy decomposition analyses in conjunction with natural orbitals for chemical valence scheme. In comparison to CO stretching frequency ( ν∼CO) in free CO, while a red shift is noted in O-side binding, the C-side binding results in a blue shift in ν∼CO. The relative change in ν∼CO values in CO bound EX3+ complexes on changing either E or X is scrutinized and possible explanation is provided in terms of polarization in the σ- and π-orbitals and the relative strength of C→E or O→E σ-donation and E→C or E→O π-back-donation. © 2016 Wiley Periodicals, Inc. PMID:27425405

  12. The improvement by a CVD silica coating of the oxidation behaviour of a 20%Cr/25%Ni niobium stabilized stainless steel in carbon dioxide

    International Nuclear Information System (INIS)

    The improvement of the oxidation behaviour of the 20%Cr-25%Ni-Nb stabilized (20/25/Nb) austenitic stainless steel, in carbon dioxide, by a silica coating, formed by a vapour reaction upon the pre-oxidized steel surface, has been examined at 8250C. The exposure periods extended to 5975 h duration. The silica coating effectiveness increased with its thickness over the range examined, 0.5 to 27 μm. Coatings > approximately 2 μm thick reduced the extent of oxidation by at least a factor of five by providing a barrier to the diffusion of cations outwards and oxidant inwards responsible for oxide growth on the 20/25/Nb steel. In addition, they completely inhibited oxide spallation because oxidation of the steel constituents occurred primarily within the silica coating whose adherence was maintained throughout the exposure. During the prolonged heat treatment of > approximately 2 μm thick silica coated steel, the iron and nickel constituents in the precoating oxide film were reduced by solid-solid reaction with manganese and probably also chromium from the underlying steel. (author)

  13. Influence of humic acid applications on modulus of rupture, aggregate stability, electrical conductivity, carbon and nitrogen content of a crusting problem soil

    Science.gov (United States)

    Gümüş, İ.; Şeker, C.

    2015-11-01

    Soil structure is often said to be the key to soil productivity since a fertile soil, with desirable soil structure and adequate moisture supply, constitutes a productive soil. Soil structure influences soil water movement and retention, erosion, crusting, nutrient recycling, root penetration and crop yield. The objective of this work is to study humic acid (HA) application on some physical and chemical properties in weakly structured soils. The approach involved establishing a plot experiment in laboratory conditions. Different rates of HA (control, 0.5, 1, 2 and 4 %) were applied to soil during three incubation periods (21, 42 and 62 days). At the end of the each incubation period, the changes in physicochemical properties were measured. Generally, HA addition increased electrical conductivity values during all incubation periods. HA applications decreased soil modulus of rupture. Application of HA at the rate of 4 % significantly increased soil organic carbon contents. HA applications at the rate of 4 % significantly increased both mean soil total nitrogen content and aggregate stability after three incubation periods (p < 0.05). Therefore, HA has the potential to improve the structure of soil in the short term.

  14. Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability

    Science.gov (United States)

    Pawar, Rajendra C.; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S.

    2016-08-01

    A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g-1) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g-1). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective.

  15. Mesoporous carbon stabilized MgO nanoparticles synthesized by pyrolysis of MgCl2 preloaded waste biomass for highly efficient CO2 capture.

    Science.gov (United States)

    Liu, Wu-Jun; Jiang, Hong; Tian, Ke; Ding, Yan-Wei; Yu, Han-Qing

    2013-08-20

    Anthropogenic CO2 emission makes significant contribution to global climate change and CO2 capture and storage is a currently a preferred technology to change the trajectory toward irreversible global warming. In this work, we reported a new strategy that the inexhaustible MgCl2 in seawater and the abundantly available biomass waste can be utilized to prepare mesoporous carbon stabilized MgO nanoparticles (mPC-MgO) for CO2 capture. The mPC-MgO showed excellent performance in the CO2 capture process with the maximum capacity of 5.45 mol kg(-1), much higher than many other MgO based CO2 trappers. The CO2 capture capacity of the mPC-MgO material kept almost unchanged in 19-run cyclic reuse, and can be regenerated at low temperature. The mechanism for the CO2 capture by the mPC-MgO was investigated by FTIR and XPS, and the results indicated that the high CO2 capture capacity and the favorable selectivity of the as-prepared materials were mainly attributed to their special structure (i.e., surface area, functional groups, and the MgO NPs). This work would open up a new pathway to slow down global warming as well as resolve the pollution of waste biomass.

  16. Conceptual design and scaled experimental validation of an actively damped carbon tie rods support system for the stabilization of future particle collider superstructures.

    Science.gov (United States)

    Collette, C; Tshilumba, D; Fueyo-Rosa, L; Romanescu, I

    2013-02-01

    This paper presents a simple solution to increase the stability of the large superstructures supporting the final electromagnets of future linear particle collider. It consists of active carbon fiber tie rods, fixed at one end on the structure and at the other end to the detector through active tendons. In the first part of the paper, the solution has been tested on a finite element model of one half of the CLIC_ILD final focus structure. With a reasonable design, it is shown numerically that the compliance can be decreased by at least a factor 4, i.e., that the structure is 4 times more robust to technical noise at low frequency. Two additional features of the active rods are that they can also actively damp the structural resonances and realign the superstructures. The second part of the paper presents a successful experimental validation of the concept, applied to a scaled test bench, especially designed to contain the same modal characteristics as the full scale superstructure.

  17. On the stability of conventional and nano-structured carbon-based catalysts in the oxidative dehydrogenation of ethylbenzene under industrially relevant conditions

    NARCIS (Netherlands)

    Zarubina, Valeriya; Talebi, Hesamoddin; Nederlof, Christian; Kapteijn, Freek; Makkee, Michiel; Melian-Cabrera, Ignacio

    2014-01-01

    Relevant carbon-based materials, home-made carbon-silica hybrids, commercial activated carbon, and nanostructured multi-walled carbon nanotubes (MWCNT) were tested in the oxidative dehydrogenation of ethylbenzene (EB). Special attention was given to the reaction conditions, using a relatively concen

  18. Potential and barriers for biogas production in Denmark at widely expanded organic farming with focus on the soil carbon content; Potentiale og barrierer for biogasproduktion i Danmark ved omfattende oekologisk jordbrug med fokus paa dyrkningsjordens kulstofforhold

    Energy Technology Data Exchange (ETDEWEB)

    Buch Salomonsen, K.

    2000-06-01

    The Ph.D. thesis describes the influence from continued expansion of organic farming systems to the potential for energy production from biogas in Denmark. The project analyses the consequence from three categories of barriers: 1) Practical barriers, 2) The attitude of organic farmers, and 3) Agricultural biological problems. Economic and political barriers are not examined. When the barriers can be quantified, they are included in the calculation of the maximum biogas potential. When not, the implications of barriers are expressed qualitatively. It has been a particular goal to provide new information on whether agricultural biological problems are a barrier to biogas production in organic farming systems. One important question in this connection is whether biogas production has a negative influence on the soil carbon content compared to composting. This question is investigated by an experiment. The project is based on technical and natural science disciplines, with an interdisciplinary basis ranging over energy planning, agricultural science, microbiology, and crop, and animal operation. (au)

  19. 47 CFR 64.1401 - Expanded interconnection.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Expanded interconnection. 64.1401 Section 64...) MISCELLANEOUS RULES RELATING TO COMMON CARRIERS Expanded Interconnection § 64.1401 Expanded interconnection. (a... 69, subpart G of this chapter, shall offer expanded interconnection for interstate special...

  20. 纳米石墨片/共聚物复合材料及其耐热、导电和气密性%Dispersion of expanded graphite as nanoplatelets in a copolymer matrix and its effect on thermal stability, electrical conductivity and permeability

    Institute of Scientific and Technical Information of China (English)

    Gyanaranjan Prusty; Sarat K Swain

    2012-01-01

    Expanded graphite/polyacrylonitrile-co-poly ( methyl methacrylate) (EG/PAN-co-PMMA) composites were prepared by the incorporation of EG at various concentrations (1,2,3,and 4%,w/w) into PAN-co-PMMA by an in situ emulsifier-free emulsion polymerization method.As-synthesized composites were characterized by UV/VIS and FT-IR,XRD,SEM,TEM and TGA.The thermal stability of the copolymer was significantly improved by the addition of EG.The oxygen permeabilities of the composites were substantially reduced and the electrical conductivities of the composites were significantly increased by increasing the EG content.%通过原位乳化聚合制备了不同膨胀石墨含量(1%、2%、3%和4%质量分数)的聚丙烯腈-聚甲基丙烯酸甲酯共聚物/膨胀石墨纳米复合材料.通过紫外-可见和傅里叶变换红外光谱验证了共聚物及纳米复合材料结构的形成.用X射线衍射、扫描电镜、透射电镜研究了膨胀石墨在聚合物基体中的分散性及其形貌.用热重考察了复合材料的耐热稳定性,同时也考察了复合材料的电导特性及其阻抗随膨胀石墨含量的变化规律.研究表明,随着复合材料中石墨含量的增加,复合材料的氧气密性和热稳定性获得较大程度的改善.

  1. Relativistically expanding cylindrical electromagnetic fields

    OpenAIRE

    Gourgouliatos, K. N.

    2009-01-01

    We study relativistically expanding electromagnetic fields of cylindrical geometry. The fields emerge from the side surface of a cylinder and are invariant under translations parallel to the axis of the cylinder. The expansion velocity is in the radial direction and is parametrized by $v=R/(ct)$. We consider force-free magnetic fields by setting the total force the electromagnetic field exerts on the charges and the currents equal to zero. Analytical and semi-analytical separable solutions ar...

  2. Durability of expanded polystyrene mortars

    OpenAIRE

    Ferrándiz Mas, Verónica; García Alcocel, Eva María

    2013-01-01

    The influence of the addition of various types and various concentrations of expanded polystyrene foam (both commercial and recycled) on the durability of Portland cement mortars is studied. In particular, the microstructure is studied utilizing the following methods: capillary absorption of water, mercury intrusion porosimetry, impedance spectroscopy and open porosity. In addition, the effects of heat cycles and freeze–thaw cycles on compressive strength are examined. Scanning electron micro...

  3. DEX: self-healing expanders

    OpenAIRE

    Pandurangan, Gopal; Robinson, Peter,; Trehan, Amitabh

    2016-01-01

    We present a fully-distributed self-healing algorithm dex that maintains a constant degree expander network in a dynamic setting. To the best of our knowledge, our algorithm provides the first efficient distributed construction of expanders—whose expansion properties holddeterministically—that works even under an all-powerful adaptive adversary that controls the dynamic changes to the network (the adversary has unlimited computational power and knowledge of the entire network state, can decid...

  4. [Effect of Long-term Fertilizer Application on the Stability of Organic Carbon in Particle Size Fractions of a Paddy Soil in Zhejiang Province, China].

    Science.gov (United States)

    Mao, Xia-li; Lu, Kou-ping; Sun, Tao; Zhang, Xiao-kai; He, Li-zhi; Wang, Hai-long

    2015-05-01

    Effects of chemical fertilizers and organic manure on the soil organic carbon (SOC) content in particle size fractions of paddy soil were investigated in a 17-year long-term fertilization field experiment in Zhejiang Province, China. The inherent chemical composition of silt- and clay-associated SOC was evaluated with solid-state 13C-NMR spectroscopy. Compared to CK (no fertilizer treatment), NPKRS (NPK fertilizers plus rice straw) , NPKOM (NPK fertilizers plus organic manure) , NPK (NPK fertilizers) and OM (organic manure alone) treatments significantly (P fertilizers alone, combined application of organic amendments and NPK fertilizers facilitated the storage of newly sequestered SOC in silt- and clay-sized fractions, which could be more conducive to the stability of SOC. Based on 13C-NMR spectra, both silt and clay fractions were composed of Alkyl-C, O-alkyl-C, Aromatic-C and carbonyl-C. Changes in the relative proportion of different C species were observed between silt and clay fractions: the clay fraction had relatively more Alkyl-C, carbonyl-C and less O-alkyl-C, Aromatic-C than those in the silt fraction. This might be ascribed to the fact that the organic matter complexed with clay was dominated by microbial products, whereas the silt appeared to be rich in aromatic residues derived from plants. The spectra also showed that the relative proportion of different C species was modified by fertilization practices. In comparison with organic amendments alone, the relative proportion of Alkyl-C was decreased by 9.1%-11.9% and 13.7%-19.9% under combined application of organic amendments and chemical fertilizers, for silt and clay, respectively, and that of O-alkyl-C was increased by 2.9%-6.3% and 13.4%-22.1%, respectively. These results indicated that NPKOM and NPKRS treatments reduced the decomposition rate of SOC. The aromaticity, hydrophobicity and, hence, chemical recalcitrance of silt- and clay-associated SOC in the NPK fertilizer treatments were lower than

  5. [Effect of Long-term Fertilizer Application on the Stability of Organic Carbon in Particle Size Fractions of a Paddy Soil in Zhejiang Province, China].

    Science.gov (United States)

    Mao, Xia-li; Lu, Kou-ping; Sun, Tao; Zhang, Xiao-kai; He, Li-zhi; Wang, Hai-long

    2015-05-01

    Effects of chemical fertilizers and organic manure on the soil organic carbon (SOC) content in particle size fractions of paddy soil were investigated in a 17-year long-term fertilization field experiment in Zhejiang Province, China. The inherent chemical composition of silt- and clay-associated SOC was evaluated with solid-state 13C-NMR spectroscopy. Compared to CK (no fertilizer treatment), NPKRS (NPK fertilizers plus rice straw) , NPKOM (NPK fertilizers plus organic manure) , NPK (NPK fertilizers) and OM (organic manure alone) treatments significantly (P NPK fertilizers alone, combined application of organic amendments and NPK fertilizers facilitated the storage of newly sequestered SOC in silt- and clay-sized fractions, which could be more conducive to the stability of SOC. Based on 13C-NMR spectra, both silt and clay fractions were composed of Alkyl-C, O-alkyl-C, Aromatic-C and carbonyl-C. Changes in the relative proportion of different C species were observed between silt and clay fractions: the clay fraction had relatively more Alkyl-C, carbonyl-C and less O-alkyl-C, Aromatic-C than those in the silt fraction. This might be ascribed to the fact that the organic matter complexed with clay was dominated by microbial products, whereas the silt appeared to be rich in aromatic residues derived from plants. The spectra also showed that the relative proportion of different C species was modified by fertilization practices. In comparison with organic amendments alone, the relative proportion of Alkyl-C was decreased by 9.1%-11.9% and 13.7%-19.9% under combined application of organic amendments and chemical fertilizers, for silt and clay, respectively, and that of O-alkyl-C was increased by 2.9%-6.3% and 13.4%-22.1%, respectively. These results indicated that NPKOM and NPKRS treatments reduced the decomposition rate of SOC. The aromaticity, hydrophobicity and, hence, chemical recalcitrance of silt- and clay-associated SOC in the NPK fertilizer treatments were lower

  6. Effects of Land Use Practices on the Organic Carbon Content, Cation Exchange Capacity and Aggregate Stability of Soils in the Catchment Zones

    Directory of Open Access Journals (Sweden)

    Mosayeb Heshmati

    2011-01-01

    Full Text Available Problem statement: Land use practice leads to changes in the physico-chemical properties of soils, such as Soil Organic Carbon (SOC, Cation Exchange Capacity (CEC and Soil Aggregate Stability (SAS that cause soil erosion. Approach: Merek catchment, Iran suffers from land degradation due to poor land use practice. A study was carried out with the objectives: (i to determine soil nutrient status in different agro-ecological zones in Merek catchment; and (ii to evaluate the influence of land use practices on SOC, CEC and SAS. Results: It was found that soil texture was silty and clay, while soil reaction was alkaline (pH was 7.75. The respective amount of carbonates was 32 and 36% in the top-soil and sub-soil respectively, indicating high level of alkalinity in the soils of the study area. The mean SAS of the surface soil layer for agriculture, rangeland and forest was 53, 61 and 64%, respectively with its mean in the topsoil of agriculture is significantly lower (P≤0.05 than the other zones. SOC level in the agriculture, rangeland and forest were 1.35, 1.56, 2.14 % in the topsoil and 1.03, 1.33 and 1.45%, in the subsoil of the respective areas. The results of t-test and ANOVA analyses showed that SOC means are significantly different from each other within soil depth and among agro-ecological zones. The CEC in the agriculture, rangeland and forest areas were 25.8, 24.6 and 35.1 cmolckg-1 for the top-soil and 31.1, 26.8 and 26.9 cmolckg-1 in the sub-soil, respectively. All the above changes are due to the negative effects of agricultural activities. Conclusion: Improper tillage practice (up-down the slope, conversion of the rangeland and forest to rain-fed areas, crop residue burning, over grazing and forest clearance contribute to reduction in SOC and SAS in the Merek catchment, Iran.

  7. Stability tables for opencast mining of coal and sedimentary deposits in inclined seams. Abacos de estabilidad para mineria de carbon y sedimentaria a cielo abierto con capas inclinadas

    Energy Technology Data Exchange (ETDEWEB)

    Ayala, F.J.; Granda, J.R.; Sarti, A.

    1985-01-01

    The six chapters of the book cover the following aspects of strata control in surface mining: design of opencast coal sites; parameters for the geomechanical design of opencast sites; methods for calculating slope stability; calculating the stability of spoil tips with a fractured cement base; calculation of stripping ratios; and stability tables.

  8. DNA-stabilized silver nanoclusters and carbon nanoparticles oxide: A sensitive platform for label-free fluorescence turn-on detection of HIV-DNA sequences.

    Science.gov (United States)

    Ye, Yu-Dan; Xia, Li; Xu, Dang-Dang; Xing, Xiao-Jing; Pang, Dai-Wen; Tang, Hong-Wu

    2016-11-15

    Based on the remarkable difference between the interactions of carbon nanoparticles (CNPs) oxide with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), and the fact that fluorescence of DNA-stabilized silver nanoclusters (AgNCs) can be quenched by CNPs oxide, DNA-functionalized AgNCs were applied as label-free fluorescence probes and a novel fluorescence resonance energy transfer (FRET) sensor was successfully constructed for the detection of human immunodeficiency virus (HIV) DNA sequences. CNPs oxide were prepared with the oxidation of candle soot, hence it is simple, time-saving and low-cost. The strategy of dual AgNCs probes was applied to improve the detection sensitivity by using dual- probe capturing the same target DNA in a sandwich mode and as the fluorescence donor, and using CNPs oxide as the acceptor. In the presence of target DNA, a dsDNA hybrid forms, leading to the desorption of the ssDNA-AgNCs probes from CNPs oxide, and the recovering of fluorescence of the AgNCs in a HIV-DNA concentration-dependent manner. The results show that HIV-DNA can be detected in the range of 1-50nM with a detection limit of 0.40nM in aqueous buffer. The method is simple, rapid and sensitive with no need of labeled fluorescent probes, and moreover, the design of fluorescent dual-probe makes full use of the excellent fluorescence property of AgNCs and further improves the detection sensitivity. PMID:27295571

  9. Preparation of Composite of CeO2/TiO2 Supported by Expanded Graphite-Activated Carbon and Its Treatment Ability to Phenol%膨胀石墨-活性炭负载CeO2/TiO2复合材料的制备及其处理苯酚的性能

    Institute of Scientific and Technical Information of China (English)

    苗峙; 陈志刚; 刘成宝; 陈丰; 付猛; 陈红

    2011-01-01

    采用沉淀工艺制了CT(CeO2/TiO2)催化剂粉,以膨胀石墨基炭/炭复合材料(EGC)为基体,将CT粉以碳膜包覆的形式引入EGC表面,制得了EGC负载CT催化剂粉的CT/EGC复合材料,研究了其对苯酚的处理性能。结果表明:铈钛物质的量比为0.002的CT催化剂粉处理苯酚的效果最好CT/EGC处理苯酚溶液时,CT粉的光催化能力与EGC的吸附作用存在协同效应,提高了营会材料对蓉酚的灰卜殚静粟.%CT catalyst powders (CeO2/TiO2) had been prepared with precipitation process. Taking expanded graphite based carbon/carbon composite (EGC) as matrix, CT powders were introduced on the EGC surface in the form of carbon-coated, and then CT/EGC composites of CT catalyst powders supported by EGC were obtained, and the property for treating phenol of the composite was studied. The results show that the treatment effect was best when the ratio of amount-of-substrance between Ce and Ti in CT catalyst powders was 0. 002. Synergetic effect between CT photo catalytic performance and EGC adsorption was found when CT/EGC was used to treat the phenol solution, which enhanced the treatment effect of the composite towards phenol.

  10. Expanding the Game Design Space

    DEFF Research Database (Denmark)

    Larsen, Lasse Juel; Majgaard, Gunver

    2016-01-01

    This article considers game design research in educational settings. Its focus is on how undergraduate students – particularly engineering students – learn computer game design. From observations conducted during our game design courses we have developed a model of expanded game design space......, providing a clear game design assignment that involves the formulation of intended player experience and a description of game mechanics. The second layer focuses on game design thinking from six different aspects of game design chosen in relation to the framing of the game design assignment. The third...

  11. Expandable intramedullary nail - experimental biomechanical evaluation

    Directory of Open Access Journals (Sweden)

    A. Kajzer

    2010-01-01

    Full Text Available Purpose: The paper presents results of experimental analysis of femur and femur – expandable intramedullary nail system. The aim of the work was to determine displacement in three models. In addition, the torsion of the system aiming at determining the moments depending on the torsional angle of the bone was carried out.Design/methodology/approach: Three femurs were selected for studies. The analysis was carried out on the femur – expandable intramedullary nail system. The influence of the loads and displacements on the bone – nail system on the results of experimental analysis was analysed. In order to carry out calculations, three models were selected: model I – bone without fracture gap, model II and III – femur with expansion intramedullary nails – fracture gap was located 100 mm under greater trochanter. The studies were performed on femur models produced by Swedish company Sawbones. The intramedullary „Fixion IM” nails (Ti-6Al-4V alloy were implanted into the bone. Displacements of determinated models were being recorded from the sensors every 100 N from 10 N to 2000 N.Findings: The analyses showed the difference in displacements, depending on the selected models.Research limitations/implications: The limitations were connected with simplification of boundary conditions during analysis which were the result of the simplification of the models. While studying, muscles and ligaments supporting the bone in anatomic position were not taken into consideration. Instead, the system has been loaded with the axial force (compression.Practical implications: The obtained results can be useful in clinical practice. They can be applied in selection of stabilization methods or rehabilitation as well as in describing the biomechanical conditions connected with type of bone fracture obtained from medical imaging.Originality/value: . The work compares the values of displacement of characteristic points of femur (healthy – model I with the

  12. Who discovered the expanding universe?

    CERN Document Server

    Nussbaumer, Harry

    2011-01-01

    Who discovered the expanding universe? Was it Hubble, or Lemaitre, or was it just the end result of a long series of investigations? In this article we summarise the main steps and contributions that led to one of the most exciting discoveries ever made, of which Lemaitre was the principal architect. In 1927 he combined his dynamical solutions of the Einstein equations with astronomical observations to conclude that the universe is expanding. He derived the linear velocity-distance relationship and calculated the first numerical value of what later was called the "Hubble constant". His discovery paper of 1927 was written in French and in 1931 it was translated into English and published in Monthly Notices. However, the translation omits the section where Lemaitre computed the "Hubble constant". Why was that done, and who was responsible? We do not speculate on this question, but present in a very condensed way the facts along the path of discovery. The documented details from primary sources can be found in o...

  13. Carbon substituting for oxygen in silicates: A novel mechanism for carbon incorporation in the deep Earth

    Science.gov (United States)

    Armentrout, M. M.; Tavakoli, A.; Ionescu, E.; Mera, G.; Riedel, R.; Navrotsky, A.

    2013-12-01

    Traditionally, carbon in the deep Earth has been thought of in terms of either carbonate at high oxygen fugacities or graphite or diamond under more reducing conditions. However, material science studies of amorphous Si-O-C polymer derived ceramics have demonstrated that carbon can be accommodated as an anion substituting for oxygen in mixed silica tetrahedra. Furthermore these structures are energetically favorable relative to a mixture of crystalline silica, silicon carbide, and graphite by ten or more kJ/g.atom. Thermodynamic stability suggests that these nano-structured composites are a potentially important storage mechanism for carbon under moderately reducing conditions. Here we expand the scope of the previous work by examining the compositional effect of geologically relevant cations (calcium and magnesium) on the thermodynamic stability, nanostructure, and ability to accommodate carbon of these composites. Silicon oxy-carbides doped with magnesium, magnesium and calcium or undoped resisted crystallization at 1100 C under inert atmosphere. 29Si NMR of the samples shows a similar distribution of silicon between end-member and mixed sites (Table 1). Results are presented from studies utilizing NMR, high temperature solution calorimetry, and microprobe. Table 1. Percentages of Si species in each material as determined by 29Si NMR.

  14. Bioreversible Derivatives of Phenol. 1. The Role of Human Serum Albumin as Related to the Stability and Binding Properties of Carbonate Esters with Fatty Acid-like Structures in Aqueous Solution and Biological Media

    Directory of Open Access Journals (Sweden)

    Claus Larsen

    2007-10-01

    Full Text Available With the overall objective of assessing the potential of utilizing plasma protein binding interactions in combination with the prodrug approach for improving the pharmacokinetics of drug substances, a series of model carbonate ester prodrugs of phenol, encompassing derivatives with fatty acid-like structures, were characterized in vitro. Stability of the derivatives was studied in aqueous solution, human serum albumin solution, human plasma, and rat liver homogenate at 37°C. Stability of the derivatives in aqueous solution varied widely, with half-lives ranging from 31 to 1.7 × 104 min at pH 7.4 and 37°C. The carbonate esters were subject to catalysis by plasma esterases except for the t-butyl and acetic acid derivatives, which were stabilized in both human plasma and human serum albumin solutions relative to buffer. In most cases, however, hydrolysis was accelerated in the presence of human serum albumin indicating that the derivatives interacted with the protein, a finding which was confirmed using the p-nitrophenyl acetate kinetic assay. Different human serum albumin binding properties of the phenol model prodrugs with fatty acid-like structure and neutral carbonate esters were observed. In the context of utilizing plasma protein binding in combination with the prodrug approach for optimizing drug pharmacokinetics, the esterase-like properties of human serum albumin towards the carbonate esters potentially allowing the protein to act as a catalyst of parent compound regenerations is interesting.

  15. A computational study on structure, stability and bonding in Noble Gas bound metal Nitrates, Sulfates and Carbonates (Metal = Cu, Ag, Au)

    Indian Academy of Sciences (India)

    MANAS GHARA; SUDIP PAN; JYOTIRMOY DEB; ANAND KUMAR; UTPAL SARKAR; PRATIM KUMAR CHATTARAJ

    2016-10-01

    A density functional theory based study is performed to investigate the noble gas (Ng = Ar-Rn) binding ability of nitrates, sulfates and carbonates of noble metal (M). Their ability to bind Ng atoms is assessed through bond dissociation energy and thermochemical parameters like dissociation enthalpy and dissociation free energy change corresponding to the dissociation of Ng bound compound producing Ngand the respective salt. The zero-point energy corrected dissociation energy values per Ng atom for the dissociation process producing Ng atom(s) and the corresponding salts range within 6.0–13.1 kcal/mol in NgCuNO₃, 3.1–9.8 kcal/mol in NgAgNO₃, 6.0–13.2 kcal/mol in NgCuSO₄, 3.2–10.1 kcal/mol in NgAgSO₄, 5.1–11.7 kcal/mol in Ng₂Cu₂SO₄, 2.5–8.6 kcal/mol in Ng₂Ag₂SO₂, 8.1–19.9 kcal/mol in Ng₂Au2SO₂, 5.7–12.4 kcal/mol in NgCuCO₃, 2.3–8.0 kcal/mol in Ng₂Ag₂CO₃ and 7.3–18.2 kcal/mol in Ng₂Au₂CO₃, with a gradual increase in moving from Ar to Rn. For a given type of system, the stability of Ng bound analogues follows the order as Au > Cu > Ag. All dissociation processes are endothermic in nature whereas they become endergonic as well in most of the cases of Kr-Rn bound analogues at 298 K. Natural population analysis along with the computation of Wiberg bond indices, and electron density analyses provide insights into the nature of the Ng-M bonds. The Ng-M bonds can be represented as partial covalent bonds as supported by the different electron density descriptors.

  16. MOF-derived, N-doped, hierarchically porous carbon sponges as immobilizers to confine selenium as cathodes for Li-Se batteries with superior storage capacity and perfect cycling stability

    Science.gov (United States)

    Li, Zhaoqiang; Yin, Longwei

    2015-05-01

    Nitrogen-doped carbon sponges (NCS) composed of hierarchical microporous carbon layers are derived from metal organic frameworks (MOFs) via carbonization at high temperatures under Ar and NH3 flow. Se is impregnated into 0.4-0.55 nm micropores by melting-diffusion and infiltration methods. The confinement of Se within small-sized micropores of NCS efficiently prevents Se loss, and mesopores between carbon layers absorb a sufficient amount of electrolyte, as well as serve as cushion spaces for large volume changes during delithiation-lithiation processes. Nitrogen doping improves the electrical conductivity of carbon matrix and facilitates rapid charge transfer, making the carbon sponge a highway for charges involved in redox reactions. When serving as cathode materials for Li-Se batteries, the NCS/Se-50 composite with 50 wt% Se exhibits excellent cycling stability, superior rate capability and high coulombic efficiency. The cathode can exhibit 443.2 mA h g-1 at the 200th cycle with a coulombic efficiency of up to 99.9% at 0.5C (C = 675 mA h g-1), which leads to 0.031% capacity loss per cycle from 5th to 200th cycles. Even at a high rate of 5C, it can still retain 286.6 mA h g-1. The unique, large surface rod-like MOF-derived, N-doped carbon sponges with hierarchical porosity could be potential candidates in the related energy-storage systems.Nitrogen-doped carbon sponges (NCS) composed of hierarchical microporous carbon layers are derived from metal organic frameworks (MOFs) via carbonization at high temperatures under Ar and NH3 flow. Se is impregnated into 0.4-0.55 nm micropores by melting-diffusion and infiltration methods. The confinement of Se within small-sized micropores of NCS efficiently prevents Se loss, and mesopores between carbon layers absorb a sufficient amount of electrolyte, as well as serve as cushion spaces for large volume changes during delithiation-lithiation processes. Nitrogen doping improves the electrical conductivity of carbon matrix and

  17. 莱钢顶底复吹转炉碳氧积稳定控制技术研究%Research of Carbon Oxygen Product Stability Control Technology on the Long Life Converter in Laiwu Steel

    Institute of Scientific and Technical Information of China (English)

    高志滨; 温福新; 于亮涛

    2015-01-01

    Through improving the design of bottom blowing air brick process, developing new type of converter slag splashing technology, optimization intelligent of converter steelmaking and bottom blowing model, to realize the combined-blowing converter low carbon oxygen deposition and stability control at a lower level. Using a laser thickness gauge to monitor the furnace type to guarantee the stability of furnace type, prevent the carbon oxygen volume fluctuations and using the static decarburization technology to further reduce carbon and oxygen. After the process implementation, the carbon oxygen volumes of the No.1, No.2 or No.3 converters were controlled in 0.002 5 and the carbon oxygen product of No.4 converter for dephosphorization was controlled in 0.002 3;The average total iron content of the final slag of 4 converters was reduced to 12.83%from 14.38%and the average oxygen content in molten steel at the end of blowing was decreased to 450 × 10-6 from 520 × 10-6. The direct economic benefit of oxygen carbon product stability control technology for long life of converter is 23.9 million Yuan.%通过改进底吹透气砖工艺设计、开发新型转炉溅渣工艺、优化转炉智能炼钢及底吹模型等,实现复吹转炉碳氧积的降低并稳定控制在较低水平;利用激光测厚仪对炉型进行监控,确保炉型稳定,防止碳氧积波动;利用静止脱碳技术进一步降低碳氧积。工艺实施后,1#~3#120 t转炉碳氧积控制在0.0025,4#脱磷炉碳氧积控制在0.0023;4座转炉终渣平均全铁含量由14.38%降为12.83%,吹炼终点钢水氧含量平均由520×10-6降为450×10-6,长寿转炉碳氧积稳定控制技术年直接经济效益2390.04万元。

  18. An experimental reciprocating expander for cryocooler application

    Science.gov (United States)

    Minta, M.; Smith, J. L., Jr.

    1985-01-01

    An experimental reciprocating expander was designed with features appropriate for cryocooler cycles. The expander has a displacer piston, simple valves, and a hydraulic/pneumatic stroking mechanism. The expander has a valve in head configuration with the valves extending out the bottom of the vacuum enclosure while the piston extends out the top. The expander was tested using a CTI 1400 liquefier to supply 13 atm in the temperature range 4.2 to 12 K. Expander efficiency was measured in the range 84 to 93% while operating the apparatus as a supercritical wet expander and in the range 91 to 93% aa a single phase expander. The apparatus can also be modified to operate as a compressor for saturated helium vapor.

  19. Compact Radiometers Expand Climate Knowledge

    Science.gov (United States)

    2010-01-01

    To gain a better understanding of Earth's water, energy, and carbon cycles, NASA plans to embark on the Soil Moisture Active and Passive mission in 2015. To prepare, Goddard Space Flight Center provided Small Business Innovation Research (SBIR) funding to ProSensing Inc., of Amherst, Massachusetts, to develop a compact ultrastable radiometer for sea surface salinity and soil moisture mapping. ProSensing incorporated small, low-cost, high-performance elements into just a few circuit boards and now offers two lightweight radiometers commercially. Government research agencies, university research groups, and large corporations around the world are using the devices for mapping soil moisture, ocean salinity, and wind speed.

  20. Discovery of Uniformly Expanding Universe

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2012-01-01

    Full Text Available Saul Perlmutter and the Brian Schmidt – Adam Riess teams reported that their Friedmann-model GR-based analysis of their supernovae magnitude-redshift data re- vealed a new phenomenon of “dark energy” which, it is claimed, forms 73% of the energy / matter density of the present-epoch universe, and which is linked to the further claim of an accelerating expansion of the universe. In 2011 Perlmutter, Schmidt and Riess received the Nobel Prize in Physics “for the discovery of the accelerating ex- pansion of the Universe through observations of distant supernovae”. Here it is shown that (i a generic model-independent analysis of this data reveals a uniformly expanding universe, (ii their analysis actually used Newtonian gravity, and finally (iii the data, as well as the CMB fluctuation data, does not require “dark energy” nor “dark matter”, but instead reveals the phenomenon of a dynamical space, which is absent from the Friedmann model.

  1. Stability of Axisymmetric Liquid Bridges

    CERN Document Server

    Rubinstein, Boris

    2016-01-01

    We study stability of axisymmetric liquid bridges between two axisymmetric solid bodies in the absence of gravity under arbitrary asymmetric perturbations which are expanded into a set of angular Fourier modes. We determine the stability region boundary for every angular mode in case of both fixed and free contact lines. Application of this approach allows us to demonstrate existence of stable convex nodoid menisci between two spheres.

  2. Expanding the Interaction Equivalency Theorem

    Directory of Open Access Journals (Sweden)

    Brenda Cecilia Padilla Rodriguez

    2015-06-01

    Full Text Available Although interaction is recognised as a key element for learning, its incorporation in online courses can be challenging. The interaction equivalency theorem provides guidelines: Meaningful learning can be supported as long as one of three types of interactions (learner-content, learner-teacher and learner-learner is present at a high level. This study sought to apply this theorem to the corporate sector, and to expand it to include other indicators of course effectiveness: satisfaction, knowledge transfer, business results and return on expectations. A large Mexican organisation participated in this research, with 146 learners, 30 teachers and 3 academic assistants. Three versions of an online course were designed, each emphasising a different type of interaction. Data were collected through surveys, exams, observations, activity logs, think aloud protocols and sales records. All course versions yielded high levels of effectiveness, in terms of satisfaction, learning and return on expectations. Yet, course design did not dictate the types of interactions in which students engaged within the courses. Findings suggest that the interaction equivalency theorem can be reformulated as follows: In corporate settings, an online course can be effective in terms of satisfaction, learning, knowledge transfer, business results and return on expectations, as long as (a at least one of three types of interaction (learner-content, learner-teacher or learner-learner features prominently in the design of the course, and (b course delivery is consistent with the chosen type of interaction. Focusing on only one type of interaction carries a high risk of confusion, disengagement or missed learning opportunities, which can be managed by incorporating other forms of interactions.

  3. Cable Stability

    CERN Document Server

    Bottura, L

    2014-01-01

    Superconductor stability is at the core of the design of any successful cable and magnet application. This chapter reviews the initial understanding of the stability mechanism, and reviews matters of importance for stability such as the nature and magnitude of the perturbation spectrum and the cooling mechanisms. Various stability strategies are studied, providing criteria that depend on the desired design and operating conditions.

  4. Geothermal ORC Systems Using Large Screw Expanders

    OpenAIRE

    Biederman, Tim R.; Brasz, Joost J.

    2014-01-01

    Geothermal ORC Systems using Large Screw Expanders Tim Biederman Cyrq Energy Abstract This paper describes a low-temperature Organic Rankine Cycle Power Recovery system with a screw expander a derivative of developed of Kaishan's line of screw compressors, as its power unit. The screw expander design is a modified version of its existing refrigeration compressor used on water-cooled chillers. Starting the ORC development program with existing refrigeration screw compre...

  5. Synthesis, characterization and properties of polyaniline/expanded vermiculite intercalated nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Lin Jianming; Tang Qunwei; Wu Jihuai; Sun Hui [Key Laboratory of Functional Materials for Fujian Higher Education, Institute of Material Physical Chemistry, Huaqiao University, Quanzhou 362021 (China)], E-mail: jhwu@hqu.edu.cn

    2008-04-15

    The synthesis characterization and conductivities of polyaniline/expanded vermiculite intercalated nanocomposite are presented in this paper. The conductive emeraldine salt form of polyaniline is inserted into the interlayer of expanded vermiculite to produce the nanocomposite with high conductivity. The structures and properties are characterized by transmission electron microscopy x-ray diffraction spectroscopy fourier transform infrared spectroscopy thermogravimetry analysis and by the measurements of conductivity and stability. The results show that an intercalated nanocomposite with high conductivity and stability is obtained. The synthesis conditions are optimized to obtain the highest conductivity which is 6.80 S cm{sup -1}.

  6. Synthesis, characterization and properties of polyaniline/expanded vermiculite intercalated nanocomposite

    Directory of Open Access Journals (Sweden)

    Jianming Lin, Qunwei Tang, Jihuai Wu and Hui Sun

    2008-01-01

    Full Text Available The synthesis characterization and conductivities of polyaniline/expanded vermiculite intercalated nanocomposite are presented in this paper. The conductive emeraldine salt form of polyaniline is inserted into the interlayer of expanded vermiculite to produce the nanocomposite with high conductivity. The structures and properties are characterized by transmission electron microscopy x-ray diffraction spectroscopy fourier transform infrared spectroscopy thermogravimetry analysis and by the measurements of conductivity and stability. The results show that an intercalated nanocomposite with high conductivity and stability is obtained. The synthesis conditions are optimized to obtain the highest conductivity which is 6.80 S cm−1.

  7. Effects of pyrolysis temperature on carbon retention and stability of biochar%热解温度对生物质炭碳保留量及稳定性的影响

    Institute of Scientific and Technical Information of China (English)

    李飞跃; 汪建飞; 谢越; 李贺; 李孝良; 李粉茹

    2015-01-01

    以核桃壳为生物质炭生产原料,研究热解温度(200~700℃)对生物质炭产率、元素组成、表面官能团分布及其稳定性的影响,以期探明生物质炭基本性质随热解温度变化的规律,为全面了解生物质炭固碳减排效果提供理论参考。结果表明,生物质炭的C含量随温度升高而增加,H和O元素含量却随温度升高而降低。此外,生物质炭的H/C和O/C随着温度增加而减少。生物质炭的产率及碳保留量随着温度的升高而降低。红外光谱分析结果表明,经过热解核桃壳原材料分子中所含的-C-O和O-CH3基团消失,随着热解温度升高,生物质炭中的烷烃基团-CH逐渐减少,芳香化程度逐渐升高。500℃制备生物质炭的K2Cr2O7和KMnO4氧化碳损失量均最低,分别为10.4%和1.66%。相关分析表明,生物质炭的产率、碳保留量及稳定性与热解温度之间均具有显著相关关系。%Turning biomass wastes into biochar under the conditions of low temperature and limited oxygen has recently proven to be a promising approach for long-term carbon sequestration. However, the ultimate carbon sequestration efficiency of biochar depends not only on the feedstock type and production condition, but also on the environmental conditions of soil. In order to reveal the effects of pyrolysis temperature which is main parameter of biochar production condition on carbon retention and biochar stability, and provide more information for further improvement of carbon sequestration potential by turning biomass into biochar, the characteristics of biochar derived from walnut shell under lab condition were analyzed. During a typical slow pyrolysis process, the biochar was heated at a speed of approximately 20℃/minin a Muffle Furnace under limited oxygen and held at 200-700℃ for 2 h; then, biochar yield, elemental composition, functional groups distribution using Fourier transform infrared spectroscopy (FTIR

  8. Impact of soybean stover- and pine needle-derived biochars on Pb and As mobility, microbial community, and carbon stability in a contaminated agricultural soil.

    Science.gov (United States)

    Ahmad, Mahtab; Ok, Yong Sik; Kim, Byung-Yong; Ahn, Jae-Hyung; Lee, Young Han; Zhang, Ming; Moon, Deok Hyun; Al-Wabel, Mohammad I; Lee, Sang Soo

    2016-01-15

    Biochar is gaining attention as a potential soil amendment to remediate and revitalize the contaminated soils. Simultaneous effects of biochar on metals mobility, microbial abundance, bacterial diversity and carbon storage in soil are scarcely addressed. This study assessed the effect of biochars on metal mobility, microbial abundance, bacterial community, and carbon storage in an agricultural soil contaminated with heavy metals. Biochars derived from soybean stover at 300 and 700 °C (S-BC300 and S-BC700, respectively) and pine needles at the same temperatures (P-BC300 and P-BC700, respectively) were used. A maximum reduction of Pb mobility by 95% was observed from a soil treated with S-BC700, associated with precipitation of chloropyromorphite and hydroxylpyromorphite. In contrast, As was desorbed from soil particles because of P competition. The abundance of Gram-positive and negative bacteria, fungi, actinomycetes, and arbuscular mycorrhizal fungi increased in the soils treated with biochar produced at 300 °C, possibly due to the high dissolved organic and active organic carbons. Microbial abundance in the soils treated with S-BC700 and P-BC700 was constant due to the existence of fixed or non-labile carbon. Changes to bacterial communities in the biochar-treated soils depended on feedstock type and pyrolysis temperature. Actinobacteria substantially increased whereas Acidobacteria and Chloroflexi decreased in the biochar-treated soils. The non-labile carbon fraction was ∼25 fold higher in the biochar-treated soil than the control soil, indicating long-term carbon storage. PMID:26496843

  9. Expanding Genomics of Mycorrhizal Symbiosis

    Directory of Open Access Journals (Sweden)

    Alan eKuo

    2014-11-01

    Full Text Available The mycorrhizal symbiosis between soil fungi and plant roots is a ubiquitous mutualism that plays key roles in plant and soil health, and carbon and nutrient cycles. The symbiosis evolved repeatedly and independently as multiple morphological types (e.g. arbuscular [AM], ectomycorrhizal [ECM] in multiple fungal clades (e.g. phyla Glomeromycota, Ascomycota, Basidiomycota. The accessibility and culturability of many mycorrhizal partners make them ideal models for symbiosis studies. Alongside molecular, physiological, and ecological investigations, sequencing led to the first 3 mycorrhizal fungal genomes, representing 3 fungal phyla and 2 mycorrhizal types. The genome of the ECM basidiomycete Laccaria bicolor showed that the mycorrhizal lifestyle can evolve through loss of plant-degrading enzymes (PDEs and expansion of lineage-specific gene families, including short secreted protein (SSP effectors and other symbiosis genes. The genome of the ECM ascomycete Tuber melanosporum showed that the ECM type can evolve without expansion of gene families in contrast to Laccaria, and thus a different set of symbiosis genes. The genome of the AM glomeromycete Rhizophagus irregularis showed that despite enormous phylogenetic distance and morphological difference from the other 2 fungi, the symbiosis can involve similar solutions as loss of PDEs and mycorrhiza-induced SSPs. The mycorrhizal community is building on these studies with 3 large-scale initiatives. The Mycorrhizal Genomics Initiative (MGI is sequencing 35 genomes of multiple fungal clades and mycorrhizal types for phylogenomic and population analyses. 17 MGI species whose symbiosis is reconstitutable in vitro are targeted for comprehensive transcriptomics of mycorrhiza formation. MGI genomes are seeding a set of 50+ reference fungal genomes for annotating metatranscriptomes sampled from 7 diverse well-described soil sites. These 3 projects address fundamental questions about the nature and role of a

  10. Effects of enhancing soil organic carbon sequestration in the topsoil by fertilization on crop productivity and stability: Evidence from long-term experiments with wheat-maize cropping systems in China.

    Science.gov (United States)

    Zhang, Xubo; Sun, Nan; Wu, Lianhai; Xu, Minggang; Bingham, Ian J; Li, Zhongfang

    2016-08-15

    Although organic carbon sequestration in agricultural soils has been recommended as a 'win-win strategy' for mitigating climate change and ensuring food security, great uncertainty still remains in identifying the relationships between soil organic carbon (SOC) sequestration and crop productivity. Using data from 17 long-term experiments in China we determined the effects of fertilization strategies on SOC stocks at 0-20cm depth in the North, North East, North West and South. The impacts of changes in topsoil SOC stocks on the yield and yield stability of winter wheat (Triticum aestivum L.) and maize (Zea mays L.) were determined. Results showed that application of inorganic fertilizers (NPK) plus animal manure over 20-30years significantly increased SOC stocks to 20-cm depth by 32-87% whilst NPK plus wheat/maize straw application increased it by 26-38% compared to controls. The efficiency of SOC sequestration differed between regions with 7.4-13.1% of annual C input into the topsoil being retained as SOC over the study periods. In the northern regions, application of manure had little additional effect on yield compared to NPK over a wide range of topsoil SOC stocks (18->50MgCha(-1)). In the South, average yield from manure applied treatments was 2.5 times greater than that from NPK treatments. Moreover, the yield with NPK plus manure increased until SOC stocks (20-cm depth) increased to ~35MgCha(-1). In the northern regions, yield stability was not increased by application of NPK plus manure compared to NPK, whereas in the South there was a significant improvement. We conclude that manure application and straw incorporation could potentially lead to SOC sequestration in topsoil in China, but beneficial effects of this increase in SOC stocks to 20-cm depth on crop yield and yield stability may only be achieved in the South. PMID:27100005

  11. Effects of enhancing soil organic carbon sequestration in the topsoil by fertilization on crop productivity and stability: Evidence from long-term experiments with wheat-maize cropping systems in China.

    Science.gov (United States)

    Zhang, Xubo; Sun, Nan; Wu, Lianhai; Xu, Minggang; Bingham, Ian J; Li, Zhongfang

    2016-08-15

    Although organic carbon sequestration in agricultural soils has been recommended as a 'win-win strategy' for mitigating climate change and ensuring food security, great uncertainty still remains in identifying the relationships between soil organic carbon (SOC) sequestration and crop productivity. Using data from 17 long-term experiments in China we determined the effects of fertilization strategies on SOC stocks at 0-20cm depth in the North, North East, North West and South. The impacts of changes in topsoil SOC stocks on the yield and yield stability of winter wheat (Triticum aestivum L.) and maize (Zea mays L.) were determined. Results showed that application of inorganic fertilizers (NPK) plus animal manure over 20-30years significantly increased SOC stocks to 20-cm depth by 32-87% whilst NPK plus wheat/maize straw application increased it by 26-38% compared to controls. The efficiency of SOC sequestration differed between regions with 7.4-13.1% of annual C input into the topsoil being retained as SOC over the study periods. In the northern regions, application of manure had little additional effect on yield compared to NPK over a wide range of topsoil SOC stocks (18->50MgCha(-1)). In the South, average yield from manure applied treatments was 2.5 times greater than that from NPK treatments. Moreover, the yield with NPK plus manure increased until SOC stocks (20-cm depth) increased to ~35MgCha(-1). In the northern regions, yield stability was not increased by application of NPK plus manure compared to NPK, whereas in the South there was a significant improvement. We conclude that manure application and straw incorporation could potentially lead to SOC sequestration in topsoil in China, but beneficial effects of this increase in SOC stocks to 20-cm depth on crop yield and yield stability may only be achieved in the South.

  12. Glycerol-stabilized NaBH4 reduction at room-temperature for the synthesis of a carbon-supported PtxFe alloy with superior oxygen reduction activity for a microbial fuel cell

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Glycerol is used as an efficient stabilizer and solvent to synthesis PtxFe alloy. • PtxFe alloy is prepared by simple two-step at room temperature;. • Pt3-Fe/C show the best ORR catalytic performance in both acidic and neutral media;. • PtxFe alloy enhanced ORR activity and durability in microbial fuel cells. - Abstract: Insufficient catalytic activity and durability are the most challenging issues in the commercial deployment of low-temperature fuel cells. In an effort to address these barriers, three carbon-supported PtxFe alloy electrocatalysts with varying Pt:Fe atom ratios (Pt3-Fe/C, Pt2-Fe/C, Pt-Fe/C) were prepared by simple NaBH4 reduction in glycerol at room temperature. All of the prepared PtxFe nanoparticles (NPs) are highly dispersed on a carbon support and show a single-phase face-centered cubic structure with a particle size of approximately 2 nm. The electrocatalytic performances of the synthesized PtxFe alloy catalysts were compared with that of commercial Pt/C by cyclic voltammetry and linear sweep voltammetry; among these NPs, the Pt3-Fe/C catalyst exhibits the highest activity and the best stability for oxygen reduction reaction (ORR) in both acidic and neutral media. As the cathode catalyst, the maximum power density produced from microbial fuel cell with Pt3-Fe/C (1680 ± 15 mW m−2) was 18% higher than that with conventional Pt/C (1422 ± 18 mW m−2), and the stability of Pt3-Fe/C was greatly improved

  13. Prótesis de cuerpo vertebral JR: dispositivo modular, anatómico y expandible, con función de jaula y placa diseñada ad hoc para estabilizar la columna después de corpectomía Prótese do corpo vertebral JR: dispositivo modular, anatômico e expansível, com função de jaula e placa desenhada ad hoc para estabilizar a coluna depois da corpectomia JR vertebral body prosthesis: a modular, anatomical and expandable device, with cage function and plate dual designed ad hoc for spine stabilization after corpectomy

    Directory of Open Access Journals (Sweden)

    Juan José Ramírez Jiménez

    2009-06-01

    função de jaula e placa separadamente, uma vez que o desenho da prótese permite aplicar força axial e fixação lateral ao mesmo tempo, por meio de um só implante. Os resultados da colocação do implante no paciente foram satisfatórios.INTRODUCTION: due to the unsatisfactory results obtained with posterior instrumentations in cases of vertebral tumors and to the economical limitations of our patients for acquiring the systems available in the market, a vertebral body prosthesis to stabilize the spine after corpectomy was designed. OBJECTIVE: to describe the structural and functional characteristics of the JR prosthesis, the biomechanical assays in cadaver and the surgical technique on the patient. METHODS: firstly, it was performed a detailed anatomical study of the vertebral bodies. A design of a modular, anatomical and expandable device was obtained. Its components once assembled make an implant with expandable cage and plate dual function. Afterwards, a biomechanical assay was performed in a cadaver and the device was implanted in a patient with vertebral body metastasis. RESULTS: the radiographs extracted from the cadaver after implant location did not show loss of fixation. When the cadaver was raised, flexion moments were generated laterally with levers 80 cm long; therefore, the prosthesis was demanded in its most vulnerable point with a force of approximately 588 N. With rotation, flexion and extensions forced, stability was preserved and no movement was observed. The device was implanted in a 50-year-old woman with metastatic thyroid cancer affecting L3. Pain improved in the postoperative immediate, as well as its motor function, which allowed her to walk with a stable and painless spine for seven years. No implant failure was observed. CONCLUSION: the dual cage function and plate integrated in a single device offers a mechanical advantage, compared with the cages and plates used separately, since the prosthesis design permits to apply a distraction

  14. Carbon Residence Times in Pedogenic Carbonate Pools

    Science.gov (United States)

    Monger, H.; Feng, Y.; Karnjanapiboonwang, A.

    2013-12-01

    Soil carbonate is a huge pool of terrestrial carbon that contains at least 930 to 940 Pg C and has influx rates on the order of 1 to 12 g CaCO3/m2/yr. Such large mass to flux ratios yield long mean residence times for carbon (e.g., 85,000 years)--assuming steady state. Like other global carbon pools, the soil carbonate pool has smaller sub-pools with higher influx rates and shorter mean residence times. For example, pedogenic carbonate in coppice dunes known to have formed since 1858 and carbonate formed on lithic artifacts in soils at archaeology sites suggests mean residence times can be as short as 120 years--again assuming steady state. Harder to assess are efflux rates as CO2 emissions or bicarbonate leaching. Some Bowen-ratio studies have nevertheless found evidence for CO2 emissions resulting from carbonate dissolution, and other studies have found evidence for bicarbonate leaching based on dissolution pipes through calcic horizons using soil morphology studies. Since an understanding of mean residence times are prerequisite for a better understanding of soil carbonate in the global carbon cycle, especially in a scenario of an expanding Aridosphere, more influx and efflux measurements are needed to evaluate the possibility of carbon sequestration by soil carbonate in hyperarid, arid, semiarid, or subhumid soils.

  15. Metagenome of a Versatile Chemolithoautotroph from Expanding Oceanic Dead Zones

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, David A.; Zaikova, Elena; Howes, Charles L.; Song, Young; Wright, Jody; Tringe, Susannah G.; Tortell, Philippe D.; Hallam, Steven J.

    2009-07-15

    Oxygen minimum zones (OMZs), also known as oceanic"dead zones", are widespread oceanographic features currently expanding due to global warming and coastal eutrophication. Although inhospitable to metazoan life, OMZs support a thriving but cryptic microbiota whose combined metabolic activity is intimately connected to nutrient and trace gas cycling within the global ocean. Here we report time-resolved metagenomic analyses of a ubiquitous and abundant but uncultivated OMZ microbe (SUP05) closely related to chemoautotrophic gill symbionts of deep-sea clams and mussels. The SUP05 metagenome harbors a versatile repertoire of genes mediating autotrophic carbon assimilation, sulfur-oxidation and nitrate respiration responsive to a wide range of water column redox states. Thus, SUP05 plays integral roles in shaping nutrient and energy flow within oxygen-deficient oceanic waters via carbon sequestration, sulfide detoxification and biological nitrogen loss with important implications for marine productivity and atmospheric greenhouse control.

  16. Microbial biomass, microbial diversity, soil carbon storage, and stability after incubation of soil from grass-clover pastures of different age

    DEFF Research Database (Denmark)

    Müller-Stöver, Dorette Sophie; Hauggaard-Nielsen, Henrik; Eriksen, Jørgen;

    2012-01-01

    A laboratory incubation study with clover grass pasture soils of seven different ages (0, 1, 2, 3, 4, 5, and 16 production years) was carried out to determine initial soil carbon (C) and nitrogen (N) stocks and potentials for greenhouse gas emissions (N2O and CO2). Compared with the soil from...

  17. Quantum Chemical Studies on Solvents for Post-Combustion Carbon Dioxide Capture: Calculation of pKa and Carbamate Stability of Disubtituted Piperazines

    NARCIS (Netherlands)

    Gangarapu, S.; Wierda, G.J.; Marcelis, A.T.M.; Zuilhof, H.

    2014-01-01

    Piperazine is a widely studied solvent for post-combustion carbon dioxide capture. To investigate the possibilities of further improving this process, the electronic and steric effects of CH3, CH2F, CH2OH, CH2NH2, COCH3, and CN groups of 2,5-disubstituted piperazines on the pKa and carbamate stabili

  18. Design of Modern Reactors for Synthesis of Thermally Expanded Graphite

    OpenAIRE

    Strativnov, Eugene V.

    2015-01-01

    One of the most progressive trends in the development of modern science and technology is the creation of energy-efficient technologies for the synthesis of nanomaterials. Nanolayered graphite (thermally exfoliated graphite) is one of the key important nanomaterials of carbon origin. Due to its unique properties (chemical and thermal stability, ability to form without a binder, elasticity, etc.), it can be used as an effective absorber of organic substances and a material for seal manufacturi...

  19. Representation theory and homological stability

    CERN Document Server

    Church, Thomas

    2010-01-01

    We introduce the idea of *representation stability* (and several variations) for a sequence of representations V_n of groups G_n. One main goal is to expand the important and well-studied concept of homological stability so that it applies to a much broader variety of examples. Representation stability also provides a framework in which to find and to predict patterns, from classical representation theory (Littlewood--Richardson and Murnaghan rules, stability of Schur functors), to cohomology of groups (pure braid, Torelli and congruence groups), to Lie algebras and their homology, to the (equivariant) cohomology of flag and Schubert varieties, to combinatorics (the (n+1)^(n-1) conjecture). The majority of this paper is devoted to exposing this phenomenon through examples. In doing this we obtain applications, theorems, and conjectures. Beyond the discovery of new phenomena, the viewpoint of representation stability can be useful in solving problems outside the theory. In addition to the applications given in...

  20. Most blood biomarkers related to vitamin status, one-carbon metabolism, and the kynurenine pathway show adequate preanalytical stability and within-person reproducibility to allow assessment of exposure or nutritional status in healthy women and cardiovascular patients.

    Science.gov (United States)

    Midttun, Oivind; Townsend, Mary K; Nygård, Ottar; Tworoger, Shelley S; Brennan, Paul; Johansson, Mattias; Ueland, Per Magne

    2014-05-01

    Knowledge of stability during sample transportation and changes in biomarker concentrations within person over time are paramount for proper design and interpretation of epidemiologic studies based on a single measurement of biomarker status. Therefore, we investigated stability and intraindividual vs. interindividual variation in blood concentrations of biomarkers related to vitamin status, one-carbon metabolism, and the kynurenine pathway. Whole blood (EDTA and heparin, n = 12) was stored with an icepack for 24 or 48 h, and plasma concentrations of 38 biomarkers were determined. Stability was calculated as change per hour, intraclass correlation coefficient (ICC), and simple Spearman correlation. Within-person reproducibility of biomarkers was expressed as ICC in samples collected 1-2 y apart from 40 postmenopausal women and in samples collected up to 3 y apart from 551 patients with stable angina pectoris. Biomarker stability was similar in EDTA and heparin blood. Most biomarkers were essentially stable, except for choline and total homocysteine (tHcy), which increased markedly. Within-person reproducibility in postmenopausal women was excellent (ICC > 0.75) for cotinine, all-trans retinol, cobalamin, riboflavin, α-tocopherol, Gly, pyridoxal, methylmalonic acid, creatinine, pyridoxal 5'-phosphate, and Ser; was good to fair (ICC of 0.74-0.40) for pyridoxic acid, kynurenine, tHcy, cholecalciferol, flavin mononucleotide, kynurenic acid, xanthurenic acid, 3-hydroxykynurenine, sarcosine, anthranilic acid, cystathionine, homoarginine, 3-hydroxyanthranilic acid, betaine, Arg, folate, total cysteine, dimethylglycine, asymmetric dimethylarginine, neopterin, symmetric dimethylarginine, and Trp; and poor (ICC of 0.39-0.15) for methionine sulfoxide, Met, choline, and trimethyllysine. Similar reproducibilities were observed in patients with coronary heart disease. Thus, most biomarkers investigated were essentially stable in cooled whole blood for up to 48 h and had a

  1. Mechanism of Fume Suppression and Performance on Asphalt of Expanded Graphite for Pavement under High Temperature Condition

    Institute of Scientific and Technical Information of China (English)

    HUANG Gang; HE Zhaoyi; HUANG Yangcheng; ZHOU Chao; YUAN Xiaoya

    2014-01-01

    Fume suppression mechanisms and the effect of expanded graphite on the performance of asphalt were studied by applying infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and comprehensive thermal analysis (TG, DSC). The experimental results confirm that asphalt which is mixed with expandable graphite will expand in the process of hot mix, and the expanded graphite layer will swell by the light component in the asphalt. The light component in the asphalt and PAHs adsorption on expanded graphite surface or part of the plug in the expanded graphite layer between plates made nucleation crystallization growth. And the Van der Waals force and the bonding of the lattice can effectively restrain the asphalt fume release. Meanwhile, the expanding agent with oxidative can spread into the asphalt, leading to asphalt oxygenated and plastic abate, while the ductility decreases. Expanded graphite, SBS modifier and environment- friendly plasticizers are used to composite modified asphalt. According to asphalt fume release experiment, normal test of asphalt performance, Brookfield viscosity test, RTFOT test and asphalt mixture tests (high temperature stability, low temperature stability, water stability), it has been proven that the modified asphalt’s performance is better than that of matrix asphalt and equivalent to that of SBS modified asphalt. Furthermore, it has good fume suppression effect.

  2. Formation of organic monolayers on hydrogen-terminated silicon surfaces via silicon-carbon bond: effect of terminal groups on stability

    International Nuclear Information System (INIS)

    Full text: Functionalization of hydrogen-terminated silicon surfaces with stable and dense aryl-terminated alkyl self-assembled monolayers (SAMs) provides opportunities for the development of low cost organic field effect transistors. In this paper we present results for one such σ-π SAMs, 3-phenylpropyl (C6H5(CH2)3-) SAMs on porous silicon, and compare its stability with octyl (CH3(CH2)7-) SAMs on Si(100). The SAMs were prepared using the Grignard reagent method and characterized using X-ray photoelectron and FT-infrared spectroscopies and contact angle measurements Our results show the 3-phenylpropyl SAMs are not as susceptible to oxidation as the octyl SAMs, and we attribute the increased stability in the former to be due to its more dense structure arising from the π-π stacking of the phenyl rings. Copyright (2005) Australian Institute of Physics

  3. Stability Analysis in a Model of 1,2-dichloroethane Biodegradation by Klebsiella Oxytoca va 8391Immobilized on Granulated Activated Carbon

    Science.gov (United States)

    Borisov, M.; Dimitrova, N.

    2011-11-01

    We consider an ecological model for biodegradation of toxic substances in aquatic and atmospheric biotic systems. The model, which is described by a nonlinear system of four ordinary differential equations, is known to be experimentally validated. We compute the equilibrium points of the model and study their asymptotic stability. The Maple package BifTools is used to calculate one- and two-parameter bifurcations of the equilibrium points.

  4. Effects of nano-sized boron nitride (BN) reinforcement in expandable graphite based in-tumescent fire retardant coating

    Science.gov (United States)

    Zulkurnain, E. S.; Ahmad, F.; Gillani, Q. F.

    2016-08-01

    The purpose of in-tumescent fire retardant coating (IFRC) is to protect substrate from fire attack by limiting heat transfer. A range of coating formulations have been prepared using Bisphenol A epoxy resin BE-188 and polyamide solidifier H-2310 as two-part binder, ammonium polyphosphate (APP) as acid source, melamine (MEL) as the blowing agent, expandable graphite (EG) as carbon source and nano-boron nitride (BN) as inorganic nano filler. The filler was used to improve the performances of the APP-EG-MEL coating. The effects of nano-BN on the char morphology and thermal degradation were investigated by fire test, thermo gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X- ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). The results showed that by substituting or reinforcing of 4% weight percentage of nano-BN, residual weight of the char increases by 23.82% compared to APP-EG-MEL coating without filler. Higher carbon content was obtained in the char and a more compact char was produced. The results indicated that nano-BN could be used as a filler to improve thermal stability of the APP-EG-MEL coating.

  5. Stabilizing a high-temperature electrochemical silver-carbonate CO2 capture membrane by atomic layer deposition of a ZrO2 overcoat.

    Science.gov (United States)

    Zhang, Peng; Tong, Jingjing; Jee, Youngseok; Huang, Kevin

    2016-07-28

    A high-selectivity and high-flux electrochemical silver-carbonate dual-phase membrane was coated with a nanoscaled ZrO2 layer by atomic layer deposition (ALD) for stable CO2 capture at high-temperature (≥800 °C); the latter has an important implication for direct dry methane reforming with the captured CO2 and O2 for syngas production. PMID:27417536

  6. Uniform carbon layer coated Mn3O4 nanorod anodes with improved reversible capacity and cyclic stability for lithium ion batteries.

    Science.gov (United States)

    Wang, Changbin; Yin, Longwei; Xiang, Dong; Qi, Yongxin

    2012-03-01

    A facile one-step solvothermal reaction route to large-scale synthesis of carbon homogeneously wrapped manganese oxide (Mn(3)O(4)@C) nanocomposites for anode materials of lithium ion batteries was developed using manganese acetate monohydrate and polyvinylpyrrolidone as precursors and reactants. The synthesized Mn(3)O(4)@C nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The synthesized tetragonal structured Mn(3)O(4) (space group I41/amd) samples display nanorodlike morphology, with a width of about 200-300 nm and a thickness of about 15-20 nm. It is shown that the carbon layers with a thickness of 5 nm are homogeneously coated on the Mn(3)O(4) nanorods. It is indicated from lithium storage capacity estimation that the Mn(3)O(4)@C samples display enhanced capacity retention on charge/discharge cycling. Even after 50 cycles, the products remains stable capacity of 473 mA h g(-1), which is as much 3.05 times as that of pure Mn(3)O(4) samples. Because of the low-cost, nonpollution, and stable capacity, the carbon homogeneously coated Mn(3)O(4)@C nanocomposites are promising anode material for lithium ion batteries. PMID:22394097

  7. Expanding Literacy and Integrating Curricula through Dance.

    Science.gov (United States)

    Birch, James R.

    2000-01-01

    Dance embodies all of the multiple intelligences and uses Sternberg's intellectual components (memory, analysis, creativity, practicality). Integrated into the curriculum, dance can expand literacy and make learning more interactive. (SK)

  8. Expanding Patient Options: Minilaparotomy for Hysterectomy

    Medline Plus

    Full Text Available Expanding Patient Options: Minilaparotomy for Hysterectomy Covidien Energy Based Devices Concord, California May 26, 2010 Welcome to this OR Live program presented by Covidien energy-based devices. Good evening, and thank ...

  9. Expandability, Reversibility, and Optimal Capacity Choice

    OpenAIRE

    Dixit, Avinash K; Robert S. Pindyck

    1998-01-01

    We develop continuous-time models of capacity choice when demand fluctuates stochastically, and the firm's opportunities to expand or contract are limited. Specifically consider costs of investing or disinvesting that vary with time, or with the amount of capacity already installed. The firm's limited opportunities to expand or contract create call and put options on incremental units of capital; we show how the values of these options affect the firm's investment decisions.

  10. Dynamical Model of an Expanding Shell

    OpenAIRE

    Pe'er, Asaf

    2012-01-01

    Expanding blast waves are ubiquitous in many astronomical sources, such as supernovae remnants (SNRs), X-ray emitting binaries (XRBs) and gamma-ray bursts (GRBs). I consider here the dynamics of such an expanding blast wave, both in the adiabatic and the radiative regimes. As the blast wave collects material from the surrounding, it decelerates. A full description of the temporal evolution of the blast wave requires consideration of both the energy density and the pressure of the shocked mate...

  11. Expandable intramedullary nail - experimental biomechanical evaluation

    OpenAIRE

    A. Kajzer; W. Kajzer; J. Marciniak

    2010-01-01

    Purpose: The paper presents results of experimental analysis of femur and femur – expandable intramedullary nail system. The aim of the work was to determine displacement in three models. In addition, the torsion of the system aiming at determining the moments depending on the torsional angle of the bone was carried out.Design/methodology/approach: Three femurs were selected for studies. The analysis was carried out on the femur – expandable intramedullary nail system. The influence of the lo...

  12. Effect of Carbonation Curing on Mechanical Strength and Volume Stability of Steel Slag Concrete%碳化养护对钢渣混凝土强度和体积稳定性的影响

    Institute of Scientific and Technical Information of China (English)

    张丰; 莫立武; 邓敏

    2016-01-01

    当前国内外对钢渣的利用率不高,急需拓展经济、高效的钢渣利用途径。以钢渣粉为主要胶凝材料组分,用钢渣砂、钢渣石为集料配制混凝土,采用 CO2进行养护,研究碳化养护对钢渣混凝土强度和体积稳定性能的影响。结果表明:经碳化养护后,混凝土抗压强度显著提高,碳化14 d 强度提高3.2~5.3倍,最高可达65.3 MPa,且碳化时间越长,试件碳化深度越大、pH 值越低、碳化程度越高,混凝土强度也越高。碳化过程中生成碳化产物方解石 CaCO3(碳酸钙镁 CaxMg1–xCO3),使混凝土结构更加致密,吸水率降低。钢渣砂和钢渣石作集料也可被碳化,碳化后钢渣砂、钢渣石混凝土强度高于天然砂、天然石混凝土强度,混凝土体积稳定性得到明显改善。%Currently the utilization ratio of steel-making slag is relatively low, and hence there is a need to seek for new economical ways to use the steel slag. In this study, steel slag concretes were prepared by using ground steel slag powders as partial replacements of Portland cement at different levels and/or using the coarse steel slag directly as aggregates as substitutions of river sands and coarse aggregates. The steel slag concretes were then exposed to CO2 curing to investigate the influences of carbonation on the compressive strength and volume stability of the concretes. The results show that the compressive strengths of steel slag concretes increased significantly after the carbonation curing, which increased by 3.2–5.3 times after 14 d of carbonation and moreover the highest compressive strength reached 65.3 MPa. Prolonging the carbonation curing time facilitated the carbonation reaction, and hence increased the carbonation depths, decreased the pH values and enhanced the strength gain of steel slag concretes. The treatment of CO2 curing decreased the water absorption of concrete specimens due to the microstructure

  13. Voltammetric Detection of Urea on an Ag-Modified Zeolite- Expanded Graphite-Epoxy Composite Electrode

    NARCIS (Netherlands)

    Manea, F.; Pop, A.; Radovan, C.; Malchev, P.G.; Bebeselea, A.; Burtica, G.; Picken, S.J.; Schoonman, J.

    2008-01-01

    In this paper, a modified expanded graphite composite electrode based on natural zeolitic volcanic tuff modified with silver (EG-Ag-Z-Epoxy) was developed. Cyclic voltammetry measurements revealed a reasonably fast electron transfer and a good stability of the electrode in 0.1 M NaOH supporting elec

  14. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

    OpenAIRE

    Andreas Krause; Susanne Dörfler; Markus Piwko; Florian M. Wisser; Tony Jaumann; Eike Ahrens; Lars Giebeler; Holger Althues; Stefan Schädlich; Julia Grothe; Andrea Jeffery; Matthias Grube; Jan Brückner; Jan Martin; Jürgen Eckert

    2016-01-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D su...

  15. Conditions for Emergence, Stability and Change in New Organizations in the Field of Citizens Climate Action

    DEFF Research Database (Denmark)

    Figueroa, Maria Josefina

    Climate change represents a crisis of tangible measure and the emergence of a field of action within which acting today needs to be motivated for what can contribute to benefit climate and transform society into a low carbon tomorrow. With the breadth and scope of citizen action on climate change...... expanding worldwide the weight of expectations can be boiled down to two: One refers to their potential for delivering specific mitigation/adaptation goals; the second refers to their organizational potential, stability and the manner in which they can ultimately affect societal transformational change....... This contribution is concerned with the latter. It proposes that using field analysis it is possible to understand conditions of emergence, stability and change in citizen engagement in climate action. The present contribution offers only a preliminary exploration of possibilities for how using field theory can...

  16. A comparison of redox polymer and enzyme co-immobilization on carbon electrodes to provide membrane-less glucose/O2 enzymatic fuel cells with improved power output and stability.

    Science.gov (United States)

    Rengaraj, Saravanan; Kavanagh, Paul; Leech, Dónal

    2011-12-15

    Glassy carbon and graphite electrodes modified with films of enzyme and osmium redox polymer, cross linked with poly (ethylene glycol) diglycidyl ether, were used for elaboration of a glucose/O(2) enzymatic fuel cell. The redox polymers [Os(4,4'-dimethoxy-2,2'-bipyridine)(2)(polyvinylimidazole)(10)Cl](+) and [Os(4,4'-dichloro-2,2'-bipyridine)(2)(polyvinylimidazole)(10)Cl](+) were selected to facilitate transfer of electrons from the glucose oxidase (GOx) active site to the T1 Cu site of multicopper oxygenases of Trametes hirsuta laccase (ThLacc) and Myrothecium verrucaria bilirubin oxidase (MvBOD). Maximum power density at pH 5.5 of 3.5 μW cm(-2) at a cell voltage of 0.35 V was obtained for an assembled membrane-less fuel cell based on ThLacc on glassy carbon as cathode, in the presence of 0.1 M glucose, 37 °C, with lower power observed at pH 7.4 and 4.5. Replacement of the ThLacc cathode with that of MvBOD produced 10 μW cm(-2) at 0.25 V under pseudo-physiological conditions. Replacement of glassy carbon with graphite as base electrode material resulted in increased redox polymer loading, leading to an increase in power output to 43 μW cm(-2) at 0.25 V under similar conditions. Improved stabilization of biofilms was achieved through covalent anchoring of enzyme and redox polymer on graphite electrodes, derivatized via electrochemical reduction of the diazonium cation generated in situ from p-phenylenediamine. Enzymatic fuel cells using this approach retained 70% power at 24 h, whereas fuel cells prepared without chemical anchoring to graphite retained only 10% of power over the same interval. PMID:22005596

  17. Si xC 1- xO 2 alloys: A possible route to stabilize carbon-based silica-like solids?

    Science.gov (United States)

    Aravindh, Assa; Arkundato, Artoto; Barman, Sonali; Baroni, Stefano; Bhargava, B. L.; Chandrakumar, K. R. S.; Chen, Wei; Cherian, Roby; Corso, Andrea Dal; Datta, Soumendu; de Gironcoli, Stefano; Dhayal, Suman S.; Dixit, Alok Kumar; Dutta, Sudipta; D'yachkov, Pavel; Floare, Calin Gabriel; Ganguli, Nirmal; Ganguly, Shreemoyee; Gebauer, Ralph; Ghosh, Saurabh; Giannozzi, Paolo; Govind; Hatt, Alison J.; Hembram, K. P. S. S.; Imam, Mighfar; Jayalakshmi, V.; Jayanthi, C. S.; Kelkar, Tuhina; Anil Kumar; Lee, Jun Hee; Lee, Mal-Soon; Lonappan, Dayana; Mahadevan, Priya; Mallajosyula, Sairam Swaroop; Marathe, Madhura; Marzari, Nicola; Melot, Brent; Miller, Nicholas; Morrone, Joseph; Nanavati, Sachin; Nanayakkara, Asiri; Nandi, Prithwish Kumar; Narasimhan, Shobhana; Natarajan, Bhaarati; Parvin, Fahmida; Paul, Sujata; Pradhan, Kalpataru; Praveena, G.; Prasad, Dasari L. V. K.; Poswal, Himanshu K.; Pujari, Bhalchandra; Pushpa, Raghani; Reddy, K. Hari Krishna; Saha, Srijan Kumar; Sbraccia, Carlo; Scandolo, Sandro; Seal, Prasenjit; Shafai, Ghazal S.; Shanavas, K. V.; Simrall, James O. H.; Srirangarajan, Aarti; Srivastava, Vipul; Talati, Mina K.; Tantirungrotechai, Yuthana; Tarafder, Kartick; Thomas, Tiju; Uthayathasan, T.

    2007-11-01

    Novel extended tetrahedral forms of CO 2 have been synthesized recently under high-pressure conditions. We perform ab initio density functional theory calculations to investigate whether doping with Si can extend the stability range of such tetrahedral forms of CO 2 to ambient pressure. Calculations are performed with a simple cubic cell containing eight formula units in a β-cristobalite-like structure. Though we find that all the Si xC 1- xO 2 structures considered by us are thermodynamically unstable with respect to decomposition into the end members at ambient pressures, the energy differences are small, suggesting that it might be possible for such phases to exist in metastable forms. At higher pressures, the heat of formation is found to be negative. The bonding between C and O atoms is more covalent than that between Si and O atoms. We also find indications that some C atoms may prefer three-fold coordination at low pressure.

  18. Stability constants important to the understanding of plutonium in environmental waters, hydroxy and carbonate complexation of PuO{sub 2}{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, D A [California Univ., Berkeley, CA (USA). Dept. of Chemistry

    1990-04-20

    The formation constants for the reactions PuO{sub 2}{sup +} + H{sub 2}O = PuO{sub 2}(OH) + H{sup +} and PuO{sub 2}{sup +} + CO{sub 3}{sup 2} = PuO{sub 2}(CO{sub 3}){sup {minus}} were determined in aqueous sodium perchlorate solutions by laser-induced photoacoustic spectroscopy. The molar absorptivity of the PuO{sub 2}{sup +} band at 569 nm decreased with increasing hydroxide concentration. Similarly, spectral changes occurred between 540 and 580 nm as the carbonate concentration was increased. The absorption data were analyzed by the non-linear least-squares program SQUAD to yield complexation constants. Using the specific ion interaction theory, both complexation constants were extrapolated to zero ionic strength. These thermodynamic complexation constants were combined with the oxidation-reduction potentials of Pu to obtain Eh versus pH diagrams. 120 refs., 35 figs., 12 tabs.

  19. Electrical Properties of Expanded Graphite Intercalation Compounds

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The intercalation compounds of CuCl2 were synthesized with expanded graphite, whose magnitude of the electrical conductivity is about 103S.cm-1. Their electrical conductivity is 3~6 times as high as that of the expanded graphite, and about 10 times as high as that of GIC made of the non-expanded graphite. The microanalysis results of chemical compounds by X-ray energy spectrum scanning of TEM testified that the atomic ratio of chloride and cupric is nonstoichoimetric. The multivalence and exchange of electrovalence of the cupric ion was confirmed by the XPS-ESCA. Vacancy of chlorine anion increases the concentration of charge carrier.The special stage structure, made of graphite and chloride, produces a weak chemical bond belt and provides a carrier space in the direction of GIC layer. These factors develop the electrical properties.

  20. Expanding maps, shrinking targets and hitting times

    International Nuclear Information System (INIS)

    We study the (metric) Diophantine approximation properties of uniformly expanding transformations and some non-uniformly expanding transformations, i.e. transformations T(x) with an associated countable (not necessarily finite) partition and a return time function R(x) (constant on the blocks of the partition) so that T-circumflex(x)=TR(x)(x) is uniformly expanding, and we obtain Borel–Cantelli results on hitting times of shrinking targets. Our arguments do not require the so-called big image property for T-circumflex and our results contain most of the diversity of examples of slowly mixing systems. We also obtain, with related techniques, results for one-sided topological Markov chains over a countable alphabet with a Gibbs measure. (paper)

  1. Bound systems in an expanding universe

    CERN Document Server

    Baker, G A

    2000-01-01

    The Schwarzchild solution insertion in an expanding universe, the so-called "Swiss cheese model," is shown to possess an extrinsic curvature miss-match. One consequence is that some trajectories are discontinuous functions of their initial conditions. An alternate metric is proposed which goes smoothly between the Schwarzchild exterior solution and the Friedmann-Lemaitre, expanding universe metric. It is further shown that the effects of the expansion on planetary motions in the solar system are too small to be currently observed for this alternate metric.

  2. Graphene for Expandable Space Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Graphene's tightly bonded impermeable single atomic layer of carbon offers unrivalled potential for lightweight flexible gas barrier applications. Graphene has been...

  3. Dispersion stability of water soluble ultrafine carbon black in N-methyl morpholine-N-oxide solution%水性超细炭黑在N-甲基吗啉-N-氧化物溶液中的分散稳定性

    Institute of Scientific and Technical Information of China (English)

    张凯; 付少海; 田安丽; 王潮霞; 张霞

    2012-01-01

    The water soluble ultrafine carbon black and encapsulated ultrafine carbon black that were suitable for dope dyeing of Lyocell fiber were prepared by direct dispersing method and emulsion polymerization method, respectively, and the particle size of the ultrafine carbon black obtained with different methods and their dispersion stabilities in the N-methyl morpholine-N-oxide (NMMO) solution were investigated. Experimental results revealed that the average particle size of encapsulated ultrafine carbon black was obviously smaller than that of dispersive ultrafine carbon black and its centrifugal stability and thermal stability in NMMO solution were higher than those of dispersive ultrafine carbon black. The apparent viscosity of NMMO solution decreased when encapsulated carbon was added,and the more amount of encapsulated carbon added,the lower viscosity of NMMO solution was.%采用直接分散法和乳液聚合法分别制备了可用于Lyocell纤维原液着色用的水性分散型超细炭黑和包覆型超细炭黑,研究了不同方法制成的超细炭黑的粒子大小以及在N-甲基吗啉-N-氧化物(NMMO)溶液中的分散稳定性.结果表明:包覆型超细炭黑的平均粒径明显小于分散型超细炭黑,且在NMMO溶液中的离心稳定性和耐热稳定性高于分散型超细炭黑;NMMO溶液中加入包覆型超细炭黑,其黏度明显下降,且加入量越大,黏度下降越明显.

  4. Decay of the Weyl curvature in expanding black hole cosmologies

    CERN Document Server

    Schlue, Volker

    2016-01-01

    This paper presents a partial proof of the non-linear stability of the expanding region of Schwarzschild de Sitter cosmologies. We show that under dynamically realistic assumptions the conformal Weyl curvature decays towards null infinity. Our assumptions are consistent with the expectation that a dynamical solution to Einstein's equations with positive cosmological constant does not converge globally to a member of the Kerr de Sitter family. In particular in this problem the geometry of null infinity is a priori unknown. One expects this result to form an essential part of a global existence proof for the cosmological region, which - along with the precise asymptotics of these solutions - is the subject of a subsequent paper.

  5. Ensuring Stability

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    "Stable"will be a key word for China’s economy in 2012.That’s the beat set at the annual Central Economic Work Conference held in Beijing on December 12-14,which reviewed this year’s development and mapped out plans for the next year.Policymakers at the conference decided to keep macroeconomic policies stable,seek a stable and relatively fast economic growth,stabilize consumer prices and maintain social stability in 2012.On the basis of stability,the government will transform the development model,deepen reform and improve people’s livelihood.

  6. Against Stabilization

    Directory of Open Access Journals (Sweden)

    Roger Mac Ginty

    2012-11-01

    Full Text Available This is a polemic against the concept and practice of stabilization as practiced by leading states from the global north in peace support interventions. It is not an argument against stability. Instead, it depicts stabilization as an essentially conservative doctrine that runs counter to its stated aims of enhancing local participation and legitimacy. It is an agenda of control that privileges notions of assimilation with international (western standards and mainstreams the military into peace-support operations. As a result, the value of peace is undercut.

  7. Carbon Farming as a Carbon Negative Technology

    Science.gov (United States)

    Anderson, C.; Laird, D.; Hayes, D. J.

    2015-12-01

    Carbon farms have a pivotal role in national and international efforts to mitigate and adapt to climate change. A carbon farm in its broadest sense is one that reduces greenhouse gas (GHG) emissions or captures and holds carbon in vegetation and soils. Their capacity to remove carbon from the air and store it safely and permanently, while providing additional human and ecosystem benefits, means they could contribute significantly to national efforts to stabilize or reduce GHGs. We examine carbon farms in the context of corn and soybean production agriculture. We illustrate, using Iowa data but with relevance across United States corn and soybean production, the potential for carbon farms to reduce human GHG emissions and sequester carbon permanently at a rate that has meaningful impact on global greenhouse gas concentration. Carbon has been viewed as a next generation cash crop in Iowa for over a decade. The carbon farm perspective, however, goes beyond carbon as cash crop to make carbon the center of an entire farm enterprise. The transformation is possible through slight adjustment crop practices mixed with advances in technology to sequester carbon through biochar. We examine carbon balance of Iowa agriculture given only the combination of slight reduction in fertilizer and sequestration by biochar. We find the following. Iowa carbon farms could turn Iowa agriculture into a carbon sink. The estimated range of GHG reduction by statewide implementation of carbon farms is 19.46 to 90.27 MMt CO2-equivalent (CO2-e), while the current agricultural CO2-e emission estimate is 35.38 MMt CO2-e. Iowa carbon farm GHG reduction would exceed Iowa GHG reduction by wind energy (8.7 MMt CO2-e) and could exceed combined reductions from wind energy and corn grain ethanol (10.7 MMt CO2-e; 19.4 MMt CO2-e combined). In fact, Iowa carbon farms alone could exceed GHG reduction from national corn grain ethanol production (39.6 MMt CO2-e). A carbon price accessible to agricultural

  8. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

    Science.gov (United States)

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M.; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M.

    2016-01-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging. PMID:27319783

  9. 碳纤维/氰酸酯复合材料尺寸稳定性能%Stability of Carbon Fiber Reinforced Cyanate Ester Composite

    Institute of Scientific and Technical Information of China (English)

    诸静; 郝旭峰; 叶周军

    2013-01-01

    对碳纤维/氰酸酯复合材料的吸湿、空间放气、吸湿变形性能进行了研究,并与传统碳纤维/环氧复合材料的性能进行对比.研究表明:氰酸酯基复合材料的吸湿性能优于碳纤维/环氧树脂复合材料,且其各项空间环境性能均与环氧树脂基复合材料相当.%In this paper,moisture absorption,outgas capacity in vacuum and deformation after moisture absorption of carbon fiber reinforced cyanate ester composite were studied,and were compared with corresponding capacity of epoxy resin composites.Result show that the moisture absorption of cyanate ester composite is lower than epoxy resin composites,and capacity in simulated space environment is compatible with epoxy resin composites.

  10. Facile one-step synthesis of nanocomposite based on carbon nanotubes and Nickel-Aluminum layered double hydroxides with high cycling stability for supercapacitors.

    Science.gov (United States)

    Bai, Caihui; Sun, Shiguo; Xu, Yongqian; Yu, Ruijin; Li, Hongjuan

    2016-10-15

    Nickel-Aluminum Layered Double Hydroxide (NiAl-LDH) and nanocomposite of Carbon Nanotubes (CNTs) and NiAl-LDH (CNTs/NiAl-LDH) were prepared by using a facile one-step homogeneous precipitation approach. The morphology, structure and electrochemical properties of the as-prepared CNTs/NiAl-LDH nanocomposite were then systematically studied. According to the galvanostatic charge-discharge curves, the CNTs/NiAl-LDH nanocomposite exhibited a high specific capacitance of 694Fg(-1) at the 1Ag(-1). Furthermore, the specific capacitance of the CNTs/NiAl-LDH nanocomposite still retained 87% when the current density was increased from 1 to 10Ag(-1). These results indicated that the CNTs/NiAl-LDH nanocomposite displayed a higher specific capacitance and rate capability than pure NiAl-LDH. And the participation of CNTs in the NiAl-LDH composite improved the electrochemical properties. Additionally, the capacitance of the CNTs/NiAl-LDH nanocomposite kept at least 92% after 3000cycles at 20Ag(-1), suggesting that the nanocomposite exhibited excellent cycling durability. This strategy provided a facile and effective approach for the synthesis of nanocomposite based on CNTs and NiAl-LDH with enhanced supercapacitor behaviors, which can be potentially applied in energy storage conversion devices. PMID:27405071

  11. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability.

    Science.gov (United States)

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M

    2016-01-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm(2). The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm(2), a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging. PMID:27319783

  12. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

    Science.gov (United States)

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M.; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M.

    2016-06-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.

  13. From carbon nanotubes to carbon atomic chains

    Science.gov (United States)

    Casillas García, Gilberto; Zhang, Weijia; José-Yacamán, Miguel

    2010-10-01

    Carbyne is a linear allotrope of carbon. It is formed by a linear arrangement of carbon atoms with sp-hybridization. We present a reliable and reproducible experiment to obtain these carbon atomic chains using few-layer-graphene (FLG) sheets and a HRTEM. First the FLG sheets were synthesized from worm-like exfoliated graphite and then drop-casted on a lacey-carbon copper grid. Once in the TEM, two holes are opened near each other in a FLG sheet by focusing the electron beam into a small spot. Due to the radiation, the carbon atoms rearrange themselves between the two holes and form carbon fibers. The beam is concentrated on the carbon fibers in order excite the atoms and induce a tension until multi wall carbon nanotube (MWCNT) is formed. As the radiation continues the MWCNT breaks down until there is only a single wall carbon nanotube (SWCNT). Then, when the SWCNT breaks, an atomic carbon chain is formed, lasts for several seconds under the radiation and finally breaks. This demonstrates the stability of this carbon structure.

  14. Expanded austenite, crystallography and residual stress

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

    2010-01-01

    The identity of expanded austenite as developing during low temperature nitriding and/or carburising of austenitic stainless steel has been under debate since the very first observation of this phase. In the present article, recent results obtained with (a) homogeneous samples of various uniform ...

  15. Expanded austenite; crystallography and residual stress

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

    2009-01-01

    The identity of expanded austenite as developing during low temperature nitriding and/or carburizing of austenitic stainless steel has been under debate since the very first observation of this phase. In the present article recent results obtained with i) homogeneous samples of various uniform co...

  16. Expanding CTE Opportunities through Blended Learning

    Science.gov (United States)

    McKinstry, Elizabeth

    2012-01-01

    The global economy, 21st century skills, knowledge society, college and career readiness, digital and project-based learning are all common terms to educators who are expanding their learning environments beyond the classroom to meet the needs of all students. It is common knowledge that the rapid technological advances of this century have…

  17. Expanding Your Horizons Conference in Geneva

    CERN Multimedia

    Chromek-Burckhart, Doris

    2011-01-01

    CERN and its experiments participated in Expanding Your Horizons (EYH) in Science and Mathematics conference in Geneva on 12th November. EYH nurture girls' interest in science and math courses to encourage them to consider careers in science, technology, engineering, and math.

  18. Expanding the collaboration between CERN and Pakistan

    CERN Multimedia

    2002-01-01

    Parvez Butt, chairman of the Pakistan Atomic Energy Commission, and CERN Director General, Luciano Maiani, signed a letter of intent last week to expand collaboration. Through an agreement which should be formalized within a few months, Pakistan would make a substantial contribution to the LHC and its detectors, coordinated by the Pakistani National Centre of Physics.

  19. Responsible implementation of expanded carrier screening

    Science.gov (United States)

    Henneman, Lidewij; Borry, Pascal; Chokoshvili, Davit; Cornel, Martina C; van El, Carla G; Forzano, Francesca; Hall, Alison; Howard, Heidi C; Janssens, Sandra; Kayserili, Hülya; Lakeman, Phillis; Lucassen, Anneke; Metcalfe, Sylvia A; Vidmar, Lovro; de Wert, Guido; Dondorp, Wybo J; Peterlin, Borut

    2016-01-01

    This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines. PMID:26980105

  20. Carbohydrate plasma expanders for passive tumor targeting

    DEFF Research Database (Denmark)

    Hoffmann, Stefan; Caysa, Henrike; Kuntsche, Judith;

    2013-01-01

    inexpensive synthesis, constant availability, a good safety profile, biodegradability and the long clinical use as plasma expanders. Three polymers have been tested for cytotoxicity and cytokine activation in cell cultures and conjugated with a near-infrared fluorescent dye: hydroxyethyl starches (HES 200 k...

  1. Expanding the applicability of Heallth Technology Assessments

    DEFF Research Database (Denmark)

    Draborg, Eva; Hansen, Helle Ploug

    2012-01-01

    The objective of the presentation is to expand the foundations of input into policy decision making relying on health technology assessments (HTA). HTAs are primarily based on systematic reviews (SR) and thereby mostly on randomized controlled trials (RCT). RCTs can be distinguished on a continuu...

  2. Refrigeration generation using expander-generator units

    Science.gov (United States)

    Klimenko, A. V.; Agababov, V. S.; Koryagin, A. V.; Baidakova, Yu. O.

    2016-05-01

    The problems of using the expander-generator unit (EGU) to generate refrigeration, along with electricity were considered. It is shown that, on the level of the temperatures of refrigeration flows using the EGU, one can provide the refrigeration supply of the different consumers: ventilation and air conditioning plants and industrial refrigerators and freezers. The analysis of influence of process parameters on the cooling power of the EGU, which depends on the parameters of the gas expansion process in the expander and temperatures of cooled environment, was carried out. The schematic diagram of refrigeration generation plant based on EGU is presented. The features and advantages of EGU to generate refrigeration compared with thermotransformer of steam compressive and absorption types were shown, namely: there is no need to use the energy generated by burning fuel to operate the EGU; beneficial use of the heat delivered to gas from the flow being cooled in equipment operating on gas; energy production along with refrigeration generation, which makes it possible to create, using EGU, the trigeneration plants without using the energy power equipment. It is shown that the level of the temperatures of refrigeration flows, which can be obtained by using the EGU on existing technological decompression stations of the transported gas, allows providing the refrigeration supply of various consumers. The information that the refrigeration capacity of an expander-generator unit not only depends on the parameters of the process of expansion of gas flowing in the expander (flow rate, temperatures and pressures at the inlet and outlet) but it is also determined by the temperature needed for a consumer and the initial temperature of the flow of the refrigeration-carrier being cooled. The conclusion was made that the expander-generator units can be used to create trigeneration plants both at major power plants and at small energy.

  3. Interactive Effects of Climate Change and Decomposer Communities on the Stabilization of Wood-Derived Carbon Pools: Catalyst for a New Study

    Energy Technology Data Exchange (ETDEWEB)

    Resh, Sigrid C. [Michigan Technological University

    2014-11-17

    Globally, forest soils store ~two-thirds as much carbon (C) as the atmosphere. Although wood makes up the majority of forest biomass, the importance of wood contributions to soil C pools is unknown. Even with recent advances in the mechanistic understanding of soil processes, integrative studies tracing C input pathways and biological fluxes within and from soils are lacking. Therefore, our research objectives were to assess the impact of different fungal decay pathways (i.e., white-rot versus brown-rot)—in interaction with wood quality, soil temperature, wood location (i.e., soil surface and buried in mineral soil), and soil texture—on the transformation of woody material into soil CO2 efflux, dissolved organic carbon (DOC), and soil C pools. The use of 13C-depleted woody biomass harvested from the Rhinelander, WI free-air carbon dioxide enrichment (Aspen-FACE) experiment affords the unique opportunity to distinguish the wood-derived C from other soil C fluxes and pools. We established 168 treatment plots across six field sites (three sand and three loam textured soil). Treatment plots consisted of full-factorial design with the following treatments: 1. Wood chips from elevated CO2, elevated CO2 + O3, or ambient atmosphere AspenFACE treatments; 2. Inoculated with white rot (Bjerkandera adusta) or brown rot (Gloeophyllum sepiarium) pure fungal cultures, or the original suite of endemic microbial community on the logs; and 3. Buried (15cm in soil as a proxy for coarse roots) or surface applied wood chips. We also created a warming treatment using open-topped, passive warming chambers on a subset of the above treatments. Control plots with no added wood (“no chip control”) were incorporated into the research design. Soils were sampled for initial δ13C values, CN concentrations, and bulk density. A subset of plots were instrumented with lysimeters for sampling soil water and temperature data loggers for measuring soil temperatures. To determine the early

  4. Exponentially Expanded Grid Network Approach (EEGNA) : An Efficient Way for the Simulation of Stiff Electrochemical Problems

    Institute of Scientific and Technical Information of China (English)

    邓兆祥; 林祥钦; 童中华

    2003-01-01

    The exponentially expanded space grid was incorporated into the network approach to overcome the problem of low simulation efficiency during the simulations of electrochemical problems with stiff kinetics or wide dlsperslon of diffusion coefficients, resulting in an effective electrochemical simulation method: exponentially expanded grid network approach (EEG-NA). The stability and accuracy of the EEGNA for the simulation of various electrode processes .coupled with different types of homogeneous reactions were investigated.

  5. 超低碳铜时效强化钢的热稳定性%Thermal stability of ultra-low-carbon copper-bearing age-hardening steel

    Institute of Scientific and Technical Information of China (English)

    刘翊之; 杨才福; 柴锋; 张永权; 苏航

    2013-01-01

    研究了400℃至800℃再加热处理后超低碳铜时效强化钢组织和性能的变化.利用光学显微镜、扫描电镜、透射电镜观察和X射线衍射分析了不同温度再加热处理后钢显微组织和ε-Cu沉淀的特征.结果表明,再加热温度不高于650℃的条件下,钢的强度和韧性未明显下降,即具有优良的热稳定性;再加热温度高于650℃则钢的屈服强度明显降低,这是由于基体组织发生明显的回复以及ε-Cu沉淀粗化;再加热温度高于700℃钢的韧性明显降低,这是大量高硬度M/A岛组织出现所造成.分析表明基体组织的回复,ε-Cu沉淀的数量和尺寸及M/A岛组织是影响超低碳铜时效强化钢热稳定性的主要因素.%Microstructure and mechamical properties of a ultra-low-carbon copper-bearing age-hardening steel under reheated treatment between 400 ℃ to 800 ℃ were investigated.OM,SEM,TEM and XRD were used to characterize microstructure and ε-Cu precipitates of the tested steel under reheat treatment at different temperatures.Strength and toughness of tested steel do not decrease significantly when reheat temperature below 650 ℃,which means the tested steel exhibits excellent thermal stability.Due to recovery of matrix microstructure and coalescence of ε-Cu precipitates,yield strength of the tested steel decreases significantly when reheat temperature above 650 ℃.Due to appearance of high hardness M/A island,toughness of the tested steel decreases markedly when reheat temperature above 700 ℃.The results indicate that recovery of matrix microstructure,size and quantity of ε-Cu precipitates and M/A island are mainly facters affecting thermal stability of the ultra-low-carbon copper-bearing age-hardening steel.

  6. Sensitive and selective determining ascorbic acid and activity of alkaline phosphatase based on electrochemiluminescence of dual-stabilizers-capped CdSe quantum dots in carbon nanotube-nafion composite.

    Science.gov (United States)

    Ma, Xiaolong; Zhang, Xin; Guo, Xinli; Kang, Qi; Shen, Dazhong; Zou, Guizheng

    2016-07-01

    Sensitive and selective determining bio-related molecule and enzyme play an important role in designing novel procedure for biological sensing and clinical diagnosis. Herein, we found that dual-stabilizers-capped CdSe quantum dots (QDs) in composite film of multi-walled carbon nanotubes (CNTs) and Nafion, displaying eye-visible monochromatic electrochemiluminescence (ECL) with fwhm of 37nm, which offers promising ECL signal for detecting ascorbic acid (AA) as well as the activity of alkaline phosphatase (ALP) in biological samples. It was also shown that the dual-stabilizers-capped CdSe QDs can preserve their highly passivated surface states with prolonged lifetime of excited states in Nafion mixtures, and facilitate electron-transfer ability of Nafion film along with CNTs. Compared with the QDs/GCE, the ECL intensity is enhanced 1.8 times and triggering potential shifted to lower energy by 0.12V on the CdSe-CNTs-Nafion/GCE. The ECL quenching degree increases with increasing concentration of AA in the range of 0.01-30nM with a limit of detection (LOD) of 5pM. The activity of ALP was determined indirectly according to the concentration of AA, generated in the hydrolysis reaction of l-ascorbic acid 2-phosphate sesquimagnesium (AA-P) in the presence of ALP as a catalyst, with an LOD of 1μU/L. The proposed strategy is favorable for developing simple ECL sensor or device with high sensitivity, spectral resolution and less electrochemical interference. PMID:27154663

  7. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell.

    Science.gov (United States)

    Demir, Teyfik

    2015-05-01

    Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8 N compared to the failure load for calf vertebrae's 1264 N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890 N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective

  8. Application of an Expanded Sequestration Estimate to the Domestic Energy Footprint of the Republic of Ireland

    Directory of Open Access Journals (Sweden)

    Bernadette O’Regan

    2010-08-01

    Full Text Available The need for global comparability has led to the recent standardization of ecological footprint methods. The use of global averages and necessary methodological assumptions has questioned the ability of the ecological footprint to represent local or national specific concerns. This paper attempts to incorporate greater national relevancy by expanding the sequestration estimate used to calculate the annual carbon footprint of domestic Irish energy use. This includes expanding existing study boundaries to include additional carbon pools such as the litter, dead and soil pools. This generated an overall estimate of 4.38 tonnes of carbon per hectare per year (t C/ha/yr, resulting in an ecological footprint estimate of 0.49 hectares per capita (ha/cap The method employed in this paper also incorporated the potential role of grassland as a carbon sink. The caveat that the resultant value is dependent on the choice of study boundary is discussed. Including the lateral movement of carbon embodied in farm products (effectively placing the boundary around the farm gate reduces the estimate of grassland carbon sequestration by approximately 44% to 1.82 t C/ha/yr. When a footprint calculated using an overall sequestration estimate (based on the distribution of Irish grassland and forestry is translated into global hectares (gha, the standardized value is reduced by 35%.

  9. Dynamical Model of an Expanding Shell

    CERN Document Server

    Pe'er, Asaf

    2012-01-01

    Expanding blast waves are ubiquitous in many astronomical sources, such as supernovae remnants (SNRs), X-ray emitting binaries (XRBs) and gamma-ray bursts (GRBs). I consider here the dynamics of such an expanding blast wave, both in the adiabatic and the radiative regimes. As the blast wave collects material from the surrounding, it decelerates. A full description of the temporal evolution of the blast wave requires consideration of both the energy density and the pressure of the shocked material. The obtained equation is different than earlier works in which only the energy was considered. The solution converges to the familiar results in both the ultra-relativistic and the sub-relativistic (Newtonian) regimes.

  10. Expanding Policy Imagination in Political Economy

    DEFF Research Database (Denmark)

    Seabrooke, Leonard

    2006-01-01

    be implemented. Historical sociology provides a way to generate information about contextual constellations through two "tonics": intentional rationality and social mechanisms. With the assistance of these tonics, historical sociology widens political economy's policy imagination.......Much of the literature in political economy seeks to capture an essential insight into the evolution of political and economic systems to provide a foundation for policy advice. This article suggests that attempts to nut out the kernels of change often restrict rather than expand policy imagination...

  11. Perspectives of Expanding Business into Russia

    OpenAIRE

    Samaeva, Naylya

    2014-01-01

    The purpose of the thesis was to analyze and evaluate the Russian market taking into account all its advantages and disadvantages and to find out whether it was profitable for the case company Hotel Vip Club International Oy to expand its business into Rus-sia. The study includes theoretical framework covering different essential theories and concepts, information about tourism and hotel related business in Russia, and the pecu-liarities of doing business in Russia including the analyses of t...

  12. GWDC Expands High-End Market Share

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ It is a decision of great significance for GWDC to expand high-end market share in order to realize its transformation of development strategy and improve its development quality. As an important step of GWDC to explore high-end market, Oman PDO Project marks the first time that the Chinese petroleum engineering service team cooperates with the transnational petroleum corporations ranking first three in the world.

  13. The Expanding Universe of Prion Diseases

    OpenAIRE

    Watts, Joel C.; Aru Balachandran; David Westaway

    2006-01-01

    Prions cause fatal and transmissible neurodegenerative disease. These etiological infectious agents are formed in greater part from a misfolded cell-surface protein called PrP(C). Several mammalian species are affected by the diseases, and in the case of "mad cow disease" (BSE) the agent has a tropism for humans, with negative consequences for agribusiness and public health. Unfortunately, the known universe of prion diseases is expanding. At least four novel prion diseases--including human d...

  14. Strings, Fivebranes and an Expanding Universe

    OpenAIRE

    Khuri, Ramzi R.; Pokotilov, Andriy

    2002-01-01

    It was recently shown that velocity-dependent forces between parallel fundamental strings moving apart in a $D-$dimensional spacetime implied an accelerating expanding universe in $D-1$-dimensional space-time. Exact solutions were obtained for the early time expansion in $D=5,6$. Here we show that this result also holds for fundamental strings in the background of a fivebrane, and argue that the feature of an accelerating universe would hold for more general $p$-brane-seeded models.

  15. Short wavelength striations on expanding plasma clouds

    International Nuclear Information System (INIS)

    The growth and evolution of short wavelength (< ion gyroradius) flute modes on a plasma expanding across an ambient magnetic field have been actively studied in recent years, both by means of experiments in the laboratory as well as in space and through numerical simulations. We review the relevant observations and simulations results, discuss the instability mechanism and related linear theory, and describe recent work to bring experiments and theory into better agreement. 30 refs., 6 figs

  16. Femoral midshaft fractures: expandable versus locked nailing.

    Science.gov (United States)

    Zhou, Zhen-Tao; Song, Yu-Chen; Zhou, Xiao-Zhong; Zhou, Hai-Bin; Luo, Zong-Ping; Dong, Qi-Rong

    2015-04-01

    Femoral midshaft fracture is one of the most common clinical injuries and is often caused by high-energy traffic accidents. Intramedullary nailings, plates, and external fixators are all used as treatment alternatives for a variety of patients depending on fracture location, displacement, comminution, soft tissue condition, and local tradition. Locked intramedullary nailing is currently the preferred treatment method for most diaphyseal fractures and has good clinical results. The goal of this study was to compare expandable and locked intramedullary nailing for the treatment of AO type 32A and 32B1 femoral midshaft fractures. The authors performed a retrospective analysis of 46 patients (33 men and 13 women; mean age, 32.3 years; range, 22-52 years) with femoral midshaft fractures who were divided into 2 groups-one treated with an expandable intramedullary nailing method and the other with a conventional locked intramedullary nailing. The 2 groups were compared with respect to operation time, fluoroscopic time, amount of estimated blood loss, hospitalization time, healing time, and complications. Patients were followed for at least 1 year. The results of this study showed that all of the patients achieved bone union within 12 to 24 months. Expandable nailing performed better than locked nailing in operation time, fluoroscopic time, amount of estimated blood loss, and healing time (P<.001). There was no difference in hospitalization time and no visible shortening or severe complications were observed in either group. Based on the results of this study, the expandable intramedullary nailing is an easy and effective treatment for AO type 32A and 32B1 diaphyseal femoral fractures. PMID:25901625

  17. Expander Graphs in Pure and Applied Mathematics

    OpenAIRE

    Lubotzky, Alexander

    2011-01-01

    Expander graphs are highly connected sparse finite graphs. They play an important role in computer science as basic building blocks for network constructions, error correcting codes, algorithms and more. In recent years they have started to play an increasing role also in pure mathematics: number theory, group theory, geometry and more. This expository article describes their constructions and various applications in pure and applied mathematics.

  18. Inextendibility of expanding cosmological models with symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Dafermos, Mihalis [University of Cambridge, Department of Pure Mathematics and Mathematical Statistics, Wilberforce Road, Cambridge CB3 0WB (United Kingdom); Rendall, Alan D [Max Planck Institute for Gravitational Physics, Albert Einstein Institute, Am Muehlenberg 1, D-14476 Golm (Germany)

    2005-12-07

    A new criterion for inextendibility of expanding cosmological models with symmetry is presented. It is applied to derive a number of new results and to simplify the proofs of existing ones. In particular, it shows that the solutions of the Einstein-Vlasov system with T{sup 2} symmetry, including the vacuum solutions, are inextendible in the future. The technique introduced adds a qualitatively new element to the available tool-kit for studying strong cosmic censorship. (letter to the editor)

  19. Radiation testing of the AeroForm co2-based breast tissue expander implant

    International Nuclear Information System (INIS)

    Tissue expanders are used in breast reconstruction after mastectomy to stretch the remaining tissue to create space for placement of permanent breast implants. The AeroForm™ Tissue Expander, developed by AirXpanders™ Inc., contains electronic components designed to activate the release of carbon dioxide from an internal reservoir to inflate the expander. Breast cancer patients who undergo mastectomy and tissue expander/implant-based breast reconstruction may require radiation therapy at doses up to 50–60 Gy while the expander is in place. The ionizing radiation used in postmastectomy radiation therapy interacts with electronic components in medical implants, which may cause degradation in performance above certain levels. Most commercial electronic components used in medical devices, such as complementary metal-oxide semiconductor or bipolar integrated circuits can withstand radiation levels in the 50 Gy range without any performance degradation. Beyond this level, the performance may still be sufficient to guarantee functionality, but this needs to be confirmed at the system and electronic circuit level. We assessed the impact of radiation levels up to 75 Gy on 32 AeroForm™ Tissue Expanders (AirXpanders, Inc., Palo Alto, CA USA) and on the associated internal printed circuit assemblies. The electronics inside the AeroForm™ Tissue Expander implant continued to function properly after exposure to radiation levels up to 75 Gy, which is well above the maximum total dose level typically used in postmastectomy radiation therapy. Standard postmastectomy radiation therapy doses do not damage or affect the functionality of the AeroForm™ Tissue Expander

  20. Measurements of an expanding surface flashover plasma

    Energy Technology Data Exchange (ETDEWEB)

    Harris, J. R., E-mail: john.harris@colostate.edu [Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States)

    2014-05-21

    A better understanding of vacuum surface flashover and the plasma produced by it is of importance for electron and ion sources, as well as advanced accelerators and other vacuum electronic devices. This article describes time-of-flight and biased-probe measurements made on the expanding plasma generated from a vacuum surface flashover discharge. The plasma expanded at velocities of 1.2–6.5 cm/μs, and had typical densities of 10{sup 10}–10{sup 12} cm{sup −3}. The expansion velocity of the plasma leading edge often exhibited a sharp increase at distances of about 50 mm from the discharge site. Comparison with biased-probe data suggests that, under most conditions, the plasma leading edge was dominated by negative ions, with the apparent increase in velocity being due to fast H{sup −} overtaking slower, heavier ions. In some cases, biased-probe data also showed abrupt discontinuities in the plasma energy distribution co-located with large changes in the intercepted plasma current, suggesting the presence of a shock in the leading edge of the expanding plasma.

  1. Optical cavity resonator in an expanding universe

    CERN Document Server

    Kopeikin, Sergei

    2014-01-01

    We study evolution of frequency of a standing electromagnetic (EM) wave in a resonant optical cavity placed to the expanding manifold described by the Robertson-Walker metric. One builds a local coordinate system in which spacetime is locally Minkowskian. However, due to the conformal nature of the Robertson-Walker metric the conventional transformation to the local inertial coordinates introduces ambiguity in the physical interpretation of the local time coordinate. Therefore, contrary to a common-sense expectation, a straightforward implementation of EEP alone does not allow us to decide whether atomic clocks ticks at the same rate as the clocks based on EM modes of a cavity. To resolve the ambiguity we analyzed the cavity rigidity and the oscillation of its EM modes in an expanding universe by employing the Maxwell equations. We found out that both the size of the cavity and the EM frequency experience an adiabatic drift in conformal coordinates as the universe expands. We set up the oscillation equation f...

  2. Lubricin in human breast tissue expander capsules.

    Science.gov (United States)

    Cheriyan, Thomas; Guo, Lifei; Orgill, Dennis P; Padera, Robert F; Schmid, Thomas M; Spector, Myron

    2012-10-01

    Capsular contraction is the most common complication of breast reconstruction surgery. While presence of the contractile protein alpha smooth muscle actin (α-SMA) is considered among the causes of capsular contraction, the exact etiology and pathophysiology is not fully understood. The objective of this study was to investigate the possible role of lubricin in capsular formation and contraction by determining the presence and distribution of the lubricating protein lubricin in human breast tissue expander capsules. Related aims were to evaluate select histopathologic features of the capsules, and the percentage of cells expressing α-SMA, which reflects the myofibroblast phenotype. Capsules from tissue expanders were obtained from eight patients. Lubricin, at the tissue-implant interface, in the extracellular matrix, and in cells, and α-SMA-containing cells were evaluated immunohistochemically. The notable finding was that lubricin was identified in all tissue expander capsules: as a discrete layer at the tissue-implant interface, extracellular, and intracellular. There was a greater amount of lubricin in the extracellular matrix in the intimal-subintimal zone when compared with the tissue away from the implant. Varying degrees of synovial metaplasia were seen at the tissue-implant interface. α-SMA-containing cells were also seen in all but one patient. The findings might help us better understand factors involved in capsule formation.

  3. Inverted porphyrins and expanded porphyrins: An overview

    Indian Academy of Sciences (India)

    S K Pushpan; S Venkatraman; V G Anand; J Sankar; H Rath; T K Chandrashekar

    2002-08-01

    Porphyrins and metallopophyrins have attracted the attention of chemists for the past 100 years or more owing to their widespread involvement in biology. More recently, synthetic porphyrins and porphyrin-like macrocycles have attracted the attention of researchers due to their diverse applications as sensitizers for photodynamic therapy, MRI contrasting agents, and complexing agents for larger metal ions and also for their anion binding abilities. The number of -electrons in the porphyrin ring can be increased either by increasing the number of conjugated double bonds between the pyrrole rings or by increasing the number of heterocyclic rings. Thus, 22 sapphyrins, 26 rubyrins, 30 heptaphyrins, 34 octaphyrins and higher cyclic polypyrrole analogues containing 40, 48, 64, 80 and 96 systems have recently been reported in the literature. These macrocycles show rich structural diversity where normal and different kinds of inverted structures have been identified. In this review, an attempt has been made to collect the literature of the inverted porphyrins and expanded porphyrins reported until December 2001. Since the meso aryl expanded porphyrins have tendency to form both inverted and non-inverted structures more emphasis has been given to meso aryl expanded porphyrins.

  4. Advanced oxidation (H₂O₂ and/or UV) of functionalized carbon nanotubes (CNT-OH and CNT-COOH) and its influence on the stabilization of CNTs in water and tannic acid solution.

    Science.gov (United States)

    Czech, Bożena; Oleszczuk, Patryk; Wiącek, Agnieszka

    2015-05-01

    The properties of carbon nanotubes (CNTs) functionalized with -OH and -COOH groups during simulated water treatment with H2O2 and/or UV were tested. There following properties of CNTs were investigated: specific surface area, elemental composition (CHN), dynamic light scattering, Raman spectroscopy, X-ray photoelectron spectroscopy and changes in the CNTs structure were observed using transmission electron microscopy. Treatment of CNTs with H2O2 and/or UV affected their properties. This effect, however, was different depending on the functionalization of CNTs and also on the factor used (UV and/or H2O2). H2O2 plays a key role as a factor modifying the surface of CNT-OHs, whereas the properties of CNT-COOHs were most affected by UV rays. A shortening of the nanotubes, exfoliation, the opening of their ends, and changes in the surface charge were observed as a result of the action of UV and/or H2O2. The changes in observed parameters may influence the stability of the aqueous suspensions of CNTs.

  5. PARALLEL STABILIZATION

    Institute of Scientific and Technical Information of China (English)

    J.L.LIONS

    1999-01-01

    A new algorithm for the stabilization of (possibly turbulent, chaotic) distributed systems, governed by linear or non linear systems of equations is presented. The SPA (Stabilization Parallel Algorithm) is based on a systematic parallel decomposition of the problem (related to arbitrarily overlapping decomposition of domains) and on a penalty argument. SPA is presented here for the case of linear parabolic equations: with distrjbuted or boundary control. It extends to practically all linear and non linear evolution equations, as it will be presented in several other publications.

  6. Simultaneous determination of the isomers of Ponceau 4R and Amaranth using an expanded graphite paste electrode.

    Science.gov (United States)

    Zhang, Jing; Wang, Meiling; Shentu, Chao; Wang, Wenchang; Chen, Zhidong

    2014-10-01

    A sensitive and convenient electrochemical method was developed for the simultaneous determination of the isomers of Ponceau 4R and Amaranth by an expanded graphite paste electrode (EGPE). The EGPE was prepared by mixing EG with solid paraffin. Compared with flake graphite paste and carbon paste electrodes, the EGPE showed higher electrocatalytic activity towards the oxidization of Ponceau 4R and Amaranth. Under optimal experimental conditions, the EGPE exhibited wide linear responses to Ponceau 4R and Amaranth ranging from 6×10(-8) to 4×10(-6) mol/L and 8×10(-8) to 4×10(-6)mol/L, respectively, and the detection limits for Ponceau 4R and Amaranth were 2 and 36 nmol/L, respectively, at a signal-to-noise ratio of 3. The EGPE showed good reproducibility, stability and reusability. The proposed method was successfully applied in the detection of Ponceau 4R and Amaranth in grape juice samples.

  7. Stabilizing Movements

    DEFF Research Database (Denmark)

    Norbäck, Maria; Helin, Jenny; Raviola, Elena

    2014-01-01

    of turbulent times. Departing from a process perspective to organizational change and insights from Bakhtin's notion of ‘double-voicing’, which means that people borrow other people's words in their own talk, two main contributions are offered. First, we show how stability cannot be taken for granted...

  8. Before Stabilization

    DEFF Research Database (Denmark)

    Plesner, Ursula; Horst, Maja

    2013-01-01

    to the literature on the relationship between ICTs and organizing, but with a distinct focus on innovation communication and distributed innovation processes taking place before ICTs are stabilized, issues which cannot be captured by studies of diffusion and adaptation of new ICTs within single organizations....

  9. Macroeconomic stability

    DEFF Research Database (Denmark)

    Jespersen, Jesper

    2004-01-01

    It is demonstrated that full employment and sustainable development not necessarily are conflicting goals. On the other hand macroeconomic stability cannot be obtained without a deliberate labour sharing policy and a shift in the composition of private consumption away from traditional material...

  10. FACTORS ON VISCOSITY STABILITY OF MOLD FLUXES

    Institute of Scientific and Technical Information of China (English)

    C.Y.Zhu; C.J.Liu; M.F.Jiang; Z.D.Yang

    2004-01-01

    Viscosity stability indexes of mold flux at high temperature and low temperature have been introduced,and the effects of flux compositions on viscosity stability indexes have been studied.Two mold fluxes have been developed by analyzing the effects of flux viscosity stability on the process and the condition of continuous casting slab of medium carbon steel.The results show that the fluxes are suitable for the process.

  11. Preparation of Expanded Graphite-based Composites 0by One Step Impregnation

    Institute of Scientific and Technical Information of China (English)

    LIU Chengbao; CHEN Zhigang; CHEN Hong; MIAO Zhi; FU Meng

    2011-01-01

    A new method for preparing expanded graphite-based composites (EGCs) was developed. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption. The experimental results indicated that the EGCs was not simply mechanical mixture of EG and activated carbon, instead the activated carbon was coated on the surface of interior and external pores of the EG in the form of thin carbon layer. The thickness of the activated carbon layer was nearly one hundred nanometers by calculation. It was shown that the higher the impregnation ratio and the activation temperature were, the easier the porosity development would be. And the BET surface area and the total pore volume were as high as 1978 m2/g and 0.9917 cm3/g respectively at 350 C with an impregnation ratio of 0.9.

  12. Boiling liquid expanding vapour explosion in CO2 small scale experiments

    OpenAIRE

    Bjerketvedt, Dag; Egeberg, Kjersti; Ke, Wei; Gaathaug, Andre Vagner; Vågsæther, Knut; Nilsen, S. H.

    2011-01-01

    Carbon capture and storage systems require handling large volumes of high pressure CO2. Having thorough knowledge of the related hazards is essential, as is knowing how to prevent, detect, control and mitigate accidents. This paper gives a short description of CO2 Boiling Liquid Expanding Vapour Explosions (BLEVEs) and presents results from preliminary, small scale experiments with CO2 BLEVEs. The mechanism of superheated liquid CO2 boiling is not fully understood. Analogies can be made betwe...

  13. Biodegradation of Trichloroethylene in Continuous-Recycle Expanded-Bed Bioreactors

    OpenAIRE

    Phelps, T. J.; Niedzielski, J. J.; Schram, R M; Herbes, S. E.; White, D. C.

    1990-01-01

    Experimental bioreactors operated as recirculated closed systems were inoculated with bacterial cultures that utilized methane, propane, and tryptone-yeast extract as aerobic carbon and energy sources and degraded trichloroethylene (TCE). Up to 95% removal of TCE was observed after 5 days of incubation. Uninoculated bioreactors inhibited with 0.5% Formalin and 0.2% sodium azide retained greater than 95% of their TCE after 20 days. Each bioreactor consisted of an expanded-bed column through wh...

  14. Expanded mode lasers for telecommunications applications

    Science.gov (United States)

    Lealman, Ian F.

    This thesis describes the development of a long wavelength (1.55 μm) expanded mode semiconductor laser. The increased spot size of the laser improves both the coupling efficiency to cleaved fibre and fibre alignment tolerances and reduces packaging cost. In this type of device the strength of the waveguide is gradually reduced towards the front facet allowing the mode to adiabatically expand so that the laser mode is better matched in size to that of a cleaved fibre. This can be achieved by either reducing the refractive index of the guide or reducing the amount of material in the core. The structure chosen was a buried heterostructure laser that utilised a twin guide consisting of an upper higher refractive index guide (the active region of the laser) above a weak passive guide. The width of the active region was reduced along part of the device allowing the mode to expand into the weak underlying guide. The guide structure was optimised using a variable grid finite difference mode solver, and the taper length calculated by an approximation to Love's method. Detailed results are presented for the measured light-current characteristic, farfield and coupling loss to cleaved fibre. These coupling losses were compared to the calculated data thus allowing the waveguide design to be optimised. Several iterations in the design of the device were undertaken, with the aim of reducing the coupling loss to cleaved single mode fibre without significantly compromising the laser performance. The final device design had extremely low coupling losses as low as 1.2 dB to cleaved fibre. Finally, the positive impact this device had on passive alignment using a silicon motherboard is examined, and the application this technology to a range of other optoelectronic components is discussed.

  15. Michelin Group Accelerating the Steps for Expanding

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    1.Investing USD 750 Million to Build All-steel Giant Tire Plant in USA The French tire manufacturer Michelin Group announced in April 10 that in order to improve the production capacity of giant tires used for engineering equipments, the Group planned to invest USD 750 million to build the second engineering tire plant in Anderson County, South Carolina, USA. The plant would start to be built within a few weeks and was expected to be completed and put into production by the end of 2013. This Group would also expand the engineering tire plant located in Lexington County of this State,

  16. Concurrent Manipulation of Expanded AVL Trees

    Institute of Scientific and Technical Information of China (English)

    章寅; 许卓群

    1998-01-01

    The concurrent manipulation of an expanded AVL tree(EAVL tree)s considered in this paper.The presented system can support any number of concurrent processes which perform searching,insertion and deletion on the tree.Simulation results indicate the high performance of the system.Elaborate techniques are used to achieve such a system unavailable based on any known algorithms.Methods developed in this paper may provide new insights into other problems in the area of concurrent search structure manipulation.

  17. Sinopec Strives to Expand Domestic Market

    Institute of Scientific and Technical Information of China (English)

    Zhang Yan

    2001-01-01

    @@ China Petrochemical Corporation (Sinopec) strives to expand its domestic market share during the Tenth Five-Year Plan period (2001~2005). The assets of Sinopec totaled 536.3 billion yuan at the end of 2000 while the business income reached 375.4billion yuan. Sinopec produced 37.24 million tons of crude oil and 3.916 billion cubic meters of natural gas and processed 105.47million tons of crude and 2.165million tons of ethylene in 2000.

  18. The study of susceptibility to carbon tetrachloride and benzene in offspring of expanded simple tandem repeats mutation mice exposed to formaldehyde%甲醛致扩张性简单串联重复序列突变小鼠子代对四氯化碳和苯暴露易感性研究

    Institute of Scientific and Technical Information of China (English)

    王超; 刘云儒; 周印; 李爱萍; 周建伟

    2011-01-01

    为5.88‰±4.55‰,F10代为8.25‰±2.06‰;C组1000 mg/kg苯染毒组:F5代为7.50‰±6.99‰,F10代为10.67‰±1.16‰;H组500 mg/kg苯染毒组:F5代为7.88‰±3.09‰,F10代为9.20‰±1.30‰;H组1000 mg/kg苯染毒组:F5代为9.63‰±4.34‰,F10代为13.33‰±2.08‰)随苯剂量的增加而增加,与溶剂对照组(C组F5代为1.13‰±0.35‰,F10代为1.20‰±0.82‰;H组F5代为1.25‰±0.46‰,F10代为1.33‰±1.03‰)的差异均有统计学意义(P<0.05,P<0.01).结论 甲醛暴露引起的基因组ESTR突变可改变子代小鼠对CCl4和苯的易感性.ESTR突变可能是影响机体对化学物易感性的生物学标志,其分子机制有待进一步阐明.%Objective To investigate the susceptibility to carbon tetrachloride and benzene in offspring of expanded simple tandem repeats (ESTR) mutation mice exposed to formaldehyde (FA). Methods F5 and F10 offspring (200 mg/m3 ×2 hours) served as H group and ICR mice were used as control group(group C). The F5 and F10 offspring were exposed to 10 ml/kg carbon tetrachloride at the doses of 0.05%, 0.50% or 5.00% for 24 hours, respectively or 500 or 1000 mg/kg benzene for 24 hours, respectively by intraperitoneal injection. Serum alanine transaminase (ALT), aspartate transaminase (AST) and the hepatic superoxide dismutase (SOD) or malondialdehyde (MDA) were detected; also the hepatic pathological changes were observed under light microscope; the micronucleus in sternum bone marrow cells as the biomarker of benzene blood toxicity were measured. Results ALT and AST activities in group C of F5 mice exposed to 0.50% and 5.00% CCl4, ALT in groups C and H of F10 mice exposed to 0.05%, 0.50%, 5.00% CCl4, AST in groups C and H of F10 mice exposed to 0.50% and 5.00% CCl4 were significantly higher than those in controls, respectively (P<0.05); as compared to the control, hepatic SOD activities in group C of F5 and F10 mice exposed to 0.50% and 5.00% CCl4, in group H of F5 mice exposed to 0.50% and 5.00% CCl4, and

  19. "Phase freezeout" in isentropically expanding matter

    CERN Document Server

    Iosilevskiy, Igor

    2014-01-01

    Features of isentropic expansion of warm dense matter (WDM) created by intense energy fluxes (strong shock compression or instant isochoric heating by laser or heavy ions) are under discussion in situation when ($i$) -- thermodynamic trajectory of such expansion crosses binodal of liquid-gas phase transition, and ($ii$) -- expansion within the two-phase region is going along equilibrium branch (not metastable one) of the two-phase mixture isentrope. It is known in the plane case that because of break in the expansion isentrope at binodal point (in $P-V$ plane) i.e. jump of sound velocity in this point, there appears extended zone ("boiling layer") of uniformity in expanding material with constant thermodynamic and kinematic parameters. It corresponds just to the state on this binodal of boiling liquid. The point is that because of self-similarity of such expansion (in plane case) this boiling layer contains finite and fixed part of whole expanding material. This property makes it possible (at least formally) ...

  20. Unintended Consequences of Expanding the Genetic Alphabet.

    Science.gov (United States)

    Pollum, Marvin; Ashwood, Brennan; Jockusch, Steffen; Lam, Minh; Crespo-Hernández, Carlos E

    2016-09-14

    The base pair d5SICS·dNaM was recently reported to incorporate and replicate in the DNA of a modified strain of Escherichia coli, thus making the world's first stable semisynthetic organism. This newly expanded genetic alphabet may allow organisms to store considerably more information in order to translate proteins with unprecedented enzymatic activities. Importantly, however, there is currently no knowledge of the photochemical properties of d5SICS or dNaM-properties that are central to the chemical integrity of cellular DNA. In this contribution, it is shown that excitation of d5SICS or dNaM with near-visible light leads to efficient trapping of population in the nucleoside's excited triplet state in high yield. Photoactivation of these long-lived, reactive states is shown to photosensitize cells, leading to the generation of reactive oxygen species and to a marked decrease in cell proliferation, thus warning scientists of the potential phototoxic side effects of expanding the genetic alphabet. PMID:27564795

  1. Historical Notes on the Expanding Universe

    Science.gov (United States)

    Way, Michael J.; Belenkyi, Ari; Nussbaumer, Harry; Peacock, John

    2014-01-01

    The article Measuring the Hubble constant by Mario Livio and Adam Riess (Physics Today, October 2013, page 41) reviewed studies of the expanding universe from the 1920s to the present. Although the history of the subject underwent considerable compression to fit the length of a magazine article, we think it may leave a misleading impression of some of the key steps to our current understanding. We therefore offer the following clarifications. Most significantly, papers by Arthur Eddington and by Willem de Sitter in 1930, who successfully promoted Georges Lematres 1927 article for the Scientific Society of Brussels, effected a paradigm shift in interpretation of extragalactic redshifts in 1930. Before then, the astronomical community was generally unaware of the existence of nonstatic cosmological solutions and did not broadly appreciate that redshifts could be thought of locally as Doppler shifts in an expanding matter distribution. Certainly, in 1929 Edwin Hubble referred only to the de Sitter solution of 1917. At the time, the relation between distance and redshift predicted in that model was generally seen purely as a manifestation of static spacetime curvature.

  2. Vibrational stability of graphene

    Directory of Open Access Journals (Sweden)

    Yangfan Hu

    2013-05-01

    Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.

  3. The Role of Genetic Polymorphisms as Related to One-Carbon Metabolism, Vitamin B6, and Gene–Nutrient Interactions in Maintaining Genomic Stability and Cell Viability in Chinese Breast Cancer Patients

    Directory of Open Access Journals (Sweden)

    Xiayu Wu

    2016-06-01

    Full Text Available Folate-mediated one-carbon metabolism (FMOCM is linked to DNA synthesis, methylation, and cell proliferation. Vitamin B6 (B6 is a cofactor, and genetic polymorphisms of related key enzymes, such as serine hydroxymethyltransferase (SHMT, methionine synthase reductase (MTRR, and methionine synthase (MS, in FMOCM may govern the bioavailability of metabolites and play important roles in the maintenance of genomic stability and cell viability (GSACV. To evaluate the influences of B6, genetic polymorphisms of these enzymes, and gene–nutrient interactions on GSACV, we utilized the cytokinesis-block micronucleus assay (CBMN and PCR-restriction fragment length polymorphism (PCR-RFLP techniques in the lymphocytes from female breast cancer cases and controls. GSACV showed a significantly positive correlation with B6 concentration, and 48 nmol/L of B6 was the most suitable concentration for maintaining GSACV in vitro. The GSACV indexes showed significantly different sensitivity to B6 deficiency between cases and controls; the B6 effect on the GSACV variance contribution of each index was significantly higher than that of genetic polymorphisms and the sample state (tumor state. SHMT C1420T mutations may reduce breast cancer susceptibility, whereas MTRR A66G and MS A2756G mutations may increase breast cancer susceptibility. The role of SHMT, MS, and MTRR genotype polymorphisms in GSACV is reduced compared with that of B6. The results appear to suggest that the long-term lack of B6 under these conditions may increase genetic damage and cell injury and that individuals with various genotypes have different sensitivities to B6 deficiency. FMOCM metabolic enzyme gene polymorphism may be related to breast cancer susceptibility to a certain extent due to the effect of other factors such as stress, hormones, cancer therapies, psychological conditions, and diet. Adequate B6 intake may be good for maintaining genome health and preventing breast cancer.

  4. The Role of Genetic Polymorphisms as Related to One-Carbon Metabolism, Vitamin B6, and Gene-Nutrient Interactions in Maintaining Genomic Stability and Cell Viability in Chinese Breast Cancer Patients.

    Science.gov (United States)

    Wu, Xiayu; Xu, Weijiang; Zhou, Tao; Cao, Neng; Ni, Juan; Zou, Tianning; Liang, Ziqing; Wang, Xu; Fenech, Michael

    2016-01-01

    Folate-mediated one-carbon metabolism (FMOCM) is linked to DNA synthesis, methylation, and cell proliferation. Vitamin B6 (B6) is a cofactor, and genetic polymorphisms of related key enzymes, such as serine hydroxymethyltransferase (SHMT), methionine synthase reductase (MTRR), and methionine synthase (MS), in FMOCM may govern the bioavailability of metabolites and play important roles in the maintenance of genomic stability and cell viability (GSACV). To evaluate the influences of B6, genetic polymorphisms of these enzymes, and gene-nutrient interactions on GSACV, we utilized the cytokinesis-block micronucleus assay (CBMN) and PCR-restriction fragment length polymorphism (PCR-RFLP) techniques in the lymphocytes from female breast cancer cases and controls. GSACV showed a significantly positive correlation with B6 concentration, and 48 nmol/L of B6 was the most suitable concentration for maintaining GSACV in vitro. The GSACV indexes showed significantly different sensitivity to B6 deficiency between cases and controls; the B6 effect on the GSACV variance contribution of each index was significantly higher than that of genetic polymorphisms and the sample state (tumor state). SHMT C1420T mutations may reduce breast cancer susceptibility, whereas MTRR A66G and MS A2756G mutations may increase breast cancer susceptibility. The role of SHMT, MS, and MTRR genotype polymorphisms in GSACV is reduced compared with that of B6. The results appear to suggest that the long-term lack of B6 under these conditions may increase genetic damage and cell injury and that individuals with various genotypes have different sensitivities to B6 deficiency. FMOCM metabolic enzyme gene polymorphism may be related to breast cancer susceptibility to a certain extent due to the effect of other factors such as stress, hormones, cancer therapies, psychological conditions, and diet. Adequate B6 intake may be good for maintaining genome health and preventing breast cancer. PMID:27347936

  5. The Role of Genetic Polymorphisms as Related to One-Carbon Metabolism, Vitamin B6, and Gene–Nutrient Interactions in Maintaining Genomic Stability and Cell Viability in Chinese Breast Cancer Patients

    Science.gov (United States)

    Wu, Xiayu; Xu, Weijiang; Zhou, Tao; Cao, Neng; Ni, Juan; Zou, Tianning; Liang, Ziqing; Wang, Xu; Fenech, Michael

    2016-01-01

    Folate-mediated one-carbon metabolism (FMOCM) is linked to DNA synthesis, methylation, and cell proliferation. Vitamin B6 (B6) is a cofactor, and genetic polymorphisms of related key enzymes, such as serine hydroxymethyltransferase (SHMT), methionine synthase reductase (MTRR), and methionine synthase (MS), in FMOCM may govern the bioavailability of metabolites and play important roles in the maintenance of genomic stability and cell viability (GSACV). To evaluate the influences of B6, genetic polymorphisms of these enzymes, and gene–nutrient interactions on GSACV, we utilized the cytokinesis-block micronucleus assay (CBMN) and PCR-restriction fragment length polymorphism (PCR-RFLP) techniques in the lymphocytes from female breast cancer cases and controls. GSACV showed a significantly positive correlation with B6 concentration, and 48 nmol/L of B6 was the most suitable concentration for maintaining GSACV in vitro. The GSACV indexes showed significantly different sensitivity to B6 deficiency between cases and controls; the B6 effect on the GSACV variance contribution of each index was significantly higher than that of genetic polymorphisms and the sample state (tumor state). SHMT C1420T mutations may reduce breast cancer susceptibility, whereas MTRR A66G and MS A2756G mutations may increase breast cancer susceptibility. The role of SHMT, MS, and MTRR genotype polymorphisms in GSACV is reduced compared with that of B6. The results appear to suggest that the long-term lack of B6 under these conditions may increase genetic damage and cell injury and that individuals with various genotypes have different sensitivities to B6 deficiency. FMOCM metabolic enzyme gene polymorphism may be related to breast cancer susceptibility to a certain extent due to the effect of other factors such as stress, hormones, cancer therapies, psychological conditions, and diet. Adequate B6 intake may be good for maintaining genome health and preventing breast cancer. PMID:27347936

  6. Architectural Characteristics and Distribution of Hydromechanical Properties within a Small Strike-Slip Fault Zone in a Carbonates Reservoir: Impact on fault stability, induced seismicity, and leakage during CO2 injection

    Science.gov (United States)

    Jeanne, P.; Cappa, F.; Guglielmi, Y.; Rinaldi, A. P.

    2014-12-01

    Within the LSBB National Underground Research Laboratory (France), we performed an in situ multidisciplinary and multi-scale analysis of a small fault zone intersecting a layered carbonates reservoir. The study area is located in a gallery at 250 m depth in the unsaturated and unaltered zone of the reservoir. In order to study the distribution of the fault zone properties, we took advantage of the gallery wall and of three vertical 20 m long boreholes located near the fault core, in the damage zone, and in the host rock. Geological, petrophysical (porosity observations and measurements), geotechnical (Q-value) and geophysical measurements (acoustic velocities, uniaxial compressive strength, electrical resistivity, borehole logging), and injection tests were conducted at various scales. We show that horizontal and vertical variations in hydromechanical properties within the damage zone are related to the initial petrophysical properties of the host rock. In the initial low-porosity and fractured layers, the deformations are accommodated by fractures and micro-cracks extending significantly from the fault core. In these layers, the Young modulus of the rock mass (Em) is low and the permeability of the rock mass (Km) is high. In the initial porous and low fractured layers, deformations are accommodated by micro-mechanical processes resulting in a decrease in micro-porosity near the fault core. There is a rapid attenuation of the damage zone. In these layers, Em is high and Km is low. The seismic signature of this kind of fault is complex and the seismic visibility low making them hard to detect. Finally, to assess fault zone stability in case of CO2 injection and the risk of CO2 leakage through the fault itself, we performed some geomechanical numerical simulations and some field hydromechanical tests. We show that the presence of hydromechanical heterogeneity favors the fluid accumulation but strengthen the fault zone and impede fluid migration upward along the fault.

  7. An Expanding Locally Anisotropic (ELA) Metric Describing Matter in an Expanding Universe

    OpenAIRE

    Ferreira, P. Castelo

    2010-01-01

    It is suggested an expanding locally anisotropic metric (ELA) ansatz describing matter in a flat expanding universe which interpolates between the Schwarzschild (SC) metric near point-like central bodies of mass 'M' and the Robertson-Walker (RW) metric for large radial coordinate: 'ds^2=Z(cdt)2 - 1/Z (dr1-(Hr1/c) Z^(alpha/2+1/2)(cdt))^2-r1^2 dOmega', where 'Z=1-U' with 'U=2GM/(c^2r1)', 'G' is the Newton constant, 'c' is the speed of light, 'H=H(t)=\\dot(a)/a' is the time-dependent Hubble rate,...

  8. Nanotube Production Devices Expand Research Capabilities

    Science.gov (United States)

    2012-01-01

    In order for the Hubble Space Telescope to take incredible, never-seen-before shots of celestial bodies and then send them back to Earth, the spacecraft needs power. While in orbit, Hubble cannot plug into an electrical outlet or stop at a store for some batteries. One of the ways NASA supplies power aboard a spacecraft is by harnessing energy from the most powerful entity in the solar system: the Sun. Since the 1960s, photovoltaic technology, or technology that converts sunlight into electricity, has been instrumental in the exploration of space. To build upon existing photovoltaic technology, NASA s Glenn Research Center has worked on a variety of innovative designs and materials to incorporate into photovoltaic cells, the building blocks of solar power systems. One of these materials is the carbon nanotube - a tiny structure about 50,000 times finer than the average human hair, with notably high electrical and thermal conductivity and an extreme amount of mechanical strength. Such properties give carbon nanotubes great potential to enhance the reliability of power generation and storage devices in space and on Earth. Dennis J. Flood, the branch chief of the photovoltaic division at Glenn in the 1990s, was looking into using carbon nanotubes to improve the efficiency of solar cells when he ran into a major roadblock - high-quality carbon nanotubes were not readily available. To address this problem, one of the chemists in Flood s group came up with a process and system for growing them. A senior chemist at Glenn, Aloysius F. Hepp, devised an injection chemical vapor deposition process using a specific organometallic catalyst in a two-zone furnace. Hepp's group found the unique process produced high-quality carbon nanotubes with less than 5 percent metal impurity. In addition, the process was more efficient than existing techniques, as it eliminated pre-patterning of the substrate used for growing the nanotubes, a timely and cost-prohibitive step.

  9. Optical cavity resonator in an expanding universe

    Science.gov (United States)

    Kopeikin, Sergei M.

    2015-02-01

    We study the cosmological evolution of frequency of a standing electromagnetic wave in a resonant optical cavity placed to the expanding manifold described by the Robertson-Walker metric. Because of the Einstein principle of equivalence (EEP), one can find a local coordinate system (a local freely falling frame), in which spacetime is locally Minkowskian. However, due to the conformal nature of the Robertson-Walker metric the conventional transformation to the local inertial coordinates introduces ambiguity in the physical interpretation of the local time coordinate, . Therefore, contrary to a common-sense expectation, a straightforward implementation of EEP alone does not allow us to unambiguously decide whether atomic clocks based on quantum transitions of atoms, ticks at the same rate as the clocks based on electromagnetic modes of a cavity. To resolve this ambiguity we have to analyse the cavity rigidity and the oscillation of its electromagnetic modes in an expanding universe by employing the full machinery of the Maxwell equations irrespectively of the underlying theory of gravity. We proceed in this way and found out that the size of the cavity and the electromagnetic frequency experience an adiabatic drift in conformal (unphysical) coordinates as the universe expands in accordance with the Hubble law. We set up the oscillation equation for the resonant electromagnetic modes, solve it by the WKB approximation, and reduce the coordinate-dependent quantities to their counterparts measured by a local observer who counts time with atomic clock. The solution shows that there is a perfect mutual cancellation of the adiabatic drift of cavity's frequency by space transformation to local coordinates and the time counted by the clocks based on electromagnetic modes of cavity has the same rate as that of atomic clocks. We conclude that if general relativity is correct and the local expansion of space is isotropic there should be no cosmological drift of frequency of a

  10. Recuperative supercritical carbon dioxide cycle

    Energy Technology Data Exchange (ETDEWEB)

    Sonwane, Chandrashekhar; Sprouse, Kenneth M; Subbaraman, Ganesan; O' Connor, George M; Johnson, Gregory A

    2014-11-18

    A power plant includes a closed loop, supercritical carbon dioxide system (CLS-CO.sub.2 system). The CLS-CO.sub.2 system includes a turbine-generator and a high temperature recuperator (HTR) that is arranged to receive expanded carbon dioxide from the turbine-generator. The HTR includes a plurality of heat exchangers that define respective heat exchange areas. At least two of the heat exchangers have different heat exchange areas.

  11. First order phase transition of expanding matter and its fragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Chikazumi, Shinpei [Tsukuba Univ., Institute of Physics, Tsukuba, Ibaraki (Japan); Iwamoto, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2002-09-01

    Using an expanding matter model with a Lennard-Jones potential, the instability of the expanding system is investigated. The pressure, the temperature, and the density fluctuations are calculated as functions of density during the time evolution of the expanding matter, which are compared to the coexistence curve calculated by the Gibbs ensemble. The expanding matter undergoes the first order phase transition in the limit of the quasistatic expansion. The resultant fragment mass distributions are also investigated. (author)

  12. Celestial Ephemerides in an Expanding Universe

    CERN Document Server

    Kopeikin, Sergei

    2012-01-01

    Post-Newtonian theory was instrumental in conducting the critical experimental tests of general relativity and in building the astronomical ephemerides of celestial bodies in the solar system with an unparalleled precision. The cornerstone of the theory is the postulate that the solar system is gravitationally isolated from the rest of the universe and the background spacetime is asymptotically flat. The present article extends this theoretical concept and formulates the principles of celestial dynamics of particles and light moving in gravitational field of a localized astronomical system embedded to the expanding Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. We formulate the precise mathematical concept of the Newtonian limit of Einstein's field equations in the conformally-flat FLRW spacetime and analyze the geodesic motion of massive particles and light in this limit. We prove that by doing conformal spacetime transformations, one can reduce the equations of motion of particles and light to the cla...

  13. Homogeneous cosmology with aggressively expanding civilizations

    CERN Document Server

    Olson, S Jay

    2014-01-01

    In the context of a homogeneous universe, we note that the appearance of aggressively expanding advanced life is geometrically similar to the process of nucleation and bubble growth in a first-order cosmological phase transition. We exploit this similarity to describe the dynamics of life saturating the universe on a cosmic scale, adapting the phase transition model to incorporate probability distributions of expansion and resource consumption strategies. Through a series of numerical solutions covering several orders of magnitude in the input assumption parameters, the resulting cosmological model is used to address basic questions related to the intergalactic spreading of life, dealing with issues such as timescales, observability, competition between strategies, and first-mover advantage. Finally, we examine physical effects on the universe itself, such as reheating and the backreaction on the evolution of the scale factor, if such life is able to control and convert a significant fraction of the available...

  14. Expanding forensic science through forensic intelligence.

    Science.gov (United States)

    Ribaux, Olivier; Talbot Wright, Benjamin

    2014-12-01

    Research and Development ('R&D') in forensic science currently focuses on innovative technologies improving the efficiency of existing forensic processes, from the detection of marks and traces at the scene, to their presentation in Court. R&D approached from this perspective provides no response to doubts raised by recent criminological studies, which question the effective contribution of forensic science to crime reduction, and to policing in general. Traces (i.e. forensic case data), as remnants of criminal activity are collected and used in various forms of crime monitoring and investigation. The aforementioned doubts therefore need to be addressed by expressing how information is conveyed by traces in these processes. Modelling from this standpoint expands the scope of forensic science and provides new R&D opportunities. Twelve propositions for R&D are stated in order to pave the way.

  15. Helical chirality induction of expanded porphyrin analogues

    Indian Academy of Sciences (India)

    Jun-Ichiro Setsune

    2012-11-01

    Expanded porphyrin analogues with unique figure-eight conformation were prepared by way of useful pyrrole intermediates such as bis(azafulvene)s and 2-borylpyrrole. Supramolecular chirogenesis of cyclooctapyrrole O1 with 32-cycloconjugation was successfully applied to determine absolute configuration of chiral carboxylic acids. Dinuclear CuII complex of cyclooctapyrrole O2 with interrupted -conjugation was resolved by HPLC into enantiomers and their helical handedness was determined by theoretical simulation of their CD spectral pattern. Enantioselective induction of helicity in the metal helicate formation in the presence of a chiral promoter was demonstrated by using ()-(+)-1-(1-phenyl)ethylamine that favoured , helicity. Dinuclear CoII complexes of cyclotetrapyrroletetrapyridine O3 were found to be substitution labile and pick up amino acid anions in water. Those amino acid complexes of O3Co2 were rendered to adopt a particular unidirectional helical conformation preferentially depending on the ligated amino acid anion.

  16. Henry Norris Russell and the Expanding Universe

    Science.gov (United States)

    DeVorkin, D.

    2013-04-01

    Henry Norris Russell, one of the most influential American astronomers of the first half of the 20th Century, had a special place in his heart for the Lowell Observatory. Although privately critical of the founder for his pronouncements about life on Mars and the superiority of the Mars Hill observing site, he always supported the Observatory in public and professional circles. He staunchly supported Tombaugh's detection of a planet as leading from Lowell's prediction, and always promoted V. M. Slipher's spectroscopic investigations of planetary and stellar phenomena. But how did he react to Slipher's puzzling detection of the extreme radial velocities of spiral nebulae starting in 1912, and how did he regard the extension and interpretation of those observations by Hubble and others in following decades? Here we describe the arc of Russell's reactions, dating from Slipher's first detection, as an indicator of how mainstream stellar astronomers reacted to the concept of an expanding universe.

  17. Henry Norris Russell and the Expanding Universe

    CERN Document Server

    DeVorkin, David H

    2013-01-01

    Henry Norris Russell, one of the most influential American astronomers of the first half of the 20th Century, had a special place in his heart for the Lowell Observatory. Although privately critical of the founder for his pronouncements about life on Mars and the superiority of the Mars Hill observing site, he always supported the Observatory in public and professional circles. He staunchly supported Tombaugh's detection of a planet as leading from Lowell's prediction, and always promoted V. M. Slipher's spectroscopic investigations of planetary and stellar phenomena. But how did he react to Slipher's puzzling detection of the extreme radial velocities of spiral nebulae starting in 1912, and how did he regard the extension and interpretation of those observations by Hubble and others in following decades? Here we describe the arc of Russell's reactions, dating from Slipher's first detection, as an indicator of how mainstream stellar astronomers reacted to the concept of an expanding universe.

  18. Rubella Seroprevalence Before Expanded Vaccination Program

    Directory of Open Access Journals (Sweden)

    Kenan Sener

    2007-10-01

    Full Text Available Altough rubella is usually a mild childhood disease, but when it occurs early in pregnancy are severe. In this study, seroprevalence of rubella antibodies have been invastegated in various age groups especially chilbearing age’s women before Expanded Vaccination Programme. IgM and IgG antibodies against rubella were tested by ELISA kits. Seropositivity of rubella IgG was 89,5% in chlidbearing age’s women. In Turkey, the vaccine has been on the market since 1989 but rubella vaccination is currently included in the national immunization programme. Hence, our results are important for comparison of the seroprevalence rates after national vaccination program. [TAF Prev Med Bull 2007; 6(5.000: 371-374

  19. Rubella Seroprevalence Before Expanded Vaccination Program

    Directory of Open Access Journals (Sweden)

    Kenan Sener

    2007-10-01

    Full Text Available Altough rubella is usually a mild childhood disease, but when it occurs early in pregnancy are severe. In this study, seroprevalence of rubella antibodies have been invastegated in various age groups especially chilbearing age’s women before Expanded Vaccination Programme. IgM and IgG antibodies against rubella were tested by ELISA kits. Seropositivity of rubella IgG was 89,5% in chlidbearing age’s women. In Turkey, the vaccine has been on the market since 1989 but rubella vaccination is currently included in the national immunization programme. Hence, our results are important for comparison of the seroprevalence rates after national vaccination program. [TAF Prev Med Bull. 2007; 6(5: 371-374

  20. Particles formation in an expanding plasma

    Energy Technology Data Exchange (ETDEWEB)

    Lescoute, E.; Hallo, L.; Chimier, B.; Tikhonchuk, V.T.; Stenz, C. [Bordeaux-1 Univ., CELIA, CNRS-CEA, 33 - Talence (France); Hebert, D.; Chevalier, J.M.; Rullier, J.L.; Palmier, S. [CEA Centre d' Etudes Scientifiques et Techniques d' Aquitaine, 33 - Le Barp (France)

    2009-08-15

    Interaction of a laser beam with a target generates a high velocity expanding plasma plume, solid debris and liquid nano- and micro-particles. They are produced from plasma recombination and vapor condensation and can be deposited on optical elements located nearby the target. Two distinct kinds of particles were observed depending on the temperature achieved in the plasma plume: large micrometer-size fragments for temperatures lower than the critical temperature, and very small nanometer-size particles for higher temperatures. The paper presents experimental observations of fragments and nano-particles in plasma plumes and a comparison with models. A good agreement has been found for nano-particle sizes and distributions. This simple modeling can also be used for nuclei production in the nanosecond time scale. Our estimates show that particle size can be correlated to laser wavelength and fluences.