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Sample records for boron carbon nitrogen

  1. Prediction of boron carbon nitrogen phase diagram

    Science.gov (United States)

    Yao, Sanxi; Zhang, Hantao; Widom, Michael

    We studied the phase diagram of boron, carbon and nitrogen, including the boron-carbon and boron-nitrogen binaries and the boron-carbon-nitrogen ternary. Based on the idea of electron counting and using a technique of mixing similar primitive cells, we constructed many ''electron precise'' structures. First principles calculation is performed on these structures, with either zero or high pressures. For the BN binary, our calculation confirms that a rhmobohedral phase can be stablized at high pressure, consistent with some experimental results. For the BCN ternary, a new ground state structure is discovered and an Ising-like phase transition is suggested. Moreover, we modeled BCN ternary phase diagram and show continuous solubility from boron carbide to the boron subnitride phase.

  2. Efficient Boron-Carbon-Nitrogen Nanotube Formation Via Combined Laser-Gas Flow Levitation

    Science.gov (United States)

    Whitney, R. Roy (Inventor); Jordan, Kevin (Inventor); Smith, Michael W. (Inventor)

    2015-01-01

    A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula BxCyNz. The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula BxCyNz.

  3. Predicted phase diagram of boron-carbon-nitrogen

    Science.gov (United States)

    Zhang, Hantao; Yao, Sanxi; Widom, Michael

    2016-04-01

    Noting the structural relationships between phases of carbon and boron carbide with phases of boron nitride and boron subnitride, we investigate their mutual solubilities using a combination of first-principles total energies supplemented with statistical mechanics to address finite temperatures. Thus we predict the solid-state phase diagram of boron-carbon-nitrogen (B-C-N). Owing to the large energy costs of substitution, we find that the mutual solubilities of the ultrahard materials diamond and cubic boron nitride are negligible, and the same for the quasi-two-dimensional materials graphite and hexagonal boron nitride. In contrast, we find a continuous range of solubility connecting boron carbide to boron subnitride at elevated temperatures. An electron-precise ternary compound B13CN consisting of B12 icosahedra with NBC chains is found to be stable at all temperatures up to melting. It exhibits an order-disorder transition in the orientation of NBC chains at approximately T =500 K. We also propose that the recently discovered binary B13N2 actually has composition B12.67N2 .

  4. Boron nitride converted carbon fiber

    Science.gov (United States)

    Rousseas, Michael; Mickelson, William; Zettl, Alexander K.

    2016-04-05

    This disclosure provides systems, methods, and apparatus related to boron nitride converted carbon fiber. In one aspect, a method may include the operations of providing boron oxide and carbon fiber, heating the boron oxide to melt the boron oxide and heating the carbon fiber, mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide, and converting at least a portion of the carbon fiber to boron nitride.

  5. Rectifying Properties of a Nitrogen/Boron-Doped Capped-Carbon-Nanotube-Based Molecular Junction

    Institute of Scientific and Technical Information of China (English)

    ZHAO Peng; LIU De-Sheng; ZHANG Ying; WANG Pei-Ji; ZHANG Zhong

    2011-01-01

    @@ Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbonnanotube-based molecular junction.Obvious rectifying behavior is observed and it is strongly dependent on the doping site.The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer.Moreover, the rectifying performance can be further improved by adjusting the distance between the Cso nanotube caps.%Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbon-nanotube-based molecular junction. Obvious rectifying behavior is observed and it is strongly dependent on the doping site. The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer. Moreover, the rectifying performance can be further improved by adjusting the distance between the C60 nanotube caps.

  6. First-principles study of palladium atom adsorption on the boron- or nitrogen-doped carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Chen Guoxiang [College of Physics and Information Technology, Shaanxi Normal University, Xi' an 710062, Shaanxi (China); School of Science, Xi' an Shiyou University, Xi' an 710065, Shaanxi (China); Zhang Jianmin, E-mail: jianm_zhang@yahoo.co [College of Physics and Information Technology, Shaanxi Normal University, Xi' an 710062, Shaanxi (China); Wang Doudou [Institute of Telecommunication Engineering of the Air Force Engineering University (AFEU1), Xi' an 710077, Shaanxi (China); Xu Kewei [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049, Shaanxi (China)

    2009-11-15

    We have performed first-principles calculation to investigate the adsorption of a single palladium atom on the surface of the pristine and boron- or nitrogen-doped carbon nanotubes (CNTs). The results show that for the adsorption of a single palladium atom on the pristine CNT surface, the most stable site is Bridge1 site above the axial carbon-carbon bond. Either boron- or nitrogen-doped CNTs can assist palladium surface adsorption, but the detailed mechanisms are different. The enhanced palladium adsorption on boron-doped CNT is attributed to the palladium d orbital strongly hybridized with both boron p orbital and carbon p orbital. The enhancement in palladium adsorption on nitrogen-doped CNT results from activating the nitrogen-neighboring carbon atoms due to the large electron affinity of nitrogen. Furthermore, the axial bond is preferred over the zigzag bond for a palladium atom adsorbed on the surface of all three types of CNTs. The most energetically favorable site for a palladium atom adsorbed on three types of CNTs is above the axial boron-carbon bond in boron-doped CNT. The enhancement in palladium adsorption is more significant for the boron-doped CNT than it is for nitrogen-doped CNT with a similar configuration. So we conclude that accordingly, the preferred adsorption site is determined by the competition between the electron affinity of doped and adsorbed atoms and preferred degree of the axial bond over the zigzag bond.

  7. Synthesis of boron/nitrogen substituted carbons for aqueous asymmetric capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Tomko, Timothy [Energy and Mineral Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Rajagopalan, Ramakrishnan, E-mail: rur12@psu.edu [Materials Research Institute, Pennsylvania State University, 270 MRL Bldg., University Park, PA 16802 (United States); Aksoy, Parvana [Energy Institute, Pennsylvania State University, University Park, PA 16802 (United States); Foley, Henry C. [Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2011-06-01

    Highlights: > Synthesis of highly substituted boron and nitrogen containing carbons (BCN) for ultracapacitor applications. > Evidence for strong electroadsorption of protons on BCN. > Increased specific capacitance per unit area and improved cell voltage in aqueous asymmetric capacitors. - Abstract: Boron/nitrogen substituted carbons were synthesized by co-pyrolysis of polyborazylene/coal tar pitch blends to yield a carbon with a boron and nitrogen content of 14 at% and 10 at%, respectively. The presence of heteroatoms in these carbons shifted the hydrogen evolution overpotential to -1.4 V vs Ag/AgCl in aqueous electrolytes, providing a large electrochemical potential window ({approx}2.4 V) as well as a specific capacitance of 0.6 F/m{sup 2}. An asymmetric capacitor was fabricated using the as-prepared low surface area carbon as the negative electrode along with a redox active manganese dioxide as the positive electrode. The energy density of the capacitor exceeded 10 Wh/kg at a power density of 1 kW/kg and had a cycle life greater than 1000 cycles.

  8. Isotope shifts in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations

    Energy Technology Data Exchange (ETDEWEB)

    Nazé, C.; Verdebout, S. [Service de Chimie Quantique et Photophysique, CP160/09, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, B 1050 Brussels (Belgium); Rynkun, P.; Gaigalas, G. [Vilnius University, Institute of Theoretical Physics and Astronomy, LT-01108 Vilnius (Lithuania); Godefroid, M., E-mail: mrgodef@ulb.ac.be [Service de Chimie Quantique et Photophysique, CP160/09, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, B 1050 Brussels (Belgium); Jönsson, P. [Group for Materials Science and Applied Mathematics, Malmö University, 205-06 Malmö (Sweden)

    2014-09-15

    Energy levels, normal and specific mass shift parameters as well as electronic densities at the nucleus are reported for numerous states along the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Combined with nuclear data, these electronic parameters can be used to determine values of level and transition isotope shifts. The calculation of the electronic parameters is done using first-order perturbation theory with relativistic configuration interaction wavefunctions that account for valence, core–valence, and core–core correlation effects as zero-order functions. Results are compared with experimental and other theoretical values, when available.

  9. Boron/nitrogen co-doped helically unzipped multiwalled carbon nanotubes as efficient electrocatalyst for oxygen reduction.

    Science.gov (United States)

    Zehtab Yazdi, Alireza; Fei, Huilong; Ye, Ruquan; Wang, Gunuk; Tour, James; Sundararaj, Uttandaraman

    2015-04-15

    Bamboo structured nitrogen doped multiwalled carbon nanotubes have been helically unzipped, and nitrogen doped graphene oxide nanoribbons (CNx-GONRs) with a multifaceted microstructure have been obtained. CNx-GONRs have then been codoped with nitrogen and boron by simultaneous thermal annealing in ammonia and boron oxide atmospheres, respectively. The effects of the codoping time and temperature on the concentration of the dopants and their functional groups have been extensively investigated. X-ray photoelectron spectroscopy results indicate that pyridinic and BC3 are the main nitrogen and boron functional groups, respectively, in the codoped samples. The oxygen reduction reaction (ORR) properties of the samples have been measured in an alkaline electrolyte and compared with the state-of-the-art Pt/C (20%) electrocatalyst. The results show that the nitrogen/boron codoped graphene nanoribbons with helically unzipped structures (CNx/CBx-GNRs) can compete with the Pt/C (20%) electrocatalyst in all of the key ORR properties: onset potential, exchange current density, four electron pathway selectivity, kinetic current density, and stability. The development of such graphene nanoribbon-based electrocatalyst could be a harbinger of precious metal-free carbon-based nanomaterials for ORR applications.

  10. Space-Confined Synthesis of Three-Dimensional Boron/Nitrogen-Doped Carbon Nanotubes/Carbon Nanosheets Line-in-Wall Hybrids and Their Electrochemical Energy Storage Applications

    DEFF Research Database (Denmark)

    Zhu, Shan; Li, Jiajun; Li, Qingfeng;

    2016-01-01

    This research demonstrates a flexible one-pot strategy for fabricating three-dimensional (3D) boron/nitrogen-doped networks of carbon nanotubes(CNTs)/carbon nanosheets "Line-in-Wall" hybrids (LIWNB) based on the space-confined template method. In the synthesis, the high rate of freezing step...... and freeze-dried process enable the CNTs and carbon-heteroatoms sources confined in the limited space of the self-assembled NaCl salts, which are then heat-treated to obtain a B/N-doped network constructed by "Line-in-Wall" type of carbon hybrids. By combining the 3D B/N-doped carbon nanosheets network...... and CNTs in this unique pattern, the LIW-NB integrates advantages of three aspects: first, the doped heteroatoms enhancing electrochemical properties of carbon matrix; second, the warp-proof nanosheets supplying high specific surface area; and the extracted and embedded CNTs serving as electron conductive...

  11. Blending materials composed of boron, nitrogen and carbon to transform approaches to liquid hydrogen stores

    Energy Technology Data Exchange (ETDEWEB)

    Whittemore, Sean M.; Bowden, Mark; Karkamkar, Abhijeet; Parab, Kshitij; Neiner, Doinita; Autrey, Tom; Ishibashi, Jacob S. A.; Chen, Gang; Liu, Shih-Yuan; Dixon, David A.

    2015-12-02

    Energy storage remains a key challenge for the advancement of fuel cell applications. Because of this, hydrogen has garnered much research attention for its potential as an energy carrier. This can be attributed to its abundance from non-petroleum sources, and its energy conversion efficiency. Our group, among others, has been studying the use of ammonia borane as a chemical hydrogen storage material for the past several years. Ammonia borane (AB, NH3BH3), a solid state complex composed of the light weight main group elements of nitrogen and boron, is isoelectronic with ethane and as such is an attractive hydrogen storage material with a high gravimetric capacity of H2 (19.6 wt%). However, the widespread use of AB as a chemical hydrogen storage material has been stalled by some undesirable properties and reactivity. Most notably, AB is a solid and this presents compatibility issues with the existing liquid fuel infrastructure. The thermal release of H2 from AB also results in the formation of volatile impurities (borazine and ammonia) that are detrimental to operation of the fuel cell. Additionally, the major products in the spent fuel are polyborazylene and amine borane oligomers that present challenges in regenerating AB. This research was funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

  12. Synthesis of thin films in boron-carbon-nitrogen ternary system by microwave plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Kukreja, Ratandeep Singh

    The Boron Carbon Nitorgen (B-C-N) ternary system includes materials with exceptional properties such as wide band gap, excellent thermal conductivity, high bulk modulus, extreme hardness and transparency in the optical and UV range that find application in most fields ranging from micro-electronics, bio-sensors, and cutting tools to materials for space age technology. Interesting materials that belong to the B-C-N ternary system include Carbon nano-tubes, Boron Carbide, Boron Carbon Nitride (B-CN), hexagonal Boron Nitride ( h-BN), cubic Boron Nitride (c-BN), Diamond and beta Carbon Nitride (beta-C3N4). Synthesis of these materials requires precisely controlled and energetically favorable conditions. Chemical vapor deposition is widely used technique for deposition of thin films of ceramics, metals and metal-organic compounds. Microwave plasma enhanced chemical vapor deposition (MPECVD) is especially interesting because of its ability to deposit materials that are meta-stable under the deposition conditions, for e.g. diamond. In the present study, attempt has been made to synthesize beta-carbon nitride (beta-C3N4) and cubic-Boron Nitride (c-BN) thin films by MPECVD. Also included is the investigation of dependence of residual stress and thermal conductivity of the diamond thin films, deposited by MPECVD, on substrate pre-treatment and deposition temperature. Si incorporated CNx thin films are synthesized and characterized while attempting to deposit beta-C3N4 thin films on Si substrates using Methane (CH4), Nitrogen (N2), and Hydrogen (H2). It is shown that the composition and morphology of Si incorporated CNx thin film can be tailored by controlling the sequence of introduction of the precursor gases in the plasma chamber. Greater than 100mum size hexagonal crystals of N-Si-C are deposited when Nitrogen precursor is introduced first while agglomerates of nano-meter range graphitic needles of C-Si-N are deposited when Carbon precursor is introduced first in the

  13. Shell-model study of boron, carbon, nitrogen and oxygen isotopes based on monopole-based-universal interaction

    CERN Document Server

    Yuan, Cenxi; Otsuka, Takaharu; Xu, Furong; Tsunoda, Naofumi; 10.1103/PhysRevC.85.064324

    2012-01-01

    We study boron, carbon, nitrogen and oxygen isotopes with a newly constructed shell-model Hamiltonian developed from monopole-based-universal interaction ($V_{MU}$). The present Hamiltonian can reproduce well the ground-state energies, energy levels, electric quadrupole properties and spin properties of these nuclei in full psd model space including $(0-3)\\hbar\\omega$ excitations. Especially, it correctly describes the drip lines of carbon and oxygen isotopes and the spins of the ground states of $^{10}$B and $^{18}$N while some former interactions such as WBP and WBT fail. We point out that the inclusion of $2\\hbar\\omega$ excitations is important in reproducing some of these properties. In the present $(0+2)\\hbar\\omega$ calculations small but constant E2 effective charges appear to work quite well. As the inclusion of the $2\\hbar\\omega$ model space makes rather minor change, this seems to be related to the smallness of $^{4}$He core. Similarly, the spin g factors are very close to free values. The applicabil...

  14. Boron/nitrogen pairs Co-doping in metallic carbon nanotubes: a first-principle study

    Institute of Scientific and Technical Information of China (English)

    Ouyang Fang-Ping; Peng Sheng-Lin; Chen Ling-Na; Sun Shu-Yuan; Xu Hui

    2011-01-01

    By using the first-principles calculations, the electronic structure and quantum transport properties of metallic carbon nanotubes with B/N pairs co-doping have been investigated. It is shown that the total energies of metallic carbon nanotubes are sensitive to the doping sites of the B/N pairs. The energy gaps of the doped metallic carbon nanotubes decrease with decreasing the concentration of the B/N pair not only along the tube axis but also around the tube. Moreover, the I-V characteristics and transmissions of the doped tubes are studied. Our results reveal that the conducting ability of the doped tube decreases with increasing the concentrations of the B/N pairs due to symmetry breaking of the system. This fact opens a new way to modulate band structures of metallic carbon nanotubes by doping B/N pair with suitable concentration and the novel characteristics are potentially useful in future applications.

  15. Control of nitrogen content in boron-added medium carbon steel%中碳含硼钢氮含量的控制

    Institute of Scientific and Technical Information of China (English)

    彭其春; 童志博; 陈立鹏; 杨柳; 彭明耀; 周春泉; 陈建新

    2013-01-01

    采用氧氮分析仪分析湖南华菱涟源钢铁集团有限公司中碳含硼钢A36-LB在生产各工序中氮含量的变化,研究其吸氮原因.结果表明,转炉终点碳含量控制不稳定是造成该厂钢中氮含量波动的主要因素;虽然转炉终点碳含量高可以降低钢中的氮含量,但同时也会导致钢中磷含量增高;在LF精炼整个过程中钢水增氮约11×10-6,增氮较多,其中原材料增氮并不是主要原因,主要原因是电弧加热过程增氮较为严重;连铸工艺段增氮较少,保护浇铸较好.%With oxygen and nitrogen analyzer, the change in nitrogen content in boron-added medium carbon steel produced by Valin Lianyuan Iron and Steel Corporation Limited in each stage of the process was analyzed and so was the nitrogen absorption mechanism. The results show that the insta-ble carbon content at BOF endpoint is the main factor for nitrogen content fluctuation. Though high carbon content at BOF endpoint may reduce the nitrogen content, it may lead to rephosphoration in BOF. Liquid steel nitrogen increase reaches 11×10-6 in LF refining process, which is rather significant. Yet the raw materials are not the main cause of nitrogen increase. Nitrogen increase mainly takes place during arc heating process. Nitrogen increase is comparatively small in CC process, which indicates protective casting is preferable.

  16. Tensile properties of a boron/nitrogen-doped carbon nanotube–graphene hybrid structure

    Directory of Open Access Journals (Sweden)

    Kang Xia

    2014-03-01

    Full Text Available Doping is an effective approach that allows for the intrinsic modification of the electrical and chemical properties of nanomaterials. Recently, a graphene and carbon nanotube hybrid structure (GNHS has been reported, which extends the excellent properties of carbon-based materials to three dimensions. In this paper, we carried out a first-time investigation on the tensile properties of the hybrid structures with different dopants. It is found that with the presence of dopants, the hybrid structures usually exhibit lower yield strength, Young’s modulus, and earlier yielding compared to that of a pristine hybrid structure. For dopant concentrations below 2.5% no significant reduction of Young’s modulus or yield strength could be observed. For all considered samples, the failure is found to initiate at the region where the nanotubes and graphene sheets are connected. After failure, monatomic chains are normally observed around the failure region. Dangling graphene layers without the separation of a residual CNT wall are found to adhere to each other after failure with a distance of about 3.4 Å. This study provides a fundamental understanding of the tensile properties of the doped graphene–nanotube hybrid structures, which will benefit the design and also the applications of graphene-based hybrid materials.

  17. Tuning electronic properties of carbon nanotubes by Boron and Nitrogen doping

    Science.gov (United States)

    Chegel, Raad

    2016-10-01

    The electronic properties of pure and doped carbon nanotubes and NC3-, BC3-, NC- and BC-nanotubes are investigated by using tight binding theory. It was found that applying the external fields and doping change the band gap. The energy gap is reduced by B/N-doping and the reduction value is sensitive to the several parameters such as nanotube diameter and chirality, external field strength, electric field direction, impurity type and concentration. The direct N (B) substitution creates a new band above (below) the Fermi level and leads to creation of n-type (p-type) semiconductor. The external fields modify the band structure and convert the doped nanotube into metal. For both XC and XC3 nanotubes (X=B/N), the gap energy reduction shows identical dependence to electric field and the XC3 nanotubes show more sensitive behavior to electric field rather than XC nanotubes.

  18. First-principles study of metallic carbon nanotubes with boron/nitrogen co-doping

    Institute of Scientific and Technical Information of China (English)

    Chen Ling-Na; Ma Song-Shan; OuYang Fang-Ping; Xiao Jin; Xu Hui

    2011-01-01

    Using the first-principles calculations, we investigate the electronic band structure and the quantum transport properties of metallic carbon nanotubes (MCNTs) with B/N pair co-doping. The results about formation energy show that the B/N pair co-doping configuration is a most stable structure. We find that the electronic structure and the transport properties are very sensitive to the doping concentration of the B/N pairs in MCNTs, where the energy gaps increase with doping concentration increasing both along the tube axis and around the tube, because the mirror symmetry of MCNT is broken by doping B/N pairs. In addition, we discuss conductance dips of the transmission spectrum of doped MCNTs. These unconventional doping effects could be used to design novel nanoelectronic devices.

  19. Two-dimensional boron-nitrogen-carbon monolayers with tunable direct band gaps

    Science.gov (United States)

    Zhang, Miao; Gao, Guoying; Kutana, Alex; Wang, Yanchao; Zou, Xiaolong; Tse, John S.; Yakobson, Boris I.; Li, Hongdong; Liu, Hanyu; Ma, Yanming

    2015-07-01

    The search for new candidate semiconductors with direct band gaps of ~1.4 eV has attracted significant attention, especially among the two-dimensional (2D) materials, which have become potential candidates for next-generation optoelectronics. Herein, we systematically studied 2D Bx/2Nx/2C1-x (0 optimization method (CALYPSO) in conjunction with density functional theory. Furthermore, we examine more stoichiometries by the cluster expansion technique based on a hexagonal lattice. The results reveal that all monolayer Bx/2Nx/2C1-x stoichiometries adopt a planar honeycomb character and are dynamically stable. Remarkably, electronic structural calculations show that most of Bx/2Nx/2C1-x phases possess direct band gaps within the optical range, thereby they can potentially be used in high-efficiency conversion of solar energy to electric power, as well as in p-n junction photovoltaic modules. The present results also show that the band gaps of Bx/2Nx/2C1-x can be widely tuned within the optical range by changing the concentration of carbon, thus allowing the fast development of band gap engineered materials in optoelectronics. These new findings may enable new approaches to the design of microelectronic devices.The search for new candidate semiconductors with direct band gaps of ~1.4 eV has attracted significant attention, especially among the two-dimensional (2D) materials, which have become potential candidates for next-generation optoelectronics. Herein, we systematically studied 2D Bx/2Nx/2C1-x (0 optimization method (CALYPSO) in conjunction with density functional theory. Furthermore, we examine more stoichiometries by the cluster expansion technique based on a hexagonal lattice. The results reveal that all monolayer Bx/2Nx/2C1-x stoichiometries adopt a planar honeycomb character and are dynamically stable. Remarkably, electronic structural calculations show that most of Bx/2Nx/2C1-x phases possess direct band gaps within the optical range, thereby they can

  20. Boron and Nitrogen Codoped Carbon Layers of LiFePO4 Improve the High-Rate Electrochemical Performance for Lithium Ion Batteries.

    Science.gov (United States)

    Zhang, Jinli; Nie, Ning; Liu, Yuanyuan; Wang, Jiao; Yu, Feng; Gu, Junjie; Li, Wei

    2015-09-16

    An evolutionary composite of LiFePO4 with nitrogen and boron codoped carbon layers was prepared by processing hydrothermal-synthesized LiFePO4. This novel codoping method is successfully applied to LiFePO4 for commercial use, and it achieved excellent electrochemical performance. The electrochemical performance can be improved through single nitrogen doping (LiFePO4/C-N) or boron doping (LiFePO4/C-B). When modifying the LiFePO4/C-B with nitrogen (to synthesis LiFePO4/C-B+N) the undesired nonconducting N-B configurations (190.1 and 397.9 eV) are generated. This decreases the electronic conductivity from 2.56×10(-2) to 1.30×10(-2) S cm(-1) resulting in weak electrochemical performance. Nevertheless, using the opposite order to decorate LiFePO4/C-N with boron (to obtain LiFePO4/C-N+B) not only eliminates the nonconducting N-B impurity, but also promotes the conductive C-N (398.3, 400.3, and 401.1 eV) and C-B (189.5 eV) configurations-this markedly improves the electronic conductivity to 1.36×10(-1) S cm(-1). Meanwhile the positive doping strategy leads to synergistic electrochemical activity distinctly compared with single N- or B-doped materials (even much better than their sum capacity at 20 C). Moreover, due to the electron and hole-type carriers donated by nitrogen and boron atoms, the N+B codoped carbon coating tremendously enhances the electrochemical property: at the rate of 20 C, the codoped sample can elevate the discharge capacity of LFP/C from 101.1 mAh g(-1) to 121.6 mAh g(-1), and the codoped product based on commercial LiFePO4/C shows a discharge capacity of 78.4 mAh g(-1) rather than 48.1 mAh g(-1). Nevertheless, the B+N codoped sample decreases the discharge capacity of LFP/C from 101.1 mAh g(-1) to 95.4 mAh g(-1), while the commercial LFP/C changes from 48.1 mAh g(-1) to 40.6 mAh g(-1).

  1. Hyperfine structures and Landé g{sub J}-factors for n=2 states in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations

    Energy Technology Data Exchange (ETDEWEB)

    Verdebout, S.; Nazé, C. [Chimie Quantique et Photophysique, CP160/09, Université Libre de Bruxelles, B 1050 Brussels (Belgium); Jönsson, P., E-mail: per.jonsson@mah.se [Faculty of Technology and Society, Group for Materials Science and Applied Mathematics, Malmö University, 205-06 Malmö (Sweden); Rynkun, P. [Institute of Theoretical Physics and Astronomy, Vilnius University, LT-01108 Vilnius (Lithuania); Godefroid, M. [Chimie Quantique et Photophysique, CP160/09, Université Libre de Bruxelles, B 1050 Brussels (Belgium); Gaigalas, G. [Institute of Theoretical Physics and Astronomy, Vilnius University, LT-01108 Vilnius (Lithuania)

    2014-09-15

    Energy levels, hyperfine interaction constants, and Landé g{sub J}-factors are reported for n=2 states in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations. Valence, core–valence, and core–core correlation effects are taken into account through single and double-excitations from multireference expansions to increasing sets of active orbitals. A systematic comparison of the calculated hyperfine interaction constants is made with values from the available literature.

  2. Boron and nitrogen doping in graphene antidot lattices

    Science.gov (United States)

    Brun, Søren J.; Pereira, Vitor M.; Pedersen, Thomas G.

    2016-06-01

    Bottom-up fabrication of graphene antidot lattices (GALs) has previously yielded atomically precise structures with subnanometer periodicity. Focusing on this type of experimentally realized GAL, we perform density functional theory calculations on the pristine structure as well as GALs with edge carbon atoms substituted with boron or nitrogen. We show that p - and n -type doping levels emerge with activation energies that depend on the level of hydrogenation at the impurity. Furthermore, a tight-binding parametrization together with a Green's function method are used to describe more dilute doping. Finally, random configurations of impurities in moderately doped systems are considered to show that the doping properties are robust against disorder.

  3. Methods of forming boron nitride

    Science.gov (United States)

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  4. Boron-nitrogen doped carbon scaffolding: organic chemistry, self-assembly and materials applications of borazine and its derivatives.

    Science.gov (United States)

    Bonifazi, Davide; Fasano, Francesco; Lorenzo-Garcia, M Mercedes; Marinelli, Davide; Oubaha, Hamid; Tasseroul, Jonathan

    2015-10-25

    Discovered by Stock and Pohland in 1926, borazine is the isoelectronic and isostructural inorganic analogue of benzene, where the C[double bond, length as m-dash]C bonds are substituted by B-N bonds. The strong polarity of such heteroatomic bonds widens the HOMO-LUMO gap of the molecule, imparting strong UV-emitting/absorption and electrical insulating properties. These properties make borazine and its derivatives valuable molecular scaffolds to be inserted as doping units in graphitic-based carbon materials to tailor their optoelectronic characteristics, and specifically their semiconducting properties. By guiding the reader through the most significant examples in the field, in this feature paper we describe the past and recent developments in the organic synthesis and functionalisation of borazine and its derivatives. These boosted the production of a large variety of tailored derivatives, broadening their use in optoelectronics, H2 storage and supramolecular functional architectures, to name a few.

  5. Boron-Filled Hybrid Carbon Nanotubes

    Science.gov (United States)

    Patel, Rajen B.; Chou, Tsengming; Kanwal, Alokik; Apigo, David J.; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-07-01

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs.

  6. Boron-Filled Hybrid Carbon Nanotubes

    Science.gov (United States)

    Patel, Rajen B.; Chou, Tsengming; Kanwal, Alokik; Apigo, David J.; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-01-01

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs. PMID:27460526

  7. Graphitized boron-doped carbon foams: Performance as anodes in lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Elena; Camean, Ignacio; Garcia, Roberto [Instituto Nacional del Carbon (CSIC), C/Francisco Pintado Fe 26, 33011 Oviedo (Spain); Garcia, Ana B., E-mail: anabgs@incar.csic.es [Instituto Nacional del Carbon (CSIC), C/Francisco Pintado Fe 26, 33011 Oviedo (Spain)

    2011-05-30

    Highlights: > Because of the catalytic effect of boron, graphite-like foams were prepared. > The presence of substitutional boron in carbon foams improves their anodic performance. > The graphitized boron-doped foams provide reversible capacities of 310 mA h g{sup -1}. - Abstract: The electrochemical performance as potential anodes in lithium-ion batteries of several boron-doped and non-doped graphitic foams with different degree of structural order was investigated by galvanostatic cycling. The boron-doped foams were prepared by the co-pyrolysis of a coal and two boron sources (boron oxide and a borane-pyridine complex), followed by heat treatment in the 2400-2800 deg. C temperature interval. The extent of the graphitization process of the carbon foams depends on boron concentration and source. Because of the catalytic effect of boron, lightweight graphite-like foams were prepared. Boron in the foams was found to be present as carbide (B{sub 4}C), in substitutional positions in the carbon lattice (B-C), bonded to nitrogen (B-N) and forming clusters. Larger reversible lithium storage capacities with values up to {approx}310 mA h g{sup -1} were achieved by using the boron oxide-based carbon foams. Moreover, since the electrochemical anodic performance of these boron-doped foams with different degree of structural order is similar, the beneficial effect of the presence of the B-C boron phase was inferred. However, the bonding of boron with nitrogen in the pyridine borane-based has a negative effect on lithium intercalation.

  8. New nanoforms of carbon and boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Pokropivny, V V [Institute for Problems of Materials Science of National Academy of Sciences of Ukraine (Ukraine); Ivanovskii, A L [Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)], e-mail: Ivanovskii@ihim.uran.ru

    2008-10-31

    Data on new carbon nanostructures including those based on fullerenes, nanotubes as well monolithic diamond-like nanoparticles, nanofibres, various nanocomposites, etc., published in the last decade are generalised. The experimental and theoretical data on their atomic and electronic structures, the nature of chemical bonds and physicochemical properties are discussed. These data are compared with the results obtained in studies of nanoforms of boron nitride, an isoelectronic analogue of carbon. Potential fields of applications of the new nanostructures are considered.

  9. New nanoforms of carbon and boron nitride

    Science.gov (United States)

    Pokropivny, V. V.; Ivanovskii, A. L.

    2008-10-01

    Data on new carbon nanostructures including those based on fullerenes, nanotubes as well monolithic diamond-like nanoparticles, nanofibres, various nanocomposites, etc., published in the last decade are generalised. The experimental and theoretical data on their atomic and electronic structures, the nature of chemical bonds and physicochemical properties are discussed. These data are compared with the results obtained in studies of nanoforms of boron nitride, an isoelectronic analogue of carbon. Potential fields of applications of the new nanostructures are considered.

  10. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    Science.gov (United States)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  11. Ceramic silicon-boron-carbon fibers from organic silicon-boron-polymers

    Science.gov (United States)

    Riccitiello, Salvatore R. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    1993-01-01

    Novel high strength ceramic fibers derived from boron, silicon, and carbon organic precursor polymers are discussed. The ceramic fibers are thermally stable up to and beyond 1200 C in air. The method of preparation of the boron-silicon-carbon fibers from a low oxygen content organosilicon boron precursor polymer of the general formula Si(R2)BR(sup 1) includes melt-spinning, crosslinking, and pyrolysis. Specifically, the crosslinked (or cured) precursor organic polymer fibers do not melt or deform during pyrolysis to form the silicon-boron-carbon ceramic fiber. These novel silicon-boron-carbon ceramic fibers are useful in high temperature applications because they retain tensile and other properties up to 1200 C, from 1200 to 1300 C, and in some cases higher than 1300 C.

  12. BORON-NITROGEN RELATIONSHIP IN WHEAT (Triticum aestivum L. GROWN WITH THE NUTRIENT SOLUTION

    Directory of Open Access Journals (Sweden)

    Mehmet ALPASLAN

    1996-03-01

    Full Text Available The effects of boron applied 0.01, 0.1, 1.0, and 10.0 µg B/ml levels as boric acid (H3 BO3, and nitrogen applied 25, 100, 200, and 400 µg N/ml as ammonium nitrate (NH4 NO3, respectively, on the amount of dry matter yield, and boron, nitrogen and nitrate contents of wheat (Triticum aestivum L. grown in perlite medium with Ruakura nutrient solution under greenhouse conditions were investigated. Dry matter yield and nitrate contents of wheat were decreased and boron content was increased with increasing boron application. Controversially, application of nitrogen increased dry matter yield, nitrogen and nitrate contents of wheat, while decreases in boron contents. Those effects of boron and nitrogen were found to be statistically significant (P

  13. Effects of carbon doping on the electronic properties of boron nitride nanotubes: Tight binding calculation

    Science.gov (United States)

    Chegel, Raad

    2016-10-01

    The electronic properties of pure and carbon doped zigzag and armchair Boron Nitride Nanotubes (BNNTs) have been investigated based on tight binding formalism. It was found that the band gap is reduced due to substitution of Boron or Nitrogen atoms by carbon atoms and the doping effects of B- and N-substituted BNNTs are different. The applied electric field converts the carbon doped BNNTs from semiconductor to metal. The gap energy reduction shows an identical dependence to electric field and doping for both armchair and zigzag carbon doped BNNTs. Our results indicate that the band gap of carbon doped BNNTs is a function of the Impurity concentration, electric field strength and the direction between the electric field and dopant location. The band gap for C-doped BNNTs with four carbon atoms decreases linearly but for two carbon atoms, it is constant at first then decreases linearly.

  14. Nitrogen doping in carbon nanotubes.

    Science.gov (United States)

    Ewels, C P; Glerup, M

    2005-09-01

    Nitrogen doping of single and multi-walled carbon nanotubes is of great interest both fundamentally, to explore the effect of dopants on quasi-1D electrical conductors, and for applications such as field emission tips, lithium storage, composites and nanoelectronic devices. We present an extensive review of the current state of the art in nitrogen doping of carbon nanotubes, including synthesis techniques, and comparison with nitrogen doped carbon thin films and azofullerenes. Nitrogen doping significantly alters nanotube morphology, leading to compartmentalised 'bamboo' nanotube structures. We review spectroscopic studies of nitrogen dopants using techniques such as X-ray photoemission spectroscopy, electron energy loss spectroscopy and Raman studies, and associated theoretical models. We discuss the role of nanotube curvature and chirality (notably whether the nanotubes are metallic or semiconducting), and the effect of doping on nanotube surface chemistry. Finally we review the effect of nitrogen on the transport properties of carbon nanotubes, notably its ability to induce negative differential resistance in semiconducting tubes.

  15. Effect of Nitrogen and Boron in Seed Yield and Yield Attributing Characters of Broccoli

    Directory of Open Access Journals (Sweden)

    A. Khanal

    2015-09-01

    Full Text Available Plant nutrient is one of the limiting factors affecting crop production. Nitrogen and boron are major nutrients in case of broccoli. So, an experiment was carried out to evaluate the effect of nitrogen and boron in seed yield and yield attributing characters of broccoli in Rampur, Chitwan during winter season. The experiment was laid out in factorial RCBD design with four levels of nitrogen and two levels of boron. Each plot consists of 25 plants which were separated by 60 * 60 cm spacing. There are altogether eight treatments replicates thrice. Local variety Calabrese was used. Significant effect of different dose of nitrogen and boron on yield attributing characters was found. Also interactive effect of nitrogen and boron in number of pods, pod length, seed yield and number of seeds per pod was found significantly different.

  16. Role of boron nutrient in nodules growth and nitrogen fixation rates in soybean genotypes under water stress conditions

    Science.gov (United States)

    Although boron has a stimulatory effect on nodule growth and nitrogen fixation, mechanisms of how boron affects nodules growth and nitrogen fixation, especially under water stress, are still unknown. The stimulatory effect of boron (B) on nodules and nitrogen fixation (NF) is influenced by biotic (s...

  17. Chemical nature of boron and nitrogen dopant atoms in graphene strongly influences its electronic properties.

    Science.gov (United States)

    Lazar, Petr; Zbořil, Radek; Pumera, Martin; Otyepka, Michal

    2014-07-21

    Boron and nitrogen doped graphenes are highly promising materials for electrochemical applications, such as energy storage, generation and sensing. The doped graphenes can be prepared by a broad variety of chemical approaches. The substitution of a carbon atom should induce n-type behavior in the case of nitrogen and p-type behavior in the case of boron-doped graphene; however, the real situation is more complex. The electrochemical experiments show that boron-doped graphene prepared by hydroboration reaction exhibits similar properties as the nitrogen doped graphene; according to theory, the electrochemical behavior of B and N doped graphenes should be opposite. Here we analyze the electronic structure of N/B-doped graphene (at ∼5% coverage) by theoretical calculations. We consider graphene doped by both substitution and addition reactions. The density of states (DOS) plots show that graphene doped by substitution of the carbon atom by N/B behaves as expected, i.e., as an n/p-doped material. N-doped graphene also has a lower value of the workfunction (3.10 eV) with respect to that of the pristine graphene (4.31 eV), whereas the workfunction of B-doped graphene is increased to the value of 5.57 eV. On the other hand, the workfunctions of graphene doped by addition of -NH2 (4.77 eV) and -BH2 (4.54 eV) groups are both slightly increased and therefore the chemical nature of the dopant is less distinguishable. This shows that mode of doping depends significantly on the synthesis method used, as it leads to different types of behaviour, and, in turn, different electronic and electrochemical properties of doped graphene, as observed in electrocatalytic experiments. This study has a tremendous impact on the design of doped graphene systems from the point of view of synthetic chemistry.

  18. Efficient Boron Nitride Nanotube Formation via Combined Laser-Gas Flow Levitation

    Science.gov (United States)

    Whitney, R. Roy (Inventor); Jordan, Kevin (Inventor); Smith, Michael W. (Inventor)

    2014-01-01

    A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B(sub x)C(sub y)N(sub z) The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B(sub x)C(sub y)N(sub z).

  19. Reactivity of boron- and nitrogen-doped carbon nanotubes functionalized by (Pt, Eu) atoms toward O2 and CO: A density functional study

    Science.gov (United States)

    Abdel Aal, S.

    2016-01-01

    The adsorption behavior and electronic properties of CO and O2 molecules at the supported Pt and Eu atoms on (5,5) armchair SWCNT have been systematically investigated within density functional theory (DFT). Fundamental aspects such as adsorption energy, natural bond orbital (NBO), charge transfer, frontier orbitals and the projected density of states (PDOS) are elucidated to analyze the adsorption properties of CO and O2 molecules. The results reveal that B- and N-doping CNTs can enhance the binding strength and catalytic activity of Pt (Eu) anchored on the doped-CNT, where boron-doping is more effective. The electronic structures of supported metal are strongly influenced by the presence of gases. After adsorption of CO and O2, the changes in binding energy, charge transfer and conductance may lead to the different response in the metal-doped CNT-based sensors. It is expected that these results could provide helpful information for the design and fabrication of the CO and O2 sensing devices. The high catalytic activity of Pt supported at doped-CNT toward the interaction with CO and O2 may be attributed to the electronic resonance particularly among Pt-5d, CO-2π* and O2-2π* antibonding orbitals. In contrast to the supported Eu at doped-CNT, the Eu atom becomes more positively charged, which leads to weaken the CO adsorption and promote the O2 adsorption, consequently enhancing the activity for CO oxidation and alleviating the CO poisoning of the europium catalysts. A notable orbital hybridization and electrostatic interaction between these two species in adsorption process being an evidence of strong interaction. The electronic structure of O2 adsorbed on Eu-doped CNT resembles that of O2-, therefore the transferred charge weakens the O-O bonds and facilitates the dissociation process, which is the precondition for the oxygen reduction reaction (ORR).

  20. Synthesis and characterization of boron-doped carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ceragioli, H J; Peterlevitz, A C; Quispe, J C R; Pasquetto, M P; Sampaio, M A; Baranauskas, V [Faculdade de Engenharia Eletrica e Computacao, Departamento de Semicondutores, Instrumentos e Fotonica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N.400, 13083-852 Campinas SP Brasil (Brazil); Larena, A [Department of Chemical Industrial Engineering and Environment, Universidad Politecnica de Madrid, E.T.S. Ingenieros Industriales, C/ Jose Gutierrez Abascal, Madrid (Spain)], E-mail: vitor.baranauskas@gmail.com

    2008-03-15

    Boron-doped carbon nanotubes have been prepared by chemical vapour deposition of ethyl alcohol doped with B{sub 2}O{sub 3} using a hot-filament system. Multi-wall carbon nanotubes of diameters in the range of 30-100 nm have been observed by field emission scanning electron microscopy (FESEM). Raman measurements indicated that the degree of C-C sp{sup 2} order decreased with boron doping. Lowest threshold fields achieved were 1.0 V/{mu}m and 2.1 V/{mu}m for undoped and boron-doped samples, respectively.

  1. A computational study of carbon dioxide adsorption on solid boron.

    Science.gov (United States)

    Sun, Qiao; Wang, Meng; Li, Zhen; Du, Aijun; Searles, Debra J

    2014-07-07

    Capturing and sequestering carbon dioxide (CO2) can provide a route to partial mitigation of climate change associated with anthropogenic CO2 emissions. Here we report a comprehensive theoretical study of CO2 adsorption on two phases of boron, α-B12 and γ-B28. The theoretical results demonstrate that the electron deficient boron materials, such as α-B12 and γ-B28, can bond strongly with CO2 due to Lewis acid-base interactions because the electron density is higher on their surfaces. In order to evaluate the capacity of these boron materials for CO2 capture, we also performed calculations with various degrees of CO2 coverage. The computational results indicate CO2 capture on the boron phases is a kinetically and thermodynamically feasible process, and therefore from this perspective these boron materials are predicted to be good candidates for CO2 capture.

  2. Nitrogen-doped hydrothermal carbons

    Energy Technology Data Exchange (ETDEWEB)

    Titirici, Maria-Magdalena; White, Robin J. [Max-Planck-Institute of Colloids and Interfaces, Potsdam (Germany). Dept. of Colloid Chemistry; Zhao, Li [Max-Planck-Institute of Colloids and Interfaces, Potsdam (Germany). Dept. of Colloid Chemistry; National Center for Nanoscience and Technology, Beijing (China)

    2012-07-01

    Nitrogen doped carbon materials are now playing an important role in cutting edge innovations for energy conversion and storage technologies such as supercapacitors and proton exchange membrane fuel cells as well as in catalytic applications, adsorption and CO{sub 2} capture. The production of such materials using benign aqueous based processes, mild temperatures and renewable precursors is of great promise in addressing growing environmental concerns for cleaner power sources at a time of increasing global demand for energy. In this perspective, we show that nitrogen doped carbons prepared using sustainable processes such as ''Hydrothermal Carbonisation'' has advantages in many applications over the conventional carbons. We also summarize an array of synthetic strategies used to create such nitrogen doped carbons, and discuss the application of these novel materials. (orig.)

  3. Superiority of boron, nitrogen and iron ternary doped carbonized graphene oxide-based catalysts for oxygen reduction in microbial fuel cells.

    Science.gov (United States)

    Cao, Chun; Wei, Liling; Wang, Gang; Shen, Jianquan

    2017-03-09

    The exploration of highly active and cost-effective catalysts for the oxygen reduction reaction is vitally important to facilitate the improvement of metal-air batteries and fuel cells. Herein, super-active catalysts made from an interesting metal-polymer network (MPN) that consist of Fe-Nx-C, B-N and Fe3O4/Fe3C alloys were prepared via facile one-pot carbonization. The achieved catalysts possessed an amazing porous structure that was derived from the MPN with the assistance of a "bubble-template". Remarkably, the content of highly active Fe-Nx-C can be regulated by introducing graphene, and the ORR activity of the catalyst was enhanced dramatically with an increase in the Fe3O4/Fe3C alloy content. The most active BNFe-C-G2 catalyst exhibited superior ORR activity/stability, and was then employed as an air cathode electrocatalyst in a microbial fuel cell. The results showed that the output voltage and power density of BNFe-C-G2 were significantly improved to 575 ± 11 mV and 1046.2 ± 35 mW m(-2), respectively. These values are 4.5% and 44.44% higher than those of commercial Pt/C. Thus, due to the synergistic electrocatalysis of the Fe-Nx-C, B-N and Fe3O4/Fe3C alloys, the super-active and low-cost BNFe-C-G2 material should be a promising ORR catalyst for application in biofuel cells, and in many other energy conversion and storage devices.

  4. Structure, Mechanics and Synthesis of Nanoscale Carbon and Boron Nitride

    Science.gov (United States)

    Rinaldo, Steven G.

    This thesis is divided into two parts. In Part I, we examine the properties of thin sheets of carbon and boron nitride. We begin with an introduction to the theory of elastic sheets, where the stretching and bending modes are considered in detail. The coupling between stretching and bending modes is thought to play a crucial role in the thermodynamic stability of atomically-thin 2D sheets such as graphene. In Chapter 2, we begin by looking at the fabrication of suspended, atomically thin sheets of graphene. We then study their mechanical resonances which are read via an optical transduction technique. The frequency of the resonators was found to depend on their temperature, as was their quality factor. We conclude by offering some interpretations of the data in terms of the stretching and bending modes of graphene. In Chapter 3, we look briefly at the fabrication of thin sheets of carbon and boron nitride nanotubes. We examine the structure of the sheets using transmission and scanning electron microscopy (TEM and SEM, respectively). We then show a technique by which one can make sheets suspended over a trench with adjustable supports. Finally, DC measurements of the resistivity of the sheets in the temperature range 600 -- 1400 C are presented. In Chapter 4, we study the folding of few-layer graphene oxide, graphene and boron nitride into 3D aerogel monoliths. The properties of graphene oxide are first considered, after which the structure of graphene and boron nitride aerogels is examined using TEM and SEM. Some models for their structure are proposed. In Part II, we look at synthesis techniques for boron nitride (BN). In Chapter 5, we study the conversion of carbon structures of boron nitride via the application of carbothermal reduction of boron oxide followed by nitridation. We apply the conversion to a wide variety of morphologies, including aerogels, carbon fibers and nanotubes, and highly oriented pyrolytic graphite. In the latter chapters, we look at the

  5. Ordering of carbon atoms in boron carbide structure

    Energy Technology Data Exchange (ETDEWEB)

    Ponomarev, V. I., E-mail: i2212@yandex.ru; Kovalev, I. D.; Konovalikhin, S. V.; Vershinnikov, V. I. [Russian Academy of Sciences, Institute of Structural Macrokinetics and Materials Science (Russian Federation)

    2013-05-15

    Boron carbide crystals have been obtained in the entire compositional range according to the phase diagram by self-propagating high-temperature synthesis (SHS). Based on the results of X-ray diffraction investigations, the samples were characterized by the unit-cell metric and reflection half-width in the entire range of carbon concentrations. A significant spread in the boron carbide unit-cell parameters for the same carbon content is found in the data in the literature; this spread contradicts the structural concepts for covalent compounds. The SHS samples have not revealed any significant spread in the unit-cell parameters. Structural analysis suggests that the spread of parameters in the literary data is related to the unique process of ordering of carbon atoms in the boron carbide structure.

  6. Structural Modification in Carbon Nanotubes by Boron Incorporation

    Directory of Open Access Journals (Sweden)

    Handuja Sangeeta

    2009-01-01

    Full Text Available Abstract We have synthesized boron-incorporated carbon nanotubes (CNTs by decomposition of ferrocene and xylene in a thermal chemical vapor deposition set up using boric acid as the boron source. Scanning and transmission electron microscopy studies of the synthesized CNT samples showed that there was deterioration in crystallinity and improvement in alignment of the CNTs as the boron content in precursor solution increased from 0% to 15%. Raman analysis of these samples showed a shift of ~7 cm−1in wave number to higher side and broadening of the G band with increasing boron concentration along with an increase in intensity of the G band. Furthermore, there was an increase in the intensity of the D band along with a decrease in its wave number position with increase in boron content. We speculate that these structural modifications in the morphology and microstructure of CNTs might be due to the charge transfer from boron to the graphite matrix, resulting in shortening of the carbon–carbon bonds.

  7. Boron isotope fractionation in magma via crustal carbonate dissolution.

    Science.gov (United States)

    Deegan, Frances M; Troll, Valentin R; Whitehouse, Martin J; Jolis, Ester M; Freda, Carmela

    2016-08-04

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ(11)B values down to -41.5‰, reflecting preferential partitioning of (10)B into the assimilating melt. Loss of (11)B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports (11)B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ(11)B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  8. Growth and characterization of BCN nanotubes with high boron and nitrogen content

    Indian Academy of Sciences (India)

    Guo Zhang; Zhiye Liu; Lianping Zhang; Liqiang Jing; Keying Shi

    2013-09-01

    Multiwalled carbon nanotubes doped with boron and nitrogen (BCNTs) have been synthesized by chemical vapour deposition at temperatures ranging from 800°C to 950°C. Their morphological and structural features have been studied by transmission electron microscope, which reveal that BCNTs have bamboo-like structure. The results of X-ray photoelectron spectroscopy demonstrated that the atomic ratio of B, C and N of BCNTs is about 1:4:1, when temperature is 850°C. Electrooxidation performance of the BCNTs for NO at the modified electrodes was investigated. The results of cyclic voltammograms and the electrochemical impedance spectroscopy of BCNT-modified electrodes indicated that the activity of NO electrooxidation on 850°C-modified electrodes is much stronger than others and the charge transfer resistance of NO electroxidation BCNT-modified electrode is the least. By this means, BCNT-modified electrodes showed excellent electrode materials for NO detection and other potential applications.

  9. Thermodynamic Model for Calculating Activity of Nitrogen and Boron in Fe-C-B-N Molten Metal

    Institute of Scientific and Technical Information of China (English)

    WANG Shi-jun; PENG Jun; DONG Yuan-chi; LIU Li-xia; ZHOU Yun; CHEN Er-bao

    2009-01-01

    The solubility of nitrogen in Fe-C-B-N system was measured at 1 758 K,and the computational model on activity (action concentration) of nitrogen and boron was established based on phase diagram and the coexistence theory about metal melt structure model.Comparing the computed results with the experimental results,satisfactory conclusion can be obtained.The result shows that BN and B4C can exist in Fe-C-B-N molten metal at high temperature,which consequently restrains the nitrogen removal from the melt.However,B4C content is extremely low.Before graphite is precipitated,the influence of carbon on activity of nitrogen in melt is higher in ternary system than in binary system; however,this effect is contrary to that after graphite is precipitated.

  10. INFLUENCE RESEARCH OF COLD PLASTIC DEFORMATION ON DIFFUSION SATURATION PROCESS BY CARBON AND BORON OF THE LOW-CARBON AND BORON-CONTAINING ALLOYS

    Directory of Open Access Journals (Sweden)

    N. Yu. Filonenko

    2010-06-01

    Full Text Available This work is devoted to the study of influence of cold prestrain with degree of deformation within the range 0…40 % on diffusion saturation with boron and carbon for low-carbon and boron steels. It is determined that the plastic prestrain with degree of deformation 20 % at temperature 750 °С for the low-carbon steel promote increasing of boron-cementation layer thickness by 25 % and microhardness of perlite layer by 20 %.

  11. Subgrains and boron distribution of low carbon bainitic steels

    Institute of Scientific and Technical Information of China (English)

    Xuemin Wang; Bing Cao; Chengjia Shang; Xueyi Liu; Xinlai He

    2005-01-01

    The structure variation of deformed austenite during the relaxation stage after deformation at various temperatures in an Nb-B ultra low carbon bainitic steel and Fe-Ni alloy was studied by the thermo-simulation. Optical microscope and TEM were applied to analyze the microstructure after RPC (Relaxation-precipitation-controlling phase transformation technique) and the evolution of dislocation configuration. The particle tracking autoradiography (PTA) technique, revealing the distribution of boron, was employed to show the change of boron segregation after different relaxation times. The results indicate that during the relaxation stage the recovery occurs in the deformed austenite, the dislocations rearrange and subgrains form. During the subsequent cooling the boron will segregate at the boundaries of subgrains.

  12. Investigating controls on boron isotope ratios in shallow marine carbonates

    Science.gov (United States)

    Zhang, Shuang; Henehan, Michael J.; Hull, Pincelli M.; Reid, R. Pamela; Hardisty, Dalton S.; Hood, Ashleigh v. S.; Planavsky, Noah J.

    2017-01-01

    The boron isotope-pH proxy has been widely used to reconstruct past ocean pH values. In both planktic foraminifera and corals, species-specific calibrations are required in order to reconstruct absolute values of pH, due to the prevalence of so-called vital effects - physiological modification of the primary environmental signals by the calcifying organisms. Shallow marine abiotic carbonate (e.g. ooids and cements) could conceivably avoid any such calibration requirement, and therefore provide a potentially useful archive for reconstructions in deep (pre-Cenozoic) time. However, shallow marine abiotic carbonates could also be affected by local shifts in pH caused by microbial photosynthesis and respiration, something that has up to now not been fully tested. In this study, we present boron isotope measurements from shallow modern marine carbonates, from the Bahama Bank and Belize to investigate the potential of using shallow water carbonates as pH archives, and to explore the role of microbial processes in driving nominally 'abiogenic' carbonate deposition. For Bahama bank samples, our boron-based pH estimates derived from a range of carbonate types (i.e. ooids, peloids, hardground cements, carbonate mud, stromatolitic micrite and calcified filament micrite) are higher than the estimated modern mean-annual seawater pH values for this region. Furthermore, the majority (73%) of our marine carbonate-based pH estimates fall out of the range of the estimated pre-industrial seawater pH values for this region. In shallow sediment cores, we did not observe a correlation between measured pore water pH and boron-derived pH estimates, suggesting boron isotope variability is a depositional rather than early diagenetic signal. For Belize reef cements, conversely, the pH estimates are lower than likely in situ seawater pH at the time of cement formation. This study indicates the potential for complications when using shallow marine non-skeletal carbonates as marine pH archives

  13. Lithium insertion into boron containing carbons prepared by co-pyrolysis of coal-tar pitch and borane-pyridine complex

    Energy Technology Data Exchange (ETDEWEB)

    Machnikowski, J.; Frackowiak, E.; Kierzek, K.; Waszak, D.; Benoit, R.; Beguin, F. [Wroclaw University of Technology, Wroclaw (Poland)

    2004-03-01

    Carbon materials of boron content ranging from 0.6 to 4 wt.% were synthesized by co-pyrolysis of QI-free coal-tar pitch with the borane-pyridine complex. The growing amount of boron introduced into the carbonaceous material is associated with an increase in nitrogen content and a progressive degradation of structural and textural ordering. The structural variations of the boron-doped materials on heat treatment up to 2500{sup o}C were monitored using X-ray diffraction and X-ray photoelectron spectroscopy. The intrinsic boron acts effectively as a catalyst of graphitization above 2100{sup o}C. The carbonaceous material with boron content of about 1.5 wt% shows the highest degree of structural ordering after thermal treatment. A high amount of oxygen was found in the graphitized boronated carbons, proving that the incorporated boron induces a strong chemisorption activity of the material when exposed to air. For a series of cokes calcined at 1000 {sup o}C, the most striking effect of increasing the boron content is an increase of irreversible capacity X-irr from 0.2 to 0.7. The reversible capacity (X-rev) amounts to about 1, with a slight tendency to decrease with the boron content. Upon increasing the temperature up to 2500{sup o}C, X-irr decreases to about 0.1 in the graphitic carbons, while X-rev reaches a minimum of 0.4-0.5 at 1700{sup o}C and next increases to a value close to 1 at 2500{sup o}C. In the boron doped graphite, X-irr has a slight tendency to increase with the boron content, due to the simultaneous presence of nitrogen in these materials and their strong affinity for oxygen from the atmosphere.

  14. Tuning the optical response in carbon doped boron nitride nanodots

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-09-04

    Time dependent density functional theory and the hybrid B3LYP functional are used to investigate the structural and optical properties of pristine and carbon doped hexagonal boron nitride nanodots. In agreement with recent experiments, the embedded carbon atoms are found to favor nucleation. Our results demonstrate that carbon clusters of different shapes promote an early onset of absorption by generating in-gap states. The nanodots are interesting for opto-electronics due to their tunable optical response in a wide energy window. We identify cluster sizes and shapes with optimal conversion efficiency for solar radiation and a wide absorption range form infrared to ultraviolet. This journal is

  15. Residual stresses in boron/tungsten and boron/carbon fibers

    Science.gov (United States)

    Behrendt, D. R.

    1977-01-01

    Longitudinal residual stress distribution is determined for 102-micron diam B/W and B/C fibers. The 102-micron diam B/W fibers are deposited on a 12.7-micron diam tungsten wire resistively heated in a BCl3-H2 reactor. The 102-micron diam B/C fibers are made by deposition of boron on a pyrolytic graphite-coated carbon fiber. The longitudinal residual stress distribution is calculated from measurements of the change in length of the fiber produced by removal of the surface through electropolishing. It is found that for both types of fibers, the residual stress vary from a compressive stress at the surface to a tensile stress in the boron near the core. Closer to the core and in the core, significant differences in the residual stresses are observed for the B/W and B/C fibers.

  16. Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I

    Science.gov (United States)

    Thibeault, Sheila A.; Fay, Catharine C.; Lowther, Sharon E.; Earle, Kevin D.; Sauti, Godfrey; Kang, Jin Ho; Park, Cheol; McMullen, Amelia M.

    2012-01-01

    The key objectives of this study are to investigate, both computationally and experimentally, which forms, compositions, and layerings of hydrogen, boron, and nitrogen containing materials will offer the greatest shielding in the most structurally robust combination against galactic cosmic radiation (GCR), secondary neutrons, and solar energetic particles (SEP). The objectives and expected significance of this research are to develop a space radiation shielding materials system that has high efficacy for shielding radiation and that also has high strength for load bearing primary structures. Such a materials system does not yet exist. The boron nitride nanotube (BNNT) can theoretically be processed into structural BNNT and used for load bearing structures. Furthermore, the BNNT can be incorporated into high hydrogen polymers and the combination used as matrix reinforcement for structural composites. BNNT's molecular structure is attractive for hydrogen storage and hydrogenation. There are two methods or techniques for introducing hydrogen into BNNT: (1) hydrogen storage in BNNT, and (2) hydrogenation of BNNT (hydrogenated BNNT). In the hydrogen storage method, nanotubes are favored to store hydrogen over particles and sheets because they have much larger surface areas and higher hydrogen binding energy. The carbon nanotube (CNT) and BNNT have been studied as potentially outstanding hydrogen storage materials since 1997. Our study of hydrogen storage in BNNT - as a function of temperature, pressure, and hydrogen gas concentration - will be performed with a hydrogen storage chamber equipped with a hydrogen generator. The second method of introducing hydrogen into BNNT is hydrogenation of BNNT, where hydrogen is covalently bonded onto boron, nitrogen, or both. Hydrogenation of BN and BNNT has been studied theoretically. Hyper-hydrogenated BNNT has been theoretically predicted with hydrogen coverage up to 100% of the individual atoms. This is a higher hydrogen content

  17. The heliospheric modulation of cosmic ray boron and carbon

    Directory of Open Access Journals (Sweden)

    M. S. Potgieter

    2004-11-01

    Full Text Available The observed boron to carbon ratio (B/C at Earth provides a good measure of the overall secondary to primary ratio of galactic cosmic rays. This makes B/C an important constraint and test for the validity and general applicability of theoretical and numerical models of galactic propagation and heliospheric modulation. For this purpose, the modulation of boron and carbon in the heliosphere must be understood in greater detail. The latest approach to heliospheric modulation, using a numerical model containing a termination shock, a heliosheath and particle drifts, is used to the study the modulation of the two species. This model also includes a more comprehensive set of diffusion coefficients. From this and previous work follows that the model is compatible with a variety of observations, for seven species, i.e. protons, anti-protons, electrons, positrons, helium, boron, and carbon, with the same set of parameters for both solar magnetic polarity cycles. Despite the rather flat interstellar spectrum for carbon below 100MeV/nuc, the modulated spectra at 1AU look very similar for boron and carbon, caused by adiabatic energy losses, implying that the carbon modulation should have a much larger radial gradient in the outer heliosphere below ~200-500MeV/nuc than boron. Significant modulation can be caused by the heliosheath but it is strongly dependent on energy and on the field polarity, with almost no effect at high energies to the largest effect at low energies. The solar wind termination shock has an important effect on the B to C ratio in the heliosphere, although small at Earth, during the A<0 cycle, with E<~600MeV/nuc, but it seems less significant for the A>0 cycle and with increasing tilt angles. Drift models produce different spectra for consecutive solar minimum conditions which may account for the modulation level differences between observations around 100MeV/nuc compared to around 500MeV/nuc. All factors taken into account

  18. Simulation of swift boron clusters traversing amorphous carbon foils

    OpenAIRE

    Heredia Ávalos, Santiago; Abril Sánchez, Isabel; Denton Zanello, Cristian D.; García Molina, Rafael

    2007-01-01

    We use a simulation code to study the interaction of swift boron clusters (Bn+, n=2–6, 14) with amorphous carbon foils. We analyze different aspects of this interaction, such as the evolution of the cluster structure inside the target, the energy and angle distributions at the detector or the stopping power ratio. Our simulation code follows in detail the motion of the cluster fragments through the target and in the vacuum until reaching a detector, taking into account the following interacti...

  19. Photoluminescence and Raman spectroscopy characterization of boron- and nitrogen-doped 6H silicon carbide

    DEFF Research Database (Denmark)

    Ou, Yiyu; Jokubavicius, Valdas; Liu, Chuan

    2011-01-01

    Boron - and nitrogen-doped 6H silicon carbide epilayers grown on low off-axis 6H silicon carbide substrates have been characterized by photoluminescence and Raman spectroscopy. Combined with secondary ion mass spectrometry results, preferable doping type and optimized concentration could...

  20. Structures of Pt clusters on graphene doped with nitrogen, boron, and silicon: a theoretical study

    Institute of Scientific and Technical Information of China (English)

    Dai Xian-Qi; Tang Ya-Nan; Dai Ya-Wei; Li Yan-Hui; Zhao Jian-Hua; Zhao Bao; Yang Zong-Xian

    2011-01-01

    The structures of Pt clusters on nitrogen-, boron-, silicon- doped graphenes are theoretically studied using densityfunctional theory. These dopants (nitrogen, boron and silicon) each do not induce a local curvature in the graphene and the doped graphenes all retain their planar form. The formation energy of the silicon-graphene system is lower than those of the nitrogen-, boron-doped graphenes, indicating that the silicon atom is easier to incorporate into the graphene.All the substitutional impurities enhance the interaction between the Pt atom and the graphene. The adsorption energy of a Pt adsorbed on the silicon-doped graphene is much higher than those on the nitrogen- and boron-doped graphenes.The doped silicon atom can provide more charges to enhance the Pt-graphene interaction and the formation of Pt clusters each with a large size. The stable structures of Pt clusters on the doped-graphenes are dimeric, triangle and tetrahedron with the increase of the Pt coverage. Of all the studied structures, the tetrahedron is the most stable cluster which has the least influence on the planar surface of doped-graphene.

  1. Methods of Boron-carbon Deposited Film Removal

    Science.gov (United States)

    Airapetov, A.; Terentiev, V.; Voituk, A.; Zakharov, A.

    Boron carbide was proposed as a material for in-situ renewable protecting coating for tungsten tiles of the ITER divertor. It is necessary to develop a method of gasification of boron-carbon film which deposits during B4C sputtering. In this paper the results of the first stage investigation of gasification methods of boron-carbon films are presented. Two gasification methods of films are investigated: interaction with the ozone-oxygen mixture and irradiation in plasma with the working gas composed of oxygen, ethanol, and, in some cases, helium. The gasification rate in the ozone-oxygen mixture at 250 °C for B/C films with different B/C ratio and carbon fiber composite (CFC), was measured. For B/C films the gasification rate decreased with increasing B/C ratio (from 45 nm/h at B/C=0.7 to 4 nm/h at B/C=2.1; for CFC - 15 μm/h). Films gasification rates were measured under ion irradiation from ethanol-oxygen-helium plasma at different temperatures, with different ion energies and different gas mixtures. The maximum obtained removal rate was near 230 nm/h in case of ethanol-oxygen plasma and at 150°C of the sample temperature.

  2. Investigating Carbonate System Perturbations across the Cretaceous-Palaeogene Transition using Boron Isotopes in Planktonic Foraminifera.

    Science.gov (United States)

    Henehan, M. J.; Hull, P. M.; Planavsky, N. J.; Huber, B. T.; Thomas, E.

    2014-12-01

    The interval spanning the latest Maastrichtian to the early Palaeocene has great potential in helping to elucidate the stabilising mechanisms on the Earth's carbonate system on both long and very short geological timescales, from the geologically-instantaneous production of sulphate-rich aerosols and nitrogen oxides from the K-Pg bolide impact to the relatively more gradual degassing from Deccan volcanism in the latest Maastrichtian. The extent to which ocean pH (and atmospheric CO2 concentrations) changed in response to these contrasting acidification pressures, and the timescales of their recovery, may provide unique insight into the efficiency of the Earth's oceans in buffering greenhouse gas increases (through carbonate dissolution, weathering-derived alkalinity flux, and biological carbon cycling). The boron isotope palaeo-pH proxy in planktic foraminifera is well suited to such investigations, but its application over this interval has been problematic, not least due to a scarcity of sample material and a near-complete turnover of planktonic foraminiferal species across the K-Pg boundary. To attempt to circumvent these issues, we investigate the biological influences on boron isotope signals in Maastrichtian and Danian planktonic foraminifera, with the goal of producing more accurate palaeo-pH reconstructions. With these findings in mind, we present preliminary constraints on ocean pH and carbonate system dynamics across this critical interval of geological time.

  3. Carbon-nitrogen interactions in forest ecosystems

    DEFF Research Database (Denmark)

    Gundersen, Per; Berg, Bjørn; Currie, W.S.;

    This report is a summary of the main results from the EU project “CarbonNitrogen Interactions in Forest Ecosystems” (CNTER). Since carbon (C) and nitrogen (N) are bound together in organic matter we studied both the effect of N deposition on C cycling in forest ecosystems, and the effect of C...

  4. Effect of Boron on Delayed Fracture Resistance of Medium-Carbon High Strength Spring Steel

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The delayed fracture behavior of medium-carbon high strength spring steel containing different amounts of boron (0. 000 5%, 0. 001 6%) was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron content from 0. 000 5 % to 0. 001 6 %. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350 ℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initiation area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3 (C, B) phase.

  5. Preparation and characterization of boron nitride/carbon fiber composite with high specific surface area

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yan; Fan, Mingwen [Wuhan Univ. (China). Key Laboratory for Oral Biomedical Engineering; Yuan, Songdong; Xiong, Kun; Hu, Kunpeng; Luo, Yi [Hubei Univ. of Technology, Wuhan (China). School of Chemistry and Chemical Engineering; Li, Dong [Hubei Univ. of Technology, Wuhan (China). School of Chemistry and Chemical Engineering; Oxford Univ. (United Kingdom). Chemistry Research Lab.

    2014-06-15

    Boron nitride can be used as a good catalyst carrier because of its high thermal conductivity and chemical stability. However, a high specific surface area of boron nitride is still desirable. In this work, a carbon fiber composite coated with boron nitride villous nano-film was prepared, and was also characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The results indicated that the carbon fibers were covered by uniform villous boron nitride films whose thickness was about 150 - 200 nm. The specific surface area of the boron nitride/carbon fiber composite material was 96 m{sup 2} g{sup -1}, which was markedly improved compared with conventional boron nitride materials. (orig.)

  6. Magnetism of single-walled silicon carbide nanotubes doped by boron, nitrogen and oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Maghnaoui, Ahmed [Laboratoire de Physique, Universite du 08 mai 45, BP 401, 24000 Guelma (Algeria); Boufelfel, Ahmed, E-mail: ahboufelfel@gmail.com [Laboratoire de Physique, Universite du 08 mai 45, BP 401, 24000 Guelma (Algeria)

    2012-09-15

    We calculated, using spin polarized density functional theory, the electronic properties of zigzag (10,0) and armchair (6,6) semiconductor silicon carbide nanotubes (SiCNTs) doped once at the time with boron, nitrogen, and oxygen. We have looked at the two possible scenarios where the guest atom X (B, N, O), replaces the silicon X{sub Si}, or the carbon atom X{sub C}, in the unit cell. We found that in the case of one atom B - SiCNT replacing a carbon atom position annotated by B{sub C} exhibits a magnetic moment of 1 {mu}{sub B}/cell in both zigzag and armchair nanotubes. Also, B replacing Si, (B{sub Si}), induce a magnetic moment of 0.46 {mu}{sub B}/cell in the zigzag (10,0) but no magnetic moment in armchair (6,6). For N substitution; (N{sub C}) and (N{sub Si}) each case induce a magnetic moment of 1 {mu}{sub B}/cell in armchair (6,6), while N{sub Si} give rise to 0.75 {mu}{sub B}/cell in zigzag (10,0) and no magnetic moment for N{sub C}. In contrast the case of O{sub C} and O{sub Si} did not produce any net magnetic moment in both zigzag and armchair geometries. - Highlights: Black-Right-Pointing-Pointer Calculation scheme the one implemented in the SIESTA. Black-Right-Pointing-Pointer Materials studied SiCNT, B - SiCNT, N - SiCNT and O - SiCNT. Black-Right-Pointing-Pointer Magnetism in single wall SiCNTs when one atom of C or Si is replaced by B or N zigzag (10,0) and armchair (6,6).

  7. Boron

    Science.gov (United States)

    ... an eye wash. Boron was used as a food preservative between 1870 and 1920, and during World Wars ... chemical symbol), B (symbole chimique), Borate, Borate de Sodium, Borates, Bore, Boric Acid, Boric Anhydride, Boric Tartrate, ...

  8. Effect of nitrogen on deposition and field emission properties of boron-doped micro-and nano-crystalline diamond films

    Institute of Scientific and Technical Information of China (English)

    L.A. Li; S.H. Cheng; H.D. Li; Q. Yu; J.W. Liu; X.Y. Lv

    2010-01-01

    In this paper, we report the effect of nitrogen on the deposition and properties of boron doped diamond films synthesized by hot filament chemical vapor deposition. The diamond films consisting of micro-grains (nano-grains) were realized with low (high) boron source flow rate during the growth processes. The transition of micro-grains to nano-grains is speculated to be strongly (weekly) related with the boron (nitrogen) flow rate. The grain size and Raman spectral feature vary insignificantly as a function of the nitrogen introduction at a certain boron flow rate. The variation of electron field emission characteristics dependent on nitrogen is different between microcrystalline and nanocrystalline boron doped diamond samples, which are related to the combined phase composition, boron doping level and texture structure. There is an optimum nitrogen proportion to improve the field emission properties of the boron-doped films.

  9. Boron-nitrogen based hydrides and reactive composites for hydrogen storage

    DEFF Research Database (Denmark)

    Jepsen, Lars H.; Ley, Morten B.; Lee, Young-Su;

    2014-01-01

    Hydrogen forms chemical compounds with most other elements and forms a variety of different chemical bonds. This fascinating chemistry of hydrogen has continuously provided new materials and composites with new prospects for rational design and the tailoring of properties. This review highlights ...... a range of new boron and nitrogen based hydrides and illustrates how hydrogen release and uptake properties can be improved. © 2014 Elsevier Ltd....

  10. A Contribution to the Understanding of the Combined Effect of Nitrogen and Boron in Grey Cast Iron

    DEFF Research Database (Denmark)

    Strande, Knud; Tiedje, Niels Skat; Chen, Ming

    2017-01-01

    iron microstructure. Both graphite flake formation and matrix formation are influenced. However, the obtained effects differ considerably between different reported investigations. This investigation deals with the combined effect of nitrogen and boron and how it is possible to utilize this effect...... to enhance material properties in heavy grey iron castings. It is shown that the controlled additions of nitrogen and boron can be used to control the microstructure of thick section grey iron castings. A plausible theory for the formation of boron nitride nuclei effective for graphite growth is presented....

  11. Growth evaluation of spondias tuberosa rootsctocks in the substrate fertilization with nitrogen and boron.

    Directory of Open Access Journals (Sweden)

    Cleiton José de Oliveira

    2009-08-01

    Full Text Available The main goal of this works was evaluate the effect of nitrogen and boron doses, in the rootstocks ‘umbu’ (Spondias tuberosa Arruda Câmara. The experiment it was led at CCA/UFPB-Campus II, located in the Areia city, state of Paraiba in Brazil. The treatments were five levels of nitrogen (0 to 4,50 g dm-3 as ureia (45% N, and five boron doses (0 to 3,0 mg dm-3, as borax (11% B, applied in the subtract constituted by the mixture of 75% of soil and 25% of manure bovine, in the randomized blocks design, with four repetitions. The experimental unit was constituted of three recipient containing three seedlings. It was evaluated height and the diameter of the stem of the seedlings, besides the mass of the matter evaporates and the areas of the root system and aerial part. The increase of the levels of nitrogen resulted in smaller growth of the seedlings. The application of 3 mg dm-3 of the boron provided the largest growth of the aerial parts and root.Key-words: Spondias tuberosa, mixture, fertilization

  12. Determination of nitrogen in boron carbide by instrumental photon activation analysis.

    Science.gov (United States)

    Merchel, Silke; Berger, Achim

    2007-05-01

    Boron carbide is widely used as industrial material, because of its extreme hardness, and as a neutron absorber. As part of a round-robin exercise leading to certification of a new reference material (ERM-ED102) which was demanded by the industry we analysed nitrogen in boron carbide by inert gas fusion analysis (GFA) and instrumental photon activation analysis (IPAA) using the 14N(gamma,n)13N nuclear reaction. The latter approach is the only non-destructive method among all the methods applied. By using photons with energy below the threshold of the 12C(gamma,n)11C reaction, we hindered activation of matrix and other impurities. A recently installed beam with a very low lateral activating flux gradient enabled us to homogeneously activate sample masses of approximately 1 g. Taking extra precautions, i.e. self-absorption correction and deconvolution of the complex decay curves, we calculated a nitrogen concentration of 2260+/-100 microg g-1, which is in good agreement with our GFA value of 2303+/-64 microg g-1. The values are the second and third highest of a rather atypical (non-S-shape) distribution of data of 14 round-robin participants. It is of utmost importance for the certification process that our IPAA value is the only one not produced by inert gas fusion analysis and, therefore, the only one which is not affected by a possible incomplete release of nitrogen from high-melting boron carbide.

  13. Convert Graphene Sheets to Boron Nitride and Boron Nitride-Carbon Sheets via a Carbon-Substitution-Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Han, W.; Yu, H.-G.; Liu. Z.

    2011-05-16

    Here we discuss our synthesis of highly crystalline pure boron nitride (BN) and BN-carbon (BN-C) sheets by using graphene sheets as templates via a carbon-substitution reaction. Typically, these sheets are several micrometers wide and have a few layers. The composition ratios of BN-C sheets can be controlled by the post-treatment (remove carbon by oxidation) temperature. We also observed pure BN and BN-C nanoribbons. We characterized the BN-C sheets via Raman spectroscopy and density functional theory calculations. The results reveal that BN-C sheets with an armchair C-BN chain, and embedded C{sub 2} or C{sub 6} units in BN-dominated regions energetically are the most favorable.

  14. Carbon-nitrogen interactions in forest ecosystems

    DEFF Research Database (Denmark)

    Gundersen, Per; Berg, Bjørn; Currie, W.S.;

    This report is a summary of the main results from the EU project “CarbonNitrogen Interactions in Forest Ecosystems” (CNTER). Since carbon (C) and nitrogen (N) are bound together in organic matter we studied both the effect of N deposition on C cycling in forest ecosystems, and the effect of C...... accumulation on N storage and release. Based on compiled databases on element pools and fluxes from several hundred forest sites, process studies in long-term nitrogen manipulation experiments and modelling efforts we estimated C sequestration and N retention in European forest soils. Further, we studied...... the impact of forest management on C sequestration, N retention and N leaching....

  15. Resonance of graphene nanoribbons doped with nitrogen and boron: a molecular dynamics study

    Directory of Open Access Journals (Sweden)

    Ye Wei

    2014-05-01

    Full Text Available Based on its enticing properties, graphene has been envisioned with applications in the area of electronics, photonics, sensors, bio-applications and others. To facilitate various applications, doping has been frequently used to manipulate the properties of graphene. Despite a number of studies conducted on doped graphene regarding its electrical and chemical properties, the impact of doping on the mechanical properties of graphene has been rarely discussed. A systematic study of the vibrational properties of graphene doped with nitrogen and boron is performed by means of a molecular dynamics simulation. The influence from different density or species of dopants has been assessed. It is found that the impacts on the quality factor, Q, resulting from different densities of dopants vary greatly, while the influence on the resonance frequency is insignificant. The reduction of the resonance frequency caused by doping with boron only is larger than the reduction caused by doping with both boron and nitrogen. This study gives a fundamental understanding of the resonance of graphene with different dopants, which may benefit their application as resonators.

  16. 造礁珊瑚碳、氮、硼同位素的海洋酸化指示意义%Isotopes ofCarbon, Nitrogen,Boron inReef Coral asProxies ofOcean Acidification

    Institute of Scientific and Technical Information of China (English)

    韩韬; 余克服; 陶士臣

    2016-01-01

    Ocean acidification, caused by the increasing atmospheric CO2levels, has not only decreased seawater pH, but also changed the carbonate equilibrium so that the aragonite saturation state has decreased, which has lead to the decrease of calcification rates. Researches show thatd13C,d11B andd15N of the coral skeleton have the capacity of recording Suess Effect, productivity, seawater pH and nutrient source. The main characteristics are: itsd11Brecords seawater pH,d13C records sea waterdissolved inorganic carbon(DIC)d13C and productivity, andd15N records terrestrial input. The combination of those proxies can indicate “the shelf carbon pumping” of the South China Sea and the coastal pollution effects on ocean acidification. However, researches on records of ocean acidification in coral reefs are insufficient, our understanding of ocean acidification, climate variability and global carbon, nitrogen cycle can be deepened by the application of such combination, which may be an important tool of revealing sea water pH change regularity.%大气CO2体积分数升高导致的海洋酸化不仅会降低海水pH,还会改变其碳酸盐平衡体系,使得海水中文石饱和度(Ω)降低,相应地会降低珊瑚钙化的速率。已有研究表明:珊瑚骨骼δ13C、δ11B和δ15N具有记录Suess Effect、生物生产力、海水pH值以及营养源的能力;主要表现为:δ11B记录的pH值、δ13C记录的海水无机碳库(DIC)δ13C和生物生产力,以及δ15N记录的陆源物质输送量相结合,可用来指示受季风影响的南海“大陆架碳泵”和近海污染与海洋酸化的联系。目前关于珊瑚对海洋酸化的记录研究仍相对较少,珊瑚碳-氮-硼同位素组合的应用将会加深对于海洋酸化与气候变率和全球碳、氮循环的关系的认识,可能成为揭示海水pH值变化规律性的重要手段。

  17. Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide

    Science.gov (United States)

    2015-06-01

    ARL-TR-7318 ● JUNE 2015 US Army Research Laboratory Effect of Carbon Doping on the Electronic Structure and Elastic Properties...Laboratory Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide by Amol B Rahane and Vijay Kumar Dr...SUBTITLE Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  18. Effect of boron on hot strips of low carbon steel produced by compact strip production

    Institute of Scientific and Technical Information of China (English)

    Hao Yu; Yonglin Kang

    2008-01-01

    The effect of boron on hot strips of low carbon steel produced by compact strip production (CSP) to reduce the strength to a certain degree was investigated, which is quite different from that of high-strength low alloy steel. The mechanical properties and microstructural evolution of the hot strip were studied using optical microscopy and tensile tests. By means of an electrolytic disso- lution technique and Thermo-Cal calculation, the precipitates containing boron were analyzed and detected. From the electron back- scattered diffraction analysis, it can be deciphered whether the microstructure has recrystallized or not. Furthermore, the effect of boron segregation on the recrystallization or non-recrystallization conditions can be distinguished. The segregation behavior of boron was investigated in boron-containing steel. The nonequilibrium segregation of boron during processing was discussed on the basis of the forming complexes with vacancies that migrate to the boundaries prior to annihilation, which was confirmed by the subsequent cold rolling with annealing experiments.

  19. Flame retardant finishing of cotton fabric based on synergistic compounds containing boron and nitrogen.

    Science.gov (United States)

    Xie, Kongliang; Gao, Aiqin; Zhang, Yongsheng

    2013-10-15

    Boric acid and compound containing nitrogen, 2,4,6-tri[(2-hydroxy-3-trimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-HTAC) were used to finish cotton fabric. The flame retardant properties of the finished cotton fabrics and the synergetic effects of boron and nitrogen elements were investigated and evaluated by limited oxygen index (LOI) method. The mechanism of cross-linking reaction among cotton fiber, Tri-HTAC, and boric acid was discussed by FTIR and element analysis. The thermal stability and surface morphology of the finished cotton fabrics were investigated by thermogravimetric analysis (TGA) and scanning electron microscope (SEM), respectively. The finishing system of the mixture containing boron and nitrogen showed excellent synergistic flame retardancy for cotton fabric. The cotton fabric finished with mixture system had excellent flame retardancy. The LOI value of the treated cotton fabric increased over 27.5. Tri-HTAC could form covalent bonds with cellulose fiber and boric acid. The flame retardant cotton fabric showed a slight decrease in tensile strength and whiteness. The surface morphology of flame retardant cotton fiber was smooth.

  20. Modelling the carbon and nitrogen cycles

    Directory of Open Access Journals (Sweden)

    Costas A Varotsos

    2014-04-01

    Full Text Available The issues of air pollution are inextricably linked to the mechanisms underlying the physicochemical functioning of the biosphere which together with the atmosphere, the cryosphere, the lithosphere, and the hydrosphere constitute the climate system. We herewith present a review of the achievements and unresolved problems concerning the modeling of the biochemical cycles of basic chemicals of the climate system, such as carbon and nitrogen. Although the achievements in this area can roughly describe the carbon and nitrogen cycles, serious problems still remain associated with the accuracy and precision of the processes and assessments employed in the relevant modeling.

  1. On The Cosmic Origins Of Carbon & Nitrogen

    CERN Document Server

    Henry, R B C; Köppen, J

    2001-01-01

    We employ analytical and numerical chemical evolution models to study observed trends in abundance ratios involving carbon, nitrogen, and oxygen. Several sets of published stellar yields for both intermediate-mass and massive stars are considered, and the most appropriate sets are selected through the use of analytical models. These yields are then used in the numerical models to match observed data trends in C/O, N/O, and O/H. We conclude that the principal production site for carbon is massive stars, while that for nitrogen is intermediate-mass stars.

  2. Worldwide organic soil carbon and nitrogen data

    Energy Technology Data Exchange (ETDEWEB)

    Zinke, P.J.; Stangenberger, A.G. [Univ. of California, Berkeley, CA (United States). Dept. of Forestry and Resource Management; Post, W.M.; Emanual, W.R.; Olson, J.S. [Oak Ridge National Lab., TN (United States)

    1986-09-01

    The objective of the research presented in this package was to identify data that could be used to estimate the size of the soil organic carbon pool under relatively undisturbed soil conditions. A subset of the data can be used to estimate amounts of soil carbon storage at equilibrium with natural soil-forming factors. The magnitude of soil properties so defined is a resulting nonequilibrium values for carbon storage. Variation in these values is due to differences in local and geographic soil-forming factors. Therefore, information is included on location, soil nitrogen content, climate, and vegetation along with carbon density and variation.

  3. Gap state related blue light emitting boron-carbon core shell structures

    Science.gov (United States)

    Singh, Paviter; Kaur, Manpreet; Singh, Bikramjeet; Kaur, Gurpreet; Singh, Kulwinder; Kumar, Manjeet; Bala, Rajni; Thakur, Anup; Kumar, Akshay

    2016-05-01

    Boron- carbon core shell structures have been synthesized by solvo-thermal synthesis route. The synthesized material is highly pure. X-ray diffraction analysis confirms the reduction of reactants in to boron and carbon. Scanning Electron Microscopy (SEM) analysis showed that the shell is uniform with average thickness of 340 nm. Photo luminescence studies showed that the material is blue light emitting with CIE color coordinates: x=0.16085, y=0.07554.

  4. Boron carbide coating deposition on tungsten substrates from atomic fluxes of boron and carbon

    Science.gov (United States)

    Sadovskiy, Y.; Begrambekov, L.; Ayrapetov, A.; Gretskaya, I.; Grunin, A.; Dyachenko, M.; Puntakov, N.

    2016-09-01

    A device used for both coating deposition and material testing is presented in the paper. By using lock chambers, sputtering targets are easily exchanged with sample holder thus allowing testing of deposited samples with high power density electron or ion beams. Boron carbide coatings were deposited on tungsten samples. Methods of increasing coating adhesion are described in the paper. 2 μm boron carbide coatings sustained 450 heating cycles from 100 to 900 C. Ion beam tests have shown satisfactory results.

  5. New Pathways and Metrics for Enhanced, Reversible Hydrogen Storage in Boron-Doped Carbon Nanospaces

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifer, Peter [University of Missouri; Wexler, Carlos [University of Missouri; Hawthorne, M. Frederick [University of Missouri; Lee, Mark W. [University of Missouri; Jalistegi, Satish S. [University of Missouri

    2014-08-14

    This project, since its start in 2007—entitled “Networks of boron-doped carbon nanopores for low-pressure reversible hydrogen storage” (2007-10) and “New pathways and metrics for enhanced, reversible hydrogen storage in boron-doped carbon nanospaces” (2010-13)—is in support of the DOE's National Hydrogen Storage Project, as part of the DOE Hydrogen and Fuel Cells Program’s comprehensive efforts to enable the widespread commercialization of hydrogen and fuel cell technologies in diverse sectors of the economy. Hydrogen storage is widely recognized as a critical enabling technology for the successful commercialization and market acceptance of hydrogen powered vehicles. Storing sufficient hydrogen on board a wide range of vehicle platforms, at energy densities comparable to gasoline, without compromising passenger or cargo space, remains an outstanding technical challenge. Of the main three thrust areas in 2007—metal hydrides, chemical hydrogen storage, and sorption-based hydrogen storage—sorption-based storage, i.e., storage of molecular hydrogen by adsorption on high-surface-area materials (carbons, metal-organic frameworks, and other porous organic networks), has emerged as the most promising path toward achieving the 2017 DOE storage targets of 0.055 kg H2/kg system (“5.5 wt%”) and 0.040 kg H2/liter system. The objective of the project is to develop high-surface-area carbon materials that are boron-doped by incorporation of boron into the carbon lattice at the outset, i.e., during the synthesis of the material. The rationale for boron-doping is the prediction that boron atoms in carbon will raise the binding energy of hydro- gen from 4-5 kJ/mol on the undoped surface to 10-14 kJ/mol on a doped surface, and accordingly the hydro- gen storage capacity of the material. The mechanism for the increase in binding energy is electron donation from H2 to electron-deficient B atoms, in the form of sp2 boron-carbon bonds. Our team is proud to have

  6. Boron Nitride Nanotubes

    Science.gov (United States)

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

    2012-01-01

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  7. Synthesis and characterization of boron incorporated diamond-like carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, L.L. [Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK S7N 5A9 (Canada); Yang, Q., E-mail: qiaoqin.yang@usask.ca [Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK S7N 5A9 (Canada); Tang, Y.; Yang, L.; Zhang, C. [Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK S7N 5A9 (Canada); Hu, Y.; Cui, X. [Canadian Light Source Inc., 101 Perimeter Road, Saskatoon, SK S7N 0X4 (Canada)

    2015-08-31

    Boron incorporated diamond-like carbon (B-DLC) (up to 8 wt.% boron) thin films were synthesized on silicon wafers using biased target ion beam deposition technique, where diamond-like carbon (DLC) was deposited by ion beam deposition and boron (B) was simultaneously incorporated by biased target sputtering of a boron carbide (B{sub 4}C) target under different conditions. Pure DLC films and B–C films were also synthesized by ion beam deposition and biased target sputtering of B{sub 4}C under similar conditions, respectively, as reference samples. The microstructure and mechanical properties of the synthesized films have been characterized by various technologies. It has been found that B exists in different states in B-DLC, including carbon-rich and B-rich boron carbides, boron suboxide and boron oxide, and the oxidation of B probably occurs during the film deposition. The incorporation of B into DLC leads to the increase of sp{sup 3} bonded carbon in the films, the increase of both film hardness and elastic modulus, and the decrease of both surface roughness and friction coefficient. Furthermore, the content of sp{sup 3} bonded carbon, film hardness and elastic modulus increase, and the film surface roughness and friction coefficient decrease with the increase of B-rich carbide in the B-DLC films. - Highlights: • Biased target ion beam deposition technique is promising to produce high quality DLC based thin films; • Boron exists in different states in B-DLC thin films; • The incorporation of B to DLC with different levels leads to improved film properties; • The fraction of sp{sup 3} bonded C in B-DLC thin films increase with the increase of B-rich carbide content in the films.

  8. Irradiation studies on carbon nanotube-reinforced boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    Aitkaliyeva, Assel [Department of Materials Science and Engineering, Texas A and M University, College Station, TX 77843 (United States); McCarthy, Michael C.; Jeong, Hae-Kwon [Artie McFerrin Department of Chemical Engineering, Texas A and M University, College Station, TX 77843 (United States); Shao, Lin, E-mail: lshao@ne.tamu.edu [Department of Materials Science and Engineering, Texas A and M University, College Station, TX 77843 (United States); Department of Nuclear Engineering, Texas A and M University, College Station, TX 77843 (United States)

    2012-02-01

    Radiation response of carbon nanotube (CNT) reinforced boron carbide composite has been studied for its application as a structural component in nuclear engineering. The composite was bombarded by 140 keV He ions at room temperature to a fluence ranging from 1 Multiplication-Sign 10{sup 14} to 1 Multiplication-Sign 10{sup 17} cm{sup -2}. Two-dimensional Raman mapping shows inhomogeneous distribution of CNTs, and was used to select regions of interest for damage characterization. For CNTs, the intensities ratio of D-G bands (I{sub D}/I{sub G}) increased with fluence up to a certain value, and decreased at the fluence of 5 Multiplication-Sign 10{sup 16} cm{sup -2}. This fluence also corresponds to a trend break in the plot of FWHM (full width at half maximum) of G band vs. I{sub D}/I{sub G} ratio, which indicates amorphization of CNTs. The study shows that Raman spectroscopy is a powerful tool to quantitatively characterize radiation damage in CNT-reinforced composites.

  9. Simulation of swift boron clusters traversing amorphous carbon foils

    Science.gov (United States)

    Heredia-Avalos, Santiago; Abril, Isabel; Denton, Cristian D.; Garcia-Molina, Rafael

    2007-01-01

    We use a simulation code to study the interaction of swift boron clusters ( Bn+ , n=2-6 , 14) with amorphous carbon foils. We analyze different aspects of this interaction, such as the evolution of the cluster structure inside the target, the energy and angle distributions at the detector or the stopping power ratio. Our simulation code follows in detail the motion of the cluster fragments through the target and in the vacuum until reaching a detector, taking into account the following interactions: (i) wake force, (ii) Coulomb repulsion among cluster fragments, (iii) stopping force, and (iv) elastic scattering with the target nuclei. Electron capture and loss by each fragment is also included in the code, affecting the above-mentioned interactions. The clusters size grows inside the foil due mainly to the Coulomb explosion but this increase is less pronounced in the plane transversal to the beam direction because of the alignment effect of the wake forces. We obtain an enhancement of the stopping power ratio that increases with the projectile energy and with the number of molecular constituents. Our results agree very well with the available experimental data for the thicker foils (≳10μg/cm2) and are compatible (within the experimental error bars) for the thinner foils.

  10. Effect of water stress and foliar boron application on seed protein oil fatty acids and nitrogen metabolism in soybean

    Science.gov (United States)

    Effects of water stress and foliar boron (FB) application on soybean (Glycine max (L) Merr.) seed composition and nitrogen metabolism have not been well investigated. Therefore, the objective of this study was to investigate the effects of water stress and FB on seed protein, oil, fatty acids, nitra...

  11. Stereocontrolled synthesis of 1,5-stereogenic centers through three-carbon homologation of boronic esters.

    Science.gov (United States)

    Unsworth, Phillip J; Leonori, Daniele; Aggarwal, Varinder K

    2014-09-08

    Allylic pinacol boronic esters are stable toward 1,3-borotropic rearrangement. We developed a Pd(II)-mediated isomerization process that gives di- or trisubstituted allylic boronic esters with high E selectivity. The combination of this method with lithiation-borylation enables the synthesis of carbon chains that bear 1,5-stereogenic centers. The utility of this method has been demonstrated in a formal synthesis of (+)-jasplakinolide.

  12. Synthesis of boron carbide nanoflakes via a bamboo-based carbon thermal reduction method

    Energy Technology Data Exchange (ETDEWEB)

    Du, Jun [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China); Li, Qianqian [Institute of Applied Mechanics, Zhejiang University, Hangzhou 310027 (China); Xia, Yang; Cheng, Xuejuan; Gan, Yongping; Huang, Hui [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China); Zhang, Wenkui, E-mail: msechem@zjut.edu.cn [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China); Tao, Xinyong, E-mail: tao@zjut.edu.cn [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China)

    2013-12-25

    Graphical abstract: B{sub 4}C nanoflakes were synthesized via a facile and cost-effective bamboo-based carbon thermal reduction method. Highlights: •Boron carbide nanoflakes were successfully synthesized via a bamboo-based carbon thermal reduction method. •A fluoride-assisted VLS nucleation and VS growth mechanism were proposed. •We studied the resistivity of boron carbide nanoflakes via in situ TEM techniques for the first time. -- Abstract: Boron carbide nanoflakes have been successfully synthesized by a facile and cost-effective bamboo-based carbon thermal reduction method. The majority of the boron carbide products exhibited a flake-like morphology with lateral dimensions of 0.5–50 μm in width and more than 50 μm in length, while the thickness was less than 150 nm. The structural, morphological, and elemental analyses demonstrated that these nanoflakes grew via the fluoride-assisted vapor–liquid–solid combined with vapor–solid growth mechanism. The corresponding growth model was proposed. In addition, the electrical property of individual boron carbide nanoflake was investigated by an in situ two point method inside a transmission electron microscope. The resistivity of boron carbide nanoflakes was measured to be 0.14 MΩ cm.

  13. Melting and spheroidization of hexagonal boron nitride in a microwave-powered, atmospheric pressure nitrogen plasma `

    Energy Technology Data Exchange (ETDEWEB)

    Gleiman, S. S. (Seth S.); Phillips, J. (Jonathan)

    2001-01-01

    We have developed a method for producing spherically-shaped, hexagonal phase boron nitride (hBN) particles of controlled diameter in the 10-100 micron size range. Specifically, platelet-shaped hBN particles are passed as an aerosol through a microwave-generated, atmospheric pressure, nitrogen plasma. In the plasma, agglomerates formed by collisions between input hBN particles, melt and forms spheres. We postulate that this unprecedented process takes place in the unique environment of a plasma containing a high N-atom concentration, because in such an environment the decomposition temperature can be raised above the melting temperature. Indeed, given the following relationship [1]: BN{sub (condensed)} {leftrightarrow} B{sub (gas)} + N{sub (gas)}. Standard equilibrium thermodynamics indicate that the decomposition temperature of hBN is increased in the presence of high concentrations of N atoms. We postulate that in our plasma system the N atom concentration is high enough to raise the decomposition temperature above the (undetermined) melting temperature. Keywords Microwave plasma, boron nitride, melting, spherical, thermodynamics, integrated circuit package.

  14. Soil Carbon and Nitrogen Cycle Modeling

    Science.gov (United States)

    Woo, D.; Chaoka, S.; Kumar, P.; Quijano, J. C.

    2012-12-01

    Second generation bioenergy crops, such as miscanthus (Miscantus × giganteus) and switchgrass (Panicum virgatum), are regarded as clean energy sources, and are an attractive option to mitigate the human-induced climate change. However, the global climate change and the expansion of perennial grass bioenergy crops have the power to alter the biogeochemical cycles in soil, especially, soil carbon storages, over long time scales. In order to develop a predictive understanding, this study develops a coupled hydrological-soil nutrient model to simulate soil carbon responses under different climate scenarios such as: (i) current weather condition, (ii) decreased precipitation by -15%, and (iii) increased temperature up to +3C for four different crops, namely miscanthus, switchgrass, maize, and natural prairie. We use Precision Agricultural Landscape Modeling System (PALMS), version 5.4.0, to capture biophysical and hydrological components coupled with a multilayer carbon and ¬nitrogen cycle model. We apply the model at daily time scale to the Energy Biosciences Institute study site, located in the University of Illinois Research Farms, in Urbana, Illinois. The atmospheric forcing used to run the model was generated stochastically from parameters obtained using available data recorded in Bondville Ameriflux Site. The model simulations are validated with observations of drainage and nitrate and ammonium concentrations recorded in drain tiles during 2011. The results of this study show (1) total soil carbon storage of miscanthus accumulates most noticeably due to the significant amount of aboveground plant carbon, and a relatively high carbon to nitrogen ratio and lignin content, which reduce the litter decomposition rate. Also, (2) the decreased precipitation contributes to the enhancement of total soil carbon storage and soil nitrogen concentration because of the reduced microbial biomass pool. However, (3) an opposite effect on the cycle is introduced by the increased

  15. Electronic properties of graphene nanoribbon doped by boron/nitrogen pair: a first-principles study

    Institute of Scientific and Technical Information of China (English)

    Xiao Jin; Yang Zhi-Xiong; Xie Wei-Tao; Xiao Li-Xin; Xu Hui; OuYang Fang-Ping

    2012-01-01

    By using the first-principles calculations,the electronic properties of graphene nanoribbon (GNR) doped by boron/nitrogen (B/N) bonded pair are investigated. It is found that B/N bonded pair tends to be doped at the edges of GNR and B/N pair doping in GNR is easier to carry out than single B doping and unbonded B/N co-doping in GNR.The electronic structure of GNR doped by B/N pair is very sensitive to doping site besides the ribbon width and chirality. Moreover,B/N pair doping can selectively adjust the energy gap of armchair GNR and can induce the semimetal-semiconductor transmission for zigzag GNR.This fact may lead to a possible method for energy band engineering of GNRs and benefit the design of graphene electronic device.

  16. Pentagonal monolayer crystals of carbon, boron nitride, and silver azide

    Energy Technology Data Exchange (ETDEWEB)

    Yagmurcukardes, M., E-mail: mehmetyagmurcukardes@iyte.edu.tr; Senger, R. T., E-mail: tugrulsenger@iyte.edu.tr [Department of Physics, Izmir Institute of Technology, 35430 Urla, Izmir (Turkey); Sahin, H.; Kang, J.; Torun, E.; Peeters, F. M. [Department of Physics, University of Antwerp, Campus Groenenborgerlaan, 2020, Antwerp (Belgium)

    2015-09-14

    In this study, we present a theoretical investigation of structural, electronic, and mechanical properties of pentagonal monolayers of carbon (p-graphene), boron nitride (p-B{sub 2}N{sub 4} and p-B{sub 4}N{sub 2}), and silver azide (p-AgN{sub 3}) by performing state-of-the-art first principles calculations. Our total energy calculations suggest feasible formation of monolayer crystal structures composed entirely of pentagons. In addition, electronic band dispersion calculations indicate that while p-graphene and p-AgN{sub 3} are semiconductors with indirect bandgaps, p-BN structures display metallic behavior. We also investigate the mechanical properties (in-plane stiffness and the Poisson's ratio) of four different pentagonal structures under uniaxial strain. p-graphene is found to have the highest stiffness value and the corresponding Poisson's ratio is found to be negative. Similarly, p-B{sub 2}N{sub 4} and p-B{sub 4}N{sub 2} have negative Poisson's ratio values. On the other hand, the p-AgN{sub 3} has a large and positive Poisson's ratio. In dynamical stability tests based on calculated phonon spectra of these pentagonal monolayers, we find that only p-graphene and p-B{sub 2}N{sub 4} are stable, but p-AgN{sub 3} and p-B{sub 4}N{sub 2} are vulnerable against vibrational excitations.

  17. Nitrogen and Carbon Dynamics Across Trophic Levels Along an Atmospheric Nitrogen Deposition Gradient

    Science.gov (United States)

    Wissinger, B. D.; Bell, M. D.; Newingham, B. A.

    2011-12-01

    Atmospheric nitrogen deposition has altered soil biogeochemical processes and plant communities across the United States. Prior investigations have demonstrated these alterations; however, little is known about the effects of elevated nitrogen on higher trophic levels. Building upon previous research that revealed an atmospheric nitrogen deposition gradient from the San Bernardino Mountains through Joshua Tree National Park in California, we investigated atmospheric nitrogen and its effects on soils, plants, and harvester ants. We measured nitrogen and carbon concentrations, along with carbon and nitrogen stable isotopes, across trophic levels at eighteen urban and unpopulated sites along the deposition gradient. Carbon and nitrogen attributes were determined in atmospheric nitric acid, soil, Larrea tridentata and Ambrosia dumosa leaves, seeds from selected plant species, and ants. We predicted carbon and nitrogen ratios and isotopes to change in areas with higher nitrogen deposition and vary along the deposition gradient. Nitrogen (p=0.02) and carbon (p=0.05) concentrations, as well as C:N ratios (p=<0.001), significantly differed in Messor pergandei individuals among sites; however, no correlation was found between these carbon and nitrogen attributes and the nitrogen deposition gradient (%N r2=0.02, %C r2=0.007, C:N r2=0.02). The δ15N and δ13C values of the ants, leaf tissues, and seeds measured across the gradient follow similar patterns with r2 values all below 0.20. Our results suggest the current and previous rates of nitrogen deposition in this area are not enough to modify nitrogen and carbon concentrations and isotope values. Compensatory nitrogen cycling processes in the soil may reduce the effects of increased nitrogen on plants and thus higher trophic levels. Nitrogen and carbon dynamics across trophic levels might change after longer ecosystem exposure to elevated nitrogen; however, other abiotic and biotic factors are likely driving current

  18. Residual stresses in boron/tungsten and boron/carbon fibers

    Science.gov (United States)

    Behrendt, D. R.

    1977-01-01

    By measuring the change in fracture stress of 203 micrometer diameter fibers of boron on tungsten (B/W) as a function of fiber diameter as reduced by chemical etching, it is shown that the flaws which limit B/W fiber strength are located at the surface and in the tungsten boride core. After etching to a diameter of 188 micrometers m virtually all fiber fractures were caused by core flaws, the average strength being 4.50 GN/sq m. If both the surface and core flaws are removed, the fracture strength, limited by flaws in the boron itself, is approximately 6.89 GN/sq m. This was measured on B/W fibers which were split longitudinally and had their cores removed by chemical etching. The longitudinal residual stress distribution was determined for 102 micrometer diameter B/W and B/C fibers.

  19. Mechanism of intracellular detection of glucose through nonenzymatic and boronic acid functionalized carbon dots.

    Science.gov (United States)

    Kiran, S; Misra, R D K

    2015-09-01

    The objective of the research described here is to elucidate the fundamental mechanism by which the new class of "inert" non-enzymatic and boronic acid functionalized carbon dots-based sensors facilitate intracellular detection of glucose. The study suggests that the mechanism of detection of glucose involved selective assembly and fluorescence quenching of the carbon dots with excellent dynamic response to varying concentration of glucose within the biological range (1-100 mM). The strong dynamic response was related to high selectivity to biomolecules and inertness of carbon dots. Furthermore, the functionalization of carbon dots with boronic acid was the governing factor response for the passive character of the carbon dots. The study lays the foundation for the new field of carbon-based nanochemosensors.

  20. Folate receptor-mediated boron-10 containing carbon nanoparticles as potential delivery vehicles for boron neutron capture therapy of nonfunctional pituitary adenomas.

    Science.gov (United States)

    Dai, Congxin; Cai, Feng; Hwang, Kuo Chu; Zhou, Yongmao; Zhang, Zizhu; Liu, Xiaohai; Ma, Sihai; Yang, Yakun; Yao, Yong; Feng, Ming; Bao, Xinjie; Li, Guilin; Wei, Junji; Jiao, Yonghui; Wei, Zhenqing; Ma, Wenbin; Wang, Renzhi

    2013-02-01

    Invasive nonfunctional pituitary adenomas (NFPAs) are difficult to completely resect and often develop tumor recurrence after initial surgery. Currently, no medications are clinically effective in the control of NFPA. Although radiation therapy and radiosurgery are useful to prevent tumor regrowth, they are frequently withheld because of severe complications. Boron neutron capture therapy (BNCT) is a binary radiotherapy that selectively and maximally damages tumor cells without harming the surrounding normal tissue. Folate receptor (FR)-targeted boron-10 containing carbon nanoparticles is a novel boron delivery agent that can be selectively taken up by FR-expressing cells via FR-mediated endocytosis. In this study, FR-targeted boron-10 containing carbon nanoparticles were selectively taken up by NFPAs cells expressing FR but not other types of non-FR expressing pituitary adenomas. After incubation with boron-10 containing carbon nanoparticles and following irradiation with thermal neutrons, the cell viability of NFPAs was significantly decreased, while apoptotic cells were simultaneously increased. However, cells administered the same dose of FR-targeted boron-10 containing carbon nanoparticles without neutron irradiation or received the same neutron irradiation alone did not show significant decrease in cell viability or increase in apoptotic cells. The expression of Bcl-2 was down-regulated and the expression of Bax was up-regulated in NFPAs after treatment with FR-mediated BNCT. In conclusion, FR-targeted boron-10 containing carbon nanoparticles may be an ideal delivery system of boron to NFPAs cells for BNCT. Furthermore, our study also provides a novel insight into therapeutic strategies for invasive NFPA refractory to conventional therapy, while exploring these new applications of BNCT for tumors, especially benign tumors.

  1. Synthesis and oxidation behavior of boron-substituted carbon powders by hot filament chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Boron-substituted carbon powder, BxC1-x with x up to 0.17, has been successfully synthesized by hot filament chemical vapor deposition. The boron concentration in prepared BxC1-x samples can be controlled by varying the relative proportions of methane and diborane. X-ray diffraction, transmission electron microscopy, and electron energy loss spectrum confirm the successful synthesis of an amorphous BC5 compound, which consists of 10―20 nm particles with disk-like morphology. Thermogravimetry measurement shows that BC5 compound starts to oxidize ap-proximately at 620℃ and has a higher oxidation resistance than carbon.

  2. Modeling boron separation from water by activated carbon, impregnated and unimpregnated

    Energy Technology Data Exchange (ETDEWEB)

    Ristic, M.; Grbavcic, Z. [Belgrade Univ., Belgrade (BA). Faculty of Technology and Metallurgy; Marinovic, V. [Belgrade Univ., Belgrade (BA). Ist. of Technical Science of the Serbian Academy of Science and Arts

    2000-10-01

    The sorption of boron from boric acid water solution by impregnated activated carbon has been studied. Barium, calcium, mannitol, tartaric acid and citric acid were used as chemical active materials. All processes were performed in a chromatographic continuous system at 22{sup 0} C. Experimental results show that activated carbon impregnated with mannitol is effective in removing boron from water. The separation of boron from the wastewater from a factory for producing enameled dishes by activated carbon impregnated with mannitol was also performed. Two models have been applied to describe published and new data on boron sorption by impregnated activated carbon. Both of them are based on the analysis of boron concentration response to the step input function. This led to a mathematical model that quite successfully described impregnation effects on adsorption capacities. [Italian] E' stato studiato l'assorbimento del boro, mediante carbone attivo impregnato, da soluzioni acquose di acido borico. Quali materiali chimici attivi sono stati utilizzati: bario, calcio, mannitolo, acido tartarico ed acido citrico. Tutti i processi sono stati condotti in un sistema cromatografico continuo a 22{sup 0}C. I risultati sperimentali mostrano che il carbone attivo impregnato con mannitolo e' efficace nella rimozione del boro dall'acqua. E' anche stata effettuata la separazione del boro da acque di scarico di un'industria per la produzione di piatti smaltati mediante carbone attivo impregnato con mannitolo. Sono stati applicati due modelli per descrivere i risultati, pubblicati e nuovi, dell'assorbimento del boro mediante carbone attivo impregnato. Entrambi sono basati sull'analisi della risposta alla concentrazione di boro successivamente incrementata a stadi. Cio' porta ad un modello matematico che descrive abbastanza soddisfacentemente gli effetti dell'impregnazione sulla capacita' di assorbimento.

  3. Boron-doped MnO{sub 2}/carbon fiber composite electrode for supercapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Hong Zhong, E-mail: hzchi@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Zhu, Hongjie [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Gao, Linhui [Center of Materials Engineering, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

    2015-10-05

    Highlights: • Interstitial ion in MnO{sub 2} lattice. • Porous film composed by interlocking worm-like nanostructure. • Boron-doped birnessite-type MnO{sub 2}/carbon fiber composite electrode. • Enhanced capacitive properties through nonmetal element doping. - Abstract: The boron-doped MnO{sub 2}/carbon fiber composite electrode has been prepared via in situ redox reaction between potassium permanganate and carbon fibers in the presence of boric acid. The addition of boron as dopant results in the increase of growth-rate of MnO{sub 2} crystal and the formation of worm-like nanostructure. Based on the analysis of binding energy, element boron incorporates into the MnO{sub 2} lattice through interstitial mode. The doped electrode with porous framework is beneficial to pseudocapacitive reaction and surface charge storage, leading to higher specific capacitance and superior rate capability. After experienced 1000 cycles, the boron-doped MnO{sub 2} still retain a higher specific capacitance by about 80% of its initial value. The fall in capacitance is blamed to be the combination of the formation of soluble Mn{sup 2+} and the absence of active site on the outer surface.

  4. Multicolor Nitrogen-Doped Carbon Dots for Live Cell Imaging.

    Science.gov (United States)

    Du, Fengyi; Li, Jianan; Hua, Ye; Zhang, Miaomiao; Zhou, Zhou; Yuan, Jing; Wang, Jun; Peng, Wanxin; Zhang, Li; Xia, Sheng; Wang, Dongqing; Yang, Shiming; Xu, Wenrong; Gong, Aihua; Shao, Qixiang

    2015-05-01

    Doping carbon dots with nitrogen atoms considerably enhances their fluorescence properties. However, the mechanism by which the carbon dots are doped is not fully understood. We developed a facile bottom-up hydrothermal carbonization (HTC) process that uses glucose and glycine as precursors for the synthesis of photoluminescent nitrogen-doped carbon dots. The as-prepared nitrogen-doped carbon dots were mono-dispersed spherical particles with a diameter of -2.8 nm. The doped nitrogen atoms assumed pyridinic type and pyrrolic type configurations to participate in the nanocrystal structure of the carbon dots. It appeared that the nitrogen doping introduces a new internal structure. The aqueous solution of nitrogen-doped carbon dots showed excitation wavelength-dependent multicolor photoluminescence. Further, these nitrogen-doped carbon dots readily entered the cytoplasm of A549 cancer cells and showed no significant cytotoxicity. The internalized nitrogen-doped carbon dots were localized to the cell membrane and cytoplasm, particularly around the nucleus. Further, the as-prepared, biocompatible, nitrogen-doped carbon dots demonstrated the potential to be used as fluorescent probes for multicolor live cell labeling, tracking, and imaging.

  5. Study on Tribological Behaviors of Boron-Nitrogen Modified Fatty Acid as Water-Based Lube Additives

    Institute of Scientific and Technical Information of China (English)

    FANG Jian-hua; CHEN Bo-shui; DONG Ling; WANG Jiu

    2008-01-01

    A new type of boron-nitrogen modified fatty acid as water base lube additive was prepared and the chemical structure characterized by infrared spectrum. The tribological properties of the additive in water were evaluated by friction testers. The morphographies and tribochemical species of the worn surfaces were analyzed by means of X-ray Photoelectron Spectroscope (XPS). The results showed that the additive is excellent in increasing loadcarrying capacity, anti-wear and friction-reducing abilities of water. The lubrication mechanism is inferred that a high strength adsorption film and a tribochemical reaction film are formed on the rubbing surfaces due to the carrier effect of the long chain fatty acid molecules, high reaction activities of nitrogen, electron-deficient orbit of boron and their synergisms.

  6. Hot ductility behavior of a low carbon advanced high strength steel (AHSS) microalloyed with boron

    Energy Technology Data Exchange (ETDEWEB)

    Mejia, I., E-mail: imejia@umich.mx [Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio ' U' , Ciudad Universitaria, 58066 Morelia, Michoacan (Mexico); Bedolla-Jacuinde, A.; Maldonado, C. [Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio ' U' , Ciudad Universitaria, 58066 Morelia, Michoacan (Mexico); Cabrera, J.M. [Departament de Ciencia dels Materials i Enginyeria Metal.lurgica, ETSEIB - Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundacio CTM Centre Tecnologic, Av. de las Bases de Manresa 1, 08240 Manresa (Spain)

    2011-05-25

    Research highlights: {yields} Effect of boron on the hot ductility behavior of a low carbon NiCrVCu AHSS. {yields} Boron addition of 117 ppm improves hot ductility over 100% in terms of RA. {yields} Hot ductility improvement is associated with segregation/precipitation of boron. {yields} Typical hot ductility recovery at lower temperatures does not appear in this steel. {yields} Hot ductility loss is associated with precipitates/inclusions coupled with voids. - Abstract: The current study analyses the influence of boron addition on the hot ductility of a low carbon advanced high strength NiCrVCu steel. For this purpose hot tensile tests were carried out at different temperatures (650, 750, 800, 900 and 1000 deg. C) at a constant true strain rate of 0.001 s{sup -1}. Experimental results showed a substantial improvement in hot ductility for the low carbon advanced high strength steel when microalloyed with boron compared with that without boron addition. Nevertheless, both steels showed poor ductility when tested at the lowest temperatures (650, 750 and 800 deg. C), and such behavior is associated to the precipitation of vanadium carbides/nitrides and inclusions, particularly MnS and CuS particles. The fracture mode of the low carbon advanced high strength steel microalloyed with boron seems to be more ductile than the steel without boron addition. Furthermore, the fracture surfaces of specimens tested at temperatures showing the highest ductility (900 and 1000 deg. C) indicate that the fracture mode is a result of ductile failure, while in the region of poor ductility the fracture mode is of the ductile-brittle type failure. It was shown that precipitates and/or inclusions coupled with voids play a meaningful role on the crack nucleation mechanism which in turn causes a hot ductility loss. Likewise, dynamic recrystallization (DRX) which always results in restoration of ductility only occurs in the range from 900 to 1000 deg. C. Results are discussed in terms of

  7. Fabrication Of Carbon-Boron Reinforced Dry Polymer Matrix Composite Tape

    Science.gov (United States)

    Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

    1999-01-01

    Future generation aerospace vehicles will require specialized hybrid material forms for component structure fabrication. For this reason, high temperature composite prepregs in both dry and wet forms are being developed at NASA Langley Research Center (LaRC). In an attempt to improve compressive properties of carbon fiber reinforced composites, a hybrid carbon-boron tape was developed and used to fabricate composite laminates which were subsequently cut into flexural and compression specimens and tested. The hybrid material, given the designation HYCARB, was fabricated by modifying a previously developed process for the manufacture of dry polymer matrix composite (PMC) tape at LaRC. In this work, boron fibers were processed with IM7/LaRC(TradeMark)IAX poly(amide acid) solution-coated prepreg to form a dry hybrid tape for Automated Tow Placement (ATP). Boron fibers were encapsulated between two (2) layers of reduced volatile, low fiber areal weight poly(amide acid) solution-coated prepreg. The hybrid prepreg was then fully imidized and consolidated into a dry tape suitable for ATP. The fabrication of a hybrid boron material form for tow placement aids in the reduction of the overall manufacturing cost of boron reinforced composites, while realizing the improved compression strengths. Composite specimens were press-molded from the hybrid material and exhibited excellent mechanical properties.

  8. Processing and Properties of Distaloy Sa Sintered Alloys with Boron and Carbon

    Directory of Open Access Journals (Sweden)

    Karwan-Baczewska J.

    2015-04-01

    Full Text Available Prealloyed iron-based powders, manufactured in Höganäs Company, are used in the automotive parts industry. The properties and life time of such sintered parts depend, first of all, on their chemical composition, the production method of the prealloyed powder as well as on the technology of their consolidation and sintering. One of simpler and conventional methods aimed at increasing the density in sintered products is the process of activated sintering, performed, for example, by adding boron as elementary boron powder. Under this research project obtained were novel sintered materials, based on prealloyed and diffusion bonded powder, type: Distaloy SA, with the following chemical composition: Fe-1.75% Ni-1.5%Cu- 0.5%Mo with carbon (0.55%; 0.75% and boron (0.2%, 0.4% and 0.6%. Distaloy SA samples alloyed with carbon and boron were manufactured by mixing powders in a Turbula mixer, then compressed using a hydraulic press under a pressure of 600 MPa and sintered in a tube furnace at 1473 K, for a 60 minute time, in the hydrogen atmosphere. After the sintering process, there were performed density and porosity measurements as well as hardness tests and mechanical properties were carried out, too. Eventually, analyzed was the effect of boron upon density, hardness and mechanical properties of novel sintered construction parts made from Distaloy SA powder.

  9. In vivo biocompatibility of boron doped and nitrogen included conductive-diamond for use in medical implants.

    Science.gov (United States)

    Garrett, David J; Saunders, Alexia L; McGowan, Ceara; Specks, Joscha; Ganesan, Kumaravelu; Meffin, Hamish; Williams, Richard A; Nayagam, David A X

    2016-01-01

    Recently, there has been interest in investigating diamond as a material for use in biomedical implants. Diamond can be rendered electrically conducting by doping with boron or nitrogen. This has led to inclusion of boron doped and nitrogen included diamond elements as electrodes and/or feedthroughs for medical implants. As these conductive device elements are not encapsulated, there is a need to establish their clinical safety for use in implants. This article compares the biocompatibility of electrically conducting boron doped diamond (BDD) and nitrogen included diamond films and electrically insulating poly crystalline diamond films against a silicone negative control and a BDD sample treated with stannous octoate as a positive control. Samples were surgically implanted into the back muscle of a guinea pig for a period of 4-15 weeks, excised and the implant site sectioned and submitted for histological analysis. All forms of diamond exhibited a similar or lower thickness of fibrotic tissue encapsulating compared to the silicone negative control samples. All forms of diamond exhibited similar or lower levels of acute, chronic inflammatory, and foreign body responses compared to the silicone negative control indicating that the materials are well tolerated in vivo.

  10. RESEARCH OF INFLUENCE OF ALLOYING BY BORON ON PROPERTIES THE IRON-CARBON ALLOYS

    Directory of Open Access Journals (Sweden)

    K. V. Kobyakov

    2014-01-01

    Full Text Available It is shown that for improvement of physical-mechanical properties of the cast products which have hard usage, the boron carbide, which can be used at carrying out process of thermo-chemical treatment of cast products of iron-carbon alloy, is of great interest.

  11. The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

    Institute of Scientific and Technical Information of China (English)

    TAN Jun; CAI Zhi-hai; ZHANG Ping

    2004-01-01

    Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.

  12. Hydrogen storage in Li-doped fullerene-intercalated hexagonal boron nitrogen layers

    Science.gov (United States)

    Cheng, Yi-Han; Zhang, Chuan-Yu; Ren, Juan; Tong, Kai-Yu

    2016-10-01

    New materials for hydrogen storage of Li-doped fullerene (C20, C28, C36, C50, C60, C70)-intercalated hexagonal boron nitrogen ( h-BN) frameworks were designed by using density functional theory (DFT) calculations. First-principles molecular dynamics (MD) simulations showed that the structures of the C n -BN ( n = 20, 28, 36, 50, 60, and 70) frameworks were stable at room temperature. The interlayer distance of the h-BN layers was expanded to 9.96-13.59 Å by the intercalated fullerenes. The hydrogen storage capacities of these three-dimensional (3D) frameworks were studied using grand canonical Monte Carlo (GCMC) simulations. The GCMC results revealed that at 77 K and 100 bar (10 MPa), the C50-BN framework exhibited the highest gravimetric hydrogen uptake of 6.86 wt% and volumetric hydrogen uptake of 58.01 g/L. Thus, the hydrogen uptake of the Li-doped C n -intercalated h-BN frameworks was nearly double that of the non-doped framework at room temperature. Furthermore, the isosteric heats of adsorption were in the range of 10-21 kJ/mol, values that are suitable for adsorbing/desorbing the hydrogen molecules at room temperature. At 193 K (-80 °C) and 100 bar for the Li-doped C50-BN framework, the gravimetric and volumetric uptakes of H2 reached 3.72 wt% and 30.08 g/L, respectively.

  13. Energetic Stabilities, Structural and Electronic Properties of Monolayer Graphene Doped with Boron and Nitrogen Atoms

    Directory of Open Access Journals (Sweden)

    Seba Sara Varghese

    2016-12-01

    Full Text Available The structural, energetic, and electronic properties of single-layer graphene doped with boron and nitrogen atoms with varying doping concentrations and configurations have been investigated here via first-principles density functional theory calculations. It was found that the band gap increases with an increase in doping concentration, whereas the energetic stability of the doped systems decreases with an increase in doping concentration. It was observed that both the band gaps and the cohesive energies also depend on the atomic configurations considered for the substitutional dopants. Stability was found to be higher in N-doped graphene systems as compared to B-doped graphene systems. The electronic structures of B- and N-doped graphene systems were also found to be strongly influenced by the positioning of the dopant atoms in the graphene lattice. The systems with dopant atoms at alternate sublattices have been found to have the lowest cohesive energies and therefore form the most stable structures. These results indicate an ability to adjust the band gap as required using B and N atoms according to the choice of the supercell, i.e., the doping density and substitutional dopant sites, which could be useful in the design of graphene-based electronic and optical devices.

  14. Carbon-nitrogen interactions in forest ecosystems; final report

    NARCIS (Netherlands)

    Gundersen, P.; Berg, B.; Currie, W.S.; Dise, N.B.; Emmett, B.A.; Gauci, V.; Holmberg, M.; Kjønaas, O.J.; Mol-Dijkstra, J.P.; Salm, van der C.; Schmidt, I.K.; Tietema, A.; Wessel, W.W.; Vestgarden, L.S.; Akselsson, C.; Vries, de W.; Forsius, M.; Kros, H.; Matzner, E.; Moldan, F.; Nadelhoffer, K.J.; Nilsson, L.O.; Reinds, G.J.; Rosengren, U.; Stuanes, A.O.; Wright, R.F.

    2006-01-01

    This report is a summary of the main results from the EU project 'Carbon' - Nitrogen Interactions in Forest Ecosystems' (CNTER). Since carbon (C) and nitrogen (N) are bound together in organic matter we studied both the effect of N deposition on C cycling in forest ecosystems, and the effect of C ac

  15. First Principles Atomistic Model for Carbon-Doped Boron Suboxide

    Science.gov (United States)

    2014-09-01

    spectroscopy (EELS). J. Solid State Chem. 1997;133:365. 3. Herrmann M, Thiele M, Jaenicke-Roessler K, Freemantle CS, Sigalas I. Oxidation resistance...boron suboxide. Mater Sci and Eng A. 2011;528:5778. 5. Herrmann M, Kleebe HJ, Raethel J, Sempf K, Lauterback S, Muller MM, Sigalas I. Field...assisted densification of superhard B6O materials with Y2O3/Al2O3 addition. J Am Ceram Soc. 2009;92:2368. 6. Herrmann , M. Raethel, J. Bales, A. Sempf, K

  16. Preferential distribution and oxidation inhibiting/catalytic effects of boron in carbon fiber reinforced carbon (CFRC) composites

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.J.; Joo, H.J.; Radovic, L.R. [Penn State University, University Park, PA (United States). Dept. of Energy & Geoenvironmental Engineering, Fuel Science Program

    2003-07-01

    Two different batches of CFRC composites were prepared in the absence/presence of boron with the expectation of increasing oxidation stability and improving the processing compatibility of CFRC composites in commercial applications. The composites were examined to reveal the nature of substitutional B in oxidation, crystallinity and distribution preference in the composites. Substitutional B acts both a catalyst and an inhibitor in carbon oxidation, depending on the content and the extent of carbon burn-off reaction. Crystallinity increases with the incorporation of B. Boron prefers to be distributed in the less ordered structure; non-graphitizable PAN-based carbon fibers have higher B contents than graphitizable coal-tar pitch, but processing conditions can change this preference. The incorporation of B in CFRC composites seems to be beneficial for improving the potential ability of the composites in applications by increasing crystallinity and oxidation stability.

  17. LARGE AREA FILTERED ARC DEPOSITION OF CARBON AND BORON BASED HARD COATINGS

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Rabi S.

    2003-12-05

    This document is a final report covering work performed under Contract No. DE-FG02-99ER82911 from the Department of Energy under a SBIR Phase II Program. Wear resistant, hard coatings can play a vital role in many engineering applications. The primary goal of this project was to develop coatings containing boron and carbon with hardness greater than 30 GPa and evaluate these coatings for machining applications. UES has developed a number of carbon and boron containing coatings with hardness in the range of 34 to 65 GPa using a combination of filtered cathodic arc and magnetron sputtering. The boron containing coatings were based on TiB2, TiBN, and TiBCN, while the carbon containing coatings ere TiC+C and hydrogen free diamond-like-carbon. Machining tests were performed with single and multilayer coated tools. The turning and milling tests were run at TechSolve Inc., under a subcontract at Ohio State University. Significant increases in tool lives were realized in end milling of H-13 die steel (8X) and titanium alloy (80%) using the TiBN coating. A multilayer TiBN/TiN performed the best in end-milling of highly abrasive Al-Si alloys. A 40% increase in life over the TiAlN benchmark coating was found. Further evaluations of these coatings with commercialization partners are currently in progress.

  18. Improved creep and oxidation behavior of a martensitic 9Cr steel by the controlled addition of boron and nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Mayr, Peter [Massachusetts Institute of Technology, Cambridge, MA (United States). Dept. of Materials Science; Graz Univ. of Technology (Austria). Inst. of Material Science and Welding; Holzer, Ivan; Mendez-Martin, Francisca [Graz Univ. of Technology (Austria). Inst. of Material Science and Welding; Albu, Mihaela; Mitsche, Stefan [Graz Univ. of Technology (Austria). Inst. for Electron Microscopy; Gonzalez, Vanessa; Agueero, Alina [Instituto Nacional de Tecnica Aeroespacial, Torrejon de Ardoz (Spain)

    2010-07-01

    This manuscript gives an overview on recent developments of a martensitic steel grade based on 9Cr3W3CoVNb with controlled additions of boron and nitrogen. Alloy design by thermodynamic equilibrium calculations and calculation of boron-nitrogen solubility is discussed. Out of this alloy design process, two melts of a 9Cr3W3CoVNbBN steel were produced. The investigation focused on microstructural evolution during high temperature exposure, creep properties and oxidation resistance in steam at 650 C. Microstructural characterization of ''as-received'' and creep exposed material was carried out using conventional optical as well as advanced electron microscopic methods. Creep data at 650 was obtained at various stress levels. Longest-running specimens have reached more than 20,000 hours of testing time. In parallel, long-term oxidation resistance has been studied at 650 C in steam atmosphere up to 5,000 hours. Preliminary results of the extensive testing program on a 9Cr3W3CoVNbBN steel show significant improvement in respect to creep strength and oxidation resistance compared to the state-of-the-art 9 wt. % Cr martensitic steel grades. Up to current testing times, the creep strength is significantly beyond the +20% scatterband of standard grade P92 material. Despite the chromium content of 9 wt % the material exhibits excellent oxidation resistance. Steam exposed plain base material shows comparable oxidation behavior to coated material, and the corrosion rate of the boron-nitrogen controlled steel is much lower compared to standard 9 wt % Cr steel grades, P91 and P92. (orig.)

  19. The Effect of Nitrogen and Boron on Growth, Yield and Concentration of Some Nutrient Elements of Tomato

    Directory of Open Access Journals (Sweden)

    N. Farzaneh

    2010-08-01

    Full Text Available A completely randomized factorial experiment was set up with 16 treatments and three replicates to study the effect of nitrogen and boron on yield, shoot and root dry weights and leaf concentration of nutrient elements in hydroponically grown tomato in greenhouse of Agricultural College of Zanjan University in 2008. In this experiment, tomato seed of Rio Grande Ug was selected and simple and interaction effect of four levels of N (100, 200, 300 and 400 mgL-1 and four levels of B (0.5, 1.0, 1.5 and 2.0 mg L-1 on tomato yield, shoot and root dry weights and leaf concentration of nutrient elements was investigated. The results indicated that the simple and interaction effect of nitrogen and boron on yield and tomato shoot and root dry weights were significant. Te highest yield and root dry weights were obtained in N200B1.0 treatment and the highest shoot dry weight was obtained in N300B1.0 treatment. By increasing the nitrogen level in the nutrient solution, leaf N and Mn concentration increased while B, Fe and Zn concentration of leaves decreased significantly. In contrast, by increasing the boron levels, leaf N, B and Zn concentration increased and Fe and Mn concentration of leaves decreased significantly. With respect to the results of this study, applications of 200 mg L-1N and 1.0 mgL-1 B of nutrient solution are recommended to obtain higher yield and better quality for tomato in hydroponic culture.

  20. Facile fabrication of boron nitride nanosheets-amorphous carbon hybrid film for optoelectronic applications

    KAUST Repository

    Wan, Shanhong

    2015-01-01

    A novel boron nitride nanosheets (BNNSs)-amorphous carbon (a-C) hybrid film has been deposited successfully on silicon substrates by simultaneous electrochemical deposition, and showed a good integrity of this B-C-N composite film by the interfacial bonding. This synthesis can potentially provide the facile control of the B-C-N composite film for the potential optoelectronic devices. This journal is

  1. Negative differential resistance in an (8, 0) carbon/boron nitride nanotube heterojunction*

    Institute of Scientific and Technical Information of China (English)

    Song Jiuxu; Yang Yintang; Liu Hongxia; Guo Lixin

    2011-01-01

    Using the method combined non-equilibrium Green's function with density functional theory, the electronic transport properties of an (8, 0) carbon/boron nitride nanotube heterojunction coupled to Au electrodes were investigated. In the current voltage characteristic of the heterojunction, negative differential resistance was found under positive and negative bias, which is the variation of the localization for corresponding molecular orbital caused by the applied bias voltage These results are meaningful to modeling and simulating on related electronic devices.

  2. Effects of boron-doping on the morphology and magnetic property of carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    JIANG Qi; QIAN Lan; YI Jing; ZHU Xiaotong; ZHAO Yong

    2007-01-01

    Boron carbide nanotubes (nano-fibers) was prepared by B powder and carbon nanotubes (CNTs) at high temperature in a vacuumed quartz tube.The morphology,microstructure,component and magnetic property of samples were characterized by transmission electron microscopy (TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and magnetic property measurement system (MPMS) controller.The results showed that B-doping CNTs have great difference in the morphology and magnetic property from those of pristine CNTs.

  3. The Effects of Radial Compression on Thermal Conductivity of Carbon and Boron Nitride Nanotubes

    OpenAIRE

    Haijun Shen

    2012-01-01

    By using molecular dynamics method, thermal conductivity of (10, 10) carbon and boron nitride (BN) nanotubes under radial compression was investigated, and the - (thermal conductivity versus temperature) curves of the two nanotubes were obtained. It is found that with the increase of temperature the thermal conductivity of two nanotubes decreases; the nanotubes, under both the local compression and whole compression, have lower thermal conductivity, and the larger the compressive deformat...

  4. Cu and Boron Doped Carbon Nitride for Highly Selective Oxidation of Toluene to Benzaldehyde.

    Science.gov (United States)

    Han, Hongling; Ding, Guodong; Wu, Tianbin; Yang, Dexin; Jiang, Tao; Han, Buxing

    2015-07-13

    A novel Cu and boron doped graphitic carbon nitride catalyst (Cu-CNB) was synthesized using cheap precursors and systematically characterized. The selective oxidation of toluene proceeded very smoothly over the catalyst at 70 °C using tert-butyl hydroperoxide (TBHP) as the oxidant to exclusively afford benzaldehyde. The catalyst can be used for at least five cycles without decrease in activity and selectivity.

  5. Synthesis of Boron-doped Diamond/Porous Ti Composite Materials——Effect of Carbon Concentration

    Institute of Scientific and Technical Information of China (English)

    MA Ming; CHANG Ming; LI Xiaowei

    2012-01-01

    Highly boron-doped diamond films were deposited on porous titanium substrates by hot filament chemical vapor deposition technique.The morphology variation of highly boron-doped diamond films grown on porous titanium substrates was investigated,and the effects of carbon concentration on nucleation density and diamond growth were also studied.The continuous change of surface morphology and structure of diamond film were characterized by scanning electron microscopy.The structures of diamond film and interlayer were analyzed by X-ray diffraction.The quality of boron-doped diamond film was confirmed by visible Raman spectroscopy.The experimental results reveal that surface morphology and quality of boron-doped diamond films are various due to the change of carbon concentration.The thickness of intermediate layer decreases with the carbon concentration increasing.

  6. Intercropping enhances soil carbon and nitrogen.

    Science.gov (United States)

    Cong, Wen-Feng; Hoffland, Ellis; Li, Long; Six, Johan; Sun, Jian-Hao; Bao, Xing-Guo; Zhang, Fu-Suo; Van Der Werf, Wopke

    2015-04-01

    Intercropping, the simultaneous cultivation of multiple crop species in a single field, increases aboveground productivity due to species complementarity. We hypothesized that intercrops may have greater belowground productivity than sole crops, and sequester more soil carbon over time due to greater input of root litter. Here, we demonstrate a divergence in soil organic carbon (C) and nitrogen (N) content over 7 years in a field experiment that compared rotational strip intercrop systems and ordinary crop rotations. Soil organic C content in the top 20 cm was 4% ± 1% greater in intercrops than in sole crops, indicating a difference in C sequestration rate between intercrop and sole crop systems of 184 ± 86 kg C ha(-1) yr(-1). Soil organic N content in the top 20 cm was 11% ± 1% greater in intercrops than in sole crops, indicating a difference in N sequestration rate between intercrop and sole crop systems of 45 ± 10 kg N ha(-1) yr(-1). Total root biomass in intercrops was on average 23% greater than the average root biomass in sole crops, providing a possible mechanism for the observed divergence in soil C sequestration between sole crop and intercrop systems. A lowering of the soil δ(15) N signature suggested that increased biological N fixation and/or reduced gaseous N losses contributed to the increases in soil N in intercrop rotations with faba bean. Increases in soil N in wheat/maize intercrop pointed to contributions from a broader suite of mechanisms for N retention, e.g., complementary N uptake strategies of the intercropped plant species. Our results indicate that soil C sequestration potential of strip intercropping is similar in magnitude to that of currently recommended management practises to conserve organic matter in soil. Intercropping can contribute to multiple agroecosystem services by increased yield, better soil quality and soil C sequestration.

  7. The response of gross nitrogen mineralization to labile carbon inputs

    Science.gov (United States)

    Bengtson, Per

    2014-05-01

    Input of labile carbon sources to forest soils commonly result in priming, i.e. an increase in the microbial decomposition of soil organic matter. Efforts aimed at quantifying the extent of priming have, to date, largely focused on soil organic matter decomposition manifested as soil respiration. Less is known about how gross nitrogen mineralization responds to input of labile carbon. It is often assumed that increased priming results in decreased soil carbon stocks. However, microbial mineralization of organic nitrogen into plant available forms is a major factor limiting primary production in forests. If increased decomposition of soil organic matter in response to labile carbon is accompanied by a concurrent increased nitrogen mineralization, this could result in elevated primary production and higher rates of plant derived organic matter input to soils. Therefore, in order to fully understand the effect of priming on net ecosystem exchange and soil carbon stocks, it is vital to consider if increased decomposition of soil organic matter caused by priming also results in increased nitrogen mineralization. Here I present the results from a series of experiments aimed at determining if, and to which extent, gross nitrogen mineralization is stimulated by input of labile carbon. The results suggest that it is by no means uncommon to find an increase in gross N mineralization rates in response to labile carbon inputs. The magnitude of the increase seems dependent on the nitrogen status of the soil, as well as the concentration and rate of labile carbon inputs. However, continuous input of labile carbon sources that also contains nitrogen, e.g. amino acids, seems to inhibit rather than increase the mineralization of organic nitrogen. These findings suggest that there is a potential for a positive feedback between priming and primary production that needs to be considered in order to fully understand the influence of priming on net ecosystem exchange and soil carbon

  8. Carbon and nitrogen balances for six shrublands across Europe

    DEFF Research Database (Denmark)

    Beier, Claus; Emmett, Bridget A.; Tietema, Albert

    2009-01-01

    and nitrogen balances of six shrublands along a climatic gradient across the European continent. The aim of the study was to provide a basis for assessing the range and variability in carbon storage in European shrublands. Across the sites the net carbon storage in the systems ranged from 1,163 g C m−2 to 18...... with a cold and wet climate where soil C constitutes 95% of the total carbon in the ecosystem. Respiration of carbon from the soil organic matter pool dominated the carbon loss at all sites while carbon loss from aboveground litter decomposition appeared less important. Total belowground carbon allocation...

  9. An unusual isotopic fractionation of boron in synthetic calcium carbonate precipitated from seawater and saline water

    Institute of Scientific and Technical Information of China (English)

    XIAO Yingkai; LI Shizhen; WEI Haizhen; SUN Aide; ZHOU Weijian; LIU Weiguo

    2006-01-01

    Inorganic calcium carbonate precipitation from natural seawater and saline water at various pH values was carried out experimentally. The results show the clear positive relationships between boron concentration and δ11B of inorganic calcium carbonate with the pH of natural seawater and saline water. However, the variations of boron isotopic fractionation between inorganic calcite and seawater/saline water with pH are inconsistent with the hypothesis that B(OH)4- is the dominant species incorporated into the biogenic calcite structure. The isotopic fractionation factors α Between synthetic calcium carbonate precipitate and parent solutions increase systematically as pH increases, from 0.9884 at pH 7.60 to 1.0072 at pH 8.60 for seawater and from 0.9826 at pH 7.60 to 1.0178 at pH 8.75 for saline water. An unusual boron isotopic fractionation factor of larger than 1 in synthetic calcium carbonate precipitated from seawater/saline water at higher pH is observed, which implies that a substantial amount of the isotopically heavier B(OH)3 species must be incorporated preferentially into synthetic inorganic carbonate. The results propose that the incorporation of B(OH)3 is attributed to the formation of Mg(OH)2 at higher pH of calcifying microenvironment during the synthetic calcium carbonate precipitation. The preliminary experiment of Mg(OH)2 precipitated from artificial seawater shows that heavier 11B is enriched in Mg(OH)2 precipitation, which suggests that isotopically heavier B(OH)3 species incorporated preferentially into Mg(OH)2 precipitation.This result cannot be applied to explain the boron isotopic fractionation of marine bio-carbonate because of the possibility that the unusual environment in this study appears in formation of marine bio-carbonate is infinitesimal. We, however, must pay more attention to this phenomenon observed in this study, which accidentally appears in especially natural environment.

  10. Tuning the electronic properties of armchair carbon nanoribbons by a selective boron doping

    Energy Technology Data Exchange (ETDEWEB)

    Navarro-Santos, P; Ricardo-Chavez, J L; Lopez-Sandoval, R [Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la presa San Jose 2055, San Luis Potosi 78216 (Mexico); Reyes-Reyes, M [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi 78000 (Mexico); Rivera, J L, E-mail: sandov@ipicyt.edu.m [Facultad de Ingenieria Quimica, Universidad Michoacana de San Nicolas de Hidalgo, Santiago Tapia 403, Morelia, Michoacan, 58000 (Mexico)

    2010-12-22

    Armchair carbon nanoribbons (ACNRs) substitutionally doped with boron atoms are investigated in the framework of first-principles density functional theory. Different boron-boron arrangements and concentrations are considered in order to simulate possible aggregation patterns, their structural stability and electronic behavior are determined as a function of ribbon size. In agreement with previous studies, our results show that the dopant atoms have in general a preference for edge sites, but specific effects appear as a function of concentration that importantly modify the properties of the ribbons compared to the pristine case. Interesting tendencies are discovered as a function of dopant concentration that significantly affect the electronic properties of the ribbons. We have found that BC{sub 3} island formation and edge doping are the most important factors for the structural stabilization of the ribbons with high boron concentration (>7%) whereas for the cases of low boron concentrations (<5%) the structural stabilities are similar. For all the doped cases, we have found that the BC{sub 3} island patterns give rise to highly localized B states on top of the Fermi level, resulting in semiconducting behavior. On the other hand, when the average distance between the B atoms increases beyond island stoichiometry, the localization of their states is reduced and the ribbons may become metallic due to a band crossing caused by the lowering of the Fermi level resulting from the positive charge doping. Thus, tuning the dopant interaction would be an appropriate way to tailor the electronic properties of the ribbons in a convenient manner in view of potential technological applications.

  11. Effect of reaction conditions on methyl red degradation mediated by boron and nitrogen doped TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Galenda, A., E-mail: galenda@ieni.cnr.it [CNR-IENI, Istituto per l’Energetica e le Interfasi, Corso Stati Uniti, 4 35127 Padova (Italy); Crociani, L.; Habra, N. El; Favaro, M. [CNR-IENI, Istituto per l’Energetica e le Interfasi, Corso Stati Uniti, 4 35127 Padova (Italy); Natile, M.M. [CNR-IENI, Istituto per l’Energetica e le Interfasi, Dipartimento di Scienze Chimiche, Università di Padova, via F. Marzolo, 1 35131 Padova (Italy); Rossetto, G. [CNR-IENI, Istituto per l’Energetica e le Interfasi, Corso Stati Uniti, 4 35127 Padova (Italy)

    2014-09-30

    Highlights: • Boron and/or nitrogen-doped TiO{sub 2} for photocatalytic wastewater treatment. • Methyl red degradation/mineralisation as a function of pH, acids and dopants. • Adsorption time influence on photocatalytic process. • Recovery of worn-out catalyst. - Abstract: Nowadays the employment of renewable and sustainable energy sources, and solar light as main option, becomes an urgent need. Photocatalytic processes received great attention in wastewater treatment due to their cheapness, environmental compatibility and optimal performances. Despite the general low selectivity of the photocatalysts, an accurate optimisation of the operational parameters needs to be carried out in order to maximise the process yield. Because of this reason, the present contribution aims to deepen either the knowledge in boron and/or nitrogen doped TiO{sub 2}-based systems and their employment in methyl red removal from aqueous solutions. The samples were obtained by coprecipitation and characterised by XRD, SEM, BET specific surface area, UV–vis and XPS techniques. The catalytic activity was for the first time carefully evaluated with respect to methyl red photodegradation in different conditions as a function of working pH, counter-ions and pre-adsorption time. An ad-hoc study was performed on the importance of the pre-adsorption of the dye, suggesting that an extended adsorption is useless for the catalyst photoactivity, while a partial coverage is preferable. The photocatalytic tests demonstrate the positive influence of boron doping in photo-activated reactions and the great importance of the operational parameters with respect to the simple methyl red bleaching rather than the overall pollutant mineralisation. It is proved, indeed, that different working pH, acidifying means and substrate pre-adsorption time can enhance or limit the catalyst performances with respect to the complete pollutant degradation rather than its partial breakage.

  12. Microcystin Biosynthesis and mcyA Expression in Geographically Distinct Microcystis Strains under Different Nitrogen, Phosphorus, and Boron Regimes

    Directory of Open Access Journals (Sweden)

    Ankita Srivastava

    2016-01-01

    Full Text Available Roles of nutrients and other environmental variables in development of cyanobacterial bloom and its toxicity are complex and not well understood. We have monitored the photoautotrophic growth, total microcystin concentration, and microcystins synthetase gene (mcyA expression in lab-grown strains of Microcystis NIES 843 (reference strain, KW (Wangsong Reservoir, South Korea, and Durgakund (Varanasi, India under different nutrient regimes (nitrogen, phosphorus, and boron. Higher level of nitrogen and boron resulted in increased growth (avg. 5 and 6.5 Chl a mg/L, resp., total microcystin concentrations (avg. 1.185 and 7.153 mg/L, resp., and mcyA transcript but its expression was not directly correlated with total microcystin concentrations in the target strains. Interestingly, Durgakund strain had much lower microcystin content and lacked microcystin-YR variant over NIES 843 and KW. It is inferred that microcystin concentration and its variants are strain specific. We have also examined the heterotrophic bacteria associated with cyanobacterial bloom in Durgakund Pond and Wangsong Reservoir which were found to be enriched in Alpha-, Beta-, and Gammaproteobacteria and that could influence the bloom dynamics.

  13. Microcystin Biosynthesis and mcyA Expression in Geographically Distinct Microcystis Strains under Different Nitrogen, Phosphorus, and Boron Regimes.

    Science.gov (United States)

    Srivastava, Ankita; Ko, So-Ra; Ahn, Chi-Yong; Oh, Hee-Mock; Ravi, Alok Kumar; Asthana, Ravi Kumar

    2016-01-01

    Roles of nutrients and other environmental variables in development of cyanobacterial bloom and its toxicity are complex and not well understood. We have monitored the photoautotrophic growth, total microcystin concentration, and microcystins synthetase gene (mcyA) expression in lab-grown strains of Microcystis NIES 843 (reference strain), KW (Wangsong Reservoir, South Korea), and Durgakund (Varanasi, India) under different nutrient regimes (nitrogen, phosphorus, and boron). Higher level of nitrogen and boron resulted in increased growth (avg. 5 and 6.5 Chl a mg/L, resp.), total microcystin concentrations (avg. 1.185 and 7.153 mg/L, resp.), and mcyA transcript but its expression was not directly correlated with total microcystin concentrations in the target strains. Interestingly, Durgakund strain had much lower microcystin content and lacked microcystin-YR variant over NIES 843 and KW. It is inferred that microcystin concentration and its variants are strain specific. We have also examined the heterotrophic bacteria associated with cyanobacterial bloom in Durgakund Pond and Wangsong Reservoir which were found to be enriched in Alpha-, Beta-, and Gammaproteobacteria and that could influence the bloom dynamics.

  14. Optimization of Carbon Nanotubes for Nitrogen Gas Adsorption

    Directory of Open Access Journals (Sweden)

    Fereydoun Ashrafi

    2010-09-01

    Full Text Available Carbon nano-tubes are one of the most significant achievements of nano-technology with important applications in the design of electronic nano-devices. The study of their properties is therefore important. Here the density functional theory (DFT of electron and the Hartree-Fock (HF method are utilized to study the adsorption of nitrogen molecules on the surface of (4, 4 and (5, 0 carbon nano-tubes. The electronic structure, single point and dipole moment of both nitrogen and carbon nuclei are thoroughly studied. The computational results, which includes, indicate that rich adsorption patterns may result from the interaction of nitrogen with the carbon nano tubes sometimes C-N bounds are formed via breaking C-C bounds and sometimes a carbon atom in the nano-tube is replaced with a nitrogen atom. Sometimes nitrogen atoms are attracted to a C-C bound. In summary, the optimized adsorption rates are calculated. Gaussian 98 software has been used to carry out quantum chemistry calculations. Keywords: Density functional theory, Hartree-Fock, carbon nano tube, Gaussian 98 software. Carbon nanotubes (CNTs are one of the most significant achievements of nano-technology because of his important applications in the design of electronic nano-devices. The study of their properties is therefore important. In this investigation the Density Functional Theory (DFT of electron and the Hartree-Fock (HF method are utilized to study the adsorption of nitrogen molecules on the surface of (4, 4 and (5, 0 carbon nanotubes. The electronic structure, single point and dipole moment of both nitrogen and carbon nuclei are thoroughly studied. The computational results, which includes, indicate that rich adsorption patterns m ay result from the interaction of nitrogen with the carbon nanotubes. Sometimes C-N bounds are formed via breaking C-C bounds and sometimes a carbon atom in the nanotube is replaced by a nitrogen atom. Sometimes nitrogen atoms are attracted to a C-C bound

  15. Growth and metabolism of Saccharomyces cerevisiae in chemostat cultures under carbon-, nitrogen-, or carbon- and nitrogen-limiting conditions.

    OpenAIRE

    Larsson, C; von Stockar, U.; Marison, I; Gustafsson, L.

    1993-01-01

    Aerobic chemostat cultures of Saccharomyces cerevisiae were performed under carbon-, nitrogen-, and dual carbon- and nitrogen-limiting conditions. The glucose concentration was kept constant, whereas the ammonium concentration was varied among different experiments and different dilution rates. It was found that both glucose and ammonium were consumed at the maximal possible rate, i.e., the feed rate, over a range of medium C/N ratios and dilution rates. To a small extent, this was due to a c...

  16. Boron isotopic fractionation in laboratory inorganic carbonate precipitation: Evidence for the incorpora-tion of B(OH)3 into carbonate

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A laboratory inorganic carbonate precipitation experiment at high pH of 8.96 to 9.34 was conducted, and the boron isotopic fractionations of the precipitated carbonate were measured. The data show that boron isotopic fractionation factors (αcarb-3) between carbonate and B(OH)3 in seawater range 0.937 and 0.965, with an average value of 0.953. Our results together with those reported by Sanyal and collabo-rators show that the αcarb-3 values between carbonate and B(OH)3 in solution are not constant but are negatively correlated with the pH of seawater. The measured boron isotopic compositions of carbonate precipitation (δ11Bcarb) do not exactly lie on the best-fit theoretical δ 11B4-pH curves and neither do they exactly parallel any theoretical δ 11B4-pH curves. Therefore, it is reasonable to argue that a changeable proportion of B(OH)3 with pH of seawater should also be incorporated into carbonate except for the dominant incorporation of B(OH)4- in carbonate . Hence, in the reconstruction of the paleo-pH of sea-water from boron isotopes in marine biogenic carbonates, the use of theoretical boron isotopic frac-tionation factor (α4-3) between B(OH)4- and B(OH)3 is not suitable. Instead, an empirical equation should be established.

  17. Spectroscopic investigation of nitrogen-functionalized carbon materials

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Kevin N. [Department of Metallurgical and Materials Engineering, Colorado School of Mines, 1500 Illinois Street Golden CO 80401 USA; Department of Mechanical Engineering, University of Michigan, Ann Arbor MI 48109 USA; Christensen, Steven T. [National Renewable Energy Laboratory, 15013 Denver West Pkwy Golden CO 80401 USA; Nordlund, Dennis [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd Menlo Park CA 94023 USA; Dameron, Arrelaine A. [National Renewable Energy Laboratory, 15013 Denver West Pkwy Golden CO 80401 USA; Ngo, Chilan [Department of Chemistry and Geochemistry, Colorado School of Mines, 1012 14th Street Golden CO 80401 USA; Dinh, Huyen [National Renewable Energy Laboratory, 15013 Denver West Pkwy Golden CO 80401 USA; Gennett, Thomas [National Renewable Energy Laboratory, 15013 Denver West Pkwy Golden CO 80401 USA; O' Hayre, Ryan [Department of Metallurgical and Materials Engineering, Colorado School of Mines, 1500 Illinois Street Golden CO 80401 USA; Pylypenko, Svitlana [Department of Chemistry and Geochemistry, Colorado School of Mines, 1012 14th Street Golden CO 80401 USA

    2016-04-07

    Carbon materials are used in a diverse set of applications ranging from pharmaceuticals to catalysis. Nitrogen modification of carbon powders has shown to be an effective method for enhancing both surface and bulk properties of as-received material for a number of applications. Unfortunately, control of the nitrogen modification process is challenging and can limit the effectiveness and reproducibility of N-doped materials. Additionally, the assignment of functional groups to specific moieties on the surface of nitrogen-modified carbon materials is not straightforward. Herein, we complete an in-depth analysis of functional groups present at the surface of ion-implanted Vulcan and Graphitic Vulcan through the use of X-ray photoelectron spectroscopy (XPS) and near edge X-ray adsorption fine structure spectroscopy (NEXAFS). Our results show that regardless of the initial starting materials used, nitrogen ion implantation conditions can be tuned to increase the amount of nitrogen incorporation and to obtain both similar and reproducible final distributions of nitrogen functional groups. The development of a well-controlled/reproducible nitrogen implantation pathway opens the door for carbon supported catalyst architectures to have improved numbers of nucleation sites, decreased particle size, and enhanced catalyst-support interactions.

  18. Microstructural study of oxidation of carbon-rich amorphous boron carbide coating

    Institute of Scientific and Technical Information of China (English)

    Bin ZENG; Zu-de FENG; Si-wei LI; Yong-sheng LIU

    2008-01-01

    Carbon-rich amorphous boron carbide (BxC) coatings were annealed at 400℃, 700℃, 1000℃ and 1200℃ for 2 h in air atmosphere. The microstructure and composition of the as-deposited and annealed coat-ings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Raman spectro-scopy and energy dispersive X-ray spectroscopy (EDS). All of the post-anneal characterizations demonstrated the ability of carbon-rich BxC coatings to protect the graphite substrate against oxidation. Different oxidation modes of the coatings were found at low temperature (400℃), moderate temperature (700℃) and high temper-ature (1000℃ and 1200℃). Finally, the feasibility of the application of carbon-rich BxC instead of pyrolytic car-bon (PyC) as a fiber/matrix interlayer in ceramics-matrix composites (CMCs) is discussed here.

  19. Effects of Boron Bearing Additives on Oxidation and Corrosion Resistance of Doloma—based carbon bonded Refractories

    Institute of Scientific and Technical Information of China (English)

    YEFangbao; ZHONGXiangchong; 等

    1998-01-01

    Oxidation of the added graphite and the bonding carbon is an imortant degradation mode of doloma-carbon refractories in service,In this work,the behavior and effects of various boron bearing materials(CaB6,ZrB2,Bc and colemanite)as an-tioxidants have been investigated and compared to the effect of Al-Mg alloy,For CaO-MgO-C mate-rials,the effect of boron bearingadditives is better than Al-Mg alloy,The borate melt formed at high temperature would retard or prevent carbon oxidation,thus contributing to improved oxidation resistance,Preliminary investigations on the effect of boron bearing additives and Al-Mg alloy on corrosion resistance of doloma-carbon materials have indicated that simultaneous addition of the two types of additives would lead to pronounced improvement of slag corrosion resistance.

  20. Carbon and nitrogen isotope variations in tree-rings as records of perturbations in regional carbon and nitrogen cycles.

    Science.gov (United States)

    Bukata, Andrew R; Kyser, T Kurtis

    2007-02-15

    Increasing anthropogenic pollution from urban centers and fossil fuel combustion can impact the carbon and nitrogen cycles in forests. To assess the impact of twentieth century anthropogenic pollution on forested system carbon and nitrogen cycles, variations in the carbon and nitrogen isotopic compositions of tree-rings were measured. Individual annual growth rings in trees from six sites across Ontario and one in New Brunswick, Canada were used to develop site chronologies of tree-ring delta 15N and delta 13C values. Tree-ring 615N values were approximately 0.5% per hundred higher and correlated with contemporaneous foliar samples from the same tree, but not with delta 15N values of soil samples. Temporal trends in carbon and nitrogen isotopic compositions of these tree-rings are consistent with increasing anthropogenic influence on both the carbon and nitrogen cycles since 1945. Tree-ring delta 13C values and delta 15N values are correlated at both remote and urban-proximal sites, with delta 15N values decreasing since 1945 and converging on 1% per hundred at urban-proximal sites and decreasing but not converging on a single delta 15N value in remote sites. These results indicate that temporal trends in tree-ring nitrogen and carbon isotopic compositions record the regional extent of pollution.

  1. Fabrication of Polyimide-Matrix/Carbon and Boron-Fiber Tape

    Science.gov (United States)

    Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

    2007-01-01

    The term HYCARB denotes a hybrid composite of polyimide matrices reinforced with carbon and boron fibers. HYCARB and an improved process for fabricating dry HYCARB tapes have been invented in a continuing effort to develop lightweight, strong composite materials for aerospace vehicles. Like other composite tapes in this line of development, HYCARB tapes are intended to be used to build up laminated structures having possibly complex shapes by means of automated tow placement (ATP) - a process in which a computer-controlled multiaxis machine lays down prepreg tape or tows. The special significance of the present process for making dry HYCARB for ATP is that it contributes to the reduction of the overall cost of manufacturing boron-reinforced composite-material structures while making it possible to realize increased compression strengths. The present process for making HYCARB tapes incorporates a "wet to dry" process developed previously at Langley Research Center. In the "wet to dry" process, a flattened bundle of carbon fiber tows, pulled along a continuous production line between pairs of rollers, is impregnated with a solution of a poly(amide acid) in N-methyl-2-pyrrolidinone (NMP), then most of the NMP is removed by evaporation in hot air. In the present case, the polyamide acid is, more specifically, that of LaRC. IAX (or equivalent) thermoplastic polyimide, and the fibers are, more specifically, Manganite IM7 (or equivalent) polyacrylonitrile- based carbon filaments that have a diameter of 5.2 m and are supplied in 12,000-filament tows. The present process stands in contrast to a prior process in which HYCARB tape was made by pressing boron fibers into the face of a wet carbon-fiber/ poly(amide acid) prepreg tape . that is, a prepreg tape from which the NMP solvent had not been removed. In the present process, one or more layer(s) of side-by-side boron fibers are pressed between dry prepreg tapes that have been prepared by the aforementioned gwet to dry h

  2. Nitrogen doped carbon nanotubes : synthesis, characterization and catalysis

    NARCIS (Netherlands)

    van Dommele, S.

    2008-01-01

    Nitrogen containing Carbon Nanotubes (NCNT) have altered physical- and chemical properties with respect to polarity, conductivity and reactivity as compared to conventional carbon nanotubes (CNT) and have potential for use in electronic applications or catalysis. In this thesis the incorporation of

  3. Decoupled carbonate chemistry controls on the incorporation of boron into Orbulina universa

    Science.gov (United States)

    Howes, Ella L.; Kaczmarek, Karina; Raitzsch, Markus; Mewes, Antje; Bijma, Nienke; Horn, Ingo; Misra, Sambuddha; Gattuso, Jean-Pierre; Bijma, Jelle

    2017-01-01

    In order to fully constrain paleo-carbonate systems, proxies for two out of seven parameters, plus temperature and salinity, are required. The boron isotopic composition (δ11B) of planktonic foraminifera shells is a powerful tool for reconstructing changes in past surface ocean pH. As B(OH)4- is substituted into the biogenic calcite lattice in place of CO32-, and both borate and carbonate ions are more abundant at higher pH, it was suggested early on that B / Ca ratios in biogenic calcite may serve as a proxy for [CO32-]. Although several recent studies have shown that a direct connection of B / Ca to carbonate system parameters may be masked by other environmental factors in the field, there is ample evidence for a mechanistic relationship between B / Ca and carbonate system parameters. Here, we focus on investigating the primary relationship to develop a mechanistic understanding of boron uptake. Differentiating between the effects of pH and [CO32-] is problematic, as they co-vary closely in natural systems, so the major control on boron incorporation remains unclear. To deconvolve the effects of pH and [CO32-] and to investigate their impact on the B / Ca ratio and δ11B, we conducted culture experiments with the planktonic foraminifer Orbulina universa in manipulated culture media: constant pH (8.05), but changing [CO32-] (238, 286 and 534 µmol kg-1 CO32-) and at constant [CO32-] (276 ± 19.5 µmol kg-1) and varying pH (7.7, 7.9 and 8.05). Measurements of the isotopic composition of boron and the B / Ca ratio were performed simultaneously using a femtosecond laser ablation system coupled to a MC-ICP-MS (multiple-collector inductively coupled plasma mass spectrometer). Our results show that, as expected, δ11B is controlled by pH but it is also modulated by [CO32-]. On the other hand, the B / Ca ratio is driven by [HCO3-], independently of pH. This suggests that B / Ca ratios in foraminiferal calcite can possibly be used as a second, independent, proxy for

  4. Genome-wide patterns of carbon and nitrogen regulation of gene expression validate the combined carbon and nitrogen (CN)-signaling hypothesis in plants

    OpenAIRE

    Palenchar, Peter M; Kouranov, Andrei; Lejay, Laurence V; Coruzzi, Gloria M.

    2004-01-01

    Background Carbon and nitrogen are two signals that influence plant growth and development. It is known that carbon- and nitrogen-signaling pathways influence one another to affect gene expression, but little is known about which genes are regulated by interactions between carbon and nitrogen signaling or the mechanisms by which the different pathways interact. Results Microarray analysis was used to study global changes in mRNA levels due to carbon and nitrogen in Arabidopsis thaliana. An in...

  5. Laser surface alloying of commercially pure titanium with boron and carbon

    Science.gov (United States)

    Makuch, N.; Kulka, M.; Dziarski, P.; Przestacki, D.

    2014-06-01

    Laser surface alloying with boron and carbon was applied to produce the composite layers, reinforced by the hard ceramic phases (titanium borides and titanium carbides), on commercially pure titanium. The external cylindrical surface of substrate material was coated by paste containing boron, boron and graphite, or graphite. Then, the laser re-melting was carried out with using the continuous-wave CO2 laser. This enabled the formation of laser-borided, laser-borocarburized, and laser-carburized layers. The microstructure or the re-melted zone consisted of the hard ceramic phases (TiB+TiB2, TiB+TiB2+TiC, or TiC) located in the eutectic mixture of Tiα'-phase with borides, borides and carbides, or carbides, respectively. All the composite layers were characterized by the sufficient cohesion. The significant increase in microhardness and in wear resistance of all the laser-alloyed layers was observed in comparison with commercially pure titanium. The percentage of hard ceramic phases in more plastic eutectic mixture influenced the measured microhardness values. The dominant wear mechanism (abrasive or adhesive) depended on the method of laser alloying, and the type of test used. The wear tests for longer duration, without the change in the counter specimen, created the favourable conditions for adhesive wear, while during the shorter tests the abrasive wear dominated, as a rule.

  6. Reduction-melting behaviors of boron-bearing iron concentrate/carbon composite pellets with addition of CaO

    Institute of Scientific and Technical Information of China (English)

    Jing-song Wang

    2015-01-01

    Although the total amount of boron resources in China is high, the grades of these resources are low. The authors have already proposed a new comprehensive utilization process of boron-bearing iron concentrate based on the iron nugget process. The present work de-scribes a further optimization of the conditions used in the previous study. The effects of CaO on the reduction–melting behavior and proper-ties of the boron-rich slag are presented. CaO improved the reduction of boron-bearing iron concentrate/carbon composite pellets when its content was less than 1wt%. Melting separation of the composite pellets became difficult with the CaO content increased. The sulfur content of the iron nugget gradually decreased from 0.16wt%to 0.046wt%as the CaO content of the pellets increased from 1wt%to 5wt%. CaO negatively affected the iron yield and boron extraction efficiency of the boron-rich slag. The mineral phase evolution of the boron-rich slag during the reduction–melting separation of the composite pellets with added CaO was also deduced.

  7. Carbon, oxygen and boron isotopic studies of Huangbaishuwan witherite deposit at Ziyang and Wenyuhe witherite deposit at Zhushan

    Institute of Scientific and Technical Information of China (English)

    Lü; Zhicheng(吕志成); LIU; Congqiang(刘丛强); LIU; Jiajun(刘家军); ZHAO; Zhiqi(赵志琦)

    2003-01-01

    Being stratiform or stratoid, the Huangbaishuwan witherite deposit at Ziyang and the Wenyuhe witherite-barite deposit at Zhushan occur in the lower Lower Cambrian siliceous rocks and the orebodies are remarkably controlled by lithological character and petrography. Boron, carbon and oxygen isotopic studies of witherite, barytocalcite and calcite have shown that the carbon, involved in the formation of these minerals, was derived mainly from hydrocarbons and biogenetic gases resulting from degradation, polycondensation and dehydroxylation of bio-organic matter in sediments at the early stage of diagenesis; the boron was a mixture of boron in pore water and that released in the process of degradation of organic matter, with a minor amount of boron from cycling brines in the deep interior of the basin. Boron, carbon and oxygen isotopic studies unanimously demonstrated that witherite was precipitated in this sort of organic carbon-rich pore water medium during the early stage of diagenesis. Extensive occurrence of biodetritus and clastic texture in witherite ores strongly evidenced that Ba2+ was concentrated and settled down in the form of bio-barite on the seafloor as a result of biological processes, thereafter forming the initially enriched orebodies of barium deposits. Biological processes in seawater and early diagenesis in sediments are the major ore-forming mechanisms of witherite deposits in the region studied.

  8. Effects of strain on carbon donors and acceptors in hexagonal boron nitride monolayers

    Science.gov (United States)

    Fujimoto, Yoshitaka; Saito, Susumu

    2016-01-01

    We present first-principles density functional calculations that clarify the electronic properties of carbon defects in hexagonal boron nitride (h -BN) monolayers under biaxially applied strains. We find that strain can control the ionization energies of both donor and acceptor states. Furthermore, we also find that strain can lead to the dramatic change in conduction channel properties of donor states due to the interchange of the conduction-band-minimum state with the nearly-free-electron state. We also report the simulated scanning tunneling microscopy (STM) images of carbon defects in h -BN monolayers for experimental identification of those defects. We show that the STM images strongly reflect distinctive spatial distributions of local density of states around carbon defects depending on the substitution sites and thereby they could be identified by using STM experiments.

  9. First-principles calculations on the structure and electronic properties of boron doping zigzag single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    WEN QingBo; YU ShanSheng; ZHENG WeiTao

    2009-01-01

    Calculations have been made for single-walled zigzag (n, 0) carbon nanotubes containing substitutional boron impurity atoms using ab initio density functional theory. It is found that the formation energies of these nanotubes depend on the tube diameter, as do the electronic properties, and show periodic fea-ture that results from their different π bonding structures compared to those of perfect zigzag carbon nanotubes. When more boron atoms are incorporated into a single-walled zigzag carbon nanotube, the substitutional boron atoms tend to come together to form structure of BC3 nanodomains, and B-doped tubes have striking acceptor states above the top of the valence bands. For the structure of BC3, there are two kinds of configurations with different electronic structures.

  10. First-principles calculations on the structure and electronic properties of boron doping zigzag single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Calculations have been made for single-walled zigzag(n,0) carbon nanotubes containing substitutional boron impurity atoms using ab initio density functional theory.It is found that the formation energies of these nanotubes depend on the tube diameter,as do the electronic properties,and show periodic fea-ture that results from their different π bonding structures compared to those of perfect zigzag carbon nanotubes.When more boron atoms are incorporated into a single-walled zigzag carbon nanotube,the substitutional boron atoms tend to come together to form structure of BC3 nanodomains,and B-doped tubes have striking acceptor states above the top of the valence bands.For the structure of BC3,there are two kinds of configurations with different electronic structures.

  11. Negative differential resistance in an (8, 0) carbon/boron nitride nanotube heterojunction

    Energy Technology Data Exchange (ETDEWEB)

    Song Jiuxu; Yang Yintang; Liu Hongxia [Key Laboratory of Ministry of Education for Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China); Guo Lixin, E-mail: songjiuxu@126.com [School of Science, Xidian University, Xi' an 710071 (China)

    2011-04-15

    Using the method combined non-equilibrium Green's function with density functional theory, the electronic transport properties of an (8, 0) carbon/boron nitride nanotube heterojunction coupled to Au electrodes were investigated. In the current voltage characteristic of the heterojunction, negative differential resistance was found under positive and negative bias, which is the variation of the localization for corresponding molecular orbital caused by the applied bias voltage. These results are meaningful to modeling and simulating on related electronic devices. (semiconductor physics)

  12. Boron-doped few-walled carbon nanotubes: novel synthesis and properties

    Science.gov (United States)

    Preston, Colin; Song, Da; Taillon, Josh; Cumings, John; Hu, Liangbing

    2016-11-01

    Few-walled carbon nanotubes offer a unique marriage of graphitic quality and robustness to ink-processing; however, doping procedures that may alter the band structure of these few-walled nanotubes are still lacking. This report introduces a novel solution-injected chemical vapor deposition growth process to fabricate the first boron-doped few-walled carbon nanotubes (B-FWNTs) reported in literature, which may have extensive applications in battery devices. A comprehensive characterization of the as-grown B-FWNTs confirms successful boron substitution in the graphitic lattice, and reveals varying growth parameters impact the structural properties of B-FWNT yield. An investigation into the optimal growth purification parameters and ink-making procedures was also conducted. This study introduces the first process technique to successfully grow intrinsically p-doped FWNTs, and provides the first investigation into the impact factors of the growth parameters, purification steps, and ink-making processes on the structural properties of the B-FWNTs and the electrical properties of the resulting spray-coated thin-film electrodes.

  13. Electronic structures of an (8, 0) boron nitride/carbon nanotube heterojunction

    Energy Technology Data Exchange (ETDEWEB)

    Liu Hongxia; Zhang Heming; Song Jiuxu [Key Laboratory of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China); Zhang Zhiyong, E-mail: liuhongxia_xidian@126.co [Information Science and Technology Institution, Northwest University, Xi' an 710069 (China)

    2010-01-15

    The electronic structure of the heterojunction is the foundation of the study on its working mechanism. Models of the heterojunctions formed by an (8, 0) boron nitride nanotube and an (8, 0) carbon nanotube with C-B or C-N interface have been established. The structures of the above heterojunctions were optimized with first-principle calculations based on density functional theory. The rearrangements of the heterojunctions concentrate mainly on their interfaces. The highest occupied molecular orbital and the lowest unoccupied molecular orbital of the heterojunctions distribute in the carbon nanotube section. As the band offsets of the above heterojunctions are achieved with the average bond energy method, the band structure is plotted. (semiconductor materials)

  14. Superior Current Carrying Capacity of Boron Nitride Encapsulated Carbon Nanotubes with Zero-Dimensional Contacts.

    Science.gov (United States)

    Huang, Jhao-Wun; Pan, Cheng; Tran, Son; Cheng, Bin; Watanabe, Kenji; Taniguchi, Takashi; Lau, Chun Ning; Bockrath, Marc

    2015-10-14

    We report fabrication and characterization of hexagonal boron nitride (hBN)-encapsulated carbon nanotube (CNT) field effect transistors, which are coupled to electrical leads via zero-dimensional contacts. Device quality is attested by the ohmic contacts and observation of Coulomb blockade with a single periodicity in small bandgap semiconducing nanotubes. Surprisingly, hBN-encapsulated CNT devices demonstrate significantly enhanced current carrying capacity; a single-walled CNT can sustain >180 μA current or, equivalently, a current density of ∼2 × 10(10) A/cm(2), which is a factor of 6-7 higher than devices supported on SiO2 substrates. Such dramatic enhancement of current carrying capacity arises from the high thermal conductivity of hBN and lower hBN-CNT interfacial thermal resistance and has implications for carbon electronic applications.

  15. In Situ Mechanical Property Measurements of Amorphous Carbon-Boron Nitride Nanotube Nanostructures

    Science.gov (United States)

    Kim, Jae-Woo; Lin, Yi; Nunez, Jennifer Carpena; Siochi, Emilie J.; Wise, Kristopher E.; Connell, John W.; Smith, Michael W.

    2011-01-01

    To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

  16. Effect of boron incorporation on the structure and electrical properties of diamond-like carbon films deposited by femtosecond and nanosecond pulsed laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, A. [Laboratoire Hubert Curien, UMR 5516 CNRS, Universite Jean Monnet, 18 Rue Pr. Benoit Lauras, 42000 Saint-Etienne (France); Bourgeois, O. [Institut Neel, UPR 2940 CNRS, 25 Avenue des Martyrs, 38042 Grenoble Cedex 9 (France); Sanchez-Lopez, J.C. [Instituto de Ciencia de Materiales de Sevilla, Avda. Americo Vespucio, 49 41092 Sevilla (Spain); Rouzaud, J.-N. [Laboratoire de Geologie, UMR 8538 CNRS, Ecole Normale Superieure, 45 Rue d' Ulm, 75230 Paris Cedex 05 (France); Rojas, T.C. [Instituto de Ciencia de Materiales de Sevilla, Avda. Americo Vespucio, 49 41092 Sevilla (Spain); Loir, A.-S. [Laboratoire Hubert Curien, UMR 5516 CNRS, Universite Jean Monnet, 18 Rue Pr. Benoit Lauras, 42000 Saint-Etienne (France); Garden, J.-L. [Institut Neel, UPR 2940 CNRS, 25 Avenue des Martyrs, 38042 Grenoble Cedex 9 (France); Garrelie, F. [Laboratoire Hubert Curien, UMR 5516 CNRS, Universite Jean Monnet, 18 Rue Pr. Benoit Lauras, 42000 Saint-Etienne (France); Donnet, C., E-mail: christophe.donnet@univ-st-etienne.f [Laboratoire Hubert Curien, UMR 5516 CNRS, Universite Jean Monnet, 18 Rue Pr. Benoit Lauras, 42000 Saint-Etienne (France)

    2009-12-31

    The influence of the incorporation of boron in diamond-like carbon (DLC) films on the microstructure of the coatings has been investigated. The boron-containing DLC films (a-C:B) have been deposited by pulsed laser deposition (PLD) at room temperature in high vacuum conditions, by ablating graphite and boron targets either with a femtosecond pulsed laser (800 nm, 150 fs, fs-DLC) or with a nanosecond pulsed laser (248 nm, 20 ns, ns-DLC). Alternative ablation of the graphite and boron targets has been carried out to deposit the a-C:B films. The film structure and composition have been highlighted by coupling Field Emission Scanning Electron Microscopy, Electron Energy Loss Spectroscopy and High Resolution Transmission Electron Microscopy. Using the B K-edge, EELS characterization reveals the boron effect on the carbon bonding. Moreover, the plasmon energy reveals a tendency of graphitization associated to the boron doping. Pure boron particles have been characterized by HRTEM and reveal that those particles are amorphous or crystallized. The nanostructures of the boron-doped ns-DLC and the boron-doped fs-DLC are thus compared. In particular, the incorporation of boron in the DLC matrix is highlighted, depending on the laser used for deposition. Electrical measurements show that some of these films have potentialities to be used in low temperature thermometry, considering their conductivity and temperature coefficient of resistance (TCR) estimated within the temperature range 160-300 K.

  17. Effect of glyphosate-boron application on seed composition and nitrogen metabolism in glyphosate-resistant soybean.

    Science.gov (United States)

    Bellaloui, Nacer; Abbas, Hamed K; Gillen, Anne M; Abel, Craig A

    2009-10-14

    The objective of this study was to evaluate the effects of foliar application of glyphosate (Gly) alone, boron (B) alone, and Gly-B combined on seed composition and nitrogen metabolism in glyphosate-resistant soybean (Glycine max (L.) Merr.). No Gly and no B application plants were used as control (C). Results showed that Gly, Gly-B, or B applications increased protein, oleic acid, and total amino acid concentrations in seed. However, oil and linolenic acid concentrations decreased under those treatments compared with the nontreated control. Gly-B combined or B treatments increased B concentration in leaves and seed, nitrate reductase activity (NRA), and nitrogenase activity and resulted in a significant positive correlation between B concentration in leaves and NRA (r = 0.54; P nutrient uptake and translocation may depend on the ion species and form of the nutrient mixed with Gly. These results demonstrate that Gly-B application alters seed composition, nitrogen metabolism, and B status in leaves and seed.

  18. Electron beam generation and structure of defects in carbon and boron nitride nano-tubes

    Energy Technology Data Exchange (ETDEWEB)

    Zobelli, A

    2007-10-15

    The nature and role of defects is of primary importance to understand the physical properties of C and BN (boron nitride) single walled nano-tubes (SWNTs). Transmission electron microscopy (TEM) is a well known powerful tool to study the structure of defects in materials. However, in the case of SWNTs, the electron irradiation of the TEM may knock out atoms. This effect may alter the native structure of the tube, and has also been proposed as a potential tool for nano-engineering of nano-tubular structures. Here we develop a theoretical description of the irradiation mechanism. First, the anisotropy of the emission energy threshold is obtained via density functional based calculations. Then, we numerically derive the total Mott cross section for different emission sites of carbon and boron nitride nano-tubes with different chiralities. Using a dedicated STEM (Scanning Transmission Electron Microscope) microscope with experimental conditions optimised on the basis of derived cross-sections, we are able to control the generation of defects in nano-tubular systems. Either point or line defects can be obtained with a spatial resolution of a few nanometers. The structure, energetics and electronics of point and line defects in BN systems have been investigated. Stability of mono- and di- vacancy defects in hexagonal boron nitride layers is investigated, and their activation energies and reaction paths for diffusion have been derived using the nudged elastic band method (NEB) combined with density functional based techniques. We demonstrate that the appearance of extended linear defects under electron irradiation is more favorable than a random distribution of point defects and this is due to the existence of preferential sites for atom emission in the presence of pre-existing defects, rather than thermal vacancy nucleation and migration. (author)

  19. XPS of nitrogen-containing functional groups on activated carbon

    NARCIS (Netherlands)

    Jansen, R.J.J.; Bekkum, van H.

    1995-01-01

    XPS is used to study the binding energy of the Cls, Nls and Ols photoelectrons of surface groups on several nitrogen-containing activated carbons. Specific binding energies are assigned to amide (399.9 eV). lactam and imidc (399.7 eV). pyridine (398.7 eV), pyrrole (400.7 eV), alkylamine. secondary a

  20. Nitrogen, carbon, and sulfur metabolism in natural Thioploca samples

    DEFF Research Database (Denmark)

    Otte, S.; Kuenen, JG; Nielsen, LP

    1999-01-01

    Filamentous sulfur bacteria of the genus Thioploca occur as dense mats on the continental shelf off the coast of Chile and Peru. Since little is known about their nitrogen, sulfur, and carbon metabolism, this study was undertaken to investigate their (eco)physiology. Thioploca is able to store in...

  1. Elastic properties of B-C-N films grown by N{sub 2}-reactive sputtering from boron carbide targets

    Energy Technology Data Exchange (ETDEWEB)

    Salas, E.; Jiménez Riobóo, R. J.; Jiménez-Villacorta, F.; Prieto, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain); Sánchez-Marcos, J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain); Dept. Química-Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Muñoz-Martín, A.; Prieto, J. E.; Joco, V. [Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2013-12-07

    Boron-carbon-nitrogen films were grown by RF reactive sputtering from a B{sub 4}C target and N{sub 2} as reactive gas. The films present phase segregation and are mechanically softer than boron carbide films (a factor of more than 2 in Young's modulus). This fact can turn out as an advantage in order to select buffer layers to better anchor boron carbide films on substrates eliminating thermally induced mechanical tensions.

  2. Intercropping enhances soil carbon and nitrogen

    NARCIS (Netherlands)

    Cong, W.; Hoffland, E.; Li, L.; Six, J.; Sun, J.H.; Bao, X.G.; Zhang, F.S.; Werf, van der W.

    2015-01-01

    Intercropping, the simultaneous cultivation of multiple crop species in a single field, increases aboveground productivity due to species complementarity. We hypothesized that intercrops may have greater belowground productivity than sole crops, and sequester more soil carbon over time due to greate

  3. Effects of Nitrogen Forms on Carbon and Nitrogen Accumulation in Tomato Seedling

    Institute of Scientific and Technical Information of China (English)

    GE Ti-da; SONG Shi-wei; CHI Ming-han; HUANG Dan-feng; K Iwasaki

    2008-01-01

    Utilization of organic nitrogen (N) is an important aspect of plant N assimilation and has potential application in sustainable agriculture. The aim of this study was to investigate the plant growth, C and N accumulation in leaves and roots of tomato seedlings in response to inorganic (NH4+-N, NO3--N) and organic nitrogen (Gly-N). Different forms of nitrogen (NH4+-N, NO3--N, Gly-N) were supplied to two tomato cultivars (Shenfen 918 and Huying 932) using a hydroponics system. The plant dry biomass, chlorophyll content, root activity, total carbon and nitrogen content in roots and leaves, and total N absorption, etc. were assayed during the cultivation. Our results showed that no significant differences in plant height, dry biomass, and total N content were found within the first 16 d among three treatments; however, significant differences in treatments on 24 d and 32 d were observed, and the order was NO3--N > GIy-N > NH4+-N. Significant differences were also observed between the two tomato cultivars. Chlorophyll contents in the two cultivars were significantly increased by the GIy-N treatment, and root activity showed a significant decrease in NH4+-N treatment. Tomato leaf total carbon content was slightly affected by different N forms; however, total carbon in root and total nitrogen in root and leaf were promoted significantly by inorganic and organic N. Among the applied N forms, the increasing effects of the NH4+-N treatment were larger than that of the Gly-N. In a word, different N resources resulted in different physiological effects in tomatoes. Organic nitrogen (e.g., Gly-N) can be a proper resource of plant N nutrition. Tomatoes of different genotypes had different responses under organic nitrogen (e.g., Gly-N) supplies.

  4. [FTIR spectroscopic studies of inner stress on boron carbon nitride thin films].

    Science.gov (United States)

    Wang, Yu-Xin; Zheng, Ya-Ru; Song, Zhe; Feng, Ke-Cheng; Zhao, Yong-Nian

    2008-07-01

    Boron carbon nitride thin films were deposited by radio frequency (RF) magnetron sputtering technique using a 50 mm-diameter composite target consisting of h-BN and graphite in an Ar-N2 gas mixture. The composite target was composed of two semi disks: one of h-BN and the other one of graphite. The distance between the target and the substrate was kept at 50 mm. The chamber base pressure was below 5 x 10(-4) Pa. During the deposition, the mixture of Ar (80%) and N2 (20%) was injected into the vacuum chamber and the total pressure was 1.3 Pa. The films were grown on silicon substrates at different deposition parameters, including sputtering power of 80-130 W, deposition temperature of 300-500 degrees C and deposition time of 1-4 h. The chemical bonding state of the samples was characterized by Fourier transform infrared absorption spectroscopy (FTIR). The results suggested that all of the films deposited at these deposition parameters are atomic-level hybrids composed of B, C and N atoms. Besides BN and carbons bonds, the boron carbide and carbon nitride bonds were formed in the BCN thin films. And the deposition parameters have important influences on the growth and inner stress of BCN thin films. That is the higher the sputtering power, the larger the inner stress; the higher or lower the deposition temperature, the larger the inner stress; the longer the deposition time, the larger the inner stress. So changing deposition parameters properly is a feasible method to relax the inner stress between the films and substrate. In the conditions of changing one parameter each time, the optimum deposition parameters to prepare BCN thin films with lower inner stress were obtained: sputtering power of 80 W, deposition temperature of 400 degrees C and deposition time of 2 h.

  5. Effect of reaction conditions on methyl red degradation mediated by boron and nitrogen doped TiO2

    Science.gov (United States)

    Galenda, A.; Crociani, L.; Habra, N. El; Favaro, M.; Natile, M. M.; Rossetto, G.

    2014-09-01

    Nowadays the employment of renewable and sustainable energy sources, and solar light as main option, becomes an urgent need. Photocatalytic processes received great attention in wastewater treatment due to their cheapness, environmental compatibility and optimal performances. Despite the general low selectivity of the photocatalysts, an accurate optimisation of the operational parameters needs to be carried out in order to maximise the process yield. Because of this reason, the present contribution aims to deepen either the knowledge in boron and/or nitrogen doped TiO2-based systems and their employment in methyl red removal from aqueous solutions. The samples were obtained by coprecipitation and characterised by XRD, SEM, BET specific surface area, UV-vis and XPS techniques. The catalytic activity was for the first time carefully evaluated with respect to methyl red photodegradation in different conditions as a function of working pH, counter-ions and pre-adsorption time. An ad-hoc study was performed on the importance of the pre-adsorption of the dye, suggesting that an extended adsorption is useless for the catalyst photoactivity, while a partial coverage is preferable. The photocatalytic tests demonstrate the positive influence of boron doping in photo-activated reactions and the great importance of the operational parameters with respect to the simple methyl red bleaching rather than the overall pollutant mineralisation. It is proved, indeed, that different working pH, acidifying means and substrate pre-adsorption time can enhance or limit the catalyst performances with respect to the complete pollutant degradation rather than its partial breakage.

  6. Carbon and nitrogen budgets of the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Somasundar, K.; Rajendran, A.; DileepKumar, M.; SenGupta, R.

    grams (Tg) for carbon, and 8.06 and 3.60 Tg for nitrogen, respectively. The carbon budget was found to be negatively balanced by 84 Tg year- t. A possible source to compensate for this deficit could be from the northward movement of Antarctic Bottom... with adjoining seas and rivers. This in turn affects the nutrient dynamics of both the Arabian Sea and the Red Sea. Bethoux ( 1988 ) further emphasized the importance of the effect of deep outflow of materials (carbon, nutrients and oxygen) from the Red Sea...

  7. Characterization of boron doped diamond-like carbon film by HRTEM

    Energy Technology Data Exchange (ETDEWEB)

    Li, X.J., E-mail: lixj@alum.imr.ac.cn [College of Material Science and Engineering, Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun 130012 (China); He, L.L., E-mail: llhe@imr.ac.cn [Shenyang National Lab of Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Li, Y.S. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada); Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada); Yang, Q. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada); Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada)

    2015-12-01

    Graphical abstract: - Highlights: • The microstructure of B-DLC film is studied by HRTEM in cross-sectional observation. • Many crystalline nanoparticles dispersed in the amorphous matrix film are observed. • Through composition and structure analysis, the nanoparticles are identified as B{sub 2}O. • The work implies the doped B element exists as oxide state in the B-DLC film. - Abstract: Boron doped diamond-like carbon (B-DLC) film was synthesized on silicon (1 0 0) wafer by biased target ion beam deposition. High-resolution transmission electron microscopy (HRTEM) is employed to investigate the microstructure of the B-DLC thin film in cross-sectional observation. Many crystalline nanoparticles randomly dispersed and embedded in the amorphous matrix film are observed. Through chemical compositional analysis of the B-DLC film, some amount of O element is confirmed to be contained. And also, some nanoparticles with near zone axes are indexed, which are accordance with B{sub 2}O phase. Therefore, the contained O element causing the B element oxidized is proposed, resulting in the formation of the nanoparticles. Our work indicates that in the B-DLC film a significant amount of the doped B element exists as boron suboxide nanoparticles.

  8. Oxygen- and Lithium-Doped Hybrid Boron-Nitride/Carbon Networks for Hydrogen Storage.

    Science.gov (United States)

    Shayeganfar, Farzaneh; Shahsavari, Rouzbeh

    2016-12-20

    Hydrogen storage capacities have been studied on newly designed three-dimensional pillared boron nitride (PBN) and pillared graphene boron nitride (PGBN). We propose these novel materials based on the covalent connection of BNNTs and graphene sheets, which enhance the surface and free volume for storage within the nanomaterial and increase the gravimetric and volumetric hydrogen uptake capacities. Density functional theory and molecular dynamics simulations show that these lithium- and oxygen-doped pillared structures have improved gravimetric and volumetric hydrogen capacities at room temperature, with values on the order of 9.1-11.6 wt % and 40-60 g/L. Our findings demonstrate that the gravimetric uptake of oxygen- and lithium-doped PBN and PGBN has significantly enhanced the hydrogen sorption and desorption. Calculations for O-doped PGBN yield gravimetric hydrogen uptake capacities greater than 11.6 wt % at room temperature. This increased value is attributed to the pillared morphology, which improves the mechanical properties and increases porosity, as well as the high binding energy between oxygen and GBN. Our results suggest that hybrid carbon/BNNT nanostructures are an excellent candidate for hydrogen storage, owing to the combination of the electron mobility of graphene and the polarized nature of BN at heterojunctions, which enhances the uptake capacity, providing ample opportunities to further tune this hybrid material for efficient hydrogen storage.

  9. Boron dipyrromethene (BODIPY) functionalized carbon nano-onions for high resolution cellular imaging

    Science.gov (United States)

    Bartelmess, Juergen; de Luca, Elisa; Signorelli, Angelo; Baldrighi, Michele; Becce, Michele; Brescia, Rosaria; Nardone, Valentina; Parisini, Emilio; Echegoyen, Luis; Pompa, Pier Paolo; Giordani, Silvia

    2014-10-01

    Carbon nano-onions (CNOs) are an exciting class of carbon nanomaterials, which have recently demonstrated a facile cell-penetration capability. In the present work, highly fluorescent boron dipyrromethene (BODIPY) dyes were covalently attached to the surface of CNOs. The introduction of this new carbon nanomaterial-based imaging platform, made of CNOs and BODIPY fluorophores, allows for the exploration of synergetic effects between the two building blocks and for the elucidation of its performance in biological applications. The high fluorescence intensity exhibited by the functionalized CNOs translates into an excellent in vitro probe for the high resolution imaging of MCF-7 human breast cancer cells. It was also found that the CNOs, internalized by the cells by endocytosis, localized in the lysosomes and did not show any cytotoxic effects. The presented results highlight CNOs as excellent platforms for biological and biomedical studies due to their low toxicity, efficient cellular uptake and low fluorescence quenching of attached probes.Carbon nano-onions (CNOs) are an exciting class of carbon nanomaterials, which have recently demonstrated a facile cell-penetration capability. In the present work, highly fluorescent boron dipyrromethene (BODIPY) dyes were covalently attached to the surface of CNOs. The introduction of this new carbon nanomaterial-based imaging platform, made of CNOs and BODIPY fluorophores, allows for the exploration of synergetic effects between the two building blocks and for the elucidation of its performance in biological applications. The high fluorescence intensity exhibited by the functionalized CNOs translates into an excellent in vitro probe for the high resolution imaging of MCF-7 human breast cancer cells. It was also found that the CNOs, internalized by the cells by endocytosis, localized in the lysosomes and did not show any cytotoxic effects. The presented results highlight CNOs as excellent platforms for biological and biomedical

  10. Encapsulation of cisplatin as an anti-cancer drug into boron-nitride and carbon nanotubes: Molecular simulation and free energy calculation

    Energy Technology Data Exchange (ETDEWEB)

    Roosta, Sara [Molecular Simulation Research Laboratory, Department of Chemistry, Iran University of Science & Technology, Tehran (Iran, Islamic Republic of); Hashemianzadeh, Seyed Majid, E-mail: hashemianzadeh@iust.ac.ir [Molecular Simulation Research Laboratory, Department of Chemistry, Iran University of Science & Technology, Tehran (Iran, Islamic Republic of); Ketabi, Sepideh, E-mail: sepidehketabi@yahoo.com [Department of Chemistry, East Tehran Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2016-10-01

    Encapsulation of cisplatin anticancer drug into the single walled (10, 0) carbon nanotube and (10, 0) boron-nitride nanotube was investigated by quantum mechanical calculations and Monte Carlo Simulation in aqueous solution. Solvation free energies and complexation free energies of the cisplatin@ carbon nanotube and cisplatin@ boron-nitride nanotube complexes was determined as well as radial distribution functions of entitled compounds. Solvation free energies of cisplatin@ carbon nanotube and cisplatin@ boron-nitride nanotube were − 4.128 kcal mol{sup −1} and − 2457.124 kcal mol{sup −1} respectively. The results showed that cisplatin@ boron-nitride nanotube was more soluble species in water. In addition electrostatic contribution of the interaction of boron- nitride nanotube complex and solvent was − 281.937 kcal mol{sup −1} which really more than Van der Waals and so the electrostatic interactions play a distinctive role in the solvation free energies of boron- nitride nanotube compounds. On the other hand electrostatic part of the interaction of carbon nanotube complex and solvent were almost the same as Van der Waals contribution. Complexation free energies were also computed to study the stability of related structures and the free energies were negative (− 374.082 and − 245.766 kcal mol{sup −1}) which confirmed encapsulation of drug into abovementioned nanotubes. However, boron-nitride nanotubes were more appropriate for encapsulation due to their larger solubility in aqueous solution. - Highlights: • Solubility of cisplatin@ boron-nitride nanotube is larger than cisplatin@ carbon nanotube. • Boron- nitride nanotube complexes have larger electrostatic contribution in solvation free energy. • Complexation free energies confirm encapsulation of drug into the nanotubes in aqueous solution. • Boron- nitride nanotubes are appropriate drug delivery systems compared with carbon nanotubes.

  11. Influence of oxygen impurity on electronic properties of carbon and boron nitride nanotubes: A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ram Sevak, E-mail: singh915@gmail.com [Department of Physics, National Institute of TechnologyKurukshetra 136119 (Haryana) (India)

    2015-11-15

    Influence of oxygen impurity on electronic properties of carbon and boron nitride nanotubes (CNTs and BNNTs) is systematically studied using first principle calculations based on density functional theory. Energy band structures and density of states of optimized zigzag (5, 0), armchair (3, 3), and chiral (4, 2) structures of CNT and BNNT are calculated. Oxygen doping in zigzag CNT exhibits a reduction in metallicity with opening of band gap in near-infrared region while metallicity is enhanced in armchair and chiral CNTs. Unlike oxygen-doped CNTs, energy bands are drastically modulated in oxygen-doped zigzag and armchair BNNTs, showing the nanotubes to have metallic behaviour. Furthermore, oxygen impurity in chiral BNNT induces narrowing of band gap, indicating a gradual modification of electronic band structure. This study underscores the understanding of different electronic properties induced in CNTs and BNNTs under oxygen doping, and has potential in fabrication of various nanoelectronic devices.

  12. Influence of oxygen impurity on electronic properties of carbon and boron nitride nanotubes: A comparative study

    Directory of Open Access Journals (Sweden)

    Ram Sevak Singh

    2015-11-01

    Full Text Available Influence of oxygen impurity on electronic properties of carbon and boron nitride nanotubes (CNTs and BNNTs is systematically studied using first principle calculations based on density functional theory. Energy band structures and density of states of optimized zigzag (5, 0, armchair (3, 3, and chiral (4, 2 structures of CNT and BNNT are calculated. Oxygen doping in zigzag CNT exhibits a reduction in metallicity with opening of band gap in near-infrared region while metallicity is enhanced in armchair and chiral CNTs. Unlike oxygen-doped CNTs, energy bands are drastically modulated in oxygen-doped zigzag and armchair BNNTs, showing the nanotubes to have metallic behaviour. Furthermore, oxygen impurity in chiral BNNT induces narrowing of band gap, indicating a gradual modification of electronic band structure. This study underscores the understanding of different electronic properties induced in CNTs and BNNTs under oxygen doping, and has potential in fabrication of various nanoelectronic devices.

  13. Improvements of stress controllability and radiation resistance by adding carbon to boron-nitride

    Energy Technology Data Exchange (ETDEWEB)

    Nakaishi, M.; Sugishima, K. (Fujitsu Limited, Advanced Technology Div., Nakahara-ku, Kawasaki 211 (JP)); Yamada, M. (Stanford Electronics Lab., Stanford Univ., Stanford, CA (US))

    1990-07-01

    The addition of an atom having different bonding radii to a matrix film is an effective method for changing the stress of the film. In a plasma-enhanced CVD of BN, it is difficult to obtain tensile stress except for extremely boron-rich films. The controllability of tensile stress in BN film was improved by introducing a small amount of carbon into the BN matrix, using plasma-enhanced CVD between 400{degrees} and 500{degrees}C. The authors have obtained transparent films with high Young's modulus and tensile stress. They report that the radiation resistance of BNC deposited at 400{degrees}C was improved five times better than that of BN deposited by low-pressure CVD at similar temperatures.

  14. Boron Nitride Coated Carbon Nanotube Arrays with Enhanced Compressive Mechanical Property

    Science.gov (United States)

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

    Vertically aligned carbon nanotube (CNT) array is one of the most promising energy dissipating materials due to its excellent temperature invariant mechanical property. However, the CNT arrays with desirable recoverability after compression is still a challenge. Here, we report on the mechanical enhancement of the CNT arrays reinforced by coating with boron nitride (BN) layers. These BN coated CNT (BN/CNT) arrays exhibit excellent compressive strength and recoverability as compared to those of the as-prepared CNT arrays which totally collapsed after compression. In addition, the BN coating also provides better resistance to oxidation due to its intrinsic thermal stability. This work presented here opens a new pathway towards tuning mechanical behavior of any arbitrary CNT arrays for promising potential such as damper, vibration isolator and shock absorber applications.

  15. Simultaneous tracing of carbon and nitrogen isotopes in human cells.

    Science.gov (United States)

    Nilsson, Roland; Jain, Mohit

    2016-05-24

    Stable isotope tracing is a powerful method for interrogating metabolic enzyme activities across the metabolic network of living cells. However, most studies of mammalian cells have used (13)C-labeled tracers only and focused on reactions in central carbon metabolism. Cellular metabolism, however, involves other biologically important elements, including nitrogen, hydrogen, oxygen, phosphate and sulfur. Tracing stable isotopes of such elements may help shed light on poorly understood metabolic pathways. Here, we demonstrate the use of high-resolution mass spectrometry to simultaneously trace carbon and nitrogen metabolism in human cells cultured with (13)C- and (15)N-labeled glucose and glutamine. To facilitate interpretation of the complex isotopomer data generated, we extend current methods for metabolic flux analysis to handle multivariate mass isotopomer distributions (MMIDs). We find that observed MMIDs are broadly consistent with known biochemical pathways. Whereas measured (13)C MIDs were informative for central carbon metabolism, (15)N isotopes provided evidence for nitrogen-carrying reactions in amino acid and nucleotide metabolism. This computational and experimental methodology expands the scope of metabolic flux analysis beyond carbon metabolism, and may prove important to understanding metabolic phenotypes in health and disease.

  16. Properties of boron and phosphorous incorporated tetrahedral amorphous carbon films grown using filtered cathodic vacuum arc process

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Khan, Mohd Alim [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Satyanarayana, B.S. [40, Sreeniketan, NDSE 24, New Delhi 110096 (India); Kumar, Sushil; Ishpal [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India)

    2010-04-15

    This paper reports the electrical, mechanical, structural and field emission properties of as grown and also boron and phosphorous incorporated tetrahedral amorphous carbon (ta-C) films, deposited using a filtered cathodic vacuum arc process. The effect of varying boron and phosphorous content (up to 2.0 at.% in to ta-C) on the conductivity ({sigma}{sub D}), activation energy ({Delta}E{sub 1}), hardness, microstructure, emission threshold (E{sub turn-ON}) and emission current density (J) at 12.5 V/{mu}m of ta-C: B and ta-C: P films deposited at a high negative substrate bias of -300 V are reported. It is observed that both boron and phosphorous incorporation leads to a nearly an order increase in {sigma}{sub D} and corresponding decrease in {Delta}E{sub 1} and a slight increase in hardness as compared to as grown ta-C films. In the case of field assisted electron emission, it is observed that E{sub turn-ON} increases and J decreases. The changes are attributed to the changes in the sp{sup 3}/sp{sup 2} ratio of the films due to boron and phosphorous incorporation. The effect of boron on ta-C is to give a p-type effect whereas the effect of phosphorous gives n-type doping effect.

  17. Preparation and characterization of boron nitride coatings on carbon fibers from borazine by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Li Junsheng, E-mail: charlesljs@163.com [State Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha, 410073 (China); Zhang Changrui; Li Bin [State Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha, 410073 (China)

    2011-06-15

    Boron nitride (BN) coatings were deposited on carbon fibers by chemical vapor deposition (CVD) using borazine as single source precursor. The deposited coatings were characterized by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The effect of temperatures on growth kinetics, morphology, composition and structure of the coatings was investigated. In the low temperature range of 900 deg. C-1000 deg. C, the growth rate increased with increasing temperature complying with Arrhenius law, and an apparent active energy of 72 kJ/mol was calculated. The coating surface was smooth and compact, and the coatings uniformly deposited on individual fibers of carbon fiber bundles. The growth was controlled by surface reaction. At 1000 deg. C, the deposition rate reached a maximum (2.5 {mu}m/h). At the same time, the limiting step of the growth translated to be mass-transportation. Above 1100 deg. C, the growth rate decreased drastically due to the occurrence of gas-phase nucleation. Moreover, the coating surface became loose and rough. Composition and structure examinations revealed that stoichiometric BN coatings with turbostratic structure were obtained below 1000 deg. C, while hexagonal BN coatings were deposited above 1100 deg. C. A penetration of carbon element from the fibers to the coatings was observed.

  18. Phase transitions of boron carbide: Pair interaction model of high carbon limit

    Science.gov (United States)

    Yao, Sanxi; Huhn, W. P.; Widom, M.

    2015-09-01

    Boron Carbide exhibits a broad composition range, implying a degree of intrinsic substitutional disorder. While the observed phase has rhombohedral symmetry (space group R 3 bar m), the enthalpy minimizing structure has lower, monoclinic, symmetry (space group Cm). The crystallographic primitive cell consists of a 12-atom icosahedron placed at the vertex of a rhombohedral lattice, together with a 3-atom chain along the 3-fold axis. In the limit of high carbon content, approaching 20% carbon, the icosahedra are usually of type B11 Cp, where the p indicates the carbon resides on a polar site, while the chains are of type C-B-C. We establish an atomic interaction model for this composition limit, fit to density functional theory total energies, that allows us to investigate the substitutional disorder using Monte Carlo simulations augmented by multiple histogram analysis. We find that the low temperature monoclinic Cm structure disorders through a pair of phase transitions, first via a 3-state Potts-like transition to space group R3m, then via an Ising-like transition to the experimentally observed R 3 bar m symmetry. The R3m and Cm phases are electrically polarized, while the high temperature R 3 bar m phase is nonpolar.

  19. [Interactions of straw, nitrogen fertilizer and bacterivorous nematodes on soil labile carbon and nitrogen and greenhouse gas emissions].

    Science.gov (United States)

    Zhang, Teng-Hao; Wang, Nan; Liu, Man-Qiang; Li, Fang-Hui; Zhu, Kang-Li; Li, Hui-Xin; Hu, Feng

    2014-11-01

    A 3 x 2 factorial design of microcosm experiment was conducted to investigate the interactive effects of straw, nitrogen fertilizer and bacterivorous nematodes on soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)), dissolved organic carbon (DOC) and nitrogen (DON), mineral nitrogen (NH(4+)-N and NO(3-)-N), and greenhouse gas (CO2, N2O and CH4) emissions. Results showed that straw amendment remarkably increased the numbers of bacterivorous nematodes and the contents of Cmic and Nmic, but Cmic and Nmic decreased with the increasing dose of nitrogen fertilization. The effects of bacterivorous nematodes strongly depended on either straw or nitrogen fertilization. The interactions of straw, nitrogen fertilization and bacterivorous nematodes on soil DOC, DON and mineral nitrogen were strong. Straw and nitrogen fertilization increased DOC and mineral nitrogen contents, but their influences on DON depended on the bacterivorous nematodes. The DOC and mineral nitrogen were negatively and positively influenced by the bacterivorous nematodes, re- spectively. Straw significantly promoted CO2 and N2O emissions but inhibited CH4 emission, while interactions between nematodes and nitrogen fertilization on emissions of greenhouse gases were obvious. In the presence of straw, nematodes increased cumulative CO2 emissions with low nitrogen fertilization, but decreased CO2 and N2O emissions with high nitrogen fertilization on the 56th day after incubation. In summary, mechanical understanding the soil ecological process would inevitably needs to consider the roles of soil microfauna.

  20. Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Well-aligned carbon nitrogen nanotube films have been synthesized successfully on mesoporous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1-xNx (x=0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds covalently with nitrogen in all the carbon nitrogen nanotube films.

  1. Growth of Structured Non-crystalline Boron-Oxygen-Nitrogen Films and Measurement of Their Electrical Properties

    Institute of Scientific and Technical Information of China (English)

    CHEN Guang-Chao(陈广超); LU Fan-Xiu(吕反修); J.-H.Boo

    2003-01-01

    The boron-oxygen-nitrogen (BON) films have been grown on Si wafer by the low-frequency rf-plasma-enhanced metal-organic chemical vapour deposition method. The homogeneous film structure of completely amorphous BON is first fabricated on a low-temperature-made buffer at 500° C with N2 plasma and is observed with a high resolution-electron microscope by the transmission-electron diffraction. The results show that the interfaces among substrate/buffer/film are clear and straight in the structured film. A heterogeneous film containing nano-sized crystalline particles is also grown by a routine growth procedure as a referential structure. The C - V characteristic is measured on both the amorphous and crystal-containing films by using the metal-oxidesemiconductor structure. The dielectric constants of the films are, therefore, deduced to be 5.9 and 10.5 for the amorphous and crystal-containing films, respectively. The C - V results also indicate that more trapped charges exist in the amorphous film. The binding energy of the B, O, and N atoms in the amorphous film is higher than that in the crystal-containing one, and the N-content in the latter is found to be higher than that in the former by x-ray photo-electron spectroscopy. The different electrical property of the films is thought to originate from the energy state of the covalent electrons.

  2. Fabrication of boron-doped carbon fibers by the decomposition of B4C and its excellent rate performance as an anode material for lithium-ion batteries

    Science.gov (United States)

    Wang, Huiqi; Ma, Canliang; Yang, Xueteng; Han, Tao; Tao, Zechao; Song, Yan; Liu, Zhanjun; Guo, Quangui; Liu, Lang

    2015-03-01

    A facile route, for the first time, was developed to fabricate boron-doped carbon fibers (BDCFs). Boron was doped into mesosphere pitch-based carbon fibers (CFs) by exposing the CFs in a vapor of boron by the decomposition of boron carbide. The microstructure of BDCFs was characterized by SEM, TEM, XRD and Raman spectroscopy. When used as anode materials for the lithium-ion batteries, BDCFs electrode exhibits an improved performance. Concretely, the specific capacity of BDCFs still had a value of over 400 mAh g-1 after 100 cycles. Moreover, BDCFs exhibits better rate capability and less hysteresis in comparison to the pristine CFs. Such enhanced lithium storage capability can be attributed to the improvement of graphitization properties and the high amount of defects induced by boron.

  3. Transesterification of triglycerides using nitrogen-functionalized carbon nanotubes.

    Science.gov (United States)

    Villa, Alberto; Tessonnier, Jean-Philippe; Majoulet, Olivier; Su, Dang Sheng; Schlögl, Robert

    2010-02-22

    Nitrogen-functionalized carbon nanotubes were synthesized by grafting amino groups to the surface of the nanotubes. The nanotubes exhibited promising results in the base-catalyzed liquid phase transesterification of glyceryl tributyrate with methanol, which is a model reaction for the production of biodiesel. The concentration of the active sites and the reaction parameters, such as temperature and glyceryl tributyrate to methanol ratio, were shown to significantly affect catalytic performance. The grafting technique employed allowed for design and control of the active sites. As a consequence, it was possible to design a nitrogen-functionalized carbon nanotube catalyst with a few strong, basic groups. This might be of interest for carbohydrate conversion reactions where strong basic sites are required but the pH of the solution should remain mild to avoid the degradation of the reactants and/or products.

  4. Methods of producing continuous boron carbide fibers

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  5. Electrical and Electrochemical Properties of Nitrogen-Containing Tetrahedral Amorphous Carbon (ta-C) Thin Films

    Science.gov (United States)

    Yang, Xingyi

    Tetrahedral amorphous carbon (ta-C) is a diamond-like carbon (DLC) material comprised of a mixture of sp2 (˜40%) and sp3-bonded (˜60%) carbon domains. The physicochemical structure and electrochemical properties depend strongly on the sp2/sp3 bonding ratio as well as the incorporation of impurities, such as hydrogen or nitrogen. The ability to grow ta-C films at lower temperatures (25-100 °C) on a wider variety of substrates is a potential advantage of these materials as compared with diamond films. In this project, the basic structural and electrochemical properties of nitrogen-incorporated ta-C thin films will be discussed. The major goal of this work was to determine if the ta-C:N films exhibit electrochemical properties more closely aligned with those of boron-doped diamond (sp 3 carbon) or glassy carbon (amorphous sp2 carbon). Much like diamond, ta-C:N thin-film electrodes are characterized by a low background voltammetric current, a wide working potential window, relatively rapid electron-transfer kinetics for aqueous redox systems, such as Fe(CN) 6-3/-4 and Ru(NH3)6+3/+2 , and weak adsorption of polar molecules from solution. For example, negligible adsorption of methylene blue was found on the ta-C:N films in contrast to glassy carbon; a surface on which this molecule strongly adsorbs. The film microstructure was studied with x-ray photoelectron microscopy (XPS), visible Raman spectroscopy and electron-energy loss spectroscopy (EELS); all of which revealed the sp2-bonded carbon content increased with increasing nitrogen. The electrical properties of ta-C:N films were studied by four-point probe resistance measurement and conductive-probe AFM (CP-AFM). The incorporation of nitrogen into ta-C films increased the electrical conductivity primarily by increasing the sp2-bonded carbon content. CP-AFM showed the distribution of the conductive sp2-carbon on the film surface was not uniform. These films have potential to be used in field emission area. The

  6. Forest defoliator pests alter carbon and nitrogen cycles

    Science.gov (United States)

    Grüning, Maren; Simon, Judy; Reinhardt, Annett-Barbara; Lamersdorf, Norbert; Thies, Carsten

    2016-01-01

    Climate change may foster pest epidemics in forests, and thereby the fluxes of elements that are indicators of ecosystem functioning. We examined compounds of carbon (C) and nitrogen (N) in insect faeces, leaf litter, throughfall and analysed the soils of deciduous oak forests (Quercus petraea L.) that were heavily infested by the leaf herbivores winter moth (Operophtera brumata L.) and mottled umber (Erannis defoliaria L.). In infested forests, total net canopy-to-soil fluxes of C and N deriving from insect faeces, leaf litter and throughfall were 30- and 18-fold higher compared with uninfested oak forests, with 4333 kg C ha−1 and 319 kg N ha−1, respectively, during a pest outbreak over 3 years. In infested forests, C and N levels in soil solutions were enhanced and C/N ratios in humus layers were reduced indicating an extended canopy-to-soil element pathway compared with the non-infested forests. In a microcosm incubation experiment, soil treatments with insect faeces showed 16-fold higher fluxes of carbon dioxide and 10-fold higher fluxes of dissolved organic carbon compared with soil treatments without added insect faeces (control). Thus, the deposition of high rates of nitrogen and rapidly decomposable carbon compounds in the course of forest pest epidemics appears to stimulate soil microbial activity (i.e. heterotrophic respiration), and therefore, may represent an important mechanism by which climate change can initiate a carbon cycle feedback. PMID:27853551

  7. On The Cosmic Origins Of Carbon And Nitrogen

    CERN Document Server

    Henry, R B C; Köppen, J

    2000-01-01

    We analyze the behavior of N/O and C/O abundance ratios as a function of metallicity as gauged by O/H in large, extant Galactic and extragalactic H II region abundance samples. Numerical chemical evolution models are computed using published stellar yields implied by comparing analytical models to the observations. Our results suggest that carbon and nitrogen originate from separate production sites and are decoupled from one another. Massive stars (M>8M_sun) dominate the production of carbon, while intermediate-mass stars between 4 and 8 solar masses, with a characteristic ejection delay time of 250 Myr after their formation, dominate nitrogen production. Carbon production is positively sensitive to metallicity through mass loss processes in massive stars and has a pseudo-secondary character. Nitrogen production in intermediate mass stars is primary at low metallicity, but clearly secondary (and perhaps tertiary) when 12+log(O/H)>8.3. The observed flat behavior of N/O versus O/H in metal-poor galaxies is exp...

  8. Encapsulation of cisplatin as an anti-cancer drug into boron-nitride and carbon nanotubes: Molecular simulation and free energy calculation.

    Science.gov (United States)

    Roosta, Sara; Hashemianzadeh, Seyed Majid; Ketabi, Sepideh

    2016-10-01

    Encapsulation of cisplatin anticancer drug into the single walled (10, 0) carbon nanotube and (10, 0) boron-nitride nanotube was investigated by quantum mechanical calculations and Monte Carlo Simulation in aqueous solution. Solvation free energies and complexation free energies of the cisplatin@ carbon nanotube and cisplatin@ boron-nitride nanotube complexes was determined as well as radial distribution functions of entitled compounds. Solvation free energies of cisplatin@ carbon nanotube and cisplatin@ boron-nitride nanotube were -4.128kcalmol(-1) and -2457.124kcalmol(-1) respectively. The results showed that cisplatin@ boron-nitride nanotube was more soluble species in water. In addition electrostatic contribution of the interaction of boron- nitride nanotube complex and solvent was -281.937kcalmol(-1) which really more than Van der Waals and so the electrostatic interactions play a distinctive role in the solvation free energies of boron- nitride nanotube compounds. On the other hand electrostatic part of the interaction of carbon nanotube complex and solvent were almost the same as Van der Waals contribution. Complexation free energies were also computed to study the stability of related structures and the free energies were negative (-374.082 and -245.766kcalmol(-1)) which confirmed encapsulation of drug into abovementioned nanotubes. However, boron-nitride nanotubes were more appropriate for encapsulation due to their larger solubility in aqueous solution.

  9. Carbon and Nitrogen Accumulation Rates in Salt Marshes in Oregon, USA

    Science.gov (United States)

    Two important ecosystem services of wetlands are carbon sequestration and filtration of nutrients and particulates. We quantified the carbon and nitrogen accumulation rates in salt marshes at 135 plots distributed across eight estuaries located in Oregon, USA. Net carbon and ...

  10. Synthesis, Characterization, and Tribological Evaluation of TiO2-Reinforced Boron and Nitrogen co-Doped Reduced Graphene Oxide Based Hybrid Nanomaterials as Efficient Antiwear Lubricant Additives.

    Science.gov (United States)

    Jaiswal, Vinay; Kalyani; Umrao, Sima; Rastogi, Rashmi B; Kumar, Rajesh; Srivastava, Anchal

    2016-05-11

    The microwave-synthesized reduced graphene oxide (MRG), boron-doped reduced graphene oxide (B-MRG), nitrogen-doped reduced graphene oxide (N-MRG), boron-nitrogen-co-doped reduced graphene oxide (B-N-MRG), and TiO2-reinforced B-N-MRG (TiO2-B-N-MRG) nanomaterials have been synthesized and characterized by various state-of-the-art techniques, like Raman spectroscopy, powder X-ray diffraction, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the tribological properties of prepared nanomaterials as antiwear additives in neutral paraffin oil have been evaluated using a four-ball machine at an optimized additive concentration (0.15% w/v). The tribological parameters, like mean wear scar diameter, coefficient of friction, and wear rates, revealed that these nanomaterials have potential to be developed as environmentally friendly sulfated-ash-, phosphorus-, and sulfur-free antiwear lubricant additives. The friction- and wear-reducing behavior of MRG increased upon successive doping of nitrogen, boron, and both nitrogen and boron. Among these additives, B-N-co-doped MRG shows superior tribological behavior in paraffin base oil. Besides this, the load-carrying properties of B-N-co-doped MRG have significantly improved after its reinforcement with TiO2 nanoparticles. A comparative study of the surface morphology of a lubricated track in the presence of various additives has been assessed by SEM and contact-mode atomic force microscopy. The X-ray photoelectron spectroscopy studies have proved that the excellent lubrication properties of TiO2-B-N-MRG are due to the in situ formation of a tribofilm composed of boron nitride, adsorbed graphene layers, and tribosintered TiO2 nanoparticles during the tribocontact. Being sulfur-, halogen-, and phosphorus-free, these graphene-based nanomaterials act as green antiwear additives, protecting interacting

  11. Remarkably efficient synthesis of 2H-indazole 1-oxides and 2H-indazoles via tandem carbon-carbon followed by nitrogen-nitrogen bond formation.

    Science.gov (United States)

    Bouillon, Isabelle; Zajícek, Jaroslav; Pudelová, Nadĕzda; Krchnák, Viktor

    2008-11-21

    Base-catalyzed tandem carbon-carbon followed by nitrogen-nitrogen bond formations quantitatively converted N-alkyl-2-nitro-N-(2-oxo-2-aryl-ethyl)-benzenesulfonamides to 2H-indazoles 1-oxides under mild conditions. Triphenylphosphine or mesyl chloride/triethylamine-mediated deoxygenation afforded 2H-indazoles.

  12. Sewage sludge composting simulation as carbon/nitrogen concentration change

    Institute of Scientific and Technical Information of China (English)

    Nassereldeen Kabbashi

    2011-01-01

    Available composting models do not describe accurately the dynamics of composting processes.Difficulty in modeling composting processes is attributed mainly to the unpredicted change in process rate caused by change in activation energy value (E).This article presented the results of an attempt made to utilize patterns of change in carbon,nitrogen and temperature profiles to model sewage sludge composting process as a multi-stage process.Results of controlled sewage sludge composting experiments were used in th estudy.All the experiments were carried out as batch experiments in a 300-liter Horizontal Drum Bioreactor (HDB).Analysis of the profiles of carbon,nitrogen and temperature has indicated that there were clear patterns that could be used to develop simple models of the process,the initial C/N ratio was between 7-8 and the final C/N ratio of the compost in most experiments were found to be around 15.0,indicating the compost was fully matured and could be used safely for agricultural purpose.Electrical conductivity of composting material decreased from 1.83 to 1.67 dS/m,after a period,it increased gradually from 2.01 to 2.23 dS/m and remained at around 2.33 dS/m till the end of composting.It is found that change in the concentration of total carbon can reasonably be described by three constant process rate coefficients (k1,k2,k3).It is found that the process starts with a certain process rate coefficient (k1) and continues until peak temperature is reached,then it reaches lower process (k2) in the declining phase of the thermophilic stage,and finally it proceeds with a faster process rate (k3) when maturation is reached.Change in the concentration of total nitrogen has shown to have the same patterns of change as carbon.

  13. Nitrogen Doped Carbon Nanotubes from Organometallic Compounds: A Review

    Directory of Open Access Journals (Sweden)

    Neil J. Coville

    2010-03-01

    Full Text Available Nitrogen doped carbon nanotubes (N-CNTs have become a topic of increased importance in the study of carbonaceous materials. This arises from the physical and chemical properties that are created when N is embedded in a CNT. These properties include modified chemical reactivity and modified conductivity and mechanical properties. A range of methodologies have been devised to synthesize N-CNTs. One of the procedures uses a floating catalyst in which an organometallic complex is decomposed in the gas phase in the presence of a nitrogen containing reactant to give N-CNTs. Most studies have been limited to ferrocene, ring substituted ferrocene and Fe(CO5. This review covers the synthesis (and properties of N-CNTs and other shaped carbon nanomaterials (SCNMs produced using organometallic complexes. It summarizes the effects that physical parameters such as temperature, pressure, gas flow rates, type and concentration of N source etc. have on the N-CNT type, size and yields as well as the nitrogen content incorporated into the tubes that are produced from organometallic complexes. Proposed growth models for N-CNT synthesis are also reported.

  14. The carbon-nitrogen balance of the nodule and its regulation under elevated carbon dioxide concentration.

    Science.gov (United States)

    Libault, Marc

    2014-01-01

    Legumes have developed a unique way to interact with bacteria: in addition to preventing infection from pathogenic bacteria like any other plant, legumes also developed a mutualistic symbiotic relationship with one gender of soil bacteria: rhizobium. This interaction leads to the development of a new root organ, the nodule, where the differentiated bacteria fix for the plant the atmospheric dinitrogen (atmN2). In exchange, the symbiont will benefit from a permanent source of carbon compounds, products of the photosynthesis. The substantial amounts of fixed carbon dioxide dedicated to the symbiont imposed to the plant a tight regulation of the nodulation process to balance carbon and nitrogen incomes and outcomes. Climate change including the increase of the concentration of the atmospheric carbon dioxide is going to modify the rates of plant photosynthesis, the balance between nitrogen and carbon, and, as a consequence, the regulatory mechanisms of the nodulation process. This review focuses on the regulatory mechanisms controlling carbon/nitrogen balances in the context of legume nodulation and discusses how the change in atmospheric carbon dioxide concentration could affect nodulation efficiency.

  15. Science Letters: Nitrogen doping of activated carbon loading Fe2O3 and activity in carbon-nitric oxide reaction

    Institute of Scientific and Technical Information of China (English)

    WAN Xian-kai; ZOU Xue-quan; SHI Hui-xiang; WANG Da-hui

    2007-01-01

    Nitrogen doping of activated carbon loading Fe2O3 was performed by annealing in ammonia, and the activity of the modified carbon for NO reduction was studied in the presence of oxygen. Results show that Fe2O3 enhances the amount of surface oxygen complexes and facilitates nitrogen incorporation in the carbon, especially in the form of pyridinic nitrogen. The modified carbon shows excellent activity for NO reduction in the low temperature regime (<500 ℃) because of the cooperative effect of Fe2O3 and the surface nitrogen species.

  16. Permafrost carbon-climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics.

    Science.gov (United States)

    Koven, Charles D; Lawrence, David M; Riley, William J

    2015-03-24

    Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon-nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw.

  17. Integration of Carbon, Nitrogen, and Oxygen Metabolism in Escherichia coli

    Science.gov (United States)

    2012-10-22

    glycolysis and the  citric   acid   cycle  and monitored the effect on RpoS degradation  in vivo. Nutrient  upshifts trigger RpoS degradation  independently...Yuan  et  al.,  2009). We  successfully combined the simplified nitrogen assimilation model with simplified models of glycolysis and the  TCA  cycle  to...TCA  cycle  (where carbon and nitrogen metabolism directly intersect). Our  investigation  yielded  significant  advances  in  the  understanding  of  E

  18. Local atomic and electronic structure of boron chemical doping in monolayer graphene.

    Science.gov (United States)

    Zhao, Liuyan; Levendorf, Mark; Goncher, Scott; Schiros, Theanne; Pálová, Lucia; Zabet-Khosousi, Amir; Rim, Kwang Taeg; Gutiérrez, Christopher; Nordlund, Dennis; Jaye, Cherno; Hybertsen, Mark; Reichman, David; Flynn, George W; Park, Jiwoong; Pasupathy, Abhay N

    2013-10-09

    We use scanning tunneling microscopy and X-ray spectroscopy to characterize the atomic and electronic structure of boron-doped and nitrogen-doped graphene created by chemical vapor deposition on copper substrates. Microscopic measurements show that boron, like nitrogen, incorporates into the carbon lattice primarily in the graphitic form and contributes ~0.5 carriers into the graphene sheet per dopant. Density functional theory calculations indicate that boron dopants interact strongly with the underlying copper substrate while nitrogen dopants do not. The local bonding differences between graphitic boron and nitrogen dopants lead to large scale differences in dopant distribution. The distribution of dopants is observed to be completely random in the case of boron, while nitrogen displays strong sublattice clustering. Structurally, nitrogen-doped graphene is relatively defect-free while boron-doped graphene films show a large number of Stone-Wales defects. These defects create local electronic resonances and cause electronic scattering, but do not electronically dope the graphene film.

  19. Long-term effect of tillage, nitrogen fertilization and cover crops on soil organic carbon and total nitrogen content

    OpenAIRE

    2011-01-01

    Metadata only record No-till practices, in conjunction with cover crops and nitrogen fertilization, have been shown to augment soil organic carbon content and total nitrogen content. However, interactions between these components in a no-till system are not well-known. This study offers a long-term (1993-2008) comparative analysis of conventional versus no-till practices as well as a some insight regarding the synergies between no-till, nitrogen fertilization, and cover crops. Maize, wheat...

  20. Carbon-to-nitrogen ratios in agricultural residues

    Energy Technology Data Exchange (ETDEWEB)

    Ilukor, J.O.; Oluka, S.O. [Department of Physics, Makerere University, Kampala (Uganda)

    1995-12-31

    Agronomic crop residues produce greenhouse gas emissions. Crops that produce residues at harvest and during processing may vary from country to country. These residues, which can be in the form of peels, husks, stalks, or straw, are generally considered to be waste products. The carbon (C) and nitrogen (N) content of 19 different agronomic and grass crops common in Uganda were determined using standard laboratory methods. The C and N content of the samples were calculated from two separate equations containing a moisture correction factor. The crop residue C/N ratios were similar to UNEP/OECD/IEA/IPCC values. 3 tabs., 7 refs.

  1. Lattice mismatch induced curved configurations of hybrid boron nitride-carbon nanotubes

    Science.gov (United States)

    Zhang, Jin

    2016-10-01

    A unique curved configuration is observed in freestanding hybrid boron nitride-carbon nanotubes (BN-CNTs) based on molecular dynamics simulations, which, in previous studies, was tacitly assumed as a straight configuration. The physical fundamentals of this phenomenon are explored by using the continuum mechanics theory, where the curved configuration of BN-CNTs is found to be induced by the bending effect due to the lattice mismatch between the C domain and the BN domain. In addition, our results show that the curvature of the curved BN-CNTs is determined by their radius and composition. The curvature of BN-CNTs decreases with growing radius of BN-CNTs and becomes ignorable when their radius is relatively large. A non-monotonic relationship is detected between the curvature and the composition of BN-CNTs. Specifically, the curvature of BN-CNTs increases with growing BN concentration when the molar fraction of BN atoms is smaller than a critical value 0.52, but decreases with growing BN concentration when the molar fraction of BN atoms is larger than this critical value.

  2. Dibenzothiophene adsorption at boron doped carbon nanoribbons studied within density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    López-Albarrán, P. [Facultad de Ingeniería en Tecnología de la Madera, Universidad Michoacana de San Nicolás de Hidalgo, Santiago Tapia 403, CP 58000, Morelia, Michoacán (Mexico); Navarro-Santos, P., E-mail: pnavarrosa@conacyt.mx [Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Santiago Tapia 403, CP 58000, Morelia, Michoacán (Mexico); Garcia-Ramirez, M. A. [Research Centre for Innovation in Aeronautical Engineering, Universidad Autónoma de Nuevo León, Ciudad Universitaria, San Nicolás de los Garza, CP 66451 Nuevo León (Mexico); Ricardo-Chávez, J. L. [Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055, Lomas 4" asección, CP 78216, San Luis Potosí, S. L. P. (Mexico)

    2015-06-21

    The adsorption of dibenzothiophene (DBT) on bare and boron-doped armchair carbon nanoribbons (ACNRs) is being investigated in the framework of the density functional theory by implementing periodic boundary conditions that include corrections from dispersion interactions. The reactivity of the ACNRs is characterized by using the Fukui functions as well as the electrostatic potential as local descriptors. Non-covalent adsorption mechanism is found when using the local Perdew-Becke-Ernzerhof functional, regardless of the DBT orientation and adsorption location. The dispersion interactions addition is a milestone to describe the adsorption process. The charge defects introduced in small number (i.e., by doping with B atoms), within the ACNRs increases the selectivity towards sulfur mainly due to the charge depletion at B sites. The DBT magnitude in the adsorption energy shows non-covalent interactions. As a consequence, the configurations where the DBT is adsorbed on a BC{sub 3} island increase the adsorption energy compared to random B arrangements. The stability of these configurations can be explained satisfactorily in terms of dipole interactions. Nevertheless, from the charge-density difference analysis and the weak Bader charge-distribution interactions cannot be ruled out completely. This is why the electronic properties of the ribbons are analyzed in order to elucidate the key role played by the B and DBT states in the adsorbed configurations.

  3. Nitrogen-doped porous carbon from Camellia oleifera shells with enhanced electrochemical performance.

    Science.gov (United States)

    Zhai, Yunbo; Xu, Bibo; Zhu, Yun; Qing, Renpeng; Peng, Chuan; Wang, Tengfei; Li, Caiting; Zeng, Guangming

    2016-04-01

    Nitrogen doped porous activated carbon was prepared by annealing treatment of Camellia oleifera shell activated carbon under NH3. We found that nitrogen content of activated carbon up to 10.43 at.% when annealed in NH3 at 800 °C. At 600 °C or above, the N-doped carbon further reacts with NH3, leads to a low surface area down to 458 m(2)/g and low graphitization degree. X-ray photoelectron spectroscope (XPS) analysis indicated that the nitrogen functional groups on the nitrogen-doped activated carbons (NACs) were mostly in the form of pyridinic nitrogen. We discovered that the oxygen groups and carbon atoms at the defect and edge sites of graphene play an important role in the reaction, leading to nitrogen atoms incorporated into the lattice of carbon. When temperatures were lower than 600 °C the nitrogen atoms displaced oxygen groups and formed nitrogen function groups, and when temperatures were higher than 600 °C and ~4 at.% carbon atoms and part of oxygen function groups reacted with NH3. When compared to pure activated carbon, the nitrogen doped activated carbon shows nearly four times the capacitance (191 vs 51 F/g).

  4. 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

  5. Electroanalytical investigation and determination of pefloxacin in pharmaceuticals and serum at boron-doped diamond and glassy carbon electrodes.

    Science.gov (United States)

    Uslu, Bengi; Topal, Burcu Dogan; Ozkan, Sibel A

    2008-02-15

    The anodic behavior and determination of pefloxacin on boron-doped diamond and glassy carbon electrodes were investigated using cyclic, linear sweep, differential pulse and square wave voltammetric techniques. In cyclic voltammetry, pefloxacin shows one main irreversible oxidation peak and additional one irreversible ill-defined wave depending on pH values for both electrodes. The results indicate that the process of pefloxacin is irreversible and diffusion controlled on boron-doped diamond electrode and irreversible but adsorption controlled on glassy carbon electrode. The peak current is found to be linear over the range of concentration 2x10(-6) to 2x10(-4)M in 0.5M H(2)SO(4) at about +1.20V (versus Ag/AgCl) for differential pulse and square wave voltammetric technique using boron-doped diamond electrode. The repeatability, reproducibility, precision and accuracy of the methods in all media were investigated. Selectivity, precision and accuracy of the developed methods were also checked by recovery studies. The procedures were successfully applied to the determination of the drug in pharmaceutical dosage forms and humans serum samples with good recovery results. No electroactive interferences from the excipients and endogenous substances were found in the pharmaceutical dosage forms and biological samples, respectively.

  6. Determinism of carbon and nitrogen reserve accumulation in legume seeds.

    Science.gov (United States)

    Munier-Jolain, Nathalie; Larmure, Annabelle; Salon, Christophe

    2008-10-01

    In legume plants, the determination of individual seed weight is a complex phenomenon that depends on two main factors. The first one corresponds to the number of cotyledon cells, which determines the potential seed weight as the cotyledon cell number is related to seed growth rate during seed filling. Since cell divisions take place between flowering and the beginning of seed filling, any stress occurring before the beginning of seed filling can affect individual seed growth rate (C and N reserve accumulation in seeds), and thus individual seed weights. The second factor concerns carbon and nitrogen supply to the growing seed to support reserve accumulation. Grain legume species produce protein-rich seeds involving high requirement of nitrogen. Since seed growth rate as determined by cotyledon cell number is hardly affected by photoassimilate availability during the filling period, a reduction of photosynthetic activity caused by nitrogen remobilization in leaves (e.g., remobilization of essential proteins involved in photosynthesis) can lead to shorten the duration of the filling period, and by that can provoke a limitation of individual seed weights. Accordingly, any biotic or abiotic stress during seed filling causing a decrease in photosynthetic activity should lead to a reduction of the duration of seed filling.

  7. Carbon-nitrogen interactions and biomass partitioning of Carex rostrata grown at three levels of nitrogen supply

    Energy Technology Data Exchange (ETDEWEB)

    Saarinen, T. [Helsinki Univ. (Finland). Dept. of Ecology and Systematics

    1996-12-31

    Biomass and production of vascular plants constitutes a major source of carbon input in peatlands. As rates of decomposition vary considerably with depth, the vertical distribution of biomass may substantially affect accumulation of carbon in peatlands. Therefore, allocation patterns between shoot and roots are particularly important when considering carbon balance of peatland ecosystems. The stimulatory effect of increasing atmospheric concentration of CO{sub 2} or photosynthesis may increase availability of carbon to most C3 plants. Availability of nitrogen may also alter both due to increased atmospheric deposition and changer in mineralisation rates associated with climate change. Most root-shoot partitioning models predict that allocation of biomass is dependent of the availability and uptake of carbon and nitrogen. A decrease in supply of carbon would favour allocation to shoots and a decrease in supply of nitrogen would increase allocation to roots. At a cellular level, non structural carbohydrates and free amino acids are thought to represent the biochemically available fraction of carbon and nitrogen, respectively. The aim of this work is study the long-term growth responses of Carex rostrata to changes in the availability of nitrogen. Special attention is paid to soluble sugars ant free amino acids, which may control partitioning of biomass. (10 refs.)

  8. Carbon and nitrogen dynamics in early stages of forest litter decomposition as affected by nitrogen addition

    Institute of Scientific and Technical Information of China (English)

    DENG Xiao-wen; LIU Ying; HAN Shi-jie

    2009-01-01

    The effects of nitrogen (N) availability and tree species on the dynamics of carbon and nitrogen at early stage of decomposition of forest litter were studied in a 13-week laboratory incubation experiment. Fresh litter samples including needle litter (Pinus koraiensis) and two types of broadleaf litters (Quercus mongolica and Tilia amurensis) were collected from a broadleaf-korean pine mixed forest in the northern slope of Changbai Mountain (China). Different doses of N (equal to 0, 30 and 50 kg·ha-1yr-1, respectively, as NH4NO3) were added to litter during the experiment period. The litter decomposition rate expressed as mass loss and respiration rate increased significantly with increasing N availability. The mass loss and cumulative CO2-C emission were higher in leaf litter compared to that in needle litter. The dissolved organic Carbon (DOC) concentrations in litter leachate varied widely between the species, but were not greatly affected by N treatments. Regardless of the N addition rate, both N treatments and species had no significant effect on dissolved organic N (DON) concentrations in litter leachate. About 52·78% of added N was retained in the litter. The percentage of N retention was positively correlated (R2=0.91, p<0.05) with the litter mass loss. This suggested that a forest floor with easily decomposed litter might have higher potential N sink strength than that with more slowly decomposed litter.

  9. Soil Carbon and Nitrogen Stocks of Different Hawaiian Sugarcane Cultivars

    Directory of Open Access Journals (Sweden)

    Rebecca Tirado-Corbalá

    2015-06-01

    Full Text Available Sugarcane has been widely used as a biofuel crop due to its high biological productivity, ease of conversion to ethanol, and its relatively high potential for greenhouse gas reduction and lower environmental impacts relative to other derived biofuels from traditional agronomic crops. In this investigation, we studied four sugarcane cultivars (H-65-7052, H-78-3567, H-86-3792 and H-87-4319 grown on a Hawaiian commercial sugarcane plantation to determine their ability to store and accumulate soil carbon (C and nitrogen (N across a 24-month growth cycle on contrasting soil types. The main study objective establish baseline parameters for biofuel production life cycle analyses; sub-objectives included (1 determining which of four main sugarcane cultivars sequestered the most soil C and (2 assessing how soil C sequestration varies among two common Hawaiian soil series (Pulehu-sandy clay loam and Molokai-clay. Soil samples were collected at 20 cm increments to depths of up to 120 cm using hand augers at the three main growth stages (tillering, grand growth, and maturity from two experimental plots at to observe total carbon (TC, total nitrogen (TN, dissolved organic carbon (DOC and nitrates (NO−3 using laboratory flash combustion for TC and TN and solution filtering and analysis for DOC and NO−3. Aboveground plant biomass was collected and subsampled to determine lignin and C and N content. This study determined that there was an increase of TC with the advancement of growing stages in the studied four sugarcane cultivars at both soil types (increase in TC of 15–35 kg·m2. Nitrogen accumulation was more variable, and NO−3 (<5 ppm were insignificant. The C and N accumulation varies in the whole profile based on the ability of the sugarcane cultivar’s roots to explore and grow in the different soil types. For the purpose of storing C in the soil, cultivar H-65-7052 (TC accumulation of ~30 kg·m−2 and H-86-3792 (25 kg·m−2 rather H-78

  10. Synthesis of polybenzoxazine based nitrogen-rich porous carbons for carbon dioxide capture

    Science.gov (United States)

    Wan, Liu; Wang, Jianlong; Feng, Chong; Sun, Yahui; Li, Kaixi

    2015-04-01

    Nitrogen-rich porous carbons (NPCs) were synthesized from 1,5-dihydroxynaphthalene, urea, and formaldehyde based on benzoxazine chemistry by a soft-templating method with KOH chemical activation. They possess high surface areas of 856.8-1257.8 m2 g-1, a large pore volume of 0.15-0.65 cm3 g-1, tunable pore structure, high nitrogen content (5.21-5.32 wt%), and high char yields. The amount of the soft-templating agent F127 has multiple influences on the textural and chemical properties of the carbons, affecting the surface area and pore structure, impacting the compositions of nitrogen species and resulting in an improvement of the CO2 capture performance. At 1 bar, high CO2 uptake of 4.02 and 6.35 mmol g-1 at 25 and 0 °C was achieved for the sample NPC-2 with a molar ratio of F127 : urea = 0.010 : 1. This can be attributed to its well-developed micropore structure and abundant pyridinic nitrogen, pyrrolic nitrogen and pyridonic nitrogen functionalities. The sample NPC-2 also exhibits a remarkable selectivity for CO2/N2 separation and a fast adsorption/desorption rate and can be easily regenerated. This suggests that the polybenzoxazine-based NPCs are desirable for CO2 capture because of possessing a high micropore surface area, a large micropore volume, appropriate pore size distribution, and a large number of basic nitrogen functionalities.Nitrogen-rich porous carbons (NPCs) were synthesized from 1,5-dihydroxynaphthalene, urea, and formaldehyde based on benzoxazine chemistry by a soft-templating method with KOH chemical activation. They possess high surface areas of 856.8-1257.8 m2 g-1, a large pore volume of 0.15-0.65 cm3 g-1, tunable pore structure, high nitrogen content (5.21-5.32 wt%), and high char yields. The amount of the soft-templating agent F127 has multiple influences on the textural and chemical properties of the carbons, affecting the surface area and pore structure, impacting the compositions of nitrogen species and resulting in an improvement of the

  11. A simple one step organic to inorganic pyrolysis route to bulk quantity boron carbonitride/carbon nanocables

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, T.; Wang, Y.P.; Yang, J.Q. [School of Materials Science and Engineering, Harbin Institute of Technology (Weihai), Weihai 264209 (China); Huang, X.X., E-mail: swliza@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wen, G., E-mail: g.w.wen.hit@gmail.com [School of Materials Science and Engineering, Harbin Institute of Technology (Weihai), Weihai 264209 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-09-15

    Highlights: • Bulk quantity boron carbonitride/carbon (BCN/C) nanocables have been synthesized by a simple one step organic to inorganic pyrolysis route. • BCN/C nanocables exhibit a much better oxidation resistance than substrate carbon nanofibers. • A probable formation mechanism of the BCN/C nanocables is proposed according to the experimental results. - Abstract: Bulk quantity boron carbonitride/carbon (BCN/C) nanocables have been successfully synthesized by a simple one step organic compounds pyrolysis route at 1100 °C. The nanocables consist of nanocarbon fibers inside covered by the cylindrical BCN coatings. The characteristics of the surface morphology and the diameters of the nanocables are determined by soaking time. It is demonstrated that the elements of B, C and N are hybridly bonded in the coating. The weight loss of the nanocables is about 12% at 1200 °C which is much better than the substrate carbon nanofibers (CNFs) (more than 20% weight loss at 1200 °C). The minimum reflection coefficient below −20 dB for the products is −24.5 dB at 14.48 GHz indicating good microwave absorption properties. The results suggest that the nanocables are favorable for achieving high performance oxidization resistance and microwave absorption properties.

  12. First-principles studies of effects of interstitial boron and carbon on the structural, elastic, and electronic properties of Ni solution and Ni3Al intermetallics

    Science.gov (United States)

    Huang, Meng-Li; Wang, Chong-Yu

    2016-10-01

    The effects of boron and carbon on the structural, elastic, and electronic properties of both Ni solution and Ni3Al intermetallics are investigated using first-principles calculations. The results agree well with theoretical and experimental data from previous studies and are analyzed based on the density of states and charge density. It is found that both boron and carbon are inclined to occupy the Ni-rich interstices in Ni3Al, which gives rise to a cubic interstitial phase. In addition, the interstitial boron and carbon have different effects on the elastic moduli of Ni and Ni3Al. The calculation results for the G/B and Poisson’s ratios further demonstrate that interstitial boron and carbon can both reduce the brittleness of Ni, thereby increasing its ductility. Meanwhile, boron can also enhance the ductility of the Ni3Al while carbon hardly has an effect on its brittleness or ductility. Project supported by the National Basic Research Program of China (Grant No. 2011CB606402).

  13. Studies on organic carbon, nitrogen and phosphorous in the sediments of Mandovi Estuary, Goa

    Digital Repository Service at National Institute of Oceanography (India)

    Nasnolkar, C.M.; Shirodkar, P.V.; Singbal, S.Y.S.

    Sediment organic carbon, total nitrogen, total phosphorous and hydrography of the overlying waters of the estuarine region in Mandovi Estuary, Goa, India have been studied. The relationship of carbon and nutrients with sediment characteristics...

  14. Boron incorporation in the foraminifer Amphistegina lessonii under a decoupled carbonate chemistry

    Directory of Open Access Journals (Sweden)

    K. Kaczmarek

    2014-12-01

    BOH4-/HCO3- of the culture media. The latter indicates that boron uptake of A. lessonii features a competition between B(OH4- and HCO3-. Furthermore, the simultaneous determination of B/Ca and δ11B on single specimens allows for assessing the relative variability of these parameters. Among different treatments the B/Ca shows an increasing variability with increasing boron concentration in the test whereas the variability in the isotope distribution is constant.

  15. Fluorescently tuned nitrogen-doped carbon dots from carbon source with different content of carboxyl groups

    Directory of Open Access Journals (Sweden)

    Hao Wang

    2015-08-01

    Full Text Available In this study, fluorescent nitrogen-doped carbon dots (NCDs were tuned via varying the sources with different number of carboxyl groups. Owing to the interaction between amino and carboxyl, more amino groups conjugate the surface of the NCDs by the source with more carboxyl groups. Fluorescent NCDs were tuned via varying the sources with different content of carboxyl groups. Correspondingly, the nitrogen content, fluorescence quantum yields and lifetime of NCDs increases with the content of carboxyl groups from the source. Furthermore, cytotoxicity assay and cell imaging test indicate that the resultant NCDs possess low cytotoxicity and excellent biocompatibility.

  16. Fluorescently tuned nitrogen-doped carbon dots from carbon source with different content of carboxyl groups

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hao; Wang, Yun; Dai, Xiao; Zou, Guifu, E-mail: kqzhang@suda.edu.cn, E-mail: zouguifu@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Gao, Peng; Zhang, Ke-Qin, E-mail: kqzhang@suda.edu.cn, E-mail: zouguifu@suda.edu.cn; Du, Dezhuang [National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou 215123 (China); Guo, Jun [Testing and Analysis Center, Soochow University, Suzhou 215123 (China)

    2015-08-01

    In this study, fluorescent nitrogen-doped carbon dots (NCDs) were tuned via varying the sources with different number of carboxyl groups. Owing to the interaction between amino and carboxyl, more amino groups conjugate the surface of the NCDs by the source with more carboxyl groups. Fluorescent NCDs were tuned via varying the sources with different content of carboxyl groups. Correspondingly, the nitrogen content, fluorescence quantum yields and lifetime of NCDs increases with the content of carboxyl groups from the source. Furthermore, cytotoxicity assay and cell imaging test indicate that the resultant NCDs possess low cytotoxicity and excellent biocompatibility.

  17. Evaluation of Aromatic Boronic Acids as Ligands for Measuring Diabetes Markers on Carbon Nanotube Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Steingrimur Stefansson

    2012-01-01

    Full Text Available Biomolecular detections performed on carbon nanotube field-effect transistors (CNT-FETs frequently use reactive pyrenes as an anchor to tether bioactive ligands to the hydrophobic nanotubes. In this paper, we explore the possibility of directly using bioactive aromatic compounds themselves as CNT-FET ligands. This would be an efficient way to functionalize CNT-FETs since many aromatic compounds bind avidly to nanotubes, and it would also ensure that ligand-binding molecules would be brought in close proximity to the nanotubes. Using a model system consisting of pyrene, phenanthrene, naphthalene, or phenyl boronic acids immobilized on CNT-FET wafers, we show that all are able to bind glycated human serum albumin (gHSA, which is an important diabetes marker. Pyrene boronic acid proved to bind CNTs with the greatest apparent affinity as measured by gHSA impedance. Interestingly, gHSA CNT-FET signal intensity, which is proportional to amount of protein bound, remained essentially unchanged for all the boronic acids tested.

  18. Soil nitrogen and carbon impacts of raising chickens on pasture

    Science.gov (United States)

    Ryals, R.; Leach, A.; Tang, J.; Hastings, M. G.; Galloway, J. N.

    2014-12-01

    Chicken is the most consumed meat in the US, and production continues to intensify rapidly around the world. Chicken manure from confined feeding operations is typically applied in its raw form to nearby croplands, resulting in hotspots of soil nitrous oxide (N2O) emissions. Pasture-raised chicken is an alternative to industrial production and is growing in popularity with rising consumer demand for more humanely raised protein sources. In this agricultural model, manure is deposited directly onto grassland soils where it is thought to increase pools of soil carbon and nitrogen. The fate of manure nitrogen from pasture-raised chicken production remains poorly understood. We conducted a controlled, replicated experiment on a permaculture farm in Charlottesville, Virginia (Timbercreek Organics) in which small chicken coops (10 ft x 12 ft) were moved daily in a pasture. We measured manure deposition rates, soil inorganic nitrogen pools, soil moisture, and soil N2O and CO2 emissions. Measurements were made for the 28-day pasture life of three separate flocks of chickens in the spring, summer, and fall. Each flock consisted of approximately 200-300 chickens occupying three to five coops (~65 chickens/coop). Measurements were also made in paired ungrazed control plots. Manure deposition rates were similar across flocks and averaged 1.5 kgdrywt ha-1 during the spring grazing event and 4.0 kgdrywt ha-1 during the summer and fall grazing events. Manure deposition was relatively constant over the four weeks pasture-lifetime of the chickens. Compared to control plots, grazed areas exhibited higher soil N2O and CO2 fluxes. The magnitude of these fluxes diminished significantly over the four-week span. Soil gas fluxes significantly increased following rainfall events. For a given rainfall event, higher fluxes were observed from transects that were grazed more recently. Soil gaseous reactive nitrogen losses were less in this pasture system compared to cultivated field amended

  19. Short and long-term impacts of nitrogen deposition on carbon sequestration by forest ecosystems

    NARCIS (Netherlands)

    Vries, de W.; Du, E.; Butterbach-Bahl, K.

    2014-01-01

    The carbon to nitrogen response of forest ecosystems depends on the possible occurrence of nitrogen limitation versus possible co-limitations by other drivers, such as low temperature or availability of phosphorus. A combination of nitrogen retention estimates and stoichiometric scaling is used to i

  20. Controllable-nitrogen doped carbon layer surrounding carbon nanotubes as novel carbon support for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, P.L.; Hsu, C.H.; Wu, H.M.; Hsu, W.S. [Department of Chemical Engineering, National Cheng Kung University, Tainan (China); Kuo, D. [Department of Biochemistry, University of Washington, Seattle, WA (United States)

    2012-08-15

    Novel nitrogen-doped carbon layer surrounding carbon nanotubes composite (NC-CNT) (N/C ratio 3.3-14.3 wt.%) as catalyst support has been prepared using aniline as a dispersant to carbon nanotubes (CNTs) and as a source for both carbon and nitrogen coated on the surface of the CNTs, where the amount of doped nitrogen is controllable. The NC-CNT so obtained were characterized with scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption and desorption isotherms. A uniform dispersion of Pt nanoparticles (ca. 1.5-2.0 nm) was then anchored on the surface of NC-CNT by using aromatic amine as a stabilizer. For these Pt/NC-CNTs, cyclic voltammogram measurements show a high electrochemical activity surface area (up to 103.7 m{sup 2} g{sup -1}) compared to the commercial E-TEK catalyst (55.3 m{sup 2} g{sup -1}). In single cell test, Pt/NC-CNT catalyst has greatly enhanced catalytic activity toward the oxygen reduction reaction, resulting in an enhancement of ca. 37% in mass activity compared with that of E-TEK. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Novel nanometer-level uniform amorphous carbon coating for boron powders by direct pyrolysis of coronene without solvent

    Science.gov (United States)

    Ye, ShuJun; Song, MingHui; Kumakura, Hiroaki

    2015-01-01

    A 3 nm coronene coating and a 4 nm amorphous carbon coating with a uniform shell-core encapsulation structure for nanosized boron (B) powders are formed by a simple process in which coronene is directly mixed with boron particles without a solvent and heated at 520 °C for 1 h or at 630 °C for 3 h in a vacuum-sealed silica tube. Coronene has a melting point lower than its decomposition temperature, which enables liquid coronene to cover B particles by liquid diffusion and penetration without the need for a solvent. The diffusion and penetration of coronene can extend to the boundaries of particles and to inside the agglomerated nanoparticles to form a complete shell-core encapsulated structure. As the temperature is increased, thermal decomposition of coronene on the B particles results in the formation of a uniform amorphous carbon coating layer. This novel and simple nanometer-level uniform amorphous carbon coating method can possibly be applied to many other powders; thus, it has potential applications in many fields at low cost.

  2. Novel nanometer-level uniform amorphous carbon coating for boron powders by direct pyrolysis of coronene without solvent.

    Science.gov (United States)

    Ye, ShuJun; Song, MingHui; Kumakura, Hiroaki

    2015-01-30

    A 3 nm coronene coating and a 4 nm amorphous carbon coating with a uniform shell-core encapsulation structure for nanosized boron (B) powders are formed by a simple process in which coronene is directly mixed with boron particles without a solvent and heated at 520 °C for 1 h or at 630 °C for 3 h in a vacuum-sealed silica tube. Coronene has a melting point lower than its decomposition temperature, which enables liquid coronene to cover B particles by liquid diffusion and penetration without the need for a solvent. The diffusion and penetration of coronene can extend to the boundaries of particles and to inside the agglomerated nanoparticles to form a complete shell-core encapsulated structure. As the temperature is increased, thermal decomposition of coronene on the B particles results in the formation of a uniform amorphous carbon coating layer. This novel and simple nanometer-level uniform amorphous carbon coating method can possibly be applied to many other powders; thus, it has potential applications in many fields at low cost.

  3. K-shell photoionization of boron-like carbon ions: analysis of 1s-2p resonances

    Institute of Scientific and Technical Information of China (English)

    Wang Guo-Li; Zhou Xiao-Xin

    2007-01-01

    Close-coupling calculations based on an R-matrix formalism are performed for the 1s-2p resonance photoionizations from the low-lying states of boron-like carbon ions. The resonance energies, widths and oscillator strengths of 1s-2p core excitations are determined by analysing the calculated photoionization cross sections. Our calculations are in reasonable agreement with the experimental and theoretical results presented by other authors. The present numerical values may help to analyse the astrophysical and laboratory plasmas.

  4. Does canopy nitrogen uptake enhance carbon sequestration by trees?

    Science.gov (United States)

    Nair, Richard K F; Perks, Micheal P; Weatherall, Andrew; Baggs, Elizabeth M; Mencuccini, Maurizio

    2016-02-01

    Temperate forest (15) N isotope trace experiments find nitrogen (N) addition-driven carbon (C) uptake is modest as little additional N is acquired by trees; however, several correlations of ambient N deposition against forest productivity imply a greater effect of atmospheric nitrogen deposition than these studies. We asked whether N deposition experiments adequately represent all processes found in ambient conditions. In particular, experiments typically apply (15) N to directly to forest floors, assuming uptake of nitrogen intercepted by canopies (CNU) is minimal. Additionally, conventional (15) N additions typically trace mineral (15) N additions rather than litter N recycling and may increase total N inputs above ambient levels. To test the importance of CNU and recycled N to tree nutrition, we conducted a mesocosm experiment, applying 54 g N/(15) N ha(-1)  yr(-1) to Sitka spruce saplings. We compared tree and soil (15) N recovery among treatments where enrichment was due to either (1) a (15) N-enriched litter layer, or mineral (15) N additions to (2) the soil or (3) the canopy. We found that 60% of (15) N applied to the canopy was recovered above ground (in needles, stem and branches) while only 21% of (15) N applied to the soil was found in these pools. (15) N recovery from litter was low and highly variable. (15) N partitioning among biomass pools and age classes also differed among treatments, with twice as much (15) N found in woody biomass when deposited on the canopy than soil. Stoichiometrically calculated N effect on C uptake from (15) N applied to the soil, scaled to real-world conditions, was 43 kg C kg N(-1) , similar to manipulation studies. The effect from the canopy treatment was 114 kg C kg N(-1) . Canopy treatments may be critical to accurately represent N deposition in the field and may address the discrepancy between manipulative and correlative studies.

  5. Current-voltage characteristics of carbon nanotubes with substitutional nitrogen

    DEFF Research Database (Denmark)

    Kaun, C.C.; Larade, B.; Mehrez, H.;

    2002-01-01

    We report ab initio analysis of current-voltage (I-V) characteristics of carbon nanotubes with nitrogen substitution doping. For zigzag semiconducting tubes, doping with a single N impurity increases current flow and, for small radii tubes, narrows the current gap. Doping a N impurity per nanotube...... unit cell generates a metallic transport behavior. Nonlinear I-V characteristics set in at high bias and a negative differential resistance region is observed for the doped tubes. These behaviors can be well understood from the alignment/mis-alignment of the current carrying bands in the nanotube leads...... due to the applied bias voltage. For a armchair metallic nanotube, a reduction of current is observed with substitutional doping due to elastic backscattering by the impurity....

  6. Nitrogen Deposition Effects on Soil Carbon Dynamics in Temperate Forests

    DEFF Research Database (Denmark)

    Ginzburg Ozeri, Shimon

    Soils contain the largest fraction of terrestrial carbon (C). Understanding the factors regulating the decomposition and storage of soil organic matter (SOM) is essential for predictions of the C sink strength of the terrestrial environment in the light of global change. Elevated long-term nitrogen...... (N) deposition into forest ecosystems has been increasing globally and was hypothesized to raise soil organic C (SOC) stocks by increasing forest productivity and by reducing SOM decomposition. Yet, these effects of N deposition on forest SOC stocks are uncertain and largely based on observations...... edges were used to study the effects of varying N deposition load on SOC stocks and fluxes as well as on the temperature sensitivity of SOM respiration. In a third study, the effects of 20 years of continuous experimental N addition (35 kg N ha-1 year-1) on soil C budget were investigated. Our general...

  7. Low Carbon Costs of Nitrogen Fixation in Tropical Dry Forests

    Science.gov (United States)

    Gei, M. G.; Powers, J. S.

    2015-12-01

    Legume tree species with the ability to fix nitrogen (N) are highly diverse and widespread across tropical forests but in particular in the dry tropics. Their ecological success in lower latitudes has been called a "paradox": soil N in the tropics is thought to be high, while acquiring N through fixation incurs high energetic costs. However, the long held assumptions that N fixation is limited by photosynthate and that N fixation penalizes plant productivity have rarely been tested, particularly in legume tree species. We show results from three different experiments where we grew eleven species of tropical dry forest legumes. We quantified plant biomass and N fixation using nodulation and the 15N natural isotope abundance (Ndfa or nitrogen derived from fixation). These data show little evidence for costs of N fixation in seedlings grown under different soil fertility, light regimes, and with different microbial communities. Seedling productivity did not incur major costs because of N fixation: indeed, the average slope between Ndfa and biomass was positive (range in slopes: -0.03 to 0.3). Moreover, foliar N, which varied among species, was tightly constrained and not correlated with Ndfa. This finding implies that legume species have a target N that does not change depending on N acquisition strategies. The process of N fixation in tropical legumes may be more carbon efficient than previously thought. This view is more consistent with the hyperabundance of members of this family in tropical ecosystems.

  8. Preparation of Poly(p-phenylene sulfi de)/Carbon Composites with Enhanced Thermal Conductivity and Electrical Insulativity via Hybrids of Boron Nitride and Carbon Fillers

    Institute of Scientific and Technical Information of China (English)

    WU Jieli; WANG Jinwen; CHEN Feng

    2015-01-01

    The present work enhanced the thermal conductivity of poly(p-phenylene sulfi de)/expanded graphites and poly(p-phenylene sulfi de)/carbon nanotubes, by incorporating composites with hexagonal boron nitride, which simultaneously succeeded in raising the electrical conductivity of the systems. A two-step mechanical processing method which includes rotating solid-state premixing and inner mixing was adopted to improve dispersion of the hybrids, contributing to the formation of an interspered thermal conductive network. Similar synergic effect in thermal conductivity enhancement was discovered in the hybrid systems regardless of the dimension difference between the two carbonfi llers. Such is postulated to be the one satisfying advantage generated by the afore-mentioned network; the other is the insulativity of the hybrid systems given by the effective blockage of hexagonal boron nitride as an insulating material in our network.

  9. Cellular Composition Changes and Nitrogen Uptake under Extra-Limited Nitrogen Conditions by Thermosynechococcus sp. CL-1 Carbon Biofixation

    Directory of Open Access Journals (Sweden)

    Tseng Chi-Ming

    2016-01-01

    Full Text Available Two types of culture systems were used (continuous and batch which were fed using a simulated absorbent from a scrubber with carbonate/bicarbonate as the carbon source and nitrate as the nitrogen source by a thermophile strain, Thermosynechococcus sp. CL-1 (TCL-1 at 50°C. The lipid, carbohydrate, and protein cellular components which can be used as bioenergy precursors along with their content as a function of various C/N ratios are quantified. Maximum lipid productivity of about 150 mg L−1 d−1 is obtained while the CO2 uptake rate is 917 mg L−1 d−1 at a dilution rate of 0.06 h−1 when both carbon and nitrogen sources are not limited. With high range of nitrogen concentrations batch culture test, TCL-1 reveals extra-high affinity on nitrogen source under limited carbon source conditions since the affinity constant is 0.12 mM. In addition, the flow of carbon fixed during photosynthesis seems to switch from the protein synthesis pathway to forming carbohydrate rather than lipid under N-limitation and a high C/N ratio for TCL-1, resulting in a maximal carbohydrate content of 61%. Consequently, TCL-1 is an appropriate candidate to treat the wastewater of environment and produce the bioenergy precursors under extreme limited nitrogen conditions.

  10. Particulate organic carbon and nitrogen export from major Arctic rivers

    Science.gov (United States)

    McClelland, J. W.; Holmes, R. M.; Peterson, B. J.; Raymond, P. A.; Striegl, R. G.; Zhulidov, A. V.; Zimov, S. A.; Zimov, N.; Tank, S. E.; Spencer, R. G. M.; Staples, R.; Gurtovaya, T. Y.; Griffin, C. G.

    2016-05-01

    Northern rivers connect a land area of approximately 20.5 million km2 to the Arctic Ocean and surrounding seas. These rivers account for ~10% of global river discharge and transport massive quantities of dissolved and particulate materials that reflect watershed sources and impact biogeochemical cycling in the ocean. In this paper, multiyear data sets from a coordinated sampling program are used to characterize particulate organic carbon (POC) and particulate nitrogen (PN) export from the six largest rivers within the pan-Arctic watershed (Yenisey, Lena, Ob', Mackenzie, Yukon, Kolyma). Together, these rivers export an average of 3055 × 109 g of POC and 368 × 109 g of PN each year. Scaled up to the pan-Arctic watershed as a whole, fluvial export estimates increase to 5767 × 109 g and 695 × 109 g of POC and PN per year, respectively. POC export is substantially lower than dissolved organic carbon export by these rivers, whereas PN export is roughly equal to dissolved nitrogen export. Seasonal patterns in concentrations and source/composition indicators (C:N, δ13C, Δ14C, δ15N) are broadly similar among rivers, but distinct regional differences are also evident. For example, average radiocarbon ages of POC range from ~2000 (Ob') to ~5500 (Mackenzie) years before present. Rapid changes within the Arctic system as a consequence of global warming make it challenging to establish a contemporary baseline of fluvial export, but the results presented in this paper capture variability and quantify average conditions for nearly a decade at the beginning of the 21st century.

  11. Rapid accurate isotopic measurements on boron in boric acid and boron carbide.

    Science.gov (United States)

    Duchateau, N L; Verbruggen, A; Hendrickx, F; De Bièvre, P

    1986-04-01

    A procedure is described whereby rapid and accurate isotopic measurements can be performed on boron in boric acid and boron carbide after fusion of these compounds with calcium carbonate. It allows the determination of the isotopic composition of boron in boric acid and boron carbide and the direct assay of boron or the (10)B isotope in boron carbide by isotope-dilution mass spectrometry.

  12. Tillage and manure effects on soil and aggregate-associated carbon and nitrogen

    OpenAIRE

    Mikha, M.M.; C. W. Rice

    2004-01-01

    Metadata only record This study assesses the impacts of tillage methods (conventional(CT) versus no-tillage(NT)) and nitrogen source (fertilizer(F) versus manure(M)) on soil aggregate size and the associated soil carbon and nitrogen. They find that both no-tillage and manure increase soil aggregate size, with the combination of the two producing the greatest soil aggregation. Likewise, there was greater total carbon and nitrogen in the soil for the no-tillage and manure treatments.

  13. Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    马旭村; 徐贵昌; 王恩哥

    2000-01-01

    Well-aligned carbon nitrogen nanotube films have been synthesized successfully on meso-porous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1-xNx( x = 0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds cova-lently with nitrogen in all the carbon nitrogen nanotube films.

  14. Soil Inorganic Nitrogen and Microbial biomass Carbon and Nitrogen Under Pine Plantations in Zhanggutai Sandy Soil

    Institute of Scientific and Technical Information of China (English)

    YU Zhan-Yuan; CHEN Fu-Sheng; ZENG De-Hui; ZHAO Qiong; CHEN Guang-Sheng

    2008-01-01

    The dynamics of soil inorganic nitrogen (NH+4-N and NO-3N) and microbial biomass carbon (Cmic) and nitrogen (Nmic) under 30-year-old fenced Pinus sylvestris L. var. mongolica Litvin (SF), unfenced P. sylvestris L. var. mongolica Litvin (SUF), and unfenced Pinus densiflora Siebold et Zucc. (DUF) plantations in the Zhanggutai sandy soil of China were studied during Apr. to Oct. 2004 by the in situ closed-top core incubation method. All mentioned C and N indices in each stand type fluctuated over time. The ranges of inorganic N, Cmic, and Nmic contents in the three stand types were 0.7-2.6, 40.0-128.9, and 5.4-15.2 μg g-1, respectively. The average contents of soil NH+4-N and Cmic under the three 30-year-old pine plantations were not different. However, soil NO-3-N and total inorganic N contents decreased in the order of SUF > SF > DUF, the Nmic content was in the order of SF = SUF > DUF, and the Cmic:Nmic ratio was in the order of SUF = DUF > SF. Seasonal variations were observed in soil inorganic N, microbial biomass, and plant growth. These seasonal variations had certain correlations with microbe and plant N use in the soil, and their competition for NH+4-N was mostly regulated by soil N availability. The influence of tree species on inorganic N and Nmic were mainly because of differences in litter quality. Lack of grazing decreased the Cmic:N ratio owing to decreased carbon output and increased the ability of soil to supply N. The soil N supply under the P. sylvestris var. mongolica plantation was lower than under the P. densiflora plantation.

  15. Nitrogen removal efficiency of iron-carbon micro-electrolysis system treating high nitrate nitrogen organic pharmaceutical wastewater

    Institute of Scientific and Technical Information of China (English)

    周健; 段送华; 陈垚; 胡斌

    2009-01-01

    The nitrate nitrogen removal efficiency of iron-carbon micro-electrolysis system was discussed in treating pharmaceutical wastewater with high nitrogen and refractory organic concentration. The results show that the granularity of fillings,pH,volume ratios of iron-carbon and gas-water,and HRT. have significant effects on the nitrogen removal efficiency of iron-carbon micro-electrolysis system. The iron-carbon micro-electrolysis system has a good removal efficiency of pharmaceutical wastewater with high nitrogen and refractory organic concentration when the influent TN,NH4+-N,NO3--N and BOD5/CODCr are 823 mg/L,30 mg/L,793 mg/L and 0.1,respectively,at the granularity of iron and carbon 0.425 mm,pH 3,iron-carbon ratio 3,gas-water ratio 5,HRT 1.5 h,and the removal rates of TN,NH4+-N and NO3--N achieve 51.5%,70% and 50.94%,respectively.

  16. Boron Nitride Nanotube: Synthesis and Applications

    Science.gov (United States)

    Tiano, Amanda L.; Park, Cheol; Lee, Joseph W.; Luong, Hoa H.; Gibbons, Luke J.; Chu, Sang-Hyon; Applin, Samantha I.; Gnoffo, Peter; Lowther, Sharon; Kim, Hyun Jung; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Kang, Jin Ho; Sauti, Godfrey; Thibeault, Sheila A.; Yamakov, Vesselin; Wise, Kristopher E.; Su, Ji; Fay, Catharine C.

    2014-01-01

    Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800 C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

  17. Nitrogen-doped mesoporous carbons for high performance supercapacitors

    Science.gov (United States)

    Wu, Kai; Liu, Qiming

    2016-08-01

    The mesoporous carbons have been synthesized by using α-D(+)-Glucose, D-Glucosamine hydrochloride or their mixture as carbon precursors and mesoporous silicas (SBA-15 or MCF) as hard templates. The as-prepared products show a large pore volume (0.59-0.97 cm3 g-1), high surface areas (352.72-1152.67 m2 g-1) and rational nitrogen content (ca. 2.5-3.9 wt.%). The results of electrochemical tests demonstrate that both heteroatom doping and suitable pore structure play a decisive role in the performance of supercapacitors. The representative sample of SBA-15 replica obtained using D-Glucosamine hydrochloride only exhibits high specific capacitance (212.8 F g-1 at 0.5 A g-1) and good cycle durability (86.1% of the initial capacitance after 2000 cycles) in 6 M KOH aqueous electrolyte, which is attributed to the contribution of double layer capacitance and pseudo-capacitance. The excellent electrochemical performance makes it a promising electrode material for supercapacitors.

  18. Nitrogen-Doped Carbon Dots for "green" Quantum Dot Solar Cells.

    Science.gov (United States)

    Wang, Hao; Sun, Pengfei; Cong, Shan; Wu, Jiang; Gao, Lijun; Wang, Yun; Dai, Xiao; Yi, Qinghua; Zou, Guifu

    2016-12-01

    Considering the environment protection, "green" materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots' excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed "green" nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells.

  19. Mechanisms controlling soil carbon sequestration under atmospheric nitrogen deposition

    Energy Technology Data Exchange (ETDEWEB)

    R.L. Sinsabaugh; D.R. Zak; D.L. Moorhead

    2008-02-19

    Increased atmospheric nitrogen (N) deposition can alter the processing and storage of organic carbon in soils. In 2000, we began studying the effects of simulated atmospheric N deposition on soil carbon dynamics in three types of northern temperate forest that occur across a wide geographic range in the Upper Great Lakes region. These ecosystems range from 100% oak in the overstory (black oak-white oak ecosystem; BOWO) to 0% overstory oak (sugar maple-basswood; SMBW) and include the sugar maple-red oak ecosystem (SMRO) that has intermediate oak abundance. The leaf litter biochemistry of these ecosystems range from highly lignified litter (BOWO) to litter of low lignin content (SMBW). We selected three replicate stands of each ecosystem type and established three plots in each stand. Each plot was randomly assigned one of three levels of N deposition (0, 30 & 80 kg N ha-1 y-1) imposed by adding NaNO3 in six equal increments applied over the growing season. Through experiments ranging from the molecular to the ecosystem scales, we produced a conceptual framework that describes the biogeochemistry of soil carbon storage in N-saturated ecosystems as the product of interactions between the composition of plant litter, the composition of the soil microbial community and the expression of extracellular enzyme activities. A key finding is that atmospheric N deposition can increase or decrease the soil C storage by modifying the expression of extracellular enzymes by soil microbial communities. The critical interactions within this conceptual framework have been incorporated into a new class of simulations called guild decomposition models.

  20. Hetero-junctions of Boron Nitride and Carbon Nanotubes: Synthesis and Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Yoke Khin

    2013-03-14

    Hetero-junctions of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) are expected to have appealing new properties that are not available from pure BNNTs and CNTs. Theoretical studies indicate that BNNT/CNT junctions could be multifunctional and applicable as memory, spintronic, electronic, and photonics devices with tunable band structures. This will lead to energy and material efficient multifunctional devices that will be beneficial to the society. However, experimental realization of BNNT/CNT junctions was hindered by the absent of a common growth technique for BNNTs and CNTs. In fact, the synthesis of BNNTs was very challenging and may involve high temperatures (up to 3000 degree Celsius by laser ablation) and explosive chemicals. During the award period, we have successfully developed a simple chemical vapor deposition (CVD) technique to grow BNNTs at 1100-1200 degree Celsius without using dangerous chemicals. A series of common catalyst have then been identified for the synthesis of BNNTs and CNTs. Both of these breakthroughs have led to our preliminary success in growing two types of BNNT/CNT junctions and two additional new nanostructures: 1) branching BNNT/CNT junctions and 2) co-axial BNNT/CNT junctions, 3) quantum dots functionalized BNNTs (QDs-BNNTs), 4) BNNT/graphene junctions. We have started to understand their structural, compositional, and electronic properties. Latest results indicate that the branching BNNT/CNT junctions and QDs-BNNTs are functional as room-temperature tunneling devices. We have submitted the application of a renewal grant to continue the study of these new energy efficient materials. Finally, this project has also strengthened our collaborations with multiple Department of Energy's Nanoscale Science Research Centers (NSRCs), including the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory, and the Center for Integrated Nanotechnologies (CINTs) at Sandia National Laboratories and Los

  1. Improved tensile and buckling behavior of defected carbon nanotubes utilizing boron nitride coating - A molecular dynamic study

    Science.gov (United States)

    Badjian, H.; Setoodeh, A. R.

    2017-02-01

    Synthesizing inorganic nanostructures such as boron nitride nanotubes (BNNTs) have led to immense studies due to their many interesting functional features such as piezoelectricity, high temperature resistance to oxygen, electrical insulation, high thermal conductivity and very long lengths as physical features. In order to utilize the superior properties of pristine and defected carbon nanotubes (CNTs), a hybrid nanotube is proposed in this study by forming BNNTs surface coating on the CNTs. The benefits of such coating on the tensile and buckling behavior of single-walled CNTs (SWCNTs) are illustrated through molecular dynamics (MD) simulations of the resulted nanostructures during the deformation. The AIREBO and Tersoff-Brenner potentials are employed to model the interatomic forces between the carbon and boron nitride atoms, respectively. The effects of chiral indices, aspect ratio, presence of mono-vacancy defects and coating dimension on coated/non-coated CNTs are examined. It is demonstrated that the coated defective CNTs exhibit remarkably enhanced ultimate strength, buckling load capacity and Young's modulus. The proposed coating not only enhances the mechanical properties of the resulted nanostructure, but also conceals it from few external factors impacting the behavior of the CNT such as humidity and high temperature.

  2. Nitrogen management and the future of food: lessons from the management of energy and carbon.

    Science.gov (United States)

    Socolow, R H

    1999-05-25

    The food system dominates anthropogenic disruption of the nitrogen cycle by generating excess fixed nitrogen. Excess fixed nitrogen, in various guises, augments the greenhouse effect, diminishes stratospheric ozone, promotes smog, contaminates drinking water, acidifies rain, eutrophies bays and estuaries, and stresses ecosystems. Yet, to date, regulatory efforts to limit these disruptions largely ignore the food system. There are many parallels between food and energy. Food is to nitrogen as energy is to carbon. Nitrogen fertilizer is analogous to fossil fuel. Organic agriculture and agricultural biotechnology play roles analogous to renewable energy and nuclear power in political discourse. Nutrition research resembles energy end-use analysis. Meat is the electricity of food. As the agriculture and food system evolves to contain its impacts on the nitrogen cycle, several lessons can be extracted from energy and carbon: (i) set the goal of ecosystem stabilization; (ii) search the entire production and consumption system (grain, livestock, food distribution, and diet) for opportunities to improve efficiency; (iii) implement cap-and-trade systems for fixed nitrogen; (iv) expand research at the intersection of agriculture and ecology, and (v) focus on the food choices of the prosperous. There are important nitrogen-carbon links. The global increase in fixed nitrogen may be fertilizing the Earth, transferring significant amounts of carbon from the atmosphere to the biosphere, and mitigating global warming. A modern biofuels industry someday may produce biofuels from crop residues or dedicated energy crops, reducing the rate of fossil fuel use, while losses of nitrogen and other nutrients are minimized.

  3. Influence of carbon and nitrogen sources on growth, nitrogenase activity, and carbon metabolism of Gluconacetobacter diazotrophicus.

    Science.gov (United States)

    Tejera, Noel A; Ortega, Eduardo; Rodés, Rosa; Lluch, Carmen

    2004-09-01

    The effects of different carbon and nitrogen sources on the growth, nitrogenase activity, and carbon metabolism of Gluconacetobacter diazotrophicus were investigated. The amino acids asparagine, aspartic acid, and glutamic acid affected microbial growth and nitrogenase activity. Several enzymatic activities involved in the tricarboxylic acid cycle were affected by the carbon source used. In addition, glucose and gluconate significantly increased the oxygen consumption (respiration rate) of whole cells of G. diazotrophicus grown under aerobic conditions. Enzymes responsible for direct oxidation of glucose and gluconate were especially active in cells grown with sucrose and gluconate. The presence of amino acids in the apoplastic and symplastic sap of sugarcane stems suggests that these compounds might be of importance in the regulation of growth and nitrogenase activity during the symbiotic association. The information obtained from the plant-bacterium association together with the results of other biochemical studies could contribute to the development of biotechnological applications of G. diazotrophicus.

  4. Mechanochemical Synthesis of Visible-light Induced Photocatalyst with Nitrogen and Carbon Doping

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nitrogen and/or carbon doped titania photocatalysts were prepared by a novel mechanochemical method. The prepared powders possessed two absorption edges around 400 and 540 nm wavelengths and showed excellent photocatalytic ability for nitrogen monoxide oxidation under visible light irradiation. Under the irradiation of visible light of wavelength >510 nm, 37% of nitrogen monoxide could be continuously removed by the carbon and nitrogen co-doped titania prepared by planetary ball milling of P-25 titania-10% hexamethylenetetramine mixture followed by calcination in air at 400 ℃.

  5. Doping of carbon nanotubes with nitrogen improves protein coverage whilst retaining correct conformation

    Science.gov (United States)

    Burch, Hilary J.; Antoranz Contera, Sonia; de Planque, Maurits R. R.; Grobert, Nicole; Ryan, J. F.

    2008-09-01

    Relevant parameters for non-covalent protein functionalization of carbon nanotubes are explored. Multiwalled carbon nanotubes are carboxylated and functionalized with metalloproteins. Using atomic force microscopy (AFM) we quantitatively determine that coverage with nitrogen-doped multiwalled carbon nanotubes is superior compared to coverage with un-doped multiwalled carbon nanotubes, due to enhanced carboxylation. Conformational analysis using a combination of AFM, antibody binding assays, circular dichroism and UV-visible spectroscopy demonstrates that the metalloproteins retain their native structure when adsorbed to nitrogen-doped multiwalled carbon nanotubes irrespective of their size, charge or folding motif.

  6. A facile approach towards increasing the nitrogen-content in nitrogen-doped carbon nanotubes via halogenated catalysts

    Science.gov (United States)

    Ombaka, L. M.; Ndungu, P. G.; Omondi, B.; McGettrick, J. D.; Davies, M. L.; Nyamori, V. O.

    2016-03-01

    Nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized at 850 °C via a CVD deposition technique by use of three ferrocenyl derivative catalysts, i.e. para-CN, -CF3 and -Cl substituted-phenyl rings. The synthesized catalysts have been characterized by NMR, IR, HR-MS and XRD. The XRD analysis of the para-CF3 catalyst indicates that steric factors influence the X-ray structure of 1,1‧-ferrocenylphenyldiacrylonitriles. Acetonitrile or pyridine was used as carbon and nitrogen sources to yield mixtures of N-CNTs and carbon spheres (CS). The N-CNTs obtained from the para-CF3 catalysts, in pyridine, have the highest nitrogen-doping level, show a helical morphology and are less thermally stable compared with those synthesized by use of the para-CN and -Cl as catalyst. This suggests that fluorine heteroatoms enhance nitrogen-doping in N-CNTs and formation of helical-N-CNTs (H-N-CNTs). The para-CF3 and para-Cl catalysts in acetonitrile yielded iron-filled N-CNTs, indicating that halogens promote encapsulation of iron into the cavity of N-CNT. The use of acetonitrile, as carbon and nitrogen source, with the para-CN and -Cl as catalysts also yielded a mixture of N-CNTs and carbon nanofibres (CNFs), with less abundance of CNFs in the products obtained using para-Cl catalysts. However, para-CF3 catalyst in acetonitrile gave N-CNTs as the only shaped carbon nanomaterials.

  7. Carbon and nitrogen cycling in intertidal sediments near Doel, Scheldt Estuary

    NARCIS (Netherlands)

    Middelburg, J.J.; Klaver, G.; Nieuwenhuize, J.; Vlug, T.

    1995-01-01

    Carbon and nitrogen cycling in intertidal mud flat sediments in the Scheldt Estuary was studied using measurements of carbon dioxide, methane and nitrous oxide emission rates and pore-water profiles of ΣCO2, ammonium and nitrate. A comparison between chamber measured carbon dioxide fluxes and those

  8. Identification of nitrogen dopants in single-walled carbon nanotubes by scanning tunneling microscopy.

    Science.gov (United States)

    Tison, Yann; Lin, Hong; Lagoute, Jérôme; Repain, Vincent; Chacon, Cyril; Girard, Yann; Rousset, Sylvie; Henrard, Luc; Zheng, Bing; Susi, Toma; Kauppinen, Esko I; Ducastelle, François; Loiseau, Annick

    2013-08-27

    Using scanning tunnelling microscopy and spectroscopy, we investigated the atomic and electronic structure of nitrogen-doped single walled carbon nanotubes synthesized by chemical vapor deposition. The insertion of nitrogen in the carbon lattice induces several types of point defects involving different atomic configurations. Spectroscopic measurements on semiconducting nanotubes reveal that these local structures can induce either extended shallow levels or more localized deep levels. In a metallic tube, a single doping site associated with a donor state was observed in the gap at an energy close to that of the first van Hove singularity. Density functional theory calculations reveal that this feature corresponds to a substitutional nitrogen atom in the carbon network.

  9. Adsorption of nitrogen and carbon monoxide on clinoptilolite: determination and prediction of pure and binary isotherms

    Energy Technology Data Exchange (ETDEWEB)

    Triebe, R.W.; Tezel, F.H. [University of Ottawa, Ottawa, ON (Canada). Department of Chemical Engineering

    1995-10-01

    The adsorption of carbon monoxide and nitrogen on clinoptilolite is studied to determine the natural zeolite`s potential for air purification. Pure and binary isotherms were determined for nitrogen and carbon monoxide on a natural Turkish clinoptilolite under near ambient conditions. Experimentally determined isotherms are compared to predictions based on various models from the literature. The Wilson form of the Vacancy Solution Theory is the only model that provides reasonable agreement with the binary isotherm. Clinoptilolite is concluded to be a promising sorbent for separation of carbon monoxide and nitrogen. 30 refs., 11 figs., 5 tabs.

  10. Superior critical current density obtained in MgB2 bulks via employing carbon-coated boron and minor Cu addition

    Science.gov (United States)

    Peng, Junming; Liu, Yongchang; Ma, Zongqing; Shahriar Al Hossain, M.; Xin, Ying; Jin, Jianxun

    2016-09-01

    High performance Cu doped MgB2 bulks were prepared by an in-situ method with carbon-coated amorphous boron as precursor. It was found that the usage of carbon-coated boron in present work leads to the formation of uniformly refined MgB2 grains, as well as a high level of homogeneous carbon doping in the MgB2 samples, which significantly enhance the Jc in both Cu doped and undoped bulks compared to MgB2 bulks with normal amorphous boron precursor. Moreover, minor Cu can service as activator, and thus facilitates the growth of MgB2 grains and improves crystallinity and grain connectivity, which can bring about the excellent critical current density (Jc) at self fields and low fields (the best values are 7 × 105 A/cm2 at self fields, and 1 × 105 A/cm2 at 2 T, 20 K, respectively). Simultaneously, minor Cu addition can reduce the amount of MgO impurity significantly, also contributing to the improvement of Jc at low fields. Our work suggests that Cu-activated sintering combined with employment of carbon-coated amorphous boron as precursor could be a promising technique to produce practical MgB2 bulks or wires with excellent Jc on an industrial scale.

  11. Long-term nitrogen addition decreases carbon leaching in nitrogen-rich forest ecosystems

    Directory of Open Access Journals (Sweden)

    X. Lu

    2013-01-01

    Full Text Available Dissolved organic carbon (DOC plays a critical role in the carbon (C cycle of forest soils, and has been recently connected with global increases in nitrogen (N deposition. Most studies on effects of elevated N deposition on DOC have been carried out in N-limited temperate regions, with far fewer data available from N-rich ecosystems, especially in the context of chronically elevated N deposition. Furthermore, mechanisms for excess N-induced changes of DOC dynamics have been suggested to be different between the two kinds of ecosystems, because of the different ecosystem N status. The purpose of this study was to experimentally examine how long-term N addition affects DOC dynamics below the primary rooting zones (the upper 20 cm soils in typically N-rich lowland tropical forests. We have a primary assumption that long-term continuous N addition minimally affects DOC concentrations and effluxes in N-rich tropical forests. Experimental N addition was administered at the following levels: 0, 50, 100 and 150 kg N ha−1 yr−1, respectively. Results showed that seven years of N addition significantly decreased DOC concentrations in soil solution, and chemo-physical controls (solution acidity change and soil sorption rather than biological controls may mainly account for the decreases, in contrast to other forests. We further found that N addition greatly decreased annual DOC effluxes from the primary rooting zone and increased water-extractable DOC in soils. Our results suggest that long-term N deposition could increase soil C sequestration in the upper soils by decreasing DOC efflux from that layer in N-rich ecosystems, a novel mechanism for continued accumulation of soil C in old-growth forests.

  12. Long-term nitrogen addition decreases carbon leaching in a nitrogen-rich forest ecosystem

    Directory of Open Access Journals (Sweden)

    X. Lu

    2013-06-01

    Full Text Available Dissolved organic carbon (DOC plays a critical role in the carbon (C cycle of forest soils, and has been recently connected with global increases in nitrogen (N deposition. Most studies on effects of elevated N deposition on DOC have been carried out in N-limited temperate regions, with far fewer data available from N-rich ecosystems, especially in the context of chronically elevated N deposition. Furthermore, mechanisms for excess N-induced changes of DOC dynamics have been suggested to be different between the two kinds of ecosystems, because of the different ecosystem N status. The purpose of this study was to experimentally examine how long-term N addition affects DOC dynamics below the primary rooting zones (the upper 20 cm soils in typically N-rich lowland tropical forests. We have a primary assumption that long-term continuous N addition minimally affects DOC concentrations and effluxes in N-rich tropical forests. Experimental N addition was administered at the following levels: 0, 50, 100 and 150 kg N ha−1 yr−1, respectively. Results showed that seven years of N addition significantly decreased DOC concentrations in soil solution, and chemo-physical controls (solution acidity change and soil sorption rather than biological controls may mainly account for the decreases, in contrast to other forests. We further found that N addition greatly decreased annual DOC effluxes from the primary rooting zone and increased water-extractable DOC in soils. Our results suggest that long-term N deposition could increase soil C sequestration in the upper soils by decreasing DOC efflux from that layer in N-rich ecosystems, a novel mechanism for continued accumulation of soil C in old-growth forests.

  13. Dry Process for Manufacturing Hybridized Boron Fiber/Carbon Fiber Thermoplastic Composite Materials from a Solution Coated Precursor

    Science.gov (United States)

    Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor)

    2003-01-01

    An apparatus for producing a hybrid boron reinforced polymer matrix composite from precursor tape and a linear array of boron fibers. The boron fibers are applied onto the precursor tapes and the precursor tape processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the precursor tape with the boron fibers becomes a hybrid boron reinforced polymer matrix composite. A driving mechanism is used to pulled the precursor tape through the method and a take-up spool is used to collect the formed hybrid boron reinforced polymer matrix composite.

  14. Effects of nitrogen content on structure and electrical properties of nitrogen-doped fluorinated diamond-like carbon films

    Institute of Scientific and Technical Information of China (English)

    XIAO Jian-rong; LI Xin-hai; WANG Zhi-xing

    2009-01-01

    Nitrogen-doped fluorinated diamond-like carbon (FN-DLC) films were prepared on single crystal silicon substrate by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) under different deposited conditions with CF4,CH4 and nitrogen as source gases.The influence of nitrogen content on the structure and electrical properties of the films was studied.The films were investigated in terms of surface morphology,microstructure,chemical composition and electrical properties.Atomic force microscopy (AFM) results revealed that the surface morphology of the films became smooth due to doping nitrogen.Fourier transform infrared absorption spectrometry (FTIR) results showed that amouts of C=N and C≡N bonds increased gradually with increasing nitrogen partial pressure r (r=p(N_2)/p(N_2+CF_4+CH_4)).Gaussian fit results of C 1s and N 1s in X-ray photoelectron spectra (XPS) showed that the incorporation of nitrogen presented mainly in the forms of β-C_3N_4 and a-CN_x (x=1,2,3) in the films.The current-voltage (I-V) measurement results showed that the electrical conductivity of the films increased with increasing nitrogen content.

  15. A one-step carbonization route towards nitrogen-doped porous carbon hollow spheres with ultrahigh nitrogen content for CO 2 adsorption

    KAUST Repository

    Wang, Yu

    2015-01-01

    © The Royal Society of Chemistry 2015. Nitrogen doped porous carbon hollow spheres (N-PCHSs) with an ultrahigh nitrogen content of 15.9 wt% and a high surface area of 775 m2 g-1 were prepared using Melamine-formaldehyde nanospheres as hard templates and nitrogen sources. The N-PCHSs were completely characterized and were found to exhibit considerable CO2 adsorption performance (4.42 mmol g-1).

  16. A Model-Based Analysis of Nitrogen Deposition: Effects on Forest Carbon Sequestration

    Science.gov (United States)

    Dezi, S.; Medlyn, B. E.; Tonon, G.; Magnani, F.

    2009-04-01

    Over the last 150 years nitrogen deposition has increased, especially in the northern hemisphere, mainly due to the use of fossil fuels, deforestation and agricultural practices. Although the impact of this increase on the terrestrial carbon cycle is still uncertain, it is likely that this large perturbation of the global nitrogen cycle will have important effects on carbon cycling, particularly via impacts on forest carbon storage. In the present work we investigated qualitatively the overall response of forest carbon sequestration to nitrogen deposition, and the relative importance of different mechanisms that bring about this response. For this purpose we used the G'DAY forest carbon-nitrogen cycling model (Comins and McMurtrie 1993), introducing some new assumptions which focus on the effect of nitrogen deposition. Specifically the new assumptions are: (i) foliar litterfall and specific leaf area (SLA) are functions of leaf nitrogen concentration; (ii) belowground C allocation is a function of net primary production (NPP); (iii) forest canopies can directly take up nitrogen; (iv) management of forests occurs; (v) leaching occurs only for nitrate nitrogen. We investigated the effect of each assumption on net ecosystem production (NEP), with a step increase in nitrogen deposition from a steady state of 0.4 gN m-2 yr-1 to 2 gN m-2 yr-1, and then running the old and new model versions for different nitrogen deposition levels. Our analysis showed that nitrogen deposition can have a large effect on forest carbon storage at ecosystem level. In particular the effect of the assumptions (ii), (iii) and (iv) seem to be of greater importance, giving rise to a markedly higher level of forest carbon sequestration than in their absence. On the contrary assumptions (i) and (v) seem not to have any particular effect on the NEP simulated. Finally, running the models for different levels of nitrogen deposition showed that estimating forest carbon exchange without taking into

  17. Modifications of multi-wall carbon nanotubes with B-containing vapor and their effects on the properties of boron carbide matrix nanocomposites.

    Science.gov (United States)

    Herth, S; Miranda, D; Doremus, R H; Siegel, R W

    2008-06-01

    Multi-wall carbon nanotubes were modified by heating them together with elemental boron powder. B4C crystals grew on the surfaces of the nanotubes, and electron diffraction patterns showed an orientation dependence of the surface B4C and the underlying carbon in the nanotubes. There was no reaction of the nanotubes with solid B2O3 alone. Composites of the modified nanotubes in a B4C matrix showed a small increase of density over sintered B4C.

  18. Decomposition rates and carbon:nitrogen ratios for different litter types, 2015

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data table contains mean decomposition rates and mean carbon:nitrogen ratios for different litter types buried in 7 marshes during 2015. Note that C:N data are...

  19. Assessment of the dynamics in nitrogen and carbon sequestration of European forest soils

    NARCIS (Netherlands)

    Vries, de W.; Salm, van der C.; Reinds, G.J.; Dise, N.B.; Gundersen, P.; Erisman, J.W.; Posch, M.

    2003-01-01

    This report describes the major result of a research project that focused on the assessment of the dynamics in nitrogen and carbon sequestration of European forest soils by estimation of the: (i) retention or release of nitrogen species for selected Intensive Monitoring plots by comparing the input,

  20. Modeling the effects of organic nitrogen uptake by plants on the carbon cycling of boreal ecosystems

    Directory of Open Access Journals (Sweden)

    Q. Zhu

    2013-08-01

    Full Text Available Boreal forest and tundra are the major ecosystems in the northern high latitudes in which a large amount of carbon is stored. These ecosystems are nitrogen-limited due to slow mineralization rate of the soil organic nitrogen. Recently, abundant field studies have found that organic nitrogen is another important nitrogen supply for boreal ecosystems. In this study, we incorporated a mechanism that allowed boreal plants to uptake small molecular amino acids into a process-based biogeochemical model, the Terrestrial Ecosystem Model (TEM, to evaluate the impact of organic nitrogen uptake on ecosystem carbon cycling. The new version of the model was evaluated at both boreal forest and tundra sites. We found that the modeled organic nitrogen uptake accounted for 36–87% of total nitrogen uptake by plants in tundra ecosystems and 26–50% for boreal forests, suggesting that tundra ecosystem might have more relied on the organic form of nitrogen than boreal forests. The simulated monthly gross ecosystem production (GPP and net ecosystem production (NEP tended to be larger with the new version of the model since the plant uptake of organic nitrogen alleviated the soil nitrogen limitation especially during the growing season. The sensitivity study indicated that the most important factors controlling the plant uptake of organic nitrogen were the maximum root uptake rate (Imax and the radius of the root (r0 in our model. The model uncertainty due to uncertain parameters associated with organic nitrogen uptake at tundra ecosystem was larger than at boreal forest ecosystems. This study suggests that considering the organic nitrogen uptake by plants is important to boreal ecosystem carbon modeling.

  1. Electrochemical Performance of Highly Mesoporous Nitrogen Doped Carbon Cathode in Lithium-Oxygen Batteries (Postprint)

    Science.gov (United States)

    2011-03-01

    Chem. Lett. 1 (2010) 2193–2203. [3] F.T. Wagner, B. Lakshmanan, M.F. Mathias, J. Phys. Chem. Lett. 1 (2010) 2204–2219. [4] D. Linden (Ed.), Handbook ...AFRL-RQ-WP-TP-2015-0052 ELECTROCHEMICAL PERFORMANCE OF HIGHLY MESOPOROUS NITROGEN DOPED CARBON CATHODE IN LITHIUM-OXYGEN BATTERIES ...01 March 2011 4. TITLE AND SUBTITLE ELECTROCHEMICAL PERFORMANCE OF HIGHLY MESOPOROUS NITROGEN DOPED CARBON CATHODE IN LITHIUM-OXYGEN BATTERIES

  2. Nitrogen-doped porous carbon monoliths from polyacrylonitrile (PAN) and carbon nanotubes as electrodes for supercapacitors

    Science.gov (United States)

    Wang, Yanqing; Fugetsu, Bunshi; Wang, Zhipeng; Gong, Wei; Sakata, Ichiro; Morimoto, Shingo; Hashimoto, Yoshio; Endo, Morinobu; Dresselhaus, Mildred; Terrones, Mauricio

    2017-01-01

    Nitrogen-doped porous activated carbon monoliths (NDP-ACMs) have long been the most desirable materials for supercapacitors. Unique to the conventional template based Lewis acid/base activation methods, herein, we report on a simple yet practicable novel approach to production of the three-dimensional NDP-ACMs (3D-NDP-ACMs). Polyacrylonitrile (PAN) contained carbon nanotubes (CNTs), being pre-dispersed into a tubular level of dispersions, were used as the starting material and the 3D-NDP-ACMs were obtained via a template-free process. First, a continuous mesoporous PAN/CNT based 3D monolith was established by using a template-free temperature-induced phase separation (TTPS). Second, a nitrogen-doped 3D-ACM with a surface area of 613.8 m2/g and a pore volume 0.366 cm3/g was obtained. A typical supercapacitor with our 3D-NDP-ACMs as the functioning electrodes gave a specific capacitance stabilized at 216 F/g even after 3000 cycles, demonstrating the advantageous performance of the PAN/CNT based 3D-NDP-ACMs. PMID:28074847

  3. Nitrogen-doped porous carbon monoliths from polyacrylonitrile (PAN) and carbon nanotubes as electrodes for supercapacitors

    Science.gov (United States)

    Wang, Yanqing; Fugetsu, Bunshi; Wang, Zhipeng; Gong, Wei; Sakata, Ichiro; Morimoto, Shingo; Hashimoto, Yoshio; Endo, Morinobu; Dresselhaus, Mildred; Terrones, Mauricio

    2017-01-01

    Nitrogen-doped porous activated carbon monoliths (NDP-ACMs) have long been the most desirable materials for supercapacitors. Unique to the conventional template based Lewis acid/base activation methods, herein, we report on a simple yet practicable novel approach to production of the three-dimensional NDP-ACMs (3D-NDP-ACMs). Polyacrylonitrile (PAN) contained carbon nanotubes (CNTs), being pre-dispersed into a tubular level of dispersions, were used as the starting material and the 3D-NDP-ACMs were obtained via a template-free process. First, a continuous mesoporous PAN/CNT based 3D monolith was established by using a template-free temperature-induced phase separation (TTPS). Second, a nitrogen-doped 3D-ACM with a surface area of 613.8 m2/g and a pore volume 0.366 cm3/g was obtained. A typical supercapacitor with our 3D-NDP-ACMs as the functioning electrodes gave a specific capacitance stabilized at 216 F/g even after 3000 cycles, demonstrating the advantageous performance of the PAN/CNT based 3D-NDP-ACMs.

  4. Thermodynamics and Kinetics of Boron Removal from Metallurgical Grade Silicon by Addition of High Basic Potassium Carbonate to Calcium Silicate Slag

    Science.gov (United States)

    Wu, Jijun; Wang, Fanmao; Ma, Wenhui; Lei, Yun; Yang, Bin

    2016-06-01

    In this study, we investigated the thermodynamics and kinetics of boron removal from metallurgical grade silicon (MG-Si) using a calcium silicate slag containing a high basic potassium carbonate. The distribution of boron between slag and silicon was theoretically derived and the distribution coefficients ( L B) of boron with different compositions of CaO, SiO2, and K2CO3 in slag reagents were determined. The maximal value of L B reached 2.08 with a high basicity slag of 40 pctCaO-40 pctSiO2-20 pctK2CO3 (Λ = 0.73). The boron removal rates from MG-Si using CaO-SiO2 and CaO-SiO2-K2CO3 slags at 1823 K (1550 °C) were investigated in an electromagnetic induction furnace. The results showed that the boron concentration in MG-Si can be reduced from 22 to 1.8 ppmw at 1823 K (1550 °C) with 20 pct K2CO3 addition to calcium silicate slag, where the removal efficiency of boron reached 91.8 pct. The mass transfer coefficient ( β S) of boron in binary 50 pctCaO-50 pctSiO2 slag was 3.16 × 10-6 m s-1 at 1823 K (1550 °C) and was 2.43 × 10-5 m s-1 in ternary 40 pctCaO-40 pctSiO2-20 pctK2CO3 slag.

  5. Highly air- and moisture-stable hole-doped carbon nanotube films achieved using boron-based oxidant

    Science.gov (United States)

    Funahashi, Kazuma; Tanaka, Naoki; Shoji, Yoshiaki; Imazu, Naoki; Nakayama, Ko; Kanahashi, Kaito; Shirae, Hiroyuki; Noda, Suguru; Ohta, Hiromichi; Fukushima, Takanori; Takenobu, Taishi

    2017-03-01

    Hole doping into carbon nanotubes can be achieved. However, the doped nanotubes usually suffer from the lack of air and moisture stability, thus, they eventually lose their improved electrical properties. Here, we report that a salt of the two-coordinate boron cation Mes2B+ (Mes: 2,4,6-trimethylphenyl group) can serve as an efficient hole-doping reagent to produce nanotubes with markedly high stability in the presence of air and moisture. Upon doping, the resistances of the nanotubes decreased, and these states were maintained for one month in air. The hole-doped nanotube films showed a minimal increase in resistance even upon humidification with a relative humidity of 90%.

  6. DFT Study on Structural and Mechanical Properties of Single-walled Carbon and Boron Nitride Nanotubes Functionalized with Carbenes

    Directory of Open Access Journals (Sweden)

    I.K. Petrushenko

    2016-10-01

    Full Text Available This paper presents quantum chemistry study on structural and mechanical properties of a series of single-walled carbon nanotubes (SWCNTs and boron nitride nanotubes (BNNTs functionalized with carbenes. At the PBE/SVP level, the obtained data on pristine nanotubes are in good accordance with the results of previous experimental and theoretical studies. The calculations show that carbenes functionalization, in general, distorts both SWNCTs and BNNTs frameworks, but there exists the difference between ‘axial’ and ‘circumferential’ functionalization. It turns out that in both cases elastic properties diminish with increasing concentration of adsorbents, however, the functionalized SWCNTs and BNNTs remain strong enough to be suitable for reinforcement of composites.

  7. Effect of reaction temperature on structure and fluorescence properties of nitrogen-doped carbon dots

    Science.gov (United States)

    Zhang, Yi; Wang, Yaling; Feng, Xiaoting; Zhang, Feng; Yang, Yongzhen; Liu, Xuguang

    2016-11-01

    To investigate the effect of reaction temperature and nitrogen doping on the structure and fluorescence properties of carbon dots (CDs), six kinds of nitrogen-doped CDs (NCDs) were synthesized at reaction temperatures of 120, 140, 160, 180, 200 and 220 °C, separately, by using citric acid as carbon source and ammonia solution as nitrogen source. Nitrogen-free CDs (N-free CDs-180) was also prepared at 180 °C by using citric acid as the only carbon source for comparison. Results show that reaction temperature has obvious effect on carbonization degree, quantum yield (QY), ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectra but less effect on functional groups, nitrogen doping degree and fluorescence lifetime of NCDs. Compared with N-free CDs-180, NCDs-180 possesses enchanced QY and longer fluorescence lifetime. Doping nitrogen has obvious effect on UV-vis absorption and PL spectra but less effect on particles sizes and carbonization degree. The formation mechanism of NCDs is explored: QY of NCDs depends largely on the number of fluorescent polymer chains (FPC), the competition between FPC formation on the surface of NCDs and carbon core growth leads to the change in number of FPC, and consequently to the NCDs with highest QY at appropriate hydrothermal temperature.

  8. Land Cover Differences in Soil Carbon and Nitrogen at Fort Benning, Georgia

    Energy Technology Data Exchange (ETDEWEB)

    Garten Jr., C.T.

    2004-02-09

    Land cover characterization might help land managers assess the impacts of management practices and land cover change on attributes linked to the maintenance and/or recovery of soil quality. However, connections between land cover and measures of soil quality are not well established. The objective of this limited investigation was to examine differences in soil carbon and nitrogen among various land cover types at Fort Benning, Georgia. Forty-one sampling sites were classified into five major land cover types: deciduous forest, mixed forest, evergreen forest or plantation, transitional herbaceous vegetation, and barren land. Key measures of soil quality (including mineral soil density, nitrogen availability, soil carbon and nitrogen stocks, as well as properties and chemistry of the O-horizon) were significantly different among the five land covers. In general, barren land had the poorest soil quality. Barren land, created through disturbance by tracked vehicles and/or erosion, had significantly greater soil density and a substantial loss of carbon and nitrogen relative to soils at less disturbed sites. We estimate that recovery of soil carbon under barren land at Fort Benning to current day levels under transitional vegetation or forests would require about 60 years following reestablishment of vegetation. Maps of soil carbon and nitrogen were produced for Fort Benning based on a 1999 land cover map and field measurements of soil carbon and nitrogen stocks under different land cover categories.

  9. Carbon and Nitrogen Stocks and Humic Fractions in Brazilian Organosols

    Directory of Open Access Journals (Sweden)

    Gustavo Souza Valladares

    Full Text Available ABSTRACT Despite limited geographic expression of Organosols in Brazil, their high carbon storage capacity and natural environmental vulnerability justifies further studies on C and N stocks in these soils and their relationship to the nature of organic matter. Evaluation of physical and chemical properties of organic soils and their ability to store C is important so as to develop sustainable management practices for their preservation. The objectives of the study were to measure the total organic carbon stock (OCst, total nitrogen stock (Nst, and humic fractions in Organosols from different environments and regions of Brazil, and to correlate the data with soil chemical (pH, P, K, Ca2+, Mg2+, Al3+, H+Al, CEC, V and physical properties (soil bulk density, Bd; organic matter density, OMd; total pore space, TPS; minimum residue, MinR; and proportion of mineral matter, MM, and degree of organic matter decomposition (rubbed fiber content; pyrophosphate index, PyI; and von Post index. For that purpose, 18 Organosol profiles, in a total of 49 horizons, were sampled under different land usage and plant coverage conditions. The profiles were located in the following Brazilian states - Alagoas, Bahia, Distrito Federal, Espírito Santo, Mato Grosso do Sul, Minas Gerais, Paraná, Rio de Janeiro, Rio Grande do Sul, Santa Catarina, and São Paulo. The OCst and Nst varied significantly among horizons and profiles. The Organosols exhibited, on average, 203.59 Mg ha-1 OCst and 8.30 Mg ha-1 Nst, and the highest values were found in profiles with pasture usage. The content of the humic fraction (humin, HUM; fulvic acid, FAF; and humic acid, HAF and C storage varied in the soil horizons and profiles according to the degree of decomposition and other factors of soil formation. The OCst, Nst, OMd and the C stocks in the humic fractions were positively correlated. The values of acidity were lower in the soils with higher contents of mineral material, and low p

  10. Impacts of Invasive Pests on Forest Carbon and Nitrogen Dynamics

    Science.gov (United States)

    Lovett, G. M.; Crowley, K. F.

    2014-12-01

    Forests of the U.S. have been subject to repeated invasions of destructive insects and diseases imported from other continents. Like other disturbances, these pests can produce short-term ecosystem effects due to tree mortality, but unlike other disturbances, they often target individual species and therefore can cause long-term species change in the forest. Because tree species vary in their influence on carbon (C) and nitrogen (N) cycles, pest-induced species change can radically alter the biogeochemistry of a forest. In this paper we use both data and modeling to examine how pest-induced species change may alter the C and N cycling in forests of the eastern U.S. We describe a new forest ecosystem model that distinguishes individual tree species and allows species composition to shift over the course of the model run. Results indicate that the mortality of eastern hemlock (Tsuga canadensis) by hemlock woolly adelgid and its replacement by faster-growing species such as black birch (Betula lenta) will reduce forest floor C stocks but increase productivity as the birch become established. Decline of American beech (Fagus grandifolia) from beech bark disease and its replacement by sugar maple (Acer saccharum) is likely to decrease soil C storage and increase N leaching from the ecosystem. Responses to other invasive pests will also be discussed. The magnitude of these species-specific effects on C and N cycling is in many cases larger than direct effects expected from changes in climate and atmospheric N deposition, indicating that species change should be included in models that predict forest ecosystem function under future environmental conditions.

  11. Anthropogenic nitrogen deposition enhances carbon sequestration in boreal soils.

    Science.gov (United States)

    Maaroufi, Nadia I; Nordin, Annika; Hasselquist, Niles J; Bach, Lisbet H; Palmqvist, Kristin; Gundale, Michael J

    2015-08-01

    It is proposed that carbon (C) sequestration in response to reactive nitrogen (Nr ) deposition in boreal forests accounts for a large portion of the terrestrial sink for anthropogenic CO2 emissions. While studies have helped clarify the magnitude by which Nr deposition enhances C sequestration by forest vegetation, there remains a paucity of long-term experimental studies evaluating how soil C pools respond. We conducted a long-term experiment, maintained since 1996, consisting of three N addition levels (0, 12.5, and 50 kg N ha(-1) yr(-1) ) in the boreal zone of northern Sweden to understand how atmospheric Nr deposition affects soil C accumulation, soil microbial communities, and soil respiration. We hypothesized that soil C sequestration will increase, and soil microbial biomass and soil respiration will decrease, with disproportionately large changes expected compared to low levels of N addition. Our data showed that the low N addition treatment caused a non-significant increase in the organic horizon C pool of ~15% and a significant increase of ~30% in response to the high N treatment relative to the control. The relationship between C sequestration and N addition in the organic horizon was linear, with a slope of 10 kg C kg(-1) N. We also found a concomitant decrease in total microbial and fungal biomasses and a ~11% reduction in soil respiration in response to the high N treatment. Our data complement previous data from the same study system describing aboveground C sequestration, indicating a total ecosystem sequestration rate of 26 kg C kg(-1) N. These estimates are far lower than suggested by some previous modeling studies, and thus will help improve and validate current modeling efforts aimed at separating the effect of multiple global change factors on the C balance of the boreal region.

  12. Overexpression of Arabidopsis NLP7 improves plant growth under both nitrogen-limiting and -sufficient conditions by enhancing nitrogen and carbon assimilation.

    Science.gov (United States)

    Yu, Lin-Hui; Wu, Jie; Tang, Hui; Yuan, Yang; Wang, Shi-Mei; Wang, Yu-Ping; Zhu, Qi-Sheng; Li, Shi-Gui; Xiang, Cheng-Bin

    2016-06-13

    Nitrogen is essential for plant survival and growth. Excessive application of nitrogenous fertilizer has generated serious environment pollution and increased production cost in agriculture. To deal with this problem, tremendous efforts have been invested worldwide to increase the nitrogen use ability of crops. However, only limited success has been achieved to date. Here we report that NLP7 (NIN-LIKE PROTEIN 7) is a potential candidate to improve plant nitrogen use ability. When overexpressed in Arabidopsis, NLP7 increases plant biomass under both nitrogen-poor and -rich conditions with better-developed root system and reduced shoot/root ratio. NLP7-overexpressing plants show a significant increase in key nitrogen metabolites, nitrogen uptake, total nitrogen content, and expression levels of genes involved in nitrogen assimilation and signalling. More importantly, overexpression of NLP7 also enhances photosynthesis rate and carbon assimilation, whereas knockout of NLP7 impaired both nitrogen and carbon assimilation. In addition, NLP7 improves plant growth and nitrogen use in transgenic tobacco (Nicotiana tabacum). Our results demonstrate that NLP7 significantly improves plant growth under both nitrogen-poor and -rich conditions by coordinately enhancing nitrogen and carbon assimilation and sheds light on crop improvement.

  13. High-rate and ultralong cycle-life LiFePO4 nanocrystals coated by boron-doped carbon as positive electrode for lithium-ion batteries

    Science.gov (United States)

    Feng, Jinpeng; Wang, Youlan

    2016-12-01

    An evolutionary modification approach, boron-doped carbon coating, has been used to improve the electrochemical performances of positive electrodes for lithium-ion batteries, and demonstrates apparent and significant modification effects. In this study, the boron-doped carbon coating is firstly adopted and used to decorate the performance of LiFePO4. The obtained composite exhibits a unique core-shell structure with an average diameter of 140 nm and a 4 nm thick boron-doped carbon shell that uniformly encapsulates the core. Owing to the boron element which could induce high amount of defects in the carbon, the electronic conductivity of LiFePO4 is greatly ameliorated. Thus, the boron-doped composite shows superior rate capability and cycle stability than the undoped sample. For instance, the reversible specific capacity of LiFePO4@B0.4-C can reach 164.1 mAh g-1 at 0.1C, which is approximately 96.5% of the theoretical capacity (170 mAh g-1). Even at high rate of 10C, it still shows a high specific capacity of 126.8 mAh g-1 and can be maintained at 124.5 mAh g-1 after 100 cycles with capacity retention ratio of about 98.2%. This outstanding Li-storage property enable the present design strategy to open up the possibility of fabricating the LiFePO4@B-C composite for high-performance lithium-ion batteries.

  14. Nitrogen-doped carbons in Li-S batteries: materials design and electrochemical mechanism

    Directory of Open Access Journals (Sweden)

    Xia eLi

    2014-11-01

    Full Text Available Li-S batteries have been considered as next generation Li batteries due to their high theoretical energy density. Over the past few years, researchers have made significant efforts in breaking through critical bottlenecks which impede the commercialization of Li-S batteries. Beginning with a basic introduction to Li-S systems and their associated mechanism, this review will highlight the application of one specific carbon family, nitrogen-doped carbon materials in sulfur based cathodes. These materials will include nitrogen doped porous carbon, carbon nanotubes, nanofibers and graphene. The article will conclude with a summary of recent research efforts in this field as well as the future prospects for the use of nitrogen-doped carbon materials in Li-S batteries.

  15. Determination of free nitrogen in carbon steels by inert gas fusion method

    Science.gov (United States)

    Tabakov, Ya. I.; Grigorovich, K. V.; Mansurova, E. R.

    2016-07-01

    The possibility to use hot extraction (thermal extraction in a carrier-gas flow) for fractional analysis of nitrogen in carbon steels is shown for cord and reinforcing-bar steels. A rapid procedure is developed for an analysis of free nitrogen in carbon steels. The validity of the analytical procedure is confirmed by high-temperature hydrogen extraction. The data obtained by the two methods correlate well with each other. A sample preparation procedure is developed for the determination of the content of dissolved nitrogen.

  16. Nitrogen-doped dual mesoporous carbon for the selective oxidation of ethylbenzene

    Science.gov (United States)

    Chen, Aibing; Yu, Yifeng; Wang, Rujie; Yu, Yunhong; Zang, Wenwei; Tang, Pei; Ma, Ding

    2015-08-01

    A nanocasting method to fabricate nitrogen-doped dual mesoporous carbon is proposed by the carbonization of nitrile functional ionic liquid (FIL) grafted SBA-15 for the first time. These carbon materials have high nitrogen content (12.8%), large specific surface areas (763 m2 g-1) and uniform rod morphologies, which are derived from FILs grafted on the surface of SBA-15. Furthermore, by adjusting the impregnation amount of ionic liquids on SBA-15, pore structures of these carbon materials can be adjusted from single to dual mesopores. The developed dual mesoporous carbon materials exhibit good catalytic performance in the selective oxidation of ethylbenzene, ascribed to the promoting effects of nitrogen-doping, high surface area and dual mesostructure. It may be concluded that the dual mesostructure has an advantage over a single mesostructure to obtain a fast mass transport rate, resulting in higher acetophenone yield.A nanocasting method to fabricate nitrogen-doped dual mesoporous carbon is proposed by the carbonization of nitrile functional ionic liquid (FIL) grafted SBA-15 for the first time. These carbon materials have high nitrogen content (12.8%), large specific surface areas (763 m2 g-1) and uniform rod morphologies, which are derived from FILs grafted on the surface of SBA-15. Furthermore, by adjusting the impregnation amount of ionic liquids on SBA-15, pore structures of these carbon materials can be adjusted from single to dual mesopores. The developed dual mesoporous carbon materials exhibit good catalytic performance in the selective oxidation of ethylbenzene, ascribed to the promoting effects of nitrogen-doping, high surface area and dual mesostructure. It may be concluded that the dual mesostructure has an advantage over a single mesostructure to obtain a fast mass transport rate, resulting in higher acetophenone yield. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03802b

  17. Synthesis of low carbon boron carbide powder using a minimal time processing route: Thermal plasma

    Directory of Open Access Journals (Sweden)

    Avinna Mishra

    2015-12-01

    Full Text Available Boron carbide powder was synthesized by thermal plasma reduction of boric acid in presence of graphite with a very minimal processing time. Subsequently, the as-synthesized products were leached to minimize the impurities content. Based on the results of X-ray diffraction and Raman spectroscopy, the effect of leaching on phase purity and crystallinity was studied. X-ray photoelectron spectroscopy was performed to identify the chemical composition which highlighted the absence of the BO bonding in the deconvoluted B 1s core-level spectrum. Finally, the temperature dependent thermal conductivity behavior of the leached materials was analyzed and presented.

  18. The modification of polyurethane foams using new boroorganic polyols (II) polyurethane foams from boron-modified hydroxypropyl urea derivatives.

    Science.gov (United States)

    Zarzyka, Iwona

    2014-01-01

    The work focuses on research related to determination of application possibility of new, ecofriendly boroorganic polyols in rigid polyurethane foams production. Polyols were obtained from hydroxypropyl urea derivatives esterified with boric acid and propylene carbonate. The influence of esterification type on properties of polyols and next on polyurethane foams properties was determined. Nitrogen and boron impacts on the foams' properties were discussed, for instance, on their physical, mechanical, and electric properties. Boron presence causes improvement of dimensional stability and thermal stability of polyurethane foams. They can be applied even at temperature 150 °C. Unfortunately, introducing boron in polyurethanes foams affects deterioration of their water absorption, which increases as compared to the foams that do not contain boron. However, presence of both boron and nitrogen determines the decrease of the foams combustibility. Main impact on the decrease combustibility of the obtained foams has nitrogen presence, but in case of proper boron and nitrogen ratio their synergic activity on the combustibility decrease can be easily seen.

  19. Carbon-nitrogen place exchange on NO exposed beta-Mo2C.

    Science.gov (United States)

    Siaj, Mohamed; Maltais, Carl; Zahidi, El Mamoune; Oudghiri-Hassani, Hicham; Wang, Jiqing; Rosei, Federico; McBreen, Peter H

    2005-08-18

    Atomic nitrogen and oxygen were deposited on beta-Mo(2)C through dissociative adsorption of NO. Reflectance absorbance infrared spectroscopy (RAIRS), thermal desorption, and synchrotron X-ray photoelectron spectroscopy (XPS) measurements were used to investigate the interplay between atomic nitrogen, carbon, and oxygen in the 400-1250 K region. The combination of the high resolution and high surface sensitivity offered by the synchrotron XPS technique was used to show that atomic nitrogen displaces interstitial carbon onto the carbide surface. Thermal desorption measurements show that the burnoff of the displaced carbon occurs at approximately 890 K. The incorporation of nitrogen into interstitial sites inhibits oxygen dissolution into the bulk. RAIRS spectroscopy was used to identify surface oxo, terminal oxygen, species formed from O(2) and NO on beta-Mo(2)C.

  20. Carbon and nitrogen balance of leaf-eating sesarmid crabs ( Neoepisesarma versicolor) offered different food sources

    Science.gov (United States)

    Thongtham, Nalinee; Kristensen, Erik

    2005-10-01

    Carbon and nitrogen budgets for the leaf-eating crab, Neoepisesarma versicolor, were established for individuals living on pure leaf diets. Crabs were fed fresh (green), senescent (yellow) and partly degraded (brown) leaves of the mangrove tree Rhizophora apiculata. Ingestion, egestion and metabolic loss of carbon and nitrogen were determined from laboratory experiments. In addition, bacterial abundance in various compartments of the crabs' digestive tract was enumerated after dissection of live individuals. Ingestion and egestion rates (in terms of dry weight) were highest, while the assimilation efficiency was poorest for crabs fed on brown leaves. The low assimilation efficiency was more than counteracted by the high ingestion rate providing more carbon for growth than for crabs fed green and yellow leaves. In any case, the results show that all types of leaves can provide adequate carbon while nitrogen was insufficient to support both maintenance (yellow leaves) and growth (green, yellow and brown leaves). Leaf-eating crabs must therefore obtain supplementary nitrogen by other means in order to meet their nitrogen requirement. Three hypotheses were evaluated: (1) crabs supplement their diet with bacteria and benthic microalgae by ingesting own faeces and/or selective grazing at the sediment surface; (2) assimilation of symbiotic nitrogen-fixing bacteria in the crabs' own intestinal system; and (3) nitrogen storage following occasional feeding on animal tissues (e.g. meiofauna and carcasses). It appears that hypothesis 1 is of limited importance for N. versicolor since faeces and sediment can only supply a minor fraction of the missing nitrogen due to physical constraints on the amount of material the crabs can consume. Hypothesis 2 can be ruled out because tests showed no nitrogen fixation activity in the intestinal system of N. versicolor. It is therefore likely that leaf-eating crabs provide most of their nitrogen requirement from intracellular deposits

  1. Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

    Directory of Open Access Journals (Sweden)

    X. Yang

    2010-04-01

    Full Text Available We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades

  2. Crystal structure of 4-(meth-oxy-carbon-yl)phenyl-boronic acid.

    Science.gov (United States)

    Flanagan, Keith J; Senge, Mathias O

    2015-10-01

    In the title compound, C8H9BO4, the meth-oxy-carbonyl group is rotated out of the plane of the benzene ring by 7.70 (6)°. In the crystal, mol-ecules are linked via pairs of O-H⋯O hydrogen bonds, involving the boronic acid OH groups, forming inversion dimers. The dimers are linked via O-H⋯O hydrogen bonds, involving a boronic acid OH group and the carbonyl O atom, forming undulating sheets parallel to (10-2). Within the sheets there are also C-H⋯O hydrogen bonds present, also involving the carbonyl O atom. The sheets are linked via C-H⋯π and offset face-to-face π-inter-actions between inversion-related mol-ecules [inter-centroid distance = 3.7843 (16) Å, inter-planar distance = 3.3427 (4) Å and offset = 1.744 Å], forming a three-dimensional structure.

  3. The first-principles study of low dimensional boron and carbon nanostructures%低维硼碳纳米材料第一原理研究

    Institute of Scientific and Technical Information of China (English)

    倪军; 杨再林

    2011-01-01

    We have reviewed our recent researches on the boron and carbon nanostructures in this paper. We show that the stable boron sheet, nanotubes, and nanoribbons have a rich variety of electronic properties. For boron carbide nanostructures, such as the ordering BC3, BC5 and BC7 sheets, we found that the hydrogenation and defects could lead to rich electronic and magnetic properties. The boron and carbon nanostructures may have the potential applications in the nanoscale devices in the future.%介绍了近年来关于低维硼碳纳米材料结构和电子性质的研究工作.通过第一原理计算,从理论上预言了稳定的低维硼纳米结构,并系统研究了以稳定硼平面为基础的硼纳米管和硼纳米带的电子性质.对于硼碳复合纳米材料,以BC3,BC5和BC7有序结构的平面为基础,发现对其剪裁、氢化修饰之后,硼碳纳米结构具有丰富的电磁学性质,可能在未来电子学器件中得到广泛的应用.

  4. The impact of nitrogen deposition on carbon sequestration by European forests and heathlands

    NARCIS (Netherlands)

    Vries, de W.; Solberg, S.; Dobbertin, M.; Sterba, H.; Laubhann, D.; Oijen, van M.; Evans, C.; Gundersen, P.; Kros, H.; Wamelink, W.; Reinds, G.J.; Sutton, M.A.

    2009-01-01

    In this study, we present estimated ranges in carbon (C) sequestration per kg nitrogen (N) addition in above-ground biomass and in soil organic matter for forests and heathlands, based on: (i) empirical relations between spatial patterns of carbon uptake and influencing environmental factors includi

  5. Modeling of carbon and nitrogen gaseous emissions from cattle manure compost windrows

    Science.gov (United States)

    Windrow composting of cattle manure is a significant source of gaseous emissions, which include ammonia (NH3) and the greenhouse gases (GHGs) of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). A manure compost model was developed to simulate carbon (C) and nitrogen (N) processes includ...

  6. Nitrogen removal from coal gasification wastewater by activated carbon technologies combined with short-cut nitrogen removal process.

    Science.gov (United States)

    Zhao, Qian; Han, Hongjun; Hou, Baolin; Zhuang, Haifeng; Jia, Shengyong; Fang, Fang

    2014-11-01

    A system combining granular activated carbon and powdered activated carbon technologies along with shortcut biological nitrogen removal (GAC-PACT-SBNR) was developed to enhance total nitrogen (TN) removal for anaerobically treated coal gasification wastewater with less need for external carbon resources. The TN removal efficiency in SBNR was significantly improved by introducing the effluent from the GAC process into SBNR during the anoxic stage, with removal percentage increasing from 43.8%-49.6% to 68.8%-75.8%. However, the TN removal rate decreased with the progressive deterioration of GAC adsorption. After adding activated sludge to the GAC compartment, the granular carbon had a longer service-life and the demand for external carbon resources became lower. Eventually, the TN removal rate in SBNR was almost constant at approx. 43.3%, as compared to approx. 20.0% before seeding with sludge. In addition, the production of some alkalinity during the denitrification resulted in a net savings in alkalinity requirements for the nitrification reaction and refractory chemical oxygen demand (COD) degradation by autotrophic bacteria in SBNR under oxic conditions. PACT showed excellent resilience to increasing organic loadings. The microbial community analysis revealed that the PACT had a greater variety of bacterial taxons and the dominant species associated with the three compartments were in good agreement with the removal of typical pollutants. The study demonstrated that pre-adsorption by the GAC-sludge process could be a technically and economically feasible method to enhance TN removal in coal gasification wastewater (CGW).

  7. Nitrogen and carbon interactions in controlling terrestrial greenhouse gas fluxes

    Science.gov (United States)

    Ineson, Phil; Toet, Sylvia; Christiansen, Jesper

    2016-04-01

    The increased input of N to terrestrial systems may have profound impacts on net greenhouse gas (GHGs) fluxes and, consequently, our future climate; however, fully capturing and quantifying these interactions under field conditions urgently requires new, more efficient, measurement approaches. We have recently developed and deployed a novel system for the automation of terrestrial GHG flux measurements at the chamber and plot scales, using the approach of 'flying' a single measurement chamber to multiple points in an experimental field arena. As an example of the value of this approach, we shall describe the results from a field experiment investigating the interactions between increasing inorganic nitrogen (N) and carbon (C) additions on net ecosystem exchanges of N2O, CH4 and CO2, enabling the simultaneous application of 25 treatments, replicated five times in a fully replicated block field design. We will describe how the ability to deliver automated GHG flux measurements, highly replicated in space and time, has revealed hitherto unreported findings on N and C interactions in field soil. In our experiments we found insignificant N2O fluxes from bare field soil, even at very high inorganic N addition rates, but the interactive addition of even small amounts of available C resulted in very large and rapid N2O fluxes. The SkyGas experimental system enabled investigation of the underlying interacting response surfaces on the fluxes of the major soil-derived GHGs (CO2, CH4 and N2O) to increasing N and C inputs, and revealed unexpected interactions. In addition to these results we will also discuss some of the technical problems which have been overcome in developing these 'flying' systems and the potential of the systems for automatically screening the impacts of large numbers of treatments on GHG fluxes, and other ecosystem responses, under field conditions. We describe here technological advances that can facilitate the development of more robust GHG mitigation

  8. Soil carbon and nitrogen stocks following forest conversion to pasture in the Western Brazilian Amazon Basin

    OpenAIRE

    2008-01-01

    We examined two chronosequences of forest, 8-and 20-year-old pasture in Rondônia-Brazil, to investigate how land use change affects the soil carbon and nitrogen stocks and organic matter dynamics of surface soil (0 to 30 cm). Soil total carbon and nitrogen stocks increased in 20-year-old pasture compared with the original forest in one chronosequence but no changes were detected in the other chronosequence. Calculations of the contributions of forest - and pasture-derived carbon from soil &et...

  9. Effect of shoot removal on remobilization of carbon and nitrogen during regrowth of nitrogen-fixing alfalfa.

    Science.gov (United States)

    Aranjuelo, Iker; Molero, Gemma; Erice, Gorka; Aldasoro, Joseba; Arrese-Igor, Cesar; Nogués, Salvador

    2015-01-01

    The contribution of carbon and nitrogen reserves to regrowth following shoot removal has been studied in the past. However, important gaps remain in understanding the effect of shoot cutting on nodule performance and its relevance during regrowth. In this study, isotopic labelling was conducted at root and canopy levels with both (15) N2 and (13) C-depleted CO2 on exclusively nitrogen-fixing alfalfa plants. As expected, our results indicate that the roots were the main sink organs before shoots were removed. Seven days after regrowth the carbon and nitrogen stored in the roots was invested in shoot biomass formation and partitioned to the nodules. The large depletion in nodule carbohydrate availability suggests that root-derived carbon compounds were delivered towards nodules in order to sustain respiratory activity. In addition to the limited carbohydrate availability, the upregulation of nodule peroxidases showed that oxidative stress was also involved during poor nodule performance. Fourteen days after cutting, and as a consequence of the stimulated photosynthetic and N2 -fixing machinery, availability of Cnew and Nnew strongly diminished in the plants due to their replacement by C and N assimilated during the post-labelling period. In summary, our study indicated that during the first week of regrowth, root-derived C and N remobilization did not overcome C- and N-limitation in nodules and leaves. However, 14 days after cutting, leaf and nodule performance were re-established.

  10. Fast Conversion of Ionic Liquids and Poly(Ionic Liquid)s into Porous Nitrogen-Doped Carbons in Air

    OpenAIRE

    2016-01-01

    Ionic liquids and poly(ionic liquid)s have been successfully converted into nitrogen-doped porous carbons with tunable surface area up to 1200 m2/g at high temperatures in air. Compared to conventional carbonization process conducted under inert gas to produce nitrogen-doped carbons, the new production method was completed in a rather shorter time without noble gas protection.

  11. B and N isolate-doped graphitic carbon nanosheets from nitrogen-containing ion-exchanged resins for enhanced oxygen reduction

    Science.gov (United States)

    Wang, Lei; Yu, Peng; Zhao, Lu; Tian, Chungui; Zhao, Dongdong; Zhou, Wei; Yin, Jie; Wang, Ruihong; Fu, Honggang

    2014-06-01

    B,N-codoped carbon nanostructures (BNCS) can serve as alternative low-cost metal-free electrocatalysts for oxygen reduction reactions (ORR). However, the compensation effect between the p- (B atoms) and n-type (N atoms) dopants would make the covalent boron-nitride (BN) easily formed during the synthesis of BNCS, leading to a unsatisfactory ORR activity. Therefore, it has been challenging to develop facile and rapid synthetic strategies for highly active BNCS without forming the direct covalent BN. Here, a facile method is developed to prepare B and N isolate-doped graphitic nanosheets (BNGS) by using iron species for saving N element and simultaneous doping the B element from nitrogen-containing ion-exchanged resins (NR). The resulting BNGS exhibits much more onset potential (Eonset) compared with the B-doped graphitic carbon nanosheets (BGS), N-doped graphitic carbon nanosheets (NGS), as well as B,N-codoped disorder carbon (BNC). Moreover, the BNGS shows well methanol tolerance propery and excellent stability (a minimal loss of activity after 5,000 potential cycles) compared to that of commercial Pt/C catalyst. The goog performance for BNGS towards ORR is attributed to the synergistic effect between B and N, and the well electrons transport property of graphitic carbon in BNGS.

  12. Single-step synthesis of crystalline h-BN quantum- and nanodots embedded in boron carbon nitride films

    Science.gov (United States)

    Matsoso, Boitumelo J.; Ranganathan, Kamalakannan; Mutuma, Bridget K.; Lerotholi, Tsenolo; Jones, Glenn; Coville, Neil J.

    2017-03-01

    Herein we report on the synthesis and characterization of novel crystalline hexagonal boron nitride (h-BN) quantum- and nanodots embedded in large-area boron carbon nitride (BCN) films. The films were grown on a Cu substrate by an atmospheric pressure chemical vapour deposition technique. Methane, ammonia, and boric acid were used as precursors for C, N and B to grow these few atomic layer thick uniform films. We observed that both the size of the h-BN quantum/nanodots and thickness of the BCN films were influenced by the vaporization temperature of boric acid as well as the H3BO3 (g) flux over the Cu substrate. These growth conditions were easily achieved by changing the position of the solid boric acid in the reactor with respect to the Cu substrate. Atomic force microscope (AFM) and TEM analyses show a variation in the h-BN dot size distribution, ranging from nanodots (∼224 nm) to quantum dots (∼11 nm) as the B-source is placed further away from the Cu foil. The distance between the B-source and the Cu foil gave an increase in the C atomic composition (42 at% C–65 at% C) and a decrease in both B and N contents (18 at% B and 14 at% N to 8 at% B and 7 at% N). UV–vis absorption spectra showed a higher band gap energy for the quantum dots (5.90 eV) in comparison with the nanodots (5.68 eV) due to a quantum confinement effect. The results indicated that the position of the B-source and its reaction with ammonia plays a significant role in controlling the nucleation of the h-BN quantum- and nanodots. The films are proposed to be used in solar cells. A mechanism to explain the growth of h-BN quantum/nanodots in BCN films is reported.

  13. Two-dimensional boron: Lightest catalyst for hydrogen and oxygen evolution reaction

    Science.gov (United States)

    Mir, Showkat H.; Chakraborty, Sudip; Jha, Prakash C.; Wärnâ, John; Soni, Himadri; Jha, Prafulla K.; Ahuja, Rajeev

    2016-08-01

    The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) have been envisaged on a two-dimensional (2D) boron sheet through electronic structure calculations based on a density functional theory framework. To date, boron sheets are the lightest 2D material and, therefore, exploring the catalytic activity of such a monolayer system would be quite intuitive both from fundamental and application perspectives. We have functionalized the boron sheet (BS) with different elemental dopants like carbon, nitrogen, phosphorous, sulphur, and lithium and determined the adsorption energy for each case while hydrogen and oxygen are on top of the doping site of the boron sheet. The free energy calculated from the individual adsorption energy for each functionalized BS subsequently guides us to predict which case of functionalization serves better for the HER or the OER.

  14. Nitrogen restrictions buffer modeled interactions of water with the carbon cycle

    Science.gov (United States)

    Huang, Yuanyuan; Gerber, Stefan

    2016-01-01

    Terrestrial carbon and water cycles are coupled at multiple spatiotemporal scales and are crucial to carbon sequestration. Water related climate extremes, such as drought and intense precipitation, can substantially affect the carbon cycle. Meanwhile, nitrogen is a limiting resource to plant and has therefore the potential to alter the coupling of water and carbon cycles on land. Here we assess the effect of nitrogen limitation on the response of the terrestrial carbon cycle to moisture anomalies using Geophysical Fluid Dynamics Laboratory's land surface model LM3V-N. We analyzed the response of three central carbon fluxes: net primary productivity (NPP), heterotrophic respiration (Rh), and net ecosystem productivity (NEP, the difference between NPP and Rh) and how these fluxes were altered under anomalies of the standardized precipitation and evapotranspiration index (SPEI). We found that globally, the correlations between each of the carbon flux and SPEI depended on the timescale and a strong legacy effect of SPEI anomalies on Rh. Consideration of nitrogen constraints reduced anomalies in carbon fluxes in response to extreme dry/wet events. This nitrogen-induced buffer constrained the growth of plants under wet extremes and allowed for enhanced growth during droughts. Extra gain of soil moisture from the downregulation of canopy transpiration by nitrogen limitation and shifts in the relative importance of water and nitrogen limitation during dry/wet extreme events are possible mechanisms contributing to the buffering of modeled NPP and NEP. Responses of Rh to moisture anomalies were much weaker compared to NPP, and N buffering effects were less evident.

  15. Nitrogen Dynamics are a Key Factor in Explaining Global Land Carbon Sink

    Science.gov (United States)

    Huntzinger, D. N.; Michalak, A. M.; Schwalm, C.; Ciais, P.; Schaefer, K. M.; King, A. W.; Wei, Y.; Cook, R. B.; Fisher, J. B.; Hayes, D. J.; Huang, M.; Ito, A.; Jain, A. K.; Lei, H.; Lu, C.; Maignan, F.; Mao, J.; Parazoo, N.; Peng, S.; Poulter, B.; Ricciuto, D. M.; Shi, X.; Tian, H.; Wang, W.; Zeng, N.; Zhao, F.

    2015-12-01

    The terrestrial carbon cycle plays a critical role in regulating the amount of anthropogenic emissions that remain in the atmosphere. Yet, land-atmosphere carbon dynamics are one of the largest sources of uncertainty in projections of future climate. Reducing this uncertainty requires understanding the relative role of various drivers to land carbon uptake. We use an ensemble of land surface models to quantify the influence of climate, land use history, atmospheric CO2, and nitrogen deposition on the strength of the net land sink over the past 110 years. Each model can be thought of as one realization of terrestrial carbon cycling and the factors most important in controlling land sink strength. Using a series of sensitivity simulations, we identify the dominant drivers to the net land sink that emerge consistently across models, both globally and regionally. We find that the relative importance of external forcing factors on the strength of net land carbon uptake varies considerably across models and depends strongly on whether nitrogen cycling is explicitly simulated. Models without a nitrogen cycle estimate cumulative land carbon uptake (since 1959) that is 3 times greater (93.3 ± 84.1 PgC) than global mass balance constraints (34.6 ± 41.6 PgC). Surprisingly, the greatest impacts are seen in the tropics, where coupled carbon-nitrogen cycle models estimate CO2 fertilization and climate affects that are ~60% weaker than models without a nitrogen cycle. The results highlight the importance of model structure on the inferred sensitivity of land carbon uptake to external forcing factors. The range in sensitivity across models is important for future climate projections since the differences in the processes that explain trends in net land sink strength between models with and without nitrogen dynamics can lead to very different future trajectories of atmospheric CO2 and thus climate.

  16. Green synthesis of luminescent nitrogen-doped carbon dots from milk and its imaging application.

    Science.gov (United States)

    Wang, Li; Zhou, H Susan

    2014-09-16

    In the present work, a completely green synthetic method for producing fluorescent nitrogen-doped carbon dots by using milk is introduced. The process is environmentally friendly, simple, and efficient. By hydrothermal heating of milk, we produced monodispersed, highly fluorescent carbon dots with a size of about 3 nm. Imaging of U87 cells, a human brain glioma cancer cell line, can be easily achieved with high resolution using the prepared carbon dots as probes and validates their use in imaging applications.

  17. Nitrogen-incorporated ultrananocrystalline diamond and multi-layer-graphene-like hybrid carbon films

    Science.gov (United States)

    Tzeng, Yonhua; Yeh, Shoupu; Fang, Wei Cheng; Chu, Yuehchieh

    2014-03-01

    Nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) and multi-layer-graphene-like hybrid carbon films have been synthesized by microwave plasma enhanced chemical vapor deposition (MPECVD) on oxidized silicon which is pre-seeded with diamond nanoparticles. MPECVD of N-UNCD on nanodiamond seeds produces a base layer, from which carbon structures nucleate and grow perpendicularly to form standing carbon platelets. High-resolution transmission electron microscopy and Raman scattering measurements reveal that these carbon platelets are comprised of ultrananocrystalline diamond embedded in multilayer-graphene-like carbon structures. The hybrid carbon films are of low electrical resistivity. UNCD grains in the N-UNCD base layer and the hybrid carbon platelets serve as high-density diamond nuclei for the deposition of an electrically insulating UNCD film on it. Biocompatible carbon-based heaters made of low-resistivity hybrid carbon heaters encapsulated by insulating UNCD for possible electrosurgical applications have been demonstrated.

  18. [Effects of different fertilizer species on carbon and nitrogen leaching in a reddish paddy soil].

    Science.gov (United States)

    Liu, Xi-Yu; Zou, Jing-Dong; Xu, Li-Li; Zhang, Xin-Yu; Yang, Feng-Ting; Dai, Xiao-Qin; Wang, Zhong-Qiang; Sun, Xiao-Min

    2014-08-01

    Enhanced fertilization could decrease nitrogen utilization rate and increase carbon and nitrogen leaching, leading to water pollution in agricultural ecosystem. A long-term field experiment had been established on a reddish paddy soil of Qianyanzhou Ecological Experimental Station (114 degrees 53'E, 26 degrees 48'N) in Jiangxi Province in 1998. Soil solution samples were collected by clay tube and vacuum pump. Four fertilizer species treatments were selected: control with no fertilizer (CK), straw return (ST), nitrogen, phosphorus and potassium mineral fertilizers (NPK) and pig manure (OM), aiming to evaluate the effects of different species of fertilizer on carbon and nitrogen leaching in a double rice cropping system. The results showed that: (1) ammonium nitrogen (NH4(+) -N) was the major type of N in soil leachate in reddish paddy soil. The application of NPK could significantly increase the ammonium nitrogen concentration (1.2 mg x L(-1) +/- 0.1 mg x L(-1)) compared with the CK, ST and OM treatments, and the application of OM could significantly increase the dissolved organic carbon (DOC) concentration (27.3 mg x L(-1) +/- 1.6 mg x L(-1)) in soil leachate. The carbon and nitrogen leaching were more notable in the vegetative growth stage than the reproductive growth stage of rice (P soil organic carbon (SOC) and total nitrogen (TN) contents. The NPK was best beneficial to improve TN contents and OM to improve SOC contents. (3) The DOC contents in soil leachate and SOC in paddy soil had a positive correlation (P soil leachate and TN contents in paddy soil had a positive correlation (P < 0.01).

  19. Nitrogen

    Science.gov (United States)

    Apodaca, Lori E.

    2013-01-01

    The article presents an overview of the nitrogen chemical market as of July 2013, including the production of ammonia compounds. Industrial uses for ammonia include fertilizers, explosives, and plastics. Other topics include industrial capacity of U.S. ammonia producers CF Industries Holdings Inc., Koch Nitrogen Co., PCS Nitrogen, Inc., and Agrium Inc., the impact of natural gas prices on the nitrogen industry, and demand for corn crops for ethanol production.

  20. Preferred orientation in carbon and boron nitride: Does a thermodynamic theory of elastic strain energy get it right. [C; BN

    Energy Technology Data Exchange (ETDEWEB)

    McCarty, K.F. (Sandia National Laboratories, Livermore, California 94550 (United States))

    1999-09-01

    We address whether the elastic strain-energy theory (minimizing the Gibbs energy of a stressed crystal) of McKenzie and co-workers [D. R. McKenzie and M. M. M. Bilek, J. Vac. Sci. Technol. A [bold 16], 2733 (1998)] adequately explains the preferred orientation observed in carbon and BN films. In the formalism, the Gibbs energy of the cubic materials diamond and cubic boron includes the strain that occurs when the phases form, through specific structural transformations, from graphitic precursors. This treatment violates the requirement of thermodynamics that the Gibbs energy be a path-independent, state function. If the cubic phases are treated using the same (path-independent) formalism applied to the graphitic materials, the crystallographic orientation of lowest Gibbs energy is not that observed experimentally. For graphitic (hexagonal) carbon and BN, an elastic strain approach seems inappropriate because the compressive stresses in energetically deposited films are orders of magnitude higher than the elastic limit of the materials. Furthermore, using the known elastic constants of either ordered or disordered graphitic materials, the theory does not predict the orientation observed by experiment. [copyright] [ital 1999 American Vacuum Society.

  1. Pure and carbon-doped boron phosphide (6,0) zigzag nanotube: A computational NMR study

    Energy Technology Data Exchange (ETDEWEB)

    Arshadi, S., E-mail: sattar_arshadi@yahoo.com [Department of Chemistry, Payame Noor University, 19395-4697, I.R. of Iran (Iran, Islamic Republic of); Bekhradnia, A.R., E-mail: abekhradnia@gmail.com [Pharmaceutical Sciences Research Center, Department of Medicinal Chemistry, Mazandaran University of Medical Sciences, Sari (Iran, Islamic Republic of); Department of Chemistry and Molecular Biology, Gothenburg University, Gothenburg (Sweden); Alipour, F.; Abedini, S. [Department of Chemistry, Payame Noor University, 19395-4697, I.R. of Iran (Iran, Islamic Republic of)

    2015-11-15

    Calculations were performed for investigation of the properties of the electronic structure of Carbon- Doped Boron Phosphide Nanotube (CDBPNT). Pristine and three models of C-doped structures of (6,0) zigzag BPNT were studied at density functional theory (DFT) in combination with 6-311G* basis set using Gaussian package of program. The calculated parameters reveal that various {sup 11}B and {sup 31}P nuclei are divided into some layers with equivalent electrostatic properties. The electronic structure properties are highly influenced by replacement of {sup 11}B and {sup 31}P atoms by {sup 12}C atoms in pristine model. Furthermore, the HOMO−LUMO gap energy for suggested doped models (I), (II) and (III) were lower than pure BPNT pristine systems. The dipole moment values of models (II) and (III) were decreased to 1.788 and 1.789, respectively while the dipole moments of model (I) were enhanced to 4.373, in compare to pure pristine one (2.586). The magnitude of changes in Chemical Shielding (CS) tensor parameters revealed that the electron density at the site of {sup 31}P was higher than that at the site of {sup 11}B due to carbon doping.

  2. Responses of Carbon Dynamics to Nitrogen Deposition in Typical Freshwater Wetland of Sanjiang Plain

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2014-01-01

    Full Text Available The effects of nitrogen deposition (N-deposition on the carbon dynamics in typical Calamagrostis angustifolia wetland of Sanjiang Plain were studied by a pot-culture experiment during two continuous plant growing seasons. Elevated atmospheric N-deposition caused significant increases in the aboveground net primary production and root biomass; moreover, a preferential partition of carbon to root was also observed. Different soil carbon fractions gained due to elevated N-deposition and their response intensities followed the sequence of labile carbon > dissolved organic carbon > microbial biomass carbon, and the interaction between N-deposition and flooded condition facilitated the release of different carbon fractions. Positive correlations were found between CO2 and CH4 fluxes and liable carbon contents with N-deposition, and flooded condition also tended to facilitate CH4 fluxes and to inhibit the CO2 fluxes with N-deposition. The increases in soil carbon fractions occurring in the nitrogen treatments were significantly correlated with increases in root, aboveground parts, total biomass, and their carbon uptake. Our results suggested that N-deposition could enhance the contents of active carbon fractions in soil system and carbon accumulation in plant of the freshwater wetlands.

  3. Palladium on Nitrogen-Doped Mesoporous Carbon: A Bifunctional Catalyst for Formate-Based, Carbon-Neutral Hydrogen Storage.

    Science.gov (United States)

    Wang, Fanan; Xu, Jinming; Shao, Xianzhao; Su, Xiong; Huang, Yanqiang; Zhang, Tao

    2016-02-08

    The lack of safe, efficient, and economical hydrogen storage technologies is a hindrance to the realization of the hydrogen economy. Reported herein is a reversible formate-based carbon-neutral hydrogen storage system that is established over a novel catalyst comprising palladium nanoparticles supported on nitrogen-doped mesoporous carbon. The support was fabricated by a hard template method and nitridated under a flow of ammonia. Detailed analyses demonstrate that this bicarbonate/formate redox equilibrium is promoted by the cooperative role of the doped nitrogen functionalities and the well-dispersed, electron-enriched palladium nanoparticles.

  4. Biophysical Controls over Carbon and Nitrogen Stocks in Desert Playa Wetlands

    Science.gov (United States)

    McKenna, O. P.; Sala, O. E.

    2014-12-01

    Playas are ephemeral desert wetlands situated at the bottom of closed catchments. Desert playas in the Southwestern US have not been intensively studied despite their potential importance for the functioning of desert ecosystems. We want to know which geomorphic and ecological variables control of the stock size of soil organic carbon, and soil total nitrogen in playas. We hypothesize that the magnitude of carbon and nitrogen stocks depends on: (a) catchment size, (b) catchment slope, (d) catchment vegetation cover, (e) bare-ground patch size, and (f) catchment soil texture. We chose thirty playas from across the Jornada Basin (Las Cruces, NM) ranging from 0.5-60ha in area and with varying catchment characteristics. We used the available 5m digital elevation map (DEM) to calculate the catchment size and catchment slope for these thirty playas. We measured percent cover, and patch size using the point-intercept method with three 10m transects in each catchment. We used the Bouyoucos-hydrometer soil particle analysis to determine catchment soil texture. Stocks of organic carbon and nitrogen were measured from soil samples at four depths (0-10 cm, 10-30 cm, 30-60 cm, 60-100 cm) using C/N combustion analysis. In terms of nitrogen and organic carbon storage, we found soil nitrogen values in the top 10cm ranging from 41.963-214.365 gN/m2, and soil organic carbon values in the top 10cm ranging from 594.339-2375.326 gC/m2. The results of a multiple regression analysis show a positive relationship between catchment slope and both organic carbon and nitrogen stock size (nitrogen: y= 56.801 +47.053, R2=0.621; organic carbon: y= 683.200 + 499.290x, R2= 0.536). These data support our hypothesis that catchment slope is one of factors controlling carbon and nitrogen stock in desert playas. We also applied our model to the 69 other playas of the Jornada Basin and estimated stock sizes (0-10cm) between 415.07-447.97 Mg for total soil nitrogen and 4627.99-5043.51 Mg for soil organic

  5. [Relationship between Fe, Al oxides and stable organic carbon, nitrogen in the yellow-brown soils].

    Science.gov (United States)

    Heng, Li-Sha; Wang, Dai-Zhang; Jiang, Xin; Rao, Wei; Zhang, Wen-Hao; Guo, Chun-Yan; Li, Teng

    2010-11-01

    The stable organic carbon and nitrogen of the different particles were gained by oxidation of 6% NaOCl in the yellow-brown soils. The relationships between the contents of selective extractable Fe/Al and the stable organic carbon/nitrogen were investigated. It shown that amounts of dithionite-citrate-(Fe(d)) and oxalate-(Fe(o)) and pyrophosphate extractable (Fe(p)) were 6-60.8 g x kg(-1) and 0.13-4.8 g x kg(-1) and 0.03-0.47 g x kg(-1) in 2-250 microm particles, respectively; 43.1-170 g x kg(-1) and 5.9-14.0 g x kg(-1) and 0.28-0.78 g x kg(-1) in soils than in arid yellow-brown soils, and that of selective extractable Al are lower in the former than in the latter. Amounts of the stable organic carbon and nitrogen, higher in paddy yellow-brown soils than in arid yellow-brown soils, were 0.93-6.0 g x kg(-1) and 0.05-0.36 g x kg(-1) in 2-250 microm particles, respectively; 6.05-19.3 g x kg(-1) and 0.61-2.1 g x kg(-1) in organic carbon and nitrogen (C(stable)/N(stable)) were 9.50-22.0 in 2-250 microm particles and 7.43-11.54 in organic carbon and nitrogen were 14.3-50.0 and 11.9-55.6 in 2-250 microm particles, respectively; 53.72-88.80 and 40.64-70.0 in soils than in paddy yellow-brown soils. The organic carbon and nitrogen are advantageously conserved in paddy yellow-brown soil. An extremely significant positive correlation of the stable organic carbon and nitrogen with selective extractable Fe/Al is observed. The most amounts between the stable organic carbon and nitrogen and selective extractable Fe/Al appear in clay particles, namely the clay particles could protect the soil organic carbon and nitrogen.

  6. Carbon and nitrogen isotopic signatures and nitrogen profile to identify adulteration in organic fertilizers.

    Science.gov (United States)

    Verenitch, Sergei; Mazumder, Asit

    2012-08-29

    Recently it has been shown that stable isotopes of nitrogen can be used to discriminate between organic and synthetic fertilizers, but the robustness of the approach is questionable. This work developed a comprehensive method that is far more robust in identifying an adulteration of organic nitrogen fertilizers. Organic fertilizers of various types (manures, composts, blood meal, bone meal, fish meal, products of poultry and plant productions, molasses and seaweed based, and others) available on the North American market were analyzed to reveal the most sensitive criteria as well as their quantitative ranges, which can be used in their authentication. Organic nitrogen fertilizers of known origins with a wide δ(15)N range between -0.55 and 28.85‰ (n = 1258) were characterized for C and N content, δ(13)C, δ(15)N, viscosity, pH, and nitrogen profile (urea, ammonia, organic N, water insoluble N, and NO3). A statistically significant data set of characterized unique organic nitrogen fertilizers (n = 335) of various known origins has been assembled. Deliberately adulterated samples of different types of organic fertilizers mixed with synthetic fertilizers at a wide range of proportions have been used to develop the quantitative critical characteristics of organic fertilizers as the key indicators of their adulteration. Statistical analysis based on the discriminant functions of the quantitative critical characteristics of organic nitrogen fertilizers from 14 different source materials revealed a very high average rate of correct classification. The developed methodology has been successfully used as a source identification tool for numerous commercial nitrogen fertilizers available on the North American market.

  7. Nitrogen-Doped Carbon Dots as A New Substrate for Sensitive Glucose Determination

    Directory of Open Access Journals (Sweden)

    Hanxu Ji

    2016-05-01

    Full Text Available Nitrogen-doped carbon dots are introduced as a novel substrate suitable for enzyme immobilization in electrochemical detection metods. Nitrogen-doped carbon dots are easily synthesised from polyacrylamide in just one step. With the help of the amino group on chitosan, glucose oxidase is immobilized on nitrogen-doped carbon dots-modified carbon glassy electrodes by amino-carboxyl reactions. The nitrogen-induced charge delocalization at nitrogen-doped carbon dots can enhance the electrocatalytic activity toward the reduction of O2. The specific amino-carboxyl reaction provides strong and stable immobilization of GOx on electrodes. The developed biosensor responds efficiently to the presence of glucose in serum samples over the concentration range from 1 to 12 mM with a detection limit of 0.25 mM. This novel biosensor has good reproducibility and stability, and is highly selective for glucose determination under physiological conditions. These results indicate that N-doped quantum dots represent a novel candidate material for the construction of electrochemical biosensors.

  8. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-01

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties.

  9. Improving representation of nitrogen uptake, allocation, and carbon assimilation in the Community Land Model

    Science.gov (United States)

    Ghimire, B.; Riley, W. J.; Koven, C.

    2013-12-01

    Nitrogen is the most important nutrient limiting plant carbon assimilation and growth, and is required for production of photosynthetic enzymes, growth and maintenance respiration, and maintaining cell structure. The forecasted rise in plant available nitrogen through atmospheric nitrogen deposition and the release of locked soil nitrogen by permafrost thaw in high latitude ecosystems is likely to result in an increase in plant productivity. However a mechanistic representation of plant nitrogen dynamics is lacking in earth system models. Most earth system models ignore the dynamic nature of plant nutrient uptake and allocation, and further lack tight coupling of below- and above-ground processes. In these models, the increase in nitrogen uptake does not translate to a corresponding increase in photosynthesis parameters, such as maximum Rubisco capacity and electron transfer rate. We present an improved modeling framework implemented in the Community Land Model version 4.5 (CLM4.5) for dynamic plant nutrient uptake, and allocation to different plant parts, including leaf enzymes. This modeling framework relies on imposing a more realistic flexible carbon to nitrogen stoichiometric ratio for different plant parts. The model mechanistically responds to plant nitrogen uptake and leaf allocation though changes in photosynthesis parameters. We produce global simulations, and examine the impacts of the improved nitrogen cycling. The improved model is evaluated against multiple observations including TRY database of global plant traits, nitrogen fertilization observations and 15N tracer studies. Global simulations with this new version of CLM4.5 showed better agreement with the observations than the default CLM4.5-CN model, and captured the underlying mechanisms associated with plant nitrogen cycle.

  10. Effect of Nitrogen Source and Carbon to Nitrogen Ratio on Hydrogen Production using C. acetobutylicum

    Directory of Open Access Journals (Sweden)

    Mohd Sahaid Kalil

    2008-01-01

    Full Text Available Problem statement: One of the main factors influenced the bacterial productivity and total yield of hydrogen is the nitrogen source and its concentration. Approach: Using different nitrogen source with different concentration on bacterial productivity of hydrogen showed to affect on both bacterial productivity of hydrogen and biomass concentration. Results: Yeast extract as nitrogen source at concentration of 13 g L-1 was the best organic nitrogen source and resulted in hydrogen yield YP/S of 308 mL g-1 glucose utilized with biomass concentration of 1.1 g L-1, hydrogen yield per biomass YP/X of 280 mL g-1 L-1, biomass per substrate utilized YX/S of 0.22 and produced hydrogen in gram per gram of glucose utilized YH2/S of 0.0275. C/N of 70 enhanced the YP/S from 308-350 mL g?1 glucose utilized with biomass concentration of 1.22 gL-1, YP/X of 287 mL g-1 L-1, YX/S of 0.244 and YH2/S of 0.03125. Conclusion: Nitrogen source with proper C:N ratio enhanced the hydrogen production.

  11. Remote Sensing of Vegetation Nitrogen Content for Spatially Explicit Carbon and Water Cycle Estimation

    Science.gov (United States)

    Zhang, Y. L.; Miller, J. R.; Chen, J. M.

    2009-05-01

    Foliage nitrogen concentration is a determinant of photosynthetic capacity of leaves, thereby an important input to ecological models for estimating terrestrial carbon and water budgets. Recently, spectrally continuous airborne hyperspectral remote sensing imagery has proven to be useful for retrieving an important related parameter, total chlorophyll content at both leaf and canopy scales. Thus remote sensing of vegetation biochemical parameters has promising potential for improving the prediction of global carbon and water balance patterns. In this research, we explored the feasibility of estimating leaf nitrogen content using hyperspectral remote sensing data for spatially explicit estimation of carbon and water budgets. Multi-year measurements of leaf biochemical contents of seven major boreal forest species were carried out in northeastern Ontario, Canada. The variation of leaf chlorophyll and nitrogen content in response to various growth conditions, and the relationship between them,were investigated. Despite differences in plant type (deciduous and evergreen), leaf age, stand growth conditions and developmental stages, leaf nitrogen content was strongly correlated with leaf chlorophyll content on a mass basis during the active growing season (r2=0.78). With this general correlation, leaf nitrogen content was estimated from leaf chlorophyll content at an accuracy of RMSE=2.2 mg/g, equivalent to 20.5% of the average measured leaf nitrogen content. Based on this correlation and a hyperspectral remote sensing algorithm for leaf chlorophyll content retrieval, the spatial variation of leaf nitrogen content was inferred from the airborne hyperspectral remote sensing imagery acquired by Compact Airborne Spectrographic Imager (CASI). A process-based ecological model Boreal Ecosystem Productivity Simulator (BEPS) was used for estimating terrestrial carbon and water budgets. In contrast to the scenario with leaf nitrogen content assigned as a constant value without

  12. First-Principles Studies on Properties of Boron-Related Impurities in c-BN

    Institute of Scientific and Technical Information of China (English)

    TIAN Fu-Bo; WANG Xiao-Li; MA Yan-Ming; CUI Tian; LIU Bing-Bing; ZOU Guang-Tian

    2009-01-01

    We investigate,by first-principles calculations,the pressure dependence of formation enthalpies and defective geometry and bulk modulus of boron-related impurities (VB,CB,NB,and OB ) with different charged states in cubic boron nitride (c-BN) using a supercell approach.It is found that the nitrogen atoms surrounding the defect relax inward in the case of CB,while the nitrogen atoms relax outward in the other cases.These boron-related impurities become much more stable and have larger concentration with increasing pressure.The impurity C+B1 is found to have the lowest formation enthalpy,make the material exhibit semiconductor characters and have the bulk modulus higher than ideal c-BN and than those in the cases of other impurities.Our results suggest that the hardness of c-BN may be strengthened when a carbon atom substitutes at a B site.

  13. Carbon and nitrogen fluxes in the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Naik, H.; DeSouza, W.; Narvekar, P.V.; Paropkari, A.L.; Bange, H.W.

    of intense water column denitrification (Deutsch et al., 2007). Substantial N 2 -fixation is also believed to occur within the Red Sea as evident from the high N:P uptake/regeneration ratio (~21). Based on the exchanges of nutrients and water across the Bab..., Yoshinari T (2001) The oceanic fixed nitrogen and nitrous oxide budgets: Moving targets as we enter the anthropocene. Sci Mar 65 (Suppl.): 85-105 Deutsch C, Sarmiento JL, Sigman DM, Gruber N, Dunne JP (2007) Spatial coupling of nitrogen inputs and losses...

  14. Nitrogen-doped mesoporous carbon of extraordinary capacitance for electrochemical energy storage

    Science.gov (United States)

    Lin, Tianquan; Chen, I.-Wei; Liu, Fengxin; Yang, Chongyin; Bi, Hui; Xu, Fangfang; Huang, Fuqiang

    2015-12-01

    Carbon-based supercapacitors can provide high electrical power, but they do not have sufficient energy density to directly compete with batteries. We found that a nitrogen-doped ordered mesoporous few-layer carbon has a capacitance of 855 farads per gram in aqueous electrolytes and can be bipolarly charged or discharged at a fast, carbon-like speed. The improvement mostly stems from robust redox reactions at nitrogen-associated defects that transform inert graphene-like layered carbon into an electrochemically active substance without affecting its electric conductivity. These bipolar aqueous-electrolyte electrochemical cells offer power densities and lifetimes similar to those of carbon-based supercapacitors and can store a specific energy of 41 watt-hours per kilogram (19.5 watt-hours per liter).

  15. Structural investigation of two carbon nitride solids produced by cathodic arc deposition and nitrogen implantation

    Energy Technology Data Exchange (ETDEWEB)

    Merchant, A.R.; McCulloch, D.; McKenzie, D.R.; Yin, Y.; Gerstner, E.G. [New South Wales Univ., Kensington, NSW (Australia)

    1996-12-31

    Carbon nitride materials have been the focus of research efforts worldwide. Most materials studied have been amorphous, with only a few groups claiming to have found a crystalline material. In this paper, carbon nitride materials prepared by two different techniques are analysed, and found to be remarkably similar in bonding and structure. The materials appear to have a primarily sp{sup 2} bonded carbon structure with a lower bond length than found in an amorphous carbon. This is explained by nitrogen substituting into `rings` to a saturation level of about one nitrogen per three carbon atoms. No evidence was found for a crystalline structure of formula C{sub 3}N{sub 4}, or any amorphous derivative of it. 16 refs., 1 tab., 5 figs.

  16. Theoretical study of interaction between Tacrine and finite-length Al-doped Carbon and Boron nitride Nanotubes: A Semiempirical drug delivery study in thermodynamic view

    Directory of Open Access Journals (Sweden)

    Nasrin Zeighami

    2014-12-01

    Full Text Available In order to extend our previous theoretical calculations that dealt with the thermochemistry of doping the single walled boron nitride nano tubes, BNNTs, and carbon nanotubes ,CNTs, with alminium atoms [1], we have used the AM 1, PM 3, and PM 6 semiempirical methods to investigate the interaction of the tacrine molecule (a drug for the treatment of Alzheimer's disease with the side-walls of aluminum doped boron nitride and carbon nano tubes in thermodynamic views.At first, the frequency calculations were carried out to confirm the stability of the involved structures. In addition, the theoretical thermodynamic study of tacrine adsorption onto the considered nanotubes was performed and the thermodynamic functions such as enthalpy changes, entropy changes and Gibbs free energy changes of the adsorption process were evaluated at different temperatures. Our results suggest the aluminum doped boron nitride nano tubes and alminium doped carbon nano tubes may be considered as the proper carries for the drug delivery of tacrine.

  17. Nitrogen-doped porous carbon derived from biomass waste for high-performance supercapacitor.

    Science.gov (United States)

    Ma, Guofu; Yang, Qian; Sun, Kanjun; Peng, Hui; Ran, Feitian; Zhao, Xiaolong; Lei, Ziqiang

    2015-12-01

    High capacitance property and low cost are the pivotal requirements for practical application of supercapacitor. In this paper, a low cost and high capacitance property nitrogen-doped porous carbon with high specific capacitance is prepared. The as-prepared nitrogen-doped porous carbon employing potato waste residue (PWR) as the carbon source, zinc chloride (ZnCl2) as the activating agent and melamine as nitrogen doping agent. The morphology and structure of the carbon materials are studied by scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray diffraction (XRD) and Raman spectra. The surface area of the nitrogen-doped carbon which prepared under 700°C is found to be 1052m(2)/g, and the specific capacitance as high as 255Fg(-1) in 2M KOH electrolyte is obtained utilize the carbon as electrode materials. The electrode materials also show excellent cyclability with 93.7% coulombic efficiency at 5Ag(-1) current density of for 5000cycles.

  18. Enhanced tunnel transport in disordered carbon superlattice structures incorporated with nitrogen

    Science.gov (United States)

    Katkov, Mikhail V.; Bhattacharyya, Somnath

    2012-06-01

    The possibility for enhanced tunnel transport through the incorporation of nitrogen in a quasi-one dimensional superlattice structure of amorphous carbon (a -C) made of sp2-C and sp3-C rich phases is shown by using a tight-binding model. The proposed superstructure can be described by a set of disordered graphite-like carbon clusters (acting as quantum wells) separated by a thin layer of diamond-like carbon (barriers) where the variation of the width and depth of the carbon clusters significantly control the electron transmission peaks. A large structural disorder in the pure carbon system, introduced through the variation of the bond length and associated deformation potential for respective carbon phases, was found to suppress the sharp features of the transmission coefficients. A small percentage of nitrogen addition to the carbon clusters can produce a distinct transmission peak at the low energy; however, it can be practically destroyed due to increase of the level of disorder of carbon sites. Whereas pronounced resonance peaks, both for C and N sites can be achieved through controlling the arrangement of the nitrogen sites of increased concentration within the disordered sp2-C clusters. The interplay of disorder associated with N and C sites illustrated the tunable nature of resistance of the structures as well as their characteristic times.

  19. The Effect of Compaction on Urease Enzyme Activity, Carbon Dioxide Evaluation and Nitrogen Mineralisation

    OpenAIRE

    Ayten KARACA; Abdullah BARAN; KAKTANIR, Koray

    2000-01-01

    The effects of compaction on urease enzyme activity, carbon dioxide evaluation and nitrogen mineralisation of urea-treated and untreated soils were investigated. Soils were compacted at compaction levels of O kgcm -2 , 2 kgcm -2 and 4 kgcm -2 and incubated for 28 days. The changes in urease enzyme activity, CO 2 evaluation and nitrogen mineralization were determined during incubation periods. Urease enzyme activity was decreased significantly (P

  20. Enhancing nitrogen removal from low carbon to nitrogen ratio wastewater by using a novel sequencing batch biofilm reactor.

    Science.gov (United States)

    Zou, Jinte; Li, Jun; Ni, Yongjiong; Wei, Su

    2016-12-01

    Removing nitrogen from wastewater with low chemical oxygen demand/total nitrogen (COD/TN) ratio is a difficult task due to the insufficient carbon source available for denitrification. Therefore, in the present work, a novel sequencing batch biofilm reactor (NSBBR) was developed to enhance the nitrogen removal from wastewater with low COD/TN ratio. The NSBBR was divided into two units separated by a vertical clapboard. Alternate feeding and aeration was performed in the two units, which created an anoxic unit with rich substrate content and an aeration unit deficient in substrate simultaneously. Therefore, the utilization of the influent carbon source for denitrification was increased, leading to higher TN removal compared to conventional SBBR (CSBBR) operation. The results show that the CSBBR removed up to 76.8%, 44.5% and 10.4% of TN, respectively, at three tested COD/TN ratios (9.0, 4.8 and 2.5). In contrast, the TN removal of the NSBBR could reach 81.9%, 60.5% and 26.6%, respectively, at the corresponding COD/TN ratios. Therefore, better TN removal performance could be achieved in the NSBBR, especially at low COD/TN ratios (4.8 and 2.5). Furthermore, it is easy to upgrade a CSBBR into an NSBBR in practice.

  1. The reactivity of lattice carbon and nitrogen species in molybdenum (oxy)carbonitrides prepared by single-source routes

    Energy Technology Data Exchange (ETDEWEB)

    AlShalwi, M. [WestCHEM, School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Hargreaves, J.S.J., E-mail: Justin.Hargreaves@glasgow.ac.uk [WestCHEM, School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Liggat, J.J.; Todd, D. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL (United Kingdom)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Molybdenum (oxy)carbonitrides have been prepared from single source routes. Black-Right-Pointing-Pointer Nitrogen species are more reactive than carbon species within the carbonitrides. Black-Right-Pointing-Pointer The reactivity of nitrogen species is a function of carbonitride composition. -- Abstract: Molybdenum (oxy)carbonitrides of different compositions have been prepared from hexamethylenetetramine molybdate and ethylenediamine molybdate precursors and the reactivity of the lattice carbon and nitrogen species within them has been determined by temperature programmed reduction and thermal volatilisation studies. Nitrogen is found to be much more reactive than carbon and the nature of its reactivity is influenced by composition with the presence of carbon enhancing the reactivity of nitrogen. The difference in reactivity observed indicates that molybdenum carbonitrides are not suitable candidates as reagents for which the simultaneous loss of nitrogen and carbon from the lattice would be desirable.

  2. Revealing the Origin of Activity in Nitrogen-Doped Nanocarbons towards Electrocatalytic Reduction of Carbon Dioxide

    DEFF Research Database (Denmark)

    Xu, Junyuan; Kan, Yuhe; Huang, Rui;

    2016-01-01

    Carbon nanotubes (CNTs) are functionalized with nitrogen atoms for reduction of carbon dioxide (CO2). The investigation explores the origin of the catalyst’s activity and the role of nitrogen chemical states therein. The catalysts show excellent performances, with about 90% current efficiency...... for CO formation and stability over 60 hours. The Tafel analyses and density functional theory calculations suggest that the reduction of CO2 proceeds through an initial rate-determining transfer of one electron to CO2, which leads to the formation of carbon dioxide radical anion (CO2C). The initial...... reduction barrier is too high on pristine CNTs, resulting in a very high overpotentials at which the hydrogen evolution reaction dominates over CO2 reduction.The doped nitrogen atoms stabilize the radical anion,thereby lowering the initial reduction barrier and improving the intrinsic activity. The most...

  3. Nitrogen-Doped Carbon Nanotube and Graphene Materials for Oxygen Reduction Reactions

    Directory of Open Access Journals (Sweden)

    Qiliang Wei

    2015-09-01

    Full Text Available Nitrogen-doped carbon materials, including nitrogen-doped carbon nanotubes (NCNTs and nitrogen-doped graphene (NG, have attracted increasing attention for oxygen reduction reaction (ORR in metal-air batteries and fuel cell applications, due to their optimal properties including excellent electronic conductivity, 4e− transfer and superb mechanical properties. Here, the recent progress of NCNTs- and NG-based catalysts for ORR is reviewed. Firstly, the general preparation routes of these two N-doped carbon-allotropes are introduced briefly, and then a special emphasis is placed on the developments of both NCNTs and NG as promising metal-free catalysts and/or catalyst support materials for ORR. All these efficient ORR electrocatalysts feature a low cost, high durability and excellent performance, and are thus the key factors in accelerating the widespread commercialization of metal-air battery and fuel cell technologies.

  4. Determination of organic milk authenticity using carbon and nitrogen natural isotopes.

    Science.gov (United States)

    Chung, Ill-Min; Park, Inmyoung; Yoon, Jae-Yeon; Yang, Ye-Seul; Kim, Seung-Hyun

    2014-10-01

    Natural stable isotopes of carbon and nitrogen ((12)C, (13)C, (14)N, (15)N) have abundances unique to each living creature. Therefore, measurement of the stable isotope ratio of carbon and nitrogen (δ(13)C=(13)C/(12)C, δ(15)N=(15)N/(14)N) in milk provides a reliable method to determine organic milk (OM) authenticity. In the present study, the mean δ(13)C value of OM was higher than that of conventional milk (CM), whereas the mean δ(15)N value of OM was lower than that of CM; nonetheless both δ(13)C and δ(15)N values were statistically different for the OM and CM (Pauthenticity using stable isotopes of carbon and nitrogen.

  5. Carbon and Nitrogen Isotope Systematics in a Sector-Zoned Diamond from the Mir Kimberlite, Yakutia

    Science.gov (United States)

    Hauri, E.; Bulanova, G.; Pearson, G.; Griffin, B.

    2002-05-01

    A single Yakutian octahedral diamond, displaying striking cubic and octahedral growth sectors surrounded by an octahedral rim, has been analysed for carbon and nitrogen isotopic compositions by SIMS and for nitrogen concentration (by SIMS and FTIR) and nitrogen aggregation state (FTIR). A graphite "seed" inclusion identified within the diamond, enriched in K, Ca, Ti, Rb and Sr, provides evidence that the diamond may have grown from a carbonate melt/fluid interacting with upper mantle rocks. Carbon and nitrogen isotope compositions become progressively heavier from the core region (d13C = -7 to -5 and d15N= -3) towards the inner rim zones (d13C = -3 and d15N = +8.9 to +5) of the diamond. Nitrogen concentration and aggregation measurements show corresponding decreases that generally correlate with the isotopic variations. These systematic variations within the core and intermediate regions of the diamond are consistent with their formation during diamond growth from CO2-rich fluids as a continuous event, accompanied by slight progressive isotopic fractionation of carbon and nitrogen. However, the observed isotope and nitrogen abundance trends are not those predicted from thermodynamic modelling of fluid-solid equilibria in a C-N-O-H-bearing system due to changes in parameters such as fO2 (Deines, 1980; Deines et al 1989). Within the finely-zoned octahedral rim region, non-systematic variations in nitrogen abundance, nitrogen aggregation, and nitrogen and carbon isotope ratios were observed. Several interpretations are given for this phenomenon, including kinetic effects during growth of the diamond rim under different conditions from those of the core-intermediate regions, or rapidly changing fluid sources during the growth. No fractionation of nitrogen isotopes between cubic and octahedral growth zones was identified within the studied diamond, in contrast with the fractionation phenomena found in synthetic diamonds of mixed growth. Our results illustrate the

  6. Amorphous Hydrogenated Carbon-Nitrogen Alloy Thin Films for Solar Cell Application

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zhi-Bin; DING Zheng-Ming; PANG Qian-Jun; CUI Rong-Qiang

    2001-01-01

    Amorphous hydrogenated carbon-nitrogen alloy (a-CNx :H) thin films have been deposited on silicon substratesby improved dc magnetron sputtering from a graphite target in nitrogen and hydrogen gas discharging. Thefilms are investigated by using Raman spectroscopy, x-ray photoelectron spectroscopy, spectral ellipsometer and electron spin resonance techniques. The optimized process condition for solar cell application is discussed. Thephotovoltaic property of a-CNx:H/silicon heterojunctions can be improved by the adjustment of the pressureratio of hydrogen to nitrogen and unbalanced magnetic field intensity. Open-circuit voltage and short-circuitcurrent reach 300mV and 5.52 Ma/cm2, respectively.

  7. Nitrogen-doped porous carbon with an ultrahigh specific surface area for superior performance supercapacitors

    Science.gov (United States)

    Long, Chao; Zhuang, Jianle; Xiao, Yong; Zheng, Mingtao; Hu, Hang; Dong, Hanwu; Lei, Bingfu; Zhang, Haoran; Liu, Yingliang

    2016-04-01

    Owing to its abundant nitrogen content, silk cocoon is a promising precursor for the synthesis of Nitrogen-doped porous carbon (N-PC). Using a simple staged KOH activation, the prepared sample displays particular nanostructure with ultrahigh specific surface area (3841 m2 g-1) and appropriate pore size, providing favorable pathways for transportation and penetration of electrolyte ions. Additionally, the doped nitrogen atoms ensure the samples with pseudocapacitive behavior. Those special characteristics endow N-PCs with high capacity, low resistance, and long-term stability, indicating a wonderful potential for application in energy-storage devices.

  8. Benthic biogeochemical cycling, nutrient stoichiometry, and carbon and nitrogen mass balances in a eutrophic freshwater bay

    Science.gov (United States)

    Klump, J.V.; Fitzgerald, S.A.; Waplesa, J.T.

    2009-01-01

    Green Bay, while representing only ,7% of the surface area and ??1.4% of the volume of Lake Michigan, contains one-third of the watershed of the lake, and receives approximately one-third of the total nutrient loading to the Lake Michigan basin, largely from the Fox River at the southern end of the bay. With a history of eutrophic conditions dating back nearly a century, the southern portion of the bay behaves as an efficient nutrient and sediment trap, sequestering much of the annual carbon and nitrogen input within sediments accumulating at up to 1 cm per year. Depositional fluxes of organic matter varied from ??0.1 mol C m-2 yr-1 to >10 mol C m-2 yr-1 and were both fairly uniform in stoichiometric composition and relatively labile. Estimates of benthic recycling derived from pore-water concentration gradients, whole-sediment incubation experiments, and deposition-burial models of early diagenesis yielded an estimated 40% of the carbon and 50% of the nitrogen recycled back into the overlying water. Remineralization was relatively rapid with ??50% of the carbon remineralized within <15 yr of deposition, and a mean residence time for metabolizable carbon and nitrogen in the sediments of 20 yr. On average, organic carbon regeneration occurred as 75% CO2, 15% CH4, and 10% dissolved organic carbon (DOC). Carbon and nitrogen budgets for the southern bay were based upon direct measurements of inputs and burial and upon estimates of export and production derived stoichiometrically from a coupled phosphorus budget. Loadings of organic carbon from rivers were ??3.7 mol m-2 yr-1, 80% in the form of DOC and 20% as particulate organic carbon. These inputs were lost through export to northern Green Bay and Lake Michigan (39%), through sediment burial (26%), and net CO2 release to the atmosphere (35%). Total carbon input, including new production, was 4.54 mol m-2 C yr-1, equivalent to ??10% of the gross annual primary production. Nitrogen budget terms were less well quantified

  9. [Assessment on the availability of nitrogen fertilization in improving carbon sequestration potential of China's cropland soil].

    Science.gov (United States)

    Lu, Fei; Wang, Xiao-Ke; Han, Bing; Ouyang, Zhi-Yun; Duan, Xiao-Nan; Zheng, Hua

    2008-10-01

    With reference to the situation of nitrogen fertilization in 2003 and the recommendations from agricultural experts on fertilization to different crops, two scenarios, namely, 'current situation' and 'fertilization as recommended', were set for estimating the current and potential carbon sequestration of China's cropland soil under nitrogen fertilization. After collecting and analyzing the typical data from the long-term agricultural experiment stations all over China, and based on the recent studies of soil organic matter and nutrient dynamics, we plotted China into four agricultural regions, and estimated the carbon sequestration rate and potential of cropland soil under the two scenarios in each province of China. Meanwhile, with the data concerning fossil fuel consumption for fertilizer production and nitrogen fertilization, the greenhouse gas leakage caused by nitrogen fertilizer production and application was estimated with the help of the parameters given by domestic studies and IPCC. We further proposed that the available carbon sequestration potential of cropland soil could be taken as the criterion of the validity and availability of carbon sequestration measures. The results showed that the application of synthetic nitrogen fertilizer could bring about a carbon sequestration potential of 21.9 Tg C x a(-1) in current situation, and 30.2 Tg C x a(-1) with fertilization as recommended. However, under the two scenarios, the greenhouse gas leakage caused by fertilizer production and application would reach 72.9 Tg C x a(-1) and 91.4 Tg C x a(-1), and thus, the actual available carbon sequestration potential would be -51.0 Tg C x a(-1) and -61.1 Tg C x a(-1), respectively. The situation was even worse under the 'fertilization as recommended' scenario, because the increase in the amount of nitrogen fertilization would lead to 10. 1 Tg C x a(-1) or more net greenhouse gas emission. All these results indicated that the application of synthetic nitrogen fertilizer

  10. Carbon and nitrogen mineralization are decoupled in organo-mineral fractions

    Science.gov (United States)

    Bimüller, Carolin; Mueller, Carsten W.; von Lützow, Margit; Kreyling, Olivia; Kölbl, Angelika; Haug, Stephan; Schloter, Michael; Kögel-Knabner, Ingrid

    2015-04-01

    To improve our comprehension how carbon and nitrogen mineralization are linked in soils, we used a controlled laboratory mineralization approach and compared carbon and nitrogen dynamics in the bulk soil and in soil fractions. Topsoil of a Rendzic Leptosol from a beech forest site near Tuttlingen, Germany, was fractionated into three particle size classes: sand (2000 to 20 µm), silt (20 to 2 µm), and clay (nitrogen mineralization dynamics, and assessed carbon respiration as well as nitrogen mineralization and microbial biomass carbon and nitrogen contents. Soil organic matter in the incubated fractions was considered by a subsequent density fractionation. The chemical composition of selected samples was qualitatively evaluated by 13C-NMR spectroscopy. When summing up the mineralization rates of the single fractions, the values for respired carbon equaled the bulk soil, whereas the mathematical recombination of mineral nitrogen in all fractions was significantly less than in bulk soil. Hence, carbon mineralization was not affected by the damage of the aggregated soil structure via fractionation, whereas nitrogen mineralization was reduced. Fractionation increased the surface area providing accessory mineral surfaces, which allowed new binding of especially nitrogen-rich compounds, besides ammonium fixation via cation exchange. Density fractionation revealed that organic matter in the sand fraction contained mainly particulate organic matter present as light material comprising partly decomposed plant remnants. The organic matter in the clay fraction was mostly adsorbed on mineral surfaces. Organic matter in the sand and in the clay fraction was dominated by O/N-alkyl C indicating low recalcitrance, but the C/N ratio of organic matter narrowed with decreasing particle size. These results also imply that the C/N ratio as well as the alkyl C to O/N-alkyl C ratio are not suitable to draw conclusions regarding biological decomposability of plant residues when

  11. The Effect of Different Nitrogen Form on Key Enzyme Activity of Sugarbeet (Vulgaris L.) Carbon and Nitrogen Metabolism

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This article analyses the effect of the proportion of the different nitrogen forms on key enzyme activity of carbon and nitrogen metabolism under the condition of nutritional water while Tian Yan-7 was used as experimental material. The result showed that nitrate reductase(NR) activity in the leaves gradually enhanced with the increase of NO-3. No matter in root or leaves ,glutamina synthetase (GS) activity first enhanced with increasing NH4+ when NH4+ was lower than that of NO-3 ,and GS activity was the highest when NH4+and NO3-was equal ,then GS activity declined with NH4+ increasing further. In the anaphase of growth ,synthetic activity in root of sucrose synthetase(SS) in the mixed NH4+ and NO3- was obviously highr than or NO3- alone. Both of the root and sugar yields were the highest when the proportion of NH4+ and NO3- was 1: 1.

  12. Nitric oxide protects carbon assimilation process of watermelon from boron-induced oxidative injury.

    Science.gov (United States)

    Farag, Mohamed; Najeeb, Ullah; Yang, Jinghua; Hu, Zhongyuan; Fang, Zhang Ming

    2017-02-01

    Nitric oxide (NO) mediates plant response to a variety of abiotic stresses; however, limited information is available on its effect on boron (B)-stressed watermelon plants. The present study investigates the mechanism through which NO protects watermelon seedlings from B deficiency and toxicity stresses. Five days old watermelon seedlings were exposed to B (0, 0.5 and 10 mg L(-1)) alone or with 75 μmole of NO donor sodium nitroprusside (SNP) for 30 days. Both low and high B concentrations in the media altered nutrient accumulation and impaired various physiological processes of watermelon seedlings, leading to a significant reduction in biomass production. The plants exposed to B deficient or toxic concentrations had 66 and 69% lower shoot dry weight, respectively compared with optimum B levels. B toxicity-induced growth inhibition of watermelon seedlings was associated with high B translocation to shoot tissues, which caused lipid membrane peroxidation (12% increase) and chlorophyll destruction (25% reduction). In contrast, B deficiency accelerated generation of reactive oxygen species (ROS), specifically OH(-1) and induced cellular oxidative injury. Exogenously applied SNP promoted leaf chlorophyll, photosynthesis and consequently biomass production in B-stressed watermelon seedlings by reducing B accumulation, lipid membrane peroxidation and ROS generation. It also activated antioxidant enzymes such as SOD, POD and APX, and protected the seedlings from ROS-induced cellular burst.

  13. Quantum Chemistry Calculation on Oxygen and Nitrogen Adsorption in Carbon Nanotude

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Oxygen and nitrogen adsorption in single-walled carbon nanotube (SWCNT) is studied by density function and discrete variational (DFT-DVM) method.The models of O2 and N2 adsorption in the SWCNT are optimized based on the energy minimization.The calculated results of density of state,populations and energy gaps of the molecular orbitals show that oxygen adsorption in SWCNT increases the carbon nanotube`s electrical conductivity more notably than nitrogen adsorption,which is consistent with the experiment.

  14. Nitrogen, Phosphorus and Carbon Excretion and Losses in Growing Pigs Fed Danish or Asian Diets

    DEFF Research Database (Denmark)

    Prapaspongsa, Trakarn; Vu, T K V; Poulsen, Hanne Damgaard

    2008-01-01

    The objectives of this study were to determine inputs and outputs of nitrogen (N), phosphorus (P) and carbon (C) and to estimate the nutrient losses during housing and storage in order to address these important parts of the whole manure management systems in pigs fed different diets.......The objectives of this study were to determine inputs and outputs of nitrogen (N), phosphorus (P) and carbon (C) and to estimate the nutrient losses during housing and storage in order to address these important parts of the whole manure management systems in pigs fed different diets....

  15. [Dynamics of carbon and nitrogen storage of Cupressus chengiana plantations in the arid valley of Minjiang River, Southwest China].

    Science.gov (United States)

    Luo, Da; Feng, Qiu-hong; Shi, Zuo-min; Li, Dong-sheng; Yang, Chang-xu; Liu, Qian-li; He, Jian-she

    2015-04-01

    The carbon and nitrogen storage and distribution patterns of Cupressus chengiana plantation ecosystems with different stand ages in the arid valley of Minjiang River were studied. The results showed that carbon contents in different organs of C. chengiana were relatively stable, while nitrogen contents were closely related to different organs, and soil organic carbon and nitrogen contents increased with the stand age. Carbon and nitrogen storage in vegetation layer, soil layer, and the whole ecosystem of the plantation increased with the stand age. The values of total carbon storage in the 13-, 11-, 8-, 6- and 4-year-old C. chengiana plantation ecosystems were 190.90, 165.91, 144.57, 119.44, and 113.49 t x hm(-2), and the values of total nitrogen storage were 19.09, 17.97, 13.82, 13.42, and 12.26 t x hm(-2), respectively. Most of carbon and nitrogen were stored in the 0-60 cm soil layer in the plantation ecosystems and occupied 92.8% and 98.8%, respectively, and the amounts of carbon and nitrogen stored in the top 0-20 cm soil layer, accounted for 54.4% and 48.9% of those in the 0-60 cm soil layer, respectively. Difference in distribution of carbon and nitrogen storage was observed in the vegetation layer. The percentage of carbon storage in tree layer (3.7%) were higher than that in understory vegetation (3.5%), while the percentage of nitrogen storage in tree layer (0.5%) was lower than that in understory (0.7%). The carbon and nitrogen storage and distribution patterns in the plantations varied obviously with the stand age, and the plantation ecosystems at these age stages could accumulate organic carbon and nitrogen continuously.

  16. Nanostructured nitrogen-doped mesoporous carbon derived from polyacrylonitrile for advanced lithium sulfur batteries

    Science.gov (United States)

    Liu, Ying; Zhao, Xiaohui; Chauhan, Ghanshyam S.; Ahn, Jou-Hyeon

    2016-09-01

    Nitrogen doping in carbon matrix can effectively improve the wettability of electrolyte and increase electric conductivity of carbon by ensuring fast transfer of ions. We synthesized a series of nitrogen-doped mesoporous carbons (CPANs) via in situ polymerization of polyacrylonitrile (PAN) in SBA-15 template followed by carbonization at different temperatures. Carbonization results in the formation of ladder structure which enhances the stability of the matrix. In this study, CPAN-800, carbon matrix synthesized by the carbonization at 800 °C, was found to possess many desirable properties such as high specific surface area and pore volume, moderate nitrogen content, and highly ordered mesoporous structure. Therefore, it was used to prepare S/CPAN-800 composite as cathode material in lithium sulfur (Li-S) batteries. The S/CPAN-800 composite was proved to be an excellent material for Li-S cells which delivered a high initial discharge capacity of 1585 mAh g-1 and enhanced capacity retention of 862 mAh g-1 at 0.1 C after 100 cycles.

  17. A comparison between the mechanical and thermal properties of single-walled carbon nanotubes and boron nitride nanotubes

    Science.gov (United States)

    Li, Ting; Tang, Zhenan; Huang, Zhengxing; Yu, Jun

    2017-01-01

    Carbon nanotubes (CNTs) are semimetallic while boron nitride nanotubes (BNNTs) are wide band gap insulators. Despite the discrepancy in their electrical properties, a comparison between the mechanical and thermal properties of CNTs and BNNTs has a significant research value for their potential applications. In this work, molecular dynamics simulations are performed to systematically investigate the mechanical and thermal properties of CNTs and BNNTs. The calculated Young's modulus is about 1.1 TPa for CNTs and 0.72 TPa for BNNTs under axial compressions. The critical bucking strain and maximum stress are inversely proportional to both diameter and length-diameter ratio and CNTs are identified axially stiffer than BNNTs. Thermal conductivities of (10, 0) CNTs and (10, 0) BNNTs follow similar trends with respect to length and temperature and are lower than that of their two-dimensional counterparts, graphene nanoribbons (GNRs) and BN nanoribbons (BNNRs), respectively. As the temperature falls below 200 K (130 K) the thermal conductivity of BNNTs (BNNRs) is larger than that of CNTs (GNRs), while at higher temperature it is lower than the latter. In addition, thermal conductivities of a (10, 0) CNT and a (10, 0) BNNT are further studied and analyzed under various axial compressive strains. Low-frequency phonons which mainly come from flexure modes are believed to make dominant contribution to the thermal conductivity of CNTs and BNNTs.

  18. Largely enhanced dielectric properties of carbon nanotubes/polyvinylidene fluoride binary nanocomposites by loading a few boron nitride nanosheets

    Science.gov (United States)

    Yang, Minhao; Zhao, Hang; He, Delong; Bai, Jinbo

    2016-08-01

    The ternary nanocomposites of boron nitride nanosheets (BNNSs)/carbon nanotubes (CNTs)/polyvinylidene fluoride (PVDF) are fabricated via a combination of solution casting and extrusion-injection processes. The effects of BNNSs on the electrical conductivity, dielectric behavior, and microstructure changes of CNTs/PVDF binary nanocomposites are systematically investigated. A low percolation value (fc) for the CNTs/PVDF binary system is obtained due to the integration of solution and melting blending procedures. Two kinds of CNTs/PVDF binary systems with various CNTs contents (fCNTs) as the matrix are discussed. The results reveal that compared with CNTs/PVDF binary systems at the same fCNTs, the ternary BNNSs/CNTs/PVDF nanocomposites exhibit largely enhanced dielectric properties due to the improvement of the CNTs dispersion state and the conductive network. The dielectric constant of CNTs/PVDF binary nanocomposite with 6 vol. % CNTs (fCNTs fc), it displays a 43.32% improvement from 1325 to 1899 after the addition of 3 vol. % BNNSs. The presence of BNNSs facilitates the formation of the denser conductive network. Meanwhile, the ternary BNNSs/CNTs/PVDF systems exhibit a low dielectric loss. The adjustable dielectric properties could be obtained by employing the ternary systems due to the microstructure changes of nanocomposites.

  19. Density functional theory study of ultrasmall diameter (2,2) boron nitride, silicon carbide, and carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Fakhrabad, Davoud Vahedi; Shahtahmassebi, Nasser [Nano Research Center, Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Movlarooy, Tayebeh [Department of Physics, Shahrood University of Technology, Shahrood (Iran, Islamic Republic of)

    2012-05-15

    We present a first principles calculation on the electronic structure and optical properties of ultrasmall-diameter (2,2) boron nitride, silicon carbide, and carbon nanotubes (BNNT, SiCNT, and CNT) by using full potential linear augmented plane wave (FP-LAPW) and pseudo potential plane wave (PP-PW) methods. The atomic geometries of all considered models are optimized. Calculations of optical spectra are performed under electric fields polarized both parallel and perpendicular with respect to the nanotube (NT) axis. Our results show that the dielectric function is anisotropic and it is revealed that (2,2) SiCNT would be better dielectric material than (2,2) BNNT. We have calculated the first, second and third optical transitions for the considered models. The value of the optical gap for (2,2) BNNT is obtained much larger than that of (2,2) SiCNT and (2,2) CNT. The results show that contrary to the (2,2) CNT being metallic, the (2,2) BNNT, and (2,2) SiCNT are wide indirect gap semiconductors. We also present the energy loss function; in this case the intertube interactions play an important role with respect to the optical spectroscopy. Our results revealed that unlike the dielectric function, the calculated energy loss function show rather weak anisotropy. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Carbon Nanotube/Boron Nitride Nanocomposite as a Significant Bifunctional Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions.

    Science.gov (United States)

    Patil, Indrajit M; Lokanathan, Moorthi; Ganesan, Balakrishnan; Swami, Anita; Kakade, Bhalchandra

    2017-01-12

    It is an immense challenge to develop bifunctional electrocatalysts for oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) in low temperature fuel cells and rechargeable metal-air batteries. Herein, a simple and cost-effective approach is developed to prepare novel materials based on carbon nanotubes (CNTs) and a hexagonal boron nitride (h-BN) nanocomposite (CNT/BN) through a one-step hydrothermal method. The structural analysis and morphology study confirms the formation of a homogeneous composite and merging of few exfoliated graphene layers of CNTs on the graphitic planes of h-BN, respectively. Moreover, the electrochemical study implies that CNT/BN nanocomposite shows a significantly higher ORR activity with a single step 4-electron transfer pathway and an improved onset potential of +0.86 V versus RHE and a current density of 5.78 mA cm(-2) in alkaline conditions. Interestingly, it exhibits appreciably better catalytic activity towards OER at low overpotential (η=0.38 V) under similar conditions. Moreover, this bifunctional catalyst shows substantially higher stability than a commercial Pt/C catalyst even after 5000 cycles. Additionally, this composite catalyst does not show any methanol oxidation reactions that nullify the issues due to fuel cross-over effects in direct methanol fuel cell applications.

  1. Torsional properties of hexagonal boron nitride nanotubes, carbon nanotubes and their hybrid structures: A molecular dynamics study

    Directory of Open Access Journals (Sweden)

    Qi-lin Xiong

    2015-10-01

    Full Text Available The torsional mechanical properties of hexagonal single-walled boron nitride nanotubes (SWBNNTs, single-walled carbon nanotubes (SWCNTs, and their hybrid structures (SWBN-CNTs are investigated using molecular dynamics (MD simulation. Two approaches - force approach and energy approach, are adopted to calculate the shear moduli of SWBNNTs and SWCNTs, the discrepancy between two approaches is analyzed. The results show that the shear moduli of single-walled nanotubes (SWNTs, including SWBNNTs and SWCNTs are dependent on the diameter, especially for armchair SWNTs. The armchair SWNTs show the better ability of resistance the twisting comparable to the zigzag SWNTs. The effects of diameter and length on the critical values of torque of SWNTs are obtained by comparing the torsional behaviors of SWNTs with different diameters and different lengths. It is observed that the MD results of the effect of diameter and length on the critical values of torque agrees well with the prediction of continuum shell model. The shear modulus of SWBN-CNT has a significant dependence on the percentages of SWCNT and the hybrid style has also an influence on shear modulus. The critical values of torque of SWBN-CNTs increase with the increase of the percentages of SWCNT. This phenomenon can be interpreted by the function relationship between the torque of different bonds (B-N-X, C-C-X, C-B-X, C-N-X and the angles of bonds.

  2. Fluorine and boron co-doped diamond-like carbon films deposited by pulsed glow discharge plasma immersion ion processing

    CERN Document Server

    He, X M; Peters, A M; Taylor, B; Nastasi, M

    2002-01-01

    Fluorine (F) and boron (B) co-doped diamond-like carbon (FB-DLC) films were prepared on different substrates by the plasma immersion ion processing (PIIP) technique. A pulse glow discharge plasma was used for the PIIP deposition and was produced at a pressure of 1.33 Pa from acetylene (C sub 2 H sub 2), diborane (B sub 2 H sub 6), and hexafluoroethane (C sub 2 F sub 6) gas. Films of FB-DLC were deposited with different chemical compositions by varying the flow ratios of the C sub 2 H sub 2 , B sub 2 H sub 6 , and C sub 2 F sub 6 source gases. The incorporation of B sub 2 H sub 6 and C sub 2 F sub 6 into PIIP deposited DLC resulted in the formation of F-C and B-C hybridized bonding structures. The levels of the F and B concentrations effected the chemical bonding and the physical properties as was evident from the changes observed in density, hardness, stress, friction coefficient, and contact angle of water on films. Compared to B-doped or F-doped DLC films, the F and B co-doping of DLC during PIIP deposition...

  3. Biofilm Removal Using Carbon Dioxide Aerosols without Nitrogen Purge.

    Science.gov (United States)

    Hong, Seongkyeol; Jang, Jaesung

    2016-11-06

    Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. Therefore, it is highly desirable to remove biofilms from surfaces. Many studies on CO2 aerosol cleaning have employed nitrogen purges to increase biofilm removal efficiency by reducing the moisture condensation generated during the cleaning. However, in this study, periodic jets of CO2 aerosols without nitrogen purges were used to remove Pseudomonas putida biofilms from polished stainless steel surfaces. CO2 aerosols are mixtures of solid and gaseous CO2 and are generated when high-pressure CO2 gas is adiabatically expanded through a nozzle. These high-speed aerosols were applied to a biofilm that had been grown for 24 hr. The removal efficiency ranged from 90.36% to 98.29% and was evaluated by measuring the fluorescence intensity of the biofilm as the treatment time was varied from 16 sec to 88 sec. We also performed experiments to compare the removal efficiencies with and without nitrogen purges; the measured biofilm removal efficiencies were not significantly different from each other (t-test, p > 0.55). Therefore, this technique can be used to clean various bio-contaminated surfaces within one minute.

  4. The role of boron oxide and carbon amounts in the mechanosynthesis of ZrB{sub 2}–SiC–ZrC nanocomposite via a self-sustaining reaction in the zircon/magnesium/boron oxide/graphite system

    Energy Technology Data Exchange (ETDEWEB)

    Jalaly, M., E-mail: maisam_jalaly@iust.ac.ir [School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Bafghi, M.Sh.; Tamizifar, M. [School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Gotor, F.J. [Instituto de Ciencia de Materiales de Sevilla (CSIC-US), Americo Vespucio 49, 41092 Sevilla (Spain)

    2014-06-15

    Highlights: • Synthesis of the ZrB{sub 2}-based composite by magnesiothermic reduction of zircon. • Study of boron oxide amount on the triggering reaction. • Investigation of the carbon role on the reaction progression. - Abstract: Herein, ZrSiO{sub 4}/B{sub 2}O{sub 3}/Mg/C system was used to synthesize a ZrB{sub 2}-based composite by means of a high energy ball milling process. A mechanically induced self-sustaining reaction was achieved in this system. A nanocomposite powder of ZrB{sub 2}–SiC–ZrC was prepared with an ignition time of approximately 6 min of milling. The role of the stoichiometric amounts of B{sub 2}O{sub 3} and carbon was investigated to clarify the governing mechanism for the formation of the product.

  5. Utilization of recovered nitrogen from hydrothermal carbonization process by Arthrospira platensis.

    Science.gov (United States)

    Yao, Changhong; Pan, Yanfei; Lu, Hongbin; Wu, Peichun; Meng, Yingying; Cao, Xupeng; Xue, Song

    2016-07-01

    In the context of sustainable cultivation of microalgae, the present study focused on the use of nitrogen from the hot-water extracted biomass residue of Arthrospira platensis by hydrothermal carbonization (HTC) and the sequential cultivation of the same alga with the HTC aqueous phase (AP). Nearly 90% of the nitrogen recovered from HTC into AP was in the organic form. Under nitrogen-limited condition with HTCAP as nitrogen source the yield and content of carbohydrate were enhanced by 21% and 15% respectively compared with that under the same nitrogen level provided by NaNO3, which entitled HTCAP for the substitution of conventional nitrate. In the same way pilot-scale cultivation of A. platensis in raceway ponds outdoors demonstrated that carbohydrate content of 43.8% DW and productivity of 10.3g/m(2)/d was achieved. Notably 54% of organic nitrogen in the HTCAP could be recycled by cultivation of pre-nitrogen starved A. platensis as seeds under nitrogen limitation.

  6. Physiology and gene expression profiles of Dekkera bruxellensis in response to carbon and nitrogen availability.

    Science.gov (United States)

    de Barros Pita, Will; Silva, Denise Castro; Simões, Diogo Ardaillon; Passoth, Volkmar; de Morais, Marcos Antonio

    2013-11-01

    The assimilation of nitrate, a nitrogenous compound, was previously described as an important factor favoring Dekkera bruxellensis in the competition with Saccharomyces cerevisiae for the industrial sugarcane substrate. In this substrate, nitrogen sources are limited and diverse, and a recent report showed that amino acids enable D. bruxellensis to grow anaerobically. Thus, understanding the regulation of nitrogen metabolism is one fundamental aspect to comprehend the competiveness of D. bruxellensis in the fermentation environment. In the present study, we evaluated the physiological and transcriptional profiles of D. bruxellensis in response to different carbon and nitrogen supplies to determine their influence on growth, sugar consumption, and ethanol production. Besides, the expression of genes coding for nitrogen permeases and enzymes involved in the biosynthesis of glutamate and energetic metabolism were investigated under these conditions. Our data revealed that genes related to nitrogen uptake in D. bruxellensis are under the control of nitrogen catabolite repression. Moreover, we provide indications that glutamate dehydrogenase and glutamate synthase may switch roles as the major pathway for glutamate biosynthesis in D. bruxellensis. Finally, our data showed that in nonoptimal growth conditions, D. bruxellensis leans toward the respiratory metabolism. The results presented herein show that D. bruxellensis and S. cerevisiae share similar regulation of GDH–GOGAT pathway, while D. bruxellensis converts less glucose to ethanol than S. cerevisiae do when nitrogen is limited. The consequence of this particularity to the industrial process is discussed.

  7. A Natural Light/Dark Cycle Regulation of Carbon-Nitrogen Metabolism and Gene Expression in Rice Shoots.

    Science.gov (United States)

    Li, Haixing; Liang, Zhijun; Ding, Guangda; Shi, Lei; Xu, Fangsen; Cai, Hongmei

    2016-01-01

    Light and temperature are two particularly important environmental cues for plant survival. Carbon and nitrogen are two essential macronutrients required for plant growth and development, and cellular carbon and nitrogen metabolism must be tightly coordinated. In order to understand how the natural light/dark cycle regulates carbon and nitrogen metabolism in rice plants, we analyzed the photosynthesis, key carbon-nitrogen metabolites, and enzyme activities, and differentially expressed genes and miRNAs involved in the carbon and nitrogen metabolic pathway in rice shoots at the following times: 2:00, 6:00, 10:00, 14:00, 18:00, and 22:00. Our results indicated that more CO2 was fixed into carbohydrates by a high net photosynthetic rate, respiratory rate, and stomatal conductance in the daytime. Although high levels of the nitrate reductase activity, free ammonium and carbohydrates were exhibited in the daytime, the protein synthesis was not significantly facilitated by the light and temperature. In mRNA sequencing, the carbon and nitrogen metabolism-related differentially expressed genes were obtained, which could be divided into eight groups: photosynthesis, TCA cycle, sugar transport, sugar metabolism, nitrogen transport, nitrogen reduction, amino acid metabolism, and nitrogen regulation. Additionally, a total of 78,306 alternative splicing events have been identified, which primarily belong to alternative 5' donor sites, alternative 3' acceptor sites, intron retention, and exon skipping. In sRNA sequencing, four carbon and nitrogen metabolism-related miRNAs (osa-miR1440b, osa-miR2876-5p, osa-miR1877 and osa-miR5799) were determined to be regulated by natural light/dark cycle. The expression level analysis showed that the four carbon and nitrogen metabolism-related miRNAs negatively regulated their target genes. These results may provide a good strategy to study how natural light/dark cycle regulates carbon and nitrogen metabolism to ensure plant growth and

  8. Biosynthetic origin of the carbon skeleton and nitrogen atom of pamamycin-607, a nitrogen-containing polyketide.

    Science.gov (United States)

    Hashimoto, Makoto; Komatsu, Haruhiko; Kozone, Ikuko; Kawaide, Hiroshi; Abe, Hiroshi; Natsume, Masahiro

    2005-02-01

    The biosynthesis of pamamycin-607 (PM-607), a sixteen-membered macrodiolide compound, was studied with 13C- and 15N-labeled precursor units in Streptomyces alboniger. Feeding experiments with 13C-labeled acetate or propionate indicate that the carbon skeleton of PM-607 was derived from six acetate, four propionate and three succinate units. MS analyses of 15N-labeled PM-607 suggest that the nitrogen atom in PM-607 was derived from the alpha-amino group of an amino acid.

  9. Carbon and carbon dioxide accumulation by marandu grass under nitrogen fertilization and irrigation

    Directory of Open Access Journals (Sweden)

    Elisângela Dupas

    2016-06-01

    Full Text Available ABSTRACT Nitrogen (N is the most limiting nutrient for growth of forage grasses, especially in conditions of low water availability. Therefore, it is important to evaluate the effect of N fertilization and irrigation on the accumulation of carbon (C and carbon dioxide (CO2 by marandu grass in the Cerrado Paulista, in the rainy and dry seasons. Experiments were conducted to evaluate N fertilization in each season, with and without irrigation. Five N rates were used (0, 50, 100, 150 and 200 kg ha-1 per cutting, using urea as N source, totaling 0, 300, 600, 900 and 1200 kg ha-1 in the rainy season and 0, 100, 200, 300 and 400 kg ha-1 in the dry season. The experiments were arranged in a split-plot randomized block design. There was no significant interaction (p > 0.05 between N and time of fertilization in the irrigated experiment. However, N promoted a quadratic effect in organic matter production (OMP, accumulation of C and CO2 by marandu grass, while there was no influence of the seasons. In the non-irrigated experiment, the interaction between N rates and seasons was significant (p < 0.05 only for the rainy season. Organic matter production and C and CO2 accumulation was greater in the rainy season than in the dry season. Irrigation provided increases of approximately 20% in C and CO2 accumulation. The use of N and irrigation increases the accumulation of C and CO2 by marandu grass, and this increase is higher during the rainy season.

  10. Carbon sequestration and Jerusalem artichoke biomass under nitrogen applications in coastal saline zone in the northern region of Jiangsu, China.

    Science.gov (United States)

    Niu, Li; Manxia, Chen; Xiumei, Gao; Xiaohua, Long; Hongbo, Shao; Zhaopu, Liu; Zed, Rengel

    2016-10-15

    Agriculture is an important source of greenhouse gases, but can also be a significant sink. Nitrogen fertilization is effective in increasing agricultural production and carbon storage. We explored the effects of different rates of nitrogen fertilization on biomass, carbon density, and carbon sequestration in fields under the cultivation of Jerusalem artichoke as well as in soil in a coastal saline zone for two years. Five nitrogen fertilization rates were tested (in guream(-2)): 4 (N1), 8 (N2), 12 (N3), 16 (N4), and 0 (control, CK). The biomass of different organs of Jerusalem artichoke during the growth cycle was significantly higher in N2 than the other treatments. Under different nitrogen treatments, carbon density in organs of Jerusalem artichoke ranged from 336 to 419gCkg(-1). Carbon sequestration in Jerusalem artichoke was higher in treatments with nitrogen fertilization compared to the CK treatment. The highest carbon sequestration was found in the N2 treatment. Soil carbon content was higher in the 0-10cm than 10-20cm layer, with nitrogen fertilization increasing carbon content in both soil layers. The highest soil carbon sequestration was measured in the N2 treatment. Carbon sequestration in both soil and Jerusalem artichoke residue was increased by nitrogen fertilization depending on the rates in the coastal saline zone studied.

  11. Endohedral nitrogen storage in carbon fullerene structures: Physisorption to chemisorption transition with increasing gas pressure

    Science.gov (United States)

    Barajas-Barraza, R. E.; Guirado-López, R. A.

    2009-06-01

    We present extensive pseudopotential density functional theory (DFT) calculations in order to analyze the structural properties and chemical reactivity of nitrogen molecules confined in spheroidal (C82) and tubelike (C110) carbon fullerene structures. For a small number of encapsulated nitrogens, the N2 species exist in a nonbonded state within the cavities and form well defined molecular conformations such as linear chains, zigzag arrays, as well as both spheroidal and tubular configurations. However, with increasing the number of stored molecules, the interaction among the confined nitrogens as well as between the N2 species and the fullerene wall is not always mainly repulsive. Actually, at high densities of the encapsulated gas, we found both adsorption of N2 to the inner carbon surface together with the formation of (N2)m molecular clusters. Total energy DFT calculations reveal that the shape of the interaction potential of a test molecule moving within the carbon cavities strongly varies with the number and proximity of the coadsorbed N2 from being purely repulsive to having short-range attractive contributions close to the inner wall. In particular, the latter are always found when a group of closely spaced nitrogens is located near the carbon cage (a fact that will naturally occur at high densities of the encapsulated gas), inducing the formation of covalent bonds between the N2 and the fullerene network. Interestingly, in some cases, the previous nitrogen adsorption to the inner surface is reversible by reducing the gas pressure. The calculated average density of states of our considered carbon compounds reveals the appearance of well defined features that clearly reflect the occurring structural changes and modifications in the adsorption properties in the systems. Our results clearly underline the crucial role played by confinement effects on the reactivity of our endohedral compounds, define this kind of materials as nonideal nanocontainers for high

  12. Modification of diamond-like carbon films by nitrogen incorporation via plasma immersion ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Flege, S., E-mail: flege@ca.tu-darmstadt.de [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Hatada, R.; Hoefling, M.; Hanauer, A.; Abel, A. [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Baba, K. [Industrial Technology Center of Nagasaki, Applied Technology Division, Omura, Nagasaki 856-0026 (Japan); Ensinger, W. [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany)

    2015-12-15

    Highlights: • Nitrogen containing diamond-like carbon films were prepared by a plasma ignited by a high voltage. • Variation of preparation method (N{sub 2} implantation, N{sub 2} and C{sub 2}H{sub 4} co-deposition). • Maximum nitrogen content similar for co-deposition and implantation. • Electrical resistivity decreases for small nitrogen contents, increases again for higher contents. - Abstract: The addition of nitrogen to diamond-like carbon films affects properties such as the inner stress of the film, the conductivity, biocompatibility and wettability. The nitrogen content is limited, though, and the maximum concentration depends on the preparation method. Here, plasma immersion ion implantation was used for the deposition of the films, without the use of a separate plasma source, i.e. the plasma was generated by a high voltage applied to the samples. The plasma gas consisted of a mixture of C{sub 2}H{sub 4} and N{sub 2}, the substrates were silicon and glass. By changing the experimental parameters (high voltage, pulse length and repetition rate and gas flow ratio) layers with different N content were prepared. Additionally, some samples were prepared using a DC voltage. The nitrogen content and bonding was investigated with SIMS, AES, XPS, FTIR and Raman spectroscopy. Their influence on the electrical resistivity of the films was investigated. Depending on the preparation conditions different nitrogen contents were realized with maximum contents around 11 at.%. Those values were compared with the nitrogen concentration that can be achieved by implantation of nitrogen into a DLC film.

  13. Carbon and nitrogen flows during a bloom of the coccolithophore Emiliania huxleyi: Modelling a mesocosm experiment

    Science.gov (United States)

    Joassin, P.; Delille, B.; Soetaert, K.; Harlay, J.; Borges, A. V.; Chou, L.; Riebesell, U.; Suykens, K.; Grégoire, M.

    2011-04-01

    A dynamic model has been developed to represent biogeochemical variables and processes observed during experimental blooms of the coccolithophore Emiliania huxleyi induced in mesocosms over a period of 23 days. The model describes carbon (C), nitrogen (N), and phosphorus (P) cycling through E. huxleyi and the microbial loop, and computes pH and the partial pressure of carbon dioxide (pCO 2) from dissolved inorganic carbon (DIC) and total alkalinity (TA). The main innovations are: 1) the representation of E. huxleyi dynamics using an unbalanced growth model in carbon and nitrogen, 2) the gathering of formulations describing typical processes involved in the export of carbon such as primary production, calcification, cellular dissolved organic carbon (DOC) excretion, transparent exopolymer (TEP) formation and viral lyses, and 3) an original and validated representation of the calcification process as a function of the net primary production with a modulation by the intra-cellular N:C ratio mimicking the effect of nutrients limitation on the onset of calcification. It is shown that this new mathematical formulation of calcification provides a better representation of the dynamics of TA, DIC and calcification rates derived from experimental data compared to classicaly used formulations (e.g. function of biomass or of net primary production without any modulation term). In a first step, the model has been applied to the simulations of present pCO 2 conditions. It adequately reproduces the observations for chemical and biological variables and provides an overall view of carbon and nitrogen dynamics. Carbon and nitrogen budgets are derived from the model for the different phases of the bloom, highlighting three distinct phases, reflecting the evolution of the cellular C:N ratio and the interaction between hosts and viruses. During the first phase, inorganic nutrients are massively consumed by E. huxleyi increasing its biomass. Uptakes of carbon and nitrogen are

  14. Mesoporous Nitrogen Doped Carbon-Glass Ceramic Cathode for High Performance Lithium-Oxygen Battery

    Science.gov (United States)

    2012-06-01

    Hardwick, and J.- M. Tarascon, Nature Materials, vol. 11, pp 19-29, 2012. 2. Linden , D. (Ed), Handbook of Batteries , 2nd Edition, Mc-Graw-Hill, New...AFRL-RQ-WP-TP-2015-0053 MESOPOROUS NITROGEN DOPED CARBON-GLASS CERAMIC CATHODE FOR HIGH PERFORMANCE LITHIUM-OXYGEN BATTERY (POSTPRINT...DOPED CARBON-GLASS CERAMIC CATHODE FOR HIGH PERFORMANCE LITHIUM-OXYGEN BATTERY (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c

  15. Conductive surface modification of LiFePO4 with nitrogen doped carbon layers for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Sukeun [ORNL; Liao, Chen [ORNL; Sun, Xiao-Guang [ORNL; Bridges, Craig A [ORNL; Unocic, Raymond R [ORNL; Nanda, Jagjit [ORNL; Dai, Sheng [ORNL; Paranthaman, Mariappan Parans [ORNL

    2012-01-01

    The LiFePO4 rod surface modified with nitrogen doped carbon layer has been prepared using hydrothermal processing followed by post-annealing in the presence of an ionic liquid. The coated LiFePO4 rod exhibits good capacity retention and high rate capability as the nitrogen doped carbon improves conductivity and prevents aggregation of the rod during cycling.

  16. Biophysical controls over concentration and depth distribution of soil organic carbon and nitrogen in desert playas

    Science.gov (United States)

    McKenna, Owen P.; Sala, Osvaldo E.

    2016-12-01

    Playa wetlands are important areas of soil organic carbon and nutrient storage in drylands. We conducted this study to assess how catchment biophysical variables control soil organic carbon and nitrogen in playas and how playas function differently than upland ecosystems. We found that playa organic carbon and nitrogen corresponded primarily with catchment vegetation cover and secondarily with catchment area, slope, and soil texture. The effect of increased organic matter production associated with high catchment vegetation cover overshadowed the potential effect of reduced run-on. We also found soil carbon and nitrogen profiles to be significantly shallower in playas than uplands. This trend is correlated with evidence of sedimentation and shallow-rooted plants in playas. Upland soils had a deeper carbon and nitrogen profile, which correlated with organic matter being generated by deeply rooted vegetation. In playas, C:N ratios remained constant through depth but in uplands, C:N ratios increased through depth. We found evidence that differences in rooting depth distributions and soil texture may explain these C:N variations between uplands and playas. In uplands, clay concentration increased with depth, whereas in playas, clay concentration did not change with depth, which highlighted the important role of sedimentation in these ecosystems. Our results suggest that small changes in playa catchment vegetation cover in response to climate change or grazing intensity would greatly impact playa soil organic carbon and nitrogen stocks. This effect would be due to the playa soils dependence on allochthonous organic matter and the large upland area that drains into playas.

  17. Oxygen and nitrogen-doped metal-free carbon catalysts for hydrochlorination of acetylene☆

    Institute of Scientific and Technical Information of China (English)

    Tongtong Zhang; Jia Zhao; Jiangtao Xu; Jinhui Xu; Xiaoxia Di; Xiaonian Li

    2016-01-01

    Activated carbon was tested as metal-free catalyst for hydrochlorination of acetylene in order to circumvent the problem of environment pollution caused by mercury and high cost by noble metals. Oxygen-doped and nitrogen-doped activated carbons were prepared and characterized by XPS, TPD and N2 physisorption methods. The influences of the surface functional groups on the catalytic performance were discussed base on these results. Among al the samples tested, a nitrogen-doped sample, AC-n-U500, exhibited the best performance, the acety-lene conversion being 92%and vinyl chloride selectivity above 99%at 240 °C and C2H2 hourly space velocity 30 h−1. Moreover, the AC-n-U500 catalyst exhibited a stable performance during a 200 h test with a conversion of acetylene higher than 76%at 210 °C at a C2H2 hourly space velocity 50 h−1. In contrary, oxygen-doped catalyst had lower catalytic activities. A linear relationship between the amount of pyrrolic-N and quaternary-N species and the catalytic activity was observed, indicating that these nitrogen-doped species might be the active sites and the key in tuning the catalytic performance. It is also found that the introduction of nitrogen species into the sample could significantly increase the adsorption amount of acetylene. The deactivation of nitrogen-doped activated carbon might be caused by the decrease of the accessibility to or the total amount of active sites.

  18. Pyrolysis of cellulose under ammonia leads to nitrogen-doped nanoporous carbon generated through methane formation.

    Science.gov (United States)

    Luo, Wei; Wang, Bao; Heron, Christopher G; Allen, Marshall J; Morre, Jeff; Maier, Claudia S; Stickle, William F; Ji, Xiulei

    2014-01-01

    Here, we present a simple one-step fabrication methodology for nitrogen-doped (N-doped) nanoporous carbon membranes via annealing cellulose filter paper under NH3. We found that nitrogen doping (up to 10.3 at %) occurs during cellulose pyrolysis under NH3 at as low as 550 °C. At 700 °C or above, N-doped carbon further reacts with NH3, resulting in a large surface area (up to 1973.3 m(2)/g). We discovered that the doped nitrogen, in fact, plays an important role in the reaction, leading to carbon gasification. CH4 was experimentally detected by mass spectrometry as a product in the reaction between N-doped carbon and NH3. When compared to conventional activated carbon (1533.6 m(2)/g), the N-doped nanoporous carbon (1326.5 m(2)/g) exhibits more than double the unit area capacitance (90 vs 41 mF/m(2)).

  19. A co-confined carbonization approach to aligned nitrogen-doped mesoporous carbon nanofibers and its application as an adsorbent

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Aibing, E-mail: chen_ab@163.com [College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018 (China); Liu, Chao [College of Gemmology and Material Technics, Shijiazhuang University of Economic, Huaian Road 136, Shijiazhuang 050031 (China); Yu, Yifeng; Hu, Yongqi; Lv, Haijun; Zhang, Yue; Shen, Shufeng [College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018 (China); Zhang, Jian, E-mail: jzhang@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2014-07-15

    Highlights: • MCNFs were synthesized by a co-confined carbonization method. • The diameter size of MCNFs with bimodal mesoporous structure can be modulated. • The obtained MCNFs manifest better adsorption capacity for SO{sub 2}, CO{sub 2} and Cd{sup 2+}. - Abstract: Nitrogen-doped carbon nanofibers (MCNFs) with an aligned mesoporous structure were synthesized by a co-confined carbonization method using anodic aluminum oxide (AAO) membrane and tetraethylorthosilicate (TEOS) as co-confined templates and ionic liquids as the precursor. The as-synthesized MCNFs with the diameter of 80–120 nm possessed a bulk nitrogen content of 5.3 wt% and bimodal mesoporous structure. The nitrogen atoms were mostly bound to the graphitic network in two forms, i.e. pyridinic and pyrrolic nitrogen, providing adsorption sites for acidic gases like SO{sub 2} and CO{sub 2}. Cyclic experiments revealed a considerable stability of MCNFs over 20 runs of SO{sub 2} adsorption and 15 runs for CO{sub 2} adsorption. The MCNFs also have a preferable adsorption performance for Cd{sup 2+}.

  20. Effects of Nitrogen and Carbon Sources on Transcription of Soluble Methyltransferases in Methanosarcina mazei Strain Gö1†

    OpenAIRE

    Veit, Katharina; Ehlers, Claudia; Schmitz, Ruth A.

    2005-01-01

    The methanogenic archaeon Methanosarcina mazei strain Gö1 uses versatile carbon sources and is able to fix molecular nitrogen with methanol as carbon and energy sources. Here, we demonstrate that when growing on trimethylamine (TMA), nitrogen fixation does not occur, indicating that ammonium released during TMA degradation is sufficient to serve as a nitrogen source and represses nif gene induction. We further report on the transcriptional regulation of soluble methyltransferases, which catal...

  1. Microtribology of Nitrogen-doped Amorphous Carbon Coatings

    Institute of Scientific and Technical Information of China (English)

    Dong F. Wang

    2004-01-01

    The friction, wear and lubrication of carbon nitride coatings on silicon substrates are studied using a spherical diamond counter-face with nano-scale asperities. The first part of this paper clarifies the coating thickness effect on frictional behavior of carbon nitride coatings. The second part of this paper reports empirical data on wear properties in repeated sliding contacts through in situ examination and post-sliding observation. The third part will concentrate on wear mechanisms for the transition from "No observable wear particles" to "Wear particle generation." In light of the above tribological study, the application of carbon nitride coatings to MicroElectroMechanical system (MEMS) is therefore discussed from view points of both microtribology and micromachining.

  2. Theoretical Investigation on Single-Wall Carbon Nanotubes Doped with Nitrogen, Pyridine-Like Nitrogen Defects, and Transition Metal Atoms

    Directory of Open Access Journals (Sweden)

    Michael Mananghaya

    2012-01-01

    Full Text Available This study addresses the inherent difficulty in synthesizing single-walled carbon nanotubes (SWCNTs with uniform chirality and well-defined electronic properties through the introduction of dopants, topological defects, and intercalation of metals. Depending on the desired application, one can modify the electronic and magnetic properties of SWCNTs through an appropriate introduction of imperfections. This scheme broadens the application areas of SWCNTs. Under this motivation, we present our ongoing investigations of the following models: (i (10, 0 and (5, 5 SWCNT doped with nitrogen (CNxNT, (ii (10, 0 and (5, 5 SWCNT with pyridine-like defects (3NV-CNxNT, (iii (10, 0 SWCNT with porphyrine-like defects (4ND-CNxNT. Models (ii and (iii were chemically functionalized with 14 transition metals (TMs: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag, Pt and Au. Using the spin-unrestricted density functional theory (DFT, stable configurations, deformations, formation and binding energies, the effects of the doping concentration of nitrogen, pyridine-like and porphyrine-like defects on the electronic properties were all examined. Results reveal that the electronic properties of SWCNTs show strong dependence on the concentration and configuration of nitrogen impurities, its defects, and the TMs adsorbed.

  3. Electrocatalytically switchable CO2 capture: first principle computational exploration of carbon nanotubes with pyridinic nitrogen.

    Science.gov (United States)

    Jiao, Yan; Zheng, Yao; Smith, Sean C; Du, Aijun; Zhu, Zhonghua

    2014-02-01

    Carbon nanotubes with specific nitrogen doping are proposed for controllable, highly selective, and reversible CO2 capture. Using density functional theory incorporating long-range dispersion corrections, we investigated the adsorption behavior of CO2 on (7,7) single-walled carbon nanotubes (CNTs) with several nitrogen doping configurations and varying charge states. Pyridinic-nitrogen incorporation in CNTs is found to induce an increasing CO2 adsorption strength with electron injecting, leading to a highly selective CO2 adsorption in comparison with N2 . This functionality could induce intrinsically reversible CO2 adsorption as capture/release can be controlled by switching the charge carrying state of the system on/off. This phenomenon is verified for a number of different models and theoretical methods, with clear ramifications for the possibility of implementation with a broader class of graphene-based materials. A scheme for the implementation of this remarkable reversible electrocatalytic CO2 -capture phenomenon is considered.

  4. Characteristics of nitrogen-doped carbon nanotubes synthesized by using PECVD and thermal CVD

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae-Bum; Kong, So-Jeo; Lee, Sung-Youp; Kim, Je-Han; Lee, Hyeong-Rag [Kyungpook National University, Daegu (Korea, Republic of); Kim, Chang-Duk [Kyungpook National University, Sangju (Korea, Republic of); Min, Bong-Ki [Yeungnam University, Gyeongsan (Korea, Republic of)

    2012-04-15

    Nitrogen-doped carbon nanotubes (N-CNTs) are synthesizd by using plasma-enhanced chemical vapor deposition (PECVD) and thermal chemical vapor deposition (TCVD) because PECVD and TCVD are attractive methods for producing N-CNTs. In this paper, we report the experimental observation of nitrogen incorporation in multiwalled carbon nanotubes grown by using these methods. XPS analysis indicates a shift and broadening of the C 1s spectra peak with increasing disorder induced by nitrogen doping. The N 1s XPS spectra of N-CNTs grown by using PECVD show various structures such as graphitic, pyridinic and N-gaseous forms, while N-CNTs grown by using TCVD have only a graphitic form. Each structure affects the electronic properties of N-CNTs in a different way. TCVD provides a more profitable synthesis method for n-type CNTs while PECVD supports the synthesis of activated N-CNTs with no post-treatment.

  5. Nitrogen fertilization effects on pasture photosynthesis, respiration, and ecosystem carbon content

    Science.gov (United States)

    Some studies have shown that increasing nitrogen (N) fertility can increase soil carbon (C) sequestration, whereas others suggest that N fertilization has no effect on sequestration. Increasing N fertilization typically increases annual photosynthetic C uptake (gross primary productivity or GPP) and...

  6. Novel porous carbon materials with ultrahigh nitrogen contents for selective CO 2 capture

    KAUST Repository

    Zhao, Yunfeng

    2012-01-01

    Nitrogen-doped carbon materials were prepared by a nanocasting route using tri-continuous mesoporous silica IBN-9 as a hard template. Rationally choosing carbon precursors and carefully controlling activation conditions result in an optimized material denoted as IBN9-NC1-A, which possesses a very high nitrogen doping concentration (∼13 wt%) and a large surface area of 890 m 2 g -1 arising from micropores (<1 nm). It exhibits an excellent performance for CO 2 adsorption over a wide range of CO 2 pressures. Specifically, its equilibrium CO 2 adsorption capacity at 25 °C reaches up to 4.50 mmol g -1 at 1 bar and 10.53 mmol g -1 at 8 bar. In particular, it shows a much higher CO 2 uptake at low pressure (e.g. 1.75 mmol g -1 at 25 °C and 0.2 bar) than any reported carbon-based materials, owing to its unprecedented nitrogen doping level. The high nitrogen contents also give rise to significantly enhanced CO 2/N 2 selectivities (up to 42), which combined with the high adsorption capacities, make these new carbon materials promising sorbents for selective CO 2 capture from power plant flue gas and other relevant applications. © 2012 The Royal Society of Chemistry.

  7. Cover crops for enriching soil carbon and nitrogen under bioenergy sorghum

    Science.gov (United States)

    Soil carbon (C) and nitrogen (N) can be enriched with cover crops under agronomic crops, but little is known about their enrichment under bioenergy crops. Legume (hairy vetch [Vicia villosa Roth]), nonlegume (rye [Secaele cereale L.]), a mixture of legume and nonlegume (hairy vetch and rye) and a co...

  8. Synthesis and drug detection performance of nitrogen-doped carbon dots

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Jingjing [Functional and Environment Materials Research Institute, College of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Nano Structure and Low Dimensional Physics Laboratory, Peking University, Beijing 100871 (China); Gao, Hui, E-mail: hope@lzu.edu.cn [Functional and Environment Materials Research Institute, College of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2014-05-01

    Recently, nitrogen-doped carbon dots (NCDs) have attracted considerable interest since nitrogen (N) doping could effectively tailor the electronic properties and the chemical reactivity of carbon dots (CDs) for advanced potential applications. Herein, a one-step pyrolysis method was presented for synthesizing the NCDs with excellent water solubility, good stability and a high quantum yield of ca. 28%. The detection performance of NCDs for the antibacterial drugs was further explored, and it was proved to effectively enhance the fluorescence due to the strong interaction between the NCDs and antibacterial drugs. - Highlights: • A facile yet economic bottom-up pyrolysis method for synthesizing nitrogen (N)-doped carbon dots (NCDs) using glutamic acid as the precursor. • Glutamic acid was the only starting material and used as a source of carbon and nitrogen; the formation and functionalization of NCDs were accomplished simultaneously. • The NCDs possess bright blue emission (with a high quantum yield of ca. 28%) and excellent excitation dependent on PL properties. • NCDs were used for the determination of antibacterial drugs based on the fluorescence enhancement.

  9. Disk Inoculum-Solid Medium Method To Test Carbon and Nitrogen Assimilation by Yeast Isolates

    OpenAIRE

    Moore, Kerry J.; Johnson, Michael G.; McClary, Shane P.

    1988-01-01

    Carbon and nitrogen assimilation for 50 yeasts isolated from White Riesling fermentation were tested by using a disk inoculum-solid medium method. This method was quicker and gave results comparable to the conventional liquid medium methods. Yeast characteristics (growth response, pigment production, morphology) could also be compared with this method.

  10. ANALYTICAL EMPLOYMENT OF STABLE ISOTOPES OF CARBON, NITROGEN, OXYGEN AND HYDROGEN FOR FOOD AUTHENTICATION

    Directory of Open Access Journals (Sweden)

    E. Novelli

    2011-04-01

    Full Text Available Stable isotopes of carbon, nitrogen, oxygen and hydrogen were used for analytical purposes for the discrimination of the type of production (farming vs. fishing in the case of sea bass and for geographical origin in the case of milk. These results corroborate similar experimental evidences and confirm the potential of this analytical tool to support of food traceability.

  11. Phase Equilibria of Three Binary Mixtures: Methanethiol + Methane, Methanethiol + Nitrogen, and Methanethiol + Carbon Dioxide

    DEFF Research Database (Denmark)

    Awan, Javeed; Tsivintzelis, Ioannis; Coquelet, Christophe;

    2012-01-01

    New vapor–liquid equilibrium (VLE) data for methanethiol (MM) + methane (CH4), methanethiol (MM) + nitrogen (N2), and methanethiol (MM) + carbon dioxide (CO2) is reported for temperatures of (304, 334, and 364) K in the pressure range (1 to 8) MPa. A “static–analytic” method was used for performi...

  12. Developing Ecological Models on Carbon and Nitrogen in Secondary Facultative Ponds

    Directory of Open Access Journals (Sweden)

    Aponte-Reyes Alexander

    2014-07-01

    Full Text Available Ecological models formulated for TOC, CO2, NH4+, NO3- and NTK, based in literature reviewed and field work were obtained monitoring three facultative secondary stabilization ponds, FSSP, pilots: conventional pond, CP, baffled pond, BP, and baffled-meshed pond, BMP. Models were sensitive to flow inlet, solar radiation, pH and oxygen content; the sensitive parameters in Carbon Model were KCOT Ba, umax Ba, umax Al, K1OX, VAl, R1DCH4, YBh. The sensitive parameters in the Nitrogen model were KCOT Ba, umax Ba, umax Al, VAl, KOPH, KOPA, r4An. The test t–paired showed a good simulating of Carbon model refers to TOC in FSSP; on the other side, the Nitrogen model showed a good simulating of NH4+. Different topological models modify ecosystem ecology forcing different transformation pathways of Nitrogen; equal transformations of the Carbon BMP topology could be achieved using lower volumes, however, a calibration for a new model would be required. Carbon and Nitrogen models developed could be coupled to hydrodynamics models for better modeling of FSSP.

  13. Fate of microbial nitrogen, carbon, hydrolysable amino acids, monosaccharides, and fatty acids in sediment

    NARCIS (Netherlands)

    Veuger, B.; van Oevelen, D.; Middelburg, J.J.

    2012-01-01

    The fate of microbial carbon, nitrogen, hydrolysable amino acids (HAAs), monosaccharides, and fatty acids in sediment was investigated experimentally. The microbial community of a tidal flat sediment was labeled with C-13-enriched glucose and N-15-enriched ammonium, and sediment was incubated for up

  14. Fate of microbial nitrogen, carbon, hydrolysable amino acids, monosaccharides, and fatty acids in sediment

    NARCIS (Netherlands)

    Veuger, B.; Van Oevelen, D.; Middelburg, J.J.

    2012-01-01

    The fate of microbial carbon, nitrogen, hydrolysable amino acids (HAAs), monosaccharides, and fatty acids in sediment was investigated experimentally. The microbial community of a tidal flat sediment was labeled with 13C-enriched glucose and 15N-enriched ammonium, and sediment was incubated for up t

  15. The ternary Fe-C-N system: Homogeneous distributions of nitrogen and carbon

    DEFF Research Database (Denmark)

    Brink, Bastian; Ståhl, Kenny; Christiansen, Thomas Lundin;

    2017-01-01

    of the nitriding and carburizing potentials, tailored nitrogen and carbon contents can be achieved, which allows assessment of a phase stability diagram for the Fe-N-C system, for which available experimental data is limited. Thermal decomposition sequences were established for the various iron carbides and (carbo...

  16. Carbon, Nitrogen, and Oxygen Abundances of Selected Stars in the Hertzsprung Gap

    Science.gov (United States)

    Vanture, Andrew D.; Wallerstein, George

    1999-01-01

    The iron, carbon, nitrogen, and oxygen abundances for several stars whose characteristics place them in the Hertzsprung gap have been derived from high-resolution spectra. These stars were selected based on the fact that previous studies have shown them to have peculiar carbon, nitrogen, or lithium abundances considering their position in the Hertzsprung-Russell diagram. When combined with the lithium abundances derived by Wallerstein and coworkers, the carbon, nitrogen, and oxygen abundances indicate that the sample of stars can generally be broken into two categories-lower luminosity dwarfs or subgiants that are unmixed and higher luminosity mixed giants. Among the sample are two stars, HR 7606 and HR 8626, which previously have been identified by Bidelman as ``low-velocity CH stars.'' These stars show metallicities of [Fe/H]~-0.5 and solar abundances of carbon, nitrogen, and oxygen. The strength of the CH band in these stars is probably an artifact of a mild metal deficiency and the absence of substantial mixing of CN processed materials to the surface of the star rather than an unusual nucleosynthetic history.

  17. Carbon respiration and nitrogen dynamics in Corsican pine litter amended with aluminium and tannins

    NARCIS (Netherlands)

    Kraal, P.; Nierop, K.G.J.; Kaal, J.; Tietema, A.

    2009-01-01

    We investigated the carbon (C) mineralisation and nitrogen (N) dynamics in litter from a Corsican pine forest in response to individual and combined additions of aluminium (M), condensed tannin (extracted from fresh Corsican pine needles) and hydrolysable tannin (commercial tannic acid). Production

  18. A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation

    NARCIS (Netherlands)

    Loisel, J.; Yu, Z.; Beilman, D.W.; Camill, P.; Alm, J.; Amesbury, M.J.; Anderson, D.; Andersson, S.; Bochicchio, C.; Barber, K.; Belyea, L.R.; Bunbury, J.; Chambers, F.M.; Charman, D.J.; De Vleeschouwer, F.; Fiałkiewicz-Kozieł, B.; Finkelstein, S.A.; Gałka, M.; Garneau, M.; Hammarlund, D; Hinchcliffe, W.; Holmquist, J.; Hughes, P.; Jones, M.C.; Klein, E.S.; Kokfelt, U.; Korhola, A.; Kuhry, P.; Lamarre, A.; Lamentowicz, M.; Large, D.; Lavoie, M.; Macdonald, G.; Magnan, G.; Mäkilä, M.; Mallon, G.; Mathijssen, P.; Mauquoy, D.; McCarroll, J.; Moore, T.R.; Nichols, J.; O'Reilly, B.; Oksanen, P.; Packalen, M.; Peteet, D.; Richard, P.J.H.; Robinson, S.; Ronkainen, T.; Rundgren, M.; Sannel, A.B.K.; Tarnocai, C.; Thom, T.; Tuittila, E.S.; Turetsky, M.; Väliranta, M.; van der Linden, M.; van Geel, B.; van Bellen, S.; Vitt, D.; Zhao, Y.; Zhou, W.

    2014-01-01

    Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45°N. It encompasses regions within which peat carb

  19. Carbon and nitrogen stocks in the soils of Central and Eastern Europe

    NARCIS (Netherlands)

    Batjes, N.H.

    2002-01-01

    Soil organic carbon and total nitrogen stocks are presented for Central and Eastern Europe. The study uses the soil geographic and attribute data held in a 1:2 500 000 scale Soil and Terrain (SOTER) database, covering Belarus, Bulgaria, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Moldova, P

  20. Contribution of chloroplast biogenesis to carbon-nitrogen balance during early leaf development in rice.

    Science.gov (United States)

    Kusumi, Kensuke; Hirotsuka, Shoko; Shimada, Hiroshi; Chono, Yoko; Matsuda, Osamu; Iba, Koh

    2010-07-01

    Chloroplast biogenesis is most significant during the changes in cellular organization associated with leaf development in higher plants. To examine the physiological relationship between developing chloroplasts and host leaf cells during early leaf development, we investigated changes in the carbon and nitrogen contents in leaves at the P4 developmental stage of rice, during which leaf blade structure is established and early events of chloroplast differentiation occur. During the P4 stage, carbon content on a dry mass basis remained constant, whereas the nitrogen content decreased by 30%. Among carbohydrates, sucrose and starch accumulated to high levels early in the P4 stage, and glucose, fructose and cellulose degradation increased during the mid-to-late P4 stage. In the chloroplast-deficient leaves of the virescent-1 mutant of rice, however, the carbon and nitrogen contents, as well as the C/N ratio during the P4 stage, were largely unaffected. These observations suggest that developing rice leaves function as sink organs at the P4 stage, and that chloroplast biogenesis and carbon and nitrogen metabolism in the leaf cell is regulated independently at this stage.

  1. Polyol synthesis in Aspergillus niger : influence of oxygen availability, carbon and nitrogen sources on the metabolism

    DEFF Research Database (Denmark)

    Diano, Audrey; Bekker-Jensen, S; Dynesen, Jens Østergaard

    2006-01-01

    Polyol production has been studied in Aspergillus niger under different conditions. Fermentations have been run using high concentration of glucose or xylose as carbon source and ammonium or nitrate as nitrogen source. The growth of biomass, as freely dispersed hyphae, led to an increase of medium...

  2. CARBON TO NITROGEN RATIO AND NITROGENOUS WASTE ACCUMULATION IN THE INTENSIVE CATFISH (Clarias gariepinus) CULTURE

    OpenAIRE

    Bambang Gunadi; Enang Harris; Eddy Supriyono; Sukenda Sukenda; Tatag Budiardi

    2011-01-01

    This experiment was carried out to determine the optimum C/N ratio for heterotrophic bacteria (biofloc) growth in order to control nitrogenous waste accumulation in the catfish (Clarias gariepinus) culture. Twenty fish with an initial individual size of about 50 g were stocked in fiberglass tanks which were filled with 200 L of water. Fish were fed with commercial floating fish feed with a protein level of 31%-33% (manufacturer label). The daily feeding rate was 2.5% of the fish biomass. The ...

  3. Application of Cycloaddition Reactions to the Syntheses of Novel Boron Compounds

    OpenAIRE

    Maguire, John A.; Hosmane, Narayan S; Yinghuai Zhu; Xiao Siwei

    2010-01-01

    This review covers the application of cycloaddition reactions in forming the boron-containing compounds such as symmetric star-shaped boron-enriched dendritic molecules, nano-structured boron materials and aromatic boronic esters. The resulting boron compounds are potentially important reagents for both materials science and medical applications such as in boron neutron capture therapy (BNCT) in cancer treatment and as drug delivery agents and synthetic intermediates for carbon-carbon cross-c...

  4. Palladium-catalyzed homo-coupling of boronic acids with supported reagents in supercritical carbon dioxide

    Institute of Scientific and Technical Information of China (English)

    Lei Zhou; Qiu Xiang Xu; Huan Feng Jiang

    2007-01-01

    Palladium-catalyzed homo-coupling of arylboronic acids could proceed smoothly with a commercially available resin functionlised by phosphino or amino group as the ligand in supercritical carbon dioxide thereby offering a simple and efficient protocol for the synthesis of symmetrical bi-aryl molecules and their higher homologues.

  5. The effects of rising atmospheric carbon dioxide on shoot-root nitrogen and water signaling

    Directory of Open Access Journals (Sweden)

    Hsien Ming eEaslon

    2013-08-01

    Full Text Available Terrestrial higher plants are composed of roots and shoots, distinct organs that conduct complementary functions in dissimilar environments. For example, roots are responsible for acquiring water and nutrients such as inorganic nitrogen from the soil, yet shoots consume the majority of these resources. The success of such a relationship depends on excellent root-shoot communications. Increased net photosynthesis and decreased shoot nitrogen and water use at elevated CO2 fundamentally alter these source-sink relations. Lower than predicted productivity gains at elevated CO2 under nitrogen or water stress may indicate shoot-root signaling lacks plasticity to respond to rising atmospheric CO2 concentrations. The following presents recent research results on shoot-root nitrogen and water signaling, emphasizing the influence that rising atmospheric carbon dioxide levels are having on these source-sink interactions.

  6. Carbon and nitrogen mineralization in vineyard acid soils amended with a bentonitic winery waste

    Science.gov (United States)

    Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula; Díaz-Raviña, Montserrat; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

    2015-04-01

    Carbon mineralization and nitrogen ammonification processes were determined in different vineyard soils. The measurements were performed in samples non-amended and amended with different bentonitic winery waste concentrations. Carbon mineralization was measured as CO2 released by the soil under laboratory conditions, whereas NH4+ was determined after its extraction with KCl 2M. The time evolution of both, carbon mineralization and nitrogen ammonification, was followed during 42 days. The released CO2 was low in the analyzed vineyard soils, and hence the metabolic activity in these soils was low. The addition of the bentonitic winery waste to the studied soils increased highly the carbon mineralization (2-5 fold), showing that the organic matter added together the bentonitic waste to the soil have low stability. In both cases, amended and non-amended samples, the maximum carbon mineralization was measured during the first days (2-4 days), decreasing as the incubation time increased. The NH4+ results showed an important effect of bentonitic winery waste on the ammonification behavior in the studied soils. In the non-amended samples the ammonification was no detected in none of the soils, whereas in the amended soils important NH4+ concentrations were detected. In these cases, the ammonification was fast, reaching the maximum values of NH4 between 7 and 14 days after the bentonitic waste additions. Also, the percentages of ammonification respect to the total nitrogen in the soil were high, showing that the nitrogen provided by the bentonitic waste to the soil is non-stable. The fast carbon mineralization found in the soils amended with bentonitic winery wastes shows low possibilities of the use of this waste for the increasing the organic carbon pools in the soil.On the other hand, the use of this waste as N-fertilizer can be possible. However, due its fast ammonification, the waste should be added to the soils during active plant growth periods.

  7. Atmospheric nitrogen deposition promotes carbon loss from peat bogs

    NARCIS (Netherlands)

    Bragazza, L.; Freeman, C.; Jones, T.; Rydin, H.; Limpens, J.; Fenner, N.; Ellis, T.; Gerdol, R.; Hajek, M.; Hajek, T.; Iacumin, P.; Kutnar, L.; Tahvanainen, T.; Toberman, H.

    2006-01-01

    Peat bogs have historically represented exceptional carbon (C) sinks because of their extremely low decomposition rates and consequent accumulation of plant remnants as peat. Among the factors favoring that peat accumulation, a major role is played by the chemical quality of plant litter itself, whi

  8. SINTERING MECHANISM OF PURE AND CARBON_DOPED BORON CARBIDE%纯B4C和掺碳B4C的烧结机制

    Institute of Scientific and Technical Information of China (English)

    尹邦跃; 王零森; 方寅初

    2001-01-01

    Sintering densificaton process of pure and carbon_doped boron carbide powders with 0.42 μm median particle size were studied. Their sintering kinetic equations were obtained according to the influence of sintering temperature and holding time on linear shrinkage rate. The sintering mechanisms were investigated by comparing the characteristic exponent n. It is deduced that the main sintering mechanisms shill be volume diffusion and grain boundary diffusion for pure boron carbide and grain boundary diffusion for carbon_doped boron carbide showing activated sintering. The relative density of the carbon_doped B4C sintered at 2 160 ℃ for 45 min is more than 90%. Apart from those dissolved in the sintered boron carbide, the rest of the added carbon is in the form of free carbon, no new phase formed. Carbon_doping also result in a great decrease of B4C grain size.%研究了中位粒径为0.42 μm的纯B4C和掺碳B4C粉末的烧结致密化过程. 根据烧结温度和保温时间对线收缩率的影响,得出了它们的烧结动力学方程;由特征指数n值对比研究了它们的烧结致密化机制. 纯B4C的烧结致密化机制为体扩散和晶界扩散,而掺碳B4C的烧结机制主要为晶界扩散,因此,掺碳对B4C起到了活化烧结的作用. 在2 160 ℃烧结45 min,掺碳B4C烧结后相对密度大于90%. 掺入的碳除了固溶于B4C晶格中之外,其它均以游离石墨形式存在,不形成新相. 掺碳还导致B4C晶粒尺寸大大减小.

  9. CARBON TO NITROGEN RATIO AND NITROGENOUS WASTE ACCUMULATION IN THE INTENSIVE CATFISH (Clarias gariepinus CULTURE

    Directory of Open Access Journals (Sweden)

    Bambang Gunadi

    2011-06-01

    Full Text Available This experiment was carried out to determine the optimum C/N ratio for heterotrophic bacteria (biofloc growth in order to control nitrogenous waste accumulation in the catfish (Clarias gariepinus culture. Twenty fish with an initial individual size of about 50 g were stocked in fiberglass tanks which were filled with 200 L of water. Fish were fed with commercial floating fish feed with a protein level of 31%-33% (manufacturer label. The daily feeding rate was 2.5% of the fish biomass. The inoculation of commercial Bacillus sp. isolates was applied in the first day of the experiment after fish stocking in order to obtain a bacterial density in water of 106 cfu/L. Molases was suplemented daily to the tanks to adjust C/N ratio in water. Four C/N ratios, i.e. 0, 7, 14, and 21, were applied as treatments in this experiment. The results showed that molasses suplementation up to C/N ratio 14 to 21 were able to support the growth of heterotrophic bacteria and to inhibit the accumulation of total ammonia nitrogen (TAN and nitrite in water therefore increase water quality for better growth of cultured catfish.

  10. Evaluation of Natural Materials as Exogenous Carbon Sources for Biological Treatment of Low Carbon-to-Nitrogen Wastewater

    Science.gov (United States)

    Ramírez-Godínez, Juan; Beltrán-Hernández, Icela; Álvarez-Hernández, Alejandro; Coronel-Olivares, Claudia; Contreras-López, Elizabeth; Quezada-Cruz, Maribel; Vázquez-Rodríguez, Gabriela

    2015-01-01

    In the bacterial processes involved in the mitigation of nitrogen pollution, an adequately high carbon-to-nitrogen (C : N) ratio is key to sustain denitrification. We evaluated three natural materials (woodchips, barley grains, and peanut shells) as carbon sources for low C : N wastewater. The amount of organic matter released from these materials to aqueous media was evaluated, as well as their pollution swapping potential by measuring the release of total Kjeldahl nitrogen, N-NH4+, NO2−, and NO3−, and total phosphorous. Barley grains yielded the highest amount of organic matter, which also showed to be the most easily biodegradable. Woodchips and peanut shells released carbon rather steadily and so they would not require frequent replenishment from biological reactors. These materials produced eluates with lower concentrations of nutrients than the leachates from barley grains. However, as woodchips yielded lower amounts of suspended solids, they constitute an adequate exogenous source for the biological treatment of carbon-deficient effluents. PMID:26495313

  11. New catalyst supports prepared by surface modification of graphene- and carbon nanotube structures with nitrogen containing carbon coatings

    Science.gov (United States)

    Oh, Eun-Jin; Hempelmann, Rolf; Nica, Valentin; Radev, Ivan; Natter, Harald

    2017-02-01

    We present a new and facile method for preparation of nitrogen containing carbon coatings (NCC) on the surface of graphene- and carbon nanotubes (CNT), which has an increased electronic conductivity. The modified carbon system can be used as catalyst support for electrocatalytic applications, especially for polymer electrolyte membrane fuel cells (PEMFC). The surface modification is performed by impregnating carbon structures with a nitrogen containing ionic liquid (IL) with a defined C:N ratio, followed by a thermal treatment under ambient conditions. We investigate the influence of the main experimental parameters (IL amount, temperature, substrate morphology) on the formation of the NCC. Additionally, the structure and the chemical composition of the resulting products are analyzed by electron microscopic techniques (SEM, TEM), energy disperse X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and hot extraction analysis. The modified surface has a nitrogen content of 29 wt% which decreases strongly at temperatures above 600 °C. The new catalyst supports are used for the preparation of PEMFC anodes which are characterized by polarization measurements and electrochemical impedance spectroscopy (EIS). Compared to unmodified graphene and CNT samples the electronic conductivity of the modified systems is increased by a factor of 2 and shows improved mass transport properties.

  12. The experimental studies on the carbon and nitrogen budgets of Pseudeuphausia sinica

    Institute of Scientific and Technical Information of China (English)

    Guo Donghui; Li Shaojing; Chen Feng; Wang Guizhong; Chen Gang

    2003-01-01

    The carbon and nitrogen budgets were estimated on the adult females, juveniles and postfurcilia larvae of Pseudeuphausia sinica fed on newly hatching nauplii of Artemia salina in the laboratory. It was found that the ingestion rate was linearly related to the food concentration, suggesting high feeding potential. The linear correlation could be established between the respirating rate (carbon consumption rate) and carbon ingestion rate, as well as carbon assimilation rate. The regression coefficients (i.e.specific dynamic action coefficients) were in the range from 9% to 16% (ingested C) or 10% to 17% (assimilated C) respectively, with lower in the post-furcilia larvae. There also existed a linear correlation equation between estimated total nitrogen excretion rate and the rates of nitrogen ingestion and assimilation separately, except for the juveniles. The defecation rates increased with the increase of the ingestion rate; as a result, assimilation efficiency was not related to the ingestion rate, ranging from 0.84 to 0.95. The results inducated that the nitrogen content in food particles was a key factor limiting the growth of P. sinica. The critical ingestion rate was 10 μgN@mg-1body dry weight per day. Assimilated N was lost mostly by excretion, following allocated to somatic growth. The nitrogen loss by moult only accounted for a minor part. As for carbon budget, respiration and somatic growth also accounted for most of assimilation, but varied with ingestion rates. Moult loss was minor. Estimated reproductive growth (C&N) in the adult females accounted for somewhat higher percent of assimilation than the moult growth. The net growth efficiency (K2) increased with the increase of the ingestion rates, but decreased slightly for juvenile and post-furcilia larvae after the rates up to a certain value.

  13. Inversion of coupled carbon-nitrogen model parameters against multiple datasets using Markov chain Monte Carlo methodology

    Science.gov (United States)

    Yang, Y.; Zhou, X.; Weng, E.; Luo, Y.

    2010-12-01

    The Markov chain Monte Carlo (MCMC) method has been widely used to estimate terrestrial ecosystem model parameters. However, inverse analysis is now mainly applied to estimate parameters involved in terrestrial ecosystem carbon models, and yet not used to inverse terrestrial nitrogen model parameters. In this study, the Bayesian probability inversion and MCMC technique were applied to inverse model parameters in a coupled carbon-nitrogen model, and then the trained ecosystem model was used to predict nitrogen pool sizes at the Duke Forests FACE site. We used datasets of soil respiration, nitrogen mineralization, nitrogen uptake, carbon and nitrogen pools in wood, foliage, litterfall, microbial, forest floor, and mineral soil under ambient and elevated CO2 plots from 1996-2005. Our results showed that, the initial values of C pools in leaf, wood, root, litter, microbial and forest floor were well constrained. The transfer coefficients from pools of leaf biomass, woody biomass, root biomass, litter, forest floor were also well constrained by the actual measurements. The observed datasets gave moderate information to the transfer coefficient from the slow soil carbon pool. The parameters in nitrogen parts, such as C: N in plant, litter, and soil were also well constrained. In addition, parameters about nitrogen dynamics (i.e. nitrogen uptake, nitrogen loss, and nitrogen input through biological fixation and deposition) were also well constrained. The predicted carbon and nitrogen pool sizes using the constrained ecosystem models were well consistent with the observed values. Overall, these results suggest that the MCMC inversion technique is an effective method to synthesize information from various sources for predicting the responses of ecosystem carbon and nitrogen cycling to elevated CO2.

  14. Potentiometric application of boron- and phosphorus-doped glassy carbon electrodes

    Directory of Open Access Journals (Sweden)

    ZORAN V. LAUSEVIC

    2001-03-01

    Full Text Available Acomparative study was carried out of the potentiometric application of boronand phosphorus-doped and undoped glassy carbon samples prepared at the same heat treatment temperature (HTT 1000°C. The electrochemical activities of the obtained electrode materials were investigated on the example of argentometric titrations. It was found that the electrochemical behaviour of the doped glassy carbon samples are very similar to a Sigri (undoped glassy carbon sample (HTT 2400°C. The experiments showed that the potentiometric response depends on the polarization mode, the nature of the sample, the pretreatment of the electrode surface, and the nature of the supporting electrolyte. The amounts of iodide, bromide, and of chloridewere determined to be 1.27 mg, 0.80 mg and 0.54 mg, respectively, with a maximum relative standard deviation of less than 1.1%. The obtained results are in good agreement with the results of comparative potentiometric titrations using a silver indicator electrode. The titrationmethod was applied to the indirect determination of pyridoxine hydrochloride, i.e., vitamin B6.

  15. Characterization of nitrogen doped silicon-carbon multi-layer nanostructures obtained by TVA method

    Science.gov (United States)

    Ciupina, Victor; Vasile, Eugeniu; Porosnicu, Corneliu; Prodan, Gabriel C.; Lungu, Cristian P.; Vladoiu, Rodica; Jepu, Ionut; Mandes, Aurelia; Dinca, Virginia; Caraiane, Aureliana; Nicolescu, Virginia; Dinca, Paul; Zaharia, Agripina

    2016-09-01

    Ionized nitrogen doped Si-C multi-layer thin films used to increase the oxidation resistance of carbon have been obtained by Thermionic Vacuum Arc (TVA) method. The 100 nm thickness carbon thin films were deposed on silicon or glass substrates and then seven N doped Si-C successively layers on carbon were deposed. To characterize the microstructure, tribological and electrical properties of as prepared N-SiC multi-layer films, Transmission Electron Microscopy (TEM, STEM), Energy Dispersive X-Ray Spectroscopy (EDXS), electrical and tribological techniques were achieved. Samples containing multi-layer N doped Si-C coating on carbon were investigated up to 1000°C. Oxidation protection is based on the reaction between SiC and elemental oxygen, resulting SiO2 and CO2, and also on the reaction involving N, O and Si-C, resulting silicon oxynitride (SiNxOy) with a continuously vary composition, and because nitrogen can acts as a trapping barrier for oxygen. The tribological properties of structures were studied using a tribometer with ball-on-disk configuration from CSM device with sapphire ball. The measurements show that the friction coefficient on the N-SiC is smaller than friction coefficient on uncoated carbon layer. Electrical conductivity at different temperatures was measured in constant current mode. The results confirm the fact that conductivity is greater when nitrogen content is greater. To justify the temperature dependence of conductivity we assume a thermally activated electrical transport mechanism.

  16. Corking Nitrogen-Doped Carbon Nanotube Cups with Gold Nanoparticles for Biodegradable Drug Delivery Applications.

    Science.gov (United States)

    Burkert, Seth C; Star, Alexander

    2015-12-02

    Carbon nanomaterials have been proposed as effective drug delivery devices; however their perceived biopersistence and toxicological profile may hinder their applications in medical therapeutics. Nitrogen doping of carbon nanotubes results in a unique "stacked-cup" structure, with cups held together through van der Waals forces. Disrupting these weak interactions yields individual and short-stacked nanocups that can subsequently be corked with gold nanoparticles, resulting in sealed containers for delivery of cargo. Peroxidase-catalyzed reactions can effectively uncork these containers, followed by complete degradation of the graphitic capsule, resulting in effective release of therapeutic cargo while minimizing harmful side effects. The protocols reported herein describe the synthesis of stacked nitrogen-doped carbon nanotube cups followed by effective separation into individual cups and gold nanoparticle cork formation resulting in loaded and sealed containers.

  17. COMPLEX COMPOST AND CIRCULATION OF NITROGEN AND CARBON AT THE AGROLANDSCAPE SYSTEMS

    Directory of Open Access Journals (Sweden)

    Belyuchenko I. S.

    2014-03-01

    Full Text Available Complex compost includes all elements of the periodic table and is valuable due to the complexity of its system. Among the elements forming a chemical composition of the complex compost we can identify two most important, which are distinguishing a specific character of the interaction with each other and defining the basic processes to ensure vegetation of living system - nitrogen and carbon. Nitrogen determines the rate of energy and connects with living forms of organic matter; it is included as the part of protein and is a major element in determining the productivity of ecosystems. At the cycle of carbon its organic forms and carbon dioxide take a part, presenting the main factors of the processes of respiration and photosynthesis

  18. Formation of complex Al-N-C layer in aluminium by successive carbon and nitrogen implantation

    Energy Technology Data Exchange (ETDEWEB)

    Uglov, V.V.; Cherenda, N.N. E-mail: info@research.bsu.unibel.by; Khodasevich, V.V.; Sokol, V.A.; Abramov, I.I.; Danilyuk, A.L.; Wenzel, A.; Gerlach, J.; Rauschenbach, B

    1999-01-01

    The results of Auger electron spectroscopy and transmission electron microscopy of the surface layer of aluminium after successive implantation by carbon and nitrogen ions are presented in this work. The energy of implanted ions is 40 keV. The implantation dose varies in the range (3.3-6.5)x10{sup 17} ions/cm{sup 2}. The findings show that successive implantation leads to the formation of two main layers in aluminium. The first layer is AlNC{sub x} (0carbon atoms form bonds with nitrogen atoms. The second layer contains disoriented Al{sub 4}C{sub 3} precipitates and carbon atoms migrated from the first layer. The mechanism of migration is discussed.

  19. Formation of complex Al-N-C layer in aluminium by successive carbon and nitrogen implantation

    Science.gov (United States)

    Uglov, V. V.; Cherenda, N. N.; Khodasevich, V. V.; Sokol, V. A.; Abramov, I. I.; Danilyuk, A. L.; Wenzel, A.; Gerlach, J.; Rauschenbach, B.

    1999-01-01

    The results of Auger electron spectroscopy and transmission electron microscopy of the surface layer of aluminium after successive implantation by carbon and nitrogen ions are presented in this work. The energy of implanted ions is 40 keV. The implantation dose varies in the range (3.3-6.5) × 10 17 ions/cm 2. The findings show that successive implantation leads to the formation of two main layers in aluminium. The first layer is AlNC x (0 < x < 0.5) layer with violated hcp. AlN structure, where carbon atoms form bonds with nitrogen atoms. The second layer contains disoriented Al 4C 3 precipitates and carbon atoms migrated from the first layer. The mechanism of migration is discussed.

  20. Investigation of carbon profiles for enhanced boron confinement and improved carrier transport in strained silicon germanium nanolayers for heterojunction bipolar transistors

    Science.gov (United States)

    Enicks, Darwin Gene

    This research covers a breadth of topics, in Chapters 1 through 7, ranging from the crystal lattice, to dopant diffusion in SiGe, to SiGe and SiGeC chemical vapor deposition, to the Si/SiGe and Si/SiGeC energy band structure, and NPN SiGeC HBT AC and DC characteristics. Chapters 8 and 9 contain the results of the research, which relates the film growth and carbon positioning to boron diffusion, sheet resistance, and device performance; specifically current gain, fmax, and noise figures of merit. The first objective of the dissertation was to investigate carbon doping profiles in nano-layers (≤32 nm) of silicon germanium (Si1-xGe x), and provide an understanding of "remote carbon boron confinement" (RCBC), which is demonstrated to exploit the advantages of carbon to increase NPN HBT (heterojunction bipolar transistor) performance, reduce base resistance, and improve overall noise figures of merit. The second objective was to investigate the noise characteristics of this method compared to the standard method of placing carbon throughout the lattice, which is known as "uniform carbon boron confinement" (UCBC). The current technological development towards smaller and faster devices has forced engineers and scientists to look into materials other than silicon, but which are highly compatible. A natural choice is the Si1-xGe x alloy, since Ge is also a Group IV. Si1-xGex has the same lattice structure as Si, but its lattice constant is 4.2% larger (aSi = 0.543nm, aGe = 0.567nm), and the bandgap is less than that of Si (Eg_Si = 1.11eV, Eg_Ge = 0.67eV). This opens the possibility of bandgap, strain, and dopant diffusion engineering, all of which affect the material and electronic properties of devices. The primary benefit of carbon is to reduce the diffusion of boron in Si1-xGex thus keeping the base narrow for significantly reduced electron transit times and increased unity gain cutoff frequencies (fT). However the utilization of carbon reduces base conductivity and

  1. Latitudinal distributions of organic nitrogen and organic carbon in marine aerosols over the western North Pacific

    Directory of Open Access Journals (Sweden)

    Y. Miyazaki

    2010-11-01

    Full Text Available Marine aerosol samples were collected over the western North Pacific along the latitudinal transect from 44° N to 10° N in late summer 2008 for measurements of organic nitrogen (ON and organic carbon (OC as well as isotopic ratios of total nitrogen (TN and total carbon (TC. Increased concentrations of methanesulfonic acid (MSA and diethylammonium (DEA+ at 40–44° N and subtropical regions (10–20° N together with averaged satellite chlorophyll a data and 5-day back trajectories suggest a significant influence of marine biological activities on aerosols in these regions. ON exhibited increased concentrations up to 260 ngN m−3 in these marine biologically influenced aerosols. Water-insoluble organic nitrogen (WION was found to be the most abundant nitrogen in the aerosols, accounting for 55 ± 16% of total aerosol nitrogen. In particular, the average WION/ON ratio was as high as 0.93 ± 0.07 at 40–44° N. These results suggest that marine biological sources significantly contributed to ON, a majority of which is composed of water-insoluble fractions in the study region. Analysis of the stable carbon isotopic ratios (δ13C indicated that, on average, marine-derived carbon accounted for ~88 ± 12% of total carbon in the aerosols. In addition, the δ13C increased from −22 to −20‰ when ON/OC ratios increased from 0.15 to 0.35 in marine biologically influenced aerosols. These results clearly show that organic nitrogen is enriched in organic aerosols originated from an oceanic region with high biological productivity, indicating a preferential transfer of nitrogen-containing organic compounds from the sea surface to the marine atmosphere. Both WION concentrations and WION/water-insoluble organic carbon (WIOC ratios showed positive correlations with local wind speeds, suggesting that sea-to-air emissions of ON via sea spray significantly contributes to marine organic aerosols over the

  2. Latitudinal distributions of organic nitrogen and organic carbon in marine aerosols over the western North Pacific

    Directory of Open Access Journals (Sweden)

    Y. Miyazaki

    2011-04-01

    Full Text Available Marine aerosol samples were collected over the western North Pacific along the latitudinal transect from 44° N to 10° N in late summer 2008 for measurements of organic nitrogen (ON and organic carbon (OC as well as isotopic ratios of total nitrogen (TN and total carbon (TC. Increased concentrations of methanesulfonic acid (MSA and diethylammonium (DEA+ at 40–44° N and subtropical regions (10–20° N together with averaged satellite chlorophyll-a data and 5-day back trajectories suggest a significant influence of marine biological activities on aerosols in these regions. ON exhibited increased concentrations up to 260 ngN m−3 in these marine biologically influenced aerosols. Water-insoluble organic nitrogen (WION was found to be the most abundant nitrogen in the aerosols, accounting for 55 ± 16% of total aerosol nitrogen. In particular, the average WION/ON ratio was as high as 0.93 ± 0.07 at 40–44° N. These results suggest that marine biological sources significantly contributed to ON, a majority of which is composed of water-insoluble fractions in the study region. Analysis of the stable carbon isotopic ratios (δ13C indicated that, on average, marine-derived carbon accounted for ~88 ± 12% of total carbon in the aerosols. In addition, the δ13C showed higher values (from −22 to −20‰ when ON/OC ratios increased from 0.15 to 0.35 in marine biologically influenced aerosols. These results clearly show that organic nitrogen is enriched in organic aerosols originated from an oceanic region with high biological productivity, indicating a preferential transfer of nitrogen-containing organic compounds from the sea surface to the marine atmosphere. Both WION concentrations and WION/water-insoluble organic carbon (WIOC ratios tended to increase with increasing local wind speeds, indicating that sea-to-air emissions of ON via sea spray contribute significantly to the marine organic

  3. Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration

    Science.gov (United States)

    Stacy, E. M.; Hart, S. C.; Hunsaker, C. T.; Johnson, D. W.; Berhe, A. A.

    2015-08-01

    Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual sediment composition and yield, for water years 2005-2011, from eight catchments in the southern part of the Sierra Nevada, California. Sediment was compared to soil at three different landform positions from the source slopes to determine if there is selective transport of organic matter or different mineral particle size classes. Sediment export varied from 0.4 to 177 kg ha-1, while export of C in sediment was between 0.025 and 4.2 kg C ha-1 and export of N in sediment was between 0.001 and 0.04 kg N ha-1. Sediment yield and composition showed high interannual variation. In our study catchments, erosion laterally mobilized OM-rich litter material and topsoil, some of which enters streams owing to the catchment topography where steep slopes border stream channels. Annual lateral sediment export was positively and strongly correlated with stream discharge, while C and N concentrations were both negatively correlated with stream discharge; hence, C : N ratios were not strongly correlated to sediment yield. Our results suggest that stream discharge, more than sediment source, is a primary factor controlling the magnitude of C and N export from upland forest catchments. The OM-rich nature of eroded sediment raises important questions about the fate of the eroded OM. If a large fraction of the soil organic matter (SOM) eroded from forest ecosystems is lost during transport or after deposition, the contribution of forest ecosystems to the erosion-induced C sink is likely to be small (compared to croplands and grasslands).

  4. Fast Conversion of Ionic Liquids and Poly(Ionic Liquids into Porous Nitrogen-Doped Carbons in Air

    Directory of Open Access Journals (Sweden)

    Yongjun Men

    2016-04-01

    Full Text Available Ionic liquids and poly(ionic liquids have been successfully converted into nitrogen-doped porous carbons with tunable surface area up to 1200 m2/g at high temperatures in air. Compared to conventional carbonization process conducted under inert gas to produce nitrogen-doped carbons, the new production method was completed in a rather shorter time without noble gas protection.

  5. Simultaneous removal of COD and nitrogen using a novel carbon-membrane aerated biofilm reactor

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A membrane aerated biofilm reactor is a promising technology for wastewater treatment. In this study, a carbon-membrane aerated biofilm reactor (CMABR) has been developed, to remove carbon organics and nitrogen simultaneously from one reactor. The results showed that CMABR has a high chemical oxygen demand (COD) and nitrogen removal efficiency, as it is operated with a hydraulic retention time (HRT) of 20 h, and it also showed a perfect performance, even if the HRT was shortened to 12 h. In this period, the removal efficiencies of COD, ammonia nitrogen (NH4+-N), and total nitrogen (TN) reached 86%, 94%, and 84%, respectively. However,the removal efficiencies of NH4+-N and TN declined rapidly as the HRT was shortened to 8 h. This is because of the excessive growth of biomass on the nonwoven fiber and very high organic loading rate. The fluorescence in situ hybridization (FISH) analysis indicated that the ammonia oxidizing bacteria (AOB) were mainly distributed in the inner layer of the biofilm. The coexistence of AOB and eubacteria in one biofilm can enhance the simultaneous removal of COD and nitrogen.

  6. PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

    Directory of Open Access Journals (Sweden)

    Y. Wu

    2013-03-01

    Full Text Available Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C and nitrogen (N cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1 daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2 competition among three plants functional types (PFTs, production and litter production of plants; (3 decomposition of peat; and (4 production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

  7. PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

    Science.gov (United States)

    Wu, Y.; Blodau, C.

    2013-08-01

    Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

  8. Carbon and Nitrogen Sources Influence Tricalcium Phosphate Solubilization and Extracellular Phosphatase Activity by Talaromyces flavus.

    Science.gov (United States)

    Stefanoni Rubio, P J; Godoy, M S; Della Mónica, I F; Pettinari, M J; Godeas, A M; Scervino, J M

    2016-01-01

    The aim of this work was to study phosphate (P) solubilization (and the processes involved in this event) by Talaromyces flavus (BAFC 3125) as a function of carbon and/or nitrogen sources. P solubilization was evaluated in NBRIP media supplemented with different carbon (glucose, sorbitol, sucrose, and fructose) and nitrogen (L-asparagine, urea, ammonium sulfate (AS), and ammonium nitrate (AN) combinations. The highest P solubilization was related to the highest organic acid production (especially gluconic acid) and pH drop for those treatments where glucose was present. Also P solubilization was higher when an inorganic nitrogen source was supplemented to the media when compared to an organic one. Although not being present an organic P source, phosphatase activity was observed. This shows that P mineralization and P solubilization can occur simultaneously, and that P mineralization is not induced by the enzyme substrate. The combination that showed highest P solubilization was for AN-glucose. The highest acid phosphatase activity was for AS-fructose, while for alkaline phosphatase were for AS-fructose and AN-fructose. Acid phosphatase activity was higher than alkaline. P solubilization and phosphatase activity (acid and alkaline) were influenced by the different carbon-nitrogen combinations. A better understanding of phosphate-solubilizing fungi could bring a better use of soil P.

  9. Functionalization of terminal carbon atoms of hydroxyl terminated polybutadiene by polyazido nitrogen rich molecules

    Indian Academy of Sciences (India)

    Rajavelu Murali Sankar; Tapta Kanchan Roy; Tushar Jana

    2011-07-01

    We report a novel synthetic approach for the attachment of the polyazido nitrogen rich molecule on to the hydroxyl terminated polybutadiene (HTPB) backbone. The terminal carbon atoms of the HTPB are functionalized by attaching cyanuric chloride (CYC) covalently on the HTPB backbone. Further reaction of this modified HTPB with sodium azide yields polyazido nitrogen rich HTPB. The unique physico-chemical properties and the microstructure of the HTPB do not get affected upon modification. IR, gel permeable chromatography (GPC) and absorption spectroscopy studies prove that the polyazido nitrogen rich molecules are covalently attached at the terminal carbon atoms of the HTPB. The π electron delocalization owing to long butadiene chain, strong electron withdrawing effect of the triazine molecules are the major driving forces for the covalent attachment of the triazine at the terminal carbon atoms of the HTPB. The disruption of the intermolecular hydrogen bonding between the terminal hydroxyl groups of the HTPB chains and the presence of hydrogen bonding between the N atoms of the triazine ring with OH group of the HTPB are observed. Theoretical study also reveals the existence of the hydrogen bonding between the OH and N. Theoretical calculation shows that the detonation performance of the polyazido nitrogen rich HTPB are very promising.

  10. The key role of metal dopants in nitrogen-doped carbon xerogel for oxygen reduction reaction

    Science.gov (United States)

    Liu, Sisi; Deng, Chengwei; Yao, Lan; Zhong, Hexiang; Zhang, Huamin

    2014-12-01

    Highly active non-precious metal catalysts based on nitrogen-doped carbon xerogel (NCX) for the oxygen reduction reaction (ORR) is prepared with resorcinol(R)-formaldehyde (F) resin as carbon precursor and NH3 as nitrogen source. NCX samples doped with various transition metal species are investigated to elucidate the effect of transition metals on the structure and ORR activity of the products. As-prepared NCX catalysts with different metals are characterized using nitrogen-adsorption analysis, X-ray diffractometry, X-ray photoelectron spectroscopy, and Raman spectroscopy. The structural properties and ORR activities of the catalysts are altered by addition of different metals, and NCX doped with iron exhibits the best ORR activity. Metal doping evidently promotes the formation of more micropores and mesopores. Raman and XPS studies reveal that iron, cobalt, and nickel can increase pyridinic-N contents and that iron can catalyse the formation of graphene structures and enhance quaternary-N contents. Whereas the total N-content does not determine ORR activity, Metal-N4/C-like species generated from the interaction of the metals with nitrogen and carbon atoms play important roles in achieving high ORR activity.

  11. Lithium and sodium storage in highly ordered mesoporous nitrogen-doped carbons derived from honey

    Science.gov (United States)

    Zhang, Yongzhi; Chen, Li; Meng, Yan; Xie, Jun; Guo, Yong; Xiao, Dan

    2016-12-01

    Honey, a widely existent biomass, consists mainly of carbohydrate and other nitrogen-containing substances such as proteins, enzymes and organic acids. It can be mixed homogeneously with mesoporous silica template for its excellent water-solubility and moderate viscosity. In this work, honey was employed as a nitrogen-containing carbon precursor to prepare nitrogen-doped ordered mesoporous carbons (OMCs). The obtained honey derived mesoporous nitrogen-doped carbons (HMNCs) with dilated interlayer spacings of 0.387-0.395 nm, narrow pore size distributions centering at around 4 nm and satisfactory N contents of 1.38-4.32 wt% offer superb dual functionality for lithium ion battery (LIB) and sodium ion battery (NIB) anodes. Tested against Li, the optimized HMNC-700 delivers a superior reversible capacity of 1359 mA h g-1 after 10 cycles at 100 mA g-1 and excellent rate capability and cycling stability of 722 mA h g-1 after 200 cycles at 1 A g-1. For NIB applications, HMNC-700 offers a high initial reversible capacity of 427 mA h g-1 and stable reversible capacity of 394 mA h g-1 at 100 mA g-1.

  12. Nitrogen Doped Macroporous Carbon as Electrode Materials for High Capacity of Supercapacitor

    Directory of Open Access Journals (Sweden)

    Yudong Li

    2017-01-01

    Full Text Available Nitrogen doped carbon materials as electrodes of supercapacitors have attracted abundant attention. Herein, we demonstrated a method to synthesize N-doped macroporous carbon materials (NMC with continuous channels and large size pores carbonized from polyaniline using multiporous silica beads as sacrificial templates to act as electrode materials in supercapacitors. By the nice carbonized process, i.e., pre-carbonization at 400 °C and then pyrolysis at 700/800/900/1000 °C, NMC replicas with high BET specific surface areas exhibit excellent stability and recyclability as well as superb capacitance behavior (~413 F ⋅ g−1 in alkaline electrolyte. This research may provide a method to synthesize macroporous materials with continuous channels and hierarchical pores to enhance the infiltration and mass transfer not only used as electrode, but also as catalyst somewhere micro- or mesopores do not work well.

  13. Crystallography, semiconductivity, thermoelectricity, and other properties of boron and its compounds, especially B6O

    Science.gov (United States)

    Slack, G. A.; Morgan, K. E.

    2015-09-01

    Electron deficient and non-deficient boron compounds are discussed as potential thermoelectric generator materials. Particular attention is paid to carbon-doped beta-boron, high-carbon boron carbide, and the alpha-boron derivative compound boron suboxide. Stoichiometric B6O shows some promise, and may have a higher ZT than the other two compounds. Carbon saturated beta-boron appears to have a higher ZT than undoped samples. Carbon saturated boron carbide at B12C3 does exist. Its thermoelectric behavior is unknown.

  14. Boronated mesophase pitch coke for lithium insertion

    Science.gov (United States)

    Frackowiak, E.; Machnikowski, J.; Kaczmarska, H.; Béguin, F.

    Boronated carbons from mesophase pitch have been used as materials for lithium storage in Li/carbon cells. Doping by boron has been realized by co-pyrolysis of coal tar pitch with the pyridine-borane complex. Amount of boron in mesocarbon microbeads (MCMB) varied from 1.4 to 1.8 wt.% affecting the texture of carbon. Optical microscopy and X-ray diffractograms have shown tendency to more disordered structure for boron-doped carbon. The values of specific reversible capacity ( x) varied from 0.7 to 1.1 depending significantly on the final temperature of pyrolysis (700-1150°C). The optimal charge/discharge performance was observed for boronated carbon heated at 1000°C.

  15. Nitrogen input effectiveness on carbon sequestration in rainfed cropping system

    Science.gov (United States)

    Novara, Agata; Gristina, Luciano; Poma, Ignazio

    2016-04-01

    The combined effect of total N and C/N ratio had a large influence on the decomposition rate and consequently on potential soil organic carbon sequestration. The aim of the work was to evaluate Carbon sequestration potentiality under three mineral N fertilization levels in interaction with two cropping systems characterized by addition of N input due to leguminous species in the rotation. The study was carried out in the semiarid Mediterranean environment in a 18years long-term experiment. Is well know that in the semiarid environment the excess of N fertilization reduces biomass yield and the consequent C input. On the contrary, both N and C input determine high difference in C/N input ratio and faster organic matter mineralization. Results showed no influence of N fertilization on SOC sequestration and a reduction of SOC stock due to crop rotation due to lower C input. Crop residue quality of durum wheat-pea crop rotation characterized by a faster decomposition rate could explain the lower ability of crop rotation to sequester C in the semiarid environment.

  16. Comparative genomic analysis of carbon and nitrogen assimilation mechanisms in three indigenous bioleaching bacteria: predictions and validations

    Directory of Open Access Journals (Sweden)

    Ehrenfeld Nicole

    2008-12-01

    Full Text Available Abstract Background Carbon and nitrogen fixation are essential pathways for autotrophic bacteria living in extreme environments. These bacteria can use carbon dioxide directly from the air as their sole carbon source and can use different sources of nitrogen such as ammonia, nitrate, nitrite, or even nitrogen from the air. To have a better understanding of how these processes occur and to determine how we can make them more efficient, a comparative genomic analysis of three bioleaching bacteria isolated from mine sites in Chile was performed. This study demonstrated that there are important differences in the carbon dioxide and nitrogen fixation mechanisms among bioleaching bacteria that coexist in mining environments. Results In this study, we probed that both Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans incorporate CO2 via the Calvin-Benson-Bassham cycle; however, the former bacterium has two copies of the Rubisco type I gene whereas the latter has only one copy. In contrast, we demonstrated that Leptospirillum ferriphilum utilizes the reductive tricarboxylic acid cycle for carbon fixation. Although all the species analyzed in our study can incorporate ammonia by an ammonia transporter, we demonstrated that Acidithiobacillus thiooxidans could also assimilate nitrate and nitrite but only Acidithiobacillus ferrooxidans could fix nitrogen directly from the air. Conclusion The current study utilized genomic and molecular evidence to verify carbon and nitrogen fixation mechanisms for three bioleaching bacteria and provided an analysis of the potential regulatory pathways and functional networks that control carbon and nitrogen fixation in these microorganisms.

  17. Increased forest carbon storage with increased atmospheric CO2 despite nitrogen limitation: a game-theoretic allocation model for trees in competition for nitrogen and light.

    Science.gov (United States)

    Dybzinski, Ray; Farrior, Caroline E; Pacala, Stephen W

    2015-03-01

    Changes in resource availability often cause competitively driven changes in tree allocation to foliage, wood, and fine roots, either via plastic changes within individuals or through turnover of individuals with differing strategies. Here, we investigate how optimally competitive tree allocation should change in response to elevated atmospheric CO2 along a gradient of nitrogen and light availability, together with how those changes should affect carbon storage in living biomass. We present a physiologically-based forest model that includes the primary functions of wood and nitrogen. From a tree's perspective, wood is an offensive and defensive weapon used against neighbors in competition for light. From a biogeochemical perspective, wood is the primary living reservoir of stored carbon. Nitrogen constitutes a tree's photosynthetic machinery and the support systems for that machinery, and its limited availability thus reduces a tree's ability to fix carbon. This model has been previously successful in predicting allocation to foliage, wood, and fine roots along natural productivity gradients. Using game theory, we solve the model for competitively optimal foliage, wood, and fine root allocation strategies for trees in competition for nitrogen and light as a function of CO2 and nitrogen mineralization rate. Instead of down-regulating under nitrogen limitation, carbon storage under elevated CO2 relative to carbon storage at ambient CO2 is approximately independent of the nitrogen mineralization rate. This surprising prediction is a consequence of both increased competition for nitrogen driving increased fine root biomass and increased competition for light driving increased allocation to wood under elevated CO2 .

  18. Adsorption behaviors of methyl orange dye on nitrogen-doped mesoporous carbon materials.

    Science.gov (United States)

    Li, He; An, Nihong; Liu, Gang; Li, Jialu; Liu, Na; Jia, Mingjun; Zhang, Wenxiang; Yuan, Xiaoling

    2016-03-15

    A series of nitrogen-doped mesoporous carbon materials (NMC) with different nitrogen contents (from 9.1 to 11.3 wt.%) were prepared using urea and ammonia as economical nitrogen resources by sol-gel method. The NMC materials possessed high surface areas (from 659 m(2)/g to 912 m(2)/g) as well as large number of oxygen-containing and nitrogen-containing groups. The adsorption behaviors of NMC materials for anionic dye methyl orange (MO) were investigated, which are fit excellent for the Langmuir isothermal adsorption equation. All the materials exhibited high adsorption capacity for MO at room temperature. Their adsorption capacity can be adjusted by changing the nitrogen contents in NMC materials. Moreover, treating the NMC material at higher temperature can significantly improve the adsorption capacity for MO. According to the results of characterization, the main features of NMC materials, like large pore size and abundant basic nitrogen-containing groups on the surface, should be related to the excellent adsorption property for MO.

  19. Nitrogen accumulation tracks carbon in multispecies system under elevated CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, H.B.; Polley, H.W.; Mayeux, H.S. [USDA-ARS, Temple, TX (United States)

    1995-09-01

    The woody legume Acacia smallii (huisache), and two perennial grasses, Schizachyrium scoparium (little bluestem) and Stipa leucotricha (Texas wintergrass) were grown as monocultures and in mixture under CO{sub 2} concentrations of 370, 700, and 1000 {mu}L/L for more than two years. The fine sandy loam soil was unfertilized, enriched in N15, and inoculated with huisache rhizobia. Elevated CO{sub 2} stimulated nitrogen fixation by huisache. After one year 33%, 64% and 76% of foliar N in the woody legume was ascribable to nitrogen fixation in the 370, 700 and 1000 {mu}L/L treatments, respectively. Percent nitrogen content of shoots decreased as CO{sub 2} increased (28% in 700 {mu}L/L and 34% 1000 {mu}L/L) relative to 370 {mu}L/L but the total nitrogen/plant increased 74% and 108% for these same concentrations due to greater plant biomass produced in the elevated CO{sub 2}. In the grass mixtures atmospheric nitrogen fixed by the wintergrass from mixtures was reduced relative to monocultures while the %N concentration was increased. These results suggest that a positive feedback between elevated CO{sub 2} and nitrogen accumulation may exist in multispecies systems containing legumes which can enhance the response of terrestrial carbon fixation to rising CO{sub 2}.

  20. Effects of nitrogen and carbon sources on the production of inulinase from strain Bacillus sp. SG113

    Science.gov (United States)

    Gavrailov, Simeon; Ivanova, Viara

    2016-03-01

    The effects of the carbon and nitrogen substrates on the growth of Bacillus sp. SG113 strain were studied. The use of organic nitrogen sources (peptone, beef extract, yeast extract, casein) leads to rapid cellular growth and the best results for the Bacillus strain were obtained with casein hydrolysate. From the inorganic nitrogen sources studied, the (NH4) 2SO4 proved to be the best nitrogen source. Casein hydrolysate and (NH4) 2SO4 stimulated the invertase synthesis. In the presence of Jerusalem artichoke, onion and garlic extracts as carbon sources the strain synthesized from 6 to 10 times more inulinase.

  1. Boronic acid functionalized N-doped carbon quantum dots as fluorescent probe for selective and sensitive glucose determination

    Science.gov (United States)

    Jiang, Guohua; Jiang, Tengteng; Li, Xia; Wei, Zheng; Du, Xiangxiang; Wang, Xiaohong

    2014-04-01

    Nitrogen doped carbon quantum dots (NCQDs) of about 10 nm in diameter have been obtained by hydrothermal reaction from collagen. Because of the superiority of water dispersion, low toxicity and ease of functionlization, the NCQDs were designed as a glucose sensor after covalent grafting by 3-aminophenylboronic (APBA) (APBA-NCQDs). The as-prepared APBA-NCQDs were imparted with glucose sensitivity and selectivity from other saccharides via fluorescence (FL) quenching effect at physiological pH and at room temperature, which show high sensitivity and specificity for glucose determination with a wide range from 1 mM to 14 mM. FL quenching mechanism of APBA-NCQDs was also investigated by adding an external quencher. The APBA-NCQDs-based platform is an environmentally friendly way to substitute inorganic quantum dots containing heavy metals which offer a facile and low cost detection method.

  2. Enhancement of oxygen reduction activity of nanoshell carbons by introducing nitrogen atoms from metal phthalocyanines

    Energy Technology Data Exchange (ETDEWEB)

    Ozaki, Jun-ichi, E-mail: jozaki@cee.gunma-u.ac.j [Department of Chemical and Environmental Engineering, Graduate School of Engineering, Gunma University, 1-5-1, Tenjin-cho, Kiryu, Gunma 376-8515 (Japan); Tanifuji, Shin-ichi; Furuichi, Atsuya; Yabutsuka, Katsutoshi [Department of Chemical and Environmental Engineering, Graduate School of Engineering, Gunma University, 1-5-1, Tenjin-cho, Kiryu, Gunma 376-8515 (Japan)

    2010-02-15

    Nanoshell carbon is a type of catalytically grown nanocarbon with a hollow, round, shell-like structure, with a diameter in the range of approximately 20-50 nm. It has been shown to possess the electrocatalytic activity for oxygen reduction reaction (ORR) and is also expected to be a non-Pt catalyst for polymer electrolyte fuel cells. This paper reports the synergetic enhancement of the ORR activity of nanoshell carbons caused by the coexistence of nitrogen atoms. The nanoshell carbons were prepared by the carbonization of furan resin in the presence of acetylacetonates (AAs) and of phthalocyanines (Pcs), which contained Fe, Co, and Ni. The Pc-derived nanoshells (MP-T series; M = Co or Fe, T = carbonization temperature) showed higher ORR activities than the AA-derived nanoshells (MA-T series; M = Co or Fe, T = carbonization temperature) when the same metal elements were employed. An XPS study revealed that nitrogen species were introduced to the surface of the nanoshells when Pcs were used as the nanoshell-forming catalysts, and that no metal species remained on the nanoshells. Principally, the ORR activity of the carbons was governed by the presence of the nanoshells and further enhancement could be achieved by the introduction of nitrogen atoms. 0.78 V of OCV and 0.21 W cm{sup -2} of the maximum power density were observed for a fuel cell whose MEA consisted of 3CoP1000 cathode and a commercial Pt/C anode, when it was operated at 80 deg. C under a pressurized condition of 0.35 MPa.

  3. Nitrogen reduction pathways in estuarine sediments: Influences of organic carbon and sulfide

    Science.gov (United States)

    Plummer, Patrick; Tobias, Craig; Cady, David

    2015-10-01

    Potential rates of sediment denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were mapped across the entire Niantic River Estuary, CT, USA, at 100-200 m scale resolution consisting of 60 stations. On the estuary scale, denitrification accounted for ~ 90% of the nitrogen reduction, followed by DNRA and anammox. However, the relative importance of these reactions to each other was not evenly distributed through the estuary. A Nitrogen Retention Index (NIRI) was calculated from the rate data (DNRA/(denitrification + anammox)) as a metric to assess the relative amounts of reactive nitrogen being recycled versus retained in the sediments following reduction. The distribution of rates and accompanying sediment geochemical analytes suggested variable controls on specific reactions, and on the NIRI, depending on position in the estuary and that these controls were linked to organic carbon abundance, organic carbon source, and pore water sulfide concentration. The relationship between NIRI and organic carbon abundance was dependent on organic carbon source. Sulfide proved the single best predictor of NIRI, accounting for 44% of its observed variance throughout the whole estuary. We suggest that as a single metric, sulfide may have utility as a proxy for gauging the distribution of denitrification, anammox, and DNRA.

  4. Hierarchical porous nitrogen-doped partial graphitized carbon monoliths for supercapacitor

    Science.gov (United States)

    Yu, Yifeng; Du, Juan; Liu, Lei; Wang, Guoxu; Zhang, Hongliang; Chen, Aibing

    2017-03-01

    Porous carbon monoliths have attracted great interest in many fields due to their easy availability, large specific surface area, desirable electronic conductivity, and tunable pore structure. In this work, hierarchical porous nitrogen-doped partial graphitized carbon monoliths (N-MC-Fe) with ordered mesoporous have been successfully synthesized by using resorcinol-formaldehyde as precursors, iron salts as catalyst, and mixed triblock copolymers as templates via a one-step hydrothermal method. In the reactant system, hexamethylenetetramine (HMT) is used as nitrogen source and one of the carbon precursors under hydrothermal conditions instead of using toxic formaldehyde. The N-MC-Fe show hierarchically porous structures, with interconnected macroporous and ordered hexagonally arranged mesoporous. Nitrogen element is in situ doped into carbon through decomposition of HMT. Iron catalyst is helpful to improve the graphitization degree and pore volume of N-MC-Fe. The synthesis strategy is user-friendly, cost-effective, and can be easily scaled up for production. As supercapacitors, the N-MC-Fe show good capacity with high specific capacitance and good electrochemical stability.

  5. Albumin and fibrinogen adsorption on boron nitride and carbon-based thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lousinian, S.; Kalfagiannis, N. [Laboratory for Thin Films - Nanosystems and Nanometrology (LTFN), Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Logothetidis, S. [Laboratory for Thin Films - Nanosystems and Nanometrology (LTFN), Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece)], E-mail: logot@auth.gr

    2008-08-25

    The haemocompatibility (in the sense of the least possibility of thrombus formation/thrombogenicity potential) of homogeneous and amorphous BN (a-BN) thin films through the adsorption of two basic blood plasma proteins, human serum albumin (HSA) and fibrinogen (Fib) is explored in this work. A comparative study of the thrombogenicity potential of BN, amorphous carbon (a-C) and amorphous hydrogenated carbon thin films (a-C:H) is also presented. a-BN and a-C thin films were produced by radio frequency (RF) magnetron sputtering onto c-Si (1 0 0) substrates under various values of substrate bias voltage. a-C:H thin films were developed by RF Reactive MS, with various values of substrate bias voltage and under different values of H{sub 2} partial pressure during deposition. For the consideration of the optical, compositional and structural properties of the films Spectroscopic Ellipsometry in the energy region of 1.5-6.5 eV was used, while for the study of surface topography and wetting properties Atomic Force Microscopy and Contact Angle measurements were additionally employed. The properties of the thin films were correlated with their thrombogenicity, through the estimation of the ratio of HSA/Fib surface concentration. a-BN films exhibit the smallest possibility of clot formation, with their wetting properties determining the thickness of the Fib layer formed on them as well as the ratio of HSA/Fib surface concentration. In the case of a-C thin films, the increase of % sp{sup 3} content is crucial, while the value of the fundamental gap seems to influence the possibility for clot formation on a-C:H thin films.

  6. Integration of Carbon, Nitrogen, and Oxygen Metabolism in Escherichia coli--Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Rabinowitz, Joshua D; Wingreen, Ned s; Rabitz, Herschel A; Xu, Yifan

    2012-10-22

    A key challenge for living systems is balancing utilization of multiple elemental nutrients, such as carbon, nitrogen, and oxygen, whose availability is subject to environmental fluctuations. As growth can be limited by the scarcity of any one nutrient, the rate at which each nutrient is assimilated must be sensitive not only to its own availability, but also to that of other nutrients. Remarkably, across diverse nutrient conditions, E. coli grows nearly optimally, balancing effectively the conversion of carbon into energy versus biomass. To investigate the link between the metabolism of different nutrients, we quantified metabolic responses to nutrient perturbations using LC-MS based metabolomics and built differential equation models that bridge multiple nutrient systems. We discovered that the carbonaceous substrate of nitrogen assimilation, -ketoglutarate, directly inhibits glucose uptake and that the upstream glycolytic metabolite, fructose-1,6-bisphosphate, ultrasensitively regulates anaplerosis to allow rapid adaptation to changing carbon availability. We also showed that NADH controls the metabolic response to changing oxygen levels. Our findings support a general mechanism for nutrient integration: limitation for a nutrient other than carbon leads to build-up of the most closely related product of carbon metabolism, which in turn feedback inhibits further carbon uptake.

  7. QQS orphan gene regulates carbon and nitrogen partitioning across species via NF-YC interactions.

    Science.gov (United States)

    Li, Ling; Zheng, Wenguang; Zhu, Yanbing; Ye, Huaxun; Tang, Buyun; Arendsee, Zebulun W; Jones, Dallas; Li, Ruoran; Ortiz, Diego; Zhao, Xuefeng; Du, Chuanlong; Nettleton, Dan; Scott, M Paul; Salas-Fernandez, Maria G; Yin, Yanhai; Wurtele, Eve Syrkin

    2015-11-24

    The allocation of carbon and nitrogen resources to the synthesis of plant proteins, carbohydrates, and lipids is complex and under the control of many genes; much remains to be understood about this process. QQS (Qua-Quine Starch; At3g30720), an orphan gene unique to Arabidopsis thaliana, regulates metabolic processes affecting carbon and nitrogen partitioning among proteins and carbohydrates, modulating leaf and seed composition in Arabidopsis and soybean. Here the universality of QQS function in modulating carbon and nitrogen allocation is exemplified by a series of transgenic experiments. We show that ectopic expression of QQS increases soybean protein independent of the genetic background and original protein content of the cultivar. Furthermore, transgenic QQS expression increases the protein content of maize, a C4 species (a species that uses 4-carbon photosynthesis), and rice, a protein-poor agronomic crop, both highly divergent from Arabidopsis. We determine that QQS protein binds to the transcriptional regulator AtNF-YC4 (Arabidopsis nuclear factor Y, subunit C4). Overexpression of AtNF-YC4 in Arabidopsis mimics the QQS-overexpression phenotype, increasing protein and decreasing starch levels. NF-YC, a component of the NF-Y complex, is conserved across eukaryotes. The NF-YC4 homologs of soybean, rice, and maize also bind to QQS, which provides an explanation of how QQS can act in species where it does not occur endogenously. These findings are, to our knowledge, the first insight into the mechanism of action of QQS in modulating carbon and nitrogen allocation across species. They have major implications for the emergence and function of orphan genes, and identify a nontransgenic strategy for modulating protein levels in crop species, a trait of great agronomic significance.

  8. Carbon and nitrogen isotope systematics in diamond: Different sensitivities to isotopic fractionation or a decoupled origin?

    Science.gov (United States)

    Hogberg, K.; Stachel, T.; Stern, R. A.

    2016-11-01

    Using stable isotope data obtained on multiple aliquots of diamonds from worldwide sources, it has been argued that carbon and nitrogen in diamond are decoupled. Here we re-investigate the carbon-nitrogen relationship based on the most comprehensive microbeam data set to date of stable isotopes and nitrogen concentrations in diamonds (n = 94) from a single locality. Our diamond samples, derived from two kimberlites in the Chidliak Field (NE Canada), show large variability in δ13C (- 28.4 ‰ to - 1.1‰, mode at - 5.8‰), δ15N (- 5.8 to + 18.8‰, mode at - 3.0‰) and nitrogen contents ([N]; 3800 to less than 1 at.ppm). In combination, cathodoluminescence imaging and microbeam analyses reveal that the diamonds grew from multiple fluid pulses, with at least one major hiatus documented in some samples that was associated with a resorption event and an abrupt change from low δ13C and [N] to mantle-like δ13C and high [N]. Overall, δ13C appears to be uncorrelated to δ15N and [N] on both the inter- and intra-diamond levels. Co-variations of δ15N-log[N], however, result in at least two parallel, negatively correlated linear arrays, which are also present on the level of the individual diamonds falling on these two trends. These arrays emerge from the two principal data clusters, are characterized by slightly negative and slightly positive δ15N (about - 3 and + 2‰, respectively) and variable but overall high [N]. Using published values for the diamond-fluid nitrogen isotope fractionation factor and nitrogen partition coefficient, these trends are perfectly reproduced by a Rayleigh fractionation model. Overall, three key elements are identified in the formation of the diamond suite studied: (1.) a low δ13C and low [N] component that possibly is directly associated with an eclogitic diamond substrate or introduced during an early stage fluid event. (2.) Repeated influx of a variably nitrogen-rich mantle fluid (mildly negative δ13C and δ15N). (3.) In waning

  9. Enhanced Fuel Cell Catalyst Durability with Nitrogen Modified Carbon Supports

    Science.gov (United States)

    2013-02-12

    1000 mg of commercially available carbon powder (Cabot Vulcan XCR72R) was placed into the barrel and the chamber was evacuated to approximately 1 × 10−6...unmodified and N-modified Vulcan were obtained on a Philips CM200 TEM. X-ray Photoelectron Spectroscopy (XPS) analysis of the synthesized catalysts was done...durability cycles Pt-Ru/ Vulcan 73 3.3 × 10−5 24 51 10 Pt-Ru/N- Vulcan 55 2.9 × 10−5 17 60 40 Pt-Ru/C JM 5000 69 3.0 × 10−5 20 48 17 tials higher than 0.7 V

  10. Variation in Foliar Nitrogen and Albedo in Response to Elevated Nitrogen and Carbon Dioxide

    Science.gov (United States)

    Wicklein, H. F.; Ollinger, S. V.; Martin, M. M.; Hollinger, D. Y.; Bartlett, M. K.; Richardson, A. D.

    2010-12-01

    It has recently been demonstrated that foliar nitrogen (N) is positively correlated with midsummer canopy albedo over a broad range of plant functional types. However, the mechanism(s) driving the N- albedo relationship remain elusive, and it is unknown whether factors affecting N availability will also influence albedo. To address these questions, we investigated leaf spectral properties from three deciduous broadleaf species subjected to either N (Harvard Forest, MA and Oak Ridge, TN) or CO2 fertilization (Oak Ridge, TN), and compared results to measured chemical and structural properties. We measured reflectance and transmittance along with foliar N, leaf mass per unit area, and water content for stacks of 1, 2, 4, and 8 leaves. For the Oak Ridge, TN site, we also obtained canopy reflectance data from the airborne visible / infrared imaging spectrometer (AVIRIS) to examine whether canopy level spectral responses were consistent with leaf-level results. At the leaf level, results showed no significant differences in reflectance or transmittance between CO2 or N treatments, despite changes in N concentration caused by N fertilization. Although foliar N was significantly correlated with leaf shortwave and near infrared reflectance across species, the slope of both relationships was negative, which ran counter to our expectations. These results do not support the hypothesis that the canopy-level pattern is driven by leaf-level relationships. In contrast to leaf-level observations, remote sensing data from Oak Ridge did indicate an increase in NIR reflectance with N fertilization. Collectively, these results suggest that altered N availability may have an effect on canopy albedo, albeit by mechanisms that involve stem or canopy level processes rather than changes in leaf structure.

  11. Improved Electrochemical Performance of LiFePO4@N-Doped Carbon Nanocomposites Using Polybenzoxazine as Nitrogen and Carbon Sources.

    Science.gov (United States)

    Wang, Ping; Zhang, Geng; Li, Zhichen; Sheng, Wangjian; Zhang, Yichi; Gu, Jiangjiang; Zheng, Xinsheng; Cao, Feifei

    2016-10-03

    Polybenzoxazine is used as a novel carbon and nitrogen source for coating LiFePO4 to obtain LiFePO4@nitrogen-doped carbon (LFP@NC) nanocomposites. The nitrogen-doped graphene-like carbon that is in situ coated on nanometer-sized LiFePO4 particles can effectively enhance the electrical conductivity and provide fast Li(+) transport paths. When used as a cathode material for lithium-ion batteries, the LFP@NC nanocomposite (88.4 wt % of LiFePO4) exhibits a favorable rate performance and stable cycling performance.

  12. Synthesis and electrochemical capacitive properties of nitrogen-doped porous carbon micropolyhedra by direct carbonization of zeolitic imidazolate framework-11

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Fei; Li, Li; Zhang, Xiaohua, E-mail: mickyxie@hnu.edu.cn; Chen, Jinhua, E-mail: chenjinhua@hnu.edu.cn

    2015-06-15

    Highlights: • Nitrogen-doped porous carbon micropolyhedra (N-PCMPs) were prepared from ZIF-11. • The activated N-PCMPs with fused KOH (N-PCMPs-A) have high specific surface area. • N-PCMPs-A exhibits high specific capacitance. • N-PCMPs-A reveals good cycling performance even at a high current density. - Abstract: Nitrogen-doped porous carbon micropolyhedra (N-PCMPs) were successfully prepared by direct carbonization of ZIF-11 polyhedra and further activated with fused KOH to obtain N-PCMPs-A. The morphology and microstructure of samples were examined by scanning electron microscopy, X-ray diffraction, and micropore and chemisorption analyzer. Electrochemical properties were characterized by cyclic voltammetry and galvanostatic charge/discharge method in 1.0 M H{sub 2}SO{sub 4} aqueous solution on a standard three-electrode system. Results show that, compared with N-PCMPs, N-PCMPs-A has higher specific surface area (2188 m{sup 2} g{sup −1}) and exhibits improved electrochemical capacitive properties (307 F g{sup −1} at 1.0 A g{sup −1}). The mass specific capacitance of N-PCMPs-A is also higher than that of most MOF-derived carbons, some carbide-derived carbons and carbon aerogel-derived carbons. In addition, the capacitance of the N-PCMPs-A retains 90% after 4000 cycles even at a high current density of 10 A g{sup −1}. These imply that N-PCMPs-A is the promising materials for the construction of a high-performance supercapacitor.

  13. Nitrogen deposition: how important is it for global terrestrial carbon uptake?

    Directory of Open Access Journals (Sweden)

    G. Bala

    2013-07-01

    Full Text Available Global carbon budget studies indicate that the terrestrial ecosystems have remained a~large sink for carbon despite widespread deforestation activities. CO2-fertilization, N deposition and re-growth of mid-latitude forests are believed to be key drivers for land carbon uptake. In this study, we assess the importance of N deposition by performing idealized near-equilibrium simulations using the Community Land Model 4.0 (CLM4. In our equilibrium simulations, only 12–17% of the deposited Nitrogen is assimilated into the ecosystem and the corresponding carbon uptake can be inferred from a C : N ratio of 20:1. We calculate the sensitivity of the terrestrial biosphere for CO2-fertilization, climate warming and N deposition as changes in total ecosystem carbon for unit changes in global mean atmospheric CO2 concentration, global mean temperature and Tera grams of Nitrogen deposition per year, respectively. Based on these sensitivities, it is estimated that about 242 PgC could have been taken up by land due to the CO2 fertilization effect and an additional 175 PgC taken up as a result of the increased N deposition since the pre-industrial period. Because of climate warming, terrestrial ecosystem could have lost about 152 PgC during the same period. Therefore, since preindustrial times terrestrial carbon losses due to warming may have been approximately compensated by effects of increased N deposition, whereas the effect of CO2-fertilization is approximately indicative of the current increase in terrestrial carbon stock. Our simulations also suggest that the sensitivity of carbon storage to increased N deposition decreases beyond current levels, indicating climate warming effects on carbon storage may overwhelm N deposition effects in the future.

  14. Nitrogen deposition: how important is it for global terrestrial carbon uptake?

    Science.gov (United States)

    Bala, G.; Devaraju, N.; Chaturvedi, R. K.; Caldeira, K.; Nemani, R.

    2013-11-01

    Global carbon budget studies indicate that the terrestrial ecosystems have remained a large sink for carbon despite widespread deforestation activities. CO2 fertilization, N deposition and re-growth of mid-latitude forests are believed to be key drivers for land carbon uptake. In this study, we assess the importance of N deposition by performing idealized near-equilibrium simulations using the Community Land Model 4.0 (CLM4). In our equilibrium simulations, only 12-17% of the deposited nitrogen is assimilated into the ecosystem and the corresponding carbon uptake can be inferred from a C : N ratio of 20 : 1. We calculate the sensitivity of the terrestrial biosphere for CO2 fertilization, climate warming and N deposition as changes in total ecosystem carbon for unit changes in global mean atmospheric CO2 concentration, global mean temperature and Tera grams of nitrogen deposition per year, respectively. Based on these sensitivities, it is estimated that about 242 PgC could have been taken up by land due to the CO2 fertilization effect and an additional 175 PgC taken up as a result of the increased N deposition since the pre-industrial period. Because of climate warming, the terrestrial ecosystem could have lost about 152 PgC during the same period. Therefore, since pre-industrial times terrestrial carbon losses due to warming may have been more or less compensated by effects of increased N deposition, whereas the effect of CO2 fertilization is approximately indicative of the current increase in terrestrial carbon stock. Our simulations also suggest that the sensitivity of carbon storage to increased N deposition decreases beyond current levels, indicating that climate warming effects on carbon storage may overwhelm N deposition effects in the future.

  15. Tracking Nonpoint Source Nitrogen and Carbon in Watersheds of Chesapeake Bay

    Science.gov (United States)

    Kaushal, S.; Pennino, M. J.; Duan, S.; Blomquist, J.

    2012-12-01

    Humans have altered nitrogen and carbon cycles in rivers regionally with important impacts on coastal ecosystems. Nonpoint source nitrogen pollution is a leading contributor to coastal eutrophication and hypoxia. Shifts in sources of carbon impact downstream ecosystem metabolism and fate and transport of contaminants in coastal zones. We used a combination of stable isotopes and optical tracers to investigate fate and transport of nitrogen and carbon sources in tributaries of the largest estuary in the U.S., the Chesapeake Bay. We analyzed isotopic composition of water samples from major tributaries including the Potomac River, Susquehanna River, Patuxent River, and Choptank River during routine and storm event sampling over multiple years. A positive correlation between δ15N-NO3- and δ18O-NO3- in the Potomac River above Washington D.C. suggested denitrification or biological uptake in the watershed was removing agriculturally-derived N during summer months. In contrast, the Patuxent River in Maryland showed elevated δ15N-NO3- (5 - 12 per mil) with no relationship to δ18O-NO3- suggesting the importance of wastewater sources. From the perspective of carbon sources, there were distinct isotopic values of the δ13C-POM of particulate organic matter and fluorescence excitation emission matrices (EEMS) for rivers influenced by their dominant watershed land use. EEMS showed that there were increases in the humic and fulvic fractions of dissolved organic matter during spring floods, particularly in the Potomac River. Stable isotopic values of δ13C-POM also showed rapid depletion suggesting terrestrial carbon "pulses" in the Potomac River each spring. The δ15N-POM peaked to 10 - 15 per mil each spring suggested a potential manure source or result of biological processing within the watershed. Overall, there were considerable changes in sources and transformations of nitrogen and carbon that varied across rivers and that contribute to nitrogen and carbon loads

  16. Effect of powdered activated carbon technology on short-cut nitrogen removal for coal gasification wastewater.

    Science.gov (United States)

    Zhao, Qian; Han, Hongjun; Xu, Chunyan; Zhuang, Haifeng; Fang, Fang; Zhang, Linghan

    2013-08-01

    A combined process consisting of a powdered activated carbon technology (PACT) and short-cut biological nitrogen removal reactor (SBNR) was developed to enhance the removal efficiency of the total nitrogen (TN) from the effluent of an upflow anaerobic sludge bed (UASB) reactor, which was used to treat coal gasification wastewater (CGW). The SBNR performance was improved with the increasing of COD and TP removal efficiency via PACT. The average removal efficiencies of COD and TP in PACT were respectively 85.80% and 90.30%. Meanwhile, the NH3-N to NO2-N conversion rate was achieved 86.89% in SBNR and the total nitrogen (TN) removal efficiency was 75.54%. In contrast, the AOB in SBNR was significantly inhibited without PACT or with poor performance of PACT in advance, which rendered the removal of TN. Furthermore, PAC was demonstrated to remove some refractory compounds, which therefore improved the biodegradability of the coal gasification wastewater.

  17. A Combined System for Biological Removal of Nitrogen and Carbon from Nylon-6 Production Wastewater

    Institute of Scientific and Technical Information of China (English)

    LIU Fang; LIU Guo-hua; TIAN Qing; ZHANG Man; CHEN Ji-hua

    2007-01-01

    A combined system consisting of hydrolysisacidification, denitrification and nitrification reactors wasused to remove carbon and nitrogen from the nylon - 6production wastewater, which was characterized by goodbiodegradability and high nitrogen concentration. Theinfluences of Chemical Oxygen Demand(COD) in theinfluent, recirculation ratio, Hydraulic Residence Time(HRT) and Dissolved Oxygen(DO) concentration on thesystem performances were investigated. From results itcould be seen that good performances have been achievedduring the overall experiments periods, and COD, TotalNitrogen(TN), NH+-N and Suspended Solids(SS) in theeffluent were 53, 16, 2 and 24 mg·L-1, respectively,which has satisfied the first standard of wastewaterdischarge established by Environmental Protection Agency(EPA) of China. Furthermore, results showed thatoperation factors, viz. COD in the influent, recirculationratio, HRT and DO concentration, all had importantinfluences on the system performances.

  18. Effects of Boron Nutrition and Water Stress on Nitrogen Fixation, Seed δ15N and δ13C Dynamics, and Seed Composition in Soybean Cultivars Differing in Maturities

    Directory of Open Access Journals (Sweden)

    Nacer Bellaloui

    2015-01-01

    Full Text Available Therefore, the objective of the current research was to investigate the effects of foliar B nutrition on seed protein, oil, fatty acids, and sugars under water stress conditions. A repeated greenhouse experiment was conducted using different maturity group (MG cultivars. Plants were well-watered with no foliar B (W − B, well-watered with foliar B (W + B, water-stressed with no foliar B (WS − B, and water-stressed with foliar B (WS + B. Foliar B was applied at rate of 0.45 kg·ha−1 and was applied twice at flowering and at seed-fill stages. The results showed that seed protein, sucrose, fructose, and glucose were higher in W + B treatment than in W − B, WS + B, and WS − B. The increase in protein in W + B resulted in lower seed oil, and the increase of oleic in WS − B or WS + B resulted in lower linolenic acid. Foliar B resulted in higher nitrogen fixation and water stress resulted in seed δ15N and δ13C alteration. Increased stachyose indicated possible physiological and metabolic changes in carbon and nitrogen pathways and their sources under water stress. This research is beneficial to growers for fertilizer management and seed quality and to breeders to use 15N/14N and 13C/12C ratios and stachyose to select for drought tolerance soybean.

  19. Carbon dynamics in subtropical forest soil. Effects of atmospheric carbon dioxide enrichment and nitrogen addition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Juxiu X.; Zhou, Guoyi Y.; Zhang, Deqiang Q.; Duan, Honglang L.; Deng, Qi; Zhao, Liang [Chinese Academy of Sciences, Guangzhou (China). South China Botanical Garden; Xu, Zhihong H. [Griffith Univ., Nathan, Queensland (Australia). Environmental Futures Centre and School of Biomolecular and Physical Sciences

    2010-06-15

    The levels of atmospheric carbon dioxide concentration ([CO{sub 2}]) are rapidly increasing. Understanding carbon (C) dynamics in soil is important for assessing the soil C sequestration potential under elevated [CO{sub 2}]. Nitrogen (N) is often regarded as a limiting factor in the soil C sequestration under future CO{sub 2} enrichment environment. However, few studies have been carried out to examine what would happen in the subtropical or tropical areas where the ambient N deposition is high. In this study, we used open-top chambers to study the effect of elevated atmospheric [CO{sub 2}] alone and together with N addition on the soil C dynamics in the first 4 years of the treatments applied in southern China. Materials and methods Above- and below-ground C input (tree biomass) into soil, soil respiration, soil organic C, and total N as well as dissolved organic C (DOC) were measured periodically in each of the open-top chambers. Soil samples were collected randomly in each chamber from each of the soil layers (0-20, 20-40, and 40-60 cm) using a standard soil sampling tube (2.5-cm inside diameter). Soil leachates were collected at the bottom of the chamber below-ground walls in stainless steel boxes. Results and discussion The highest above- and below-ground C input into soil was found in the high CO{sub 2} and high N treatment (CN), followed by the only high N treatment (N+), the only high CO{sub 2} treatment (C+), and then the control (CK) without any CO{sub 2} enrichment or N addition. DOC in the leachates was small for all the treatments. Export of DOC played a minor role in C cycling in our experiment. Generally, soil respiration rate in the chambers followed the order: CN treatment > C + treatment > N + treatment > the control. Except for the C+ treatment, there were no significant differences in soil total N among the CN treatment, N + treatment, and the control. Overall, soil organic C (SOC) was significantly affected by the treatments (p < 0.0001). SOC

  20. Cometary origin of carbon, nitrogen, and water on the earth

    Science.gov (United States)

    Delsemme, A. H.

    1992-01-01

    In this paper, two assumptions on the origin of the earth are substantiated: (1) that the earth accreted from fine hot degassed dust particles containing no volatiles; and (2) that, after the accretion was finished, all the volatiles of the biosphere, including the atmosphere and the oceans, were brought to the earth by cometary bombardment. A temperature of more than 1000 K is deduced at the time when the dust that was going to form the earth was separated from the gas phase. This implies grains of anhydrous silicates and of reduced iron, without either water, carbon, or any labile elements, which remained in gas phase; thus, the minor bodies could not produce atmosphere or oceans. The second assumption is based on the evidence that cometary nuclei are formed in the outer space, by accumulation of frosty particles containing large amounts of ice and volatile molecules. It is shown that the icy bodies which hit the earth are more than enough to explain the whole biosphere.

  1. [Effects of carbon and nitrogen sources on 5-keto-gluconic acid production].

    Science.gov (United States)

    Tan, Zhilei; Wang, Hongcui; Wei, Yuqiao; Li, Yanyan; Zhong, Cheng; Jia, Shiru

    2014-01-01

    Gluconobacter oxydans is known to oxidize glucose to gluconic acid (GA), and subsequently, to 2-keto-gluconic acid (2KGA) and 5-keto-gluconic acid (5KGA), while 5KGA can be converted to L-(+)-tartaric acid. In order to increase the production of 5KGA, Gluconobacter oxydans HGI-1 that converts GA to 5KGA exclusively was chosen in this study, and effects of carbon sources (lactose, maltose, sucrose, amylum and glucose) and nitrogen sources (yeast extract, fish meal, corn steep liquor, soybean meal and cotton-seed meal) on 5KGA production were investigated. Results of experiment in 500 mL shake-flask show that the highest yield of 5KGA (98.20 g/L) was obtained using 100 g/L glucose as carbon source. 5KGA reached 100.20 g/L, 109.10 g/L, 99.83 g/L with yeast extract, fish meal and corn steep liquor as nitrogen source respectively, among which the optimal nitrogen source was fish meal. The yield of 5KGA by corn steep liquor is slightly lower than that by yeast extract. For the economic reason, corn steep liquor was selected as nitrogen source and scaled up to 5 L stirred-tank fermentor, and the final concentration of 5KGA reached 93.80 g/L, with its maximum volumetric productivity of 3.48 g/(L x h) and average volumetric productivity of 1.56 g/(L x h). The result obtained in this study showed that carbon and nitrogen sourses for large-scale production of 5KGA by Gluconobacter oxydans HGI-1 were glucose and corn steep liquor, respectively, and the available glucose almost completely (85.93%) into 5KGA.

  2. The effect of nutrients on carbon and nitrogen fixation by the UCYN-A-haptophyte symbiosis.

    Science.gov (United States)

    Krupke, Andreas; Mohr, Wiebke; LaRoche, Julie; Fuchs, Bernhard M; Amann, Rudolf I; Kuypers, Marcel M M

    2015-07-01

    Symbiotic relationships between phytoplankton and N2-fixing microorganisms play a crucial role in marine ecosystems. The abundant and widespread unicellular cyanobacteria group A (UCYN-A) has recently been found to live symbiotically with a haptophyte. Here, we investigated the effect of nitrogen (N), phosphorus (P), iron (Fe) and Saharan dust additions on nitrogen (N2) fixation and primary production by the UCYN-A-haptophyte association in the subtropical eastern North Atlantic Ocean using nifH expression analysis and stable isotope incubations combined with single-cell measurements. N2 fixation by UCYN-A was stimulated by the addition of Fe and Saharan dust, although this was not reflected in the nifH expression. CO2 fixation by the haptophyte was stimulated by the addition of ammonium nitrate as well as Fe and Saharan dust. Intriguingly, the single-cell analysis using nanometer scale secondary ion mass spectrometry indicates that the increased CO2 fixation by the haptophyte in treatments without added fixed N is likely an indirect result of the positive effect of Fe and/or P on UCYN-A N2 fixation and the transfer of N2-derived N to the haptophyte. Our results reveal a direct linkage between the marine carbon and nitrogen cycles that is fuelled by the atmospheric deposition of dust. The comparison of single-cell rates suggests a tight coupling of nitrogen and carbon transfer that stays balanced even under changing nutrient regimes. However, it appears that the transfer of carbon from the haptophyte to UCYN-A requires a transfer of nitrogen from UCYN-A. This tight coupling indicates an obligate symbiosis of this globally important diazotrophic association.

  3. 硼在烟草生产中的应用研究进展%Research Advances on Application of Boron in Tobacco Production

    Institute of Scientific and Technical Information of China (English)

    冯晓红; 杨宇虹

    2012-01-01

    This paper makes a review of the studies on boron, such as the distribution ,absorption and transportation of boron in plant, the effect of boron on carbohydrate, plant hormone, proteins, nucleic acid, physiological function, carbon and nitrogen metabolism and growth - development , yield and quality of flue - cured tobacco. Boron deficiency symptoms , threshold of boron and the principle and method of boron fertilizer application are also summarized. Boron nutrition mechanism and application on flue - cured tobacco are prospected according to application effect of boron and new type of fertilizer application.%综述了硼在植物体内的分布、吸收、运转;硼对植物碳水化合物、植物激素、蛋白质、核酸等生理功能的影响;硼对烟草的生理功能和碳氮代谢的影响及硼素对烟草生长发育和产质量的影响.分析了烟草缺硼症状、烟草硼临界值,烟草施用硼肥的原则、方法;并从烟草硼素施用效果及新型硼肥的应用等方面,对今后硼对烟草营养机理方面的研究及硼素在烟草上的应用进行了展望.

  4. Mechanism of the initial stages of nitrogen-doped single-walled carbon nanotube growth.

    Science.gov (United States)

    Susi, Toma; Lanzani, Giorgio; Nasibulin, Albert G; Ayala, Paola; Jiang, Tao; Bligaard, Thomas; Laasonen, Kari; Kauppinen, Esko I

    2011-06-21

    We have studied the mechanism of the initial stages of nitrogen-doped single-walled carbon nanotube growth illustrated for the case of a floating catalyst chemical vapor deposition system, which uses carbon monoxide (CO) and ammonia (NH(3)) as precursors and iron as a catalyst. We performed first-principles electronic-structure calculations, fully incorporating the effects of spin polarization and magnetic moments, to investigate the bonding and chemistry of CO, NH(3), and their fragments on a model Fe(55) icosahedral cluster. A possible dissociation path for NH(3) to atomic nitrogen and hydrogen was identified, with a reaction barrier consistent with an experimentally determined value we measured by tandem infrared and mass spectrometry. Both C-C and C-N bond formation reactions were found to be barrierless and exothermic, while a parasitic reaction of HCN formation had a barrier of over 1 eV.

  5. Determination of the geographical origin of Chinese teas based on stable carbon and nitrogen isotope ratios

    Institute of Scientific and Technical Information of China (English)

    Long ZHANG; Jia-rong PAN; Cheng ZHU

    2012-01-01

    The objective of this study was to investigate the geographical origin of Chinese teas using carbon and nitrogen stable isotope ratio technology.The results showed that inter-provincial dispersion of teas in Guangdong (GD),Guangxi (GX),Hainan (HA),Fujian (F J),Shandong (SD),Sichuan (SC),Chongqing (CQ),and Henan (HN) provinces was high,while in Zhejiang (ZJ),Hubei (HB),Yunnan (YN),and Anhui (AH) provinces,it was low.Tea samples from GD,GX,HA,and FJ provinces were clustered in one group and separated from those from AH and HB provinces.Thus,carbon and nitrogen stable isotope ratio technology could discriminate teas from among some provinces of China,but not from among others.Better separation might be obtained with a combination of isotopic ratios and other indexes,such as elemental data and organic components.

  6. Reprocessing of Ices in Turbulent Protoplanetary Disks: Carbon and Nitrogen Chemistry

    CERN Document Server

    Furuya, Kenji

    2014-01-01

    We study the influence of the turbulent transport on ice chemistry in protoplanetary disks, focusing on carbon and nitrogen bearing molecules. Chemical rate equations are solved with the diffusion term, mimicking the turbulent mixing in the vertical direction. Turbulence can bring ice-coated dust grains from the midplane to the warm irradiated disk surface, and the ice mantles are reprocessed by photoreactions, thermal desorption, and surface reactions. The upward transport decreases the abundance of methanol and ammonia ices at r < 30 AU, because warm dust temperature prohibits their reformation on grain surfaces. This reprocessing could explain the smaller abundances of carbon and nitrogen bearing molecules in cometary coma than those in low-mass protostellar envelopes. We also show the effect of mixing on the synthesis of complex organic molecules (COMs) are two ways: (1) transport of ices from the midplane to the disk surface and (2) transport of atomic hydrogen from the surface to the midplane. The fo...

  7. The influence of land use on soil organic carbon and nitrogen content and redox potential

    DEFF Research Database (Denmark)

    Kusliene, Gedrime

    2010-01-01

    The aim of the research was to evaluate organic matter status in the soil according to the organic carbon content, total and mineral nitrogen amounts, carbon to nitrogen (C:N) ratio and redox potential depending on land usage and plant spieces. Soil samples were taken from the fields under...... different farming systems (conventional and organic) as well as abandoned lands. We choose the plants of two botanical species (Poaceae and Fabaceae) in organic and conventional farming systems as well as abandoned lands. Experimental results show that the best soil organic matter status according...... to the investigated indexes is in the soils of conventional and orgaic farming systems occupied with mixtures of Poaceae and Fabaceae and the worst - in the soils of abandoned Poaceae meadowa. In the abandoned lands, Fabaceae (galega) had better influence on soil organic matter status than Poaceae....

  8. Changes in soil carbon, nitrogen and phosphorus due to land-use changes in Brazil

    Directory of Open Access Journals (Sweden)

    J. D. Groppo

    2015-02-01

    vegetation. The original vegetation soil phosphorus stocks were equal to 11, 22, and 43 kg ha−1 in the three soil depths, respectively. The soil phosphorus stocks increased in the CPS systems to 30, 50, and 63 kg ha−1, respectively, and in the pasture pair sites to 22, 47, and 68 kg ha−1, respectively. In the regional pasture survey, the soil phosphorus stocks were lower than in the native vegetation, and equal to 9 and 15 kg ha−1 at 0–10 and 0–30 depth layer. The findings of this paper illustrate that land-use changes that are currently common in Brazil alter soil concentrations, stocks and elemental ratios of carbon, nitrogen and phosphorus. These changes could have an impact on the subsequent vegetation, decreasing soil carbon, increasing nitrogen limitation, but alleviating soil phosphorus deficiency.

  9. Effect of Carbon and Nitrogen Content on Deformation and Fracture of AISI 304 Austenitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    C. Menapace

    2008-04-01

    Full Text Available The effect of small differences in the content of carbon and nitrogen on the room temperature tensile deformation and fracture behaviour of an AISI 304 stainless steel was studied. In the steel containing the lower amount of carbon and nitrogen, a higher amount of strain induced alfa’ martensite is formed, which increases strain hardening rate and both uniform and total elongation at fracture. The presence of large martensitic areas in the cross section causes strain localization at the austenite/martensite interface, which promotes the nucleation of cracks and their propagation along the interface. This results in a decrease of Ultimate Tensile Strength. Strain induced transformation slightly reduces strain rate sensitivity, as well.

  10. Synthesis of carbon-11, fluorine-18, and nitrogen-13 labeled radiotracers for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, J.S.; Wolf, A.P.

    1981-01-01

    A number of reviews, many of them recent, have appeared on various aspects of /sup 11/C, /sup 18/F and /sup 13/N-labeled radiotracers. This monograph treats the topic principally from the standpoint of synthetic organic chemistry while keeping in perspective the necessity of integrating the organic chemistry with the design and ultimate application of the radiotracer. Where possible, recent examples from the literature of organic synthesis are introduced to suggest potentially new routes which may be applied to problems in labeling organic molecules with the short-lived positron emitters, carbon-11, fluorine-18, and nitrogen-13. The literature survey of carbon-11, fluorine-18 and nitrogen-13 labeled compounds presented are of particular value to scientists working in this field. Two appendices are also included to provide supplementary general references. A subject index concludes this volume.

  11. Synthesis and Explosive Consolidation of Titanium, Aluminium, Boron and Carbon Containing Powders

    Science.gov (United States)

    Chikhradze, Mikheil; Oniashvili, George; Chikhradze, Nikoloz; D. S Marquis, Fernand

    2016-10-01

    The development of modern technologies in the field of materials science has increased the interest towards the bulk materials with improved physical, chemical and mechanical properties. Composites, fabricated in Ti-Al-B-C systems are characterized by unique physical and mechanical properties. They are attractive for aerospace, power engineering, machine and chemical applications. The technologies to fabricate ultrafine grained powder and bulk materials in Ti-Al-B-C system are described in the paper. It includes results of theoretical and experimental investigation for selection of powders composition and determination of thermodynamic conditions for bland preparation, as well as optimal technological parameters for mechanical alloying and adiabatic compaction. The crystalline coarse Ti, Al, C powders and amorphous B were used as precursors and blends with different compositions of Ti-Al, Ti-Al-C, Ti-B-C and Ti-Al-B were prepared. Preliminary determination/selection of blend compositions was made on the basis of phase diagrams. The powders were mixed according to the selected ratios of components to produce the blend. Blends were processed in “Fritsch” Planetary premium line ball mill for mechanical alloying, syntheses of new phases, amorphization and ultrafine powder production. The blends processing time was variable: 1 to 20 hours. The optimal technological regimes of nano blend preparation were determined experimentally. Ball milled nano blends were placed in metallic tube and loaded by shock waves for realization of consolidation in adiabatic regime. The structure and properties of the obtained ultrafine grained materials depending on the processing parameters are investigated and discussed. For consolidation of the mixture, explosive compaction technology is applied at room temperatures. The prepared mixtures were located in low carbon steel tube and blast energies were used for explosive consolidation compositions. The relationship of ball milling

  12. Nutrient amendment does not increase mineralisation of sequestered carbon during incubation of a nitrogen limited mangrove soil

    KAUST Repository

    Keuskamp, Joost A.

    2013-02-01

    Mangrove forests are sites of intense carbon and nutrient cycling, which result in soil carbon sequestration on a global scale. Currently, mangrove forests receive increasing quantities of exogenous nutrients due to coastal development. The present paper quantifies the effects of nutrient loading on microbial growth rates and the mineralisation of soil organic carbon (SOC) in two mangrove soils contrasting in carbon content. An increase in SOC mineralisation rates would lead to the loss of historically sequestered carbon and an enhanced CO2 release from these mangrove soils.In an incubation experiment we enriched soils from Avicennia and Rhizophora mangrove forests bordering the Red Sea with different combinations of nitrogen, phosphorus and glucose to mimic the effects of wastewater influx. We measured microbial growth rates as well as carbon mineralisation rates in the natural situation and after enrichment. The results show that microbial growth is energy limited in both soils, with nitrogen as a secondary limitation. Nitrogen amendment increased the rate at which labile organic carbon was decomposed, while it decreased SOC mineralisation rates. Such an inhibitory effect on SOC mineralisation was not found for phosphorus enrichment.Our data confirm the negative effect of nitrogen enrichment on the mineralisation of recalcitrant carbon compounds found in other systems. Based on our results it is not to be expected that nutrient enrichment by itself will cause degradation of historically sequestered soil organic carbon in nitrogen limited mangrove forests. © 2012 Elsevier Ltd.

  13. Study on nitrogen doped carbon atom chains with negative differential resistance effect

    Science.gov (United States)

    Shen, Ji-Mei; Liu, Jing; Min, Yi; Zhou, Li-Ping

    2016-05-01

    Recent calculations (Mahmoud and Lugli, 2013, [21]) of gold leads sandwiching carbon chains which are separated by diphenyl-dimethyl demonstrated that the negative differential resistance (NDR) effect appears only for ;odd; numbers of carbon atoms. In this paper, according to a first-principles study based on non-equilibrium Green's function combining density functional theory, we find that the NDR effect appears both for ;odd; and for ;even; numbers of carbon atoms when the chains are doped by nitrogen atom. Our calculations remove the restriction of ;odd/even; chains for the NDR effect, which may promise the potential applications of carbon chains in the nano-scale or molecular devices in the future.

  14. Fuzzy Control of Nitrate Recirculation and External Carbon Addition in A/O Nitrogen Removal Process

    Institute of Scientific and Technical Information of China (English)

    马勇; 彭永臻; 王淑莹; 王晓莲

    2005-01-01

    Nitrogen and phosphorous concentrations of effluent water must be taken into account for the design and operation of wastewater treatment plants. In addition, the requirement for effluent quality is becoming strict.Therefore, intelligent control approaches are recently required in removing biological nutrient. In this study, fuzzy control has been successfully applied to improve the nitrogen removal. Experimental results showed that a close relationship between nitrate concentration and oxidation-reduction potential (ORP) at the end of anoxic zone was found for anoxic/oxic (A/O) nitrogen removal process treating synthetic wastewater. ORP can be used as online fuzzy control parazneter of nitrate recirculation and external carbon addition. The established fuzzy logic controller that includes two inputs and one output can maintain ORP value at-86 mV and -90 mV by adjusting the nitrate recirculation flow and external carbon dosage respectively to realize the optimal control of nitrogen removal, improving the effluent quality and reducing the operating cost.

  15. Changes of the electronic structure of the atoms of nitrogen in nitrogen-doped multiwalled carbon nanotubes under the influence of pulsed ion radiation

    Energy Technology Data Exchange (ETDEWEB)

    Korusenko, P.M., E-mail: korusenko@obisp.oscsbras.ru [Omsk Scientific Centre, Siberian Branch, Russian Academy of Sciences, Karl Marx Avenue, 15, Omsk 644024 (Russian Federation); Bolotov, V.V.; Nesov, S.N.; Povoroznyuk, S.N. [Omsk Scientific Centre, Siberian Branch, Russian Academy of Sciences, Karl Marx Avenue, 15, Omsk 644024 (Russian Federation); Khailov, I.P. [Tomsk Polytechnic University, Lenin Ave. 2a, Tomsk 634028 (Russian Federation)

    2015-09-01

    With the use of X-ray photoelectron spectroscopy (XPS) there have been investigated the changes of the chemical state of nitrogen atoms in the structure of nitrogen-doped multiwalled carbon nanotubes (CN{sub x}-MWCNTs) resulting from the impact of pulsed ion beam at various parameters of the beam (energy density, number of pulses). It has been established that irradiation with the pulsed ion beam leads to a reduction of the total amount of nitrogen in CN{sub x} nanotubes. It has been shown that a single pulse irradiation of ion beam at the energy densities of 0.5, 1, 1.5 J/cm{sup 2} leads to restructuring of the nitrogen from pyridinic and pyrrolic configuration to graphitic state. Complete removal of nitrogen (pyridinic, pyrrolic, graphitic) embedded in the structure of the walls of CN{sub x} nanotubes occurs at ten pulses and 1.5 J/cm{sup 2}.

  16. Hybrid Quantum Device with Nitrogen-Vacancy Centers in Diamond Coupled to Carbon Nanotubes

    Science.gov (United States)

    Li, Peng-Bo; Xiang, Ze-Liang; Rabl, Peter; Nori, Franco

    2016-07-01

    We show that nitrogen-vacancy (NV) centers in diamond interfaced with a suspended carbon nanotube carrying a dc current can facilitate a spin-nanomechanical hybrid device. We demonstrate that strong magnetomechanical interactions between a single NV spin and the vibrational mode of the suspended nanotube can be engineered and dynamically tuned by external control over the system parameters. This spin-nanomechanical setup with strong, intrinsic, and tunable magnetomechanical couplings allows for the construction of hybrid quantum devices with NV centers and carbon-based nanostructures, as well as phonon-mediated quantum information processing with spin qubits.

  17. ADSORPTION ISOTHERMS AND POTENTIAL DISTRIBUTIONS OF NITROGEN ON VARIOUS ACTIVATED CARBONS

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The adsorption isotherms of four activated carbons (Norit RB1, Chemviron BPL, Monolit, and Ambersorb-572) have been examined by nitrogen adsorption at 77.5 K. A method for adsorption potential distribution calculation has been proposed based on the adsorption isotherms. This distribution provides information about possible changes in the Gibbs free energy caused by the energetic and geometrical heterogeneities of an activated carbon as well as by the adsorbate-related entropic effects. The general character of the adsorption potential distribution is clearly visible by its simple relation to the micropore and mesopore distribution.

  18. Bonding preference of carbon, nitrogen, and oxygen in niobium-based rock-salt structures.

    Science.gov (United States)

    Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro; Wada, Satoshi; Magome, Eisuke; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2013-09-03

    Carbon, nitrogen, and oxygen are essential components in solid-state materials. However, understanding their preference on the bonding to metals has not been straightforward. Here, niobium carbide, nitride, and oxide with simple rock-salt-based structures were analyzed by first-principles calculations and synchrotron X-ray diffraction. We found that an increase in the atomic number from carbon to oxygen formed fewer and shorter bonds to metals with better hybridization of atomic orbitals. This can provide a simple guiding principle for understanding the bonding and designing carbides, nitrides, oxides, and mixed-anion compounds.

  19. Nitrogen--sulfur--carbon nanocomposites and their application as cathode materials in lithium--sulfur batteries

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng; Sun, Xiao-Guang; Guo, Bingkun; Wang, Xiqing; Mayes, Richard T.; Ben, Teng; Qiu, Shilun

    2016-09-27

    The invention is directed in a first aspect to electron-conducting porous compositions comprising an organic polymer matrix doped with nitrogen atoms and having elemental sulfur dispersed therein, particularly such compositions having an ordered framework structure. The invention is also directed to composites of such S/N-doped electron-conducting porous aromatic framework (PAF) compositions, or composites of an S/N-doped mesoporous carbon composition, which includes the S/N-doped composition in admixture with a binder, and optionally, conductive carbon. The invention is further directed to cathodes for a lithium-sulfur battery in which such composites are incorporated.

  20. Raman spectra of nitrogen-doped tetrahedral amorphous carbon from first principles

    Institute of Scientific and Technical Information of China (English)

    NIU Li; ZHU JiaQi; GAO Wei; HAN Xiao; DU ShanYi

    2009-01-01

    The non-resonant vibrational Raman spectra of nitrogen-doped tetrahedral amorphous carbon have been calculated from first principles, including the generation of s structural model, and the calculation of vibrational frequencies, vibrational eigenmodes and Raman coupling tensors. The calculated Raman spectra are in good agreement with the experimental results. The broad band at around 500 cm~(-1) arises from mixed bonds. The T peak originates from the vibrations of sp~3 carbon and the G peak comes from the stretching vibrations of sp~2-type bonding of C=C and C=N. The simulation results indicate the direct contribution of N vibrations to Raman spectra.

  1. Cement Pastes and Mortars Containing Nitrogen-Doped and Oxygen-Functionalized Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Mauricio Martínez-Alanis

    2016-01-01

    Full Text Available Cement pastes and mortars based on ordinary Portland cement containing nitrogen-doped multiwalled carbon nanotubes (MWCNT-Nx or oxygen-functionalized multiwalled carbon nanotubes (MWCNT-Ox are investigated. To incorporate MWCNTs into the cementitious matrix, the as-produced carpets are dispersed over periods of 1 and 2 hours in distilled water at pH levels of 1 and 7. The cement pastes are prepared by adding 0.1 wt% of MWCNTs to cement powder, followed by characterization with SEM and X-ray diffraction (XRD at an early age (first hours of hydration. The mortars are mechanically characterized during the hydration process for a period of 28 days. SEM characterization of cement pastes revealed that the carbon nanotubes are well incorporated in the cementitious matrix, with the hydrated cement grains interconnected by long carbon nanotubes. XRD characterizations demonstrated that, during the hydration of cement pastes, different peaks emerged that were associated with ettringite, hydrated calcium silicate, and calcium hydroxide, among other structures. Results of the compressive strength measurements for mortars simultaneously mixed with MWCNT-Nx and MWCNT-Ox reached an increment of approximately 30% in compressive strength. In addition, density functional theory calculations were performed in nitrogen-doped and oxygen-functionalized carbon nanotubes interacting with a cement grain.

  2. Soil carbon quality and nitrogen fertilization structure bacterial communities with predictable responses of major bacterial phyla

    OpenAIRE

    2014-01-01

    Agricultural practices affect the soil ecosystem in multiple ways and the soil microbial communities represent an integrated and dynamic measure of soil status. Our aim was to test whether the soil bacterial community and the relative abundance of major bacterial phyla responded predictably to long-term organic amendments representing different carbon qualities (peat and straw) in combination with nitrogen fertilization levels and if certain bacterial groups were indicative of specific treatm...

  3. Biotransformation of Meloxicam by Cunninghamella blakesleeana: Significance of Carbon and Nitrogen Source

    OpenAIRE

    Shyam Prasad, Gurram; Narasimha Rao, Kollu; Preethi, Rama; Girisham, Sivasri; S. M. Reddy

    2011-01-01

    Influence of carbon and nitrogen source, on biotransformation of meloxicam was studied by employing Cunninghamella blakesleeana NCIM 687 with an aim to achieve maximum transformation of meloxicam and in search of new metabolites. The transformation was confirmed by HPLC and based on LC–MS–MS data and previous reports the metabolites were predicted as 5-hydroxymethyl meloxicam, 5-carboxy meloxicam and a novel metabolite. The quantification of metabolites was performed using HPLC peak areas. Th...

  4. Influence of advective bio-irrigation on carbon and nitrogen cycling in sandy sediments

    OpenAIRE

    Na, T.; Gribsholt, B.; Galaktionov, O. S.; T. Lee; Meysman, F. J. R.

    2008-01-01

    In sandy sediments, the burrow ventilation activity of benthic macrofauna can generate substantial advective flows within the sediment surrounding their burrows. Here we investigated the effects of such advective bio-irrigation on carbon and nitrogen cycling in sandy sediments. To this end, we combined a range of complementary experimental and modelling approaches in a microcosm study of the lugworm Arenicola marina (Polychaeta: Annelida). Bio-irrigation rates were determined using uranine as...

  5. Fate of microbial nitrogen, carbon, hydrolysable amino acids, monosaccharides, and fatty acids in sediment

    OpenAIRE

    Veuger, Bart; van Oevelen, Dick; Middelburg, Jack J.

    2012-01-01

    The fate of microbial carbon, nitrogen, hydrolysable amino acids (HAAs), monosaccharides, and fatty acids in sediment was investigated experimentally. The microbial community of a tidal flat sediment was labeled with C-13-enriched glucose and N-15-enriched ammonium, and sediment was incubated for up to 371 days. Analysis of total concentrations and C-13- and N-15 content of bulk sediment, hydrolysable amino acids (including D-alanine), monosaccharides, total fatty acids (TFAs), and phospholip...

  6. Enhancement of Photocatalytic Activity on TiO2-Nitrogen-Doped Carbon Nanotubes Nanocomposites

    OpenAIRE

    Lingling Wang; Long Shen; Yihuai Li; Luping Zhu; Jiaowen Shen; Lijun Wang

    2013-01-01

    TiO2-nitrogen-doped carbon nanotubes (TiO2-CNx) nanocomposites are successfully synthesized via a facile hydrothermal method. The prepared photocatalysts were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric and differential scanning calorimetry analyses (TGA-DSC). The results show that the TiO2 nanoparticles with a narrow size of 7 nm are uniformly deposited on CNx. The photocatalytic ac...

  7. Growth of metal-catalyst-free nitrogen-doped metallic single-wall carbon nanotubes

    Science.gov (United States)

    Li, Jin-Cheng; Hou, Peng-Xiang; Zhang, Lili; Liu, Chang; Cheng, Hui-Ming

    2014-09-01

    Nitrogen-doped (N-doped) single-wall carbon nanotubes (SWCNTs) were synthesized by chemical vapor deposition using SiOx nanoparticles as a catalyst and ethylenediamine as the source of both carbon and nitrogen. The N-doped SWCNTs have a mean diameter of 1.1 nm and a narrow diameter range, with 92% of them having diameters from 0.7 to 1.4 nm. Multi-wavelength laser Raman spectra and temperature-dependent electrical resistance indicate that the SWCNT sample is enriched with metallic nanotubes. These N-doped SWCNTs showed excellent electrocatalytic activity for the oxygen reduction reaction and highly selective and sensitive sensing ability for dopamine detection.Nitrogen-doped (N-doped) single-wall carbon nanotubes (SWCNTs) were synthesized by chemical vapor deposition using SiOx nanoparticles as a catalyst and ethylenediamine as the source of both carbon and nitrogen. The N-doped SWCNTs have a mean diameter of 1.1 nm and a narrow diameter range, with 92% of them having diameters from 0.7 to 1.4 nm. Multi-wavelength laser Raman spectra and temperature-dependent electrical resistance indicate that the SWCNT sample is enriched with metallic nanotubes. These N-doped SWCNTs showed excellent electrocatalytic activity for the oxygen reduction reaction and highly selective and sensitive sensing ability for dopamine detection. Electronic supplementary information (ESI) available: Additional information including Raman spectra, ORR polarization curves, CV curves, etc. See DOI: 10.1039/c4nr03172e

  8. Nitrogen-Doped Carbon as a Cathode Material for Lithium-air Batteries (Postprint)

    Science.gov (United States)

    2010-04-01

    Handbook of Batteries and Fuel Cells, D. Linden , Editor, Chapter 38, Mc-Graw-Hil, New York (1984). [3] J. Read, J. Electrochem. Soc., 153, (2006) A96...MATERIAL FOR LITHIUM-AIR BATTERIES (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62203F 6. AUTHOR( S ...AFRL-RQ-WP-TP-2015-0050 NITROGEN-DOPED CARBON AS A CATHODE MATERIAL FOR LITHIUM-AIR BATTERIES (POSTPRINT) Padmakar Kichambare and Stanley

  9. Short-term carbon and nitrogen cycling in urine patches assessed by combined carbon-13 and nitrogen-15 labelling

    DEFF Research Database (Denmark)

    Ambus, Per; Petersen, S.O.; Soussana, J.F.

    2007-01-01

    sources for C include the urine itself, increased solubility of soil C, lysis of microbial cells and leakage of C from scorched roots. The objective of this experiment was to test the hypothesis that: (i) urine deposition causes an increase in root-derived degradable C compounds in the soil, which (ii......Urine deposition by grazing animals is known to, induce large NO emissions as a result of increased nitrification and denitrification in the soil. This is brought about by the increased N availability from the urine, in combination very likely also with increased organic C availability. Possible...... application was equal to the quantity of organic C added. Immediately after the application, 87% of the respired CO2 appeared to be from the urine, and respiration of plant-derived C was temporarily decreased. The cumulated amount of respired C-13 plant carbon, however, was unaltered by the urine treatment...

  10. CO{sub 2} removal potential of carbons prepared by co-pyrolysis of sugar and nitrogen containing compounds

    Energy Technology Data Exchange (ETDEWEB)

    Arenillas, A.; Drage, T.C.; Smith, K.; Snape, C.E. [University of Nottingham, Fuel Science Group, School of Chemical, Environmental and Mining Engineering, University Park, Nottingham NG7 2RD (United Kingdom)

    2005-08-15

    The nitrogen enrichment of active carbons is reported to be effective in enhancing the specific adsorbate-adsorbent interactions for CO{sub 2}. In this work, nitrogen-enriched carbons were prepared by co-pyrolysis of sugar and a series of nitrogen compounds with different nitrogen functionalities. The results show that although the amount of nitrogen incorporated to the final adsorbent is important, the N-functionality seems to be more relevant for increasing CO{sub 2} uptake. Thus, the adsorbent obtained from urea co-pyrolysis presents the highest nitrogen content but the lowest CO{sub 2} adsorption capacity. However, the adsorbent obtained from carbazole co-pyrolysis, despite the lower amount of N incorporated, shows high CO{sub 2} uptake, up to 9wt.%, probably because the presence of more basic functionalities as determined by XPS analysis.

  11. Influence of oxygen on nitrogen-doped carbon nanofiber growth directly on nichrome foil

    Science.gov (United States)

    Vishwakarma, Riteshkumar; Shinde, Sachin M.; Saufi Rosmi, Mohamad; Takahashi, Chisato; Papon, Remi; Mahyavanshi, Rakesh D.; Ishii, Yosuke; Kawasaki, Shinji; Kalita, Golap; Tanemura, Masaki

    2016-09-01

    The synthesis of various nitrogen-doped (N-doped) carbon nanostructures has been significantly explored as an alternative material for energy storage and metal-free catalytic applications. Here, we reveal a direct growth technique of N-doped carbon nanofibers (CNFs) on flexible nichrome (NiCr) foil using melamine as a solid precursor. Highly reactive Cr plays a critical role in the nanofiber growth process on the metal alloy foil in an atmospheric pressure chemical vapor deposition (APCVD) process. Oxidation of Cr occurs in the presence of oxygen impurities, where Ni nanoparticles are formed on the surface and assist the growth of nanofibers. Energy-dispersive x-ray spectroscopy (EDXS) and x-ray photoelectron spectroscopy (XPS) clearly show the transformation process of the NiCr foil surface with annealing in the presence of oxygen impurities. The structural change of NiCr foil assists one-dimensional (1D) CNF growth, rather than the lateral two-dimensional (2D) growth. The incorporation of distinctive graphitic and pyridinic nitrogen in the graphene lattice are observed in the synthesized nanofiber, owing to better nitrogen solubility. Our finding shows an effective approach for the synthesis of highly N-doped carbon nanostructures directly on Cr-based metal alloys for various applications.

  12. The interdependence of the reactive species of oxygen, nitrogen, and carbon.

    Science.gov (United States)

    Bild, Walther; Ciobica, Alin; Padurariu, Manuela; Bild, Veronica

    2013-03-01

    This mini-review tries to summarize the main interdependences between the free radicals of oxygen, nitrogen, and carbon. Also, the main metabolic pathways for these radical species are described, as well as how these affect their interaction and functional implications. Emphasis is made on the metabolic disturbances induced by stressing aggressions that produce radical species. In this way, cellular oxidative imbalances created by the superiority of reactive oxygen species over the antioxidant systems produce both activation of nitroxide synthases and the oxidation of terminal nitrogen from L-arginine, as well as the metabolization of heme until carbon monoxide by nitric oxide-activated hemoxygenase. Also, multiple cellular protein and nucleoprotein alterations determined by these three kinds of radical species are completed by the involvement of hydrogen sulfide, which results from the degradation of L-cysteine by cistationine-γ-lyase. In this way, sufficient experimental data tend to demonstrate the involvement of hydrogen sulfide and other thiol derivatives in the interrelations between oxygen, nitrogen, and carbon, which results in a true radical cascade. Thus, oxidative stress, together with nitrosative and carbonilic stress, may constitute a central point where other factors of vulnerability meet, and their interactions could have an important impact in many modern diseases. Considering that the actions of reactive species can be most of the time corrected, future studies need to establish the therapeutical importance of various agents which modulate oxidative, nitrosative, or carbonilic stress.

  13. Effects of bimetallic catalysts on synthesis of nitrogen-doped carbon nanotubes as nanoscale energetic materials

    Institute of Scientific and Technical Information of China (English)

    Hao Liu; Yong Zhang; Ruying Li; Xueliang Sun; Hakima Abou-Rachid

    2011-01-01

    Well aligned nitrogen-doped carbon nanotubes (CNx-NTs),as energetic materials,are synthesized on a silicon substrate by aerosol-assisted chemical vapor deposition.Tungsten (W) and molybdenum (Mo) metals are respectively introduced to combine with iron (Fe) to act as a bimetallic co-catalyst layer.Correlations between the composition and shape of the co-catalyst and morphology,size,growth rate and nitrogen doping amount of the synthesized CNx-NTs are investigated by secondary and backscattered electron imaging in a field emission scanning electron microscope (FESEM) and X-ray photoelectron spectrometer (XPS).Compared to pure iron catalyst.W-Fe co-catalyst can result in lower growth rate,larger diameter and wider size distribution of the CNx-NTs; while incorporation of molybdenum into the iron catalyst layer can reduce the diameter and size distribution of the nanotubes.Compared to the sole iron catalyst,Fe-W catalyst impedes nitrogen doping while Fe-Mo catalyst promotes the incorporation of nitrogen into the nanotubes.The present work indicates that CNx-NTs with modulated size,growth rate and nitrogen doping concentration are expected to be synthesized by tuning the size and composition of co-catalysts,which may find great potential in producing CNx-NTs with controlled structure and properties.

  14. Carbon dioxide level and form of soil nitrogen regulate assimilation of atmospheric ammonia in young trees.

    Science.gov (United States)

    Silva, Lucas C R; Salamanca-Jimenez, Alveiro; Doane, Timothy A; Horwath, William R

    2015-08-21

    The influence of carbon dioxide (CO2) and soil fertility on the physiological performance of plants has been extensively studied, but their combined effect is notoriously difficult to predict. Using Coffea arabica as a model tree species, we observed an additive effect on growth, by which aboveground productivity was highest under elevated CO2 and ammonium fertilization, while nitrate fertilization favored greater belowground biomass allocation regardless of CO2 concentration. A pulse of labelled gases ((13)CO2 and (15)NH3) was administered to these trees as a means to determine the legacy effect of CO2 level and soil nitrogen form on foliar gas uptake and translocation. Surprisingly, trees with the largest aboveground biomass assimilated significantly less NH3 than the smaller trees. This was partly explained by declines in stomatal conductance in plants grown under elevated CO2. However, unlike the (13)CO2 pulse, assimilation and transport of the (15)NH3 pulse to shoots and roots varied as a function of interactions between stomatal conductance and direct plant response to the form of soil nitrogen, observed as differences in tissue nitrogen content and biomass allocation. Nitrogen form is therefore an intrinsic component of physiological responses to atmospheric change, including assimilation of gaseous nitrogen as influenced by plant growth history.

  15. Synthesis of High-Surface-Area Nitrogen-Doped Porous Carbon Microflowers and Their Efficient Carbon Dioxide Capture Performance.

    Science.gov (United States)

    Li, Yao; Cao, Minhua

    2015-07-01

    Sustainable carbon materials have received particular attention in CO2 capture and storage owing to their abundant pore structures and controllable pore parameters. Here, we report high-surface-area hierarchically porous N-doped carbon microflowers, which were assembled from porous nanosheets by a three-step route: soft-template-assisted self-assembly, thermal decomposition, and KOH activation. The hydrazine hydrate used in our experiment serves as not only a nitrogen source, but also a structure-directing agent. The activation process was carried out under low (KOH/carbon=2), mild (KOH/carbon=4) and severe (KOH/carbon=6) activation conditions. The mild activated N-doped carbon microflowers (A-NCF-4) have a hierarchically porous structure, high specific surface area (2309 m(2)  g(-1)), desirable micropore size below 1 nm, and importantly large micropore volume (0.95 cm(3)  g(-1)). The remarkably high CO2 adsorption capacities of 6.52 and 19.32 mmol g(-1) were achieved with this sample at 0 °C (273 K) and two pressures, 1 bar and 20 bar, respectively. Furthermore, this sample also exhibits excellent stability during cyclic operations and good separation selectivity for CO2 over N2.

  16. Impact of carbon on the surface and activity of silica-carbon supported copper catalysts for reduction of nitrogen oxides

    Science.gov (United States)

    Spassova, I.; Stoeva, N.; Nickolov, R.; Atanasova, G.; Khristova, M.

    2016-04-01

    Composite catalysts, prepared by one or more active components supported on a support are of interest because of the possible interaction between the catalytic components and the support materials. The supports of combined hydrophilic-hydrophobic type may influence how these materials maintain an active phase and as a result a possible cooperation between active components and the support material could occur and affects the catalytic behavior. Silica-carbon nanocomposites were prepared by sol-gel, using different in specific surface areas and porous texture carbon materials. Catalysts were obtained after copper deposition on these composites. The nanocomposites and the catalysts were characterized by nitrogen adsorption, TG, XRD, TEM- HRTEM, H2-TPR, and XPS. The nature of the carbon predetermines the composite's texture. The IEPs of carbon materials and silica is a force of composites formation and determines the respective distribution of the silica and carbon components on the surface of the composites. Copper deposition over the investigated silica-carbon composites leads to formation of active phases in which copper is in different oxidation states. The reduction of NO with CO proceeds by different paths on different catalysts due to the textural differences of the composites, maintaining different surface composition and oxidation states of copper.

  17. Anodic behavior of sertindole and its voltammetric determination in pharmaceuticals and human serum using glassy carbon and boron-doped diamond electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Altun, Yuksel [Gazi University, Faculty of Education, Department of Chemistry, 06500 Teknikokullar, Ankara (Turkey); Dogan-Topal, Burcu; Uslu, Bengi [Ankara University, Faculty of Pharmacy, Department of Analytical Chemistry, 06100 Tandogan, Ankara (Turkey); Ozkan, Sibel A. [Ankara University, Faculty of Pharmacy, Department of Analytical Chemistry, 06100 Tandogan, Ankara (Turkey)], E-mail: ozkan@pharmacy.ankara.edu.tr

    2009-02-15

    The electrochemical oxidation of sertindole was investigated using cyclic, linear sweep voltammetry at a glassy carbon and boron-doped diamond electrodes. The aim of this study was to determine sertindole levels in serum and pharmaceutical formulations, by means of electrochemical methods. In cyclic voltammetry, depending on pH values, sertindole showed one or two irreversible oxidation responses. These two responses were found related to the different electroactive part of the molecule. Using second and sharp oxidation peak, two voltammetric methods were described for the determination of sertindole by differential pulse and square wave voltammetry at the glassy carbon and boron-doped diamond electrodes. Under optimized conditions, the current showed a linear dependence with concentration in the range between 1 x 10{sup -6} and 1 x 10{sup -4} M in acetate buffer at pH 3.5 and between 4 x 10{sup -6} and 1 x 10{sup -4} M in spiked human serum samples for both methods. The repeatability, reproducibility, selectivity, precision and accuracy of all the methods in all media were investigated and calculated. These methods were successfully applied for the analysis of sertindole pharmaceutical dosage forms and human serum samples. No electroactive interferences from the tablet excipients and endogenous substances from biological material were found.

  18. The effects of chronic nitrogen fertilization on alpine tundra soil microbial communities: implications for carbon and nitrogen cycling.

    Science.gov (United States)

    Nemergut, Diana R; Townsend, Alan R; Sattin, Sarah R; Freeman, Kristen R; Fierer, Noah; Neff, Jason C; Bowman, William D; Schadt, Christopher W; Weintraub, Michael N; Schmidt, Steven K

    2008-11-01

    Many studies have shown that changes in nitrogen (N) availability affect primary productivity in a variety of terrestrial systems, but less is known about the effects of the changing N cycle on soil organic matter (SOM) decomposition. We used a variety of techniques to examine the effects of chronic N amendments on SOM chemistry and microbial community structure and function in an alpine tundra soil. We collected surface soil (0-5 cm) samples from five control and five long-term N-amended plots established and maintained at the Niwot Ridge Long-term Ecological Research (LTER) site. Samples were bulked by treatment and all analyses were conducted on composite samples. The fungal community shifted in response to N amendments, with a decrease in the relative abundance of basidiomycetes. Bacterial community composition also shifted in the fertilized soil, with increases in the relative abundance of sequences related to the Bacteroidetes and Gemmatimonadetes, and decreases in the relative abundance of the Verrucomicrobia. We did not uncover any bacterial sequences that were closely related to known nitrifiers in either soil, but sequences related to archaeal nitrifiers were found in control soils. The ratio of fungi to bacteria did not change in the N-amended soils, but the ratio of archaea to bacteria dropped from 20% to less than 1% in the N-amended plots. Comparisons of aliphatic and aromatic carbon compounds, two broad categories of soil carbon compounds, revealed no between treatment differences. However, G-lignins were found in higher relative abundance in the fertilized soils, while proteins were detected in lower relative abundance. Finally, the activities of two soil enzymes involved in N cycling changed in response to chronic N amendments. These results suggest that chronic N fertilization induces significant shifts in soil carbon dynamics that correspond to shifts in microbial community structure and function.

  19. Advanced low carbon-to-nitrogen ratio wastewater treatment by electrochemical and biological coupling process.

    Science.gov (United States)

    Deng, Shihai; Li, Desheng; Yang, Xue; Zhu, Shanbin; Xing, Wei

    2016-03-01

    Nitrogen pollution in ground and surface water significantly affects the environment and its organisms, thereby leading to an increasingly serious environmental problem. Such pollution is difficult to degrade because of the lack of carbon sources. Therefore, an electrochemical and biological coupling process (EBCP) was developed with a composite catalytic biological carrier (CCBC) and applied in a pilot-scale cylindrical reactor to treat wastewater with a carbon-to-nitrogen (C/N) ratio of 2. The startup process, coupling principle, and dynamic feature of the EBCP were examined along with the effects of hydraulic retention time (HRT), dissolved oxygen (DO), and initial pH on nitrogen removal. A stable coupling system was obtained after 51 days when plenty of biofilms were cultivated on the CCBC without inoculation sludge. Autotrophic denitrification, with [Fe(2+)] and [H] produced by iron-carbon galvanic cells in CCBC as electron donors, was confirmed by equity calculation of CODCr and nitrogen removal. Nitrogen removal efficiency was significantly influenced by HRT, DO, and initial pH with optimal values of 3.5 h, 3.5 ± 0.1 mg L(-1), and 7.5 ± 0.1, respectively. The ammonia, nitrate, and total nitrogen (TN) removal efficiencies of 90.1 to 95.3 %, 90.5 to 99.0 %, and 90.3 to 96.5 % were maintained with corresponding initial concentrations of 40 ± 2 mg L(-1) (NH3-N load of 0.27 ± 0.01 kg NH3-N m(-3) d(-1)), 20 ± 1 mg L(-1), and 60 ± 2 mg L(-1) (TN load of 0.41 ± 0.02 kg TN m(-3) d(-1)). Based on the Eckenfelder model, the kinetics equation of the nitrogen transformation along the reactor was N e  = N 0 exp (-0.04368 h/L(1.8438)). Hence, EBCP is a viable method for advanced low C/N ratio wastewater treatment.

  20. Carbon, nitrogen and pH regulate the production and activity of a polygalacturonase isozyme produced by Penicillium expansum

    Science.gov (United States)

    The influence of carbon, nitrogen and pH on polygalacturonase activity produced by Penicillium expansum were investigated. P. expansum mycelial growth was greatest on lyophilized fruit tissue and the highest PG activity occurred in apple pectin medium. Nitrogen source influenced PG activity and was ...

  1. Carbon and Nitrogen Use Efficiency in Microbial Communities in Antarctic Soils

    Science.gov (United States)

    Prommer, Judith; Spohn, Marie; Klaus, Karoline; Kusch, Stephanie; Wanek, Wolfgang; Dercon, Gerd; Richter, Andreas

    2016-04-01

    Terrestrial ecosystems in the Antarctic experience harsh environmental conditions including very low temperatures and a low carbon input leading to poorly developed ecosystems with low diversity and a low soil organic matter content, which may be vulnerable to perturbations in a future climate. Microbial transformation and decomposition of soil organic matter under the extreme climatic conditions in the Antarctic has received little attention so far. Specifically, little is known about microbial process rates and how they might be affected by climate warming. We here report on C and N transformation rates and their corresponding microbial use efficiencies in two soil horizons of two sites on King George Island, the maritime Antarctica. We used novel isotope techniques to estimate microbial carbon use efficiency (CUE; based on incorporation of 18O from water into DNA) and nitrogen use efficiency (NUE; based on a 15N isotope pool dilution assays). The investigated two contrasting sites at marine terraces on basaltic rocks that were characterized by a stable surface. While both sites were similar in exposition, distance from sea and elevation, they differed in their vegetation cover and several biogeochemical parameters, such as soil pH and soil organic carbon and nitrogen content. Surprisingly, we found low soil C:N ratios at both sites and for both horizons, i.e. below 12 in the organic crust and below 8 in the first mineral horizon. This indicates a low carbon availability relative to nitrogen and would thus imply a high microbial CUE. However, our results showed also a low CUE at both sites and in both horizons (CUE of 24% and 9% in the organic crust and mineral layer, respectively). In contrast, NUE was very high in organic layers (98%), pointing towards a strong nitrogen limitation, while in the mineral horizons, NUE was lower (between 84% and 72%), as expected for soil horizons with a C:N ratio below 8. Thus, the NUE pattern followed stoichiometric theory (i

  2. Mesoporous Nitrogen-Doped Carbon-Glass Ceramic Cathodes for Solid-State Lithium-Oxygen Batteries (Postprint)

    Science.gov (United States)

    2012-01-01

    A. C.; Swanson, S .; Wilcke, W. J. Phys. Chem. Lett. 2010, 1, 2193−2203. (3) In Handbook of Batteries and Fuel Cells, 2nd ed.; Linden , D., Ed...AFRL-RZ-WP-TP-2012-0057 MESOPOROUS NITROGEN-DOPED CARBON-GLASS CERAMIC CATHODES FOR SOLID-STATE LITHIUM−OXYGEN BATTERIES (Postprint...November 2011 4. TITLE AND SUBTITLE MESOPOROUS NITROGEN-DOPED CARBON-GLASS CERAMIC CATHODES FOR SOLID-STATE LITHIUM−OXYGEN BATTERIES (Postprint

  3. Reassessing carbon sequestration in the North China Plain via addition of nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Wenxu, E-mail: dongwx@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China); Duan, Yongmei, E-mail: 106086193@QQ.com [Geological Survey of Jiangxi Province, Nanchang 330030 (China); Wang, Yuying, E-mail: wangyy@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China); Hu, Chunsheng, E-mail: cshu@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China)

    2016-09-01

    Soil inorganic carbon (SIC) exerts a strong influence on the carbon (C) sequestered in response to nitrogen (N) additions in arid and semi-arid ecosystems, but limited information is available on in situ SIC storage and dissolution at the field level. This study determined the soil organic/inorganic carbon storage in the soil profile at 0–100 cm depths and the concentration of dissolved inorganic carbon (DIC) in soil leachate in 4 N application treatments (0, 200, 400, and 600 kg N ha{sup −1} yr{sup −1}) for 15 years in the North China Plain. The objectives were to evaluate the effect of nitrogen fertilizer on total amount of carbon sequestration and the uptake of atmospheric CO{sub 2} in an agricultural system. Results showed that after 15 years of N fertilizer application the SOC contents at depths of 0–100 cm significantly increased, whereas the SIC contents significantly decreased at depths of 0–60 cm. However, the actual measured loss of carbonate was far higher than the theoretical maximum values of dissolution via protons from nitrification. Furthermore, the amount of HCO{sub 3}{sup −} and the HCO{sub 3}{sup −} / (Ca{sup 2+} + Mg{sup 2+}) ratio in soil leachate were higher in the N application treatments than no fertilizer input (CK) for the 0–80 cm depth. The result suggested that the dissolution of carbonate was mainly enhanced by soil carbonic acid, a process which can absorb soil or atmosphere CO{sub 2} and less influenced by protons through the nitrification which would release CO{sub 2}. To accurately evaluate soil C sequestration under N input scenarios in semi-arid regions, future studies should include both changes in SIC storage as well as the fractions of dissolution with different sources of acids in soil profiles. - Highlights: • The SOC contents significantly increased after long-term nitrogen application, while SIC decreased. • The measured loss of carbonate was far higher than the theoretical values of dissolution from

  4. A natural light/dark cycle regulation of carbon-nitrogen metabolism and gene expression in rice shoots

    Directory of Open Access Journals (Sweden)

    Haixing Li

    2016-08-01

    Full Text Available Light and temperature are two particularly important environmental cues for plant survival. Carbon and nitrogen are two essential macronutrients required for plant growth and development, and cellular carbon and nitrogen metabolism must be tightly coordinated. In order to understand how the natural light/dark cycle regulates carbon and nitrogen metabolism in rice plants, we analyzed the photosynthesis, key carbon-nitrogen metabolites and enzyme activities, and differentially expressed genes and miRNAs involved in the carbon and nitrogen metabolic pathway in rice shoots at the following times: 2:00, 6:00, 10:00, 14:00, 18:00 and 22:00. Our results indicated that more CO2 was fixed into carbohydrates by a high net photosynthetic rate, respiratory rate and stomatal conductance in the daytime. Although high levels of the nitrate reductase activity, free ammonium and carbohydrates were exhibited in the daytime, the protein synthesis was not significantly facilitated by the light and temperature. In mRNA sequencing, the carbon and nitrogen metabolism-related differentially expressed genes were obtained, which could be divided into eight groups: photosynthesis, TCA cycle, sugar transport, sugar metabolism, nitrogen transport, nitrogen reduction, amino acid metabolism and nitrogen regulation. Additionally, a total of 78,306 alternative splicing events have been identified, which primarily belong to alternative 5' donor sites, alternative 3' acceptor sites, intron retention and exon skipping. In sRNA sequencing, four carbon and nitrogen metabolism-related miRNAs (osa-miR1440b, osa-miR2876-5p, osa-miR1877 and osa-miR5799 were determined to be regulated by natural light/dark cycle. The expression level analysis showed that the four carbon and nitrogen metabolism-related miRNAs negatively regulated their target genes. These results may provide a good strategy to study how natural light/dark cycle regulates carbon and nitrogen metabolism to ensure plant

  5. Effects of carbon and nitrogen sources on fatty acid contents and composition in the green microalga, Chlorella sp. 227.

    Science.gov (United States)

    Cho, Sunja; Lee, Dukhaeng; Luong, Thao Thanh; Park, Sora; Oh, You-Kwan; Lee, Taeho

    2011-10-01

    In order to investigate and generalize the effects of carbon and nitrogen sources on the growth of and lipid production in Chlorella sp. 227, several nutritional combinations consisting of different carbon and nitrogen sources and concentrations were given to the media for cultivation of Chlorella sp. 227, respectively. The growth rate and lipid content were affected largely by concentration rather than by sources. The maximum specific growth was negatively affected by low concentrations of carbon and nitrogen. There is a maximum allowable inorganic carbon concentration (less than 500~1,000 mM bicarbonate) in autotrophic culture, but the maximum lipid content per gram dry cell weight (g DCW) was little affected by the concentration of inorganic carbon within the concentration. The lipid content per g DCW was increased when the microalga was cultured with the addition of glucose and bicarbonate (mixotrophic) at a fixed nitrogen concentration and with the lowest nitrogen concentration (0.2 mM), relatively. Considering that lipid contents per g DCW increased in those conditions, it suggests that a high ratio of carbon to nitrogen in culture media promotes lipid accumulation in the cells. Interestingly, a significant increase of the oleic acid amount to total fatty acids was observed in those conditions. These results showed the possibility to induce lipid production of high quality and content per g DCW by modifying the cultivation conditions.

  6. 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.

  7. Global terrestrial carbon and nitrogen cycling insensitive to estimates of biological N fixation

    Science.gov (United States)

    Steinkamp, J.; Weber, B.; Werner, C.; Hickler, T.

    2015-12-01

    Dinitrogen (N2) is the most abundant molecule in the atmosphere and incorporated in other molecules an essential nutrient for life on earth. However, only few natural processes can initiate a reaction of N2. These natural processes are fire, lightning and biological nitrogen fixation (BNF) with BNF being the largest source. In the course of the last century humans have outperformed the natural processes of nitrogen fixation by the production of fertilizer. Industrial and other human emission of reactive nitrogen, as well as fire and lightning lead to a deposition of 63 Tg (N) per year. This is twice the amount of BNF estimated by the default setup of the dynamic global vegetation model LPJ-GUESS (30 Tg), which is a conservative approach. We use different methods and parameterizations for BNF in LPJ-GUESS: 1.) varying total annual amount; 2.) annual evenly distributed and daily calculated fixation rates; 3.) an improved dataset of BNF by cryptogamic covers (free-living N-fixers). With this setup BNF is ranging from 30 Tg to 60 Tg. We assess the impact of BNF on carbon storage and grand primary production (GPP) of the natural vegetation. These results are compared to and evaluated against available independent datasets. We do not see major differences in the productivity and carbon stocks with these BNF estimates, suggesting that natural vegetation is insensitive to BNF on a global scale and the vegetation can compensate for the different nitrogen availabilities. Current deposition of nitrogen compounds and internal cycling through mineralization and uptake is sufficient for natural vegetation productivity. However, due to the coarse model grid and spatial heterogeneity in the real world this conclusion does not exclude the existence of habitats constrained by BNF.

  8. Phenol Adsorption on Nitrogen-enriched Activated Carbon Prepared from Bamboo Residues

    Directory of Open Access Journals (Sweden)

    Ji Zhang

    2013-12-01

    Full Text Available Nitrogen-enriched activated carbons prepared from bamboo residues were characterized by means of BET, XPS, and elemental analysis. Then adsorption experiments were carried out to study the effects of various physicochemical parameters such as contact time, temperature, pH, and initial concentration. Adsorption equilibrium was achieved within 120 min at a phenol concentration of 250 mg/L. When the pH was 4 and 0.1 g of the carbon absorbent and 100 mL of phenol solution at 250 mg/L were used, the phenol adsorption of the ACs with melamine and urea modifications were 219.09 mg/g and 214.45 mg/g, respectively. Both were greater than the capacity of unmodified AC, which was 163.82 mg/g. The Langmuir isotherm adsorption equation well described the experimental adsorption isotherms. The adsorption kinetics was well explained by pseudo-second-order kinetics rather than the pseudo-first-order. In conclusion, the nitrogen-enriched activated carbon proposed as adsorbents of the phenol wastewater were shown to be effective, which also means that bamboo residues have promise as activated carbon precursors for liquid phase adsorbents for environmental protection.

  9. Simulated effects of nitrogen saturation on the global carbon budget using the IBIS model

    Science.gov (United States)

    Lu, Xuehe; Jiang, Hong; Liu, Jinxun; Zhang, Xiuying; Jin, Jiaxin; Zhu, Qiuan; Zhang, Zhen; Peng, Changhui

    2016-12-01

    Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr‑1, respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling.

  10. Simulated effects of nitrogen saturation the global carbon budget using the IBIS model

    Science.gov (United States)

    Lu, Xuehe; Jiang, Hong; Liu, Jinxun; Zhang, Xiuying; Jin, Jiaxin; Zhu, Qiuan; Zhang, Zhen; Peng, Changhui

    2016-01-01

    Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr−1, respectively. The negative effects of N saturation on