METABOLIC ENGINEERING TO DEVELOP A PATHWAY FOR THE SELECTIVE CLEAVAGE OF CARBON-NITROGEN BONDS

Energy Technology Data Exchange (ETDEWEB)

John J. Kilbane II

2004-10-01

The objective of the project is to develop biochemical pathways for the selective cleavage of C-N bonds in molecules found in petroleum. The initial phase of the project was focused on the isolation or development of an enzyme capable of cleaving the C-N bond in aromatic amides, specifically 2-aminobiphenyl. The objective of the second phase of the research will be to construct a biochemical pathway for the selective removal of nitrogen from carbazole by combining the carA genes from Sphingomonas sp. GTIN11 with the gene(s) encoding an appropriate deaminase. The objective of the final phase of the project will be to develop derivative C-N bond cleaving enzymes that have broader substrate ranges and to demonstrate the use of such strains to selectively remove nitrogen from petroleum. During the first year of the project (October, 2002-September, 2003) enrichment culture experiments resulted in the isolation of microbial cultures that utilize aromatic amides as sole nitrogen sources, several amidase genes were cloned and were included in directed evolution experiments to obtain derivatives that can cleave C-N bonds in aromatic amides, and the carA genes from Sphingomonas sp. GTIN11, and Pseudomonas resinovorans CA10 were cloned in vectors capable of replicating in Escherichia coli. During the second year of the project (October, 2003-September, 2004) enrichment culture experiments succeeded in isolating a mixed bacterial culture that can utilize 2-aminobiphenyl as a sole nitrogen source, directed evolution experiments were focused on the aniline dioxygenase enzyme that is capable of deaminating aniline, and expression vectors were constructed to enable the expression of genes encoding C-N bond cleaving enzymes in Rhodococcus hosts. The construction of a new metabolic pathway to selectively remove nitrogen from carbazole and other molecules typically found in petroleum should lead to the development of a process to improve oil refinery efficiency by reducing the

Building carbon-carbon bonds using a biocatalytic methanol condensation cycle.

Science.gov (United States)

Bogorad, Igor W; Chen, Chang-Ting; Theisen, Matthew K; Wu, Tung-Yun; Schlenz, Alicia R; Lam, Albert T; Liao, James C

2014-11-11

Methanol is an important intermediate in the utilization of natural gas for synthesizing other feedstock chemicals. Typically, chemical approaches for building C-C bonds from methanol require high temperature and pressure. Biological conversion of methanol to longer carbon chain compounds is feasible; however, the natural biological pathways for methanol utilization involve carbon dioxide loss or ATP expenditure. Here we demonstrated a biocatalytic pathway, termed the methanol condensation cycle (MCC), by combining the nonoxidative glycolysis with the ribulose monophosphate pathway to convert methanol to higher-chain alcohols or other acetyl-CoA derivatives using enzymatic reactions in a carbon-conserved and ATP-independent system. We investigated the robustness of MCC and identified operational regions. We confirmed that the pathway forms a catalytic cycle through (13)C-carbon labeling. With a cell-free system, we demonstrated the conversion of methanol to ethanol or n-butanol. The high carbon efficiency and low operating temperature are attractive for transforming natural gas-derived methanol to longer-chain liquid fuels and other chemical derivatives.

Chemical constraints governing the origin of metabolism: the thermodynamic landscape of carbon group transformations under mild aqueous conditions

Science.gov (United States)

Weber, Arthur L.

2002-01-01

The thermodynamics of organic chemistry under mild aqueous conditions was examined in order to begin to understand its influence on the structure and operation of metabolism and its antecedents. Free energies (deltaG) were estimated for four types of reactions of biochemical importance carbon-carbon bond cleavage and synthesis, hydrogen transfer between carbon groups, dehydration of alcohol groups, and aldo-keto isomerization. The energies were calculated for mainly aliphatic groups composed of carbon, hydrogen, and oxygen. The energy values showed (1) that generally when carbon-carbon bond cleavage involves groups from different functional group classes (i.e., carboxylic acids, carbonyl groups, alcohols, and hydrocarbons), the transfer of the shared electron-pair to the more reduced carbon group is energetically favored over transfer to the more oxidized carbon group, and (2) that the energy of carbon-carbon bond transformation is primarily determined by the functional group class of the group that changes oxidation state in the reaction (i.e., the functional group class of the group that donates the shared electron-pair during cleavage, or that accepts the incipient shared electron-pair during synthesis). In contrast, the energy of hydrogen transfer between carbon groups is determined by the functional group class of both the hydrogen-donor group and the hydrogen-acceptor group. From these and other observations we concluded that the chemistry involved in the origin of metabolism (and to a lesser degree modern metabolism) was strongly constrained by (1) the limited redox-based transformation energy of organic substrates that is readily dissipated in a few energetically favorable irreversible reactions; (2) the energy dominance of a few transformation half-reactions that determines whether carbon-carbon bond transformation (cleavage or synthesis) is energetically favorable (deltaG +3.5 kcal/mol); and (3) the dependence of carbon group transformation energy on the

Mechanisms of Bond Cleavage during Manganese Oxide and UV Degradation of Glyphosate: Results from Phosphate Oxygen Isotopes and Molecular Simulations.

Science.gov (United States)

Jaisi, Deb P; Li, Hui; Wallace, Adam F; Paudel, Prajwal; Sun, Mingjing; Balakrishna, Avula; Lerch, Robert N

2016-11-16

Degradation of glyphosate in the presence of manganese oxide and UV light was analyzed using phosphate oxygen isotope ratios and density function theory (DFT). The preference of C-P or C-N bond cleavage was found to vary with changing glyphosate/manganese oxide ratios, indicating the potential role of sorption-induced conformational changes on the composition of intermediate degradation products. Isotope data confirmed that one oxygen atom derived solely from water was incorporated into the released phosphate during glyphosate degradation, and this might suggest similar nucleophilic substitution at P centers and C-P bond cleavage both in manganese oxide- and UV light-mediated degradation. The DFT results reveal that the C-P bond could be cleaved by water, OH - or • OH, with the energy barrier opposing bond dissociation being lowest in the presence of the radical species, and that C-N bond cleavage is favored by the formation of both nitrogen- and carbon-centered radicals. Overall, these results highlight the factors controlling the dominance of C-P or C-N bond cleavage that determines the composition of intermediate/final products and ultimately the degradation pathway.

Bonded carbon or ceramic fiber composite filter vent for radioactive waste

Science.gov (United States)

Brassell, Gilbert W.; Brugger, Ronald P.

1985-02-19

Carbon bonded carbon fiber composites as well as ceramic or carbon bonded ceramic fiber composites are very useful as filters which can separate particulate matter from gas streams entraining the same. These filters have particular application to the filtering of radioactive particles, e.g., they can act as vents for containers of radioactive waste material.

METABOLIC ENGINEERING TO DEVELOP A PATHWAY FOR THE SELECTIVE CLEAVAGE OF CARBON-NITROGEN BONDS

Energy Technology Data Exchange (ETDEWEB)

John J. Kilbane III

2003-12-01

The objective of the project is to develop biochemical pathways for the selective cleavage of C-N bonds in molecules found in petroleum. The initial phase of the project will focus on the isolation or development of an enzyme capable of cleaving the C-N bond in aromatic amides, specifically 2-aminobiphenyl. The objective of the second phase of the research will be to construct a biochemical pathway for the selective removal of nitrogen from carbazole by combining the carA genes from Sphingomonas sp. GTIN11 with the gene(s) encoding an appropriate amidase. The objective of the final phase of the project will be to develop derivative CN bond cleaving enzymes that have broader substrate ranges and to demonstrate the use of such strains to selectively remove nitrogen from petroleum. The project is on schedule and no major difficulties have been encountered. During the first year of the project (October, 2002-September, 2003) enrichment culture experiments have resulted in the isolation of promising cultures that may be capable of cleaving C-N bonds in aromatic amides, several amidase genes have been cloned and are currently undergoing directed evolution to obtain derivatives that can cleave C-N bonds in aromatic amides, and the carA genes from Sphingomonas sp. GTIN11, and Pseudomonas resinovorans CA10 were cloned in vectors capable of replicating in Escherichia coli. Future research will address expression of these genes in Rhodococcus erythropolis. Enrichment culture experiments and directed evolution experiments continue to be a main focus of research activity and further work is required to obtain an appropriate amidase that will selectively cleave C-N bonds in aromatic substrates. Once an appropriate amidase gene is obtained it must be combined with genes encoding an enzyme capable of converting carbazole to 2'aminobiphenyl-2,3-diol: specifically carA genes. The carA genes from two sources have been cloned and are ready for construction of C-N bond cleavage

Biodesulfurization of Naphthothiophene and Benzothiophene through Selective Cleavage of Carbon-Sulfur Bonds by Rhodococcus sp. Strain WU-K2R

Science.gov (United States)

Kirimura, Kohtaro; Furuya, Toshiki; Sato, Rika; Ishii, Yoshitaka; Kino, Kuniki; Usami, Shoji

2002-01-01

Naphtho[2,1-b]thiophene (NTH) is an asymmetric structural isomer of dibenzothiophene (DBT), and in addition to DBT derivatives, NTH derivatives can also be detected in diesel oil following hydrodesulfurization treatment. Rhodococcus sp. strain WU-K2R was newly isolated from soil for its ability to grow in a medium with NTH as the sole source of sulfur, and growing cells of WU-K2R degraded 0.27 mM NTH within 7 days. WU-K2R could also grow in the medium with NTH sulfone, benzothiophene (BTH), 3-methyl-BTH, or 5-methyl-BTH as the sole source of sulfur but could not utilize DBT, DBT sulfone, or 4,6-dimethyl-DBT. On the other hand, WU-K2R did not utilize NTH or BTH as the sole source of carbon. By gas chromatography-mass spectrometry analysis, desulfurized NTH metabolites were identified as NTH sulfone, 2′-hydroxynaphthylethene, and naphtho[2,1-b]furan. Moreover, since desulfurized BTH metabolites were identified as BTH sulfone, benzo[c][1,2]oxathiin S-oxide, benzo[c][1,2]oxathiin S,S-dioxide, o-hydroxystyrene, 2-(2′-hydroxyphenyl)ethan-1-al, and benzofuran, it was concluded that WU-K2R desulfurized NTH and BTH through the sulfur-specific degradation pathways with the selective cleavage of carbon-sulfur bonds. Therefore, Rhodococcus sp. strain WU-K2R, which could preferentially desulfurize asymmetric heterocyclic sulfur compounds such as NTH and BTH through the sulfur-specific degradation pathways, is a unique desulfurizing biocatalyst showing properties different from those of DBT-desulfurizing bacteria. PMID:12147483

Electron spectroscopy of the interface carbon layer formation on the cleavage surfaces of the layered semiconductor In4Se3 crystals

International Nuclear Information System (INIS)

Galiy, P.V.; Musyanovych, A.V.; Nenchuk, T.M.

2005-01-01

The results of the quantitative X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) of the interface carbon layer formation on the cleavage surfaces of the layered semiconductor In 4 Se 3 crystals are presented. The carbon coating formation occurs as the result of interaction of the air and residual gases atmosphere in ultra high vacuum (UHV) Auger spectrometer chamber with atomic clean interlayer cleavage surfaces of the crystals. The kinetics and peculiarities of interfacial carbon layer formation on the cleavage surfaces of the crystals, elemental and phase composition of the interface have been studied by quantitative XPS, AES and mass-spectroscopy

Hydrogen Transfer from Hantzsch 1,4-Dihydropyridines to Carbon-Carbon Double Bonds under Microwave Irradiation

OpenAIRE

Jean Jacques Vanden Eynde; Didier Barbry; Guy Cordonnier; Séverine Torchy

2002-01-01

1,4-Dihydropyridines (DHPs) have been used in the reduction of carbon-carbon double bonds under microwave irradiation without solvent. The efficiency of the reactions is dramatically dependent on the steric effects in the DHPs and on the electronic effects in the olefins.

Method for producing bio-fuel that integrates heat from carbon-carbon bond-forming reactions to drive biomass gasification reactions

Science.gov (United States)

Cortright, Randy D [Madison, WI; Dumesic, James A [Verona, WI

2011-01-18

A low-temperature catalytic process for converting biomass (preferably glycerol recovered from the fabrication of bio-diesel) to synthesis gas (i.e., H.sub.2/CO gas mixture) in an endothermic gasification reaction is described. The synthesis gas is used in exothermic carbon-carbon bond-forming reactions, such as Fischer-Tropsch, methanol, or dimethylether syntheses. The heat from the exothermic carbon-carbon bond-forming reaction is integrated with the endothermic gasification reaction, thus providing an energy-efficient route for producing fuels and chemicals from renewable biomass resources.

A dense and strong bonding collagen film for carbon/carbon composites

Energy Technology Data Exchange (ETDEWEB)

Cao, Sheng; Li, Hejun, E-mail: lihejun@nwpu.edu.cn; Li, Kezhi; Lu, Jinhua; Zhang, Leilei

2015-08-30

Graphical abstract: - Highlights: • Significantly enhancement of biocompatibility on C/C composites by preparing a collagen film. • The dense and continuous collagen film had a strong bonding strength with C/C composites after dehydrathermal treatment (DHT) crosslink. • Numerous oxygen-containing functional groups formed on the surface of C/C composites without matrix damage. - Abstract: A strong bonding collagen film was successfully prepared on carbon/carbon (C/C) composites. The surface conditions of the modified C/C composites were detected by contact angle measurements, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectra. The roughness, optical morphology, bonding strength and biocompatibility of collagen films at different pH values were detected by confocal laser scanning microscope (CLSM), universal test machine and cytology tests in vitro. After a 4-h modification in 30% H{sub 2}O{sub 2} solution at 100 °C, the contact angle on the surface of C/C composites was decreased from 92.3° to 65.3°. Large quantities of hydroxyl, carboxyl and carbonyl functional groups were formed on the surface of the modified C/C composites. Then a dense and continuous collagen film was prepared on the modified C/C substrate. Bonding strength between collagen film and C/C substrate was reached to 8 MPa level when the pH value of this collagen film was 2.5 after the preparing process. With 2-day dehydrathermal treatment (DHT) crosslinking at 105 °C, the bonding strength was increased to 12 MPa level. At last, the results of in vitro cytological test showed that this collagen film made a great improvement on the biocompatibility on C/C composites.

A dense and strong bonding collagen film for carbon/carbon composites

International Nuclear Information System (INIS)

Cao, Sheng; Li, Hejun; Li, Kezhi; Lu, Jinhua; Zhang, Leilei

2015-01-01

Graphical abstract: - Highlights: • Significantly enhancement of biocompatibility on C/C composites by preparing a collagen film. • The dense and continuous collagen film had a strong bonding strength with C/C composites after dehydrathermal treatment (DHT) crosslink. • Numerous oxygen-containing functional groups formed on the surface of C/C composites without matrix damage. - Abstract: A strong bonding collagen film was successfully prepared on carbon/carbon (C/C) composites. The surface conditions of the modified C/C composites were detected by contact angle measurements, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectra. The roughness, optical morphology, bonding strength and biocompatibility of collagen films at different pH values were detected by confocal laser scanning microscope (CLSM), universal test machine and cytology tests in vitro. After a 4-h modification in 30% H 2 O 2 solution at 100 °C, the contact angle on the surface of C/C composites was decreased from 92.3° to 65.3°. Large quantities of hydroxyl, carboxyl and carbonyl functional groups were formed on the surface of the modified C/C composites. Then a dense and continuous collagen film was prepared on the modified C/C substrate. Bonding strength between collagen film and C/C substrate was reached to 8 MPa level when the pH value of this collagen film was 2.5 after the preparing process. With 2-day dehydrathermal treatment (DHT) crosslinking at 105 °C, the bonding strength was increased to 12 MPa level. At last, the results of in vitro cytological test showed that this collagen film made a great improvement on the biocompatibility on C/C composites

Utilization of Glyphosate as Phosphate Source: Biochemistry and Genetics of Bacterial Carbon-Phosphorus Lyase

Science.gov (United States)

Zechel, David L.; Jochimsen, Bjarne

2014-01-01

SUMMARY After several decades of use of glyphosate, the active ingredient in weed killers such as Roundup, in fields, forests, and gardens, the biochemical pathway of transformation of glyphosate phosphorus to a useful phosphorus source for microorganisms has been disclosed. Glyphosate is a member of a large group of chemicals, phosphonic acids or phosphonates, which are characterized by a carbon-phosphorus bond. This is in contrast to the general phosphorus compounds utilized and metabolized by microorganisms. Here phosphorus is found as phosphoric acid or phosphate ion, phosphoric acid esters, or phosphoric acid anhydrides. The latter compounds contain phosphorus that is bound only to oxygen. Hydrolytic, oxidative, and radical-based mechanisms for carbon-phosphorus bond cleavage have been described. This review deals with the radical-based mechanism employed by the carbon-phosphorus lyase of the carbon-phosphorus lyase pathway, which involves reactions for activation of phosphonate, carbon-phosphorus bond cleavage, and further chemical transformation before a useful phosphate ion is generated in a series of seven or eight enzyme-catalyzed reactions. The phn genes, encoding the enzymes for this pathway, are widespread among bacterial species. The processes are described with emphasis on glyphosate as a substrate. Additionally, the catabolism of glyphosate is intimately connected with that of aminomethylphosphonate, which is also treated in this review. Results of physiological and genetic analyses are combined with those of bioinformatics analyses. PMID:24600043

Financing renewable energy infrastructure: Formulation, pricing and impact of a carbon revenue bond

International Nuclear Information System (INIS)

Tang, Amy; Chiara, Nicola; Taylor, John E.

2012-01-01

Renewable energy systems depend on large financial incentives to compete with conventional generation methods. Market-based incentives, including state-level REC markets and international carbon markets have been proposed as solutions to increase renewable energy investment. In this paper we introduce and formulate a carbon revenue bond, a financing tool to complement environmental credit markets to encourage renewable energy investment. To illustrate its use, we value the bond by predicting future revenue using stochastic processes after analyzing historical price data. Three illustrative examples are presented for renewable energy development in three different markets: Europe, Australia and New Jersey. Our findings reveal that the sale of a carbon revenue bond with a ten year maturity can finance a significant portion of a project's initial cost. - Highlights: ► Current financial incentives for renewable energy in the US are inadequate. ► We introduce and structure a “carbon revenue bond” as an innovative financing tool. ► Stochastic models of environmental credit prices are used to illustrate bond pricing. ► Three examples illustrate revenue bond impact on initial cost of infrastructure.

Fabrication and characterization of reaction bonded silicon carbide/carbon nanotube composites

International Nuclear Information System (INIS)

Thostenson, Erik T; Karandikar, Prashant G; Chou, T.-W.

2005-01-01

Carbon nanotubes have generated considerable excitement in the scientific and engineering communities because of their exceptional mechanical and physical properties observed at the nanoscale. Carbon nanotubes possess exceptionally high stiffness and strength combined with high electrical and thermal conductivities. These novel material properties have stimulated considerable research in the development of nanotube-reinforced composites (Thostenson et al 2001 Compos. Sci. Technol. 61 1899, Thostenson et al 2005 Compos. Sci. Technol. 65 491). In this research, novel reaction bonded silicon carbide nanocomposites were fabricated using melt infiltration of silicon. A series of multi-walled carbon nanotube-reinforced ceramic matrix composites (NT-CMCs) were fabricated and the structure and properties were characterized. Here we show that carbon nanotubes are present in the as-fabricated NT-CMCs after reaction bonding at temperatures above 1400 deg. C. Characterization results reveal that a very small volume content of carbon nanotubes, as low as 0.3 volume %, results in a 75% reduction in electrical resistivity of the ceramic composites. A 96% decrease in electrical resistivity was observed for the ceramics with the highest nanotube volume fraction of 2.1%

Structural Insights Into The Bacterial Carbon-Phosphorus Lyase Machinery

DEFF Research Database (Denmark)

Brodersen, Ditlev Egeskov

the proteins encoded in the phn operon act in concert to catabolise phosphonate remain unknown. We have determined the crystal structure of a 240 kDa Escherichia coli carbon-phosphorus lyase core complex at 1.7 Å and show that it comprises a highly intertwined network of subunits with several unexpected......Phosphonate compounds act as a nutrient source for some microorganisms when phosphate is limiting but require a specialised enzymatic machinery due to the presence of the highly stable carbon-phosphorus bond. Despite the fundamental importance to microbial metabolism, the details of how...... structural features. The complex contains at least two different active sites and suggest a revision of current models of carbon-phosphorus bond cleavage. Using electron microscopy, we map the binding site of an additional protein subunit, which may use ATP for driving conformational changes during...

Regioselectivity in the Reductive Bond Cleavage of Diarylalkylsulfonium Salts

DEFF Research Database (Denmark)

Kampmeier, Jack; Mansurul Hoque, AKM; D. Saeva, Franklin

2009-01-01

products vary from regiospecific alkyl cleavage to predominant aryl cleavage as a function of the potential of the reducing agent. We conclude that differences between the reductive cleavages of mono- and diarylsulfonium salts are direct consequences of the structures of the sulfuranyl radical......- tolylethylsulfonium and di-4-tolyl-2-phenylethylsulfonium salts by a variety of one-electron reducing agents ranging in potential from -0.77 to +2.5 eV (vs SCE) and including thermal reductants, indirect electrolyses mediated by a series of cyanoaromatics, and excited singlet states. We report that the cleavage...... intermediates and the bond dissociation energies of the alkyl and aryl bonds. Competitions between the rates of cleavage and oxidation of the intermediate sulfuranyl radicals and between concerted and stepwise mechanisms are discussed to explain the variations in bond cleavage products as a function...

Anodic carbon-boron bond cleavage through the intermediacy of electrogenerated bromonium ion

International Nuclear Information System (INIS)

Shi Deqing; Gitkis, Anna; Becker, James Y.

2007-01-01

The electrochemical properties of a series of cyclic arylboronic esters, XC 6 H 4 B(OR) 2 [RR = CH 2 CH 2 ; X = H (1a); p-Me (1b); p-OMe (1c); p-Cl (1d); p-Ph (1e); m-Cl (1f); m-OMe (1g); CF 3 (1h); OMe (1i); 2,6-dimethyl (1j); 1b with RR = (CH 2 ) 3 , (1k); 1b with RR = CMe 2 CMe 2 , (1m)] has been studied in acetonitrile by cyclic voltammetry (CV) and controlled-potential electrolysis (CPE). The CV of representative examples of aryl borates with different substituents show one irreversible oxidation wave on a Pt cathode, at 1.8-1.9 V (vs. Ag/AgCl), with a negligible substituent effect. The cathodic CPE process led to small amounts of biaryls only, whereas the direct anodic CPE could not be carried out practically due to low currents. However, in the presence of electrogenerated bromonium (or iodonium) ions a C-B bond cleavage does take place to yield the corresponding bromoaryls, brominated phenols, and arylboronic acids as the major products

Anodic carbon-boron bond cleavage through the intermediacy of electrogenerated bromonium ion

Energy Technology Data Exchange (ETDEWEB)

Shi Deqing; Gitkis, Anna [Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel); Becker, James Y. [Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel)], E-mail: becker@bgu.ac.il

2007-12-31

The electrochemical properties of a series of cyclic arylboronic esters, XC{sub 6}H{sub 4}B(OR){sub 2} [RR = CH{sub 2}CH{sub 2}; X = H (1a); p-Me (1b); p-OMe (1c); p-Cl (1d); p-Ph (1e); m-Cl (1f); m-OMe (1g); CF{sub 3} (1h); OMe (1i); 2,6-dimethyl (1j); 1b with RR = (CH{sub 2}){sub 3}, (1k); 1b with RR = CMe{sub 2}CMe{sub 2}, (1m)] has been studied in acetonitrile by cyclic voltammetry (CV) and controlled-potential electrolysis (CPE). The CV of representative examples of aryl borates with different substituents show one irreversible oxidation wave on a Pt cathode, at 1.8-1.9 V (vs. Ag/AgCl), with a negligible substituent effect. The cathodic CPE process led to small amounts of biaryls only, whereas the direct anodic CPE could not be carried out practically due to low currents. However, in the presence of electrogenerated bromonium (or iodonium) ions a C-B bond cleavage does take place to yield the corresponding bromoaryls, brominated phenols, and arylboronic acids as the major products.

Thermal and bonding properties of nano size carbon black filled PDMS

CSIR Research Space (South Africa)

Chen, H

2009-12-01

Full Text Available is varied from 10% to 25%. The mechanical property is characterized by testing the bond strength of the bond between pure PDMS and PDMS-CB composite. The bond between pure PDMS and 10% carbon black filled PDMS broke at 0.72 MPa. The bond has become very...

Hydrogen-bond acidic functionalized carbon nanotubes (CNTs) with covalently-bound hexafluoroisopropanol groups

Energy Technology Data Exchange (ETDEWEB)

Fifield, Leonard S.; Grate, Jay W.

2010-06-01

Fluorinated hydrogen-bond acidic groups are directly attached to the backbone of single walled carbon nanotubes (SWCNTs) without the introduction of intermediate electron donating surface groups. Hexafluoroalcohol functional groups are exceptionally strong hydrogen bond acids, and are added to the nanotube surface using the aryl diazonium approach to create hydrogen-bond acidic carbon nanotube (CNT) surfaces. These groups can promote strong hydrogen-bonding interactions with matrix materials in composites or with molecular species to be concentrated and sensed. In the latter case, this newly developed material is expected to find useful application in chemical sensors and in CNT-based preconcentrator devices for the detection of pesticides, chemical warfare agents and explosives.

Material and orientation dependent activity for heterogeneously catalyzed carbon-bromine bond homolysis

Energy Technology Data Exchange (ETDEWEB)

Walch, Hermann; Gutzler, Rico; Sirtl, Thomas; Eder, Georg; Lackinger, Markus [LMU Munich, Section Crystallography (Germany)

2010-07-01

Adsorption of the organic molecule 1,3,5-tris(4-bromophenyl)benzene on different metallic substrates, namely Cu(111), Ag(111) and Ag(110) has been studied by variable temperature Scanning Tunneling Microscopy (STM). Depending on substrate temperature, material and orientation, we observe a surface-catalyzed dehalogenation reaction. Deposition onto the catalytically active substrates Cu(111) and Ag(110) held at room temperature leads to cleavage of the carbon-bromine bonds and subsequent formation of protopolymers, i.e radical metal coordination complexes. However upon deposition on Ag(111) no such reaction has been observed. Instead, various self-assembled ordered structures based on intact molecules could be identified. Also sublimation onto either substrate held at 80 K did not result in any dehalogenation, thereby exemplifying that the dehalogenation reaction is thermally activated. We explain the differences in catalytic activity by charge transfer into unoccupied molecular orbitals and subsequent destabilization of the C-Br bond, whereby enhanced molecule-substrate interaction leads to an increasing magnitude of charge transfer. The interaction strength follows the general reactivity order Cu>Ag>Au for (111) faces and is generally enhanced on higher corrugated surfaces as the (110) facet in case of fcc substrates.

Direct synthesis of sp-bonded carbon chains on graphite surface by femtosecond laser irradiation

International Nuclear Information System (INIS)

Hu, A.; Rybachuk, M.; Lu, Q.-B.; Duley, W. W.

2007-01-01

Microscopic phase transformation from graphite to sp-bonded carbon chains (carbyne) and nanodiamond has been induced by femtosecond laser pulses on graphite surface. UV/surface enhanced Raman scattering spectra and x-ray photoelectron spectra displayed the local synthesis of carbyne in the melt zone while nanocrystalline diamond and trans-polyacetylene chains form in the edge area of gentle ablation. These results evidence possible direct 'writing' of variable chemical bonded carbons by femtosecond laser pulses for carbon-based applications

A cerium(IV)-carbon multiple bond

Energy Technology Data Exchange (ETDEWEB)

Gregson, Matthew; Lu, Erli; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T. [Nottingham Univ. (United Kingdom). School of Chemistry

2013-12-02

Straightforward access to a cerium(IV)-carbene complex was provided by one-electron oxidation of an anionic ''ate'' cerium(III)-carbene precursor, thereby avoiding decomposition reactions that plague oxidations of neutral cerium(III) compounds. The cerium(IV)-carbene complex is the first lanthanide(IV)-element multiple bond and involves a twofold bonding interaction of two electron pairs between cerium and carbon. [German] Auf direktem Wege zu einem Cer(IV)-Carbenkomplex gelangt man durch die Einelektronenoxidation einer anionischen Carben-Cerat(III)-Vorstufe. So werden Zersetzungsprozesse vermieden, die die Oxidation neutraler Cer(III)-Verbindungen erschweren. Der Cer(IV)-Carbenkomplex enthaelt die erste Lanthanoid(IV)-Element-Mehrfachbindung; dabei binden Cer und Kohlenstoff ueber zwei Elektronenpaare.

Thermocompression bonding of vertically aligned carbon nanotube turfs to metalized substrates

International Nuclear Information System (INIS)

Johnson, R D; Bahr, D F; Richards, C D; Richards, R F; McClain, D; Green, J; Jiao, J

2009-01-01

Vertically aligned carbon nanotube turfs (VACNTs), consisting of entwined, nominally vertical carbon nanotubes, are being proposed for use as electrical and thermal contact materials. Issues in their implementation include high contact resistance, the van der Waals interactions of carbon nanotubes, and a low temperature limit during processing. One route for circumventing the 750 deg. C temperatures required for VACNT growth using chemical vapor deposition is for the VACNTs to be grown separately, and then transferred to the device. A method of mechanical transfer, using thermocompression bonding, has been developed, allowing dry mechanical transfer of the VACNTs at 150 deg. C. This method can be used for the construction of both a thermal switch or a permanent conducting channel. The conductivity of the bonded structure is shown to be independent of the imposed strain, up to strains in excess of 100%.

Study of the damaging mechanisms of a carbon - carbon composite bonded to copper under thermomechanical loading; Etude des mecanismes d'endommagement d'un assemblage cuivre / composite carbone - carbone sous chargement thermomecanique

Energy Technology Data Exchange (ETDEWEB)

Moncel, L

1999-06-15

The purpose of this work is to understand and to identify the damaging mechanisms of Carbon-Carbon composite bonded to copper under thermomechanical loading. The study of the composite allowed the development of non-linear models. These ones have been introduced in the finite elements analysis code named CASTEM 2000. They have been validated according to a correlation between simulation and mechanical tests on multi-material samples. These tests have also permitted us to better understand the behaviour of the bonding between composite and copper (damaging and fracture modes for different temperatures) under shear and tensile loadings. The damaging mechanisms of the bond under thermomechanical loading have been studied and identified according to microscopic observations on mock-ups which have sustained thermal cycling tests: some cracks appear in the composite, near the bond between the composite and the copper. The correlation between numerical and experimental results have been improved because of the reliability of the composite modelization, the use of residual stresses and the results of the bond mechanical characterisation. (author)

Synthesis of chemically bonded graphene/carbon nanotube composites and their application in large volumetric capacitance supercapacitors.

Science.gov (United States)

Jung, Naeyoung; Kwon, Soongeun; Lee, Dongwook; Yoon, Dong-Myung; Park, Young Min; Benayad, Anass; Choi, Jae-Young; Park, Jong Se

2013-12-17

Chemically bonded graphene/carbon nanotube composites as flexible supercapacitor electrode materials are synthesized by amide bonding. Carbon nanotubes attached along the edges and onto the surface of graphene act as spacers to increase the electrolyte-accessible surface area. Our lamellar structure electrodes demonstrate the largest volumetric capacitance (165 F cm(-3) ) ever shown by carbon-based electrodes. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct approaches to nitriles via highly efficient nitrogenation strategy through C-H or C-C bond cleavage.

Science.gov (United States)

Wang, Teng; Jiao, Ning

2014-04-15

Because of the importance of nitrogen-containing compounds in chemistry and biology, organic chemists have long focused on the development of novel methodologies for their synthesis. For example, nitrogen-containing compounds show up within functional materials, as top-selling drugs, and as bioactive molecules. To synthesize these compounds in a green and sustainable way, researchers have focused on the direct functionalization of hydrocarbons via C-H or C-C bond cleavage. Although researchers have made significant progress in the direct functionalization of simple hydrocarbons, direct C-N bond formation via C-H or C-C bond cleavage remains challenging, in part because of the unstable character of some N-nucleophiles under oxidative conditions. The nitriles are versatile building blocks and precursors in organic synthesis. Recently, chemists have achieved the direct C-H cyanation with toxic cyanide salts in the presence of stoichiometric metal oxidants. In this Account, we describe recent progress made by our group in nitrile synthesis. C-H or C-C bond cleavage is a key process in our strategy, and azides or DMF serve as the nitrogen source. In these reactions, we successfully realized direct nitrile synthesis using a variety of hydrocarbon groups as nitrile precursors, including methyl, alkenyl, and alkynyl groups. We could carry out C(sp(3))-H functionalization on benzylic, allylic, and propargylic C-H bonds to produce diverse valuable synthetic nitriles. Mild oxidation of C═C double-bonds and C≡C triple-bonds also produced nitriles. The incorporation of nitrogen within the carbon skeleton typically involved the participation of azide reagents. Although some mechanistic details remain unclear, studies of these nitrogenation reactions implicate the involvement of a cation or radical intermediate, and an oxidative rearrangement of azide intermediate produced the nitrile. We also explored environmentally friendly oxidants, such as molecular oxygen, to make our

Chemical bonding modifications of tetrahedral amorphous carbon and nitrogenated tetrahedral amorphous carbon films induced by rapid thermal annealing

International Nuclear Information System (INIS)

McCann, R.; Roy, S.S.; Papakonstantinou, P.; Bain, M.F.; Gamble, H.S.; McLaughlin, J.A.

2005-01-01

Tetrahedral amorphous carbon (ta-C) and nitrogenated tetrahedral amorphous carbon films (ta-CN x ), deposited by double bend off plane Filtered Vacuum Cathodic Arc were annealed up to 1000 deg. C in flowing argon for 2 min. Modifications on the chemical bonding structure of the rapidly annealed films, as a function of temperature, were investigated by NEXAFS, X-ray photoelectron and Raman spectroscopies. The interpretation of these spectra is discussed. The results demonstrate that the structure of undoped ta-C films prepared at floating potential with an arc current of 80 A remains stable up to 900 deg. C, whereas that of ta-CN x containing 12 at.% nitrogen is stable up to 700 deg. C. At higher temperatures, all the spectra indicated the predominant formation of graphitic carbon. Through NEXAFS studies, we clearly observed three π* resonance peaks at the ' N K edge structure. The origin of these three peaks is not well established in the literature. However our temperature-dependant study ascertained that the first peak originates from C=N bonds and the third peak originates from the incorporation of nitrogen into the graphite like domains

Carbon dioxide utilization via carbonate-promoted C-H carboxylation.

Science.gov (United States)

Banerjee, Aanindeeta; Dick, Graham R; Yoshino, Tatsuhiko; Kanan, Matthew W

2016-03-10

Using carbon dioxide (CO2) as a feedstock for commodity synthesis is an attractive means of reducing greenhouse gas emissions and a possible stepping-stone towards renewable synthetic fuels. A major impediment to synthesizing compounds from CO2 is the difficulty of forming carbon-carbon (C-C) bonds efficiently: although CO2 reacts readily with carbon-centred nucleophiles, generating these intermediates requires high-energy reagents (such as highly reducing metals or strong organic bases), carbon-heteroatom bonds or relatively acidic carbon-hydrogen (C-H) bonds. These requirements negate the environmental benefit of using CO2 as a substrate and limit the chemistry to low-volume targets. Here we show that intermediate-temperature (200 to 350 degrees Celsius) molten salts containing caesium or potassium cations enable carbonate ions (CO3(2-)) to deprotonate very weakly acidic C-H bonds (pKa > 40), generating carbon-centred nucleophiles that react with CO2 to form carboxylates. To illustrate a potential application, we use C-H carboxylation followed by protonation to convert 2-furoic acid into furan-2,5-dicarboxylic acid (FDCA)--a highly desirable bio-based feedstock with numerous applications, including the synthesis of polyethylene furandicarboxylate (PEF), which is a potential large-scale substitute for petroleum-derived polyethylene terephthalate (PET). Since 2-furoic acid can readily be made from lignocellulose, CO3(2-)-promoted C-H carboxylation thus reveals a way to transform inedible biomass and CO2 into a valuable feedstock chemical. Our results provide a new strategy for using CO2 in the synthesis of multi-carbon compounds.

Bonding Characteristics of Macrosynthetic Fiber in Latex-Modified Fiber-Reinforced Cement Composites as a Function of Carbon Nanotube Content

Directory of Open Access Journals (Sweden)

Ji-Hong Jean

2016-01-01

Full Text Available The effect of carbon nanotube content (0, 0.5, 1.0, 1.5, and 2.0% of the cement weight on the bonding properties of macrosynthetic fiber in latex-modified hybrid fiber cement-based composites (LMHFRCCs was evaluated. The slump value, compressive strength, and bonding strength were measured for each LMHFRCC. As the carbon nanotube content increased to 1.5%, the bonding properties of the macrosynthetic fiber improved. However, the bonding performance deteriorated at a carbon nanotube content of 2.0%. A decrease in the fluidity of the mix negatively affected the dispersion of the nanotubes in the LMHFRCCs. The addition of carbon nanotubes also affected the relative bonding strength independently of the improvement in compressive strength. Microscopic analysis of the macrosynthetic fiber surfaces was used to understand changes in the bonding behavior.

Hydrogen bonds, interfacial stiffness moduli, and the interlaminar shear strength of carbon fiber-epoxy matrix composites

Directory of Open Access Journals (Sweden)

John H. Cantrell

2015-03-01

Full Text Available The chemical treatment of carbon fibers used in carbon fiber-epoxy matrix composites greatly affects the fraction of hydrogen bonds (H-bonds formed at the fiber-matrix interface. The H-bonds are major contributors to the fiber-matrix interfacial shear strength and play a direct role in the interlaminar shear strength (ILSS of the composite. The H-bond contributions τ to the ILSS and magnitudes KN of the fiber-matrix interfacial stiffness moduli of seven carbon fiber-epoxy matrix composites, subjected to different fiber surface treatments, are calculated from the Morse potential for the interactions of hydroxyl and carboxyl acid groups formed on the carbon fiber surfaces with epoxy receptors. The τ calculations range from 7.7 MPa to 18.4 MPa in magnitude, depending on fiber treatment. The KN calculations fall in the range (2.01 – 4.67 ×1017 N m−3. The average ratio KN/|τ| is calculated to be (2.59 ± 0.043 × 1010 m−1 for the seven composites, suggesting a nearly linear connection between ILSS and H-bonding at the fiber-matrix interfaces. The linear connection indicates that τ may be assessable nondestructively from measurements of KN via a technique such as angle beam ultrasonic spectroscopy.

Synthetic Applications and Mechanistic Studies of the Hydroxide-Mediated Cleavage of Carbon-Carbon Bonds in Ketones

DEFF Research Database (Denmark)

Mazziotta, Andrea; Makarov, Ilya S.; Fristrup, Peter

2017-01-01

The hydroxide-mediated cleavage of ketones into alkanes and carboxylic acids has been reinvestigated and the substrate scope extended to benzyl carbonyl compounds. The transformation is performed with a 0.05 M ketone solution in refluxing xylene in the presence of 10 equiv of potassium hydroxide....... The studies were complemented by a theoretical investigation where two possible pathways were characterized by DFT/M06-2X. The calculations showed that the scission takes place by nucleophilic attack of hydroxide on the ketone followed by fragmentation of the resulting oxyanion into the carboxylic acid...

Can We Make Green Bonds An Effective Tool For Urban Carbon Management?

Science.gov (United States)

Yamagata, Y.; Murakami, D.

2016-12-01

The "Paris Agreement" requires major carbon emitting countries to conduct massive reduction efforts during the 21st century. At the same time, new carbon financing mechanisms are emerging. Among others, Green Bonds (GBs) is rapidly developing. In this paper, we discuss about the potential use of GBs for financing city level carbon management. In order to make the application effective, there are several issues to be studied with financial and environmental researchers together. Especially at city level, it is necessary to develop new GBs assessment methods to check the comprehensive environmental implications of the GBs projects. For this purpose, we discuss about the enhancement of currently developing district level Green Building standards and certification systems (LEED-ND). We also report about our new research results regarding city scale monitoring system (CO2, energy, transport, ecosystem etc.) for the reporting. *This paper is related to a Future Earth (Global Carbon Project) project proposal. It is also linked with development regarding the Knowledge Action Networks.

Elastomeric binders for Li-SOCl2 cell carbon electrodes

Science.gov (United States)

Carter, B. J.; Jeffries, B.; Yen, S. P. S.

1987-01-01

Nonoptimized elastomer bonded carbon electrodes made with 100-percent compressed Gulf Acetylene Black have demonstrated performance comparable to that of optimized Teflon bonded carbon electrodes, made from the same carbon, when tested at 1-10 mA/sq cm, at 24 and -26 C. The enhanced performance of elastomer bonded carbon electrodes appears to be due to the more uniform utilization of the carbon electrode to store insoluble discharge products, as compared to Teflon bonded carbon electrodes. With even minimal optimization of elastomer bonded carbon electrodes, significant improvement in Li-SOCl2 cell performance can be expected.

Study on the decomposition mechanism of alkyl carbonate on lithium metal by pyrolysis-gas chromatography-mass spectroscopy

Science.gov (United States)

Mogi, Ryo; Inaba, Minoru; Iriyama, Yasutoshi; Abe, Takeshi; Ogumi, Zempachi

The surface films formed on deposited lithium in electrolyte solutions based on ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were analyzed by pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS). In 1 M LiClO 4/EC, the main component of the surface film was easily hydrolyzed to give ethylene glycol after exposure to air, and hence was considered to have a chemical structure of ROCH 2CH 2OR', of which OR and OR' are OLi or OCO 2Li. Ethylene oxide, acetaldehyde, and 1,4-dioxane were detected in decomposition products, and they were considered to have been formed by pyrolysis of ROCH 2CH 2OR' in the pyrolyzer. The presence of ethanol in decomposition products confirmed that ring cleavage at the CH 2O bonds of EC occurs by one electron reduction. In addition, the presence of methanol implied the cleavage of the CC bond of EC upon reduction. From the surface films formed in 1 M LiClO 4/DEC and /DMC, ethanol and methanol, respectively, were detected, which suggested that corresponding lithium alkoxides and/or lithium alkyl carbonates were the main components. In 1 M LiClO 4/EC+DEC (1:1), EC dominantly decomposed to form the surface film. The surface film formed in 1 M LiPF 6/EC+DEC (1:1) contained a much smaller amount of organic compounds.

The effect of carbon-chain oxygenation in the carbon-carbon dissociation.

Science.gov (United States)

Dos Santos, Lisandra Paulino; Baptista, Leonardo

2018-06-01

Currently, there is a trend of moving away from the use of fossil fuels to the use of biofuels. This modification changes the molecular structure of gasoline and diesel constituents, which should impact pollutant emissions and engine efficiency. An important property of automotive fuels is the resistance to autoignition. The goal of the present work is to evaluate thermochemical and kinetic parameters that govern the carbon-carbon bond dissociation and relate these parameters, in conjunction with molecular properties, to autoignition resistance. Three model reactions were investigated in the present work: dissociation of ethane, ethanol, and ethanal. All studies were conducted at the multiconfigurational level of theory, and the rate coefficients were evaluated from 300 to 2000 K. The comparison of dissociation energies and Arrhenius expressions indicates that autoignition resistance is related to the kinetic control of dissociation reactions and it is possible to relate the higher octane number of ethanol based fuels to the kinetics parameters of carbon-carbon bond fission. Graphical abstract Effect of the functional group in the Arrhenius parameters of the C-C dissociation. Arrhenius curves calculated at NEVPT2(6,6)/6-311G(2df,2pd).

Change of chemical bond and wettability of polylacticacid implanted with high-flux carbon ion

International Nuclear Information System (INIS)

Zhang Jizhong; Kang Jiachen; Zhang Xiaoji; Zhou Hongyu

2008-01-01

Polylacticacid (PLA) was submitted to high-flux carbon ion implantation with energy of 40 keV. It was investigated to the effect of ion fluence (1 x 10 12 -1 x 10 15 ions/cm 2 ) on the properties of the polymer. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), wettability, and roughness were employed to study change of structure and properties of the as-implanted PLA samples. Six carbon bonds, that is, C, C-H, C-O-C, C-O, O-C-O, and >C=O, were observed on surfaces of the as-implanted PLA samples. The intensities of various chemical bonds changed with increasing ion fluence. AFM images displayed that there was irradiation damage and that it was related closely with ion fluence. At fluence as high as 1 x 10 15 ions/cm 2 surface-restructuring phenomenum took place on the surface of the PLA. Wettability was also affected by the variation on the fluence. With increasing ion fluence, the water contact angle of the as-implanted PLA samples changed gradually reaching a maximum of 76.5 deg. with 1 x 10 13 ions/cm 2 . The experimental results revealed that carbon ion fluence strongly affected surface chemical bond, morphology, wettability, and roughness of the PLA samples

Ultrafast cooling by covalently bonded graphene-carbon nanotube hybrid immersed in water

DEFF Research Database (Denmark)

Chen, Jie; Walther, Jens Honore; Koumoutsakos, Petros

2016-01-01

, we demonstrate, through transient heat-dissipation simulations, that a covalently bonded graphene-carbon nanotube (G-CNT) hybrid immersed in water is a promising solution for the ultrafast cooling of such high-temperature and high heat-flux surfaces. The G-CNT hybrid offers a unique platform...

Designing electronic anisotropy of three-dimensional carbon allotropes for the all-carbon device

Energy Technology Data Exchange (ETDEWEB)

Xu, Li-Chun, E-mail: xulichun@tyut.edu.cn; Song, Xian-Jiang; Yang, Zhi; Li, Xiu-Yan [College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); Wang, Ru-Zhi; Yan, Hui [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China)

2015-07-13

Extending two-dimensional (2D) graphene nanosheets to a three-dimensional (3D) network can enhance the design of all-carbon electronic devices. Based on the great diversity of carbon atomic bonding, we have constructed four superlattice-type carbon allotrope candidates, containing sp{sup 2}-bonding transport channels and sp{sup 3}-bonding insulating layers, using density functional theory. It was demonstrated through systematic simulations that the ultra-thin insulating layer with only three-atom thickness can switch off the tunneling transport and isolate the electronic connection between the adjacent graphene strips, and these alternating perpendicular strips also extend the electron road from 2D to 3D. Designing electronic anisotropy originates from the mutually perpendicular π bonds and the rare partial charge density of the corresponding carriers in insulating layers. Our results indicate the possibility of producing custom-designed 3D all-carbon devices with building blocks of graphene and diamond.

Reversible insertion of carbon dioxide into Pt(II)-hydroxo bonds.

Science.gov (United States)

Lohr, Tracy L; Piers, Warren E; Parvez, Masood

2013-10-01

The reactivity of three monomeric diimine Pt(II) hydroxo complexes, (NN)Pt(OH)R (NN = bulky diimine ligand; R = OH, ; R = C6H5, ; R = CH3, ) towards carbon dioxide has been investigated. Insertion into the Pt-OH bonds was found to be facile and reversible at low temperature for all compounds; the reaction with bis-hydroxide gives an isolable κ(2)-carbonato compound , with elimination of water.

Method for production of carbon nanofiber mat or carbon paper

Science.gov (United States)

Naskar, Amit K.

2015-08-04

Method for the preparation of a non-woven mat or paper made of carbon fibers, the method comprising carbonizing a non-woven mat or paper preform (precursor) comprised of a plurality of bonded sulfonated polyolefin fibers to produce said non-woven mat or paper made of carbon fibers. The preforms and resulting non-woven mat or paper made of carbon fiber, as well as articles and devices containing them, and methods for their use, are also described.

Bond Behavior of Wet-Bonded Carbon Fiber-Reinforced Polymer-Concrete Interface Subjected to Moisture

OpenAIRE

Yiyan Lu; Tao Zhu; Shan Li; Zhenzhen Liu

2018-01-01

The use of carbon fiber-reinforced polymer (CFRP) composite materials to strengthen concrete structures has become popular in coastal regions with high humidity levels. However, many concrete structures in these places remain wet as a result of tides and wave-splashing, so they cannot be completely dried before repair. Therefore, it is vital to investigate the effects of moisture on the initial and long-term bond behavior between CFRP and wet concrete. This research assesses the effects of mo...

Catalytic-site mapping of pyruvate formate lyase. Hypophosphite reaction on the acetyl-enzyme intermediate affords carbon-phosphorus bond synthesis (1-hydroxyethylphosphonate).

Science.gov (United States)

Plaga, W; Frank, R; Knappe, J

1988-12-15

Pyruvate formate-lyase of Escherichia coli cells, a homodimeric protein of 2 x 85 kDa, is distinguished by the property of containing a stable organic free radical (g = 2.0037) in its resting state. The enzyme (E-SH) achieves pyruvate conversion to acetyl-CoA via two distinct half-reactions (E-SH + pyruvate in equilibrium E-S-acetyl + formate; E-S-acetyl + CoA in equilibrium E-SH + acetyl-CoA), the first of which has been proposed to involve reversible homolytic carbon-carbon bond cleavage [J. Knappe et al. (1984) Proc. Natl Acad. Sci. USA 81, 1332-1335]. Present studies identified Cys-419 as the covalent-catalytic cysteinyl residue via CNBr fragmentation of E-S-[14C]acetyl and radio-sequencing of the isolated peptide CB-Ac (amino acid residues 406-423). Reaction of the formate analogue hypophosphite with E-S-acetyl was investigated and found to produce 1-hydroxyethylphosphonate with a thioester linkage to the adjacent Cys-418. The structure was determined from the chymotryptic peptide CH-P (amino acid residues 415-425), using 31P-NMR spectroscopy (delta = 44 ppm) and by chemical characterisation through degradation into 1-hydroxyethylphosphonate with phosphodiesterase or bromine. This novel P-C-bond synthesis involves the enzyme-based free radical and is proposed to resemble the physiological C-C-bond synthesis (pyruvate production) from formate and E-S-acetyl. These findings are interpreted as proof of a radical mechanism for the action of pyruvate formate-lyase. The central Cys-418/Cys-419 pair of the active site shows a distinctive thiolate property even in the inactive (nonradical) form of the enzyme, as determined using an iodoacetate probe.

Glutamic Acid Selective Chemical Cleavage of Peptide Bonds.

Science.gov (United States)

Nalbone, Joseph M; Lahankar, Neelam; Buissereth, Lyssa; Raj, Monika

2016-03-04

Site-specific hydrolysis of peptide bonds at glutamic acid under neutral aqueous conditions is reported. The method relies on the activation of the backbone amide chain at glutamic acid by the formation of a pyroglutamyl (pGlu) imide moiety. This activation increases the susceptibility of a peptide bond toward hydrolysis. The method is highly specific and demonstrates broad substrate scope including cleavage of various bioactive peptides with unnatural amino acid residues, which are unsuitable substrates for enzymatic hydrolysis.

Influence of disorder on localization and density of states in amorphous carbon nitride thin films systems rich in π-bonded carbon atoms

International Nuclear Information System (INIS)

Alibart, F.; Lejeune, M.; Durand Drouhin, O.; Zellama, K.; Benlahsen, M.

2010-01-01

We discuss in this paper the evolution of both the density of states (DOS) located between the band-tail states and the DOS around the Fermi level N(E F ) in amorphous carbon nitride films (a-CN x ) as a function of the total nitrogen partial pressure ratio in the Ar/N 2 plasma mixture. The films were deposited by three different deposition techniques and their microstructure was characterized using a combination of infrared and Raman spectroscopy and optical transmission experiments, completed with electrical conductivity measurements, as a function of temperature. The observed changes in the optoelectronic properties are attributed to the modification in the atomic bonding structures, which were induced by N incorporation, accompanied by an increase in the sp 2 carbon bonding configurations and their relative disorder. The electrical conductivity variation was interpreted in terms of local effects on the nature and energy distribution of π and π* states.

Carbon elimination from silicon kerf: Thermogravimetric analysis and mechanistic considerations.

Science.gov (United States)

Vazquez-Pufleau, Miguel; Chadha, Tandeep S; Yablonsky, Gregory; Biswas, Pratim

2017-01-18

40% of ultrapure silicon is lost as kerf during slicing to produce wafers. Kerf is currently not being recycled due to engineering challenges and costs associated with removing its abundant impurities. Carbon left behind from the lubricant remains as one of the most difficult contaminants to remove in kerf without significant silicon oxidation. The present work enables to better understand the mechanism of carbon elimination in kerf which can aid the design of better processes for kef recycling and low cost photovoltaics. In this paper, we studied the kinetics of carbon elimination from silicon kerf in two atmospheres: air and N 2, under a regime of no-diffusion-limitation. We report the apparent activation energy in both atmospheres using three methods: Kissinger, and two isoconversional approaches. In both atmospheres, a bimodal apparent activation energy is observed, suggesting a two stage process. A reaction mechanism is proposed in which (a) C-C and C-O bond cleavage reactions occur in parallel with polymer formation; (b) at higher temperatures, this polymer fully degrades in air but leaves a tarry residue in N 2 that accounts for about 12% of the initial total carbon.

Synthetic Applications and Mechanistic Studies of the Hydroxide-Mediated Cleavage of Carbon-Carbon Bonds in Ketones

DEFF Research Database (Denmark)

Mazziotta, Andrea; Makarov, Ilya S.; Fristrup, Peter

2017-01-01

The hydroxide-mediated cleavage of ketones into alkanes and carboxylic acids has been reinvestigated and the substrate scope extended to benzyl carbonyl compounds. The transformation is performed with a 0.05 M ketone solution in refluxing xylene in the presence of 10 equiv of potassium hydroxide....... The reaction constitutes a straightforward protocol for the synthesis of certain phenyl-substituted carboxylic acids from 2-phenylcycloalkanones. The mechanism was investigated by kinetic experiments which indicated a first order reaction in hydroxide and a full negative charge in the rate-determining step....... The studies were complemented by a theoretical investigation where two possible pathways were characterized by DFT/M06-2X. The calculations showed that the scission takes place by nucleophilic attack of hydroxide on the ketone followed by fragmentation of the resulting oxyanion into the carboxylic acid...

Synthetic Applications and Mechanistic Studies of the Hydroxide-Mediated Cleavage of Carbon-Carbon Bonds in Ketones.

Science.gov (United States)

Mazziotta, Andrea; Makarov, Ilya S; Fristrup, Peter; Madsen, Robert

2017-06-02

The hydroxide-mediated cleavage of ketones into alkanes and carboxylic acids has been reinvestigated and the substrate scope extended to benzyl carbonyl compounds. The transformation is performed with a 0.05 M ketone solution in refluxing xylene in the presence of 10 equiv of potassium hydroxide. The reaction constitutes a straightforward protocol for the synthesis of certain phenyl-substituted carboxylic acids from 2-phenylcycloalkanones. The mechanism was investigated by kinetic experiments which indicated a first order reaction in hydroxide and a full negative charge in the rate-determining step. The studies were complemented by a theoretical investigation where two possible pathways were characterized by DFT/M06-2X. The calculations showed that the scission takes place by nucleophilic attack of hydroxide on the ketone followed by fragmentation of the resulting oxyanion into the carboxylic acid and a benzyl anion.

Carbon films produced from ionic liquid carbon precursors

Science.gov (United States)

Dai, Sheng; Luo, Huimin; Lee, Je Seung

2013-11-05

The invention is directed to a method for producing a film of porous carbon, the method comprising carbonizing a film of an ionic liquid, wherein the ionic liquid has the general formula (X.sup.+a).sub.x(Y.sup.-b).sub.y, wherein the variables a and b are, independently, non-zero integers, and the subscript variables x and y are, independently, non-zero integers, such that ax=by, and at least one of X.sup.+ and Y.sup.- possesses at least one carbon-nitrogen unsaturated bond. The invention is also directed to a composition comprising a porous carbon film possessing a nitrogen content of at least 10 atom %.

Novamene: A new class of carbon allotropes

Directory of Open Access Journals (Sweden)

Larry A Burchfield

2017-02-01

Full Text Available We announce a new class of carbon allotropes. The basis of this new classification resides on the concept of combining hexagonal diamond (sp3 bonded carbon − lonsdaleite and ring carbon (sp2 bonded carbon − graphene. Since hexagonal diamond acts as an insulator and sp2 bonded rings act as conductors, these predicted materials have potential applications for transistors and other electronic components. We describe the structure of a proposed series of carbon allotropes, novamene, and carry out a detailed computational analysis of the structural and electronic properties of the simplest compound in this class: the single-ring novamene. In addition, we suggest how hundreds of different allotropes of carbon could be constructed within this class.

Low temperature thermocompression bonding between aligned carbon nanotubes and metallized substrate

Energy Technology Data Exchange (ETDEWEB)

Chen, M X; Gan, Z Y; Liu, S [School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Song, X H, E-mail: chimish@163.com [Division of MOEMS, Wuhan National Lab for Optoelectronics, Wuhan 430074 (China)

2011-08-26

Vertically aligned carbon nanotube (VACNT) turf is proposed for use as an electrical and thermal contact material. For these applications, one route for circumventing the high temperatures required for VACNT growth using chemical vapor deposition (CVD) is used to grow firstly VACNTs on one substrate and then transfer them to other substrates. In this work, a nano thermocompression bonding technique between VACNTs and a metallized substrate is developed to allow dry mechanical transfer of the VACNTs. Unlike the diffusion bonding between two bulk materials, nano metal clusters have a high surface energy and the atoms are very active to form alloy with the contacted bulk metal material even at much lower temperatures, so nano thermocompression bonding can decrease the bonding temperature (150 deg. C) and pressure (1 MPa) and greatly shorten the bonding time from hours to 20 min. A debonding experiment shows that the bonding strength between VACNTs and the metallized layer is so high that a break is less likely to occur at the bonding interface.

Cleavage of thymine N3-H bonds by low-energy electrons attached to base π* orbitals

International Nuclear Information System (INIS)

Theodore, Magali; Sobczyk, Monika; Simons, Jack

2006-01-01

In this work, we extend our earlier studies on single strand break (SSB) formation in DNA to consider the possibility of cleaving a thymine N 3 -H bond to generate a nitrogen-centered anion and a hydrogen radical which might proceed to induce further bond cleavages. In earlier studies, we considered SSBs induced by low-energy electrons that attach to DNA bases' π* orbitals or to phosphate P=O π* orbitals to cleave sugar-phosphate C-O bonds or base-sugar N 1 -C bonds. We also studied the effects of base π-stacking on the rates of such bond cleavages. To date, our results suggest that sugar-phosphate C-O bonds have the lowest barriers to cleavage, that attachment of electrons with energies below 2 eV most likely occurs at the base π* orbitals, that electrons with energy above 2 eV can also attach to phosphate P=O π* orbitals, and that base π stacking has a modest but slowing effect on the rates of SSB formation. However, we had not yet examined the possibility that base N 3 -H bonds could rupture subsequent to base π* orbital capture. In the present work, the latter possibility is considered and it is found that the barrier to cleavage of the N 3 -H bond in thymine is considerably higher than for cleaving sugar-phosphate C-O bonds, so our prediction that SSB formation is dominated by C-O bond cleavage remains intact

Cleavage of sp3 C-O bonds via oxidative addition of C-H bonds.

Science.gov (United States)

Choi, Jongwook; Choliy, Yuriy; Zhang, Xiawei; Emge, Thomas J; Krogh-Jespersen, Karsten; Goldman, Alan S

2009-11-04

(PCP)Ir (PCP = kappa(3)-C(6)H(3)-2,6-[CH(2)P(t-Bu)(2)](2)) is found to undergo oxidative addition of the methyl-oxygen bond of electron-poor methyl aryl ethers, including methoxy-3,5-bis(trifluoromethyl)benzene and methoxypentafluorobenzene, to give the corresponding aryloxide complexes (PCP)Ir(CH(3))(OAr). Although the net reaction is insertion of the Ir center into the C-O bond, density functional theory (DFT) calculations and a significant kinetic isotope effect [k(CH(3))(OAr)/k(CD(3))(OAr) = 4.3(3)] strongly argue against a simple insertion mechanism and in favor of a pathway involving C-H addition and alpha-migration of the OAr group to give a methylene complex followed by hydride-to-methylene migration to give the observed product. Ethoxy aryl ethers, including ethoxybenzene, also undergo C-O bond cleavage by (PCP)Ir, but the net reaction in this case is 1,2-elimination of ArO-H to give (PCP)Ir(H)(OAr) and ethylene. DFT calculations point to a low-barrier pathway for this reaction that proceeds through C-H addition of the ethoxy methyl group followed by beta-aryl oxide elimination and loss of ethylene. Thus, both of these distinct C-O cleavage reactions proceed via initial addition of a C(sp(3))-H bond, despite the fact that such bonds are typically considered inert and are much stronger than C-O bonds.

Reactive bonding mediated high mass loading of individualized single-walled carbon nanotubes in an elastomeric polymer

Science.gov (United States)

Zhao, Liping; Li, Yongjin; Qiu, Jishan; You, Jichun; Dong, Wenyong; Cao, Xiaojun

2012-09-01

A reactive chemical bonding strategy was developed for the incorporation of a high mass loading of individual single-wall carbon nanotubes (SWCNTs) into an elastomeric matrix using a reactive ionic liquid as a linker. This method simultaneously prevented the agglomeration of SWCNTs and caused strong interfacial bonding, while the electronic properties of the SWCNTs remained intact. As a result, the high conductivity of the carbon nanotubes (CNTs) and the flexibility of the elastomeric matrix were retained, producing optimum electrical and mechanical properties. A composite material with a loading of 20 wt% SWCNTs was fabricated with excellent mechanical properties and a high conductivity (9500 S m-1). The method could be used to form transparent thin conductive films that could tolerate over 800 bend cycles at a bending angle of 180° while maintaining a constant sheet resistance.A reactive chemical bonding strategy was developed for the incorporation of a high mass loading of individual single-wall carbon nanotubes (SWCNTs) into an elastomeric matrix using a reactive ionic liquid as a linker. This method simultaneously prevented the agglomeration of SWCNTs and caused strong interfacial bonding, while the electronic properties of the SWCNTs remained intact. As a result, the high conductivity of the carbon nanotubes (CNTs) and the flexibility of the elastomeric matrix were retained, producing optimum electrical and mechanical properties. A composite material with a loading of 20 wt% SWCNTs was fabricated with excellent mechanical properties and a high conductivity (9500 S m-1). The method could be used to form transparent thin conductive films that could tolerate over 800 bend cycles at a bending angle of 180° while maintaining a constant sheet resistance. Electronic supplementary information (ESI) available: Conductivity test of the SEBS-SWCNTs film, transmission spectra and sheet resistance for the spin-coated SEBS-SWCNTs thin films on PET slides. See DOI: 10

New carbon-carbon linked amphiphilic carboranyl-porphyrins as boron neutron capture agents

International Nuclear Information System (INIS)

Vicente, M.G.H.; Wickramasinghe, A.; Shetty, S.J.; Smith, K.M.

2000-01-01

Novel amphiphilic carboranyl-porphyrins have been synthesized for Boron Neutron Capture Therapy (BNCT). These compounds have carbon-carbon bonds between the carborane residues and the porphyrin meso-phenyl groups, and contain 28-31% boron by weight . (author)

Tendances Carbone no. 66 'Understanding the link between macro-economic environment and the EU carbon price'

International Nuclear Information System (INIS)

Chevallier, Julien

2012-01-01

Among the publications of CDC Climat Research, 'Tendances Carbone' bulletin specifically studies the developments of the European market for CO 2 allowances. This issue addresses the following points: The reaction of the carbon price to changes in macro-economic fundamentals can be understood from different levels. My recent academic research has identified two strong linkages. First, there is a link between the EU carbon price and financial markets, such as equity and bond markets. These analyses emphasize how the volatility of the carbon price is affected when financial markets enter 'bull' or 'bear' periods. By estimating various volatility models, carbon futures prices may be weakly forecasted on the basis of two variables from the stock and bond markets, i.e equity dividend yields (returns on stocks) and the 'junk bond' premium (spread between BAA- and AAA-rated bonds). Moreover, by assessing the transmission of international shocks to the carbon market, carbon prices tend to respond negatively to an exogenous recessionary shock on global economic indicators. In consequence, for investments managers, carbon assets such as EUA appear to be well-suited for portfolio diversification since they do not match exactly the business cycle. The second relationship addresses the physical association between industrial production and carbon price changes though the emissions level. The first objective of an academic researcher is to identify the most explanatory variable: in our case, the monthly Eurostat aggregated industrial production index to proxy for changes in macro-economic fundamentals. In the light of the recent periods of economic expansion (2005-2007) and recession (since 2008), several studies can bring fruitful results: - Our results tend to confirm that the carbon market adjusts to the macro-economic environment with a delay due to the specific institutional constraints of the EU ETS. - The relationship between carbon prices and EU industrial production has

A rechargeable carbon-oxygen battery

DEFF Research Database (Denmark)

2014-01-01

The invention relates to a rechargeable battery and a method to operate a rechargeable battery having high efficiency and high energy density for storing energy. The battery stores electrical energy in the bonds of carbon and oxygen atoms by converting carbon dioxide into solid carbon and oxygen....

Experiment-Based Sensitivity Analysis of Scaled Carbon-Fiber-Reinforced Elastomeric Isolators in Bonded Applications

Directory of Open Access Journals (Sweden)

Farshad Hedayati Dezfuli

2016-01-01

Full Text Available Fiber-reinforced elastomeric isolators (FREIs are a new type of elastomeric base isolation systems. Producing FREIs in the form of long laminated pads and cutting them to the required size significantly reduces the time and cost of the manufacturing process. Due to the lack of adequate information on the performance of FREIs in bonded applications, the goal of this study is to assess the performance sensitivity of 1/4-scale carbon-FREIs based on the experimental tests. The scaled carbon-FREIs are manufactured using a fast cold-vulcanization process. The effect of several factors including the vertical pressure, the lateral cyclic rate, the number of rubber layers, and the thickness of carbon fiber-reinforced layers are explored on the cyclic behavior of rubber bearings. Results show that the effect of vertical pressure on the lateral response of base isolators is negligible. However, decreasing the cyclic loading rate increases the lateral flexibility and the damping capacity. Additionally, carbon fiber-reinforced layers can be considered as a minor source of energy dissipation.

K{sub 6} carbon: A metallic carbon allotrope in sp{sup 3} bonding networks

Energy Technology Data Exchange (ETDEWEB)

Niu, Chun-Yao; Wang, Xin-Quan; Wang, Jian-Tao, E-mail: wjt@aphy.iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-02-07

We identify by first-principles calculations a new cubic carbon phase in I4{sub 1}32 (O{sup 8}) symmetry, named K{sub 6} carbon, which has a six atom primitive cell comprising sp{sup 3} hybridized C{sub 3} triangle rings. The structural stability is verified by phonon mode analysis. The calculated elastic constants show that the K{sub 6} carbon is a high ductile material with a density even lower than graphite. Electronic band and density of states calculations reveal that it is a metallic carbon allotrope with a high electronic density of states of ∼0.10 states/eV per atom at the Fermi level. These results broaden our understanding of the structural and electronic properties of carbon allotropes.

Carbon-tuned bonding method significantly enhanced the hydrogen storage of BN-Li complexes.

Science.gov (United States)

Deng, Qing-ming; Zhao, Lina; Luo, You-hua; Zhang, Meng; Zhao, Li-xia; Zhao, Yuliang

2011-11-01

Through first-principles calculations, we found doping carbon atoms onto BN monolayers (BNC) could significantly strengthen the Li bond on this material. Unlike the weak bond strength between Li atoms and the pristine BN layer, it is observed that Li atoms are strongly hybridized and donate their electrons to the doped substrate, which is responsible for the enhanced binding energy. Li adsorbed on the BNC layer can serve as a high-capacity hydrogen storage medium, without forming clusters, which can be recycled at room temperature. Eight polarized H(2) molecules are attached to two Li atoms with an optimal binding energy of 0.16-0.28 eV/H(2), which results from the electrostatic interaction of the polarized charge of hydrogen molecules with the electric field induced by positive Li atoms. This practical carbon-tuned BN-Li complex can work as a very high-capacity hydrogen storage medium with a gravimetric density of hydrogen of 12.2 wt%, which is much higher than the gravimetric goal of 5.5 wt % hydrogen set by the U.S. Department of Energy for 2015.

Graphene-carbon nanotube hybrid materials and use as electrodes

Science.gov (United States)

Tour, James M.; Zhu, Yu; Li, Lei; Yan, Zheng; Lin, Jian

2016-09-27

Provided are methods of making graphene-carbon nanotube hybrid materials. Such methods generally include: (1) associating a graphene film with a substrate; (2) applying a catalyst and a carbon source to the graphene film; and (3) growing carbon nanotubes on the graphene film. The grown carbon nanotubes become covalently linked to the graphene film through carbon-carbon bonds that are located at one or more junctions between the carbon nanotubes and the graphene film. In addition, the grown carbon nanotubes are in ohmic contact with the graphene film through the carbon-carbon bonds at the one or more junctions. The one or more junctions may include seven-membered carbon rings. Also provided are the formed graphene-carbon nanotube hybrid materials.

Chromate adsorption mechanism on nanodiamond-derived onion-like carbon

Energy Technology Data Exchange (ETDEWEB)

Ko, Young-Jin [Center for Electronic Materials, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea (Korea, Republic of); Choi, Keunsu [Computational Science Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea (Korea, Republic of); Lee, Soonjae [Department of Earth and Environmental Sciences, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea (Korea, Republic of); Cho, Jung-Min [Center for Electronic Materials, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea (Korea, Republic of); Department of Materials Science and Engineering, Yonsei University, 262 Seongsanno, Seodaemun-Gu, Seoul 120-749, Republic of Korea (Korea, Republic of); Choi, Heon-Jin [Department of Materials Science and Engineering, Yonsei University, 262 Seongsanno, Seodaemun-Gu, Seoul 120-749, Republic of Korea (Korea, Republic of); Hong, Seok Won [Center for Water Resource Cycle Research, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea (Korea, Republic of); Choi, Jae-Woo, E-mail: plead36@kist.re.kr [Center for Water Resource Cycle Research, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea (Korea, Republic of); Department of Energy and Environmental Engineering, University of Science and Technology (UST), Daejeon 305-350, Republic of Korea (Korea, Republic of); Mizuseki, Hiroshi, E-mail: mizuseki@kist.re.kr [Computational Science Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea (Korea, Republic of); Lee, Wook-Seong, E-mail: wsleemk@gmail.com [Center for Electronic Materials, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea (Korea, Republic of)

2016-12-15

The onion-like carbon (OLC) was prepared as adsorbent and tested for the removal of chromate ions from aqueous solutions. The OLC was thermally derived from nanodiamond by vacuum annealing at 1000-2000 °C. An investigation was conducted the chromate adsorption mechanism of OLC, by analysing the temperature-dependent evolution of the various oxygen-carbon bonds and the chemisorbed water by X-ray photo electron spectroscopy, as well as by the first principle calculation of the bond energies for relevant bond configurations. The present work demonstrated the importance of the carbon-oxygen bond type and carbon dangling bonds for chromate adsorption, as well as for other anionic heavy metals adsorbed from wastewater and sewage.

ATP-Dependent C–F Bond Cleavage Allows the Complete Degradation of 4-Fluoroaromatics without Oxygen

Directory of Open Access Journals (Sweden)

Oliver Tiedt

2016-08-01

Full Text Available Complete biodegradation of the abundant and persistent fluoroaromatics requires enzymatic cleavage of an arylic C–F bond, probably the most stable single bond of a biodegradable organic molecule. While in aerobic microorganisms defluorination of fluoroaromatics is initiated by oxygenases, arylic C–F bond cleavage has never been observed in the absence of oxygen. Here, an oxygen-independent enzymatic aryl fluoride bond cleavage is described during the complete degradation of 4-fluorobenzoate or 4-fluorotoluene to CO2 and HF in the denitrifying Thauera aromatica: the ATP-dependent defluorination of 4-fluorobenzoyl-coenzyme A (4-F-BzCoA to benzoyl-coenzyme A (BzCoA and HF, catalyzed by class I BzCoA reductase (BCR. Adaptation to growth with the fluoroaromatics was accomplished by the downregulation of a promiscuous benzoate-CoA ligase and the concomitant upregulation of 4-F-BzCoA-defluorinating/dearomatizing BCR on the transcriptional level. We propose an unprecedented mechanism for reductive arylic C–F bond cleavage via a Birch reduction-like mechanism resulting in a formal nucleophilic aromatic substitution. In the proposed anionic 4-fluorodienoyl-CoA transition state, fluoride elimination to BzCoA is favored over protonation to a fluorinated cyclic dienoyl-CoA.

Electrostrictive deformations in small carbon clusters, hydrocarbon molecules, and carbon nanotubes

International Nuclear Information System (INIS)

Cabria, I.; Lopez, M. J.; Alonso, J. A.; Amovilli, C.; March, N. H.

2006-01-01

The electrostrictive response of small carbon clusters, hydrocarbon molecules, and carbon nanotubes is investigated using the density functional theory. For ringlike carbon clusters, one can get insight on the deformations induced by an electric field from a simple two-dimensional model in which the positive charge of the carbon ions is smeared out in a circular homogeneous line of charge and the electronic density is calculated for a constant applied electric field within a two-dimensional Thomas-Fermi method. According to the Hellmann-Feynman theorem, this model predicts, for fields of about 1 V/A ring , only a small elongation of the ring clusters in the direction of the electric field. Full three-dimensional density functional calculations with an external electric field show similar small deformations in the ring carbon clusters compared to the simple model. The saturated benzene and phenanthrene hydrocarbon molecules do not experience any deformation, even under the action of relatively intense (1 V/A ring ) electric fields. In contrast, finite carbon nanotubes experience larger elongations (∼2.9%) induced by relatively weak (0.1 V/A ring ) applied electric fields. Both C-C bond length elongation and the deformation of the honeycomb structure contribute equally to the nanotube elongation. The effect of the electric field in hydrogen terminated nanotubes is reduced with respect to the nanotubes with dangling bonds in the edges

Effect of carbon coating on cycle performance of LiFePO4/C composite cathodes using Tween80 as carbon source

International Nuclear Information System (INIS)

Huang, You-Guo; Zheng, Feng-Hua; Zhang, Xiao-Hui; Li, Qing-Yu; Wang, Hong-Qiang

2014-01-01

Highlights: • The Tween80 addition could enhance cycle stability of LiFePO 4 material. • The FTIR spectrum confirms Tween80 surfactant can bond with LiFePO 4 particles. • Some chemical bonds between material and carbon layer still exist after sintering. - Abstract: The influence of carbon coating on the cycle performance of LiFePO 4 /C composite cathodes using polyoxyethylenesorbitan monooleate (Tween80) as carbon source against lithium metal foil anode for Li-ion batteries was investigated in this paper. According to Infrared spectrum analysis (FTIR), the Tween80 surfactant molecules bond to the surface of LiFePO 4 and form an adsorption layer, which contribute to the formation of a homogeneous carbon layer tightly coating on the surface of LiFePO 4 particles in the process of sintering, due to a strong binding force provided by surface chemical bonds. The transmission electron microscopy (TEM) shows that the carbon layer around LiFePO 4 using Tween80 as carbon source still coating on the surface of LiFePO 4 after 200 cycles at 5 C rate while the carbon layer shed from the surface of LiFePO 4 using glucose as carbon source. As a result, the carbon-coated LiFePO 4 using Tween80 as carbon source exhibits much higher capacity retention than the sample using glucose as carbon source. Electrochemical impedance measurement (EIS) reveals that the carbon-coated LiFePO 4 electrode using Tween80 surfactant has a lower charge transfer resistance than the electrode using glucose as carbon source electrode after 100 and 200 cycles at 5 C rate

Study on the bonding state for carbon-boron nitrogen with different ball milling time

International Nuclear Information System (INIS)

Xiong, Y.H.; Xiong, C.S.; Wei, S.Q.; Yang, H.W.; Mai, Y.T.; Xu, W.; Yang, S.; Dai, G.H.; Song, S.J.; Xiong, J.; Ren, Z.M.; Zhang, J.; Pi, H.L.; Xia, Z.C.; Yuan, S.L.

2006-01-01

The varied bonding state and microstructure characterization were discussed for carbon-boron nitrogen (CBN) with abundant phase structure and nanostructure, which were synthesized directly by mechanical alloying technique at room temperature. According to the results of SEM and X-ray photoelectron spectroscopy (XPS) of CBN with different ball milling time, it is substantiated that the bonding state and microstructure for CBN were closely related to the ball milling time. With the increase of the ball milling time, some new chemical bonding states of CBN were observed, which implies that some new bonding state and microstructures have been formed. The results of XPS are accordance with that of X-ray diffraction of CBN

Determination of Double Bond Positions in Polyunsaturated Fatty Acids Using the Photochemical Paternò-Büchi Reaction with Acetone and Tandem Mass Spectrometry.

Science.gov (United States)

Murphy, Robert C; Okuno, Toshiaki; Johnson, Christopher A; Barkley, Robert M

2017-08-15

The positions of double bonds along the carbon chain of methylene interrupted polyunsaturated fatty acids are unique identifiers of specific fatty acids derived from biochemical reactions that occur in cells. It is possible to obtain direct structural information as to these double bond positions using tandem mass spectrometry after collisional activation of the carboxylate anions of an acetone adduct at each of the double bond positions formed by the photochemical Paternò-Büchi reaction with acetone. This reaction can be carried out by exposing a small portion of an inline fused silica capillary to UV photons from a mercury vapor lamp as the sample is infused into the electrospray ion source of a mass spectrometer. Collisional activation of [M - H] - yields a series of reverse Paternò-Büchi reaction product ions that essentially are derived from cleavage of the original carbon-carbon double bonds that yield an isopropenyl carboxylate anion corresponding to each double bond location. Aldehydic reverse Paternò-Büchi product ions are much less abundant as the carbon chain length and number of double bonds increase. The use of a mixture of D 0 /D 6 -acetone facilitates identification of these double bonds indicating product ions as shown for arachidonic acid. If oxygen is present in the solvent stream undergoing UV photoactivation, ozone cleavage ions are also observed without prior collisional activation. This reaction was used to determine the double bond positions in a 20:3 fatty acid that accumulated in phospholipids of RAW 264.7 cells cultured for 3 days.

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O

Energy Technology Data Exchange (ETDEWEB)

Kharlamov, Alexey [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine); Bondarenko, Marina, E-mail: mebondarenko@ukr.net [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine); Kharlamova, Ganna [Taras Shevchenko National University of Kiev, Volodymyrs' ka St. 64, 01601 Kiev (Ukraine); Fomenko, Veniamin [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine)

2016-09-15

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists of weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets. - Graphical abstract: XRD pattern and schematic atomic model of one layer of reduced carbon nitride, carbon nitride oxide and synthesized carbon nitride. For the first time at the reduction by hydroquinone of the water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O is obtained the reduced carbon nitride (or reduced multi-layer azagraphene). Display Omitted - Highlights: • First the reduced carbon nitride (RCN) at the reduction of the carbon nitride oxide was obtained. • Water-soluble carbon nitride oxide was reduced by hydroquinone. • The chemical bonds in a heteroatomic plane of RCN correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. • Reduced carbon nitride consists of poorly connected heteroatomic azagraphene layers.

A comparison of hydrogen-bonded and van der Waals isomers of phenolṡṡnitrogen and phenolṡṡcarbon monoxide: An ab initio study

Science.gov (United States)

Chapman, Darren M.; Müller-Dethlefs, Klaus; Peel, J. Barrie

1999-08-01

The hydrogen-bonded and van der Waals isomers of phenolṡṡnitrogen and phenolṡṡcarbon monoxide in their neutral electronic (S0) and cation ground state (D0) were studied using ab initio HF/6-31G*, MP2/6-31G*, and B3LYP/6-31G* methods. The hydrogen-bonded isomers have the ligand bound via the hydroxyl group of the phenol ring, while the van der Waals isomers studied have the ligand located above the aromatic ring. For both complexes, the hydrogen-bonded isomer was found to be the most stable form for both the S0 and the D0 states. For phenolṡṡcarbon monoxide, twice as many isomers as compared to phenolṡṡnitrogen were found. The hydrogen-bonded isomer with the carbon end bonded to the hydroxyl group was the most stable structure for both the S0 and the D0 states.

Enhancing Protein Disulfide Bond Cleavage by UV Excitation and Electron Capture Dissociation for Top-Down Mass Spectrometry.

Science.gov (United States)

Wongkongkathep, Piriya; Li, Huilin; Zhang, Xing; Loo, Rachel R Ogorzalek; Julian, Ryan R; Loo, Joseph A

2015-11-15

The application of ion pre-activation with 266 nm ultraviolet (UV) laser irradiation combined with electron capture dissociation (ECD) is demonstrated to enhance top-down mass spectrometry sequence coverage of disulfide bond containing proteins. UV-based activation can homolytically cleave a disulfide bond to yield two separated thiol radicals. Activated ECD experiments of insulin and ribonuclease A containing three and four disulfide bonds, respectively, were performed. UV-activation in combination with ECD allowed the three disulfide bonds of insulin to be cleaved and the overall sequence coverage to be increased. For the larger sized ribonuclease A with four disulfide bonds, irradiation from an infrared laser (10.6 µm) to disrupt non-covalent interactions was combined with UV-activation to facilitate the cleavage of up to three disulfide bonds. Preferences for disulfide bond cleavage are dependent on protein structure and sequence. Disulfide bonds can reform if the generated radicals remain in close proximity. By varying the time delay between the UV-activation and the ECD events, it was determined that disulfide bonds reform within 10-100 msec after their UV-homolytic cleavage.

Role of direct covalent bonding in enhanced heat dissipation property of flexible graphene oxide–carbon nanotube hybrid film

International Nuclear Information System (INIS)

Hwang, Yongseon; Kim, Myeongjin; Kim, Jooheon

2013-01-01

The thermal conductivity of graphene oxide/multiwalled carbon nanotube (GO/MWCNT) hybrid films with and without covalent bonding is examined in this study. To fabricate chemically bonded GO/MWCNT hybrid films, chlorinated GO and amino-functionalized MWCNTs are bonded covalently. The mixtures of surface modified GO and MWCNT were filtered and then subjected to hot pressing to fabricate stacked films. Examination of these chemically bonded hybrid films reveal that chlorine-doped GO exhibits enhanced electrical properties because it creates hole charge carriers by attracting the electrons in GO towards chlorine. Enhanced electrical conductivity and low sheet resistance are observed also with increasing MWCNT loadings. On comparing the through-plane thermal properties, the chemically bonded hybrid films were found to exhibit higher thermal conductivity than do the physically bonded hybrid films because of the synergetic interaction of functional groups in GO and MWCNTs in the former films. However, excess addition of MWCNTs to the films leads to an increasing phonon scattering density and a decreased thermal conductivity. - Highlights: • Graphene oxide/carbon nanotube (GO/CNT) films are bonded covalently. • GO/CNT hybrid films are prepared through filtering and hot-pressing method. • Chemically bonded hybrid films exhibit enhanced electrical and thermal properties. • Enhanced thermal conductivity is explained according to increasing CNT contents

Ionic liquid [OMIm][OAc] directly inducing oxidation cleavage of the β-O-4 bond of lignin model compounds.

Science.gov (United States)

Yang, Yingying; Fan, Honglei; Meng, Qinglei; Zhang, Zhaofu; Yang, Guanying; Han, Buxing

2017-08-03

We explored the oxidation reactions of lignin model compounds directly induced by ionic liquids under metal-free conditions. In this work, it was found that ionic liquid 1-octyl-3-methylimidazolium acetate as a solvent could promote the aerobic oxidation of lignin model compound 2-phenoxyacetophenone (1) and the yields of phenol and benzoic acid from 1 could be as high as 96% and 86%, respectively. A possible reaction pathway was proposed based on a series of control experiments. An acetate anion from the ionic liquid attacked the hydrogen from the β-carbon thereby inducing the cleavage of the C-O bond of the aromatic ether. Furthermore, it was found that 2-(2-methoxyphenoxy)-1-phenylethanone (4) with a methoxyl group could also be transformed into aromatic products in this simple reaction system and the yields of phenol and benzoic acid from 4 could be as high as 98% and 85%, respectively. This work provides a simple way for efficient transformation of lignin model compounds.

Copper-catalyzed transformation of ketones to amides via C(CO)-C(alkyl) bond cleavage directed by picolinamide.

Science.gov (United States)

Ma, Haojie; Zhou, Xiaoqiang; Zhan, Zhenzhen; Wei, Daidong; Shi, Chong; Liu, Xingxing; Huang, Guosheng

2017-09-13

Copper catalyzed chemoselective cleavage of the C(CO)-C(alkyl) bond leading to C-N bond formation with chelation assistance of N-containing directing groups is described. Inexpensive Cu(ii)-acetate serves as a convenient catalyst for this transformation. This method highlights the emerging strategy to transform unactivated alkyl ketones into amides in organic synthesis and provides a new strategy for C-C bond cleavage.

Structural properties of water around uncharged and charged carbon nanotubes

International Nuclear Information System (INIS)

Dezfoli, Amir Reza Ansari; Mehrabian, Mozaffar Ali; Rafsanjani, Hassan Hashemipour

2013-01-01

Studying the structural properties of water molecules around the carbon nanotubes is very important in a wide variety of carbon nanotubes applications. We studied the number of hydrogen bonds, oxygen and hydrogen density distributions, and water orientation around carbon nanotubes. The water density distribution for all carbon nanotubes was observed to have the same feature. In water-carbon nanotubes interface, a high-density region of water molecules exists around carbon nanotubes. The results reveal that the water orientation around carbon nanotubes is roughly dependent on carbon nanotubes surface charge. The water molecules in close distances to carbon nanotubes were found to make an HOH plane nearly perpendicular to the water-carbon nanotubes interface for carbon nanotubes with negative surface charge. For uncharged carbon nanotubes and carbon nanotubes with positive surface charge, the HOH plane was in tangential orientation with water-carbon nanotubes interface. There was also a significant reduction in hydrogen bond of water region around carbon nanotubes as compared with hydrogen bond in bulk water. This reduction was very obvious for carbon nanotubes with positive surface charge. In addition, the calculation of dynamic properties of water molecules in water-CNT interface revealed that there is a direct relation between the number of Hbonds and self-diffusion coefficient of water molecules

Bond length and electric current oscillation of long linear carbon chains: Density functional theory, MpB model, and quantum spin transport studies

International Nuclear Information System (INIS)

Oeiras, R. Y.; Silva, E. Z. da

2014-01-01

Carbon linear atomic chains attached to graphene have experimentally been produced. Motivated by these results, we study the nature of the carbon bonds in these nanowires and how it affects their electrical properties. In the present study we investigate chains with different numbers of atoms and we observe that nanowires with odd number of atoms present a distinct behavior than the ones with even numbers. Using graphene nanoribbons as leads, we identify differences in the quantum transport of the chains with the consequence that even and odd numbered chains have low and high electrical conduction, respectively. We also noted a dependence of current with the wire size. We study this unexpected behavior using a combination of first principles calculations and simple models based on chemical bond theory. From our studies, the electrons of carbon nanowires present a quasi-free electron behavior and this explains qualitatively the high electrical conduction and the bond lengths with unexpected values for the case of odd nanowires. Our study also allows the understanding of the electric conduction dependence with the number of atoms and their parity in the chain. In the case of odd number chains a proposed π-bond (MpB) model describes unsaturated carbons that introduce a mobile π-bond that changes dramatically the structure and transport properties of these wires. Our results indicate that the nature of bonds plays the main role in the oscillation of quantum electrical conduction for chains with even and odd number of atoms and also that nanowires bonded to graphene nanoribbons behave as a quasi-free electron system, suggesting that this behavior is general and it could also remain if the chains are bonded to other materials

Bonded Joints with “Nano-Stitches”: Effect of Carbon Nanotubes on Load Capacity and Failure Modes

Directory of Open Access Journals (Sweden)

Henrique N. P. Oliva

Full Text Available Abstract Carbon nanotubes were employed as adhesive reinforcement/nano-stitches to aluminum bonded joints. The CNT addition to an epoxy adhesive not only lead to an increase on load capacity but it is also the most probable cause of the mixed failure mode (adhesive/cohesive. The damage evolution was described as the stiffness decrease and the failure mixed modes were related to the load capacity. Although the presence of CNT cluster were observed, in small concentrations (< 1.0 wt. %, these clusters acted as crack stoppers and lead to an increase on lap joint shear strength. The addition of 2.0 wt. % carbon nanotubes lead to an increase on load capacity of approximately 116.2 % when the results were compared against the single lap joints without carbon nanotubes.

Carbon for sensing devices

CERN Document Server

Tagliaferro, Alberto

2015-01-01

This book reveals why carbon is playing such an increasingly prominent role as a sensing material. The various steps that transform a raw material in a sensing device are thoroughly presented and critically discussed.  The authors deal with all aspects of carbon-based sensors, starting from the various hybridization and allotropes of carbon, with specific focus on micro and nanosized carbons (e.g., carbon nanotubes, graphene) and their growth processes. The discussion then moves to the role of functionalization and the different routes to achieve it. Finally, a number of sensing applications in various fields are presented, highlighting the connection with the basic properties of the various carbon allotropes.  Readers will benefit from this book’s bottom-up approach, which starts from the local bonding in carbon solids and ends with sensing applications, linking the local hybridization of carbon atoms and its modification by functionalization to specific device performance. This book is a must-have in th...

Can laccases catalyze bond cleavage in lignin?

DEFF Research Database (Denmark)

Munk, Line; Sitarz, Anna Katarzyna; Kalyani, Dayanand

2015-01-01

illustrations of the putative laccase catalyzed reactions, including the possible reactions of the reactive radical intermediates taking place after the initial oxidation of the phenol-hydroxyl groups, we show that i) Laccase activity is able to catalyze bond cleavage in low molecular weight phenolic lignin......-substituted phenols, benzenethiols, polyphenols, and polyamines, which may be oxidized. In addition, the currently available analytical methods that can be used to detect enzyme catalyzed changes in lignin are summarized, and an improved nomenclature for unequivocal interpretation of the action of laccases on lignin...

Ag-catalysed cutting of multi-walled carbon nanotubes

International Nuclear Information System (INIS)

La Torre, A; Rance, G A; Miners, S A; Lucas, C Herreros; Smith, E F; Giménez-López, M C; Khlobystov, A N; Fay, M W; Brown, P D; Zoberbier, T; Kaiser, U

2016-01-01

In this work, the cutting of carbon nanotubes is investigated using silver nanoparticles deposited on arc discharge multi-walled carbon nanotubes. The composite is subsequently heated in air to fabricate shortened multi-walled nanotubes. Complementary transmission electron microscopy and spectroscopy techniques shed light on the cutting mechanism. The nanotube cutting is catalysed by the fundamental mechanism based on the coordination of the silver atoms to the π-bonds of carbon nanotubes. As a result of the metal coordination, the strength of the carbon–carbon bond is reduced, promoting the oxidation of carbon at lower temperature when heated in air, or lowering the activation energy required for the removal of carbon atoms by electron beam irradiation, assuring in both cases the cutting of the nanotubes. (paper)

Microstructure and chemical bond evolution of diamond-like carbon films machined by femtosecond laser

Energy Technology Data Exchange (ETDEWEB)

Wang, Jing; Wang, Chunhui [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Yongsheng, E-mail: yongshengliu@nwpu.edu.cn [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Cheng, Laifei [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Weinan [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China); Zhang, Qing [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Yang, Xiaojun [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China)

2015-06-15

Highlights: • The machining depth was essentially proportional to the laser power. • The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. And the number of nanoparticles increased with the processing power as well. • It revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. • It showed that a great decrease of sp{sup 3}/sp{sup 2} after laser treatment. - Abstract: Femtosecond laser is of great interest for machining high melting point and hardness materials such as diamond-like carbon, SiC ceramic, et al. In present work, the microstructural and chemical bond evolution of diamond-like carbon films were investigated using electron microscopy and spectroscopy techniques after machined by diverse femtosecond laser power in air. The results showed the machining depth was essentially proportional to the laser power. The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. Considering the D and G Raman band parameters on the laser irradiation, it revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. X-ray photoelectron spectroscopy analysis showed a great decrease of sp{sup 3}/sp{sup 2} after laser treatment.

First principles investigation of interaction between impurity atom (Si, Ge, Sn) and carbon atom in diamond-like carbon system

International Nuclear Information System (INIS)

Li, Xiaowei; Wang, Aiying; Lee, Kwang-Ryeol

2012-01-01

The interaction between impurity atom (Si, Ge, and Sn) and carbon atom in diamond-like carbon (DLC) system was investigated by the first principles simulation method based on the density functional theory. The tetrahedral configuration was selected as the calculation model for simplicity. When the bond angle varied in a range of 90°–130° from the equivalent state of 109.471°, the distortion energy and the electronic structures including charge density of the highest occupied molecular orbital (HOMO) and partial density of state (PDOS) in the different systems were calculated. The results showed that the addition of Si, Ge and Sn atom into amorphous carbon matrix significantly decreased the distortion energy of the system as the bond angles deviated from the equilibrium one. Further studies of the HOMO and PDOS indicated that the weak covalent bond between Si(Ge, Sn) and C atoms was formed with the decreased strength and directionality, which were influenced by the electronegative difference. These results implied that the electron transfer behavior at the junction of carbon nano-devices could be tailored by the impurity element, and the compressive stress in DLC films could be reduced by the incorporation of Si, Ge and Sn because of the formation of weaker covalent bonds. - Highlights: ►Distortion energy after bond angle distortion was decreased comparing with C-C unit. ►The weak covalent bond was formed between impurity atoms and corner carbon atoms. ►Observed electron transfer behavior affected the strength and directionality of bond. ►Reduction of strength and directionality of bond contributed to small energy change.

A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry MechanismsChemistry Mechanisms

Science.gov (United States)

We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2) into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU). Compared to CB05TU, RAC...

Bump Bonding Using Metal-Coated Carbon Nanotubes

Science.gov (United States)

Lamb, James L.; Dickie, Matthew R.; Kowalczyk, Robert S.; Liao, Anna; Bronikowski, Michael J.

2012-01-01

Bump bonding hybridization techniques use arrays of indium bumps to electrically and mechanically join two chips together. Surface-tension issues limit bump sizes to roughly as wide as they are high. Pitches are limited to 50 microns with bumps only 8-14 microns high on each wafer. A new process uses oriented carbon nanotubes (CNTs) with a metal (indium) in a wicking process using capillary actions to increase the aspect ratio and pitch density of the connections for bump bonding hybridizations. It merges the properties of the CNTs and the metal bumps, providing enhanced material performance parameters. By merging the bumps with narrow and long CNTs oriented in the vertical direction, higher aspect ratios can be obtained if the metal can be made to wick. Possible aspect ratios increase from 1:1 to 20:1 for most applications, and to 100:1 for some applications. Possible pitch density increases of a factor of 10 are possible. Standard capillary theory would not normally allow indium or most other metals to be drawn into the oriented CNTs, because they are non-wetting. However, capillary action can be induced through the ability to fabricate oriented CNT bundles to desired spacings, and the use of deposition techniques and temperature to control the size and mobility of the liquid metal streams and associated reservoirs. This hybridization of two technologies (indium bumps and CNTs) may also provide for some additional benefits such as improved thermal management and possible current density increases.

Mo-Mo Quintuple Bond is Highly Reactive in H-H, C-H, and O-H σ-Bond Cleavages Because of the Polarized Electronic Structure in Transition State.

Science.gov (United States)

Chen, Yue; Sakaki, Shigeyoshi

2017-04-03

The recently reported high reactivity of the Mo-Mo quintuple bond of Mo 2 (N ∧ N) 2 (1) {N ∧ N = μ-κ 2 -CH[N(2,6-iPr 2 C 6 H 3 )] 2 } in the H-H σ-bond cleavage was investigated. DFT calculations disclosed that the H-H σ-bond cleavage by 1 occurs with nearly no barrier to afford the cis-dihydride species followed by cis-trans isomerization to form the trans-dihydride product, which is consistent with the experimental result. The O-H and C-H bond cleavages by 1 were computationally predicted to occur with moderate (ΔG° ⧧ = 9.0 kcal/mol) and acceptable activation energies (ΔG° ⧧ = 22.5 kcal/mol), respectively, suggesting that the Mo-Mo quintuple bond can be applied to various σ-bond cleavages. In these σ-bond cleavage reactions, the charge-transfer (CT Mo→XH ) from the Mo-Mo quintuple bond to the X-H (X = H, C, or O) bond and that (CT XH→Mo ) from the X-H bond to the Mo-Mo bond play crucial roles. Though the HOMO (dδ-MO) of 1 is at lower energy and the LUMO + 2 (dδ*-MO) of 1 is at higher energy than those of RhCl(PMe 3 ) 2 (LUMO and LUMO + 1 of 1 are not frontier MO), the H-H σ-bond cleavage by 1 more easily occurs than that by the Rh complex. Hence, the frontier MO energies are not the reason for the high reactivity of 1. The high reactivity of 1 arises from the polarization of dδ-type MOs of the Mo-Mo quintuple bond in the transition state. Such a polarized electronic structure enhances the bonding overlap between the dδ-MO of the Mo-Mo bond and the σ*-antibonding MO of the X-H bond to facilitate the CT Mo→XH and reduce the exchange repulsion between the Mo-Mo bond and the X-H bond. This polarized electronic structure of the transition state is similar to that of a frustrated Lewis pair. The easy polarization of the dδ-type MOs is one of the advantages of the metal-metal multiple bond, because such polarization is impossible in the mononuclear metal complex.

Single walled carbon nanotube network—Tetrahedral amorphous carbon composite film

Energy Technology Data Exchange (ETDEWEB)

Iyer, Ajai, E-mail: ajai.iyer@aalto.fi; Liu, Xuwen; Koskinen, Jari [Department of Materials Science and Engineering, School of Chemical Technology, Aalto University, POB 16200, 00076 Espoo (Finland); Kaskela, Antti; Kauppinen, Esko I. [NanoMaterials Group, Department of Applied Physics, School of Science, Aalto University, POB 15100, 00076 Espoo (Finland); Johansson, Leena-Sisko [Department of Forest Products Technology, School of Chemical Technology, Aalto University, POB 16400, 00076 Espoo (Finland)

2015-06-14

Single walled carbon nanotube network (SWCNTN) was coated by tetrahedral amorphous carbon (ta-C) using a pulsed Filtered Cathodic Vacuum Arc system to form a SWCNTN—ta-C composite film. The effects of SWCNTN areal coverage density and ta-C coating thickness on the composite film properties were investigated. X-Ray photoelectron spectroscopy measurements prove the presence of high quality sp{sup 3} bonded ta-C coating on the SWCNTN. Raman spectroscopy suggests that the single wall carbon nanotubes (SWCNTs) forming the network survived encapsulation in the ta-C coating. Nano-mechanical testing suggests that the ta-C coated SWCNTN has superior wear performance compared to uncoated SWCNTN.

Unlocking the Electrocatalytic Activity of Chemically Inert Amorphous Carbon-Nitrogen for Oxygen Reduction: Discerning and Refactoring Chaotic Bonds

DEFF Research Database (Denmark)

Zhang, Caihong; Zhang, Wei; Wang, Dong

2017-01-01

Mild annealing enables inactive nitrogen (N)-doped amorphous carbon (a-C) films abundant with chaotic bonds prepared by magnetron sputtering to become effective for the oxygen reduction reaction (ORR) by virtue of generating pyridinic N. The rhythmic variation of ORR activity elaborates well...... on the subtle evolution of the amorphous C−N bonds conferred by spectroscopic analysis....

Mixed resin and carbon fibres surface treatment for preparation of carbon fibres composites with good interfacial bonding strength

International Nuclear Information System (INIS)

He, Hongwei; Wang, Jianlong; Li, Kaixi; Wang, Jian; Gu, Jianyu

2010-01-01

The objective of this work is to improve the interlaminar shear strength of composites by mixing epoxy resin and modifying carbon fibres. The effect of mixed resin matrix's structure on carbon fibres composites was studied. Anodic oxidation treatment was used to modify the surface of carbon fibres. The tensile strength of multifilament and interlaminar shear strength of composites were investigated respectively. The morphologies of untreated and treated carbon fibres were characterized by scanning electron microscope and X-ray photoelectron spectroscopy. Surface analysis indicates that the amount of carbon fibres chemisorbed oxygen-containing groups, active carbon atom, the surface roughness, and wetting ability increases after treatment. The tensile strength of carbon fibres decreased little after treatment by anodic oxidation. The results show that the treated carbon fibres composites could possess excellent interfacial properties with mixed resins, and interlaminar shear strength of the composites is up to 85.41 MPa. The mechanism of mixed resins and treated carbon fibres to improve the interfacial property of composites is obtained.

Elastic Moduli of Carbon Nanohorns

Directory of Open Access Journals (Sweden)

Dinesh Kumar

2011-01-01

Full Text Available Carbon nanotube is a special case of carbon nanohorns or carbon nanocones with zero apex angle. Research into carbon nanohorns started almost at the same time as the discovery of nanotubes in 1991. Most researchers focused on the investigation of nanotubes, and the exploration of nanohorns attracted little attention. To model the carbon nanohorns, we make use of a more reliable second-generation reactive empirical bond-order potential by Brenner and coworkers. We investigate the elastic moduli and conclude that these nanohorns are equally strong and require in-depth investigation. The values of Young's and Shear moduli decrease with apex angle.

Neutron vibrational spectroscopic studies of novel tire-derived carbon materials.

Science.gov (United States)

Li, Yunchao; Cheng, Yongqiang; Daemen, Luke L; Veith, Gabriel M; Levine, Alan M; Lee, Richard J; Mahurin, Shannon M; Dai, Sheng; Naskar, Amit K; Paranthaman, Mariappan Parans

2017-08-23

Sulfonated tire-derived carbons have been demonstrated to be high value-added carbon products of tire recycling in several energy storage system applications including lithium, sodium, potassium ion batteries and supercapacitors. In this communication, we compared different temperature pyrolyzed sulfonated tire-derived carbons with commercial graphite and unmodified/non-functionalized tire-derived carbon by studying the surface chemistry and properties, vibrational spectroscopy of the molecular structure, chemical bonding such as C-H bonding, and intermolecular interactions of the carbon materials. The nitrogen adsorption-desorption studies revealed the tailored micro and meso pore size distribution of the carbon during the sulfonation process. XPS and neutron vibrational spectra showed that the sulfonation of the initial raw tire powders could remove the aliphatic hydrogen containing groups ([double bond splayed left]CH 2 and -CH 3 groups) and reduce the number of heteroatoms that connect to carbon. The absence of these functional groups could effectively improve the first cycle efficiency of the material in rechargeable batteries. Meanwhile, the introduced -SO 3 H functional group helped in producing terminal H at the edge of the sp 2 bonded graphite-like layers. This study reveals the influence of the sulfonation process on the recovered hard carbon from used tires and provides a pathway to develop and improve advanced energy storage materials.

Control Carbon to Prevent corium Stratification In-Vessel Retention

Energy Technology Data Exchange (ETDEWEB)

Go, A Ra; Hong, Seung Hyun; Kim, Sang Nyung [Kyung Hee Univ., Yongin (Korea, Republic of)

2013-10-15

As a result, the thermal margin decreases, and the nuclear reactor vessel may be destroyed. To control Carbons, which is the major cause of stratification, Ruthenium and Hafnium are inserted inside the lower reactor head which initiates a chemical reaction with Carbon. SPARTAN program is used to confirm a reaction probability which is measured in bond energy and strength etc. To analyze the possibility of bonding with Carbon, the initial property of Ruthenium and Carbon are measured during the calculated absorbing process. After following that theory, the Spartan program is able to determine if it can insert the metal. After verifying the combination of Ruthenium and Carbon, the Spartan program analyzes the impact of the Carbon to prevent the corium stratification. It determines the possibility of the success with the introduction of the IVR concept. Ruthenium is suitable to Carbon bonding process to decrease affect to corium behavior which do not form stratification. The metal which can combine with Carbon should be satisfied with temperature as high as 2800 .deg. C. Therefore, the further research works are determined by using the Spartan program to calculate the Carbon and Ruthenium bonding energy, and to check other bonding results as follows. After check the results, review this theory to insert the Ruthenium in reactor vessel. APR1400 and OPR1000, Korea Hydro and Nuclear power plant core meltdown accident has been evaluated a high level in severe accident. When the reactor core is melted down, it is stratified into the metal layer and the ceramic layer. As the heat conductivity of metal layer is higher than that of the ceramic layer, heat concentration occurs in the upper part of the bottom hemisphere which comes into contact with the metal layer.

Cohesion Energetics of Carbon Allotropes: Quantum Monte Carlo Study

Energy Technology Data Exchange (ETDEWEB)

Shin, Hyeondeok [Konkuk University, South Korea; Kang, Sinabro [Konkuk University, South Korea; Koo, Jahyun [Konkuk University, South Korea; Lee, Hoonkyung [Konkuk University, South Korea; Kim, Jeongnim [ORNL; Kwon, Yongkyung [Konkuk University, South Korea

2014-01-01

We have performed quantum Monte Carlo calculations to study the cohesion energetics of carbon allotropes, including sp3-bonded diamond, sp2-bonded graphene, sp-sp2 hybridized graphynes, and sp-bonded carbyne. The comput- ed cohesive energies of diamond and graphene are found to be in excellent agreement with the corresponding values de- termined experimentally for diamond and graphite, respectively, when the zero-point energies, along with the interlayer binding in the case of graphite, are included. We have also found that the cohesive energy of graphyne decreases system- atically as the ratio of sp-bonded carbon atoms increases. The cohesive energy of -graphyne, the most energetically- stable graphyne, turns out to be 6.766(6) eV/atom, which is smaller than that of graphene by 0.698(12) eV/atom. Experi- mental difficulty in synthesizing graphynes could be explained by their significantly smaller cohesive energies. Finally we conclude that the cohesive energy of a newly-proposed two-dimensional carbon network can be accurately estimated with the carbon-carbon bond energies determined from the cohesive energies of graphene and three different graphynes.

Nanostructural characterization of amorphous diamondlike carbon films

Energy Technology Data Exchange (ETDEWEB)

Siegal, M. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Tallant, D. R. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Martinez-Miranda, L. J. [University of Maryland, Department of Materials and Nuclear Engineering, College Park, Maryland 20742 (United States); Barbour, J. C. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Simpson, R. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Overmyer, D. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2000-04-15

Nanostructural characterization of amorphous diamondlike carbon (a-C) films grown on silicon using pulsed-laser deposition (PLD) is correlated to both growth energetics and film thickness. Raman spectroscopy and x-ray reflectivity probe both the topological nature of three- and four-fold coordinated carbon atom bonding and the topographical clustering of their distributions within a given film. In general, increasing the energetics of PLD growth results in films becoming more ''diamondlike,'' i.e., increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is different for material near the substrate interface compared to material within the bulk portion of an a-C film. A simple model balancing the energy of residual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding clusters in a growing a-C film. (c) 2000 The American Physical Society.

Nanostructural characterization of amorphous diamondlike carbon films

Energy Technology Data Exchange (ETDEWEB)

SIEGAL,MICHAEL P.; TALLANT,DAVID R.; MARTINEZ-MIRANDA,L.J.; BARBOUR,J. CHARLES; SIMPSON,REGINA L.; OVERMYER,DONALD L.

2000-01-27

Nanostructural characterization of amorphous diamondlike carbon (a-C) films grown on silicon using pulsed-laser deposition (PLD) is correlated to both growth energetic and film thickness. Raman spectroscopy and x-ray reflectivity probe both the topological nature of 3- and 4-fold coordinated carbon atom bonding and the topographical clustering of their distributions within a given film. In general, increasing the energetic of PLD growth results in films becoming more ``diamondlike'', i.e. increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is different for material near the substrate interface compared to material within the bulk portion of an a-C film. A simple model balancing the energy of residual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding clusters in a growing a-C film.

Carbon particle induced foaming of molten sucrose for the preparation of carbon foams

International Nuclear Information System (INIS)

Narasimman, R.; Vijayan, Sujith; Prabhakaran, K.

2014-01-01

Graphical abstract: - Highlights: • An easy method for the preparation of carbon foam from sucrose is presented. • Wood derived activated carbon particles are used to stabilize the molten sucrose foam. • The carbon foams show relatively good mechanical strength. • The carbon foams show excellent CO 2 adsorption and oil absorption properties. • The process could be scaled up for the preparation of large foam bodies. - Abstract: Activated carbon powder was used as a foaming and foam setting agent for the preparation of carbon foams with a hierarchical pore structure from molten sucrose. The rheological measurements revealed the interruption of intermolecular hydrogen bonding in molten sucrose by the carbon particles. The carbon particles stabilized the bubbles in molten sucrose by adsorbing on the molten sucrose–gas interface. The carbon foams obtained at the activated carbon powder to sucrose weight ratios in the range of 0–0.25 had a compressive strength in the range of 1.35–0.31 MPa. The produced carbon foams adsorb 2.59–3.04 mmol/g of CO 2 at 760 mmHg at 273 K and absorb oil from oil–water mixtures and surfactant stabilized oil-in-water emulsions with very good selectivity and recyclability

Supplementary data for the mechanism for cleavage of three typical glucosidic bonds induced by hydroxyl free radical

Directory of Open Access Journals (Sweden)

Yujie Dai

2017-12-01

Full Text Available The data presented in this article are related to the research article entitled “The mechanism for cleavage of three typical glucosidic bonds induced by hydroxyl free radical” (Dai et al., 2017 [1]. This article includes the structures of three kinds of disaccharides such as maltose, fructose and cellobiose, the diagrammatic sketch of the hydrogen abstraction reaction of the disaccharides by hydroxyl radical, the structure of the transition states for pyran ring opening of moiety A and cleavage of α(1→2 glycosidic bond starting from the hydrogen abstraction of C6–H in moiety A of sucrose, the transition state structure for cleavage of α(1→2 glycosidic bond starting from the hydrogen abstraction of C1′-H in moiety B of sucrose, the transition state structure, sketch for the reaction process and relative energy change of the reaction pathway for direct cleavage of α(1→4 glycosidic bond starting from hydrogen abstraction of C6′–H of moiety B of maltose.

Bonding titanium on multi-walled carbon nanotubes for hydrogen storage: An electrochemical approach

Energy Technology Data Exchange (ETDEWEB)

Brieno-Enriquez, K.M.; Ledesma-Garcia, J. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S.C., Parque Tecnologico Queretaro-Sanfandila, Pedro Escobedo, Qro, C.P. 76703 (Mexico); Perez-Bueno, J.J., E-mail: jperez@cideteq.mx [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S.C., Parque Tecnologico Queretaro-Sanfandila, Pedro Escobedo, Qro, C.P. 76703 (Mexico); Godinez, Luis A. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S.C., Parque Tecnologico Queretaro-Sanfandila, Pedro Escobedo, Qro, C.P. 76703 (Mexico); Terrones, H. [Instituto Potosino de Investigacion Cientifica y Tecnologica, Division de Materiales Avanzados, Camino a la Presa San Jose 2055, Col. Lomas 4o Seccion C.P. 78216, San Luis Potosi (Mexico); Angeles-Chavez, C. [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas 152, A.P. 14-805, 07730 Mexico D.F. (Mexico)

2009-06-15

This work explores the use of some procedures, involving electrochemistry, in order to bond atomic Ti on the outer surface of multi-walled carbon nanotubes (MWNTs). It is assumed that each titanium atom has the potential of host up to four hydrogen molecules and relinquish them by heated. As a way to spread and stick nanotubes on an electrode, a tested route was drying a solution with nanotubes on a glassy carbon flat electrode. The MWNTs were treated by anodic polarization in organic media. Dichloromethane was selected as the medium and titanium tetrachloride as the precursor for attaching atomic Ti onto the nanotubes. The hydrogen adsorption, estimated from voltamperometry was five times higher on Ti-MWNTs that on bare nanotubes. The use of anodic polarization during the preparation of Ti-MWNTs may represent great significance in procedure, which was manifest during the voltamperometric evaluation of samples.

Study of the damaging mechanisms of a copper / carbon - carbon composite under thermomechanical loading; Etude des mecanismes d'endommagement d'un assemblage cuivre / composite carbone - carbone sous chargement thermomecanique

Energy Technology Data Exchange (ETDEWEB)

Moncel, L

1999-06-18

The purpose of this work is to understand and to identify the damaging mechanisms of Carbon-Carbon composite bonded to copper under thermomechanical loading. The study of the composite allowed the development of non-linear models. These ones have been introduced in the finite elements analysis code named CASTEM2000. They have been validated according to a correlation between simulation and mechanical tests on multi-material samples. These tests have also permitted us to better understand the behaviour of the bonding between composite and copper (damaging and fracture modes for different temperatures) under shear and tensile loadings. The damaging mechanisms of the bond under thermomechanical loading have been studied and identified according to microscopic observations on mock-ups which have sustained thermal cycling tests: some cracks appear in the composite, near the bond between the composite and the copper. The correlation between numerical and experimental results have been improved because of the reliability of the composite modelization, the use of residual stresses and the results of the bond mechanical characterization. (author)

Topological Characterization of Carbon Graphite and Crystal Cubic Carbon Structures.

Science.gov (United States)

Siddiqui, Wei Gao Muhammad Kamran; Naeem, Muhammad; Rehman, Najma Abdul

2017-09-07

Graph theory is used for modeling, designing, analysis and understanding chemical structures or chemical networks and their properties. The molecular graph is a graph consisting of atoms called vertices and the chemical bond between atoms called edges. In this article, we study the chemical graphs of carbon graphite and crystal structure of cubic carbon. Moreover, we compute and give closed formulas of degree based additive topological indices, namely hyper-Zagreb index, first multiple and second multiple Zagreb indices, and first and second Zagreb polynomials.

Simulation of dual carbon-bromine stable isotope fractionation during 1,2-dibromoethane degradation.

Science.gov (United States)

Jin, Biao; Nijenhuis, Ivonne; Rolle, Massimo

2018-06-01

We performed a model-based investigation to simultaneously predict the evolution of concentration, as well as stable carbon and bromine isotope fractionation during 1,2-dibromoethane (EDB, ethylene dibromide) transformation in a closed system. The modelling approach considers bond-cleavage mechanisms during different reactions and allows evaluating dual carbon-bromine isotopic signals for chemical and biotic reactions, including aerobic and anaerobic biological transformation, dibromoelimination by Zn(0) and alkaline hydrolysis. The proposed model allowed us to accurately simulate the evolution of concentrations and isotope data observed in a previous laboratory study and to successfully identify different reaction pathways. Furthermore, we illustrated the model capabilities in degradation scenarios involving complex reaction systems. Specifically, we examined (i) the case of sequential multistep transformation of EDB and the isotopic evolution of the parent compound, the intermediate and the reaction product and (ii) the case of parallel competing abiotic pathways of EDB transformation in alkaline solution.

Hydrogen spillover in Pt-single-walled carbon nanotube composites: formation of stable C-H bonds.

Science.gov (United States)

Bhowmick, Ranadeep; Rajasekaran, Srivats; Friebel, Daniel; Beasley, Cara; Jiao, Liying; Ogasawara, Hirohito; Dai, Hongjie; Clemens, Bruce; Nilsson, Anders

2011-04-13

Using in situ electrical conductivity and ex situ X-ray photoelectron spectroscopy (XPS) measurements, we have examined how the hydrogen uptake of single-walled carbon nanotubes (SWNTs) is influenced by the addition of Pt nanoparticles. The conductivity of platinum-sputtered single-walled carbon nanotubes (Pt-SWNTs) during molecular hydrogen exposure decreased more rapidly than that of the corresponding pure SWNTs, which supports a hydrogenation mechanism facilitated by "spillover" of dissociated hydrogen from the Pt nanoparticles. C 1s XPS spectra indicate that the Pt-SWNTs store hydrogen by means of chemisorption, that is, covalent C-H bond formation: molecular hydrogen charging at elevated pressure (8.27 bar) and room temperature yielded Pt-SWNTs with up to 16 ± 1.5 at. % sp(3)-hybridized carbon atoms, which corresponds to a hydrogen-storage capacity of 1.2 wt % (excluding the weight of Pt nanoparticles). Pt-SWNTs prepared by the Langmuir-Blodgett (LB) technique exhibited the highest Pt/SWNT ratio and also the best hydrogen uptake. © 2011 American Chemical Society

Low carbon content and carbon-free refractory materials with high thermal shock resistance; Thermoschockbestaendige feuerfeste Erzeugnisse mit geringerem Kohlenstoffgehalt bzw. kohlenstofffreie Erzeugnisse

Energy Technology Data Exchange (ETDEWEB)

Brachhold, Nora; Aneziris, C.G.; Stein, Volker; Roungos, Vasileios; Moritz, Kirsten [TU Bergakademie Freiberg (TUBAF) (DE). Inst. fuer Keramik, Glas- und Baustofftechnik (IKGB)

2012-07-01

Carbon bonded refractories are essential for steelmaking due to their excellent thermal shock resistance. The research on carbon reduced and carbon-free materials is necessary to manufacture high quality stainless steels tending carbon pick-up in contact to conventional refractory materials. Further advantages are reduced emissions of CO{sub 2} and energy saving potentials due to better heat insulation properties. The challenge is to develop alternative materials with lower carbon contents but with the necessary thermal shock resistance. The Priority Programme 1418 funded by the German Research Foundation (DFG) concentrates on this problem. In this article two materials are presented. First, the carbon content could be reduced by nanoscaled additives resulting in better bonding between matrix and oxidic components. Second, an AL{sub 2}O{sub 3}-rich carbon-free material is presented showing a very good thermal shock resistance due to its designed microstructure. Finally, a steel casting simulator is introduced to test the new materials under nearly real conditions. (orig.)

S center dot center dot center dot N chalcogen bonded complexes of carbon disulfide with diazines. Theoretical study

Czech Academy of Sciences Publication Activity Database

Zierkiewicz, W.; Fanfrlík, Jindřich; Michalczyk, M.; Michalska, D.; Hobza, Pavel

2018-01-01

Roč. 500, Jan 26 (2018), s. 37-44 ISSN 0301-0104 Institutional support: RVO:61388963 Keywords : chalcogen bond * carbon disulfide * diazines * DFT Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 1.767, year: 2016

Pentaatomic planar tetracoordinate carbon molecules [XCAl(3)](q) [(X,q) = (B,-2), (C,-1), (N,0)] with C-X multiple bonding.

Science.gov (United States)

Cui, Zhong-Hua; Shao, Chang-Bin; Gao, Si-Meng; Ding, Yi-Hong

2010-11-07

Among the fascinating planar tetracoordinate carbon (ptC) species, pentaatomic molecules belong to the smallest class, well-known as "pptC". It has been generally accepted that the planarity of pptC structure is realized via the "delocalization" of the p(z) lone pair at the central carbon and the ligand-ligand bonding interaction. Although "localization" is as key driving force in organic chemistry as "delocalization", the "localization" concept has not been applied to the design of pptC molecules, to the best of our knowledge. In this paper, we apply the "localization" strategy to design computationally a series of new pptC. It is shown that the central carbon atom and one "electronegative" ligand atom X (compared to the Al ligand) effectively form a highly localized C-X multiple bond, converting the lone pair at the central carbon to a two-center two-electron π-bond. At the aug-cc-pVTZ-B3LYP, MP2 and CCSD(T) levels, the designed 18-valence-electron pptC species [XCAl(3)](q); [(X,q) = (B,-2), (C,-1), (N,0)] are found to each possess a stable ptC structure bearing a C-X double bond, indicated by the structural, molecular orbital, Wiberg bonding, potential energy surface and Born-Oppenheimer molecular dynamics (BOMD) analysis. Moreover, our OVGF calculations showed that the presently disclosed (yet previously unconsidered) pptC structure of [C(2)Al(3)](-) could well account for the observed photoelectron spectrum (previously only ascribed to a close-energy fan-like structure). Therefore, [C(2)Al(3)](-) could be the first pptC that bears the highly localized C-X double bond that has been experimentally generated. Notably, the pptC structure is the respective global minimum point for [BCAl(3)](2-) and [NCAl(3)], and the counterion(s) would further stabilize [BCAl(3)](2-) and [C(2)Al(3)](-). Thus, these newly designed pptC species with interesting bonding structure should be viable for future experimental characterization. The presently applied "localization" approach

Characterization of amorphous and nanocrystalline carbon films

International Nuclear Information System (INIS)

Chu, Paul K.; Li Liuhe

2006-01-01

Amorphous and nanocrystalline carbon films possess special chemical and physical properties such as high chemical inertness, diamond-like properties, and favorable tribological proprieties. The materials usually consist of graphite and diamond microstructures and thus possess properties that lie between the two. Amorphous and nanocrystalline carbon films can exist in different kinds of matrices and are usually doped with a large amount of hydrogen. Thus, carbon films can be classified as polymer-like, diamond-like, or graphite-like based on the main binding framework. In order to characterize the structure, either direct bonding characterization methods or the indirect bonding characterization methods are employed. Examples of techniques utilized to identify the chemical bonds and microstructure of amorphous and nanocrystalline carbon films include optical characterization methods such as Raman spectroscopy, Ultra-violet (UV) Raman spectroscopy, and infrared spectroscopy, electron spectroscopic and microscopic methods such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, transmission electron microscopy, and electron energy loss spectroscopy, surface morphology characterization techniques such as scanning probe microscopy (SPM) as well as other characterization methods such as X-ray reflectivity and nuclear magnetic resonance. In this review, the structures of various types of amorphous carbon films and common characterization techniques are described

Synthesis and reactivity of compounds containing ruthenium-carbon, -nitrogen, and -oxygen bonds

International Nuclear Information System (INIS)

Hartwig, J.F.

1990-12-01

The products and mechanisms of the thermal reactions of several complexes of the general structure (PMe 3 ) 4 Ru(X)(Y) and (DMPM) 2 Ru(X)(Y) where X and Y are hydride, aryl, and benzyl groups, have been investigated. The mechanism of decomposition depends critically on the structure of the complex and the medium in which the thermolysis is carried out. The alkyl hydride complexes are do not react with alkane solvent, but undergo C-H activation processes with aromatic solvents by several different mechanisms. Thermolysis of (PMe 3 ) 4 Ru(Ph)(Me) or (PMe 3 ) 4 Ru(Ph) 2 leads to the ruthenium benzyne complex (PMe 3 ) 4 Ru(η 2 -C 6 H 4 ) (1) by a mechanism which involves reversible dissociation of phosphine. In many ways its chemistry is analogous to that of early rather than late organo transition metal complexes. The synthesis, structure, variable temperature NMR spectroscopy and reactivity of ruthenium complexes containing aryloxide or arylamide ligands are reported. These complexes undergo cleavage of a P-C bond in coordinated trimethylphosphine, insertion of CO and CO 2 and hydrogenolysis. Mechanistic studies on these reactions are described. The generation of a series of reactive ruthenium complexes of the general formula (PMe 3 ) 4 Ru(R)(enolate) is reported. Most of these enolates have been shown to bind to the ruthenium center through the oxygen atom. Two of the enolate complexes 8 and 9 exist in equilibrium between the O- and C-bound forms. The reactions of these compounds are reported, including reactions to form oxygen-containing metallacycles. The structure and reactivity of these ruthenium metallacycles is reported, including their thermal chemistry and reactivity toward protic acids, electrophiles, carbon monoxide, hydrogen and trimethylsilane. 243 refs., 10 tabs

Synthesis and reactivity of compounds containing ruthenium-carbon, -nitrogen, and -oxygen bonds

Energy Technology Data Exchange (ETDEWEB)

Hartwig, J.F.

1990-12-01

The products and mechanisms of the thermal reactions of several complexes of the general structure (PMe{sub 3}){sub 4}Ru(X)(Y) and (DMPM){sub 2}Ru(X)(Y) where X and Y are hydride, aryl, and benzyl groups, have been investigated. The mechanism of decomposition depends critically on the structure of the complex and the medium in which the thermolysis is carried out. The alkyl hydride complexes are do not react with alkane solvent, but undergo C-H activation processes with aromatic solvents by several different mechanisms. Thermolysis of (PMe{sub 3}){sub 4}Ru(Ph)(Me) or (PMe{sub 3}){sub 4}Ru(Ph){sub 2} leads to the ruthenium benzyne complex (PMe{sub 3}){sub 4}Ru({eta}{sup 2}-C{sub 6}H{sub 4}) (1) by a mechanism which involves reversible dissociation of phosphine. In many ways its chemistry is analogous to that of early rather than late organo transition metal complexes. The synthesis, structure, variable temperature NMR spectroscopy and reactivity of ruthenium complexes containing aryloxide or arylamide ligands are reported. These complexes undergo cleavage of a P-C bond in coordinated trimethylphosphine, insertion of CO and CO{sub 2} and hydrogenolysis. Mechanistic studies on these reactions are described. The generation of a series of reactive ruthenium complexes of the general formula (PMe{sub 3}){sub 4}Ru(R)(enolate) is reported. Most of these enolates have been shown to bind to the ruthenium center through the oxygen atom. Two of the enolate complexes 8 and 9 exist in equilibrium between the O- and C-bound forms. The reactions of these compounds are reported, including reactions to form oxygen-containing metallacycles. The structure and reactivity of these ruthenium metallacycles is reported, including their thermal chemistry and reactivity toward protic acids, electrophiles, carbon monoxide, hydrogen and trimethylsilane. 243 refs., 10 tabs.

Copolymerization of Carbon–carbon Double-bond Monomer (Styrene with Cyclic Monomer (Tetrahydrofuran

Directory of Open Access Journals (Sweden)

Sari Fouad

2012-12-01

Full Text Available We reported in this work that the cationic copolymerization in one step takes place between carbon–carbon double-bond monomer styrene with cyclic monomer tetrahydrofuran. The comonomers studied belong to different families: vinylic and cyclic ether. The reaction is initiated with maghnite-H+ an acid exchanged montmorillonite as acid solid ecocatalyst. Maghnite-H+ is already used as catalyst for polymerization of many vinylic and heterocyclic monomers. The oxonium ion of tetrahydrofuran and carbonium ion of styrene propagated the reaction of copolymerization. The acetic anhydride is essential for the maintenance of the ring opening of tetrahydrofuran and the entry in copolymerization. The temperature was kept constant at 40°C in oil bath heating for 6 hours. A typical reaction product was analyzed by 1H-NMR, 13C-NMR and IR and the formation of the copolymer was confirmed. The reaction was proved by matched with analysis. The maghnite-H+ allowed us to obtain extremely pure copolymer in good yield by following a simples operational conditions. Copyright © 2012 by BCREC UNDIP. All rights reservedReceived: 29th October 2012; Revised: 29th November 2012; Accepted: 29th November 2012[How to Cite: S. Fouad, M.I. Ferrahi, M. Belbachir. (2012. Copolymerization of Carbon–carbon Double-bond Monomer (Styrene with Cyclic Monomer (Tetrahydrofuran. Bulletin of Chemical Reaction Engineering & Catalysis, 7(2: 165-171. (doi:10.9767/bcrec.7.2.4074.165-171][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.2.4074.165-171 ] | View in 

Bonding Unidirectional Carbon Nanotube with Carbon for High Performance

Science.gov (United States)

2015-06-24

samples in a dilute aqueous solution of AgNO3 and placing them under a UV lamp . After 30 minutes of UV exposure, an obvious color change from black...purposefully avoided due to the potential damages to CNTs and the uncertainty on their effect on carbonization. Millimeter-long CNTs were used to develop...inter-connected network of the sheet, which led to foam-like recovery of the structure after compression. The ACNT/C foams can be tuned by changing

Effect of oxygen and nitroaromatic cell radiosensitizers on radiation-induced cleavage of internucleotide bonds: ApA, dApA, and poly(A)

International Nuclear Information System (INIS)

Raleigh, J.A.; Kremers, W.; Whitehouse, R.

1975-01-01

Irradiation of the dinucleoside monophosphates ApA and dApA in deoxygenated solution leads to a preferential cleavage of the 3' end of the internucleotide bond. Cleavage at the 3' bond is favored to the extent of 2 to 1 over 5' cleavage. Oxygen and nitroaromatic compounds inhibit 3' bond breaking in ApA and dApA in agreement with earlier findings from studies of 3'- and 5'-mononucleotides. In contrast to the mononucleotide results, no enhancement of 5' cleavage is observed for ApA and dApA irradiated in the presence of oxygen or the nitroaromatic additives. The over-all effect of the additives is to decrease the combined (3' and 5') yield of internucleotide bond breaking in ApA and dApA. This phenomenon is also observed for polyadenylic acid in the presence of the nitroaromatics. Oxygen marginally enhances internucleotide bond breaking in polyadenylic acid (factor 1.1) over that seen in deoxygenated solution. Postirradiation alkaline hydrolysis of dApA leads to further ester cleavage revealing the presence of radiation-induced alkali-labile bonds. The number of these bonds decreases in the order oxygen greater than nitrofurans greater than nitrobenzenes approximately irradiation in the absence of additives

Copper-Catalyzed Oxidative Reaction of β-Keto Sulfones with Alcohols via C-S Bond Cleavage: Reaction Development and Mechanism Study.

Science.gov (United States)

Du, Bingnan; Wang, Wenmin; Wang, Yang; Qi, Zhenghang; Tian, Jiaqi; Zhou, Jie; Wang, Xiaochen; Han, Jianlin; Ma, Jing; Pan, Yi

2018-02-16

A Cu-catalyzed cascade oxidative radical process of β-keto sulfones with alcohols has been achieved by using oxygen as an oxidant. In this reaction, β-keto sulfones were converted into sulfinate esters under the oxidative conditions via cleavage of C-S bond. Experimental and computational studies demonstrate that a new pathway is involved in this reaction, which proceeds through the formation of the key four-coordinated Cu II intermediate, O-O bond homolysis induced C-S bond cleavage and Cu-catalyzed esterification to form the final products. This reaction provides a new strategy to sulfonate esters and enriches the research content of C-S bond cleavage and transformations. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Actinide-carbon bonds: insertion reactions of carbon monoxide, tert-butyl isocyanide, and tert-butyl cyanide into [(Me3Si)2N]2MCH2Si(Me)2NSiMe3

International Nuclear Information System (INIS)

Simpson, S.J.; Andersen, R.A.

1981-01-01

The thorium or uranium metallacycles [(Me 2 Si) 2 N] 2 MCH 2 Si(Me) 2 NSiMe 3 (I) react with tert-butyl cyanide to give the six-membered ring compounds [(Me 3 Si) 2 N] 2 MN = C(t-Bu)CH 2 Si(Me) 2 NSiMe 3 . The metallacycles (I) also react with the isoelectronic molecules tert-butyl isocyanide and carbon monoxide to give the unique five-membered ring compounds with exocyclic carbon-carbon double bonds, [(Me 3 Si) 2 N] 2 MXC(=CH 2 )Si(Me) 2 NSiMe 3 , where X is t-BuN or oxygen. The four-membered ring metallacycles (I) give simple coordination complexes of the type [(Me 3 Si) 2 N] 2 MCH 2 Si-(Me) 2 NSiMe 3 (N 3 SiMe 3 ) with trimethylsilyl azide

A Carbon Nanotube Cable for a Space Elevator

Science.gov (United States)

Bochnícek, Zdenek

2013-01-01

In this paper the mechanical properties of carbon nanotubes are discussed in connection with the possibility to use them for the construction of a space elevator. From the fundamental information about the structure of a carbon nanotube and the chemical bond between carbon atoms, Young's modulus and the ultimate tensile strength are…

Special Advanced Studies for Pollution Prevention. Delivery Order 0017: Sol-Gel Surface Preparation for Carbon Steel and Stainless Steel Bonding

National Research Council Canada - National Science Library

Zheng, Haixing

1997-01-01

The objective of this program is to study the feasibility of using sol-gel active alumina coatings for the surface preparation of carbon steel and stainless steel for adhesive bonding, and to optimize...

Session 6: Catalytic hydro-dehalogenation of halon 1211 (CBrClF{sub 2}) over carbon supported Pd-Fe, Pd-Co and Pd-Ni bimetallic catalysts

Energy Technology Data Exchange (ETDEWEB)

Hai, Yu; Kennedy, E.M.; Md Azhar, Uddin; Dlugogorski, B.Z. [Newcastle Univ., Process Safety and Environment Protection Group, School of Engineering, Callaghan, NSW (Australia)

2004-07-01

In the current study, we present the result of our investigation on the hydro-dehalogenation of halon 1211 with hydrogen over carbon supported Pd-Fe, Pd-Co and Pd-Ni bimetallic catalysts. In addition to dissociatively adsorbing hydrogen, Fe, Co and Ni themselves can facilitate cleavage of C-halogen bonds. The effect of the interaction of a second metal (Fe, Co and Ni) with Pd on the conversion of halon 1211 and selectivity to CH{sub 2}F{sub 2} for the catalytic hydro-dehalogenation of halon 1211 is discussed. Activated carbon is chosen as support in order to minimize the interaction of support with the metals. The obtained experimental results show that the introduction of Fe, Co and Ni to Pd catalysts has a significant influence on the catalytic hydro-dehalogenation of halon 1211, especially with respect to the selectivity to CH{sub 2}F{sub 2}. The presence of Fe increases the amount of halon 1211 adsorbed on the surface of catalysts and enhances the cleavage of C-halogen bonds in halon 1211, resulting in a higher halon 1211 conversion level and selectivity to hydrocarbons. Higher selectivity to CHBrF{sub 2} is ascribed to the secondary reaction: CF{sub 2} + HBr {yields} CHBrF{sub 2}. (authors)

Mechanistic Insights on C-O and C-C Bond Activation and Hydrogen Insertion during Acetic Acid Hydrogenation Catalyzed by Ruthenium Clusters in Aqueous Medium

Energy Technology Data Exchange (ETDEWEB)

Shangguan, Junnan; Olarte, Mariefel V.; Chin, Ya-Huei [Cathy

2016-06-07

Catalytic pathways for acetic acid (CH3COOH) and hydrogen (H2) reactions on dispersed Ru clusters in the aqueous medium and the associated kinetic requirements for C-O and C-C bond cleavages and hydrogen insertion are established from rate and isotopic assessments. CH3COOH reacts with H2 in steps that either retain its carbon backbone and lead to ethanol, ethyl acetate, and ethane (47-95 %, 1-23 %, and 2-17 % carbon selectivities, respectively) or break its C-C bond and form methane (1-43 % carbon selectivities) at moderate temperatures (413-523 K) and H2 pressures (10-60 bar, 298 K). Initial CH3COOH activation is the kinetically relevant step, during which CH3C(O)-OH bond cleaves on a metal site pair at Ru cluster surfaces nearly saturated with adsorbed hydroxyl (OH*) and acetate (CH3COO*) intermediates, forming an adsorbed acetyl (CH3CO*) and hydroxyl (OH*) species. Acetic acid turnover rates increase proportionally with both H2 (10-60 bar) and CH3COOH concentrations at low CH3COOH concentrations (<0.83 M), but decrease from first to zero order as the CH3COOH concentration and the CH3COO* coverages increase and the vacant Ru sites concomitantly decrease. Beyond the initial CH3C(O)-OH bond activation, sequential H-insertions on the surface acetyl species (CH3CO*) lead to C2 products and their derivative (ethanol, ethane, and ethyl acetate) and the competitive C-C bond cleavage of CH3CO* causes the eventual methane formation. The instantaneous carbon selectivities towards C2 species (ethanol, ethane, and ethyl acetate) increase linearly with the concentration of proton-type Hδ+ (derived from carboxylic acid dissociation) and chemisorbed H*. The selectivities towards C2 products decrease with increasing temperature, because of higher observed barriers for C-C bond cleavage than H-insertion. This study offers an interpretation of mechanism and energetics and provides kinetic evidence of carboxylic acid assisted proton-type hydrogen (Hδ+) shuffling during H

HTGR fuel rods: carbon-carbon composites designed for high weight and low strength

International Nuclear Information System (INIS)

Bullock, R.E.

1977-01-01

The evolution of the process for fabricating fuel rods for the high-temperature gas-cooled reactor (HTGR) by injection and carbonization of a thermoplastic matrix that bonds close-packed beds of pyrocarbon-coated fuel particles together is reviewed for the fresh-fuel cycle, and a variant process involving a thermosetting matrix that would allow free-standing carbonization of refabricated fuel is discussed. Previous attempts to fabricate such injection-bonded fuel rods from undiluted thermosetting binders filled with powdered graphite were unsuccessful, because of damage to coatings on fuel particles that resulted from strong particle-to-matrix bonding in conjunction with large matrix shrinkage on carbonization and subsequent irradiation. These problems have now been overcome through the use of a diluted thermosetting matrix with a low-char-yield additive (fugitive), which produces a more porous char similar to that from the pitch-based thermoplastic used in fabrication of fresh fuel. A 1-to-1 dilution of resin with fugitive produced the optimum binder for injection and carbonization, where the fired matrix in such rods contained about 20 wt% binder char and 80 wt% powdered graphite. Thermosetting fuel rods diluted with various amounts of fugitive to give binder chars that range from 12 to 48 wt% of the fired matrix have been subjected to irradiation screening tests, and rods with no more than 32 wt% binder char appear to perform about as well under irradiation as do pitch-based rods. However, particle damage does begin to occur in those lightly diluted rods in which the less-stable binder char constitutes more than 32 wt% of the fired matrix. (author)

Carotenoid Cleavage Oxygenases from Microbes and Photosynthetic Organisms: Features and Functions

Directory of Open Access Journals (Sweden)

Oussama Ahrazem

2016-10-01

Full Text Available Apocarotenoids are carotenoid-derived compounds widespread in all major taxonomic groups, where they play important roles in different physiological processes. In addition, apocarotenoids include compounds with high economic value in food and cosmetics industries. Apocarotenoid biosynthesis starts with the action of carotenoid cleavage dioxygenases (CCDs, a family of non-heme iron enzymes that catalyze the oxidative cleavage of carbon–carbon double bonds in carotenoid backbones through a similar molecular mechanism, generating aldehyde or ketone groups in the cleaving ends. From the identification of the first CCD enzyme in plants, an increasing number of CCDs have been identified in many other species, including microorganisms, proving to be a ubiquitously distributed and evolutionarily conserved enzymatic family. This review focuses on CCDs from plants, algae, fungi, and bacteria, describing recent progress in their functions and regulatory mechanisms in relation to the different roles played by the apocarotenoids in these organisms.

Crystal structure of a diaryl carbonate: 1,3-phenylene bis(phenyl carbonate

Directory of Open Access Journals (Sweden)

Marina A. Solomos

2017-12-01

Full Text Available The whole molecule of the title compound, C20H14O6, is generated by mirror symmetry, the mirror bisecting the central benzene ring. The carbonate groups adopt an s-cis-s-cis conformation, with torsion angles of 58.7 (2 and 116.32 (15°. The crystal structure of 1,3-phenylene bis(phenyl carbonate contains no strong hydrogen bonds, though weak C—H...O and offset π–π interactions are observed, forming layers parallel to the ac plane.

Electrocatalytic reduction of H2O2 by Pt nanoparticles covalently bonded to thiolated carbon nanostructures

International Nuclear Information System (INIS)

You, Jung-Min; Kim, Daekun; Jeon, Seungwon

2012-01-01

Highlights: ► Novel thiolated carbon nanostructures – platinum nanoparticles [t-GO-C(O)-pt and t-MWCNT-C(O)-S-pt] have been synthesized, and [t-GO-C(O)-pt and t-MWCNT-C(O)-S-pt] denotes as t-GO-pt and t-MWCNT-Pt in manuscript, respectively. ► The modified electrode denoted as PDDA/t-GO-pt/GCE was used for the electrochemical determination of H 2 O 2 for the first time. ► The results show that PDDA/t-GO-pt nanoparticles have the promising potential as the basic unit of the electrochemical biosensors for the detection of H 2 O 2 . ► The proposed H 2 O 2 biosensors exhibited wide linear ranges and low detection limits, giving fast responses within 10 s. - Abstract: Glassy carbon electrodes were coated with thiolated carbon nanostructures – multi-walled carbon nanotubes and graphene oxide. The subsequent covalent addition of platinum nanoparticles and coating with poly(diallydimethylammonium chloride) resulted in biosensors that detected hydrogen peroxide through its electrocatalytic reduction. The sensors were easily and quickly prepared and showed improved sensitivity to the electrocatalytic reduction of H 2 O 2 . The Pt nanoparticles covalently bonded to the thiolated carbon nanostructures were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. Cyclic voltammetry and amperometry were used to characterize the biosensors’ performances. The sensors exhibited wide linear ranges and low detection limits, giving fast responses within 10 s, thus demonstrating their potential for use in H 2 O 2 analysis.

Co-implantation of carbon and nitrogen into silicon dioxide for synthesis of carbon nitride materials

CERN Document Server

Huang, M B; Nuesca, G; Moore, R

2002-01-01

Materials synthesis of carbon nitride has been attempted with co-implantation of carbon and nitrogen into thermally grown SiO sub 2. Following implantation of C and N ions to doses of 10 sup 1 sup 7 cm sup - sup 2 , thermal annealing of the implanted SiO sub 2 sample was conducted at 1000 degree sign C in an N sub 2 ambient. As evidenced in Fourier transform infrared measurements and X-ray photoelectron spectroscopy, different bonding configurations between C and N, including C-N single bonds, C=N double bonds and C=N triple bonds, were found to develop in the SiO sub 2 film after annealing. Chemical composition profiles obtained with secondary ion mass spectroscopy were correlated with the depth information of the chemical shifts of N 1s core-level electrons, allowing us to examine the formation of C-N bonding for different atomic concentration ratios between N and C. X-ray diffraction and transmission electron microscopy showed no sign of the formation of crystalline C sub 3 N sub 4 precipitates in the SiO ...

Grafting the surface of carbon nanotubes and carbon black with the chemical properties of hyperbranched polyamines

Science.gov (United States)

Morales-Lara, Francisco; Domingo-García, María; López-Garzón, Rafael; Luz Godino-Salido, María; Peñas-Sanjuán, Antonio; López-Garzón, F. Javier; Pérez-Mendoza, Manuel; Melguizo, Manuel

2016-01-01

Controlling the chemistry on the surface of new carbon materials is a key factor to widen the range of their applicability. In this paper we show a grafting methodology of polyalkylamines to the surface of carbon nanomaterials, in particular, carbon nanotubes and a carbon black. The aim of this work is to reach large degrees of covalent functionalization with hyperbranched polyethyleneimines (HBPEIs) and to efficiently preserve the strong chelating properties of the HBPEIs when they are fixed to the surface of these carbon materials. This functionalization opens new possibilities of using these carbon nanotubes-based hybrids. The results show that the HBPEIs are covalently attached to the carbon materials, forming hybrids. These hybrids emerge from the reaction of amine functions of the HBPEIs with carbonyls and carboxylic anhydrides of the carbon surface which become imine and imide bonds. Thus, due to the nature of these bonds, the pre-oxidized samples with relevant number of C=O groups showed an increase in the degree of functionalization with the HBPEIs. Furthermore, both the acid-base properties and the coordination capacity for metal ions of the hybrids are equivalent to that of the free HBPEIs in solution. This means that the chemical characteristics of the HBPEIs have been efficiently transferred to the hybrids. To reach this conclusion we have developed a novel procedure to assess the acid-base and the coordination properties of the hybrids (solids) by means of potentiometric titration. The good agreement of the values obtained for the hybrids and for the free HBPEIs in aqueous solution supports the reliability of the procedure. Moreover, the high capacity of the hybrids to capture Ni2+ by complexation opens new possibilities of using these hybrids to capture high-value metal ions such as Pd2+ and Pt2+.

A metallization and bonding approach for high performance carbon nanotube thermal interface materials

International Nuclear Information System (INIS)

Cross, Robert; Graham, Samuel; Cola, Baratunde A; Fisher, Timothy; Xu Xianfan; Gall, Ken

2010-01-01

A method has been developed to create vertically aligned carbon nanotube (VACNT) thermal interface materials that can be attached to a variety of metallized surfaces. VACNT films were grown on Si substrates using standard CVD processing followed by metallization using Ti/Au. The coated CNTs were then bonded to metallized substrates at 220 deg. C. By reducing the adhesion of the VACNTs to the growth substrate during synthesis, the CNTs can be completely transferred from the Si growth substrate and used as a die attachment material for electronic components. Thermal resistance measurements using a photoacoustic technique showed thermal resistances as low as 1.7 mm 2 K W -1 for bonded VACNT films 25-30 μm in length and 10 mm 2 K W -1 for CNTs up to 130 μm in length. Tensile testing demonstrated a die attachment strength of 40 N cm -2 at room temperature. Overall, these metallized and bonded VACNT films demonstrate properties which are promising for next-generation thermal interface material applications.

Hydrogen adsorption in carbon nanostructures compared

International Nuclear Information System (INIS)

Schimmel, H.G.; Nijkamp, G.; Kearley, G.J.; Rivera, A.; Jong, K.P. de; Mulder, F.M.

2004-01-01

Recent reports continue to suggest high hydrogen storage capacities for some carbon nanostructures due to a stronger interaction between hydrogen and carbon. Here the interaction of hydrogen with activated charcoal, carbon nanofibers, single walled carbon nanotubes (SWNT), and electron beam 'opened' SWNT are compared and shown to be similar. The storage capacity below 77 K of these materials correlates with the surface area of the material with the activated charcoal having the largest. SWNT and 'opened' SWNT have a relatively low accessible surface area due to bundling of the tubes. Pressure-temperature curves give the interaction potential, which was found to be ∼580 K or 50 meV in all samples, leading to significant adsorption below ∼50 K. Using the inelastic neutron scattering signal associated with rotation of the hydrogen molecule as a sensitive probe for the surroundings of the molecule, no difference was found between the hydrogen molecules adsorbed in the investigated materials. These combined spectroscopic and macroscopic results show that SWNT, nanofibers and activated carbons store molecular hydrogen due to their graphitic nature and not because they possess special morphologies. Results from a density functional theory computer calculation suggest molecular hydrogen bonding to an aromatic C-C bond of graphite, irrespective of the surface morphology farther away

Doping of silicon by carbon during laser ablation process

Science.gov (United States)

Raciukaitis, G.; Brikas, M.; Kazlauskiene, V.; Miskinis, J.

2007-04-01

Effect of laser ablation on properties of remaining material was investigated in silicon. It was established that laser cutting of wafers in air induced doping of silicon by carbon. The effect was found to be more distinct by the use of higher laser power or UV radiation. Carbon ions created bonds with silicon in the depth of silicon. Formation of the silicon carbide type bonds was confirmed by SIMS, XPS and AES measurements. Modeling of the carbon diffusion was performed to clarify its depth profile in silicon. Photo-chemical reactions of such type changed the structure of material and could be a reason for the reduced quality of machining. A controlled atmosphere was applied to prevent carbonization of silicon during laser cutting.

Doping of silicon by carbon during laser ablation process

International Nuclear Information System (INIS)

Raciukaitis, G; Brikas, M; Kazlauskiene, V; Miskinis, J

2007-01-01

Effect of laser ablation on properties of remaining material was investigated in silicon. It was established that laser cutting of wafers in air induced doping of silicon by carbon. The effect was found to be more distinct by the use of higher laser power or UV radiation. Carbon ions created bonds with silicon in the depth of silicon. Formation of the silicon carbide type bonds was confirmed by SIMS, XPS and AES measurements. Modeling of the carbon diffusion was performed to clarify its depth profile in silicon. Photo-chemical reactions of such type changed the structure of material and could be a reason for the reduced quality of machining. A controlled atmosphere was applied to prevent carbonization of silicon during laser cutting

Doping of silicon with carbon during laser ablation process

Science.gov (United States)

Račiukaitis, G.; Brikas, M.; Kazlauskienė, V.; Miškinis, J.

2006-12-01

The effect of laser ablation on properties of remaining material in silicon was investigated. It was found that laser cutting of wafers in the air induced the doping of silicon with carbon. The effect was more distinct when using higher laser power or UV radiation. Carbon ions created bonds with silicon atoms in the depth of the material. Formation of the silicon carbide type bonds was confirmed by SIMS, XPS and AES measurements. Modeling of the carbon diffusion to clarify its depth profile in silicon was performed. Photochemical reactions of such type changed the structure of material and could be the reason of the reduced machining quality. The controlled atmosphere was applied to prevent carbonization of silicon during laser cutting.

A Precisely Assembled Carbon Source to Synthesize Fluorescent Carbon Quantum Dots for Sensing Probes and Bioimaging Agents.

Science.gov (United States)

Qiao, Yiqiang; Luo, Dan; Yu, Min; Zhang, Ting; Cao, Xuanping; Zhou, Yanheng; Liu, Yan

2018-02-09

A broad range of carbon sources have been used to fabricate varieties of carbon quantum dots (CQDs). However, the majority of these studies concern the influence of primary structures and chemical compositions of precursors on the CQDs; it is still unclear whether or not the superstructures of carbon sources have effects on the physiochemical properties of the synthetic CQDs. In this work, the concept of molecular assembly is first introduced into the design of a new carbon source. Compared with the tropocollagen molecules, the hierarchically assembled collagen scaffolds, as a new carbon source, immobilize functional groups of the precursors through hydrogen bonds, electrostatic attraction, and hydrophobic forces. Moreover, the accumulation of functional groups in collagen self-assembly further promotes the covalent bond formation in the obtained CQDs through a hydrothermal process. Both of these two chemical superiorities give rise to high quality CQDs with enhanced emission. The assembled collagen scaffold-based CQDs with heteroatom doping exhibit superior stability, and could be further applied as effective fluorescent probes for Fe 3+ detection and cellular cytosol imaging. These findings open a wealth of possibilities to explore more nanocarbons from precursors with assembled superstructures. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selective C(sp2)-C(sp) bond cleavage: the nitrogenation of alkynes to amides.

Science.gov (United States)

Qin, Chong; Feng, Peng; Ou, Yang; Shen, Tao; Wang, Teng; Jiao, Ning

2013-07-22

Breakthrough: A novel catalyzed direct highly selective C(sp2)-C(sp) bond functionalization of alkynes to amides has been developed. Nitrogenation is achieved by the highly selective C(sp2)-C(sp) bond cleavage of aryl-substituted alkynes. The oxidant-free and mild conditions and wide substrate scope make this method very practical. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymerization initated at sidewalls of carbon nanotubes

Science.gov (United States)

Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

2011-01-01

The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

Direct Carboxylation of the Diazo Group ipso-C(sp2)-H bond with Carbon Dioxide: Access to Unsymmetrical Diazomalonates and Derivatives.

Science.gov (United States)

Liu, Qianyi; Li, Man; Xiong, Rui; Mo, Fanyang

2017-12-15

The direct carboxylation of the ipso-C(sp 2 )-H bond of a diazo compound with carbon dioxide under mild reaction conditions is described. This method is transition-metal-free, uses a weak base, and proceeds at ambient temperature under atmospheric pressure in carbon dioxide. The carboxylation exhibits high reactivity and is amenable to subsequent diversification. A series of unsymmetrical 1,3-diester/keto/amide diazo compounds are obtained with moderate to excellent yields (up to 99%) with good functional group compatibility.

SAXS study on activated carbons

International Nuclear Information System (INIS)

Bota, A.; Heringer, D.; Mihalffy, T.

1999-01-01

SAXS fractal analysis of activated carbons is presented. It gives very useful information about the structural changes of the carbon skeleton. From the fact, that the sequence of the activation and the heat treatment affect the fractal behaviours more drastically than the particle size distribution of the structural units, it follows that all changes in the pore and matrix structure may reduce principally to the bonding of the crystallite units. (K.A.)

From Carbon to Buckypaper

Indian Academy of Sciences (India)

hedral, connected by covalent bonds, and forms a 3-dimensional network. The rigid .... increasing number of applications in various sectors [15, 16, 17]. 1. .... [9] Bill Howard, (30 July 2013), BMW i3: Cheap, mass-produced carbon fiber.

Ultrahard carbon nanocomposite films

Energy Technology Data Exchange (ETDEWEB)

SIEGAL,MICHAEL P.; TALLANT,DAVID R.; PROVENCIO,PAULA P.; OVERMYER,DONALD L.; SIMPSON,REGINA L.; MARTINEZ-MIRANDA,L.J.

2000-01-27

Modest thermal annealing to 600 C of diamondlike amorphous-carbon (a-C) films grown at room temperature results in the formation of carbon nanocomposites with hardness similar to diamond. These nanocomposite films consist of nanometer-sized regions of high density a-C embedded in an a-C matrix with a reduced density of 5--10%. The authors report on the evolution of density and bonding topologies as a function of annealing temperature. Despite a decrease in density, film hardness actually increases {approximately} 15% due to the development of the nanocomposite structure.

A brief 100 year history of carbon.

Science.gov (United States)

Kemp, Terence J

2017-09-01

Elemental carbon has been known from time immemorial in its forms of diamond and graphite, while the Industrial Revolution was powered by coal. The molecular structures of diamond and graphite were established following the inception of X-ray crystallography while the complex natures of charcoal and coal have been investigated for 100 years. Recent developments in activated charcoal are described in an article in this issue of Science Progress. However, no-one could have guessed that carbon would have presented such structural surprises as those of C60 fullerene, carbon nanotubes, and graphene. Materials science has benefited from the discovery of carbon fibres, and our understanding of the spectroscopy and bonding in the simplest carbon molecule, C2, has reached new depths.

Facile insertion of a cyclic alkyl(amino) carbene carbon into the B-B bond of diboron(4) reagents.

Science.gov (United States)

Eichhorn, Antonius F; Kuehn, Laura; Marder, Todd B; Radius, Udo

2017-10-24

We report herein the room temperature insertion of the carbene carbon atom of the cyclic (alkyl)(amino) carbene cAAC Me into the B-B single bonds of the diboron(4) compounds B 2 pin 2 , B 2 cat 2 , B 2 neop 2 , and B 2 eg 2 (pin = pinacolato, cat = catecholato, neop = neopentylglycolato, eg = ethyleneglycolato).

Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site

Science.gov (United States)

Buss, Joshua A.; Agapie, Theodor

2016-01-01

Carbon dioxide is the ultimate source of the fossil fuels that are both central to modern life and problematic: their use increases atmospheric levels of greenhouse gases, and their availability is geopolitically constrained. Using carbon dioxide as a feedstock to produce synthetic fuels might, in principle, alleviate these concerns. Although many homogeneous and heterogeneous catalysts convert carbon dioxide to carbon monoxide, further deoxygenative coupling of carbon monoxide to generate useful multicarbon products is challenging. Molybdenum and vanadium nitrogenases are capable of converting carbon monoxide into hydrocarbons under mild conditions, using discrete electron and proton sources. Electrocatalytic reduction of carbon monoxide on copper catalysts also uses a combination of electrons and protons, while the industrial Fischer-Tropsch process uses dihydrogen as a combined source of electrons and electrophiles for carbon monoxide coupling at high temperatures and pressures. However, these enzymatic and heterogeneous systems are difficult to probe mechanistically. Molecular catalysts have been studied extensively to investigate the elementary steps by which carbon monoxide is deoxygenated and coupled, but a single metal site that can efficiently induce the required scission of carbon-oxygen bonds and generate carbon-carbon bonds has not yet been documented. Here we describe a molybdenum compound, supported by a terphenyl-diphosphine ligand, that activates and cleaves the strong carbon-oxygen bond of carbon monoxide, enacts carbon-carbon coupling, and spontaneously dissociates the resulting fragment. This complex four-electron transformation is enabled by the terphenyl-diphosphine ligand, which acts as an electron reservoir and exhibits the coordinative flexibility needed to stabilize the different intermediates involved in the overall reaction sequence. We anticipate that these design elements might help in the development of efficient catalysts for

Studies of the pH dependence of 13C shifts and carbon-carbon coupling constants of [U-13C]aspartic and -glutamic acids

International Nuclear Information System (INIS)

London, R.E.; Walker, T.E.; Kollman, V.H.; Matwiyoff, N.A.

1978-01-01

13 C NMR studies of the chemical shifts and carbon--carbon spin--spin coupling constants of 90% [U- 13 C]aspartic and -glutamic acids are reported. Effects of titration of the two carboxyl groups are separated computationally and the results compared with those for asparagine and glutamine, aspartate and glutamate containing peptides, and a series of amino-n-butyric acids. The results indicate that the carboxyl carbon shift resulting from titration of the carboxyl group is strongly dependent on its distance (number of bonds) from an amino group. Alternatively, remote methyl groups exhibit a much smaller titration induced shift than carboxyl groups in the corresponding position. Significant remote effects of pH titration on the one-bond carbon-carbon coupling are also observed, particularly for couplings involving the side-chain carboxyl carbons. These results are discussed in terms of polarization of the C--O bonds in response to titration of a remote carboxyl group. Values of 3 J/sub CC/ in asparate and glutamate indicate a strong conformational dependence. Rotamer populations predicted on the basis of the observed couplings and theoretical INDO calculations are in good agreement with values based on analysis of the 3 J/sub HH/ and 3 J/sub CH/ couplings. For a given conformation of glutamic acid, it is found that 3 J 14 is considerably smaller than 3 J 25 . This result is consistent with obsrvations on a number of other 13 C-labeled amino acids. 5 figures, 4 tables

Probing Electron-Induced Bond Cleavage at the Single-Molecule Level Using DNA Origami Templates

DEFF Research Database (Denmark)

Keller, Adrian Clemens; Bald, Ilko; Rotaru, Alexandru

2012-01-01

Low-energy electrons (LEEs) play an important role in nanolithography, atmospheric chemistry, and DNA radiation damage. Previously, the cleavage of specific chemical bonds triggered by LEEs has been demonstrated in a variety of small organic molecules such as halogenated benzenes and DNA nucleoba...

Partitioning of One-Carbon Units in Folate and Methionine Metabolism Is Essential for Neural Tube Closure

Directory of Open Access Journals (Sweden)

Kit-Yi Leung

2017-11-01

Full Text Available Summary: Abnormal folate one-carbon metabolism (FOCM is implicated in neural tube defects (NTDs, severe malformations of the nervous system. MTHFR mediates unidirectional transfer of methyl groups from the folate cycle to the methionine cycle and, therefore, represents a key nexus in partitioning one-carbon units between FOCM functional outputs. Methionine cycle inhibitors prevent neural tube closure in mouse embryos. Similarly, the inability to use glycine as a one-carbon donor to the folate cycle causes NTDs in glycine decarboxylase (Gldc-deficient embryos. However, analysis of Mthfr-null mouse embryos shows that neither S-adenosylmethionine abundance nor neural tube closure depend on one-carbon units derived from embryonic or maternal folate cycles. Mthfr deletion or methionine treatment prevents NTDs in Gldc-null embryos by retention of one-carbon units within the folate cycle. Overall, neural tube closure depends on the activity of both the methionine and folate cycles, but transfer of one-carbon units between the cycles is not necessary. : Leung at al. find that embryonic neural tube closure depends both on the supply of one-carbon units to the folate cycle from glycine cleavage and on the methionine cycle. In contrast, transfer of one-carbon units from the folate cycle to the methionine cycle by MTHFR is dispensable. Keywords: one-carbon metabolism, folic acid, neural tube defects, spina bifida, glycine cleavage system, non-ketotic hyperglycinemia, eye, Mthfr, Gldc

Structure and photoluminescence of films composed of carbon nanoflakes

Energy Technology Data Exchange (ETDEWEB)

Wang, Yi, E-mail: wangyi@cqut.edu.cn [College of Mechanical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054, P R China (China); Li, Lin [College of Chemistry, Chongqing Normal University, Chongqing 401331, P R China (China); Cheng, Qijin [School of Energy Research, Xiamen University, Xiamen 361005, P R China (China); He, Chunlin [Liaoning Provincial Key Laboratory of Advanced Materials, Shenyang University, Shenyang 110044, P R China (China)

2015-05-15

Carbon nanoflake films (CNFFs) were directly synthesized by plasma-enhanced hot filament chemical vapor deposition. The results of field emission scanning electron microscope, transmission electron microscope, micro-Raman spectroscope, X-ray photoelectron spectroscope and Fourier transform infrared spectroscope indicate that the CNFFs are composed of bending carbon nanoflakes with the hydrocarbon and hydroxyl functional groups, and the carbon nanoflakes become thin in a long deposition time. The structural change of carbon nanoflakes is related to the formation of structural units and the aggregation of hydrocarbon radicals near the carbon nanoflakes. Moreover, the photoluminescence (PL) properties of CNFFs were studied in a Ramalog system and a PL spectroscope. The PL results indicate that the PL intensity of CNFFs is lowered with the increase of thickness of CNFFs. The lowering of PL intensity for the thick CNFFs originates from the effect of more dangling bonds in the CNFFs. In addition, we studied the structural difference of carbon nanoflakes grown by different CVD systems and the PL difference of carbon nanoflakes in different measurement systems. The results achieved here are important to control the growth and structure of graphene-based materials and fabricate the optoelectronic devices related to carbon-based materials. - Highlights: • Carbon nanoflake films (CNFFs) were synthesized by PEHFCVD. • The structure of CNFFs is related to the aggregation of carbon hydrocarbon radicals. • The PL intensity of CNFFs is lowered with the thickness increase of CNFFs. • The change of PL intensity of CNFFs is due to the dangling bonds in CNFFs. • The widening of PL bands of CNFFs results from the diversity of carbon nanofalkes.

Covalent bond force profile and cleavage in a single polymer chain

Science.gov (United States)

Garnier, Lionel; Gauthier-Manuel, Bernard; van der Vegte, Eric W.; Snijders, Jaap; Hadziioannou, Georges

2000-08-01

We present here the measurement of the single-polymer entropic elasticity and the single covalent bond force profile, probed with two types of atomic force microscopes (AFM) on a synthetic polymer molecule: polymethacrylic acid in water. The conventional AFM allowed us to distinguish two types of interactions present in this system when doing force spectroscopic measurements: the first interaction is associated with adsorption sites of the polymer chains onto a bare gold surface, the second interaction is directly correlated to the rupture process of a single covalent bond. All these bridging interactions allowed us to stretch the single polymer chain and to determine the various factors playing a role in the elasticity of these molecules. To obtain a closer insight into the bond rupture process, we moved to a force sensor stable in position when measuring attractive forces. By optimizing the polymer length so as to fulfill the elastic stability conditions, we were able for the first time to map out the entire force profile associated with the cleavage of a single covalent bond. Experimental data coupled with molecular quantum mechanical calculations strongly suggest that the breaking bond is located at one end of the polymer chain.

Covalently Bonded Graphene-Carbon Nanotube Hybrid for High-Performance Thermal Interfaces

DEFF Research Database (Denmark)

Chen, Jie; Walther, Jens H.; Koumoutsakos, Petros

2015-01-01

The remarkable thermal properties of graphene and carbon nanotubes (CNTs) have been the subject of intensive investigations for the thermal management of integrated circuits. However, the small contact area of CNTs and the large anisotropic heat conduction of graphene have hindered...... their applications as effective thermal interface materials (TIMs). Here, a covalently bonded graphene–CNT (G-CNT) hybrid is presented that multiplies the axial heat transfer capability of individual CNTs through their parallel arrangement, while at the same time it provides a large contact area for efficient heat...... extraction. Through computer simulations, it is demonstrated that the G-CNT outperforms few-layer graphene by more than 2 orders of magnitude for the c-axis heat transfer, while its thermal resistance is 3 orders of magnitude lower than the state-of-the-art TIMs. We show that heat can be removed from the G...

Discharge cleaning of carbon deposits

International Nuclear Information System (INIS)

Mozetic, M.; Vesel, A.; Drenik, A.

2006-01-01

Experimental results of discharge cleaning of carbon deposits are presented. Deposits were prepared by creating plasma in pure methane. The methane was cracked in RF discharge at the output power of 250 W. The resultant radicals were bonded to the wall of discharge vessel forming a thin film of hydrogenated black carbon with the thickness of about 200nm. The film was then cleaned in situ by oxygen plasma with the density of about 1x10 16 m -3 , electron temperature of 5 eV, neutral gas kinetic temperature of about 100 0 C and neutral atom density of 6x10 21 m -3 . The treatment time was 30 minutes. The efficiency of plasma cleaning was monitored by optical emission spectroscopy. As long as the wall was contaminated with carbon deposit, substantial emission of the CO molecules was detected. As the cleaning was in progress, the CO emission was decreasing and vanished after 30 minutes when the discharge vessel became free of any carbon. The results are explained by interaction of plasma radicals with carbon deposits. (author)

Cohesion energetics of carbon allotropes: Quantum Monte Carlo study

Energy Technology Data Exchange (ETDEWEB)

Shin, Hyeondeok; Kang, Sinabro; Koo, Jahyun; Lee, Hoonkyung; Kwon, Yongkyung, E-mail: ykwon@konkuk.ac.kr [Division of Quantum Phases and Devices, School of Physics, Konkuk University, Seoul 143-701 (Korea, Republic of); Kim, Jeongnim, E-mail: jnkim@ornl.gov [Materials Science and Technology Division and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

2014-03-21

We have performed quantum Monte Carlo calculations to study the cohesion energetics of carbon allotropes, including sp{sup 3}-bonded diamond, sp{sup 2}-bonded graphene, sp–sp{sup 2} hybridized graphynes, and sp-bonded carbyne. The computed cohesive energies of diamond and graphene are found to be in excellent agreement with the corresponding values determined experimentally for diamond and graphite, respectively, when the zero-point energies, along with the interlayer binding in the case of graphite, are included. We have also found that the cohesive energy of graphyne decreases systematically as the ratio of sp-bonded carbon atoms increases. The cohesive energy of γ-graphyne, the most energetically stable graphyne, turns out to be 6.766(6) eV/atom, which is smaller than that of graphene by 0.698(12) eV/atom. Experimental difficulty in synthesizing graphynes could be explained by their significantly smaller cohesive energies. Finally, we conclude that the cohesive energy of a newly proposed graphyne can be accurately estimated with the carbon–carbon bond energies determined from the cohesive energies of graphene and three different graphynes considered here.

Vertically aligned multiwalled carbon nanotubes as electronic interconnects

Science.gov (United States)

Gopee, Vimal Chandra

The drive for miniaturisation of electronic circuits provides new materials challenges for the electronics industry. Indeed, the continued downscaling of transistor dimensions, described by Moore’s Law, has led to a race to find suitable replacements for current interconnect materials to replace copper. Carbon nanotubes have been studied as a suitable replacement for copper due to its superior electrical, thermal and mechanical properties. One of the advantages of using carbon nanotubes is their high current carrying capacity which has been demonstrated to be three orders of magnitude greater than that of copper. Most approaches in the implementation of carbon nanotubes have so far focused on the growth in vias which limits their application. In this work, a process is described for the transfer of carbon nanotubes to substrates allowing their use for more varied applications. Arrays of vertically aligned multiwalled carbon nanotubes were synthesised by photo-thermal chemical vapour deposition with high growth rates. Raman spectroscopy was used to show that the synthesised carbon nanotubes were of high quality. The carbon nanotubes were exposed to an oxygen plasma and the nature of the functional groups present was determined using X-ray photoelectron spectroscopy. Functional groups, such as carboxyl, carbonyl and hydroxyl groups, were found to be present on the surface of the multiwalled carbon nanotubes after the functionalisation process. The multiwalled carbon nanotubes were metallised after the functionalisation process using magnetron sputtering. Two materials, solder and sintered silver, were chosen to bind carbon nanotubes to substrates so as to enable their transfer and also to make electrical contact. The wettability of solder to carbon nanotubes was investigated and it was demonstrated that both functionalisation and metallisation were required in order for solder to bond with the carbon nanotubes. Similarly, functionalisation followed by metallisation

Microstructure study of PAN-pitch-based carbon-carbon composite

International Nuclear Information System (INIS)

Lee, K.J.; Chen, Z.Y.

2003-01-01

Scanning electron microscopy (SEM), polarized light microscopy (PLM), and transmission electron microscopy (TEM) techniques have been used to characterize the normal surface and flank surface microstructure of a two-dimensional polyacrylonitrile (PAN)-based fiber reinforced mesophase pitch-based matrix carbon-carbon (C-C) composite. Optical and SEM results indicate that the mesophase pitch appears generally well bonded to the fibers, as well as internal pores and cracks exist in both interbundle and intrabundle regions. TEM shows that matrix platelets were highly parallel to the fiber axis. Numerous microcracks, parallel to the fiber axis, were formed along fiber-matrix interface and within the matrix. The selected-area diffraction (SAD) patterns show that a random orientation of basal planes in the transverse fiber of flank surface and the domain near the fiber surface exhibited a better alignment

Two-dimensional gold nanostructures with high activity for selective oxidation of carbon-hydrogen bonds

Science.gov (United States)

Wang, Liang; Zhu, Yihan; Wang, Jian-Qiang; Liu, Fudong; Huang, Jianfeng; Meng, Xiangju; Basset, Jean-Marie; Han, Yu; Xiao, Feng-Shou

2015-04-01

Efficient synthesis of stable two-dimensional (2D) noble metal catalysts is a challenging topic. Here we report the facile synthesis of 2D gold nanosheets via a wet chemistry method, by using layered double hydroxide as the template. Detailed characterization with electron microscopy and X-ray photoelectron spectroscopy demonstrates that the nanosheets are negatively charged and [001] oriented with thicknesses varying from single to a few atomic layers. X-ray absorption spectroscopy reveals unusually low gold-gold coordination numbers. These gold nanosheets exhibit high catalytic activity and stability in the solvent-free selective oxidation of carbon-hydrogen bonds with molecular oxygen.

Ultrahard carbon nanocomposite films

Energy Technology Data Exchange (ETDEWEB)

Siegal, M. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Tallant, D. R. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Provencio, P. N. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Overmyer, D. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Simpson, R. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Martinez-Miranda, L. J. [Department of Materials and Nuclear Engineering, University of Maryland, College Park, Maryland 20742 (United States)

2000-05-22

Modest thermal annealing to 600 degree sign C of diamondlike amorphous-carbon (a-C) films grown at room temperature results in the formation of carbon nanocomposites with hardness similar to diamond. These nanocomposite films consist of nanometer-sized regions of high density a-C embedded in an a-C matrix with a reduced density of 5%-10%. We report on the evolution of density and bonding topologies as a function of annealing temperature. Despite a decrease in density, film hardness actually increases {approx}15% due to the development of the nanocomposite structure. (c) 2000 American Institute of Physics.

Cogeneration and Carbon bonds: clean development; Cogeneracion y bonos de carbono: desarrollo limpio

Energy Technology Data Exchange (ETDEWEB)

Navarro Perez, Nidia [Facultad de Contaduria y Administracion, Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

2004-06-15

The growing preoccupation for the environment in our country and its interest to ratify the Kyoto Protocol with respect to the contamination of the atmosphere, offers great opportunities for the cogeneration so that it fortifies the scientific and technological research and gives a good international image about the sustainable development and care of the environment, so that companies that invest in clean technology will be able to assign a monetary value to their environmental patrimony, this through the so called Green Bonds or Carbon Bonds, this opens a new dimension to finance projects by means of these bonds that can be negotiated at an international level; by means of the Clean of Energy Production the investment can be stimulated and revenues for projects that contribute to the sustainable development of the country and the power efficiency. At the moment the country has at least 13 projects in different analysis stages to enter the carbon bond market, which are presented as co-generation projects of energy, in addition to the formation of the Mexican Committee for Projects of Reduction and Capture of Gas Discharges of Greenhouse Effect. [Spanish] La creciente preocupacion por el medio ambiente en nuestro pais y su interes por ratificar el Protocolo de Kyoto en lo referente a la contaminacion de la atmosfera, ofrece grandes oportunidades para la cogeneracion de manera que fortalezca la investigacion cientifica y tecnologica y dar una buena imagen internacional en torno a temas de desarrollo sustentable y cuidado del medio ambiente, de manera que empresas que invierten en tecnologia limpia podran asignar un valor monetario a su patrimonio ambiental, esto a traves de los llamados Bonos Verdes o Bonos de Carbono, esto abre una dimension nueva para financiar proyectos por medio de estos bonos que pueden negociarse a nivel internacional; por medio de la Produccion Limpia de energia se puede estimular inversion y ganancias para proyectos que contribuyan al

Electronic structure of incident carbon ions on a graphite surface

International Nuclear Information System (INIS)

Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.

1997-01-01

The electronic structure of an incident carbon ion on a graphite surface is discussed on the basis of ab initio molecular orbital calculations. A carbon cation forms a covalent bond with the graphite, and a carbon nonion is attracted to the graphite surface through van der Waals interaction. A carbon anion has no stable state on a graphite surface. The charge effects of incident ions become clear upon detailed examination of the electronic structure. (author)

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)

1997-12-31

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.

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.

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

International Nuclear Information System (INIS)

Merchant, A.R.; McCulloch, D.; McKenzie, D.R.; Yin, Y.; Gerstner, E.G.

1996-01-01

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 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 3 N 4 , or any amorphous derivative of it. 16 refs., 1 tab., 5 figs

Multi-functional carbon nanomaterials: Tailoring morphology for multidisciplinary applications

Energy Technology Data Exchange (ETDEWEB)

Dervishi, Enkeleda [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-05-14

Carbon based nanomaterials are being developed to have many new properties and applications. Graphene, is a mono-layer 2D atomic thick structure formed from hexagons of carbon atoms bound together by sp^2hybrid bonds. A carbon nanotube (CNT) can be viewed as a sheet of graphene rolled up into a cylinder, usually 1-2 nanometers in diameter and a few microns thick. A few applications of graphene and carbon nanotubes include the development of Nanoelectronics, nanocomposite materials, Hydrogen storage and Li⁺ battery, etc.

Research on the Development of Green Finance in Shenzhen to Boost the Carbon Trading Market

Science.gov (United States)

Zhou, Jiping; Xiong, Siqin; Zhou, Yucheng; Zou, Zijian; Ma, Xiaoming

2017-08-01

This paper analyses the current development situations of Shenzhen carbon trading market and China’s green finance, and makes the policy recommendations for promoting the carbon trading market by developing green finance in Shenzhen. Shenzhen should take the lead in driving the localized application of green principle, and formulate Shenzhen green bond guidelines ASAP, to promote carbon trading associated enterprises to finance by using green bonds; it shall work to lower the threshold for financial institutions to participate in carbon trading market, and explore development of carbon derivatives.

Carbon foam/hydroxyapatite coating for carbon/carbon composites: Microstructure and biocompatibility

Energy Technology Data Exchange (ETDEWEB)

Zhang, Leilei, E-mail: zhangleilei1121@aliyun.com; Li, Hejun; Li, Kezhi; Zhang, Shouyang; Lu, Jinhua; Li, Wei; Cao, Sheng; Wang, Bin

2013-12-01

To improve the surface biocompatibility of carbon/carbon composites, a carbon foam/hydroxyapatite coating was applied using a combination method of slurry procedure and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The biocompatibility of the carbon foam/hydroxyapatite coating was investigated by osteoblast-like MG63 cell culture tests. The results showed that the carbon foam could provide a large number of pores on the surface of carbon/carbon composites. The hydroxyapatite crystals could infiltrate into the pores and form the carbon foam/hydroxyapatite coating. The coating covered the carbon/carbon composites fully and uniformly with slice morphology. The cell response tests showed that the MG63 cells on carbon foam/hydroxyapatite coating had a better cell adhesion and cell proliferation than those on uncoated carbon/carbon composites. The carbon foam/hydroxyapatite coatings were cytocompatible and were beneficial to improve the biocompatibility. The approach presented here may be exploited for fabrication of carbon/carbon composite implant surfaces.

Carbon foam/hydroxyapatite coating for carbon/carbon composites: Microstructure and biocompatibility

International Nuclear Information System (INIS)

Zhang, Leilei; Li, Hejun; Li, Kezhi; Zhang, Shouyang; Lu, Jinhua; Li, Wei; Cao, Sheng; Wang, Bin

2013-01-01

To improve the surface biocompatibility of carbon/carbon composites, a carbon foam/hydroxyapatite coating was applied using a combination method of slurry procedure and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The biocompatibility of the carbon foam/hydroxyapatite coating was investigated by osteoblast-like MG63 cell culture tests. The results showed that the carbon foam could provide a large number of pores on the surface of carbon/carbon composites. The hydroxyapatite crystals could infiltrate into the pores and form the carbon foam/hydroxyapatite coating. The coating covered the carbon/carbon composites fully and uniformly with slice morphology. The cell response tests showed that the MG63 cells on carbon foam/hydroxyapatite coating had a better cell adhesion and cell proliferation than those on uncoated carbon/carbon composites. The carbon foam/hydroxyapatite coatings were cytocompatible and were beneficial to improve the biocompatibility. The approach presented here may be exploited for fabrication of carbon/carbon composite implant surfaces.

All carbon nanotubes are not created equal

International Nuclear Information System (INIS)

Geohegan, David B.; Puretzky, Alexander A.; Rouleau, Christopher M.

2010-01-01

This chapter presents the various factors that enter into consideration when choosing the source of carbon nanotubes for a specific application. Carbon nanotubes are giant molecules made of pure carbon. They have captured the imagination of the scientific community by the unique structure that provides superior physical, chemical, and electrical properties. However, a surprisingly wide disparity exists between the intrinsic properties determined under ideal conditions and the properties that carbon nanotubes exhibit in real world situations. The lack of uniformity in carbon nanotube properties is likely to be the main obstacle holding back the development of carbon nanotube applications. This tutorial addresses the nonuniformity of carbon nanotube properties from the synthesis standpoint. This synthesis-related nonuniformity is on top of the intrinsic chirality distribution that gives the ∼1:2 ratio of metallic to semiconducting nanotubes. From the standpoint of carbon bonding chemistry the variation in the quality and reproducibility of carbon nanotube materials is not unexpected. It is an intrinsic feature that is related to the metastability of carbon structures. The extent to which this effect is manifested in carbon nanotube formation is governed by the type and the kinetics of the carbon nanotube synthesis reaction. Addressing this variation is critical if nanotubes are to live up to the potential already demonstrated by their phenomenal physical properties.

Role of dispersion corrected hybrid GGA class in accurately calculating the bond dissociation energy of carbon halogen bond: A benchmark study

Science.gov (United States)

Kosar, Naveen; Mahmood, Tariq; Ayub, Khurshid

2017-12-01

Benchmark study has been carried out to find a cost effective and accurate method for bond dissociation energy (BDE) of carbon halogen (Csbnd X) bond. BDE of C-X bond plays a vital role in chemical reactions, particularly for kinetic barrier and thermochemistry etc. The compounds (1-16, Fig. 1) with Csbnd X bond used for current benchmark study are important reactants in organic, inorganic and bioorganic chemistry. Experimental data of Csbnd X bond dissociation energy is compared with theoretical results. The statistical analysis tools such as root mean square deviation (RMSD), standard deviation (SD), Pearson's correlation (R) and mean absolute error (MAE) are used for comparison. Overall, thirty-one density functionals from eight different classes of density functional theory (DFT) along with Pople and Dunning basis sets are evaluated. Among different classes of DFT, the dispersion corrected range separated hybrid GGA class along with 6-31G(d), 6-311G(d), aug-cc-pVDZ and aug-cc-pVTZ basis sets performed best for bond dissociation energy calculation of C-X bond. ωB97XD show the best performance with less deviations (RMSD, SD), mean absolute error (MAE) and a significant Pearson's correlation (R) when compared to experimental data. ωB97XD along with Pople basis set 6-311g(d) has RMSD, SD, R and MAE of 3.14 kcal mol-1, 3.05 kcal mol-1, 0.97 and -1.07 kcal mol-1, respectively.

An in situ infrared study of dimethyl carbonate synthesis from carbon dioxide and methanol over zirconia

International Nuclear Information System (INIS)

Jung, Kyeong Taek; Bell, Alexis T.

2001-01-01

The mechanism of dimethyl carbonate (DMC) synthesis from methanol and carbon dioxide over monoclinic zirconia has been investigated using in situ infrared spectroscopy. The dissociative adsorption of methanol occurs more slowly than the adsorption of carbon dioxide, but the species formed from methanol are bound more strongly. Upon adsorption, the oxygen atom of methanol binds to coordinately unsaturated Zr4+ cations present at the catalyst surface. Rapid dissociation of the adsorbed methanol leads to the formation of a methoxide group (Zr-OCH3) and the release of a proton, which reacts with a surface hydroxyl group to produce water. Carbon dioxide inserts in the Zr-O bond of the methoxide to form a mondentate methyl carbonate group (Zr-OC(O)OCH3). This process is facilitated by the interactions of C and O atoms in CO2 with Lewis acid-base pairs of sites (Zr4+O2-) on the surface of the catalyst. Methyl carbonate species can also be produced via the reaction of methanol with carbon dioxide adsorbed in the form of bicarbonate species with methanol, a process that results in the transfer of a methyl group to the carbonate and restores a hydroxyl group to the zirconia surface. The decomposition of DMC on monoclinic zirconia has also been investigated and has been observed to occur via the reverse of the processes described for the synthesis of DMC

Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

Science.gov (United States)

Schobben, Martin; van de Velde, Sebastiaan; Gliwa, Jana; Leda, Lucyna; Korn, Dieter; Struck, Ulrich; Vinzenz Ullmann, Clemens; Hairapetian, Vachik; Ghaderi, Abbas; Korte, Christoph; Newton, Robert J.; Poulton, Simon W.; Wignall, Paul B.

2017-11-01

Bulk-carbonate carbon isotope ratios are a widely applied proxy for investigating the ancient biogeochemical carbon cycle. Temporal carbon isotope trends serve as a prime stratigraphic tool, with the inherent assumption that bulk micritic carbonate rock is a faithful geochemical recorder of the isotopic composition of seawater dissolved inorganic carbon. However, bulk-carbonate rock is also prone to incorporate diagenetic signals. The aim of the present study is to disentangle primary trends from diagenetic signals in carbon isotope records which traverse the Permian-Triassic boundary in the marine carbonate-bearing sequences of Iran and South China. By pooling newly produced and published carbon isotope data, we confirm that a global first-order trend towards depleted values exists. However, a large amount of scatter is superimposed on this geochemical record. In addition, we observe a temporal trend in the amplitude of this residual δ13C variability, which is reproducible for the two studied regions. We suggest that (sub-)sea-floor microbial communities and their control on calcite nucleation and ambient porewater dissolved inorganic carbon δ13C pose a viable mechanism to induce bulk-rock δ13C variability. Numerical model calculations highlight that early diagenetic carbonate rock stabilization and linked carbon isotope alteration can be controlled by organic matter supply and subsequent microbial remineralization. A major biotic decline among Late Permian bottom-dwelling organisms facilitated a spatial increase in heterogeneous organic carbon accumulation. Combined with low marine sulfate, this resulted in varying degrees of carbon isotope overprinting. A simulated time series suggests that a 50 % increase in the spatial scatter of organic carbon relative to the average, in addition to an imposed increase in the likelihood of sampling cements formed by microbial calcite nucleation to 1 out of 10 samples, is sufficient to induce the observed signal of carbon

Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

Directory of Open Access Journals (Sweden)

M. Schobben

2017-11-01

Full Text Available Bulk-carbonate carbon isotope ratios are a widely applied proxy for investigating the ancient biogeochemical carbon cycle. Temporal carbon isotope trends serve as a prime stratigraphic tool, with the inherent assumption that bulk micritic carbonate rock is a faithful geochemical recorder of the isotopic composition of seawater dissolved inorganic carbon. However, bulk-carbonate rock is also prone to incorporate diagenetic signals. The aim of the present study is to disentangle primary trends from diagenetic signals in carbon isotope records which traverse the Permian–Triassic boundary in the marine carbonate-bearing sequences of Iran and South China. By pooling newly produced and published carbon isotope data, we confirm that a global first-order trend towards depleted values exists. However, a large amount of scatter is superimposed on this geochemical record. In addition, we observe a temporal trend in the amplitude of this residual δ13C variability, which is reproducible for the two studied regions. We suggest that (sub-sea-floor microbial communities and their control on calcite nucleation and ambient porewater dissolved inorganic carbon δ13C pose a viable mechanism to induce bulk-rock δ13C variability. Numerical model calculations highlight that early diagenetic carbonate rock stabilization and linked carbon isotope alteration can be controlled by organic matter supply and subsequent microbial remineralization. A major biotic decline among Late Permian bottom-dwelling organisms facilitated a spatial increase in heterogeneous organic carbon accumulation. Combined with low marine sulfate, this resulted in varying degrees of carbon isotope overprinting. A simulated time series suggests that a 50 % increase in the spatial scatter of organic carbon relative to the average, in addition to an imposed increase in the likelihood of sampling cements formed by microbial calcite nucleation to 1 out of 10 samples, is sufficient to induce the

Progress Toward Sequestering Carbon Nanotubes in PmPV

Science.gov (United States)

Bley, Richard A.

2009-01-01

Sequestration of single-walled carbon nanotubes (SWNTs) in molecules of poly(m-phenylenevinylene-co-2,5-diocty-loxy-p-phenylenevinylene) [PmPV] is a candidate means of promoting dissolution of single-walled carbon nanotubes (SWNTs) into epoxies for making strong, lightweight epoxy-matrix/carbon-fiber composite materials. Bare SWNTs cannot be incorporated because they are not soluble in epoxies. In the present approach, one exploits the tendency of PmPV molecules to wrap themselves around SWNTs without chemically bonding to them.

Accounting for nanometer-thick adventitious carbon contamination in X-ray absorption spectra of carbon-based materials.

Science.gov (United States)

Mangolini, Filippo; McClimon, J Brandon; Rose, Franck; Carpick, Robert W

2014-12-16

Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is a powerful technique for characterizing the composition and bonding state of nanoscale materials and the top few nanometers of bulk and thin film specimens. When coupled with imaging methods like photoemission electron microscopy, it enables chemical imaging of materials with nanometer-scale lateral spatial resolution. However, analysis of NEXAFS spectra is often performed under the assumption of structural and compositional homogeneity within the nanometer-scale depth probed by this technique. This assumption can introduce large errors when analyzing the vast majority of solid surfaces due to the presence of complex surface and near-surface structures such as oxides and contamination layers. An analytical methodology is presented for removing the contribution of these nanoscale overlayers from NEXAFS spectra of two-layered systems to provide a corrected photoabsorption spectrum of the substrate. This method relies on the subtraction of the NEXAFS spectrum of the overlayer adsorbed on a reference surface from the spectrum of the two-layer system under investigation, where the thickness of the overlayer is independently determined by X-ray photoelectron spectroscopy (XPS). This approach is applied to NEXAFS data acquired for one of the most challenging cases: air-exposed hard carbon-based materials with adventitious carbon contamination from ambient exposure. The contribution of the adventitious carbon was removed from the as-acquired spectra of ultrananocrystalline diamond (UNCD) and hydrogenated amorphous carbon (a-C:H) to determine the intrinsic photoabsorption NEXAFS spectra of these materials. The method alters the calculated fraction of sp(2)-hybridized carbon from 5 to 20% and reveals that the adventitious contamination can be described as a layer containing carbon and oxygen ([O]/[C] = 0.11 ± 0.02) with a thickness of 0.6 ± 0.2 nm and a fraction of sp(2)-bonded carbon of 0.19 ± 0.03. This

Nanostructured Deep Carbon: A Wealth of Possibilities

Science.gov (United States)

Navrotsky, A.

2012-12-01

The materials science community has been investigating novel forms of carbon including C60 buckyballs, nanodiamond, graphene, carbon "onion" structures with a mixture of sp2 and sp3 bonding , and multicomponent nanostructured Si-O-C-N polymer derived ceramics. Though such materials are generally viewed as metastable, recently measured energetics of several materials suggest that this may not always be the case in multicomponent systems. Finely disseminated carbon phases, including nanodiamonds, have been found in rocks from a variety of deep earth settings. The question then is whether some of the more exotic forms of carbon can also exist in the deep earth or other planetary interiors. This presentation discusses thermodynamic constraints related to surface and interface energies, nanodomain structures, and compositional effects on the possible existence of complex carbon, carbide and oxycarbide nanomaterials at high pressure.

Contrasting bonding behavior of thiol molecules on carbon fullerene structures

International Nuclear Information System (INIS)

Mixteco-Sanchez, J.C.; Guirado-Lopez, R.A.

2003-01-01

We have performed semiempirical as well as ab initio density-functional theory (DFT) calculations at T=0 to analyze the equilibrium configurations and electronic properties of spheroidal C 60 as well as of cylindrical armchair (5,5) and (8,8) fullerenes passivated with SCH 3 and S(CH 2 ) 2 CH 3 thiols. Our structural results reveal that the lowest-energy configurations of the adsorbates strongly depend on their chain length and on the structure of the underlying substrate. In the low-coverage regime, both SCH 3 and S(CH 2 ) 2 CH 3 molecules prefer to organize into a molecular cluster on one side of the C 60 surface, providing thus a less protective organic coating for the carbon structure. However, with increasing the number of adsorbed thiols, a transition to a more uniform distribution is obtained, which actually takes place for six and eight adsorbed molecules when using S(CH 2 ) 2 CH 3 and SCH 3 chains, respectively. In contrast, for the tubelike arrangements at the low-coverage regime, a quasi-one-dimensional zigzag organization of the adsorbates along the tubes is always preferred. The sulfur-fullerene bond is considerably strong and is at the origin of outward and lateral displacements of the carbon atoms, leading to the stabilization of three-membered rings on the surface (spheroidal structures) as well as to sizable nonuniform radial deformations (cylindrical configurations). The electronic spectrum of our thiol-passivated fullerenes shows strong variations in the energy difference between the highest occupied and lowest unoccupied molecular orbitals as a function of the number and distribution of adsorbed thiols, opening thus the possibility to manipulate the transport properties of these compounds by means of selective adsorption mechanisms

Reactivity of rhodium during co-deposition of rhodium and carbon

International Nuclear Information System (INIS)

Marot, Laurent; Steiner, Roland; De Temmerman, Gregory; Oelhafen, Peter

2009-01-01

The detailed characterizations of rhodium/carbon films prepared by co-deposition using a dual magnetron sputtering have been carried out on silicon substrates at room temperature. Effects of the carbon incorporated in the film on the chemical bonding state, optical reflectivity and crystallinity were investigated using XPS, reflectivity measurements, XRD and SEM. The incorporation of carbon changes the films' crystallinity and thus producing amorphous films. The reflectivity of the films decreases linearly as the rhodium concentration decreases. It is important to note that no chemical bonding was observed between rhodium and carbon whatever the deposition conditions, even at high deposition temperature. Concerning the reactivity of rhodium films with oxygen, after long term storage in air the rhodium surface is covered with a thin rhodium oxide (few nanometers). However, for these films no variation of the optical reflectivity was observed after long air storage.

Role of contact bonding on electronic transport in metal-carbon nanotube-metal systems

International Nuclear Information System (INIS)

Deretzis, I; La Magna, A

2006-01-01

We have investigated the effects of the interfacial bond arrangement on the electronic transport features of metal-nanotube-metal systems. The transport properties of finite, defect-free armchair and zigzag single-walled carbon nanotubes attached to Au(111) metallic contacts have been calculated by means of the non-equilibrium Green functional formalism with the tight-binding and the extended Hueckel Hamiltonians. Our calculations show that the electrode material is not the only factor which rules contact transparency. Indeed, for the same electrode, but changing nanotube helicities, we have observed an overall complex behaviour of the transmission spectra due to band mixing and interference. A comparison of the two models shows that the tight-binding approach fails to give a satisfactory representation of the transmission function when a more accurate description of the C-C and Au-C chemical bonds has to be considered. We have furthermore examined the effect of interface geometry variance on conduction and found that the contact-nanotube distance has a significant impact, while the contact-nanotube symmetry plays a marginal, yet evident role

The effects of carbon nanotube addition and oxyfluorination on the glucose-sensing capabilities of glucose oxidase-coated carbon fiber electrodes

Energy Technology Data Exchange (ETDEWEB)

Im, Ji Sun; Yun, Jumi; Kim, Jong Gu [Department of Fine Chemical Engineering and Applied Chemistry, BK21-E2 M, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Bae, Tae-Sung [Department of Fine Chemical Engineering and Applied Chemistry, BK21-E2 M, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Korea Basic Science Institute (KBSI), Jeonju 561-756 (Korea, Republic of); Lee, Young-Seak, E-mail: youngslee@cnu.ac.kr [Department of Fine Chemical Engineering and Applied Chemistry, BK21-E2 M, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

2012-01-15

Glucose-sensing electrodes were constructed from carbon fibers by electrospinning and heat treatment. By controlling the pore size, the specific surface area and pore volume of the electrospun carbon fibers were increased for efficient immobilization of the glucose oxidase. Carbon nanotubes were embedded as an electrically conductive additive to improve the electrical property of the porous carbon fibers. In addition, the surface of the porous carbon fibers was modified with hydrophilic functional groups by direct oxyfluorination to increase the affinity between the hydrophobic carbon surface and the hydrophilic glucose oxidase molecules. The porosity of the carbon fibers was improved significantly with approximately 28- and 35-fold increases in the specific surface area and pore volume, respectively. The number of chemical bonds between carbon and oxygen were increased with higher oxygen content during oxyfluorination based on the X-ray photoelectron spectroscopy results. Glucose sensing was carried out by current voltagram and amperometric methods. A high-performance glucose sensor was obtained with high sensitivity and rapid response time as a result of carbon nanotube addition, physical activation and surface modification. The mechanism of the highly sensitive prepared glucose sensor was modeled by an enzyme kinetics study using the Michaelis-Menten equation.

X-ray photoelectron spectroscopy characterization of high dose carbon-implanted steel and titanium alloys

Science.gov (United States)

Viviente, J. L.; García, A.; Alonso, F.; Braceras, I.; Oñate, J. I.

1999-04-01

A study has been made of the depth dependence of the atomic fraction and chemical bonding states of AISI 440C martensitic stainless steel and Ti-6Al-4V alloy implanted with 75 keV C + at very high doses (above 10 18 ions cm -2), by means of X-ray photoelectron spectroscopy combined with an Ar + sputtering. A Gaussian-like carbon distribution was observed on both materials at the lowest implanted dose. More trapezoidal carbon depth-profiles were found with increasing implanted doses, and a pure carbon layer was observed only on the titanium alloy implanted at the highest dose. The implanted carbon was combined with both base metal and carbon itself to form metallic carbides and graphitic carbon. Furthermore, carbon-enriched carbides were also found by curve fitting the C 1s spectra. The titanium alloy showed a higher carbidic contribution than the steel implanted at the same C + doses. A critical carbon concentrations of about 33 at.% and 23 at.% were measured for the formation of C-C bonds in Ti-6Al-4V and steel samples, respectively. The carbon atoms were bound with metal to form carbidic compounds until these critical concentrations were reached; when this C concentration was exceeded the proportion of C-C bonds increased and resulted in the growth of carbonaceous layers.

Sputtered carbon as a corrosion barrier for x-ray detector windows

Energy Technology Data Exchange (ETDEWEB)

Rowley, Joseph; Pei, Lei; Davis, Robert C., E-mail: davis@byu.edu; Vanfleet, Richard R. [Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602 (United States); Liddiard, Steven; Harker, Mallorie; Abbott, Jonathan [Moxtek, Inc., 452 W 1260 N, Orem, Utah 84057 (United States)

2016-09-15

Sputtered amorphous carbon thin films were explored as corrosion resistant coatings on aluminum thin films to be incorporated into x-ray detector windows. The requirements for this application include high corrosion resistance, low intrinsic stress, high strains at failure, and high x-ray transmission. Low temperature sputtering was used because of its compatibility with the rest of the window fabrication process. Corrosion resistance was tested by exposure of carbon coated and uncoated Al thin films to humidity. Substrate curvature and bulge testing measurements were used to determine intrinsic stress and ultimate strain at failure. The composition and bonding of the carbon films were further characterized by electron energy loss spectroscopy, Raman spectroscopy, and carbon, hydrogen, and nitrogen elemental analyses. Samples had low compressive stress (down to.08 GPa), a high strain at failure (3%), and a low fraction of sp{sup 3} carbon–carbon bonds (less than 5%). The high breaking strain and excellent x-ray transmission of these sputtered carbon films indicate that they will work well as corrosion barriers in this application.

Stability of sp{sup 2}-carbon single layer nanostructures

Energy Technology Data Exchange (ETDEWEB)

Bourgeois, L N; Bursill, L A [University of Melbourne, Parkville, VIC (Australia). School of Physics

1997-12-31

Full text: Sp{sup 2}-hybridised carbon is quite versatile in its ability to build atomic structures. Although graphite is the most common and best known sp{sup 2}-carbon compound, recent discoveries of the C{sub 60} molecule and the related nanotubes have shown that networks of three-fold coordinated carbon atoms may result in a wide range of geometries. This has led to the postulation that structures such as the negatively curved schwarzites and tori may also be synthesized. In particular, theoretical calculations have shown the cohesive energy of schwarzites to be higher than that of C{sub 60}. Presented here is an analytical model describing the energetics of the most common sp{sup 2}-carbon single nanostructures as well as the hypothetical P-schwarzite. An expression for the energy with respect to a flat graphite sheet is written as the sum of a strain energy term (arising from curving of the carbon network) and a dangling bond energy term (not negligible in an inert environment). The relative stability of carbon spheres, tubes, planes and minimal surfaces is then investigated as a function of the dangling bond energy. In an inert atmosphere (large dangling bond energy), the cylinder appears to be the most stable geometry up to a certain size (about 40 atoms only). Above this number of atoms, the sphere is found to be energetically favoured. In a reactive environment, flat sheets are found to have the lowest energy, as expected. The other structures appeared to be always less stable than tubes, spheres and planes. However, small proportions of negatively curved sheets may occur at high temperatures. These results are compared with known experimental facts

Interfacial enhancement of carbon fiber/nylon 12 composites by grafting nylon 6 to the surface of carbon fiber

Science.gov (United States)

Hui, Chen; Qingyu, Cai; Jing, Wu; Xiaohong, Xia; Hongbo, Liu; Zhanjun, Luo

2018-05-01

Nylon 6 (PA6) grafted onto carbon fiber (CF) after chemical oxidation treatment was in an attempt to reinforce the mechanical properties of carbon fiber composites. Scanning electronic microscopy (SEM), Fourier transform infrared analysis (FT-IR), X-ray photoelectron spectroscope (XPS) and thermogravimetric analysis (TG) were selected to characterize carbon fibers with different surface treated. Experimental results showed that PA6 was grafted uniformly on the fiber surface through the anionic polymerization. A large number of functional groups were introduced to the fiber surface and the surface roughness was increased. After grafting PA6 on the oxidized carbon fibers, it played an important role on improving the interfacial adhesion between the fibers and the matrix by improving PA12 wettability, increasing chemical bonding and mechanical interlocking. Compared with the desized CF composites, the tensile strength of PA6-CF/PA12 composites was increased by 30.8% from 53.9 MPa to 70.2 MPa. All results indicated that grafting PA6 onto carbon fiber surface was an effective method to enhance the mechanical strength of carbon fiber/nylon 12 composites.

Crystalline and amorphous carbon nitride films produced by high-energy shock plasma deposition

International Nuclear Information System (INIS)

Bursilll, L.A.; Peng, Julin; Gurarie, V.N.; Orlov, A.V.; Prawer, S.

1995-01-01

High-energy shock plasma deposition techniques are used to produce carbon-nitride films containing both crystalline and amorphous components. The structures are examined by high-resolution transmission electron microscopy, parallel-electron-energy loss spectroscopy and electron diffraction. The crystalline phase appears to be face-centered cubic with unit cell parameter approx. a=0.63nm and it may be stabilized by calcium and oxygen at about 1-2 at % levels. The carbon atoms appear to have both trigonal and tetrahedral bonding for the crystalline phase. There is PEELS evidence that a significant fraction of the nitrogen atoms have sp 2 trigonal bonds in the crystalline phase. The amorphous carbon-nitride film component varies from essentially graphite, containing virtually no nitrogen, to amorphous carbon-nitride containing up to 10 at % N, where the fraction of sp 3 bonds is significant. 15 refs., 5 figs

Determination of the conformation of 2-hydroxy- and 2-aminobenzoic acid dimers using 13C NMR and density functional theory/natural bond order analysis: the central importance of the carboxylic acid carbon.

Science.gov (United States)

Burnette, Ronald R; Weinhold, Frank

2006-07-20

The 13C chemical shift for the carboxylic acid carbon provides a powerful diagnostic probe to determine the preferred isomeric dimer structures of benzoic acid derivatives undergoing intra- and intermolecular H-bonding in the gas, solution and crystalline phases. We have employed hybrid density functional calculations and natural bond orbital analysis to elucidate the electronic origins of the observed 13C shieldings and their relationship to isomeric stability. We find that delocalizing interactions from the carbonyl oxygen lone pairs (nO) into vicinal carbon-oxygen and carbon-carbon antibonds (sigmaCO*,sigmaCC*) make critical contributions to the 13C shieldings, and these nO --> sigmaCO*, nO --> sigmaCC* interactions are in turn sensitive to the intramolecular interactions that dictate dimer structure and stability. The carboxyl carbon atom can thus serve as a useful detector of subtle structural and conformational features in this pharmacologically important class of carboxylic acid interactions.

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

International Nuclear Information System (INIS)

Bahk, Yeon Kyoung; He, Xu; Gitsis, Emmanouil; Kuo, Yu-Ying; Kim, Nayoung; Wang, Jing

2015-01-01

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

Pt coating on flame-generated carbon particles

International Nuclear Information System (INIS)

Choi, In Dae; Lee, Dong Geun

2008-01-01

Carbon black, activated carbon and carbon nanotube have been used as supporting materials for precious metal catalysts used in fuel cell electrodes. One-step flame synthesis method is used to coat 2-5nm Pt dots on flame-generated carbon particles. By adjusting flame temperature, gas flow rates and resident time of particles in flame, we can obtain Pt/C nano catalyst-support composite particles. Additional injection of hydrogen gas facilitates pyrolysis of Pt precursor in flame. The size of as-incepted Pt dots increases along the flame due to longer resident time and sintering in high temperature flame. Surface coverage and dispersion of the Pt dots is varied at different sampling heights and confirmed by Transmission Electron Microscopy (TEM), Energy Dispersive Spectra (EDS) and X-Ray Diffraction (XRD). Crystallinity and surface bonding groups of carbon are investigated through X-ray Photoelectron Spectroscoy (XPS) and Raman spectroscopy

Influence of cation size and surface coverage upon the infrared spectrum of carbon monoxide

OpenAIRE

Huang, Jimin

1991-01-01

Adsorbed carbon monoxide is utilized as a double layer probe molecule because of its strong absorption in infrared region and because of the high sensitivity of the carbon-oxygen bond to changes in the environment local to the electrode surface. Potential Difference Infrared Spectroscopy was used to investigate the structural behavior of CO adsorbed on a platinum electrode. Carbon monoxide was found to be exclusively linear-bonded on platinum electrode in the presence of tetran...

Electrocatalytic reduction of H{sub 2}O{sub 2} by Pt nanoparticles covalently bonded to thiolated carbon nanostructures

Energy Technology Data Exchange (ETDEWEB)

You, Jung-Min; Kim, Daekun [Department of Chemistry and Institute of Basic Science, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Jeon, Seungwon [Department of Chemistry and Institute of Basic Science, Chonnam National University, Gwangju 500-757 (Korea, Republic of)

2012-03-30

Highlights: Black-Right-Pointing-Pointer Novel thiolated carbon nanostructures - platinum nanoparticles [t-GO-C(O)-pt and t-MWCNT-C(O)-S-pt] have been synthesized, and [t-GO-C(O)-pt and t-MWCNT-C(O)-S-pt] denotes as t-GO-pt and t-MWCNT-Pt in manuscript, respectively. Black-Right-Pointing-Pointer The modified electrode denoted as PDDA/t-GO-pt/GCE was used for the electrochemical determination of H{sub 2}O{sub 2} for the first time. Black-Right-Pointing-Pointer The results show that PDDA/t-GO-pt nanoparticles have the promising potential as the basic unit of the electrochemical biosensors for the detection of H{sub 2}O{sub 2}. Black-Right-Pointing-Pointer The proposed H{sub 2}O{sub 2} biosensors exhibited wide linear ranges and low detection limits, giving fast responses within 10 s. - Abstract: Glassy carbon electrodes were coated with thiolated carbon nanostructures - multi-walled carbon nanotubes and graphene oxide. The subsequent covalent addition of platinum nanoparticles and coating with poly(diallydimethylammonium chloride) resulted in biosensors that detected hydrogen peroxide through its electrocatalytic reduction. The sensors were easily and quickly prepared and showed improved sensitivity to the electrocatalytic reduction of H{sub 2}O{sub 2}. The Pt nanoparticles covalently bonded to the thiolated carbon nanostructures were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. Cyclic voltammetry and amperometry were used to characterize the biosensors' performances. The sensors exhibited wide linear ranges and low detection limits, giving fast responses within 10 s, thus demonstrating their potential for use in H{sub 2}O{sub 2} analysis.

Microwave plasma induced surface modification of diamond-like carbon films

Science.gov (United States)

Rao Polaki, Shyamala; Kumar, Niranjan; Gopala Krishna, Nanda; Madapu, Kishore; Kamruddin, Mohamed; Dash, Sitaram; Tyagi, Ashok Kumar

2017-12-01

Tailoring the surface of diamond-like carbon (DLC) film is technically relevant for altering the physical and chemical properties, desirable for useful applications. A physically smooth and sp3 dominated DLC film with tetrahedral coordination was prepared by plasma-enhanced chemical vapor deposition technique. The surface of the DLC film was exposed to hydrogen, oxygen and nitrogen plasma for physical and chemical modifications. The surface modification was based on the concept of adsorption-desorption of plasma species and surface entities of films. Energetic chemical species of microwave plasma are adsorbed, leading to desorbtion of the surface carbon atoms due to energy and momentum exchange. The interaction of such reactive species with DLC films enhanced the roughness, surface defects and dangling bonds of carbon atoms. Adsorbed hydrogen, oxygen and nitrogen formed a covalent network while saturating the dangling carbon bonds around the tetrahedral sp3 valency. The modified surface chemical affinity depends upon the charge carriers and electron covalency of the adsorbed atoms. The contact angle of chemically reconstructed surface increases when a water droplet interacts either through hydrogen or van dear Waals bonding. These weak interactions influenced the wetting property of the DLC surface to a great extent.

A “fullerene-carbon nanotube” structure with tunable mechanical properties

Science.gov (United States)

Ji, W. M.; Zhang, L. W.; Liew, K. M.

2018-03-01

Carbon-based nanostructures have drawn tremendous research interest and become promising building blocks for the new generation of smart sensors and devices. Utilizing a bottom-up strategy, the chemical interconnecting sp 3 covalent bond between carbon building blocks is an efficient way to enhance its Young's modulus and ductility. The formation of sp 3 covalent bond, however, inevitably degrades its ultimate tensile strength caused by stress concentration at the junction. By performing a molecular dynamics simulation of tensile deformation for a fullerene-carbon nanotube (FCNT) structure, we propose a tunable strategy in which fullerenes with various angle energy absorption capacities are utilized as building blocks to tune their ductile behavior, while still maintaining a good ultimate tensile strength of the carbon building blocks. A higher ultimate tensile strength is revealed with the reduction of stress concentration at the junction. A brittle-to-ductile transition during the tensile deformation is detected through the structural modification. The development of ductile behavior is attributed to the improvement of energy propagation ability during the fracture initiation, in which the released energy from bonds fracture is mitigated properly, leading to the further development of mechanical properties.

Base substitutions at scissile bond sites are sufficient to alter RNA-binding and cleavage activity of RNase III.

Science.gov (United States)

Kim, Kyungsub; Sim, Se-Hoon; Jeon, Che Ok; Lee, Younghoon; Lee, Kangseok

2011-02-01

RNase III, a double-stranded RNA-specific endoribonuclease, degrades bdm mRNA via cleavage at specific sites. To better understand the mechanism of cleavage site selection by RNase III, we performed a genetic screen for sequences containing mutations at the bdm RNA cleavage sites that resulted in altered mRNA stability using a transcriptional bdm'-'cat fusion construct. While most of the isolated mutants showed the increased bdm'-'cat mRNA stability that resulted from the inability of RNase III to cleave the mutated sequences, one mutant sequence (wt-L) displayed in vivo RNA stability similar to that of the wild-type sequence. In vivo and in vitro analyses of the wt-L RNA substrate showed that it was cut only once on the RNA strand to the 5'-terminus by RNase III, while the binding constant of RNase III to this mutant substrate was moderately increased. A base substitution at the uncleaved RNase III cleavage site in wt-L mutant RNA found in another mutant lowered the RNA-binding affinity by 11-fold and abolished the hydrolysis of scissile bonds by RNase III. Our results show that base substitutions at sites forming the scissile bonds are sufficient to alter RNA cleavage as well as the binding activity of RNase III. © 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Nickel-Catalyzed Synthesis of Primary Aryl and Heteroaryl Amines via C–O Bond Cleavage

KAUST Repository

Yue, Huifeng

2017-03-13

A nickel-catalyzed protocol for the conversion of aryl and heteroaryl alcohol derivatives to primary and secondary aromatic amines via C(sp2)-O bond cleavage is described. The new amination protocol can be applied to a range of substrates bearing diverse functional groups and uses readily available benzophenone imines as an effective nitrogen source.

Nickel-Catalyzed Synthesis of Primary Aryl and Heteroaryl Amines via C–O Bond Cleavage

KAUST Repository

Yue, Huifeng; Guo, Lin; Liu, Xiangqian; Rueping, Magnus

2017-01-01

A nickel-catalyzed protocol for the conversion of aryl and heteroaryl alcohol derivatives to primary and secondary aromatic amines via C(sp2)-O bond cleavage is described. The new amination protocol can be applied to a range of substrates bearing diverse functional groups and uses readily available benzophenone imines as an effective nitrogen source.

Novel phase of carbon, ferromagnetism, and conversion into diamond

International Nuclear Information System (INIS)

Narayan, Jagdish; Bhaumik, Anagh

2015-01-01

We report the discovery of a new phase of carbon (referred to as Q-carbon) and address fundamental issues related to direct conversion of carbon into diamond at ambient temperatures and pressures in air without any need for catalyst and presence of hydrogen. The Q-carbon is formed as result of quenching from super undercooled state by using high-power nanosecond laser pulses. We discuss the equilibrium phase diagram (P vs. T) of carbon and show that by rapid quenching kinetics can shift thermodynamic graphite/diamond/liquid carbon triple point from 5000 K/12 GPa to super undercooled carbon at atmospheric pressure in air. It is shown that nanosecond laser heating of diamond-like amorphous carbon on sapphire, glass, and polymer substrates can be confined to melt carbon in a super undercooled state. By quenching the carbon from the super undercooled state, we have created a new state of carbon (Q-carbon) from which nanodiamond, microdiamond, microneedles, and single-crystal thin films are formed depending upon the nucleation and growth times allowed for diamond formation. The Q-carbon quenched from liquid is a new state of solid carbon with a higher mass density than amorphous carbon and a mixture of mostly fourfold sp 3 (75%–85%) with the rest being threefold sp 2 bonded carbon (with distinct entropy). It is expected to have new and improved mechanical hardness, electrical conductivity, chemical, and physical properties, including room-temperature ferromagnetism (RTFM) and enhanced field emission. Here we present interesting results on RTFM, enhanced electrical conductivity and surface potential of Q-carbon to emphasize its unique properties. The Q-carbon exhibits robust bulk ferromagnetism with estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g −1 . From the Q-carbon, diamond phase is nucleated and a variety of micro- and nanostructures and large-area single-crystal diamond sheets are grown by allowing growth times

Catalytic applications of immobilized ionic liquids for synthesis of cyclic carbonates from carbon dioxide and epoxides

International Nuclear Information System (INIS)

Kim, Dong-Woo; Roshan, Roshith; Tharun, Jose; Cherian, Amal; Park, Dae-Won

2013-01-01

The catalytic applicability of ionic liquids immobilized on various support materials such as silica, polystyrene and biopolymers in the cycloaddition of carbon dioxide with epoxides is reviewed in this work. Comparisons of the catalytic efficiency of these various catalysts have been done from the aspect of turnover number and reusability. The studies revealed that ionic liquids or support materials possessing hydrogen bonding capable groups exhibited enhanced catalytic activity towards cyclic carbonate synthesis. Moreover, the increased quest towards environmentally benign materials has renewed the search for biocompatible materials as support for ionic liquids

Boron-doped diamond electrodes for the electrochemical oxidation and cleavage of peptides.

Science.gov (United States)

Roeser, Julien; Alting, Niels F A; Permentier, Hjalmar P; Bruins, Andries P; Bischoff, Rainer

2013-07-16

Electrochemical oxidation of peptides and proteins is traditionally performed on carbon-based electrodes. Adsorption caused by the affinity of hydrophobic and aromatic amino acids toward these surfaces leads to electrode fouling. We compared the performance of boron-doped diamond (BDD) and glassy carbon (GC) electrodes for the electrochemical oxidation and cleavage of peptides. An optimal working potential of 2000 mV was chosen to ensure oxidation of peptides on BDD by electron transfer processes only. Oxidation by electrogenerated OH radicals took place above 2500 mV on BDD, which is undesirable if cleavage of a peptide is to be achieved. BDD showed improved cleavage yield and reduced adsorption for a set of small peptides, some of which had been previously shown to undergo electrochemical cleavage C-terminal to tyrosine (Tyr) and tryptophan (Trp) on porous carbon electrodes. Repeated oxidation with BDD electrodes resulted in progressively lower conversion yields due to a change in surface termination. Cathodic pretreatment of BDD at a negative potential in an acidic environment successfully regenerated the electrode surface and allowed for repeatable reactions over extended periods of time. BDD electrodes are a promising alternative to GC electrodes in terms of reduced adsorption and fouling and the possibility to regenerate them for consistent high-yield electrochemical cleavage of peptides. The fact that OH-radicals can be produced by anodic oxidation of water at elevated positive potentials is an additional advantage as they allow another set of oxidative reactions in analogy to the Fenton reaction, thus widening the scope of electrochemistry in protein and peptide chemistry and analytics.

Investigation of the histology and interfacial bonding between carbonated hydroxyapatite cement and bone

International Nuclear Information System (INIS)

Mao Keya; Hao Libo; Tang Peifu; Wang Zheng; Wen Ning; Du Mingkui; Wang Jifang; Wang Yan; Yang Yun; Li Jiangtao

2009-01-01

An ideal bone implant should facilitate the formation of a new bone layer as an osteo-integrated interface between bone and the implanted biomaterials. In the present work, the interface between carbonated hydroxyapatite (CHA) cement and bone was evaluated by interfacial bonding strength measurements and histological characterizations. CHA cement was implanted into a mongrel dog's femoral supracondylar and below the tibial plateau area, and was then tested ex vivo by, respectively, detaching and pullout experiments. Polymethylmethacrylate (PMMA) was used as a control. CHA cement could be directly injected and solidified in situ to repair bone defects. Histology results showed that CHA bonded with bone through gradual remodeling and was replaced by new bone tissue, which is an attribute for excellent biocompatibility. The interfacial bonding strength increased with implantation time. After 16 weeks implantation, the measured detaching force and the pullout force between CHA and bone were 281 ± 16 N and 512.5 ± 14.5 N, respectively. These values were several times higher compared to 5 days implantation. In contrast, the control showed a fibrous microstructure between PMMA and bone, and the detaching force and the pullout force decreased with implantation time. The results strongly suggest that CHA can form a better osteo-integrated interface compared to PMMA, and could be used as an ideal biomaterial for bone defect repair.

Fabrication of Carbon Nanotube/SiO2and Carbon Nanotube/SiO2/Ag Nanoparticles Hybrids by Using Plasma Treatment

Directory of Open Access Journals (Sweden)

Li Haiqing

2009-01-01

Full Text Available Abstract Based on plasma-treated single wall carbon nanotubes (SWCNTs, SWCNT/SiO2and thiol groups-functionalized SWCNT/SiO2hybrids have been fabricated through a sol–gel process. By means of thiol groups, Ag nanoparticles have been in situ synthesized and bonded onto the SiO2shell of SWCNT/SiO2in the absence of external reducing agent, resulting in the stable carbon nanotube/SiO2/Ag nanoparticles hybrids. This strategy provides a facile, low–cost, and green methodology for the creation of carbon nanotube/inorganic oxides-metal nanoparticles hybrids.

Carbon-On-Carbon Manufacturing

Science.gov (United States)

Mungas, Gregory S. (Inventor); Buchanan, Larry (Inventor); Banzon, Jr., Jose T. (Inventor)

2017-01-01

The presently disclosed technology relates to carbon-on-carbon (C/C) manufacturing techniques and the resulting C/C products. One aspect of the manufacturing techniques disclosed herein utilizes two distinct curing operations that occur at different times and/or using different temperatures. The resulting C/C products are substantially non-porous, even though the curing operation(s) substantially gasify a liquid carbon-entrained filler material that saturates a carbon fabric that makes up the C/C products.

Selection criteria for oxidation method in total organic carbon measurement.

Science.gov (United States)

Yoon, GeunSeok; Park, Sang-Min; Yang, Heuiwon; Tsang, Daniel C W; Alessi, Daniel S; Baek, Kitae

2018-05-01

During the measurement of total organic carbon (TOC), dissolved organic carbon is converted into CO 2 by using high temperature combustion (HTC) or wet chemical oxidation (WCO). However, the criteria for selecting the oxidation methods are not clear. In this study, the chemical structures of organic material were considered as a key factor to select the oxidation method used. Most non-degradable organic compounds showed a similar oxidation efficiency in both methods, including natural organic compounds, dyes, and pharmaceuticals, and thus both methods are appropriate to measure TOC in waters containing these compounds. However, only a fraction of the carbon in the halogenated compounds (perfluorooctanoic acid and trifluoroacetic acid) were oxidized using WCO, resulting in measured TOC values that are considerably lower than those determined by HTC. This result is likely due to the electronegativity of halogen elements which inhibits the approach of electron-rich sulfate radicals in the WCO, and the higher bond strength of carbon-halogen pairs as compared to carbon-hydrogen bonds, which results in a lower degree of oxidation of the compounds. Our results indicate that WCO could be used to oxidize most organic compounds, but may not be appropriate to quantify TOC in organic carbon pools that contain certain halogenated compounds. Copyright © 2018 Elsevier Ltd. All rights reserved.

Atmospheric pressure plasma treatment of glassy carbon for adhesion improvement

DEFF Research Database (Denmark)

Kusano, Yukihiro; Mortensen, Henrik Junge; Stenum, Bjarne

2007-01-01

density increased with the plasma treatments. Adhesion test of the treated glassy carbon covered with cured epoxy showed cohesive failure, indicating strong bonding after the treatments. This is in contrast to the adhesion tests of untreated samples where the epoxy readily peeled off the glassy carbon....

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-10-15

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

Grafting of activated carbon cloths for selective adsorption

Energy Technology Data Exchange (ETDEWEB)

Gineys, M.; Benoit, R.; Cohaut, N.; Béguin, F.; Delpeux-Ouldriane, S., E-mail: delpeux@cnrs-orleans.fr

2016-05-01

Graphical abstract: - Highlights: • A controlled grafting of carboxylic functions on activated carbon fibers. • The carbon material nanotextural properties preservation after grafting. • An identification of the grafting mechanism through ToF SIMS analysis. • A chemical mapping of the grafted surface using ToF SIMS technique and imaging. - Abstract: Chemical functionalization of an activated carbon cloth with 3-aminophthalic acid and 4-aminobenzoic acid groups by the in situ formation of the corresponding diazonium salt in aqueous acidic solution is reported. The nature and amount of selected functions on an activated carbon surface, in particular the grafted density, were determined by potentiometric titration, elemental analysis and X-ray photoelectron spectroscopy (XPS). The nanotextural properties of the modified carbon were explored by gas adsorption. Functionalized activated carbon cloth was obtained at a discrete grafting level while preserving interesting textural properties and a large porous volume. Finally, the grafting homogeneity of the carbon surface and the nature of the chemical bonding were investigated using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) technique.

Carbons and carbon supported catalysts in hydroprocessing

Energy Technology Data Exchange (ETDEWEB)

Furimsky, Edward

2009-07-01

This book is a comprehensive summary of recent research in the field and covers all areas of carbons and carbon materials. The potential application of carbon supports, particularly those of carbon black (CB) and activated carbon (AC) in hydroprocessing catalysis are covered. Novel carbon materials such as carbon fibers and carbon nano tubes (CNT) are also covered, including the more recent developments in the use of fullerenes in hydroprocessing applications. Although the primary focus of this book is on carbons and carbon supported catalysts, it also identifies the difference in the effect of carbon supports compared with the oxidic supports, particularly that of the Al{sub 2}O{sub 3}. The difference in catalyst activity and stability was estimated using both model compounds and real feeds under variable conditions. The conditions applied during the preparation of carbon supported catalysts are also comprehensively covered and include various methods of pretreatment of carbon supports to enhance catalyst performance. The model compounds results consistently show higher hydrodesulfurization and hydrodeoxygenation activities of carbon supported catalysts than that of the Al{sub 2}O{sub 3} supported catalysts. Also, the deactivation of the former catalysts by coke deposition was much less evident. Chapter 6.3.1.3 is on carbon-supported catalysts: coal-derived liquids.

Carbon-sulfur bond formation by reductive elimination of gold(iii) thiolates.

Science.gov (United States)

Currie, Lucy; Rocchigiani, Luca; Hughes, David L; Bochmann, Manfred

2018-04-10

Whereas the reaction of the gold(iii) pincer complex (C^N^C)AuCl with 1-adamantyl thiol (AdSH) in the presence of base affords (C^N^C)AuSAd, the same reaction in the absence of base leads to formation of aryl thioethers as the products of reductive elimination of the Au-C and Au-S ligands (C^N^C = dianion of 2-6-diphenylpyridine or 2-6-diphenylpyrazine). Although high chemical stability is usually taken as a characteristic of pincer complexes, results show that thiols are capable of cleaving one of the pincer Au-C bonds. This reaction is not simply a function of S-H acidity, since no cleavage takes place with other more acidic X-H compounds, such as carbazole, amides, phenols and malonates. The reductive C-S elimination follows a second-order rate law, -d[1a]/dt = k[1a][AdSH]. Reductive elimination is enabled by displacement of the N-donor by thiol; this provides the conformational flexibility necessary for C-S bond formation to occur. Alternatively, reductive C-S bond formation can be induced by reaction of pre-formed thiolates (C^N^C)AuSR with a strong Brønsted acid, followed by addition of SMe2 as base. On the other hand, treatment of (C^N^C)AuR (R = Me, aryl, alkynyl) with thiols under similar conditions leads to selective C-C rather than C-S bond formation. The reaction of (C^N^C)AuSAd with H+ in the absence of a donor ligand affords the thiolato-bridged complex [{(C^N-CH)Au(μ-SAd)}2]2+ which was crystallographically characterised.

Coated powder for electrolyte matrix for carbonate fuel cell

International Nuclear Information System (INIS)

Iacovangelo, C.D.; Browall, K.W.

1985-01-01

A plurality of electrolyte carbonate-coated ceramic particle which does not differ significantly in size from that of the ceramic particle and wherein no significant portion of the ceramic particle is exposed is fabricated into a porous tape comprised of said coated-ceramic particles bonded together by the coating for use in a molten carbonate fuel cell

C-N bond cleavage of anilines by a (salen)ruthenium(VI) nitrido complex.

Science.gov (United States)

Man, Wai-Lun; Xie, Jianhui; Pan, Yi; Lam, William W Y; Kwong, Hoi-Ki; Ip, Kwok-Wa; Yiu, Shek-Man; Lau, Kai-Chung; Lau, Tai-Chu

2013-04-17

We report experimental and computational studies of the facile oxidative C-N bond cleavage of anilines by a (salen)ruthenium(VI) nitrido complex. We provide evidence that the initial step involves nucleophilic attack of aniline at the nitrido ligand of the ruthenium complex, which is followed by proton and electron transfer to afford a (salen)ruthenium(II) diazonium intermediate. This intermediate then undergoes unimolecular decomposition to generate benzene and N2.

Synthesis, model and stability of helically coiled carbon nanotubes

DEFF Research Database (Denmark)

Fejes, Dora; Raffai, Manuella; Hernadi, Klara

2013-01-01

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

C{sub 60} fullerene decoration of carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Demin, V. A., E-mail: victordemin88@gmail.com [Russian Academy of Sciences, Emanuel Institute of Biochemical Physics (Russian Federation); Blank, V. D.; Karaeva, A. R.; Kulnitskiy, B. A.; Mordkovich, V. Z. [Technological Institute for Superhard and Novel Carbon Materials (Russian Federation); Parkhomenko, Yu. N. [National University of Science and Technology MISiS (Russian Federation); Perezhogin, I. A.; Popov, M. Yu. [Technological Institute for Superhard and Novel Carbon Materials (Russian Federation); Skryleva, E. A. [National University of Science and Technology MISiS (Russian Federation); Urvanov, S. A. [Technological Institute for Superhard and Novel Carbon Materials (Russian Federation); Chernozatonskii, L. A. [Russian Academy of Sciences, Emanuel Institute of Biochemical Physics (Russian Federation)

2016-12-15

A new fully carbon nanocomposite material is synthesized by the immersion of carbon nanotubes in a fullerene solution in carbon disulfide. The presence of a dense layer of fullerene molecules on the outer nanotube surface is demonstrated by TEM and XPS. Fullerenes are redistributed on the nanotube surface during a long-term action of an electron beam, which points to the existence of a molecular bond between a nanotube and fullerenes. Theoretical calculations show that the formation of a fullerene shell begins with the attachment of one C{sub 60} molecule to a defect on the nanotube surface.

Trapping behaviour of deuterium ions implanted into tungsten simultaneously with carbon ions

International Nuclear Information System (INIS)

Kobayashi, Makoto; Suzuki, Sachiko; Wang, Wanjing; Kurata, Rie; Kida, Katsuya; Oya, Yasuhisa; Okuno, Kenji; Ashikawa, Naoko; Sagara, Akio; Yoshida, Naoaki

2009-01-01

The trapping behaviour of deuterium ions implanted into tungsten simultaneously with carbon ions was investigated by thermal desorption spectroscopy (TDS) and x-ray photoelectron spectroscopy (XPS). The D 2 TDS spectrum consisted of three desorption stages, namely desorption of deuterium trapped by intrinsic defects, ion-induced defects and carbon with the formation of the C-D bond. Although the deuterium retention trapped by intrinsic defects was almost constant, that by ion-induced defects increased as the ion fluence increased. The retention of deuterium with the formation of the C-D bond was saturated at an ion fluence of 0.5x10 22 D + m -2 , where the major process was changed from the sputtering of tungsten with the formation of a W-C mixture to the formation of a C-C layer, and deuterium retention as the C-D bond decreased. It was concluded that the C-C layer would enhance the chemical sputtering of carbon with deuterium with the formation of CD x and the chemical state of carbon would control the deuterium retention in tungsten under C + -D 2 + implantation.

The hydrogen and oxygen content of self-supporting carbon foils prepared by dc glow discharge in ethylene

International Nuclear Information System (INIS)

Tait, N.R.S.; Tolfree, D.W.L.; John, P.; Odeh, I.M.; Thomas, M.J.K.; Tricker, M.J.; Wilson, J.J.B.; England, J.B.A.; Newton, D.

1980-01-01

The hydrogen and oxygen content of self-supporting carbon films produced by dc glow discharge have been determined using a precise method involving the elastic scattering of 25 MeV α-particles. The number of carbon-hydrogen bonds has been determined for similar samples using infrared spectroscopy. The results are compared with those for samples made by the carbon arc process. Assuming that the glow discharge carbon contains graphitic regions surrounded by amorphous tetrahedrally bonded material to which hydrogen can attach, a simple estimate is made of the relative numbers of carbon atoms in the two forms. (orig.)

Direct synthesis of nitrogen-containing carbon nanotubes on carbon paper for fuel cell electrode

Science.gov (United States)

Yin, Wong Wai; Daud, Wan Ramli Wan; Mohamad, Abu Bakar; Kadhum, Abdul Amir Hassan; Majlan, Edy Herianto; Shyuan, Loh Kee

2012-06-01

Organic catalyst has recently been identified as the potential substitution for expensive platinum electrocatalyst for fuel cell application. Numerous studies have shown that the nitrogen-containing carbon nanotubes (N-CNT) can be synthesized through spray pyrolysis or floating chemical vapor deposition (CVD) technique using various type of organometallic as precursors. This paper presents the method of synthesis and the initial findings of the growth of N-CNT directly on carbon paper using a modified CVD technique. In this research, nickel (II) phthalocyanines (Ni-Pc) as precursor was dissolved in ethanol solvent, stirred and sonicated to become homogenized. The solution was poured into a bubbler and heated up to allow the mixture to vaporize. Subsequently, the solution vapor was flowed into the tubical reactor maintained at 900°C. Carbon paper sputtered with nickel nanoparticles was used as the substrate. The synthesized sample was examined through Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM) and Fourier Transform Infra-Red (FTIR). Long, entangled and compartmentalized nanotubes with tube diameter ranging 23-27 nm were found covered the carbon paper surface with approximate of 5.5-6.0 μm in thickness. EDX analysis has successfully showed the presence of nitrogen in the carbon nanotube. FTIR analysis showed the presence of the C-N bond on CNT.

Carbon/Carbon Pistons for Internal Combustion Engines

Science.gov (United States)

Taylor, A. H.

1986-01-01

Carbon/carbon piston performs same function as aluminum pistons in reciprocating internal combustion engines while reducing weight and increasing mechanical and thermal efficiencies of engine. Carbon/carbon piston concept features low piston-to-cylinder wall clearance - so low piston rings and skirts unnecessary. Advantages possible by negligible coefficient of thermal expansion of carbon/carbon.

Carbon dioxide conversion over carbon-based nanocatalysts.

Science.gov (United States)

Khavarian, Mehrnoush; Chai, Siang-Piao; Mohamed, Abdul Rahman

2013-07-01

The utilization of carbon dioxide for the production of valuable chemicals via catalysts is one of the efficient ways to mitigate the greenhouse gases in the atmosphere. It is known that the carbon dioxide conversion and product yields are still low even if the reaction is operated at high pressure and temperature. The carbon dioxide utilization and conversion provides many challenges in exploring new concepts and opportunities for development of unique catalysts for the purpose of activating the carbon dioxide molecules. In this paper, the role of carbon-based nanocatalysts in the hydrogenation of carbon dioxide and direct synthesis of dimethyl carbonate from carbon dioxide and methanol are reviewed. The current catalytic results obtained with different carbon-based nanocatalysts systems are presented and how these materials contribute to the carbon dioxide conversion is explained. In addition, different strategies and preparation methods of nanometallic catalysts on various carbon supports are described to optimize the dispersion of metal nanoparticles and catalytic activity.

Influence of different adhesive systems on bond strength of carbon fiber posts used to restore endodontically treated teeth

OpenAIRE

Silva, Lorena dos Santos; Reis, Kátia Rodrigues; Ambrosano, Glaucia Maria Bovi; Chuí, Fabíola Mendonça da Silva; Sena, Neylla Teixeira; Carvalhal, Cintia Iara Oda; Oliveira, Jonas Alves de

2013-01-01

The aim of this study was to evaluate the influence of three adhesive systems on resinous bonding of carbon fiber posts on roots of endodontically treated bovine incisors. Thirty bovine lower incisors with similar dimensions were selected for this study. The roots were endodontically treated and subsequently prepared for post cementation. The posts were treated with adhesive systems Scotchbond MultiPurpose Plus – 3M chemical cure (Group I), light cure (Group II) and dual cure (Group III). Car...

Patterned functional carbon fibers from polyethylene

Energy Technology Data Exchange (ETDEWEB)

Hunt, Marcus A [ORNL; Saito, Tomonori [ORNL; Brown, Rebecca H [ORNL; Kumbhar, Amar S [University of North Carolina, Chapel Hill; Naskar, Amit K [ORNL

2012-01-01

Patterned, continuous carbon fibers with controlled surface geometry were produced from a novel melt-processible carbon precursor. This portends the use of a unique technique to produce such technologically innovative fibers in large volume for important applications. The novelties of this technique include ease of designing and fabricating fibers with customized surface contour, the ability to manipulate filament diameter from submicron scale to a couple of orders of magnitude larger scale, and the amenable porosity gradient across the carbon wall by diffusion controlled functionalization of precursor. The geometry of fiber cross-section was tailored by using bicomponent melt-spinning with shaped dies and controlling the melt-processing of the precursor polymer. Circular, trilobal, gear-shaped hollow fibers, and solid star-shaped carbon fibers of 0.5 - 20 um diameters, either in self-assembled bundle form, or non-bonded loose filament form, were produced by carbonizing functionalized-polyethylene fibers. Prior to carbonization, melt-spun fibers were converted to a char-forming mass by optimizing the sulfonation on polyethylene macromolecules. The fibers exhibited distinctly ordered carbon morphologies at the outside skin compared to the inner surface or fiber core. Such order in carbon microstructure can be further tuned by altering processing parameters. Partially sulfonated polyethylene-derived hollow carbon fibers exhibit 2-10 fold surface area (50-500 m2/g) compared to the solid fibers (10-25 m2/g) with pore sizes closer to the inside diameter of the filaments larger than the sizes on the outer layer. These specially functionalized carbon fibers hold promise for extraordinary performance improvements when used, for example, as composite reinforcements, catalyst support media, membranes for gas separation, CO2 sorbents, and active electrodes and current collectors for energy storage applications.

Carbon dioxide enhances fragility of ice crystals

International Nuclear Information System (INIS)

Qin Zhao; Buehler, Markus J

2012-01-01

Ice caps and glaciers cover 7% of the Earth, greater than the land area of Europe and North America combined, and play an important role in global climate. The small-scale failure mechanisms of ice fracture, however, remain largely elusive. In particular, little understanding exists about how the presence and concentration of carbon dioxide molecules, a significant component in the atmosphere, affects the propensity of ice to fracture. Here we use atomic simulations with the first-principles based ReaxFF force field capable of describing the details of chemical reactions at the tip of a crack, applied to investigate the effects of the presence of carbon dioxide molecules on ice fracture. Our result shows that increasing concentrations of carbon dioxide molecules significantly decrease the fracture toughness of the ice crystal, making it more fragile. Using enhanced molecular sampling with metadynamics we reconstruct the free energy landscape in varied chemical microenvironments and find that carbon dioxide molecules affect the bonds between water molecules at the crack tip and decrease their strength by altering the dissociation energy of hydrogen bonds. In the context of glacier dynamics our findings may provide a novel viewpoint that could aid in understanding the breakdown and melting of glaciers, suggesting that the chemical composition of the atmosphere can be critical to mediate the large-scale motion of large volumes of ice.

Cathode spot movements along the carbon fibres in carbon/carbon composites

International Nuclear Information System (INIS)

Zhang Chengyu; Qiao Shengru; Yang Zhimao; Ding Bingjun

2007-01-01

The cathode spot movements on a polyacrilonitrile (PAN)-based carbon felt reinforced C/C composite and a three dimensional PAN-based carbon fibre reinforced C/C composite (3D-C/C) were investigated by a scanning electron microscope and a digital high-speed video camera. It was found that the carbon fibres have a higher ability to withstand the vacuum arc erosion than the carbon matrix. The cathode spot walks on the matrix, rather than on the carbon fibres. The cathode spot motion is controlled by the architecture of carbon fibres in C/C. The cathode spots move along the carbon fibres by a step-by-step manner rather than a random walk. The cathode spot tracks spread over a wide zone on the 3D-C/C surface parallel to the carbon fibre. The average arc spreading velocity is estimated to be about 0.9 m s -1 and the transient arc spreading velocity is in the range of 0.54-4.5 m s -1

Radiation damage in carbon-carbon composites

International Nuclear Information System (INIS)

Burchell, T.D.; Eartherly, W.P.; Nelson, G.E.

1992-01-01

Graphite and carbon-carbon composite materials are widely used in plasma facing applications in current Tokamak devices such as TFTR and DIIID in the USA, JET, Tore Supra and TEXTOR in Europe, and JT-60U in Japan. Carbon-carbon composites are attractive choices for Tokamak limiters and diverters because of their low atomic number, high thermal shock resistance, high melting point, and high thermal conductivity. Next generation machines such as the International Thermonuclear Experimental Reactor (ITER) will utilize carbon-carbon composites in their first wall and diverter. ITER will be an ignition machine and thus will produce substantial neutron fluences from the D-T fusion reaction. The resultant high energy neutrons will cause carbon atom displacements in the plasma facing materials which will markedly affect their structure and physical properties. The effect of neutron damage on graphite has been studied for over forty years. Recently the effects of neutron irradiation on the fusion relevant graphite GraphNOL N3M was reviewed. In contrast to graphite, relatively little work has been performed to elucidate the effects of neutron irradiation on carbon-carbon composites. The results of our previous irradiation experiments have been published elsewhere. Here the irradiation induced dimensional changes in 1D, 2D, and 3D carbon-carbon composites are reported for fluences up to 4.7 dpa at an irradiation temperature of 600 degree C

Photo-assisted cyanation of transition metal nitrates coupled with room temperature C-C bond cleavage of acetonitrile.

Science.gov (United States)

Zou, Shihui; Li, Renhong; Kobayashi, Hisayoshi; Liu, Juanjuan; Fan, Jie

2013-03-07

It is a challenge to use acetonitrile as a cyanating agent because of the difficulty in cleaving its C-CN bond. Herein, we report a mild photo-assisted route to conduct the cyanation of transition metal nitrates using acetonitrile as the cyanating agent coupled with room-temperature C-C bond cleavage. DFT calculations and experimental observations suggest a radical-involved reaction mechanism, which excludes toxicity from free cyanide ions.

Fullerenic structures and such structures tethered to carbon materials

Science.gov (United States)

Goel, Anish; Howard, Jack B.; Vander Sande, John B.

2010-01-05

The fullerenic structures include fullerenes having molecular weights less than that of C.sub.60 with the exception of C.sub.36 and fullerenes having molecular weights greater than C.sub.60. Examples include fullerenes C.sub.50, C.sub.58, C.sub.130, and C.sub.176. Fullerenic structure chemically bonded to a carbon surface is also disclosed along with a method for tethering fullerenes to a carbon material. The method includes adding functionalized fullerene to a liquid suspension containing carbon material, drying the suspension to produce a powder, and heat treating the powder.

Palladium-catalyzed Suzuki-Miyaura coupling of amides by carbon-nitrogen cleavage: general strategy for amide N-C bond activation.

Science.gov (United States)

Meng, Guangrong; Szostak, Michal

2016-06-15

The first palladium-catalyzed Suzuki-Miyaura cross-coupling of amides with boronic acids for the synthesis of ketones by sterically-controlled N-C bond activation is reported. The transformation is characterized by operational simplicity using bench-stable, commercial reagents and catalysts, and a broad substrate scope, including substrates with electron-donating and withdrawing groups on both coupling partners, steric-hindrance, heterocycles, halides, esters and ketones. The scope and limitations are presented in the synthesis of >60 functionalized ketones. Mechanistic studies provide insight into the catalytic cycle of the cross-coupling, including the first experimental evidence for Pd insertion into the amide N-C bond. The synthetic utility is showcased by a gram-scale cross-coupling and cross-coupling at room temperature. Most importantly, this process provides a blueprint for the development of a plethora of metal catalyzed reactions of typically inert amide bonds via acyl-metal intermediates. A unified strategy for amide bond activation to enable metal insertion into N-C amide bond is outlined ().

In-Space Repair of Reinforced Carbon-Carbon Thermal Protection System Structures

Science.gov (United States)

Singh, Mrityunjay

2006-01-01

Advanced repair and refurbishment technologies are critically needed for the thermal protection system of current space transportation system as well as for future Crew Exploration Vehicles (CEV). The damage to these components could be caused by impact during ground handling or due to falling of ice or other objects during launch. In addition, in-orbit damage includes micrometeoroid and orbital debris impact as well as different factors (weather, launch acoustics, shearing, etc.) during launch and re-entry. The GRC developed GRABER (Glenn Refractory Adhesive for Bonding and Exterior Repair) material has shown multiuse capability for repair of small cracks and damage in reinforced carbon-carbon (RCC) material. The concept consists of preparing an adhesive paste of desired ceramic with appropriate additives and then applying the paste to the damaged/cracked area of the RCC composites with adhesive delivery system. The adhesive paste cures at 100-120 C and transforms into a high temperature ceramic during simulated entry conditions. A number of plasma torch and ArcJet tests were carried out to evaluate the crack repair capability of GRABER materials for Reinforced Carbon-Carbon (RCC) composites. For the large area repair applications, integrated system for tile and leading edge repair (InSTALER) have been developed. In this presentation, critical in-space repair needs and technical challenges as well as various issues and complexities will be discussed along with the plasma performance and post test characterization of repaired RCC materials.

The application of Car-Parrinello molecular dynamics to the study of tetrahedral amorphous carbon

International Nuclear Information System (INIS)

McKenzie, D.R.; McCulloch, D.G.; Goringe, C.M.

1998-01-01

The Car-Parrinello method for carrying out molecular dynamics enables the forces between atoms to be calculated by solving Schroedinger's equation for the valence electrons using Density Functional Theory. The method is capable of giving good structural predictions for amorphous network solids by quenching from the melt, even in situations where the bonding changes from one site to another. In amorphous carbon where, depending on its environment, carbon may show sp 2 or sp 3 bonds. The method is applied here to the study of network solids using the example of tetrahedral amorphous carbon

Characteristics of carbonized sludge for co-combustion in pulverized coal power plants

International Nuclear Information System (INIS)

Park, Sang-Woo; Jang, Cheol-Hyeon

2011-01-01

Co-combustion of sewage sludge can destabilize its combustion profile due to high volatility, which results in unstable flame. We carried out fuel reforming for sewage sludge by way of carbonization at pyrolysis temperature of 300-500 deg. C. Fuel characteristics of carbonized sludge at each temperature were analyzed. As carbonization temperature increased, fuel ratio increased, volatile content reduced, and atomic ratio relation of H/C and O/C was similar to that of lignite. The analysis result of FT-IR showed the decrease of aliphatic C-H bond and O-C bond in carbonization. In the analysis result of TG-DTG, the thermogravimetry reduction temperature of carbonized sludge (CS400) was proven to be higher than that of dried sludge, but lower than that of sub-bituminous coal. Hardgrove grindability index increased in proportion to fuel ratio increase, where the carbonized sludge value of 43-110 was similar or higher than the coal value of 49-63. As for ash deposits, slagging and fouling index were higher than that of coal. When carbonized sludge (CS400) and coal were co-combusted in 1-10% according to calorific value, slagging tendency was low in all conditions, and fouling tendency was medium or high according to the compositions of coal.

Trial manufacturing of titanium-carbon steel composite overpack

International Nuclear Information System (INIS)

Honma, Nobuyuki; Chiba, Takahiko; Tanai, Kenji

1999-11-01

This paper reports the results of design analysis and trial manufacturing of full-scale titanium-carbon steel composite overpacks. The overpack is one of the key components of the engineered barrier system, hence, it is necessary to confirm the applicability of current technique in their manufacture. The required thickness was calculated according to mechanical resistance analysis, based on models used in current nuclear facilities. The Adequacy of the calculated dimensions was confirmed by finite-element methods. To investigate the necessity of a radiation shielding function of the overpack, the irradiation from vitrified waste has been calculated. As a result, it was shown that shielding on handling and transport equipment is a more reasonable and practical approach than to increase thickness of overpack to attain a self-shielding capability. After the above investigation, trial manufacturing of full-scale model of titanium-carbon steel composite overpack has been carried out. For corrosion-resistant material, ASTM Grade-2 titanium was selected. The titanium layer was bonded individually to a cylindrical shell and fiat cover plates (top and bottom) made of carbon steel. For the cylindrical shell portion, a cylindrically formed titanium layer was fitted to the inner carbon steel vessel by shrinkage. For the flat cover plates (top and bottom), titanium plate material was coated by explosive bonding. Electron beam welding and gas metal arc welding were combined to weld of the cover plates to the body. No significant failure was evident from inspections of the fabrication process, and the applicability of current technology for manufacturing titanium-carbon steel composite overpack was confirmed. Future research and development items regarding titanium-carbon steel composite overpacks are also discussed. (author)

Production of activated carbons from almond shell

Energy Technology Data Exchange (ETDEWEB)

Nabais, Joao M. Valente; Laginhas, Carlos Eduardo C.; Carrott, P.J.M.; Ribeiro Carrott, M.M.L. [Evora Univ. (Portugal). Centro de Quimica de Evora

2011-02-15

The production of activated carbons from almond shell, using physical activation by CO{sub 2} is reported in this work. The used method has produced activated carbons with apparent BET surface areas and micropore volume as high as 1138 m{sup 2} g{sup -1} and 0.49 cm{sup 3} g{sup -1}, respectively. The activated carbons produced have essentially primary micropores and only a small volume of wider micropores. By FTIR analysis it was possible to identify, in the surface of the activated carbons, several functional groups, namely hydroxyls (free and phenol), ethers, esters, lactones, pyrones and Si-H bonds. By the analysis of the XRD patterns it was possible to calculate the microcrystallites dimensions with height between 1.178 and 1.881 nm and width between 3.106 and 5.917 nm. From the XRD it was also possible to identify the presence of traces of inorganic heteroatoms such as Si, Pb, K, Fe and P. All activated carbons showed basic characteristics with point of zero charge between 9.42 and 10.43. (author)

Carbon-Based Supercapacitors Produced by Activation of Graphene

Energy Technology Data Exchange (ETDEWEB)

Zhu, Y.; Su, D.; Murali, S.; Stoller, M.D.; Ganesh, K.J.; Cai, W.; Ferreira, P.J.; Pirkle, A.; Wallace, R.M.; Cychosz, K.A., Thommes, M.; Stach, E.A.; Ruoff, R.S.

2011-06-24

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp{sup 2}-bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

Carbon-Based Supercapacitors Produced by Activation of Graphene

Science.gov (United States)

Zhu, Yanwu; Murali, Shanthi; Stoller, Meryl D.; Ganesh, K. J.; Cai, Weiwei; Ferreira, Paulo J.; Pirkle, Adam; Wallace, Robert M.; Cychosz, Katie A.; Thommes, Matthias; Su, Dong; Stach, Eric A.; Ruoff, Rodney S.

2011-06-01

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp2-bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

Carbon-based Supercapacitors Produced by Activation of Graphene

Energy Technology Data Exchange (ETDEWEB)

Y Zhu; S Murali; M Stoller; K Ganesh; W Cai; P Ferreira; A Pirkle; R Wallace; K Cychosz; et al.

2011-12-31

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp{sup 2}-bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

Improving the wettability of aluminum on carbon nanotubes

International Nuclear Information System (INIS)

So, Kang Pyo; Lee, Il Ha; Duong, Dinh Loc; Kim, Tae Hyung; Lim, Seong Chu; An, Kay Hyeok; Lee, Young Hee

2011-01-01

Research highlights: → The wettability of CNT in Al metal was improved by electroplating method. → This involves two steps: (i) Al electroplating and (ii) additional Al wetting. → The large surface tension difference was overcome by forming Al-C covalent bonds. → Al-C covalent bond was verified by Raman spectroscopy and XPS. → Density functional calculations confirmed structural model of CNT-vacancy-O-Al. - Abstract: The wetting of a metal on carbon nanotubes is fundamentally difficult due to the unusually large difference between their surface tensions and is a bottleneck for making metal-carbon nanotube (CNT) composites. Here, we report a simple method to enhance the wettability of metal particles on the CNT surface by applying aluminum, which is the material with the largest surface tension. This method involves two steps: (i) Al nanoparticles are decorated on multiwalled carbon nanotubes by electroplating and (ii) Al powder is further spread on Al-electroplated CNTs, followed by high-temperature annealing to accommodate complete wetting of the aluminum. The large surface tension difference is overcome by forming strong Al-C covalent bonds initiated by defects of the CNTs. The decrease in the D-band intensity, the G-band shift in the Raman spectroscopy and the formation of Al-C covalent bonds, as confirmed by X-ray photoelectron spectroscopy, were in agreement with our structural model of CNT-vacancy-O-Al determined by density functional calculations.

Hydrogenation of surface carbon on alumina-supported nickel

Energy Technology Data Exchange (ETDEWEB)

Mccarthy, J.G.; Wise, H.

1979-05-01

The methanation of carbon deposited by CO or ethylene decomposition on Girdler G-65 catalyst (25Vertical Bar3< nickel, 8Vertical Bar3< alkali, mostly CaO, 4Vertical Bar3< C as graphite, on alumina) was studied by temperature-programed desorption and temperature-programed surface reaction. Four types of carbon were identified: ..cap alpha..-carbon consisted of isolated carbon atoms bonded to nickel and reacting with hydrogen at 470/sup 0/ +/- 20/sup 0/K; ..gamma..-carbon was probably a bulk carbide, most likely Ni/sub 3/C, which had a reaction peak at 550/sup 0/K; ..beta..-carbon consisted of amorphous, polymerized carbon, which had a reaction peak at 680/sup 0/K; and an unreactive crystalline graphite-like species. The ..cap alpha..-form was thermally unstable and transformed into the ..beta..-form above 600/sup 0/K. Both ..cap alpha..- and ..beta..-forms slowly converted to inert graphite above 600/sup 0/K. The evidence suggested that synthesis gas methanation proceeds by dissociative adsorption of CO as the rate-determining step which forms a very reactive carbon adatom state (..cap alpha..') which converts to the ..cap alpha..-state in the absence of hydrogen and to methane in the presence of hydrogen.

Flexural behaviour of partially bonded carbon fibre reinforced polymers strengthened concrete beams: Application to fire protection systems design

International Nuclear Information System (INIS)

Firmo, J.P.; Arruda, M.R.T.; Correia, J.R.; Tiago, C.

2015-01-01

Highlights: • The mechanical behaviour of partially bonded CFRP strengthened beams was modelled. • Two dimensional non-linear finite element models were developed. • Partially bonded beams can present similar flexural strength to fully bonded ones. • Relations between the bonded length and the strength reduction were proposed. • The proposed relations were used for the design of fire protection systems. - Abstract: Recent fire resistance tests on reinforced concrete (RC) beams strengthened with carbon fibre reinforced polymers (CFRP) laminates showed that it is possible to attain considerable fire endurance provided that thermal insulation is applied at the anchorage zones of the strengthening system. With such protection, although the CFRP laminate prematurely debonds in the central part of the beam, it transforms into a cable fixed at the extremities until one of the anchorage zones loses its bond strength. The main objective of this paper is to propose a simplified methodology for the design of fire protection systems for CFRP strengthened-RC beams, which is based on applying thicker insulation at the anchorage zones (promoting the above mentioned “cable behaviour”) and a thinner one at the current zone (avoiding tensile rupture of the carbon fibres). As a first step towards the validation of this methodology, finite element (FE) models were developed to simulate the flexural behaviour at ambient temperature of full-scale RC beams strengthened with CFRP laminates according to the externally bonded reinforcement (EBR) and near surface mounted (NSM) techniques, in both cases fully or partially bonded (the latter simulating the cable). The FE models were calibrated with results of 4-point bending tests on small-scale beams and then extended for different beam geometries, with spans (L) varying from 2 m to 5 m, in which the influence of the CFRP bonded length (l b ) and the loading type (point or uniformly distributed) on the strength reduction was

Failure behavior investigation of a unidirectional carbon–carbon composite

International Nuclear Information System (INIS)

Cheng, Jing; Li, He-jun; Zhang, Shou-yang; Xue, Li-zhen; Luo, Wen-fei; Li, Wei

2014-01-01

Highlights: • One unidirectional carbon-carbon composite was manufactured by ICVI. • Failure behavior of the composite material can be described as three stages. • Two kinds of cracks alternately result in deformation evolution of the composite. • Interfacial bonding and cracks orientation play key roles to failure behavior. - Abstract: The failure behavior and morphology of a carbon–carbon composite (C–C composite) manufactured by isothermal chemical vapor infiltration was studied by three-point bending tests, polarized light microscope and scanning electron microscope, respectively. The C–C composite was reinforced by PAN-based carbon fiber aligned in only one direction. Flexural strength and modulus of the composite were 200.9 MPa and 50.5 GPa, respectively. Failure behavior of the unidirectional C–C composite can be described as three stages including brittle fracture behavior at beginning, quasi-ductile behavior finally, and fluctuation behavior between them. Two main kinds of cracks, namely cracks parallel and perpendicular to loading direction alternately resulted in deformation evolution of the composite. The strength of interfacial bonding and cracks orientation played key roles to failure behavior of C–C composite

Conditions for forming composite carbon nanotube-diamond like carbon material that retain the good properties of both materials

Energy Technology Data Exchange (ETDEWEB)

Ren, Wei, E-mail: wei.ren@helsinki.fi; Avchaciov, Konstantin; Nordlund, Kai [Department of Physics, University of Helsinki, P.O. Box 43, FIN-00014 Helsinki (Finland); Iyer, Ajai; Koskinen, Jari [Department of Materials Science and Engineering, School of Chemical Technology, Aalto University, P.O. Box 16200, 00076 Espoo (Finland); Kaskela, Antti; Kauppinen, Esko I. [NanoMaterials Group, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, 00076 Aalto (Finland)

2015-11-21

Carbon nanotubes are of wide interest due to their excellent properties such as tensile strength and electrical and thermal conductivity, but are not, when placed alone on a substrate, well resistant to mechanical wear. Diamond-like carbon (DLC), on the other hand, is widely used in applications due to its very good wear resistance. Combining the two materials could provide a very durable pure carbon nanomaterial enabling to benefit from the best properties of both carbon allotropes. However, the synthesis of high-quality diamond-like carbon uses energetic plasmas, which can damage the nanotubes. From previous works it is neither clear whether the quality of the tubes remains good after DLC deposition, nor whether the DLC above the tubes retains the high sp{sup 3} bonding fraction. In this work, we use experiments and classical molecular dynamics simulations to study the mechanisms of DLC formation on various carbon nanotube compositions. The results show that high-sp{sup 3}-content DLC can be formed provided the deposition conditions allow for sidewards pressure to form from a substrate close beneath the tubes. Under optimal DLC formation energies of around 40–70 eV, the top two nanotube atom layers are fully destroyed by the plasma deposition, but layers below this can retain their structural integrity.

Multiple C-H Bond Activations and Ring-Opening C-S Bond Cleavage of Thiophene by Dirhenium Carbonyl Complexes.

Science.gov (United States)

Adams, Richard D; Dhull, Poonam; Tedder, Jonathan D

2018-06-14

The reaction of Re 2 (CO) 8 (μ-C 6 H 5 )(μ-H) (1) with thiophene in CH 2 Cl 2 at 40 °C yielded the new compound Re 2 (CO) 8 (μ-η 2 -SC 4 H 3 )(μ-H) (2), which contains a bridging σ-π-coordinated thienyl ligand formed by the activation of the C-H bond at the 2 position of the thiophene. Compound 2 exhibits dynamical activity on the NMR time scale involving rearrangements of the bridging thienyl ligand. The reaction of compound 2 with a second 1 equiv of 1 at 45 °C yielded the doubly metalated product [Re 2 (CO) 8 (μ-H)] 2 (μ-η 2 -2,3-μ-η 2 -4,5-C 4 H 2 S) (3), formed by the activation of the C-H bond at the 5 position of the thienyl ligand in 2. Heating 3 in a hexane solvent to reflux transformed it into the ring-opened compound Re(CO) 4 [μ-η 5 -η 2 -SCC(H)C(H)C(H)][Re(CO) 3 ][Re 2 (CO) 8 (μ-H)] (4) by the loss of one CO ligand. Compound 4 contains a doubly metalated 1-thiapentadienyl ligand formed by the cleavage of one of the C-S bonds. When heated to reflux (125 °C) in an octane solvent in the presence of H 2 O, the new compound Re(CO) 4 [η 5 -μ-η 2 -SC(H)C(H)C(H)C(H)]Re(CO) 3 (5) was obtained by cleavage of the Re 2 (CO) 8 (μ-H) group from 4 with formation of the known coproduct [Re(CO) 3 (μ 3 -OH)] 4 . All new products were characterized by single-crystal X-ray diffraction analyses.

Integral Ring Carbon-Carbon Piston

Science.gov (United States)

Northam, G. Burton (Inventor)

1999-01-01

An improved structure for a reciprocating internal combustion engine or compressor piston fabricate from carbon-carbon composite materials is disclosed. An integral ring carbon-carbon composite piston, disclosed herein, reduces the need for piston rings and for small clearances by providing a small flexible, integral component around the piston that allows for variation in clearance due to manufacturing tolerances, distortion due to pressure and thermal loads, and variations in thermal expansion differences between the piston and cylinder liner.

Physical properties of chemical vapour deposited nanostructured carbon thin films

International Nuclear Information System (INIS)

Mahadik, D.B.; Shinde, S.S.; Bhosale, C.H.; Rajpure, K.Y.

2011-01-01

Research highlights: In the present paper, nanostructured carbon films are grown using a natural precursor 'turpentine oil (C 10 H 16 )' as a carbon source in the simple thermal chemical vapour deposition method. The influence of substrate surface topography (viz. stainless steel, fluorine doped tin oxide coated quartz) and temperature on the evolution of carbon allotropes surfaces topography/microstructural and structural properties are investigated and discussed. - Abstract: A simple thermal chemical vapour deposition technique is employed for the deposition of carbon films by pyrolysing the natural precursor 'turpentine oil' on to the stainless steel (SS) and FTO coated quartz substrates at higher temperatures (700-1100 deg. C). In this work, we have studied the influence of substrate and deposition temperature on the evolution of structural and morphological properties of nanostructured carbon films. The films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle measurements, Fourier transform infrared (FTIR) and Raman spectroscopy techniques. XRD study reveals that the films are polycrystalline exhibiting hexagonal and face-centered cubic structures on SS and FTO coated glass substrates respectively. SEM images show the porous and agglomerated surface of the films. Deposited carbon films show the hydrophobic nature. FTIR study displays C-H and O-H stretching vibration modes in the films. Raman analysis shows that, high ID/IG for FTO substrate confirms the dominance of sp 3 bonds with diamond phase and less for SS shows graphitization effect with dominant sp 2 bonds. It reveals the difference in local microstructure of carbon deposits leading to variation in contact angle and hardness, which is ascribed to difference in the packing density of carbon films, as observed also by Raman.

Mechanical Behavior of Steel Fiber-Reinforced Concrete Beams Bonded with External Carbon Fiber Sheets.

Science.gov (United States)

Gribniak, Viktor; Tamulenas, Vytautas; Ng, Pui-Lam; Arnautov, Aleksandr K; Gudonis, Eugenijus; Misiunaite, Ieva

2017-06-17

This study investigates the mechanical behavior of steel fiber-reinforced concrete (SFRC) beams internally reinforced with steel bars and externally bonded with carbon fiber-reinforced polymer (CFRP) sheets fixed by adhesive and hybrid jointing techniques. In particular, attention is paid to the load resistance and failure modes of composite beams. The steel fibers were used to avoiding the rip-off failure of the concrete cover. The CFRP sheets were fixed to the concrete surface by epoxy adhesive as well as combined with various configurations of small-diameter steel pins for mechanical fastening to form a hybrid connection. Such hybrid jointing techniques were found to be particularly advantageous in avoiding brittle debonding failure, by promoting progressive failure within the hybrid joints. The use of CFRP sheets was also effective in suppressing the localization of the discrete cracks. The development of the crack pattern was monitored using the digital image correlation method. As revealed from the image analyses, with an appropriate layout of the steel pins, brittle failure of the concrete-carbon fiber interface could be effectively prevented. Inverse analysis of the moment-curvature diagrams was conducted, and it was found that a simplified tension-stiffening model with a constant residual stress level at 90% of the strength of the SFRC is adequate for numerically simulating the deformation behavior of beams up to the debonding of the CFRP sheets.

Characterization of products from hydrothermal carbonization of pine.

Science.gov (United States)

Wu, Qiong; Yu, Shitao; Hao, Naijia; Wells, Tyrone; Meng, Xianzhi; Li, Mi; Pu, Yunqiao; Liu, Shouxin; Ragauskas, Arthur J

2017-11-01

This study aims to reveal the structural features and reaction pathways for solid-liquid products from hydrothermal carbonization of Loblolly pine, where the solid products can be used as catalysts, adsorbents and electrode materials while liquid products can be treated yielding fuels and platform chemicals. Results revealed when treated at 240°C, cellulose and hemicellulose were degraded, in part, to 5-hydroxy-methyl furfural and furfural which were further transformed to aromatic structures via ring opening and Diels Alder reactions. Lignin degradation and formation of carbon-carbon bonds, forming aromatic motifs in the presence of furanic compounds connected via aliphatic bridges, ether or condensation reactions. After hydrothermal treatment, condensed aromatic carbon materials with methoxy groups were recovered with high fixed carbon content and HHV. The recovered liquid products are lignin-like value-added chemicals consisting of furfural and polyaromatic structure with alkanes and carboxyl, their total hydroxyl group content decreased when increasing reaction time. Copyright © 2017 Elsevier Ltd. All rights reserved.

Carbon nanotubes for thermal interface materials in microelectronic packaging

Science.gov (United States)

Lin, Wei

, an in situ functionalization process has for the first time been demonstrated. The in situ functionalization renders the vertically aligned carbon nanotubes a proper chemical reactivity for forming chemical bonding with other substrate materials such as gold and silicon. 2. An ultrafast microwave annealing process has been developed to reduce the defect density in vertically aligned carbon nanotubes. Raman and thermogravimetric analyses have shown a distinct defect reduction in the CNTs annealed in microwave for 3 min. Fibers spun from the as-annealed CNTs, in comparison with those from the pristine CNTs, show increases of ˜35% and ˜65%, respectively, in tensile strength (˜0.8 GPa) and modulus (˜90 GPa) during tensile testing; an ˜20% improvement in electrical conductivity (˜80000 S m-1) was also reported. The mechanism of the microwave response of CNTs was discussed. Such a microwave annealing process has been extended to the preparation of reduced graphene oxide. 3. Based on the fundamental understanding of interfacial thermal transport and surface chemistry of metals and carbon nanotubes, two major transfer/assembling processes have been developed: molecular bonding and metal bonding. Effective improvement of the interfacial thermal transport has been achieved by the interfacial bonding. 4. The thermal diffusivity of vertically aligned carbon nanotube (VACNT, multi-walled) films was measured by a laser flash technique, and shown to be ˜30 mm2 s-1 along the tube-alignment direction. The calculated thermal conductivities of the VACNT film and the individual CNTs are ˜27 and ˜540 W m-1 K-1, respectively. The technique was verified to be reliable although a proper sampling procedure is critical. A systematic parametric study of the effects of defects, buckling, tip-to-tip contacts, packing density, and tube-tube interaction on the thermal diffusivity was carried out. Defects and buckling decreased the thermal diffusivity dramatically. An increased packing

Proposal of new bonding technique 'Instantaneous Liquid Phase (ILP) Bonding'

International Nuclear Information System (INIS)

Zhang, Yue-Chang; Nakagawa, Hiroji; Matsuda, Fukuhisa.

1987-01-01

A new bonding technique named ''Instantaneous Liquid Phase (ILP) bonding'' suitable mainly for welding dissimilar materials was proposed by which instantaneous melting of one or two of the faying surfaces is utilized. The processes of ILP bonding are mainly consisted of three stages, namely the first stage forming thin liquid layer by rapid heating, the second stage joining both specimens by thin liquid layer, and the third stage cooling the specimens rapidly to avoid the formation of brittle layer. The welding temperatures of the specimens to be welded in ILP bonding are generally differentiated from each other. ILP bonding was applied for a variety of combinations of dissimilar materials of aluminum, aluminum alloys, titanium, titanium alloy, carbon steel, austenitic stainless steel, copper and tungsten, and for similar materials of stainless steel and nickel-base alloy. There were no microvoids in these welding joints, and the formation of brittle layer at the bonding interface was suppressed. The welded joints of Al + Ti, Cu + carbon steel and Cu + austenitic stainless steel showed the fracture in base metal having lower tensile strength. Further, the welded joints of Al + carbon steel, Al alloy + Ti, Al alloy + carbon steel or + austenitic stainless steel, Ti + carbon steel or + austenitic stainless steel showed better tensile properties in the comparison with diffusion welding. Furthermore, ILP bonding was available for welding same materials susceptible to hot cracking. Because of the existence of liquid layer, the welding pressure required was extremely low, and preparation of faying surface by simple tooling or polishing by no.80 emery paper was enough. The change in specimen length before and after welding was relatively little, only depending on the thickness of liquid layer. The welding time was very short, and thus high welding efficiency was obtained. (author)

In silico carbon molecular beam epitaxial growth of graphene on the h-BN substrate: carbon source effect on van der Waals epitaxy

Science.gov (United States)

Lee, Jonghoon; Varshney, Vikas; Park, Jeongho; Farmer, Barry L.; Roy, Ajit K.

2016-05-01

during the initial phase of graphene growth simulation using a carbon trimer beam is captured. An initially sp hybridized carbon atom (red colored) becomes sp2 hybridized as a result of additional covalent bonding with the impinging carbon trimer. As the bond angle around the red carbon changes from 180 degree (sp) to 120 degree (sp2), nearby carbon atoms enclose to form a hexagon structure composed of 6 carbon atoms. See DOI: 10.1039/c6nr01396a

XPS analysis of the carbon fibers surface modified via HMDSO to carbon nanotube growth

International Nuclear Information System (INIS)

Cardoso, L.D.R.; Gomes, M.C.B.; Trava-Airoldi, V.J.; Corat, E.J.; Lugo, D.C.

2016-01-01

Full text: Carbon fibers (CF) have been widely used to reinforce structural composites. Due to their strength-to-weight properties, CF composites are finding increased structural uses in areas such as aerospace, aeronautical, automobile and others. The strength of the fiber-resin interface bond has been found to be the limiting factor to the mechanical properties of CF-epoxy materials, due to their non-polar nature that limit the affinity of CF to bind chemically to any matrix. The growth of carbon nanotubes (CNTs) on the surface of CF is a promising approach for improving mechanical, electrical and thermal properties of structural composites. However growing CNTs on CF presents some obstacles, such as diffusion of metal catalyst particles on CF, uneven CNT growth and loss of mechanical properties of CF. To avoid the diffusion of catalyst particles we modified the CF surface with hexamethyldisiloxane (HMDSO) at low temperature (400 °C), also preventing the loss of mechanical properties and allowing uniform CNTs growth. We deposited CNTs via floating catalyst method, with ferrocene providing the catalyst particle and the oxidative dehydrogenation reaction of acetylene providing the carbon. The CF surface modification was analyzed via X-ray photoelectron spectroscopy (XPS) and CNTs growth via scanning electron microscopy with field emission gun. The XPS analysis showed that HMDSO promotes the binding of oxygen to carbon and silicon present on CF surface, the chemical modification of the surface of the CF enables the uniform growth of carbon nanotubes. (author)

XPS analysis of the carbon fibers surface modified via HMDSO to carbon nanotube growth

Energy Technology Data Exchange (ETDEWEB)

Cardoso, L.D.R.; Gomes, M.C.B.; Trava-Airoldi, V.J.; Corat, E.J.; Lugo, D.C. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil)

2016-07-01

Full text: Carbon fibers (CF) have been widely used to reinforce structural composites. Due to their strength-to-weight properties, CF composites are finding increased structural uses in areas such as aerospace, aeronautical, automobile and others. The strength of the fiber-resin interface bond has been found to be the limiting factor to the mechanical properties of CF-epoxy materials, due to their non-polar nature that limit the affinity of CF to bind chemically to any matrix. The growth of carbon nanotubes (CNTs) on the surface of CF is a promising approach for improving mechanical, electrical and thermal properties of structural composites. However growing CNTs on CF presents some obstacles, such as diffusion of metal catalyst particles on CF, uneven CNT growth and loss of mechanical properties of CF. To avoid the diffusion of catalyst particles we modified the CF surface with hexamethyldisiloxane (HMDSO) at low temperature (400 °C), also preventing the loss of mechanical properties and allowing uniform CNTs growth. We deposited CNTs via floating catalyst method, with ferrocene providing the catalyst particle and the oxidative dehydrogenation reaction of acetylene providing the carbon. The CF surface modification was analyzed via X-ray photoelectron spectroscopy (XPS) and CNTs growth via scanning electron microscopy with field emission gun. The XPS analysis showed that HMDSO promotes the binding of oxygen to carbon and silicon present on CF surface, the chemical modification of the surface of the CF enables the uniform growth of carbon nanotubes. (author)

Yeast ribonuclease III uses a network of multiple hydrogen bonds for RNA binding and cleavage.

Science.gov (United States)

Lavoie, Mathieu; Abou Elela, Sherif

2008-08-19

Members of the bacterial RNase III family recognize a variety of short structured RNAs with few common features. It is not clear how this group of enzymes supports high cleavage fidelity while maintaining a broad base of substrates. Here we show that the yeast orthologue of RNase III (Rnt1p) uses a network of 2'-OH-dependent interactions to recognize substrates with different structures. We designed a series of bipartite substrates permitting the distinction between binding and cleavage defects. Each substrate was engineered to carry a single or multiple 2'- O-methyl or 2'-fluoro ribonucleotide substitutions to prevent the formation of hydrogen bonds with a specific nucleotide or group of nucleotides. Interestingly, introduction of 2'- O-methyl ribonucleotides near the cleavage site increased the rate of catalysis, indicating that 2'-OH are not required for cleavage. Substitution of nucleotides in known Rnt1p binding site with 2'- O-methyl ribonucleotides inhibited cleavage while single 2'-fluoro ribonucleotide substitutions did not. This indicates that while no single 2'-OH is essential for Rnt1p cleavage, small changes in the substrate structure are not tolerated. Strikingly, several nucleotide substitutions greatly increased the substrate dissociation constant with little or no effect on the Michaelis-Menten constant or rate of catalysis. Together, the results indicate that Rnt1p uses a network of nucleotide interactions to identify its substrate and support two distinct modes of binding. One mode is primarily mediated by the dsRNA binding domain and leads to the formation of stable RNA/protein complex, while the other requires the presence of the nuclease and N-terminal domains and leads to RNA cleavage.

Using hydrocarbon as a carbon source for synthesis of carbon nanotube by electric field induced needle-pulsed plasma

International Nuclear Information System (INIS)

Kazemi Kia, Kaveh; Bonabi, Fahimeh

2013-01-01

In this work different hydrocarbons are used as the carbon source, in the production of carbon nanotubes (CNTs) and nano onions. An electric field induced needle pulse arc-discharge reactor is used. The influence of starting carbon on the synthesis of CNTs is investigated. The production efficiency is compared for Acetone, Isopropanol and Naphthalene as simple hydrocarbons. The hydrocarbons are preheated and then pretreated by electric field before being exposed to plasma. The hydrocarbon vapor is injected into plasma through a graphite spout in the cathode assembly. The pulsed plasma takes place between two graphite rods while a strong electric field has been already established alongside the electrodes. The pulse width is 0.3 μs. Mechanism of precursor decomposition is discussed by describing three forms of energy that are utilized to disintegrate the precursor molecules: thermal energy, electric field and kinetic energy of plasma. Molecular polarity of a hydrocarbon is one of the reasons for choosing carbon raw material as a precursor in an electric field induced low power pulsed-plasma. The results show that in order to obtain high quality carbon nanotubes, Acetone is preferred to Isopropanol and Naphthalene. Scanning probe microscopy techniques are used to investigate the products. - Highlights: • We synthesized CNTs (carbon nano tubes) by needle pulsed plasma. • We use different hydrocarbons as carbon source in the production of CNTs. • We investigated the influence of starting carbon on the synthesis of CNTs. • Thermal energy, electric field and kinetic energy are used to break carbon bonds. • Polar hydrocarbon molecules are more efficient than nonpolar ones in production

Solid-phase extraction of polar pesticides from environmental water samples on graphitized carbon and Empore-activated carbon disks and on-line coupling to octadecyl-bonded silica analytical columns.

Science.gov (United States)

Slobodník, J; Oztezkizan, O; Lingeman, H; Brinkman, U A

1996-10-25

The suitability of Empore-activated carbon disks (EACD), Envi-Carb graphitized carbon black (GCB) and CPP-50 graphitized carbon for the trace enrichment of polar pesticides from water samples was studied by means of off-line and on-line solid-phase extraction (SPE). In the off-line procedure, 0.5-2 l samples spiked with a test mixture of oxamyl, methomyl and aldicarb sulfoxide were enriched on EnviCarb SPE cartridges or 47 mm diameter EACD and eluted with dichloromethane-methanol. After evaporation, a sample was injected onto a C18-bonded silica column and analysed by liquid chromatography with ultraviolet (LC-UV) detection. EACD performed better than EnviCarb cartridges in terms of breakthrough volumes (> 2 l for all test analytes), reproducibility (R.S.D. of recoveries, 4-8%, n = 3) and sampling speed (100 ml/min); detection limits in drinking water were 0.05-0.16 microgram/l. In the on-line experiments, 4.6 mm diameter pieces cut from original EACD and stacked onto each other in a 9 mm long precolumn, and EnviCarb and CPP-50 packed in 10 x 2.0 mm I.D. precolumn, were tested, and 50-200 ml spiked water samples were preconcentrated. Because of the peak broadening caused by the strong sorption of the analytes on carbon, the carbon-packed precolumns were eluted by a separate stream of 0.1 ml/min acetonitrile which was mixed with the gradient LC eluent in front of the C18 analytical column. The final on-line procedure was also applied for the less polar propoxur, carbaryl and methiocarb. EnviCarb could not be used due to its poor pressure resistance. CPP-50 provided less peak broadening than EACD: peak widths were 0.1-0.3 min and R.S.D. of peak heights 4-14% (n = 3). In terms of analyte trapping efficiency on-line SPE-LC-UV with a CPP-50 precolumn also showed better performance than when Bondesil C18/OH or polymeric PLRP-S was used, but chromatographic resolution was similar. With the CPP-50-based system, detection limits of the test compounds were 0.05-1 microgram

Optical Excitation of Carbon Nanotubes Drives Localized Diazonium Reactions

Science.gov (United States)

2016-01-01

Covalent chemistries have been widely used to modify carbon nanomaterials; however, they typically lack the precision and efficiency required to directly engineer their optical and electronic properties. Here, we show, for the first time, that visible light which is tuned into resonance with carbon nanotubes can be used to drive their functionalization by aryldiazonium salts. The optical excitation accelerates the reaction rate 154-fold (±13) and makes it possible to significantly improve the efficiency of covalent bonding to the sp2 carbon lattice. Control experiments suggest that the reaction is dominated by a localized photothermal effect. This light-driven reaction paves the way for precise nanochemistry that can directly tailor carbon nanomaterials at the optical and electronic levels. PMID:27588432

Optical excitation of carbon nanotubes drives stoichiometric reaction with diazonium salts

Science.gov (United States)

Powell, Lyndsey; Piao, Yanmei; Wang, Yuhuang; YuHuang Wang Research Group Team

Covalent chemistry is known to lack the precision required to tailor the physical properties of carbon nanostructures. Here we show that, for the first time, light can be used to drive a typically inefficient reaction with single-walled carbon nanotubes in a more stoichiometric fashion. Specifically, our experimental results suggest that light can enhance the reaction rate of diazonium salt with carbon nanotubes by as much as 35-fold, making possible stoichiometric control of the covalent bonding of a functional group to the sp2 carbon lattice. This light-controlled reaction paves the way for the possibility of highly selective and precise chemistry on single-walled carbon nanotubes and other graphitic nanostructures.

Diiridium Bimetallic Complexes Function as a Redox Switch To Directly Split Carbonate into Carbon Monoxide and Oxygen.

Science.gov (United States)

Chen, Tsun-Ren; Wu, Fang-Siou; Lee, Hsiu-Pen; Chen, Kelvin H-C

2016-03-23

A pair of diiridium bimetallic complexes exhibit a special type of oxidation-reduction reaction that could directly split carbonate into carbon monoxide and molecular oxygen via a low-energy pathway needing no sacrificial reagent. One of the bimetallic complexes, Ir(III)(μ-Cl)2Ir(III), can catch carbonato group from carbonate and reduce it to CO. The second complex, the rare bimetallic complex Ir(IV)(μ-oxo)2Ir(IV), can react with chlorine to release O2 by the oxidation of oxygen ions with synergistic oxidative effect of iridium ions and chlorine atoms. The activation energy needed for the key reaction is quite low (∼20 kJ/mol), which is far less than the dissociation energy of the C═O bond in CO2 (∼750 kJ/mol). These diiridium bimetallic complexes could be applied as a redox switch to split carbonate or combined with well-known processes in the chemical industry to build up a catalytic system to directly split CO2 into CO and O2.

Investing for a low carbon economy. Special issue COP21

International Nuclear Information System (INIS)

Guez, Herve; Basselier, Clotilde; Bennani, Zineb; Coeslier, Manuel; Dufour, Mathilde; Dunand-Chatellet, Lea; Guez, Herve; Lauverjat Celine; Ostiari, Emmanuelle; Smia, Ladislas; Bonnin, Marguerite; Briand, Marc; Favier, Julien; Finidori, Esther; Wigley, Chris; Dobie, Jacqueline; Mary Ellis, Susannah; Kiernan, Shannon; Lefer, Elizabeth; Perrin, Elsa; Treadwell, Christopher; Zerner, Rachel

2015-11-01

Mirova, an asset management firm dedicated to responsible investment, has published today Investing in a low-carbon economy, a guide for investors to become COP21 compliant. Mirova's study provides an in-depth analysis highlighting the challenges of climate change and presents methods for investors to effectively measure their carbon footprint. Mirova offers a unique range of investment solutions promoting energy transition across all asset classes. COP21: mobilising private investors is a necessity To maintain the economy in a '2 degree' trajectory, it is vital to redirect savings towards companies and projects promoting energy transition. Philippe Zaouati, Head of Mirova explains: 'The energy transition can only succeed if we manage to mobilise private investors' savings. The success of COP21 therefore also depends on the ability of asset management firms to propose solutions in response to the climate challenge, whilst delivering the returns expected by investors'. Accurately measuring your carbon footprint. In response to growing demands on investors to make greener investments, Mirova, in partnership with the leading carbon strategy specialist consultant Carbone 4, has developed an innovative methodology to measure the carbon footprint of an investment portfolio. This decision-making tool assesses a company's contribution to the reduction of global greenhouse gas emissions (GGE). Measuring the overall impact of a business on the environment is an essential step towards acting against global warming. Assessing the carbon footprint is therefore an indispensable stage in the construction of portfolios contributing to energy transition. Low-carbon investments across all asset classes In order to redirect capital towards investments promoting energy transition, Mirova is proposing solutions involving all asset classes: - Renewable energy infrastructures: 100% low carbon allocation For more than 10 years now, Mirova has provided European institutions with access to

Effect of trastuzumab interchain disulfide bond cleavage on Fcγ receptor binding and antibody-dependent tumour cell phagocytosis.

Science.gov (United States)

Suzuki, Mami; Yamanoi, Ayaka; Machino, Yusuke; Ootsubo, Michiko; Izawa, Ken-ichi; Kohroki, Junya; Masuho, Yasuhiko

2016-01-01

The Fc domain of human IgG1 binds to Fcγ receptors (FcγRs) to induce effector functions such as phagocytosis. There are four interchain disulfide bonds between the H and L chains. In this study, the disulfide bonds within the IgG1 trastuzumab (TRA), which is specific for HER2, were cleaved by mild S-sulfonation or by mild reduction followed by S-alkylation with three different reagents. The cleavage did not change the binding activities of TRA to HER2-bearing SK-BR-3 cells. The binding activities of TRA to FcγRIIA and FcγRIIB were greatly enhanced by modification with mild reduction and S-alkylation with ICH2CONH2 or N-(4-aminophenyl) maleimide, while the binding activities of TRA to FcγRI and FcγRIIIA were decreased by any of the four modifications. However, the interchain disulfide bond cleavage by the different modifications did not change the antibody-dependent cell-mediated phagocytosis (ADCP) of SK-BR-3 cells by activated THP-1 cells. The order of FcγR expression levels on the THP-1 cells was FcγRII > FcγRI > FcγRIII and ADCP was inhibited by blocking antibodies against FcγRI and FcγRII. These results imply that the effect of the interchain disulfide bond cleavage on FcγRs binding and ADCP is dependent on modifications of the cysteine residues and the FcγR isotypes. © The Authors 2015. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

Rhenium-Promoted C-C Bond-Cleavage Reactions of Internal Propargyl Alcohols.

Science.gov (United States)

Lee, Kui Fun; Bai, Wei; Sung, Herman H Y; Williams, Ian D; Lin, Zhenyang; Jia, Guochen

2018-06-07

The first examples of C-C bond cleavage reactions of internal propargyl alcohols to give vinylidene complexes are described. Treatment of [Re(dppm) 3 ]I with RC≡CC(OH)R'R'' (R=aryl, alkyl; C(OH)R'R''=C(OH)Ph 2, C(OH)Me 2 , C(OH)HPh, C(OH)H 2 ) produced the vinylidene complexes ReI(=C=CHR)(dppm) 2 with the elimination of C(O)R'R''. Computational studies support that the reactions proceed through a β-alkynyl elimination of alkoxide intermediates Re{OC(R')(R'')C≡CR}(dppm) 2 . © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hierarchical carbon nanostructure design: ultra-long carbon nanofibers decorated with carbon nanotubes

International Nuclear Information System (INIS)

El Mel, A A; Achour, A; Gautron, E; Angleraud, B; Granier, A; Le Brizoual, L; Djouadi, M A; Tessier, P Y; Xu, W; Choi, C H

2011-01-01

Hierarchical carbon nanostructures based on ultra-long carbon nanofibers (CNF) decorated with carbon nanotubes (CNT) have been prepared using plasma processes. The nickel/carbon composite nanofibers, used as a support for the growth of CNT, were deposited on nanopatterned silicon substrate by a hybrid plasma process, combining magnetron sputtering and plasma-enhanced chemical vapor deposition (PECVD). Transmission electron microscopy revealed the presence of spherical nanoparticles randomly dispersed within the carbon nanofibers. The nickel nanoparticles have been used as a catalyst to initiate the growth of CNT by PECVD at 600 deg. C. After the growth of CNT onto the ultra-long CNF, SEM imaging revealed the formation of hierarchical carbon nanostructures which consist of CNF sheathed with CNTs. Furthermore, we demonstrate that reducing the growth temperature of CNT to less than 500 deg. C leads to the formation of carbon nanowalls on the CNF instead of CNT. This simple fabrication method allows an easy preparation of hierarchical carbon nanostructures over a large surface area, as well as a simple manipulation of such material in order to integrate it into nanodevices.

Characteristics of carbonized sludge for co-combustion in pulverized coal power plants.

Science.gov (United States)

Park, Sang-Woo; Jang, Cheol-Hyeon

2011-03-01

Co-combustion of sewage sludge can destabilize its combustion profile due to high volatility, which results in unstable flame. We carried out fuel reforming for sewage sludge by way of carbonization at pyrolysis temperature of 300-500°C. Fuel characteristics of carbonized sludge at each temperature were analyzed. As carbonization temperature increased, fuel ratio increased, volatile content reduced, and atomic ratio relation of H/C and O/C was similar to that of lignite. The analysis result of FT-IR showed the decrease of aliphatic C-H bond and O-C bond in carbonization. In the analysis result of TG-DTG, the thermogravimetry reduction temperature of carbonized sludge (CS400) was proven to be higher than that of dried sludge, but lower than that of sub-bituminous coal. Hardgrove grindability index increased in proportion to fuel ratio increase, where the carbonized sludge value of 43-110 was similar or higher than the coal value of 49-63. As for ash deposits, slagging and fouling index were higher than that of coal. When carbonized sludge (CS400) and coal were co-combusted in 1-10% according to calorific value, slagging tendency was low in all conditions, and fouling tendency was medium or high according to the compositions of coal. Copyright © 2010 Elsevier Ltd. All rights reserved.

Sol-gel coatings on carbon/carbon composites

International Nuclear Information System (INIS)

Sim, S.M.; Krabill, R.M.; Dalzell, W.J. Jr.; Chu, P.Y.; Clark, D.E.

1986-01-01

The need for structural materials that can withstand severe environments up to 4000 0 F has promulgated the investigation of sol-gel derived ceramic and composite coatings on carbon/carbon composite materials. Alumina and zirconia sols have been deposited via thermophoresis on carbon/carbon substrates

Interaction between fullerene halves C_n (n ≤ 40) and single wall carbon nanotube

International Nuclear Information System (INIS)

Sharma, Amrish; Kaur, Sandeep; Mudahar, Isha

2016-01-01

We have investigated the structural and electronic properties of carbon nanotube with small fullerene halves C_n (n ≤ 40) which are covalently bonded to the side wall of an armchair single wall carbon nanotube (SWCNT) using first principle method based on density functional theory. The fullerene size results in weak bonding between fullerene halves and carbon nanotube (CNT). Further, it was found that the C-C bond distance that attaches the fullerene half and CNT is of the order of 1.60 Å. The calculated binding energies indicate the stability of the complexes formed. The HOMO-LUMO gaps and electron density of state plots points towards the metallicity of the complex formed. Our calculations on charge transfer reveal that very small amount of charge is transferred from CNT to fullerene halves.

Carbon K-edge spectra of carbonate minerals.

Science.gov (United States)

Brandes, Jay A; Wirick, Sue; Jacobsen, Chris

2010-09-01

Carbon K-edge X-ray spectroscopy has been applied to the study of a wide range of organic samples, from polymers and coals to interstellar dust particles. Identification of carbonaceous materials within these samples is accomplished by the pattern of resonances in the 280-320 eV energy region. Carbonate minerals are often encountered in the study of natural samples, and have been identified by a distinctive resonance at 290.3 eV. Here C K-edge and Ca L-edge spectra from a range of carbonate minerals are presented. Although all carbonates exhibit a sharp 290 eV resonance, both the precise position of this resonance and the positions of other resonances vary among minerals. The relative strengths of the different carbonate resonances also vary with crystal orientation to the linearly polarized X-ray beam. Intriguingly, several carbonate minerals also exhibit a strong 288.6 eV resonance, consistent with the position of a carbonyl resonance rather than carbonate. Calcite and aragonite, although indistinguishable spectrally at the C K-edge, exhibited significantly different spectra at the Ca L-edge. The distinctive spectral fingerprints of carbonates provide an identification tool, allowing for the examination of such processes as carbon sequestration in minerals, Mn substitution in marine calcium carbonates (dolomitization) and serpentinization of basalts.

Carbon K-edge Spectra of Carbonate Minerals

Energy Technology Data Exchange (ETDEWEB)

Brandes, J.; Wirick, S; Jacobsen, C

2010-01-01

Carbon K-edge X-ray spectroscopy has been applied to the study of a wide range of organic samples, from polymers and coals to interstellar dust particles. Identification of carbonaceous materials within these samples is accomplished by the pattern of resonances in the 280-320 eV energy region. Carbonate minerals are often encountered in the study of natural samples, and have been identified by a distinctive resonance at 290.3 eV. Here C K-edge and Ca L-edge spectra from a range of carbonate minerals are presented. Although all carbonates exhibit a sharp 290 eV resonance, both the precise position of this resonance and the positions of other resonances vary among minerals. The relative strengths of the different carbonate resonances also vary with crystal orientation to the linearly polarized X-ray beam. Intriguingly, several carbonate minerals also exhibit a strong 288.6 eV resonance, consistent with the position of a carbonyl resonance rather than carbonate. Calcite and aragonite, although indistinguishable spectrally at the C K-edge, exhibited significantly different spectra at the Ca L-edge. The distinctive spectral fingerprints of carbonates provide an identification tool, allowing for the examination of such processes as carbon sequestration in minerals, Mn substitution in marine calcium carbonates (dolomitization) and serpentinization of basalts.

Mussel byssus-inspired engineering of synergistic nanointerfacial interactions as sacrificial bonds into carbon nanotube-reinforced soy protein/nanofibrillated cellulose nanocomposites: Versatile mechanical enhancement

Science.gov (United States)

Wang, Zhong; Zhao, Shujun; Kang, Haijiao; Zhang, Wei; Zhang, Shifeng; Li, Jianzhang

2018-03-01

Achieving flexible and stretchable biobased nanocomposites combining high strength and toughness is still a very challenging endeavor. Herein, we described a novel and versatile biomimetic design for tough and high-performance TEMPO-oxidized nanofibrillated cellulose (TONFC)/soy protein isolate (SPI) nanocomposites, which are triggered by catechol-mimetic carbon nanotubes (PCT) and iron ions (Fe(III)) to yield a strong yet sacrificial metal-ligand motifs into a chemically cross-linked architecture network. Taking advantage of self-polymerization of catechol-inspired natural tannic acid, PCT nanohybrid was prepared through adhering reactive poly-(tannic acid) (PTA) layer onto surfaces of carbon nanotubes via a simple dip-coating process. The high-functionality PCT induced the formation of the metal-ligand bonds through the ionic coordinates between the catechol groups in PCT and -COOH groups of TONFC skeleton with Fe(III) mediation that mimicked mussel byssus. Upon stretching, this tailored TONFC-Fe(III)-catechol coordination bonds served as sacrificial bonds that preferentially detach prior to the covalent network, which gave rise to efficient energy dissipation that the nanocomposites integrity was survived. As a result of these kind of synergistic interfacial interactions (sacrificial and covalent bonding), the optimal nanocomposite films processed high tensile strength (ca. 11.5 MPa), large elongation (ca. 79.3%), remarkable toughness (ca. 6.9 MJ m-3), and favorable water resistance as well as electrical conductivity. The proposed bioinspired strategy for designing plant protein-based materials enables control over their mechanical performance through the synergistic engineering of sacrificial bonds into the composite interface.

Preparation and characterization of carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating for carbon/carbon composites

International Nuclear Information System (INIS)

Leilei, Zhang; Hejun, Li; Kezhi, Li; Shouyang, Zhang; Qiangang, Fu; Yulei, Zhang; Jinhua, Lu; Wei, Li

2014-01-01

Highlights: • CSH coatings were prepared by combination of magnetron sputter ion plating, CVD and UECD. • Na + and CO 3 2− were developed to co-substitute hydroxyapatite. • SiC nanowires were introduced into Na-doped carbonated hydroxyapatite. • CSH coatings showed excellent cell activity and cell proliferation behavior. - Abstract: A carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating (CSH coating) was prepared on carbon/carbon composites using a combination method of magnetron sputter ion plating, chemical vapor deposition and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the CSH coating was consisted of three components: carbon layer, SiC nanowires and Na-doped carbonated hydroxyapatite. The carbon layer provided a dense and uniform surface structure for the growth of SiC nanowires. The SiC nanowires exhibited a porous structure, favoring the infiltration of Na-doped carbonated hydroxyapatite crystals. The Na-doped carbonated hydroxyapatite could infiltrate into the pores of SiC nanowires and finally cover the SiC nanowires entirely with a needle shape. The osteoblast-like MG63 cells were employed to assess the in vitro biocompatibility of the CSH coating. The MG63 cells favorably spread and grew well across the CSH coating surface with plenty of filopods and microvilli, exhibiting excellent cell activity. Moreover, the CSH coating elicited higher cell proliferation as compared to bare carbon/carbon composites. In conclusion, the CSH offers great potential as a coating material for future medical application in hard tissue replacement

Preparation and characterization of carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating for carbon/carbon composites

Energy Technology Data Exchange (ETDEWEB)

Leilei, Zhang, E-mail: zhangleilei1121@aliyun.com; Hejun, Li; Kezhi, Li; Shouyang, Zhang; Qiangang, Fu; Yulei, Zhang; Jinhua, Lu; Wei, Li

2014-09-15

Highlights: • CSH coatings were prepared by combination of magnetron sputter ion plating, CVD and UECD. • Na{sup +} and CO{sub 3}{sup 2−} were developed to co-substitute hydroxyapatite. • SiC nanowires were introduced into Na-doped carbonated hydroxyapatite. • CSH coatings showed excellent cell activity and cell proliferation behavior. - Abstract: A carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating (CSH coating) was prepared on carbon/carbon composites using a combination method of magnetron sputter ion plating, chemical vapor deposition and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the CSH coating was consisted of three components: carbon layer, SiC nanowires and Na-doped carbonated hydroxyapatite. The carbon layer provided a dense and uniform surface structure for the growth of SiC nanowires. The SiC nanowires exhibited a porous structure, favoring the infiltration of Na-doped carbonated hydroxyapatite crystals. The Na-doped carbonated hydroxyapatite could infiltrate into the pores of SiC nanowires and finally cover the SiC nanowires entirely with a needle shape. The osteoblast-like MG63 cells were employed to assess the in vitro biocompatibility of the CSH coating. The MG63 cells favorably spread and grew well across the CSH coating surface with plenty of filopods and microvilli, exhibiting excellent cell activity. Moreover, the CSH coating elicited higher cell proliferation as compared to bare carbon/carbon composites. In conclusion, the CSH offers great potential as a coating material for future medical application in hard tissue replacement.

Synthesis of Antimony Doped Amorphous Carbon Films

Science.gov (United States)

Okuyama, H.; Takashima, M.; Akasaka, H.; Ohtake, N.

2013-06-01

We report the effects of antimony (Sb) doping on the electrical and optical properties of amorphous carbon (a-C:H) films grown on silicon and copper substrates by magnetron sputtering deposition. For film deposition, the mixture targets fabricated from carbon and antimony powders was used. The atomic concentration of carbon, hydrogen, and antimony, in the film deposited from the 1.0 mol% Sb containing target were 81, 17, 2 at.%, respectively. These elements were homogeneously distributed in the film. On the structural effect, the average continuous sp2 carbon bonding networks decreased with Sb concentration increasing, and defects in the films were increased with the Sb incorporation because atomic radius of Sb atoms is twice larger size than that of carbon. The optical gap and the electrical resistivity were carried out before and after the Sb doping. The results show that optical gap dropped from 3.15 to 3.04 eV corresponding to non-doping to Sb-doping conditions, respectively. The electrical resistivity reduced from 10.5 to 1.0 MΩm by the Sb doping. These results suggest the doping level was newly formed in the forbidden band.

Synthesis of Antimony Doped Amorphous Carbon Films

International Nuclear Information System (INIS)

Okuyama, H; Takashima, M; Akasaka, H; Ohtake, N

2013-01-01

We report the effects of antimony (Sb) doping on the electrical and optical properties of amorphous carbon (a-C:H) films grown on silicon and copper substrates by magnetron sputtering deposition. For film deposition, the mixture targets fabricated from carbon and antimony powders was used. The atomic concentration of carbon, hydrogen, and antimony, in the film deposited from the 1.0 mol% Sb containing target were 81, 17, 2 at.%, respectively. These elements were homogeneously distributed in the film. On the structural effect, the average continuous sp 2 carbon bonding networks decreased with Sb concentration increasing, and defects in the films were increased with the Sb incorporation because atomic radius of Sb atoms is twice larger size than that of carbon. The optical gap and the electrical resistivity were carried out before and after the Sb doping. The results show that optical gap dropped from 3.15 to 3.04 eV corresponding to non-doping to Sb-doping conditions, respectively. The electrical resistivity reduced from 10.5 to 1.0 MΩm by the Sb doping. These results suggest the doping level was newly formed in the forbidden band.

Carbon and carbon-14 in lunar soil 14163

International Nuclear Information System (INIS)

Fireman, E.L.; Stoenner, R.W.

1981-01-01

Carbon is removed from the surface of lunar soil 14163 size fractions by combustions at 500 and 1000 0 C in an oxygen stream and the carbon contents and the carbon-14 activities are measured. The carbon contents are inversely correlated with grain size. A measured carbon content of 198 ppM for bulk 14163, obtained by combining the size fraction results, is modified to 109 +- 12 ppM by a carbon contamination correction. This value is in accord with a previous determination, 110 ppM, for bulk 14163. The small ( 53 μ) grains, 11.2 +- 2.0 dpm/kg. The combusted carbon and carbon-14 are attributed mainly to solar-wind implantation. Melt extractions of carbon-14 from the combusted soil samples gave essentially identical activities, 21.0 +- 1.5 and 19.2 +- 2.0 dpm/kg for the small and large grains, and are attributed to cosmic-ray spallation-produced carbon-14

Carbon black vs. black carbon and other airborne materials containing elemental carbon: Physical and chemical distinctions

International Nuclear Information System (INIS)

Long, Christopher M.; Nascarella, Marc A.; Valberg, Peter A.

2013-01-01

Airborne particles containing elemental carbon (EC) are currently at the forefront of scientific and regulatory scrutiny, including black carbon, carbon black, and engineered carbon-based nanomaterials, e.g., carbon nanotubes, fullerenes, and graphene. Scientists and regulators sometimes group these EC-containing particles together, for example, interchangeably using the terms carbon black and black carbon despite one being a manufactured product with well-controlled properties and the other being an undesired, incomplete-combustion byproduct with diverse properties. In this critical review, we synthesize information on the contrasting properties of EC-containing particles in order to highlight significant differences that can affect hazard potential. We demonstrate why carbon black should not be considered a model particle representative of either combustion soots or engineered carbon-based nanomaterials. Overall, scientific studies need to distinguish these highly different EC-containing particles with care and precision so as to forestall unwarranted extrapolation of properties, hazard potential, and study conclusions from one material to another. -- Highlights: •Major classes of elemental carbon-containing particles have distinct properties. •Despite similar names, carbon black should not be confused with black carbon. •Carbon black is distinguished by a high EC content and well-controlled properties. •Black carbon particles are characterized by their heterogenous properties. •Carbon black is not a model particle representative of engineered nanomaterials. -- This review demonstrates the significant physical and chemical distinctions between elemental carbon-containing particles e.g., carbon black, black carbon, and engineered nanomaterials

Integration of Computer Tomography and Simulation Analysis in Evaluation of Quality of Ceramic-Carbon Bonded Foam Filter

Directory of Open Access Journals (Sweden)

Karwiński A.

2013-12-01

Full Text Available Filtration of liquid casting alloys is used in casting technologies for long time. The large quantity of available casting filters allows using them depending on casting technology, dimensions of casting and used alloys. Technological progress of material science allows of using new materials in production of ceramic filters. In this article the Computed Tomography (CT technique was use in order to evaluate the thickness of branch in cross section of 20ppi ceramic-carbon bonded foam filter. Than the 3D image of foam filter was used in computer simulation of flow of liquid metal thru the running system.

Cu-catalyzed esterification reaction via aerobic oxygenation and C-C bond cleavage: an approach to α-ketoesters.

Science.gov (United States)

Zhang, Chun; Feng, Peng; Jiao, Ning

2013-10-09

The Cu-catalyzed novel aerobic oxidative esterification reaction of 1,3-diones for the synthesis of α-ketoesters has been developed. This method combines C-C σ-bond cleavage, dioxygen activation and oxidative C-H bond functionalization, as well as provides a practical, neutral, and mild synthetic approach to α-ketoesters which are important units in many biologically active compounds and useful precursors in a variety of functional group transformations. A plausible radical process is proposed on the basis of mechanistic studies.

Bioactive carbon-PEEK composites prepared by chemical surface treatment.

Science.gov (United States)

Miyazaki, Toshiki; Matsunami, Chisato; Shirosaki, Yuki

2017-01-01

Polyetheretherketone (PEEK) has attracted much attention as an artificial intervertebral spacer for spinal reconstruction. Furthermore, PEEK plastic reinforced with carbon fiber has twice the bending strength of pure PEEK. However, the PEEK-based materials do not show ability for direct bone bonding, i.e., bioactivity. Although several trials have been conducted for enabling PEEK with bioactivity, few studies have reported on bioactive surface modification of carbon-PEEK composites. In the present study, we attempted the preparation of bioactive carbon-PEEK composites by chemical treatments with H 2 SO 4 and CaCl 2 . Bioactivity was evaluated by in vitro apatite formation in simulated body fluid (SBF). The apatite formation on the carbon-PEEK composite was compared with that of pure PEEK. Both pure PEEK and carbon-PEEK composite formed the apatite in SBF when they were treated with H 2 SO 4 and CaCl 2 ; the latter showed higher apatite-forming ability than the former. It is conjectured that many functional groups able to induce the apatite nucleation, such as sulfo and carboxyl groups, are incorporated into the dispersed carbon phase in the carbon-PEEK composites. Copyright © 2016 Elsevier B.V. All rights reserved.

6. international conference on Nano-technology in Carbon: from synthesis to applications of nano-structured carbon and related materials

International Nuclear Information System (INIS)

2004-01-01

This is the sixth international conference sponsored this year by the French Carbon Group (GFEC), the European Research Group on Nano-tubes GDRE 'Nano-E', in collaboration with the British Carbon Group and the 'Institut des Materiaux Jean Rouxel' (local organizer). The aim of this conference is to promote carbon science in the nano-scale as, for example, nano-structured carbons, nano-tubes, nano-wires, fullerenes, etc. This conference is designed to introduce those with an interest in materials to current research in nano-technology and to bring together research scientists working in various disciplines in the broad area of nano-structured carbons, nano-tubes and fullerene-related nano-structures. Elemental carbon is the simplest exemplar of this nano-technology based on covalent bonding, however other systems (for example containing hetero-atoms) are becoming important from a research point of view, and provide alternative nano-materials with unique properties opening a broad field of applications. Nano-technology requires an understanding of these materials on a structural and textural point of view and this will be the central theme. This year the conference will feature sessions on: S1. Control and synthesis of nano-materials 1.1 Nano-structured carbons: pyrolysis of polymers, activation, templates,... 1.2 Nano-tubes: Catalytic method, HiPCO, graphite vaporization, electrolysis,... 1.3 Fullerenes S2. Chemistry of carbon nano-materials 2.1 Purification of carbon nano-tubes 2.2 Functionalization - Self-assembling S3. Structural characterization S4. Theory and modelling S5. Relationship between structure and properties S6. Applications Water and air purification, Gas and energy storage, Composite materials, Field emission, Nano-electronics, Biotechnology,... S7. Environmental impact. Only one paper concerning carbon under irradiation has been added to the INIS database. (authors)

Nanoporous-carbon films for microsensor preconcentrators

Science.gov (United States)

Siegal, M. P.; Overmyer, D. L.; Kottenstette, R. J.; Tallant, D. R.; Yelton, W. G.

2002-05-01

Nanoporous-carbon (NPC) films are grown using physical processes such as low-power pulsed-laser deposition with attenuation of the ablated carbon species kinetic energy attained by using an inert background gas. With room-temperature growth and negligible residual stress, NPC can coat nearly any substrate to any desired thickness. Control of the deposition energetics yields precise morphology, density, and hence, porosity, with no discernable variation in chemical bonding. We produce NPC films 8 μm thick with density <0.2 g/cm3. The well-controlled porosity, i.e., available surface area, is demonstrated by using films with different thicknesses as a preconcentrator for a nerve-gas simulant.

Comparison of cellular toxicity between multi-walled carbon nanotubes and onion-like shell-shaped carbon nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Kang, Seunghyon [Seoul National University, School of Mechanical and Aerospace Engineering (Korea, Republic of); Kim, Ji-Eun [Korea Research Institute of Standard and Science, Center for NanoSafety Metrology, Division of Convergence Technology (Korea, Republic of); Kim, Daegyu [LG Electronics (Korea, Republic of); Woo, Chang Gyu [Korea Institute of Machinery and Materials, Environmental and Energy Systems Research Division (Korea, Republic of); Pikhitsa, Peter V. [Seoul National University, School of Mechanical and Aerospace Engineering (Korea, Republic of); Cho, Myung-Haing, E-mail: mchotox@snu.ac.kr [Seoul National University, Laboratory of Toxicology, College of Veterinary Medicine (Korea, Republic of); Choi, Mansoo, E-mail: mchoi@snu.ac.kr [Seoul National University, School of Mechanical and Aerospace Engineering (Korea, Republic of)

2015-09-15

The cellular toxicity of multi-walled carbon nanotubes (MWCNTs) and onion-like shell-shaped carbon nanoparticles (SCNPs) was investigated by analyzing the comparative cell viability. For the reasonable comparison, physicochemical characteristics were controlled thoroughly such as crystallinity, carbon bonding characteristic, hydrodynamic diameter, and metal contents of the particles. To understand relation between cellular toxicity of the particles and generation of reactive oxygen species (ROS), we measured unpaired singlet electrons of the particles and intracellular ROS, and analyzed cellular toxicity with/without the antioxidant N-acetylcysteine (NAC). Regardless of the presence of NAC, the cellular toxicity of SCNPs was found to be lower than that of MWCNTs. Since both particles show similar crystallinity, hydrodynamic size, and Raman signal with negligible contribution of remnant metal particles, the difference in cell viability would be ascribed to the difference in morphology, i.e., spherical shape (aspect ratio of one) for SCNP and elongated shape (high aspect ratio) for MWCNT.

Comparison of cellular toxicity between multi-walled carbon nanotubes and onion-like shell-shaped carbon nanoparticles

International Nuclear Information System (INIS)

Kang, Seunghyon; Kim, Ji-Eun; Kim, Daegyu; Woo, Chang Gyu; Pikhitsa, Peter V.; Cho, Myung-Haing; Choi, Mansoo

2015-01-01

The cellular toxicity of multi-walled carbon nanotubes (MWCNTs) and onion-like shell-shaped carbon nanoparticles (SCNPs) was investigated by analyzing the comparative cell viability. For the reasonable comparison, physicochemical characteristics were controlled thoroughly such as crystallinity, carbon bonding characteristic, hydrodynamic diameter, and metal contents of the particles. To understand relation between cellular toxicity of the particles and generation of reactive oxygen species (ROS), we measured unpaired singlet electrons of the particles and intracellular ROS, and analyzed cellular toxicity with/without the antioxidant N-acetylcysteine (NAC). Regardless of the presence of NAC, the cellular toxicity of SCNPs was found to be lower than that of MWCNTs. Since both particles show similar crystallinity, hydrodynamic size, and Raman signal with negligible contribution of remnant metal particles, the difference in cell viability would be ascribed to the difference in morphology, i.e., spherical shape (aspect ratio of one) for SCNP and elongated shape (high aspect ratio) for MWCNT

Adsorbed Carbon Formation and Carbon Hydrogenation for CO_2 Methanation on the Ni(111) Surface: ASED-MO Study

International Nuclear Information System (INIS)

Choe, Sang Joon; Kang, Hae Jin; Kim, Su Jin; Park, Sung Bae; Park, Dong Ho; Huh, Do Sung

2005-01-01

Using the ASED-MO (Atom Superposition and Electron Delocalization-Molecular Orbital) theory, we investigated carbon formation and carbon hydrogenation for CO_2 methanation on the Ni (111) surface. For carbon formation mechanism, we calculated the following activation energies, 1.27 eV for CO_2 dissociation, 2.97 eV for the CO, 1.93 eV for 2CO dissociation, respectively. For carbon methanation mechanism, we also calculated the following activation energies, 0.72 eV for methylidyne, 0.52 eV for methylene and 0.50 eV for methane, respectively. We found that the calculated activation energy of CO dissociation is higher than that of 2CO dissociation on the clean surface and base on these results that the CO dissociation step are the ratedetermining of the process. The C-H bond lengths of CH_4 the intermediate complex are 1.21 A, 1.31 A for the C···H_(_1_), and 2.82 A for the height, with angles of 105 .deg. for H_(_1_)CH and 98 .deg. for H_(_1_)CH_(_1_)

Carbon/carbon composite materials

International Nuclear Information System (INIS)

Thebault, J.; Orly, P.

2006-01-01

Carbon/carbon composites are singular materials from their components, their manufacturing process as well as their characteristics. This paper gives a global overview of these particularities and applications which make them now daily used composites. (authors)

NMR experiments for the measurement of proton-proton and carbon-carbon residual dipolar couplings in uniformly labelled oligosaccharides

Energy Technology Data Exchange (ETDEWEB)

Martin-Pastor, Manuel [Universidad de Santiago de Compostela, Laboratorio Integral de Estructura de Biomoleculas Jose. R. Carracido, Unidade de Resonancia Magnetica, RIAIDT (Spain)], E-mail: mmartin@usc.es; Canales-Mayordomo, Angeles; Jimenez-Barbero, Jesus [Departamento de Estructura y funcion de proteinas, Centro de Investigaciones Biologicas, CSIC (Spain)], E-mail: jjbarbero@cib.csic.es

2003-08-15

A 2D-HSQC-carbon selective/proton selective-constant time COSY, 2D-HSQC-(sel C, sel H)-CT COSY experiment, which is applicable to uniformly {sup 13}C isotopically enriched samples (U-{sup 13}C) of oligosaccharides or oligonucleotides is proposed for the measurement of proton-proton RDC in crowded regions of 2D-spectra. In addition, a heteronuclear constant time-COSY experiment, {sup 13}C-{sup 13}C CT-COSY, is proposed for the measurement of one bond carbon-carbon RDC in these molecules. These two methods provide an extension, to U-{sup 13}C molecules, of the original homonuclear constant time-COSY experiment proposed by Tian et al. (1999) for saccharides. The combination of a number of these RDC with NOE data may provide the method of choice to study oligosaccharide conformation in the free and receptor-bound state.

Synthesis of carbon nanorods by reduction of carbon bisulfide

International Nuclear Information System (INIS)

Lou Zhengsong; He Minglong; Zhao Dejian; Li Zhongchun; Shang Tongming

2010-01-01

Research highlights: Our manuscript is a concise preliminary account of original and of significant research, which illuminates carbon nanorods and variously shaped Y-junction carbon nanorods are successfully fabricated on a large scale through a carbon bisulfide thermal reduction process. Various shaped Y-junction carbon nanorods can be used as studying the electronic and transport properties of the nano-meter carbon material. - Abstract: Carbon nanorods are synthesized at large scale by the reduction of carbon bisulfide at 600 o C. Moreover, novel Y-junction carbon nanorods are detected in the samples. The X-ray power diffraction pattern indicates that the products are hexagonal graphite. Scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and N 2 physisorption studies show that carbon nanorods predominate in the product. Based on the supercritical carbon bisulfide system, the possible growth mechanism of the carbon nanorods was discussed. This method provides a simple and cheap route to large-scale synthesis of carbon nanorods.

Unusually short chalcogen bonds involving organoselenium: insights into the Se-N bond cleavage mechanism of the antioxidant ebselen and analogues.

Science.gov (United States)

Thomas, Sajesh P; Satheeshkumar, K; Mugesh, Govindasamy; Guru Row, T N

2015-04-27

Structural studies on the polymorphs of the organoselenium antioxidant ebselen and its derivative show the potential of organic selenium to form unusually short Se⋅⋅⋅O chalcogen bonds that lead to conserved supramolecular recognition units. Se⋅⋅⋅O interactions observed in these polymorphs are the shortest such chalcogen bonds known for organoselenium compounds. The FTIR spectral evolution characteristics of this interaction from solution state to solid crystalline state further validates the robustness of this class of supramolecular recognition units. The strength and electronic nature of the Se⋅⋅⋅O chalcogen bonds were explored using high-resolution X-ray charge density analysis and atons-in-molecules (AIM) theoretical analysis. A charge density study unravels the strong electrostatic nature of Se⋅⋅⋅O chalcogen bonding and soft-metal-like behavior of organoselenium. An analysis of the charge density around Se-N and Se-C covalent bonds in conjunction with the Se⋅⋅⋅O chalcogen bonding modes in ebselen and its analogues provides insights into the mechanism of drug action in this class of organoselenium antioxidants. The potential role of the intermolecular Se⋅⋅⋅O chalcogen bonding in forming the intermediate supramolecular assembly that leads to the bond cleavage mechanism has been proposed in terms of electron density topological parameters in a series of molecular complexes of ebselen with reactive oxygen species (ROS). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Glycoside bond cleavage in the radiolysis of aqueous solutions of methylglycosides and disaccharides

International Nuclear Information System (INIS)

Shadyro, O.I.; Kisel', R.M.

2007-01-01

The kinetics of formation of methylglycoside and disaccharide radiolysis products resulting from the O-glycoside bond cleavage under the action of 137 Cs γ-radiation (0-2.5 kGy radiation doses, 0.28 Gy/s dose rate) was studied, and the yields of these products were determined. It was found that oxygen inhibits these processes. The findings suggest that the fragmentation reaction of C' 2 radicals plays an important role in the formation of carbohydrate degradation products in the radiolysis of aqueous carbohydrate solutions [ru

Carbon dioxide sequestration by mineral carbonation

NARCIS (Netherlands)

Huijgen, W.J.J.

2007-01-01

The increasing atmospheric carbon dioxide (CO2) concentration, mainly caused by fossil fuel combustion, has lead to concerns about global warming. A possible technology that can contribute to the reduction of carbon dioxide emissions is CO2 sequestration by mineral carbonation. The basic concept

X-ray photoelectron spectroscopy of graphitic carbon nanomaterials doped with heteroatoms

Directory of Open Access Journals (Sweden)

Toma Susi

2015-01-01

Full Text Available X-ray photoelectron spectroscopy (XPS is one of the best tools for studying the chemical modification of surfaces, and in particular the distribution and bonding of heteroatom dopants in carbon nanomaterials such as graphene and carbon nanotubes. Although these materials have superb intrinsic properties, these often need to be modified in a controlled way for specific applications. Towards this aim, the most studied dopants are neighbors to carbon in the periodic table, nitrogen and boron, with phosphorus starting to emerge as an interesting new alternative. Hundreds of studies have used XPS for analyzing the concentration and bonding of dopants in various materials. Although the majority of works has concentrated on nitrogen, important work is still ongoing to identify its precise atomic bonding configurations. In general, care should be taken in the preparation of a suitable sample, consideration of the intrinsic photoemission response of the material in question, and the appropriate spectral analysis. If this is not the case, incorrect conclusions can easily be drawn, especially in the assignment of measured binding energies into specific atomic configurations. Starting from the characteristics of pristine materials, this review provides a practical guide for interpreting X-ray photoelectron spectra of doped graphitic carbon nanomaterials, and a reference for their binding energies that are vital for compositional analysis via XPS.

Laser annealing effects of the Raman laser on nitrogen implanted glassy carbon

International Nuclear Information System (INIS)

Barbara, D.; Prawer, S.; Jamieson, D.N.

1996-01-01

Raman analysis is a popular method of investigating crystallite sizes, ordering and the types of bonds that exist in ion irradiated carbon materials, namely graphite, diamond and glassy carbon (G.C.). In particular Raman spectroscopy is used in determining the tetrahedral bonding required for the elusive and potentially important new material called carbon nitride. Carbon nitride, β-C 3 N 4 , is predicted to exist in several forms. Forming the tetrahedral bond between C and N has proved troublesome bain of many experimenters. A proven method for synthesizing novel materials is ion implantation. Thus G.C. was implanted with N at low temperatures so that diffusion of the implanted N would be hindered. G.C. is a relatively hard, chemically inert, graphitic material. The opaque property of G.C. means that Raman spectroscopy will only give information about the structures that exist at the surface and near surface layers. It was decided, after observing conflicting Raman spectra at different laser powers, that an investigation of the laser annealing effects of the Raman laser on the N implanted G.C. was warranted. The results of the preliminary investigation of the effects of increasing the Raman laser power and determining a power density threshold for high dose N implanted G.C. are discussed. 4 refs., 4 figs

Carbon Micronymphaea: Graphene on Vertically Aligned Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Jong Won Choi

2013-01-01

Full Text Available This paper describes the morphology of carbon nanomaterials such as carbon nanotube (CNT, graphene, and their hybrid structure under various operating conditions during a one-step synthesis via plasma-enhanced chemical vapor deposition (PECVD. We focus on the synthetic aspects of carbon hybrid material composed of heteroepitaxially grown graphene on top of a vertical array of carbon nanotubes, called carbon micronymphaea. We characterize the structural features of this unique nanocomposite by uses of electron microscopy and micro-Raman spectroscopy. We observe carbon nanofibers, poorly aligned and well-aligned vertical arrays of CNT sequentially as the growth temperature increases, while we always discover the carbon hybrids, called carbon micronymphaea, at specific cooling rate of 15°C/s, which is optimal for the carbon precipitation from the Ni nanoparticles in this study. We expect one-pot synthesized graphene-on-nanotube hybrid structure poses great potential for applications that demand ultrahigh surface-to-volume ratios with intact graphitic nature and directional electronic and thermal transports.

Carbon Impact Analytics - Designing low carbon indices based on Carbon Impact Analytics indicators

International Nuclear Information System (INIS)

2016-01-01

Investors are increasingly exposed to carbon risks and now face the challenge of managing these risks and developing climate-resilient investment strategies. Carbon Impact Analytics (CIA), an innovative methodology for analyzing the full carbon impact of a portfolio or index, equips investors and asset managers with the tools necessary to reduce their climate-related risks but also to seize the opportunities offered by the ongoing energy transition. Investors, asset managers and other financial institutions may use CIA results to: - measure and manage risks, - optimize their contribution to the energy transition, - seize opportunities associated with climate change mitigation, - report on GHG emissions and savings (for regulatory purposes or voluntarily), - engage in dialogue with companies, - reallocate investment portfolios, - and build new low-carbon indices. In this report, Carbone 4 offers a detailed look into how CIA indicators can be used to either 1) reallocate an existing portfolio or index to achieve maximal carbon performance or 2) build new low carbon indices from the ground up, drawn from Carbone 4's ever-growing database of CIA-analyzed firms. Two main levers were used to optimize CIA output: 1. Sectorial reallocation: exclusion of fossil fuel-related sectors or insertion of low carbon pure players; 2. Intra-sectorial reallocation: best-in-class approach within a sector. Sectorial and intra-sectorial methods may be applied in conjunction with one another to maximize results. For example, a best-in-class + fossil fuel-free index may be constructed by first excluding the fossil fuel sector and then applying a CIA best-in-class approach to all remaining sectors. This report offers a detailed look into how CIA indicators can be used to rework portfolios or indices to maximize carbon performance or to build low carbon indices from the ground up. These methods are illustrated via two preliminary examples of indices designed by Carbone 4: the reallocated

Catalytic diastereoselective tandem conjugate addition-elimination reaction of Morita-Baylis-Hillman C adducts by C-C bond cleavage

KAUST Repository

Yang, Wenguo; Tan, Davin; Lee, Richmond; Li, Lixin; Pan, Yuanhang; Huang, Kuo-Wei; Tan, Choonhong; Jiang, Zhiyong

2012-01-01

Through the cleavage of the C-C bond, the first catalytic tandem conjugate addition-elimination reaction of Morita-Baylis-Hillman C adducts has been presented. Various S N2′-like C-, S-, and P-allylic compounds could be obtained with exclusive E

Carbon tetrachloride desorption from activated carbon

International Nuclear Information System (INIS)

Jonas, L.A.; Sansone, E.B.

1981-01-01

Carbon tetrachloride was desorbed from a granular activated carbon subsequent to its adsorption under various vapor exposure periods. The varied conditions of exposure resulted in a range of partially saturated carbon beds which, when followed by a constant flow rate for desorption, generated different forms of the desorbing concentration versus time curve. A method of analyzing the desorption curves is presented which permits extraction of the various desorbing rates from the different desorption and to relate this to the time required for such regeneration. The Wheeler desorption kinetic equation was used to calculate the pseudo first order desorption rate constant for the carbon. The desorption rate constant was found to increase monotonically with increasing saturation of the bed, permitting the calculation of the maximum desorption rate constant for the carbon at 100% saturation. The Retentivity Index of the carbon, defined as the dimensionless ratio of the adsorption to the desorption rate constant, was found to be 681

Funcionalização de nanotubos de Carbono Functionalization of carbon nanotubes

Directory of Open Access Journals (Sweden)

Antônio Gomes de Souza Filho

2007-01-01

Full Text Available Carbon nanotubes are very stable systems having considerable chemical inertness due to the strong covalent bonds of the carbon atoms on the nanotube surface. Many applications of carbon nanotubes require their chemical modification in order to tune/control their physico-chemical properties. One way of achieving this control is carrying out functionalization processes where atoms and molecules interact (covalent or non-covalent with the nanotubes. We review some of the progress that has been made in chemical functionalization of carbon nanotubes. Emphasis is given to chemical strategies, the most used techniques, and applications.

Multilayer oxidation resistant coating for SiC coated carbon/carbon composites at high temperature

International Nuclear Information System (INIS)

Li Hejun; Jiao Gengsheng; Li Kezhi; Wang Chuang

2008-01-01

To prevent carbon/carbon (C/C) composites from oxidation, a multilayer coating based on molybdenum disilicide and titanium disilicide was formed using a two-step pack cementation technique in argon atmosphere. XRD and SEM analysis showed that the internal coating was a bond SiC layer that acts as a buffer layer, and that the external multilayer coating formed in the two-step pack cementation was composed of two MoSi 2 -TiSi 2 -SiC layers. This coating, which is characterized by excellent thermal shock resistance, could effectively protect the composites from exposure to an oxidizing atmosphere at 1773 K for 79 h. The oxidation of the coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating

Carbon-carbon mirrors for exoatmospheric and space applications

Science.gov (United States)

Krumweide, Duane E.; Wonacott, Gary D.; Woida, Patrick M.; Woida, Rigel Q.; Shih, Wei

2007-09-01

The cost and leadtime associated with beryllium has forced the MDA and other defense agencies to look for alternative materials with similar structural and thermal properties. The use of carbon-carbon material, specifically in optical components has been demonstrated analytically in prior SBIR work at San Diego Composites. Carbon-carbon material was chosen for its low in-plane and through-thickness CTE (athermal design), high specific stiffness, near-zero coefficient of moisture expansion, availability of material (specifically c-c honeycomb for lightweight substrates), and compatibility with silicon monoxide (SiO) and silicon dioxide (SiO II) coatings. Subsequent development work has produced shaped carbon-carbon sandwich substrates which have been ground, polished, coated and figured using traditional optical processing. Further development has also been done on machined monolithic carbon-carbon mirror substrates which have also been processed using standard optical finishing techniques.

Quasiparticle and excitonic gaps of one-dimensional carbon chains.

Science.gov (United States)

Mostaani, E; Monserrat, B; Drummond, N D; Lambert, C J

2016-06-01

We report diffusion quantum Monte Carlo (DMC) calculations of the quasiparticle and excitonic gaps of hydrogen-terminated oligoynes and extended polyyne. The electronic gaps are found to be very sensitive to the atomic structure in these systems. We have therefore optimised the geometry of polyyne by directly minimising the DMC energy with respect to the lattice constant and the Peierls-induced carbon-carbon bond-length alternation. We find the bond-length alternation of polyyne to be 0.136(2) Å and the excitonic and quasiparticle gaps to be 3.30(7) and 3.4(1) eV, respectively. The DMC zone-centre longitudinal optical phonon frequency of polyyne is 2084(5) cm(-1), which is consistent with Raman spectroscopic measurements for large oligoynes.

Ultrafast fragmentation dynamics of triply charged carbon dioxide: Vibrational-mode-dependent molecular bond breakage

Science.gov (United States)

Yang, HongJiang; Wang, Enliang; Dong, WenXiu; Gong, Maomao; Shen, Zhenjie; Tang, Yaguo; Shan, Xu; Chen, Xiangjun

2018-05-01

The a b i n i t i o molecular dynamics (MD) simulations using an atom-centered density matrix propagation method have been carried out to investigate the fragmentation of the ground-state triply charged carbon dioxide, CO23 +→C+ + Oa+ + Ob+ . Ten thousands of trajectories have been simulated. By analyzing the momentum correlation of the final fragments, it is demonstrated that the sequential fragmentation dominates in the three-body dissociation, consistent with our experimental observations which were performed by electron collision at impact energy of 1500 eV. Furthermore, the MD simulations allow us to have detailed insight into the ultrafast evolution of the molecular bond breakage at a very early stage, within several tens of femtoseconds, and the result shows that the initial nuclear vibrational mode plays a decisive role in switching the dissociation pathways.

Interaction between fullerene halves C{sub n} (n ≤ 40) and single wall carbon nanotube

Energy Technology Data Exchange (ETDEWEB)

Sharma, Amrish, E-mail: amrish99@gmail.com; Kaur, Sandeep, E-mail: sipusukhn@gmail.com [Department of Physics, Punjabi University, Patiala (India); Mudahar, Isha, E-mail: isha@pbi.ac.in [Department of Basic and Applied Sciences, Punjabi University, Patiala (India)

2016-05-06

We have investigated the structural and electronic properties of carbon nanotube with small fullerene halves C{sub n} (n ≤ 40) which are covalently bonded to the side wall of an armchair single wall carbon nanotube (SWCNT) using first principle method based on density functional theory. The fullerene size results in weak bonding between fullerene halves and carbon nanotube (CNT). Further, it was found that the C-C bond distance that attaches the fullerene half and CNT is of the order of 1.60 Å. The calculated binding energies indicate the stability of the complexes formed. The HOMO-LUMO gaps and electron density of state plots points towards the metallicity of the complex formed. Our calculations on charge transfer reveal that very small amount of charge is transferred from CNT to fullerene halves.

Structural Characterization of N-Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N-C Cleavage.

Science.gov (United States)

Hu, Feng; Lalancette, Roger; Szostak, Michal

2016-04-11

Herein, we describe the first structural characterization of N-alkylated twisted amides prepared directly by N-alkylation of the corresponding non-planar lactams. This study provides the first experimental evidence that N-alkylation results in a dramatic increase of non-planarity around the amide N-C(O) bond. Moreover, we report a rare example of a molecular wire supported by the same amide C=O-Ag bonds. Reactivity studies demonstrate rapid nucleophilic addition to the N-C(O) moiety of N-alkylated amides, indicating the lack of n(N) to π*(C=O) conjugation. Most crucially, we demonstrate that N-alkylation activates the otherwise unreactive amide bond towards σ N-C cleavage by switchable coordination. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon Sequestered, Carbon Displaced and the Kyoto Context

International Nuclear Information System (INIS)

Marland, G.; Schlamadinger, B.

1999-01-01

The integrated system that embraces forest management, forest products, and land-use change impacts the global carbon cycle - and hence the net emission of the greenhouse gas carbon dioxide - in four fundamental ways. Carbon is stored in living and dead biomass, carbon is stored in wood products and landfills, forest products substitute in the market place for products made from other materials, and forest harvests can be used wholly or partially to displace fossil fuels in the energy sector. Implementation of the Kyoto Protocol to the United Nations Framework Convention on Climate Change would result in the creation of international markets for carbon dioxide emissions credits, but the current Kyoto text does not treat all carbon identically. We have developed a carbon accounting model, GORCAM, to examine a variety of scenarios for land management and the production of forest products. In this paper we explore, for two simple scenarios of forest management, the carbon flows that occur and how these might be accounted for under the Kyoto text. The Kyoto protocol raises questions about what activities can result in emissions credits, which carbon reservoirs will be counted, who will receive the credits, and how much credit will be available? The Kyoto Protocol would sometimes give credits for carbon sequestered, but it would always give credits when fossil-fuel carbon dioxide emissions are displaced

Retention and effective diffusion of model metabolites on porous graphitic carbon.

Science.gov (United States)

Lunn, Daniel B; Yun, Young J; Jorgenson, James W

2017-12-29

The study of metabolites in biological samples is of high interest for a wide range of biological and pharmaceutical applications. Reversed phase liquid chromatography is a common technique used for the separation of metabolites, but it provides little retention for polar metabolites. An alternative to C18 bonded phases, porous graphitic carbon has the ability to provide significant retention for both non-polar and polar analytes. The goal of this work is to study the retention and effective diffusion properties of porous graphitic carbon, to see if it is suitable for the wide injection bands and long run times associated with long, packed capillary-scale separations. The retention of a set of standard metabolites was studied for both stationary phases over a wide range of mobile phase conditions. This data showed that porous graphitic carbon benefits from significantly increased retention (often >100 fold) under initial gradient conditions for these metabolites, suggesting much improved ability to focus a wide injection band at the column inlet. The effective diffusion properties of these columns were studied using peak-parking experiments with the standard metabolites under a wide range of retention conditions. Under the high retention conditions, which can be associated with retention after injection loading for gradient separations, D eff /D m ∼0.1 for both the C18-bonded and porous graphitic carbon columns. As C18 bonded particles are widely, and successfully utilized for long gradient separations without issue of increasing peak width from longitudinal diffusion, this suggests that porous graphitic carbon should be amenable for long runtime gradient separations as well. Copyright © 2017 Elsevier B.V. All rights reserved.

Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

Science.gov (United States)

Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

2016-07-01

The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

Metal corrosion in a supercritical carbon dioxide - liquid sodium power cycle.

Energy Technology Data Exchange (ETDEWEB)

Moore, Robert Charles; Conboy, Thomas M.

2012-02-01

A liquid sodium cooled fast reactor coupled to a supercritical carbon dioxide Brayton power cycle is a promising combination for the next generation nuclear power production process. For optimum efficiency, a microchannel heat exchanger, constructed by diffusion bonding, can be used for heat transfer from the liquid sodium reactor coolant to the supercritical carbon dioxide. In this work, we have reviewed the literature on corrosion of metals in liquid sodium and carbon dioxide. The main conclusions are (1) pure, dry CO{sub 2} is virtually inert but can be highly corrosive in the presence of even ppm concentrations of water, (2) carburization and decarburization are very significant mechanism for corrosion in liquid sodium especially at high temperature and the mechanism is not well understood, and (3) very little information could be located on corrosion of diffusion bonded metals. Significantly more research is needed in all of these areas.

Synthesis and Characterization Carbon Nanotubes Doped Carbon Aerogels

Science.gov (United States)

Xu, Yuelong; Yan, Meifang; Liu, Zhenfa

2017-12-01

Polycondensation of phloroglucinol, resorcinol and formaldehyde with carbon nanotube (CNT) as the additives, using sodium carbonate as the catalyst, leads to the formation of CNT - doped carbon aerogels. The structure of carbon aerogels (CAs) with carbon nanotubes (CNTs) were characterized by X-ray diffraction and scanning electron microscopy. The specific surface area, pore size distribution and pore volume were measured by surface area analyzer. The results show that when the optimum doping dosage is 5%, the specific surface area of CNT - doped carbon aerogel is up to 665 m2 g-1 and exhibit plentiful mesoporous.

Carbon Management In the Post-Cap-and-Trade Carbon Economy

Science.gov (United States)

DeGroff, F. A.

2013-12-01

This abstract outlines an economic model that integrates carbon externalities seamlessly into the national and international economies. The model incorporates a broad carbon metric used to value all carbon in the biosphere, as well as all transnational commerce. The model minimizes the cost associated with carbon management, and allows for the variation in carbon avidity between jurisdictions. When implemented over time, the model reduces the deadweight loss while minimizing social cost, thus maximizing the marginal social benefit commonly associated with Pigouvian taxes. Once implemented, the model provides a comprehensive economic construct for governments, industry and consumers to efficiently weigh the cost of carbon, and effectively participate in helping to reduce their direct and indirect use of carbon, while allowing individual jurisdictions to decide their own carbon value, without the need for explicit, express agreement of all countries. The model uses no credits, requires no caps, and matches climate changing behavior to costs. The steps to implement the model for a particular jurisdiction are: 1) Define the Carbon Metric to value changes in Carbon Quality. 2) Apply the Carbon Metric to assess the Carbon Toll a) for all changes in Carbon Quality and b) for imports and exports. This economic model has 3 clear advantages. 1) The carbon pricing and cost scheme use existing and generally accepted accounting methodologies to ensure the veracity and verifiability of carbon management efforts with minimal effort and expense using standard auditing protocols. Implementing this economic model will not require any special training, tools, or systems for any entity to achieve their minimum carbon target goals within their jurisdictional framework. 2) Given the spectrum of carbon affinities worldwide, the model recognizes and provides for flexible carbon pricing regimes, but does not penalize domestic carbon-consuming producers subject to imports from exporters in

Measurement of carbon capture efficiency and stored carbon leakage

Science.gov (United States)

Keeling, Ralph F.; Dubey, Manvendra K.

2013-01-29

Data representative of a measured carbon dioxide (CO.sub.2) concentration and of a measured oxygen (O.sub.2) concentration at a measurement location can be used to determine whether the measured carbon dioxide concentration at the measurement location is elevated relative to a baseline carbon dioxide concentration due to escape of carbon dioxide from a source associated with a carbon capture and storage process. Optionally, the data can be used to quantify a carbon dioxide concentration increase at the first location that is attributable to escape of carbon dioxide from the source and to calculate a rate of escape of carbon dioxide from the source by executing a model of gas-phase transport using at least the first carbon dioxide concentration increase. Related systems, methods, and articles of manufacture are also described.

Thermodynamics and vibrational study of hydrogenated carbon nanotubes: A DFT study

Science.gov (United States)

Khalil, Rana M. Arif; Hussain, Fayyaz; Rana, Anwar Manzoor; Imran, Muhammad

2018-02-01

Thermodynamic stability of the hydrogenated carbon nanotubes has been explored in the chemisorption limit. Statistical physics and density functional theory calculations have been used to predict hydrogen release temperatures at standard pressure in zigzag and armchair carbon nanotubes. It is found that hydrogen release temperatures decrease with increase in diameters of hydrogenated zigzag carbon nanotubes (CNTs) but opposite trend is noted in armchair CNTs at standard pressure of 1 bar. The smaller diameter hydrogenated zigzag CNTs have large values of hydrogen release temperature due to the stability of Csbnd H bonds. The vibrational density of states for hydrogenated carbon nanotubes have been calculated to confirm the Csbnd H stretching mode caused by sp3 hybridization.

Effect of Interface Modified by Graphene on the Mechanical and Frictional Properties of Carbon/Graphene/Carbon Composites

Science.gov (United States)

Yang, Wei; Luo, Ruiying; Hou, Zhenhua

2016-01-01

In this work, we developed an interface modified by graphene to simultaneously improve the mechanical and frictional properties of carbon/graphene/carbon (C/G/C) composite. Results indicated that the C/G/C composite exhibits remarkably improved interfacial bonding mode, static and dynamic mechanical performance, thermal conductivity, and frictional properties in comparison with those of the C/C composite. The weight contents of carbon fibers, graphene and pyrolytic carbon are 31.6, 0.3 and 68.1 wt %, respectively. The matrix of the C/G/C composite was mainly composed of rough laminar (RL) pyrocarbon. The average hardness by nanoindentation of the C/G/C and C/C composite matrices were 0.473 and 0.751 GPa, respectively. The flexural strength (three point bending), interlaminar shear strength (ILSS), interfacial debonding strength (IDS), internal friction and storage modulus of the C/C composite were 106, 10.3, 7.6, 0.038 and 12.7 GPa, respectively. Those properties of the C/G/C composite increased by 76.4%, 44.6%, 168.4% and 22.8%, respectively, and their internal friction decreased by 42.1% in comparison with those of the C/C composite. Owing to the lower hardness of the matrix, improved fiber/matrix interface bonding strength, and self-lubricating properties of graphene, a complete friction film was easily formed on the friction surface of the modified composite. Compared with the C/C composite, the C/G/C composite exhibited stable friction coefficients and lower wear losses at simulating air-plane normal landing (NL) and rejected take-off (RTO). The method appears to be a competitive approach to improve the mechanical and frictional properties of C/C composites simultaneously. PMID:28773613

Supercritical carbon dioxide versus toluene as reaction media in silica functionalisation: Synthesis and characterisation of bonded aminopropyl silica intermediate.

Science.gov (United States)

Ashu-Arrah, Benjamin A; Glennon, Jeremy D

2017-06-09

This research reports supercritical carbon dioxide versus toluene as reaction media in silica functionalisation for use in liquid chromatography. Bonded aminopropyl silica (APS) intermediates were prepared when porous silica particles (Exsil-pure, 3μm) were reacted with 3-aminopropyltriethoxysilane (3-APTES) or N,N-dimethylaminopropyltrimethoxysilane (DMAPTMS) using supercritical carbon dioxide (sc-CO 2 ) and toluene as reaction media. Covalent bonding to silica was confirmed using elemental microanalysis (CHN), thermogravimetric analysis (TGA), zeta potential (ξ), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, scanning electron microscopy (SEM) and solid-state nuclear magnetic resonance (CP/MAS NMR) spectroscopy. The results demonstrate that under sc-CO 2 conditions of 100°C/414bar in a substantial reduced time of 3h, the surface coverage of APS (evaluated from%C obtained from elemental analysis) prepared with APTES (%C: 8.03, 5.26μmol/m -2 ) or DMAPTES (%C: 5.12, 4.58μmol/m 2 ) is somewhat higher when compared to organic based reactions under reflux in toluene at a temperature of 110°C in 24h with APTES (%C: 7.33, 4.71μmol/m 2 ) and DMAPTMS (%C: 4.93, 4.38μmol/m 2 ). Zeta potential measurements revealed a change in electrostatic surface charge from negative values for bare Exsil-pure silica to positive for functionalised APS materials indicating successful immobilization of the aminosilane onto the surface of silica. Copyright © 2017 Elsevier B.V. All rights reserved.

Biomass derived porous nitrogen doped carbon for electrochemical devices

Directory of Open Access Journals (Sweden)

Litao Yan

2017-04-01

Full Text Available Biomass derived porous nanostructured nitrogen doped carbon (PNC has been extensively investigated as the electrode material for electrochemical catalytic reactions and rechargeable batteries. Biomass with and without containing nitrogen could be designed and optimized to prepare PNC via hydrothermal carbonization, pyrolysis, and other methods. The presence of nitrogen in carbon can provide more active sites for ion absorption, improve the electronic conductivity, increase the bonding between carbon and sulfur, and enhance the electrochemical catalytic reaction. The synthetic methods of natural biomass derived PNC, heteroatomic co- or tri-doping into biomass derived carbon and the application of biomass derived PNC in rechargeable Li/Na batteries, high energy density Li–S batteries, supercapacitors, metal-air batteries and electrochemical catalytic reaction (oxygen reduction and evolution reactions, hydrogen evolution reaction are summarized and discussed in this review. Biomass derived PNCs deliver high performance electrochemical storage properties for rechargeable batteries/supercapacitors and superior electrochemical catalytic performance toward hydrogen evolution, oxygen reduction and evolution, as promising electrodes for electrochemical devices including battery technologies, fuel cell and electrolyzer. Keywords: Biomass, Nitrogen doped carbon, Batteries, Fuel cell, Electrolyzer

Neutron scattering investigation of carbon/carbon composites

International Nuclear Information System (INIS)

Prem, M.; Krexner, G.; Peterlik, H.

2005-01-01

Full text: Carbon/Carbon (C/C) composites, built up from bi-directionally woven fabrics from PAN based carbon fibers, pre-impregnated with phenolic resin followed by pressure curing and carbonization at 1000 o C and a final heat treatment at either 1800 o C or 2400 o C, were investigated by means of small-angle as well as wideangle elastic neutron scattering. Sample orientations arranging the carbon fibers parallel and perpendicular to the incoming beam were examined. Structural features of the composites, i.e. of the fibers as well as the inherently existing pores, are presented and the influence of the heat treatment on the structural properties is discussed. (author)

Fracture of Carbon Nanotube - Amorphous Carbon Composites: Molecular Modeling

Science.gov (United States)

Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

2015-01-01

Carbon nanotubes (CNTs) are promising candidates for use as reinforcements in next generation structural composite materials because of their extremely high specific stiffness and strength. They cannot, however, be viewed as simple replacements for carbon fibers because there are key differences between these materials in areas such as handling, processing, and matrix design. It is impossible to know for certain that CNT composites will represent a significant advance over carbon fiber composites before these various factors have been optimized, which is an extremely costly and time intensive process. This work attempts to place an upper bound on CNT composite mechanical properties by performing molecular dynamics simulations on idealized model systems with a reactive forcefield that permits modeling of both elastic deformations and fracture. Amorphous carbon (AC) was chosen for the matrix material in this work because of its structural simplicity and physical compatibility with the CNT fillers. It is also much stiffer and stronger than typical engineering polymer matrices. Three different arrangements of CNTs in the simulation cell have been investigated: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. The SWNT and MWNT array systems are clearly idealizations, but the SWNT bundle system is a step closer to real systems in which individual tubes aggregate into large assemblies. The effect of chemical crosslinking on composite properties is modeled by adding bonds between the CNTs and AC. The balance between weakening the CNTs and improving fiber-matrix load transfer is explored by systematically varying the extent of crosslinking. It is, of course, impossible to capture the full range of deformation and fracture processes that occur in real materials with even the largest atomistic molecular dynamics simulations. With this limitation in mind, the simulation results reported here provide a plausible upper limit on

Making Activated Carbon by Wet Pressurized Pyrolysis

Science.gov (United States)

Fisher, John W.; Pisharody, Suresh; Wignarajah, K.; Moran, Mark

2006-01-01

A wet pressurized pyrolysis (wet carbonization) process has been invented as a means of producing activated carbon from a wide variety of inedible biomass consisting principally of plant wastes. The principal intended use of this activated carbon is room-temperature adsorption of pollutant gases from cooled incinerator exhaust streams. Activated carbon is highly porous and has a large surface area. The surface area depends strongly on the raw material and the production process. Coconut shells and bituminous coal are the primary raw materials that, until now, were converted into activated carbon of commercially acceptable quality by use of traditional production processes that involve activation by use of steam or carbon dioxide. In the wet pressurized pyrolysis process, the plant material is subjected to high pressure and temperature in an aqueous medium in the absence of oxygen for a specified amount of time to break carbon-oxygen bonds in the organic material and modify the structure of the material to obtain large surface area. Plant materials that have been used in demonstrations of the process include inedible parts of wheat, rice, potato, soybean, and tomato plants. The raw plant material is ground and mixed with a specified proportion of water. The mixture is placed in a stirred autoclave, wherein it is pyrolized at a temperature between 450 and 590 F (approximately between 230 and 310 C) and a pressure between 1 and 1.4 kpsi (approximately between 7 and 10 MPa) for a time between 5 minutes and 1 hour. The solid fraction remaining after wet carbonization is dried, then activated at a temperature of 500 F (260 C) in nitrogen gas. The activated carbon thus produced is comparable to commercial activated carbon. It can be used to adsorb oxides of sulfur, oxides of nitrogen, and trace amounts of hydrocarbons, any or all of which can be present in flue gas. Alternatively, the dried solid fraction can be used, even without the activation treatment, to absorb

Characterization of sp3 bond content of carbon films deposited by high power gas injection magnetron sputtering method by UV and VIS Raman spectroscopy

Science.gov (United States)

Zdunek, Krzysztof; Chodun, Rafał; Wicher, Bartosz; Nowakowska-Langier, Katarzyna; Okrasa, Sebastian

2018-04-01

This paper presents the results of investigations of carbon films deposited by a modified version of the magnetron sputtering method - HiPGIMS (High Power Gas Injection Magnetron Sputtering). In this experiment, the magnetron system with inversely polarized electrodes (sputtered cathode at ground potential and positively biased, spatially separated anode) was used. This arrangement allowed us to conduct the experiment using voltages ranging from 1 to 2 kV and a power supply system equipped with 25/50 μF capacitor battery. Carbon films were investigated by VIS/UV Raman spectroscopy. Sp3/sp2 bonding ratio was evaluated basing the elementary components of registered spectra. Our investigation showed that sp3 bond content increases with discharge power but up to specific value only. In extreme conditions of generating plasma impulses, we detected a reversed relation of the sp3/sp2 ratio. In our opinion, a energy of plasma pulse favors nucleation of a sp3 phase because of a relatively higher ionization state but in extreme cases the influence of energy is reversed.

Characterization of sp3 bond content of carbon films deposited by high power gas injection magnetron sputtering method by UV and VIS Raman spectroscopy.

Science.gov (United States)

Zdunek, Krzysztof; Chodun, Rafał; Wicher, Bartosz; Nowakowska-Langier, Katarzyna; Okrasa, Sebastian

2018-04-05

This paper presents the results of investigations of carbon films deposited by a modified version of the magnetron sputtering method - HiPGIMS (High Power Gas Injection Magnetron Sputtering). In this experiment, the magnetron system with inversely polarized electrodes (sputtered cathode at ground potential and positively biased, spatially separated anode) was used. This arrangement allowed us to conduct the experiment using voltages ranging from 1 to 2kV and a power supply system equipped with 25/50μF capacitor battery. Carbon films were investigated by VIS/UV Raman spectroscopy. Sp 3 /sp 2 bonding ratio was evaluated basing the elementary components of registered spectra. Our investigation showed that sp 3 bond content increases with discharge power but up to specific value only. In extreme conditions of generating plasma impulses, we detected a reversed relation of the sp 3 /sp 2 ratio. In our opinion, a energy of plasma pulse favors nucleation of a sp 3 phase because of a relatively higher ionization state but in extreme cases the influence of energy is reversed. Copyright © 2018 Elsevier B.V. All rights reserved.

Mercury bonds with carbon (OC and EC) in small aerosols (PM1) in the urbanized coastal zone of the Gulf of Gdansk (southern Baltic).

Science.gov (United States)

Lewandowska, A U; Bełdowska, M; Witkowska, A; Falkowska, L; Wiśniewska, K

2018-08-15

PM1 aerosols were collected at the coastal station in Gdynia between 1st January and 31st December 2012. The main purpose of the study was to determine the variability in concentrations of mercury Hg(p), organic carbon (OC) and elemental carbon (EC) in PM1 aerosols under varying synoptic conditions in heating and non-heating periods. Additionally, sources of origin and bonds of mercury with carbon species were identified. The highest concentrations of Hg(p), OC and EC were found during the heating period. Then all analyzed PM1 components had a common, local origin related to the consumption of fossil fuels for heating purposes under conditions of lower air temperatures and poor dispersion of pollutants. Long periods without precipitation also led to the increase in concentration of all measured PM1 compounds. In heating period mercury correlated well with elemental carbon and primary and secondary organic carbon when air masses were transported from over the land. At that time, the role of transportation was of minor importance. In the non-heating period, the concentration of all analyzed compounds were lower than in the heating period, which could be associated with the reduced influence of combustion processes, higher precipitation and, in the case of mercury, also the evaporation of aerosols at higher air temperatures. However, when air masses were transported from over the sea or from the port/shipyard areas the mercury concentration increased significantly. In the first case higher air humidity, solar radiation and ozone concentration as well as the presence of marine aerosols could further facilitate the conversion of gaseous mercury into particulate mercury and its concentration increase. In the second case Hg(p) could be adsorbed on particles rich in elemental carbon and primary organic carbon emitted from ships. Copyright © 2018 Elsevier Inc. All rights reserved.

Carbon Bonds and the saving of energy; Bonos de carbono y el ahorro de energia

Energy Technology Data Exchange (ETDEWEB)

Alvarez Ramirez, Alejandro [NovaEnergia (Mexico)

2005-07-01

This document deals with the development of the carbon bond project, the energy saving and the entry into force of the Kyoto Protocol at a world-wide level. In this project Mexico opts for a development model in which the economic growth brakes ties with the discharge of greenhouse effect gases and in which the progress does not mean more damages to our planet. [Spanish] Este documento trata sobre el desarrollo del proyecto de bonos de carbono, ahorro de energia y la entrada en vigor del Protocolo de Kyoto a nivel mundial, en el cual Mexico opta por un modelo de desarrollo en el que el crecimiento economico esta desvinculado de la emision de gases de efecto invernadero y en donde el progreso no signifique mas danos a nuestro planeta.

Oxidative C-C bond cleavage of 1,2-diols by silver(II)

International Nuclear Information System (INIS)

Kumar, A.

1981-01-01

Oxidation of ethylene glycol and related compounds by Ag(II) has been investigated. Complexation of these substrates by Ag(II) precedes their oxidation. Oxidation occurs through electron transfer from an OH group to the Ag(II) within the complex resulting in the formation of alkoxyl-type radicals. The radicals thus formed undergo β-scission to give cleavage products. For ethylene glycol a complexation rate 1.3 x 10 6 M -1 s -1 and oxidation rate approx. 3 x 10 3 s -1 were observed. A general trend for the type of the substrates which would undergo C-C bond scission by Ag(II) is discussed

Spectroscopic and thermal characterization of carbon nanotubes functionalized through diazonium salt reduction

International Nuclear Information System (INIS)

Pandurangappa, Malingappa; Ramakrishnappa, Thippeswamy

2010-01-01

Chemical reduction of anthraquinone diazonium chloride (Fast Red AL salt) in presence of hypophosphorous acid and carbon nanotubes results in anthraquinonyl functionalized carbon nanotubes. The surface functionalized moieties have been examined electrochemically by immobilizing them onto the surface of basal plane pyrolytic graphite electrode and studying its voltammetric behaviour. The effect of pH, and scan rate has revealed that the modified species are confined on the electrode surface. The spectroscopic characterization of the modified single walled carbon nanotubes using Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy, thermogravimetric analysis and transmission electron microscopy have revealed that the modifier molecules are covalently bonded on the surface of carbon nanotubes.

Spectroscopic and thermal characterization of carbon nanotubes functionalized through diazonium salt reduction

Energy Technology Data Exchange (ETDEWEB)

Pandurangappa, Malingappa, E-mail: mprangachem@gmail.com [Department of Chemistry, Bangalore University, Central College Campus, Dr Ambedkar Veedhi, Bangalore 560 001 (India); Ramakrishnappa, Thippeswamy [Department of Chemistry, Bangalore University, Central College Campus, Dr Ambedkar Veedhi, Bangalore 560 001 (India)

2010-08-01

Chemical reduction of anthraquinone diazonium chloride (Fast Red AL salt) in presence of hypophosphorous acid and carbon nanotubes results in anthraquinonyl functionalized carbon nanotubes. The surface functionalized moieties have been examined electrochemically by immobilizing them onto the surface of basal plane pyrolytic graphite electrode and studying its voltammetric behaviour. The effect of pH, and scan rate has revealed that the modified species are confined on the electrode surface. The spectroscopic characterization of the modified single walled carbon nanotubes using Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy, thermogravimetric analysis and transmission electron microscopy have revealed that the modifier molecules are covalently bonded on the surface of carbon nanotubes.

Energetics of carbon nanotubes: insights from calorimetry and neutron scattering

International Nuclear Information System (INIS)

Levchenko, Andrey A.; Kolesnikov, Alexander I.; Trofymluk, Olga; Navrotsky, Alexandra

2011-01-01

Single-wall carbon nanotubes (SWCNTs) are only moderately less stable than graphite, and are significantly more stable than their fullerene counterparts. They are 7 kJ mol-1 metastable relative to graphite, and just 5 kJ mol-1 less stable than diamond. Despite striking differences in vibrational dynamics of carbon atoms in SWCNTs and graphite, their thermodynamic properties at room and higher temperatures are dominated by the same set of high energy vibrations, reflected in very similar vibrational entropies. However, the energetics of SWCNT are governed by counter-acting enthalpic contributions of the diameter-dependent strain induced by the roll-up of graphene sheets into tubes and of carbon-carbon bonding at the edges of graphene sheets in the graphite, but not the specifics of phonon density of states (PDOS).

Porous carbons prepared by direct carbonization of MOFs for supercapacitors

Science.gov (United States)

Yan, Xinlong; Li, Xuejin; Yan, Zifeng; Komarneni, Sridhar

2014-07-01

Three porous carbons were prepared by direct carbonization of HKUST-1, MOF-5 and Al-PCP without additional carbon precursors. The carbon samples obtained by carbonization at 1073 K were characterized by XRD, TEM and N2 physisorption techniques followed by testing for electrochemical performance. The BET surface areas of the three carbons were in the range of 50-1103 m2/g. As electrode materials for supercapacitor, the MOF-5 and Al-PCP derived carbons displayed the ideal capacitor behavior, whereas the HKUST-1 derived carbon showed poor capacitive behavior at various sweep rates and current densities. Among those carbon samples, Al-PCP derived carbons exhibited highest specific capacitance (232.8 F/g) in 30% KOH solution at the current density of 100 mA/g.

Carbon futures and macroeconomic risk factors. A view from the EU ETS

International Nuclear Information System (INIS)

Chevallier, Julien

2009-01-01

This article examines the empirical relationship between the returns on carbon futures - a new class of commodity assets traded since 2005 on the European Union Emissions Trading Scheme (EU ETS) - and changes in macroeconomic conditions. By using variables which possess forecast power for equity and commodity returns, we document that carbon futures returns may be weakly forecast on the basis of two variables from the stock and bond markets, i.e. equity dividend yields and the 'junk bond' premium. Our results also suggest that the forecast abilities of two variables related to interest rates variation and economic trends on global commodity markets, respectively the U.S. Treasury bill yields and the excess return on the Reuters/CRB Index, are not robust on the carbon market. This latter result reinforces the belief that the EU ETS is currently operating as a very specific commodity market, with distinct fundamentals linked to allowance supply and power demand. The sensitivity of carbon futures to macroeconomic influences is carefully identified following a sub-sample decomposition before and after August 2007, which attempts to take into account the potential impact of the 'credit crunch' crisis. Collectively, these results challenge the market observers' viewpoint that carbon futures prices are immediately correlated with changes in the macroeconomic environment, and rather suggest that the carbon market is only remotely connected to macroeconomic variables. The economic logic behind these results may be related to the fuel-switching behavior of power producers in influencing primarily carbon futures price changes. (author)

Water Pollutants Adsorption through an Enhanced Activated Carbon Derived from Agriculture Waste

Directory of Open Access Journals (Sweden)

Mojtaba Fazeli

2016-09-01

Full Text Available Background & Aims of the Study: A high nitrate and arsenic concentration in water resources represent a potential risk to the environment and public health. The present work improved a chemo-physically modified activated carbon derived from walnut shells as an adsorbent to improve nitrate and arsenic removal ability from water. Materials & Methods: To increase removal efficiency, activated carbon surface characteristics were improved by acidification. Chemical activation was achieved when the carbon was mixed with water and 5% (v/v phosphoric acid. After adsorbent preparation, the contact time, pH and the initial concentration were studied as variables. Results:  The effective pH for adsorption onto activated carbon was 6.5. The results indicated that 70 s and 3 mins was the sufficient time to attain equilibrium for a maximum removal efficiency of 78.44% and 98% for nitrate and arsenic, respectively. The adsorption capacity of the adsorbent was 10.60 mg nitrate/g carbon and 120 μg arsenic/g carbon. Removal obeyed the Langmuir isotherm and pseudo-second-order kinetic model. Conclusion: The results showed a noticeable improvement in activated walnut-shell carbon absorbance (improvement in crystalline structure, chemical bonds, and morphology of micropores by chemo-physical activation. Chemo-physical activation increased the surface area of the adsorbent from 1067 to 1437 m2g‒1 and decreased the mean pore size from 3.28 to 2.08 nm. The characterization results showed the major reasons of adsorption could be structure, size and distributions of pores, high surface area and chemical bonds.

Radiation damage in carbon-carbon composites: Structure and property effects

International Nuclear Information System (INIS)

Burchell, T.D.

1995-01-01

Carbon-carbon composites are an attractive choice for fusion reactor plasma facing components because of their low atomic number, superior thermal shock resistance, and low neutron activation. Next generation tokamak reactors such as the International Thermonuclear Experimental Reactor (ITER), will require high thermal conductivity carbon-carbon composites and other materials, such as beryllium, to protect their plasma facing components from the anticipated high heat fluxes. Moreover, ignition machines such as ITER will produce a large neutron flux. Consequently, the influence of neutron damage on the structure and properties of carbon-carbon composite materials must be evaluated. Data from two irradiation experiments are reported and discussed here. Carbon-carbon composite materials were irradiated in target capsules in the High Flux Isotope Reactor (HAIR) at Oak Ridge National Laboratory (ORAL). A peak damage dose of 4.7 displacements per atom (da) at an irradiation temperature of ∼600 degrees C was attained. The carbon materials irradiated here included unidirectional, two- directional, and three-directional carbon-carbon composites. Irradiation induced dimensional changes are reported for the materials and related to single crystal dimensional changes through fiber and composite structural models. Moreover, carbon-carbon composite material dimensional changes are discussed in terms of their architecture, fiber type, and graphitization temperature. Neutron irradiation induced reductions in the thermal conductivity of two, three-directional carbon-carbon composites are reported, and the recovery of thermal conductivity due to thermal annealing is demonstrated. Irradiation induced strength changes are reported for several carbon-carbon composite materials and are explained in terms of in-crystal and composite structural effects

Laser annealing effects of the Raman laser on nitrogen implanted glassy carbon

Energy Technology Data Exchange (ETDEWEB)

Barbara, D.; Prawer, S.; Jamieson, D.N. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

1996-12-31

Raman analysis is a popular method of investigating crystallite sizes, ordering and the types of bonds that exist in ion irradiated carbon materials, namely graphite, diamond and glassy carbon (G.C.). In particular Raman spectroscopy is used in determining the tetrahedral bonding required for the elusive and potentially important new material called carbon nitride. Carbon nitride, {beta}-C{sub 3}N{sub 4}, is predicted to exist in several forms. Forming the tetrahedral bond between C and N has proved troublesome bain of many experimenters. A proven method for synthesizing novel materials is ion implantation. Thus G.C. was implanted with N at low temperatures so that diffusion of the implanted N would be hindered. G.C. is a relatively hard, chemically inert, graphitic material. The opaque property of G.C. means that Raman spectroscopy will only give information about the structures that exist at the surface and near surface layers. It was decided, after observing conflicting Raman spectra at different laser powers, that an investigation of the laser annealing effects of the Raman laser on the N implanted G.C. was warranted. The results of the preliminary investigation of the effects of increasing the Raman laser power and determining a power density threshold for high dose N implanted G.C. are discussed. 4 refs., 4 figs.

Laser annealing effects of the Raman laser on nitrogen implanted glassy carbon

Energy Technology Data Exchange (ETDEWEB)

Barbara, D; Prawer, S; Jamieson, D N [Melbourne Univ., Parkville, VIC (Australia). School of Physics

1997-12-31

Raman analysis is a popular method of investigating crystallite sizes, ordering and the types of bonds that exist in ion irradiated carbon materials, namely graphite, diamond and glassy carbon (G.C.). In particular Raman spectroscopy is used in determining the tetrahedral bonding required for the elusive and potentially important new material called carbon nitride. Carbon nitride, {beta}-C{sub 3}N{sub 4}, is predicted to exist in several forms. Forming the tetrahedral bond between C and N has proved troublesome bain of many experimenters. A proven method for synthesizing novel materials is ion implantation. Thus G.C. was implanted with N at low temperatures so that diffusion of the implanted N would be hindered. G.C. is a relatively hard, chemically inert, graphitic material. The opaque property of G.C. means that Raman spectroscopy will only give information about the structures that exist at the surface and near surface layers. It was decided, after observing conflicting Raman spectra at different laser powers, that an investigation of the laser annealing effects of the Raman laser on the N implanted G.C. was warranted. The results of the preliminary investigation of the effects of increasing the Raman laser power and determining a power density threshold for high dose N implanted G.C. are discussed. 4 refs., 4 figs.

Rivers of Carbon: Carbon Fluxes in a Watershed Context

Science.gov (United States)

Wohl, E.; Tom, B.; Hovius, N.

2017-12-01

Research within the past decade has identified the roles of diverse terrestrial processes in mobilizing terrestrial carbon from bedrock, soil, and vegetation and in redistributing this carbon among the atmosphere, biota, geosphere, and oceans. Rivers are central to carbon redistribution, serving as the primary initial receptor of mobilized terrestrial carbon, as well as governing the proportions of carbon sequestered within sediment, transported to oceans, or released to the atmosphere. We use a riverine carbon budget to examine how key questions regarding carbon dynamics can be addressed across diverse spatial and temporal scales from sub-meter areas over a few hours on a single gravel bar to thousands of square kilometers over millions of years across an entire large river network. The portion of the budget applying to the active channel(s) takes the form of ,in which Cs is organic carbon storage over time t. Inputs are surface and subsurface fluxes from uplands (CIupl) and the floodplain (CIfp), including fossil, soil, and biospheric organic carbon; surface and subsurface fluxes of carbon dioxide to the channel (CICO2); and net primary productivity in the channel (CINPP). Outputs occur via respiration within the channel and carbon dioxide emissions (COgas) and fluxes of dissolved and particulate organic carbon to the floodplain and downstream portions of the river network (COriver). The analogous budget for the floodplain portion of a river corridor is .

Natural deep eutectic solvents (NADES) as green solvents for carbon dioxide capture

Science.gov (United States)

Mulia, Kamarza; Putri, Sylvania; Krisanti, Elsa; Nasruddin

2017-03-01

This study was conducted to determine the effectiveness of Natural Deep Eutectic Solvent (NADES), consisting of choline chloride and a hydrogen bonding donor (HBD) compound, in terms of carbon dioxide absorption. Solubility of carbon dioxide in NADES was found to be influenced HBD compound used and choline chloride to HBD ratio, carbon dioxide pressure, and contact time. HBD and choline/HBD ratios used were 1,2-propanediol (1:2), glycerol (1:2), and malic acid (1:1). The carbon dioxide absorption measurement was conducted using an apparatus that utilizes the volumetric method. Absorption curves were obtained up to pressures of 30 bar, showing a linear relationship between the amount absorbed and the final pressure of carbon dioxide. The choline and 1,2-propanediol eutectic mixture absorbs the highest amount of carbon dioxide, approaching 0.1 mole-fraction at 3.0 MPa and 50°C. We found that NADES ability to absorb carbon dioxide correlates with its polarity as tested using Nile Red as a solvatochromic probe.

Reactions of carbon radicals generated by 1,5-transposition of reactive centers

Directory of Open Access Journals (Sweden)

ZIVORAD CEKOVIC

2005-03-01

Full Text Available Radical intermediates can undergo specific reactions, such as intramolecular rearrangements, i.e., the transpositions of radical centers, which are not known in classical ionic organic reactions. 1,5-Transposition of a radical center to a non-activated carbon atom are of great synthetic importance. It can be successfully applied for the introduction of different functional groups (oxygen, nitrogen, sulfur, halogens onto a carbon atom remote from the present functional group. In addition to functionalization of a remote non-activated carbon atom, the formation of new C-C bonds on the d-carbon atom have also been achieved. 1,5-Transposition of the radical centers takes place from alkoxyl, aminyl and carbon radicals to a remote carbon atom. Relocation of the radical centers preferentially involves 1,5-transfer of a hydrogen atom, although migrations of some other groups are known. The reactions of the carbon radical generated by 1,5-relocation of the radical center are presented and their synthetic applications are reviewed.

Thermal Oxidation of a Carbon Condensate Formed in High-Frequency Carbon and Carbon-Nickel Plasma Flow

Science.gov (United States)

Churilov, G. N.; Nikolaev, N. S.; Cherepakhin, A. V.; Dudnik, A. I.; Tomashevich, E. V.; Trenikhin, M. V.; Bulina, N. G.

2018-02-01

We have reported on the comparative characteristics of thermal oxidation of a carbon condensate prepared by high-frequency arc evaporation of graphite rods and a rod with a hollow center filled with nickel powder. In the latter case, along with different forms of nanodisperse carbon, nickel particles with nickel core-carbon shell structures are formed. It has been found that the processes of the thermal oxidation of carbon condensates with and without nickel differ significantly. Nickel particles with the carbon shell exhibit catalytic properties with respect to the oxidation of nanosized carbon structures. A noticeable difference between the temperatures of the end of the oxidation process for various carbon nanoparticles and nickel particles with the carbon shell has been established. The study is aimed at investigations of the effect of nickel nanoparticles on the dynamics of carbon condensate oxidation upon heating in the argon-oxygen flow.

Graphitization in Carbon MEMS and Carbon NEMS

Science.gov (United States)

Sharma, Swati

Carbon MEMS (CMEMS) and Carbon NEMS (CNEMS) are an emerging class of miniaturized devices. Due to the numerous advantages such as scalable manufacturing processes, inexpensive and readily available precursor polymer materials, tunable surface properties and biocompatibility, carbon has become a preferred material for a wide variety of future sensing applications. Single suspended carbon nanowires (CNWs) integrated on CMEMS structures fabricated by electrospinning of SU8 photoresist on photolithographially patterned SU8 followed by pyrolysis are utilized for understanding the graphitization process in micro and nano carbon materials. These monolithic CNW-CMEMS structures enable the fabrication of very high aspect ratio CNWs of predefined length. The CNWs thus fabricated display core---shell structures having a graphitic shell with a glassy carbon core. The electrical conductivity of these CNWs is increased by about 100% compared to glassy carbon as a result of enhanced graphitization. We explore various tunable fabrication and pyrolysis parameters to improve graphitization in the resulting CNWs. We also suggest gas-sensing application of the thus fabricated single suspended CNW-CMEMS devices by using the CNW as a nano-hotplate for local chemical vapor deposition. In this thesis we also report on results from an optimization study of SU8 photoresist derived carbon electrodes. These electrodes were applied to the simultaneous detection of traces of Cd(II) and Pb(II) through anodic stripping voltammetry and detection limits as low as 0.7 and 0.8 microgL-1 were achieved. To further improve upon the electrochemical behavior of the carbon electrodes we elucidate a modified pyrolysis technique featuring an ultra-fast temperature ramp for obtaining bubbled porous carbon from lithographically patterned SU8. We conclude this dissertation by suggesting the possible future works on enhancing graphitization as well as on electrochemical applications

Reversible Heterolytic Cleavage of the H-H Bond by Molybdenum Complexes: Controlling the Dynamics of Exchange Between Proton and Hydride

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shaoguang; Appel, Aaron M.; Bullock, R. Morris

2017-05-18

Controlling the heterolytic cleavage of the H-H bond of dihydrogen is critically important in catalytic hydrogenations and in the catalytic oxidation of H2. We show how the rate of reversible heterolytic cleavage of H2 can be controlled over nearly four orders of magnitude at 25 °C, from 2.1 × 103 s-1 to ≥107 s-1. Bifunctional Mo complexes, [CpMo(CO)(κ3-P2N2)]+ (P2N2 = 1,5-diaza-3,7-diphosphacyclooctane with alkyl/aryl groups on N and P), have been developed for heterolytic cleavage of H2 into a proton and a hydride, akin to Frustrated Lewis Pairs. The H-H bond cleavage is enabled by the basic amine in the second coordination sphere. The products of heterolytic cleavage of H2, Mo hydride complexes bearing protonated amines, [CpMo(H)(CO)(P2N2H)]+, were characterized by spectroscopic studies and by X-ray crystallography. Variable temperature 1H, 15N and 2-D 1H-1H ROESY NMR spectra indicated rapid exchange of the proton and hydride. The exchange rates are in the order [CpMo(H)(CO)(PPh2NPh2H)]+ > [CpMo(H)(CO)(PtBu2NPh2H)]+ > [CpMo(H)(CO)(PPh2NBn2H)]+ > [CpMo(H)(CO)(PtBu2NBn2H)]+ > [CpMo(H)(CO)(PtBu2NtBu2H)]+. The pKa values determined in acetonitrile range from 9.3 to 17.7, and show a linear correlation with the logarithm of the exchange rates. Thus the exchange dynamics are controlled through the relative acidity of the [CpMo(H)(CO)(P2N2H)]+ and [CpMo(H2)(CO)(P2N2)]+ isomers, providing a design principle for controlling heterolytic cleavage of H2.

Study of small carbon and semiconductor clusters using negative ion threshold photodetachment spectroscopy

International Nuclear Information System (INIS)

Arnold, C.C.

1994-08-01

The bonding and electronics of several small carbon and semiconductor clusters containing less than ten atoms are probed using negative ion threshold photodetachment (zero electron kinetic energy, or ZEKE) spectroscopy. ZEKE spectroscopy is a particularly advantageous technique for small cluster study, as it combines mass selection with good spectroscopic resolution. The ground and low-lying electronic states of small clusters in general can be accessed by detaching an electron from the ground anion state. The clusters studied using this technique and described in this work are C 6 - /C 6 , Si n - /Si n (n = 2, 3, 4), Ge 2 - /Ge 2 , In 2 P - /In 2 P,InP 2 - /InP 2 , and Ga 2 As - . The total photodetachment cross sections of several other small carbon clusters and the ZEKE spectrum of the I - ·CH 3 I S N 2 reaction complex are also presented to illustrate the versatility of the experimental apparatus. Clusters with so few atoms do not exhibit bulk properties. However, each specie exhibits bonding properties that relate to the type of bonding found in the bulk. C 6 , as has been predicted, exhibits a linear cumulenic structure, where double bonds connect all six carbon atoms. This double bonding reflects how important π bonding is in certain phases of pure carbon (graphite and fullerenes). The symmetric stretch frequencies observed in the C 6 - spectra, however, are in poor agreement with the calculated values. Also observed as sharp structure in total photodetachment cross section scans was an excited anion state bound by only ∼40 cm -1 relative to the detachment continuum. This excited anion state appears to be a valence bound state, possible because of the high electron affinity of C 6 , and the open shell of the anion

Low-dimensional carbon and MXene-based electrochemical capacitor electrodes.

Science.gov (United States)

Yoon, Yeoheung; Lee, Keunsik; Lee, Hyoyoung

2016-04-29

Due to their unique structure and outstanding intrinsic physical properties such as extraordinarily high electrical conductivity, large surface area, and various chemical functionalities, low-dimension-based materials exhibit great potential for application in electrochemical capacitors (ECs). The electrical properties of electrochemical capacitors are determined by the electrode materials. Because energy charge storage is a surface process, the surface properties of the electrode materials greatly influence the electrochemical performance of the cell. Recently, graphene, a single layer of sp(2)-bonded carbon atoms arrayed into two-dimensional carbon nanomaterial, has attracted wide interest as an electrode material for electrochemical capacitor applications due to its unique properties, including a high electrical conductivity and large surface area. Several low-dimensional materials with large surface areas and high conductivity such as onion-like carbons (OLCs), carbide-derived carbons (CDCs), carbon nanotubes (CNTs), graphene, metal hydroxide, transition metal dichalcogenides (TMDs), and most recently MXene, have been developed for electrochemical capacitors. Therefore, it is useful to understand the current issues of low-dimensional materials and their device applications.

Low-dimensional carbon and MXene-based electrochemical capacitor electrodes

International Nuclear Information System (INIS)

Yoon, Yeoheung; Lee, Hyoyoung; Lee, Keunsik

2016-01-01

Due to their unique structure and outstanding intrinsic physical properties such as extraordinarily high electrical conductivity, large surface area, and various chemical functionalities, low-dimension-based materials exhibit great potential for application in electrochemical capacitors (ECs). The electrical properties of electrochemical capacitors are determined by the electrode materials. Because energy charge storage is a surface process, the surface properties of the electrode materials greatly influence the electrochemical performance of the cell. Recently, graphene, a single layer of sp 2 -bonded carbon atoms arrayed into two-dimensional carbon nanomaterial, has attracted wide interest as an electrode material for electrochemical capacitor applications due to its unique properties, including a high electrical conductivity and large surface area. Several low-dimensional materials with large surface areas and high conductivity such as onion-like carbons (OLCs), carbide-derived carbons (CDCs), carbon nanotubes (CNTs), graphene, metal hydroxide, transition metal dichalcogenides (TMDs), and most recently MXene, have been developed for electrochemical capacitors. Therefore, it is useful to understand the current issues of low-dimensional materials and their device applications. (topical review)

Facile preparation of porous carbon from coffee bean waste using low temperature solvothermal method

Science.gov (United States)

Baroroh, L. A. Al; Fitria, D.; Amal, M. I.; Wismogroho, A. S.; Widayatno, W. B.

2018-03-01

In this study, porous carbon made from coffee bean waste (CBW) was carbonized at 500 °C, 600 °C, and 700 °C to find effective temperature. It is verified from the IR spectrum that carbonization process at certain temperature can effectively break cellulose bonding and make aromatics functional group while preserving its carbon structure. The TG-DTA curve shows four stages of decomposition process and confirms most effective carbonization temperature. Activation process of as-carbonized CBW was carried out using solvothermal method in KOH and NH4OH steam environment at 200 °C with variation of 30%, 40%, and 50% solvothermal volume. Scanning electron micrographs reveals significant increase of porosity on the carbon surface and differences of structural pores between the variations. The results show the possible potential of utilizing low temperature-solvothermal method for nanoporous carbon material.

Combined HRTEM and PEELS analysis of nanoporous and amorphous carbon

International Nuclear Information System (INIS)

Peng, J.L.; Fan, X. D.; Bursill, L.A.

1997-01-01

Both the mass density (1.37 kgm/m 3 ) and sp 2 +sp 3 bonding fraction (0.15) were determined for an unusual nanoporous amorphous carbon consisting of curved single graphitic sheets. A combination of high-resolution transmission electron microscopy (HRTEM) and parallel electron energy loss spectroscopy (PEELS) was used. The values of these two parameters provide important constraints for the determination of the structure of this relatively low density variety of nanoporous carbon. The results are relevant also in the search for negatively-curved Schwarzite-related carbon structures. New date are also presented for highly-oriented pyrollytic graphite (HOPG), chemically vapour deposited (CVD) diamond, C 60 , glassy carbon (GC) and evaporated amorphous carbon (EAC); these are compared with the results for NAC. Kramers-Kronig analysis (KKA) of the low-loss PEELS data shows that the band gaps of both NAC and EAC are collapsed relative to that of CVD diamond. 18 refs., 2 tabs., 3 figs

Combined HRTEM and PEELS analysis of nanoporous and amorphous carbon

Energy Technology Data Exchange (ETDEWEB)

Peng, J.L.; Fan, X. D.; Bursill, L.A.

1997-06-01

Both the mass density (1.37 kgm/m{sup 3}) and sp{sup 2}+sp{sup 3} bonding fraction (0.15) were determined for an unusual nanoporous amorphous carbon consisting of curved single graphitic sheets. A combination of high-resolution transmission electron microscopy (HRTEM) and parallel electron energy loss spectroscopy (PEELS) was used. The values of these two parameters provide important constraints for the determination of the structure of this relatively low density variety of nanoporous carbon. The results are relevant also in the search for negatively-curved Schwarzite-related carbon structures. New date are also presented for highly-oriented pyrollytic graphite (HOPG), chemically vapour deposited (CVD) diamond, C{sub 60}, glassy carbon (GC) and evaporated amorphous carbon (EAC); these are compared with the results for NAC. Kramers-Kronig analysis (KKA) of the low-loss PEELS data shows that the band gaps of both NAC and EAC are collapsed relative to that of CVD diamond. 18 refs., 2 tabs., 3 figs.

Limits on carbon sequestration in arid blue carbon ecosystems.

Science.gov (United States)

Schile, Lisa M; Kauffman, J Boone; Crooks, Stephen; Fourqurean, James W; Glavan, Jane; Megonigal, J Patrick

2017-04-01

Coastal ecosystems produce and sequester significant amounts of carbon ("blue carbon"), which has been well documented in humid and semi-humid regions of temperate and tropical climates but less so in arid regions where mangroves, marshes, and seagrasses exist near the limit of their tolerance for extreme temperature and salinity. To better understand these unique systems, we measured whole-ecosystem carbon stocks in 58 sites across the United Arab Emirates (UAE) in natural and planted mangroves, salt marshes, seagrass beds, microbial mats, and coastal sabkha (inter- and supratidal unvegetated salt flats). Natural mangroves held significantly more carbon in above- and belowground biomass than other vegetated ecosystems. Planted mangrove carbon stocks increased with age, but there were large differences for sites of similar age. Soil carbon varied widely across sites (2-367 Mg C/ha), with ecosystem averages that ranged from 49 to 156 Mg C/ha. For the first time, microbial mats were documented to contain soil carbon pools comparable to vascular plant-dominated ecosystems, and could arguably be recognized as a unique blue carbon ecosystem. Total ecosystem carbon stocks ranged widely from 2 to 515 Mg C/ha (seagrass bed and mangrove, respectively). Seagrass beds had the lowest carbon stock per unit area, but the largest stock per total area due to their large spatial coverage. Compared to similar ecosystems globally, mangroves and marshes in the UAE have lower plant and soil carbon stocks; however, the difference in soil stocks is far larger than with plant stocks. This incongruent difference between stocks is likely due to poor carbon preservation under conditions of weakly reduced soils (200-350 mV), coarse-grained sediments, and active shoreline migration. This work represents the first attempt to produce a country-wide coastal ecosystem carbon accounting using a uniform sampling protocol, and was motivated by specific policy goals identified by the Abu Dhabi Global

Comparison Between Elemental Carbon Measured Using Thermal-Optical Analysis and Black Carbon Measurements Using A Novel Cellphone-Based System

Science.gov (United States)

Ramanathan, N.; Khan, B.; Leong, I.; Lukac, M.

2011-12-01

Black carbon (BC) is produced through the incomplete combustion of fossil and solid fuels. Current BC emissions inventories have large uncertainties of factors of 2 or more due to sparse measurements and because BC is often emitted by local sources that vary over time and space (Bond et al, 2004). Those uncertainties are major sources of error in air pollution models. Emissions from a variety of improved cookstove/fuel/combustion conditions were collected on pre-conditioned 47 mm quartz-fiber filters and analyzed for organic carbon (OC) and elemental carbon (EC) using thermal-optical analysis (TOA). The samples were then analyzed for BC concentration by using cellphone-based instrumentation developed by Ramanathan et al., 2011. The cellphone-based monitoring system (CBMS) is a wireless, low-cost, low-power system that monitors BC emissions. The CBMS is comprised of an aerosol filter sampler containing a battery-powered air pump and a 25mm filter holder that draws air in through a quartz-fiber filter. As black carbon deposits increase, the filter darkens--the darkest color representing the highest loading. A cellphone photograph of the filter with the black carbon deposit is taken and relayed to an analytics unit for comparison to a reference scale to estimate airborne BC concentration. The BC concentration can then be compared to the thermally derived EC concentration. TOA was conducted on a Sunset Laboratory Dual Optics Carbon Analyzer using a modified version of the Birch and Cary (1996) NIOSH 5040 protocol. The dual-optical instrument permitted simultaneous monitoring of the transmission (TOT) and reflectance (TOR). 619 samples were collected; EC was obtained using NIOSH TOT and NIOSH TOR methods, and BC was obtained using the CBMS analytics unit. The mean BC value reported by the CBMS agrees within 20% of the reference values for EC, confirming the findings in Ramanathan et al. (2011) based on samples from India. Given this accuracy, we conclude that the CBMS

Electronic properties of bromine-doped carbon nanotubes

CERN Document Server

Jhi, S H; Cohen, M L

2002-01-01

Intercalation of bromine molecules (Br2) into single-wall carbon nanotube (SWNT) ropes is studied using the ab initio pseudopotential density functional method. Electronic and vibrational properties of the SWNT and Br2 are studied for various bromine concentrations. A drastic change in the charge transfer, bromine stretching-mode, and bromine bond-length is observed when the bromine-bromine distance decreases. Calculated electronic structures show that, at high bromine concentrations, the bromine ppsigma level broadens due to the interbromine interaction. These states overlap with the electronic bands of the SWNT near the Fermi level which results in a substantial charge transfer from carbon to bromine.

Squaroglitter: A 3,4-Connected Carbon Net

KAUST Repository

Prasad, Dasari L. V. K.

2013-08-13

Theoretical calculations are presented on a new hypothetical 3,4-connected carbon net (called squaroglitter) incorporating 1,4 cyclohexadiene units. The structure has tetragonal space group P4/mmm (No. 123) symmetry. The optimized geometry shows normal distances, except for some elongated bonds in the cyclobutane ring substructures in the network. Squaroglitter has an indirect bandgap of about 1.0 eV. The hypothetical lattice, whose density is close to graphite, is more stable than other 3,4-connected carbon nets. A relationship to a (4,4)nanotube is explored, as is a potential threading of the lattice with metal needles. © 2013 American Chemical Society.

Analysis of Carbon Nanotubes on the Mechanical Properties at Atomic Scale

Directory of Open Access Journals (Sweden)

Xiaowen Lei

2011-01-01

Full Text Available This paper aims at developing a mathematic model to characterize the mechanical properties of single-walled carbon nanotubes (SWCNTs. The carbon-carbon (C–C bonds between two adjacent atoms are modeled as Euler beams. According to the relationship of Tersoff-Brenner force theory and potential energy acting on C–C bonds, material constants of beam element are determined at the atomic scale. Based on the elastic deformation energy and mechanical equilibrium of a unit in graphite sheet, simply form ED equations of calculating Young's modulus of armchair and zigzag graphite sheets are derived. Following with the geometrical relationship of SWCNTs in cylindrical coordinates and the structure mechanics approach, Young's modulus and Poisson's ratio of armchair and zigzag SWCNTs are also investigated. The results show that the approach to research mechanical properties of SWCNTs is a concise and valid method. We consider that it will be useful technique to progress on this type of investigation.

Preparation polystyrene/multiwalled carbon nanotubes nanocomposites by copolymerization of styrene and styryl-functionalized multiwalled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Hua, Jing, E-mail: huajing72@qust.edu.cn [Key Laboratory of Rubber-Plastics Ministry of Education, Qingdao University of Science and Technology, Qingdao (China); Wang, Zhongguang; Xu, Ling; Wang, Xin; Zhao, Jian; Li, Feifei [Key Laboratory of Rubber-Plastics Ministry of Education, Qingdao University of Science and Technology, Qingdao (China)

2013-01-15

Styryl-functionalized multiwalled carbon nanotubes (p-MWNTs) were prepared by esterification based on the carboxylate salt of carbon nanotubes and p-chloromethylstyrene in toluene. Then in situ radical copolymerization of p-MWNTs and styrene initiated by 2,2 Prime -azobis(isobutyronitrile) (AIBN) was applied to synthesize composites of styryl-functionalized multiwalled carbon nanotubes and polystyrene (PS) (p-MWNTs/PS). Characterizations carried out by FT-IR, {sup 1}H NMR, UV-vis show that styryl group covalently bond to the surface of MWNTs. The results of UV showed that the solutions of p-MWNTs/PS in chloroform have the hyperchromic effect. Transmission electron microscopy (TEM) images of p-MWNTs/PS composites and scanning electron microscopy (SEM) images of fracture surface of p-MWNTs/PS composites showed the functionalized nanotubes had a better dispersion than that of the unfunctionalized MWNTs in the matrix. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) suggested that the thermal stability of p-MWNTs/PS composites improved in the presence of MWNTs. -- Highlights: Black-Right-Pointing-Pointer A facile and simple way to successfully prepare the polystyrene/MWNTs nanocomposites. Black-Right-Pointing-Pointer Characterizations show that styryl group covalently bond to the surface of MWNTs. Black-Right-Pointing-Pointer The solutions of p-MWNTs/PS in chloroform have the hyperchromic effect. Black-Right-Pointing-Pointer Thermal stability of p-tpas composites improved in the presence of MWNTs. Black-Right-Pointing-Pointer The performance of polymer prepared by this method have great potential for exploitation.

Covalent Functionalization of Carbon Nanotube by Tetrasubtituted Amino Manganese Phthalocyanine

Institute of Scientific and Technical Information of China (English)

Zheng Long YANG; Hong Zheng CHEN; Lei CAO; Han Yin LI; Mang WANG

2004-01-01

The multiwall carbon nanotube (MWCNT) bonded to 2, 9, 16, 23-tetraamino manganese phthalocyanine (TAMnPc) was obtained by covalent functionalization, and its chemical structure was characterized by TEM. The photoconductivity of single-layered photoreceptors, where MWCNT bonded by TAMnPc (MWCNT-b-TAMnPc) served as the charge generation material (CGM), was also studied.

Stable carbon, nitrogen and sulfur isotopes in non-carbonate fractions of cold-seep carbonates

Science.gov (United States)

Feng, Dong; Peng, Yongbo; Peckmann, Jörn; Roberts, Harry; Chen, Duofu

2017-04-01

Sulfate-driven anaerobic oxidation of methane (AOM) supports chemosynthesis-based communities and limits the release of methane from marine sediments. This process promotes the formation of carbonates close to the seafloor along continental margins. The geochemical characteristics of the carbonate minerals of these rocks are increasingly understood, questions remain about the geochemical characteristics of the non-carbonate fractions. Here, we report stable carbon, nitrogen and sulfur isotope patterns in non-carbonate fractions of seep carbonates. The authigenic carbonates were collected from three modern seep provinces (Black Sea, Gulf of Mexico, and South China Sea) and three ancient seep deposits (Marmorito, northern Italy, Miocene; SR4 deposit of the Lincoln Creek Formation and Whiskey Creek, western Washington, USA, Eocene to Oligocene). The δ13C values of non-carbonate fractions range from ˜-25‰ to -80‰ VPDB. These values indicate that fossil methane mixed with varying amounts of pelagic organic matter is the dominant source of carbon in these fractions. The relatively small offset between the δ34S signatures of the non-carbonate fractions and the respective sulfide minerals suggests that locally produced hydrogen sulfide is the main source of sulfur in seep environments. The δ15N values of the non-carbonate fractions are generally lower than the corresponding values of deep-sea sediments, suggesting that organic nitrogen is mostly of a local origin. This study reveals the potential of using δ13C, δ15N, δ34S values to discern seep and non-seep deposits. In cases where δ13Ccarbonate values are only moderately low due to mixing processes and lipid biomarkers have been erased in the course of burial, it is difficult to trace back AOM owing to the lack of other records. This problem is even more pronounced when authigenic carbonate is not available in ancient seep environments. Acknowledgments: The authors thank BOEM and NOAA for their years' support

Comparison of protons, carbon and fullerene impacts on a carbon cylinder

CERN Document Server

Webb, R P

2003-01-01

The use of protons in radiation treatment has been much studied and is widely used in the treatment of cancer cells. The proton causes damage to the strands of DNA in the cells largely by interaction with the electronic system. The proton interactions largely result in bond breakage in the DNA molecules. Sometimes the resulting damage to the DNA molecule is insufficient to cause both strands of the molecule to be broken and consequently the cell can reproduce despite being irradiated. Heavy ion therapy using carbon ions has been used to try and introduce more damage into the molecule structure, ensuring that both strands of the DNA are broken and hence preventing the cell from replicating. However, it seems that even the use of ions as heavy as carbon still result in DNA that is not fully damaged. The simulations reported here form a preliminary investigation on the possible use of a molecular species to deliver multiple impacting particles to the molecular structure thereby increasing the energy density of t...

Carbon dioxide sequestration by direct mineral carbonation with carbonic acid

Energy Technology Data Exchange (ETDEWEB)

O' Connor, William K.; Dahlin, David C.; Nilsen, David N.; Walters, Richard P.; Turner, Paul C.

2000-01-01

The Albany Research Center (ARC) of the U.S. Dept. of Energy (DOE) has been conducting a series of mineral carbonation tests at its Albany, Oregon, facility over the past 2 years as part of a Mineral Carbonation Study Program within the DOE. Other participants in this Program include the Los Alamos National Laboratory, Arizona State University, Science Applications International Corporation, and the DOE National Energy Technology Laboratory. The ARC tests have focused on ex-situ mineral carbonation in an aqueous system. The process developed at ARC utilizes a slurry of water mixed with a magnesium silicate mineral, olivine [forsterite end member (Mg2SiO4)], or serpentine [Mg3Si2O5(OH)4]. This slurry is reacted with supercritical carbon dioxide (CO2) to produce magnesite (MgCO3). The CO2 is dissolved in water to form carbonic acid (H2CO3), which dissociates to H+ and HCO3 -. The H+ reacts with the mineral, liberating Mg2+ cations which react with the bicarbonate to form the solid carbonate. The process is designed to simulate the natural serpentinization reaction of ultramafic minerals, and for this reason, these results may also be applicable to in-situ geological sequestration regimes. Results of the baseline tests, conducted on ground products of the natural minerals, have been encouraging. Tests conducted at ambient temperature (22 C) and subcritical CO2 pressures (below 73 atm) resulted in very slow conversion to the carbonate. However, when elevated temperatures and pressures are utilized, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant reaction occurs within much shorter reaction times. Extent of reaction, as measured by the stoichiometric conversion of the silicate mineral (olivine) to the carbonate, is roughly 90% within 24 hours, using distilled water, and a reaction temperature of 185?C and a partial pressure of CO2 (PCO2) of 115 atm. Recent tests using a bicarbonate solution, under identical reaction

Carbon dioxide sequestration by direct mineral carbonation with carbonic acid

Energy Technology Data Exchange (ETDEWEB)

O' Connor, W.K.; Dahlin, D.C.; Nilsen, D.N.; Walters, R.P.; Turner, P.C.

2000-07-01

The Albany Research Center (ARC) of the US Department of Energy (DOE) has been conducting a series of mineral carbonation tests at its Albany, Oregon, facility over the past 2 years as part of a Mineral Carbonation Study Program within the DOE. The ARC tests have focused on ex-situ mineral carbonation in an aqueous system. The process developed at ARC utilizes a slurry of water mixed with a magnesium silicate mineral, olivine [forsterite and member (mg{sub 2}SiO{sub 4})], or serpentine [Mg{sub 3}Si{sub 2}O{sub 5}(OH){sub 4}]. This slurry is reacted with supercritical carbon dioxide (CO{sub 2}) to produce magnesite (MgCO{sub 3}). The CO{sub 2} is dissolved in water to form carbonic acid (H{sub 2}CO{sub 3}), which dissociates to H{sup +} and HCO{sub 3}{sup {minus}}. The H{sup +} reacts with the mineral, liberating Mg{sup 2+} cations which react with the bicarbonate to form the solid carbonate. The process is designed to simulate the natural serpentinization reaction of ultramafic minerals, and for this reason, these results may also be applicable to in-situ geological sequestration regimes. Results of the baseline tests, conducted on ground products of the natural minerals, have been encouraging. Tests conducted at ambient temperature (22 C) and subcritical CO{sub 2} pressures (below 73 atm) resulted in very slow conversion to the carbonate. However, when elevated temperatures and pressures are utilized, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant reaction occurs within much shorter reaction times. Extent of reaction, as measured by the stoichiometric conversion of the silicate mineral (olivine) to the carbonate, is roughly 90% within 24 hours, using distilled water, and a reaction temperature of 185 C and a partial pressure of CO{sub 2} (P{sub CO{sub 2}}) of 115 atm. Recent tests using a bicarbonate solution, under identical reaction conditions, have achieved roughly 83% conversion of heat treated serpentine

Synthesis and mechanical behavior of carbon nanotube-magnesium composites hybridized with nanoparticles of alumina

International Nuclear Information System (INIS)

Thakur, Sanjay Kumar; Srivatsan, T.S.; Gupta, Manoj

2007-01-01

Carbon nanotubes reinforced magnesium based composites were prepared with diligence and care using the powder metallurgy route coupled with rapid microwave sintering. Nanometer-sized particles of alumina were used to hybridize the carbon nanotubes reinforcement in the magnesium matrix so as to establish the intrinsic influence of hybridization on mechanical behavior of the resultant composite material. The yield strength, tensile strength and strain-to-failure of the carbon nanotubes-magnesium composites were found to increase with the addition of nanometer-sized alumina particles to the composite matrix. Scanning electron microscopy observations of the fracture surfaces of the samples deformed and failed in uniaxial tension revealed the presence of cleavage-like features on the fracture surface indicative of the occurrence of locally brittle fracture mechanism in the composite microstructure

Molecular dynamics study of the solvation of calcium carbonate in water.

Science.gov (United States)

Bruneval, Fabien; Donadio, Davide; Parrinello, Michele

2007-10-25

We performed molecular dynamics simulations of diluted solutions of calcium carbonate in water. To this end, we combined and tested previous polarizable models. The carbonate anion forms long-living hydrogen bonds with water and shows an amphiphilic character, in which the water molecules are expelled in a region close to its C(3) symmetry axis. The calcium cation forms a strongly bound ion pair with the carbonate. The first hydration shell around the CaCO(3) pair is found to be very similar to the location of the water molecules surrounding CaCO(3) in ikaite, the hydrated mineral.

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

International Nuclear Information System (INIS)

Zhang, L.L.; Yang, Q.; Tang, Y.; Yang, L.; Zhang, C.; Hu, Y.; Cui, X.

2015-01-01

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 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 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 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 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 3 bonded C in B-DLC thin films increase with the increase of B-rich carbide content in the films

Carbon fuel cells with carbon corrosion suppression

Science.gov (United States)

Cooper, John F [Oakland, CA

2012-04-10

An electrochemical cell apparatus that can operate as either a fuel cell or a battery includes a cathode compartment, an anode compartment operatively connected to the cathode compartment, and a carbon fuel cell section connected to the anode compartment and the cathode compartment. An effusion plate is operatively positioned adjacent the anode compartment or the cathode compartment. The effusion plate allows passage of carbon dioxide. Carbon dioxide exhaust channels are operatively positioned in the electrochemical cell to direct the carbon dioxide from the electrochemical cell.

An expedient procedure for the oxidative cleavage of olefinic bonds with PhI(OAc)2, NMO, and catalytic OsO4.

Science.gov (United States)

Nicolaou, K C; Adsool, Vikrant A; Hale, Christopher R H

2010-04-02

PhI(OAc)(2) in the presence of OsO(4) (cat.) and 2,6-lutidine cleaves olefinic bonds to yield the corresponding carbonyl compounds, albeit, in some cases, with alpha-hydroxy ketones as byproduct. A more practical and clean protocol to effect oxidative cleavage of olefinic bonds involves NMO, OsO(4) (cat.), 2,6-lutidine, and PhI(OAc)(2).

Carbon Fiber Reinforced Carbon Composite Valve for an Internal Combustion Engine

Science.gov (United States)

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor)

1999-01-01

A carbon fiber reinforced carbon composite valve for internal combustion engines and the like formed of continuous carbon fibers throughout the valve's stem and head is disclosed. The valve includes braided carbon fiber material over axially aligned unidirectional carbon fibers forming a valve stem; the braided and unidirectional carbon fibers being broomed out at one end of the valve stem forming the shape of the valve head; the valve-shaped structure being densified and rigidized with a matrix of carbon containing discontinuous carbon fibers: and the finished valve being treated to resist oxidation. Also disclosed is a carbon matrix plug containing continuous and discontinuous carbon fibers and forming a net-shape valve head acting as a mandrel over which the unidirectional and braided carbon fibers are formed according to textile processes. Also disclosed are various preform valves and processes for making finished and preform carbon fiber reinforced carbon composite valves.

Carbon dioxide sequestration using NaHSO4 and NaOH: A dissolution and carbonation optimisation study.

Science.gov (United States)

Sanna, Aimaro; Steel, Luc; Maroto-Valer, M Mercedes

2017-03-15

The use of NaHSO 4 to leach out Mg fromlizardite-rich serpentinite (in form of MgSO 4 ) and the carbonation of CO 2 (captured in form of Na 2 CO 3 using NaOH) to form MgCO 3 and Na 2 SO 4 was investigated. Unlike ammonium sulphate, sodium sulphate can be separated via precipitation during the recycling step avoiding energy intensive evaporation process required in NH 4 -based processes. To determine the effectiveness of the NaHSO 4 /NaOH process when applied to lizardite, the optimisation of the dissolution and carbonation steps were performed using a UK lizardite-rich serpentine. Temperature, solid/liquid ratio, particle size, concentration and molar ratio were evaluated. An optimal dissolution efficiency of 69.6% was achieved over 3 h at 100 °C using 1.4 M sodium bisulphate and 50 g/l serpentine with particle size 75-150 μm. An optimal carbonation efficiency of 95.4% was achieved over 30 min at 90 °C and 1:1 magnesium:sodium carbonate molar ratio using non-synthesised solution. The CO 2 sequestration capacity was 223.6 g carbon dioxide/kg serpentine (66.4% in terms of Mg bonded to hydromagnesite), which is comparable with those obtained using ammonium based processes. Therefore, lizardite-rich serpentinites represent a valuable resource for the NaHSO 4 /NaOH based pH swing mineralisation process. Copyright © 2016 Elsevier Ltd. All rights reserved.

Molecular dynamics simulation for the influence of incident angles of energetic carbon atoms on the structure and properties of diamond-like carbon films

International Nuclear Information System (INIS)

Li, Xiaowei; Ke, Peiling; Lee, Kwang-Ryeol; Wang, Aiying

2014-01-01

The influence of incident angles of energetic carbon atoms (0–60°) on the structure and properties of diamond-like carbon (DLC) films was investigated by the molecular dynamics simulation using a Tersoff interatomic potential. The present simulation revealed that as the incident angles increased from 0 to 60°, the surface roughness of DLC films increased and the more porous structure was generated. Along the growth direction of DLC films, the whole system could be divided into four regions including substrate region, transition region, stable region and surface region except the case at the incident angle of 60°. When the incident angle was 45°, the residual stress was significantly reduced by 12% with little deterioration of mechanical behavior. The further structure analysis using both the bond angles and bond length distributions indicated that the compressive stress reduction mainly resulted from the relaxation of highly distorted C–C bond length. - Highlights: • The dependence of films properties on different incident angles was investigated. • The change of incident angles reduced the stress without obvious damage of density. • The stress reduction attributed to the relaxation of highly distorted bond length

Carbonate-silicate cycle models of the long-term carbon cycle, carbonate accumulation in the oceans, and climate

International Nuclear Information System (INIS)

Caldeira, K.G.

1991-01-01

Several models of the long-term carbon cycle, incorporating models of the carbonate-silicate cycle, were developed and utilized to investigate issues relating to global climate and the causes and consequences of changes in calcium carbonate accumulation in the oceans. Model results indicate that the marked mid-Cretaceous (120 Ma) global warming could be explained by increased rates of release of carbon dioxide from subduction-zone metamorphism and mid-ocean-ridges, in conjunction with paleogeographic factors. Since the mid-Cretaceous, the primary setting for calcium carbonate accumulation in the oceans has shifted from shallow-water to deep-water environments. Model results suggest that this shift could have major consequences for the carbonate-silicate cycle and climate, and lead to significant increases in the flux of metamorphic carbon dioxide to the atmosphere. Increases in pelagic carbonate productivity, and decreases in tropical shallow-water area available for neritic carbonate accumulation, have both been proposed as the primary cause of this shift. Two lines of evidence developed here (one involving a statistical analysis of Tertiary carbonate-accumulation and oxygen-isotope data, and another based on modeling the carbonate-silicate cycle and ocean chemistry) suggest that a decrease in tropical shallow-water area was more important than increased pelagic productivity in explaining this shift. Model investigations of changes in ocean chemistry at the Cretaceous/Tertiary (K/T) boundary (66 Ma) indicate that variations in deep-water carbonate productivity may affect shallow-water carbonate accumulation rates through a mechanism involving surface-water carbonate-ion concentration. In the aftermath of the K/T boundary event, deep-water carbonate production and accumulation were significantly reduced as a result of the extinction of calcareous plankton

Quantitative characterization of cleavage and hydrogen-assisted quasi-cleavage fracture surfaces with the use of confocal laser scanning microscopy

International Nuclear Information System (INIS)

Merson, E.; Kudrya, A.V.; Trachenko, V.A.; Merson, D.; Danilov, V.; Vinogradov, A.

2016-01-01

“True” cleavage (TC) and quasi-cleavage (QC) fracture surfaces of low-carbon steel specimens tested in liquid nitrogen and after hydrogen charging respectively were investigated by quantitative confocal laser scanning microscopy (CLSM) and conventional scanning electron microscopy (SEM) with electron-backscattered diffraction (EBSD). Topological and crystallographic features of the TC fracture surface are found in good agreement with the generally accepted cleavage mechanism: TC facets diameters correspond to those of grains; the crack path strictly follows the crystallographic orientation of grains and the most of the cleavage cracks are parallel to {100} planes. On the 2D SEM images, the QC facets appeared resembling the TC ones in terms of river line patterns, shapes and sizes. However, the substantial differences between the topography of these two kinds of fracture surfaces were revealed by 3D CLSM: the average misorientation angle between QC facets and the roughness of the QC fracture surface were much lower than those measured for TC. It is demonstrated that all these features are attributed to the specific fracture mechanism operating during hydrogen-assisted cracking.

Quantitative characterization of cleavage and hydrogen-assisted quasi-cleavage fracture surfaces with the use of confocal laser scanning microscopy

Energy Technology Data Exchange (ETDEWEB)

Merson, E. [Institute of Advanced Technologies, Togliatti State University, 445667 (Russian Federation); Kudrya, A.V.; Trachenko, V.A. [Department of Physical Metallurgy and the Physics of Strength, NUST MISiS, Moscow 119490 (Russian Federation); Merson, D. [Institute of Advanced Technologies, Togliatti State University, 445667 (Russian Federation); Laboratory for Advanced Materials, Kazan Federal University, Naberezhnye Chelny 423812, Republic of Tatarstan (Russian Federation); Danilov, V. [Institute of Advanced Technologies, Togliatti State University, 445667 (Russian Federation); Vinogradov, A. [Institute of Advanced Technologies, Togliatti State University, 445667 (Russian Federation); Department of Engineering Design and Materials, Norwegian University of Science and Technology – NTNU, N-7491 Trondheim (Norway)

2016-05-17

“True” cleavage (TC) and quasi-cleavage (QC) fracture surfaces of low-carbon steel specimens tested in liquid nitrogen and after hydrogen charging respectively were investigated by quantitative confocal laser scanning microscopy (CLSM) and conventional scanning electron microscopy (SEM) with electron-backscattered diffraction (EBSD). Topological and crystallographic features of the TC fracture surface are found in good agreement with the generally accepted cleavage mechanism: TC facets diameters correspond to those of grains; the crack path strictly follows the crystallographic orientation of grains and the most of the cleavage cracks are parallel to {100} planes. On the 2D SEM images, the QC facets appeared resembling the TC ones in terms of river line patterns, shapes and sizes. However, the substantial differences between the topography of these two kinds of fracture surfaces were revealed by 3D CLSM: the average misorientation angle between QC facets and the roughness of the QC fracture surface were much lower than those measured for TC. It is demonstrated that all these features are attributed to the specific fracture mechanism operating during hydrogen-assisted cracking.

The research of a method for determination of total carbon, combination carbon and free carbon in beryllium metal

International Nuclear Information System (INIS)

Yang Xingzhong; Zhu Xiaohong

1996-02-01

A method for determination of total carbon, combination carbon and free carbon in beryllium metal with LECO CS-344 carbon/sulphur determinant has been studied. Tungsten-copper mixed pellets are used as flux to the determination of total carbon. Ratio of weight of the flux to the sample is greater than 20:1. Good analytical results are got. By this method the relative standard deviation is <10% when the content of total carbon in the range of 0.050%∼0.080% in beryllium. A standard steel sample of carbon is added into beryllium, the recoveries are 94%∼106%. For determination of free carbon, the sample are decomposed with 3 mol/L HCl, filtered and followed determination. By this method the relative standard deviation is ≤10% when the content of free carbon in the range of 0.006%∼0.020% in beryllium. the balance of total carbon and free carbon is equal to combination carbon. The method is used to determine the sample of content of total carbon in the range of 0.050%∼1.00%, free carbon in the range of 0.006%∼0.500% in metal beryllium. (6 refs., 1 fig., 13 tabs.)

Lightning-produced Carbon Species in the Atmosphere of Saturn

Science.gov (United States)

Delitsky, Mona; Baines, K. H.

2010-10-01

Recent studies by Baines et al (2009) indicate that thunderstorm-associated clouds on Saturn are spectrally dark from 0.7 to 4 um, darker than regular clouds. This darkening is found to be consistent with the presence of particles of elemental carbon, such as in the form of soot particles mixed in with spectrally bright condensates. This carbon is thought to be generated by lightning-induced dissociation of methane. Lightning on Saturn will input large amounts of energy to a narrow column of atmosphere and generate products at high energies such as radicals and ions. After the column cools down, the new chemical species recombine and are frozen into a new chemical equilibrium. Experimental studies in the literature of reactions of methane and other gases in plasma discharges (which simulate lightning) indicate that, even with high ratios of hydrogen/methane, the elemental carbon obtained will form solid dark particles that persist and have a very high C/H ratio. Basically, they are mostly pure carbon, in the form of soot, amorphous carbon, graphite, graphene, polycyclic aromatic hydrocarbons, carbon black, carbon onions, etc. Hydrogen will act as a sealant onto the particles and attach to dangling bonds on their growing surfaces. Even in experiments to form the most crystalline allotrope of carbon, that is, diamond, the presence of hydrogen does not inhibit diamond formation, even at the low pressures in the atmospheres of the Jovian planets or in the interstellar medium (Allamandola et al 1991). Therefore, some form of elemental carbon is likely produced in Saturnian storm clouds and may occur as dark particles of either amorphous carbon, PAHs or crystalline carbon in a form such as graphite. ..Refs: Baines et al., PSS 57, 1650-1658 (2009) ; Allamandola et al., Meteoritics 26, 313 (1991).

Reactive carbon-chain molecules: synthesis of 1-diazo-2,4-pentadiyne and spectroscopic characterization of triplet pentadiynylidene (H-C[triple bond]C-:C-C[triple bond]C-H).

Science.gov (United States)

Bowling, Nathan P; Halter, Robert J; Hodges, Jonathan A; Seburg, Randal A; Thomas, Phillip S; Simmons, Christopher S; Stanton, John F; McMahon, Robert J

2006-03-15

1-Diazo-2,4-pentadiyne (6a), along with both monodeuterio isotopomers 6b and 6c, has been synthesized via a route that proceeds through diacetylene, 2,4-pentadiynal, and 2,4-pentadiynal tosylhydrazone. Photolysis of diazo compounds 6a-c (lambda > 444 nm; Ar or N2, 10 K) generates triplet carbenes HC5H (1) and HC5D (1-d), which have been characterized by IR, EPR, and UV/vis spectroscopy. Although many resonance structures contribute to the resonance hybrid for this highly unsaturated carbon-chain molecule, experiment and theory reveal that the structure is best depicted in terms of the dominant resonance contributor of penta-1,4-diyn-3-ylidene (diethynylcarbene, H-C[triple bond]C-:C-C[triple bond]C-H). Theory predicts an axially symmetric (D(infinity h)) structure and a triplet electronic ground state for 1 (CCSD(T)/ANO). Experimental IR frequencies and isotope shifts are in good agreement with computed values. The triplet EPR spectrum of 1 (absolute value(D/hc) = 0.6157 cm(-1), absolute value(E/hc) = 0.0006 cm(-1)) is consistent with an axially symmetric structure, and the Curie law behavior confirms that the triplet state is the ground state. The electronic absorption spectrum of 1 exhibits a weak transition near 400 nm with extensive vibronic coupling. Chemical trapping of triplet HC5H (1) in an O2-doped matrix affords the carbonyl oxide 16 derived exclusively from attack at the central carbon.

Ternary electrocatalysts for oxidizing ethanol to carbon dioxide: making ir capable of splitting C-C bond.

Science.gov (United States)

Li, Meng; Cullen, David A; Sasaki, Kotaro; Marinkovic, Nebojsa S; More, Karren; Adzic, Radoslav R

2013-01-09

Splitting the C-C bond is the main obstacle to electrooxidation of ethanol (EOR) to CO(2). We recently demonstrated that the ternary PtRhSnO(2) electrocatalyst can accomplish that reaction at room temperature with Rh having a unique capability to split the C-C bond. In this article, we report the finding that Ir can be induced to split the C-C bond as a component of the ternary catalyst. We characterized and compared the properties of several carbon-supported nanoparticle (NP) electrocatalysts comprising a SnO(2) NP core decorated with multimetallic nanoislands (MM' = PtIr, PtRh, IrRh, PtIrRh) prepared using a seeded growth approach. An array of characterization techniques were employed to establish the composition and architecture of the synthesized MM'/SnO(2) NPs, while electrochemical and in situ infrared reflection absorption spectroscopy studies elucidated trends in activity and the nature of the reaction intermediates and products. Both EOR reactivity and selectivity toward CO(2) formation of several of these MM'/SnO(2)/C electrocatalysts are significantly higher compared to conventional Pt/C and Pt/SnO(2)/C catalysts. We demonstrate that the PtIr/SnO(2)/C catalyst with high Ir content shows outstanding catalytic properties with the most negative EOR onset potential and reasonably good selectivity toward ethanol complete oxidation to CO(2).

Carbon paint anode for reinforced concrete bridges in coastal environments

Energy Technology Data Exchange (ETDEWEB)

Cramer, Stephen D.; Bullard, Sophie J.; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Russell, James H.; Cryer, C.B. (ODOT); Laylor, H.M. (ODOT)

2002-01-01

Solvent-based acrylic carbon paint anodes were installed on the north approach spans of the Yaquina Bay Bridge (Newport OR) in 1985. The anodes continue to perform satisfactorily after more than 15 years service. The anodes were inexpensive to apply and field repairs are easily made. Depolarization potentials are consistently above 100 mV with long-term current densities around 2 mA/m 2. Bond strength remains adequate, averaging 0.50 MPa (73 psi). Some deterioration of the anode-concrete interface has occurred in the form of cracks and about 4% of the bond strength measurements indicated low or no bond. Carbon anode consumption appears low. The dominant long-term anode reaction appears to be chlorine evolution, which results in limited further acidification of the anode-concrete interface. Chloride profiles were depressed compared to some other coastal bridges suggesting chloride extraction by the CP system. Further evidence of outward chloride migration was a flat chloride profile between the anode and the outer rebar.

Modeling equilibrium adsorption of organic micropollutants onto activated carbon

KAUST Repository

De Ridder, David J.

2010-05-01

Solute hydrophobicity, polarizability, aromaticity and the presence of H-bond donor/acceptor groups have been identified as important solute properties that affect the adsorption on activated carbon. However, the adsorption mechanisms related to these properties occur in parallel, and their respective dominance depends on the solute properties as well as carbon characteristics. In this paper, a model based on multivariate linear regression is described that was developed to predict equilibrium carbon loading on a specific activated carbon (F400) for solutes reflecting a wide range of solute properties. In order to improve prediction accuracy, groups (bins) of solutes with similar solute properties were defined and solute removals were predicted for each bin separately. With these individual linear models, coefficients of determination (R2) values ranging from 0.61 to 0.84 were obtained. With the mechanistic approach used in developing this predictive model, a strong relation with adsorption mechanisms is established, improving the interpretation and, ultimately, acceptance of the model. © 2010 Elsevier Ltd.

A cascade of acid-promoted C-O bond cleavage and redox reactions: from oxa-bridged benzazepines to benzazepinones.

Science.gov (United States)

Zhang, Yuewei; Yang, Fengzhi; Zheng, Lianyou; Dang, Qun; Bai, Xu

2014-12-05

A sequence of C-O bond cleavage and redox reactions in oxa-bridged azepines was realized under acid promoted conditions. This protocol provides an atom-economical and straightforward approach to access benzo[b]azepin-5(2H)-ones in high yields. The formal synthesis of tolvaptan was achieved by exploiting this new transformation.

Nickel–carbon nanocomposites: Synthesis, structural changes and strengthening mechanisms

International Nuclear Information System (INIS)

Nunes, D.; Vilarigues, M.; Correia, J.B.; Carvalho, P.A.

2012-01-01

The present work investigates Ni–nanodiamond and Ni–graphite composites produced by mechanical synthesis and subsequent heat treatments. Processing of nickel–carbon nanocomposites by this powder metallurgy route poses specific challenges, as carbon phases are prone to carbide conversion and amorphization. The processing window for carbide prevention has been established through X-ray diffraction by a systematic variation of the milling parameters. Transmission electron microscopy confirmed the absence of carbide and showed homogeneous particle distributions, as well as intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of chemically extracted carbon phases demonstrated that milled nanodiamond preserved crystallinity, while an essentially amorphous nature could be inferred for milled graphite. Raman spectra confirmed that nanodiamond particles remained largely unaffected by mechanical synthesis, whereas the bands of milled graphite were significantly changed into the typical amorphous carbon fingerprint. The results on the annealed nanocomposites showed that milling with Ni accelerated graphitization of the carbon phases during heat treatments at 973 and 1073 K in both composites. At the finer scales, the nanocomposites exhibited a remarkable microhardness enhancement (∼70%) compared with pure nanostructured nickel. The Hall–Petch relation and the Orowan–Ashby equation are used to discuss strengthening mechanisms and the load transfer ability to the reinforcing particles.

Characterization of two bacterial hydroxynitrile lyases with high similarity to cupin superfamily proteins

NARCIS (Netherlands)

Hussain, Z.; Wiedner, R.; Steiner, K.; Hajek, T.; Avi, M.; Hecher, B.; Sessitsch, A.; Schwab, H.

2012-01-01

Hydroxynitrile lyases (HNLs) catalyze the cleavage of cyanohydrins. In the reverse reaction, they catalyze the formation of carbon-carbon bonds by enantioselective condensation of hydrocyanic acid with carbonyls. In this study, we describe two proteins from endophytic bacteria that display activity

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

Ion-irradiation-induced defects in bundles of carbon nanotubes

International Nuclear Information System (INIS)

Salonen, E.; Krasheninnikov, A.V.; Nordlund, K.

2002-01-01

We study the structure and formation yields of atomic-scale defects produced by low-dose Ar ion irradiation in bundles of single-wall carbon nanotubes. For this, we employ empirical potential molecular dynamics and simulate ion impact events over an energy range of 100-1000 eV. We show that the most common defects produced at all energies are vacancies on nanotube walls, which at low temperatures are metastable but long-lived defects. We further calculate the spatial distribution of the defects, which proved to be highly non-uniform. We also show that ion irradiation gives rise to the formations of inter-tube covalent bonds mediated by carbon recoils and nanotube lattice distortions due to dangling bond saturation. The number of inter-tube links, as well as the overall damage, linearly grows with the energy of incident ions

Laser Raman microprobe spectroscopy as a diagnostic for the characterisation of diamond and diamond like carbon (DLC) thin films

International Nuclear Information System (INIS)

Johnston, C.

1990-10-01

Invariably when manufacturing an artificial diamond film a mixture of carbon is deposited - tetragonally bonded (diamond), trigonally bonded (graphite) and other allotropic crystalline forms and amorphous carbons. This imposes a need for careful analysis to determine exactly what carbon types constitute the films. Raman spectroscopy is particularly sensitive to crystal and atomic structure and has a number of advantages which make it one of the most useful techniques for interrogating diamond and DLC thin films. Although Raman spectroscopy alone cannot fully characterise the film, it can give more information than simply what particular form of carbon or other impurities are present in the film. It can be used to determine the ratio of sp 2 to sp 3 bonding within the film, and to some extent the crystallite or domain size and the internal stress of the film. The use of laser Raman microprobe spectroscopy as a diagnostic tool in the analysis of diamond and DLC thin films is demonstrated for a variety of carbon films on various substrates and the characterisation of these films is discussed. (author)

Charge transfer in carbon nanotube actuators investigated using in situ Raman spectroscopy

International Nuclear Information System (INIS)

Gupta, S.; Hughes, M.; Windle, A.H.; Robertson, J.

2004-01-01

Charge transfer dynamics on the surface of single-wall carbon nanotube sheets is investigated using in situ Raman spectroscopy in order to understand the actuation mechanism of an electrochemical actuator and to determine associated parameters. We built an actuator from single-wall carbon nanotube mat and studied its actuation in several alkali metal (Li, Na, and K) and alkaline earth (Ca) halide and sulfate solutions in order to clarify the role of counterion as mobile ions in the film. The variation of bonding with applied potential was monitored using in situ Raman spectroscopy. This is because Raman can detect changes in C-C bond length: the radial breathing mode at ∼190 cm-1 varies inversely with the nanotube diameter, and the G band at ∼1590 cm-1 varies with the axial bond length. In addition, the intensities of both the modes vary with the emptying/depleting or filling of the bonding and antibonding states due to electrochemical charge injection. We discussed the variation of peak height and wave numbers of these modes providing valuable information concerning electrochemical charge injection on the carbon nanotube mat surface. We found in-plane microscopic compressive strain (∼-0.25%) and the equivalent charge transfer per carbon atom (f c ∼-0.005) as an upper bound for the actuators studied hereby. It is demonstrated that though the present analysis does comply with the proposition for the actuation principle made earlier, the quantitative estimates are significantly lower if compared with those of reported values. Furthermore, the extent of variation, i.e., coupled electro-chemo-mechanical response of single-wall carbon nanotubes (SWNT) mat depended upon the type of counterion used (Group I versus Group II). The cyclic voltammetry and ac electrochemical impedance spectroscopy results were described briefly, which help to demonstrate well-developed capacitive behavior of SWNT mat and to estimate the specific capacitances as well. Summarizing, the

Effects of carbonyl bond, metal cluster dissociation, and evaporation rates on predictions of nanotube production in high-pressure carbon monoxide

Science.gov (United States)

Scott, Carl D.; Smalley, Richard E.

2003-01-01

The high-pressure carbon monoxide (HiPco) process for producing single-wall carbon nanotubes (SWNTs) uses iron pentacarbonyl as the source of iron for catalyzing the Boudouard reaction. Attempts using nickel tetracarbonyl led to no production of SWNTs. This paper discusses simulations at a constant condition of 1300 K and 30 atm in which the chemical rate equations are solved for different reaction schemes. A lumped cluster model is developed to limit the number of species in the models, yet it includes fairly large clusters. Reaction rate coefficients in these schemes are based on bond energies of iron and nickel species and on estimates of chemical rates for formation of SWNTs. SWNT growth is measured by the conformation of CO2. It is shown that the production of CO2 is significantly greater for FeCO because of its lower bond energy as compared with that of NiCO. It is also shown that the dissociation and evaporation rates of atoms from small metal clusters have a significant effect on CO2 production. A high rate of evaporation leads to a smaller number of metal clusters available to catalyze the Boudouard reaction. This suggests that if CO reacts with metal clusters and removes atoms from them by forming MeCO, this has the effect of enhancing the evaporation rate and reducing SWNT production. The study also investigates some other reactions in the model that have a less dramatic influence.

High-Melt Carbon-Carbon Coating for Nozzle Extensions

Science.gov (United States)

Thompson, James

2015-01-01

Carbon-Carbon Advanced Technologies, Inc. (C-CAT), has developed a high-melt coating for use in nozzle extensions in next-generation spacecraft. The coating is composed primarily of carbon-carbon, a carbon-fiber and carbon-matrix composite material that has gained a spaceworthy reputation due to its ability to withstand ultrahigh temperatures. C-CAT's high-melt coating embeds hafnium carbide (HfC) and zirconium diboride (ZrB2) within the outer layers of a carbon-carbon structure. The coating demonstrated enhanced high-temperature durability and suffered no erosion during a test in NASA's Arc Jet Complex. (Test parameters: stagnation heat flux=198 BTD/sq ft-sec; pressure=.265 atm; temperature=3,100 F; four cycles totaling 28 minutes) In Phase I of the project, C-CAT successfully demonstrated large-scale manufacturability with a 40-inch cylinder representing the end of a nozzle extension and a 16-inch flanged cylinder representing the attach flange of a nozzle extension. These demonstrators were manufactured without spalling or delaminations. In Phase II, C-CAT worked with engine designers to develop a nozzle extension stub skirt interfaced with an Aerojet Rocketdyne RL10 engine. All objectives for Phase II were successfully met. Additional nonengine applications for the coating include thermal protection systems (TPS) for next-generation spacecraft and hypersonic aircraft.

Multiporous carbon allotropes transformed from symmetry-matched carbon nanotubes

Directory of Open Access Journals (Sweden)

Yingxiang Cai

2016-06-01

Full Text Available Carbon nanotubes (CNTs with homogeneous diameters have been proven to transform into new carbon allotropes under pressure but no studies on the compression of inhomogeneous CNTs have been reported. In this study, we propose to build new carbon allotropes from the bottom-up by applying pressure on symmetry-matched inhomogeneous CNTs. We find that the (3,0 CNT with point group C3v and the (6,0 CNT with point group C6v form an all sp3 hybridized hexagonal 3060-Carbon crystal, but the (4,0 CNT with point group D4h and the (8,0 CNT with point group D8h polymerize into a sp2+sp3 hybridized tetragonal 4080-Carbon structure. Their thermodynamic, mechanical and dynamic stabilities show that they are potential carbon allotropes to be experimentally synthesized. The multiporous structures, excellently mechanical properties and special electronic structures (semiconductive 3060-Carbon and semimetallic 4080-Carbon imply their many potential applications, such as gases purification, hydrogen storage and lightweight semiconductor devices. In addition, we simulate their feature XRD patterns which are helpful for identifying the two carbon crystals in future experimental studies.

Multiporous carbon allotropes transformed from symmetry-matched carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Cai, Yingxiang, E-mail: yingxiangcai@ncu.edu.cn; Wang, Hao; Xu, Shengliang; Hu, Yujie; Liu, Ning; Xu, Xuechun [Department of Physics, NanChang University, Jiangxi, Nanchang 330031 (China)

2016-06-15

Carbon nanotubes (CNTs) with homogeneous diameters have been proven to transform into new carbon allotropes under pressure but no studies on the compression of inhomogeneous CNTs have been reported. In this study, we propose to build new carbon allotropes from the bottom-up by applying pressure on symmetry-matched inhomogeneous CNTs. We find that the (3,0) CNT with point group C{sub 3v} and the (6,0) CNT with point group C{sub 6v} form an all sp{sup 3} hybridized hexagonal 3060-Carbon crystal, but the (4,0) CNT with point group D{sub 4h} and the (8,0) CNT with point group D{sub 8h} polymerize into a sp{sup 2}+sp{sup 3} hybridized tetragonal 4080-Carbon structure. Their thermodynamic, mechanical and dynamic stabilities show that they are potential carbon allotropes to be experimentally synthesized. The multiporous structures, excellently mechanical properties and special electronic structures (semiconductive 3060-Carbon and semimetallic 4080-Carbon) imply their many potential applications, such as gases purification, hydrogen storage and lightweight semiconductor devices. In addition, we simulate their feature XRD patterns which are helpful for identifying the two carbon crystals in future experimental studies.

Magneto-carbonization method for production of carbon fiber, and high performance carbon fibers made thereby

Science.gov (United States)

Naskar, Amit K.; Ozcan, Soydan; Eberle, Claude C.; Abdallah, Mohamed Gabr; Mackiewicz, Ludtka Gail; Ludtka, Gerard Michael; Paulauskas, Felix Leonard; Rivard, John Daniel Kennedy

2017-08-08

Method for the preparation of carbon fiber from fiber precursor, wherein the fiber precursor is subjected to a magnetic field of at least 3 Tesla during a carbonization process. The carbonization process is generally conducted at a temperature of at least 400.degree. C. and less than 2200.degree. C., wherein, in particular embodiments, the carbonization process includes a low temperature carbonization step conducted at a temperature of at least or above 400.degree. C. or 500.degree. C. and less than or up to 1000.degree. C., 1100.degree. C., or 1200.degree. C., followed by a high temperature carbonization step conducted at a temperature of at least or above 1200.degree. C. In particular embodiments, particularly in the case of a polyacrylonitrile (PAN) fiber precursor, the resulting carbon fiber may possess a minimum tensile strength of at least 600 ksi, a tensile modulus of at least 30 Msi, and an ultimate elongation of at least 1.5%.

NanoCarbon 2011. Selected works from the Brazilian carbon meeting

Energy Technology Data Exchange (ETDEWEB)

Avellaneda, Cesar (ed.) [Univ. Federal de Pelotas (Brazil). Centro de Desenvolvimento Tecnologico

2013-02-01

This book presents eight selected papers from the Brazilian Carbon Meeting 2011. It contains the following topics: Review of field emission from carbon Nanotubes: Highlighting measuring energy spread. - Synthesis and characterisation of carbon nanocomposites. - Performance of Ni/MgAl{sub 2}O{sub 4} catalyst obtained by a metal-chitosan complex method in methane decomposition reaction with production of carbon nanotubes. - The use of nanostructures for DNA transfection. - Applications of carbon nanotubes in oncology. - CNTs/TiO2 composites. - Synthesis of vertically aligned carbon nanotubes by CVD Technique: A review. - Thermoset three-component composite systems using carbon nantubes.

Calculation on uranium carbon oxygen system molecular structure by DFT

International Nuclear Information System (INIS)

Zhang Guangfeng; Wang Xiaolin; Zou Lexi; Sun Ying; Xue Weidong; Zhu Zhenghe; Wang Hongyan

2001-01-01

The authors study on the possible molecular structures U-C-O, U-O-C, C-U-O (angular structure C a nd linear structure C ∞υ ) of carbon monoxide interacting on uranium metal surface by Density functional theory (DFT). The uranium atom is used RECP (Relativistic Effective Core Potential) and contracted valence basis sets (6s5p2d4f)/[3s3p2d2f], and for carbon and oxygen atoms all are 6-311G basis sets. The author presents the results of energy optimum which shows that triple and quintuple state are more stable. The authors get the electronic state, geometry structure, energy, harmonic frequency, mechanical property, etc. of these twelve triple and quintuple state relative stable structures. The normal vibrational analytical figure of angular structure (C s ) and linear structure (C ∞υ ) is given at the same time. It is indicated that angular structure has lower energy than linear structure, moreover the angular structure of U-C-O( 3 A ) has the lowest energy. The bond strength between uranium atom and carbon monoxide is weak and between uranium atom and oxygen atom is slightly stronger than between uranium atom and carbon atom which the authors can know by superposition population and bond energy analysis among atoms

Hybrid Composites Based on Carbon Fiber/Carbon Nanofilament Reinforcement

Directory of Open Access Journals (Sweden)

Mehran Tehrani

2014-05-01

Full Text Available Carbon nanofilament and nanotubes (CNTs have shown promise for enhancing the mechanical properties of fiber-reinforced composites (FRPs and imparting multi-functionalities to them. While direct mixing of carbon nanofilaments with the polymer matrix in FRPs has several drawbacks, a high volume of uniform nanofilaments can be directly grown on fiber surfaces prior to composite fabrication. This study demonstrates the ability to create carbon nanofilaments on the surface of carbon fibers employing a synthesis method, graphitic structures by design (GSD, in which carbon structures are grown from fuel mixtures using nickel particles as the catalyst. The synthesis technique is proven feasible to grow nanofilament structures—from ethylene mixtures at 550 °C—on commercial polyacrylonitrile (PAN-based carbon fibers. Raman spectroscopy and electron microscopy were employed to characterize the surface-grown carbon species. For comparison purposes, a catalytic chemical vapor deposition (CCVD technique was also utilized to grow multiwall CNTs (MWCNTs on carbon fiber yarns. The mechanical characterization showed that composites using the GSD-grown carbon nanofilaments outperform those using the CCVD-grown CNTs in terms of stiffness and tensile strength. The results suggest that further optimization of the GSD growth time, patterning and thermal shield coating of the carbon fibers is required to fully materialize the potential benefits of the GSD technique.

Diffusion bonding of commercially pure titanium to low carbon steel using a silver interlayer

International Nuclear Information System (INIS)

Atasoy, Evren; Kahraman, Nizamettin

2008-01-01

Titanium and low carbon steel plates were joined through diffusion bonding using a silver interlayer at various temperatures for various diffusion times. In order to determine the strength of the resulting joints, tensile-shear tests and hardness tests were applied. Additionally, optical, scanning electron microscopy examinations and energy dispersive spectrometry elemental analyses were carried out to determine the interface properties of the joint. The work showed that the highest interface strength was obtained for the specimens joined at 850 deg. C for 90 min. It was seen from the hardness results that the highest hardness value was obtained for the interlayer material and the hardness values on the both sides of the interlayer decreased gradually as the distance from the joint increased. In energy dispersive spectrometry analyses, it was seen that the amount of silver in the interlayer decreased markedly depending on the temperature rise. In addition, increasing diffusion time also caused some slight decrease in the amount of silver

HF treatment effect for carbon deposition on silicon (111) by DC sputtering technique

Energy Technology Data Exchange (ETDEWEB)

Aji, A. S., E-mail: aji.ravazes70@gmail.com; Darma, Y., E-mail: aji.ravazes70@gmail.com [Quantum Semiconductor and Devices Lab., Physics of Material Electronics Research Division, Department of Physics, Institut Teknologi Bandung (Indonesia)

2014-03-24

Surface modifications of Si (111) substrate by HF solution for thin film carbon deposition have been systematically studied. Thin film carbon on Si (111) has been deposited using DC Unbalanced Magnetron Sputtering with carbon pellet doped by 5% Fe as the target. EDAX characterization confirmed that the carbon fraction on Si substrate much higher by dipping a clean Si substrate by HF solution before sputtering process in comparison with carbon fraction on Si substrate just after conventional RCA. Moreover, SEM and AFM images show the uniform thin film carbon on Si with HF treatment, in contrast to the Si without HF solution treatment. These experimental results suggest that HF treatment of Si surface provide Si-H bonds on top Si surface that useful to enhance the carbon deposition during sputtering process. Furthermore, we investigate the thermal stability of thin film carbon on Si by thermal annealing process up to 900 °C. Atomic arrangements during annealing process were characterized by Raman spectroscopy. Raman spectra indicate that thin film carbon on Si is remaining unchanged until 600 °C and carbon atoms start to diffuse toward Si substrate after annealing at 900 °C.

Influence of chemical structure on carbon isotope composition of lignite

Science.gov (United States)

Erdenetsogt, Bat-Orshikh; Lee, Insung; Ko, Yoon-Joo; Mungunchimeg, Batsaikhan

2017-04-01

During the last two decades, a number of studies on carbon isotopes in terrestrial organic matter (OM) have been carried out and used to determine changes in paleoatmospheric δ13C value as well as assisting in paleoclimate analysis. Coal is abundant terrestrial OM. However, application of its δ13C value is very limited, because the understanding of changes in isotopic composition during coalification is relatively insufficient. The purpose of this study was to examine the influence of the chemical structure on the carbon isotope composition of lignite. Generally, lignite has more complex chemical structures than other higher rank coal because of the existence of various types of oxygen-containing functional groups that are eliminated at higher rank level. A total of sixteen Lower Cretaceous lignite samples from Baganuur mine (Mongolia) were studied by ultimate, stable carbon isotope and solid-state 13C CP/MAS NMR analyses. The carbon contents of the samples increase with increase in depth, whereas oxygen content decreases continuously. This is undoubtedly due to normal coalification process and also consistent with solid state NMR results. The δ13C values of the samples range from -23.54‰ to -21.34‰ and are enriched in 13C towards the lowermost samples. Based on the deconvolution of the NMR spectra, the ratios between carbons bonded to oxygen (60-90 ppm and 135-220 ppm) over carbons bonded to carbon and hydrogen (0-50 ppm and 90-135 ppm) were calculated for the samples. These correlate well with δ13C values (R2 0.88). The results indicate that the δ13C values of lignite are controlled by two mechanisms: (i) depletion in 13C as a result of loss of isotopically heavy oxygen-bounded carbons and (ii) enrichment in 13C caused by a loss of isotopically light methane from aliphatic and aromatic carbons. At the rank of lignite, coal is enriched in 13C because the amount of isotopically heavy CO2 and CO, released from coal as a result of changes in the chemical

Quantitative Analysis of Carbon Flow into Photosynthetic Products Functioning as Carbon Storage in the Marine Coccolithophore, Emiliania huxleyi.

Science.gov (United States)

Tsuji, Yoshinori; Yamazaki, Masatoshi; Suzuki, Iwane; Shiraiwa, Yoshihiro

2015-08-01

The bloom-forming coccolithophore Emiliania huxleyi (Haptophyta) is a dominant marine phytoplankton, cells of which are covered with calcareous plates (coccoliths). E. huxleyi produces unique lipids of C37-C40 long-chain ketones (alkenones) with two to four trans-unsaturated bonds, β-glucan (but not α-glucan) and acid polysaccharide (AP) associated with the morphogenesis of CaCO3 crystals in coccoliths. Despite such unique features, there is no detailed information on the patterns of carbon allocation into these compounds. Therefore, we performed quantitative estimation of carbon flow into various macromolecular products by conducting (14)C-radiotracer experiments using NaH(14)CO3 as a substrate. Photosynthetic (14)C incorporation into low molecular-mass compounds (LMC), extracellular AP, alkenones, and total lipids except alkenones was estimated to be 35, 13, 17, and 25 % of total (14)C fixation in logarithmic growth phase cells and 33, 19, 18, and 18 % in stationary growth phase cells, respectively. However, less than 1 % of (14)C was incorporated into β-glucan in both cells. (14)C-mannitol occupied ca. 5 % of total fixed (14)C as the most dominant LMC product. Levels of all (14)C compounds decreased in the dark. Therefore, alkenones and LMC (including mannitol), but not β-glucan, function in carbon/energy storage in E. huxleyi, irrespective of the growth phase. Compared with other algae, the low carbon flux into β-glucan is a unique feature of carbon metabolism in E. huxelyi.

Carbon composites composites with carbon fibers, nanofibers, and nanotubes

CERN Document Server

Chung, Deborah D L

2017-01-01

Carbon Composites: Composites with Carbon Fibers, Nanofibers, and Nanotubes, Second Edition, provides the reader with information on a wide range of carbon fiber composites, including polymer-matrix, metal-matrix, carbon-matrix, ceramic-matrix and cement-matrix composites. In contrast to other books on composites, this work emphasizes materials rather than mechanics. This emphasis reflects the key role of materials science and engineering in the development of composite materials. The applications focus of the book covers both the developing range of structural applications for carbon fiber composites, including military and civil aircraft, automobiles and construction, and non-structural applications, including electromagnetic shielding, sensing/monitoring, vibration damping, energy storage, energy generation, and deicing. In addition to these new application areas, new material in this updated edition includes coverage of cement-matrix composites, carbon nanofibers, carbon matrix precursors, fiber surface ...

Anthropogenic Forcing of Carbonate and Organic Carbon Preservation in Marine Sediments.

Science.gov (United States)

Keil, Richard

2017-01-03

Carbon preservation in marine sediments, supplemented by that in large lakes, is the primary mechanism that moves carbon from the active surficial carbon cycle to the slower geologic carbon cycle. Preservation rates are low relative to the rates at which carbon moves between surface pools, which has led to the preservation term largely being ignored when evaluating anthropogenic forcing of the global carbon cycle. However, a variety of anthropogenic drivers-including ocean warming, deoxygenation, and acidification, as well as human-induced changes in sediment delivery to the ocean and mixing and irrigation of continental margin sediments-all work to decrease the already small carbon preservation term. These drivers affect the cycling of both carbonate and organic carbon in the ocean. The overall effect of anthropogenic forcing in the modern ocean is to decrease delivery of carbon to sediments, increase sedimentary dissolution and remineralization, and subsequently decrease overall carbon preservation.

Singlet versus Triplet Excited State Mediated Photoinduced Dehalogenation Reactions of Itraconazole in Acetonitrile and Aqueous Solutions.

Science.gov (United States)

Zhu, Ruixue; Li, Ming-de; Du, Lili; Phillips, David Lee

2017-04-06

Photoinduced dehalogenation of the antifungal drug itraconazole (ITR) in acetonitrile (ACN) and ACN/water mixed solutions was investigated using femtosecond and nanosecond time-resolved transient absorption (fs-TA and ns-TA, respectively) and nanosecond time-resolved resonance Raman spectroscopy (ns-TR 3 ) experiments. An excited resonance energy transfer is found to take place from the 4-phenyl-4,5-dihydro-3H-1,2,4-triazol-3-one part of the molecule to the 1,3-dichlorobenzene part of the molecule when ITR is excited by ultraviolet light. This photoexcitation is followed by a fast carbon-halogen bond cleavage that leads to the generation of radical intermediates via either triplet and/or singlet excited states. It is found that the singlet excited state-mediated carbon-halogen cleavage is the predominant dehalogenation process in ACN solvent, whereas a triplet state-mediated carbon-halogen cleavage prefers to occur in the ACN/water mixed solutions. The singlet-to-triplet energy gap is decreased in the ACN/water mixed solvents and this helps facilitate an intersystem crossing process, and thus, the carbon-halogen bond cleavage happens mostly through an excited triplet state in the aqueous solutions examined. The ns-TA and ns-TR 3 results also provide some evidence that radical intermediates are generated through a homolytic carbon-halogen bond cleavage via predominantly the singlet excited state pathway in ACN but via mainly the triplet state pathway in the aqueous solutions. In strong acidic solutions, protonation at the oxygen and/or nitrogen atoms of the 1,2,4-triazole-3-one group appears to hinder the dehalogenation reactions. This may offer the possibility that the phototoxicity of ITR due to the generation of aryl or halogen radicals can be reduced by protonation of certain moieties in suitably designed ITR halogen-containing derivatives.

Ascorbic acid as a bifunctional hydrogen bond donor for the synthesis of cyclic carbonates from CO2 under ambient conditions

KAUST Repository

Arayachukiat, Sunatda; Kongtes, Chutima; Barthel, Alexander; Vummaleti, Sai V. C.; Poater, Albert; Wannakao, Sippakorn; Cavallo, Luigi; D'Elia, Valerio

2017-01-01

Readily available ascorbic acid was discovered as an environmentally benign hydrogen bond donor (HBD) for the synthe-sis of cyclic organic carbonates from CO2 and epoxides in the presence of nucleophilic co-catalysts. The ascorbic acid/TBAI (TBAI: tetrabutylammonium iodide) binary system could be applied for the cycloaddition of CO2 to various epoxides under ambient or mild conditions. DFT calculations and catalysis experiments revealed an intriguing bifunctional mechanism in the step of CO2 insertion involving different hydroxyl moieties (enediol, ethyldiol) of the ascorbic acid scaffold.

Ascorbic acid as a bifunctional hydrogen bond donor for the synthesis of cyclic carbonates from CO2 under ambient conditions

KAUST Repository

Arayachukiat, Sunatda

2017-07-14

Readily available ascorbic acid was discovered as an environmentally benign hydrogen bond donor (HBD) for the synthe-sis of cyclic organic carbonates from CO2 and epoxides in the presence of nucleophilic co-catalysts. The ascorbic acid/TBAI (TBAI: tetrabutylammonium iodide) binary system could be applied for the cycloaddition of CO2 to various epoxides under ambient or mild conditions. DFT calculations and catalysis experiments revealed an intriguing bifunctional mechanism in the step of CO2 insertion involving different hydroxyl moieties (enediol, ethyldiol) of the ascorbic acid scaffold.

Yields of primary products from chloroethylenes in air under electron beam irradiation

International Nuclear Information System (INIS)

Hakoda, Teruyuki; Hashimoto, Shoji; Kojima, Takuji

2003-01-01

The quantitative analysis of toxic primary irradiation products was carried out for the development of the purification technology of chloroethylenes/air mixtures using an electron beam (EB). Degradation of chloroethylenes in humid air proceeded through the formation of primary products retaining a carbon-carbon (C-C) bond such as chloroacetyl chlorides and chloroacetyl aldehyde as well as that of primary products of COCl 2 and HCOCl through C-C bond cleavage. Chloroethylenes having one carbon bonded to two Cl atoms was decomposed into the primary products retaining a C-C bond prior to breaking a C-C bond. The number of Cl atoms of a chloroethylene molecule enhanced the formation ratio of primary products retaining a C-C bond. On the other hand, chloroethylene having two carbons bonded to one Cl atom was degraded thought the scission of a C-C bond predominantly C-C bond maintenance. (author)

A carbon in molten carbonate anode model for a direct carbon fuel cell

Energy Technology Data Exchange (ETDEWEB)

Li Hongjiao; Liu Qinghua [Tianjin Key Laboratory of Catalysis Science and Technology, School of Chemical Engineering, Tianjin University, Weijing Road 92, Tianjin 300072 (China); State Key Laboratory for Chemical Engineering (Tianjin University), School of Chemical Engineering, Tianjin University, Weijing Road 92, Tianjin 300072 (China); Li Yongdan, E-mail: ydli@tju.edu.c [Tianjin Key Laboratory of Catalysis Science and Technology, School of Chemical Engineering, Tianjin University, Weijing Road 92, Tianjin 300072 (China); State Key Laboratory for Chemical Engineering (Tianjin University), School of Chemical Engineering, Tianjin University, Weijing Road 92, Tianjin 300072 (China)

2010-02-15

The electrochemical oxidation of carbon at the anode of a direct carbon fuel cell (DCFC) includes charge transfer steps and chemical steps. A microstructural model of carbon particle is built, in which perfect graphene stacks are taken as the basic building blocks of carbon. A modified mechanism taking account of the irreversibility of the process and supposing that the electrochemical oxidation of carbon takes place only at the edges of the graphene sheets is proposed. A Tafel type overall rate equation is deduced along with expressions of exchange current density (j{sub 0}) and activation polarization (eta{sub act}). The performance of carbon black and graphite as the fuel of DCFC is examined. It has been found that j{sub 0} is in the range of 0.10-6.12 mA cm{sup -2} at 923-1123 K and eta{sub act} is in the range of 0.024-0.28 V at 923-1123 K with current density in 10-120 mA cm{sup -2}. Analysis of the j{sub 0}, eta{sub act} values and the product composition reveals that the charge transfer steps as well as the oxygen ion absorption steps are both important for the reaction rate. The activity of the carbon material with respect to atom location is introduced to the open circuit potential difference (OCP) calculation with Nernst equation.

Oxidative Attack of Carbon/Carbon Substrates through Coating Pinholes

Science.gov (United States)

Jacobson, Nathan S.; Leonhardt, Todd; Curry, Donald; Rapp, Robert A.

1998-01-01

A critical issue with oxidation protected carbon/carbon composites used for spacecraft thermal protection is the formation of coating pinholes. In laboratory experiments, artificial pinholes were drilled through SiC-coatings on a carbon/carbon material and the material was oxidized at 600, 1000, and 1400 C at reduced pressures of air. The attack of the carbon/carbon was quantified by both weight loss and a novel cross-sectioning technique. A two-zone, one dimensional diffusion control model was adapted to analyze this problem. Agreement of the model with experiment was reasonable at 1000 and 1400 C; however results at lower temperatures show clear deviations from the theory suggesting that surface reaction control plays a role.

Carbon flows, carbon markets, and low-carbon lifestyles: reflecting on the role of markets in climate governance

NARCIS (Netherlands)

Spaargaren, G.; Mol, A.P.J.

2013-01-01

The role of carbon markets in governing global carbon flows triggers substantial debates among policymakers, social movements and social scientists. The present debate on carbon markets is different from the earlier debate on market-based instruments in environmental politics. Carbon markets

Carbon dioxide sensor

Science.gov (United States)

Dutta, Prabir K [Worthington, OH; Lee, Inhee [Columbus, OH; Akbar, Sheikh A [Hilliard, OH

2011-11-15

The present invention generally relates to carbon dioxide (CO.sub.2) sensors. In one embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor that incorporates lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3). In another embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor has a reduced sensitivity to humidity due to a sensing electrode with a layered structure of lithium carbonate and barium carbonate. In still another embodiment, the present invention relates to a method of producing carbon dioxide (CO.sub.2) sensors having lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3).

Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires

Directory of Open Access Journals (Sweden)

Alberto Milani

2015-02-01

Full Text Available Graphene, nanotubes and other carbon nanostructures have shown potential as candidates for advanced technological applications due to the different coordination of carbon atoms and to the possibility of π-conjugation. In this context, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level. Carbon-atom wires (CAWs can be arranged in two possible structures: a sequence of double bonds (cumulenes, resulting in a 1D metal, or an alternating sequence of single–triple bonds (polyynes, expected to show semiconducting properties. The electronic and optical properties of CAWs can be finely tuned by controlling the wire length (i.e., the number of carbon atoms and the type of termination (e.g., atom, molecular group or nanostructure. Although linear, sp-hybridized carbon systems are still considered elusive and unstable materials, a number of nanostructures consisting of sp-carbon wires have been produced and characterized to date. In this short review, we present the main CAW synthesis techniques and stabilization strategies and we discuss the current status of the understanding of their structural, electronic and vibrational properties with particular attention to how these properties are related to one another. We focus on the use of vibrational spectroscopy to provide information on the structural and electronic properties of the system (e.g., determination of wire length. Moreover, by employing Raman spectroscopy and surface enhanced Raman scattering in combination with the support of first principles calculations, we show that a detailed understanding of the charge transfer between CAWs and metal nanoparticles may open the possibility to tune the electronic structure from alternating to equalized bonds.

Carbon fuel particles used in direct carbon conversion fuel cells

Science.gov (United States)

Cooper, John F.; Cherepy, Nerine

2012-10-09

A system for preparing particulate carbon fuel and using the particulate carbon fuel in a fuel cell. Carbon particles are finely divided. The finely dividing carbon particles are introduced into the fuel cell. A gas containing oxygen is introduced into the fuel cell. The finely divided carbon particles are exposed to carbonate salts, or to molten NaOH or KOH or LiOH or mixtures of NaOH or KOH or LiOH, or to mixed hydroxides, or to alkali and alkaline earth nitrates.

Carbon Fuel Particles Used in Direct Carbon Conversion Fuel Cells

Science.gov (United States)

Cooper, John F.; Cherepy, Nerine

2008-10-21

A system for preparing particulate carbon fuel and using the particulate carbon fuel in a fuel cell. Carbon particles are finely divided. The finely dividing carbon particles are introduced into the fuel cell. A gas containing oxygen is introduced into the fuel cell. The finely divided carbon particles are exposed to carbonate salts, or to molten NaOH or KOH or LiOH or mixtures of NaOH or KOH or LiOH, or to mixed hydroxides, or to alkali and alkaline earth nitrates.

Feasibility demonstration of consolidating porous beryllium/carbon structures. Final report

International Nuclear Information System (INIS)

Browning, M.J.; Hoover, G.E.; Mueller, J.J.; Hanes, H.D.

1977-01-01

A preliminary feasibility study was initiated to determine if porous beryllium structures could be fabricated by consolidating beryllium-coated microballoons into a rigid structure. The target specifications were to coat nominally 1-mm diameter microspheres with 0.5-mil beryllium coatings and then bond into a structure. Because of the very short time period, it was agreeable to use existing or quickly-available materials. The general approach was to apply coatings to carbon or quartz microspheres. Physical vapor deposition and ''snow-balling'' of fine beryllium powder were the two methods investigated. Once the particles were coated, HIP (pressure bonding) and pressureless sintering were to be investigated as methods for consolidating the microballoons. A low level of effort was to be spent to look at means of fabricating an all-carbon structure

A thermodynamic approach to assess organic solute adsorption onto activated carbon in water

KAUST Repository

De Ridder, David J.; Verliefde, Arne R. D.; Heijman, Bas G J; Gelin, Simon; Pereira, Manuel Fernando Ribeiro; Rocha, Raquel P.; Figueiredo, José Luí s M; Amy, Gary L.; Van Dijk, Hans C.

2012-01-01

In this paper, the hydrophobicity of 13 activated carbons is determined by various methods; water vapour adsorption, immersion calorimetry, and contact angle measurements. The quantity and type of oxygen-containing groups on the activated carbon were measured and related to the methods used to measure hydrophobicity. It was found that the water-activated carbon adsorption strength (based on immersion calorimetry, contact angles) depended on both type and quantity of oxygen-containing groups, while water vapour adsorption depended only on their quantity. Activated carbon hydrophobicity measurements alone could not be related to 1-hexanol and 1,3-dichloropropene adsorption. However, a relationship was found between work of adhesion and adsorption of these solutes. The work of adhesion depends not only on activated carbon-water interaction (carbon hydrophobicity), but also on solute-water (solute hydrophobicity) and activated carbon-solute interactions. Our research shows that the work of adhesion can explain solute adsorption and includes the effect of hydrogen bond formation between solute and activated carbon. © 2012 Elsevier Ltd. All rights reserved.

A thermodynamic approach to assess organic solute adsorption onto activated carbon in water

KAUST Repository

De Ridder, David J.

2012-08-01

In this paper, the hydrophobicity of 13 activated carbons is determined by various methods; water vapour adsorption, immersion calorimetry, and contact angle measurements. The quantity and type of oxygen-containing groups on the activated carbon were measured and related to the methods used to measure hydrophobicity. It was found that the water-activated carbon adsorption strength (based on immersion calorimetry, contact angles) depended on both type and quantity of oxygen-containing groups, while water vapour adsorption depended only on their quantity. Activated carbon hydrophobicity measurements alone could not be related to 1-hexanol and 1,3-dichloropropene adsorption. However, a relationship was found between work of adhesion and adsorption of these solutes. The work of adhesion depends not only on activated carbon-water interaction (carbon hydrophobicity), but also on solute-water (solute hydrophobicity) and activated carbon-solute interactions. Our research shows that the work of adhesion can explain solute adsorption and includes the effect of hydrogen bond formation between solute and activated carbon. © 2012 Elsevier Ltd. All rights reserved.

Experimental Studies of Carbon Nanotube Materials for Space Radiators

Science.gov (United States)

SanSoucie, MIchael P.; Rogers, Jan R.; Craven, Paul D.; Hyers, Robert W.

2012-01-01

Game ]changing propulsion systems are often enabled by novel designs using advanced materials. Radiator performance dictates power output for nuclear electric propulsion (NEP) systems. Carbon nanotubes (CNT) and carbon fiber materials have the potential to offer significant improvements in thermal conductivity and mass properties. A test apparatus was developed to test advanced radiator designs. This test apparatus uses a resistance heater inside a graphite tube. Metallic tubes can be slipped over the graphite tube to simulate a heat pipe. Several sub ]scale test articles were fabricated using CNT cloth and pitch ]based carbon fibers, which were bonded to a metallic tube using an active braze material. The test articles were heated up to 600 C and an infrared (IR) camera captured the results. The test apparatus and experimental results are presented here.

Strongly coupled inorganic-nano-carbon hybrid materials for energy storage.

Science.gov (United States)

Wang, Hailiang; Dai, Hongjie

2013-04-07

The global shift of energy production from fossil fuels to renewable energy sources requires more efficient and reliable electrochemical energy storage devices. In particular, the development of electric or hydrogen powered vehicles calls for much-higher-performance batteries, supercapacitors and fuel cells than are currently available. In this review, we present an approach to synthesize electrochemical energy storage materials to form strongly coupled hybrids (SC-hybrids) of inorganic nanomaterials and novel graphitic nano-carbon materials such as carbon nanotubes and graphene, through nucleation and growth of nanoparticles at the functional groups of oxidized graphitic nano-carbon. We show that the inorganic-nano-carbon hybrid materials represent a new approach to synthesize electrode materials with higher electrochemical performance than traditional counterparts made by simple physical mixtures of electrochemically active inorganic particles and conducting carbon materials. The inorganic-nano-carbon hybrid materials are novel due to possible chemical bonding between inorganic nanoparticles and oxidized carbon, affording enhanced charge transport and increased rate capability of electrochemical materials without sacrificing specific capacity. Nano-carbon with various degrees of oxidation provides a novel substrate for nanoparticle nucleation and growth. The interactions between inorganic precursors and oxidized-carbon substrates provide a degree of control over the morphology, size and structure of the resulting inorganic nanoparticles. This paper reviews the recent development of inorganic-nano-carbon hybrid materials for electrochemical energy storage and conversion, including the preparation and functionalization of graphene sheets and carbon nanotubes to impart oxygen containing groups and defects, and methods of synthesis of nanoparticles of various morphologies on oxidized graphene and carbon nanotubes. We then review the applications of the SC

Trading forest carbon

Science.gov (United States)

The nature of carbon in forests is discussed from the perspective of carbon trading. Carbon inventories, specifically in the area of land use and forestry are reviewed for the Pacific Northwest. Carbon turnover in forests is discussed as it relates to carbon sequestration. Scient...