WorldWideScience

Sample records for carbon surfaces mechanism

  1. Evaluation of Mechanical Property of Carbon Fiber/Polypropylene Composite According to Carbon Fiber Surface Treatment

    International Nuclear Information System (INIS)

    In this study, the mechanical properties of a carbon fiber/polypropylene composite were evaluated according to the carbon fiber surface treatment. Carbon fiber surface treatments such as silane coupling agents and plasma treatment were performed to enhance the interfacial strength between carbon fibers and polypropylene. The treated carbon fiber surface was characterized by XP S, Sem, and single-filament tensile test. The interlaminar shear strength (Ilks) of the composite with respect to the surface treatment was determined by a short beam shear test. The test results showed that the Ilks of the plasma-treated specimen increased with the treatment time. The Ilks of the specimen treated with a silane coupling agent after plasma treatment increased by 48.7% compared to that of the untreated specimen

  2. Further insights into the role of carbon surface functionalities in the mechanism of phenol adsorption.

    Science.gov (United States)

    Terzyk, Artur P

    2003-12-15

    The presented study describes the temperature as well as pH dependence of phenol adsorption (and adsorption kinetics) on four carbons with different chemical compositions of the surface layer but almost identical porosity. In the first part, it is shown, applying the most sophisticated method of carbon porosity characterization (i.e., the method of Do and co-workers-ND method), that the porosity does not change much after the chemical modification of carbons. Then it is shown that the ND method leads to the same results as the DFT (density functional theory) does. Next, the TPD results for D43/1 carbons (initial, modified with HNO(3), fuming H(2)SO(4), and with NH(3)) are described. The TPD results for carbon modified with fuming sulphuric acid has not been reported yet by others. The deconvolution of peaks is performed. The obtained results, together with those already published, lead to the chemical structures of surface functionalities for all studied carbons. The thermogravimetric analysis of phenol adsorption shows that the amount of chemically bonded molecules is small. Then it is shown that the adsorption at the acidic pH (1.5) level is lower for all studied carbons than that at the neutral one. The description of the isotherms applying adsorbability, quasi-Freundlich and DA models, together with enthalpy measurements, lead to the mechanism of phenol adsorption at both pH values. The mechanism is, furthermore, confirmed by some empirical correlations. The analysis of the average hysteresis on adsorption-desorption isotherms as well as the comparison of phenol adsorption in oxic and anoxic conditions leads to the mechanism of irreversible phenol adsorption. It is suggested that the irreversibility is caused by two effects: the creation of strong complexes between phenol and surface carbonyl and lactones as well as by the polymerization. The last effect is due to the ability of carbon to adsorb the oxygen from solution and form superoxo ions. Finally, the

  3. Mechanical Properties, Surface Structure, and Morphology of Carbon Fibers Pre-heated for Liquid Aluminum Infiltration

    Science.gov (United States)

    Kachold, Franziska S.; Kozera, Rafal; Singer, Robert F.; Boczkowska, Anna

    2016-04-01

    To efficiently produce carbon fiber-reinforced aluminum on a large scale, we developed a special high-pressure die casting process. Pre-heating of the fibers is crucial for successful infiltration. In this paper, the influence of heating carried out in industrial conditions on the mechanical properties of the fibers was investigated. Therefore, polyacrylonitrile-based high-tensile carbon fiber textiles were heated by infrared emitters in an argon-rich atmosphere to temperatures between 450 and 1400 °C. Single fiber tensile tests revealed a decrease in tensile strength and strain at fracture. Young's modulus was not affected. Scanning electron microscopy identified cavities on the fiber surface as the reason for the decrease in mechanical properties. They were caused by the attack of atmospheric oxygen. The atomic structure of the fibers did not change at any temperature, as x-ray diffraction confirmed. Based on these data, the pre-heating for the casting process can be optimized.

  4. Carbon nanotubes dispersed polymer nanocomposites: mechanical, electrical, thermal properties and surface morphology

    Indian Academy of Sciences (India)

    Nitin Sankar; Mamilla Nagarjun Reddy; R Krishna Prasad

    2016-02-01

    The various properties and surface morphology of the carbon nanotubes (CNTs) dispersed polydimethyl siloxane (PDMS) matrix were studied to determine their usefulness in various applications. The tensile strength, Young's modulus and electrical breakdown strength of CNT/polymer composites were 0.35MPa, 1.2MPa and 8.1 kV, respectively. The thermal conductivity and dielectric constant for the material having 4.28 wt% CNT were 0.225 W m−1 K−1 and 2.329, respectively. The CNT/polymer composites are promising functional composites with improved mechanical and electrical properties. The scanning electron microscope analysis of surface morphology of PDMS/CNT composite showed that the rough surface texture on nanocomposite has large surface area with circular pores. The Fourier transform infrared spectroscopy showed the functional groups present in polymer nanocomposite.

  5. Film forming kinetics and reaction mechanism of γ-glycidoxypropyltrimethoxysilane on low carbon steel surfaces

    International Nuclear Information System (INIS)

    The film forming kinetics and reaction mechanism of γ-GPS on low carbon steel surfaces was investigated by FTIR-ATR, AFM, NSS and theoretical calculation method. The results from experimental section indicated that the reaction of γ-GPS on low carbon steel surfaces followed the conventional reaction mechanism, which can be described as reaction (I) (Me (Metal)-OH + HO-Si → Me-O-Si + H2O) and reaction (II) (Si-OH + Si-OH → Si-O-Si + H2O). During film forming process, the formation of Si-O-Fe bond (reaction (I)) exhibited oscillatory phenomenon, the condensation degree of silanol monomers (reaction (II)) increased continuously. The metal hydroxyl density had significant influence on the growth mechanisms and corrosion resisting property of γ-GPS films. The results from theoretical calculation section indicated that the patterns of reaction (I) and reaction (II) were similar, involving a nucleophilic attack on the silicon center. The formation of Si-O-Fe bond (reaction (I)) was kinetically and thermodynamically preferred, which had catalytic effect on its condensation with neighboring silanol monomers (reaction (II)). Our DFT calculations were good consistent with the experimental measurements.

  6. Growth mechanism of graphene on platinum: Surface catalysis and carbon segregation

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jie, E-mail: jie.sun@chalmers.se; Lindvall, Niclas; Yurgens, August [Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Nam, Youngwoo [Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Cole, Matthew T. [Electrical Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, CB3 0FA Cambridge (United Kingdom); Teo, Kenneth B. K. [AIXTRON Nanoinstruments Ltd., Swavesey, CB24 4FQ Cambridge (United Kingdom); Woo Park, Yung [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-04-14

    A model of the graphene growth mechanism of chemical vapor deposition on platinum is proposed and verified by experiments. Surface catalysis and carbon segregation occur, respectively, at high and low temperatures in the process, representing the so-called balance and segregation regimes. Catalysis leads to self-limiting formation of large area monolayer graphene, whereas segregation results in multilayers, which evidently “grow from below.” By controlling kinetic factors, dominantly monolayer graphene whose high quality has been confirmed by quantum Hall measurement can be deposited on platinum with hydrogen-rich environment, quench cooling, tiny but continuous methane flow and about 1000 °C growth temperature.

  7. Growth mechanism of graphene on platinum: Surface catalysis and carbon segregation

    International Nuclear Information System (INIS)

    A model of the graphene growth mechanism of chemical vapor deposition on platinum is proposed and verified by experiments. Surface catalysis and carbon segregation occur, respectively, at high and low temperatures in the process, representing the so-called balance and segregation regimes. Catalysis leads to self-limiting formation of large area monolayer graphene, whereas segregation results in multilayers, which evidently “grow from below.” By controlling kinetic factors, dominantly monolayer graphene whose high quality has been confirmed by quantum Hall measurement can be deposited on platinum with hydrogen-rich environment, quench cooling, tiny but continuous methane flow and about 1000 °C growth temperature

  8. Understanding the growth mechanism of carbon nanotubes via the ``cluster volume to surface area" model

    Science.gov (United States)

    Mandati, Sreekanth; Kunstmann, Jens; Boerrnert, Felix; Schoenfelder, Ronny; Ruemmeli, Mark; Kar, Kamal K.; Cuniberti, Gianaurelio

    2010-03-01

    The influence of mixed catalysts for the high yield production of carbon nanotubes (CNTs) has been studied systematically. Based on extensive experimental data a ``Catalyst Volume to Surface Area'' (CVSA) model was developed to understand the influence of the process parameters on the yield and CNT diameter distribution [1]. In our study, we present a refined version of the CVSA model developed by combining experiments and simulations. We discuss our current understanding of the growth mechanism and how the model might be used to increase CNT yields by using mixed catalysts.[4pt] [1] S. Tetali et al., ACS Nano (2009), DOI: 10.1021/nn9012548.

  9. Microstructural evolution and mechanical behaviour of surface hardened low carbon hot rolled steel

    Energy Technology Data Exchange (ETDEWEB)

    Tewary, N.K. [Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711103 (India); Syed, B. [R and D Division, Tata Steel Limited, Jamshedpur 831007 (India); Ghosh, S.K., E-mail: skghosh@metal.becs.ac.in [Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711103 (India); Kundu, S. [R and D Division, Tata Steel Limited, Jamshedpur 831007 (India); Shariff, S.M.; Padmanabham, G. [Centre for Laser Processing, ARCI-Hyderabad, Balapur PO, AP 500005 (India)

    2014-06-01

    Surface hardening of low carbon hot rolled C–Mn steel has been successfully performed by high power diode laser with an achievable case depth of about 300 μm. The laser treated samples have been characterised using optical microscope, scanning electron microscope, transmission electron microscope, and X-ray diffraction techniques. Higher hardness level is achieved in laser surface hardened zone (≈300 HV) than in the base alloy region (≈140 HV). The variation in hardness as a function of distance across the laser tracks is observed during multi-track laser hardening. Laser hardened steel sheets show enhanced mechanical strength (YS: 383–443 MPa, UTS: 476–506 MPa) with the lowering of percentage total elongation (23–28%) compared to the base alloy (YS: 351 MPa, UTS: 450 MPa and total elongation is 32%). Strain hardening exponent (‘n’) has been evaluated from true tensile stress–strain diagram and it shows a similar nature for both base alloy and laser treated steels. The microstructure in the base alloy region consists of a mixture of ferrite and pearlite, whereas predominantly lath martensite is present in the laser hardened surface layer. The improvement of mechanical strength is discussed in terms of the formation of this hardened layer on the surface.

  10. Microstructural evolution and mechanical behaviour of surface hardened low carbon hot rolled steel

    International Nuclear Information System (INIS)

    Surface hardening of low carbon hot rolled C–Mn steel has been successfully performed by high power diode laser with an achievable case depth of about 300 μm. The laser treated samples have been characterised using optical microscope, scanning electron microscope, transmission electron microscope, and X-ray diffraction techniques. Higher hardness level is achieved in laser surface hardened zone (≈300 HV) than in the base alloy region (≈140 HV). The variation in hardness as a function of distance across the laser tracks is observed during multi-track laser hardening. Laser hardened steel sheets show enhanced mechanical strength (YS: 383–443 MPa, UTS: 476–506 MPa) with the lowering of percentage total elongation (23–28%) compared to the base alloy (YS: 351 MPa, UTS: 450 MPa and total elongation is 32%). Strain hardening exponent (‘n’) has been evaluated from true tensile stress–strain diagram and it shows a similar nature for both base alloy and laser treated steels. The microstructure in the base alloy region consists of a mixture of ferrite and pearlite, whereas predominantly lath martensite is present in the laser hardened surface layer. The improvement of mechanical strength is discussed in terms of the formation of this hardened layer on the surface

  11. Formation mechanism of carbonate cemented zones adjacent to the top overpressured surface in the central Junggar Basin,NW China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Carbonate cemented zones are normally adjacent to the top overpressured surface in the central Junggar Basin,NW China.Stable carbon and oxygen isotopic compositions and petrological investigations of carbonate cements in the carbonate cemented zones indicate that:(1) carbonate cements are composed dominantly of ferrocalcite,ferroan dolomite,and ankerite;(2) carbonate cements are formed under a high temperature circumstance in the subsurface,and organic fluid migration has an important effect on the formation of them;and(3) carbon and oxygen ions in the carbonate cements migrate from the underlying overpressured system.This suggests that the occurrence of carbonate cemented zones in this region results from multiple phases of organic fluid expulsion out of the overpressure compartment through geological time.This study provides a plausible mechanism of the formation of carbonate cemented zones adjacent to the top overpressured surface in the clastic sedimentary basins,and has an important implication for understanding the internal correlation between the formation of carbonate cemented zones adjacent to top overpressured surface and geofluids expulsion out of overpressured system.

  12. Effect of surface nanocrystallization induced by fast multiple rotation rolling on mechanical properties of a low carbon steel

    International Nuclear Information System (INIS)

    Highlights: ► Effect of surface nanocrystallization on a low carbon steel. ► A novel and efficient surface nanocrystallization technique was developed. ► Average grain size is about 14 nm in the top surface layer. ► The mechanical properties were markedly improved by the new method. -- Abstract: Fast multiple rotation rolling (FMRR), a novel and efficient surface nanocrystallization technique, was used to fabricate a nanostructured layer in the surface of low carbon steel. The microstructure of the surface layer was characterized by transmission electron microscopy, optical microscope and scanning electron microscopy, and mechanical properties were investigated by microhardness measurements, tensile measurements and friction and wear tests. In addition, the fracture and wear scars morphologies were observed by scanning electron microscopy. Experimental results indicated that a deformation layer with thickness about 200 μm is clearly observed in the FMRR sample surface. A nanostructured layer of 30 μm thick is obtained, with grain size ranging from 8 to 18 nm and average grain size about 14 nm in the top surface layer. The microhardness of the FMRR sample change gradiently along the depth from about 316 HV in the top surface layer to about 160 HV in the matrix, which is nearly twice harder than that of the original sample. The ultimate tensile strength has also been markedly improved. And the friction and wear experiments show that tribological properties of the low carbon steel have been enhanced by FMRR treatment.

  13. Thermal instability of the microstructure and surface mechanical properties of hydrogenated amorphous carbon films

    International Nuclear Information System (INIS)

    The thermal stability of the microstructure and surface mechanical properties of two types of hydrogenated carbon film (''hard'' and ''soft'' versions, both about 2000 A thick) deposited from methane onto Si(100) wafers by a r.f.-plasma-assisted chemical vapour deposition process have been investigated. Whilst Raman spectroscopy indicates the presence of some degree of sp3 bonding in the hard film, the soft coating luminesced and burned away easily in the laser beam. IR reflectance shows the presence of CHx in both films but the amount, and whether it is CH2 or CH3, could not be deduced owing to the strong IR absorbance of the silicon substrate. On annealing in air (in the temperature range 20-600degC), scanning electron microscopy and energy-dispersive X-ray analysis show that both films are completely oxidized by 500degC. On annealing in vacuum (at 10-6 Torr or less) a system of bubbles forms in the hard film at about 530degC, owing to the liberation of trapped argon, and leads to a decohesion of the coating-substrate interface. Also, after annealing in vacuum, transmission electron microscopy shows further marked changes in the nanostructure of the films at elevated temperatures. As expected from these microstructural changes, the microhardness and contact damage resistance of both films are drastically degraded at only relatively modest temperatures. Further, the hard composite exhibits thermal hysteresis of hardness, suggesting the presence of significant compressive residual stress in the film. These results are presented and discussed alongside further insights gained from surface displacement experiments with a nanoindenter. (orig.)

  14. Radiation-curing of acrylate composites including carbon fibres: A customized surface modification for improving mechanical performances

    Science.gov (United States)

    Martin, Arnaud; Pietras-Ozga, Dorota; Ponsaud, Philippe; Kowandy, Christelle; Barczak, Mariusz; Defoort, Brigitte; Coqueret, Xavier

    2014-12-01

    The lower transverse mechanical properties of radiation-cured acrylate-based composites reinforced with carbon-fibre with respect to the thermosettable analogues was investigated from the viewpoint of chemical interactions at the interface between the matrix and the carbon material. XPS analysis of representative commercial carbon fibres revealed the presence of a significant amount of chemical functions potentially exerting an adverse effect on the initiation and propagation of the free radical polymerization initiated under high energy radiation. The EB-induced polymerization of n-butyl acrylate as a simple model monomer was conducted in the presence of various aromatic additives exhibiting a strong inhibiting effect, whereas thiols efficiently sensitize the initiation mechanism and undergo transfer reactions. A method based on the surface modification of sized fibres by thiomalic acid is proposed for overcoming the localized inhibition phenomenon and for improving the mechanical properties of the resulting acrylate-based composites.

  15. Mechanical, Microstructure and Surface Characterizations of Carbon Fibers Prepared from Cellulose after Liquefying and Curing

    Directory of Open Access Journals (Sweden)

    Xiaojun Ma

    2013-12-01

    Full Text Available In this study, Cellulose-based carbon fibers (CBCFs were prepared from cellulose after phenol liquefaction and curing. The characteristics and properties of CBCFs were examined by scanning electron microscopy (SEM, Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS. The results showed that, with increasing carbonization temperature, the La, Lc, and Lc/d(002 of CBCFs increased gradually, whereas the degree of disorder R decreased. The –OH, –CH2–, –O–C– and phenyl group characteristic absorption peaks of CBCFs reduced gradually. The cross-linked structure of CBCFs was converted into a graphite structure with a six-ring carbon network during carbonization. The surface of CBCFs were mainly comprised of C–C, C–O, and C=O. The tensile strength, carbonization yield and carbon content of CBCFs obtained at 1000 °C were 1015 MPa, 52%, and 95.04%, respectively.

  16. Mechanical and Surface Characterization of Diamond-Like Carbon Coatings onto Polymeric Substrate

    OpenAIRE

    Martí-González, Joan; Bertran, Enric

    2015-01-01

    In this master thesis, diamond-like carbon DLC/Cr bilayer systems, with thickness up to 1278 nm were formed on ABS, glass and Si substrates. Substrates surface were prepared by oxygen plasma cleaning process. The chromium thin film, which acts as a buffer layer, was grown by magnetron sputtering deposition. Diamond-like carbon was deposited by pulsed-DC PECVD, with methane and hydrogen as reactants. A Plackett-Burman experimental design was carried out in order to determine the influence of t...

  17. Comparison of H2 and He carbon cleaning mechanisms in extreme ultraviolet induced and surface wave discharge plasmas

    CERN Document Server

    Dolgov, A; Rachimova, T; Kovalev, A; Vasilyeva, A; Lee, C J; Krivtsun, V M; Yakushev, O; Bijkerk, F

    2013-01-01

    Cleaning of contamination of optical surfaces by amorphous carbon (a-C) is highly relevant for extreme ultraviolet (EUV) lithography. We have studied the mechanisms for a-C removal from a Si surface. By comparing a-C removal in a surface wave discharge (SWD) plasma and an EUV-induced plasma, the cleaning mechanisms for hydrogen and helium gas environments were determined. The C-atom removal per incident ion was estimated for different sample bias voltages and ion fluxes. It was found that H2 plasmas generally had higher cleaning rates than He plasmas: up to seven times higher for more negatively biased samples in EUV induced plasma. Moreover, for H2, EUV induced plasma was found to be 2-3 times more efficient at removing carbon than the SWD plasma. It was observed carbon removal during exposure to He is due to physical sputtering by He+ ions. In H2, on the other hand, the increase in carbon removal rates is due to chemical sputtering. This is a new C cleaning mechanism for EUV-induced plasma, which we call "E...

  18. Effect of surface treatment of carbon nanotubes on mechanical properties of cement composite

    Directory of Open Access Journals (Sweden)

    KONDAKOV Alexander Igorevich

    2014-08-01

    Full Text Available The aim of the paper is to explore the influence of the carbon nanotubes functionalized by oxygen groups on the physical and mechanical properties of cement composites. Advantages and disadvantages of the main methods for the homogeneous distribution of carbon nanotubes (CNTs in solution are discussed. A method for covalent functionalization of CNTs is described. An acid-base titration and dispersion analysis of solutions containing functionalized carbon nanotubes (f-CNTs was performed. The research data made it possible to propose new technology of preparation of modified concrete. The results of the work can be used for designing of the additives commonly used in the construction industry, as well as for further studies of the effects of CNTs on the physical and mechanical and structural properties of building materials. Efficient modification of cement composite with f-CNTs was achieved at the concentration of f-CNTs ranging from 0.0004% to 0.0008% by weight of the binder. The observed increase of the concrete mechanical properties is explained by the fact that the CNTs act as nucleation centers for the cement hydration products.

  19. Rebar corrosion due to carbonation in structural reinforced concretes for near-surface LLW repositories: A critical failure mechanism

    International Nuclear Information System (INIS)

    The concrete roof of a near-surface radioactive waste repository is the principle protection against water infiltration and intrusion. The following potential roof failure mechanism is examined: carbon dioxide generated by the biodegradation of organic materials in the repository initiates corrosion of reinforcing steel embedded in the concrete roof. Because the bottom surface of the roof is mostly under tension, it is susceptible to cracking. The migration path for carbon dioxide is through cracks in the concrete between the bottom of the roof and the reinforcing bars. Carbonate corrosion of the reinforcing bars may result in concrete spalling, more extensive rebar corrosion and ultimately structural failure. Attention is brought to this failure mechanism because it has generally been overlooked in repository performance assessments. Literature relevant to the above failure is reviewed. Prerequisites for rebar corrosion are the presence of carbon dioxide and oxygen in the repository gas, high relative humidity and through-cracks in the concrete. High carbon dioxide concentrations and relative humidity are expected in the repository. The oxygen concentration in the repository is expected to be very low, and that is expected to minimize rebar corrosion rates. Cracks are likely to form in locations with high tensile stresses. Healing of the cracks could be a mitigating factor, but based on our analysis, it can not be relied on. To minimize the potential of this failure mechanism occurring with the Intrusion Resistant Underground Structure (IRUS), Canada's proposed near-surface repository, carbon dioxide from the repository gas will be absorbed by the reactive, porous concrete placed between the waste and the roof. (author). 4 refs

  20. Carbon out-diffusion mechanism for direct graphene growth on a silicon surface

    International Nuclear Information System (INIS)

    Direct growth of graphene on silicon (Si) through chemical vapor deposition has predominantly focused on surface-mediated processes due to the low carbon (C) solubility in Si. However, a considerable quantity of C atoms was incorporated in Si and formed Si1−xCx alloy with a reduced lattice dimension even in the initial stage of direct graphene growth. Subsequent high temperature annealing promoted active C out-diffusion, resulting in the formation of a graphitic layer on the Si surface. Furthermore, the significantly low thermal conductivity of the Si1−xCx alloy shows that the incorporated C atoms affect the properties of a semiconductor adjacent to the graphene. These findings provide a key guideline for controlling desirable properties of graphene and designing hybrid semiconductor/graphene architectures for various applications

  1. A study of the chemical, mechanical, and surface properties of thin films of hydrogenated amorphous carbon

    Energy Technology Data Exchange (ETDEWEB)

    Vandentop, G.J.

    1990-07-01

    Amorphous hydrogenated carbon (a-C:H) films were studied with the objective of elucidating the nucleation and growth mechanisms, and the origin of their unique physical properties. The films were deposited onto Si(100) substrates both on the powered (negatively self-biased) and on the grounded electrodes from methane in an rf plasma (13.56 MHz) at 65 mTorr and 300 to 370 K. The films produced at the powered electrode exhibited superior mechanical properties, such as high hardness. A mass spectrometer was used to identify neutral species and positive ions incident on the electrodes from the plasma, and also to measure ion energies. The effect of varying ion energy flux on the properties of a-C:H films was investigated using a novel pulsed biasing technique. It was demonstrated that ions were not the dominant deposition species as the total ion flux measured was insufficient to account for the observed deposition rate. The interface between thin films of a-C:H and silicon substrates was investigated using angle resolved x-ray photoelectron spectroscopy. A silicon carbide layer was detected at the interface of a hard a-C:H film formed at the powered electrode. At the grounded electrode, where the kinetic energy is low, no interfacial carbide layer was observed. Scanning tunneling microscopy and high energy electron energy loss spectroscopy was used to investigate the initial stages of growth of a-C:H films. On graphite substrates, films formed at the powered electrode were observed to nucleate in clusters approximately 50 {Angstrom} in diameter, while at the grounded electrode no cluster formation was observed. 58 figs.

  2. On the mechanism of carbon monoxide oxidation on the surface of gold nanoclusters supported on titanium oxide

    Science.gov (United States)

    Tvauri, I. V.; Remar, D. F.; Turiev, A. M.; Tsidaeva, N. I.; Fukutani, K.; Magkoev, T. T.

    2010-05-01

    The process of carbon monoxide (CO) oxidation on the surface of a system comprising nanodimensional gold clusters deposited onto thin films of titanium oxide of variable stoichiometry formed on a Re(1000) single crystal surface has been studied by methods of thermodesorption, IR, and X-ray photoelectron spectroscopy. It is established that oxygen contained in titanium oxide plays an important role in the conversion of CO into CO2. The efficiency of this process on the Au/TiO x ( x < 2) system surface is significantly higher that that on the Au/TiO2 system.

  3. Analysis of mechanism of carbon removal from GaAs(1 0 0) surface by atomic hydrogen

    International Nuclear Information System (INIS)

    Etching of carbon contaminations from the GaAs(1 0 0) surface by irradiating with atomic hydrogen, which is one of the key reactions to promote high-quality thin films growth by molecular beam epitaxy (MBE), has been investigated by mass spectrometry (MS), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It is shown that during the cleaning process at room temperature a total reduction of the Auger carbon signal, accompanied by desorption of methane as major reaction product, can be observed. The reaction pathways as well as the processes responsible for the observed carbon removal are discussed in detail to give a support for etching and growth quality enhancement not only in thin films epitaxy but in all atomic hydrogen promoted gas-phase III-V semiconductor processes

  4. Carbon speciation and surface tension of fog

    Science.gov (United States)

    Capel, P.D.; Gunde, R.; Zurcher, F.; Giger, W.

    1990-01-01

    The speciation of carbon (dissolved/particulate, organic/inorganic) and surface tension of a number of radiation fogs from the urban area of Zurich, Switzerland, were measured. The carbon species were dominated by "dissolved" organic carbon (DOC; i.e., the fraction that passes through a filter), which was typically present at levels of 40-200 mg/L. Less than 10% of the DOC was identified as specific individual organic compounds. Particulate organic carbon (POC) accounted for 26-41% of the mass of the particles, but usually less than 10% of the total organic carbon mass. Inorganic carbon species were relatively minor. The surface tensions of all the measured samples were less than pure water and were correlated with their DOC concentrations. The combination of high DOC and POC and low surface tension suggests a mechanism for the concentration of hydrophobic organic contaminants in the fog droplet, which have been observed by numerous investigators. ?? 1990 American Chemical Society.

  5. Friction contact mechanisms of layered surface

    Institute of Scientific and Technical Information of China (English)

    Fan Xue; Diao Dongfeng

    2013-01-01

    In this paper,we firstly review the carbon layered surface prepared with electron cyclotron resonance (ECR) plasma sputtering.Secondly,the friction behavior of carbon layered surface under pin-on-disk testing is described.Furthermore,the contact stress evolution processes of layered surface with and without transfer layer during wear are given for understanding the contact mechanisms.Finally,a three-dimension (3D) local yield map of layered surface is introduced,which is useful to predict the possible contact mechanisms.

  6. Physicochemical, mechanical and vacuum properties of carbon glass ceramics and its surface erosion under hydrogen and helium ions bombardment

    International Nuclear Information System (INIS)

    Results of investigations and review of properties of new high-temperature high-strength chemically resistant carbon- containing material-carbon glass ceramics, having fine-grained quasiisotropic structure, are presented. It is established that gas permeability of carbon glass ceramics is 104-105 times less than that of graphite. Carbon glass ceramics, properly heat treated has elevated radiation resistance in fast neutron flux. Threshold automization energy of carbon glass ceramics with Hg+ ions 2-3 times surpasses the graphite automization threshold. Carbon glass ceramics degasses well in vacuum at 660-840 deg C

  7. The patterning mechanism of carbon nanotubes using surface acoustic waves: the acoustic radiation effect or the dielectrophoretic effect.

    Science.gov (United States)

    Ma, Zhichao; Guo, Jinhong; Liu, Yan Jun; Ai, Ye

    2015-09-01

    In this study, we present a simple technique capable of assembling and patterning suspended CNTs using a standing surface acoustic wave (SSAW) field. Individual CNTs could be assembled into larger CNT bundles and patterned in periodic positions on a substrate surface. The mechanism of the SSAW-based patterning technique has been investigated using both numerical simulation and experimental study. It has been found that the acoustic radiation effect due to the acoustic pressure field and the dielectrophoretic (DEP) effect induced by the electric field co-existing in the patterning process however play different roles depending on the properties of the suspended particles and the suspension medium. In the SSAW-based patterning of highly conductive CNTs with high aspect ratio geometry, the positive DEP effect dominates over the acoustic radiation effect. In contrast, the acoustic radiation effect dominates over the DEP effect when manipulating less conductive, spherical or low aspect ratio particles or biological cells. These results provide a meaningful insight into the mechanism of SSAW-based patterning, which is of great help to guide the effective use of this patterning technique for various applications. PMID:26239679

  8. Luminescent Surface Quaternized Carbon Dots

    KAUST Repository

    Bourlinos, Athanasios B.

    2012-01-10

    Thermal oxidation of a salt precursor made from the acid base combination of tris(hydroxymethyl)aminomethane and betaine hydrochloride results in light-emitting surface quaternized carbon dots that are water-dispersible, display anion exchange properties, and exhibit uniform size/surface charge. © 2011 American Chemical Society.

  9. Influence of deposition parameters on surface roughness and mechanical properties of boron carbon nitride coatings synthesized by ion beam assisted deposition

    International Nuclear Information System (INIS)

    Boron carbon nitride (BCN) coatings were deposited on Si(100) wafers and Si3N4 disks by using ion beam assisted deposition from a boron carbide target. The BCN coatings were synthesized by the reaction between boron and carbon vapor as well as nitrogen ion simultaneously. The influence of deposition parameters such as ion acceleration voltage, ion acceleration current density and deposition ratio on the surface roughness and mechanical properties of the BCN coatings was investigated. The surface roughness was determined by using atomic force microscopy and the mechanical properties of the BCN coatings were evaluated by nano-indentation tests and friction tests in N2 gas. The composition and chemical bonding of the BCN coatings were analyzed by using X-ray photoelectron spectroscopy. The results showed that the lower deposition rate, the smaller surface roughness and higher nano-hardness the BCN coatings were. The BCN coating with the smoothest surface (R a = 0.25 nm and R P-V = 2.8 nm) and the highest nanohardness of 33 GPa as well as excellent friction property were obtained at 0.5 nm/s and the nitrogen ions were generated at 2.0 kV and 60 μA/cm2, and the chemical composition of this BCN coating was 49 at.% B, 42 at.% C and 9 at.% N. Moreover, there were several bonding states such as B-N, B-C and C-N with B-C-N hybridization in this BCN coating

  10. Amorphous carbon and its surfaces

    International Nuclear Information System (INIS)

    Graphical abstract: Some examples of 2.0 g/cm3 surfaces. The cell contained 64 atoms. The top figure shows some tube-like formation, the central figure is an example of a wave-like surface, and the bottom figure is an example of the bending over of the carbons at the surface to form a surface sheet when the sheets in the bulk are not parallel to the surface. - Abstract: We have investigated bulk amorphous carbon at three densities (3.2, 2.6, and 2.0 g/cm3) using density functional theory (DFT). The variation in the structure with density is discussed. The bulk structures are used to create surface structures. If the surfaces are relaxed at 700 K, the surface structures, as a function of density, are more similar than the analogous bulk structures. The relaxed surfaces appear to be graphene sheets with defects, sizable distortions, and have covalently bonded carbon chains holding the sheets together.

  11. Quantifying the success of onshore carbon capture and storage from surface deformation measurement and geo-mechanical modeling

    Science.gov (United States)

    Gourmelen, N.; Shepherd, A.; Angus, D.; Fisher, Q.; Lesnic, D.; Gouldson, A.

    2012-04-01

    Although Carbon capture and storage (CCS) is an attractive technology in the drive to mitigate global warming, the approach is controversial because long-term containment and accounting of the stored CO2 have yet to be demonstrated. Options for monitoring CO2 storage are varied and range from discrete chemical well sampling programs to full field time-lapse seismic surveys. Crucial for any monitoring program is that it be as cost effective as possible yet yielding sufficiently accurate measurement. Time-lapse seismics has generally proven to be a sufficiently accurate means of monitoring CO2 in the subsurface. However, there is debate as to whether seismics is the most cost effective approach in the quantitative measurement of CO2 flow and containment. The cost of monitoring is compounded potentially further by the various international regulations related to CO2 sequestration, where, for example, it can be argued that CO2 storage monitoring requirements are much stricter than those for natural gas storage. For on-shore sequestration, there has been a significant drive to integrate satellite interferometric synthetic aperture radar (InSAR) with geomechanical modeling to link surface deformation with the movement and storage of injected CO2. At the In Salah CO2 storage project, export gas specifications require the removal of CO2 from the produced natural gas with strict long term monitoring requirements to ensure that CO2 is contained indefinitely. Thus there has been significant research into linking geomechanical modeling with InSAR observations (e.g., Rutqvist et al., 2010; Vasco et al., 2010). We analyze the surface deformation resulting from CO2 storage at In Salah in order to provide constraints on the temporal and spatial evolution of CO2 within the reservoir. Specifically, we process InSAR from the pre-injection period 1992-2004 and the injection period 2004-2009 and combine the InSAR observations with geomechanical modeling of reservoir deformation to

  12. Improvement of carbon fiber surface properties using electron beam irradiation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Carbon fiber-reinforced advance composites have been used for struetural applications, mainly on account of their mechanical properties. The main factor for a good mechanical performance of carbon fiber-reinforced composite is the interfacial interaction between its components, which are carbon fiber and polymeric matrix. The aim of this study is to improve the surface properties of the carbon fiber using ionizing radiation from an electron beam to obtain better adhesion properties in the resultant composite. EB radiation was applied on the carbon fiber itself before preparing test specimens for the mechanical tests. Experimental results showed that EB irradiation improved the tensile strength of carbon fiber samples. The maximum value in tensile strength was reached using doses of about 250kGy. After breakage, the morphology aspect of the tensile specimens prepared with irradiated and non-irradiated carbon fibers were evaluated. SEM micrographs showed modifications on the carbon fiber surface.

  13. Mechanics of filled carbon nanotubes

    KAUST Repository

    Monteiro, A.O.

    2014-04-01

    The benefits of filling carbon nanotubes (CNTs) with assorted molecular and crystalline substances have been investigated for the past two decades. Amongst the study of new structural phases, defects, chemical reactions and varied types of host-guest interactions, there is one fundamental characterisation aspect of these systems that continues to be overlooked: the mechanical behaviour of filled CNTs. In contrast to their empty counterparts, the mechanics of filled CNTs is a subject where reports appear far and apart, this despite being key to the application of these materials in technological devices. In the following paragraphs, we review the work that has been carried out up to the present on the mechanics of filled CNTs. The studies discussed range from experimental resonant frequency essays performed within electron microscopes to modelling, via molecular dynamics, of three-point bending of nanotubes filled with gases. (C) 2014 Elsevier B.V. All rights reserved.

  14. Mobile ions on carbonate surfaces

    Science.gov (United States)

    Kendall, Treavor A.; Martin, Scot T.

    2005-07-01

    Surface ions move during the dissolution and growth of minerals. The present study investigates the density and the mobility of surface ions and the structure of the adsorbed water layer with changes in relative humidity (RH). The time evolution of the polarization force, which is induced by an electrically biased tip of an atomic force microscope, shows that the density and the mobility of surface ions increase with rising humidity, a finding which is consistent with increasing surface hydration. A marked change in the observations above 55% RH indicates a transition from a water layer formed by heteroepitaxial two-dimensional growth at low RH to one formed by multilayer three-dimensional growth at high RH. A comparison of the results of several rhombohedral carbonates ( viz. CaCO 3, FeCO 3, ZnCO 3, MgCO 3, and MnCO 3) shows that a long relaxation time of the polarization force at high RH is predictive of a rapid dissolution rate. This finding is rationalized by long lifetimes in terrace positions and hence greater opportunities for detachment of the ion to aqueous solution (i.e., dissolution). Our findings on the density and the mobility of surface ions therefore help to better constrain mechanistic models of hydration, ion exchange, and dissolution/growth.

  15. Surface analysis of plasma grafted carbon fiber

    International Nuclear Information System (INIS)

    The surface characteristics of carbon fibers were studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and wetting measurements. The surface of carbon fiber was modified by means of plasma graft silsesquioxane. The oxygen/carbon and silicon/carbon ratio increased rapidly after treatments. Fitting the C 1s, O 1s, and Si 2p spectra demonstrated that new photopeaks were emerged, which were indicated C-Si, Si-O groups, respectively. The degree of surface roughness and the wettability of carbon fiber surface were both increased by plasma graft silsesquioxane. The results may shed some light on the design of the appropriate surface structure, which could react with resin, and the manufacture of the carbon fiber reinforced composites

  16. Mechanisms of Soil Carbon Sequestration

    Science.gov (United States)

    Lal, Rattan

    2015-04-01

    Carbon (C) sequestration in soil is one of the several strategies of reducing the net emission of CO2 into the atmosphere. Of the two components, soil organic C (SOC) and soil inorganic C (SIC), SOC is an important control of edaphic properties and processes. In addition to off-setting part of the anthropogenic emissions, enhancing SOC concentration to above the threshold level (~1.5-2.0%) in the root zone has numerous ancillary benefits including food and nutritional security, biodiversity, water quality, among others. Because of its critical importance in human wellbeing and nature conservancy, scientific processes must be sufficiently understood with regards to: i) the potential attainable, and actual sink capacity of SOC and SIC, ii) permanence of the C sequestered its turnover and mean residence time, iii) the amount of biomass C needed (Mg/ha/yr) to maintain and enhance SOC pool, and to create a positive C budget, iv) factors governing the depth distribution of SOC, v) physical, chemical and biological mechanisms affecting the rate of decomposition by biotic and abiotic processes, vi) role of soil aggregation in sequestration and protection of SOC and SIC pool, vii) the importance of root system and its exudates in transfer of biomass-C into the SOC pools, viii) significance of biogenic processes in formation of secondary carbonates, ix) the role of dissolved organic C (DOC) in sequestration of SOC and SIC, and x) importance of weathering of alumino-silicates (e.g., powered olivine) in SIC sequestration. Lack of understanding of these and other basic processes leads to misunderstanding, inconsistencies in interpretation of empirical data, and futile debates. Identification of site-specific management practices is also facilitated by understanding of the basic processes of sequestration of SOC and SIC. Sustainable intensification of agroecosystems -- producing more from less by enhancing the use efficiency and reducing losses of inputs, necessitates thorough

  17. Kinetic Analysis of the Anodic Carbon Oxidation Mechanism in a Molten Carbonate Medium

    International Nuclear Information System (INIS)

    The oxidation mechanism for carbon in a carbonate melt was modelled using an electrochemical kinetic approach. Through the Butler-Volmer equation for electrode kinetics, a series of expressions was derived assuming each step of the proposed carbon oxidation mechanism is in turn the rate determining step (RDS). Through the derived expressions the transfer coefficient and Tafel slope were calculated for each possible RDS of the proposed mechanism and these were compared with real data collected on carbon based electrodes including graphite and coal. It was established that the RDS of the electrochemical oxidation process is dependent on both the carbon type and the potential region of oxidation. The simplified kinetic analysis suggested that the RDS in the main oxidation region is likely to be the first or second electron transfer on a graphite electrode surface, which occurs following initial adsorption of an oxygen anion to an active carbon site. This is contrary to previous suggestions that adsorption of the second anion to the carbon surface will be rate determining. It was further shown that use of a coal based carbon introduces a change in mechanism with an additional reaction region where a different mechanism is proposed to be operating

  18. Structure and multiscale mechanics of carbon nanomaterials

    CERN Document Server

    2016-01-01

    This book aims at providing a broad overview on the relationship between structure and mechanical properties of carbon nanomaterials from world-leading scientists in the field. The main aim is to get an in-depth understanding of the broad range of mechanical properties of carbon materials based on their unique nanostructure and on defects of several types and at different length scales. Besides experimental work mainly based on the use of (in-situ) Raman and X-ray scattering and on nanoindentation, the book also covers some aspects of multiscale modeling of the mechanics of carbon nanomaterials.

  19. The Adsorption Mechanism of Modified Activated Carbon on Phenol

    Directory of Open Access Journals (Sweden)

    Lin J. Q.

    2016-01-01

    Full Text Available Modified activated carbon was prepared by thermal treatment at high temperature under nitrogen flow. The surface properties of the activated carbon were characterized by Boehm titration, BET and point of zero charge determination. The adsorption mechanism of phenol on modified activated carbon was explained and the adsorption capacity of modified activated carbon for phenol when compared to plain activated carbon was evaluated through the analysis of adsorption isotherms, thermodynamic and kinetic properties. Results shows that after modification the surface alkaline property and pHpzc value of the activated carbon increase and the surface oxygen-containing functional groups decrease. The adsorption processes of the plain and modified carbon fit with Langmuir isotherm equation well, and the maximum adsorption capacity increase from 123.46, 111.11, 103.09mg/g to 192.31, 178.57, 163,93mg/g under 15, 25 and 35°C after modification, respectively. Thermodynamic parameters show that the adsorption of phenol on activated carbon is a spontaneously exothermic process of entropy reduction, implying that the adsorption is a physical adsorption. The adsorption of phenol on activated carbon follows the pseudo-second-order kinetics (R2>0.99. The optimum pH of adsorption is 6~8.

  20. Process entanglement as a neuronal anchorage mechanism to rough surfaces

    International Nuclear Information System (INIS)

    The organization of neurons and glia cells on substrates composed of pristine carbon nanotube islands was investigated using high resolution scanning electron microscopy, immunostaining and confocal microscopy. Neurons were found bound and preferentially anchored to the rough surfaces; moreover, the morphology of the neuronal processes on the small, isolated islands of high density carbon nanotubes was found to be conspicuously curled and entangled. We further demonstrate that the roughness of the surface must match the diameter of the neuronal processes in order to allow them to bind. The results presented here suggest that entanglement, a mechanical effect, may constitute an additional mechanism by which neurons (and possibly other cell types) anchor themselves to rough surfaces. Understanding the nature of the interface between neurons and carbon nanotubes is essential to effectively harness carbon nanotube technology in neurological applications such as neuro-prosthetic and retinal electrodes.

  1. Process entanglement as a neuronal anchorage mechanism to rough surfaces

    Science.gov (United States)

    Sorkin, Raya; Greenbaum, Alon; David-Pur, Moshe; Anava, Sarit; Ayali, Amir; Ben-Jacob, Eshel; Hanein, Yael

    2009-01-01

    The organization of neurons and glia cells on substrates composed of pristine carbon nanotube islands was investigated using high resolution scanning electron microscopy, immunostaining and confocal microscopy. Neurons were found bound and preferentially anchored to the rough surfaces; moreover, the morphology of the neuronal processes on the small, isolated islands of high density carbon nanotubes was found to be conspicuously curled and entangled. We further demonstrate that the roughness of the surface must match the diameter of the neuronal processes in order to allow them to bind. The results presented here suggest that entanglement, a mechanical effect, may constitute an additional mechanism by which neurons (and possibly other cell types) anchor themselves to rough surfaces. Understanding the nature of the interface between neurons and carbon nanotubes is essential to effectively harness carbon nanotube technology in neurological applications such as neuro-prosthetic and retinal electrodes.

  2. Kinetics and mechanism of nitric oxidation of carbon black

    International Nuclear Information System (INIS)

    After some generalities about carbon blacks (preparation by various processes, structure, industrial use), the author notices that carbon black is often dispersed in aqueous solutions and, as it is hydrophobic, must therefore be submitted to treatment to become hydrophilic. Oxidation in liquid phase suits perfectly, and oxidation by nitric acid gives good results. Thus, this research thesis reports the study of the oxidation reaction mechanism in the case of oxidation of carbon black by nitric acid in aqueous solution. After having defined the different types of carbon blacks used in this study, and given an overview of the oxidation process (methods, purification and purity control of the obtained blacks, determination of the efficiency in terms of oxidised or purified black, difficulties faced during the elemental analysis of oxidised blacks), the author discusses the mechanism of formation of carbon dioxide during the oxidation of Philblack 0 carbon black by nitric acid. He reports the study of the oxidation kinetics, and the study of a thermal treatment of oxidised carbon blacks. The last part reports the study of the evolution of various properties of carbon blacks during oxidation: specific surface (BET method), density, examination by electronic microscopy and X-rays, magnetic susceptibility

  3. Surface bioactivity of plasma implanted silicon and amorphous carbon

    Institute of Scientific and Technical Information of China (English)

    Paul K CHU

    2004-01-01

    Plasma immersion ion implantation and deposition (PⅢ&D) has been shown to be an effective technique to enhance the surface bioactivity of materials. In this paper, recent progress made in our laboratory on plasma surface modification single-crystal silicon and amorphous carbon is reviewed. Silicon is the most important material in the integrated circuit industry but its surface biocompatibility has not been investigated in details. We have recently performed hydrogen PⅢ into silicon and observed the biomimetic growth of apatite on its surface in simulated body fluid. Diamond-like carbon (DLC) is widely used in the industry due to its excellent mechanical properties and chemical inertness. The use of this material in biomedical engineering has also attracted much attention. It has been observed in our laboratory that doping DLC with nitrogen by means of PⅢ can improve the surface blood compatibility. The properties as well as in vitro biological test results will be discussed in this article.

  4. Texturing Carbon-carbon Composite Radiator Surfaces Utilizing Atomic Oxygen

    Science.gov (United States)

    Raack, Taylor

    2004-01-01

    Future space nuclear power systems will require radiator technology to dissipate excess heat created by a nuclear reactor. Large radiator fins with circulating coolant are in development for this purpose and an investigation of how to make them most efficient is underway. Maximizing the surface area while minimizing the mass of such radiator fins is critical for obtaining the highest efficiency in dissipating heat. Processes to develop surface roughness are under investigation to maximize the effective surface area of a radiator fin. Surface roughness is created through several methods including oxidation and texturing. The effects of atomic oxygen impingement on carbon-carbon surfaces are currently being investigated for texturing a radiator surface. Early studies of atomic oxygen impingement in low Earth orbit indicate significant texturing due to ram atomic oxygen. The surface morphology of the affected surfaces shows many microscopic cones and valleys which have been experimentally shown to increase radiation emittance. Further study of this morphology proceeded in the Long Duration Exposure Facility (LDEF). Atomic oxygen experiments on the LDEF successfully duplicated the results obtained from materials in spaceflight by subjecting samples to 4.5 eV atomic oxygen from a fixed ram angle. These experiments replicated the conical valley morphology that was seen on samples subjected to low Earth orbit.

  5. Mechanical and tribological properties of ion beam-processed surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kodali, P.

    1998-01-01

    The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation; (2) characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation; and (3) developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness.

  6. Mechanical and tribological properties of ion beam-processed surfaces

    International Nuclear Information System (INIS)

    The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation; (2) characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation; and (3) developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness

  7. Quantum mechanical studies of carbon structures

    Energy Technology Data Exchange (ETDEWEB)

    Bartelt, Norman Charles [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Ward, Donald [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Zhou, Xiaowang [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Foster, Michael E. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Schultz, Peter A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wang, Bryan M. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Univ. of California, Riverside, CA (United States); McCarty, Kevin F. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2015-10-01

    Carbon nanostructures, such as nanotubes and graphene, are of considerable interest due to their unique mechanical and electrical properties. The materials exhibit extremely high strength and conductivity when defects created during synthesis are minimized. Atomistic modeling is one technique for high resolution studies of defect formation and mitigation. To enable simulations of the mechanical behavior and growth mechanisms of C nanostructures, a high-fidelity analytical bond-order potential for the C is needed. To generate inputs for developing such a potential, we performed quantum mechanical calculations of various C structures.

  8. Quantum mechanical studies of carbon structures

    International Nuclear Information System (INIS)

    Carbon nanostructures, such as nanotubes and graphene, are of considerable interest due to their unique mechanical and electrical properties. The materials exhibit extremely high strength and conductivity when defects created during synthesis are minimized. Atomistic modeling is one technique for high resolution studies of defect formation and mitigation. To enable simulations of the mechanical behavior and growth mechanisms of C nanostructures, a high-fidelity analytical bond-order potential for the C is needed. To generate inputs for developing such a potential, we performed quantum mechanical calculations of various C structures.

  9. Nanoscale Etching and Indentation of Silicon Surfaces with Carbon Nanotubes

    Science.gov (United States)

    Dzegilenko, Fedor N.; Srivastava, Deepak; Saini, Subhash

    1998-01-01

    The possibility of nanolithography of silicon and germanium surfaces with bare carbon nanotube tips of scanning probe microscopy devices is considered with large scale classical molecular dynamics (MD) simulations employing Tersoff's reactive many-body potential for heteroatomic C/Si/Ge system. Lithography plays a key role in semiconductor manufacturing, and it is expected that future molecular and quantum electronic devices will be fabricated with nanolithographic and nanodeposition techniques. Carbon nanotubes, rolled up sheets of graphene made of carbon, are excellent candidates for use in nanolithography because they are extremely strong along axial direction and yet extremely elastic along radial direction. In the simulations, the interaction of a carbon nanotube tip with silicon surfaces is explored in two regimes. In the first scenario, the nanotubes barely touch the surface, while in the second they are pushed into the surface to make "nano holes". The first - gentle scenario mimics the nanotube-surface chemical reaction induced by the vertical mechanical manipulation of the nanotube. The second -digging - scenario intends to study the indentation profiles. The following results are reported in the two cases. In the first regime, depending on the surface impact site, two major outcomes outcomes are the selective removal of either a single surface atom or a surface dimer off the silicon surface. In the second regime, the indentation of a silicon substrate by the nanotube is observed. Upon the nanotube withdrawal, several surface silicon atoms are adsorbed at the tip of the nanotube causing significant rearrangements of atoms comprising the surface layer of the silicon substrate. The results are explained in terms of relative strength of C-C, C-Si, and Si-Si bonds. The proposed method is very robust and does not require applied voltage between the nanotube tips and the surface. The implications of the reported controllable etching and hole-creating for

  10. Mechanical Design of Carbon Ion Optics

    Science.gov (United States)

    Haag, Thomas

    2005-01-01

    Carbon Ion Optics are expected to provide much longer thruster life due to their resistance to sputter erosion. There are a number of different forms of carbon that have been used for fabricating ion thruster optics. The mechanical behavior of carbon is much different than that of most metals, and poses unique design challenges. In order to minimize mission risk, the behavior of carbon must be well understood, and components designed within material limitations. Thermal expansion of the thruster structure must be compatible with thermal expansion of the carbon ion optics. Specially designed interfaces may be needed so that grid gap and aperture alignment are not adversely affected by dissimilar material properties within the thruster. The assembled thruster must be robust and tolerant of launch vibration. The following paper lists some of the characteristics of various carbon materials. Several past ion optics designs are discussed, identifying strengths and weaknesses. Electrostatics and material science are not emphasized so much as the mechanical behavior and integration of grid electrodes into an ion thruster.

  11. Mechanical properties of functionalized carbon nanotubes

    International Nuclear Information System (INIS)

    Carbon nanotubes (CNTs) used to reinforce polymer matrix composites are functionalized to form covalent bonds with the polymer in order to enhance the CNT/polymer interfaces. These bonds destroy the perfect atomic structures of a CNT and degrade its mechanical properties. We use atomistic simulations to study the effect of hydrogenization on the mechanical properties of single-wall carbon nanotubes. The elastic modulus of CNTs gradually decreases with the increasing functionalization (percentage of C-H bonds). However, both the strength and ductility drop sharply at a small percentage of functionalization, reflecting their sensitivity to C-H bonds. The cluster C-H bonds forming two rings leads to a significant reduction in the strength and ductility. The effect of carbonization has essentially the same effect as hydrogenization

  12. Carbon Sequestration on Surface Mine Lands

    Energy Technology Data Exchange (ETDEWEB)

    Donald H. Graves; Christopher Barton; Richard Sweigard; Richard Warner

    2005-10-02

    During this quarter a general forest monitoring program was conducted to measure treatment effects on above ground and below ground carbon C and Nitrogen (N) pools for the tree planting areas. Detailed studies to address specific questions pertaining to Carbon cycling was initiated with the development of plots to examine the influence of mycorrhizae, spoil chemical and mineralogical properties, and use of amendment on forest establishment and carbon sequestration. Efforts continued during this period to examine decomposition and heterotrophic respiration on C cycling in the reforestation plots. Projected climate change resulting from elevated atmospheric carbon dioxide has given rise to various strategies to sequester carbon in various terrestrial ecosystems. Reclaimed surface mine soils present one such potential carbon sink where traditional reclamation objectives can complement carbon sequestration. New plantings required the modification and design and installation on monitoring equipment. Maintenance and data monitoring on past and present installations are a continuing operation. The Department of Mining Engineering continued the collection of penetration resistance, penetration depth, and bulk density on both old and new treatment areas. Data processing and analysis is in process for these variables. Project scientists and graduate students continue to present results at scientific meetings, tours and field days presentations of the research areas are being conducted on a request basis.

  13. A new mechanism for carbon nanotube evolution

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Key discoveries on the growth mechanism of carbon nanotubes(CNTs) have recently been achieved by CAS researcher ZHU Zhenping and his research group at the State Key Laboratory of Coal Conversion,the Institute of Coal Chemistry of CAS, funded by the National Natural Science Foundation of China and the CAS Bairen Program.

  14. Wet oxidation of ordered mesoporous carbon FDU-15 by using (NH4)2S2O8 for fast adsorption of Sr(II): An investigation on surface chemistry and adsorption mechanism

    Science.gov (United States)

    Song, Yang; Ye, Gang; Chen, Jing; Lv, Dachao; Wang, Jianchen

    2015-12-01

    Surface modification of ordered mesoporous carbon (OMC) by wet oxidation provides an oxygen-enriched platform for complexation of metal ions. Here, we present a comprehensive study on the surface chemistry and textual property of OMC FDU-15 modified by wet oxidation using (NH4)2S2O8 as a benign oxidant. And, for the first time, the adsorption behavior and mechanism of wet-oxidized OMC FDU-15 toward Sr(II) in aqueous solutions were investigated. The mesostructural regularity of the OMC FDU-15 was well-reserved under wet oxidation. Compared to OMC CMK-type counterparts prepared via nanocasting, the OMC FDU-15 by soft template method showed much-enhanced structural stability. Due to the introduction of abundant oxygen-containing species, the oxidized OMC FDU-15 exhibited excellent hydrophilicity and dispersibility in aqueous solutions. The adsorption behavior toward Sr(II) was fully investigated, showing a super-fast adsorption kinetics (equilibrium) and a Langmuir adsorption isotherm. Moreover, an in-depth X-ray photoelectron spectroscopy analysis through deconvolution of high resolution C1s and O1s spectra was implemented to identify the chemical species of the surface functional groups, while probing the adsorption mechanism. The results suggested that oxygen donor atoms in Csbnd O single bonds mainly contribute to the adsorption of Sr(II) via formation of metal-ligand complexation.

  15. Weathering controls on mechanisms of carbon storage in grassland soils

    Energy Technology Data Exchange (ETDEWEB)

    Masiello, C.A.; Chadwick, O.A.; Southon, J.; Torn, M.S.; Harden, J.W.

    2004-09-01

    On a sequence of soils developed under similar vegetation, temperature, and precipitation conditions, but with variations in mineralogical properties, we use organic carbon and 14C inventories to examine mineral protection of soil organic carbon. In these soils, 14C data indicate that the creation of slow-cycling carbon can be modeled as occurring through reaction of organic ligands with Al3+ and Fe3+ cations in the upper horizons, followed by sorption to amorphous inorganic Al compounds at depth. Only one of these processes, the chelation of Al3+ and Fe3+ by organic ligands, is linked to large carbon stocks. Organic ligands stabilized by this process traverse the soil column as dissolved organic carbon (both from surface horizons and root exudates). At our moist grassland site, this chelation and transport process is very strongly correlated with the storage and long-term stabilization of soil organic carbon. Our 14C results show that the mechanisms of organic carbon transport and storage at this site follow a classic model previously believed to only be significant in a single soil order (Spodosols), and closely related to the presence of forests. The presence of this process in the grassland Alfisol, Inceptisol, and Mollisol soils of this chronosequence suggests that this process is a more significant control on organic carbon storage than previously thought.

  16. Self-Assembly of Graphene on Carbon Nanotube Surfaces

    Science.gov (United States)

    Li, Kaiyuan; Eres, Gyula; Howe, Jane; Chuang, Yen-Jun; Li, Xufan; Gu, Zhanjun; Zhang, Litong; Xie, Sishen; Pan, Zhengwei

    2013-08-01

    The rolling up of a graphene sheet into a tube is a standard visualization tool for illustrating carbon nanotube (CNT) formation. However, the actual processes of rolling up graphene sheets into CNTs in laboratory syntheses have never been demonstrated. Here we report conformal growth of graphene by carbon self-assembly on single-wall and multi-wall CNTs using chemical vapor deposition (CVD) of methane without the presence of metal catalysts. The new graphene layers roll up into seamless coaxial cylinders encapsulating the existing CNTs, but their adhesion to the primary CNTs is weak due to the existence of lattice misorientation. Our study shows that graphene nucleation and growth by self-assembly of carbon on the inactive carbon basal plane of CNTs occurs by a new mechanism that is markedly different from epitaxial growth on metal surfaces, opening up the possibility of graphene growth on many other non-metal substrates by simple methane CVD.

  17. Mechanical characterization of epoxy composite with multiscale reinforcements: Carbon nanotubes and short carbon fibers

    International Nuclear Information System (INIS)

    Highlights: • Multiscale composite was prepared by incorporation of carbon nanotubes and fibers. • Carbon nanotubes were also grown on short carbon fibers to enhance stress transfer. • Significant improvements were achieved in mechanical properties of composites. • Synergic effect of carbon nanotubes and fibers was demonstrated. - Abstract: Carbon nanotubes (CNT) and short carbon fibers were incorporated into an epoxy matrix to fabricate a high performance multiscale composite. To improve the stress transfer between epoxy and carbon fibers, CNT were also grown on fibers through chemical vapor deposition (CVD) method to produce CNT grown short carbon fibers (CSCF). Mechanical characterization of composites was performed to investigate the synergy effects of CNT and CSCF in the epoxy matrix. The multiscale composites revealed significant improvement in elastic and storage modulus, strength as well as impact resistance in comparison to CNT–epoxy or CSCF–epoxy composites. An optimum content of CNT was found which provided the maximum stiffness and strength. The synergic reinforcing effects of combined fillers were analyzed on the fracture surface of composites through optical and scanning electron microscopy (SEM)

  18. Continuum mechanical modeling aspects of self-cleaning surface mechanisms

    OpenAIRE

    Osman, Muhammad

    2016-01-01

    The aim of this work is to study and analyze the fluid-structure interactions taking place in self-cleaning mechanisms observed in natural and fabricated hydrophobic surfaces. These surfaces have a hierarchical structure representing its multi-scale nature which is a characteristic feature of self-cleaning surfaces. Analyzing the wetting behavior on such surfaces, therefore, becomes a challenging problem which requires a numerical treatment. We propose robust models which are able to capture ...

  19. Liquid surface model for carbon nanotube energetics

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Mathew, Maneesh; Solov'yov, Andrey V.;

    2008-01-01

    In the present paper we developed a model for calculating the energy of single-wall carbon nanotubes of arbitrary chirality. This model, which we call as the liquid surface model, predicts the energy of a nanotube with relative error less than 1% once its chirality and the total number of atoms are...... an important insight in the energetics and stability of nanotubes of different chirality and might be important for the understanding of nanotube growth process. For the computations we use empirical Brenner and Tersoff potentials and discuss their applicability to the study of carbon nanotubes. From...... the calculated energies we determine the elastic properties of the single-wall carbon nanotubes (Young modulus, curvature constant) and perform a comparison with available experimental measurements and earlier theoretical predictions....

  20. On the mechanical characterization of carbon nanotube reinforced epoxy adhesives

    International Nuclear Information System (INIS)

    Highlights: • We examine the mechanical properties of carbon nanotube reinforced epoxy adhesives. • We identify a critical nanotube concentration that results in the largest improvements. • Critical concentration is shown to be a result of nanotube agglomeration. • Rheological assessments indicate that agglomeration is due to increased resin viscosity. - Abstract: In this work, the mechanical properties of carbon nanotube reinforced epoxy adhesives are investigated experimentally. The investigations are intended to characterize the physical and mechanical properties of nano-reinforced structural epoxy adhesives and to further highlight some of the complex phenomena associated with these materials. We describe the dispersion methodology used to disperse the carbon nanotubes into the considered adhesive and provide details pertaining to adherent surface preparation, bondline thickness control and adhesive curing conditions. Furthermore, the following tests are described: (i) dogbone tensile testing, (ii) tensile bond testing, (iii) double lap shear and (iv) double cantilever beam fracture toughness testing. The experimental observations indicate a critical carbon nanotube concentration in the vicinity of 1.5 wt% that results in the largest improvements in the measured properties. At concentrations exceeding this critical value, the properties begin to degrade, in some cases, to levels below that of the pure epoxy. Advanced electron microscopy techniques and rheological assessments indicate that this is mainly due to the agglomeration of the carbon nanotubes at higher concentrations as a result of increased resin viscosity and the consequent resistance to dispersion

  1. The mechanism of elution of gold cyanide from activated carbon

    Science.gov (United States)

    van Deventer, J. S. J.; van der Merwe, P. F.

    1994-12-01

    Numerous articles have appeared on the mechanism of the adsorption of gold cyanide onto activated carbon. In contrast, little information is available on the mechanism of elution of the adsorbed gold. It is the objective of this article to formulate such a mechanism on the basis of batch and column elution tests without analyzing adsorbed species on the carbon directly. The presence of spectator cations (M n+) enhances the formation of M n+{Au(CN){2/-}} n ion pairs on the carbon, which in turn suppress the elution of gold cyanide. The dynamics of removal of these cations determine the horizontal position of the gold peak in an elution profile. When the concentration of cations in the eluant is high and no cyanide is present in the solution or on the carbon, very little desorption of gold is observed. The quantitative effect of the concentration of spectator cations on the equilibrium for desorption of aurocyanide can be estimated from the elution profiles for gold and cations. Free cyanide in the eluant, which causes some competitive adsorption of cyanide with aurocyanide, therefore plays a minor role at the elevated temperatures used in industry. A more important effect of cyanide is its reaction with functional groups on the carbon, the products of which passivate the surface for adsorption of aurocyanide, and thereby cyanide promotes the elution of aurocyanide. The degree of passivation, which is determined to a large extent by the temperature of pretreatment, also affects the elution of cations and the degradation/adsorption of cyanide itself. Reactivation of the carbon surface occurs when the adsorbed/decomposed cyanide is removed by the eluant. At high temperatures of pretreatment, such as used in practice, it is not necessary to include a reactivation term in the mathematical model for elution.

  2. Carbon stabilization mechanisms in Ecuadorian Andosols

    Science.gov (United States)

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

    2010-05-01

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

  3. High surface area silicon carbide-coated carbon aerogel

    Science.gov (United States)

    Worsley, Marcus A; Kuntz, Joshua D; Baumann, Theodore F; Satcher, Jr, Joe H

    2014-01-14

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust. Carbon aerogels can be coated with sol-gel silica and the silica can be converted to silicone carbide, improved the thermal stability of the carbon aerogel.

  4. The mechanical property and resistance ability to atomic oxygen corrosion of boron modified carbon/carbon composites

    International Nuclear Information System (INIS)

    Before being densified by chemical vapor deposition, carbon preform was modified by boron. The mechanical property and resistance to atomic oxygen corrosion of carbon/carbon composites were investigated. The results show that fiber surface modification induces the deposition of high texture pyrocarbon and a moderate interfacial transition layer between carbon fibers and matrix carbon. After being modified by boron, the flexural and compressive strength of carbon/carbon composite is significantly increased. The bending curve has been adjusted with obvious pseudo-ductility phenomenon. The resistance ability to atomic oxygen corrosion is improved significantly. The mass loss and corrosion degree of the modified composite are lower than that of pure carbon/carbon composite

  5. Carbon syntactic foam mechanical properties testing

    Energy Technology Data Exchange (ETDEWEB)

    McEachen, G.W.

    1998-01-01

    This project was started early in the redevelopment of the carbon syntactic foam. The new mixture of carbon microballoons with the APO-BMI resin had not been fully characterized, but that was the actual purpose of this effort. During the forming of the billets for these tests, a problem began to surface; but full understanding of the problem did not evolve until samples were cured and tests were conducted. Material compressive strengths varied between 200 and 990 psi where anything below 700 was rejected. The cure cycle was adjusted in an iterative manner in an attempt to maximize the material strength. The result of this effort was that the material strength was almost doubled and was achieving strengths of 1,500 psi toward the end of the parts produced. As a consequence, some of the strength tests actually run and reported in the text of this report may not reflect data that would be obtained today. The material strength was continuously being improved over the entire year. A complete series of compression test data is reported, but subsequent tensile and flexural strength tests were not repeated. At a time when it is considered that there are no further changes to be incorporated, a repeat of these tests would be warranted. Some development remains to be done on the carbon microballoon material. Improved carbon material is now available and its effect of the material strength should be evaluated.

  6. Mechano-activated surface modification of calcium carbonate in wet stirred mill and its properties

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Surface modification of calcium carbonate particles using sodium stearate(SDS) as a modification agent incorporated with the simultaneous wet ultra-fine grinding in the laboratory stirred mill was investigated. The physical properties and application properties of modified calcium carbonate were measured and evaluated. The action mechanism between SDS and calcium carbonate in the modification was studied by infrared spectrometry(IR) and X-ray photoelectron energy spectroscopy(XPS). The results indicate that the crushing mechanic force intensity can obviously influence the modification effect of calcium carbonate because of mechano-chemical effect. The hydrophilic surface of calcium carbonate is turned into hydrophobic after modification. The properties of polyethylene(PE) filled by modified calcium carbonate powder is markedly improved. And the adsorption of SDS could occur by chemical reaction with calcium carbonate surface.

  7. Experimental study of different carbon dust growth mechanisms

    International Nuclear Information System (INIS)

    Laboratory experiments are proposed to understand the growth mechanisms of spherical carbonous particulates observed in Tokamak dust samples. Examples can be reproduced when carbon is injected in a plasma discharge by sputtering. The particulates morphology, size, structure, mass density depend on the discharge geometry and parameters. At relatively low pressure, nano-metric primary particles are observed either individually or in the form of spherical agglomerates. The charge threshold from which the agglomeration process is stopped by Coulomb repulsion is established. At higher pressure, the produced grains have a high surface porosity never observed at low pressure, this change being due to a difference in the kinetic energy of the surface deposited species. A comparison was done of the surface structure of laboratory dusts and pieces of carbon deposits from the Toroidal Pumped Limiter of Tore Supra. The observed differences can be explained by different production mechanisms and by the fact that the Tokamak deposits could have undergo heating yielding structural graphitization. Further studies are under way in order to obtain a better understanding of the various particulate morphologies. For instance, we plan to use transmission electron microscopy (TEM) and to complete the XANES structure analysis by Raman spectroscopy. A correlation between the new diagnostics results and the transport of neutral and ion species in our discharges is expected. (authors)

  8. Thick backed carbon targets via mechanical rolling

    International Nuclear Information System (INIS)

    For targets requiring thick backing foils, the straight-forward and usual method is to deposit the target material directly on the backing by thermal evaporation. In some instances the reverse is more desirable, adding a backing to an already existing target foil, for example. A recent study involving measurement of the lifetime of the first 2+ excited state in 36Ar by the Doppler shift attenuation method required 0.5 mg/cm2 natural carbon targets on thick (18 mg/cm2) gold and lead backings. Problems of delamination had arisen after beam irradiation using thick gold backings for these experiments. Carbon target foils were then prepared by mechanical rolling in direct contact with a thick lead backing using an intermediate layer of indium to assure good adhesion of the layers. Details of the method will be discussed. (author)

  9. Adsorption mechanism of different organic chemicals on fluorinated carbon nanotubes.

    Science.gov (United States)

    Li, Hao; Zheng, Nan; Liang, Ni; Zhang, Di; Wu, Min; Pan, Bo

    2016-07-01

    Multi-walled carbon nanotubes (MC) were fluorinated by a solid-phase reaction method using polytetrafluoroethylene (PTFE). The surface alteration of carbon nanotubes after fluorination (MC-F) was confirmed based on surface elemental analysis, TEM and SEM. The incorporation of F on MC surface was discussed as F incorporation on carbon defects, replacement of carboxyl groups, as well as surface coating of PTFE. The adsorption performance and mechanisms of MC-F for five kinds of representative organic compounds: sulfamethoxazole (SMX), ofloxacin (OFL), norfloxacin (NOR), bisphenol a (BPA) and phenanthrene (PHE) were investigated. Although BET-N2 surface area of the investigated CNTs decreased after fluorination, the adsorption of all five chemicals increased. Because of the glassification of MC-F surface coating during BET-N2 surface area measurement, the accessible surface area of MC-F was underestimated. Desorption hysteresis was generally observed in all the sorption systems in this study, and the desorption hysteresis of MC-F were stronger than the pristine CNTs. The enhanced adsorption of MC-F may be attributed the pores generated on the coated PTFE and the dispersed CNT aggregates due to the increased electrostatic repulsion after fluorination. The rearrangement of the bundles or diffusion of the adsorbates in MC-F inner pores were the likely reason for the strong desorption hysteresis of MC-F. The butterfly structure of BPA resulted in its high sorption and strong desorption hysteresis. The exothermic sorption character of OFL on CNTs resulted in its strong desorption hysteresis. PMID:27058918

  10. Evidence for Carbonate Surface Complexation during Forsterite Carbonation in Wet Supercritical Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Loring, John S.; Chen, Jeffrey; Benezeth Ep Gisquet, Pascale; Qafoku, Odeta; Ilton, Eugene S.; Washton, Nancy M.; Thompson, Christopher J.; Martin, Paul F.; McGrail, B. Peter; Rosso, Kevin M.; Felmy, Andrew R.; Schaef, Herbert T.

    2015-07-14

    Continental flood basalts are attractive formations for geologic sequestration of carbon dioxide because of their reactive divalent-cation containing silicates, such as forsterite (Mg2SiO4), suitable for long-term trapping of CO2 mineralized as metal carbonates. The goal of this study was to investigate at a molecular level the carbonation products formed during the reaction of forsterite with supercritical CO2 (scCO2) as a function of the concentration of H2O adsorbed to the forsterite surface. Experiments were performed at 50 °C and 90 bar using an in situ IR titration capability, and post-reaction samples were examined by ex situ techniques, including SEM, XPS, FIB-TEM, TGA-MS, and MAS-NMR. Carbonation products and reaction extents varied greatly with adsorbed H2O. We show for the first time evidence of Mg-carbonate surface complexation under wet scCO2 conditions. Carbonate is found to be coordinated to Mg at the forsterite surface in a predominately bidentate fashion at adsorbed H2O concentrations below 27 µmol/m2. Above this concentration and up to 76 µmol/m2, monodentate coordinated complexes become dominant. Beyond a threshold adsorbed H2O concentration of 76 µmol/m2, crystalline carbonates continuously precipitate as magnesite, and the particles that form are hundreds of times larger than the estimated thicknesses of the adsorbed water films of about 7 to 15 Å. At an applied level, these results suggest that mineral carbonation in scCO2 dominated fluids near the wellbore and adjacent to caprocks will be insignificant and limited to surface complexation, unless adsorbed H2O concentrations are high enough to promote crystalline carbonate formation. At a fundamental level, the surface complexes and their dependence on adsorbed H2O concentration give insights regarding forsterite dissolution processes and magnesite nucleation and growth.

  11. The Fluid Mechanics of Carbon Dioxide Sequestration

    Science.gov (United States)

    Huppert, Herbert E.; Neufeld, Jerome A.

    2014-01-01

    Humans are faced with a potentially disastrous global problem owing to the current emission of 32 gigatonnes of carbon dioxide (CO2) annually into the atmosphere. A possible way to mitigate the effects is to store CO2 in large porous reservoirs within the Earth. Fluid mechanics plays a key role in determining both the feasibility and risks involved in this geological sequestration. We review current research efforts looking at the propagation of CO2 within the subsurface, the possible rates of leakage, the mechanisms that act to stably trap CO2, and the geomechanical response of the crust to large-scale CO2 injection. We conclude with an outline for future research.

  12. Carbon Market Regulation Mechanism Research Based on Carbon Accumulation Model with Jump Diffusion

    OpenAIRE

    Dongmei Guo; Yi Hu; Bingjie Zhang

    2014-01-01

    In order to explore carbon market regulation mechanism more effectively, based on carbon accumulation model with jump diffusion, this paper studies the carbon price from two perspectives of quantity instrument and price instrument and quantitatively simulates carbon price regulation mechanisms in the light of actual operation of EU carbon market. The results show that quantity instrument and price instrument both have certain effects on carbon market; according to the comparison of the elasti...

  13. Mechanical Resonances of Helically Coiled Carbon Nanowires

    Science.gov (United States)

    Saini, D.; Behlow, H.; Podila, R.; Dickel, D.; Pillai, B.; Skove, M. J.; Serkiz, S. M.; Rao, A. M.

    2014-07-01

    Despite their wide spread applications, the mechanical behavior of helically coiled structures has evaded an accurate understanding at any length scale (nano to macro) mainly due to their geometrical complexity. The advent of helically coiled micro/nanoscale structures in nano-robotics, nano-inductors, and impact protection coatings has necessitated the development of new methodologies for determining their shear and tensile properties. Accordingly, we developed a synergistic protocol which (i) integrates analytical, numerical (i.e., finite element using COMSOL®) and experimental (harmonic detection of resonance; HDR) methods to obtain an empirically validated closed form expression for the shear modulus and resonance frequency of a singly clamped helically coiled carbon nanowire (HCNW), and (ii) circumvents the need for solving 12th order differential equations. From the experimental standpoint, a visual detection of resonances (using in situ scanning electron microscopy) combined with HDR revealed intriguing non-planar resonance modes at much lower driving forces relative to those needed for linear carbon nanotube cantilevers. Interestingly, despite the presence of mechanical and geometrical nonlinearities in the HCNW resonance behavior the ratio of the first two transverse modes f2/f1 was found to be similar to the ratio predicted by the Euler-Bernoulli theorem for linear cantilevers.

  14. Reduction mechanism of stainless steelmaking dust and carbon pellets

    Institute of Scientific and Technical Information of China (English)

    PENG Bing; SONG Hai-chen; CHAI Li-yuan; WANG Ja; WANG Yun-yan; MIN Xiao-bo; HE De-wen

    2005-01-01

    The reduction mechanism of stainless steelmaking dust and carbon pellets was investigated. The metal oxides present in the dust were reduced by carbon with a new direct reduction technology. The direct reduction parameters were determined by measuring the rates of dust melting and reduction. The results show that the rate of reduction is faster than that of the melting. Both melting and reduction processes are accelerated by the direct transfer of heat from the smelting slag. The recovery of metals is improved while the pellets were added to argon oxygen decarburization(AOD) or vacuum oxygen decarburization(VOD) vessels in the late period of the first smelting stage. More carbon travels to the slag instead of to the steel because the diffusion coefficient of carbon, impacted by the viscosity of slag and surface tension between slag and melted steel, is larger in the slag than in the steel. The viscosity of slag is about 2.54Pa·s and the surface tension between slag and steel is about 490mN/m.

  15. Potential for carbon adsorption on concrete: surface XPS analyses.

    Science.gov (United States)

    Haselbach, Liv M; Ma, Shuguo

    2008-07-15

    The concrete industry is a contributor to the global carbon cycle particularly with respect to the contribution of carbon dioxide in the manufacturing of cement (calcination). The reverse reaction of carbonation is known to occur in concrete, but is usually limited to exterior surfaces exposed to carbon dioxide and humidity in the air. As alternate concrete uses expand which have more surface area, such as crushed concrete for recycling, it is important to understand surface adsorption of carbon dioxide and the positive impacts it might have on the carbon cycle. X-ray photoelectron spectroscopy (XPS) is used in this study to evaluate carbon species on hydrated cement mortar surfaces. Initial estimates for carbon absorption in concrete using othertechniques predictthe potential for carbonate species to be a fraction of the calcination stoichiometric equivalent The XPS results indicate that there is a rapid and substantial uptake of carbon dioxide on the surfaces of these mortars, sometimes exceeding the calcination stoichiometric equivalents, indicative of carbon dioxide surface complexation species. On pure calcite, the excess is on the order of 30%. This accelerated carbon dioxide surface adsorption phenomenon may be importantfor determining novel and effective carbon sequestration processes using recycled concrete. PMID:18754389

  16. Effect of surface modification on carbon fiber and its reinforced phenolic matrix composite

    International Nuclear Information System (INIS)

    Highlights: ► We used very simple and effective modification method to treat PAN-based carbon fiber by liquid oxidation and coupling agent. ► Carbon fiber surface functional groups were analyzed by LRS and XPS. ► Proper treatment of carbon fiber can prove an effective way to increase composite's performance. ► Carbon fiber surface modifications by oxidation and APS could strengthen fiber activity and enlarge surface area as well as its roughness. - Abstract: In this work, polyacrylonitrile (PAN)-based carbon fiber were chemically modified with H2SO4, KClO3 and silane coupling agent (γ-aminopropyltriethoxysilane, APS), and carbon fiber reinforced phenolic matrix composites were prepared. The structural and surface characteristics of the carbon fiber were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), laser Raman scattering (LRS) and Fourier transform infrared spectroscopy (FTIR). Single fiber mechanical properties, specific surface area, composite impact properties and interfacial shear strength (ILSS) were researched to indicate the effects of surface modification on fibers and the interaction between modified fiber surface and phenolic matrix. The results showed that carbon fiber surface modification by oxidation and APS can strengthen fiber surface chemical activity and enlarge the fiber surface area as well as its roughness. When carbon fiber (CF) is oxidized treatment, the oxygen content as well as the O/C ratio will be obviously increased. Oxygen functional groups increase with oxidation time increasing. Carbon fiber treated with APS will make C-O-R content increase and O-C=O content decrease due to surface reaction. Proper treatment of carbon fiber with acid and silane coupling agent prove an effective way to increase the interfacial adhesion and improve the mechanical and outdoor performance of the resulting fiber/resin composites.

  17. Apparatus and process for the surface treatment of carbon fibers

    Energy Technology Data Exchange (ETDEWEB)

    Paulauskas, Felix Leonard; Ozcan, Soydan; Naskar, Amit K.

    2016-05-17

    A method for surface treating a carbon-containing material in which carbon-containing material is reacted with decomposing ozone in a reactor (e.g., a hollow tube reactor), wherein a concentration of ozone is maintained throughout the reactor by appropriate selection of at least processing temperature, gas stream flow rate, reactor dimensions, ozone concentration entering the reactor, and position of one or more ozone inlets (ports) in the reactor, wherein the method produces a surface-oxidized carbon or carbon-containing material, preferably having a surface atomic oxygen content of at least 15%. The resulting surface-oxidized carbon material and solid composites made therefrom are also described.

  18. Evidence for Carbonate Surface Complexation during Forsterite Carbonation in Wet Supercritical Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Loring, John S.; Chen, Jeffrey; Benezeth, Pascale; Qafoku, Odeta; Ilton, Eugene S.; Washton, Nancy M.; Thompson, Christopher J.; Martin, Paul F.; McGrail, B. Peter; Rosso, Kevin M.; Felmy, Andrew R.; Schaef, Herbert T.

    2015-06-16

    Continental flood basalts are attractive formations for geologic sequestration of carbon dioxide because of their reactive divalent-cation containing silicates, such as forsterite (Mg2SiO4), suitable for long-term trapping of CO2 mineralized as metal carbonates. The goal of this study was to investigate at a molecular level the carbonation products formed during the reaction of forsterite with supercritical CO2 (scCO2) as a function of the concentration of H2O adsorbed to the forsterite surface. Experiments were performed at 50 °C and 90 bar using an in situ IR titration capability, and post-reaction samples were examined by ex situ techniques, including SEM, XPS, FIB-TEM, TGA-MS, and MAS-NMR. Carbonation products and reaction extents varied greatly with adsorbed H2O. We show for the first time evidence of Mg-carbonate surface complexation under wet scCO2 conditions. Carbonate is found to be coordinated to Mg at the forsterite surface in a predominately bidentate fashion at adsorbed H2O concentrations below 27 µmol/m2. Above this concentration and up to 76 µmol/m2, monodentate coordinated complexes become dominant. Beyond a threshold adsorbed H2O concentration of 76 µmol/m2, crystalline carbonates continuously precipitate as magnesite, and the particles that form are hundreds of times larger than the estimated thicknesses of the adsorbed water films of about 7 to 15 Å. At an applied level, the implication of these results is that mineral trapping in scCO2 dominated fluids will be insignificant and limited to surface complexation unless adsorbed H2O concentrations are high enough to promote crystalline carbonate formation. At a fundamental level, the surface complexes and their dependence on adsorbed H2O concentration give insights regarding forsterite dissolution processes and magnesite nucleation and growth.

  19. Monitoring carbon dioxide in mechanically ventilated patients during hyperbaric treatment

    DEFF Research Database (Denmark)

    Bjerregård, Asger; Jansen, Erik

    2012-01-01

    Measurement of the arterial carbon dioxide (P(a)CO(2)) is an established part of the monitoring of mechanically ventilated patients. Other ways to get information about carbon dioxide in the patient are measurement of end-tidal carbon dioxide (P(ET)CO(2)) and transcutaneous carbon dioxide (PTCCO2...

  20. Mechanical and chemical decontamination of surfaces

    International Nuclear Information System (INIS)

    Decontamination does not mean more than a special technique of cleaning surfaces by methods well known in the industry. The main difference consists in the facts that more than just the visible dirt is to be removed and that radioactive contamination cannot be seen. Especially, intensive mechanical and chemical carry-off methods are applied to attack the surfaces. In order to minimize damages caused to the surfaces, the decontamination method is to adapt to the material and the required degree of decontamination. The various methods, their advantages and disadvantages are described, and the best known chemical solutions are shown. (orig./RW)

  1. Mechanical strength of carbon nanotube nickel nanocomposites

    Science.gov (United States)

    Sun, Ying; Sun, Jianren; Liu, Miao; Chen, Quanfang

    2007-12-01

    Carbon nanotubes (CNTs), including single-walled CNT (SWCNT) and multi-walled CNT (MWCNT), have been regarded as the stiffest and strongest materials ever developed and are promising reinforcement fillers for developing nanocomposites. However, the scientific community has been puzzled about the reinforcement efficiency. Here we report CNT-reinforced nickel nanocomposites fabricated with an innovative electrochemical co-deposition process for achieving good interfacial bonding between CNT and metallic matrices. Test results show that Ni/SWCNT composite produces a tensile strength as high as 2 GPa, which is more than three times stronger than that of pure nickel. The mechanical strength of Ni/CNT nanocomposites is dependent on CNT addition, while the fracture strain remains similar or better than that of pure nickel. The good reinforcement of CNT/metal nanocomposites is attributed to the good interfacial bonding as well as the stiffer matrix nature.

  2. Carbon nanotube DNA sensor and sensing mechanism.

    Science.gov (United States)

    Tang, Xiaowu; Bansaruntip, Sarunya; Nakayama, Nozomi; Yenilmez, Erhan; Chang, Ying-Lan; Wang, Qian

    2006-08-01

    We report the fabrication of single-walled carbon nanotube (SWNT) DNA sensors and the sensing mechanism. The simple and generic protocol for label-free detection of DNA hybridization is demonstrated with random sequence 15mer and 30mer oligonucleotides. DNA hybridization on gold electrodes, instead of on SWNT sidewalls, is mainly responsible for the acute electrical conductance change due to the modulation of energy level alignment between SWNT and gold contact. This work provides concrete experimental evidence on the effect of SWNT-DNA binding on DNA functionality, which will help to pave the way for future designing of SWNT biocomplexes for applications in biotechnology in general and also DNA-assisted nanotube manipulation techniques. PMID:16895348

  3. CARBON SEQUESTRATION ON SURFACE MINE LANDS

    Energy Technology Data Exchange (ETDEWEB)

    Donald H. Graves; Christopher Barton; Richard Sweigard; Richard Warner

    2004-08-02

    The April-June 2004 quarter was dedicated to the establishment of monitoring systems for all the new research areas. Hydrology and water quality monitoring continues to be conducted on all areas as does weather data pertinent to the research. Studies assessing specific questions pertaining to carbon flux has been established and the invasion of the vegetation by small mammals is being quantified. The approval of two experimental practices associated with this research by the United States Office of Surface Mining was a major accomplishment during this period of time. These experimental practices will eventually allow for tree planting on long steep slopes with loose grading systems and for the use of loose dumped spoil on mountain top removal areas with no grading in the final layer of rooting material for tree establishment.

  4. An Alternative Mechanism for Accelerated Carbon Sequestration in Concrete

    Energy Technology Data Exchange (ETDEWEB)

    Haselbach, Liv M.; Thomle, Jonathan N.

    2014-07-01

    The increased rate of carbon dioxide sequestration (carbonation) is desired in many primary and secondary life applications of concrete in order to make the life cycle of concrete structures more carbon neutral. Most carbonation rate studies have focused on concrete exposed to air under various conditions. An alternative mechanism for accelerated carbon sequestration in concrete was investigated in this research based on the pH change of waters in contact with pervious concrete which have been submerged in carbonate laden waters. The results indicate that the concrete exposed to high levels of carbonate species in water may carbonate faster than when exposed to ambient air, and that the rate is higher with higher concentrations. Validation of increased carbon dioxide sequestration was also performed via thermogravimetric analysis (TGA). It is theorized that the proposed alternative mechanism reduces a limiting rate effect of carbon dioxide dissolution in water in the micro pores of the concrete.

  5. Mechanical properties of carbon fiber composites for environmental applications

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, R.; Grulke, E.; Kimber, G. [Univ. of Kentucky, Lexington, KY (United States)

    1996-12-31

    Activated carbon fiber composites show great promise as fixed-bed catalytic reactors for use in environmental applications such as flue gas clean-up and ground water decontamination. A novel manufacturing process produces low density composites from chopped carbon fibers and binders. These composites have high permeability, can be activated to have high surface area, and have many potential environmental applications. This paper reports the mechanical and flow properties of these low density composites. Three point flexural strength tests were used to measure composite yield strength and flexural moduli. Composites containing over 10 pph binder had an adequate yield strength of about 200 psi at activations up to 40% weight loss. The composites were anisotropic, having along-fiber to cross-fiber yield strength ratios between 1.2 and 2.0. The pressure drop of air through the composites correlated with the gas velocity, and showed a dependence on sample density.

  6. Mechanical properties of carbon fiber composites for environmental applications

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, R.; Grulke, E. [Univ. of Kentucky, Lexington, KY (United States)

    1996-10-01

    Activated carbon fiber composites show great promise as fixed-bed catalytic reactors for use in environmental applications such as flue gas clean-up and ground water decontamination. A novel manufacturing process produces low density composites from chopped carbon fibers and binders. These composites have high permeability, can be activated to have high surface area, and have many potential environmental applications. This paper reports the mechanical and flow properties of these low density composites. Three point flexural strength tests were used to measure composite yield strength and flexural moduli. Composites containing over 10 pph binder had an adequate yield strength of about 200 psi at activations up to 40% weight loss. The composites were anisotropic, having along-fiber to cross-fiber yield strength ratios between 1.2 and 2.0. The friction factor for flow through the composites can be correlated using the fiber Reynolds number, and is affected by the composite bulk density.

  7. MWNT Surface Self-Assembling in Fire Retardant Polyethylene-Carbon nanotubes nanocomposites

    OpenAIRE

    Bocchini, Sergio; Frache, Alberto; Camino, Giovanni

    2008-01-01

    Multiwall carbon nanotubes (MWNT) were melt blended at different concentration with linear low density polyethylene (LLDPE). The nanotubes impart the fire-retardant characteristics to the polymer by formation of a thin protective film of MWNT/carbon char generated on the surface of the nanocomposites. The film formation mechanism is discussed

  8. Surface modification of multiwall carbon nanotubes by sulfonitric treatment

    Science.gov (United States)

    Gómez, Sofía; Rendtorff, Nicolás M.; Aglietti, Esteban F.; Sakka, Yoshio; Suárez, Gustavo

    2016-08-01

    Carbon nanotubes are widely used for electronic, mechanical, and optical devices due to their unique structural and quantum characteristics. The species generated by oxidation on the surface of these materials permit binding new reaction chains, which improves the dispersibility, processing and compatibility with other materials. Even though different acid treatments and applications of these CNT have been reported, relatively few research studies have focused on the relationship between the acid treatment and the formation of nanodefects, specific oxidized species or CNT surface defects. In this work, multiwall carbon nanotube (MWCNT) oxidation at 90 °C was characterized in order to determine the acid treatment effect on the surface. It was found that oxidized species are already present in MWCNT without an acid treatment, but there are not enough to cause water-based dispersion. The species were identified and quantified by infrared spectroscopy and X-ray photoelectron spectroscopy. Also, transmission electron microscopy observations showed not only modifications of the oxidized species, but also morphological damage on the surfaces of MWCNT after being subjected to the acid treatment. This effect was also confirmed by Raman spectroscopy. The acid treatment generates higher oxidized species, decreasing the zeta potential in the whole pH range.

  9. Flame retardant polypropylene nanocomposites reinforced with surface treated carbon nanotubes

    Science.gov (United States)

    Guleria, Abhishant

    Polypropylene nanocomposites are prepared by reinforcing carbon nanotubes by ex-situ solution mixing method. Interfacial dispersion of carbon nanotubes in polypropylene have been improved by surface modification of CNTs and adding surfactants. Polypropylene nanocomposites fabrication was done after treating CNTs. Firstly, oxidation of CNTs followed by silanization for addition of functionalized groups on the surface of CNTs. Maleic anhydride grafted PPs were used as surfactants. Maleic anhydrides with two different molecular weights were LAMPP and HMAPP. Successful oxidation of CNTs by nitric acid and functionalized CNTs by 3-Aminopropyltriethoxysilane was confirmed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) with evidence of absorption peak at 1700 and 1100-1000 cm-1. Scanning electron microscopy (SEM) micrographs revealed that the CNTs dispersion quality was improved by directly adding LMAPP/HMAPP into PP/CNTs system and the PP-CNTs adhesion was enhanced through both the CNTs surface treatment and the addition of surfactant. Thermal gravimetric analysis (TGA) revealed an enhanced thermal stability in the PP/CNTs and PP/CNTs/MAPP. Differential scanning calorimetry (DSC) characterization demonstrated that the crystalline temperature, fusion heat and crystalline fraction of hosting PP were decreased with the introduction of CNTs and surface treated CNTs; however, melting temperature was only slightly changed. Melting rheological behaviors including complex viscosity, storage modulus, and loss modulus indicated significant changes in the PP/MAPP/CNTs system before and after functionalization of CNTs, and the mechanism were also discussed in details.

  10. Mechanism of Surface Modification for Sericite

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Surface modification of sericite by wet method was conducted with the addition of 1.0% (w/w) silane. The resulting wetting contact angle and activity ratio of sericite were 130° and 98% respectively.Good pre-evaluation indexes of oil value (40.8%) and dispersivity (14.0 mL) were obtained. When 30% of sericite was filled into acrylonitrile butadiene styrene(ABS) plastic, the bending strength and tensile strength of the composite material were reduced by 7% and 14.3% in comparison to those of pure ABS plastic, while the rigidity was increased by 3 times, and the impact strength and breaking elongation were reduced significantly.The mechanism of surface modification was investigated and the configuration of silane coupling agent on the surface of sericite was given. Infrared (IR) spectroscopic analysis indicates that the adsorption of silane on the surface of sericite belongs to chemical adsorption.

  11. How many carbonic anhydrase inhibition mechanisms exist?

    Science.gov (United States)

    Supuran, Claudiu T

    2016-01-01

    Six genetic families of the enzyme carbonic anhydrase (CA, EC 4.2.1.1) were described to date. Inhibition of CAs has pharmacologic applications in the field of antiglaucoma, anticonvulsant, anticancer, and anti-infective agents. New classes of CA inhibitors (CAIs) were described in the last decade with enzyme inhibition mechanisms differing considerably from the classical inhibitors of the sulfonamide or anion type. Five different CA inhibition mechanisms are known: (i) the zinc binders coordinate to the catalytically crucial Zn(II) ion from the enzyme active site, with the metal in tetrahedral or trigonal bipyramidal geometries. Sulfonamides and their isosters, most anions, dithiocarbamates and their isosters, carboxylates, and hydroxamates bind in this way; (ii) inhibitors that anchor to the zinc-coordinated water molecule/hydroxide ion (phenols, carboxylates, polyamines, 2-thioxocoumarins, sulfocoumarins); (iii) inhibitors which occlude the entrance to the active site cavity (coumarins and their isosters), this binding site coinciding with that where CA activators bind; (iv) compounds which bind out of the active site cavity (a carboxylic acid derivative was seen to inhibit CA in this manner), and (v) compounds for which the inhibition mechanism is not known, among which the secondary/tertiary sulfonamides as well as imatinib/nilotinib are the most investigated examples. As CAIs are used clinically in many pathologies, with a sulfonamide inhibitor (SLC-0111) in Phase I clinical trials for the management of metastatic solid tumors, this review updates the recent findings in the field which may be useful for a structure-based drug design approach of more selective/potent modulators of the activity of these enzymes. PMID:26619898

  12. Low-temperature facile synthesis of graphene and graphene-carbon nanotubes hybrid on dielectric surfaces

    International Nuclear Information System (INIS)

    Various carbon based nanostructures (graphene, graphene-CNTs hybrid and three-dimensional (3D) carbon network) have been grown separately on low-temperature (600 °C) substrates by using a chemical vapor deposition system with a two-heating reactor. The two-heating reactor is utilized to offer sufficient, well-proportioned floating C atoms and provide a simple method for low-temperature deposition. Morphology and electrical properties of the carbon based nanostructures can be controlled by the substrate surfaces. A relatively flat surface is beneficial for the synthesis of graphene and surfaces with nanodots are required to directly grow graphene-carbon nanotube hybrids. A chemical vapor deposition mechanism dependent on the temperature gradient is proposed, suggesting that the transfer-free carbon nanostructures can be deposited on different substrates. These results open an easy way for direct and high-efficiency deposition of various carbon nanostructures on the low-temperature dielectric substrates. (papers)

  13. Multiwalled Carbon Nanotube Deposition on Model Environmental Surfaces

    Science.gov (United States)

    Deposition of multiwalled carbon nanotubes (MWNTs) on model environmental surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Deposition behaviors of MWNTs on positively and negatively charged surfaces were in good agreement with Der...

  14. The formation of carbon nanostructures by in situ TEM mechanical nanoscale fatigue and fracture of carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J J; Lockwood, A J; Peng, Y; Xu, X; Inkson, B J [Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD (United Kingdom); Bobji, M S, E-mail: beverley.inkson@sheffield.ac.u [Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, Karnataka (India)

    2009-07-29

    A technique to quantify in real time the microstructural changes occurring during mechanical nanoscale fatigue of ultrathin surface coatings has been developed. Cyclic nanoscale loading, with amplitudes less than 100 nm, is achieved with a mechanical probe miniaturized to fit inside a transmission electron microscope (TEM). The TEM tribological probe can be used for nanofriction and nanofatigue testing, with 3D control of the loading direction and simultaneous TEM imaging of the nano-objects. It is demonstrated that fracture of 10-20 nm thick amorphous carbon films on sharp gold asperities, by a single nanoscale shear impact, results in the formation of <10 nm diameter amorphous carbon filaments. Failure of the same carbon films after cyclic nanofatigue, however, results in the formation of carbon nanostructures with a significant degree of graphitic ordering, including a carbon onion.

  15. Growth Mechanism of Silicon Carbide (SIC) on Clean Silicon Surfaces

    International Nuclear Information System (INIS)

    products. For low acetylene exposure, almost the entire surface appears sqrt(3)xsqrt(3)-R30 degrees reconstructed but islands, mainly decorating the step edges, are generally surrounded by 7x7 reconstructed areas, located deeper with respect to the plane of sqrt(3)xsqrt(3)-R degrees reconstruction. For highest acetylene dose, the surface is characterized by nanostructures and large holes (as deep as 3-5 nm) that occupy one of more terraces between the original silicon surface step edges with their inner side constituted of islands itself. For intermediate acetylene exposure, the small increase (from 50 degrees to 700 degrees) of substrate temperature during the reaction is sufficient to make the resulting carbonization mechanism switch towards the highest exposure behaviour. The process can be described as the competitive effect of three mechanisms all providing silicon atoms for the reaction: the first involves the first stages of carbonization when carbon atoms are incorporated in substitutional sites in the silicon matrix and silicon atoms are released free to move on the surface and to participate to nanostructure formation; the second, occurring after the first nucleus of the nanostructure has grown, attracts silicon atoms from neighbouring areas towards the nanostructure itself and produces around it depleted zones characterized by silicon 7x7 reconstruction; the third, prevailing at highest acetylene doses, supplies silicon atoms from the bulk towards the surface to react with carbon atoms leaving voids in the matrix beneath. Experimental conditions, i.e. substrate temperature during reaction and acetylene dose, are found to condition the growth process by favouring one or more mechanisms

  16. Nano surface generation of grinding process using carbon nano tubes

    Indian Academy of Sciences (India)

    S Prabhu; B K Vinayagam

    2010-12-01

    Nano surface finish has become an important parameter in the semiconductor, optical, electrical and mechanical industries. The materials used in these industries are classified as difficult to machine materials such as ceramics, glasses and silicon wafers. Machining of these materials up to nano accuracy is a great challenge in the manufacturing industry. Finishing of micro components such as micro-moulds, micro-lenses and micro-holes need different processing techniques. Conventional finishing methods used so far become almost impossible or cumbersome. In this paper, a nano material especially multi wall carbon nano tube is used in the machining process like grinding to improve the surface characteristics from micro to nano level.

  17. Scan mechanical damage surface design elements

    OpenAIRE

    В.В. Астанін; Г.О. Олефір

    2006-01-01

     A method of the comparative estimation of mechanical damages of different materials and construction elements with the elaborated device is suggested. The principle of the device’s work is a transfer of the information about the profile of the threedimensionally deformated surface, that is scanned with a feeler and represented digitally with an optical reading system, to a computer with its following recalculation and analysis in a special program soft.

  18. Scan mechanical damage surface design elements

    Directory of Open Access Journals (Sweden)

    В.В. Астанін

    2006-01-01

    Full Text Available  A method of the comparative estimation of mechanical damages of different materials and construction elements with the elaborated device is suggested. The principle of the device’s work is a transfer of the information about the profile of the threedimensionally deformated surface, that is scanned with a feeler and represented digitally with an optical reading system, to a computer with its following recalculation and analysis in a special program soft.

  19. Surface-functionalized mesoporous carbon materials

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng; Gorka, Joanna; Mayes, Richard T.

    2016-02-02

    A functionalized mesoporous carbon composition comprising a mesoporous carbon scaffold having mesopores in which polyvinyl polymer grafts are covalently attached, wherein said mesopores have a size of at least 2 nm and up to 50 nm. Also described is a method for producing the functionalized mesoporous composition, wherein a reaction medium comprising a precursor mesoporous carbon, vinyl monomer, initiator, and solvent is subjected to sonication of sufficient power to result in grafting and polymerization of the vinyl monomer into mesopores of the precursor mesoporous carbon. Also described are methods for using the functionalized mesoporous carbon, particularly in extracting metal ions from metal-containing solutions.

  20. Optimization of interfacial microstructure and mechanical properties of carbon fiber/epoxy composites via carbon nanotube sizing

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Hongwei; Sui, Xianhang; Zhao, Zhongbo; Xu, Zhiwei; Chen, Lei, E-mail: chenlei@tjpu.edu.cn; Deng, Hui; Liu, Ya; Qian, Xiaoming, E-mail: qianxiaoming@tjpu.edu.cn

    2015-08-30

    Highlights: • Multiple sizing treatments were used to modify the surface of carbon fiber with carbon nanotubes. • The distribution state of carbon nanotubes in interface had a great effect on the performance of carbon fiber composites. • Interfacial microstructure changes brought by sizing treatment were detected by energy dispersive X-ray spectroscopy and atomic force microscope. • Gradient interphase composed of carbon nanotubes and epoxy was favorable to improve the mechanical properties of carbon composites. - Abstract: Repetitious sizing treatment was used to modify the carbon fiber (CF) surface with carbon nanotubes (CNTs) for improving interfacial properties of CF/epoxy composites. Interlaminar shear and flexural results showed that mechanical properties of composites were significantly depended on the dispersion state and contents of CNTs in interfacial regions. Increases of 13.45% in interlaminar shear strength and 20.31% in flexural strength were achieved in quintuple sized-CF/epoxy composites, whereas excessive CNTs led to decrease of interfacial performance due to defects induced by agglomerated CNTs. Energy dispersive X-ray spectroscopy and force modulation atomic force microscope were used to detect the structure of interfacial phase and results indicated that gradient interfacial structure with various thicknesses was formed due to CNT incorporation. This means that such a simple and efficient method to improve interfacial performance of composites via regulating the fiber–matrix interphase structure was developed and showed great commercial application potential.

  1. Optimization of interfacial microstructure and mechanical properties of carbon fiber/epoxy composites via carbon nanotube sizing

    International Nuclear Information System (INIS)

    Highlights: • Multiple sizing treatments were used to modify the surface of carbon fiber with carbon nanotubes. • The distribution state of carbon nanotubes in interface had a great effect on the performance of carbon fiber composites. • Interfacial microstructure changes brought by sizing treatment were detected by energy dispersive X-ray spectroscopy and atomic force microscope. • Gradient interphase composed of carbon nanotubes and epoxy was favorable to improve the mechanical properties of carbon composites. - Abstract: Repetitious sizing treatment was used to modify the carbon fiber (CF) surface with carbon nanotubes (CNTs) for improving interfacial properties of CF/epoxy composites. Interlaminar shear and flexural results showed that mechanical properties of composites were significantly depended on the dispersion state and contents of CNTs in interfacial regions. Increases of 13.45% in interlaminar shear strength and 20.31% in flexural strength were achieved in quintuple sized-CF/epoxy composites, whereas excessive CNTs led to decrease of interfacial performance due to defects induced by agglomerated CNTs. Energy dispersive X-ray spectroscopy and force modulation atomic force microscope were used to detect the structure of interfacial phase and results indicated that gradient interfacial structure with various thicknesses was formed due to CNT incorporation. This means that such a simple and efficient method to improve interfacial performance of composites via regulating the fiber–matrix interphase structure was developed and showed great commercial application potential

  2. Influence of Carbonation on Mechanical Properties of Concrete

    Institute of Scientific and Technical Information of China (English)

    梁发云; 陈龙珠; 李检保

    2003-01-01

    As one of the most important factors that determine the lifespan of a reinforced concrete structure, car-bonation not only corrodes the reinforcing steel, but also changes the mechanical properties of concrete. For betterunderstanding the performance of carbonated concrete structure, it is necessary to study the mechanical propertiesof carbonated concrete. The strees-strain relationship of carbonated concrete was analyzed on the basis of experi-ments. The specimens were made by means of accelerated carbonation and then compressed on the testing ma-chine. Some very important characteristics of carbonated concrete were revealed by the testing results. In addition,a useful constitutive model of carbonated concrete, which proved to be suitable for analyzing carbonated concretemembers, was established in this research.

  3. Carbon Sequestration on Surface Mine Lands

    Energy Technology Data Exchange (ETDEWEB)

    Donald Graves; Christopher Barton; Richard Sweigard; Richard Warner; Carmen Agouridis

    2006-03-31

    Since the implementation of the federal Surface Mining Control and Reclamation Act of 1977 (SMCRA) in May of 1978, many opportunities have been lost for the reforestation of surface mines in the eastern United States. Research has shown that excessive compaction of spoil material in the backfilling and grading process is the biggest impediment to the establishment of productive forests as a post-mining land use (Ashby, 1998, Burger et al., 1994, Graves et al., 2000). Stability of mine sites was a prominent concern among regulators and mine operators in the years immediately following the implementation of SMCRA. These concerns resulted in the highly compacted, flatly graded, and consequently unproductive spoils of the early post-SMCRA era. However, there is nothing in the regulations that requires mine sites to be overly compacted as long as stability is achieved. It has been cultural barriers and not regulatory barriers that have contributed to the failure of reforestation efforts under the federal law over the past 27 years. Efforts to change the perception that the federal law and regulations impede effective reforestation techniques and interfere with bond release must be implemented. Demonstration of techniques that lead to the successful reforestation of surface mines is one such method that can be used to change perceptions and protect the forest ecosystems that were indigenous to these areas prior to mining. The University of Kentucky initiated a large-scale reforestation effort to address regulatory and cultural impediments to forest reclamation in 2003. During the three years of this project 383,000 trees were planted on over 556 acres in different physiographic areas of Kentucky (Table 1, Figure 1). Species used for the project were similar to those that existed on the sites before mining was initiated (Table 2). A monitoring program was undertaken to evaluate growth and survival of the planted species as a function of spoil characteristics and

  4. Mechanical and Wear Properties of Nanostructured Surface Layer in Iron Induced by Surface Mechanical Attrition Treatment

    Institute of Scientific and Technical Information of China (English)

    Nairong TAO; Weiping TONG; Zhenbo WANG; Wei WANG; Manling SUI; Jian LU; Ke LU

    2003-01-01

    A porosity-free and contamination-free surface layer with grain sizes ranging from nanometer to micrometer in Fe samples was obtained by surface mechanical attrition treatment (SMAT) technique. Mechanical and wear properties of the surface layer in the SMATed and annealed Fe samples were measured by means of nanoindentation and nanoscratch tests, respectively. Experimental results showed that the hardness of the surface layer in the SMATed Fe sample increased evidently due to the grain refinement. The elastic noduli of the surface layers in the SMATed and annealed Fe samples were unchanged, independent of grain size in the present grain size regime. Compared with the original Fe sample, the wear resistance enhanced and the coefficient of friction decreased in the surface layer of the SMATed Fe sample.

  5. A statistical mechanics model of carbon nanotube macro-films

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Carbon nanotube macro-films are two-dimensional films with micrometer thickness and centimeter by centimeter in-plane dimension.These carbon nanotube macroscopic assemblies have attracted significant attention from the material and mechanics communities recently because they can be easily handled and tailored to meet specific engineering needs.This paper reports the experimental methods on the preparation and characterization of single-walled carbon nanotube macro-films,and a statistical mechanics model on ...

  6. Surface State of Carbon Fibers Modified by Electrochemical Oxidation

    Institute of Scientific and Technical Information of China (English)

    Yunxia GUO; Jie LIU; Jieying LIANG

    2005-01-01

    Surface of polyacrylonitrile (PAN)-based carbon fibers was modified by electrochemical oxidation. The modification effect on carbon fibers surface was explored using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Results showed that on the modified surface of carbon fibers, the carbon contents decreased by 9.7% and the oxygen and nitrogen contents increased by 53.8% and 7.5 times, respectively. The surface roughness and the hydroxyl and carbonyl contents also increased. The surface orientation index was reduced by 1.5%which decreased tensile strength of carbon fibers by 8.1%, and the microcrystalline dimension also decreased which increased the active sites of carbon fiber surface by 78%. The physical and chemical properties of carbon fibers surface were modified through the electrochemical oxidative method, which improved the cohesiveness between the fibers and resin matrix and increased the interlaminar shear strength (ILSS) of carbon fibers reinforced epoxy composite (CFRP) over 20%.

  7. Mechanism of field electron emission from carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-bing; DENG Shao-zhi; XU Ning-sheng

    2006-01-01

    Field electron emission (FE) is a quantum tunneling process in which electrons are injected from materials (usually metals) into a vacuum under the influence of an applied electric field.In order to obtain usable electron current,the conventional way is to increase the local field at the surface of an emitter.For a plane metal emitter with a typical work function of 5 eV,an applied field of over 1000V/μm is needed to obtain a significant current.The high working field (and/or the voltage between the electrodes)has been the bottleneck for many applications of the FE technique.Since the 1960s,enormous effort has been devoted to reduce the working macroscopic field (voltage).A widely adopted idea is to sharpen the emitters to get a large surface field enhancement.The materials of emitters should have good electronic conductivity,high melting points,good chemical inertness,and high mechanical stiffness.Carbon nanotubes (CNTs) are built with such needed properties.As a quasi-one-dimensional material,the CNT is expected to have a large surface field enhancement factor.The experiments have proved the excellent FE performance of CNTs.The turn-on field (the macroscopic field for obtaining a density of 10 μA/cm2 ) of CNT based emitters can be as low as 1 V/μm.However,this turn-on field is too good to be explained by conventional theory.There are other observations,such as the non-linear Fowler-Nordheim plot and multi-peaks field emission energy distribution spectra,indicating that the field enhancement is not the only story in the FE of CNTs.Since the discovery of CNTs,people have employed more serious quantum mechanical methods,including the electronic band theory,tight-binding theory,scattering theory and density function theory,to investigate FE of CNTs.A few theoretical models have been developed at the same time.The multi-walled carbon nanotubes (MWCNTs)should be assembled with a sharp metal needle of nano-scale radius,for which the FE mechanism is more or less clear

  8. Investigation of Structure and Physico-Mechanical Properties of Composite Materials Based on Copper - Carbon Nanoparticles Powder Systems

    Directory of Open Access Journals (Sweden)

    Kovtun V.

    2015-04-01

    Full Text Available Physico-mechanical and structural properties of electrocontact sintered copper matrix- carbon nanoparticles composite powder materials are presented. Scanning electron microscopy revealed the influence of preliminary mechanical activation of the powder system on distribution of carbon nanoparticles in the metal matrix. Mechanical activation ensures mechanical bonding of nanoparticles to the surface of metal particles, thus giving a possibility for manufacture of a composite with high physico-mechanical properties.

  9. Surface and corrosion characteristics of carbon plasma implanted and deposited nickel-titanium alloy

    Science.gov (United States)

    Poon, R. W. Y.; Liu, X. Y.; Chung, C. Y.; Chu, P. K.; Yeung, K. W. K.; Lu, W. W.; Cheung, K. M. C.

    2005-05-01

    Nickel-titanium shape memory alloys (NiTi) are potentially useful in orthopedic implants on account of their super-elastic and shape memory properties. However, the materials are prone to surface corrosion and the most common problem is out-diffusion of harmful Ni ions from the substrate into body tissues and fluids. In order to improve the corrosion resistance and related surface properties, we used the technique of plasma immersion ion implantation and deposition to deposit an amorphous hydrogenated carbon coating onto NiTi and implant carbon into NiTi. Both the deposited amorphous carbon film and carbon plasma implanted samples exhibit much improved corrosion resistances and surface mechanical properties and possible mechanisms are suggested.

  10. Tribological behavior and film formation mechanisms of carbon nanopearls

    Science.gov (United States)

    Hunter, Chad Nicholas

    Carbon nanopearls (CNPs) are amorphous carbon spheres that contain concentrically-oriented nanometer-sized graphitic flakes. Because of their spherical shape, size (˜150 nm), and structure consisting of concentrically oriented nano-sized sp2 flakes, CNPs are of interest for tribological applications, in particular for use in solid lubricant coatings. These studies were focused on investigating mechanisms of CNP lubrication, development of methods to deposit CNP onto substrates, synthesizing CNP-gold hybrid films using Matrix Assisted Pulsed Laser Evaporation (MAPLE) and magnetron sputtering, and studying plasmas and other species present during film deposition using an Electrostatic Quadrupole Plasma (EQP) analyzer. CNPs deposited onto silicon using drop casting with methanol showed good lubricating properties in sliding contacts under dry conditions, where a transfer film was created in which morphology changed from nano-sized spheres to micron-sized agglomerates consisting of many highly deformed CNPs in which the nano-sized graphene flakes are sheared from the wrapped layer structure of the CNPs. The morphology of carbon nanopearl films deposited using a MAPLE system equipped with a 248 nm KrF excimer laser source was found to be influenced by multiple factors, including composition of the matrix solvent, laser energy and repetition rate, background pressure, and substrate temperature. The best parameters for depositing CNP films that are disperse, droplet-free and have the maximum amount of material deposited are as follows: toluene matrix, 700 mJ, 1 Hz, 100°C substrate temperature, and unregulated vacuum pressure. During depositions using MAPLE and sputtering in argon, electron ionization of toluene vapor generated from the MAPLE target and charge exchange reactions between toluene vapor and the argon plasma generated by the magnetron caused carbon to be deposited onto the gold sputter target. Thin films deposited under these conditions contained high

  11. Surface modification, characterization and adsorptive properties of a coconut activated carbon

    Science.gov (United States)

    Lu, Xincheng; Jiang, Jianchun; Sun, Kang; Xie, Xinping; Hu, Yiming

    2012-08-01

    A coconut activated carbon was modified using chemical methods. Different concentration of nitric acid oxidation of the conventional sample produced samples with weakly acidic functional groups. The oxidized samples were characterized by scanning electron micrograph, nitrogen absorption-desorption, Fourier transform infra red spectroscopy, Bothem method, pH titration, adsorption capacity of sodium and formaldehyde, and the adsorption mechanism of activated carbons was investigated. The results showed that BET surface area and pore volume of activated carbons were decreased after oxidization process, while acidic functional groups were increased. The surface morphology of oxidized carbons looked clean and eroded which was caused by oxidization of nitric acid. The oxidized carbons showed high adsorption capacity of sodium and formaldehyde, and chemical properties of activated carbon played an important role in adsorption of metal ions and organic pollutants.

  12. Surface modification, characterization and adsorptive properties of a coconut activated carbon

    International Nuclear Information System (INIS)

    A coconut activated carbon was modified using chemical methods. Different concentration of nitric acid oxidation of the conventional sample produced samples with weakly acidic functional groups. The oxidized samples were characterized by scanning electron micrograph, nitrogen absorption-desorption, Fourier transform infra red spectroscopy, Bothem method, pH titration, adsorption capacity of sodium and formaldehyde, and the adsorption mechanism of activated carbons was investigated. The results showed that BET surface area and pore volume of activated carbons were decreased after oxidization process, while acidic functional groups were increased. The surface morphology of oxidized carbons looked clean and eroded which was caused by oxidization of nitric acid. The oxidized carbons showed high adsorption capacity of sodium and formaldehyde, and chemical properties of activated carbon played an important role in adsorption of metal ions and organic pollutants.

  13. Mechanical properties of carbon nanotube/polymer composites

    OpenAIRE

    B. Arash; Wang, Q.(The University of Kansas, Lawrence, USA); Varadan, V. K.

    2014-01-01

    The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the compos...

  14. Theoretical analysis of hydrogen spillover mechanism on carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Rosalba eJuarez Mosqueda

    2015-02-01

    Full Text Available The spillover mechanism of molecular hydrogen on carbon nanotubes in the presence of catalytically active platinum clusters was critically and systematically investigated by using density-functional theory. Our simulation model includes a Pt4 cluster for the catalyst nanoparticle and curved and planar circumcoronene for two exemplary single-walled carbon nanotubes (CNT, the (10,10 CNT and one of large diameter, respectively. Our results show that the H2 molecule dissociates spontaneously on the Pt4 cluster. However, the dissociated H atoms have to overcome a barrier of more than 2 eV to migrate from the catalyst to the CNT, even if the Pt4 cluster is at full saturation with six adsorbed and dissociated hydrogen molecules. Previous investigations have shown that the mobility of hydrogen atoms on the CNT surface is hindered by a barrier. We find that instead the Pt4 catalyst may move along the outer surface of the CNT with activation energy of only 0.16 eV, and that this effect offers the possibility of full hydrogenation of the CNT. Thus, although we have not found a low-energy pathway to spillover onto the CNT, we suggest, based on our calculations and calculated data reported in the literature, that in the hydrogen-spillover process the observed saturation of the CNT at hydrogen background pressure occurs through mobile Pt nanoclusters, which move on the substrate more easily than the substrate-chemisorbed hydrogens, and deposit or reattach hydrogens in the process. Initial hydrogenation of the carbon substrate, however, is thermodynamically unfavoured, suggesting that defects should play a significant role.

  15. Inhibition of surface bound carbonate stabilization of tetragonal zirconia

    DEFF Research Database (Denmark)

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

    2011-01-01

    Water is known to initiate a tetragonal to monoclinic phase transformation in zirconia particles. Carbonates on the zirconia surface react with water molecules and hence reduce the transformation rate. This study investigates the possibility of inhibition of the reaction between surface carbonates...... and water in order to increase the transformation rate in the zirconia crystals. It was found possible to limit the reaction by reacting the surface carbonates with alcohols, a thiol and a primary amide prior to reaction with water. It was also concluded that di- and trialcohols are able to stabilize...

  16. STUDY OF DEPENDENCE OF POLYETHYLENE AND CARBON FIBERS COMPOSITES PROPERNIES ON SURFACE CHARACTERISTICS OF FIBER AND TYPE OF SAMPLES

    Directory of Open Access Journals (Sweden)

    Petukhova E. S.

    2015-06-01

    Full Text Available PE2NT11 and chopped carbon fibers and PE2NT11 and modified carbon fibers composites were investigated. It was shown that the mechanical properties depend on the surface characteristics of fibers. It was found that laboratory and tube samples have some difference in mechanical properties that connected with specific distribution of fibers in samples

  17. STUDY OF DEPENDENCE OF POLYETHYLENE AND CARBON FIBERS COMPOSITES PROPERNIES ON SURFACE CHARACTERISTICS OF FIBER AND TYPE OF SAMPLES

    OpenAIRE

    Petukhova E. S.

    2015-01-01

    PE2NT11 and chopped carbon fibers and PE2NT11 and modified carbon fibers composites were investigated. It was shown that the mechanical properties depend on the surface characteristics of fibers. It was found that laboratory and tube samples have some difference in mechanical properties that connected with specific distribution of fibers in samples

  18. Effect of plasma surface treatment of recycled carbon fiber on carbon fiber-reinforced plastics (CFRP) interfacial properties

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hooseok, E-mail: hooseok.lee@gmail.com; Ohsawa, Isamu; Takahashi, Jun

    2015-02-15

    Highlights: • Plasma treatment was used to improve the adhesion property between the recycled CF and polymer matrix. • In order to evaluate the adhesion between plasma treated recycled CF and polymer, micro droplet test was conducted. • The interfacial shear strength and the interfacial adhesion of recycled carbon fiber increased. - Abstract: We studied the effects of plasma surface treatment of recycled carbon fiber on adhesion of the fiber to polymers after various treatment times. Conventional surface treatment methods have been attempted for recycled carbon fiber, but most require very long processing times, which may increase cost. Hence, in this study, plasma processing was performed for 0.5 s or less. Surface functionalization was quantified by X-ray photoelectron spectroscopy. O/C increased from approximately 11% to 25%. The micro-droplet test of adhesion properties and the mechanical properties of CFRP were also investigated.

  19. Effect of plasma surface treatment of recycled carbon fiber on carbon fiber-reinforced plastics (CFRP) interfacial properties

    International Nuclear Information System (INIS)

    Highlights: • Plasma treatment was used to improve the adhesion property between the recycled CF and polymer matrix. • In order to evaluate the adhesion between plasma treated recycled CF and polymer, micro droplet test was conducted. • The interfacial shear strength and the interfacial adhesion of recycled carbon fiber increased. - Abstract: We studied the effects of plasma surface treatment of recycled carbon fiber on adhesion of the fiber to polymers after various treatment times. Conventional surface treatment methods have been attempted for recycled carbon fiber, but most require very long processing times, which may increase cost. Hence, in this study, plasma processing was performed for 0.5 s or less. Surface functionalization was quantified by X-ray photoelectron spectroscopy. O/C increased from approximately 11% to 25%. The micro-droplet test of adhesion properties and the mechanical properties of CFRP were also investigated

  20. Effect of electropolymer sizing of carbon fiber on mechanical properties of phenolic resin composites

    Institute of Scientific and Technical Information of China (English)

    LI Jin; FAN Qun; CHEN Zhen-hua; HUANG Kai-bing; CHENG Ying-liang

    2006-01-01

    Carbon fiber/phenolic resin composites were reinforced by the carbon fiber sized with the polymer films of phenol,m-phenylenediamine or acrylic acid,which was electropolymerized by cyclic voltammetry or chronopotentiometry. The contact angles of the sized carbon fibers with deionized water and diiodomethane were measured by the wicking method based on the modified Washburn equation,to show the effects of the different electropolymer film on the surface free energy of the carbon fiber after sizing by the electropolymerization. Compared with the unsized carbon fiber,which has 85.6°of contact angle of water,52.2° of contact angle of diiodomethane,and 33.1 mJ/m2 of surface free energy with 29.3 mJ/m2 of dispersive components (γL) and 3.8 mJ/m2 of polar components (γsp),respectively. It is found that the electropolymer sized carbon fiber tends to reduce the surface energy due to the decrease of dispersive γL with the increase of the polymer film on the surface of the carbon fiber that plays an important role in improving the mechanical properties of carbon/phenolic resin composites. Compared with the phenolic resin composites reinforced by the unsized carbon fiber,the impact,flexural and interlaminar shear strength of the phenolic resin composites were improved by 44 %,68% and 87% when reinforced with the carbon fiber sized by the electropolymer of m-phenylenediamine,66%,100%,and 112% by the electropolymer of phenol,and 20%,80 %,100% by the electropolymer of acrylic acid. The results indicate the skills of electropolymerization may provide a feasible method for the sizing of carbon fiber in a composite system,so as to improve the interfacial performance between the reinforce materials and the matrix and to increase the mechanical properties of the composites.

  1. Cathodic carbon peroxidation process. Surface modifications through oxygen bonding

    OpenAIRE

    Simonet, Jacques

    2013-01-01

    The reduction of oxygen of the air at carbon electrodes in organic aprotic polar solvents in the presence of organic electrophiles such as alkyl iodides may reveal the formation of films of surface-attached alkyl peroxides. Electrochemical charge of carbons (glassy carbon, graphite, industrial coke) in the presence of tetraalkylammonium salt TAAX permits the building of poly-nucleophilic materials that may spontaneously react with air during the work up. This way, a TAA+ hydroperoxydate layer...

  2. The clean development mechanism in a globalized carbon market

    OpenAIRE

    Thierry Bréchet; Yann Ménière; Picard, Pierre M

    2011-01-01

    This paper discusses the role of the Clean DevelopmentMechanisms (CDM) on the market for carbon quotas and countries' commitments to reduce their carbon emission levels. We show that the CDM contributes to an efficient funding of clean technology investments in least developed countries. How- ever, the CDM is not neutral on the global level of carbon emissions as it entices countries to raise their emission caps. The CDM may also make inap- propriate the inclusion of any country that makes no...

  3. High-energy radiation technique treat on the surface of carbon fiber

    International Nuclear Information System (INIS)

    Co60 γ-ray irradiation as a novel method for modification of carbon fiber (CF) surface was introduced in this paper. After surface treatment by mutual irradiation the interlaminar shear strength (ILSS) of CF/epoxy composites was enhanced by about 37%. Surface elements of CF were determined by XPS analysis, which indicated that the oxygen/carbon ratio increased rapidly. Fitting the C 1s spectra demonstrated that two new photopeaks were emerged which was indicated -C=O and plasmon, respectively. Surface topography of carbon fibers was analyzed by atomic force microscopy (AFM). It could be found that the degree of surface roughness was increased by lower absorbed dose (30 kGy), but excessive irradiation (>250 kGy) was not beneficial for mechanical interlocking between CF and epoxy resin. The impregnating performance of CF was also improved after irradiation

  4. Molecular mechanics applied to single-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Antonio Ferreira Ávila

    2008-09-01

    Full Text Available Single-walled carbon nanotubes, with stiffness of 1.0 TPa and strength of 60 GPa, are a natural choice for high strength materials. A problem, however, arises when experimental data are compiled. The large variability of experimental data leads to the development of numerical models denominated molecular mechanics, which is a "symbiotic" association of molecular dynamics and solid mechanics. This paper deals with molecular mechanics simulations of single-walled carbon nanotubes. To be able to evaluate the molecular mechanics model, the three major carbon nanotube configurations (armchair, zigzag and chiral were simulated. It was proven that the carbon nanotube configuration has influence on stiffness. By varying the radius, hence the curvature, the Young's modulus changed from 0.95 TPa to 5.5 TPa, and the Poisson's ratio ranged from 0.15 to 0.29. The numerical simulations were in good agreement with those presented in the literature.

  5. Study on the Reaction Mechanism for Carbon Dioxide Reforming of Methane over supported Nickel Catalyst

    Institute of Scientific and Technical Information of China (English)

    Ling QIAN; Zi Feng YAN

    2003-01-01

    The adsorption and dissociation of methane and carbon dioxide for reforming on nickelcatalyst were extensively investigated by TPSR and TPD experiments. It showed that thedecomposition of methane results in the formation of at least three kinds of surface carbon specieson supported nickel catalyst, while CO2 adsorbed on the catalyst weakly and only existed in onekind of adsorption state. Then the mechanism of interaction between the species dissociatedfrom CH4 and CO2 during reforming was proposed.

  6. Parameterizing A Surface Water Model for Multiwalled Carbon Nanotubes

    Science.gov (United States)

    The unique electronic, mechanical, and structural properties of carbon nanotubes (CNTs) has lead to increasing production of these versatile materials; currently, the use of carbon-based nanomaterials in consumer products is second only to that of nano-scale silver. Although ther...

  7. Random surfaces, statistical mechanics and string theory

    International Nuclear Information System (INIS)

    These notes are based on an eight-lecture course held at Lausanne in the fall of 1990. The aim of the course was to provide a reasonable self-contained introduction to the subject of sub-critical strings and matrix models together with their connections with some problems in statistical mechanics. After a general introduction to string theory with its relations with the theory of random surfaces and conformal invariant theories conformal quantum field theories, the minimal conformal models, and the Coulomb gas representation of their correlation functions are briefly introduced. Then some results are derived, which lead to the gravitational dressing of conformal primary fields and their gravitationally dressed dimensions. Thereafter large-N field theory techniques for the simulation of the sum over two-dimensional geometries and the properties and definitions of critical exponents for statistical mechanics models are presented. Finally the relation between sub-critical strings, the KdV hierarchy, the Douglas equation, the double scaling limit for the Kazakov multi-critical points, the c=1 string theory, and the two-dimensional Ising model in the presence of gravity and an external magnetic field, and the loop equations, the Virasoro constraints, and the non-perturbative properties of pure two-dimensional gravity are briefly commented. (HSI)

  8. Heterogeneous nucleation of ice on model carbon surfaces

    Science.gov (United States)

    Molinero, V.; Lupi, L.; Hudait, A.

    2014-12-01

    Carbonaceous particles account for 10% of the particulate matter in the atmosphere. The experimental investigation of heterogeneous freezing of water droplets by carbonaceous particles reveals widespread ice freezing temperatures. The origin of the soot and its oxidation and aging modulate its ice nucleation ability, however, it is not known which structural and chemical characteristics of soot account for the variability in ice nucleation efficiency. We find that atomically flat carbon surfaces promote heterogeneous nucleation of ice, while molecularly rough surfaces with the same hydrophobicity do not. We investigate a large set of graphitic surfaces of various dimensions and radii of curvature consistent with those of soot in experiments, and find that variations in nanostructures alone could account for the spread in the freezing temperatures of ice on soot in experiments. A characterization of the nanostructure of soot is needed to predict its ice nucleation efficiency. Atmospheric oxidation and aging of soot modulates its ice nucleation ability. It has been suggested that an increase in the ice nucleation ability of aged soot results from an increase in the hydrophilicity of the surfaces upon oxidation. Oxidation, however, also impacts the nanostructure of soot, making it difficult to assess the separate effects of soot nanostructure and hydrophilicity in experiments. We investigate the effect of changes in hydrophilicity of model graphitic surfaces on the freezing temperature of ice. Our results indicate that the hydrophilicity of the surface is not in general a good predictor of ice nucleation ability. We find a correlation between the ability of a surface to promote nucleation of ice and the layering of liquid water at the surface. The results of this work suggest that ordering of liquid water in contact with the surface plays an important role in the heterogeneous ice nucleation mechanism. References: L. Lupi, A. Hudait and V. Molinero, J. Am. Chem. Soc

  9. Nanotextured gold coatings on carbon nanofiber scaffolds as ultrahigh surface-area electrodes

    OpenAIRE

    COLAVITA, PAULA

    2012-01-01

    PUBLISHED High surface area metal electrodes are desirable for applications in energy storage and energy conversion. Here, the formation and electrochemical characterization of a hybrid material made by electroless deposition of gold onto a scaffolding of vertically aligned carbon nanofibers is described. Vertically aligned carbon nanofibers, ~80 nm in diameter, provided mechanical support and electrical contact to the highly textured nanoscale gold coatings. By chemically functionalizing ...

  10. Structural and surface features of multiwall carbon nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Hembram, K.P.S.S., E-mail: hembram@isu.iisc.ernet.in [Department of Instrumentation, Indian Institute of Science, Bangalore, 560012 (India); Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, 560064 (India); Rao, G. Mohan [Department of Instrumentation, Indian Institute of Science, Bangalore, 560012 (India)

    2011-04-15

    We present the direct evidence of defective and disorder places on the surface of multiwall carbon nanotube (MWCNT), visualizing the presence of amorphous carbon at those sites. These defective surfaces being higher in energy are the key features of functionalization with different materials. The interaction of the {pi} orbital electrons of different carbon atoms of adjacent layers is more at the bent portion, than that of regular portion of the CNT. Hence the tubular structure of the bent portion of nanotubes is spaced more than that of regular portion of the nanotubes, minimizing the stress.

  11. Structural and surface features of multiwall carbon nanotube

    Science.gov (United States)

    Hembram, K. P. S. S.; Rao, G. Mohan

    2011-04-01

    We present the direct evidence of defective and disorder places on the surface of multiwall carbon nanotube (MWCNT), visualizing the presence of amorphous carbon at those sites. These defective surfaces being higher in energy are the key features of functionalization with different materials. The interaction of the π orbital electrons of different carbon atoms of adjacent layers is more at the bent portion, than that of regular portion of the CNT. Hence the tubular structure of the bent portion of nanotubes is spaced more than that of regular portion of the nanotubes, minimizing the stress.

  12. Carbon Footprint Management of Road Freight Transport under the Carbon Emission Trading Mechanism

    Directory of Open Access Journals (Sweden)

    Jin Li

    2015-01-01

    Full Text Available Growing concern over environmental issues has considerably increased the number of regulations and legislation that aim to curb carbon emissions. Carbon emission trading mechanism, which is one of the most effective means, has been broadly adopted by several countries. This paper presents a road truck routing problem under the carbon emission trading mechanism. By introducing a calculation method of carbon emissions that considers the load and speed of the vehicle among other factors, a road truck routing optimizing model under the cap and trade mechanism based on the Travelling Salesman Problem (TSP is described. Compared with the classical TSP model that only considers the economic cost, this model suggests that the truck routing decision under the cap and trade mechanism is more effective in reducing carbon emissions. A modified tabu search algorithm is also proposed to obtain solutions within a reasonable amount of computation time. We theoretically and numerically examine the impacts of carbon trading, carbon cap, and carbon price on truck routing decision, carbon emissions, and total cost. From the results of numerical experiments, we derive interesting observations about how to control the total cost and reduce carbon emissions.

  13. Effect of Hybrid Surface Modifications on Tensile Properties of Polyacrylonitrile- and Pitch-Based Carbon Fibers

    Science.gov (United States)

    Naito, Kimiyoshi

    2016-05-01

    Recent interest has emerged in techniques that modify the surfaces of carbon fibers, such as carbon nanotube (CNT) grafting or polymer coating. Hybridization of these surface modifications has the potential to generate highly tunable, high-performance materials. In this study, the mechanical properties of surface-modified polyacrylonitrile (PAN)-based and pitch-based carbon fibers were investigated. Single-filament tensile tests were performed for fibers modified by CNT grafting, dipped polyimide coating, high-temperature vapor deposition polymerized polyimide coating, grafting-dipping hybridization, and grafting-vapor deposition hybridization. The Weibull statistical distributions of the tensile strengths of the surface-modified PAN- and pitch-based carbon fibers were examined. All surface modifications, especially hybrid modifications, improved the tensile strengths and Weibull moduli of the carbon fibers. The results exhibited a linear relationship between the Weibull modulus and average tensile strength on a log-log scale for all surface-modified PAN- and pitch-based carbon fibers.

  14. Mechanisms of carbon aging and their effects on the retention of organic iodides by carbon

    International Nuclear Information System (INIS)

    The activated carbon used to treat the off-gas from the Savannah River Plant production reactor building was studied to determine the chemical changes occuring in this carbon during its service life. The carbon is a coconut-shell charcoal impregnated with 1% triethylenediamine (TEDA) and 2% KI. It was known that during its 30-month service life the carbon becomes more acidic and less effective for retaining iodine in organic form. The study showed that the most important change occurring in the carbon is the reaction of KI to give other chemical forms of iodine. The results suggest that the carbon reacts with KI to form organic compounds, but small amounts of oxidized iodine may also be present. The TEDA impregnant is lost from the carbon very quickly, and has no importance after a few months. Mathematical analysis of the carbon performance data show that they are consistent with the reaction of iodide impregnant with impurities in the air flowing through the carbon bed. Additional mathematical analysis, based on electron microscopic observation of the carbon particles, indicates that the external surfaces of the carbon are mainly responsible for their effectiveness in retaining iodine. Consequently, the condition of the impregnants on a relatively small fraction of the carbon surface can have a large effect on its performance. (author)

  15. The mechanics and biocompatibility characteristics of carbon nanotubes-polyurethane composite membranes:a preliminary study

    International Nuclear Information System (INIS)

    Objective: To discuss the mechanics and biocompatibility characteristics of carbon nanotubes-polyurethane composite membranes. Methods: The mechanics property of carbon nanotubes-polyurethane composite membranes with different carbon nanotubes contents were tested by universal material testing machine. The surface of the membranes was observed by electron microscope when the stent was bent 90 degree. And its cytotoxicity was tested by cultivating study with 7721 cell. The metallic stent that was covered with carbon nanotubes-polyurethane composite membrane by using dip-coating method was inserted in rabbit esophagus in order to evaluate its biocompatibility in vivo. Results: Composite membranes tensile strength (MPa) and elongation at break (%) were 4.62/900, 6.05/730, 8.26/704 and 5.7/450 when the carbon nanotubes contents were 0%, 0.1%, 0.3% and 0.5%, respectively. If the stent was bent at 90 degree, its surface was still smooth without any fractures when it was scanned by electron microscope.Composite membranes had critical cytotoxicity when its carbon nanotubes content was up to 0.5% and 1.0%. No fissure nor degradation of composite membranes occurred at 30 days after composite membrane covered metallic stent was inserted in rabbit esophagus. Conclusion: When moderate carbon nanotubes are added into polyurethane composite membrane, the mechanics and biocompatibility characteristics of the polyurethane composite membrane can be much improved. (authors)

  16. Surface modified carbon nanoparticle papers and applications on polymer composites

    Science.gov (United States)

    Ouyang, Xilian

    Free-standing paper like materials are usually employed as protective layers, chemical filters, components of electrical batteries or supercapacitors, adhesive layers, and electronic or optoelectric components. Free-standing papers made from carbon nanoparticles have drawn increased interest because they have a variety of superior chemical and physical characteristics, such as light weight, high intrinsic mechanical properties, and extraordinary high electrical conductivity. Nanopapers fabricated from 1- D shape carbon nanofibers (CNFs) and carbon nanotubes (CNTs) are promising reinforcing materials for polymer composites, because the highly porous CNF and CNT nanopapers (porosity ˜80% and ˜70% respectively) can be impregnated with matrix polymers. In the first part of this work, polyaniline (PANI) was used to functionalize the surface of CNFs, and the resultant carbon nanopapers presented impressive mechanical strength and electrical conductivity that it could be used in the in-mold coating (IMC)/ injection molding process to achieve high electromagnetic interference (EMI) shielding effectiveness. Aniline modified (AF) CNT nanopapers were used as a 3D network in gas separation membranes. The resultant composite membranes demonstrated better and stable CO2 permeance and CO 2/H2 selectivity in a high temperature (107°C) and high pressure (15-30 atm) gas separation process, not achievable by conventional polymer membranes. In the second part, we demonstrated that 2-D graphene (GP) or graphene oxide (GO) nanosheets could be tightly packed into a film which was impermeable to most gases and liquids. GP or GO nanopapers could be coated on polymer composites. In order to achieve well-dispersed single-layer graphene in aqueous medium, we developed a facile approach to synthesize functional GP bearing benzenesulfonic acid groups which allow the preparation of nanopapers by water based assembly. With the optimized processing conditions, our best GP nanopapers could reach

  17. Carbon Sequestration on Surface Mine Lands

    Energy Technology Data Exchange (ETDEWEB)

    Donald H. Graves; Christopher Barton; Bon Jun Koo; Richard Sweigard; Richard Warner

    2004-11-30

    The first quarter of 2004 was dedicated to tree planting activities in two locations in Kentucky. During the first year of this project there was not available mine land to plant in the Hazard area, so 107 acres were planted in the Martin County mine location. This year 120 acres were planted in the Hazard area to compensate for the prior year and an additional 57 acres were planted on Peabody properties in western Kentucky. Additional sets of special plots were established on each of these areas that contained 4800 seedlings each for carbon sequestration demonstrations. Plantings were also conducted to continue compaction and water quality studies on the newly established areas as well as continual measurements of the first year's plantings. Total plantings on this project now amount to 357 acres containing 245,960 seedlings. During the second quarter of this year monitoring systems were established for all the new research areas. Weather data pertinent to the research as well as hydrology and water quality monitoring continues to be conducted on all areas. Studies established to assess specific questions pertaining to carbon flux and the invasion of the vegetation by small mammals are being quantified. Experimental practices initiated with this research project will eventually allow for the planting on long steep slopes with loose grading systems and allow mountain top removal areas to be constructed with loose spoil with no grading of the final layers of rooting material when establishing trees for the final land use designation. Monitoring systems have been installed to measure treatment effects on both above and below ground carbon and nitrogen pools in the planting areas. Soil and tissue samples were collected from both years planting and analyses were conducted in the laboratory. Examination of decomposition and heterotropic respiration on carbon cycling in the reforestation plots continued during the reporting period. Entire planted trees were

  18. Growth limit of carbon onions – A continuum mechanical study

    DEFF Research Database (Denmark)

    Todt, Melanie; Bitsche, Robert; Hartmann, Markus A.;

    2014-01-01

    The growth of carbon onions is simulated using continuum mechanical shell models. With this models it is shown that, if a carbon onion has grown to a critical size, the formation of an additional layer leads to the occurrence of a structural instability. This instability inhibits further growth of...... carbon onions and, thus, can be a reason for the limited size of such particles. The loss of stability is mainly evoked by van der Waals interactions between misfitting neighboring layers leading to self-equilibrating stress states in the layers due to mutual accommodation. The influence of the curvature...... model gives insight into mechanisms which are assumed to limit the size of carbon onions and can serve as basis for further investigations, e.g., of the formation of nanodiamonds in the center of carbon onions. © 2013 Elsevier Ltd. All rights reserved....

  19. Mechanisms of soil carbon storage in experimental grasslands

    Science.gov (United States)

    Steinbeiss, S.; Temperton, V. M.; Gleixner, G.

    2007-10-01

    We investigated the fate of root and litter derived carbon into soil organic matter and dissolved organic matter in soil profiles, in order to explain unexpected positive effects of plant diversity on carbon storage. A time series of soil and soil solution samples was investigated at the field site of The Jena Experiment. In addition to the main biodiversity experiment with C3 plants, a C4 species (Amaranthus retroflexus L.) naturally labeled with 13C was grown on an extra plot. Changes in organic carbon concentration in soil and soil solution were combined with stable isotope measurements to follow the fate of plant carbon into the soil and soil solution. A split plot design with plant litter removal versus double litter input simulated differences in biomass input. After 2 years, the no litter and double litter treatment, respectively, showed an increase of 381 g C m-2 and 263 g C m-2 to 20 cm depth, while 71 g C m-2 and 393 g C m-2 were lost between 20 and 30 cm depth. The isotopic label in the top 5 cm indicated that 11 and 15% of soil organic carbon were derived from plant material on the no litter and the double litter treatment, respectively. Without litter, this equals the total amount of carbon newly stored in soil, whereas with double litter this corresponds to twice the amount of stored carbon. Our results indicate that litter input resulted in lower carbon storage and larger carbon losses and consequently accelerated turnover of soil organic carbon. Isotopic evidence showed that inherited soil organic carbon was replaced by fresh plant carbon near the soil surface. Our results suggest that primarily carbon released from soil organic matter, not newly introduced plant organic matter, was transported in the soil solution and contributed to the observed carbon storage in deeper horizons.

  20. Surface plasmon observed for carbon nanotubes

    International Nuclear Information System (INIS)

    This paper presents parallel electron energy loss spectra (PEELS) results, obtained for individual carbon nanotubes, using nanoprobe techniques (1-2 nm diameter electron beam), energy resolution 0.5 eV and collection times of 4-25 sec. The aim was to use a nanoprobe to compare PEELS spectra from different parts of a tube, in order to search for variations in sp2/sp3 bonding ratios as well as to look for orientation dependent plasmon and core-loss phenomena. It also seemed interesting to compare results for nanotubes with those for other varieties of graphitized carbons. The most interesting result so far was the appearance of a 15 eV plasmon peak, which appeared only for tubes containing ≤ about 12 graphite-like layers. This peak did not shift significantly with tube size. A low-loss peaks at 6 eV of variable relative intensity was also observed this peak was relatively very weak for amorphous tubes; it appears to be characteristic of graphite-like layers, as found for nanotubes and, of course, graphite itself. This paper is restricted to discussion of the low-loss results. The experimental techniques are first described, including some details of the methods which may be used to disperse and support sooty carbons for high-resolution transmission electron microscopy. The results are then presented, followed by an interpretation of all the low-loss PEELS results, including those of the other authors. 14 refs., 2 figs

  1. Formation mechanism of diamond nanocrystal from catalysed carbon black

    International Nuclear Information System (INIS)

    Recently, our group has synthesized nanocrystal n-diamond and diamond-like carbon (DLC) from catalysed carbon black. Based on the results of XRD, TGA and DTA, a formation mechanism has been proposed to explain the phase transformation from carbon black to diamond nanocrystal. With the increase of temperature and hence the carbon diffusion in iron, the phase sequence is from Fe(OH)3 into Fe2O3, α-Fe, γ-Fe, then liquid iron. When the carbon in the liquid iron is saturated, DLC or graphite separates out of the liquid iron. With decrease of temperature, the carbon in γ-Fe is separated out, and n-diamond nuclei form and grow

  2. Formation mechanism of diamond nanocrystal from catalysed carbon black

    Science.gov (United States)

    Wen, Bin; Li, Tingju; Dong, Chuang; Zhang, Xingguo; Yao, Shan; Cao, Zhiqiang; Wang, Dehe; Ji, Shouhua; Jin, Junze

    2004-10-01

    Recently, our group has synthesized nanocrystal n-diamond and diamond-like carbon (DLC) from catalysed carbon black. Based on the results of XRD, TGA and DTA, a formation mechanism has been proposed to explain the phase transformation from carbon black to diamond nanocrystal. With the increase of temperature and hence the carbon diffusion in iron, the phase sequence is from Fe(OH)3 into Fe2O3, agr-Fe, ggr-Fe, then liquid iron. When the carbon in the liquid iron is saturated, DLC or graphite separates out of the liquid iron. With decrease of temperature, the carbon in ggr-Fe is separated out, and n-diamond nuclei form and grow.

  3. Formation mechanism of diamond nanocrystal from catalysed carbon black

    Energy Technology Data Exchange (ETDEWEB)

    Wen Bin [Department of Materials Engineering, Dalian University of Technology, Dalian 116023 (China); Li Tingju [Laboratory of Special Processing of Raw Materials, Dalian University of Technology, Dalian 116023 (China); Dong Chuang [Department of Materials Engineering, Dalian University of Technology, Dalian 116023 (China); Zhang Xingguo [Laboratory of Special Processing of Raw Materials, Dalian University of Technology, Dalian 116023 (China); Yao Shan [Laboratory of Special Processing of Raw Materials, Dalian University of Technology, Dalian 116023 (China); Cao Zhiqiang [Laboratory of Special Processing of Raw Materials, Dalian University of Technology, Dalian 116023 (China); Wang Dehe [Department of Materials Engineering, Dalian University of Technology, Dalian 116023 (China); Ji Shouhua [Department of Materials Engineering, Dalian University of Technology, Dalian 116023 (China); Jin Junze [Laboratory of Special Processing of Raw Materials, Dalian University of Technology, Dalian 116023 (China)

    2004-10-06

    Recently, our group has synthesized nanocrystal n-diamond and diamond-like carbon (DLC) from catalysed carbon black. Based on the results of XRD, TGA and DTA, a formation mechanism has been proposed to explain the phase transformation from carbon black to diamond nanocrystal. With the increase of temperature and hence the carbon diffusion in iron, the phase sequence is from Fe(OH){sub 3} into Fe{sub 2}O{sub 3}, {alpha}-Fe, {gamma}-Fe, then liquid iron. When the carbon in the liquid iron is saturated, DLC or graphite separates out of the liquid iron. With decrease of temperature, the carbon in {gamma}-Fe is separated out, and n-diamond nuclei form and grow.

  4. Covalent modification of carbon surfaces with cyclodextrins by mediated oxidation of β-cyclodextrin monoanions

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • >Covalent grafting of carbon surfaces by mediated oxidation of cyclodextrin monoanions > The use of ferrocene as redox catalyst to prepare electrochemically modified electrodes. • EPR spectrum of electrochemically generated cyclodextrin radicals. • Electrochemical polymerization of cyclodextrine over glassy carbon surfaces. • Formation of inclusion complexes between ferrocene and β-cyclodextrin in dimethylsulfoxide. - Abstract: The covalent grafting of glassy carbon and highly oriented pyrolytic graphite with cyclodextrins is reported in this work. The modification procedure is based in the concept that oxidation of organic anions generates radicals which react with carbon surfaces. These radical species are generated through a redox catalysis mechanism involving the formation of ferrocenium ion, which in turn oxidizes the cyclodextrin monoanion to afford an oxygen-centered free radical that ultimately reacts either in solution or with the surface, affording a strong attachment of cyclodextrin molecules to the carbon surface. The intervention of this radical was established from spectroelectrochemical EPR experiments. Atomic force microscopy imaging showed that the attached organic layer is thick while cyclic voltammetry experiments confirmed that this modified surface behaves as an ultramicroelectrode array. This kind of modification allows incorporate cyclodextrin to an electrode surface without a binder, making the modified electrode useful to be tested in forthcoming sensor studies

  5. Surface properties of diamond-like carbon films prepared by CVD and PVD methods

    Institute of Scientific and Technical Information of China (English)

    Liu Dong-Ping; Liu Yan-Hong; Chen Bao-Xiang

    2006-01-01

    Diamond-like carbon (DLC) films have been deposited using three different techniques: (a) electron cyclotron resonance-plasma source ion implantation, (b) low-pressure dielectric barrier discharge, (c) filtered-pulsed cathodic arc discharge. The surface and mechanical properties of these films are compared using atomic force microscopebased tests. The experimental results show that hydrogenated DLC films are covered with soft surface layers enriched with hydrogen and sp3 hybridized carbon while the soft surface layers of tetrahedral amorphous carbon (ta-C) films have graphite-like structure. The formation of soft surface layers can be associated with the surface diffusion and growth induced by the low-energy deposition process. For typical CVD methods, the atomic hydrogen in the plasmas can contribute to the formation of hydrogen and sp3 hybridized carbon enriched surface layers. The high-energy ion implantation causes the rearrangement of atoms beneath the surface layer and leads to an increase in film density. The ta-C films can be deposited using the medium energy carbon ions in the highly-ionized plasma.

  6. Mechanical work makes important contributions to surface chemistry at steps

    OpenAIRE

    Francis, M. F.; Curtin, W. A.

    2015-01-01

    The effect of mechanical strain on the binding energy of adsorbates to late transition metals is believed to be entirely controlled by electronic factors, with tensile stress inducing stronger binding. Here we show, via computation, that mechanical strain of late transition metals can modify binding at stepped surfaces opposite to well-established trends on flat surfaces. The mechanism driving the trend is mechanical, arising from the relaxation of stored mechanical energy. The mechanical ene...

  7. Numerical Simulation of The Mechanical Properties of Carbon Nanotube Using the Atomistic-Continuum Mechanics

    OpenAIRE

    Wu, C. -J.; Chou, C. -Y.; Han, C. -N.; Chiang, K.-N.

    2006-01-01

    This paper the utilizes atomistic-continuum mechanics (ACM) to investigate the mechanical properties of single-walled carbon nanotubes (SWCNTs). By establishing a linkage between structural mechanics and molecular mechanics, not only the Young's moduli could be obtained but also the modal analysis could be achieved. In addition, according to atomistic-continuum mechanics and finite element method, an effective atomistic-continuum model is constructed to investigate the above two mechanical pr...

  8. Mechanisms for catalytic carbon nanofiber growth studied by ab initio density functional theory calculations

    DEFF Research Database (Denmark)

    Abild-Pedersen, Frank; Nørskov, Jens Kehlet; Rostrup-Nielsen, Jens;

    2006-01-01

    Mechanisms and energetics of graphene growth catalyzed by nickel nanoclusters were studied using ab initio density functional theory calculations. It is demonstrated that nickel step-edge sites act as the preferential growth centers for graphene layers on the nickel surface. Carbon is transported...

  9. Atmospheric pressure plasma surface modification of carbon fibres

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Løgstrup Andersen, Tom; Michelsen, Poul

    2008-01-01

    Carbon fibres are continuously treated with dielectric barrier discharge plasma at atmospheric pressure in various gas conditions for adhesion improvement in mind. An x-ray photoelectron spectroscopic analysis indicated that oxygen is effectively introduced onto the carbon fibre surfaces by He, He...... temperature for a month the O/C ratio at the plasma treated surfaces decreased to 0.151, which is close to that of the untreated ones. It can be attributed to the adsorption of hydrocarbon contamination at the plasma treated surfaces....

  10. Glass carbon surface modified by the fluorine ion irradiation

    Science.gov (United States)

    Teranishi, Yoshikazu; Ishizuka, Masanori; Kobayashi, Tomohiro; Nakamura, Isao; Uematu, Takahiko; Yasuda, Takeshi; Mitsuo, Atsushi; Morikawa, Kazuo

    2012-02-01

    Application of nano and micro fabrication techniques in industry requires solution to some crucial problems. One of the significant problems is the sticking interface between mold surface and imprinted polymer. In this study, we report a solution to the sticking interface problem by modification of nano imprinting mold using fluorine ion implantation. After the fluorine implantation, anti sticking layer appeared on the nano imprinting mold surface. After the implantation, a mold made from glass like carbon was patterned by focused ion beam lithography. The pattern was made up of word "TIRI". The line width was varied with 300 nm, 500 nm, and 1 μm. The line depth was about 200 ˜ 300 nm. The average depth of implanted fluorine was approximately 90 nm. After imprinting, the resin was removed from the mold by mechanical lift-off process. Transferred pattern was observed and confirmed by a scanning electron microscope (SEM) and an atomic force microscope (AFM). The pattern transferred from mold to resin was found to be successful.

  11. Glass carbon surface modified by the fluorine ion irradiation

    International Nuclear Information System (INIS)

    Application of nano and micro fabrication techniques in industry requires solution to some crucial problems. One of the significant problems is the sticking interface between mold surface and imprinted polymer. In this study, we report a solution to the sticking interface problem by modification of nano imprinting mold using fluorine ion implantation. After the fluorine implantation, anti sticking layer appeared on the nano imprinting mold surface. After the implantation, a mold made from glass like carbon was patterned by focused ion beam lithography. The pattern was made up of word “TIRI”. The line width was varied with 300 nm, 500 nm, and 1 μm. The line depth was about 200 ∼ 300 nm. The average depth of implanted fluorine was approximately 90 nm. After imprinting, the resin was removed from the mold by mechanical lift-off process. Transferred pattern was observed and confirmed by a scanning electron microscope (SEM) and an atomic force microscope (AFM). The pattern transferred from mold to resin was found to be successful.

  12. Glass carbon surface modified by the fluorine ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Teranishi, Yoshikazu, E-mail: teranishi.yoshikazu@iri-tokyo.jp [Tokyo Metropolitan Industrial Technology Research Institute (TIRI), Nishigaoka 3-13-10, Kitaku, Tokyo 115-8586 (Japan); Ishizuka, Masanori [Tokyo University, Inst. of Phys. and Chem. Res., RIKEN (Japan); Kobayashi, Tomohiro [Chuo University, Inst. of Phys. and Chem. Res., RIKEN (Japan); Nakamura, Isao; Uematu, Takahiko; Yasuda, Takeshi; Mitsuo, Atsushi; Morikawa, Kazuo [Tokyo Metropolitan Industrial Technology Research Institute (TIRI), Nishigaoka 3-13-10, Kitaku, Tokyo 115-8586 (Japan)

    2012-02-01

    Application of nano and micro fabrication techniques in industry requires solution to some crucial problems. One of the significant problems is the sticking interface between mold surface and imprinted polymer. In this study, we report a solution to the sticking interface problem by modification of nano imprinting mold using fluorine ion implantation. After the fluorine implantation, anti sticking layer appeared on the nano imprinting mold surface. After the implantation, a mold made from glass like carbon was patterned by focused ion beam lithography. The pattern was made up of word 'TIRI'. The line width was varied with 300 nm, 500 nm, and 1 {mu}m. The line depth was about 200 {approx} 300 nm. The average depth of implanted fluorine was approximately 90 nm. After imprinting, the resin was removed from the mold by mechanical lift-off process. Transferred pattern was observed and confirmed by a scanning electron microscope (SEM) and an atomic force microscope (AFM). The pattern transferred from mold to resin was found to be successful.

  13. Anodization of carbon fibers on interfacial mechanical properties of epoxy matrix composites.

    Science.gov (United States)

    Park, Soo-Jin; Chang, Yong-Hwan; Kim, Yeong-Cheol; Rhee, Kyong-Yop

    2010-01-01

    The influence of anodic oxidation on the mechanical interfacial properties of carbon-fiber-reinforced epoxy resin composites was investigated. The surface properties of the anodized carbon fibers were studied through the measurement of contact angles and through SEM, XPS, and FT-IR analyses. The mechanical interfacial properties of the composites were studied through measurements of interlaminar shear strength (ILSS), critical stress intensity factor (K(IC)), and critical strain energy release rate (G(IC)). It was shown that the surface functional groups containing oxygen on the anodized carbon fibers exert great effects on the surface energetics of fibers and the mechanical interfacial properties, e.g., ILSS, of the resulting composites. Contact angle measurements based on the wicking rate of a test liquid showed that anodic oxidation lead to an increase in the surface free energy of the carbon fibers, mainly in its specific (or polar) component. In terms of surface energetics, it was found that wetting played an important role in increasing the degree of adhesion at interfaces between the fibers and the resin matrices of the composites. PMID:20352820

  14. Influence of surface chemistry on inkjet printed carbon nanotube films

    International Nuclear Information System (INIS)

    Carbon nanotube ink chemistry and the proper formulation are crucial for direct-write printing of nanotubes. Moreover, the correct surface chemistry of the self-assembled monolayers that assist the direct deposition of carbon nanotubes onto the substrate is equally important to preserve orientation of the printed carbon nanotubes. We report that the successful formulation of two single walled carbon nanotube (SWNT) inks yields a consistent, homogenous printing pattern possessing the requisite viscosities needed for flow through the microcapillary nozzles of the inkjet printer with fairly modest drying times. The addition of an aqueous sodium silicate allows for a reliable method for forming a uniform carbon nanotube network deposited directly onto unfunctionalized surfaces such as glass or quartz via inkjet deposition. Furthermore, this sodium silicate ingredient helps preserve applied orientation to the printed SWNT solution. Sheet resistivity of this carbon nanotube ink formula printed on quartz decreases as a function of passes and is independent of the substrate. SWNTs were successfully patterned on Au. This amine-based surface chemistry dramatically helps improve the isolation stabilization of the printed SWNTs as seen in the atomic force microscopy (AFM) image. Lastly, using our optimized SWNT ink formula and waveform parameters in the Fuji materials printer, we are able to directly write/print SWNTs into 2D patterns. Dried ink pattern expose and help orient roped carbon nanotubes that are suspended in ordered arrays across the cracks.

  15. CARBON SEQUESTRATION ON SURFACE MINE LANDS

    Energy Technology Data Exchange (ETDEWEB)

    Donald H. Graves; Christopher Barton; Richard Sweigard; Richard Warner

    2005-06-22

    An area planted in 2004 on Bent Mountain in Pike County was shifted to the Department of Energy project to centralize an area to become a demonstration site. An additional 98.3 acres were planted on Peabody lands in western Kentucky and Bent Mountain to bring the total area under study by this project to 556.5 acres as indicated in Table 2. Major efforts this quarter include the implementation of new plots that will examine the influence of differing geologic material on tree growth and survival, water quality and quantity and carbon sequestration. Normal monitoring and maintenance was conducted and additional instrumentation was installed to monitor the new areas planted.

  16. Surface plasma functionalization influences macrophage behavior on carbon nanowalls

    Energy Technology Data Exchange (ETDEWEB)

    Ion, Raluca [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Vizireanu, Sorin [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, PO Box MG-36, 077125, Magurele, Bucharest (Romania); Stancu, Claudia Elena [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, PO Box MG-36, 077125, Magurele, Bucharest (Romania); Leibniz Institute for Plasma Science and Technology (INP Greifswald), Felix-Hausdorff-Str. 2, 17489 Greifswald (Germany); Luculescu, Catalin [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, PO Box MG-36, 077125, Magurele, Bucharest (Romania); Cimpean, Anisoara, E-mail: anisoara.cimpean@bio.unibuc.ro [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Dinescu, Gheorghe [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, PO Box MG-36, 077125, Magurele, Bucharest (Romania)

    2015-03-01

    The surfaces of carbon nanowall samples as scaffolds for tissue engineering applications were treated with oxygen or nitrogen plasma to improve their wettability and to functionalize their surfaces with different functional groups. X-ray photoelectron spectroscopy and water contact angle results illustrated the effective conversion of the carbon nanowall surfaces from hydrophobic to hydrophilic and the incorporation of various amounts of carbon, oxygen and nitrogen functional groups during the treatments. The early inflammatory responses elicited by un-treated and modified carbon nanowall surfaces were investigated by quantifying tumor necrosis factor-alpha and macrophage inflammatory protein-1 alpha released by attached RAW 264.7 macrophage cells. Scanning electron microscopy and fluorescence studies were employed to investigate the changes in macrophage morphology and adhesive properties, while MTT assay was used to quantify cell proliferation. All samples sustained macrophage adhesion and growth. In addition, nitrogen plasma treatment was more beneficial for cell adhesion in comparison with un-modified carbon nanowall surfaces. Instead, oxygen plasma functionalization led to increased macrophage adhesion and spreading suggesting a more activated phenotype, confirmed by elevated cytokine release. Thus, our findings showed that the chemical surface alterations which occur as a result of plasma treatment, independent of surface wettability, affect macrophage response in vitro. - Highlights: • N{sub 2} and O{sub 2} plasma treatments alter the CNW surface chemistry and wettability. • Cells seeded on CNW scaffolds are viable and metabolically active. • Surface functional groups, independent of surface wettability, affect cell response. • O{sub 2} plasma treatment of CNW leads to a more activated macrophage phenotype.

  17. Surface plasma functionalization influences macrophage behavior on carbon nanowalls

    International Nuclear Information System (INIS)

    The surfaces of carbon nanowall samples as scaffolds for tissue engineering applications were treated with oxygen or nitrogen plasma to improve their wettability and to functionalize their surfaces with different functional groups. X-ray photoelectron spectroscopy and water contact angle results illustrated the effective conversion of the carbon nanowall surfaces from hydrophobic to hydrophilic and the incorporation of various amounts of carbon, oxygen and nitrogen functional groups during the treatments. The early inflammatory responses elicited by un-treated and modified carbon nanowall surfaces were investigated by quantifying tumor necrosis factor-alpha and macrophage inflammatory protein-1 alpha released by attached RAW 264.7 macrophage cells. Scanning electron microscopy and fluorescence studies were employed to investigate the changes in macrophage morphology and adhesive properties, while MTT assay was used to quantify cell proliferation. All samples sustained macrophage adhesion and growth. In addition, nitrogen plasma treatment was more beneficial for cell adhesion in comparison with un-modified carbon nanowall surfaces. Instead, oxygen plasma functionalization led to increased macrophage adhesion and spreading suggesting a more activated phenotype, confirmed by elevated cytokine release. Thus, our findings showed that the chemical surface alterations which occur as a result of plasma treatment, independent of surface wettability, affect macrophage response in vitro. - Highlights: • N2 and O2 plasma treatments alter the CNW surface chemistry and wettability. • Cells seeded on CNW scaffolds are viable and metabolically active. • Surface functional groups, independent of surface wettability, affect cell response. • O2 plasma treatment of CNW leads to a more activated macrophage phenotype

  18. Concrete surface treatments quantification by means of mechanical profilometry

    OpenAIRE

    Courard, Luc; Garbacz, Andrzej; Gorka, M.

    2004-01-01

    Existing concrete surfaces need to be roughened to a profile necessary to achieve mechanical interlock with repair material. Surface mechanical morphometry is based on the measurement of surface profile - profilometry - which can be extended to 3D representation with surfometry by means of a stylus registering the profile. Profilometry and surfometry analysis were realized on concrete after different surface treatments (grinding, sandblasting, shotblasting, hand- and mechanical milling). ...

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

    Science.gov (United States)

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

    2015-06-01

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

  20. Mechanical properties of carbon nanostructures investigated by Monte Carlo simulations

    International Nuclear Information System (INIS)

    Full text: Carbon nanostructures are a fascinating class of materials combining high stiffness with low weight and exceptional toughness that makes carbon a promising candidate for applications in structural mechanics. Understanding the mechanical behavior of carbon structures also on atomistic length scales is inevitable in describing the mechanical performance and stability of large, hierarchical structures like carbon onions and fibers. In the presented work ab initio calculations were used to extract classical potentials describing stretching, bending and torsion deformations of carbon bonds that were used in subsequent Monte Carlo simulations to perform computational mechanical tests on graphene, carbon nanotubes and fullerenes. These tests included the application of hydrostatic pressure, the application of a ring load and the deformation of a fullerene between two plates. We analyzed the elastic response, as well as the stability limits and post buckling behavior of the structures for different sizes. The simulation results were compared to the predictions of nite element methods to evaluate macroscopic parameters like elastic modulus or Poisson ratio of the investigated structures. In fullerenes special attention was paid to the influence of pentagons that are inherently present in these structures. It was observed that the pentagons deform less than the atomic bonds in hexagonal geometry. (author)

  1. Surface selective membranes for carbon dioxide separation

    Energy Technology Data Exchange (ETDEWEB)

    Luebke, D.R.; Pennline, H.W.; Myers, C.R.

    2005-09-01

    In this study, hybrid membranes have been developed for the selective separation of CO2 from mixtures containing H2. Beginning with commercially available Pall alumina membrane tubes with nominal pore diameter of 5 nm, hybrids were produced by silation with a variety of functionalities designed to facilitate the selective adsorption of CO2 onto the pore surface. The goal is to produce a membrane which can harness the power of surface diffusion to give the selectivity of polymer membranes with the permeance of inorganic membranes.

  2. Carbon dioxide production during mechanical ventilation

    DEFF Research Database (Denmark)

    Henneberg, S; Söderberg, D; Groth, T;

    1987-01-01

    studied CO2 production (VCO2) and oxygen consumption (VO2) in mechanically ventilated ICU patients, where CO2 stores were altered by: a) changing minute ventilation by 15%, b) reducing body temperature, and c) changing the level of sedation. Expired gases went through a mixing chamber and were analyzed...

  3. Effects of Thickness and Amount of Carbon Nanofiber Coated Carbon Fiber on Improving the Mechanical Properties of Nanocomposites

    Directory of Open Access Journals (Sweden)

    Ferial Ghaemi

    2016-01-01

    Full Text Available In the current study, carbon nanofibers (CNFs were grown on a carbon fiber (CF surface by using the chemical vapor deposition method (CVD and the influences of some parameters of the CVD method on improving the mechanical properties of a polypropylene (PP composite were investigated. To obtain an optimum surface area, thickness, and yield of the CNFs, the parameters of the chemical vapor deposition (CVD method, such as catalyst concentration, reaction temperature, reaction time, and hydrocarbon flow rate, were optimized. It was observed that the optimal surface area, thickness, and yield of the CNFs caused more adhesion of the fibers with the PP matrix, which enhanced the composite properties. Besides this, the effectiveness of reinforcement of fillers was fitted with a mathematical model obtaining good agreement between the experimental result and the theoretical prediction. By applying scanning electronic microscope (SEM, transmission electron microscope (TEM, and Raman spectroscopy, the surface morphology and structural information of the resultant CF-CNF were analyzed. Additionally, SEM images and a mechanical test of the composite with a proper layer of CNFs on the CF revealed not only a compactness effect but also the thickness and surface area roles of the CNF layers in improving the mechanical properties of the composites.

  4. Removal of carbon contaminations by RF plasma generated reactive species and subsequent effects on optical surface

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, P. K., E-mail: praveenyadav@rrcat.gov.in; Rai, S. K.; Modi, M. H.; Nayak, M.; Lodha, G. S. [Indus Synchrotron Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Kumar, M.; Chakera, J. A.; Naik, P. A. [Laser Plasma Laboratory, Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India)

    2015-06-24

    Carbon contamination on optical elements is a serious issue in synchrotron beam lines for several decades. The basic mechanism of carbon deposition on optics and cleaning strategies are not fully understood. Carbon growth mechanism and optimized cleaning procedures are worldwide under development stage. Optimized RF plasma cleaning is considered an active remedy for the same. In present study carbon contaminated optical test surfaces (carbon capped tungsten thin film) are exposed for 30 minutes to four different gases, rf plasma at constant power and constant dynamic pressure. Structural characterization (thickness, roughness and density) of virgin samples and plasma exposed samples was done by soft x-ray (λ=80 Å) reflectivity measurements at Indus-1 reflectivity beam line. Different gas plasma removes carbon with different rate (0.4 to 0.65 nm /min). A thin layer 2 to 9 nm of different roughness and density is observed at the top surface of tungsten film. Ar gas plasma is found more suitable for cleaning of tungsten surface.

  5. Removal of carbon contaminations by RF plasma generated reactive species and subsequent effects on optical surface

    International Nuclear Information System (INIS)

    Carbon contamination on optical elements is a serious issue in synchrotron beam lines for several decades. The basic mechanism of carbon deposition on optics and cleaning strategies are not fully understood. Carbon growth mechanism and optimized cleaning procedures are worldwide under development stage. Optimized RF plasma cleaning is considered an active remedy for the same. In present study carbon contaminated optical test surfaces (carbon capped tungsten thin film) are exposed for 30 minutes to four different gases, rf plasma at constant power and constant dynamic pressure. Structural characterization (thickness, roughness and density) of virgin samples and plasma exposed samples was done by soft x-ray (λ=80 Å) reflectivity measurements at Indus-1 reflectivity beam line. Different gas plasma removes carbon with different rate (0.4 to 0.65 nm /min). A thin layer 2 to 9 nm of different roughness and density is observed at the top surface of tungsten film. Ar gas plasma is found more suitable for cleaning of tungsten surface

  6. Removal of carbon contaminations by RF plasma generated reactive species and subsequent effects on optical surface

    Science.gov (United States)

    Yadav, P. K.; Kumar, M.; Rai, S. K.; Modi, M. H.; Chakera, J. A.; Nayak, M.; Naik, P. A.; Lodha, G. S.

    2015-06-01

    Carbon contamination on optical elements is a serious issue in synchrotron beam lines for several decades. The basic mechanism of carbon deposition on optics and cleaning strategies are not fully understood. Carbon growth mechanism and optimized cleaning procedures are worldwide under development stage. Optimized RF plasma cleaning is considered an active remedy for the same. In present study carbon contaminated optical test surfaces (carbon capped tungsten thin film) are exposed for 30 minutes to four different gases, rf plasma at constant power and constant dynamic pressure. Structural characterization (thickness, roughness and density) of virgin samples and plasma exposed samples was done by soft x-ray (λ=80 Å) reflectivity measurements at Indus-1 reflectivity beam line. Different gas plasma removes carbon with different rate (0.4 to 0.65 nm /min). A thin layer 2 to 9 nm of different roughness and density is observed at the top surface of tungsten film. Ar gas plasma is found more suitable for cleaning of tungsten surface.

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

    International Nuclear Information System (INIS)

    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

  8. Thermal and Mechanical Performance of a Carbon/Carbon Composite Spacecraft Radiator

    Science.gov (United States)

    Kuhn, Jonathan; Benner, Steve; Butler, Dan; Silk, Eric

    1999-01-01

    Carbon-carbon composite materials offer greater thermal efficiency, stiffness to weight ratio, tailorability, and dimensional stability than aluminum. These lightweight thermal materials could significantly reduce the overall costs associated with satellite thermal control and weight. However, the high cost and long lead-time for carbon-carbon manufacture have limited their widespread usage. Consequently, an informal partnership between government and industrial personnel called the Carbon-Carbon Spacecraft Radiator Partnership (CSRP) was created to foster carbon-carbon composite use for thermally and structurally demanding space radiator applications. The first CSRP flight opportunity is on the New Millennium Program (NMP) Earth Orbiter-1 (EO-1) spacecraft, scheduled for launch in late 1999. For EO-1, the CSRP designed and fabricated a Carbon-Carbon Radiator (CCR) with carbon-carbon facesheets and aluminum honeycomb core, which will also serve as a structural shear panel. While carbon-carbon is an ideal thermal candidate for spacecraft radiators, in practice there are technical challenges that may compromise performance. In this work, the thermal and mechanical performance of the EO-1 CCR is assessed by analysis and testing. Both then-nal and mechanical analyses were conducted to predict the radiator response to anticipated launch and on-orbit loads. The thermal model developed was based on thermal balance test conditions. The thermal analysis was performed using SINDA version 4.0. Structural finite element modeling and analysis were performed using SDRC/1-DEAS and UAI/NASTRAN, respectively. In addition, the CCR was subjected to flight qualification thermal/vacuum and vibration tests. The panel meets or exceeds the requirements for space flight and demonstrates promise for future satellite missions.

  9. Raman spectra of electrochemically hydrogenated diamond like carbon surface

    OpenAIRE

    Biswas, Hari Shankar; Datta, Jagannath; Sen, Pintu; Ghosh, Uday Chand; Ray, Nihar Ranjan

    2013-01-01

    Raman spectroscopy has been employed to distinguish between the Raman spectrum of pristine hydrogenated diamond like carbon (PHDLC) and that of electrochemically hydrogenated diamond like carbon (ECHDLC). The enhancement of the background photoluminescence (PL) in the Raman spectrum and broadening of PL spectrum of ECHDLC are identified to be due to increase of sp3 C-H density onto the PHDLC surface, during novel electrochemical process of hydrogenation of sp2 C=C into sp3 C-H.

  10. Quantum-chemical basis of adsorption mechanism of hydrogen and carbon oxide on cadmium telluride

    International Nuclear Information System (INIS)

    Results of quantum-chemical calculations of the cluster model of H2 and CO adsorption on CdTe surface enabled to support the basic conclusions concerning the nature of adsorption centers and adsorption mechanism, made on the basis of experimental investigation of the system: 1) hydrogen can be adsorbed in two forms - molecular and dissociative ones versus carbon monoxide which doesn't dissociate during adsorption: 2) predominant centers of molecular hydrogen adsorption are presented by surface VTe vacancies and F-centers; 3) formed hydrogen atoms can advantageously bind with surface coordination-ionsaturated Te atoms: 4) hydrogen adsorption result in the positive charging of the surface

  11. Combined Hydrophobicity and Mechanical Durability through Surface Nanoengineering

    Science.gov (United States)

    Elliott, Paul R.; Stagon, Stephen P.; Huang, Hanchen; Furrer, David U.; Burlatsky, Sergei F.; Filburn, Thomas P.

    2015-04-01

    This paper reports combined hydrophobicity and mechanical durability through the nanoscale engineering of surfaces in the form of nanorod-polymer composites. Specifically, the hydrophobicity derives from nanoscale features of mechanically hard ZnO nanorods and the mechanical durability derives from the composite structure of a hard ZnO nanorod core and soft polymer shell. Experimental characterization correlates the morphology of the nanoengineered surfaces with the combined hydrophobicity and mechanical durability, and reveals the responsible mechanisms. Such surfaces may find use in applications, such as boat hulls, that benefit from hydrophobicity and require mechanical durability.

  12. Method for in-situ cleaning of carbon contaminated surfaces

    Science.gov (United States)

    Klebanoff, Leonard E.; Grunow, Philip; Graham, Jr., Samuel

    2006-12-12

    Activated gaseous species generated adjacent a carbon contaminated surface affords in-situ cleaning. A device for removing carbon contamination from a surface of the substrate includes (a) a housing defining a vacuum chamber in which the substrate is located; (b) a source of gaseous species; and (c) a source of electrons that are emitted to activate the gaseous species into activated gaseous species. The source of electrons preferably includes (i) a filament made of a material that generates thermionic electron emissions; (ii) a source of energy that is connected to the filament; and (iii) an electrode to which the emitted electrons are attracted. The device is particularly suited for photolithography systems with optic surfaces, e.g., mirrors, that are otherwise inaccessible unless the system is dismantled. A method of removing carbon contaminants from a substrate surface that is housed within a vacuum chamber is also disclosed. The method employs activated gaseous species that react with the carbon contaminants to form carbon containing gaseous byproducts.

  13. Effect of nanoporous carbon surface chemistry on the removal of endocrine disruptors from water phase.

    Science.gov (United States)

    Vidal, Carla B; Seredych, Mykola; Rodríguez-Castellón, Enrique; Nascimento, Ronaldo F; Bandosz, Teresa J

    2015-07-01

    Wood-based activated carbon and its sulfur-doped counterpart were used as adsorbents of endocrine disruptor chemicals (EDC) from aqueous solution. Adsorption process was carried out in dynamic conditions and Thomas model was used to predict the performance of the column. The results showed a good fitting of the theoretical curve to the experimental data. S-doped carbon exhibited a higher adsorption capacity of trimethoprim (TMP) and smaller of sulfamethoxazole (SMX) and diclofenac (DCF) in comparison with the carbon with no sulfur incorporated into the matrix. The surface features of the initial carbons and those exposed to EDC were evaluated in order to derive the adsorption mechanism and elucidate the role of surface features. An increase in the amount of TMP from a low concentration solution (10 mg/L) on sulfur-doped carbon was linked to acid-base interactions and the reactive adsorption/oxidation of TMP. A decrease in SMX and DCF after sulfur doping was explained by a considerable increase in surface hydrophobicity, which does not favor the retention of polar DCF and SMX molecules. When the adsorption was measured from a high concentration solution at equilibrium conditions at the dark or under solar light irradiation different trends in the adsorption capacities were found. This was linked to the photoactivity of carbons and the degradation of EDC in the pore system promoted by visible light followed by the adsorption of the products of surface reactions. PMID:25527089

  14. Compositional, mechanical and transport properties of carbonate fault rocks and the seismic cycle in limestone terrains : A case study of surface exposures on the Longmenshan Fault, Sichuan, China (Utrecht Studies in Earth Sciences 076)

    NARCIS (Netherlands)

    Chen, Jianye

    2015-01-01

    Destructive earthquakes are common in tectonically active regions dominated by carbonate cover rocks. The catastrophic Wenchuan earthquake that struck Sichuan, China, also affected a section of carbonate cover terrain. Numerous studies have focused on characterizing the compositional, transport and

  15. Fatigue failure mechanisms of single-walled carbon nanotube ropes embedded in epoxy

    International Nuclear Information System (INIS)

    In this work, fatigue failure mechanisms of single-walled carbon nanotube (SWCNT) bundles embedded in epoxy matrix under repeated tensile load were studied. Observed damage and failure modes include: (1) splitting of SWCNT bundles, (2) kink formation and subsequent failure in SWCNTs, and (3) fracture of SWCNT bundles. Patterns of crack propagation under tension in SWCNTs were studied by molecular mechanics simulations, where defect-free SWCNTs and SWCNTs with two different modes of Stone-Wales defects were studied. It is demonstrated by the results of molecular mechanics simulation that the observed fracture surfaces of SWCNT can be reproduced reasonably well, suggesting possible fatigue failure mechanisms of SWCNT in the composite

  16. Fatigue failure mechanisms of single-walled carbon nanotube ropes embedded in epoxy

    Science.gov (United States)

    Ren, Y.; Fu, Y. Q.; Liao, K.; Li, F.; Cheng, H. M.

    2004-04-01

    In this work, fatigue failure mechanisms of single-walled carbon nanotube (SWCNT) bundles embedded in epoxy matrix under repeated tensile load were studied. Observed damage and failure modes include: (1) splitting of SWCNT bundles, (2) kink formation and subsequent failure in SWCNTs, and (3) fracture of SWCNT bundles. Patterns of crack propagation under tension in SWCNTs were studied by molecular mechanics simulations, where defect-free SWCNTs and SWCNTs with two different modes of Stone-Wales defects were studied. It is demonstrated by the results of molecular mechanics simulation that the observed fracture surfaces of SWCNT can be reproduced reasonably well, suggesting possible fatigue failure mechanisms of SWCNT in the composite.

  17. Growth processes and surface properties of diamondlike carbon films

    International Nuclear Information System (INIS)

    In this study, we compare the deposition processes and surface properties of tetrahedral amorphous carbon (ta-C) films from filtered pulsed cathodic arc discharge (PCAD) and hydrogenated amorphous carbon (a-C:H) films from electron cyclotron resonance (ECR)-plasma source ion implantation. The ion energy distributions (IEDs) of filtered-PCAD at various filter inductances and Ar gas pressures were measured using an ion energy analyzer. The IEDs of the carbon species in the absence of background gas and at low gas pressures are well fitted by shifted Maxwellian distributions. Film hardness and surface properties show a clear dependence on the IEDs. ta-C films with surface roughness at an atomic level and thin (0.3-0.9 nm) graphitelike layers at the film surfaces were deposited at various filter inductances in the highly ionized plasmas with the full width at half maximum ion energy distributions of 9-16 eV. The a-C:H films deposited at higher H/C ratios of reactive gases were covered with hydrogen and sp3 bonded carbon-enriched layers due to the simultaneous interaction of hydrocarbon species and atomic hydrogen. The effects of deposited species and ion energies on film surface properties were analyzed. Some carbon species have insufficient energies to break the delocalized π(nC) bonds at the graphitelike film surface, and they can govern film formation via surface diffusion and coalescence of nuclei. Dangling bonds created by atomic hydrogen lead to uniform chemisorption of hydrocarbon species from the ECR plasmas. The deposition processes of ta-C and a-C:H films are discussed on the basis of the experimental results

  18. Mechanism of Carbon Nanotubes Aligning along Applied Electric Field

    Institute of Scientific and Technical Information of China (English)

    MA Shao-Jie; GUO Wan-Lin

    2008-01-01

    The mechanism of single-walled carbon nanotubes (SWCNTS)aligning in the direction of external electric field is studied by quantum mechanics calculations.The rotational torque on the carbon nanotubes is proportional to the difference between the longitudinal and transverse polarizabilities and varies with the angle of SWCNTs to the external electric field.The longitudinal polarizability increases with second power of length,while the transverse polarizability increases linearly with length.A zigzag SWCNT has larger longitudinal and transverse polarizabilities than an armchair SWCNT with the same diameter and the discrepancy becomes larger for longer tubes.

  19. Microstructure and surface properties of lignocellulosic-based activated carbons

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Garcia, P., E-mail: pegonzal@quim.ucm.es [Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutense, E-28040, Madrid (Spain); Centeno, T.A. [Instituto Nacional del Carbon-CSIC, Apartado 73, E-33080 Oviedo (Spain); Urones-Garrote, E. [Centro Nacional de Microscopia Electronica, Universidad Complutense, E-28040, Madrid (Spain); Avila-Brande, D.; Otero-Diaz, L.C. [Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutense, E-28040, Madrid (Spain)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Activated carbons were produced by KOH activation at 700 Degree-Sign C. Black-Right-Pointing-Pointer The observed nanostructure consists of highly disordered graphene-like layers with sp{sup 2} bond content Almost-Equal-To 95%. Black-Right-Pointing-Pointer Textural parameters show high surface area ( Almost-Equal-To 1000 m{sup 2}/g) and pore width of 1.3-1.8 nm. Black-Right-Pointing-Pointer Specific capacitance reaches values as high as 161 F/g. - Abstract: Low cost activated carbons have been produced via chemical activation, by using KOH at 700 Degree-Sign C, from the bamboo species Guadua Angustifolia and Bambusa Vulgaris Striata and the residues from shells of the fruits of Castanea Sativa and Juglans Regia as carbon precursors. The scanning electron microscopy micrographs show the conservation of the precursor shape in the case of the Guadua Angustifolia and Bambusa Vulgaris Striata activated carbons. Transmission electron microscopy analyses reveal that these materials consist of carbon platelet-like particles with variable length and thickness, formed by highly disordered graphene-like layers with sp{sup 2} content Almost-Equal-To 95% and average mass density of 1.65 g/cm{sup 3} (25% below standard graphite). Textural parameters indicate a high porosity development with surface areas ranging from 850 to 1100 m{sup 2}/g and average pore width centered in the supermicropores range (1.3-1.8 nm). The electrochemical performance of the activated carbons shows specific capacitance values at low current density (1 mA/cm{sup 2}) as high as 161 F/g in the Juglans Regia activated carbon, as a result of its textural parameters and the presence of pseudocapacitance derived from surface oxygenated acidic groups (mainly quinones and ethers) identified in this activated carbon.

  20. Surface characterization of silver and palladium modified glassy carbon

    Indian Academy of Sciences (India)

    Aleksandra A Perić-Grujić; Olivera M Nešković; Miomir V Veljković; Zoran V Laušević; Mila D Laušević

    2007-12-01

    In this work, the influence of silver and palladium on the surface of undoped, boron doped and phosphorus doped glassy carbon has been studied. The silver and palladium concentrations in solution, after metal deposition, were measured by atomic absorption spectrophotometer. The morphology of metal coatings was characterized by scanning electron microscopy. In order to investigate the nature and thermal stability of surface oxygen groups, temperature-programmed desorption method combined with mass spectrometric analyses, was performed. The results obtained have shown that silver and palladium spontaneously deposit from their salt solutions at the surface of glassy carbon samples. Silver deposits have dendrite structure, whilst palladium forms separate clusters. The highest amount of both silver and palladium deposits at the surface of sample containing the highest quantity of surface oxide complexes. It has been concluded that carboxyl groups and structure defects are responsible for metal reduction. Calculated desorption energies have shown that the surface modification by metal deposition leads to the formation of more stable surface of undoped and doped glassy carbon samples.

  1. Carbon induced magnetism of SnO2 surfaces

    International Nuclear Information System (INIS)

    The magnetism induced by Carbon (C) in SnO2 surfaces are investigated by first principle calculations. The results show that C substitution at the outmost surface oxygen sites can induce magnetism in (110), (001) and (101) surfaces of SnO2. (110) surface is the most stable surface and the magnetism in which is stronger than that in other two surfaces, indicating that it is (110), but not other surfaces provides the main contribution to the surface magnetism of C-doped SnO2 (SnO2:C). The magnetic moments predominantly come from C-2p orbitals, which arise from the crystal field transformation induced by the loss of coordinated atoms and the destroy of the local symmetry, and is enhanced by the local lattice distortion due to the Jahn–Teller effect. In all three surface slabs, the magnetism decays when C dopants are deeper from the outmost surfaces and disappears eventually. This work provides more rational understanding to the observed magnetism in SnO2:C materials than ever. - Highlights: • We investigate surface magnetism in (110), (001) and (101) surfaces of SnO2:C. • (110) surface provides the main contribution to the surface magnetism of SnO2:C. • Magnetism predominantly come from C-2p orbitals and crystal field transformation

  2. Vibrational modes of ultrathin carbon nanomembrane mechanical resonators

    International Nuclear Information System (INIS)

    We report measurements of vibrational mode shapes of mechanical resonators made from ultrathin carbon nanomembranes (CNMs) with a thickness of approximately 1 nm. CNMs are prepared from electron irradiation induced cross-linking of aromatic self-assembled monolayers and the variation of membrane thickness and/or density can be achieved by varying the precursor molecule. Single- and triple-layer freestanding CNMs were made by transferring them onto Si substrates with square/rectangular orifices. The vibration of the membrane was actuated by applying a sinusoidal voltage to a piezoelectric disk on which the sample was glued. The vibrational mode shapes were visualized with an imaging Mirau interferometer using a stroboscopic light source. Several mode shapes of a square membrane can be readily identified and their dynamic behavior can be well described by linear response theory of a membrane with negligible bending rigidity. By applying Fourier transformations to the time-dependent surface profiles, the dispersion relation of the transverse membrane waves can be obtained and its linear behavior verifies the membrane model. By comparing the dispersion relation to an analytical model, the static stress of the membranes was determined and found to be caused by the fabrication process

  3. Grafting process of ethyltrimethoxysilane and polyphosphoric acid on calcium carbonate surface

    International Nuclear Information System (INIS)

    Graphical abstract: XPS survey spectra of (a) CaCO3 untreated, treated with (b) ethyltrimethoxysilane or (c) polyphosphoric acid. (b) Zoom on the silane area. Highlights: ► Calcium carbonate has been treated with ethyltrimethoxysilane and polyphosphoric acid. ► Treated calcium carbonate has been analyzed by X-ray photoelectron spectroscopy. ► Silanol groups are adsorbed onto calcium carbonate through hydrogen interactions. ► Phosphoric acid is adsorbed on calcium carbonate through a P-O-C bonds formation. - Abstract: In order to facilitate its incorporation into a polymer matrix (mostly hydrophobic), calcium carbonate (CaCO3), which is strongly hydrophilic, has to be chemically treated to avoid the formation of aggregates and to improve the compatibility with the polymer. The objective of this study is to analyze, by using contact angle measurements and X-ray photoelectron spectroscopy (XPS), the CaCO3 surface after a chemical surface treatment with ethyltrimethoxysilane (ETMO) and polyphosphoric acid (PPA) in an organic solvent, in order to verify if these molecules are able to interact with the CaCO3 surface, and to propose some hypothesis about the surface grafting mechanism. After several solvent washings were performed to remove all species in excess, contact angle results have pointed out the presence of an organic layer after the chemical treatment of CaCO3 with ETMO and PPA. Based on XPS results, we propose a grafting mechanism of silane and phosphoric acid molecules. Ethyltrimethoxysilane induce an hydrolysis process of the CaCO3 surface which leads to a condensation phenomenon. This Si-OH network is adsorbed through hydrogen interactions with some hydroxyl groups. In the case of phosphoric acid, the molecules are adsorbed on carbon atoms through P-O-C bonds formation. This original grafting points out the major role of the solvent nature with CaCO3 surface reactivity.

  4. Mechanical properties and biocompatibility of functionalized carbon nanotubes/polypropylene composites.

    Science.gov (United States)

    Ma, Jing; Nan, Xi; Larsen, Raino Mikael; Huang, Xiaobo; Yu, Bowen

    2016-07-01

    This study investigates the efficiency of carbon nanotubes (CNTs) as reinforcement for polypropylene (PP) for biocompatible application as a function of different surface functionalization of CNTs. PP composites were reinforced using various CNTs: single- and multi-walled carbon nanotubes (SWCNTs, MWCNTs), SWCNTs were covalently functionalized by plasma, for comparison, the MWCNTs were functionalized noncovalently. Different CNTs were incorporated into PP by solution blending. The type of CNTs and surface functionalization affects the mechanical and biocompatibility results significantly. Differences in nanostructure and the chemical compositions, number of functional groups, and structural defects for the CNTs may be the key factors affecting the mechanical properties and biocompatibility of PP nanocomposites compared to the neat PP. Finally, suitable CNTs and surface functionalization of CNTs were selected for making the PP/CNTs composites. PMID:27052820

  5. Mechanical and wet tribological properties of carbon fabric/phenolic composites with different weave filaments counts

    Science.gov (United States)

    Wenbin, Li; Jianfeng, Huang; Jie, Fei; Liyun, Cao; Chunyan, Yao

    2015-10-01

    Carbon fabric/phenolic composites with different weave filaments counts were prepared by dip-coating and hot-press techniques, and then their mechanical and wet tribological properties were investigated based on the analysis of the three-dimensional surface profiles and the pore structures. Results show that the mechanical properties (elastic modulus, flexural modulus, tensile modulus, flexural strength and tensile strength) of the 3K carbon fabric/phenolic composites (Composite A) are better than that of the 12K carbon fabric/phenolic composites (Composite B). Fractured surfaces observation suggests that the dominant tensile failure mechanism is fiber breakage for Composite A and matrix fracture for Composite B. Compared with Composite B, Composite A possesses high friction coefficient in different loads and at different sliding speeds, and the friction coefficient of Composite A is more sensitive to load and sliding speed. The wear rate of Composite B is 39% greater than that of Composite A and the wear features of worn surfaces demonstrate the excellent wear resistance for Composite A. Based on the observation of worn surface, the wear mechanisms are presented.

  6. Thermodynamic analysis of carbon migration in W1-1.0C steel in plasma surface chromizing

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    W1-1.0C steel was chromized at 1173 K with double glow plasma surface alloying process, and the distribution of Fe, Cr,and C contents in the chromized layer was measured using glow discharge spectrum analysis (GDA).The behavior and mechanism of carbon migration during the formation of chromized layer were studied through thermodynamic analysis and calculation.The gradient of carbon chemical potential was regarded as the driving force of carbon migration.An equation was derived to describe the carbon content varying with the chromium content within the carbon-rich region.The calculated results from the equation approximated closely to the experimental ones.

  7. Mechanical Reinforcement of Diopside Bone Scaffolds with Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Cijun Shuai

    2014-10-01

    Full Text Available Carbon nanotubes are ideal candidates for the mechanical reinforcement of ceramic due to their excellent mechanical properties, high aspect ratio and nanometer scale diameter. In this study, the effects of multi-walled carbon nanotubes (MWCNTs on the mechanical properties of diopside (Di scaffolds fabricated by selective laser sintering were investigated. Results showed that compressive strength and fracture toughness improved significantly with increasing MWCNTs from 0.5 to 2 wt %, and then declined with increasing MWCNTs to 5 wt %. Compressive strength and fracture toughness were enhanced by 106% and 21%, respectively. The reinforcing mechanisms were identified as crack deflection, MWCNTs crack bridging and pull-out. Further, the scaffolds exhibited good apatite-formation ability and supported adhesion and proliferation of cells in vitro.

  8. Mechanically generated surface chirality at the nanoscale.

    Science.gov (United States)

    Ferjani, Sameh; Choi, Yoonseuk; Pendery, Joel; Petschek, Rolfe G; Rosenblatt, Charles

    2010-06-25

    A substrate coated with an achiral polyimide alignment layer was scribed bidirectionally with the stylus of an atomic force microscope to create an easy axis for liquid crystal orientation. The resulting noncentrosymmetric topography resulted in a chiral surface that manifests itself at the molecular level. To show this unambiguously, a planar-aligned negative dielectric aniostropy achiral nematic liquid crystal was placed in contact with the surface and subjected to an electric field E. The nematic director was found to undergo an azimuthal rotation approximately linear in E. This so-called "surface electroclinic effect" is a signature of surface chirality and was not observed when the polyimide was treated for a centrosymmetric topography, and therefore was nonchiral. PMID:20867414

  9. Effects of Surface Oxygen on the Performance of Carbon as an Anode in Lithium-Ion Batteries

    Science.gov (United States)

    Hung, Ching-Cheh; Clark, Gregory W.

    2001-01-01

    Carbon materials with similar bulk structure but different surface oxygen were compared for their performance as anodes in lithium-ion battery. The bulk structure was such that the graphene planes were perpendicular to the surface. Three types of surfaces were examined: surface containing C=O type oxygen. surface containing -O-C type oxygen, and surface containing high concentration of active sites. The test involved cycles of lithium insertion into and release from the carbon materials, which was in the half cells of carbon/saturated LiI-50/50 (vol %) EC and DMC/lithium. During the first cycle of lithium insertion, the presence of adsorbed oxygen, -O-C type oxygen, active carbon sites, and C=O type oxygen resulted in the formation of solid-electrolyte interface (SEI) when the carbon's voltage relative to lithium metal was >1.35, 1 to 1.35, 0.5 to 1, and 0.67 to 0.7 V, respectively. An optimum -O-C type oxygen and a minimum C=O type oxygen was found to increase the reversible and decrease the irreversible capacity of carbon. Active sites on the carbon surface result in a large irreversible capacity and a second lithium insertion-release mechanism. However, this new mechanism has a short cycle life.

  10. Actuation mechanisms of carbon nanotube-based architectures

    OpenAIRE

    Geier, Sebastian; Mahrholz, Thorsten; Wierach, Peter; Sinapius, Michael

    2016-01-01

    State of the art smart materials such as piezo ceramics or electroactive polymers cannot feature both, mechanical stiffness and high active strain. Moreover, properties like low density, high mechanical stiffness and high strain at the same time driven by low energy play an increasingly important role for their future application. Carbon nanotubes (CNT), show this behavior. Their active behavior was observed 1999 the first time using paper-like mats made of CNT. Therefore the CNT-...

  11. Optical and mechanical characterization of zirconia-carbon nanocomposite films

    International Nuclear Information System (INIS)

    The focus of the present work is the study of carbon co-deposition effect on the optical and mechanical properties of zirconia films. Optical and dielectric constant, band gap and transition lifetime of such composite systems were determined, as well as their elasticity properties. The thin ZrO2-x-C films were sputter-deposited on silicon and polycarbonate, from a pure ZrO2 and graphite targets in a radio-frequency argon plasma. Besides the zirconia phase and crystalline parameter changes induced by carbon addition, the electronic properties to the films were significantly modified: a drastical optical gap lowering was observed along an increased electronic dielectric constant and refractive index. The invariance of the film elasticity modulus and the similarity of the optical transition lifetime values with those of pure amorphous carbon films indicate an immiscibility of the ceramic and carbon components of the film structure

  12. Optical and mechanical characterization of zirconia-carbon nanocomposite films

    Energy Technology Data Exchange (ETDEWEB)

    Laidani, N. [ITC-IRST, Divisione Fisica-Chimica delle Superfici ed Interfacce, Via Sommarive 18, 38050 Povo (Trento) (Italy)], E-mail: laidani@itc.it; Micheli, V.; Bartali, R.; Gottardi, G.; Anderle, M. [ITC-IRST, Divisione Fisica-Chimica delle Superfici ed Interfacce, Via Sommarive 18, 38050 Povo (Trento) (Italy)

    2008-02-15

    The focus of the present work is the study of carbon co-deposition effect on the optical and mechanical properties of zirconia films. Optical and dielectric constant, band gap and transition lifetime of such composite systems were determined, as well as their elasticity properties. The thin ZrO{sub 2-x}-C films were sputter-deposited on silicon and polycarbonate, from a pure ZrO{sub 2} and graphite targets in a radio-frequency argon plasma. Besides the zirconia phase and crystalline parameter changes induced by carbon addition, the electronic properties to the films were significantly modified: a drastical optical gap lowering was observed along an increased electronic dielectric constant and refractive index. The invariance of the film elasticity modulus and the similarity of the optical transition lifetime values with those of pure amorphous carbon films indicate an immiscibility of the ceramic and carbon components of the film structure.

  13. The performance of a surface-applied corrosion inhibitor for the carbon steel in saturated Ca(OH)2 solutions

    International Nuclear Information System (INIS)

    In the present work, the performance of an amino alcohol based surface applied inhibitor was studied by the electrochemical techniques in saturated Ca(OH)2 solutions. The surface morphology of the carbon steel was observed by scanning electron microscope, and the energy diffraction spectrum was also tested. Results showed that the inhibitor used in this work demonstrated obvious inhibition efficiency on the carbon steel in saturated Ca(OH)2 solutions. The inhibition mechanism of the inhibitor lies in the quick adsorption of the active component on carbon steel surface

  14. An AES and LEED study of carbon and oxygen sorption on copper surfaces

    OpenAIRE

    Oda, O.; Hanekamp, L.J.; Bootsma, G.A.

    1981-01-01

    The sorption of carbon and oxygen on cooper surfaces has been studied by AES and LEED. The carbon coverage has been estimated by measuring the substrate Auger peak attenuation upon changing the carbon coverage and by studying the coadsorption of oxygen and carbon on the surface. The effect of carbon on the background of derivative spectra is also reported.

  15. Fracture mechanical evaluation of allowable surface flaw for core support graphite components in the HTTR

    International Nuclear Information System (INIS)

    Graphite and carbon materials are used for core support components in the High Temperature Engineering Test Reactor(HTTR) due to their excellent heat-resistant properties. In the machining or handling process of the component fabrication surface flaws and so forth are possibly formed since these materials are brittle. In order to determine the pass/fail criteria in a visual inspection, it is necessary to quantitatively determine the allowable flaw size on the surface of the core support components. Accordingly, allowable flaw sizes for these graphite and carbon materials are quantitatively evaluated on the basis of the fracture mechanics approach in this report. (author)

  16. The mechanism of the surface alloy layer creation for cast steel

    Directory of Open Access Journals (Sweden)

    A. Walasek

    2012-01-01

    Full Text Available The paper presents a detailed description of the process of creation of a surface alloy layer (using high-carbon ferrochromium on the cast steel casting. The mechanism of the surface alloy layer is based on the known theories [5,6]. The proposed course of formation of the layers has been extended to decarburization stage of steel. The research included proving the presence of carbon-lean zone. The experiment included the analysis of the distribution of elements and microhardness measurement.

  17. Adsorption of ciprofloxacin on surface-modified carbon materials.

    Science.gov (United States)

    Carabineiro, S A C; Thavorn-Amornsri, T; Pereira, M F R; Figueiredo, J L

    2011-10-01

    The adsorption capacity of ciprofloxacin (CPX) was determined on three types of carbon-based materials: activated carbon (commercial sample), carbon nanotubes (commercial multi-walled carbon nanotubes) and carbon xerogel (prepared by the resorcinol/formaldehyde approach at pH 6.0). These materials were used as received/prepared and functionalised through oxidation with nitric acid. The oxidised materials were then heat treated under inert atmosphere (N2) at different temperatures (between 350 and 900°C). The obtained samples were characterised by adsorption of N2 at -196 °C, determination of the point of zero charge and by temperature programmed desorption. High adsorption capacities ranging from approximately 60 to 300 mgCPxgC(-1) were obtained (for oxidised carbon xerogel, and oxidised thermally treated activated carbon Norit ROX 8.0, respectively). In general, it was found that the nitric acid treatment of samples has a detrimental effect in adsorption capacity, whereas thermal treatments, especially at 900 °C after oxidation, enhance adsorption performance. This is due to the positive effect of the surface basicity. The kinetic curves obtained were fitted using 1st or 2nd order models, and the Langmuir and Freundlich models were used to describe the equilibrium isotherms obtained. The 2nd order and the Langmuir models, respectively, were shown to present the best fittings. PMID:21733541

  18. Estimation of mechanical properties of single wall carbon nanotubes using molecular mechanics approach

    Indian Academy of Sciences (India)

    P Subba Rao; Sunil Anandatheertha; G Narayana Naik; G Gopalakrishnan

    2015-06-01

    Molecular mechanics based finite element analysis is adopted in the current work to evaluate the mechanical properties of Zigzag, Armchair and Chiral Single wall Carbon Nanotubes (SWCNT) of different diameters and chiralities. Three different types of atomic bonds, that is Carbon–Carbon covalent bond and two types of Carbon–Carbon van der Waals bonds are considered in the carbon nanotube system. The stiffness values of these bonds are calculated using the molecular potentials, namely Morse potential function and Lennard-Jones interaction potential function respectively and these stiffness’s are assigned to spring elements in the finite element model of the CNT. The geometry of CNT is built using a macro that is developed for the finite element analysis software. The finite element model of the CNT is constructed, appropriate boundary conditions are applied and the behavior of mechanical properties of CNT is studied.

  19. Mechanical properties of carbon nanotube/polymer composites

    Science.gov (United States)

    Arash, B.; Wang, Q.; Varadan, V. K.

    2014-10-01

    The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region.

  20. Formation Mechanism of the First Carbon-Carbon Bond and the First Olefin in the Methanol Conversion into Hydrocarbons.

    Science.gov (United States)

    Liu, Yue; Müller, Sebastian; Berger, Daniel; Jelic, Jelena; Reuter, Karsten; Tonigold, Markus; Sanchez-Sanchez, Maricruz; Lercher, Johannes A

    2016-05-01

    The elementary reactions leading to the formation of the first carbon-carbon bond during early stages of the zeolite-catalyzed methanol conversion into hydrocarbons were identified by combining kinetics, spectroscopy, and DFT calculations. The first intermediates containing a C-C bond are acetic acid and methyl acetate, which are formed through carbonylation of methanol or dimethyl ether even in presence of water. A series of acid-catalyzed reactions including acetylation, decarboxylation, aldol condensation, and cracking convert those intermediates into a mixture of surface bounded hydrocarbons, the hydrocarbon pool, as well as into the first olefin leaving the catalyst. This carbonylation based mechanism has an energy barrier of 80 kJ mol(-1) for the formation of the first C-C bond, in line with a broad range of experiments, and significantly lower than the barriers associated with earlier proposed mechanisms. PMID:27037603

  1. Release of Crude Oil from Silica and Calcium Carbonate Surfaces

    DEFF Research Database (Denmark)

    Liu, Xiaoyan; Yan, Wei; Stenby, Erling Halfdan;

    2016-01-01

    on the bare surfaces, surfaces with an adsorbed oil layer, and surfaces after being exposed to aqueous salt solutions. This showed that the silica surface became more hydrophobic after oil adsorption, while the wettability of the calcium carbonate surface was not significantly changed by adsorption of an oil...... oil was investigated by exposing the surfaces with an adsorbed oil layer to a series of NaCl and CaCl2 solutions of decreasing salt concentrations. Here, it was found that the oil release from silica was achieved only by injections of low-salinity solutions, and it is suggested that this observation...... or reduction in ion bridging in the presence of high-salinity NaCl, while the low-salinity effect again was attributed to an expansion of the electrical double layer....

  2. Role of the surface chemistry of activated carbons in dye removal from aqueous solution

    Science.gov (United States)

    Zhou, Hua-lei; Zhen, Wen-juan; Zhu, Qian; Wu, Xiao-bin; Chang, Zhi-dong; Li, Wen-jun

    2015-07-01

    Commercial activated carbons were modified by a series of chemical or physical treatments using H2O2, NH3, and heating under N2 flow without notably changing their pore structures. The resultant carbons were characterized by N2 adsorption and Bohem titration and then used to remove Ponceau 4R, methyl orange and brilliant blue from aqueous solutions. Surface chemistry was found to play a significantly different role in removing these three compounds. The removal of anionic Ponceau 4R increases with increasing carbon surface basicity due to the predominant dispersive interaction mechanism. In contrast, surface chemistry has little effect on the removal of anionic methyl orange, which can be explained by two parallel mechanisms involving electrostatic and dispersive interactions due to the basic amine group in a dye molecule. The influence of surface chemistry on the removal of amphoteric brilliant blue dye can also be ignored due to a weak interaction between the carbons and dye molecules, which is resulted from strong cohesive energy from electrostatic forces inside amphoteric dye molecules.

  3. Crystal structure searching by free energy surface trekking: application to carbon at 1 TPa

    International Nuclear Information System (INIS)

    We have developed an ab-initio crystal structure searching method, free energy surface trekking (FEST). This method consists of an ascent-run and a descent-run. First, the system is forced to climb up a free energy surface following by the inversion of the restoring forces acting on the simulation cell (ascent-run). Then, the system climbs down the surface toward neighboring local minima according to the release from the constraint of the inversion immediately after the system crosses the ridges of the surface (descent-run). We have applied the FEST simulations to carbon at terapascal pressures and obtained a BC8-like structure with a tetragonal I41 in addition to the earlier-predicted BC8, R8, and simple cubic structures. This structure is mechanically stable in the pressure range of at least 0.5-3.5 TPa, and has a potential to survive as a metastable structure in carbon at terapascal pressures.

  4. Crystal structure searching by free energy surface trekking: application to carbon at 1 TPa

    Science.gov (United States)

    Ishikawa, T.; Suzuki, N.; Shimizu, K.

    2014-05-01

    We have developed an ab-initio crystal structure searching method, free energy surface trekking (FEST). This method consists of an ascent-run and a descent-run. First, the system is forced to climb up a free energy surface following by the inversion of the restoring forces acting on the simulation cell (ascent-run). Then, the system climbs down the surface toward neighboring local minima according to the release from the constraint of the inversion immediately after the system crosses the ridges of the surface (descent-run). We have applied the FEST simulations to carbon at terapascal pressures and obtained a BC8-like structure with a tetragonal I41 in addition to the earlier-predicted BC8, R8, and simple cubic structures. This structure is mechanically stable in the pressure range of at least 0.5-3.5 TPa, and has a potential to survive as a metastable structure in carbon at terapascal pressures.

  5. Phenol removal onto novel activated carbons made from lignocellulosic precursors: influence of surface properties.

    Science.gov (United States)

    Nabais, J M Valente; Gomes, J A; Suhas; Carrott, P J M; Laginhas, C; Roman, S

    2009-08-15

    The adsorption of phenol from dilute aqueous solutions onto new activated carbons (AC) was studied. The novel activated carbon was produced from lignocellulosic (LC) precursors of rapeseed and kenaf. Samples oxidised with nitric acid in liquid phase were also studied. The results have shown the significant potential of rapeseed and kenaf for the activated carbon production. The activated carbons produced by carbon dioxide activation were mainly microporous with BET apparent surface area up to 1350 m(2)g(-1) and pore volume 0.5 cm(3)g(-1). The effects of concentration (0.1-2 mM) and pH (3-13) were studied. The phenol adsorption isotherms at 25 degrees C followed the Freundlich model with maximum adsorption capacities of approximately 80 and 50 mg g(-1) for the pristine and oxidised activated carbons, respectively. The influence of pH on the adsorption has two trends for pH below and above 10. It was possible to conclude that when phenol is predominantly in the molecular form the most probable mechanism is based on the pi-pi dispersion interaction between the phenol aromatic ring and the delocalised pi electrons present in the activated carbon aromatic structure. When phenolate is the major component the electrostatic repulsion that occurs at high pH values is the most important aspect of the adsorption mechanism. PMID:19233559

  6. Effect of anodic surface treatment on PAN-based carbon fiber and its relationship to the fracture toughness of the carbon fiber-reinforced polymer composites

    DEFF Research Database (Denmark)

    Sarraf, Hamid; Skarpova, Ludmila

    2008-01-01

    The effect of anodic surface treatment on the polyacrylonitrile (PAN)-based carbon fibers surface properties and the mechanical behavior of the resulting carbon fiber-polymer composites has been studied in terms of the contact angle measurements of fibers and the fracture toughness of composites...... that the K-IC of the composite continually increases with increased current densities of the treatments up to 0.5 A m(-2), and a maximum strength value is found about 294 MPa cm(1/2) at the anodic treatment of 0.5 A m(-2). It can be concluded that the anodic surface treatment is largely influenced in...... the fiber surface nature and the mechanical interfacial properties between the carbon fiber and epoxy resin matrix of the resulting composites, i.e., the fracture toughness. We suggest that good wetting plays an important role in improving the degree of adhesion at interfaces between fibers and...

  7. Carbon deposition on nickel ferrites and nickel-magnetite surfaces

    International Nuclear Information System (INIS)

    Carbon deposition on Commercial Advanced Gas-Cooled Reactor (CAGR) fuel cladding and heat exchanger surfaces lowers heat transfer efficiency and increases fuel pin temperatures. Several types of deposit have been identified including both thin dense layers and also low density columnar deposits with filamentary or convoluted laminar structure. The low-density types are often associated with particles containing iron, nickel or manganese. To identify the role of nickel in the deposition process surfaces composed of nickel-iron spinels or metallic nickel/magnetite mixtures have been exposed to γ radiation in a gas environment simulating that in the reactor. Examination of these surfaces by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) have shown that while metallic nickel (Ni(O)) catalyses the formation of filamentary low density carbon deposits, the presence of divalent nickel (Ni(II)) sites in spinel type oxides is associated only with dense deposits. (author)

  8. Femtosecond laser-induced surface structures on carbon fibers.

    Science.gov (United States)

    Sajzew, Roman; Schröder, Jan; Kunz, Clemens; Engel, Sebastian; Müller, Frank A; Gräf, Stephan

    2015-12-15

    The influence of different polarization states during the generation of periodic nanostructures on the surface of carbon fibers was investigated using a femtosecond laser with a pulse duration τ=300  fs, a wavelength λ=1025  nm, and a peak fluence F=4  J/cm². It was shown that linear polarization results in a well-aligned periodic pattern with different orders of magnitude concerning their period and an alignment parallel and perpendicular to fiber direction, respectively. For circular polarization, both types of uniform laser-induced periodic surface structures (LIPSS) patterns appear simultaneously with different dominance in dependence on the position at the fiber surface. Their orientation was explained by the polarization-dependent absorptivity and the geometrical anisotropy of the carbon fibers. PMID:26670499

  9. Surface Functionalization of Multiwalled Carbon Nanotube with Trifluorophenyl

    Directory of Open Access Journals (Sweden)

    Li-Pei Zhang

    2006-09-01

    Full Text Available A new approach to dispersion of multiwalled carbon nanotube (MWNT in common polar solvents was reported. Here, a detailed study of nanotube chemistry by using trifluorophenyl (TFP to modify the surface of MWNT was discussed, which was not reported before. A characterization of the reaction products using a variety of techniques was provided. The results confirmed that the surface of MWNT was successfully functionalized. Furthermore, trifluorophenyl multiwalled carbon nanotube (TFP-MWNT was well dispersed in polar solvents, such as tetrahydrofuran (THF, acetic acid (Ac, N,N-dimethyl formamide (DMF, dimethyl sulfoxide (DMSO, due to the adsorption of trifluorophenyl groups on the surface of raw MWNT. Following chemical modification, dispersed individual nanotube suggests the potentials for wide applications.

  10. High Surface Area of Nano Pores Activated Carbon Derived From Agriculture Waste

    International Nuclear Information System (INIS)

    In this study, the high surface area of nano pores activated carbon rice husk originated from local biomass was investigated. The comparison in terms of surface area, porosity and behavior in electrochemical analysis with commercial activated carbon was studied in details. The nano pores activated carbon rice husk was synthesis using consecutive of carbonization and activation under purified nitrogen and carbon dioxide purge. Interestingly, the surface area and capacity of the nano pores activated carbon rice indicated higher in comparison to commercial activated carbon. This indicated that the nano pores activated carbon has potential to be developed further as an alternative material in reducing suspension on commercial activated carbon. (author)

  11. Shrinkage Cracking: A mechanism for self-sustaining carbon mineralization reactions in olivine rocks

    Science.gov (United States)

    Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xing, T.; Xiao, X.; De Andrade, V. J. D.; Karato, S. I.

    2015-12-01

    The hydration and carbonation of olivine results in an up to ~44% increase in solid molar volume, which may choke off of fluid supply and passivate reactive surfaces, thus preventing further carbonation reactions. The carbonation of olivine has ben studied extensively in the laboratory. To date, observations from these experimental studies indicate that carbonation reaction rates generally decrease with time and the extent of carbonation is limited in olivine rocks. Field studies, however, show that 100% hydration and carbonation occur naturally in ultramafic rocks. The disagreement between the laboratory results under controlled conditions and the field observations underlines the lack of understanding of the mechanisms responsible for the self-sustaining carbonation interaction in nature. We developed a state-of-the-art pressurized hydrothermal cell that is transparent to X-rays to characterize the real-time evolution of pore geometry during fluid-rock interaction using in-situ synchrotron-based X-ray microtomography. Through a time series of high-resolution 3-dimensional images, we document the microstructural evolution of a porous olivine aggregate reacting with a sodium bicarbonate solution at elevated pressure and temperature conditions. We observed porosity increases, near constant rate of crystal growth, and pervasive reaction-induced fractures. Based on the nanometer scale tomography data, we propose that shrinkage cracking is the mechanism responsible for producing new reactive surface and keep the carbonation reaction self-sustaining in our experiment. Shrinkage cracks are commonly observed in drying mud ponds, cooling lava flows and ice wedge fields. Stretching of a contracting surface bonded to a substrate of nearly constant dimensions leads to a stress buildup in the surface layer. When the stress exceeds the tensile strength, polygonal cracks develop in the surface layer. In our experiments, the stretching mismatch between the surface and interior of

  12. A Pareto Optimal Auction Mechanism for Carbon Emission Rights

    Directory of Open Access Journals (Sweden)

    Mingxi Wang

    2014-01-01

    Full Text Available The carbon emission rights do not fit well into the framework of existing multi-item auction mechanisms because of their own unique features. This paper proposes a new auction mechanism which converges to a unique Pareto optimal equilibrium in a finite number of periods. In the proposed auction mechanism, the assignment outcome is Pareto efficient and the carbon emission rights’ resources are efficiently used. For commercial application and theoretical completeness, both discrete and continuous markets—represented by discrete and continuous bid prices, respectively—are examined, and the results show the existence of a Pareto optimal equilibrium under the constraint of individual rationality. With no ties, the Pareto optimal equilibrium can be further proven to be unique.

  13. Carbonate Hydroxyapatite and Silicon-Substituted Carbonate Hydroxyapatite: Synthesis, Mechanical Properties, and Solubility Evaluations

    OpenAIRE

    2014-01-01

    The present study investigates the chemical composition, solubility, and physical and mechanical properties of carbonate hydroxyapatite (CO3Ap) and silicon-substituted carbonate hydroxyapatite (Si-CO3Ap) which have been prepared by a simple precipitation method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF) spectroscopy, and inductively coupled plasma (ICP) techniques were used to characterize the formation of CO3Ap and Si-CO3Ap. The results...

  14. Adsorption of naphthenic acids on high surface area activated carbons.

    Science.gov (United States)

    Iranmanesh, Sobhan; Harding, Thomas; Abedi, Jalal; Seyedeyn-Azad, Fakhry; Layzell, David B

    2014-01-01

    In oil sands mining extraction, water is an essential component; however, the processed water becomes contaminated through contact with the bitumen at high temperature, and a portion of it cannot be recycled and ends up in tailing ponds. The removal of naphthenic acids (NAs) from tailing pond water is crucial, as they are corrosive and toxic and provide a substrate for microbial activity that can give rise to methane, which is a potent greenhouse gas. In this study, the conversion of sawdust into an activated carbon (AC) that could be used to remove NAs from tailings water was studied. After producing biochar from sawdust by a slow-pyrolysis process, the biochar was physically activated using carbon dioxide (CO2) over a range of temperatures or prior to producing biochar, and the sawdust was chemically activated using phosphoric acid (H3PO4). The physically activated carbon had a lower surface area per gram than the chemically activated carbon. The physically produced ACs had a lower surface area per gram than chemically produced AC. In the adsorption tests with NAs, up to 35 mg of NAs was removed from the water per gram of AC. The chemically treated ACs showed better uptake, which can be attributed to its higher surface area and increased mesopore size when compared with the physically treated AC. Both the chemically produced and physically produced AC provided better uptake than the commercially AC. PMID:24766592

  15. Surface Analysis of sp2 Carbon in Ag and Al Covetic Alloys*

    Science.gov (United States)

    Jaim, H. M. Iftekhar; Cole, Daniel P.; Salamanca-Riba, Lourdes G.

    Ag, Al-6061 and Al-7075 were doped with carbon by an electrocharging assisted process where high electric current is applied to the molten metal containing particles of activated carbon. This process gives rise to epitaxial growth of graphene nanoribbons (GNR) and carbon nanostructures within the metal matrix. Alloys produced with such technique are named Covetics. Al-6061 and Al-7075 covetics have shown superior mechanical, electrical and anti-corrosion properties. The nanostructured carbon incorporation has been confirmed by XPS, Raman, and TEM studies. Here, we present detailed surface characterization of the carbon nanostructures in these new alloys. Raman and EELS mapping of carbon nanostructure were carried out to identify the nature of bonding, strain and defect characteristics. Mostly, crystalline GNR or graphene sheets were found to create networks with sp2 character, under compressive strain with high concentration of defects. AFM and KPFM showed contrast in phases and potentials for ribbon like features. Incorporation of sp2 carbon in metals is an initial step for the integration of carbon nanostructures for future applications requiring high strength and conductivity.

  16. Parametric strong mode-coupling in carbon nanotube mechanical resonators

    Science.gov (United States)

    Li, Shu-Xiao; Zhu, Dong; Wang, Xin-He; Wang, Jiang-Tao; Deng, Guang-Wei; Li, Hai-Ou; Cao, Gang; Xiao, Ming; Guo, Guang-Can; Jiang, Kai-Li; Dai, Xing-Can; Guo, Guo-Ping

    2016-08-01

    Carbon nanotubes (CNTs) have attracted much attention for use in nanomechanical devices because of their exceptional properties, such as large resonant frequencies, low mass, and high quality factors. Here, we report the first experimental realization of parametric strong coupling between two mechanical modes on a single CNT nanomechanical resonator, by applying an extra microwave pump. This parametric pump method can be used to couple mechanical modes with arbitrary frequency differences. The properties of the mechanical resonator are detected by single-electron tunneling at low temperature, which is found to be strongly coupled to both modes. The coupling strength between the two modes can be tuned by the pump power, setting the coupling regime from weak to strong. This tunability may be useful in further phonon manipulations in carbon nanotubes.Carbon nanotubes (CNTs) have attracted much attention for use in nanomechanical devices because of their exceptional properties, such as large resonant frequencies, low mass, and high quality factors. Here, we report the first experimental realization of parametric strong coupling between two mechanical modes on a single CNT nanomechanical resonator, by applying an extra microwave pump. This parametric pump method can be used to couple mechanical modes with arbitrary frequency differences. The properties of the mechanical resonator are detected by single-electron tunneling at low temperature, which is found to be strongly coupled to both modes. The coupling strength between the two modes can be tuned by the pump power, setting the coupling regime from weak to strong. This tunability may be useful in further phonon manipulations in carbon nanotubes. Electronic supplementary information (ESI) available: Fit of the quality factor and similar results in more devices. See DOI: 10.1039/c6nr02853e

  17. Sea surface temperature variability: patterns and mechanisms.

    Science.gov (United States)

    Deser, Clara; Alexander, Michael A; Xie, Shang-Ping; Phillips, Adam S

    2010-01-01

    Patterns of sea surface temperature (SST) variability on interannual and longer timescales result from a combination of atmospheric and oceanic processes. These SST anomaly patterns may be due to intrinsic modes of atmospheric circulation variability that imprint themselves upon the SST field mainly via surface energy fluxes. Examples include SST fluctuations in the Southern Ocean associated with the Southern Annular Mode, a tripolar pattern of SST anomalies in the North Atlantic associated with the North Atlantic Oscillation, and a pan-Pacific mode known as the Pacific Decadal Oscillation (with additional contributions from oceanic processes). They may also result from coupled ocean-atmosphere interactions, such as the El Niño-Southern Oscillation phenomenon in the tropical Indo-Pacific, the tropical Atlantic Niño, and the cross-equatorial meridional modes in the tropical Pacific and Atlantic. Finally, patterns of SST variability may arise from intrinsic oceanic modes, notably the Atlantic Multidecadal Oscillation. PMID:21141660

  18. A REVIEW OF OXYGEN-CONTAINING SURFACE GROUPS AND SURFACE MODIFICATION OF ACTIVATED CARBON

    Institute of Scientific and Technical Information of China (English)

    WU Yongwen; LI Zhong; XI Hongxia; XIA Qibin

    2004-01-01

    This review focused on the recent reports related to the function, characterization and modification of oxygen-containing surface groups of activated carbon (AC). The Oxygen-containing surface groups were briefly described, and the most frequently used techniques for characterization of the oxygen-containing surface groups on ACs were also briefly stated. A detailed discussion of the effects of the oxygen-containing surface groups on the adsorptive capacity of AC was given. The recent progresses in modification of the oxygen-containing surface groups of AC were also reviewed.

  19. Nanocrystallization of aluminized surface of carbon steel for enhanced resistances to corrosion and corrosive wear

    International Nuclear Information System (INIS)

    Aluminizing is often used to improve steel's resistances to corrosion, oxidation and wear. This article reports our recent attempts to further improve aluminized carbon steel through surface nanocrystallization for higher resistances to corrosion and corrosive wear. The surface nanocrystallization was achieved using a process combining sandblasting and recovery heat treatment. The entire surface modification process includes dipping carbon steel specimens into a molten Al pool to form an Al coat, subsequent diffusion treatment at elevated temperature to form an aluminized layer, sandblasting to generate dislocation network or cells, and recovery treatment to turn the dislocation cells into nano-sized grains. The grain size of the nanocrystallized aluminized surface layer was in the range of 20-100 nm. Electrochemical properties, electron work function (EWF), and corrosive wear of the nanocrystalline alloyed surfaces were investigated. It was demonstrated that the nanocrystalline aluminized surface of carbon steel exhibited improved resistances to corrosion, wear and corrosive wear. The passive film developed on the nanocrystallized aluminized surface was also evaluated in terms of its mechanical properties and adherence to the substrate.

  20. Nanocrystallization of aluminized surface of carbon steel for enhanced resistances to corrosion and corrosive wear

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C. [Dept. of Materials Physical and Chemical, University of Science and Technology Beijing, Beijing 100083 (China); Dept. of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4 (Canada); Li, D.Y., E-mail: dongyang.li@ualberta.c [Dept. of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4 (Canada); Shang, C.J. [Dept. of Materials Physical and Chemical, University of Science and Technology Beijing, Beijing 100083 (China)

    2009-12-15

    Aluminizing is often used to improve steel's resistances to corrosion, oxidation and wear. This article reports our recent attempts to further improve aluminized carbon steel through surface nanocrystallization for higher resistances to corrosion and corrosive wear. The surface nanocrystallization was achieved using a process combining sandblasting and recovery heat treatment. The entire surface modification process includes dipping carbon steel specimens into a molten Al pool to form an Al coat, subsequent diffusion treatment at elevated temperature to form an aluminized layer, sandblasting to generate dislocation network or cells, and recovery treatment to turn the dislocation cells into nano-sized grains. The grain size of the nanocrystallized aluminized surface layer was in the range of 20-100 nm. Electrochemical properties, electron work function (EWF), and corrosive wear of the nanocrystalline alloyed surfaces were investigated. It was demonstrated that the nanocrystalline aluminized surface of carbon steel exhibited improved resistances to corrosion, wear and corrosive wear. The passive film developed on the nanocrystallized aluminized surface was also evaluated in terms of its mechanical properties and adherence to the substrate.

  1. Superhydrophobic surfaces : from fluid mechanics to optics

    OpenAIRE

    Rathgen, Helmut

    2008-01-01

    In this thesis optical diraction was used to study the static and dynamic properties of microscopic liquid-gas interfaces that span between adjacent ridges of a superhydrophobic surface. An observed interference phenomenon at grazing incident angle led to the development of optical gratings with a large spectral bandwidth, and an observed sensitive response of the liquid-gas interfaces to ultrasound led to the development of a superhydrophobic ber optical micro cavity that enables interferome...

  2. Surface and Mechanical studies of Bismaleimide coatings

    OpenAIRE

    Bhattacharyya, A. S.; Paul, D.; Dutta, P. P.; Bhattacharjee, G.

    2015-01-01

    Bismaleimide (BMI) resins are a new breed of thermosetting resins used mainly for high temperature applications and have major usage in aerospace. BMI polymer coatings were deposited on aluminum and mild steel substrates. The effect of corrosion on mild steel and aluminum by Ringers Solution and there protection using BMI coatings were observed. X-ray diffraction studies showed crystalline nature of the BMI coatings. Surface contact angle measurements were carried out using goniometer.

  3. Effect of fiber surface on flexural strength in carbon fabric reinforced epoxy composites

    International Nuclear Information System (INIS)

    The effect of carbon fiber surface characteristics on flexural properties of structural composites is studied in this work. Two types of intermediate modulus carbon fibers were used: T800HB and IM7. Results revealed that higher mechanical properties are linked with higher interfacial adhesion. Morphologies and chemical compositions of commercial carbon fibers (CF) were characterized by Fourier Transformed Infra Red (FTIR) and Scanning Electronic Microscopy (SEM). Comparing the results, the T800HB apparently has more roughness, since the IM7 seems to be recovered for a polymeric film. On other hand, the IM7 one shows higher interactivity with epoxy resin system Cycom 890 RTM. Composites produced with Resin Transfer Molding (RTM) were tested on a flexural trial. Interfacial adhesion difference was showed with SEM and Dynamic Mechanical Analyses (DMA), justifying the higher flexural behavior of composites made with IM7 fibers.

  4. A high efficient method for introducing reactive amines onto carbon fiber surfaces using hexachlorocyclophosphazene as a new coupling agent

    International Nuclear Information System (INIS)

    Highlights: • An innovative chemical method for surface modification of carbon fiber was proposed. • Hexachlorocyclophosphazene was used as a new multifunctional coupling agent. • The hydroxyl on the fiber surface were consumed and converted into C-O-P bonds. • A great amount of free amines were grafted onto the carbon fiber surfaces. • The interfacial shear strength (IFSS) of carbon fiber composites increased by 71.2%. - Abstract: To improve the interfacial properties of carbon fiber (CF) reinforced composites, an innovative and simple functionalized strategy has been proposed by grafting 4,4′-oxydianiline (ODA) onto carbon fiber surface using hexachlorocyclophosphazene (HCCP) as a novel coupling agent at mild reaction conditions. The chemical composition of the CF surface was confirmed by X-ray photoelectron spectra (XPS). The surface topography and surface energy of CF were examined by atomic force microscope (AFM) and dynamic contact angle tests (DCA), respectively. The interfacial shear strength (IFSS) of CF reinforced composites was studied by microbond test. The tensile strength of CF was measured by single filament tensile test. After functionalization treatment, the grafted amine groups on the fiber surface enhanced the surface wettability of modified CF and formed strong chemical bonding between fiber and matrix, improving the interfacial adhesion strength of composites. The interfacial shear strength of modified CF reinforced composites increased by 71.2% compared with that of desized CF. The interfacial enhancement mechanism was also discussed in detail. Moreover, the modified CF almost kept the original mechanical properties after functionalization

  5. The interaction of oxygen and carbon monoxide with a carbided Ni(111) surface

    OpenAIRE

    Geus, John W.; Vink, T.J.; Zandvoort, M.M.J. van; Gijzeman, O.L.J.

    1984-01-01

    The thermal decomposition of ethylene on Ni(111) at 250°C is shown to lead to carbon deposition on and - in a later stage - below the surface. Independent of the amount of carbon below the surface, CO is adsorbed with an isosteric heat of adsorption of 105 kJ/mol. The surface carbon reacts with oxygen at 250°C. The reaction rate is independent of the surface carbon coverage and first order in oxygen pressure. The subsurface carbon segregates to the surface after removal of the surface carbon ...

  6. Trends in nanoscale mechanics mechanics of carbon nanotubes, graphene, nanocomposites and molecular dynamics

    CERN Document Server

    2014-01-01

    This book contains a collection of the state-of-the-art reviews written by the leading researchers in the areas of nanoscale mechanics, molecular dynamics, nanoscale modeling of nanocomposites and mechanics of carbon nanotubes. No other book has reviews of the recent discoveries such as a nanoscale analog of the Pauli’s principle, i.e., effect of the spatial exclusion of electrons or the SEE effect, a new Registry Matrix Analysis for the nanoscale interfacial sliding and new data on the effective viscosity of interfacial electrons in nanoscale stiction at the interfaces. This volume is also an exceptional resource on the well tested nanoscale modeling of carbon nanotubes and nanocomposites, new nanoscale effects, unique evaluations of the effective thickness of carbon nanotubes under different loads, new data on which size of carbon nanotubes is safer and many other topics. Extensive bibliography concerning all these topics is included along with the lucid short reviews. Numerous illustrations are provided...

  7. Anodic Oxidation on Structural Evolution and Tensile Properties of Polyacrylonitrile Based Carbon Fibers with Different Surface Morphology

    Institute of Scientific and Technical Information of China (English)

    Zhaorui Li; Jianbin Wang; Yuanjian Tong; Lianghua Xu

    2012-01-01

    Polyacrylonitrile (PAN) based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface structures, surface morphology and residual mechanical properties were characterized. The crystallite size (La) of carbon fibers would be interrupted due to excessive electrochemical etching, while the crystallite spacing (d(002)) increased as increasing current density. The disordered structures on the surface of carbon fiber with rough surface increased at the initial oxidation stage and then removed by further electrochemical etching, which resulting in continuous increase of the extent of graphitization on the fiber surface. However, the electrochemical etching was beneficial to getting ordered morphology on the surface for carbon fiber with smooth surface, especially when the current density was lower than 1.77 A/m 2 . The tensile strength and tensile modulus could be improved by 17.27% and 5.75%, respectively, and was dependent of surface morphology. The decreasing density of carbon fibers probably resulted from the volume expansion of carbon fibers caused by the abundant oxygen functional groups intercalated between the adjacent graphite layers.

  8. Adsorption Mechanism and Collapse Propensities of the Full-Length, Monomeric Aβ1-42 on the Surface of a Single-Walled Carbon Nanotube: A Molecular Dynamics Simulation Study

    OpenAIRE

    Jana, Asis K.; Sengupta, Neelanjana

    2012-01-01

    Though nanomaterials such as carbon nanotubes have gained recent attention in biology and medicine, there are few studies at the single-molecule level that explore their interactions with disease-causing proteins. Using atomistic molecular-dynamics simulations, we have investigated the interactions of the monomeric Aβ1-42 peptide with a single-walled carbon nanotube of small diameter. Starting with peptide-nanotube complexes that delineate the interactions of different segments of the peptide...

  9. Dispersion and reinforcing mechanism of carbon nanotubes in epoxy nanocomposites

    Indian Academy of Sciences (India)

    Smrutisikha Bal

    2010-02-01

    Carbon nanotube based epoxy composites have been fabricated at room temperature and refrigeration process using sonication principle. Flexural moduli, electrical conductivity, glass transition temperature of epoxy resin as well as nanocomposite samples have been determined. Distribution behaviour of carbon nanotubes in the epoxy matrix was examined through scanning electron microscopy. Composite samples showed better properties than resin samples due to strengthening effect of the filled nanotubes. Refrigerated nanocomposites obtained increasing mechanical property because of better dispersion due to low temperature settlement of polymers. Improvement of electrical conductivity was due to the fact that aggregated phases form a conductive three-dimensional network throughout the whole sample. The increasing glass transition temperature was indicative of restricting movement of polymer chains that ascribe strong interaction presented between carbon nanotubes and epoxy chains that was again supplemented by Raman study and SEM.

  10. Enhancement of Mechanical and Thermal Properties of Polycaprolactone/Chitosan Blend by Calcium Carbonate Nanoparticles

    OpenAIRE

    Asma Fatehi; Susan Azizi; Mohamad Zaki Ab. Rahman; Wan Md Zin Wan Yunus; Samira Siyamak; Nor Azowa Ibrahim; Sanaz Abdolmohammadi

    2012-01-01

    This study investigates the effects of calcium carbonate (CaCO3) nanoparticles on the mechanical and thermal properties and surface morphology of polycaprolactone (PCL)/chitosan nanocomposites. The nanocomposites of PCL/chitosan/CaCO3 were prepared using a melt blending technique. Transmission electron microscopy (TEM) results indicate the average size of nanoparticles to be approximately 62 nm. Tensile measurement results show an increase in the tensile modulus with CaCO3 nanoparticle loadin...

  11. Synergetic Effects of Mechanical Properties on Graphene Nanoplatelet and Multiwalled Carbon Nanotube Hybrids Reinforced Epoxy/Carbon Fiber Composites

    OpenAIRE

    2015-01-01

    Graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) are novel nanofillers possessing attractive characteristics, including robust compatibility with most polymers, high absolute strength, and cost effectiveness. In this study, an outstanding synergetic effect on the grapheme nanoplatelets (GNPs) and multiwalled carbon nanotubes (CNTs) hybrids were used to reinforce epoxy composite and epoxy/carbon fiber composite laminates to enhance their mechanical properties. The mechanical propertie...

  12. Scaling up the Fabrication of Mechanically-Robust Carbon Nanofiber Foams

    Directory of Open Access Journals (Sweden)

    William Curtin

    2016-02-01

    Full Text Available This work aimed to identify and address the main challenges associated with fabricating large samples of carbon foams composed of interwoven networks of carbon nanofibers. Solutions to two difficulties related with the process of fabricating carbon foams, maximum foam size and catalyst cost, were developed. First, a simple physical method was invented to scale-up the constrained formation of fibrous nanostructures process (CoFFiN to fabricate relatively large foams. Specifically, a gas deflector system capable of maintaining conditions supportive of carbon nanofiber foam growth throughout a relatively large mold was developed. ANSYS CFX models were used to simulate the gas flow paths with and without deflectors; the data generated proved to be a very useful tool for the deflector design. Second, a simple method for selectively leaching the Pd catalyst material trapped in the foam during growth was successfully tested. Multiple techniques, including scanning electron microscopy, surface area measurements, and mechanical testing, were employed to characterize the foams generated in this study. All results confirmed that the larger foam samples preserve the basic characteristics: their interwoven nanofiber microstructure forms a low-density tridimensional solid with viscoelastic behavior. Fiber growth mechanisms are also discussed. Larger samples of mechanically-robust carbon nanofiber foams will enable the use of these materials as strain sensors, shock absorbers, selective absorbents for environmental remediation and electrodes for energy storage devices, among other applications.

  13. Nanocomposite Scaffold for Chondrocyte Growth and Cartilage Tissue Engineering: Effects of Carbon Nanotube Surface Functionalization

    OpenAIRE

    Chahine, Nadeen O.; Collette, Nicole M.; Thomas, Cynthia B.; Genetos, Damian C.; Loots, Gabriela G

    2014-01-01

    The goal of this study was to assess the long-term biocompatibility of single-wall carbon nanotubes (SWNTs) for tissue engineering of articular cartilage. We hypothesized that SWNT nanocomposite scaffolds in cartilage tissue engineering can provide an improved molecular-sized substrate for stimulation of chondrocyte growth, as well as structural reinforcement of the scaffold's mechanical properties. The effect of SWNT surface functionalization (-COOH or -PEG) on chondrocyte viability and bioc...

  14. Surface modification and characterization of carbon black; UV cured colored epoxy composites

    OpenAIRE

    Atif, Muhammad

    2014-01-01

    Carbon Black is inexpensive widely used industrial filler, but its dispersability in solvents/polymeric media has always been a critical point. As a result either surfactants or higher mechanical forces have been utilized to disperse it well in the media. First part of research was aimed at surface modification of CB to increase its dispersability in different solvents and epoxy that directly effects filler-medium interactions. Type and magnitude of this interaction differs with structure and...

  15. Effects of Surface-modification of Carbon Black on the Characteristics of Polymerized Toner

    International Nuclear Information System (INIS)

    Carbon black was surface-modified to prepare styrene-based suspension polymerized toner with excellent carbon black dispersibility inside toner particles. Carbon black was oxidized first to introduce hydroxyl groups on the surfaces, then esterification between the hydroxyl groups and carboxyl groups of organic acids (oleic acid, palmitic acid, acrylic acid) was followed to obtain organically surface-modified carbon black. The surface-modification of carbon black was confirmed by FTIR. Apparent carbon black dispersibility in the monomer mixture of the binder resin was tested and the particle size of dispersed carbon black was measured by particle size analyzer. Optical micrographs showed that carbon black dispersibility inside toner particles was improved considerably when the carbon black surface-modified with oleic acid was used. The polymerized toner prepared with the carbon black surface-modified with oleic acid showed ideal particle size and size distribution as a toner

  16. Effects of Surface-modification of Carbon Black on the Characteristics of Polymerized Toner

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Eun Ho; Kim, Dae Su [Chungbuk National University, Cheongju (Korea, Republic of)

    2013-10-15

    Carbon black was surface-modified to prepare styrene-based suspension polymerized toner with excellent carbon black dispersibility inside toner particles. Carbon black was oxidized first to introduce hydroxyl groups on the surfaces, then esterification between the hydroxyl groups and carboxyl groups of organic acids (oleic acid, palmitic acid, acrylic acid) was followed to obtain organically surface-modified carbon black. The surface-modification of carbon black was confirmed by FTIR. Apparent carbon black dispersibility in the monomer mixture of the binder resin was tested and the particle size of dispersed carbon black was measured by particle size analyzer. Optical micrographs showed that carbon black dispersibility inside toner particles was improved considerably when the carbon black surface-modified with oleic acid was used. The polymerized toner prepared with the carbon black surface-modified with oleic acid showed ideal particle size and size distribution as a toner.

  17. Improved Composites Using Crosslinked, Surface-Modified Carbon Nanotube Materials

    Science.gov (United States)

    Baker, James Stewart

    2014-01-01

    Individual carbon nanotubes (CNTs) exhibit exceptional tensile strength and stiffness; however, these properties have not translated well to the macroscopic scale. Premature failure of bulk CNT materials under tensile loading occurs due to the relatively weak frictional forces between adjacent CNTs, leading to poor load transfer through the material. When used in polymer matrix composites (PMCs), the weak nanotube-matrix interaction leads to the CNTs providing less than optimal reinforcement.Our group is examining the use of covalent crosslinking and surface modification as a means to improve the tensile properties of PMCs containing carbon nanotubes. Sheet material comprised of unaligned multi-walled carbon nanotubes (MWCNT) was used as a drop-in replacement for carbon fiber in the composites. A variety of post-processing methods have been examined for covalently crosslinking the CNTs to overcome the weak inter-nanotube shear interactions, resulting in improved tensile strength and modulus for the bulk sheet material. Residual functional groups from the crosslinking chemistry may have the added benefit of improving the nanotube-matrix interaction. Composites prepared using these crosslinked, surface-modified nanotube sheet materials exhibit superior tensile properties to composites using the as received CNT sheet material.

  18. Adventitious Carbon on Primary Sample Containment Metal Surfaces

    Science.gov (United States)

    Calaway, M. J.; Fries, M. D.

    2015-01-01

    Future missions that return astromaterials with trace carbonaceous signatures will require strict protocols for reducing and controlling terrestrial carbon contamination. Adventitious carbon (AC) on primary sample containers and related hardware is an important source of that contamination. AC is a thin film layer or heterogeneously dispersed carbonaceous material that naturally accrues from the environment on the surface of atmospheric exposed metal parts. To test basic cleaning techniques for AC control, metal surfaces commonly used for flight hardware and curating astromaterials at JSC were cleaned using a basic cleaning protocol and characterized for AC residue. Two electropolished stainless steel 316L (SS- 316L) and two Al 6061 (Al-6061) test coupons (2.5 cm diameter by 0.3 cm thick) were subjected to precision cleaning in the JSC Genesis ISO class 4 cleanroom Precision Cleaning Laboratory. Afterwards, the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.

  19. Ocean Surface Carbon Dioxide Fugacity Observed from Space

    Science.gov (United States)

    Liu, W. Timothy; Xie, Xiaosu

    2014-01-01

    We have developed and validated a statistical model to estimate the fugacity (or partial pressure) of carbon dioxide (CO2) at sea surface (pCO2sea) from space-based observations of sea surface temperature (SST), chlorophyll, and salinity. More than a quarter million in situ measurements coincident with satellite data were compiled to train and validate the model. We have produced and made accessible 9 years (2002-2010) of the pCO2sea at 0.5 degree resolutions daily over the global ocean. The results help to identify uncertainties in current JPL Carbon Monitoring System (CMS) model-based and bottom-up estimates over the ocean. The utility of the data to reveal multi-year and regional variability of the fugacity in relation to prevalent oceanic parameters is demonstrated.

  20. Friction Properties of Surface-Fluorinated Carbon Nanotubes

    Science.gov (United States)

    Wal, R. L. Vander; Miyoshi, K.; Street, K. W.; Tomasek, A. J.; Peng, H.; Liu, Y.; Margrave, J. L.; Khabashesku, V. N.

    2005-01-01

    Surface modification of the tubular or sphere-shaped carbon nanoparticles through chemical treatment, e.g., fluorination, is expected to significantly affect their friction properties. In this study, a direct fluorination of the graphene-built tubular (single-walled carbon nanotubes) structures has been carried out to obtain a series of fluorinated nanotubes (fluoronanotubes) with variable C(n)F (n =2-20) stoichiometries. The friction coefficients for fluoronanotubes, as well as pristine and chemically cut nanotubes, were found to reach values as low as 0.002-0.07, according to evaluation tests run in contact with sapphire in air of about 40% relative humidity on a ball-on-disk tribometer which provided an unidirectional sliding friction motion. These preliminary results demonstrate ultra-low friction properties and show a promise in applications of surface modified nanocarbons as a solid lubricant.

  1. Mechanical performance of styrene-butadiene-rubber filled with carbon nanoparticles prepared by mechanical mixing

    International Nuclear Information System (INIS)

    Highlights: → We compare influence of carbon blacks and carbon nanotube on properties of SBR. → We model mechanical behavior of SBR nanocomposites by the micromechanical model. → Mechanical properties of carbon black/SBR is greatly dominated by bound rubber. → Mechanical properties of SBR/nanotube is governed by big aspect ratio of nanotube. - Abstract: Reinforcement of styrene-butadiene-rubber (SBR) was investigated using two different carbon blacks (CBs) with similar particle sizes, including highly structured CB and conventional CB, as well as multi-walled carbon nanotube (MWCNT) prepared by mechanical mixing. The attempts were made to examine reinforcing mechanism of these two different classes of carbon nanoparticles. Scanning electron microscopy and electrical conductivity measurement were used to investigate morphology. Tensile, cyclic tensile and stress relaxation analyses were performed. A modified Halpin-Tsai model based on the concept of an equivalent composite particle, consisting of rubber bound, occluded rubber and nanoparticle, was proposed. It was found that properties of CB filled SBR are significantly dominated by rubber shell and occluded rubber in which molecular mobility is strictly restricted. At low strains, these rubber constituents can contribute in hydrodynamic effects, leading to higher elastic modulus. However, at higher strains, they contribute in stress hardening resulting in higher elongation at break and higher tensile strength. These elastomeric regions can also influence stress relaxation behaviors of CB filled rubber. For SBR/MWCNT, the extremely great inherent mechanical properties of nanotube along with its big aspect ratio were postulated to be responsible for the reinforcement while their interfacial interaction was not so efficient.

  2. Superlubricity mechanism of diamond-like carbon with glycerol. Coupling of experimental and simulation studies

    International Nuclear Information System (INIS)

    We report a unique tribological system that produces superlubricity under boundary lubrication conditions with extremely little wear. This system is a thin coating of hydrogen-free amorphous Diamond-Like-Carbon (denoted as ta-C) at 353 K in a ta-C/ta-C friction pair lubricated with pure glycerol. To understand the mechanism of friction vanishing we performed ToF-SIMS experiments using deuterated glycerol and 13C glycerol. This was complemented by first-principles-based computer simulations using the ReaxFF reactive force field to create an atomistic model of ta-C. These simulations show that DLC with the experimental density of 3.24 g/cc leads to an atomistic structure consisting of a 3D percolating network of tetrahedral (sp3) carbons accounting for 71.5% of the total, in excellent agreement with the 70% deduced from our Auger spectroscopy and XANES experiments. The simulations show that the remaining carbons (with sp2 and sp1 character) attach in short chains of length 1 to 7. In sliding simulations including glycerol molecules, the surface atoms react readily to form a very smooth carbon surface containing OH-terminated groups. This agrees with our SIMS experiments. The simulations find that the OH atoms are mostly bound to surface sp1 atoms leading to very flexible elastic response to sliding. Both simulations and experiments suggest that the origin of the superlubricity arises from the formation of this OH-terminated surface

  3. The mechanisms for filling carbon nanotubes with molten salts: carbon nanotubes as energy landscape filters

    International Nuclear Information System (INIS)

    The mechanisms for filling carbon nanotubes with molten salts are investigated using molecular dynamics computer simulation. Inorganic nanotubular structures, whose morphologies can be rationalized in terms of the folding, or the removal of sections from, planes of square nets are found to form. The formation mechanisms are found to follow a 'chain-by-chain' motif in which the structures build systematically from charge neutral M-X-M-Xc chains. The formation mechanisms are rationalized in terms of the ion-ion interactions (intra-chain and inter-chain terms). In addition, the mechanisms of filling are discussed in terms of a 'hopping' between basins on the underlying energy landscape. The role of the carbon nanotube as an energy landscape filter is discussed.

  4. Creation of surface defects on carbon nanofibers by steam treatment

    Institute of Scientific and Technical Information of China (English)

    Zhengfeng; Shao; Min; Pang; Wei; Xia; Martin; Muhler; Changhai; Liang

    2013-01-01

    A direct strategy for the creation of defects on carbon nanofibers (CNFs) has been developed by steam treatment.Nitrogen physisorption,XRD,Raman spectra,SEM and TEM analyses proved the existence of the new defects on CNFs.BET surface area of CNFs after steam treatment was enhanced from 20 to 378 m2/g.Pd catalysts supported on CNFs were also prepared by colloidal deposition method.The different activity of Pd/CNFs catalysts in the partial hydrogenation of phenylacetylene further demonstrated the diverse surfaces of CNFs could be formed by steam treatment.

  5. Osteoblast cell response to surface-modified carbon nanotubes

    International Nuclear Information System (INIS)

    In order to investigate the interaction of cells with modified multi-walled carbon nanotubes (MWCNTs) for their potential biomedical applications, the MWCNTs were chemically modified with carboxylic acid groups (–COOH), polyvinyl alcohol (PVA) polymer and biomimetic apatite on their surfaces. Additionally, human osteoblast MG-63 cells were cultured in the presence of the surface-modified MWCNTs. The metabolic activities of osteoblastic cells, cell proliferation properties, as well as cell morphology were studied. The surface modification of MWCNTs with biomimetic apatite exhibited a significant increase in the cell viability of osteoblasts, up to 67.23%. In the proliferation phases, there were many more cells in the biomimetic apatite-modified MWCNT samples than in the MWCNTs–COOH. There were no obvious changes in cell morphology in osteoblastic MG-63 cells cultured in the presence of these chemically-modified MWCNTs. The surface modification of MWCNTs with apatite achieves an effective enhancement of their biocompatibility.

  6. GENERAL EQUATIONS OF CARBONIZATION OF EUCALYPTUS SPP KINETIC MECHANISMS

    OpenAIRE

    Túlio Jardim Raad; Paulo César da C. Pinheiro; Maria Irene Yoshida

    2006-01-01

    In the present work, a set of general equations related to kinetic mechanism of wood compound carbonization: hemicelluloses, cellulose and lignin was obtained by Avrami-Eroffev and Arrhenius equations and Thermogravimetry of Eucalyptus cloeziana, Eucalyptus camaldulensis, Corymbia citriodora, Eucalyptus urophylla and Eucalyptus grandis samples, TG-Isothermal and TG-Dynamic. The different thermal stabilities and decomposition temperature bands of those species compounds were applied as strateg...

  7. Mechanical testing of unidirectional carbon fiber reinforced plastics

    OpenAIRE

    Näreikkö, Aleksi

    2015-01-01

    The area of composites testing has been a major topic of research since the early adoption of composites in the aerospace industry, nearly 50 years ago. Today, the mechanical characterization of different material systems is of even greater importance, since most modelling software require material data to produce accurate results. This thesis studied a component consisting of 4 pultruded carbon fiber reinforced epoxy elements coated with a thermoplastic polyurethane coating. The obje...

  8. Mechanical and Tribological Properties of Carbon-Based Graded Coatings

    OpenAIRE

    Kot, M; Ł. Major; Lackner, J. M.; K. Chronowska-Przywara; Janusz, M.; Rakowski, W

    2016-01-01

    The paper presents research on coatings with advanced architecture, composed of a Cr/Cr2N ceramic/metal multilayer and graded carbon layers with varying properties from Cr/a-C:H to a-C:N. The microstructure of the coatings was analysed using transmission electron microscopy and Energy Dispersive Spectroscopy, the mechanical properties were tested by nanoindentation, spherical indentation, and scratch testing, and tribological tests were also conducted. The proper selection of subsequent layer...

  9. Asphalt-derived high surface area activated porous carbons for carbon dioxide capture.

    Science.gov (United States)

    Jalilov, Almaz S; Ruan, Gedeng; Hwang, Chih-Chau; Schipper, Desmond E; Tour, Josiah J; Li, Yilun; Fei, Huilong; Samuel, Errol L G; Tour, James M

    2015-01-21

    Research activity toward the development of new sorbents for carbon dioxide (CO2) capture have been increasing quickly. Despite the variety of existing materials with high surface areas and high CO2 uptake performances, the cost of the materials remains a dominant factor in slowing their industrial applications. Here we report preparation and CO2 uptake performance of microporous carbon materials synthesized from asphalt, a very inexpensive carbon source. Carbonization of asphalt with potassium hydroxide (KOH) at high temperatures (>600 °C) yields porous carbon materials (A-PC) with high surface areas of up to 2780 m(2) g(-1) and high CO2 uptake performance of 21 mmol g(-1) or 93 wt % at 30 bar and 25 °C. Furthermore, nitrogen doping and reduction with hydrogen yields active N-doped materials (A-NPC and A-rNPC) containing up to 9.3% nitrogen, making them nucleophilic porous carbons with further increase in the Brunauer-Emmett-Teller (BET) surface areas up to 2860 m(2) g(-1) for A-NPC and CO2 uptake to 26 mmol g(-1) or 114 wt % at 30 bar and 25 °C for A-rNPC. This is the highest reported CO2 uptake among the family of the activated porous carbonaceous materials. Thus, the porous carbon materials from asphalt have excellent properties for reversibly capturing CO2 at the well-head during the extraction of natural gas, a naturally occurring high pressure source of CO2. Through a pressure swing sorption process, when the asphalt-derived material is returned to 1 bar, the CO2 is released, thereby rendering a reversible capture medium that is highly efficient yet very inexpensive. PMID:25531980

  10. A novel surface modification of carbon fiber for high-performance thermoplastic polyurethane composites

    Science.gov (United States)

    Zhang, Yuanyuan; Zhang, Yizhen; Liu, Yuan; Wang, Xinling; Yang, Bin

    2016-09-01

    Properties of carbon fiber (CF) reinforced composites depend largely on the interfacial bonding strength between fiber and the matrix. In the present work, CF was grafted by 4,4‧-diphenylmethane diisocyanate (MDI) molecules after electrochemical oxidation treatment. The existence of functional groups introduced to the fiber surface and the changes of surface roughness were confirmed by FTIR, AFM, XPS, SEM and Raman spectroscopy. To evaluate the possible applications of this surface modification of carbon fiber, we examined the mechanical properties as well as the friction and wear performance of pristine CF and MDI-CF reinforced thermoplastic polyurethane (TPU) composites with 5-30 wt.% fiber contents, and found that the mechanical properties of TPU composites were all significantly improved. It is remarkable that when fiber content was 30 wt.%, the tensile strength of TPU/MDI-CF was increased by 99.3%, which was greater than TPU/CF (53.2%), and the friction loss of TPU/MDI-CF was decreased by 49.09%. The results of DMA and SEM analysis indicated the positive effects of MDI modification on the interfacial bonding between fibers and matrix. We believed that this simple and effective method could be used to the development of surface modified carbon fiber for high-performance TPU.

  11. Effect of Carbon Nanofiber on Mechanical Behavior of Asphalt Concrete

    Directory of Open Access Journals (Sweden)

    Saeed Ghaffarpour Jahromi

    2015-09-01

    Full Text Available Uses of fibers to improve material properties have a scientific background in recent years in civil engineering. Use of Nanofiber reinforcement of materials refers to incorporating materials with desired properties within some other materials lacking those properties. Use of fibers for improvement is not a new phenomenon as the technique of fiber-reinforced bitumen began as early as 1950, but using nanofiber is a new idea. In this research the mechanical properties of asphalt mixture that have been modified with carbon nanofiber were investigated using mechanical tests, which can improve the performance of flexible pavements. To evaluate the effect of nanofiber contents on bituminous mixtures, laboratory investigations were carried out on the samples with and without nanofibers. During the course of this study, various tests were undertaken applying the Marshall test, indirect tensile test, resistance to fatigue cracking by using repeated load indirect tensile test and creep test. Carbon nanofiber exhibited consistency in results and it was observed that the addition of nanofiber can change the properties of bituminous mixtures, increase its stability and decrease the flow value. Results indicate that nanofiber have the potential to resist structural distress in the pavement and thus improve fatigue by increasing resistance to cracks or permanent deformation, when growing traffic loads. On the whole, the results show that the addition of carbon nanofiber will improve some of the mechanical properties such as fatigue and deformation in the flexible pavement.

  12. Atomistic simulations of the mechanical properties of 'super' carbon nanotubes

    International Nuclear Information System (INIS)

    The mechanical properties of the so-called 'super' carbon nanotubes (STs) are investigated using classical molecular dynamics simulations. The STs are built from single-walled carbon nanotubes (SWCNTs) connected by Y-like junctions forming an ordered carbon nanotube network that is then rolled into a seamless cylinder. We observed that the ST behaviour under tensile tests is similar to the one presented by fishing nets. This interesting behaviour provides a way to vary the accessible channels to the inner parts of STs by applying an external mechanical load. The Young's modulus is dependent on the ST chirality and it inversely varies with the ST radius. Smaller reduction of breaking strain values due to temperature increase is predicted for zigzag STs compared to SWCNTs. The results show that, for STs with radius ∼5 nm, the junctions between the constituent SWCNTs play an important role in the fracture process. The Young's modulus and tensile strength were estimated for hierarchical higher-order STs using scaling laws related to the ST fractal dimension. The obtained mechanical properties suggest that STs may be used in the development of new porous, flexible, and high-strength materials

  13. Carbon-based nanostructured surfaces for enhanced phase-change cooling

    Science.gov (United States)

    Selvaraj Kousalya, Arun

    To maintain acceptable device temperatures in the new generation of electronic devices under development for high-power applications, conventional liquid cooling schemes will likely be superseded by multi-phase cooling solutions to provide substantial enhancement to the cooling capability. The central theme of the current work is to investigate the two-phase thermal performance of carbon-based nanostructured coatings in passive and pumped liquid-vapor phase-change cooling schemes. Quantification of the critical parameters that influence thermal performance of the carbon nanostructured boiling surfaces presented herein will lead to improved understanding of the underlying evaporative and boiling mechanisms in such surfaces. A flow boiling experimental facility is developed to generate consistent and accurate heat transfer performance curves with degassed and deionized water as the working fluid. New means of boiling heat transfer enhancement by altering surface characteristics such as surface energy and wettability through light-surface interactions is explored in this work. In this regard, carbon nanotube (CNT) coatings are exposed to low-intensity irradiation emitted from a light emitting diode and the subcooled flow boiling performance is compared against a non-irradiated CNT-coated copper surface. A considerable reduction in surface superheat and enhancement in average heat transfer coefficient is observed. In another work involving CNTs, the thermal performance of CNT-integrated sintered wick structures is evaluated in a passively cooled vapor chamber. A physical vapor deposition process is used to coat the CNTs with varying thicknesses of copper to promote surface wetting with the working fluid, water. Thermal performance of the bare sintered copper powder sample and the copper-functionalized CNT-coated sintered copper powder wick samples is compared using an experimental facility that simulates the capillary fluid feeding conditions of a vapor chamber

  14. Surface chemistry of CO2 - Adsorption of carbon dioxide on clean surfaces at ultrahigh vacuum

    Science.gov (United States)

    Burghaus, Uwe

    2014-05-01

    Carbon dioxide chemistry has attracted significant interest in recent years. Although the field is diverse, a current and more comprehensive review of the surface science literature may be of interest for a variety of communities since environmental chemistry, energy technology, materials science, catalysis, and nanocatalysis are certainly affected by gas-surface properties. The review describes surface phenomena and characterization strategies highlighting similarities and differences, instead of providing only a list of system-specific information. The various systems are roughly distinguished as those that clearly form carbonates and those that merely physisorb CO2 at ultra-high vacuum conditions. Nevertheless, extended sections about specific systems including rarely studied surfaces and unusual materials are included, making this review also useful as a reference.

  15. Adhesion enhancement of Al coatings on carbon/epoxy composite surfaces by atmospheric plasma

    International Nuclear Information System (INIS)

    Adhesion strengths between aluminium thin film coatings and manufactured carbon/epoxy composite surfaces were measured by assessing fracture tensile strengths using pull-off tests. The effect of the substrate roughness (nm to μm) of these composite surfaces on adhesion was studied by examining the surface free energies and adhesion strengths. The adhesion strengths of the coatings varied significantly. To improve the coating adhesion, each composite surface was treated with atmospheric plasma prior to deposition, which resulted in an increase in the surface free energy from approximately 40 mJ/m2 to 70 mJ/m2 because the plasma pretreatment led to the formation of hydrophilic C-O and C=O bonds on the composite surfaces, as demonstrated by X-ray photoelectron spectroscopy analyses. The adhesion strengths of the coatings were enhanced for all surface roughnesses studied. In our study, the effect of mechanical adhesion due to roughness was separated from the effect of modifying the chemical bonds with plasma activation. The adhesion ability of the pure resin was relatively weak. Increasing the surface roughness largely improved the adhesion of the resin surface. Plasma treatment of the pure resin also increased the surface adhesion. Our study shows that plasma activation effectively enhances the adhesion of manufactured composites, even when the surface roughness is on the order of microns. The ageing of the surface activation was also investigated, and the results demonstrate that atmospheric plasma has potential for use in the pretreatment of composite materials.

  16. On the formation and bonding of a surface carbonate on Ni(100)

    Science.gov (United States)

    Behm, R. J.; Brundle, C. R.

    1991-09-01

    The formation, stability, adsorption geometry and electronic structure of a surface carbonate on Ni(100) have been investigated by photoemission (XPS, UPS) and temperature-programmed reaction (TPR). The core level binding energies of 531.2 eV for 0(1s) and 289.0 eV for C(1s) are comparable to those of bulk carbonates. The He(II) spectrum of the carbonate valence levels is not well defined because of the coexisting adsorbed and oxidic oxygen. The angular dependence of the carbonate core level intensities is characteristic of the carbonate being present as an overlayer species rather than a thicker surface phase. The XPS data and isotope labelled TPR experiments indicate the oxygen atoms of the carbonate to be electronically and chemically equivalent, and on this basis we favor a structure in which the carbonate is attached to the metal via all three oxygen atoms. This is supported by comparision with the core level binding energies of HCOO ab and chemisorbed CO 2,ad, which are similarly attached to the surface. From the core level angular behavior, the close similarity of core level binding energies and available vibrational spectroscopic data, a (nearly) planar geometry of the CO 3,ad on Ni(100) is concluded, which is comparable to the planar bulk carbonate anion and the planar carbonate species on Ag(110). The activation barrier for decomposition is estimated from the observed maximum in TPR at 420 K to be 25 ± 2 kcal/mol. CO 2 does not accumulate on the clean or O ad-precovered Ni(100) surface at 130 K. The stabilized, chemisorbed CO 2,ad species often observed on other metal surfaces therefore does not play a critical role for carbonate formation on Ni(100). Also a mechanism involving the disproportionation of a CO 2… CO 2,ad- dimer anion can be ruled out from TPR data. The evidence of the experiments discussed in this paper suggests that the carbonate is predominantly formed by reaction of CO 2,ad with a less stable, defect (disordered) O ad species rather

  17. Molecular simulation of multi-component adsorption processes related to carbon capture in a high surface area, disordered activated carbon

    OpenAIRE

    Di Biase, Emanuela; Sarkisov, Lev

    2015-01-01

    We employ a previously developed model of a high surface area activated carbon, based on a random packing of small fragments of a carbon sheet, functionalized with hydroxyl surface groups, to explore adsorption of water and multicomponent mixtures under conditions representing typical carbon capture processes. Adsorption of water is initialized and proceeds through the growth of clusters around the surface groups, in a process predominantly governed by hydrogen bond interactions. In contrast,...

  18. Uptake of Reactive Black 5 by pumice and walnut activated carbon: Chemistry and adsorption mechanisms

    OpenAIRE

    Heibati, B.; Rodriguez-Couto, S.; Amrane, A; M. Rafatullah; Hawari, A.; Al-Ghouti, M. A.

    2014-01-01

    The potential of using pumice and walnut wood activated carbon as low-cost adsorbents for the removal of the diazo dye Reactive Black 5 (RB5) from aqueous solutions was investigated. The Langmuir isotherm fit to the data specified the presence of two different natures of adsorption sites with different binding energies on the AC-W surface. Kinetic modelling showed that the adsorption behaviour and mechanism of RB5 for both adsorbents is believed to happen via surface adsorption followed by di...

  19. Carbon Acquisition by Cyanobacteria: Mechanisms, Comparative Genomics, and Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Aaron; Hagemann, Martin; Bauwe, Hermann; Kahlon, Shira; Ogawa, Teruo

    2008-01-01

    In this chapter we mainly focus on the mechanisms of inorganic carbon uptake, photorespiration, and the regulation between the metabolic fluxes involved in photoautotrophic, photomixotrophic and heterotrophic growth. We identify the genes involved, their regulation and phylogeny. Living in an environment where the CO₂ concentration is considerably lower than required to saturate their carboxylating enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), cyanobacteria acquired the CO₂ concentrating mechanism (CCM) that enables them to accumulate CO₂ at the carboxylation site. All the cyanobacteria examined to date are able to fix CO₂ into carbohydrates. However, in addition to variance in the range of physical growth conditions, cyanobacteria also vary substantially in their ability to consume organic carbon from their surroundings. Many strains are obligate photoautotrophs where the sole carbon source is CO₂, while others are able to perform photomixotrophic or even heterotrophic growth using a wide variety of organic substances (c.f. Rippka et al., 1979; Stal and Moezelaar, 1997b). Cyanobacteria constitute a unique case where the anabolic and catabolic carbohydrate metabolisms function in the same cellular compartment. In addition, the photosynthetic and respiratory electron transport pathways share components in the thylakoid membranes. Despite its importance to our understanding of cyanobacterial metabolism, little is known about the mechanisms involved in the shifts between photoautotrophic, heterotrophic and photomixotrophic modes of growth, and their regulation; between the different pathways of carbohydrate breakdown- glycolysis, fermentation, the oxidative pentose phosphate, the Krebs cycle and the photorespiratory pathways. In this chapter we shall briefly focus on recent advances in our understanding of the CCM and carbon metabolism in cyanobacteria.

  20. Carbon acquisition by Cyanobacteria: Mechanisms, Comparative Genomics and Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Aaron; Hagemann, Martin; Bauwe, Hermann; Kahlon, Shira; Ogawa, Teruo

    2008-01-01

    In this chapter we mainly focus on the mechanisms of inorganic carbon uptake, photorespiration, and the regulation between the metabolic fluxes involved in photoautotrophic, photomixotrophic and heterotrophic growth. We identify the genes involved, their regulation and phylogeny. Living in an environment where the CO₂ concentration is considerably lower than required to saturate their carboxylating enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), cyanobacteria acquired the CO₂ concentrating mechanism (CCM) that enables them to accumulate CO₂ at the carboxylation site. All the cyanobacteria examined to date are able to fix CO₂ into carbohydrates. However, in addition to variance in the range of physical growth conditions, cyanobacteria also vary substantially in their ability to consume organic carbon from their surroundings. Many strains are obligate photoautotrophs where the sole carbon source is CO₂, while others are able to perform photomixotrophic or even heterotrophic growth using a wide variety of organic substances (c.f. Rippka et al., 1979; Stal and Moezelaar, 1997b). Cyanobacteria constitute a unique case where the anabolic and catabolic carbohydrate metabolisms function in the same cellular compartment. In addition, the photosynthetic and respiratory electron transport pathways share components in the thylakoid membranes. Despite its importance to our understanding of cyanobacterial metabolism, little is known about the mechanisms involved in the shifts between photoautotrophic, heterotrophic and photomixotrophic modes of growth, and their regulation; between the different pathways of carbohydrate breakdown- glycolysis, fermentation, the oxidative pentose phosphate, the Krebs cycle and the photorespiratory pathways. In this chapter we shall briefly focus on recent advances in our understanding of the CCM and carbon metabolism in cyanobacteria.

  1. Surface aging phenomena in multidimensional sp2 carbon allotropes

    Science.gov (United States)

    Chang, Yun-Hsiang; Santos, Sergio; Chiesa, Matteo

    Despite the current interest in the scientific community in exploiting divergent surface properties of graphitic carbon allotropes, conclusive differentiation remains elusive even when dealing with parameters as fundamental as adhesion. Here we set out to provide conclusive experimental evidence on the time evolution of the surface properties of highly oriented pyrolytic graphite (HOPG), graphene monolayer (GML) and multiwalled carbon nanotubes (MWCNTs) as we expose these materials to airborne contaminants, by providing 1) statistically significant results based on large data-sets, i.e. thousands of force measurements, and 2) errors sufficiently self-consistent to treat the comparison between data-sets in atomic force microscopy measurements. We first consider HOPG as a model system and then employ our results to draw conclusions from the GML and MWCNT samples. We find that, in terms of surface properties and thus regarding surface functionality, aged HOPG and GML are more similar than aged HOPG and cleaved HOPG. The state of the HOPG samples is also as relevant for the comparison between HOPG and MWCNTs.

  2. Characterization of a surface modified carbon cryogel and a carbon supported Pt catalyst

    Directory of Open Access Journals (Sweden)

    BILJANA M. BABIĆ

    2007-08-01

    Full Text Available A carbon cryogel, synthesized by carbonization of a resorcinol/formaldehyde cryogel and oxidized in nitric acid, was used as catalyst support for Pt nano-particles. The Pt/C catalyst was prepared by a modified polyol synthesis method in an ethylene glycol (EG solution. Characterization by nitrogen adsorption showed that the carbon cryogel support and the Pt/C catalyst were mesoporous materials with high specific surface areas (SBET > 400 m2 g-1 and large mesoporous volumes. X-Ray diffraction of the catalyst demonstrated the successful reduction of the Pt precursor to metallic form. TEM Images of the Pt/C catalyst and Pt particle size distribution showed that the mean Pt particle size was about 3.3 nm. Cyclic voltammetry (CV experiments at various scan rates (from 2 to 200 mV s-1 were performed in 0.5 mol dm-3 HClO4 solution. The large capacitance of the oxidized carbon cryogel electrode, which arises from a combination of the double-layer capacitance and pseudocapacitance, associated with the participation of surface redox-type reactions was demonstrated. For the oxidized carbon cryogel, the total specific capacitance determined by 1/C vs. ν0.5 extrapolation method was found to be 386 F g-1. The hydrogen oxidation reaction at the investigated Pt/C catalyst proceeded as an electrochemically reversible, two-electron direct discharge reaction.

  3. An essential mechanism of heat dissipation in carbon nanotube electronics

    OpenAIRE

    Rotkin, Slava V.; Perebeinos, Vasili; Petrov, Alexey G.; Avouris, Phaedon

    2009-01-01

    Excess heat generated in integrated circuits is one of the major problems of modern electronics. Surface phonon-polariton scattering is shown here to be the dominant mechanism for hot charge carrier energy dissipation in a nanotube device fabricated on a polar substrate, such as $SiO_2$. Using microscopic quantum models the Joule losses were calculated for the various energy dissipation channels as a function of the electric field, doping, and temperature. The polariton mechanism must be take...

  4. The interaction of oxygen and carbon monoxide with a carbided Ni(111) surface

    NARCIS (Netherlands)

    Geus, John W.; Vink, T.J.; Zandvoort, M.M.J. van; Gijzeman, O.L.J.

    1984-01-01

    The thermal decomposition of ethylene on Ni(111) at 250°C is shown to lead to carbon deposition on and - in a later stage - below the surface. Independent of the amount of carbon below the surface, CO is adsorbed with an isosteric heat of adsorption of 105 kJ/mol. The surface carbon reacts with oxyg

  5. Computational investigation of the mechanical and tribological responses of amorphous carbon nanoparticles

    Science.gov (United States)

    Bucholz, Eric W.; Sinnott, Susan B.

    2013-02-01

    Nanoparticles are a class of materials that have seen increasing use as friction and wear reducers in tribological applications. Amorphous carbon (a-C) films have been the subject of significant scientific and industrial interest for use as solid-state lubricants. Here, we present classical molecular dynamics simulations to investigate the mechanical and tribological responses of a-C nanoparticles that are subjected to external forces between hydrogen-terminated diamond surfaces. Over the range of a-C nanoparticle diameters (2-5 nm) and hydrogenation (0%-50%) considered, the simulations predict a consistent mechanical response where each nanoparticle is highly elastic. The simulations predict that the transition from elastic to plastic response is directly related to an increase in the percentage of carbon-carbon crosslinking within the individual nanoparticles. Contrarily, the simulations also predict that the tribological response is noticeably impacted by changes in diameter and hydrogenation. This is because during friction, hydrogen passivates the unsaturated carbon atoms near the nanoparticle's surface, which prevents interfacial bond formation and allows the nanoparticle to roll within the interface. From these findings, it is demonstrated that a-C nanoparticles are able to provide good tribological performance only when sufficient chemical passivation of the nanoparticles is maintained.

  6. Measurement of anode surface temperature in carbon nanomaterial production by arc discharge method

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Feng; Tanaka, Manabu; Choi, Sooseok [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Watanabe, Takayuki, E-mail: watanabe@chem-eng.kyushu-u.ac.jp [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Department of Chemical Engineering, Kyushu University, Fukuoka 819-0395 (Japan)

    2014-12-15

    Highlights: • We measured the temperature of anode surface by two-color pyrometry combined with a high speed camera successfully. • Growth temperature of pyrolytic graphite, MWNTs, and nano-graphite particles were in ranges of 2400–2600 K, 2600–2700 K, and 2700–3500 K, respectively. • High temperature contributes to form thermodynamically unstable material. - Abstract: Nano-graphite particles, multi-wall carbon nanotube (MWNT), and pyrolytic graphite were prepared at different positions of the anode surface in an arc discharge. Graphite electrodes were employed for the arc discharge under helium environment at atmospheric pressure. Nano-sized carbon products were characterized by scanning electron microscopy and transmission electron microscopy. During the arc discharge, two-color pyrometry combined with a high-speed camera was conducted to measure the temperature distribution of the anode surface. The growth temperature of pyrolytic graphite, MWNT, and nano-graphite particles were in the ranges of 2400–2600 K, 2600–2700 K, and 2700–3500 K, respectively. The local temperature of anode surface is a critical parameter to determine the products with different morphologies. The formation mechanism of these carbon nanomaterials is suggested based on the local temperature of anode surface and their thermodynamic stability.

  7. Measurement of anode surface temperature in carbon nanomaterial production by arc discharge method

    International Nuclear Information System (INIS)

    Highlights: • We measured the temperature of anode surface by two-color pyrometry combined with a high speed camera successfully. • Growth temperature of pyrolytic graphite, MWNTs, and nano-graphite particles were in ranges of 2400–2600 K, 2600–2700 K, and 2700–3500 K, respectively. • High temperature contributes to form thermodynamically unstable material. - Abstract: Nano-graphite particles, multi-wall carbon nanotube (MWNT), and pyrolytic graphite were prepared at different positions of the anode surface in an arc discharge. Graphite electrodes were employed for the arc discharge under helium environment at atmospheric pressure. Nano-sized carbon products were characterized by scanning electron microscopy and transmission electron microscopy. During the arc discharge, two-color pyrometry combined with a high-speed camera was conducted to measure the temperature distribution of the anode surface. The growth temperature of pyrolytic graphite, MWNT, and nano-graphite particles were in the ranges of 2400–2600 K, 2600–2700 K, and 2700–3500 K, respectively. The local temperature of anode surface is a critical parameter to determine the products with different morphologies. The formation mechanism of these carbon nanomaterials is suggested based on the local temperature of anode surface and their thermodynamic stability

  8. Effect of carbon nanofibre addition on the mechanical properties of different f carbon-epoxy composites

    Indian Academy of Sciences (India)

    I Srikanth; Suresh Kumar; Vajinder Singh; B Rangababu; Partha Ghosal; Ch Subrahmanyam

    2015-04-01

    Carbon-epoxy (C-epoxy) laminated composites having different fibre volume fractions (40, 50, 60 and 70) were fabricated with and without the addition of aminofunctionalized carbon nanofibres (A-CNF). Flexural strength, interlaminar shear strength (ILSS) and tensile strength of the composite laminates were determined. It was observed that, the ability of A-CNF to enhance the mechanical properties of C-epoxy diminished significantly as the fibre volume fraction (f) of the C-epoxy increased from 40 to 60. At 70f, the mechanical properties of the A-CNF reinforced C-epoxy were found to be lower compared to the C-epoxy composite made without the addition of A-CNF. In this paper suitable mechanisms for the observed trends are proposed on the basis of the fracture modes of the composite.

  9. Microstructure and Mechanical Property of Ni Metal Treated by Surface Mechanical Attrition

    Institute of Scientific and Technical Information of China (English)

    Wen Chun-sheng; Rong Yong-hua; T.Y. Hsu (Xu Zu-yao)

    2004-01-01

    A nanostructured surface layer can be formed in Ni metal treated by surface mechanical attrition (SMA). The microstructure was investigated by using optical microscope, X-ray diffractometer and transmission electron microscope,respectively. Mechanical property measurements indicate that the yield strength of the surface layer raises significantly while the tensile strength somewhat changes and the elongation percentage reduces severely compared with that of the inside layer. Meanwhile, yield-drop-like phenomenon occurs in the surface layer after SMA treatment. In order to compare the mechanical behavior of nanostructured materials with two phases, Fe-30Ni nanostructured alloy was also investigated.

  10. Almen intensity effect on microstructure and mechanical properties of low carbon steel subjected to severe shot peening

    Science.gov (United States)

    Unal, Okan; Varol, Remzi

    2014-01-01

    This paper discusses alteration of microstructure and mechanical properties of low carbon steel after severe shot peening process. An ultra fine grained surface layer was formed on AISI 1017 mild steel by means of severe shot peening process. Surface characteristics were affirmed using optical microscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Nano hardness measurements were taken along the depth from shot peened surface using nanoindentation methods. The results showed that severe (unconventional) air blast shot peening process is an effective way to obtain ultra fine grained surface layer and to obtain superior mechanical properties.

  11. Almen intensity effect on microstructure and mechanical properties of low carbon steel subjected to severe shot peening

    Energy Technology Data Exchange (ETDEWEB)

    Unal, Okan, E-mail: ounal@bartin.edu.tr [Department of Mechanical Engineering, Bartin University, 74100, Bartin (Turkey); Varol, Remzi, E-mail: remzivarol@sdu.edu.tr [Department of Mechanical Engineering, Suleyman Demirel University, 32260 Isparta (Turkey)

    2014-01-30

    This paper discusses alteration of microstructure and mechanical properties of low carbon steel after severe shot peening process. An ultra fine grained surface layer was formed on AISI 1017 mild steel by means of severe shot peening process. Surface characteristics were affirmed using optical microscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Nano hardness measurements were taken along the depth from shot peened surface using nanoindentation methods. The results showed that severe (unconventional) air blast shot peening process is an effective way to obtain ultra fine grained surface layer and to obtain superior mechanical properties.

  12. Mechanical Properties and Corrosion Behavior of Low Carbon Steel Weldments

    Directory of Open Access Journals (Sweden)

    Mohamed Mahdy

    2013-01-01

    Full Text Available This research involves studying the mechanical properties and corrosion behavior of “low carbon steel” (0.077wt% C before and after welding using Arc, MIG and TIG welding. The mechanical properties include testing of microhardness, tensile strength, the results indicate that microhardness of TIG, MIG welding is more than arc welding, while tensile strength in arc welding more than TIG and MIG.The corrosion behavior of low carbon weldments was performed by potentiostat at scan rate 3mV.sec-1 in 3.5% NaCl to show the polarization resistance and calculate the corrosion rate from data of linear polarization by “Tafel extrapolation method”. The results indicate that the TIG welding increase the corrosion current density and anodic Tafel slop, while decrease the polarization resistance compared with unwelded low carbon steel. Cyclic polarization were measured to show resistance of specimens to pitting corrosion and to calculate the forward and reveres potentials. The results show shifting the forward, reverse and pitting potentials toward active direction for weldments samples compared with unwelded sample.

  13. A new mechanism about the process of preparing nanoporous silica with activated carbon mold

    International Nuclear Information System (INIS)

    Supercritical fluids can be used to proceed nanoscale casting, during which silica precursor dissolved in supercritical CO2 and the supercritical CO2 was in contact with the active carbon templates. After removal of active carbon templates by calcinations, microporous and mesoporous silica samples replicating not only mesostructures, but also macroscopic of active carbon molds were obtained and the product have better porous capacity and specific surface area. Here, we studied the influences of a variety of factors upon nanoscale casting using supercritical fluids (NC-SCF), and determined the best casting condition. Also, we compared nanoscale casting by using supercritical fluids to simple liquid casting and on the basis of these studies, a new mechanism about preparing nanoporous silica with supercritical CO2-assisted method and with simple liquid casting was proposed

  14. Influence of Structure and Surface Chemistry of Porous Carbon Electrodes on Supercapacitor Performance

    Science.gov (United States)

    Dyatkin, Boris

    Electrochemical double layer capacitors, which rely on electrosorption of ions in nanostructured carbon electrodes, can supplement or even replace traditional batteries in energy harvesting and storage applications. While supercapacitors offer > 10 kW/kg power densities, their ~5 Wh/kg energy densities are insufficient for many automotive and grid storage applications. Most prior efforts have focused on novel high-performing ionic liquid electrolytes and porous carbons with tunable pore diameters and high specific surface areas. However, existing research lacks fundamental understanding of the influence of surface heterogeneity and disorder, such as graphitic defects and functional groups, on key electrosorption properties at electrode-electrolyte interfaces. These interactions significantly impact charge accumulation densities, ion transport mechanisms, and electrolyte breakdown processes. Subsequently, they must be investigated to optimize ion screening, charge mobilities, and operating voltage windows of the devices. The research in this dissertation examined the influence of surface functional groups and structural ordering on capacitance, electrosorption dynamics, and electrochemical stability of external and internal surface of carbon electrodes. High-temperature vacuum annealing, air oxidation, hydrogenation, and amination were used to tune pore surface compositions and decouple key structural and chemical properties of carbide-derived carbons. The approach combined materials characterization by a variety of techniques, neutron scattering studies of ion dynamics, electrochemical testing, and MD simulations to investigate the fundamental intermolecular interactions and dynamics of ions electrosorption in different pore architectures and on planar graphene surfaces. Contrary to expected results and existing theories, defect removal via defunctionalization and graphitization decreased capacitance. Hydrogenated surfaces benefitted electrosorption, while oxygen

  15. Measurement of dynamic surface tension by mechanically vibrated sessile droplets

    Science.gov (United States)

    Iwata, Shuichi; Yamauchi, Satoko; Yoshitake, Yumiko; Nagumo, Ryo; Mori, Hideki; Kajiya, Tadashi

    2016-04-01

    We developed a novel method for measuring the dynamic surface tension of liquids using mechanically vibrated sessile droplets. Under continuous mechanical vibration, the shape of the deformed droplet was fitted by numerical analysis, taking into account the force balance at the drop surface and the momentum equation. The surface tension was determined by optimizing four parameters: the surface tension, the droplet's height, the radius of the droplet-substrate contact area, and the horizontal symmetrical position of the droplet. The accuracy and repeatability of the proposed method were confirmed using drops of distilled water as well as viscous aqueous glycerol solutions. The vibration frequency had no influence on surface tension in the case of pure liquids. However, for water-soluble surfactant solutions, the dynamic surface tension gradually increased with vibration frequency, which was particularly notable for low surfactant concentrations slightly below the critical micelle concentration. This frequency dependence resulted from the competition of two mechanisms at the drop surface: local surface deformation and surfactant transport towards the newly generated surface.

  16. Measurement of dynamic surface tension by mechanically vibrated sessile droplets.

    Science.gov (United States)

    Iwata, Shuichi; Yamauchi, Satoko; Yoshitake, Yumiko; Nagumo, Ryo; Mori, Hideki; Kajiya, Tadashi

    2016-04-01

    We developed a novel method for measuring the dynamic surface tension of liquids using mechanically vibrated sessile droplets. Under continuous mechanical vibration, the shape of the deformed droplet was fitted by numerical analysis, taking into account the force balance at the drop surface and the momentum equation. The surface tension was determined by optimizing four parameters: the surface tension, the droplet's height, the radius of the droplet-substrate contact area, and the horizontal symmetrical position of the droplet. The accuracy and repeatability of the proposed method were confirmed using drops of distilled water as well as viscous aqueous glycerol solutions. The vibration frequency had no influence on surface tension in the case of pure liquids. However, for water-soluble surfactant solutions, the dynamic surface tension gradually increased with vibration frequency, which was particularly notable for low surfactant concentrations slightly below the critical micelle concentration. This frequency dependence resulted from the competition of two mechanisms at the drop surface: local surface deformation and surfactant transport towards the newly generated surface. PMID:27131706

  17. Al current collector surface treatment and carbon nano tubes influences on Carbon / Carbon super-capacitors performances

    Energy Technology Data Exchange (ETDEWEB)

    Portet, C.; Taberna, P.L.; Simon, P. [Universite Paul Sabatier, CIRIMAT-LCMIE, 31 - Toulouse (France)

    2004-07-01

    Performances of 4 cm{sup 2} carbon/carbon super-capacitors cells using Al current collectors foils in organic electrolyte are presented; the improvement of electrode material has been investigated. In a first part, a surface treatment of the Al current collector is proposed in order to improve contact surface between the current collector and the active material leading to an internal resistance decrease. The process consists in an etching of the Al foil and is followed by a carbonaceous sol-gel deposit. Galvano-static cycling and Electrochemical Impedance Spectroscopy measurements of super-capacitors all assembled with treated Al foil were tested over 10,000 cycles: an ESR of 0.5 {omega} cm{sup 2} and a capacitance of 95 F g{sup -1} of activated carbon are obtained and performances remain stable during cycling. The second part is devoted to the study of Carbon Nano Tubes (CNTs) adding into the active material on the performances of super-capacitors. A content of 15% of CNTs appears to be the best composition; the ESR is 0.4 {omega} cm{sup 2} (20% lowered as compared to a cell using activated carbon based electrode) and the capacitance remain high 93 F g{sup -1} of carbonaceous active material. (authors)

  18. Mechanical testing and modelling of carbon-carbon composites for aircraft disc brakes

    Science.gov (United States)

    Bradley, Luke R.

    The objective of this study is to improve the understanding of the stress distributions and failure mechanisms experienced by carbon-carbon composite aircraft brake discs using finite element (FE) analyses. The project has been carried out in association with Dunlop Aerospace as an EPSRC CASE studentship. It therefore focuses on the carbon-carbon composite brake disc material produced by Dunlop Aerospace, although it is envisaged that the approach will have broader applications for modelling and mechanical testing of carbon-carbon composites in general. The disc brake material is a laminated carbon-carbon composite comprised of poly(acrylonitrile) (PAN) derived carbon fibres in a chemical vapour infiltration (CVI) deposited matrix, in which the reinforcement is present in both continuous fibre and chopped fibre forms. To pave the way for the finite element analysis, a comprehensive study of the mechanical properties of the carbon-carbon composite material was carried out. This focused largely, but not entirely, on model composite materials formulated using structural elements of the disc brake material. The strengths and moduli of these materials were measured in tension, compression and shear in several orientations. It was found that the stress-strain behaviour of the materials were linear in directions where there was some continuous fibre reinforcement, but non-linear when this was not the case. In all orientations, some degree of non-linearity was observed in the shear stress-strain response of the materials. However, this non-linearity was generally not large enough to pose a problem for the estimation of elastic moduli. Evidence was found for negative Poisson's ratio behaviour in some orientations of the material in tension. Additionally, the through-thickness properties of the composite, including interlaminar shear strength, were shown to be positively related to bulk density. The in-plane properties were mostly unrelated to bulk density over the range of

  19. Novel exchange mechanisms in the surface diffusion of oxides

    International Nuclear Information System (INIS)

    We use temperature-accelerated dynamics to show the importance of exchange mechanisms in surface diffusion and growth of simple oxides. Such mechanisms can dominate transport processes both on terraces and steps for both homoepitaxial and heteroepitaxial growth. We suggest that the mixing inevitable when an exchange mechanism is present must be considered when attempts are made to grow sharp interfaces in oxide nanostructures. (letter to the editor)

  20. Surface morphology, cohesive and adhesive properties of amorphous hydrogenated carbon nanocomposite films

    International Nuclear Information System (INIS)

    In this work, amorphous hydrogenated carbon (a-C:H), SiOx containing a-C:H (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) thin films were deposited on chromium thin film coated glass using a closed drift ion beam source. Acetylene gas, hexamethyldisiloxane and hydrogen or 20% nitrogen/hydrogen mixture were used as precursors. Resulting hydrogenated carbon thin film surface morphology as well as their cohesive and adhesive properties were studied using progressive loading scratch tests followed by optical microscopy analysis. Surface analysis was also performed using atomic force microscopy via topography, surface morphology parameter, height distribution histogram and bearing ratio curve based hybrid parameter measurements. The a-C:H/SiOx and a-C:H:N/SiOx thin films showed better mechanical strength as compared to the conventional a-C:H films. X-ray photoelectron spectroscopy was used to determine the chemical composition of these films. It showed increased amounts of silicon and absence of terminal oxygenated carbon bonds in a-C:H:N/SiOx thin film which was attributed to its improved mechanical properties.

  1. Carbon stabilization mechanisms in soils in the Andes

    Science.gov (United States)

    Jansen, Boris; Cammeraat, Erik

    2015-04-01

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

  2. Plasmon-assisted photoluminescence enhancement of single-walled carbon nanotubes on metal surfaces

    OpenAIRE

    Sakashita, Takerou; Miyauchi, Yuhei; Matsuda, Kazunari; Kanemitsu, Yoshihiko

    2010-01-01

    We demonstrated photoluminescence (PL) enhancement in single carbon nanotubes using localized surface plasmons. Single nanotube spectroscopy revealed triple the PL intensity enhancement for carbon nanotubes on rough Au surfaces as on fused silica surfaces. The PL enhancement depends on the excitation wavelength and distance between the carbon nanotubes and the Au surface. The degree of PL enhancement is determined by the electric field enhancement from the localized surface plasmon and the en...

  3. Carbon spheres surface modification and dispersion in polymer matrix

    International Nuclear Information System (INIS)

    Highlights: ► Vinyl groups were grafted onto the surface of CSs by acryloyl chloride. ► Vinyl-functionalized CSs were dispersed well in organic solvent. ► Non-covalent functionalization was used to functionalize the surface of CSs. ► Functionalized CSs dispersed uniformly in the PMMA matrix with good compatibility. - Abstract: Polymer/carbon spheres (CSs) composite materials, in which polymer was used as continuous phase and CSs as dispersed phase, were synthesized by in situ bulk polymerization. In order to improve CSs dispersibility in polymer matrix and compatibility with polymer matrix, the functional double bonds were introduced onto the surface of CSs by covalent and non-covalent method. Covalent functionalization was accompolished through mixed acid oxidation and subsequent reaction with acryloyl chloride. Field-emission scanning electron microscopy, Fourier-transform Infrared spectrometry and thermogravimetry were used to characterize the morphology, structure and effect of functionalization of CSs. Vinyl-functionalized CSs by acryloyl chloride were well dispersed in organic solvents, such as DMF, acetone and chloroform. Non-covalent functionalization by surfactant was accompolished by electrostatic interaction. Covalent and non-covalent functionalization enabled CSs to be homogeneously dispersed in poly(methyl methacrylate) (PMMA) matrix with good compatibility. These studies lay the foundation of preparing the non-close packed three-dimensional carbon-based photonic crystals.

  4. Fracture Mechanics Analyses of Subsurface Defects in Reinforced Carbon-Carbon Joggles Subjected to Thermo-Mechanical Loads

    Science.gov (United States)

    Knight, Norman F., Jr.; Raju, Ivatury S.; Song, Kyongchan

    2011-01-01

    Coating spallation events have been observed along the slip-side joggle region of the Space Shuttle Orbiter wing-leading-edge panels. One potential contributor to the spallation event is a pressure build up within subsurface voids or defects due to volatiles or water vapor entrapped during fabrication, refurbishment, or normal operational use. The influence of entrapped pressure on the thermo-mechanical fracture-mechanics response of reinforced carbon-carbon with subsurface defects is studied. Plane-strain simulations with embedded subsurface defects are performed to characterize the fracture mechanics response for a given defect length when subjected to combined elevated-temperature and subsurface-defect pressure loadings to simulate the unvented defect condition. Various subsurface defect locations of a fixed-length substrate defect are examined for elevated temperature conditions. Fracture mechanics results suggest that entrapped pressure combined with local elevated temperatures have the potential to cause subsurface defect growth and possibly contribute to further material separation or even spallation. For this anomaly to occur, several unusual circumstances would be required making such an outcome unlikely but plausible.

  5. Surface modification of multi-wall carbon nanotube with ultraviolet-curable hyperbranched polymer

    International Nuclear Information System (INIS)

    Surface modification is a general and efficient approach to improve the compatibility of carbon nanotube (CNT) with various matrixes. Here we report the modification of multi-wall carbon nanotube (MWCNT) with hyperbranched polymer which contains UV reactive functional groups. The modification promotes the incorporation of CNT into UV-curable resin, and when cured under UV irradiation to form a homogeneous film, the CNT will be chemically bonded with the matrix by crosslinking photopolymerization. For the unique mechanical properties of CNT, the mechanical properties of the cured MWCNT/UV-curable resin film were greatly improved compared with pure resin film as indicated by the increasing of Young's modulus, tensile strength, and toughness

  6. Surface modification of multi-wall carbon nanotube with ultraviolet-curable hyperbranched polymer

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Wei; Xu Jianwen [Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Shi Wenfang [Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)], E-mail: wfshi@ustc.edu

    2008-04-30

    Surface modification is a general and efficient approach to improve the compatibility of carbon nanotube (CNT) with various matrixes. Here we report the modification of multi-wall carbon nanotube (MWCNT) with hyperbranched polymer which contains UV reactive functional groups. The modification promotes the incorporation of CNT into UV-curable resin, and when cured under UV irradiation to form a homogeneous film, the CNT will be chemically bonded with the matrix by crosslinking photopolymerization. For the unique mechanical properties of CNT, the mechanical properties of the cured MWCNT/UV-curable resin film were greatly improved compared with pure resin film as indicated by the increasing of Young's modulus, tensile strength, and toughness.

  7. Carbon substituting for oxygen in silicates: A novel mechanism for carbon incorporation in the deep Earth

    Science.gov (United States)

    Armentrout, M. M.; Tavakoli, A.; Ionescu, E.; Mera, G.; Riedel, R.; Navrotsky, A.

    2013-12-01

    Traditionally, carbon in the deep Earth has been thought of in terms of either carbonate at high oxygen fugacities or graphite or diamond under more reducing conditions. However, material science studies of amorphous Si-O-C polymer derived ceramics have demonstrated that carbon can be accommodated as an anion substituting for oxygen in mixed silica tetrahedra. Furthermore these structures are energetically favorable relative to a mixture of crystalline silica, silicon carbide, and graphite by ten or more kJ/g.atom. Thermodynamic stability suggests that these nano-structured composites are a potentially important storage mechanism for carbon under moderately reducing conditions. Here we expand the scope of the previous work by examining the compositional effect of geologically relevant cations (calcium and magnesium) on the thermodynamic stability, nanostructure, and ability to accommodate carbon of these composites. Silicon oxy-carbides doped with magnesium, magnesium and calcium or undoped resisted crystallization at 1100 C under inert atmosphere. 29Si NMR of the samples shows a similar distribution of silicon between end-member and mixed sites (Table 1). Results are presented from studies utilizing NMR, high temperature solution calorimetry, and microprobe. Table 1. Percentages of Si species in each material as determined by 29Si NMR.

  8. Increasing corrosion resistance of carbon steels by surface laser cladding

    Science.gov (United States)

    Polsky, V. I.; Yakushin, V. L.; Dzhumaev, P. S.; Petrovsky, V. N.; Safonov, D. V.

    2016-04-01

    This paper presents results of investigation of the microstructure, elemental composition and corrosion resistance of the samples of low-alloy steel widely used in the engineering, after the application of laser cladding. The level of corrosion damage and the corrosion mechanism of cladded steel samples were established. The corrosion rate and installed discharge observed at the total destruction of cladding were obtained. The regularities of structure formation in the application of different powder compositions were obtained. The optimal powder composition that prevents corrosion of samples of low-carbon low-alloy steel was established.

  9. High temperature mechanical properties of zirconia reinforced with carbon nanotubes

    International Nuclear Information System (INIS)

    Full text: Composites made of zirconia (3Y-TZP) reinforced with multiwalled carbon nanotubes (CNTs) were processed by spark plasma sintering with various amounts of CNTs (3Y-TZP/X wt% CNT, X=0, 0.5, 1.5, 3 and 5). High temperature mechanical properties were investigated using mechanical spectroscopy and low stress (8 MPa) creep. The general mechanical loss spectrum consists of a mechanical loss peak at a frequency of about 0.1 Hz, which is superimposed on an exponential increase at low frequency. The absence of a well-marked peak in monolithic 3Y-TZP is justified considering that the restoring force due to the elasticity of neighboring grains decreases at low frequencies or high temperatures. However, with CNT additions the mechanical loss and creep rate decreases and a better resolved peak was observed. These results can be interpreted by the pinning effect of CNTs, which can hinder grain boundary sliding at high temperatures, resulting in a creep resistance improvement. (author)

  10. Unique effect of mechanical crushing on the electrochemical intercalation of lithium in carbons of different morphologies; Effet unique du broyage mecanique sur l`intercalation electrochimique du lithium dans des carbones de morphologies differentes

    Energy Technology Data Exchange (ETDEWEB)

    Salver-Disma, F.; Tarascon, J.M. [Universite de Picardie, 80 - Amiens (France)

    1996-12-31

    Lithium ion batteries use an oxide as a positive electrode and a carbon material as a negative electrode. The performances of carbon electrodes have rapidly evolved during the last years thanks to the substitution of soft carbons of Conoco or MCMB-2510 type by graphites (F-399, MCMB-2528) and then by hard carbons. These high capacity carbons (700 mAh/g) have higher service life and volume capacity than graphites but their irreversible losses are greater (>20%). In this work, materials with similar electrochemical performances are prepared by mechanical crushing. Mechanical crushing allows to obtain a wide range of carbon materials with various morphologies, specific surfaces and levels of disorder. The formation of the passivation film is directly linked with the surface of materials. A reaction scheme of the reversible and irreversible capacities has been defined and has permitted to obtain compounds with reversible capacities of 720 mAh/g (2 lithium for 6 carbon). (J.S.)

  11. Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon

    CERN Document Server

    Garion, Cédric

    2014-01-01

    Despite its good physical properties, the glassy carbon material is not widely used, especially for structural applications. Nevertheless, its transparency to particles and temperature resistance are interesting properties for the applications to vacuum chambers and components in high energy physics. For example, it has been proposed for fast shutter valve in particle accelerator [1] [2]. The mechanical properties have to be carefully determined to assess the reliability of structures in such a material. In this paper, mechanical tests have been carried out to determine the elastic parameters, the strength and toughness on commercial grades. A statistical approach, based on the Weibull’s distribution, is used to characterize the material both in tension and compression. The results are compared to the literature and the difference of properties for these two loading cases is shown. Based on a Finite Element analysis, a statistical approach is applied to define the reliability of a structural component in gl...

  12. Preparation and mechanical properties of chitosan/carbon nanotubes composites.

    Science.gov (United States)

    Wang, Shao-Feng; Shen, Lu; Zhang, Wei-De; Tong, Yue-Jin

    2005-01-01

    Biopolymer chitosan/multiwalled carbon nanotubes (MWNTs) nanocomposites have been successfully prepared by a simple solution-evaporation method. The morphology and mechanical properties of the chitosan/MWNTs nanocomposites have been characterized with field emission scanning electron microscopy (SEM), bright field transmission electron microscopy (TEM), optical microscopy (OM), wide-angle X-ray diffraction (XRD), and tensile as well as nanoindentation tests. The MWNTs were observed to be homogeneously dispersed throughout the chitosan matrix. When compared with neat chitosan, the mechanical properties, including the tensile modulus and strength, of the nanocomposites are greatly improved by about 93% and 99%, respectively, with incorporation of only 0.8 wt % of MWNTs into the chitosan matrix. PMID:16283728

  13. Surface modification of carbon black for the reinforcement of polycarbonate/acrylonitrile–butadiene–styrene blends

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, B.B. [School of Chemical Engineering, Fuzhou University, Fuzhou 350108 (China); Chen, Y. [School of materials Engineering, Fujian Agriculture and Forestry University, Fuzhou 350002 (China); Wang, F. [School of Chemical Engineering, Fuzhou University, Fuzhou 350108 (China); Hong, R.Y., E-mail: rhong@suda.edu.cn [School of Chemical Engineering, Fuzhou University, Fuzhou 350108 (China); College of Chemistry, Chemical Engineering and Materials Science & Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, SIP, Suzhou 215123 (China)

    2015-10-01

    Highlights: • CB was modified through the method of oxygen plasma treatment. • Surface modified CB applied in PC/ABS blends. • The treated CB showed better compatibility in PC/ABS blends. • PC/ABS blends with treated CB showed better mechanical and thermal properties. - Abstract: The surface of carbon black was modified by oxygen plasma treatment for different times (10, 20 and 30 min). In order to increase the applicability of carbon black (CB), functional groups were grafted on the generally inert surface of CB using oxygen plasma. The surface compositional and structural changes that occurred on CB were investigated by SEM, FT-IR, Raman spectroscopy, XRD and BET. Subsequently, CB reinforced polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) composites were prepared by internal batch mixing with the addition of different content of CB (3, 6, 9, 12 wt%). The morphology of PC/ABS/CB (7/3/6 wt%) nanocomposites was studied through scanning electron microscopy. Observations of SEM images showed that the plasma-treated CB had a better dispersion in the blend matrix. Moreover, the mechanical tests showed that the tensile strength and impact strength were improved by 32.4% and 22.5%, respectively, with the addition of plasma-treated CB. In addition, the thermal stability was improved and glass transition temperatures of both PC and ABS increased as shown by TGA and DSC, respectively.

  14. Surface modification of carbon black for the reinforcement of polycarbonate/acrylonitrile–butadiene–styrene blends

    International Nuclear Information System (INIS)

    Highlights: • CB was modified through the method of oxygen plasma treatment. • Surface modified CB applied in PC/ABS blends. • The treated CB showed better compatibility in PC/ABS blends. • PC/ABS blends with treated CB showed better mechanical and thermal properties. - Abstract: The surface of carbon black was modified by oxygen plasma treatment for different times (10, 20 and 30 min). In order to increase the applicability of carbon black (CB), functional groups were grafted on the generally inert surface of CB using oxygen plasma. The surface compositional and structural changes that occurred on CB were investigated by SEM, FT-IR, Raman spectroscopy, XRD and BET. Subsequently, CB reinforced polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) composites were prepared by internal batch mixing with the addition of different content of CB (3, 6, 9, 12 wt%). The morphology of PC/ABS/CB (7/3/6 wt%) nanocomposites was studied through scanning electron microscopy. Observations of SEM images showed that the plasma-treated CB had a better dispersion in the blend matrix. Moreover, the mechanical tests showed that the tensile strength and impact strength were improved by 32.4% and 22.5%, respectively, with the addition of plasma-treated CB. In addition, the thermal stability was improved and glass transition temperatures of both PC and ABS increased as shown by TGA and DSC, respectively

  15. The Adsorption of Polyatomic Molecules on Carbon Surfaces

    Science.gov (United States)

    Burde, Jared T.

    Carbon nanotubes exhibit the structure and chemical properties that make them apt substrates for many adsorption applications. Of particular interest are carbon nanotube bundles, whose unique geometry is conducive to the formation of pseudo-one-dimensional phases of matter, and graphite, whose simple planar structure allows ordered phases to form in the absence of surface effects. Although both of these structures have been the focus of many research studies, knowledge gaps still remain. Much of the work with carbon nanotubes has used simple adsorbates1-43, and there is little kinetic data available. On the other hand, there are many studies of complex molecules adsorbing on graphite; however, there is almost no kinetic data reported for this substrate. We seek to close these knowledge gaps by performing a kinetic study of linear molecules of increasing length adsorbing on carbon nanotube bundles and on graphite. We elucidated the process of adsorption of complex admolecules on carbon nanotube bundles, while at the same time producing some of the first equilibrium results of the films formed by large adsorbates on these structures. We also extended the current knowledge of adsorption on graphite to include the kinetics of adsorption. The kinetic data that we have produced enables a more complete understanding of the process of adsorption of large admolecules on carbon nanotube bundles and graphite. We studied the adsorption of particles on carbon nanotube bundles and graphite using analytical and computational techniques. By employing these methods separately but in parallel, we were able to constantly compare and verify our results. We calculated and simulated the behavior of a given system throughout its evolution and then analyzed our results to determine which system parameters have the greatest effect on the kinetics of adsorption. Our analytical and computational results show good agreement with each other and with the experimental isotherm data provided by

  16. Study of the mechanism of electrochemical hydrogen storage in nano-porous carbons

    International Nuclear Information System (INIS)

    An efficient method of hydrogen storage in nano-porous carbons is its reversible sorption by electrochemical decomposition of a KOH water solution according to the following equation: C + xH2O + xe- → (CHx) + xOH- where (CHx) stands for the hydrogen inserted into the nano-porous carbon during charging and oxidized during discharging. Although various carbon materials have been investigated as hydrogen adsorbents, the information about the storage mechanism as well as the nature of the hydrogen/carbon interaction is still not sufficient. In order to extend the understanding of the process, carbon samples charged electrochemically were investigated by temperature programmed desorption (TPD). The nature of the hydrogen/carbon interaction was studied by electrochemical analysis at different temperatures. The TPD experiments consist of heating the samples from room temperature to 950 C and of quantitative analysis by On-line mass spectrometry, the di-hydrogen evolved from the carbon material. Fig 1 shows the desorption rate of hydrogen during the TPD experiment carried out on an activated carbon cloth loaded at -500 mA/g during 12 hours. The first peak below 300 C corresponds to the desorption of hydrogen fixed on the carbon surface during the charging process. The shape and the position of this peak suggests that the gas is released from sites of different and relatively high energies. The second hydrogen peak results from the reaction between the carbon material and KOH as already mentioned in literature. Carbon materials were also loaded at - 500 mA/g during different times (3, 6, 12 and 24 hours), and then analysed by TPD, showing that the intensity of the peak below 300 C increases with the charging time. Hence TPD gives the direct proof that hydrogen is really stored in nano-porous carbons by this electrochemical process. Moreover, the position of the desorption peaks demonstrates that at least a part of hydrogen presents stronger interactions than in the state

  17. Interaction between Palladium Nanoparticles and Surface-Modified Carbon Nanotubes: Role of Surface Functionalities

    DEFF Research Database (Denmark)

    Zhang, Bingsen; Shao, Lidong; Zhang, Wei;

    2014-01-01

    feature, instability, and subtle response of the components upon application of an external field. Herein, we use insitu TEM, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy techniques to record the interaction in palladium on carbon nanotubes (CNTs) from room temperature to 600...... degrees C. We focus on probing the effects of oxygen and nitrogen-containing functional groups on supported palladium nanoparticles (NPs) in the model catalytic system. The stability of palladium NPs supported on CNTs depends strongly on the surface properties of CNTs. Moreover, the oxygen......-containing functional groups on the CNT surfaces, such as carboxylic acids and anhydrides, have an even stronger interaction with palladium NPs than the nitrogen-containing counterparts. Our work contributes to elucidation of the complex metal-carbon interaction and unlocks potential in activity and selectivity control...

  18. Carbon-Based Nano-Electro-Mechanical-Systems

    Science.gov (United States)

    Kaul, A. B.; Khan, A. R.; Megerian, K. G.; Epp, L.; LeDuc, G.; Bagge, L.; Jennings, A. T.; Jang, D.; Greer, J. R.

    2011-01-01

    We provide an overview of our work where carbon-based nanostructures have been applied to two-dimensional (2D) planar and three-dimensional (3D) vertically-oriented nano-electro-mechanical (NEM) switches. In the first configuration, laterally oriented single-walled nanotubes (SWNTs) synthesized using thermal chemical vapor deposition (CVD) were implemented for forming bridge-type 2D NEMS switches, where switching voltages were on the order of a few volts. In the second configuration, vertically oriented carbon nanofibers (CNFs) synthesized using plasma-enhanced (PE) CVD have been explored for their potential application in 3D NEMS. We have performed nanomechanical measurements on such vertically oriented tubes using nanoindentation to determine the mechanical properties of the CNFs. Electrostatic switching was demonstrated in the CNFs synthesized on refractory metallic nitride substrates, where a nanoprobe was used as the actuating electrode inside a scanning-electron-microscope. The switching voltages were determined to be in the tens of volts range and van der Waals interactions at these length scales appeared significant, suggesting such structures are promising for nonvolatile memory applications. A finite element model was also developed to determine a theoretical pull-in voltage which was compared to experimental results.

  19. Modeling mechanical energy storage in springs based on carbon nanotubes

    International Nuclear Information System (INIS)

    A modeling study of the potential for storing energy in the elastic deformation of springs comprised of carbon nanotubes (CNTs) is presented. Analytic models were generated to estimate the ideal achievable energy density in CNTs subject to axial tension, compression, bending and torsion, taking into account limiting mechanisms such as the strength of individual CNTs, the onset of buckling, and the packing density limitations of CNT groupings. The stored energy density in CNT springs is predicted to be highest under tensile loading, with maximum values more than three orders of magnitude greater than the energy density of steel springs, and approximately eight times greater than the energy density of lithium-ion batteries. Densely packed bundles of precisely aligned, small diameter single-walled carbon nanotubes are identified as the best structure for high performance springs. The conceptual design and modeling of a portable electric power source that stores energy in a CNT spring are presented as tools for studying the potential performance of a system for generating electricity from the CNTs' stored mechanical energy.

  20. Depleted soil carbon and nitrogen pools beneath impervious surfaces

    International Nuclear Information System (INIS)

    Urban soils and vegetation contain large pools of carbon (C) and nitrogen (N) and may sequester these elements at considerable rates; however, there have been no systematic studies of the composition of soils beneath the impervious surfaces that dominate urban areas. This has made it impossible to reliably estimate the net impact of urbanization on terrestrial C and N pools. In this study, we compared open area and impervious-covered soils in New York City and found that the C and N content of the soil (0–15 cm) under impervious surfaces was 66% and 95% lower, respectively. Analysis of extracellular enzyme activities in the soils suggests that recalcitrant compounds dominate the organic matter pool under impervious surfaces. If the differences between impervious-covered and open area soils represent a loss of C and N from urban ecosystems, the magnitude of these losses could offset sequestration in other parts of the urban landscape. - The soils beneath impervious surfaces are depleted in C and N, which may have implications for the energy and nutrient balance of urban ecosystems.

  1. Quantitative Analysis on Carbon Migration in Double-Glow Discharge Plasma Surface Alloying Process

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhen-xia; WANG Cong-zeng; ZHANG Wen-quan; SU Xue-kuan

    2004-01-01

    Carbon migration is of great significance in double-glow discharge plasma surface alloying process, but literature of quantitative analysis about carbon migration is relatively scarce. In this paper differential equations of the carbon and metal concentration distribution were established. By means of differential equations carbon migration was described and a numerical solution was acquired. The computational results fit the experiment results quite well.

  2. Microscopic view of osseointegration and functional mechanisms of implant surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Han, Guang; Shen, Zhijian, E-mail: shen@mmk.su.se

    2015-11-01

    Argon ion beam polishing technique was applied to prepare the cross sections of implants feasible for high resolution scanning electron microscope investigation. The interfacial microstructure between newly formed bone and implants with three modified surfaces retrieved after in vivo test using three different animal models was characterized. By this approach it has become possible to directly observe early bone formation, the increase of bone density, and the evolution of bone structure. The two bone growth mechanisms, distant osteogenesis and contact osteogenesis, can also be distinguished. These direct observations give, at microscopic level, a better view of osseointegration and expound the functional mechanisms of various implant surfaces for osseointegration. - Highlights: • Argon ion beam polishing was used for cross sections of interface. • The interfaces between new bone and implants can be distinguished. • Two bone growth mechanisms were verified. • The functional mechanisms of three modified implants were expounded.

  3. Microscopic view of osseointegration and functional mechanisms of implant surfaces

    International Nuclear Information System (INIS)

    Argon ion beam polishing technique was applied to prepare the cross sections of implants feasible for high resolution scanning electron microscope investigation. The interfacial microstructure between newly formed bone and implants with three modified surfaces retrieved after in vivo test using three different animal models was characterized. By this approach it has become possible to directly observe early bone formation, the increase of bone density, and the evolution of bone structure. The two bone growth mechanisms, distant osteogenesis and contact osteogenesis, can also be distinguished. These direct observations give, at microscopic level, a better view of osseointegration and expound the functional mechanisms of various implant surfaces for osseointegration. - Highlights: • Argon ion beam polishing was used for cross sections of interface. • The interfaces between new bone and implants can be distinguished. • Two bone growth mechanisms were verified. • The functional mechanisms of three modified implants were expounded

  4. Surface Leakage Mechanisms in III-V Infrared Barrier Detectors

    Science.gov (United States)

    Sidor, D. E.; Savich, G. R.; Wicks, G. W.

    2016-09-01

    Infrared detector epitaxial structures employing unipolar barriers exhibit greatly reduced dark currents compared to simple pn-based structures. When correctly positioned within the structure, unipolar barriers are highly effective at blocking bulk dark current mechanisms. Unipolar barriers are also effective at suppressing surface leakage current in infrared detector structures employing absorbing layers that possess the same conductivity type in their bulk and at their surface. When an absorbing layer possesses opposite conductivity types in its bulk and at its surface, unipolar barriers are not solutions to surface leakage. This work reviews empirically determined surface band alignments of III-V semiconductor compounds and modeled surface band alignments of both gallium-free and gallium-containing type-II strained layer superlattice material systems. Surface band alignments are used to predict surface conductivity types in several detector structures, and the relationship between surface and bulk conductivity types in the absorbing layers of these structures is used as the basis for explaining observed surface leakage characteristics.

  5. Surface and mechanical properties of polypropylene/clay nanocomposite

    OpenAIRE

    Dibaei Asl Husein; Abdouss Majid; Torabi Angaji Mahmoud; Haji Aminoddin

    2013-01-01

    Huge consumption of polypropylene in the industries like automotive motivates academic and industrial R&Ds to find new and excellent approaches to improve the mechanical properties of this polymer, which has no degradation effect on other required performance properties like impact resistance, controlled crystallinity, toughness and shrinkage. Nowadays, nanoparticles play a key role in improving the mechanical and surface properties of polypropylene. In this study, three compositions of...

  6. On the mechanics of thin films and growing surfaces

    KAUST Repository

    Holland, M. A.

    2013-05-24

    Many living structures are coated by thin films, which have distinct mechanical properties from the bulk. In particular, these thin layers may grow faster or slower than the inner core. Differential growth creates a balanced interplay between tension and compression and plays a critical role in enhancing structural rigidity. Typical examples with a compressive outer surface and a tensile inner core are the petioles of celery, caladium, or rhubarb. While plant physiologists have studied the impact of tissue tension on plant rigidity for more than a century, the fundamental theory of growing surfaces remains poorly understood. Here, we establish a theoretical and computational framework for continua with growing surfaces and demonstrate its application to classical phenomena in plant growth. To allow the surface to grow independently of the bulk, we equip it with its own potential energy and its own surface stress. We derive the governing equations for growing surfaces of zero thickness and obtain their spatial discretization using the finite-element method. To illustrate the features of our new surface growth model we simulate the effects of growth-induced longitudinal tissue tension in a stalk of rhubarb. Our results demonstrate that different growth rates create a mechanical environment of axial tissue tension and residual stress, which can be released by peeling off the outer layer. Our novel framework for continua with growing surfaces has immediate biomedical applications beyond these classical model problems in botany: it can be easily extended to model and predict surface growth in asthma, gastritis, obstructive sleep apnoea, brain development, and tumor invasion. Beyond biology and medicine, surface growth models are valuable tools for material scientists when designing functionalized surfaces with distinct user-defined properties. © The Author(s) 2013.

  7. Surface and sub-surface degradation of unidirectional carbon fiber reinforced epoxy composites under dry and wet reciprocating sliding

    OpenAIRE

    Dhieb, H.; Buijnsters, J. G.; Eddoumy, F.; Vázquez, Luis; Celis, J. P.

    2013-01-01

    The role of water on the sub-surface degradation of unidirectional carbon fiber reinforced epoxy composite is examined. The correlation between the debonding of carbon fibers at the fiber-epoxy interface, and the wear behavior of the carbon fiber composite are discussed based on an in-depth analysis of the worn surfaces. We demonstrate that a reciprocating sliding performed along an anti-parallel direction to the fiber orientation under dry conditions results in a large degradation by debondi...

  8. Study of the damaging mechanisms of a carbon - carbon composite bonded to copper under thermomechanical loading

    International Nuclear Information System (INIS)

    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)

  9. Study of the damaging mechanisms of a copper / carbon - carbon composite under thermomechanical loading

    International Nuclear Information System (INIS)

    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)

  10. Distinctive sorption mechanisms of 4-chlorophenol with black carbons as elucidated by different pH.

    Science.gov (United States)

    Shih, Yang-hsin; Su, Yuh-fan; Ho, Ren-yu; Su, Po-hsin; Yang, Chien-ying

    2012-09-01

    Black carbon (BC) has been considered as an important sorbent in the environment in recent years due to its high sorption capacity and unique sorption behavior. Sorption characteristics of black carbons from two main sources were investigated to get a better understanding of organic chemical fate in the environment. The present study showed sorption mechanisms of 4-chlorophenol, a common organic contaminant in the surroundings, in two kinds of black carbons, soot surrogate (BC1) and environmental char (BC2) derived from rice straw. Sorption capacity of 4-chlorophenol was much higher in BC1 than on BC2 due to the larger surface area of BC1. However, the surface-area normalized sorption coefficients (sorption capacity per surface area) of BC2 were higher than those of BC1, indicating electrostatic attraction and actions of polar foundational groups on BC2 can react with 4-chlorophenol. With increasing temperature, sorption of BC1 decreased but the sorption of BC2 significantly increased at pH 10 and only slightly increased at pH 4. An exothermic sorption reaction was found for BC1; however, an endothermic reaction of chemical sorption occurred on BC2 at pH 10 due to the electrostatic attraction. At pH4, sorption capacity of BC2 decreased and the small positive sorption enthalpy indicated that less electrostatic attractions occurred because of the neutral form of 4-chlorophenol and the domination of mainly hydrophobic interactions. PMID:22842752

  11. Reaction mechanisms for on-surface synthesis of covalent nanostructures

    Science.gov (United States)

    Björk, J.

    2016-03-01

    In recent years, on-surface synthesis has become an increasingly popular strategy to form covalent nanostructures. The approach has great prospects for facilitating the manufacture of a range of fascinating materials with atomic precision. However, the on-surface reactions are enigmatic to control, currently restricting its bright perspectives and there is a great need to explore how the reactions are governed. The objective of this topical review is to summarize theoretical work that has focused on comprehending on-surface synthesis protocols through studies of reaction mechanisms.

  12. Specific features and the mechanism of the adsorption of carbon monoxide on the surface of films prepared from solid solutions and binary compounds of the InSb-ZnSe system

    International Nuclear Information System (INIS)

    Adsorption properties (towards CO) of solid solutions and binary compounds in the system InSb-ZnSe in the range of 273-553 K were studied and compared. The previously identified acid-base and other physicochemical characteristics of the adsorbents were used for analyzing the results obtained. By comparing adsorption properties of the binary compounds (InSb, ZnSe) and solid solutions (InSb)x(ZnSe)1-x their common features in behavior and specific features of the solid solutions as multicomponent systems were revealed. The mechanism and regularities of the adsorption processes, depending on occurrence conditions and system composition, were ascertained

  13. Nanosized carbon coating formed on different surfaces at the result of carbon emission from graphite under millisecond pulses of glass: Yb, Er laser

    Science.gov (United States)

    Zulina, N. A.; Belikov, A. V.; Skrypnik, A. V.

    2013-11-01

    Possibility of nanosized carbon coatings synthesis on metal and dielectric surfaces at the result of carbon emission from different impurity amount graphite materials under millisecond pulses of Glass: Yb, Er laser. Size of particles and morphology of obtained coatings were investigated with scanning electron microscopy. It was found experimentally, that separated particles of obtained carbon coating has a size about 50-100 nm. Also Raman spectras of nanosized carbon coatings were obtained to investigate a structure. At the result of Raman spectras analysis was found, that coatings are contained of different structural units depends on graphite material impurity amount. For graphite material 99.9% products of laser evaporation are amorphous carbon nanoparticles, and for graphite material with impurity amount about 30% - graphitized nanoparticles. In this article mechanical properties, such as microhardness, of obtained coatings were estimated. It is shown that microhardness of metal surfaces and surface of substrates prepared from human tooth enamel and dentin could be increased significantly due to nanosized carbon coating. Also for tooth enamel and dentin substrates was observed an ability to increase its acid resistance and protective property of obtained coatings to the action of phosphic acid (37.5%).

  14. Influence of the carbon fiber surface microstructure on the surface chemistry generated by a thermo-chemical surface treatment

    Science.gov (United States)

    Vautard, F.; Ozcan, S.; Paulauskas, F.; Spruiell, J. E.; Meyer, H.; Lance, M. J.

    2012-11-01

    Carbon fibers made of textile and aerospace grade polyacrylonitrile precursor fibers were surface treated by a continuous gas phase thermochemical treatment. The surface chemistry generated by the surface treatment was characterized by X-ray photoelectron spectroscopy. The surface and the average entire microstructure of the fibers were characterized by Raman spectroscopy and X-ray diffraction, respectively. Depending on the grade of the precursor, the final surface concentration of oxygen was comprised between 14% and 24%, whereas the typical commercial electrochemical surface treatments led to concentrations of around 8% with the same fibers. The final concentration of oxygen was directly correlated to the size of the crystallites which was a function of the grade of the polyacrylonitrile precursor and to the corresponding surface microstructure. The thermochemical surface treatment enabled a better control of the nature of the oxygen-containing functionalities as well. Whatever the grade of the precursor, desired hydroxyl groups and carboxylic acid functionalities were preferably generated, which is observed to be difficult with electrochemical surface treatments.

  15. Superlubricity mechanism of diamond-like carbon with glycerol. Coupling of experimental and simulation studies

    Energy Technology Data Exchange (ETDEWEB)

    Bouchet, M I De Barros [Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon, 69134 Ecully (France); Matta, C [Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon, 69134 Ecully (France); Le-Mogne, Th [Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon, 69134 Ecully (France); Martin, J Michel [Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon, 69134 Ecully (France); Zhang, Q [Materials and Process Simulation Center, California Institute of Technology, Pasadena CA (United States); III, W Goddard [Materials and Process Simulation Center, California Institute of Technology, Pasadena CA (United States); Kano, M [Nissan Research Center, to Kanagawa Industrial Technology Center, 705-1, 1 Shimo-imaizumi, Ebina, Kanagawa 243-0435 (Japan); Mabuchi, Y [Materials Engineering Department, Nissan Motor Co., Ltd., 6-1, Daikoku-cho, Tsurumi-ku, Yokohama (Japan); Ye, J [Research Department, NISSAN ARC LTD., 1 Natsushima-cho, Yokosuka 237-8523 (Japan)

    2007-11-15

    We report a unique tribological system that produces superlubricity under boundary lubrication conditions with extremely little wear. This system is a thin coating of hydrogen-free amorphous Diamond-Like-Carbon (denoted as ta-C) at 353 K in a ta-C/ta-C friction pair lubricated with pure glycerol. To understand the mechanism of friction vanishing we performed ToF-SIMS experiments using deuterated glycerol and {sup 13}C glycerol. This was complemented by first-principles-based computer simulations using the ReaxFF reactive force field to create an atomistic model of ta-C. These simulations show that DLC with the experimental density of 3.24 g/cc leads to an atomistic structure consisting of a 3D percolating network of tetrahedral (sp{sup 3}) carbons accounting for 71.5% of the total, in excellent agreement with the 70% deduced from our Auger spectroscopy and XANES experiments. The simulations show that the remaining carbons (with sp{sup 2} and sp{sup 1} character) attach in short chains of length 1 to 7. In sliding simulations including glycerol molecules, the surface atoms react readily to form a very smooth carbon surface containing OH-terminated groups. This agrees with our SIMS experiments. The simulations find that the OH atoms are mostly bound to surface sp{sup 1} atoms leading to very flexible elastic response to sliding. Both simulations and experiments suggest that the origin of the superlubricity arises from the formation of this OH-terminated surface.

  16. Influence of surface vacancy defects on the carburisation of Fe 110 surface by carbon monoxide.

    Science.gov (United States)

    Chakrabarty, Aurab; Bouhali, Othmane; Mousseau, Normand; Becquart, Charlotte S; El-Mellouhi, Fedwa

    2016-07-28

    Adsorption and dissociation of gaseous carbon monoxide (CO) on metal surfaces is one of the most frequently occurring processes of carburisation, known as primary initiator of metal dusting corrosion. Among the various factors that can significantly influence the carburisation process are the intrinsic surface defects such as single surface vacancies occurring at high concentrations due to their low formation energy. Intuitively, adsorption and dissociation barriers of CO are expected to be lowered in the vicinity of a surface vacancy, due to the strong attractive interaction between the vacancy and the C atom. Here the adsorption energies and dissociation pathways of CO on clean and defective Fe 110 surface are explored by means of density functional theory. Interestingly, we find that the O adatom, resulting from the CO dissociation, is unstable in the electron-deficit neighbourhood of the vacancy due to its large electron affinity, and raises the barrier of the carburisation pathway. Still, a full comparative study between the clean surface and the vacancy-defected surface reveals that the complete process of carburisation, starting from adsorption to subsurface diffusion of C, is more favourable in the vicinity of a vacancy defect. PMID:27475389

  17. Influence of surface vacancy defects on the carburisation of Fe 110 surface by carbon monoxide

    Science.gov (United States)

    Chakrabarty, Aurab; Bouhali, Othmane; Mousseau, Normand; Becquart, Charlotte S.; El-Mellouhi, Fedwa

    2016-07-01

    Adsorption and dissociation of gaseous carbon monoxide (CO) on metal surfaces is one of the most frequently occurring processes of carburisation, known as primary initiator of metal dusting corrosion. Among the various factors that can significantly influence the carburisation process are the intrinsic surface defects such as single surface vacancies occurring at high concentrations due to their low formation energy. Intuitively, adsorption and dissociation barriers of CO are expected to be lowered in the vicinity of a surface vacancy, due to the strong attractive interaction between the vacancy and the C atom. Here the adsorption energies and dissociation pathways of CO on clean and defective Fe 110 surface are explored by means of density functional theory. Interestingly, we find that the O adatom, resulting from the CO dissociation, is unstable in the electron-deficit neighbourhood of the vacancy due to its large electron affinity, and raises the barrier of the carburisation pathway. Still, a full comparative study between the clean surface and the vacancy-defected surface reveals that the complete process of carburisation, starting from adsorption to subsurface diffusion of C, is more favourable in the vicinity of a vacancy defect.

  18. Surface modification of carbon fibers by a polyether sulfone emulsion sizing for increased interfacial adhesion with polyether sulfone

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Haojie [National Engineering Laboratory for Carbon Fiber Technology, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Shouchun, E-mail: zschun@sxicc.ac.cn [National Engineering Laboratory for Carbon Fiber Technology, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Lu, Chunxiang [National Engineering Laboratory for Carbon Fiber Technology, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)

    2014-10-30

    Highlights: • A polyether sulfone emulsion (PES) sizing was prepared for the first time. • The sizing enhanced the surface activity and wettability of carbon fibers. • Compared to the original sizing, the PES emulsion sizing resulted in an 18.4% increase in the interlaminar shear strength of carbon fiber/PES composites. • Important influences of emulsifier on the fiber surface and composite interface were demonstrated. • The reinforcing mechanisms are the improved fiber surface wettability and interfacial compatibility in composites. - Abstract: Interests on carbon fiber-reinforced thermoplastic composites are growing rapidly, but the challenges with poor interfacial adhesion have slowed their adoption. In this work, a polyether sulfone (PES) emulsion sizing was prepared successfully for increased interfacial adhesion of carbon fiber/PES composites. To obtain a high-quality PES emulsion sizing, the key factor, emulsifier concentration, was studied by dynamic light scattering technique. The results demonstrated that the suitable weight ratio of PES to emulsifier was 8:3, and the resulting PES emulsion sizing had an average particle diameter of 117 nm and Zeta potential of −52.6 mV. After sizing, the surface oxygen-containing functional groups, free energy and wettability of carbon fibers increased significantly, which were advantageous to promote molecular-level contact between carbon fiber and PES. Finally, short beam shear tests were performed to evaluate the interfacial adhesion of carbon fiber/PES composites. The results indicated that PES emulsion sizing played a critical role for the enhanced interfacial adhesion in carbon fiber/PES composites, and a 26% increase of interlaminar shear strength was achieved, because of the improved fiber surface wettability and interfacial compatibility between carbon fiber and PES.

  19. Surface modification of carbon fibers by a polyether sulfone emulsion sizing for increased interfacial adhesion with polyether sulfone

    International Nuclear Information System (INIS)

    Highlights: • A polyether sulfone emulsion (PES) sizing was prepared for the first time. • The sizing enhanced the surface activity and wettability of carbon fibers. • Compared to the original sizing, the PES emulsion sizing resulted in an 18.4% increase in the interlaminar shear strength of carbon fiber/PES composites. • Important influences of emulsifier on the fiber surface and composite interface were demonstrated. • The reinforcing mechanisms are the improved fiber surface wettability and interfacial compatibility in composites. - Abstract: Interests on carbon fiber-reinforced thermoplastic composites are growing rapidly, but the challenges with poor interfacial adhesion have slowed their adoption. In this work, a polyether sulfone (PES) emulsion sizing was prepared successfully for increased interfacial adhesion of carbon fiber/PES composites. To obtain a high-quality PES emulsion sizing, the key factor, emulsifier concentration, was studied by dynamic light scattering technique. The results demonstrated that the suitable weight ratio of PES to emulsifier was 8:3, and the resulting PES emulsion sizing had an average particle diameter of 117 nm and Zeta potential of −52.6 mV. After sizing, the surface oxygen-containing functional groups, free energy and wettability of carbon fibers increased significantly, which were advantageous to promote molecular-level contact between carbon fiber and PES. Finally, short beam shear tests were performed to evaluate the interfacial adhesion of carbon fiber/PES composites. The results indicated that PES emulsion sizing played a critical role for the enhanced interfacial adhesion in carbon fiber/PES composites, and a 26% increase of interlaminar shear strength was achieved, because of the improved fiber surface wettability and interfacial compatibility between carbon fiber and PES

  20. Biomimetic surface modification of polyurethane with phospholipids grafted carbon nanotubes.

    Science.gov (United States)

    Tan, Dongsheng; Liu, Liuxu; Li, Zhen; Fu, Qiang

    2015-08-01

    To improve blood compatibility of polyurethane (PU), phospholipids grafted carbon nanotubes (CNTs) were prepared through zwitterion-mediated cycloaddition reaction and amide condensation, and then were added to the PU as fillers via solution mixing to form biomimetic surface. The properties of phospholipids grafted CNTs (CNT-PC) were investigated by thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and proton nuclear magnetic resonance ((1) H NMR). The results indicated that the phospholipids were grafted onto CNTs in high efficiency, and the hydrophilicity and dispersibility of the modified CNTs were improved effectively. The structures and properties of composites containing CNT-PC were investigated by optical microscope, XPS, and water contact angles. The results indicated that phospholipids were enriched on the surface with addition of 0.1 wt % of CNT-PC, which significantly reduced protein adsorption and platelet adhesion. The method of carrying phospholipids on the nanofiller to modify polymers has provided a promising way of constructing biomimetic phospholipid membrane on the surface to improve blood compatibility. PMID:25630300

  1. Mechanisms regulating osteoblast response to surface microtopography and vitamin D

    Science.gov (United States)

    Bell, Bryan Frederick, Jr.

    A comprehensive understanding of the interactions between orthopaedic and dental implant surfaces with the surrounding host tissue is essential in the design of advanced biomaterials that better promote bone growth and osseointegration of implants. Dental implants with roughened surfaces and high surface energy are well known to promote osteoblast differentiation in vitro and promote increased bone-to-implant contact in vivo. In addition, increased surface roughness increases osteoblasts response to the vitamin D metabolite 1alpha,25(OH)2D3. However, the exact mechanisms mediating cell response to surface properties and 1alpha,25(OH)2D3 are still being elucidated. The central aim of the thesis is to investigate whether integrin signaling in response to rough surface microtopography enhances osteoblast differentiation and responsiveness to 1alpha,25(OH)2D3. The hypothesis is that the integrin alpha5beta1 plays a role in osteoblast response to surface microtopography and that 1alpha,25(OH) 2D3 acts through VDR-independent pathways involving caveolae to synergistically enhance osteoblast response to surface roughness and 1alpha,25(OH) 2D3. To test this hypothesis the objectives of the studies performed in this thesis were: (1) to determine if alpha5beta 1 signaling is required for osteoblast response to surface microstructure; (2) to determine if increased responsiveness to 1alpha,25(OH)2D 3 requires the vitamin D receptor, (3) to determine if rough titanium surfaces functionalized with the peptides targeting integrins (RGD) and transmembrane proteoglycans (KRSR) will enhance both osteoblast proliferation and differentiation, and (4) to determine whether caveolae, which are associated with integrin and 1alpha,25(OH)2D3 signaling, are required for enhance osteogenic response to surface microstructure and 1alpha,25(OH)2D 3. The results demonstrate that integrins, VDR, and caveolae play important roles in mediating osteoblast response to surface properties and 1alpha,25

  2. Influence of processing history on the mechanical properties and electrical resistivity of polycarbonate - multi-walled carbon nanotubes nanocomposites

    Science.gov (United States)

    Choong, Gabriel Y. H.; De Focatiis, Davide S. A.

    2015-05-01

    In this work we investigate the effects of compounding temperature and secondary melt processing on the mechanical response and electrical behaviour of polycarbonate filled with 3 wt% carbon nanotubes. The nanocomposites were melt compounded in an industrial setting at a range of temperatures, and subsequently injection moulded or compression moulded. The surface hardness, uniaxial tensile properties and electrical resistivity were measured. Secondary melt processing is found to be the dominant process in determining the final mechanical properties and resistivity of these materials.

  3. Development of a Landing Mechanism for Asteroids with Soft Surface

    Directory of Open Access Journals (Sweden)

    Zhijun Zhao

    2013-01-01

    Full Text Available A landing mechanism to an asteroid with soft surface is developed. It consists of three landing feet, landing legs, cardan element, damping element, equipment base, anchoring system, and so on. Static structural analysis and modal analysis are carried out to check the strength and natural frequency of the landing mechanism with FEA. Testing platform for the anchoring system is introduced, and then the penetrating and anchoring tests of the anchoring system are carried out in different media. It shows that cohesion of the media has large influence on the penetrating and anchoring performance of the anchoring system. Landing tests of the landing mechanism with different velocities under simulated microgravity environment are carried out on the air-floating platform, and the impact accelerations are measured by the sensors on the landing mechanism. At the same time, these impact accelerations are processed by spectrum analysis to find the natural frequency of the landing mechanism.

  4. The importance of a surface organic layer in simulating permafrost thermal and carbon dynamics

    Science.gov (United States)

    Jafarov, Elchin; Schaefer, Kevin

    2016-03-01

    Permafrost-affected soils contain twice as much carbon as currently exists in the atmosphere. Studies show that warming of the perennially frozen ground could initiate significant release of the frozen soil carbon into the atmosphere. Initializing the frozen permafrost carbon with the observed soil carbon distribution from the Northern Circumpolar Soil Carbon Database reduces the uncertainty associated with the modeling of the permafrost carbon feedback. To improve permafrost thermal and carbon dynamics we implemented a dynamic surface organic layer with vertical carbon redistribution, and introduced dynamic root growth controlled by active layer thickness, which improved soil carbon exchange between frozen and thawed pools. These changes increased the initial amount of simulated frozen carbon from 313 to 560 Gt C, consistent with observed frozen carbon stocks, and increased the spatial correlation of the simulated and observed distribution of frozen carbon from 0.12 to 0.63.

  5. Heliox Improves Carbon Dioxide Removal during Lung Protective Mechanical Ventilation

    Directory of Open Access Journals (Sweden)

    Charlotte J. Beurskens

    2014-01-01

    Full Text Available Introduction. Helium is a noble gas with low density and increased carbon dioxide (CO2 diffusion capacity. This allows lower driving pressures in mechanical ventilation and increased CO2 diffusion. We hypothesized that heliox facilitates ventilation in patients during lung-protective mechanical ventilation using low tidal volumes. Methods. This is an observational cohort substudy of a single arm intervention study. Twenty-four ICU patients were included, who were admitted after a cardiac arrest and mechanically ventilated for 3 hours with heliox (50% helium; 50% oxygen. A fixed protective ventilation protocol (6 mL/kg was used, with prospective observation for changes in lung mechanics and gas exchange. Statistics was by Bonferroni post-hoc correction with statistical significance set at P<0.017. Results. During heliox ventilation, respiratory rate decreased (25±4 versus 23±5 breaths min−1, P=0.010. Minute volume ventilation showed a trend to decrease compared to baseline (11.1±1.9 versus 9.9±2.1 L min−1, P=0.026, while reducing PaCO2 levels (5.0±0.6 versus 4.5±0.6 kPa, P=0.011 and peak pressures (21.1±3.3 versus 19.8±3.2 cm H2O, P=0.024. Conclusions. Heliox improved CO2 elimination while allowing reduced minute volume ventilation in adult patients during protective mechanical ventilation.

  6. Heliox Improves Carbon Dioxide Removal during Lung Protective Mechanical Ventilation.

    Science.gov (United States)

    Beurskens, Charlotte J; Brevoord, Daniel; Lagrand, Wim K; van den Bergh, Walter M; Vroom, Margreeth B; Preckel, Benedikt; Horn, Janneke; Juffermans, Nicole P

    2014-01-01

    Introduction. Helium is a noble gas with low density and increased carbon dioxide (CO2) diffusion capacity. This allows lower driving pressures in mechanical ventilation and increased CO2 diffusion. We hypothesized that heliox facilitates ventilation in patients during lung-protective mechanical ventilation using low tidal volumes. Methods. This is an observational cohort substudy of a single arm intervention study. Twenty-four ICU patients were included, who were admitted after a cardiac arrest and mechanically ventilated for 3 hours with heliox (50% helium; 50% oxygen). A fixed protective ventilation protocol (6 mL/kg) was used, with prospective observation for changes in lung mechanics and gas exchange. Statistics was by Bonferroni post-hoc correction with statistical significance set at P < 0.017. Results. During heliox ventilation, respiratory rate decreased (25 ± 4 versus 23 ± 5 breaths min(-1), P = 0.010). Minute volume ventilation showed a trend to decrease compared to baseline (11.1 ± 1.9 versus 9.9 ± 2.1 L min(-1), P = 0.026), while reducing PaCO2 levels (5.0 ± 0.6 versus 4.5 ± 0.6 kPa, P = 0.011) and peak pressures (21.1 ± 3.3 versus 19.8 ± 3.2 cm H2O, P = 0.024). Conclusions. Heliox improved CO2 elimination while allowing reduced minute volume ventilation in adult patients during protective mechanical ventilation. PMID:25548660

  7. Ni-P-SiC composite coatings electroplated on carbon steel assisted by mechanical attrition

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Ni-P-SiC composite coatings were electroplated on carbon steel substrate assisted by mechanical attrition(MA).The MA action was conducted by dispersing glass balls on the cathodic surface,vibrating in the horizontal direction.The experimental results show that,under the assistant of MA action,the adhesion of Ni-P-SiC coating on the steel substrate can be improved effectively,and the Ni-P-SiC coatings exhibit a crystallized structure and Ni-P matrix can combine tightly with SiC particles,and the hardness and...

  8. Bonding Mechanisms in Resistance Microwelding of 316 Low-Carbon Vacuum Melted Stainless Steel Wires

    Science.gov (United States)

    Khan, M. I.; Kim, J. M.; Kuntz, M. L.; Zhou, Y.

    2009-04-01

    Resistance microwelding (RMW) is an important joining process used in the fabrication of miniature instruments, such as electrical and medical devices. The excellent corrosion resistance of 316 low-carbon vacuum melted (LVM) stainless steel (SS) wire makes it ideal for biomedical applications. The current study examines the microstructure and mechanical properties of crossed resistance microwelded 316LVM wire. Microtensile and microhardness testing was used to analyze the mechanical performance of welds, and fracture surfaces were examined using scanning electron microscopy. Finally, a bonding mechanism is proposed based on optimum joint breaking force (JBF) using metallurgical observations of weld cross sections. Moreover, comparisons with RMWs of Ni, Au-plated Ni, and SUS304 SS wire are discussed.

  9. SURFACE HYDROPHILIC MODIFICATION FOR CARBON/CARBON COMPOSITES AND ITS EFFECT ON THE BONDING STRENGTH OF HYDROXYAPATITE COATING

    OpenAIRE

    LEILEI ZHANG; HEJUN LI; QIANG SONG; KEZHI LI; JINHUA LU; WEI LI; Mikhalovsky, Sergey V.; SHENG CAO

    2014-01-01

    In order to improve the bonding strength of hydroxyapatite coating on carbon/carbon composites, a surface hydrophilic modification was performed on carbon/carbon composites using a combination of H2O2 and FeSO4 ⋅ 7H2O under ultraviolet irradiation. The hydroxyapatite coating was prepared by an ultrasound-assisted electrochemical deposition method. The results showed that the surface hydrophilic modification introduced a large number of oxygen-containing functional groups (C=O, C–O and COOH gr...

  10. Effects of surface treating methods of high-strength carbon fibers on interfacial properties of epoxy resin matrix composite

    Science.gov (United States)

    Ma, Quansheng; Gu, Yizhuo; Li, Min; Wang, Shaokai; Zhang, Zuoguang

    2016-08-01

    This paper aims to study the effects of surface treating methods, including electrolysis of anodic oxidation, sizing and heat treatment at 200 °C, on physical and chemical properties of T700 grade high-strength carbon fiber GQ4522. The fiber surface roughness, surface energy and chemical properties were analyzed for different treated carbon fibers, using atom force microscopy, contact angle, Fourier transformed infrared and X-ray photoelectron spectroscopy, respectively. The results show that the adopted surface treating methods significantly affect surface roughness, surface energy and active chemical groups of the studied carbon fibers. Electrolysis and sizing can increase the roughness, surface energy and chemical groups on surface, while heat treatment leads to decreases in surface energy and chemical groups due to chemical reaction of sizing. Then, unidirectional epoxy 5228 matrix composite laminates were prepared using different treated GQ4522 fibers, and interlaminar shear strength and flexural property were measured. It is revealed that the composite using electrolysis and sizing-fiber has the strongest interfacial bonding strength, indicating the important roles of the two treating processes on interfacial adhesion. Moreover, the composite using heat-treating fiber has lower mechanical properties, which is attributed to the decrease of chemical bonding between fiber surface and matrix after high temperature treatment of fiber.

  11. The mechanism of transforming diamond nanowires to carbon nanostructures

    International Nuclear Information System (INIS)

    The transformation of diamond nanowires (DNWs) with different diameters and geometries upon heating is investigated with density-functional-based tight-binding molecular dynamics. DNWs of 〈100〉 and 〈111〉 oriented cross-section with projected average line density between 7 and 20 atoms Å−1 transform into carbon nanotubes (CNTs) under gradual heating up to 3500–4000 K. DNWs with projected average line density larger than 25 atoms Å−1 transform into double-wall CNTs. The route of transformation into CNTs clearly exhibits three stages, with the intriguing intermediate structural motif of a carbon nanoscroll (CNS). Moreover, the morphology plays an important role in the transformation involving the CNS as one important intermediate motif to form CNTs. When starting with 〈 2-bar 11〉 oriented DNWs with a square cross-section consisting of two {111} facets facing each other, one interesting structure with ‘nano-bookshelf’ shape emerges: a number of graphene ‘shelves’ located inside the CNT, bonding to the CNT walls with sp3 hybridized atoms. The nano-bookshelf structures exist in a wide range of temperatures up to 3000 K. The further transformation from nano-bookshelf structures depends on the strength of the joints connecting shelves with CNT walls. Notably, the nano-bookshelf structure can evolve into two end products: one is CNT via the CNS pathway, the other is graphene transformed directly from the nano-bookshelf structure at high temperature. This work sheds light on the microscopic insight of carbon nanostructure formation mechanisms with the featured motifs highlighted in the pathways. (paper)

  12. Mechanical assessment of grit blasting surface treatments of dental implants.

    Science.gov (United States)

    Shemtov-Yona, K; Rittel, D; Dorogoy, A

    2014-11-01

    This paper investigates the influence of surface preparation treatments of dental implants on their potential (mechanical) fatigue failure, with emphasis on grit-blasting. The investigation includes limited fatigue testing of implants, showing the relationship between fatigue life and surface damage condition. Those observations are corroborated by a detailed failure analysis of retrieved fracture dental implants. In both cases, the negative effect of embedded alumina particles related to the grit-blasting process is identified. The study also comprises a numerical simulation part of the grit blasting process that reveals, for a given implant material and particle size, the existence of a velocity threshold, below which the rough surface is obtained without damage, and beyond which the creation of significant surface damage will severely reduce the fatigue life, thus increasing fracture probability. The main outcome of this work is that the overall performance of dental implants comprises, in addition to the biological considerations, mechanical reliability aspects. Fatigue fracture is a central issue, and this study shows that uncontrolled surface roughening grit-blasting treatments can induce significant surface damage which accelerate fatigue fracture under certain conditions, even if those treatments are beneficial to the osseointegration process. PMID:25173238

  13. Mechanical strength of carbon nanotube-nickel nanocomposites

    International Nuclear Information System (INIS)

    Carbon nanotubes (CNTs), including single-walled CNT (SWCNT) and multi-walled CNT (MWCNT), have been regarded as the stiffest and strongest materials ever developed and are promising reinforcement fillers for developing nanocomposites. However, the scientific community has been puzzled about the reinforcement efficiency. Here we report CNT-reinforced nickel nanocomposites fabricated with an innovative electrochemical co-deposition process for achieving good interfacial bonding between CNT and metallic matrices. Test results show that Ni/SWCNT composite produces a tensile strength as high as 2 GPa, which is more than three times stronger than that of pure nickel. The mechanical strength of Ni/CNT nanocomposites is dependent on CNT addition, while the fracture strain remains similar or better than that of pure nickel. The good reinforcement of CNT/metal nanocomposites is attributed to the good interfacial bonding as well as the stiffer matrix nature

  14. Mechanical and Tribological Properties of Carbon-Based Graded Coatings

    Directory of Open Access Journals (Sweden)

    M. Kot

    2016-01-01

    Full Text Available The paper presents research on coatings with advanced architecture, composed of a Cr/Cr2N ceramic/metal multilayer and graded carbon layers with varying properties from Cr/a-C:H to a-C:N. The microstructure of the coatings was analysed using transmission electron microscopy and Energy Dispersive Spectroscopy, the mechanical properties were tested by nanoindentation, spherical indentation, and scratch testing, and tribological tests were also conducted. The proper selection of subsequent layers in graded coatings allowed high hardness and fracture resistance to be obtained as well as good adhesion to multilayers. Moreover, these coatings have higher wear resistance than single coatings and a friction coefficient equal to 0.25.

  15. Kinetics and mechanisms of interactions of nitrogen and carbon monoxide with liquid niobium

    International Nuclear Information System (INIS)

    The kinetics and mechanisms of interactions of N2 and CO with liquid niobium were investigated in the temperature range of 2,700 to 3,000 K in samples levitated in N2/Ar and CO/Ar streams. The nitrogen absorption and desorption processes were found to be second-order with respect to nitrogen concentration, indicating that the rate controlling step is either the adsorption of nitrogen molecules on the liquid surface or dissociation of absorbed nitrogen molecules into adsorbed atoms. The carbon and oxygen dissolution in liquid niobium from CO gas is an exothermic process and the solubilities of carbon and oxygen (CCe, COe in at%) are related to the temperature and the partial pressure of CO. The reaction CO → [C] + [O] along with the evaporation of niobium oxide takes place during C and O dissolution, whereas C and O desorption occurs via CO evolution only

  16. Preparation of Dispersed Platinum Nanoparticles on a Carbon Nanostructured Surface Using Supercritical Fluid Chemical Deposition

    Directory of Open Access Journals (Sweden)

    Mineo Hiramatsu

    2010-03-01

    Full Text Available We have developed a method of forming platinum (Pt nanoparticles using a metal organic chemical fluid deposition (MOCFD process employing a supercritical fluid (SCF, and have demonstrated the synthesis of dispersed Pt nanoparticles on the surfaces of carbon nanowalls (CNWs, two-dimensional carbon nanostructures, and carbon nanotubes (CNTs. By using SCF-MOCFD with supercritical carbon dioxide as a solvent of metal-organic compounds, highly dispersed Pt nanoparticles of 2 nm diameter were deposited on the entire surface of CNWs and CNTs. The SCF-MOCFD process proved to be effective for the synthesis of Pt nanoparticles on the entire surface of intricate carbon nanostructures with narrow interspaces.

  17. Effect of ion irradiation on the surface, structural and mechanical properties of brass

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Shahbaz; Bashir, Shazia, E-mail: shaziabashir@gcu.edu.pk; Ali, Nisar; Umm-i-Kalsoom,; Yousaf, Daniel; Faizan-ul-Haq,; Naeem, Athar; Ahmad, Riaz; Khlaeeq-ur-Rahman, M.

    2014-04-01

    Highlights: • Brass targets were exposed to carbon ions of energy 2 MeV. • The effect of ion dose has been investigated. • The surface morphology is investigated by SEM analysis. • XRD analysis is performed to reveal structural modification. • Mechanical properties were investigated by tensile testing and microhardness testing. - Abstract: Modifications to the surface, structural and mechanical properties of brass after ion irradiation have been investigated. Brass targets were bombarded by carbon ions of 2 MeV energy from a Pelletron linear accelerator for various fluences ranging from 56 × 10{sup 12} to 26 × 10{sup 13} ions/cm{sup 2}. A scanning electron microscope and X-ray diffractometer were utilized to analyze the surface morphology and crystallographic structure respectively. To explore the mechanical properties e.g., yield stress, ultimate tensile strength and microhardness of irradiated brass, an universal tensile testing machine and Vickers microhardness tester were used. Scanning electron microscopy results revealed an irregular and randomly distributed sputter morphology for a lower ion fluence. With increasing ion fluence, the incoherently shaped structures were transformed into dendritic structures. Nano/micro sized craters and voids, along with the appearance of pits, were observed at the maximum ion fluence. From X-ray diffraction results, no new phases were observed to be formed in the brass upon irradiation. However, a change in the peak intensity and higher and lower angle shifting were observed, which represents the generation of ion-induced defects and stresses. Analyses confirmed modifications in the mechanical properties of irradiated brass. The yield stress, ultimate tensile strength and hardness initially decreased and then increased with increasing ion fluence. The changes in the mechanical properties of irradiated brass are well correlated with surface and crystallographic modifications and are attributed to the generation

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

    Science.gov (United States)

    Rinaldo, Steven G.

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

  19. Surface-induced patterns from evaporating droplets of aqueous carbon nanotube dispersions

    KAUST Repository

    Zeng, Hongbo

    2011-06-07

    Evaporation of aqueous droplets of carbon nanotubes (CNTs) coated with a physisorbed layer of humic acid (HA) on a partially hydrophilic substrate induces the formation of a film of CNTs. Here, we investigate the role that the global geometry of the substrate surfaces has on the structure of the CNT film. On a flat mica or silica surface, the evaporation of a convex droplet of the CNT dispersion induces the well-known "coffee ring", while evaporation of a concave droplet (capillary meniscus) of the CNT dispersion in a wedge of two planar mica sheets or between two crossed-cylinder sheets induces a large area (>mm 2) of textured or patterned films characterized by different short- and long-range orientational and positional ordering of the CNTs. The resulting patterns appear to be determined by two competing or cooperative sedimentation mechanisms: (1) capillary forces between CNTs giving micrometer-sized filaments parallel to the boundary line of the evaporating droplet and (2) fingering instability at the boundary line of the evaporating droplet and subsequent pinning of CNTs on the surface giving micrometer-sized filaments of CNTs perpendicular to this boundary line. The interplay between substrate surface geometry and sedimentation mechanisms gives an extra control parameter for manipulating patterns of self-assembling nanoparticles at substrate surfaces. © 2011 American Chemical Society.

  20. An essential mechanism of heat dissipation in carbon nanotube electronics.

    Science.gov (United States)

    Rotkin, Slava V; Perebeinos, Vasili; Petrov, Alexey G; Avouris, Phaedon

    2009-05-01

    Excess heat generated in integrated circuits is one of the major problems of modern electronics. Surface phonon-polariton scattering is shown here to be the dominant mechanism for hot charge carrier energy dissipation in a nanotube device fabricated on a polar substrate, such as SiO(2). By use of microscopic quantum models, the Joule losses were calculated for the various energy dissipation channels as a function of the electric field, doping, and temperature. The polariton mechanism must be taken into account to obtain an accurate estimate of the effective thermal coupling of the nonsuspended nanotube to the substrate, which was found to be 0.1-0.2 W/(m x K) even in the absence of the bare phononic thermal coupling. PMID:19334687

  1. Surface and mechanical properties of polypropylene/clay nanocomposite

    Directory of Open Access Journals (Sweden)

    Dibaei Asl Husein

    2013-01-01

    Full Text Available Huge consumption of polypropylene in the industries like automotive motivates academic and industrial R&Ds to find new and excellent approaches to improve the mechanical properties of this polymer, which has no degradation effect on other required performance properties like impact resistance, controlled crystallinity, toughness and shrinkage. Nowadays, nanoparticles play a key role in improving the mechanical and surface properties of polypropylene. In this study, three compositions of "Polypropylene/nanoclay", containing 0%, 2% and 5% of nanoclay were prepared in internal mixer. For characterizing the nanoclay dispersion in polymer bulk, TEM and XRD tests were used. For scratch resistance test, scratch lines were created on the load of 900 grain on sheets and SEM images were taken and compared with neat PP scratch image. Crystallinity and mechanical behavior were studied. The results showed that mechanical properties and scratch resistance of the composites have been improved.

  2. XPS study on the surface reaction of uranium metal with carbon monoxide at 200 degree C

    International Nuclear Information System (INIS)

    The surface reaction of uranium metal with carbon monoxide at 200 degree C has been studied by X-ray photoelectron spectroscopy (XPS). The carbon monoxide adsorption on the surface oxide layer resulted in U4f peak shifting to the lower binding energy and the content of oxygen in the oxide is decreased. O/U radio decreases with increasing the exposure of carbon monoxide to the surface layer. The investigation indicated the surface layer of uranium metal was further reduced in the atmosphere of carbon monoxide at high temperature. (3 refs., 5 figs.)

  3. Resonance Scattering Mechanisms in Solids and at Solid Surfaces.

    Science.gov (United States)

    Gerber, Andrew D.

    1987-09-01

    The concept of resonance electron scattering is applied to two very different solid state systems, one at the surface of a solid and one in the bulk. In part I, the problem of resonance scattering of electrons from molecules adsorbed on a metallic surface is examined. An analysis is made of the factors leading to the broadening and energy shift of the e -N _{2} vibrational excitation cross sections as compared to their gas phase analogues. Two effects are found to be important: the breaking of the molecular symmetry by the surface, and the influence of the metallic image potential. Multiple scattering calculations verify that these mechanisms produce a broadening and energy shift in the range of those seen experimentally. In part II, a new mechanism is formulated for the attenuation of ultrasound in mixed valence metals. The mechanism is based on the coupling of phonons to electrons in localized, atomic-like f-levels. The local nature of the interaction gives rise to a large enhancement over the standard (Pippard) result, especially in the limit of short electron mean free path. The mechanism also produces a 'bump' in the attenuation coefficient as a function of temperature, offering an explanation for the experimentally observed 12 K feature of UPt_{3} . A calculation of the attenuation coefficient for a mixed valence lattice reveals further enhancement and structure caused by coherent absorption at f-levels in many unit cells. The effects of degeneracy and correlation are examined in a calculation of the ultrasound attenuation for a system containing dilute Kondo impurities. The unifying theme of this work is the strong interaction between electrons and vibrational modes resulting from the trapping of electrons in localized resonance states. This mechanism has previously been seen to be of great importance for electron-molecule collisions in the gas phase. In the present work, its importance is demonstrated for scattering processes in solids and at solid surfaces

  4. Carbonate Hydroxyapatite and Silicon-Substituted Carbonate Hydroxyapatite: Synthesis, Mechanical Properties, and Solubility Evaluations

    Directory of Open Access Journals (Sweden)

    L. T. Bang

    2014-01-01

    Full Text Available The present study investigates the chemical composition, solubility, and physical and mechanical properties of carbonate hydroxyapatite (CO3Ap and silicon-substituted carbonate hydroxyapatite (Si-CO3Ap which have been prepared by a simple precipitation method. X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, X-ray fluorescence (XRF spectroscopy, and inductively coupled plasma (ICP techniques were used to characterize the formation of CO3Ap and Si-CO3Ap. The results revealed that the silicate (SiO44- and carbonate (CO32- ions competed to occupy the phosphate (PO43- site and also entered simultaneously into the hydroxyapatite structure. The Si-substituted CO3Ap reduced the powder crystallinity and promoted ion release which resulted in a better solubility compared to that of Si-free CO3Ap. The mean particle size of Si-CO3Ap was much finer than that of CO3Ap. At 750°C heat-treatment temperature, the diametral tensile strengths (DTS of Si-CO3Ap and CO3Ap were about 10.8±0.3 and 11.8±0.4 MPa, respectively.

  5. The Mechanism of Surface Chemical Kinetics of Dissolution of Minerals

    Institute of Scientific and Technical Information of China (English)

    谭凯旋; 张哲儒; 等

    1996-01-01

    This paper deals with the mechanism of dissolution reaction kinetics of minerals in aqueous solution based on the theory of surface chemistry.Surface chemical catalysis would lead to an obvous decrease in active energy of dissolution reaction of minerals.The dissolution rate of minerals is controlled by suface adsorption,surface exchange reaction and desorption,depending on pH of the solution and is directly proportional to δHn0+,When controlled by surface adsorption,i.e.,nθ=1,the dissolution rate will decrease with increasing pH;when controlled by surface exchane reaction,i.e.,nθ=0,the dissolution rate is independent of pH;when controlled by desorption,nθis a positive decimal between 0 and 1 in acidic solution and a negative decimal between-1 and 0 in alkaline solution.Dissolution of many minerals is controlled by surface adsorption and/or surface exchange reactions under acid conditions and by desorption under alkaline conditions.

  6. The effects of surface modification on the supercapacitive behaviors of novel mesoporous carbon derived from rod-like hydroxyapatite template

    International Nuclear Information System (INIS)

    Highlights: ► A novel porous carbon with rod-like pore structure was prepared using hydroxyapatite as templates. ► The N and O contained mesoporous carbon was obtained by modified by HNO3 solution. ► The role of hydroxyapatite as double-template and mechanism of surface modification were supposed. ► The modified mesoporous carbon exhibited good electrochemical performances. -- Abstract: Novel mesoporous carbon has been synthesized using rod-like nano-hydroxyapatite (HA) particles as templates, sucrose as carbon precursor by polymerizing, carbonizing and the removal of templates with HCl solution. In the process, HA not only acted as an endotemplate but also an exotemplate producing micropores and mesopores. Subsequently, mesoporous carbon was modified by HNO3 solution with different concentration. The morphology, pore structure, and surface functional groups of the as-obtained samples are analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller method (BET), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The electrochemical performance for electrochemical capacitors is evaluated in a 1 M H2SO4 aqueous solution. The results manifest that the structrue of resultant carbon with a high surface area (719.7 m2 g−1) and large pore volume (1.51 cm3 g−1) is the replica of HA. After modification, the surface area and pore volume mesoporous carbons slightly decrease, while their electrochemical performance have been significantly improved with the increase of the capacitance from 125.7 to 170.1 F g−1 and a non-decayed cycle life over 5000 cycles for HA-C-0.15N

  7. Mechanical response of wall-patterned GaAs surface

    International Nuclear Information System (INIS)

    Wall-patterned GaAs surfaces have been elaborated by photolithography and dry etching. Different surfaces were produced in order to change the aspect ratio of the walls formed at the substrate surface. The mechanical behaviour of individual walls was investigated by nanoindentation and the responses were compared to that of a standard bulk reference (flat surface). Deviation from the bulk response is detected in a load range of 1-25 mN depending on the aspect ratio of the walls. A central plastic zone criterion is proposed in view of transmission electron microscopy images of indented walls and allows the prediction of the response deviation of a given wall if its width is known. The mechanical response of the different types of walls is further investigated in terms of stiffness, total penetration of indenter and apparent hardness, and is scanned in relation to the proximity of a wall side. Overall results show that contact stiffness remains almost unaffected by aspect ratio, while penetration drastically increases because of the free sides of the wall as compared to a flat surface (bulk substrate). The application of substrate patterning for optoelectronic devices is discussed in the perspective of eliminating residual dislocations appearing in mismatched structures

  8. Role of electronic mechanisms in surface erosion and glow phenomena

    International Nuclear Information System (INIS)

    Experimental studies of desorption induced by electronic transitions (DIET) are described. Such studies are producing an increasingly complete picture of the dynamical pathways through which incident electronic energy is absorbed and rechanneled to produce macroscopic erosion and glow. These mechanistic studies can determine rate constants for erosion and glow processes in model materials and provide valuable guidance in materials selection and development. Extensive experiments with electron, photon, and heavy particle irradiation of alkali halides and other simple model materials have produced evidence showing that: (1) surface erosion, consisting primarily in the ejection or desorption of ground-state neutral atoms, occurs with large efficiencies for all irradiated species; (2) surface glow, resulting from the radiative decay of desorbed atoms, likewise occurs for all irradiating species; (3) the typical mechanism for ground-state neutral desorption is exciton formation, followed by relaxation to a permanent, mobile electronic defect which is the precursor to bond-breaking in the surface or near-surface bulk of the material; and (4) the mechanisms for excited atom formation may include curve crossing in atomic collisions, interactions with surface defect or impurity states, or defect diffusion

  9. Effects of deposited pyrolytic carbon on some mechanical properties of zircaloy-4 tubes. Vol. 3

    International Nuclear Information System (INIS)

    Zircaloy cladding tubes are not compatible with the uranium fuel pellets as they suffer from failure due to pelletclad interaction (PCI). A carbon coating, as used in the canadian CANLUB fuel elements, is thought to improve the cladding performance with respect to the PCI problem. In this paper pyrolytic carbon coating was deposited on zircaloy-4 cladding tubes by the thermal cracking of commercial butant gas at the temperature range 250-450 degree C. In order to evaluate the effect of gaseous species on the mechanical properties of the tubes tensile and microhardness testing measurements were performed on samples prepared from the coated tubes. The fractured surface of the tensile zircaloy tubes and the deposited carbon coating, both, were examined by the SEM. The results of the tensile tests of zircaloy-4 tubes indicated that the coating process has insignificant effect on the ultimate strength of the tubes tested. The values of Vickers hardness numbers were not significantly changed across the tubes thickness. The microstructure of deposited carbon, due to the cracking process, was granular in all the temperature range (250-450 degree C) studied. 9 figs., 1 tab

  10. Complete reaction mechanisms of mercury oxidation on halogenated activated carbon.

    Science.gov (United States)

    Rungnim, Chompoonut; Promarak, Vinich; Hannongbua, Supa; Kungwan, Nawee; Namuangruk, Supawadee

    2016-06-01

    The reaction mechanisms of mercury (Hg) adsorption and oxidation on halogenated activated carbon (AC) have been completely studied for the first time using density functional theory (DFT) method. Two different halogenated AC models, namely X-AC and X-AC-X (X=Cl, Br, I), were adopted. The results revealed that HgX is found to be stable-state on the AC edge since its further desorption from the AC as HgX, or further oxidation to HgX2, are energetically unfavorable. Remarkably, the halide type does not significantly affect the Hg adsorption energy but it strongly affects the activation energy barrier of HgX formation, which obviously increases in the order HgIelimination significantly decreases as I-AC>Br-AC>Cl-AC. Thus, the study of the complete reaction mechanism is essential because the adsorption energy can not be used as a guideline for the rational material design in the halide impregnated AC systems. The activation energy is an important descriptor for the predictions of sorbent reactivity to the Hg oxidation process. PMID:26943019

  11. Ultra-fine grinding and mechanical activation of mine waste rock using a high-speed stirred mill for mineral carbonation

    Institute of Scientific and Technical Information of China (English)

    Jia-jie Li; Michael Hitch

    2015-01-01

    CO2 sequestration by mineral carbonation can permanently store CO2 and mitigate climate change. However, the cost and reaction rate of mineral carbonation must be balanced to be viable for industrial applications. In this study, it was attempted to reduce the carbonation costs by using mine waste rock as a feed stock and to enhance the reaction rate using wet mechanical activation as a pre-treatment method. Slurry rheological properties, particle size distribution, specific surface area, crystallinity, and CO2 sequestration reaction efficiency of the initial and mechanically activated mine waste rock and olivine were characterized. The results show that serpentine acts as a catalyst, in-creasing the slurry yield stress, assisting new surface formation, and hindering the size reduction and structure amorphization. Mechanically activated mine waste rock exhibits a higher carbonation conversion than olivine with equal specific milling energy input. The use of a high-speed stirred mill may render the mineral carbonation suitable for mining industrial practice.

  12. The relative importance of decomposition and transport mechanisms in accounting for soil organic carbon profiles

    Science.gov (United States)

    Guenet, B.; Eglin, T.; Vasilyeva, N.; Peylin, P.; Ciais, P.; Chenu, C.

    2013-04-01

    Soil is the major terrestrial reservoir of carbon and a substantial part of this carbon is stored in deep layers, typically deeper than 50 cm below the surface. Several studies underlined the quantitative importance of this deep soil organic carbon (SOC) pool and models are needed to better understand this stock and its evolution under climate and land-uses changes. In this study, we tested and compared three simple theoretical models of vertical transport for SOC against SOC profiles measurements from a long-term bare fallow experiment carried out by the Central-Chernozem State Natural Biosphere Reserve in the Kursk Region of Russia. The transport schemes tested are diffusion, advection and both diffusion and advection. They are coupled to three different formulations of soil carbon decomposition kinetics. The first formulation is a first order kinetics widely used in global SOC decomposition models; the second one, so-called "priming" model, links SOC decomposition rate to the amount of fresh organic matter, representing the substrate interactions. The last one is also a first order kinetics, but SOC is split into two pools. Field data are from a set of three bare fallow plots where soil received no input during the past 20, 26 and 58 yr, respectively. Parameters of the models were optimised using a Bayesian method. The best results are obtained when SOC decomposition is assumed to be controlled by fresh organic matter (i.e., the priming model). In comparison to the first-order kinetic model, the priming model reduces the overestimation in the deep layers. We also observed that the transport scheme that improved the fit with the data depended on the soil carbon mineralisation formulation chosen. When soil carbon decomposition was modelled to depend on the fresh organic matter amount, the transport mechanism which improved best the fit to the SOC profile data was the model representing both advection and diffusion. Interestingly, the older the bare fallow is, the

  13. ANALYSIS OF MATERIAL MECHANICAL PROPERTIES FOR SINGLE-WALLED CARBON NANOTUBES

    Institute of Scientific and Technical Information of China (English)

    Fu Yiming; Xu Xiaoxian

    2005-01-01

    Abstract The carbon-carbon bond between two nearest-neighboring atoms is modeled as a beam and the single-walled carbon nanotubes are treated as the space frame structures in order to analyze the mechanical properties of carbon nanotubes. Based on the theory of TersoffBrenner force field, the energy relationships between the carbon-carbon bond and the beam model are obtained, and the stiffness parameters of the beam are determined. By applying the present model, the Young's moduli of the single-walled carbon nanotubes with different tube diameters are determined. And the present results are compared with available data.

  14. Simulating carbon exchange using a regional atmospheric model coupled to an advanced land-surface model

    Directory of Open Access Journals (Sweden)

    H. W. Ter Maat

    2010-08-01

    Full Text Available This paper is a case study to investigate what the main controlling factors are that determine atmospheric carbon dioxide content for a region in the centre of The Netherlands. We use the Regional Atmospheric Modelling System (RAMS, coupled with a land surface scheme simulating carbon, heat and momentum fluxes (SWAPS-C, and including also submodels for urban and marine fluxes, which in principle should include the dominant mechanisms and should be able to capture the relevant dynamics of the system. To validate the model, observations are used that were taken during an intensive observational campaign in central Netherlands in summer 2002. These include flux-tower observations and aircraft observations of vertical profiles and spatial fluxes of various variables.

    The simulations performed with the coupled regional model (RAMS-SWAPS-C are in good qualitative agreement with the observations. The station validation of the model demonstrates that the incoming shortwave radiation and surface fluxes of water and CO2 are well simulated. The comparison against aircraft data shows that the regional meteorology (i.e. wind, temperature is captured well by the model. Comparing spatially explicitly simulated fluxes with aircraft observed fluxes we conclude that in general latent heat fluxes are underestimated by the model compared to the observations but that the latter exhibit large variability within all flights. Sensitivity experiments demonstrate the relevance of the urban emissions of carbon dioxide for the carbon balance in this particular region. The same tests also show the relation between uncertainties in surface fluxes and those in atmospheric concentrations.

  15. Decoration of Silver Nanoparticles on Multiwalled Carbon Nanotubes: Antibacterial Mechanism and Ultrastructural Analysis

    Directory of Open Access Journals (Sweden)

    Ngo Xuan Dinh

    2015-01-01

    Full Text Available Recently, development of carbon nanocomposites composed of carbon nanostructures and metal nanoparticles has attracted much interests because of their large potential for technological applications such as catalyst, sensor, biomedicine, and disinfection. In this work, we established a simple chemistry method to synthesize multiwalled carbon nanotubes (MWCNTs decorated with silver nanoparticles (Ag-NPs using a modified photochemical reaction (Tollens process. The formation and interaction of Ag-NPs with functionalized groups on the surface of MWCNTs were analyzed by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The average size of Ag-NPs on the MWCNTs was approximately ~7 nm with nearly uniform size distribution. Antibacterial effect of Ag-MWCNTs nanocomposites was evaluated against two pathogenic bacteria including Gram-negative Escherichia Coli and Gram-positive Staphylococcus aureus bacteria. Interaction and bactericidal mechanism of Ag-MWCNTs with tested bacteria was studied by adapting the electron microscopy. Analysis on ultrastructural changes of bacterial cells indicates that antibacterial action mechanism of Ag-MWCNTs is physical interaction with cell membrane, the large formation of cell-Ag-MWCNTs aggregates, and faster destructibility of cell membrane and disruption of membrane function, hence resulting in cells death.

  16. Surface modification in mixture of ZnO + 3%C nanocrystals stimulated by mechanical processing

    Directory of Open Access Journals (Sweden)

    Tetyana Torchynska

    2016-02-01

    Full Text Available The photoluminescence (PL, Raman scattering and SEM images for the mixture of ZnO + 3% C nanocrystals (NCs have been studied before and after of intensive mechanical processing (MP with the aim to identify the nature of defects. The study reflects the diversity of physical processes occurring at MP: amorphizating the surface of ZnO NCs, crushing the individual ZnO NCs and carbon nanoparticles, covering the ZnO NC surface by the graphene layers, the oxidation partially of the graphene layers, carbon and ZnO NCs etc. Three stages of MP have been revealed which are accompanied by PL spectrum transformations: i amorphizating the ZnO NC surface together with the generation of nonradiative recombination centers, ii passivating the ZnO NC surface by the graphene layer with its oxidation partially and iii further crushing of ZnO NCs, the oxidation of ZnO NCs and the formation of graphene (graphite oxides. The new PL band peaked at 2.88 eV has been detected after 9 min of MP. Note that the passivation of the ZnO NC surface by graphene layer can be interesting for future technological applications.

  17. The effects of surface modification on carbon felt electrodes for use in vanadium redox flow batteries

    International Nuclear Information System (INIS)

    Highlights: ► We observed the physical and chemical changes on the surface of carbon felts after various surface modifications. ► The surface area and chemistry of functional groups formed on the surface of carbon felt are critical to determine the kinetics of the redox reactions of vanadium ions. ► By incorporation of the surface modifications into the electrode preparation, the electrochemical activity of carbon felts could be notably enhanced. - Abstract: The surface of carbon felt electrodes has been modified for improving energy efficiency of vanadium redox flow batteries. For comparative purposes, the effects of various surface modifications such as mild oxidation, plasma treatment, and gamma-ray irradiation on the electrochemical properties of carbon felt electrodes were investigated at optimized conditions. The cell energy efficiency was improved from 68 to 75% after the mild oxidation of the carbon felt at 500 °C for 5 h. This efficiency improvement could be attributed to the increased surface area of the carbon felt electrode and the formation of functional groups on its surface as a result of the modification. On the basis of various structural and electrochemical characterizations, a relationship between the surface nature and electrochemical activity of the carbon felt electrodes is discussed.

  18. High-Temperature Oxide Regrowth on Mechanically-Damaged Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL; Lowe, Tracie M [ORNL

    2008-01-01

    Here we report the effects of mechanical damage from a sharp stylus on the regrowth of oxide layers on a Ni-based superalloy known as Pyromet 80A . It was found that the oxide that reformed on the damaged portion of a pre-oxidized surface differed from that which formed on undamaged areas after the equal exposures to elevated temperature in air. These findings have broad implications for modeling the processes of material degradation in applications such as exhaust valves in internal combustion engines because they imply that static oxidation data for candidate materials may not adequately reflect their reaction to operating environments that involve both mechanical contact and oxidation.

  19. Neutralization mechanisms in He{sup +}-Al surface collisions

    Energy Technology Data Exchange (ETDEWEB)

    Bajales, N. [Instituto de Desarrollo Tecnologico para la Industria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina); Ferron, J. [Instituto de Desarrollo Tecnologico para la Industria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina); Depto. de Ing. de Materiales, Facultad de Ingenieria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina)], E-mail: jferron@intec.unl.edu.ar; Goldberg, E.C. [Instituto de Desarrollo Tecnologico para la Industria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina); Depto. de Ing. de Materiales, Facultad de Ingenieria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina)

    2007-10-31

    From a quantum mechanical calculation where the populations of He ground and first excited states are properly taken into account, we can identify for the first time the neutralization to the He first excited state as an operative mechanism in He{sup +}-Al surface collisions. This identification allows us to understand the presence of high energy electrons in the ion induced electron emission spectra, through the inclusion of Auger deexcitation as an electron emission source, as well as to suggest a possible cause for the disagreement still found between theory and experiments in low energy ion scattering (LEIS) for this system.

  20. Neutralization mechanisms in He+-Al surface collisions

    International Nuclear Information System (INIS)

    From a quantum mechanical calculation where the populations of He ground and first excited states are properly taken into account, we can identify for the first time the neutralization to the He first excited state as an operative mechanism in He+-Al surface collisions. This identification allows us to understand the presence of high energy electrons in the ion induced electron emission spectra, through the inclusion of Auger deexcitation as an electron emission source, as well as to suggest a possible cause for the disagreement still found between theory and experiments in low energy ion scattering (LEIS) for this system

  1. A quantitative study of the carbon impurity production mechanisms from an inertial limiter in Tore Supra as determined by visible spectroscopy

    International Nuclear Information System (INIS)

    This document deals with carbon impurity production mechanisms in Tore Supra. The observed temperature dependence of the methane and carbon flux is presented, showing that the methane flux is significantly reduced above surface temperatures of 1100 degree Celsius and negligible above 1300 degree Celsius. Chemical sputtering has a small impact on the C+ flux, while Radiation Enhanced Sublimation has a strong impact on it, but neither of these processes contribute noticeably to the core carbon content. (TEC). 9 refs., 3 figs

  2. Operation Mechanism of Farmers’ Professional Cooperatives from the Point of Low-Carbon Agricultural Products

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    We firstly take a look at internal logic of cluster development of low-carbon agricultural products.In combination with operation features of farmers’ professional cooperatives and actual requirements for cluster development of low-carbon agricultural products;we elaborate establishing benefit allocation mechanism,bearing education and training functions,forming low-carbon value,building low-carbon identification system,as well as realizing low-carbon value.According to these situations,we systematically analyze operation mechanism of farmers’ professional cooperatives suitable for cluster development of low-carbon agricultural products.To promote cluster development of low-carbon agricultural products,we put forward following suggestions,including government guidance and encouragement,social acceptance and active cooperation,and integration into global low-carbon development system to share benefit of low-carbon development.

  3. [Seagrass ecosystems: contributions to and mechanisms of carbon sequestration].

    Science.gov (United States)

    Qiu, Guang-Long; Lin, Hsing-Juh; Li, Zong-Shan; Fan, Hang-Qing; Zhou, Hao-Lang; Liu, Guo-Hua

    2014-06-01

    The ocean's vegetated habitats, in particular seagrasses, mangroves and salt marshes, each capture and store a comparable amount of carbon per year, forming the Earth's blue carbon sinks, the most intense carbon sinks on the planet. Seagrass meadows, characterized by high primary productivity, efficient water column filtration and sediment stability, have a pronounced capacity for carbon sequestration. This is enhanced by low decomposition rates in anaerobic seagrass sediments. The carbon captured by seagrass meadows contributes significantly to the total blue carbon. At a global scale, seagrass ecosystems are carbon sink hot spots and have profound influences on the global carbon cycle. This importance combined with the many other functions of seagrass meadows places them among the most valuable ecosystems in the world. Unfortunately, seagrasses are declining globally at an alarming rate owing to anthropogenic disturbances and climate change, making them also among the most threatened ecosystems on the Earth. The role of coastal systems in carbon sequestration has received far too little attention and thus there are still many uncertainties in evaluating carbon sequestration of global seagrass meadows accurately. To better assess the carbon sequestration of global seagrass ecosystems, a number of scientific issues should be considered with high priorities: 1) more accurate measurements of seagrass coverage at national and global levels; 2) more comprehensive research into species- and location-specific carbon sequestration efficiencies; 3) in-depth exploration of the effects of human disturbance and global climate change on carbon capture and storage by seagrass ecosystems. PMID:25223044

  4. Mechanical surface treatment of steel-Optimization parameters of regime

    Science.gov (United States)

    Laouar, L.; Hamadache, H.; Saad, S.; Bouchelaghem, A.; Mekhilef, S.

    2009-11-01

    Mechanical treatment process by superficial plastic deformation is employed for finished mechanical part surface. It introduces structural modifications that offer to basic material new properties witch give a high quality of physical and geometrical on superficial layers. This study focuses on the application of burnishing treatment (ball burnishing) on XC48 steel and parameters optimisation of treatment regime. Three important parameters were considered: burnishing force ' Py', burnishing feed 'f' and ball radius 'r'. An empirical model has been developed to illustrate the relationship between these parameters and superficial layer characteristics defined by surface roughness ' Ra' and superficial hardness ' Hv'. A program was developed in order to determine the optimum treatment regimes for each characteristic.

  5. Surface roughness of an asphalt concrete and its mechanical behavior

    OpenAIRE

    MOMM, L; DE LA ROCHE, C; Domingues, A.

    2003-01-01

    The surface roughness of asphalt concrete is studied according to the maximum aggregate size and to the equation of the aggregate graduation curve, on asphalt concrete plates made in laboratory. The macrotexture increases when the maximum aggregate size increases and it decreases when the aggregate fine contents increases. The asphalt concrete structural behaviour is evaluated with rutting, complex modulus and fatigue tests. The study shows stronger mechanical performances on the asphalt conc...

  6. India’s Carbon Governance: The Clean Development Mechanism

    OpenAIRE

    Moniz, Maria da Graça Canto

    2013-01-01

    Carbon Governance systems – institutional arrangements in place for mitigating greenhouse gas emissions – are different in emerging countries. Indeed, carbon is the same everywhere but Carbon Governance isn’t: in Brazil, the financial community is actively interested in carbon trading, but Chinese banks have hardly any interest in it; and while the Chinese government takes an active interest in providing capacity to project developers, the Brazilian authorities see their role uniquely as guar...

  7. MECHANICAL AND THERMO–MECHANICAL PROPERTIES OF BI-DIRECTIONAL AND SHORT CARBON FIBER REINFORCED EPOXY COMPOSITES

    Directory of Open Access Journals (Sweden)

    G. AGARWAL

    2014-10-01

    Full Text Available This paper based on bidirectional and short carbon fiber reinforced epoxy composites reports the effect of fiber loading on physical, mechanical and thermo-mechanical properties respectively. The five different fiber loading, i.e., 10wt. %, 20wt. %, 30wt. %, 40wt. % and 50wt. % were taken for evaluating the above said properties. The physical and mechanical properties, i.e., hardness, tensile strength, flexural strength, inter-laminar shear strength and impact strength are determined to represent the behaviour of composite structures with that of fiber loading. Thermo-mechanical properties of the material are measured with the help of Dynamic Mechanical Analyser to measure the damping capacity of the material that is used to reduce the vibrations. The effect of storage modulus, loss modulus and tan delta with temperature are determined. Finally, Cole–Cole analysis is performed on both bidirectional and short carbon fiber reinforced epoxy composites to distinguish the material properties of either homogeneous or heterogeneous materials. The results show that with the increase in fiber loading the mechanical properties of bidirectional carbon fiber reinforced epoxy composites increases as compared to short carbon fiber reinforced epoxy composites except in case of hardness, short carbon fiber reinforced composites shows better results. Similarly, as far as Loss modulus, storage modulus is concerned bidirectional carbon fiber shows better damping behaviour than short carbon fiber reinforced composites.

  8. Mechanical properties and thermal stability of nanocrystallized pure aluminum produced by surface mechanical attrition treatment

    International Nuclear Information System (INIS)

    By means of surface mechanical attrition treatment (SMAT), nanocrystalline surface layers were generated in pure aluminum (Al) sheet. The microstructure of the nanocrystalline surface layer was systematically characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that dislocation slip is the main mechanism for grain refinement of Al with SMAT. The mechanical properties were tested by uniaxial tensile and micro-hardness tests. After SMAT, the yield strength of the nanostructured Al was about two times higher than that of the coarse-grained counterpart, with compromise of elongation. The relationship between microstructure and mechanical properties of Al with SMAT was discussed. Moreover, the Al sample after SMAT exhibits a much faster strain hardening rate reduction and a weaker strain hardening than the one without SMAT. Furthermore, the thermal stability of the nanocrystalline surface layer was studied by isothermal and isochronal annealing treatments at the temperature range from 155 °C to 355 °C. It reveals that such nanocrystalline surface layer of Al exhibits high thermal stability, which can be retained up to 275 °C. The growth kinetics of nano-sized grain of Al subjected to SMAT was investigated

  9. Surface Modification Mechanism of Fine Coal by Electrochemical Methods

    Institute of Scientific and Technical Information of China (English)

    ZHU Hong; WANG Fang-hui; WANG Dian-zuo; OU Ze-shen

    2006-01-01

    In order to reveal the surface modification mechanism of fine coal by electrochemical methods, the structural changes of the coal surface before and after electrochemical modification were investigated by Fourier Transform Infrared Spectra (FTIR) and Raman Spectra. The results show that under certain electrochemical conditions, the oxygen-containing functional group in the coal structure and the oxygen content of absorption could be reduced and the floatability of coal improved. At the same time, the sulfur in the coal was reduced to the hydrophilic S2- which could be separated easily from coal. Thus electrochemical modification methods could be used to change the structure and functional group on the coal surface and to enhance the floatability of coal.

  10. Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, R.F.

    1998-10-15

    All of the technical goals of the World Ocean Circulation Experiment (WOCE) field program which were supported under the Department of Energy research grant ''Measurements of Surface Ocean Carbon Dioxide Partial Pressure During WOCE'' (DE-FG03-90ER60981) have been met. This has included the measurement of the partial pressures of carbon dioxide (C0{sub 2}) and nitrous oxide (N{sub 2}O) in both the surface ocean and the atmosphere on 24 separate shipboard expedition legs of the WOCE Hydrographic Programme. These measurements were made in the Pacific, Indian and Atlantic Oceans over a six-and-a-half year period, and over a distance of nearly 200,000 kilometers of ship track. The total number of measurements, including ocean measurements, air measurements and standard gas measurements, is about 136,000 for each gas, or about 34,000 measurements of each gas in the ocean and in the air. This global survey effort is directed at obtaining a better understanding of the role of the oceans in the global atmospheric budgets of two important natural and anthropogenic modulators of climate through the ''greenhouse effect'', CO{sub 2} and N{sub 2}O, and an important natural and anthropogenic modulator of the Earth's protective ozone layer through catalytic processes in the stratosphere, N{sub 2}O. For both of these compounds, the oceans play a major role in their global budgets. In the case of CO{sub 2}, roughly half of the anthropogenic production through the combustion of fossil fuels has been absorbed by the world's oceans. In the case of N{sub 2}O, roughly a third of the natural flux to the atmosphere originates in the oceans. As the interpretation of the variability in the oceanic distributions of these compounds improves, measurements such as those supported by this research project are playing an increasingly important role in improving our understanding of natural and anthropogenic influences on climate and ozone. (B204)

  11. Differences and similarities between carbon nanotubes and asbestos fibers during mesothelial carcinogenesis: shedding light on fiber entry mechanism.

    Science.gov (United States)

    Nagai, Hirotaka; Toyokuni, Shinya

    2012-08-01

    The emergence of nanotechnology represents an important milestone, as it opens the way to a broad spectrum of applications for nanomaterials in the fields of engineering, industry and medicine. One example of nanomaterials that have the potential for widespread use is carbon nanotubes, which have a tubular structure made of graphene sheets. However, there have been concerns that they may pose a potential health risk due to their similarities to asbestos, namely their high biopersistence and needle-like structure. We recently found that despite these similarities, carbon nanotubes and asbestos differ in certain aspects, such as their mechanism of entry into mesothelial cells. In the study, we showed that non-functionalized, multi-walled carbon nanotubes enter mesothelial cells by directly piercing through the cell membrane in a diameter- and rigidity-dependent manner, whereas asbestos mainly enters these cells through the process of endocytosis, which is independent of fiber diameter. In this review, we discuss the key differences, as well as similarities, between asbestos fibers and carbon nanotubes. We also summarize previous reports regarding the mechanism of carbon nanotube entry into non-phagocytic cells. As the entry of fibers into mesothelial cells is a crucial step in mesothelial carcinogenesis, we believe that a comprehensive study on the differences by which carbon nanotubes and asbestos fibers enter into non-phagocytic cells will provide important clues for the safer manufacture of carbon nanotubes through strict regulation on fiber characteristics, such as diameter, surface properties, length and rigidity. PMID:22568550

  12. Growth mechanisms of carbon nanotrees with branched carbon nanofibers synthesized by plasma-enhanced chemical vapour deposition

    OpenAIRE

    He, Zhanbing; Maurice, Jean-Luc; Lee, Chang Seok; Cojocaru, Costel Sorin; Pribat, D.

    2014-01-01

    Y- and comb-type carbon nanotrees formed from branched carbon nanofibres grown by plasma-enhanced chemical vapour deposition were studied by transmission electron microscopy. Different growth mechanisms are proposed for the two types of nanotrees based on the observed and reconstituted dynamic transformations of the catalyst particles during synthesis. However, the splitting of the larger catalyst particles is required for both kinds of nanotrees, whatever the involved growth mechanism. The c...

  13. Carbon fiber masculinity: Disability and surfaces of homosociality

    OpenAIRE

    Hickey-Moody, Anna Catherine

    2015-01-01

    In this paper I am concerned with instances in which carbon fiber extends performances of masculinity that are attached to particular kinds of hegemonic male bodies. In examining carbon fiber as a prosthetic form of masculinity, I advance three main arguments. Firstly, carbon fiber can be a site of the supersession of disability that is affected through masculinized technology. Disability can be ‘overcome’ through carbon fiber. Disability is often culturally coded as feminine (Pedersen, 2001;...

  14. Carbon nanotube reinforced polylactide-caprolactone copolymer: mechanical strengthening and interaction with human osteoblasts in vitro.

    Science.gov (United States)

    Lahiri, D; Rouzaud, F; Namin, S; Keshri, A K; Valdés, J J; Kos, L; Tsoukias, N; Agarwal, A

    2009-11-01

    This study proposes the use of carbon nanotubes (CNTs) as reinforcement to enhance the mechanical properties of a polylactide-caprolactone copolymer (PLC) matrix. Biological interaction of PLC-CNT composites with human osteoblast cells is also investigated. Addition of 2 wt % CNT shows very uniform dispersion in the copolymer matrix, whereas 5 wt % CNT shows severe agglomeration and high porosity. PLC-2 wt % CNT composite shows an improvement in the mechanical properties with an increase in the elastic modulus by 100% and tensile strength by 160%, without any adverse effect on the ductility up to 240% elongation. An in vitro biocompatibility study on the composites shows an increase in the viability of human osteoblast cells compared to the PLC matrix, which is attributed to the combined effect of CNT content and surface roughness of the composite films. PMID:20356116

  15. Surface contamination and changes of mechanical damping in Berea sandstone

    Science.gov (United States)

    Brunner, Will Marlin

    Small changes in the pore fluid chemistry of Berea sandstone cause significant changes in mechanical damping. A method of detecting contaminants in porous rocks is under ongoing development. Here I report several laboratory measurements done in support of this development, including that of a large difference in mechanical damping between clean and chemically treated Berea sandstone. I develop a model of a surface-chemistry related damping mechanism, and qualitatively compare results from calculations to experimental results. I rule out other damping mechanisms, and conclude that the observed damping is due to surface chemistry effects (contact angle hysteresis). To help verify experimental results, an anelastic structure with calculable damping properties was built. Damping of this structure was measured by the same method used for damping measurements on Berea sandstone. Results from these measurements show good agreement to the calculated response of the structure in the frequency range 0.03--1 Hz.* *This dissertation includes a CD that is compound (contains both a paper copy and a D as part of the dissertation. The CD requires the following applications: Adobe Acrobat.

  16. The effect of surface treatment on the interfacial properties in carbon fibre/epoxy matrix composites

    OpenAIRE

    Bogoeva-Gaceva, Gordana; Janevski, Aco; Dekanski, Aleksandar; D. BUREVSKI

    1995-01-01

    Carbon fibres with different degrees of surface oxidation, as well as epoxy-sized fibres, were used to prepare epoxy composites in order to compare the effects of the fibres surface chemistry on the interfacial properties. X-ray photoelectron spectroscopy, water vapour adsorption measurements and contact angle examination were applied to characterize the carbon fibre surfaces. A correlation was found between the content of primary adsorption sites on the fibre surface and interlaminar shear s...

  17. Adsorbed Natural Gas Storage in Optimized High Surface Area Microporous Carbon

    Science.gov (United States)

    Romanos, Jimmy; Rash, Tyler; Nordwald, Erik; Shocklee, Joshua Shawn; Wexler, Carlos; Pfeifer, Peter

    2011-03-01

    Adsorbed natural gas (ANG) is an attractive alternative technology to compressed natural gas (CNG) or liquefied natural gas (LNG) for the efficient storage of natural gas, in particular for vehicular applications. In adsorbants engineered to have pores of a few molecular diameters, a strong van der Walls force allows reversible physisorption of methane at low pressures and room temperature. Activated carbons were optimized for storage by varying KOH:C ratio and activation temperature. We also consider the effect of mechanical compression of powders to further enhance the volumetric storage capacity. We will present standard porous material characterization (BET surface area and pore-size distribution from subcritical N2 adsorption) and methane isotherms up to 250 bar at 293K. At sufficiently high pressure, specific surface area, methane binding energy and film density can be extracted from supercritical methane adsorption isotherms. Research supported by the California Energy Commission (500-08-022).

  18. Influence of surface topography in the boiling mechanisms

    International Nuclear Information System (INIS)

    Highlights: • Pool boiling heat transfer. • Use of micro-textured surfaces to enhance heat transfer. • Importance of the bubble dynamics and of the interaction mechanisms in the overall heat transfer efficiency. • Effect of the micro-textures on bubble dynamics as a way to enhance pool boiling heat transfer. - Abstract: The present paper addresses the qualitative and quantitative analysis of the pool boiling heat transfer over micro-structured surfaces. The surfaces are made from silicon chips, in the context of pool boiling heat transfer enhancement of immersion liquid cooling schemes for electronic components. The first part of the analysis deals with the effect of the liquid properties. Then the effect of surface micro-structuring is discussed, covering different configurations, from cavities to pillars being the latter used to infer on the potential profit of a fin-like configuration. The use of rough surfaces to enhance pool boiling mainly stands on the arguments that the surface roughness will increase the liquid–solid contact area, thus enhancing the convection heat transfer coefficient and will promote the generation of nucleation sites. However, one should not disregard bubble dynamics. Indeed, the results show a strong effect of bubble dynamics and particularly of the interaction mechanisms in the overall cooling performance of the pair liquid–surface. The inaccurate control of these mechanisms leads to the formation of large bubbles and strong vertical and horizontal coalescence effects promote the very fast formation of a vapor blanket, which causes a steep decrease of the heat transfer coefficient. This effect can be strong enough to prevail over the benefit of increasing the contact area by roughening the surface. For the micro-patterns used in the present work, the results evidence that one can reasonably determine guiding pattern characteristics to evaluate the intensity of the interaction mechanisms and take out the most of the

  19. Mechanism of glucose electrochemical oxidation on gold surface

    KAUST Repository

    Pasta, Mauro

    2010-08-01

    The complex oxidation of glucose at the surface of gold electrodes was studied in detail in different conditions of pH, buffer and halide concentration. As observed in previous studies, an oxidative current peak occurs during the cathodic sweep showing a highly linear dependence on glucose concentration, when other electrolyte conditions are unchanged. The effect of the different conditions on the intensity of this peak has stressed the limitations of the previously proposed mechanisms. A mechanism able to explain the presence of this oxidative peak was proposed. The mechanism takes into account ion-sorption and electrochemical adsorption of OH-, buffer species (K2HPO4/KH2PO4) and halides. © 2010 Elsevier Ltd. All rights reserved.

  20. CO2 adsorption-assisted CH4 desorption on carbon models of coal surface: A DFT study

    Science.gov (United States)

    Xu, He; Chu, Wei; Huang, Xia; Sun, Wenjing; Jiang, Chengfa; Liu, Zhongqing

    2016-07-01

    Injection of CO2 into coal is known to improve the yields of coal-bed methane gas. However, the technology of CO2 injection-enhanced coal-bed methane (CO2-ECBM) recovery is still in its infancy with an unclear mechanism. Density functional theory (DFT) calculations were performed to elucidate the mechanism of CO2 adsorption-assisted CH4 desorption (AAD). To simulate coal surfaces, different six-ring aromatic clusters (2 × 2, 3 × 3, 4 × 4, 5 × 5, 6 × 6, and 7 × 7) were used as simplified graphene (Gr) carbon models. The adsorption and desorption of CH4 and/or CO2 on these carbon models were assessed. The results showed that a six-ring aromatic cluster model (4 × 4) can simulate the coal surface with limited approximation. The adsorption of CO2 onto these carbon models was more stable than that in the case of CH4. Further, the adsorption energies of single CH4 and CO2 in the more stable site were -15.58 and -18.16 kJ/mol, respectively. When two molecules (CO2 and CH4) interact with the surface, CO2 compels CH4 to adsorb onto the less stable site, with a resulting significant decrease in the adsorption energy of CH4 onto the surface of the carbon model with pre-adsorbed CO2. The Mulliken charges and electrostatic potentials of CH4 and CO2 adsorbed onto the surface of the carbon model were compared to determine their respective adsorption activities and changes. At the molecular level, our results showed that the adsorption of the injected CO2 promoted the desorption of CH4, the underlying mechanism of CO2-ECBM.

  1. Molecular dynamics for lateral surface adhesion and peeling behavior of single-walled carbon nanotubes on gold surfaces

    International Nuclear Information System (INIS)

    Highlights: ► Adhesion and peeling behaviors of SWCNTs are investigated by detailed, fully atomistic MD simulations. ► Adhesion energy of SWCNTs are discussed. ► Dynamical behaviors of SWCNTs in low temperature adhesion are analyzed. ► Adhesion strengths of SWCNTs obtained from MD simulations are compared with the predictions of Hamaker theory and JKR model. - Abstract: Functional gecko-inspired adhesives have attracted a lot of research attention in the last decade. In this work, the lateral surface adhesion and normal peeling-off behavior of single-walled carbon nanotubes (SWCNTs) on gold substrates are investigated by performing detailed, fully atomistic molecular dynamics (MD) simulations. The effects of the diameter and adhered length of CNTs on the adhesive properties were systematically examined. The simulation results indicate that adhesion energies between the SWCNTs and the Au surface varied from 220 to 320 mJ m−2 over the reported chirality range. The adhesion forces on the lateral surface and the tip of the nanotubes obtained from MD simulations agree very well with the predictions of Hamaker theory and Johnson–Kendall–Roberts (JKR) model. The analyses of covalent bonds indicate that the SWCNTs exhibited excellent flexibility and extensibility when adhering at low temperatures (∼100 K). This mechanism substantially increases adhesion time compared to that obtained at higher temperatures (300–700 K), which makes SWCNTs promising for biomimetic adhesives in ultra-low temperature surroundings.

  2. Molecular dynamics for lateral surface adhesion and peeling behavior of single-walled carbon nanotubes on gold surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Pei-Hsing, E-mail: phh@mail.npust.edu.tw [Department of Mechanical Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan (China)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Adhesion and peeling behaviors of SWCNTs are investigated by detailed, fully atomistic MD simulations. Black-Right-Pointing-Pointer Adhesion energy of SWCNTs are discussed. Black-Right-Pointing-Pointer Dynamical behaviors of SWCNTs in low temperature adhesion are analyzed. Black-Right-Pointing-Pointer Adhesion strengths of SWCNTs obtained from MD simulations are compared with the predictions of Hamaker theory and JKR model. - Abstract: Functional gecko-inspired adhesives have attracted a lot of research attention in the last decade. In this work, the lateral surface adhesion and normal peeling-off behavior of single-walled carbon nanotubes (SWCNTs) on gold substrates are investigated by performing detailed, fully atomistic molecular dynamics (MD) simulations. The effects of the diameter and adhered length of CNTs on the adhesive properties were systematically examined. The simulation results indicate that adhesion energies between the SWCNTs and the Au surface varied from 220 to 320 mJ m{sup -2} over the reported chirality range. The adhesion forces on the lateral surface and the tip of the nanotubes obtained from MD simulations agree very well with the predictions of Hamaker theory and Johnson-Kendall-Roberts (JKR) model. The analyses of covalent bonds indicate that the SWCNTs exhibited excellent flexibility and extensibility when adhering at low temperatures ({approx}100 K). This mechanism substantially increases adhesion time compared to that obtained at higher temperatures (300-700 K), which makes SWCNTs promising for biomimetic adhesives in ultra-low temperature surroundings.

  3. Study of the mechanism of electrochemical hydrogen storage in nano-porous carbons

    International Nuclear Information System (INIS)

    An efficient method of hydrogen storage in nano-porous carbons is its reversible sorption by electrochemical decomposition of a KOH water solution [1-3] according to the following equation: C + xH2O + xe- → (CHx) + xOH- where (CHx) stands for the hydrogen inserted into the nano-porous carbon during charging and oxidized during discharging. Although various carbon materials have been investigated as hydrogen adsorbents, the information about the storage mechanism as well as the nature of the hydrogen/carbon interaction is still not sufficient. In order to extend the understanding of the process, carbon samples charged electrochemically were investigated by temperature programmed desorption (TPD). The nature of the hydrogen/carbon interaction was studied by electrochemical analysis at different temperatures. The TPD experiments consist of heating the samples from room temperature to 950 C and of quantitative analysis by on-line mass spectrometry, the di-hydrogen evolved from the carbon material. Fig 1 shows the desorption rate of hydrogen during the TPD experiment carried out on an activated carbon cloth loaded at -500 mA/g during 12 hours. The first peak below 300 C corresponds to the desorption of hydrogen fixed on the carbon surface during the charging process. The shape and the position of this peak suggests that this gas is released from sites of different and relatively high energies. The second hydrogen peak results from the reaction between the carbon material and KOH as already mentioned in literature [4]. Carbon materials were also loaded at -500 mA/g during different times (3, 6, 12 and 24 hours), and then analysed by TPD, showing that the intensity of the peak below 300 C increases with the charging time. Hence TPD gives the direct proof that hydrogen is really stored in nano-porous carbons by this electrochemical process. Moreover, the position of the desorption peaks demonstrates that at least a part of hydrogen presents stronger interactions than in

  4. Reaction mechanism of active carbon manufactured by chemicals activation method using potassium carbonate from a raw material of tofu refuse; Okara wo genryo toshi tansankariumu wo mochiita yakuhinfukatsuho niyoru kasseitan seizo niokeru hannokiko

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Jun' ichi; Muroyama, Katsuhiko; Furukawa, Akira; Takemoto, Shin [Kasai University, Osaka (Japan)

    1999-02-05

    The authors attempted to manufacture active carbon using potassium carbonate as an activator from a raw material of tofu refuse. As the results, the active carbon having a large specific surface area of 2,656 m{sup 2}/g at a carbide and an activation temperature of 800 degrees C could be manufactured. It was clarified as follows after investigating the activation mechanism: potassium carbonate changed to potassium peroxide and potassium sulfate in the reaction of tofu refuse and potassium carbonate in the impregnation and dry process. The tofu refuse was changed into a low molecular weight component and a water soluble organic constituent increased. As the results, the weight loss behavior of he tofu refuse changed up to the carbonization - activation temperature of 500 degrees C and then the carbide having a large specific surface area which had a different pore structure of carbide made independently from the tofu refuse was generated. With further increasing the temperature up to 700 degrees C, it was considered that carbon consumed due to a reduction of potassium carbonate by carbon of carbide, the specific surface area was greatly increased, and active carbon having a high specific surface area was manufactured. (translated by NEDO)

  5. Surface modification of activated carbon for enhanced adsorption of perfluoroalkyl acids from aqueous solutions.

    Science.gov (United States)

    Zhi, Yue; Liu, Jinxia

    2016-02-01

    The objective of the research was to examine the effect of increasing carbon surface basicity on uptake of perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) by activated carbon. Granular activated carbons made from coal, coconut shell, wood, and phenolic-polymer-based activated carbon fibers were modified through high-temperature and ammonia gas treatments to facilitate systematical evaluation of the impact of basicity of different origins. Comparison of adsorption isotherms and adsorption distribution coefficients showed that the ammonia gas treatment was more effective than the high-temperature treatment in enhancing surface basicity. The resultant higher point of zero charges and total basicity (measured by total HCl uptake) correlated with improved adsorption affinity for PFOS and PFOA. The effectiveness of surface modification to enhance adsorption varied with carbon raw material. Wood-based carbons and activated carbon fibers showed enhancement by one to three orders of magnitudes while other materials could experience reduction in adsorption towards either PFOS or PFOA. PMID:26469934

  6. Surface heterogeneity effects of activated carbons on the kinetics of paracetamol removal from aqueous solution

    Science.gov (United States)

    Ruiz, B.; Cabrita, I.; Mestre, A. S.; Parra, J. B.; Pires, J.; Carvalho, A. P.; Ania, C. O.

    2010-06-01

    The removal of a compound with therapeutic activity (paracetamol) from aqueous solutions using chemically modified activated carbons has been investigated. The chemical nature of the activated carbon material was modified by wet oxidation, so as to study the effect of the carbon surface chemistry and composition on the removal of paracetamol. The surface heterogeneity of the carbon created upon oxidation was found to be a determinant in the adsorption capability of the modified adsorbents, as well as in the rate of paracetamol removal. The experimental kinetic data were fitted to the pseudo-second order and intraparticle diffusion models. The parameters obtained were linked to the textural and chemical features of the activated carbons. After oxidation the wettability of the carbon is enhanced, which favors the transfer of paracetamol molecules to the carbon pores (smaller boundary layer thickness). At the same time the overall adsorption rate and removal efficiency are reduced in the oxidized carbon due to the competitive effect of water molecules.

  7. Fluid Mechanics of Biological Surfaces and their Technological Application

    Science.gov (United States)

    Bechert, D. W.; Bruse, M.; Hage, W.; Meyer, R.

    A survey is given on fluid-dynamic effects caused by the structure and properties of biological surfaces. It is demonstrated that the results of investigations aiming at technological applications can also provide insights into biophysical phenomena. Techniques are described both for reducing wall shear stresses and for controlling boundary-layer separation. (a) Wall shear stress reduction was investigated experimentally for various riblet surfaces including a shark skin replica. The latter consists of 800 plastic model scales with compliant anchoring. Hairy surfaces are also considered, and surfaces in which the no-slip condition is modified. Self-cleaning surfaces such as that of lotus leaves represent an interesting option to avoid fluid-dynamic deterioration by the agglomeration of dirt. An example of technological implementation is discussed for riblets in long-range commercial aircraft. (b) Separation control is also an important issue in biology. After a few brief comments on vortex generators, the mechanism of separation control by bird feathers is described in detail. Self-activated movable flaps (=artificial bird feathers) represent a high-lift system enhancing the maximum lift of airfoils by about 20%. This is achieved without perceivable deleterious effects under cruise conditions. Finally, flight experiments on an aircraft with laminar wing and movable flaps are presented.

  8. Effect of surface mechanical attrition treatment (SMAT) on microhardness, surface roughness and wettability of AISI 316L

    NARCIS (Netherlands)

    Arifvianto, B.; Suyitno, [No Value; Mahardika, M.; Dewo, P.; Iswanto, P. T.; Salim, U. A.

    2011-01-01

    Surface roughness and wettability are among the surface properties which determine the service lifetime of materials. Mechanical treatments subjected to the surface layer of materials are often performed to obtain the desired surface properties and to enhance the mechanical strength of materials. In

  9. Adsorption of perfluoroalkyl acids by carbonaceous adsorbents: Effect of carbon surface chemistry

    International Nuclear Information System (INIS)

    Adsorption by carbonaceous sorbents is among the most feasible processes to remove perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) from drinking and ground waters. However, carbon surface chemistry, which has long been recognized essential for dictating performance of such sorbents, has never been considered for PFOS and PFOA adsorption. Thus, the role of surface chemistry was systematically investigated using sorbents with a wide range in precursor material, pore structure, and surface chemistry. Sorbent surface chemistry overwhelmed physical properties in controlling the extent of uptake. The adsorption affinity was positively correlated carbon surface basicity, suggesting that high acid neutralizing or anion exchange capacity was critical for substantial uptake of PFOS and PFOA. Carbon polarity or hydrophobicity had insignificant impact on the extent of adsorption. Synthetic polymer-based Ambersorb and activated carbon fibers were more effective than activated carbon made of natural materials in removing PFOS and PFOA from aqueous solutions. - Highlights: • Adsorption of PFOS and PFOA by ten carbonaceous adsorbents were compared. • Surface chemistry of the adsorbents controlled adsorption affinity. • Carbon surface basicity was positively correlated with the extent of PFOS and PFOA uptake. • Carbon polarity or hydrophobicity was not correlated with adsorption affinity. • Synthetic polymer-based adsorbents were more effective in removing PFOS and PFOA. - Carbon surface basicity is the primary factor that influences adsorption affinity of the carbonaceous sorbents for perfluorooctane sulfonic and carboxylic acids

  10. Elucidation of mechanism wear carbon steel with structure of martensite

    Directory of Open Access Journals (Sweden)

    I. A. Vakulenko

    2013-04-01

    Full Text Available Purpose. The purpose of the paper is an estimation of degree of metal hardness change for the railway wheel with martensite structure during rolling. Methodology. As strength characteristic the Rockwell hardness is used. Wear tests were conducted in the conditions of normal loading with (10% and without sliding on the test equipment SMTs-2. Parameters of the fine crystalline structure (tetragonality degree of the crystalline grid, dislocation density, scale of coherent scattering regions, and disturbance value of the crystalline grid of second kind are determined by the methods of X-ray structural analysis. Findings. During operation of the railway wheels with different strength level, origin of defects on the wheel thread is caused by simultaneous action of both the friction forces and the cyclically changing loadings. Considering that formation of damage centers is largely determined by the state of metal volumes near the wheel thread, one should expect the differences in friction processes development at high contact stress for the wheels with different strength level and structural state. Originality. During the wear tests softening effect of carbon steel with martensite quenching structure is obtained. Softening effect equaled 3.5–7% from the level of quenched metal hardness. The softening effect is accompanied by the reduction of tetragonality degree of the crystalline structure of martensite, reduction of coherent scattering regions, dislocation density increase and crystalline grid disturbance of the second kind. Practical value. The results point out the necessity for further studies to clarify the resulted softening effect mechanism.

  11. Energy costs of carbon dioxide concentrating mechanisms in aquatic organisms.

    Science.gov (United States)

    Raven, John A; Beardall, John; Giordano, Mario

    2014-09-01

    Minimum energy (as photon) costs are predicted for core reactions of photosynthesis, for photorespiratory metabolism in algae lacking CO2 concentrating mechanisms (CCMs) and for various types of CCMs; in algae, with CCMs; allowance was made for leakage of CO2 from the internal pool. These predicted values are just compatible with the minimum measured photon costs of photosynthesis in microalgae and macroalgae lacking or expressing CCMs. More energy-expensive photorespiration, for example for organisms using Rubiscos with lower CO2-O2 selectivity coefficients, would be less readily accommodated within the lowest measured photon costs of photosynthesis by algae lacking CCMs. The same applies to the cases of CCMs with higher energy costs of active transport of protons or inorganic carbon species, or greater allowance for significant leakage from the accumulated intracellular pool of CO2. High energetic efficiency can involve a higher concentration of catalyst to achieve a given rate of reaction, adding to the resource costs of growth. There are no obvious mechanistic interpretations of the occurrence of CCMs algae adapted to low light and low temperatures using the rationales adopted for the occurrence of C4 photosynthesis in terrestrial flowering plants. There is an exception for cyanobacteria with low-selectivity Form IA or IB Rubiscos, and those dinoflagellates with low-selectivity Form II Rubiscos, for which very few natural environments have high enough CO2:O2 ratios to allow photosynthesis in the absence of CCMs. PMID:24390639

  12. Mechanical Properties of Triaxial Braided Carbon/Epoxy Composites

    Science.gov (United States)

    Bowman, C. L.; Roberts, G. D.; Braley, M. S.; Xie, M.; Booker, M. J.

    2003-01-01

    In an on-going effort to increase the safety and efficiency of turbine engines, the National Aeronautics and Space Administration is exploring lightweight alternatives to the metal containment structures that currently encase commercial jet engines. Epoxy reinforced with braided carbon fibers is a candidate structural material which may be suitable for an engine case. This paper reports flat-coupon mechanical-property experiments performed to compliment previously reported subcomponent impact testing and analytical simulation of containment structures. Triaxial-braid T700/5208 epoxy and triaxial-braid T700h436 toughened epoxy composites were evaluated. Also, two triaxial-braid architectures (0 degrees plus or minus 60 degrees, and 0 degrees plus or minus 45 degrees) with the M36 resin were evaluated through tension, compression, and shear testing. Tensile behavior was compared between standard straight-sided specimens (ASTM D3039) and bow-tie specimens. Both double-notch shear (ASTM D3846) and Iosepescu (ASTM D5379) tests were performed as well. The M36/O degrees plus or minus 45 degrees configuration yield the best response when measurements were made parallel to the axial tows. Conversely, the M36/0 degrees plus or minus 60 degrees configuration was best when measurements were made perpendicular to the axial tows. The results were used to identify critical properties and to augment the analysis of impact experiments.

  13. Preparation of re-constructed carbon nanosheet powders and their efficient lithium-ion storage mechanism

    International Nuclear Information System (INIS)

    Highlights: • Novel folding re-constructed carbon nanosheet powders (re-CNSs) with unique microstructure and higher lithium-ion storage capacity than prototype graphite powders are prepared. • The wrinkles on the surface of the re-CNSs play an important role on the enhanced lithium-ions storage and provide a new way to improve the capacity of anode materials for lithium ion batteries (LIBs). • A dislocation mechanism is used to describe the role of the wrinkles for the enhanced lithium-ion storage. - Abstract: Based on the re-construction idea of carbon nanomaterials, novel folding re-constructed carbon nanosheets (re-CNSs) with unique microstructure and higher lithium-ion storage capacity than prototype graphite powders are prepared. The nanoscale carbon-fragment suspension is firstly prepared through a successive chemical oxidation of graphite and ultrasonic crushing operation, and the re-CNS powders are then obtained by spray drying the suspension and a subsequent high-temperature reducing process. The as-prepared re-CNSs exhibit a folding appearance with a width of several micrometers, with a maximum initial specific capacity of 903 mAh g−1 for the re-CNSs sample thermally reduced at 500 °C (re-CNSs500). After 100 cycles, the reversible capacity is maintained at about 400 mAh g−1 for the re-CNSs500. The abundant carboxylic and hydroxide groups, edges, and defective sites of individual graphite oxide fragments facilitate the dislocation formation in the re-CNSs. In addition, a dislocation mechanism is thus used to describe the enhanced lithium-ion storage

  14. High capacity mercury adsorption on freshly ozone-treated carbon surfaces

    OpenAIRE

    Manchester, Shawn; Wang, Xuelei; Kulaots, Indrek; Gao, Yuming; Hurt, Robert H.

    2008-01-01

    A set of carbon materials was treated by a choice of common oxidizers to investigate the mercury capture capacities at varying temperature conditions. It was found that ozone treatment dramatically increases the mercury capture capacity of carbon surfaces by factors up to 134, but the activity is easily destroyed by exposure to the atmosphere, to water vapor, or by mild heating. Freshly ozone-treated carbon surfaces are shown to oxidize iodide to iodine in solution and this ability fades with...

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

    OpenAIRE

    Sekkal, W.; Zaoui, A.

    2013-01-01

    Under earth surface conditions, in ocean and natural water, calcium carbonate is ubiquitous, forming anhydrous and hydrous minerals. These hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. Atomistic simulation techniques have been employed here to perform a comprehensive and quantitative study of the structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. Resul...

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

    International Nuclear Information System (INIS)

    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

  17. Effects of Surface Area and Flow Rate on Marine Bacterial Growth in Activated Carbon Columns

    OpenAIRE

    Shimp, Robert J.; Pfaender, Frederic K.

    1982-01-01

    The colonization of granular activated carbon columns by bacteria can have both beneficial and potentially detrimental consequences. Bacterial growth on the carbon surface can remove adsorbed organics and thus partially regenerate the carbon bed. However, growth can also increase the levels of bacteria in the column effluents, which can adversely affect downstream uses of the treated water. This study of a sand column and several activated carbon columns demonstrated that considerable marine ...

  18. Control of Photoluminescence of Carbon Nanodots via Surface Functionalization using Para-substituted Anilines

    OpenAIRE

    Woosung Kwon; Sungan Do; Ji-Hee Kim; Mun Seok Jeong; Shi-Woo Rhee

    2015-01-01

    Carbon nanodots (C-dots) are a kind of fluorescent carbon nanomaterials, composed of polyaromatic carbon domains surrounded by amorphous carbon frames, and have attracted a great deal of attention because of their interesting properties. There are still, however, challenges ahead such as blue-biased photoluminescence, spectral broadness, undefined energy gaps and etc. In this report, we chemically modify the surface of C-dots with a series of para-substituted anilines to control their photolu...

  19. Effect of heat treatment on carbon fiber surface properties and fibers/epoxy interfacial adhesion

    International Nuclear Information System (INIS)

    Carbon fiber surface properties are likely to change during the molding process of carbon fiber reinforced matrix composite, and these changes could affect the infiltration and adhesion between carbon fiber and resin. T300B fiber was heat treated referring to the curing process of high-performance carbon fiber reinforced epoxy matrix composites. By means of X-ray photoelectron spectroscopy (XPS), activated carbon atoms can be detected, which are defined as the carbon atoms conjunction with oxygen and nitrogen. Surface chemistry analysis shows that the content of activated carbon atoms on treated carbon fiber surface, especially those connect with the hydroxyl decreases with the increasing heat treatment temperature. Inverse gas chromatography (IGC) analysis reveals that the dispersive surface energy γSd increases and the polar surface energy γSsp decreases as the heat treatment temperature increases to 200. Contact angle between carbon fiber and epoxy E51 resin, which is studied by dynamic contact angle test (DCAT) increases with the increasing heat treatment temperature, indicating the worse wettability comparing with the untreated fiber. Moreover, micro-droplet test shows that the interfacial shear strength (IFSS) of the treated carbon fiber/epoxy is lower than that of the untreated T300B fiber which is attributed to the decrement of the content of reactive functional groups including hydrogen group and epoxy group.

  20. Surface treatment of 0.20% C carbon steel by high-current pulsed electron beam

    Institute of Scientific and Technical Information of China (English)

    XU Guo-cheng; FU Shi-you; GUAN Qing-feng

    2006-01-01

    A high-current pulsed electron beam(HCPEB) generated on the system of Nadezhda-2 was applied to improve the microstructure and performance of 0.20% C low carbon steel. Surface layers of the samples bombarded by explosive electron beam at different pulses was observed by using electron microscopy. The physical model of the thermal-stress process and related modification mechanism as a result of HCPEB irradiation was also investigated. After HCPEB post treatments, obvious changes in microstructure and significant hardening occur in the depth of 200-250 μm from the surface after HCPEB irradiation. Rapid heating and subsequent rapid solidification induce heavy plastic deformation, which results in that the laminated structure of pearlite is substituted by dispersive rounded-like cementites in the near-surface. The effect of HCPEB treatment can reach more than 500 m depth from the surface. The original crystalline structure is changed to a different degree that grows with the numbers of bombardment, and in the surface layer amorphous states and nanocrystaline structures consisting of grains of γ-phase and cementite are found. The violent stress induced by HCPEB irradiation is the origin of the nanostructured and amorphous structure formation.

  1. Carbon dioxide transport in molten calcium carbonate occurs through an oxo-Grotthuss mechanism via a pyrocarbonate anion

    Science.gov (United States)

    Corradini, Dario; Coudert, François-Xavier; Vuilleumier, Rodolphe

    2016-05-01

    The reactivity, speciation and solvation structure of CO2 in carbonate melts are relevant for both the fate of carbon in deep geological formations and for its electroreduction to CO (to be used as fuel) when solvated in a molten carbonate electrolyte. In particular, the high solubility of CO2 in carbonate melts has been tentatively attributed to the formation of the pyrocarbonate anion, C2O52–. Here we study, by first-principles molecular dynamics simulations, the behaviour of CO2 in molten calcium carbonate. We find that pyrocarbonate forms spontaneously and the identity of the CO2 molecule is quickly lost through O2– exchange. The transport of CO2 in this molten carbonate thus occurs in a fashion similar to the Grotthuss mechanism in water, and is three times faster than molecular diffusion. This shows that Grotthuss-like transport is more general than previously thought.

  2. COST COMPARISONS FOR CARBON DIOXIDE AND MECHANICAL MULTI-TEMPERATURE REFRIGERATION SYSTEMS ON HIGHWAY TRAILERS

    OpenAIRE

    Hoke, K.E.; Buxton, F.K.

    1989-01-01

    Liquid carbon dioxide refrigeration offers a simple, reliable alternative to mechanical transport refrigeration for food delivery trailers operated in an upper midwestern area that could be cost effective when the refrigerant's cost is $87 or less per ton. Operating and ownership costs were compared for both systems. Under the conditions of the study, a carbon dioxide system was more economical than a mechanical refrigeration system when the cost of the liquid carbon dioxide was $87 per ton o...

  3. Characterization of Carbon Mat Thermoplastic Composites: Flow and Mechanical Properties

    OpenAIRE

    Caba, Aaron C.

    2005-01-01

    Carbon mat thermoplastics (CMT) consisting of 12.7 mm or 25.4 mm long, 7.2 micrometer diameter, chopped carbon fibers in a polypropylene (PP) or poly(ethylene terephthalate) (PET) thermoplastic matrix were manufactured using the wetlay technique. This produces a porous mat with the carbon fibers well dispersed and randomly oriented in a plane. CMT composites offer substantial cost and weight savings over typical steel construction in new automotive applications. In production vehicles, aut...

  4. Investigations on mechanical and two-body abrasive wear behaviour of glass/carbon fabric reinforced vinyl ester composites

    International Nuclear Information System (INIS)

    The aim of the research article is to study the mechanical and two-body abrasive wear behaviour of glass/carbon fabric reinforced vinyl ester composites. The measured wear volume loss increases with increase in abrading distance/abrasive particle size. However, the specific wear rate decreases with increase in abrading distance and decrease in abrasive particle size. The results showed that the highest specific wear rate is for glass fabric reinforced vinyl ester composite with a value of 10.89 x 10-11 m3/Nm and the lowest wear rate is for carbon fabric reinforced vinyl ester composite with a value of 4.02 x 10-11 m3/Nm. Mechanical properties were evaluated and obtained values are compared with the wear behaviour. The worn surface features have been examined using scanning electron microscope (SEM). Photomicrographs of the worn surfaces revealed higher percentage of broken glass fiber as compared to carbon fiber. Also better interfacial adhesion between carbon and vinyl ester in carbon reinforced vinyl ester composite was observed.

  5. Thermo-mechanical correlations to erosion performance of short carbon fibre reinforced vinyl ester resin composites

    International Nuclear Information System (INIS)

    Research highlights: → Composite with 30 wt.% of short carbon fibres exhibit highest energy dissipation. → Optimum erosion resistance conditions have been found. → A direct correlation emerged between erosive wear rate and loss-modulus inverse. → Mechanistic equivalence between erosion and dynamic loading modes is established. -- Abstract: Thermo-mechanical properties and erosion performance of short carbon fibre reinforced vinyl ester resin based isotropic polymer composites with four different fibre weight fractions have been investigated. The storage, loss and damping characteristics were analysed to assess the energy absorption/viscous recoverable energy dissipation and reinforcement efficiency of the composites as a function of fibre content in the temperature range of 0-140 oC. The composite with 30 wt.% of short carbon fibres has been observed to exhibit superior thermo-mechanical response with highest energy dissipation/damping ability accompanied with a constant storage modulus without any substantial decay till 60 oC. The erosion rates (Er) of these composites are evaluated at different impingement angles (30-90o), fibre loadings (20-50 wt.%), impact velocities (43-76 m/s), stand-off distances (55-85 mm) and erodent sizes (250-600 μm) following the erosion test schedule in an air jet type test rig. An optimal parameter combination is determined and subsequently validated for erosion rate minimization following Taguchi method and by conducting confirmation experiments. A correlation between the loss-modulus inverse and the erosion rate has been observed which conceptually establishes a possible mechanistic equivalence between erosion and dynamic mechanical loading modes. The morphologies of eroded surface are examined by the scanning electron microscopy to investigate the nature of wear-craters, material damage mode and other qualitative attributes responsible for promoting erosion.

  6. Influence of carbon monoxide to the surface layer of uranium metal and its oxides

    International Nuclear Information System (INIS)

    The surface structures of uranium metal and triuranium octaoxide (U3O8) and the influence of carbon monoxide to the surface layers have been studied by X-ray photoelectron spectroscopy (XPS). After exposure to carbon monoxide, contents of oxygen in the surface oxides of uranium metal and U3O8 are decreased and O/U ratios decrease 7.2%, 8.0% respectively. The investigation indicated the surface layers of uranium metal and its oxides were forbidden to further oxidation in the atmosphere of carbon monoxide. (11 refs., 9 figs., 2 tabs.)

  7. Coating curly carbon nanotubes with monocrystalline Zn(BO2)2 and the mechanism of straightening the tubes

    Institute of Scientific and Technical Information of China (English)

    LIU; Jinzhang; YAN; Pengxun; YUE; Guanghui

    2006-01-01

    We overgrew single-crystalline Zn(BO2)2 coatings on carbon nanotubes (CNTs) for the first time. Scanning electron microscopy and transmission electron microscopy analyses revealed that the carbon nanotube-zinc borate composite rods are from tens to hundreds of nm in diameter. It is notable that the original curly tubes were straightened by the monocrystalline coatings. In addition, the crystal nucleation and growth on the surface of CNT were explained. We set a two-dimensional model, which is based on our experimental result, to qualitatively explain the mechanism of straightening the curly tubes by coating them with single-crystals.

  8. Carbon activation process for increased surface accessibility in electrochemical capacitors

    Science.gov (United States)

    Doughty, Daniel H.; Eisenmann, Erhard T.

    2001-01-01

    A process for making carbon film or powder suitable for double capacitor electrodes having a capacitance of up to about 300 F/cm.sup.3 is disclosed. This is accomplished by treating in aqueous nitric acid for a period of about 5 to 15 minutes thin carbon films obtained by carbonizing carbon-containing polymeric material having a high degree of molecular directionality, such as polyimide film, then heating the treated carbon film in a non-oxidizing atmosphere at a non-graphitizing temperature of at least 350.degree. C. for about 20 minutes, and repeating alternately the nitric acid step and the heating step from 7 to 10 times. Capacitors made with this carbon may find uses ranging from electronic devices to electric vehicle applications.

  9. Analysis of interlaminar fracture toughness and damage mechanisms in composite laminates reinforced with sprayed multi-walled carbon nanotubes

    KAUST Repository

    Almuhammadi, Khaled

    2014-01-01

    The present work is focused on the nanoreinforcement of prepreg based carbon fiber composite laminates to improve delamination resistance. Functionalized multi-walled carbon nanotubes (MWCNTs) were dispersed over the interface between prepreg layers through solvent spraying and the resulting mode I interlaminar fracture toughness was determined. For comparison, baseline samples with neat prepregs were also prepared. Results indicate that the introduction of functionalized MWCNTs can favorably affect the interlaminar fracture toughness, and the associated mechanisms of failure have been investigated. The manufacturing procedures and the interfacial reinforcing mechanism were explored by analyzing (i) the wettability between CNTs-solvent solution and prepreg surface, (ii) CNTs dispersion and (iii) the fractured surfaces through high resolution scanning electron microscopy and Raman mapping. © 2013 Elsevier Ltd.

  10. Carbon and Oxygen Isotopic Composition of Surface-Sediment Carbonate in Bosten Lake (Xinjiang, China) and its Controlling Factors

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chengjun; Steffen MISCHKE; ZHENG Mianping; Alexander PROKOPENKO; GUO Fangqin; FENG Zhaodong

    2009-01-01

    and carbonate mineralogy influence of the surface-sediment carbonate in Bosten Lake. The lake water residence time and the CO2 exchange between the atmosphere and the water body control the carbon and oxygen isotope composition of the carbonate sediment. In addition, organic matter pollution and decomposition result in the abnormally low carbon isotope values of the lake surface-sediment carbonate.

  11. Production and mechanical properties of aligned multi-walled carbon nanotubes-M140 composites

    Institute of Scientific and Technical Information of China (English)

    XU ShiLang; GAO LiangLi; JIN WeiJun

    2009-01-01

    This study investigated the production of M140, aligned multi-walled carbon nanotubes (A-MWNTs)reinforced M140 composites (A-MWNTs-M140) and their mechanical properties including their compressive and bending properties as well as their microstructure characteristic of bend fracture surface.M140 was first produced by speed change mixing technics with commercial materials, water-bath curing at normal temperature. In addition, two different A-MWNTs dispersions including carbonyl dispersions of A-MWNTs (C-A-MWNTs) and aqueous dispersions of A-MWNTs (A-A-MWNTs) with the addition of 0.01wt% A-MWNTs were utilized to obtain enhanced mechanical properties with respect to plain M140. The results indicated that the use of A-MWNTs dispersions allows increasing compressive strength and flexural strength by 8.4% and 5.4%, respectively for the C-A-MWNTs-M140, and by 15.9% and 20.7% for the A-A-MWNTs-M140, respectively. The SEM and EPMA examinations of fracture surface also showed that the bond interface between the nanotubes and matrix is moderate and the main reinforcing mechanisms are microfilling effect, CNTs pull-out and debond. The aqueous dispersion of A-MWNTs is an appropriate method and is more compatible with the M140.

  12. Production and mechanical properties of aligned multi-walled carbon nanotubes-M140 composites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    This study investigated the production of M140, aligned multi-walled carbon nanotubes (A-MWNTs) reinforced M140 composites (A-MWNTs-M140) and their mechanical properties including their compressive and bending properties as well as their microstructure characteristic of bend fracture surface. M140 was first produced by speed change mixing technics with commercial materials, water-bath curing at normal temperature. In addition, two different A-MWNTs dispersions including carbonyl disper- sions of A-MWNTs (C-A-MWNTs) and aqueous dispersions of A-MWNTs (A-A-MWNTs) with the addition of 0.01wt% A-MWNTs were utilized to obtain enhanced mechanical properties with respect to plain M140. The results indicated that the use of A-MWNTs dispersions allows increasing compressive strength and flexural strength by 8.4% and 5.4%, respectively for the C-A-MWNTs-M140, and by 15.9% and 20.7% for the A-A-MWNTs-M140, respectively. The SEM and EPMA examinations of fracture surface also showed that the bond interface between the nanotubes and matrix is moderate and the main reinforcing mechanisms are microfilling effect, CNTs pull-out and debond. The aqueous dispersion of A-MWNTs is an appropriate method and is more compatible with the M140.

  13. Pressureless sintering and mechanical properties of hydroxyapatite/functionalized multi-walled carbon nanotube composite.

    Science.gov (United States)

    Abden, M J; Afroze, J D; Alam, M S; Bahadur, N M

    2016-10-01

    This work aims to study the optimum sintering conditions of hydroxyapatite/functionalized multi-walled carbon nanotube (HA/f-MWCNT) composite with improved mechanical properties for bone implant applications using a pressureless sintering technique. The carboxyl functional group (COOH) introduced by the acid treatment on the MWCNT surface by which HA molecules are grafted onto the surface of functionalized MWCNT with strong interfacial bonding. The composite exhibits a lower hemolytic rate of 1.27%. The flexible nature of f-MWCNT makes them bend and attached to the HA grains, indicates that f-MWCNT bear significant stress by sharing a portion of the load and it leads to improve their mechanical properties. The maximum Vickers hardness of 3.6GPa is obtained for the HA/f-MWCNT composite sintered at 1100°C, whereas the highest compressive strength of 481.7MPa and fracture toughness of 2.38MPa.m(1/2) achieved after sintering at 1150°C. This study demonstrated that HA/f-MWCNT composite create suitable structures by vacuum pressureless sintering technique to satisfy the mechanical requirements for bone tissues. PMID:27287138

  14. Improvement of Mechanical Properties on a Surface of Bulk Ceramics

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Kraus, L.

    Trollhättan : University West, 2009 - (Sudarshan, T.; Nylen, P.), s. 247-254 ISBN 978-0-9817065-1-1. [International Conference on Surface Modification Technologies SMT22/22./. Trollhättan (SE), 22.09.2008-24.09.2008] R&D Projects: GA AV ČR 1QS200430560 Institutional research plan: CEZ:AV0Z20430508 Keywords : Bulk ceramics * plasma post-treatment * diode laser * wear resistance * mechanical testing Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  15. Piezoresistivity of mechanically drawn single-walled carbon nanotube (SWCNT) thin films-: mechanism and optimizing principle

    Science.gov (United States)

    Obitayo, Waris

    The individual carbon nanotube (CNT) based strain sensors have been found to have excellent piezoresistive properties with a reported gauge factor (GF) of up to 3000. This GF on the other hand, has been shown to be structurally dependent on the nanotubes. In contrast, to individual CNT based strain sensors, the ensemble CNT based strain sensors have very low GFs e.g. for a single walled carbon nanotube (SWCNT) thin film strain sensor, GF is ~1. As a result, studies which are mostly numerical/analytical have revealed the dependence of piezoresistivity on key parameters like concentration, orientation, length and diameter, aspect ratio, energy barrier height and Poisson ratio of polymer matrix. The fundamental understanding of the piezoresistive mechanism in an ensemble CNT based strain sensor still remains unclear, largely due to discrepancies in the outcomes of these numerical studies. Besides, there have been little or no experimental confirmation of these studies. The goal of my PhD is to study the mechanism and the optimizing principle of a SWCNT thin film strain sensor and provide experimental validation of the numerical/analytical investigations. The dependence of the piezoresistivity on key parameters like orientation, network density, bundle diameter (effective tunneling area), and length is studied, and how one can effectively optimize the piezoresistive behavior of a SWCNT thin film strain sensors. To reach this goal, my first research accomplishment involves the study of orientation of SWCNTs and its effect on the piezoresistivity of mechanically drawn SWCNT thin film based piezoresistive sensors. Using polarized Raman spectroscopy analysis and coupled electrical-mechanical test, a quantitative relationship between the strain sensitivity and SWCNT alignment order parameter was established. As compared to randomly oriented SWCNT thin films, the one with draw ratio of 3.2 exhibited ~6x increase on the GF. My second accomplishment involves studying the

  16. High intensity pulsed plasma beams modification of surface morphology and mechanical properties of steels

    International Nuclear Information System (INIS)

    Surface engineering technology is well-known method used to obtain, investigate and apply surface layers with different improved properties, than the base material. High energy ion or plasma pulse is one of contemporary intensively investigated methods used for surface modification. Achieved up to now results show, that steel irradiation with high-intensive pulsed beam can change surface morphology and the mechanical properties of material. The aim of this work was to investigate the correlation of carbon concentration and type of ion used on those changes. Intense pulsed nitrogen and argon plasma beam were used for modification of constructional, unalloyed steels. The duration of pulse was in the range of microseconds, density of energy was about 6 J/cm2. Each sample was irradiated with 5 impulses. Heating and cooling processes were on non-equilibrium type. The surface morphology was analysed using scanning electron microscopy. Measurements of surface roughness, hardness HV5 and wear resistance (the pin-on-disc method) were carried out. Obtained results are presented in this work. (author)

  17. DFT Thermodynamic Research of the Pyrolysis Mechanism of the Carbon Matrix Precursor Toluene for Carbon Material

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Based on the experiments, the standard enthalpy △H of the possible pyrolysis reactions of the carbon matrix precursor toluene was investigated by means of DFT method UB3LYP/ 3-21G* (based on semi-empirical method UAM1 and ab initio method UHF/3-21G* ). The com putation results with UB3LYP/3-21G* coincide with the experimental values well. Then, the mechanism for all types of the pyrolysis reactions of toluene was studied by UB3LYP/3-2lG*. The geometries of the reactant and the product radicals were optimized, meanwhile, the standard thermodynamic parameters of the pyrolysis reaction at different temperatures (298, 773, 843, 963 and 1 073 K) were calculated. The thermodynamic computation result shows that when the pyrolysis temperature of toluene is lower than 963 K, the reaction path supported by thermody namics is that the C-H bond of the methyl on the benzene ring breaks and bitoluene form, while the temperature increases (about 1 073 K), the thermodynamic calculation result turns to sup port the reaction path producing phenyl radicals and methyl radicals. This mechanism is in accord with the experiments.

  18. Self-Diffusion Mechanisms of Adatom on Al(001), (011)and (111) Surfaces

    Institute of Scientific and Technical Information of China (English)

    孙煜杰; 李家明

    2003-01-01

    Using the first-principle molecular dynamical calculations, we have studied the adatom self-diffusion mechanisms on fcc Al (001), (011) and (111) surfaces. On each surface, there are several mechanisms, among which there is one favour mechanism with the minimum barrier energy. The atomic exchange mechanism along the [100]direction on the (001) surface, the long bridge hopping mechanism along the [110] direction on the (011) surface,and the bridge hopping mechanism along the [112] direction on the (111) surface are the favour mechanisms. The activation energy profiles for various self-diffusion mechanisms are studied in details.

  19. Image formation mechanisms in scanning electron microscopy of carbon nanotubes,and retrieval of their intrinsic dimensions.

    OpenAIRE

    Jackman, Henrik; Krakhmalev, Pavel; Svensson, Krister

    2013-01-01

    We present a detailed analysis of the image formation mechanisms that are involved in the imaging of carbon nanotubes with scanning electron microscopy (SEM). We show how SEM images can be modelled by accounting for surface enhancement effects together with the absorption coefficient for secondary electrons, and the electron-probe shape. Images can then be deconvoluted, enabling retrieval of the intrinsic nanotube dimensions. Accurate estimates of their dimensions can thereby be obtained even...

  20. The research on the interfacial compatibility of polypropylene composite filled with surface treated carbon fiber

    Energy Technology Data Exchange (ETDEWEB)

    Li, J., E-mail: lijian2006d@sina.com [School of Mechanical and Electronic Engineering, Shanghai Second Polytechnic University, Shanghai 201209 (China)

    2009-07-30

    Dielectric barrier discharges (DBD) in ambient air are used on carbon fiber to improve the fiber surface activity. Carbon fibers with length of 75 {mu}m are placed into the plasma configuration. The interaction between modified carbon fibers and polypropylene (PP) was studied by three-point bending (TPB) test. The chemical changes induced by the treatments on carbon fiber surface are examined using X-ray photoelectron spectroscopy (XPS). XPS results reveal that the carbon fiber modified with the DBD at atmospheric pressure show a significant increase in oxygen and nitrogen concentration. These results demonstrate that the surface of the carbon fiber is more active and hydrophilic after plasma treatments using a DBD operating in ambient air.

  1. The research on the interfacial compatibility of polypropylene composite filled with surface treated carbon fiber

    International Nuclear Information System (INIS)

    Dielectric barrier discharges (DBD) in ambient air are used on carbon fiber to improve the fiber surface activity. Carbon fibers with length of 75 μm are placed into the plasma configuration. The interaction between modified carbon fibers and polypropylene (PP) was studied by three-point bending (TPB) test. The chemical changes induced by the treatments on carbon fiber surface are examined using X-ray photoelectron spectroscopy (XPS). XPS results reveal that the carbon fiber modified with the DBD at atmospheric pressure show a significant increase in oxygen and nitrogen concentration. These results demonstrate that the surface of the carbon fiber is more active and hydrophilic after plasma treatments using a DBD operating in ambient air.

  2. Redistribution of soil nitrogen, carbon and organic matter by mechanical disturbance during whole-tree harvesting in northern hardwoods

    Science.gov (United States)

    Ryan, D.F.; Huntington, T.G.; Wayne, Martin C.

    1992-01-01

    To investigate whether mechanical mixing during harvesting could account for losses observed from forest floor, we measured surface disturbance on a 22 ha watershed that was whole-tree harvested. Surface soil on each 10 cm interval along 81, randomly placed transects was classified immediately after harvesting as mineral or organic, and as undisturbed, depressed, rutted, mounded, scarified, or scalped (forest floor scraped away). We quantitatively sampled these surface categories to collect soil in which preharvest forest floor might reside after harvest. Mechanically mixed mineral and organic soil horizons were readily identified. Buried forest floor under mixed mineral soil occurred in 57% of mounds with mineral surface soil. Harvesting disturbed 65% of the watershed surface and removed forest floor from 25% of the area. Mechanically mixed soil under ruts with organic or mineral surface soil, and mounds with mineral surface soil contained organic carbon and nitrogen pools significantly greater than undisturbed forest floor. Mechanical mixing into underlying mineral soil could account for the loss of forest floor observed between the preharvest condition and the second growing season after whole-tree harvesting. ?? 1992.

  3. Surface characterization in composite and titanium bonding: Carbon fiber surface treatments for improved adhesion to thermoplastic polymers

    Science.gov (United States)

    Devilbiss, T. A.; Wightman, J. P.

    1987-01-01

    The effect of anodization in NaOH, H2SO4, and amine salts on the surface chemistry of carbon fibers was examined by X-ray photoelectron spectroscopy (XPS). The surfaces of carbon fibers after anodization in NaOH and H2SO4 were examined by scanning transmission electron microscopy (STEM), angular dependent XPS, UV absorption spectroscopy of the anodization bath, secondary ion mass spectrometry, and polar/dispersive surface energy analysis. Hercules AS-4, Dexter Hysol XAS, and Union Carbide T-300 fibers were examined by STEM, angular dependent XPS, and breaking strength measurement before and after commercial surface treatment. Oxygen and nitrogen were added to the fiber surfaces by anodization in amine salts. Analysis of the plasmon peak in the carbon 1s signal indicated that H2SO4 anodization affected the morphological structure of the carbon fiber surface. The work of adhesion of carbon fibers to thermoplastic resins was calculated using the geometric mean relationship. A correlation was observed between the dispersive component of the work of adhesion and the interfacial adhesion.

  4. The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Y.S., E-mail: yshzou75@gmail.com [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu, 210094 (China); Wu, Y.F.; Yang, H.; Cang, K. [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu, 210094 (China); Song, G.H. [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang, Liaoning, 110178 (China); Li, Z.X.; Zhou, K. [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu, 210094 (China)

    2011-12-01

    Protective hard coatings deposited on magnesium alloys are believed to be effective for overcoming their poor wear properties. In this work, diamond-like carbon (DLC) films as hard protective films were deposited on AZ91 magnesium alloy by arc ion plating under negative pulse bias voltages ranging from 0 to -200 V. The microstructure, composition and mechanical properties of the DLC films were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. The tribological behavior of uncoated and coated AZ91 magnesium alloy was investigated using a ball-on-disk tribotester. The results show that the negative pulse bias voltage used for film deposition has a significant effect on the sp{sup 3} carbon content and mechanical properties of the deposited DLC films. A maximum sp{sup 3} content of 33.3% was obtained at -100 V, resulting in a high hardness of 28.6 GPa and elastic modulus of 300.0 GPa. The DLC films showed very good adhesion to the AZ91 magnesium alloy with no observable cracks and delamination even during friction testing. Compared with the uncoated AZ91 magnesium alloy, the magnesium alloy coated with DLC films exhibits a low friction coefficient and a narrow, shallow wear track. The wear resistance and surface hardness of AZ91 magnesium alloy can be significantly improved by coating a layer of DLC protective film due to its high hardness and low friction coefficient.

  5. The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy

    International Nuclear Information System (INIS)

    Protective hard coatings deposited on magnesium alloys are believed to be effective for overcoming their poor wear properties. In this work, diamond-like carbon (DLC) films as hard protective films were deposited on AZ91 magnesium alloy by arc ion plating under negative pulse bias voltages ranging from 0 to -200 V. The microstructure, composition and mechanical properties of the DLC films were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. The tribological behavior of uncoated and coated AZ91 magnesium alloy was investigated using a ball-on-disk tribotester. The results show that the negative pulse bias voltage used for film deposition has a significant effect on the sp3 carbon content and mechanical properties of the deposited DLC films. A maximum sp3 content of 33.3% was obtained at -100 V, resulting in a high hardness of 28.6 GPa and elastic modulus of 300.0 GPa. The DLC films showed very good adhesion to the AZ91 magnesium alloy with no observable cracks and delamination even during friction testing. Compared with the uncoated AZ91 magnesium alloy, the magnesium alloy coated with DLC films exhibits a low friction coefficient and a narrow, shallow wear track. The wear resistance and surface hardness of AZ91 magnesium alloy can be significantly improved by coating a layer of DLC protective film due to its high hardness and low friction coefficient.

  6. The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy

    Science.gov (United States)

    Zou, Y. S.; Wu, Y. F.; Yang, H.; Cang, K.; Song, G. H.; Li, Z. X.; Zhou, K.

    2011-12-01

    Protective hard coatings deposited on magnesium alloys are believed to be effective for overcoming their poor wear properties. In this work, diamond-like carbon (DLC) films as hard protective films were deposited on AZ91 magnesium alloy by arc ion plating under negative pulse bias voltages ranging from 0 to -200 V. The microstructure, composition and mechanical properties of the DLC films were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. The tribological behavior of uncoated and coated AZ91 magnesium alloy was investigated using a ball-on-disk tribotester. The results show that the negative pulse bias voltage used for film deposition has a significant effect on the sp3 carbon content and mechanical properties of the deposited DLC films. A maximum sp3 content of 33.3% was obtained at -100 V, resulting in a high hardness of 28.6 GPa and elastic modulus of 300.0 GPa. The DLC films showed very good adhesion to the AZ91 magnesium alloy with no observable cracks and delamination even during friction testing. Compared with the uncoated AZ91 magnesium alloy, the magnesium alloy coated with DLC films exhibits a low friction coefficient and a narrow, shallow wear track. The wear resistance and surface hardness of AZ91 magnesium alloy can be significantly improved by coating a layer of DLC protective film due to its high hardness and low friction coefficient.

  7. Effect of Surface Chemistry on the Mechanisms and Governing Laws of Friction and Wear.

    Science.gov (United States)

    Dai, Ling; Sorkin, Viacheslav; Zhang, Yong-Wei

    2016-04-01

    Recent studies have shown that interface chemistry, that is, the formation and breaking of chemical bonds across contacting interfaces, is closely related to the wear and friction behavior at the nanoscale. In reality, the dangling bond density (DBD) at contacting surfaces can vary greatly. Currently, it remains unclear how friction and wear mechanisms depend on DBDs and whether the Archard's law for wear and Amonton's law for friction are still applicable for contacting surfaces with different DBDs. In this work, we address these issues by studying the wear and friction behavior between two sliding diamond-like carbon surfaces by controlling DBDs via hydrogenation using molecular dynamics simulations. It is found that the chemical bond breaking and remaking across the contacting interface play the key role in determining the friction and wear behavior. During the sliding, a higher DBD leads to more chemical bond formations across the interface, causing stronger wear via either atom or cluster detachments. With the same DBD, a mechanism transition from an atom-by-atom to cluster detachments is observed by increasing the normal load. Remarkably, a fully saturated surface can exhibit a wearless friction. We further show that after necessary modifications, the Archard's law for wear and the Amonton's law for friction may be applicable at the nanoscale. The present work reveals insights into the effect of interface chemistry on the friction and wear, and it provides guidelines for effective antiwear design. PMID:27004415

  8. Surface functionalization of carbon nanofibers by sol-gel coating of zinc oxide

    International Nuclear Information System (INIS)

    In this paper the functional carbon nanofibers were prepared by the carbonization of ZnO coated PAN nanofibers to expand the potential applications of carbon nanofibers. Polyacrylonitrile (PAN) nanofibers were obtained by electrospinning. The electrospun PAN nanofibers were then used as substrates for depositing the functional layer of zinc oxide (ZnO) on the PAN nanofiber surfaces by sol-gel technique. The effects of coating, pre-oxidation and carbonization on the surface morphology and structures of the nanofibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM), respectively. The results of SEM showed a significant increase of the size of ZnO nanograins on the surface of nanofibers after the treatments of coating, pre-oxidation and carbonization. The observations by SEM also revealed that ZnO nanoclusters were firmly and clearly distributed on the surface of the carbon nanofibers. FTIR examination also confirmed the deposition of ZnO on the surface of carbon nanofibers. The XRD analysis indicated that the crystal structure of ZnO nanograins on the surface of carbon nanofibers

  9. Surface functionalization of carbon nanofibers by sol gel coating of zinc oxide

    Science.gov (United States)

    Shao, Dongfeng; Wei, Qufu; Zhang, Liwei; Cai, Yibing; Jiang, Shudong

    2008-08-01

    In this paper the functional carbon nanofibers were prepared by the carbonization of ZnO coated PAN nanofibers to expand the potential applications of carbon nanofibers. Polyacrylonitrile (PAN) nanofibers were obtained by electrospinning. The electrospun PAN nanofibers were then used as substrates for depositing the functional layer of zinc oxide (ZnO) on the PAN nanofiber surfaces by sol-gel technique. The effects of coating, pre-oxidation and carbonization on the surface morphology and structures of the nanofibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM), respectively. The results of SEM showed a significant increase of the size of ZnO nanograins on the surface of nanofibers after the treatments of coating, pre-oxidation and carbonization. The observations by SEM also revealed that ZnO nanoclusters were firmly and clearly distributed on the surface of the carbon nanofibers. FTIR examination also confirmed the deposition of ZnO on the surface of carbon nanofibers. The XRD analysis indicated that the crystal structure of ZnO nanograins on the surface of carbon nanofibers.

  10. Ex vivo surface and mechanical properties of coated orthodontic archwires.

    Science.gov (United States)

    Elayyan, Firas; Silikas, Nick; Bearn, David

    2008-12-01

    This study examined the mechanical and physical properties of retrieved coated nickel-titanium (NiTi) archwires compared with unused samples. Ultraesthetic 0.016 inch coated archwires (G&H(R) Wire Company) were investigated. Ten as-received wires were subjected to a three-point bending test using conventional and self-ligating bracket systems. Surface roughness of the coating was measured with a contact stylus profilometer. Optical and scanning electron microscopes were used to assess surface topography. Ten archwires were used in vivo for a period of between 4 and 6 weeks. Retrieved archwires were subjected to the same tests. The percentage of the remaining coating was calculated using digital photography. Coated archwires were used in vivo for a mean period of 33 days. Differences between the mean values of the as-received and retrieved archwires were determined using t-tests. In the three-point bending test, with conventional elastomeric ligation, retrieved wires produced a lower unloading force (P self-ligating bracket system, retrieved and as-received coated archwires produced the same amount of force (P > 0.05). With surface profilometry, all measured roughness parameters (except R(sm)) had greater surface roughness for the retrieved coated archwires (P < 0.05). Under microscopy, retrieved coated archwires showed discolouration, ditching, and delamination. Only 75 per cent of the coating was present in retrieved coated archwires. Retrieved coated archwires produced lower unloading force values than as-received coated archwires with conventional ligation. Surface roughness of coated archwires increased after use. Coated archwires have a low aesthetic value, with 25 per cent of the coating lost within 33 days in vivo. PMID:19011166

  11. Hybrid direct carbon fuel cells and their reaction mechanisms - a review

    DEFF Research Database (Denmark)

    Deleebeeck, Lisa; Kammer Hansen, Kent

    2014-01-01

    with carbon capture and storage (CCS) due to the high purity of CO2 emitted in the exhaust gas. Direct carbon (or coal) fuel cells (DCFCs) are directly fed with solid carbon to the anode chamber. The fuel cell converts the carbon at the anode and the oxygen at the cathode into electricity, heat and...... efforts is discussed on the fuel cell stack and system levels. The range of DCFC types can be roughly broken down into four fuel cell types: aqueous hydroxide, molten hydroxide, molten carbonate and solid oxide fuel cells. Emphasis is placed on the electrochemical reactions occurring at the anode and the...... proposed mechanism(s) of these reactions for molten carbonate, solid oxide and hybrid direct carbon fuel cells. Additionally, the criteria of choosing the ‘best’ DCFC technology is explored, including system design (continuous supply of solid fuel), performance (power density, efficiency), environmental...

  12. Synthesis and Growth Mechanism of Carbon Filaments by Chemical Vapor Deposition without Catalyst

    Institute of Scientific and Technical Information of China (English)

    Shuhe Liu; Feng Li; Shuo Bai

    2009-01-01

    Carbon filaments with diameter from several to hundreds micrometers were synthesized by chemical vapor deposition of methane without catalyst. The morphology, microstructure and mechanical properties of the carbon filament were investigated by scanning electronic microscopy, optical microscopy, X-ray diffraction and mechanical testing. The results show that the carbon filament is inverted cone shape and grows up along the gas flow direction. The stem of it is formed of annular carbon layers arranged in a tree ring structure while the head is made up of concentrical layers. The tensile strength of the carbon filament is increased after graphitization for the restructuring and growing large of graphene. The growth mechanism of carbon filament was proposed according to the results of two series of experiments with different deposition time and intermittent deposition cycles.

  13. Process Integrated Heat Treatment of a Microalloyed Medium Carbon Steel: Microstructure and Mechanical Properties

    Science.gov (United States)

    Herbst, Sebastian; Schledorn, Mareike; Maier, Hans Jürgen; Milenin, Andrij; Nürnberger, Florian

    2016-04-01

    Air-water spray cooling was employed during a heat treatment to enhance the mechanical properties of microalloyed medium carbon steel test cylinders (38MnVS6, 88 mm diameter). Using appropriate cooling times and intensities, the test cylinders' surfaces could be quenched and subsequently self-tempered by the residual heat of the core. Simultaneously, it was possible to keep the core regions of the cylinders in the bainitic regime and carry out a quasi-isothermal holding. The resulting microstructures consisted of tempered martensite (near-surface) and bainite with pearlite and ferrite (core). Compared to the standard heat treatment (controlled air cooling), the tensile properties (proof stress and ultimate tensile strength) could be improved for both near-surface and core regions with the adapted spray cooling. A hardness profile with 450 HV10 surface hardness and a hardening depth of more than 11 mm could be realized. In addition, an increase of the impact toughness for the core was achieved, resulting in approximately 25 J charpy impact energy. This is a substantial improvement compared to standard heat treatment procedure and values reported in the literature and can be attributed to the reduced pearlite volume fraction and the increased amount of fine bainite.

  14. Effect of ammonium-salt solutions on the surface properties of carbon fibers in electrochemical anodic oxidation

    International Nuclear Information System (INIS)

    Highlights: ► Longitudinal grooves on the fiber surface became more well-defined and much deeper after surface treatment. ► The concentration of oxygen and nitrogen on the fiber surface increased after surface treatment. ► The intensity of oxidative reaction varied with the change of ammonium-salt solutions. ► The higher the concentration of OH− ions in the electrolytes, the violent the oxidative reaction happened. - Abstract: The surfaces of polyacrylonitrile-based carbon fibers were treated by an electrochemical anodic method. Three different kinds of ammonium-salt solutions namely NH4HCO3, (NH4)2CO3 and (NH4)3PO4 were respectively chosen as the electrolytes. The effect of these electrolytes on the surface structure was studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that longitudinal grooves on the fiber surface became more well-defined and much deeper after surface treatment, and the root mean square roughness (RMS) of carbon fiber surface increased from 4.6 nm for untreated fibers to 13.5 nm for treated fibers in (NH4)3PO4 electrolytes. The concentration of oxygen and nitrogen atomic on the fiber surface increased after surface treatment. The tensile strength of oxidized fibers had an obvious decrease, whereas the interlaminar shear strength (ILSS) value of corresponding carbon fiber reinforced polymers (CFRPs) increased in a large extent. The intensity of oxidative reaction varied with the change of ammonium-salt solutions and electrochemical oxidation in (NH4)3PO4 electrolyte was of the most violence. The corresponding mechanism was also discussed and the result showed that the higher the concentration of OH− ions in the electrolytes, the violent the oxidative reaction happened.

  15. Corrosion Inhibiting Mechanism of Nitrite Ion on the Passivation of Carbon Steel and Ductile Cast Iron for Nuclear Power Plants

    Directory of Open Access Journals (Sweden)

    K. T. Kim

    2015-01-01

    Full Text Available While NaNO2 addition can greatly inhibit the corrosion of carbon steel and ductile cast iron, in order to improve the similar corrosion resistance, ca. 100 times more NaNO2 addition is needed for ductile cast iron compared to carbon steel. A corrosion and inhibition mechanism is proposed whereby NO2- ion is added to oxidize. The NO2- ion can be reduced to nitrogen compounds and these compounds may be absorbed on the surface of graphite. Therefore, since nitrite ion needs to oxidize the surface of matrix and needs to passivate the galvanic corroded area and since it is absorbed on the surface of graphite, a greater amount of corrosion inhibitor needs to be added to ductile cast iron compared to carbon steel. The passive film of carbon steel and ductile cast iron, formed by NaNO2 addition showed N-type semiconductive properties and its resistance, is increased; the passive current density is thus decreased and the corrosion rate is then lowered. In addition, the film is mainly composed of iron oxide due to the oxidation by NO2- ion; however, regardless of the alloys, nitrogen compounds (not nitrite were detected at the outermost surface but were not incorporated in the inner oxide.

  16. Tumour angiogenesis as a chemo-mechanical surface instability

    Science.gov (United States)

    Giverso, Chiara; Ciarletta, Pasquale

    2016-03-01

    The hypoxic conditions within avascular solid tumours may trigger the secretion of chemical factors, which diffuse to the nearby vasculature and promote the formation of new vessels eventually joining the tumour. Mathematical models of this process, known as tumour angiogenesis, have mainly investigated the formation of the new capillary networks using reaction-diffusion equations. Since angiogenesis involves the growth dynamics of the endothelial cells sprouting, we propose in this work an alternative mechanistic approach, developing a surface growth model for studying capillary formation and network dynamics. The model takes into account the proliferation of endothelial cells on the pre-existing capillary surface, coupled with the bulk diffusion of the vascular endothelial growth factor (VEGF). The thermo-dynamical consistency is imposed by means of interfacial and bulk balance laws. Finite element simulations show that both the morphology and the dynamics of the sprouting vessels are controlled by the bulk diffusion of VEGF and the chemo-mechanical and geometric properties at the capillary interface. Similarly to dendritic growth processes, we suggest that the emergence of tree-like vessel structures during tumour angiogenesis may result from the free boundary instability driven by competition between chemical and mechanical phenomena occurring at different length-scales.

  17. PALADYN, a comprehensive land surface-vegetation-carbon cycle model of intermediate complexity

    Science.gov (United States)

    Willeit, Matteo; Ganopolski, Andrey

    2016-04-01

    PALADYN is presented, a new comprehensive and computationally efficient land surface-vegetation-carbon cycle model designed to be used in Earth system models of intermediate complexity for long-term simulations and paleoclimate studies. The model treats in a consistent manner the interaction between atmosphere, terrestrial vegetation and soil through the fluxes of energy, water and carbon. Energy, water and carbon are conserved. The model explicitly treats permafrost, both in physical processes and as important carbon pool. The model distinguishes 9 surface types of which 5 are different vegetation types, bare soil, land ice, lake and ocean shelf. Including the ocean shelf allows to treat continuous changes in sea level and shelf area associated with glacial cycles. Over each surface type the model solves the surface energy balance and computes the fluxes of sensible, latent and ground heat and upward shortwave and longwave radiation. It includes a single snow layer. The soil model distinguishes between three different macro surface types which have their own soil column: vegetation and bare soil, ice sheet and ocean shelf. The soil is vertically discretized into 5 layers where prognostic equations for temperature, water and carbon are consistently solved. Phase changes of water in the soil are explicitly considered. A surface hydrology module computes precipitation interception by vegetation, surface runoff and soil infiltration. The soil water equation is based on Darcy's law. Given soil water content, the wetland fraction is computed based on a topographic index. Photosynthesis is computed using a light use efficiency model. Carbon assimilation by vegetation is coupled to the transpiration of water through stomatal conductance. The model includes a dynamic vegetation module with 5 plant functional types competing for the gridcell share with their respective net primary productivity. Each macro surface type has its own carbon pools represented by a litter, a fast

  18. Optical and Electrical characterization of Carbon Nanotube based high-Q mechanical resonators

    OpenAIRE

    Palou Garcia, Xavier

    2014-01-01

    [ANGLÈS] Carbon Nanotubes have been one of the most intensively studied materials in the last two decades. Because of their combination of outstanding properties (mechanical, thermal, electrical, optical, etc.) the community expects to exploit their potential in a myriad of different applications. One of them is that of sensing ultra small forces using mechanical resonators as probes. In this work, a mechanical resonator based in a suspended Carbon Nanotube is optically characterized by means...

  19. Effects of Multi-Walled Carbon Nanotubes on The Mechanical Properties of Glass/Polyester Composites

    OpenAIRE

    M. Mehrdad Shokrieh; A Saeedi; M. Chitsazzadeh

    2012-01-01

    Excellent mechanical properties of carbon nanotubes (CNTs) make them outstanding candidate reinforcements to enhance mechanical properties of conventional composites. The glass/polyester composites are widely used in many industries and applications. Improving the mechanical properties of such composites with addition of CNTs can increase their applications. In this research, multi-walled carbon nanotube (MWCNT) at different weight ratios (0.05, 0.1, 0.3, 0.5 wt.%) were added to chopped stran...

  20. Mechanical and tribological properties of acrylonitrile–butadiene rubber filled with graphite and carbon black

    International Nuclear Information System (INIS)

    Highlights: ► Graphite/carbon black/rubber micro- and nano-composites were prepared. ► Nanocomposites showed better mechanical properties and wear resistance. ► The effect of load and sliding speed on friction and wear is significant. ► Graphite lubricant film can reduce friction coefficient and wear rate. -- Abstract: In this work, acrylonitrile–butadiene rubber (NBR)/expanded graphite (EG)/carbon black (CB) micro- and nanocomposites were prepared by two different methods, and the resulting mechanical and tribological properties were compared with those of NBR/CB composites. Meanwhile, the effects of graphite dispersion and loading content, as well as the applied load and sliding velocity on the tribological behavior of the above composites under dry friction condition were also evaluated. The worn surfaces were analyzed by scanning electron microscopy (SEM) to disclose wear mechanism. As expected, the better the dispersion of graphite, the more remarkable enhancement on tensile and dynamic mechanical properties, and the greater reduction in the coefficient of friction (COF) and specific wear rate (Ws). It was found that a small amount of EG could effectively decrease COF and Ws of NBR/CB composites because of the formation of graphite lubricant films. The COF and Ws of NBR/CB/EG composites show a decreasing trend with a rise in applied load and sliding velocity. NBR/CB/EG nanocomposite always shows a stable wearing process with relatively low COF and Ws. It is thought that well-dispersed graphite nano-sheets were beneficial to the formation of a fine and durable lubricant film.

  1. One way of surface alloying treatment on iron surface based on surface mechanical attrition treatment and heat treatment

    International Nuclear Information System (INIS)

    A method of surface alloying treatment has been developed: Ni powders were welded into the surface of iron plates by Surface Mechanical Attrition Treatment (SMAT), followed by annealing at certain temperature for 30 min. A Ni-Fe alloy layer with thickness about 100 μm in the sample surface was fabricated on pure iron plate. Scanning electron microscope (SEM), glow discharge spectrum (GDS), and X-ray diffraction (XRD) methods were used to analyze the microstructure, the composition and the phases of the alloy layer. Studies on the interface microstructure indicated that there was significant atomic diffusion and formation of multilayer of intermetallic compound and solid solution in SMAT process. Subsequent annealing accelerates the alloying process. The corrosion test shows the sample by SMAT treated with Ni powders exhibit the best corrosion resistance.

  2. Dust Tolerant Commodity Transfer Interface Mechanisms for Planetary Surfaces

    Science.gov (United States)

    Townsend, Ivan I.; Mueller, Robert P.; Tamasy, Gabor J.

    2014-01-01

    Regolith is present on most planetary surfaces such as Earth's moon, Mars, and Asteroids. If human crews and robotic machinery are to operate on these regolith covered surfaces, they must face the consequences of interacting with regolith fines which consist of particles below 100 microns in diameter down to as small as submicron scale particles. Such fine dust will intrude into mechanisms and interfaces causing a variety of problems such as contamination of clean fluid lines, jamming of mechanisms and damaging connector seals and couplings. Since multiple elements must be assembled in space for system level functionality, it will be inevitable that interfaces will be necessary for structural connections, and to pass commodities such as cryogenic liquid propellants, purge and buffer gases, water, breathing air, pressurizing gases, heat exchange fluids, power and data. When fine regolith dust is present in the environment it can be lofted into interfaces where it can compromise the utility of the interface by preventing the connections from being successfully mated, or by inducing fluid leaks or degradation of power and data transmission. A dust tolerant, hand held "quick-disconnect" cryogenic fluids connector housing has been developed at NASA KSC which can be used by astronaut crews to connect flex lines that will transfer propellants and other useful fluids to the end user. In addition, a dust tolerant, automated, cryogenic fluid, multiple connector, power and data interface mechanism prototype has been developed, fabricated and demonstrated by NASA at Kennedy Space Center (KSC). The design and operation of these prototypes are explained and discussed.

  3. Investigation of carbonized layer on surface of NaAlSi glass fibers

    Science.gov (United States)

    Pentjuss, E.; Lusis, A.; Bajars, G.; Gabrusenoks, J.

    2013-12-01

    There are presented and discussed experimental results about carbonate shell on the sodium rich alumosilicate (NaAlSi) glass fibers and carbonization in wet air atmosphere and water uptake kinetic of such fiber fabrics. The analyzes of water uptake kinetic by regression technique, leaching and heating of carbonized glass fabrics helped to separate stages of fast and slow processes between fiber and carbonate shell and air atmosphere. The shell contains mixture of trona and hydrated sodium carbonate. Heating converts both substances to sodium carbonate. The weight uptake after heating encounters two fast exponential processes associated with water absorption on the surface of carbonated shell and its diffusion into volume. The slow process associates with CO2 and H2O absorption from air, hydration and sodium carbonate conversion to trona.

  4. Investigation of carbonized layer on surface of NaAlSi glass fibers

    International Nuclear Information System (INIS)

    There are presented and discussed experimental results about carbonate shell on the sodium rich alumosilicate (NaAlSi) glass fibers and carbonization in wet air atmosphere and water uptake kinetic of such fiber fabrics. The analyzes of water uptake kinetic by regression technique, leaching and heating of carbonized glass fabrics helped to separate stages of fast and slow processes between fiber and carbonate shell and air atmosphere. The shell contains mixture of trona and hydrated sodium carbonate. Heating converts both substances to sodium carbonate. The weight uptake after heating encounters two fast exponential processes associated with water absorption on the surface of carbonated shell and its diffusion into volume. The slow process associates with CO2 and H2O absorption from air, hydration and sodium carbonate conversion to trona

  5. The role of surface pretreatment and surface analysis in the bondability of carbon fiber-polyimide matrix composites

    OpenAIRE

    Moyer, Denise Joy DeGeorge

    1989-01-01

    The effect of surface pretreatment on the physical and chemical properties of carbon fiber-polyimide matrix composite surfaces was evaluated. Eight pretreatments were studied: methanol wash, gritblast, sulfuric acid soak, ammonia plasma, argon plasma, argon plasma followed by ammonia plasma, nitrogen plasma, and oxygen plasma. The pretreated surfaces were chemically characterized through the use of XPS (X-ray photoelectron spectroscopy), ISS (ion scattering spectroscop...

  6. Impact of carbon on the surface and activity of silica-carbon supported copper catalysts for reduction of nitrogen oxides

    Science.gov (United States)

    Spassova, I.; Stoeva, N.; Nickolov, R.; Atanasova, G.; Khristova, M.

    2016-04-01

    Composite catalysts, prepared by one or more active components supported on a support are of interest because of the possible interaction between the catalytic components and the support materials. The supports of combined hydrophilic-hydrophobic type may influence how these materials maintain an active phase and as a result a possible cooperation between active components and the support material could occur and affects the catalytic behavior. Silica-carbon nanocomposites were prepared by sol-gel, using different in specific surface areas and porous texture carbon materials. Catalysts were obtained after copper deposition on these composites. The nanocomposites and the catalysts were characterized by nitrogen adsorption, TG, XRD, TEM- HRTEM, H2-TPR, and XPS. The nature of the carbon predetermines the composite's texture. The IEPs of carbon materials and silica is a force of composites formation and determines the respective distribution of the silica and carbon components on the surface of the composites. Copper deposition over the investigated silica-carbon composites leads to formation of active phases in which copper is in different oxidation states. The reduction of NO with CO proceeds by different paths on different catalysts due to the textural differences of the composites, maintaining different surface composition and oxidation states of copper.

  7. Mechanical Testing of Carbon-Carbon Composite for Applications in Human Spine Surgery in the Form of Intervertebral Cages

    Czech Academy of Sciences Publication Activity Database

    Sochor, M.; Balík, Karel; Suchý, Tomáš; Sedláček, R.; Tichý, P.

    Praha : Ústav struktury a mechaniky hornin AV ČR, 2003 - (Kolář, F.), s. - [Czech-Polish Workshop on Testing of Composite Materials. Praha (CZ), 11.09.2003-12.09.2003] R&D Projects: GA ČR GA106/00/1407 Institutional research plan: CEZ:AV0Z3046908 Keywords : carbon-carbon composite * mechanical testing * biocompatibility Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  8. Mechanical behavior of carbon nanotube and graphene junction as a building block for 3D carbon nanostructures

    OpenAIRE

    Mina Moradi; Jamshid Aghazadeh Mohandesi

    2015-01-01

    The incorporation of defects in junction area of 1D and 2D carbon nanostructures has a major impact on properties of their 3D structures. In the present study, molecular dynamics simulation is utilized to examine the mechanical behavior of graphene sheet (GS) in carbon nanotube (CNT)-GS junctions. The tensile load was applied along the GS in connection with CNTs of different chiralities. The adaptive intermolecular reactive empirical bond order potential was chosen to model C-C interactions. ...

  9. Effects of fibre-surface morphology on the mechanical properties of Porifera-inspired rubber-matrix composites

    Science.gov (United States)

    Alam, Parvez; Stillfried, Daniela Graf; Celli, Jessika; Toivakka, Martti

    2013-06-01

    In this paper, mineralised organic fibre morphologies, inspired by the structures of Porifera (sponges) are correlated to the mechanical performance of fibre reinforced rubbers. The mineralised structures are rich in calcium carbonate and silica. These compounds nucleate and precipitate on the fibre surfaces yielding different morphologies as a function of mineral ion concentrations. Smaller mineralised precipitates manifestly improve the mechanical performance of composites while thicker precipitates enveloping the fibres give rise to inferior properties. Mechanisms and evidenced reasoning for these differences are reported herein.

  10. Zeolites for nitrosamine and pharmaceutical removal from demineralised and surface water: Mechanisms and efficacy

    KAUST Repository

    De Ridder, David J.

    2012-03-01

    Zeolites with a high Si/Al ratio can be used as selective adsorbents in water treatment, targeting organic micropollutants which are removed poorly with activated carbon. Due to size exclusion, many Natural Organic Matter (NOM) components cannot access the pores, thus limiting adsorption competition between organic micropollutant and NOM. Furthermore, zeolite channel diameters are close to molecule diameters, which results in strong van der Waals interaction. MOR200 and ZSM5, the two most hydrophobic zeolites, showed the highest removal of neutral nitrosamines in demineralised water, with higher efficacy than activated carbon. DAY and MOR30, which were relatively hydrophilic zeolites, did not show appreciable removal of any of the nitrosamines. When nitrosamines were adsorbed from surface water, there was no influence of competition with, or pore blockage by, NOM components on nitrosamine removal for ZSM5 zeolite, in contrast to activated carbon. Repulsion of negatively charged pharmaceuticals was significant for ZSM5, which had a Si/Al ratio of 80. MOR200 had a Si/Al ratio of 200, indicating a lower Al content than ZSM5 and, as such, a lower negative surface charge. Charge effects were not observed for MOR200. A relationship was found between the Stokes diameter of the pharmaceuticals and nitrosamines, and their removal by ZSM5 and MOR200, indicating that a "close fit" adsorption mechanism is more likely than hydrophobic interaction in these zeolites. Due to their selective nature, adsorption on zeolites should only be considered as an additional treatment step to existing processes, dedicated for the removal of specific organic micropollutants. Less specific treatment techniques, such as activated carbon filtration, are still required to ensure a broad barrier for organic micropollutants in water treatment. © 2012 Elsevier B.V. All rights reserved.

  11. Energy costs of carbon dioxide concentrating mechanisms in aquatic organisms

    Czech Academy of Sciences Publication Activity Database

    Raven, John A.; Beardall, J.; Giordano, Mario

    2014-01-01

    Roč. 121, 2-3 (2014), s. 111-124. ISSN 0166-8595 Institutional support: RVO:61388971 Keywords : carbon dioxide * environmental change * radiation Subject RIV: EE - Microbiology, Virology Impact factor: 3.502, year: 2014

  12. Mechanisms of Microwave Absorption in Carbon Compounds from Shungite

    OpenAIRE

    S. Emelyanov; A. Kuzmenko; V. Rodionov; M. Dobromyslov

    2013-01-01

    According to SEM, X-ray phase analysis, Raman scattering data features of nanostructural changes in shungite carbon structure were found when processing shungite in 52 % hydrofluoric acid. It is found that conductivity increases up to the values of electrical graphite and absorption of microwave radiation also increases at frequencies up to 40 GHz, which, along with dielectric losses, is due to intense processes of both scattering at laminar carbon structures and absorption of electromagnetic...

  13. Mechanisms of Microwave Absorption in Carbon Compounds from Shungite

    Directory of Open Access Journals (Sweden)

    S. Emelyanov

    2013-12-01

    Full Text Available According to SEM, X-ray phase analysis, Raman scattering data features of nanostructural changes in shungite carbon structure were found when processing shungite in 52 % hydrofluoric acid. It is found that conductivity increases up to the values of electrical graphite and absorption of microwave radiation also increases at frequencies up to 40 GHz, which, along with dielectric losses, is due to intense processes of both scattering at laminar carbon structures and absorption of electromagnetic energy.

  14. Mechanical and thermal stability of mechanically induced near-surface nanostructures

    International Nuclear Information System (INIS)

    Mechanical surface treatments, such as deep rolling, shot peening, hammering, etc., can significantly improve the fatigue behaviour of metallic materials owing to near-surface nanocrystallisation, strain hardening and compressive residual stresses. In this paper, we investigate the stability of near-surface microstructures of deep rolled austenitic stainless steel AISI 304 and turbine blade alloy Ti-6Al-4V during high temperature fatigue (up to 600 deg. C) by transmission electron microscopy and X-ray diffraction. The investigated nanocrystalline regions are stable during short time annealing and unstable during long time annealing at 600 deg. C. Isothermal fatigue in the low cycle fatigue regime at high stress amplitudes does not alter the nanocrystalline region up to 600 deg. C

  15. Calcium carbonate scaling in seawater desalination by ammonia-carbon dioxide forward osmosis: Mechanism and implications

    KAUST Repository

    Li, Zhenyu

    2015-02-07

    Forward osmosis (FO) is an osmotically driven membrane process, where the membrane separates a draw solution (DS) with high salinity from a feed solution (FS) with low salinity. There can be a counter direction flow of salt (i.e., salt leakage) that may interact with the water flux through the FO membrane. For the first time reported, this study describes a new calcium carbonate scaling phenomenon in the seawater FO desalination process using ammonium bicarbonate as the DS. The scaling on the membrane surface at the feed side is caused by the interaction between an anion reversely diffused from the DS and a cation present in the FS, causing a significant decline of the water flux. The composition of the scaling layer is dominated by the solubility (represented as solubility product constant, Ksp) of salt formed by the paired anion and cation. Membrane surface morphology plays a crucial role in the reversibility of the scaling. If the scaling occurs on the active layer of the FO membrane, hydraulic cleaning (increasing crossflow velocity) efficiency to restore the water flux is up to 82%. When scaling occurs on the support layer of the FO membrane, the hydraulic cleaning efficiency is strongly reduced, with only 36% of the water flux recovered. The present study reveals the risk of scaling induced by the interaction of feed solute and draw solute, which is different from the scaling caused by the supersaturation in reverse osmosis and other FO studies reported. The scaling investigated in this study can occur with a very low solute concentration at an early stage of the FO process. This finding provides an important implication for selection of draw solution and development of new membranes in the FO process.

  16. Effect of surface modification of activated carbon on its adsorption capacity for NH3

    Institute of Scientific and Technical Information of China (English)

    SHAN Xiao-mei; ZHU Shu-quan; ZHANG Wen-hui

    2008-01-01

    To investigate the effects of carbon surface characteristics on NH3 adsorption, coal-based and coconut shell activated carbons were modified by treatment with oxidants. The surface properties of the carbons were characterized by low temperature nitrogen sorption, by Boehm's titrations and by XPS techniques. NH3 adsorption isotherms of the original and the modified carbons were determined. The results show that the carbons were oxidized by HNO3 and (NH4)2S2O8, and that there was an increase in oxygen containing functional groups on the surface. However, the pore-size distribution of the coal-based carbons was changed after KMnO4 treatment. It was found that the NH3 adsorption capacity of the modified carbons was enhanced and that the most pronounced enhancement results from (NH4)2S2O8 oxidation. Under our experimental conditions, the capacity is positively corrected to the number of surface functional groups containing oxygen, and to the number of micro-pores. Furthermore, an empirical model of the relationship between NH3 adsorption and multiple factors on the carbon surface was fit using a complex regression method.

  17. Corrosion Products and Formation Mechanism During Initial Stage of Atmospheric Corrosion of Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    XIAO Kui; DONG Chao-fang; LI Xiao-gang; WANG Fu-ming

    2008-01-01

    The formation and development of corrosion products on carbon steel surface during the initial stage of atmospheric corrosion in a laboratory simulated environment have been studied by scanning electron microscopy (SEM)and Raman spectroscopy.The results showed that two different shapes of corrosion products,that is,ring and chain,were formed in the initial stage of corrosion.MnS clusters were found in the nuclei of corrosion products at the active local corrosion sites.The ring-shaped products were composed of lepidocrocite (γ-FeOOH) and maghemite(γ-Fe2 O3) transformed from lepidocrocite.The chain-type products were goethite (α-FeOOH).A formation mechanism of the corrosion products is proposed.

  18. Mechanically durable carbon nanotube-composite hierarchical structures with superhydrophobicity, self-cleaning, and low-drag.

    Science.gov (United States)

    Jung, Yong Chae; Bhushan, Bharat

    2009-12-22

    Superhydrophobic surfaces with high contact angle and low contact angle hysteresis exhibit a self-cleaning effect and low drag for fluid flow. The lotus (Nelumbo nucifera) leaf is one of the examples found in nature for superhydrophobic surfaces. For the development of superhydrophobic surfaces, which is important for various applications such as glass windows, solar panels, and microchannels, materials and fabrication methods need to be explored to provide mechanically durable surfaces. It is necessary to perform durability studies on these surfaces. Carbon nanotube (CNT), composite structures which would lead to superhydrophobicity, self-cleaning, and low-drag, were prepared using a spray method. As a benchmark, structured surfaces with lotus wax were also prepared to compare with the durability of CNT composite structures. To compare the durability of the various fabricated surfaces, waterfall/jet tests were conducted to determine the loss of superhydrophobicity by changing the flow time and pressure conditions. Wear and friction studies were also performed using an atomic force microscope (AFM) and a ball-on-flat tribometer. The changes in the morphology of the structured surfaces were examined by AFM and optical imaging. We find that superhydrophobic CNT composite structures showed good mechanical durability, superior to the structured surfaces with lotus wax, and may be suitable for real world applications. PMID:19947581

  19. MECHANICAL AND THERMO–MECHANICAL PROPERTIES OF BI-DIRECTIONAL AND SHORT CARBON FIBER REINFORCED EPOXY COMPOSITES

    OpenAIRE

    G. AGARWAL; Patnaik, A.; Sharma, R. K.

    2014-01-01

    This paper based on bidirectional and short carbon fiber reinforced epoxy composites reports the effect of fiber loading on physical, mechanical and thermo-mechanical properties respectively. The five different fiber loading, i.e., 10wt. %, 20wt. %, 30wt. %, 40wt. % and 50wt. % were taken for evaluating the above said properties. The physical and mechanical properties, i.e., hardness, tensile strength, flexural strength, inter-laminar shear strength and impact strength are determined to re...

  20. Self-Assembly of Graphene on Carbon Nanotube Surfaces

    OpenAIRE

    Li, Kaiyuan; Eres, Gyula; Howe, Jane; Chuang, Yen-Jun; Li, Xufan; Gu, Zhanjun; Zhang, Litong; Xie, Sishen; Pan, Zhengwei

    2013-01-01

    The rolling up of a graphene sheet into a tube is a standard visualization tool for illustrating carbon nanotube (CNT) formation. However, the actual processes of rolling up graphene sheets into CNTs in laboratory syntheses have never been demonstrated. Here we report conformal growth of graphene by carbon self-assembly on single-wall and multi-wall CNTs using chemical vapor deposition (CVD) of methane without the presence of metal catalysts. The new graphene layers roll up into seamless coax...

  1. Surface-initiated graft polymerization on multiwalled carbon nanotubes pretreated by corona discharge at atmospheric pressure.

    Science.gov (United States)

    Xu, Lihua; Fang, Zhengping; Song, Ping'an; Peng, Mao

    2010-03-01

    Surface-initiated graft polymerization on multi-walled carbon nanotubes pretreated with a corona discharge at atmospheric pressure was explored. The mechanism of the corona-discharge-induced graft polymerization is discussed. The results indicate that MWCNTs were encapsulated by poly(glycidyl methacrylate) (PGMA), demonstrating the formation of PGMA-grafted MWCNTs (PGMA-g-MWCNTs), with a grafting ratio of about 22 wt%. The solubility of PGMA-g-MWCNTs in ethanol was dramatically improved compared to pristine MWCNTs, which could contribute to fabricating high-performance polymer/MWCNTs nanocomposites in the future. Compared with most plasma processes, which operate at low pressures, corona discharge has the merit of working at atmospheric pressure. PMID:20644821

  2. Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

    Energy Technology Data Exchange (ETDEWEB)

    Jennifer Anne Harnisch

    2002-06-27

    The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic performance both in conventional liquid chromatographic columns and EMLC columns. Additionally, one may also exploit the creation of aryl films to by electroreduction of arenediazonium salts in the creation of nanostructured materials. The formation of mercaptobenzene film on the surface of a GC electrode provides a linking platform for the chemisorption of gold nanoparticles. After deposition of nanoparticles, the surface chemistry of the gold can be further altered by self-assembled monolayer (SAM) formation via the chemisorption of a second thiol species. Finally, the properties of gold films can be altered such that they display carbon-like behavior through the formation of benzenehexathiol (BHT) SAMs. BHT chemisorbs to the gold surface in a previously unprecedented planar fashion. Carbon and gold substrates can be chemically altered by several methodologies resulting in new surface properties. The development of modification protocols and their application in the analytical arena is considered herein.

  3. Mechanical desorption of immobilized proteins using carbon dioxide aerosols for reusable biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Renu; Hong, Seongkyeol [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of); Jang, Jaesung, E-mail: jjang@unist.ac.kr [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of); Department of Biomedical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of); School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of)

    2015-01-01

    Highlights: • Immobilized proteins were removed using carbon dioxide aerosols. • We observed high removal efficiencies due to the aerosol treatment. • We confirmed the removal with FTIR and X-ray photoelectron spectroscopy. • This CO{sub 2} aerosol treatment did not undermine re-functionalization. • This technique is a fast and damage-free method to reuse a sensor surface. - Abstract: Reusability of a biosensor has recently received considerable attention, and it is closely related with the effective desorption of probe molecules. We present a novel mechanical desorption technique to reuse biosensors by using periodic jets of carbon dioxide (CO{sub 2}) aerosols (a mixture of solid and gaseous CO{sub 2}), and demonstrate its feasibility by removing physically adsorbed and covalently bonded fluorescent proteins i.e., Escherichia coli fluorescein isothiocyanate antibody and bovine serum albumin (E. coli FITC–Ab and FITC–BSA) from silicon chips. The proteins on the chip surfaces were measured by fluorescent images before and after applying the aerosols. The removal efficiency of the aerosol treatment was measured for various concentrations (1–20 μg mL{sup −1}) of E. coli FITC–Ab and FITC–BSA with two different removal cycles (5 and 11 cycles; each cycle: 8 s). We observed high removal efficiencies (>93.5% for physically adsorbed Ab and >84.6% for covalently bonded Ab) at 11 cycle aerosol treatment. This CO{sub 2} aerosol treatment did not undermine re-functionalization, which was confirmed by the fluorescent images of FITC–Abs for fresh and reused chips. Desorption of the immobilized layers was validated by Fourier transform infrared and X-ray photoelectron spectroscopic analyses. We also conducted an experiment on the regeneration of E. coli sensing chips using this aerosol treatment, and the chips were re-used 5 times successfully. This mechanical desorption technique is a highly effective and novel strategy for reusable biosensors.

  4. Mechanical desorption of immobilized proteins using carbon dioxide aerosols for reusable biosensors

    International Nuclear Information System (INIS)

    Highlights: • Immobilized proteins were removed using carbon dioxide aerosols. • We observed high removal efficiencies due to the aerosol treatment. • We confirmed the removal with FTIR and X-ray photoelectron spectroscopy. • This CO2 aerosol treatment did not undermine re-functionalization. • This technique is a fast and damage-free method to reuse a sensor surface. - Abstract: Reusability of a biosensor has recently received considerable attention, and it is closely related with the effective desorption of probe molecules. We present a novel mechanical desorption technique to reuse biosensors by using periodic jets of carbon dioxide (CO2) aerosols (a mixture of solid and gaseous CO2), and demonstrate its feasibility by removing physically adsorbed and covalently bonded fluorescent proteins i.e., Escherichia coli fluorescein isothiocyanate antibody and bovine serum albumin (E. coli FITC–Ab and FITC–BSA) from silicon chips. The proteins on the chip surfaces were measured by fluorescent images before and after applying the aerosols. The removal efficiency of the aerosol treatment was measured for various concentrations (1–20 μg mL−1) of E. coli FITC–Ab and FITC–BSA with two different removal cycles (5 and 11 cycles; each cycle: 8 s). We observed high removal efficiencies (>93.5% for physically adsorbed Ab and >84.6% for covalently bonded Ab) at 11 cycle aerosol treatment. This CO2 aerosol treatment did not undermine re-functionalization, which was confirmed by the fluorescent images of FITC–Abs for fresh and reused chips. Desorption of the immobilized layers was validated by Fourier transform infrared and X-ray photoelectron spectroscopic analyses. We also conducted an experiment on the regeneration of E. coli sensing chips using this aerosol treatment, and the chips were re-used 5 times successfully. This mechanical desorption technique is a highly effective and novel strategy for reusable biosensors

  5. Effect of carbon on hydrogen desorption and absorption of mechanically milled MgH 2

    Science.gov (United States)

    Shang, C. X.; Guo, Z. X.

    The use of MgH 2, instead of pure Mg, in the mechanical synthesis of Mg-based hydrogen storage materials offers added benefit to powder size refinement and reduced oxygen contamination. Alloying additions can further improve the sorption kinetics at a relatively low temperature. This paper examines the effect of graphitic carbon on the desorption and absorption of MgH 2. Graphite powder of different concentrations were mechanically milled with MgH 2 particles. The milled powder was characterised by XRD, SEM and simultaneous TG and DSC techniques. The results show that graphite poses little influence on the desorption properties of MgH 2. However, it does benefit the absorption process, leading to rapid hydrogen uptake in the re-hydrogenated sample. After dehydrogenation, 5 wt.% of hydrogen was re-absorbed within 30 min at 250 °C for the ( MgH 2+10 G) mixture prior-milled for 8 h, while only 0.8 wt.% for the pure MgH 2 milled for 8 h, the effect may be attributed to the interaction between crystalline graphite with H 2 disassociation close to the MgH 2 or Mg surface. Moreover, graphite can also inhibit the formation of a new oxide layer on the surface of Mg particles.

  6. Effects of Carbon Structure and Surface Oxygen on the Carbon's Performance as the Anode in Lithium-Ion Battery Determined

    Science.gov (United States)

    Hung, Ching-Cheh

    2000-01-01

    Four carbon materials (C1, C2, C3, and C4) were tested electrochemically at the NASA Glenn Research Center at Lewis Field to determine their performance in lithium-ion batteries. They were formed as shown in the figure. This process caused very little carbon loss. Products C1 and C3 contained very little oxygen because of the final overnight heating at 540 C. Products C2 and C4, on the other hand, contained small amounts of basic oxide. The electrochemical test involved cycles of lithium intercalation and deintercalation using C/saturated LiI-50/50 (vol %) ethylene carbonate (EC) and dimethyl carbonate (DMC)/Li half cell. The cycling test, which is summarized in the table, resulted in three major conclusions. The capacity of the carbon with a basic oxide surface converges to a constant 1. value quickly (within 4 cycles), possibly because the oxide prevents solvent from entering the carbon structure and, therefore, prolongs the carbon s cycle life. Under certain conditions, the disordered carbon can store more lithium than its 2. precursor. These samples and their precursor can intercalate at 200 mA/g and deintercalate at 3. a rate of 2000 mA/g without significant capacity loss.

  7. Integrated Experimental and Modeling Studies of Mineral Carbonation as a Mechanism for Permanent Carbon Sequestration in Mafic/Ultramafic Rocks

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhengrong [Yale Univ., New Haven, CT (United States); Qiu, Lin [Yale Univ., New Haven, CT (United States); Zhang, Shuang [Yale Univ., New Haven, CT (United States); Bolton, Edward [Yale Univ., New Haven, CT (United States); Bercovici, David [Yale Univ., New Haven, CT (United States); Ague, Jay [Yale Univ., New Haven, CT (United States); Karato, Shun-Ichiro [Yale Univ., New Haven, CT (United States); Oristaglio, Michael [Yale Univ., New Haven, CT (United States); Zhu, Wen-Iu [Univ. of Maryland, College Park, MD (United States); Lisabeth, Harry [Univ. of Maryland, College Park, MD (United States); Johnson, Kevin [Univ. of Hawaii, Honolulu, HI (United States)

    2014-09-30

    A program of laboratory experiments, modeling and fieldwork was carried out at Yale University, University of Maryland, and University of Hawai‘i, under a DOE Award (DE-FE0004375) to study mineral carbonation as a practical method of geologic carbon sequestration. Mineral carbonation, also called carbon mineralization, is the conversion of (fluid) carbon dioxide into (solid) carbonate minerals in rocks, by way of naturally occurring chemical reactions. Mafic and ultramafic rocks, such as volcanic basalt, are natural candidates for carbonation, because the magnesium and iron silicate minerals in these rocks react with brines of dissolved carbon dioxide to form carbonate minerals. By trapping carbon dioxide (CO2) underground as a constituent of solid rock, carbonation of natural basalt formations would be a secure method of sequestering CO2 captured at power plants in efforts to mitigate climate change. Geochemical laboratory experiments at Yale, carried out in a batch reactor at 200°C and 150 bar (15 MPa), studied carbonation of the olivine mineral forsterite (Mg2SiO4) reacting with CO2 brines in the form of sodium bicarbonate (NaHCO3) solutions. The main carbonation product in these reactions is the carbonate mineral magnesite (MgCO3). A series of 32 runs varied the reaction time, the reactive surface area of olivine grains and powders, the concentration of the reacting fluid, and the starting ratio of fluid to olivine mass. These experiments were the first to study the rate of olivine carbonation under passive conditions approaching equilibrium. The results show that, in a simple batch reaction, olivine carbonation is fastest during the first 24 hours and then slows significantly and even reverses. A natural measure of the extent of carbonation is a quantity called the carbonation fraction, which compares the amount of carbon removed from solution, during a run, to the maximum amount

  8. Calcium Carbonate Nucleation in an Alkaline Lake Surface Water, Pyramid Lake, Nevada, USA

    Science.gov (United States)

    Reddy, M.M.; Hoch, A.

    2012-01-01

    Calcium concentration and calcite supersaturation (??) needed for calcium carbonate nucleation and crystal growth in Pyramid Lake (PL) surface water were determined during August of 1997, 2000, and 2001. PL surface water has ?? values of 10-16. Notwithstanding high ??, calcium carbonate growth did not occur on aragonite single crystals suspended PL surface water for several months. However, calcium solution addition to PL surface-water samples caused reproducible calcium carbonate mineral nucleation and crystal growth. Mean PL surface-water calcium concentration at nucleation was 2.33 mM (n = 10), a value about nine times higher than the ambient PL surface-water calcium concentration (0.26 mM); mean ?? at nucleation (109 with a standard deviation of 8) is about eight times the PL surface-water ??. Calcium concentration and ?? regulated the calcium carbonate formation in PL nucleation experiments and surface water. Unfiltered samples nucleated at lower ?? than filtered samples. Calcium concentration and ?? at nucleation for experiments in the presence of added particles were within one standard deviation of the mean for all samples. Calcium carbonate formation rates followed a simple rate expression of the form, rate (mM/min) = A (??) + B. The best fit rate equation "Rate (?? mM/?? min) = -0.0026 ?? + 0.0175 (r = 0.904, n = 10)" was statistically significant at greater than the 0.01 confidence level and gives, after rearrangement, ?? at zero rate of 6.7. Nucleation in PL surface water and morphology of calcium carbonate particles formed in PL nucleation experiments and in PL surface-water samples suggest crystal growth inhibition by multiple substances present in PL surface water mediates PL calcium carbonate formation, but there is insufficient information to determine the chemical nature of all inhibitors. ?? 2011 U.S. Government.

  9. Droplet Transport Mechanism on Horizontal Hydrophilic/Hydrophobic Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Myong, Hyon Kook [Kookmin University, Seoul (Korea, Republic of)

    2014-06-15

    A fluid transport technique is a key issue for the development of microfluidic systems. In this study, the movement of a droplet on horizontal hydrophilic/hydrophobic surfaces, which is a new concept to transport droplets without external power sources that was recently proposed by the author, was simulated using an in-house solution code(PowerCFD). This code employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The droplet transport mechanism is examined through numerical results that include velocity vectors, pressure contours, and total kinetic energy inside and around the droplet.

  10. The Surface Photovoltage Mechanism of a Silicon Nanoporous Pillar Array

    Science.gov (United States)

    Hu, Zhen-Gang; Tian, Yong-Tao; Li, Xin-Jian

    2013-08-01

    The surface photovoltage (SPV) mechanism of a silicon nanoporous pillar array (Si-NPA) is investigated by using SPV spectroscopy in different external electric fields. Through comparisons with the SPV spectrum of single crystal silicon (sc-Si), the silicon nano-crystallite (nc-Si)/SiOx nanostructure of Si-NPA is proved to be capable of producing obvious SPV in the wavelength range 300-580 nm. The SPV for the sc-Si layer and the nc-Si/SiOx nanostructure has shown certain contrary characters in different external electric fields. Through analysis, the localized states in the amorphous SiOx matrix are believed to dominate the SPV for the nc-Si/SiOx nanostructure.

  11. Influence of activated carbon characteristics on toluene and hexane adsorption: Application of surface response methodology

    OpenAIRE

    Izquierdo Pantoja, María Teresa; Yuso, A. M. de; Valenciano, Raquel; Rubio Villa, Begoña; Pino, María Rosa

    2013-01-01

    The objective of this study was to evaluate the adsorption capacity of toluene and hexane over activated carbons prepared according an experimental design, considering as variables the activation temperature, the impregnation ratio and the activation time. The response surface methodology was applied to optimize the adsorption capacity of the carbons regarding the preparation conditions that determine the physicochemical characteristics of the activated carbons. The methodology of preparation...

  12. The impact of a carbon nanotube on the cholesterol domain localized on a protein surface

    CERN Document Server

    Gburski, Zygmunt; Raczynski, Przemyslaw; 10.1016/j.ssc.2009.12.005

    2011-01-01

    The influence of a single walled carbon nanotube on the structure of a cholesterol cluster (domain) developed over the surface of the endothelial protein 1LQV has been investigated using the classical molecular dynamics (MD) simulation technique. We have observed a substantial impact of carbon nanotube on the arrangement of the cholesterol domain. The carbon nanotube can drag out cholesterol molecules, remarkable reducing the volume of the domain settled down on the protein.

  13. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr, Joe H.

    2016-07-05

    A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

  14. Electro-oxidation of perfluorooctanoic acid by carbon nanotube sponge anode and the mechanism.

    Science.gov (United States)

    Xue, An; Yuan, Zi-Wen; Sun, Yan; Cao, An-Yuan; Zhao, Hua-Zhang

    2015-12-01

    As an emerging persistent organic pollutant (POPs), perfluorooctanoic acid (PFOA) exists widely in natural environment. It is of particular significance to develop efficient techniques to remove low-concentration PFOA from the contaminated waters. In this work, we adopted a new material, carbon nanotube (CNT) sponge, as electrode to enhance electro-oxidation and achieve high removal efficiency of low-concentration (100μgL(-1)) PFOA from water. CNT sponge was pretreated by mixed acids to improve the surface morphology, hydrophilicity and the content of carbonyl groups on the surface. The highest removal efficiencies for low-concentration PFOA electrolyzed by acid-treated CNT sponge anode proved higher than 90%. The electro-oxidation mechanism of PFOA on CNT sponge anode was also discussed. PFOA is adsorbed on the CNT sponge rapidly increasing the concentration of PFOA on anode surface. When the potential on the anode is adjusted to more than 3.5V, the adsorbed PFOA undergoes electrochemically oxidation and hydrolysis to produce shorter-chain perfluorocarboxylic acids with less CF2 unit. The efficient electro-oxidation of PFOA by CNT sponge anode is due to the combined effect of adsorption and electrochemical oxidation. These findings provide an efficient method to remove actual concentration PFOA from water. PMID:26172515

  15. Probability fracture mechanics analysis of plates with surface cracks

    International Nuclear Information System (INIS)

    Background: The uncertainties of input parameters in an deterministic structural integrity assessment of pressure vessels may affect the assessment results. This can be improved by performing probability fracture mechanics (PFM) analysis. Purpose: This work investigates the effect of uncertainties of load, defect size, fracture toughness and failure criteria on the failure probability of semi-elliptical surface cracks in plates under combined tension and bending. Methods: The correction factor method provided by EPRI is used to estimate the stress intensity factor (SIF). The J-integral values at the deepest point of the surface crack tip are evaluated using the reference stress method and the globe limit load solution developed by Goodall and Webster and Lei. PFM analysis is performed with considering the uncertainty of crack size, yield strength and fracture toughness and Monte-Carlo (MC) simulation is used to calculate the failure probability. Results: Failure probability increases with increase of load level, Lr, for all load ratio values considered in this work for a given failure criterion. However, the failure probability based on the elastic-plastic fracture criterion is higher than that based on the linear elastic fracture criterion for a given load lever, Lr. Conclusions: The load level and the failure criteria have significant effect on the failure probability. However, the load ratio makes a little contribution to the failure probability for a given failure criterion. (authors)

  16. Study on suppression mechanism of electron emission from Mo grid coated with carbon film by dual ion beam deposition

    International Nuclear Information System (INIS)

    It is problematic that electrons are emitted from the Mo grid of pulsed-controlled grid traveling wave tubes, caused by the contamination of cathode evaporation material, i.e. BaO. Some studies show that a Mo grid coated with carbon can greatly suppress grid electron emission. However, the reason for the electron emission suppression is not completely clear. To understand the mechanism of electron emission suppression of a BaO/C/Mo system, carbon films were prepared on Mo substrates at room temperature by means of DIBSD (dual ion beam sputtering deposition), and BaO layers were coated by using a chemical method. Post-annealing was conducted under a flowing nitrogen ambient at 700 .deg. C for 1.5 hours. The structure of the as-deposited carbon films was evaluated by TEM, AES and Raman spectroscopy. The annealed samples, the BaO/ Mo and BaO/C/Mo systems, were analyzed by XPS. The results suggest that the chemical reaction between BaO and C at high temperature eliminates the concentrations of Ba or BaO on the surface of the C/Mo system. It can be believed that the high work function material used as the grid surface coating and elimination of BaO on its surface have a critical effect on grid electron emission suppression. Moreover, the carbon film was characterized by density, homogeneity and high adhesion, owing to the features of DIBSD.

  17. Near-surface monitoring strategies for geologic carbon dioxide storage verification

    Energy Technology Data Exchange (ETDEWEB)

    Oldenburg, Curtis M.; Lewicki, Jennifer L.; Hepple, Robert P.

    2003-10-31

    Geologic carbon sequestration is the capture of anthropogenic carbon dioxide (CO{sub 2}) and its storage in deep geologic formations. Geologic CO{sub 2} storage verification will be needed to ensure that CO{sub 2} is not leaking from the intended storage formation and seeping out of the ground. Because the ultimate failure of geologic CO{sub 2} storage occurs when CO{sub 2} seeps out of the ground into the atmospheric surface layer, and because elevated concentrations of CO{sub 2} near the ground surface can cause health, safety, and environmental risks, monitoring will need to be carried out in the near-surface environment. The detection of a CO{sub 2} leakage or seepage signal (LOSS) in the near-surface environment is challenging because there are large natural variations in CO{sub 2} concentrations and fluxes arising from soil, plant, and subsurface processes. The term leakage refers to CO{sub 2} migration away from the intended storage site, while seepage is defined as CO{sub 2} passing from one medium to another, for example across the ground surface. The flow and transport of CO{sub 2} at high concentrations in the near-surface environment will be controlled by its high density, low viscosity, and high solubility in water relative to air. Numerical simulations of leakage and seepage show that CO{sub 2} concentrations can reach very high levels in the shallow subsurface even for relatively modest CO{sub 2} leakage fluxes. However, once CO{sub 2} seeps out of the ground into the atmospheric surface layer, surface winds are effective at dispersing CO{sub 2} seepage. In natural ecological systems with no CO{sub 2} LOSS, near-surface CO{sub 2} fluxes and concentrations are controlled by CO{sub 2} uptake by photosynthesis, and production by root respiration, organic carbon biodegradation in soil, deep outgassing of CO{sub 2}, and by exchange of CO{sub 2} with the atmosphere. Existing technologies available for monitoring CO{sub 2} in the near-surface environment

  18. Interactive effects between carbon allotrope fillers on the mechanical reinforcement of polyisoprene based nanocomposites

    OpenAIRE

    Galimberti, M; Agnelli, S.; V. Cipolletti; S. Musto; M. Coombs; L. Conzatti; S. Pandini; T. Ricco

    2014-01-01

    Interactive effects of carbon allotropes on the mechanical reinforcement of polymer nanocomposites were investigated. Carbon nanotubes (CNT) and nano-graphite with high shape anisotropy (nanoG) were melt blended with poly(1,4-cis-isoprene), as the only fillers or in combination with carbon black (CB), measuring the shear modulus at low strain amplitudes for peroxide crosslinked composites. The nanofiller was found to increase the low amplitude storage modulus of the matrix, with or without CB...

  19. Optimized preparation for large surface area activated carbon from date (Phoenix dactylifera L.) stone biomass

    International Nuclear Information System (INIS)

    The preparation of activated carbon from date stone treated with phosphoric acid was optimized using rotatable central composite design of response surface methodology (RSM). The chemical activating agent concentration and temperature of activation plays a crucial role in preparation of large surface area activated carbons. The optimized activated carbon was characterized using thermogravimetric analysis, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the larger surface area of activated carbon from date stone can be achieved under optimum activating agent (phosphoric acid) concentration, 50.0% (8.674 mol L−1) and activation temperature, 900 °C. The Brunauer–Emmett–Teller (BET) surface area of optimized activated carbon was found to be 1225 m2 g−1, and thermogravimetric analysis revealed that 55.2% mass of optimized activated carbon was found thermally stable till 900 °C. The leading chemical functional groups found in the date stone activated carbon were aliphatic carboxylic acid salt ν(C=O) 1561.22 cm−1 and 1384.52 cm−1, aliphatic hydrocarbons ν(C–H) 2922.99 cm−1 (C–H sym./asym. stretch frequency), aliphatic phosphates ν(P–O–C) 1054.09 cm−1, and secondary aliphatic alcohols ν(O–H) 3419.81 cm−1 and 1159.83 cm−1. - Highlights: • RSM optimization was done for the production of large surface area activated carbon. • Two independent variables with two responses were selected for optimization. • Characterization was done for surface area, morphology and chemical constituents. • Optimized date stone activated carbon achieved surface area 1225 m2 g−1

  20. Coefficient of friction between carbon steel and perlite concrete surfaces. Test report

    International Nuclear Information System (INIS)

    The results of coefficient of friction, μ, tests conducted on perlite blocks and carbon steel plates under various conditions are discussed. Variables included in the test entailed the use of lubricants (i.e. water and simulated radioactive waste solution) abrasives (120 grit, 60 grit, 40 grit sand paper) applied to the surfaces of the perlite block and carbon steel plates

  1. Amino-functionalized green fluorescent carbon dots as surface energy transfer biosensors for hyaluronidase

    Science.gov (United States)

    Liu, Siyu; Zhao, Ning; Cheng, Zhen; Liu, Hongguang

    2015-04-01

    Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis.Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00070j

  2. Hydrophobic-hydrophilic nanostructures synthesis on the polymers surfaces in low temperature carbon plasma

    International Nuclear Information System (INIS)

    Low-temperature (20-60 deg C) surface modification of polymers (polyethylene and polyurethane) by a method of pulsed ion-plasma carbon deposition was investigated. Optimal parameters suitable for 0.3-15 nm thick deposition of carbon mosaic hydrophobic-hydrophilic nanostructures having 10-500 nm sized clusters were determined

  3. Evaluation of carbon fiber surface treated by chemical and cold plasma processes

    Directory of Open Access Journals (Sweden)

    Liliana Burakowski Nohara

    2005-09-01

    Full Text Available Sized PAN-based carbon fibers were treated with hydrochloric and nitric acids, as well as argon and oxygen cold plasmas, and the changes on their surfaces evaluated. The physicochemical properties and morphological changes were investigated by atomic force microscopy (AFM, scanning electron microscopy (SEM, X-ray photoelectron spectroscopy (XPS, tensile strength tests and Raman spectroscopy. The nitric acid treatment was found to cause the most significant chemical changes on the carbon fiber surface, introducing the largest number of chemical groups and augmenting the roughness. The oxygen plasma treatments caused ablation of the carbon fiber surface, removing carbon atoms such as CO and CO2 molecules. In addition, the argon plasma treatment eliminated defects on the fiber surface, reducing the size of critical flaws and thus increasing the fiber's tensile strength.

  4. Effect of EB irradiation on the structures of carbon fiber surface

    International Nuclear Information System (INIS)

    The object of this work is to investigate the effect of EB irradiation on carbon fiber surface. The laser Raman spectroscopy, X ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X ray diffraction were used to observe the surface changes including an enhancement in oxygen and nitrogen containing groups, smooth degree of carbon fiber surface and in size of graphite crystal layers. It showed that polar groups on carbon-fiber surface were influenced by the active species created in the media during EB irradiation. The self-quenching reaction or disengage reaction took place in activated groups. The group C=O was increased in the former reaction, on the other hand, the group C-O in the latter reaction. The crystal structure of the bulk carbon fiber was not effected by EB irradiation

  5. Comparison of various sources of high surface area carbon prepared by different types of activation

    International Nuclear Information System (INIS)

    Activated carbon has been known as an excellent adsorbent and is widely used due to its large adsorption capacity. Activation condition and types of activation influence the surface area and porosity of the activated carbon produced. In this study, palm kernel shells and commercially activated carbon were used. To convert palm kernel shells into coal, two methods were employed, namely chemical activation and physical activation. For chemical activation, two activating agents, zinc chloride and potassium carbonate, were used. The activated carbons were analyzed using Fourier Transform Infrared (FTIR) spectroscopy, single point BET and free emission scanning electron microscopy (FESEM). The commercial activated carbon was also characterized. FTIR results indicate that all the palm kernel shells were successfully converted to carbon. Single point BET surface area of all the carbons prepared were obtained. From FESEM micrograph, the chemically activated palm kernel shells shows well highly defined cavities and pores. This study also shows that palm kernel shells can be used to be a better source of high surface area carbon. (author)

  6. Effects of Size and Surfaee Modification of Multi-walled Carbon Nanotubes on Mechanical Properties of Polyurethane-based Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    ZHANG Fang; HUANGJin; ZHANG Hao; SU Zhongmin; ZHANG Qiaoxin

    2012-01-01

    Polyurethanes/multi-walled carbon nanotube (PU/CNT) composites were prepared with a help of ultrasonically dispersing CNT in the traditional procedure of synthesizing polyurethane.In this case,the various loading levels,sizes and surface-modified groups were considered to regulate the mechanical performances of the PU/CNT nanocomposites.Moreover,the structure and mechanical properties of all the PU/CNT nanocomposites were investigated by attenuated total reflection-Fourier transform infrared spectroscopy,dynamic mechanical analysis,scanning electron microscope,transmission electron microscope,and tensile testing.The experimental results showed that a moderate loading-level of 0.1 wt% and a diameter of 10-15 nm for CNT could produce the maximum tensile strength and elongation while it was worth noting that the surface carboxylation of CNT could further enhance the tensile strength and elongation of the PU/CNT nanocomposites.

  7. The role of beaded activated carbon's surface oxygen groups on irreversible adsorption of organic vapors.

    Science.gov (United States)

    Jahandar Lashaki, Masoud; Atkinson, John D; Hashisho, Zaher; Phillips, John H; Anderson, James E; Nichols, Mark

    2016-11-01

    The objective of this study is to determine the contribution of surface oxygen groups to irreversible adsorption (aka heel formation) during cyclic adsorption/regeneration of organic vapors commonly found in industrial systems, including vehicle-painting operations. For this purpose, three chemically modified activated carbon samples, including two oxygen-deficient (hydrogen-treated and heat-treated) and one oxygen-rich sample (nitric acid-treated) were prepared. The samples were tested for 5 adsorption/regeneration cycles using a mixture of nine organic compounds. For the different samples, mass balance cumulative heel was 14 and 20% higher for oxygen functionalized and hydrogen-treated samples, respectively, relative to heat-treated sample. Thermal analysis results showed heel formation due to physisorption for the oxygen-deficient samples, and weakened physisorption combined with chemisorption for the oxygen-rich sample. Chemisorption was attributed to consumption of surface oxygen groups by adsorbed species, resulting in formation of high boiling point oxidation byproducts or bonding between the adsorbates and the surface groups. Pore size distributions indicated that different pore sizes contributed to heel formation - narrow micropores (<7Å) in the oxygen-deficient samples and midsize micropores (7-12Å) in the oxygen-rich sample. The results from this study help explain the heel formation mechanism and how it relates to chemically tailored adsorbent materials. PMID:27295065

  8. Ultrathin carbon nanopainting of LiFePO4 by oxidative surface polymerization of dopamine

    Science.gov (United States)

    Ding, Bo; Tang, Wei Chin; Ji, Ge; Ma, Yue; Xiao, Pengfei; Lu, Li; Lee, Jim Yang

    2014-11-01

    The common strategy to address the low electronic conductivity of LiFePO4 is to downsize LiFePO4 and to coat the nanocrystal with conductive carbon film. The major issues with existing carbon coating techniques are thickness and quality control. This paper reports a facile carbon coating method which can provide ultrathin, uniform and fully encapsulating carbon coating on LiFePO4. This coating method capitalizes on the redox chemistry of surface Fe3+ on solvothermally synthesized LiFePO4 nanocrystal, to deposit uniform thin films of polydopamine films. The polymer film is easily carbonized into ultrathin carbon film. The carbon coated LiFePO4 exhibits very high rate performance (143 mAh g-1 at current density of 1700 mA g-1) with excellent capacity retention.

  9. Mechanical Properties of Heat-treated Carbon Fibers

    Science.gov (United States)

    Effinger, Michael R.; Patel, Bhavesh; Koenig, John; Cuneo, Jaques; Neveux, Michael G.; Demos, Chrystoph G.

    2004-01-01

    Carbon fibers are selected for ceramic matrix composites (CMC) are based on their as-fabricated properties or on "that is what we have always done" technical culture while citing cost and availability when there are others with similar cost and availability. However, the information is not available for proper selection of carbon fibers since heat-treated properties are not known for the fibers on the market currently. Heat-treating changes the fiber's properties. Therefore, an effort was undertaken to establish fiber properties on 19 different types of fibers from six different manufactures for both PAN and pitch fibers. Heat-treating has been done at three different temperatures.

  10. Electron irradiation-induced change of structure and damage mechanisms in multi-walled carbon nanotubes

    Science.gov (United States)

    Yang, Jian-Qun; Li, Xing-Ji; Liu, Chao-Ming; Ma, Guo-Liang; Gao, Feng

    2015-11-01

    Owing to their unique structure and excellent electrical property, carbon nanotubes (CNTs) as an ideal candidate for making future electronic components have great application potentiality. In order to meet the requirements for space application in electronic components, it is necessary to study structural changes and damage mechanisms of multi-walled carbon nanotubes (MWCNTs), caused by the irradiations of 70 and 110 keV electrons. In the paper, the changes of structure and damage mechanisms in the irradiated MWCNTs, induced by the irradiations of 70 and 110 keV electrons, are investigated. The changes in surface morphology and structure of the irradiated MWCNT film are characterized using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, x-ray diffraction analysis (XRD), and electron paramagnetic resonance (EPR) spectroscopy. It is found that the MWCNTs show different behaviors in structural changes after 70 and 110 keV electron irradiation due to different damage mechanisms. SEM results reveal that the irradiation of 70 keV electrons does not change surface morphology of the MWCNT film, while the irradiation of 110 keV electrons with a high fluence of 5 × 1015 cm-2 leads to evident morphological changes, such as the formation of a rough surface, the entanglement of nanotubes and the shrinkage of nanotubes. Based on Raman spectroscopy, XPS, and XRD analyses, it is confirmed that the irradiation of 70 keV electrons increases the interlayer spacing of the MWCNTs and disorders their structure through electronic excitations and ionization effects, while the irradiation of 110 keV electrons obviously reduces the interlayer spacing of the MWCNTs and improves their graphitic order through knock-on atom displacements. The improvement of the irradiated MWCNTs by 110 keV electrons is attributed to the restructuring of defect sites induced by knock-on atom displacements. EPR spectroscopic analyses reveal that the MWCNTs exposed

  11. Electron irradiation-induced change of structure and damage mechanisms in multi-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    杨剑群; 李兴冀; 刘超铭; 马国亮; 高峰

    2015-01-01

    Owing to their unique structure and excellent electrical property, carbon nanotubes (CNTs) as an ideal candidate for making future electronic components have great application potentiality. In order to meet the requirements for space appli-cation in electronic components, it is necessary to study structural changes and damage mechanisms of multi-walled carbon nanotubes (MWCNTs), caused by the irradiations of 70 and 110 keV electrons. In the paper, the changes of structure and damage mechanisms in the irradiated MWCNTs, induced by the irradiations of 70 and 110 keV electrons, are investigated. The changes in surface morphology and structure of the irradiated MWCNT film are characterized using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, x-ray diffraction analysis (XRD), and electron paramagnetic resonance (EPR) spectroscopy. It is found that the MWCNTs show different behaviors in structural changes after 70 and 110 keV electron irradiation due to different damage mechanisms. SEM results reveal that the irra-diation of 70 keV electrons does not change surface morphology of the MWCNT film, while the irradiation of 110 keV electrons with a high fluence of 5 × 1015 cm−2 leads to evident morphological changes, such as the formation of a rough surface, the entanglement of nanotubes and the shrinkage of nanotubes. Based on Raman spectroscopy, XPS, and XRD analyses, it is confirmed that the irradiation of 70 keV electrons increases the interlayer spacing of the MWCNTs and disorders their structure through electronic excitations and ionization effects, while the irradiation of 110 keV electrons obviously reduces the interlayer spacing of the MWCNTs and improves their graphitic order through knock-on atom dis-placements. The improvement of the irradiated MWCNTs by 110 keV electrons is attributed to the restructuring of defect sites induced by knock-on atom displacements. EPR spectroscopic analyses reveal that the MWCNTs

  12. Mechanisms of aqueous wollastonite carbonation as a possible CO2 sequestration process

    International Nuclear Information System (INIS)

    The mechanisms of aqueous wollastonite carbonation as a possible carbon dioxide sequestration process were investigated experimentally by systematic variation of the reaction temperature, CO2 pressure, particle size, reaction time, liquid to solid ratio and agitation power. The carbonation reaction was observed to occur via the aqueous phase in two steps: (1) Ca leaching from the CaSiO3 matrix and (2) CaCO3 nucleation and growth. Leaching is hindered by a Ca-depleted silicate rim resulting from incongruent Ca-dissolution. Two temperature regimes were identified in the overall carbonation process. At temperatures below an optimum reaction temperature, the overall reaction rate is probably limited by the leaching rate of Ca. At higher temperatures, nucleation and growth of calcium carbonate is probably limiting the conversion, due to a reduced (bi)carbonate activity. The mechanisms for the aqueous carbonation of wollastonite were shown to be similar to those reported previously for an industrial residue and a Mg-silicate. The carbonation of wollastonite proceeds rapidly relative to Mg-silicates, with a maximum conversion in 15 min of 70% at 200C, 20 bar CO2 partial pressure and a particle size of <38 μm. The obtained insight in the reaction mechanisms enables the energetic and economic assessment of CO2 sequestration by wollastonite carbonation, which forms an essential next step in its further development

  13. Influence of the pore structure and surface chemical properties of activated carbon on the adsorption of mercury from aqueous solutions

    International Nuclear Information System (INIS)

    Highlights: • Activated carbons with different pore structure and surface chemical properties were prepared by modification process. • HgCl2 as a pollution target to evaluate the adsorption performance. • Influence of pore structure and surface chemical properties of activated carbon on adsorption of mercury was investigated. -- Abstract: Reactivation and chemical modification were used to obtain modified activated carbons with different pore structure and surface chemical properties. The samples were characterized by nitrogen absorption–desorption, Fourier transform infrared spectroscopy and the Bothem method. Using mercury chloride as the target pollutant, the Hg2+ adsorption ability of samples was investigated. The results show that the Hg2+ adsorption capacity of samples increased significantly with increases in micropores and acidic functional groups and that the adsorption process was exothermic. Different models and thermodynamic parameters were evaluated to establish the mechanisms. It was concluded that the adsorption occurred through a monolayer mechanism by a two-speed process involving both rapid adsorption and slow adsorption. The adsorption rate was determined by chemical reaction

  14. Ammonia removal using activated carbons: effect of the surface chemistry in dry and moist conditions

    OpenAIRE

    Gonçalves, Maraisa; Sánchez García, Laura; Jardim, Erika de Oliveira; Silvestre Albero, Joaquín; Rodríguez Reinoso, Francisco

    2011-01-01

    The effect of surface chemistry (nature and amount of oxygen groups) in the removal of ammonia was studied using a modified resin-based activated carbon. NH3 breakthrough column experiments show that the modification of the original activated carbon with nitric acid, that is, the incorporation of oxygen surface groups, highly improves the adsorption behavior at room temperature. Apparently, there is a linear relationship between the total adsorption capacity and the amount of the more acidic ...

  15. STUDY ON THE SURFACE MODIFICATION OF NANOMETER CARBON PARTICLES IN ATMOSPHERIC PLASMA

    Institute of Scientific and Technical Information of China (English)

    Y.J. Ge; G.Q. Zhang; Y.M. Liu; X.G. Guo; Z.F. Zhao

    2002-01-01

    The surface modification of nanometer carbon material has been studied by usingan Induced Dielectric Barrier Discharge Plasma device (IDBD). The experimentalresults show that with different work gases and different discharge conditions, thesurface behaviors of carbon black can be changed according to needs, including theuse of different functional groups and the change of the surface roughness of carbonparticles etc., which increased the grinding and dispersion abilities in binder.

  16. An investigation of the functional groups on the surface of activated carbons

    OpenAIRE

    MARYTE DERVINYTE; JURGIS BARKAUSKAS

    2004-01-01

    Activated carbons were produced in the laboratory from wood using a 20-run PlackettBurman experimental design for 19 factors. The obtained batches of activated carbon were analysed by potentiometric titration and FTIR spectroscopy to determine the surface functional groups. The results obtained by potentiometric titration displayed the distribution of individual acidity constants of those groups in the pK range. Considering this parameter, the surface functional groups were divided into carbo...

  17. Carbon Surface Layers on a High-Rate LiFePO4

    OpenAIRE

    Gabrisch, Heike; Wilcox, James D.; Doeff, Marca M.

    2005-01-01

    Transmission electron microscopy (TEM) was used to image particles of a high-rate LiFePO4 sample containing a small amount of in situ carbon. The particle morphology is highly irregular, with a wide size distribution. Nevertheless, coatings, varying from about 5-10 nm in thickness, could readily be detected on surfaces of particles as well as on edges of agglomerates. Elemental mapping using Energy Filtered TEM (EFTEM) indicates that these very thin surface layers are composed of carbon....

  18. Electrophoretic Deposition of Carbon Nanotubes on 3-Amino-Propyl-Triethoxysilane (APTES) Surface Functionalized Silicon Substrates

    OpenAIRE

    Theda Daniels-Race; Anirban Sarkar

    2013-01-01

    Fabrication of uniform thin coatings of multi-walled carbon nanotubes (MWCNTs) by electrophoretic deposition (EPD) on semiconductor (silicon) substrates with 3-aminopropyl-triethoxysilane (APTES) surface functionalization has been studied extensively in this report. The gradual deposition and eventual film formation of the carbon nanotubes (CNTs) is greatly assisted by the Coulombic force of attraction existing between the positively charged –NH2 surface groups of APTES and the acid treated, ...

  19. Impact of Carbon Quota Allocation Mechanism on Emissions Trading: An Agent-Based Simulation

    Directory of Open Access Journals (Sweden)

    Wei Jiang

    2016-08-01

    Full Text Available This paper establishes an agent-based simulation system of the carbon emissions trading in accordance with the complex feature of the trading process. This system analyzes the impact of the carbon quota allocation mechanism on emissions trading for three different aspects including the amount of emissions reduction, the economic effect on the emitters, and the emissions reduction cost. Based on the data of the carbon emissions of different industries in China, several simulations were made. The results indicate that the emissions trading policy can effectively reduce carbon emissions in a perfectly competitive market. Moreover, by comparing separate quota allocation mechanisms, we obtain the result that the scheme with a small extent quota decrease in a comprehensive allocation mechanism can minimize the unit carbon emission cost. Implementing this scheme can also achieve minimal effects of carbon emissions limitation on the economy on the basis that the environment is not destroyed. However, excessive quota decrease cannot promote the emitters to reduce emission. Taking into account that several developing countries have the dual task of limiting carbon emissions and developing the economy, it is necessary to adopt a comprehensive allocation mechanism of the carbon quota and increase the initial proportion of free allocation.

  20. Carbon Nanofiber-Based, High-Frequency, High-Q, Miniaturized Mechanical Resonators

    Science.gov (United States)

    Kaul, Anupama B.; Epp, Larry W.; Bagge, Leif

    2011-01-01

    High Q resonators are a critical component of stable, low-noise communication systems, radar, and precise timing applications such as atomic clocks. In electronic resonators based on Si integrated circuits, resistive losses increase as a result of the continued reduction in device dimensions, which decreases their Q values. On the other hand, due to the mechanical construct of bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators, such loss mechanisms are absent, enabling higher Q-values for both BAW and SAW resonators compared to their electronic counterparts. The other advantages of mechanical resonators are their inherently higher radiation tolerance, a factor that makes them attractive for NASA s extreme environment planetary missions, for example to the Jovian environments where the radiation doses are at hostile levels. Despite these advantages, both BAW and SAW resonators suffer from low resonant frequencies and they are also physically large, which precludes their integration into miniaturized electronic systems. Because there is a need to move the resonant frequency of oscillators to the order of gigahertz, new technologies and materials are being investigated that will make performance at those frequencies attainable. By moving to nanoscale structures, in this case vertically oriented, cantilevered carbon nanotubes (CNTs), that have larger aspect ratios (length/thickness) and extremely high elastic moduli, it is possible to overcome the two disadvantages of both bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators. Nano-electro-mechanical systems (NEMS) that utilize high aspect ratio nanomaterials exhibiting high elastic moduli (e.g., carbon-based nanomaterials) benefit from high Qs, operate at high frequency, and have small force constants that translate to high responsivity that results in improved sensitivity, lower power consumption, and im - proved tunablity. NEMS resonators have recently been demonstrated using topdown