WorldWideScience

Sample records for carbon surface chemical

  1. Influence of process parameters on the surface and chemical properties of activated carbon obtained from biochar by chemical activation.

    Science.gov (United States)

    Angın, Dilek; Altintig, Esra; Köse, Tijen Ennil

    2013-11-01

    Activated carbons were produced from biochar obtained through pyrolysis of safflower seed press cake by chemical activation with zinc chloride. The influences of process variables such as the activation temperature and the impregnation ratio on textural and chemical-surface properties of the activated carbons were investigated. Also, the adsorptive properties of activated carbons were tested using methylene blue dye as the targeted adsorbate. The experimental data indicated that the adsorption isotherms are well described by the Langmuir equilibrium isotherm equation. The optimum conditions resulted in activated carbon with a monolayer adsorption capacity of 128.21 mg g(-1) and carbon content 76.29%, while the BET surface area and total pore volume corresponded to 801.5m(2)g(-1) and 0.393 cm(3)g(-1), respectively. This study demonstrated that high surface area activated carbons can be prepared from the chemical activation of biochar with zinc chloride as activating agents. PMID:24080293

  2. 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.

  3. IR study on surface chemical properties of catalytic grown carbon nanotubes and nanofibers

    Institute of Scientific and Technical Information of China (English)

    Li-hua TENG; Tian-di TANG

    2008-01-01

    In this study, the surface chemical properties of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) grown by catalytic decomposition of methane on nickel and cobalt based catalysts were studied by DRIFT (Diffuse Reflectance Infrared Fourier Transform) and transmission Infrared (IR) spectroscopy. The results show that the surface exists not only carbon-hydrogen groups, but also carboxyl, ketene or quinone (carbonyl) oxygen-containing groups. These functional groups were formed in the process of the material growth, which result in large amount of chemical defect sites on the walls.

  4. 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.

  5. High specific surface area carbon nanotubes from catalytic chemical vapor deposition process

    OpenAIRE

    Bacsa, Revathi; Laurent, Christophe; Peigney, Alain; Bacsa, Wolfgang; Vaugien, Thibaud; Rousset, Abel

    2000-01-01

    A carbon nanotube specimen with a carbon content of 83 wt.% (95 vol.%) and a specific surface area equal to 790 m2/g (corresponding to 948 m2/g of carbon) is prepared by a catalytic chemical vapor deposition method. The nanotubes, 90% of which are single- and double-walled, are individual rather than in bundles. High-resolution electron microscopy shows a diameter distribution in the range 0.8-5 nm and Raman spectroscopy shows a high proportion of tubular carbon. Both techniques reveal a maxi...

  6. Evaluation of carbon fiber surface treated by chemical and cold plasma processes

    OpenAIRE

    Liliana Burakowski Nohara; Gilberto Petraconi Filho; Evandro Luís Nohara; Maurício Urban Kleinke; Mirabel Cerqueira Rezende

    2005-01-01

    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 fi...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-01-07

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

  8. Chemical Bath Deposition of Aluminum Oxide Buffer on Curved Surfaces for Growing Aligned Carbon Nanotube Arrays.

    Science.gov (United States)

    Wang, Haitao; Na, Chongzheng

    2015-07-01

    Direct growth of vertically aligned carbon nanotube (CNT) arrays on substrates requires the deposition of an aluminum oxide buffer (AOB) layer to prevent the diffusion and coalescence of catalyst nanoparticles. Although AOB layers can be readily created on flat substrates using a variety of physical and chemical methods, the preparation of AOB layers on substrates with highly curved surfaces remains challenging. Here, we report a new solution-based method for preparing uniform layers of AOB on highly curved surfaces by the chemical bath deposition of basic aluminum sulfate and annealing. We show that the thickness of AOB layer can be increased by extending the immersion time of a substrate in the chemical bath, following the classical Johnson-Mehl-Avrami-Kolmogorov crystallization kinetics. The increase of AOB thickness in turn leads to the increase of CNT length and the reduction of CNT curviness. Using this method, we have successfully synthesized dense aligned CNT arrays of micrometers in length on substrates with highly curved surfaces including glass fibers, stainless steel mesh, and porous ceramic foam. PMID:26053766

  9. Effect of activation agents on the surface chemical properties and desulphurization performance of activated carbon

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Flue gas pollution is a serious environmental problem that needs to be solved for the sustainable development of China.The surface chemical properties of carbon have great influence on its desulphurization performance.A series of activated carbons (ACs) were prepared using HNO3,H2O2,NH3·H2O and steam as activation agents with the aim to introduce functional groups to carbon surface in the ACs preparation process.The ACs were physically and chemically characterized by iodine and SO2 adsorption,ultimate analysis,Boehm titration,and temperature-programmed reduction (TPR).Results showed that the iodine number and desulphurization capacity of NH3·H2O activated carbon (AC-NH3) increase with both activation time,and its desulphurization capacity also increases with the concentration of activation agent.However,HNO3 activated carbon (AC-HNO3) and H2O2 activated carbon (AC-H2O2) exhibit more complex behavior.Only their iodine numbers increase monotonously with activation time.Compared with steam activated AC (AC-H2O),the nitrogen content increases 0.232% in AC-NH3 and 0.077% in AC-HNO3.The amount of total basic site on AC-HNO3 is 0.19 mmol·g-1 higher than that on AC-H2O.H2O2 activation introduces an additional 0.08 mmol·g-1 carboxyl groups to AC surface than that introduced by steam activation.The desulphurization capacity of ACs in simulate flue gas desulphurization decreases as follows: AC-NH3 > AC-HNO3 > AC-H2O2 > AC-H2O.This sequence is in accord with the SO2 catalytic oxidation/oxidation ratio in the absence of oxygen and the oxidation property reflected by TPR.In the presence of oxygen,all adsorbed SO2 on ACs can be oxidized into SO3.The desulphurization capacity increases differently according to the activation agents;the desulphurization capacity of AC-NH3 and AC-HNO3 improves by 4.8 times,yet AC-H2O increases only by 2.62 as compared with the desulphurization of corresponding ACs in absence of oxygen.

  10. Tuning photoluminescence and surface properties of carbon nanodots for chemical sensing

    Science.gov (United States)

    Zhang, Zhaomin; Pan, Yi; Fang, Yaning; Zhang, Lulu; Chen, Junying; Yi, Changqing

    2015-12-01

    Obtaining tunable photoluminescence (PL) with improved emission properties is crucial for successfully implementing fluorescent carbon nanodots (fCDs) in all practical applications such as multicolour imaging and multiplexed detection by a single excitation wavelength. In this study, we report a facile hydrothermal approach to adjust the PL peaks of fCDs from blue, green to orange by controlling the surface passivation reaction during the synthesis. This is achieved by tuning the passivating reagents in a step-by-step manner. The as-prepared fCDs with narrow size distribution show improved PL properties with different emission wavelengths. Detailed characterization of fCDs using elemental analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy suggested that the surface chemical composition results in this tunable PL emission. Surface passivation significantly alters the surface status, resulting in fCDs with either stronger surface oxidation or N element doping that ultimately determine their PL properties. Further experiments suggested that the as-prepared orange luminescent fCDs (O-fCDs) were sensitive and specific nanosensing platforms towards Fe3+ determination in a complex biological environment, emphasizing their potential practical applications in clinical and biological fields.Obtaining tunable photoluminescence (PL) with improved emission properties is crucial for successfully implementing fluorescent carbon nanodots (fCDs) in all practical applications such as multicolour imaging and multiplexed detection by a single excitation wavelength. In this study, we report a facile hydrothermal approach to adjust the PL peaks of fCDs from blue, green to orange by controlling the surface passivation reaction during the synthesis. This is achieved by tuning the passivating reagents in a step-by-step manner. The as-prepared fCDs with narrow size distribution show improved PL properties with different emission wavelengths. Detailed

  11. 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.

  12. Incorporation of nitrogen into amorphous carbon films produced by surface-wave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    In order to study the influence of nitrogen incorporated into amorphous carbon films, nitrogenated amorphous carbon films have been deposited by using surface wave plasma chemical vapor deposition under various ratios of N2/CH4 gas flow. Optical emission spectroscopy has been used to monitor plasma features near the deposition zone. After deposition, the samples are checked by Raman spectroscopy and x-ray photo spectroscopy (XPS). Optical emission intensities of CH and N atom in the plasma are found to be enhanced with the increase in the N2/CH4 gas flow ratio, and then reach their maximums when the N2/CH4 gas flow ratio is 5%. A contrary variation is found in Raman spectra of deposited films. The intensity ratio of the D band to the G band (ID/IG) and the peak positions of the G and D bands all reach their minimums when the N2/CH4 gas flow ratio is 5%. These show that the structure of amorphous carbon films has been significantly modified by introduction of nitrogen

  13. Chemically Synthesised Pt Particles on Surface Oxidized Carbon Nanotubes as an Effective Catalyst for Direct Methanol Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    Mohammad; yari; Sajjad; Sadaghat; Sharehjini

    2007-01-01

    1 Results The synthesis, physical characterization and electrochemical analysis of Pt particles prepared using the surface oxidized carbon nanotubes prepared by chemically anchoring Pt onto the surface of the CNTs with 2.0 mol/L HNO3 by refluxing for 10 h to introduce surface functional groups.The particles of Pt are synthesized by reduction with sodium borohydride of H2PtCl6. The electro-oxidation of liquid methanol of this catalyst as a thin layer on glassy carbon electrode is investigated at room te...

  14. Hydrogen Storage in High Surface Area Carbon Nanotubes Produced by Catalytic Chemical Vapor Deposition

    OpenAIRE

    Bacsa, Revathi; Laurent, Christophe; Morishima, Ryuta; Suzuki, Hiroshi; Le Lay, Mikako

    2004-01-01

    Carbon nanotubes, mostly single- and double-walled, are prepared by a catalytic chemical vapor deposition method using H2-CH4 atmospheres with different CH4 contents. The maximum hydrogen storage at room temperatures and 10 MPa is 0.5 wt %. Contrary to expectations, purification of the carbon nanotube specimens by oxidative acid treatments or by heating in inert gas decreases the hydrogen storage. Decreasing the residual catalyst content does not necessarily lead to an increase in ASH. Moreov...

  15. Chemical surface modification of calcium carbonate particles with stearic acid using different treating methods

    Science.gov (United States)

    Cao, Zhi; Daly, Michael; Clémence, Lopez; Geever, Luke M.; Major, Ian; Higginbotham, Clement L.; Devine, Declan M.

    2016-08-01

    Calcium carbonate (CaCO3) is often treated with stearic acid (SA) to decrease its polarity. However, the method of application of the SA treatments has a strong influence on CaCO3 thermoplastic composite's interfacial structure and distribution. Several of papers describe the promising effects of SA surface treatment, but few compare the treatment process and its effect on the properties of the final thermoplastic composite. In the current study, we assessed a new SA treatment method, namely, complex treatment for polymer composite fabrication with HDPE. Subsequently, a comparative study was performed between the "complex" process and the other existing methods. The composites were assessed using different experiments included scanning electron microscopy (SEM), void content, density, wettability, differential scanning calorimetry (DSC), and tensile tests. It was observed that the "complex" surface treatment yielded composites with a significantly lower voids content and higher density compared to other surface treatments. This indicates that after the "complex" treatment process, the CaCO3 particles and HDPE matrix are more tightly packed than other methods. DSC and wettability results suggest that the "wet" and "complex" treated CaCO3 composites had a significantly higher heat of fusion and moisture resistance compared to the "dry" treated CaCO3 composites. Furthermore, "wet" and "complex" treated CaCO3 composites have a significantly higher tensile strength than the composites containing untreated and "dry" treated CaCO3. This is mainly because the "wet" and "complex" treatment processes have increased adsorption density of stearate, which enhances the interfacial interaction between matrix and filler. These results confirm that the chemical adsorption of the surfactant ions at the solid-liquid interface is higher than at other interface. From this study, it was concluded that the utilization of the "complex" method minimised the negative effects of void

  16. 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

  17. Catalytic Chemical Vapor Deposition Synthesis of Carbon Aerogels of High-Surface Area and Porosity

    Directory of Open Access Journals (Sweden)

    Armando Peña

    2012-01-01

    Full Text Available In this work carbon aerogels were synthesized by catalytic chemical vapor deposition method (CCVD. Ferrocene were employed as a source both of catalytic material (Fe and of carbon. Gaseous hydrogen and argon were used as reductant and carrier gas, respectively. The products of reaction were collected over alumina. The morphology and textural properties of the soot produced in the reaction chamber were investigated using Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, X-ray photoelectron spectroscopy, and N2 physisorption (BET and BHJ methods. After the evaluation of the porous structure of the synthesized products, 780 ± 20 m2/g of SBET and 0.55 ± 0.02 cm3/g of VBJH were found. The presence of iron carbide and the partial oxidation of carbon nanostructures were revealed by XPS.

  18. Low-toxic and safe nanomaterials by surface-chemical design, carbon nanotubes, fullerenes, metallofullerenes, and graphenes

    Science.gov (United States)

    YanEqual Contribution, Liang; Zhao, Feng; Li, Shoujian; Hu, Zhongbo; Zhao, Yuliang

    2011-02-01

    The toxicity grade for a bulk material can be approximately determined by three factors (chemical composition, dose, and exposure route). However, for a nanomaterial it depends on more than ten factors. Interestingly, some nano-factors (like huge surface adsorbability, small size, etc.) that endow nanomaterials with new biomedical functions are also potential causes leading to toxicity or damage to the living organism. Is it possible to create safe nanomaterials if such a number of complicated factors need to be regulated? We herein try to find answers to this important question. We first discuss chemical processes that are applicable for nanosurface modifications, in order to improve biocompatibility, regulate ADME, and reduce the toxicity of carbon nanomaterials (carbon nanotubes, fullerenes, metallofullerenes, and graphenes). Then the biological/toxicological effects of surface-modified and unmodified carbon nanomaterials are comparatively discussed from two aspects: the lowered toxic responses or the enhanced biomedical functions. We summarize the eight biggest challenges in creating low-toxicity and safer nanomaterials and some significant topics of future research needs: to find out safer nanofactors; to establish controllable surface modifications and simpler chemistries for low-toxic nanomaterials; to explore the nanotoxicity mechanisms; to justify the validity of current toxicological theories in nanotoxicology; to create standardized nanomaterials for toxicity tests; to build theoretical models for cellular and molecular interactions of nanoparticles; and to establish systematical knowledge frameworks for nanotoxicology.

  19. Surface transformations of carbon (graphene, graphite, diamond, carbide), deposited on polycrystalline nickel by hot filaments chemical vapour deposition

    International Nuclear Information System (INIS)

    The deposition of carbon has been studied at high temperature on polycrystalline nickel by hot filaments activated chemical vapor deposition (HFCVD). The sequences of carbon deposition are studied by surface analyses: Auger electron spectroscopy (AES), electron loss spectroscopy (ELS), X-ray photoelectron spectroscopy (XPS) in a chamber directly connected to the growth chamber. A general scale law of the (C/Ni) intensity lines is obtained with a reduced time. Both, shape analysis of the AES C KVV line and the C1s relative intensity suggest a three-step process: first formation of graphene and a highly graphitic layer, then multiphase formation with graphitic, carbidic and diamond-like carbon and finally at a critical temperature that strongly depends on the pretreatment of the polycrystalline nickel surface, a rapid transition to diamond island formation. Whatever the substrate diamond is always the final product and some graphene layers the initial product. Moreover it is possible to stabilize a few graphene layers at the initial sequences of carbon deposition. The duration of this stabilization step is strongly depending however on the pre-treatment of the Ni surface.

  20. The Surface Interface Characteristics of Vertically Aligned Carbon Nanotube and Graphitic Carbon Fiber Arrays Grown by Thermal and Plasma Enhanced Chemical Vapor Deposition

    Science.gov (United States)

    Delzeit, Lance; Nguyen, Cattien; Li, Jun; Han, Jie; Meyyappan, M.

    2002-01-01

    The development of nano-arrays for sensors and devices requires the growth of arrays with the proper characteristics. One such application is the growth of vertically aligned carbon nanotubes (CNTs) and graphitic carbon fibers (GCFs) for the chemical attachment of probe molecules. The effectiveness of such an array is dependent not only upon the effectiveness of the probe and the interface between that probe and the array, but also the array and the underlaying substrate. If that array is a growth of vertically aligned CNTs or GCFs then the attachment of that array to the surface is of the utmost importance. This attachment provides the mechanical stability and durability of the array, as well as, the electrical properties of that array. If the detection is to be acquired through an electrical measurement, then the appropriate resistance between the array and the surface need to be fabricated into the device. I will present data on CNTs and GCFs grown from both thermal and plasma enhanced chemical vapor deposition. The focus will be on the characteristics of the metal film from which the CNTs and GCFs are grown and the changes that occur due to changes within the growth process.

  1. 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.

  2. Amyloid fibrillation in native and chemically-modified forms of carbonic anhydrase II: role of surface hydrophobicity.

    Science.gov (United States)

    Es-Haghi, Ali; Shariatizi, Sajad; Ebrahim-Habibi, Azadeh; Nemat-Gorgani, Mohsen

    2012-03-01

    Chemical modification or mutation of proteins may bring about significant changes in the net charge or surface hydrophobicity of a protein structure. Such events may be of major physiological significance and may provide important insights into the genetics of amyloid diseases. In the present study, fibrillation potential of native and chemically-modified forms of bovine carbonic anhydrase II (BCA II) were investigated. Initially, various denaturing conditions including low pH and high temperatures were tested to induce fibrillation. At a low pH of around 2.4, where the protein is totally dissociated, the apo form was found to take up a pre-molten globular (PMG) conformation with the capacity for fibril formation. Upon increasing the pH to around 3.6, a molten globular (MG) form became abundant, forming amorphous aggregates. Charge neutralization and enhancement of hydrophobicity by methylation, acetylation and propionylation of lysine residues appeared very effective in promoting fibrillation of both the apo and holo forms under native conditions, the rates and extents of which were directly proportional to surface hydrophobicity, and influenced by salt concentration and temperature. These modified structures underwent more pronounced fibrillation under native conditions, than the PMG intermediate form, observed under denaturing conditions. The nature of the fibrillation products obtained from intermediate and modified structures were characterized and compared and their possible cytotoxicity determined. Results are discussed in terms of the importance of surface net charge and hydrophobicity in controlling protein aggregation. A discussion on the physiological significance of the observations is also presented. PMID:22251892

  3. 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.

  4. Critical role of surface chemical modifications induced by length shortening on multi-walled carbon nanotubes-induced toxicity

    Directory of Open Access Journals (Sweden)

    Bussy Cyrill

    2012-11-01

    Full Text Available Abstract Given the increasing use of carbon nanotubes (CNT in composite materials and their possible expansion to new areas such as nanomedicine which will both lead to higher human exposure, a better understanding of their potential to cause adverse effects on human health is needed. Like other nanomaterials, the biological reactivity and toxicity of CNT were shown to depend on various physicochemical characteristics, and length has been suggested to play a critical role. We therefore designed a comprehensive study that aimed at comparing the effects on murine macrophages of two samples of multi-walled CNT (MWCNT specifically synthesized following a similar production process (aerosol-assisted CVD, and used a soft ultrasonic treatment in water to modify the length of one of them. We showed that modification of the length of MWCNT leads, unavoidably, to accompanying structural (i.e. defects and chemical (i.e. oxidation modifications that affect both surface and residual catalyst iron nanoparticle content of CNT. The biological response of murine macrophages to the two different MWCNT samples was evaluated in terms of cell viability, pro-inflammatory cytokines secretion and oxidative stress. We showed that structural defects and oxidation both induced by the length reduction process are at least as responsible as the length reduction itself for the enhanced pro-inflammatory and pro-oxidative response observed with short (oxidized compared to long (pristine MWCNT. In conclusion, our results stress that surface properties should be considered, alongside the length, as essential parameters in CNT-induced inflammation, especially when dealing with a safe design of CNT, for application in nanomedicine for example.

  5. Chemical State of Surface Oxygen on Carbon and Its Effects on the Capacity of the Carbon Anode in a Lithium-Ion Battery Investigated

    Science.gov (United States)

    Hung, Ching-Cheh

    2001-01-01

    In a lithium-ion battery, the lithium-storage capacity of the carbon anode is greatly affected by a surface layer formed during the first half cycle of lithium insertion and release into and out of the carbon anode. The formation of this solid-electrolyte interface, in turn, is affected by the chemistry of the carbon surface. A study at the NASA Glenn Research Center examined the cause-and-effect relations. Information obtained from this research could contribute in designing a high-capacity lithium-ion battery and, therefore, small, powerful spacecraft. In one test, three types of surfaces were examined: (1) a surface with low oxygen content (1.5 at.%) and a high concentration of active sites, (2) a surface with 4.5 at.% -OH or -OC type oxygen, and (3) a surface with 6.5 at.% O=C type oxygen. The samples were made from the same precursor and had similar bulk properties. They were tested under a constant current of 10 mA/g in half cells that used lithium metal as the counter electrode and 0.5 M lithium iodide in 50/50 (vol%) ethylene carbonate and dimethyl carbonate as the electrolyte. For the first cycle of the electrochemical test, the graph describes the voltage of the carbon anode versus the lithium metal as a function of the capacity (amount of lithium insertion or release). From these data, it can be observed that the surface with low oxygen and a high concentration of active sites could result in a high irreversible capacity. Such a high irreversible capacity could be prevented if the active sites were allowed to react with oxygen in air, producing -OH or -OC type oxygen. The O=C type oxygen, on the other hand, could greatly reduce the capacity of lithium intercalation and, therefore, needs to be avoided during battery fabrication.

  6. Surface chemical analysis on the carbon-doped mesoporous TiO2 photocatalysts after post-thermal treatment: XPS and FTIR characterization

    Science.gov (United States)

    He, Zuoli; Que, Wenxiu; Chen, Jing; He, Yucheng; Wang, Gangfeng

    2013-07-01

    Mesoporous carbon-doped TiO2 nanoparticle was prepared by combining a hydrothermal process with a post-thermal treatment, where glucose was used as a carbon-doping source. Physicochemical properties of the carbon-doped TiO2 nanoparticle were characterized by X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform-infrared spectroscopy, and N2 adsorption/desorption. Results indicate that post-thermal treatment of the carbon-doped TiO2 has not only little influence on the crystal size but also can increase the specific surface area and the pore volume slightly, Also a slightly increase of the specific surface area and the pore volume of the sample was due to the removing of carbonaceous organic materials during post-thermal process. And the post-thermal treatment is an effective and facile method to change the surface chemical structure of the carbon-doped TiO2 for using as photocatalysts.

  7. Surface-Induced Dissociation and Chemical Reactions of C2D4+ on Stainless Steel, Carbon (HOPG), and Two Different Diamond Surfaces

    Czech Academy of Sciences Publication Activity Database

    Feketeová, L.; Žabka, Ján; Zappa, F.; Grill, V.; Scheier, P.; Märk, T. D.; Herman, Zdeněk

    2009-01-01

    Roč. 20, č. 6 (2009), s. 927-938. ISSN 1044-0305 Institutional research plan: CEZ:AV0Z40400503 Keywords : surface-induced process * diamond surfaces * chemical reactions Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.391, year: 2009

  8. Surface characteristic of chemically converted graphene coated low carbon steel by electro spray coating method for polymer electrolyte membrane fuel cell bipolar plate.

    Science.gov (United States)

    Kim, Jungsoo; Kim, Yang Do; Nam, Dae Geun

    2013-05-01

    Graphene was coated on low carbon steel (SS400) by electro spray coating method to improve its properties of corrosion resistance and contact resistance. Exfoliated graphite was made of the graphite by chemical treatment (Chemically Converted Graphene, CCG). CCG is distributed using dispersing agent, and low carbon steel was coated with diffuse graphene solution by electro spray coating method. The structure of the CCG was analyzed using XRD and the coating layer of surface was analyzed using SEM. Analysis showed that multi-layered graphite structure was destroyed and it was transformed in to fine layers graphene structure. And the result of SEM analysis on the surface and the cross section, graphene layer was uniformly formed with 3-5 microm thickness on the surface of substrate. Corrosion resistance test was applied in the corrosive solution which is similar to the polymer electrolyte membrane fuel cell (PEMFC) stack inside. And interfacial contact resistance (ICR) test was measured to simulate the internal operating conditions of PEMFC stack. As a result of measuring corrosion resistance and contact resistance, it could be confirmed that low carbon steel coated with CCG was revealed to be more effective in terms of its applicability as PEMFC bipolar plate. PMID:23858864

  9. Microstructure of carbon fiber preform and distribution of pyrolytic carbon by chemical vapor infiltration

    Institute of Scientific and Technical Information of China (English)

    陈建勋; 黄伯云

    2004-01-01

    The carbon/carbon composites were made by chemical vapor infiltration(CVI) with needled felt preform. The distribution of the pyrolytic carbon in the carbon fiber preform was studied by polarized light microscope(PLM) and scanning electronic microscope(SEM). The experimental results indicate that the amount of pyrolytic carbon deposited on the surface of chopped carbon fiber is more than that on the surface of long carbon fiber. The reason is the different porosity between the layer of chopped carbon fiber and long carbon fiber. The carbon precursor gas which passes through the part of chopped carbon fibers decomposes and deposits on the surface of chopped carbon fiber. The pyrolytic carbon on the surface of long carbon fibers is produced by the carbon precursor gas diffusing from the chopped fiber and the Z-d fiber. Uniform pore distribution and porosity in preform are necessary for producing C/C composites with high properties.

  10. Gas barrier properties of hydrogenated amorphous carbon films coated on polymers by surface-wave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Gas barrier characteristics of hydrogenated amorphous carbon (a-C:H) thin films coated on polymer sheets using the large-area surface-wave plasma (SWP) were studied. With SWP in He and CH4 gas mixture, a-C:H films were deposited over about 100 mm in diameter on high density polyethylene or polyethylene terephthalate (PET) sheets at temperature less than 70 deg. C. Experimental results show that gas permeation in the case of a-C:H film coating on PET sheet was reduced by a factor of more than 150 (0.27 cm3/m2 day atm), compared with that before coating. Plasma characteristics of SWP, such as electron density and electron energy distribution functions, and other film characteristics measured with Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscope are presented and discussed

  11. Surface free energy ( γsd) of active carbons determined by inverse gas chromatography: influences of the origin of precursors, the burn off level and the chemical modification

    Science.gov (United States)

    Cossarutto, L.; Vagner, C.; Finqueneisel, G.; Weber, J. V.; Zimny, T.

    2001-06-01

    The dispersive component of the surface free energies ( γsd) of commercial active carbons (AC) from various origins were determined by inverse gas chromatography at infinite dilution (IGC-ID). This method discriminates clearly the AC produced from wood (and activated/carbonised with phosphoric acid) and those from coconut-shell (carbonised and steam activated at 850°C). The values for the last AC (from coconut) are twice higher than the values for AC of wood origin. The structure and shape of the pores have to be considered to explain these values. It seems that for AC, IGC-ID globally characterises the most energetic micropores. This can be observed, in this work, by two ways: (i) washing of commercial AC (chemically activated) allows to liberate a part of the micropores blocked by soluble phosphate and consequently increases the γsd value; (ii) modifying coconuts AC by chemical treatment (formamide) results in a strong decrease of both microporosity and γsd value. On the contrary, thermal activation of the modified AC increases at the same time the microporosity and the surface free energy. Finally, we demonstrate that the IGC method is also an useful tool to monitor in situ the evolutions of the surface properties of carbonaceous materials.

  12. 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.

  13. The influence of the carbon surface chemical composition on Dubinin-Astakhov equation parameters calculated from SF{sub 6} adsorption data-grand canonical Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Furmaniak, Sylwester; Terzyk, Artur P; Gauden, Piotr A [Department of Chemistry, Physicochemistry of Carbon Materials Research Group, N Copernicus University, Gagarin Street 7, 87-100 Torun (Poland); Kowalczyk, Piotr [Nanochemistry Research Institute, Curtin University, PO Box U1987, Perth, WA 6845 (Australia); Harris, Peter J F, E-mail: aterzyk@chem.uni.torun.pl [Centre for Advanced Microscopy, University of Reading, Whiteknights, Reading RG6 6AF (United Kingdom)

    2011-10-05

    Using grand canonical Monte Carlo simulation we show, for the first time, the influence of the carbon porosity and surface oxidation on the parameters of the Dubinin-Astakhov (DA) adsorption isotherm equation. We conclude that upon carbon surface oxidation, the adsorption decreases for all carbons studied. Moreover, the parameters of the DA model depend on the number of surface oxygen groups. That is why in the case of carbons containing surface polar groups, SF{sub 6} adsorption isotherm data cannot be used for characterization of the porosity. (paper)

  14. Chemical Gel for Surface Decontamination

    International Nuclear Information System (INIS)

    Many chemical decontamination processes operate by immersing components in aggressive chemical solutions. In these applications chemical decontamination technique produce large amounts of radioactive liquid waste. Therefore it is necessary to develop processes using chemical gels instead of chemical solutions, to avoid the well-known disadvantages of chemical decontamination techniques while retaining their high efficiency. Chemical gels decontamination process consists of applying the gel by spraying it onto the surface of large area components (floors, walls, etc) to be decontaminated. The gel adheres to any vertical or complex surface due to their thixotropic properties and operates by dissolving the radioactive deposit, along with a thin layer of the gel support, so that the radioactivity trapped at the surface can be removed. Important aspects of the gels are that small quantities can be used and they show thixitropic properties : liquid during spraying, and solid when stationary, allowing for strong adherence to surfaces. This work investigates the decontamination behaviors of organic-based chemical gel for SS 304 metallic surfaces contaminated with radioactive materials

  15. Production of activated carbon with high specific surface area from bean-curd refuse by chemical activation; Okara wo genryo toshita yakuhin fukatsuho ni yoru kohihyomenseki kasseitan no seizo

    Energy Technology Data Exchange (ETDEWEB)

    Muroyama, K.; Hayashi, J.; Sato, A.; Takemoto, S. [Kansai Univ., Osaka (Japan). Faculty of Engineering

    1996-05-15

    A large amount of bean-curd refuse is exhausted as-product of tofu in Japan. On the other hand, activated carbon is used widely from old times in chemicals, medicines and food industry. Recently, since environmental contamination has come to head, the demand of activated carbon is more increased. The authors tried to produce activated carbons with high specific surface area from bean-curd refuse by chemical activation using several alkali metal compounds. The effects of carbonization temperature, holding time and impregnation ratio of reagent to dried bean-curd refuse on pore structure of activated carbons produced were investigated. Among the chemicals tested K2CO3 is found to be the most effective as the impregnation reagent. In a range of carbonization temperature above 700{degree}C, the specific surface area of the activated carbon produced increases rapidly, takes a maximum at a carbonization temperature of about 800{degree}C and decreases with further increase in temperature above 800{degree}C. The specific surface area attains a maximum at a holding time of about 60 min. The specific surface area increases with increasing impregnation ratio up to an impregnation ratio of 1.00. 7 refs., 7 figs., 1 tab.

  16. Scattering and Chemical Investigations of Semiconductor Surfaces.

    Science.gov (United States)

    Wallace, Robert Milo

    1988-12-01

    This two-part thesis describes: (i) the design of an ion scattering system to examine the surface and near-surface region of semiconductors, and (ii) the chemical reaction channels of unsaturated hydrocarbons on the silicon (100) surface. Details on the design and construction of an ultrahigh vacuum, high-energy ion scattering system are presented. The use of MeV ion scattering to investigate surface and near -surface regions of materials is described and the combination of ion scattering with complimentary surface science techniques is stressed. The thermal activation of chemical bonds of the adsorbed unsaturated hydrocarbon molecules ethylene, propylene, and acetylene is investigated on the Si(100)-(2 times 11) surface with a goal of understanding the surface chemistry of Si-C formation. The use of precision dosing techniques, Low Energy Electron Diffraction, Auger Electron Spectroscopy, and Temperature Programmed Desorption in the investigation of the remaining carbonaceous species is described. Comparisons of the adsorption and desorption behavior of these molecules is made in terms of the carbon -carbon double and triple bonds (ethylene to acetylene) and the methyl functional group (ethylene to propylene). We find that the monolayer saturation coverage of these hydrocarbons is in very good agreement with the number of dimer sites on the surface estimated from scanning-tunneling microscopy, which suggests that the bonding of these hydrocarbons to the Si(100) surface is similar. It is also found that ethylene, in particular, does not provide an efficient Si-C reaction channel upon thermal activation, with nearly 100% of the ethylene molecules desorbing. In contrast, acetylene is found to be very efficient in SiC formation: >=q90% of the adsorbed acetylene thermally dissociates and eventually leads to SiC formation. Propylene has an efficiency of roughly 70% upon heating. Evidence for the diffusion of carbon into the bulk is seen at >=q850 K for propylene and

  17. Substrate and material transfer effects on the surface chemistry and texture of diamond-like carbon deposited by plasma-enhanced chemical vapour deposition

    OpenAIRE

    Jones, Benjamin; Ojeda, J. J.

    2012-01-01

    Diamond-like carbon (DLC), a thin amorphous carbon film, has many uses in tribological systems. Exploiting alternative substrates and interlayers can enable the control of the hardness and modulus of the multilayer system and improve wear or friction properties. We used XPS and atomic force microscopy to examine DLC that had been concurrently coated on an epoxy interlayer and a steel substrate by plasma-enhanced chemical vapour deposition. sp2/sp3 ratios were calculated both by the deconvolut...

  18. The chemical physics of surfaces

    CERN Document Server

    Morrison, Stanley Roy

    1990-01-01

    Even more importantly, some authors who have contributed substantially to an area may have been overlooked. For this I apologize. I have, however, not attempted to trace techniques or observa­ tions historically, so there is no implication (unless specified) that the authors referred to were or were not the originators of a given method or observation. I would like to acknowledge discussions with co-workers at SFU for input relative to their specialties, to acknowledge the help of students who have pointed out errors and difficulties in the earlier presentation, and to acknowledge the infinite patience of my wife Phyllis while I spent my sabbatical and more in libraries and punching computers. S. Roy Morrison 0 1 Contents Notation XV 1. Introduction 1 1. 1. Surface States and Surface Sites . 1 1. 1. 1. The Chemical versus Electronic Representation of the Surface. 1 1. 1. 2. The Surface State on the Band Diagram 4 1. 1. 3. The Fermi Energy in the Surface State Model. 6 1. 1. 4. Need for Both Surface...

  19. 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.

  20. Water Condensation on Zinc Surfaces Treated by Chemical Bath Deposition

    OpenAIRE

    Narhe, R.D. (Ramchandra D.); González-Viñas, W.; Beysens, D.A. (Daniel A.)

    2010-01-01

    Water condensation, a complex and challenging process, is investigated on a metallic (Zn) surface, regularly used as anticorrosive surface. The Zn surface is coated with hydroxide zinc carbonate by chemical bath deposition, a very simple, low-cost and easily applicable process. As the deposition time increases, the surface roughness augments and the contact angle with water can be varied from 75º to 150º , corresponding to changing the surface properties from hydrophobic to ultrahydrophobic a...

  1. Chemical Oceanography and the Marine Carbon Cycle

    Science.gov (United States)

    Emerson, Steven; Hedges, John

    The principles of chemical oceanography provide insight into the processes regulating the marine carbon cycle. The text offers a background in chemical oceanography and a description of how chemical elements in seawater and ocean sediments are used as tracers of physical, biological, chemical and geological processes in the ocean. The first seven chapters present basic topics of thermodynamics, isotope systematics and carbonate chemistry, and explain the influence of life on ocean chemistry and how it has evolved in the recent (glacial-interglacial) past. This is followed by topics essential to understanding the carbon cycle, including organic geochemistry, air-sea gas exchange, diffusion and reaction kinetics, the marine and atmosphere carbon cycle and diagenesis in marine sediments. Figures are available to download from www.cambridge.org/9780521833134. Ideal as a textbook for upper-level undergraduates and graduates in oceanography, environmental chemistry, geochemistry and earth science and a valuable reference for researchers in oceanography.

  2. 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.

  3. Activated coconut shell charcoal carbon using chemical-physical activation

    Science.gov (United States)

    Budi, Esmar; Umiatin, Nasbey, Hadi; Bintoro, Ridho Akbar; Wulandari, Futri; Erlina

    2016-02-01

    The use of activated carbon from natural material such as coconut shell charcoal as metal absorbance of the wastewater is a new trend. The activation of coconut shell charcoal carbon by using chemical-physical activation has been investigated. Coconut shell was pyrolized in kiln at temperature about 75 - 150 °C for about 6 hours in producing charcoal. The charcoal as the sample was shieved into milimeter sized granule particle and chemically activated by immersing in various concentration of HCl, H3PO4, KOH and NaOH solutions. The samples then was physically activated using horizontal furnace at 400°C for 1 hours in argon gas environment with flow rate of 200 kg/m3. The surface morphology and carbon content of activated carbon were characterized by using SEM/EDS. The result shows that the pores of activated carbon are openned wider as the chemical activator concentration is increased due to an excessive chemical attack. However, the pores tend to be closed as further increasing in chemical activator concentration due to carbon collapsing.

  4. Preparation of activated carbon by chemical activation under vacuum.

    Science.gov (United States)

    Juan, Yang; Ke-Qiang, Qiu

    2009-05-01

    Activated carbons especially used for gaseous adsorption were prepared from Chinesefir sawdust by zinc chloride activation under vacuum condition. The micropore structure, adsorption properties, and surface morphology of activated carbons obtained under atmosphere and vacuum were investigated. The prepared activated carbons were characterized by SEM, FTIR, and nitrogen adsorption. It was found that the structure of the starting material is kept after activation. The activated carbon prepared under vacuum exhibited higher values of the BET surface area (up to 1079 m2 g(-1)) and total pore volume (up to 0.5665 cm3 g(-1)) than those of the activated carbon obtained under atmosphere. This was attributed to the effect of vacuum condition that reduces oxygen in the system and limits the secondary reaction of the organic vapor. The prepared activated carbon has well-developed microstructure and high microporosity. According to the data obtained, Chinese fir sawdust is a suitable precursor for activated carbon preparation. The obtained activated carbon could be used as a low-cost adsorbent with favorable surface properties. Compared with the traditional chemical activation, vacuum condition demands less energy consumption, simultaneity, and biomass-oil is collected in the procedure more conveniently. FTIR analysis showed that heat treatment would result in the aromatization of the carbon structure. PMID:19534162

  5. Chemical separation of carbon -14 in radwastes

    International Nuclear Information System (INIS)

    Carbon-14 has a long half-life of 5730 years and decays by beta emission of 156KeV to the stable nuclide, Nitrogen-14. Carbon-14 is produced mostly by the neutron activation of naturally occurring oxygen-17 in water molecules of the reactor coolant and Nitrogen-14 from nitrogen gas dissolved in the reactor coolant. Most of these carbon-14 are known to be discharged as gaseous wastes. The chemical forms of the gaseous emissions of carbon-14 from PWR stations range from 10∼26% as 14CO2 and 74∼90% as 14CH4 and other hydrocarbons, compared to about 95% as 14CO2 and 5% as 14CH4 and other hydrocarbons in BWR station gaseous emissions. Knowles reported that although the exact nature of these organic compounds was not identified, most of the carbon-14 was present as forms of organic species in a PWR primary coolant. Praudic measured the contents of the total organic and inorganic carbon-14 in waste trench leachates of New York commercial LLW disposal site and found that 74 ∼ 98% of carbon-14 was organic. In 1991, Dayal and Kirby reported that carbon-14 identified in LLW trench leachates from the Maxi Fiats site were carbonate and bicarbonate as inorganic carbon-14 and citric acid and palmitic acid as organic carbon-14. Thus concentrated Boric acid waste solutions(CB) which has generated from domestic NPP were classified into organic and inorganic carbon-14 with wet oxidation method in order to grasping a existing ratio of organic carbon-14 from total one due to affecting an environment

  6. 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.

  7. Geometric effects on carbon-13 chemical shifts

    International Nuclear Information System (INIS)

    In the course of our investigations on carbon-13 chemical shifts of tetracyclic dodecanes, we managed to show that a large number of chemical shift differences between members of the series and models provided by bicyclic analogs could be attributed to steric effects. There are examples, however, where this is clearly not the case. In order to investigate apparent anomalies we calculated structures of interest and looked into the relationships between molecular geometry and chemical shifts. As the assignment of some of the key structures in these analysis were made by comparison with model compounds and crucial experiments that could remove ambiguities were missing, we prepared and interpreted two spectra which are presented

  8. Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al2O3 Catalysts via CH4 Chemical Vapor Deposition.

    Science.gov (United States)

    Page, Alister J; Saha, Supriya; Li, Hai-Bei; Irle, Stephan; Morokuma, Keiji

    2015-07-29

    We present quantum chemical simulations demonstrating how single-walled carbon nanotubes (SWCNTs) form, or "nucleate", on the surface of Al2O3 nanoparticles during chemical vapor deposition (CVD) using CH4. SWCNT nucleation proceeds via the formation of extended polyyne chains that only interact with the catalyst surface at one or both ends. Consequently, SWCNT nucleation is not a surface-mediated process. We demonstrate that this unusual nucleation sequence is due to two factors. First, the π interaction between graphitic carbon and Al2O3 is extremely weak, such that graphitic carbon is expected to desorb at typical CVD temperatures. Second, hydrogen present at the catalyst surface actively passivates dangling carbon bonds, preventing a surface-mediated nucleation mechanism. The simulations reveal hydrogen's reactive chemical pathways during SWCNT nucleation and that the manner in which SWCNTs form on Al2O3 is fundamentally different from that observed using "traditional" transition metal catalysts. PMID:26148208

  9. Fabrication of carbon nanofiber-reinforced aluminum matrix composites assisted by aluminum coating formed on nanofiber surface by in situ chemical vapor deposition

    International Nuclear Information System (INIS)

    The van der Waals agglomeration of carbon nanofibers (CNFs) and the weight difference and poor wettability between CNFs and aluminum hinder the fabrication of dense CNF-reinforced aluminum matrix composites with superior properties. In this study, to improve this situation, CNFs were coated with aluminum by a simple and low-cost in situ chemical vapor deposition (in situ CVD). Iodine was used to accelerate the transport of aluminum atoms. The coating layer formed by the in situ CVD was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Fourier transform-infrared spectroscopy, and x-ray photoelectron spectroscopy. The results confirmed that the CNFs were successfully coated with aluminum. The composites were fabricated to investigate the effect of the aluminum coating formed on the CNFs. The dispersion of CNFs, density, Vickers micro-hardness and thermal conductivity of the composites fabricated by powder metallurgy were improved. Pressure-less infiltration experiments were conducted to fabricate composites by casting. The results demonstrated that the wettability and infiltration were dramatically improved by the aluminum coating layer on CNFs. The aluminum coating formed by the in situ CVD technique was proved to be effective for the fabrication of CNF-reinforced aluminum matrix composites. (paper)

  10. Fabrication of carbon nanofiber-reinforced aluminum matrix composites assisted by aluminum coating formed on nanofiber surface by in situ chemical vapor deposition

    Science.gov (United States)

    Ogawa, Fumio; Masuda, Chitoshi

    2015-01-01

    The van der Waals agglomeration of carbon nanofibers (CNFs) and the weight difference and poor wettability between CNFs and aluminum hinder the fabrication of dense CNF-reinforced aluminum matrix composites with superior properties. In this study, to improve this situation, CNFs were coated with aluminum by a simple and low-cost in situ chemical vapor deposition (in situ CVD). Iodine was used to accelerate the transport of aluminum atoms. The coating layer formed by the in situ CVD was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Fourier transform-infrared spectroscopy, and x-ray photoelectron spectroscopy. The results confirmed that the CNFs were successfully coated with aluminum. The composites were fabricated to investigate the effect of the aluminum coating formed on the CNFs. The dispersion of CNFs, density, Vickers micro-hardness and thermal conductivity of the composites fabricated by powder metallurgy were improved. Pressure-less infiltration experiments were conducted to fabricate composites by casting. The results demonstrated that the wettability and infiltration were dramatically improved by the aluminum coating layer on CNFs. The aluminum coating formed by the in situ CVD technique was proved to be effective for the fabrication of CNF-reinforced aluminum matrix composites.

  11. Physical properties of chemical vapour deposited nanostructured carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mahadik, D.B.; Shinde, S.S.; Bhosale, C.H. [Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur, Maharashtra 416004 (India); Rajpure, K.Y., E-mail: rajpure@yahoo.com [Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur, Maharashtra 416004 (India)

    2011-02-03

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

  12. Potential energy surfaces for chemical reactions

    International Nuclear Information System (INIS)

    Research into potential energy surfaces for chemical reactions at Lawrence Berkeley Laboratory during 1976 is described. Topics covered include: the fuzzy interface between surface chemistry catalysis and organometallic chemistry; potential energy surfaces for elementary fluorine hydrogen reactions; structure, energetics, and reactivity of carbenes; and the theory of self-consistent electron pairs

  13. 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%.

  14. Synthesis and characterization of carbon nanofilms for chemical sensing

    Science.gov (United States)

    Kumar, Vivek

    Carbon nanofilms obtained by high temperature graphitization of diamond surface in inert atmospheres or vacuum are modified by treatment in plasma of different precursor gases. At temperatures above 1000 °C, a stable conductive film of thickness between 10 - 100 nm and specific resistivity 10-3-10-4 Ωm, depending upon the heating conditions and the growth atmosphere, is formed on diamond surface. A gray, thin film of high surface resistivity is obtained in high vacuum, while at low vacuum (below 10-4 mbar), a thick black film of low surface resistivity forms. It is observed that the exposure to plasma reduces the surface conductance of carbon nanofilms as result of a partial removal of carbon and the plasma-stimulated amorphization. The rate of the reduction of conductance and hence the etching ability of plasma depends on the type of precursor gas. Hydrogen reveals the strongest etching ability, followed by oxygen and argon, whereas SF6 is ineffective. The carbon nanofilms show significant sensitivity of their electrical conductance to temperature and exposure to the vapors of common organic compounds. The oxygen plasma treated films exhibit selective response to acetone and water vapors. The fast response and recovery of the conductance are the features of the carbon nanofilms. The plasma-treated carbon nanofilm on graphitized diamond surface is discussed as a promising sensing material for development of all-carbon chemical sensors, which may be suitable for biological and medical applications. An alternative approach of fabrication of temperature and chemical sensitive carbon nanofilms on insulating substrates is proposed. The films are obtained by direct deposition of sputtered carbon on highly polished quartz substrates followed by subsequent annealing at temperatures above 400 °C. It is observed that the as-deposited films are essentially amorphous, while the heating induces irreversible structural ordering and gradual conversion of amorphous carbon in

  15. Chemical Properties of Carbon Nanotubes Prepared Using Camphoric Carbon by Thermal-CVD

    International Nuclear Information System (INIS)

    Chemical properties and surface study on the influence of starting carbon materials by using thermal chemical vapor deposition (Thermal-CVD) to produced carbon nanotubes (CNTs) is investigated. The CNTs derived from camphor were synthesized as the precursor material due to low sublimation temperature. The major parameters are also evaluated in order to obtain high-yield and high-quality CNTs. The prepared CNTs are examined using field emission scanning electron microscopy (FESEM) to determine the microstructure of nanocarbons. The FESEM investigation of the CNTs formed on the support catalysts provides evidence that camphor is suitable as a precursor material for nanotubes formation. The chemical properties of the CNTs were conducted using FTIR spectroscopy and PXRD analysis. The high-temperature graphitization process induced by the Thermal-CVD enables the hydrocarbons to act as carbon sources and changes the aromatic species into the layered graphite structure of CNTs.

  16. Chemical Properties of Carbon Nanotubes Prepared Using Camphoric Carbon by Thermal-CVD

    Science.gov (United States)

    Azira, A. A.; Rusop, M.

    2010-03-01

    Chemical properties and surface study on the influence of starting carbon materials by using thermal chemical vapor deposition (Thermal-CVD) to produced carbon nanotubes (CNTs) is investigated. The CNTs derived from camphor were synthesized as the precursor material due to low sublimation temperature. The major parameters are also evaluated in order to obtain high-yield and high-quality CNTs. The prepared CNTs are examined using field emission scanning electron microscopy (FESEM) to determine the microstructure of nanocarbons. The FESEM investigation of the CNTs formed on the support catalysts provides evidence that camphor is suitable as a precursor material for nanotubes formation. The chemical properties of the CNTs were conducted using FTIR spectroscopy and PXRD analysis. The high-temperature graphitization process induced by the Thermal-CVD enables the hydrocarbons to act as carbon sources and changes the aromatic species into the layered graphite structure of CNTs.

  17. Chemical Reactions at Surfaces. Final Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    None

    2003-02-21

    The Gordon Research Conference (GRC) on Chemical Reactions at Surfaces was held at Holiday Inn, Ventura, California, 2/16-21/03. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  18. 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

  19. Laser Induced Surface Chemical Epitaxy

    Science.gov (United States)

    Stinespring, Charter D.; Freedman, Andrew

    1990-02-01

    Studies of the thermal and photon-induced surface chemistry of dimethyl cadmium (DMCd) and dimethyl tellurium (DMTe) on GaAs(100) substrates under ultrahigh vacuum conditions have been performed for substrate temperatures in the range of 123 K to 473 K. Results indicate that extremely efficient conversion of admixtures of DMTe and DMCd to CdTe can be obtained using low power (5 - 10 mJ cm-2) 193 nm laser pulses at substrate temperatures of 123 K. Subsequent annealing at 473 K produces an epitaxial film.

  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. Dissolved black carbon in Antarctic lakes: Chemical signatures of past and present sources

    Science.gov (United States)

    Khan, Alia L.; Jaffé, Rudolf; Ding, Yan; McKnight, Diane M.

    2016-06-01

    The perennially ice-covered, closed-basin lakes in the McMurdo Dry Valleys, Antarctica, serve as sentinels for understanding the fate of dissolved black carbon from glacial sources in aquatic ecosystems. Here we show that dissolved black carbon can persist in freshwater and saline surface waters for thousands of years, while preserving the chemical signature of the original source materials. The ancient brines of the lake bottom waters have retained dissolved black carbon with a woody chemical signature, representing long-range transport of black carbon from wildfires. In contrast, the surface waters are enriched in contemporary black carbon from fossil fuel combustion. Comparison of samples collected 25 years apart from the same lake suggests that the enrichment in anthropogenic black carbon is recent. Differences in the chemical composition of dissolved black carbon among the lakes are likely due to biogeochemical processing such as photochemical degradation and sorption on metal oxides.

  2. 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

  3. Carbon-Nanotube-Based Chemical Gas Sensor

    Science.gov (United States)

    Kaul, Arunpama B.

    2010-01-01

    Conventional thermal conductivity gauges (e.g. Pirani gauges) lend themselves to applications such as leak detectors, or in gas chromatographs for identifying various gas species. However, these conventional gauges are physically large, operate at high power, and have a slow response time. A single-walled carbon-nanotube (SWNT)-based chemical sensing gauge relies on differences in thermal conductance of the respective gases surrounding the CNT as it is voltage-biased, as a means for chemical identification. Such a sensor provides benefits of significantly reduced size and compactness, fast response time, low-power operation, and inexpensive manufacturing since it can be batch-fabricated using Si integrated-circuit (IC) process technology.

  4. Chemical equilibrium of glycerol carbonate synthesis from glycerol

    International Nuclear Information System (INIS)

    Research highlights: → Transesterification of glycerol with cyclic carbonates or alkyl carbonates is thermodynamically favourable for the preparation of glycerol carbonate from glycerol. → The reaction of glycerol and carbon dioxide is thermodynamically limited. → High temperature and low pressure is favourable to the reaction of glycerol and urea. → Increasing temperature can increase the chemical equilibrium constant for the reaction of glycerol and dimethyl carbonate. → For the reaction of glycerol and ethylene carbonate, increasing temperature can decrease the chemical equilibrium constant. - Abstract: In this paper, the chemical equilibrium for the glycerol carbonate preparation from glycerol was investigated. The chemical equilibrium constants were calculated for the reactions to produce glycerol carbonate from glycerol. The theoretical calculation was compared with the experimental results for the transesterification of glycerol with dimethyl carbonate. Transesterification of glycerol with cyclic carbonates or alkyl carbonates is thermodynamically favourable for producing glycerol carbonate from glycerol according to the equilibrium constant. Increasing temperature can increase the chemical equilibrium constant for the reaction of glycerol with dimethyl carbonate. For the reaction of glycerol with ethylene carbonate, increasing temperature can decrease the chemical equilibrium constant. The reaction of glycerol with carbon dioxide is thermodynamically limited. High temperature and low pressure are favourable to the reaction of glycerol and urea.

  5. 9 CFR 313.5 - Chemical; carbon dioxide.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Chemical; carbon dioxide. 313.5... INSPECTION AND CERTIFICATION HUMANE SLAUGHTER OF LIVESTOCK § 313.5 Chemical; carbon dioxide. The slaughtering of sheep, calves and swine with the use of carbon dioxide gas and the handling in...

  6. Cell behaviour on chemically microstructured surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Magnani, Agnese; Priamo, Alfredo; Pasqui, Daniela; Barbucci, Rolando

    2003-03-03

    Micropatterned surfaces with different chemical topographies were synthesised in order to investigate the influence of surface chemistry and topography on cell behaviour. The microstructured materials were synthesised by photoimmobilising natural Hyaluronan (Hyal) and its sulphated derivative (HyalS), both adequately functionalised with a photorective moiety, on glass substrates. Four different grating patterns (10, 25, 50 and 100 {mu}m) were used to pattern the hyaluronan. The micropatterned samples were analysed by Secondary Ions Mass Spectrometry, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy to investigate the chemistry and the topography of the surfaces. The spectroscopic and microscopic analysis of the microstructured surfaces revealed that the photoimmobilisation process was successful, demonstrating that the photomask patterns were well reproduced on the sample surface. The influence of chemical topographies on the cell behaviour was then analysed. Human and 3T3 fibroblasts, bovine aortic and human (HGTFN line) endothelial cells were used and their behaviour on the micropatterned surfaces was analysed in terms of adhesion, proliferation, locomotion and orientation. Both chemical and topographical controls were found to be important for cell guidance. By decreasing the stripe dimensions, a more fusiform shape of cell was observed. At the same time, the cell locomotion and orientation parallel to the structure increased. However, differences in cell behaviour were detected according to both cell type and micropattern dimensions.

  7. 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

  8. Preliminary studies of epoxidized palm oil as sizing chemical for carbon fibers

    International Nuclear Information System (INIS)

    Epoxidized palm oil is derived from palm oil through chemical reaction with peracetic acid. Preliminary studies to coat carbon fibers have shown promising result towards applying natural product in carbon fibre composites. Mechanical studies of sized carbon fibers with epoxidized palm oil showed significant increase in tensile and interfacial shear strength. Surface morphology of sized or coated carbon fibers with epoxidized palm oil reveals clear increase in root means square-roughness (RMS). This indicates the change of the surface topography due to sized or coated carbon fibers with epoxidized palm oil. (author)

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

    International Nuclear Information System (INIS)

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

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Trends in the chemical properties in early transition metal carbide surfaces: A density functional study

    DEFF Research Database (Denmark)

    Kitchin, J.R.; Nørskov, Jens Kehlet; Barteau, M.A.;

    2005-01-01

    In this paper we present density functional theory (DFT) investigations of the physical, chemical and electronic structure properties of several close-packed surfaces of early transition metal carbides, including beta-Mo2C(0 0 0 1), and the (1 1 1) surfaces of TiC, VC, NbC, and TaC. The results are...... closest-packed pure metal surfaces, due to the tensile strain induced in the carbide surfaces upon incorporation of carbon into the lattice. Hydrogen atoms were found to adsorb more weakly on carbide surfaces than on the corresponding closest-packed pure metal surfaces only when there were surface carbon...

  15. Carbon Nanotube Based Chemical Sensors for Space and Terrestrial Applications

    Science.gov (United States)

    Li, Jing; Lu, Yijiang

    2009-01-01

    A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs), on a pair of interdigitated electrodes (IDE) processed with a silicon-based microfabrication and micromachining technique. The IDE fingers were fabricated using photolithography and thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to nitrogen dioxide, acetone, benzene, nitrotoluene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing of carbon nanotubes in our sensor platform can be understood by intra- and inter-tube electron modulation in terms of charge transfer mechanisms. As a result of the charge transfer, the conductance of p-type or hole-richer SWNTs in air will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost. Additionally, a wireless capability of such a sensor chip can be used for networked mobile and fixed-site detection and warning systems for military bases, facilities and battlefield areas.

  16. 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

  17. Surface chemical studies of chemical vapour deposited diamond thin films

    International Nuclear Information System (INIS)

    Polycrystalime diamond grown by low pressure chemical vapour deposition (CVD) techniques has emerged in recent years as a new material with applications in such areas as optics, electronics, radiation detectors, chemical sensors and electrochemistry. A main aim of this thesis has been to advance current knowledge of the surface chemical properties of CVD diamond to underpin the development of our understanding of the properties and potential applications of this material. Cl2 is found to adsorb dissociatively on the clean, hydrogen-free diamond surface up to sub-monolayer coverage with a sticking probability of ∼1.2x10-3. Adsorption is a non-activated process, and the sticking probability and extent of coverage decreased with increasing temperature. This was shown to contrast with the behaviour found for the interaction of chlorine with the hydrogenated diamond surface where increased sticking probabilities and saturation surface coverages were observed, and where the reactivity also increased with temperature. Thermal desorption of atomic Cl occurred over a broad temperature range m both chemisorption systems, indicating the presence of more than one binding state. Atomic hydrogen was successful in efficiently etching the bound Cl from the surface. XeF2 was found to adsorb dissociatively onto the clean diamond surface to give up to monolayer coverages of F, which formed two distinct binding states. The first state, populated at low coverage, was predominantly covalent in character, while the second state, occurring at high surface coverages, had more ionic bonding character. Pre-hydrogenation of the diamond surface increased the reactive sticking probability observed, but decreased the extent of coverage by blocking reactive sites. The semi-ionic F was readily etched by atomic hydrogen, and underwent thermal desorption at temperatures as low as 300 deg C. The covalent form was more stable, being seemingly resistant to etching and persistent to high temperatures

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Carbon nanostructures and networks produced by chemical vapor deposition

    OpenAIRE

    Kowlgi, N.K.K.; Koper, G.J.M.; Raalten, R.A.D.

    2012-01-01

    The invention pertains to a method for manufacturing crystalline carbon nanostructures and/or a network of crystalline carbon nanostructures, comprising: (i) providing a bicontinuous micro-emulsion containing metal nanoparticles having an average particle size between 1and 100nm; (ii) bringing said bicontinuous micro-emulsion into contact with a substrate; and (iii) subjecting said metal nanoparticles and a gaseous carbon source to chemical vapor deposition, thus forming carbon nanostructures...

  3. 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...

  4. 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.

  5. Computed potential energy surfaces for chemical reactions

    Science.gov (United States)

    Walch, Stephen P.

    1994-01-01

    Quantum mechanical methods have been used to compute potential energy surfaces for chemical reactions. The reactions studied were among those believed to be important to the NASP and HSR programs and included the recombination of two H atoms with several different third bodies; the reactions in the thermal Zeldovich mechanism; the reactions of H atom with O2, N2, and NO; reactions involved in the thermal De-NO(x) process; and the reaction of CH(squared Pi) with N2 (leading to 'prompt NO'). These potential energy surfaces have been used to compute reaction rate constants and rates of unimolecular decomposition. An additional application was the calculation of transport properties of gases using a semiclassical approximation (and in the case of interactions involving hydrogen inclusion of quantum mechanical effects).

  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. Single-wall carbon nanotube chemical attachment at platinum electrodes

    Science.gov (United States)

    Rosario-Castro, Belinda I.; Contés-de-Jesús, Enid J.; Lebrón-Colón, Marisabel; Meador, Michael A.; Scibioh, M. Aulice; Cabrera, Carlos R.

    2010-11-01

    Self-assembled monolayer (SAM) techniques were used to adsorb 4-aminothiophenol (4-ATP) on platinum electrodes in order to obtain an amino-terminated SAM as the base for the chemical attachment of single-wall carbon nanotubes (SWCNTs). A physico-chemical, morphological and electrochemical characterizations of SWCNTs attached onto the modified Pt electrodes was done by using reflection-absorption infrared spectroscopy (RAIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and cyclic voltammetry (CV) techniques. The SWNTs/4-ATP/Pt surface had regions of small, medium, and large thickness of carbon nanotubes with heights of 100-200 nm, 700 nm to 1.5 μm, and 1.0-3.0 μm, respectively. Cyclic voltammetries (CVs) in sulfuric acid demonstrated that attachment of SWNTs on 4-ATP/Pt is markedly stable, even after 30 potential cycles. CV in ruthenium hexamine was similar to bare Pt electrodes, suggesting that SWNTs assembly is similar to a closely packed microelectrode array.

  8. 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.

  9. Wetting films on chemically patterned surfaces.

    Science.gov (United States)

    Karakashev, Stoyan I; Stöckelhuber, Klaus W; Tsekov, Roumen

    2011-11-15

    The behavior of thin wetting films on chemically patterned surfaces was investigated. The patterning was performed by means of imprinting of micro-grid on methylated glass surface with UV-light (λ=184.8 nm). Thus imprinted image of the grid contained hydrophilic cells and hydrophobic bars on the glass surface. For this aim three different patterns of grids were utilized with small, medium and large size of cells. The experiment showed that the drainage of the wetting aqueous films was not affected by the type of surface patterning. However, after film rupturing in the cases of small and medium cells of the patterned grid the liquid from the wetting film underwent fast self-organization in form of regularly ordered droplets covering completely the cells of the grid. The droplets reduced significantly their size upon time due to evaporation. In the cases of the largest cell grid, a wet spot on the place of the imprinted grid was formed after film rupturing. This wet spot disassembled slowly in time. In addition, formation of a periodical zigzag three-phase contact line (TPCL) was observed. This is a first study from the planned series of studies on this topic. PMID:21875710

  10. Accessible surface area from NMR chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Hafsa, Noor E.; Arndt, David; Wishart, David S., E-mail: david.wishart@ualberta.ca [University of Alberta, Department of Computing Science (Canada)

    2015-07-15

    Accessible surface area (ASA) is the surface area of an atom, amino acid or biomolecule that is exposed to solvent. The calculation of a molecule’s ASA requires three-dimensional coordinate data and the use of a “rolling ball” algorithm to both define and calculate the ASA. For polymers such as proteins, the ASA for individual amino acids is closely related to the hydrophobicity of the amino acid as well as its local secondary and tertiary structure. For proteins, ASA is a structural descriptor that can often be as informative as secondary structure. Consequently there has been considerable effort over the past two decades to try to predict ASA from protein sequence data and to use ASA information (derived from chemical modification studies) as a structure constraint. Recently it has become evident that protein chemical shifts are also sensitive to ASA. Given the potential utility of ASA estimates as structural constraints for NMR we decided to explore this relationship further. Using machine learning techniques (specifically a boosted tree regression model) we developed an algorithm called “ShiftASA” that combines chemical-shift and sequence derived features to accurately estimate per-residue fractional ASA values of water-soluble proteins. This method showed a correlation coefficient between predicted and experimental values of 0.79 when evaluated on a set of 65 independent test proteins, which was an 8.2 % improvement over the next best performing (sequence-only) method. On a separate test set of 92 proteins, ShiftASA reported a mean correlation coefficient of 0.82, which was 12.3 % better than the next best performing method. ShiftASA is available as a web server ( http://shiftasa.wishartlab.com http://shiftasa.wishartlab.com ) for submitting input queries for fractional ASA calculation.

  11. Accessible surface area from NMR chemical shifts

    International Nuclear Information System (INIS)

    Accessible surface area (ASA) is the surface area of an atom, amino acid or biomolecule that is exposed to solvent. The calculation of a molecule’s ASA requires three-dimensional coordinate data and the use of a “rolling ball” algorithm to both define and calculate the ASA. For polymers such as proteins, the ASA for individual amino acids is closely related to the hydrophobicity of the amino acid as well as its local secondary and tertiary structure. For proteins, ASA is a structural descriptor that can often be as informative as secondary structure. Consequently there has been considerable effort over the past two decades to try to predict ASA from protein sequence data and to use ASA information (derived from chemical modification studies) as a structure constraint. Recently it has become evident that protein chemical shifts are also sensitive to ASA. Given the potential utility of ASA estimates as structural constraints for NMR we decided to explore this relationship further. Using machine learning techniques (specifically a boosted tree regression model) we developed an algorithm called “ShiftASA” that combines chemical-shift and sequence derived features to accurately estimate per-residue fractional ASA values of water-soluble proteins. This method showed a correlation coefficient between predicted and experimental values of 0.79 when evaluated on a set of 65 independent test proteins, which was an 8.2 % improvement over the next best performing (sequence-only) method. On a separate test set of 92 proteins, ShiftASA reported a mean correlation coefficient of 0.82, which was 12.3 % better than the next best performing method. ShiftASA is available as a web server ( http://shiftasa.wishartlab.com http://shiftasa.wishartlab.com ) for submitting input queries for fractional ASA calculation

  12. 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

  13. 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...

  14. Decrudding and chemical cleaning of carbon steel components - an evaluation

    International Nuclear Information System (INIS)

    Corrosion and accumulation of corrosion products on the surfaces of structural components and plant equipments can cause se vereoperational problems during service. An illustration is the heat exchanger systems in nuclear power stations. Development and standardisation of appropriate chemical cleaning and decontamination procedures and their evaluation hence merit serious consideration. A number of chemical cleaning procedures using formulations based on hydrochloric and citric acid solutions have been examined to study their crud dissolving and derusting ability in addition to the attack on base material. The compositions were chosen: (1) along with complexing agents EDTA and ammonium citrate, (2) with pH control, and (3) with the use of inhibitors acridine, rhodine, hexamine and phenyl-thiourea. The evaluations have been made at 28 and 60 deg C. Rusted carbon steel coupons having a rust of 10-12 mg/cm2 on the surface have been used for the purpose of the above evaluations. Data on corrosion rates of monel and cupronickel (70:30) in the descaling solutions have also been presented. Results on the above evaluation studies have been discussed. (author)

  15. Effect of pore structure and surface chemical properties on adsorption properties of activated carbons%孔结构和表面化学性质对活性炭吸附性能的影响

    Institute of Scientific and Technical Information of China (English)

    刘立恒; 辜敏; 鲜学福

    2012-01-01

    Adsorption isotherms of CO2,CH4 and N2 on three granular activated carbons(GAC-C,GAC-P and GAC-T) were determined at room temperature.Pore structure and surface chemical properties of granular activated carbons were characterized,and the effect of them on adsorption properties was investigated.The results showed that the relationships of gases adsorption capacity and uptake coefficient on granular activated carbons were CO2〉CH4〉N2,because of the differences of adsorption mechanism,pore structure,surface functional groups and molecular polarity.The adsorption capacities of CH4 and N2 were mainly controlled by micropore volume of activated carbon,and the differences of N2 and CO2 adsorption capacity were affected by micropores from 0.572 to 2.0 nm and pores from 0.4 to 6.0 nm,respectively.And uptake coefficient of CH4,was more relational with mesopore and macropore,while uptake coefficients of N2 and CO2 were mainly controlled by micropore and macropore,respectively.%测定了室温下3种活性炭(GAC-C、GAC-P和GAC-T)对CO2、CH4和N2的吸附性能,并对颗粒活性炭孔结构和表面化学性质进行了表征,探讨了孔结构和表面化学性质对活性炭吸附性能的影响。结果表明:由于吸附机理、孔结构、表面含氧官能团和分子极性的差异,CO2、CH4和N2在活性炭上的饱和吸附量和吸附常数的关系为CO2〉CH4〉N2;CH4和N2的饱和吸附量主要受活性炭微孔孔容的影响,N2和CO2饱和吸附量的差异分别是由0.572~2.0 nm的微孔和0.4~6 nm的孔引起的;CH4吸附常数主要受较大中孔和大孔影响,N2吸附常数与微孔密切相关,大孔对CO2的吸附常数影响最大。

  16. 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....

  17. 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)

  18. Carbon coated (carbonous) catalyst in ebullated bed reactor for production of oxygenated chemicals from syngas/CO2

    International Nuclear Information System (INIS)

    This report summarizes the work completed under DOE's Support of Advanced Fuel Research program, Contract No. DE-FG26-99FT40681. The contract period was October 2000 through September 2002. This R and D program investigated the modification of the mechanical strength of catalyst extrudates using Hydrocarbon Technologies, Inc. (HTI) carbon-coated catalyst technology so that the ebullated bed technology can be utilized to produce valuable oxygenated chemicals from syngas/CO2 efficiently and economically. Exothermic chemical reactions benefit from the temperature control and freedom from catalyst fouling provided by the ebullated bed reactor technology. The carbon-coated extrudates prepared using these procedures had sufficient attrition resistance and surface area for use in ebullated bed operation. The low cost of carbon coating makes the carbon-coated catalysts highly competitive in the market of catalyst extrudates

  19. Physico-chemical characterization of powdered activated carbons obtained by thermo-chemical conversion of brown municipal waste

    Directory of Open Access Journals (Sweden)

    Momčilović Milan Z.

    2011-01-01

    Full Text Available Cones of the European Black pine and Horse chestnut kernel, regarded as brown municipal waste, was utilized in this work as a precursor for powdered activated carbons. Chemical activation was employed at 500°C in inert atmosphere of nitrogen. Standard physico-chemical analyses were performed to examine obtained products. FTIR method was employed to determine fuctional groups which were found to be typical for activated carbons. Acidic oxygen groups were quantitatively determined using Boehm titrations. It was established that carboxylic groups on pine cone activated carbon, and phenolic groups on chestnut kernel activated carbon were dominant from all acidic oxygen groups. Since both contact pH and pHPZC were determined to be fairly acidic, it could be concluded that obtained activated carbons belong to L-type. Shape and layout of micrometer dimensioned particles were observed by scanning electron microscopy. Particles of different shapes and dimensions along with small cracks and wide crevices and voids were noticed. Textural analysis was used to determine specific surface area and pore distribution of obtained activated carbons. Obtained products possess highly developed surface area and wide pore distribution.

  20. Does density fractionation of SOC represent chemically different carbon pools?

    OpenAIRE

    Mulvaney, Michael J.; Graham, M.; Xia, K.; Barrera, Victor H.; Botello, Rubén; Saavedra, Ana Karina; Mamani, P.

    2012-01-01

    Organic matter stabilization is thought to be a process of physical protection and chemical recalcitrance. The determination of recalcitrant soil organic carbon (SOC) often relies on operational definitions provided by various fractionation techniques, usually particle size or density fractionation. However, it is unknown if these operational definitions represent true chemical recalcitrance.

  1. Gravity Effects in Carbon Nanotube Growth by Thermal Chemical Vapor Deposition

    Science.gov (United States)

    Zhu, S.; Su, C. H.; Cochrane, J. C.; Lehoczky, S. L.; Cui, Y.; Burger, A.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Carbon nanotubes are synthesized using thermal chemical vapor deposition. The sizes of these carbon nanotubes (CNT) are quite uniform and the length of the tube is up to several tens of micrometers. With the substrate surface normal either along or against the gravity vector, different growth orientations of CNT are observed by scanning electron microscopy although the Raman spectra are similar for samples synthesized at different locations. These results suggest the gravitation effects in the growth of long and small diameter CNT.

  2. 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.

  3. Carbon Nanotubes: Detection of Chemical and Biological Warfare Agents

    Directory of Open Access Journals (Sweden)

    Om Kumar

    2008-09-01

    Full Text Available Discovery of carbon nanotubes has great impact on the development of newer methodologies and devicesuseful for the analysis of various types of chemicals. The functionalisation of CNTs with biomolecules relatedto chemical and biological warfare agents makes these useful for the detection of these agents. The detectionsensitivity can be increased manyfold. Various types of chemical and biological sensors were developed usingvarious type of carbon nanotubes as well as nano particles of different metals.Defence Science Journal, 2008, 58(5, pp.617-625, DOI:http://dx.doi.org/10.14429/dsj.58.1684

  4. Physical and chemical characterization of surfaces of nitrogen implanted steels

    International Nuclear Information System (INIS)

    The studied steels are of industrial type (42CD4, 100C6, Z200C13). Very often, the low carbon steel XCO6 has been used as a reference material. The aim of the research is to understand and to explain the mechanisms of wear resistance to improvement. A good characterization of the implanted layer is thus necessary. It implies to establish the distribution profiles of the implanted ions to identify the chemical and structural state of the phases created during implantation as a function of various implantation parameters (dose, temperature). Temperature is the particularly parameter. Its influence is put in evidence both during implantation and during annealings under vacuum. Nitrogen distribution profiles are performed thanks to the non destructive 15N(p,αγ)12C nuclear reaction. The chemical state of the Fe-N phases formed by implantation is determined using first Electron Conversion Moessbauer Spectroscopy and secondly, as a complement, using grazing angle X ray diffraction. The detected compounds are ε-nitrides, ε-carbonitrides, (N) - martensite and α-Fe16N2 whose evolution is carefully followed versus temperature. The diffraction technique reveals a texture of the implanted layer. This preferentiel orientation is found to be temperature dependent but dose independent. The carbon presence at the surface is studied as a function of implantation conditions (vacuum, temperature, dose). Carbon profiling is obtained using α backscattering (12C(α,α') reaction at 5,7 MeV). Thus is achieved a complete characterization of the implanted zone whose evolution as a function of implantation parameters (especially temperature) is correlated with tribological results

  5. Chemical surface tuning electrocatalysis of redox-active nanoparticles

    DEFF Research Database (Denmark)

    Zhu, Nan; Ulstrup, Jens; Chi, Qijin

    This work focuses on electron transfer (ET) and electrocatalysis of inorganic hybrid Prussian blue nanoparticles (PBNPs, 6 nm) immobilized on different chemical surfaces. Through surface self-assembly chemistry, we have enabled to tune chemical properties of the electrode surface. Stable immobili...

  6. Current understanding of the growth of carbon nanotubes in catalytic chemical vapour deposition

    OpenAIRE

    Jourdain, Vincent; Bichara, Christophe

    2013-01-01

    Due to its higher degree of control and its scalability, catalytic chemical vapour deposition is now the prevailing synthesis method of carbon nanotubes. Catalytic chemical vapour deposition implies the catalytic conversion of a gaseous precursor into a solid material at the surface of reactive particles or of a continuous catalyst film acting as a template for the growing material. Significant progress has been made in the field of nanotube synthesis by this method although nanotube samples ...

  7. 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.

  8. 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.

  9. 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.

  10. Synthesis and Characterization of Carbon nanofibers on Co and Cu Catalysts by Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Park, Eunsil; Kim, Jongwon; Lee, Changseop [Keimyung Univ., Daegu (Korea, Republic of)

    2014-06-15

    This study reports on the synthesis of carbon nanofibers via chemical vapor deposition using Co and Cu as catalysts. In order to investigate the suitability of their catalytic activity for the growth of nanofibers, we prepared catalysts for the synthesis of carbon nanofibers with Cobalt nitrate and Copper nitrate, and found the optimum concentration of each respective catalyst. Then we made them react with Aluminum nitrate and Ammonium Molybdate to form precipitates. The precipitates were dried at a temperature of 110 .deg. C in order to be prepared into catalyst powder. The catalyst was sparsely and thinly spread on a quartz tube boat to grow carbon nanofibers via thermal chemical vapor deposition. The characteristics of the synthesized carbon nanofibers were analyzed through SEM, EDS, XRD, Raman, XPS, and TG/DTA, and the specific surface area was measured via BET. Consequently, the characteristics of the synthesized carbon nanofibers were greatly influenced by the concentration ratio of metal catalysts. In particular, uniform carbon nanofibers of 27 nm in diameter grew when the concentration ratio of Co and Cu was 6:4 at 700 .deg. C of calcination temperature; carbon nanofibers synthesized under such conditions showed the best crystallizability, compared to carbon nanofibers synthesized with metal catalysts under different concentration ratios, and revealed 1.26 high amorphicity as well as 292 m{sup 2}g{sup -1} high specific surface area.

  11. Chemically enhanced self-sputtering of carbon

    International Nuclear Information System (INIS)

    New results obtained for graphite self-sputtering, in the presence of thermal atomic hydrogen, show that Chemically Enhanced Self-Sputtering (CES) can exceed unity erosion yield even at normal angles of incidence. CES yields were found to depend on the ΦC+/ΦHo flux ratio and graphite temperature, with peak erosion occurring at about 800K. No dependence on angle of incidence was observed

  12. 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.

  13. Densification and microstructure of carbon/carbon composites prepared by chemical vapor infiltration using ethanol as precursor

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Chemical vapor infiltration of carbon fiber felts with uniform initial bulk density of 0.47 g·cm-3 was investigated at the ethanol partial pressures of 5-20 kPa,as well as the temperatures of 1050,1100,1150 and 1200°C.Ethanol,diluted by nitrogen,was employed as the precursor of pyrolytic carbon.Polarized light microscopy(PLM),scanning electron microscopy and X-ray diffraction were adopted to study the texture of pyrolytic carbon deposited at various temperatures.A change from medium-to high-textured pyrolytic carbon was observed in the sample infiltrated at 1050°C.Whereas,homogeneous high-textured pyrolytic carbons were deposited at the temperatures of 1100,1150 and 1200°C.Extinction angles of 19°-21° were determined for different regions in the samples densified at the temperatures ranging from 1100 to 1200°C.Scanning electron microscopy of the fracture surface after bending test indicated that the prepared carbon/carbon composite samples exhibited a pseudo-plastic fracture behavior.In addition,fracture behavior of the carbon/carbon samples was obviously effected by their infiltration temperature.The fracture mode of C/C composites was transformed from shearing failure to tensile breakage with increasing infiltration temperature. Results of this study show that ethanol is a promising carbon source to synthesize carbon/carbon composites with homogeneously high-textured pyrolytic carbon over a wide range of temperatures(from 1100 to 1200°C).

  14. 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)

  15. Evaporation of elongated droplets on chemically stripe-patterned surfaces

    NARCIS (Netherlands)

    Jansen, H.P.; Zandvliet, H.J.W.; Kooij, E.S.

    2015-01-01

    We investigate the evaporation of elongated droplets on chemically striped patterned surfaces. Variation of elongation is achieved by depositing droplets on surfaces with varying ratios of hydrophobic and hydrophilic stripe widths. Elongated droplets evaporate faster than more spherical droplets. Bo

  16. Textural and chemical properties of zinc chloride activated carbons prepared from pistachio-nut shells

    International Nuclear Information System (INIS)

    The effects of activation temperature on the textural and chemical properties of the activated carbons prepared from pistachio-nut shells using zinc chloride activation under both inert nitrogen gas atmosphere and vacuum condition were studied. Relatively low temperature of 400 deg. C was beneficial for the development of pore structures. Too high an activation temperature would lead to sintering of volatiles and shrinkage of the carbon structure. The microstructures and microcrystallinity of the activated carbons prepared were examined by scanning electron microscope and powder X-ray diffraction techniques, respectively, while Fourier transform infrared spectra determined the changes in the surface functional groups at the various stages of preparation

  17. Effect of the nature the carbon precursor on the physico-chemical characteristics of the resulting activated carbon materials

    International Nuclear Information System (INIS)

    Carbon materials, including amorphous carbon, graphite, carbon nanospheres (CNSs) and different types of carbon nanofibers (CNFs) [platelet, herringbone and ribbon], were chemically activated using KOH. The pore structure of carbon materials was analyzed using N2/77 K adsorption isotherms. The presence of oxygen groups was analyzed by temperature programmed desorption in He and acid-base titration. The structural order of the materials was studied by X-ray diffraction and temperature programmed oxidation. The morphology and diameter distribution of CNFs and CNSs were characterized by transmission electron microscopy. The materials were also characterized by temperature-desorption programmed of H2 and elemental composition. The ways in which the different structures were activated are described, showing the type of pores generated. Relationships between carbon yield, removed carbon, activation degree and graphitic character were also examined. The oxygen content in the form of oxygen-containing surface groups increased after the activation giving qualitative information about them. The average diameter of both CNFs and CNSs was decreased after the activation process as consequence of the changes produced on the material surface.

  18. 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

  19. An immersion calorimetric study of the interactions between some organic molecules and functionalized carbon nanotube surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Castillejos-López, E.; Bachiller-Baeza, B. [Instituto de Catálisis y Petrol., CSIC, Campus Cantoblanco, 28046 Madrid (Spain); Guerrero-Ruiz, A. [Dpto. Química Inorgánica y Técnica, UNED, 28040 Madrid (Spain); Rodriguez-Ramos, I., E-mail: irodriguez@icp.csic.es [Instituto de Catálisis y Petrol., CSIC, Campus Cantoblanco, 28046 Madrid (Spain)

    2013-09-10

    Highlights: ► The interaction of organic chemicals with the surface of modified CNTs was studied. ► Specific π–π interactions between graphitic CNTs and toluene have been considered. ► Confinement effects in CNTs increase the adsorption strength of aromatic compounds. ► Methanol molecules form H-bonds with the oxygen functional groups on CNT surfaces. - Abstract: The interaction of organic chemicals with the surface of carbon nanotubes has been studied by immersion calorimetry revealing significant differences in the properties when these materials are modified thermally or chemically. Therefore, multiwall carbon nanotubes have been synthesized using a chemical vapour deposition procedure and subsequently aliquots were treated with HNO{sub 3} at reflux, maintaining the reaction during different times, in order to incorporate oxygen surface groups, or were treated at 2873 K under inert atmosphere. The aim of this thermal treatment is to eliminate structural defects of the carbon nanostructures and to graphitize the amorphous carbon phases. These features were confirmed by high-resolution transmission electron microscopy. The immersion in organic compounds, including toluene, methanol and methylcyclohexane, of all these carbon nanotubes samples reveals that the surface properties are remarkably modified. Thus, the formation of different types of interaction, depending on the surface, gives place to changes in the immersion enthalpies.

  20. Highly Porous Carbon Materials from Biomass by Chemical and Carbonization Method: A Comparison Study

    OpenAIRE

    Wan Nor Roslam Wan Isahak; Mohamed Wahab Mahamed Hisham; Mohd Ambar Yarmo

    2013-01-01

    Porous carbon obtained by dehydrating agent, concentrated sulfuric acid (H2SO4), from biomass containing high cellulose (filter paper (FP), bamboo waste, and empty fruit bunches (EFB)) shows very high surface area and better thermal behavior. At room temperature (without heating), treatment of H2SO4 removed all the water molecules in the biomass and left the porous carbon without emitting any gaseous byproducts. Brunauer-Emmett-Teller (BET) surface analysis has shown that bamboo-based carbon ...

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Surface chemical studies of chemical vapour deposited diamond thin films

    CERN Document Server

    Proffitt, S

    2001-01-01

    could not easily be correlated to the bulk film properties. It is suggested that electron emission arises from the graphite component of graphite- diamond grain boundaries that are present in the nanocrystalline films. species. The adsorbed O and Cl species are more strongly bound to the K layer than they are to the diamond substrate, so thermal desorption of K from the K/CI/diamond or K/O/diamond surface results also in the simultaneous loss ofO and Cl. The phosphorus precursor trisdimethylaminophosphine (TDMAP) has a negligible reactive sticking probability on the clean diamond surface. This can be increased by thermal cracking of the gas phase precursor by a heated filament, resulting in non-activated adsorption to produce an adlayer containing a mixture of surface-bound ligands and phosphorus containing species. The ligands were readily lost upon heating, leaving P, some of which was lost from the surface at higher temperatures. Pre-hydrogenation of the diamond surface inhibited the uptake of cracked TDMA...

  6. Carbon Nanomaterials: Applications in Physico-chemical Systemsand Biosystems

    Directory of Open Access Journals (Sweden)

    Maheshwar Sharon

    2008-07-01

    Full Text Available In the present article, various forms of carbon and carbon nanomaterials (CNMs and a new approach to classify them on the basis of sp2-sp3 configuration are presented. Utilising the concept of junction formation (like p:n junction a concept is developed to explain the special reactivity of nanosized carbon materials. Geometric consideration of chiral and achiral symmetry of single-walled carbon nanotubes is presented which is also responsible for manifesting special propertiesof carbon nanotubes. A brief introduction to various common synthesis techniques of CNMs is given. These is increased chemical and biological activities have resulted in many engineer ednanoparticles, which are being designed for specific purposes, including diagnostic or the rapeuticmedical uses and environmental remediation.Defence Science Journal, 2008, 58(4, pp.460-485, DOI:http://dx.doi.org/10.14429/dsj.58.1668

  7. Carbon Nanotubes/Nanofibers by Plasma Enhanced Chemical Vapour Deposition

    Science.gov (United States)

    Teo, K. B. K.; Hash, D. B.; Bell, M. S.; Chhowalla, M.; Cruden, B. A.; Amaratunga, G. A. J.; Meyyappan, M.; Milne, W. I.

    2005-01-01

    Plasma enhanced chemical vapour deposition (PECVD) has been recently used for the production of vertically aligned carbon nanotubedfibers (CN) directly on substrates. These structures are potentially important technologically as electron field emitters (e.g. microguns, microwave amplifiers, displays), nanoelectrodes for sensors, filter media, superhydrophobic surfaces and thermal interface materials for microelectronics. A parametric study on the growth of CN grown by glow discharge dc-PECVD is presented. In this technique, a substrate containing thin film Ni catalyst is exposed to C2H2 and NH3 gases at 700 C. Without plasma, this process is essentially thermal CVD which produces curly spaghetti-like CN as seen in Fig. 1 (a). With the plasma generated by biasing the substrate at -6OOV, we observed that the CN align vertically during growth as shown in Fig. l(b), and that the magnitude of the applied substrate bias affects the degree of alignment. The thickness of the thin film Ni catalyst was found to determine the average diameter and inversely the length of the CN. The yield and density of the CN were controlled by the use of different diffusion barrier materials under the Ni catalyst. Patterned CN growth [Fig. l(c)], with la variation in CN diameter of 4.1% and 6.3% respectively, is achieved by lithographically defining the Ni thin film prior to growth. The shape of the structures could be varied from very straight nanotube-like to conical tip-like nanofibers by increasing the ratio of C2H2 in the gas flow. Due to the plasma decomposition of C2H2, amorphous carbon (a-C) is an undesirable byproduct which could coat the substrate during CN growth. Using a combination of depth profiled Auger electron spectroscopy to study the substrate and in-situ mass spectroscopy to examine gas phase neutrals and ions, the optimal conditions for a-C free growth of CN is determined.

  8. 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

  9. Theoretical and practical aspects of chemical functionalization of carbon nanofibers (CNFs): DFT calculations and adsorption study.

    Science.gov (United States)

    Rokhina, Ekaterina V; Lahtinen, Manu; Makarova, Katerina; Jegatheesan, Veeriah; Virkutyte, Jurate

    2012-06-01

    The nitric acid-functionalized commercial carbon nanofibers (CNFs) were comprehensively studied by instrumental (XRD, BET, SEM, TGA) and theoretical (DFT calculations) methods. The detailed surface study revealed the variation in the characteristics of functionalized CNFs, such as a decreased (up to 34%) surface area and impacted structural, electronic and chemical properties. The effects of functional groups were studied by comparison with pristine nanofibers. The results showed that the C-C bond lengths of the modified CNFs varied significantly. Chemical functionalization altered the frontier orbitals of the pristine material, and therefore altered the nature of their interactions with other substances. Moreover, the pristine and modified CNFs were tested for the removal of phenol from aqueous solutions. It was observed that surface modification tuned the adsorption capacity of carbon nanofibers (up to 0.35 mmol g(-1)), whereas original fibers did not demonstrate any adsorption capacity of phenol. PMID:22209137

  10. 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

  11. Carbon Monoxide Isotopes: On the Trail of Galactic Chemical Evolution

    Science.gov (United States)

    Langer, W.

    1995-01-01

    From the early days of the discovery of radio emission from carbon monoxide it was realized that it offered unusual potential for under- standing the chemical evolution of the Galaxy and external galaxies through measurements of molecular isotopes. These results bear on stellar nucleosynthesis, star formation, and gases in the interstellar medium. Progress in isotopic radio measurements will be reviewed.

  12. Carbon Footprint Calculations: An Application of Chemical Principles

    Science.gov (United States)

    Treptow, Richard S.

    2010-01-01

    Topics commonly taught in a general chemistry course can be used to calculate the quantity of carbon dioxide emitted into the atmosphere by various human activities. Each calculation begins with the balanced chemical equation for the reaction that produces the CO[subscript 2] gas. Stoichiometry, thermochemistry, the ideal gas law, and dimensional…

  13. 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.

  14. Effect of properties of carbon fiber surface modified by anodic treatment and a coupling agent on electron beam cured epoxy composites

    International Nuclear Information System (INIS)

    A double modification method of carbon fiber surface physical and chemical properties was presented by which the carbon fibers were electrochemically oxidized and subsequently coated with an electron beam compatible coupling agent. The treated and untreated carbon fiber surface chemical properties and morphology were analyzed using atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). And the carbon fiber surface energy was calculated through Kaelble method using contract angle measurement. The results show that the roughness and reactive groups of carbon fiber surface increase after anodic oxidization, moreover, polar composition of surface energy increase obviously. During EB curing the nitrogen-containing groups and basic species chemisorbed by carbon fiber surface restrain the initiators in the interface of composites, resulting in the weaker adhesion between the carbon fiber and the matrix. The coupling agent, acting as chemical bridge between the carbon fibers and the matrix, improves the interfacial properties of EB cured composites

  15. Anthropogenic chemical carbon cycle for a sustainable future.

    Science.gov (United States)

    Olah, George A; Prakash, G K Surya; Goeppert, Alain

    2011-08-24

    Nature's photosynthesis uses the sun's energy with chlorophyll in plants as a catalyst to recycle carbon dioxide and water into new plant life. Only given sufficient geological time, millions of years, can new fossil fuels be formed naturally. The burning of our diminishing fossil fuel reserves is accompanied by large anthropogenic CO(2) release, which is outpacing nature's CO(2) recycling capability, causing significant environmental harm. To supplement the natural carbon cycle, we have proposed and developed a feasible anthropogenic chemical recycling of carbon dioxide. Carbon dioxide is captured by absorption technologies from any natural or industrial source, from human activities, or even from the air itself. It can then be converted by feasible chemical transformations into fuels such as methanol, dimethyl ether, and varied products including synthetic hydrocarbons and even proteins for animal feed, thus supplementing our food chain. This concept of broad scope and framework is the basis of what we call the Methanol Economy. The needed renewable starting materials, water and CO(2), are available anywhere on Earth. The required energy for the synthetic carbon cycle can come from any alternative energy source such as solar, wind, geothermal, and even hopefully safe nuclear energy. The anthropogenic carbon dioxide cycle offers a way of assuring a sustainable future for humankind when fossil fuels become scarce. While biosources can play a limited role in supplementing future energy needs, they increasingly interfere with the essentials of the food chain. We have previously reviewed aspects of the chemical recycling of carbon dioxide to methanol and dimethyl ether. In the present Perspective, we extend the discussion of the innovative and feasible anthropogenic carbon cycle, which can be the basis of progressively liberating humankind from its dependence on diminishing fossil fuel reserves while also controlling harmful CO(2) emissions to the atmosphere. We also

  16. Vegetation of stormwater basins : flora inventory and physico-chemical characterization of vegetated surface

    OpenAIRE

    Saulais, Muriel

    2011-01-01

    Urban stormwater basins surfaces can be highly contaminated and can be spontaneously or intentionaly vegetated. The aim of this work is to better characterize the role of the vegetation on heavy metal (Zn, Cd, Cu) mobility. Firstly, vegetation inventory has pointed out the high species diversity in these devices (from ruderal vegetation to wetland plants). Then, a physico-chemical characterization of surface samples vegetated by dominant species has been carried out. We have shown that carbon...

  17. Chemical vapor deposition of pyrolytic carbon on polished substrates

    OpenAIRE

    DesprÉs, J.-F.; Vahlas, C.; Oberlin, A.

    1993-01-01

    Pyrolytic carbon thin (4-100 nm) films were obtained from méthane in a hot wall reactor on optically polished inert substrates by varying the déposition time and temperature. They were characterized by all modes of TEM. They are composed in majority of lamellar pyrocarbon whose thickness and disorder increases with increasing temperature. Isotropic carbon islands are also observed at the upper surface of the film.

  18. Effect of chemical treatments on hydrogen storage behaviors of multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    In this work, the hydrogen storage behaviors of chemically treated multi-walled carbon nanotubes (MWNTs) were investigated. The surface properties of the functionalized MWNTs were confirmed by Fourier transfer infrared spectroscopy, X-ray diffraction, the Boehm titration method, and zeta-potential measurements. The hydrogen storage capacity of the MWNTs was evaluated at 298 K and 100 bar. In the experimental results, it was found that the chemical treatments introduced functional groups onto the MWNT surfaces. The amount of hydrogen storage was enhanced, by acidic surface treatment, to 0.42 wt.% in the acidic-treated MWNTs compared with 0.26 wt.% in the as-received MWNTs. Meanwhile, the basic surface treatment actually reduced the hydrogen storage capacity, to 0.24 wt.% in the basic-treated MWNTs sample. Consequently, it could be concluded that hydrogen storage is greatly influenced by the acidic characteristics of MWNT surfaces, resulting in enhanced electron acceptor-donor interaction at interfaces.

  19. Synthesis of Aligned Carbon Nanotubes by Thermal Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    LI Gang; ZHOU Ming; MA Weiwei; CAI Lan

    2009-01-01

    Single crystal silicon was found to be very beneficial to the growth of aligned carbon nanotubes by chemical vapor deposition with C2H2 as carbon source. A thin film of Ni served as catalyst was deposited on the Si substrate by the K575X Peltier Cooled High Resolution Sputter Coater before growth. The growth properties of carbon nanotubes were studied as a function of the Ni catalyst layer thickness. The diameter, growth rate and areal density of the carbon nanotubes were controlled by the initial thickness of the catalyst layer. Steric hindrance between nanotubes forces them to grow in well-aligned manner at an initial stage of growth. Transmission electron microscope analysis revealed that nanotubes grew by a tip growth mechanism.

  20. Characterization of Carbon Nanotubes Grown by Chemical Vapor Deposition

    Science.gov (United States)

    Cochrane, J. C.; Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Since the superior properties of multi-wall carbon nanotubes (MWCNT) could improve numerous devices such as electronics and sensors, many efforts have been made in investigating the growth mechanism of MWCNT to synthesize high quality MWCNT. Chemical vapor deposition (CVD) is widely used for MWCNT synthesis, and scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) are useful methods for analyzing the structure, morphology and composition of MWCNT. Temperature and pressure are two important growth parameters for fabricating carbon nanotubes. In MWCNT growth by CVD, the plasma assisted method is normally used for low temperature growth. However a high temperature environment is required for thermal CVD. A systematic study of temperature and pressure-dependence is very helpful to understanding MWCNT growth. Transition metal particles are commonly used as catalysis in carbon nanotube growth. It is also interesting to know how temperature and pressure affect the interface of carbon species and catalyst particles

  1. Synthesis of sulfonated porous carbon nanospheres solid acid by a facile chemical activation route

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Binbin, E-mail: changbinbin806@163.com; Guo, Yanzhen; Yin, Hang; Zhang, Shouren; Yang, Baocheng, E-mail: baochengyang@yahoo.com

    2015-01-15

    Generally, porous carbon nanospheres materials are usually prepared via a template method, which is a multi-steps and high-cost strategy. Here, we reported a porous carbon nanosphere solid acid with high surface area and superior porosity, as well as uniform nanospheical morphology, which prepared by a facile chemical activation with ZnCl{sub 2} using resorcinol-formaldehyde (RF) resins spheres as precursor. The activation of RF resins spheres by ZnCl{sub 2} at 400 °C brought high surface area and large volume, and simultaneously retained numerous oxygen-containing and hydrogen-containing groups due to the relatively low processing temperature. The presence of these functional groups is favorable for the modification of –SO{sub 3}H groups by a followed sulfonation treating with sulphuric acid and organic sulfonic acid. The results of N{sub 2} adsorption–desorption and electron microscopy clearly showed the preservation of porous structure and nanospherical morphology. Infrared spectra certified the variation of surface functional groups after activation and the successful modification of –SO{sub 3}H groups after sulfonation. The acidities of catalysts were estimated by an indirect titration method and the modified amount of –SO{sub 3}H groups were examined by energy dispersive spectra. The results suggested sulfonated porous carbon nanospheres catalysts possessed high acidities and –SO{sub 3}H densities, which endowed their significantly catalytic activities for biodiesel production. Furthermore, their excellent stability and recycling property were also demonstrated by five consecutive cycles. - Graphical abstract: Sulfonated porous carbon nanospheres with high surface area and superior catalytic performance were prepared by a facile chemical activation route. - Highlights: • Porous carbon spheres solid acid prepared by a facile chemical activation. • It owns high surface area, superior porosity and uniform spherical morphology. • It possesses

  2. Synthesis of sulfonated porous carbon nanospheres solid acid by a facile chemical activation route

    International Nuclear Information System (INIS)

    Generally, porous carbon nanospheres materials are usually prepared via a template method, which is a multi-steps and high-cost strategy. Here, we reported a porous carbon nanosphere solid acid with high surface area and superior porosity, as well as uniform nanospheical morphology, which prepared by a facile chemical activation with ZnCl2 using resorcinol-formaldehyde (RF) resins spheres as precursor. The activation of RF resins spheres by ZnCl2 at 400 °C brought high surface area and large volume, and simultaneously retained numerous oxygen-containing and hydrogen-containing groups due to the relatively low processing temperature. The presence of these functional groups is favorable for the modification of –SO3H groups by a followed sulfonation treating with sulphuric acid and organic sulfonic acid. The results of N2 adsorption–desorption and electron microscopy clearly showed the preservation of porous structure and nanospherical morphology. Infrared spectra certified the variation of surface functional groups after activation and the successful modification of –SO3H groups after sulfonation. The acidities of catalysts were estimated by an indirect titration method and the modified amount of –SO3H groups were examined by energy dispersive spectra. The results suggested sulfonated porous carbon nanospheres catalysts possessed high acidities and –SO3H densities, which endowed their significantly catalytic activities for biodiesel production. Furthermore, their excellent stability and recycling property were also demonstrated by five consecutive cycles. - Graphical abstract: Sulfonated porous carbon nanospheres with high surface area and superior catalytic performance were prepared by a facile chemical activation route. - Highlights: • Porous carbon spheres solid acid prepared by a facile chemical activation. • It owns high surface area, superior porosity and uniform spherical morphology. • It possesses high acidity and high –SO3H density. • It

  3. Plasma-chemical surface engineering of wood

    Directory of Open Access Journals (Sweden)

    A. Sokołowska

    2009-12-01

    Full Text Available Purpose: Wood infiltrated with nano-silica hydrosol forms a “weak”, irregular composite of components bound with hydrogen bonds only. The purpose of this study was to investigate the influence of low-energy ions bombardment on the structure and properties of the surface of this composite. The aim of these investigations was to produce a shallow “buried” layer of a dense wood-ceramic composite on a wood surface .Design/methodology/approach: D.c. glow-discharge in N2/H2 (9:11 atmosphere under a pressure of 4hPa was the source of ions. A beech plate was placed on the cathode. The temperature of wood was 200°C. The material collected from the wood-silica composite surface was investigated with FTIR spectroscopy and SEM observations. The surface energy was determined with the use of contact angle measurements.Findings: The ions influenced silica only. The nano-particles underwent sintering changing its medium size twice and a small I.R. peak of N2 trapped in SiO2 suggest the possibility of silica nitriding. A buried, continual surface layer of sintered silica did not form. The surface energy of the “wood-silica” plate was slightly decreased after plasma treatment.Research limitations/implications: The results proved the possibility of plasma treatment of wood even in a d.c. glow-discharge under low pressure. Silica sintering, a difficult process which in a thermal way has to be carried out at a temperature of 1000°C, taking place in a plasma at a temperature of 200°C showed the very special nature of an influence of ions.Originality/value: The plasma surface treatment of wood in the d.c. glow-discharge (GD under reduced pressure has not been investigated. There are only publications about glow-dielectric-barrier-discharge (GDBD at atmospheric pressure applications for wood surface modification. The energy of ions in GDBD is much smaller than that of ions in GD and therefore the application of glow discharge under reduced pressure to

  4. Physical and chemical study of the influence of oxidation on the structure of carbon black

    International Nuclear Information System (INIS)

    This research thesis reports the study of the influence of an oxidising attack on carbon black particles by using chemical, physical and electrochemical methods to highlight the oxidation process. The carbon black particle is a spherical set essentially made of amorphous and crystalline carbon. It appears that the oxidising attack mainly occurs against the amorphous parts which surround the crystallites. If the attack is strong enough, crystallites are freed and the particle collapses. This process has been observed by using electronic microscopy, X rays, the BET nitrogen absorption method, and infra-reds. Chemical analysis revealed the presence of carboxyl, hydroxyl and quinone functional groups on the oxidised particle surface. These groups have been dosed by different methods (methylation, calcium acetate dosing, polarography and potassium borohydride reduction)

  5. Multi-wall carbon nanotubes supported on carbon fiber paper synthesized by simple chemical vapor deposition

    International Nuclear Information System (INIS)

    Highlights: • We deposited multi-wall carbon nanotubes on carbon fiber paper with a simple CVD. • We investigated the inherent mechanism of Ni particle's self-dispersion. • The MWCNTs/CFP composite possesses wonderful electrical conductivity. - Abstract: Aiming at developing a novel carbon/carbon composite as an electrode in the electrochemical capacitor applications, multi-wall carbon nanotubes (MWCNTs)/carbon fiber paper (CFP) composite has been synthesized using a simple chemical vapor deposition, in which different metal catalysts such as Fe, Ni and Cu are used. However, randomly oriented MWCNTs were only obtained on Ni particles. The mechanism for this unique phenomenon is investigated in this article. The physical and electrochemical properties of as-prepared MWCNTs/CFP composite are characterized and the results show that the as-prepared composite is a promising substrate for electrochemical capacitor applications

  6. 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...

  7. Low carbon fuel and chemical production from waste gases

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, S.; Liew, F.M.; Daniell, J.; Koepke, M. [LanzaTech, Ltd., Auckland (New Zealand)

    2012-07-01

    LanzaTech has developed a gas fermentation platform for the production of alter native transport fuels and commodity chemicals from carbon monoxide, hydrogen and carbon dioxide containing gases. LanzaTech technology uses these gases in place of sugars as the carbon and energy source for fermentation thereby allowing a broad spectrum of resources to be considered as an input for product synthesis. At the core of the Lanzatech process is a proprietary microbe capable of using gases as the only carbon and energy input for product synthesis. To harness this capability for the manufacture of a diverse range of commercially valuable products, the company has developed a robust synthetic biology platform to enable a variety of novel molecules to be synthesised via gas fermentation. LanzaTech initially focused on the fermentation of industrial waste gases for fuel ethanol production. The company has been operating pilot plant that uses direct feeds of steel making off gas for ethanol production for over 24 months. This platform technology has been further successfully demonstrated using a broad range of gas inputs including gasified biomass and reformed natural gas. LanzaTech has developed the fermentation, engineering and control systems necessary to efficiently convert gases to valuable products. A precommercial demonstration scale unit processing steel mill waste gases was commissioned in China during the 2{sup nd} quarter of 2012. Subsequent scale-up of this facility is projected for the 2013 and will represent the first world scale non-food based low carbon ethanol project. More recently LanzaTech has developed proprietary microbial catalysts capable of converting carbon dioxide in the presence of hydrogen directly to value added chemicals, where-in CO{sub 2} is the sole source of carbon for product synthesis. Integrating the LanzaTech technology into a number of industrial facilities, such as steel mills, oil refineries and other industries that emit Carbon bearing

  8. Wetting behaviour of carbon nitride nanostructures grown by plasma enhanced chemical vapour deposition technique

    International Nuclear Information System (INIS)

    Highlights: • Carbon nitride films were prepared by using radio frequency plasma enhanced chemical vapour deposition system by altering the electrode distance. • The effect of electrode distance on surface morphology, surface roughness, chemical bonding and hydrophobic behaviour has been studied. • Hydrophobic behaviour were studied by measuring contact angle and calculating surface energy. • CNx nanostructures show super-hydrophobic behaviour. • We report a tunable transition of hydrophilic to super-hydrophobic behaviour of film as electrode distance is reduced. - Abstract: Tuning the wettability of various coating materials by simply controlling the deposition parameters is essential for various specific applications. In this work, carbon nitride (CNx) films were deposited on silicon (1 1 1) substrates using radio-frequency plasma enhanced chemical vapour deposition employing parallel plate electrode configuration. Effects of varying the electrode distance (DE) on the films’ structure and bonding properties were investigated using Field emission scanning electron microscopy, Atomic force microscopy, Fourier transform infrared and X-ray photoemission spectroscopy. The wettability of the films was analyzed using water contact angle measurements. At high DE, the CNx films’ surface was smooth and uniform. This changed into fibrous nanostructures when DE was decreased. Surface roughness of the films increased with this morphological transformation. Nitrogen incorporation increased with decrease in DE which manifested the increase in both relative intensities of C=N to C=C and N−H to O−H bonds. sp2-C to sp3-C ratio increased as DE decreased due to greater deformation of sp2 bonded carbon at lower DE. The films’ characteristics changed from hydrophilic to super-hydrophobic with the decrease in DE. Roughness ratio, surface porosity and surface energy calculated from contact angle measurements were strongly dependent on the morphology, surface

  9. Activated Carbons From Grape Seeds By Chemical Activation With Potassium Carbonate And Potassium Hydroxide

    Science.gov (United States)

    Okman, Irem; Karagöz, Selhan; Tay, Turgay; Erdem, Murat

    2014-02-01

    Activated carbons were produced from grape seed using either potassium carbonate (K2CO3) or potassium hydroxide (KOH). The carbonization experiments were accomplished at 600 and 800 °C. The effects of the experimental conditions (i.e., type of activation reagents, reagent concentrations, and carbonization temperatures) on the yields and the properties of these activated carbons were analyzed under identical conditions. An increase in the temperature at the same concentrations for both K2CO3 and KOH led to a decrease in the yields of the activated carbons. The lowest activated carbon yields were obtained at 800 °C at the highest reagent concentration (100 wt%) for both K2CO3 and KOH. The activated carbon with the highest surface area of 1238 m2g-1 was obtained at 800 °C in K2CO3 concentration of 50 wt% while KOH produced the activated carbon with the highest surface area of 1222 m2g-1 in a concentration of 25wt% at 800 °C. The obtained activated carbons were mainly microporous.

  10. Structure of adsorbed monolayers. The surface chemical bond

    International Nuclear Information System (INIS)

    This paper attempts to provide a summary of what has been learned about the structure of adsorbed monolayers and about the surface chemical bond from molecular surface science. While the surface chemical bond is less well understood than bonding of molecules in the gas phase or in the solid state, our knowledge of its properties is rapidly accumulating. The information obtained also has great impact on many surface science based technologies, including heterogeneous catalysis and electronic devices. It is hoped that much of the information obtained from studies at solid-gas interfaces can be correlated with molecular behavior at solid-liquid interfaces. 31 references, 42 figures, 1 table

  11. Surface Chemical Functionalization based on Plasma Techniques

    OpenAIRE

    Ricciardi, Serena

    2012-01-01

    Biomaterials research has undergone a variety of evolutionary developments in recent years. In this perspective, bulk materials properties and biomechanics took relevance in view of the stringent mechanical and tribological demands of the bio-implants. However, such issues cannot be the sole determinants of clinical outcome. Interest in bulk properties has inevitably shifted to the important consideration of the surface with the interfacial phenomena, conditioning their performance. These eve...

  12. OPTIMIZATION OF CHEMICALS USE FOR HIGHLY FILLED MECHANICAL GRADE PAPERS WITH PRECIPITATED CALCIUM CARBONATE

    OpenAIRE

    Yizhou Sang,; Michael McQuaid; Peter Englezos

    2011-01-01

    Response surface methodology was used with four factors to screen for the best starch and optimize the use of chemicals in order to maximize precipitated calcium carbonate (PCC) filler retention in a peroxide-bleached TMP suspension. Three commercial starches were used in conjunction with colloidal silica and flocculant. The PCC loading level and the interactions between PCC level, starch, flocculant, and silica were investigated, and empirical models were constructed. The empirical process m...

  13. Carbon nanosheets by microwave plasma enhanced chemical vapor deposition in CH4-Ar system

    International Nuclear Information System (INIS)

    We employ a new gas mixture of CH4-Ar to fabricate carbon nanosheets by microwave plasma enhanced chemical vapor deposition at the growth temperature of less than 500 deg. C. The catalyst-free nanosheets possess flower-like structures with a large amount of sharp edges, which consist of a few layers of graphene sheets according to the observation by transmission electron microscopy. These high-quality carbon nanosheets demonstrated a faster electron transfer between the electrolyte and the nanosheet surface, due to their edge defects and graphene structures.

  14. 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.

  15. 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.

  16. 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 ...

  17. Preparation and Characterization of Sisal Fiber-based Activated Carbon by Chemical Activation with Zinc Chloride

    International Nuclear Information System (INIS)

    Sisal fiber, an agricultural resource abundantly available in China, has been used as raw material to prepare activated carbon with high surface area and huge pore volume by chemical activation with zinc chloride. The orthogonal test was designed to investigate the influence of zinc chloride concentration, impregnation ratio, activation temperature and activation time on preparation of activated carbon. Scanning electron micrograph, Thermo-gravimetric, N2-adsorption isotherm, mathematical models such as t-plot, H-K equation, D-R equation and BJH methods were used to characterize the properties of the prepared carbons and the activation mechanism was discussed. The results showed that ZnCl2 changed the pyrolysis process of sisal fiber. Characteristics of activated carbon are: BET surface area was 1628 m2/g, total pore volume was 1.316 m3/g and ratio of mesopore volume to total pore volume up to 94.3%. These results suggest that sisal fiber is an attractive source to prepare mesoporous high-capacity activated carbon by chemical activation with zinc chloride

  18. 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

  19. 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.

  20. Chemical Reactions in the Processing of Mosi2 + Carbon Compacts

    Science.gov (United States)

    Jacobson, Nathan S.; Lee, Kang N.; Maloy, Stuart A.; Heuer, Arthur H.

    1993-01-01

    Hot-pressing of MoSi2 powders with carbon at high temperatures reduces the siliceous grain boundary phase in the resultant compact. The chemical reactions in this process were examined using the Knudsen cell technique. A 2.3 wt pct oxygen MoSi2 powder and a 0.59 wt pct oxygen MoSi2 powder, both with additions of 2 wt pct carbon, were examined. The reduction of the siliceous grain boundary phase was examined at 1350 K and the resultant P(SiO)/P(CO) ratios interpreted in terms of the SiO(g) and CO(g) isobars on the Si-C-O predominance diagram. The MoSi2 + carbon mixtures were then heated at the hot-pressing temperature of 2100 K. Large weight losses were observed and could be correlated with the formation of a low-melting eutectic and the formation and vaporization of SiC.

  1. Plasma Enhanced Chemical Vapour Deposition of Horizontally Aligned Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Matthew T. Cole

    2013-05-01

    Full Text Available A plasma-enhanced chemical vapour deposition reactor has been developed to synthesis horizontally aligned carbon nanotubes. The width of the aligning sheath was modelled based on a collisionless, quasi-neutral, Child’s law ion sheath where these estimates were empirically validated by direct Langmuir probe measurements, thereby confirming the proposed reactors ability to extend the existing sheath fields by up to 7 mm. A 7 mbar growth atmosphere combined with a 25 W plasma permitted the concurrent growth and alignment of carbon nanotubes with electric fields of the order of 0.04 V μm−1 with linear packing densities of up to ~5 × 104 cm−1. These results open up the potential for multi-directional in situ alignment of carbon nanotubes providing one viable route to the fabrication of many novel optoelectronic devices.

  2. Controls on dissolved organic carbon quantity and chemical character in temperate rivers of North America

    Science.gov (United States)

    Hanley, Kevin W.; Wollheim, Wilfred M.; Salisbury, Joseph; Huntington, Thomas; Aiken, George

    2013-04-01

    the processes controlling the transfer and chemical composition of dissolved organic carbon (DOC) in freshwater systems is crucial to understanding the carbon cycle and the effects of DOC on water quality. Previous studies have identified watershed-scale controls on bulk DOC flux and concentration among small basins but fewer studies have explored controls among large basins or simultaneously considered the chemical composition of DOC. Because the chemical character of DOC drives riverine biogeochemical processes such as metabolism and photodegradation, accounting for chemical character in watershed-scale studies will improve the way bulk DOC variability in rivers is interpreted. We analyzed DOC quantity and chemical character near the mouths of 17 large North American rivers, primarily between 2008 and 2010, and identified watershed characteristics that controlled variability. We quantified DOC chemical character using both specific ultraviolet absorbance at 254 nm (SUVA254) and XAD-resin fractionation. Mean DOC concentration ranged from 2.1 to 47 mg C L-1 and mean SUVA254 ranged from 1.3 to 4.7 L mg C-1 m-1. We found a significant positive correlation between basin wetland cover and both bulk DOC concentration (R2 = 0.78; p river systems with long surface water residence times. However, synoptic DOC sampling of both quantity and character throughout river networks will be needed to more rigorously test this finding. The inclusion of DOC chemical character will be vital to achieving a more complete understanding of bulk DOC dynamics in large river systems.

  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. 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.

  5. Hydrotalcites: a highly efficient ecomaterial for effluent treatment originated from carbon nanotubes chemical processing

    Science.gov (United States)

    Alves, O. L.; Stéfani, D.; Parizotto, N. V.; Souza Filho, A. G.

    2011-07-01

    It has been reported that a mixture of carboxylated carbonaceous fragments (CCFs), so called oxidation debris, are generated during carbon nanotubes chemical processing using oxidant agents such as HNO3. The elimination of these fragments from carbon nanotubes surface has been point out to be a crucial step for an effective functionalization of the nanotubes as well as for improving the material. However, this process can introduce a potential environmental problem related water contamination because these CCFs can be viewed as a mixture of carbonaceous polyaromatic systems similar to humic substances and dissolved organic matter (DOM). The negative aspects of humic substances and DOM to water quality and wastewater treatment are well known. Since carbon nanotubes industry expands at high rates it is expected that effluent containing oxidation debris will increase since HNO3 chemical processing is the most applied method for purification and functionalization of carbon nanotubes. In this work, we have demonstrated that Hydrotalcites (HT) are highly efficient to remove oxidation debris from effluent solution originated from HNO3-treated multiwalled carbon nanotubes. The strategy presented here is a contribution towards green chemistry practices and life cycle studies in carbon nanotubes field.

  6. Improvement on the electrochemical characteristics of graphite anodes by coating of the pyrolytic carbon using tumbling chemical vapor deposition

    International Nuclear Information System (INIS)

    The electrochemical characteristics of graphite coated with pyrolytic carbon materials using tumbling chemical vapor deposition (CVD) process have been studied for the active material of anodes in lithium ion secondary batteries. Coating of pyrolytic carbons on the surface of graphite particles, which tumble in a rotating reactor tube, was performed through the pyrolysis of liquid propane gas (LPG). The surface morphology of these graphite particles coated with pyrolytic carbon has been observed with scanning electron microscopy (SEM). The surface of graphite particles can well be covered with pyrolytic carbon by tumbling CVD. High-resolution transmission electron microscopy (HRTEM) image of these carbon particles shows that the core part is highly ordered carbon, while the shell part is disordered carbon. We have found that the new-type carbon obtained from tumbling CVD has a uniform core (graphite)-shell (pyrolytic carbon) structure. The electrochemical property of the new-type carbons has been examined using a charge-discharge cycler. The coating of pyrolytic carbon on the surface of graphite can effectively reduce the initial irreversible capacity by 47.5%. Cyclability and rate-capability of theses carbons with the core-shell structure are much better than those of bare graphite. From electrochemical impedance spectroscopy (EIS) spectra, it is found that the coating of pyrolytic carbon on the surface of graphite causes the decrease of the contact resistance in the carbon electrodes, which means the formation of solid electrolyte interface (SEI) layer is suppressed. We suggest that coating of pyrolytic carbon by the tumbling CVD is an effective method in improving the electrochemical properties of graphite electrodes for lithium ion secondary batteries

  7. Optical measurements of chemically heterogeneous particulate surfaces

    Science.gov (United States)

    Zubko, Nataliya; Gritsevich, Maria; Zubko, Evgenij; Hakala, Teemu; Peltoniemi, Jouni I.

    2016-07-01

    We experimentally study light scattering by particulate surfaces consisting of two high-contrast materials. Using the Finnish Geodetic Institute field goniospectropolarimeter, reflectance and degree of linear polarization are measured in dark volcanic sand, bright salt (NaCl) and bright ferric sulfate (Fe2(SO4)3); and in mixtures of bright and dark components. We found that the light-scattering response monotonically changes with volume ratio of dark and bright components. In contrast to previous finding, we do not detect an enhancement of the negative polarization amplitude in two-component high-contrast mixtures. Two-component mixtures reveal an inverse correlation between maximum of their linear polarization and reflectance near backscattering, the so-called Umov effect. In log-log scales this inverse correlation takes a linear form for the dark and moderate-dark samples, while for the brightest samples there is a noticeable deviation from the linear trend.

  8. Analytical evaluation of the solid rocket motor nozzle surface recession by the alumina-carbon reaction

    OpenAIRE

    Matsukawa, Yutaka; Sato, Yutaka; 松川 豊; 佐藤 裕

    2008-01-01

    A theoretical model describing the chemical ablation of a solid rocket motor nozzle ablator by the alumina-carbon reaction is presented. An application of it to a typical solid rocket motor with a graphite nozzle ablator indicates a large influence of the reaction on the nozzle surface recession.

  9. Surface Chemical Properties of Colloids in Main Soils of China

    Institute of Scientific and Technical Information of China (English)

    MAYI-JIE; YUANCHAO-LIANG

    1991-01-01

    Surface chemical properties of soil colloids are the important factor affecting soil fertility and genesis.To provide scientific basis for soil genetic classification,promotion of soil fertility and reasonable fertilizqation,the specific surface area and electric charge of soil colloids in relation to clay minerals and organic matter are further discussed on the basis of the results obtained from the studies on surface chemical properties of soil colloids in five main soils of China.Results from the studies show that the effect of clay minerals and organic matter on the surface chemical properties of soil colloids is very complicated because the siloxane surface,hydrated oxide surface and organic matter surface do not exist separately,but they are always mixed together and influenced each other.The understanding of the relationship among clay minerals,organic matter and surface chemical properties of soil colloids depends upon further study of the relevant disciplines of soil science,especially the study on the mechanisms of organo-mineral complexes.

  10. 2011 Chemical Reactions at Surfaces Gordon Research Conference

    Energy Technology Data Exchange (ETDEWEB)

    Peter Stair

    2011-02-11

    The Gordon Research Conference on Chemical Reactions at Surfaces is dedicated to promoting and advancing the fundamental science of interfacial chemistry and physics by providing surface scientists with the foremost venue for presentation and discussion of research occurring at the frontiers of their fields.

  11. Characterization of mesoporous carbon prepared from date stems by H3PO4 chemical activation

    International Nuclear Information System (INIS)

    The present work was focused on the determination of texture, morphology, crystanillity and oxygenated surface groups characteristics of an activated carbon prepared from date stems. Chemical activation of this precursor at different temperatures (450, 550 and 650 °C) was adopted using phosphoric acid as dehydrating agent at (2/1) impregnation ratio. Fourier transform infrared spectroscopy study was carried out to identify surface groups in date stems activated carbons. The microscopic structure was examined by nitrogen adsorption at 77 K. The interlayer spacing (d200 and d100), stack height (Lc), stack width (La) and effective dimension L of the turbostratic crystallites (microcrystallite) in the date stems activated carbons were estimated from X-ray diffraction data (XRD). Results yielded a surface area, SBET, and total pore volume of 682, 1455, 1319 m2/g and 0,343, 1,045 and 0.735 cm3/g, for the carbon prepared at 450, 550 and 650 °C, respectively. Scanning electron microscopy exhibits a highly developed porosity which is in good agreement with the porous texture derived from gas adsorption data and these results confirm that the activated carbon is dominated by network of slit-shaped mesopores morphology and in some cases by varied micropores morphologies.

  12. 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.

  13. Chemical changes induced on a TiO2 surface by electron bombardment

    International Nuclear Information System (INIS)

    We study the TiO2 (Ti4+) chemical reduction induced by electron bombardment using Auger electron spectroscopy and factor analysis. We show that the electron irradiation of a TiO2 sample is characterized by the appearance of a lower Ti oxidation state, Ti2O3 (Ti3+), followed by a further deposition of carbon, which is present inevitably in the environment even under ultra-high vacuum conditions. The appearance of C over the surface is found to be a complex mechanism which affects the reduction process through passivation of the electron-induced oxygen desorption and formation of titanium carbide. For very high irradiation doses, we also found that the chemical changes on the surface are stopped due to the deposition of carbon in a graphitic form

  14. Chemical changes induced on a TiO{sub 2} surface by electron bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Vergara, L.I. [Laboratorio de Superficies e Interfaces, Instituto de Desarrollo Tecnologico para la Industria Quimica, INTEC (CONICET-UNL), Gueemes 3450, (S3000GLN) Santa Fe (Argentina); Passeggi, M.C.G. [Laboratorio de Superficies e Interfaces, Instituto de Desarrollo Tecnologico para la Industria Quimica, INTEC (CONICET-UNL), Gueemes 3450, (S3000GLN) Santa Fe (Argentina)], E-mail: mpggih@intec.unl.edu.ar; Ferron, J. [Laboratorio de Superficies e Interfaces, Instituto de Desarrollo Tecnologico para la Industria Quimica, INTEC (CONICET-UNL), Gueemes 3450, (S3000GLN) Santa Fe (Argentina); Departamento de Materiales, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2829, (S3000AOM) Santa Fe (Argentina)

    2007-09-14

    We study the TiO{sub 2} (Ti{sup 4+}) chemical reduction induced by electron bombardment using Auger electron spectroscopy and factor analysis. We show that the electron irradiation of a TiO{sub 2} sample is characterized by the appearance of a lower Ti oxidation state, Ti{sub 2}O{sub 3} (Ti{sup 3+}), followed by a further deposition of carbon, which is present inevitably in the environment even under ultra-high vacuum conditions. The appearance of C over the surface is found to be a complex mechanism which affects the reduction process through passivation of the electron-induced oxygen desorption and formation of titanium carbide. For very high irradiation doses, we also found that the chemical changes on the surface are stopped due to the deposition of carbon in a graphitic form.

  15. 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

  16. Collisions of polyatomic ions with surfaces: incident energy partitioning and chemical reactions

    International Nuclear Information System (INIS)

    Collision of polyatomic ions with surfaces were investigated in ion-surface scattering experiments to obtain more information on energy partitioning in ion-surface collision and on chemical reactions at surfaces. Mass spectra, translation energy and angular distributions of product ions were measured in dependence on the incident energy and the incident angle of polyatomic projectiles. From these data distributions of energy fractions resulting in internal excitation of the projectile, translation energy of the product ions, and energy absorbed by the surface were determined. The surface investigated were a standard stainless steel surface, covered by hydrocarbons, carbon surfaces at room and elevated temperatures, and several surfaces covered by a self-assembled monolayers (C12-hydrocarbon SAM, C11-perfluorohydrocarbon SAM, and C11 hydrocarbon with terminal -COOH group SAM). The main processes observed at collision energies of 10 - 50 eV were: neutralization of the ions at surfaces, inelastic scattering and dissociations of the projectile ions, quasi elastic scattering of the projectile ions, and chemical reactions with the surface material (usually hydrogen-atom transfer reactions). The ion survival factor was estimated to be a few percent for even-electron ions (like protonated ethanol ion, C2H5O+, CD5+) and about 10 - 102 times lower for radical ions (like ethanol and benzene molecular ions, CD4+). In the polyatomic ion -surface energy transfer experiments, the ethanol molecular ion was used as a well-characterized projectile ion. The results with most of the surfaces studied showed in the collision energy range of 13 - 32 eV that most collisions were strongly inelastic with about 6 - 8 % of the incident projectile energy transformed into internal excitation of the projectile (independent of the incident angle) and led partially to its further dissociation in a unimolecular way after the interaction with the surface. The incident energy transformed into the

  17. Characterization of Surface Chemical States of a Thick Insulator: Chemical State Imaging on MgO Surface

    Science.gov (United States)

    Yi, Yeonjin; Cho, Sangwan; Noh, Myungkeun; Whang, Chung-Nam; Jeong, Kwangho; Shin, Hyun-Joon

    2005-02-01

    We report a surface characterization tool that can be effectively used to investigate the chemical state and subtle radiation damage on a thick insulator surface. It has been used to examine the MgO surface of a plasma display panel (PDP) consisting of a stack of insulator layers of approximately 51 μm thickness on a 2-mm-thick glass plate. The scanning photoelectron microscopy (SPEM) image of the insulating MgO surface was obtained by using the difference in Au 4f peak shift due to the surface charging at each pixel, where a Au adlayer of approximately 15 {\\AA} thickness was formed on the surface to overcome the serious charging shift of the peak position and the spectral deterioration in the photoelectron spectra. The observed contrast in the SPEM image reveals the chemical modification of the underlying MgO surface induced by the plasma discharge damage. The chemical state analysis of the MgO surface was carried out by comparing the Mg 2p, C 1s and O 1s photoemission spectra collected at each pixel of the SPEM image. We assigned four suboxide phases, MgO, MgCO3, Mg(OH)2 and Mg1+, on the initial MgO surface, where the Mg(OH)2 and Mg1+ phases vanished rapidly as the discharge-induced surface damage began.

  18. Growth and morphology of carbon nanostructures on nickel oxide nanoparticles in catalytic chemical vapor deposition

    Science.gov (United States)

    Jana, M.; Sil, A.; Ray, S.

    2014-07-01

    The present study explores the conditions favorable for the growth of cylindrical carbon nanostructures such as multi-walled carbon nanotube (MWCNT) and carbon nanofiber by catalytic chemical vapor deposition (CCVD) method using nickel oxide-based catalyst nanoparticles of different average sizes as well as different levels of doping by copper oxide. The role of doping and the average size have been related to the observed melting behavior of nanoparticles of nickel oxide by thermal and diffraction analysis, and the importance of melting has been highlighted in the context of growth of cylindrical nanostructures. In the reducing environment prevailing in the CCVD chamber due to decomposition of flowing acetylene gas at elevated temperature, there is extensive reduction of oxide nanoparticles. Lack of melting and faster flow of carbon-bearing gases favor the formation of a carbon deposit cover over the catalyst nanoparticles giving rise to the formation of nanobeads. Melting allows rapid diffusion of carbon from the surface to inside catalyst particles, and reduced flow of gas lowers the rate of carbon deposit, both creating conditions favorable for the formation of cylindrical nanostructures, which grows around the catalyst particles. Smaller particle size and lower doping favor growth of MWCNT, while growth of fiber is commonly observed on larger particles having relatively higher level of doping.

  19. Atomic Resolution Imaging and Quantification of Chemical Functionality of Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Udo [Yale University

    2014-12-10

    The work carried out from 2006-2014 under DoE support was targeted at developing new approaches to the atomic-scale characterization of surfaces that include species-selective imaging and an ability to quantify chemical surface interactions with site-specific accuracy. The newly established methods were subsequently applied to gain insight into the local chemical interactions that govern the catalytic properties of model catalysts of interest to DoE. The foundation of our work was the development of three-dimensional atomic force microscopy (3D-AFM), a new measurement mode that allows the mapping of the complete surface force and energy fields with picometer resolution in space (x, y, and z) and piconewton/millielectron volts in force/energy. From this experimental platform, we further expanded by adding the simultaneous recording of tunneling current (3D-AFM/STM) using chemically well-defined tips. Through comparison with simulations, we were able to achieve precise quantification and assignment of local chemical interactions to exact positions within the lattice. During the course of the project, the novel techniques were applied to surface-oxidized copper, titanium dioxide, and silicon oxide. On these materials, defect-induced changes to the chemical surface reactivity and electronic charge density were characterized with site-specific accuracy.

  20. Turbulent Chemical Diffusion in Convectively Bounded Carbon Flames

    CERN Document Server

    Lecoanet, Daniel; Quataert, Eliot; Bildsten, Lars; Timmes, F X; Burns, Keaton J; Vasil, Geoffrey M; Oishi, Jeffrey S; Brown, Benjamin P

    2016-01-01

    It has been proposed that mixing induced by convective overshoot can disrupt the inward propagation of carbon deflagrations in super-asymptotic giant branch stars. To test this theory, we study an idealized model of convectively bounded carbon flames with 3D hydrodynamic simulations of the Boussinesq equations using the pseudospectral code Dedalus. Because the flame propagation timescale is $\\sim 10^5$ times longer than the convection timescale, we approximate the flame as fixed in space, and only consider its effects on the buoyancy of the fluid. By evolving a passive scalar field, we derive a turbulent chemical diffusivity produced by the convection as a function of height, $D_t(z)$. Convection can stall a flame if the chemical mixing timescale, set by the turbulent chemical diffusivity, $D_t$, is shorter than the flame propagation timescale, set by the thermal diffusivity, $\\kappa$, i.e., when $D_t>\\kappa$. However, we find $D_t<\\kappa$ for most of the flame because convective plumes are not dense enoug...

  1. 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

  2. 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...

  3. Chemical splitting of multiwalled carbon nanotubes to enhance electrochemical capacitance for supercapacitors

    Science.gov (United States)

    Li, Xinlu; Li, Tongtao; Zhang, Xinlin; Zhong, Qineng; Li, Hongyi; Huang, Jiamu

    2014-06-01

    Multiwalled carbon nanotubes (MWCNTs) were chemically split and self-assembled to a flexible porous paper made of graphene oxide nanoribbons (GONRs). The morphology and microstructure of the pristine MWCNTs and GONRs were analyzed by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. And the specific surface area and porosity structure were measured by N2 adsorption-desorption. The longitudinally split MWCNTs show an enhancement in specific capacitance from 21 F g-1 to 156 F g-1 compared with the pristine counterpart at 0.1 A g-1 in a 6 M KOH aqueous electrolytes. The electrochemical experiments prove that the chemical splitting of MWCNTs will make inner carbon layers opened and exposed to electrochemical double layers, which can effectively improve the electrochemical capacitance for supercapacitors.

  4. Nanoscale carbon materials from hydrocarbons pyrolysis: Structure, chemical behavior, utilisation for non-aqueous supercapacitors

    International Nuclear Information System (INIS)

    Highlights: • N-doped and regular carbon nanomaterials were obtained by pyrolitic technique. • Dynamic vapor sorption of different solvents reveals smaller SBET values. • Steric hindrance and specific chemical interactions are the reasons for this. • Nitrogen doping leads to raise of capacitance and coulombic efficiency with non-aqueous N-containing electrolyte. - Abstract: This work systematically studies adsorption properties of carbon nanomaterials that are synthesized through hydrocarbons that is a powerful technique to fabricate different kinds of carbon materials, e.g., nanotubes, nanoshells, onions, including nitrogen substituted. The adsorption properties of the as-synthesized carbons are achieved by low temperature nitrogen adsorption and organic vapors sorption. Heptane, acetonitrile, water, ethanol, benzene and 1-methylimidazole, which are of great importance for development of supercapacitors, are used as substrates. It is discovered that while nitrogen adsorption reveals a high specific surface area, this parameter for most of organic compounds is rather small depending not only on the size of its molecule but also on chemical interactions for a pair adsorbent–adsorbate. The experimental values of heat of adsorption for carbon and N-substituted structures, when Coulomb cross-coupling of nitrogen atoms in adsorbent and adsorbate takes place, confirms this supposition

  5. Nanoscale carbon materials from hydrocarbons pyrolysis: Structure, chemical behavior, utilisation for non-aqueous supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Savilov, Serguei V., E-mail: savilov@chem.msu.ru [Lomonosov Moscow State University, Chemistry Department (Russian Federation); Strokova, Natalia E.; Ivanov, Anton S.; Arkhipova, Ekaterina A. [Lomonosov Moscow State University, Chemistry Department (Russian Federation); Desyatov, Andrey V. [D. Mendeleyev University of Chemical Technology of Russia (Russian Federation); Hui, Xia [Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology (China); Aldoshin, Serguei M. [Lomonosov Moscow State University, Faculty of Fundamental Physical and Chemical Engineering (Russian Federation); Lunin, Valery V. [Lomonosov Moscow State University, Chemistry Department (Russian Federation)

    2015-09-15

    Highlights: • N-doped and regular carbon nanomaterials were obtained by pyrolitic technique. • Dynamic vapor sorption of different solvents reveals smaller S{sub BET} values. • Steric hindrance and specific chemical interactions are the reasons for this. • Nitrogen doping leads to raise of capacitance and coulombic efficiency with non-aqueous N-containing electrolyte. - Abstract: This work systematically studies adsorption properties of carbon nanomaterials that are synthesized through hydrocarbons that is a powerful technique to fabricate different kinds of carbon materials, e.g., nanotubes, nanoshells, onions, including nitrogen substituted. The adsorption properties of the as-synthesized carbons are achieved by low temperature nitrogen adsorption and organic vapors sorption. Heptane, acetonitrile, water, ethanol, benzene and 1-methylimidazole, which are of great importance for development of supercapacitors, are used as substrates. It is discovered that while nitrogen adsorption reveals a high specific surface area, this parameter for most of organic compounds is rather small depending not only on the size of its molecule but also on chemical interactions for a pair adsorbent–adsorbate. The experimental values of heat of adsorption for carbon and N-substituted structures, when Coulomb cross-coupling of nitrogen atoms in adsorbent and adsorbate takes place, confirms this supposition.

  6. 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.

  7. Effects of Temperature on Polymer/Carbon Chemical Sensors

    Science.gov (United States)

    Manfireda, Allison; Lara, Liana; Homer, Margie; Yen, Shiao-Pin; Kisor, Adam; Ryan, Margaret; Zhou, Hanying; Shevade, Abhijit; James, Lim; Manatt, Kenneth

    2009-01-01

    Experiments were conducted on the effects of temperature, polymer molecular weight, and carbon loading on the electrical resistances of polymer/carbon-black composite films. The experiment were performed in a continuing effort to develop such films as part of the JPL Electronic Nose (ENose), that would be used to detect, identify, and quantify parts-per-million (ppm) concentration levels of airborne chemicals in the space shuttle/space station environments. The polymers used in this study were three formulations of poly(ethylene oxide) [PEO] that had molecular weights of 20 kilodaltons, 600 kilodaltons, and 1 megadalton, respectively. The results of one set of experiments showed a correlation between the polymer molecular weight and the percolation threshold. In a second set of experiments, differences among the temperature dependences of resistance were observed for different carbon loadings; these differences could be explained by a change in the conduction mechanism. In a third set of experiments, the responses of six different polymer/carbon composite sensors to three analytes (water vapor, methanol, methane) were measured as a function of temperature (28 to 36 C). For a given concentration of each analyte, the response of each sensor decreased with increasing temperature, in a manner different from those of the other sensors.

  8. Relationship between the surface chemical composition of implants and contact with the substrate.

    Science.gov (United States)

    Lima da Costa Valente, Mariana; Shimano, Antonio Carlos; Marcantonio Junior, Elcio; Reis, Andréa Candido Dos

    2015-02-01

    The purpose of the study was to use scanning electron microscopy and energy dispersive x-ray spectrometry to assess possible morphologic and chemical changes after performing double-insertion and pullout tests of implants of different shapes and surface treatments. Four different types of implants were used-cylindrical machined-surface implants, cylindrical double-surface-treated porous implants, cylindrical surface-treated porous implants, and tapered surface-treated porous implants-representing a total of 32 screws. The implants were inserted into synthetic bone femurs, totaling 8 samples, before performing each insertion with standardized torque. After each pullout the implants were analyzed by scanning electron microscopy and energy dispersive x-ray spectrometry using a universal testing machine and magnified 35 times. No structural changes were detected on morphological surface characterization, only substrate accumulation. As for composition, there were concentration differences in the titanium, oxygen, and carbon elements. Implants with surface acid treatment undergo greater superficial changes in chemical composition than machined implants, that is, the greater the contact area of the implant with the substrate, the greater the oxide layer change. In addition, prior manipulation can alter the chemical composition of implants, typically to a greater degree in surface-treated implants. PMID:23339297

  9. In-situ observations of catalyst dynamics during surface-bound carbon nanotube nucleation

    DEFF Research Database (Denmark)

    Hofmann, S; Sharma, R; Du, G;

    2007-01-01

    We present atomic-scale, video-rate environmental transmission electron microscopy and in situ time-resolved X-ray photoelectron spectroscopy of surface-bound catalytic chemical vapor deposition of single-walled carbon nanotubes and nanofibers. We observe that transition metal catalyst nanopartic......We present atomic-scale, video-rate environmental transmission electron microscopy and in situ time-resolved X-ray photoelectron spectroscopy of surface-bound catalytic chemical vapor deposition of single-walled carbon nanotubes and nanofibers. We observe that transition metal catalyst....... For a carbon nanofiber, the graphene layer stacking is determined by the successive elongation and contraction of the catalyst nanoparticle at its tip....

  10. Chemical tethering of motile bacteria to silicon surfaces

    OpenAIRE

    Bearinger, Jane P.; Dugan, Lawrence C.; Wu, Ligang; Hill, Haley; Christian, Allen T.; Hubbell, Jeffrey A.

    2009-01-01

    We chemically immobilized live, motile Escherichia coli on micrometer-scale, photocatalytically patterned silicon surfaces via amine- and carboxylic acid–based chemistries. Immobilization facilitated (i) controlled positioning; (ii) high resolution cell wall imaging via atomic force microscopy (AFM); and (iii) chemical analysis with time-of-flight-secondary ion mass spectrometry (ToF-SIMS). Spinning motion of tethered bacteria, captured with fast-acquisition video, proved microbe viability. W...

  11. Plasma-enhanced chemical vapor deposition of multiwalled carbon nanofibers

    Science.gov (United States)

    Matthews, Kristopher; Cruden, Brett A.; Chen, Bin; Meyyappan, M.; Delzeit, Lance

    2002-01-01

    Plasma-enhanced chemical vapor deposition is used to grow vertically aligned multiwalled carbon nanofibers (MWNFs). The graphite basal planes in these nanofibers are not parallel as in nanotubes; instead they exhibit a small angle resembling a stacked cone arrangement. A parametric study with varying process parameters such as growth temperature, feedstock composition, and substrate power has been conducted, and these parameters are found to influence the growth rate, diameter, and morphology. The well-aligned MWNFs are suitable for fabricating electrode systems in sensor and device development.

  12. Guiding catalytically active particles with chemically patterned surfaces

    CERN Document Server

    Uspal, W E; Dietrich, S; Tasinkevych, M

    2016-01-01

    Catalytically active Janus particles suspended in solution create gradients in the chemical composition of the solution along their surfaces, as well as along any nearby container walls. The former leads to self-phoresis, while the latter gives rise to chemi-osmosis, providing an additional contribution to self-motility. Chemi-osmosis strongly depends on the molecular interactions between the diffusing chemical species and the wall. We show analytically, using an approximate "point-particle" approach, that by chemically patterning a planar substrate one can direct the motion of Janus particles: the induced chemi-osmotic flows can cause particles to either "dock" at the chemical step between the two materials, or to follow a chemical stripe. These theoretical predictions are confirmed by full numerical calculations. Generically, docking occurs for particles which tend to move away from their catalytic caps, while stripe-following occurs in the opposite case. Our analysis reveals the physical mechanisms governi...

  13. Physical Characterization and Steam Chemical Reactivity of Carbon Fiber Composites

    Energy Technology Data Exchange (ETDEWEB)

    Anderl, Robert Andrew; Pawelko, Robert James; Smolik, Galen Richard

    2001-05-01

    This report documents experiments and analyses that have been done at the Idaho National Engineering and Environmental Laboratory (INEEL) to measure the steam chemical reactivity of two types of carbon fiber composites, NS31 and NB31, proposed for use at the divertor strike points in an ITER-like tokamak. These materials are 3D CFCs constituted by a NOVOLTEX preform and densified by pyrocarbon infiltration and heat treatment. NS31 differs from NB31 in that the final infiltration was done with liquid silicon to reduce the porosity and enhance the thermal conductivity of the CFC. Our approach in this work was twofold: (1) physical characterization measurements of the specimens and (2) measurements of the chemical reactivity of specimens exposed to steam.

  14. Surface modification of silica-coated zirconia by chemical treatments

    Energy Technology Data Exchange (ETDEWEB)

    Lung, Christie Ying Kei, E-mail: yklung@graduate.hku.hk [Dental Materials Science, Faculty of Dentistry, University of Hong Kong (Hong Kong); Kukk, Edwin, E-mail: ekukk@utu.fi [Department of Physics and Astronomy, Faculty of Mathematics and Natural Sciences, University of Turku (Finland); Haegerth, Toni, E-mail: tjhage@utu.fi [Department of Physics and Astronomy, Faculty of Mathematics and Natural Sciences, University of Turku (Finland); Matinlinna, Jukka Pekka, E-mail: jpmat@hku.hk [Dental Materials Science, Faculty of Dentistry, University of Hong Kong (Hong Kong)

    2010-12-01

    Zirconia surface modification by various chemical treatments after silica coating by sandblasting was investigated in this study. The surface of silica-coated dental zirconia was hydroxylated by treatment with different acids at room temperature for 4 h, rinsed with deionized water and air-dried. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Shifts in binding energies for Zr 3d{sub 5/2} and Si 2p peaks were observed after treatment with acids, thereby showing a change in the chemical states of zirconium and silicon on the surface layer of silica-coated zirconia. The XPS analysis revealed that the silica-coated zirconia (SiO{sub 2}-ZrO{sub 2}) surfaces had changed to hydrous silica-coated zirconia (SiO{sub 2}-ZrO{sub 2}.nH{sub 2}O). One-way ANOVA analysis revealed there was significant difference in both surface roughness parameters of silica-coated zirconia after chemical treatments and the surface topography varied depending on the acid treatment.

  15. 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...

  16. Application of surface plasmons to biological and chemical sensors

    International Nuclear Information System (INIS)

    Surface plasmons (SPs) are a collective normal mode of electrons localized at a metallic surface. It has been used for biological sensors since 1990s. This is because it has the following specific characters: (a) The resonance condition is sensitive to the surrounding dielectric constants (refractive indexes) and (b) Highly enhanced optical-electric-fields are produced adjacent to SPs. A brief introduction is given on the principle of the biological and chemical sensors based on SPs for the readers working in the fields other than SPs, followed by a review on the recent developments of the biological and chemical sensors. (author)

  17. Synthesis and chemical modification of carbon nanostructures for materials applications

    Science.gov (United States)

    Higginbotham, Amanda Lynn

    This dissertation explores the structure, chemical reactivities, electromagnetic response, and materials properties of various carbon nanostructures, including single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphite, and graphene nanoribbons (GNRs). Efficient production and modification of these unique structures, each with their own distinct properties, will make them more accessible for applications in electronics, materials, and biology. A method is reported for controlling the permittivity from 1--1000 MHz of SWCNT-polymer composites (0.5 wt%) for radio frequency applications including passive RF antenna structures and EMI shielding. The magnitude of the real permittivity varied between 20 and 3.3, decreasing as higher fractions of functionalized-SWCNTs were added. The microwave absorbing properties and subsequent heating of carbon nanotubes were used to rapidly cure ceramic composites. With less than 1 wt% carbon nanotube additives and 30--40 W of directed microwave power (2.45 GHz), bulk composite samples reached temperatures above 500°C within 1 min. Graphite oxide (GO) polymer nanocomposites were developed at 1, 5, and 10 wt% for the purpose of evaluating the flammability reduction and materials properties of the resulting systems. Microscale oxygen consumption calorimetry revealed that addition of GO reduced the total heat release in all systems, and GO-polycarbonate composites demonstrated very fast self-extinguishing times in vertical open flame tests. A simple solution-based oxidative process using potassium permanganate in sulfuric acid was developed for producing nearly 100% yield of graphene nanoribbons (GNRs) by lengthwise cutting and unraveling of MWCNT sidewalls. Subsequent chemical reduction of the GNRs resulted in restoration of electrical conductivity. The GNR synthetic conditions were investigated in further depth, and an improved method which utilized a two-acid reaction medium was found to produce GNRs with

  18. A broad chemical and structural characterization of the damaged region of carbon implanted alumina

    International Nuclear Information System (INIS)

    As candidate materials for future thermonuclear fusion reactors, isolating ceramics will be submitted to high energy gamma and neutron radiation fluxes together with an intense particle flux. Amorphization cannot be tolerated in ceramics for fusion applications, due to the associated volume change and the deterioration of mechanical properties. Therefore, a comprehensive study was carried out to examine the effects of carbon beam irradiation on polycrystalline aluminium oxide (Al2O3), a ceramic component of some diagnostic and plasma heating systems. Complementary techniques have allowed a complete chemical and structural surface analysis of the implanted alumina. Implantation with 75 keV, mono-energetic carbon ions at doses of 1 x 1017 and 5 x 1017 ions/cm2 was performed on polished and thermally treated ceramic discs. The alumina targets were kept below 120 deg. C. The structural modifications induced during ion irradiation were studied by the GXRD and TEM techniques. Under these conditions, alumina is readily amorphized by carbon ions, the thickness of the ion-beam induced disordered area increasing with the ion dose. Matrix elements and ion implanted profiles were followed as a function of depth by using ToF-SIMS, indicating the maximum concentration of implanted ions to be in the deeper half of the amorphous region. Ion distribution and chemical modifications caused in the Al2O3 substrate by carbon irradiation were corroborated with XPS. The amount of oxygen in the vicinity of the implanted alumina surface was reduced, suggesting that this element was selectively sputtered during carbon irradiation. The intensity of those peaks referring to Al-O bonds diminishes, while contributions of reduced aluminium and metal carbides are found at the maximum of the carbon distribution. TEM observations on low temperature thermally annealed specimens indicate partial recovery of the initial crystalline structure.

  19. Doping level influence on chemical surface of diamond electrodes

    Science.gov (United States)

    Azevedo, A. F.; Baldan, M. R.; Ferreira, N. G.

    2013-04-01

    The modification of surface bond termination promoted by the doping level on diamond electrodes is analyzed. The films were prepared by hot filament chemical vapor deposition technique using the standard mixture of H2/CH4 with an extra H2 flux passing through a bubbler containing different concentrations of B2O3 dissolved in methanol. Diamond morphology and quality were characterized by scanning electron microscopy and Raman scattering spectroscopy techniques while the changes in film surfaces were analyzed by contact angle, cyclic voltammetry and synchrotron X-ray photoelectron spectroscopy (XPS). The boron-doped diamond (BDD) films hydrophobicity, reversibility, and work potential window characteristics were related to their physical properties and chemical surface, as a function of the doping level. From the Mott-Schottky plots (MSP) and XPS analyzes, for the lightly (1018 cm-3) and highly (1020 cm-3) BDD films, the relationship between the BDD electrochemical responses and their surface bond terminations is discussed.

  20. Surface modification of coconut shell based activated carbon for the improvement of hydrophobic VOC removal.

    Science.gov (United States)

    Li, Lin; Liu, Suqin; Liu, Junxin

    2011-08-30

    In this study, coconut shell based carbons were chemically treated by ammonia, sodium hydroxide, nitric acid, sulphuric acid, and phosphoric acid to determine suitable modification for improving adsorption ability of hydrophobic volatile organic compounds (VOCs) on granular activated carbons (GAC). The saturated adsorption capacities of o-xylene, a hydrophobic volatile organic compound, were measured and adsorption effects of the original and modified activated carbons were compared. Results showed that GAC modified by alkalis had better o-xylene adsorption capacity. Uptake amount was enhanced by 26.5% and reduced by 21.6% after modification by NH(3)H(2)O and H(2)SO(4), respectively. Compared with the original, GAC modified by acid had less adsorption capacity. Both SEM/EDAX and BET were used to identify the structural characteristics of the tested GAC, while IR spectroscopy and Boehm's titration were applied to analysis the surface functional groups. Relationships between physicochemical characteristics of GAC and their adsorption performances demonstrated that o-xylene adsorption capacity was related to surface area, pore volume, and functional groups of the GAC surface. Removing surface oxygen groups, which constitute the source of surface acidity, and reducing hydrophilic carbon surface favors adsorption capacity of hydrophobic VOCs on carbons. The performances of modified GACs were also investigated in the purification of gases containing complex components (o-xylene and steam) in the stream. PMID:21683520

  1. Chemical treatment of zinc surface and its corrosion inhibition studies

    Indian Academy of Sciences (India)

    S K Rajappa; T V Venkatesha; B M Praveen

    2008-02-01

    The surface treatment of zinc and its corrosion inhibition was studied using a product (BTSC) formed in the reaction between benzaldehyde and thiosemicarbozide. The corrosion behaviour of chemically treated zinc surface was investigated in aqueous chloride–sulphate medium using galvanostatic polarization technique. Zinc samples treated in BTSC solution exhibited good corrosion resistance. The measured electrochemical data indicated a basic modification of the cathode reaction during corrosion of treated zinc. The corrosion protection may be explained on the basis of adsorption and formation of BTSC film on zinc surface. The film was binding strongly to the metal surface through nitrogen and sulphur atoms of the product. The formation of film on the zinc surface was established by surface analysis techniques such as scanning electron microscopy (SEM–EDS) and Fourier transform infrared spectroscopy (FTIR).

  2. 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

  3. Chemical and structural evaluation of activated carbon prepared from jute sticks for Brilliant Green dye removal from aqueous solution.

    Science.gov (United States)

    Asadullah, Mohammad; Asaduzzaman, Mohammad; Kabir, Mohammad Shajahan; Mostofa, Mohammad Golam; Miyazawa, Tomohisa

    2010-02-15

    Activated carbons have been prepared from jute sticks by chemical activation using ZnCl(2) and physical activation using steam for the removal of Brilliant Green dye from aqueous solution. The activated carbons and charcoal prepared from jute sticks were characterized by evaluating the surface chemistry, structural features and surface morphology. The maximum BET surface area was obtained to be 2304 m(2)/g for chemical activated carbon (ACC) while it is 730 and 80 m(2)/g for steam activated carbon (ACS) and charcoal, respectively. The FT-IR spectra exhibited that the pyrolysis and steam activation of jute sticks resulted in the release of aliphatic and O-containing functional groups by thermal effect. However, the release of functional groups is the effect of chemical reaction in the ZnCl(2) activation process. A honeycomb-type carbon structure in ACC was formed as observed on SEM images. Although charcoal and ACC were prepared at 500 degrees C the ACC exhibited much lower Raman sensitivity due to the formation of condensed aromatic ring systems. Due to high surface area and high porous structure with abundance of functional groups, the ACC adsorbed dye molecules with much higher efficiency than those of ACS and charcoal. PMID:19815339

  4. Influence of surface coverage on the chemical desorption process

    Energy Technology Data Exchange (ETDEWEB)

    Minissale, M.; Dulieu, F., E-mail: francois.dulieu@obspm.fr [LERMA, Université de Cergy Pontoise et Observatoire de Paris, UMR 8112 du CNRS. 5, mail Gay Lussac, 95031 Cergy Pontoise (France)

    2014-07-07

    In cold astrophysical environments, some molecules are observed in the gas phase whereas they should have been depleted, frozen on dust grains. In order to solve this problem, astrochemists have proposed that a fraction of molecules synthesized on the surface of dust grains could desorb just after their formation. Recently the chemical desorption process has been demonstrated experimentally, but the key parameters at play have not yet been fully understood. In this article, we propose a new procedure to analyze the ratio of di-oxygen and ozone synthesized after O atoms adsorption on oxidized graphite. We demonstrate that the chemical desorption efficiency of the two reaction paths (O+O and O+O{sub 2}) is different by one order of magnitude. We show the importance of the surface coverage: for the O+O reaction, the chemical desorption efficiency is close to 80% at zero coverage and tends to zero at one monolayer coverage. The coverage dependence of O+O chemical desorption is proved by varying the amount of pre-adsorbed N{sub 2} on the substrate from 0 to 1.5 ML. Finally, we discuss the relevance of the different physical parameters that could play a role in the chemical desorption process: binding energy, enthalpy of formation, and energy transfer from the new molecule to the surface or to other adsorbates.

  5. Adsorption uptake of synthetic organic chemicals by carbon nanotubes and activated carbons

    International Nuclear Information System (INIS)

    Carbon nanotubes (CNTs) have shown great promise as high performance materials for adsorbing priority pollutants from water and wastewater. This study compared uptake of two contaminants of interest in drinking water treatment (atrazine and trichloroethylene) by nine different types of carbonaceous adsorbents: three different types of single walled carbon nanotubes (SWNTs), three different sized multi-walled nanotubes (MWNTs), two granular activated carbons (GACs) and a powdered activated carbon (PAC). On a mass basis, the activated carbons exhibited the highest uptake, followed by SWNTs and MWNTs. However, metallic impurities in SWNTs and multiple walls in MWNTs contribute to adsorbent mass but do not contribute commensurate adsorption sites. Therefore, when uptake was normalized by purity (carbon content) and surface area (instead of mass), the isotherms collapsed and much of the CNT data was comparable to the activated carbons, indicating that these two characteristics drive much of the observed differences between activated carbons and CNT materials. For the limited data set here, the Raman D:G ratio as a measure of disordered non-nanotube graphitic components was not a good predictor of adsorption from solution. Uptake of atrazine by MWNTs having a range of lengths and diameters was comparable and their Freundlich isotherms were statistically similar, and we found no impact of solution pH on the adsorption of either atrazine or trichloroethylene in the range of naturally occurring surface water (pH = 5.7–8.3). Experiments were performed using a suite of model aromatic compounds having a range of π-electron energy to investigate the role of π–π electron donor–acceptor interactions on organic compound uptake by SWNTs. For the compounds studied, hydrophobic interactions were the dominant mechanism in the uptake by both SWNTs and activated carbon. However, comparing the uptake of naphthalene and phenanthrene by activated carbon and SWNTs, size exclusion

  6. Adsorption uptake of synthetic organic chemicals by carbon nanotubes and activated carbons

    Science.gov (United States)

    Brooks, A. J.; Lim, Hyung-nam; Kilduff, James E.

    2012-07-01

    Carbon nanotubes (CNTs) have shown great promise as high performance materials for adsorbing priority pollutants from water and wastewater. This study compared uptake of two contaminants of interest in drinking water treatment (atrazine and trichloroethylene) by nine different types of carbonaceous adsorbents: three different types of single walled carbon nanotubes (SWNTs), three different sized multi-walled nanotubes (MWNTs), two granular activated carbons (GACs) and a powdered activated carbon (PAC). On a mass basis, the activated carbons exhibited the highest uptake, followed by SWNTs and MWNTs. However, metallic impurities in SWNTs and multiple walls in MWNTs contribute to adsorbent mass but do not contribute commensurate adsorption sites. Therefore, when uptake was normalized by purity (carbon content) and surface area (instead of mass), the isotherms collapsed and much of the CNT data was comparable to the activated carbons, indicating that these two characteristics drive much of the observed differences between activated carbons and CNT materials. For the limited data set here, the Raman D:G ratio as a measure of disordered non-nanotube graphitic components was not a good predictor of adsorption from solution. Uptake of atrazine by MWNTs having a range of lengths and diameters was comparable and their Freundlich isotherms were statistically similar, and we found no impact of solution pH on the adsorption of either atrazine or trichloroethylene in the range of naturally occurring surface water (pH = 5.7-8.3). Experiments were performed using a suite of model aromatic compounds having a range of π-electron energy to investigate the role of π-π electron donor-acceptor interactions on organic compound uptake by SWNTs. For the compounds studied, hydrophobic interactions were the dominant mechanism in the uptake by both SWNTs and activated carbon. However, comparing the uptake of naphthalene and phenanthrene by activated carbon and SWNTs, size exclusion effects

  7. Evaluation of Finite-Rate GasSurface Interaction Models for a Carbon Based Ablator

    Science.gov (United States)

    Chen, Yih-Kanq; Goekcen, Tahir

    2015-01-01

    Two sets of finite-rate gas-surface interaction model between air and the carbon surface are studied. The first set is an engineering model with one-way chemical reactions, and the second set is a more detailed model with two-way chemical reactions. These two proposed models intend to cover the carbon surface ablation conditions including the low temperature rate-controlled oxidation, the mid-temperature diffusion-controlled oxidation, and the high temperature sublimation. The prediction of carbon surface recession is achieved by coupling a material thermal response code and a Navier-Stokes flow code. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and Ablation Program, which predicts charring material thermal response and shape change on hypersonic space vehicles. The flow code solves the reacting full Navier-Stokes equations using Data Parallel Line Relaxation method. Recession analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities with heat fluxes ranging from 45 to 1100 wcm2 are performed and compared with data for model validation. The ablating material used in these arc-jet tests is Phenolic Impregnated Carbon Ablator. Additionally, computational predictions of surface recession and shape change are in good agreement with measurement for arc-jet conditions of Small Probe Reentry Investigation for Thermal Protection System Engineering.

  8. Chemical erosion of carbon at ITER relevant plasma fluxes: Results from the linear plasma generator Pilot-PSI

    NARCIS (Netherlands)

    van Rooij, G. J.; Westerhout, J.; Brezinsek, S.; Rapp, J.

    2011-01-01

    The chemical erosion of carbon was investigated in the linear plasma device Pilot-PSI for ITER divertor relevant hydrogen plasma flux densities 10(23) < Gamma < 10(25) m(-2) s(-1). The erosion was analyzed in situ by optical emission spectroscopy and post mortem by surface profilometry. The ex

  9. Simulating the Formation of Carbon-rich Molecules on an idealised Graphitic Surface

    CERN Document Server

    Marshall, David W

    2015-01-01

    There is accumulating evidence for the presence of complex molecules, including carbon-bearing and organic molecules, in the interstellar medium. Much of this evidence comes to us from studies of chemical composition, photo- and mass-spectroscopy in cometary, meteoritic and asteroid samples, indicating a need to better understand the surface chemistry of astrophysical objects. There is also considerable interest in the origins of life-forming and life-sustaining molecules on Earth. Here, we perform reactive molecular dynamics simulations to probe the formation of carbon-rich molecules and clusters on carbonaceous surfaces resembling dust grains and meteoroids. Our results show that large chains form on graphitic surfaces at low temperatures (100K - 500K) and smaller fullerene-like molecules form at higher temperatures (2000K - 3000K). The formation is faster on the surface than in the gas at low temperatures but slower at high temperatures as surface interactions prevent small clusters from coagulation. We fi...

  10. Quantum-Chemical Calculation of Carbododecahedron Formation in Carbon Plasma.

    Science.gov (United States)

    Poklonski, Nikolai A; Ratkevich, Sergey V; Vyrko, Sergey A

    2015-08-27

    The ground state of the molecule consisting of 10 carbon atoms in C10(rg) "ring" conformation and the energy of its metastable C10(st) "star" conformation are reported. The reaction coordinate for the isomeric transition C10(st) → C10(rg) was calculated using density functional theory (DFT) with UB3LYP/6-31G(d,p). It was established that a 5-fold symmetry axis is conserved in this isomeric transition. The total energy of the ring isomer is by 10.33 eV (9.16 eV as zero-point energy corrected) lower than that of the star isomer. The energy barrier for the transition from the metastable star state to the ring state is 2.87 eV (3.57 eV as zero-point energy corrected). An analysis of possible chemical reactions in carbon plasma involving C10(st) and C10(rg) and leading to the formation of C20 fullerenes was performed. It was revealed that the presence of the C10(st) conformation in the reaction medium is a necessary condition for C20 fullerene formation. It was shown that the presence of hydrogen atoms in carbon plasma and UV radiation accelerate the C10(st) → C10(rg) transition and thus suppress the C20 fullerene formation. PMID:26267290

  11. 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...

  12. 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

  13. 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.

  14. 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.

  15. Local Chemical Reactivity of a Metal Alloy Surface

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Scheffler, Matthias

    1995-01-01

    The chemical reactivity of a metal alloy surface is studied by density functional theory investigating the interaction of H2 with NiAl(110). The energy barrier for H2 dissociation is largely different over the Al and Ni sites without, however, reflecting the barriers over the single component metal...

  16. Laser interrogation of surface agents (LISA) for chemical agent reconnaissance

    Science.gov (United States)

    Higdon, N. S.; Chyba, Thomas H.; Richter, Dale A.; Ponsardin, Patrick L.; Armstrong, Wayne T.; Lobb, C. T.; Kelly, Brian T.; Babnick, Robert D.; Sedlacek, Arthur J., III

    2002-06-01

    Laser Interrogation of Surface Agents (LISA) is a new technique which exploits Raman scattering to provide standoff detection and identification of surface-deposited chemical agents. ITT Industries, Advanced Engineering and Sciences Division is developing the LISA technology under a cost-sharing arrangement with the US Army Soldier and Biological Chemical Command for incorporation on the Army's future reconnaissance vehicles. A field-engineered prototype LISA-Recon system is being designed to demonstrate on-the- move measurements of chemical contaminants. In this article, we will describe the LISA technique, data form proof-of- concept measurements, the LISA-Recon design, and some of the future realizations envisioned for military sensing applications.

  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. Chemical and carbon isotopic composition of dissolved organic carbon in a regional confined methanogenic aquifer

    Science.gov (United States)

    Aravena, R.; Wassenaar, L.I.; Spiker, E. C.

    2004-01-01

    This study demonstrates the advantage of a combined use of chemical and isotopic tools to understand the dissolved organic carbon (DOC) cycle in a regional confined methanogenic aquifer. DOC concentration and carbon isotopic data demonstrate that the soil zone is a primary carbon source of groundwater DOC in areas close to recharge zones. An in-situ DOC source linked to organic rich sediments present in the aquifer matrix is controlling the DOC pool in the central part of the groundwater flow system. DOC fractions, 13C-NMR on fulvic acids and 14C data on DOC and CH4 support the hypothesis that the in-situ DOC source is a terrestrial organic matter and discard the Ordovician bedrock as a source of DOC. ?? 2004 Taylor and Francis Ltd.

  19. 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.

  20. Surface chemical states of barium zirconate titanate thin films prepared by chemical solution deposition

    International Nuclear Information System (INIS)

    Ba(Zr0.05Ti0.95)O3 (BZT) thin films grown on Pt/Ti/SiO2/Si(1 0 0) substrates were prepared by chemical solution deposition. The structural and surface morphology of BZT thin films has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed that the random oriented BZT thin film grown on Pt/Ti/SiO2/Si(1 0 0) substrate with a perovskite phase. The SEM surface image showed that the BZT thin film was crack-free. And the average grain size and thickness of the BZT film are 35 and 400 nm, respectively. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Ti, and Zr exist mainly in the forms of BZT perovskite structure.

  1. 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

  2. Development of nanoporous structure in carbons by chemical activation with zinc chloride.

    Science.gov (United States)

    Rajbhandari, Rinita; Shrestha, Lok Kumar; Pokharel, Bhadra Prasad; Pradhananga, Raja Ram

    2013-04-01

    Series of activated carbons (ACs) have been prepared from Lapsi (Choerospondias axillaris) seed powder (LSP) by chemical activation with zinc chloride (ZnCI2) and the effects of ZnCl2 impregnation ratio, carbonization time, and precursor sources on the structure and properties of ACs have been systematically investigated. Carbonization was carried out at 400 degrees C and the ratio of LSP and ZnCI2 was varied from LSP:ZnCl2 = 1:0.25 (AC-0.25), 1:0.50 (AC-0.50) 1:1 (AC-1), 1:2 (AC-2), and 1:4 (AC-4). The ACs were characterized by Fourier transform-infrared (FTIR) spectroscopy, Raman scattering, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Surface properties (effective surface areas, pore volumes, and pore size distributions) were studied by nitrogen adsorption-desorption measurements. The electrochemical and vapor sensing properties were investigated by cyclic voltammetry, and quartz crystal microbalance (QCM) method, respectively. All the ACs are amorphous materials containing oxygenated surface functional groups and having nanoporous (microporous and mesoporous) structures. We found that surface properties depend on the LSP:ZnCI2 ratio, carbonization time, and also on the precursor type. The effective surface area increased significantly with increasing LSP:ZnCI2 ratio from 1:0.25 to 1:0.5 and then remain apparently constant. However, total pore volume increased continuously with ZnCI2 ratio. Increase in the carbonization time above 4 h decreased both the surface area and pore volume. ACs prepared from bamboo and coconut shell showed better surface properties compared to AC prepared from sugarcane; surface area and pore volume of the former systems are nearly double of the later system. AC derived from LSP (AC-4) showed excellent electrochemical performance giving specific capacitance value of 328 F/g in 1 M H2SO4 solution demonstrating the potential use of this material for supercapacitor electrodes. Our

  3. Chemically Conjugated Carbon Nanotubes and Graphene for Carrier Modulation.

    Science.gov (United States)

    Kim, Ki Kang; Kim, Soo Min; Lee, Young Hee

    2016-03-15

    Nanocarbons such as fullerene and carbon nanotubes (CNT) in late 20th century have blossomed nanoscience and nanotechnology in 21st century, which have been further proliferated by the new finding of graphene and have indeed opened a new carbon era. Several new branches of research, for example, zero-dimensional nanoparticles, one-dimensional nanowires, and two-dimensional insulating hexagonal boron nitride, and semiconducting and metallic transition metal dichalcogenides including the recently emerging black phosphorus, have been explored and numerous unprecedented quantum mechanical features have been revealed, that have been hardly accessible otherwise. Extensive research has been done on devices and applications related to such materials. Many experimental instruments have been developed with high sensitivity and improved spatial and temporal resolution to detect such tiny objects. The need for multidisciplinary research has been growing stronger than ever, which will be the tradition in the next few decades. In this Account, we will demonstrate an example of multidisciplinary effort of utilizing CNTs and graphene for electronics by modulating electronic structures. While there are several methods of modifying electronic structures of nanocarbons such as gate bias, contact metal, and conventional substitutional doping, we focus on chemical doping approaches here. We first introduce the concept of chemical doping on CNTs and graphene in terms of electronegativity of molecules and electrochemical potential of CNTs and graphene. To understand the relationship of electrochemical potential of CNTs and graphene to electronegativity of molecules, we propose a simple water bucket model: how to fill or drain water (electrons in CNTs or graphene) in the bucket (density of states) by the chemical dopants. The doping concept is then demonstrated experimentally by tracking the absorption spectroscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy

  4. The effects of activation temperature on physico-chemical characteristics of activated carbons derived from biomass wastes

    Science.gov (United States)

    Sutrisno, Bachrun; Hidayat, Arif

    2015-12-01

    This research focused on investigating in the effect of activation temperature on the physico-chemical properties of palm empty fruit bunch (PEFB) based activated carbon prepared by physical activation with carbon dioxide. The activation temperature was studied in the range of 400-800°C by keeping the activation temperature at 800°C for 120 min. It was found that the porous properties of activated carbon decreased with an increase in carbonization temperature. The activated carbons prepared at the highest activation temperature at 800°C and activation time of 120 min gave the activated carbon with the highest of BET surface area and pore volume of 938 m2/g and 0.4502 cm3/g, respectively

  5. 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

  6. 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....

  7. Scanning Auger and XPS studies of fracture surfaces of B4C hot pressed with excess carbon

    International Nuclear Information System (INIS)

    A series of boron carbide materials was hot pressed with 0-7% excess carbon. The strength of each material was determined by four point bending, and found to decrease from about 600 MPa to 300 MPa as the carbon content increased from 0% to 7%. Diamond indentation yielded hardness values that decreased from 28.3 to 25.0 GPa and toughness values that increased over the same carbon range. Each sample was fractured in situ in ultrahigh vacuum (UHV) and examined by scanning Auger microanalysis (SAM) and XPS to determine both the elemental and chemical state distributions. For the samples with excess carbon, localized carbon rich regions are observed on fracture surfaces by SAM. XPS reveals a 50% enhancement of excess carbon on the fracture surface compared to the bulk for the sample with 7% excess carbon

  8. Chemical properties of surface peat on forest land in Estonia

    Directory of Open Access Journals (Sweden)

    R. Kõlli

    2010-10-01

    Full Text Available The chemical properties of surface peat cover (SPC were studied in the context of Estonian pedoecological conditions. SPC comprises the superficial layers of fens (Group 1 and transitional bogs (Group 2, together with slightly acid peaty mull / strongly acid peaty moder (Group 3 and very strongly acid peaty mor (Group 4 layers overlying mineral soils. Thus, it spans organic soils, namely Histosols (Groups 1 and 2; together with Histic Gleysols (Group 3 and Histic Podzols (Group 4, which are developmentally intermediate between organic and mineral soils. Moderately acid eutrophic (Group 1 and very strongly acid mesotrophic (Group 2 peats (forest litter layers excluded were uniformly characterised up to 40 cm depth; whereas for Groups 3 and 4 we examined the full thickness of available peat layers, which ranged from 10 to 30 cm. The results show that Al, K and heavy metal contents are significantly higher and organic carbon content is lower in Histic Soils (3, 4 than in Histosols (1, 2. The amounts of Ca, Mg, Mn and Fe are significantly higher and C:N ratio, exchangeable acidity and content of free H+ lower in less acidic (1, 3 than in more acidic (2, 4 soil types. The total concentration of elements (excluding heavy metals extracted by nitro-hydrochloric acid (aqua regia is considerably higher in less acidic soils, at 28–45 g kg-1 (1, 3 versus 10–12 g kg-1 (2, 4; and mean contents of individual elements decrease in the order Ca(51% > Fe(20% > S(10% ≥ Al(10% > Mg(3% ≥ P(3% > K(2% > Mn(1% > Na(<1%. The most abundant heavy metals are Pb (12–33 mg kg-1, Zn (7–41 mg kg-1, Cu (3–12 mg kg-1, Cr (2–23 mg kg-1 and Ni (2–8 mg kg-1; Cd and Hg contents are very low, ranging from 0.2 to 0.5 mg kg-1. The dominant exchangeable basic cations are Ca2+ (78–93% and Mg2+ (7–15%, and the peat contains much smaller amounts of K+ (1–6% and Na+ (<2%. The total exchangeable acidic cations (1–14 cmol kg-1 are dominated by H+ (51–83% and Al3

  9. 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.

  10. Heat, Mass and Charge Transport, and Chemical Reactions at Surfaces

    Directory of Open Access Journals (Sweden)

    Signe Kjelstrup

    2005-03-01

    Full Text Available In this work we derive the excess entropy production rate for heat, mass and charge transport into, out of and across a surface, using as basic variables the excess densities proposed by Gibbs. With the help of these variables we define the surface as an autonomous system (i.e. a surface in local equilibrium and find its excess entropy production rate. This then determines the conjugate fluxes and forces. Equivalent forms of the entropy production rate are given. The forms contain finite differences of intensive variables into and across the surface as driving forces. The general form of the force-flux relations is given. The expressions for the fluxes serve as boundary conditions for integration across heterogeneous systems. Two examples are discussed in more detail. The first example is the practically important coupled transport of heat and mass into and through a liquid-vapor surface. The second example concerns phenomena at electrode surfaces: the coupled transport of heat, mass and charge and a chemical reaction. By assuming that the two sides of the surface can be described as resistances in series, we are able to reduce the number of unknown transport coefficients considerably. For both examples it is shown that the coupling coefficients for heat and mass flow are large at the surface, when the homogeneous phases have a large enthalpy difference. As a consequence it is not sufficient to use, for instance, Fourier’s law for transport of heat across surfaces.

  11. 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

  12. 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.

  13. Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Hydrogen

    Institute of Scientific and Technical Information of China (English)

    Fandong Meng; Genhui Xu; Zhenhua Li; Pa Du

    2002-01-01

    The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.

  14. Molecular Dynamics Simulation of Chemical Vapor Deposition of Amorphous Carbon: Dependence on H/C Ratio of Source Gas

    OpenAIRE

    Ito, Atsushi M.; Takayama, Arimichi; Saito, Seiki; Ohno, Noriyasu; Kajita, Shin; Nakamura, Hiroaki

    2010-01-01

    By molecular dynamics simulation, the chemical vapor deposition of amorphous carbon onto graphite and diamond surfaces was studied. In particular, we investigated the effect of source H/C ratio, which is the ratio of the number of hydrogen atoms to the number of carbon atoms in a source gas, on the deposition process. In the present simulation, the following two source gas conditions were tested: one was that the source gas was injected as isolated carbon and hydrogen atoms, and the other was...

  15. Interaction of bacteria and a chemically patterned surface

    Science.gov (United States)

    Jalali, Maryam; Molaei, Mehdi; Sheng, Jian

    2012-11-01

    We are investigating the mechanisms involved in the interactions between bacteria and chemically patched oil-water interface. Using micro-fabrication and soft-lithography, we have engineered a chemically patterned solid surface to mimic the real interfacial environment. Arrays of 2D geometries whose characteristic size ranges from 10 μm to 100 μm are patterned onto a glass substrate and subsequently functionalized using Octadecyltrichlorosilane (OTS). The photoresist covering geometries is further removed after functionalization. Consequently, a chemically patterned surface with alternating hydrophobic and hydrophilic regions is produced as the substrate for microfluidics. The effects of this surface on bacteria attachment and detachment are evaluated in-situ. The growth rates of biofilm are quantified by measuring the morphology of bacterial colony. To elucidate hydrodynamic mechanism involved, bacteria swimming characteristics, such as swimming velocity, angle, tumbling frequency and dispersion, is measured within a microfluidics with a patterned substrate using 3D digital holographic microscopy. Comparative studies on smooth swimming and tumbling capable strains over such surfaces will also be presented. GoMRI.

  16. SYNTHESIS OF CARBON NANOSTRUCTURES BY PLASMA ENHANCED CHEMICAL VAPOUR DEPOSITION AT ATMOSPHERIC PRESSURE

    OpenAIRE

    Jašek Ondřej; Synek Petr; Zajíčková Lenka; Eliáš Marek; Kudrle Vít

    2010-01-01

    Carbon nanostructures present leading field in nanotechnology research. Wide range of chemical and physical methods was used for carbon nanostructures synthesis including arc discharges, laser ablation and chemical vapour deposition. Plasma enhanced chemical vapour deposition (PECVD) with its application in modern microelectronics industry became soon target of research in carbon nanostructures synthesis. The selection of the ideal growth process depends on the application. Most of PECVD tech...

  17. Tailoring the Surface Chemistry of Zeolite Templated Carbon by Electrochemical Methods

    Directory of Open Access Journals (Sweden)

    R. Berenguer

    2013-01-01

    Full Text Available One option to optimize carbon materials forsupercapacitor applications is the generation ofsurface functional groups that contribute to thepseudocapacitance without losing the designedphysical properties. This requires suitablefunctionalization techniques able to selectivelyintroduce a given amount of electroactive oxygengroups. In this work, the influence of the chemical andelectrochemical oxidation methods, on the chemicaland physical properties of a zeolite templated carbon(ZTC, as a model carbon material, have beenstudied and compared. Although both oxidationmethods generally produce a loss of the originalZTC physical properties with increasing amount ofoxidation, the electrochemical method shows muchbetter controllability and, unlike chemical treatments,enables the generation of a large number of oxygengroups (O = 11000- 3300 μmol/g, with a higherproportion of active functionalities, while retaining ahigh surface area (ranging between 1900-3500 m2/g,a high microporosity and an ordered 3-D structure.

  18. Limiting factors for carbon based chemical double layer capacitors

    Science.gov (United States)

    Rose, M. Frank; Johnson, C.; Owens, T.; Stevens, B.

    1993-01-01

    The Chemical Double Layer (CDL) capacitor improves energy storage density dramatically when compared with conventional electrolytic capacitors. When compared to batteries, the CDL Capacitor is much less energy dense; however, the power density is orders of magnitude better. As a result, CDL-battery combinations present an interesting pulse power system with many potential applications. Due to the nature of the CDL it is inherently a low voltage device. The applications of the CDL can be tailored to auxiliary energy and burst mode storages which require fast charge/discharge cycles. Typical of the applications envisioned are power system backup, directed energy weapons concepts, electric automobiles, and electric actuators. In this paper, we will discuss some of the general characteristics of carbon-based CDL technology describing the structure, performance parameters, and methods of construction. Further, analytical and experimental results which define the state of the art are presented and described in terms of impact on applications.

  19. Production of granular activated carbon from agricultural wastes and determination of their physical, chemical and adsorption properties

    Energy Technology Data Exchange (ETDEWEB)

    Ayguen, A.; Duman, I. [Istanbul Technical Univ., Inst. of Science and Technology, Dept. of Metallurgical Engineering, Istanbul (Turkey); Yenisoy-Karakas, S. [TUeBITAK Marmara Research Center (MRC), Materials and Chemical Technologies Research Inst., Gebze Kocaeli (Turkey)

    2004-07-01

    The aim of this study is to produce activated carbons with good mechanical strength and high adsorption capacities toward various organics from food wastes such as walnut, almond, hazelnut shells and apricot stones. Turkey has huge amounts of these wastes in canning industry. The chemical activation with ZnCl{sub 2} was preferred to manufacture activated carbons. The best activation temperature and time were determined. Granular activated carbons were discussed with respect to their physical, chemical, surface area and adsorption properties. For all raw materials, the specific surface areas of greater than 730 m{sup 2} g{sup -1} were reached. As a result of the adsorption studies, adsorption capacities were in order of hazelnut> apricot stones> walnut> almond. The correlation coefficients obtained from Langmuir and Freundlich isotherms are in good agreement with the experimental results. (orig.)

  20. Rapid chemical agent identification by surface-enhanced Raman spectroscopy

    Science.gov (United States)

    Lee, Yuan-Hsiang; Farquharson, Stuart

    2001-08-01

    Although the Chemical Weapons Convention prohibits the development, production, stockpiling, and use of chemical warfare agents (CWAs), the use of these agents persists due to their low cost, simplicity in manufacturing and ease of deployment. These attributes make these weapons especially attractive to low technology countries and terrorists. The military and the public at large require portable, fast, sensitive, and accurate analyzers to provide early warning of the use of chemical weapons. Traditional laboratory analyzers such as the combination of gas chromatography and mass spectroscopy, although sensitive and accurate, are large and require up to an hour per analysis. New, chemical specific analyzers, such as immunoassays and molecular recognition sensors, are portable, fast, and sensitive, but are plagued by false-positives (response to interferents). To overcome these limitations, we have been investigating the potential of surface-enhanced Raman spectroscopy (SERS) to identify and quantify chemical warfare agents in either the gas or liquid phase. The approach is based on the extreme sensitivity of SERS demonstrated by single molecule detection, a new SERS material that we have developed to allow reproducible and reversible measurements, and the molecular specific information provided by Raman spectroscopy. Here we present SER spectra of chemical agent simulants in both the liquid and gas phase, as well as CWA hydrolysis phase.

  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. Surface chemical composition of human maxillary first premolar as assessed by X-ray photoelectron spectroscopy (XPS)

    Energy Technology Data Exchange (ETDEWEB)

    Lou, Leo [Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta (Canada); Nelson, Alan E. [Department of Chemical and Materials Engineering, University of Alberta (Canada)], E-mail: aenelson@dow.com; Heo, Giseon [Department of Statistics, Department of Dentistry, University of Alberta (Canada); Major, Paul W. [Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta (Canada)

    2008-08-30

    The surface chemical composition of dental enamel has been postulated as a contributing factor in the variation of bond strength of brackets bonded to teeth, and hence, the probability of bracket failure during orthodontic treatment. This study systematically investigated the chemical composition of 98 bonding surfaces of human maxillary premolars using X-ray photoelectron spectroscopy (XPS) to ascertain compositional differences between right and left first premolars. The major elements detected in all samples were calcium, phosphorus, oxygen, nitrogen and carbon. Surface compositions were highly variable between samples and several elements were found to be highly correlated. No statistical significant difference in the chemical composition of the maxillary right and left first premolars was found (p > 0.05). Knowledge of the chemical composition of enamel surfaces will facilitate future studies that relate this information to the variations in dental enamel bond strength.

  3. Surface chemical composition of human maxillary first premolar as assessed by X-ray photoelectron spectroscopy (XPS)

    Science.gov (United States)

    Lou, Leo; Nelson, Alan E.; Heo, Giseon; Major, Paul W.

    2008-08-01

    The surface chemical composition of dental enamel has been postulated as a contributing factor in the variation of bond strength of brackets bonded to teeth, and hence, the probability of bracket failure during orthodontic treatment. This study systematically investigated the chemical composition of 98 bonding surfaces of human maxillary premolars using X-ray photoelectron spectroscopy (XPS) to ascertain compositional differences between right and left first premolars. The major elements detected in all samples were calcium, phosphorus, oxygen, nitrogen and carbon. Surface compositions were highly variable between samples and several elements were found to be highly correlated. No statistical significant difference in the chemical composition of the maxillary right and left first premolars was found ( p > 0.05). Knowledge of the chemical composition of enamel surfaces will facilitate future studies that relate this information to the variations in dental enamel bond strength.

  4. Surface chemical composition of human maxillary first premolar as assessed by X-ray photoelectron spectroscopy (XPS)

    International Nuclear Information System (INIS)

    The surface chemical composition of dental enamel has been postulated as a contributing factor in the variation of bond strength of brackets bonded to teeth, and hence, the probability of bracket failure during orthodontic treatment. This study systematically investigated the chemical composition of 98 bonding surfaces of human maxillary premolars using X-ray photoelectron spectroscopy (XPS) to ascertain compositional differences between right and left first premolars. The major elements detected in all samples were calcium, phosphorus, oxygen, nitrogen and carbon. Surface compositions were highly variable between samples and several elements were found to be highly correlated. No statistical significant difference in the chemical composition of the maxillary right and left first premolars was found (p > 0.05). Knowledge of the chemical composition of enamel surfaces will facilitate future studies that relate this information to the variations in dental enamel bond strength

  5. Effect of different chemical modification of carbon nanotubes for the oxygen reduction reaction in alkaline media

    International Nuclear Information System (INIS)

    The electrochemical reduction of oxygen on chemically modified multi-walled carbon nanotubes (CNTs) electrodes in 1 M KOH solution has been studied using the rotating ring disc electrode (RDE). The surface modification of CNTs has been estimated by XPS and Raman spectroscopy. The effect of different oxygen functionalities on the surface of carbon nanotube for the oxygen reduction reaction (ORR) is considered in terms of the number of electrons (n) involved. Electrochemical studies indicate that in the case of the modification of CNTs with citric acid and diazonium salts the n values were close to two in the measured potential range, and the electrochemical reduction is limited to the production of peroxide as the final product. In the case of the modification of carbon nanotubes with peroxymonosulphuric acid, in the measured potential range, the n value is close to 4 indicating the four-electron pathway for the ORR. By correlating ORR measurements with the XPS analysis, we propose that the increase in electrocatalytic activity towards the ORR, for CNT can be attributed to the increase in C-O groups on the surface of CNTs after modification with peroxymonosulphuric acid

  6. Surface modification on PMMA : PVDF polyblend: hardening under chemical environment

    Indian Academy of Sciences (India)

    R Bajpai; V Mishra; Pragyesh Agrawal; S C Datt

    2002-02-01

    The influence of chemical environment on polymers include the surface alteration as well as other deep modifications in surface layers. The surface hardening, as an effect of organic liquids on poly(methyl methacrylate): poly(vinylidene fluoride) (PMMA: PVDF), which is one of the few known miscible blends, has been detected using microhardness testing. Organic liquids like acetone, toluene, xylene and benzene were introduced on the surface of blend specimens for different durations. Vickers microhardness (v) was measured for treated and untreated specimens. The study reveals both hardening and plasticization of specimens at different exposure times. The degree of surface hardening is maximum under acetone treatment. All the specimens exhibit surface hardening at an exposure time of 1 h with all the four liquids. This feature is prominent with longer exposures for specimens with increasing content of PVDF. However, the degree of hardening decreases with the time of exposure in the respective environments. In general, acetone and toluene impart surface hardening, whereas, xylene and benzene soften the specimen. PMMA: PVDF (83 : 17) blend exhibits surface hardening under all the four treatments when compared with the respective untreated specimens.

  7. Passive standoff detection of chemical warfare agents on surfaces.

    Science.gov (United States)

    Thériault, Jean-Marc; Puckrin, Eldon; Hancock, Jim; Lecavalier, Pierre; Lepage, Carmela Jackson; Jensen, James O

    2004-11-01

    Results are presented on the passive standoff detection and identification of chemical warfare (CW) liquid agents on surfaces by the Fourier-transform IR radiometry. This study was performed during surface contamination trials at Defence Research and Development Canada-Suffield in September 2002. The goal was to verify that passive long-wave IR spectrometric sensors can potentially remotely detect surfaces contaminated with CW agents. The passive sensor, the Compact Atmospheric Sounding Interferometer, was used in the trial to obtain laboratory and field measurements of CW liquid agents, HD and VX. The agents were applied to high-reflectivity surfaces of aluminum, low-reflectivity surfaces of Mylar, and several other materials including an armored personnel carrier. The field measurements were obtained at a standoff distance of 60 m from the target surfaces. Results indicate that liquid contaminant agents deposited on high-reflectivity surfaces can be detected, identified, and possibly quantified with passive sensors. For low-reflectivity surfaces the presence of the contaminants can usually be detected; however, their identification based on simple correlations with the absorption spectrum of the pure contaminant is not possible. PMID:15540446

  8. Passive Standoff Detection of Chemical Warfare Agents on Surfaces

    Science.gov (United States)

    Thériault, Jean-Marc; Puckrin, Eldon; Hancock, Jim; Lecavalier, Pierre; Lepage, Carmela Jackson; Jensen, James O.

    2004-11-01

    Results are presented on the passive standoff detection and identification of chemical warfare (CW) liquid agents on surfaces by the Fourier-transform IR radiometry. This study was performed during surface contamination trials at Defence Research and Development Canada-Suffield in September 2002. The goal was to verify that passive long-wave IR spectrometric sensors can potentially remotely detect surfaces contaminated with CW agents. The passive sensor, the Compact Atmospheric Sounding Interferometer, was used in the trial to obtain laboratory and field measurements of CW liquid agents, HD and VX. The agents were applied to high-reflectivity surfaces of aluminum, low-reflectivity surfaces of Mylar, and several other materials including an armored personnel carrier. The field measurements were obtained at a standoff distance of 60 m from the target surfaces. Results indicate that liquid contaminant agents deposited on high-reflectivity surfaces can be detected, identified, and possibly quantified with passive sensors. For low-reflectivity surfaces the presence of the contaminants can usually be detected; however, their identification based on simple correlations with the absorption spectrum of the pure contaminant is not possible.

  9. Reactions of the inner surface of carbon nanotubes and nanoprotrusion processes imaged at the atomic scale

    Science.gov (United States)

    Chamberlain, Thomas W.; Meyer, Jannik C.; Biskupek, Johannes; Leschner, Jens; Santana, Adriano; Besley, Nicholas A.; Bichoutskaia, Elena; Kaiser, Ute; Khlobystov, Andrei N.

    2011-09-01

    Although the outer surface of single-walled carbon nanotubes (atomically thin cylinders of carbon) can be involved in a wide range of chemical reactions, it is generally thought that the interior surface of nanotubes is unreactive. In this study, we show that in the presence of catalytically active atoms of rhenium inserted into nanotubes, the nanotube sidewall can be engaged in chemical reactions from the inside. Aberration-corrected high-resolution transmission electron microscopy operated at 80 keV allows visualization of the formation of nanometre-sized hollow protrusions on the nanotube sidewall at the atomic level in real time at ambient temperature. Our direct observations and theoretical modelling demonstrate that the nanoprotrusions are formed in three stages: (i) metal-assisted deformation and rupture of the nanotube sidewall, (ii) the fast formation of a metastable asymmetric nanoprotrusion with an open edge and (iii) a slow symmetrization process that leads to a stable closed nanoprotrusion.

  10. Surface structure and optical property of amorphous carbon nanotubes hybridized with cadmium selenide quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Kim Han, E-mail: kimhan8419@gmail.com; Johan, Mohd Rafie [University of Malaya, Nanomaterials Engineering Research Group, Advanced Materials Research Laboratory, Department of Mechanical Engineering (Malaysia)

    2013-09-15

    Amorphous carbon nanotubes ({alpha}-CNTs) were synthesized by a chemical reaction between ferrocene and ammonium chloride at low temperature. The as-synthesized {alpha}-CNTs were then hybridized with cadmium selenide quantum dots (CdSe QDs) through a simple chemical process. Raman spectra reveal the amorphous nature of the {alpha}-CNTs surface. X-ray diffraction pattern confirmed the amorphous phase of carbon and the formation of CdSe QDs crystalline phase. Field emission scanning electron microscopy and transmission electron microscopy (TEM and HRTEM) indicate that the successfully formed hybridized {alpha}-CNTs-CdSe QDs possess an average outer diameter in the range of 110-130 nm. The CdSe QDs fall in the size range of 15-40 nm. UV-visible spectroscopy showed quantum confinement effect due to the attachment of CdSe QDs on the surface of {alpha}-CNTs.

  11. [Immobilization and characterization of carbonic anhydrase on the surface of hollow fiber membrane of polymethyl pentene].

    Science.gov (United States)

    Wang, Qinmei; Zhang, Dihua; Zhang, Jingxia

    2009-07-01

    We immobilized carbonic anhydrase (CA) onto the surface of membrane oxygenator of polymethyl pentene (PMP) to enhance the removal of carbon dioxide in blood by two steps. We first introduced hydroxyl groups onto PMP surface by water plasma treatment, and then coupled CA onto PMP surface by using cyanate bromide (CNBr) as a crosslinker. After plasma treatment, the contact angle with water and chemical composition of PMP surface were characterized by analysis system of surface contact angle and XPS. Using p-nitrophenyl acetate (p-NPA) as a substrate, the activity, concentration, storage stability and re-usability of immobilized CA on PMP hollow fibers were studied by ultraviolet spectrophotometer. The preliminary data showed that hydroxyl groups could be introduced on the surface of PMP by water plasma treatment, and CA with catalysis activity could be successfully introduced onto PMP surface in high immobilization efficiency. The activity of covalently immobilized CA increased with the increase of concentration of CNBr, and the maximum was 73% of the theoretical activity of CA spread on PMP surface in monolayer in studied range. Covalently immobilized CA showed higher reusability compared to physically adsorbed CA, and higher storage stability compared to free CA in solution at 37 degrees C. The method would be used potentially in the membrane oxygenator to improve the capacity of removal of carbon dioxide in blood in the future. PMID:19835148

  12. Simulating the formation of carbon-rich molecules on an idealized graphitic surface

    Science.gov (United States)

    Marshall, David W.; Sadeghpour, H. R.

    2016-01-01

    There is accumulating evidence for the presence of complex molecules, including carbon-bearing and organic molecules, in the interstellar medium. Much of this evidence comes to us from studies of chemical composition, photo- and mass spectroscopy in cometary, meteoritic and asteroid samples, indicating a need to better understand the surface chemistry of astrophysical objects. There is also considerable interest in the origins of life-forming and life-sustaining molecules on the Earth. Here, we perform reactive molecular dynamics simulations to probe the formation of carbon-rich molecules and clusters on carbonaceous surfaces resembling dust grains and meteoroids. Our results show that large chains form on graphitic surfaces at low temperatures (100-500 K) and smaller fullerene-like molecules form at higher temperatures (2000-3000 K). The formation is faster on the surface than in the gas at low temperatures but slower at high temperatures as surface interactions prevent small clusters from coagulation. We find that for efficient formation of molecular complexity, mobility about the surface is important and helps to build larger carbon chains on the surface than in the gas phase at low temperatures. Finally, we show that the temperature of the surface strongly determines what kind of structures forms and that low turbulent environments are needed for efficient formation.

  13. Surface nanosegregation of the chemical composition of complex oxides

    International Nuclear Information System (INIS)

    A brief review of theoretical and experimental studies in the field of surface nanosegregation of chemical composition of oxides SrTiO3, LiNbO3, LiTaO3, Gd2(MoO4)3, KNbO3, PbFe0.5Nb0.5O3, induced by temperature and other factors, is provided. Results of experimental studies of the relevant oxide monocrystals by the methods of electron spectrometry and model presentations suggest diffusion mechanism of segregation. It proved possible to predict the character of changes in surface composition of the oxides on the basis of the models considered

  14. Electronic dissipation processes during chemical reactions on surfaces

    CERN Document Server

    Stella, Kevin

    2012-01-01

    Hauptbeschreibung Every day in our life is larded with a huge number of chemical reactions on surfaces. Some reactions occur immediately, for others an activation energy has to be supplied. Thus it happens that though a reaction should thermodynamically run off, it is kinetically hindered. Meaning the partners react only to the thermodynamically more stable product state within a mentionable time if the activation energy of the reaction is supplied. With the help of catalysts the activation energy of a reaction can be lowered. Such catalytic processes on surfaces are widely used in industry. A

  15. 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.

  16. A major biopolymeric component to dissolved organic carbon in surface sea water

    Science.gov (United States)

    Aluwihare, Lihini I.; Repeta, Daniel J.; Chen, Robert F.

    1997-05-01

    Organic carbon dissolved in sea water is an important component of the global carbon cycle1. Concentrations of dissolved organic carbon (DOC) in the ocean's surface mixed layer are at least twice those in the deep sea2,3, because of the production of soluble carbon compounds by marine algae in the euphotic zone4,5. But very little is known about the chemical composition of DOC, and the connection between photosynthetic production and DOC accumulation is not well understood6,7. Here we report the chemical characterization of macromolecular DOC at several sites in the Atlantic and Pacific oceans. Neutral sugars, acetate and lipids show similar distributions, suggesting that these constituents are linked together in a common macromolecular structure. Chemical linkage patterns between the oligosaccharide portions of dissolved organic matter subjected to ultrafiltration are highly specific, with little variation between ocean basins. We show that laboratory culture experiments on the decomposition of algal exudate produce macromolecular organic matter with similar compositions and linkage characteristics. We propose that a significant fraction of DOC in sea surface water consists of structurally related and biosynthetically derived acyl oligosaccharides that persist after more labile organic matter has been degraded.

  17. Surface chemical modification for exceptional wear life of MEMS materials

    Directory of Open Access Journals (Sweden)

    R. Arvind Singh

    2011-12-01

    Full Text Available Micro-Electro-Mechanical-Systems (MEMS are built at micro/nano-scales. At these scales, the interfacial forces are extremely strong. These forces adversely affect the smooth operation and cause wear resulting in the drastic reduction in wear life (useful operating lifetime of actuator-based devices. In this paper, we present a surface chemical modification method that reduces friction and significantly extends the wear life of the two most popular MEMS structural materials namely, silicon and SU-8 polymer. The method includes surface chemical treatment using ethanolamine-sodium phosphate buffer, followed by coating of perfluoropolyether (PFPE nanolubricant on (i silicon coated with SU-8 thin films (500 nm and (ii MEMS process treated SU-8 thick films (50 μm. After the surface chemical modification, it was observed that the steady-state coefficient of friction of the materials reduced by 4 to 5 times and simultaneously their wear durability increased by more than three orders of magnitude (> 1000 times. The significant reduction in the friction coefficients is due to the lubrication effect of PFPE nanolubricant, while the exceptional increase in their wear life is attributed to the bonding between the -OH functional group of ethanolamine treated SU-8 thin/thick films and the -OH functional group of PFPE. The surface chemical modification method acts as a common route to enhance the performance of both silicon and SU-8 polymer. It is time-effective (process time ≤ 11 min, cost-effective and can be readily integrated into MEMS fabrication/assembly processes. It can also work for any kind of structural material from which the miniaturized devices are/can be made.

  18. Surface chemical modification for exceptional wear life of MEMS materials

    Science.gov (United States)

    Singh, R. Arvind; Satyanarayana, N.; Sinha, Sujeet Kumar

    2011-12-01

    Micro-Electro-Mechanical-Systems (MEMS) are built at micro/nano-scales. At these scales, the interfacial forces are extremely strong. These forces adversely affect the smooth operation and cause wear resulting in the drastic reduction in wear life (useful operating lifetime) of actuator-based devices. In this paper, we present a surface chemical modification method that reduces friction and significantly extends the wear life of the two most popular MEMS structural materials namely, silicon and SU-8 polymer. The method includes surface chemical treatment using ethanolamine-sodium phosphate buffer, followed by coating of perfluoropolyether (PFPE) nanolubricant on (i) silicon coated with SU-8 thin films (500 nm) and (ii) MEMS process treated SU-8 thick films (50 μm). After the surface chemical modification, it was observed that the steady-state coefficient of friction of the materials reduced by 4 to 5 times and simultaneously their wear durability increased by more than three orders of magnitude (> 1000 times). The significant reduction in the friction coefficients is due to the lubrication effect of PFPE nanolubricant, while the exceptional increase in their wear life is attributed to the bonding between the -OH functional group of ethanolamine treated SU-8 thin/thick films and the -OH functional group of PFPE. The surface chemical modification method acts as a common route to enhance the performance of both silicon and SU-8 polymer. It is time-effective (process time ≤ 11 min), cost-effective and can be readily integrated into MEMS fabrication/assembly processes. It can also work for any kind of structural material from which the miniaturized devices are/can be made.

  19. Surface chemical modification of fullerene by mechanochemical treatment

    International Nuclear Information System (INIS)

    In this study different encapsulating agents have been used for chemical modification of fullerenes. Fullerenes have reacted with tetrahydrofuran, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and ethylene vinyl acetate-ethylene vinyl versatate at room temperature under mechanical milling. The obtained powder has been dispersed in water by ultrasonication. The fullerene based colloids have been characterized by UV-vis, FTIR, Raman spectroscopy and atomic force microscopy. FTIR and Raman analysis have shown the presence of C60 after surface functionalization.

  20. Influence of surface coverage on the chemical desorption process

    CERN Document Server

    Marco, Minissale

    2014-01-01

    In cold astrophysical environments, some molecules are observed in the gas phase whereas they should have been depleted, frozen on dust grains. In order to solve this problem, astrochemists have proposed that a fraction of molecules synthesized on the surface of dust grains could desorb just after their formation. Recently the chemical desorption process has been demonstrated experimentally, but the key parameters at play have not yet been fully understood. In this article we propose a new procedure to analyze the ratio of di-oxygen and ozone synthesized after O atoms adsorption on oxidized graphite. We demonstrate that the chemical desorption efficiency of the two reaction paths (O+O and O+O$_2$) is different by one order of magnitude. We show the importance of the surface coverage: for the O+O reaction, the chemical desorption efficiency is close to 80 $\\%$ at zero coverage and tends to zero at one monolayer coverage. The coverage dependence of O+O chemical desorption is proved by varying the amount of pre-...

  1. Physico-chemical characterization of powdered activated carbons obtained by thermo-chemical conversion of brown municipal waste

    OpenAIRE

    Momčilović Milan Z.; Purenović Milovan M.; Miljković Milena N.; Bojić Aleksandar Lj.; Zarubica Aleksandra R.; Ranđelović Marjan S.

    2011-01-01

    Cones of the European Black pine and Horse chestnut kernel, regarded as brown municipal waste, was utilized in this work as a precursor for powdered activated carbons. Chemical activation was employed at 500°C in inert atmosphere of nitrogen. Standard physico-chemical analyses were performed to examine obtained products. FTIR method was employed to determine fuctional groups which were found to be typical for activated carbons. Acidic oxygen groups were quantitatively determined using B...

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

    International Nuclear Information System (INIS)

    Boron nitride can be used as a good catalyst carrier because of its high thermal conductivity and chemical stability. However, a high specific surface area of boron nitride is still desirable. In this work, a carbon fiber composite coated with boron nitride villous nano-film was prepared, and was also characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The results indicated that the carbon fibers were covered by uniform villous boron nitride films whose thickness was about 150 - 200 nm. The specific surface area of the boron nitride/carbon fiber composite material was 96 m2 g-1, which was markedly improved compared with conventional boron nitride materials. (orig.)

  3. Selective formation of diamond-like carbon coating by surface catalyst patterning

    DEFF Research Database (Denmark)

    Palnichenko, A.V.; Mátéfi-Tempfli, M.; Mátéfi-Tempfli, Stefan;

    2004-01-01

    The selective formation of diamond-like carbon coating by surface catalyst patterning was studied. DLC films was deposited using plasma enhanced chemical vapor deposition, filtered vacuum arc deposition, laser ablation, magnetron sputtering and ion-beam lithography methods. The DLC coatings were...... obtained by means of a single short and intensive carbon plasma deposition pulse. The deposited DLC coating was characterized by micro-Raman spectroscopy measurements. The DLC coating process gave rise to wide potential possibilities in micro-devices manufacturing productions....

  4. Chemical composition and surface charge properties of montmorillonite

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-wen; HU Min; HU Yue-hua

    2008-01-01

    The effects of the cell parameter and chemical composition on the surface charge properties of five kinds of different colour montmorillonites were studied. The results indicate that the surface isoelectric point(IEP) of the montmorillonite shows positive correlation with the mass fractions of Fe2O3 and K20, but it has little relation to the mass fractions of other chemical compositions. At around pH=6.8, the surface zeta potential of the montmorillonite shows the negative relationship with the mass fractions of Fe2O3 and MgO, but it does not linearly correlate to the mass fractions of other chemical compositions. Cell parameter(b0) of the montmofillonite expresses negative linear relationship with mass fractions of K2O and Na2O, so does c0sinβ with mass fractions of SiO2 and Fe2O3. And there is no specific relationship between bo and IEP of different montmori Uonites, but there is positive correlation between c0sinβ and IEP of different montmorillonite samples.

  5. Plasmon-mediated chemical surface functionalization at the nanoscale

    Science.gov (United States)

    Nguyen, Mai; Lamouri, Aazdine; Salameh, Chrystelle; Lévi, Georges; Grand, Johan; Boubekeur-Lecaque, Leïla; Mangeney, Claire; Félidj, Nordin

    2016-04-01

    Controlling the surface grafting of species at the nanoscale remains a major challenge, likely to generate many opportunities in materials science. In this work, we propose an original strategy for chemical surface functionalization at the nanoscale, taking advantage of localized surface plasmon (LSP) excitation. The surface functionalization is demonstrated through aryl film grafting (derived from a diazonium salt), covalently bonded at the surface of gold lithographic nanostripes. The aryl film is specifically grafted in areas of maximum near field enhancement, as confirmed by numerical calculation based on the discrete dipole approximation method. The energy of the incident light and the LSP wavelength are shown to be crucial parameters to monitor the aryl film thickness of up to ~30 nm. This robust and versatile strategy opens up exciting prospects for the nanoscale confinement of functional layers on surfaces, which should be particularly interesting for molecular sensing or nanooptics.Controlling the surface grafting of species at the nanoscale remains a major challenge, likely to generate many opportunities in materials science. In this work, we propose an original strategy for chemical surface functionalization at the nanoscale, taking advantage of localized surface plasmon (LSP) excitation. The surface functionalization is demonstrated through aryl film grafting (derived from a diazonium salt), covalently bonded at the surface of gold lithographic nanostripes. The aryl film is specifically grafted in areas of maximum near field enhancement, as confirmed by numerical calculation based on the discrete dipole approximation method. The energy of the incident light and the LSP wavelength are shown to be crucial parameters to monitor the aryl film thickness of up to ~30 nm. This robust and versatile strategy opens up exciting prospects for the nanoscale confinement of functional layers on surfaces, which should be particularly interesting for molecular sensing

  6. Chemical surface modification of glass beads for the treatment of paper machine process waters

    Energy Technology Data Exchange (ETDEWEB)

    Jradi, Khalil, E-mail: khalil.jradi@uqtr.c [Centre de Recherche en Pates et Papiers, Universite du Quebec a Trois Rivieres, 3351 boul. des forges, C.P. 500, Trois Rivieres, QC, G9A-5H7 (Canada); Daneault, Claude [Canada Research Chair in Value-Added Paper Manufacturing (Canada); Chabot, Bruno [Centre de Recherche en Pates et Papiers, Universite du Quebec a Trois Rivieres, 3351 boul. des forges, C.P. 500, Trois Rivieres, QC, G9A-5H7 (Canada)

    2011-04-29

    Adsorption of detrimental contaminants on a solid sorbent is proposed to remove these contaminants from process waters to increase water recycling and reduce effluent loads in the papermaking industry. A self-assembly process of attaching (covalent grafting) cationic aminosilane molecules to glass beads was investigated. The existence and the hydrolytic stability of self-assembled monolayers and multilayers were confirmed by X-Ray Photoelectron Spectroscopy and contact angle measurements. Effects of reaction time and curing on aminosilane layer structures are also discussed. The curing step after silanization seems to be crucial in the hydrophobization of the quaternary ammonium silane coated onto glass beads, and curing could affect the final chemical structure of the ammonium groups of grafted organosilane. Results indicated that modified glass beads have a strong hydrophobicity, which is attributed to the hydrophobic property of the longest carbon chain grafted onto the glass surface. Adsorption of a model contaminant (stearic acid) onto chemically modified glass beads was determined using colloidal titration. Hydrophobic interactions could be the main driving force involved between the long carbon chains of stearic acid and the carbon chains of the aminosilane layers on glass bead surfaces. Finally, self-assembly processes applied onto glass beads may have two promising applications for papermaking and self-cleaning systems.

  7. Chemical surface modification of glass beads for the treatment of paper machine process waters

    International Nuclear Information System (INIS)

    Adsorption of detrimental contaminants on a solid sorbent is proposed to remove these contaminants from process waters to increase water recycling and reduce effluent loads in the papermaking industry. A self-assembly process of attaching (covalent grafting) cationic aminosilane molecules to glass beads was investigated. The existence and the hydrolytic stability of self-assembled monolayers and multilayers were confirmed by X-Ray Photoelectron Spectroscopy and contact angle measurements. Effects of reaction time and curing on aminosilane layer structures are also discussed. The curing step after silanization seems to be crucial in the hydrophobization of the quaternary ammonium silane coated onto glass beads, and curing could affect the final chemical structure of the ammonium groups of grafted organosilane. Results indicated that modified glass beads have a strong hydrophobicity, which is attributed to the hydrophobic property of the longest carbon chain grafted onto the glass surface. Adsorption of a model contaminant (stearic acid) onto chemically modified glass beads was determined using colloidal titration. Hydrophobic interactions could be the main driving force involved between the long carbon chains of stearic acid and the carbon chains of the aminosilane layers on glass bead surfaces. Finally, self-assembly processes applied onto glass beads may have two promising applications for papermaking and self-cleaning systems.

  8. 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.

  9. 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.

  10. CO2 adsorption on chemically modified activated carbon.

    Science.gov (United States)

    Caglayan, Burcu Selen; Aksoylu, A Erhan

    2013-05-15

    CO2 adsorption capacity of a commercial activated carbon was improved by using HNO3 oxidation, air oxidation, alkali impregnation and heat treatment under helium gas atmosphere. The surface functional groups produced were investigated by diffuse reflectance infrared Fourier transform spectrometer (DRIFTS). CO2 adsorption capacities of the samples were determined by gravimetric analyses for 25-200°C temperature range. DRIFTS studies revealed the formation of carboxylic acid groups on the HNO3 oxidized adsorbents. Increased aromatization and uniform distribution of the Na particles were observed on the samples prepared by Na2CO3 impregnation onto HNO3 oxidized AC support. The adsorption capacities of the nonimpregnated samples were increased by high temperature helium treatments or by increasing the adsorption temperature; both leading to decomposition of surface oxygen groups, forming sites that can easily adsorb CO2. The adsorption capacity loss due to cyclic adsorption/desorption procedures was overcome with further surface stabilization of Na2CO3 modified samples with high temperature He treatments. With Na2CO3 impregnation the mass uptakes of the adsorbents at 20 bars and 25 °C were improved by 8 and 7 folds and at 1 bar were increased 15 and 16 folds, on the average, compared to their air oxidized and nitric acid oxidized supports, respectively. PMID:23500788

  11. Intracellular degradation of chemically functionalized carbon nanotubes using a long-term primary microglial culture model

    Science.gov (United States)

    Bussy, Cyrill; Hadad, Caroline; Prato, Maurizio; Bianco, Alberto; Kostarelos, Kostas

    2015-12-01

    Chemically functionalized carbon nanotubes (f-CNTs) have been used in proof-of-concept studies to alleviate debilitating neurological conditions. Previous in vivo observations in brain tissue have suggested that microglia - acting as resident macrophages of the brain - play a critical role in the internalization of f-CNTs and their partial in situ biodegradation following a stereotactic administration in the cortex. At the same time, several reports have indicated that immune cells such as neutrophils, eosinophils and even macrophages could participate in the processing of carbon nanomaterials via oxidation processes leading to degradation, with surface properties acting as modulators of CNT biodegradability. In this study we questioned whether degradability of f-CNTs within microglia could be modulated depending on the type of surface functionalization used. We investigated the kinetics of degradation of multi-walled carbon nanotubes (MWNTs) functionalized via different chemical strategies that were internalized within isolated primary microglia over three months. A cellular model of rat primary microglia that can be maintained in cell culture for a long period of time was first developed. The Raman structural signature of the internalized f-CNTs was then studied directly in cells over a period of up to three months, following a single exposure to a non-cytotoxic concentration of three different f-CNTs (carboxylated, aminated and both carboxylated and aminated). Structural modifications suggesting partial but continuous degradation were observed for all nanotubes irrespective of their surface functionalization. Carboxylation was shown to promote more pronounced structural changes inside microglia over the first two weeks of the study.Chemically functionalized carbon nanotubes (f-CNTs) have been used in proof-of-concept studies to alleviate debilitating neurological conditions. Previous in vivo observations in brain tissue have suggested that microglia - acting as

  12. Fiber Optic Chemical Nanosensors Based on Engineered Single-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    A. Cusano

    2008-09-01

    Full Text Available In this contribution, a review of the development of high-performance optochemical nanosensors based on the integration of carbon nanotubes with the optical fiber technology is presented. The paper first provide an overview of the amazing features of carbon nanotubes and their exploitation as highly adsorbent nanoscale materials for gas sensing applications. Successively, the attention is focused on the operating principle, fabrication, and characterization of fiber optic chemosensors in the Fabry-Perot type reflectometric configuration, realized by means of the deposition of a thin layer of single-walled carbon nanotubes (SWCNTs upon the distal end of standard silica optical fibers. This is followed by an extensive review of the excellent sensing capabilities of the realized SWCNTs-based chemical nanosensors against volatile organic compounds and other pollutants in different environments (air and water and operating conditions (room temperature and cryogenic temperatures. The experimental results reported here reveal that ppm and sub-ppm chemical detection limits, low response times, as well as fast and complete recovery of the sensor responses have been obtained in most of the investigated cases. This evidences the great potentialities of the proposed photonic nanosensors based on SWCNTs to be successfully employed for practical environmental monitoring applications both in liquid and vapor phase as well as for space. Furthermore, the use of novel SWCNTs-based composites as sensitive fiber coatings is proposed to enhance the sensing performance and to improve the adhesion of carbon nanotubes to the fiber surface. Finally, new advanced sensing configurations based on the use of hollow-core optical fibers coated and partially filled by carbon nanotubes are also presented.

  13. 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

  14. 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.

  15. Limnological characteristics of Northern and Central Yakutian lakes (Siberia) – Physical and chemical properties of surface sediments and water samples

    OpenAIRE

    Kausche, Moritz

    2008-01-01

    Physical and chemical properties of surface sediments and waters of 65 lakes in Northern and Central Yakutia were analysed. The studies included hydrochemical analyses as well as sedimentological, organic and inorganic geochemical analyses, the analysis of stable carbon isotope ratios and the analysis of magnetic susceptibilities. The objectives of this work were a) to characterise Yakutian lakes by their waters and surface sediments. Additionally, the geographical setting, i.e. the clima...

  16. 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

  17. An operando surface enhanced Raman spectroscopy (SERS) study of carbon deposition on SOFC anodes.

    Science.gov (United States)

    Li, Xiaxi; Liu, Mingfei; Lee, Jung-pil; Ding, Dong; Bottomley, Lawrence A; Park, Soojin; Liu, Meilin

    2015-09-01

    Thermally robust and chemically inert Ag@SiO2 nanoprobes are employed to provide the surface enhanced Raman scattering (SERS) effect for an in situ/operando study of the early stage of carbon deposition on nickel-based solid oxide fuel cell (SOFC) anodes. The enhanced sensitivity to carbon enables the detection of different stages of coking, offering insights into intrinsic coking tolerance of material surfaces. Application of a thin coating of gadolinium doped ceria (GDC) enhances the resistance to coking of nickel surfaces. The electrochemically active Ni-YSZ interface appears to be more active for hydrocarbon reforming, resulting in the accumulation of different hydrocarbon molecules, which can be readily removed upon the application of an anodic current. Operando SERS is a powerful tool for the mechanistic study of coking in SOFC systems. It is also applicable to the study of other catalytic and electrochemical processes in a wide range of conditions. PMID:25599129

  18. Plasma-Chemical Synthesis of Nanosized Powders-Nitrides, Carbides, Oxides, Carbon Nanotubes and Fullerenes

    International Nuclear Information System (INIS)

    In this article the plasma-chemical synthesis of nanosized powders (nitrides, carbides, oxides, carbon nanotubes and fullerenes) is reviewed. Nanosized powders - nitrides, carbides, oxides, carbon nanotubes and fullerenes have been successfully produced using different techniques, technological apparatuses and conditions for their plasma-chemical synthesis. (plasma technology)

  19. Carbon-13 magnetic resonance chemical shift additivity relationships of clinically used furocoumarins and furchromones

    International Nuclear Information System (INIS)

    The natural abundance carbon-13 nuclear magnetic resonance spectra of various clinically used furocoumarins and furochromones have been studied. The assignments of carbon chemical shift values were based on the theory of chemical shift, additivity rules, SFORD spectra and model compounds. (author)

  20. The energetic and chemical fingerprints of persistent soil organic carbon

    Science.gov (United States)

    Barré, Pierre; Plante, Alain F.; Cécillon, Lauric; Lutfalla, Suzanne; Baudin, François; Bernard, Sylvain; Christensen, Bent T.; Fernandez, Jose M.; Houot, Sabine; Kätterer, Thomas; Macdonald, Andy; van Oort, Folkert; Le Guillou, Corentin; Chenu, Claire

    2016-04-01

    A better understanding of soil organic carbon (SOC) persistence is needed to better predict SOC vulnerability to global change. The absence of convincing physical or chemical procedures to define, characterize or isolate relatively labile versus persistent SOC pools makes the study of persistent SOC difficult. Long-term bare fallow (LTBF) experiments, in which C inputs have been stopped for several decades, provide a unique opportunity to study persistent SOC without the inherent artefacts induced by extraction procedures, the hypothesis being that SOC is gradually enriched in persistent C with time as labile components decompose. We determined the evolution of thermal and chemical characteristics of bulk SOC in five LTBF experiments across Europe: Askov (DK), Grignon (FR), Rothamsted (UK), Ultuna (SW) and Versailles (FR), using a multi-technique approach involving Rock-Eval pyrolysis, thermogravimetry and differential scanning calorimetry (TG-DSC), mid-infrared diffuse reflectance spectroscopy (DRIFT-MIRS), and Near Edge X-Ray Absorption Fine Structure (NEXAFS). Results of Rock-Eval and TG analyses showed that the temperature needed to combust the SOC increased with bare fallow duration at all sites. Conversely, SOC energy density (in mJ mg-1 C) measured by DSC decreased with bare fallow duration. Rock-Eval pyrolysis results showed that hydrogen index (HI) tended to decrease with bare fallow duration whereas the oxygen index (OI) did not show consistent trends across sites. NEXAFS signals presented little differences and were dominated by carboxyl peak. Nonetheless, NEXAFS results showed a trend of increasing carboxyl groups and decreasing ketone and amide groups with bare fallow duration. Due to the mineral matrix, only a reduced part of the DRIFT-MIRS signals has been used. We observed that the bulk chemistry of aliphatic SOC (CH3 vs. CH2 functional groups) showed different trends for the different sites. Our results showed that in spite of the heterogeneity of

  1. Surface modification of carbon fibers and its effect on the fiber–matrix interaction of UHMWPE based composites

    Energy Technology Data Exchange (ETDEWEB)

    Chukov, D.I., E-mail: dil_chukov@yahoo.com; Stepashkin, A.A.; Gorshenkov, M.V.; Tcherdyntsev, V.V.; Kaloshkin, S.D.

    2014-02-15

    Highlights: • Both chemical and thermal treatments of UKN 5000 carbon fibers allow one to obtain well-developed surface. • The changes of structure and properties of VMN-4 fibers after both thermal and chemical oxidation are insignificant due to more perfect initial structure of these fibers. • The oxidative treatment of carbon fibers allows one to improve the interfacial interaction in the UHMWPE-based composites. • The oxidative treatment of the fibers allows one to a triple increase of Young’s modulus of the modified fibers reinforced UHMWPE composites. -- Abstract: The PAN-based carbon fibers (CF) were subjected to thermal and chemical oxidation under various conditions. The variation in the surface morphology of carbon fibers after surface treatment was analyzed by scanning electron microscopy (SEM). It was found that the tensile strength of carbon fibers changed after surface modification. The interaction between the fibers and the matrix OF ultra-high molecular weight polyethylene (UHMWPE) was characterized by the Young modulus of produced composites. It was shown that the Young modulus of composites reinforced with modified carbon fibers was significantly higher than that of composites reinforced with non-modified fibers.

  2. Surface modification of carbon fibers and its effect on the fiber–matrix interaction of UHMWPE based composites

    International Nuclear Information System (INIS)

    Highlights: • Both chemical and thermal treatments of UKN 5000 carbon fibers allow one to obtain well-developed surface. • The changes of structure and properties of VMN-4 fibers after both thermal and chemical oxidation are insignificant due to more perfect initial structure of these fibers. • The oxidative treatment of carbon fibers allows one to improve the interfacial interaction in the UHMWPE-based composites. • The oxidative treatment of the fibers allows one to a triple increase of Young’s modulus of the modified fibers reinforced UHMWPE composites. -- Abstract: The PAN-based carbon fibers (CF) were subjected to thermal and chemical oxidation under various conditions. The variation in the surface morphology of carbon fibers after surface treatment was analyzed by scanning electron microscopy (SEM). It was found that the tensile strength of carbon fibers changed after surface modification. The interaction between the fibers and the matrix OF ultra-high molecular weight polyethylene (UHMWPE) was characterized by the Young modulus of produced composites. It was shown that the Young modulus of composites reinforced with modified carbon fibers was significantly higher than that of composites reinforced with non-modified fibers

  3. Carbon compounds in the atmosphere and their chemical reactions

    OpenAIRE

    Martišová, Petra

    2013-01-01

    The essay dissert on compounds of carbon in the atmosphere and its reaction. The most important are carbon dioxide, carbon monoxide and methane. Included among important compounds of carbon are volatile organic substances, polycyclic aromatic hydrocarbon and dioxin. Carbon dioxide and methane representing greenhouse gases have also indispensable meaning. As they, together with water vapour, nitrogen monoxide and other gases are causing the major part of greenhouse effect. Primarily because of...

  4. Fabrication of superhydrophobic and oleophobic Al surfaces by chemical etching and surface fluorination

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hak-Jong; Shin, Ju-Hyeon; Choo, Soyoung; Ryu, Sang-Woo; Kim, Yang-Doo; Lee, Heon, E-mail: heonlee@korea.ac.kr

    2015-06-30

    Hierarchical Al surfaces were fabricated using three different kinds of alkaline-based chemical etching processes. The surface morphology changes to a needle-like microstructure or to nanoscale flakes on a microscale porous structure depending on the chemical solution used. These surfaces were characterized by field-emission scanning electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and contact angle measurements. After the hydrophobic treatment, the etched Al surface shows non-wetting properties, exhibiting a static contact angle over 150° and a dynamic contact angle less than 5° for deionized water. Oleophobic properties for diiodomethane and N,N-dimethylformamide are exhibited by all etched Al surfaces. - Highlights: • This research fabricated and analyzed the etched Al surface via a simple wet etching process. • The morphology of Al surface is changed according to the presence of Zn ions. • The wettability of Al surface is controlled by roughness and surface treatment. • Superhydrophobicity and superoleophobicity are achieved on the wet etched Al mesh.

  5. Effect of chemical potential on the computer simulation of hydrogen storage in single walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    ZHENG; Hong; WANG; Shaoqing; CHENG; Huiming

    2004-01-01

    Grand canonical Monte Carlo molecular simulations were carried out for hydrogen adsorption in single-walled carbon nanotubes. It was found that variations in chemical potential may result in a great change in the hydrogen storage capacity of single-walled carbon nanotubes. Hydrogen adsorption isotherms of single-walled carbon nanotubes at 298.15 K were calculated using a modified chemical potential, and the result obtained is closer to the experimental results. By comparing the experimental and simulation results, it is proposed that chemical adsorption may exist for hydrogen adsorption in single-walled carbon nanotubes.

  6. Surface modification of oil fly ash and its application in selective capturing of carbon dioxide

    Science.gov (United States)

    Yaumi, Ali L.; Hussien, Ibnelwaleed A.; Shawabkeh, Reyad A.

    2013-02-01

    Oil fly ash from power generation plants was activated with 30% NH4OH and used for selective adsorption of carbon dioxide from CO2/N2 mixture. The treated samples were characterized for their surface area, morphology, crystalline phase, chemical composition and surface functional groups. Energy dispersive X-ray analysis showed an increase in the carbon contents from 45 to 73 wt% as a result of leaching out metal oxides. XRD proved that chemical activation of ash resulted in diminishing of major crystalline phases of zeolite, and other alumino-silicates leaving only quartz and mullite. BET analysis showed an increase in surface area from 59 to 318 m2/g after chemical activation and the pore volume increased from 0.0368 to 0.679 cm3/g. This increase in pore volume is supported by the results of SEM, where more micropores were opened with well-defined particle sizes and porous structure. The TGA of the treated fly ash showed stability at higher temperature as the weight loss decreased with increasing temperature. For treated ash, the FTIR displayed new peaks of amine functional group. The treated ash was used for the removal of CO2 from CO2/N2 mixture and the maximum adsorption/capturing capacity was found to be 240 mg/g. This capacity increases with increase in initial gas concentration, inlet flow rate and temperature suggesting the endothermic nature of the interaction between the gas molecules and the surface of the ash.

  7. Amorphous Silica- and Carbon- rich nano-templated surfaces as model interstellar dust surfaces for laboratory astrochemistry

    Science.gov (United States)

    Pascual, Natalia; Dawes, Anita; González-Posada, Fernando; Thompson, Neil; Chakarov, Dinko; Mason, Nigel J.; Fraser, Helen Jane

    2015-08-01

    Experimental studies on surface astrochemistry are vital to our understanding of chemical evolution in the interstellar medium (ISM). Laboratory surface-astrochemists have recently begun to study chemical reactions on interstellar dust-grain mimics, ranging from graphite, HOPG and graphene (representative of PAHs or large C-grains in the ISM) to amorphous olivine (representative of silicate dust) and ablated meteoritic samples (representative of interplanetary dust). These pioneering experiments show that the nature of the surface fundamentally affects processes at the substrate surface, substrate-ice interface, and ice over-layer. What these experiments are still lacking is the ability to account for effects arising from the discrete nano-scale of ISM grains, which might include changes to electronic structure, optical properties and surface-kinetics in comparison to bulk materials. The question arises: to what extent are the chemical and optical properties of interstellar ices affected by the size, morphology and material of the underlying ISM dust?We have designed, fabricated and characterised a set of nano-structured surfaces, where nanoparticles, representative of ISM grains, are adhered to an underlying support substrate. Here we will show the nanoparticles that have been manufactured from fused-silica (FS), glassy carbon (GC) and amorphous-C (aC). Our optical characterisation data shows that the nanostructured surfaces have different absorption cross-sections and significant scattering in comparison to the support substrates, which has implications for the energetic processing of icy ISM dust. We have been able to study how water-ice growth differs on the nanoparticles in comparison to the “flat” substrates, indicating increased ice amorphicity when nanoparticles are present, and on C-rich surfaces, compared to Si-rich particles. These data will be discussed in the context of interstellar water-ice features.

  8. CHEMICALLY MODIFIED ZEOLITES: SURFACES AND INTERACTION WITH Cs AND Co

    Directory of Open Access Journals (Sweden)

    Pavel Dillinger

    2007-06-01

    Full Text Available Inorganic exchangers, including zeolites, have interesting properties such as resistance to decomposition in the presence of ionizing radiation or to high temperatures, what make them applicable for the purification of low and middle polluted radioactive waste waters. The research was focused on model radioactive waste effluents and the investigated metals were cobalt (Co and cesium (Cs. The performance of natural zeolite of clinoptilolite type and zeolite chemically modified with NaOH solutions was determined by studying their surface and sorption properties using volumetric method and static radioindicator method. The measurements of zeolite´s surfaces showed the double increase of the specific surface along with an increase of mesopore’s diameter. The reason is the extraction of silicon from zeolite caused by NaOH solution what creates secondary mesoporous structure. The radioactive tracer technique was used to evaluate sorption properties of zeolites and the best sorbent was selected based on KD, μ, Γ and S values. The sorption abilities of natural and chemically modified zeolites for Cs uptake were comparable. The uptake of Co with natural zeolite was negligible and it increased up to 14 times for modified zeolites depending on the concentration of treated NaOH solution.

  9. 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.

  10. 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

  11. Early Stages of the Chemical Vapor Deposition of Pyrolytic Carbon Investigated by Atomic Force Microscopy

    OpenAIRE

    Pfrang, Andreas; WAN Yong-Zhong; Schimmel, Thomas

    2009-01-01

    The early stages of chemical vapor deposition of pyrolytic carbon on planar silicon substrates were studied by the atomic force microscopy-based technique of chemical contrast imaging. Short deposition times were chosen to focus on the early stages of the deposition process, and three different types of nucleation were found: random nucleation of single islands, nucleation of carbon islands along lines and secondary nucleation which corresponds to the nucleation of carbon islands at the edges...

  12. Radiation induced chemical reaction of carbon monoxide and hydrogen mixture

    International Nuclear Information System (INIS)

    Previous studies of radiation induced chemical reactions of CO-H2 mixture have revealed that the yields of oxygen containing products were larger than those of hydrocarbons. In the present study, methane was added to CO-H2 mixture in order to increase further the yields of the oxygen containing products. The yields of most products except a few products such as formaldehyde increased with the addition of small amount of methane. Especially, the yields of trioxane and tetraoxane gave the maximum values when CO-H2 mixture containing 1 mol% methane was irradiated. When large amounts of methane were added to the mixture, the yields of aldehydes and carboxylic acids having more than two carbon atoms increased, whereas those of trioxane and tetraoxane decreased. From the study at reaction temperature over the range of 200 to 473 K, it was found that the yields of aldehydes and carboxylic acids showed maxima at 323 K. The studies on the effects of addition of cationic scavenger (NH3) and radical scavenger (O2) on the products yields were also carried out on the CO-H2-CH4 mixture. (author)

  13. Hierarchical Porous and High Surface Area Tubular Carbon as Dye Adsorbent and Capacitor Electrode.

    Science.gov (United States)

    Chen, Long; Ji, Tuo; Brisbin, Logan; Zhu, Jiahua

    2015-06-10

    Hierarchically porous tubular carbon (HPTC) with large surface area of 1094 m(2)/g has been successfully synthesized by selectively removing lignin from natural wood. No templates or chemicals are involved during the process. By further KOH activation, surface area of activated HPTC reaches up to 2925 m(2)/g. These materials show unprecedented high adsorption capacity toward organic dyes (methylene blue, 838 mg/g; methyl orange, 264 mg/g) and large electrochemical capacitance of >200 F/g. The sustainable feature of the wood precursor and demonstrated superior adsorption and energy storage properties allow promising applications of the processed materials in energy and environmental related fields. PMID:25980528

  14. 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....

  15. Can environmental conditions trigger cyanobacterial surfaces and following carbonate formation: implication for biomineralization and biotechnology

    Science.gov (United States)

    Paulo, C.; Dittrich, M.; Zhu, T.

    2015-12-01

    In this presentation we will give an overview what kind of the factors may trigger carbonate formations at the cell surfaces under a variety of environmental conditions. As examples, we will present the results from our recent studies on formation of calcium carbonates, dolomites and bio-cements. The extracellular polymeric substances (EPS) in the Synechococcuscell envelope are recognized key players in the nucleation of carbonates in marine and freshwater environments. Yet, little is known about a nutrient contents control over the molecular composition of Synechococcus cell envelope, and consequently, biomineralization. In the first study, we investigated how a variation of the phosphorus (P) in the growth media can lead to changes in the surface reactivity of the cells and impact their ability to form carbonates. The objective of the second study is to gain insights into the spatial distribution of cyanobacterial EPS and dolomite from different sediment layers of Khor Al-Adaid sabkha (Qatar). Here, we characterized microbial mats on molecular level in respect of organic and inorganic components using in-situ 2D Raman spectroscopy and Atomic Force Microscopy (AFM) were used. Additionally, 2D chemical maps of sediment layers documented spectral characterizations of minerals and organic matter of microbial origins at high spatial resolution. Finally, we will show the results from the experiments with auto-phototrophic cyanobacteria Gloeocapsa PCC73106, which habitat on the monument surfaces, towards its application for bio-concrete, a product of microbial carbonate precipitation. We studied the biomineralization in biofilm forming Gloeocapsa PCC73106 on the concrete surface as a pre-requirement for microbial carbonate precipitation. Biomineralization on the concrete surface by live cells and killed cells were compared with that under the abiotic condition. Our experiments allow us to conclude that environmental conditions play a significant role in the control of

  16. Photoelectron spectroscopy study of metallic nanocluster arrangement at the surface of reactively sputtered amorphous hydrogenated carbon

    International Nuclear Information System (INIS)

    We report on the results of the arrangement of isolated surface metallic nanoclusters embedded in amorphous hydrogenated carbon (a-C:H) thin films, studied by photoelectron spectroscopy. As a model system we used gold-containing amorphous hydrogenated carbon (a-C:H/Au), due to the lack of reactivity between carbon and gold. The a-C:H/Au samples are obtained by simultaneous magnetron sputtering of Au target by argon and plasma-enhanced chemical vapor deposition of methane. Photoelectron spectroscopy with x-ray and ultraviolet excitation has been employed for surface studies that comprise as-deposited sample spectra recordings, measurements at off-normal takeoff angle, in situ in-depth profiling by Ar+ ion etching, and thiophene adsorption at the sample surface. The results of these extended studies firmly support previously drawn conclusions [I. R. Videnovic, V. Thommen, P. Oelhafen, D. Mathys, M. Dueggelin, and R. Guggenheim, Appl. Phys. Lett 80, 2863 (2002)] that by deposition on electrically grounded substrates one obtains samples with topmost Au clusters covered with a thin layer of a-C:H. Introducing a dc substrate bias voltage results in bald Au clusters on the surface and increased sp2/sp3 coordinated carbon ratio in the a-C:H matrix

  17. Highly surface functionalized carbon nano-onions for bright light bioimaging

    Science.gov (United States)

    Frasconi, Marco; Maffeis, Viviana; Bartelmess, Juergen; Echegoyen, Luis; Giordani, Silvia

    2015-12-01

    Carbon-based nanomaterials functionalized with fluorescent and water-soluble groups have emerged as platforms for biological imaging because of their low toxicity and ability to be internalized by cells. The development of imaging probes based on carbon nanomaterials for biomedical studies requires the understanding of their biological response as well as the efficient and safety exposition of the nanomaterial to the cell compartment where it is designed to operate. Here, we present a fluorescent probe based on surface functionalized carbon nano-onions (CNOs) for biological imaging. The modification of CNOs by chemical oxidation of the defects on the outer shell of these carbon nanoparticles results in an extensive surface functionalization with carboxyl groups. We have obtained fluorescently labelled CNOs by a reaction involving the amide bond formation between fluoresceinamine and the carboxylic acids groups on the surface of the CNOs. The functionalized CNOs display high emission properties and dispersability in water due to the presence of high surface coverage of carboxylic acid groups that translate in an efficient fluorescent probe for in vitro imaging of HeLa cells, without significant cytotoxicity. The resulting nanomaterial represents a promising platform for biological imaging applications due to the high dispersability in water, its efficient internalization by cancer cells and localization in specific cell compartments.

  18. 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.

  19. Organic Carbon--water Concentration Quotients (IIsocS and [pi]pocS): Measuring Apparent Chemical Disequilibria and Exploring the Impact of Black Carbon in Lake Michigan

    Science.gov (United States)

    When black carbon (bc) and biologically derived organic carbon (bioc) phases are present in sediments or suspended particulates, both forms of carbon act additively to sorb organic chemicals but the bc phase has more sorption capacity per unit mass. . . .

  20. Preparation and characterization of activated carbon from reedy grass leaves by chemical activation with H3PO4

    International Nuclear Information System (INIS)

    Highlights: • Activated carbons were produced from reedy grass leaves by activation with phosphoric acid. • The activated carbons have a large number of oxygen- and phosphorus-containing surface groups. • The structure of activated carbons was bight fibers features on the surface and the external surface of the activated carbons was slightly corrugated and abundant pores. - Abstract: Activated carbons were produced from reedy grass leaves by chemical activation with H3PO4 in N2 atmosphere and their characteristics were investigated. The effects of activation temperature and time were examined. Adsorption capacity was demonstrated with BET and iodine number. Micropore volume and pore size distribution of activated carbons were characterized by N2 adsorption isotherms. The surface area and iodine number of the activated carbons produced at 500 °C for 2 h were 1474 m2/g and 1128 mg/g, respectively. Thermal decomposition of pure reedy grass leaves and H3PO4-impregnated reedy grass leaves have been investigated with thermogravimetric/mass spectroscopy (TG–MS) technique. It was found that the temperature and intensity of maximum evolution of H2O and CO2 of H3PO4-impregnated reedy grass leaves were lower than that of pure reedy grass leaves. This implies that H3PO4 as an activating reagent changed the thermal degradation of the reedy grass leaves, stabilized the cellulose structure, leading to a subsequent change in the evolution of porosity. The results of X-ray photoelectron spectroscopy and Fourier-infrared spectroscopy analysis indicate that the produced activated carbons have rich functional groups on surface

  1. Modofications to the surface chemistry of Low-rank Coal-Based carbon Catalysts to improve flue gas nitric oxide removal

    OpenAIRE

    Izquierdo Pantoja, María Teresa; Rubio Villa, Begoña

    2001-01-01

    The effectiveness of carbons as low temperatures SCR catalyst will depend upon their physical and chemical properties. Surface functional groups containing oxygen are closely related to the catalytic activity of carbons. These groups are expected to change the interaction between the carbon surface and the reactants through a variation in adsorption and reaction characteristics. This paper presents a more detailed study of the effects of either gas-phase sulfuric acid or oxygen oxidation tre...

  2. INTERACTION-MEDIATED GROWTH OF CARBON NANOTUBES ON ACICULAR SILICA-COATED α-Fe CATALYST BY CHEMICAL VAPOR DEPOSITION

    Institute of Scientific and Technical Information of China (English)

    Qixiang Wang; Guoqing Ning; Fei Wei; Guohua Luo

    2003-01-01

    Multi-walled carbon nanotubes (MWNTs) with 20 nm outer diameter were prepared by chemical vapor deposition of ethylene using ultrafine surface-modified acicular α-Fe catalyst particles. The growth mechanism of MWNTs on the larger catalyst particles are attributed to the interaction between the Fe nanoparticles with the surface-modified silica layer. This interaction-mediated growth mechanism is illustrated by studying the electronic, atomic and crystal properties of surface-modified catalysts and MWNTs products by characterization with X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), thermal gravimetric analysis (TGA) and Raman spectra.

  3. Synthesis of carbon nanotubes using the cobalt nanocatalyst by thermal chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Madani, S.S. [Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Zare, K. [Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Department of Chemistry, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Ghoranneviss, M. [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Salar Elahi, A., E-mail: Salari_phy@yahoo.com [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2015-11-05

    The three main synthesis methods of Carbon nanotubes (CNTs) are the arc discharge, the laser ablation and the chemical vapour deposition (CVD) with a special regard to the latter one. CNTs were produced on a silicon wafer by Thermal Chemical Vapor Deposition (TCVD) using acetylene as a carbon source, cobalt as a catalyst and ammonia as a reactive gas. The DC-sputtering system was used to prepare cobalt thin films on Si substrates. A series of experiments was carried out to investigate the effects of reaction temperature and deposition time on the synthesis of the nanotubes. The deposition time was selected as 15 and 25 min for all growth temperatures. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the Co nanocatalyst deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface topography of the Co nanocatalyst deposited on Si substrates. The as-grown CNTs were characterized under Field Emission Scanning Electron Microscopy (FESEM) to study the morphological properties of CNTs. Also, the grown CNTs have been investigated by High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results demonstrated that increasing the temperature leads to increasing the diameter of CNTs. The ideal reaction temperature was 850 °C and the deposition time was 15 min. - Graphical abstract: FESEM images of CNTs grown on the cobalt catalyst at growth temperatures of (a) 850 °C, (b) 900 °C, (c) 950 °C and (d) 1000 °C during the deposition time of 15 min. - Highlights: • Carbon nanotubes (CNTs) were produced on a silicon wafer by TCVD technique. • EDX and AFM were used to investigate the elemental composition and surface topography. • FESEM was used to study the morphological properties of CNTs. • The grown CNTs have been investigated by HRTEM and Raman spectroscopy.

  4. Synthesis of carbon nanotubes using the cobalt nanocatalyst by thermal chemical vapor deposition technique

    International Nuclear Information System (INIS)

    The three main synthesis methods of Carbon nanotubes (CNTs) are the arc discharge, the laser ablation and the chemical vapour deposition (CVD) with a special regard to the latter one. CNTs were produced on a silicon wafer by Thermal Chemical Vapor Deposition (TCVD) using acetylene as a carbon source, cobalt as a catalyst and ammonia as a reactive gas. The DC-sputtering system was used to prepare cobalt thin films on Si substrates. A series of experiments was carried out to investigate the effects of reaction temperature and deposition time on the synthesis of the nanotubes. The deposition time was selected as 15 and 25 min for all growth temperatures. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the Co nanocatalyst deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface topography of the Co nanocatalyst deposited on Si substrates. The as-grown CNTs were characterized under Field Emission Scanning Electron Microscopy (FESEM) to study the morphological properties of CNTs. Also, the grown CNTs have been investigated by High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results demonstrated that increasing the temperature leads to increasing the diameter of CNTs. The ideal reaction temperature was 850 °C and the deposition time was 15 min. - Graphical abstract: FESEM images of CNTs grown on the cobalt catalyst at growth temperatures of (a) 850 °C, (b) 900 °C, (c) 950 °C and (d) 1000 °C during the deposition time of 15 min. - Highlights: • Carbon nanotubes (CNTs) were produced on a silicon wafer by TCVD technique. • EDX and AFM were used to investigate the elemental composition and surface topography. • FESEM was used to study the morphological properties of CNTs. • The grown CNTs have been investigated by HRTEM and Raman spectroscopy

  5. 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)

  6. 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

  7. 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.

  8. 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)

  9. Effects of pore structure on the high-performance capacitive deionization using chemically activated carbon nanofibers.

    Science.gov (United States)

    Im, Ji Sun; Kim, Jong Gu; Lee, Young-Seak

    2014-03-01

    Capacitive deionization (CDI) electrodes were constructed from activated carbon fibers prepared using electrospinning and chemical activation. The CDI efficiencies of these electrodes were studied as a function of their specific surface areas, pore volumes and pore sizes via salt ion adsorption. The specific surface areas increased approximately 90 fold and the pore volume also increased approximately 26 fold with the use of greater amounts of the chemical activation agent. There was a relative increase in the mesopore fraction with higher porosity. A NaCI solution was passed through a prepared CDI system, and the salt removal efficiency of the CDI system was determined by the separation of the Na+ and Cl- ions toward the anode and cathode. The CDI efficiency increased with greater specific surface areas and pore volumes. In addition, the efficiency per unit pore volume increased with a reduction in the micropore fraction, resulting in the suppressed overlapping effect. In conclusion, the obtained improvements in CDI efficiency were mainly attributed to mesopores, but the micropores also played an important role in the high-performance CDI under conditions of high applied potential and high ion concentrations. PMID:24745222

  10. The Chemical Origin of SEY at Technical Surfaces

    CERN Document Server

    Larciprete, R; Commisso, M; Flammini, R; Cimino, R

    2013-01-01

    The secondary emission yield (SEY) properties of colaminated Cu samples for LHC beam screens are correlated to the surface chemical composition determined by X-ray photoelectron spectroscopy. The surface of the "as received" samples is characterized by the presence of significant quantities of contaminating adsorbates and by the maximum of the SEY curve (dmax) being as high as 2.2. After extended electron scrubbing at kinetic energy of 10 and 500 eV, the dmax value drops to the ultimate values of 1.35 and 1.1, respectively. In both cases the surface oxidized phases are significantly reduced, whereas only in the sample scrubbed at 500 eV the formation of a graphitic-like C layer is observed. We find that the electron scrubbing of technical Cu surfaces can be described as occurring in two steps, where the first step consists in the electron induced desorption of weakly bound contaminants that occurs indifferently at 10 and at 500 eV and corresponds to a partial decrease of dmax, and the second step, activated b...

  11. Palladium nanoparticles on hierarchical carbon surfaces: A new architecture for robust nano-catalysts

    Science.gov (United States)

    Vijwani, Hema; Mukhopadhyay, Sharmila M.

    2012-12-01

    Surface activity of heterogeneous catalysts can be enhanced if their sizes are reduced to nanometers. However, loose nanomaterials pose potential health and environmental risks. This issue has been addressed by attachment of palladium nanoparticles on multi-scale hierarchical carbon supports that have exceptionally high surface area per volume. The supports consist of porous carbon foam whose surface has been either chemically functionalized, or morphologically altered by grafting of carbon-nanotubes. It is seen that whereas chemical functionalization does provide some increase in nano-catalyst loading, morphological modification is significantly more powerful. It has the potential to create orders of magnitude increase in catalytic activity within the same overall volume. The synthesis techniques have been investigated in sufficient detail to provide significant control over the density and size of nanoparticles. Abundant distribution of nanoparticles is observed even within the deeper pores of the microcellular foam. The nanoparticles are seen to be metallic Pd having face centered cubic structure. Additionally, the nano-particles and nanotubes are durable, and remain attached to the base support after long periods of rapid rotation in water. These robust hybrid structures show promise in future applications such as sensors, water purification systems, fuel cell electrodes and hydrogen storage sponges.

  12. 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.

  13. Chemical agent detection by surface-enhanced Raman spectroscopy

    Science.gov (United States)

    Farquharson, Stuart; Gift, Alan; Maksymiuk, Paul; Inscore, Frank E.; Smith, Wayne W.; Morrisey, Kevin; Christesen, Steven D.

    2004-03-01

    In the past decade, the Unites States and its allies have been challenged by a different kind of warfare, exemplified by the terrorist attacks of September 11, 2001. Although suicide bombings are the most often used form of terror, military personnel must consider a wide range of attack scenarios. Among these is the intentional poisoning of water supplies to obstruct military operations in Afghanistan and Iraq. To counter such attacks, the military is developing portable analyzers that can identify and quantify potential chemical agents in water supplies at microgram per liter concentrations within 10 minutes. To aid this effort we have been investigating the value of a surface-enhanced Raman spectroscopy based portable analyzer. In particular we have been developing silver-doped sol-gels to generate SER spectra of chemical agents and their hydrolysis products. Here we present SER spectra of several chemical agents measured in a generic tap water. Repeat measurements were performed to establish statistical error associated with SERS obtained using the sol-gel coated vials.

  14. Interfacial characterization and analytical applications of chemically-modified surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J.

    1998-02-23

    The goal of this work is to explore several new strategies and approaches to the surface modification and the microscopic characterization of interfaces in the areas mainly targeting sensor technologies that are of interest to environmental control or monitoring, and scanning probe microscopies techniques that can monitor interfacial chemical reactions in real time. Centered on the main theme, four specific topics are presented as four chapters in this dissertation following the general introduction. Chapter 1 describes the development of two immobilization schemes for covalently immobilizing fluoresceinamine at cellulose acetate and its application as a pH sensing film. Chapter 2 investigates the applicability of SFM to following the base-hydrolysis of a dithio-bis(succinimidylundecanoate) monolayer at gold in situ. Chapter 3 studies the mechanism for the accelerated rate of hydrolysis of the dithio-bis(succinimidylundecanoate) monolayer at Au(111) surface. Chapter 4 focuses on the development of an electrochemical approach to the elimination of chloride interference in Chemical Oxygen Demand (COD) analysis of waste water. The procedures, results and conclusions are described in each chapter. This report contains the introduction, references, and general conclusions. Chapters have been processed separately for inclusion on the data base. 95 refs.

  15. 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.

  16. Preparation of surface-functionalized porous clay heterostructures via carbonization of soft-template and their adsorption performance for toluene

    Science.gov (United States)

    Wang, Yuebo; Su, Xiaoli; Xu, Zhen; Wen, Ke; Zhang, Ping; Zhu, Jianxi; He, Hongping

    2016-02-01

    A new type of surface-functionalized porous clay heterostructures (SF-PCH) was synthesized via carbonization of the template agents with sulfuric acid. The converted carbons deposited on the porous surface of the SF-PCH samples and changed their surface chemical properties. The composites possessed a maximum carbon content of 5.35%, a large specific surface area of 428 m2/g and micropore volume of approximately 0.2 cm3/g. The layered and porous structure of SF-PCH was retained after carbonization and calcination when sulfuric acid solution with a mild concentration was used. Analysis by XPS confirmed that the carbonaceous matter in the pore channels was functionalized with various organic groups, including carbonaceous, nitrogenous, and sulfated groups. Both the surface chemical property and structural characteristic of adsorbents have effects on the adsorption properties of SF-PCH for toluene. The SF-PCH samples exhibited a stronger adsorption affinity to toluene compared with untreated PCH in the low pressure region, which is more valuable in the practical applications. These results demonstrate that carbonization of soft-template is a feasible process for the surface modification of PCH, enabling the resulting composites to become promising candidates for application in toluene emission control.

  17. 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 ...

  18. Acid-base properties and chemical composition of the surface of the InSb-ZnTe system

    International Nuclear Information System (INIS)

    The acid-base properties and chemical composition of the surface of solid solutions and binary components of the InSb-ZnTe system were studied by the hydrolytic adsorption, nonaqueous conductometric titration, mechanochemistry, IR spectroscopy, and mass spectrometry methods. The strength, nature, and concentration of acid centers were determined. Changes in the concentration of acid centers caused by surface exposure to CO and changes in the composition of the system were also studied. The mechanism of acid-base interactions was established. The chemical composition of the surface of system components exposed to air included adsorbed H2O molecules, OH- groups, hydrocarbon and oxo carbon compounds, and the products of surface atom oxidation. After thermal treatment in a vacuum, the composition of the surface approached the stoichiometric composition

  19. Reduction of uranyl carbonate and hydroxyl complexes and neptunyl carbonate complexes studied with chemical-electrochemical methods and rixs spectroscopy

    International Nuclear Information System (INIS)

    actinides have been mobilised through oxidation, they can migrate away from this potentially oxidising region and will encounter an oxygen free, reducing environment caused by the anaerobic corrosion of the cast iron insert. The actinyl species are no longer thermodynamically stable and reduction to the tetravalent state will be possible. There is, however, an open question whether the reduction kinetics will be sufficiently high to cause reduction in solution and if sorption onto the corroding iron surface will be accompanied by an electron transfer sufficiently rapid to reduce the actinide back to the tetravalent state. This report contains the results of experimental studies of uranium reduction-depletion from water solutions in the presence of corroding iron and spectroscopic studies of the oxidation state of uranium and neptunium sorbed/precipitated onto iron under oxygen free conditions using resonant inelastic soft x-ray scattering (RIXS) spectroscopy. The RIXS measurements show that at least partial reduction of both uranyl carbonate complexes and neptunyl carbonate complexes take place on the corroding iron surface. The chemical/electrochemical measurements indicate that reduction of uranyl carbonate complexes also take place in solution in a system containing corroding iron, i.e. sorption onto the iron/iron oxide surface may not be necessary in order for reduction to take place. Reduction of uranyl hydroxyl complexes was also found to take place in solution, but at a rate that was noticeably lower than for the uranyl carbonate complexes

  20. Carbon cycle, chemical erosion of continents and transfers to the oceans

    International Nuclear Information System (INIS)

    This study tries to define the processes that control the CO2 consumption due to the chemical erosion of continents, to appreciate the spatial-temporal fluxes of consumed CO2, and to estimate the transfers of dissolved mineral carbon from the continents to the oceans. Complementary approaches using different scales of time and space are necessary to study all these processes. Chemical alteration of minerals from continental rocks is due to the carbonic acid indirectly produced by atmospheric CO2 via the photosynthesis and the degradation of organic matter in soils. The transfer of dissolved CO2 towards the oceans is done by the drainage waters of the river basins. Continental erosion develops at the interfaces of the biosphere, atmosphere and ocean reservoirs and is controlled by numerous geological, hydro-climatical, biological and anthropic factors. Seasonal variations of CO2 consumption has been studied for the Garonne (France), Congo and Ubangui basins to determine the mechanisms that control this consumption. A predictive model has been developed to simulate the consumed CO2 fluxes on continental surfaces for which the spatial distribution of lithology and drainage is known. This model has been validated using available data from the Garonne (France), Congo and Amazone basins. (J.S.). 272 refs., 78 figs., 41 tabs., 1 annexe

  1. Chemical unzipping of multiwalled carbon nanotubes for high-capacity lithium storage

    International Nuclear Information System (INIS)

    Highlights: • MWCNTs were longitudinally split to be unzipped by a chemical oxidative etching. • UCNTs were self-folded and entangled to interlace a nanoporous 3D network. • UCNTs show high reversible Li+ storage, good rate capability and cycle stability. - Abstract: Multiwalled carbon nanotubes (MWCNTs) were longitudinally split to be unzipped by a facile chemical oxidative etching. Transmission electron microscope images and Raman spectra confirmed that most of MWCNTs were opened and some were transformed to multi-layered graphene nanoribbons. Scanning electron microscope images showed that unzipped carbon nanotubes (UCNTs) were interwined each other to form a tridimensional porous film. The N2 adsorption/desorption analysis showed that the UCNTs had larger specific surface area and more mesopores compared to MWCNTs. The galvanostatic charge-discharge experiments showed that the reversible capacity of UCNTs were up to 765 mAh g−1 at 0.1 A g−1 and kept 635 mAh g−1 at various current densities. The reversible capacity remained stable around 420 and 330 mAh g−1 at current rates of 0.6 and 1 A g−1 with coulombic efficiency above 99% over 300 cycles

  2. Structure and composition of chemically prepared and vacuum annealed InSb(0 0 1) surfaces

    Science.gov (United States)

    Tereshchenko, O. E.

    2006-08-01

    The InSb(0 0 1) surfaces chemically treated in HCl-isopropanol solution and annealed in vacuum were studied by means of X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and electron energy-loss spectroscopy (EELS). The HCl-isopropanol treatment removes indium and antimony oxides and leaves on the surface about 3 ML of physisorbed overlayer, containing indium chlorides and small amounts of antimony, which can be thermally desorbed at 230 °C. The residual carbon contaminations were around 0.2-0.4 ML and consisted of the hydrocarbon molecules. These hydrocarbon contaminations were removed from the surface together with the indium chlorides and antimony overlayer. With increased annealing temperature, a sequence of reconstructions were identified by LEED: (1 × 1), (1 × 3), (4 × 3), and (4 × 1)/c(8 × 2), in the order of decreasing Sb/In ratio. The structural properties of chemically prepared InSb(0 0 1) surface were found to be similar to those obtained by decapping of Sb-capped epitaxial layers.

  3. ZnO Functionalization of Surface Pre-treated Multi-walled Carbon Nanotubes for Methane Sensing

    Science.gov (United States)

    Bare carbon nanotubes (CNTs) cannot be used to sense most gases due to poor bonding between the chemically inert graphitic surface and the different compounds CNTs are exposed to. Consequently, for gas sensing applications, functionalization of CNTs with reactive compounds is req...

  4. Effect of precursors on the growth of carbon filaments onto clay surface

    International Nuclear Information System (INIS)

    The successful growth of carbon filaments on two different precursors, i.e., the pristine sodium-montmorillonite (Na+MMT), which undergoes reflux at 100 deg. C (r-MMT), and the Na+MMT exchanged with Fe3+ ions (MMT(Fe)), was attained through chemical vapor deposition (CVD). The products obtained were characterized by X-ray diffraction, thermogravimetry, scanning electron microscopy, and transmission electron microscopy. Refluxing can make the Fe3+ ions in the octahedral layer of Na+MMT migrate to the interlayer and exchange with Na+ ions. Furthermore, through calcination at 500 deg. C, the Fe3+ ions migrate again to the surface of the clay layer and form iron oxides, which can serve as precursors for the deposition of carbon. Although r-MMT contained less iron than the MMT(Fe), the ultimate yield of carbon components grown was almost the same, indicating that the iron species in r-MMT possess higher catalytic activity. However, on the surface of r-MMT, CVD hardly generated carbon nanotubes with a clear hollow structure but that those with a carbon fiber structure instead.

  5. Structural and surface modifications of carbon nanotubes when submitted to high temperature annealing treatments

    Energy Technology Data Exchange (ETDEWEB)

    Castillejos, E. [Instituto de Catalisis y Petroleoquimica, ICP-CSIC, Campus de Cantoblanco, 28046 Madrid (Spain); Bachiller-Baeza, B. [Instituto de Catalisis y Petroleoquimica, ICP-CSIC, Campus de Cantoblanco, 28046 Madrid (Spain); Unidad Asociada UNED/ICP-CSIC Group for Molecular Design of Heterogeneous Catalysts, Madrid (Spain); Perez-Cadenas, M.; Gallegos-Suarez, E. [Dpto. de Quimica Inorganica y Tecnica, UNED, 28040 Madrid (Spain); Rodriguez-Ramos, I. [Instituto de Catalisis y Petroleoquimica, ICP-CSIC, Campus de Cantoblanco, 28046 Madrid (Spain); Unidad Asociada UNED/ICP-CSIC Group for Molecular Design of Heterogeneous Catalysts, Madrid (Spain); Guerrero-Ruiz, A. [Unidad Asociada UNED/ICP-CSIC Group for Molecular Design of Heterogeneous Catalysts, Madrid (Spain); Dpto. de Quimica Inorganica y Tecnica, UNED, 28040 Madrid (Spain); Tamargo-Martinez, K., E-mail: katia@incar.csic.es [Instituto Nacional del Carbon, INCAR-CSIC, Apartado 73, 33080 Oviedo (Spain); Martinez-Alonso, A.; Tascon, J.M.D. [Instituto Nacional del Carbon, INCAR-CSIC, Apartado 73, 33080 Oviedo (Spain)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Multiwall carbon nanotubes (MWCNTs), pristine and heat-treated at 2873 K, were comparatively characterized using HRTEM, SEM, nitrogen adsorption, Raman spectroscopy and immersion calorimetry. Black-Right-Pointing-Pointer Annealing at 2873 K produced removal of amorphous phases, ordering of graphene layers and structural changes inside the cylindrical mesopores. Black-Right-Pointing-Pointer Immersion enthalpies in organic liquids indicated the existence of specific {pi}-{pi} electronic interactions between aromatic molecules and the surface of heat-treated MWCNTs. - Abstract: Multiwall carbon nanotubes (MWCNTs) were synthesized using a chemical vapour deposition procedure using acetylene as source of carbon, iron pentacarbonyl as catalyst and an inert carrier gas. An aliquot of these MWCNTs was heat-treated at 2873 K under inert atmosphere (Ar). The two carbon nanotube samples where characterized using high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy, nitrogen adsorption at 77 K, Raman spectroscopy, and immersion calorimetry in toluene, methanol and methylcyclohexane. HRTEM images confirmed that high-temperature treatment removed amorphous carbon, the graphene layers being better graphitized, and also some structural changes inside the cylindrical mesopores took place. Immersion enthalpies in toluene, in which molecules are present as aromatic functions, indicated the existence of specific {pi}-{pi} electronic interactions between such molecules and the surface of heat-treated MWCNTs.

  6. Application of phosphating techniques to aluminium and carbon steel surfaces using nitro guanidine as oxidizing agent

    International Nuclear Information System (INIS)

    Phosphate coatings are inorganic crystalline deposits laid down uniformly on properly prepared surfaces by a chemical reaction with the treated base metal. The reaction consists in dissolving some surface metal by acid attack and then causing surface neutralization of the phosphate solution with consequent precipitation of the phosphate coating. Phosphate coatings do not provide appreciable corrosion protection in themselves. They are useful mainly as a base for paints, ensuring good adherence of paint to steel and decreasing the tendency for corrosion to under cut the paint film at scratches or other defects. In this work firstly were realized phosphate on standard carbon steel, employing technical of cold phosphate (at 40 Centigrade degrees and with a treatment time of 30 minutes) and hot phosphate (at 88 Centigrade degrees and with a treatment time of 15 minutes), where with this last were obtained the best results. Both methods used phosphate solutions of Zn/Mn and using as catalyst Nitro guanidine. Aluminium surfaces were phosphate used solutions of Cr and as catalyst Sodium bi fluoride. The phosphating on this surface were realized at temperature of 50 Centigrade degrees and with a treatment time of 10 minutes. In this work were obtained a new phosphate coatings on steel surfaces, these coatings were realized with a phosphate solution manufactured with the precipitates gathered during the hot phosphating on carbon steel. These coatings show excellent physical characteristics and of corrosion resistance. Were determined the physical testings of the coatings phosphate obtained on carbon steel and aluminium surfaces. These testing were: roughness, thickness, microhardness and adhesion. The best results were showed in carbon steel phosphate with precipitated solutions. The technical of analysis for activation with thermic neutrons was used to determine the phosphate coatings composition. Finally, corrosion testings were realized by means of two methods

  7. 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

  8. Adsorption studies of methylene blue and phenol onto vetiver roots activated carbon prepared by chemical activation

    International Nuclear Information System (INIS)

    Vetiver roots have been utilized for the preparation of activated carbon (AC) by chemical activation with different impregnation ratios of phosphoric acid, XP (g H3PO4/g precursor): 0.5:1; 1:1 and 1.5:1. Textural characterization, determined by nitrogen adsorption at 77 K shows that mixed microporous and mesoporous structures activated carbons (ACs) with high surface area (>1000 m2/g) and high pore volume (up to 1.19 cm3/g) can be obtained. The surface chemical properties of these ACs were investigated by X-ray photoelectron spectroscopy (XPS) and Boehm titration. Their textural and chemical characteristics were compared to those of an AC sample obtained by steam activation of vetiver roots. Classical molecules used for characterizing liquid phase adsorption, phenol and methylene blue (MB), were used. Adsorption kinetics of MB and phenol have been studied using commonly used kinetic models, i.e., the pseudo-first-order model, the pseudo-second-order model, the intraparticle diffusion model and as well the fractal, BWS (Brouers, Weron and Sotolongo) kinetic equation. The correlation coefficients (R2) and the normalized standard deviation Δq (%) were determined showing globally, that the recently derived fractal kinetic equation could best describe the adsorption kinetics for the adsorbates tested here, indicating a complex adsorption mechanism. The experimental adsorption isotherms of these molecules on the activated carbon were as well analysed using four isotherms: the classical Freundlich, Langmuir, Redlich-Peterson equations, but as well the newly published deformed Weibull Brouers-Sotolongo isotherm. The results obtained from the application of the equations show that the best fits were achieved with the Brouers-Sotolongo equation and with the Redlich-Peterson equation. Influence of surface functional groups towards MB adsorption is as well studied using various ACs prepared from vetiver roots and sugar cane bagasse. Opposite effects governing MB and phenol

  9. Adsorption studies of methylene blue and phenol onto vetiver roots activated carbon prepared by chemical activation

    Energy Technology Data Exchange (ETDEWEB)

    Altenor, Sandro [COVACHIMM, EA 3592 Universite des Antilles et de la Guyane, BP 250, 97157 Pointe a Pitre Cedex, Guadeloupe (France); LAQUE, Universite Quisqueya d' Haiti, Port-au-Prince (Haiti); Carene, Betty [COVACHIMM, EA 3592 Universite des Antilles et de la Guyane, BP 250, 97157 Pointe a Pitre Cedex, Guadeloupe (France); Emmanuel, Evens [LAQUE, Universite Quisqueya d' Haiti, Port-au-Prince (Haiti); Lambert, Jacques; Ehrhardt, Jean-Jacques [Laboratoire de Chimie Physique et Microbiologie pour l' Environnement, UMR 7564 CNRS-Nancy Universities, 405 rue de Vandoeuvre, F 54600 Villers-les-Nancy Cedex (France); Gaspard, Sarra, E-mail: sgaspard@univ-ag.fr [COVACHIMM, EA 3592 Universite des Antilles et de la Guyane, BP 250, 97157 Pointe a Pitre Cedex, Guadeloupe (France)

    2009-06-15

    Vetiver roots have been utilized for the preparation of activated carbon (AC) by chemical activation with different impregnation ratios of phosphoric acid, X{sub P} (g H{sub 3}PO{sub 4}/g precursor): 0.5:1; 1:1 and 1.5:1. Textural characterization, determined by nitrogen adsorption at 77 K shows that mixed microporous and mesoporous structures activated carbons (ACs) with high surface area (>1000 m{sup 2}/g) and high pore volume (up to 1.19 cm{sup 3}/g) can be obtained. The surface chemical properties of these ACs were investigated by X-ray photoelectron spectroscopy (XPS) and Boehm titration. Their textural and chemical characteristics were compared to those of an AC sample obtained by steam activation of vetiver roots. Classical molecules used for characterizing liquid phase adsorption, phenol and methylene blue (MB), were used. Adsorption kinetics of MB and phenol have been studied using commonly used kinetic models, i.e., the pseudo-first-order model, the pseudo-second-order model, the intraparticle diffusion model and as well the fractal, BWS (Brouers, Weron and Sotolongo) kinetic equation. The correlation coefficients (R{sup 2}) and the normalized standard deviation {Delta}q (%) were determined showing globally, that the recently derived fractal kinetic equation could best describe the adsorption kinetics for the adsorbates tested here, indicating a complex adsorption mechanism. The experimental adsorption isotherms of these molecules on the activated carbon were as well analysed using four isotherms: the classical Freundlich, Langmuir, Redlich-Peterson equations, but as well the newly published deformed Weibull Brouers-Sotolongo isotherm. The results obtained from the application of the equations show that the best fits were achieved with the Brouers-Sotolongo equation and with the Redlich-Peterson equation. Influence of surface functional groups towards MB adsorption is as well studied using various ACs prepared from vetiver roots and sugar cane bagasse

  10. Adsorption studies of methylene blue and phenol onto vetiver roots activated carbon prepared by chemical activation.

    Science.gov (United States)

    Altenor, Sandro; Carene, Betty; Emmanuel, Evens; Lambert, Jacques; Ehrhardt, Jean-Jacques; Gaspard, Sarra

    2009-06-15

    Vetiver roots have been utilized for the preparation of activated carbon (AC) by chemical activation with different impregnation ratios of phosphoric acid, X(P) (gH(3)PO(4)/g precursor): 0.5:1; 1:1 and 1.5:1. Textural characterization, determined by nitrogen adsorption at 77K shows that mixed microporous and mesoporous structures activated carbons (ACs) with high surface area (>1000 m(2)/g) and high pore volume (up to 1.19 cm(3)/g) can be obtained. The surface chemical properties of these ACs were investigated by X-ray photoelectron spectroscopy (XPS) and Boehm titration. Their textural and chemical characteristics were compared to those of an AC sample obtained by steam activation of vetiver roots. Classical molecules used for characterizing liquid phase adsorption, phenol and methylene blue (MB), were used. Adsorption kinetics of MB and phenol have been studied using commonly used kinetic models, i.e., the pseudo-first-order model, the pseudo-second-order model, the intraparticle diffusion model and as well the fractal, BWS (Brouers, Weron and Sotolongo) kinetic equation. The correlation coefficients (R(2)) and the normalized standard deviation Deltaq (%) were determined showing globally, that the recently derived fractal kinetic equation could best describe the adsorption kinetics for the adsorbates tested here, indicating a complex adsorption mechanism. The experimental adsorption isotherms of these molecules on the activated carbon were as well analysed using four isotherms: the classical Freundlich, Langmuir, Redlich-Peterson equations, but as well the newly published deformed Weibull Brouers-Sotolongo isotherm. The results obtained from the application of the equations show that the best fits were achieved with the Brouers-Sotolongo equation and with the Redlich-Peterson equation. Influence of surface functional groups towards MB adsorption is as well studied using various ACs prepared from vetiver roots and sugar cane bagasse. Opposite effects governing MB

  11. A novel surface cleaning method for chemical removal of fouling lead layer from chromium surfaces

    International Nuclear Information System (INIS)

    Most products especially metallic surfaces require cleaning treatment to remove surface contaminations that remain after processing or usage. Lead fouling is a general problem which arises from lead fouling on the chromium surfaces of bores and other interior parts of systems which have interaction with metallic lead in high temperatures and pressures. In this study, a novel chemical solution was introduced as a cleaner reagent for removing metallic lead pollution, as a fouling metal, from chromium surfaces. The cleaner aqueous solution contains hydrogen peroxide (H2O2) as oxidizing agent of lead layer on the chromium surface and acetic acid (CH3COOH) as chelating agent of lead ions. The effect of some experimental parameters such as acetic acid concentration, hydrogen peroxide concentration and temperature of the cleaner solution during the operation on the efficiency of lead cleaning procedure was investigated. The results of scanning electron microscopy (SEM) showed that using this procedure, the lead pollution layer could be completely removed from real chromium surfaces without corrosion of the original surface. Finally, the optimum conditions for the complete and fast removing of lead pollution layer from chromium surfaces were proposed. The experimental results showed that at the optimum condition (acetic acid concentration 28% (V/V), hydrogen peroxide 8% (V/V) and temperature 35 deg. C), only 15-min time is needed for complete removal of 3 g fouling lead from a chromium surface.

  12. Role of carbon in titania as visible-light photocatalyst prepared by flat-flame chemical vapor condensation method

    International Nuclear Information System (INIS)

    In this article, the authors report that titania nanopowders synthesized by low-pressure flat-flame metal-organic chemical vapor condensation show visible-light photocatalytic ability. Using acetylene and oxygen as fuel and oxidizer for the flame, the titanium isopropoxide was decomposed and oxidized, and the nanoparticles of titania were formed. From the methylene blue decomposition study they found that the powder synthesized under low precursor feed rate possesses high photocatalytic efficiency under illumination of visible light. The visible-light absorption is resort to the presence of carbon since no other chemical elements were found associated with titania. The presence of carbon species is coincident with the presence of visible-light absorption and carbon is in the form of C-C bond. It also suggests that carbon species are associated with catalytic site on anatase surface so that carriers generated by photon absorption by the carbon species can transfer quickly onto catalytic sites and perform the subsequent catalytic reactions. A possibly unreported mechanism of visible-light TiO2 photocatalysis induced by carbon doping is identified.

  13. 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

  14. 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.

  15. Characterization and use of high surface area activated carbons prepared from cane pith for liquid-phase adsorption

    International Nuclear Information System (INIS)

    Carbonaceous adsorbents with controllable surface areas were chemically activated with KOH at 780 deg. C from char that had been carbonized from cane pith at 450 deg. C. The pore properties including the BET surface area, pore volume, pore size distribution, and mean pore diameter of these activated carbons were characterized and derived using the t-plot method based on N2 adsorption isotherms. The activated cane pith carbons, with KOH/char ratios of 2-6, exhibited BET surface areas ranging from 912 to 2299 m2 g-1. The scanning electron microscopic (SEM) observations revealed that the surface morphology of honeycombed holes on all activated cane pith carbons was significantly influenced by the KOH/char ratio. The adsorption kinetics and equilibrium isotherms of acid blue 74, methylene blue, basic brown 1, p-nitrophenol, p-chlorophenol, p-cresol, and phenol from water at 30 deg. C on the activated carbons were studied. The adsorption kinetics were suitably described by a simplified kinetic model, the Elovich equation. All adsorption equilibrium isotherms were in agreement with the Langmuir equation, and were used to compare the covered area (S c/S p) of the activated carbons at different KOH/char ratios. The high-surface-area activated carbons were proven to be promising adsorbents for pollution control and for other applications

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. Numerical simulation of isothermal chemical vapor infiltration process in fabrication of carbon-carbon composites by finite element method

    Institute of Scientific and Technical Information of China (English)

    李克智; 李贺军; 姜开宇

    2000-01-01

    The chemical vapor infiltration process in fabrication of carbon-carbon composites is highly inefficient and requires long processing time. These limitations add considerably to the cost of fabrication and restrict the application of this material. Efforts have been made to study the CVI process in fabrication of carbon-carbon composites by computer simulation and predict the process parameters, density, porosity, etc. According to the characteristics of CVI process, the basic principle of FEM and mass transport, the finite element model has been established. Incremental finite element equations and the elemental stiffness matrices have been derived for the first time. The finite element program developed by the authors has been used to simulate the ICVI process in fabrication of carbon-carbon composites. Computer color display of simulated results can express the densification and distributions of density and porosity in preform clearly. The influence of process parameters on the densification of prefo

  3. Orthogonal chemical functionalization of patterned gold on silica surfaces

    Directory of Open Access Journals (Sweden)

    Francisco Palazon

    2015-12-01

    Full Text Available Single-step orthogonal chemical functionalization procedures have been developed with patterned gold on silica surfaces. Different combinations of a silane and a thiol were simultaneously deposited on a gold/silica heterogeneous substrate. The orthogonality of the functionalization (i.e., selective grafting of the thiol on the gold areas and the silane on the silica was demonstrated by X-ray photoelectron spectroscopy (XPS as well as time-of-flight secondary ion mass spectrometry (ToF–SIMS mapping. The orthogonal functionalization was used to immobilize proteins onto gold nanostructures on a silica substrate, as demonstrated by atomic force microscopy (AFM. These results are especially promising in the development of future biosensors where the selective anchoring of target molecules onto nanostructured transducers (e.g., nanoplasmonic biosensors is a major challenge.

  4. Evaluation of chemical surface treatment methods for mitigation of PWSCC

    International Nuclear Information System (INIS)

    As part of its mission to propose innovative and safe technologies to mitigate Primary Water Stress Corrosion Cracking (PWSCC) in Pressurized Water Reactors (PWR), EPRI recently initiated a program to evaluate potential new chemical surface treatments that might delay the occurrence of PWSCC such that no failure of components would be observed during their lifetime. Among the initial screening of more than thirty technologies, seven were selected for a more detailed review. The selected technologies were: nickel and nickel alloy plating, organic inhibitors, chromium-based inhibitors, silicon carbide, titanium-based inhibitors, rare earth metal (REM)-based inhibitors and encapsulation. The conclusions of the review of these technologies were that two of them were worth pursuing, titanium-based and REM-based inhibitors, and that evaluating the radiological consequences of injecting these products in the primary system, as well as assessing their efficacy to mitigate PWSCC, should be prioritized as the next required steps in qualification for implementation. (authors)

  5. Effect of MWCNT surface and chemical modification on in vitro cellular response

    International Nuclear Information System (INIS)

    The aim of this study was to evaluate the impact of multi-walled carbon nanotubes (MWCNTs with diameter in the range of 10–30 nm) before and after chemical surface functionalisation on macrophages response. The study has shown that the detailed analysis of the physicochemical properties of this particular form of carbon nanomaterial is a crucial issue to interpret properly its impact on the cellular response. Effects of carbon nanotubes (CNTs) characteristics, including purity, dispersity, chemistry and dimension upon the nature of the cell environment–material interaction were investigated. Various techniques involving electron microscopy (SEM, TEM), infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectrometry, X-ray photoelectron spectroscopy have been employed to evaluate the physicochemical properties of the materials. The results demonstrate that the way of CNT preparation prior to biological tests has a fundamental impact on their behavior, cell viability and the nature of cell–nanotube interaction. Chemical functionalisation of CNTs in an acidic ambient (MWCNT-Fs) facilitates interaction with cells by two possible mechanisms, namely, endocytosis/phagocytosis and by energy-independent passive process. The results indicate that MWCNT-F in macrophages may decrease the cell proliferation process by interfering with the mitotic apparatus without negative consequences on cell viability. On the contrary, the as-prepared MWCNTs, without any surface treatment produce the least reduction in cell proliferation with reference to control, and the viability of cells exposed to this sample was substantially reduced with respect to control. A possible explanation of such a phenomenon is the presence of MWCNT’s agglomerates surrounded by numerous cells releasing toxic substances.

  6. Prism-C2n carbon dimer, trimer, and nano-sheets: A quantum chemical study

    Science.gov (United States)

    Ohno, Koichi; Satoh, Hiroko; Iwamoto, Takeaki

    2015-07-01

    Quantum chemical calculations have predicted the existence of a new carbon family with double-layered structures formed by arranging prism-C2n (n = 6, 8, and 12) units. Theoretical explorations of potential energy surfaces suggest the lowest barriers of the reaction channels to be ca. 30 kJ mol-1 for a D2h prism-C16 dimer and a D3h prism-C24 trimer. Geometry optimizations under periodic boundary conditions yield some prism-C2n sheets composed of CC single bonds of ca. 0.15-0.16 nm. The relative energies per one atom with respect to graphene are 90-160 kJ mol-1. Van der Waals thickness is estimated to be ca. 0.5 nm.

  7. Green chemical functionalization of multiwalled carbon nanotubes with poly({epsilon}-caprolactone) in ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Yang Yingkui, E-mail: yingkuiyang@gmail.com [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan 430062 (China); Qiu Shengqiang; He Chengen; He Wenjie; Yu Linjuan [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan 430062 (China); Xie Xiaolin, E-mail: xlxie@mail.hust.edu.cn [School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2010-11-15

    Multiwalled carbon nanotubes (MWNTs) have been successfully functionalized by free radical addition of 4,4'-azobis(4-cyanopentanol) in aqueous media to generate the terminal-hydroxyl-modified MWNTs (MWNT-OH), followed by surface-initiated in situ ring-opening polymerization of {epsilon}-caprolactone in 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF{sub 4}) to obtain poly({epsilon}-caprolactone)-grafted MWNTs (MWNT-g-PCL). Spectroscopic methods in conjunction with electron microscopy clearly revealed that hairy PCL chains were chemically attached to the surface of MWNTs to form core-shell nanostructures with the latter as core and the former as shell. With increasing polymerization time from 2 to 8 h, the amount of the grafted-PCL synthesized in BmimBF{sub 4} varies from 30.6 to 62.7 wt%, which is clearly higher than that (41.5 wt%) obtained in 1,2-dichlorobenzene under comparable conditions (8 h). The proposed methodology here uses water and room temperature ionic liquids (RTILs) as the reaction media and promises a green chemical process for functionalizing nanotubes.

  8. Carbon nanostructures and networks produced by chemical vapor deposition

    NARCIS (Netherlands)

    Kowlgi, N.K.K.; Koper, G.J.M.; Van Raalten, R.A.D.

    2012-01-01

    The invention pertains to a method for manufacturing crystalline carbon nanostructures and/or a network of crystalline carbon nanostructures, comprising: (i) providing a bicontinuous micro-emulsion containing metal nanoparticles having an average particle size between 1and 100nm; (ii) bringing said

  9. 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.

  10. A review of chemical absorption of carbon dioxide for biogas upgrading

    Institute of Scientific and Technical Information of China (English)

    Fouad RH Abdeen; Maizirwan Mel; Mohammed Saedi Jami; Sany Izan Ihsan; Ahmad Faris Ismail

    2016-01-01

    Significant attention has been given to biogas production, purification and upgrading as a renewable and clean fuel supplement. Biogas is a product of an anaerobic digestion process comprising methane, carbon dioxide, and trace amounts of other gases. Biogas purification removes trace gases in biogas for safe utilisation. Biogas upgrading produces methane-rich biogas by removing bulk carbon dioxide from the gas mixture. Several carbon dioxide removal techniques can be applied for biogas upgrading. However, chemical absorption of carbon dioxide for biogas upgrading is of special significance due to its operation at ambient or near ambient temperature and pressure, thus reducing energy consumption. This paper reviews the chemical absorption of carbon dioxide using amine scrubbing, caustic solvent scrubbing, and amino acid salt solution scrubbing. Each of these tech-niques for biogas upgrading is discussed. The paper concludes that an optimised implementation of the chemical absorption techniques for biogas upgrading requires further research.

  11. Optimizing the Binding Energy of Hydrogen on Nanostructured Carbon Materials through Structure Control and Chemical Doping

    Energy Technology Data Exchange (ETDEWEB)

    Jie Liu

    2011-02-01

    The DOE Hydrogen Sorption Center of Excellence (HSCoE) was formed in 2005 to develop materials for hydrogen storage systems to be used in light-duty vehicles. The HSCoE and two related centers of excellence were created as follow-on activities to the DOE Office of Energy Efficiency and Renewable Energy’s (EERE’s) Hydrogen Storage Grand Challenge Solicitation issued in FY 2003. The Hydrogen Sorption Center of Excellence (HSCoE) focuses on developing high-capacity sorbents with the goal to operate at temperatures and pressures approaching ambient and be efficiently and quickly charged in the tank with minimal energy requirements and penalties to the hydrogen fuel infrastructure. The work was directed at overcoming barriers to achieving DOE system goals and identifying pathways to meet the hydrogen storage system targets. To ensure that the development activities were performed as efficiently as possible, the HSCoE formed complementary, focused development clusters based on the following four sorption-based hydrogen storage mechanisms: 1. Physisorption on high specific surface area and nominally single element materials 2. Enhanced H2 binding in Substituted/heterogeneous materials 3. Strong and/or multiple H2 binding from coordinated but electronically unsatruated metal centers 4. Weak Chemisorption/Spillover. As a member of the team, our group at Duke studied the synthesis of various carbon-based materials, including carbon nanotubes and microporous carbon materials with controlled porosity. We worked closely with other team members to study the effect of pore size on the binding energy of hydrogen to the carbon –based materials. Our initial project focus was on the synthesis and purification of small diameter, single-walled carbon nanotubes (SWNTs) with well-controlled diameters for the study of their hydrogen storage properties as a function of diameters. We developed a chemical vapor deposition method that synthesized gram quantities of carbon nanotubes with

  12. 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,...

  13. A Density Functional Theory study of the chemical surface modification of {beta}-SiC nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Calvino, M.; Trejo, A.; Cuevas, J.L.; Carvajal, E.; Duchen, G.I. [Instituto Politecnico Nacional, ESIME-Culhuacan, Av. Santa Ana 1000, 04430, D.F. (Mexico); Cruz-Irisson, M., E-mail: irisson@ipn.mx [Instituto Politecnico Nacional, ESIME-Culhuacan, Av. Santa Ana 1000, 04430, D.F. (Mexico)

    2012-09-20

    The dependence of the electronic band structure and density of states on the chemical surface passivation of cubic porous silicon carbide (PSiC) is investigated by means of the ab-initio Density Functional Theory and the supercell method in which pores with different sizes and morphologies were created. The porous structures were modeled by removing atoms in the [0 0 1] direction producing two different surface chemistries; one with both Silicon (Si) and Carbon (C) atoms and the other with only Si or C atoms. The changes in the electronic band gap due to a Si-rich and C-rich phase in the porous surfaces are studied with two kind of surface passivation, one with hydrogen atoms and other with a combination between hydrogen and oxygen atoms. The calculations show that for the hydrogenated case, the band gap is larger for the C-rich than for the Si-rich case. For the partial oxygenation the tendency is contrary, by decreasing and increasing the band gap for the C-rich and Si-rich configuration, respectively, according to the percentage of oxygen in the pore surface.

  14. 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.

  15. 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.

  16. 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.

  17. Chemical attachment of functionalized multiwalled carbon nanotubes on glassy carbon electrode for electrocatalytic application

    International Nuclear Information System (INIS)

    Highlights: • FMWCNTs were covalently attached on GC surface with the aid of alkyldiamine. • The attached FMWCNTs were stable for a wide potential window due to the robust C−N bond. • The composite electrode was prepared by electropolymerizing thiadiazole on FMWCNTs. • The detection limit of 0.27 μM (S/N = 3) of GMP was achieved using composite modified electrode. - Abstract: The covalent attachment of acid functionalized multiwalled carbon nanotubes (FMWCNTs) on glassy carbon (GC) electrode using 1,8-octanediamine (OD) as a linker via carbodiimide chemistry was described. The attachment of FMWCNTs on GC electrode were confirmed by attenuated total reflectance Fourier transform infra-red (ATR-FT-IR) spectroscopy, Raman, scanning electron microscopy (SEM) and electrochemical impedance studies. Raman spectrum of FMWCNTs modified surface shows the characteristic G and D bands at 1563 cm−1 and 1340 cm−1, respectively. This confirmed the successful attachment of FMWCNTs on the OD modified GC surface. Further, the attachment of FMWCNTs on OD modified surface via amide linkage was confirmed from the observed characteristic peak at 1681 cm−1 in the ATR-FT-IR spectrum. The SEM images showed that the covalently attached FMWCNTs retained their morphology similar to powder and the average diameter of them was found to be 58 nm. Unlike modification of FMWCNTs on gold substrates with the aid of conventional thiol linkers (Au−S bond), modification of them by the present method was stable for a wide positive potential window due to the robust C−N bond. To demonstrate the electrochemical stability of the MWCNTs modified electrode at more positive potential, guanosine 5′-monophosphate (GMP) was selected as a representative probe because its oxidation occurs at more than 1 V. It was found that the FMWCNTs modified electrode not only showed a stable signal for GMP but also enhanced its oxidation current when compared to bare GC electrode. Further, the present

  18. 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.

  19. 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

  20. Influence of hydrogen on chemical vapour synthesis of different carbon nanostructures using propane as precursor and nickel as catalyst

    Indian Academy of Sciences (India)

    R K Sahoo; H Mamgain; C Jacob

    2014-10-01

    The role of hydrogen in the catalytic chemical vapour deposition of carbon nanotubes using sputtered nickel thin film as a catalyst is explained in this work. The growth of different carbon nanostructures with the variation in the precursor gas content was studied by keeping all other process parameters constant and using sputtered Ni thin film as a catalyst. The catalyst granule size, its external morphology and the resulting products were analysed. Carbon nanotubes (CNTs), carbon nanofibres (CNFs) and carbon nanoribbons (CNRs) were observed under different growth conditions. The different conditions of growth leading to form tubes, fibres or ribbons were analysed by varying the flow ratio of propane and hydrogen gas during the high temperature growth. Scanning and transmission electron microscopies confirmed the above structures under different growth conditions. The role of hydrogen on the surface passivation behaviour of the Ni catalyst and its correlative effect on the growth of carbon nanostructures is analysed. This direct approach can, in principle, be used to synthesize different types of carbon nanostructures by tailoring the hydrogen concentration.

  1. 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...

  2. The over-step coalescence of carbon atoms on copper surface in the CVD growth of graphene: density functional calculations

    Directory of Open Access Journals (Sweden)

    Yingfeng Li

    2013-05-01

    Full Text Available The ways in which carbon atoms coalesce over the steps on copper (111 surface are ascertained by density functional theory (DFT calculations in the context of chemical vapor deposition (CVD growth of graphene. Two strategies, (1 by putting carbon atoms on and under the steps separately and (2 by importing additional carbon atoms between the ones separated by the steps, have been attempted to investigate if an over-step coalescence of carbon atoms could take place. Based on analyses about the optimized configurations and adsorption energies of carbon atoms nearby the steps, as well as the energy evolution curve of the system throughout the geometry optimizations process, we determined the main way in which graphene grows over the steps continuously: the carbon atoms, adsorbed additionally on the locations between the already existing ones which are separated by the steps, link them (these carbon atoms separated by the steps together. The direct over-step coalescence of the carbon atoms separated by the steps is very difficult, although the energy barrier preventing their coalescence can be weakened by importing carbon atoms on and under the steps gradually. Our results imply potential applications in directing the fabrication of graphene with particular structure by controlling the surface topography of copper substrate.

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

    International Nuclear Information System (INIS)

    Approximately 250,000 tonnes of irradiated graphite waste exists worldwide and that quantity is expected to increase with decommissioning of Generation II reactors and deployment of Generation IV gas-cooled, graphite moderated reactors. This situation indicates the need for a graphite waste management strategy. Of greatest concern for long-term disposal of irradiated graphite is carbon-14 (C-14), with a half-life of 5730 years. Study of irradiated graphite from some nuclear reactors indicates C-14 is concentrated on the outer 5 mm of the graphite structure. The aim of the research presented last year and updated here is to identify the chemical form of C-14 in irradiated graphite and develop a practical method by which C-14 can be removed. A nuclear-grade graphite, NBG-18, and a high-surface-area graphite foam, POCOFoamR, were exposed to liquid nitrogen (to increase the quantity of C-14 precursor) and neutron-irradiated (1013 neutrons/cm2/s). Finer grained NBG-25 was not exposed to liquid nitrogen prior to irradiation at a neutron flux on the order of 1014 /cm2/s. Characterization of pre- and post-irradiation graphite was conducted to determine the chemical environment and quantity of C-14 and its precursors via the use of surface sensitive characterization techniques. Scanning Electron Microscopy (SEM) was used to evaluate the morphological features of graphite samples. The concentration, chemical composition, and bonding characteristics of C-14 and its precursors were determined through X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (SIMS), and Energy Dispersive X-ray Analysis Spectroscopy (EDX). Results of post-irradiation characterization of these materials indicate a variety of surface functional groups containing carbon, oxygen, nitrogen and hydrogen. During thermal treatment, irradiated graphite samples are heated in the presence of an inert carrier gas (with or without oxidant gas), which carries off gaseous products

  4. 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.

  5. 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

  6. Chemical and biological evolution of (U-14C)phenol sorbed on activated carbon

    International Nuclear Information System (INIS)

    Methods describing the chemical and biological evolution of (U-14C)phenol adsorbed on activated carbon are given with or without the use of bacteria. Without bacteria, the (U-14C)phenol initially adsorbed is not removed from the carbon after adding a solution of unlabelled phenol through the column for eight days. With bacteria, the (U-14C)phenol initially present, is removed (60-70%) from activated carbon with a solution containing unlabelled phenol, nitrogen and phosphorus. (author)

  7. Structural and dynamical properties of water on chemically modified surfaces: The role of the instantaneous surface

    Science.gov (United States)

    Bekele, Selemon; Tsige, Mesfin

    Surfaces of polymers such as atactic polystyrene (aPS) represent very good model systems for amorphous material surfaces. Such polymer surfaces are usually modified either chemically or physically for a wide range of applications that include friction, lubrication and adhesion. It is thus quite important to understand the structural and dynamical properties of liquids that come in contact with them to achieve the desired functional properties. Using molecular dynamics (MD) simulations, we investigate the structural and dynamical properties of water molecules in a slab of water in contact with atactic polystyrene surfaces of varying polarity. We find that the density of water molecules and the number distribution of hydrogen bonds as a function of distance relative to an instantaneous surface exhibit a structure indicative of a layering of water molecules near the water/PS interface. For the dynamics, we use time correlation functions of hydrogen bonds and the incoherent structure function for the water molecules. Our results indicate that the polarity of the surface dramatically affects the dynamics of the interfacial water molecules with the dynamics slowing down with increasing polarity. This work was supported by NSF Grant DMR1410290.

  8. 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)

  9. Surface Catalytic Efficiency of Advanced Carbon Carbon Candidate Thermal Protection Materials for SSTO Vehicles

    Science.gov (United States)

    Stewart, David A.

    1996-01-01

    The catalytic efficiency (atom recombination coefficients) for advanced ceramic thermal protection systems was calculated using arc-jet data. Coefficients for both oxygen and nitrogen atom recombination on the surfaces of these systems were obtained to temperatures of 1650 K. Optical and chemical stability of the candidate systems to the high energy hypersonic flow was also demonstrated during these tests.

  10. Equilibrium thermodynamic analyses of methanol production via a novel Chemical Looping Carbon Arrestor process

    International Nuclear Information System (INIS)

    Highlights: • A novel Chemical Looping Carbon Arrestor Reforming process has been developed. • Energy efficiency of the process is found to be ∼64–70%. • The process emits only about 0.14 mole of carbon dioxide per mole of methanol. • The process offers an efficient and low-emission option for methanol production. - Abstract: Methanol economy is considered as an alternative to hydrogen economy due to the better handling and storage characteristics of methanol fuel than liquid hydrogen. This paper is concerned about a comprehensive equilibrium thermodynamic analysis carried out on methanol production via an innovative Chemical Looping Carbon Arrestor/Reforming process being developed at the University of Newcastle in order to reduce both energy consumption and carbon emissions. The detailed simulation revealed thermodynamic limitations within the Chemical Looping Carbon Reforming process however on the other hand it also confirmed that the new concept is a low energy requirement and low emission option compared to other methanol production technologies. Specifically, the mass and energy balance study showed that the Chemical Looping Carbon Reforming process typically consumes approximately 0.76–0.77 mole methane, 0.25–0.27 mole carbon dioxide, 0.49–0.50 mole water, and 0.51 mole iron oxide (in a chemical looping manner) per mole of methanol production. Moreover, the energy efficiency of Chemical Looping Carbon Reforming process was found to be ∼64–70% and its emission profile was found as low as 0.14 mole carbon dioxide per mole of methanol, which is about 82–88% less than the conventional methanol production process and well below the emission levels of other emerging methanol production technologies

  11. 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.

  12. 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...

  13. 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.

  14. Reproducibly creating hierarchical 3D carbon to study the effect of Si surface functionalization on the oxygen reduction reaction

    Science.gov (United States)

    Zeng, Yuze; Flores, Jose F.; Shao, Yu-Cheng; Guo, Jinghua; Chuang, Yi-De; Lu, Jennifer Q.

    2016-06-01

    We report a new method to reproducibly fabricate functional 3D carbon structures directly on a current collector, e.g. stainless steel. The 3D carbon platform is formed by direct growth of upright arrays of carbon nanofiber bundles on a roughened surface of stainless steel via the seed-assisted approach. Each bundle consists of about 30 individual carbon nanofibers with a diameter of 18 nm on average. We have found that this new platform offers adequate structural integrity. As a result, no reduction of the surface area during downstream chemical functionalization was observed. With a fixed and reproducible 3D structure, the effect of the chemistry of the grafted species on the oxygen reduction reaction has been systematically investigated. This investigation reveals for the first time that non-conductive Si with an appropriate electronic structure distorts the carbon electronic structure and consequently enhances ORR electrocatalysis. The strong interface provides excellent electron connectivity according to electrochemical analysis. This highly reproducible and stable 3D platform can serve as a stepping-stone for the investigation of the effect of carbon surface functionalization on electrochemical reactions in general.We report a new method to reproducibly fabricate functional 3D carbon structures directly on a current collector, e.g. stainless steel. The 3D carbon platform is formed by direct growth of upright arrays of carbon nanofiber bundles on a roughened surface of stainless steel via the seed-assisted approach. Each bundle consists of about 30 individual carbon nanofibers with a diameter of 18 nm on average. We have found that this new platform offers adequate structural integrity. As a result, no reduction of the surface area during downstream chemical functionalization was observed. With a fixed and reproducible 3D structure, the effect of the chemistry of the grafted species on the oxygen reduction reaction has been systematically investigated. This

  15. Industrial Scale Synthesis of Carbon Nanotubes Via Fluidized Bed Chemical Vapor Deposition: A Senior Design Project

    Science.gov (United States)

    Smith, York R.; Fuchs, Alan; Meyyappan, M.

    2010-01-01

    Senior year chemical engineering students designed a process to produce 10 000 tonnes per annum of single wall carbon nanotubes (SWNT) and also conducted bench-top experiments to synthesize SWNTs via fluidized bed chemical vapor deposition techniques. This was an excellent pedagogical experience because it related to the type of real world design…

  16. Immobilization of redox mediators on functionalized carbon nanotube: A material for chemical sensor fabrication and amperometric determination of hydrogen peroxide

    Indian Academy of Sciences (India)

    D R Shobha Jeykumari; S Senthil Kumar; S Sriman Narayanan

    2005-10-01

    Chemical functionalization of single-walled carbon nanotubes with redox mediators, namely, toluidine blue and thionin have been carried out and the performance of graphite electrode modified with functionalized carbon nanotubes is described. Mechanical immobilization of functionalized single-walled nanotube (SWNT) on graphite electrode was achieved by gently rubbing the electrode surface on carbon nanotubes supported on a glass slide. The electrochemical behaviour of the modified electrodes was investigated by cyclic voltammetry. The SWNT-modified electrodes showed excellent electrocatalytic effect for the reduction of hydrogen peroxide. A decrease in overvoltage was observed as well as an enhanced peak current compared to a bare graphite electrode for the reduction of hydrogen peroxide. The catalytic current was found to be directly proportional to the amount of hydrogen peroxide taken.

  17. The chemical composition of carbon stars: The R-type stars

    OpenAIRE

    Zamora, Olga; Abia, Carlos; PLEZ, Bertrand; Dominguez, Inmaculada; Cristallo, Sergio

    2009-01-01

    The aim of this work is to shed some light on the problem of the formation of carbon stars of R-type from a detailed study of their chemical composition. We use high-resolution and high signal-to-noise optical spectra of 23 R-type stars selected from the Hipparcos catalogue. The chemical analysis is made using spectral synthesis in LTE and state-of-the-art carbon-rich spherical model atmospheres. We derive their CNO content (including the carbon isotopic ratio), average metallicity, lithium, ...

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

    Science.gov (United States)

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

    1974-01-01

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

  19. 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.

  20. Effects of rf power on chemical composition and surface roughness of glow discharge polymer films

    Science.gov (United States)

    Zhang, Ling; He, Xiaoshan; Chen, Guo; Wang, Tao; Tang, Yongjian; He, Zhibing

    2016-03-01

    The glow discharge polymer (GDP) films for laser fusion targets were successfully fabricated by plasma enhanced chemical vapor deposition (PECVD) at different radio frequency (rf) powers. The films were deposited using trans-2-butene (T2B) mixed with hydrogen as gas sources. The composition and state of plasma were diagnosed by quadrupole mass spectrometer (QMS) and Langmuir probe during the deposition process. The composition, surface morphology and roughness were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and white-light interferometer (WLI), respectively. Based on these observation and analyses, the growth mechanism of defects in GDP films were studied. The results show that, at low rf power, there is a larger probability for secondary polymerization and formation of multi-carbon C-H species in the plasma. In this case, the surface of GDP film turns to be cauliflower-like. With the increase of rf power, the degree of ionization is high, the relative concentration of smaller-mass hydrocarbon species increases, while the relative concentration of larger-mass hydrocarbon species decreases. At higher rf power, the energy of smaller-mass species are high and the etching effects are strong correspondingly. The GDP film's surface roughness shows a trend of decrease firstly and then increase with the increasing rf power. At rf power of 30 W, the surface root-mean-square roughness (Rq) drops to the lowest value of 12.8 nm, and no "void" defect was observed.

  1. Studies on surface chemical states of some metals and ceramics bombarded with energetic light-ions

    International Nuclear Information System (INIS)

    An electron spectroscopy was applied to the investigation of surface chemical state of some metals and ceramics bombarded with energetic light ions. Bombardments of keV-order hydrogen ions on Sc, Ti, V, Y, Zr and Nb induced the XPS core-line chemical shifts to higher binding-energies by 0.2 - 1.4 eV, the appearence of new photopeaks at 3.0 - 5.0 eV below the Fermi level. Although the peak energies are lower by 1 - 3 eV than those calculated for MeH2 (Me = metal) by molecular-orbital theory, the peaks are assigned to the metal-H bonds. The chemical shifts induced by bombarding hydrogen-ions were also observed in the X-ray-induced Auger electron spectra (XAES) For Y, Zr and Nb. The hydride layers produced by the ion-implantation are more stable at high temperature than those obtained by thermal synthesis, because of the surface damages which prevent thermal diffusion of hydrogen. In the case of hydrogen-ion bombarded SiC, carbon enriched layer was observed in the near surface region, while the surfaces of Si3N4 and SiO2 became silicon-rich after the bombardments. On the other hand, the bombardments of H2+, D2+ and He+-ions on TiC, TiN and TiO2 made their surfaces titanium-rich. At high fluences, the X/Ti (X = C, N, O) become constant. The energy dependences of the steady state values of the C/Ti ratios have maximum at 2 - 4 keV/atom of incident ion, while those of the N/Ti and O/Ti ratios decreased with the increase in the ion energies. Incident-energy dependences of the Ti+/X+ ratios determined by SIMS substantiate that the sputtering is responsible for the surface compositional change of the binary compounds. The surface of TiO2 was easily reduced to Ti2O3 by the H2+ and D2+, or to TiO by the He+ and Ar+-ion bombardments. The difference in the reduced species is correlated with the thermodynamical parameters of the corresponding reduction reactions. (J.P.N.)

  2. Surface Cleaning or Activation?Control of Surface Condition Prior to Thermo-Chemical Heat Treatment

    Institute of Scientific and Technical Information of China (English)

    Brigitte Haase; Juan Dong; Jens Heinlein

    2004-01-01

    Actual heat treatment processes must face increasing specifications with reference to process quality, safety and results in terms of reproducibility and repeatability. They can be met only if the parts' surface condition is controlled during manufacturing and, especially, prior to the treatment. An electrochemical method for the detection of a steel part's surface condition is presented, together with results, consequences, and mechanisms concerning surface pre-treatment before the thermochemical process. A steel surface's activity or passivity can be detected electrochemically, independently from the chemical background. The selected method was the recording of potential vs. time curves at small constant currents, using a miniaturized electrochemical cell, a (nearly) non-destructive electrolyte and a potentio-galvanostatic setup. The method enables to distinguish types of surface contamination which do not interfere with the thermochemical process, from passive layers which do and must be removed. Whereas some types of passive layers can be removed using conventional cleaning processes and agents, others are so stable that their effects can only be overcome by applying an additional activation pre-treatment, e.g. oxynitriding.

  3. 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

  4. 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.

  5. Charge effect of superparamagnetic iron oxide nanoparticles on their surface functionalization by photo-initiated chemical vapour deposition

    International Nuclear Information System (INIS)

    Diverse applications of superparamagnetic iron oxide nanoparticles (SPIONs) in the chemical and biomedical industry depend on their surface properties. In this paper, we investigate the effect of initial surface charge (bare, positively and negatively charged SPIONs) on the resulting physicochemical properties of the particles following treatment through photo-initiated chemical vapour deposition (PICVD). Transmission electron microscopy shows a nanometric polymer coating on the SPIONs and contact angle measurements with water demonstrate that their surface became non-polar following functionalization using PICVD. FTIR and XPS data confirm the change in the chemical composition of the treated SPIONs. Indeed, XPS data reveal an initial charge-dependent increase in the surface oxygen content in the case of treated SPIONs. The O/C percentage ratios of the bare SPIONs increase from 1.7 to 1.9 after PICVD treatment, and decrease from 1.7 to 0.7 in the case of negatively charged SPIONs. The ratio remains unchanged for positively charged SPIONs (1.7). This indicates that bare and negatively charged SPIONs showed opposite preference for the oxygen or carbon attachment to their surface during their surface treatment. These results reveal that both the surface charge and stereochemical effects have determinant roles in the polymeric coating of SPIONs with PICVD. Our findings suggest that this technique is appropriate for the treatment of nanoparticles.Graphical Abstract

  6. Charge effect of superparamagnetic iron oxide nanoparticles on their surface functionalization by photo-initiated chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Javanbakht, Taraneh [Ecole Polytechnique of Montreal, Department of Chemical Engineering (Canada); Laurent, Sophie; Stanicki, Dimitri [University of Mons, Laboratory of NMR and Molecular Imaging (Belgium); Raphael, Wendell; Tavares, Jason Robert, E-mail: jason.tavares@polymtl.ca [Ecole Polytechnique of Montreal, Department of Chemical Engineering (Canada)

    2015-12-15

    Diverse applications of superparamagnetic iron oxide nanoparticles (SPIONs) in the chemical and biomedical industry depend on their surface properties. In this paper, we investigate the effect of initial surface charge (bare, positively and negatively charged SPIONs) on the resulting physicochemical properties of the particles following treatment through photo-initiated chemical vapour deposition (PICVD). Transmission electron microscopy shows a nanometric polymer coating on the SPIONs and contact angle measurements with water demonstrate that their surface became non-polar following functionalization using PICVD. FTIR and XPS data confirm the change in the chemical composition of the treated SPIONs. Indeed, XPS data reveal an initial charge-dependent increase in the surface oxygen content in the case of treated SPIONs. The O/C percentage ratios of the bare SPIONs increase from 1.7 to 1.9 after PICVD treatment, and decrease from 1.7 to 0.7 in the case of negatively charged SPIONs. The ratio remains unchanged for positively charged SPIONs (1.7). This indicates that bare and negatively charged SPIONs showed opposite preference for the oxygen or carbon attachment to their surface during their surface treatment. These results reveal that both the surface charge and stereochemical effects have determinant roles in the polymeric coating of SPIONs with PICVD. Our findings suggest that this technique is appropriate for the treatment of nanoparticles.Graphical Abstract.

  7. Interface study between nanostructured tantalum nitride films and carbon nanotubes grown by chemical vapour deposition

    International Nuclear Information System (INIS)

    Highlights: • Our paper deals with the understanding of the carbon nanotubes growth parameters following the use of specific thin nitride buffer films. • For a large choice of buffer, we use ultra thin films elaborated by the very new method: high power pulsed magnetron sputtering; it allows a larger nitrogen incorporation in the films and lead to out of equilibrium phase formation. • Then by a multiscale investigation, developing a structural, a chemical and a morphology approach, we lead to some conclusion on the correlation between the phase transition for the buffer and morphology transition for the CNTs. • That is a new and deep approach. - Abstract: We present the role of nitrogen content in tantalum nitride ultra-thin buffers, on the carbon nanotubes (CNTs) growth by chemical vapour deposition at 850 °C, assisted by ferrocene as catalyst source. Tantalum nitride (TaNx) films with a very large range of concentration x = [0, 1.8] and various nanostructures, from amorphous Ta(N) to Ta3N5, were deposited by Highly Pulsed Plasma Magnetron Sputtering. The buffer films are characterized after heat treatment at 850 °C, and after the CNT growth, by wide angle X-ray scattering in grazing incidence and scanning electron microscopy. The CNT diameter explored by transition electron microscopy shows an all-out value for under stoichiometric thin films (Ta1-N1−δ, Ta3-N5−δ) and a minimum value just above the stoichiometric phases (Ta1-N1+δ, Ta3-N5+δ). Firstly one shows that the buffer films under the heat treatment present surface modification highly dependent on their initial state, which influences the catalyst particles diffusion. Secondly at the stoichiometric TaN phase we show that a specific ternary phase FeTa2O6 is formed at the interface CNT/buffer, not present in the other cases, leading to a special CNT growth condition

  8. Reaction from Dimethyl Carbonate to Diphenyl Carbonate. 1. Experimental Determination of the Chemical Equilibria

    NARCIS (Netherlands)

    Haubrock, J.; Raspe, M.; Versteeg, G.F.; Kooijman, H.A.; Taylor, R.; Hogendoorn, J.A.

    2008-01-01

    New experimental equilibrium data of the reaction of dimethyl carbonate (DMC) and phenol to methyl phenyl carbonate (MPC) and the subsequent disproportion and transesterification reaction of MPC to diphenyl carbonate (DPC) are presented and interpreted in terms of the reaction equilibrium coefficien

  9. 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.

  10. Development of international standards for surface analysis by ISO technical committee 201 on surface chemical analysis

    International Nuclear Information System (INIS)

    Full text: The International Organization for Standardization (ISO) established Technical Committee 201 on Surface Chemical Analysis in 1991 to develop documentary standards for surface analysis. ISO/TC 201 met first in 1992 and has met annually since. This committee now has eight subcommittees (Terminology, General Procedures, Data Management and Treatment, Depth Profiling, AES, SIMS, XPS, and Glow Discharge Spectroscopy (GDS)) and one working group (Total X-Ray Fluorescence Spectroscopy). Each subcommittee has one or more working groups to develop standards on particular topics. Australia has observer-member status on ISO/TC 201 and on all ISO/TC 201 subcommittees except GDS where it has participator-member status. I will outline the organization of ISO/TC 201 and summarize the standards that have been or are being developed. Copyright (1999) Australian X-ray Analytical Association Inc

  11. Preparation of porous bio-char and activated carbon from rice husk by leaching ash and chemical activation.

    Science.gov (United States)

    Ahiduzzaman, Md; Sadrul Islam, A K M

    2016-01-01

    Preparation porous bio-char and activated carbon from rice husk char study has been conducted in this study. Rice husk char contains high amount silica that retards the porousness of bio-char. Porousness of rice husk char could be enhanced by removing the silica from char and applying heat at high temperature. Furthermore, the char is activated by using chemical activation under high temperature. In this study no inert media is used. The study is conducted at low oxygen environment by applying biomass for consuming oxygen inside reactor and double crucible method (one crucible inside another) is applied to prevent intrusion of oxygen into the char. The study results shows that porous carbon is prepared successfully without using any inert media. The adsorption capacity of material increased due to removal of silica and due to the activation with zinc chloride compared to using raw rice husk char. The surface area of porous carbon and activated carbon are found to be 28, 331 and 645 m(2) g(-1) for raw rice husk char, silica removed rice husk char and zinc chloride activated rice husk char, respectively. It is concluded from this study that porous bio-char and activated carbon could be prepared in normal environmental conditions instead of inert media. This study shows a method and possibility of activated carbon from agro-waste, and it could be scaled up for commercial production. PMID:27536531

  12. Multiwalled Carbon Nanotube Forest Grown via Chemical Vapor Deposition from Iron Catalyst Nanoparticles, by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, David S.; Kanyal, Supriya S.; Madaan, Nitesh; Vail, Michael A.; Dadson, Andrew; Engelhard, Mark H.; Linford, Matthew R.

    2013-09-25

    Carbon nanotubes (CNTs) have unique chemical and physical properties. Herein, we report an XPS analysis of a forest of multiwalled CNTs using monochromatic Al Kα radiation. Survey scans show only one element: carbon. The carbon 1s peak is centered 284.5 eV. The C 1s envelope also shows the expected π → π* shake-up peak at ca. 291 eV. The valence band and carbon KVV Auger signals are presented. When patterned, the CNT forests can be used as a template for subsequent deposition of metal oxides to make thin layer chromatography plates.1-3

  13. Chemical analysis and molecular models for calcium-oxygen-carbon interactions in black carbon found in fertile Amazonian anthrosoils.

    Science.gov (United States)

    Archanjo, Braulio S; Araujo, Joyce R; Silva, Alexander M; Capaz, Rodrigo B; Falcão, Newton P S; Jorio, Ado; Achete, Carlos A

    2014-07-01

    Carbon particles containing mineral matter promote soil fertility, helping it to overcome the rather unfavorable climate conditions of the humid tropics. Intriguing examples are the Amazonian Dark Earths, anthropogenic soils also known as "Terra Preta de Índio'' (TPI), in which chemical recalcitrance and stable carbon with millenary mean residence times have been observed. Recently, the presence of calcium and oxygen within TPI-carbon nanoparticles at the nano- and mesoscale ranges has been demonstrated. In this work, we combine density functional theory calculations, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed infrared spectroscopy, and high resolution X-ray photoelectron spectroscopy of TPI-carbons to elucidate the chemical arrangements of calcium-oxygen-carbon groups at the molecular level in TPI. The molecular models are based on graphene oxide nanostructures in which calcium cations are strongly adsorbed at the oxide sites. The application of material science techniques to the field of soil science facilitates a new level of understanding, providing insights into the structure and functionality of recalcitrant carbon in soil and its implications for food production and climate change. PMID:24892495

  14. VERIFICATION OF THE EFFECT OF CONCRETE SURFACE PROTECTION ON THE PERMEABILITY OF ACID GASES USING ACCELERATED CARBONATION DEPTH TEST IN AN ATMOSPHERE OF 98% CO2

    OpenAIRE

    JIŘÍ NOVÁK; MICHAL STEHLÍK

    2011-01-01

    Carbonation is one of the corrosion processes negatively influencing the properties of mature concrete. It is caused by a chemical reaction between carbon dioxide infiltrating the surface of a concrete structure and the minerals of the mastic cement. The surface of a concrete structure can be protected from the effects of atmospheric CO2 by coating with modern waterborne epoxy dispersions. Out of the four types of dispersions tested (dispersion A – CHS Epoxy 200 V 55 + hardener Telalit 180, 2...

  15. Surface analysis of zinc-porphyrin functionalized carbon nano-onions.

    Science.gov (United States)

    Spampinato, Valentina; Ceccone, Giacomo; Giordani, Silvia

    2015-01-01

    Multishell fullerenes, known as carbon nano-onions (CNOs), are an interesting class of carbon-based nanomaterials. They display several unique properties, such as a large surface area to volume ratio, a low density, and a graphitic multilayer morphology, which have made them appealing for several applications in many fields, including biology. Chemical functionalization of CNOs dramatically enhances their solubility and attenuates their inflammatory properties, thereby increasing their applicability especially in the fields of biology and medicine. CNOs functionalized with fluorescent probes can be used for cellular imaging. In this article, detailed surface characterization of CNOs functionalized with a zinc porphyrin (ZnTPP) as the fluorescent probe is presented. In particular, time-of-flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy provide a detailed surface characterization of the organic functionalities introduced via "click chemistry" and clearly demonstrate the success of the CNOs functionalization process. XPS data reveal the presence of Zn and N, whilst ToF-SIMS is able to identify specific fragments related to the presence of the ZnTPP, such as the quasimolecular mass peak [C32N4H20Zn](+) and the molecular mass peak [C44N4H28Zn](+). Moreover, ions fragments deriving from the triazole ring formed by the click chemistry reaction have been identified by ToF-SIMS analysis, proving unambiguously the covalent binding of the fluorescent molecules to the CNOs surfaces. PMID:25708636

  16. Functional carbons and carbon nanohybrids for the catalytic conversion of biomass to renewable chemicals in the condensed phase

    Energy Technology Data Exchange (ETDEWEB)

    Matthiesen, John; Hoff, Thomas; Liu, Chi; Pueschel, Charles; Rao, Radhika; Tessonnier, Jean-Philippe

    2014-06-01

    The production of chemicals from lignocellulosic biomass provides opportunities to synthesize chemicals with new functionalities and grow a more sustainable chemical industry. However, new challenges emerge as research transitions from petrochemistry to biorenewable chemistry. Compared to petrochemisty, the selective conversion of biomass-derived carbohydrates requires most catalytic reactions to take place at low temperatures (< 300°C) and in the condensed phase to prevent reactants and products from degrading. The stability of heterogeneous catalysts in liquid water above the normal boiling point represents one of the major challenges to overcome. Herein, we review some of the latest advances in the field with an emphasis on the role of carbon materials and carbon nanohybrids in addressing this challenge.

  17. Functional carbons and carbon nanohybrids for the catalytic conversion of biomass to renewable chemicals in the condensed phase

    Institute of Scientific and Technical Information of China (English)

    John Matthiesen; Thomas Hoff; Chi Liu; Charles Pueschel; Radhika Rao; Jean-Philippe Tessonnier

    2014-01-01

    The production of chemicals from lignocellulosic biomass provides opportunities to synthesize chemicals with new functionalities and grow a more sustainable chemical industry. However, new challenges emerge as research transitions from petrochemistry to biorenewable chemistry. Com-pared to petrochemisty, the selective conversion of biomass-derived carbohydrates requires most catalytic reactions to take place at low temperatures (<300 °C) and in the condensed phase to pre-vent reactants and products from degrading. The stability of heterogeneous catalysts in liquid water above the normal boiling point represents one of the major challenges to overcome. Herein, we review some of the latest advances in the field with an emphasis on the role of carbon materials and carbon nanohybrids in addressing this challenge.

  18. 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...

  19. 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.

  20. 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.

  1. Carbon speciation in ash, residual waste and contaminated soil by thermal and chemical analyses.

    Science.gov (United States)

    Kumpiene, Jurate; Robinson, Ryan; Brännvall, Evelina; Nordmark, Désirée; Bjurström, Henrik; Andreas, Lale; Lagerkvist, Anders; Ecke, Holger

    2011-01-01

    Carbon in waste can occur as inorganic (IC), organic (OC) and elemental carbon (EC) each having distinct chemical properties and possible environmental effects. In this study, carbon speciation was performed using thermogravimetric analysis (TGA), chemical degradation tests and the standard total organic carbon (TOC) measurement procedures in three types of waste materials (bottom ash, residual waste and contaminated soil). Over 50% of the total carbon (TC) in all studied materials (72% in ash and residual waste, and 59% in soil) was biologically non-reactive or EC as determined by thermogravimetric analyses. The speciation of TOC by chemical degradation also showed a presence of a non-degradable C fraction in all materials (60% of TOC in ash, 30% in residual waste and 13% in soil), though in smaller amounts than those determined by TGA. In principle, chemical degradation method can give an indication of the presence of potentially inert C in various waste materials, while TGA is a more precise technique for C speciation, given that waste-specific method adjustments are made. The standard TOC measurement yields exaggerated estimates of organic carbon and may therefore overestimate the potential environmental impacts (e.g. landfill gas generation) of waste materials in a landfill environment. PMID:20630737

  2. The linkage between uranium, iron and carbon cycling. Processes at interfaces: evidences from combined solution chemical and spectroscopic studies

    International Nuclear Information System (INIS)

    Interfacial processes have a critical role in many reactions and phenomena in the environment, including mineral weathering, particle stability in surface waters, transport of chemical species and element cycling in natural environments. In order to predict the environmental impact of human activities such as uranium mining and radioactive waste disposal, it is necessary to understand the migration of actinides, uranium among them, in the environment. Iron oxides and oxyhydroxides are ubiquitous in nature and they are of particular interest due to their large capacity to sorb radionuclides onto their surface. The Fe and U cycles are also linked to the carbon one and aqueous carbonate plays a major role in the transport of radionuclides due to its high affinity to form complexes with hexavalent uranium. On the other hand, dissolved carbonate can compete for the sorption sites of the iron oxides, promoting the dissolution of these oxides and consequently increasing the mobility of the associated radionuclides in natural systems. Our understanding of how radionuclides impact the environment is dependent on our ability to measure chemical reactions at environmental interfaces. (orig.)

  3. Fibrous hydroxyapatite–carbon nanotube composites by chemical vapor deposition: In situ fabrication, structural and morphological characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kosma, Vassiliki; Tsoufis, Theodoros; Koliou, Theodora [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece); Kazantzis, Antonios [Department of Applied Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747AG Groningen (Netherlands); Beltsios, Konstantinos [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece); De Hosson, Jeff Th. M. [Department of Applied Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747AG Groningen (Netherlands); Gournis, Dimitrios, E-mail: dgourni@cc.uoi.gr [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece)

    2013-04-20

    Highlights: ► CNTs synthesized on fibrous HA surfaces supporting Fe–Co bi- metallic catalysts by CVD. ► CNTs are rooted on HA distinct needle-like monocrystals and needle spherulitic aggregates. ► Reaction temperature and metal loading are critical parameters for CNT production. -- Abstract: Fibrous hydroxyapatite (HA)–carbon nanotube composites were synthesized by the catalytic decomposition of acetylene over Fe–Co bimetallic catalysts supported on the fibrous HA. Two forms of fibrous HA (distinct needle-like monocrystals and spherulitic aggregates of needles) were synthesized using a simple precipitation method and loaded with bimetallic catalysts (from 2 up to 20 wt%) by a wet chemical impregnation method. The HA supported catalysts were evaluated for the in situ growth of carbon nanotubes using the catalytic chemical vapor deposition method. The effect of reaction temperature and metal loading on the yield, structural perfection and morphology of the carbon products were investigated using a combination of X-ray diffraction, thermal analysis, Raman spectroscopy and scanning and transmission electron microscopies. The results revealed that both the selection of the growing conditions and the metal loading determine the yield and overall quality of the synthesized carbon nanotubes, which exhibit high graphitization degree when synthesized in high yields.

  4. Fibrous hydroxyapatite–carbon nanotube composites by chemical vapor deposition: In situ fabrication, structural and morphological characterization

    International Nuclear Information System (INIS)

    Highlights: ► CNTs synthesized on fibrous HA surfaces supporting Fe–Co bi- metallic catalysts by CVD. ► CNTs are rooted on HA distinct needle-like monocrystals and needle spherulitic aggregates. ► Reaction temperature and metal loading are critical parameters for CNT production. -- Abstract: Fibrous hydroxyapatite (HA)–carbon nanotube composites were synthesized by the catalytic decomposition of acetylene over Fe–Co bimetallic catalysts supported on the fibrous HA. Two forms of fibrous HA (distinct needle-like monocrystals and spherulitic aggregates of needles) were synthesized using a simple precipitation method and loaded with bimetallic catalysts (from 2 up to 20 wt%) by a wet chemical impregnation method. The HA supported catalysts were evaluated for the in situ growth of carbon nanotubes using the catalytic chemical vapor deposition method. The effect of reaction temperature and metal loading on the yield, structural perfection and morphology of the carbon products were investigated using a combination of X-ray diffraction, thermal analysis, Raman spectroscopy and scanning and transmission electron microscopies. The results revealed that both the selection of the growing conditions and the metal loading determine the yield and overall quality of the synthesized carbon nanotubes, which exhibit high graphitization degree when synthesized in high yields

  5. Synthesis of iron-based chemical looping sorbents integrated with pH swing carbon mineral sequestration.

    Science.gov (United States)

    Kim, Hyung Ray; Lee, Dong Hyun; Fan, Liang-Shih; Park, Ah-Hyung Alissa

    2009-12-01

    The previously developed pH swing carbon mineral sequestration immobilizes the gaseous CO2 into a thermodynamically stable solid, MgCO3, using Mg-bearing minerals such as serpentine. This mineral carbonation technology is particularly promising since it generates value-added solid products: high surface area silica, iron oxide, and magnesium carbonate, while providing a safe and permanent storage option for CO2. By carefully controlling the pH of the system, these solids products can be produced with high purity. This study focuses on the synthesis of iron oxide particles as a chemical looping sorbent in order to achieve the integration between carbon capture and storage technologies. Since the solubility of Fe in aqueous phase is relatively low at neutral pH, the effect of the weak acid and chelating agents on the extraction of Fe from serpentine was investigated. The synthesized iron-based chemical looping sorbent was found to be as effective as commercially available iron oxide nanoparticles at converting syngas into high purity H2, while producing a sequestration-ready CO2 stream. PMID:19908801

  6. Effect of carbon embedding on the tribological properties of magnetic media surface with and without a perfluoropolyether (PFPE) layer

    International Nuclear Information System (INIS)

    Carbon embedding (≤1 nm) in the top surface of cobalt (∼100 nm) sputtered on a silicon surface is used as a surface modification technique to evaluate the tribological properties with or without an ultra-thin layer of perfluoropolyether (PFPE) lubricant. The carbon embedding is achieved using the filtered cathodic vacuum arc technique at an ion energy of 90 eV. Transport of ions in matter simulations, time-of-flight secondary ion spectroscopy, transmission electron microscopy and x-ray photoelectron spectroscopy (XPS) are used to study the carbon embedding profiles and surface chemical composition. The XPS results show that carbon embedding using the ion energy of 90 eV results in the formation of about 58 ± 6% of tetrahedral (sp3) carbon hybridization. Furthermore, the XPS results also show that the carbon embedding is effective in improving the anti-oxidation resistance of cobalt. Ball-on-disk tribological tests are conducted at a contact pressure of 0.26 GPa on the modified cobalt surface with or without the PFPE layer. It is observed that the average coefficient of friction is reduced considerably from a value of approximately 0.7 to 0.42 after the surface modification. The coefficient of friction is further reduced to ∼0.26 after the deposition of an ultra-thin layer of PFPE over the modified surface, which is lower than a friction coefficient of 0.4 from commercial media. The modified cobalt surface also shows much better wear life than the present day commercial media.

  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. Device for applying organic chemicals to lysimeter surfaces

    International Nuclear Information System (INIS)

    One of the aims of environmental research at the GSF Research Centre for the Environment and Health is to determine the behaviour of environmentally consequential chemicals in terrestrial ecosystems under as natural conditions as possible. The GSF lysimeter plant in Neuherberg permits studying the environmental behaviour of organic chemicals in different soils. Collaborators at GSF have developed a means of applying -14-marked substances in field lysimeters so as to be able to refind released chemicals, identify their conversion products and set up mass balances for the chemicals

  9. Microwave plasma-enhanced chemical vapour deposition growth of carbon nanostructures

    Directory of Open Access Journals (Sweden)

    Shivan R. Singh

    2010-05-01

    Full Text Available The effect of various input parameters on the production of carbon nanostructures using a simple microwave plasma-enhanced chemical vapour deposition technique has been investigated. The technique utilises a conventional microwave oven as the microwave energy source. The developed apparatus is inexpensive and easy to install and is suitable for use as a carbon nanostructure source for potential laboratory-based research of the bulk properties of carbon nanostructures. A result of this investigation is the reproducibility of specific nanostructures with the variation of input parameters, such as carbon-containing precursor and support gas flow rate. It was shown that the yield and quality of the carbon products is directly controlled by input parameters. Transmission electron microscopy and scanning electron microscopy were used to analyse the carbon products; these were found to be amorphous, nanotubes and onion-like nanostructures.

  10. 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.

  11. 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.

  12. Evaluation of the attachment, proliferation, and differentiation of osteoblast on a calcium carbonate coating on titanium surface

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yi; Jiang Tao; Zhou Yi; Zhang Zhen; Wang Zhejun [Key Laboratory for Oral Biomedical Engineering, Ministry of Education, School and Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan 430079 (China); Tong Hua; Shen Xinyu [College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); Wang Yining, E-mail: wang.yn@whu.edu.cn [Key Laboratory for Oral Biomedical Engineering, Ministry of Education, School and Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan 430079 (China)

    2011-07-20

    Titanium has been reported to have some limitations in dental and orthopaedic clinical application. This study described a coating process using a simple chemical method to prepare calcium carbonate coatings on smooth titanium (STi) and sandblasted and acid-etched titanium (SATi), and evaluated the biological response of the materials in vitro. The surfaces of STi, SATi, calcium carbonate coated STi (CC-STi) and calcium carbonate coated SATi (CC-SATi) were characterized for surface roughness, contact angles, surface morphology and surface chemistry. The morphology of MG63 cells cultured on the surfaces was observed by SEM and Immuno-fluorescence staining. Cell attachment/proliferation was assessed by MTT assay, and cell differentiation was evaluated by alkaline phosphatase (ALP) activity. MG63 was found to attach favorably to calcium carbonate crystals with longer cytoplasmic extensions on CC-STi and CC-SATi, resulting in lower cell proliferation but higher ALP activity when compared to STi and SATi respectively. Moreover, CC-SATi is more favorable than CC-STi in terms of biological response. In conclusion, the calcium carbonate coatings on titanium were supposed to improve the osteointegration process and stimulate osteoblast differentiation, especially in early stage. And this method could possibly be a feasible alternative option for future clinical application. Highlights: {yields} Calcium carbonate coatings were prepared on titanium substrates. {yields} The coating process is simple and cost-effective. {yields} Calcium carbonate coating could induce differentiation toward an osteoblastic phenotype. {yields} Calcium carbonate coating could enhance the osteointegration process especially in early stage.

  13. Evaluation of the attachment, proliferation, and differentiation of osteoblast on a calcium carbonate coating on titanium surface

    International Nuclear Information System (INIS)

    Titanium has been reported to have some limitations in dental and orthopaedic clinical application. This study described a coating process using a simple chemical method to prepare calcium carbonate coatings on smooth titanium (STi) and sandblasted and acid-etched titanium (SATi), and evaluated the biological response of the materials in vitro. The surfaces of STi, SATi, calcium carbonate coated STi (CC-STi) and calcium carbonate coated SATi (CC-SATi) were characterized for surface roughness, contact angles, surface morphology and surface chemistry. The morphology of MG63 cells cultured on the surfaces was observed by SEM and Immuno-fluorescence staining. Cell attachment/proliferation was assessed by MTT assay, and cell differentiation was evaluated by alkaline phosphatase (ALP) activity. MG63 was found to attach favorably to calcium carbonate crystals with longer cytoplasmic extensions on CC-STi and CC-SATi, resulting in lower cell proliferation but higher ALP activity when compared to STi and SATi respectively. Moreover, CC-SATi is more favorable than CC-STi in terms of biological response. In conclusion, the calcium carbonate coatings on titanium were supposed to improve the osteointegration process and stimulate osteoblast differentiation, especially in early stage. And this method could possibly be a feasible alternative option for future clinical application. Highlights: → Calcium carbonate coatings were prepared on titanium substrates. → The coating process is simple and cost-effective. → Calcium carbonate coating could induce differentiation toward an osteoblastic phenotype. → Calcium carbonate coating could enhance the osteointegration process especially in early stage.

  14. Comparison of chemical hydrogeology of the carbonate peninsulas of Florida and Yucatan

    Science.gov (United States)

    Back, W.; Hanshaw, B.B.

    1970-01-01

    Aquifers of the peninsulas of Florida and northern Yucatan are Tertiary marine carbonate formations showing many lithologic and faunal similarities. In addition, the tropical to subtropical climates of the two areas are similar, each having annual rainfall of about 1000 to 1500 mm. Despite similarities in these fundamental controls, contrasts in the hydrologic and geochemical systems are numerous and striking. For example, Florida has many rivers; Yucatan has none. Maximum thickness of fresh ground water in Florida is about 700 meters; in the Yucatan it is less than 70 meters. In Florida the gradient of the potentiometric surface averages about 1 meter per kilometer; in the Yucatan it is exceedingly low, averaging about 0.02 meter per kilometer. In Florida the chemical character of water changes systematically downgradient, owing to solution of minerals of the aquifer and corresponding increases in total dissolved solids, sulfate, calcium, and Mg-Ca ratio; in the Yucatan no downgradient change exists, and dominant processes controlling the chemical character of the water are solution of minerals and simple mixing of the fresh water and the body of salt water that underlies the peninsula at shallow depth. Hydrologic and chemical differences are caused in part by the lower altitude of the Yucatan plain. More important, however, these differences are due to the lack of an upper confining bed in Yucatan that is hydrologically equivalent to the Hawthorn Formation of Florida. The Hawthorn cover prevents recharge and confines the artesian water except where it is punctured by sinkholes, but sands and other unconsolidated sediments fill sinkholes and cavities and impede circulation. In the Yucatan the permeability of the entire section is so enormous that rainfall immediately infiltrates to the water table and then moves laterally to discharge areas along the coasts. ?? 1970.

  15. Decomposition Process of Alane and Gallane Compounds in Metal-Organic Chemical Vapor Deposition Studied by Surface Photo-Absorption

    Science.gov (United States)

    Yamauchi, Yoshiharu; Kobayashi, Naoki

    1992-09-01

    We used surface photo-absorption (SPA) to study trimethylamine alane (TMAA) and dimethylamine gallane (DMAG) decomposition processes on a substrate surface in metal-organic chemical vapor deposition. The decomposition onset temperatures of these group III hydride sources correspond to the substrate temperature at which the SPA reflectivity starts to increase during the supply of the group III source onto a group V stabilized surface. It was found that TMAA and DMAG start to decompose at about 150°C on an As-stabilized surface, which is much lower than the decomposition onsets of trialkyl Al and Ga compounds. Low temperature photoluminescence spectra exhibit dominant excitionic emissions for GaAs layers grown by DMAG at substrate temperatures above 400°C, indicating that carbon incorporation and the crystal quality deterioration due to incomplete decomposition on surface is much suppressed by using DMAG. A comparison of AlGaAs photoluminescence between layers by TMAA/triethylgallium and triethylaluminum/triethylgallium shows that the band-to-carbon acceptor transition is greatly reduced by using TMAA. TMAA and DMAG were verified to be promising group III sources for low-temperature and high-purity growth with low-carbon incorporation.

  16. 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

  17. Quantum Chemical Simulations Reveal Acetylene-Based Growth Mechanisms in the Chemical Vapor Deposition Synthesis of Carbon Nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Eres, Gyula [ORNL; Wang, Ying [Nagoya University, Japan; Gao, Xingfa [Institute of High Energy Physics, Chinese Academy of Sciences, China; Qian, Hu-Jun [Jilin University, Changchun; Ohta, Yasuhito [Fukui Institute of Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan; Wu, Xiaona [Nagoya University, Japan; Morokuma, Keiji [Fukui Institute of Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan; Irle, Stephan [WPI-Institute of Transformative Bio-Molecules and Department of Chemistry, Nagoya University, Japan

    2014-01-01

    Nonequilibrium quantum chemical molecular dynamics (QM/MD) simulation of early stages in the nucleation process of carbon nanotubes from acetylene feedstock on an Fe38 cluster was performed based on the density-functional tight-binding (DFTB) potential. Representative chemical reactions were studied by complimentary static DFTB and density functional theory (DFT) calculations. Oligomerization and cross-linking reactions between carbon chains were found as the main reaction pathways similar to that suggested in previous experimental work. The calculations highlight the inhibiting effect of hydrogen for the condensation of carbon ring networks, and a propensity for hydrogen disproportionation, thus enriching the hydrogen content in already hydrogen-rich species and abstracting hydrogen content in already hydrogen-deficient clusters. The ethynyl radical C2H was found as a reactive, yet continually regenerated species, facilitating hydrogen transfer reactions across the hydrocarbon clusters. The nonequilibrium QM/MD simulations show the prevalence of a pentagon-first nucleation mechanism where hydrogen may take the role of one arm of an sp2 carbon Y-junction. The results challenge the importance of the metal carbide formation for SWCNT cap nucleation in the VLS model and suggest possible alternative routes following hydrogen-abstraction acetylene addition (HACA)-like mechanisms commonly discussed in combustion synthesis.

  18. Chemically modified Si(111) surfaces simultaneously demonstrating hydrophilicity, resistance against oxidation, and low trap state densities

    Science.gov (United States)

    Brown, Elizabeth S.; Hlynchuk, Sofiya; Maldonado, Stephen

    2016-03-01

    Chemically modified Si(111) surfaces have been prepared through a series of wet chemical surface treatments that simultaneously show resistance towards surface oxidation, selective reactivity towards chemical reagents, and areal defect densities comparable to unannealed thermal oxides. Specifically, grazing angle attenuated total reflectance infrared and X-ray photoelectron (XP) spectroscopies were used to characterize allyl-, 3,4-methylenedioxybenzene-, or 4-[bis(trimethylsilyl)amino]phenyl-terminated surfaces and the subsequently hydroxylated surfaces. Hydroxylated surfaces were confirmed through reaction with 4-(trifluoromethyl)benzyl bromide and quantified by XP spectroscopy. Contact angle measurements indicated all surfaces remained hydrophilic, even after secondary backfilling with CH3sbnd groups. Surface recombination velocity measurements by way of microwave photoconductivity transients showed the relative defect-character of as-prepared and aged surfaces. The relative merits for each investigated surface type are discussed.

  19. Investigation of Black Carbon Effects on Precipitation and Surface Hydrology over the Western United States

    Science.gov (United States)

    Tseng, H. L. R.; Liou, K. N.; Gu, Y.; Fovell, R. G.; Li, Q.

    2015-12-01

    The current Exceptional Drought (US Drought Monitor) over the western United States warrants an in-depth investigation of possible causes of decreased precipitation and surface hydrology. Black carbon (BC), being the most radiatively-absorptive of any aerosol species, has the potential to semi-directly influence atmospheric physics and dynamics. Aloft, BC can exacerbate the aridity in some areas while increasing precipitation in other locations. On the surface, BC can also alter surface hydrology parameters such as surface runoff and snow water equivalent. In this study, we examine the role of BC and its possible effect on spatial precipitation redistribution and surface hydrology west of and over the Rocky Mountains from an online and coupled meteorological and chemical perspective. In particular, we utilize the Weather Research and Forecasting-Chemistry (WRF-Chem) model at the horizontal resolution of 30 km, employing the Fu-Liou-Gu plane-parallel radiation scheme and a three-dimensional radiation parameterization over mountainous areas to account for BC feedback with clouds, radiation, local circulation, and precipitation. Preliminary results of a January 2005 low pressure system show the inclusion of BC increases (decreases) precipitation on the windward (leeward) side of the Transverse and Peninsular Ranges, and the Sierra Nevada. Results also show BC contributes to an increase in surface runoff on the windward side of the Transverse and Peninsular Ranges, the Sierra Nevada, and Rocky Mountains, but a decrease in snow water equivalent over Sierra Nevada and Rocky Mountains.

  20. A facile electrodeposition process to fabricate corrosion-resistant superhydrophobic surface on carbon steel

    Science.gov (United States)

    Fan, Yi; He, Yi; Luo, Pingya; Chen, Xi; Liu, Bo

    2016-04-01

    Superhydrophobic Fe film with hierarchical micro/nano papillae structures is prepared on C45 steel surface by one-step electrochemical method. The superhydrophobic surface was measured with a water contact angle of 160.5 ± 0.5° and a sliding angle of 2 ± 0.5°. The morphology of the fabricated surface film was characterized by field emission scanning electron microscopy (FE-SEM), and the surface structure seems like accumulated hierarchical micro-nano scaled particles. Furthermore, according to the results of Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectroscopy (XPS), the chemical composition of surface film was iron complex with organic acid. Besides, the electrochemical measurements showed that the superhydrophobic surface improved the corrosion resistance of carbon steel in 3.5 wt.% NaCl solution significantly. The superhydrophobic layer can perform as a barrier and provide a stable air-liquid interface which inhibit penetration of corrosive medium. In addition, the as-prepared steel exhibited an excellent self-cleaning ability that was not favor to the accumulation of contaminants.

  1. Electrocatalysis of chemically synthesized noble metal nanoparticles on carbon electrodes

    DEFF Research Database (Denmark)

    Zhang, Ling; Ulstrup, Jens; Zhang, Jingdong

    on their interfacial interaction with the supporting electrodes. In this work we aim at chemical production of size and shape controlled, specifically 22 nm cubic Pd NPs, and further understanding of the Pd NPs as electrocatalysts at the nanometer scale using both scanning tunneling microscopy (STM......) will be investigated by electrochemical SPM. This study offers promise for development of new high-efficiency catalyst types with low-cost for fuel cell technology...

  2. Chemical doping of individual semiconducting carbon-nanotube ropes

    OpenAIRE

    Bockrath, Marc; Hone, J.; Zettl, A.; McEuen, Paul L.; Rinzler, Andrew G.; Smalley, Richard E.

    2000-01-01

    We report the effects of potassium doping on the conductance of individual semiconducting single-walled carbon nanotube ropes. We are able to control the level of doping by reversibly intercalating and de-intercalating potassium. Potassium doping changes the carriers in the ropes from holes to electrons. Typical values for the carrier density are found to be ∼100–1000 electrons/μm. The effective mobility for the electrons is μeff∼20–60 cm2 V-1 s-1, a value similar to that reported for the hol...

  3. 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

  4. 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.

  5. C1-carbon sources for chemical and fuel production by microbial gas fermentation.

    Science.gov (United States)

    Dürre, Peter; Eikmanns, Bernhard J

    2015-12-01

    Fossil resources for production of fuels and chemicals are finite and fuel use contributes to greenhouse gas emissions and global warming. Thus, sustainable fuel supply, security, and prices necessitate the implementation of alternative routes to the production of chemicals and fuels. Much attention has been focussed on use of cellulosic material, particularly through microbial-based processes. However, this is still costly and proving challenging, as are catalytic routes to biofuels from whole biomass. An alternative strategy is to directly capture carbon before incorporation into lignocellulosic biomass. Autotrophic acetogenic, carboxidotrophic, and methanotrophic bacteria are able to capture carbon as CO, CO2, or CH4, respectively, and reuse that carbon in products that displace their fossil-derived counterparts. Thus, gas fermentation represents a versatile industrial platform for the sustainable production of commodity chemicals and fuels from diverse gas resources derived from industrial processes, coal, biomass, municipal solid waste (MSW), and extracted natural gas. PMID:25841103

  6. 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

  7. Carbon stripping - a critical process step in chemical looping combustion of solid fuels

    Energy Technology Data Exchange (ETDEWEB)

    Kramp, M.; Thon, A.; Hartge, E.U.; Heinrich, S.; Werther, J. [Hamburg University of Technology, Institute of Solids Process Engineering and Particle Technology, Hamburg (Germany)

    2012-03-15

    In chemical looping combustion of solid fuels the well-mixed solids flow from the fuel reactor consisting of char, ash, and oxygen carrier particles cannot be completely separated into its constituents before it enters the air reactor. The slip of carbon will thus lead to char oxidation in the wrong reactor. Process simulation was applied to investigate the carbon stripping process in chemical looping combustion of solid fuels. Depending on the fuel choice, without carbon stripping CO{sub 2} capture rates below 50 % are calculated for 4 min of solids residence time in the fuel reactor. In a process with carbon stripper, however, CO{sub 2} capture rates exceeding 90 % can be achieved for both fuels investigated in this work. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. 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.

  9. Surface and near-surface passivation, chemical reaction, and Schottky barrier formation at ZnO surfaces and interfaces

    International Nuclear Information System (INIS)

    Using a combination of depth-resolved cathodoluminescence spectroscopy, electronic transport, and surface science techniques, we have demonstrated the primary role of native defects within ZnO single crystals as well as native defects created by metallization on metal-ZnO Schottky barrier heights and their ideality factors. Native defects and impurities resident within the ZnO depletion region as well as defects extending into the bulk from the intimate metal-ZnO interface contribute to barrier thinning of, carrier hopping across, and tunneling through these Schottky barriers. Chemical reactions at clean ZnO-metal interfaces lead to metal-specific eutectic or oxide formation with pronounced transport effects. These results highlight the importance of bulk crystal quality, surface cleaning, metal interaction, and post-metallization annealing for controlling Schottky barriers

  10. Vegetation change impacts on soil organic carbon chemical composition in subtropical forests.

    Science.gov (United States)

    Guo, Xiaoping; Meng, Miaojing; Zhang, Jinchi; Chen, Han Y H

    2016-01-01

    Changes in the chemical composition of soil organic carbon (SOC) might strongly affect the global carbon cycle as it controls the SOC decomposition rate. Vegetation change associated with long-term land use changes is known to strongly impact the chemical composition of SOC; however, data on the impacts of vegetation change following disturbance events of short durations and succession that occur frequently in forest ecosystems via diverse management objectives on SOC chemical composition are negligible. Here we examined the impacts of vegetation changes on the chemical composition of SOC by sampling soils of native broad-leaved forests, planted mixed broad-leaved and coniferous forests, and tea gardens in eastern China. We used nuclear magnetic resonance spectroscopy to quantify SOC chemical composition. We found that among all components of SOC chemical composition, alkyl carbon (C) and aryl C were more liable to change with vegetation than other SOC components. Soil pH was negatively correlated to the relative abundances of alkyl C and N-alkyl C, and Shannon's index of overstory plant species was positively correlated to the relative abundances of phenolic C and aromaticity. Our results suggest that vegetation changes following short disturbance events and succession may strongly alter SOC chemical composition in forest ecosystems. PMID:27403714

  11. Carbon diffusion in uncoated and titanium nitride coated iron substrates during microwave plasma assisted chemical vapor deposition of diamond

    International Nuclear Information System (INIS)

    Auger Electron Spectroscopy has been employed to investigate the effectiveness of thin films of TiN as barriers to carbon diffusion during Chemical Vapor Deposition (CVD) of diamond onto Fe substrates. Auger Depth Profiling was used to monitor the C concentration in the TiN layer, through the interface and into the substrate both before and after CVD diamond deposition. The results show that a layer of TiN only 250 Angstroems thick is sufficient to inhibit soot formation on the Fe surface and C diffusion into the Fe bulk. 14 refs., 4 figs

  12. 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...

  13. Effects of aluminium surface morphology and chemical modification on wettability

    DEFF Research Database (Denmark)

    Rahimi, Maral; Fojan, Peter; Gurevich, Leonid;

    2014-01-01

    -life aluminium surfaces of different morphology: unpolished aluminium, polished aluminium, and aluminium foil, were subjected to surface modification procedures which involved the formation of a layer of hydrophilic hyperbranched polyethyleneglycol via in situ polymerization, molecular vapour deposition of a...... monolayer of fluorinated silane, and a combination of those. The effect of these surface modification techniques on roughness and wettability of the aluminium surfaces was elucidated by ellipsometry, contact angle measurements and atomic force microscopy. We demonstrated that by employing different types of...

  14. Electro-Optical Properties of Carbon Nanotubes Obtained by High Density Plasma Chemical Vapor Deposition

    OpenAIRE

    Ana Paula Mousinho; Ronaldo D. Mansano

    2011-01-01

    In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a new concept of plasma generation: a planar coil is coupled to an RF system for plasma generation. This was used together with an electrostatic shield, for plasma densification, thereby obtaining high-density plasmas. The carbon nanotubes were deposited using pure methane plasmas. T...

  15. Purification of Single-walled Carbon Nanotubes Grown by a Chemical Vapour Deposition (CVD) Method

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A procedure for purification of single-walled carbon nanotubes(SWNTs) grown by the chemical vapour deposition (CVD) of carbon monooxide has been developed. Based on the result from TGA/DTA of as-prepared sample, the oxidation temperature was determined. The process included sonication, oxidation and acid washing steps. The purity and yield after purification were determined and estimated by TEM. Moreover, for the first time, a loop structure for CVD SWNTs has been observed.

  16. Spectroscopy of Individual Single-Walled Carbon Nanotubes and their Synthesis via Chemical Vapor Deposition

    OpenAIRE

    Kiowski, Oliver

    2008-01-01

    A chemical vapor deposition (CVD) reactor was designed, built and used to grow vertically and horizontally aligned carbon nanotube arrays. The as-grown nanotubes were investigated on a single tube level using nearinfrared photoluminescence (PL) microscopy as well as Raman, atomic force and scanning electron microscopy (SEM). For photoluminescence excitation (PLE) spectroscopy of individual, semiconducting single-walled carbon nanotubes (SWNTs), a specialized PL set-up was constructed.

  17. Growth of Large-Area Single- and Bi-Layer Graphene by Controlled Carbon Precipitation on Polycrystalline Ni Surfaces

    OpenAIRE

    Reina, Alfonso; Thiele, Stefan; Jia, Xiaoting; Bhaviripudi, Sreekar; Dresselhaus, Mildred S.; Schaefer, Juergen A.; Kong, Jing

    2009-01-01

    We report graphene films composed mostly of one or two layers of graphene grown by controlled carbon precipitation on the surface of polycrystalline Ni thin films during atmospheric chemical vapor deposition (CVD). Controlling both the methane concentration during CVD and the substrate cooling rate during graphene growth can significantly improve the thickness uniformity. As a result, one- or two- layer graphene regions occupy up to 87% of the film area. Single layer coverage accounts for 5%–...

  18. Evaluation of chemical and structural properties of germanium-carbon coatings deposited by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Jamali, Hossein, E-mail: h.jamali@mut-es.ac.ir; Mozafarinia, Reza; Eshaghi, Akbar

    2015-10-15

    Germanium-carbon coatings were deposited on silicon and glass substrates by plasma enhanced chemical vapor deposition (PECVD) using three different flow ratios of GeH{sub 4} and CH{sub 4} precursors. Elemental analysis, structural evaluation and microscopic investigation of coatings were performed using laser-induced breakdown spectroscopy (LIBS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. Based on the results, the coatings exhibited a homogeneous and dense structure free of pores with a very good adhesion to substrate. The structural evaluation revealed that the germanium-carbon coatings were a kind of a Ge-rich composite material containing the amorphous and crystalline germanium and amorphous carbon with the mixture of Ge–Ge, Ge–C, C–C, Ge–H and C–H bonds. The result suggested that the amorphisation of the coatings could be increased with raising CH{sub 4}:GeH{sub 4} flow rate ratio and subsequently increasing C amount incorporated into the coating. - Highlights: • Germanium-carbon coatings were prepared by PECVD technique. • The germanium-carbon coatings were a kind of composite material. • The amorphisation of the coatings were increased with raising CH{sub 4}:GeH{sub 4} flow ratio.

  19. Evaluation of chemical and structural properties of germanium-carbon coatings deposited by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Germanium-carbon coatings were deposited on silicon and glass substrates by plasma enhanced chemical vapor deposition (PECVD) using three different flow ratios of GeH4 and CH4 precursors. Elemental analysis, structural evaluation and microscopic investigation of coatings were performed using laser-induced breakdown spectroscopy (LIBS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. Based on the results, the coatings exhibited a homogeneous and dense structure free of pores with a very good adhesion to substrate. The structural evaluation revealed that the germanium-carbon coatings were a kind of a Ge-rich composite material containing the amorphous and crystalline germanium and amorphous carbon with the mixture of Ge–Ge, Ge–C, C–C, Ge–H and C–H bonds. The result suggested that the amorphisation of the coatings could be increased with raising CH4:GeH4 flow rate ratio and subsequently increasing C amount incorporated into the coating. - Highlights: • Germanium-carbon coatings were prepared by PECVD technique. • The germanium-carbon coatings were a kind of composite material. • The amorphisation of the coatings were increased with raising CH4:GeH4 flow ratio

  20. Energetic changes in the surface of activated carbons and relationship with Ni(II) adsorption from aqueous solution

    Science.gov (United States)

    Rodríguez-Estupiñan, Paola; Giraldo, Liliana; Moreno-Piraján, Juan Carlos

    2013-12-01

    This study investigated Ni(II) ion adsorption from aqueous solution on activated carbons obtained by chemically modifying the surface with the oxidizing agents nitric acid and hydrogen peroxide (CAGoxP and CAGoxN, respectively). The activated carbons were characterized by total acidity and basicity, pH at the point of charge zero determination and IR spectroscopy. Textural parameters such as the BET area and pore volumes were evaluated by gas adsorption. The BET area of the materials was between 816 and 876 m2 g-1. Additionally, the immersion enthalpies of the activated carbons in water and benzene were determined. The experimental results on adsorption in solution were adjusted to the Langmuir and Freundlich models, obtaining values for the monolayer capacity between 29.68 and 50.97 mg g-1, which indicates that the adsorption capacity depends largely on solid surface chemistry.

  1. Immobilization of carbon nanotubes on functionalized graphene film grown by chemical vapor deposition and characterization of the hybrid material

    Directory of Open Access Journals (Sweden)

    Prashanta Dhoj Adhikari

    2014-01-01

    Full Text Available We report the surface functionalization of graphene films grown by chemical vapor deposition and fabrication of a hybrid material combining multi-walled carbon nanotubes and graphene (CNT–G. Amine-terminated self-assembled monolayers were prepared on graphene by the UV-modification of oxidized groups introduced onto the film surface. Amine-termination led to effective interaction with functionalized CNTs to assemble a CNT–G hybrid through covalent bonding. Characterization clearly showed no defects of the graphene film after the immobilization reaction with CNT. In addition, the hybrid graphene material revealed a distinctive CNT–G structure and p–n type electrical properties. The introduction of functional groups on the graphene film surface and fabrication of CNT–G hybrids with the present technique could provide an efficient, novel route to device fabrication.

  2. Immobilization of carbon nanotubes on functionalized graphene film grown by chemical vapor deposition and characterization of the hybrid material

    International Nuclear Information System (INIS)

    We report the surface functionalization of graphene films grown by chemical vapor deposition and fabrication of a hybrid material combining multi-walled carbon nanotubes and graphene (CNT–G). Amine-terminated self-assembled monolayers were prepared on graphene by the UV-modification of oxidized groups introduced onto the film surface. Amine-termination led to effective interaction with functionalized CNTs to assemble a CNT–G hybrid through covalent bonding. Characterization clearly showed no defects of the graphene film after the immobilization reaction with CNT. In addition, the hybrid graphene material revealed a distinctive CNT–G structure and p–n type electrical properties. The introduction of functional groups on the graphene film surface and fabrication of CNT–G hybrids with the present technique could provide an efficient, novel route to device fabrication. (paper)

  3. From Detailed Description of Chemical Reacting Carbon Particles to Subgrid Models for CFD

    Directory of Open Access Journals (Sweden)

    Schulze S.

    2013-04-01

    Full Text Available This work is devoted to the development and validation of a sub-model for the partial oxidation of a spherical char particle moving in an air/steam atmosphere. The particle diameter is 2 mm. The coal particle is represented by moisture- and ash-free nonporous carbon while the coal rank is implemented using semi-global reaction rate expressions taken from the literature. The submodel includes six gaseous chemical species (O2, CO2, CO, H2O, H2, N2. Three heterogeneous reactions are employed, along with two homogeneous semi-global reactions, namely carbon monoxide oxidation and the water-gas-shift reaction. The distinguishing feature of the subgrid model is that it takes into account the influence of homogeneous reactions on integral characteristics such as carbon combustion rates and particle temperature. The sub-model was validated by comparing its results with a comprehensive CFD-based model resolving the issues of bulk flow and boundary layer around the particle. In this model, the Navier-Stokes equations coupled with the energy and species conservation equations were used to solve the problem by means of the pseudo-steady state approach. At the surface of the particle, the balance of mass, energy and species concentration was applied including the effect of the Stefan flow and heat loss due to radiation at the surface of the particle. Good agreement was achieved between the sub-model and the CFD-based model. Additionally, the CFD-based model was verified against experimental data published in the literature (Makino et al. (2003 Combust. Flame 132, 743-753. Good agreement was achieved between numerically predicted and experimentally obtained data for input conditions corresponding to the kinetically controlled regime. The maximal discrepancy (10% between the experiments and the numerical results was observed in the diffusion-controlled regime. Finally, we discuss the influence of the Reynolds number, the ambient O2 mass fraction and the ambient

  4. Chemical bonding in hard and elastic amorphous carbon-nitride films

    Science.gov (United States)

    Gammon, Wesley Jason

    In this study, the chemical bonding in hard and elastic amorphous carbon nitride (a-CNx) films is investigated with x-ray photoelectron spectroscopy (XPS) and 15N, 13C, and 1H nuclear magnetic resonance (NMR) spectroscopy. The films were deposited by DC Magnetron sputtering in a pure nitrogen discharge on Si(001) substrates at 300--400°C. Nanoindentation measurements reveal an elastic modulus of ˜50 GPa and a hardness of ˜5 GPa, thus confirming our films are highly elastic but resist plastic deformation. Our 13C NMR study demonstrates the absence of sp 3-bonded carbon in this material. Collectively, our N(1s) XPS, 13C NMR, and 15N NMR data suggest a film-bonding model that has an aromatic carbon structure with sp2-hybridized nitrogen incorporated in heterocyclic rings. We demonstrate that the nitrogen bonding is predominantly in configurations similar to those in pyridine and pyrrole. In addition, the data indicate that the a-CNx films prepared for this study have low hydrogen content, but are hydrophilic. Specifically, results from 15N and 13C cross polarization (CP) and 1H magic angle spinning (MAS) NMR experiments suggest that nitrogen sites are susceptible to protonation from water absorbed during sample preparation for the NMR experiments. The sensitivity of the surface of a-CNx to water absorption may impact tribological applications for this material. In accord with our XPS and NMR spectroscopic studies on a-CN x films, we propose a film-structure model consisting of buckled graphitic planes that are cross-linked together by sp2 hybridized carbons. The curvature and cross-linking is attributed to a type of compound defect, which is formed by placing a pentagon next to single-atom vacancy in a graphite layer. Our proposed film structure is called the pentagon-with-vacancy-defect (5VD) model. Using Hartree-Fock calculations, we show that the 5VD, film-structure model is compatible with our XPS, NMR, and nanoindentation measurements and with previous

  5. Chemical sputtering of carbon in Tore-Supra outboard pump limiter

    International Nuclear Information System (INIS)

    The use of a large amount of carbon in tokamaks induces two major problems mainly due to the chemical sputtering: erosion and tritium retention. In the Tore-Supra outboard pump limiter, the in situ chemical sputtering yield of the carbon neutralizer plate has been studied. Investigation of methane and heavier hydrocarbon (C2Dx and C3Dy) emission has been performed in ohmic and lower hybrid heated discharges, by means of mass spectrometry and optical spectroscopy. Simulation performed with a Monte Carlo code (BBQ) allows validation of the sputtering yield calculation method and show good agreement with experimental data

  6. Surface charging, discharging and chemical modification at a sliding contact

    DEFF Research Database (Denmark)

    Singh, Shailendra Vikram; Kusano, Yukihiro; Morgen, Per;

    2012-01-01

    Electrostatic charging, discharging, and consequent surface modification induced by sliding dissimilar surfaces have been studied. The surface-charge related phenomena were monitored by using a home-built capacitive, non-contact electrical probe, and the surface chemistry was studied by X...... are also able to comment on the behavior and the charge decay time in the ambient air-like condition, once the sliding contact is discontinued. XPS analysis showed a marginal deoxidation effect on the polyester disks due to the charging and discharging of the surfaces. Moreover, these XPS results...

  7. Effect of chemical treatment on the thermoelectric properties of single walled carbon nanotube networks

    Energy Technology Data Exchange (ETDEWEB)

    Piao, Mingxing; Alam, Mina Rastegar; Kim, Gyutae; Dettlaff-Weglikowska, Urszula; Roth, Siegmar [School of Electrical Engineering, WCU Flexible Nano-Systems, Korea University, Seoul (Korea, Republic of)

    2012-12-15

    Carbon nanotube networks showing superior electric properties, high chemical stability, strong mechanical properties, and flexibility are also known to exhibit thermoelectric effects. However, the experimental thermoelectric figure of merit, ZT, of pristine carbon nanotubes is typically in the range of 10{sup -3}-10{sup -2}, which is still not attractive for thermal energy conversion applications. In this work, we show possible ways to improve the thermoelectric properties of single walled carbon nanotubes (SWCNTs) by means of chemical treatments. In this study, we primarily investigated the effect of chemical treatment on the electrical conductivity and thermoelectric power (TEP) of the entangled network of nanotubes, also, known as ''buckypaper''. This chemical treatment increased the electrical conductivity due to p-type doping, thereby, showing a decrease in the TEP given by the Seebeck coefficient, whereas the n-type dopants changed the sign and value of the TEP from about 40 to -40 {mu}V K{sup -1}. Neutral polymers, in terms of doping, such as PVDF, PMMA, PVA, PS, and PC, were expected to hinder phonon transport through the nanotube network, increasing the Seebeck coefficient up to ca. 50 {mu}V K{sup -1}. Our results reveal the importance of chemical doping determining the sign and the magnitude of the TEP, and role of the polymer matrix in the development of more effective thermoelectric composites based on carbon nanotubes. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Effect of chemical treatment on the thermoelectric properties of single walled carbon nanotube networks

    International Nuclear Information System (INIS)

    Carbon nanotube networks showing superior electric properties, high chemical stability, strong mechanical properties, and flexibility are also known to exhibit thermoelectric effects. However, the experimental thermoelectric figure of merit, ZT, of pristine carbon nanotubes is typically in the range of 10-3-10-2, which is still not attractive for thermal energy conversion applications. In this work, we show possible ways to improve the thermoelectric properties of single walled carbon nanotubes (SWCNTs) by means of chemical treatments. In this study, we primarily investigated the effect of chemical treatment on the electrical conductivity and thermoelectric power (TEP) of the entangled network of nanotubes, also, known as ''buckypaper''. This chemical treatment increased the electrical conductivity due to p-type doping, thereby, showing a decrease in the TEP given by the Seebeck coefficient, whereas the n-type dopants changed the sign and value of the TEP from about 40 to -40 μV K-1. Neutral polymers, in terms of doping, such as PVDF, PMMA, PVA, PS, and PC, were expected to hinder phonon transport through the nanotube network, increasing the Seebeck coefficient up to ca. 50 μV K-1. Our results reveal the importance of chemical doping determining the sign and the magnitude of the TEP, and role of the polymer matrix in the development of more effective thermoelectric composites based on carbon nanotubes. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Surface chemical composition analysis of heat-treated bamboo

    Science.gov (United States)

    Meng, Fan-dan; Yu, Yang-lun; Zhang, Ya-mei; Yu, Wen-ji; Gao, Jian-min

    2016-05-01

    In this study, the effect of heat treatment on the chemical composition of bamboo slivers was studied. The chemical properties of the samples were examined by chemical analysis. Results showed a decrease in the contents of holocellulose and α-cellulose, as well as an increase in the contents of lignin and extractives. Changes in the chemical structure of bamboo components were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). FTIR spectroscopy results indicated that hemicellulose contents decrease, whereas lignin contents increase after heat treatment. Ester formation linked to lignin decreased the hygroscopicity of the bamboo samples and consequently improved their dimensional stability and durability. XPS spectroscopy results showed that hemicelluloses and celluloses are relatively more sensitive to the heating process than lignin. As a consequence, hemicellulose and cellulose contents decreased, whereas lignin contents increased during heat treatment. The results obtained in this study provide useful information for the future utilization of heat-treated bamboo.

  10. Chemical preparation and shock wave compression of carbon nitride precursors

    International Nuclear Information System (INIS)

    Two synthetic routes have been developed to produce high-molecular-weight organic precursors containing a high weight fraction of nitrogen. One of the precursors is a pyrolysis residue of melamine-formaldehyde resin. The second precursor is the byproduct of an unusual low-temperature combustion reaction of tetrazole and its sodium salt. These precursors have been shock compressed under typical conditions for diamond and wurtzite boron nitride synthesis in an attempt to recover a new ultrahard carbon nitride. The recovered material has been analyzed by X-ray diffraction, FTIR, and Raman microprobe analysis. Diamond is present in the recovered material. This diamond is well ordered relative to diamond shock synthesized from carbonaceous starting materials

  11. Numerical simulation of isothermal chemical vapor infiltration process in fabrication of carbon-carbon composites by finite element method

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The chemical vapor infiltration process in fabrication of carbon-carbon composites is highly inefficient and requires long processing time. These limitations add considerably to the cost of fabrication and restrict the application of this material. Efforts have been made to study the CVI process in fabrication of carbon-carbon composites by computer simulation and predict the process parameters, density, porosity, etc. According to the characteristics of CVI process, the basic principle of FEM and mass transport, the finite element model has been established. Incremental finite element equations and the elemental stiffness matrices have been derived for the first time. The finite element program developed by the authors has been used to simulate the ICVI process in fabrication of carbon-carbon composites. Computer color display of simulated results can express the densification and distributions of density and porosity in preform clearly. The influence of process parameters on the densification of preform has been analyzed. The numerically simulated and experimental results give a good agreement.

  12. 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

  13. Synthesis of carbon nanotube array using corona discharge plasma-enhanced chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A corona discharge plasma-enhanced chemical vapor deposition with the features of atmospheric pressure and low temperature has been developed to synthesize the carbon nanotube array. The array was synthesized from methane and hydrogen mixture in anodic aluminum oxide template channels in that cobalt was electrodeposited at the bottom. The characterization results by the scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy indicate that the array consists of carbon nanotubes with the diameter of about 40 nm and the length of more than 4 -m, and the carbon nanotubes are mainly restrained within the channels of templates.

  14. Growth of straight carbon nanotubes by simple thermal chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    ZOU Xiao-ping; H. ABE; T. SHIMIZU; A. ANDO; H. TOKUMOTO; ZHU Shen-ming; ZHOU Hao-shen

    2006-01-01

    Straight carbon nanotubes (CNTs) were achieved by simple thermal chemical vapor deposition(STCVD) catalyzed by Mo-Fe alloy catalyst on silica supporting substrate at 700 ℃. High-resolution transmission electron microscopy images show that the straight CNTs are well graphitized with no attached amorphous carbon. Mo-Fe alloy catalyst particles play a very crucial role in the growth of straight CNTs. The straight carbon nanotubes contain much less defects than the curved nanotubes and might have potential applications for nanoelectrical devices in the future. The simple synthesis of straight CNTs may have benefit for large-scale productions.

  15. Electromechanical Behavior of Chemically Reduced Graphene Oxide and Multi-walled Carbon Nanotube Hybrid Material

    OpenAIRE

    Benchirouf, Abderrahmane; Müller, Christian; Kanoun, Olfa

    2016-01-01

    In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content,...

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

    Institute of Scientific and Technical Information of China (English)

    马旭村; 徐贵昌; 王恩哥

    2000-01-01

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

  17. Ion-radical intermediates of the radiation-chemical transformations of organic carbonates

    Science.gov (United States)

    Shiryaeva, Ekaterina S.; Sosulin, Ilya S.; Saenko, Elizaveta V.; Feldman, Vladimir I.

    2016-07-01

    The spectral features and reactions of ion-radical intermediates produced from organic carbonates in low-temperature matrices were investigated by EPR spectroscopy and quantum-chemical calculations. It was shown that radical cations of diethyl carbonate and dimethyl carbonate underwent intramolecular hydrogen transfer to yield alkyl-type species, as was suggested previously. Meanwhile, radical cation of EC demonstrates a ring cleavage even at 77 K, while radical cation of PC is probably intrinsically stable and undergo an ion-molecule reaction with a neighboring neutral molecule in dimers or associates. Radical anions were obtained in glassy matrices of diethyl ether or perdeuteroethanol. The radical anions of linear carbonates show photoinduced fragmentation to yield the corresponding alkyl radicals; such process may also occur directly under radiolysis. Radical anions of cyclic carbonates are relatively stable and yield only trace amounts of fragmentation products under similar conditions.

  18. 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.

  19. Chemical and structural properties of carbonaceous products obtained by hydrothermal carbonization of saccharides.

    Science.gov (United States)

    Sevilla, Marta; Fuertes, Antonio B

    2009-01-01

    Carbon-rich-quick scheme: A carbon-rich solid product made up of uniform micrometer-sized spheres of tunable diameter has been synthesized by the hydrothermal carbonization of saccharides. These microspheres possess a core-shell chemical structure based on the different nature of the oxygen functionalities between the core and the outer layer (see figure).A carbon-rich solid product, here denoted as hydrochar, has been synthesized by the hydrothermal carbonization of three different saccharides (glucose, sucrose, and starch) at temperatures ranging from 170 to 240 degrees C. This material is made up of uniform spherical micrometer-sized particles that have a diameter in the 0.4-6 mum range, which can be modulated by modifying the synthesis conditions (i.e., the concentration of the aqueous saccharide solution, the temperature of the hydrothermal treatment, the reaction time, and type of saccharide). The formation of the carbon-rich solid through the hydrothermal carbonization of saccharides is the consequence of dehydration, condensation, or polymerization and aromatization reactions. The microspheres thus obtained possess, from a chemical point of view, a core-shell structure consisting of a highly aromatic nucleus (hydrophobic) and a hydrophilic shell containing a high concentration of reactive oxygen functional groups (i.e., hydroxyl/phenolic, carbonyl, or carboxylic). PMID:19248078

  20. 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.)

  1. Effects of aluminium surface morphology and chemical modification on wettability

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, M., E-mail: mar@sbi.aau.dk [Department of Energy and Environment, Danish Building Research Institute, Aalborg University, A.C. Meyers Vænge 15, 2450 København SV (Denmark); Fojan, P.; Gurevich, L. [Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4, DK-9220 Aalborg East (Denmark); Afshari, A. [Department of Energy and Environment, Danish Building Research Institute, Aalborg University, A.C. Meyers Vænge 15, 2450 København SV (Denmark)

    2014-03-01

    Highlights: • Successful surface modification procedures on aluminium samples were performed involving formation of the layer of hydrophilic hyperbranched polyethyleneglycol (PEG) via in situ polymerization, molecular vapour deposition of a monolayer of fluorinated silane, and a combination of those. • The groups of surfaces with hydrophobic behavior were found to follow the Wenzel model. • A transition from Cassie–Baxter's to Wenzel's regime was observed due to changing of the surface roughness upon mechanical polishing in aluminium samples. - Abstract: Aluminium alloys are some of the predominant metals in industrial applications such as production of heat exchangers, heat pumps. They have high heat conductivity coupled with a low specific weight. In cold working conditions, there is a risk of frost formation on the surface of aluminium in the presence of water vapour, which can lead to the deterioration of equipment performance. This work addresses the methods of surface modification of aluminium and their effect of the underlying surface morphology and wettability, which are the important parameters for frost formation. Three groups of real-life aluminium surfaces of different morphology: unpolished aluminium, polished aluminium, and aluminium foil, were subjected to surface modification procedures which involved the formation of a layer of hydrophilic hyperbranched polyethyleneglycol via in situ polymerization, molecular vapour deposition of a monolayer of fluorinated silane, and a combination of those. The effect of these surface modification techniques on roughness and wettability of the aluminium surfaces was elucidated by ellipsometry, contact angle measurements and atomic force microscopy. We demonstrated that by employing different types of surface modifications the contact angle of water droplets on aluminium samples can be varied from 12° to more than 120°. A crossover from Cassie–Baxter to Wenzel regime upon changing the surface

  2. Chemical imaging of surfaces with the scanning electrochemical microscope.

    Science.gov (United States)

    Bard, A J; Fan, F R; Pierce, D T; Unwin, P R; Wipf, D O; Zhou, F

    1991-10-01

    Scanning electrochemical microscopy is a scanning probe technique that is based on faradaic current changes as a small electrode is moved across the surface of a sample. The images obtained depend on the sample topography and surface reactivity. The response of the scanning electrochemical microscope is sensitive to the presence of conducting and electroactive species, which makes it useful for imaging heterogeneous surfaces. The principles and instrumentation used to obtain images and surface reaction-kinetic information are discussed, and examples of applications to the study of electrodes, minerals, and biological samples are given. PMID:17739954

  3. Effects of aluminium surface morphology and chemical modification on wettability

    Science.gov (United States)

    Rahimi, M.; Fojan, P.; Gurevich, L.; Afshari, A.

    2014-03-01

    Aluminium alloys are some of the predominant metals in industrial applications such as production of heat exchangers, heat pumps. They have high heat conductivity coupled with a low specific weight. In cold working conditions, there is a risk of frost formation on the surface of aluminium in the presence of water vapour, which can lead to the deterioration of equipment performance. This work addresses the methods of surface modification of aluminium and their effect of the underlying surface morphology and wettability, which are the important parameters for frost formation. Three groups of real-life aluminium surfaces of different morphology: unpolished aluminium, polished aluminium, and aluminium foil, were subjected to surface modification procedures which involved the formation of a layer of hydrophilic hyperbranched polyethyleneglycol via in situ polymerization, molecular vapour deposition of a monolayer of fluorinated silane, and a combination of those. The effect of these surface modification techniques on roughness and wettability of the aluminium surfaces was elucidated by ellipsometry, contact angle measurements and atomic force microscopy. We demonstrated that by employing different types of surface modifications the contact angle of water droplets on aluminium samples can be varied from 12° to more than 120°. A crossover from Cassie-Baxter to Wenzel regime upon changing the surface roughness was also observed.

  4. 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.

  5. 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.

  6. 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.

  7. Common Wet Chemical Agents for Purifying Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Rasel Das

    2014-01-01

    Full Text Available Purification and functionalization of multiwalled carbon nanotubes (MWCNTs are challenging but vital for their effective applications in various fields including water purification technologies, optoelectronics, biosensors, fuel cells, and electrode arrays. The currently available purification techniques, often complicated and time consuming, yielded shortened and curled MWCNTs that are not suitable for applications in certain fields such as membrane technologies, hybrid catalysis, optoelectronics, and sensor developments. Here we described the H2O2 synergy on the actions of HCl and KOH in purifying and functionalizing pristine MWCNTs. The method (HCl/H2O2 showed 100% purification yield as compared to HCl and KOH/H2O2 with purification yields 93.46 and 3.92%, respectively. We probed the findings using transmission electron microscope, energy dispersive X-ray spectroscope, attenuated total reflectance infrared spectroscope, Raman spectroscope, thermal gravimetric analysis, and X-ray powder diffraction. The study is a new avenue for simple, rapid, low cost, and scalable purification of pristine MWCNTs for application in versatile fields.

  8. Chemical sensors using coated or doped carbon nanotube networks

    Science.gov (United States)

    Li, Jing (Inventor); Meyyappan, Meyya (Inventor)

    2010-01-01

    Methods for using modified single wall carbon nanotubes ("SWCNTs") to detect presence and/or concentration of a gas component, such as a halogen (e.g., Cl.sub.2), hydrogen halides (e.g., HCl), a hydrocarbon (e.g., C.sub.nH.sub.2n+2), an alcohol, an aldehyde or a ketone, to which an unmodified SWCNT is substantially non-reactive. In a first embodiment, a connected network of SWCNTs is coated with a selected polymer, such as chlorosulfonated polyethylene, hydroxypropyl cellulose, polystyrene and/or polyvinylalcohol, and change in an electrical parameter or response value (e.g., conductance, current, voltage difference or resistance) of the coated versus uncoated SWCNT networks is analyzed. In a second embodiment, the network is doped with a transition element, such as Pd, Pt, Rh, Ir, Ru, Os and/or Au, and change in an electrical parameter value is again analyzed. The parameter change value depends monotonically, not necessarily linearly, upon concentration of the gas component. Two general algorithms are presented for estimating concentration value(s), or upper or lower concentration bounds on such values, from measured differences of response values.

  9. OPTIMIZATION OF CHEMICALS USE FOR HIGHLY FILLED MECHANICAL GRADE PAPERS WITH PRECIPITATED CALCIUM CARBONATE

    Directory of Open Access Journals (Sweden)

    Yizhou Sang

    2011-02-01

    Full Text Available Response surface methodology was used with four factors to screen for the best starch and optimize the use of chemicals in order to maximize precipitated calcium carbonate (PCC filler retention in a peroxide-bleached TMP suspension. Three commercial starches were used in conjunction with colloidal silica and flocculant. The PCC loading level and the interactions between PCC level, starch, flocculant, and silica were investigated, and empirical models were constructed. The empirical process models were then employed to predict the retention and drainage. It was found that medium-charged cationic starch (S858 gave the highest total and filler retention, whereas high-charged cationic starch (S880 resulted in the best drainage. The ash content of the handsheet can be pushed up to 40% using the retention system with medium (S858 and high (S880 charged cationic starch. The high-charged cationic starch (S880 gave stronger paper, probably because of its higher affinity with the fiber and fines.

  10. Surface modification of nitrogen-doped carbon nanotubes by ozone via atomic layer deposition

    International Nuclear Information System (INIS)

    The use of ozone as an oxidizing agent for atomic layer deposition (ALD) processes is rapidly growing due to its strong oxidizing capabilities. However, the effect of ozone on nanostructured substrates such as nitrogen-doped multiwalled carbon nanotubes (NCNTs) and pristine multiwalled carbon nanotubes (PCNTs) are not very well understood and may provide an avenue toward functionalizing the carbon nanotube surface prior to deposition. The effects of ALD ozone treatment on NCNTs and PCNTs using 10 wt. % ozone at temperatures of 150, 250, and 300 °C are studied. The effect of ozone pulse time and ALD cycle number on NCNTs and PCNTs was also investigated. Morphological changes to the substrate were observed by scanning electron microscopy and high resolution transmission electron microscopy. Brunauer-Emmett-Teller measurements were also conducted to determine surface area, pore size, and pore size distribution following ozone treatment. The graphitic nature of both NCNTs and PCNTs was determined using Raman analysis while x-ray photoelectron spectroscopy (XPS) was employed to probe the chemical nature of NCNTs. It was found that O3 attack occurs preferentially to the outermost geometric surface of NCNTs. Our research also revealed that the deleterious effects of ozone are found only on NCNTs while little or no damage occurs on PCNTs. Furthermore, XPS analysis indicated that ALD ozone treatment on NCNTs, at elevated temperatures, results in loss of nitrogen content. Our studies demonstrate that ALD ozone treatment is an effective avenue toward creating low nitrogen content, defect rich substrates for use in electrochemical applications and ALD of various metal/metal oxides

  11. Alignment of liquid crystals : on geometrically and chemically modified surfaces

    NARCIS (Netherlands)

    Zhang, Jing

    2013-01-01

    This thesis consists of two main parts. The first part describes a new model to explain the complex role of surface materials and surface geometry in the liquid crystal (LC) alignment, which has been a subject of intensive debate over the last 40 years. The second part presents a potentially cost ef

  12. An efficient synthesis of graphenated carbon nanotubes over the tailored mesoporous molecular sieves by chemical vapor deposition

    International Nuclear Information System (INIS)

    Highlights: ► Tailored 3D cubic Ni/KIT-6 with large pores was synthesized successfully. ► The new hybrid g-CNTs in large scale were synthesized using Ni/KIT-6 by CVD method. ► The use of mesoporous material by CVD method would be an ideal choice to prepare g-CNTs at reasonable cost. ► This type of g-CNTs might be a new avenue for nano-electronic applications. - Abstract: The new hybrid of graphenated carbon nanotubes (g-CNTs) was superior to either CNTs or graphene. Mesoporous 3D cubic Ni/KIT-6 were synthesized hydrothermally through organic template route and then were used as catalytic template for the production of g-CNTs using acetylene as a carbon precursor by chemical vapor deposition (CVD) method. The deposited new hybrid carbon materials were purified and analyzed by various physico-chemical techniques such as XRD, TGA, SEM, TEM and Raman spectroscopy techniques. The graphitization of CNTs was confirmed by TGA and HRTEM studies. Thermal stability, surface morphology, and structural morphology of these materials were revealed by TGA, SEM and TEM analysis, respectively. Moreover, the tailored mesoporous Ni/KIT-6 molecular sieves were found to possess better quality and massive quantity of g-CNTs produced compared to other catalytic template route

  13. An efficient synthesis of graphenated carbon nanotubes over the tailored mesoporous molecular sieves by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Atchudan, R. [Department of Applied Chemistry, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Department of Chemistry, CEG Campus, Anna University, Chennai 600025 (India); Joo, Jin., E-mail: joojin@knu.ac.kr [Department of Applied Chemistry, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Pandurangan, A., E-mail: pandurangan_a@yahoo.com [Department of Chemistry, CEG Campus, Anna University, Chennai 600025 (India)

    2013-06-01

    Highlights: ► Tailored 3D cubic Ni/KIT-6 with large pores was synthesized successfully. ► The new hybrid g-CNTs in large scale were synthesized using Ni/KIT-6 by CVD method. ► The use of mesoporous material by CVD method would be an ideal choice to prepare g-CNTs at reasonable cost. ► This type of g-CNTs might be a new avenue for nano-electronic applications. - Abstract: The new hybrid of graphenated carbon nanotubes (g-CNTs) was superior to either CNTs or graphene. Mesoporous 3D cubic Ni/KIT-6 were synthesized hydrothermally through organic template route and then were used as catalytic template for the production of g-CNTs using acetylene as a carbon precursor by chemical vapor deposition (CVD) method. The deposited new hybrid carbon materials were purified and analyzed by various physico-chemical techniques such as XRD, TGA, SEM, TEM and Raman spectroscopy techniques. The graphitization of CNTs was confirmed by TGA and HRTEM studies. Thermal stability, surface morphology, and structural morphology of these materials were revealed by TGA, SEM and TEM analysis, respectively. Moreover, the tailored mesoporous Ni/KIT-6 molecular sieves were found to possess better quality and massive quantity of g-CNTs produced compared to other catalytic template route.

  14. Surface chemical and morphological properties of mechanical pulps, fibers and fines

    OpenAIRE

    Kangas, Heli

    2007-01-01

    The aim of this work was to study the surface chemical and morphological properties of different mechanical pulps with special focus on the effects of refining, bleaching and enzymatic modification on the surface properties of the isolated pulp fractions, namely fibers, fibrillar fines and flake-like fines. Special emphasis was placed on evaluating the suitability of time-of-flight secondary ion mass spectroscopy (ToF-SIMS) for studying the surface chemical properties of pulps and pulp fracti...

  15. Mathematical model on surface reaction diffusion in the presence of front chemical reaction

    OpenAIRE

    Permikin, D. V.; Zverev, V. S.

    2013-01-01

    The article discusses a mathematical model of solid-phase diffusion over substance surface accompanied a frontal chemical reaction. The purpose of our article is to describe the concentration distribution and surface reacted layer growth. The model is a system parabolic equations, complicated with the presence of mobile front. It takes account of diffusive fluxes redistribution, sublimation from the surface, chemical reaction reversibility. The asymptotic approximation of the obtained nonline...

  16. Chemical surface modification of poly(p-xylylene) thin films.

    Science.gov (United States)

    Herrera-Alonso, Margarita; McCarthy, Thomas J

    2004-10-12

    Electrophilic aromatic substitution reactions were studied at poly(p-xylylene) (PPX) film surface-reaction medium interfaces. The extent of the reactions (depth of penetration and degree of substitution) was determined by the interaction of the polymer with the reaction solution. Reaction with chlorosulfonic acid to produce sulfonyl chloride and sulfone functionalities occurred readily in the bulk of PPX, and yields were sensitive to time and temperature. Confinement of this reaction to the PPX surface was achieved by controlling the concentration of the acid. Functionalization of PPX with N-methylol-2-chloroacetamide in sulfuric acid to produce the chloroamidomethylated derivative occurred in high yield and was confined to the surface region of PPX. Hydrolysis of the amide to generate aminomethylated PPX was assessed by XPS and a derivatization reaction. Friedel-Crafts type chemistry (acylation and alkylation reactions) also produced functionalized surfaces, but with lower degrees of substitution than the other two reactions and was strictly surface-confined. PMID:15461504

  17. Surface Study of Carbon Nanotubes Prepared by Thermal-CVD of Camphor Precursor

    Science.gov (United States)

    Azira, A. A.; Rusop, M.

    2010-03-01

    Surface morphology study on the influence of starting carbon materials by using thermal chemical vapor deposition (Thermal-CVD) to produced carbon nanotubes (CNTs) is investigated. The CNTs derived from camphor were synthesized as the precursor material due to low sublimation temperature, which indirectly maybe cost effective. The major parameters are also evaluated in order to obtain high-yield and high-quality CNTs. The prepared CNTs are examined using field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscope (HR-TEM) to determine the microstructure of nanocarbons. The FESEM investigation of the CNTs formed on the support catalysts provides evidence that camphor is suitable as a precursor material for nanotubes formation. The high-temperature graphitization process induced by the Thermal-CVD enables the hydrocarbons to act as carbon sources and changes the aromatic species into the layered graphite structure of CNTs. The camphoric hydrocarbons not only found acts as the precursors but also enhances the production rate and the quality of CNTs.

  18. Use of chemically activated cotton nut shell carbon for the removal of fluoride contaminated drinking water:Kinetics evaluation☆

    Institute of Scientific and Technical Information of China (English)

    Rajan Mariappan; Raj Vairamuthu; Alagumuthu GanapathY

    2015-01-01

    Chemically activated cotton nut shell carbons (CTNSCs) were prepared by different chemicals and they were used for the removal of fluoride from aqueous solution. Effects of adsorption time, adsorbent dose, pH of the solution, initial concentration of fluoride, and temperature of the solution were studied with equilibrium, ther-modynamics and kinetics of the adsorption process by various CTNSC adsorbents. It showed that the chemical y activated CTNSCs can effectively remove fluoride from the solution. The adsorption equilibrium data correlate well with the Freundlich isotherm model. The adsorption of fluoride by the chemical y activated CTNSC is spon-taneous and endothermic in nature. The pseudo first order, pseudo second order and intra particle diffusion kinetic models were applied to test the experimental data. The pseudo second order kinetic model provided a better correlation of the experimental data in comparison with the pseudo-first-order and intra particle diffusion models. A mechanism of fluoride adsorption associating chemisorption and physisorption processes is presented allowing the discussion of the variations in adsorption behavior between these materials in terms of specific surface area and porosity. These data suggest that chemically activated CTNSCs are promising materials for fluoride sorption.

  19. Chemical production from waste carbon monoxide: its potential for energy conservation

    Energy Technology Data Exchange (ETDEWEB)

    Rohrmann, C.A.; Schiefelbein, G.F.; Molton, P.M.; Li, C.T.; Elliott, D.C.; Baker, E.G.

    1977-11-01

    Results of a study of the potential for energy conservation by producing chemicals from by-product or waste carbon monoxide (CO) from industrial sources are summarized. Extensive compilations of both industrial sources and uses for carbon monoxide were developed and included. Reviews of carbon monoxide purification and concentration technology and preliminary economic evaluations of carbon monoxide concentration, pipeline transportation and utilization of CO in the synthesis of ammonia and methanol are included. Preliminary technical and economic feasibility studies were made of producing ammonia and methanol from the by-product CO produced by a typical elemental phosphorus plant. Methanol synthesis appears to be more attractive than ammonia synthesis when using CO feedstock because of reduced water gas shift and carbon dioxide removal requirements. The economic studies indicate that methanol synthesis from CO appears to be competitive with conventional technology when the price of natural gas exceeds $0.82/million Btu, while ammonia synthesis from CO is probably not competitive until the price of natural gas exceeds $1.90/million Btu. It is concluded that there appears to be considerable potential for energy conservation in the chemical industry, by collecting CO rather than flaring it, and using it to make major chemicals such as ammonia and methanol.

  20. Influence of Chemical and Physical Properties of Activated Carbon Powders on Oxygen Reduction and Microbial Fuel Cell Performance

    KAUST Repository

    Watson, Valerie J.

    2013-06-03

    Commercially available activated carbon (AC) powders made from different precursor materials (coal, peat, coconut shell, hardwood, and phenolic resin) were electrochemically evaluated as oxygen reduction catalysts and tested as cathode catalysts in microbial fuel cells (MFCs). AC powders were characterized in terms of surface chemistry and porosity, and their kinetic activities were compared to carbon black and platinum catalysts in rotating disk electrode (RDE) tests. Cathodes using the coal-derived AC had the highest power densities in MFCs (1620 ± 10 mW m-2). Peat-based AC performed similarly in MFC tests (1610 ± 100 mW m-2) and had the best catalyst performance, with an onset potential of Eonset = 0.17 V, and n = 3.6 electrons used for oxygen reduction. Hardwood based AC had the highest number of acidic surface functional groups and the poorest performance in MFC and catalysis tests (630 ± 10 mW m-2, Eonset = -0.01 V, n = 2.1). There was an inverse relationship between onset potential and quantity of strong acid (pKa < 8) functional groups, and a larger fraction of microporosity was negatively correlated with power production in MFCs. Surface area alone was a poor predictor of catalyst performance, and a high quantity of acidic surface functional groups was determined to be detrimental to oxygen reduction and cathode performance. © 2013 American Chemical Society.

  1. Chemical studies of single-walled carbon nanotubes

    CERN Document Server

    Xu, C

    2001-01-01

    WCl sub 6 has also been introduced into arc-vapourised SWNTs. Chapter 6 gives the details for all the experimental work of the thesis. of H sub 2 have also been studied. Chapter four describes the various processes used to purify arc-vapourised SWNTs on a laboratory scale. Two potentially scalable processes have also been studied. Both acid and gas oxidants have been used to purify SWNTs grown in the CVD method. The chemical resistance of CVD SWNTs (48 h of conc. HNO sub 3 treatment) has been shown for the first time. Various assembly behaviours of purified SWNTs, including loop and spiral structures, straight long bundles or somewhat aligned structures, are also described. Chapter five presents the filling of arc-vapourised SWNTs with LnX sub n (X = Cl, Br and I, n = 2 or 3) using the capallarity method at high temperature (570-910 deg C). The first example of a polycrystalline structure within SWNTs filled with a single material (SmCl sub 3) has been provided. Fullerenes within SWNTs in the SWNT samples ext...

  2. Surface chemical characterization of PM{sub 10} samples by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Atzei, Davide, E-mail: datzei@unica.it [Dipartimento di Scienze Chimiche e Geologiche, Università di Cagliari, Complesso Universitario di Monserrato, S.S. 554 Bivio per Sestu, I-09042 Monserrato, Cagliari (Italy); Fantauzzi, Marzia; Rossi, Antonella [Dipartimento di Scienze Chimiche e Geologiche, Università di Cagliari, Complesso Universitario di Monserrato, S.S. 554 Bivio per Sestu, I-09042 Monserrato, Cagliari (Italy); Fermo, Paola [Dipartimento di Chimica, Università degli Studi Milano, Via Golgi 19, I-20133 Milano (Italy); Piazzalunga, Andrea [Dipartimento di Chimica, Università degli Studi Milano, Via Golgi 19, I-20133 Milano (Italy); Dipartimento di Scienze dell’Ambiente e del territorio, Università degli Studi di Milano-Bicocca, Piazza della Scienza 1, I-20122 Milano (Italy); Valli, Gianluigi; Vecchi, Roberta [Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, I-20133 Milano (Italy)

    2014-07-01

    Samples of particulate matter (PM) collected in the city of Milan during wintertime were analyzed by X-ray photoelectron spectroscopy (XPS), thermal optical transmittance (TOT), ionic chromatography (IC) and X-ray fluorescence (XRF) in order to compare quantitative bulk analysis and surface analysis. In particular, the analysis of surface carbon is here presented following a new approach for the C1s curve fitting aiming this work to prove the capability of XPS to discriminate among elemental carbon (EC) and organic carbon (OC) and to quantify the carbon-based compounds that might be present in the PM. Since surface of urban PM is found to be rich in carbon it is important to be able to distinguish between the different species. XPS results indicate that aromatic and aliphatic species are adsorbed on the PM surface. Higher concentrations of (EC) are present in the bulk. Also nitrogen and sulfur were detected on the surfaces and a qualitative and quantitative analysis is provided. Surface concentration of sulfate ion is equal to that found by bulk analysis; moreover surface analysis shows an additional signal due to organic sulfur not detectable by the other methods. Surface appears to be also enriched in nitrogen.

  3. Influence of carbonate intercalation in the surface-charging behavior of Zn-Cr layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, R., E-mail: rrojas@mail.fcq.unc.edu.ar [INFIQC, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Barriga, C. [Departamento de Quimica Inorganica e Ingenieria Quimica, Edificio Marie Curie, Campus de Rabanales, Universidad de Cordoba, 14071 Cordoba (Spain); De Pauli, C.P. [INFIQC, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Avena, M.J. [Departamento de Quimica, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahia Blanca (Argentina)

    2010-01-15

    The influence of interlayer composition in the surface charge and reactivity of layered double hydroxides (LDHs) has been explored. With this purpose, a chloride-intercalated Zn-Cr-LDH has been synthesized by the constant pH coprecipitation method and afterwards exchanged with carbonate to obtain solids with different Cl{sup -}/CO{sub 3}{sup 2-} ratios. The solids structure has been characterized by elemental chemical analysis, powder X-ray diffraction and infrared spectroscopy, while its surface-charging behavior and reactivity have been studied by acid-base potentiometric titrations and electrophoretic mobility determinations. The chloride-intercalated sample shows an increasing hydroxyl adsorption with increasing pH and decreasing support electrolyte concentration and the particles present positive electrophoretic mobility in the measured pH range. As carbonate content increases in the samples, the total OH{sup -} uptake diminishes and the samples show an isoelectric point at pH around 10. When the gallery is totally occupied by carbonate anions, the OH uptake vs. pH curves registered at different electrolyte concentrations merge at around pH 10. A LDH-water interface model has been used to give an interpretation to the experimental data. The model indicates that as carbonate content increases, the sample behavior becomes similar to that of a metal (hydr)oxide and that surface (bi)carbonate anions undergo acid-base reactions.

  4. Rapid growth of amorphous carbon films on the inner surface of micron-thick and hollow-core fibers

    International Nuclear Information System (INIS)

    Ultrathick (> 25 μm) carbon films were obtained on the inner surface of hollow and micron-thick quartz fibers by confining CH4/He or C2H2/He microplasmas in their hollow cores. The resulting carbon films were studied by using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The microplasma-enhanced chemical vapor deposition (CVD) technique resulted in the uniform growth of amorphous carbon films on the inner surface of very long (> 1 m) hollow-core fibers. Film deposition is performed by using microplasmas at atmospheric pressure and at 50 Pa. The carbon films obtained with the latter show the smooth inner surfaces and the well continuity across the film/optical fiber. Low-pressure CH4/He and C2H2/He microplasmas can lead to a rapid growth (∼ 2.00 μm/min) of carbon films with their thickness of > 25 μm. The optical emission measurements show that various hydrocarbon species were formed in these depositing microplasmas due to the collisions between CH4/C2H2 molecules and energetic species. The microplasma-enhanced CVD technique running without the complicated fabrication processes shows its potentials for rapidly depositing the overlong carbon tubes with their inner diameters of tens of microns. - Highlights: • The microplasma device is applied for coating deposition inside hollow-core fibers. • The microplasma device results in > 25 μm-thick carbon films. • The microplasma device is simple for deposition of ultralong carbon tubes

  5. Inorganic Carbon Limitation and Chemical Composition of Two Freshwater Green Microalgae †

    Science.gov (United States)

    Goldman, Joel C.; Graham, Stephen J.

    1981-01-01

    Two freshwater chlorophytes, Chlorella vulgaris and Scenedesmus obliquus, were grown in inorganic carbon-limited continuous cultures in which HCO3− was the sole source of inorganic carbon. The response of the steady-state growth rate to the external total inorganic carbon concentration was reasonably well described by the Monod equation; however, the response to the internal nutrient concentration was only moderately well represented by the Droop equation when the internal carbon concentration was defined on a cellular basis. The Droop equation was totally inapplicable when total biomass (dry weight) was used to define internal carbon because the ratio of carbon to dry weight did not vary over the entire growth rate spectrum. In batch cultures, maximum growth rates were achieved at the CO2 levels present in atmospheric air and at HCO3− concentrations of 3 mM. No growth was observed at 100% CO2. Both nitrogen uptake and chlorophyll synthesis were tightly coupled to carbon assimilation, as indicated by the constant C/N and C/chlorophyll ratios found at all growth rates. The main influence of inorganic carbon limitation appears to be not on the chemical structure of the biomass, but rather on cell size; higher steady-state growth rates lead to bigger cells. PMID:16345701

  6. Inorganic carbon limitation and chemical composition of two freshwater green microalgae

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, J.C. (Woods Hole Oceanographic Inst., MA); Graham, S.J.

    1981-01-01

    Two freshwater Chlorophytes, Chlorella vulgaris and Scenedesmus obliquus, were grown in inorganic carbon-limited continuous cultures in which HCO/sub 3//sup -/ was the sole source of inorganic carbon. The response of the steady-state growth rate to the external total inorganic carbon concentration was reasonably well described by the Monod equation; however, the response to the internal nutrient concentration was only moderately well represented by the Droop equation when the internal carbon concentration was defined on a cellular basis. The Droop equation was totally inapplicable when total biomass (dry weight) was used to define internal carbon because the ratio of carbon to dry weight did not vary over the entire growth rate spectrum. In batch cultures, maximum growth rates were achieved at the CO/sub 2/ levels present in atmospheric air and at HCO/sub 3//sup -/ concentrations of 3 mM. No growth was observed at 100% CO/sub 2/. Both nitrogen uptake and chlorophyll synthesis were tightly coupled to carbon assimilation, as indicated by the constant C/N and C/chlorophyll ratios found at all growth rates. The main influence of inorganic carbon limitation appears to be not on the chemical structure of the biomass, but rather on cell size; higher steady-state growth rates lead to bigger cells.

  7. Understanding the physical and chemical properties of carbon-based granular fuels

    Science.gov (United States)

    Marchand, David J.

    Coal and oil have been used as fuel sources for centuries, but the way they have been used has not fundamentally changed: coal is ground into pieces then burned, and oil is distilled into various liquid fractions that are then burned. This dissertation explores newer methods of utilizing those fuel sources. Coal gasification is the process where coal is heated in a low oxygen environment so that the solid carbon is converted into a mixture of gaseous products. But some aspects of gasification, such as the role of catalysts and the structural evolution of coal particles throughout the reaction, remain unclear. These aspects were studied by analyzing, ex situ, the physical and chemical changes of coal feedstock samples extracted from a fluidized bed gasifier at various times throughout gasification. The changes in feed particle composition and size distribution composition showed that the gasification reaction rate was slower than the gas diffusion rates inside the coal particle at a typical catalytic gasification temperature of 800oC. Detailed composition analysis of samples with and without added catalyst showed that the catalyst increased the overall reaction rate by promoting the dissociative oxidation of the coal by gas phase oxidants, which provided more active sites for carbon-carbon bond breakage. The conclusions drawn from studying the feedstock can be combined with the data from in situ analysis of the gasification reactor to provide a fuller picture of the gasification process. Petroleum coke, or petcoke, is a carbonaceous solid produced during oil distillation. Though petcoke could be an important energy source, its use is hindered by practical and environmental concerns. Producing a slurry with petcoke and water has been studied as an alternative method for utilizing petcoke, but the effective use of petcoke slurries requires that they have low viscosity while remaining stable against settling of the particles due to gravity. These rheological properties

  8. Chemical and Molecular Characterization of Biofilm on Metal Surfaces

    Digital Repository Service at National Institute of Oceanography (India)

    Bhosle, N.B.

    and Molecular Characterization of Biofilm on Metal Surfaces Narayan B Bhosle Marine Corrosion and Material Research Division, National Institute of Oceanography,Dona Paula 403004, Goa, India Sonak and Bhosle, 1995). As compared to this a few researchers have... to assess development of conditioning film and biofilm on metal surfaces (Bhosle et al., 1989; Bhosle et al., 1990; Sonak and Bhosle, 1995; Bhosle and Wagh, 1997, D?Souza and Bhosle, 2003). This chapter is a compilation of relevant information...

  9. 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)

  10. The effect of surface oxides on multi-walled carbon nanotube aqueous colloidal properties

    Science.gov (United States)

    Smith, Billy

    Carbonaceous nanomaterials are being produced and integrated into consumer products and specialized applications at an accelerating rate. Recently, however, concerns have increased about the environmental, health and safety risks of these nanomaterials, particularly those chemically functionalized to enhance their aqueous colloidal stability and biocompatibility. In this dissertation research, I have investigated the role that surface-oxide concentration plays in the aqueous colloidal stability of multi-walled carbon nanotubes (MWCNTs), a prominent class of engineered nanomaterials. To vary the concentration of surface oxides on the MWCNTs' surface, pristine (unmodified) tubes were treated with a wet-chemical oxidant (e.g., HNO3, H2SO4 /HNO3, KMnO4); the concentration of surface oxides imparted was measured by x-ray photoelectron spectroscopy (XPS). In conjunction with XPS, previously developed chemical derivatization techniques were used to determine the distribution of hydroxyl, carboxyl, and carbonyl functional groups present on the MWCNTs' surface. The length distribution and structural integrity of pristine and oxidized MWCNTs were characterized using atomic force microscopy and transmission electron microscopy, respectively. To examine the aqueous colloidal stability and aggregation properties of oxidized MWCNTs, sedimentation and time-resolved dynamic light scattering (TR-DLS) experiments were conducted on neat (i.e., ideal) suspensions prepared by prolonged sonication of MWCNTs in Milli-Q water. Over a range of environmentally relevant pH values (4--9) and electrolyte (NaCL, CaCl2) concentrations (0.001--1.000 M), the aggregation and colloidal properties of MWCNTs were found to agree with the basic tenants of DLVO theory, in that ( i) more highly oxidized, negatively charged MWCNTs remained stable over a wider range of solution conditions than lowly oxidized tubes, ( ii) oxidized MWCNTs adhered to the empirical Schulze-Hardy rule, and (iii) in early

  11. 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;...

  12. Integration of plasma-assisted surface chemical modification, soft lithography, and protein surface activation for single-cell patterning

    Science.gov (United States)

    Cheng, Q.; Komvopoulos, K.

    2010-07-01

    Surface patterning for single-cell culture was accomplished by combining plasma-assisted surface chemical modification, soft lithography, and protein-induced surface activation. Hydrophilic patterns were produced on Parylene C films deposited on glass substrates by oxygen plasma treatment through the windows of polydimethylsiloxane shadow masks. After incubation first with Pluronic F108 solution and then serum medium overnight, surface seeding with mesenchymal stem cells in serum medium resulted in single-cell patterning. The present method provides a means of surface patterning with direct implications in single-cell culture.

  13. 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...

  14. The influence of carbon surface chemistry on supported palladium nanoparticles in heterogeneous reactions.

    Science.gov (United States)

    Ding, Yuxiao; Zhang, Liyun; Wu, Kuang-Hsu; Feng, Zhenbao; Shi, Wen; Gao, Qiang; Zhang, Bingsen; Su, Dang Sheng

    2016-10-15

    The surface chemistry of nanocarbon support can tailor chemical properties of precious metal nanoparticle/nanocarbon hybrid catalyst in heterogeneous reactions. We report on modified reduced graphene oxide (rGO) support with ionic liquid-derived carbonaceous surface for palladium nanoparticle (Pd NPs) decoration and their actions in different heterogeneous reactions. The surface chemistry of support materials was characterized in detail, and the influence of which on the formation and distribution of metal particles was further investigated. Three different types of reactions including Suzuki-Miyaura coupling reaction, CO oxidation and phenol reduction were examined in terms of reactivity and selectivity. The roles of substituted nitrogen in graphitic lattice and grafted groups on the carbon surface were exploited. Nitrogen-doping can give rise to changes in electronic properties of supported metals, and the Lewis basicity of the doped nitrogen atoms can favor the adsorption of acidic reactants in phenol reduction. The grafted groups derived a negative impact to the Suzuki-Miyaura coupling reaction, due to the involvement of larger reactant molecules, despite that they could prevent significant sintering of Pd NPs in the CO oxidation. PMID:27442144

  15. Microscale chemical and electrostatic surface patterning of Dow Cyclotene by N 2 plasma

    Science.gov (United States)

    Yang, D.-Q.; Poulin, S.; Martinu, L.; Klemberg-Sapieha, J. E.; Zabeida, O.; Sacher, E.

    2005-04-01

    Using TEM grids as masks, we have chemically modified selected areas of the surface of Dow Cyclotene, a low permittivity polymer, by a N 2 plasma (chemical surface patterning), grafting a maximum of ˜3% N; this was verified by XPS (X-ray photoelectron spectroscopy) and TOF-S-SIMS (time-of-flight static secondary ion mass spectrometry) chemical imaging. Contact mode AFM (atomic force microscopy) studies of the modified surface morphology show unexpected, initially large, values of both etch depth and friction in the treated areas, which decrease on exposure to atmosphere; similar results were absent in tapping mode images. When Cu, which forms nanoclusters on Cyclotene, was deposited by evaporation onto freshly etched Cyclotene, the large etch depth and friction in the etched areas decreased to much lower values. The depth and friction differences occurring on surface modification, which were revealed through our use of patterning, are apparent, and are, in fact, caused by enhanced electrostatic interaction of the chemically modified surface with the AFM tip, as confirmed by the tapping mode data. Some of the electrostatic surface charge, introduced by the positively charged species chemically modifying the Cyclotene surface, is reduced by subsequent charge neutralization. XPS has shown this to be due to the oxidation of these surface charges on atmospheric exposure, initially ˜70%, to form alcohol, carbonyl and carboxylic acid groups. Contact mode AFM imaging of plasma-patterned surfaces is revealed as an excellent tool for the high-resolution characterization of such surfaces.

  16. Chemical state of real surface of A2B6 type compounds

    International Nuclear Information System (INIS)

    Investigation results for chemical composition of real surface of zinc and cadmium chalcogenides (ZnSe, ZnTe, CdSe, CdTe) are generalized. Effect of impurities and oxide phase on adsorption and charging is considered. Determinating role of water in surface charging is shown. It is found that surface active centers are not screened by oxide phase

  17. Carbon coated Fe3O4 hybrid material prepared by chemical vapor deposition for high performance lithium-ion batteries

    International Nuclear Information System (INIS)

    A hybrid material of carbon coated Fe3O4 (Fe3O4@C) is synthesized by chemical vapor deposition method using Fe2O3 as starting material and acetylene as carbon source. The obtained material is Fe3O4 spheres of ∼400 nm coated by thin carbon layer with a thickness of ∼10 nm. As an anode material for lithium ion batteries, Fe3O4@C shows an improved electrochemical performance in the reversible capacity and cycling stability, together with excellent rate capability. The performance is much better than the results obtained from bare Fe2O3 and commercial Fe3O4 of the same size. In addition to the comparison of electrochemical impedance spectra of the Fe2O3, Fe3O4 and Fe3O4@C electrodes before and after 50 charge/discharge cycles, a surface contrast of the three electrodes before and after cycling is systematically investigated to explore the influence of carbon layer on the electrochemical performance of the Fe3O4 spheres

  18. Physical and Electrical Characteristics of Carbon Nanotube Network Field-Effect Transistors Synthesized by Alcohol Catalytic Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Chin-Lung Cheng

    2011-01-01

    Full Text Available Carbon nanotubes (CNTs have been explored in nanoelectronics to realize desirable device performances. Thus, carbon nanotube network field-effect transistors (CNTNFETs have been developed directly by means of alcohol catalytic chemical vapor deposition (ACCVD method using Co-Mo catalysts in this work. Various treated temperatures, growth time, and Co/Mo catalysts were employed to explore various surface morphologies of carbon nanotube networks (CNTNs formed on the SiO2/n-type Si(100 stacked substrate. Experimental results show that most semiconducting single-walled carbon nanotube networks with 5–7 nm in diameter and low disorder-induced mode (D-band were grown. A bipolar property of CNTNFETs synthesized by ACCVD and using HfO2 as top-gate dielectric was demonstrated. Various electrical characteristics, including drain current versus drain voltage (Id-Vd, drain current versus gate voltage (Id-Vg, mobility, subthreshold slope (SS, and transconductance (Gm, were obtained.

  19. Effect of chemical vapor infiltration treatment on the wave-absorbing performance of carbon fiber/cement composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Short carbon fibers were treated at high temperatures around 1100℃ through chemical vapor infiltration technology.A thinner layer ofpyrocarbon was deposited on the fiber surface.The dispersion of carbon fibers in a cement matrix and the mechanical properties of carbon fiber/cement composites were investigated by scanning electron microscopy (SEM) and other tests.The reflectivity of electromagnetic waves by the composites was measured in the frequency range of 8.0-18 GHz for different carbon fiber contents of 0.2wt%,0.4wt%,0.6wt% ,and 1.0wt%.The results show that the reflectivity tends to increase with the increase of fiber content above 0.4wt%.The minimum reflectivity is -19.3 dB and the composites exhibit wave-absorbing performances.After pyrocarbon is deposited on the fiber,all the reflectivity data are far greater.They are all above -10 dB and display mainly wave-reflecting performances.

  20. Growth of crystals of several boron-carbon compositions by chemical vapor deposition

    Science.gov (United States)

    Kevill, D. N.; Rissmann, T. J.; Brewe, D.; Wood, C.

    1986-01-01

    Boron-carbon compounds have been deposited by the flow of carbon tetrachloride and boron trichloride, in the presence of a large excess of hydrogen, over a graphite surface maintained at 1000-1300 C. Deposits were formed on either an RF-heated disc or a tube or insert heated by a resistance furnace. Crystalline materials ranging in composition from B2C to B17C have been obtained.