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Sample records for amorphous carbon nitride

  1. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    Science.gov (United States)

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

    2016-01-01

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

  2. Recent progress in the synthesis and characterization of amorphous and crystalline carbon nitride coatings

    CERN Document Server

    Widlow, I

    2000-01-01

    This review summarizes our most recent findings in the structure and properties of amorphous and crystalline carbon nitride coatings, synthesized by reactive magnetron sputtering. By careful control of the plasma conditions via proper choice of process parameters such as substrate bias, target power and gas pressure, one can precisely control film structure and properties. With this approach, we were able to produce amorphous carbon nitride films with controlled hardness and surface roughness. In particular, we can synthesize ultrathin (1 nm thick) amorphous carbon nitride films to be sufficiently dense and uniform that they provide adequate corrosion protection for hard disk applications. We demonstrated the strong correlation between ZrN (111) texture and hardness in CN sub x /ZrN superlattice coatings. Raman spectroscopy and near-edge X-ray absorption show the predominance of sp sup 3 -bonded carbon in these superlattice coatings.

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

    KAUST Repository

    Wan, Shanhong

    2015-01-01

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

  4. Electrical behavior of multi-walled carbon nanotube network embedded in amorphous silicon nitride

    Directory of Open Access Journals (Sweden)

    Buiculescu Raluca

    2011-01-01

    Full Text Available Abstract The electrical behavior of multi-walled carbon nanotube network embedded in amorphous silicon nitride is studied by measuring the voltage and temperature dependences of the current. The microstructure of the network is investigated by cross-sectional transmission electron microscopy. The multi-walled carbon nanotube network has an uniform spatial extension in the silicon nitride matrix. The current-voltage and resistance-temperature characteristics are both linear, proving the metallic behavior of the network. The I-V curves present oscillations that are further analyzed by computing the conductance-voltage characteristics. The conductance presents minima and maxima that appear at the same voltage for both bias polarities, at both 20 and 298 K, and that are not periodic. These oscillations are interpreted as due to percolation processes. The voltage percolation thresholds are identified with the conductance minima.

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

    Science.gov (United States)

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

    2011-01-01

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

  6. Substrate temperature influence on the trombogenicity in amorphous carbon nitride thin coatings

    International Nuclear Information System (INIS)

    Galeano-Osorio, D.S.; Vargas, S.; Lopez-Cordoba, L.M.; Ospina, R.; Restrepo-Parra, E.; Arango, P.J.

    2010-01-01

    Carbon nitride thin films were obtained through plasma assisted physical vapor deposition technique by pulsed arc, varying the substrate temperature and investigating the influence of this parameter on the films hemocompatibility. For obtaining approaches of blood compatibility, environmental scanning electron microscopy (ESEM) was used in order to study the platelets adherence and their morphology. Moreover, the elemental chemical composition was determined by using energy dispersive spectroscopy (EDS), finding C, N and O. The coatings hemocompatibility was evaluated by in vitro thrombogenicity test, whose results were correlated with the microstructure and roughness of the films obtained. During the films growth process, the substrate temperature was varied, obtaining coatings under different temperatures, room temperature (T room ), 100 deg. C, 150 deg. C and 200 deg. C. Parameters as interelectrodic distance, voltage, work pressure and number of discharges, were remained constant. By EDS, carbon and nitrogen were found in the films. Visible Raman spectroscopy was used, and it revealed an amorphous lattice, with graphitic process as the substrate temperature was increased. However, at a critical temperature of 150 deg. C, this tendency was broken, and the film became more amorphous. This film showed the lowest roughness, 2 ± 1 nm. This last characteristic favored the films hemocompatibility. Also, it was demonstrated that the blood compatibility of carbon nitride films obtained were affected by the I D /I G or sp 3 /sp 2 ratio and not by the absolute sp 3 or sp 2 concentration.

  7. Substrate temperature influence on the trombogenicity in amorphous carbon nitride thin coatings

    Energy Technology Data Exchange (ETDEWEB)

    Galeano-Osorio, D.S.; Vargas, S.; Lopez-Cordoba, L.M.; Ospina, R. [Laboratorio de Fisica del Plasma, Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Laboratorio de Fisica del Plasma, Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia); Arango, P.J. [Laboratorio de Fisica del Plasma, Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia)

    2010-10-01

    Carbon nitride thin films were obtained through plasma assisted physical vapor deposition technique by pulsed arc, varying the substrate temperature and investigating the influence of this parameter on the films hemocompatibility. For obtaining approaches of blood compatibility, environmental scanning electron microscopy (ESEM) was used in order to study the platelets adherence and their morphology. Moreover, the elemental chemical composition was determined by using energy dispersive spectroscopy (EDS), finding C, N and O. The coatings hemocompatibility was evaluated by in vitro thrombogenicity test, whose results were correlated with the microstructure and roughness of the films obtained. During the films growth process, the substrate temperature was varied, obtaining coatings under different temperatures, room temperature (T{sub room}), 100 deg. C, 150 deg. C and 200 deg. C. Parameters as interelectrodic distance, voltage, work pressure and number of discharges, were remained constant. By EDS, carbon and nitrogen were found in the films. Visible Raman spectroscopy was used, and it revealed an amorphous lattice, with graphitic process as the substrate temperature was increased. However, at a critical temperature of 150 deg. C, this tendency was broken, and the film became more amorphous. This film showed the lowest roughness, 2 {+-} 1 nm. This last characteristic favored the films hemocompatibility. Also, it was demonstrated that the blood compatibility of carbon nitride films obtained were affected by the I{sub D}/I{sub G} or sp{sup 3}/sp{sup 2} ratio and not by the absolute sp{sup 3} or sp{sup 2} concentration.

  8. Optical properties of plasma deposited amorphous carbon nitride films on polymer substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mohamed, S.H., E-mail: abo_95@yahoo.co [Physics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); El-Hossary, F.M. [Physics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); Gamal, G.A.; Kahlid, M.M. [Physics Department, Faculty of Science, South Valley University, 83523 Qena (Egypt)

    2010-01-01

    Amorphous carbon nitride thin films were deposited on polymer substrates using radio frequency (rf) plasma in a mixture of nitrogen (N{sub 2}) and acetylene (C{sub 2}H{sub 2}) gasses. The samples were prepared at different rf plasma power (350, 400, 450, 500, and 550 W), at constant plasma exposure time of 10 min, and constant N{sub 2}/C{sub 2}H{sub 2} ratio of 50%. The crystal structure and surface morphology of the prepared samples were examined using X-ray diffraction and atomic force microscopy analysis, respectively. The absence of the carbon nitride diffraction peaks confirms the amorphous nature of these films. The root mean square roughness of the films increased from 3.77 to 25.22 nm as the power increased from 350 to 550 W. The thickness and the deposition rate were found to increase with increasing plasma power. Over the whole studied wavelength range, from 200 to 2500 nm, the transmittance decreased with increasing plasma power. A shift in the onset of absorption towards higher wavelengths with increasing plasma power, indicating a decrease in the optical band gap, has been observed. The refractive index values were found to decrease while the extinction coefficient increased with increasing plasma power.

  9. Optical properties of plasma deposited amorphous carbon nitride films on polymer substrates

    Science.gov (United States)

    Mohamed, S. H.; El-Hossary, F. M.; Gamal, G. A.; Kahlid, M. M.

    2010-01-01

    Amorphous carbon nitride thin films were deposited on polymer substrates using radio frequency (rf) plasma in a mixture of nitrogen (N 2) and acetylene (C 2H 2) gasses. The samples were prepared at different rf plasma power (350, 400, 450, 500, and 550 W), at constant plasma exposure time of 10 min, and constant N 2/C 2H 2 ratio of 50%. The crystal structure and surface morphology of the prepared samples were examined using X-ray diffraction and atomic force microscopy analysis, respectively. The absence of the carbon nitride diffraction peaks confirms the amorphous nature of these films. The root mean square roughness of the films increased from 3.77 to 25.22 nm as the power increased from 350 to 550 W. The thickness and the deposition rate were found to increase with increasing plasma power. Over the whole studied wavelength range, from 200 to 2500 nm, the transmittance decreased with increasing plasma power. A shift in the onset of absorption towards higher wavelengths with increasing plasma power, indicating a decrease in the optical band gap, has been observed. The refractive index values were found to decrease while the extinction coefficient increased with increasing plasma power.

  10. Deposit of thin films of nitrided amorphous carbon using the laser ablation technique

    International Nuclear Information System (INIS)

    Rebollo, P.B.; Escobar A, L.; Camps C, E.; Haro P, E.; Camacho L, M.A.; Muhl S, S.

    2000-01-01

    It is reported the synthesis and characterization of thin films of amorphous carbon (a-C) nitrided, deposited by laser ablation in a nitrogen atmosphere at pressures which are from 4.5 x 10 -4 Torr until 7.5 x 10 -2 Torr. The structural properties of the films are studied by Raman spectroscopy obtaining similar spectra at the reported for carbon films type diamond. The study of behavior of the energy gap and the ratio nitrogen/carbon (N/C) in the films, shows that the energy gap is reduced when the nitrogen incorporation is increased. It is showed that the refraction index of the thin films diminish as nitrogen pressure is increased, indicating the formation of graphitic material. (Author)

  11. Screen-printed carbon electrode modified on its surface with amorphous carbon nitride thin film: Electrochemical and morphological study

    Energy Technology Data Exchange (ETDEWEB)

    Ghamouss, F. [Universite de Nantes, UMR 6006-CNRS, FR-2465-CNRS, Laboratoire d' Analyse isotopique et Electrochimique de Metabolismes (LAIEM) (France); Tessier, P.-Y. [Universite de Nantes, UMR CNRS 6502, Institut des Materiaux Jean Rouxel - IMN Faculte des Sciences and des Techniques de Nantes, 2 rue de la Houssiniere, 44322 Nantes Cedex 3 (France); Djouadi, A. [Universite de Nantes, UMR CNRS 6502, Institut des Materiaux Jean Rouxel - IMN Faculte des Sciences and des Techniques de Nantes, 2 rue de la Houssiniere, 44322 Nantes Cedex 3 (France); Besland, M.-P. [Universite de Nantes, UMR CNRS 6502, Institut des Materiaux Jean Rouxel - IMN Faculte des Sciences and des Techniques de Nantes, 2 rue de la Houssiniere, 44322 Nantes Cedex 3 (France); Boujtita, M. [Universite de Nantes, UMR 6006-CNRS, FR-2465-CNRS, Laboratoire d' Analyse isotopique et Electrochimique de Metabolismes (LAIEM) (France)]. E-mail: mohammed.boujtita@univ-nantes.fr

    2007-04-20

    The surface of a screen-printed carbon electrode (SPCE) was modified by using amorphous carbon nitride (a-CN {sub x}) thin film deposited by reactive magnetron sputtering. Scanning electron microscopy and photoelectron spectroscopy measurements were used to characterise respectively the morphology and the chemical structure of the a-CN {sub x} modified electrodes. The incorporation of nitrogen in the amorphous carbon network was demonstrated by X ray photoelectron spectroscopy. The a-CN {sub x} layers were deposited on both carbon screen-printed electrode (SPCE) and silicon (Si) substrates. A comparative study showed that the nature of substrate, i.e. SPCE and Si, has a significant effect on both the surface morphology of deposited a-CN {sub x} film and their electrochemical properties. The improvement of the electrochemical reactivity of SPCE after a-CN {sub x} film deposition was highlighted both by comparing the shapes of voltammograms and calculating the apparent heterogeneous electron transfer rate constant.

  12. Synthesis and characterization of thin films of nitrided amorphous carbon deposited by laser ablation

    International Nuclear Information System (INIS)

    Rebollo P, B.

    2001-01-01

    The objective of this work is the synthesis and characterization of thin films of amorphous carbon (a-C) and thin films of nitrided amorphous carbon (a-C-N) using the laser ablation technique for their deposit. For this purpose, the physical properties of the obtained films were studied as function of diverse parameters of deposit such as: nitrogen pressure, power density, substrate temperature and substrate-target distance. For the characterization of the properties of the deposited thin films the following techniques were used: a) Raman spectroscopy which has demonstrated being a sensitive technique to the sp 2 and sp 3 bonds content, b) Energy Dispersive Spectroscopy which allows to know semi-quantitatively way the presence of the elements which make up the deposited films, c) Spectrophotometry, for obtaining the absorption spectra and subsequently the optical energy gap of the deposited material, d) Ellipsometry for determining the refraction index, e) Scanning Electron Microscopy for studying the surface morphology of thin films and, f) Profilemetry, which allows the determination the thickness of the deposited thin films. (Author)

  13. Highly Efficient Performance and Conversion Pathway of Photocatalytic NO Oxidation on SrO-Clusters@Amorphous Carbon Nitride.

    Science.gov (United States)

    Cui, Wen; Li, Jieyuan; Dong, Fan; Sun, Yanjuan; Jiang, Guangming; Cen, Wanglai; Lee, S C; Wu, Zhongbiao

    2017-09-19

    This work demonstrates the first molecular-level conversion pathway of NO oxidation over a novel SrO-clusters@amorphous carbon nitride (SCO-ACN) photocatalyst, which is synthesized via copyrolysis of urea and SrCO 3 . The inclusion of SrCO 3 is crucial in the formation of the amorphous carbon nitride (ACN) and SrO clusters by attacking the intralayer hydrogen bonds at the edge sites of graphitic carbon nitride (CN). The amorphous nature of ACN can promote the transportation, migration, and transformation of charge carriers on SCO-ACN. And the SrO clusters are identified as the newly formed active centers to facilitate the activation of NO via the formation of Sr-NO δ(+) , which essentially promotes the conversion of NO to the final products. The combined effects of the amorphous structure and SrO clusters impart outstanding photocatalytic NO removal efficiency to the SCO-ACN under visible-light irradiation. To reveal the photocatalytic mechanism, the adsorption and photocatalytic oxidation of NO over CN and SCO-ACN are analyzed by in situ DRIFTS, and the intermediates and conversion pathways are elucidated and compared. This work presents a novel in situ DRIFTS-based strategy to explore the photocatalytic reaction pathway of NO oxidation, which is quite beneficial to understand the mechanism underlying the photocatalytic reaction and advance the development of photocatalytic technology for environmental remediation.

  14. Crystalline and amorphous phases in carbon nitride films produced by intense high-pressure plasma

    Energy Technology Data Exchange (ETDEWEB)

    Gurarie, V.N.; Orlov, A.V.; Bursill, L.A.; JuLin, P.; Nugent, K.W.; Chon, J.W.; Prawer, S

    1997-12-31

    Carbon-nitride films are prepared using a high-intensity pulsed plasma deposition technique. A wide range of nitrogen pressure and discharge intensity are used to investigate their effect on the morphology, nitrogen content, structure, bonding, phase composition and mechanical characteristics of the CN films deposited. Increasing the nitrogen pressure from 0.1 atm to 10 atm results in an increase of nitrogen incorporation into CN films to maximum of 45 at %. Under the high-energy density deposition conditions which involve ablation of the quartz substrate the CN films are found to incorporate in excess of 60 at %N. Raman spectra of these films contain sharp peaks characteristic of a distinct crystalline CN phase. TEM diffraction patterns for the films deposited below 1 atm unambiguously show the presence of micron-sized crystals displaying a cubic symmetry. (authors). 12 refs., 4 figs.

  15. Light emission in forward and reverse bias operation in OLED with amorphous silicon carbon nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, R [Facultad de Ingenieria Quimica y Textil, Universidad Nacional de Ingenieria, Av. Tupac Amaru SN, Lima (Peru); Cremona, M [Departamento de Fisica, PontifIcia Universidade Catolica de Rio de Janeiro, PUC-Rio, Cx. Postal 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil); Achete, C A, E-mail: rreyes@uni.edu.pe [Departamento de Engenheria Metalurgica e de Materiais, Universidade Federal do Rio de Janeiro, Cx. Postal 68505, Rio de Janeiro, RJ, CEP 21945-970 (Brazil)

    2011-01-01

    Amorphous silicon carbon nitride (a-SiC:N) thin films deposited by magnetron sputtering were used in the structure of an organic light emitting diode (OLED), obtaining an OLED operating in forward and reverse bias mode. The device consist of the heterojunction structure ITO/a-SiC:N/Hole Transport Layer (HTL)/ Electron Transport Layer (ETL)/a-SiC:N/Al. As hole transporting layer was used a thin film of 1-(3-methylphenyl)-1,2,3,4 tetrahydroquinoline - 6 - carboxyaldehyde - 1,1'- diphenylhydrazone (MTCD), while the tris(8-hydroxyquinoline aluminum) (Alq{sub 3}) is used as electron transport and emitting layer. A significant increase in the voltage operation compared to the conventional ITO/MTCD/Alq{sub 3}/Al structure was observed, so the onset of electroluminescence occurs at about 22 V in the forward and reverse bias mode of operation. The electroluminescence spectra is similar in both cases, only slightly shifted 0.14 eV to lower energies in relation to the conventional device.

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  17. Synthesis of ternary metal nitride nanoparticles using mesoporous carbon nitride as reactive template.

    Science.gov (United States)

    Fischer, Anna; Müller, Jens Oliver; Antonietti, Markus; Thomas, Arne

    2008-12-23

    Mesoporous graphitic carbon nitride was used as both a nanoreactor and a reactant for the synthesis of ternary metal nitride nanoparticles. By infiltration of a mixture of two metal precursors into mesoporous carbon nitride, the pores act first as a nanoconfinement, generating amorphous mixed oxide nanoparticles. During heating and decomposition, the carbon nitride second acts as reactant or, more precisely, as a nitrogen source, which converts the preformed mixed oxide nanoparticles into the corresponding nitride (reactive templating). Using this approach, ternary metal nitride particles with diameters smaller 10 nm composed of aluminum gallium nitride (Al-Ga-N) and titanium vanadium nitride (Ti-V-N) were synthesized. Due to the confinement effect of the carbon nitride matrix, the composition of the resulting metal nitride can be easily adjusted by changing the concentration of the preceding precursor solution. Thus, ternary metal nitride nanoparticles with continuously adjustable metal composition can be produced.

  18. Deposit of thin films of nitrided amorphous carbon using the laser ablation technique; Deposito de peliculas delgadas de carbono amorfo nitrurado utilizando la tecnica de ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Rebollo, P.B.; Escobar A, L.; Camps C, E. [Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, C.P. 52045 Salazar, Estado de Mexico (Mexico); Haro P, E.; Camacho L, M.A. [Departamento de Fisica, Universidad Autonoma Metropolitana Iztapalapa (Mexico); Muhl S, S. [Instituto de Investigacion en Materiales, UNAM (Mexico)

    2000-07-01

    It is reported the synthesis and characterization of thin films of amorphous carbon (a-C) nitrided, deposited by laser ablation in a nitrogen atmosphere at pressures which are from 4.5 x 10 {sup -4} Torr until 7.5 x 10 {sup -2} Torr. The structural properties of the films are studied by Raman spectroscopy obtaining similar spectra at the reported for carbon films type diamond. The study of behavior of the energy gap and the ratio nitrogen/carbon (N/C) in the films, shows that the energy gap is reduced when the nitrogen incorporation is increased. It is showed that the refraction index of the thin films diminish as nitrogen pressure is increased, indicating the formation of graphitic material. (Author)

  19. Amorphous iron (II) carbonate

    DEFF Research Database (Denmark)

    Sel, Ozlem; Radha, A.V.; Dideriksen, Knud

    2012-01-01

    Abstract The synthesis, characterization and crystallization energetics of amorphous iron (II) carbonate (AFC) are reported. AFC may form as a precursor for siderite (FeCO3). The enthalpy of crystallization (DHcrys) of AFC is similar to that of amorphous magnesium carbonate (AMC) and more...

  20. Synthesis and characterization of thin films of nitrided amorphous carbon deposited by laser ablation; Sintesis y caracterizacion de peliculas delgadas de carbono amorfo nitrurado, depositadas por ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Rebollo P, B

    2001-07-01

    The objective of this work is the synthesis and characterization of thin films of amorphous carbon (a-C) and thin films of nitrided amorphous carbon (a-C-N) using the laser ablation technique for their deposit. For this purpose, the physical properties of the obtained films were studied as function of diverse parameters of deposit such as: nitrogen pressure, power density, substrate temperature and substrate-target distance. For the characterization of the properties of the deposited thin films the following techniques were used: a) Raman spectroscopy which has demonstrated being a sensitive technique to the sp{sup 2} and sp{sup 3} bonds content, b) Energy Dispersive Spectroscopy which allows to know semi-quantitatively way the presence of the elements which make up the deposited films, c) Spectrophotometry, for obtaining the absorption spectra and subsequently the optical energy gap of the deposited material, d) Ellipsometry for determining the refraction index, e) Scanning Electron Microscopy for studying the surface morphology of thin films and, f) Profilemetry, which allows the determination the thickness of the deposited thin films. (Author)

  1. Graphitic Carbon Nitride Materials for Energy Applications

    OpenAIRE

    Belen Jorge, A.; Dedigama, I.; Mansor, N.; Jervis, R.; Corà, F.; McMillan, P. F.; Brett, D.

    2015-01-01

    Polymeric layered carbon nitrides were investigated for use as catalyst support materials for proton exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs). Three different carbon nitride materials were prepared: a heptazine-based graphitic carbon nitride material (gCNM), poly (triazine) imide carbon nitride intercalated with LiCl component (PTI-Li+Cl-) and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride mate...

  2. New amorphous interface for precipitate nitrides in steel

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Kadkhodazadeh, Shima; Grumsen, Flemming Bjerg

    2014-01-01

    According to classical theories precipitate interfaces are described by their degree of coherency with the matrix, which affects their strengthening contribution. Investigations of nitride precipitate interfaces in 12% Cr steels with transmission electron microscopy have shown the nitrides...... to be enveloped in an amorphous shell a few nm thick, thus leaving them without any coherency with the matrix. The amorphous nature of the shells could be ascertained with high resolution microscopy and dark field techniques. When extracted from the ferrite matrix the amorphous shells were observed to crystallize...

  3. Electron Cloud in Steel Beam Pipe vs Titanium Nitride Coated and Amorphous Carbon Coated Beam Pipes in Fermilab's Main Injector

    Energy Technology Data Exchange (ETDEWEB)

    Backfish, Michael

    2013-04-01

    This paper documents the use of four retarding field analyzers (RFAs) to measure electron cloud signals created in Fermilab’s Main Injector during 120 GeV operations. The first data set was taken from September 11, 2009 to July 4, 2010. This data set is used to compare two different types of beam pipe that were installed in the accelerator. Two RFAs were installed in a normal steel beam pipe like the rest of the Main Injector while another two were installed in a one meter section of beam pipe that was coated on the inside with titanium nitride (TiN). A second data run started on August 23, 2010 and ended on January 10, 2011 when Main Injector beam intensities were reduced thus eliminating the electron cloud. This second run uses the same RFA setup but the TiN coated beam pipe was replaced by a one meter section coated with amorphous carbon (aC). This section of beam pipe was provided by CERN in an effort to better understand how an aC coating will perform over time in an accelerator. The research consists of three basic parts: (a) continuously monitoring the conditioning of the three different types of beam pipe over both time and absorbed electrons (b) measurement of the characteristics of the surrounding magnetic fields in the Main Injector in order to better relate actual data observed in the Main Injector with that of simulations (c) measurement of the energy spectrum of the electron cloud signals using retarding field analyzers in all three types of beam pipe.

  4. Boron nitride converted carbon fiber

    Science.gov (United States)

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

    2016-04-05

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

  5. Modelling structure and properties of amorphous silicon boron nitride ceramics

    Directory of Open Access Journals (Sweden)

    Johann Christian Schön

    2011-06-01

    Full Text Available Silicon boron nitride is the parent compound of a new class of high-temperature stable amorphous ceramics constituted of silicon, boron, nitrogen, and carbon, featuring a set of properties that is without precedent, and represents a prototypical random network based on chemical bonds of predominantly covalent character. In contrast to many other amorphous materials of technological interest, a-Si3B3N7 is not produced via glass formation, i.e. by quenching from a melt, the reason being that the binary components, BN and Si3N4, melt incongruently under standard conditions. Neither has it been possible to employ sintering of μm-size powders consisting of binary nitrides BN and Si3N4. Instead, one employs the so-called sol-gel route starting from single component precursors such as TADB ((SiCl3NH(BCl2. In order to determine the atomic structure of this material, it has proven necessary to simulate the actual synthesis route.Many of the exciting properties of these ceramics are closely connected to the details of their amorphous structure. To clarify this structure, it is necessary to employ not only experimental probes on many length scales (X-ray, neutron- and electron scattering; complex NMR experiments; IR- and Raman scattering, but also theoretical approaches. These address the actual synthesis route to a-Si3B3N7, the structural properties, the elastic and vibrational properties, aging and coarsening behaviour, thermal conductivity and the metastable phase diagram both for a-Si3B3N7 and possible silicon boron nitride phases with compositions different from Si3N4: BN = 1 : 3. Here, we present a short comprehensive overview over the insights gained using molecular dynamics and Monte Carlo simulations to explore the energy landscape of a-Si3B3N7, model the actual synthesis route and compute static and transport properties of a-Si3BN7.

  6. NMR STUDIES OF Co-BASED NITRIDE AMORPHOUS FILMS

    OpenAIRE

    Le Dang, K.; Veillet, P.; Sakakima, H.; Krishnan, R.

    1988-01-01

    We have carried out at 4 K spin-echo measurements in both single and multilayer (nitride and nonnitride layers) amorphous films of (Co83Nb11Ta2Zr4)1-x N100x. The average Co hyperfine field and the local in-plane anisotropy (K) increase with N (x) content in agreement with magnetization measurements. Annealing leads to a slight increase in K for single layer but a strong decrease for multilayer which remains amorphous contrary to the non-nitride films.

  7. Microstructure and properties of ultrathin amorphous silicon nitride protective coating

    International Nuclear Information System (INIS)

    Yen, Bing K.; White, Richard L.; Waltman, Robert J.; Dai Qing; Miller, Dolores C.; Kellock, Andrew J.; Marchon, Bruno; Kasai, Paul H.; Toney, Michael F.; York, Brian R.; Deng Hong; Xiao Qifan; Raman, Vedantham

    2003-01-01

    The effect of N content on the structure and properties of rf reactively sputtered amorphous silicon nitride (a-SiN x ) has been studied by Rutherford backscattering spectrometry, x-ray reflectivity, ellipsometry, and nano-indentation. The N content in the film increased with the N 2 concentration in the sputtering gas until the Si 3 N 4 stoichiometry was reached. The hardness of a-SiN x increased with density, which in turn increased with the N content. The maximum hardness of 25 GPa and density of 3.2 g/cm 3 were attained at the stoichiometric Si 3 N 4 composition. With the application of a protective overcoat for magnetic disks in mind, thin a-SiN x films were deposited on CoPtCr media to examine their coverage, pinhole density, and wear resistance. According to x-ray photoelectron spectroscopy, the minimum thickness of a-SiN x required to protect the CoPtCr alloy from oxidation was 10 A, which was 10 A thinner than that of the reference amorphous nitrogenated carbon (a-CN x ). A statistic model showed this lower thickness required for a-SiN x can be attributed to its high density, which corresponds to 93% bulk density of Si 3 N 4 . Compared with 45 A a-CN x coated disks, 15 A a-SiN x coated disks had lower pinhole defect density and superior wear resistance

  8. Structural morphology of amorphous conducting carbon film

    Indian Academy of Sciences (India)

    Unknown

    been found to be having a lot of technological applica- tions. The properties of these amorphous carbons sensi- tively depend on the relative concentration of sp3 and sp2 hybridized carbons. The resulting amorphous materials are variously referred to as tetrahedral amorphous carbon. (ta-C), amorphous carbon (a-C), ...

  9. The atomic and electronic structure of amorphous silicon nitride

    CERN Document Server

    Alvarez, F

    2002-01-01

    Using a novel approach to the ab initio generation of random networks we constructed two nearly stoichiometric samples of amorphous silicon nitride with the same content x= 1.29. The two 64-atom periodically-continued cubic diamond-like cells contain 28 silicons and 36 nitrogens randomly substituted, and were amorphized with a 6 f s time step by heating them to just below their melting temperature with a Harris-functional based, molecular dynamics code in the LDA approximation. The averaged total radial distribution function (RDF) obtained is compared with some existing Tersoff-like potential simulations and with experiment; ours agree with experiment. All the partial radial features are calculated and the composition of the second peak also agrees with experiment. The electronic structure is calculated and the optical gaps obtained using both a HOMO-LUMO approach and the Tauc-like procedure developed recently that gives reasonable gaps. (Author)

  10. Structural morphology of amorphous conducting carbon film

    Indian Academy of Sciences (India)

    Unknown

    in nanotubes and sp3 rich amorphous carbons for their application in field emission, device application, etc in- vestigations on sp2 rich amorphous carbon forms are very few. Though DLC films have potential application in field emission (FE) due to their low threshold voltage, the carbon centres, which are believed to play ...

  11. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells.

    OpenAIRE

    Mansor, N.; Jorge, A. B.; Corà, F.; Gibbs, C.; Jervis, R.; McMillan, P. F.; Wang, X.; Brett, D. J.

    2014-01-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li(+)Cl(-)), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion...

  12. Hard carbon nitride and method for preparing same

    Science.gov (United States)

    Haller, E.E.; Cohen, M.L.; Hansen, W.L.

    1992-05-05

    Novel crystalline [alpha](silicon nitride-like)-carbon nitride and [beta](silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate. 1 figure.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-31

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

  14. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells

    Science.gov (United States)

    2014-01-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li+Cl–), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li+Cl– catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

  15. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells.

    Science.gov (United States)

    Mansor, Noramalina; Jorge, A Belen; Corà, Furio; Gibbs, Christopher; Jervis, Rhodri; McMillan, Paul F; Wang, Xiaochen; Brett, Daniel J L

    2014-04-03

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li + Cl - ), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li + Cl - catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA.

  16. Conductive Carbon Nitride for Excellent Energy Storage.

    Science.gov (United States)

    Xu, Jijian; Xu, Feng; Qian, Meng; Xu, Fangfang; Hong, Zhanglian; Huang, Fuqiang

    2017-08-01

    Conductive carbon nitride, as a hypothetical carbon material demonstrating high nitrogen doping, high electrical conductivity, and high surface area, has not been fabricated. A major challenge towards its fabrication is that high conductivity requires high temperature synthesis, but the high temperature eliminates nitrogen from carbon. Different from conventional methods, a facile preparation of conductive carbon nitride from novel thermal decomposition of nickel hydrogencyanamide in a confined space is reported. New developed nickel hydrogencyanamide is a unique precursor which provides self-grown fragments of ⋅NCN⋅ or NCCN and conductive carbon (C-sp 2 ) catalyst of Ni metal during the decomposition. The final product is a tubular structure of rich mesoporous and microporous few-layer carbon with extraordinarily high N doping level (≈15 at%) and high extent of sp 2 carbon (≈65%) favoring a high conductivity (>2 S cm -1 ); the ultrahigh contents of nongraphitic nitrogen, redox active pyridinic N (9 at%), and pyrrolic N (5 at%), are stabilized by forming NiN bonds. The conductive carbon nitride harvests a large capacitance of 372 F g -1 with >90% initial capacitance after 10 000 cycles as a supercapacitor electrode, far exceeding the activated carbon electrodes that have <250 F g -1 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Nanotribological performance of fullerene-like carbon nitride films

    International Nuclear Information System (INIS)

    Flores-Ruiz, Francisco Javier; Enriquez-Flores, Christian Ivan; Chiñas-Castillo, Fernando; Espinoza-Beltrán, Francisco Javier

    2014-01-01

    Highlights: • Fullerene-like CNx samples show an elastic recovery of 92.5% and 94.5% while amorphous CNx samples had only 75% elastic recovery. • Fullerene-like CNx films show an increment of 34.86% and 50.57% in fractions of C 1s and N 1s. • Fullerene-like CNx samples show a lower friction coefficient compared to amorphous CNx samples. • Friction reduction characteristics of fullerene-like CNx films are strongly related to the increase of sp 3 CN bonds. - Abstract: Fullerene-like carbon nitride films exhibit high elastic modulus and low friction coefficient. In this study, thin CNx films were deposited on silicon substrate by DC magnetron sputtering and the tribological behavior at nanoscale was evaluated using an atomic force microscope. Results show that CNx films with fullerene-like structure have a friction coefficient (CoF ∼ 0.009–0.022) that is lower than amorphous CNx films (CoF ∼ 0.028–0.032). Analysis of specimens characterized by X-ray photoelectron spectroscopy shows that films with fullerene-like structure have a higher number of sp 3 CN bonds and exhibit the best mechanical properties with high values of elastic modulus (E > 180 GPa) and hardness (H > 20 GPa). The elastic recovery determined on specimens with a fullerene-like CNx structure was of 95% while specimens of amorphous CNx structure had only 75% elastic recovery

  18. Nanotribological performance of fullerene-like carbon nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Ruiz, Francisco Javier; Enriquez-Flores, Christian Ivan [Centro de Investigación y Estudios Avanzados (CINVESTAV) IPN, Unidad Querétaro, Lib. Norponiente 2000, Real de Juriquilla, C.P. 76230, Querétaro, Qro., México (Mexico); Chiñas-Castillo, Fernando, E-mail: fernandochinas@gmail.com [Department of Mechanical Engineering, Instituto Tecnológico de Oaxaca, Oaxaca, Oax. Calz. Tecnológico No. 125, CP. 68030, Oaxaca, Oax. (Mexico); Espinoza-Beltrán, Francisco Javier [Centro de Investigación y Estudios Avanzados (CINVESTAV) IPN, Unidad Querétaro, Lib. Norponiente 2000, Real de Juriquilla, C.P. 76230, Querétaro, Qro., México (Mexico)

    2014-09-30

    Highlights: • Fullerene-like CNx samples show an elastic recovery of 92.5% and 94.5% while amorphous CNx samples had only 75% elastic recovery. • Fullerene-like CNx films show an increment of 34.86% and 50.57% in fractions of C 1s and N 1s. • Fullerene-like CNx samples show a lower friction coefficient compared to amorphous CNx samples. • Friction reduction characteristics of fullerene-like CNx films are strongly related to the increase of sp{sup 3} CN bonds. - Abstract: Fullerene-like carbon nitride films exhibit high elastic modulus and low friction coefficient. In this study, thin CNx films were deposited on silicon substrate by DC magnetron sputtering and the tribological behavior at nanoscale was evaluated using an atomic force microscope. Results show that CNx films with fullerene-like structure have a friction coefficient (CoF ∼ 0.009–0.022) that is lower than amorphous CNx films (CoF ∼ 0.028–0.032). Analysis of specimens characterized by X-ray photoelectron spectroscopy shows that films with fullerene-like structure have a higher number of sp{sup 3} CN bonds and exhibit the best mechanical properties with high values of elastic modulus (E > 180 GPa) and hardness (H > 20 GPa). The elastic recovery determined on specimens with a fullerene-like CNx structure was of 95% while specimens of amorphous CNx structure had only 75% elastic recovery.

  19. Stoichiometric carbon nitride synthesized by ion beam sputtering and post nitrogen ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Valizadeh, R.; Colligon, J.S. [Salford Univ. (United Kingdom). DMM Institute; Katardiev, I.V. [Uppsala Univ. (Sweden). Angstrom Laboratory; Faunce, C.A.; Donnelly, S.E. [Salford Univ. (United Kingdom). Science Institute

    1998-06-01

    Full text: Carbon nitride films have been deposited on Si (100) by ion beam sputtering a vitreous graphite target with nitrogen and argon ions with and without concurrent N2 ion bombardment at room temperature. The sputtering beam energy was 1000 eV and the assisted beam energy was 300 eV with ion / atom arrival ratio ranging from 0.5 to 5. The carbon nitride films were deposited both as single layer directly on silicon substrate and as multilayer between two layers of stoichiometric amorphous silicon nitride and polycrystalline titanium nitride. The deposited films were implanted ex-situ with 30 keV nitrogen ions with various doses ranging from 1E17 to 4E17 ions.cm{sup -2} and 2 GeV xenon ion with a dose of 1E12 ions.cm{sup -2} . The nitrogen concentration of the films was measured with Rutherford Backscattering (RBS), Secondary Neutral Mass Spectrometry (SNMS) and Parallel Electron Energy Loss Spectroscopy (PEELS). The nitrogen concentration for as deposited sample was 34 at% and stoichiometric carbon nitride C{sub 3}N{sub 4} was achieved by post nitrogen implantation of the multi-layered films. Post bombardment of single layer carbon nitride films lead to reduction in the total nitrogen concentration. Carbon K edge structure obtained from PEELS analysis suggested that the amorphous C{sub 3}N{sub 4} matrix was predominantly sp{sup 2} bonded. This was confirmed by Fourier Transforrn Infra-Red Spectroscopy (FTIR) analysis of the single CN layer which showed the nitrogen was mostly bonded with carbon in nitrile (C{identical_to}N) and imine (C=N) groups. The microstructure of the film was determined by Transmission Electron Microscopy (TEM) which indicated that the films were amorphous.

  20. Thermochemical, structural and electronic properties of amorphous oxides, nitrides and sulfides

    Science.gov (United States)

    Zawadzki, Pawel; Lany, Stephan

    2015-03-01

    Amorphous thin films materials become increasingly important components of many functional devices such as thin film displays, photovoltaic cells or thin film transistors. Due to lack of grain boundaries, they have superior uniformity and smoothest, flexibility and corrosion resistance. Amorphous thin films are typically prepared using physical vapor deposition (PVD) techniques at temperatures well below the melting point of deposited material (<0.2Tm). Computational models of amorphous structures, however, are almost elusively constructed from a high temperature equilibrated crystal melt using simulated annealing (SA) protocol. To account for low temperature growth conditions of amorphous thin films we recently developed a new simulation technique. The method, kinetically limited minimization (KLM), starts from a randomly initialized structure and minimizes the total energy in a number of local structural perturbation-relaxation events. We apply KLM to model amorphous structures of 20 binary oxides, nitrides and sulfides and compare their thermochemical, structural and electronic properties.

  1. Characterization of amorphous and nanocrystalline carbon films

    International Nuclear Information System (INIS)

    Chu, Paul K.; Li Liuhe

    2006-01-01

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

  2. Phase transitions in biogenic amorphous calcium carbonate.

    Science.gov (United States)

    Gong, Yutao U T; Killian, Christopher E; Olson, Ian C; Appathurai, Narayana P; Amasino, Audra L; Martin, Michael C; Holt, Liam J; Wilt, Fred H; Gilbert, P U P A

    2012-04-17

    Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC · H(2)O) → dehydrated amorphous calcium carbonate (ACC) → calcite. Unexpectedly, we find ACC · H(2)O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACC · H(2)O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACC · H(2)O in vitro.

  3. Chemical vapor deposition of amorphous tungsten nitride for applications in ultra-large scale interconnect technologies

    Science.gov (United States)

    Kelsey, Jean E.

    Increasing demands on computer chip technology require exploration of novel materials and deposition techniques. The driving need to reduce device dimensions without increasing device delay time has forced a move towards copper interconnects. Copper interconnects require an encapsulating barrier layer to prevent diffusion into the dielectric layer, as well as a passivation layer to protect against oxidation. One potential material for the barrier layer is tungsten nitride (WNx). Tungsten nitride is expected to perform well as a barrier because of its refractory nature and excellent thermal, chemical, and mechanical properties. In addition, it can be deposited in amorphous form. Amorphous materials have no grain boundaries, thereby making grain boundary diffusion, a fast path diffusion mechanism, impossible. In this work, a chemical vapor deposition (CVD) process was developed for the deposition of tungsten nitride. CVD was selected because it has the potential to deposit highly conformal film. High conformality is critical in a barrier layer in order to ensure viable coverage at the bottom and sides of device structures without sacrificing critical space that would be better used by the copper metal. In this manner, the total resistivity of the interconnect is minimized. The CVD WNx process was systematically optimized for film conformality, resistivity and growth rate. This was achieved by thoroughly examining film nucleation and growth characteristics, and analyzing resulting film properties. Adhesion of copper to the CVD films was qualified using stud pull tests, while X-ray diffraction was implemented to determine crystallization temperature of the amorphous phase. Additionally, diffusion barrier properties of the CVD tungsten nitride were assessed using sputter deposited copper, and compared to those of sputter deposited tungsten nitride. Thermally activated barrier failure was studied as a function of barrier thickness using Rutherford backscattering

  4. Characterization of amorphous hydrogenated carbon films ...

    Indian Academy of Sciences (India)

    Amorphous hydrogenated carbon films (-C:H) on -type (100) silicon wafers were prepared with a middle frequency pulsed unbalanced magnetron sputtering technique (MFPUMST) at different ratios of methane–argon gases. The band characteristics, mechanical properties as well as refractive index were measured by ...

  5. Characterization of amorphous hydrogenated carbon films ...

    Indian Academy of Sciences (India)

    †Key Laboratory of Radiation and Technology of Education Ministry of China, Institute of Nuclear Science and. Technology, Sichuan University, Chengdu 610064, P. R. China. MS received 14 March 2011; revised 29 October 2011. Abstract. Amorphous hydrogenated carbon films (a-C:H) on p-type (100) silicon wafers were ...

  6. Structural morphology of amorphous conducting carbon film

    Indian Academy of Sciences (India)

    Amorphous conducting carbon films deposited over quartz substrates were analysed using X-ray diffraction and AFM technique. X-ray diffraction data reveal disorder and roughness in the plane of graphene sheet as compared to that of graphite. This roughness increases with decrease in preparation temperature. The AFM ...

  7. Amorphous Carbon: State of the Art - Proceedings of the 1st International Specialist Meeting on Amorphous Carbon (smac '97)

    Science.gov (United States)

    Silva, S. R. P.; Robertson, J.; Milne, W. I.; Amaratunga, G. A. J.

    1998-05-01

    The Table of Contents for the full book PDF is as follows: * Preface * GROWTH AND STRUCTURE * The Structure of Tetrahedral Amorphous Carbon * Growth of DLC Films and Related Structure and Properties * Deposition Mechanism of Diamond-Like Carbon * Relaxation of sp3 Bonds in Hydrogen Free Carbon Films During Growth * MODELLING * Correlations Between Microstructure and Electronic Properties in Amorphous Carbon Based Materials * Review of Monte Carlo Simulations of Diamondlike Amorphous Carbon: Bulk, Surface, and Interface Structural Properties * DEPOSITION * Preparation of Disordered Amorphous and Partially Ordered Nano Clustered Carbon Films by Arc Deposition: A Critical Review * Plasma Deposition of Diamond-Like Carbon in an ECR-RF Discharge * Deposition of Amorphous Hydrogenated Carbon-Nitrogen Films by PECVD Using Several Hydrocarbon / Nitrogen Containing Gas Mixtures * ELECTRONIC STRUCTURE * 'Defects' and Their Detection in a-C and a-C:H * Valence Band and Gap State Spectroscopy of Amorphous Carbon by Photoelectron Emission Techniques * Photoluminescence Spectroscopy: A Probe for Inhomogeneous Structure in Polymer-Like Amorphous Carbon * Raman Characterization of Amorphous and Nanocrystalline sp3 Bonded Structures * Ultraviolet Raman Spectroscopy of Tetrahedral Amorphous Carbon Thin Films * Excitation Energy Dependent Raman and Photoluminescence Spectra of Hydrogenated Amorphous Carbon * MECHANICAL PROPERTIES * Pulsed Laser Deposited a-C: Growth, Structure and Mechanical Properties * Mechanical Properties of Laser-Assisted Deposited Amorphous Carbon Films * Mechanical and Morphology Study on Tetrahedral Amorphous Carbon Films * Time-Dependent Changes in the Mechanical Properties of Diamond-Like Carbon Films * ELECTRONIC PROPERTIES * Electronic Transport in Amorphous Carbon * Electronic Properties of Undoped/Doped Tetrahedral Amorphous Carbon * The Inclusion of Graphitic Nanoparticles in Semiconducting Amorphous Carbon to Enhance Electronic Transport Properties

  8. Amorphous Silicon-Carbon Nanostructure Photovoltaic Devices

    OpenAIRE

    Schriver, Maria Christine

    2012-01-01

    A novel solar cell architecture made completely from the earth abundant elements silicon and carbon has been developed. Hydrogenated amorphous silicon (aSi:H), rather than crystalline silicon, is used as the active material due to its high absorption through a direct band gap of 1.7eV, well matched to the solar spectrum to ensure the possibility of improved cells in this architecture with higher efficiencies. The cells employ a Schottky barrier design wherein the amorphous silicon absorber la...

  9. The Electronic Structure of Amorphous Carbon Nanodots.

    Science.gov (United States)

    Margraf, Johannes T; Strauss, Volker; Guldi, Dirk M; Clark, Timothy

    2015-06-18

    We have studied hydrogen-passivated amorphous carbon nanostructures with semiempirical molecular orbital theory in order to provide an understanding of the factors that affect their electronic properties. Amorphous structures were first constructed using periodic calculations in a melt/quench protocol. Pure periodic amorphous carbon structures and their counterparts doped with nitrogen and/or oxygen feature large electronic band gaps. Surprisingly, descriptors such as the elemental composition and the number of sp(3)-atoms only influence the electronic structure weakly. Instead, the exact topology of the sp(2)-network in terms of effective conjugation defines the band gap. Amorphous carbon nanodots of different structures and sizes were cut out of the periodic structures. Our calculations predict the occurrence of localized electronic surface states, which give rise to interesting effects such as amphoteric reactivity and predicted optical band gaps in the near-UV/visible range. Optical and electronic gaps display a dependence on particle size similar to that of inorganic colloidal quantum dots.

  10. Amorphous calcium carbonate particles form coral skeletons

    Science.gov (United States)

    Mass, Tali; Giuffre, Anthony J.; Sun, Chang-Yu; Stifler, Cayla A.; Frazier, Matthew J.; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V.; Marcus, Matthew A.; Gilbert, Pupa U. P. A.

    2017-09-01

    Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene-Eocene Thermal Maximum that occurred 56 Mya.

  11. Methods of forming boron nitride

    Science.gov (United States)

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

    2015-03-03

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

  12. Memristive effects in oxygenated amorphous carbon nanodevices

    Science.gov (United States)

    Bachmann, T. A.; Koelmans, W. W.; Jonnalagadda, V. P.; Le Gallo, M.; Santini, C. A.; Sebastian, A.; Eleftheriou, E.; Craciun, M. F.; Wright, C. D.

    2018-01-01

    Computing with resistive-switching (memristive) memory devices has shown much recent progress and offers an attractive route to circumvent the von-Neumann bottleneck, i.e. the separation of processing and memory, which limits the performance of conventional computer architectures. Due to their good scalability and nanosecond switching speeds, carbon-based resistive-switching memory devices could play an important role in this respect. However, devices based on elemental carbon, such as tetrahedral amorphous carbon or ta-C, typically suffer from a low cycling endurance. A material that has proven to be capable of combining the advantages of elemental carbon-based memories with simple fabrication methods and good endurance performance for binary memory applications is oxygenated amorphous carbon, or a-CO x . Here, we examine the memristive capabilities of nanoscale a-CO x devices, in particular their ability to provide the multilevel and accumulation properties that underpin computing type applications. We show the successful operation of nanoscale a-CO x memory cells for both the storage of multilevel states (here 3-level) and for the provision of an arithmetic accumulator. We implement a base-16, or hexadecimal, accumulator and show how such a device can carry out hexadecimal arithmetic and simultaneously store the computed result in the self-same a-CO x cell, all using fast (sub-10 ns) and low-energy (sub-pJ) input pulses.

  13. Nanostructural characterization of amorphous diamondlike carbon films

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-01-27

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

  14. Extracting Crystal Chemistry from Amorphous Carbon Structures.

    Science.gov (United States)

    Deringer, Volker L; Csányi, Gábor; Proserpio, Davide M

    2017-04-19

    Carbon allotropes have been explored intensively by ab initio crystal structure prediction, but such methods are limited by the large computational cost of the underlying density functional theory (DFT). Here we show that a novel class of machine-learning-based interatomic potentials can be used for random structure searching and readily predicts several hitherto unknown carbon allotropes. Remarkably, our model draws structural information from liquid and amorphous carbon exclusively, and so does not have any prior knowledge of crystalline phases: it therefore demonstrates true transferability, which is a crucial prerequisite for applications in chemistry. The method is orders of magnitude faster than DFT and can, in principle, be coupled with any algorithm for structure prediction. Machine-learning models therefore seem promising to enable large-scale structure searches in the future. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Hydrogenated amorphous silicon nitride photonic crystals for improved-performance surface electromagnetic wave biosensors.

    Science.gov (United States)

    Sinibaldi, Alberto; Descrovi, Emiliano; Giorgis, Fabrizio; Dominici, Lorenzo; Ballarini, Mirko; Mandracci, Pietro; Danz, Norbert; Michelotti, Francesco

    2012-10-01

    We exploit the properties of surface electromagnetic waves propagating at the surface of finite one dimensional photonic crystals to improve the performance of optical biosensors with respect to the standard surface plasmon resonance approach. We demonstrate that the hydrogenated amorphous silicon nitride technology is a versatile platform for fabricating one dimensional photonic crystals with any desirable design and operating in a wide wavelength range, from the visible to the near infrared. We prepared sensors based on photonic crystals sustaining either guided modes or surface electromagnetic waves, also known as Bloch surface waves. We carried out for the first time a direct experimental comparison of their sensitivity and figure of merit with surface plasmon polaritons on metal layers, by making use of a commercial surface plasmon resonance instrument that was slightly adapted for the experiments. Our measurements demonstrate that the Bloch surface waves on silicon nitride photonic crystals outperform surface plasmon polaritons by a factor 1.3 in terms of figure of merit.

  16. Protective amorphous carbon coatings on glass substrates

    Science.gov (United States)

    Silins, Kaspars; Baránková, Hana; Bardos, Ladislav

    2017-11-01

    Thick amorphous carbon films were deposited by the Magnets-in-Motion (M-M) rf linear hollow cathode at varying acetylene contents in Ar in a hybrid PVD/PE-CVD process directly on glass substrates. The hollow cathode plates manufactured from graphite were used as the PVD target. The measurements show that the films can reach thickness of up to 50 μm at deposition rates of up to 2.5 μm/min. Scratch test measurements confirm that well adhering films several μm thick can be achieved at C2H2 contents of up to 0.5%.

  17. On the temperature dependence of the photoconductivity of amorphous silicon nitride (a-Si Nx: H)

    International Nuclear Information System (INIS)

    Tessler, L.R.; Alvarez, F.; Chambouleyron, I.

    1984-01-01

    Experimental results on the photoconducticity of amorphous hydrogenated silicon nitride a-SiNx: H prepared from plasma decomposition of a gaseus mixture of silane and nitrogen ([Si H 4 ]/[N 2 ] ∼ 0.33) are presented. The material is deposited in a capacitively coupled glow discharge system and nitrogen content was continuously increased by increasing the RF power dissipated in the plasma. Studies of the photocurrent as a function of temperature as a function of temperature and lig ht intensities are reported. (Author) [pt

  18. Photoluminescence and Raman Spectroscopy Studies of Carbon Nitride Films

    Directory of Open Access Journals (Sweden)

    J. Hernández-Torres

    2016-01-01

    Full Text Available Amorphous carbon nitride films with N/C ratios ranging from 2.24 to 3.26 were deposited by reactive sputtering at room temperature on corning glass, silicon, and quartz as substrates. The average chemical composition of the films was obtained from the semiquantitative energy dispersive spectroscopy analysis. Photoluminescence measurements were performed to determine the optical band gap of the films. The photoluminescence spectra displayed two peaks: one associated with the substrate and the other associated with CNx films located at ≈2.13±0.02 eV. Results show an increase in the optical band gap from 2.11 to 2.15 eV associated with the increase in the N/C ratio. Raman spectroscopy measurements showed a dominant D band. ID/IG ratio reaches a maximum value for N/C ≈ 3.03 when the optical band gap is 2.12 eV. Features observed by the photoluminescence and Raman studies have been associated with the increase in the carbon sp2/sp3 ratio due to presence of high nitrogen content.

  19. Laser ablation of molecular carbon nitride compounds

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, D., E-mail: d.fischer@fkf.mpg.de [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Schwinghammer, K. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), 80799 Munich (Germany); Sondermann, C. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Lau, V.W.; Mannhart, J. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Lotsch, B.V. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), 80799 Munich (Germany)

    2015-09-15

    We present a method for the preparation of thin films on sapphire substrates of the carbon nitride precursors dicyandiamide (C{sub 2}N{sub 4}H{sub 4}), melamine (C{sub 3}N{sub 6}H{sub 6}), and melem (C{sub 6}N{sub 10}H{sub 6}), using the femtosecond-pulsed laser deposition technique (femto-PLD) at different temperatures. The depositions were carried out under high vacuum with a femtosecond-pulsed laser. The focused laser beam is scanned on the surface of a rotating target consisting of the pelletized compounds. The resulting polycrystalline, opaque films were characterized by X-ray powder diffraction, infrared, Raman, and X-ray photoelectron spectroscopy, photoluminescence, SEM, and MALDI-TOF mass spectrometry measurements. The crystal structures and optical/spectroscopic results of the obtained rough films largely match those of the bulk materials.

  20. Room temperature synthesis of biodiesel using sulfonated graphitic carbon nitride

    OpenAIRE

    Baig, R. B. Nasir; Verma, Sanny; Nadagouda, Mallikarjuna N.; Varma, Rajender S.

    2016-01-01

    Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.

  1. Room temperature synthesis of biodiesel using sulfonated graphitic carbon nitride

    Science.gov (United States)

    Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.

  2. Defect complexes in carbon and boron nitride nanotubes

    CSIR Research Space (South Africa)

    Mashapa, MG

    2012-05-01

    Full Text Available The effect of defect complexes on the stability, structural and electronic properties of single-walled carbon nanotubes and boron nitride nanotubes is investigated using the ab initio pseudopotential density functional method implemented...

  3. Nanostructural characterization of amorphous diamondlike carbon films

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-04-15

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

  4. Triple templating of graphitic carbon nitride to enhance photocatalytic properties

    Directory of Open Access Journals (Sweden)

    Z. Yang

    2016-01-01

    Full Text Available Graphitic carbon nitride materials show some promising properties for applications such as photocatalytic water splitting. However, the conversion efficiency is still low due to factors such as a low surface area and limited light absorption. In this paper, we describe a “triple templating” approach to generating porous graphitic carbon nitride. The introduction of pores on several length-scales results in enhanced photocatalytic properties.

  5. Triple templating of graphitic carbon nitride to enhance photocatalytic properties

    OpenAIRE

    Z. Yang; A. E. Danks; J. Wang; Y. Zhang; Z. Schnepp

    2016-01-01

    Graphitic carbon nitride materials show some promising properties for applications such as photocatalytic water splitting. However, the conversion efficiency is still low due to factors such as a low surface area and limited light absorption. In this paper, we describe a “triple templating” approach to generating porous graphitic carbon nitride. The introduction of pores on several length-scales results in enhanced photocatalytic properties.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-15

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

  7. Coaxial carbon plasma gun deposition of amorphous carbon films

    Science.gov (United States)

    Sater, D. M.; Gulino, D. A.; Rutledge, S. K.

    1984-01-01

    A unique plasma gun employing coaxial carbon electrodes was used in an attempt to deposit thin films of amorphous diamond-like carbon. A number of different structural, compositional, and electrical characterization techniques were used to characterize these films. These included scanning electron microscopy, scanning transmission electron microscopy, X ray diffraction and absorption, spectrographic analysis, energy dispersive spectroscopy, and selected area electron diffraction. Optical absorption and electrical resistivity measurements were also performed. The films were determined to be primarily amorphous, with poor adhesion to fused silica substrates. Many inclusions of particulates were found to be present as well. Analysis of these particulates revealed the presence of trace impurities, such as Fe and Cu, which were also found in the graphite electrode material. The electrodes were the source of these impurities. No evidence of diamond-like crystallite structure was found in any of the film samples. Details of the apparatus, experimental procedure, and film characteristics are presented.

  8. Polymeric photocatalysts based on graphitic carbon nitride.

    Science.gov (United States)

    Cao, Shaowen; Low, Jingxiang; Yu, Jiaguo; Jaroniec, Mietek

    2015-04-01

    Semiconductor-based photocatalysis is considered to be an attractive way for solving the worldwide energy shortage and environmental pollution issues. Since the pioneering work in 2009 on graphitic carbon nitride (g-C3N4) for visible-light photocatalytic water splitting, g-C3N4 -based photocatalysis has become a very hot research topic. This review summarizes the recent progress regarding the design and preparation of g-C3N4 -based photocatalysts, including the fabrication and nanostructure design of pristine g-C3N4 , bandgap engineering through atomic-level doping and molecular-level modification, and the preparation of g-C3N4 -based semiconductor composites. Also, the photo-catalytic applications of g-C3N4 -based photocatalysts in the fields of water splitting, CO2 reduction, pollutant degradation, organic syntheses, and bacterial disinfection are reviewed, with emphasis on photocatalysis promoted by carbon materials, non-noble-metal cocatalysts, and Z-scheme heterojunctions. Finally, the concluding remarks are presented and some perspectives regarding the future development of g-C3N4 -based photocatalysts are highlighted. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Radiofrequency cold plasma nitrided carbon steel: Microstructural and micromechanical characterizations

    International Nuclear Information System (INIS)

    Bouanis, F.Z.; Bentiss, F.; Bellayer, S.; Vogt, J.B.; Jama, C.

    2011-01-01

    Highlights: → C38 carbon steel samples were plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge. → RF plasma treatment enables nitriding for non-heated substrates. → The morphological and chemical analyses show the formation of a uniform thickness on the surface of the nitrided C38 steel. → Nitrogen plasma active species diffuse into the samples and lead to the formation of Fe x N. → The increase in microhardness values for nitrided samples with plasma processing time is interpreted by the formation of a thicker nitrided layer on the steel surface. - Abstract: In this work, C38 carbon steel was plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge on non-heated substrates. General characterizations were performed to compare the chemical compositions, the microstructures and hardness of the untreated and plasma treated surfaces. The plasma nitriding was carried out on non-heated substrates at a pressure of 16.8 Pa, using N 2 gas. Surface characterizations before and after N 2 plasma treatment were performed by means of the electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS) and Vickers microhardness measurements. The morphological and chemical analysis showed the formation of a uniform structure on the surface of the nitrided sample with enrichment in nitrogen when compared to untreated sample. The thickness of the nitride layer formed depends on the treatment time duration and is approximately 14 μm for 10 h of plasma treatment. XPS was employed to obtain chemical-state information of the plasma nitrided steel surfaces. The micromechanical results show that the surface microhardness increases as the plasma-processing time increases to reach, 1487 HV 0.005 at a plasma processing time of 8 h.

  10. Novel low Wigner energy amorphous carbon-carbon composite

    Science.gov (United States)

    Dasgupta, Kinshuk; Prakash, Jyoti; Tripathi, B. M.

    2014-02-01

    A novel amorphous carbon-carbon composite has been developed using carbon black dispersed in carbonized phenolic resin matrix in order to avoid Wigner energy problem associated with graphite. The as prepared sample showed a density of 1320 kg m-3. This has been further densified by resin impregnation and chemical vapour infiltration. The effect of processing parameters on final density (1517 kg m-3) has been investigated. This composite possesses the compressive strength of 65 Mpa, coefficient of thermal expansion of 3 × 10-6 K-1 and the specific heat of 1.2 J g-1 K-1. This novel composite was subjected to 145 MeV Ne+6 heavy ion irradiation at different doses. The highest dose was kept at 3 × 10-4 dpa. The stored energy in the composite was found to be 212 J g-1 at the highest dose of irradiation, which is much below than that of graphite. The composite remained amorphous after irradiation as confirmed by X-ray diffraction.

  11. Graphitic carbon nitride based nanocomposites: a review

    Science.gov (United States)

    Zhao, Zaiwang; Sun, Yanjuan; Dong, Fan

    2014-11-01

    Graphitic carbon nitride (g-C3N4), as an intriguing earth-abundant visible light photocatalyst, possesses a unique two-dimensional structure, excellent chemical stability and tunable electronic structure. Pure g-C3N4 suffers from rapid recombination of photo-generated electron-hole pairs resulting in low photocatalytic activity. Because of the unique electronic structure, the g-C3N4 could act as an eminent candidate for coupling with various functional materials to enhance the performance. According to the discrepancies in the photocatalytic mechanism and process, six primary systems of g-C3N4-based nanocomposites can be classified and summarized: namely, the g-C3N4 based metal-free heterojunction, the g-C3N4/single metal oxide (metal sulfide) heterojunction, g-C3N4/composite oxide, the g-C3N4/halide heterojunction, g-C3N4/noble metal heterostructures, and the g-C3N4 based complex system. Apart from the depiction of the fabrication methods, heterojunction structure and multifunctional application of the g-C3N4-based nanocomposites, we emphasize and elaborate on the underlying mechanisms in the photocatalytic activity enhancement of g-C3N4-based nanocomposites. The unique functions of the p-n junction (semiconductor/semiconductor heterostructures), the Schottky junction (metal/semiconductor heterostructures), the surface plasmon resonance (SPR) effect, photosensitization, superconductivity, etc. are utilized in the photocatalytic processes. Furthermore, the enhanced performance of g-C3N4-based nanocomposites has been widely employed in environmental and energetic applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation, carbon dioxide reduction, disinfection, and supercapacitors. This critical review ends with a summary and some perspectives on the challenges and new directions in exploring g-C3N4-based advanced nanomaterials.

  12. Preparation and characterization of electrochemically deposited carbon nitride films on silicon substrate

    International Nuclear Information System (INIS)

    Yan Xingbin; Xu Tao; Chen Gang; Yang Shengrong; Liu Huiwen; Xue Qunji

    2004-01-01

    Carbon nitride films (CN x films) were deposited on Si(100) substrates by the electrolysis of methanol-urea solution at high voltage, atmospheric pressure, and low temperature. The microstructure and morphology of the resulting CN x films were analysed by means of Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectrometry (FTIR), x-ray diffraction (XRD), and atomic force microscopy. The tribological properties of the CN x films were examined on an UMT-2MT friction and wear test rig. The Raman spectrum showed two characteristic bands: a graphite G band and a disordered D band of carbon, which suggested the presence of an amorphous carbon matrix. XPS and FTIR measurements suggested the existence of both single and double carbon-nitride bonds in the film and the hydrogenation of the carbon nitride phase. The XRD spectrum showed various peaks of different d values, which could confirm the existence of the polycrystalline carbon nitride phase. The hydrogenated CN x films were compact and uniform, with a root mean square roughness of about 18 nm. The films showed excellent friction-reduction and wear-resistance, with the friction coefficient in the stable phase being about 0.08. In addition, the growth mechanism of the CN x films in liquid phase electro-deposition was discussed as well. It was assumed that the molecules of CH 3 OH and CO(NH 2 ) 2 were polarized under high electric field, and the CN x film was formed on the substrate through the reaction of the -CH 3 and -NH 2 groups on the cathode

  13. Ge nitride formation in N-doped amorphous Ge2Sb2Te5

    International Nuclear Information System (INIS)

    Jung, M.-C.; Lee, Y. M.; Kim, H.-D.; Kim, M. G.; Shin, H. J.; Kim, K. H.; Song, S. A.; Jeong, H. S.; Ko, C. H.; Han, M.

    2007-01-01

    The chemical state of N in N-doped amorphous Ge 2 Sb 2 Te 5 (a-GST) samples with 0-14.3 N at. % doping concentrations was investigated by high-resolution x-ray photoelectron spectroscopy (HRXPS) and Ge K-edge x-ray absorption spectroscopy (XAS). HRXPS showed negligible change in the Te 4d and Sb 4d core-level spectra. In the Ge 3d core-level spectra, a Ge nitride (GeN x ) peak developed at the binding energy of 30.2 eV and increased in intensity as the N-doping concentration increased. Generation of GeN x was confirmed by the Ge K-edge absorption spectra. These results indicate that the N atoms bonded with the Ge atoms to form GeN x , rather than bonding with the Te or Sb atoms. It has been suggested that the formation of Ge nitride results in increased resistance and phase-change temperature

  14. Formation of graphitic carbon nitride and boron carbon nitride film on sapphire substrate

    Science.gov (United States)

    Kosaka, Maito; Urakami, Noriyuki; Hashimoto, Yoshio

    2018-02-01

    As a novel production method of boron carbon nitride (BCN) films, in this paper, we present the incorporation of B into graphitic carbon nitride (g-C3N4). First, we investigated the formation of g-C3N4 films via chemical vapor deposition (CVD) using melamine powder as the precursor. The formation of g-C3N4 films on a c-plane sapphire substrate was confirmed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy measurements. The deposition temperature of g-C3N4 films was found to be suitable between 550 and 600 °C since the degradation and desorption of hexagonal C–N bonds should be suppressed. As for BCN films, we prepared BCN films via two-zone extended CVD using ammonia borane as the B precursor. Several XPS signals from B, C, and N core levels were detected from B-incorporated g-C3N4 films. While the N composition was almost constant, the marked tendencies for increasing B composition and decreasing C composition were achieved with the increase in the B incorporation, indicating the incorporation of B atoms by the substitution for C atoms. Optical absorptions were shifted to the high-energy side by B incorporation, which indicates the successful formation of BCN films using melamine and ammonia borane powders as precursors.

  15. Designed synthesis of tunable amorphous carbon nanotubes (a ...

    Indian Academy of Sciences (India)

    Administrator

    Page 1. Electronic Supplementary Material. Graphical abstract. Designed synthesis of tunable amorphous carbon nanotubes (a-CNTs) by a novel route and their oxidation resistance properties by Longlong. Xu et al (pp 1397–1402).

  16. Optical properties of amorphous hydrogenated carbon films

    Science.gov (United States)

    Chen, Jing Qiu

    Carbon can be formed either as fully crystalline structures, such as diamond, graphite, and fullerene (C60). or as mostly amorphous structures, like amorphous hydrogenated carbon (a-C:H). A study was made of a-C:H films which had been deposited by plasma enhanced chemical vapor deposition (PECVD) using CH4, H2 and Ar (or N2 for doping) gas mixtures. Each film exhibits unique physical, optical and electronic properties dependent upon the specific deposition parameters. The study is intended to extend our understanding of the properties of a-C:H films. Samples prepared by James Johnson, similar to those used in his previous studies (using mainly 4 separate sets of deposition parameters), were evaluated along with other samples which were unique to this study. Film preparation parameters were varied to allow an examination of the effects induced through the variation of deposition power level, partial substitution of nitrogen for methane in the deposition process gasses and post-deposition thermal annealing. The film optical properties were evaluated using combination of non-destructive test methods, including Raman scattering, photoluminescence (PL), optical absorption and photoluminescence excitation (PLE) spectroscopies. Different PL responses at low temperature (6 K) were recorded for doped and/or annealed samples deriving from the main set of samples. Two new features at 564 and 637 nm of nitrogen doped films replaced the 597 and 703 nm of undoped films. For the first time, three Raman phonon peaks were observed in a nitrogen doped and annealed film. Additional FTIR data indicated that the third Raman phonon peak was associated with CH2 and CH3 bonding structures. The Raman scattering data contributed to an improved understanding of the two-phase (sp2, sp3) model developed by Robertson. Optical absorption measurements could only be obtained for the films deposited on fused quartz. All other measurements were made on films deposited on silicon, which is opaque in

  17. Synthesis of carbon nitride powder by selective etching of TiC0.3N0.7 in chlorine-containing atmosphere at moderate temperature

    International Nuclear Information System (INIS)

    Sui Jian; Lu Jinjun

    2010-01-01

    We reported the synthesis of carbon nitride powder by extracting titanium from single inorganic precursor TiC 0.3 N 0.7 in chlorine-containing atmosphere at ambient pressure and temperature not exceeding 500 deg. C. The TiC 0.3 N 0.7 crystalline structure acted as a template, supplying active carbon and nitrogen atoms for carbon nitride when it was destroyed in chlorination. X-ray diffraction data showed that the obtained carbon nitride powders were amorphous, which was in good agreement with transmission electron microscope analysis. The composition and structure of carbon nitride powders were analyzed by employing Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Results indicated that disorder structure was most likely for the carbon nitride powders and the N content depended greatly on the chlorination temperature. Thermal analysis in flowing N 2 indicated that the mass loss started from 300 deg. C and the complete decomposition occurred at around 650 deg. C, confirming the low thermal stability of the carbon nitride material.

  18. Vacancy complexes in carbon and boron nitride nanotubes

    CSIR Research Space (South Africa)

    Mashapa, MG

    2012-10-01

    Full Text Available The effect of divacancies on the stability, structural and electronic properties of carbon and boron nitride nanotubes is studied using the ab initio density functional method. VBBN is more stable in the boron-rich and less stable in the nitrogen...

  19. Designed synthesis of tunable amorphous carbon nanotubes (a ...

    Indian Academy of Sciences (India)

    Administrator

    Amorphous carbon nanotubes; chemical synthesis; structures; oxidation resistance properties. 1. Introduction. Since the discovery of carbon ... novel route for the synthesis of a-CNTs using V3O7∙H2O and glucose solution as the starting .... symmetric band, although its asymmetric band at about. 3080 cm–1 is not observed, ...

  20. Amorphous carbon enhancement of hydrogen penetration into UO2

    International Nuclear Information System (INIS)

    Zalkind, S.; Shamir, N.; Gouder, T.; Akhvlediani, R.; Hoffman, A.

    2014-01-01

    In a previous study, it was demonstrated that an amorphous carbon layer, deposited on a native oxide covered uranium surface, significantly enhances the interaction of hydrogen with the uranium metal. Fig. 1[2], demonstrates the preferential hydrogen attack (forming uranium hydride) on the carbon covered area of the naturally oxidized uranium metal

  1. Preparation and characterization of morph-genetic aluminum nitride/carbon composites from filter paper

    International Nuclear Information System (INIS)

    Wang Wei; Xue Tao; Jin Zhihao; Qiao Guanjun

    2008-01-01

    Morph-genetic aluminum nitride/carbon composites with cablelike structure were prepared from filter paper template through the surface sol-gel process and carbothermal nitridation reaction. The resulting materials have a hierarchical structure originating from the morphology of cellulose paper. The aluminum nitride/carbon composites have the core-shell microstructure, the core is graphitic carbon, and the shell is aluminum nitride nanocoating formed by carbothermal nitridation reduction of alumina with the interfacial carbon in nitrogen atmosphere. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscope were employed to characterize the structural morphology and phase compositions of the final products

  2. Synthesis of graphitic carbon nitride by reaction of melamine and uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Dante, Roberto C., E-mail: rcdante@yahoo.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martin-Ramos, Pablo, E-mail: pablomartinramos@gmail.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Correa-Guimaraes, Adriana, E-mail: acg@iaf.uva.es [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martin-Gil, Jesus, E-mail: jesusmartingil@gmail.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain)

    2011-11-01

    Highlights: {yields} Graphitic carbon nitrides by CVD of melamine and uric acid on alumina. {yields} The building blocks of carbon nitrides are heptazine nuclei. {yields} Composite particles with alumina core and carbon nitride coating. - Abstract: Graphitic carbon nitrides were synthesized starting from melamine and uric acid. Uric acid was chosen because it thermally decomposes, and reacts with melamine by condensation at temperatures in the range of 400-600 deg. C. The reagents were mixed with alumina and subsequently the samples were treated in an oven under nitrogen flux. Alumina favored the deposition of the graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in situ chemical vapor deposition (CVD). Infrared (IR) spectra, as well as X-ray diffraction (XRD) patterns, are in accordance with the formation of a graphitic carbon nitride with a structure based on heptazine blocks. These carbon nitrides exhibit poor crystallinity and a nanometric texture, as shown by transmission electron microscopy (TEM) analysis. The thermal degradation of the graphitic carbon nitride occurs through cyano group formation, and involves the bridging tertiary nitrogen and the bonded carbon, which belongs to the heptazine ring, causing the ring opening and the consequent network destruction as inferred by connecting the IR and X-ray photoelectron spectroscopy (XPS) results. This seems to be an easy and promising route to synthesize graphitic carbon nitrides. Our final material is a composite made of an alumina core covered by carbon nitride layers.

  3. Fracture of Carbon Nanotube - Amorphous Carbon Composites: Molecular Modeling

    Science.gov (United States)

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

    2015-01-01

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

  4. Hydrogenated amorphous carbon next deposit after heat treatment

    International Nuclear Information System (INIS)

    Salancon, E.; Durbeck, T.; Schwarz-Selinger, T.; Jacob, W.

    2006-01-01

    One of the main safety problems in the ITER tokamak project is the tritium adsorption in the reactor walls and in particular the deposits which appear after the plasma discharge. These deposits are amorphous hydrogenated carbon films, type polymer (soft a-C:H). The heating of these deposits with a pulse laser is a proposed solution for the tritium desorption. Meanwhile, Gibson and al show that in experimental conditions, products are deposed on the walls before entering the mass spectrometer. The authors present thermo-desorption spectra of different amorphous carbon films. (A.L.B.)

  5. Anti corrosion layer for stainless steel in molten carbonate fuel cell - comprises phase vapour deposition of titanium nitride, aluminium nitride or chromium nitride layer then oxidising layer in molten carbonate electrolyte

    DEFF Research Database (Denmark)

    2000-01-01

    Forming an anticorrosion protective layer on a stainless steel surface used in a molten carbonate fuel cell (MCFC) - comprises the phase vapour deposition (PVD) of a layer comprising at least one of titanium nitride, aluminium nitride or chromium nitride and then forming a protective layer in situ...

  6. Amorphous Metal Tungsten Nitride and its Application for Micro and Nanoelectromechanical Applications

    KAUST Repository

    Mayet, Abdulilah M.

    2016-05-01

    The objective of this doctoral thesis is to develop, engineer and investigate an amorphous metal tungsten nitride (aWNx) and to study its functionality for applications focused on electromechanical system at the nano-scale. Charge transport based solid state device oriented complementary metal oxide semiconductor (CMOS) electronics have reached a level where they are scaled down to nearly their fundamental limits regarding switching speed, off state power consumption and the on state power consumption due to the fundamental limitation of sub-threshold slope (SS) remains at 60 mV/dec. NEM switch theoretically and practically offers the steepest sub-threshold slope and practically has shown zero static power consumption due to their physical isolation originated from the nature of their mechanical operation. Fundamental challenges remain with NEM switches in context of their performance and reliability: (i) necessity of lower pull-in voltage comparable to CMOS technology; (ii) operation in ambient/air; (iii) increased ON current and decreased ON resistance; (iv) scaling of devices and improved mechanical and electrical contacts; and (v) high endurance. The “perfect” NEM switch should overcome all the above-mentioned challenges. Here, we show such a NEM switch fabricated with aWNx to show (i) sub-0.3-volt operation; (ii) operation in air and vacuum; (iii) ON current as high as 0.5 mA and ON resistance lower than 5 kΩ; (iv) improved mechanical contact; and the most importantly (v) continuous switching of 8 trillion cycles for more than 10 days with the highest switching speed is 30 nanosecond without hysteresis. In addition, tungsten nitride could be the modern life vine by fulfilling the demand of biodegradable material for sustainable life regime. Transient electronics is a form of biodegradable electronics as it is physically disappearing totally or partially after performing the required function. The fabricated aWNx suites this category very well, despite not

  7. Synthesis of carbon black/carbon nitride intercalation compound composite for efficient hydrogen production.

    Science.gov (United States)

    Wu, Zhaochun; Gao, Honglin; Yan, Shicheng; Zou, Zhigang

    2014-08-21

    The photoactivity of g-C3N4 is greatly limited by its high recombination rate of photogenerated carriers. Coupling g-C3N4 with other materials has been demonstrated to be an effective way to facilitate the separation and transport of charge carriers. Herein we report a composite of conductive carbon black and carbon nitride intercalation compound synthesized through facile one-step molten salt method. The as-prepared carbon black/carbon nitride intercalation compound composite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), UV-vis absorption spectrum and photoluminescence spectroscopy (PL). The carbon black nanoparticles, homogeneously dispersed on the surface of carbon nitride intercalation compound, efficiently enhanced separation and transport of photogenerated carriers, thus improving the visible-light photocatalytic activity. The composite of 0.5 wt% carbon black and carbon nitride intercalation compound exhibited a H2 production rate of 68.9 μmol h(-1), which is about 3.2 times higher than hydrogen production on pristine carbon nitride intercalation compound.

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

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-09-04

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

  9. Designed synthesis of tunable amorphous carbon nanotubes (a ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 6. Designed synthesis of tunable amorphous carbon nanotubes (a-CNTs) by a novel route and their oxidation resistance properties. Longlong Xu Yifu Zhang Xiongzhi Zhang Yu Huang Xiaoyu Tan Chi Huang Xiao Mei Fei Niu Changgong Meng Gongzhen ...

  10. Modeling of amorphous carbon structures with arbitrary structural constraints.

    Science.gov (United States)

    Jornada, F H; Gava, V; Martinotto, A L; Cassol, L A; Perottoni, C A

    2010-10-06

    In this paper we describe a method to generate amorphous structures with arbitrary structural constraints. This method employs the simulated annealing algorithm to minimize a simple yet carefully tailored cost function (CF). The cost function is composed of two parts: a simple harmonic approximation for the energy-related terms and a cost that penalizes configurations that do not have atoms in the desired coordinations. Using this approach, we generated a set of amorphous carbon structures spawning nearly all the possible combinations of sp, sp(2) and sp(3) hybridizations. The bulk moduli of this set of amorphous carbons structures was calculated using Brenner's potential. The bulk modulus strongly depends on the mean coordination, following a power-law behavior with an exponent ν = 1.51 ± 0.17. A modified cost function that segregates carbon with different hybridizations is also presented, and another set of structures was generated. With this new set of amorphous materials, the correlation between the bulk modulus and the mean coordination weakens. The method proposed can be easily modified to explore the effects on the physical properties of the presence of hydrogen, dangling bonds, and structural features such as carbon rings.

  11. Encapsulated Vanadium-Based Hybrids in Amorphous N-Doped Carbon Matrix as Anode Materials for Lithium-Ion Batteries.

    Science.gov (United States)

    Long, Bei; Balogun, Muhammad-Sadeeq; Luo, Lei; Luo, Yang; Qiu, Weitao; Song, Shuqin; Zhang, Lei; Tong, Yexiang

    2017-11-01

    Recently, researchers have made significant advancement in employing transition metal compound hybrids as anode material for lithium-ion batteries and developing simple preparation of these hybrids. To this end, this study reports a facile and scalable method for fabricating a vanadium oxide-nitride composite encapsulated in amorphous carbon matrix by simply mixing ammonium metavanadate and melamine as anode materials for lithium-ion batteries. By tuning the annealing temperature of the mixture, different hybrids of vanadium oxide-nitride compounds are synthesized. The electrode material prepared at 700 °C, i.e., VM-700, exhibits excellent cyclic stability retaining 92% of its reversible capacity after 200 cycles at a current density of 0.5 A g -1 and attractive rate performance (220 mAh g -1 ) under the current density of up to 2 A g -1 . The outstanding electrochemical properties can be attributed to the synergistic effect from heterojunction form by the vanadium compound hybrids, the improved ability of the excellent conductive carbon for electron transfer, and restraining the expansion and aggregation of vanadium oxide-nitride in cycling. These interesting findings will provide a reference for the preparation of transition metal oxide and nitride composites as well. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. On new allotropes and nanostructures of carbon nitrides

    OpenAIRE

    Bojdys, Michael Janus

    2010-01-01

    In the first section of the thesis graphitic carbon nitride was for the first time synthesised using the high-temperature condensation of dicyandiamide (DCDA) – a simple molecular precursor – in a eutectic salt melt of lithium chloride and potassium chloride. The extent of condensation, namely next to complete conversion of all reactive end groups, was verified by elemental microanalysis and vibrational spectroscopy. TEM- and SEM-measurements gave detailed insight into the well-defined morpho...

  13. Towards efficient solar hydrogen production by intercalated carbon nitride photocatalyst.

    Science.gov (United States)

    Gao, Honglin; Yan, Shicheng; Wang, Jiajia; Huang, Yu An; Wang, Peng; Li, Zhaosheng; Zou, Zhigang

    2013-11-07

    The development of efficient photocatalytic material for converting solar energy to hydrogen energy as viable alternatives to fossil-fuel technologies is expected to revolutionize energy shortage and environment issues. However, to date, the low quantum yield for solar hydrogen production over photocatalysts has hindered advances in the practical applications of photocatalysis. Here, we show that a carbon nitride intercalation compound (CNIC) synthesized by a simple molten salt route is an efficient polymer photocatalyst with a high quantum yield. We found that coordinating the alkali metals into the C-N plane of carbon nitride will induce the un-uniform spatial charge distribution. The electrons are confined in the intercalated region while the holes are in the far intercalated region, which promoted efficient separation of photogenerated carriers. The donor-type alkali metal ions coordinating into the nitrogen pots of carbon nitrides increase the free carrier concentration and lead to the formation of novel nonradiative paths. This should favor improved transport of the photogenerated electron and hole and decrease the electron-hole recombination rate. As a result, the CNIC exhibits a quantum yield as high as 21.2% under 420 nm light irradiation for solar hydrogen production. Such high quantum yield opens up new opportunities for using cheap semiconducting polymers as energy transducers.

  14. Distribution patterns of different carbon nanostructures in silicon nitride composites.

    Science.gov (United States)

    Tapasztó, Orsolya; Markó, Márton; Balázsi, Csaba

    2012-11-01

    The dispersion properties of single- and multi-walled carbon nanotubes as well as mechanically exfoliated few layer graphene flakes within the silicon nitride ceramic matrix have been investigated. Small angle neutron scattering experiments have been employed to gain information on the dispersion of the nano-scale carbon fillers throughout the entire volume of the samples. The neutron scattering data combined with scanning electron microscopy revealed strikingly different distribution patterns for different types of carbon nanostructures. The scattering intensities for single wall carbon nanotubes (SWCNTs) reveal a decay exponent characteristic to surface fractals, which indicate that the predominant part of nanotubes can be found in loose networks wrapping the grains of the polycrystalline matrix. By contrast, multi wall carbon nanotubes (MWCNTs) were found to be present mainly in the form of bulk aggregate structures, while few-layer graphene (FLG) flakes have been individually dispersed within the host matrix, under the very same preparation and processing conditions.

  15. Nitrides

    International Nuclear Information System (INIS)

    Uehlls, A.

    1987-01-01

    The structure and certain properties of the ionic and covalent nitrides of alkali earth, rare earth, transition elements, cadmium, boron, indium and thorium are considered briefly. Peculiarities of the crystal structure, the structure of coordinated polyhedrons, the character and parameters of chemical bond depending on nitride composition are discussed

  16. Preparation of multilayer carbon microspheres by using graphitic carbon nitride as precursor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xuefei, E-mail: wuxt12@mails.jlu.edu.cn; Wu, Xingtong

    2015-11-15

    Multilayer carbon microspheres were synthesized by using graphitic Carbon Nitride as precursor. The result of SEM and TEM showed that micrometer-sized multilayer spherical carbon structure had been prepared without the designed addition of any catalyst or template. The composition of the sample indicated that the sample was pure carbon materials. The result of XRD and Raman revealed low graphitization degree of carbon microspheres. FTIR and the analysis of theoretical spectra calculated by using GAUSSIAN 03 program indicated carbon microspheres structure model consisted of many five-member carbon rings. It also can be the cause of the low graphitized degree.

  17. Magnetic graphitic carbon nitride: its application in the C–H activation of amines

    Science.gov (United States)

    Magnetic graphitic carbon nitride, Fe@g-C3N4, has been synthesized by adorning graphitic carbon nitride (g-C3N4) support with iron oxide via non-covalent interaction. The magnetically recyclable catalyst showed excellent reactivity for expeditious C-H activation and cyanation of ...

  18. Generation and Characteristics of IV-VI transition Metal Nitride and Carbide Nanoparticles using a Reactive Mesoporous Carbon Nitride

    KAUST Repository

    Alhajri, Nawal Saad

    2016-02-22

    Interstitial nitrides and carbides of early transition metals in groups IV–VI exhibit platinum-like electronic structures, which make them promising candidates to replace noble metals in various catalytic reactions. Herein, we present the preparation and characterization of nano-sized transition metal nitries and carbides of groups IV–VI (Ti, V, Nb, Ta, Cr, Mo, and W) using mesoporous graphitic carbon nitride (mpg-C3N4), which not only provides confined spaces for restricting primary particle size but also acts as a chemical source of nitrogen and carbon. We studied the reactivity of the metals with the template under N2 flow at 1023 K while keeping the weight ratio of metal to template constant at unity. The produced nanoparticles were characterized by powder X-ray diffraction, CHN elemental analysis, nitrogen sorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results show that Ti, V, Nb, Ta, and Cr form nitride phases with face centered cubic structure, whereas Mo and W forme carbides with hexagonal structures. The tendency to form nitride or carbide obeys the free formation energy of the transition metal nitrides and carbides. This method offers the potential to prepare the desired size, shape and phase of transition metal nitrides and carbides that are suitable for a specific reaction, which is the chief objective of materials chemistry.

  19. Graphitization of amorphous carbon on a multiwall carbon nanotube surface by catalyst-free heating

    Science.gov (United States)

    Asaka, Koji; Karita, Motoyuki; Saito, Yahachi

    2011-08-01

    Structural changes in amorphous carbon coating the surfaces of multiwall carbon nanotubes (MWNTs) under applying an electric current were investigated by in situ transmission electron microscopy with simultaneous measurements of the bias voltage and electric current. Joule heating transformed amorphous carbon on the surfaces of individual MWNTs suspended between gold electrodes into graphite layers even without a metal catalyst through a phase of glasslike carbon. The MWNTs after the formation of ordered surface layers sustained a high current with a density of up to 3.1 × 108 A/cm2.

  20. Synthesis, Characterization, and Application of Novel Ni-P-Carbon Nitride Nanocomposites

    Directory of Open Access Journals (Sweden)

    Eman M. Fayyad

    2018-01-01

    Full Text Available Dispersion of 2D carbon nitride (C3N4 nanosheets into a nickel phosphorous (NiP matrix was successfully achieved by ultrasonication during the electroless plating of NiP from an acidic bath. The morphology and thickness, elemental analysis, phases, roughness, and wettability for as-plated and heat-treated nanocomposite were determined by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, atomic force microscopy, and contact angle measurements, respectively. C3N4 showed a homogeneous distribution morphology in the nanocomposite that changed from amorphous in case of the NiP to a mixed crystalline-amorphous structure in the NiP-C3N4 nanocomposite. The microhardness and corrosion resistance of the as-plated nanocomposite and the heat-treated nanocomposite coating were significantly enhanced compared to the Ni-P. The nanocomposite showed a superior corrosion protection efficiency of ~95%, as observed from the electrochemical impedance spectroscopy (EIS measurements. On the other hand, the microhardness of the nanocomposite was significantly increased from 780 to reach 1175 HV200 for NiP and NiP-C3N4, respectively.

  1. Nitrided FeB amorphous thin films for magneto mechanical systems

    International Nuclear Information System (INIS)

    Fernandez-Martinez, I.; Martin-Gonzalez, M.S.; Gonzalez-Arrabal, R.; Alvarez-Sanchez, R.; Briones, F.; Costa-Kraemer, J.L.

    2008-01-01

    The structural, magnetic and magnetoelastic properties of Fe-B-N amorphous films, sputtered from a Fe 80 B 20 target, in a mixture of argon and nitrogen gas, are studied for different nitrogen partial pressures. Nitrogen incorporates into the film preserving the amorphous structure, and modifying magnetic properties. The amount of nitrogen that incorporates into the amorphous structure is found to scale linearly with the nitrogen partial pressure during film growth. The structure, magnetization, field evolution, magnetic anisotropy and magnetostrictive behaviour are determined for films with different nitrogen content. An ∼20% increase of both the saturation magnetization and the magnetostriction constant values is found for moderate (∼8%) nitrogen content when compared to those for pure Fe 80 B 20 amorphous films. These improved properties, together with the still low coercivity of the amorphous films offer great potential for their use in magnetostrictive micro and nano magneto mechanical actuator devices

  2. Nitrided FeB amorphous thin films for magneto mechanical systems

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Martinez, I.; Martin-Gonzalez, M.S. [Instituto de Microelectronica de Madrid, IMM-CNM-CSIC, Isaac Newton 8 PTM, 28760 Tres Cantos, Madrid (Spain); Gonzalez-Arrabal, R. [Instituto de Microelectronica de Madrid, IMM-CNM-CSIC, Isaac Newton 8 PTM, 28760 Tres Cantos, Madrid (Spain); Centro de Microanalisis de Materiales de Materiales, Universidad Autonoma de Madrid, Cantoblanco 28049, Madrid (Spain); Alvarez-Sanchez, R.; Briones, F. [Instituto de Microelectronica de Madrid, IMM-CNM-CSIC, Isaac Newton 8 PTM, 28760 Tres Cantos, Madrid (Spain); Costa-Kraemer, J.L. [Instituto de Microelectronica de Madrid, IMM-CNM-CSIC, Isaac Newton 8 PTM, 28760 Tres Cantos, Madrid (Spain)], E-mail: kramer@imm.cnm.csic.es

    2008-01-15

    The structural, magnetic and magnetoelastic properties of Fe-B-N amorphous films, sputtered from a Fe{sub 80}B{sub 20} target, in a mixture of argon and nitrogen gas, are studied for different nitrogen partial pressures. Nitrogen incorporates into the film preserving the amorphous structure, and modifying magnetic properties. The amount of nitrogen that incorporates into the amorphous structure is found to scale linearly with the nitrogen partial pressure during film growth. The structure, magnetization, field evolution, magnetic anisotropy and magnetostrictive behaviour are determined for films with different nitrogen content. An {approx}20% increase of both the saturation magnetization and the magnetostriction constant values is found for moderate ({approx}8%) nitrogen content when compared to those for pure Fe{sub 80}B{sub 20} amorphous films. These improved properties, together with the still low coercivity of the amorphous films offer great potential for their use in magnetostrictive micro and nano magneto mechanical actuator devices.

  3. Bonding topologies in diamondlike amorphous-carbon films

    Energy Technology Data Exchange (ETDEWEB)

    SIEGAL,MICHAEL P.; PROVENCIO,PAULA P.; TALLANT,DAVID R.; SIMPSON,REGINA L.; KLEINSORGE,B.; MILNE,W.I.

    2000-01-27

    The carbon ion energy used during filtered cathodic vacuum arc deposition determines the bonding topologies of amorphous-carbon (a-C) films. Regions of relatively low density occur near the substrate/film and film/surface interfaces and their thicknesses increase with increasing deposition energy. The ion subplantation growth results in mass density gradients in the bulk portion of a-C in the growth direction; density decreases with distance from the substrate for films grown using ion energies < 60 eV and increases for films grown using ion energies > 160 eV. Films grown between these energies are the most diamondlike with relatively uniform bulk density and the highest optical transparencies. Bonding topologies evolve with increasing growth energy consistent with the propagation of subplanted carbon ions inducing a partial transformation of 4-fold to 3-fold coordinated carbon atoms.

  4. Bonding topologies in diamondlike amorphous-carbon films

    International Nuclear Information System (INIS)

    Siegal, M. P.; Provencio, P. N.; Tallant, D. R.; Simpson, R. L.; Kleinsorge, B.; Milne, W. I.

    2000-01-01

    The carbon ion energy used during filtered cathodic vacuum arc deposition determines the bonding topologies of amorphous-carbon (a-C) films. Regions of relatively low density occur near the substrate/film and film/surface interfaces; their thicknesses increase with deposition energy. The ion subplantation growth results in mass density gradients in the bulk portion of a-C in the growth direction; density decreases with distance from the substrate for films grown using ion energies 160 eV. Films grown between these energies are the most diamondlike with relatively uniform bulk density and the highest optical transparencies. Bonding topologies evolve with increasing growth energy consistent with the propagation of subplanted carbon ions inducing a partial transformation of σ- to π-bonded carbon atoms. (c) 2000 American Institute of Physics

  5. Bonding topologies in diamondlike amorphous-carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Siegal, M. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Provencio, P. N. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Tallant, D. R. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Simpson, R. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Kleinsorge, B. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ, (United Kingdom); Milne, W. I. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ, (United Kingdom)

    2000-04-10

    The carbon ion energy used during filtered cathodic vacuum arc deposition determines the bonding topologies of amorphous-carbon (a-C) films. Regions of relatively low density occur near the substrate/film and film/surface interfaces; their thicknesses increase with deposition energy. The ion subplantation growth results in mass density gradients in the bulk portion of a-C in the growth direction; density decreases with distance from the substrate for films grown using ion energies <60 eV and increases for films grown using ion energies >160 eV. Films grown between these energies are the most diamondlike with relatively uniform bulk density and the highest optical transparencies. Bonding topologies evolve with increasing growth energy consistent with the propagation of subplanted carbon ions inducing a partial transformation of {sigma}- to {pi}-bonded carbon atoms. (c) 2000 American Institute of Physics.

  6. Synthesis and characterization of boron carbon nitride thin films as protective overcoat for hard disk drives

    Science.gov (United States)

    Chen, Yanfeng

    The current goal in the magnetic storage industry is to reach the areal density of 1Tbit/in2 in a few years. This requires the head-media spacing (HMS), which includes media overcoat, lubricant layer, air bearing, and head overcoat, not to exceed 5.0 nm. Trade-off between these layers results in requiring the protective overcoat to be 1.0 nm or less. The protective overcoat must be hard, wear-resistant, continuous, thermally stable, and compatible with the magnetic layer and lubricant. This thesis work is mainly to develop protective overcoat for ultra high density hard disk drives (HDD). Amorphous carbon nitride (a-CNx) thin films were synthesized using pulseDC magnetron sputtering. The influence of substrate bias, substrate tilt, and substrate rotation on film growth and properties was studied. X-ray reflectivity (XRR) was used to measure film density, roughness and thickness. Surface roughness and thickness measurements from XRR are comparable to AFM and surface profiler measurements respectively. a-CNx films have good mechanical properties. Auger electron spectroscopy (AES) and high resolution transmission microscope (HRTEM) were used to obtain the film composition and microstructure. HRTEM cross sectioned experiments showed that CN x film is amorphous. Chemical corrosion experiments display drastic decrease of corrosion spots for thin films synthesized under optimum conditions. In pursuit of new materials for hard disk drive protective overcoat, boron carbide (B4C) and boron carbon nitride (BxC yNz) thin films were synthesized by pulse-DC magnetron sputtering. Effects of target power, target pulse frequency, substrate bias and pulse frequency on surface roughness were studied by AFM. Nitrogen incorporation into B4C films, which gives BxCyNz thin films, has a beneficial effect to decrease the film roughness. Auger electron spectroscopy was used to characterize the film composition. High-resolution cross-sectioned TEM studies showed that both films are amorphous

  7. Electronic structure of carbon-boron nitride nanotubes

    Science.gov (United States)

    Sanginés-Mendoza, Raúl; Martinez, Edgar

    2013-03-01

    Structures of carbon and boron nitride nanotubes (CNTs, BNNTs) are quite similar, conversely, electronic properties are radically different from each other. Carbon nanotubes, whose electronic properties can be either metallic or semiconducting depending on their chiral structure, boron nitride nanotubes are always semiconductors with bandgaps over 4 eV. We have looked to hybrid systems, to predict a new kind of nanostructures with novel electronic properties. In this way, we explore the electronic properties of C-BN nanotubes. In particular, we studied the electronic structure of armchair C-BN nanotubes. The calculations were performed using the pseudopotential LCAO method with a Generalized Gradient Approximation for the exchange-correlation energy functional. The band structure of most of these systems have semiconductor character with an indirect gap smaller than its analogous BNNTs. In addition, the most prominent feature of these systems is the existence of flat bands both at the valence band top and at the conduction band minimum. Such flat bands results in sharp and narrow peaks on the total density of states. The behavior of these flat bands mainly indicates that electrons are largely localized. Thus, a detailed analysis on the electronic band structure shows that hybridization between those orbitals on the interfaces is responsible to exhibit localization effects on the hybrid systems.This research was supported by Conacyt under Grant No. 133022.

  8. Intrinsic half-metallicity in fractal carbon nitride honeycomb lattices.

    Science.gov (United States)

    Wang, Aizhu; Zhao, Mingwen

    2015-09-14

    Fractals are natural phenomena that exhibit a repeating pattern "exactly the same at every scale or nearly the same at different scales". Defect-free molecular fractals were assembled successfully in a recent work [Shang et al., Nature Chem., 2015, 7, 389-393]. Here, we adopted the feature of a repeating pattern in searching two-dimensional (2D) materials with intrinsic half-metallicity and high stability that are desirable for spintronics applications. Using first-principles calculations, we demonstrate that the electronic properties of fractal frameworks of carbon nitrides have stable ferromagnetism accompanied by half-metallicity, which are highly dependent on the fractal structure. The ferromagnetism increases gradually with the increase of fractal order. The Curie temperature of these metal-free systems estimated from Monte Carlo simulations is considerably higher than room temperature. The stable ferromagnetism, intrinsic half-metallicity, and fractal characteristics of spin distribution in the carbon nitride frameworks open an avenue for the design of metal-free magnetic materials with exotic properties.

  9. Template-free synthesis of porous graphitic carbon nitride/carbon composite spheres for electrocatalytic oxygen reduction reaction.

    Science.gov (United States)

    Fu, Xiaorui; Hu, Xiaofei; Yan, Zhenhua; Lei, Kaixiang; Li, Fujun; Cheng, Fangyi; Chen, Jun

    2016-01-28

    Porous graphitic carbon nitride/carbon composite spheres were synthesized using melamine and cyanuric acid, and glucose as the carbon nitride and carbon precursor, respectively. The 3D hierarchical composites efficiently catalyzed the oxygen reduction reaction with an onset potential of 0.90 V and a kinetic current density of 23.92 mA cm(-2). These merit their promising applications in fuel cells and metal-air batteries.

  10. Graphitic Carbon Nitride Materials: Sensing, Imaging and Therapy.

    Science.gov (United States)

    Dong, Yongqiang; Wang, Qian; Wu, Haishan; Chen, Yingmei; Lu, Chun-Hua; Chi, Yuwu; Yang, Huang-Hao

    2016-10-01

    Graphitic carbon nitrides (g-C 3 N 4 ) are a class of 2D polymeric materials mainly composed of carbon and nitrogen atoms. g-C 3 N 4 are attracting dramatically increasing interest in the areas of sensing, imaging, and therapy, due to their unique optical and electronic properties. Here, the luminescent properties (mainly includes photoluminescence and electrochemiluminescence), and catalytic and photoelectronic properties related to sensing and therapy applications of g-C 3 N 4 materials are reviewed. Furthermore, the fabrication and advantages of sensing, imaging and therapy systems based on g-C 3 N 4 materials are summarized. Finally, the future perspectives for developing the sensing, imaging and therapy applications of the g-C 3 N 4 materials are discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Electron emission induced modifications in amorphous tetrahedral diamondlike carbon

    International Nuclear Information System (INIS)

    Mercer, T.W.; DiNardo, N.J.; Rothman, J.B.; Siegal, M.P.; Friedmann, T.A.; Martinez-Miranda, L.J.

    1998-01-01

    The cold-cathode electron emission properties of amorphous tetrahedral diamondlike carbon are promising for flat-panel display and vacuum microelectronics technologies. The onset of electron emission is, typically, preceded by open-quotes conditioningclose quotes where the material is stressed by an applied electric field. To simulate conditioning and assess its effect, we combined the spatially localized field and current of a scanning tunneling microscope tip with high-spatial-resolution characterization. Scanning force microscopy shows that conditioning alters surface morphology and electronic structure. Spatially resolved electron-energy-loss spectroscopy indicates that the predominant bonding configuration changes from predominantly fourfold to threefold coordination. copyright 1998 American Institute of Physics

  12. Triazine-Based Graphitic Carbon Nitride: a Two-Dimensional Semiconductor

    OpenAIRE

    Gerardo Algara-Siller; Nikolai Severin; Samantha Y. Chong; Torbjörn Björkman; Robert G. Palgrave; Andrea Laybourn; Markus Antonietti; Yaroslav Z. Khimyak; Arkady V. Krasheninnikov; J\\xfcrgen P. Rabe; Ute Kaiser; Andrew I. Cooper; Arne Thomas; Michael J. Bojdys

    2014-01-01

    Graphitic carbon nitride has been predicted to be structurally analogous to carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and ...

  13. Metachromasy of methylene blue due to aggregation over phosphate-modified polymeric carbon nitride

    Science.gov (United States)

    Lakshminarasimhan, N.; Sangeetha, D. N.; Nivetha, G.

    2017-05-01

    Polymeric carbon nitride in graphitic form (g-C3N4) is an emerging visible light active photocatalyst. In this work, phosphate-modified polymeric carbon nitride (PCN) was synthesized by thermal condensation of melamine in the presence of ammonium dihydrogen phosphate (ADP). The addition of PCN to methylene blue (MB) solution showed the color intensification. The hypsochromic shift in the absorption spectrum of MB is due to metachromasy, a phenomenon in which aggregation of dye molecules occurs over the surface of a material. The polymerization of melamine into carbon nitride and MB trimerization depend on the amount of ADP and nature of phosphate species, respectively.

  14. Magnetic graphitic carbon nitride: its applicationin the C-& H-activation of amines.

    Science.gov (United States)

    Magnetic graphitic carbon nitride, Fe@g-C3N4, has been synthesized by adorning graphitic carbon nitride (g-C3N4) support with iron oxide via non-covalent interaction. The magnetically recyclable catalyst showed excellent reactivity for expeditious C-H activation and cyanation of amines.This dataset is associated with the following publication:Verma, S., R.B. Nasir Baig, H. Changseok, M. Nadagouda , and R. Varma. Magnetic graphitic carbon nitride: its applicationin the C–H activation of amines. CHEMICAL COMMUNICATIONS. Royal Society of Chemistry, Cambridge, UK, 51(85): 15554 - 15557, (2015).

  15. Preparing microspheres of actinide nitrides from carbon containing oxide sols

    International Nuclear Information System (INIS)

    Triggiani, L.V.

    1975-01-01

    A process is given for preparing uranium nitride, uranium oxynitride, and uranium carboxynitride microspheres and the microspheres as compositions of matter. The microspheres are prepared from carbide sols by reduction and nitriding steps. (Official Gazette)

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

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  17. Formation of carbon nanotubes on an amorphous Ni{sub 25}Ta{sub 58}N{sub 17} alloy film by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gromov, D. G.; Dubkov, S. V., E-mail: sv.dubkov@gmail.com [National Research University of Electronic Technology MIET (Russian Federation); Pavlov, A. A. [Russian Academy of Sciences, Institute of Nanotechnologies of Microelectronics (Russian Federation); Skorik, S. N. [Technological Center Research and Production Complex (Russian Federation); Trifonov, A. Yu. [Lukin Scientific Research Institute of Physical Problems (Russian Federation); Kirilenko, E. P.; Shulyat’ev, A. S. [National Research University of Electronic Technology MIET (Russian Federation); Shaman, Yu. P. [Technological Center Research and Production Complex (Russian Federation); Rygalin, B. N. [National Research University of Electronic Technology MIET (Russian Federation)

    2016-12-15

    It is shown that it is possible to grow carbon nanotubes on the surface of an amorphous Ni–Ta–N metal alloy film with a low Ni content (~25 at %) by chemical deposition from acetylene at temperature 400–800°C. It is established that the addition of nitrogen into the Ni–Ta alloy composition is favorable for the formation of tantalum nitride and the expulsion of Ni clusters, which act as a catalyst of the growth of carbon nanotubes, onto the surface. From Raman spectroscopy studies, it is found that, as the temperature of synthesis is raised, the quality of nanotubes is improved.

  18. Neon ion beam induced pattern formation on amorphous carbon surfaces

    Directory of Open Access Journals (Sweden)

    Omar Bobes

    2018-02-01

    Full Text Available We investigate the ripple pattern formation on amorphous carbon surfaces at room temperature during low energy Ne ion irradiation as a function of the ion incidence angle. Monte Carlo simulations of the curvature coefficients applied to the Bradley-Harper and Cater-Vishnyakov models, including the recent extensions by Harrison-Bradley and Hofsäss predict that pattern formation on amorphous carbon thin films should be possible for low energy Ne ions from 250 eV up to 1500 eV. Moreover, simulations are able to explain the absence of pattern formation in certain cases. Our experimental results are compared with prediction using current linear theoretical models and applying the crater function formalism, as well as Monte Carlo simulations to calculate curvature coefficients using the SDTrimSP program. Calculations indicate that no patterns should be generated up to 45° incidence angle if the dynamic behavior of the thickness of the ion irradiated layer introduced by Hofsäss is taken into account, while pattern formation most pronounced from 50° for ion energy between 250 eV and 1500 eV, which are in good agreement with our experimental data.

  19. Graphitic Carbon Nitride Polymers toward Sustainable Photoredox Catalysis.

    Science.gov (United States)

    Zheng, Yun; Lin, Lihua; Wang, Bo; Wang, Xinchen

    2015-10-26

    As a promising two-dimensional conjugated polymer, graphitic carbon nitride (g-C3 N4 ) has been utilized as a low-cost, robust, metal-free, and visible-light-active photocatalyst in the field of solar energy conversion. This Review mainly describes the latest advances in g-C3 N4 photocatalysts for water splitting. Their application in CO2 conversion, organosynthesis, and environmental purification is also briefly discussed. The methods to modify the electronic structure, nanostructure, crystal structure, and heterostructure of g-C3 N4 , together with correlations between its structure and performance are illustrated. Perspectives on the challenges and opportunities for the future exploration of g-C3 N4 photocatalysts are provided. This Review will promote the utilization of g-C3 N4 materials in the fields of photocatalysis, energy conversion, environmental remediation, and sensors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Oxygen functional groups in graphitic carbon nitride for enhanced photocatalysis.

    Science.gov (United States)

    Liu, Shizhen; Li, Degang; Sun, Hongqi; Ang, Ha Ming; Tadé, Moses O; Wang, Shaobin

    2016-04-15

    Metal-free semiconductors offer a new opportunity for environmental photocatalysis toward a potential breakthrough in high photo efficiency with complete prevention of metal leaching. In this study, graphitic carbon nitride (GCN) modified by oxygen functional groups was synthesized by a hydrothermal treatment of pristine GCN at different temperatures with H2O2. Insights into the emerging characteristics of the modified GCN in photocatalysis were obtained by determining the optical properties, band structure, electrochemical activity and pollutant degradation efficiency. It was found that the introduction of GCN with oxygen functional groups can enhance light absorption and accelerate electron transfer so as to improve the photocatalytic reaction efficiency. The photoinduced reactive radicals and the associated photodegradation were investigated by in situ electron paramagnetic resonance (EPR). The reactive radicals, O2(-) and OH, were responsible for organic degradation. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Graphitic carbon nitride embedded hydrogels for enhanced gel electrophoresis.

    Science.gov (United States)

    Zarei, Mohammad; Ahmadzadeh, Hossein; Goharshadi, Elaheh K; Farzaneh, Ali

    2015-08-05

    Here, we show, for the first time, the use of graphitic carbon nitride (g-C3N4) nanosheets to improve the resolution and efficiency of protein separation in gel electrophoresis. By loading 0.04% (m/v) g-C3N4 nanosheets into the polyacrylamide gel at 25 °C, the thermal conductivity increased approximately 80% which resulted in 20% reduction in Joule heating and overall increase of separation efficiency. Also, polymerization of acrylamide occurred in the absence of tetramethylethylenediamine (TEMED) when the polyacrylamide gel contained g-C3N4 nanosheets. Hence, the g-C3N4 act simultaneously as a polymerization catalyst as well as heat sinks to lower Joule heating effect on band broadening. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Graphitic carbon nitride "reloaded": emerging applications beyond (photo)catalysis.

    Science.gov (United States)

    Liu, Jian; Wang, Hongqiang; Antonietti, Markus

    2016-04-21

    Despite being one of the oldest materials described in the chemical literature, graphitic carbon nitride (g-C3N4) has just recently experienced a renaissance as a highly active photocatalyst, and the metal-free polymer was shown to be able to generate hydrogen under visible light. The semiconductor nature of g-C3N4 has triggered tremendous endeavors on its structural manipulation for enhanced photo(electro)chemical performance, aiming at an affordable clean energy future. While pursuing the stem of g-C3N4 related catalysis (photocatalysis, electrocatalysis and photoelectrocatalysis), a number of emerging intrinsic properties of g-C3N4 are certainly interesting, but less well covered, and we believe that these novel applications outside of conventional catalysis can be favorably exploited as well. Thanks to the general efforts devoted to the exploration and enrichment of g-C3N4 based chemistry, the boundaries of this area have been possibly pushed far beyond what people could imagine in the beginning. This review strives to cover the achievements of g-C3N4 related materials in these unconventional application fields for depicting the broader future of these metal-free and fully stable semiconductors. This review starts with the general protocols to engineer g-C3N4 micro/nanostructures for practical use, and then discusses the newly disclosed applications in sensing, bioimaging, novel solar energy exploitation including photocatalytic coenzyme regeneration, templating, and carbon nitride based devices. Finally, we attempt an outlook on possible further developments in g-C3N4 based research.

  3. Photocatalytic CO₂ Reduction by Mesoporous Polymeric Carbon Nitride Photocatalysts.

    Science.gov (United States)

    Tasbihi, Minoo; Acharjya, Amitava; Thomas, Arne; Reli, Martin; AmbroŽová, Nela; Kočcí, Kamila; Schomäcker, Reinhard

    2018-08-01

    In this paper, a sol-gel derived mesoporous polymeric carbon nitride has been investigated as a photocatalyst for CO2 photocatalytic reduction. Noble-metal Pt nanoparticles were deposited on carbon nitride (sg-CN) in order to investigate the performance of both Pt-sg-CN and sg-CN for photocatalytic CO2 reduction. Physicochemical properties of prepared nanocomposites were comprehensively characterized by using powder XRD, N2 physisorption, UV-Vis DRS, ICP-AES, FTIR, solid-state NMR, SEM, TEM and photoelectrochemical measurements. Compared with pure sg-CN, the resulting Pt-loaded sg-CN (Pt-sg-CN) exhibited significant improvement on the CO2 photocatalytic reduction to CH4 in the presence of water vapor at ambient condition under UV irradiation. 1.5 wt.% Pt-loaded sg-CN (Pt-sg-CN) photocatalyst formed the highest methane yield of 13.9 μmol/gcat. after 18 h of light irradiation, which was almost 2 times and 32 times improvement in comparison to pure sg-CN and commercial TiO2 Evonik P25, respectively. The substantial photocatalytic activity of Pt-sg-CN photocatalyst for the yield product of the CO2 photocatalytic reduction was attributed to the efficient interfacial transfer of photogenerated electrons from sg-CN to Pt due to the lower Fermi level of Pt in the Pt-sg-CN hybrid heterojunctions as also evidenced by photo-electrochemical measurements. This resulted in the reduction of electron-hole pairs recombination for effective spatial charge separation, consequently increasing the photocatalytic efficiency.

  4. Graphitic carbon nitride: synthesis, properties, and applications in catalysis.

    Science.gov (United States)

    Zhu, Junjiang; Xiao, Ping; Li, Hailong; Carabineiro, Sónia A C

    2014-10-08

    Graphitic carbon nitride, g-C3N4, is a polymeric material consisting of C, N, and some impurity H, connected via tris-triazine-based patterns. Compared with the majority of carbon materials, it has electron-rich properties, basic surface functionalities and H-bonding motifs due to the presence of N and H atoms. It is thus regarded as a potential candidate to complement carbon in material applications. In this review, a brief introduction to g-C3N4 is given, the methods used for synthesizing this material with different textural structures and surface morphologies are described, and its physicochemical properties are referred. In addition, four aspects of the applications of g-C3N4 in catalysis are discussed: (1) as a base metal-free catalyst for NO decomposition, (2) as a reference material in differentiating oxygen activation sites for oxidation reactions over supported catalysts, (3) as a functional material to synthesize nanosized metal particles, and (4) as a metal-free catalyst for photocatalysis. The reasons for the use of g-C3N4 for such applications are also given, and we expect that this paper will inspire readers to search for further new applications for this material in catalysis and in other fields.

  5. Revealing the 1 nm/s Extensibility of Nanoscale Amorphous Carbon in a Scanning Electron Microscope

    DEFF Research Database (Denmark)

    Zhang, Wei

    2013-01-01

    In an ultra-high vacuum scanning electron microscope, the edged branches of amorphous carbon film (∼10 nm thickness) can be continuously extended with an eye-identifying speed (on the order of ∼1 nm/s) under electron beam. Such unusual mobility of amorphous carbon may be associated with deformation...

  6. Preparation and mechanical properties of carbon nanotube-silicon nitride nano-ceramic matrix composites

    Science.gov (United States)

    Tian, C. Y.; Jiang, H.

    2018-01-01

    Carbon nanotube–silicon nitride nano-ceramic matrix composites were fabricated by hot-pressing nano-sized Si3N4 powders and carbon nanotubes. The effect of CNTs on the mechanical properties of silicon nitride was researched. The phase compositions and the microstructure characteristics of the samples as well as the distribution of carbon nanotube in the silicon nitride ceramic were analyzed by X-ray diffraction and scanning electron microscope. The results show that the microstructure of composites consists mainly of α-Si3N4, β-Si3N4, Si2N2O and carbon natubes. The addition of proper amount of carbon nanotubes can improve the fracture toughness and the flexural strength, and the optimal amount of carbon nanotube are both 3wt.%. However the Vickers hardness values decrease with the increase of carbon nanotubes content.

  7. Structure-property relations in amorphous carbon for photovoltaics

    International Nuclear Information System (INIS)

    Risplendi, Francesca; Cicero, Giancarlo; Bernardi, Marco; Grossman, Jeffrey C.

    2014-01-01

    Carbon is emerging as a material with great potential for photovoltaics (PV). However, the amorphous form (a-C) has not been studied in detail as a PV material, even though it holds similarities with amorphous Silicon (a-Si) that is widely employed in efficient solar cells. In this work, we correlate the structure, bonding, stoichiometry, and hydrogen content of a-C with properties linked to PV performance such as the electronic structure and optical absorption. We employ first-principles molecular dynamics and density functional theory calculations to generate and analyze a set of a-C structures with a range of densities and hydrogen concentrations. We demonstrate that optical and electronic properties of interest in PV can be widely tuned by varying the density and hydrogen content. For example, sunlight absorption in a-C films can significantly exceed that of a same thickness of a-Si for a range of densities and H contents in a-C. Our results highlight promising features of a-C as the active layer material of thin-film solar cells.

  8. Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer

    Science.gov (United States)

    Prabaswara, Aditya; Min, Jung-Wook; Zhao, Chao; Janjua, Bilal; Zhang, Daliang; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; Ng, Tien Khee; Ooi, Boon S.

    2018-02-01

    Consumer electronics have increasingly relied on ultra-thin glass screen due to its transparency, scalability, and cost. In particular, display technology relies on integrating light-emitting diodes with display panel as a source for backlighting. In this study, we undertook the challenge of integrating light emitters onto amorphous quartz by demonstrating the direct growth and fabrication of a III-nitride nanowire-based light-emitting diode. The proof-of-concept device exhibits a low turn-on voltage of 2.6 V, on an amorphous quartz substrate. We achieved 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits a broad linewidth spectrum of light centered at true yellow color ( 590 nm), an important wavelength bridging the green-gap in solid-state lighting technology, with significantly less strain and dislocations compared to conventional planar quantum well nitride structures. Our endeavor highlighted the feasibility of fabricating III-nitride optoelectronic device on a scalable amorphous substrate through facile growth and fabrication steps. For practical demonstration, we demonstrated tunable correlated color temperature white light, leveraging on the broadly tunable nanowire spectral characteristics across red-amber-yellow color regime.

  9. Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer

    KAUST Repository

    Prabaswara, Aditya

    2018-02-06

    Consumer electronics have increasingly relied on ultra-thin glass screen due to its transparency, scalability, and cost. In particular, display technology relies on integrating light-emitting diodes with display panel as a source for backlighting. In this study, we undertook the challenge of integrating light emitters onto amorphous quartz by demonstrating the direct growth and fabrication of a III-nitride nanowire-based light-emitting diode. The proof-of-concept device exhibits a low turn-on voltage of 2.6 V, on an amorphous quartz substrate. We achieved ~ 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits a broad linewidth spectrum of light centered at true yellow color (~ 590 nm), an important wavelength bridging the green-gap in solid-state lighting technology, with significantly less strain and dislocations compared to conventional planar quantum well nitride structures. Our endeavor highlighted the feasibility of fabricating III-nitride optoelectronic device on a scalable amorphous substrate through facile growth and fabrication steps. For practical demonstration, we demonstrated tunable correlated color temperature white light, leveraging on the broadly tunable nanowire spectral characteristics across red-amber-yellow color regime.

  10. Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer.

    Science.gov (United States)

    Prabaswara, Aditya; Min, Jung-Wook; Zhao, Chao; Janjua, Bilal; Zhang, Daliang; Albadri, Abdulrahman M; Alyamani, Ahmed Y; Ng, Tien Khee; Ooi, Boon S

    2018-02-06

    Consumer electronics have increasingly relied on ultra-thin glass screen due to its transparency, scalability, and cost. In particular, display technology relies on integrating light-emitting diodes with display panel as a source for backlighting. In this study, we undertook the challenge of integrating light emitters onto amorphous quartz by demonstrating the direct growth and fabrication of a III-nitride nanowire-based light-emitting diode. The proof-of-concept device exhibits a low turn-on voltage of 2.6 V, on an amorphous quartz substrate. We achieved ~ 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits a broad linewidth spectrum of light centered at true yellow color (~ 590 nm), an important wavelength bridging the green-gap in solid-state lighting technology, with significantly less strain and dislocations compared to conventional planar quantum well nitride structures. Our endeavor highlighted the feasibility of fabricating III-nitride optoelectronic device on a scalable amorphous substrate through facile growth and fabrication steps. For practical demonstration, we demonstrated tunable correlated color temperature white light, leveraging on the broadly tunable nanowire spectral characteristics across red-amber-yellow color regime.

  11. Selective and Regenerative Carbon Dioxide Capture by Highly Polarizing Porous Carbon Nitride.

    Science.gov (United States)

    Oh, Youngtak; Le, Viet-Duc; Maiti, Uday Narayan; Hwang, Jin Ok; Park, Woo Jin; Lim, Joonwon; Lee, Kyung Eun; Bae, Youn-Sang; Kim, Yong-Hyun; Kim, Sang Ouk

    2015-09-22

    Energy-efficient CO2 capture is a stringent demand for green and sustainable energy supply. Strong adsorption is desirable for high capacity and selective capture at ambient conditions but unfavorable for regeneration of adsorbents by a simple pressure control process. Here we present highly regenerative and selective CO2 capture by carbon nitride functionalized porous reduced graphene oxide aerogel surface. The resultant structure demonstrates large CO2 adsorption capacity at ambient conditions (0.43 mmol·g(-1)) and high CO2 selectivity against N2 yet retains regenerability to desorb 98% CO2 by simple pressure swing. First-principles thermodynamics calculations revealed that microporous edges of graphitic carbon nitride offer the optimal CO2 adsorption by induced dipole interaction and allows excellent CO2 selectivity as well as facile regenerability. This work identifies a customized route to reversible gas capture using metal-free, two-dimensional carbonaceous materials, which can be extended to other useful applications.

  12. Nanoscale density variations induced by high energy heavy ions in amorphous silicon nitride and silicon dioxide

    Science.gov (United States)

    Mota-Santiago, P.; Vazquez, H.; Bierschenk, T.; Kremer, F.; Nadzri, A.; Schauries, D.; Djurabekova, F.; Nordlund, K.; Trautmann, C.; Mudie, S.; Ridgway, M. C.; Kluth, P.

    2018-04-01

    The cylindrical nanoscale density variations resulting from the interaction of 185 MeV and 2.2 GeV Au ions with 1.0 μm thick amorphous SiN x :H and SiO x :H layers are determined using small angle x-ray scattering measurements. The resulting density profiles resembles an under-dense core surrounded by an over-dense shell with a smooth transition between the two regions, consistent with molecular-dynamics simulations. For amorphous SiN x :H, the density variations show a radius of 4.2 nm with a relative density change three times larger than the value determined for amorphous SiO x :H, with a radius of 5.5 nm. Complementary infrared spectroscopy measurements exhibit a damage cross-section comparable to the core dimensions. The morphology of the density variations results from freezing in the local viscous flow arising from the non-uniform temperature profile in the radial direction of the ion path. The concomitant drop in viscosity mediated by the thermal conductivity appears to be the main driving force rather than the presence of a density anomaly.

  13. Scanning transmission electron microscopy analysis of Ge(O)/(graphitic carbon nitride) nanocomposite powder

    Energy Technology Data Exchange (ETDEWEB)

    Kawasaki, Masahiro [JEOL USA Inc., 11 Dearborn Road, Peabody, MA 01960 (United States); Sompetch, Kanganit [Department of Chemistry and Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Sarakonsri, Thapanee, E-mail: tsarakonsri@gmail.com [Department of Chemistry and Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Shiojiri, Makoto [Kyoto Institute of Technology, Kyoto 606-8585 (Japan); School of Science and Engineering, University of Toyama, Toyama 930-8555 (Japan)

    2015-12-15

    Analytical electron microscopy has revealed the structure of particles that were synthesized by chemical reaction of GeO{sub 2} with NaBH{sub 4} in the basic solution including graphitic carbon nitride (g-C{sub 3}N{sub 4}) powders. The g-C{sub 3}N{sub 4} was arranged by recrystallization of melamine at 600 °C under N{sub 2} gas atmosphere. The samples were dried at 60 °C or 180 °C for 4 h. The g-C{sub 3}N{sub 4} was observed as lamellae of several ten nm or less in size and had an amorphous-like structure with a distorted lattice in an area as small as a few hundred pm in size. The reaction product was Ge(O) particles as fine as several nm in size and composed of Ge and O atoms. Most of the particles must be of GeO{sub 2−x} with the amorphous-like structure that has also a distorted lattice in an area of a few hundred pm in size. In the sample dried at 60 °C, the particles were found to be dispersed in a wide area on the g-C{sub 3}N{sub 4} lamella. It is hard to recognize those particles in TEM images. The particles in the sample dried at 180 °C became larger and were easily observed as isolated lumps. Hence, these powders can be regarded as GeO{sub 2}/g-C{sub 3}N{sub 4} or Ge/GeO{sub 2}/g-C{sub 3}N{sub 4} nanocomposites, and expected to be applicable to anode materials for high energy Li-ion batteries due to Ge catalysis effect, accordingly. - Graphical abstract: STEM analysis of Ge(O)/(graphitic carbon nitride) nanocomposite powder. - Highlights: • Graphitic (g)-C{sub 3}N{sub 4} powder was prepared at 600 °C by recrystallization of melamine. • Ge(O) was prepared by chemical reaction in a solution including the g-C{sub 3}N{sub 4} powders. • The products can be regarded as GeO{sub 2}/g-C{sub 3}N{sub 4} or Ge/GeO{sub 2}/g-C{sub 3}N{sub 4} nanocomposites. • GeO{sub 2} was amorphous several-nm particles and g-C{sub 3}N{sub 4} was amorphous lamella of several 10 nm in size. • We expect them to be applicable for high energy Li-ion battery anode

  14. Amorphous carbon nanofibres inducing high specific capacitance of deposited hydrous ruthenium oxide

    International Nuclear Information System (INIS)

    Barranco, V.; Pico, F.; Ibanez, J.; Lillo-Rodenas, M.A.; Linares-Solano, A.; Kimura, M.; Oya, A.; Rojas, R.M.; Amarilla, J.M.; Rojo, J.M.

    2009-01-01

    Composites consisting of ruthenium oxide particles deposited on amorphous carbon nanofibres are prepared by a repetitive impregnation procedure. The choice of amorphous carbon nanofibres as support of amorphous ruthenium oxide leads to composites in which the deposited oxide consists of aggregates of extremely small primary particles (1-1.5 nm-size) and showing high porosity (specific surface area of 450 m 2 g -1 ). This special deposition of the oxide seems to favour: (i) high oxide capacitance (1000 Fg -1 ) at high oxide loadings (up to 20 wt%) and (ii) high capacitance retention (ca. 80% from the initial oxide capacitance) at high current densities (200 mA cm -2 ). Amorphous carbon nanofibres are suitable supports for amorphous ruthenium oxide and perhaps for other amorphous oxides acting as active electrode materials.

  15. Elemental distribution in fluorinated amorphous carbon thin films.

    Science.gov (United States)

    Lamperti, A; Bottani, C E; Ossi, P M

    2005-01-01

    Focused ion beam-secondary ion mass spectrometry (FIB-SIMS) with 20 nm spatial resolution has been used to analyze amorphous fluorinated carbon thin films, deposited by plasma assisted chemical vapor deposition (PACVD), at micro- to nano-scale. Mass spectra and ion imaging of film surface were acquired and the presence and distribution of contaminants were investigated. Surface images show the secondary ion distribution for F(-), CH(-), CF(-). A change in size and topology of fluorine-rich areas is correlated with film hardness and with microstructure transition from diamond-like to polymer-like, as indicated by infrared and Raman spectroscopies. Based on the surface distributions of CF(-) and CH(-) and on the vibrational spectroscopy results, a mechanism of fluorine substitution for hydrogen and an attempt to explain the film structure and microstructure is proposed.

  16. Systematic study of amorphous hydrogenated and fluorinated carbon films

    Science.gov (United States)

    Lamperti, A.; Ossi, P. M.

    2003-01-01

    Amorphous fluorinated carbon films were grown from CF 4 and C 2H 2 mixtures, using a Plasma Assisted Chemical Vapour Deposition (PACVD) apparatus. Two sets of films were deposited, changing in a systematic way the CF 4 flux and the bias voltage ( Vb). Film composition and structure were analysed by secondary ion mass spectroscopy (SIMS), infrared (IR) and Raman spectroscopies. Film hardness was obtained by micro-indentation measurements. On increasing fluorine content in films, hardness decreases and a fluorescence background in Raman spectra appears at high fluorine content, showing a diamond- to polymer-like structural transition. Infrared spectra indicate the presence of CF x, CCHF and CCF 2 groups in the films. Our data are compared with previous results in the literature and the mechanisms involved in film formation are discussed, especially regarding fluorine substitution for hydrogen.

  17. Presence of Amorphous Carbon Nanoparticles in Food Caramels

    Science.gov (United States)

    Sk, Md Palashuddin; Jaiswal, Amit; Paul, Anumita; Ghosh, Siddhartha Sankar; Chattopadhyay, Arun

    2012-01-01

    We report the finding of the presence of carbon nanoparticles (CNPs) in different carbohydrate based food caramels, viz. bread, jaggery, sugar caramel, corn flakes and biscuits, where the preparation involves heating of the starting material. The CNPs were amorphous in nature; the particles were spherical having sizes in the range of 4–30 nm, depending upon the source of extraction. The results also indicated that particles formed at higher temperature were smaller than those formed at lower temperature. Excitation tuneable photoluminescence was observed for all the samples with quantum yield (QY) 1.2, 0.55 and 0.63%, for CNPs from bread, jaggery and sugar caramels respectively. The present discovery suggests potential usefulness of CNPs for various biological applications, as the sources of extraction are regular food items, some of which have been consumed by humans for centuries, and thus they can be considered as safe. PMID:22540029

  18. Resistance switching at the nanometre scale in amorphous carbon

    International Nuclear Information System (INIS)

    Sebastian, Abu; Rossel, Christophe; Pozidis, Haralampos; Eleftheriou, Evangelos; Pauza, Andrew; Shelby, Robert M; RodrIguez, Arantxa Fraile

    2011-01-01

    The electrical transport and resistance switching mechanism in amorphous carbon (a-C) is investigated at the nanoscale. The electrical conduction in a-C thin films is shown to be captured well by a Poole-Frenkel transport model that involves nonisolated traps. Moreover, at high electric fields a field-induced threshold switching phenomenon is observed. The following resistance change is attributed to Joule heating and subsequent localized thermal annealing. We demonstrate that the mechanism is mostly due to clustering of the existing sp 2 sites within the sp 3 matrix. The electrical conduction behaviour, field-induced switching and Joule-heating-induced rearrangement of atomic order resulting in a resistance change are all reminiscent of conventional phase-change memory materials. This suggests the potential of a-C as a similar nonvolatile memory candidate material.

  19. Heat treatment of cathodic arc deposited amorphous hard carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Anders, S.; Ager, J.W. III; Brown, I.G. [and others

    1997-02-01

    Amorphous hard carbon films of varying sp{sup 2}/sp{sup 3} fractions have been deposited on Si using filtered cathodic are deposition with pulsed biasing. The films were heat treated in air up to 550 C. Raman investigation and nanoindentation were performed to study the modification of the films caused by the heat treatment. It was found that films containing a high sp{sup 3} fraction sustain their hardness for temperatures at least up to 400 C, their structure for temperatures up to 500 C, and show a low thickness loss during heat treatment. Films containing at low sp{sup 3} fraction graphitize during the heat treatment, show changes in structure and hardness, and a considerable thickness loss.

  20. Infrared analysis of thin films amorphous, hydrogenated carbon on silicon

    CERN Document Server

    Jacob, W; Schwarz-Selinger, T

    2000-01-01

    The infrared analysis of thin films on a thick substrate is discussed using the example of plasma-deposited, amorphous, hydrogenated carbon layers (a-C:H) on silicon substrates. The framework for the optical analysis of thin films is presented. The main characteristic of thin film optics is the occurrence of interference effects due to the coherent superposition of light multiply reflected at the various internal and external interfaces of the optical system. These interference effects lead to a sinusoidal variation of the transmitted and reflected intensity. As a consequence, the Lambert-Beer law is not applicable for the determination of the absorption coefficient of thin films. Furthermore, observable changes of the transmission and reflection spectra occur in the vicinity of strong absorption bands due to the Kramers-Kronig relation. For a sound data evaluation these effects have to be included in the analysis. To be able to extract the full information contained in a measured optical thin film spectrum, ...

  1. Mechanical dissipation at elevated temperatures in tetrahedral amorphous carbon.

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, John P.; Friedmann, Thomas Aquinas; Czaplewski, David A.; Wendt, Joel Robert

    2005-05-01

    We have measured the temperature dependence of mechanical dissipation in tetrahedral amorphous carbon flexural and torsional resonators over the temperature range from 300 to 1023 K. The mechanical dissipation was found to be controlled by defects within the material, and the magnitude and temperature dependence of the dissipation were found to depend on whether flexural or torsional vibrational modes were excited. The defects that were active under flexural stresses have a relatively flat concentration from 0.4 to 0.7 eV with an ever increasing defect concentration up to 1.9 eV. Under shear stresses (torsion), the defect activation energies increase immediately beginning at 0.4 eV, with increasing defect concentration at higher energies.

  2. Mechanochemical treatment of amorphous carbon from brown sphagnum moss for the preparation of carbon nanotubes

    International Nuclear Information System (INIS)

    Onishchenko, D.V.

    2013-01-01

    Under consideration is the mechanism of multiwalled nanotubes formation during mechanical activation of amorphous carbon synthesized by pyrolysis of sphagnum moss. The formation of nanotubes has been shown to take place in the array of carbon particles. A complex study of the sorption characteristics of carbon nanotubes has been carried out. The dependence of the sorption capacity of carbon nanotubes on their storage time, as well as the effect of the process parameters of nanotubes formation on their ability for oxidative modification, is represented. (authors)

  3. Graphitic carbon growth on crystalline and amorphous oxide substrates using molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Kim Christine

    2011-01-01

    Full Text Available Abstract We report graphitic carbon growth on crystalline and amorphous oxide substrates by using carbon molecular beam epitaxy. The films are characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The formations of nanocrystalline graphite are observed on silicon dioxide and glass, while mainly sp2 amorphous carbons are formed on strontium titanate and yttria-stabilized zirconia. Interestingly, flat carbon layers with high degree of graphitization are formed even on amorphous oxides. Our results provide a progress toward direct graphene growth on oxide materials. PACS: 81.05.uf; 81.15.Hi; 78.30.Ly.

  4. Research Update: Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air

    International Nuclear Information System (INIS)

    Narayan, Jagdish; Bhaumik, Anagh

    2015-01-01

    We report on fundamental discovery of conversion of amorphous carbon into diamond by irradiating amorphous carbon films with nanosecond lasers at room-temperature in air at atmospheric pressure. We can create diamond in the form of nanodiamond (size range <100 nm) and microdiamond (>100 nm). Nanosecond laser pulses are used to melt amorphous diamondlike carbon and create a highly undercooled state, from which various forms of diamond can be formed upon cooling. The quenching from the super undercooled state results in nucleation of nanodiamond. It is found that microdiamonds grow out of highly undercooled state of carbon, with nanodiamond acting as seed crystals

  5. Measuring the dielectric and optical response of millimeter-scale amorphous and hexagonal boron nitride films grown on epitaxial graphene

    Science.gov (United States)

    Rigosi, Albert F.; Hill, Heather M.; Glavin, Nicholas R.; Pookpanratana, Sujitra J.; Yang, Yanfei; Boosalis, Alexander G.; Hu, Jiuning; Rice, Anthony; Allerman, Andrew A.; Nguyen, Nhan V.; Hacker, Christina A.; Elmquist, Randolph E.; Hight Walker, Angela R.; Newell, David B.

    2018-01-01

    Monolayer epitaxial graphene (EG), grown on the Si face of SiC, is an advantageous material for a variety of electronic and optical applications. EG forms as a single crystal over millimeter-scale areas and consequently, the large scale single crystal can be utilized as a template for growth of other materials. In this work, we present the use of EG as a template to form millimeter-scale amorphous and hexagonal boron nitride (a-BN and h-BN) films. The a-BN is formed with pulsed laser deposition and the h-BN is grown with triethylboron (TEB) and NH3 precursors, making it the first metal organic chemical vapor deposition (MOCVD) process of this growth type performed on epitaxial graphene. A variety of optical and non-optical characterization methods are used to determine the optical absorption and dielectric functions of the EG, a-BN, and h-BN within the energy range of 1 eV–8.5 eV. Furthermore, we report the first ellipsometric observation of high-energy resonant excitons in EG from the 4H polytype of SiC and an analysis on the interactions within the EG and h-BN heterostructure.

  6. Carbon isotope fractionation between amorphous calcium carbonate and calcite in earthworm-produced calcium carbonate

    International Nuclear Information System (INIS)

    Versteegh, E.A.A.; Black, S.; Hodson, M.E.

    2017-01-01

    In this study we investigate carbon isotope fractionation during the crystallization of biogenic calcium carbonate. Several species of earthworm including Lumbricus terrestris secrete CaCO 3 . Initially a milky fluid comprising micro-spherules of amorphous CaCO 3 (ACC) is secreted into pouches of the earthworm calciferous gland. The micro-spherules coalesce and crystalize to form millimetre scale granules, largely comprising calcite. These are secreted into the earthworm intestine and from there into the soil. L. terrestris were cultured for 28 days in two different soils, moistened with three different mineral waters at 10, 16 and 20 °C. The milky fluid in the calciferous glands, granules in the pouches of the calciferous glands and granules excreted into the soil were collected and analysed by FTIR spectroscopy to determine the form of CaCO 3 present and by IRMS to determine δ 13 C values. The milky fluid was ACC. Granules removed from the pouches and soil were largely calcite; the granules removed from the pouches contained more residual ACC than those recovered from the soil. The δ 13 C values of milky fluid and pouch granules became significantly more negative with increasing temperature (p ≤ 0.001). For samples from each temperature treatment, δ 13 C values became significantly (p ≤ 0.001) more negative from the milky fluid to the pouch granules to the soil granules (−13.77, −14.69 and −15.00 respectively at 10 °C; −14.37, −15.07 and −15.18 respectively at 16 °C and −14.89, −15.41 and −15.65 respectively at 20 °C). Fractionation of C isotopes occurred as the ACC recrystallized to form calcite with the fractionation factor ε calcite-ACC  = −1.20 ± 0.52‰. This is consistent with the crystallization involving dissolution and reprecipitation rather than a solid state rearrangement. Although C isotopic fractionation has previously been described between different species of dissolved inorganic carbon and

  7. Mesoporous Metal-Containing Carbon Nitrides for Improved Photocatalytic Activities

    Directory of Open Access Journals (Sweden)

    Jie Luo

    2013-01-01

    Full Text Available Graphitic carbon nitrides (g-C3N4 have attracted increasing interest due to their unusual properties and promising applications in water splitting, heterogeneous catalysis, and organic contaminant degradation. In this study, a new method was developed for the synthesis of mesoporous Fe contained g-C3N4 (m-Fe-C3N4 photocatalyst by using SiO2 nanoparticles as hard template and dicyandiamide as precursor. The physicochemical properties of m-Fe-C3N4 were thoroughly investigated. The XRD and XPS results indicated that Fe was strongly coordinated with the g-C3N4 matrix and that the doping and mesoporous structure partially deteriorated its crystalline structure. The UV-visible absorption spectra revealed that m-Fe-C3N4 with a unique electronic structure displays an increased band gap in combination with a slightly reduced absorbance, implying that mesoporous structure modified the electronic properties of g-Fe-C3N4. The photocatalytic activity of m-Fe-C3N4 for photodegradation of Rhodamine B (RhB was much higher than that of g-Fe-C3N4, clearly demonstrating porous structure positive effect.

  8. Two-dimensional graphitic carbon nitride nanosheets for biosensing applications.

    Science.gov (United States)

    Xiong, Mengyi; Rong, Qiming; Meng, Hong-Min; Zhang, Xiao-Bing

    2017-03-15

    Two-dimensional graphitic carbon nitride nanosheets (CNNSs) with planar graphene-like structure have stimulated increasingly research interest in recent years due to their unique physicochemical properties. CNNSs possess superior stability, high fluorescence quantum yield, low-toxicity, excellent biocompatibility, unique electroluminescent and photoelectrochemical properties, which make them appropriate candidates for biosensing. In this review, we first introduce the preparation and unique properties of CNNSs, with emphasis on their superior properties for biosensing. Then, recent advances of CNNSs in photoelectrochemical biosensing, electrochemiluminescence biosensing and fluorescence biosensing are highlighted. An additional attention is paid to the marriage of CNNSs and nucleic acids, which exhibits great potentials in both biosensing and intracellular imaging. Finally, current challenges and opportunities of this 2D material are outlined. Inspired by the unique properties of CNNSs and their advantages in biological applications, we expect that more attention will be drawn to this promising 2D material and extensive applications can be found in bioanalysis and diseases diagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Synthesis of beta carbon nitride nanosized crystal through mechanochemical reaction

    CERN Document Server

    Yin Long Wei; Liu Yu Xian; Sui Jin Ling; Wang Jing Min

    2003-01-01

    Nanosized beta carbon nitride (beta-C sub 3 N sub 4), of grain size several tens of nanometres, has been synthesized by mechanochemical reaction processing. The low-cost synthetic method developed facilitates the novel and effective synthesis of nanosized crystalline beta-C sub 3 N sub 4 (a = 6.36 A, c = 4.648 A) powders. The graphite powders were first milled to a nanoscale state, then the nanosized graphite powders were milled in an atmosphere of NH sub 3 gas. It was found that nanosized beta-C sub 3 N sub 4 was formed after high-energy ball milling under an NH sub 3 atmosphere. After thermal annealing, the shape of the beta-C sub 3 N sub 4 changes from flake-like to sphere-like. The nanosized beta-C sub 3 N sub 4 formed was characterized by x-ray diffraction, Fourier transformation infrared spectroscopy, and transmission electron microscopy. A solid-gas reaction mechanism was proposed for the formation of nanosized beta-C sub 3 N sub 4 at room temperature induced by mechanochemical activation.

  10. DFT Perspective on the Thermochemistry of Carbon Nitride Synthesis

    KAUST Repository

    Melissen, Sigismund T. A. G.

    2016-10-11

    Graphitic (g)-CxNyHz has become a popular family of photoharvesters in photocatalytic water splitting cells, as well as other applications in chemistry. In this Article, different g-CxNyHz structures were studied thermochemically using DFT. Following a benchmark study with different families of functionals, the B3LYP functional was shown to accurately capture the thermochemistry of carbon nitride synthesis. A triple-ζ polarized basis set, in combination with Civalleri’s modification to Grimme’s D2 formalism (with s6 = 0.5) for dispersion interactions, yielded accurate geometries. Grimme’s D3 formalism with Becke–Johnson damping was used to refine the energetic description of dispersion interactions. The stepwise cycloaddition of cyanamide to form melamine was shown to be exergonic, whereas the stepwise deamination of melamine to form g-C3N4 was shown to be endergonic. Of those structures respecting the [C6N9H3]n chemical formula, the structure commonly known as “melon” was found to be most stable, whereas the sp3-hybridized [C6N9H3]n elucidated by Horvath-Bordon et al. was found to be the least stable. Fully polymerized triazine-based g-C3N4 appeared slightly more stable than heptazine-based g-C3N4.

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

    International Nuclear Information System (INIS)

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

    1998-01-01

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

  12. Solubility and bioavailability of stabilized amorphous calcium carbonate.

    Science.gov (United States)

    Meiron, Oren E; Bar-David, Elad; Aflalo, Eliahu D; Shechter, Assaf; Stepensky, David; Berman, Amir; Sagi, Amir

    2011-02-01

    Since its role in the prevention of osteoporosis in humans was proven some 30 years ago, calcium bioavailability has been the subject of numerous scientific studies. Recent technology allowing the production of a stable amorphous calcium carbonate (ACC) now enables a bioavailability analysis of this unique form of calcium. This study thus compares the solubility and fractional absorption of ACC, ACC with chitosan (ACC-C), and crystalline calcium carbonate (CCC). Solubility was evaluated by dissolving these preparations in dilute phosphoric acid. The results demonstrated that both ACC and ACC-C are more soluble than CCC. Fractional absorption was evaluated by intrinsically labeling calcium carbonate preparations with (45)Ca, orally administrated to rats using gelatin capsules. Fractional absorption was determined by evaluating the percentage of the administrated radioactive dose per milliliter that was measured in the serum, calcium absorption in the femur, and whole-body retention over a 34-hour period. Calcium serum analysis revealed that calcium absorption from ACC and ACC-C preparations was up to 40% higher than from CCC, whereas retention of ACC and ACC-C was up to 26.5% higher than CCC. Absorbed calcium in the femurs of ACC-administrated rats was 30% higher than in CCC-treated animals, whereas 15% more calcium was absorbed following ACC-C treatment than following CCC treatment. This study demonstrates the enhanced solubility and bioavailability of ACC over CCC. The use of stable ACC as a highly bioavailable dietary source for calcium is proposed based on the findings of this study. Copyright © 2011 American Society for Bone and Mineral Research.

  13. Boron nitride composites

    Science.gov (United States)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2017-02-21

    According to one embodiment, a composite product includes: a matrix material including hexagonal boron nitride and one or more borate binders; and a plurality of cubic boron nitride particles dispersed in the matrix material. According to another embodiment, a composite product includes: a matrix material including hexagonal boron nitride and amorphous boron nitride; and a plurality of cubic boron nitride particles dispersed in the matrix material.

  14. Conformational analysis and electronic structure of chiral carbon and carbon nitride nanotubes

    Directory of Open Access Journals (Sweden)

    Cristiano Geraldo de Faria

    2011-12-01

    Full Text Available Geometry and electronic structure of chiral carbon and carbon nitride (CNx nanotubes were investigated through quantum chemical methods. Finite nanotubes with diameters ranging from 5 to 10 Å and containing up to 500 atoms were considered. CNx structures were built through random substitution of carbon atoms by nitrogen. The molecules were fully optimized by semi-empirical quantum chemical method (PM3. Our results show that the energy associated with nitrogen incorporation depends strongly upon the tube helicity and diameter. The doping of nanotubes with nitrogen contributes to reduce the stress caused by the small diameter of the studied systems. Density of States (DOS results for pure carbon and CNx nanostructures, obtained through DFT and Hartree-Fock calculations, were analyzed. The introduction of nitrogen in the tube produce states in the gap region which characterizes the metallic behavior, as expected for these systems after N-doping.

  15. Supramolecular intermediates in the synthesis of polymeric carbon nitride from melamine cyanurate

    Energy Technology Data Exchange (ETDEWEB)

    Dante, Roberto C., E-mail: rcdante@yahoo.com [Facultad de Mecánica, Escuela Politécnica Nacional (EPN), Ladrón de Guevara E11-253, Quito (Ecuador); Sánchez-Arévalo, Francisco M. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, Apdo. Postal 70-360, Cd. Universitaria, Mexico D.F. 04510 (Mexico); Chamorro-Posada, Pedro [Dpto. de Teoría de la Señal y Comunicaciones e IT, Universidad de Valladolid, ETSI Telecomunicación, Paseo Belén 15, 47011 Valladolid (Spain); Vázquez-Cabo, José [Dpto. de Teoría de la Señal y Comunicaciones, Universidad de Vigo, ETSI Telecomunicación, Lagoas Marcosende s/n, Vigo (Spain); Huerta, Lazaro [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, Apdo. Postal 70-360, Cd. Universitaria, Mexico D.F. 04510 (Mexico); Lartundo-Rojas, Luis [Centro de Nanociencias y Micro y Nanotecnologías—IPN, Luis Enrique Erro s/n, U. Prof. Adolfo López Mateos, 07738 Ciudad de Mexico, Distrito Federal (Mexico); Santoyo-Salazar, Jaime [Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, CINVESTAV-IPN, Apdo. Postal 14-740, Mexico D.F. 07360 (Mexico); and others

    2015-03-15

    The adduct of melamine and cyanuric acid (MCA) was used in past research to produce polymeric carbon nitride and precursors. The reaction yield was considerably incremented by the addition of sulfuric acid. The polymeric carbon nitride formation occurs around 450 °C at temperatures above the sublimation of the adduct components, which occurs around 400 °C. In this report the effect of sulfuric acid on MCA was investigated. It was found that the MCA rosette supramolecular channel structures behave as a solid solvent able to host small molecules, such as sulfuric acid, inside these channels and interact with them. Therefore, the sulfuric acid effect was found to be close to that of a solute that causes a temperature increment of the “solvent sublimation” enough to allowing the formation of polymeric carbon nitride to occur. Sulfate ions are presumably hosted in the rosette channels of MCA as shown by simulations. - Graphical abstract: The blend of melamine cyanurate and sulfuric acid behaves like a solution so that melamine cyanurate decomposition is shifted to temperatures high enough to react and form polymeric carbon nitride. - Highlights: • The adduct of melamine and cyanuric acid behaves as a solid solvent. • The blend of sulfuric acid and melamine cyanurate behaves like a solution. • Melamine cyanurate decomposition is shifted to higher temperatures by sulfuric acid. • The formation of polymeric carbon nitride occurs for these higher temperatures.

  16. Supramolecular intermediates in the synthesis of polymeric carbon nitride from melamine cyanurate

    International Nuclear Information System (INIS)

    Dante, Roberto C.; Sánchez-Arévalo, Francisco M.; Chamorro-Posada, Pedro; Vázquez-Cabo, José; Huerta, Lazaro; Lartundo-Rojas, Luis; Santoyo-Salazar, Jaime

    2015-01-01

    The adduct of melamine and cyanuric acid (MCA) was used in past research to produce polymeric carbon nitride and precursors. The reaction yield was considerably incremented by the addition of sulfuric acid. The polymeric carbon nitride formation occurs around 450 °C at temperatures above the sublimation of the adduct components, which occurs around 400 °C. In this report the effect of sulfuric acid on MCA was investigated. It was found that the MCA rosette supramolecular channel structures behave as a solid solvent able to host small molecules, such as sulfuric acid, inside these channels and interact with them. Therefore, the sulfuric acid effect was found to be close to that of a solute that causes a temperature increment of the “solvent sublimation” enough to allowing the formation of polymeric carbon nitride to occur. Sulfate ions are presumably hosted in the rosette channels of MCA as shown by simulations. - Graphical abstract: The blend of melamine cyanurate and sulfuric acid behaves like a solution so that melamine cyanurate decomposition is shifted to temperatures high enough to react and form polymeric carbon nitride. - Highlights: • The adduct of melamine and cyanuric acid behaves as a solid solvent. • The blend of sulfuric acid and melamine cyanurate behaves like a solution. • Melamine cyanurate decomposition is shifted to higher temperatures by sulfuric acid. • The formation of polymeric carbon nitride occurs for these higher temperatures

  17. Functionalizing carbon nitride with heavy atom-free spin converters for enhanced 1 O 2 generation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Wenting; Han, Congcong; Zhang, Qinhua; Zhang, Qinggang; Li, Zhongtao; Gosztola, David J.; Wiederrecht, Gary P.; Wu, Mingbo

    2018-05-01

    advanced photosensitizers for singlet oxygen (1O2) generation. However, the intersystem crossing (ISC) process is quite insufficient in carbon nitride, limiting the 1O2 generation. Here, we report a facile and general strategy to confined benzophenone as a heavy atom-free spin converter dopant in carbon nitride via the facile copolymerization. With proper energy level matching between the heavy atom-free spin converter and various ligands based on carbon nitride precursors, the proper combination can decrease the singlet-triplet energy gap (DEST) and hence generate 1O2 effectively. Due to its significant and selectivity for 1O2 generation, the as-prepared carbon nitride-based photosensitizer shows a high selective photooxidation activity for 1,5-dihydroxy-naphthalene (1,5-DHN). The product yield reached 71.8% after irradiation for 60 min, which was higher than that of cyclometalated PtII complexes (53.6%) in homogeneous photooxidation. This study can broaden the application of carbon nitride in the field of selective heterogeneous photooxidation due to simple operation, low cost, and high efficiency, making it a strong candidate for future industrialization.

  18. Electron-trapping-triggered anneal of defect states in silicon-rich hydrogenated amorphous silicon nitride

    International Nuclear Information System (INIS)

    Oversluizen, G.; Lodders, W.H.; Johnson, M.T.; van der Put, A.A.

    1997-01-01

    The dc-current stress behavior of Mo/a-SiN x H y /Mo thin-film diodes is discussed for several a-SiN x H y -plasma-deposition conditions. Current transport is governed by thermionic field emission of electrons over a reverse biased Schottky barrier. The barrier height is determined by the a-SiN x H y -plasma-deposition conditions. Therefore these back-to-back Schottky devices provide an elegant way to perform dc-current stressing at several well defined carrier densities for similar stress fields. It is shown that such experiments allow assessment of defect-state creation/anneal mechanisms in a-SiN x H y . An electron-trapping-triggered anneal mechanism accounts for the observed dependence of the defect density at the electrode injecting contact (cathode) on the hole-barrier height at the anode. Also a new microscopically detailed anneal reaction scheme is proposed. The defect-state creation/anneal mechanism is expected to be generally applicable for all silicon-rich hydrogenated amorphous silicon alloys. copyright 1997 American Institute of Physics

  19. Hard template synthesis of porous carbon nitride materials with improved efficiency for photocatalytic CO{sub 2} utilization

    Energy Technology Data Exchange (ETDEWEB)

    Ovcharov, M. [L.V Pysarzhevsky Institute of Physical Chemistry, NAS of Ukraine, 31 pr. Nauky, 03028 Kyiv (Ukraine); Shcherban, N., E-mail: nataliyalisenko@ukr.net [L.V Pysarzhevsky Institute of Physical Chemistry, NAS of Ukraine, 31 pr. Nauky, 03028 Kyiv (Ukraine); Filonenko, S.; Mishura, A. [L.V Pysarzhevsky Institute of Physical Chemistry, NAS of Ukraine, 31 pr. Nauky, 03028 Kyiv (Ukraine); Skoryk, M. [NanoMedTech LLC, 68 Gorkogo str., Kyiv (Ukraine); Shvalagin, V.; Granchak, V. [L.V Pysarzhevsky Institute of Physical Chemistry, NAS of Ukraine, 31 pr. Nauky, 03028 Kyiv (Ukraine)

    2015-12-15

    Graphical abstract: - Highlights: • Porous carbon nitrides were obtained via bulk and matrix pyrolysis of melamine. • Carbon nitride obtained in MCF has the highest bandgap and photocatalytic activity. • Acetaldehyde was the major product of the photoreduction reaction of CO2. - Abstract: Porous carbon nitrides of different morphology were obtained via bulk and hard template (SBA-15 and MCF) pyrolysis of melamine. Matrix method allowed obtaining ordered porous C{sub 3}N{sub 4} with higher bandgap (2.87 eV) in the contrary to the bulk sample (2.45 eV). Obtained carbon nitrides were found to be p-type semiconductors with catalytic activity towards photoreduction of carbon dioxide with water vapour. Carbon nitride obtained in MCF has the higher bandgap, developed surface, sponge-like morphology, spatially ordering and it's characterized by the highest photocatalytic activity.

  20. Piezoresistive gauge factor of hydrogenated amorphous carbon films

    Science.gov (United States)

    Tibrewala, A.; Peiner, E.; Bandorf, R.; Biehl, S.; Lüthje, H.

    2006-06-01

    In this paper we report on the transport properties of hydrogenated amorphous carbon (a-C:H) which is an attractive material for strain gauges and can also be used in flow meters, accelerometers and vibrational sensors. The a-C:H films were deposited at -350 V bias voltage on silicon (Si) substrates using plasma assisted chemical vapor deposition (PACVD). Current-voltage characteristics of a-C:H/n-Si heterojunctions show ohmic behavior within operating voltages of ±1 V. In the higher voltage range the Frenkel-Poole mechanism is dominant. Conduction is thermally activated at temperatures ranging from 23 °C to 150 °C. The activation energy amounts to 0.48 eV. A-C:H resistors are successfully integrated as strain gauges in Si bulk micromachined force sensors. Piezoresistive gauge factors are measured for the a-C:H strain gauge resistors in the temperature range 23-60 °C. The measured piezoresistive gauge factors are in between 40 and 90 for a-C:H with resistivities in the range 100-700 MΩ cm.

  1. Structures and properties of fluorinated amorphous carbon films

    Science.gov (United States)

    Huang, K. P.; Lin, P.; Shih, H. C.

    2004-07-01

    Fluorinated amorphous carbon (a-C:F) films were deposited by radio frequency bias assisted microwave plasma electron cyclotron resonance chemical vapor deposition with tetrafluoromethane (CF4) and acetylene (C2H2) as precursors. The deposition process was performed at two flow ratios R=0.90 and R=0.97, where R=CF4/(CF4+C2H2). The samples were annealed at 300 °C for 30 min. in a N2 atmosphere. Both Fourier transform infrared and electron spectroscopy for chemical analyzer were used to characterize the a-C:F film chemical bond and fluorine concentration, respectively. A high resolution electron energy loss spectrometer was applied to detect the electronic structure. The higher CF4 flow ratio (R=0.97) produced more sp3 linear structure, and it made the a-C:F film smoother and softer. A lifetime of around 0.34 μs and an energy gap of ˜2.75 eV were observed in both the as-deposited and after annealing conditions. The short carriers lifetime in the a-C:F film made the photoluminescence peak blueshift. The annealing changed both the structure and composition of the a-C:F film. The type of fluorocarbon bond and electronic structure characterized the mechanical and physical properties of a-C:F film.

  2. Influence of plasma nitriding on the hardness of AISI 304 and low carbon steel

    International Nuclear Information System (INIS)

    Suprapto; Sudjatmoko; Tjipto Sujitno

    2010-01-01

    Nitriding with plasma/ion nitriding technique for surface treatment of AISI 304 and low carbon steel as a machine component material has been done. Surface treatment is meant to improve the surface quality of metal especially its hardness. To reach the optimum condition it has been done a variation of nitriding pressure, while to analyse the result it has been done the hardness and microstructure test, and the nitrogen content. Result of the test indicates that: the optimum hardness obtained at 1.8 mbar of pressure that is 624.9 VHN or 2.98 times while the initial hardness is 210.3 VHN for AISI 304 and 581.6 VHN or 3.07 times compare with initial hardness 142.9 VHN for low carbon steel. The thickness of nitride layer for AISI 304 and low carbon steel is around 30 µm. Nitrogen contents after nitriding are 10.74% mass or 30.32% atom for AISI 304 and 6.81% mass or 21.76% atom for low carbon steel. (author)

  3. Erection of duct-like graphitic carbon nitride with enhanced photocatalytic activity for ACB photodegradation

    Science.gov (United States)

    Muhmood, Tahir; Xia, Mingzhu; Lei, Wu; Wang, Fengyun

    2018-02-01

    Novel duct graphitic carbon nitride (DCN) was successfully prepared using the temperature control method in a quartz tube furnace from commercially available melamine and evaluated against the photo-degradation of latent organic pollutants, acarbose (ACB). These prepared materials were characterized by UV-Vis spectroscopy, Fourier transform infrared spectra, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The characterization results indicated that the synthesized material was in the form of a duct-like structure and has greater adsorption capacity and photocatalytic ability as compared to traditionally synthesized graphitic carbon nitride materials. The DCN split theACB completely into many intermediates, which were depicted in the HPLC-MS spectrum for knowing the acarbose photo-degrdation pathway. The duct-like morphology of graphitic carbon nitride has improved properties, such as increasing the surface area and decelerating the e -/h + recombination, which increase the light absorbance ability with enhanced photoactivity.

  4. Band gap-tunable potassium doped graphitic carbon nitride with enhanced mineralization ability.

    Science.gov (United States)

    Hu, Shaozheng; Li, Fayun; Fan, Zhiping; Wang, Fei; Zhao, Yanfeng; Lv, Zhenbo

    2015-01-21

    Band gap-tunable potassium doped graphitic carbon nitride with enhanced mineralization ability was prepared using dicyandiamide monomer and potassium hydrate as precursors. X-ray diffraction (XRD), N2 adsorption, UV-Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared catalysts. The CB and VB potentials of graphitic carbon nitride could be tuned from -1.09 and +1.56 eV to -0.31 and +2.21 eV by controlling the K concentration. Besides, the addition of potassium inhibited the crystal growth of graphitic carbon nitride, enhanced the surface area and increased the separation rate for photogenerated electrons and holes. The visible-light-driven Rhodamine B (RhB) photodegradation and mineralization performances were significantly improved after potassium doping. A possible influence mechanism of the potassium concentration on the photocatalytic performance was proposed.

  5. Modulating Crystallinity of Graphitic Carbon Nitride for Photocatalytic Oxidation of Alcohols.

    Science.gov (United States)

    Zhou, Min; Yang, Pengju; Yuan, Rusheng; Asiri, Abdullah M; Wakeel, Muhammad; Wang, Xinchen

    2017-11-23

    Exploiting efficient photocatalysts with strengthened structure for solar-driven alcohol oxidation is of great significance. The photocatalytic performance of graphitic carbon nitrides can be considerably promoted by modulating its crystallinity. Results confirmed that a high crystallinity accelerates the separation and transfer of photogenerated charge carriers, thus providing more free charges for photoredox reactions. More importantly, the high crystallinity facilitated the adsorption of benzyl alcohol and desorption of benzaldehyde and simultaneously lowered the energy barrier for O 2 activation. As a result, the crystalline carbon nitride exhibited a roughly twelvefold promotion with respect to the normal carbon nitride. The remarkable enhancement of activity can be attributed to the synergistic effects of increased electron-hole separation and increased surface reaction kinetics. These findings will open up new opportunities to modulate the structure of polymers for a wide variety of organic reactions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Microcontact-printing-assisted access of graphitic carbon nitride films with favorable textures toward photoelectrochemical application.

    Science.gov (United States)

    Liu, Jian; Wang, Hongqiang; Chen, Zu Peng; Moehwald, Helmuth; Fiechter, Sebastian; van de Krol, Roel; Wen, Liping; Jiang, Lei; Antonietti, Markus

    2015-01-27

    An "ink" (cyanamide) infiltrated anodic aluminum oxide (AAO) stamp is found capable of printing carbon nitride films featuring regular microstructures of the stamp onto the substrates via in situ "chemical vapor deposition". A photocurrent density of 30.2 μA cm(-2 --) at 1.23 VRHE is achieved for a film on a conductive substrate, which is so far the highest value for pure carbon nitride based photoelectrochemical devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Exfoliated graphitic carbon nitride nanosheets as efficient catalysts for hydrogen evolution under visible light.

    Science.gov (United States)

    Yang, Shubin; Gong, Yongji; Zhang, Jinshui; Zhan, Liang; Ma, Lulu; Fang, Zheyu; Vajtai, Robert; Wang, Xinchen; Ajayan, Pulickel M

    2013-05-07

    Graphitic carbon nitride nanosheets are extracted, produced via simple liquid-phase exfoliation of a layered bulk material, g-C3N4. The resulting nanosheets, having ≈2 nm thickness and N/C atomic ratio of 1.31, show an optical bandgap of 2.65 eV. The carbon nitride nanosheets are demonstrated to exhibit excellent photocatalytic activity for hydrogen evolution under visible light. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Hydrogen production using zinc-doped carbon nitride catalyst irradiated with visible light

    OpenAIRE

    Bing Yue, Qiuye Li, Hideo Iwai, Tetsuya Kako and Jinhua Ye

    2011-01-01

    Recently, graphitic carbon nitride (g-C3N4) has been investigated as a photocatalyst for water splitting and organic dye degradation. In this study, we have developed a simple soft-chemical method of doping Zn into g-C3N4 to prepare a metal-containing carbon nitride. The doping was confirmed by x-ray photoelectron spectroscopy, and diffusion reflectance spectra revealed a significant red shift in the absorption edge of Zn/g-C3N4. This hybrid material shows high photocatalytic activity and goo...

  9. Optical and passivating properties of hydrogenated amorphous silicon nitride deposited by plasma enhanced chemical vapour deposition for application on silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wight, Daniel Nilsen

    2008-07-01

    Within this thesis, several important subjects related to the use of amorphous silicon nitride made by plasma enhanced chemical vapour deposition as an anti-reflective coating on silicon solar cells are presented. The first part of the thesis covers optical simulations to optimise single and double layer anti-reflective coatings with respect to optical performance when situated on a silicon solar cell. The second part investigates the relationship between important physical properties of silicon nitride films when deposited under different conditions. The optical simulations were either based on minimising the reflectance off a silicon nitride/silicon wafer stack or maximising the transmittance through the silicon nitride into the silicon wafer. The former method allowed consideration of the reflectance off the back surface of the wafer, which occurs typically at wavelengths above 1000 nm due to the transparency of silicon at these wavelengths. However, this method does not take into consideration the absorption occurring in the silicon nitride, which is negligible at low refractive indexes but quite significant when the refractive index increases above 2.1. For high-index silicon nitride films, the latter method is more accurate as it considers both reflectance and absorbance in the film to calculate the transmittance into the Si wafer. Both methods reach similar values for film thickness and refractive index for optimised single layer anti-reflective coatings, due to the negligible absorption occurring in these films. For double layer coatings, though, the reflectance based simulations overestimated the optimum refractive index for the bottom layer, which would have lead to excessive absorption if applied to real anti-reflective coatings. The experimental study on physical properties for silicon nitride films deposited under varying conditions concentrated on the estimation of properties important for its applications, such as optical properties, passivation

  10. The preferential permeation of ions across carbon and boron nitride nanotubes

    International Nuclear Information System (INIS)

    Sardroodi, Jaber Jahanbin; Azamat, Jafar; Rastkar, Alireza; Yousefnia, Negar Rad

    2012-01-01

    Highlights: ► The permeation of ions through carbon and boron nitride nanotubes has been investigated by molecular dynamics simulation. ► The considered ions have been included Ca 2+ and Cl − . ► It has been shown that the ions permeate selectively. ► The radial distribution functions and the potential of mean force of the ions have been evaluated. -- Abstract: The preferential permeation of Ca 2+ and Cl − ions across (7, 7) and (8, 8) carbon and boron nitride nanotubes have been investigated by molecular dynamics simulation method. The simulated systems composed from a carbon, or boron nitride nanotube inserted in a silicon nitride membrane immersed in the aqueous ionic solution, in the presence of an electrical field. The water structure inside nanotubes has been analyzed and the retention time of the ions, the radial distribution functions and normalized transport rate of water with respect to the number of transported ions have been calculated. The results show that the permeation of ions across the nanotubes is dependent on the diameter of the considered nanotubes. The considered nanotubes have been fixed in a silicon-nitride membrane and an external electrical field has been applied on the systems along the axis of nanotubes.

  11. Biomolecule-assisted synthesis of carbon nitride and sulfur-doped carbon nitride heterojunction nanosheets: An efficient heterojunction photocatalyst for photoelectrochemical applications

    Directory of Open Access Journals (Sweden)

    Hua Bing Tao

    2014-06-01

    Full Text Available A biomolecule-assisted pyrolysis method has been developed to synthesize sulfur-doped graphitic carbon nitride (CNS nanosheets. During the synthesis, sulfur could be introduced as a dopant into the lattice of carbon nitride (CN. Sulfur doping changed the texture as well as relative band positions of CN. By growing CN on preformed sulfur-doped CN nanosheets, composite CN/CNS heterojunction nanosheets were constructed, which significantly enhanced the photoelectrochemical performance as compared with various control counterparts including CN, CNS and physically mixed CN and CNS (CN+CNS. The enhanced photoelectrochemical performance of CN/CNS heterojunction nanosheets could be ascribed to the efficient separation of photoexcited charge carriers across the heterojunction interface. The strategy of designing and preparing CN/CNS heterojunction photocatalysts in this work can open up new directions for the construction of all CN-based heterojunction photocatalysts.

  12. Revealing the 1 nm/s extensibility of nanoscale amorphous carbon in a scanning electron microscope.

    Science.gov (United States)

    Zhang, Wei

    2013-01-01

    In an ultra-high vacuum scanning electron microscope, the edged branches of amorphous carbon film (∼10 nm thickness) can be continuously extended with an eye-identifying speed (on the order of ∼1 nm/s) under electron beam. Such unusual mobility of amorphous carbon may be associated with deformation promoted by the electric field, which resulted from an inner secondary electron potential difference from the main trunk of carbon film to the tip end of branches under electron beam. This result demonstrates importance of applying electrical effects to modify properties of carbon materials. It may have positive implications to explore some amorphous carbon as electron field emission device. © Wiley Periodicals, Inc.

  13. Synthesis of amorphous carbon from bio-products by drying method

    Science.gov (United States)

    Pamungkas, Diajeng I.; Haikal, Anas; Baqiya, Malik A.; Cahyono, Yoyok; Darminto

    2018-04-01

    Amorphous carbon (a-C) has extensively been studied in the last two decades due to many superior properties. Amorphous carbon was successfully prepared by carbonization of organic compounds exposed up to 200°C. Organic compounds that used in this research were coconut sap, lontar palm sap and their derivatives. The X-ray diffraction pattern shows that carbonization of organic compounds produce amorphous carbon phase at 2θ =20°. The infrared absorption in the region from 500 to 4000 cm-1 were resolved into several peaks, which were assigned to C-H, C=C, C-O, C=O and O-H. Four point probe method was also used to measure the conductivity and band gap of each material, resulting in 1.73 - 29.6 S/m and 0.08 - 0.49 eV respectively.

  14. Gold Nanoparticles Supported on Carbon Nitride: Influence of Surface Hydroxyls on Low Temperature Carbon Monoxide Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Joseph A [ORNL; Dudney, Nancy J [ORNL; Li, Meijun [ORNL; Overbury, Steven {Steve} H [ORNL; Veith, Gabriel M [ORNL

    2012-01-01

    This paper reports the synthesis of 2.5 nm gold clusters on the oxygen free and chemically labile support carbon nitride (C3N4). Despite having small particle sizes and high enough water partial pressure these Au/C3N4 catalysts are inactive for the gas phase and liquid phase oxidation of carbon monoxide. The reason for the lack of activity is attributed to the lack of surface OH groups on the C3N4. These OH groups are argued to be responsible for the activation of CO in the oxidation of CO. The importance of basic OH groups explains the well document dependence of support isoelectric point versus catalytic activity.

  15. Effects of Nitride on the Tribological Properties of the Low Carbon Alloy Steel

    Directory of Open Access Journals (Sweden)

    Yuh-Ping Chang

    2013-01-01

    Full Text Available The technology of composite heat treatment is used popularly for low friction and wear resistance of drive elements. A large number of papers about the heat treatment technology had been proposed. Especially, the nitride treatment has been used widely for the purpose of wear resistance and low friction in the industry. Therefore, the self-developed vertical ball/disk friction tester with the measurement system was used to study the effects of nitride on the tribological properties of the low carbon alloy steel—SCM415— in this study. The experiments were conducted under dry and severe wear conditions. The variations of friction coefficient and surface magnetization were simultaneously recorded during dynamic friction process. After each test, the microstructures of the wear particles were observed and analyzed under a SEM, and the depth of wear track is measured by means of a surface tester. According to the experimental results, the wear resistance of the specimens with carburizing-nitride is significantly larger than the case of nitride-carburizing. Moreover, the surface magnetization was especially larger for the case of nitride-carburizing. As a result, the wear particles always stay in the interfaces and the wear mechanism becomes complex. Therefore, it is necessary to put nitride after carburizing for the composite heat treatments.

  16. Amorphous silicon-carbon based nano-scale thin film anode materials for lithium ion batteries

    International Nuclear Information System (INIS)

    Datta, Moni Kanchan; Maranchi, Jeffrey; Chung, Sung Jae; Epur, Rigved; Kadakia, Karan; Jampani, Prashanth; Kumta, Prashant N.

    2011-01-01

    Research highlights: → Thin film amorphous C/Si. Good cycling response validates carbon matrix for Silicon anodes. → Thin film amorphous C/Si/C. Good cycling response validates carbon as an interface and matrix. - Abstract: The buffering effect of carbon on the structural stability of amorphous silicon films, used as an anode for lithium ion rechargeable batteries, has been studied during long term discharge/charge cycles. To this extent, the electrochemical performance of a prototype material consisting of amorphous Si thin film (∼250 nm) deposited by radio frequency magnetron sputtering on amorphous carbon (∼50 nm) thin films, denoted as a-C/Si, has been investigated. In comparison to pure amorphous Si thin film (a-Si) which shows a rapid fade in capacity after 30 cycles, the a-C/Si exhibits excellent capacity retention displaying ∼0.03% fade in capacity up to 50 cycles and ∼0.2% after 50 cycles when cycled at a rate of 100 μA/cm 2 (∼C/2) suggesting that the presence of thin amorphous C layer deposited between the Cu substrate and a-Si acts as a buffer layer facilitating the release of the volume induced stresses exhibited by pure a-Si during the charge/discharge cycles. This structural integrity combined with microstructural stability of the a-C/Si thin film during the alloying/dealloying process with lithium has been confirmed by scanning electron microscopy (SEM) analysis. The buffering capacity of the thin amorphous carbon layer lends credence to its use as the likely compliant matrix to curtail the volume expansion related cracking of silicon validating its choice as the matrix for bulk and thin film battery systems.

  17. The effect of empirical potential functions on modeling of amorphous carbon using molecular dynamics method

    International Nuclear Information System (INIS)

    Li, Longqiu; Xu, Ming; Song, Wenping; Ovcharenko, Andrey; Zhang, Guangyu; Jia, Ding

    2013-01-01

    Empirical potentials have a strong effect on the hybridization and structure of amorphous carbon and are of great importance in molecular dynamics (MD) simulations. In this work, amorphous carbon at densities ranging from 2.0 to 3.2 g/cm 3 was modeled by a liquid quenching method using Tersoff, 2nd REBO, and ReaxFF empirical potentials. The hybridization, structure and radial distribution function G(r) of carbon atoms were analyzed as a function of the three potentials mentioned above. The ReaxFF potential is capable to model the change of the structure of amorphous carbon and MD results are in a good agreement with experimental results and density function theory (DFT) at low density of 2.6 g/cm 3 and below. The 2nd REBO potential can be used when amorphous carbon has a very low density of 2.4 g/cm 3 and below. Considering the computational efficiency, the Tersoff potential is recommended to model amorphous carbon at a high density of 2.6 g/cm 3 and above. In addition, the influence of the quenching time on the hybridization content obtained with the three potentials is discussed.

  18. Facile synthesis of phosphorus doped graphitic carbon nitride polymers with enhanced visible-light photocatalytic activity

    International Nuclear Information System (INIS)

    Zhang, Ligang; Chen, Xiufang; Guan, Jing; Jiang, Yijun; Hou, Tonggang; Mu, Xindong

    2013-01-01

    Graphical abstract: - Highlights: • P-doped g-C 3 N 4 has been prepared by a one-pot green synthetic approach. • The incorporation of P resulted in favorable textural and electronic properties. • Doping with P enhanced the visible-light photocatalytic activity of g-C 3 N 4 . • A postannealing treatment further enhanced the activity of P-doped g-C 3 N 4 . • Photogenerated holes were the main species responsible for the activity. - Abstract: Phosphorus-doped carbon nitride materials were prepared by a one-pot green synthetic approach using dicyandiamide monomer and a phosphorus containing ionic liquid as precursors. The as-prepared materials were subjected to several characterizations and investigated as metal-free photocatalysts for the degradation of organic pollutants (dyes like Rhodamine B, Methyl orange) in aqueous solution under visible light. Results revealed that phosphorus-doped carbon nitride have a higher photocatalytic activity for decomposing Rhodamine B and Methyl orange in aqueous solution than undoped g-C 3 N 4 , which was attributed to the favorable textural, optical and electronic properties caused by doping with phosphorus heteroatoms into carbon nitride host. A facile postannealing treatment further improved the activity of the photocatalytic system, due to the higher surface area and smaller structural size in the postcalcined catalysts. The phosphorus-doped carbon nitride showed high visible-light photocatalytic activity, making them promising materials for a wide range of potential applications in photochemistry

  19. Nitrogen rich carbon nitride thin films deposited by hybrid PLD technique

    Czech Academy of Sciences Publication Activity Database

    Jelínek, Miroslav; Kulish, W.; Lančok, Ján; Popov, C.; Bulíř, Jiří; Delplancke-Ogletree, M. P.

    2002-01-01

    Roč. 374, - (2002), s. 207-210 ISSN 1058-725X Institutional research plan: CEZ:AV0Z1010914 Keywords : laser deposition * carbon nitride * radiofrequency discharge * hollow cathode discharge Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.457, year: 2002

  20. Potential of P-doped carbon nanocone and Si-doped boron nitride ...

    Indian Academy of Sciences (India)

    22

    The mechanisms of N2O reduction via CO on surfaces of P-doped carbon nanocone (CNC) and. Si-doped boron nitride nanocone (BNNC) by density functional theory were investigated. The adsorption energies of P and Si on surfaces of CNC and BNNC were -293.1 and -325.7 kcal/mol, respectively. The decomposition of ...

  1. Toward an Aqueous Solar Battery: Direct Electrochemical Storage of Solar Energy in Carbon Nitrides.

    Science.gov (United States)

    Podjaski, Filip; Kröger, Julia; Lotsch, Bettina V

    2018-03-01

    Graphitic carbon nitrides have emerged as an earth-abundant family of polymeric materials for solar energy conversion. Herein, a 2D cyanamide-functionalized polyheptazine imide (NCN-PHI) is reported, which for the first time enables the synergistic coupling of two key functions of energy conversion within one single material: light harvesting and electrical energy storage. Photo-electrochemical measurements in aqueous electrolytes reveal the underlying mechanism of this "solar battery" material: the charge storage in NCN-PHI is based on the photoreduction of the carbon nitride backbone and charge compensation is realized by adsorption of alkali metal ions within the NCN-PHI layers and at the solution interface. The photoreduced carbon nitride can thus be described as a battery anode operating as a pseudocapacitor, which can store light-induced charge in the form of long-lived, "trapped" electrons for hours. Importantly, the potential window of this process is not limited by the water reduction reaction due to the high intrinsic overpotential of carbon nitrides for hydrogen evolution, potentially enabling new applications for aqueous batteries. Thus, the feasibility of light-induced electrical energy storage and release on demand by a one-component light-charged battery anode is demonstrated, which provides a sustainable solution to overcome the intermittency of solar radiation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Ion coordination significantly enhances the photocatalytic activity of graphitic-phase carbon nitride.

    Science.gov (United States)

    Gao, Honglin; Yan, Shicheng; Wang, Jiajia; Zou, Zhigang

    2014-06-14

    Here we report a facile surface modification route, metal ion coordination, to improve the photoactivity of carbon nitride. The metal ions coordinating into the plane of g-C3N4 significantly contribute to a drastic increase of the photocatalytic activity in solar hydrogen production as well as in the photodegradation of organic pollutants.

  3. Hydrogenated amorphous carbon films on steel balls and Si substrates: Nanostructural evolutions and their trigging tribological behaviors

    Science.gov (United States)

    Wang, Yongfu; Wang, Yan; Zhang, Xingkai; Shi, Jing; Gao, Kaixiong; Zhang, Bin; Zhang, Junyan

    2017-10-01

    In this study, we prepared hydrogenated amorphous carbon films on steel balls and Si substrates (steel ball- and Si substrate-films) with different deposition time, and discussed their carbon nanostructural evolutions and tribological behaviors. The steel ball-film structure started to be graphite-like structure and then gradually transformed into fullerene-like (FL) structure. The Si substrate-film structure began in FL structure and kept it through the thickness. The difference may be result from the competition between high starting substrate temperature after additional nitriding applied on the steel balls (its supply power is higher than that in the film deposition), and relaxation of compressive stress from energized ion bombardment in film deposition process. The FL structural film friction couples could achieve ultra-low friction in open air. In particular, the Si substrate-film with 3 h, against the steel ball-film with 2 h and 3 h, exhibited super-low friction (∼0.009) and superlong wear life (∼5.5 × 105 cycles). Our result could widen the superlubricity scope from previously high load and velocity, to middle load and velocity.

  4. Strong Metal-Support Interaction: Growth of Individual Carbon Nanofibers from Amorphous Carbon Interacting with an Electron Beam

    DEFF Research Database (Denmark)

    Zhang, Wei; Kuhn, Luise Theil

    2013-01-01

    The article discusses the growth behavior of carbon nanofibers (CNFs). It mentions that CNFs can be synthesized using methods such as arc-discharge, laser ablation and chemical vapor deposition. It further states that CNFs can be grown from a physical mixing of amorphous carbon and CGO...

  5. Low-energy electron irradiation induced top-surface nanocrystallization of amorphous carbon film

    Science.gov (United States)

    Chen, Cheng; Fan, Xue; Diao, Dongfeng

    2016-10-01

    We report a low-energy electron irradiation method to nanocrystallize the top-surface of amorphous carbon film in electron cyclotron resonance plasma system. The nanostructure evolution of the carbon film as a function of electron irradiation density and time was examined by transmission electron microscope (TEM) and Raman spectroscopy. The results showed that the electron irradiation gave rise to the formation of sp2 nanocrystallites in the film top-surface within 4 nm thickness. The formation of sp2 nanocrystallite was ascribed to the inelastic electron scattering in the top-surface of carbon film. The frictional property of low-energy electron irradiated film was measured by a pin-on-disk tribometer. The sp2 nanocrystallized top-surface induced a lower friction coefficient than that of the original pure amorphous film. This method enables a convenient nanocrystallization of amorphous surface.

  6. Synthesis, Characterization, and Fabrication of Boron Nitride and Carbon Nanomaterials, their Applications, and the Extended Pressure Inductively Coupled Plasma Synthesis of Boron Nitride Nanotubes

    OpenAIRE

    Fathalizadeh, Aidin

    2016-01-01

    Nanoscale materials made of carbon, boron, and nitrogen, namely BCN nanostructures, exhibit many remarkable properties making them uniquely suitable for a host of applications. Boron nitride (BN) and carbon (C) nanomaterials are structurally similar. The forms studied here originate from a two-dimensional hexagonally arranged structure of sp2 bonded atoms. These nanomaterials exhibit extraordinary mechanical and thermal properties. However, the unique chemical compositions of carbon and bo...

  7. Divalent Fe Atom Coordination in Two-Dimensional Microporous Graphitic Carbon Nitride.

    Science.gov (United States)

    Oh, Youngtak; Hwang, Jin Ok; Lee, Eui-Sup; Yoon, Minji; Le, Viet-Duc; Kim, Yong-Hyun; Kim, Dong Ha; Kim, Sang Ouk

    2016-09-28

    Graphitic carbon nitride (g-C3N4) is a rising two-dimensional material possessing intrinsic semiconducting property with unique geometric configuration featuring superimposed heterocyclic sp(2) carbon and nitrogen network, nonplanar layer chain structure, and alternating buckling. The inherent porous structure of heptazine-based g-C3N4 features electron-rich sp(2) nitrogen, which can be exploited as a stable transition metal coordination site. Multiple metal-functionalized g-C3N4 systems have been reported for versatile applications, but local coordination as well as its electronic structure variation upon incoming metal species is not well understood. Here we present detailed bond coordination of divalent iron (Fe(2+)) through micropore sites of graphitic carbon nitride and provide both experimental and computational evidence supporting the aforementioned proposition. In addition, the utilization of electronic structure variation is demonstrated through comparative photocatalytic activities of pristine and Fe-g-C3N4.

  8. Triazine-based graphitic carbon nitride: a two-dimensional semiconductor.

    Science.gov (United States)

    Algara-Siller, Gerardo; Severin, Nikolai; Chong, Samantha Y; Björkman, Torbjörn; Palgrave, Robert G; Laybourn, Andrea; Antonietti, Markus; Khimyak, Yaroslav Z; Krasheninnikov, Arkady V; Rabe, Jürgen P; Kaiser, Ute; Cooper, Andrew I; Thomas, Arne; Bojdys, Michael J

    2014-07-14

    Graphitic carbon nitride has been predicted to be structurally analogous to carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Self-assembly of graphitic carbon nitride nanosheets–carbon nanotube composite for electrochemical simultaneous determination of catechol and hydroquinone

    International Nuclear Information System (INIS)

    Zhang, Hanqiang; Huang, Yihong; Hu, Shirong; Huang, Qitong; Wei, Chan; Zhang, Wuxiang; Yang, Weize; Dong, Peihui; Hao, Aiyou

    2015-01-01

    Graphical abstract: Schematic diagram of hydrothermal synthesis graphitic carbon nitride nanosheets-carbon nanotube composite and theirs application for electrochemical sensing catechol and hydroquinone. - Highlights: • Self-assembly of graphitic carbon nitride nanosheets-carbon nanotube composite. • CNNS-CNT show more stronger conductivity than CNNS and CNT. • CNNS-CNT has been performed for detection of catechol and hydroquinone. • The probe was applied to detect practical samples with satisfactory results. - Abstract: In this paper, three-dimensional (3D) graphitic carbon nitride nanosheets-carbon nanotube (CNNS-CNT) composite was synthesized via hydrothermal reaction of 2D CNNS and 1D CNT-COOH by π-π stacking and electrostatic interactions. This CNNS-CNT composite was characterized by transmission electron microscope, scanning electron microscope, x-ray diffraction and fourier-transform infrared. In addition, the CNNS-CNT composite displayed excellent conductivity comparing with CNNS and CNT-COOH monomer. This composite was applied for electrochemical simultaneous determination of catechol (CC) and hydroquinone (HQ) with good sensitivity, wide linear range and low detection limit. In addition, this CNNS-CNT composite modified electrode was also applied to detect practical samples with satisfactory results

  10. In vitro cytocompatibility assessment of amorphous carbon structures using neuroblastoma and Schwann cells.

    Science.gov (United States)

    Jain, Shilpee; Sharma, Ashutosh; Basu, Bikramjit

    2013-05-01

    The development of scaffolds for neural tissue engineering application requires an understanding of cell adhesion, proliferation, and migration of neuronal cells. Considering the potential application of carbon as scaffold materials and the lack of understanding of compatibility of amorphous carbon with neuronal cells, the carbon-based materials in the forms of carbon films and continuous electrospun carbon nanofibers having average diameter of ~200 nm are being investigated with or without ultraviolet (UV) and oxy-plasma (OP) treatments for cytocompatibility property using mouse Neuroblastoma (N2a) and rat Schwann cells (RT4-D6P2T). The use of Raman spectroscopy in combination with Fourier transform infrared (FTIR) and X-ray diffraction establishes the amorphous nature and surface-bonding characteristics of the studied carbon materials. Although both UV and OP treatments make carbon surfaces more hydrophilic, the cell viability of N2a cells is statistically more significant on OP treated fibers/films compared to UV fiber/film substrates after 4 days in culture. The electrospun carbon fibrous substrate provides the physical guidance to the cultured Schwann cells. Overall, the experimental results of this study demonstrate that the electrospun amorphous carbon nanofibrous scaffolds can be used as a suitable biomaterial substrate for supporting cell adhesion and proliferation of neuronal cells in the context of their applications as artificial nerve implants. Copyright © 2013 Wiley Periodicals, Inc.

  11. Growth Mechanism for Low Temperature PVD Graphene Synthesis on Copper Using Amorphous Carbon

    Science.gov (United States)

    Narula, Udit; Tan, Cher Ming; Lai, Chao Sung

    2017-03-01

    Growth mechanism for synthesizing PVD based Graphene using Amorphous Carbon, catalyzed by Copper is investigated in this work. Different experiments with respect to Amorphous Carbon film thickness, annealing time and temperature are performed for the investigation. Copper film stress and its effect on hydrogen diffusion through the film grain boundaries are found to be the key factors for the growth mechanism, and supported by our Finite Element Modeling. Low temperature growth of Graphene is achieved and the proposed growth mechanism is found to remain valid at low temperatures.

  12. Graphitic carbon nitride nanosheets doped graphene oxide for electrochemical simultaneous determination of ascorbic acid, dopamine and uric acid

    International Nuclear Information System (INIS)

    Zhang, Hanqiang; Huang, Qitong; Huang, Yihong; Li, Feiming; Zhang, Wuxiang; Wei, Chan; Chen, Jianhua; Dai, Pingwang; Huang, Lizhang; Huang, Zhouyi; Kang, Lianping; Hu, Shirong; Hao, Aiyou

    2014-01-01

    Graphical abstract: Schematic drawing of electrochemical oxidize AA, DA and UA on graphitic carbon nitride nanosheets-graphene oxide composite modified electrode. - Highlights: • Synthesize g-C 3 N 4 , GO and CNNS-GO composite. • CNNS-GO composite was the first time for simultaneous determination of AA, DA and UA. • CNNS-GO/GCE displays fantastic selectivity and sensitivity for AA, DA and UA. • CNNS-GO/GCE was applied to detect real sample with satisfactory results. - Abstract: Graphitic carbon nitride nanosheets with a graphite-like structure have strong covalent bonds between carbon and nitride atoms, and nitrogen atoms in the carbon architecture can accelerate the electron transfer and enhance electrical properties effectually. The graphitic carbon nitride nanosheets-graphene oxide composite was synthesized. And the electrochemical performance of the composite was investigated by cyclic voltammetry and differential pulse voltammetry ulteriorly. Due to the synergistic effects of layer-by-layer structures by π-π stacking or charge-transfer interactions, graphitic carbon nitride nanosheets-graphene oxide composite can improved conductivity, electro-catalytic and selective oxidation performance. The proposed graphitic carbon nitride nanosheets-graphene oxide composite modified electrode was employed for simultaneous determination of ascorbic acid, dopamine and uric acid in their mixture solution, it exhibited distinguished sensitivity, wide linear range and low detection limit. Moreover, the modified electrode was applied to detect urine and dopamine injection sample, and then the samples were spiked with certain concentration of three substances with satisfactory recovery results

  13. Adsorption of bovine serum albumin on amorphous carbon surfaces studied with dip pen nanolithography

    Science.gov (United States)

    Yadav, Pradeep K.; McKavanagh, Fiona; Maguire, Paul D.; Lemoine, Patrick

    2011-10-01

    This article reports the use of dip pen nanolithography (DPN) for the study of adsorption of bovine serum albumin (BSA) proteins on amorphous carbon surfaces; tetrahedral amorphous carbon (t-aC) and silicon doped hydrogenated amorphous carbon (a-C:H:Si). Contact angle study shows that the BSA proteins reduce the contact angle on both carbon materials. We also noticed that the drop volume dependence is consistent with a negative line tension, i.e. due to an attractive protein/surface interaction. The DPN technique was used to write short-spaced (100 nm) BSA line patterns on both samples. We found a line merging effect, stronger in the case of the a-C:H:Si material. We discuss possible contributions from tip blunting, scratching, cross-talk between lever torsion and bending and nano-shaving of the patterns. We conclude that the observed effect is caused in large measure by the diffusion of BSA proteins on the amorphous carbon surfaces. This interpretation of the result is consistent with the contact angle data and AFM force curve analysis indicating larger tip/surface adhesion and spreading for the a-C:H:Si material. We conclude by discussing the advantages and limitations of DPN lithography to study biomolecular adsorption in nanoscale wetting environments.

  14. Metal-functionalized single-walled graphitic carbon nitride nanotubes: a first-principles study on magnetic property

    OpenAIRE

    Pan, Hui; Zhang, Yong-Wei; Shenoy, Vivek B; Gao, Huajian

    2011-01-01

    Abstract The magnetic properties of metal-functionalized graphitic carbon nitride nanotubes were investigated based on first-principles calculations. The graphitic carbon nitride nanotube can be either ferromagnetic or antiferromagnetic by functionalizing with different metal atoms. The W- and Ti-functionalized nanotubes are ferromagnetic, which are attributed to carrier-mediated interactions because of the coupling between the spin-polarized d and p electrons and the formation of the impurit...

  15. Solid State Synthesis and Characterization of Carbo-Nitride Materials

    National Research Council Canada - National Science Library

    Khabashesku, Valery

    2000-01-01

    The preparation of stoichiometric sp(sup 2)-bonded amorphous carbon nitride a-C3N4 in gram quantities was successfully achieved by performing a solid-state reaction of cyanuric halides C3N3X3 (X=Cl, F...

  16. Preparation and properties of amorphous carbon and hydrocarbon films

    Energy Technology Data Exchange (ETDEWEB)

    Richter, F. (Fachbereich Physik, TU Chemnitz (Germany)); Bewilogua, K. (Fraunhofer-Inst. fuer Schicht- und Oberflaechentechnik, Hamburg (Germany)); Kupfer, H.; Muehling, I.; Rau, B.; Rother, B. (Fachbereich Physik, TU Chemnitz (Germany)); Schumacher, D. (Lehrstuhl fuer Oberflaechenwissenschaft, Univ. Duesseldorf (Germany))

    1992-05-15

    This paper deals with amorphous carbonaceous films deposited by different ion/or plasma assisted methods (cathodic arc evaporation, ion plating, and magnetron sputtering), which show remarkable differences in density, composition and energetic state of the particle fluxes arriving at the substrate surface. The structure of the layers was characterized by electron energy loss spectroscopy, high energy electron diffraction, Raman spectroscopy, and electron microscopy. Moreover, the hardness and mass density of the layers were measured. The three deposition methods are compared with regard to their growth conditions yielding a specific layer structure. (orig.).

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

    CERN Document Server

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

    2002-01-01

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

  18. Ab initio study of aspirin adsorption on single-walled carbon and carbon nitride nanotubes

    Science.gov (United States)

    Lee, Yongju; Kwon, Dae-Gyeon; Kim, Gunn; Kwon, Young-Kyun

    We use ab intio density functional theory to investigate the adsorption properties of acetylsalicylic acid or aspirin on a (10, 0) carbon nanotube (CNT) and a (8, 0) triazine-based graphitic carbon nitride nanotube (CNNT). It is found that an aspirin molecule binds stronger to the CNNT with its adsorption energy of 0.67 eV than to the CNT with 0.51 eV. The stronger adsorption energy on the CNNT is ascribed to the high reactivity of its N atoms with high electron affinity. The CNNT exhibits local electric dipole moments, which cause strong charge redistribution in the aspirin molecule adsorbed on the CNNT than on the CNT. We also explore the influence of an external electric field on the adsorption properties of aspirin on these nanotubes by examining the modifications in their electronic band structures, partial densities of states, and charge distributions. It is found that an electric field applied along a particular direction induces aspirin molecular states in the in-gap region of the CNNT implying a potential application of aspirin detection.

  19. Theoretical investigation of magnetic properties in interfaces of magnetic nanoparticles and amorphous carbons

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Shih-Jye, E-mail: sjs@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan (China); Hsu, Hua-Shu [Department of Applied Physics, National Pingtung University, Pingtung 900, Taiwan (China); Ovchinnikov, Sergei [Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk 660036 (Russian Federation); Chen, Guan-Long [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan (China)

    2017-06-15

    Highlights: • The interfaces of amorphous carbons will be graphited and antiferromagnetic. • The ferromagnetism on the Co interfaces is induced by the medium electrons. • The spin-wave excitation will change between the acoustic and optical modes. • The charge exchange in the interfaces changes the magnetism of the interfaces. - Abstract: Based on the experimental finding of the exchange bias in amorphous carbon samples with embedded Co nanoparticles and on the graphited character of the amorphous carbon interface confirmed by molecular dynamics simulations we have proposed the interface of graphited carbon to be antiferromagnetic. A theoretical model, which comprises the Kondo interactions in the interfaces of Co nanoparticles and the induced antiferromagnetic interactions in the graphited carbons, is employed to evaluate the ferromagnetism of the interfaces of Co nanoparticles. We have shown that the ferromagnetism of interfaces of Co nanoparticles will be enhanced by the increase of antiferromagnetic interaction as well as the increase of electron density in the graphited carbons. In particular, we found that the antiferromagnetic interactions in graphited carbons will change the spin-wave excitation in interfaces of Co nanoparticles from the quasiacoustic mode to the quasioptical one.

  20. Hydrogen production using zinc-doped carbon nitride catalyst irradiated with visible light

    Directory of Open Access Journals (Sweden)

    Bing Yue, Qiuye Li, Hideo Iwai, Tetsuya Kako and Jinhua Ye

    2011-01-01

    Full Text Available Recently, graphitic carbon nitride (g-C3N4 has been investigated as a photocatalyst for water splitting and organic dye degradation. In this study, we have developed a simple soft-chemical method of doping Zn into g-C3N4 to prepare a metal-containing carbon nitride. The doping was confirmed by x-ray photoelectron spectroscopy, and diffusion reflectance spectra revealed a significant red shift in the absorption edge of Zn/g-C3N4. This hybrid material shows high photocatalytic activity and good stability for hydrogen evolution from an aqueous methanol solution under visible light irradiation (λ≥420 nm. The hydrogen evolution rate was more than 10 times higher for a 10%-Zn/g-C3N4 sample (59.5 μmol h−1 than for pure g-C3N4. The maximum quantum yield was 3.2% at 420 nm.

  1. Self-healing in carbon nitride evidenced as material inflation and superlubric behavior.

    Science.gov (United States)

    Bakoglidis, Konstantinos D; Palisaitis, Justinas; Dos Santos, Renato Batista; Rivelino, Roberto; Persson, Per O Å; Gueorguiev, Gueorgui K; Hultman, Lars

    2018-05-01

    All known materials wear under extended mechanical contacting. Superlubricity may present solutions, but is an expressed mystery in C-based materials. We report negative wear of carbon nitride films; a wear-less condition with mechanically-induced material inflation at the nanoscale and friction coefficient approaching ultralow values (0.06). Superlubricity in carbon nitride is expressed as C-N bond breaking for reduced coupling between graphitic-like sheets and eventual N 2 desorption. The transforming surface layer acts as a solid lubricant, while the film bulk retains its high elasticity. The present findings offer new means for materials design at the atomic level, and for property optimization in wear-critical applications like magnetic reading devices or nanomachines.

  2. Uniform graphitic carbon nitride nanorod for efficient photocatalytic hydrogen evolution and sustained photoenzymatic catalysis.

    Science.gov (United States)

    Liu, Jian; Huang, Jianhui; Zhou, Han; Antonietti, Markus

    2014-06-11

    Uniform graphitic carbon nitride nanorods (CNR) were facilely obtained by a morphology-preserving strategy by templating a chiral mesostructured silica nanorod. The hexagonal mesostructured pore structures of one-dimensional silica nanorods can provide nanoconfinement space for carbon nitride condensation to perfect layered structures. CNR demonstrated excellent photocatalytic capability in generating hydrogen from water even with a small specific surface area, compared with its mesoporous counterpart. For further application demonstration, the CNR was used for photocatalytic regeneration of NAD(+) to NADH, the biological form of hydrogen. The in situ NADH regeneration system was further coupled with l-glutamate dehydrogenase for sustainable generation of l-glutamate from α-ketoglutarate. The high yield and high efficiency obtained here point a high-throughput and sustainable way for practical enzymatic applications.

  3. Hydrogen production using zinc-doped carbon nitride catalyst irradiated with visible light

    Science.gov (United States)

    Yue, Bing; Li, Qiuye; Iwai, Hideo; Kako, Tetsuya; Ye, Jinhua

    2011-01-01

    Recently, graphitic carbon nitride (g-C3N4) has been investigated as a photocatalyst for water splitting and organic dye degradation. In this study, we have developed a simple soft-chemical method of doping Zn into g-C3N4 to prepare a metal-containing carbon nitride. The doping was confirmed by x-ray photoelectron spectroscopy, and diffusion reflectance spectra revealed a significant red shift in the absorption edge of Zn/g-C3N4. This hybrid material shows high photocatalytic activity and good stability for hydrogen evolution from an aqueous methanol solution under visible light irradiation (λ≥420 nm). The hydrogen evolution rate was more than 10 times higher for a 10%-Zn/g-C3N4 sample (59.5 μmol h−1) than for pure g-C3N4. The maximum quantum yield was 3.2% at 420 nm. PMID:27877392

  4. Hydrogen production using zinc-doped carbon nitride catalyst irradiated with visible light

    Science.gov (United States)

    Yue, Bing; Li, Qiuye; Iwai, Hideo; Kako, Tetsuya; Ye, Jinhua

    2011-06-01

    Recently, graphitic carbon nitride (g-C3N4) has been investigated as a photocatalyst for water splitting and organic dye degradation. In this study, we have developed a simple soft-chemical method of doping Zn into g-C3N4 to prepare a metal-containing carbon nitride. The doping was confirmed by x-ray photoelectron spectroscopy, and diffusion reflectance spectra revealed a significant red shift in the absorption edge of Zn/g-C3N4. This hybrid material shows high photocatalytic activity and good stability for hydrogen evolution from an aqueous methanol solution under visible light irradiation (λ>=420 nm). The hydrogen evolution rate was more than 10 times higher for a 10%-Zn/g-C3N4 sample (59.5 μmol h-1) than for pure g-C3N4. The maximum quantum yield was 3.2% at 420 nm.

  5. Ammonia-induced robust photocatalytic hydrogen evolution of graphitic carbon nitride

    Science.gov (United States)

    Yang, Pengju; Zhao, Jianghong; Qiao, Wei; Li, Li; Zhu, Zhenping

    2015-11-01

    We report a new and effective method to prepare high activity graphitic carbon nitride (g-C3N4) by a simple ammonia etching treatment. The obtained g-C3N4 displays a high BET surface area and enhanced electron/hole separation efficiency. The hydrogen evolution rates improved from 52 μmol h-1 to 316.7 μmol h-1 under visible light.We report a new and effective method to prepare high activity graphitic carbon nitride (g-C3N4) by a simple ammonia etching treatment. The obtained g-C3N4 displays a high BET surface area and enhanced electron/hole separation efficiency. The hydrogen evolution rates improved from 52 μmol h-1 to 316.7 μmol h-1 under visible light. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05570a

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

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  7. Total reflection amorphous carbon mirrors for vacuum ultraviolet free electron lasers

    Czech Academy of Sciences Publication Activity Database

    Steeg, B.; Juha, Libor; Feldhaus, J.; Jacobi, S.; Sobierajski, R.; Michaelsen, C.; Andrejczuk, A.; Krzywinski, J.

    2004-01-01

    Roč. 84, č. 5 (2004), s. 657-659 ISSN 0003-6951 R&D Projects: GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z1010921 Keywords : free-electron laser * amorphous carbon * radiation damage Subject RIV: BH - Optics, Masers, Lasers Impact factor: 4.308, year: 2004

  8. Evaluation of optical properties of the amorphous carbon film on fused silica

    International Nuclear Information System (INIS)

    Baydogan, Nilguen Dogan

    2004-01-01

    Deposition was done using a pulsed filtered cathodic arc with a graphite cathode. The carbon plasma is fully ionised and condenses on the substrate, forming diamond-like material but with amorphous structure. Optical properties of amorphous carbon films on fused-silica glass were investigated and the curves of optical density have a characteristic band at approximately 950 nm. Changes of the colourimetric quantities were evaluated and compared to uncoated fused silica glass. These changes were investigated as a function of the applied substrate bias voltage using the CIE and CIELAB colour systems. It is suggested that the mechanism of absorption is related to an allowed direct transition at the amorphous carbon films on fused silica glass. The optical energy gap of the amorphous carbon film depends on the bias voltage applied to the substrate holder. The optical colour parameters and optical band gap indicated that there is a relation between the dominant wavelength of the reflectance in the visible range and the wavelength of the optical band gap

  9. Low-Temperature Synthesis of Hierarchical Amorphous Basic Nickel Carbonate Particles for Water Oxidation Catalysis.

    Science.gov (United States)

    Yang, Yisu; Liang, Fengli; Li, Mengran; Rufford, Thomas E; Zhou, Wei; Zhu, Zhonghua

    2015-07-08

    Amorphous nickel carbonate particles are catalysts for the oxygen evolution reaction (OER), which plays a critical role in the electrochemical splitting of water. The amorphous nickel carbonate particles can be prepared at a temperature as low as 60 °C by an evaporation-induced precipitation (EIP) method. The products feature hierarchical pore structures. The mass-normalized activity of the catalysts, measured at an overpotential of 0.35 V, was 55.1 A g(-1) , with a Tafel slope of only 60 mV dec(-1) . This catalytic activity is superior to the performance of crystalline NiOx particles and β-Ni(OH)2 particles, and compares favorably to state-of-the-art RuO2 catalysts. The activity of the amorphous nickel carbonate is remarkably stable during a 10 000 s chronoamperometry test. Further optimization of synthesis parameters reveals that the amorphous structure can be tuned by adjusting the H2 O/Ni ratio in the precursor mixture. These results suggest the potential application of easily prepared hierarchical basic nickel carbonate particles as cheap and robust OER catalysts with high activity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Hard graphitelike hydrogenated amorphous carbon grown at high rates by a remote plasma

    DEFF Research Database (Denmark)

    Singh, Shailendra Vikram; Zaharia, T.; Creatore, M.

    2010-01-01

    Hydrogenated amorphous carbon (a-C:H) deposited from an Ar-C 2H2 expanding thermal plasma chemical vapor deposition (ETP-CVD) is reported. The downstream plasma region of an ETP is characterized by a low electron temperature (∼0.3 eV), which leads to an ion driven chemistry and negligible physical...

  11. Low-energy electron irradiation induced top-surface nanocrystallization of amorphous carbon film

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Cheng [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Fan, Xue, E-mail: fanx@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Diao, Dongfeng, E-mail: dfdiao@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China)

    2016-10-30

    Graphical abstract: Low-energy electron irradiation was proposed to nanocrystallize the top-surface of the as-deposited amorphous carbon film, and sp{sup 2} nanocrystallites formed in the film top-surface within 4 nm thickness. Display Omitted - Abstract: We report a low-energy electron irradiation method to nanocrystallize the top-surface of amorphous carbon film in electron cyclotron resonance plasma system. The nanostructure evolution of the carbon film as a function of electron irradiation density and time was examined by transmission electron microscope (TEM) and Raman spectroscopy. The results showed that the electron irradiation gave rise to the formation of sp{sup 2} nanocrystallites in the film top-surface within 4 nm thickness. The formation of sp{sup 2} nanocrystallite was ascribed to the inelastic electron scattering in the top-surface of carbon film. The frictional property of low-energy electron irradiated film was measured by a pin-on-disk tribometer. The sp{sup 2} nanocrystallized top-surface induced a lower friction coefficient than that of the original pure amorphous film. This method enables a convenient nanocrystallization of amorphous surface.

  12. Self-selection in size and structure in argon clusters formed on amorphous carbon

    NARCIS (Netherlands)

    Krainyukova, Nina V.; van de Waal, B.W.

    2004-01-01

    Argon clusters formed on an amorphous carbon substrate as deposited from the vapor phase were studied by means of transmission high energy electron diffraction using the liquid helium cryostat. Electron diffractograms were analysed on the basis of assumption that there exist a cluster size

  13. Damage threshold of amorphous carbon mirror for 177 eV FEL radiation

    NARCIS (Netherlands)

    Dastjani Farahani, Sh.; Chalupsky, Jaromir; Burian, T.; Chapman, Henry; Gleeson, A.J.; Hajkoya, V.; Juha, L.; Jurek, M.; Klinger, Dorota; Sinn, Harald; Sobierajski, R.; Störmer, M.; Tiedtke, K.; Toleikis, S.; Tschentscher, Thomas; Wabnitz, H.; Gaudin, Jerome

    2011-01-01

    We present results of damage studies performed at the Free-Electron LASer in Hamburg (FLASH) on amorphous carbon (a-C). The experiment was performed in the total external reflection geometry representing the working configuration of X-ray mirrors. The 177 eV photon laser beam was focused on a 40 nm

  14. Hot isostatic pressing of silicon nitride with boron nitride, boron carbide, and carbon additions

    Science.gov (United States)

    Mieskowski, Diane M.; Sanders, William A.

    1989-01-01

    Si3N4 test bars containing additions of BN, B4C, and C, were hot isostatically pressed in Ta cladding at 1900 and 2050 C to 98.9 percent to 99.5 percent theoretical density. Room-temperature strength data on specimens containing 2 wt pct BN and 0.5 wt pct C were comparable to data obtained for Si3N4 sintered with Y2O3, Y2O3 and Al2O3, or ZrO2. The 1370 C strengths were less than those obtained for additions of Y2O3 or ZrO2 but greater than those obtained from a combination of Y2O3 and Al2O3. SEM fractography indicated that, as with other types of Si3N4, room-temperature strength was controlled by processing flaws. The decrease in strength at 1370 C was typical of Si3N4 having an amorphous grain-boundary phase. The primary advantage of nonoxide additions appears to be in facilitating specimen removal from the Ta cladding.

  15. Opto-electrical properties of amorphous carbon thin film deposited from natural precursor camphor

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, Debabrata [Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400 076 (India)]. E-mail: dpradhan@sciborg.uwaterloo.ca; Sharon, Maheshwar [Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400 076 (India)

    2007-06-30

    A simple thermal chemical vapor deposition technique is employed for the pyrolysis of a natural precursor 'camphor' and deposition of carbon films on alumina substrate at higher temperatures (600-900 deg. C). X-ray diffraction measurement reveals the amorphous structure of these films. The carbon films properties are found to significantly vary with the deposition temperatures. At higher deposition temperature, films have shown predominately sp{sup 2}-bonded carbon and therefore, higher conductivity and lower optical band gap (Tauc gap). These amorphous carbon (a-C) films are also characterized with Raman and X-ray photoelectron spectroscopy. In addition, electrical and optical properties are measured. The thermoelectric measurement shows these as-grown a-C films are p-type in nature.

  16. Cobalt-doped graphitic carbon nitride photocatalysts with high activity for hydrogen evolution

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Pei-Wen; Li, Kui; Yu, Yu-Xiang; Zhang, Wei-De, E-mail: zhangwd@scut.edu.cn

    2017-01-15

    Graphical abstract: Cobalt-doped graphitic carbon nitride (Co−CN) was synthesized by one-step thermal polycondensation using cobalt phthalocyanine and melamine as precursors. The obtained photocatalysts display high and stable activity for photocatalytic generation of hydrogen through water splitting. - Highlights: • Cobalt-doped g-C{sub 3}N{sub 4} photocatalysts were prepared. • High and stable visible light photocatalytic activity for H{sub 2} evolution. • Efficient separation and transfer of photo-induced electron-hole pairs. - Abstract: Cobalt-doped graphitic carbon nitride (Co−CN) was synthesized by one-step thermal polycondensation using cobalt phthalocyanine (CoPc) and melamine as precursors. The π-π interaction between melamine and CoPc promotes cobalt doping into the framework of g-C{sub 3}N{sub 4}. The prepared samples were carefully characterized and the results demonstrated that Co-doped graphitic carbon nitride inhibited the crystal growth of graphitic carbon nitride (CN), leading to larger specific surface area (33.1 m{sup 2} g{sup −1}) and abundant Co-N{sub x} active sites, narrower band gap energy and more efficient separation of photogenerated electrons and holes. 0.46% Co−CN exhibited higher hydrogen evolution rate (28.0 μmol h{sup −1}) under visible light irradiation, which is about 3.0 times of that over the pure CN and about 2.2 times of that over cobalt-doped CN using CoCl{sub 2} ∙ 6H{sub 2}O as a cobalt source. This study provides a valuable strategy to modify CN with enhanced photocatalytic performance.

  17. 2D to 3D transition of polymeric carbon nitride nanosheets

    International Nuclear Information System (INIS)

    Chamorro-Posada, Pedro; Vázquez-Cabo, José; Sánchez-Arévalo, Francisco M.; Martín-Ramos, Pablo; Martín-Gil, Jesús; Navas-Gracia, Luis M.; Dante, Roberto C.

    2014-01-01

    The transition from a prevalent turbostratic arrangement with low planar interactions (2D) to an array of polymeric carbon nitride nanosheets with stronger interplanar interactions (3D), occurring for samples treated above 650 °C, was detected by terahertz-time domain spectroscopy (THz-TDS). The simulated 3D material made of stacks of shifted quasi planar sheets composed of zigzagged polymer ribbons, delivered a XRD simulated pattern in relatively good agreement with the experimental one. The 2D to 3D transition was also supported by the simulation of THz-TDS spectra obtained from quantum chemistry calculations, in which the same broad bands around 2 THz and 1.5 THz were found for 2D and 3D arrays, respectively. This transition was also in accordance with the tightening of the interplanar distance probably due to an interplanar π bond contribution, as evidenced also by a broad absorption around 2.6 eV in the UV–vis spectrum, which appeared in the sample treated at 650 °C, and increased in the sample treated at 700 °C. The band gap was calculated for 1D and 2D cases. The value of 3.374 eV for the 2D case is, within the model accuracy and precision, in a relative good agreement with the value of 3.055 eV obtained from the experimental results. - Graphical abstract: 2D lattice mode vibrations and structural changes correlated with the so called “2D to 3D transition”. - Highlights: • A 2D to 3D transition has been detected for polymeric carbon nitride. • THz-TDS allowed us to discover and detect the 2D to 3D transition of polymeric carbon nitride. • We propose a structure for polymeric carbon nitride confirming it with THz-TDS

  18. One Dimensional Graphitic Carbon Nitrides as Effective Metal-Free Oxygen Reduction Catalysts

    Science.gov (United States)

    Tahir, Muhammad; Mahmood, Nasir; Zhu, Jinghan; Mahmood, Asif; Butt, Faheem K.; Rizwan, Syed; Aslam, Imran; Tanveer, M.; Idrees, Faryal; Shakir, Imran; Cao, Chuanbao; Hou, Yanglong

    2015-07-01

    To explore the effect of morphology on catalytic properties of graphitic carbon nitride (GCN), we have studied oxygen reduction reaction (ORR) performance of two different morphologies of GCN in alkaline media. Among both, tubular GCN react with dissolved oxygen in the ORR with an onset potential close to commercial Pt/C. Furthermore, the higher stability and excellent methanol tolerance of tubular GCN compared to Pt/C emphasizes its suitability for fuel cells.

  19. One Dimensional Graphitic Carbon Nitrides as Effective Metal-Free Oxygen Reduction Catalysts

    Science.gov (United States)

    Tahir, Muhammad; Mahmood, Nasir; Zhu, Jinghan; Mahmood, Asif; Butt, Faheem K.; Rizwan, Syed; Aslam, Imran; Tanveer, M.; Idrees, Faryal; Shakir, Imran; Cao, Chuanbao; Hou, Yanglong

    2015-01-01

    To explore the effect of morphology on catalytic properties of graphitic carbon nitride (GCN), we have studied oxygen reduction reaction (ORR) performance of two different morphologies of GCN in alkaline media. Among both, tubular GCN react with dissolved oxygen in the ORR with an onset potential close to commercial Pt/C. Furthermore, the higher stability and excellent methanol tolerance of tubular GCN compared to Pt/C emphasizes its suitability for fuel cells. PMID:26201998

  20. Synthesis and photocatalytic properties of graphitic carbon nitride nanofibers using porous anodic alumina templates

    Science.gov (United States)

    Suchitra, S. M.; Udayashankar, N. K.

    2017-12-01

    In the present study, we describe an effective method for the synthesis of Graphitic carbon nitride (GCN) nanostructures using porous anodic alumina (AAO) membrane as template by simple thermal condensation of cyanamide. Synthesized nanostructure was fully analysed by various techniques to detect its crystalline nature, morphology, luminescent properties followed by the evaluation of its photocatalytic activity in the degradation of Methylene blue dye. Structural analysis of synthesized GCNNF was systematically carried out using x-ray powder diffraction (XRD) and scanning electron microscope (SEM), and. The results confirmed the growth of GCN inside the nanochannels of anodic alumina templates. Luminescent properties of GCNNF were studied using photoluminescence (PL) spectroscopy. PL analysis showed the presence of a strong emission peak in the wavelength range of 350–600 nm in blue region. GCNNF displays higher photocatalytic performance in the photodegradation of methylene blue compare to the bulk GCN. Highlights 1. In the present paper, we report the synthesis of graphitic carbon nitride nanofibers (GCNNF) using porous anodic aluminium oxide membranes as templates through thermal condensation of cyanamide at 500 °C. 2. The synthesis of Graphitic carbon nitride nanofibers using porous andic alumina template is the efficient approach for increasing crystallinity and surface area. 3. The high surface area of graphitic carbon nitride nanofibers has a good impact on novel optical and photocatalytic properties of the bulkGCN. 4. AAO templating of GCN is one of the versatile method to produce tailorable GCN nanostructures with higher surface area and less number of structural defects. 5. Towards photocatalytic degradation of dyes, the tuning of physical properties is very essential thing hence we are succeeded in achieving better catalytic performance of GCN nanostructures by making use of AAO templates.

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

    Directory of Open Access Journals (Sweden)

    Hongling Han

    2015-07-01

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

  2. 2D to 3D transition of polymeric carbon nitride nanosheets

    Energy Technology Data Exchange (ETDEWEB)

    Chamorro-Posada, Pedro [Dpto. de Teoría de la Señal y Comunicaciones e IT, Universidad de Valladolid, ETSI Telecomunicación, Paseo Belén 15, 47011 Valladolid (Spain); Vázquez-Cabo, José [Dpto. de Teoría de la Señal y Comunicaciones, Universidad de Vigo, ETSI Telecomunicación, Lagoas Marcosende s/n, Vigo (Spain); Sánchez-Arévalo, Francisco M. [Instituto de Investigaciones en Materiales (IIM), Universidad Nacional Autónoma de México, Apdo. Postal 70–360, Cd. Universitaria, México D.F. 04510 (Mexico); Martín-Ramos, Pablo [Dpto. de Teoría de la Señal y Comunicaciones e IT, Universidad de Valladolid, ETSI Telecomunicación, Paseo Belén 15, 47011 Valladolid (Spain); Laboratorio de Materiales Avanzados (Advanced Materials Laboratory) ETSIIAA, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martín-Gil, Jesús; Navas-Gracia, Luis M. [Laboratorio de Materiales Avanzados (Advanced Materials Laboratory) ETSIIAA, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Dante, Roberto C., E-mail: rcdante@yahoo.com [Laboratorio de Materiales Avanzados (Advanced Materials Laboratory) ETSIIAA, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain)

    2014-11-15

    The transition from a prevalent turbostratic arrangement with low planar interactions (2D) to an array of polymeric carbon nitride nanosheets with stronger interplanar interactions (3D), occurring for samples treated above 650 °C, was detected by terahertz-time domain spectroscopy (THz-TDS). The simulated 3D material made of stacks of shifted quasi planar sheets composed of zigzagged polymer ribbons, delivered a XRD simulated pattern in relatively good agreement with the experimental one. The 2D to 3D transition was also supported by the simulation of THz-TDS spectra obtained from quantum chemistry calculations, in which the same broad bands around 2 THz and 1.5 THz were found for 2D and 3D arrays, respectively. This transition was also in accordance with the tightening of the interplanar distance probably due to an interplanar π bond contribution, as evidenced also by a broad absorption around 2.6 eV in the UV–vis spectrum, which appeared in the sample treated at 650 °C, and increased in the sample treated at 700 °C. The band gap was calculated for 1D and 2D cases. The value of 3.374 eV for the 2D case is, within the model accuracy and precision, in a relative good agreement with the value of 3.055 eV obtained from the experimental results. - Graphical abstract: 2D lattice mode vibrations and structural changes correlated with the so called “2D to 3D transition”. - Highlights: • A 2D to 3D transition has been detected for polymeric carbon nitride. • THz-TDS allowed us to discover and detect the 2D to 3D transition of polymeric carbon nitride. • We propose a structure for polymeric carbon nitride confirming it with THz-TDS.

  3. Hydrothermally Induced Oxygen Doping of Graphitic Carbon Nitride with a Highly Ordered Architecture and Enhanced Photocatalytic Activity.

    Science.gov (United States)

    Wang, Chao; Fan, Huiqing; Ren, Xiaohu; Ma, Jiangwei; Fang, Jiawen; Wang, Weijia

    2018-02-22

    As an amorphous or semicrystalline material, graphitic carbon nitride (g-C 3 N 4 ) displays poor photocatalytic activity owing to rapid recombination of the photogenerated charge carriers, which is mainly caused by a high density of defects in the graphitic structure. In this work, a porous O-doped g-C 3 N 4 (P-CNO) nanosheet with a highly ordered architecture is fabricated by introducing a novel hydrothermal treatment to the precursor before the final thermal condensation. The photocatalytic hydrogen evolution rate (HER) and HER per surface area of P-CNO are 13.9 and 1.7 times higher than that of bulk g-C 3 N 4 . The improved photocatalytic activity is ascribed to a synergistic effect of O doping, a porous sheet-like morphology, and increased crystallinity. This work also provides a new approach for the synthesis of other polymer-based photocatalysts with high crystallinity and excellent performance. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Graphitic carbon nitride/graphene oxide/reduced graphene oxide nanocomposites for photoluminescence and photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Aleksandrzak, Malgorzata, E-mail: malgorzata.aleksandrzak@o2.pl; Kukulka, Wojciech; Mijowska, Ewa

    2017-03-15

    Highlights: • Graphitic carbon nitride modified with graphene nanostructures. • Influence of graphene nanostructures size in photocatalytic properties of g-C{sub 3}N{sub 4}. • Improved photocatalysis resulted from up-converted photoluminescence. - Abstract: The study presents a modification of graphitic carbon nitride (g-C{sub 3}N{sub 4}) with graphene oxide (GO) and reduced graphene oxide (rGO) and investigation of photoluminescent and photocatalytic properties. The influence of GO and rGO lateral sizes used for the modification was investigated. The nanomaterials were characterized with atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance UV–vis spectroscopy (DR-UV-vis) and photoluminescence spectroscopy (PL). PL revealed that pristine graphitic carbon nitride and its nanocomposites with GO and rGO emitted up-converted photoluminescence (UCPL) which could contribute to the improvement of photocatalytic activity of the materials. The photoactivity was evaluated in a process of phenol decomposition under visible light. A hybrid composed of rGO nanoparticles (rGONPs, 4–135 nm) exhibited the highest photoactivity compared to rGO with size of 150 nm–7.2 μm and graphene oxide with the corresponding sizes. The possible reason of the superior photocatalytic activity is the most enhanced UCPL of rGONPs, contributing to the emission of light with higher energy than the incident light, resulting in improved photogeneration of electron-hole pairs.

  5. Charge Modulation in Graphitic Carbon Nitride as a Switchable Approach to High-Capacity Hydrogen Storage.

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A; Smith, Sean C

    2015-11-01

    Electrical charging of graphitic carbon nitride nanosheets (g-C4 N3 and g-C3 N4 ) is proposed as a strategy for high-capacity and electrocatalytically switchable hydrogen storage. Using first-principle calculations, we found that the adsorption energy of H2 molecules on graphitic carbon nitride nanosheets is dramatically enhanced by injecting extra electrons into the adsorbent. At full hydrogen coverage, the negatively charged graphitic carbon nitride achieves storage capacities up to 6-7 wt %. In contrast to other hydrogen storage approaches, the storage/release occurs spontaneously once extra electrons are introduced or removed, and these processes can be simply controlled by switching on/off the charging voltage. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Importantly, g-C4 N3 has good electrical conductivity and high electron mobility, which can be a very good candidate for electron injection/release. These predictions may prove to be instrumental in searching for a new class of high-capacity hydrogen storage materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Phenyl-doped graphitic carbon nitride: photoluminescence mechanism and latent fingerprint imaging.

    Science.gov (United States)

    Song, Zhiping; Li, Zhihong; Lin, Lihua; Zhang, Yongfan; Lin, Tianran; Chen, Ling; Cai, Zhuang; Lin, Sen; Guo, Liangqia; Fu, Fengfu; Wang, Xinchen

    2017-11-23

    The photoluminescence (PL) emission mechanism of graphitic carbon nitride (g-C 3 N 4 ) is still ambiguous and the application of PL g-C 3 N 4 powder as a solid sensing platform has not been explored. Herein we highlight a strategy to prepare g-C 3 N 4 powder with strong green PL by doping phenyl groups in a carbon nitride network. Compared with pristine g-C 3 N 4 , doping of phenyl groups greatly enhances the PL efficiency and Stokes shift. Theoretical calculations based on density function theory indicate that phenyl groups change the electronic structure of the carbon nitride network and have an obvious contribution to the LUMO of phenyl-doped g-C 3 N 4 , which may be the main reason for the enhancement of the PL efficiency and Stokes shift. Taking advantage of the high PL efficiency, large Stokes shift and high photo-stability, phenyl-doped g-C 3 N 4 powder shows promising application for the imaging of latent fingerprints.

  7. Cobalt-doped graphitic carbon nitride photocatalysts with high activity for hydrogen evolution

    Science.gov (United States)

    Chen, Pei-Wen; Li, Kui; Yu, Yu-Xiang; Zhang, Wei-De

    2017-01-01

    Cobalt-doped graphitic carbon nitride (Cosbnd CN) was synthesized by one-step thermal polycondensation using cobalt phthalocyanine (CoPc) and melamine as precursors. The π-π interaction between melamine and CoPc promotes cobalt doping into the framework of g-C3N4. The prepared samples were carefully characterized and the results demonstrated that Co-doped graphitic carbon nitride inhibited the crystal growth of graphitic carbon nitride (CN), leading to larger specific surface area (33.1 m2 g-1) and abundant Co-Nx active sites, narrower band gap energy and more efficient separation of photogenerated electrons and holes. 0.46% Cosbnd CN exhibited higher hydrogen evolution rate (28.0 μmol h-1) under visible light irradiation, which is about 3.0 times of that over the pure CN and about 2.2 times of that over cobalt-doped CN using CoCl2 • 6H2O as a cobalt source. This study provides a valuable strategy to modify CN with enhanced photocatalytic performance.

  8. Amorphous calcium carbonate controls avian eggshell mineralization: A new paradigm for understanding rapid eggshell calcification.

    Science.gov (United States)

    Rodríguez-Navarro, Alejandro B; Marie, Pauline; Nys, Yves; Hincke, Maxwell T; Gautron, Joel

    2015-06-01

    Avian eggshell mineralization is the fastest biogenic calcification process known in nature. How this is achieved while producing a highly crystalline material composed of large calcite columnar single crystals remains largely unknown. Here we report that eggshell mineral originates from the accumulation of flat disk-shaped amorphous calcium carbonate (ACC) particles on specific organic sites on the eggshell membrane, which are rich in proteins and sulfated proteoglycans. These structures known as mammillary cores promote the nucleation and stabilization of a amorphous calcium carbonate with calcitic short range order which predetermine the calcite composition of the mature eggshell. The amorphous nature of the precursor phase was confirmed by the diffuse scattering of X-rays and electrons. The nascent calcitic short-range order of this transient mineral phase was revealed by infrared spectroscopy and HRTEM. The ACC mineral deposited around the mammillary core sites progressively transforms directly into calcite crystals without the occurrence of any intermediate phase. Ionic speciation data suggest that the uterine fluid is equilibrated with amorphous calcium carbonate, throughout the duration of eggshell mineralization process, supporting that this mineral phase is constantly forming at the shell mineralization front. On the other hand, the transient amorphous calcium carbonate mineral deposits, as well as the calcite crystals into which they are converted, form by the ordered aggregation of nanoparticles that support the rapid mineralization of the eggshell. The results of this study alter our current understanding of avian eggshell calcification and provide new insights into the genesis and formation of calcium carbonate biominerals in vertebrates. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Effects of Atomic-Scale Structure on the Fracture Properties of Amorphous Carbon - Carbon Nanotube Composites

    Science.gov (United States)

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

    2015-01-01

    The fracture of carbon materials is a complex process, the understanding of which is critical to the development of next generation high performance materials. While quantum mechanical (QM) calculations are the most accurate way to model fracture, the fracture behavior of many carbon-based composite engineering materials, such as carbon nanotube (CNT) composites, is a multi-scale process that occurs on time and length scales beyond the practical limitations of QM methods. The Reax Force Field (ReaxFF) is capable of predicting mechanical properties involving strong deformation, bond breaking and bond formation in the classical molecular dynamics framework. This has been achieved by adding to the potential energy function a bond-order term that varies continuously with distance. The use of an empirical bond order potential, such as ReaxFF, enables the simulation of failure in molecular systems that are several orders of magnitude larger than would be possible in QM techniques. In this work, the fracture behavior of an amorphous carbon (AC) matrix reinforced with CNTs was modeled using molecular dynamics with the ReaxFF reactive forcefield. Care was taken to select the appropriate simulation parameters, which can be different from those required when using traditional fixed-bond force fields. The effect of CNT arrangement was investigated with three systems: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. For each arrangement, covalent bonds are added between the CNTs and AC, with crosslink fractions ranging from 0-25% of the interfacial CNT atoms. The SWNT and MWNT array systems represent ideal cases with evenly spaced CNTs; the SWNT bundle system represents a more realistic case because, in practice, van der Waals interactions lead to the agglomeration of CNTs into bundles. The simulation results will serve as guidance in setting experimental processing conditions to optimize the mechanical properties of CNT

  10. Sea Urchin Spine Calcite Forms via a Transient Amorphous Calcium Carbonate Phase

    Science.gov (United States)

    Politi, Yael; Arad, Talmon; Klein, Eugenia; Weiner, Steve; Addadi, Lia

    2004-11-01

    The skeletons of adult echinoderms comprise large single crystals of calcite with smooth convoluted fenestrated morphologies, raising many questions about how they form. By using water etching, infrared spectroscopy, electron diffraction, and environmental scanning electron microscopy, we show that sea urchin spine regeneration proceeds via the initial deposition of amorphous calcium carbonate. Because most echinoderms produce the same type of skeletal material, they probably all use this same mechanism. Deposition of transient amorphous phases as a strategy for producing single crystals with complex morphology may have interesting implications for the development of sophisticated materials.

  11. Production of amorphous hydrated impure magnesium carbonate through ex situ carbonation

    International Nuclear Information System (INIS)

    Orlando, Andrea; Lelli, Matteo; Marini, Luigi

    2012-01-01

    The evaluation of the feasibility of ex situ carbonation in landfills utilizing raw natural substances (namely serpentinites as Mg-source and the CO 2 -rich fraction of biogas as C-source) was tested through a laboratory procedure comprising three steps. The first step is the acid attack of a serpentinite at 70 °C, by means of HCl 2 M, to get MgCl 2 -rich solutions. Attacks of different durations were performed to evaluate the time needed. The second step is the neutralization of the MgCl 2 -rich solution by addition of concentrated ammonia. The third (carbonation) step is mixing of the neutralized MgCl 2 -rich solution with a solution of ammonium carbonate. This was produced in a landfill by absorption of CO 2 contained in biogas in a solution of ammonia. The neutralization of acid MgCl 2 -rich solutions caused the precipitation of ferrihydrite with secondary ammonium carnallite and salammoniac, whereas abundant precipitation of Amorphous Hydrated Impure Magnesium Carbonate (AHIMC), sometimes with minor nesquehonite, occurred in the third step. This solid carbonate acts as a stable CO 2 sink up to 380 °C. The geochemical behavior of some minor elements was also investigated during the experimental processes revealing that Al, Cr and Ni were removed during neutralization (second step), in contrast to Ca which remained in the circumneutral MgCl 2 -rich solution and entered into the structure of AHIMC. During the carbonation step, precipitation of artinite, hydromagnesite, lansfordite, magnesite and nesquehonite was thermodynamically impossible as the aqueous phase was undersaturated with respect to these solid phases upon separation of AHIMC. The CO 2 sequestered through this multi-step procedure is 0.34 ton for 1 ton of serpentinite utilized. However, despite that the use of Mg-rich silicates is a suitable approach to ex situ carbonation, due to their huge availability worldwide, the CO 2 produced in making the chemicals and the overall energy balance of the

  12. Activation of peroxymonosulfate by graphitic carbon nitride loaded on activated carbon for organic pollutants degradation.

    Science.gov (United States)

    Wei, Mingyu; Gao, Long; Li, Jun; Fang, Jia; Cai, Wenxuan; Li, Xiaoxia; Xu, Aihua

    2016-10-05

    Graphitic carbon nitride supported on activated carbon (g-C3N4/AC) was prepared through an in situ thermal approach and used as a metal free catalyst for pollutants degradation in the presence of peroxymonosulfate (PMS) without light irradiation. It was found that g-C3N4 was highly dispersed on the surface of AC with the increase of surface area and the exposition of more edges and defects. The much easier oxidation of C species in g-C3N4 to CO was also observed from XPS spectra. Acid Orange 7 (AO7) and other organic pollutants could be completely degraded by the g-C3N4/AC catalyst within 20min with PMS, while g-C3N4+PMS and AC+PMS showed no significant activity for the reaction. The performance of the catalyst was significantly influenced by the amount of g-C3N4 loaded on AC; but was nearly not affected by the initial solution pH and reaction temperature. In addition, the catalysts presented good stability. A nonradical mechanism accompanied by radical generation (HO and SO4(-)) in AO7 oxidation was proposed in the system. The CO groups play a key role in the process; while the exposure of more N-(C)3 group can further increase its electron density and basicity. This study can contribute to the development of green materials for sustainable remediation of aqueous organic pollutants. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Graphitic Carbon Nitride as a Catalyst Support in Fuel Cells and Electrolyzers

    International Nuclear Information System (INIS)

    Mansor, Noramalina; Miller, Thomas S.; Dedigama, Ishanka; Jorge, Ana Belen; Jia, Jingjing; Brázdová, Veronika; Mattevi, Cecilia; Gibbs, Chris; Hodgson, David; Shearing, Paul R.; Howard, Christopher A.; Corà, Furio; Shaffer, Milo; Brett, Daniel J.L.

    2016-01-01

    Highlights: • Graphitic carbon nitride (gCN) describes many materials with different structures. • gCNs can exhibit excellent mechanical, chemical and thermal resistance. • A major obstacle for pure gCN catalyst supports is limited electronic conductivity. • Composite/Hybrid gCN structures show excellent performance as catalyst supports. • gCNs have great potential for use in fuel calls and water electrolyzers. - Abstract: Electrochemical power sources, such as polymer electrolyte membrane fuel cells (PEMFCs), require the use of precious metal catalysts which are deposited as nanoparticles onto supports in order to minimize their mass loading and therefore cost. State-of-the-art/commercial supports are based on forms of carbon black. However, carbon supports present disadvantages including corrosion in the operating fuel cell environment and loss of catalyst activity. Here we review recent work examining the potential of different varieties of graphitic carbon nitride (gCN) as catalyst supports, highlighting their likely benefits, as well as the challenges associated with their implementation. The performance of gCN and hybrid gCN-carbon materials as PEMFC electrodes is discussed, as well as their potential for use in alkaline systems and water electrolyzers. We illustrate the discussion with examples taken from our own recent studies.

  14. Amorphous Carbon Gold Nanocomposite Thin Films: Structural and Spectro-ellipsometric Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Montiel-Gonzalez, Z., E-mail: zeuzmontiel@hotmail.com [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, Ciudad Universitaria, Coyoacan 04510, Mexico D.F (Mexico); Rodil, S.E.; Muhl, S. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, Ciudad Universitaria, Coyoacan 04510, Mexico D.F (Mexico); Mendoza-Galvan, A. [Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Unidad Queretaro, 76010 Queretaro, Queretaro (Mexico); Rodriguez-Fernandez, L. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica, Ciudad Universitaria, 04510, Mexico D.F (Mexico)

    2011-07-01

    Spectroscopic Ellipsometry was used to determine the optical and structural properties of amorphous carbon:gold nanocomposite thin films deposited by dc magnetron co-sputtering at different deposition power. The incorporation of gold as small particles distributed in the amorphous carbon matrix was confirmed by X-ray Diffraction, Rutherford Backscattering measurements and High Resolution Transmission Electron Microscopy. Based on these results, an optical model for the films was developed using the Maxwell-Garnett effective medium with the Drude-Lorentz model representing the optical response of gold and the Tauc-Lorentz model for the amorphous carbon. The gold volume fraction and particle size obtained from the fitting processes were comparable to those from the physical characterization. The analysis of the ellipsometric spectra for all the samples showed strong changes in the optical properties of the carbon films as a consequence of the gold incorporation. These changes were correlated to the structural modification observed by Raman Spectroscopy, which indicated a clustering of the sp{sup 2} phase with a subsequent decrease in the optical gap. Finally, measurements of Reflection and Transmission Spectroscopy were carried out and Transmission Electron Microscopy images were obtained in order to support the ellipsometric model results.

  15. Sulfur-Doped Carbon Nitride Polymers for Photocatalytic Degradation of Organic Pollutant and Reduction of Cr(VI).

    Science.gov (United States)

    Zheng, Yun; Yu, Zihao; Lin, Feng; Guo, Fangsong; Alamry, Khalid A; Taib, Layla A; Asiri, Abdullah M; Wang, Xinchen

    2017-04-01

    As a promising conjugated polymer, binary carbon nitride has attracted extensive attention as a metal-free and visible-light-responsive photocatalyst in the area of photon-involving purification of water and air. Herein, we report sulfur-doped polymeric carbon nitride microrods that are synthesized through thermal polymerization based on trithiocyanuric acid and melamine (TM) supramolecular aggregates. By tuning the polymerization temperature, a series of sulfur-doped carbon nitride microrods are prepared. The degradation of Rhodamine B (RhB) and the reduction of hexavalent chromium Cr(VI) are selected as probe reactions to evaluate the photocatalytic activities. Results show that increasing pyrolysis temperature leads to a large specific surface area, strong visible-light absorption, and accelerated electron-hole separation. Compared to bulk carbon nitride, the highly porous sulfur-doped carbon nitride microrods fabricated at 650 °C exhibit remarkably higher photocatalytic activity for degradation of RhB and reduction of Cr(VI). This work highlights the importance of self-assembly approach and temperature-control strategy in the synthesis of photoactive materials for environmental remediation.

  16. Improving the photocatalytic activity of s-triazine based graphitic carbon nitride through metal decoration: an ab initio investigation.

    Science.gov (United States)

    Srinivasu, K; Modak, Brindaban; Ghosh, Swapan K

    2016-09-29

    Graphitic carbon nitride based semiconductor materials are found to be potential photocatalysts for generating hydrogen through solar water splitting. Through more accurate hybrid density functional theory calculations, we attempted to tune the electronic band structure of poly s-triazine based graphitic carbon nitride by decorating it with different metal atoms and clusters for improving its visible light absorption efficiency. For deposition on the two-dimensional carbon nitride surface, a range of metals have been considered which include all the 3d transition metals and the noble metals (Ag, Au, Pt and Pd). Our study reveals that though the band gaps of all the metal decorated systems were less than that of pristine carbon nitride, in most of the cases, metal decoration leads to the formation of mid gap impurity states, which can hinder the mobility of charge carriers. However, in the case of Ag and its four atom cluster deposited systems, no mid gap states were observed. In all the metal decorated systems, the measured band edge potentials were also found to satisfy the thermodynamic criterion for overall water splitting. The calculated optical absorption spectra show a shift in the absorption band towards the visible region upon metal decoration. Our results indicate that among all the considered metal atoms silver is the preferred candidate for deposition on the carbon nitride surface for improved photocatalytic activity.

  17. Study of SEY degradation of amorphous carbon coatings

    CERN Document Server

    Bundaleski, N.; Santos, A.; Teodoro, O.M.N.D.; Silva, A.G.

    2013-04-22

    Deposition of low secondary electron yield (SEY) carbon coatings by magnetron sputtering onto the inner walls of the accelerator seems to be the most promising solution for suppressing the electron cloud problem. However, these coatings change their electron emission properties during long term exposure to air. The ageing process of carbon coated samples with initial SEY of about 0.9 received from CERN is studied as a function of exposure to different environments. It is shown that samples having the same initial SEY may age with different rates. The SEY increase can be correlated with the surface concentration of oxygen. Annealing of samples in air at 100-200 {\\deg}C reduces the ageing rate and even recovers previously degraded samples. The result of annealing is reduction of the hydrogen content in the coatings by triggering its surface segregation followed by desorption.

  18. A near-wearless and extremely long lifetime amorphous carbon film under high vacuum.

    Science.gov (United States)

    Wang, Liping; Zhang, Renhui; Jansson, Ulf; Nedfors, Nils

    2015-06-10

    Prolonging wear life of amorphous carbon films under vacuum was an enormous challenge. In this work, we firstly reported that amorphous carbon film as a lubricant layer containing hydrogen, oxygen, fluorine and silicon (a-C:H:O:F:Si) exhibited low friction (~0.1), ultra-low wear rate (9.0 × 10(-13) mm(3) N(-1) mm(-1)) and ultra-long wear life (>2 × 10(6) cycles) under high vacuum. We systematically examined microstructure and composition of transfer film for understanding of the underlying frictional mechanism, which suggested that the extraordinarily excellent tribological properties were attributed to the thermodynamically and structurally stable FeF2 nanocrystallites corroborated using first-principles calculations, which were induced by the tribochemical reaction.

  19. Thermal stability of amorphous tungsten/tungsten nitride synthesis using HFCVD as a diffusion barrier for copper

    Energy Technology Data Exchange (ETDEWEB)

    Asgary, Somayeh; Hantehzadeh, Mohammad Reza; Ghoranneviss, Mahmood [Islamic Azad University, Plasma Physics Research Center, Science and Research Branch, Tehran (Iran, Islamic Republic of); Boochani, Arash [Islamic Azad University, Department of Physics, Kermanshah Branch, Kermanshah (Iran, Islamic Republic of)

    2016-05-15

    The amorphous W/WN bi-layer with excellent thermal stability was successfully prepared by hot-filament chemical vapor deposition method on SiO{sub 2}/Si substrate. It was found that the W/WN bi-layer is technological importance because of its low resistivity and good diffusion barrier properties between Cu and Si up to 700 C for 30 min. The thermal stability was evaluated by X-ray diffractometer (XRD) and scanning electron microscope. The XRD results show that the Cu{sub 3}Si phase was formed by Cu diffusion through W/WN barrier for the 800 C annealed sample. The formation of the Cu-Si compounds denotes the failure of the W/WN diffusion barrier with rapid increase in sheet resistance of the film. The microstructure of the interface between W/WN and Cu reflects the stability and breakdown of the barriers. The failure of this amorphous barrier occurs with heat treatment when the deposited amorphous barrier material crystallizes. The major part of Cu diffusion in polycrystalline structure with disordered grain boundaries is controlled by grain boundaries. AFM results indicated a rapid increase in surface roughness at the diffusion barrier failure temperature. It was found that the grain size plays an important factor to control the thermally stability of the W/WN bi-layer. (orig.)

  20. Structure of ion-plated amorphous hydrogenated carbon films investigated by electron energy loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Muehling, I.; Bewilogua, K.; Breuer, K. (Sektion Physik/Elektronische Bauelemente, Technische Univ., Karl-Marx-Stadt (German Democratic Republic))

    1990-05-15

    Thin ion-plated amorphous hydrogenated carbon films were investigated by electron energy loss spectroscopy. From an analysis of the dielectric function, information on the film structure could be obtained. The results will be compared with those of electron diffraction studies. Differences between insulating and conducting substrates could be verified in the film structure and are related to surface charging effects. From an analysis of the oscillator strength sum rule the content of C sp{sup 2} atoms was estimated. (orig.).

  1. Short pulse laser-induced optical damage and fracto-emission of amorphous, diamond-like carbon

    Energy Technology Data Exchange (ETDEWEB)

    SOKOLOWSKI-TINTEN,K.; VON DER LINDE,D.; SIEGAL,MICHAEL P.; OVERMYER,DONALD L.

    2000-02-07

    Short pulse laser damage and ablation of amorphous, diamond-like carbon films is investigated. Material removal is due to fracture of the film and ejection of large fragments, which exhibit a broadband emission of microsecond duration.

  2. Activated Carbon Supported Mo-Ti-N Binary Transition Metal Nitride as Catalyst for Acetylene Hydrochlorination

    Directory of Open Access Journals (Sweden)

    Hui Dai

    2017-06-01

    Full Text Available Recently, many scientists have focused on the development of green industrial technology. However, the process of synthesizing vinyl chloride faces the problem of Hg pollution. Via a novel approach, we used two elements Mo and Ti to prepare an inexpensive and green binary transition metal nitride (BTMN as the active ingredient in a catalyst with nano-sized particles and an excellent degree of activation, which was supported on activated carbon. When the Mo/Ti mole ratio was 3:1, the conversion of acetylene reached 89% and the selectivity exceeded 98.5%. The doping of Ti in Mo-based catalysts reduced the capacity of adsorption for acetylene and also increased the adsorption of hydrogen chloride. Most importantly, the performance of the BTMN excelled those of the individual transition metal nitrides, due to the synergistic activity between Mo and Ti. This will expand the new epoch of the employment of transition metal nitrides as catalysts in the hydrochlorination of acetylene reaction.

  3. The effect of Argon ion irradiation on the thickness and structure of ultrathin amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Xie, J.; Komvopoulos, K., E-mail: kyriakos@me.berkeley.edu [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States)

    2016-03-07

    Carbon films synthesized by plasma-enhanced chemical vapor deposition (PECVD) and filtered cathodic vacuum arc (FCVA) exhibit a layered structure consisting of a bottom (interface) and a top (surface) layer rich in sp{sup 2} atomic carbon bonding and a middle (bulk) layer of much higher sp{sup 3} content. Because of significant differences in the composition, structure, and thickness of these layers, decreasing the film thickness may negatively affect its properties. In this study, transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) were used to examine the effect of Ar{sup +} ion irradiation on the structure and thickness of ultrathin films of hydrogenated amorphous carbon (a-C:H) and hydrogen-free amorphous carbon (a-C) deposited by PECVD and FCVA, respectively. The TEM and EELS results show that 2-min ion irradiation decreases the film thickness without markedly changing the film structure and composition, whereas 4-min ion irradiation results in significant film thinning and a moderate decrease of the sp{sup 3} content of the bulk layer. This study demonstrates that Ar{sup +} ion irradiation is an effective post-deposition process for reducing the thickness and tuning the structure of ultrathin carbon films. This capability has direct implications in the synthesis of ultrathin protective carbon overcoats for extremely high-density magnetic recording applications.

  4. Activation of peroxymonosulfate by graphitic carbon nitride loaded on activated carbon for organic pollutants degradation

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Mingyu; Gao, Long; Li, Jun [School of Environmental Engineering, Wuhan Textile University, Wuhan 430073 (China); Fang, Jia [School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430073 (China); Cai, Wenxuan [School of Environmental Engineering, Wuhan Textile University, Wuhan 430073 (China); Li, Xiaoxia [School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430073 (China); Xu, Aihua, E-mail: xahspinel@sina.com [School of Environmental Engineering, Wuhan Textile University, Wuhan 430073 (China); Engineering Research Center for Clean Production of Textile Dyeing and Printing, Ministry of Education, Wuhan 430073 (China)

    2016-10-05

    Highlights: • Supported g-C{sub 3}N{sub 4} on AC catalysts with different loadings were prepared. • The metal free catalysts exhibited high efficiency for dyes degradation with PMS. • The catalyst presented a long-term stability for multiple runs. • The C=O groups played a key role in the oxidation process. - Abstract: Graphitic carbon nitride supported on activated carbon (g-C{sub 3}N{sub 4}/AC) was prepared through an in situ thermal approach and used as a metal free catalyst for pollutants degradation in the presence of peroxymonosulfate (PMS) without light irradiation. It was found that g-C{sub 3}N{sub 4} was highly dispersed on the surface of AC with the increase of surface area and the exposition of more edges and defects. The much easier oxidation of C species in g-C{sub 3}N{sub 4} to C=O was also observed from XPS spectra. Acid Orange 7 (AO7) and other organic pollutants could be completely degraded by the g-C{sub 3}N{sub 4}/AC catalyst within 20 min with PMS, while g-C{sub 3}N{sub 4}+PMS and AC+PMS showed no significant activity for the reaction. The performance of the catalyst was significantly influenced by the amount of g-C{sub 3}N{sub 4} loaded on AC; but was nearly not affected by the initial solution pH and reaction temperature. In addition, the catalysts presented good stability. A nonradical mechanism accompanied by radical generation (HO· and SO{sub 4}·{sup −}) in AO7 oxidation was proposed in the system. The C=O groups play a key role in the process; while the exposure of more N-(C){sub 3} group can further increase its electron density and basicity. This study can contribute to the development of green materials for sustainable remediation of aqueous organic pollutants.

  5. Voids padding induced further enhancement in photocatalytic performance of porous graphene-like carbon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Guohui [Hubei Key Laboratory of Accoutrement Technique in Fluid Machinery and Power Engineering, Wuhan university, Hubei 430072 (China); Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China); Chen, Dong [Hubei Key Laboratory of Accoutrement Technique in Fluid Machinery and Power Engineering, Wuhan university, Hubei 430072 (China); Luo, Jianmin [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China); The Graduate School of Chinese Academy of Science, Beijing, 100049 (China); Zhu, Yunqing [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China); Zeng, Yubin, E-mail: zengyubin@whu.edu.cn [Hubei Key Laboratory of Accoutrement Technique in Fluid Machinery and Power Engineering, Wuhan university, Hubei 430072 (China); Wang, Chuanyi, E-mail: cywang@ms.xjb.ac.cn [Hubei Key Laboratory of Accoutrement Technique in Fluid Machinery and Power Engineering, Wuhan university, Hubei 430072 (China); Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China)

    2017-08-05

    Highlights: • We synthesized an NH{sub 4}Cl padded C{sub 6}N{sub 9}H{sub 3} by calcining melamine hydrochloride in a vertical pit furnace. • The padded Cl{sup −} serves as a conjugate center to increase the conjugation fidelity of C{sub 6}N{sub 9}H{sub 3}. • Interface electric field can be constructed between Cl{sup −} and NH{sub 4}{sup +} to inhibit the surface recombination of carriers. • NH{sub 4}Cl padded C{sub 6}N{sub 9}H{sub 3} exhibits enhanced photocatalytic activity in terms of NO removal and water splitting. - Abstract: Design of 2-Dimensional nanostructured photocatalyst is an effective way to improve the photocatalytic activity of its bulk counterpart. However, the remaining (or newborn) drawbacks, such as enlarged band gap and the surface recombination of photogenerated charge carries, extremely limited the practical application of nanosheeted photocatalysts in solar energy conversion. In this study, we demonstrated that the voids padding with NH{sub 4}Cl can eliminate part of quantum size effect to reduce the band gap of nanosheeted carbon nitride. In addition, the padded NH{sub 4}Cl can create conjugate center and interface electric field in nanosheeted carbon nitride, and therefore to inhibit the surface recombination of photogenerated charge carries. This work not only provides a facile strategy to eliminate the drawbacks of nanosheeted carbon nitride, but also paves a new way to further improve the photocatalytic activity of other nano-sheeted materials.

  6. Pulsed dc discharge in the presence of active screen for nitriding of high carbon steel

    OpenAIRE

    Saeed, Adnan; Khan, Abdul Waheed; Jan, Faiq; Waqar, Muhammad; Abrar, Muhammad; Mujahid, Zaka - Ul - Islam; Hussnain, Ali; Zakaullah, Muhammad

    2014-01-01

    A discharge of nitrogen - hydrogen mixture by 50 Hz pulsed dc in the presence of active screen cage is investigated by optical emission spectroscopy (OES). The aim is to identify the parameters (mixture ratio, filling pressure and current density) that may lead to high concentration of active species (N2, N2+ and N). The maximum concentration in this experiment is found with 40% H2 - 60% N2, at filling pressure of 3 mbar with current density of 5 mAcm-2. High carbon steel samples are nitrided...

  7. Thermal and quantum phase slips in niobium-nitride nanowires based on suspended carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Kohei; Takagi, Tasuku; Hashimoto, Takayuki [Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 223-8522 (Japan); Moriyama, Satoshi, E-mail: MORIYAMA.Satoshi@nims.go.jp; Komatsu, Katsuyoshi [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Morita, Yoshifumi, E-mail: morita@gunma-u.ac.jp [Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515 (Japan); Miki, Norihisa [Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 223-8522 (Japan); Tanabe, Takasumi [Department of Electronics and Electrical Engineering, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 223-8522 (Japan); Maki, Hideyuki, E-mail: maki@appi.keio.ac.jp [Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 223-8522 (Japan); JST-PRESTO, Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2016-05-30

    Superconducting nanowires have attracted considerable attention due to their unique quantum-mechanical properties, as well as their potential as next-generation quantum nanodevices, such as single-photon detectors, phase-slip (PS) qubits, and other hybrid structures. In this study, we present the results of one-dimensional (1D) superconductivity in nanowires fabricated by coating suspended carbon nanotubes with a superconducting thin niobium nitride (NbN) film. In the resistance-temperature characteristic curves, hallmarks of 1D superconductivity with PS events are observed with unconventional negative magnetoresistance. We also confirm that a crossover occurs between thermal and quantum PSs as the temperature is lowered.

  8. Structural investigation of graphitic carbon nitride via XRD and neutron diffraction

    OpenAIRE

    Fina, Federica; Callear, Samantha; Carins, George Michael; Irvine, John Thomas Sirr

    2015-01-01

    We thank EPSRC for support through the EPSRC/NSF chemistry programme and the Royal Society for a Wolfson Merit award. Graphitic carbon nitride (g-C3N4) has, since 2009, attracted great attention for its activity as a visible-light-active photocatalyst for hydrogen evolution. Since it was synthesized in 1834, g-C3N4 has been extensively studied both catalytically and structurally. Although its 2D structure seems to have been solved, its 3D crystal structure has not yet been confirmed. This ...

  9. Graphitic carbon nitride “reloaded”: emerging applications beyond (photo)catalysis

    OpenAIRE

    Liu, J.; Wang, H.; Antonietti, M.

    2016-01-01

    Despite being one of the oldest materials described in the chemical literature, graphitic carbon nitride (g-C3N4) has just recently experienced a renaissance as a highly active photocatalyst, and the metal-free polymer was shown to be able to generate hydrogen under visible light. The semiconductor nature of g-C3N4 has triggered tremendous endeavors on its structural manipulation for enhanced photo(electro)chemical performance, aiming at an affordable clean energy future. While pursuing the s...

  10. Molecular carbon nitride ion beams for enhanced corrosion resistance of stainless steel

    Science.gov (United States)

    Markwitz, A.; Kennedy, J.

    2017-10-01

    A novel approach is presented for molecular carbon nitride beams to coat stainless surfaces steel using conventional safe feeder gases and electrically conductive sputter targets for surface engineering with ion implantation technology. GNS Science's Penning type ion sources take advantage of the breaking up of ion species in the plasma to assemble novel combinations of ion species. To test this phenomenon for carbon nitride, mixtures of gases and sputter targets were used to probe for CN+ ions for simultaneous implantation into stainless steel. Results from mass analysed ion beams show that CN+ and a variety of other ion species such as CNH+ can be produced successfully. Preliminary measurements show that the corrosion resistance of stainless steel surfaces increased sharply when implanting CN+ at 30 keV compared to reference samples, which is interesting from an application point of view in which improved corrosion resistance, surface engineering and short processing time of stainless steel is required. The results are also interesting for novel research in carbon-based mesoporous materials for energy storage applications and as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost.

  11. Electronic structure of carbon doped boron nitride nanotubes: a first-principles study.

    Science.gov (United States)

    Kahaly, Mousumi Upadhyay; Waghmare, Umesh V

    2008-08-01

    We determine atomic and electronic structures of arm-chair and zigzag boron nitride nanotubes (BN-NTs) of different diameters using first-principles pseudopotential-based density functional theory calculations. We find that the structure of BN-NTs in bundled form is slightly different from that of the isolated BN-NTs, reflecting on the inter-tube interactions. Effects of carbon doping on the electronic structure of (5,5) and (5,0) BN-NTs are determined: carbon substitution either at B-site, being energetically very stable, or at N-site can yield magnetically polarized semiconducting state, whereas carbon substitution at neighbouring B and N sites yields a non-magnetic insulating structure.

  12. Surface modification of aluminum nitride by polysilazane and its polymer-derived amorphous silicon oxycarbide ceramic for the enhancement of thermal conductivity in silicone rubber composite

    Science.gov (United States)

    Chiu, Hsien Tang; Sukachonmakul, Tanapon; Kuo, Ming Tai; Wang, Yu Hsiang; Wattanakul, Karnthidaporn

    2014-02-01

    Polysilazane (PSZ) and its polymer-derived amorphous silicon oxycarbide (SiOC) ceramic were coated on aluminum nitride (AlN) by using a dip-coating method to allow moisture-crosslinking of PSZ on AlN, followed by heat treatment at 700 °C in air to convert PSZ into SiOC on AlN. The results from FTIR, XPS and SEM indicated that the surface of AlN was successfully coated by PSZ and SiOC film. It was found that the introduction of PSZ and SiOC film help improve in the interfacial adhesion between the modified AlN (PSZ/AlN and SiOC/AlN) and silicone rubber lead to the increase in the thermal conductivity of the composites since the thermal boundary resistance at the filler-matrix interface was decreased. However, the introduction of SiOC as an intermediate layer between AlN and silicone rubber could help increase the thermal energy transport at the filler-matrix interface rather than using PSZ. This result was due to the decrease in the surface roughness and thickness of SiOC film after heat treatment at 700 °C in air. Thus, in the present work, a SiOC ceramic coating could provide a new surface modification for the improvement of the interfacial adhesion between the thermally conductive filler and the matrix in which can enhance the thermal conductivity of the composites.

  13. Amorphous and nanocrystalline titanium nitride and carbonitride materials obtained by solution phase ammonolysis of Ti(NMe2)4

    International Nuclear Information System (INIS)

    Jackson, Andrew W.; Shebanova, Olga; Hector, Andrew L.; McMillan, Paul F.

    2006-01-01

    Solution phase reactions between tetrakisdimethylamidotitanium (Ti(NMe 2 ) 4 ) and ammonia yield precipitates with composition TiC 0.5 N 1.1 H 2.3 . Thermogravimetric analysis (TGA) indicates that decomposition of these precursor materials proceeds in two steps to yield rocksalt-structured TiN or Ti(C,N), depending upon the gas atmosphere. Heating to above 700 deg. C in NH 3 yields nearly stoichiometric TiN. However, heating in N 2 atmosphere leads to isostructural carbonitrides, approximately TiC 0.2 N 0.8 in composition. The particle sizes of these materials range between 4-12 nm. Heating to a temperature that corresponds to the intermediate plateau in the TGA curve (450 deg. C) results in a black powder that is X-ray amorphous and is electrically conducting. The bulk chemical composition of this material is found to be TiC 0.22 N 1.01 H 0.07 , or Ti 3 (C 0.17 N 0.78 H 0.05 ) 3.96 , close to Ti 3 (C,N) 4 . Previous workers have suggested that the intermediate compound was an amorphous form of Ti 3 N 4 . TEM investigation of the material indicates the presence of nanocrystalline regions x (C,N) y crystalline phases

  14. Silicon nitride and intrinsic amorphous silicon double antireflection coatings for thin-film solar cells on foreign substrates

    International Nuclear Information System (INIS)

    Li, Da; Kunz, Thomas; Wolf, Nadine; Liebig, Jan Philipp; Wittmann, Stephan; Ahmad, Taimoor; Hessmann, Maik T.; Auer, Richard; Göken, Mathias; Brabec, Christoph J.

    2015-01-01

    Hydrogenated intrinsic amorphous silicon (a-Si:H) was investigated as a surface passivation method for crystalline silicon thin film solar cells on graphite substrates. The results of the experiments, including quantum efficiency and current density-voltage measurements, show improvements in cell performance. This improvement is due to surface passivation by an a-Si:H(i) layer, which increases the open circuit voltage and the fill factor. In comparison with our previous work, we have achieved an increase of 0.6% absolute cell efficiency for a 40 μm thick 4 cm 2 aperture area on the graphite substrate. The optical properties of the SiN x /a-Si:H(i) stack were studied using spectroscopic ellipsometer techniques. Scanning transmission electron microscopy inside a scanning electron microscope was applied to characterize the cross section of the SiN x /a-Si:H(i) stack using focus ion beam preparation. - Highlights: • We report a 10.8% efficiency for thin-film silicon solar cell on graphite. • Hydrogenated intrinsic amorphous silicon was applied for surface passivation. • SiN x /a-Si:H(i) stacks were characterized by spectroscopic ellipsometer techniques. • Cross-section micrograph was obtained by scanning transmission electron microscopy. • Quantum efficiency and J-V measurements show improvements in the cell performance

  15. Crystalline boron nitride aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-12-12

    This disclosure provides methods and materials related to boron nitride aerogels. For example, one aspect relates to a method for making an aerogel comprising boron nitride, comprising: (a) providing boron oxide and an aerogel comprising carbon; (b) heating the boron oxide to melt the boron oxide and heating the aerogel; (c) mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide; and (d) converting at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride. Another aspect relates to a method for making an aerogel comprising boron nitride, comprising heating boron oxide and an aerogel comprising carbon under flow of a nitrogen-containing gas, wherein boron oxide vapor and the nitrogen-containing gas convert at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride.

  16. Highly Selective and Stable Reduction of CO2 to CO by a Graphitic Carbon Nitride/Carbon Nanotube Composite Electrocatalyst.

    Science.gov (United States)

    Lu, Xunyu; Tan, Tze Hao; Ng, Yun Hau; Amal, Rose

    2016-08-16

    A stable and selective electrocatalyst for CO2 reduction was fabricated by covalently attaching graphitic carbon nitride onto multiwall carbon nanotubes (g-C3 N4 /MWCNTs). The as-prepared composite is able to reduce CO2 exclusively to CO with a maximum Faraday efficiency of 60 %, and no decay in the catalytic activity was observed even after 50 h of reaction. The enhanced catalytic activity towards CO2 reduction is attributed to the formation of active carbon-nitrogen bonds, high specific surface area, and improved material conductivity of the g-C3 N4 /MWCNT composite. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. A ternary hybrid of carbon nanotubes/graphitic carbon nitride nanosheets/gold nanoparticles used as robust substrate electrodes in enzyme biofuel cells.

    Science.gov (United States)

    Gai, Panpan; Song, Rongbin; Zhu, Cheng; Ji, Yusheng; Chen, Yun; Zhang, Jian-Rong; Zhu, Jun-Jie

    2015-10-11

    A novel ternary hybrid of carbon nanotubes/graphitic carbon nitride nanosheets/gold nanoparticles was prepared and used as robust substrate electrodes for fabricating membrane-less glucose/O2 enzyme biofuel cells (EBFCs), and a remarkably improved power output was observed for the prepared EBFC.

  18. Large quantity production of carbon and boron nitride nanotubes by mechano-thermal process

    International Nuclear Information System (INIS)

    Chen, Y.; Fitzgerald, J.D.; Chadderton, L.; Williams, J.S.; Campbell, S.J.

    2002-01-01

    Full text: Nanotube materials including carbon and boron nitride have excellent properties compared with bulk materials. The seamless graphene cylinders with a high length to diameter ratio make them as superstrong fibers. A high amount of hydrogen can be stored into nanotubes as future clean fuel source. Theses applications require large quantity of nanotubes materials. However, nanotube production in large quantity, fully controlled quality and low costs remains challenges for most popular synthesis methods such as arc discharge, laser heating and catalytic chemical decomposition. Discovery of new synthesis methods is still crucial for future industrial application. The new low-temperature mechano-thermal process discovered by the current author provides an opportunity to develop a commercial method for bulk production. This mechano-thermal process consists of a mechanical ball milling and a thermal annealing processes. Using this method, both carbon and boron nitride nanotubes were produced. I will present the mechano-thermal method as the new bulk production technique in the conference. The lecture will summarise main results obtained. In the case of carbon nanotubes, different nanosized structures including multi-walled nanotubes, nanocells, and nanoparticles have been produced in a graphite sample using a mechano-thermal process, consisting of I mechanical milling at room temperature for up to 150 hours and subsequent thermal annealing at 1400 deg C. Metal particles have played an important catalytic effect on the formation of different tubular structures. While defect structure of the milled graphite appears to be responsible for the formation of small tubes. It is found that the mechanical treatment of graphite powder produces a disordered and microporous structure, which provides nucleation sites for nanotubes as well as free carbon atoms. Multiwalled carbon nanotubes appear to grow via growth of the (002) layers during thermal annealing. In the case of BN

  19. The ir emission features: Emission from PAH [Polycyclic Aromatic Hydrocarbons] molecules and amorphous carbon particles

    International Nuclear Information System (INIS)

    Allamandola, L.J.; Tielens, A.G.G.M.; Barker, J.R.

    1986-01-01

    PAHs can have several forms in the interstellar medium. To assess the importance of each requires the availability of a collection of high quality, complete mid-ir interstellar emission spectra, a collection of laboratory spectra of PAH samples prepared under realistic conditions and a firm understanding of the microscopic emission mechanism. Given what we currently know about PAHs, the spectroscopic data suggests that there are at least two components which contribute to the interstellar emission spectrum: free molecule sized PAHs producing the narrow features and amorphous carbon particles (which are primarily made up of an irregular ''lattice'' of PAHs) contributing to the broad underlying components. An exact treatment of the ir fluorescence from highly vibrationally excited large molecules shows that species containing between 20 and 30 carbon atoms are responsible for the narrow features, although the spectra match more closely with the spectra of amorphous carbon particles. Since little is known about the spectroscopic properties of free PAHs and PAH clusters, much laboratory work is called for in conjunction with an observational program which focuses on the spatial characteristics of the spectra. In this way the distribution and evolution of carbon from molecule to particle can be traced. 38 refs., 9 figs

  20. Crystalline and Amorphous Phosphorus – Carbon Nanotube Composites as Promising Anodes for Lithium-Ion Batteries

    KAUST Repository

    Smajic, Jasmin

    2016-05-04

    Battery research has been going full steam and with that the search for alternative anodes. Among many proposed electrode materials, little attention has been given to phosphorus. Phosphorus boasts the third highest gravimetric charge capacity and the highest volumetric charge capacity of all elements. Because of that, it would be an attractive battery anode material were it not for its poor cyclability with significant capacity loss immediately after the first cycle. This is known to be the consequence of considerable volume changes of phosphorus during charge/discharge cycles. In this work, we propose circumventing this issue by mixing amorphous red phosphorus with carbon nanotubes. By employing a non-destructive sublimation-deposition method, we have synthesized composites where the synergetic effect between phosphorus and carbon nanotubes allow for an improvement in the electrochemical performance of battery anodes. In fact, it has been shown that carbon nanotubes can act as an effective buffer to phosphorus volumetric expansions and contractions during charging and discharging of the half-cells [1]. By modifying the synthesis parameters, we have also been able to change the degree of crystallinity of the phosphorus matrix in the composites. In fact, the less common phase of red phosphorus, named fibrous phosphorus, was obtained, and that explains some of the varying electrochemical performances observed in the composites. Overall, it is found that a higher surface area of amorphous phosphorus allows for a better anode material when using single-walled carbon nanotubes as fillers.

  1. Ternary graphene/amorphous carbon/nickel nanocomposite film for outstanding superhydrophobicity

    Science.gov (United States)

    Zhu, Xiaobo; Zhou, Shengguo; Yan, Qingqing

    2018-04-01

    A novel superhydrophobic ternary graphene/amorphous carbon/nickel (G-Ni/a-C:H) carbon-based film was fabricated by a green approach of high-voltage electrochemical deposition without using aqueous solution, which was systematically investigated including the structure and relating applications on self-cleaning and corrosion resistance. Graphene and nickel nano-particle inserts were effective to tailor the feature of nanocrystallite/amorphous microstructure as well as micro-nanoscale hierarchical rose-petal-like surface for G-Ni/a-C:H carbon-based film. Surprisingly, this deposit could present outstanding superhydrophobicity with the contact angle of 158.98 deg and sliding angle of 2.75 deg without any further surface modification meanwhile it could possess fairly well adhesion. Furthermore, the superhydrophobic G-Ni/a-C:H carbon-based film could exhibit excellent corrosion resistance and self-cleaning performances compared to no graphene incorporated deposit. The procedure of fabricating deposit might be simple, scalable, and environmental friendly, indicating a promising prospect for industrial applications in the field of anti-fouling, anti-corrosion and drag resistance.

  2. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation.

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-27

    Light isotopes separation, such as (3)He/(4)He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as (3)He/(4)He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high (3)He/(4)He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

  3. Facile synthesis and enhanced visible-light photocatalysis of graphitic carbon nitride composite semiconductors.

    Science.gov (United States)

    Li, Huiquan; Liu, Yuxing; Gao, Xing; Fu, Cong; Wang, Xinchen

    2015-04-13

    The semiconductor heterojunction has been an effective architecture to enhance photocatalytic activity by promoting photogenerated charge separation. Here, graphitic carbon nitride (CN) and B-modified graphitic carbon nitride (CNB) composite semiconductors were fabricated by a facile calcination process using cheap, sustainable, and easily available sodium tetraphenylboron and urea as precursors. The synthetic CN-CNB-25 semiconductor with a suitable CNB content showed the highest visible-light activity. Its degradation ratio for methyl orange and phenol was more than twice that of CN and CNB and its H2 evolution rate was ∼3.4 and ∼1.8 times higher than that of CN and CNB, respectively. It also displayed excellent stability and reusability. The enhanced activity of CN-CNB-25 was attributed predominantly to the efficient separation of photoinduced electrons and holes. This paper describes a visible-light-responsive CN composite semiconductor with great potential in environmental and energy applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Integrated oxygen-doping and dye sensitization of graphitic carbon nitride for enhanced visible light photodegradation.

    Science.gov (United States)

    Liu, Shizhen; Sun, Hongqi; Ang, H M; Tade, Moses O; Wang, Shaobin

    2016-08-15

    Graphitic carbon nitride (GCN) is a promising metal-free photocatalyst while suffering from low charge mobility induced inefficient photocatalysis. In this work, oxygen doping was employed to enhance the photodegradation of organic pollutants in water on graphitic carbon nitride (GCNO) under visible light. For further absorption extension, four organic dyes (Eosin-Y, Perylene, Nile-red and Coumarin) were adopted to dye-sensitize the GCNO photocatalyst. It was found that O-doping can promote dye sensitization, which was dependent on the type of dyes and influenced the photodegradation efficiencies of methylene blue (MB) and phenol. Nile-red sensitized GCNO presented the best activity in MB degradation under λ>480nm irradiations while Eosin-Y showed the best sensitization performance for phenol degradation under λ>420nm light source. However, dye sensitization was not effective for enhanced pollutant degradation on GCN without O-doping. UV-vis diffuse reflectance spectra (UV-vis DRS), photoluminescence (PL) spectra, and photocurrent analyses were applied to investigate the mechanism of carriers' transfer, which indicated that dye molecules could inject extra electrons into GCNO energy band and the energy dislocation could suppress electron/hole recombination, enhancing photocatalytic performances. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Surface engineering of graphitic carbon nitride polymers with cocatalysts for photocatalytic overall water splitting.

    Science.gov (United States)

    Zhang, Guigang; Lan, Zhi-An; Wang, Xinchen

    2017-08-01

    Graphitic carbon nitride based polymers, being metal-free, accessible, environmentally benign and sustainable, have been widely investigated for artificial photosynthesis in recent years for the photocatalytic splitting of water to produce hydrogen fuel. However, the photocatalytic stoichiometric splitting of pure water into H 2 and O 2 with a molecular ratio of 2 : 1 is far from easy, and is usually hindered by the huge activation energy barrier and sluggish surface redox reaction kinetics. Herein, we provide a concise overview of cocatalyst modified graphitic carbon nitride based photocatalysts, with our main focus on the modulation of the water splitting redox reaction kinetics. We believe that a timely and concise review on this promising but challenging research topic will certainly be beneficial for general readers and researchers in order to better understand the property-activity relationship towards overall water splitting, which could also trigger the development of new organic architectures for photocatalytic overall water splitting through the rational control of surface chemistry.

  6. Dispersing molecular cobalt in graphitic carbon nitride frameworks for photocatalytic water oxidation.

    Science.gov (United States)

    Zhang, Guigang; Huang, Caijin; Wang, Xinchen

    2015-03-01

    The development of water oxidation catalysts (WOCs) to cooperate with light-energy transducers for solar energy conversion by water splitting and CO2 fixation is a demanding challenge. The key measure is to develop efficient and sustainable WOCs that can support a sustainable photocatalyst to reduce over-potentials and thus to enhance reaction rate of water oxidation reaction. Cobalt has been indentified as active component of WOCs for photo/electrochemical water oxidation, and its performance relies strongly on the contact and adhesion of the cobalt species with photoactive substrates. Here, cobalt is homogeneously engineered into the framework of pristine graphitic carbon nitride (g-C3 N4 ) via chemical interaction, establishing surface junctions on the polymeric photocatalyst for the water oxidation reaction. This modification promotes the surface kinetics of oxygen evolution reaction by the g-C3 N4 -based photocatalytic system made of inexpensive substances, and further optimizations in the optical and textural structure of Co-g-C3 N4 is envisaged by considering ample choice of modification schemes for carbon nitride materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Rational design of carbon nitride photocatalysts by identification of cyanamide defects as catalytically relevant sites

    Science.gov (United States)

    Lau, Vincent Wing-Hei; Moudrakovski, Igor; Botari, Tiago; Weinberger, Simon; Mesch, Maria B.; Duppel, Viola; Senker, Jürgen; Blum, Volker; Lotsch, Bettina V.

    2016-07-01

    The heptazine-based polymer melon (also known as graphitic carbon nitride, g-C3N4) is a promising photocatalyst for hydrogen evolution. Nonetheless, attempts to improve its inherently low activity are rarely based on rational approaches because of a lack of fundamental understanding of its mechanistic operation. Here we employ molecular heptazine-based model catalysts to identify the cyanamide moiety as a photocatalytically relevant `defect'. We exploit this knowledge for the rational design of a carbon nitride polymer populated with cyanamide groups, yielding a material with 12 and 16 times the hydrogen evolution rate and apparent quantum efficiency (400 nm), respectively, compared with the unmodified melon. Computational modelling and material characterization suggest that this moiety improves coordination (and, in turn, charge transfer kinetics) to the platinum co-catalyst and enhances the separation of the photogenerated charge carriers. The demonstrated knowledge transfer for rational catalyst design presented here provides the conceptual framework for engineering high-performance heptazine-based photocatalysts.

  8. An alkali treating strategy for the colloidization of graphitic carbon nitride and its excellent photocatalytic performance.

    Science.gov (United States)

    Cheng, Fuxing; Yan, Jing; Zhou, Chenjuan; Chen, Binhe; Li, Peiran; Chen, Zhi; Dong, Xiaoping

    2016-04-15

    The colloid of graphitic carbon nitride (g-C3N4) was of great importance for practical application. Herein we introduced an alkali treatment route to efficiently colloidize g-C3N4 under mild conditions by destroying the hydrogen bonds between linearly polymeric melon chains and hydrolyzing partial C−NH−C bonds linked two tri-s-triazine units. The obtained colloidal suspension was extremely stable due to its negative charges on surface, and the particle size of several hundred nanometers and the nanobelt-like morphology were revealed by electron microscopy and dynamic light scattering technologies. The structural, optical and functional group analysis demonstrated that the structure of CN heterocycles was preserved after the alkali treatment, and the produced colloidal g-C3N4 can be re-assembled by an electrostatic interaction. Moreover, contributing to the reduced electron-hole recombination, the photocatalytic performance of restacked carbon nitride colloids had more enhanced photocatalytic performance than bulk g-C3N4. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

  10. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application. PMID:26813491

  11. Cross-Linked Graphitic Carbon Nitride with Photonic Crystal Structure for Efficient Visible-Light-Driven Photocatalysis.

    Science.gov (United States)

    Sun, Lu; Hong, Wei; Liu, Jing; Yang, Meijia; Lin, Wensheng; Chen, Guojian; Yu, Dingshan; Chen, Xudong

    2017-12-27

    Highly cross-linked graphitic carbon nitride has been prepared by a thermal copolymerization of dicyanodiamide with tetramethylammonium salts. The cross-linking can be evidenced by (i) increased C/N ratio without new carbon species, (ii) decreased specific surface area, and (iii) Tyndall effect after dissolution in concentrated sulfuric acid. The cross-linked graphitic carbon nitride with photonic crystal structure has highly efficient photocatalytic activity for water splitting under visible light due to the synergistic enhancement by the greatly suppressed photoluminescence, red-shifted absorption edges, strong inner reflections, and effective PCs stop band overlaps. It exhibits an enhanced photodegradation kinetic of methyl orange and a high visible-light-driven hydrogen-evolution rate of 166.9 μmol h -1 (25 times higher than that of the pristine graphitic carbon nitride counterpart). This work presents a facile method for designing and developing high-performance graphitic carbon nitride photocatalysts, providing a broad range of application prospects in the fields of electronics and energy conversion.

  12. Improvement of orthodontic friction by coating archwire with carbon nitride film

    Energy Technology Data Exchange (ETDEWEB)

    Wei Songbo [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shao Tianmin, E-mail: shaotm@mail.tsinghua.edu.cn [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Ding Peng [Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081 (China)

    2011-10-01

    In order to reduce frictional resistance between archwire and bracket during orthodontic tooth movement, carbon nitride (CNx) thin films were deposited on the surface of archwires with ion beam assisted deposition (IBAD). The energy-dispersive X-ray spectrometer (EDS) analysis showed that the CNx film was successfully deposited on the surface of the orthodontic wires. X-ray photoelectron spectroscopy (XPS) analysis suggested that the deposited CNx film was sp{sup 2} carbon dominated structures, and diversiform bonds (N-C, N{identical_to}C, et al.) coexisted in the film. The friction tests indicated that the CNx film significantly reduced the wire-bracket friction both in ambient air and in artificial saliva. The sp{sup 2}C rich structure of the CNx film as well as its protection function for the archwire was responsible for the low friction of the wire-bracket sliding system.

  13. Biopolymer-activated graphitic carbon nitride towards a sustainable photocathode material.

    Science.gov (United States)

    Zhang, Yuanjian; Schnepp, Zoë; Cao, Junyu; Ouyang, Shuxin; Li, Ying; Ye, Jinhua; Liu, Songqin

    2013-01-01

    Photoelectrochemical (PEC) conversion of solar light into chemical fuels is one of the most promising solutions to the challenge of sustainable energy. Graphitic carbon (IV) nitride polymer (g-CN) is an interesting sustainable photocathode material due to low-cost, visible-light sensitivity, and chemical stability up to 500 °C in air. However, grain boundary effects and limited active sites greatly hamper g-CN activity. Here, we demonstrate biopolymer-activation of g-CN through simultaneous soft-templating of a sponge-like structure and incorporation of active carbon-dopant sites. This facile approach results in an almost 300% increase in the cathodic PEC activity of g-CN under simulated solar-irradiation.

  14. Reversible Assembly of Graphitic Carbon Nitride 3D Network for Highly Selective Dyes Absorption and Regeneration.

    Science.gov (United States)

    Zhang, Yuye; Zhou, Zhixin; Shen, Yanfei; Zhou, Qing; Wang, Jianhai; Liu, Anran; Liu, Songqin; Zhang, Yuanjian

    2016-09-27

    Responsive assembly of 2D materials is of great interest for a range of applications. In this work, interfacial functionalized carbon nitride (CN) nanofibers were synthesized by hydrolyzing bulk CN in sodium hydroxide solution. The reversible assemble and disassemble behavior of the as-prepared CN nanofibers was investigated by using CO2 as a trigger to form a hydrogel network at first. Compared to the most widespread absorbent materials such as active carbon, graphene and previously reported supramolecular gel, the proposed CN hydrogel not only exhibited a competitive absorbing capacity (maximum absorbing capacity of methylene blue up to 402 mg/g) but also overcame the typical deficiencies such as poor selectivity and high energy-consuming regeneration. This work would provide a strategy to construct a 3D CN network and open an avenue for developing smart assembly for potential applications ranging from environment to selective extraction.

  15. Biopolymer-Activated Graphitic Carbon Nitride towards a Sustainable Photocathode Material

    Science.gov (United States)

    Zhang, Yuanjian; Schnepp, Zoë; Cao, Junyu; Ouyang, Shuxin; Li, Ying; Ye, Jinhua; Liu, Songqin

    2013-01-01

    Photoelectrochemical (PEC) conversion of solar light into chemical fuels is one of the most promising solutions to the challenge of sustainable energy. Graphitic carbon (IV) nitride polymer (g-CN) is an interesting sustainable photocathode material due to low-cost, visible-light sensitivity, and chemical stability up to 500°C in air. However, grain boundary effects and limited active sites greatly hamper g-CN activity. Here, we demonstrate biopolymer-activation of g-CN through simultaneous soft-templating of a sponge-like structure and incorporation of active carbon-dopant sites. This facile approach results in an almost 300% increase in the cathodic PEC activity of g-CN under simulated solar-irradiation. PMID:23831846

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-01-15

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

  17. Amorphous-tetrahedral diamondlike carbon layered structures resulting from film growth energetics

    Science.gov (United States)

    Siegal, M. P.; Barbour, J. C.; Provencio, P. N.; Tallant, D. R.; Friedmann, T. A.

    1998-08-01

    High-resolution transmission electron microscopy (HRTEM) shows that amorphous-tetrahedral diamondlike carbon (a-tC) films grown by pulsed-laser deposition on Si(100) consist of three-to-four layers, depending on the growth energetics. We estimate the density of each layer using both HRTEM image contrast and Rutherford backscattering spectrometry. The first carbon layer and final surface layer have relatively low density. The bulk of the film between these two layers has higher density. For films grown under the most energetic conditions, there exists a superdense a-tC layer between the interface and bulk layers. The density of all four layers, and the thickness of the surface and interfacial layers, correlate well with the energetics of the depositing carbon species.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zobelli, A

    2007-10-15

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

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

    International Nuclear Information System (INIS)

    Zobelli, A.

    2007-10-01

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

  20. Distinct Short-Range Order Is Inherent to Small Amorphous Calcium Carbonate Clusters (<2 nm)

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Shengtong [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany; School of Chemical Engineering, State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, East China University of Science and Technology, 130 Meilong Road Shanghai 200237 P.R. China; Chevrier, Daniel M. [Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax Nova Scotia B3H 4R2 Canada; Zhang, Peng [Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax Nova Scotia B3H 4R2 Canada; Gebauer, Denis [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany; Cölfen, Helmut [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany

    2016-09-09

    Amorphous intermediate phases are vital precursors in the crystallization of many biogenic minerals. While inherent short-range orders have been found in amorphous calcium carbonates (ACCs) relating to different crystalline forms, it has never been clarified experimentally whether such orders already exist in very small clusters less than 2 nm in size. Here, we studied the stability and structure of 10,12-pentacosadiynoic acid (PCDA) protected ACC clusters with a core size of ca. 1.4 nm consisting of only seven CaCO3 units. Ligand concentration and structure are shown to be key factors in stabilizing the ACC clusters. More importantly, even in such small CaCO3 entities, a proto-calcite short-range order can be identified but with a relatively high degree of disorder that arises from the very small size of the CaCO3 core. Our findings support the notion of a structural link between prenucleation clusters, amorphous intermediates, and final crystalline polymorphs, which appears central to the understanding of polymorph selection.

  1. Strength and tribology of bulk and electroformed nickel amorphized by implantation of titanium and carbon

    International Nuclear Information System (INIS)

    Myers, S.M.; Knapp, J.A.; Follstaedt, D.M.; Dugger, M.T.; Christenson, T.R.

    1997-01-01

    Dual ion implantation of titanium and carbon was shown to produce an amorphous layer of exceptional strength within annealed bulk Ni and electroformed Ni and Ni 80 Fe 20 materials used in micro-electromechanical systems. The intrinsic elastic and plastic mechanical properties of the implanted region were quantified using nanoindentation testing in conjunction with finite-element modeling, and the results were interpreted in the light of microstructures observed by electron microscopy. The implantation treatment was found to produce substantial reductions in unlubricated friction and wear

  2. Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

    Science.gov (United States)

    Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

    2011-12-23

    Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Structural, electronic and magnetic properties of carbon doped boron nitride nanowire: Ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Jalilian, Jaafar, E-mail: JaafarJalilian@gmail.com [Young Researchers and Elite Club, Kermanshah Br anch, Islamic Azad University, P.O. Box: 6718997551, Kermanshah (Iran, Islamic Republic of); Kanjouri, Faramarz, E-mail: kanjouri@khu.ac.ir [Physics Department, Faculty of Science, Kharazmi University, University Square, P.O. Box: 3197937551, Karaj (Iran, Islamic Republic of)

    2016-11-15

    Using spin-polarized density functional theory calculations, we demonstrated that carbon doped boron nitride nanowire (C-doped BNNW) has diverse electronic and magnetic properties depending on position of carbon atoms and their percentages. Our results show that only when one carbon atom is situated on the edge of the nanowire, C-doped BNNW is transformed into half-metal. The calculated electronic structure of the C-doped BNNW suggests that doping carbon can induce localized edge states around the Fermi level, and the interaction among localized edge states leads to semiconductor to half-metal transition. Overall, the bond reconstruction causes of appearance of different electronic behavior such as semiconducting, half-metallicity, nonmagnetic metallic, and ferromagnetic metallic characters. The formation energy of the system shows that when a C atom is doped on surface boron site, system is more stable than the other positions of carbon impurity. Our calculations show that C-doped BNNW may offer unique opportunities for developing nanoscale spintronic materials.

  4. Broccoli-like porous carbon nitride from ZIF-8 and melamine for high performance supercapacitors

    Science.gov (United States)

    Cai, Chenglong; Zou, Yongjin; Xiang, Cuili; Chu, Hailiang; Qiu, Shujun; Sui, Qingli; Xu, Fen; Sun, Lixian; Shah, Afzal

    2018-05-01

    Broccoli-like porous carbon nitride is synthesized by simple one-step carbonization of a composite comprising a Zn-based zeolitic imidazolate framework (ZIF-8) and melamine. The introduction of melamine into the ZIF-8 framework not only increases the N content of the composite and the surface area of the carbonization product, but also induces the formation of a flower-like structure. The carbon obtained from the ZIF-8/melamine composite by the proposed carbonization process at a temperature of 800 °C (ZM-C-800) is found to have a unique three-dimensional broccoli-like shape, a nanoscale size, and an extremely high doping N content (28.3 at.%). These properties substantially improve the electrochemical performance of ZM-C-800, as represented by a high specific capacitance of 359.1 F g-1 at a current density of 1 A g-1, much higher than that of ZIF-8. Furthermore, a symmetric supercapacitor fabricated with two ZM-C-800 electrodes exhibits a power density of 498.5 W kg-1 for an energy density of 11.4 Wh kg-1. This indicates the strong potential of ZM-C-800 for use in the fabrication of energy storage devices.

  5. Precipitation of Co(2+) carbonates from aqueous solution: insights on the amorphous to crystalline transformation.

    Science.gov (United States)

    González-López, Jorge; Fernández-González, Ángeles; Jiménez, Amalia

    2016-04-01

    Cobalt is toxic metal that is present only as a trace in the Earth crust. However, Co might concentrate on specific areas due to both natural and anthropogenic factors and thus, soils and groundwater can be contaminated. It is from this perspective that we are interested in the precipitation of cobalt carbonates, since co-precipitation with minerals phases is a well-known method for metal immobilization in the environment. In particular, the carbonates are widely used due to its reactivity and natural abundance. In order to evaluate the cobalt carbonate precipitation at room temperature, a simple experimental work was carried out in this work. The precipitation occurred via reaction of two common salts: 0.05M of CoCl2 and 0.05M of Na2CO3 in aqueous solution. After reaction, the precipitated solid was kept in the remaining water at 25 oC and under constant stirring for different aging times of 5 min, 1 and 5 hours, 1, 2, 4, 7, 30 and 60 days. In addition to the aging and precipitation experiments, we carried out experiments to determine the solubility of the solids. In these experiments each precipitate was dissolved in Milli-Q water until equilibrium was reached and then the aqueous solution was analyzed regarding Co2+ and total alkalinity. Furthermore, acid solution calorimetry of the products were attained. Finally, we modeled the results using the PHREEQC code. Solid and aqueous phase identification and characterization have been extensively reported in a previous work (González-López et al., 2015). The main results of our investigation were the initial precipitation of an amorphous cobalt carbonate that evolve towards a poorly crystalline cobalt hydroxide carbonate with aging treatment. Solubility of both phases have been calculated under two different approaches: precipitation and dissolution. Values of solubility from each approach were obtained with a general error due to differences in experiment conditions, for instance, ionic strength, temperature and

  6. Gas uptake and thermal stability analysis of boron nitride and carbon nanotubes

    Science.gov (United States)

    Guan, Mengyu

    Carbon nanotubes (CNTs) exist in many forms and can have critical pore diameters on the angstrom length scale, making them suitable for molecular capture. By combining the porous structure of CNTs with the chemical stability of carbide and/or nitride materials, one can create a more robust, nanoporous material for gas capture in high temperature conditions. Boron nitride nanotubes (BNNTs) are more chemically and thermally robust than pure CNTs, and were synthesized using CNTs as a structural precursor. However, this reaction mechanism was found to be unfavorable to produce high-yield and purity BNNTs. Adsorption tests using gases of interest (N2, He) were performed on commercial CNTs and BNNTs to determine their porosity and gas uptake abilities. Their thermal stability and oxidation resistance when heated up to 1773 K in air was also studied using differential scanning calorimetry and thermogravimetric analysis. While the CNTs began to oxidize between 450 °C and 750 °C, depending on the nanotube diameter, the BNNTs remained stable up until 1000 °C.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-10-01

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

  8. Facile fabrication of ordered mesoporous graphitic carbon nitride for RhB photocatalytic degradation

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Lei; Zhang, Anfeng [State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China); Janik, Michael J. [EMS Energy Institute, PSU-DUT Joint Center for Energy Research and Department of Energy & Mineral Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Li, Keyan [State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China); Song, Chunshan [State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China); EMS Energy Institute, PSU-DUT Joint Center for Energy Research and Department of Energy & Mineral Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Guo, Xinwen, E-mail: guoxw@dlut.edu.cn [State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China)

    2017-02-28

    Highlights: • Ordered mesoporous graphitic carbon nitrides with S{sub BET} = 279.3 m{sup 2}/g were prepared. • Enhanced photocatalytic activity and reusability were presented. • Improved S{sub BET} and charge carrier separation efficiency contribute to the activity. - Abstract: Ordered mesoporous graphitic carbon nitrides were prepared by directly condensing the uniform mixtures of melamine and KIT-6. After removal of the KIT-6 sacrificial template, the carbon nitrides were characterized with TEM, N{sub 2} physical adsorption, XRD, FT-IR, XPS, UV–vis and PL spectrometries, and tested for their RhB photocatalytic degradation activity. Together, these characterizations confirmed the as-prepared tunable mesoporous materials with enhanced charge separation efficiency and superior photocatalytic performance. Compared with a conventional bulk g-C{sub 3}N{sub 4}, ordered mesoporous g-C{sub 3}N{sub 4} exhibits a larger specific surface area of 279.3 m{sup 2}/g and a pore size distribution about 4.0 nm and 13.0 nm. Meanwhile, the reduced bandgap energy of 2.77 eV and lower photogenerated electron-hole pair recombination frequency were evidenced by UV–Vis and PL spectra. The RhB photocatalytic degradation activity maximizes with a mass ratio of KIT-6/melamine of 80% (KCN80), and the kinetic constant reaches 0.0760 min{sup −1} which is 16 times higher than that of the bulk sample. Reusability of KCN80 was demonstrated by a lack of evident deactivation after three consecutive reaction periods. The direct condensation of the KIT-6 and melamine mixture does not require pre-casting of the precursor into the pore system of the templates. Owing to its high product yield, improved S{sub BET}, reduced bandgap energy and limited charge recombination, the facile-prepared ordered mesoporous g-C{sub 3}N{sub 4} is a practical candidate for further modification.

  9. Graphitic carbon nitride: Synthesis, characterization and photocatalytic decomposition of nitrous oxide

    Energy Technology Data Exchange (ETDEWEB)

    Praus, Petr, E-mail: petr.praus@vsb.cz [Institute of Environmental Technology, VŠB-Technical University of Ostrava, 17. Listopadu 15/2172, Ostrava 708 33 (Czech Republic); Department of Chemistry, Faculty of Metallurgy and Materials Engineering, VŠB-Technical University of Ostrava, 17. Listopadu 15/2172, Ostrava 708 33 (Czech Republic); Svoboda, Ladislav [Institute of Environmental Technology, VŠB-Technical University of Ostrava, 17. Listopadu 15/2172, Ostrava 708 33 (Czech Republic); Department of Chemistry, Faculty of Metallurgy and Materials Engineering, VŠB-Technical University of Ostrava, 17. Listopadu 15/2172, Ostrava 708 33 (Czech Republic); Ritz, Michal [Department of Chemistry, Faculty of Metallurgy and Materials Engineering, VŠB-Technical University of Ostrava, 17. Listopadu 15/2172, Ostrava 708 33 (Czech Republic); Troppová, Ivana; Šihor, Marcel; Kočí, Kamila [Institute of Environmental Technology, VŠB-Technical University of Ostrava, 17. Listopadu 15/2172, Ostrava 708 33 (Czech Republic)

    2017-06-01

    Graphitic carbon nitride (g-C{sub 3}N{sub 4}) was synthetized by condensation of melamine at the temperatures of 400–700 °C in air for 2 h and resulting products were characterized and finally tested for the photocatalytic decomposition of nitrous oxide. The characterization methods were elemental analysis, UV–Vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), Fourier transform infrared (FTIR) and Raman spectroscopy, measurement of specific surface area (SSA), X-ray powder diffraction (XRD), scanning (SEM) and transmission (TEM) electron microscopy. The XRD patterns, FTIR and Raman spectra proved the presence of g-C{sub 3}N{sub 4} at above 550 °C but the optimal synthesis temperature of 600–650 °C was found. Under these conditions graphitic carbon nitride of the overall empirical composition of C{sub 6}N{sub 9}H{sub 2} was formed. At lower temperatures g-C{sub 3}N{sub 4} with a higher content of hydrogen was formed but at higher temperatures g-C{sub 3}N{sub 4} was decomposed. At the temperatures above 650 °C, its exfoliation was observed. The photocatalytic experiments showed that the activity of all the samples synthetized at 400–700 °C was very similar, that is, within the range of experimental error (5 %). The total conversion of N{sub 2}O reached about 43 % after 14 h. - Highlights: • Graphitic carbon nitride (g-C{sub 3}N{sub 4}) was thermally synthetized from melamine in the range of 400–700 °C. • The optimal temperature was determined at 600–650 °C. • All synthesis products were properly characterized by physico-chemical methods. • Exfoliation of g-C{sub 3}N{sub 4} at above 600 °C was observed. • g-C{sub 3}N{sub 4} was used for the photocatalytic decomposition of N{sub 2}O.

  10. Vertical electric field stimulated neural cell functionality on porous amorphous carbon electrodes.

    Science.gov (United States)

    Jain, Shilpee; Sharma, Ashutosh; Basu, Bikramjit

    2013-12-01

    We demonstrate the efficacy of amorphous macroporous carbon substrates as electrodes to support neuronal cell proliferation and differentiation in electric field mediated culture conditions. The electric field was applied perpendicular to carbon substrate electrode, while growing mouse neuroblastoma (N2a) cells in vitro. The placement of the second electrode outside of the cell culture medium allows the investigation of cell response to electric field without the concurrent complexities of submerged electrodes such as potentially toxic electrode reactions, electro-kinetic flows and charge transfer (electrical current) in the cell medium. The macroporous carbon electrodes are uniquely characterized by a higher specific charge storage capacity (0.2 mC/cm(2)) and low impedance (3.3 kΩ at 1 kHz). The optimal window of electric field stimulation for better cell viability and neurite outgrowth is established. When a uniform or a gradient electric field was applied perpendicular to the amorphous carbon substrate, it was found that the N2a cell viability and neurite length were higher at low electric field strengths (≤ 2.5 V/cm) compared to that measured without an applied field (0 V/cm). While the cell viability was assessed by two complementary biochemical assays (MTT and LDH), the differentiation was studied by indirect immunostaining. Overall, the results of the present study unambiguously establish the uniform/gradient vertical electric field based culture protocol to either enhance or to restrict neurite outgrowth respectively at lower or higher field strengths, when neuroblastoma cells are cultured on porous glassy carbon electrodes having a desired combination of electrochemical properties. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. X-ray and neutron scattering from amorphous diamondlike carbon and hydrocarbon films

    International Nuclear Information System (INIS)

    Findeisen, E.

    1994-10-01

    In this report amorphous, diamondlike, carbon and hydrocarbon films are investigated by two different methods, namely, X-ray scattering and a combination of X-ray and neutron reflectivity. As specular reflectivity probes the scattering length density profile of a sample perpendicular to its surface, the combination of X-ray and neutron reflectivity reveals the nuclei density of both carbon and hydrogen separately. This allows to calculate the concentration of hydrogen in the films, which varies in the presented experiments between 0 and 36 atomic %. This method is a new and nondestructive technique to determine the concentration of hydrogen within an error of about ±1 at. % in samples with sharp interfaces. It is well suited for thin diamondlike carbon films. X-ray scattering is used to obtain structural information on the atomic scale, especially the average carbon-carbon distance and the average coordination number of the carbon atoms. As grazing incidence diffraction experiments were not successful, free-standing films are used for the scattering experiments with synchrotron light. However, the scattered intensity for large scattering vectors is, in spite of the intense primary beam, very weak, and therefore the accuracy of the obtained structural parameter is not sufficient to prove the diamondlike properties also on the atomic scale. (au) (10 tabs., 76 ills., 102 refs.)

  12. Computational Evaluation of Amorphous Carbon Coating for Durable Silicon Anodes for Lithium-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Jeongwoon Hwang

    2015-10-01

    Full Text Available We investigate the structural, mechanical, and electronic properties of graphite-like amorphous carbon coating on bulky silicon to examine whether it can improve the durability of the silicon anodes of lithium-ion batteries using molecular dynamics simulations and ab-initio electronic structure calculations. Structural models of carbon coating are constructed using molecular dynamics simulations of atomic carbon deposition with low incident energies (1–16 eV. As the incident energy decreases, the ratio of sp2 carbons increases, that of sp3 decreases, and the carbon films become more porous. The films prepared with very low incident energy contain lithium-ion conducting channels. Also, those films are electrically conductive to supplement the poor conductivity of silicon and can restore their structure after large deformation to accommodate the volume change during the operations. As a result of this study, we suggest that graphite-like porous carbon coating on silicon will extend the lifetime of the silicon anodes of lithium-ion batteries.

  13. A Facile Steam Reforming Strategy to Delaminate Layered Carbon Nitride Semiconductors for Photoredox Catalysis.

    Science.gov (United States)

    Yang, Pengju; Ou, Honghui; Fang, Yuanxing; Wang, Xinchen

    2017-03-27

    The delamination of layered crystals that produces single or few-layered nanosheets while enabling exotic physical and chemical properties, particularly for semiconductor functions in optoelectronic applications, remains a challenge. Here, we report a facile and green approach to prepare few-layered polymeric carbon nitride (PCN) semiconductors by a one-step carbon/nitrogen steam reforming reaction. Bulky PCN, obtained from typical precursors including urea, melamine, dicyandiamide, and thiourea, are exfoliated into few-layered nanosheets, while engineering its surface carbon vacancies. The unique sheet structures with strengthened surface properties endow PCNs with more active sites, and an increased charge separation efficiency with a prolonged charge lifetime, drastically promoting their photoredox performance. After an assay of a H 2 evolution reaction, an apparent quantum yield of 11.3 % at 405 nm was recorded for the PCN nanosheets, which is much higher than those of PCN nanosheets. This delamination method is expandable to other carbon-based 2D materials for advanced applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Implantation of xenon in amorphous carbon and silicon for brachytherapy application

    International Nuclear Information System (INIS)

    Marques, F.C.; Barbieri, P.F.; Viana, G.A.; Silva, D.S. da

    2013-01-01

    We report a procedure to implant high dose of xenon atoms (Xe) in amorphous carbon, a-C, and amorphous silicon, a-Si, for application in brachytherapy seeds. An ion beam assisted deposition (IBAD) system was used for the deposition of the films, where one ion gun was used for sputtering a carbon (or silicon) target, while the other ion gun was used to simultaneously bombard the growing film with a beam of xenon ion Xe + in the 0–300 eV range. Xe atoms were implanted into the film with concentration up to 5.5 at.%, obtained with Xe bombardment energy in the 50–150 eV range. X-ray absorption spectroscopy was used to investigate the local arrangement of the implanted Xe atoms through the Xe L III absorption edge (4.75 keV). It was observed that Xe atoms tend to agglomerate in nanoclusters in a-C and are dispersed in a-Si.

  15. Transformation of amorphous calcium carbonate to rod-like single crystal calcite via "copying" collagen template.

    Science.gov (United States)

    Xue, Zhonghui; Hu, Binbin; Dai, Shuxi; Du, Zuliang

    2015-10-01

    Collagen Langmuir films were prepared by spreading the solution of collagen over deionized water, CaCl2 solution and Ca(HCO3)2 solution. Resultant collagen Langmuir monolayers were then compressed to a lateral pressure of 10 mN/m and held there for different duration, allowing the crystallization of CaCO3. The effect of crystallization time on the phase composition and microstructure of CaCO3 was investigated. It was found that amorphous calcium carbonate (ACC) was obtained at a crystallization time of 6 h. The amorphous CaCO3 was transformed to rod-like single crystal calcite crystals at an extended crystallization time of 12 h and 24 h, via "copying" the symmetry and dimensionalities of collagen fibers. Resultant calcite crystallites were well oriented along the longitudinal axis of collagen fibers. The ordered surface structure of collagen fibers and electrostatic interactions played key roles in tuning the oriented nucleation and growth of the calcite crystallites. The mineralized collagen possessing both desired mechanical properties of collagen fiber and good biocompatibility of calcium carbonate may be assembled into an ideal biomaterial for bone implants. Copyright © 2015. Published by Elsevier B.V.

  16. Cell survival in carbon beams - comparison of amorphous track model predictions

    DEFF Research Database (Denmark)

    Grzanka, L.; Greilich, S.; Korcyl, M.

    distribution models, and gamma response models was developed. This software can be used for direct numerical comparison between the models, submodels and their parameters and experimental data. In the present paper, we look at 10%-survival data from cell lines irradiated in vitro with carbon and proton beams...... neutrons, stopped pions, and heavy ion beams. Nucl Instrum Meth. 1973;111:93-116. 2.Weyrather WK, Kraft G. RBE of carbon ions: experimental data and the strategy of RBE calculation for treatment planning. Radiother Oncol. 2004;73(Suppl 2):161-9. 3.Greilich S, Grzanka L, Bassler N, Andersen CE, Jäkel O...... irradiation. The aim of this paper is to compare the predictions from different amorphous approaches found in the literature - more specifically the phenomenological, analytical model by Katz and co-workers [1] and a Monte-Carlo based full as implemented for example in the local effect model by Scholz et al...

  17. Photodegradation of methyl red under visible light by mesoporous carbon nitride

    Science.gov (United States)

    Hu, Yueyue; Zhang, Min; Xiao, Zaozao; Jiang, Tao; Yan, Bing; Li, Jian

    2018-02-01

    Mesoporous carbon nitride (mpg-C3N4) with tunable microstructure has been successfully prepared through a simple polymerization reaction of cyanamide by a nano hard-templating approach. The obtained materials have been characterized using X-ray diffraction (XRD), N2 adsorption, and Fourier transform infrared (FT-IR) spectroscopy. The results show that the pore diameter of the mpg-C3N4 materials can be easily tuned from 3.8 to 10.5 nm. The mpg-C3N4 materials are demonstrated to exhibit much higher visible light photocatalytic activity than that of g-C3N4 for the degradation of aqueous methyl red (MR). The high surface areas and large pore volume contributed to the efficient visible light photocatalytic activity.

  18. Sulfur (VI) modified graphite carbon nitride nanosheets with chrysanthemum-like structure and enhanced photocatalytic activity

    Science.gov (United States)

    Xie, Lili; Dai, Yunrong; Zhou, Yijing; Chang, Xin; Yin, Lifeng

    2018-02-01

    Chrysanthemum-like sulfur (VI) modified graphite carbon nitride (s/g-C3N4) was synthesized by sulfuring and sonicating bulk g-C3N4 at 800 kHz. The sulfuring relaxed the interlayer force of g-C3N4, and the sonication constructed its chrysanthemum-like structure which enhances the separation of photo-generated carriers and photochemical response. Density functional calculation and diffusion reflection spectra (DRS) verified that sulfur (VI) modification shifted down the valence band edge of g-C3N4 and improved the redox potentials of g-C3N4. The photocatalytic degradation efficiency of 4-nitrophenol (10 mg L-1) by s/g-C3N4 was 49.3 times higher than that by bulk g-C3N4 under visible light irradiation (>400 nm).

  19. Role of defects in the process of graphene growth on hexagonal boron nitride from atomic carbon

    International Nuclear Information System (INIS)

    Dabrowski, J.; Lippert, G.; Schroeder, T.; Lupina, G.

    2014-01-01

    Hexagonal boron nitride (h-BN) is an attractive substrate for graphene, as the interaction between these materials is weak enough for high carrier mobility to be retained in graphene but strong enough to allow for some epitaxial relationship. We deposited graphene on exfoliated h-BN by molecular beam epitaxy (MBE), we analyzed the atomistic details of the process by ab initio density functional theory (DFT), and we linked the DFT and MBE results by random walk theory. Graphene appears to nucleate around defects in virgin h-BN. The DFT analysis reveals that sticking of carbon to perfect h-BN is strongly reduced by desorption, so that pre-existing seeds are needed for the nucleation. The dominant nucleation seeds are C N C B and O N C N pairs and B 2 O 3 inclusions in the virgin substrate

  20. Visible Light Neural Stimulation on graphitic-Carbon Nitride/Graphene Photocatalytic Fibers

    DEFF Research Database (Denmark)

    Zhang, Zhongyang; Xu, Ruodan; Wang, Zegao

    2017-01-01

    Light stimulation allows remote and spatiotemporally accurate operation that has been applied as effective, non-invasive means of therapeutic interventions. Here, visible light neural stimulation of graphitic carbon nitride (g-C3N4), an emerging photocatalyst with visible-light optoelectronic...... conversion, was for the first time investigated. Specifically, g-C3N4 was combined with graphene oxide (GO) in a 3D manner on the surfaces of electrospun polycaprolactone/gelatin (PG) fibers and functioned as a biocompatible interface for visible-light stimulating neuronal differentiation. The enhanced...... was confirmed by the Lactate Dehydrogenase (LDH) assay, live dead staining and colorimetric cell viability assay CCK-8. Under a bidaily, monochromatic light stimulation at a wavelength of 450 nm at 10mW/cm2, a 18.5-fold increase of neurite outgrowth of PC12 was found on g-C3N4 coated fibers; while AA reduced GO...

  1. Challenges in calculating the bandgap of triazine-based carbon nitride structures

    KAUST Repository

    Steinmann, Stephan N.

    2017-02-08

    Graphitic carbon nitrides form a popular family of materials, particularly as photoharvesters in photocatalytic water splitting cells. Recently, relatively ordered g-C3N4 and g-C6N9H3 were characterized by X-ray diffraction and their ability to photogenerate excitons was subsequently estimated using density functional theory. In this study, the ability of triazine-based g-C3N4 and g-C6N9H3 to photogenerate excitons was studied using self-consistent GW computations followed by solving the Bethe–Salpeter Equation (BSE). In particular, monolayers, bilayers and 3D-periodic systems were characterized. The predicted optical band gaps are in the order of 1 eV higher than the experimentally measured ones, which is explained by a combination of shortcomings in the adopted model, small defects in the experimentally obtained structures and the particular nature of the experimental determination of the band gap.

  2. Influence of porewidening duration on the template assisted growth of graphitic carbon nitride nanostructures

    Science.gov (United States)

    Suchitra, S. M.; Udayashankar, N. K.

    2018-01-01

    Porous anodic aluminium oxide (AAO) membranes with a highly ordered pore arrangement are typically used as ideal templates for the synthesis of numerous nanostructured materials. Highly ordered templates gained significant attraction due to the fact that they are readily fabricated through self-organised simple anodization process. In this paper, the effect of different pore-widening treatments on the quality of the pores of the AAO templates prepared with different electrolytes were inspected. Results confirmed that, without altering the interpore distance different pore dimensions and diameters of the AAO templates can be easily achieved by chemical pore widening process at room temperature. Also, graphitic carbon nitride nanorods of different dimension have been fabricated from AAO template after porewidening process. These nanostructures are widely used in case of metal free visible light driven photo catalysis, photo degradation of organic pollutants, photo electric conversion and water splitting applications.

  3. Graphitic Carbon Nitride Film: An Emerging Star for Catalytic and Optoelectronic Applications.

    Science.gov (United States)

    Bian, Juncao; Huang, Chao; Zhang, Rui-Qin

    2016-10-06

    Graphitic carbon nitride (g-CN) is a unique organic semiconductor that has been widely applied as a visible-light-driven photocatalyst. However, these applications are primarily based on g-CN powders. Applications of g-CN in devices are hindered because of difficulties associated with the synthesis of high-quality g-CN films. This work reviews the latest advances in g-CN films. The deposition methods are summarized and the structural, optical, and electronic properties of g-CN films and their applications in catalysis, solar cells, and light-emitting diodes are outlined. Moreover, the challenges remaining in this field are also discussed. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Copper Phthalocyanine-Functionalized Graphitic Carbon Nitride: A Hybrid Heterostructure toward Photoelectrochemical and Photocatalytic Degradation Applications.

    Science.gov (United States)

    Liu, Zhong-Guo; Wan, Jia-Yun; Yang, Ze; Wang, Shi-Quan; Wang, Hang-Xing

    2016-07-05

    In this work, alcian blue 8GX (AB), a copper(II) phthalocyanine derivative, was employed to functionalize graphitic carbon nitride (g-C3 N4 ) for the preparation of a highly efficient photocatalyst. The approach relies on a facile AB-assisted ethanol/water mixed-solvent exfoliation of bulk g-C3 N4 . The as-prepared g-C3 N4 /AB hybrid possesses significantly enhanced solution dispersibility and photoelectrochemical performance resulting from the synergistic effect between g-C3 N4 and AB, which involves the optimization of intimate interfacial contact, extension of light absorption range, and enhancement of charge-transfer efficiency. This synergy contributes enormously to the photocatalytic degradation of rhodamine 6G (R6G) under light irradiation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Phosphorus doped graphitic carbon nitride nanosheets as fluorescence probe for the detection of baicalein.

    Science.gov (United States)

    Wang, Xuan; Li, Xuebing; Chen, Wenfang; Wang, Rulin; Bian, Wei; Choi, Martin M F

    2018-02-24

    Phosphorus doped graphitic carbon nitride (P-g-C 3 N 4 ) nanosheets were synthesized by calcination. P-g-C 3 N 4 nanosheets were characterized by XRD, XPS, TEM, fluorescence, ultraviolet-visible absorption and Fourier transform infrared spectroscopy. The fluorescence of the P-g-C 3 N 4 nanosheets was gradually quenched with the increase in the concentration of baicalein at room temperature. The proposed probe was used for the determination of baicalein in the concentration 2.0-30μM with a detection limit of 53nM. The quenching mechanism was discussed. The P-g-C 3 N 4 nanosheets have been successfully applied for effective and selective detection of baicalein in human urine samples and blood samples. Copyright © 2018 Elsevier B.V. All rights reserved.

  6. Photocatalytically Active Oligomeric Graphitic Carbon Nitride: Conformational Flexibility, Electronic Levels, Carrier Localization

    Science.gov (United States)

    Blum, Volker; Lau, Vincent; Botari, Tiago; Huhn, William; Lotsch, Bettina V.

    2015-03-01

    Polymers consisting of bridged heptazine units (often called ``graphitic carbon nitride'' or ``g-C3N4'') show considerable promise as photocatalysts for solar hydrogen evolution. Recent experimental evidence suggests that oligomeric rather than fully polymerized ``g-C3N4'' exhibits increased intrinsic photocatalytic activity. Using density-functional theory (DFT; van der Waals corrected PBE functional for conformers, hybrid DFT and GW for electronic levels), we show that considerable conformational flexibility exists for the heptazine trimers and tetramers. Analysis of HOMO and LUMO locations as well as trends in photocatalytic activity among heptazine oligomers and polymers reveals the NH2 groups of the oligomers as potential charge-transfer sites. We show that conformational variations of the oligomers can lead to significant, electrostatically motivated carrier localization effects. We suggest that NH2 side groups and the intrinsic conformational variations of the oligomeric species lead to the observed enhanced catalytic activity.

  7. Structural insights into photocatalytic performance of carbon nitrides for degradation of organic pollutants

    Science.gov (United States)

    Oh, Junghoon; Shim, Yeonjun; Lee, Soomin; Park, Sunghee; Jang, Dawoon; Shin, Yunseok; Ohn, Saerom; Kim, Jeongho; Park, Sungjin

    2018-02-01

    Degradation of organic pollutants has a large environmental impact, with graphitic carbon nitride (g-C3N4) being a promising metal-free, low cost, and environment-friendly photocatalyst well suited for this purpose. Herein, we investigate the photocatalytic performance of g-C3N4-based materials and correlate it with their structural properties, using three different precursors (dicyandiamide, melamine, and urea) and two heating processes (direct heating at 550 °C and sequential heating at 300 and 550 °C) to produce the above photocatalysts. We further demonstrate that sequential heating produces photocatalysts with grain sizes and activities larger than those of the catalysts produced by direct heating and that the use of urea as a precursor affords photocatalysts with larger surface areas, allowing efficient rhodamine B degradation under visible light.

  8. Nickel Oxide and Nickel Co-doped Graphitic Carbon Nitride Nanocomposites and its Octylphenol Sensing Application

    KAUST Repository

    Gong, Wanyun

    2015-11-16

    Nickel oxide and nickel co-doped graphitic carbon nitride (NiO-Ni-GCN) nanocomposites were successfully prepared by thermal treatment of melamine and NiCl2 6H2O. NiO-Ni-GCN nanocomposites showed superior electrochemical catalytic activity for the oxidation of octylphenol to pure GCN. A detection method of octylphenol in environmental water samples was developed based at NiO-Ni-GCN nanocomposites modified electrode under infrared light irradiation. Differential pulse voltammetry was used as the analytic technique of octylphenol, exhibiting stable and specific concentration-dependent oxidation signal in the presence of octylphenol in the range of 10nM to 1μM and 1μM to 50μM, with a detection limit of 3.3nM (3S/N). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Harvesting solar light with crystalline carbon nitrides for efficient photocatalytic hydrogen evolution

    KAUST Repository

    Bhunia, Manas Kumar

    2014-08-14

    Described herein is the photocatalytic hydrogen evolution using crystalline carbon nitrides (CNs) obtained by supramolecular aggregation followed by ionic melt polycondensation (IMP) using melamine and 2,4,6-triaminopyrimidine as a dopant. The solid state NMR spectrum of 15N-enriched CN confirms the triazine as a building unit. Controlling the amount and arrangements of dopants in the CN structure can dramatically enhance the photocatalytic performance for H2 evolution. The polytriazine imide (PTI) exhibits the apparent quantum efficiency (AQE) of 15% at 400 nm. This method successfully enables a substantial amount of visible light to be harvested for H2 evolution, and provides a promising route for the rational design of a variety of highly active crystalline CN photocatalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Electrochemical treatment of domestic wastewater using boron-doped diamond and nanostructured amorphous carbon electrodes.

    Science.gov (United States)

    Daghrir, Rimeh; Drogui, Patrick; Tshibangu, Joel; Delegan, Nazar; El Khakani, My Ali

    2014-05-01

    The performance of the electrochemical oxidation process for efficient treatment of domestic wastewater loaded with organic matter was studied. The process was firstly evaluated in terms of its capability of producing an oxidant agent (H2O2) using amorphous carbon (or carbon felt) as cathode, whereas Ti/BDD electrode was used as anode. Relatively high concentrations of H2O2 (0.064 mM) was produced after 90 min of electrolysis time, at 4.0 A of current intensity and using amorphous carbon at the cathode. Factorial design and central composite design methodologies were successively used to define the optimal operating conditions to reach maximum removal of chemical oxygen demand (COD) and color. Current intensity and electrolysis time were found to influence the removal of COD and color. The contribution of current intensity on the removal of COD and color was around 59.1 and 58.8%, respectively, whereas the contribution of treatment time on the removal of COD and color was around 23.2 and 22.9%, respectively. The electrochemical treatment applied under 3.0 A of current intensity, during 120 min of electrolysis time and using Ti/BDD as anode, was found to be the optimal operating condition in terms of cost/effectiveness. Under these optimal conditions, the average removal rates of COD and color were 78.9 ± 2 and 85.5 ± 2 %, whereas 70% of total organic carbon removal was achieved.

  11. Transformation of Mg-bearing amorphous calcium carbonate to Mg-calcite - In situ monitoring

    Science.gov (United States)

    Purgstaller, Bettina; Mavromatis, Vasileios; Immenhauser, Adrian; Dietzel, Martin

    2016-02-01

    The formation of Mg-bearing calcite via an amorphous precursor is a poorly understood process that is of relevance for biogenic and abiogenic carbonate precipitation. In order to gain an improved insight on the controls of Mg incorporation in calcite formed via an Mg-rich amorphous calcium carbonate (Mg-ACC) precursor, the precipitation of Mg-ACC and its transformation to Mg-calcite was monitored by in situ Raman spectroscopy. The experiments were performed at 25.0 ± 0.03 °C and pH 8.3 ± 0.1 and revealed two distinct pathways of Mg-calcite formation: (i) At initial aqueous Mg/Ca molar ratios ⩽ 1:6, Mg-calcite formation occurs via direct precipitation from solution. (ii) Conversely, at higher initial Mg/Ca molar ratios, Mg-calcite forms via an intermediate Mg-rich ACC phase. In the latter case, the final product is a calcite with up to 20 mol% Mg. This Mg content is significant higher than that of the Mg-rich ACC precursor phase. Thus, a strong net uptake of Mg ions from the solution into the crystalline precipitate throughout and also subsequent to ACC transformation is postulated. Moreover, the temporal evolution of the geochemical composition of the reactive solution and the Mg-ACC has no significant effect on the obtained ;solubility product; of Mg-ACC. The enrichment of Mg in calcite throughout and subsequent to Mg-ACC transformation is likely affected by the high aqueous Mg/Ca ratio and carbonate alkalinity concentrations in the reactive solution. The experimental results have a bearing on the formation mechanism of Mg-rich calcites in marine early diagenetic environments, where high carbonate alkalinity concentrations are the rule rather than the exception, and on the insufficiently investigated inorganic component of biomineralisation pathways in many calcite secreting organisms.

  12. Highly efficient cobalt-doped carbon nitride polymers for solvent-free selective oxidation of cyclohexane

    Directory of Open Access Journals (Sweden)

    Yu Fu

    2017-04-01

    Full Text Available Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer (g-C3N4, was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C3N4 matrix and the characteristic structure of polymeric g-C3N4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet–visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C3N4 matrix as the form of Co(IIN bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C3N4 catalyst due to the synergistic effect of Co species and g-C3N4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C3N4 catalysts, among which the catalyst with 9.0 wt% Co content exhibited the highest yield (9.0% of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C3N4 catalysts was elaborated. Keywords: Selective oxidation of cyclohexane, Oxygen oxidant, Carbon nitride, Co-doping

  13. Electrochemiluminescence of graphitic carbon nitride and its application in ultrasensitive detection of lead(II) ions.

    Science.gov (United States)

    Zhang, Yan; Zhang, Lina; Kong, Qingkun; Ge, Shenguang; Yan, Mei; Yu, Jinghua

    2016-10-01

    Graphitic carbon nitride (g-C3N4) materials with a layered structure have unusual physicochemical properties. Herein it was shown that g-C3N4 quantum dots (QDs) obtained through a thermal-chemical etching route exhibited attractive upconversion and electrochemiluminescence (ECL) properties. After modification on nanoporous gold (NPG) with a sponge-like porous structure, g-C3N4 QDs were employed to fabricate an ECL sensor for the determination of Pb(2+) using target - dependent DNAzyme as the recognition unit. Moreover, magnetic reduced graphene oxide nanosheets (rGO) attached with Fe3O4 nanoparticles (rGO-Fe3O4) were obtained via a one-pot in situ reduction approach, and used as carriers of DNAzyme. To make full use of the unique magnetic property the prepared rGO-Fe3O4, a flow injection ECL detecting cell was designed using indium tin oxide (ITO) glass as working electrode. Due to the unique separation and enrichment properties of magnetic Fe3O4-rGO materials as well as wire-like conductivity of NPG, high sensitivity and selectivity for the determination of Pb(2+) in real water samples were achieved. This indicates that g-C3N4 has excellent anodic ECL performance in the presence of triethanolamine, and could be applied in real environmental samples analyses. Graphical Abstract Graphitic carbon nitride based electrochemiluminescence sensor for the sensitive monitor of lead(II) ions in real samples was constructed.

  14. In situ X-ray diffraction study of solid state transformations during catalytic graphitisation of amorphous carbon

    CERN Document Server

    Krivoruchko, O P; Zaikovskii, V I

    2001-01-01

    Here we report on the results of an in situ X-ray diffraction study of phase transformations during catalytic graphitisation of amorphous carbon. It is demonstrated that there is unusual change of iron catalyst reflection intensity at low temperature approx 640 deg. C. This unusual intensity change may possibly be caused by the transition of some part of metal into liquid state at low temperature. It was also shown by electron microscopy that although no graphite reflections were detected 80-90% of amorphous carbon becomes graphite after sample heating in a high temperature vacuum chamber.

  15. Ab initio studies of vacancies in (8,0) and (8,8) single-walled carbon and boron nitride nanotubes

    CSIR Research Space (South Africa)

    Mashapa, MG

    2012-09-01

    Full Text Available A systematic study of vacancies in single-walled carbon nanotubes and boron nitride nanotubes was carried out. First principles calculations within the framework of density functional theory using the CASTEP code are used to optimize fully...

  16. Nanostructural study of the thermal transformation of diamond-like amorphous carbon into an ultrahard carbon nanocomposite

    International Nuclear Information System (INIS)

    Martinez-Miranda, L. J.; Siegal, M. P.; Provencio, P. P.

    2001-01-01

    We studied the structural transformation of diamond-like amorphous carbon (a-C) films into ultrahard carbon nanocomposites via postannealing to 600 C using transmission electron microscopy, x-ray reflectivity, and small-angle scattering. Film density decreases monotonically above 200 C. Film surfaces roughen upon annealing to 300 C; however, a-C recovers its smoothness with higher temperature annealing. Finally, there exists some quasiperiodic nanostructural feature with a lattice spacing that increases with annealing, correlating well with purely a-C nanocomposite structures imaged from samples annealed at 600 C. We propose that these annealing-induced nanostructural changes are a derivative of localized stress fields in as-grown a-C films

  17. Nanostructural study of the thermal transformation of diamond-like amorphous carbon into an ultrahard carbon nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Miranda, L. J.; Siegal, M. P.; Provencio, P. P.

    2001-07-23

    We studied the structural transformation of diamond-like amorphous carbon (a-C) films into ultrahard carbon nanocomposites via postannealing to 600 C using transmission electron microscopy, x-ray reflectivity, and small-angle scattering. Film density decreases monotonically above 200 C. Film surfaces roughen upon annealing to 300 C; however, a-C recovers its smoothness with higher temperature annealing. Finally, there exists some quasiperiodic nanostructural feature with a lattice spacing that increases with annealing, correlating well with purely a-C nanocomposite structures imaged from samples annealed at 600 C. We propose that these annealing-induced nanostructural changes are a derivative of localized stress fields in as-grown a-C films.

  18. Nanostructural study of the thermal transformation of diamond-like amorphous carbon into an ultrahard carbon nanocomposite

    Science.gov (United States)

    Martínez-Miranda, L. J.; Siegal, M. P.; Provencio, P. P.

    2001-07-01

    We studied the structural transformation of diamond-like amorphous carbon (a-C) films into ultrahard carbon nanocomposites via postannealing to 600 °C using transmission electron microscopy, x-ray reflectivity, and small-angle scattering. Film density decreases monotonically above 200 °C. Film surfaces roughen upon annealing to 300 °C; however, a-C recovers its smoothness with higher temperature annealing. Finally, there exists some quasiperiodic nanostructural feature with a lattice spacing that increases with annealing, correlating well with purely a-C nanocomposite structures imaged from samples annealed at 600 °C. We propose that these annealing-induced nanostructural changes are a derivative of localized stress fields in as-grown a-C films.

  19. Electromagnetic wave absorption properties of composites with micro-sized magnetic particles dispersed in amorphous carbon

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bin Peng [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Tianjin Binhai New Area Finance Bureau, Tianjin 300450 (China); Wang, Cheng Guo, E-mail: sduwangchg@gmail.com [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Wang, Wen [Norinco Group China North Material Science and Engineering Technology Group Corporation, Jinan 250031 (China); Yu, Mei Jie; Gao, Rui; Chen, Yang; Xiang Wang, Yan [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China)

    2014-09-01

    Composites with micro-sized magnetic particles dispersed in amorphous carbon were fabricated conveniently and economically by carbonizing polyacrylonitrile (PAN) fibers mixed with micro-sized iron particles under different temperatures. The composites were characterized by X-ray diffraction (XRD) and scanning electric microscope (SEM). The electromagnetic (EM) properties were measured by a vector network analyzer in the frequency range of 2–18 GHz based on which analog computations of EM wave absorption properties were carried out. The influences of temperature on phase composition and EM wave absorption properties were also investigated, indicating that the composites had good electromagnetic absorption properties with both electrical loss and magnetic loss. Effective reflection loss (RL<−10 dB) was observed in a large frequency range of 7.5–18 GHz with the absorber thickness of 2.0–3.0 mm for the paraffin samples with composite powders heated up to 750 °C and the minimum absorption peak around −40 dB appeared at approximately 10 GHz with matching thickness of 2.0 mm for the paraffin sample with composite powders heated up to 800 °C. - Highlights: • High-performance electromagnetic wave absorption materials were fabricated conveniently and economically. • The materials are composites with micro-sized magnetic particles dispersed in porous amorphous carbon. • The influences of temperature on phase composition and electromagnetic wave absorption properties were investigated. • The composites heated up to 750 °C and 800 °C had good electromagnetic wave absorption property.

  20. Study on effects of carbon impurities and oxygen vacancies in amorphous alumina phosphor prepared via a solution method

    Energy Technology Data Exchange (ETDEWEB)

    Wakui, Yoshinori; Takahashi, Kanako [Department of Material and Environmental Chemistry, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya-shi, Tochigi 321-8585 (Japan); Shan, Yue Jin, E-mail: shan@cc.utsunomiya-u.ac.jp [Department of Material and Environmental Chemistry, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya-shi, Tochigi 321-8585 (Japan); Tezuka, Keitaro; Imoto, Hideo [Department of Material and Environmental Chemistry, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya-shi, Tochigi 321-8585 (Japan); Hosokawa, Shogo; Shinozaki, Norifumi [Tatsumori Ltd., 50 Minami-Kawada, Kami-Yukiai, Tamura-cho, Koriyama-shi, Fukushima 963-0724 (Japan); Ando, Mariko; Maekawa, Hideki [Graduate School of Engineering, Tohoku University, 6-6-04 Aramaki Aoba, Sendai-shi, Miyagi 980-8579 (Japan)

    2015-01-15

    The amorphous alumina phosphors without containing expensive or toxic elements were prepared via a solution method. The obtained sample indicates bluish-white emission centered at 390–430 nm by UV excitation. According to the measurement results of Electron Spin Resonance (ESR), Fourier Transform Infrared Spectroscopy (FT-IR) and organic microanalysis, it is found that the carbon impurities exist in the sample and they are essential for luminescence. On the other hand, {sup 27}Al NMR measurements indicate the presence of Al of 5-coordination. Moreover, there is good correspondence among the excitation spectra of the emission samples, the experimental optical properties of amorphous alumina, and the calculated oxygen vacancies levels in amorphous alumina model. Therefore, the new luminescence mechanism can be proposed as follows; the electrons in valence band are excited to oxygen vacancies bands by UV light and return to ground state through the carbon impurities band, being accompanied by the bluish-white emission. - Highlights: • The amorphous alumina prepared via solution method shows bluish-white emission. • According to the ESR results, carbon impurities are necessary for luminescence. • FT-IR, NMR and UV–vis measurements of the samples were conducted. • Our results indicated that oxygen vacancies play an important role. • We proposed the new luminescence mechanism for amorphous alumina phosphor.

  1. Study of CVD diamond layers with amorphous carbon admixture by Raman scattering spectroscopy

    Directory of Open Access Journals (Sweden)

    Dychalska Anna

    2015-12-01

    Full Text Available Raman spectroscopy is a most often used standard technique for characterization of different carbon materials. In this work we present the Raman spectra of polycrystalline diamond layers of different quality, synthesized by Hot Filament Chemical Vapor Deposition method (HF CVD. We show how to use Raman spectroscopy for the analysis of the Raman bands to determine the structure of diamond films as well as the structure of amorphous carbon admixture. Raman spectroscopy has become an important technique for the analysis of CVD diamond films. The first-order diamond Raman peak at ca. 1332 cm−1 is an unambiguous evidence for the presence of diamond phase in the deposited layer. However, the existence of non-diamond carbon components in a CVD diamond layer produces several overlapping peaks in the same wavenumber region as the first order diamond peak. The intensities, wavenumber, full width at half maximum (FWHM of these bands are dependent on quality of diamond layer which is dependent on the deposition conditions. The aim of the present work is to relate the features of diamond Raman spectra to the features of Raman spectra of non-diamond phase admixture and occurrence of other carbon structures in the obtained diamond thin films.

  2. Coupled dissolution-precipitation as a mechanism for amorphous-to-crystalline calcium carbonate phase transition

    Science.gov (United States)

    Rodriguez-Navarro, Carlos Manuel; Kudłacz, Krzysztof; Ruiz-Agudo, Encarnacion

    2014-05-01

    Growing evidence shows that several calcium carbonate biominerals form via an amorphous precursor phase. Such a biomineralization strategy could also be applicable for the biomimetic synthesis of novel functional materials. A crucial step in this process is the transformation of amorphous calcium carbonate (ACC) into calcite. However, controversy exists as to what is the actual mechanism of this transformation: Is it a solid-solid (solid state) or a dissolution/precipitation mechanism? Determining the transition mechanism is critical for example in interpreting the formation of oriented crystalline structures in biominerals (e.g., echinoderm spicles). We studied calcium carbonate precipitation and phase transitions according to the overall reaction Ca(OH)2 + CO2 = CaCO3+ H2O. Mineral phase transformations during this reaction were studied using transmission electron microscopy (TEM). Our TEM analysis showed that two different types of ACC are sequentially formed during this reaction. Type I ACC shows no well-defined short-range order, while Type II ACC shows a short-range order corresponding to calcite. Following e-beam irradiation, Type I ACC particles transform into randomly oriented CaO nanocrystals, while irradiation of Type II ACC leads to the formation of pseudomorphs made up of perfectly oriented aggregates of calcite nanocrystals. Moreover, calcite crystals formed in solution or in air (85 % relative humidity) after Type II ACC are also pseudomorphs made up of porous aggregates of preferentially oriented calcite nanocrystals. Our results give experimental evidence showing that the ACC to calcite transformation under relevant biomineralization conditions (low T and P), also applicable in the biomimetic synthesis of calcite, is a pseudomorphic dissolution-precipitation process. This mechanism involves the tightly interface-coupled dissolution of the precursor amorphous phase (with the crystalline phase protostructure) and concomitant deposition of the

  3. Correlation between substrate bias, growth process and structural properties of phosphorus incorporated tetrahedral amorphous carbon films

    International Nuclear Information System (INIS)

    Liu Aiping; Zhu Jiaqi; Han Jiecai; Wu Huaping; Jia Zechun

    2007-01-01

    We investigate the growth process and structural properties of phosphorus incorporated tetrahedral amorphous carbon (ta-C:P) films which are deposited at different substrate biases by filtered cathodic vacuum arc technique with PH 3 as the dopant source. The films are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, Raman spectroscopy, residual stress measurement, UV/VIS/NIR absorption spectroscopy and temperature-dependent conductivity measurement. The atomic fraction of phosphorus in the films as a function of substrate bias is obtained by XPS analysis. The optimum bias for phosphorus incorporation is about -80 V. Raman spectra show that the amorphous structures of all samples with atomic-scaled smooth surface are not remarkably changed when PH 3 is implanted, but some small graphitic crystallites are formed. Moreover, phosphorus impurities and higher-energetic impinging ions are favorable for the clustering of sp 2 sites dispersed in sp 3 skeleton and increase the level of structural ordering for ta-C:P films, which further releases the compressive stress and enhances the conductivity of the films. Our analysis establishes an interrelationship between microstructure, stress state, electrical properties, and substrate bias, which helps to understand the deposition mechanism of ta-C:P films

  4. Highly ordered amorphous silicon-carbon alloys obtained by RF PECVD

    CERN Document Server

    Pereyra, I; Carreno, M N P; Prado, R J; Fantini, M C A

    2000-01-01

    We have shown that close to stoichiometry RF PECVD amorphous silicon carbon alloys deposited under silane starving plasma conditions exhibit a tendency towards c-Si C chemical order. Motivated by this trend, we further explore the effect of increasing RF power and H sub 2 dilution of the gaseous mixtures, aiming to obtain the amorphous counterpart of c-Si C by the RF-PECVD technique. Doping experiments were also performed on ordered material using phosphorus and nitrogen as donor impurities and boron and aluminum as acceptor ones. For nitrogen a doping efficiency close to device quality a-Si:H was obtained, the lower activation energy being 0,12 eV with room temperature dark conductivity of 2.10 sup - sup 3 (OMEGA.cm). Nitrogen doping efficiency was higher than phosphorous for all studied samples. For p-type doping, results indicate that, even though the attained conductivity values are not device levels, aluminum doping conducted to a promising shift in the Fermi level. Also, aluminum resulted a more efficie...

  5. Transformation and Crystallization Energetics of Synthetic and Biogenic Amorphous Calcium Carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Radha, A. V. [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States); Forbes, Tori Z. [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States); Killian, Christopher E. [Univ. of Wisconsin, Madison, WI (United States); Gilbert, P.U.P.A [Univ. of Wisconsin, Madison, WI (United States); Navrotsky, Alexandra [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States)

    2010-01-01

    Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC→anhydrous ACC ~ biogenic anhydrous ACC→vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO₂ sequestration.

  6. Visible light photoreactivity from hybridization states between carbon nitride bandgap states and valence states in Nb and Ti oxides

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hosik, E-mail: hosiklee@gmail.com [School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology (UNIST), Unist-gil 100 Eonyang-eup, Ulsan 689-798 (Korea, Republic of); Ohno, Takahisa, E-mail: OHNO.Takahisa@nims.go.jp [Global Research Center for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Material Science, 1-2-1 Sengen, Tsukuba (Japan); Computational Materials Science Unit (CMSU), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0047 (Japan)

    2013-03-29

    Highlights: ► Origin of bandgap reduction for visible photoreactivity is suggested. ► Carbon nitride adsorption in interlayer space can induce the bandgap reduction. ► The electronic structures are studied by density functional theory calculations. - Abstract: For better efficiency as photocatalysts, N-doping for visible light reactivity has been intensively studied in Lamellar niobic and titanic solid acids (HNb{sub 3}O{sub 8}, H{sub 2}Ti{sub 4}O{sub 9}), and its microscopic structures have been debated in this decade. We calculate the layered solid acids’ structures and bandgaps. Bandgap reduction by carbon nitride adsorption in interlayer space is observed computationally. It originates from localized nitrogen states which form delocalized top-valence states by hybridizing with the host oxygen states and can contribute to photo-current.

  7. Metal-functionalized single-walled graphitic carbon nitride nanotubes: a first-principles study on magnetic property

    Science.gov (United States)

    2011-01-01

    The magnetic properties of metal-functionalized graphitic carbon nitride nanotubes were investigated based on first-principles calculations. The graphitic carbon nitride nanotube can be either ferromagnetic or antiferromagnetic by functionalizing with different metal atoms. The W- and Ti-functionalized nanotubes are ferromagnetic, which are attributed to carrier-mediated interactions because of the coupling between the spin-polarized d and p electrons and the formation of the impurity bands close to the band edges. However, Cr-, Mn-, Co-, and Ni-functionalized nanotubes are antiferromagnetic because of the anti-alignment of the magnetic moments between neighboring metal atoms. The functionalized nanotubes may be used in spintronics and hydrogen storage. PMID:21711614

  8. Metal-functionalized single-walled graphitic carbon nitride nanotubes: a first-principles study on magnetic property

    Directory of Open Access Journals (Sweden)

    Shenoy Vivek

    2011-01-01

    Full Text Available Abstract The magnetic properties of metal-functionalized graphitic carbon nitride nanotubes were investigated based on first-principles calculations. The graphitic carbon nitride nanotube can be either ferromagnetic or antiferromagnetic by functionalizing with different metal atoms. The W- and Ti-functionalized nanotubes are ferromagnetic, which are attributed to carrier-mediated interactions because of the coupling between the spin-polarized d and p electrons and the formation of the impurity bands close to the band edges. However, Cr-, Mn-, Co-, and Ni-functionalized nanotubes are antiferromagnetic because of the anti-alignment of the magnetic moments between neighboring metal atoms. The functionalized nanotubes may be used in spintronics and hydrogen storage.

  9. Tunable hole injection of solution-processed polymeric carbon nitride towards efficient organic light-emitting diode

    Science.gov (United States)

    Zhang, Xiaowen; Zheng, Qinghong; Tang, Zhenyu; Li, Wanshu; Zhang, Yan; Xu, Kai; Xue, Xiaogang; Xu, Jiwen; Wang, Hua; Wei, Bin

    2018-02-01

    Polymeric carbon nitride (CNxHy) has been facilely synthesized from dicyandiamide and functions as a solution-processed hole injection layer in organic light-emitting diodes (OLEDs). The measurements using X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and impedance spectroscopy elucidate that CNxHy exhibits superior film morphology and extra electric properties such as tailored work function and tunable hole injection. The luminous efficiency of CNxHy-based OLED is found to improve by 76.6% in comparison to the counterpart using favorite solution-processed poly(ethylene dioxythiophene):poly(styrene sulfonate) as the hole injection layer. Our results also pave a way for broadening carbon nitride applications in organic electronics using the solution process.

  10. A Low-Stress, Elastic, and Improved Hardness Hydrogenated Amorphous Carbon Film

    Directory of Open Access Journals (Sweden)

    Qi Wang

    2015-01-01

    Full Text Available The evolution of hydrogenated amorphous carbon films with fullerene-like microstructure was investigated with a different proportion of hydrogen supply in deposition. The results showed at hydrogen flow rate of 50 sccm, the deposited films showed a lower compressive stress (lower 48.6%, higher elastic recovery (higher 19.6%, near elastic recovery rate 90%, and higher hardness (higher 7.4% compared with the films deposited without hydrogen introduction. Structural analysis showed that the films with relatively high sp2 content and low bonded hydrogen content possessed high hardness, elastic recovery rate, and low compressive stress. It was attributed to the curved graphite microstructure, which can form three-dimensional covalently bonded network.

  11. Amorphous carbon film growth on Si: Correlation between stress and generation of defects into the substrate

    International Nuclear Information System (INIS)

    Brusa, R.S.; Macchi, C.; Mariazzi, S.; Karwasz, G.P.; Laidani, N.; Bartali, R.; Anderle, M.

    2005-01-01

    Amorphous carbon films of several thicknesses were prepared by graphite sputtering on crystalline silicon substrate. The samples were depth profiled with positron annihilation spectroscopy for open-volume measurements and characterized for their residual internal stress. It was found that after film growth the substrate presents vacancy-like defects decorated by oxygen in a layer extending in the substrate by several tens of nanometers beyond the film/Si interface. The width of the defected layer and the decoration of vacancy-like defects are directly and inversely proportional to the measured intensity of the residual stress, respectively. These findings indicate the existence of a relaxation mechanism of the stress in the films that involves deeply the substrate. The decorated vacancy-like defects are suggested to be bounded to dislocations induced in the substrate by the stress relaxation

  12. Low-emissivity coating of amorphous diamond-like carbon/Ag-alloy multilayer on glass

    International Nuclear Information System (INIS)

    Chiba, Kiyoshi; Takahashi, Toshiyuki; Kageyama, Takashi; Oda, Hironori

    2005-01-01

    Transparent low-emissivity (low-e) coatings comprising dielectrics of amorphous diamond-like carbon (DLC) and Ag-alloy films are investigated. All films have been prepared by dc magnetron sputtering. An index of refraction of the DLC film deposited in a gas mixture of Ar/H 2 (4%) shows n = 1.80 + 0.047i at 500 nm wavelength. A multilayer stack of DLC (70 nm thick)/Ag 87.5 Cu 12.5 -alloy (10 nm)/DLC (140 nm)/Ag 87.5 Cu 12.5 -alloy (10 nm)/DLC (70 nm) has revealed clear interference spectra with spectra selectivity. This coating performs low emittance less than 0.1 for black body radiation at 297 K, exhibiting a transparent heat mirror property embedded in DLC films

  13. Field Emission and Radial Distribution Function Studies of Fractal-like Amorphous Carbon Nanotips

    Directory of Open Access Journals (Sweden)

    Lebrón-Colón M

    2009-01-01

    Full Text Available Abstract The short-range order of individual fractal-like amorphous carbon nanotips was investigated by means of energy-filtered electron diffraction in a transmission electron microscope (TEM. The nanostructures were grown in porous silicon substrates in situ within the TEM by the electron beam-induced deposition method. The structure factorS(k and the reduced radial distribution functionG(r were calculated. From these calculations a bond angle of 124° was obtained which suggests a distorted graphitic structure. Field emission was obtained from individual nanostructures using two micromanipulators with sub-nanometer positioning resolution. A theoretical three-stage model that accounts for the geometry of the nanostructures provides a value for the field enhancement factor close to the one obtained experimentally from the Fowler-Nordheim law.

  14. Effect of tetrahedral amorphous carbon coating on the resistivity and wear of single-walled carbon nanotube network

    Energy Technology Data Exchange (ETDEWEB)

    Iyer, Ajai, E-mail: ajai.iyer@aalto.fi; Etula, Jarkko; Liu, Xuwen; Koskinen, Jari [Department of Materials Science and Engineering, School of Chemical Technology, Aalto University, P.O. Box 16200, 00076 Espoo (Finland); Kaskela, Antti; Kauppinen, Esko I. [NanoMaterials Group, Department of Applied Physics, School of Science, Aalto University, P.O. Box 15100, 00076 Espoo (Finland); Novikov, Serguei [Department of Micro and Nanosciences, Aalto University, P.O. Box 13500, 00076 Aalto (Finland)

    2016-05-14

    Single walled carbon nanotube networks (SWCNTNs) were coated by tetrahedral amorphous carbon (ta-C) to improve the mechanical wear properties of the composite film. The ta-C deposition was performed by using pulsed filtered cathodic vacuum arc method resulting in the generation of C+ ions in the energy range of 40–60 eV which coalesce to form a ta-C film. The primary disadvantage of this process is a significant increase in the electrical resistance of the SWCNTN post coating. The increase in the SWCNTN resistance is attributed primarily to the intrinsic stress of the ta-C coating which affects the inter-bundle junction resistance between the SWCNTN bundles. E-beam evaporated carbon was deposited on the SWCNTNs prior to the ta-C deposition in order to protect the SWCNTN from the intrinsic stress of the ta-C film. The causes of changes in electrical resistance and the effect of evaporated carbon thickness on the changes in electrical resistance and mechanical wear properties have been studied.

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

    DEFF Research Database (Denmark)

    Zhang, Caihong; Zhang, Wei; Wang, Dong

    2017-01-01

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

  16. Interdispersed amorphous MnO{sub x}-carbon nanocomposites with superior electrochemical performance as lithium-storage material

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Juchen; Wang, Chunsheng [Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD (United States); Liu, Qing; Zachariah, Michael R. [Department of Chemistry and Biochemistry, University of Maryland, College Park, MD (United States)

    2012-02-22

    The realization of manganese oxide anode materials for lithium-ion batteries is hindered by inferior cycle stability, rate capability, and high overpotential induced by the agglomeration of manganese metal grains, low conductivity of manganese oxide, and the high stress/strain in the crystalline manganese oxide structure during the repeated lithiation/delithiation process. To overcome these challenges, unique amorphous MnO{sub x}-C nanocomposite particles with interdispersed carbon are synthesized using aerosol spray pyrolysis. The carbon filled in the pores of amorphous MnO{sub x} blocks the penetration of liquid electrolyte to the inside of MnO{sub x}, thus reducing the formation of a solid electrolyte interphase and lowering the irreversible capacity. The high electronic and lithium-ion conductivity of carbon also enhances the rate capability. Moreover, the interdispersed carbon functions as a barrier structure to prevent manganese grain agglomeration. The amorphous structure of MnO{sub x} brings additional benefits by reducing the stress/strain of the conversion reaction, thus lowering lithiation/delithiation overpotential. As the result, the amorphous MnO{sub x}-C particles demonstrated the best performance as an anode material for lithium-ion batteries to date. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Nano-solenoid: helicoid carbon-boron nitride hetero-nanotube.

    Science.gov (United States)

    Zhang, Zi-Yue; Miao, Chunyang; Guo, Wanlin

    2013-12-07

    As a fundamental element of a nanoscale passive circuit, a nano-inductor is proposed based on a hetero-nanotube consisting of a spiral carbon strip and a spiral boron nitride strip. It is shown by density functional theory associated with nonequilibrium Green function calculations that the nanotube exhibits attractive transport properties tunable by tube chirality, diameter, component proportion and connection manner between the two strips, with excellent 'OFF' state performance and high current on the order of 10-100 μA. All the hetero-nanotubes show negative differential resistance. The transmission peaks of current are absolutely derived from the helicoid carbon strips or C-BN boundaries, giving rise to a spiral current analogous with an energized nano-solenoid. According to Ampere's Law, the energized nano-solenoid can generate a uniform and tremendous magnetic field of more than 1 tesla, closing to that generated by the main magnet of medical nuclear magnetic resonance. Moreover, the magnitude of magnetic field can be easily modulated by bias voltage, providing great promise for a nano-inductor to realize electromagnetic conversion at the nanoscale.

  18. Nitrogen-Deficient Graphitic Carbon Nitride with Enhanced Performance for Lithium Ion Battery Anodes.

    Science.gov (United States)

    Chen, Jingjing; Mao, Zhiyong; Zhang, Lexi; Wang, Dajian; Xu, Ran; Bie, Lijian; Fahlman, Bradley D

    2017-12-26

    Graphitic carbon nitride (g-C 3 N 4 ) behaving as a layered feature with graphite was indexed as a high-content nitrogen-doping carbon material, attracting increasing attention for application in energy storage devices. However, poor conductivity and resulting serious irreversible capacity loss were pronounced for g-C 3 N 4 material due to its high nitrogen content. In this work, magnesiothermic denitriding technology is demonstrated to reduce the nitrogen content of g-C 3 N 4 (especially graphitic nitrogen) for enhanced lithium storage properties as lithium ion battery anodes. The obtained nitrogen-deficient g-C 3 N 4 (ND-g-C 3 N 4 ) exhibits a thinner and more porous structure composed of an abundance of relatively low nitrogen doping wrinkled graphene nanosheets. A highly reversible lithium storage capacity of 2753 mAh/g was obtained after the 300th cycle with an enhanced cycling stability and rate capability. The presented nitrogen-deficient g-C 3 N 4 with outstanding electrochemical performances may unambiguously promote the application of g-C 3 N 4 materials in energy-storage devices.

  19. Visible-Light-Responsive Graphitic Carbon Nitride: Rational Design and Photocatalytic Applications for Water Treatment.

    Science.gov (United States)

    Zheng, Qinmin; Durkin, David P; Elenewski, Justin E; Sun, Yingxue; Banek, Nathan A; Hua, Likun; Chen, Hanning; Wagner, Michael J; Zhang, Wen; Shuai, Danmeng

    2016-12-06

    Graphitic carbon nitride (g-C 3 N 4 ) has recently emerged as a promising visible-light-responsive polymeric photocatalyst; however, a molecular-level understanding of material properties and its application for water purification were underexplored. In this study, we rationally designed nonmetal doped, supramolecule-based g-C 3 N 4 with improved surface area and charge separation. Density functional theory (DFT) simulations indicated that carbon-doped g-C 3 N 4 showed a thermodynamically stable structure, promoted charge separation, and had suitable energy levels of conduction and valence bands for photocatalytic oxidation compared to phosphorus-doped g-C 3 N 4 . The optimized carbon-doped, supramolecule-based g-C 3 N 4 showed a reaction rate enhancement of 2.3-10.5-fold for the degradation of phenol and persistent organic micropollutants compared to that of conventional, melamine-based g-C 3 N 4 in a model buffer system under the irradiation of simulated visible sunlight. Carbon-doping but not phosphorus-doping improved reactivity for contaminant degradation in agreement with DFT simulation results. Selective contaminant degradation was observed on g-C 3 N 4 , likely due to differences in reactive oxygen species production and/or contaminant-photocatalyst interfacial interactions on different g-C 3 N 4 samples. Moreover, g-C 3 N 4 is a robust photocatalyst for contaminant degradation in raw natural water and (partially) treated water and wastewater. In summary, DFT simulations are a viable tool to predict photocatalyst properties and oxidation performance for contaminant removal, and they guide the rational design, fabrication, and implementation of visible-light-responsive g-C 3 N 4 for efficient, robust, and sustainable water treatment.

  20. The thermal conductivity of embedded nano-aluminum nitride-doped multi-walled carbon nanotubes in epoxy composites containing micro-aluminum nitride particles.

    Science.gov (United States)

    Choi, Seran; Im, Hyungu; Kim, Jooheon

    2012-02-17

    Amino-functionalized nano-aluminum nitride (nano-AlN) particles were doped onto the surfaces of chlorinated multi-walled carbon nanotubes (MWCNTs) to act as fillers in thermally conducting composites. These synthesized materials were embedded in epoxy resin. Then, the untreated micro-aluminum nitride (micro-AlN) particles were added to this resin, whereby the composites filled with nano-AlN-doped MWCNTs (0, 0.5, 1, 1.5, 2 wt%) and micro-AlN (25.2, 44.1, 57.4 vol%) were fabricated. As a result, the thermal diffusivity and conductivity of all composites continuously improved with increasing nano-AlN-doped MWCNT content and micro-AlN filler loading. The thermal conductivity reached its maximum, which was 31.27 times that of the epoxy alone, when 2 wt% nano-AlN-doped MWCNTs and 57.4 vol% micro-AlN were added to the epoxy resin. This result is due to the high aspect ratio of the MWCNTs and the surface polarity of the doped nano-AlN and micro-AlN particles, resulting in the improved thermal properties of the epoxy composite.

  1. The thermal conductivity of embedded nano-aluminum nitride-doped multi-walled carbon nanotubes in epoxy composites containing micro-aluminum nitride particles

    International Nuclear Information System (INIS)

    Choi, Seran; Im, Hyungu; Kim, Jooheon

    2012-01-01

    Amino-functionalized nano-aluminum nitride (nano-AlN) particles were doped onto the surfaces of chlorinated multi-walled carbon nanotubes (MWCNTs) to act as fillers in thermally conducting composites. These synthesized materials were embedded in epoxy resin. Then, the untreated micro-aluminum nitride (micro-AlN) particles were added to this resin, whereby the composites filled with nano-AlN-doped MWCNTs (0, 0.5, 1, 1.5, 2 wt%) and micro-AlN (25.2, 44.1, 57.4 vol%) were fabricated. As a result, the thermal diffusivity and conductivity of all composites continuously improved with increasing nano-AlN-doped MWCNT content and micro-AlN filler loading. The thermal conductivity reached its maximum, which was 31.27 times that of the epoxy alone, when 2 wt% nano-AlN-doped MWCNTs and 57.4 vol% micro-AlN were added to the epoxy resin. This result is due to the high aspect ratio of the MWCNTs and the surface polarity of the doped nano-AlN and micro-AlN particles, resulting in the improved thermal properties of the epoxy composite. (paper)

  2. Polymeric Graphitic Carbon Nitride Doped with CuO Dispersed on Dealuminated Clinoptilolite (CuO/HCP): Synthesis and Characterisation

    OpenAIRE

    Sanni, Saheed Olalekan; Idemudia, Omoruyi Gold

    2015-01-01

    CuO dispersed on dealuminated clinoptilolite (CuO/HCP) and further doped with polymeric graphitic carbon nitride (CuO/HCP-g-C3N4) was synthesized through 2 facile routes: precipitation method for CuO/HCP and impregnation through ultrasonication method for the hybrid composite material. The hybrid composite material crystalline phase, surface morphology, and structural and thermal properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-r...

  3. Solar hydrogen evolution using metal-free photocatalytic polymeric carbon nitride/CuInS2 composites as photocathodes

    OpenAIRE

    Yang, Florent; Kuznietsov, Vadym; Lublow, Michael; Merschjann, Christoph; Steigert, Alexander; Klaer, Joachim; Thomas, Arne; Schedel-Niedrig, Thomas

    2013-01-01

    Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich. This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively. Polymeric carbon nitride (g-C3N4) films were synthesized on polycrystalline semiconductor CuInS2 chalcopyrite thin film electrodes by thermal polycondensation and were inves...

  4. Characterization and antibacterial performance of ZrCN/amorphous carbon coatings deposited on titanium implants

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Chih-Ho [School of Medicine, China Medical University, Taichung, 404 Taiwan (China); Chang, Yin-Yu, E-mail: yinyu@mail2000.com.tw [Department of Mechanical and Computer-Aided Engineering, National Formosa University, Yunlin, Taiwan (China); Huang, Heng-Li [School of Dentistry, China Medical University, Taichung, Taiwan (China); Kao, Ho-Yi [Department of Materials Science and Engineering, Mingdao University, Changhua, Taiwan (China)

    2011-12-30

    Titanium (Ti)-based materials have been used for dental/orthopedic implants due to their excellent biological compatibility, superior mechanical strength and high corrosion resistance. The osseointegration of Ti implants is related to their composition and surface treatment. Better biocompatibility and anti-bacterial performances of Ti implant are beneficial for the osseointegration and for avoiding the infection after implantation surgery. In this study, nanocomposite ZrCN/amorphous carbon (a-C) coatings with different carbon contents were deposited on a bio-grade pure Ti implant material. A cathodic-arc evaporation system with plasma enhanced duct equipment was used for the deposition of ZrCN/a-C coatings. Reactive gas (N{sub 2}) and C{sub 2}H{sub 2} activated by the zirconium plasma in the evaporation process were used to deposit the ZrCN/a-C coatings. To verify the susceptibility of implant surface to bacterial adhesion, Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans), one of the major pathogen frequently found in the dental implant-associated infections, was chosen for in vitro anti-bacterial analyses. In addition, the biocompatibility of human gingival fibroblast (HGF) cells on coatings was also evaluated by a cell proliferation assay. The results suggested that the ZrCN/a-C coatings with carbon content higher than 12.7 at.% can improve antibacterial performance with excellent HGF cell compatibility as well.

  5. Characterization and antibacterial performance of ZrCN/amorphous carbon coatings deposited on titanium implants

    International Nuclear Information System (INIS)

    Lai, Chih-Ho; Chang, Yin-Yu; Huang, Heng-Li; Kao, Ho-Yi

    2011-01-01

    Titanium (Ti)-based materials have been used for dental/orthopedic implants due to their excellent biological compatibility, superior mechanical strength and high corrosion resistance. The osseointegration of Ti implants is related to their composition and surface treatment. Better biocompatibility and anti-bacterial performances of Ti implant are beneficial for the osseointegration and for avoiding the infection after implantation surgery. In this study, nanocomposite ZrCN/amorphous carbon (a-C) coatings with different carbon contents were deposited on a bio-grade pure Ti implant material. A cathodic-arc evaporation system with plasma enhanced duct equipment was used for the deposition of ZrCN/a-C coatings. Reactive gas (N 2 ) and C 2 H 2 activated by the zirconium plasma in the evaporation process were used to deposit the ZrCN/a-C coatings. To verify the susceptibility of implant surface to bacterial adhesion, Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans), one of the major pathogen frequently found in the dental implant-associated infections, was chosen for in vitro anti-bacterial analyses. In addition, the biocompatibility of human gingival fibroblast (HGF) cells on coatings was also evaluated by a cell proliferation assay. The results suggested that the ZrCN/a-C coatings with carbon content higher than 12.7 at.% can improve antibacterial performance with excellent HGF cell compatibility as well.

  6. Spectroscopic properties of nitrogen doped hydrogenated amorphous carbon films grown by radio frequency plasma-enhanced chemical vapor deposition

    OpenAIRE

    Y., Hayashi; G., Yu; M. M., Rahman; K. M., Krishna; Tetsuo, Soga; Takashi, Jimbo; Masayoshi, Umeno

    2001-01-01

    Nitrogen doped hydrogenated amorphous carbon thin films have been deposited by rf plasma-enhanced chemical vapor deposition using CH4 as the source of carbon and with different nitrogen flow rates (N2/CH4 gas ratios between 0 and 3), at 300 K. The dependence modifications of the optical and the structural properties on nitrogen incorporation were investigated using different spectroscopic techniques, such as, Raman spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spe...

  7. Carbon Nitride Decorated Ball-Flower like Co3O4 Hybrid Composite: Hydrothermal Synthesis and Ethanol Gas Sensing Application

    Directory of Open Access Journals (Sweden)

    Yuxiao Gong

    2018-02-01

    Full Text Available Recently, semiconducting metal oxide (SMO gas sensors have attracted the attention of researchers for high conductivity, labile features by environment, low cost, easy preparation, etc. However, traditional SMOs have some defects such as higher operating temperature and lower response value, which greatly limit their application in the field of gas sensor. In this work, the carbon nitride decorated ball-flower like Co3O4 composite was successfully synthesized via a facile hydrothermal method, the composition and morphology of the as-synthesized samples were studied by the techniques of X-ray powder diffraction (XRD, Field-emission scanning electron microscopy (FESEM, Transmission electron microscopy (TEM, Fourier transform infrared spectrometer (FT-IR and N2-sorption. As a consequence, the pure Co3O4 and the carbon nitride decorated Co3O4 both possess ball-flower like structure, and the as-synthesized carbon nitride decorated Co3O4 composite exhibits significant sensing properties to ethanol which is 1.6 times higher than that of pure Co3O4, furthermore, the composite possesses high selectivity and stability towards ethanol detection.

  8. Hollow mesoporous carbon nitride nanosphere/three-dimensional graphene composite as high efficient electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Qin, Yong; Li, Juan; Yuan, Jie; Kong, Yong; Tao, Yongxin; Lin, Furong; Li, Shan

    2014-12-01

    Hollow mesoporous carbon nitride nanosphere (HMCN) is firstly prepared via an etching route using hollow mesoporous silica as a sacrificial template. The as-obtained HMCN is a uniform spherical particle with a diameter of ∼300 nm,and possesses a high specific surface area up to 439 m2 g-1. Hollow mesoporous carbon nitride nanosphere/three-dimensional (3D) graphene composite (HMCN-G) is subsequently fabricated via a hydrothermal treatment of HMCN with graphene oxide. As an electrocatalyst for oxygen reduction reaction (ORR), the HMCN-G shows significantly enhanced electrocatalytic activity compared to bulk graphitic carbon nitride (g-C3N4) and HMCN in terms of the electron-transfer number, current density and onset potential. Increased density of catalytically active sites and improved accessibility to electrolyte enabled by the hollow and mesoporous architecture of HMCN, and high conductivity induced from graphene are considered to contribute to the remarkable electrocatalytic performance of the HMCN-G. Furthermore, HMCN-G exhibits superior methanol tolerance to Pt/C catalyst, suggesting that it is a promising metal-free electrocatalyst for polymer electrolyte membrane fuel cell (PEMFC).

  9. Nickel-supported carbon nitride photocatalyst combined with organic dye for visible-light-driven hydrogen evolution from water.

    Science.gov (United States)

    Mori, Kohsuke; Itoh, Taiki; Kakudo, Hiroki; Iwamoto, Tomoyuki; Masui, Yoichi; Onaka, Makoto; Yamashita, Hiromi

    2015-10-07

    A noble-metal-free photocatalytic H2 production system consisting of a Ni-based catalyst, visible-light-responsive organic dye, and graphitic carbon nitride (g-C3N4) as a support has been developed. Characterization by means of XAFS revealed that the deposition of a trinuclear Ni precursor complex, Ni(NiL2)2Cl2 (L = β-mercaptoethylamine), on the g-C3N4 affords a monomeric Ni(ii) species involving β-mercaptoethylamine and aqua ligands in an octahedral coordination geometry. Such a Ni species acts as a hydrogen production site from an aqueous solution without an electron relay reagent by combining with thiazole orange (TO) as a photosensitizer. The emission of the attached TO at around 550 nm decreases with increasing loading amount of Ni catalyst, suggesting electron transfer from TO to the Ni catalyst via the g-C3N4 support. Leaching and agglomeration of the active Ni catalyst and TO are not observed during the photocatalytic reaction. Moreover, the use of highly porous carbon nitride (nanoporous carbon nitride; nanoC3N4) is proven to significantly enhance the photocatalytic activity because of the high surface area due to the unique porous structure as well as high absorption and emission properties of TO associated with nanoC3N4.

  10. Nanocomposite metal amorphous-carbon thin films deposited by hybrid PVD and PECVD technique.

    Science.gov (United States)

    Teixeira, V; Soares, P; Martins, A J; Carneiro, J; Cerqueira, F

    2009-07-01

    Carbon based films can combine the properties of solid lubricating graphite structure and hard diamond crystal structure, i.e., high hardness, chemical inertness, high thermal conductivity and optical transparency without the crystalline structure of diamond. Issues of fundamental importance associated with nanocarbon coatings are reducing stress, improving adhesion and compatibility with substrates. In this work new nanocomposite coatings with improved toughness based in nanocrystalline phases of metals and ceramics embedded in amorphous carbon matrix are being developed within the frame of a research project: nc-MeNxCy/a-C(Me) with Me = Mo, Si, Al, Ti, etc. Carbide forming metal/carbon (Me/C) composite films with Me = Mo, W or Ti possess appropriate properties to overcome the limitation of pure DLC films. These novel coating architectures will be adopted with the objective to decrease residual stress, improve adherence and fracture toughness, obtain low friction coefficient and high wear-resistance. Nanocomposite DLC's films were deposited by hybrid technique using a PVD-Physically Vapor Deposition (magnetron sputtering) and Plasma Enhanced Chemical Vapor Deposition (PECVD), by the use of CH4 gas. The parameters varied were: deposition time, substrate temperature (180 degrees C) and dopant (Si + Mo) of the amorphous carbon matrix. All the depositions were made on silicon wafers and steel substrates precoated with a silicon inter-layer. The characterisation of the film's physico-mechanical properties will be presented in order to understand the influence of the deposition parameters and metal content used within the a-C matrix in the thin film properties. Film microstructure and film hybridization state was characterized by Raman Spectroscopy. In order to characterize morphology SEM and AFM will be used. Film composition was measured by Energy-Dispersive X-ray analysis (EDS) and by X-ray photoelectron spectroscopy (XPS). The contact angle for the produced DLC's on

  11. Carbon nanodot decorated graphitic carbon nitride: new insights into the enhanced photocatalytic water splitting from ab initio studies.

    Science.gov (United States)

    Gao, Guoping; Jiao, Yan; Ma, Fengxian; Jiao, Yalong; Waclawik, Eric; Du, Aijun

    2015-12-14

    Interfacing carbon nanodots (C-dots) with graphitic carbon nitride (g-C3N4) produces a metal-free system that has recently demonstrated significant enhancement of photo-catalytic performance for water splitting into hydrogen [Science, 2015, 347, 970-974]. However, the underlying photo-catalytic mechanism is not fully established. Herein, we have carried out density functional theory (DFT) calculations to study the interactions between g-C3N4 and trigonal/hexagonal shaped C-dots. We find that hybrid C-dots/g-C3N4 can form a type-II van der Waals heterojunction, leading to significant reduction of band gap. The C-dot decorated g-C3N4 enhances the separation of photogenerated electron and hole pairs and the composite's visible light response. Interestingly, the band alignment of C-dots and g-C3N4 calculated by the hybrid functional method indicates that C-dots act as a spectral sensitizer in hybrid C-dots/g-C3N4 for water splitting. Our results offer new theoretical insights into this metal-free photocatalyst for water splitting.

  12. Phototransformation-Induced Aggregation of Functionalized Single-Walled Carbon Nanotubes: The Importance of Amorphous Carbon

    Science.gov (United States)

    Single-walled carbon nanotubes (SWCNTs) with proper functionalization are desirable for applications that require dispersion in aqueous and biological environments, and functionalized SWCNTs also serve as building blocks for conjugation with specific molecules in these applicatio...

  13. Nanodiamonds on tetrahedral amorphous carbon significantly enhance dopamine detection and cell viability.

    Science.gov (United States)

    Peltola, Emilia; Wester, Niklas; Holt, Katherine B; Johansson, Leena-Sisko; Koskinen, Jari; Myllymäki, Vesa; Laurila, Tomi

    2017-02-15

    We hypothesize that by using integrated carbon nanostructures on tetrahedral amorphous carbon (ta-C), it is possible to take the performance and characteristics of these bioelectrodes to a completely new level. The integrated carbon electrodes were realized by combining nanodiamonds (NDs) with ta-C thin films coated on Ti-coated Si-substrates. NDs were functionalized with mixture of carboxyl and amine groups ND andante or amine ND amine , carboxyl ND vox or hydroxyl groups ND H and drop-casted or spray-coated onto substrate. By utilizing these novel structures we show that (i) the detection limit for dopamine can be improved by two orders of magnitude [from 10µM to 50nM] in comparison to ta-C thin film electrodes and (ii) the coating method significantly affects electrochemical properties of NDs and (iii) the ND coatings selectively promote cell viability. ND andante and ND H showed most promising electrochemical properties. The viability of human mesenchymal stem cells and osteoblastic SaOS-2 cells was increased on all ND surfaces, whereas the viability of mouse neural stem cells and rat neuroblastic cells was improved on ND andante and ND H and reduced on ND amine and ND vox. The viability of C6 cells remained unchanged, indicating that these surfaces will not cause excess gliosis. In summary, we demonstrated here that by using functionalized NDs on ta-C thin films we can significantly improve sensitivity towards dopamine as well as selectively promote cell viability. Thus, these novel carbon nanostructures provide an interesting concept for development of various in vivo targeted sensor solutions. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Electromagnetic wave absorption properties of composites with micro-sized magnetic particles dispersed in amorphous carbon

    Science.gov (United States)

    Li, Bin Peng; Wang, Cheng Guo; Wang, Wen; Yu, Mei Jie; Gao, Rui; Chen, Yang; Xiang Wang, Yan

    2014-09-01

    Composites with micro-sized magnetic particles dispersed in amorphous carbon were fabricated conveniently and economically by carbonizing polyacrylonitrile (PAN) fibers mixed with micro-sized iron particles under different temperatures. The composites were characterized by X-ray diffraction (XRD) and scanning electric microscope (SEM). The electromagnetic (EM) properties were measured by a vector network analyzer in the frequency range of 2-18 GHz based on which analog computations of EM wave absorption properties were carried out. The influences of temperature on phase composition and EM wave absorption properties were also investigated, indicating that the composites had good electromagnetic absorption properties with both electrical loss and magnetic loss. Effective reflection loss (RL<-10 dB) was observed in a large frequency range of 7.5-18 GHz with the absorber thickness of 2.0-3.0 mm for the paraffin samples with composite powders heated up to 750 °C and the minimum absorption peak around -40 dB appeared at approximately 10 GHz with matching thickness of 2.0 mm for the paraffin sample with composite powders heated up to 800 °C.

  15. Thermal stability of amorphous carbon films grown by pulsed laser deposition

    Science.gov (United States)

    Friedmann, T. A.; McCarty, K. F.; Barbour, J. C.; Siegal, M. P.; Dibble, Dean C.

    1996-03-01

    The thermal stability in vacuum of amorphous tetrahedrally coordinated carbon (a-tC) films grown on Si has been assessed by in situ Raman spectroscopy. Films were grown in vacuum on room-temperature substrates using laser fluences of 12, 22, and 45 J/cm2 and in a background gas of either hydrogen or nitrogen using a laser fluence of 45 J/cm2. The films grown in vacuum at high fluence (≳20J/cm2) show little change in the a-tC Raman spectra with temperature up to 800 °C. Above this temperature the films convert to glassy carbon (nanocrystalline graphite). Samples grown in vacuum at lower fluence or in a background gas (H2 or N2) at high fluence are not nearly as stable. For all samples, the Raman signal from the Si substrate (observed through the a-tC film) decreases in intensity with annealing temperature indicating that the transparency of the a-tC films is decreasing with temperature. These changes in transparency begin at much lower temperatures (˜200 °C) than the changes in the a-tC Raman band shape and indicate that subtle changes are occurring in the a-tC films at lower temperatures.

  16. Optical Properties Of As-Deposited Amorphous Carbon Film Fromvarious Substrate Temperaturesvia Custom-Made-CVD

    Directory of Open Access Journals (Sweden)

    A. Ishak

    2015-01-01

    Full Text Available Abstract We were deposited the as-deposited amorphous carbon via a modified custom-made-CVD in the range of 350oC to 550oC at atmospheric pressure with constant of negative bias -40V and argon gas for 1 hour deposition. We used vaporized of palm oil as a carbon source into the chamber. It was observed above 90 of light were transmitted to the samples instead of sample 500oC 80. The as-deposited thin film grown on glass and p-type silicon we found uniform smooth dark grey colored and thickness in the range of 155 to 190nm. It was found thickness less than 170nm brought less significant impact to the reduction of transmission percentage. In relationship with structural image in FESEM the absorption coefficient was found high as the size of particles were big rough and agglomerated. The result showed the optical band gaps for 550oC to 350oC were 0.5eV 1.3eV 0.1eV 0.7eV and 1.4eV respectively. The optical band gaps of 400oC and 350oC were suitable for solar cell applications.

  17. Synthesis and characterization of amorphous poly(ethylene oxide)/poly(trimethylene carbonate) polymer blend electrolytes

    International Nuclear Information System (INIS)

    Rodrigues, L.C.; Silva, M.M.; Smith, M.J.

    2012-01-01

    Solid polymer electrolytes (SPEs) have been proposed as substitutes for conventional non-aqueous electrolytes in various electrochemical devices. These promising materials may be of interest in various practical devices including batteries, sensors and electrochromic displays as they can offer high performance in terms of specific energy and specific power (batteries), safe operation, form flexibility in device arquitecture and low manufacturing costs. Many different host polymers have been characterized over the last 30 years, however a relatively un-explored strategy involves the use of interpenetrating blends incorporating two or more polymers. Electrolyte systems based on interpenetrating blends of known host polymers, poly(ethylene oxide) and poly(trimethylene carbonate), doped with lithium perchlorate, were prepared by co-dissolution in acetonitrile. This combination of polymer components results in the formation of a material that may be applicable in batteries and electrochromic devices. The results of characterization of polymer electrolyte systems based on interpenetrating blends of amorphous poly(ethylene oxide) and poly(trimethylene carbonate) host matrices, with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as guest salt, are described in this study. Electrolytes with compositions of n between 5 and 15 (where n represents the total number of cation-coordinating units per lithium ion) were obtained as flexible, transparent and free-standing films that were characterized by measurements of conductivity, cyclic voltammetry, differential scanning calorimetry and thermogravimetry.

  18. Channeling implantation of high energy carbon ions in a diamond crystal: Determination of the induced crystal amorphization

    Science.gov (United States)

    Erich, M.; Kokkoris, M.; Fazinić, S.; Petrović, S.

    2018-02-01

    This work reports on the induced diamond crystal amorphization by 4 MeV carbon ions implanted in the 〈1 0 0〉 oriented crystal and its determination by application of RBS/C and EBS/C techniques. The spectra from the implanted samples were recorded for 1.2, 1.5, 1.75 and 1.9 MeV protons. For the two latter ones the strong resonance of the nuclear elastic scattering 12C(p,p0)12C at 1.737 MeV was explored. The backscattering channeling spectra were successfully fitted and the ion beam induced crystal amorphization depth profile was determined using a phenomenological approach, which is based on the properly defined Gompertz type dechanneling functions for protons in the 〈1 0 0〉 diamond crystal channels and the introduction of the concept of ion beam amorphization, which is implemented through our newly developed computer code CSIM.

  19. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture.

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A; Smith, Sean C

    2015-12-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 10(13) cm(-2) or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

  20. Plasmon mediated enhancement and tuning of optical emission properties of two dimensional graphitic carbon nitride nanosheets

    Science.gov (United States)

    Bayan, Sayan; Gogurla, Narendar; Midya, Anupam; Singha, Achintya; Ray, Samit K.

    2017-12-01

    We demonstrate surface plasmon induced enhancement and tunablilty in optical emission properties of two dimensional graphitic carbon nitride (g-C3N4) nanosheets through the attachment of gold (Au) nanoparticles. Raman spectroscopy has revealed surface enhanced Raman scattering that arises due to the combined effect of the charge transfer process and localized surface plasmon induced enhancement in electromagnetic field, both occurring at the nanoparticle–nanosheet interface. Photoluminescence studies suggest that at an optimal concentration of nanoparticles, the emission intensity can be enhanced, which is maximum within the 500–525 nm region. Further, the fabricated electroluminescent devices reveal that the emission feature can be tuned from bluish-green to red (∼160 nm shift) upon attaching Au nanoparticles. We propose that the π*→π transition in g-C3N4 can trigger surface plasmon oscillation in Au, which subsequently increases the excitation process in the nanosheets and results in enhanced emission in the green region of the photoluminescence spectrum. On the other hand, electroluminescence of g-C3N4 can induce plasmon oscillation more efficiently and thus can lead to red emission from Au nanoparticles through the radiative damping of particle plasmons. The influence of nanoparticle size and coverage on the emission properties of two dimensional g-C3N4, nanosheets has also been studied in detail.

  1. Recent advances in functional mesoporous graphitic carbon nitride (mpg-C3N4) polymers.

    Science.gov (United States)

    Sun, Shaodong; Liang, Shuhua

    2017-08-03

    Mesoporous micro-/nanostructures acting as supports for catalysts or used directly in catalysis reactions generally show fascinating performances that could lead to great potential for application. In the past few decades, extensive efforts have been devoted to the exploration and enrichment of graphitic carbon nitride (g-C 3 N 4 ) based research. Especially, mesoporous g-C 3 N 4 (mpg-C 3 N 4 ) with controllable porosity and electronic/atomic structure can bring to bear unique physicochemical properties and has been widely applied in the fields of photocatalysis, adsorbents, sensors and chemical templates. However, a comprehensive summary on mpg-C 3 N 4 micro/nanostructures is less reported and there is an urgent need to further promote the development of function-oriented mpg-C 3 N 4 -based materials. Herein, we will overview the significant advances in functional mpg-C 3 N 4 polymers, including general synthesis strategies and growth mechanisms, modifications of electronic/atomic structures and interfacial properties (such as exfoliation, doping and hybridizing), as well as their current applications. Finally, several emerging issues and perspectives are also proposed.

  2. Preparation and characterization of photoactive antimicrobial graphitic carbon nitride (g-C3N4) films

    Science.gov (United States)

    Thurston, John H.; Hunter, Necia M.; Cornell, Kenneth A.

    2016-01-01

    Photoactive films derived from nanostructured samples of metal-free, intermediate band gap semiconductor graphitic carbon nitride (ns-g-C3N4) have been synthesized and characterized for their particle properties and antimicrobial activity. Physical characterization reveals that these materials are composed of discrete nanoparticles whose dimensions range from 200 nm to 700 nm. Investigation of the photochemical reactivity of ns-g-C3N4 using coumarin-3-carboxylic acid (3-CCA) indicates that this material produces reactive oxygen species (ROS) under visible radiation. When irradiated with 0.31J visible light, ns-g-C3N4-based materials reduced the viability of both gram-negative Escherichia coli O157:H7 and gram-positive Staphylococcus aureus by approximately 50%. Nearly complete inactivation of both strains of microorganisms was achieved upon administration of a 0.62J dose of visible radiation. Importantly, no biocidal activity was observed for non-irradiated samples, indicating that the g-C3N4-derived films are not inherently toxic in the absence of visible light. The results of this study suggest that materials and, by extention, films and coatings derived from g-C3N4 may present a novel route for controlling pathogenic microorganisms on surfaces in the environment, and could be useful in reducing incidents of hospital-acquired infections. PMID:27672437

  3. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A.; Smith, Sean C.

    2015-12-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 1013 cm-2 or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

  4. Hypophosphite/Graphitic Carbon Nitride Hybrids: Preparation and Flame-Retardant Application in Thermoplastic Polyurethane.

    Science.gov (United States)

    Shi, Yongqian; Fu, Libi; Chen, Xilei; Guo, Jin; Yang, Fuqiang; Wang, Jingui; Zheng, Yuying; Hu, Yuan

    2017-09-05

    A series of aluminum hypophosphite (AHPi)/graphite-like carbon nitride (g-C₃N₄) (designated as CAHPi) hybrids were prepared, followed by incorporation into thermoplastic polyurethane (TPU). The introduction of CAHPi hybrids into TPU led to a marked reduction in the peak of the heat release rate (pHRR), total heat release, weight loss rate, smoke production rate and total smoke production (TSP). For instance, pHRR and TSP decreased by 40% and 50% for TPU/CAHPi20. Furthermore, the increasing fire growth index and decreasing fire performance index were obtained for TPU/CAHPi systems, suggesting reduced fire hazards. It was found that improved fire safety of TPU nanocomposites was contributed by condensed phase and gas phase mechanisms. On one hand, g-C₃N₄ accelerated the thermal decomposition of AHPi for the formation of more char layers. On the other hand, g-C₃N₄ induced AHPi to generate more free radical capture agents when exposed to flame, besides protecting AHPi against thermal oxidation.

  5. Precisely tunable thickness of graphitic carbon nitride nanosheets for visible-light-driven photocatalytic hydrogen evolution.

    Science.gov (United States)

    Hong, Yuanzhi; Li, Changsheng; Li, Di; Fang, Zhenyuan; Luo, Bifu; Yan, Xu; Shen, Hongqiang; Mao, Baodong; Shi, Weidong

    2017-09-28

    Graphitic carbon nitride (GCN) nanosheets with unique physicochemical properties have received increasing attention in the area of photocatalysis, yet tunable thickness for the straightforward production of this graphite-like two-dimensional (2D) nanomaterial remains a challenge. In this work, GCN nanosheets with different thicknesses were firstly prepared by a direct calcination of melamine supramolecular aggregates (MSA) obtained from a hydrochloric acid (HCl)-induced hydrothermal assembly approach. The resultant nanosheets over nanometer scale thickness could be precisely controlled via simply adjusting the HCl concentration. Compared to the bulk GCN (BGCN), the thinner nanosheets possessed a high specific surface area, a large electronic-band structure, and fast charge separation ability. The thinnest nanosheets with a thickness of approximately 4 nm exhibited excellent visible-light-driven photocatalytic water splitting performance in hydrogen evolution (524 μmol h -1 g -1 ), which is over 9-fold higher than the BGCN powder. This work provides a thickness-dependent strategy for the preparation of metal-free GCN nanosheets and develops a promising 2D photocatalyst for application in solar energy conversion.

  6. Multifunctional fiber reinforced polymer composites using carbon and boron nitride nanotubes

    Science.gov (United States)

    Ashrafi, Behnam; Jakubinek, Michael B.; Martinez-Rubi, Yadienka; Rahmat, Meysam; Djokic, Drazen; Laqua, Kurtis; Park, Daesun; Kim, Keun-Su; Simard, Benoit; Yousefpour, Ali

    2017-12-01

    Recent progress in nanotechnology has made several nano-based materials available with the potential to address limitations of conventional fiber reinforced polymer composites, particularly in reference to multifunctional structures. Carbon nanotubes (CNTs) are the most prevalent case and offer amazing properties at the individual nanotube level. There are already a few high-profile examples of the use of CNTs in space structures to provide added electrical conductivity for static dissipation and electromagnetic shielding. Boron nitride nanotubes (BNNTs), which are structurally analogous to CNTs, also present a range of attractive properties. Like the more widely explored CNTs, individual BNNTs display remarkable mechanical properties and high thermal conductivity but with contrasting functional attributes including substantially higher thermal stability, high electrical insulation, polarizability, high neutron absorption and transparency to visible light. This presents the potential of employing either or both BNNTs and CNTs to achieve a range of lightweight, functional composites for space structures. Here we present the case for application of BNNTs, in addition to CNTs, in space structures and describe recent advances in BNNT production at the National Research Council Canada (NRC) that have, for the first time, provided sufficiently large quantities to enable commercialization of high-quality BNNTs and accelerate development of chemistry, composites and applications based on BNNTs. Early demonstrations showing the fabrication and limited structural testing of polymer matrix composites, including glass fiber-reinforced composite panels containing BNNTs will be discussed.

  7. Polymeric carbon nitride/mesoporous silica composites as catalyst support for Au and Pt nanoparticles.

    Science.gov (United States)

    Xiao, Ping; Zhao, Yanxi; Wang, Tao; Zhan, Yingying; Wang, Huihu; Li, Jinlin; Thomas, Arne; Zhu, Junjiang

    2014-03-03

    Small and homogeneously dispersed Au and Pt nanoparticles (NPs) were prepared on polymeric carbon nitride (CNx )/mesoporous silica (SBA-15) composites, which were synthesized by thermal polycondensation of dicyandiamide-impregnated preformed SBA-15. By changing the condensation temperature, the degree of condensation and the loading of CNx can be controlled to give adjustable particle sizes of the Pt and Au NPs subsequently formed on the composites. In contrast to the pure SBA-15 support, coating of SBA-15 with polymeric CNx resulted in much smaller and better-dispersed metal NPs. Furthermore, under catalytic conditions the CNx coating helps to stabilize the metal NPs. However, metal NPs on CNx /SBA-15 can show very different catalytic behaviors in, for example, the CO oxidation reaction. Whereas the Pt NPs already show full CO conversion at 160 °C, the catalytic activity of Au NPs seems to be inhibited by the CNx support. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Plasmon mediated enhancement and tuning of optical emission properties of two dimensional graphitic carbon nitride nanosheets.

    Science.gov (United States)

    Bayan, Sayan; Gogurla, Narendar; Midya, Anupam; Singha, Achintya; Ray, Samit K

    2017-12-01

    We demonstrate surface plasmon induced enhancement and tunablilty in optical emission properties of two dimensional graphitic carbon nitride (g-C 3 N 4 ) nanosheets through the attachment of gold (Au) nanoparticles. Raman spectroscopy has revealed surface enhanced Raman scattering that arises due to the combined effect of the charge transfer process and localized surface plasmon induced enhancement in electromagnetic field, both occurring at the nanoparticle-nanosheet interface. Photoluminescence studies suggest that at an optimal concentration of nanoparticles, the emission intensity can be enhanced, which is maximum within the 500-525 nm region. Further, the fabricated electroluminescent devices reveal that the emission feature can be tuned from bluish-green to red (∼160 nm shift) upon attaching Au nanoparticles. We propose that the π*→π transition in g-C 3 N 4 can trigger surface plasmon oscillation in Au, which subsequently increases the excitation process in the nanosheets and results in enhanced emission in the green region of the photoluminescence spectrum. On the other hand, electroluminescence of g-C 3 N 4 can induce plasmon oscillation more efficiently and thus can lead to red emission from Au nanoparticles through the radiative damping of particle plasmons. The influence of nanoparticle size and coverage on the emission properties of two dimensional g-C 3 N 4 , nanosheets has also been studied in detail.

  9. Graphitic carbon nitride as high-resolution stationary phase for gas chromatographic separations.

    Science.gov (United States)

    Zheng, Yunzhong; Qi, Meiling; Fu, Ruonong

    2016-07-08

    This work presents the first example of utilization of graphitic carbon nitride (g-C3N4) as stationary phase for capillary gas chromatographic (GC) separations. The statically coated g-C3N4 column showed the column efficiencies of 3760 plates/m and weak polarity. Its resolving capability and retention behaviours were investigated by using the Grob test mixture, and mixtures of diverse types of analytes, and structural and positional isomers. The results showed superior separation performance of the g-C3N4 stationary phase for some critical analytes and preferential retention for aromatic analytes. Specifically, it exhibited high-resolution capability for aromatic and aliphatic isomers such as methylnaphthalenes and dimethylnaphthalenes, phenanthrene and anthracene and alkane isomers. In addition, g-C3N4 column showed excellent thermal stability up to 280°C and good repeatability with relative standard deviation (RSD) values less than 0.09% for intra-day, below 0.23% for inter-day and in the range of 1.9-8.4% for between-column, respectively. The advantageous separation performance shows the potential of g-C3N4 and related materials as stationary phase in GC and other separation technologies. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Graphitic carbon nitride nanosheet electrode-based high-performance ionic actuator

    Science.gov (United States)

    Wu, Guan; Hu, Ying; Liu, Yang; Zhao, Jingjing; Chen, Xueli; Whoehling, Vincent; Plesse, Cédric; Nguyen, Giao T. M.; Vidal, Frédéric; Chen, Wei

    2015-01-01

    Ionic actuators have attracted attention due to their remarkably large strain under low-voltage stimulation. Because actuation performance is mainly dominated by the electrochemical and electromechanical processes of the electrode layer, the electrode material and structure are crucial. Here, we report a graphitic carbon nitride nanosheet electrode-based ionic actuator that displays high electrochemical activity and electromechanical conversion abilities, including large specific capacitance (259.4 F g−1) with ionic liquid as the electrolyte, fast actuation response (0.5±0.03% in 300 ms), large electromechanical strain (0.93±0.03%) and high actuation stability (100,000 cycles) under 3 V. The key to the high performance lies in the hierarchical pore structure with dominant size <2 nm, optimal pyridinic nitrogen active sites (6.78%) and effective conductivity (382 S m−1) of the electrode. Our study represents an important step towards artificial muscle technology in which heteroatom modulation in electrodes plays an important role in promoting electrochemical actuation performance. PMID:26028354

  11. Graphitic carbon nitride nanofibers in seaweed-like architecture for gas chromatographic separations.

    Science.gov (United States)

    Zheng, Yunzhong; Han, Qing; Qi, Meiling; Qu, Liangti

    2017-05-05

    Seaweed-like graphitic carbon nitride (g-C 3 N 4 ) has a unique porous architecture composed of interlocking g-C 3 N 4 nanofibers (NF-C 3 N 4 ) with much higher surface area than bulk g-C 3 N 4 and shows good potential in separation science. This work investigated the separation performance of NF-C 3 N 4 as stationary phase for capillary gas chromatographic (GC) separations. The NF-C 3 N 4 column exhibits weak polarity and high column efficiency of 4728 plates/m for n-dodecane. Importantly, it displays good separation performance for a wide range of analytes and shows different retention behaviors from the bulk g-C 3 N 4 column and commercial HP-5MS column with 5% phenylpolysiloxane. Particularly, it shows high resolving capability for both aliphatic and aromatic isomers. In addition, NF-C 3 N 4 column has high thermal stability up to 280°C and good separation repeatability with relative standard deviation (RSD) values in the range of 0.29-0.61% for intra-day, 0.56-1.1% for inter-day and 2.0-4.9% for between-column, respectively. Moreover, it was applied for the determination of isomer impurities in real samples, showing good potential in GC applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Graphitic carbon nitride/BiOCl composites for sensitive photoelectrochemical detection of ciprofloxacin.

    Science.gov (United States)

    Xu, Li; Li, Henan; Yan, Pengcheng; Xia, Jiexiang; Qiu, Jingxia; Xu, Qian; Zhang, Shanqing; Li, Huaming; Yuan, Shouqi

    2016-12-01

    Ciprofloxacin, as a second generation of fluoroquinolone antibiotics, has been proved to cause environmental harm and exhibits toxic effects on the wastewater and surface water even at low concentrations due to their continuous input and persistence. Despite tremendous efforts, developing ciprofloxacin detection method with accuracy and sensitivity at low-cost remains a great challenge. Herein, graphitic carbon nitride/BiOCl composite (g-CN/BiOCl) has been designed for a facile and sensitive photoelectrochemical (PEC) monitoring platform of ciprofloxacin at first time. BiOCl can be modified with the g-CN nanosheets which are obtained via solvothermal process at low-temperature conditions. The use of g-CN is shown to strongly enhance the PEC response of BiOCl due to the formation of heterojunctions. The photocurrent generated at the g-CN/BiOCl-modified ITO (with 13wt%g-CN content) is much higher and more stable than that of a BiOCl-modified ITO. Based on these findings, the g-CN/BiOCl-modified ITO was used to design a PEC assay for the antibiotic ciprofloxacin. Furthermore, the limit of detection of the ciprofloxacin PEC sensor has been significantly lowered to 0.2ngmL(-1). In addition, the PEC sensor can detect ciprofloxacin in the wide range of 0.5-1840ngmL(-1). Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Magnetic graphitic carbon nitride anion exchanger for specific enrichment of phosphopeptides.

    Science.gov (United States)

    Zhu, Gang-Tian; He, Xiao-Mei; Chen, Xi; Hussain, Dilshad; Ding, Jun; Feng, Yu-Qi

    2016-03-11

    Anion-exchange chromatography (AEX) is one of the chromatography-based methods effectively being used for phosphopeptide enrichment. However, the development of AEX materials with high specificity toward phosphopeptides is still less explored as compared to immobilized metal affinity chromatography (IMAC) or metal oxide affinity chromatography (MOAC). In this work, magnetic graphitic carbon nitride (MCN) was successfully prepared and introduced as a promising AEX candidate for phosphopeptide enrichment. Due to the extremely abundant content of nitrogen with basic functionality on the surface, this material kept excellent retention for phosphopeptides at pH as low as 1.8. Benefiting from the large binding capacity at such low pH, MCN showed remarkable specificity to capture phosphopeptides from tryptic digests of standard protein mixtures as well as nonfat milk and human serum. In addition, MCN was also applied to selective enrichment of phosphopeptides from the tryptic digests of rat brain lysate and 2576 unique phosphopeptides were successfully identified. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Sonophotocatalytic degradation of bisphenol A and its intermediates with graphitic carbon nitride.

    Science.gov (United States)

    Sunasee, Sharmini; Leong, Kah Hon; Wong, Kien Tiek; Lee, Gooyong; Pichiah, Saravanan; Nah, InWook; Jeon, Byong-Hun; Yoon, Yeomin; Jang, Min

    2017-03-13

    Since bisphenol A (BPA) exhibits endocrine disrupting action and high toxicity in aqueous system, there are high demands to remove it completely. In this study, the BPA removal by sonophotocatalysis coupled with nano-structured graphitic carbon nitride (g-C 3 N 4 , GCN) was conducted with various batch tests using energy-based advanced oxidation process (AOP) based on ultrasound (US) and visible light (Vis-L). Results of batch tests indicated that GCN-based sonophotocatalysis (Vis-L/US) had higher rate constants than other AOPs and especially two times higher degradation rate than TiO 2 -based Vis-L/US. This result infers that GCN is effective in the catalytic activity in Vis-L/US since its surface can be activated by Vis-L to transport electrons from valence band (VB) for utilizing holes (h + VB ) in the removal of BPA. In addition, US irradiation exfoliated the GCN effectively. The formation of BPA intermediates was investigated in detail by using high-performance liquid chromatography-mass spectrometry (HPLC/MS). The possible degradation pathway of BPA was proposed.

  15. Bioinspired Mesoporous Chiral Nematic Graphitic Carbon Nitride Photocatalysts modulated by Polarized Light.

    Science.gov (United States)

    Lin, Wensheng; Hong, Wei; Sun, Lu; Yu, Di; Yu, Dingshan; Chen, Xudong

    2018-01-10

    Endowing materials with chirality and exploring the responses of the material under circularly polarized light (CPL) can enable further insight into the physical and chemical properties of the semiconductors to be gained, thus expanding on optoelectronic applications. Herein a bioinspired mesoporous chiral nematic graphitic carbon nitride (g-C 3 N 4 ) for efficient hydrogen evolution with polarized light modulation based on chiral nematic cellulose nanocrystal films prepared through silica templating is described. The mesoporous nematic chiral g-C 3 N 4 exhibits an ultrahigh hydrogen evolution rate of 219.9 μmol h -1 (for 20 mg catalyst), corresponding to a high enhancement factor of 55 when compared to the bulk g-C 3 N 4 under λ>420 nm irradiation. Furthermore, the chiral g-C 3 N 4 material exhibits unique photocatalytic activity modulated by CPL within the absorption region. This CPL-assisted photocatalytic regulation strategy holds great promise for a wide range of applications including optical devices, asymmetric photocatalysis, and chiral recognition/separation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Tuning the Photocatalytic Activity of Graphitic Carbon Nitride by Plasma-Based Surface Modification.

    Science.gov (United States)

    Ji, Xueqiang; Yuan, Xiaohong; Wu, Jiajie; Yu, Lan; Guo, Huiyun; Wang, Hannian; Zhang, Haiquan; Yu, Dongli; Zhao, Yuanchun

    2017-07-26

    In this study, we demonstrate that plasma treatment can be a facile and environmentally friendly approach to perform surface modification of graphitic carbon nitride (g-CN), leading to a remarkable modulation on its photocatalytic activity. The bulk properties of g-CN, including the particle size, structure, composition, and electronic band structures, have no changes after being treated by oxygen or nitrogen plasma; however, its surface composition and specific surface area exhibit remarkable differences corresponding to an oxygen functionalization induced by the plasma post-treatment. The introduced oxygen functional groups play a key role in reducing the recombination rate of the photoexcited charge carries. As a consequence, the oxygen-plasma-treated sample shows a much superior photocatalytic activity, which is about 4.2 times higher than that of the pristine g-CN for the degradation of rhodamine B (RhB) under visible light irradiation, while the activity of nitrogen-plasma-treated sample exhibits a slight decrease. Furthermore, both of the plasma-treated samples are found to possess impressive photocatalytic stabilities. Our results suggest that plasma treatment could be a conventional strategy to perform surface modification of g-CN in forms of both powders and thin films, which holds broad interest not only for developing g-CN-based high-performance photocatalysts but also for constructing photoelectrochemical cells and photoelectronic devices with improved energy conversion efficiencies.

  17. Green synthesis of graphitic carbon nitride nanodots using sodium chloride template

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Bo [National University of Defense Technology, College of Science (China); Zou, Xianshuai; Yan, Tingnan; Fei, Junjie [Xiangtan University, College of Chemistry (China); Chu, Zengyong, E-mail: chuzy@nudt.edu.cn [National University of Defense Technology, College of Science (China)

    2016-05-15

    Graphitic carbon nitride (g-C{sub 3}N{sub 4}) nanodots are simply prepared by a thermal treatment of dicyandiamide (DCDA) confined within NaCl templates. Cyano groups are introduced to the nanodots due to the catalytic effect of NaCl. NaCl could facilitate the polymerization of DCDA at lower temperatures, but will promote the decomposition when the temperature is above 550 °C. Thermal treatment at 600 °C for 30 min is the optimal condition for the scalable synthesis of g-C{sub 3}N{sub 4} nanodots with an average diameter of ~9 nm. g-C{sub 3}N{sub 4} nanodots have a higher band gap of 3.1 eV, which can emit bright blue light due to the decreased diameter, the introduction of cyano groups, and the incorporation of some sodium ions. The residue sodium ions and the cyano groups might lead to the local distortion of the graphitic crystals, or act as recombination centers for the enhanced photoluminescence.Graphical Abstract.

  18. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A.; Smith, Sean C.

    2015-01-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 1013 cm−2 or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility. PMID:26621618

  19. A graphitic carbon nitride based fluorescence resonance energy transfer detection of riboflavin.

    Science.gov (United States)

    Han, Jing; Zou, Hong Yan; Gao, Ming Xuan; Huang, Cheng Zhi

    2016-01-01

    Fluorescence resonance energy transfer (FRET), which occurs between two luminescent chromophores, can greatly improve the selectivity and sensitivity of a fluorescent assay when a ratiometric signaling with the fluorescence enhancement of the acceptor at the expense of the donor is adopted. In this study, a fluorescence ratiometric detection (FRD) of riboflavin (RF) has been made based on FRET, as the strong overlap occurred between the emission spectrum of graphitic carbon nitride (g-C3N4) and absorption spectrum of RF, in which g-C3N4 acts as the energy donor and RF as the energy acceptor. With increasing concentration of RF, the fluorescence intensity of g-C3N4 emission at 444 nm decreased and the fluorescence peak at 523 nm for RF increased regularly, making the fluorescence intensity ratio of 523 nm to 444 nm linearly dependent on the concentration of RF in the range from 0.4 μM to 10 μM, giving a limit of the detection of 170 nM. This method can be used to quantify RF in complex systems such as milk and drink, showing that the novel FRET-based fluorescence ratiometric detection can enable an attractive assay platform for analytes of interest. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Mode-locked Tm-doped fiber laser based on iron-doped carbon nitride nanosheets

    Science.gov (United States)

    Luo, Yongfeng; Zhou, Yan; Tang, Yulong; Xu, Jianqiu; Hu, Chenxia; Gao, Linfeng; Zhang, Haoli; Wang, Qiang

    2017-11-01

    Solution based nanosheets of iron-doped graphitic carbon nitrides (Fe-g-CN) have been prepared and their optical properties (both linear and nonlinear) are studied. These two-dimensional (2D) nanosheets show an absorption spectrum extending to over 2 µm, and in particular they possess strong nonlinear (saturable) absorption in the 2 µm spectral region. A saturable absorber (SA) manufactured from 2D Fe-g-CN nanosheets gives a modulation depth and saturation intensity of 12.9% and 8.9 MW cm‑2, respectively. This SA is further used to mode-lock thulium-doped fiber lasers, producing 2 µm laser pulses with a duration of 16.6 ps (dechirped to 2.2 ps), an average power of 96.4 mW, a pulse energy of 6.3 nJ, and a repetition rate of 15.3 MHz. As a new type of 2D nonlinear material with strong modulation capabilities, solution-based Fe-g-CN nanosheets can be potentially integrated into photonic and optoelectrionic devices, particuarly in the 2 µm spectral region.

  1. The application of graphitic carbon nitride for the adsorption of Pb2+ ion from aqueous solution

    Science.gov (United States)

    Zhu, Lin; You, Liangjun; Wang, Ya; Shi, Zhaoxin

    2017-07-01

    This study appraised the potential application of graphitic carbon nitride (g-C3N4) as an adsorbent for removal of Pb2+ ion from aqueous solution. The g-C3N4 was prepared by direct calcination of the low-cost melamine, and its morphology and microstructure were analyzed. Moreover, the effects of initial solution pH, initial Pb2+ ion concentration, adsorption time, and adsorbent dosage on the adsorption properties of the g-C3N4 were investigated. Two widely used isotherm models were used to describe the experimental equilibrium data, and the Freundlich isotherm model described well. Two widely used kinetic models were used to the fit of the adsorption experimental data, and the pseudo-second-order kinetic model fitted well. The maximum adsorption percentage and maximum adsorption capacity were 98.5% and 7.4 mg g-1, respectively. In addition, the recycling of g-C3N4 for the removal of Pb2+ was investigated, and the results indicated that g-C3N4 owned a good reusability.

  2. Switching Oxygen Reduction Pathway by Exfoliating Graphitic Carbon Nitride for Enhanced Photocatalytic Phenol Degradation.

    Science.gov (United States)

    Zhang, Hui; Guo, Liang-Hong; Zhao, Lixia; Wan, Bin; Yang, Yu

    2015-03-19

    The selectivity of molecular oxygen activation on the exfoliated graphitic carbon nitride (g-C3N4) and its influence on the photocatalytic phenol degradation process were demonstrated. Compared with bulk g-C3N4, the exfoliated nanosheet yielded a 3-fold enhancement in photocatalytic phenol degradation. ROS trapping experiments demonstrated that although the direct hole oxidation was mainly responsible for phenol photodegradation on both g-C3N4 catalysts, molecular oxygen activation processes on their surface greatly influenced the whole phenol degradation efficiency. Reactive oxygen species and Raman spectroscopy measurements revealed that oxygen was preferentially reduced to ·O2(-) by one-electron transfer on bulk g-C3N4, while on g-C3N4 nanosheet the production of H2O2 via a two-electron transfer process was favored due to the rapid formation of surface-stabilized 1,4-endoperoxide. The latter process not only promotes the separation of photogenerated electron-hole pairs but also greatly facilitates reactive oxygen species formation and subsequently enhances phenol degradation.

  3. Immobilizing photogenerated electrons from graphitic carbon nitride for an improved visible-light photocatalytic activity

    Science.gov (United States)

    Sun, Han; Cao, Yue; Feng, Leiyu; Chen, Yinguang

    2016-01-01

    Reducing the recombination probability of photogenerated electrons and holes is pivotal in enhancing the photocatalytic ability of graphitic carbon nitride (g-C3N4). Speeding the departure of photogenerated electrons is the most commonly used method of achieving this. To the best of our knowledge, there is no report on suppressing the recombination of photogenerated electron–hole pairs by immobilizing the electrons with ester functional groups. Here, for the first time the mesoporous g-C3N4 (mpg-C3N4) was integrated with polymethyl methacrylate, a polymer abundant in ester groups, which showed a photocatalytic activity unexpectedly higher than that of the original mpg-C3N4 under visible-light irradiation. Experimental observations, along with theoretical calculations, clarified that the impressive photocatalytic ability of the as-modified mpg-C3N4 was mainly derived from the immobilization of photogenerated electrons via an electron-gripping effect imposed by the ester groups in the polymethyl methacrylate. This novel strategy might also be applied in improving the photocatalytic performance of other semiconductors. PMID:26948968

  4. First principle modeling of oxygen-doped monolayer graphitic carbon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Jie [School of Materials Science and Engineering, Xi' an University of Technology, Xi' an 710048 (China); Shaanxi Province Key Laboratory for Electrical Materials and Infiltration Technology, Xi' an University of Technology, Xi' an 710048 (China); Liang, Shuhua, E-mail: liangsh@xaut.edu.cn [School of Materials Science and Engineering, Xi' an University of Technology, Xi' an 710048 (China); Shaanxi Province Key Laboratory for Electrical Materials and Infiltration Technology, Xi' an University of Technology, Xi' an 710048 (China); Wang, Xianhui [School of Materials Science and Engineering, Xi' an University of Technology, Xi' an 710048 (China); Shaanxi Province Key Laboratory for Electrical Materials and Infiltration Technology, Xi' an University of Technology, Xi' an 710048 (China); Zhang, Jianmin [College of Physics and Information Technology, Shaanxi Normal University, Xi' an 710062 (China)

    2015-07-01

    The effect of oxygen doping on the electronic and geometric structures of monolayer graphitic carbon nitride was calculated by first principle. It reveals the favorable O doping configurations over all the Fermi levels utilizing the Ab initio thermodynamics approach. The valence charge density difference contour map presents a weaker covalent nature on O–C bonds for O{sub N2}-doped structure and a complex ionic-covalent character associated with O–N{sub 2} bonds for O{sub i}-doped structure. Based on the analysis of the electronic structures of the doped and un-doped systems, it is found that O doping facilitates the visible-light absorption of monolayer g-C{sub 3}N{sub 4}. Especially, O{sub i} doping shows an intrinsic semiconductor behavior and the occupied doping band can be avoided to be the recombination center. In addition, O doping causes slightly stronger delocalization of the HOMO and LUMO which facilitates the enhancement of the carrier mobility. Moreover, O{sub i} doping can induce more activity sites, and, thus, is beneficial for the separation of photogenerated e{sup −}/h{sup +} pairs to some extent. - Highlights: • We reveal the favorable O doping configurations over all the Fermi levels. • O doping facilitates the visible-light absorption of monolayer g-C{sub 3}N{sub 4}. • O doping causes slightly stronger delocalization of the HOMO and LUMO.

  5. Uncondensed Graphitic Carbon Nitride on Reduced Graphene Oxide for Oxygen Sensing via a Photoredox Mechanism.

    Science.gov (United States)

    Ellis, James E; Sorescu, Dan C; Burkert, Seth C; White, David L; Star, Alexander

    2017-08-16

    Melon, a polymeric, uncondensed graphitic carbon nitride with a two-dimensional structure, has been coupled with reduced graphene oxide (rGO) to create an oxygen chemiresistor sensor that is active under UV photoactivation. Oxygen gas is an important sensor target in a variety of areas including industrial safety, combustion process monitoring, as well as environmental and biomedical fields. Because of the intimate electrical interface formed between melon and rGO, charge transfer of photoexcited electrons occurs between the two materials when under UV (λ = 365 nm) irradiation. A photoredox mechanism wherein oxygen is reduced on the rGO surface provides the basis for sensing oxygen gas in the concentration range 300-100 000 ppm. The sensor response was found to be logarithmically proportional to oxygen gas concentration. DFT calculations of a melon-oxidized graphene composite found that slight protonation of melon leads to charge accumulation on the rGO layer and a corresponding charge depletion on the melon layer. This work provides an example of a metal-free system for solid-gas interface sensing via a photoredox mechanism.

  6. Palladium Nanoparticles Supported on Titanium-Doped Graphitic Carbon Nitride for Formic Acid Dehydrogenation.

    Science.gov (United States)

    Wu, Yongmei; Wen, Meicheng; Navlani-García, Miriam; Kuwahara, Yasutaka; Mori, Kohsuke; Yamashita, Hiromi

    2017-04-18

    Pd nanoparticles (NPs) supported on Ti-doped graphitic carbon nitride (g-C 3 N 4 ) were synthesized by a deposition-precipitation route and a subsequent reduction with NaBH 4 . The features of the NPs were studied by XRD, TEM, FTIR, XPS, EXAFS and N 2 -physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti-doped g-C 3 N 4 . Compared to Pd loaded on pristine g-C 3 N 4 , the Pd NPs supported on Ti-doped g-C 3 N 4 exhibited a high catalytic activity in formic acid dehydrogenation in water at room temperature. The enhanced activity could be attributed to the small Pd NPs size, as well as the strong interaction between Pd NPs and Ti-doped g-C 3 N 4 . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Ag nanoparticles loaded on porous graphitic carbon nitride with enhanced photocatalytic activity for degradation of phenol

    Science.gov (United States)

    Han, Zhenwei; Wang, Nan; Fan, Hai; Ai, Shiyun

    2017-03-01

    Highly efficient photocatalyst of visible-light-driven Ag nanoparticles loaded on porous graphitic carbon nitride (g-C3N4) was prepared by the reduction of Ag ions on porous g-C3N4. The obtained Ag/porous g-C3N4 composite products were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflection spectra (DRS), thermal gravimetric analysis (TGA). The results demonstrated that a homogeneous distribution of Ag NPs of 10 nm was attached onto the surface of the porous g-C3N4. The prepared Ag/porous g-C3N4 samples were applied for catalyzing the degradation of phenol in water under visible light irradiation. Porous g-C3N4 demonstrated an excellent support for the formation and dispersion of small uniform Ag NPs. When the weight percentage of Ag reaches 5%, the nanohybrid exhibits superior photocatalytic activities compared to bulk g-C3N4, porous g-C3N4, and 2% Ag/porous g-C3N4 hybrids. The enhanced photocatalytic performance is due to the synergic effect between Ag and porous g-C3N4, which suppressed the recombination of photogenerated electron-hole pairs.

  8. Synthesis of potassium-modified graphitic carbon nitride with high photocatalytic activity for hydrogen evolution.

    Science.gov (United States)

    Wu, Ming; Yan, Jun-Min; Tang, Xian-nian; Zhao, Ming; Jiang, Qing

    2014-09-01

    Potassium-modified graphitic carbon nitride (K-g-C3N4) nanosheets are synthesized by a facile KCl-template method that holds the advantage of easy removal of residual template. A combination of XRD, X-ray photoelectron spectroscopy, and inductively coupled plasma analyses are utilized to characterize the obtained resultant K-g-C3N4 architectures, which are composed of nanosheets of variable thickness (Photocatalytic hydrogen evolution experiments under visible light irradiation showed that K-g-C3N4 nanosheets have high photocatalytic activities (up to about thirteen times higher than that of pure g-C3 N4 ) as well as good stability (no reduction in activity within 16 h); both features emanate from their unique structural characteristics. These results illustrate the viability of this methodology for the facile synthesis of efficient heterogeneous photocatalysts for potential commercial applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. A facile method of activating graphitic carbon nitride for enhanced photocatalytic activity.

    Science.gov (United States)

    Liao, Yongliang; Zhu, Shenmin; Chen, Zhixin; Lou, Xianghong; Zhang, Di

    2015-11-07

    Activated graphitic carbon nitride (g-C3N4) with enhanced photocatalytic capability under visible light irradiation was fabricated by using a facile chemical activation treatment method. In the chemical activation, a mixed solution of hydrogen peroxide and ammonia was employed. The yield can reach as high as 90% after the activation process. The activation process did not change the crystal structure, functional group, morphology and specific surface area of pristine g-C3N4, but it introduced H and O elements into the CN framework of g-C3N4, resulting in a broader optical absorption range, higher light absorption capability and more efficient separation of photogenerated electrons and holes. The photoactivity was investigated by the degradation of rhodamine B (RhB) under visible light irradiation. As compared to the pristine g-C3N4, the activated g-C3N4 exhibited a distinct and efficient two-step degradation process. It was found that the RhB dye in the activated g-C3N4 was mainly oxidized by the photogenerated holes. It is believed that sufficient holes account for the two-step degradation process because they would significantly improve the efficiency of the N-de-ethylation reaction of RhB.

  10. Time-Resolved Study on Xanthene Dye-Sensitized Carbon Nitride Photocatalytic Systems.

    Science.gov (United States)

    Zhang, Huiyu; Li, Shuang; Lu, Rong; Yu, Anchi

    2015-10-07

    Dye sensitization is a promising strategy to extend the visible light absorption of carbon nitride (C3N4) and increase the photocatalytic hydrogen evolution efficiency of C3N4 under visible light irradiation. However, the interaction dynamics between C3N4 and a sensitized dye has not been reported in the literature. Herein, we selected four commonly used xanthene dyes such as fluorescein, dibromofluorescein, eosin Y, and erythrosine B and prepared their corresponding dye-sensitized-C3N4 composites. For the first time, we derived the electron transfer rate from the LUMO of each photoexcited xanthene dye to the conduction band of C3N4 using picoesecond time-resolved fluorescence measurements. We also obtained the reduction potentials of all selected xanthene dyes and C3N4 with cyclic voltammetry measurements. The cyclic voltammetry measurements gave a consistent result with the picosecond time-resolved fluorescence measurements. Besides, the possibility of the selected xanthene dye as an acceptor for the hole of the photoexcited C3N4 was also discussed. We believe this study is significant for the researcher to understanding the fundamental aspects in the xanthene dye-sensitized-C3N4 photocatalytic systems.

  11. Adsorption of Paraquat Dichloride by Graphitic Carbon Nitride Synthesized from Melamine Scraps

    Science.gov (United States)

    Watcharenwong, A.; Kaeokan, A.; Rammaroeng, R.; Upama, P.; Kajitvichyanukul, P.

    2017-07-01

    In this research, graphitic carbon nitride (g-C3N4) was synthesized from useless melamine scraps. Mixture of melamine powder and urea was directly burned in the muffle furnace at 550 °C. Later as-synthesized g-C3N4 was modified with hydrochloric acid. The g-C3N4 powder was characterized by several techniques including X-ray diffraction, scanning electron microscope, and specific surface area analyser. Adsorption of the herbicide paraquat from an aqueous solution to suspended particles of g-C3N4 was investigated, taking into consideration several parameters such as initial concentration of paraquat, initial pH, and dosage of g-C3N4. The results showed that with the same amount of g-C3N4, the increase in the paraquat concentration caused the reduction in the removal efficiency and the higher the amount of g-C3N4, the less residual paraquat remained in the bulk solution. G-C3N4 showed better adsorption behaviour in the basic condition. Finally, Langmuir and Freundlich adsorption isotherms were also evaluated. Paraquat adsorption by g-C3N4 was in accordance with Langmuir more than Freundlich adsorption isotherm.

  12. Composition-dependent buckling behaviour of hybrid boron nitride-carbon nanotubes.

    Science.gov (United States)

    Zhang, Jin; Meguid, S A

    2015-05-21

    The buckling of hybrid boron nitride-carbon nanotubes (BN-CNTs) with various BN compositions and locations of the BN domain is investigated using molecular dynamics. We find that BN-CNTs with large BN composition (>38%) only undergo local shell-like buckling in their BN domain. Although similar local shell-like buckling can occur in BN-CNTs with a relatively small BN composition, it can transfer to the global column-like buckling of the whole BN-CNT with increasing strains. The critical strains for local shell-like and global column-like buckling decrease with increasing BN composition. In addition, critical strains and buckling modes of the global column-like buckling of BN-CNTs also strongly depend on the location of their BN domain. As a possible application of the buckling of BN-CNTs, we demonstrate that the BN-CNT can serve as a water channel integrated with a local natural valve using the local buckling of its BN domain.

  13. Sulfur-Modified Graphitic Carbon Nitride Nanostructures as an Efficient Electrocatalyst for Water Oxidation.

    Science.gov (United States)

    Kale, Vinayak S; Sim, Uk; Yang, Jiwoong; Jin, Kyoungsuk; Chae, Sue In; Chang, Woo Je; Sinha, Arun Kumar; Ha, Heonjin; Hwang, Chan-Cuk; An, Junghyun; Hong, Hyo-Ki; Lee, Zonghoon; Nam, Ki Tae; Hyeon, Taeghwan

    2017-05-01

    There is an urgent need to develop metal-free, low cost, durable, and highly efficient catalysts for industrially important oxygen evolution reactions. Inspired by natural geodes, unique melamine nanogeodes are successfully synthesized using hydrothermal process. Sulfur-modified graphitic carbon nitride (S-modified g-CN x ) electrocatalysts are obtained by annealing these melamine nanogeodes in situ with sulfur. The sulfur modification in the g-CN x structure leads to excellent oxygen evolution reaction activity by lowering the overpotential. Compared with the previously reported nonmetallic systems and well-established metallic catalysts, the S-modified g-CN x nanostructures show superior performance, requiring a lower overpotential (290 mV) to achieve a current density of 10 mA cm -2 and a Tafel slope of 120 mV dec -1 with long-term durability of 91.2% retention for 18 h. These inexpensive, environmentally friendly, and easy-to-synthesize catalysts with extraordinary performance will have a high impact in the field of oxygen evolution reaction electrocatalysis. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Electroanalytical performance of nitrogen-containing tetrahedral amorphous carbon thin-film electrodes.

    Science.gov (United States)

    Yang, Xingyi; Haubold, Lars; DeVivo, Gabriel; Swain, Greg M

    2012-07-17

    Tetrahedral amorphous carbon (ta-C) consists of a mixture of sp(3)- and sp(2)-bonded carbon ranging from 60 to 40% (sp(3)/sp(3)+sp(2)) depending on the deposition conditions. The physical, chemical, and electrochemical properties depend on the sp(2)/sp(3) bonding ratio as well as the presence of incorporated impurities, such as hydrogen or nitrogen. The ability to grow ta-C at lower temperatures (25-100 °C) on a wider variety of substrates as compared to CVD diamond is an advantage of this material. Herein, we report on the structural and electrochemical properties of nitrogen-incorporated ta-C thin films (ta-C:N). The incorporation of nitrogen into the films decreases the electrical resistivity from 613 ± 60 (0 sccm N(2)) to 1.10 ± 0.07 Ω-cm (50 sccm N(2)), presumably by increasing the sp(2)-bonded carbon content and the connectedness of these domains. Similar to boron-doped diamond, these materials are characterized by a low background voltammetric current, a wide working potential window (~ 3 V), and relatively rapid electron-transfer kinetics for aqueous redox systems, including Fe(CN)(6)(-3/-4) and Ru(NH(3))(6)(+3/+2), without conventional pretreatment. Additionally, there is weak molecular adsorption of polar molecules (methylene blue) on the ta-C surface. Overall, the properties of the ta-C and ta-C:N electrodes are such that they could be excellent new choices for electroanalytical measurements.

  15. Carbonate mineralization via an amorphous calcium carbonate (ACC) pathway: Tuning polymorph selection by Mg, pH, and mixing environment

    Science.gov (United States)

    Dove, P. M.; Blue, C.; Mergelsberg, S. T.; Giuffre, A. J.; Han, N.; De Yoreo, J. J.

    2017-12-01

    Mineral formation by nonclassical processes is widespread with many pathways that include aggregation of nanoparticles, oriented attachment of fully formed crystals, and sequential nucleation/transformation of amorphous phases (De Yoreo et al., 2015, Science). Field observations indicate amorphous calcium carbonate (ACC) can be the initial precipitate when local conditions promote high supersaturations for short time periods. Examples include microbial mats, marine porewaters that undergo pulses of increased alkalinity, closed basin lakes, and sabkhas. The crystalline products exhibit diverse morphologies and complex elemental and isotopic signatures. This study quantifies relationships between solution composition and the crystalline polymorphs that transform from ACC (Blue et al., GCA, 2017). Our experimental design synthesized ACC under controlled conditions for a suite of compositions by tuning input pH, Mg/Ca, and total carbonate concentration. ACC products were allowed to transform within output suspensions under stirred or quiescent mixing while characterizing the polymorph and composition of evolving solutions and solids. We find that ACC transforms to crystalline polymorphs with a systematic relationship to solution composition to give a quantitative framework based upon solution aMg2+/aCa2+ and aCO32-/aCa2+. We also measure a polymorph-specific evolution of pH and Mg/Ca during the transformation that indicates the initial polymorph to form. Pathway is further modulated by stirring versus quiescent conditions. The findings reconcile discrepancies among previous studies of ACC to crystalline products and supports claims that monohydrocalcite may be an overlooked, transient phase during formation of some aragonite and calcite deposits. Organic additives and extreme pH are not required to tune composition and polymorph. Insights from this study reiterate the need to revisit long-standing dogmas regarding controls on CaCO3 polymorph selection. Classical models

  16. Transformation of Graphitic and Amorphous Carbon Dust to Complex Organic Molecules in a Massive Carbon Cycle in Protostellar Nebulae

    Science.gov (United States)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    More than 95% of silicate minerals and other oxides found in meteorites were melted, or vaporized and recondensed in the Solar Nebula prior to their incorporation into meteorite parent bodies. Gravitational accretion energy and heating via radioactive decay further transformed oxide minerals accreted into planetesimals. In such an oxygen-rich environment the carbonaceous dust that fell into the nebula as an intimate mixture with oxide grains should have been almost completely converted to CO. While some pre-collapse, molecular-cloud carbonaceous dust does survive, much in the same manner as do pre-solar oxide grains, such materials constitute only a few percent of meteoritic carbon and are clearly distinguished by elevated D/H, N-15/N-16, C-13/C-12 ratios or noble gas patterns. Carbonaceous Dust in Meteorites: We argue that nearly all of the carbon in meteorites was synthesized in the Solar Nebula from CO and that this CO was generated by the reaction of carbonaceous dust with solid oxides, water or OH. It is probable that some fraction of carbonaceous dust that is newly synthesized in the Solar Nebula is also converted back into CO by additional thermal processing. CO processing might occur on grains in the outer nebula through irradiation of CO-containing ice coatings or in the inner nebula via Fischer-Tropsch type (FTT) reactions on grain surfaces. Large-scale transport of both gaseous reaction products and dust from the inner nebula out to regions where comets formed would spread newly formed carbonaceous materials throughout the solar nebula. Formation of Organic Carbon: Carbon dust in the ISM might easily be described as inorganic graphite or amorphous carbon, with relatively low structural abundances of H, N, O and S . Products of FTT reactions or organics produced via irradiation of icy grains contain abundant aromatic and aliphatic hydrocarbons. aldehydes, keytones, acids, amines and amides.. The net result of the massive nebular carbon cycle is to convert

  17. Amorphous and crystalline calcium carbonate phases during carbonation of nanolimes: implications in heritage conservation

    Czech Academy of Sciences Publication Activity Database

    Rodriguez-Navarro, C.; Elert, K.; Ševčík, Radek

    2016-01-01

    Roč. 18, č. 35 (2016), s. 6594-6607 ISSN 1466-8033 R&D Projects: GA ČR(CZ) GP14-20374P; GA MŠk(CZ) LO1219 Keywords : carbonation * nanolime * kinetics * CaCO3 polymorphs Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 3.474, year: 2016 http://pubs.rsc.org/en/Content/ArticleLanding/2016/CE/c6ce01202g#!divAbstract

  18. Effect of silicon and oxygen dopants on the stability of hydrogenated amorphous carbon under harsh environmental conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mangolini, Filippo [Univ. of Texas, Austin, TX (United States); Krick, Brandon A. [Lehigh Univ., Bethlehem, PA (United States); Jacobs, Tevis D. B. [Univ. of Pittsburgh, PA (United States); Khanal, Subarna R. [Univ. of Pittsburgh, PA (United States); Streller, Frank [Univ. of Pennsylvania, Philadelphia, PA (United States); McClimon, J. Brandon [Univ. of Pennsylvania, Philadelphia, PA (United States); Hilbert, James [Univ. of Pennsylvania, Philadelphia, PA (United States); Prasad, Somuri V. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Scharf, Thomas W. [Univ. of North Texas, Denton, TX (United States); Ohlhausen, James A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lukes, Jennifer R. [Univ. of Pennsylvania, Philadelphia, PA (United States); Sawyer, W. Gregory [Univ. of Florida, Gainesville, FL (United States); Carpick, Robert W. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    2018-04-01

    Harsh environments pose materials durability challenges across the automotive, aerospace, and manufacturing sectors, and beyond. While amorphous carbon materials have been used as coatings in many environmentally-demanding applications owing to their unique mechanical, electrical, and optical properties, their limited thermal stability and high reactivity in oxidizing environments have impeded their use in many technologies. Silicon- and oxygen-containing hydrogenated amorphous carbon (a-C:H:Si:O) films are promising for several applications because of their higher thermal stability and lower residual stress compared to hydrogenated amorphous carbon (a-C:H). However, an understanding of their superior thermo-oxidative stability compared to a-C:H is lacking, as it has been inhibited by the intrinsic challenge of characterizing an amorphous, multi-component material. Here, we show that introducing silicon and oxygen in a-C:H slightly enhances the thermal stability in vacuum, but tremendously increases the thermo-oxidative stability and the resistance to degradation upon exposure to the harsh conditions of low Earth orbit (LEO). The latter is demonstrated by having mounted samples of a-C:H:Si:O on the exterior of the International Space Station via the Materials International Space Station (MISSE) mission 7b. Exposing lightly-doped a-C:H:Si:O to elevated temperatures under aerobic conditions or to LEO causes carbon volatilization in the near-surface region, producing a silica surface layer that protects the underlying carbon from further removal. In conclusion, these findings provide a novel physically-based understanding of the superior stability of a-C:H:Si:O in harsh environments compared to a-C:H.

  19. Plasma-enhanced chemical-vapor deposition of titanium aluminum carbonitride/amorphous-carbon nanocomposite thin films

    Science.gov (United States)

    Shieh, Jiann; Hon, Min Hsiung

    2002-01-01

    A new nanocomposite, titanium aluminum carbonitride/amorphous-carbon thin film was prepared by radio-frequency (rf) plasma-enhanced chemical-vapor deposition using titanium tetrachloride, aluminum trichloride, methane, and nitrogen as reactants. Hydrogen was used as carrier gases. A substrate temperature of 500 °C and an rf power of 100 W were used in all depositions. The films were characterized by x-ray powder diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy. The results show that nanograins of titanium aluminum carbonitride were embedded in an amorphous-carbon matrix. The nanograins had a (200) preferred orientation with columnar cross-section morphology. Mechanical properties were analyzed by nanoindentation and hardness was demonstrated to increase via this microstructure design approach. The effects of microstructure on mechanical properties were also determined.

  20. Plasma-enhanced chemical-vapor deposition of titanium aluminum carbonitride/amorphous-carbon nanocomposite thin films

    International Nuclear Information System (INIS)

    Shieh Jiann; Hon, M.H.

    2002-01-01

    A new nanocomposite, titanium aluminum carbonitride/amorphous-carbon thin film was prepared by radio-frequency (rf) plasma-enhanced chemical-vapor deposition using titanium tetrachloride, aluminum trichloride, methane, and nitrogen as reactants. Hydrogen was used as carrier gases. A substrate temperature of 500 deg. C and an rf power of 100 W were used in all depositions. The films were characterized by x-ray powder diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy. The results show that nanograins of titanium aluminum carbonitride were embedded in an amorphous-carbon matrix. The nanograins had a (200) preferred orientation with columnar cross-section morphology. Mechanical properties were analyzed by nanoindentation and hardness was demonstrated to increase via this microstructure design approach. The effects of microstructure on mechanical properties were also determined

  1. Effects of Nitride on the Tribological Properties of the Low Carbon Alloy Steel

    OpenAIRE

    Chang, Yuh-Ping; Wang, Jin-Chi; Horng, Jeng-Haur; Chu, Li-Ming; Hwang, Yih-Chyun

    2013-01-01

    The technology of composite heat treatment is used popularly for low friction and wear resistance of drive elements. A large number of papers about the heat treatment technology had been proposed. Especially, the nitride treatment has been used widely for the purpose of wear resistance and low friction in the industry. Therefore, the self-developed vertical ball/disk friction tester with the measurement system was used to study the effects of nitride on the tribological properties of the low ...

  2. Improved Tribological Performance of Amorphous Carbon (a-C Coating by ZrO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Jinzhu Tang

    2016-09-01

    Full Text Available Nanomaterials, such as Graphene, h-BN nanoparticles and MoS2 nanotubes, have shown their ability in improving the tribological performance of amorphous carbon (a-C coatings. In the current study, the effectiveness of ZrO2 nanoparticles (ZrO2-NPs in lubricating the self-mated nonhydrogenated a-C contacts was investigated in boundary lubrication regime. The results showed that 13% less friction and 50% less wear compared to the base oil were achieved by employing ZrO2-NPs in the base oil in self-mated a-C contacts. Via analyzing the ZrO2-NPs and the worn a-C surface after tests, it was found that the improved lubrication by ZrO2-NPs was based on “polishing effects”, which is a new phenomenon observed between a-C and nanoparticles. Under the “polishing effect”, micro-plateaus with extremely smooth surface and uniform height were produced on the analyzed a-C surface. The resulting topography of the a-C coating is suitable for ZrO2-NPs to act as nano-bearings between rubbing surfaces. Especially, the ZrO2-NPs exhibited excellent mechanical and chemical stability, even under the severe service condition, suggesting that the combination of nonhydrogenated a-C coating with ZrO2-NPs is an effective, long lasting and environment-friendly lubrication solution.

  3. Electron-beam broadening in amorphous carbon films in low-energy scanning transmission electron microscopy.

    Science.gov (United States)

    Drees, H; Müller, E; Dries, M; Gerthsen, D

    2018-02-01

    Resolution in scanning transmission electron microscopy (STEM) is ultimately limited by the diameter of the electron beam. The electron beam diameter is not only determined by the properties of the condenser lens system but also by electron scattering in the specimen which leads to electron-beam broadening and degradation of the resolution with increasing specimen thickness. In this work we introduce a new method to measure electron-beam broadening which is based on STEM imaging with a multi-segmented STEM detector. We focus on STEM at low electron energies between 10 and 30 keV and use an amorphous carbon film with known thickness as test object. The experimental results are compared with calculated beam diameters using different analytical models and Monte-Carlo simulations. We find excellent agreement of the experimental data with the recently published model by Gauvin and Rudinsky [1] for small t/λ el (thickness to elastic mean free path) values which are considered in our study. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Origin of temperature-induced low friction of sputtered Si-containing amorphous carbon coatings

    International Nuclear Information System (INIS)

    Jantschner, O.; Field, S.K.; Holec, D.; Fian, A.; Music, D.; Schneider, J.M.; Zorn, K.; Mitterer, C.

    2015-01-01

    This work reports on a tribological study of magnetron-sputtered silicon-containing amorphous carbon thin films vs. their alumina counterparts. Temperature cycling during ball-on-disk tests in humid air revealed a decrease in the coefficient of friction from 0.3 to <0.02 beyond 240 ± 15 °C. Systematic variation of the environment confirmed oxygen to be responsible for the low friction. X-ray photoelectron spectroscopy of the wear tracks indicates oxidation of Si-C bonds and formation of Si-O-C bonds, followed by further oxidation to SiO 2 above 450 °C. Ab initio molecular dynamics simulations of gas interactions with the a-C surface revealed dissociation of O 2 and the formation of oxides. Additional density functional theory calculations of Si incorporation into a graphene layer, resembling the surface of the film, showed preferential attraction of gaseous species (H, O, -OH, H 2 O), to Si-sites as compared to C-sites. Hence, the temperature- and atmosphere-induced changes in friction coefficient can be understood based on correlative X-ray photoelectron spectroscopy and ab initio data: the formation of Si-O-C bonds stemming from a reaction of the as-deposited coating with atmosphere in the tribological contact is observed by theory and experiment

  5. Characterisation of electrodeposited Co-W-P amorphous coatings on carbon steel

    International Nuclear Information System (INIS)

    Yun, Hyeong Jin; Dulal, S.M.S.I.; Shin, Chee Burm; Kim, Chang-Koo

    2008-01-01

    Electrochemistry and nucleation mechanism of induced co-deposition of cobalt, tungsten and phosphorus from a citrate bath was investigated using voltammetry and chronoamperometry techniques. It was found that the induced co-deposition of the species occurred under diffusion control and followed instantaneous nucleation mechanism. Co-W-P coatings were electrodeposited potentiostatically on plain carbon steels from a citrate bath containing CoSO 4 , Na 2 WO 4 and NaH 2 PO 2 . X-ray diffraction studies of the coatings revealed that the as-deposited Co 81 W 10 P 9 coatings had amorphous structure. The formation of some stoichiometric compounds like Co 3 W, Co 2 P and WP 2 , however, was observed upon annealing at 600 deg. C. The hardness of the Co-W-P coatings increased with annealing temperature which was possibly due to the formation of these inter-elemental compounds. The corrosion resistance of the Co-W-P coatings increased with increase in annealing temperature which might also be due to the formation of the stoichiometric compounds at elevated temperatures. A comparison between coating characteristics of Co-W-P and chromium showed that the Co-W-P coatings exhibited nobler corrosion potential than chromium coatings

  6. Ion-Assisted Pulsed Laser Deposition of amorphous tetrahedral-coordinated carbon films

    Science.gov (United States)

    Friedmann, T. A.; Tallant, D. R.; Sullivan, J. P.; Siegal, M. P.; Simpson, R. L.

    1994-04-01

    A parametric study has been performed of amorphous tetrahedral carbon (a-tC) films produced by ion-assisted pulsed laser deposition (IAPLD). The ion voltage, current density, and feed gas composition (nitrogen in argon) have been varied. The resultant films were characterized by thickness, residual stress, Raman spectroscopy, and electrical resistivity. The Raman spectra have been fit to two gaussian peaks, the so called graphitic (G) peak and the disorder (D) peak. It has been found that the magnitude of the D peak and the residual compressive stress are inversely correlated. At low beam voltages and currents, the magnitude of the D peak is low, increasing as the ion beam voltage and current are raised. The ion beam voltage has the most dramatic effect on the magnitude of the D peak. At low voltages (200-500 V) the magnitude of the D peak is greater for ion beams with high percentages of nitrogen possibly indicative of C-N bonding in the films. At higher voltages (500-1500 V) the D peak intensity is less sensitive to the nitrogen content of the beam.

  7. Amorphous Carbon Deposited by a Novel Aerosol-Assisted Chemical Vapor Deposition for Photovoltaic Solar Cells

    Science.gov (United States)

    Ahmad, Nurfadzilah; Kamaruzzaman, Dayana; Rusop, Mohamad

    2012-06-01

    Amorphous carbon (a-C) solar cells were successfully prepared using a novel and self-designed aerosol-assisted chemical vapor deposition (AACVD) method using camphor oil as a precursor. The fabricated solar cell with the configuration of Au/p-C/n-Si/Au achieved an efficiency of 0.008% with a fill factor of 0.15 for the device deposited at 0.5 h. The current-voltage (I-V) graph emphasized on the linear graph (ohmic) for the a-C thin films, whereas for the p-n device structure, a rectifying curve was obtained. The rectifying curves signify the heterojunction between the p-type a-C film and the n-Si substrate and designate the generation of electron-hole pair of the samples under illumination. Photoresponse characteristics of the deposited a-C was highlighted when being illuminated (AM 1.5 illumination: 100 mW/cm2, 25 °C). Transmittance spectrum exhibit a large transmittance value (>85%) and absorption coefficient value of 103-104 cm-1 at the visible range of 390 to 790 nm. The atomization of a liquid precursor solution into fine sub-micrometre-sized aerosol droplets in AACVD induced the smooth surface of a-C films. To the best of our knowledge, fabrication of a-C solar cell using this AACVD method has not yet been reported.

  8. The kinetics and mechanisms of amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite.

    Science.gov (United States)

    Rodriguez-Blanco, Juan Diego; Shaw, Samuel; Benning, Liane G

    2011-01-01

    The kinetics and mechanisms of nanoparticulate amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite, were studied at a range of environmentally relevant temperatures (7.5-25 °C) using synchrotron-based in situ time-resolved Energy Dispersive X-ray Diffraction (ED-XRD) in conjunction with high-resolution electron microscopy, ex situ X-ray diffraction and infrared spectroscopy. The crystallization process occurs in two stages; firstly, the particles of ACC rapidly dehydrate and crystallize to form individual particles of vaterite; secondly, the vaterite transforms to calcite via a dissolution and reprecipitation mechanism with the reaction rate controlled by the surface area of calcite. The second stage of the reaction is approximately 10 times slower than the first. Activation energies of calcite nucleation and crystallization are 73±10 and 66±2 kJ mol(-1), respectively. A model to calculate the degree of calcite crystallization from ACC at environmentally relevant temperatures (7.5-40 °C) is also presented.

  9. The multilayered structure of ultrathin amorphous carbon films synthesized by filtered cathodic vacuum arc deposition

    KAUST Repository

    Wang, Na

    2013-08-01

    The structure of ultrathin amorphous carbon (a-C) films synthesized by filtered cathodic vacuum arc (FCVA) deposition was investigated by high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy. Results of the plasmon excitation energy shift and through-thickness elemental concentration show a multilayered a-C film structure comprising an interface layer consisting of C, Si, and, possibly, SiC, a buffer layer with continuously increasing sp 3 fraction, a relatively thicker layer (bulk film) of constant sp 3 content, and an ultrathin surface layer rich in sp 2 hybridization. A detailed study of the C K-edge spectrum indicates that the buffer layer between the interface layer and the bulk film is due to the partial backscattering of C+ ions interacting with the heavy atoms of the silicon substrate. The results of this study provide insight into the minimum thickness of a-C films deposited by FCVA under optimum substrate bias conditions. Copyright © 2013 Materials Research Society.

  10. Strength and Fracture Resistance of Amorphous Diamond-Like Carbon Films for MEMS

    Directory of Open Access Journals (Sweden)

    K. N. Jonnalagadda

    2009-01-01

    Full Text Available The mechanical strength and mixed mode I/II fracture toughness of hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C films, grown by pulsed laser deposition, are discussed in connection to material flaws and its microstructure. The failure properties of ta-C were obtained from films with thicknesses 0.5–3 μm and specimen widths 10–20 μm. The smallest test samples with 10 μm gage section averaged a strength of 7.3 ± 1.2 GPa, while the strength of 20-μm specimens with thicknesses 0.5–3 μm varied between 2.2–5.7 GPa. The scaling of the mechanical strength with specimen thickness and dimensions was owed to deposition-induced surface flaws, and, only in the smallest specimens, RIE patterning generated specimen sidewall flaws. The mode I fracture toughness of ta-C films is KIc=4.4±0.4 MPam, while the results from mixed mode I/II fracture experiments with cracks arbitrarily oriented in the plane of the film compared very well with theoretical predictions.

  11. Etching characteristics and application of physical-vapor-deposited amorphous carbon for multilevel resist

    International Nuclear Information System (INIS)

    Kim, H. T.; Kwon, B. S.; Lee, N.-E.; Park, Y. S.; Cho, H. J.; Hong, B.

    2008-01-01

    For the fabrication of a multilevel resist (MLR) based on a very thin, physical-vapor-deposited (PVD) amorphous carbon (a-C) layer, the etching characteristics of the PVD a-C layer with a SiO x hard mask were investigated in a dual-frequency superimposed capacitively coupled plasma etcher by varying the following process parameters in O 2 /N 2 /Ar plasmas: high-frequency/low-frequency combination (f HF /f LF ), HF/LF power ratio (P HF /P LF ), and O 2 and N 2 flow rates. The very thin nature of the a-C layer helps to keep the aspect ratio of the etched features low. The etch rate of the PVD a-C layer increased with decreasing f HF /f LF combination and increasing P LF and was initially increased but then decreased with increasing N 2 flow rate in O 2 /N 2 /Ar plasmas. The application of a 30 nm PVD a-C layer in the MLR structure of ArF PR/BARC/SiO x /PVD a-C/TEOS oxide supported the possibility of using a very thin PVD a-C layer as an etch-mask layer for the TEOS-oxide layer

  12. Ti doped amorphous carbon (Al/Ti-a:C/p-Si/Al) photodiodes for optoelectronic applications

    Science.gov (United States)

    Aslan, Naim; Koç, Mümin Mehmet; Dere, Ayşegül; Arif, Bilal; Erkovan, Mustafa; Al-Sehemi, Abdullah G.; Al-Ghamdi, Ahmed A.; Yakuphanoglu, Fahrettin

    2018-03-01

    Electrochemical deposition technique was used to fabricate titanium doped amorphous carbon (Ti doped a:C) Al/Ti-a:C/p-Si/Al photodiode. The effects of illumination on the current-voltage (I-V) characteristics of the Al/a:C/p-Si/Al doped Ti diode for optoelectronic applications were investigated. The reverse current of the diode increased with the increasing illumination intensities when the bias voltage was applied. By using the forward bias I-V characteristics, the ideality factor (n) and barrier height (Φb) of Al/Ti-a:C/p-Si photodiode structure was found as 1,84 and 0,50 eV, respectively. In addition, the capacitance-voltage (C-V) and conductance-voltage (G-V) measurements of the diode were studied in the frequency range of 100 kHz-600 kHz. The measured values of the capacitance decreased with the increasing frequency. The photoelectrical properties of Al/Ti-a:C/p-Si/Al device indicates that the photodiode investigated in this paper has great potential to be used in optoelectronic device applications and in industry.

  13. Pseudo first ordered adsorption of noxious textile dyes by low-temperature synthesized amorphous carbon nanotubes

    Science.gov (United States)

    Banerjee, D.; Bhowmick, P.; Pahari, D.; Santra, S.; Sarkar, S.; Das, B.; Chattopadhyay, K. K.

    2017-03-01

    Amorphous carbon nanotubes (a-CNTs) were synthesized by solid state reaction. The as prepared a-CNTs were characterized by X-ray diffraction, field emission scanning and high resolution transmission electron microscope and Raman spectroscopy. As-synthesized a-CNTs were used for, the first time, for removing different organic dyes from water. The dyes mainly include Rhodamine B and Methyl Orange and systematic batch mode studies of a-CNTs assisted adsorption have been executed in detail. The removing efficiency of a-CNTs has also been investigated for various sorption parameters like contact time, dosage, pH, initial dye concentration, contact time etc. It is seen that a-CNTs can be material of potential for removal of dyes. In case of Rhodamine B, the maximum time for removal was 45 min whereas for Methyl orange rapid removal was plausible in about 30 min even in ambient condition. The experimental data have been well correlated with classical Langmuir-Freundlich and Temkin adsorption models.

  14. Enhanced electrochemical performance of amorphous carbon nanotube-manganese-di-oxide-poly-pyrrole ternary nanohybrid

    Science.gov (United States)

    Pahari, D.; Das, N. S.; Das, B.; Howli, P.; Chattopadhyay, K. K.; Banerjee, D.

    2017-12-01

    Amorphous carbon nanotubes (a-CNTs) manganese di oxide (MnO2)-poly pyrrole (PPy) ternary nanocomposites have been synthesized by a simple chemical route. The as prepared samples have been characterized with different characterization tools that include field emission scanning and high resolution transmission electron microscopy, Raman, Fourier transformed infrared as well as UV-Vis spectroscopy. The electrochemical performance of all the as prepared pure and hybrid samples have been studied in detail. It has been seen that the ternary hybrid shows efficient electrochemical performance with high value of specific capacitance with good stability even up to 2000 cycles. The superior performance of the hybrid samples can be attributed to the strong synergistic effect between the components resulting electron shuttling along PPy main chains and inter-chain raising built-in continuous conductive network. The ternary composite approach offers an effective solution to enhance the device performance of metal-oxide based supercapacitors for long cycling applications. These studies can well speculate the existence of another supercapacitor hybrid for the use in environment friendly electrode and thus a pollution free nature.

  15. Short-pulse-laser-induced optical damage and fracto-emission of amorphous, diamond-like carbon films

    Science.gov (United States)

    Sokolowski-Tinten, Klaus; Ziegler, Wolfgang; von der Linde, Dietrich; Siegal, Michael P.; Overmyer, D. L.

    2005-03-01

    Short-pulse-laser-induced damage and ablation of thin films of amorphous, diamond-like carbon have been investigated. Material removal and damage are caused by fracture of the film and ejection of large fragments. The fragments exhibit a delayed, intense and broadband emission of microsecond duration. Both fracture and emission are attributed to the laser-initiated relaxation of the high internal stresses of the pulse laser deposition-grown films.

  16. Characterization of the bonding structure of nanocrystalline diamond and amorphous carbon films prepared by plasma assisted techniques

    Czech Academy of Sciences Publication Activity Database

    Popov, C.; Kulisch, W.; Bliznakov, S.; Mednikarov, B.; Spasov, G.; Pirov, J.; Jelínek, Miroslav; Kocourek, Tomáš; Zemek, Josef

    2007-01-01

    Roč. 89, č. 1 (2007), s. 209-212 ISSN 0947-8396 Grant - others:NATO(XE) CBP.EAP.CLG 981519; Marie-Curie EIF(XE) MEIF-CT-2004-500038 Institutional research plan: CEZ:AV0Z10100520 Keywords : nanocrystalline diamond * amorphous carbon * CVD * PLD * magnetron Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.857, year: 2007

  17. Formation of hydrogenated amorphous carbon films of controlled hardness from a methane plasma

    International Nuclear Information System (INIS)

    Vandentop, G.J.; Kawasaki, M.; Nix, R.M.; Brown, I.G.; Salmeron, M.; Somorjai, G.A.; Department of Chemistry, University of California at Berkeley, Berkeley, California 94720)

    1990-01-01

    Studies of amorphous hydrogenated carbon (a-C:H) film deposition revealed that methyl radicals are the precursor species responsible for the bulk mass deposition of the films, while the ions act to improve the mechanical properties. The films were deposited on Si(100) substrates both on the powered (negatively self-biased) and on the grounded electrodes from a methane rf plasma (13.56 MHz) at 68 to 70 mTorr and 300 to 370 K. The films produced on 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. Methyl radicals were incident on the electrode surface with an estimated flux of 10 16 cm -2 s -1 , for a rf power of 50 W. Methyl radicals appear to be the dominant intermediates in the growth of the soft carbon polymer, and there is a remarkable decrease in deposition rate due to the introduction of NO, a radical scavenger. A novel pulsed biasing technique was used so that the role of ions in the plasma could be studied separately. It was found that the hardness of the films depends on the power supplied by the ions to the growing film surface (the time averaged difference between the plasma potential and the electrode potential), but not on the energy of individual ions. The pulsed biasing technique offers an efficient method to adjust the film hardness by independent control of the neutral radical and ion fluxes to the surface

  18. Rational design of coaxial mesoporous birnessite manganese dioxide/amorphous-carbon nanotubes arrays for advanced asymmetric supercapacitors

    KAUST Repository

    Zhu, Shijin

    2015-03-01

    Coaxial mesoporous MnO2/amorphous-carbon nanotubes have been synthesized via a facile and cost-effective strategy at room temperature. The coaxial double nanotubes of inner (outer) MnO2 and outer (inner) amorphous carbon can be obtained via fine tuning the preparative factors (e.g., deposition order and processing temperature). Furthermore, the electrochemical properties of the coaxial nanotubes were evaluated by cycle voltammetric (CV) and galvanostatic charge-discharge (GC) measurements. The as-prepared coaxial double nanotubes of outer MnO2 and inner amorphous carbon exhibit the optimized pseudocapacitance performance (362 F g-1) with good cycling stability, and ideal rate capability owning to the unique nanostructures. When assembled into two-electrode asymmetric supercapacitor, an energy density of 22.56 W h kg-1 at a power density of 224.9 W kg-1 is obtained. These findings provide a new and facile approach to fabricate high-performance electrode for supercapacitors.

  19. Enhanced visible-light-driven photocatalytic performance of porous graphitic carbon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Fei, E-mail: feichang@usst.edu.cn [School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Li, Chenlu; Luo, Jieru; Xie, Yunchao; Deng, Baoqing [School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Hu, Xuefeng, E-mail: xfhu@yic.ac.cn [Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, Shandong 264003 (China)

    2015-12-15

    Graphical abstract: - Highlights: • Porous g-C{sub 3}N{sub 4} samples were fabricated by a facile pyrolysis method. • As-prepared porous g-C{sub 3}N{sub 4} samples showed remarkably enhanced photocatalytic performance. • Holes and radicals ·O{sub 2}{sup −} exerted dominant roles on the photocatalytic process. - Abstract: In this study, a series of porous graphitic carbon nitride (g-C{sub 3}N{sub 4}) materials were fabricated through a direct pyrolysis of protonated melamine by nitric acid solution. These as-prepared porous samples were characterized by a collection of analytical techniques. It was found that a proper concentration of nitric acid solution involved facilitated to generate samples in tube-like morphology with numerous pores, identified with X-ray diffraction patterns, FT-IR spectra, SEM, TEM, and BET measurements. These g-C{sub 3}N{sub 4} samples were subjected to photocatalytic degradation of dye Rhodamine B (RhB) in aqueous under visible-light irradiation. Under identical conditions, those porous g-C{sub 3}N{sub 4} samples showed significantly improved catalytic performance in comparison with the sample prepared without the introduction of nitric acid. In particularly, the best candidate, sample M1:1, showed an apparent reaction rate nearly 6.2 times that of the unmodified counterpart. The enhancement of photocatalytic performance could be attributed to the favorable porous structure with the enlarged specific surface area and the suitable electronic structure as well. In addition, ESR measurements were conducted for the sake of proposing a photocatalytic degradation mechanism.

  20. Resonance energy transfer based electrochemiluminescence and fluorescence sensing of riboflavin using graphitic carbon nitride quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huan [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070 (China); The Phytochemistry Key Laboratory of Tibetan Plateau of Qinghai Province, College of Pharmacy, Qinghai Nationalities University, Xining, Qinghai 810007 (China); Ma, Qin; Wang, Yanfeng; Wang, Caihe; Qin, Dongdong; Shan, Duoliang; Chen, Jing [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070 (China); Lu, Xiaoquan, E-mail: luxq@nwnu.edu.cn [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070 (China)

    2017-06-22

    Graphitic carbon nitride quantum dots (g-CNQDs) are rarely used in the field of electrochemiluminescence. In this paper, g-CNQDs have a strong and stable electrochemiluminescence (ECL) signal generated in the presence of co-reactant K{sub 2}S{sub 2}O{sub 8}. The ECL signal of g-CNQDs was quenched by the mechanism of resonance energy transfer (RET) between donor g-CNQDs and receptor riboflavin (RF) that is proved by UV-vis absorption spectroscopy, electrochemiluminescence and fluorescence emission spectroscopy analysis technology. Therefore, we achieved detection of the riboflavin content in the drug tablets of vitamin B{sub 2} using ECL and FL. The determination results of ECL showed that the riboflavin content of the drug vitamin B{sub 2} (VB{sub 2}) tablets was consistent with the fluorescence (FL) analysis, with wider linear range of 0.02–11 μM and lower minimum detection limit of 0.63 nM (S/N = 3) than FL. Hence, the riboflavin content in human serum was further detected using ECL. The relative standard deviation is less than 6.5%, with an acceptable recovery of 95.33%–104.22%, which means that this sensor has potential applications in the actual sample analysis. As a new ECL luminary, g-CNQDs have opened a new field for the development and application of ECL sensor. - Highlights: • G-CNQDs proposed as a new luminophore for ECL. • ECL signal was strong and stable in the presence of co-reactant K{sub 2}S{sub 2}O{sub 8}. • Based on the resonance energy transfer between g-CNQDs and riboflavin. • ECL has wider linear range and lower detection limit than FL.

  1. Resonance energy transfer based electrochemiluminescence and fluorescence sensing of riboflavin using graphitic carbon nitride quantum dots

    International Nuclear Information System (INIS)

    Wang, Huan; Ma, Qin; Wang, Yanfeng; Wang, Caihe; Qin, Dongdong; Shan, Duoliang; Chen, Jing; Lu, Xiaoquan

    2017-01-01

    Graphitic carbon nitride quantum dots (g-CNQDs) are rarely used in the field of electrochemiluminescence. In this paper, g-CNQDs have a strong and stable electrochemiluminescence (ECL) signal generated in the presence of co-reactant K 2 S 2 O 8 . The ECL signal of g-CNQDs was quenched by the mechanism of resonance energy transfer (RET) between donor g-CNQDs and receptor riboflavin (RF) that is proved by UV-vis absorption spectroscopy, electrochemiluminescence and fluorescence emission spectroscopy analysis technology. Therefore, we achieved detection of the riboflavin content in the drug tablets of vitamin B 2 using ECL and FL. The determination results of ECL showed that the riboflavin content of the drug vitamin B 2 (VB 2 ) tablets was consistent with the fluorescence (FL) analysis, with wider linear range of 0.02–11 μM and lower minimum detection limit of 0.63 nM (S/N = 3) than FL. Hence, the riboflavin content in human serum was further detected using ECL. The relative standard deviation is less than 6.5%, with an acceptable recovery of 95.33%–104.22%, which means that this sensor has potential applications in the actual sample analysis. As a new ECL luminary, g-CNQDs have opened a new field for the development and application of ECL sensor. - Highlights: • G-CNQDs proposed as a new luminophore for ECL. • ECL signal was strong and stable in the presence of co-reactant K 2 S 2 O 8 . • Based on the resonance energy transfer between g-CNQDs and riboflavin. • ECL has wider linear range and lower detection limit than FL.

  2. Self-floating graphitic carbon nitride/zinc phthalocyanine nanofibers for photocatalytic degradation of contaminants

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tiefeng; Ni, Dongjing; Chen, Xia; Wu, Fei; Ge, Pengfei; Lu, Wangyang, E-mail: luwy@zstu.edu.cn; Hu, Hongguang; Zhu, ZheXin; Chen, Wenxing, E-mail: wxchen@zstu.edu.cn

    2016-11-05

    Highlights: • A facile synthetic strategy to prepare visible-light responsive electrospun nanofibers. • Self-floating nanofiber photocatalyts for the effective utilization of solar. • Possible degradation pathway of RhB and CBZ under visible light and solar irradiation. • Present a method for removing highly hazardous contaminants. - Abstract: The effective elimination of micropollutants by an environmentally friendly method has received extensive attention recently. In this study, a photocatalyst based on polyacrylonitrile (PAN)-supported graphitic carbon nitride coupled with zinc phthalocyanine nanofibers (g-C{sub 3}N{sub 4}/ZnTcPc/PAN nanofibers) was successfully prepared, where g-C{sub 3}N{sub 4}/ZnTcPc was introduced as the catalytic entity and the PAN nanofibers were employed as support to overcome the defects of easy aggregation and difficult recycling. Herein, rhodamine B (RhB), 4-chlorophenol and carbamazepine (CBZ) were selected as the model pollutants. Compared with the typical hydroxyl radical-dominated catalytic system, g-C{sub 3}N{sub 4}/ZnTcPc/PAN nanofibers displayed the targeted adsorption and degradation of contaminants under visible light or solar irradiation in the presence of high additive concentrations. According to the results of the radical scavenging techniques and the electron paramagnetic resonance technology, the degradation of target substrates was achieved by the attack of active species, including photogenerated hole, singlet oxygen, superoxide radicals and hydroxyl radicals. Based on the results of ultra-performance liquid chromatography and mass spectrometry, the role of free radicals on the photocatalytic degradation intermediates was identified and the final photocatalytic degradation products of both RhB and CBZ were some biodegradable small molecules.

  3. In situ synthesis of cylindrical spongy polypyrrole doped protonated graphitic carbon nitride for cholesterol sensing application.

    Science.gov (United States)

    Shrestha, Bishnu Kumar; Ahmad, Rafiq; Shrestha, Sita; Park, Chan Hee; Kim, Cheol Sang

    2017-08-15

    Herein, we demonstrate the exfoliation of bulk graphitic carbon nitrides (g-C 3 N 4 ) into ultra-thin (~3.4nm) two-dimensional (2D) nanosheets and their functionalization with proton (g-C 3 N 4 H + ). The layered semiconductor g-C 3 N 4 H + nanosheets were doped with cylindrical spongy shaped polypyrrole (CSPPy-g-C 3 N 4 H + ) using chemical polymerization method. The as-prepared nanohybrid composite was utilized to fabricate cholesterol biosensors after immobilization of cholesterol oxidase (ChOx) at physiological pH. Large specific surface area and positive charge nature of CSPPy-g-C 3 N 4 H + composite has tendency to generate strong electrostatic attraction with negatively charged ChOx, and as a result they formed stable bionanohybrid composite with high enzyme loading. A detailed electrochemical characterization of as-fabricated biosensor electrode (ChOx-CSPPy-g-C 3 N 4 H + /GCE) exhibited high-sensitivity (645.7 µAmM -1 cm -2 ) in wide-linear range of 0.02-5.0mM, low detection limit (8.0μM), fast response time (~3s), long-term stability, and good selectivity during cholesterol detection. To the best of our knowledge, this novel nanocomposite was utilized for the first time for cholesterol biosensor fabrication that resulted in high sensing performance. Hence, this approach opens a new prospective to utilize CSPPy-g-C 3 N 4 H + composite as cost-effective, biocompatible, eco-friendly, and superior electrocatalytic as well as electroconductive having great application potentials that could pave the ways to explore many other new sensors fabrication and biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. The Multiple Effects of Precursors on the Properties of Polymeric Carbon Nitride

    Directory of Open Access Journals (Sweden)

    Wendong Zhang

    2013-01-01

    Full Text Available Polymeric graphitic carbon nitride (g-C3N4 materials were prepared by direct pyrolysis of thiourea, dicyandiamide, melamine, and urea under the same conditions, respectively. In order to investigate the effects of precursors on the intrinsic physicochemical properties of g-C3N4, a variety of characterization tools were employed to analyze the samples. The photocatalytic activity of the samples was evaluated by the removal of NO in gas phase under visible light irradiation. The results showed that the as-prepared CN-T (from thiourea, CN-D (from dicyandiamide, CN-M (from melamine, and CN-U (from urea exhibited significantly different morphologies and microstructures. The band gaps of CN-T, CN-D, CN-M, and CN-U were 2.51, 2.58, 2.56, and 2.88 eV, respectively. Both thermal stability and yield are in the following order: CN-M > CN-D > CN-T > CN-U. The photoactivity of CN-U (31.9% is higher than that of CN-T (29.6%, CN-D (22.2%, and CN-M (26.8%. Considering the cost, toxicity, and yield of the precursors and the properties of g-C3N4, the best precursor for preparation of g-C3N4 was melamine. The present work could provide new insights into the selection of suitable precursor for g-C3N4 synthesis and in-depth understanding of the microstructure-dependent photocatalytic activity of g-C3N4.

  5. Visible-Light Neural Stimulation on Graphitic-Carbon Nitride/Graphene Photocatalytic Fibers.

    Science.gov (United States)

    Zhang, Zhongyang; Xu, Ruodan; Wang, Zegao; Dong, Mingdong; Cui, Bianxiao; Chen, Menglin

    2017-10-11

    Light stimulation allows remote and spatiotemporally accurate operation that has been applied as effective, noninvasive means of therapeutic interventions. Here, visible-light neural stimulation of graphitic carbon nitride (g-C 3 N 4 ), an emerging photocatalyst with visible-light optoelectronic conversion, was for the first time investigated. Specifically, g-C 3 N 4 was combined with graphene oxide (GO) in a three-dimensional manner on the surfaces of electrospun polycaprolactone/gelatin (PG) fibers and functioned as a biocompatible interface for visible-light stimulating neuronal differentiation. The enhanced photocatalytic function of g-C 3 N 4 was realized by spreading g-C 3 N 4 on GO coated electrospun (PG) microfibers to improve both charge separation and surface area. Ascorbic acid (AA) was used in the cell culture medium not only as a photoexcited hole scavenger but also as a mediator of GO reduction to further improve the electrical conductivity. The successful coatings of g-C 3 N 4 , GO, and AA-mediated GO reduction were confirmed using scanning electron microscopy, photoluminescence, Raman spectroscopy, and X-ray photoelectron spectroscopy. Biocompatibility of g-C 3 N 4 (0.01-0.9 mg/mL) to PC12 cells was confirmed by the lactate dehydrogenase (LDH) assay, Live-Dead staining, and colorimetric cell viability assay CCK-8. Under a bidaily, monochromatic light stimulation at a wavelength of 450 nm at 10 mW/cm 2 , a 18.5-fold increase of neurite outgrowth of PC12 was found on g-C 3 N 4 -coated fibers, while AA-reduced GO-g-C 3 N 4 hybrid brought a further 2.6-fold increase, suggesting its great potential as a visible-light neural stimulator that could optically enhance neural growth in a spatiotemporal-specific manner.

  6. C=C π Bond Modified Graphitic Carbon Nitride Films for Enhanced Photoelectrochemical Cell Performance.

    Science.gov (United States)

    Bian, Juncao; Xi, Lifei; Li, Jianfu; Xiong, Ze; Huang, Chao; Lange, Kathrin M; Tang, Jinyao; Shalom, Menny; Zhang, Rui-Qin

    2017-05-04

    Applications of graphitic carbon nitride (g-CN) in photoelectrochemical and optoelectronic devices are still hindered due to the difficulties in synthesis of g-CN films with tunable chemical, physical and catalytic properties. Herein we present a general method to alter the electronic and photoelectrochemical properties of g-CN films by annealing. We found that N atoms can be removed from the g-CN networks after annealing treatment. Assisted by theoretical calculations, we confirm that upon appropriate N removal, the adjacent C atoms will form new C=C π bonds. Detailed calculations demonstrate that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are located at the structure unit with C=C π bonds and the electrons are more delocalized. Valence band X-ray photoelectron spectroscopy spectra together with optical absorption spectra unveil that the structure changes result in the alteration of the g-CN energy levels and position of band edges. Our results show that the photocurrent density of the annealed g-CN film is doubled compared with the pristine one, thanks to the better charge separation and transport within the film induced by the new C=C π bonds. An ultrathin TiO 2 film (2.2 nm) is further deposited on the g-CN film as stabilizer and the photocurrent density is kept at 0.05 mA cm -2 at 1.23 V versus reversible hydrogen electrode after two-cycle stability assessment. This work enables the applications of g-CN films in many electronic and optoelectronic devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Graphitic carbon nitride supported platinum nanocomposites for rapid and sensitive colorimetric detection of mercury ions.

    Science.gov (United States)

    Wang, Yi-Wei; Wang, Lixing; An, Fengping; Xu, Hui; Yin, Zejin; Tang, Shurong; Yang, Huang-Hao; Song, Hongbo

    2017-08-08

    In this study, graphitic carbon nitride supported platinum nanocomposites (g-C 3 N 4 /PtNPs) have been synthesized for the first time by an ultrasonic-assisted chemical reduction method. By using g-C 3 N 4 as the stabilizer, Pt ions could be reduced to PtNPs by NaBH 4 and uniformly deposited on the surface of g-C 3 N 4 . The resulting g-C 3 N 4 /PtNPs exhibited enhanced catalytic activity for the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) compared to that of g-C 3 N 4 or PtNPs alone. After interaction with Hg 2+ , the catalytic activity of g-C 3 N 4 /PtNPs was effectively inhibited due to the formation of HgPt amalgam. On the basis of this effect, a novel label free colorimetric sensor has been developed for sensitive detection of Hg 2+ through the g-C 3 N 4 /PtNPs mediated catalytic reaction. A detection limit as low as 1.23 nM was achieved. This assay also exhibited excellent selectivity toward Hg 2+ over other metal ions. In addition, it was successfully applied to the determination of Hg 2+ in real water samples. In view of the advantages, such as simple operation, cost-effective, rapid response and naked-eye observation, the developed colorimetric sensor hold great potential for the detection of toxic Hg 2+ in environmental and biological samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Preparation and enhanced visible-light photocatalytic activity of graphitic carbon nitride/bismuth niobate heterojunctions.

    Science.gov (United States)

    Zhang, Shengqu; Yang, Yuxin; Guo, Yingna; Guo, Wan; Wang, Mei; Guo, Yihang; Huo, Mingxin

    2013-10-15

    A series of graphitic carbon nitride/bismuth niobate (g-C3N4/Bi5Nb3O15) heterojunctions with g-C3N4 doping level of 10-90 wt% were prepared by a facile milling-heat treatment method. The phase and chemical structures, surface compositions, electronic and optical properties as well as morphologies of the prepared g-C3N4/Bi5Nb3O15 were well-characterized. Subsequently, the photocatalytic activity and stability of g-C3N4/Bi5Nb3O15 were evaluated by the degradation of aqueous methyl orange (MO) and 4-chlorophenol (4-CP) under the visible-light irradiation. At suitable g-C3N4 doping levels, g-C3N4/Bi5Nb3O15 exhibited enhanced visible-light photocatalytic activity compared with pure g-C3N4 or Bi5Nb3O15. This excellent photocatalytic activity was revealed in terms of the extension of visible-light response and efficient separation and transportation of the photogenerated electrons and holes due to coupling of g-C3N4 and Bi5Nb3O15. Additionally, the active species yielded in the pure g-C3N4- and g-C3N4/Bi5Nb3O15-catalyzed 4-CP photodegradation systems were investigated by the free radical and hole scavenging experiments. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Development of graphite carbon nitride based fluorescent immune sensor for detection of alpha fetoprotein

    Science.gov (United States)

    Li, Yike; Dong, Lingyu; Wang, Xiangfeng; Liu, Yuan; Liu, Hailing; Xie, Mengxia

    2018-05-01

    A novel fluorescent immunosensor for determination of alpha fetoprotein (AFP) in serum samples has been developed based on the nano graphite carbon nitride (g-C3N4) as fluorophore and immunomagnetic beads (MBs) as separation material. The bulk g-C3N4 was obtained by thermal polymerization of melamine, and then carboxylated and exfoliated to acquire the carboxylated nano g-C3N4 (c-n-g-C3N4), which has been characterized and the results showed that it had excellent fluorescent properties. The antibodies of AFP (Ab1, Ab2) were conjugated to the MBs and the c-n-g-C3N4, respectively. In assay of AFP detection, the magnetic part of the immunosensor, MBs-Ab1, would form the sandwich type complex with the signal part of the sensor, c-n-g-C3N4-Ab2. The developed immunosensor could simplify the process of separation due to the MBs. The results illustrated that proposed approach held a good linearity between the fluorescence intensity of the sensor and the AFP concentration ranging from 5-600 ng/mL with the limit of detection as low as 0.43 ng/mL, and its spiking recoveries ranged from 98.2% to 105.9% with RSD from 2.1% to 3.5%. The fabricated fluorescent immunosensor possesses the merits of good sensitivity, excellent selectivity, high biocompatibility and low cost, and the results provide a novel clue to develop immunosensor for determination of the biomarkers in complex matrices.

  10. Design and synthesis of palladium/graphitic carbon nitride/carbon black hybrids as high-performance catalysts for formic acid and methanol electrooxidation

    Science.gov (United States)

    Qian, Huayu; Huang, Huajie; Wang, Xin

    2015-02-01

    Here we report a facile two-step method to synthesize high-performance palladium/graphitic carbon nitride/carbon black (Pd/g-C3N4/carbon black) hybrids for electrooxidizing formic acid and methanol. The coating of g-C3N4 on carbon black surface is realized by a low-temperature heating treatment, followed by the uniform deposition of palladium nanoparticles (Pd NPs) via a wet chemistry route. Owning to the significant synergistic effects of the individual components, the preferred Pd/g-C3N4/carbon black electrocatalyst exhibits exceptional forward peak current densities as high as 2155 and 1720 mA mg-1Pd for formic acid oxidation in acid media and methanol oxidation in alkaline media, respectively, far outperforming the commercial Pd-C catalyst. The catalyst also shows reliable stability, demonstrating that the newly-designed hybrids have great promise in constructing high-performance portable fuel cell systems.

  11. Novel band gap-tunable K–Na co-doped graphitic carbon nitride prepared by molten salt method

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jiannan [Institute of Eco-environmental Sciences, Liaoning Shihua University, Fushun 113001 (China); School of Environmental and Biological Engineering, Liaoning Shihua University, Fushun 113001 (China); Ma, Lin [School of Petrochemical Engineering, Liaoning Shihua University, Fushun 113001 (China); Wang, Haoying; Zhao, Yanfeng [School of Environmental and Biological Engineering, Liaoning Shihua University, Fushun 113001 (China); Zhang, Jian [School of Petrochemical Engineering, Liaoning Shihua University, Fushun 113001 (China); Hu, Shaozheng, E-mail: hushaozhenglnpu@163.com [Institute of Eco-environmental Sciences, Liaoning Shihua University, Fushun 113001 (China)

    2015-03-30

    Graphical abstract: K and Na ions co-doped into g-C{sub 3}N{sub 4} crystal lattice can tune the position of CB and VB potentials, influence the structural and optical properties, and thus improve the photocatalytic degradation and mineralization ability. - Highlights: • K, Na co-doped g-C{sub 3}N{sub 4} was prepared in KCl/NaCl molten salt system. • The structural and optical properties of g-C{sub 3}N{sub 4} were greatly influenced by co-doping. • The position of VB and CB can be tuned by controlling the weight ratio of eutectic salts to melamine. • Co-doped g-C{sub 3}N{sub 4} showed outstanding photodegradation ability, mineralization ability, and catalytic stability. - Abstract: Novel band gap-tunable K–Na co-doped graphitic carbon nitride was prepared by molten salt method using melamine, KCl, and NaCl as precursor. X-ray diffraction (XRD), N{sub 2} adsorption, Scanning electron microscope (SEM), UV–vis spectroscopy, Photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared catalysts. The CB and VB potentials of graphitic carbon nitride could be tuned from −1.09 and +1.55 eV to −0.29 and +2.25 eV by controlling the weight ratio of eutectic salts to melamine. Besides, ions doping inhibited the crystal growth of graphitic carbon nitride, enhanced the surface area, and increased the separation rate of photogenerated electrons and holes. The visible-light-driven Rhodamine B (RhB) photodegradation and mineralization performances were significantly improved after K–Na co-doping.

  12. Optical and structural characterization of silicon-carbon-nitride thin films for optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Swatowska, Barbara; Stapinski, Tomasz [Department of Electronics, AGH University of Science and Technology, Krakow (Poland)

    2010-04-15

    Amorphous a-SiCN:H films were deposited by radio frequency Plasma Enhanced Chemical Vapour Deposition (PECVD) at 13.56 MHz from silane-methane-ammonia (SiH{sub 4}+CH{sub 4}+NH{sub 3}) gaseous mixture. Morphological, structural and optical characterization of a-SiCN:H in correlation with process parameters was done. High growth rate of films was influenced mainly by presence of ammonia and silane in technological process. FTIR spectra analysis of films revealed the influence of gaseous mixture content in PECVD process on their structure. The refractive index and optical gap depended on elemental composition of films. The total reflectivity of a-SiCN:H on monocrystalline silicon revealed increase with the decrease in carbon and nitrogen content. The a-SiCN:H films are smooth, homogeneous, chemically inert and wear resistive and also hydrogen rich, which is important from the application point of view (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Ultrathin MoS2 sheets supported on N-rich carbon nitride nanospheres with enhanced lithium storage properties

    Science.gov (United States)

    Chenrayan, Senthil; S. Chandra, Kishore; Manickam, Sasidharan

    2017-07-01

    Deciphering the structural and volume changes occurring during electrode reactions in lithium-ion batteries is perhaps a boon for high energy density batteries. Here, we report the synthesis of 3D network of dichalcogenide molybdenum disulfide (MoS2) encapsulated over nitrogen rich graphitic carbon nitride nanosphere (g-C3N4) forming an interconnected and uniform g-C3N4/MoS2 scaffolds. The crystallinity, phase purity, morphological features and elemental composition were evaluated through XRD, FESEM, TEM, HRTEM, BET and XPS analyses. The electrochemical properties of N-rich g-C3N4/MoS2 scaffolds were investigated as potential anode materials for lithium-ion batteries. Electrochemical testing of the g-C3N4/MoS2 constructured electrode delivered reversible capacity of 857 mAh g-1at 0.1 C rate after fifty cycles and exhibited a high rate performance with reversible capacity of 383 mAh g-1 at 10 C rate (higher than theoretical capacity of graphite, 372 mAh g-1). The superior electrochemical property of g-C3N4/MoS2 is attributed to N-rich carbon support which favors better electronic conductivity, and affords more sites for Li+ ions. The nitrogen rich carbon nitride accommodates volume changes caused during repeated charge/discharges and maintains high structural integrity and specific capacity.

  14. Application of magnetic graphitic carbon nitride nanocomposites for the solid-phase extraction of phthalate esters in water samples.

    Science.gov (United States)

    Wang, Man; Yang, Xiaodi; Bi, Wentao

    2015-02-01

    Magnetic graphitic carbon nitride nanocomposites were successfully prepared in situ and used to develop a highly sensitive magnetic solid-phase extraction method for the preconcentration of phthalate esters such as di-n-butyl phthalate, butyl phthalate, dihexyl phthalate, and di-(2-ethyl hexyl) phthalate from water. The adsorption and desorption of the phthalate esters on magnetic graphitic carbon nitride nanocomposites were investigated and the parameters affecting the partition of the phthalate esters, such as adsorption, desorption, recovery, were assessed. Under the optimized conditions, the proposed method showed excellent sensitivity with limits of detection (S/N = 3) in the range of 0.05-0.1 μg/L and precision in the range of 1.1-2.6% (n = 5). This method was successfully applied to the analysis of real water samples, and good spiked recoveries over the range of 79.4-99.4% were obtained. This research provides a possibility to apply this nanocomposite for adsorption, preconcentration, or even removal of various carbon-based ring or hydrophobic pollutants. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Nanoscale, conformal films of graphitic carbon nitride deposited at room temperature: a method for construction of heterojunction devices.

    Science.gov (United States)

    Ladva, Satyam A; Travis, William; Quesada-Cabrera, Raul; Rosillo-Lopez, Martin; Afandi, Abdulkareem; Li, Yaomin; Jackman, Richard B; Bear, Joseph C; Parkin, Ivan P; Blackman, Christopher; Salzmann, Christoph G; Palgrave, Robert G

    2017-11-09

    Graphitic carbon nitrides (GCNs) represent a family of 2D materials composed of carbon and nitrogen with variable amounts of hydrogen, used in a wide variety of applications. We report a method of room temperature thin film deposition which allows ordered GCN layers to be deposited on a very wide variety of substrates, including conductive glass, flexible plastics, nanoparticles and nano-structured surfaces, where they form a highly conformal coating on the nanoscale. Film thicknesses of below 20 nm are achievable. In this way we construct functional nanoscale heterojunctions between TiO 2 nanoparticles and GCN, capable of producing H 2 photocatalytically under visible light irradiation. The films are hydrogen rich, have a band gap around 1.7 eV, display transmission electron microscopy lattice fringes as well as X-ray diffraction peaks despite being deposited at room temperature, and show characteristic Raman and IR bands. We use cluster etching to reveal the chemical environments of C and N in GCN using X-ray photoelectron spectroscopy. We elucidate the mechanism of this deposition, which operates via sequential surface adsorption and reaction analogous to atomic layer deposition. The mechanism may have implications for current models of carbon nitride formation.

  16. Enhancing Photocatalytic Activity of Graphitic Carbon Nitride by Codoping with P and C for Efficient Hydrogen Generation.

    Science.gov (United States)

    Wang, Hao; Wang, Bo; Bian, Yaru; Dai, Liming

    2017-07-05

    The generation of clean hydrogen gas from photocatalytic water splitting by using graphitic carbon nitride (g-C 3 N 4 ) as the photocatalyst has attracted considerable research interest. For practical applications, however, the photocatalytic activity of g-C 3 N 4 needs to be further improved by, for example, band gap engineering through heteroatom doping. In this study, we found that doping of carbon nitride with carbon and phosphorus (P) could tune energy level of the conduction band. Subsequent hydrothermal treatment led to an increase in the specific surface area from 24.9 up to 141.1 m 2 g -1 , which was accompanied by increasing C concentration of the resultant C, P-doped g-C 3 N 4 to reduce the hole-electron recombination and enhance the conductivity. Consequently, the C, P-codoped g-C 3 N 4 (i.e., CPCN-1*) exhibited a much enhanced photocatalytic activity for efficient generation of H 2 by photocatalytic water splitting under visible-light irradiation (1493.3 μmol g -1 h -1 -about 9.7 times enhancement from that of bulk g-C 3 N 4 ).

  17. Graphitic Carbon Nitride/Nitrogen-Rich Carbon Nanofibers: Highly Efficient Photocatalytic Hydrogen Evolution without Cocatalysts.

    Science.gov (United States)

    Han, Qing; Wang, Bing; Gao, Jian; Qu, Liangti

    2016-08-26

    An interconnected framework of mesoporous graphitic-C3 N4 nanofibers merged with in situ incorporated nitrogen-rich carbon has been prepared. The unique composition and structure of the nanofibers as well as strong coupling between the components endow them with efficient light-harvesting properties, improved charged separation, and a multidimensional electron transport path that enhance the performance of hydrogen production. The as-obtained catalyst exhibits an extremely high hydrogen-evolution rate of 16885 μmol h(-1)  g(-1) , and a remarkable apparent quantum efficiency of 14.3 % at 420 nm without any cocatalysts, which is much higher than most reported g-C3 N4 -based photocatalysts even in the presence of Pt-based cocatalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Rich interfacial chemistry and properties of carbon-doped hexagonal boron nitride nanosheets revealed by electronic structure calculations

    Science.gov (United States)

    Xie, Wei; Tamura, Takahiro; Yanase, Takashi; Nagahama, Taro; Shimada, Toshihiro

    2018-04-01

    The effect of C doping to hexagonal boron nitride (h-BN) to its electronic structure is examined by first principles calculations using the association from π-electron systems of organic molecules embedded in a two-dimensional insulator. In a monolayered carbon-doped structure, odd-number doping with carbon atoms confers metallic properties with different work functions. Various electronic interactions occur between two layers with odd-number carbon substitution. A direct sp3 covalent chemical bond is formed when C replaces adjacent B and N in different layers. A charge transfer complex between layers is found when C replaces B and N in the next-neighboring region, which results in narrower band gaps (e.g., 0.37 eV). Direct bonding between C and B atoms is found when two C atoms in different layers are at a certain distance.

  19. The transformation of amorphous calcium carbonate, ACC, to crystalline phases as function of time and temperature.

    Science.gov (United States)

    Gies, Hermann; Happel, Marian; Niedermayr, Andrea; Immenhauser, Adrian

    2017-04-01

    We present results from a structural study of the transformation of freeze dried amorphous calcium carbonate, ACC, in crystalline material using pair distribution function analysis, PDF analysis, of X-ray powder diffraction data, XPD data. PDF analysis allows for the analysis of local order of structural subunit in the range between molecular unit (1. and 2. coordination sphere) and long range periodicity as in crystalline materials. ACC was precipitated from aqueous solutions at 298 K and 278 K using different amounts of Mg cations as stabilizer. The samples were immediately separated from the solution and freeze dried. For the transformation study, the samples were heated and analysed using XPD until they were crystallized. The radial distribution obtained from the XPD data were compared to simulated radial distributions of the calcium carbonate polymorphs and their hydrated phases. An ACC precipitated from a solution with Ca:Mg:CO3 = 1:5:4 at 298 K (ration in mmol, pH = 8.2) and freeze dried right after isolation from the solution revealed a close resemblance with ikaite in its local order. Another ACC with Ca:Mg:CO3 = 1:10:1.4 (T = 298, pH = 8.7) showed distinctly different local order resembling monohydrocalcite. Both ACC, however, still had considerable amounts of water dominating the Ca-coordination sphere. During the transformation to calcite, the structural changes in the sample concerned the hydrate water coordinating Ca which was removed and replaced by the carbonate oxygens. The study shows that ACC obtained from different starting solutions show specific local order. Freeze drying leads to solid ACC powder which still contain considerable amounts of hydrate water. Structural subunits are distinct in ACC and different from the crystalline phase. The study supplements recent reports presented by Konrad et al., Purgstaller et al., and Tobler et al.. F. Konrad et al., Cryst. Growth Des. 16, 6310-6317(2016) B. Purgstaller et al., Geochimica et Cosmochimica

  20. Enhanced visible light photocatalytic degradation of Rhodamine B over phosphorus doped graphitic carbon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Bo, E-mail: willycb@163.com; Yan, Juntao; Wang, Chunlei; Ren, Zhandong; Zhu, Yuchan

    2017-01-01

    Highlights: • The phosphorus doped g-C{sub 3}N{sub 4} photocatalysts are synthesized by a co-pyrolysis procedure. • The crystal phase, morphology, and optical property of P doped g-C{sub 3}N{sub 4} are characterized. • The P doped g-C{sub 3}N{sub 4} photocatalysts show the improved photocatalytic activity. • The possible mechanism for enhanced photocatalytic activity is proposed. - Abstract: Phosphorus doped graphitic carbon nitride (g-C{sub 3}N{sub 4}) was easily synthesized using ammonium hexafluorophosphate (NH{sub 4}PF{sub 6}) as phosphorus source, and ammonium thiocyanate (NH{sub 4}SCN) as g-C{sub 3}N{sub 4} precursor, through a direct thermal co-polycondensation procedure. The obtained phosphorus doped g-C{sub 3}N{sub 4} was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), UV–vis diffuse reflectance absorption spectra (UV-DRS), photoelectrochemical measurement and photoluminescence spectra (PL). The photocatalytic activities of phosphorus doped g-C{sub 3}N{sub 4} samples were evaluated by degradation of Rhodamine B (RhB) solution under visible light irradiation. The results showed that the phosphorus doped g-C{sub 3}N{sub 4} had a superior photocatalytic activity than that of pristine g-C{sub 3}N{sub 4}, attributing to the phosphorus atoms substituting carbon atoms of g-C{sub 3}N{sub 4} frameworks to result in light harvesting enhancement and delocalized π-conjugated system of this copolymer, beneficial for the increase of photocatalytic performance. The photoelectrochemical measurements also verified that the charge carrier separation efficiency was promoted by phosphorus doping g-C{sub 3}N{sub 4}. Moreover, the tests of radical scavengers demonstrated that the holes (h{sup +}) and superoxide radicals (·O{sub 2}{sup −}) were the main active species for the

  1. Facile One-Step Synthesis of Hybrid Graphitic Carbon Nitride and Carbon Composites as High-Performance Catalysts for CO2 Photocatalytic Conversion.

    Science.gov (United States)

    Wang, Yangang; Bai, Xia; Qin, Hengfei; Wang, Fei; Li, Yaguang; Li, Xi; Kang, Shifei; Zuo, Yuanhui; Cui, Lifeng

    2016-07-13

    Utilizing and reducing carbon dioxide is a key target in the fight against global warming. The photocatalytic performance of bulk graphitic carbon nitride (g-C3N4) is usually limited by its low surface area and rapid charge carrier recombination. To develop g-C3N4 more suitable for photocatalysis, researchers have to enlarge its surface area and accelerate the charge carrier separation. In this work, novel hybrid graphitic carbon nitride and carbon (H-g-C3N4/C) composites with various carbon contents have been developed for the first time by a facile one-step pyrolysis method using melamine and natural soybean oil as precursors. The effect of carbon content on the structure of H-g-C3N4/C composites and the catalytic activity for the photoreduction of CO2 with H2O were investigated. The results indicated that the introduction of carbon component can effectively improve the textural properties and electronic conductivity of the composites, which exhibited imporved photocatalytic activity for the reduction of CO2 with H2O in comparison with bulk g-C3N4. The highest CO and CH4 yield of 22.60 μmol/g-cat. and 12.5 μmol/g-cat., respectively, were acquired on the H-g-C3N4/C-6 catalyst with the carbon content of 3.77 wt % under 9 h simulated solar irradiation, which were more than twice as high as that of bulk g-C3N4. The remarkably increased photocatalytic performance arises from the synergistic effect of hybrid carbon and g-C3N4.

  2. Spectroscopic properties of nitrogen doped hydrogenated amorphous carbon films grown by radio frequency plasma-enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Hayashi, Y.; Yu, G.; Rahman, M. M.; Krishna, K. M.; Soga, T.; Jimbo, T.; Umeno, M.

    2001-01-01

    Nitrogen doped hydrogenated amorphous carbon thin films have been deposited by rf plasma-enhanced chemical vapor deposition using CH 4 as the source of carbon and with different nitrogen flow rates (N 2 /CH 4 gas ratios between 0 and 3), at 300 K. The dependence modifications of the optical and the structural properties on nitrogen incorporation were investigated using different spectroscopic techniques, such as, Raman spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy, electron spin resonance (ESR), photoluminescence (PL) and spectroscopic ellipsometry (SE). Raman spectroscopy and IR absorption reveal an increase in sp 2 -bonded carbon or a change in sp 2 domain size with increasing nitrogen flow rate. It is found that the configuration of nitrogen atoms incorporated into an amorphous carbon network gradually changes from nitrogen atoms surrounded by three (σ bonded) to two (π bonded) neighboring carbons with increasing nitrogen flow rate. Tauc optical gap is reduced from 2.6 to 2.0 eV, and the ESR spin density and the peak-to-peak linewidth increase sharply with increasing nitrogen flow rate. Excellent agreement has been found between the measured SE data and modeled spectra, in which an empirical dielectric function of amorphous materials and a linear void distribution along the thickness have been assumed. The influence of nitrogen on the electronic density of states is explained based on the optical properties measured by UV-VIS and PL including nitrogen lone pair band. [copyright] 2001 American Institute of Physics

  3. Synthesis and Processing of Nanocrystalline Aluminum Nitride

    OpenAIRE

    Duarte, Matthew Albert

    2016-01-01

    Synthesis, processing and characterization of nanocrystalline aluminum nitride has been systematically studied. Non-carbon based gas nitridation was used to reduce nanocrystalline γ-alumina, having a grain size of ~80 nm. Single phase aluminum nitride powder was obtained at firing temperatures of 1200°C. Further processing of AlN powders was performed by CAPAD (Current Activated Pressure Assisted Densification) to obtain dense single phase aluminum nitride. Dense bulk aluminum nitride was ob...

  4. 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.

  5. Studies of hydrogen incorporation in hydrogenated amorphous carbon films by infrared absorption spectroscopy

    International Nuclear Information System (INIS)

    Alameh, R.; Bounouh, Y.; Sadki, A.; Naud, C.; Theye, M.L.

    1997-01-01

    Author.Hydrogenated amorphous carbon (a-C:H) films presently attract considerable interest because of their potential applications in the domain of multifunctional coatings: transparent in the infrared, very hard, chemically inert, etc...This material is rather complex since it contains C atoms in both sp 3 (diamond) and sp 2 (graphite) electronic configurations, as well as a large concentration of H atoms. Its properties are strongly dependent on the deposition conditions which determine the film microstructure, i.e. the relative proportions of sp 3 and sp 2 C sites, their connection in the network and the hydrogen bonding modes. It has been suggested that the sp 2 C sites tend to cluster into unsaturated chains ans rings, which are then embedded in the sp 3 C sites m atrix . Hydrogen incorporation plays a crucial role in this intrinsic microheterogeneity, which determines the electronic properties, and especially the gap value, of a-C:H. We here present and discuss the results of Fourrier transform infrared absorption spectroscopy measurements performed on a-C:H films prepared under different conditions and submitted to controlled annealing cycles, which exhibit quite different optical gap values (from 1 to 2.5 eV). We carefully analyze the absorption bands detected in the 400-7500 cm -1 spectral range in terms of the vibration modes of C-H and C-C bonds in different local environments and we interpret the results in relation with the film microstructure and optical properties. Special attention is also paid to the absorption background and to the variations of the whole absorption spectra with measurement temperature

  6. Development of amorphous carbon protective coatings on poly(vinyl)chloride

    International Nuclear Information System (INIS)

    Rangel, Elidiane C.; Souza, Eduardo S. de; Moraes, Francine S. de; Marins, Nazir M.S.; Schreiner, Wido H.; Cruz, Nilson C.

    2010-01-01

    The great versatility of polymers has promoted their application in a series of ordinary situations. The development of specific devices from polymers, however, requires modifications to fit specific stipulations. In this work the surface properties of thin films grown onto polyvinylchloride (PVC) were investigated. Hydrogenated amorphous carbon films were deposited onto commercial PVC plates from acetylene and argon plasmas excited by radiofrequency (13.56 MHz, 70 W) power. The proportion of acetylene in the gas feed was varied against that of argon, keeping the total pressure constant at 2.5 Pa. Deposition time was 1800 s. Film elemental composition was analyzed by X-ray photoelectron spectroscopy, XPS. Water contact angle measurements were performed using the sessile drop technique. The root mean squared roughness was derived from 50 x 50 μm 2 surface topographic images, acquired by scanning probe microscopy. Nanoindentation and pin-on-disk techniques were employed on the determination of film hardness and sliding wear, respectively. Oxidation resistance was obtained through the etching rate of the samples in oxygen radiofrequency (1.3 Pa, 50 W) plasmas. From XPS analysis it was detected oxygen and nitrogen contamination in all the samples. It was also found that sp 3 /sp 2 ratio depends on the proportion of argon in the plasma. At lower argon concentrations, hardness, wear and oxidation resistances were all improved with respect to the uncoated PVC. In such conditions, the surface wettability is low indicating a moderate receptivity to water. This combination of properties, ascribed to a balance between the ion bombardment and deposition processes, is suitable for materials exposed to rigorous weathering conditions.

  7. Tribological properties, corrosion resistance and biocompatibility of magnetron sputtered titanium-amorphous carbon coatings

    Energy Technology Data Exchange (ETDEWEB)

    Dhandapani, Vishnu Shankar [PG & Research Department of Physics, PSG College of Arts & Science, Coimbatore 641 014, Tamil Nadu (India); Center for Nano-Wear, Yonsei University, Seoul 120-749 (Korea, Republic of); Subbiah, Ramesh [Center for Biomaterials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Department of Biomedical Engineering, Korea University of Science and Technology (UST), Daejon 305-333 (Korea, Republic of); Thangavel, Elangovan [PG & Research Department of Physics, PSG College of Arts & Science, Coimbatore 641 014, Tamil Nadu (India); Center for Nano-Wear, Yonsei University, Seoul 120-749 (Korea, Republic of); Arumugam, Madhankumar [Center of Research Excellence in Corrosion, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Park, Kwideok [Center for Biomaterials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Department of Biomedical Engineering, Korea University of Science and Technology (UST), Daejon 305-333 (Korea, Republic of); Gasem, Zuhair M. [Center of Research Excellence in Corrosion, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Veeraragavan, Veeravazhuthi, E-mail: vv.vazhuthi@gmail.com [PG & Research Department of Physics, PSG College of Arts & Science, Coimbatore 641 014, Tamil Nadu (India); Kim, Dae-Eun, E-mail: kimde@yonsei.ac.kr [Center for Nano-Wear, Yonsei University, Seoul 120-749 (Korea, Republic of); Department of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2016-05-15

    Highlights: • a-C:Ti nanocomposite coatings were prepared on 316L stainless steel by using R.F. magnetron sputtering method. • Properties of the nanocomposite coatings were analyzed with respect to titanium content. • Corrosion resistance, biocompatibility and hydrophobicity of nanocomposite coating were enhanced with increasing titanium content. • Coating with 2.33 at.% titanium showed superior tribological properties compared to other coatings. - Abstract: Amorphous carbon incorporated with titanium (a-C:Ti) was coated on 316L stainless steel (SS) by magnetron sputtering technique to attain superior tribological properties, corrosion resistance and biocompatibility. The morphology, topography and functional groups of the nanostructured a-C:Ti coatings in various concentrations were analyzed using atomic force microscopy (AFM), Raman, X-Ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Raman and XPS analyses confirmed the increase in sp{sup 2} bonds with increasing titanium content in the a-C matrix. TEM analysis confirmed the composite nature of the coating and the presence of nanostructured TiC for Ti content of 2.33 at.%. This coating showed superior tribological properties compared to the other a-C:Ti coatings. Furthermore, electrochemical corrosion studies were performed against stimulated body fluid medium in which all the a-C:Ti coatings showed improved corrosion resistance than the pure a-C coating. Preosteoblasts proliferation and viability on the specimens were tested and the results showed that a-C:Ti coatings with relatively high Ti (3.77 at.%) content had better biocompatibility. Based on the results of this work, highly durable coatings with good biocompatibility could be achieved by incorporation of optimum amount of Ti in a-C coatings deposited on SS by magnetron sputtering technique.

  8. Oxidation and Carbidation of Laser-Ablated Amorphized Ti Particles in Carbon Monoxide

    Czech Academy of Sciences Publication Activity Database

    Jandová, Věra; Kupčík, Jaroslav; Bastl, Zdeněk; Šubrt, Jan; Pola, Josef

    2013-01-01

    Roč. 19, MAY (2013), s. 104-110 ISSN 1293-2558 Institutional support: RVO:67985858 ; RVO:61388980 ; RVO:61388955 Keywords : titanium * laser ablation * amorphization Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.679, year: 2013

  9. Sugarcane juice derived carbon dot–graphitic carbon nitride composites for bisphenol A degradation under sunlight irradiation

    Science.gov (United States)

    Wong, Jing Lin; Hak, Chen Hong; Tai, Jun Yan; Leong, Kah Hon; Saravanan, Pichiah

    2018-01-01

    Carbon dots (CDs) and graphitic carbon nitride (g-C3N4) composites (CD/g-C3N4) were successfully synthesized by a hydrothermal method using urea and sugarcane juice as starting materials. The chemical composition, morphological structure and optical properties of the composites and CDs were characterized using various spectroscopic techniques as well as transmission electron microscopy. X-ray photoelectron spectroscopy (XPS) results revealed new signals for carbonyl and carboxyl groups originating from the CDs in CD/g-C3N4 composites while X-ray diffraction (XRD) results showed distortion of the host matrix after incorporating CDs into g-C3N4. Both analyses signified the interaction between g-C3N4 and CDs. The photoluminescence (PL) analysis indicated that the presence of too many CDs will create trap states at the CD/g-C3N4 interface, decelerating the electron (e−) transport. However, the CD/g-C3N4(0.5) composite with the highest coverage of CDs still achieved the best bisphenol A (BPA) degradation rate at 3.87 times higher than that of g-C3N4. Hence, the charge separation efficiency should not be one of the main factors responsible for the enhancement of the photocatalytic activity of CD/g-C3N4. Instead, the light absorption capability was the dominant factor since the photoreactivity correlated well with the ultraviolet–visible diffuse reflectance spectra (UV–vis DRS) results. Although the CDs did not display upconversion photoluminescence (UCPL) properties, the π-conjugated CDs served as a photosensitizer (like organic dyes) to sensitize g-C3N4 and injected electrons to the conduction band (CB) of g-C3N4, resulting in the extended absorption spectrum from the visible to the near-infrared (NIR) region. This extended spectral absorption allows for the generation of more electrons for the enhancement of BPA degradation. It was determined that the reactive radical species responsible for the photocatalytic activity were the superoxide anion radical (O2

  10. Sugarcane juice derived carbon dot-graphitic carbon nitride composites for bisphenol A degradation under sunlight irradiation.

    Science.gov (United States)

    Sim, Lan Ching; Wong, Jing Lin; Hak, Chen Hong; Tai, Jun Yan; Leong, Kah Hon; Saravanan, Pichiah

    2018-01-01

    Carbon dots (CDs) and graphitic carbon nitride (g-C 3 N 4 ) composites (CD/g-C 3 N 4 ) were successfully synthesized by a hydrothermal method using urea and sugarcane juice as starting materials. The chemical composition, morphological structure and optical properties of the composites and CDs were characterized using various spectroscopic techniques as well as transmission electron microscopy. X-ray photoelectron spectroscopy (XPS) results revealed new signals for carbonyl and carboxyl groups originating from the CDs in CD/g-C 3 N 4 composites while X-ray diffraction (XRD) results showed distortion of the host matrix after incorporating CDs into g-C 3 N 4 . Both analyses signified the interaction between g-C 3 N 4 and CDs. The photoluminescence (PL) analysis indicated that the presence of too many CDs will create trap states at the CD/g-C 3 N 4 interface, decelerating the electron (e - ) transport. However, the CD/g-C 3 N 4 (0.5) composite with the highest coverage of CDs still achieved the best bisphenol A (BPA) degradation rate at 3.87 times higher than that of g-C 3 N 4 . Hence, the charge separation efficiency should not be one of the main factors responsible for the enhancement of the photocatalytic activity of CD/g-C 3 N 4 . Instead, the light absorption capability was the dominant factor since the photoreactivity correlated well with the ultraviolet-visible diffuse reflectance spectra (UV-vis DRS) results. Although the CDs did not display upconversion photoluminescence (UCPL) properties, the π-conjugated CDs served as a photosensitizer (like organic dyes) to sensitize g-C 3 N 4 and injected electrons to the conduction band (CB) of g-C 3 N 4 , resulting in the extended absorption spectrum from the visible to the near-infrared (NIR) region. This extended spectral absorption allows for the generation of more electrons for the enhancement of BPA degradation. It was determined that the reactive radical species responsible for the photocatalytic activity were

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

    Energy Technology Data Exchange (ETDEWEB)

    Badjian, H.; Setoodeh, A.R., E-mail: setoodeh@sutech.ac.ir

    2017-02-15

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

  12. Graphitic carbon nitride nanodots: As reductant for the synthesis of silver nanoparticles and its biothiols biosensing application.

    Science.gov (United States)

    Lu, Qiujun; Wang, Haiyan; Liu, Yalan; Hou, Yuxin; Li, Haitao; Zhang, Youyu

    2017-03-15

    The graphitic carbon nitride nanodots (g-C 3 N 4 -dots) were synthesized by a simple electrochemical "tailoring" process from bulk graphitic carbon nitride (g-C 3 N 4 ) under alkaline solution for the first time. Compared with the bulk g-C 3 N 4 , the novel g-C 3 N 4 -dots not only exhibit enhanced fluorescence and excellent dispersion stability in water but also show the reducibility for the reduction of Ag + to AgNPs at 60°C. The biothiols can bound with Ag + through formation of biothiol-Ag + complex to consume the Ag + and act as capping agent to prevent the growth of AgNPs, which cause the decrease of the absorption peak of the AgNPs. Therefore, an optical sensor was developed for the detection of biothiols based on the change of the plasmon resonance absorption peak of the AgNPs. The proposed method exhibits excellent sensitivity and selectivity to biothiols with low detection limit for cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) with 11.5, 16.1, and 15.5nM, respectively. This method also has been successfully applied for the detection of biothiols in human serum with satisfactory results. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Efficient Production of N-Butyl Levulinate Fuel Additive from Levulinic Acid Using Amorphous Carbon Enriched with Oxygenated Groups

    Directory of Open Access Journals (Sweden)

    Jinfan Yang

    2018-01-01

    Full Text Available The aim of this study was to develop an effective carbonaceous solid acid for synthesizing green fuel additive through esterification of lignocellulose-derived levulinic acid (LA and n-butanol. Two different sulfonated carbons were prepared from glucose-derived amorphous carbon (GC400 and commercial active carbon (AC400. They were contrastively studied by a series of characterizations (N2 adsorption, X-ray diffraction, elemental analysis, transmission electron microscopy, Fourier transform infrared spectroscopy and NH3 temperature programmed desorption. The results indicated that GC400 possessed stronger acidity and higher –SO3H density than AC400, and the amorphous structure qualified GC400 for good swelling capacity in the reaction solution. Assessment experiments showed that GC400 displayed remarkably higher catalytic efficiency than AC400 and other typical solid acids (HZSM-5, Hβ, Amberlyst-15 and Nafion-212 resin. Up to 90.5% conversion of LA and 100% selectivity of n-butyl levulinate could be obtained on GC400 under the optimal reaction conditions. The sulfonated carbon retained 92% of its original catalytic activity even after five cycles.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Yoke Khin

    2013-03-14

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

  15. A color-tunable luminescent material with functionalized graphitic carbon nitride as multifunctional supports

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Jiutian; Cao, Yudong; Fan, Hai; Hou, Juying; Ai, Shiyun, E-mail: ashy@sdau.edu.cn

    2015-12-15

    A color-tunable luminescent material was prepared based on the composition of functionalized graphitic carbon nitride (g-C{sub 3}N{sub 4}) and europium (III). The functionalized g-C{sub 3}N{sub 4} layers not only behave as multifunctional supports including ligand coordinated with europium (III) and a support structure for the formation of the luminescent material, but exhibit excitation wavelength-dependent luminescence, thus the energy transfer between the functionalized g-C{sub 3}N{sub 4} and europium (III) can match very well by controlling the emission wavelength of functionalized g-C{sub 3}N{sub 4}. The as-prepared materials was comprehensively characterized via X-ray photoelectron spectroscopy, Fourier Transform Infrared spectroscopy, X-ray scattering techniques, Ultraviolet and Visible spectrophotometer, fluorescence spectrophotometer, thermogravimetric analysis, etc. The luminescent material exhibits multi-color emissions which are consistent with the characteristic emissions of europium (III) and functionalized g-C{sub 3}N{sub 4}, and the photoluminescence quality and density of the europium (III) can be greatly enhanced. The brilliant optical properties of the materials make them suiting for multipurpose applications in practical fields. - Graphical abstract: Schematic illustration of the synthesis and basic composition of the luminescent material. Inset figures were luminescence emission spectra of g-C{sub 3}N{sub 4} (A), europium (III) complex (a) and luminescent material (b) with the same concentration in (B) (K{sub ex}=350 nm) and photographs of (left) H{sub 2}O and (right) the H{sub 2}O dispersion of luminescence emission spectra under 350 nm UV radiation. The energy transfer in the luminescent material matchs very well and it exhibits multi-color emissions simultaneously. The enhanced photoluminescence quality and density of the europium (III) makes them suiting for multipurpose applications in practical fields. - Highlights: • Luminescent

  16. Dendritic Tip-on Polytriazine-Based Carbon Nitride Photocatalyst with High Hydrogen Evolution Activity

    KAUST Repository

    Bhunia, Manas Kumar

    2015-11-23

    Developing stable, ubiquitous and efficient water-splitting photocatalyst material that has extensive absorption in the visible-light range is desired for a sustainable solar energy-conversion device. We herein report a triazine-based carbon nitride (CN) material with different C/N ratios achieved by varying the monomer composition ratio between melamine (Mel) and 2,4,6-triaminopyrimidine (TAP). The CN material with a different C/N ratio was obtained through a two-step synthesis protocol: starting with the solution state dispersion of the monomers via hydrogen-bonding supramolecular aggregate, followed by a salt-melt high temperature polycondensation. This protocol ensures the production of a highly crystalline polytriazine imide (PTI) structure con-sisting of a copolymerized Mel-TAP network. The observed bandgap narrowing with an increasing TAP/Mel ratio is well simulated by density functional theory (DFT) calculations, revealing a positive shift in the valence band upon substitution of N with CH in the aromatic rings. Increasing the TAP amount could not maintain the crystalline PTI structure, consistent with DFT calculation showing the repulsion associated with additional C-H introduced in the aromatic rings. Due to the high exciton binding energy calculated by DFT for the obtained CN, the cocatalyst must be close to any portion of the material to assist the separation of excit-ed charge carriers for an improved photocatalytic performance. The photocatalytic activity was improved by providing a dendritic tip-on-like shape grown on a porous fibrous silica KCC-1 spheres, and highly dispersed Pt nanoparticles (<5 nm) were photodepos-ited to introduce heterojunction. As a result, the Pt/CN/KCC-1 photocatalyst exhibited an apparent quantum efficiency (AQE) as high as 22.1 ± 3% at 400 nm and the silica was also beneficial for improving photocatalytic stability. The results obtained by time-resolved transient absorption spectroscopy measurements were consistent with

  17. The Effect of Mesoporous Carbon Nitride Modification by Titanium Oxide Nanoparticles on Photocatalytic Degradation of 1,3-Dinitrobenzene

    Directory of Open Access Journals (Sweden)

    Seyyed Ershad Moradi

    2015-11-01

    Full Text Available In the present work, well ordered, mesoporous carbon nitride (MCN sorbent with uniform mesoporous wall, high surface area and pore volume has been fabricated using the simple polymerization reaction between ethylene diamine and carbon tetrachloride in mesoporous silica media, and then modified by TiO2 nanoparticles (Ti-MCN. The structural order and textural properties of the nanoporous materials were studied by XRD, elemental analysis, and nitrogen adsorption–desorption experiments. Photodegradation experiments for 1,3-dinitrobenzene were conducted in batch mode, the Ti-MCN catalysts were found to be more active compared to the free TiO2 nanoparticles for 1,3-dinitrobenzene degradation.

  18. Establishing the solubility and local structure(s) of Amorphous Calcium Carbonate (ACC): Toward an understanding of invertebrate biomineralization

    Science.gov (United States)

    Mergelsberg, S. T.; Ulrich, R. N.; Michel, F. M.; Dove, P. M.

    2017-12-01

    Recent advances in high-resolution imaging show the widespreadd occurrence of multistep pathways to mineralization in biological and geological settings (De Yoreo et al., 2015, Science). For example, carbonate biomineralization often involves precipitation of amorphous calcium carbonate (ACC) as a reactive intermediate that subsequently transforms to crystalline products with diverse structures. Although current carbonate mineral proxies are based upon the composition of final crystalline products, the final signatures may be recording the properties of the initial amorphous phase. Thus, it is critical to establish the physical properties of ACC and understand the factors that influence its evolution to final products at conditions that approximate biological environments. This disconnect limits our ability to build a process-based understanding of when/how minor and trace elements are recorded in mineral composition proxies. In this experimental study, we quantified the chemical and physical properties of ACC and its evolution to final products. We first determined ACC solubility under controlled chemical conditions using a new type of flow-through reactor developed by our research group (Blue and Dove, 2015, GCA; Blue et al., 2017, GCA). The experimental design varied Mg concentration and total alkalinity while maintaining a mild pH that approximates biological environments. ACC solubility was measured at specific time points during the precipitation (from super- and undersaturated conditions) and during its subsequent evolution. Parallel experiments characterized the structure of the corresponding amorphous products using in situ pair distribution function (PDF) and small-angle x-ray scattering (SAXS) analyses. The measurements demonstrate at least two types of ACC can be produced by tuning Mg concentration and alkalinity. Each "phase" exhibits distinct short-range ordering that demonstrates structure-specific solubility. We also find temporal changes in the

  19. Heterogeneous polymer modification: Polyolefin maleation in supercritical carbon dioxide and amorphous fluoropolymer surface modification

    Science.gov (United States)

    Hayes, Heather J.

    1999-11-01

    Three distinct heterogeneous polymer modification reactions are explored in this work. The first is a bulk reaction commonly conducted on polyolefins---the free radical addition of maleic anhydride. This reaction was run using supercritical carbon dioxide (SC CO2) as the solvent. The second was the chemical surface modification of an amorphous fluorocopolymer of tetrafluoroethylene and a perfluorodioxole monomer (Teflon AF). Several reactions were explored to reduce the surface of the fluorocopolymer for the enhancement of wettability. The last modification was also on Teflon AF and involved the physical modification of the surface through the transport polymerization of xylylene in order to synthesize a novel bilayer membrane. The bulk maleation of poly-4-methyl-1-pentene (PMP) was the focus of the first project. SC CO2 was utilized as both solvent and swelling agent to promote this heterogeneous reaction and led to successful grafting of anhydride groups on both PMP and linear low density polyethylene. Varying the reaction conditions and reagent concentrations allowed optimization of the reaction. The grafted anhydride units were found to exist as single maleic and succinic grafts, and the PMP became crosslinked upon maleation. The surface of a fluoropolymer can be difficult to alter. An examination of three reactions was made to determine the reactivity of Teflon AF: sodium naphthalenide treatment (Na-Nap), aluminum metal modification through deposition and dissolution, and mercury/ammonia photosensitization. The fluorocopolymer with the lower perfluorodioxole percentage was found to be more reactive towards modification with the Na-Nap treatment. The other modification reactions appeared to be nearly equally reactive toward both fluorocopolymers. The functionality of the Na-Nap-treated surface was examined in detail with the use of several derivatization reactions. In the final project, an asymmetric gas separation membrane was synthesized using Teflon AF as

  20. Distinct Short-Range Order Is Inherent to Small Amorphous Calcium Carbonate Clusters (<2 nm).

    Science.gov (United States)

    Sun, Shengtong; Chevrier, Daniel M; Zhang, Peng; Gebauer, Denis; Cölfen, Helmut

    2016-09-26

    Amorphous intermediate phases are vital precursors in the crystallization of many biogenic minerals. While inherent short-range orders have been found in amorphous calcium carbonates (ACCs) relating to different crystalline forms, it has never been clarified experimentally whether such orders already exist in very small clusters less than 2 nm in size. Here, we studied the stability and structure of 10,12-pentacosadiynoic acid (PCDA) protected ACC clusters with a core size of ca. 1.4 nm consisting of only seven CaCO3 units. Ligand concentration and structure are shown to be key factors in stabilizing the ACC clusters. More importantly, even in such small CaCO3 entities, a proto-calcite short-range order can be identified but with a relatively high degree of disorder that arises from the very small size of the CaCO3 core. Our findings support the notion of a structural link between prenucleation clusters, amorphous intermediates, and final crystalline polymorphs, which appears central to the understanding of polymorph selection. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Damage of amorphous carbon induced by soft x-ray femtosecond pulses above and below the critical angle

    Czech Academy of Sciences Publication Activity Database

    Chalupský, Jaromír; Hájková, Věra; Altapova, V.; Burian, T.; Gleeson, A.J.; Juha, Libor; Jurek, M.; Sinn, H.; Störmer, M.; Sobierajski, R.; Tiedtke, K.; Toleikis, S.; Tschentscher, T.; Vyšín, Luděk; Wabnitz, H.; Gaudin, J.

    2009-01-01

    Roč. 95, č. 3 (2009), 031111/1-031111/3 ISSN 0003-6951 R&D Projects: GA AV ČR KAN300100702; GA MŠk LC510; GA MŠk(CZ) LC528; GA MŠk LA08024; GA AV ČR IAAX00100903; GA AV ČR IAA400100701 Institutional research plan: CEZ:AV0Z10100523 Keywords : amorphous state * carbon * coatings * graphitisation * laser beam effects * nanostructured materials * phase transformations * reflectivity Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.554, year: 2009

  2. Discovery of amorphous carbon veins in the 2008 Wenchuan earthquake fault zone: implications for the fault weakening mechanism

    Science.gov (United States)

    Liu, J.; Zhang, J.; Zhang, B.; Li, H.

    2013-12-01

    The 2008 Wenchuan earthquake generated 270- and 80-km-long surface ruptures along Yingxiu-Beichuan fault and Guanxian-Anxian fault, respectively. At the outcrop near Hongkou village, southwest segment of Yingxiu-Beichuan rupture, network black amorphous carbon veins were discovered near fault planes in the 190-m-wide earthquake fault zone. These veins are mainly composed of ultrafine- and fine-grained amorphous carbon, usually narrower than 5mm and injected into faults and cracks as far as several meter. Flowage structures like asymmetrical structures around few stiff rock fragments indicate materials flew when the veins formed. Fluidization of cataclastic amorphous carbon and the powerful driving force in the veins imply high pore pressure built up during earthquakes. High pore pressure solution and graphite reported in the fault gouge (Togo et al., 2011) can lead very low dynamic friction during the Wenchuan earthquake. This deduction hypothesis is in accordance with the very low thermal abnormal measured on the principle fault zone following the Wenchuan earthquake (Mori et al., 2010). Furthermore, network amorphous carbon veins of different generations suggest similar weakening mechanism also worked on historical earthquakes in Longmenshan fault zone. Reference: Brodsky, E. E., Li, H., Mori, J. J., Kano, Y., and Xue, L., 2012, Frictional Stress Measured Through Temperature Profiles in the Wenchuan Scientific Fault Zone Drilling Project. American Geophysical Union, Fall Meeting. San Francisco, T44B-07 Li, H., Xu, Z., Si, J., Pei, J., Song, S., Sun, Z., and Chevalier, M., 2012, Wenchuan Earthquake Fault Scientific Drilling program (WFSD): Overview and Results. American Geophysical Union, Fall Meeting. San Francisco, T44B-01 Mori, J. J., Li, H., Wang, H., Kano, Y., Pei, J., Xu, Z., and Brodsky, E. E., 2010, Temperature measurements in the WFSD-1 borehole following the 2008 Wenchuan earthquake (MW7.9). American Geophysical Union, Fall Meeting. San Francisco, T53E

  3. The effect of titanium nickel nitride decorated carbon nanotubes-reduced graphene oxide hybrid support for methanol oxidation

    Science.gov (United States)

    Liu, Gen; Pan, Zhanchang; Li, Wuyi; Yu, Ke; Xia, Guowei; Zhao, Qixiang; Shi, Shikun; Hu, Guanghui; Xiao, Chumin; Wei, Zhigang

    2017-07-01

    Titanium nickel nitride (TiNiN) decorated three-dimensional (3D) carbon nanotubes-reduced graphene oxide (CNT-rGO), a fancy 3D platinum (Pt)-based catalyst hybrid support, is prepared by a solvothermal process followed by a nitriding process, which is tested as anodic catalyst support for the methanol oxidation reaction (MOR). The structure, morphology and composition of the synthesized TiNiN/CNT-rGO exhibits a uniform particle dispersion with high purity and interpenetrating 3D network structure. Notably, Pt/TiNiN/CNT-rGO catalyst exhibits significantly improved catalytic activity and durability for methanol oxidation in comparison with Pt/CNT-rGO and conventional Pt/C (JM). The outstanding electrochemical performance was attributed to structure and properties. That is, the 3D CNT-rGO provided a fast transport network for charge-transfer and mass-transfer as well as TiNiN NPs with good synergistic effect and the strong electronic coupling between different domains in TiNiN/CNT-rGO, thus the catalytic activity of the novel catalyst is greatly improved. These results evidences 3D TiNiN/CNT-rGO as a promising catalyst support for a wide range of applications in fuel cells.

  4. Tribological behaviors of diamond-like carbon coatings on plasma nitrided steel using three BN-containing lubricants

    International Nuclear Information System (INIS)

    Jia Zhengfeng; Wang Peng; Xia Yanqiu; Zhang Haobo; Pang Xianjuan; Li Bin

    2009-01-01

    In this work, diamond-like carbon (DLC) coatings were deposited on plasma nitrided AISI 1045 steel by magnetron sputtering. Three BN-containing additives and molybdenum dithiocarbamate (MoDTC) were added to poly-alpha-olefin (PAO) as additives. The additive content (mass fraction) in PAO was fixed at 0.5 wt%. The friction and wear characters of DLC coatings on nitrided steel discs sliding against AISI 52100 steel balls were tested under the lubricated conditions. It was found that borate esters have a higher load carrying capacity and much better anti-wear and friction-reducing ability than that of MoDTC. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were employed to explore the properties of the worn surface and the mechanism of friction and wear. According to the XPS analysis, the adsorbed organic N-containing compounds and BN are, possibly, the primary reason for the novel borate esters to possess a relatively constant coefficient of friction and lower wear rate. On the other hand, possibly, the MoDTC molecules break down during sliding and produce many Mo-oxides, and then the Mo-oxides destroy the DLC coating because of its sharp edge crystalline solid structure. After destroying the DLC coating, the MoDTC react with metals and form MoS 2 tribofilm, and decrease coefficient of friction of rubbing pairs.

  5. Effect of mating materials on wear properties of amorphous hydrogenated carbon (a-C:H coating and tetrahedral amorphous carbon (ta-C coating in base oil boundary lubrication condition

    Directory of Open Access Journals (Sweden)

    Xiang Li

    2017-12-01

    Full Text Available In this study, wear behavior of amorphous hydrogenated carbon (a-C:H coating and tetrahedral amorphous carbon (ta-C coating when sliding against various mating materials in base oil boundary lubrication condition is comparatively investigated to find out the optimal combinations of DLC/mating material and corresponding wear mechanism of both DLC coating. Tribological tests were performed in a cylinder-on-disc tribometer, Field Emission Scanning Electron Microscopy, Raman spectroscopy is used for characterization of ta-C and a-C:H worn surface. The results show that the specific wear rate of ta-C coating increases along with the hardness and roughness of mating material increases, while the specific wear rate of a-C:H coating increases together with an increment in the ID/IG ratio. It is concluded that for ta-C coating, local stress concentration-induced microfracture is the main wear mechanism in relative high wear scenario, along with minor graphitization-induced wear which prevails in low wear scenario. On the other hand, a-C:H coating showed that simultaneous generation and removal of the graphitized layer on the contact surface is the predominant wear mechanism.

  6. Potential of P-doped carbon nanocone and Si-doped boron nitride ...

    Indian Academy of Sciences (India)

    22

    Si-doped boron nitride nanocone (BNNC) by density functional theory were investigated. The adsorption energies of P and Si on surfaces of CNC and BNNC were -293.1 and -325.7 kcal/mol, respectively. The decomposition of CNC-P-N2O and BNNC-Si-N2O and reduction of CNC-P-. O* and BNNC-Si-O* by CO molecule ...

  7. A Tunable Molten-Salt Route for Scalable Synthesis of Ultrathin Amorphous Carbon Nanosheets as High-Performance Anode Materials for Lithium-Ion Batteries.

    Science.gov (United States)

    Wang, Yixian; Tian, Wei; Wang, Luhai; Zhang, Haoran; Liu, Jialiang; Peng, Tingyue; Pan, Lei; Wang, Xiaobo; Wu, Mingbo

    2018-02-14

    Amorphous carbon is regarded as a promising alternative to commercial graphite as the lithium-ion battery anode due to its capability to reversibly store more lithium ions. However, the structural disorder with a large number of defects can lead to low electrical conductivity of the amorphous carbon, thus limiting its application for high power output. Herein, ultrathin amorphous carbon nanosheets were prepared from petroleum asphalt through tuning the carbonization temperature in a molten-salt medium. The amorphous nanostructure with expanded carbon interlayer spacing can provide substantial active sites for lithium storage, while the two-dimensional (2D) morphology can facilitate fast electrical conductivity. As a result, the electrodes deliver a high reversible capacity, outstanding rate capability, and superior cycling performance (579 and 396 mAh g -1 at 2 and 5 A g -1 after 900 cycles). Furthermore, full cells consisting of the carbon anodes coupled with LiMn 2 O 4 cathodes exhibit high specific capacity (608 mAh g -1 at 50 mA g -1 ) and impressive cycling stability with slow capacity loss (0.16% per cycle at 200 mA g -1 ). The present study not only paves the way for industrial-scale synthesis of advanced carbon materials for lithium-ion batteries but also deepens the fundamental understanding of the intrinsic mechanism of the molten-salt method.

  8. Studies on Preparation and Characterization of Aluminum Nitride-Coated Carbon Fibers and Thermal Conductivity of Epoxy Matrix Composites

    Directory of Open Access Journals (Sweden)

    Hyeon-Hye Kim

    2017-08-01

    Full Text Available In this work; the effects of an aluminum nitride (AlN ceramic coating on the thermal conductivity of carbon fiber-reinforced composites were studied. AlN were synthesized by a wet-thermal treatment (WTT method in the presence of copper catalysts. The WTT method was carried out in a horizontal tube furnace at above 1500 °C under an ammonia (NH3 gas atmosphere balanced by a nitrogen using aluminum chloride as a precursor. Copper catalysts pre-doped enhance the interfacial bonding of the AlN with the carbon fiber surfaces. They also help to introduce AlN bonds by interrupting aluminum oxide (Al2O3 formation in combination with oxygen. Scanning electron microscopy (SEM; Transmission electron microscopy (TEM; and X-ray diffraction (XRD were used to analyze the carbon fiber surfaces and structures at each step (copper-coating step and AlN formation step. In conclusion; we have demonstrated a synthesis route for preparing an AlN coating on the carbon fiber surfaces in the presence of a metallic catalyst.

  9. Thionyl chloride assisted functionalization of amorphous carbon nanotubes: A better field emitter and stable nanofluid with better thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, S.K.; Jha, A. [School of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700 032 (India); Chattopadhyay, K.K., E-mail: kalyan_chattopadhyay@yahoo.com [Thin Film & Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata 700 032 (India); School of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700 032 (India)

    2015-06-15

    Highlights: • Thionyl chloride assisted functionalization of amorphous carbon nanotubes (a-CNTs). • Improved dispersion enhanced thermal conductivity of engine oil. • Again f-a-CNTs showed enhanced field emission property compared to pure a-CNTs. - Abstract: Amorphous carbon nanotubes (a-CNTs) were synthesized at low temperature in open atmosphere and further functionalized by treating them in thionyl chloride added stearic acid-dichloro methane solution. The as prepared functionalized a-CNTs (f-a-CNTs) were characterized by Raman spectroscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, transmission and scanning electron microscopy. The nanofluid was prepared by dispersing f-a-CNTs in engine oil using ultrasonic treatment. The effective thermal conductivity of as prepared nanofluid was investigated at different loading (volume fraction of f-a-CNTs). Obtained experimental data of thermal conductivity were compared with the predicted values, calculated using existing theoretical models. Stability of the nanofluid was tested by means of zeta potential measurement to optimize the loading. The as prepared f-a-CNTs sample also showed improved field emission result as compared to pristine a-CNTs. Dependence of field emission behavior on inter electrode distance was investigated too.

  10. Amorphous Mixed-Valence Vanadium Oxide/Exfoliated Carbon Cloth Structure Shows a Record High Cycling Stability.

    Science.gov (United States)

    Song, Yu; Liu, Tian-Yu; Yao, Bin; Kou, Tian-Yi; Feng, Dong-Yang; Liu, Xiao-Xia; Li, Yat

    2017-04-01

    Previous studies show that vanadium oxides suffer from severe capacity loss during cycling in the liquid electrolyte, which has hindered their applications in electrochemical energy storage. The electrochemical instability is mainly due to chemical dissolution and structural pulverization of vanadium oxides during charge/discharge cyclings. In this study the authors demonstrate that amorphous mixed-valence vanadium oxide deposited on exfoliated carbon cloth (CC) can address these two limitations simultaneously. The results suggest that tuning the V 4+ /V 5+ ratio of vanadium oxide can efficiently suppress the dissolution of the active materials. The oxygen-functionalized carbon shell on exfoliated CC can bind strongly with VO x via the formation of COV bonding, which retains the electrode integrity and suppresses the structural degradation of the oxide during charging/discharging. The uptake of structural water during charging and discharging processes also plays an important role in activating the electrode material. The amorphous mixed-valence vanadium oxide without any protective coating exhibits record-high cycling stability in the aqueous electrolyte with no capacitive decay in 100 000 cycles. This work provides new insights on stabilizing vanadium oxide, which is critical for the development of vanadium oxide based energy storage devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Influence of Nitrided Layer on The Properties of Carbon Coatings Produced on X105CrMo17 Steel Under DC Glow-Discharge Conditions

    Directory of Open Access Journals (Sweden)

    Tomasz BOROWSKI

    2016-09-01

    Full Text Available In most cases, machine components, which come in contact with each other, are made of steel. Common steel types include 100Cr6 and X105CrMo17 are widely used in rolling bearings, which are subjected to high static loads. However, more and more sophisticated structural applications require increasingly better performance from steel. The most popular methods for improving the properties of steel is carburisation or nitriding. Unfortunately, when very high surface properties of steel are required, this treatment may be insufficient. Improvement of tribological properties can be achieved by increasing the hardness of the surface, reducing roughness or reducing the coefficient of friction. The formation of composite layers on steel, consisting of a hard nitride diffusion layer and an external carbon coating with a low coefficient of friction, seems to be a prospect with significant potential. The article describes composite layers produced on X105CrMo17 steel and defines their morphology, surface roughness and their functional properties such as: resistance to friction-induced wear, coefficient of friction and corrosion resistance. The layers have been formed at a temperature of 370°C in successive processes of: nitriding in low-temperature plasma followed by deposition of a carbon coating under DC glow-discharge conditions. An evaluation was also made of the impact of the nitrided layers on the properties and morphology of the carbon coatings formed by comparing them to coatings formed on non-nitrided X105CrMo17 steel substrates. A study of the surface topography, adhesion, resistance to friction-induced wear and corrosion shows the significant importance of the substrate type the carbon coatings are formed on.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.7532

  12. Recent Advances of Graphitic Carbon Nitride-Based Structures and Applications in Catalyst, Sensing, Imaging, and LEDs

    Science.gov (United States)

    Wang, Aiwu; Wang, Chundong; Fu, Li; Wong-Ng, Winnie; Lan, Yucheng

    2017-10-01

    The graphitic carbon nitride (g-C3N4) which is a two-dimensional conjugated polymer has drawn broad interdisciplinary attention as a low-cost, metal-free, and visible-light-responsive photocatalyst in the area of environmental remediation. The g-C3N4-based materials have excellent electronic band structures, electron-rich properties, basic surface functionalities, high physicochemical stabilities and are "earth-abundant." This review summarizes the latest progress related to the design and construction of g-C3N4-based materials and their applications including catalysis, sensing, imaging, and white-light-emitting diodes. An outlook on possible further developments in g-C3N4-based research for emerging properties and applications is also included.

  13. Unique Static Magnetic and Dynamic Electromagnetic Behaviors in Titanium Nitride/Carbon Composites Driven by Defect Engineering

    Science.gov (United States)

    Gong, Chunhong; Meng, Hongjie; Zhao, Xiaowei; Zhang, Xuefeng; Yu, Laigui; Zhang, Jingwei; Zhang, Zhijun

    2016-01-01

    Recently, the defect-induced static magnetic behaviours of nanomaterials have been a cutting-edge issue in diluted magnetic semiconductor materials. However, the dynamic magnetic properties of nanomaterials are commonly ignored if their bulk counterparts are non-magnetic. In the present research, titanium nitride-carbon (TiN/C) nanocomposites were found to exhibit both static and dynamic magnetic properties that vary in the opposite trend. Moreover, novel unconventional electromagnetic resonance behaviour was demonstrated in TiN/C systems, and their permeability and permittivity show similar trend. This is challenging for the traditional understanding of electromagnetism and makes it possible to achieve an appropriate balance between the permeability and permittivity simultaneously in a simple system. Hopefully, the results could provide some valuable clues to revealing the magnetism and electromagnetism of nanostructures. PMID:26739853

  14. Functionalized carbon nitride (g-CN) monolayer as a promising energy storage material: A density functional theory study

    Science.gov (United States)

    Hussain, T.; Kaewmaraya, T.; Hankel, M.; Amornkitbamrung, V.

    2017-10-01

    Two-dimensional graphitic carbon nitride (g-CN) sheet, functionalized with polylithiated molecules (CLi2, OLi2), has been investigated to study their structural, electronic and hydrogen (H2) storage properties by van der Waals corrected first principles calculation. A strong binding of both CLi2/OLi2 with two-sided coverage and large enough molecular distance ensures their uniform dispersion over the g-CN monolayer without forming clusters. Each Li in g-CN@2CLi2 (g-CN@2OLi2) adsorbs 3H2, due to its cationic nature through transferring a portion of its charge, resulting into a high H2 storage capacity of 10.34% (9.76%). The calculated H2 adsorption energies are well suited for practical applications.

  15. Efficient emission facilitated by multiple energy level transitions in uniform graphitic carbon nitride films deposited by thermal vapor condensation.

    Science.gov (United States)

    Bian, Juncao; Li, Jianfu; Kalytchuk, Sergii; Wang, Yu; Li, Qian; Lau, Tsz Chun; Niehaus, Thomas A; Rogach, Andrey L; Zhang, Rui-Qin

    2015-04-07

    Graphitic carbon nitride (g-CN) films are important components of optoelectronic devices, but current techniques for their production, such as drop casting and spin coating, fail to deliver uniform and pinhole-free g-CN films on solid substrates. Here, versatile, cost-effective, and large-area growth of uniform and pinhole-free g-CN films is achieved by using a thermal vapor condensation method under atmospheric pressure. A comparison of the X-ray diffraction and Fourier transform infrared data with the calculated infrared spectrum confirmed the graphitic build-up of films composed of tri-s-triazine units. These g-CN films possess multiple active energy states including π*, π, and lone-pair states, which facilitate their efficient (6% quantum yield in the solid state) photoluminescence, as confirmed by both experimental measurements and theoretical calculations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Visible-Light-Irradiated Graphitic Carbon Nitride Photocatalyzed Diels-Alder Reactions with Dioxygen as Sustainable Mediator for Photoinduced Electrons.

    Science.gov (United States)

    Zhao, Yubao; Antonietti, Markus

    2017-08-01

    Photocatalytic Diels-Alder (D-A) reactions with electron rich olefins are realized by graphitic carbon nitride (g-C 3 N 4 ) under visible-light irradiation and aerobic conditions. This heterogeneous photoredox reaction system is highly efficient, and the apparent quantum yield reaches a remarkable value of 47 % for the model reaction. Dioxygen plays a critical role as electron mediator, which is distinct from the previous reports in the homogeneous Ru II complex photoredox system. Moreover, the reaction intermediate vinylcyclobutane is captured and monitored during the reaction, serving as a direct evidence for the proposed reaction mechanism. The cycloaddition process is thereby determined to be the combination of direct [4+2] cycloaddition and [2+2] cycloaddition followed by photocatalytic rearrangement of the vinylcyclobutane intermediate. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Construction of carbon quantum dots/proton-functionalized graphitic carbon nitride nanocomposite via electrostatic self-assembly strategy and its application

    Energy Technology Data Exchange (ETDEWEB)

    Jian, Xuan; Liu, Xian; Yang, Hui-min; Li, Jia-gang; Song, Xiu-li; Dai, Hong-yan; Liang, Zhen-hai, E-mail: liangzhenh@sina.com

    2016-05-01

    Highlights: • An electrostatic self-assembly strategy was proposed to prepare CQDs/HpCN nanocomposite. • Carbon quantum dots (CQDs) attached onto surface of proton-functionalized graphitic carbon nitride (HpCN) through electrostatic attraction. • The CQDs/HpCN nanocomposite exhibited excellent photocatalytic and photoelectrochemical properties. - Abstract: Carbon quantum dots (CQDs) and graphitic carbon nitride (g-C{sub 3}N{sub 4}), as advanced metal-free material catalysts have been the focus of considerable attention because of their superior photocatalytic activities. In this study, we developed a novel approach to obtain CQDs/g-C{sub 3}N{sub 4} nanocomposite with effective interfacial contact by incorporating negatively charged CQDs and tailor-made proton-functionalized g-C{sub 3}N{sub 4}via the electrostatic self-assembly strategy. Then, the morphology and microstructure of the new nanocomposite were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The CQDs and proton-functionalized g-C{sub 3}N{sub 4} nanocomposite exhibited excellent electron transfer properties though electrochemical impedance spectroscopy (EIS), significantly enhanced photoactivity in the photoelectrochemical i–t curve test and degradation of methylene blue solution under visible light irradiation. These results demonstrated that the electrostatic self-assembly strategy process is a promising method of fabricating uniform metal-free material catalysts for an extensive range of applications.

  18. Dispersed conductive polymer nanoparticles on graphitic carbon nitride for enhanced solar-driven hydrogen evolution from pure water

    Science.gov (United States)

    Sui, Yi; Liu, Jinghai; Zhang, Yuewei; Tian, Xike; Chen, Wei

    2013-09-01

    Developing new methods to improve the photocatalytic activity of graphitic carbon nitride (g-C3N4) for hydrogen (H2) evolution has attracted intensive research interests. Here, we report that the g-C3N4 exhibits photocatalytic activity for H2 evolution from pure water. And, the activity is dramatically improved by loading highly dispersed conductive polymer nanoparticles. The H2 evolution rate increases up to 50 times for g-C3N4 with 1.5 wt% polypyrrole (PPy) nanoparticles on the surface. The reaction proceeding in a pure water system excludes the need for sacrificial agents. The role of the highly conductive PPy in enhancing H2 evolution is as a surface junction to increase the number of photoinduced electrons, and to facilitate electron transfer to the interface.Developing new methods to improve the photocatalytic activity of graphitic carbon nitride (g-C3N4) for hydrogen (H2) evolution has attracted intensive research interests. Here, we report that the g-C3N4 exhibits photocatalytic activity for H2 evolution from pure water. And, the activity is dramatically improved by loading highly dispersed conductive polymer nanoparticles. The H2 evolution rate increases up to 50 times for g-C3N4 with 1.5 wt% polypyrrole (PPy) nanoparticles on the surface. The reaction proceeding in a pure water system excludes the need for sacrificial agents. The role of the highly conductive PPy in enhancing H2 evolution is as a surface junction to increase the number of photoinduced electrons, and to facilitate electron transfer to the interface. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02413j

  19. Boron nitride - Composition, optical properties, and mechanical behavior

    Science.gov (United States)

    Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

    1987-01-01

    A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at. percent. The carbon and oxygen impurities were in the 5 to 8 at. percent range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

  20. Boron nitride: Composition, optical properties and mechanical behavior

    Science.gov (United States)

    Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

    1987-01-01

    A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at %. The carbon and oxygen impurities were in the 5 to 8 at % range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

  1. Surface morphology and grain analysis of successively industrially grown amorphous hydrogenated carbon films (a-C:H) on silicon

    Science.gov (United States)

    Catena, Alberto; McJunkin, Thomas; Agnello, Simonpietro; Gelardi, Franco M.; Wehner, Stefan; Fischer, Christian B.

    2015-08-01

    Silicon (1 0 0) has been gradually covered by amorphous hydrogenated carbon (a-C:H) films via an industrial process. Two types of these diamond-like carbon (DLC) coatings, one more flexible (f-DLC) and one more robust (r-DLC), have been investigated. Both types have been grown by a radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. Surface morphologies have been studied in detail by atomic force microscopy (AFM) and Raman spectroscopy has been used to investigate the DLC structure. Both types appeared to have very similar morphology and sp2 carbon arrangement. The average height and area for single grains have been analyzed for all depositions. A random distribution of grain heights was found for both types. The individual grain structures between the f- and r-type revealed differences: the shape for the f-DLC grains is steeper than for the r-DLC grains. By correlating the average grain heights to the average grain areas for all depositions a limited region is identified, suggesting a certain regularity during the DLC deposition mechanisms that confines both values. A growth of the sp2 carbon entities for high r-DLC depositions is revealed and connected to a structural rearrangement of carbon atom hybridizations and hydrogen content in the DLC structure.

  2. Immobilization of sericin molecules via amorphous carbon plasma modified-polystyrene dish for serum-free culture

    Science.gov (United States)

    Tunma, Somruthai; Song, Doo-Hoon; Kim, Si-Eun; Kim, Kyoung-Nam; Han, Jeon-Geon; Boonyawan, Dheerawan

    2013-10-01

    In this study, we focused on sericin hydrolysates, originating from silkworm used in serum-free human bone marrow-derived mesenchymal stem cells (hBM-MSCs) culture. We reported the effect of a covalent linkage between a bioactive protein molecule and polystyrene dish surface via a carbon intermediate layer which can slow down the release rate of protein compounds into the phosphate buffer saline (PBS) solution. Films of amorphous carbon (a-C) and functionalized-carbon were deposited on PS culture dish surfaces by using a DC magnetron sputtering system and RF PECVD system. We found that a-C based-films can increase the hydrophilicity and biocompatibility of polystyrene (PS) dishes, especially a-C films and a-C:N2 films showed good attachment of hBM-MSCs at 24 h. However, in the case of silica surface (a-C:SiOx films), the cells showed a ragged and unattached boundary resulting from the presence of surface silanol groups. For the UV-vis absorbance, all carbon modified-PS dishes showed a lower release rate of sericin molecules into PBS solution than PS control. This revealed that the functionalized carbon could be enhanced by specific binding properties with given molecules. The carbon-coated PS dishes grafting with sericin protein were used in a serum-free condition. We also found that hBM-MSCs have higher percentage of proliferated cells at day 7 for the modified dishes with carbon films and coated with sericin than the PS control coated with sericin. The physical film properties were measured by atomic force microscopy (AFM), scanning electron microscope (SEM) and contact angle measurement. The presence of sbnd NH2 groups of sericin compounds on the PS dish was revealed by Fourier transform infrared spectroscopy (FTIR). The stability of covalent bonds of sericin molecules after washing out ungrafted sericin was confirmed by X-ray photoelectron spectroscopy (XPS).

  3. Immobilization of sericin molecules via amorphous carbon plasma modified-polystyrene dish for serum-free culture

    Energy Technology Data Exchange (ETDEWEB)

    Tunma, Somruthai [The Graduate School, Chiang Mai University, 239 Huay Kaew Road, Muang District, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP), 239 Huay Kaew Road, Muang District, Chiang Mai 50200 (Thailand); Song, Doo-Hoon [Research Center for Orofacial Hard Tissue Regeneration, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752 (Korea, Republic of); Kim, Si-Eun; Kim, Kyoung-Nam [Research Center for Orofacial Hard Tissue Regeneration, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752 (Korea, Republic of); Department and Research Institute of Dental Biomaterials and Bioengineering, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752 (Korea, Republic of); Han, Jeon-Geon [Center for Advanced Plasma Surface Technology, Sungkyunkwan University, 300 Chunchun-dong, Jangan-gu, Suwon 440-746 (Korea, Republic of); Boonyawan, Dheerawan, E-mail: dheerawan.b@cmu.ac.th [Thailand Center of Excellence in Physics (ThEP), 239 Huay Kaew Road, Muang District, Chiang Mai 50200 (Thailand); Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, 239 Huay Kaew Road, Muang District, Chiang Mai 50200 (Thailand)

    2013-10-15

    In this study, we focused on sericin hydrolysates, originating from silkworm used in serum-free human bone marrow-derived mesenchymal stem cells (hBM-MSCs) culture. We reported the effect of a covalent linkage between a bioactive protein molecule and polystyrene dish surface via a carbon intermediate layer which can slow down the release rate of protein compounds into the phosphate buffer saline (PBS) solution. Films of amorphous carbon (a-C) and functionalized-carbon were deposited on PS culture dish surfaces by using a DC magnetron sputtering system and RF PECVD system. We found that a-C based-films can increase the hydrophilicity and biocompatibility of polystyrene (PS) dishes, especially a-C films and a-C:N{sub 2} films showed good attachment of hBM-MSCs at 24 h. However, in the case of silica surface (a-C:SiO{sub x} films), the cells showed a ragged and unattached boundary resulting from the presence of surface silanol groups. For the UV–vis absorbance, all carbon modified-PS dishes showed a lower release rate of sericin molecules into PBS solution than PS control. This revealed that the functionalized carbon could be enhanced by specific binding properties with given molecules. The carbon-coated PS dishes grafting with sericin protein were used in a serum-free condition. We also found that hBM-MSCs have higher percentage of proliferated cells at day 7 for the modified dishes with carbon films and coated with sericin than the PS control coated with sericin. The physical film properties were measured by atomic force microscopy (AFM), scanning electron microscope (SEM) and contact angle measurement. The presence of -NH{sub 2} groups of sericin compounds on the PS dish was revealed by Fourier transform infrared spectroscopy (FTIR). The stability of covalent bonds of sericin molecules after washing out ungrafted sericin was confirmed by X-ray photoelectron spectroscopy (XPS).

  4. Immobilization of sericin molecules via amorphous carbon plasma modified-polystyrene dish for serum-free culture

    International Nuclear Information System (INIS)

    Tunma, Somruthai; Song, Doo-Hoon; Kim, Si-Eun; Kim, Kyoung-Nam; Han, Jeon-Geon; Boonyawan, Dheerawan

    2013-01-01

    In this study, we focused on sericin hydrolysates, originating from silkworm used in serum-free human bone marrow-derived mesenchymal stem cells (hBM-MSCs) culture. We reported the effect of a covalent linkage between a bioactive protein molecule and polystyrene dish surface via a carbon intermediate layer which can slow down the release rate of protein compounds into the phosphate buffer saline (PBS) solution. Films of amorphous carbon (a-C) and functionalized-carbon were deposited on PS culture dish surfaces by using a DC magnetron sputtering system and RF PECVD system. We found that a-C based-films can increase the hydrophilicity and biocompatibility of polystyrene (PS) dishes, especially a-C films and a-C:N 2 films showed good attachment of hBM-MSCs at 24 h. However, in the case of silica surface (a-C:SiO x films), the cells showed a ragged and unattached boundary resulting from the presence of surface silanol groups. For the UV–vis absorbance, all carbon modified-PS dishes showed a lower release rate of sericin molecules into PBS solution than PS control. This revealed that the functionalized carbon could be enhanced by specific binding properties with given molecules. The carbon-coated PS dishes grafting with sericin protein were used in a serum-free condition. We also found that hBM-MSCs have higher percentage of proliferated cells at day 7 for the modified dishes with carbon films and coated with sericin than the PS control coated with sericin. The physical film properties were measured by atomic force microscopy (AFM), scanning electron microscope (SEM) and contact angle measurement. The presence of -NH 2 groups of sericin compounds on the PS dish was revealed by Fourier transform infrared spectroscopy (FTIR). The stability of covalent bonds of sericin molecules after washing out ungrafted sericin was confirmed by X-ray photoelectron spectroscopy (XPS).

  5. Molecular dynamics simulation of chemical vapor deposition of amorphous carbon. Dependence on H/C ratio of source gas

    International Nuclear Information System (INIS)

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

    2011-01-01

    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 that the source gas was injected as hydrocarbon molecules. Under the former condition, we found that as the source H/C ratio increases, the deposition rate of carbon atoms decreases exponentially. This exponential decrease in the deposition rate with increasing source H/C ratio agrees with experimental data. However, under the latter molecular source condition, the deposition rate did not decrease exponentially because of a chemical reaction peculiar to the type of hydrocarbon in the source gas. (author)

  6. The role of pH and Mg on the stability and crystallization of amorphous calcium carbonate

    International Nuclear Information System (INIS)

    Rodriguez-Blanco, J.D.; Shaw, S.; Bots, P.; Roncal-Herrero, T.; Benning, L.G.

    2012-01-01

    Highlights: ► We studied the effect of pH and Mg in the crystallization of amorphous CaCO 3 (ACC). ► The study combined synchrotron-based scattering with electron microscopy. ► The pH-dependent C speciation and hydration strength of Mg 2+ control ACC structure. ► This ACC structure governs the ACC dissolution rate and crystallization pathway. - Abstract: The effects of pH and Mg on the crystallization of amorphous calcium carbonate (ACC) to vaterite and/or calcite were studied using a combination of in situ time resolved synchrotron-based techniques and electron microscopy. The experiments showed that Mg increased the stability of ACC and favoured the formation of calcite over vaterite. A neutral (∼7) starting pH during mixing promoted the transformation of ACC into calcite via a dissolution/reprecipitation mechanism. Conversely, when ACC formed in a solution that started with a high initial pH (∼11.5), the transformation to calcite occurred via metastable vaterite, which formed via a spherulitic growth mechanism. In a second stage this vaterite transformed to calcite via a surface-controlled dissolution and recrystallization mechanism. These crystallization pathways can be explained as a consequence of the pH-dependent composition, local structure, stability and dissolution rates of ACC.

  7. The effect of titanium nickel nitride decorated carbon nanotubes-reduced graphene oxide hybrid support for methanol oxidation

    International Nuclear Information System (INIS)

    Liu, Gen; Pan, Zhanchang; Li, Wuyi; Yu, Ke; Xia, Guowei; Zhao, Qixiang; Shi, Shikun; Hu, Guanghui; Xiao, Chumin; Wei, Zhigang

    2017-01-01

    Highlights: • TiNiN/CNT-rGO support with an interactive three-dimensional structure and high surface area was synthesized. • Pt nanoparticles with small size were well dispersed on TiNiN/CNT-rGO support. • Pt/TiNiN/CNT-rGO shows remarkably enhanced methanol oxidation activity and durability. - Abstract: Titanium nickel nitride (TiNiN) decorated three-dimensional (3D) carbon nanotubes-reduced graphene oxide (CNT-rGO), a fancy 3D platinum (Pt)-based catalyst hybrid support, is prepared by a solvothermal process followed by a nitriding process, which is tested as anodic catalyst support for the methanol oxidation reaction (MOR). The structure, morphology and composition of the synthesized TiNiN/CNT-rGO exhibits a uniform particle dispersion with high purity and interpenetrating 3D network structure. Notably, Pt/TiNiN/CNT-rGO catalyst exhibits significantly improved catalytic activity and durability for methanol oxidation in comparison with Pt/CNT-rGO and conventional Pt/C (JM). The outstanding electrochemical performance was attributed to structure and properties. That is, the 3D CNT-rGO provided a fast transport network for charge-transfer and mass-transfer as well as TiNiN NPs with good synergistic effect and the strong electronic coupling between different domains in TiNiN/CNT-rGO, thus the catalytic activity of the novel catalyst is greatly improved. These results evidences 3D TiNiN/CNT-rGO as a promising catalyst support for a wide range of applications in fuel cells.

  8. The effect of titanium nickel nitride decorated carbon nanotubes-reduced graphene oxide hybrid support for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gen [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, Guangdong 510006 (China); Pan, Zhanchang, E-mail: panzhanchang@163.com [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, Guangdong 510006 (China); Li, Wuyi; Yu, Ke [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, Guangdong 510006 (China); Xia, Guowei; Zhao, Qixiang; Shi, Shikun [Victory Giant Technology (Hui Zhou) Co., Ltd., Huizhou 516083 (China); Hu, Guanghui; Xiao, Chumin; Wei, Zhigang [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, Guangdong 510006 (China)

    2017-07-15

    Highlights: • TiNiN/CNT-rGO support with an interactive three-dimensional structure and high surface area was synthesized. • Pt nanoparticles with small size were well dispersed on TiNiN/CNT-rGO support. • Pt/TiNiN/CNT-rGO shows remarkably enhanced methanol oxidation activity and durability. - Abstract: Titanium nickel nitride (TiNiN) decorated three-dimensional (3D) carbon nanotubes-reduced graphene oxide (CNT-rGO), a fancy 3D platinum (Pt)-based catalyst hybrid support, is prepared by a solvothermal process followed by a nitriding process, which is tested as anodic catalyst support for the methanol oxidation reaction (MOR). The structure, morphology and composition of the synthesized TiNiN/CNT-rGO exhibits a uniform particle dispersion with high purity and interpenetrating 3D network structure. Notably, Pt/TiNiN/CNT-rGO catalyst exhibits significantly improved catalytic activity and durability for methanol oxidation in comparison with Pt/CNT-rGO and conventional Pt/C (JM). The outstanding electrochemical performance was attributed to structure and properties. That is, the 3D CNT-rGO provided a fast transport network for charge-transfer and mass-transfer as well as TiNiN NPs with good synergistic effect and the strong electronic coupling between different domains in TiNiN/CNT-rGO, thus the catalytic activity of the novel catalyst is greatly improved. These results evidences 3D TiNiN/CNT-rGO as a promising catalyst support for a wide range of applications in fuel cells.

  9. Formation of amorphous carbon during microcrystalline graphite melting under the action of laser picosecond pulses

    International Nuclear Information System (INIS)

    Agranat, M.B.; Ashitkov, S.I.; Kirillin, A.V.; Kostanovskij, A.V.; Fortov, V.E.; Anisimov, S.I.; Kondratenko, P.S.

    1997-01-01

    Formation of a liquid phase with a transition to a homogeneous amorphous state under the surface layer solidification is detected under picosecond laser pulse effect on the microcrystalline graphite. A periodic surface structure is produced in the heating region with the period of the order of the length of the heating pulse wave, its strokes following the direction of this pulse polarization. Study of the probing laser pulse reflection kinetics has shown, that the typical time of liquid phase and solidification life makes up ∼ 10 -10 s

  10. Rapid synthesis of graphitic carbon nitride powders by metathesis reaction between CaCN{sub 2} and C{sub 2}Cl{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Pang Linlin [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan, 250061 (China); Carbon Fiber Engineering Research Center of Shandong Province, Shandong University, Jinan 250061 (China); Bi Jianqiang [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan, 250061 (China); Bai Yujun [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan, 250061 (China) and Carbon Fiber Engineering Research Center of Shandong Province, Shandong University, Jinan 250061 (China)], E-mail: byj97@126.com; Qi Yongxin [Carbon Fiber Engineering Research Center of Shandong Province, Shandong University, Jinan 250061 (China); Zhu Huiling [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan, 250061 (China); Carbon Fiber Engineering Research Center of Shandong Province, Shandong University, Jinan 250061 (China); Wang Chengguo; Wu Jiwei [Carbon Fiber Engineering Research Center of Shandong Province, Shandong University, Jinan 250061 (China); Lu Chengwei [Department of Equipment, Shandong University of Science and Technology, Jinan 250031 (China)

    2008-12-20

    Carbon nitride powders were rapidly synthesized at low temperature via the chemical metathesis reaction between CaCN{sub 2} and C{sub 2}Cl{sub 6}. X-ray diffraction results confirm the formation of crystalline graphitic carbon nitride. Besides the dominant morphology of nanoparticles, flakes, nanorods, hollow and solid spheres can be observed by transmission electron microscopy. The absorption peaks of C-N, C=N and s-triazine rings, as well as the absence of C{identical_to}N peak in the infrared spectra, further verify the formation of graphite-like sp{sup 2}-bonded structure with planar networks. Elemental analysis gives an atomic ratio of N/C around 0.3. X-ray photoelectron spectra exhibit the existence of chemical bonding between C and N.

  11. Separation and concentration of natural products by fast forced adsorption using well-dispersed velvet-like graphitic carbon nitride with response surface methodology optimisation.

    Science.gov (United States)

    Ding, Xinru; Zhu, Jun; Zhang, Yue; Xia, Qian; Bi, Wentao; Yang, Xiaodi; Yang, Jinfei

    2016-07-01

    Well-dispersed velvet-like graphitic carbon nitride nanoparticles with a large surface area were prepared and utilized for separation and concentration of bioactive compounds from fruit extracts by fast (20s) forced adsorption. The large surface area, enhanced non-covalent interactions of this nanoparticle with bioactive compounds and good dispersity in different solvents benefited its application as a good sorbent. To evaluate their adsorption capabilities, these carbon nitride nanoparticles were used for separation and concentration of flavonoids from fruit extracts by a forced-adsorption dispersive solid phase extraction method. The combined use of this nanoparticle and our experimental conditions showed excellent precision (3.6-4.7%) and sensitivity (limits of detection (S/N=3): 0.6-3.75ng/mL). This research provides an alternative strategy to prepare suitable sorbents for adsorption, separation and concentration of various compounds from different extracts. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Amorphous to crystalline phase transition in carbon induced by intense femtosecond x-ray free-electron laser pulses

    Czech Academy of Sciences Publication Activity Database

    Gaudin, J.; Peyrusse, O.; Chalupský, Jaromír; Toufarová, Martina; Vyšín, Luděk; Hájková, Věra; Sobierajski, R.; Burian, Tomáš; Dastjani-Farahani, S.; Graf, A.; Amati, M.; Gregoratti, L.; Hau-Riege, S.P.; Hoffmann, G.; Juha, Libor; Krzywinski, J.; London, R.A.; Moeller, S.; Sinn, H.; Schorb, S.; Störmer, M.; Tschentscher, T.; Vorlíček, Vladimír; Vu, H.; Bozek, J.; Bostedt, C.

    2012-01-01

    Roč. 86, č. 2 (2012), "024103-1"-"024103-7" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP108/11/1312; GA ČR GAP205/11/0571; GA ČR GAP208/10/2302; GA AV ČR IAAX00100903; GA MŠk EE.2.3.20.0087 Grant - others:OP VK 2 LaserGen(XE) CZ.1.07/2.3.00/20.0087 Institutional research plan: CEZ:AV0Z10100523 Keywords : amorphous carbon * phase transition * graphitization * x-ray laser * free-electron laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.767, year: 2012

  13. Enhanced efficiency of hybrid amorphous silicon solar cells based on single-walled carbon nanotubes and polymer composite thin film

    Science.gov (United States)

    Rajanna, Pramod M.; Gilshteyn, Evgenia P.; Yagafarov, Timur; Aleekseeva, Alena K.; Anisimov, Anton S.; Neumüller, Alex; Sergeev, Oleg; Bereznev, Sergei; Maricheva, Jelena; Nasibulin, Albert G.

    2018-03-01

    We report a simple approach to fabricate hybrid solar cells (HSCs) based on a single-walled carbon nanotube (SWCNT) film and thin film hydrogenated amorphous silicon (a-Si:H). Randomly oriented high-quality SWCNTs with conductivity enhanced by means of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate are used as a window layer and a front electrode. A series of HSCs are fabricated in ambient conditions with varying SWCNT film thicknesses. The polymethylmethacrylate layer drop-casted on fabricated HSCs reduces the reflection fourfold and enhances the short-circuit J sc , open-circuit V oc , and efficiency by nearly 10%. A state-of-the-art J-V performance is shown for SWCNT/a-Si HSC with an open-circuit voltage of 900 mV and an efficiency of 3.4% under simulated one-sun AM 1.5 G direct illumination.

  14. Thin films of hydrogenated amorphous carbon (a-C:H) obtained through chemical vapor deposition assisted by plasma

    International Nuclear Information System (INIS)

    Mejia H, J.A.; Camps C, E.E.; Escobar A, L.; Romero H, S.; Chirino O, S.; Muhl S, S.

    2004-01-01

    Films of hydrogenated amorphous carbon (a-C:H) were deposited using one source of microwave plasma with magnetic field (type ECR), using mixtures of H 2 /CH 4 in relationship of 80/20 and 95/05 as precursory gases, with work pressures of 4X10 -4 to 6x10 -4 Torr and an incident power of the discharge of microwaves with a constant value of 400 W. It was analyzed the influence among the properties of the films, as the deposit rate, the composition and the bonding types, and the deposit conditions, such as the flow rates of the precursory gases and the polarization voltage of the sample holders. (Author)

  15. Cu incorporated amorphous diamond like carbon (DLC) composites: An efficient electron field emitter over a wide range of temperature

    Science.gov (United States)

    Ahmed, Sk Faruque; Alam, Md Shahbaz; Mukherjee, Nillohit

    2018-03-01

    The effect of temperature on the electron field emission properties of copper incorporated amorphous diamond like carbon (a-Cu:DLC) thin films have been reported. The a-Cu:DLC thin films have been deposited on indium tin oxide (ITO) coated glass and silicon substrate by the radio frequency sputtering process. The chemical composition of the films was investigated using X-ray photoelectron spectroscopy and the micro structure was established using high resolution transmission electron microscopy. The sp2 and sp3 bonding ratio in the a-Cu:DLC have been analyzed by the Fourier transformed infrared spectroscopy studies. The material showed excellent electron field emission properties; which was optimized by varying the copper atomic percentage and temperature of the films. It was found that the threshold field and effective emission barrier were reduced significantly by copper incorporation as well as temperature and a detailed explanation towards emission mechanism has been provided.

  16. Efficient cold cathode emission in crystalline-amorphous hybrid: Study on carbon nanotube-cadmium selenide system

    Science.gov (United States)

    Sarkar, S.; Banerjee, D.; Das, N. S.; Ghorai, U. K.; Sen, D.; Chattopadhyay, K. K.

    2018-03-01

    Cadmium Selenide (CdSe) quantum dot (QD) decorated amorphous carbon nanotubes (a-CNTs) hybrids have been synthesized by simple chemical process. The samples were characterized by field emission scanning and transmission electron microscopy, Fourier transformed infrared spectroscopy, Raman and UV-Vis spectroscopy. Lattice image obtained from transmission electron microscopic study confirms the successful attachment of CdSe QDs. It is seen that hybrid samples show an enhanced cold emission properties with good stability. The results have been explained in terms of increased roughness, more numbers of emitting sites and favorable band bending induced electron transport. ANSYS software based calculation has also supported the result. Also a first principle based study has been done which shows that due to the formation of hybrid structure there is a profound upward shift in the Fermi level, i.e. a decrease of work function, which is believed to be another key reason for the observed improved field emission performance.

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

    KAUST Repository

    Wang, N.

    2013-01-01

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

  18. MoS{sub 2}-coated microspheres of self-sensitized carbon nitride for efficient photocatalytic hydrogen generation under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Quan [Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, 710062 (China); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Sun, Huaming; Xie, Zunyuan; Gao, Ziwei [Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, 710062 (China); Xue, Can, E-mail: cxue@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2017-02-28

    Highlights: • Successful coating of MoS{sub 2} onto self-sensitized carbon nitride microspheres. • The carbon nitride@MoS{sub 2} core-shell structure show enhanced H{sub 2} generation in visible light. • Synergistic effect of surface dyes and MoS{sub 2} coating enhances photocatalytic activities. - Abstract: We have successfully coated the self-sensitized carbon nitride (SSCN) microspheres with a layer of MoS{sub 2} through a facile one-pot hydrothermal method by using (NH{sub 4}){sub 2}MoS{sub 4} as the precursor. The resulted MoS{sub 2}-coated SSCN photocatalyst appears as a core-shell structure and exhibits enhanced visible-light activities for photocatalytic H{sub 2} generation as compared to the un-coated SSCN and the standard g-C{sub 3}N{sub 4} reference with MoS{sub 2} coating. The photocatalytic test results suggest that the oligomeric s-triazine dyes on the SSCN surface can provide additional light-harvesting capability and photogenerated charge carriers, and the coated MoS{sub 2} layer can serve as active sites for proton reduction towards H{sub 2} evolution. This synergistic effect of surface triazine dyes and MoS{sub 2} coating greatly promotes the activity of carbon nitride microspheres for vishible-light-driven H{sub 2} generation. This work provides a new way of future development of low-cost noble-metal-free photocatalysts for efficient solar-driven hydrogen production.

  19. A highly sensitive electrochemiluminescence biosensor for the detection of organophosphate pesticides based on cyclodextrin functionalized graphitic carbon nitride and enzyme inhibition.

    Science.gov (United States)

    Wang, Bingxin; Wang, Haijun; Zhong, Xia; Chai, Yaqin; Chen, Shihong; Yuan, Ruo

    2016-04-11

    A signal on an electrochemiluminescence (ECL) biosensor using β-cyclodextrin (CD) functionalized graphitic carbon nitride (g-C3N4) as the luminophore was constructed for sensitive organophosphate pesticides (OPs) detection based on the enzyme inhibition of OPs, showing that the consumption of coreactant triethylamine (Et3N) decreased with a lessening of the acetic acid (HAc) in situ generated by enzymatic reaction.

  20. Biological characteristics of the MG-63 human osteosarcoma cells on composite tantalum carbide/amorphous carbon films.

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    Yin-Yu Chang

    Full Text Available Tantalum (Ta is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC and TaC/amorphous carbon (a-C coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C, was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics.