Sample records for boron doped graphite

  1. Atomic structure of highly ordered pyrolytic graphite doped with boron

    E-print Network

    Kwak, Juhyoun

    Atomic structure of highly ordered pyrolytic graphite doped with boron Eunkyung Kim, Ilwhan Oh 3 September 2001; accepted 3 September 2001 Abstract Boron-doped carbon was prepared by the high of the boron doping on the HOPG structure, several experimental tools were employed such as X-ray photoelectron

  2. Structure and electrochemical applications of boron-doped graphitized carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Yeo, Jae-Seong; Jang, Sang-Min; Miyawaki, Jin; An, Bai; Mochida, Isao; Rhee, Choong Kyun; Yoon, Seong-Ho

    2012-08-01

    Boron-doped graphitized carbon nanofibers (CNFs) were prepared by optimizing CNFs preparation, surface treatment, graphitization and boron-added graphitization. The interlayer spacing (d002) of the boron-doped graphitized CNFs reached 3.356 Å, similar to that of single-crystal graphite. Special platelet CNFs (PCNFs), for which d002 is less than 3.400 Å, were selected for further heat treatment. The first heat treatment of PCNFs at 2800?°C yielded a d002 between 3.357 and 3.365 Å. Successive nitric acid treatment and a second heat treatment with boric acid reduced d002 to 3.356 Å. The resulting boron-doped PCNFs exhibited a high discharge capacity of 338 mAh g-1 between 0 and 0.5 V versus Li/Li+ and 368 mAh g-1 between 0 and 1.5 V versus Li/Li+. The first-cycle Coulombic efficiency was also enhanced to 71-80%. Such capacity is comparable to that of natural graphite under the same charge/discharge conditions. The boron-doped PCNFs also exhibited improved rate performance with twice the capacity of boron-doped natural graphite at a discharge rate of 5 C.

  3. Structure and electrochemical applications of boron-doped graphitized carbon nanofibers.

    PubMed

    Yeo, Jae-Seong; Jang, Sang-Min; Miyawaki, Jin; An, Bai; Mochida, Isao; Rhee, Choong Kyun; Yoon, Seong-Ho

    2012-08-10

    Boron-doped graphitized carbon nanofibers (CNFs) were prepared by optimizing CNFs preparation, surface treatment, graphitization and boron-added graphitization. The interlayer spacing (d???) of the boron-doped graphitized CNFs reached 3.356 ?, similar to that of single-crystal graphite. Special platelet CNFs (PCNFs), for which d??? is less than 3.400 ?, were selected for further heat treatment. The first heat treatment of PCNFs at 2800?°C yielded a d??? between 3.357 and 3.365 ?. Successive nitric acid treatment and a second heat treatment with boric acid reduced d??? to 3.356 ?. The resulting boron-doped PCNFs exhibited a high discharge capacity of 338 mAh g?¹ between 0 and 0.5 V versus Li/Li? and 368 mAh g?¹ between 0 and 1.5 V versus Li/Li?. The first-cycle Coulombic efficiency was also enhanced to 71-80%. Such capacity is comparable to that of natural graphite under the same charge/discharge conditions. The boron-doped PCNFs also exhibited improved rate performance with twice the capacity of boron-doped natural graphite at a discharge rate of 5 C. PMID:22797214

  4. Precipitation of Boron in Highly Boron-Doped Silicon

    Microsoft Academic Search

    Ichiro Mizushima; Yuichiro Mitani; Mitsuo Koike; Masahiko Yoshiki; Mitsuhiro Tomita; Sigeru Kambayashi

    1998-01-01

    The clustering of boron in highly boron-doped silicon and its influence on electrical deactivation are reported. Highly boron-doped crystalline silicon was fabricated as a starting material by solid phase epitaxy of boron-doped amorphous silicon films. Boron can be supersaturated in the crystallized samples annealed at a low temperature of about 600°C. A lot of precipitates, containing clustered boron, were observed

  5. Synthesis, characterization and oxidation of boron-doped carbons

    NASA Astrophysics Data System (ADS)

    Cermignani, William

    The goal of this study was to gain a fundamental understanding of the role of boron in carbon oxidation. Boron-doped carbons were synthesized via CVD, ion implantation and high temperature doping and subsequently characterized. It was found that high temperature doped HOPG carbons were ideal for oxidation studies because their surface could be reproduced, their surface structures were determined and they were able to be characterized by XPS, AFM and SEM. The direct analysis of the chemical structures and atomic arrangements in boron-doped carbon or carbon surfaces by these techniques was critical in determining the effect of boron on carbon oxidation. XPS was utilized in this work to determine the local bonding environment of boron in carbon before and after oxidation. It was necessary to obtain an accurate calibration of the B1s binding energy scale which was accomplished by obtaining photoemission spectra of boron-doped carbons with known structures (local boron bonding environments), such as boron oxide, boron carbide, triphenylboroxine, tourmaline, boric acid, danburite and high temperature boron-doped graphite. All of the aforementioned standards contain boron in a unique bonding environment and thus their spectra formulated a complete conversion of B1s binding energies to boron chemical environments which had not been reported in the past. It was clearly established that a chemical shift for substitutional boron in graphite exists at 186.5 eV with a FWHM of 1.2. The chemical structures of the boron in the standards were related to the binding energy using a Pauling charge distribution model and a modification of the Sanderson electronegativity method. This approach was used to determine whether the B1s binding energy would change depending upon the specific location of boron in the graphite or graphite surface. This model was used, along with XPS, TEM and Raman results, to show that edge sites are preferred lattice sites in graphite for boron substitution. The oxidation behaviors of the synthesized high temperature doped samples were studied with TGA, SEM, XPS and AFM. It was found that boron caused the gasification rates of the carbons to decrease. The SEM and AFM results showed that the pits that were formed in the undoped and doped carbons were different in size, depth and orientation. A semi-empirical Molecular Orbital Package method and experimental results were used to show that the reactivity of the zig-zag edge sites of a pit wall could be reduced by the replacement of carbon atoms with boron atoms at these sites; hence, the oxidation would be inhibited in the a-direction of a graphene layer. Conversely, boron doping on an armchair edge surface of a pit wall results in increased reactivity at these sites and the subsequent formation of boron oxide during oxidation, which does not prevent oxidation in the a-direction of a graphene layer. Rather, the build-up of boron oxide clusters prevented oxidation in the c-direction. A model was proposed for the oxidation inhibition mechanism in boron-doped graphite based upon the stability of pits with boron substitution on the zig-zag sites.

  6. Controlled boron doping of silicon

    Microsoft Academic Search

    Lin

    1986-01-01

    A method is described of making a semiconductor device by steps comprising doping a vertical surface of a silicon body with boron characterized in that the doping is accomplished by steps comprising: forming a layer of silicon dioxide on the vertical surface; forming a layer of silicon on the silicon dioxide on the vertical surface, and on a horizontal surface

  7. Boron doping a semiconductor particle

    SciTech Connect

    Stevens, G.D.; Reynolds, J.S.; Brown, L.K.

    1998-06-09

    A method of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried, with the boron film then being driven into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out into piles and melted/fused with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements. 2 figs.

  8. Boron doping a semiconductor particle

    DOEpatents

    Stevens, Gary Don (18912 Ravenglen Ct., Dallas, TX 75287); Reynolds, Jeffrey Scott (703 Horizon, Murphy, TX 75094); Brown, Louanne Kay (2530 Poplar Tr., Garland, TX 75042)

    1998-06-09

    A method (10,30) of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried (16), with the boron film then being driven (18) into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out (38) into piles and melted/fused (40) with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements.

  9. Catalyst-free synthesis of crumpled boron and nitrogen co-doped graphite layers with tunable bond structure for oxygen reduction reaction.

    PubMed

    Jin, Jutao; Pan, Fuping; Jiang, Luhua; Fu, Xiaogang; Liang, Aiming; Wei, Zhiyang; Zhang, Junyan; Sun, Gongquan

    2014-04-22

    Two-dimensional materials based on ternary system of B, C and N are useful ranging from electric devices to catalysis. The bonding arrangement within these BCN nanosheets largely determines their electronic structure and thus chemical and (or) physical properties, yet it remains a challenge to manipulate their bond structures in a convenient and controlled manner. Recently, we developed a synthetic protocol for the synthesis of crumpled BCN nanosheets with tunable B and N bond structure using urea, boric acid and polyethylene glycol (PEG) as precursors. By carefully selecting the synthesis condition, we can tune the structure of BCN sheets from s-BCN with B and N bond together to h-BCN with B and N homogenously dispersed in BCN sheets. Detailed experiments suggest that the final bond structure of B and N in graphene depends on the preferentially doped N structure in BCN nanosheets. When N substituted the in-plane carbon atom with all its electrons configured into the ? electron system of graphene, it facilitates the formation of h-BCN with B and N in separated state. On the contrary, when nitrogen substituted the edge-plane carbon with the nitrogen dopant surrounded with the lone electron pairs, it benefits for the formation of B-N structure. Specially, the compound riched with h-BCN shows excellent ORR performance in alkaline solution due to the synergistic effect between B and N, while s-BCN dominant BCN shows graphite-like activity for ORR, suggesting the intrinsic properties differences of BCN nanosheets with different dopants bond arrangement. PMID:24601550

  10. Characterisation of graphite using boron as a marker element

    SciTech Connect

    Kamble, Granthali S.; Pandey, Shailaja; Thakur, Neha; Kumar, Sanjukta A.; Venkatesh, K.; Kumar, Sangita D.; Kameswaran, R.; Reddy, A. V. R. [Analytical Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai- 400 085 (India)

    2013-06-12

    Graphite has many industrial applications. Two of the most important applications are as electrodes in industries and as moderator in nuclear industry. Determination of the Boron Equivalent of the impurity elements in graphite is the most important parameter for certifying the grade of graphite electrode [1]. The use of a suitable method with low limits of determination of boron is therefore necessary. A method has been standardised in Analytical Chemistry Division, BARC for determining trace amounts of boron in graphite electrodes. It involves controlled dissolution of graphite sample powder and measurement of boron by Inductively Coupled Plasma Mass Spectrometer (ICP-MS) using matrix matched standards. The method detection limit is 1 {mu}g g{sup -1}. The method Relative Standard Deviation was 5%. The method was verified by spike recovery experiments. Recoveries were found to be within 100{+-}2% in the concentration range of 1 to 100 {mu}g g{sup -1}. The developed method has been adopted for the compositional characterization of several graphite electrode samples.

  11. Characterisation of graphite using boron as a marker element

    NASA Astrophysics Data System (ADS)

    Kamble, Granthali S.; Pandey, Shailaja; Thakur, Neha; Kumar, Sanjukta A.; Venkatesh, K.; Kumar, Sangita D.; Kameswaran, R.; Reddy, A. V. R.

    2013-06-01

    Graphite has many industrial applications. Two of the most important applications are as electrodes in industries and as moderator in nuclear industry. Determination of the Boron Equivalent of the impurity elements in graphite is the most important parameter for certifying the grade of graphite electrode [1]. The use of a suitable method with low limits of determination of boron is therefore necessary. A method has been standardised in Analytical Chemistry Division, BARC for determining trace amounts of boron in graphite electrodes. It involves controlled dissolution of graphite sample powder and measurement of boron by Inductively Coupled Plasma Mass Spectrometer (ICP-MS) using matrix matched standards. The method detection limit is 1 ?g g-1. The method Relative Standard Deviation was 5%. The method was verified by spike recovery experiments. Recoveries were found to be within 100±2% in the concentration range of 1 to 100 ?g g-1. The developed method has been adopted for the compositional characterization of several graphite electrode samples.

  12. Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords

    E-print Network

    Gao, Hongjun

    Influence of Si Co-doping on electrical transport properties of magnesium- doped boron nanoswords://apl.aip.org/about/rights_and_permissions #12;Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords; published online 9 March 2012) Magnesium-doped boron nanoswords were synthesized via a thermoreduction

  13. Boron Doping Carbon Structures Using Decaborane? A Theoretical Study

    NASA Astrophysics Data System (ADS)

    Wexler, Carlos; Connolly, Matthew; Beckner, Matthew; Pfeifer, Peter

    2012-02-01

    Boron-doped carbon materials have been shown to improve hydrogen storage. Boron-doped activated carbons have been produced using a novel process involving the pyrolysis of a boron containing compound and subsequent high-temperature annealing. A model for the boron doping process based on a Langmuir isotherm is presented. A theoretical study of the interaction of the boron containing compound with the undoped carbon precursor will be presented. Ab-initio calculations of the potential energy surface and the Langmuir isotherm parameters derived from them are also presented. The theoretical study outlines the unique capabilities and limits of this doping procedure.

  14. Photoinduced doping in heterostructures of graphene and boron nitride

    E-print Network

    Zhang, Guangyu

    Photoinduced doping in heterostructures of graphene and boron nitride L. Ju1 , J. Velasco Jr1 , E in van der Waals heterostructures consisting of graphene and boron nitride layers. It enables flex- ible that this photoinduced doping maintains the high carrier mobility of the graphene/ boron nitride heterostructure, thus

  15. Doping and Raman Characterization of Boron and Phosphorus Atoms in

    E-print Network

    Wang, Zhong L.

    Doping and Raman Characterization of Boron and Phosphorus Atoms in Germanium Nanowires Naoki Fukata. The chemical bonding states and electrical activity of boron (B) and phosphorus (P) atoms in germanium

  16. Synthesis, characterization and oxidation of boron-doped carbons

    Microsoft Academic Search

    William Cermignani

    1997-01-01

    The goal of this study was to gain a fundamental understanding of the role of boron in carbon oxidation. Boron-doped carbons were synthesized via CVD, ion implantation and high temperature doping and subsequently characterized. It was found that high temperature doped HOPG carbons were ideal for oxidation studies because their surface could be reproduced, their surface structures were determined and

  17. Energetics of Boron Doping of Carbon Pores

    NASA Astrophysics Data System (ADS)

    Wexler, Carlos; St. John, Alexander; Connolly, Matthew

    2014-03-01

    Carbon-based materials show promise, given their light weight, large surface areas and low cost for storage of hydrogen and other gases, e.g., for energy applications. Alas, the interaction of H2 and carbon, 4-5kJ/mol, is insufficient for room-temperature operation. Boron doping of carbon materials could raise the binding energy of H2 to 12-15kJ/mol. The nature of the incorporation of boron into a carbon structure has not been studied so far. In this talk we will address the energetics of boron incorporation into a carbon matrix via adsorption and decomposition of decaborane by first principles calculations. These demonstrate: (a) A strong adsorption of decaborane to carbon (70-80kJ/mol) resulting in easy incorporation of decaborane, sufficient for up to 10-20% B:C at low decaborane vapour pressures. (b) Identification that boron acts as an electron acceptor when incorporated substitutionally into a graphene-like material, as expected due to its valence. (c) The electrostatic field near the molecule is responsible for ca. 2/3 of the enhancement of the H2-adsorbent interaction in aromatic compounds such as pyrene, coronene and ovalene. Supported by DOE DE-FG36-08GO18142, ACS-PRF 52696-ND5, and NSF 1069091.

  18. First-Principles Study of Superconductivity in boron-doped SiC

    NASA Astrophysics Data System (ADS)

    Noffsinger, Jesse; Giustino, Feliciano; Louie, Steven; Cohen, Marvin

    2008-03-01

    The discovery of superconductivity in materials such as intercalated graphite, alkali-doped fullerenes, and boron-doped diamond has drawn significant interest to carbon-based superconductors. Recent experiments indicate that boron-doped cubic SiC may superconduct above 1 K [1]. We investigate the superconductivity in cubic SiC using a first-principles approach. We describe the electronic structure within density functional theory and the lattice dynamics within density functional perturbation theory. The electron-phonon interaction matrix elements are calculated via a recently developed method based on Wannier functions [2]. The boron doping is accounted for by a virtual crystal approximation. In addition to the coupling of Fermi surface electronic states to optical phonon modes, there appears to be a non-negligible contribution to the electron-phonon coupling arising from acoustic phonons. Superconductivity is discussed by analyzing the similarities and the differences with respect to the closely related boron-doped diamond. [1] Z-A. Ren et. al, private communication. [2] F. Giustino et. al, Phys. Rev. B 76, 165108 (2007)

  19. Measured Enthalpies of Adsorption of Boron-Doped Activated Carbons

    NASA Astrophysics Data System (ADS)

    Beckner, M.; Romanos, J.; Dohnke, E.; Singh, A.; Schaeperkoetter, J.; Stalla, D.; Burress, J.; Jalisatgi, S.; Suppes, G.; Hawthorne, M. F.; Yu, P.; Wexler, C.; Pfeifer, P.

    2012-02-01

    There is significant interest in the properties of boron-doped activated carbons for their potential to improve hydrogen storage.ootnotetextMultiply Surface-Functionalized Nanoporous Carbon for Vehicular Hydrogen Storage, P. Pfeifer et al. DOE Hydrogen Program 2011 Annual Progress Report, IV.C.3, 444-449 (2011). Boron-doped activated carbons have been produced using a process involving the pyrolysis of decaborane (B10H14) and subsequent high-temperature annealing. In this talk, we will present a systematic study of the effect of different boron doping processes on the samples' structure, hydrogen sorption, and surface chemistry. Initial room temperature experiments show a 20% increase in the hydrogen excess adsorption per surface area compared to the undoped material. Experimental enthalpies of adsorption will be presented for comparison to theoretical predictions for boron-doped carbon materials. Additionally, results from a modified version of the doping process will be presented.

  20. Growth and electronic structure of boron-doped graphene

    NASA Astrophysics Data System (ADS)

    Gebhardt, J.; Koch, R. J.; Zhao, W.; Höfert, O.; Gotterbarm, K.; Mammadov, S.; Papp, C.; Görling, A.; Steinrück, H.-P.; Seyller, Th.

    2013-04-01

    The doping of graphene to tune its electronic properties is essential for its further use in carbon-based electronics. Adapting strategies from classical silicon-based semiconductor technology, we use the incorporation of heteroatoms in the 2D graphene network as a straightforward way to achieve this goal. Here, we report on the synthesis of boron-doped graphene on Ni(111) in a chemical vapor deposition process of triethylborane on the one hand and by segregation of boron from the bulk of the substrate crystal on the other hand. The chemical environment of boron was determined by x-ray photoelectron spectroscopy, and angle-resolved photoelectron spectroscopy was used to analyze the impact on the band structure. Doping with boron leads to a shift of the graphene bands to lower binding energies. The shift depends on the doping concentration and for a doping level of 0.3 ML a shift of up to 1.2 eV is observed. The experimental results are in agreement with density-functional calculations. Furthermore, our calculations suggest that doping with boron leads to graphene preferentially adsorbed in the top-fcc geometry, since the boron atoms in the graphene lattice are then adsorbed at substrate fcc-hollow sites. The smaller distance of boron atoms incorporated into graphene compared to graphene carbon atoms leads to a bending of the doped graphene sheet in the vicinity of the boron atoms. By comparing calculations of doped and undoped graphene on Ni(111), as well as the respective freestanding cases, we are able to distinguish between the effects that doping and adsorption have on the band structure of graphene. Both doping and bonding to the surface result in opposing shifts on the graphene bands.

  1. Boron Redistribution During Crystallization of Phosphorus-Doped Amorphous Silicon

    Microsoft Academic Search

    R. Simola; D. Mangelinck; A. Portavoce; J. Bernardini; P. Fornara

    2006-01-01

    The redistribution of boron has been studied during solid phase crystallization (SPC) of a homogeneous phosphorus-doped amorphous silicon layer deposited by low pressure chemical vapor deposition, for different thermal annealing. We show that for the lower temperature annealing (T = 586 °C, 1h) boron diffuses without changing the P profile, while for the higher temperature annealing (T = 800 °C,

  2. Spatially-correlated microstructure and superconductivity in polycrystalline Boron-doped diamond

    E-print Network

    Paris-Sud XI, Université de

    Spatially-correlated microstructure and superconductivity in polycrystalline Boron-doped diamond F are performed below 100 mK on polycrystalline Boron-doped diamond films characterized by Transmission Electron superconductivity appears at the same doping level than the metallic state created by heavy Boron doping.4 Evidence

  3. Photoinduced doping in heterostructures of graphene and boron nitride.

    PubMed

    Ju, L; Velasco, J; Huang, E; Kahn, S; Nosiglia, C; Tsai, Hsin-Zon; Yang, W; Taniguchi, T; Watanabe, K; Zhang, Y; Zhang, G; Crommie, M; Zettl, A; Wang, F

    2014-05-01

    The design of stacks of layered materials in which adjacent layers interact by van der Waals forces has enabled the combination of various two-dimensional crystals with different electrical, optical and mechanical properties as well as the emergence of novel physical phenomena and device functionality. Here, we report photoinduced doping in van der Waals heterostructures consisting of graphene and boron nitride layers. It enables flexible and repeatable writing and erasing of charge doping in graphene with visible light. We demonstrate that this photoinduced doping maintains the high carrier mobility of the graphene/boron nitride heterostructure, thus resembling the modulation doping technique used in semiconductor heterojunctions, and can be used to generate spatially varying doping profiles such as p-n junctions. We show that this photoinduced doping arises from microscopically coupled optical and electrical responses of graphene/boron nitride heterostructures, including optical excitation of defect transitions in boron nitride, electrical transport in graphene, and charge transfer between boron nitride and graphene. PMID:24727687

  4. Femtosecond-laser-induced destruction of boron-nitride nanotubes and boron-nitride doped graphene

    NASA Astrophysics Data System (ADS)

    Bauerhenne, Bernd; Eschstruth, Nils; Zijlstra, Eeuwe S.; Garcia, Martin E.

    2013-11-01

    By means of first principles calculations we studied the intense femtosecond-laser excitation of several boron­ nitride nanotubes and a boron-nitride doped graphene layer up to irradiation levels where these structures disintegrate. We performed molecular dynamics simulations using our in-house Code for Highly excited Valence Electron Systems (CHIVES). For different boron-nitride nanotubes we determined the damage threshold in terms of the electronic temperature and the absorbed energy per atom. We found that all nanotubes studied were destroyed in the first 200 fs after an ultrafast laser excitation heating the electrons to 108 mHa (34103 K). Some tubes also disintegrated at lower electronic temperatures. For the boron-nitride doped graphene we found that at a laser-induced electronic temperature of 100 mHa (31577 K) bonds break and the boron-nitride dimer leaves the structure.

  5. Flexible Boron-Doped Laser-Induced Graphene Microsupercapacitors.

    PubMed

    Peng, Zhiwei; Ye, Ruquan; Mann, Jason A; Zakhidov, Dante; Li, Yilun; Smalley, Preston R; Lin, Jian; Tour, James M

    2015-06-23

    Heteroatom-doped graphene materials have been intensely studied as active electrodes in energy storage devices. Here, we demonstrate that boron-doped porous graphene can be prepared in ambient air using a facile laser induction process from boric acid containing polyimide sheets. At the same time, active electrodes can be patterned for flexible microsupercapacitors. As a result of boron doping, the highest areal capacitance of as-prepared devices reaches 16.5 mF/cm(2), 3 times higher than nondoped devices, with concomitant energy density increases of 5-10 times at various power densities. The superb cyclability and mechanical flexibility of the device are well-maintained, showing great potential for future microelectronics made from this boron-doped laser-induced graphene material. PMID:25978090

  6. Boron-doped back-surface fields using an aluminum-alloy process

    SciTech Connect

    Gee, J.M.; Bode, M.D.; Silva, B.L.

    1997-10-01

    Boron-doped back-surface fields (BSF`s) have potentially superior performance compared to aluminum-doped BSF`s due to the higher solid solubility of boron compared to aluminum. However, conventional boron diffusions require a long, high temperature step that is both costly and incompatible with many photovoltaic-grade crystalline-silicon materials. We examined a process that uses a relatively low-temperature aluminum-alloy process to obtain a boron-doped BSF by doping the aluminum with boron. In agreement with theoretical expectations, we found that thicker aluminum layers and higher boron doping levels improved the performance of aluminum-alloyed BSF`s.

  7. FIELD EMISSION FROM BORON-DOPING POLYCRYSTALLINE DIAMOND FILMS ON SILICON

    E-print Network

    FIELD EMISSION FROM BORON-DOPING POLYCRYSTALLINE DIAMOND FILMS ON SILICON J. A. N. Gonçalves, G. M material fail. The field emission current from boron-doped polycrystalline diamond films grown by hot

  8. Evolution of ^311 type defects in boron-doped structures: Experimental evidence of boroninterstitial cluster formation

    E-print Network

    Florida, University of

    Evolution of ^311 type defects in boron-doped structures: Experimental evidence of boron for publication 13 January 1999 Boron-doped well structures formed in Czochralski silicon are subjected to a self is then used to measure the residual interstitials trapped in the 311 defects as a function of boron

  9. Spatially-Correlated Microstructure and Superconductivity in Polycrystalline Boron-Doped Diamond

    E-print Network

    Spatially-Correlated Microstructure and Superconductivity in Polycrystalline Boron-Doped Diamond F tunneling spectroscopies are performed below 100 mK on nano-crystalline boron-doped diamond films than the metal- lic state created by heavy boron doping [4, 5, 6]. Evi- dence for a pairing mechanism

  10. Pairwise cobalt doping of boron carbides with cobaltocene

    SciTech Connect

    Ignatov, A. Yu.; Losovyj, Ya. B.; Carlson, L.; LaGraffe, D.; Brand, J. I.; Dowben, P. A. [Center for Advanced Microstructures and Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, Louisiana 70806 (United States); Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, Ohio 45433-7765 (United States); College of Engineering and Technology, N245 Walter Scott Engineering Center, 17th and Vine Streets, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0511 (United States); Department of Physics and Astronomy, Behlen Laboratory of Physics, University of Nebraska, P.O. Box 880111, Lincoln, Nebraska 68588-0111 (United States) and the Nebraska Center for Materials and Nanoscience, Behlen Laboratory of Physics, University of Nebraska, P.O. Box 880111, Lincoln, Nebraska 68588-0111 (United States)

    2007-10-15

    We have performed Co K-edge x-ray absorption fine structure and x-ray absorption near edge structure measurements of Co-doped plasma enhanced chemical vapor phase deposition (PECVD) grown 'C{sub 2}B{sub 10}H{sub x}' semiconducting boron carbides, using cobaltocene. Cobalt does not dope PECVD grown boron carbides as a random fragment of the cobaltocene source gas. The Co atoms are fivefold boron coordinated (R=2.10{+-}0.02 A) and are chemically bonded to the icosahedral cages of B{sub 10}CH{sub x} or B{sub 9}C{sub 2}H{sub y}. Pairwise Co doping occurs, with the cobalt atoms favoring sites some 5.28{+-}0.02 A apart.

  11. Characteristics of boron doped mesophase pitch-based carbon fibers as anode materials for lithium secondary cells

    SciTech Connect

    Tamaki, Toshio; Kawamura, Toshifumi; Yamazaki, Yoshinori

    1998-07-01

    Mesophase pitch-based Carbon Fibers(MCF) have been investigated as anode materials for lithium secondary cells by examining their physical and electrochemical properties. Discharge capacity and initial charge-discharge efficiency of the materials were studied in relation to the heat treatment temperatures of MCF. MCF heat treated at about 3,000 C gave high discharge capacity over 310mAh/g, good efficiency (93%) and superior current capability of 600mA/g (6mA/cm2). On the other hand, to improve the battery capacity, Boron was doped to the fiber about several {degree} by adding B{sub 4}C to the pre-carbonized milled fibers and then heat-treated up to 3,000 C in Ar. Then heat treated at 2,500 C under vacuum condition to remove remained B{sub 4}C. The structure of Boron-doped fibers was characterized and compared with that of non-doped standard fibers, and also Li ion battery performances are evaluated. The Boron-doped MCF indicated improvement in graphitization and increased discharge capacity as high as 360mAh/g. The voltammograms of both fibers are different from each other. The cell mechanism is discussed based on the unique structure of Boron-doping to the MCF is very effective for the battery performance.

  12. Wide-gap boron-doped microcrystalline silicon nitride

    Microsoft Academic Search

    S. Hasegawa; M. Segawa; Y. Kurata

    1986-01-01

    The effects of a nitrogen addition on the electrical and optical properties of a boron-doped microcrystalline Si:H film are investigated. The degree of crystallization was examined using Raman scattering. It is observed that the volume fraction of the crystalline phase, the crystallite size, dark conductivity, and optical gap decrease with an increase in N content.

  13. Modeling a Growth Instability in Stressed Boron Doped Silicon

    Microsoft Academic Search

    A.-V. Phan; T. Kaplan; L. J. Gray; W. Barvosa-Carter; M. J. Aziz

    The eects of rate-enhancing dopants and externally applied stress on interfacial growth during silicon crys- tallization are modeled using advanced numerical meth- ods. The boron doped crystalline Si is modeled as an isotropic linear elastic solid, and the amorphous as a viscous uid with a time dependent viscosity to reect structural relaxation. The eect of the dopant is in- cluded

  14. APPLICATION OF BORON-DOPED DIAMOND ELECTRODES FOR WASTEWATER TREATMENT

    Microsoft Academic Search

    Marco Panizza; Enric Brillas; Christos Comninellis

    Boron-doped diamond (BDD) thin film is a new electrode material that has received great attention recently because it possesses several technologically important characteristics such as an inert surface with low adsorption properties, remarkable corrosion stability, even in strong acidic media, and an extremely wide potential window in aqueous and non-aqueous electrolytes. Due to these properties, diamond electrodes are promising anodes

  15. Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords

    SciTech Connect

    Tian Yuan; Lu Hongliang; Tian Jifa; Li Chen; Hui Chao; Shi Xuezhao; Huang Yuan; Shen Chengmin; Gao Hongjun [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2012-03-05

    Magnesium-doped boron nanoswords were synthesized via a thermoreduction method. The as-prepared nanoswords are single crystalline and {beta}-rhombohedral ({beta}-rh) phase. Electrical transport measurements show that variable range hopping conductivity increases with temperature, and carrier mobility has a greater influence than carrier concentration. These results are consistent with the three dimensional Mott's model (M. Cutler and N. F. Mott, Phys. Rev. 181, 1336 (1969)) besides a high density of localized states at the Fermi level compared with bulk {beta}-rh boron. Conductivity of Mg-doped boron nanoswords is significantly lower than that of ''pure'' (free of magnesium) boron nanoswords. Electron energy loss spectroscopy studies confirm that the poorer conductivity arises from silicon against magnesium doping.

  16. Effects of Boron Doping on the Properties of Ultrananocrystalline Diamond Films

    NASA Astrophysics Data System (ADS)

    Yuan, Wen-Xiang; WU, Q. X.; Luo, Z. K.; Wu, H. S.

    2014-04-01

    Boron-doped ultrananocrystalline diamond (UNCD) films were fabricated on silicon substrates by microwave plasma chemical vapor deposition. UNCD films containing different concentrations of boron were prepared by using trimethylboron (B(CH3)3, TMB) as boron doping source and varying the amount of boron in the gas mixture from 0 ppm to 1000 ppm. The effects of boron doping on morphology, lattice parameter, phase composition, crystal size, and residual stress of UNCD films were investigated. No obvious change of the morphology was observed on doping with boron, and all the films had the UNCD crystal grains. Boron doping enhanced (111) growth. The preferred growth direction of the UNCD films was . Residual tensile stress was present in all the films, and increased with increasing the amount of boron in the gas mixture.

  17. Pure Boron-Doped Photodiodes: a Solution for Radiation Detection in EUV Lithography

    E-print Network

    Technische Universiteit Delft

    Pure Boron-Doped Photodiodes: a Solution for Radiation Detection in EUV Lithography F. Sarubbi, L-Technische Bundesanstalt (PTB) Abbestraße 2-12, D-10587, Berlin, Germany frank.scholze@ptb.de Abstract--A pure boron chemical vapor deposition (CVD) technology, which forms delta-doped boron surface layers during diborane B2

  18. Raman characterization of boron-doped multiwalled carbon nanotubes J. Maultzsch,a)

    E-print Network

    Nabben, Reinhard

    Raman characterization of boron-doped multiwalled carbon nanotubes J. Maultzsch,a) S. Reich, and C of boron-doped multiwalled carbon nanotubes. The Raman intensities are analyzed as a function of the nominal boron concentration. The intensities of both the D mode and the high-energy mode in the first

  19. Theoretical buckling loads of boron/aluminum and graphite/resin fiber composite anisotropic plates

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1971-01-01

    Theoretical results are presented for the buckling of anisotropic plates. The plates are subjected to simple and combined in-plane loading. The plates are made from fiber composite material of boron/aluminum or high-modulus graphite/resin. The results are presented in nondimensional form as buckling load against fiber orientation angle for various plate aspect ratios. The results indicate that buckling loads of boron/aluminum plates are independent of fiber direction if the plate aspect ratios are greater than about 1, and moderately dependent when this ratio is less than about 1. In addition, the results indicate that the buckling loads are independent of aspect ratio for plates with aspect ratios greater than about 2. Boron/ aluminum composite plates can resist buckling loads more efficiently than graphite/resin composites on a specific buckling stress basis. The numerical algorithm and a listing of the computer code used to obtain the results are included.

  20. Peculiarities of boron distribution in as-grown boron-doped diamond

    NASA Astrophysics Data System (ADS)

    Blank, V. D.; Kulnitskiy, B. A.; Perezhogin, I. A.; Terentiev, S. A.; Nosukhin, S. A.; Kuznetsov, M. S.

    2014-09-01

    Boron doped diamond (BDD) single crystals have been grown under conditions of high isostatic pressure by the temperature gradient method. Numerous equilateral triangles were found on the fluorescence images of {111}-diamond facets. Structural peculiarities of BDD were investigated by JEM-2010 transmission electron microscope with GIF Quantum attachment for electron energy loss spectroscopy (EELS). High resolution image of diamond lattice revealed some distorted {111}-layers. EELS testifies the presence of boron in distorted regions of diamond lattice. The crystallographic features of BDD and their connection with the superconductivity are discussed.

  1. Phase transformations of nano-sized cubic boron nitride to white graphene and white graphite

    SciTech Connect

    Dang, Hongli; Liu, Yingdi; Xue, Wenhua; Anderson, Ryan S.; Sewell, Cody R. [Department of Physics and Engineering Physics, The University of Tulsa, Tulsa, Oklahoma 74104 (United States); Xue, Sha; Crunkleton, Daniel W. [Department of Chemical Engineering, The University of Tulsa, Tulsa, Oklahoma 74104 (United States); Institute of Alternate Energy, The University of Tulsa, Tulsa, Oklahoma 74104 (United States); Shen, Yaogen [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon (Hong Kong); Wang, Sanwu, E-mail: sanwu-wang@utulsa.edu [Department of Physics and Engineering Physics, The University of Tulsa, Tulsa, Oklahoma 74104 (United States); Institute of Alternate Energy, The University of Tulsa, Tulsa, Oklahoma 74104 (United States)

    2014-03-03

    We report quantum-mechanical investigations that predict the formation of white graphene and nano-sized white graphite from the first-order phase transformations of nano-sized boron nitride thin-films. The phase transformations from the nano-sized diamond-like structure, when the thickness d?>?1.4?nm, to the energetically more stable nano-sized white graphite involve low activation energies of less than 1.0?eV. On the other hand, the diamond-like structure transforms spontaneously to white graphite when d???1.4?nm. In particular, the two-dimensional structure with single-layer boron nitride, the so-called white graphene, could be formed as a result of such transformation.

  2. Electrochemical hydrogen termination of boron-doped diamond

    SciTech Connect

    Hoffmann, Rene; Kriele, Armin; Obloh, Harald; Hees, Jakob; Wolfer, Marco; Smirnov, Waldemar; Yang Nianjun; Nebel, Christoph E. [Fraunhofer Institute for Applied Solid State Physics (IAF), Tullastrasse 72, Freiburg 79108 (Germany)

    2010-08-02

    Boron-doped diamond is a promising transducer material for numerous devices which are designed for contact with electrolytes. For optimized electron transfer the surface of diamond needs to be hydrogen terminated. Up to now H-termination of diamond is done by plasma chemical vapor deposition techniques. In this paper, we show that boron-doped diamond can be H-terminated electrochemically by applying negative voltages in acidic solutions. Electrochemical H-termination generates a clean surface with virtually no carbon-oxygen bonds (x-ray photoelectron spectroscopy), a reduced electron affinity (scanning electron microscopy), a highly hydrophobic surface (water contact angle), and a fast electron exchange with Fe(CN){sub 6}{sup -3/-4} (cyclic voltammetry).

  3. A New Technique of Boron Doping in Si: H Films

    Microsoft Academic Search

    Toshihiko Hamasaki; Hiroyuki Kurata; Masataka Hirose; Yukio Osaka

    1981-01-01

    Very high doping efficiency of boron atoms in hydrogenated silicon has been achieved using the glow discharge of a SiH4-B2H6 mixture gas under conditions of a low concentration of SiH4 and application of magnetic field to the plasma column. A maximum conductivity of 7.8 Omega-1 cm-1 has been obtained at a doping ratio of NB2H6\\/NSiH4{=}2.6%. This high conductivity is found

  4. Electrochemical oxidation of phenol at boron-doped diamond electrode

    Microsoft Academic Search

    J. Iniesta; P. A. Michaud; M. Panizza; G. Cerisola; A. Aldaz; Ch. Comninellis

    2001-01-01

    The electrochemical oxidation of phenol at synthetic boron-doped diamond thin film electrode (BDD) has been studied in acid media by cyclic voltammetry, chronoamperometry and bulk electrolysis. The results have shown that in the potential region of water stability (E<2.3 V vs. SHE) they can occur direct electron transfer reactions on BDD surface that results in electrode fouling due to the

  5. New synthesis and physical property of low resistivity boron-doped multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ishii, S.; Watanabe, T.; Ueda, S.; Tsuda, S.; Yamaguchi, T.; Takano, Y.

    2008-09-01

    A novel growth technique of boron-doped multi-walled carbon nanotubes (MWNTs) was developed. Our new technique uses a methanol solution of boric acid as a source material. Resistivity of the boron-doped MWNTs was successfully reduced independently of chirality by our technique. Temperature dependence of resistivity in each individual boron-doped MWNT was measured by using small-sized four-point contacts, which were fabricated by electron beam (EB) lithography technique. Conduction carriers were introduced into the MWNT effectively by boron-doping.

  6. Selection of candidate doped graphite materials as plasma facing components for HT7U device

    Microsoft Academic Search

    Q. G Guo; J. G Li; N Noda; Y Kubota; J. L Chen; Zh. J Liu; L Liu; J. R Song

    2003-01-01

    Selection of candidate materials for plasma facing material (PFM) in HT-7U device and plasma–wall interactions are critically important to reach high plasma performance. Based on concentrated research on multi-element doped graphite containing B, Si and Ti, two kinds of doped graphites have been chosen as candidates for PFM in HT-7U. Doped graphite GBST1308 with the dopant concentration of 1% B,

  7. Superconductivity in Li-doped {alpha}-rhombohedral boron

    SciTech Connect

    Nagatochi, T.; Sumiyoshi, A.; Kimura, K. [Department of Advanced Materials Science, University of Tokyo (Japan); Hyodo, H.; Soga, K. [Department of Materials Science and Technology, Tokyo University of Science (Japan); Sato, Y.; Terauchi, M. [Institute for Multidisciplinary Research for Advanced Materials, Tohoku University (Japan); Esaka, F. [Japan Atomic Energy Agency (Japan)

    2011-05-01

    Metal transition and superconductivity were observed in Li-doped {alpha}-rhombohedral boron ({alpha}-B{sub 12}). The authors have established a purification method and obtained a large amount of high-purity {alpha}-B{sub 12} powder. Li doping into purified {alpha}-B{sub 12} was attempted by vapor diffusion processing (VDP) in a Mo or Ta tube. Li-doped {alpha}-B{sub 12} contained metallic glittering particles. Meissner effects were observed in such a compound with the nominal composition Li{sub x}B{sub 12} (x = 1.0, 1.4, 1.5, 1.7, or 2.5) (T{sub c} = 3.2-7 K). As for Li{sub 2.5}B{sub 12}, the temperature dependence of its electrical conductivity indicates a metallic character and its electrical resistivity drop is detected near the Meissner temperature. The existence of Li and Fermi edges in Li-doped {alpha}-B{sub 12} crystals was verified by transmission electron microscopy-electron energy loss spectroscopy (TEM-EELS). Lattice expansion, which is a well-known indicator of metal doping into a crystal, was also observed. Thus, Li doping into {alpha}-B{sub 12} was successfully achieved. Our work also suggests that it is possible to dope a larger amount of Li into {alpha}-B{sub 12} and to increase its T{sub c}.

  8. Synthesis and Raman Characterization of Boron Doped Single Walled Carbon Nanotubes (SWNTs)

    NASA Astrophysics Data System (ADS)

    McGuire, K.; Gothard, N.; Gai, P. L.; Chao, S. G.; Dresselhaus, M. S.; Rao, A. M.

    2003-11-01

    Boron-doped SWNTs were prepared by pulsed laser vaporization of carbon targets containing boron with concentrations ranging between 0.5 - 10 at%. As-prepared samples were characterized using Raman spectroscopy and HRTEM measurements. Above a threshold boron concentration of 3 at%, the growth of SWNT bundles ceases due to the low solubility of boron in carbon at ˜1200 ^oC. Interestingly, a few ˜0.5 nm diameter single walled tubes are found, along with nanographitic material in the soot generated from a target with a boron concentration of ˜7 at%. As expected, the intensity of the ˜1350 cm-1 D-band increases with increasing boron concentration due to boron substitution into the honeycomb lattice. Both the radial breathing mode and tangential G- bands were observed in the Raman spectra in samples with <3 at % boron at ˜186 cm-1 and ˜1591 cm-1, respectively. Implications of boron doping in the nanotube shell will be discussed.

  9. Synthesis and Raman Characterization of Boron Doped Single Walled Carbon Nanotubes (SWNTs)

    NASA Astrophysics Data System (ADS)

    McGuire, K.; Gothard, N.; Gai, P. L.; Chou, S. G.; Dresselhaus, M. S.; Rao, A. M.

    2003-03-01

    Boron-doped SWNTs were prepared by pulsed laser vaporization of carbon targets containing boron with concentrations ranging between 0.5 - 10 at%. As-prepared samples were characterized using Raman spectroscopy and HRTEM measurements. Above a threshold boron concentration of 3 at%, the growth of SWNT bundles ceases due to the low solubility of boron in carbon at ˜1200 ^oC. Interestingly, a few ˜0.5 nm diameter single walled tubes are found, along with nanographitic material in the soot generated from a target with a boron concentration of ˜7 at%. As expected, the intensity of the ˜1350 cm-1 D-band increases with increasing boron concentration due to boron substitution into the honeycomb lattice. Both the radial breathing mode and tangential G- bands were observed in the Raman spectra in samples with <3 at % boron at ˜186 cm-1 and ˜1591 cm-1, respectively. Implications of boron doping in the nanotube shell will be discussed.

  10. Surface characteristics of boron-doped diamond exposed to high-temperature annealing: Effect of hydrogen atmosphere

    E-print Network

    Pfeifer, Holger

    Surface characteristics of boron-doped diamond exposed to high-temperature annealing: Effect of the surface of epitaxial (100)- oriented and highly boron-doped diamond (NA > 1020 cm-3 ), which was annealed

  11. Doping and characterization of boron atoms in nanocrystalline silicon particles

    SciTech Connect

    Sato, Keisuke [World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science - NIMS, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Fukata, Naoki [World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science - NIMS, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Hirakuri, Kenji [Department of Electrical and Electronic Engineering, Tokyo Denki University, 2-2 Kandanishiki, Chiyoda, Tokyo 101-8457 (Japan)

    2009-04-20

    Boron (B) doping into nanocrystalline-silicon (nc-Si) particles was achieved by cosputtering of Si chips/B chips/silica disk targets and subsequent annealing at 1100 deg. C. The average diameter of B-doped particles was less than 4.3 nm, and the content of B was about 14.3 at. %. The observation of EELS spectrum of B-K edge and x-ray photoelectron spectroscopy spectra of B 1s, and that of B local vibrational peaks and the Fano effect by micro-Raman scattering measurements clearly demonstrate that B atoms were doped and electrically activated in the particles, indicating the formation of electrically active p-type nc-Si particles.

  12. Reverse annealing of boron doped polycrystalline silicon

    Microsoft Academic Search

    Beop-Jong Jin; Won-Eui Hong; Deok Hoi Kim; Tstomu Uemoto; Chi Woo Kim; Jae-Sang Ro

    2008-01-01

    Thermal activation was carried out using polycrystalline silicon (poly-Si) produced through sequential-lateral-solidification or excimer-laser-crystallization (ELC) after B+ ion shower doping. The activation efficiency of the ELC samples was found to be higher than that of the SLS ones. In this regard, grain boundaries seemed to play a critical role in terms of the activation of dopants in poly-Si at low

  13. Suzuki effect on {0 0 1} stacking faults in boron-doped FeAl intermetallics

    Microsoft Academic Search

    Emmanuel Cadel; Anna Fraczkiewicz; Didier Blavette

    2004-01-01

    Three dimensional atom probe (3DAP) investigations of boron doped (400 ppm) FeAl40Ni3.8 samples aged at 400 °C for 1800 h, combined with electron microscopy observations, reveal that {001} planar faults are boron enriched and aluminium depleted. The structure of such high energy defect is discussed and is thought to be stabilised by the segregation of boron.

  14. Kinetics of boron reactivation in doped silicon from Hall effect and spreading resistance techniques

    E-print Network

    Florida, University of

    Kinetics of boron reactivation in doped silicon from Hall effect and spreading resistance 2002 In this work, a series of 13 boron implants were performed into Czochralski silicon substrates with doses of 2 1014 ­1.6 1015 cm 2 at energies of 10­80 keV. The boron was deliberately clustered with a 750

  15. Degenerate crystalline silicon films by aluminum-induced crystallization of boron-doped amorphous silicon

    NASA Astrophysics Data System (ADS)

    Hwang, J. D.; Luo, L. C.; Hsueh, T. J.; Hwang, S. B.

    2012-10-01

    Degenerate p-type crystalline silicon film with a hole concentration of 4 × 1021 cm-3 was investigated using aluminum-induced crystallization (AIC) of boron-doped amorphous silicon (a-Si). The AIC mechanism is different from that in the undoped AIC-Si. Boron atoms accumulate at Al layer forming a boron bump and segregate the Al atoms into Si layer, resulting to the formation of AlSi alloy. The degeneracy is not attributed to boron doping but instead to the AlSi alloy. Observations show that Al and Si layer transfer occurs not at original interface of Al and Si, but at the boron bump.

  16. Nitrogen-Doped Graphitic Nanoribbons: Synthesis, Characterization and Transport

    SciTech Connect

    Jia, Xiaoting [Massachusetts Institute of Technology (MIT); Dresselhaus, M [Massachusetts Institute of Technology (MIT); Cruz Silva, Eduardo [ORNL; Munoz-Sandoval, E [Instituto de Microelectronica de Madrid (CNM, CSIC); Sumpter, Bobby G [ORNL; Terrones Maldonado, Humberto [ORNL; Terrones Maldonado, Humberto [ORNL; Lopez, Florentino [IPICyT

    2013-01-01

    Nitrogen-doped graphitic nanoribbons (Nx-GNRs), synthesized by chemical vapor deposition (CVD) using pyrazine as a nitrogen precursor, are reported for the first time. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) reveal that the synthesized materials are formed by multi-layered corrugated graphitic nanoribbons (GNRs) which in most cases exhibit the formation of curved graphene edges (loops). This suggests that during growth, nitrogen atoms promote loop formation; undoped GNRs do not form loops at their edges. Transport measurements on individual pure carbon GNRs exhibit a linear I-V (current-voltage) behavior, whereas Nx-GNRs show reduced current responses following a semiconducting-like behavior, which becomes more prominent for high nitrogen concentrations. To better understand the experimental findings, electron density of states (DOS), quantum conductance for nitrogen doped zigzag and armchair single-layer GNRs are calculated for different N doping concentrations using Density Functional Theory (DFT) and non-equilibrium Green functions. These calculations confirm the crucial role of nitrogen atoms in the transport properties, confirming that the nonlinear I-V curves are due to the presence of nitrogen atoms within the Nx-GNRs lattice that act as scattering sites. These characteristic Nx-GNRs transport could be advantageous in the fabrication of electronic devices including sensors in which metal-like undoped GNRs are unsuitable.

  17. Resistivity of boron-doped diamond microcrystals M. D. Jaeger, S. Hyun, A. R. Day,a)

    E-print Network

    Thorpe, Michael

    single crystals of boron-doped CVD diamond with dimensions of a few m grown on oxidized-Si substrates. WeResistivity of boron-doped diamond microcrystals M. D. Jaeger, S. Hyun, A. R. Day,a) M. F. Thorpe We describe measurements of the electrical resistivity of micron-size crystallites of boron-doped

  18. Resistivity reduction of boron-doped multiwalled carbon nanotubes synthesized from a methanol solution containing boric acid

    NASA Astrophysics Data System (ADS)

    Ishii, Satoshi; Watanabe, Tohru; Ueda, Shinya; Tsuda, Shunsuke; Yamaguchi, Takahide; Takano, Yoshihiko

    2008-05-01

    Boron-doped multiwalled carbon nanotubes (MWNTs) were synthesized using a methanol solution of boric acid as a source material. Accurate measurements of the electrical resistivity of an individual boron-doped MWNT was performed with a four-point contact, which was fabricated using an electron beam lithography technique. The doped boron provides conduction carriers, which reduces the resistivity of the MWNT.

  19. Surface impurity removal from DIII-D graphite tiles by boron carbide grit blasting

    SciTech Connect

    Lee, R.L.; Hollerbach, M.A.; Holtrop, K.L.; Kellman, A.G.; Taylor, P.L.; West, W.P.

    1993-11-01

    During the latter half of 1992, the DIII-D tokamak at General Atomics (GA) underwent several modifications of its interior. One of the major tasks involved the removal of accumulated metallic impurities from the surface of the graphite tiles used to line the plasma facing surfaces inside of the tokamak. Approximately 1500 graphite tiles and 100 boron nitride tiles from the tokamak were cleaned to remove the metallic impurities. The cleaning process consisted of several steps: the removed graphite tiles were permanently marked, surface blasted using boron carbide (B{sub 4}C) grit media (approximately 37 {mu}m. diam.), ultrasonically cleaned in ethanol to remove loose dust, and outgassed at 1000{degrees}C. Tests were done using, graphite samples and different grit blaster settings to determine the optimum propellant and abrasive media pressures to remove a graphite layer approximately 40-50 {mu}m deep and yet produce a reasonably smooth finish. EDX measurements revealed that the blasting technique reduced the surface Ni, Cr, and Fe impurity levels to those of virgin graphite. In addition to the surface impurity removal, tritium monitoring was performed throughout the cleaning process. A bubbler system was set up to monitor the tritium level in the exhaust gas from the grit blaster unit. Surface wipes were also performed on over 10% of the tiles. Typical surface tritium concentrations of the tiles were reduced from about 500 dpm/100 cm{sup 2} to less than 80 dpm/100 cm{sup 2} following the cleaning. This tile conditioning, and the installation of additional graphite tiles to cover a high fraction of the metallic plasma facing surfaces, has substantially reduced metallic impurities in the plasma discharges which has allowed rapid recovery from a seven-month machine opening and regimes of enhanced plasma energy confinement to be more readily obtained. Safety issues concerning blaster operator exposure to carcinogenic metals and radioactive tritium will also be addressed.

  20. Intersubband absorption in boron-doped multiple Ge quantum dots J. L. Liu,a)

    E-print Network

    Intersubband absorption in boron-doped multiple Ge quantum dots J. L. Liu,a) W. G. Wu, A. Balandin; accepted for publication 3 November 1998 The intersubband absorption in self-assembled boron-doped multiple and undoped Si barriers. The infrared absorption as a function of wavelength is measured by Fourier transform

  1. Development of a synthetic diamond radiation detector with a boron doped CVD diamond contact

    Microsoft Academic Search

    Junichi Kaneko; Masaki Katagiri; Yujiro Ikeda; Takeo Nishitani

    1999-01-01

    A boron doped CVD diamond contact was applied to a diamond radiation detector for suppressing a polarization phenomenon. A boron doped CVD diamond layer was grown on a synthetic type IIa single crystal diamond; it was then used as a contact. The contact was completely free from radiation damage which is unavoidable in a contact made by an ordinary ion

  2. Study on boron doped silicon quantum dots superlattices for all-silicon tandem solar cells

    Microsoft Academic Search

    Xiaojing Hao; Eunchel Cho; Sangwook Park; Yansong Shen; Gavin Conibeer; Martin Andrew Green

    2008-01-01

    Optimized chemical structure was proposed for boron-doped Si quantum dots superlattices. Boron-doped Si quantum dots superlattices were then synthesized by a co-sputtering technique, and characterized for their promising application in all-Si tandem solar cells. The formation of Si quantum dots was confirmed by transmission electron microscopy. The effect of boron dopant concentration on the Si crystallization was investigated. Lateral resistivity

  3. Degradation of 4,6-dinitro- o-cresol from water by anodic oxidation with a boron-doped diamond electrode

    Microsoft Academic Search

    Cristina Flox; José Antonio Garrido; Rosa María Rodríguez; Francesc Centellas; Pere-Lluís Cabot; Conchita Arias; Enric Brillas

    2005-01-01

    Anodic oxidation of 4,6-dinitro-o-cresol (DNOC) has been studied in a cell of 100ml with a boron-doped diamond anode and a graphite cathode, both of 3-cm2 area. Solutions containing up to approximately 240mgl?1 of compound in the pH range 2.0–12.0 have been treated at 100, 300 and 450mA between 15 and 50°C. Total mineralization is always achieved due to the great

  4. Rewritable densification gratings in boron-doped fibers

    NASA Astrophysics Data System (ADS)

    Grubsky, Victor; Feinberg, Jack

    2005-06-01

    We show that the strength of long-period gratings recorded in boron-doped fibers by CO2 radiation can be significantly enhanced by a uniform pre-exposure by the same laser. The resultant gratings could be erased by a similar uniform exposure and then recorded again multiple times with no loss of fiber sensitivity. We suggest that such gratings are formed by reversible densification of the fiber core. These densification gratings have higher thermal stability than gratings written with ultraviolet light.

  5. Effect of temperature and strain rate on the tensile properties of aluminum- -boron, epoxy--boron, and epoxy--graphite composites. Final report

    Microsoft Academic Search

    D. A. Meyn; P. Shahinian

    1973-01-01

    The effects of strain rates from 0.00008 to 0.4\\/sec on tensile strengths ; and moduli of 6061 aluminum-46.5 vol% boron at temperatures up to 1000 deg F, of ; unidirectional and cross-ply epoxy-50 vol% boron composites at temperatures up to ; 500 deg F and of crossply epoxy --80 vol% graphite composites at temperatures up ; to 250 deg F

  6. Structural and elastic properties characterization of Be and Mg doped boron nitride nanotubes using DFT calculations

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Malakpour, S.

    2015-06-01

    Through doping boron nitride nanotubes, their band gaps could be controlled which results in extending the range of their applications particularly in nanosensors. In this article, the structural and elastic properties of Be and Mg doped boron nitride nanotubes with various chiralities are studied based on ab initio density functional calculations. In order to perform the density functional theory (DFT) calculations, the exchange correlation of Perdew-Burke-Ernzerhof within the generalized gradient approximation (GGA) framework is employed. It is observed that doping Be and Mg atoms increases the equilibrium strain energy of boron nitride nanotubes. Furthermore, it is found that among all of the considered nanotubes, an increase in the value of Young's modulus of (4, 4) armchair boron nitride nanotube through doping Be atom instead of boron atom is so considerable.

  7. Local boron environment in B-doped nanocrystalline diamond films.

    PubMed

    Turner, Stuart; Lu, Ying-Gang; Janssens, Stoffel D; Da Pieve, Fabiana; Lamoen, Dirk; Verbeeck, Jo; Haenen, Ken; Wagner, Patrick; Van Tendeloo, Gustaaf

    2012-09-28

    Thin films of heavily B-doped nanocrystalline diamond (B:NCD) have been investigated by a combination of high resolution annular dark field scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy performed on a state-of-the-art aberration corrected instrument to determine the B concentration, distribution and the local B environment. Concentrations of ~1 to 3 at.% of boron are found to be embedded within individual grains. Even though most NCD grains are surrounded by a thin amorphous shell, elemental mapping of the B and C signal shows no preferential embedding of B in these amorphous shells or in grain boundaries between the NCD grains, in contrast with earlier work on more macroscopic superconducting polycrystalline B-doped diamond films. Detailed inspection of the fine structure of the boron K-edge and comparison with density functional theory calculated fine structure energy-loss near-edge structure signatures confirms that the B atoms present in the diamond grains are substitutional atoms embedded tetrahedrally into the diamond lattice. PMID:22903371

  8. Graphitic electrodes modified with boron and nitrogen for electrochemical energy storage enhancement

    NASA Astrophysics Data System (ADS)

    Xiong, Guoping; Paul, Rajib; Reifenberger, Ron; Fisher, Timothy

    2013-03-01

    Electrodes based on carbon nanomaterials (carbon nanotubes or graphitic nanopetals) have been modified with boron (B) and nitrogen (N) through a facile microwave heating cycle. During the microwave heating, the electrodes are immersed in a precursor solution consisting of urea and boric acid dissolved in either water or methanol. After microwave heating and overnight vacuum drying, the electrodes are again heated in nitrogen to remove unreacted chemicals and to form CxBN. Hydrogen plasma was then used to remove any residual boron oxide from the surface of the electrodes. Carbon nanotubes modified with B and N exhibited higher lithium storage capacity as compared to pure carbon nanotube electrodes. We note that the modification appears to produce a highly unexpected and substantial cycle-to-cycle improvement in battery capacity as the electrode cycles through hundreds of charge-discharge iterations. This process can be applied to other carbon-based electrodes, which themselves are recognized for their high performance, to add further improvements. Electrodes based on carbon nanomaterials (carbon nanotubes or graphitic nanopetals) have been modified with boron (B) and nitrogen (N) through a facile microwave heating cycle. During the microwave heating, the electrodes are immersed in a precursor solution consisting of urea and boric acid dissolved in either water or methanol. After microwave heating and overnight vacuum drying, the electrodes are again heated in nitrogen to remove unreacted chemicals and to form CxBN. Hydrogen plasma was then used to remove any residual boron oxide from the surface of the electrodes. Carbon nanotubes modified with B and N exhibited higher lithium storage capacity as compared to pure carbon nanotube electrodes. We note that the modification appears to produce a highly unexpected and substantial cycle-to-cycle improvement in battery capacity as the electrode cycles through hundreds of charge-discharge iterations. This process can be applied to other carbon-based electrodes, which themselves are recognized for their high performance, to add further improvements. AFOSR MURI No. 105800

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  10. Controlling the Bandgap of Boron Nitride Nanotubes with Carbon Doping

    NASA Astrophysics Data System (ADS)

    Mousavi, Hamze; Bagheri, Mehran

    2015-03-01

    This study explores the effects of doping by carbon (C) atoms on electronic properties of (10,10) and (16,0) boron nitride (BN) nanotubes (NTs). We exploit the random tight-binding model with Green's function technique and coherent potential approximation to show that the C dopant causes a decrease in the bandgap of the BN NTs, and their matching Van Hove singularities (VHS) in the density of states (DOS) are broadened. When the impurity concentration is large enough, the form of the DOS of the BN NTs becomes similar to that of metallic (10,10) and semiconducting (16,0) C NTs and their VHS get sharpened. This work might provide opportunities for creating new optoelectronic devices based on BN honeycomb nanosystems.

  11. Inductively coupled plasma-assisted RF magnetron sputtering deposition of boron-doped microcrystalline Si films

    Microsoft Academic Search

    S. Y. Huang; Q. J. Cheng; S. Xu; K. Ostrikov

    2010-01-01

    An innovative custom-designed inductively coupled plasma-assisted RF magnetron sputtering deposition system has been developed to synthesize B-doped microcrystalline silicon thin films using a pure boron sputtering target in a reactive silane and argon gas mixture. Films were deposited using different boron target powers ranging from 0 to 350W at a substrate temperature of 250°C. The effect of the boron target

  12. Boron-doped carbon nanotube coating for transparent, conducting, flexible photonic devices

    Microsoft Academic Search

    Quinton L. Williams; Xi Liu; Wilbur Walters; Jian-Ge Zhou; Tylvia Y. Edwards; Franchesca L. Smith; Gregory E. Williams; Brenitra L. Mosley

    2007-01-01

    Conducting transparent polymer materials were made by applying boron-doped single-walled carbon nanotubes to the surfaces of glass and flexible polyethylene terephthalate film substrates. Optical transmission and sheet resistance measurements showed that the boron-doped coated samples had sheet resistances of ~7 kOmega\\/□ and flat optical transmission of ~89% for visible light. Temperature and humidity tests showed that the materials remained conductive

  13. Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Gou, Li; Ran, Junguo; Zhu, Hong; Zhang, Xiang

    2015-07-01

    Boron-doped nanocrystalline diamond (NCD) exhibits extraordinary mechanical properties and chemical stability, making it highly suitable for biomedical applications. For implant materials, the impact of boron-doped NCD films on the character of cell growth (i.e., adhesion, proliferation) is very important. Boron-doped NCD films with resistivity of 10?2 ?·cm were grown on Si substrates by the microwave plasma chemical vapor deposition (MPCVD) process with H2 bubbled B2O3. The crystal structure, diamond character, surface morphology, and surface roughness of the boron-doped NCD films were analyzed using different characterization methods, such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope (SKFM). The cytotoxicity of films was studied by in vitro tests, including fluorescence microscopy, SEM and MTT assay. Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates. MG-63 cells adhered well and exhibited a significant growth on the surface of films, suggesting that the boron-doped NCD films were non-toxic to cells. supported by the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices (University of Electronic Science and Technology of China) (No. KFJJ201313)

  14. Laser annealing of neutron irradiated boron-10 isotope doped diamond

    SciTech Connect

    Jagannadham, K. [North Carolina State University; Butler, J. E. [North Carolina State University

    2011-01-01

    10B isotope doped p-type diamond epilayer grown by chemical vapor deposition on (110) oriented type IIa diamond single crystal substrate was subjected to neutron transmutation at a fluence of 2.4 9 1020 thermal and 2.4 9 1020 fast neutrons. After neutron irradiation, the epilayer and the diamond substrate were laser annealed using Nd YAG laser irradiation with wave length, 266 nm and energy, 150 mJ per pulse. The neutron irradiated diamond epilayer and the substrate were characterized before and after laser annealing using different techniques. The characterization techniques include optical microscopy, secondary ion mass spectrometry, X-ray diffraction, Raman, photoluminescence and Fourier Transform Infrared spectroscopy, and electrical sheet conductance measurement. The results indicate that the structure of the irradiation induced amorphous epilayer changes to disordered graphite upon laser annealing. The irradiated substrate retains the (110) crystalline structure with neutron irradiation induced defects.

  15. Properties of boron-doped thin films of polycrystalline silicon

    NASA Astrophysics Data System (ADS)

    Merabet, Souad

    2013-12-01

    The properties of polycrystalline-silicon films deposited by low pressure chemical vapor deposition and doped heavily in situ boron-doped with concentration level of around 2×1020cm-3 has been studied. Their properties are analyzed using electrical and structural characterization means by four points probe resistivity measurements and X-ray diffraction spectra. The thermal-oxidation process are performed on sub-micron layers of 200nm/c-Si and 200nm/SiO2 deposited at temperatures Td ranged between 520°C and 605°C and thermally-oxidized in dry oxygen ambient at 945°C. Compared to the as-grown resistivity with silicon wafers is known to be in the following sequence < and < . The measure X-ray spectra is shown, that the Bragg peaks are marked according to the crystal orientation in the film deposited on bare substrates (poly/c-Si), for the second series of films deposited on bare oxidized substrates (poly/SiO2) are clearly different.

  16. Properties of boron-doped thin films of polycrystalline silicon

    SciTech Connect

    Merabet, Souad [Electronic Department, Faculty of Science and Technology, University of Jijel, Cité Ouled-Aissa B. P. 98 Jijel, 18 000 Jijel (Algeria)

    2013-12-16

    The properties of polycrystalline-silicon films deposited by low pressure chemical vapor deposition and doped heavily in situ boron-doped with concentration level of around 2×10{sup 20}cm{sup ?3} has been studied. Their properties are analyzed using electrical and structural characterization means by four points probe resistivity measurements and X-ray diffraction spectra. The thermal-oxidation process are performed on sub-micron layers of 200nm/c-Si and 200nm/SiO{sub 2} deposited at temperatures T{sub d} ranged between 520°C and 605°C and thermally-oxidized in dry oxygen ambient at 945°C. Compared to the as-grown resistivity with silicon wafers is known to be in the following sequence < and < . The measure X-ray spectra is shown, that the Bragg peaks are marked according to the crystal orientation in the film deposited on bare substrates (poly/c-Si), for the second series of films deposited on bare oxidized substrates (poly/SiO{sub 2}) are clearly different.

  17. Diffusion-induced dislocations in highly boron-doped silicon layers used for bulk micromachining applications

    NASA Astrophysics Data System (ADS)

    Gaiseanu, Florin; Esteve, Jaume; Kissinger, Gudrun; Kruger, D.

    1998-08-01

    Boron-doped silicon layers with sufficiently high doping levels become effective stop-layers during the chemical etching of silicon in alkaline type solutions (KOH, NaOH, LiOH) or in EDP (ethylene-diamine-pyrocatechol). An advantageous chemical solution consisting in tetramethyl ammonium hydroxide (TMAH) with isopropyl alcohol (IPA), showing similar etching properties was also proposed. The property as a stop layer of the boron-doped silicon is currently used as the most convenient etch-stop technique, because it is easy to define the thickness of the structure by the depth of boron diffusion in silicon. However, the boron diffusion profile in silicon is not a step-like distribution, but it presents a continuous decrease of the concentration from the silicon surface to the bulk, that depending on the diffusion conditions, i.e. diffusion time, temperature and doping technique. It is therefore expected that such a decrease will result to a continuous variation of the etching rate and a consequently variation of the etching time with the diffusion depth. In this paper we present firstly the doping properties of the silicon layers doped by the termo-chemical method using chemical sources. It is shown that the doping properties vary within the boron-doped layers. Boron diffusion profiles determined by SIMS method and electrical method are presented in order show the specific behavior of the concentration distribution in the silicon bulk. Misfit dislocations are induced by the boron diffusion in silicon at high concentrations. The conditions of the generation of the misfit dislocations in the boron-doped layers depends on the processing conditions, especially on the diffusion time and temperature. We show that the density distribution of the misfit dislocations in the silicon bulk is not uniform after the boron prediffusion and diffusion processes. From the point of view of the micromechanical applications, the inhomogeneity of the structural and doping properties of the silicon layer can influence the stress properties of such silicon-doped layers. Therefore, in order to reduce the stress gradient in the silicon membranes and micromechanical elements, it is necessary to obtain layers with uniform material properties. Both the doping and structural properties of the boron doped layers are to be therefore better knowledged and controlled. However, the doping properties obtained after the boron doping by termo-chemical method or by implantation doping technique cannot provide uniformly doped silicon layers. Therefore, a careful chemical etching during the self-limitation process of the boron-doped silicon layers offers such a possibility, as it will be presented in the paper. In order to eliminate from the silicon doped layers the regions were the properties of the silicon layers are not uniform, it is necessary to control the chemical etching process which is the next important step in the bulk micromachining technology useful to prepare the micromechanical elements. These key parameters of the chemical etching process are the chemical etching rate and the chemical etching time. It is shown that it is possible to calculate the chemical etching rate and the chemical etching time for some specified etching conditions. Such a possibility allows to control the thickness of the micromechanical elements and to eliminate the stress gradient induced by the non-uniform doping and by the misfit dislocations in the silicon micromechanical elements.

  18. Measurements of Increased Enthalpies of Adsorption for Boron-Doped Activated Carbons

    NASA Astrophysics Data System (ADS)

    Gillespie, Andrew; Beckner, Matthew; Chada, Nagaraju; Schaeperkoetter, Joseph; Singh, Anupam; Lee, Mark; Wexler, Carlos; Burress, Jacob; Pfeifer, Peter

    2013-03-01

    Boron-doping of activated carbons has been shown to increase the enthalpies of adsorption for hydrogen as compared to their respective undoped precursors (>10kJ/mol compared to ca. 5kJ/mol). This has brought significant interest to boron-doped carbons for their potential to improve hydrogen storage. Boron-doped activated carbons have been produced using a process involving the deposition of decaborane (B10H14) and high-temperature annealing resulting in boron contents up to 15%. In this talk, we will present a systematic study of the effect that boron content has on the samples' structure, hydrogen sorption, and surface chemistry. Measurements have shown a significant increase in the areal hydrogen excess adsorption and binding energy. Experimental enthalpies of adsorption will be presented for comparison to theoretical predictions. Additionally, samples have been characterized by thermal gravimetric analysis, gas chromatography-mass spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. TGA and GC-MS results investigated the decomposition of the decaborane in the carbon. Boron-carbon bonds are shown in the FTIR and XPS spectra, indicating that boron has been incorporated into the carbon matrix. Boron-doping of activated carbons has been shown to increase the enthalpies of adsorption for hydrogen as compared to their respective undoped precursors (>10kJ/mol compared to ca. 5kJ/mol). This has brought significant interest to boron-doped carbons for their potential to improve hydrogen storage. Boron-doped activated carbons have been produced using a process involving the deposition of decaborane (B10H14) and high-temperature annealing resulting in boron contents up to 15%. In this talk, we will present a systematic study of the effect that boron content has on the samples' structure, hydrogen sorption, and surface chemistry. Measurements have shown a significant increase in the areal hydrogen excess adsorption and binding energy. Experimental enthalpies of adsorption will be presented for comparison to theoretical predictions. Additionally, samples have been characterized by thermal gravimetric analysis, gas chromatography-mass spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. TGA and GC-MS results investigated the decomposition of the decaborane in the carbon. Boron-carbon bonds are shown in the FTIR and XPS spectra, indicating that boron has been incorporated into the carbon matrix. Work supported by DOE-EERE, Award No. DE-FG36-08GO18142

  19. Structure and Electrochemical Properties of Boron-Doped LiCoO 2

    NASA Astrophysics Data System (ADS)

    Alcántara, R.; Lavela, P.; Tirado, J. L.; Stoyanova, R.; Zhecheva, E.

    1997-12-01

    XRD, 6Li and 11B MAS NMR, IR, and EPR of low-spin Ni 3+probes were used for the structural characterization of boron-doped LiCoO 2. Up to 5 atom % boron additives were shown to dissolve in trigonal LiCoO 2. The structure of the CoO 2sandwiches remained unaffected by this treatment. The boron environment was assessed by spectroscopic analysis, which showed a distorted tetrahedral coordination. The boron-doped LiCoO 2samples were used as active electrode materials in lithium cells. Step potential electrochemical spectroscopy and galvanostatic cycling revealed that boron dopants improve the reversibility of the lithium deintercalation-intercalation process and favor lattice adaptation to lithium order-disorder in the depleted LiO 2layers.

  20. First principle investigations on Boron doped Fe2VAl Heusler alloy

    NASA Astrophysics Data System (ADS)

    Venkatesh, Ch.; Srivastava, S. K.; Rao, V. V.

    2014-09-01

    The role of atomic size of sp-element is investigated through theoretical calculations and basic experiments to understand the physical properties of Boron doped Fe2VAl alloy. The results of ab-initio calculations on ordered L21 structure of Fe2VAl1-xBx (x=0, 0.5, 1) alloys have been compared to understand the role of sp-element size on the hybridization among their respective valance states. Interestingly, semi-metallic and paramagnetic like ground states were found in the Boron doped alloys in similar to Fe2VAl, eliminating the role of size of the doppent sp-atom. These calculations result in hybridization where the covalent distribution of valance states among the atoms is responsible to produce a finite pseudo-gap at the Fermi level. The observed features could be explained on the basis of covalent theory of magnetism in which an amount of spectral weight transfer occurs in the DOS spectrum among the same spin orbitals, leading to symmetric distribution of bonding and anti-bonding states. However, the obtained experimental findings on Boron doped alloys are in contrast with these calculations, indicating that experimentally the alloy formation into an ideal L21 lattice does not happen while doping with Boron. Further, the micro structural analysis shows Boron segregation across the grain boundaries that may form magnetic inhomogeneities in the lattice of Boron doped Fe2VAl alloys which preferably cause these experimental anomalies.

  1. Defect behavior in electron-irradiated boron- and gallium-doped silicon

    NASA Technical Reports Server (NTRS)

    Drevinsky, P. J.; Deangelis, H. M.

    1982-01-01

    Production and anneal of defects in electron-irradiated, float-zone silicon solar cells were studied by DLTS. In boron- and gallium-doped, n+-p cells, dominant defects were due to the divacancy, carbon interstitial, and carbon complex. Results suggest that the DLTS peak normally ascribed to carbon complexes also involves gallium. For gallium- and, to a lesser extent, boron-doped samples, damaged lifetime shows substantial recovery only when the carbon-complex peak has annealed out at 400 C. In boron-doped, n+-p-p+ cells, a minority carrier trap (E1) was also observed by DLTS in cells with a boron p+, but not in those with an aluminum p+ back. A level at Ev + 0.31 eV appeared upon 150 C annealing (E1 out) in both p+ back types of samples.

  2. Effects of magnesium doping on growth and electric conductivity of nanocrystalline cubic boron nitride thin films

    Microsoft Academic Search

    K. Kojima; K. Nose; M. Kambara; T. Yoshida

    2009-01-01

    We have achieved in situ magnesium doping into nanocrystalline cubic boron nitride thin films during sputter deposition. It was clarified, through x-ray diffraction, Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy, that less than 1 at% magnesium doping does not significantly affect the growth of the cubic phase. Magnesium-doped films deposited in pure argon showed electric conductivity up to 104

  3. Experimental studies of graphite-epoxy and boron-epoxy angle ply laminates in compression

    NASA Technical Reports Server (NTRS)

    Weller, T.

    1977-01-01

    A test program aimed at studying the nonlinear/inelastic response under axial compression across a wide range of angle ply was graphite-epoxy and boron-epoxy laminates was presented and described. The strength allowables corresponding to the various laminate configurations were defined and the failure mechanisms which dictate their mode of failure were detected. The program involved two types of specimens for each laminate configuration: compression sandwich coupons and compression tubes. The test results indicate that the coupons perform better than the tubes displaying considerably high stress-strain allowables and mechanical properties relative to the tubes. Also, it is observed that depending on their dimensions the coupons are susceptible to very pronounced edge effects. This sensitivity results in assigning to the laminate conservative mechanical properties rather than the actual ones.

  4. Experimental studies of graphite-epoxy and boron-epoxy angle ply laminates in shear

    NASA Technical Reports Server (NTRS)

    Weller, T.

    1977-01-01

    The nonlinear/inelastic response under inplane shear of a large variety of graphite-epoxy and boron-epoxy angle-ply laminates was tested. Their strength allowables were obtained and the mechanisms which govern their mode of failure were determined. Two types of specimens for the program were chosen, tested, and evaluated: shear panels stabilized by an aluminum honeycomb core and shear tubes. A modified biaxially compression/tension loaded picture frame was designed and utilized in the test program with the shear panels. The results obtained with this test technique categorically prefer the shear panels, rather than the tubes, for adequate and satisfactory experimental definition of the objectives. Test results indicate the existence of a so-called core-effect which ought to be considered when reducing experimental data for weak in shear laminates.

  5. High-concentration boron doping of graphene nanoplatelets by simple thermal annealing and their supercapacitive properties.

    PubMed

    Yeom, Da-Young; Jeon, Woojin; Tu, Nguyen Dien Kha; Yeo, So Young; Lee, Sang-Soo; Sung, Bong June; Chang, Hyejung; Lim, Jung Ah; Kim, Heesuk

    2015-01-01

    For the utilization of graphene in various energy storage and conversion applications, it must be synthesized in bulk with reliable and controllable electrical properties. Although nitrogen-doped graphene shows a high doping efficiency, its electrical properties can be easily affected by oxygen and water impurities from the environment. We here report that boron-doped graphene nanoplatelets with desirable electrical properties can be prepared by the simultaneous reduction and boron-doping of graphene oxide (GO) at a high annealing temperature. B-doped graphene nanoplatelets prepared at 1000?°C show a maximum boron concentration of 6.04?±?1.44 at %, which is the highest value among B-doped graphenes prepared using various methods. With well-mixed GO and g-B2O3 as the dopant, highly uniform doping is achieved for potentially gram-scale production. In addition, as a proof-of-concept, highly B-doped graphene nanoplatelets were used as an electrode of an electrochemical double-layer capacitor (EDLC) and showed an excellent specific capacitance value of 448?F/g in an aqueous electrolyte without additional conductive additives. We believe that B-doped graphene nanoplatelets can also be used in other applications such as electrocatalyst and nano-electronics because of their reliable and controllable electrical properties regardless of the outer environment. PMID:25940534

  6. High-concentration boron doping of graphene nanoplatelets by simple thermal annealing and their supercapacitive properties

    PubMed Central

    Yeom, Da-Young; Jeon, Woojin; Tu, Nguyen Dien Kha; Yeo, So Young; Lee, Sang-Soo; Sung, Bong June; Chang, Hyejung; Lim, Jung Ah; Kim, Heesuk

    2015-01-01

    For the utilization of graphene in various energy storage and conversion applications, it must be synthesized in bulk with reliable and controllable electrical properties. Although nitrogen-doped graphene shows a high doping efficiency, its electrical properties can be easily affected by oxygen and water impurities from the environment. We here report that boron-doped graphene nanoplatelets with desirable electrical properties can be prepared by the simultaneous reduction and boron-doping of graphene oxide (GO) at a high annealing temperature. B-doped graphene nanoplatelets prepared at 1000?°C show a maximum boron concentration of 6.04?±?1.44 at %, which is the highest value among B-doped graphenes prepared using various methods. With well-mixed GO and g-B2O3 as the dopant, highly uniform doping is achieved for potentially gram-scale production. In addition, as a proof-of-concept, highly B-doped graphene nanoplatelets were used as an electrode of an electrochemical double-layer capacitor (EDLC) and showed an excellent specific capacitance value of 448?F/g in an aqueous electrolyte without additional conductive additives. We believe that B-doped graphene nanoplatelets can also be used in other applications such as electrocatalyst and nano-electronics because of their reliable and controllable electrical properties regardless of the outer environment. PMID:25940534

  7. Polyoxometalate-Modified Boron-Doped Diamond Electrodes

    NASA Astrophysics Data System (ADS)

    Kondo, Takeshi; Taniguchi, Yuichi; Yuasa, Makoto; Kawai, Takeshi

    2012-09-01

    Polyoxometalates were immobilized on a boron-doped diamond (BDD) surface modified by a photochemical modification method. The BDD surface was first modified with allyltriethylammonium bromide (ATAB) to form surface quaternary ammonium groups. The ATAB-BDD was then immersed in a phosphomolybdic acid (H3PMo12O40, denoted as PMo12) solution to fabricate PMo12-adsorbed ATAB-BDD (PMo12-ATAB-BDD). The electrostatic interaction between PMo12 and the quaternary ammonium group on ATAB-BDD is considered to be critical to the stable immobilization. Polyoxometalate-modified BDD was also fabricated from phosphonic-acid-terminated BDD. BDD was first modified with vinylphosphonic acid (VPA), followed by the reaction of the surface phosphonic acid groups with ammonium molybdate to generate a lacunary phosphomolybdic acid (PMox) group. Although the coverage of the PMox group on PMox-BDD was less than that of PMo12-ATAB-BDD, PMox-BDD was found to be more stable to potential cycling than PMo12-ATAB-BDD, indicating that covalent modification methods are effective for creating stable functional groups on diamond.

  8. Crystallinity, morphology, and conductivity of boron-doped microcrystalline silicon

    SciTech Connect

    Rajeswaran, G.; Tafto, J.; Sabatini, R.L.; Vanier, P.E.

    1983-01-01

    Boron-doped microcrystalline (..mu..c) silicon films produced by rf glow discharge from dilute (1%) mixtures of SiH/sub 4/ in H/sub 2/ show a critical dependence of conductivity on deposition conditions. The dark conductivity was related to the microscopic features using electron microscopy. The ..mu..c-Si:H films contain clusters of crystallites embedded in an amorphous matrix. The size of the crystalline clusters is typically 0.2 ..mu..m in diameter, and the size of the individual crystallites is about 2.5 nm. Electron micrographs of samples prepared at substrate temperatures T/sub s/=135/sup 0/C, 150/sup 0/C, 165/sup 0/C, and 180/sup 0/C show that the number of crystalline clusters increases with T/sub s/ up to 165/sup 0/C. At T/sub s/=180/sup 0/C, the crystallites completely disappear. When the concentration of SiH/sub 4/ in H/sub 2/ is decreased to 0.25%, the microstructure shows a high density of crystallites with no apparent clustering.

  9. Tribological properties of undoped and boron-doped nanocrystalline diamond films

    PubMed Central

    Liang, Qi; Stanishevsky, Andrei; Vohra, Yogesh K.

    2009-01-01

    Undoped and boron-doped nanocrystalline (NCD) diamond films were deposited on mirror polished Ti–6Al–4V substrates in a Microwave Plasma Assisted Chemical Vapor Deposition system. Sliding wear tests were conducted in ambient air with a nanotribometer. A systematic study of the tribological properties for both undoped and boron-doped NCD films were carried out. It was found for diamond/diamond sliding, coefficient of friction decreases with increasing normal loads. It was also found that the wear rate of boron-doped NCD films is about 10 times higher than that of undoped films. A wear rate of ~5.2×10?9 mm3/Nm was found for undoped NCD films. This value is comparable to the best known value of that of polished polycrystalline diamond films. Although no surface deformation, film delamination or micro-cracking were observed for undoped films, boron-doped NCD film undergoes a critical failure at a normal stress of 2.2 GPa, above which surface deformation is evident. Combined with high hardness and modulus, tunable conductivity and improved open air thermal stability, boron-doped nanocrystalline diamond film has tremendous potentials for applications such as Atomic Force Microscope probes, Micro-Electro-Mechanical System devices and biomedical sensors. PMID:19946362

  10. Thermodynamic Studies of Decane on Boron Nitride and Graphite Substrates Using Synchrotron Radiation and Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Strange, Nicholas; Arnold, Thomas; Forster, Matthew; Parker, Julia; Larese, J. Z.; Diamond Light Source Collaboration; University of Tennessee Team

    2014-03-01

    Hexagonal boron nitride (hBN) has a lattice structure similar to that of graphite with a slightly larger lattice parameter in the basal plane. This, among other properties, makes it an excellent substrate in place of graphite, eliciting some important differences. This work is part of a larger effort to examine the interaction of alkanes with magnesium oxide, graphite, and boron nitride surfaces. In our current presentation, we will discuss the interaction of decane with these surfaces. Decane exhibits a fully commensurate structure on graphite and hBN at monolayer coverages. In this particular experiment, we have examined the monolayer structure of decane adsorbed on the basal plane of hBN using synchrotron x-ray radiation at Diamond Light Source. Additionally, we have examined the system experimentally with volumetric isotherms as well as computationally using molecular dynamics simulations. The volumetric isotherms allow us to calculate properties which provide important information about the adsorbate's interaction with not only neighboring molecules, but also the interaction with the adsorbent boron nitride.

  11. Multiple delta doping of single crystal cubic boron nitride films heteroepitaxially grown on (001)diamonds

    NASA Astrophysics Data System (ADS)

    Yin, H.; Ziemann, P.

    2014-06-01

    Phase pure cubic boron nitride (c-BN) films have been epitaxially grown on (001) diamond substrates at 900 °C. The n-type doping of c-BN epitaxial films relies on the sequential growth of nominally undoped (p-) and Si doped (n-) layers with well-controlled thickness (down to several nanometer range) in the concept of multiple delta doping. The existence of nominally undoped c-BN overgrowth separates the Si doped layers, preventing Si dopant segregation that was observed for continuously doped epitaxial c-BN films. This strategy allows doping of c-BN films can be scaled up to multiple numbers of doped layers through atomic level control of the interface in the future electronic devices. Enhanced electronic transport properties with higher hall mobility (102 cm2/V s) have been demonstrated at room temperature as compared to the normally continuously Si doped c-BN films.

  12. Multiple delta doping of single crystal cubic boron nitride films heteroepitaxially grown on (001)diamonds

    SciTech Connect

    Yin, H., E-mail: hyin@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Ziemann, P. [Institute of Solid State Physics, Ulm University, D-89069 Ulm (Germany)

    2014-06-23

    Phase pure cubic boron nitride (c-BN) films have been epitaxially grown on (001) diamond substrates at 900?°C. The n-type doping of c-BN epitaxial films relies on the sequential growth of nominally undoped (p-) and Si doped (n-) layers with well-controlled thickness (down to several nanometer range) in the concept of multiple delta doping. The existence of nominally undoped c-BN overgrowth separates the Si doped layers, preventing Si dopant segregation that was observed for continuously doped epitaxial c-BN films. This strategy allows doping of c-BN films can be scaled up to multiple numbers of doped layers through atomic level control of the interface in the future electronic devices. Enhanced electronic transport properties with higher hall mobility (10{sup 2} cm{sup 2}/V s) have been demonstrated at room temperature as compared to the normally continuously Si doped c-BN films.

  13. Boron deactivation in heavily boron-doped Czochralski silicon during rapid thermal anneal: Atomic level understanding

    SciTech Connect

    Gao, Chao; Dong, Peng; Yi, Jun; Ma, Xiangyang, E-mail: luyh@zju.edu.cn, E-mail: mxyoung@zju.edu.cn; Yang, Deren [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Lu, Yunhao, E-mail: luyh@zju.edu.cn, E-mail: mxyoung@zju.edu.cn [International Center for New-Structured Materials and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2014-01-20

    The changes in hole concentration of heavily boron (B)-doped Czochralski silicon subjected to high temperature rapid thermal anneal (RTA) and following conventional furnace anneal (CFA) have been investigated. It is found that decrease in hole concentration, namely, B deactivation, is observed starting from 1050?°C and increases with RTA temperature. The following CFA at 300–500?°C leads to further B deactivation, while that at 600–800?°C results in B reactivation. It is supposed that the interaction between B atoms and silicon interstitials (I) thus forming BI pairs leads to the B deactivation during the high temperature RTA, and, moreover, the formation of extended B{sub 2}I complexes results in further B deactivation in the following CFA at 300–500?°C. On the contrary, the dissociation of BI pairs during the following CFA at 600–800?°C enables the B reactivation. Importantly, the first-principles calculation results can soundly account for the above-mentioned supposition.

  14. Boron doping effects in electrochromic properties of NiO films prepared by sol-gel

    SciTech Connect

    Lou, Xianchun; Zhao, Xiujian; He, Xin [Key Laboratory of Silicate Materials Science and Engineering, Wuhan University of Technology, Ministry of Education, 122 Luoshi Road, Hongshan District, Wuhan, Hubei 430070 (China)

    2009-12-15

    In this paper, NiO films doped with B{sub 2}O{sub 3} were first prepared by sol-gel. The effects of boron content on the structure and electrochromic properties of NiO films were studied with X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetric (CV) and UV-vis spectrophotometer, respectively. In addition, the roughness and phase of the bleached/colored were studied by atom force microscopy (AFM). B-doped prevent the crystallization of the films. The colored state transmittance could be significantly lowered when the boron added. The NiO film doped with boron exhibited a noticeable electrochromism with a variation of transmittance up to {proportional_to}60% at the wavelength range of 300-500 nm. (author)

  15. Synthesis and characterization of p-type boron-doped IIb diamond large single crystals

    NASA Astrophysics Data System (ADS)

    Li, Shang-Sheng; Ma, Hong-An; Li, Xiao-Lei; Su, Tai-Chao; Huang, Guo-Feng; Li, Yong; Jia, Xiao-Peng

    2011-02-01

    High-quality p-type boron-doped IIb diamond large single crystals are successfully synthesized by the temperature gradient method in a china-type cubic anvil high-pressure apparatus at about 5.5 GPa and 1600 K. The morphologies and surface textures of the synthetic diamond crystals with different boron additive quantities are characterized by using an optical microscope and a scanning electron microscope respectively. The impurities of nitrogen and boron in diamonds are detected by micro Fourier transform infrared technique. The electrical properties including resistivities, Hall coefficients, Hall mobilities and carrier densities of the synthesized samples are measured by a four-point probe and the Hall effect method. The results show that large p-type boron-doped diamond single crystals with few nitrogen impurities have been synthesized. With the increase of quantity of additive boron, some high-index crystal faces such as {113} gradually disappear, and some stripes and triangle pits occur on the crystal surface. This work is helpful for the further research and application of boron-doped semiconductor diamond.

  16. Analysis of hydrogen sorption characteristics of boron-doped activated carbons

    NASA Astrophysics Data System (ADS)

    Beckner, M.; Romanos, J.; Stalla, D.; Dohnke, E.; Singh, A.; Lee, M.; Suppes, G.; Hawthorne, M. F.; Yu, P.; Wexler, C.; Pfeifer, P.

    2011-03-01

    There is significant interest in the properties of boron-doped activated carbons for their potential to improve hydrogen storage. Boron-doped activated carbons have been produced using a novel process involving the pyrolysis of a boron containing compound and subsequent high-temperature annealing. In this talk we will present a systematic study of the effect of different boron doping processes on the samples' surface area, micropore structure, and hydrogen sorption. Experimental results include boron content from prompt gamma neutron activation analysis, boron-carbon chemistry from Fourier transform infrared spectroscopy (FTIR), nitrogen subcritical adsorption, and 80K and 90K hydrogen adsorption isotherms which allow us to evaluate the hydrogen binding energy for each sorptive material. This material is based on work supported by the US Department of Defense under Awards No. N00164-07-P-1306 and N00164-08-C-GS37, the US Department of Energy under Awards No. DE-FG02-07ER46411 and DE-FG36-08GO18142.

  17. An insight into what superconducts in polycrystalline boron-doped diamonds based on investigations of microstructure

    PubMed Central

    Dubrovinskaia, N.; Wirth, R.; Wosnitza, J.; Papageorgiou, T.; Braun, H. F.; Miyajima, N.; Dubrovinsky, L.

    2008-01-01

    The discovery of superconductivity in polycrystalline boron-doped diamond (BDD) synthesized under high pressure and high temperatures [Ekimov, et al. (2004) Nature 428:542–545] has raised a number of questions on the origin of the superconducting state. It was suggested that the heavy boron doping of diamond eventually leads to superconductivity. To justify such statements more detailed information on the microstructure of the composite materials and on the exact boron content in the diamond grains is needed. For that we used high-resolution transmission electron microscopy and electron energy loss spectroscopy. For the studied superconducting BDD samples synthesized at high pressures and high temperatures the diamond grain sizes are ?1–2 ?m with a boron content between 0.2 (2) and 0.5 (1) at %. The grains are separated by 10- to 20-nm-thick layers and triangular-shaped pockets of predominantly (at least 95 at %) amorphous boron. These results render superconductivity caused by the heavy boron doping in diamond highly unlikely. PMID:18697937

  18. Submicron-sized boron carbide particles encapsulated in turbostratic graphite prepared by laser fragmentation in liquid medium.

    PubMed

    Ishikawa, Yoshie; Sasaki, Takeshi; Koshizaki, Naoto

    2010-08-01

    Submicron-sized B4C spherical particles were obtained by laser fragmentation of large B4C particles dispersed in ethyl acetate. The irradiated surface of large B4C raw particles was heated and melted by laser energy absorption. B4C droplets were then cooled down, and finally B4C spherical particles were obtained. Moreover, each B4C particle obtained was encapsulated in a graphitic layer that is useful for medical functionalization of particles. Thus, obtained B4C particles encapsulated in graphitic layer may have potential uses in boron neutron capture therapy. PMID:21125920

  19. Electronic and structural properties of Au-doped zigzag boron nitride nanotubes: A DFT study

    NASA Astrophysics Data System (ADS)

    Bagheri, Mosahhar; Bahari, Ali; Amiri, Masoud; Dehbandi, Behnam

    2014-07-01

    In this paper, structural and electronic properties of zigzag single-walled boron nitride nanotubes are investigated within density functional theory by adding one gold atom as an impurity. One boron and one nitrogen atoms are substituted by one gold atom separately. Calculations show that the substitution of Au atom on boron atom turns the BNNT into a p-type semiconductor with a band gap of 2.435 eV. On the other hand, doping the Au atom on N site diminishes the pristine BNNT gap to 3.905 eV.

  20. Growth of boron-doped diamond nanoclusters using the HFCVD technique

    NASA Astrophysics Data System (ADS)

    Azadfar, P.; Ghoranneviss, M.; Elahi, S. M.; Farhadyar, N.; Salar Elahi, A.

    2015-04-01

    Boron-doped diamond nanocrystals were grown on Si wafers through introduction of the gas mixture of B2O3 dissolved in ethanol and hydrogen by a hot filament chemical vapor deposition (HFCVD) technique. Boron level in diamond films were controlled in the range from 100 to 500 ppm by adjusting the B/C ratios of gas mixtures in order to synthesize and improve the conductivity and quality of HFCVD diamond films with cluster size of nanometer. To investigate the effect of different boron percentage in the chamber on deposited films, Raman spectroscopy, field emission scanning electron microscopy and four point probe techniques were applied to characterize the properties of diamond films. Experimental results indicated that higher boron incorporation in the diamond films introduced bigger crystal clusters, better crystal quality and smaller film resistivity when the level of boron increased from 100 to 300 ppm, while they showed an opposite trend with a further increase of boron level from 300 to 500 ppm. However, in any case the higher boron-doping level led to a decrease of the non-diamond phase in the nanodiamond films.

  1. Impact resistance of composite fan blades. [fiber reinforced graphite and boron epoxy blades for STOL operating conditions

    NASA Technical Reports Server (NTRS)

    Premont, E. J.; Stubenrauch, K. R.

    1973-01-01

    The resistance of current-design Pratt and Whitney Aircraft low aspect ratio advanced fiber reinforced epoxy matrix composite fan blades to foreign object damage (FOD) at STOL operating conditions was investigated. Five graphite/epoxy and five boron/epoxy wide chord fan blades with nickel plated stainless steel leading edge sheath protection were fabricated and impact tested. The fan blades were individually tested in a vacuum whirlpit under FOD environments. The FOD environments were typical of those encountered in service operations. The impact objects were ice balls, gravel, stralings and gelatin simulated birds. Results of the damage sustained from each FOD impact are presented for both the graphite boron reinforced blades. Tests showed that the present design composite fan blades, with wrap around leading edge protection have inadequate FOD impact resistance at 244 m/sec (800 ft/sec) tip speed, a possible STOL operating condition.

  2. Converting graphene oxide monolayers into boron carbonitride nanosheets by substitutional doping.

    PubMed

    Lin, Tsung-Wu; Su, Ching-Yuan; Zhang, Xin-Quan; Zhang, Wenjing; Lee, Yi-Hsien; Chu, Chih-Wei; Lin, Hsin-Yu; Chang, Mu-Tung; Chen, Fu-Rong; Li, Lain-Jong

    2012-05-01

    To realize graphene-based electronics, bandgap opening of graphene has become one of the most important issues that urgently need to be addressed. Recent theoretical and experimental studies show that intentional doping of graphene with boron and nitrogen atoms is a promising route to open the bandgap, and the doped graphene might exhibit properties complementary to those of graphene and hexagonal boron nitride (h-BN), largely extending the applications of these materials in the areas of electronics and optics. This work demonstrates the conversion of graphene oxide nanosheets into boron carbonitride (BCN) nanosheets by reacting them with B(2) O(3) and ammonia at 900 to 1100 °C, by which the boron and nitrogen atoms are incorporated into the graphene lattice in randomly distributed BN nanodomains. The content of BN in BN-doped graphene nanosheets can be tuned by changing the reaction temperature, which in turn affects the optical bandgap of these nanosheets. Electrical measurements show that the BN-doped graphene nanosheet exhibits an ambipolar semiconductor behavior and the electrical bandgap is estimated to be ?25.8 meV. This study provides a novel and simple route to synthesize BN-doped graphene nanosheets that may be useful for various optoelectronic applications. PMID:22378619

  3. Controlled in situ boron doping of diamond thin films using solution phase

    NASA Astrophysics Data System (ADS)

    Roy, M.; Dua, A. K.; Nuwad, J.; Girija, K. G.; Tyagi, A. K.; Kulshreshtha, S. K.

    2006-12-01

    Controlled boron doping of diamond film using nontoxic reagents is a challenge in itself. During the present study, attempts have been made to dope diamond films in situ with boron from a solution of boric acid (H3BO3) in methanol (CH3OH) using a specially designed bubbler that ensured continuous and controlled flow of vapors of boron precursors during deposition. The samples are thoroughly characterized using a host of techniques comprising of x-ray photoelectron spectroscopy, Raman, x-ray diffraction, and current-voltage measurements (I-V). Cross-sectional micro-Raman spectroscopy has been used to obtain depth profile of boron in diamond films. Boron concentration ([B]) in the films is found to vary linearly on a semilog scale with molarity (M) of H3BO3 in CH3OH. Lattice constant of our samples is smaller than the reported American society for testing and materials (ASTM) values due to oxygen incorporation and it increases with [B] in the diamond samples. Heavily boron doped samples exhibit Fano deformation of the Raman line shape and negative and/zero activation barrier in temperature dependent I-V measurements that indicate the formation of metallic phase in the samples. The present study illustrates the feasibility of safe and controlled boron doping of diamond films using a solution of H3BO3 in CH3OH over a significant range of [B] from semiconductor to metallic regime but with a little adverse effect due to unintentional but unavoidable incorporation of oxygen.

  4. Study of electrical and structural properties of boron doped polysilicon films with a low nitrogen content

    Microsoft Academic Search

    H. Bouridah; F. Mansour; R. Mahamdi; P. Temple-Boyer

    2005-01-01

    In this work we propose, the study of nitrogen doped Silicon films for an application as a poly-Si gate material for metal-oxide-semiconductor devices. Nitrogen doped silicon films have been deposited at amorphous phase by low-pressure chemical vapor deposition (LPCVD) from disilane Si2H6 and ammonia NH3 at low temperature (480?C). The films with varied nitrogen contents have been boron implanted, and

  5. Electric conductivity of boron nitride thin films enhanced by in situ doping of zinc

    Microsoft Academic Search

    K. Nose; H. Oba; T. Yoshida

    2006-01-01

    The authors demonstrate that the electric conductivities of cubic and hexagonal boron nitride (c-BN and h-BN) thin films increased markedly by the in situ doping of zinc. The doped films were electrically semiconducting, and conductivities at room temperature increased from 10-8 to 10-2 Omega-1 cm-1 with increasing zinc concentration from 400 to 20 000 ppm. Activation energies for electric conduction

  6. BORON

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of boron chemical speciation is important in understanding bioavailability, excretion, and retention of boron derived from supplemental dietary sources. Undissociated boric acid is the predominant species of boron in most natural freshwater systems. Five antibiotics, one with apparent pote...

  7. Cat-doping: Novel method for phosphorus and boron shallow doping in crystalline silicon at 80 °C

    SciTech Connect

    Matsumura, Hideki; Hayakawa, Taro; Ohta, Tatsunori; Nakashima, Yuki; Miyamoto, Motoharu; Thi, Trinh Cham; Koyama, Koichi; Ohdaira, Keisuke [Japan Advanced Institute of Science and Technology (JAIST), Asahidai, Nomi-shi, Ishikawa-ken 923-1292 (Japan)

    2014-09-21

    Phosphorus (P) or boron (B) atoms can be doped at temperatures as low as 80 to 350 °C, when crystalline silicon (c-Si) is exposed only for a few minutes to species generated by catalytic cracking reaction of phosphine (PH?) or diborane (B?H?) with heated tungsten (W) catalyzer. This paper is to investigate systematically this novel doping method, “Cat-doping”, in detail. The electrical properties of P or B doped layers are studied by the Van der Pauw method based on the Hall effects measurement. The profiles of P or B atoms in c-Si are observed by secondary ion mass spectrometry mainly from back side of samples to eliminate knock-on effects. It is confirmed that the surface of p-type c-Si is converted to n-type by P Cat-doping at 80 °C, and similarly, that of n-type c-Si is to p-type by B Cat-doping. The doping depth is as shallow as 5 nm or less and the electrically activated doping concentration is 10¹? to 10¹?cm?³ for both P and B doping. It is also found that the surface potential of c-Si is controlled by the shallow Cat-doping and that the surface recombination velocity of minority carriers in c-Si can be enormously lowered by this potential control.

  8. Delta-doping of boron atoms by photoexcited chemical vapor deposition

    SciTech Connect

    Akazawa, Housei [NTT Microsystem Integration Laboratories, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

    2012-03-15

    Boron delta-doped structures in Si crystals were fabricated by means of photoexcited chemical vapor deposition (CVD). Core electronic excitation with high-energy photons ranging from vacuum ultraviolet to soft x rays decomposes B{sub 2}H{sub 6} molecules into fragments. Combined with in situ monitoring by spectroscopic ellipsometry, limited number of boron hydrides can be delivered onto a Si(100) surface by using the incubation period before the formation of a solid boron film. The boron-covered surface is subsequently embedded in a Si cap layer by Si{sub 2}H{sub 6} photo-excited CVD. The crystallinity of the Si cap layer depended on its thickness and the substrate temperature. The evaluation of the boron depth profile by secondary ion mass spectroscopy revealed that boron atoms were confined within the delta-doped layer at a concentration of 2.5 x 10{sup 20} cm{sup -3} with a full width at half maximum of less than 9 nm, while the epitaxial growth of a 130-nm-thick Si cap layer was sustained at 420 deg. C.

  9. Heavily boron-doped Si layers grown below 700 C by molecular beam epitaxy using a HBO2 source

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Fathauer, R. W.; Grunthaner, P. J.

    1989-01-01

    Boron doping in Si layers grown by molecular beam epitaxy (MBE) at 500-700 C using an HBO2 source has been studied. The maximum boron concentration without detectable oxygen incorporation for a given substrate temperature and Si growth rate has been determined using secondary-ion mass spectrometry analysis. Boron present in the Si MBE layers grown at 550-700 C was found to be electrically active, independent of the amount of oxygen incorporation. By reducing the Si growth rate, highly boron-doped layers have been grown at 600 C without detectable oxygen incorporation.

  10. Boron concentration profiling by high angle annular dark field-scanning transmission electron microscopy in homoepitaxial ?-doped diamond layers

    SciTech Connect

    Araújo, D.; Alegre, M. P.; Piñero, J. C. [Dpto Ciencia de los Materiales, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain)] [Dpto Ciencia de los Materiales, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain); Fiori, A.; Bustarret, E. [Institut Néel, CNRS-Université Joseph Fourier, 25 av. des Martyrs, 38042 Grenoble (France)] [Institut Néel, CNRS-Université Joseph Fourier, 25 av. des Martyrs, 38042 Grenoble (France); Jomard, F. [Groupe d'Etude de la Matière Condensée (GEMaC), UMR 8635 du CNRS, UVSQ, 45 av. des Etats-Unis, 78035 Versailles Cedex (France)] [Groupe d'Etude de la Matière Condensée (GEMaC), UMR 8635 du CNRS, UVSQ, 45 av. des Etats-Unis, 78035 Versailles Cedex (France)

    2013-07-22

    To develop further diamond related devices, the concentration and spatial location of dopants should be controlled down to the nanometer scale. Scanning transmission electron microscopy using the high angle annular dark field mode is shown to be sensitive to boron doping in diamond epilayers. An analytical procedure is described, whereby local boron concentrations above 10{sup 20} cm{sup ?3} were quantitatively derived down to nanometer resolution from the signal dependence on thickness and boron content. Experimental boron local doping profiles measured on diamond p{sup ?}/p{sup ++}/p{sup ?} multilayers are compared to macroscopic profiles obtained by secondary ion mass spectrometry, avoiding reported artefacts.

  11. Mechanism of the electrochemical dehydrogenation of hexahydropyrimidine on a boron-doped diamond electrode

    NASA Astrophysics Data System (ADS)

    Vedenyapina, M. D.; Simakova, A. P.; Kuznetsov, V. V.; Makhova, N. N.; Vedenyapin, A. A.

    2015-04-01

    The electrochemical behavior of hexahydropyrimidine (HHP) on a boron-doped diamond electrode was studied. The obtained data were compared with the results of previous studies on the electrooxidation of HHP on platinum and gold electrodes. It was shown that different products can be obtained from one organic substance using different electrode materials.

  12. Microstructure effect on the HNO3-HF etching of LPCVD boron-doped polycrystalline silicon

    E-print Network

    Paris-Sud XI, Université de

    671 Microstructure effect on the HNO3-HF etching of LPCVD boron-doped polycrystalline silicon F Physics Abstracts 81.00 - 81.60 1. Introduction. Polycrystalline silicon (p-Si) is more and more used and UV Reflectrometry. They evidence that the changes in the etching rate of polycrystalline Si films

  13. Mineralization of bisphenol A (BPA) by anodic oxidation with boron-doped diamond (BDD) electrode

    Microsoft Academic Search

    M. Murugananthan; S. Yoshihara; T. Rakuma; T. Shirakashi

    2008-01-01

    Anodic oxidation of bisphenol A (BPA), a representative endocrine disrupting chemical, was carried out using boron-doped diamond (BDD) electrode at galvanostatic mode. The electro-oxidation behavior of BPA at BDD electrode was investigated by means of cyclic voltammetric technique. The extent of degradation and mineralization of BPA were monitored by HPLC and total organic carbon (TOC) value, respectively. The results obtained,

  14. Silicon-doped boron nitride coated fibers in silicon melt infiltrated composites

    SciTech Connect

    Corman, Gregory Scot (Ballston Lake, NY); Luthra, Krishan Lal (Schenectady, NY)

    1999-01-01

    A fiber-reinforced silicon--silicon carbide matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is produced. The invention also provides a method for protecting the reinforcing fibers in the silicon--silicon carbide matrix composites by coating the fibers with a silicon-doped boron nitride coating.

  15. Silicon-doped boron nitride coated fibers in silicon melt infiltrated composites

    SciTech Connect

    Corman, G.S.; Luthra, K.L.

    1999-09-14

    A fiber-reinforced silicon-silicon carbide matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is produced. The invention also provides a method for protecting the reinforcing fibers in the silicon-silicon carbide matrix composites by coating the fibers with a silicon-doped boron nitride coating.

  16. Silicon-doped boron nitride coated fibers in silicon melt infiltrated composites

    DOEpatents

    Corman, Gregory Scot (Ballston Lake, NY); Luthra, Krishan Lal (Schenectady, NY)

    2002-01-01

    A fiber-reinforced silicon-silicon carbide matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is produced. The invention also provides a method for protecting the reinforcing fibers in the silicon-silicon carbide matrix composites by coating the fibers with a silicon-doped boron nitride coating.

  17. Boosting activation of oxygen molecules on C60 fullerene by boron doping.

    PubMed

    Li, Qiao-Zhi; Zheng, Jia-Jia; Dang, Jing-Shuang; Zhao, Xiang

    2015-02-01

    The activation of oxygen molecules on boron-doped C60 fullerene (C59 B) and the subsequent water formation reaction are systematically investigated by using hybrid density functional calculations. Results indicate that C59 B shows a favorable ability to activate oxygen molecules both kinetically and thermodynamically. The oxygen molecule is first adsorbed on the boron atom, which is identified to be the most reactive site in C59 B for O2 adsorption because of its high positive charge and spin density. The adsorption structure C59 B?O2 can further isomerize to form two products with small reaction barriers. Water formation reactions upon these two structures are energetically favorable and suggest a four-electron mechanism for the oxygen reduction reaction catalyzed by C59 B. This work provides a reliable theoretical insight into the catalytic properties of boron-doped fullerene, which is believed to be helpful to explore fullerene catalysts. PMID:25399745

  18. Synthesis, Characterization, and Thermoelectric Properties of Electrospun Boron-Doped Barium-Stabilized Bismuth-Cobalt Oxide Nanoceramics

    NASA Astrophysics Data System (ADS)

    Çinar, Emre; Koçyi?it, Serhat; Aytimur, Arda; Uslu, ?brahim; Akdemir, Ahmet

    2014-08-01

    In this study, the boron-doped barium-stabilized bismuth cobalt oxide thermoelectric nanocrystalline ceramic powders were produced by the polymeric precursor technique. The powders were characterized by X-ray diffraction, scanning electron microscopy, and the physical properties measurement system. The X-ray diffraction results showed that these patterns have mixture of two phases as face-centered cubic and body-centered cubic. Values of the crystallite size, the dislocation density, and the microstrain were calculated by the Scherrer equation. According to these values, the crystallite size decreased from 60 to 51 nm with the boron addition in the boron-undoped and boron-doped samples, respectively. The scanning electron microscope results showed that nanograins are rarely seen in the boron-undoped samples, but nanograins turn into needle-like and layered structures with boron addition. The diameters distribution of nanofibers was calculated. The average diameter of the boron-doped sample is smaller than the boron-undoped sample. The physical properties measurement system values showed that the electrical and thermal conductivity, the Seebeck coefficient, and the figure of merit increased with the temperature rise for both samples. The boron-doping effect increased the electrical and thermal conductivity, decreased the Seebeck coefficient, and decreased the figure of merit.

  19. Nitrogen-doped, boron-doped and undoped multiwalled carbon nanotube/polymer composites in WORM memory devices.

    PubMed

    Mamo, Messai A; Sustaita, Alan O; Tetana, Zikhona N; Coville, Neil J; Hümmelgen, Ivo A

    2013-03-29

    We report the preparation of write-once-read-many times memory devices using composites of carbon nanotubes and poly(vinyl phenol) sandwiched between Al electrodes. Three types of nanotubes (undoped multiwalled carbon nanotubes, nitrogen-doped multiwalled carbon nanotubes and boron-doped multiwalled carbon nanotubes) are investigated for this application. The OFF to ON state switching threshold is only slightly dependent on nanotube type, but the ON/OFF current ratio depends on both nanotube type and concentration and varies up to 10(6), decreasing for nanotube concentrations larger than 0.50 wt% in the composite. PMID:23466515

  20. Photo-induced Modulation Doping in Graphene/Boron nitride Heterostructures

    NASA Astrophysics Data System (ADS)

    Velasco, Jairo, Jr.; Ju, Long; Hwang, Edwin; Kahn, Salman; Nosiglia, Casey; Tsai, Hsin-Zon; Yang, Wei; Zhang, Guangyu; Taniguchi, Takashi; Watanabe, Kenji; Zhang, Yuanbo; Crommie, Michael; Zettl, Alex; Wang, Feng

    2014-03-01

    Van der Waals heterostructures (VDH) provide an exciting new platform for materials engineering, where a variety of layered materials with different electrical, optical and mechanical responses can be stacked together to enable new physics and novel functionalities. We report an emerging optoelectronic phenomenon (i.e. photo-induced modulation doping) in the graphene-boron nitride VDH (G/BN heterostructure). We find it enables flexible and repeatable writing and erasing of charge doping in graphene with optical light. We show that the photo-induced modulation doping maintains the remarkable carrier mobility of the G/BN heterostructure, and it can be used to generate spatially varying doping profiles like pn junctions. Our work contributes towards understanding light matter interactions in VDHs, and introduces a simple technique for creating inhomogeneous doping in high mobility graphene devices. J. Velasco Jr. acknowledges support from UC President's Postdoctoral Fellowship.

  1. Boron-Doped Strontium-Stabilized Bismuth Cobalt Oxide Thermoelectric Nanocrystalline Ceramic Powders Synthesized via Electrospinning

    NASA Astrophysics Data System (ADS)

    Koçyi?it, Serhat; Aytimur, Arda; Ç?nar, Emre; Uslu, ?brahim; Akdemir, Ahmet

    2014-01-01

    Boron-doped strontium-stabilized bismuth cobalt oxide thermoelectric nanocrystalline ceramic powders were produced by using a polymeric precursor technique. The powders were characterized by using x-ray diffraction (XRD), scanning electron microscopy (SEM), and physical properties measurement system (PPMS) techniques. The XRD results showed that these patterns have a two-phase mixture. The phases are face-centered cubic (fcc) and body-centered cubic (bcc). Values of the crystallite size, dislocation density, and microstrain were calculated by using the Scherrer equation. The lattice parameters were calculated for fcc and bcc phases. The SEM results showed that needle-like grains are formed in boron-undoped composite materials, but the needle-like grains changed to the plate-like grains with the addition of boron. The distribution of the nanofiber diameters was calculated and the average diameter of the boron-doped sample is smaller than the boron-undoped one. PPMS values showed that the electrical resistivity values decreased, but the thermal conductivity values, the Seebeck coefficients, and figure of merit ( ZT) increased with increasing temperature for the two samples.

  2. Effects of boron doping on the structural and optical properties of silicon nanocrystals in a silicon dioxide matrix

    Microsoft Academic Search

    X J Hao; E-C Cho; C Flynn; Y S Shen; G Conibeer; M A Green

    2008-01-01

    Doping of Si nanocrystals is an important topic in the emerging field of Si nanocrystals based all-Si tandem solar cells. Boron-doped Si nanocrystals embedded in a silicon dioxide matrix were realized by a co-sputtering process, followed by high temperature annealing. The x-ray photoelectron spectroscopy B 1s signal attributable to Si–B (187 eV) and\\/or B–B (188 eV) indicates that the boron

  3. Effects of boron doping on the structural and optical properties of silicon nanocrystals in a silicon dioxide matrix

    Microsoft Academic Search

    X. J. Hao; E.-C. Cho; C. Flynn; Y. S. Shen; G. Conibeer; M. A. Green

    2008-01-01

    Doping of Si nanocrystals is an important topic in the emerging field of Si nanocrystals based all-Si tandem solar cells. Boron-doped Si nanocrystals embedded in a silicon dioxide matrix were realized by a co-sputtering process, followed by high temperature annealing. The x-ray photoelectron spectroscopy B 1s signal attributable to Si-B (187 eV) and\\/or B-B (188 eV) indicates that the boron

  4. One-pot synthesis of boron-doped mesoporous carbon with boric acid as a multifunction reagent

    Microsoft Academic Search

    Shilei Ding; Sujuan Zheng; Mingjiang Xie; Luming Peng; Xuefeng Guo; Weiping Ding

    2011-01-01

    An effective method for modification of ordered mesoporous carbons is to dope boron incorporated into carbon network for improving their properties in many aspects. A one-pot synthesis is proposed with the combination of boron doping and fabrication of mesoporous carbon through sol–gel method using boric acid as the catalyst, dopant and pore-forming agent. The as-prepared materials were characterized by TEM,

  5. EPR study of hydrogen-related defects in boron-doped p-type CVD homoepitaxial diamond films

    Microsoft Academic Search

    N. Mizuochi; M. Ogura; H. Watanabe; J. Isoya; H. Okushi; S. Yamasaki

    2004-01-01

    Boron-doped p-type single crystalline chemical vapor deposition (CVD) homoepitaxial diamond films were investigated by electron paramagnetic resonance (EPR). Carbon dangling bond defects, which were accompanied by a nearby hydrogen atom, were observed in boron-doped p-type CVD diamond films on a IIa substrate similar to those observed in undoped diamond. This result suggested that the energy level position of the defects

  6. Compressive behavior of kinking nonlinear elastic solids: Titanium silicon carbide, graphite, mica and boron nitride

    NASA Astrophysics Data System (ADS)

    Zhen, Tiejun

    Dislocation-based deformation in crystalline solids is almost always plastic. Once dislocations are generated they entangle and render the process irreversible. In our recent work we show that this does not apply to a new class of materials, best characterized as kinking nonlinear elastic (KNE) solids. KNE solids include the MAX phases, mica, graphite, boron nitride, so called nonlinear mesoscopic elastic (NME) solids discussed in geological literature and most probably ice. The MAX phases are a new class of layered machinable ternary carbides and nitrides, with the chemical formula M n+1AXn, where M is an early transition metal, A is an A-group element (mostly IIIA and IVA) and X is C or N. The compressive loading-unloading stress-strain curves of KNE solids in the elastic regime outline nonlinear, fully reversible, reproducible, rate-independent, closed hysteresis loops whose shape and extent of energy dissipated are strongly influenced by grain size with the energy dissipated being significantly larger in the coarse-grained material. This unique property is attributed to the formation and annihilation of incipient kink bands (IKBs), defined to be thin plates of sheared material bounded by opposite walls of dislocations. As long as the dislocation walls remain attached, the response is fully reversible. Furthermore, because the dislocations are confined to the basal planes work hardening does not occur and the dislocations can move reversibly over relatively large distances. This kind of dislocation motion renders KNE solids potentially high damping material. The loss factor for Ti3SiC2, a prime member of KNE solids, is higher than most woods, and comparable to polypropylene and nylon. At higher temperatures or stress, since the IKB dissociate and coalesce to form regular irreversible kink bands. The close hystesis loops are open, the response is strain-rate dependent, and cyclic hardening is observed even at 1200°C.

  7. Influence of the boron precursor and drying method on surface properties and electrochemical behavior of boron-doped carbon gels.

    PubMed

    Zapata-Benabihe, Zulamita; Moreno-Castilla, Carlos; Carrasco-Marín, Francisco

    2014-02-18

    Two series of B-doped carbon gels were prepared by the polymerization of resorcinol and formaldehyde in water using either boric acid or phenyl boronic acid as dopants. Both organic hydrogels were dried by four methods: supercritical, freeze, microwave oven, and vacuum oven drying. The effects of the boron precursor and drying method on the surface characteristics were studied by N2 and CO2 adsorption at -196 and 0 °C, respectively, immersion calorimetry into benzene and water, temperature-programmed desorption coupled with mass spectrometry, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Electrochemical characterization was carried out in a three-electrode cell, using Ag/AgCl as a reference electrode and a Pt wire as a counter electrode. The surface area obtained from immersion calorimetry into benzene was more realistic than that yielded by the Brunauer-Emmett-Teller (BET) equation. The hydrophobicity of the samples decreased linearly with a higher oxygen content. In addition, the oxygen content of the B-doped carbon gels increased linearly with a higher B content, and the interfacial or areal capacitance decreased linearly with a larger surface area. The capacitance was increased by B addition because of the pseudocapacitance effects of the higher oxygen content of the samples. The cryogel and vacuum-dried xerogel obtained from the boric acid series, Bc and Bv, respectively, showed the largest gravimetric and volumetric capacitances, around 140 F/g and 95 F/cm(3), respectively. PMID:24460055

  8. Isolated boron and nitrogen sites on porous graphitic carbon synthesized from nitrogen-containing chitosan for supercapacitors.

    PubMed

    Sun, Li; Fu, Yu; Tian, Chungui; Yang, Ying; Wang, Lei; Yin, Jie; Ma, Jing; Wang, Ruihong; Fu, Honggang

    2014-06-01

    Separated boron and nitrogen porous graphitic carbon (BNGC) is fabricated by a facile hydrothermal coordination/ZnCl2-activation process from renewable and inexpensive nitrogen-containing chitosan. In this synthetic pathway, chitosan, which has a high nitrogen content, first coordinates with Fe(3+) ions to form chitosan-Fe that subsequently reacts with boric acid (boron source) to generate the BNGC precursor. After simultaneous carbonization and ZnCl2 activation followed by removal of the Fe catalyst, BNGC, containing isolated boron and nitrogen centers and having a high surface area of 1567?m(2) ?g(-1) and good conductivity, can be obtained. Results indicate that use of chitosan as a nitrogen-containing carbon source effectively prevents nitrogen atoms from direct combination with boron atoms. In addition, the incorporation of Fe(3+) ions not only endows BNGC with high graphitization, but also favors for nitrogen fixation. Remarkably, the unique microstructure of BNGC enables its use as an advanced electrode material for energy storage. As electrode material for supercapacitors, BNGC shows a high capacitance of 313?F?g(-1) at 1?A?g(-1), and also long-term durability and coulombic efficiency of >99.5?% after 5000?cycles. Notably, in organic electrolytes, the energy density could be up to 50.1?Wh?kg(-1) at a power density of 10.5?kW?kg(-1). The strategy developed herein opens a new avenue to prepare BNGC without inactive B?N bonds from commercially available chitosan for high-performance supercapacitors. PMID:24692324

  9. Effect of boron doping on optical properties of sol-gel based nanostructured zinc oxide films on glass

    SciTech Connect

    Jana, Sunirmal, E-mail: sjana@cgcri.res.in [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute, (Council of Scientific and Industrial Research, CSIR, India), 196 Raja S. C. Mullick Road, Kolkata 700032 (India)] [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute, (Council of Scientific and Industrial Research, CSIR, India), 196 Raja S. C. Mullick Road, Kolkata 700032 (India); Vuk, Angela Surca [National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana (Slovenia)] [National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana (Slovenia); Mallick, Aparajita [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute, (Council of Scientific and Industrial Research, CSIR, India), 196 Raja S. C. Mullick Road, Kolkata 700032 (India)] [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute, (Council of Scientific and Industrial Research, CSIR, India), 196 Raja S. C. Mullick Road, Kolkata 700032 (India); Orel, Boris [National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana (Slovenia)] [National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana (Slovenia); Biswas, Prasanta Kumar [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute, (Council of Scientific and Industrial Research, CSIR, India), 196 Raja S. C. Mullick Road, Kolkata 700032 (India)] [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute, (Council of Scientific and Industrial Research, CSIR, India), 196 Raja S. C. Mullick Road, Kolkata 700032 (India)

    2011-12-15

    Graphical abstract: Room temperature fine structured UV-vis PL emissions (a) as phonon replicas in 1 at.% boron doped film originated from LO phonon evidenced from Near Grazing Incidence Angle (NGIA) IR spectral study (b). Highlights: Black-Right-Pointing-Pointer Sol-gel based boron doped nanostructured ZnO thin films deposited on pure silica glass using crystalline boric acid as boron source. Black-Right-Pointing-Pointer Observed first time, room temperature fine structured PL emissions in 1 at.% doped film as phonon replicas originated from LO phonon (both IR and Raman active). Black-Right-Pointing-Pointer Boron doping controls the LO phonon energy in addition to visible reflection, band gap and grain size. Black-Right-Pointing-Pointer The films possessed mixed crystal phases with hexagonal as major phase. -- Abstract: Boron doped zinc oxide thin films ({approx}80 nm) were deposited onto pure silica glass by sol-gel dip coating technique from the precursor sol/solution of 4.0 wt.% equivalent oxide content. The boron concentration was varied from 0 to 2 at.% w.r.t. Zn using crystalline boric acid. The nanostructured feature of the films was visualized by FESEM images and the largest cluster size of ZnO was found in 1 at.% boron doped film (B1ZO). The presence of mixed crystal phases with hexagonal as major phase was identified from XRD reflections of the films. Particle size, optical band gap, visible specular reflection, room temperature photoluminescence (PL) emissions (3.24-2.28 eV), infra-red (IR) and Raman active longitudinal optical (LO) phonon vibration were found to be dependent on dopant concentration. For the first time, we report the room temperature fine structured PL emissions as phonon replicas originated from the LO phonon (both IR and Raman active) in 1 at.% boron doped zinc oxide film.

  10. The location and doping effect of boron in Si nanocrystals embedded silicon oxide film

    SciTech Connect

    Xie, Min; Li, Dongsheng; Chen, Le; Wang, Feng; Zhu, Xiaodong; Yang, Deren [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)] [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2013-03-25

    Electrically activated doping of boron (B) atoms into the Si-nanocrystals (Si-NCs) embedded silicon oxide film is achieved by co-sputtering technique following with the annealing treatment. The evolution of the size, the shape, and the density of Si-NCs with the doping of B atoms is investigated. The observation of x-ray photoelectron spectroscopy of Si 2p and B 1s and the decrease in lattice spacing of Si (111) plane suggest that B atoms are doped into Si-NCs. The activated doping is confirmed by the Fano effect of the micro-Raman spectra for Si-NCs and the drastic decrease of the sheet resistance.

  11. Electrical properties of boron-doped MWNTs synthesized by hot-filament chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ishii, S.; Nagao, M.; Watanabe, T.; Tsuda, S.; Yamaguchi, T.; Takano, Y.

    2009-10-01

    We have synthesized a large amount of boron-doped multiwalled carbon nanotubes (MWNTs) by hot-filament chemical vapor deposition. The synthesis was carried out in a flask using a methanol solution of boric acid as a source material. The scanning electron microscopy, transmission electron microscopy, and micro-Raman spectroscopy were performed to evaluate the structural properties of the obtained MWNTs. In order to evaluate the electrical properties, temperature dependence of resistivity was measured in an individual MWNTs with four metal electrodes. The Raman shifts suggest carrier injection into the boron-doped MWNTs, but the resistivity of the MWNTs was high and increased strongly with decreasing temperature. Defects induced by the plasma may cause this enhanced resistivity.

  12. Doping effect in N-type rare earth boron carbonitrides

    Microsoft Academic Search

    Takao Mori; Toshiyuki Nishimura

    2007-01-01

    For possible waste heat applications, there is a large incentive to develop thermoelectric materials which can function at high temperature. Boron-rich cluster compounds are attractive as materials because of their stability under high temperature and ldquounfriendlyrdquo (e.g. acidic, corrosive) conditions. B12 icosahedra compounds have been predominantly p-type. However, we have recently discovered n-type behavior in a homologous series of compounds.

  13. Synthesis of boron, nitrogen co-doped porous carbon from asphaltene for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhou, Ying; Wang, Dao-Long; Wang, Chun-Lei; Jin, Xin-Xin; Qiu, Jie-Shan

    2014-08-01

    Oxidized asphaltene (OA), a thermosetting material with plenty of functional groups, is synthesized from asphaltene (A) using HNO3/H2SO4 as the oxidizing agent. Boron, nitrogen co-doped porous carbon (BNC—OA) is prepared by carbonization of the mixture of boric acid and OA at 1173 K in an argon atmosphere. X-ray photoelectron spectroscopy (XPS) characterization reveals that the BNC—OA has a nitrogen content of 3.26 at.% and a boron content of 1.31 at.%, while its oxidation-free counterpart (BNC—SA) has a nitrogen content of 1.61 at.% and a boron content of 3.02 at.%. The specific surface area and total pore volume of BNC—OA are 1103 m2·g-1 and 0.921 cm3·g-1, respectively. At a current density of 0.1 A·g-1, the specific capacitance of BNC-OA is 335 F·g-1 and the capacitance retention can still reach 83% at 1 A·g-1. The analysis shows that the superior electrochemical performance of the BNC—OA is attributed to the pseudocapacitance behavior of surface heteroatom functional groups and an abundant pore-structure. Boron, nitrogen co-doped porous carbon is a promising electrode material for supercapacitors.

  14. Local impedance imaging of boron-doped polycrystalline diamond thin films

    SciTech Connect

    Zieli?ski, A.; Ryl, J.; Burczyk, L.; Darowicki, K. [Department of Electrochemistry, Corrosion and Material Engineering, Gdansk University of Technology, 11/12 Narutowicza St., 80-233 Gdansk (Poland); Bogdanowicz, R., E-mail: rbogdan@eti.pg.gda.pl [Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, 11/12 G. Narutowicza St., 80-233 Gdansk (Poland)

    2014-09-29

    Local impedance imaging (LII) was used to visualise surficial deviations of AC impedances in polycrystalline boron-doped diamond (BDD). The BDD thin film electrodes were deposited onto the highly doped silicon substrates via microwave plasma-enhanced CVD. The studied boron dopant concentrations, controlled by the [B]/[C] ratio in plasma, ranged from 1 × 10{sup 16} to 2 × 10{sup 21} atoms cm{sup ?3}. The BDD films displayed microcrystalline structure, while the average size of crystallites decreased from 1 to 0.7??m with increasing [B]/[C] ratios. The application of LII enabled a direct and high-resolution investigation of local distribution of impedance characteristics within the individual grains of BDD. Such an approach resulted in greater understanding of the microstructural control of properties at the grain level. We propose that the obtained surficial variation of impedance is correlated to the areas of high conductance which have been observed at the grain boundaries by using LII. We also postulate that the origin of high conductivity is due to either preferential boron accumulation, the presence of defects, or sp{sup 2} regions in the intragrain regions. The impedance modulus recorded by LII was in full agreement with the bulk impedance measurements. Both variables showed a decreasing trend with increasing [B]/[C] ratios, which is consistent with higher boron incorporation into BDD film.

  15. Structural investigations of RTA boron-doped thin aSi layers

    Microsoft Academic Search

    L. Popova; St. Peneva; P. Aleksandrova; G. Beshkov

    2005-01-01

    The structural changes in as- sputtered thin a-Si layer, and after boron doping with rapid thermal annealing are investigated by transmission electron microscopy. Stable hexagonal amorphous\\/crystalline series of SiO2 structures, as signed as SiO2 (SnO2-V), not revealed in high temperature SiO2 layers, are observed in all films investigated. Different types of crystalline and high ordered SiO2 structures are obtained in

  16. Structure and 1\\/f noise of boron doped polymorphous silicon films

    Microsoft Academic Search

    S. B. Li; Z. M. Wu; Y. D. Jiang; W. Li; N. M. Liao; J. S. Yu

    2008-01-01

    The influence of structure variation on the 1\\/f noise of nanometric boron doped hydrogenated polymorphous silicon (pm-Si:H) films was investigated. The films were grown by the conventional radio frequency plasma enhanced chemical vapor deposition (PECVD) method. Raman spectroscopy was used to reveal the crystalline volume fraction (Xc) and crystal size of the pm-Si:H. The measurement of optical and structure properties

  17. Anodic oxidation of 2-naphthol at boron-doped diamond electrodes

    Microsoft Academic Search

    M. Panizza; P. A. Michaud; G. Cerisola; Ch. Comninellis

    2001-01-01

    The anodic oxidation of 2-naphthol in acid media was investigated at a synthetic boron-doped diamond thin film electrode (BDD) using cyclic voltammetry and bulk electrolysis. The results have shown that in the potential region, where the supporting electrolyte is stable, reactions involving simple electron transfer, such as oxidation of 2-naphthol to naphthoxy radical and 1,4-naphthoquinone occur. Polymeric materials, which lead

  18. Effects of boron doping on the structural and optical properties of silicon nanocrystals in a silicon dioxide matrix.

    PubMed

    Hao, X J; Cho, E-C; Flynn, C; Shen, Y S; Conibeer, G; Green, M A

    2008-10-22

    Doping of Si nanocrystals is an important topic in the emerging field of Si nanocrystals based all-Si tandem solar cells. Boron-doped Si nanocrystals embedded in a silicon dioxide matrix were realized by a co-sputtering process, followed by high temperature annealing. The x-ray photoelectron spectroscopy B 1s signal attributable to Si-B (187 eV) and/or B-B (188 eV) indicates that the boron may exist inside Si nanocrystals. A higher probability of effective boron doping was suggested for Si-rich oxide films with a low oxygen content, Then, structural and optical properties were characterized with a focus on the effects of the boron content on Si quantum dots. The results show that as the boron content increases, the nanocrystal size is slightly reduced and the Si crystallization is suppressed. The photoluminescence intensity of the films is decreased as the boron content increases. This is due to boron-induced defects and/or Auger processes induced by effective doping. These results can provide optimal conditions for future Si quantum dot based solar cells. PMID:21832679

  19. Microscopic evidence for evolution of superconductivity by effective carrier doping in boron-doped diamond: B11-NMR study

    NASA Astrophysics Data System (ADS)

    Mukuda, H.; Tsuchida, T.; Harada, A.; Kitaoka, Y.; Takenouchi, T.; Takano, Y.; Nagao, M.; Sakaguchi, I.; Oguchi, T.; Kawarada, H.

    2007-01-01

    We have investigated the superconductivity discovered in boron-doped diamonds by means of B11-NMR on heteroepitaxially grown (111) and (100) films. B11-NMR spectra for all of the films are identified to arise from the substitutional B(1) site as single occupation and lower symmetric B(2) site substituted as boron+hydrogen (B+H) complex, respectively. Clear evidence is presented that the effective carriers introduced by B(1) substitution are responsible for the superconductivity, whereas the charge neutral B(2) sites does not offer the carriers effectively. The result is also corroborated by the density of states deduced by 1/T1T measurement, indicating that the evolution of superconductivity is driven by the effective carrier introduced by substitution at B(1) site.

  20. Evolution of helium from irradiated boron-containing materials with a graphite carbon base

    Microsoft Academic Search

    I. Ya. Emel'yanov; R. V. Grebennikov; D. N. Moiseev; V. S. Karasev; V. S. Kislik; Yu. F. Shved; Yu. P. Mel'nik-Kutsyn; N. M. Lutsenko; P. I. Demidov; N. G. Sumets

    1971-01-01

    One method of increasing the radiation resistance of boron-containing materials is the creation of conditions promoting the extraction of the helium as it is formed by the neutron irradiation. In this paper we shall present the results of a study of the emission of helium which takes place on heating samples comprising dispersions of boron-containing particles of various sizes in

  1. Boron-doped cadmium oxide composite structures and their electrochemical measurements

    SciTech Connect

    Lokhande, B.J., E-mail: bjlokhande@yahoo.com [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Ambare, R.C. [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Mane, R.S. [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606 (India); Bharadwaj, S.R. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2013-08-01

    Graphical abstract: Conducting nano-fibrous 3% boron doped cadmium oxide thin films were prepared by SILAR and its super capacitive properties were studied. - Highlights: • Samples are of nanofibrous nature. • All samples shows pseudocapacitive behavior. • 3% B doped CdO shows good specific capacitance. • 3% B doped CdO shows maximum 74.93% efficiency at 14 mA/cm{sup 2}. • 3% B doped CdO shows 0.8 ? internal resistance. - Abstract: Boron-doped and undoped cadmium oxide composite nanostructures in thin film form were prepared onto stainless steel substrates by a successive ionic layer adsorption and reaction method using aqueous solutions of cadmium nitrate, boric acid and 1% H{sub 2}O{sub 2}. As-deposited films were annealed at 623 K for 1 h. The X-ray diffraction study shows crystalline behavior for both doped and undoped films with a porous topography and nano-wires type architecture, as observed in SEM image. Wettability test confirms the hydrophilic surface with 58° contact angle value. Estimated band gap energy is around 1.9 eV. Electrochemical behavior of the deposited films is attempted in 1 M KOH electrolyte using cyclic voltammetry (CV), electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Maximum values of the specific capacitance, specific energy and specific power obtained for 3% B doped CdO film at 2 mV/s scan rate are 20.05 F/g, 1.22 Wh/kg and 3.25 kW/kg, respectively.

  2. Metal-to-insulator transition and superconductivity in boron-doped diamond.

    PubMed

    Bustarret, E; Achatz, P; Sacépé, B; Chapelier, C; Marcenat, C; Ortéga, L; Klein, T

    2008-01-28

    The experimental discovery of superconductivity in boron-doped diamond came as a major surprise to both the diamond and the superconducting materials communities. The main experimental results obtained since then on single-crystal diamond epilayers are reviewed and applied to calculations, and some open questions are identified. The critical doping of the metal-to-insulator transition (MIT) was found to coincide with that necessary for superconductivity to occur. Some of the critical exponents of the MIT were determined and superconducting diamond was found to follow a conventional type II behaviour in the dirty limit, with relatively high critical temperature values quite close to the doping-induced insulator-to-metal transition. This could indicate that on the metallic side both the electron-phonon coupling and the screening parameter depend on the boron concentration. In our view, doped diamond is a potential model system for the study of electronic phase transitions and a stimulating example for other semiconductors such as germanium and silicon. PMID:18024360

  3. Growth and nucleation regimes in boron doped silicon by dynamical x-ray diffraction

    SciTech Connect

    Will, J., E-mail: johannes.will@fau.de; Gröschel, A.; Bergmann, C.; Weißer, M.; Magerl, A. [Crystallography and Structural Physics, University of Erlangen-Nürnberg, Staudtstr. 3, 91058 Erlangen (Germany)

    2014-09-15

    The oxygen precipitation of highly (17.5 m? cm) and moderately (4.5 ? cm) boron (B) doped silicon (Si) crystals at 780?°C is investigated by following in-situ the evolution of diffraction Pendellösung oscillations. All samples show an initial diffusion-driven growth process which may change over into Ostwald ripening. For the highly doped sample and involving a nucleation step at 450?°C for 30?h, the precipitate density ? is enhanced by a factor of 8 as compared to the moderately doped sample. The influence of a high B concentration on ? is dramatically higher for the samples directly heated to 780?°C, where an enhancement factor of 80 is found. Considering Ostwald ripening as a second growth regime reveals consistent ripening rates and surface energies ? with those found at 900?°C in a previous publication.

  4. Growth and nucleation regimes in boron doped silicon by dynamical x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Will, J.; Gröschel, A.; Bergmann, C.; Weißer, M.; Magerl, A.

    2014-09-01

    The oxygen precipitation of highly (17.5 m? cm) and moderately (4.5 ? cm) boron (B) doped silicon (Si) crystals at 780 °C is investigated by following in-situ the evolution of diffraction Pendellösung oscillations. All samples show an initial diffusion-driven growth process which may change over into Ostwald ripening. For the highly doped sample and involving a nucleation step at 450 °C for 30 h, the precipitate density ? is enhanced by a factor of 8 as compared to the moderately doped sample. The influence of a high B concentration on ? is dramatically higher for the samples directly heated to 780 °C, where an enhancement factor of 80 is found. Considering Ostwald ripening as a second growth regime reveals consistent ripening rates and surface energies ? with those found at 900 °C in a previous publication.

  5. Boron laser doping using spin-on dopant for textured crystalline silicon solar cell

    NASA Astrophysics Data System (ADS)

    Nishimura, Hideki; Manabe, Mitsuaki; Sakagawa, Hideki; Fuyuki, Takashi

    2015-06-01

    A novel precursor layer, polyboron film (PBF), was applied in the laser doping (LD) process. Localized LD using PBF was applied to a high-efficiency solar cell structure as a selective emitter (SE). Interface adhesion was improved by using an organic-polymer-based doping precursor, PBF. A strongly adhered interface contributed to the preservation of textured formations after disruption by LD, and to the homogeneous introduction of impurities. Surface geometries were retained almost completely even after LD. Sheet resistances were decreased by additional boron doping by LD. The photovoltaic characteristics were improved by SE formation using PBF with an optimum average laser power. Consequently, the SE formed by LD showed an increase in fill factor (FF), which contributed to the improvement in solar cell efficiency.

  6. Thermoelectric properties of heavily boron- and phosphorus-doped silicon

    NASA Astrophysics Data System (ADS)

    Ohishi, Yuji; Xie, Jun; Miyazaki, Yoshinobu; Aikebaier, Yusufu; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke; Uchida, Noriyuki; Tada, Tetsuya

    2015-07-01

    In recent years, nanostructured thermoelectric materials have attracted much attention. However, despite this increasing attention, available information on the thermoelectric properties of single-crystal Si is quite limited, especially for high doping concentrations at high temperatures. In this study, the thermoelectric properties of heavily doped (1018–1020 cm?3) n- and p-type single-crystal Si were studied from room temperature to above 1000 K. The figures of merit, ZT, were calculated from the measured data of electrical conductivity, Seebeck coefficient, and thermal conductivity. The maximum ZT values were 0.015 for n-type and 0.008 for p-type Si at room temperature. To better understand the carrier and phonon transport and to predict the thermoelectric properties of Si, we have developed a simple theoretical model based on the Boltzmann transport equation with the relaxation-time approximation.

  7. Radiation tolerance of boron doped dendritic web silicon solar cells

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.

    1980-01-01

    The potential of dendritic web silicon for giving radiation hard solar cells is compared with the float zone silicon material. Solar cells with n(+)-p-P(+) structure and approximately 15% (AMl) efficiency were subjected to 1 MeV electron irradiation. Radiation tolerance of web cell efficiency was found to be at least as good as that of the float zone silicon cell. A study of the annealing behavior of radiation-induced defects via deep level transient spectroscopy revealed that E sub v + 0.31 eV defect, attributed to boron-oxygen-vacancy complex, is responsible for the reverse annealing of the irradiated cells in the temperature range of 150 to 350 C.

  8. Synthesis of boron and nitrogen doped graphene supporting PtRu nanoparticles as catalysts for methanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Lu, Jiming; Zhou, Yingke; Tian, Xiaohui; Xu, Xiao; Zhu, Hongxi; Zhang, Shaowei; Yuan, Tao

    2014-10-01

    In this study, we demonstrate a single-step heat treatment approach to synthesize boron and nitrogen doped graphene supporting PtRu electrocatalysts for methanol electro-oxidation reaction. The reduction of graphene oxide, boron or nitrogen doping of graphene and loading of PtRu nanoparticles happened simultaneously during the reaction process. The morphologies and microstructures of the as-prepared catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic methanol oxidation activity and durability of the obtained catalysts were evaluated by the cyclic voltammetry and chronoamperometric techniques. The results reveal that the boron and nitrogen doped graphene supporting PtRu electrocatalysts can be successfully prepared by the single step heat treatment technique, and the introduction of boron or nitrogen containing function groups into the reduced graphene sheets could modulate the particle size and dispersion of the supporting PtRu nanoparticles and improve the electrocatalytic performance of methanol oxidation reaction. The optimal annealing temperature is 800 °C, the preferable heat treatment time is 60 min for the nitrogen-doped catalysts and 90 min for the boron-doped catalysts, and the catalysts prepared under such conditions present superior catalytic activities for methanol oxidation than those prepared under other heat treatment conditions.

  9. Boron concentration profiling by high angle annular dark field-scanning transmission electron microscopy in homoepitaxial d-doped diamond layers

    E-print Network

    Boyer, Edmond

    Boron concentration profiling by high angle annular dark field-scanning transmission electron the high angle annular dark field mode is shown to be sensitive to boron doping in diamond epilayers. An analytical procedure is described, whereby local boron concentrations above 1020 cmÀ3 were quantitatively

  10. LIGHT-INDUCED DEGRADATION OF THE CARRIER LIFETIME IN N-TYPE CZOCHRALSKI-GROWN SILICON DOPED WITH BORON AND PHOSPHORUS

    E-print Network

    WITH BORON AND PHOSPHORUS Bianca Lim1 , Karsten Bothe1 , Vladimir Voronkov2 , Robert Falster2 , and Jan as the fast forming recombination-center observed in p-Si. Keywords: Czochralski silicon, boron, phosphorus], while Schutz-Kuchly et al. observed LID in n-type Cz-Si that was doped with both boron and phosphorus

  11. Photodegradation of aniline by goethite doped with boron under ultraviolet and visible light irradiation

    SciTech Connect

    Liu, Guanglong [Laboratory of Plant Nutrition and Ecological Environment Research, Centre for Microelement Research of Huazhong Agricultural University, Key Laboratory of Subtropical Agriculture and Environment, Ministry of Agriculture, Wuhan 430070 (China)] [Laboratory of Plant Nutrition and Ecological Environment Research, Centre for Microelement Research of Huazhong Agricultural University, Key Laboratory of Subtropical Agriculture and Environment, Ministry of Agriculture, Wuhan 430070 (China); Liao, Shuijiao [Laboratory of Plant Nutrition and Ecological Environment Research, Centre for Microelement Research of Huazhong Agricultural University, Key Laboratory of Subtropical Agriculture and Environment, Ministry of Agriculture, Wuhan 430070 (China) [Laboratory of Plant Nutrition and Ecological Environment Research, Centre for Microelement Research of Huazhong Agricultural University, Key Laboratory of Subtropical Agriculture and Environment, Ministry of Agriculture, Wuhan 430070 (China); College of Basic Sciences of Huazhong Agricultural University, Wuhan 430070 (China); Zhu, Duanwei, E-mail: zhudw@mail.hzau.edu.cn [Laboratory of Plant Nutrition and Ecological Environment Research, Centre for Microelement Research of Huazhong Agricultural University, Key Laboratory of Subtropical Agriculture and Environment, Ministry of Agriculture, Wuhan 430070 (China)] [Laboratory of Plant Nutrition and Ecological Environment Research, Centre for Microelement Research of Huazhong Agricultural University, Key Laboratory of Subtropical Agriculture and Environment, Ministry of Agriculture, Wuhan 430070 (China); Liu, Linghua; Cheng, Dongsheng; Zhou, Huaidong [China Institute of Water Resources and Hydropower Research, Beijing 100038 (China)] [China Institute of Water Resources and Hydropower Research, Beijing 100038 (China)

    2011-08-15

    Highlights: {yields} Goethite modified by boron was prepared by sol-gel method in presence of boron acid at the low temperature. {yields} B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. {yields} The results showed that semiconductor photocatalytic reaction mechanism should exist in the process of aniline degradation with goethite and B-goethite as photocatalyst. -- Abstract: In the present study, goethite and goethite doped with boron (B-goethite) were employed to detect the presence or absence of semiconductor photocatalytic reaction mechanism in the reaction systems. B-goethite was prepared by sol-gel method in presence of boron acid in order to improve its photocatalystic efficiency under the ultraviolet and visible light irradiation. The optical properties of goethite and B-goethite were characterized by ultraviolet and visible absorption spectra and the result indicated that B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. Degradation of aniline was investigated in presence of goethite and B-goethite in aqueous solution. It was found that the B-goethite photocatalyst exhibited enhanced ultraviolet and visible light photocatalytic activity in degradation of aniline compared with the pristine goethite. The photocatalytic degradation mechanism of B-goethite was discussed.

  12. CVD Delta-Doped Boron Surface Layers for Ultra-Shallow Junction Formation F. Sarubbi, L. K. Nanver, and T. L. M. Scholtes

    E-print Network

    Technische Universiteit Delft

    atmospheric/low- pressure chemical vapor deposition (AP/LPCVD) to form -doped boron surface layers. Our). This layer has semi-metallic properties with a high resistivity in the range of 106 cm. The as-deposited -BCVD Delta-Doped Boron Surface Layers for Ultra-Shallow Junction Formation F. Sarubbi, L. K. Nanver

  13. The effect of boron doping on the thermal conductivity of zigzag carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Rezania, Hamed

    2015-11-01

    The temperature behavior of thermal conductivity of zigzag carbon nanotube (CNT) doped with boron atoms, as acceptor impurities, has been investigated in the context of tight binding model hamiltonian. A local energy term is added to the hamiltonian of the original clean system in order to obtain the effect of scattering of the electrons from impurities on the electronic spectrum. Green's function approach has been implemented to find the behavior of thermal conductivity of CNTs within linear response theory. Depending on the temperature regions, thermal conductivity shows two different behaviors. Thermal transport is found to be decreasing with dopant concentration at low temperatures. It is not the case of higher temperatures where thermal conductivity rises due to increase of boron concentration.

  14. Synthesis and properties of boron doped ZnO nanorods on silicon substrate by low-temperature hydrothermal reaction

    NASA Astrophysics Data System (ADS)

    Yu, Qi; Li, Liuan; Li, Hongdong; Gao, Shiyong; Sang, Dandan; Yuan, Jujun; Zhu, Pinwen

    2011-05-01

    Boron doped ZnO nanorods were fabricated by hydrothermal technique on silicon substrate covered with a ZnO seed layer. It is found that the concentration of boric acid in the reaction solution plays a key role in varying the morphology and properties of the products. The growth rate along the [0 0 0 1] orientation (average size in diameter) of the doped ZnO nanorods decreased (increased) with the increase of boric acid concentration. Based on the results of XRD, EDX and XPS, it is demonstrated that the boron dopants tend to occupy the octahedral interstice sites. The photoluminescence of the ZnO nanorods related to boron doping are investigated.

  15. Analytical and experimental studies of graphite-epoxy and boron-epoxy angle ply laminates in shear

    NASA Technical Reports Server (NTRS)

    Weller, T.

    1977-01-01

    The results of a comparison study between a test program on the inelastic response under inplane shear over a wide range of graphite-epoxy and boron-epoxy angle-ply laminates are reported. This investigation was aimed at evaluating the applicability and adequacy of these analyses to predict satisfactorily the responses of angle-ply laminates. It was observed that these analytical tools are inadequate for this purpose as they fail to predict with sufficient confidence the shape of response and in particular the strength values associated with a given laminate configuration. Consequently, they do not provide the sought-after information about failure mechanisms which trigger failure of a particular designed laminate.

  16. Plasma Synthesized Doped Boron Nanopowder for MgB2 Superconductors

    SciTech Connect

    James V. Marzik

    2012-03-26

    Under this program, a process to synthesize nano-sized doped boron powder by a plasma synthesis process was developed and scaled up from 20 gram batches at program start to over 200 grams by program end. Over 75 batches of boron nanopowder were made by RF plasma synthesis. Particle sizes were typically in the 20-200 nm range. The powder was synthesized by the reductive pyrolysis of BCl{sub 3} in hydrogen in an RF plasma. A wide range of process parameters were investigated including plasma power, torch geometry, gas flow rates, and process pressure. The powder-in-tube technique was used to make monofilament and multifilament superconducting wires. MgB{sub 2} wire made with Specialty Materials plasma synthesized boron nanopowder exhibited superconducting properties that significantly exceeded the program goals. Superconducting critical currents, J{sub c}, in excess of 10{sup 5} A cm{sup -2} at magnetic fields of 8 tesla were reproducibly achieved. The upper critical magnetic field in wires fabricated with program boron powder were H{sub c2}(0) = 37 tesla, demonstrating the potential of these materials for high field magnet applications. T{sub c} in carbon-doped MgB{sub 2} powder showed a systematic decrease with increasing carbon precursor gas flows, indicating the plasma synthesis process can give precise control over dopant concentrations. Synthesis rates increased by a factor of 400% over the course of the program, demonstrating the scalability of the powder synthesis process. The plasma synthesis equipment at Specialty Materials has successfully and reproducibly made high quality boron nanopowder for MgB{sub 2} superconductors. Research and development from this program enabled Specialty Materials to successfully scale up the powder synthesis process by a factor of ten and to double the size of its powder pilot plant. Thus far the program has been a technical success. It is anticipated that continued systematic development of plasma processing parameters, dopant chemistry and concentration, wire processing technology, and collection technology will lead to the commercialization of boron nanopowder as a precursor for MgB{sub 2} superconductors. Potential commercial applications include magnets for magnetic resonance imaging (MRI), fault current limiters, wind turbine generators.

  17. Boron- and Nitrogen-Doped Phenalenyls: Unexpected 2e/ and 4e/all-sites pi-pi Covalency and Genuine Pancake Double Bonding

    SciTech Connect

    Tian, Yong-Hui [Georgetown University; Huang, Jingsong [ORNL; Sumpter, Bobby G [ORNL

    2015-01-01

    Phenalenyl is an important neutral pi-radical due to its capability to form unconventional pancake pi-pi bonding interactions, whereas its analogues with graphitic boron (B) or nitrogen (N)-doping have been regarded as closed-shell systems and therefore received much less attention. By using high-level quantum chemistry calculations, we show that the B- and N-doped closed-shell phenalenyls unexpectedly form open-shell singlet pi-dimers with diradicaloid character featuring 2e/all-sites double pi-pi bonding. Moreover, by proper substitutions, the doped phenalenyl derivatives can be made open-shell species that form closed shell singlet pi-dimers bound by stronger 4e/all-sites double pi-pi bonding. The covalent pi-pi bonding overlap is distributed on all of the atomic sites giving robust and genuine pancake-shaped pi-dimers which, depending on the number of electrons available in the bonding interactions, are equally or more stable than the pi-dimers of the pristine phenalenyl.

  18. Effect of rapid thermal annealing on recombination centres in boron-doped Czochralski-grown silicon

    SciTech Connect

    Walter, D. C., E-mail: d.walter@isfh.de; Lim, B.; Bothe, K.; Schmidt, J. [Institute for Solar Energy Research Hamelin (ISFH), Am Ohrberg 1, 31860 Emmerthal (Germany); Voronkov, V. V.; Falster, R. [SunEdison, Via Nazionale 59, 39012 Merano (Italy)

    2014-01-27

    Rapid thermal annealing in a belt furnace results in a dramatic change of the recombination properties of boron-doped Czochralski silicon: (1) the lifetime degraded by applying a prolonged illumination at room temperature was significantly improved, (2) after subsequent dark recovery, the lifetime has a remarkably high value, and (3) the permanent recovery, by annealing at 185?°C under illumination, is enormously accelerated, and the finally achieved stable lifetime acquires a record value of 1.5 ms, as compared to 110??s after permanent recovery of not-annealed reference samples.

  19. Electron-phonon interaction via electronic and lattice Wannier functions: superconductivity in boron-doped diamond reexamined.

    PubMed

    Giustino, Feliciano; Yates, Jonathan R; Souza, Ivo; Cohen, Marvin L; Louie, Steven G

    2007-01-26

    We present a first-principles technique for investigating the electron-phonon interaction with millions of k points in the Brillouin zone, which exploits the spatial localization of electronic and lattice Wannier functions. We demonstrate the effectiveness of our technique by elucidating the phonon mechanism responsible for superconductivity in boron-doped diamond. Our calculated phonon self-energy and Eliashberg spectral function show that superconductivity cannot be explained without taking into account the finite-wave-vector Fourier components of the vibrational modes introduced by boron, as well as the breaking of the diamond crystal periodicity induced by doping. PMID:17358802

  20. Suggestions regarding thermal diffusivity measurements on pyrolytic graphite and pyrolytic boron nitride by the laser pulse method/sup 1/

    SciTech Connect

    He, G.H.; Di, Z.Q.; Dong, S.Q.; Wei, Z.; Zhang, X.Z.; Hanley, H.J.M.; Cezairliyan, A.

    1986-07-01

    The laser pulse method can be successfully applied to the measurement of thermal diffusivity of isotropic materials subject to some assumptions. For anisotropic materials, this method is applicable to the measurement of principal thermal diffusivity only on the condition that there is no difference in direction between the principal axis and that of the temperature gradient. After analyzing the heat conduction process in an anisotropic solid, it has been shown that large errors in the measurement of thermal diffusivity would exist if the direction of the principal axis deviates inconspicously from that of the temperature gradient. The experimental results of thermal diffusivity of highly oriented pyrolytic graphite (HOPG) samples with various deviation angles have been compared with the analytical results. The laser pulse method is not applicable to measurements on semitransparent pyrolytic boron nitride (PBN). We adopted a two-layer composite sample to measure the thermal diffusivity of PBN in the c direction and a particular graphite-PBN composite sample has been prepared which has a very low thermal resistance at the interface. The thermal diffusivity and thermal conductivity of PG (below 2300/sup 0/C) and PBN (below 1000/sup 0/C) are given.

  1. Increasing strengths of boron fiber and graphite fiber plastic composites. Final report May--Dec 1971

    Microsoft Academic Search

    G. J. Mills; W. M. Wochos; G. G. Brown

    1971-01-01

    Prestressing of boron\\/epoxy prepreg tape material yields composites with substantial improvements in both average tensile strength and standard deviation over that obtained with conventional prepreg to laminate processing. The process has a fundamental effect on the prepreg fiber strength properties by prebreaking the fibers at their weak sites, and these induced changes are then carried into the composite as a

  2. Theoretical studies of H 2 desorption processes in chemical vapor deposition of boron-doped silicon surfaces

    Microsoft Academic Search

    P. Jeffrey Hay; Randall C. Boehm; Joel D. Kress; Richard L. Martin

    1999-01-01

    The desorption of hydrogen in the chemical vapor deposition (CVD) of boron-doped silicon (100) surfaces is investigated using density functional theory and cluster models. The cluster models examine reactions of hydrogen atoms bound to adjacent B?Si surface sites that would arise during the decomposition of B2H6 and SiH4 on a B-doped polysilicon film that is being formed by CVD. Comparisons

  3. Bipolar doping of double-layer graphene vertical heterostructures with hydrogenated boron nitride.

    PubMed

    Liu, Zhun; Wang, Ru-Zhi; Liu, Li-Min; Lau, Woon-Ming; Yan, Hui

    2015-05-01

    Using first-principles calculations, we examined the bipolar doping of double-layer graphene vertical heterostructures, which are constructed by hydrogenated boron nitride (BN) sheets sandwiched into two parallel graphene monolayers. The built-in potential difference in hydrogenated BN breaks the interlayer symmetry, resulting in the p- and n-type doping of two graphene layers at 0.83 and -0.8 eV, respectively. By tuning the interlayer spacing between the graphene and hydrogenated BN, the interfacial dipole and screening charge distribution can be significantly affected, which produces large modulations in band alignments, doping levels and tunnel barriers. Furthermore, we present an analytical model to predicate the doping level as a function of the average interlayer spacing. With large interlayer spacings, the "pillow effect" (Pauli repulsion at the highly charge overlapped interface) is diminished and the calculated Dirac point shifts are in good accordance with our prediction models. Our investigations suggest that this double-layer graphene heterostructures constructed using two-dimensional Janus anisotropic materials offer exciting opportunities for developing novel nanoscale optoelectronic and electronic devices. PMID:25866036

  4. Simultaneous increase in electrical conductivity and Seebeck coefficient in highly boron-doped nanocrystalline Si.

    PubMed

    Neophytou, Neophytos; Zianni, Xanthippi; Kosina, Hans; Frabboni, Stefano; Lorenzi, Bruno; Narducci, Dario

    2013-05-24

    A large thermoelectric power factor in heavily boron-doped p-type nanograined Si with grain sizes ?30 nm and grain boundary regions of ?2 nm is reported. The reported power factor is ?5 times higher than in bulk Si. It originates from the surprising observation that for a specific range of carrier concentrations, the electrical conductivity and Seebeck coefficient increase simultaneously. The two essential ingredients for this observation are nanocrystallinity and extremely high boron doping levels. This experimental finding is interpreted within a theoretical model that considers both electron and phonon transport within the semiclassical Boltzmann approach. It is shown that transport takes place through two phases so that high conductivity is achieved in the grains, and high Seebeck coefficient by the grain boundaries. This together with the drastic reduction in the thermal conductivity due to boundary scattering could lead to a significant increase of the figure of merit ZT. This is one of the rare observations of a simultaneous increase in the electrical conductivity and Seebeck coefficient, resulting in enhanced thermoelectric power factor. PMID:23598565

  5. Simultaneous increase in electrical conductivity and Seebeck coefficient in highly boron-doped nanocrystalline Si

    NASA Astrophysics Data System (ADS)

    Neophytou, Neophytos; Zianni, Xanthippi; Kosina, Hans; Frabboni, Stefano; Lorenzi, Bruno; Narducci, Dario

    2013-05-01

    A large thermoelectric power factor in heavily boron-doped p-type nanograined Si with grain sizes ?30 nm and grain boundary regions of ?2 nm is reported. The reported power factor is ?5 times higher than in bulk Si. It originates from the surprising observation that for a specific range of carrier concentrations, the electrical conductivity and Seebeck coefficient increase simultaneously. The two essential ingredients for this observation are nanocrystallinity and extremely high boron doping levels. This experimental finding is interpreted within a theoretical model that considers both electron and phonon transport within the semiclassical Boltzmann approach. It is shown that transport takes place through two phases so that high conductivity is achieved in the grains, and high Seebeck coefficient by the grain boundaries. This together with the drastic reduction in the thermal conductivity due to boundary scattering could lead to a significant increase of the figure of merit ZT. This is one of the rare observations of a simultaneous increase in the electrical conductivity and Seebeck coefficient, resulting in enhanced thermoelectric power factor.

  6. Ab Initio Search for Global Minimum Structures of Pure and Boron Doped Silver Clusters.

    PubMed

    Jin, Yuanyuan; Tian, Yonghong; Kuang, Xiaoyu; Zhang, Chuanzhao; Lu, Cheng; Wang, Jingjing; Lv, Jian; Ding, Liping; Ju, Meng

    2015-06-25

    The global minimum structures of pure and boron doped silver clusters up to 16 atoms are determined through ab initio calculations and unbiased structure searching methods. The structural and electronic properties of neutral, anionic, and cationic AgnB (n ? 15) and AgnB2 (n ? 14) clusters are much distinct from those of the corresponding pure silver. Considering that Ag and B possess one and three valence electrons, respectively, both the single and the double boron-atom doped silver clusters with even number of valence electrons are more stable than those with odd number of electrons, a feature also observed in the pure silver clusters. We demonstrate that the species with a valence count of 8 and 14 appear to be magic numbers with enhanced stability irrespective of component or the charged state. A new putative global minimum structure of Ag13(-) cluster, with high symmetry of C2v, is unexpectedly observed as the ground state, which is lower in energy than the previous suggested bilayer structure. PMID:26046686

  7. Iron-boron pairing kinetics in illuminated p-type and in boron/phosphorus co-doped n-type silicon

    SciTech Connect

    Möller, Christian, E-mail: cmoeller@cismst.de [CiS Forschungsinstitut für Mikrosensorik und Photovoltaik GmbH, Konrad-Zuse-Str. 14, 99099 Erfurt (Germany); TU Ilmenau, Institut für Physik, Weimarer Str. 32, 98693 Ilmenau (Germany); Bartel, Til; Gibaja, Fabien [Calisolar GmbH, Magnusstraße 11, 12489 Berlin (Germany); Lauer, Kevin [CiS Forschungsinstitut für Mikrosensorik und Photovoltaik GmbH, Konrad-Zuse-Str. 14, 99099 Erfurt (Germany)

    2014-07-14

    Iron-boron (FeB) pairing is observed in the n-type region of a boron and phosphorus co-doped silicon sample which is unexpected from the FeB pair model of Kimerling and Benton. To explain the experimental data, the existing FeB pair model is extended by taking into account the electronic capture and emission rates at the interstitial iron (Fe{sub i}) trap level as a function of the charge carrier densities. According to this model, the charge state of the Fe{sub i} may be charged in n-type making FeB association possible. Further, FeB pair formation during illumination in p-type silicon is investigated. This permits the determination of the charge carrier density dependent FeB dissociation rate and in consequence allows to determine the acceptor concentration in the co-doped n-type silicon by lifetime measurement.

  8. Boron and nitrogen co-doped titania with enhanced visible-light photocatalytic activity for hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Li, Yuexiang; Ma, Gangfeng; Peng, Shaoqin; Lu, Gongxuan; Li, Shuben

    2008-08-01

    A visible-light boron and nitrogen co-doped titania (B-N-TiO 2) photocatalyst was prepared by sol-gel method with titanium tetra- n-butyl oxide, urea and boric acid as precursors. The photocatalyst was characterized by Fourier Transform Infrared (FT-IR), UV-vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), BET and electrochemistry method. Photocatalytic activity for hydrogen production over platinized B-N-TiO 2 under visible-light ( ? ? 420 nm) irradiation was investigated. In nitrogen doped titania (N-TiO 2) N sbnd Ti sbnd O bond is formed, which extends the absorption edge to the visible-light region. A part of doping boron enters into titania lattice and most of the boron exists at the surface of the catalyst. The crystallite size of B-N-TiO 2 decreases compared to N-TiO 2, while its photocurrent and the surface hydroxyl group increase. Furthermore, doping boron could act as shallow traps for photoinduced electrons to prolong the life of the electrons and holes. Therefore, the visible-light activity of B-N-iO 2 increases greatly compared with that of N-TiO 2.

  9. Journal of Crystal Growth 241 (2002) 4550 Boron doping of silicon layers grown by liquid phase epitaxy

    E-print Network

    2002-01-01

    ; B1. Boron; B1. Silicon; B3. Solar cells 1. Introduction Thin film silicon solar cells film solar cell applications as it allows the growth of a back surface field and a lightly doped bulk a reduced consumption of silicon compared with wafer based cells. Thin film layers have been grown

  10. Anodic oxidation of ketoprofen—An anti-inflammatory drug using boron doped diamond and platinum electrodes

    Microsoft Academic Search

    M. Murugananthan; S. S. Latha; G. Bhaskar Raju; S. Yoshihara

    2010-01-01

    The mineralization of ketoprofen (KP) by anodic oxidation was studied by employing boron doped diamond (BDD) and Pt electrodes. The redox behavior of KP molecule, fouling of electrodes, generation of oxygen and active chlorine species were studied by cyclic voltammetry. The effect of electrolyte, pH of aqueous medium and applied current density on the mineralization behavior of KP was also

  11. Chemical vapor deposition of epitaxial silicon-germanium from silane and germane. 2: In situ boron, arsenic, and phosphorus doping

    SciTech Connect

    Jang, S.M.; Liao, K.; Reif, R. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Microsystems Technology Labs.

    1995-10-01

    The authors have studied in situ boron, arsenic, and phosphorus doping of epitaxial silicon and Si{sub 1{minus}x}Ge{sub x} layers grown on silicon substrates at 620 C and at very low pressure ({approximately}7 mTorr) with silane, germane, and diborane, and arsine and phosphine diluted in silane as gas sources. Structural quality was characterized by cross-sectional transmission electron microscopy and the germanium and dopant depth profiles were probed by secondary ion mass spectrometry. The results confirmed tat strained Si/Si{sub 1{minus}x}Ge{sub x}/Si heterostructures with 13 atom percent germanium doped to 2{times}10{sup 20} boron atom/cm{sup 3} and 5{times}10{sup 19} arsenic atom/cm{sup 3} have been achieved. Phosphorus doped Si{sub 1{minus}x}Ge{sub x}/Si multilayer structures with highly perfect surface Si{sub 1{minus}x}Ge{sub x} and silicon layers were also obtained. The addition of arsine and phosphine were found to severely degrade the growth rates of both silicon and Si{sub 1{minus}x}Ge{sub x} layers. Germanium incorporation appeared to enhance the n-type doping process by compensating the depressed growth rate resulted for surface poisoning and by improving the abruptness of dopant profiles. However, deposition of Si{sub 1{minus}x}Ge{sub x} was not greatly affected by boron doping.

  12. Electronic and physico-chemical properties of nanometric boron delta-doped diamond structures

    NASA Astrophysics Data System (ADS)

    Chicot, G.; Fiori, A.; Volpe, P. N.; Tran Thi, T. N.; Gerbedoen, J. C.; Bousquet, J.; Alegre, M. P.; Piñero, J. C.; Araújo, D.; Jomard, F.; Soltani, A.; De Jaeger, J. C.; Morse, J.; Härtwig, J.; Tranchant, N.; Mer-Calfati, C.; Arnault, J. C.; Delahaye, J.; Grenet, T.; Eon, D.; Omnès, F.; Pernot, J.; Bustarret, E.

    2014-08-01

    Heavily boron doped diamond epilayers with thicknesses ranging from 40 to less than 2 nm and buried between nominally undoped thicker layers have been grown in two different reactors. Two types of [100]-oriented single crystal diamond substrates were used after being characterized by X-ray white beam topography. The chemical composition and thickness of these so-called delta-doped structures have been studied by secondary ion mass spectrometry, transmission electron microscopy, and spectroscopic ellipsometry. Temperature-dependent Hall effect and four probe resistivity measurements have been performed on mesa-patterned Hall bars. The temperature dependence of the hole sheet carrier density and mobility has been investigated over a broad temperature range (6 K < T < 450 K). Depending on the sample, metallic or non-metallic behavior was observed. A hopping conduction mechanism with an anomalous hopping exponent was detected in the non-metallic samples. All metallic delta-doped layers exhibited the same mobility value, around 3.6 ± 0.8 cm2/Vs, independently of the layer thickness and the substrate type. Comparison with previously published data and theoretical calculations showed that scattering by ionized impurities explained only partially this low common value. None of the delta-layers showed any sign of confinement-induced mobility enhancement, even for thicknesses lower than 2 nm.

  13. Electronic and physico-chemical properties of nanometric boron delta-doped diamond structures

    SciTech Connect

    Chicot, G., E-mail: gauthier.chicot@neel.cnrs.fr; Fiori, A.; Tran Thi, T. N.; Bousquet, J.; Delahaye, J.; Grenet, T.; Eon, D.; Omnès, F.; Bustarret, E. [Université Grenoble Alpes, Institut NEEL, 38042 Grenoble (France); CNRS, Institut NEEL, 38042 Grenoble (France); Volpe, P. N.; Tranchant, N.; Mer-Calfati, C.; Arnault, J. C. [CEA, LIST, Diamond Sensors Laboratory, 91191 Gif-sur-Yvette (France); Gerbedoen, J. C.; Soltani, A.; De Jaeger, J. C. [IEMN, UMR-CNRS 8520, Avenue Poincaré, Université de Lille 1, 59652 Villeneuve d'Ascq (France); Alegre, M. P.; Piñero, J. C.; Araújo, D. [Dpto Ciencia de los Materiales, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain); Jomard, F. [Groupe d'Étude de la Matière Condensée (GEMaC), UMR 8635 du CNRS, UVSQ, 45 Avenue des États-Unis, 78035 Versailles Cedex (France); and others

    2014-08-28

    Heavily boron doped diamond epilayers with thicknesses ranging from 40 to less than 2?nm and buried between nominally undoped thicker layers have been grown in two different reactors. Two types of [100]-oriented single crystal diamond substrates were used after being characterized by X-ray white beam topography. The chemical composition and thickness of these so-called delta-doped structures have been studied by secondary ion mass spectrometry, transmission electron microscopy, and spectroscopic ellipsometry. Temperature-dependent Hall effect and four probe resistivity measurements have been performed on mesa-patterned Hall bars. The temperature dependence of the hole sheet carrier density and mobility has been investigated over a broad temperature range (6?K?doped layers exhibited the same mobility value, around 3.6?±?0.8?cm{sup 2}/Vs, independently of the layer thickness and the substrate type. Comparison with previously published data and theoretical calculations showed that scattering by ionized impurities explained only partially this low common value. None of the delta-layers showed any sign of confinement-induced mobility enhancement, even for thicknesses lower than 2?nm.

  14. Investigation on cubic boron nitride crystals doped with Si by high temperature thermal diffusion

    NASA Astrophysics Data System (ADS)

    Li, Xinlu; Feng, Shuang; Liu, Xiuhuan; Hou, Lixin; Gao, Yanjun; Wang, Qi; Liu, Nian; Zhang, Hai; Chen, Zhanguo; Zheng, Jie; Jia, Gang

    2014-07-01

    The method of high temperature thermal diffusion was successfully applied for doping Si impurities into cubic boron nitride (cBN) crystals. X-ray photoelectron spectra (XPS) and the current-voltage (I-V) characteristics at different temperatures were respectively used for analyzing the chemical states and the activation energy of Si impurity in cBN. According to the XPS results, Si impurities mainly replace B atoms bonding with the adjacent N atoms and become donors in cBN. Without surface cleaning, there are a lot of C and O contaminations on the surface of cBN, so a small quantity of C-Si and Si-N-O bonds also exist at the surface of cBN. Most Si impurities distribute in the shallow layer underneath the surface of cBN. Based on the electric measurement, Si impurities in cBN usually have the activation energy beyond 0.4 eV, and they can only be slightly ionized at room temperature, therefore the resistivity of Si-doped cBN is still high, and the space charge limited current becomes the main conductive mechanism in cBN. However, the conductivity of Si-doped cBN can rapidly increase with the temperature. In addition, the activation energy and the concentration of Si impurity in cBN can be affected by the temperature and the time of thermal diffusion, which needs to be verified further.

  15. Boron-doped, carbon-coated SnO2/graphene nanosheets for enhanced lithium storage.

    PubMed

    Liu, Yuxin; Liu, Ping; Wu, Dongqing; Huang, Yanshan; Tang, Yanping; Su, Yuezeng; Zhang, Fan; Feng, Xinliang

    2015-03-27

    Heteroatom doping is an effective method to adjust the electrochemical behavior of carbonaceous materials. In this work, boron-doped, carbon-coated SnO2 /graphene hybrids (BCTGs) were fabricated by hydrothermal carbonization of sucrose in the presence of SnO2/graphene nanosheets and phenylboronic acid or boric acid as dopant source and subsequent thermal treatment. Owing to their unique 2D core-shell architecture and B-doped carbon shells, BCTGs have enhanced conductivity and extra active sites for lithium storage. With phenylboronic acid as B source, the resulting hybrid shows outstanding electrochemical performance as the anode in lithium-ion batteries with a highly stable capacity of 1165?mA?h?g(-1) at 0.1?A?g(-1) after 360 cycles and an excellent rate capability of 600?mA?h?g(-1) at 3.2?A?g(-1), and thus outperforms most of the previously reported SnO2-based anode materials. PMID:25694249

  16. A computational study on the hydrogen adsorption capacity of various lithium-doped boron hydrides.

    PubMed

    Pan, Sudip; Giri, Santanab; Chattaraj, Pratim K

    2012-02-01

    An aromatic boron hydride B(3)H(3)(2-) and its various Li/Li(+) doped isomers have been studied at the B3LYP/6-311+G(d) and M06/6-311+G(d) levels of theory to assess their hydrogen storage potential. Different types of interaction energies, reaction enthalpies and reaction electrophilicities associated with the hydrogen adsorption process suggest that B(3)H(3)(2-) itself and some of its Li-decorated analogues may turn out to be effective hydrogen storage material. Nucleus independent chemical shift and conceptual density functional theory based reactivity descriptors lend additional support. The temperature-pressure phase diagram identifies the temperature-pressure zone where the reaction Gibbs free energy for the hydrogen adsorption is negative making it a thermodynamically feasible process. PMID:22121031

  17. Pulsed-laser crystallized highly conductive boron-doped microcrystalline silicon

    SciTech Connect

    Nebel, C.E.; Dahlheimer, B.; Karrer, U.; Stutzmann, M.

    1997-07-01

    The preparation of seed lattices, using three interfering beams (TIB) from a pulsed Nd:YAG laser in a-Si layers of 100 to 400 nm thickness is introduced and applied for seeded laser or thermally induced crystallization of a-Si on Corning 7059 glass. The structural and electronic properties of the {micro}c-Si layers are investigated by X-ray, electron- and atomic force microscopy, Hall and conductivity measurements. In highly boron-doped {micro}c-Si, grains up to 1.3 {micro}m in diameter are detected, giving rise to conductivities of {approx}2,000 S/cm and hole mobilities of {approx}10 cm{sup 2}/Vs.

  18. Neutral and charged boron-doped fullerenes for CO2 adsorption

    PubMed Central

    de Silva, Suchitra W; Du, Aijun; Senadeera, Wijitha

    2014-01-01

    Summary Recently, the capture and storage of CO2 have attracted research interest as a strategy to reduce the global emissions of greenhouse gases. It is crucial to find suitable materials to achieve an efficient CO2 capture. Here we report our study of CO2 adsorption on boron-doped C60 fullerene in the neutral state and in the 1e ?-charged state. We use first principle density functional calculations to simulate the CO2 adsorption. The results show that CO2 can form weak interactions with the BC59 cage in its neutral state and the interactions can be enhanced significantly by introducing an extra electron to the system. PMID:24778968

  19. Synergistic effect on the visible light activity of Ti3+ doped TiO2 nanorods/boron doped graphene composite

    NASA Astrophysics Data System (ADS)

    Xing, Mingyang; Li, Xiao; Zhang, Jinlong

    2014-06-01

    TiO2/graphene (TiO2-x/GR) composites, which are Ti3+ self-doped TiO2 nanorods decorated on boron doped graphene sheets, were synthesized via a simple one-step hydrothermal method using low-cost NaBH4 as both a reducing agent and a boron dopant on graphene. The resulting TiO2 nanorods were about 200 nm in length with exposed (100) and (010) facets. The samples were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, X-band electron paramagnetic resonance (EPR), X-ray photoelectron spectra (XPS), transmission electron microscope (TEM), Raman, and Fourier-transform infrared spectroscopy (FTIR). The XRD results suggest that the prepared samples have an anatase crystalline structure. All of the composites tested exhibited improved photocatalytic activities as measured by the degradation of methylene blue and phenol under visible light irradiation. This improvement was attributed to the synergistic effect of Ti3+ self-doping on TiO2 nanorods and boron doping on graphene.

  20. Synergistic effect on the visible light activity of Ti3+ doped TiO2 nanorods/boron doped graphene composite

    PubMed Central

    Xing, Mingyang; Li, Xiao; Zhang, Jinlong

    2014-01-01

    TiO2/graphene (TiO2-x/GR) composites, which are Ti3+ self-doped TiO2 nanorods decorated on boron doped graphene sheets, were synthesized via a simple one-step hydrothermal method using low-cost NaBH4 as both a reducing agent and a boron dopant on graphene. The resulting TiO2 nanorods were about 200?nm in length with exposed (100) and (010) facets. The samples were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, X-band electron paramagnetic resonance (EPR), X-ray photoelectron spectra (XPS), transmission electron microscope (TEM), Raman, and Fourier-transform infrared spectroscopy (FTIR). The XRD results suggest that the prepared samples have an anatase crystalline structure. All of the composites tested exhibited improved photocatalytic activities as measured by the degradation of methylene blue and phenol under visible light irradiation. This improvement was attributed to the synergistic effect of Ti3+ self-doping on TiO2 nanorods and boron doping on graphene. PMID:24974890

  1. Surface chemistry of boron-doped SiO{sub 2} CVD: Enhanced uptake of tetraethyl orthosilicate by hydroxyl groups bonded to boron

    SciTech Connect

    Bartram, M.E.; Moffat, H.K.

    1993-12-31

    Insight into how dopants can enhance deposition rates has been obtained by comparing reactivities of tetraethyl orthosilicate (TEOS, Si(OCH{sub 2}CH{sub 3}){sub 4}) with silanol and boranol groups on SiO{sub 2}. This comparison is relevant for boron-doped SiO{sub 2} film growth from TEOS and trimethyl borate (TMB, B(OCH{sub 3}){sub 3}) sources since boranols and silanols are expected to be present on surface during the (CVD). A silica substrate having coadsorbed deuterated silanols (SIOD) and boranols (BOD) was reacted with TEOS in a cold-wall reactor in the mTorr pressure regime at 1000K. Reactions were followed with Fourier transform infrared spectroscopy. Use of deuterated hydroxyls allowed consumption of hydroxyls by TEOS chemisorption to be distinguished from concurrent formation of SIOH and BOH that results from TEOS decomposition. It was found that TEOS reacts with BOD at twice the rate observed for SIOD demonstrating that hydroxyl groups bonded to boron increase the rate of TEOS chemisorption. Surface ethoxy groups produced by chemisorption of TEOS decompose at a slower rate in the presence of TMB decomposition products. Possible dependencies on reactor geometries and other deposition conditions may determine which of these two competing effects will control deposition rates. This may explain (in part) why the rate enhancement effect is not always observed in boron-doped SiO{sub 2} CVD processes.

  2. Study of plasma enhanced chemical vapor deposition of boron-doped hydrogenated amorphous silicon thin films and the application to p-channel thin film transistor 

    E-print Network

    Nominanda, Helinda

    2004-01-01

    The material and process characteristics of boron doped hydrogenated amorphous silicon (a-Si:H) thin film deposited by plasma enhanced chemical vapor deposition technique (PECVD) have been studied. The goal is to apply the high quality films...

  3. Study of plasma enhanced chemical vapor deposition of boron-doped hydrogenated amorphous silicon thin films and the application to p-channel thin film transistor

    E-print Network

    Nominanda, Helinda

    2004-01-01

    The material and process characteristics of boron doped hydrogenated amorphous silicon (a-Si:H) thin film deposited by plasma enhanced chemical vapor deposition technique (PECVD) have been studied. The goal is to apply the high quality films...

  4. Synthesis and characterization of aluminum–boron co-doped ZnO nanostructures

    SciTech Connect

    Kumar, Vinod, E-mail: vinod.phy@gmail.com [Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India) [Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Department of Physics, Gurukula Kangri University, Haridwar 249404 (India); Singh, R.G. [Department of Electronic Science, Maharaja Agrasen College, University of Delhi 110096 (India)] [Department of Electronic Science, Maharaja Agrasen College, University of Delhi 110096 (India); Singh, Neetu; Kapoor, Avinashi [Department of Electronic Science, University of Delhi South Campus, New Delhi 110021 (India)] [Department of Electronic Science, University of Delhi South Campus, New Delhi 110021 (India); Mehra, R.M. [School of Engineering and Technology, Sharda University, Greater Noida 201306 (India)] [School of Engineering and Technology, Sharda University, Greater Noida 201306 (India); Purohit, L.P. [Department of Physics, Gurukula Kangri University, Haridwar 249404 (India)] [Department of Physics, Gurukula Kangri University, Haridwar 249404 (India)

    2013-02-15

    Graphical abstract: In this paper, we have reported the development of aluminum boron co-doped ZnO (AZB) nanostructures deposited by sol–gel method using spin coating technique. The structure of AZB nanostructure films has been found to exhibit the hexagonal wurtzite structure. The shape of nanostructures has been changed from seed structure to tetra-pods, tetra-pods to nanorods and finally nanorods to nanofiber with variation in Al concentration. The structural, electrical and optical properties of AZB nanostructures are tuned with shape and size of the nanostructures. The effect of Al concentration on the resistivity (?), carrier concentration (n) and mobility (?) of nanostructure films is shown in graph below. A minimum resistivity of 6.8 × 10{sup ?4} ? cm is obtained in AZB films at doping concentration of B 0.6 at.% and Al 0.4 at.% with a sheet resistance of 24 ?/? and transmittance of ?88% for nanorods structure. These nanostructures could be applicable for a various nano-regime devices such as photovolatics, gas sensing and field emission device. Display Omitted Highlights: ? Synthesis of Al and B co-doped ZnO (AZB) nanostructures. ? Minimum resistivity (?) of 6.8 × 10{sup ?4} ? cm in AZB films. ? Minimum sheet resistance (R{sub s}) 24 ?/? in nanorods (NRs). ? Maximum transmittance ?88% in NRs. ? Application in nano-electronic devices. -- Abstract: In this paper, we have reported the development of aluminum boron co-doped ZnO (AZB) nanostructures deposited by sol–gel method using spin coating technique. The structure of AZB nanostructure films has been found to exhibit the hexagonal wurtzite structure. The shape of AZB nanostructures has changed from seed structure to tetra-pods, tetra-pods to nanorods and finally to nanofibers with increase in aluminum concentration. The structural, electrical and optical properties of AZB films are tuned with shape and size of the nanostructures. These AZB nanostructures could be applicable for various nano-regime devices such as photovoltaic cells, gas sensors and field emission devices.

  5. Semiconducting properties of zinc-doped cubic boron nitride thin films

    SciTech Connect

    Nose, K.; Yoshida, T. [Department of Materials Engineering, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2007-09-15

    We have examined the electronic properties of zinc-doped cubic boron nitride (cBN) thin films prepared by sputter deposition. The electric conductivity of films deposited in pure Ar increased as the concentration of zinc dopant increased, and hole conduction was identified by the measurement of thermoelectric currents. It was also found that the conductivity increment in such films was accompanied by a linear increase in the B/(B+N) ratio. At the same time, no modification of the composition and the conductivity by incorporated zinc was observed when film growth took place in presence of nitrogen gas. The effect of the excess boron on the conductivity emerged only when films show semi-insulating behavior. These results suggest that Zn substitution for nitrogen causes high electric conductivity of cBN. The electric contact between Ti electrode and semiconducting cBN was examined by the transfer length method, and Ohmic conduction was observed in the Ti/cBN contact. The specific contact resistance was affected by the specific resistance of cBN films, and it was reduced from 10{sup 5} to 100 {omega} cm{sup 2} by increasing the concentration of incorporated Zn.

  6. Molecular beam epitaxial growth of Si on heavily boron-doped Si(111) surface: From initial stages to the growth of Si polytypes

    Microsoft Academic Search

    Andreas Fissel; Jan Krügener; Eberhard Bugiel; Tammo Block; Hans Jörg Osten

    2008-01-01

    Epitaxial growth of silicon on heavily boron-doped Si(111) surface was investigated. In our experiments, we found a new growth mode in the very initial stage for boron-coverage below 0.5 monolayer (ML) likely associated with defect-induced nucleation of Si islands. The initially stage of growth on boron-covered Si(111) could be interpreted by a quasi van der Waals like epitaxy, where Si

  7. Friction and wear performance of boron doped, undoped microcrystalline and fine grained composite diamond films

    NASA Astrophysics Data System (ADS)

    Wang, Xinchang; Wang, Liang; Shen, Bin; Sun, Fanghong

    2015-01-01

    Chemical vapor deposition (CVD) diamond films have attracted more attentions due to their excellent mechanical properties. Whereas as-fabricated traditional diamond films in the previous studies don't have enough adhesion or surface smoothness, which seriously impact their friction and wear performance, and thus limit their applications under extremely harsh conditions. A boron doped, undoped microcrystalline and fine grained composite diamond (BD-UM-FGCD) film is fabricated by a three-step method adopting hot filament CVD (HFCVD) method in the present study, presenting outstanding comprehensive performance, including the good adhesion between the substrate and the underlying boron doped diamond (BDD) layer, the extremely high hardness of the middle undoped microcrystalline diamond (UMCD) layer, as well as the low surface roughness and favorable polished convenience of the surface fine grained diamond (FGD) layer. The friction and wear behavior of this composite film sliding against low-carbon steel and silicon nitride balls are studied on a ball-on-plate rotational friction tester. Besides, its wear rate is further evaluated under a severer condition using an inner-hole polishing apparatus, with low-carbon steel wire as the counterpart. The test results show that the BD-UM-FGCD film performs very small friction coefficient and great friction behavior owing to its high surface smoothness, and meanwhile it also has excellent wear resistance because of the relatively high hardness of the surface FGD film and the extremely high hardness of the middle UMCD film. Moreover, under the industrial conditions for producing low-carbon steel wires, this composite film can sufficiently prolong the working lifetime of the drawing dies and improve their application effects. This research develops a novel composite diamond films owning great comprehensive properties, which have great potentials as protecting coatings on working surfaces of the wear-resistant and anti-frictional components.

  8. Homoepitaxial Boron Doped Diamond Anvils as Heating Elements in a Diamond Anvil Cell

    NASA Astrophysics Data System (ADS)

    Montgomery, Jeffrey; Samudrala, Gopi; Smith, Spencer; Tsoi, Georgiy; Vohra, Yogesh; Weir, Samuel

    2013-03-01

    Recent advances in designer-diamond technology have allowed for the use of electrically and thermally conducting homoepitaxially-grown layers of boron-doped diamond (grown at 1200 °C with a 2% mixture of CH4 in H, resulting in extremely high doping levels ~ 1020/cm3) to be used as heating elements in a diamond anvil cell (DAC). These diamonds allow for precise control of the temperature inside of the diamond anvil itself, particularly when coupled with a cryostat. Furthermore, the unmatched thermally conducting nature of diamond ensures that no significant lateral gradient in temperature occurs across the culet area. Since a thermocouple can easily be attached anywhere on the diamond surface, we can also measure diamond temperatures directly. With two such heaters, one can raise sample temperatures uniformly, or with any desired gradient along the pressure axis while preserving optical access. In our continuing set of benchmark experiments, we use two newly created matching heater anvils with 500 ?m culets to analyze the various fluorescence emission lines of ruby microspheres, which show more complicated behavior than traditional ruby chips. We also report on the temperature dependence of the high-pressure Raman modes of paracetamol (C8H9NO2) up to 20 GPa.

  9. Exploratory study of the new B-doped diamond heater at high pressure and temperature and its application to in situ XRD experiments on hydrous Mg-silicate melt

    Microsoft Academic Search

    Akihiro Yamada; Tetsuo Irifune; Hitoshi Sumiya; Yuji Higo; Toru Inoue; Ken-Ichi Funakoshi

    2008-01-01

    We demonstrate the successful application of a new heating material, B-doped graphite (boron 10 wt%), to 23 GPa and 2000 °C. The heater resistance increases significantly at temperatures greater than 1200–1400 °C, similar to the diamond transition observed for a pure graphite heater. However, we find that the B-doped graphite furnace can be used at temperatures and pressures higher than that of diamond stability

  10. A first principles study of pristine and Al-doped boron nitride nanotubes interacting with platinum-based anticancer drugs

    NASA Astrophysics Data System (ADS)

    Shakerzadeh, Ehsan; Noorizadeh, Siamak

    2014-03-01

    Interaction of cis-platin and neda-platin, two conventional platinum-based anticancer drugs, with pristine [8,8] and Al-doped [8,0] boron nitride nanotubes (BNNTs) are investigated using the density functional theory (DFT) method. The obtained results indicate that cis-platin and neda-platin weakly interact with pristine zig zag or armchair BNNTs with a little dependency on the adsorbing positions; while both cis-platin and neda-platin are preferentially adsorbed onto the Al atom of the Al-doped BNNT with considerable adsorption energies. Therefore the Al-doped-BNNT might be an efficient carrier for delivery of these drugs in nanomedicine domain. The electronic structures of the stable configurations are also investigated through both DOS and PDOS spectra. The obtained results introduce the Al-doped-BNNT as an efficient carrier for delivery of cis-platin and neda-platin in nanomedicine domain.

  11. Analysis of laser doping of silicon using different boron dopant sources

    NASA Astrophysics Data System (ADS)

    Prathap, P.; Bartringer, J.; Slaoui, A.

    2014-05-01

    Implementation of selective emitter that decouples the requirements for front doping and metallization leads to improve the efficiency of crystalline silicon solar cells. Formation of such an efficient selective emitter using a laser beam with a suitable wavelength is an attractive method. The present work focuses on the analysis of laser doping of boron using different finite sources such as borosilicate glass (BSG) deposited by PECVD, spin-on solution and BCl3 gas source. KrF excimer laser (248 nm) was used for the selective doping. The surface dopant concentration and depth, as measured using SIMS, were controlled by variation of the laser fluence, pulse number and dopant source thickness. Depending on the type of BSG source, sheet resistance close to 20 ?/sq was achieved at the laser fluences in the range, 2.5-5 J/cm2. The PECVD-BSG layers with a relatively higher thickness resulted in a lower sheet resistance of 20 ?/sq with a junction of depth of ?1 ?m at a moderate laser fluence of 2.5 J/cm2. In the case of BSG deposited by spin-on source, a deeper junction of depth of ?2.7 ?m with a plateau profile of 1 ?m was formed at a laser fluence of 3.1 J/cm2 that resulted in a lower sheet resistance of ?31 ?/sq. Redistribution of the dopant with pulse repetition was observed for the BSG deposited by BCl3 gas source. Pulse repetition at relatively lower laser fluences (>threshold energy) resulted in the best electrical results in combination with a limited laser induced damage in the silicon crystal. Also, multiple laser annealing resulted in redistribution of the dopant profiles in terms of enhanced junction depth.

  12. Enhanced photocatalytic performance of boron doped Bi?WO? nanosheets under simulated solar light irradiation.

    PubMed

    Fu, Yu; Chang, Chun; Chen, Peng; Chu, Xiaolong; Zhu, Lingyan

    2013-06-15

    Bi?WO6 doped with different amounts of boron atoms (0.1, 0.5, 1.0, 5.0 and 10% B) were synthesized using hydrothermal method and their photocatalytic activities to degrade rhodamine B (RhB) under simulated solar light was investigated. The successful incorporation of B atoms in Bi?WO? was proved by FT-IR, Raman spectra and XPS. Doping with B could affect the pore structure and volume. 0.5% B/Bi?WO? displayed more mesopores with higher total pore volume than pure Bi?W?; while the pores of 10% B/Bi?WO? mainly distributed in microporous range with much less total pore volume. As a result, 0.5% B/Bi?WO? displayed stronger adsorption capacity to RhB, favoring the photodegradation. In addition, the doped B atoms could act as electron traps and facilitate the separation of photogenerated electron-hole pairs due to its electron deficient and oxytropic characteristics. 0.5% B/Bi?WO? displayed the highest photocatalytic activity under simulated solar light with rate constant (kobs) 8.8 times of that using pure Bi?WO?. Its photoactivity was affected by solution pH and the optimum was achieved at pH 7. At this condition, around 100% of RhB (10(-5)mol/L) was degraded in 180 min. The photogenerated holes were the main active species responsible for the photodegradation of RhB by B/Bi?WO?. PMID:23618657

  13. Hard magnetic property enhancement of Co7Hf-based ribbons by boron doping

    NASA Astrophysics Data System (ADS)

    Chang, H. W.; Liao, M. C.; Shih, C. W.; Chang, W. C.; Yang, C. C.; Hsiao, C. H.; Ouyang, H.

    2014-11-01

    Hard magnetic property enhancement of melt spun Co88Hf12 ribbons by boron doping is demonstrated. B-doping could not only remarkably enhance the magnetic properties from energy product ((BH)max) of 2.6 MGOe and intrinsic coercivity (iHc) of 1.5 kOe for B-free Co88Hf12 ribbons to (BH)max = 7.7 MGOe and iHc = 3.1 kOe for Co85Hf12B3 ribbons but also improve the Curie temperature (TC) of 7:1 phase. The (BH)max value achieved in Co85Hf12B3 ribbons is the highest in Co-Hf alloy ribbons ever reported, which is about 15% higher than that of Co11Hf2B ribbons spun at 16 m/s [M. A. McGuire, O. Rios, N. J. Ghimire, and M. Koehler, Appl. Phys. Lett. 101, 202401 (2012)]. The structural analysis confirms that B enters the orthorhombic Co7Hf (7:1) crystal structure as interstitial atoms, forming Co7HfBx, in the as-spun state. Yet B may diffuse out from the 7:1 phase after post-annealing, leading to the reduction of Curie temperature and the magnetic properties. The uniformly refined microstructure with B-doping results in high remanence (Br) and improves the squareness of demagnetization curve. The formation of interstitial-atom-modified Co7HfBx phase and the microstructure refinement are the main reasons to give rise to the enhancement of hard magnetic properties in the B-containing Co7Hf-based ribbons.

  14. Elemental boron-doped p(+)-SiGe layers grown by molecular beam epitaxy for infrared detector applications

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; George, T.; Jones, E. W.; Ksendzov, A.; Huberman, M. L.

    1992-01-01

    SiGe/Si heterojunction internal photoemission (HIP) detectors have been fabricated utilizing molecular beam epitaxy of p(+)-SiGe layers on p(-)-Si substrates. Elemental boron from a high-temperature effusion cell was used as the dopant source during MBE growth, and high doping concentrations have been achieved. Strong infrared absorption, mainly by free-carrier absorption, was observed for the degenerately doped SiGe layers. The use of elemental boron as the dopant source allows a low MBE growth temperature, resulting in improved crystalline quality and smooth surface morphology of the Si(0.7)Ge(0.3) layers. Nearly ideal thermionic emission dark current characteristics have been obtained. Photoresponse of the HIP detectors in the long-wavelength infrared regime has been demonstrated.

  15. Determination of barrier height of boron doped polycrystalline diamond thin film Schottky diodes using a capacitance-voltage technique

    SciTech Connect

    Zhao, G.; Charlson, E.; Stacy, T. [Univ. of Missouri, Columbia, MO (United States)] [and others

    1995-12-31

    Distinctive frequency dependent capacitance-voltage (C-V) characteristics of boron-doped chemical vapor deposited (CVD) diamond thin film Schottky diodes were observed. The results exhibited not only small signal differential capacitance dependence on both the reverse bias voltage and test frequency, but also linear inverse squared capacitance-voltage characteristics at all test frequencies, ranging from 1 kHz to 1 MKz. The Schottky barrier heights of both Al- and Au-hot filament CVD diamond Schottky diodes were determined to be 1.04 and 1.09 eV, respectively. An effective carrier concentration in the range of 0.5 to 1.5 x 10{sup 17}cm {sup {minus}3} was estimated. The distinct C-V characteristics obtained in this study are attributed to careful surface cleaning and the use of moderate boron doped diamond thin films.

  16. Influence of boron doping and hydrogen passivation on recombination of photoexcited charge carriers in silicon nanocrystal/SiC multilayers

    NASA Astrophysics Data System (ADS)

    Ko?ínek, M.; Schnabel, M.; Canino, M.; Kozák, M.; Trojánek, F.; Salava, J.; Löper, P.; Janz, S.; Summonte, C.; Malý, P.

    2013-08-01

    The influence of boron (B)-doping and remote plasma hydrogen passivation on the photoexcited charge carrier recombination in silicon nanocrystal/SiC multilayers was investigated in detail. The samples were prepared by high temperature annealing of amorphous (intrinsic and B-doped) Si1-xCx/SiC superlattices. The photoluminescence (PL) intensity of samples with B-doped silicon rich carbide layers was found to be up to two orders of magnitude larger and spectrally red shifted in comparison with that of the other samples. Hydrogen passivation leads to an additional increase in PL intensities. The PL decay can be described well by a mono-exponential function with a characteristic decay time of a few microseconds. This behavior agrees well with the picture of localized PL centers (surface states) together with the passivation of non-radiative defects by boron. The samples with B-doped SiC layers exhibit an additional PL band in the green spectral region that is quenched by hydrogen passivation. Its origin is attributed to defects due to suppression of crystallization of amorphous SiC layers as a result of B-doping. Measurement of ultrafast transient transmission allowed us to study the initial (picosecond) carrier dynamics. It was found to be dependent of pump intensity and interpreted in terms of multiparticle electron-hole recombination.

  17. Lead detection using micro/nanocrystalline boron-doped diamond by square-wave anodic stripping voltammetry.

    PubMed

    Arantes, Tatiane M; Sardinha, André; Baldan, Mauricio R; Cristovan, Fernando H; Ferreira, Neidenei G

    2014-10-01

    Monitoring heavy metal ion levels in water is essential for human health and safety. Electroanalytical techniques have presented important features to detect toxic trace heavy metals in the environment due to their high sensitivity associated with their easy operational procedures. Square-wave voltammetry is a powerful electrochemical technique that may be applied to both electrokinetic and analytical measurements, and the analysis of the characteristic parameters of this technique also enables the mechanism and kinetic evaluation of the electrochemical process under study. In this work, we present a complete optimized study on the heavy metal detection using diamond electrodes. It was analyzed the influence of the morphology characteristics as well as the doping level on micro/nanocrystalline boron-doped diamond films by means of square-wave anodic stripping voltammetry (SWASV) technique. The SWASV parameters were optimized for all films, considering that their kinetic response is dependent on the morphology and/or doping level. The films presented reversible results for the Lead [Pb (II)] system studied. The Pb (II) analysis was performed in ammonium acetate buffer at pH 4.5, varying the lead concentration in the range from 1 to 10 ?g L(-1). The analytical responses were obtained for the four electrodes. However, the best low limit detection and reproducibility was found for boron doped nanocrystalline diamond electrodes (BDND) doped with 2000 mg L(-1) in B/C ratio. PMID:25059140

  18. ELECTROCHEMICAL ADVANCED OXIDATION TREATMENTS OF ACIDIC AQUEOUS SOLUTIONS CONTAINING THE AMINOACID ?-METHYLPHENYLGLYCINE USING A BORON-DOPED DIAMOND ANODE

    Microsoft Academic Search

    Anna Serra; Xavier Domènech; José Peral; Conchita Arias; Enric Brillas

    The degradation of a solution containing 500 mg L-1 of the aminoacid ?-methylphenylglycine, 10 mg L-1 Fe2+ and 0.05 M Na2O4 at pH 3.0 has been studied by means of electrochemical advanced oxidation processes like electro-Fenton (EF) and solar photoelectro-Fenton (SPEF) using an undivided electrolytic cell with a boron-doped diamond (BDD) anode and an O2-diffusion cathode. Under these conditions, very

  19. Square?Wave Voltammetry Determination of Aspartame in Dietary Products Using a Boron?Doped Diamond Electrode

    Microsoft Academic Search

    Roberta Antigo Medeiros; Adriana Evaristo de Carvalho

    2007-01-01

    The use of square?wave voltammetry in conjunction with a cathodically pretreated boron?doped diamond electrode for the analytical determination of aspartame in dietary products is described. In this determination, the samples were analyzed without previous treatment in a 0.5 mol l H2SO4 solution. A single oxidation peak at a potential of 1.6 V vs. Ag\\/AgCl (3.0 mol l KCl) with the characteristics of an irreversible reaction

  20. Kinetics and mechanism of the deep electrochemical oxidation of sodium diclofenac on a boron-doped diamond electrode

    NASA Astrophysics Data System (ADS)

    Vedenyapina, M. D.; Borisova, D. A.; Rosenwinkel, K.-H.; Weichgrebe, D.; Stopp, P.; Vedenyapin, A. A.

    2013-08-01

    The kinetics and mechanism of the deep oxidation of sodium diclofenac on a boron-doped diamond electrode are studied to develop a technique for purifying wastewater from pharmaceutical products. The products of sodium diclofenac electrolysis are analyzed using cyclic voltammetry and nuclear magnetic resonance techniques. It is shown that the toxicity of the drug and products of its electrolysis decreases upon its deep oxidation.

  1. Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products.

    PubMed

    Kojima, Taiki; Obata, Rika; Saito, Tsuyoshi; Einaga, Yasuaki; Nishiyama, Shigeru

    2015-01-01

    The electroreduction reaction of methyl cinnamate on a boron-doped diamond (BDD) electrode was investigated. The hydrodimer, dimethyl 3,4-diphenylhexanedioate (racemate/meso = 74:26), was obtained in 85% yield as the major product, along with small amounts of cyclic methyl 5-oxo-2,3-diphenylcyclopentane-1-carboxylate. Two new neolignan-type products were synthesized from the hydrodimer. PMID:25815070

  2. Improvements in the Formation of Boron-Doped Diamond Coatings on Platinum Wires Using the Novel Nucleation Process (NNP)

    PubMed Central

    Fhaner, Mathew; Zhao, Hong; Bian, Xiaochun; Galligan, James J.; Swain, Greg M.

    2010-01-01

    In order to increase the initial nucleation density for the growth of boron-doped diamond on platinum wires, we employed the novel nucleation process (NNP) originally developed by Rotter et al. and discussed by others [1–3]. This pretreatment method involves (i) the initial formation of a thin carbon layer over the substrate followed by (ii) ultrasonic seeding of this “soft” carbon layer with nanoscale particles of diamond. This two-step pretreatment is followed by the deposition of boron-doped diamond by microwave plasma-assisted CVD. Both the diamond seed particles and sites on the carbon layer itself function as the initial nucleation zones for diamond growth from an H2-rich source gas mixture. We report herein on the characterization of the pre-growth carbon layer formed on Pt as well as boron-doped films grown for 2, 4 and 6 h post NNP pretreatment. Results from scanning electron microscopy, Raman spectroscopy and electrochemical studies are reported. The NNP method increases the initial nucleation density on Pt and leads to the formation of a continuous diamond film in a shorter deposition time than is typical for wires pretreated by conventional ultrasonic seeding. The results indicate that the pregrowth layer itself consists of nanoscopic domains of diamond and functions well to enhance the initial nucleation of diamond without any diamond powder seeding. PMID:21617759

  3. General scalable strategy toward heterogeneously doped hierarchical porous graphitic carbon bubbles for lithium-ion battery anodes.

    PubMed

    Song, Huawei; Yang, Gongzheng; Wang, Chengxin

    2014-12-10

    Novel carbon nanostructures, e.g., carbon nanotubes (CNTs), graphene, hierarchical porous graphitic carbon (HPGC), and ordered mesoporous carbon (CMK-3), have been significantly forwarding the progress of energy storage and conversion. Advanced electrodes or hybrid electrodes based on them are springing up one after another. To step further, a generic synthetic approach to large scale hierarchical porous graphitic carbon microbubbles (HPGCMBs) is developed by zinc powder templated organic precursor impregnation method. The facile technique features scalable (yield: once more than 200 mg), in situ heteroatom's doping (doping ratio: more than 26%) and hierarchical-pore-creating traits (pore volume: 1.01 cm(3) g(-1)). Adjustable graphitic content, doping species and amount are readily realized through varying the organic precursors. Rationally, good conductivity, fast kinetics, and abundant ion reservoirs are entirely achieved. To be applied in practice, state-of-the-art anodes for lithium-ion batteries are fabricated. Benefiting from the large specific surface area, rich heteroatoms, and hierarchical pores, the HPGCMBs electrodes exhibit excellent electrochemical properties. Besides superior storage capability of more than 1000 mAh g(-1) at 100 mA g(-1), stable cycling and excellent retention of 370 mAh g(-1) at large rate of 10 A g(-1) are achieved in the meantime. PMID:25408550

  4. Sulfur doping effects on the electronic and geometric structures of graphitic carbon nitride photocatalyst: insights from first principles

    NASA Astrophysics Data System (ADS)

    Stolbov, Sergey; Zuluaga, Sebastian

    2013-02-01

    We present here results of our first-principles studies of the sulfur doping effects on the electronic and geometric structures of graphitic carbon nitride (g-C3N4). Using the ab initio thermodynamics approach combined with some kinetic analysis, we reveal the favorable S-doping configurations. By analyzing the valence charge densities of the doped and undoped systems, we find that sulfur partially donates its px- and py- electrons to the system with some back donation to the S pz-states. To obtain an accurate description of the excited electronic states, we calculate the electronic structure of the systems using the GW method. The band gap width calculated for g-C3N4 is found to be equal to 2.7 eV, which is in agreement with experiment. We find the S doping causes a significant narrowing of the gap. Furthermore, the electronic states just above the gap become occupied upon doping, making the material a conductor. Analysis of the projected local density of states provides an insight into the mechanism underlying such changes in the electronic structure of g-C3N4 upon S doping. Based on our results, we propose a possible explanation for the S-doping effect on the photocatalytic properties of g-C3N4 observed in experiments.

  5. Sulfur doping effects on the electronic and geometric structures of graphitic carbon nitride photocatalyst: insights from first principles.

    PubMed

    Stolbov, Sergey; Zuluaga, Sebastian

    2013-02-27

    We present here results of our first-principles studies of the sulfur doping effects on the electronic and geometric structures of graphitic carbon nitride (g-C(3)N(4)). Using the ab initio thermodynamics approach combined with some kinetic analysis, we reveal the favorable S-doping configurations. By analyzing the valence charge densities of the doped and undoped systems, we find that sulfur partially donates its p(x)- and p(y)- electrons to the system with some back donation to the S p(z)-states. To obtain an accurate description of the excited electronic states, we calculate the electronic structure of the systems using the GW method. The band gap width calculated for g-C(3)N(4) is found to be equal to 2.7 eV, which is in agreement with experiment. We find the S doping causes a significant narrowing of the gap. Furthermore, the electronic states just above the gap become occupied upon doping, making the material a conductor. Analysis of the projected local density of states provides an insight into the mechanism underlying such changes in the electronic structure of g-C(3)N(4) upon S doping. Based on our results, we propose a possible explanation for the S-doping effect on the photocatalytic properties of g-C(3)N(4) observed in experiments. PMID:23363533

  6. Highly graphitized nitrogen-doped porous carbon nanopolyhedra derived from ZIF-8 nanocrystals as efficient electrocatalysts for oxygen reduction reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Linjie; Su, Zixue; Jiang, Feilong; Yang, Lingling; Qian, Jinjie; Zhou, Youfu; Li, Wenmu; Hong, Maochun

    2014-05-01

    Nitrogen-doped graphitic porous carbons (NGPCs) have been synthesized by using a zeolite-type nanoscale metal-organic framework (NMOF) as a self-sacrificing template, which simultaneously acts as both the carbon and nitrogen sources in a facile carbonization process. The NGPCs not only retain the nanopolyhedral morphology of the parent NMOF, but also possess rich nitrogen, high surface area and hierarchical porosity with well-conducting networks. The promising potential of NGPCs as metal-free electrocatalysts for oxygen reduction reactions (ORR) in fuel cells is demonstrated. Compared with commercial Pt/C, the optimized NGPC-1000-10 (carbonized at 1000 °C for 10 h) catalyst exhibits comparable electrocatalytic activity via an efficient four-electron-dominant ORR process coupled with superior methanol tolerance as well as cycling stability in alkaline media. Furthermore, the controlled experiments reveal that the optimum activity of NGPC-1000-10 can be attributed to the synergetic contributions of the abundant active sites with high graphitic-N portion, high surface area and porosity, and the high degree of graphitization. Our findings suggest that solely MOF-derived heteroatom-doped carbon materials can be a promising alternative for Pt-based catalysts in fuel cells.Nitrogen-doped graphitic porous carbons (NGPCs) have been synthesized by using a zeolite-type nanoscale metal-organic framework (NMOF) as a self-sacrificing template, which simultaneously acts as both the carbon and nitrogen sources in a facile carbonization process. The NGPCs not only retain the nanopolyhedral morphology of the parent NMOF, but also possess rich nitrogen, high surface area and hierarchical porosity with well-conducting networks. The promising potential of NGPCs as metal-free electrocatalysts for oxygen reduction reactions (ORR) in fuel cells is demonstrated. Compared with commercial Pt/C, the optimized NGPC-1000-10 (carbonized at 1000 °C for 10 h) catalyst exhibits comparable electrocatalytic activity via an efficient four-electron-dominant ORR process coupled with superior methanol tolerance as well as cycling stability in alkaline media. Furthermore, the controlled experiments reveal that the optimum activity of NGPC-1000-10 can be attributed to the synergetic contributions of the abundant active sites with high graphitic-N portion, high surface area and porosity, and the high degree of graphitization. Our findings suggest that solely MOF-derived heteroatom-doped carbon materials can be a promising alternative for Pt-based catalysts in fuel cells. Electronic supplementary information (ESI) available: Additional SEM and TEM images, EDS, crystal structures illustration, XRD, Raman, N2 sorption, XPS, FTIR, TGA and supplementary reaction tests. See DOI: 10.1039/c4nr00348a

  7. Effect of substrate temperature on conductivity and microstructures of boron-doped silicon nanocrystals in SiCx thin films

    NASA Astrophysics Data System (ADS)

    Cheng, Qiang; Zeng, Yuheng; Huang, Junjun; Dai, Ning; Yang, Ye; Tan, Ruiqin; Liang, Xingbo; Song, Weijie

    2013-09-01

    Boron (B)-doped silicon-rich SiC (SiCx, 0doped SiCx thin films were studied. The crystalline fraction increased by 5%, while the conductivity increased by 10-100 times, in the annealed thin films deposited at about 200 °C, comparing to that deposited at RT -400 °C. The face-centered cubic (fcc) Si nanocrystals (Si-NCs) formed in the surface layer when Ts was about 200 °C. It was suggested that Ts influenced the crystallization, conductivity and even the microstructures of Si-NCs. The proper Ts was helpful to improve the crystallization and conductivity of the B-doped Si-NCs in SiCx thin film.

  8. Visualization of Photo-induced Doping patterns in Graphene/Boron Nitride Heterostructures via Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Velasco, Jairo, Jr.; Ju, Long; Wong, Dillon; Lee, Juwon; Kahn, Salman; Tsai, Hsin-Zon; Germany, Chad; Taniguchi, Takashi; Watanabe, Kenji; Zettl, Alex; Wang, Feng; Crommie, Mike

    2015-03-01

    Photo-induced doping in graphene-boron nitride (G/BN) heterostructures enables flexible and repeatable writing and erasing of charge doping in graphene using optical irradiation. So far, however, this phenomenon has been explored using spatially averaging probes such as electron transport, and there have been no local studies into the underlying microscopic behavior. Here we report a combined scanning tunneling microscopy (STM) and optoelectronic measurement scheme that has been utilized to investigate the microscopic mechanisms at work in this process. We will discuss the latest experimental progress towards the visualization of light-induced charge doping patterns on G/BN heterostructures via STM. J.V.J. acknowledges support from the UC President's Postdoctoral Fellowship.

  9. Rapid-thermal-processing-based internal gettering for heavily boron-doped Czochralski silicon

    NASA Astrophysics Data System (ADS)

    Fu, Liming; Yang, Deren; Ma, Xiangyang; Tian, Daxi; Que, Duanlin

    2006-11-01

    The effect of rapid-thermal processing (RTP) ambients on the formation of oxygen precipitates and denuded zone (DZ) in heavily boron-doped (HB) Czochralski (Cz) silicon by a low-high (L-H) two-step annealing (800°C/4h+1000°C/16h) has been investigated. It was found that after the L-H two-step annealing, there was a high density of bulk microdefects (BMDs) and no observable DZ was formed near the surface in HB Cz silicon wafers preannealed by the RTP in Ar ambient, while the BMD density was quite low in HB Cz silicon wafers preannealed by the RTP in O2 ambient. However, applying the preannealing of RTP sequentially in Ar and O2 ambients allowed us to obtain a high density of BMDs in combination with a sufficient DZ by the subsequent L-H two-step annealing. This approach offers a pathway to optimize internal gettering for HB Cz silicon.

  10. Structure and 1/f noise of boron doped polymorphous silicon films.

    PubMed

    Li, S B; Wu, Z M; Jiang, Y D; Li, W; Liao, N M; Yu, J S

    2008-02-27

    The influence of structure variation on the 1/f noise of nanometric boron doped hydrogenated polymorphous silicon (pm-Si:H) films was investigated. The films were grown by the conventional radio frequency plasma enhanced chemical vapor deposition (PECVD) method. Raman spectroscopy was used to reveal the crystalline volume fraction (X(c)) and crystal size of the pm-Si:H. The measurement of optical and structure properties was carried out with spectroscopic ellipsometry (SE) in the Tauc-Lorentz model. A Fourier transform infrared (FTIR) spectrometer was used to characterize the presence of nanostructure-sized silicon clusters in pm-Si:H film deposited on KBr substrate. The electrical properties of the films were measured using evaporated coplanar nickel as the electrode. A semiconductor system was designed to obtain the 1/f noise of pm-Si:H film as well as that of amorphous and microcrystalline silicon films. The results demonstrate that the 1/f noise of pm-Si:H is nearly as low as that of microcrystalline silicon and much lower than that of amorphous silicon. The disorder to order transition mechanism of crystallization was used to analyze the decrease of noise compared with amorphous silicon. PMID:21730737

  11. Simultaneous Chronoamperometric Sensing of Ascorbic Acid and Acetaminophen at a Boron-Doped Diamond Electrode

    PubMed Central

    Cofan, Codru?a; Radovan, Ciprian

    2008-01-01

    Cyclic voltammetry (CV) and chronoamperometry (CA) have been used to sense and determine simultaneously L-ascorbic acid (AA) and acetaminophen (AC) at a boron-doped diamond electrode (BDDE) in a Britton-Robinson buffer solution. The calibration plots of anodic current peak versus concentration obtained from CV and CA data for both investigated compounds in single and di-component solutions over the concentration range 0.01 mM – 0.1 mM proved to be linear, with very good correlation parameters. Sensitivity values and RSD of 2-3% were obtained for various situations, involving both individual and simultaneous presence of AA and AC. The chronoamperometric technique associated with standard addition in sequential one step and/or two successive and continuous chronoamperograms at two characteristic potential levels represented a feasible option for the simultaneous determination of AA and AC in real sample systems such as pharmaceutical formulations. The average values indicated by the supplier were confirmed to a very close approximation from chronoamperomgrams by using several additions with the application of suitable current correction factors.

  12. Multichannel Boron Doped Nanocrystalline Diamond Ultramicroelectrode Arrays: Design, Fabrication and Characterization

    PubMed Central

    Kiran, Raphael; Rousseau, Lionel; Lissorgues, Gaëlle; Scorsone, Emmanuel; Bongrain, Alexandre; Yvert, Blaise; Picaud, Serge; Mailley, Pascal; Bergonzo, Philippe

    2012-01-01

    We report on the fabrication and characterization of an 8 × 8 multichannel Boron Doped Diamond (BDD) ultramicro-electrode array (UMEA). The device combines both the assets of microelectrodes, resulting from conditions in mass transport from the bulk solution toward the electrode, and of BDD's remarkable intrinsic electrochemical properties. The UMEAs were fabricated using an original approach relying on the selective growth of diamond over pre-processed 4 inches silicon substrates. The prepared UMEAs were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results demonstrated that the electrodes have exhibited a very fast electrode transfer rate (k0) up to 0.05 cm·s?1 (in a fast redox couple) and on average, a steady state limiting current (in a 0.5 M potassium chloride aqueous solution containing 1 mM Fe(CN)64? ion at 100 mV·s?1) of 1.8 nA. The UMEAs are targeted for electrophysiological as well as analytical applications. PMID:22969367

  13. Effect of nitro substituent on electrochemical oxidation of phenols at boron-doped diamond anodes.

    PubMed

    Jiang, Yi; Zhu, Xiuping; Li, Hongna; Ni, Jinren

    2010-02-01

    In order to investigate nitro-substitutent's effect on degradation of phenols at boron-doped diamond (BDD) anodes, cyclic voltammetries of three nitrophenol isomers: 2-nitrophenol (2NP), 3-nitrophenol (3NP) and 4-nitrophenol (4NP) were studied, and their bulk electrolysis results were compared with phenol's (Ph) under alkaline condition. The voltammetric study showed nitrophenols could be attacked by hydroxyl radicals and nitro-group was released from the aromatic ring. Results of bulk electrolysis showed degradation of all phenols were fit to a pseudo first-order equation and followed in this order: 2NP>4NP>3NP>Ph. Molecular structures, especially carbon atom charge, significantly influenced the electrochemical oxidation of these isomers. Intermediates were analyzed during the electrolysis process, and were mainly catechol, resorcinol, hydroquinone, and carboxylic acids, such as acetic acid and oxalic acid. A simple degradation pathway was proposed. Moreover, a linear increasing relationship between degradation rates and Hammett constants of the studied phenols was observed, which demonstrated that electrochemical oxidation of these phenols was mainly initiated by electrophilic attack of hydroxyl radicals at BDD anodes. PMID:20060999

  14. Use of seawater for the boron-doped diamond electrochemical treatment of diluted vinasse wastewater.

    PubMed

    Daskalaki, V M; Marakas, H; Mantzavinos, D; Katsaounis, A; Gikas, P

    2013-01-01

    Vinasse wastewater of high organic content (COD = 131,000 mg/L) and low biodegradability (BOD5/COD = 0.11) cannot be easily managed and usually require several consecutive treatment steps. The objective of this work was to dilute vinasse wastewater with seawater and then subject them to electrochemical oxidation over boron-doped diamond (BDD) electrodes. The use of seawater is a rational and novel approach for plants close to the seashore since it may achieve the desirable levels of effluent concentration and conductivity without consuming other water resources and extra electrolytes. Experiments were conducted at initial COD values of 830-8,400 mg/L, NaCl concentrations of 34-200 mM and current densities of 70-200 mA/cm(2) for up to 5 hours. The effect of current density and NaCl concentration was marginal on the electrochemical treatment, while the single most important parameter was the initial COD concentration. The order of reaction for COD reduction appears to be 'first' at low effluent concentrations and it decreases to 'zero' at higher concentrations, denoting the importance of the ratio of organics to reactive radicals concentration. Based on COD and total organic carbon data, it is postulated that degradation occurs predominantly through total oxidation (i.e. mineralization) to carbon dioxide and water, which is characteristic of BDD anodes. PMID:24334881

  15. Crystallinity, morphology, and conductivity of boron-doped microcrystal-line silicon

    SciTech Connect

    Rajeswaran, G.; Tafto, J.; Sabatini, R.L.; Vanier, P.E.

    1984-01-01

    Boron-doped microcrystalline (..mu..c) silicon films produced by rf glow discharge from dilute (1%) mixtures of SiH/sub 4/ in H/sub 2/ show a critical dependence of conductivity on deposition conditions. The dark conductivity was related to the microscopic features using electron microscopy. The ..mu..c-Si:H films contain clusters of crystallites embedded in an amorphous matrix. The size of the crystalline clusters is typically 0.2 ..mu..m in diameter, and the size of the individual crystallites is about 2.5 nm. Electron micrographs of samples prepared at substrate temperatures T/sub s/ = 135/sup 0/C, 150/sup 0/C, 165/sup 0/C, and 180/sup 0/C show that the number of crystalline clusters increases with T/sub s/ up to 165/sup 0/C. At T/sub s/ = 180/sup 0/C, the crystallites completely disappear. When the concentration of SiH/sub 4/ in H/sub 2/ is decreased to 0.25%, the microstructure shows a high density of crystallites with no apparent clustering. 6 references, 7 figures.

  16. Origin of anomalous strain effects on the molecular adsorption on boron-doped graphene

    NASA Astrophysics Data System (ADS)

    Kang, Joongoo; Kim, Yong-Hyun; Glatzmaier, Greg C.; Wei, Su-Huai

    2013-07-01

    When compressive strain is applied to a single-layered material, the layer generally ripples along the third dimension to release the strain energy. In contrast, such a rippling effect is not favored when it is under tensile strain. Here, using first-principles density-functional calculations, we show that molecular adsorption on boron-doped graphene (BG) can be largely tuned by exploiting the rippling effect of the strained graphene. Under tensile strain, the adsorption energy of K2CO3, NO2, and NH3 on BG, for which the molecular adsorption is a chemisorption characterized by a covalent B-molecule bond, exhibits a superlinear dependence on the applied strain. In contrast, when microscopic ripples are present in the BG under compressive strain, the adsorption strength is significantly enhanced with increasing the strain. Such a nonlinear and asymmetric effect of strain on the molecular adsorption is a characteristic of two-dimensional systems, because a general elastic theory of molecular adsorption on three-dimensional systems gives a linear and symmetric strain effect on the adsorption strength. We provide the underlying mechanism of the anomalous strain effect on the chemical molecular adsorption on BG, in which the microscopic rippling of the graphene and the creation of the ?-dangling bond state near the Dirac point play an important role. Our finding can be used to modify chemical reactivity of graphene with a wide range of application.

  17. Energy consumption of electrooxidation systems with boron-doped diamond electrodes in the pulse current mode

    NASA Astrophysics Data System (ADS)

    Wei, Jun-jun; Gao, Xu-hui; Hei, Li-fu; Askari, Jawaid; Li, Cheng-ming

    2013-01-01

    A pulse current technique was conducted in a boron-doped diamond (BDD) anode system for electrochemical wastewater treatment. Due to the strong generation and weak absorption of hydroxyl radicals on the diamond surface, the BDD electrode possesses a powerful capability of electrochemical oxidation of organic compounds, especially in the pulse current mode. The influences of pulse current parameters such as current density, pulse duty cycle, and frequency were investigated in terms of chemical oxygen demand (COD) removal, average current efficiency, and specific energy consumption. The results demonstrated that the relatively high COD removal and low specific energy consumption were obtained simultaneously only if the current density or pulse duty cycle was adjusted to a reasonable value. Increasing the frequency slightly enhanced the COD removal and average current efficiency. A pulse-BDD anode system showed a stronger energy saving ability than a constant-BDD anode system when the electrochemical oxidation of phenol of the two systems was compared. The results prove that the pulse current technique is more cost-effective and more suitable for a BDD anode system for real wastewater treatment. A kinetic analysis was presented to explain the above results.

  18. Diamond-modified AFM probes: from diamond nanowires to atomic force microscopy-integrated boron-doped diamond electrodes.

    PubMed

    Smirnov, Waldemar; Kriele, Armin; Hoffmann, René; Sillero, Eugenio; Hees, Jakob; Williams, Oliver A; Yang, Nianjun; Kranz, Christine; Nebel, Christoph E

    2011-06-15

    In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are suitable for probing, manipulating, sculpting, and sensing at single digit nanoscale. PMID:21534601

  19. Highly graphitized nitrogen-doped porous carbon nanopolyhedra derived from ZIF-8 nanocrystals as efficient electrocatalysts for oxygen reduction reactions.

    PubMed

    Zhang, Linjie; Su, Zixue; Jiang, Feilong; Yang, Lingling; Qian, Jinjie; Zhou, Youfu; Li, Wenmu; Hong, Maochun

    2014-06-21

    Nitrogen-doped graphitic porous carbons (NGPCs) have been synthesized by using a zeolite-type nanoscale metal-organic framework (NMOF) as a self-sacrificing template, which simultaneously acts as both the carbon and nitrogen sources in a facile carbonization process. The NGPCs not only retain the nanopolyhedral morphology of the parent NMOF, but also possess rich nitrogen, high surface area and hierarchical porosity with well-conducting networks. The promising potential of NGPCs as metal-free electrocatalysts for oxygen reduction reactions (ORR) in fuel cells is demonstrated. Compared with commercial Pt/C, the optimized NGPC-1000-10 (carbonized at 1000 °C for 10 h) catalyst exhibits comparable electrocatalytic activity via an efficient four-electron-dominant ORR process coupled with superior methanol tolerance as well as cycling stability in alkaline media. Furthermore, the controlled experiments reveal that the optimum activity of NGPC-1000-10 can be attributed to the synergetic contributions of the abundant active sites with high graphitic-N portion, high surface area and porosity, and the high degree of graphitization. Our findings suggest that solely MOF-derived heteroatom-doped carbon materials can be a promising alternative for Pt-based catalysts in fuel cells. PMID:24806824

  20. Boron Substitution in Disordered Graphene-like Carbon

    NASA Astrophysics Data System (ADS)

    Schaeperkoetter, Joe; Gillespie, Andrew; Wexler, Carlos; Pfeifer, Peter; Materials Research Institute-Missouri S&T Collaboration; Paul Rulis Collaboration

    2015-03-01

    X-ray photoelectron spectroscopy was used to determine both the elemental composition of boron doped carbons as well as gain insight into the arrangement of atoms in the material. The hypothesized arrangement of atoms is a direct substitution of boron for carbon into a graphene like sheet, maintaining the hexagonal honeycomb lattice of sp2 sigma bonds. Such a boron atom would have an electronic configuration of 1s2(sp2)3 . With a graphitic carbon atom, the pz orbitals are maintained and participate in mobile pi bonds with neighboring carbon atoms, as understood in the aromatic model. Boron, however, would require a charge donation to fill its pz orbital. Thus, three possible models are proposed for the out of plane electron density: (1) the orbital remains unoccupied and the boron is a free radical, (2) charge is donated from a neighboring atom and the boron atom is ionic, (3) the delocalization of charge in the aromatic system results in a partial charge transfer with an effective charge somewhere between neutral and anionic. Our results suggest that boron is not in an anionic state, and, by doing a quantitative and simultaneous analysis from multiple elemental spectra, we conclude that no more than 2 wt% of boron is being substitutionally doped into the system.

  1. Development of boron-doped diamond thin-films as voltammetric and amperometric detectors

    NASA Astrophysics Data System (ADS)

    Xu, Jishou

    2000-10-01

    The utilization of boron-doped diamond thin-films for applications in electroanalysis was investigated. Voltammetric analysis in static solution, and amperometric detection coupled with flow injection analysis and HPLC were performed. The results were compared to those for glassy carbon. The electroactivity, the merit of detection figures, the adsorption of polar organic molecules, and the resistance to fouling were studied. Surface characterization was performed to elucidate the surface property-electroacticvity relationship. The results showed that diamond thin-films, compared with glassy carbon, had comparable electroactivity to simple electron transfer processes (e.g., Ru(NH3)6+2/+3, Fe(CN)6 -3/-4, IrCl6-2/-3, azide, chlorpromazine), but had lower electroactivity for the electron transfer processes involving surface-confined intermediate (e.g., hydrogen evolution, oxygen evolution, 4-methyl catechol, hydrazine). The diamond thin-films had a wide working potential up to 4.0 V in aqueous media. They also had small double layer capacitance, voltammetric background current, and amperometric residual current. These properties had leaded to higher signal-to-background ratios and signal-to-noise ratios. The diamond thin-films had lower limits of detection in voltammetric measurements of several analytes, and had lower limits of detection in amperometric measurements of all compounds studied. The diamond thin-films had negligible adsorption of polar organic molecules (e.g., anthraquinone 2,6-disulfonate, chlorpromazine), compared to glassy carbon. This is due to the fact that the diamond surfaces are primarily composed of sp3 carbon and hydrogen terminated. This leaded to less decay of the electroactivity by storage and operation, and higher resistance to fouling. The surface property-electroactivity relationship depends on the specific mechanism for electron transfer. The extent of non-diamond impurities (e.g., oxygen evolution), diamond crystalline size, surface termination (e.g., azide), and surface boron sites (hydrazine) could all affect the electroactivity for diamond thin-films.

  2. Diffusion-driven precipitate growth and ripening of oxygen precipitates in boron doped silicon by dynamical x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Will, J.; Gröschel, A.; Bergmann, C.; Spiecker, E.; Magerl, A.

    2014-03-01

    X-ray Pendellösung fringes from three silicon single crystals measured at 900 °C are analyzed with respect to density and size of oxygen precipitates within a diffusion-driven growth model and compared with TEM investigations. It appears that boron doped (p+) material shows a higher precipitate density and a higher strain than moderately (p-) boron crystals. In-situ diffraction reveals a diffusion-driven precipitate growth followed by a second growth regime in both materials. An interpretation of the second growth regime in terms of Ostwald ripening yields surface energy values (around 70 erg/cm2) similar to published data. Further, an increased nucleation rate by a factor of ˜13 is found in the p+ sample as compared to a p- sample at a nucleation temperature of 450 °C.

  3. Diffusion-driven precipitate growth and ripening of oxygen precipitates in boron doped silicon by dynamical x-ray diffraction

    SciTech Connect

    Will, J., E-mail: will@krist.uni-erlangen.de; Gröschel, A.; Bergmann, C.; Magerl, A. [Crystallography and Structural Physics, University of Erlangen-Nürnberg, Staudtstr. 3, 91058 Erlangen (Germany); Spiecker, E. [Center for Nanoanalysis and Electron Microscopy, University of Erlangen-Nürnberg, Cauerstr. 6, 91058 Erlangen (Germany)

    2014-03-28

    X-ray Pendellösung fringes from three silicon single crystals measured at 900?°C are analyzed with respect to density and size of oxygen precipitates within a diffusion-driven growth model and compared with TEM investigations. It appears that boron doped (p+) material shows a higher precipitate density and a higher strain than moderately (p-) boron crystals. In-situ diffraction reveals a diffusion-driven precipitate growth followed by a second growth regime in both materials. An interpretation of the second growth regime in terms of Ostwald ripening yields surface energy values (around 70?erg/cm{sup 2}) similar to published data. Further, an increased nucleation rate by a factor of ?13 is found in the p+ sample as compared to a p- sample at a nucleation temperature of 450?°C.

  4. Oxidation resistance and compressive creep behavior of boron doped Mo{sub 5}Si{sub 3}

    SciTech Connect

    Meyer, M.K.; Akinc, M. [Ames Lab., IA (United States)]|[Iowa State Univ., Ames, IA (United States). Dept. of Materials Science and Engineering; Kramer, M.J. [Ames Lab., IA (United States)

    1995-10-01

    Use of Mo{sub 5}Si{sub 3} in high temperature applications is limited by oxidation induced catastrophic failure above 800 C. Oxidation resistance of Mo{sub 5}Si{sub 3} is substantially improved from 800--1,300 C by the addition of boron. The oxidation rate at 1,200 C was decreased by five orders of magnitude with less than 2 weight percent boron addition. The improvement in oxidation resistance of B doped Mo{sub 5}Si{sub 3} is due to formation of a protective scale layer due to viscous flow. The compressive creep rate of B doped Mo{sub 5}Si{sub 3} was measured at various temperature/stress levels and found to be similar to that of the undoped material. The creep rate of B doped Mo{sub 5}Si{sub 3} was measured as 1.8 {times} 10{sup {minus}7} s{sup {minus}1} at 1,242 C and 138 MPa. Creep tests were conducted at 140--180 MPa and 1,220--1,320 C. Average creep activation energy and stress exponent in this range were found to be E{sub a} {approx} 400 kJ/mol and n = 4.3 respectively.

  5. Reagentless polyol detection by conductivity increase in the course of self-doping of boronate-substituted polyaniline.

    PubMed

    Andreyev, Egor A; Komkova, Maria A; Nikitina, Vita N; Zaryanov, Nikolay V; Voronin, Oleg G; Karyakina, Elena E; Yatsimirsky, Anatoly K; Karyakin, Arkady A

    2014-12-01

    We report on the novel reagentless and label-free detection principle based on electroactive (conducting) polymers considering sensors for polyols, particularly, saccharides and hydroxy acids. Unlike the majority of impedimetric and conductometric (bio)sensors, which specific and unspecific signals are directed in the same way (resistance increase), making doubtful their real applications, the response of the reported system results in resistance decrease, which is directed oppositely to the background. The mechanism of the resistance decrease is the polyaniline self-doping, i.e., as an alternative to proton doping, an appearance of the negatively charged aromatic ring substituents in polymer chain. Negative charge "freezing" at the boron atom is indeed a result of complex formation with di- and polyols, specific binding. Changes in Raman spectra of boronate-substituted polyaniline after addition of glucose are similar to those caused by proton doping of the polymer. Thermodynamic data on interaction of the electropolymerized 3-aminophenylboronic acid with saccharides and hydroxy acids also confirm that the observed resistance decrease is due to polymer interaction with polyols. The first reported conductivity increase as a specific signal opens new horizons for reagentless affinity sensors, allowing the discrimination of specific affinity bindings from nonspecific interactions. PMID:25363870

  6. Electrical transport properties of the Si-doped cubic boron nitride thin films prepared by in situ cosputtering

    SciTech Connect

    Ying, J.; Zhang, X. W.; Yin, Z. G.; Tan, H. R.; Zhang, S. G.; Fan, Y. M. [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2011-01-15

    Si-doped cubic boron nitride (c-BN) films with various Si concentrations were achieved by in situ cosputtering during ion beam assisted deposition. Effects of the Si concentration and rapid thermal annealing (RTA) conditions on the electrical transport properties of Si-doped c-BN thin films were investigated systematically. The results suggest that the optimum RTA condition is at the temperature of 1000 deg. C for 3 min. The resistance of Si-doped c-BN films gradually decreases as the Si concentration increases, indicating an electrical doping effect of the Si impurity. The temperature dependent electrical conductivity of the Si-doped c-BN films suggests that different conduction mechanisms are dominant over the different temperature ranges. Based on the Davis-Mott model, we propose that the extended-state conduction, band tail-state conduction and short-range hopping conduction are responsible for the respective temperature ranges. In addition, the reduction in activation energy of Si impurities is observed as the Si concentration increases.

  7. Boron doped ZnO thin films fabricated by RF-magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Gao, Li; Zhang, Yan; Zhang, Jian-Min; Xu, Ke-Wei

    2011-01-01

    By using the radio frequency-magnetron sputtering (RF-MS) method, both pure ZnO and boron doped ZnO (ZnO:B) thin films were deposited on glass substrates at ambient temperature and then annealed at 450 °C for 2 h in air. It is found that both ZnO and ZnO:B thin films have wurtzite structure of ZnO with (0 0 2) preferred orientation and high average optical transmission (?80%). Compared with the resistivity of 6.3 × 102 ? cm for ZnO film, both as-deposited and annealed ZnO:B films exhibit much lower resistivity of 9.2 × 10-3 ? cm and 7.5 × 10-3 ? cm, respectively, due to increase in the carrier concentration. Furthermore, the optical band gaps of 3.38 eV and 3.42 eV for as-deposited and annealed ZnO:B films are broader than that of 3.35 eV for ZnO film. The first-principles calculations show that in ZnO:B thin films not only the band gap becomes narrower but also the Fermi level shifts up into the conduction band with respect to the pure ZnO film. These are consistent with their lower resistivities and suggest that in the process of annealing some substituted B in the lattice change into interstitial B because of its smaller ion radius and this transformation widens the optical band gap of ZnO:B thin film.

  8. Advanced treatment of biologically pretreated coking wastewater by electrochemical oxidation using boron-doped diamond electrodes.

    PubMed

    Zhu, Xiuping; Ni, Jinren; Lai, Peng

    2009-09-01

    Electrochemical oxidation is a promising technology to treatment of bio-refractory wastewater. Coking wastewater contains high concentration of refractory and toxic compounds and the water quality usually cannot meet the discharge standards after conventional biological treatment processes. This paper initially investigated the electrochemical oxidation using boron-doped diamond (BDD) anode for advanced treatment of coking wastewater. Under the experimental conditions (current density 20-60mAcm(-2), pH 3-11, and temperature 20-60 degrees C) using BDD anode, complete mineralization of organic pollutants was almost achieved, and surplus ammonia-nitrogen (NH(3)-N) was further removed thoroughly when pH was not adjusted or at alkaline value. Moreover, the TOC and NH(3)-N removal rates in BDD anode cell were much greater than those in other common anode systems such as SnO(2) and PbO(2) anodes cells. Given the same target to meet the National Discharge Standard of China, the energy consumption of 64kWhkgCOD(-1) observed in BDD anode system was only about 60% as much as those observed in SnO(2) and PbO(2) anode systems. Further investigation revealed that, in BDD anode cell, organic pollutants were mainly degraded by reaction with free hydroxyl radicals and electrogenerated oxidants (S(2)O(8)(2-), H(2)O(2), and other oxidants) played a less important role, while direct electrochemical oxidation and indirect electrochemical oxidation mediated by active chlorine can be negligible. These results showed great potential of BDD anode system in engineering application as a final treatment of coking wastewater. PMID:19595422

  9. Effect of hydrogen dilution on carrier transport in hydrogenated boron-doped nanocrystalline silicon-silicon carbide alloys

    NASA Astrophysics Data System (ADS)

    Myong, Seung Yeop; Lim, Koeng Su; Konagai, Makoto

    2006-03-01

    The effect of the hydrogen dilution ratio on characteristics of hydrogenated boron-doped nanocrystalline silicon-silicon carbide alloy (p-nc-Si-SiC:H) films is investigated. Hydrogen coverage near the growing surface causes nanocrystallization by retarding the reactions of the precursors. It was found that p-nc-Si -SiC:H alloys have two different kinds of carrier transport mechanisms: one is the thermally activated hopping conduction between neighboring crystallites near room temperature and the other is the band tail hopping conduction below 150K. However, the film at the onset of the nanocrystalline growth exhibits a different behavior due to a large band tail disorder.

  10. High density and taper-free boron doped Si{sub 1?x}Ge{sub x} nanowire via two-step growth process

    SciTech Connect

    Periwal, Priyanka; Salem, Bassem; Bassani, Franck; Baron, Thierry, E-mail: thierry.baron@cea.fr [University of Grenoble Alpes LTM, F-38000 Grenoble, France and CNRS LTM, UMR-5129, F-38000 Grenoble (France); Barnes, Jean-Paul [CEA-Leti, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2014-07-01

    The authors study Au catalyzed chemical vapor growth of Si{sub 1?x}Ge{sub x} alloyed nanowires in the presence of diborane, serving as a dopant precursor. Our experiments reveal that introduction of diborane has a significant effect on doping and morphology. Boron exposure poisons the Au catalyst surface, suppresses catalyst activity, and causes significantly tapered wires, as a result of conformal growth. The authors develop here a two-step method to obtain high density and taper-free boron doped Si{sub 1?x}Ge{sub x} alloy nanowires. The two-step process consists of: (1) growth of a small undoped Si{sub 1?x}Ge{sub x} section and (2) introduction of diborane to form a boron doped Si{sub 1?x}Ge{sub x} section. The catalyst preparation step remarkably influences wire yield, quality and morphology. The authors show that dopant-ratio influences wire resistivity and morphology. Resistivity for high boron doped Si{sub 1?x}Ge{sub x} nanowire is 6 m?-cm. Four probe measurements show that it is possible to dope Si{sub 1?x}Ge{sub x} alloy nanowires with diborane.

  11. Roughness-based monitoring of transparency and conductivity in boron-doped ZnO thin films prepared by spray pyrolysis

    SciTech Connect

    Gaikwad, Rajendra S. [Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 130-650 (Korea, Republic of) [Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 130-650 (Korea, Republic of); Department of Physics, Yashwantrao Mohite College, Bharati Vidyapeeth Deemed University, Pune 411038, Maharashtra (India); Bhande, Sambhaji S. [Centre for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramand Teerth Marathwada University, Nanded (India)] [Centre for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramand Teerth Marathwada University, Nanded (India); Mane, Rajaram S., E-mail: rsmane_2000@yahoo.com [Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 130-650 (Korea, Republic of); Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-791 (Korea, Republic of); Centre for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramand Teerth Marathwada University, Nanded (India); Pawar, Bhagwat N. [Department of Physics, Yashwantrao Mohite College, Bharati Vidyapeeth Deemed University, Pune 411038, Maharashtra (India)] [Department of Physics, Yashwantrao Mohite College, Bharati Vidyapeeth Deemed University, Pune 411038, Maharashtra (India); Gaikwad, Sanjay L. [Centre for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramand Teerth Marathwada University, Nanded (India)] [Centre for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramand Teerth Marathwada University, Nanded (India); Han, Sung-Hwan [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-791 (Korea, Republic of)] [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-791 (Korea, Republic of); Joo, Oh-Shim, E-mail: jookat@kist.ac.kr [Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 130-650 (Korea, Republic of)] [Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 130-650 (Korea, Republic of)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ? We report surface roughness dependent transparency and conductivity in ZnO films. ? The surface roughness with respected to boron doping concentrations is studied. ? Boron doped and pristine Zinc oxide thin films have showed ?95% transmittance. ? Increased carrier concentration of 9.21 × 10{sup 21} cm{sup ?3} revealed from Hall measurement. -- Abstract: Sprayed polycrystalline ZnO and boron-doped ZnO thin films composed of spherical grains of 25–32 nm in diameters are used in roughness measurement and further correlated with the transparency and the conductivity characteristics. The surface roughness is increased up to Zn{sub 0.98}B{sub 0.02}O and then declined at higher boron concentrations. The sprayed ZnO films revealed ?95% transmittance in the visible wavelength range, 1.956 × 10{sup ?4} ? cm electrical resistivity, 46 cm{sup 2}/V s Hall mobility and 9.21 × 10{sup 21} cm{sup ?3} charge carrier concentration. The X-ray photoelectron spectroscopy study has confirmed 0.15 eV binding energy change for Zn 2p{sub 3/2} when 2 at% boron content is mixed without altering electro-optical properties substantially. Finally, using soft modeling importance of these textured ZnO over non-textured films for enhancing the solar cells performance is explored.

  12. Electrochemical performances of B doped and undoped diamond-like carbon (DLC) films deposited by femtosecond pulsed laser ablation for heavy metal detection using square wave anodic stripping voltammetric (SWASV) technique

    Microsoft Academic Search

    B. Khadro; A. Sikora; A.-S. Loir; A. Errachid; F. Garrelie; C. Donnet; N. Jaffrezic-Renault

    2011-01-01

    Pure diamond-like carbon (DLC) thin films and boron-doped DLC thin films have been deposited on silicon substrates using femtosecond pulsed laser. The amorphous carbon materials (DLC), have been deposited at room temperature by ablating graphite targets with an amplified Ti:sapphire laser of 800nm wavelength and a pulse duration of 150fs in high vacuum conditions. Doping with boron has been performed

  13. Influence of Boron doping on the structural, optical and electrical properties of CdO thin films by spray pyrolysis technique

    SciTech Connect

    Velusamy, P., E-mail: rampap2k@yahoo.co.in; Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Films Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli- 620024, Tamil Nadu (India); Ramamurthi, K. [Department of Physics and Nanotechnology, Faculty of Engineering and Technology, SRM University, Kattankulathur - 603203, Tamil Nadu (India)

    2014-04-24

    Cadmium oxide and Boron (B) doped Cadmium oxide thin films were deposited using spray pyrolysis technique. The structural, morphological, electrical and optical properties of undoped and B doped CdO films are analyzed by varying the dopant concentration in the solution. The structural study shows the polycrystalline nature and cubic structure of undoped and B doped CdO thin films. Surface morphological study reveals that the grains are spherical in shape. Optical and electrical studies showed n-type semiconducting nature and optical band gap of 2.44 eV of deposited thin films.

  14. The boron heterofullerenes C 59B and C 69B: generation, extraction, mass spectrometric and XPS characterization

    NASA Astrophysics Data System (ADS)

    Muhr, H.-J.; Nesper, R.; Schnyder, B.; Kötz, R.

    1996-02-01

    Boron heterofullerenes can be generated by arc evaporation of doped graphite rods in a modified fullerene reactor. According to mass spectrometric analysis only mono-substituted fullerenes like C 59B, C 69B and higher homologues can be extracted and enriched by the use of pyridine as the solvent. They are strong Lewis acids and undergo a decomposition reaction to boric acid with traces of oxygen. XPS analysis of the extracts reveals the boron in the fullerene cage to be in a higher oxidation state compared to ordinary boron-carbon compounds. The synthesis and extraction procedure opens a viable route for the macroscopic production of these compounds.

  15. Luminescence properties of boron and nitrogen doped graphene quantum dots prepared from arc-discharge-generated doped graphene samples

    NASA Astrophysics Data System (ADS)

    Dey, Sunita; Govindaraj, A.; Biswas, Kanishka; Rao, C. N. R.

    2014-03-01

    Substitution of heteroatoms in graphene is known to tailor its band gap. Another approach to alter the band gap of graphene is to create zero-dimensional graphene quantum dots (GQDs). Here we present the synthesis and photoluminescence properties of B-doped graphene quantum dots (B-GQDs) for the first time, having prepared the B-GQDs by chemical scissoring of B-doped graphene generated by arc-discharge in gas phase. We compare the photoluminescence properties of B-GQDs with nitrogen-doped GQDs and pristine GQDs. Besides, excitation wavelength independent PL emission, excellent upconversion of PL emission is observed in GQDs as well as B- and N-doped GQDs.

  16. Nitrogen- and boron-co-doped core-shell carbon nanoparticles as efficient metal-free catalysts for oxygen reduction reactions in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Zhong, Shengkui; Zhou, Lihua; Wu, Ling; Tang, Lianfeng; He, Qiyi; Ahmed, Jalal

    2014-12-01

    The most severe bottleneck hindering the widespread application of fuel cell technologies is the difficulty in obtaining an inexpensive and abundant oxygen reduction reaction (ORR) catalyst. The concept of a heteroatom-doped carbon-based metal-free catalyst has recently attracted interest. In this study, a metal-free carbon nanoparticles-based catalyst hybridized with dual nitrogen and boron components was synthesized to catalyze the ORR in microbial fuel cells (MFCs). Multiple physical and chemical characterizations confirmed that the synthetic method enabled the incorporation of both nitrogen and boron dopants. The electrochemical measurements indicated that the co-existence of nitrogen and boron could enhance the ORR kinetics by reducing the overpotential and increasing the current density. The results from the kinetic studies indicated that the nitrogen and boron induced an oxygen adsorption mechanism and a four-electron-dominated reaction pathway for the as-prepared catalyst that was very similar to those induced by Pt/C. The MFC results showed that a maximum power density of ?642 mW m-2 was obtained using the as-prepared catalyst, which is comparable to that obtained using expensive Pt catalyst. The prepared nitrogen- and boron-co-doped carbon nanoparticles might be an alternative cathode catalyst for MFC applications if large-scale applications and price are considered.

  17. Enhanced Growth and Osteogenic Differentiation of Human Osteoblast-Like Cells on Boron-Doped Nanocrystalline Diamond Thin Films

    PubMed Central

    Grausova, Lubica; Kromka, Alexander; Burdikova, Zuzana; Eckhardt, Adam; Rezek, Bohuslav; Vacik, Jiri; Haenen, Ken; Lisa, Vera; Bacakova, Lucie

    2011-01-01

    Intrinsic nanocrystalline diamond (NCD) films have been proven to be promising substrates for the adhesion, growth and osteogenic differentiation of bone-derived cells. To understand the role of various degrees of doping (semiconducting to metallic-like), the NCD films were deposited on silicon substrates by a microwave plasma-enhanced CVD process and their boron doping was achieved by adding trimethylboron to the CH4:H2 gas mixture, the B?C ratio was 133, 1000 and 6700 ppm. The room temperature electrical resistivity of the films decreased from >10 M? (undoped films) to 55 k?, 0.6 k?, and 0.3 k? (doped films with 133, 1000 and 6700 ppm of B, respectively). The increase in the number of human osteoblast-like MG 63 cells in 7-day-old cultures on NCD films was most apparent on the NCD films doped with 133 and 1000 ppm of B (153,000±14,000 and 152,000±10,000 cells/cm2, respectively, compared to 113,000±10,000 cells/cm2 on undoped NCD films). As measured by ELISA per mg of total protein, the cells on NCD with 133 and 1000 ppm of B also contained the highest concentrations of collagen I and alkaline phosphatase, respectively. On the NCD films with 6700 ppm of B, the cells contained the highest concentration of focal adhesion protein vinculin, and the highest amount of collagen I was adsorbed. The concentration of osteocalcin also increased with increasing level of B doping. The cell viability on all tested NCD films was almost 100%. Measurements of the concentration of ICAM-1, i.e. an immunoglobuline adhesion molecule binding inflammatory cells, suggested that the cells on the NCD films did not undergo significant immune activation. Thus, the potential of NCD films for bone tissue regeneration can be further enhanced and tailored by B doping and that B doping up to metallic-like levels is not detrimental for cells. PMID:21695172

  18. Growth of boric acid crystallites on the surface of boron-doped silicon carbide samples

    SciTech Connect

    Vassen, R.; Stoever, D. [Forschungszentrum Juelich (Germany)

    1996-06-01

    White crystallites were visually observed on fractured or polished surfaces of SiC samples (grain sizes below {approx}500 nm) during exposure to air at room temperature for several days. Characterization of the crystallites by scanning electron microscopy, secondary ion mass spectroscopy, and X-ray diffraction identified B(OH){sub 3} crystals with a strong (002) texture. The rate of boric acid formation was determined by a gravimetric experiment. The rate of weight gain increased significantly after an incubation period of 1 week. Nucleation is initially the rate-limiting process. Subsequently small B(OH){sub 3} crystals form on the surface, whose growth rate is determined by grain boundary diffusion of boron to the SiC surface. An estimated grain boundary boron to the SiC surface. An estimated grain boundary diffusion coefficient of boron in SiC was many orders of magnitude higher than extrapolated literature values.

  19. Carbon 40 (2002) 22852289 Flexible graphite as a heating element

    E-print Network

    Chung, Deborah D.L.

    2002-01-01

    the intercalate). As a graphite deposited on boron nitride has been used [16]. result, flexible graphite and boilers. Flexible graphite is being somewhat connected perpendicular to the sheet (i.e. thus attractive

  20. Study of the Thermoelectric Properties of Lead Selenide Doped with Boron, Gallium, Indium, or Thallium

    SciTech Connect

    Zhang, Qian; Cao, Feng; Lukas, K; Liu, W S; Esfarjani, Keivan; Opeil, C; Broido, D; Parker, David; Singh, David J.; Chen, Gang; Ren, Z. F.

    2012-01-01

    Group IIIA elements (B, Ga, In, and Tl) have been doped into PbSe for enhancement of thermoelectric properties. The electrical conductivity, Seebeck coefficient, and thermal conductivity were systematically studied. Room-temperature Hall measurements showed an effective increase in the electron concentration upon both Ga and In doping and the hole concentration upon Tl doping to 7 × 10{sup 19} cm{sup –3}. No resonant doping phenomenon was observed when PbSe was doped with B, Ga, or In. The highest room-temperature power factor 2.5 × 10{sup –3} W m{sup –1} K{sup –2} was obtained for PbSe doped with 2 atom % B. However, the power factor in B-doped samples decreased with increasing temperature, opposite to the trend for the other dopants. A figure of merit (ZT) of 1.2 at 873 K was achieved in PbSe doped with 0.5 atom % Ga or In. With Tl doping, modification of the band structure around the Fermi level helped to increase the Seebeck coefficient, and the lattice thermal conductivity decreased, probably as a result of effective phonon scattering by both the heavy Tl{sup 3+} ions and the increased grain boundary density after ball milling. The highest p-type ZT value was 1.0 at 723 K.

  1. In vivo pH monitoring using boron doped diamond microelectrode and silver needles: Application to stomach disorder diagnosis

    NASA Astrophysics Data System (ADS)

    Fierro, Stéphane; Seishima, Ryo; Nagano, Osamu; Saya, Hideyuki; Einaga, Yasuaki

    2013-11-01

    This study presents the in vivo electrochemical monitoring of pH using boron doped diamond (BDD) microelectrode and silver needles for potential application in medical diagnosis. Accurate calibration curve for pH determination were obtained through in vitro electrochemical measurements. The increase induced in stomach pH by treatment with pantoprazole was used to demonstrate that it is possible to monitor the pH in vivo using the simple and noninvasive system proposed herein. Using the results of the in vivo and in vitro experiments, a quantitative analysis of the increase in stomach pH is also presented. It is proposed that the catheter-free pH monitoring system presented in this study could be potentially employed in any biological environment.

  2. Controlling the diffusion profile of electroactive species for selective anodic stripping voltammetry of cadmium at boron-doped diamond electrodes.

    PubMed

    Sugitani, Ai; Watanabe, Takeshi; Ivandini, Tribidasari A; Iguchi, Tatsuo; Einaga, Yasuaki

    2013-01-01

    Selective anodic stripping voltammetry of trace metal ions in a mixture solution with another interfering metal was developed based on Fick's law concerning the diffusion profile of interfering metals at the electrode surface after electrolysis treatment. A boron-doped diamond film was used as the sensing electrode, while a perforated carbon sheet was used for the interference-depleting electrode. The influence of the electrode distance and the time of electrolysis on the formation of the diffusion profile was studied. As a working model, the detection of cadmium with copper interference was investigated. The advantage of the method in comparison to general electrolysis was also discussed. The method offers a new perspective for improving the selective detection of metal ions by analyzing the diffusion profiles of the interfering species at the surface of electrodes. PMID:23147907

  3. In vitro evaluation of the tribological response of Mo-doped graphite-like carbon film in different biological media.

    PubMed

    Huang, Jinxia; Wang, Liping; Liu, Bin; Wan, Shanhong; Xue, Qunji

    2015-02-01

    Complicated tribochemical reactions with the surrounding media often occur at the prosthesis material, which is a dominant factor causing the premature failure in revision surgery. Graphite-like carbon (GLC) film has been proven to be an excellent tribological adaption to water-based media, and this work focused on the friction and wear behavior of Mo-doped GLC (Mo-GLC)-coated poly(aryl ether ether ketone) sliding against Al2O3 counterpart in physiological saline, simulated body fluid, and fetal bovine serum (FBS), which mainly emphasized the interface interactions of the prosthetic materials/lubricant. Results showed different tribological responses of Mo-GLC/Al2O3 pairs strongly correlated with the interfacial reactions of the contacting area. Particularly, a transfer layer was believed to be responsible for the excellent wear reduction of Mo-GLC/Al2O3 pair in FBS medium, in which graphitic carbon and protein species were contained. The wear mechanisms are tentatively discussed according to the morphologies and chemical compositions of the worn surfaces examined by scanning electron microscope as well as X-ray photoelectron spectroscopy. PMID:25580834

  4. Raman spectroscopy of graphene and graphite: Disorder, electron–phonon coupling, doping and nonadiabatic effects

    Microsoft Academic Search

    Andrea C. Ferrari

    2007-01-01

    We review recent work on Raman spectroscopy of graphite and graphene. We focus on the origin of the D and G peaks and the second order of the D peak. The G and 2D Raman peaks change in shape, position and relative intensity with number of graphene layers. This reflects the evolution of the electronic structure and electron–phonon interactions. We

  5. The effect of copper on the crystallization of hexagonal boron nitride

    Microsoft Academic Search

    Milan Hubacek; Tadao Sato

    1997-01-01

    The crystallization process of hexagonal boron nitride in the presence of copper has been investigated. The positive effect of copper on the crystallinity of boron nitride was observed in the three studied systems of: nitrided boron, nitrided boron–carbon, and previously prepared turbostratic boron nitride. However, the presence of copper hindered the formation of boron carbonitride and produced graphite and boron

  6. Molecular dynamics investigations of boron doping in a-Si:H

    SciTech Connect

    Fedders, P.A.; Drabold, D.A.

    1997-07-01

    The rather low doping efficiency of B in a-Si:H is almost always explained by the argument that almost all of the B is incorporated into three-fold coordinated sites and that B is inert or non-doping in this configuration. Using ab initio molecular dynamics, the authors have studied the energetics and doping (electronic structure) consequences of B incorporation into a-Si:H both with and without H passivation. Their results suggest that the conventional view is in error and that the low doping efficiency is primarily due to H passivation. These results are consistent with the low doping efficiency of B as well as NMR studies on the large electric field gradients experienced by the B atoms and on NMR double resonance studies of B-H neighboring distances.

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

    SciTech Connect

    Zhang, Ligang [Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chen, Xiufang; Guan, Jing; Jiang, Yijun; Hou, Tonggang [Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101 (China); Mu, Xindong, E-mail: muxd@qibebt.ac.cn [Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101 (China)

    2013-09-01

    Graphical abstract: - Highlights: • P-doped g-C{sub 3}N{sub 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{sub 3}N{sub 4}. • A postannealing treatment further enhanced the activity of P-doped g-C{sub 3}N{sub 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{sub 3}N{sub 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.

  8. Magnetization Study of Sulfur-doped Graphitic Nano-platelets and Single Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Oliveira, L.; Podila, R.; Neeleshwar, S.; Chen, Y. Y.; He, J.; Skove, M.; Rao, A. M.; Department of Physics and Astronomy, Clemson University Collaboration; Institute of Physics, Academia Sinica Collaboration

    2013-03-01

    Recently we investigated the magnetic behavior of as-prepared and sulfur doped chemically exfoliated graphene nano-platelets (GNPs) and single walled carbon nanotubes (SWCNTs). The doping was achieved by annealing desired carbon nanostructures with 0, 1.0, 1.5 and 3 at% sulfur in an evacuated quartz tube at 1000 °C for 1 day, followed by multiple rinsing in alcohol and drying in vacuum to remove excess sulfur. The isothermal M vs. H as well as the temperature-dependent M vs. T measurements were obtained using a vibrating sample magnetometer. We found that sulfur doping drastically changes the magnetic behavior of the as-prepared samples (both SWCNTs and GNPs). The results of zero-field-cooling (ZFC) and field-cooling (FC) in M vs. T measurements indicated the existence of large amount of coupled super-paramagnetic domains, along with antiferromagnetic domains. The saturation magnetization decreased in S doped GNPs, while a contrasting trend was observed in S doped SWCNTs. The role of edge states and structural defects in carbon nanostructures in the observed magnetic properties will be discussed.

  9. Fabrication route for the production of coplanar, diamond insulated, boron doped diamond macro- and microelectrodes of any geometry.

    PubMed

    Joseph, Maxim B; Bitziou, Eleni; Read, Tania L; Meng, Lingcong; Palmer, Nicola L; Mollart, Tim P; Newton, Mark E; Macpherson, Julie V

    2014-06-01

    Highly doped, boron doped diamond (BDD) is an electrode material with great potential, but the fabrication of suitable electrodes in a variety of different geometries both at the macro- and microscale, with an insulating material that does not compromise the material properties of the BDD, presents technical challenges. In this Technical Note, a novel solution to this problem is presented, resulting in the fabrication of coplanar macro- and microscale BDD electrodes, insulated by insulating diamond, at the single and multiple, individually addressable level. Using a laser micromachining approach, the required electrode(s) geometry is machined into an insulating diamond substrate, followed by overgrowth of high quality polycrystalline BDD (pBDD) and polishing to reveal approximately nanometer roughness, coplanar all-diamond structures. Electrical contacting is possible using both top and bottom contacts, where the latter are defined using the laser to produce non-diamond-carbon (NDC) in the vicinity of the back side of the BDD. We present the fabrication of individually addressable ring, band, and disk electrodes with minimum, reproducible controlled dimensions of 50 ?m (limited only by the laser system employed). The pBDD grown into the insulating diamond recesses is shown to be free from NDC and possesses excellent electrochemical properties, in terms of extended solvent windows, electrochemical reversibility, and capacitance. PMID:24814161

  10. Evidence for substitutional boron in doped single-walled carbon nanotubes

    SciTech Connect

    Ayala, P.; Pichler, T. [Faculty of Physics, University of Vienna, 1090 Wien (Austria); Reppert, J.; Rao, A. M. [Department of Physics and Astronomy and COMSET, Clemson University (United States); Grobosch, M.; Knupfer, M. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany)

    2010-05-03

    Precise determination of acceptors in the laser ablation grown B doped single-walled carbon nanotubes (SWCNTs) has been elusive. Photoemission spectroscopy finds evidence for subpercent substitutional B in this material, which leads to superconductivity in thin film SWNT samples.

  11. Interactions and magnetic relaxation in boron doped Mn3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Laha, S. S.; Mukherjee, R.; Lawes, G.

    2014-04-01

    We have studied magnetic interactions in phase pure Mn3O4 and composite Mn2O3/Mn3O4 nanoparticle systems having different interparticle separations between the Mn3O4 ferrimagnetic cores. We characterized the morphology and structure of these nanoparticles using x-ray diffraction and transmission electron microscopy. We find that the incorporation of boron stabilizes the Mn3O4 spinel structure resulting in the formation of phase pure nanoparticles, while in the absence of boron, the sample consists of both Mn3O4 and antiferromagnetic Mn2O3 nanoparticles. We correlate the morphology of these systems with their magnetic properties using ac susceptibility studies. The low temperature frequency dependent relaxation exhibits larger magnetic interactions in the phase pure Mn3O4 nanoparticles as compared to the Mn3O4/Mn2O3 composites, which we attribute to differences in the separation between the ferrimagnetic cores in these two samples.

  12. Low temperature deposition of boron-doped microcrystalline Si:H thin film and its application in silicon based thin film solar cells

    Microsoft Academic Search

    Ke Tao; Dexian Zhang; Jingfang Zhao; Linshen Wang; Hongkun Cai; Yun Sun

    2010-01-01

    Boron-doped hydrogenated microcrystalline silicon thin films (p-?c-Si:H) have been deposited by RF-PECVD method at different temperature, and the temperature dependence of growth kinetics and optoelectronic properties of p-?c-Si:H thin films have been studied. Both the deposition rate and the dark-conductivity of the p-?c-Si:H thin films drop down when the substrate temperature decreases. XRD and Raman measurements are used to characterize

  13. Charge transfer, bonding conditioning and solvation effect in the activation of the oxygen reduction reaction on unclustered graphitic-nitrogen-doped graphene.

    PubMed

    Ferre-Vilaplana, Adolfo; Herrero, Enrique

    2015-07-01

    The monodentate associative chemisorption of molecular oxygen on unclustered graphitic-nitrogen-doped graphene requires two nitrogen dopants per activated molecule. Significant charge transfers from regions corresponding to distant nitrogen-dopants, the presence of a nitrogen-dopant adjacent to the carbon atom acting as an active site, which favours its transition from a sp(2) hybridization state to sp(3), and the solvation effect turn the investigated mechanism to a favourable process. PMID:26054255

  14. Ab initio study of phase transition of boron nitride between zinc-blende and rhombohedral structures

    SciTech Connect

    Nishida, S.; Funashima, H.; Sato, K.; Katayama-Yoshida, H. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

    2013-12-04

    Boron nitride has polymorphs such as zinc-blende (c-BN), wurtzite (w-BN), rhombohedral (r-BN), and graphite-like (h-BN) forms. We simulate the direct conversion of r-BN to c-BN through electronic excitation. In our calculation, the conversion is made possible by increasing the hole concentration to over 0.06/atom. This conversion should be experimentally possible by hole-doping via an electric double layer transistor (EDLT) or capacitor.

  15. Characterization and properties of boron-doped aluminum hydroxide for Mn 2+ adsorption and soil acidification

    Microsoft Academic Search

    Shuijiao Liao; Guanglong Liu; Duanwei Zhu; Yue Li; Liying Ren; Jingzhen Cui

    2011-01-01

    Al hydroxide was prepared by hydrolysis of Al(NO3)3, and oc-B-Al hydroxide was prepared by hydrolysis of Al(NO3)3 in the presence of boric acid solution. Curve-fitted B1s XPS spectrum of oc-B-Al hydroxide demonstrated that the boron atom was probably incorporated with Al hydroxide to some extent.\\u000a The IR band of Al–OH at 1,074 cm?1 of oc-B-Al hydroxide was weaker than that of

  16. Medium-gain erbium doped fiber amplifier ring laser passively mode-locked by graphite nano-powder adhered thin PVA film

    NASA Astrophysics Data System (ADS)

    Lin, Yung-Hsiang; Lin, Gong-Ru

    2012-06-01

    A direct brushing process of graphite nano-powder adhered on the single-mode fiber end-face with the use of an ultrathin PVA film is demonstrated, such a graphite nano-powder adhered ultra-thin PVA film is introduced to passively mode-lock a medium-gain Erbium-doped fiber laser (EDFL). The structural property of the graphite nano-powder is investigated by Raman spectroscopy. Numerous structural defects induced when abrading the graphite into nano-powder are found to broaden the 2D band Raman scattered signal and attenuate its peak intensity. The graphite nano-powders exhibit the featureless transmittance to show the potential as being a broadband tuning saturable absorber. In addition, the modulation depth of 0.43 is comparable with the graphene saturable absorber. The central wavelength of the passively mode-locked medium-gain EDFL is at 1561.2 nm with the full width at half maximum (FHWM) of 1.62 nm, and the pulsewidth is 1.58 ps. Under the limited intra-cavity power of 18 dBm, a nearly transform-limited passively mode-locking EDFL with TBP of 0.32 is generated.

  17. A chemical mechanism for in situ boron doping during silicon chemical vapor deposition

    Microsoft Academic Search

    Istvan Lengyel; Klavs F. Jensen

    2000-01-01

    We present a systematic approach to formulating chemical mechanisms to chemical vapor deposition processes with the unusually large growth rate enhancement observed for in situ B doping of Si as a case study. The basic computational tools needed for mechanism development; quantum chemistry calculations, sensitivity analysis, and finite element simulations are combined to develop a mechanism for the process and

  18. Effect of Polishing on the Friction Behaviors and Cutting Performance of Boron-Doped Diamond Films on WC-Co Inserts

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Shen, Bin; Sun, Fanghong; Zhang, Zhiming

    2014-04-01

    Boron doped (B-doped) diamond films are deposited onto WC-Co inserts by HFCVD with the mixture of acetone, trimethyl borate (C3H9BO3) and H2. The as-deposited B-doped diamond films are characterized with scanning electron microscope (SEM), X-ray diffraction (XRD) spectroscopy, Raman spectroscopy, 3D surface topography based on white-light interferometry and Rockwell hardness tester. The effects of mechanical polishing on the friction behavior and cutting performance of B-doped diamond are evaluated by ball-on-plate type reciprocating tribometer and turning of aluminum alloy 7075 materials, respectively. For comparison, the same tests are also conducted for the bare WC-Co inserts with smooth surface. Friction tests suggest that the unpolished and polished B-doped diamond films possess relatively low fluctuation of friction coefficient than as-received bare WC-Co samples. The average stable friction coefficient for B-doped diamond films decreases apparently after mechanical polishing. The values for WC-Co sample, unpolished and polished B-doped diamond films are approximately 0.38, 0.25 and 0.11, respectively. The cutting results demonstrate that the low friction coefficient and high adhesive strength of B-doped diamond films play an essential role in the cutting performance enhancement of the WC-Co inserts. However, the mechanical polishing process may lower the adhesive strength of B-doped diamond films. Consequently, the polished B-doped diamond coated inserts show premature wear in the machining of adhesive aluminum alloy materials.

  19. The analysis of estrogenic compounds by flow injection analysis with amperometric detection using a boron-doped diamond electrode.

    PubMed

    Brocenschi, Ricardo F; Rocha-Filho, Romeu C; Duran, Boris; Swain, Greg M

    2014-08-01

    We report on the use of flow injection analysis with amperometric detection (FIA-EC) to evaluate the potential of using diamond electrodes for the analysis of three estrogenic compounds: estrone, 17-?-estradiol, and estriol. Amperometric detection was performed using a cathodically pretreated boron-doped diamond electrode that offered low background current, relatively low limits of detection, and good response reproducibility and stability. For all three compounds, response linearity was observed over the concentration range tested, 0.10 to 3.0?mol L(-1), the sensitivity was ca. 10mA L mol(-1), and the minimum concentration detection (S/N?3) was 0.10?mol L(-1) (~27?g L(-1)). The response variability with multiple injections was ca. 10% (RSD) over 20 injections. For estrone, the oxidation reaction on diamond does not proceed through an adsorbed state like it does on glassy carbon. After an initial current attenuation, the diamond electrode exhibited a stable response (oxidation current) for 3 days of continuous use, indicative of minimal surface contamination or fouling by reaction intermediates and products. The method for estrone was assessed using spiked city tap and local river water. Estrone recoveries in spiked city and river water samples presented standard deviations of less than 10%. In summary, the FIA-EC method with a diamond electrode enables sensitive, reproducible, stable, quick, and inexpensive determination of estrogenic compounds in water samples. PMID:24881529

  20. Removal of organic contaminants from secondary effluent by anodic oxidation with a boron-doped diamond anode as tertiary treatment.

    PubMed

    Garcia-Segura, Sergi; Keller, Jürg; Brillas, Enric; Radjenovic, Jelena

    2015-02-11

    Electrochemical advanced oxidation processes (EAOPs) have been widely investigated as promising technologies to remove trace organic contaminants from water, but have rarely been used for the treatment of real waste streams. Anodic oxidation with a boron-doped diamond (BDD) anode was applied for the treatment of secondary effluent from a municipal sewage treatment plant containing 29 target pharmaceuticals and pesticides. The effectiveness of the treatment was assessed from the contaminants decay, dissolved organic carbon and chemical oxygen demand removal. The effect of applied current and pH was evaluated. Almost complete mineralization of effluent organic matter and trace contaminants can be obtained by this EAOP primarily due to the action of hydroxyl radicals formed at the BDD surface. The oxidation of Cl(-) ions present in the wastewater at the BDD anode gave rise to active chlorine species (Cl2/HClO/ClO(-)), which are competitive oxidizing agents yielding chloramines and organohalogen byproducts, quantified as adsorbable organic halogen. However, further anodic oxidation of HClO/ClO(-) species led to the production of ClO3(-) and ClO4(-) ions. The formation of these species hampers the application as a single-stage tertiary treatment, but posterior cathodic reduction of chlorate and perchlorate species may reduce the risks associated to their presence in the environment. PMID:25464295

  1. Electrochemical disinfection using boron-doped diamond electrode--the synergetic effects of in situ ozone and free chlorine generation.

    PubMed

    Rajab, Mohamad; Heim, Carolin; Letzel, Thomas; Drewes, Jörg E; Helmreich, Brigitte

    2015-02-01

    This work investigated the capability of using a boron-doped diamond (BDD) electrode for bacterial disinfection in different water matrices containing varying amounts of chloride. The feed water containing Pseudomonas aeruginosa was electrochemically treated while applying different electrode conditions. Depending on the applied current density and the exposure time, inactivation between 4- and 8-log of the targeted microorganisms could be achieved. The disinfection efficiency was driven by the generation of free chlorine as a function of chloride concentration in the water. A synergetic effect of generating both free chlorine and ozone in situ during the disinfection process resulted in an effective bactericidal impact. The formation of the undesired by-products chlorate and perchlorate depended on the water matrix, the applied current density and the desired target disinfection level. In case of synthetic water with a low chloride concentration (20 mg L(-1)) and an applied current density of 167 mA cm(-2), a 6-log inactivation of Pseudomonas aeruginosa could be achieved after 5 min of exposure. The overall energy consumption ranged between 0.3 and 0.6 kW h m(-3) depending on the applied current density and water chemistry. Electrochemical water disinfection represents a suitable and efficient process for producing pathogen-free water without the use of any chemicals. PMID:25434271

  2. Surface Transfer Doping of Cubic Boron Nitride Films by MoO3 and Tetrafluoro-tetracyanoquinodimethane (F4-TCNQ).

    PubMed

    He, Bin; Ng, Tsz-Wai; Lo, Ming-Fai; Lee, Chun-Sing; Zhang, Wenjun

    2015-05-13

    Cubic boron nitride (cBN) has strong potential for the applications in high-temperature and high-power electronics and deep ultraviolet devices due to its outstanding combined physical and chemical properties. P-type surface transfer doping of heteroepitaxial cBN films was achieved by employing MoO3 and tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) as the surface dopants. The surface conductivities of hydrogenated cBN films increased by 3-6 orders after the deposition of surface dopants. The photoemission spectroscopy (PES) measurements revealed the variation of electronic structures at the interface regions, which suggested that the electron transfer from cBN films to the surface dopants induced hole accumulation at the cBN surface and the increase of surface conductivity. Based on the PES results, the energy level diagrams at MoO3/cBN and F4-TCNQ/cBN interfaces were determined. The achievement provided a potential approach for fabricating cBN-based electronic devices, especially on micrometer and nanometer scales. PMID:25915092

  3. Synergetic antibacterial activity of reduced graphene oxide and boron doped diamond anode in three dimensional electrochemical oxidation system.

    PubMed

    Qi, Xiujuan; Wang, Ting; Long, Yujiao; Ni, Jinren

    2015-01-01

    A 100% increment of antibacterial ability has been achieved due to significant synergic effects of boron-doped diamond (BDD) anode and reduced graphene oxide (rGO) coupled in a three dimensional electrochemical oxidation system. The rGO, greatly enhanced by BDD driven electric field, demonstrated strong antibacterial ability and even sustained its excellent performance during a reasonable period after complete power cut in the BDD-rGO system. Cell damage experiments and TEM observation confirmed much stronger membrane stress in the BDD-rGO system, due to the faster bacterial migration and charge transfer by the expanded electro field and current-carrying efficiency by quantum tunnel. Reciprocally the hydroxyl-radical production was eminently promoted with expanded area of electrodes and delayed recombination of the electron-hole pairs in presence of the rGO in the system. This implied a huge potential for practical disinfection with integration of the promising rGO and the advanced electrochemical oxidation systems. PMID:25994309

  4. Pilot scale performance of the electro-oxidation of landfill leachate at boron-doped diamond anodes.

    PubMed

    Anglada, Angela; Urtiaga, Ane; Ortiz, Inmaculada

    2009-03-15

    During the electrochemical oxidation of real wastewaters, the different species present in the effluent may interact creating complex scenarios making the prediction of the behavior of the whole system difficult. In this paper the different phenomena that occur during the electro-oxidation process of landfill leachate at a pilot plant scale with boron-doped diamond (BDD) anodes are elucidated. The total BDD anode area of the pilot plant was 1.05 m2. The evolution of the concentration of chloride ions, chlorate, and inorganic carbon and the value of pH and redox potential were found to be inter-related. In turn, the concentration of chloride affected the oxidation of ammonia, which took place through indirect oxidation by active chlorine. Moreover, chloride ions competed with organic matter to be oxidized at the anode. The effect of current density was also investigated. Organic matter and ammonia oxidation were highly influenced by the applied current density value. A change in the mechanism of organic matter oxidation was observed when high current densities were applied. Two mathematical models, previously applied to the oxidation of synthetic wastewaters in the literature, were able to predict the evolution of chemical oxygen demand and ammonia for low current density values. PMID:19368210

  5. Experimental Approach to Controllably Vary Protein Oxidation While Minimizing Electrode Adsorption for Boron-Doped Diamond Electrochemical Surface Mapping Applications

    SciTech Connect

    McClintock, Carlee [ORNL; Hettich, Robert {Bob} L [ORNL

    2013-01-01

    Oxidative protein surface mapping has become a powerful approach for measuring the solvent accessibility of folded protein structures. A variety of techniques exist for generating the key reagent hydroxyl radicals for these measurements; however, many of these approaches require use of radioactive sources or caustic oxidizing chemicals. The purpose of this research was to evaluate and optimize the use of boron-doped diamond (BDD) electrochemistry as a highly accessible tool for producing hydroxyl radicals as a means to induce a controllable level of oxidation on a range of intact proteins. These experiments utilize a relatively high flow rates to reduce protein residence time inside the electrochemical flow chamber, along with a unique cell activation approach to improve control over the intact protein oxidation yield. Studies were conducted to evaluate the level of protein adsorption onto the electrode surface. This report demonstrates a robust protocol for the use of BDD electrochemistry and high performance LC-MS/MS as a high-throughput experimental pipeline for probing higher order protein structure, and illustrates how it is complementary to predictive computational modeling efforts.

  6. Photovoltaic devices based on high density boron-doped single-walled carbon nanotube/n-Si heterojunctions

    DOE PAGESBeta

    Saini, Viney; Li, Zhongrui; Bourdo, Shawn; Kunets, Vasyl P.; Trigwell, Steven; Couraud, Arthur; Rioux, Julien; Boyer, Cyril; Nteziyaremye, Valens; Dervishi, Enkeleda; et al

    2011-01-13

    A simple and easily processible photovoltaic device has been developed based on borondoped single-walled carbon nanotubes (B-SWNTs) and n-type silicon (n-Si) heterojunctions. The single-walled carbon nanotubes (SWNTs) were substitutionally doped with boron atoms by thermal annealing, in the presence of B2O3. The samples used for these studies were characterized by Raman spectroscopy, thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). The fully functional solar cell devices were fabricated by airbrush deposition that generated uniform B-SWNT films on top of the n-Si substrates. The carbon nanotube films acted as exciton-generation sites, charge collection and transportation, whilemore »the heterojunctions formed between B-SWNTs and n-Si acted as charge dissociation centers. The current-voltage characteristics in the absence of light and under illumination, as well as optical transmittance spectrum are reported here. It should be noted that the device fabrication process can be made amenable to scalability by depositing direct and uniform films using airbrushing, inkjet printing, or spin-coating techniques.« less

  7. Application of electrochemical technology for removing petroleum hydrocarbons from produced water using lead dioxide and boron-doped diamond electrodes.

    PubMed

    Gargouri, Boutheina; Gargouri, Olfa Dridi; Gargouri, Bochra; Trabelsi, Souhel Kallel; Abdelhedi, Ridha; Bouaziz, Mohamed

    2014-12-01

    Although diverse methods exist for treating polluted water, the most promising and innovating technology is the electrochemical remediation process. This paper presents the anodic oxidation of real produced water (PW), generated by the petroleum exploration of the Petrobras plant-Tunisia. Experiments were conducted at different current densities (30, 50 and 100 mA cm(-2)) using the lead dioxide supported on tantalum (Ta/PbO2) and boron-doped diamond (BDD) anodes in an electrolytic batch cell. The electrolytic process was monitored by the chemical oxygen demand (COD) and the residual total petroleum hydrocarbon [TPH] in order to know the feasibility of electrochemical treatment. The characterization and quantification of petroleum wastewater components were performed by gas chromatography mass spectrometry. The COD removal was approximately 85% and 96% using PbO2 and BDD reached after 11 and 7h, respectively. Compared with PbO2, the BDD anode showed a better performance to remove petroleum hydrocarbons compounds from produced water. It provided a higher oxidation rate and it consumed lower energy. However, the energy consumption and process time make useless anodic oxidation for the complete elimination of pollutants from PW. Cytotoxicity has shown that electrochemical oxidation using BDD could be efficiently used to reduce more than 90% of hydrocarbons compounds. All results suggest that electrochemical oxidation could be an effective approach to treat highly concentrated organic pollutants present in the industrial petrochemical wastewater and significantly reduce the cost and time of treatment. PMID:25129707

  8. Photovoltaic devices based on high density boron-doped single-walled carbon nanotube/n-Si heterojunctions

    SciTech Connect

    Saini, Viney [Univ. of Arkansas, Little Rock, AR (United States); Li, Zhongrui [Univ. of Arkansas, Little Rock, AR (United States); Bourdo, Shawn [Univ. of Arkansas, Little Rock, AR (United States); Kunets, Vasyl P. [Univ. of Arkansas, Fayetteville, AR (United States); Trigwell, Steven [ASRC Aerospace Corp., Kennedy Space Center, FL (United States); Couraud, Arthur [Univ. of Arkansas, Little Rock, AR (United States) and Ecole d'Ingenieurs de CESI-EIA, La Couronne (France); Rioux, Julien [Univ. of Arkansas, Little Rock, AR (United States) and Ecole d'Ingenieurs du CESI-EIA, La Couronne (France); Boyer, Cyril [Univ. of Arkansas, Little Rock, AR (United States) and Ecole d'Ingenieurs du CESI-EIA, La Couronne (France); Nteziyaremye, Valens [Univ. of Arkansas, Little Rock, AR (United States); Dervishi, Enkeleda [Univ. of Arkansas, Little Rock, AR (United States); Biris, Alexandru R. [National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca (Romania); Salamo, Gregory J. [Univ. of Arkansas, Fayetteville, AR (United States); Viswanathan, Tito [Univ. of Arkansas, Little Rock, AR (United States); Biris, Alexandru S. [Univ. of Arkansas, Little Rock, AR (United States)

    2011-01-13

    A simple and easily processible photovoltaic device has been developed based on borondoped single-walled carbon nanotubes (B-SWNTs) and n-type silicon (n-Si) heterojunctions. The single-walled carbon nanotubes (SWNTs) were substitutionally doped with boron atoms by thermal annealing, in the presence of B2O3. The samples used for these studies were characterized by Raman spectroscopy, thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). The fully functional solar cell devices were fabricated by airbrush deposition that generated uniform B-SWNT films on top of the n-Si substrates. The carbon nanotube films acted as exciton-generation sites, charge collection and transportation, while the heterojunctions formed between B-SWNTs and n-Si acted as charge dissociation centers. The current-voltage characteristics in the absence of light and under illumination, as well as optical transmittance spectrum are reported here. It should be noted that the device fabrication process can be made amenable to scalability by depositing direct and uniform films using airbrushing, inkjet printing, or spin-coating techniques.

  9. Electrochemical degradation of a real textile effluent using boron-doped diamond or ?-PbO2 as anode.

    PubMed

    Aquino, José M; Pereira, Gabriel F; Rocha-Filho, Romeu C; Bocchi, Nerilso; Biaggio, Sonia R

    2011-09-15

    Constant current electrolyses are carried out in a filter-press reactor using a boron-doped diamond (Nb/BDD) or a Ti-Pt/?-PbO(2) anode, varying current density (j) and temperature. The degradation of the real textile effluent is followed by its decolorization and chemical oxygen demand (COD) abatement. The effect of adding NaCl (1.5 g L(-1)) on the degradation of the effluent is also investigated. The Nb/BDD anode yields much higher decolorization (attaining the DFZ limit) and COD-abatement rates than the Ti-Pt/?-PbO(2) anode, at any experimental condition. The best conditions are j = 5 mA cm(-2) and 55 °C, for the system's optimized hydrodynamic conditions. The addition of chloride ions significantly increases the decolorization rate; thus a decrease of more than 90% of the effluent relative absorbance is attained using an applied electric charge per unit volume of the electrolyzed effluent (Q(ap)) of only about 2 kA h m(-3). Practically total abatement of the effluent COD is attained with the Nb/BDD anode using a Q(ap) value of only 7 kA h m(-3), with an energy consumption of about 30 kW h m(-3). This result allows to conclude that the Nb/BDD electrode might be an excellent option for the remediation of textile effluents. PMID:21742436

  10. Boron ion implantation on Al-doped ZnO films for OLEDs transparent conducting electrodes

    Microsoft Academic Search

    Sang-Jin Hong; Gi-Seok Heo; Bum-Ho Choi; Dong-Chan Shin

    2006-01-01

    B+-implanted Al-doped ZnO (AZO) films were fabricated by ion implantation with various ion energies and doses for transparent conducting oxide (TCO) electrodes of organic light-emitting diodes (OLEDs). The resistance of the B-implanted AZO films was decreased with increasing ion dose. The work function of the implanted films was increased compared to the un-implanted AZO films. All implanted films exhibited high

  11. Accurate computational studies of carbon doped two-dimensional boron-nitride

    NASA Astrophysics Data System (ADS)

    Park, Hyoungki; Wadehra, Amita; Wilkins, John W.; Castro Neto, Antonio H.

    2012-02-01

    Advances in development of atomic-layer crystals with a plethora of new materials are greatly extending the range of possible applications of these two-dimensional (2D) materials. One of these materials is the hexagonal structure of boron nitride (h-BN). Hexagonal BN has a wide band gap and a lattice constant similar to that of graphene. We show that even small quantities of C atoms can offer new functionalities and transform h-BN to be an amazing playground for 2D physics. Large-scale accurate density-functional-theory calculations with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional reveal the electronic and the magnetic properties of h-BN with substitutionally embedded carbon atoms. Results of local magnetic moments induced by substitution and their interactions are presented for low C concentrations. We also show the electronic structures of quantum dots made of carbon nano-domains for applications in optics and opto-electronics.

  12. Facile synthesis of boron- and nitride-doped MoS2 nanosheets as fluorescent probes for the ultrafast, sensitive, and label-free detection of Hg(2.).

    PubMed

    Liu, Xiaojia; Li, Liping; Wei, Yuanjie; Zheng, Yizhi; Xiao, Qian; Feng, Bo

    2015-06-15

    Bulk MoS2, a prototypical transition metal chalcogenide material, is an indirect band gap semiconductor with negligible photoluminescence. In this study, we have developed, for the first time, a simple and low-cost synthetic strategy to prepare boron- and nitrogen-doped MoS2 (B,N-MoS2) nanosheets. Through boron and nitrogen doping, the band gap of MoS2 increases from 1.20 eV to 1.61 eV, and the obtained B,N-MoS2 nanosheets exhibit an enhanced fluorescence. The B,N-MoS2 nanosheets can be used as a green and facile sensing platform for label-free detection of Hg(2+) because of their high sensitivity and selectivity toward Hg(2+). In addition, detection can be easily accomplished through one-step rapid (within 2 min) operation, with a limit as low as 1 nM. This study demonstrates that the introduction of boron and nitrogen elements into ultrathin MoS2 nanosheets for enhanced fluorescence properties is feasible through a facile and general preparation strategy and may also offer a unique idea as a potential way to design more efficient MoS2-based sensors and fluorescent materials. PMID:25988202

  13. A rapid and sensitive method for hydroxyl radical detection on a microfluidic chip using an N-doped porous carbon nanofiber modified pencil graphite electrode.

    PubMed

    Ouyang, Jun; Li, Zhong-Qiu; Zhang, Jing; Wang, Chen; Wang, Jiong; Xia, Xing-Hua; Zhou, Guo-Jun

    2014-07-01

    Hydroxyl radicals (?OH) play an important role in human diseases. Traditional detection methods are time consuming and require expensive instruments. Here, we present a simple and sensitive method for the detection of hydroxyl radicals on a microfluidic chip using an electrochemical technique. Aniline monomer is electrochemically polymerized on the surface of a pencil graphite electrode and carbonized at 800 °C. The resulting N-doped porous carbon nanofiber-modified pencil graphite electrode is embedded into a microfluidic chip directly as a working electrode. 4-Hydroxybenzoic acid (4-HBA) is selected as the trapping agent owing to its unique 3,4-DHBA product and high trapping efficiency. A low detection limit of 1.0 × 10(-6) M is achieved on the microfluidic chip. As a demonstration, the microfluidic chip is successfully utilized for the detection of ?OH in cigarette smoke. The strong ?-? stacking and hydrophobic interactions between the nitrogen-doped carbon materials and the pencil graphite make the modified electrode well-suited for the microfluidic chip. PMID:24834984

  14. Evidence of loss of active lithium in titanium-doped LiNi0.5Mn1.5O4/graphite cells

    NASA Astrophysics Data System (ADS)

    Höweling, Andres; Glatthaar, Sven; Nötzel, Dorit; Binder, Joachim R.

    2015-01-01

    Lithium-ion batteries require higher energy densities to meet with a broad acceptance in the fields of electric vehicles and grid storage solutions. LiNi0.5Mn1.5O4 (LNMO) can fulfill this goal due to its high operating voltage. Cycling of LNMO is known to be stable vs. lithium metal anode. Cycling in an LNMO/graphite configuration leads to severe capacity fade. Ti-doped LNMO (LNMTO)/graphite cells experience a lower, but still strong loss of capacity. In order to understand capacity fade, cycling tests of LNMTO vs. graphite and vs. lithium metal were carried out and additionally, three electrode tests were performed. Both cell configurations showed similar Coulombic efficiencies correlating with the applied C-rate. Experimental data and mathematical modeling indicated that loss of active lithium with a constant reaction rate of (3.76 ± 0.46) · 10-8 mol Li h-1 is responsible for capacity fade in LNMTO/graphite cells and that no degradation of the active material occurs. It was concluded that lithium loss also occurs when lithium metal anodes are used. Here, the lithium metal anode can compensate for lithium consumption, as a result of which the capacity is not influenced. Further support for lithium consumption is given by a three-electrode cell with a lithiated graphite anode. The lithium in the graphite anode can compensate the lithium loss for 120 cycles. During this time, the cell experienced hardly any capacity fade and the voltage profile was similar to that of a cell with LNMTO/Li configuration.

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

    PubMed

    Xia, Kang; Zhan, Haifei; Wei, Ye; Gu, Yuantong

    2014-01-01

    Doping is an effective approach that allows for the intrinsic modification of the electrical and chemical properties of nanomaterials. Recently, a graphene and carbon nanotube hybrid structure (GNHS) has been reported, which extends the excellent properties of carbon-based materials to three dimensions. In this paper, we carried out a first-time investigation on the tensile properties of the hybrid structures with different dopants. It is found that with the presence of dopants, the hybrid structures usually exhibit lower yield strength, Young's modulus, and earlier yielding compared to that of a pristine hybrid structure. For dopant concentrations below 2.5% no significant reduction of Young's modulus or yield strength could be observed. For all considered samples, the failure is found to initiate at the region where the nanotubes and graphene sheets are connected. After failure, monatomic chains are normally observed around the failure region. Dangling graphene layers without the separation of a residual CNT wall are found to adhere to each other after failure with a distance of about 3.4 Å. This study provides a fundamental understanding of the tensile properties of the doped graphene-nanotube hybrid structures, which will benefit the design and also the applications of graphene-based hybrid materials. PMID:24778956

  16. Hydrogen Diffusion and Microstructure in Undoped and Boron-Doped Hydrogenated Amorphous Silicon: AN IR and SIMS STUDY*

    NASA Astrophysics Data System (ADS)

    Mitra, Saibal

    Hydrogenated amorphous silicon (a-Si:H) prepared by rf sputtering of a polycrystalline Si target at various rf powers 50 <= P <= 550 W (0.27-2.97 W/cm^2), target to substrate distance 1 <= d <= 2^{' '}, and varying hydrogen partial pressures. Doping was accomplished by introducing diborane (B_2H_6) in the plasma. Hydrogen diffusion was studied from the depth profiles obtained from the SIMS on multilayered a -Si:H/a-Si:(H,D)/a-Si:H samples. The properties of the samples were characterized by IR absorption, optical gap measurements and ESR. IR yielded quantitative and qualitative information total hydrogen content and the nature of hydrogen bonding, respectively. Hence the hydrogen microstructure of the samples could be varied in a systematic manner and monitored from the hydrogen vibrational modes. The ESR gave information on the number of paramagnetic defects per unit volume in the samples. The IR absorption of both as-deposited and annealed samples were closely monitored and the results clearly demonstrate a strong correlation between hydrogen diffusion and its microstructure. It is shown that microvoids in a-Si:H play a critical role in the process of diffusion by inducing deep hydrogen trapping sites that render them immobile. Consequently, as the microvoid density increases beyond a critical density (corresponding to N_ {rm d} >= 6.5 at. %) hydrogen diffusion is totally quenched. The diffusion results are discussed both in the context of multiple trapping transport of hydrogen in an exponential distribution of trapping sites and the floating bond model. As expected the hydrogen diffusion in boron-doped a-Si:H is faster than undoped material by a few orders of magnitude. The diffusion results have shown a significant departure from the power-law time dependence upon prolonged annealing. Such a departure has not been reported before. It is suspected that this deviation is caused by structural relaxations of the silicon network. ftn*DOE Report IS -T-1506. This work was performed under contract No W-7405 -Eng-82 with US Department of Energy.

  17. Determination of parabens in shampoo using high performance liquid chromatography with amperometric detection on a boron-doped diamond electrode.

    PubMed

    Martins, Isarita; Carreira, Franciely Cristiani; Canaes, Larissa S; de Souza Campos Junior, Francisco Alberto; da Silva Cruz, Letícia Maria; Rath, Susanne

    2011-07-15

    Methylparaben (MePa), ethylparaben (EtPa) and propylparaben (PrPa) have been widely used, among others, as chemical preservatives in cosmetics, drugs and foods. As these compounds are linked with allergies, dermatitis and estrogenic properties, it is necessary to control the concentration of these substances in different matrices. The aim of this paper are: to evaluate the electrochemical behavior of parabens on the boron-doped diamond (BDD) electrode and the development of a chromatographic method, with electrochemical detection (HPLC-ED), for determination of parabens in shampoo. A BDD (8000 ppm) electrode was adapted in a thin layer mode analytical cell consisting of a stainless steel and a platinum wire as reference and auxiliary electrodes, respectively. Chromatographic separations were obtained with a reversed phase C8 analytical column and a mobile phase of 0.025 molL(-1) disodium phosphate, pH 7.0, and acetonitrile (40:60, v/v), delivered at a flow rate of 1.0 mL min(-1). Sample preparation was performed by solid phase extraction using C18 cartridges and acetonitrile for elution. Benzylparaben was employed as internal standard. The HPLC-ED method developed, using the BDD electrode, was validated for the determination of parabens in shampoos and presented adequate linearity (>0.999), in the range of 0.0125-0.500% (w/w), detectability 0.01% (w/w), precision (RSD of 2.3-9.8%) and accuracy (93.1-104.4%) and could be applied for routine quality control of shampoos containing MePa, EtPa and PrPa. PMID:21645663

  18. Doping inhomogeneity and staging of ultra-thin graphite intercalation compound flakes probed by visible and near-infrared Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Yan; Zhang, Xin; Wu, Jiang-Bin; Li, Xiao-Li; Li, Qiao-Qiao; Tan, Ping-Heng

    2015-07-01

    When ultra-thin graphite intercalation compounds (GICs) are deposited on the SiO2/Si substrate, it is found that their colors are dependent on the thickness of GIC flakes. The sample colors of ultrathin GIC flakes can no longer provide qualitative information on the stage index. Here, multi-wavelength Raman spectroscopy is thus applied to study the doping inhomogeneity and staging of ultra-thin GICs by FeCl3 intercalation. The G band intensity of stage-1 GIC flakes is strongly enhanced by 532-nm laser excitation, while that of stage-2 and stage-3 flakes exhibits strong intensity enhancement for 785-nm laser excitation. The near-infrared lasers are suggested to probe the doping inhomogeneity and staging of ultra-thin GIC flakes. Project supported by the National Natural Science Foundation of China (Grant Nos. 11225421, 11474277, and 11434010).

  19. Electronic transport in heavily Si doped cubic boron nitride films epitaxially grown on diamond(001)

    NASA Astrophysics Data System (ADS)

    Yin, Hong; Pongrac, Ivan; Ziemann, Paul

    2008-07-01

    Structural phase analysis and measurements of electronic transport properties were carried out on heavily Si-implanted cubic (c-) BN films heteroepitaxially grown on diamond(001). Pure cubic phase can be conserved after Si implantation up to a concentration of 2×1020cm-3 and a related implantation damage of 0.9 displacements per atom. As a result, the temperature dependent sheet resistance is lowered by seven orders of magnitude as compared to undoped films. By temperature dependent Hall effect measurements, n-type conduction is confirmed for these heavily Si-implanted c-BN films. Due to the high Si doping levels a semiconductor-to-metal transition is approached as signaled by the extremely small activation energies of typically 0.05eV as well as by an almost temperature independent negative carrier concentration up to 470K. At higher temperatures an additional activated process sets in resulting in a further increase in carrier concentration with an activation energy of 0.4eV.

  20. Carrier transport properties of the Group-IV ferromagnetic semiconductor Ge{sub 1-x}Fe{sub x} with and without boron doping

    SciTech Connect

    Ban, Yoshisuke, E-mail: ban@cryst.t.u-tokyo.ac.jp; Wakabayashi, Yuki; Akiyama, Ryota; Nakane, Ryosho; Tanaka, Masaaki, E-mail: masaaki@ee.t.u-tokyo.ac.jp [Department of Electronic Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2014-09-15

    We have investigated the transport and magnetic properties of group-IV ferromagnetic semiconductor Ge{sub 1-x}Fe{sub x} films (x = 1.0 and 2.3%) with and without boron doping grown by molecular beam epitaxy (MBE). In order to accurately measure the transport properties of 100-nm-thick Ge{sub 1-x}Fe{sub x} films, (001)-oriented silicon-on-insulator (SOI) wafers with an ultra-thin Si body layer (?5 nm) were used as substrates. Owing to the low Fe content, the hole concentration and mobility in the Ge{sub 1-x}Fe{sub x} films were exactly estimated by Hall measurements because the anomalous Hall effect in these films was found to be negligibly small. By boron doping, we increased the hole concentration in Ge{sub 1-x}Fe{sub x} from ?10{sup 18} cm{sup ?3} to ?10{sup 20} cm{sup ?3} (x = 1.0%) and to ?10{sup 19} cm{sup ?3} (x = 2.3%), but no correlation was observed between the hole concentration and magnetic properties. This result presents a contrast to the hole-induced ferromagnetism in III-V ferromagnetic semiconductors.

  1. Effects of surfactant and boron doping on the BWF feature in the Raman spectrum of single-wall carbon nanotube aqueous dispersions.

    PubMed

    Blackburn, Jeff L; Engtrakul, Chaiwat; McDonald, Timothy J; Dillon, Anne C; Heben, Michael J

    2006-12-21

    We examine the Breit-Wigner-Fano (BWF) line shape in the Raman spectra of carbon single-wall nanotubes (SWNTs) dispersed in aqueous suspensions. Bundling and electronic effects are studied by comparing undoped SWNTs (C-SWNTs) to boron-doped nanotubes (B-SWNTs) in a variety of different surfactant solutions. For SWNTs dispersed with nonionic surfactants that are less effective in debundling than ionic surfactants, the Raman spectra retain a large BWF feature. However, we demonstrate that even for SWNTs dispersed as isolated nanotubes by ionic surfactants the BWF feature may be present and that the intensity of the BWF is highly sensitive to the specific surfactant. In particular, surfactants with electron-donating groups tend to enhance the BWF feature. Also, modification of the SWNT electronic properties by boron doping leads to enhanced surfactant dispersion relative to undoped C-SWNTs and also to modification of the BWF feature. These observations are in agreement with reports demonstrating an enhancement of the BWF by bundling but also agree with reports that suggest electron donation can enhance the BWF feature even for isolated SWNTs. Importantly, these results serve to caution against using the lack or presence of a BWF feature as an independent measure of SWNT aggregation in surfactant dispersions. PMID:17166007

  2. Effects of bimetallic doping on small cyclic and tubular boron clusters: B7M2 and B14M2 structures with M = Fe, Co.

    PubMed

    Pham, Hung Tan; Nguyen, Minh Tho

    2015-06-24

    Using density functional theory with the TPSSh functional and the 6-311+G(d) basis set, we extensively searched for the global minima of two metallic atoms doped boron clusters B6M2, B7M2, B12M2 and B14M2 with transition metal element M being Co and Fe. Structural identifications reveal that B7Co2, B7Fe2 and B7CoFe clusters have global minima in a B-cyclic motif, in which a perfectly planar B7 is coordinated with two metallic atoms placed along the C7 axis. The B6 cluster is too small to form a cycle with the presence of two metals. Similarly, the B12 cluster is not large enough to stabilize the metallic dimer within a double ring 2 × B6 tube. The doped B14M2 clusters including B14Co2, B14Fe2 and B14CoFe have a double ring 2 × B7 tubular shape in which one metal atom is encapsulated by the B14 tube and the other is located at an exposed position. Dissociation energies demonstrate that while bimetallic cyclic cluster B7M2 prefers a fragmentation channel that generates the B7 global minimum plus metallic dimer, the tubular structure B14M2 tends to dissociate giving a bimetallic cyclic structure B7M2 and a B@B6 cluster. The enhanced stability of the bimetallic doped boron clusters considered can be understood from the stabilizing interactions between the anti-bonding MOs of metal-metal dimers and the levels of a disk aromatic configuration (for bimetallic cyclic structures), or the eigenstates of the B14 tubular form (in case of bimetallic tubular structure). PMID:26073876

  3. (Fe,Co)@nitrogen-doped graphitic carbon nanocubes derived from polydopamine-encapsulated metal-organic frameworks as a highly stable and selective non-precious oxygen reduction electrocatalyst.

    PubMed

    Xi, Jiangbo; Xia, Yating; Xu, Yangyang; Xiao, Junwu; Wang, Shuai

    2015-06-16

    A facile approach is reported to synthesize (Fe,Co)@nitrogen-doped graphitic carbon (NGC) nanocubes (NCs) via the pyrolysis of polydopamine-encapsulated Fe3[Co(CN)6]2 NCs at 700 °C. Besides the comparable catalytic activity for oxygen reduction reaction (ORR) to the Pt/C catalyst, it showed much more outstanding catalytic selectivity and superior durability. PMID:26027817

  4. Fillers for improved graphite fiber retention by polymer matrix composites

    NASA Technical Reports Server (NTRS)

    House, E. E.; Sheppard, C. H.

    1981-01-01

    The results of a program designed to determine the extent to which elemental boron and boron containing fillers added to the matrix resin of graphite/epoxy composites prevent the release of graphite fibers when the composites are exposed to fire and impact conditions are described. The fillers evaluated were boron, boron carbide and aluminum boride. The conditions evaluated were laboratory simulations of those that could exist in the event of an aircraft crash and burn situation. The baseline (i.e., unfilled) laminates evaluated were prepared from commercially available graphite/epoxy. The baseline and filled laminates' mechanical properties, before and after isothermal and humidity aging, also were compared. It was found that a small amount of graphite fiber was released from the baseline graphite/epoxy laminates during the burn and impact conditions used in this program. However, the extent to which the fibers were released is not considered a severe enough problem to preclude the use of graphite reinforced composites in civil aircraft structure. It also was found that the addition of boron and boron containing fillers to the resin matrix eliminated this fiber release. Mechanical properties of laminates containing the boron and boron containing fillers were lower than those of the baseline laminates. These property degradations for two systems: boron (5 micron) at 2.5 percent filler loading, and boron (5 micron) at 5.0 percent filler loading do not appear severe enough to preclude their use in structural composite applications.

  5. Longitudinal Cutting of Pure and Doped Carbon Nanotubes to Form Graphitic Nanoribbons Using Metal Clusters as Nanoscalpels

    Microsoft Academic Search

    Ana Laura Elías; Andrés R. Botello-Méndez; David Meneses-Rodríguez; Viviana Jehová González; Daniel Ramírez-González; Lijie Ci; Emilio Muñoz-Sandoval; Pulickel M. Ajayan; Humberto Terrones; Mauricio Terrones

    2010-01-01

    We report the use of transition metal nanoparticles (Ni or Co) to longitudinally cut open multiwalled carbon nanotubes in order to create graphitic nanoribbons. The process consists of catalytic hydrogenation of carbon, in which the metal particles cut sp 2 hybridized carbon atoms along nanotubes that results in the liberation of hydrocarbon species. Observations reveal the presence of unzipped nanotubes

  6. Nucleation Control for Large, Single Crystalline Domains of Monolayer Hexagonal Boron Nitride via Si-Doped Fe Catalysts

    E-print Network

    Caneva, Sabina; Weatherup, Robert S.; Bayer, Bernhard C.; Brennan, Barry; Spencer, Steve J.; Mingard, Ken; Cabrero-Vilatela, Andrea; Baehtz, Carsten; Pollard, Andrew J.; Hofmann, Stephan

    2015-02-09

    The scalable chemical vapor deposition of monolayer hexagonal boron nitride (h-BN) single crystals, with lateral dimensions of ?0.3 mm, and of continuous h-BN monolayer films with large domain sizes (>25 ?m) is demonstrated via an admixture of Si...

  7. Influence of boron doping on magnetic properties and microwave characteristics of MnIr/FeCoB multilayers

    SciTech Connect

    Phuoc, Nguyen N. [Temasek Laboratories, National University of Singapore, 5 A Engineering Drive 2, Singapore 117411 (Singapore); Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive3, Singapore 117542 (Singapore)

    2012-04-15

    A detailed investigation of the influence of B doping on the magnetic properties and high frequency characteristics of FeCoB/MnIr multilayered thin films was carried out. Exchange bias was found to decrease monotonically with B doping possibly due to less favorable of AF phase of MnIr in the samples with rich B concentration. However, with small amount of doping up to 9% of B concentration, the MnIr fcc (111) peaks become more prominent and the real part of permeability enhanced. Our results suggest no correlation between the structural phase of MnIr and the exchange bias. Also, the influences of B doping on several static and dynamic parameters, such as rotational magnetic anisotropy field, coercivity, saturation magnetization, resonance frequency, and effective damping factor are presented and discussed. Our results support the claim that the coercivity enhancement and the arising of rotational anisotropy may have the same physical origin.

  8. P-type doping of hydrogenated amorphous silicon films with boron by reactive radio-frequency co-sputtering

    NASA Astrophysics Data System (ADS)

    Ohmura, Y.; Takahashi, M.; Suzuki, M.; Sakamoto, N.; Meguro, T.

    2001-12-01

    B has been successfully doped into the hydrogenated amorphous Si films without using explosive and/or toxic gases SiH 4 or B 2H 6 by reactive radio-frequency co-sputtering. The target used for co-sputtering was a composite target composed of a B-doped Si wafer and B chips attached on the Si wafer with silver powder bond. The maximum area fraction of B chips used was 0.11. Argon and hydrogen pressures were 5×10 -3 and 5×10 -4 Torr, respectively. Substrates were kept at 200°C or 250°C during sputtering. The maximum B concentration in the film obtained was 2×10 19 cm -3 from secondary ion mass spectroscopy measurement. Films with resistivity of 10 4-10 5 ? cm were obtained, which was low for the above acceptor concentration, compared with other group III impurities doping, indicating the high doping efficiency of B. A heterostructure, which was prepared by co-sputtering these B-doped films on an n-type crystalline Si, shows a good rectification characteristic. A small photovoltaic effect is also observed.

  9. Depth Profiling of Electronic Transport Parameters in n-on- p Boron-Ion-Implanted Vacancy-Doped HgCdTe

    NASA Astrophysics Data System (ADS)

    Umana-Membreno, G. A.; Kala, H.; Antoszewski, J.; Ye, Z. H.; Hu, W. D.; Ding, R. J.; Chen, X. S.; Lu, W.; He, L.; Dell, J. M.; Faraone, L.

    2013-11-01

    We report results of a detailed study of electronic transport in n-on- p junctions formed by 150-keV boron-ion implantation in vacancy-doped p-type Hg0.769Cd0.231Te without postimplantation thermal annealing. A mobility spectrum analysis methodology in conjunction with a wet chemical etching-based surface removal approach has been employed to depth profile the transport characteristics of the samples. In the as-implanted samples, three distinct electron species were detected which are shown to be associated with (a) low-mobility electrons in the top 220-nm surface-damaged layer ( E 1: ? 80K = 2940 cm2/Vs), (b) the B-ion implantation region in the top 500-nm region ( E 2: ? 80K = 7490 cm2/Vs), and (c) high-mobility electrons in the n-to- p transition region at a depth of 600 nm to 700 nm ( E 3: ? 80K = 25,640 cm2/Vs). Due to the maximum magnetic field employed (2 T), hole carriers from the underlying vacancy-doped p-type region were detected only after the removal of the top 220 nm of the profiled sample ( ? 80K = 126 cm2/Vs), revealing fully p-type character 800 nm below the original sample surface. A comparison of the extracted E 2 electron concentration and calculated B-impurity profile suggests that the n-type region is due primarily to near-surface implantation-induced lattice damage.

  10. In situ control of local pH using a boron doped diamond ring disk electrode: optimizing heavy metal (mercury) detection.

    PubMed

    Read, Tania L; Bitziou, Eleni; Joseph, Maxim B; Macpherson, Julie V

    2014-01-01

    A novel electrochemical approach to modifying aqueous solution pH in the vicinity of a detector electrode in order to optimize the electrochemical measurement signal is described. A ring disk electrode was employed where electrochemical decomposition of water on the ring was used to generate a flux of protons which adjusts the local pH controllably and quantifiably at the disk. Boron doped diamond (BDD) functioned as the electrode material given the stability of this electrode surface especially when applying high potentials (to electrolyze water) for significant periods of time. A pH sensitive iridium oxide electrode electrodeposited on the disk electrode demonstrated that applied positive currents on the BDD ring, up to +50 ?A, resulted in a local pH decrease of over 4 orders of magnitude, which remained stable over the measurement time of 600 s. pH generation experiments were found to be in close agreement with finite element simulations. The dual electrode arrangement was used to significantly improve the stripping peak signature for Hg in close to neutral conditions by the generation of pH = 2.0, locally. With the ability to create a localized pH change electrochemically in the vicinity of the detector electrode, this system could provide a simple method for optimized analysis at the source, e.g., river and sea waters. PMID:24321045

  11. Fabrication and characterization of n-type aluminum-boron co-doped ZnO on p-type silicon (n-AZB/p-Si) heterojunction diodes

    SciTech Connect

    Kumar, Vinod, E-mail: vinod.phy@gmail.com [Department of Physics, University of the Free State, Bloemfontein ZA-9300 (South Africa); Singh, Neetu [Department of Electronic Science, University of Delhi South Campus, New Delhi 110 021 (India); Department of Electronics, Keshav Mahavidyalaya, University of Delhi 110 034 (India); Kapoor, Avinashi [Department of Electronic Science, University of Delhi South Campus, New Delhi 110 021 (India); Ntwaeaborwa, Odireleng M.; Swart, Hendrik C. [Department of Physics, University of the Free State, Bloemfontein ZA-9300 (South Africa)

    2013-11-15

    Graphical abstract: - Highlights: • n-AZB/p-Si heterojunction diodes were formed. • n-AZB/p-Si diode annealed at 700 °C showed best rectifying behavior. • Zn{sub 2}SiO{sub 4} was formed at 800 °C. • n and ?{sub b} were estimated to be 1.63 and 0.4 eV, respectively, at 700 °C. • Tailoring of BG was attributed to annealing induced stresses in the films. - Abstract: In this paper, the growth of n-type aluminum boron co-doped ZnO (n-AZB) on a p-type silicon (p-Si) substrate by sol–gel method using spin coating technique is reported. The n-AZB/p-Si heterojunctions were annealed at different temperatures ranging from 400 to 800 °C. The crystallite size of the AZB nanostructures was found to vary from 28 to 38 nm with the variation in annealing temperature. The band gap of the AZB decreased from 3.29 to 3.27 eV, with increasing annealing temperature from 400 to 700 °C and increased to 3.30 eV at 800 °C probably due to the formation of Zn{sub 2}SiO{sub 4} at the interface. The band gap variation is explained in terms of annealing induced stress in the AZB. The n-AZB/p-Si heterojunction exhibited diode behavior. The best rectifying behavior was exhibited at 700 °C.

  12. Development of solar-driven electrochemical and photocatalytic water treatment system using a boron-doped diamond electrode and TiO2 photocatalyst.

    PubMed

    Ochiai, Tsuyoshi; Nakata, Kazuya; Murakami, Taketoshi; Fujishima, Akira; Yao, Yanyan; Tryk, Donald A; Kubota, Yoshinobu

    2010-02-01

    A high-performance, environmentally friendly water treatment system was developed. The system consists mainly of an electrochemical and a photocatalytic oxidation unit, with a boron-doped diamond (BDD) electrode and TiO(2) photocatalyst, respectively. All electric power for the mechanical systems and the electrolysis was able to be provided by photovoltaic cells. Thus, this system is totally driven by solar energy. The treatment ability of the electrolysis and photocatalysis units was investigated by phenol degradation kinetics. An observed rate constant of 5.1 x 10(-3)dm(3)cm(-2)h(-1) was calculated by pseudo-first-order kinetic analysis for the electrolysis, and a Langmuir-Hinshelwood rate constant of 5.6 microM(-1)min(-1) was calculated by kinetic analysis of the photocatalysis. According to previous reports, these values are sufficient for the mineralization of phenol. In a treatment test of river water samples, large amounts of chemical and biological contaminants were totally wet-incinerated by the system. This system could provide 12L/day of drinking water from the Tama River using only solar energy. Therefore, this system may be useful for supplying drinking water during a disaster. PMID:19863989

  13. Mineralization of Acid Yellow 36 azo dye by electro-Fenton and solar photoelectro-Fenton processes with a boron-doped diamond anode.

    PubMed

    Ruiz, Edgar J; Arias, Conchita; Brillas, Enric; Hernández-Ramírez, Aracely; Peralta-Hernández, J M

    2011-01-01

    The degradation of the Acid Yellow 36 (AY36) azo dye is studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF) using a recirculation flow plant with an undivided cell containing a boron-doped diamond anode and an air-diffusion cathode for H?O? electrogeneration, coupled with a solar photoreactor. A solution of 2.5L with 108 mg L?¹ of the dye and 0.5 mM Fe²(+) at pH 3.0 was comparatively treated at constant current. Hydroxyl radicals formed from Fenton's reaction and at the anode surface are the main oxidants. Total mineralization is almost achieved in SPEF, while EF yields poor TOC removal. Both processes are accelerated with increasing current. AY36 decays with similar rate in EF and SPEF following a pseudo first-order reaction, but the solution is more slowly decolorized because of the formation of conjugated byproducts. NH?(+) ion is released in SPEF, while NO?? ion is mainly lost in EF. Tartronic, maleic, fumaric, oxalic, formic and oxamic acids are detected as generated carboxylic acids. Fe(III)-oxalate complexes are largely accumulated in EF and their quick photodecomposition in SPEF explains its higher oxidation power. The SPEF method yields greater current efficiency and lower energy cost as current decreases, and then it is more viable at low currents. PMID:21112608

  14. An Experimental Approach to Controllably Vary Protein Oxidation While Minimizing Electrode Adsorption for Boron-Doped Diamond Electrochemical Surface Mapping Applications

    PubMed Central

    McClintock, Carlee S; Hettich, Robert L.

    2012-01-01

    Oxidative protein surface mapping has become a powerful approach for measuring the solvent accessibility of folded protein structures. A variety of techniques exist for generating the key reagent – hydroxyl radicals – for these measurements; however, these approaches range significantly in their complexity and expense of operation. This research expands upon earlier work to enhance the controllability of boron-doped diamond (BDD) electrochemistry as an easily accessible tool for producing hydroxyl radicals in order to oxidize a range of intact proteins. Efforts to modulate oxidation level while minimizing the adsorption of protein to the electrode involved the use of relatively high flow rates to reduce protein residence time inside the electrochemical flow chamber. Additionally, a different cell activation approach using variable voltage to supply a controlled current allowed us to precisely tune the extent of oxidation in a protein-dependent manner. In order to gain perspective on the level of protein adsorption onto the electrode surface, studies were conducted to monitor protein concentration during electrolysis and gauge changes in the electrode surface between cell activation events. This report demonstrates the successful use of BDD electrochemistry for greater precision in generating a target number of oxidation events upon intact proteins. PMID:23210708

  15. Nucleation control for large, single crystalline domains of monolayer hexagonal boron nitride via Si-doped Fe catalysts.

    PubMed

    Caneva, Sabina; Weatherup, Robert S; Bayer, Bernhard C; Brennan, Barry; Spencer, Steve J; Mingard, Ken; Cabrero-Vilatela, Andrea; Baehtz, Carsten; Pollard, Andrew J; Hofmann, Stephan

    2015-03-11

    The scalable chemical vapor deposition of monolayer hexagonal boron nitride (h-BN) single crystals, with lateral dimensions of ?0.3 mm, and of continuous h-BN monolayer films with large domain sizes (>25 ?m) is demonstrated via an admixture of Si to Fe catalyst films. A simple thin-film Fe/SiO2/Si catalyst system is used to show that controlled Si diffusion into the Fe catalyst allows exclusive nucleation of monolayer h-BN with very low nucleation densities upon exposure to undiluted borazine. Our systematic in situ and ex situ characterization of this catalyst system establishes a basis for further rational catalyst design for compound 2D materials. PMID:25664483

  16. Two types of resonances in long-period gratings induced by arc discharges in boron/ germanium co-doped fibers.

    PubMed

    Rego, Gaspar; Ivanov, Oleg V

    2007-10-15

    We demonstrate that under certain conditions it is possible to fabricate in a B/Ge co-doped fiber an arc-induced long-period grating whose spectrum contains a dual set of resonances. These two sets of resonances are formed by distinct mechanisms and are caused by coupling to cladding modes of different symmetries. They behave differently at high temperatures: the set produced by symmetric perturbation disappears during annealing at a temperature of 800 degrees C, while the other set produced by an antisymmetric mechanism can withstand temperatures above 1000 degrees C. PMID:17938674

  17. THE DEVELOPMENT OF MATERIALS FOR APPLICATION TO CONTROL ROD SYSTEMS IN GRAPHITE-MODERATED REACTORS

    Microsoft Academic Search

    G. E. Wade; F. J. Kempf

    1963-01-01

    Test and fabrication experience with control m terials for graphite ; moderated tube type reactors indicated that a wide variety of satisfactory rod ; designs are possible using either boron which is integral with the control rod ; sheath or BâC graphite and sintered BiC--aluminum within metallic rod ; sheaths. The control effectiveness of tubular boron stainless steel rods can

  18. Influence of LOTUS concrete structure, boron-loaded sheets, and B[sub 4]C filter on the integral tritium production of a nature lithium graphite-reflected blanket and comparison with experiment

    SciTech Connect

    Joneja, O.P.; Schneeberger, J.P. (Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland)); Nargundkar, V.R. (Bhabha Atomic Research Centre, Bombay (India))

    1993-07-01

    Integral tritium production rate (TPR) measurements are important in comparisons of calculations to ascertain the suitability of computer codes and cross-section sets used in calculation. At the LOTUS facility, one of the objectives is to make measurements with different types of pure fusion and hybrid blankets and compare the results with calculations. Since the concrete cavity housing the blankets is small, it is of direct relevance to determine the influence of room-reflected neutrons on the integral TPR and, if possible, to reduce this effect by special absorbers. The effects on the TPR of a stainless steel-natural lithium-graphite-reflected blanket due to the concrete structure, B[sub 4]C filter, and boron-loaded sheets covering the assembly are studied. Calculations are performed by the MCNP Monte Carlo code. Since the room-returned component depends strongly on the composition of the concrete and, more-over, does not correspond to a real blanket situation, it is advisable to compare measurements with calculations for the region where such interference is minimal. A central region is identified for the purpose of comparison. In addition to calculations for a fully homogenized blanket, the important central blanket region is considered in the form of rods, and the remaining blanket as a homogeneous region, to assess the effect of neutron streaming on the TPR of the assembly. An experiment is done by irradiating several Li[sub 2]CO[sub 3] probes positioned in each tube so that the central region of interest is fully covered. The activity of the probes is measured by the standard liquid scintillation method, and the TPR for the entire region can be derived from the experimental reaction rate data. The complete details of the calculational model and the experimental procedure are provided. Good agreement is found between the calculated and experimental TPRs after accounting for various sources of errors. 14 refs., 6 figs., 4 tabs.

  19. Boron- and phosphorus-doped silicon germanium alloy nanocrystals—Nonthermal plasma synthesis and gas-phase thin film deposition

    SciTech Connect

    Rowe, David J., E-mail: rowex108@umn.edu, E-mail: kortshagen@umn.edu; Kortshagen, Uwe R., E-mail: rowex108@umn.edu, E-mail: kortshagen@umn.edu [Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2014-02-01

    Alloyed silicon-germanium (SiGe) nanostructures are the topic of renewed research due to applications in modern optoelectronics and high-temperature thermoelectric materials. However, common techniques for producing nanostructured SiGe focus on bulk processing; therefore little is known of the physical properties of SiGe nanocrystals (NCs) synthesized from molecular precursors. In this letter, we synthesize and deposit thin films of doped SiGe NCs using a single, flow-through nonthermal plasma reactor and inertial impaction. Using x-ray and vibrational analysis, we show that the SiGe NC structure appears truly alloyed for Si{sub 1?x}Ge{sub x} for 0.16 < x < 0.24, and quantify the atomic dopant incorporation within the SiGe NC films.

  20. Absence of boron aggregates in superconducting silicon confirmed by atom probe tomography

    E-print Network

    Paris-Sud XI, Université de

    Absence of boron aggregates in superconducting silicon confirmed by atom probe tomography K November 2012) Superconducting boron-doped silicon films prepared by gas immersion laser doping (GILD reveals that boron atoms are incorporated into crystalline silicon in the atomic percent concentration

  1. Boron incorporation into mullite

    NASA Astrophysics Data System (ADS)

    Griesser, K. J.; Beran, A.; Voll, D.; Schneider, H.

    2008-03-01

    Boron-doped mullites were synthesized using aluminium nitrate-nonahydrate, tetraethoxysilane and boric acid in a sol gel process with subsequent annealing at 950 and 1300 °C for five hours. Two different bulk compositions with constant Al2O3 contents (60 and 70 mol%, respectively) and varying SiO2 plus B2O3 contents were investigated. X-ray powder diffraction analyses yielded a linear decrease of the lattice parameters with increasing bulk B2O3 content, which was interpreted as to be due to boron incorporation. Related to the increasing boron content, corresponding infrared spectra revealed a slight and continuous shift for most of the absorption bands. These data show that mullite is able to incorporate large amounts of boron into its structure (up to about 20 mol% B2O3 depending on the bulk composition of the starting materials). Infrared analyses suggest that boron is incorporated into the mullite structure in form of planar three-fold coordinated BO3 groups.

  2. Suppression of boron transient enhanced diffusion in SiGe heterojunction bipolar transistors by carbon incorporation

    E-print Network

    Suppression of boron transient enhanced diffusion in SiGe heterojunction bipolar transistors the outdiffusion of boron from the base under postgrowth implantation and annealing procedures. Without the base sheet resistance using base boron doping levels greater than 1020 cm 3 .1 However, high boron

  3. Inhibition of Oxidation in Nuclear Graphite

    SciTech Connect

    Phil Winston; James W. Sterbentz; William E. Windes

    2013-10-01

    Graphite is a fundamental material of high temperature gas cooled nuclear reactors, providing both structure and neutron moderation. Its high thermal conductivity, chemical inertness, thermal heat capacity, and high thermal structural stability under normal and off normal conditions contribute to the inherent safety of these reactor designs. One of the primary safety issues for a high temperature graphite reactor core is the possibility of rapid oxidation of the carbon structure during an off normal design basis event where an oxidizing atmosphere (air ingress) can be introduced to the hot core. Although the current Generation IV high temperature reactor designs attempt to mitigate any damage caused by a postualed air ingress event, the use of graphite components that inhibit oxidation is a logical step to increase the safety of these reactors. Recent experimental studies of graphite containing between 5.5 and 7 wt% boron carbide (B4C) indicate that oxidation is dramatically reduced even at prolonged exposures at temperatures up to 900°C. The proposed addition of B4C to graphite components in the nuclear core would necessarily be enriched in B-11 isotope in order to minimize B-10 neutron absorption and graphite swelling. The enriched boron can be added to the graphite during billet fabrication. Experimental oxidation rate results and potential applications for borated graphite in nuclear reactor components will be discussed.

  4. Sputtered boron nitride films for graphene devices

    NASA Astrophysics Data System (ADS)

    Miller, David L.; Keller, Mark W.; Shaw, Justin M.; Zhu, Zixu; Joshi, Saumil; Moddel, Garret

    2012-02-01

    For exfoliated graphene, hexagonal boron nitride substrates yield better transport properties than the more common SiO2 substrates. We deposited boron nitride films onto a variety of substrates using rf magnetron sputtering at substrate temperatures between 30 ^oC and 350 ^oC. The amount of amorphous and hexagonal phases depends on sputtering parameters and type of substrate. Regardless of crystallinity, the films are smooth and suitable for graphene exfoliation or transfer of graphene grown by CVD. We compare the roughness, optical contrast, mobility, and substrate-induced doping for graphene on amorphous boron nitride, hexagonal boron nitride, and SiO2.

  5. Terahertz emission and absorption characteristics of silicon containing boron and phosphorous impurity dopants and the effect of temperature

    Microsoft Academic Search

    Guy Matmon; Stephen A. Lynch; Paul Townsend; Douglas J. Paul; Mike Bain; Harry S. Gamble; Jing Zhang; Zoran Ikonic; Robert W. Kelsall; Paul Harrison

    2005-01-01

    The emission and absorption characteristics of boron-doped and phosphorous-doped silicon at terahertz frequencies are investigated. Different doping concentrations are considered and individual terahertz optical transitions are identified. The effect of temperature is considered.

  6. Mechanism of Enhanced Electrochemical Oxidation of 2,4-dichlorophenoxyacetic Acid with in situ Microwave Activated Boron-doped Diamond and Platinum Anodes

    NASA Astrophysics Data System (ADS)

    Gao, Junxia; Zhao, Guohua; Liu, Meichuan; Li, Dongming

    2009-09-01

    Remarkable enhancement in degradation effect is achieved at in situ activated boron-doped diamond (BDD) and Pt anodes with different extent through electrochemical oxidation (EC) of 2,4-dichlorophenoxyacetic acid (2,4-D) with microwave (MW) radiation in a flow system. Results show that when EC is activated with MW radiation, the complete mineralization time of 2,4-D at the BDD is reduced quickly from 10 to 4 h while Chemical oxygen demand (COD) removal at Pt is increased from 37.7 to 58.3% at 10 h; the initial current efficiency is both improved about 1.5 times while the pseudo-first-order rate constant is increased by 153 and 119% at the BDD and Pt, respectively. To gain insight into the higher efficiency in microwave activated EC, the mechanism has therefore been systematically evaluated from the essence of electrochemical reaction and the accumulated hydroxyl radical concentration. 2,4-Dichlorophenol, catechol, benquinone, and maleic and oxalic acids are the main intermediates on the Pt anode measured by high performance liquid chromatography (HPLC), while the intermediates on the BDD electrode include 2,4-dichlorophenol, hydroquinone, and maleic and oxalic acids. The reaction pathway with microwave radiation is the same as that in a conventional electrochemical oxidation on both electrodes. While less and lower aromatic intermediates produce at the BDD with MW, which suggests the higher ring-open ratio and the faster oxidation of carboxylic acids. With microwave radiation, the ring-open ratio at the BDD is increased to 98.8% from 85.6%; the value at Pt is increased to 67.3% from 35.9%. So microwave radiation can activate the electrochemical oxidation, which leads to the higher efficiency. This promotion is mainly due to the higher accumulated hydroxyl radical concentration and the effects by microwave radiation. All the results prove that the BDD electrode presents much better mineralization performance with MW. To the best of our knowledge, it is the first time the systematic analysis of the mechanism of microwave activated EC has been reported.

  7. Boron reclamation

    SciTech Connect

    Smith, R.M.

    1980-07-01

    A process to recover high purity /sup 10/B enriched crystalline boron powder from a polymeric matrix was developed on a laboratory basis and ultimately scaled up to production capacity. The process is based on controlled pyrolysis of boron-filled scrap followed by an acid leach and dry sieving operation to return the powder to the required purity and particle size specifications. Typically, the recovery rate of the crystalline powder is in excess of 98.5 percent, and some of the remaining boron is recovered in the form of boric acid. The minimum purity requirement of the recovered product is 98.6 percent total boron.

  8. Electroextraction of boron from boron carbide scrap

    SciTech Connect

    Jain, Ashish [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Anthonysamy, S., E-mail: sas@igcar.gov.in [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ghosh, C. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ravindran, T.R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Divakar, R.; Mohandas, E. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India)

    2013-10-15

    Studies were carried out to extract elemental boron from boron carbide scrap. The physicochemical nature of boron obtained through this process was examined by characterizing its chemical purity, specific surface area, size distribution of particles and X-ray crystallite size. The microstructural characteristics of the extracted boron powder were analyzed by using scanning electron microscopy and transmission electron microscopy. Raman spectroscopic examination of boron powder was also carried out to determine its crystalline form. Oxygen and carbon were found to be the major impurities in boron. Boron powder of purity ? 92 wt. % could be produced by the electroextraction process developed in this study. Optimized method could be used for the recovery of enriched boron ({sup 10}B > 20 at. %) from boron carbide scrap generated during the production of boron carbide. - Highlights: • Recovery of {sup 10}B from nuclear grade boron carbide scrap • Development of process flow sheet • Physicochemical characterization of electroextracted boron • Microscopic examination of electroextracted boron.

  9. Oxygen-assisted low-pressure chemical vapor deposition for the low-temperature direct growth of graphitic nanofibers on fluorine-doped tin oxide glass as a counter electrode for dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Sheng; Hsieh, Chien-Kuo

    2014-11-01

    In this paper, we report an oxygen-assisted low-pressure chemical vapor deposition (LPCVD) method for the direct growth of graphitic nanofibers (GNFs) on a fluorine-doped tin oxide (FTO) glass substrate at a low temperature (550 °C). By adding moderate concentrations of oxygen in a gas mixture of argon, ethylene, and hydrogen during LPCVD, an extremely dense GNF forest can be obtained on a nickel-coated FTO glass substrate. Though this process, the graphitic nanofibers are grown homogenously on a large area of FTO glass. It was observed that oxygen-assisted LPCVD leads to the direct growth of high-quality GNFs as a counter electrode for dye-sensitized solar cells (DSSCs). In combination with an N719 dye-sensitized TiO2 working electrode and an iodine-based electrolyte, the DSSC with a GNF counter electrode showed a power conversion efficiency of 5.51% under AM 1.5 (100 mW cm?2) illumination, which approached that of the DSSC with a Pt counter electrode (5.44%). The results demonstrated that our directly grown GNFs could be promising candidates for counter electrodes to achieve high performance in DSSCs.

  10. Antimony-doped graphene nanoplatelets

    PubMed Central

    Jeon, In-Yup; Choi, Min; Choi, Hyun-Jung; Jung, Sun-Min; Kim, Min-Jung; Seo, Jeong-Min; Bae, Seo-Yoon; Yoo, Seonyoung; Kim, Guntae; Jeong, Hu Young; Park, Noejung; Baek, Jong-Beom

    2015-01-01

    Heteroatom doping into the graphitic frameworks have been intensively studied for the development of metal-free electrocatalysts. However, the choice of heteroatoms is limited to non-metallic elements and heteroatom-doped graphitic materials do not satisfy commercial demands in terms of cost and stability. Here we realize doping semimetal antimony (Sb) at the edges of graphene nanoplatelets (GnPs) via a simple mechanochemical reaction between pristine graphite and solid Sb. The covalent bonding of the metalloid Sb with the graphitic carbon is visualized using atomic-resolution transmission electron microscopy. The Sb-doped GnPs display zero loss of electrocatalytic activity for oxygen reduction reaction even after 100,000 cycles. Density functional theory calculations indicate that the multiple oxidation states (Sb3+ and Sb5+) of Sb are responsible for the unusual electrochemical stability. Sb-doped GnPs may provide new insights and practical methods for designing stable carbon-based electrocatalysts. PMID:25997811

  11. Effect of nitrogen on the diffusion and the activation of the boron implanted in polysilicon thin layers

    Microsoft Academic Search

    R. Mahamdi; F. Mansour; P. Temple-Boyer; E. Scheid

    2004-01-01

    This work deals with the study of polysilicon thin layers doped in-situ with nitrogen, know as nitrogen doped silicon (NIDOS), strongly doped boron. These films are used in microelectronics technology as P+ MOS transistors gates, etc. The study of nitrogen effect on the redistribution and the activation of boron during annealing in NIDOS film is necessary. These films were deposited

  12. Boron mullite: Formation and basic characterization

    SciTech Connect

    Lührs, Hanna, E-mail: hanna.luehrs@uni-bremen.de [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany)] [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany); Fischer, Reinhard X. [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany)] [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany); Schneider, Hartmut [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany) [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany); Universität Köln, Institut für Kristallographie, Greinstraße 6, D-50939 Kölm (Germany)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ? Decrease of B-mullite formation temperature with increasing boron content. ? Decrease of lattice parameters b and c with increasing boron content. ? Significant reduction of thermal expansion (?15%) due to incorporation of boron. ? Decomposition of B-mullite at 1400 °C, long-term stability at 800 °C. -- Abstract: A series of boron doped mullites (B-mullite) was prepared from single-phase gels with initial compositions based on a 1:1 isomorphous substitution of Si by B, starting from a 3:2 mullite composition (Al{sub 4.5}Si{sub 1.5}O{sub 9.75}). A high amount of boron (>10 mol.%) can be incorporated into the crystal structure of mullite where it most likely replaces Si. In situ phase formation of B-mullites was studied with high temperature X-ray diffraction and thermal analysis. A decrease of the formation temperature for B-mullite with increasing boron content was observed. With increasing boron content lattice parameters b and c significantly decrease, while no systematic evolution of a is observed. Long annealing at 1400 °C results in decomposition of B-mullite to boron free mullite and ?-alumina. At 800 °C B-mullite appears to be stable over a period of at least 12 days. The mean thermal expansion coefficient was reduced by 15% upon incorporation of boron which makes the material technologically interesting.

  13. BORON-OXYGEN DEFECTS IN COMPENSATED P-TYPE CZOCHRALSKI SILICON D. Macdonald1

    E-print Network

    BORON-OXYGEN DEFECTS IN COMPENSATED P-TYPE CZOCHRALSKI SILICON D. Macdonald1 , A. Liu1 , F: The extent of formation of the well-known boron-oxygen defect has been measured in deliberately compensated p showing that the amount of boron-oxygen defects formed is determined by the net doping p0=NA-ND, rather

  14. Temperature effect on structural properties of boron oxide thin films deposited by MOCVD method

    E-print Network

    Boo, Jin-Hyo

    and optoelectronic devices. Among them, boron oxides are very important for ceramic and glass industries and high refractive index. Because of these natures, boron oxides are used widely in glass ceramics composition. For example, boron oxides doped on the ceramics system enhance conductivity and structural stabil

  15. Boron induced recrystallization of amorphous silicon film by a rapid thermal process

    Microsoft Academic Search

    Ching-Hsun Chao; Ko-Wei Weng; Horng-Long Cheng; Chien-Hung Chan; Shui-Yang Lien

    2010-01-01

    Rapid thermal process (RTP) is to induce boron-doped amorphous silicon into a high degree of crystallization of polycrystalline silicon in 5min. In addition to the short time characteristic, it also provides a relatively lower temperature route to prepare high percentage of polycrystalline silicon in comparison with solid phase crystallization method. Before RTP, boron is homogeneously doped into the amorphous silicon

  16. Effect of boron doping on the rectification effect and photovoltaic performance of CdS/Si heterostructure based on Si nanoporous pillar array

    NASA Astrophysics Data System (ADS)

    Yan, Ling Ling; Wang, Xiao Bo; Liu, Wei Kang; Li, Xin Jian

    2015-07-01

    A series of CdS/Si heterostructures were prepared through growing B-doped CdS thin films on silicon nanoporous pillar array (Si-NPA) by a chemical bath deposition (CBD) method. The experimental data show that B-doping concentration of CdS thin films could be tuned effectively through controlling the mole ratio of [B]/[Cd] of the initial CBD solution without causing obvious variation of the crystal phase and surface morphology of CdS/Si-NPA. Both the electrical rectification and photovoltaic parameters of CdS/Si-NPA show strong dependence upon B-doping concentration, and the optimal characteristics are achieved for the samples prepared with [B]/[Cd] = 0.01. Compared with CdS/Si-NPA solar cells without B-doping, an increment over 300 times for energy conversion efficiency is realized. The mechanism for the efficiency increment is analyzed based on the effect of B-doping on the band structure of CdS/Si-NPA. These results indicate that B-doping might be an effective path for promoting the device performance of solar cells based on CdS/Si-NPA.

  17. Growth and oxidation resistance of boron-modified and germanium-doped silicide diffusion coatings formed by the halide-activated pack cementation method

    Microsoft Academic Search

    Brian V. Cockeram

    1995-01-01

    Niobium-base and titanium-base alloys and intermetallic compounds possess many attractive properties, but practical application at high temperature is limited by their rapid scaling and embrittlement by oxygen dissolution. Since alloying schemes have not provided an acceptable balance of oxidation resistance and mechanical properties, protective coatings are required.Procedures for codepositing either silicon and boron, or else silicon and germanium, in a

  18. Nuclear graphite

    Microsoft Academic Search

    R. A. Mercuri; J. M. Criscione

    1985-01-01

    A high strength, high coefficient of thermal expansion fine-grained isotropic graphite article produced from 30% to 70% of attritor milled gilsonite coke or other high CTE carbon filler particles and minor amounts of a binder such a coal tar pitch and petroleum pitch, the article being formed by warm isostatic molding at a temperature of between 50° C. and 70°

  19. Boron Segregation and Electrical Properties in Polycrystalline SiGeC E. J. Stewart, M. S. Carroll*, and J.C. Sturm

    E-print Network

    Boron Segregation and Electrical Properties in Polycrystalline SiGeC E. J. Stewart, M. S. Carroll been reported that PMOS capacitors with heavily boron-doped polycrystalline SiGeC gates are less susceptible to boron penetration than those with poly Si gates [1]. Boron appears to accumulate in the poly Si

  20. Thermal evolution of boron irradiation induced defects in predoped Si revealed by positron annihilation experiments

    NASA Astrophysics Data System (ADS)

    Nambissan, P. M. G.; Bhagwat, P. V.; Kurup, M. B.

    2007-06-01

    The isochronal annealing behavior of high energy (25-72 MeV) boron ion irradiation induced defects in boron-doped silicon is monitored through measurements of positron lifetimes and three distinct defect-evolution stages are identified. The initial boron doping created a defect environment where positrons could sensitively annihilate with the boron electrons, suggesting boron-decorated Si monovacancies as potential trapping sites. The irradiation results in the dissolution of boron from these sites and positrons are then trapped by the empty divacancies of Si. Charge neutralization of divacancies through interaction with boron atoms leads to enhanced positron trapping in the initial stages of isochronal annealing. The divacancies start annealing above 673 K. However, a remarkable defect evolution stage due to the diffusion of the boron atoms beyond their initial depths of penetration is seen above 873 K and it leaves the sample with defects still present even at the highest annealing temperature 1273 K used in this work.

  1. Development and fabrication of a graphite polyimide box beam

    NASA Technical Reports Server (NTRS)

    Nadler, M. A.; Darms, F. J.

    1972-01-01

    The state-of-the-art of graphite/polyimide structures was evaluated and key design and fabrication issues to be considered in future hardware programs are defined. The fabrication and testing at 500 F of a graphite/polyimide center wing box beam using OV-10A aircraft criteria was accomplished. The baseline design of this box was developed in a series of studies of other advanced composite materials: glass/epoxy, boron/epoxy, and boron/polyimide. The use of this basic design permits ready comparison of the performance of graphite/polyimide with these materials. Modifications to the baseline composite design were made only in those areas effected by the change of materials. Processing studies of graphite fiber polyimide resins systems resulted in the selection of a Modmor II/Gemon L material.

  2. Thermoelectric Properties of Boron-Rich Solids and their Possibilities of Technical Application

    Microsoft Academic Search

    H. Werheit

    2006-01-01

    The thermoelectric properties of beta-rhombohedral boron and boron carbide, the best-investigated icosahedral boron-rich solids, are reviewed. Because of its high density of gap states (~1021 cm -3) generated by intrinsic defects, p-type boron carbide behaves electronically extrinsic up to at least 2000 K, and therefore it exhibits excellent thermoelectric performance. This can even be considerably improved by suitable interstitial doping

  3. Direct current sputtering of boron from boron/boron mixtures

    DOEpatents

    Timberlake, J.R.; Manos, D.; Nartowitz, E.

    1994-12-13

    A method for coating a substrate with boron by sputtering includes lowering the electrical resistance of a boron-containing rod to allow electrical conduction in the rod; placing the boron-containing rod inside a vacuum chamber containing substrate material to be coated; applying an electrical potential between the boron target material and the vacuum chamber; countering a current avalanche that commences when the conduction heating rate exceeds the cooling rate, and until a steady equilibrium heating current is reached; and, coating the substrate material with boron by sputtering from the boron-containing rod. 2 figures.

  4. Boron carbonitride films deposited by pulsed laser ablation

    Microsoft Academic Search

    A. Perrone; A. P Caricato; A Luches; M Dinescu; C Ghica; V Sandu; A Andrei

    1998-01-01

    Boron carbonitride (BCN) thin films were deposited on Si (100) substrates at room temperature by sequential pulsed laser ablation (PLA) of graphite and hexagonal boron nitride (h-BN) targets in vacuum and in nitrogen atmosphere in the pressure range 1–100 Pa. Different analysis techniques as transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) pointed out the synthesis

  5. Local order and electrical properties of boron carbonitride films

    Microsoft Academic Search

    Laurent Filipozzi; Alain Derré; Jacques Conard; Luc Piraux; André Marchand

    1995-01-01

    Thin films of carbon-boron-nitrogen alloys were prepared by chemical vapor deposition from gaseous mixtures of C2H2, BCl3, NH3, and H2. Their turbostratic graphitic structure was investigated by electron probe micro analysis (EPMA), X-ray diffraction (XRD), Raman spectroscopy, and nuclear magnetic resonance. Those compounds were shown to be solid solutions with compositions varying in a continuous domain bounded by carbon, boron

  6. Doping dependence of optical properties of solid-phase crystallized evaporated poly-Si thin films on glass

    Microsoft Academic Search

    Song He; Alistair B. Sproul; Armin G. Aberle

    2008-01-01

    Boron and phosphorus doped polycrystalline silicon films with moderate and heavy doping of ~5times1017cm-3 and ~1times1019 cm-3 respectively are investigated to observe the impacts of doping on the optical properties, with \\

  7. Raman Spectrum of Graphite

    Microsoft Academic Search

    F. Tuinstra; J. L. Koenig

    1970-01-01

    Raman spectra are reported from single crystals of graphite and other graphite materials. Single crystals of graphite show one single line at 1575 cm?1. For the other materials like stress-annealed pyrolitic graphite, commercial graphites, activated charcoal, lampblack, and vitreous carbon another line is detected at 1355 cm?1. The Raman intensity of this band is inversely proportional to the crystallite size

  8. Thermally exfoliated graphite oxide

    NASA Technical Reports Server (NTRS)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

    2011-01-01

    A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

  9. Density Functional Study of Interaction of Atomic Pt with Pristine and Stone-Wales-Defective Single-Walled Boron Nitride Nanotubes

    E-print Network

    Wang, Yan Alexander

    -Walled Boron Nitride Nanotubes Ya Kun Chen, Lei Vincent Liu, and Yan Alexander Wang* Department of Chemistry or Stone-Wales-defective (5,5) single-walled boron nitride nanotubes (BNNTs) were studied using density are extended to form layered hexagonal boron nitride (hBN) and carbon graphite networks, their very different

  10. On the nature of boron-carbon-nitrogen compounds synthesised from organic precursors

    Microsoft Academic Search

    Yuri G. Andreev; Torsten Lundström; Robin K. Harris; Se-Woung Oh; David C. Apperley; Derek P. Thompson

    1995-01-01

    Three compounds were prepared through pyrolysis of organic precursors, namely pyridine-borane, piperazine-borane, poly(acrylonitrile)-BCl3, following the routes proposed in the literature for the synthesis of single-phase boron carbonitrides of various compositions. X-ray diffraction and MAS NMR studies performed on the powders obtained suggest that the resulting compounds are mixtures of amorphous boron and turbostratically distorted hexagonal boron nitride and graphite rather

  11. Bridged graphite oxide materials

    NASA Technical Reports Server (NTRS)

    Herrera-Alonso, Margarita (Inventor); McAllister, Michael J. (Inventor); Aksay, Ilhan A. (Inventor); Prud'homme, Robert K. (Inventor)

    2010-01-01

    Bridged graphite oxide material comprising graphite sheets bridged by at least one diamine bridging group. The bridged graphite oxide material may be incorporated in polymer composites or used in adsorption media.

  12. Silicon LEDs with room-temperature dislocation-related luminescence, fabricated by erbium ion implantation and chemical-vapor deposition of polycrystalline silicon layers heavily doped with boron and phosphorus

    SciTech Connect

    Sobolev, N. A., E-mail: nick@sobolev.ioffe.rssi.ru; Emel'yanov, A. M.; Zabrodskii, V. V.; Zabrodskaya, N. V.; Sukhanov, V. L.; Shek, E. I. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

    2007-05-15

    Light-emitting diodes (LEDs) have been fabricated in which optically active centers are formed by implantation of erbium ions into silicon and subsequent high-temperature annealing in an oxidizing atmosphere and the p-n junction and the ohmic contact are formed by chemical vapor deposition of polycrystalline silicon layers doped with boron and phosphorus, respectively. The luminescent properties of the LEDs have been studied. Use of polycrystalline layers makes it possible to eliminate the losses in the bulk of the light-emitting Si:Er layer. These losses are inevitable if the conventional ion implantation and diffusion methods are employed. At 80 K, the variation of electroluminescence spectra in the spectral range of the dislocation-related luminescence with the drive current is well described if the spectrum is decomposed into three Gaussian components whose peak positions and widths are current-independent and amplitudes linearly increase with the current. At 300 K, a single peak is observed in the spectral range of the dislocation-related luminescence at {approx}1.6 {mu}m.

  13. Synthesis of boron and nitrogen co-doped graphene nano-platelets using a two-step solution process and catalytic properties for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Han, Jongwoo; Cheon, Jae Yeong; Joo, Sang Hoon; Park, Sungjin

    2014-07-01

    Chemically modified graphenes (CMGs) show great promise for various applications owing to the feasibility of their low-cost mass production and good solution processability. Recently, hetero-atom-doped CMGs have been suggested as good candidate materials for electrochemical catalysts in oxygen reduction reaction (ORR). In this study, we synthesized B, N co-doped graphene nano-platelets (BN-rG-O) using a two-step solution process with sequential reaction of graphene oxide with borane tetrahydrofuran and hydrazine monohydrate. In the ORR measured in a basic medium (0.1 M KOH), BN-rG-O exhibits an onset potential of 0.81 V (vs. reversible hydrogen electrode), follows near four electron pathway, and shows excellent stability against methanol poisoning and during durability tests.

  14. Boron and sulfur co-doped TiO2 nanofilm as effective photoanode for high efficiency CdS quantum-dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Li, Ling; Yang, Xichuan; Zhang, Wenming; Zhang, Huayan; Li, Xiaowei

    2014-12-01

    A modified polysulfide redox couple, (CH3)4N)2S/((CH3)4N)2Sn, was employed in CdS quantum dots (QDs) sensitized B/S co-doped TiO2 solar cell with NiS as counter electrode, followed by chemical bath deposition (CBD) in an organic solution to prepare the QDs-cell to ensure high wettability and superior penetration ability of the B/S co-doped TiO2 films, with the co-doping of B/S in TiO2, its band-gap was narrowed and significantly extended the light capture range, and an enhanced energy conversion efficiency of up to 3.6% was observed under AM 1.5 G illuminations, with a significantly high Voc of 1.217 V, a high ff of 88.2% and a short-circuit photocurrent (Jsc) of 3.35 mA cm-2.

  15. Boron induced charge traps near the interface of Si/SiO2 probed by second harmonic generation

    E-print Network

    Weiss, Sharon

    Boron induced charge traps near the interface of Si/SiO2 probed by second harmonic generation for highly boron-doped Si/SiO2 systems. Using electric field sensitive time-dependent SHG (TD-SHG), we determined that the direction of the initial DC electric field at the interface induced by boron induced

  16. Boron segregation and electrical properties in polycrystalline Si1xyGexCy and Si1yCy alloys

    E-print Network

    Boron segregation and electrical properties in polycrystalline Si1ÀxÀyGexCy and Si1ÀyCy alloys E. J 2003 In this article, we report strong boron segregation to polycrystalline Si1 x yGexCy from of p-channel metal oxide semiconductor field effect transistors with boron-doped polycrystalline Si1 x

  17. LEO degradation of graphite and carbon-based composites aboard Space Shuttle Flight STS-46

    NASA Technical Reports Server (NTRS)

    Spady, Blaine R.; Synowicki, R. A.; Hale, Jeffrey S.; Devries, M. J.; Woollam, John A.; Moore, Arthur W.; Lake, Max

    1995-01-01

    Six different types of carbon and carbon-boron nitride composites were exposed to low Earth orbit aboard Space Shuttle flight STS-46. The samples received a nominal atomic oxygen fluence of 2.2 x 10(exp 20) atoms/sq cm in 42 hours of exposure. Pyrolytic graphite and highly oriented pyrolytic graphite showed significant degradation, and the measured erosion yield was within a factor of two of published values. The erosion yield of pyrolytic boron nitride was found to be 2.6 x 10(exp 26) cu cm/atom in plasma asher exposure, over 42 times lower than that of pyrolytic graphite. This low erosion yield makes graphite plus boron nitride mixtures quite resistant to low Earth orbit exposure. Evidence suggests that the graphitic component was preferentially etched, leaving the surface boron nitride rich. Degradation resistance increases with boron nitride composition. Carbon fiber/carbon composites degraded in low Earth orbit, and the carbon pitch binder was found to etch more easily than the graphite fibers which have much higher degradation resistance.

  18. Optical properties and electrical resistivity of boron-doped ZnO thin films grown by sol-gel dip-coating method

    NASA Astrophysics Data System (ADS)

    Kim, Soaram; Yoon, Hyunsik; Kim, Do Yeob; Kim, Sung-O.; Leem, Jae-Young

    2013-10-01

    Sol-gel dip-coating was used to grow ZnO thin films doped with various concentrations of B ranging from 0 to 2.5 at.% on quartz substrates. The effects of B doping on the absorption coefficient (?), optical band gap (Eg), Urbach energy (EU), refractive index (n), refractive index at infinite wavelength (n?), extinction coefficient (k), single-oscillator energy (Eo), dispersion energy (Ed), average oscillator strength (So), average oscillator wavelength (?o), moments M-1 and M-3, dielectric constant (?), optical conductivity (?), and electrical resistivity (?) of the BZO thin films were investigated. The transmittance spectra of the ZnO and BZO thin films show that the transmittance of the BZO thin films was significantly higher than that of the ZnO thin films in the visible region of the spectrum and that the absorption edge of the BZO thin films was blue-shifted. The BZO thin films exhibited higher Eg, EU, and Eo and lower Ed, ?o, M-1 and M-3 moments, So, n?, and ? than the ZnO thin films.

  19. Two-acceptor levels in the band gap of boron-doped diamondsemiconductors analyzed by soft x-ray absorption spectroscopy and dv-xalpha calculations

    SciTech Connect

    Muramatsu, Y.; Takebe, T.; Sawamura, A.; Iihara, J.; Nanba, A.; Imai, T., Denlinger, J.D.; Perera, R.C.C.

    2007-01-10

    To clarify the electronic structure of semiconductingboron-doped diamond, especially the two-acceptor levels observed in thesoft x-ray absorption spectra in the C K region, the density of states(DOS) of a B-doped diamond cluster model, BC146H148, were calculatedusing discrete variational (DV)-X MO methods. The results were comparedto the measured x-ray spectra. In the calculations, the localizedacceptor levels (lowest unoccupied molecular orbitals: (LUMOs)) appearedjust above the highest occupied molecular orbitals (HOMOs) of the C atomthat was directly bonded to the B atom, and the other C atoms that werebonded to the C atoms next to the B atom. However, a chemical shift ofthe LUMOs was not observed between the C atoms. On the other hand, achemical shift of the occupied C 1s orbitals was observed between these Catoms. Therefore, it is concluded that the two-acceptor levels in the Catoms result from the chemical shift of the inner C 1s orbitals due tothe local structure differences between the C atoms in B-dopeddiamond.

  20. Ultralow Contact Resistivity for a Metal/p-Type Silicon Interface by High-Concentration Germanium and Boron Doping Combined with Low-Temperature Annealing

    NASA Astrophysics Data System (ADS)

    Murakoshi, Atsushi; Iwase, Masao; Niiyama, Hiromi; Koike, Mitsuo; Suguro, Kyoichi

    2013-07-01

    A contact resistivity of 6.9×10-9 ?.cm2 has been obtained in an AlSi (1 wt %)-Cu (0.5 wt %) alloy/silicon system by using heavy-dose ion implantations of germanium and boron combined with low-temperature annealing. The analysis of the combined state showed that B12 cluster was incorporated and the supersaturation activation layer was formed into the region where germanium separated. Separated germanium is expected to have high interface state density. It is considered that this interface state density also has a Fermi level, and in order to reduce the difference from the Fermi level of the substrate, the charge moves to interface state density from the substrate. As a result, it is not based on a metallic material but a work function becomes small because pinning by which a Fermi level is fixed to interface state density occurs owing to the substrate/metal interface. It is considered to be attributable to the existence of a Ge-rich layer formed by low-temperature annealing, and a supersaturation activation layer that lowers contact resistance was formed.

  1. Boron Nitride Nanotubes

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  2. Boron nitride nanotubes

    DOEpatents

    Smith, Michael W. (Newport News, VA); Jordan, Kevin (Newport News, VA); Park, Cheol (Yorktown, VA)

    2012-06-06

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

  3. "White graphenes": boron nitride nanoribbons via boron nitride nanotube unwrapping.

    PubMed

    Zeng, Haibo; Zhi, Chunyi; Zhang, Zhuhua; Wei, Xianlong; Wang, Xuebin; Guo, Wanlin; Bando, Yoshio; Golberg, Dmitri

    2010-12-01

    Inspired by rich physics and functionalities of graphenes, scientists have taken an intensive interest in two-dimensional (2D) crystals of h-BN (analogue of graphite, so-called "white" graphite). Recent calculations have predicted the exciting potentials of BN nanoribbons in spintronics due to tunable magnetic and electrical properties; however no experimental evidence has been provided since fabrication of such ribbons remains a challenge. Here, we show that few- and single-layered BN nanoribbons, mostly terminated with zigzag edges, can be produced under unwrapping multiwalled BN nanotubes through plasma etching. The interesting stepwise unwrapping and intermediate states were observed and analyzed. Opposed to insulating primal tubes, the nanoribbons become semiconducting due to doping-like conducting edge states and vacancy defects, as revealed by structural analyses and ab initio simulations. This study paves the way for BN nanoribbon production and usage as functional semiconductors with a wide range of applications in optoelectronics and spintronics. PMID:21028887

  4. Effect of various dopant elements on primary graphite growth

    NASA Astrophysics Data System (ADS)

    Valle, N.; Theuwissen, K.; Sertucha, J.; Lacaze, J.

    2012-01-01

    Five spheroidal graphite cast irons were investigated, a usual ferritic grade and four pearlitic alloys containing Cu and doped with Sb, Sn and Ti. These alloys were remelted in a graphite crucible, leading to volatilization of the magnesium added for spheroidization and to carbon saturation of the liquid. The alloys were then cooled down and maintained at a temperature above the eutectic temperature. During this step, primary graphite could develop showing various features depending on the doping elements added. The largest effects were that of Ti which greatly reduces graphite nucleation and growth, and that of Sb which leads to rounded agglomerates instead of lamellar graphite. The samples have been investigated with secondary ion mass spectrometry to enlighten distribution of elements in primary graphite. SIMS analysis showed almost even distribution of elements, including Mg and Al (from the inoculant) in the ferritic grade, while uneven distribution was evident in all doped alloys. Investigations are going on to clarify if the uneven distribution is associated with structural defects in the graphite precipitates.

  5. Friction and wear of carbon-graphite materials for high energy brakes

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1975-01-01

    Caliper-type brakes simulation experiments were conducted on seven different carbon-graphite material formulations against a steel disk material and against a carbon-graphite disk material. The effects of binder level, boron carbide (B4C) additions, graphite fiber additions, and graphite cloth reinforcement on friction and wear behavior were investigated. Reductions in binder level and additions of B4C each resulted in increased wear. The wear rate was not affected by the addition of graphite fibers. Transition to severe wear and high friction was observed in the case of graphite-cloth-reinforced carbon sliding against a disk of similar composition. This transition was related to the disruption of a continuous graphite shear film that must form on the sliding surfaces if low wear is to occur. The exposure of the fiber structure of the cloth constituent is believed to play a role in the shear film disruption.

  6. Investigation of the matrix effect in determining microimpurities in boron and its compounds by atomic-emission spectrometry

    NASA Astrophysics Data System (ADS)

    Lebedeva, R. V.; Tumanova, A. N.; Mashin, N. I.

    2007-07-01

    We carried out a systematic study of the influence of the main component on the change of analytical signal during atomic-emission analysis of boron compounds. Changes in the intensity of spectral lines of microimpurities as functions of their concentrations in the analytical system based on graphite powder with a variable content of boric acid and boron oxide are presented.

  7. Superconductivity in doped cubic silicon.

    PubMed

    Bustarret, E; Marcenat, C; Achatz, P; Kacmarcik, J; Lévy, F; Huxley, A; Ortéga, L; Bourgeois, E; Blase, X; Débarre, D; Boulmer, J

    2006-11-23

    Although the local resistivity of semiconducting silicon in its standard crystalline form can be changed by many orders of magnitude by doping with elements, superconductivity has so far never been achieved. Hybrid devices combining silicon's semiconducting properties and superconductivity have therefore remained largely underdeveloped. Here we report that superconductivity can be induced when boron is locally introduced into silicon at concentrations above its equilibrium solubility. For sufficiently high boron doping (typically 100 p.p.m.) silicon becomes metallic. We find that at a higher boron concentration of several per cent, achieved by gas immersion laser doping, silicon becomes superconducting. Electrical resistivity and magnetic susceptibility measurements show that boron-doped silicon (Si:B) made in this way is a superconductor below a transition temperature T(c) approximately 0.35 K, with a critical field of about 0.4 T. Ab initio calculations, corroborated by Raman measurements, strongly suggest that doping is substitutional. The calculated electron-phonon coupling strength is found to be consistent with a conventional phonon-mediated coupling mechanism. Our findings will facilitate the fabrication of new silicon-based superconducting nanostructures and mesoscopic devices with high-quality interfaces. PMID:17122852

  8. Chapter 20: Graphite

    SciTech Connect

    Burchell, Timothy D [ORNL

    2012-01-01

    Graphite is truly a unique material. Its structure, from the nano- to the millimeter scale give it remarkable properties that lead to numerous and diverse applications. Graphite bond anisotropy, with strong in-plane covalent bonds and weak van der Waals type bonding between the planes, gives graphite its unique combination of properties. Easy shear of the crystal, facilitated by weak interplaner bonds allows graphite to be used as a dry lubricant, and is responsible for the substances name! The word graphite is derived from the Greek to write because of graphites ability to mark writing surfaces. Moreover, synthetic graphite contains within its structure, porosity spanning many orders of magnitude in size. The thermal closure of these pores profoundly affects the properties for example, graphite strength increases with temperature to temperatures in excess of 2200 C. Consequently, graphite is utilized in many high temperature applications. The basic physical properties of graphite are reviewed here. Graphite applications include metallurgical; (aluminum and steel production), single crystal silicon production, and metal casting; electrical (motor brushes and commutators); mechanical (seals, bearings and bushings); and nuclear applications, (see Chapter 91, Nuclear Graphite). Here we discuss the structure, manufacture, properties, and applications of Graphite.

  9. Electronic structure and optical properties of boron-sulfur symmetric codoping in 4 × 4 graphene systems

    NASA Astrophysics Data System (ADS)

    Huang, Chen; Han, Lihong; Wu, Liyuan; Su, Rui; Chen, Jun; Lu, Pengfei

    2015-06-01

    The electronic structure and optical properties of boron-doped, sulfur-doped, and boron-sulfur-codoped graphene systems have been studied by using first-principles calculations. Energy band structure and density of states are presented to describe the electronic properties. The doping can open the band gap and change the optical properties of graphene. For all optical properties of doped graphene systems, parallel ( E ?) polarization and perpendicular ( E ?) polarization are presented. The optical properties under two kinds of polarizations are reflected in the range of peak height and the change of some extraordinary features.

  10. The effects of boron penetration on p+ polysilicon gated PMOS devices

    Microsoft Academic Search

    JAMES R. PFIESTER; FRANK K. BAKER; T. C. Mele; H.-H. Tseng; P. J. Tobin; J. D. Hayden; J. W. Miller; C. D. Gunderson; L. C. Parrillo

    1990-01-01

    The penetration of boron into and through the gate oxides of PMOS devices which employ p+ doped polysilicon gates is studied. Boron penetration results in large positive shifts in VFB , increased PMOS subthreshold slope and electron trapping rate, and decreased low-field mobility and interface trap density. Fluorine-related effects caused by BF2 implantations into the polysilicon gate are shown to

  11. Incorporation of boron and vanadium during PVT growth of 6H-SiC crystals

    Microsoft Academic Search

    M. Bickermann; B. M. Epelbaum; D. Hofmann; T. L. Straubinger; R. Weingärtner; A. Winnacker

    2001-01-01

    To obtain semi-insulating SiC by vanadium and boron co-doping during PVT growth, a detailed understanding of the dopant (B,V) incorporation is required. Crystal growth of 1.4?? 6H-SiC on either Si or C face, doped with boron or vanadium, respectively, was performed. For reference purposes, also nominally undoped SiC crystals were grown. It is shown that in nominally undoped crystals nitrogen

  12. The role of substitutional boron in carbon oxidation: Inhibitor and catalyst!

    SciTech Connect

    Radovic, L.R.; Karra, M.; Thrower, P.A. [Penn State Univ., University Park, PA (United States)

    1996-10-01

    Boron is considered to be one of the very few promising candidates for chemical protection of carbon/carbon composite materials against oxidation. The conventional wisdom is that boron inhibits carbon oxidation. Its inhibiting effect can be manifested in three different ways: (1) Substitutional boron enhances the graphitization of carbon. (2) As the surface carbon atoms are consumed, substitutional boron forms an oxide surface film, which acts as an O{sub 2} diffusion harrier and an active site blocker. (3) Substitutional boron redistributes the {pi} electrons in the basal plane (graphene layer), lowers the Fermi level of carbon, and hence presumably inhibits the desorption of CO and CO{sub 2}. This last mode of inhibition is of great fundamental interest; it had not been verified in the past. Upon closer examination of some early studies, its closer scrutiny is wan-anted. We provide such a scrutiny in the present communication. Three widely differing carbon materials were used: a heat-treated ({open_quote}graphitized{close_quote}) carbon black (Graphon), Saran char and a glassy carbon. Boron was introduced substitutionally into the quasi-graphitic lattice by heating these carbons, physically mixed with boron powder. Isothermal carbon oxidation experiments were performed. In selected cases, the reactive surface area of the carbons was determined.

  13. The Graphite Page

    NSDL National Science Digital Library

    Jaszczak, John A.

    John A. Jaszczak at Michigan Technological University presents the characteristics of graphite at this website. Students can find concise descriptions and helpful images about graphite properties, spirals, and structures. The website offers images and descriptions of graphite found all over the world. Using Macromedia Flash Player, students can observe graphite levitating due to its diamagnetic susceptibility. The website also offers an interactive applet presenting the atom positions for nano-tubes and nano-cones.

  14. Fabrication of boron articles

    Microsoft Academic Search

    Benton

    1976-01-01

    This invention is directed to the fabrication of boron articles by a powder metallurgical method wherein the articles are of a density close to the theoretical density of boron and are essentially crackfree. The method comprises the steps of admixing 1 to 10 weight percent carbon powder with amorphous boron powder, cold pressing the mixture and then hot pressing the

  15. Study of high resistance inorganic coatings on graphite fibers. [for graphite-epoxy composite materials

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Veltri, R. D.; Scola, D. A.

    1979-01-01

    Coatings made of boron, silicon carbide, silica, and silica-like materials were studied to determine their ability to increase resistance of graphite fibers. The most promising results were attained by chemical vapor depositing silicon carbide on graphite fiber followed by oxidation, and drawing graphite fiber through ethyl silicate followed by appropriate heat treatments. In the silicon carbide coating studies, no degradation of the graphite fibers was observed and resistance values as high as three orders of magnitude higher than that of the uncoated fiber was attained. The strength of a composite fabricated from the coated fiber had a strength which compared favorably with those of composites prepared from uncoated fiber. For the silica-like coated fiber prepared by drawing the graphite fiber through an ethyl silicate solution followed by heating, coated fiber resistances about an order of magnitude greater than that of the uncoated fiber were attained. Composites prepared using these fibers had flexural strengths comparable with those prepared using uncoated fibers, but the shear strengths were lower.

  16. Preparation and characterization of BxC1-x thin films with the graphite structure

    Microsoft Academic Search

    J. R. Dahn; T. Tiedje; K. Myrtle; M. Kasrai

    1992-01-01

    Using chemical vapor deposition (CVD), we have prepared BxC1-x solid solutions for 0graphite structure. By varying the relative proportions of benzene and boron trichloride in the CVD reactor, we are able to control the boron concentration in our thin-film samples. Grazing-incidence x-ray diffraction shows that for a series of films prepared at 900 °C, BxC1-x becomes

  17. Surface protection of graphite fabric/PMR-15 composites subjected to thermal oxidation

    NASA Technical Reports Server (NTRS)

    Hanson, M. P.; Serafini, T. T.

    1985-01-01

    Graphite fabric/PMR-15 laminates develop matrix cracks during long-term exposure in air at temperatures in the range of 500 to 600 F. This study was performed to demonstrate the effectiveness of incorporating graphite mat surface plies as a means of reducing the developing of matrix cracks. Celion 3000 graphite fabric/PMR-15 laminates were fabricated with graphite or graphite mat/325-mesh boron powder surface plies. Laminates without mat surface plies were also fabricated for control purposes. Composite flexural strength, flexural modulus, and interlaminar shear strength were determined at 288 C before and after long-term exposure (up to 1500 hr) in air at 316 C. The results of this study showed that the incorporation of graphite mat surface plies reduces matrix cracking and improves the elevated temperature mechanical property retention characteristics of the composites.

  18. Structure and reactivity of boron-ate complexes derived from primary and secondary boronic esters.

    PubMed

    Feeney, Kathryn; Berionni, Guillaume; Mayr, Herbert; Aggarwal, Varinder K

    2015-06-01

    Boron-ate complexes derived from primary and secondary boronic esters and aryllithiums have been isolated, and the kinetics of their reactions with carbenium ions studied. The second-order rate constants have been used to derive nucleophilicity parameters for the boron-ate complexes, revealing that nucleophilicity increased with (i) electron-donating aromatics on boron, (ii) neopentyl glycol over pinacol boronic esters, and (iii) 12-crown-4 ether. PMID:25973673

  19. Synthesis and Characterization of Boron Carbonitride Thin Films

    NASA Astrophysics Data System (ADS)

    Wang, E. G.; Yu, Jie; Xu, Guichang

    1998-03-01

    Boron carbonitride films were prepared by bias-assisted hot filament chemical vapor deposition from gaseous mixtures of CH_4, B_2H_6, N_2, and H2 on polycrystalline Ni, quartz, and graphite substrates. The crystalline films with various morphologies, structures, and compositions were grown under different conditions. The electrical properties of the obtained films, including resistivity, magnetoresistance, and field emission, were investigated systematically. In addition, it is believed that this type of films might have a higher hardness, which is important to cold cathode application. Therefore, the desired boron carbonitrides by varying the structure and composition should be listed as one of the candidates for field emitting materials.

  20. Ab initio study of boron nitride lines on graphene

    NASA Astrophysics Data System (ADS)

    Mata-Carrizal, Berenice; Sanginés-Mendoza, Raúl; Martinez, Edgar

    2013-03-01

    Graphene has unusual electronic properties which make it a promising material for electronic devices. Neverthless, the absence of a band gap sets limitations on its practical applications. Thus, it is crucial to find methods to create and tune the band gap of systems based on graphene. In this way, we explore the modulation of the electronic properties of graphene through doping with boron nitride lines. In particular, we studied the electronic structure of graphene sheets doped with boron nitride lines armchair and zigzag type. The calculations were performed using the pseudopotential LCAO method with a Generalized Gradient Approximation (GGA) for the exchange-correlation energy functional. We found that both doping lines type induce a bandgap and that the energy gap increases as the length of doping lines increases. Accordingly to our DFT calculations, we found that the energy gap on graphene doped with armchair and zigzag lines is due to a two different mechanisms to drain charge from pi- to sigma- orbitals. Thus, we found that doping graphene with boron nitride lines is a useful way to induce and modulate the bandgap on graphene. This research was supported by Consejo Nacional de Ciencia y Tecnología (Conacyt) under Grant No. 133022.

  1. Properties of boron/boron-nitride multilayers

    SciTech Connect

    Jankowski, A.F.; Wall, M.A.; Hayes, J.P. [Lawrence Livermore National Lab., CA (United States); Alexander, K.B. [Oak Ridge National Lab., TN (United States)

    1996-06-01

    Boron-Nitride films are of interest for their high hardness and wear resistance. Large intrinsic stresses and poor adhesion which often accompany high hardness materials can be moderated through the use of a layered structure. Alternate layers of boron (B) and boron-nitride (BN) are formed by modulating the composition of the sputter gas during deposition from a pure B target. The thin films are characterized with TEM to evaluate the microstructure and with nanoindentation to determine hardness. Layer pair spacing and continuity effects on hardness are evaluated for the B/BN films.

  2. Growth of crystals of several boron-carbon compositions by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kevill, D. N.; Rissmann, T. J.; Brewe, D.; Wood, C.

    1986-01-01

    Boron-carbon compounds have been deposited by the flow of carbon tetrachloride and boron trichloride, in the presence of a large excess of hydrogen, over a graphite surface maintained at 1000-1300 C. Deposits were formed on either an RF-heated disc or a tube or insert heated by a resistance furnace. Crystalline materials ranging in composition from B2C to B17C have been obtained.

  3. Thermal annealing effects on chemical states of deuterium implanted into boron coating film

    Microsoft Academic Search

    H. Kodama; T. Sugiyama; Y. Morimoto; Y. Oya; K. Okuno; N. Inoue; A. Sagara; N. Noda

    2003-01-01

    To reveal interaction between boron coating film and energetic hydrogen isotopes, chemical states of deuterium implanted into the boron coating films deposited on graphite by using DC glow discharge in a diborane diluted helium have been studied. The XPS measurements showed the possibility of the formation of B–D and C–D bonds by D2+ ion implantation. The TDS experiments indicated that

  4. Annealing kinetics of boron-containing centers in electron-irradiated silicon

    SciTech Connect

    Feklisova, O. V., E-mail: feklisov@iptm.ru; Yarykin, N. A. [Russian Academy of Sciences, Institute of Microelectronics Technology and High Purity Materials (Russian Federation); Weber, J. [Technische Universitaet Dresden (Germany)

    2013-02-15

    The annealing kinetics of B{sub i}O{sub i} pairs created by fast-electron irradiation in Si wafers is studied. The wafers are grown by the Czochralski method and doped with boron to different levels. It is found that, at a particular temperature, the annealing rate steadily increases with increasing boron concentration. The results are described with a simple model that takes into consideration the interaction of interstitial boron atoms with oxygen atoms and substitutional boron atoms. In the context of the model, the temperature dependence of the dissociation rate of the B{sub i}O{sub i} complex is calculated.

  5. The role of boron in ductilizing Ni3Al

    NASA Technical Reports Server (NTRS)

    Vedula, K.; Shabel, B. S.; Khadkikar, P. S.

    1987-01-01

    Ductilization of Ni3Al at room temperature by microalloying with boron has been primarily attributed to the increased grain boundary cohesion in the presence of boron. However, another aspect of the role played by boron in ductilizing Ni3Al is revealed when the Hall-Petch relationships for Ni3Al and B-doped Ni3Al are compared. A shallower slope for the B-doped Ni3Al compared to that for Ni3Al indicates a reduced resistance to slip propagation across grain boundaries, and therefore reduced stress concentration at boundaries, in the presence of boron. This comparison of Hall-Petch relationships was carried out by generating data for powder processed B-doped Ni3Al at various grain sizes and by compiling data for Ni3Al from the literature. In addition, the room temperature fracture of B-doped Ni3Al has been shown to initiate along certain grain boundaries. The fracture eventually occurs by transgranular ductile tearing.

  6. Producing graphite with desired properties

    NASA Technical Reports Server (NTRS)

    Dickinson, J. M.; Imprescia, R. J.; Reiswig, R. D.; Smith, M. C.

    1971-01-01

    Isotropic or anisotropic graphite is synthesized with precise control of particle size, distribution, and shape. The isotropic graphites are nearly perfectly isotropic, with thermal expansion coefficients two or three times those of ordinary graphites. The anisotropic graphites approach the anisotropy of pyrolytic graphite.

  7. Boron implantation\\/in situ annealing procedure for optimal p -type properties of diamond

    Microsoft Academic Search

    F. Fontaine; C. Uzan-Saguy; B. Philosoph; R. Kalish

    1996-01-01

    Boron is a p-type dopant in diamond. It can be intro- duced into the diamond crystal or into polycrystalline ~CVD! diamond films by ion-implantation or during CVD growth. However, the doping efficiencies and carrier mobilities are limited, for CVD diamond, by the presence of compensating impurities and defects introduced during CVD growth, or for implantation doped single crystals, by residual

  8. Boron: elementary challenge for experimenters and theoreticians.

    PubMed

    Albert, Barbara; Hillebrecht, Harald

    2009-01-01

    Many of the fundamental questions regarding the solid-state chemistry of boron are still unsolved, more than 200 years after its discovery. Recently, theoretical work on the existence and stability of known and new modifications of the element combined with high-pressure and high-temperature experiments have revealed new aspects. A lot has also happened over the last few years in the field of reactions between boron and main group elements. Binary compounds such as B(6)O, MgB(2), LiB(1-x), Na(3)B(20), and CaB(6) have caused much excitement, but the electron-precise, colorless boride carbides Li(2)B(12)C(2), LiB(13)C(2), and MgB(12)C(2) as well as the graphite analogue BeB(2)C(2) also deserve special attention. Physical properties such as hardness, superconductivity, neutron scattering length, and thermoelectricity have also made boron-rich compounds attractive to materials research and for applications. The greatest challenges to boron chemistry, however, are still the synthesis of monophasic products in macroscopic quantities and in the form of single crystals, the unequivocal identification and determination of crystal structures, and a thorough understanding of their electronic situation. Linked polyhedra are the dominating structural elements of the boron-rich compounds of the main group elements. In many cases, their structures can be derived from those that have been assigned to modifications of the element. Again, even these require a critical revision and discussion. PMID:19830749

  9. Structural Modification in Carbon Nanotubes by Boron Incorporation

    NASA Astrophysics Data System (ADS)

    Handuja, Sangeeta; Srivastava, P.; Vankar, V. D.

    2009-08-01

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

  10. Synthesis and Characterization of Boron Carbonitride Thin Films

    Microsoft Academic Search

    E. G. Wang; Jie Yu; Guichang Xu

    1998-01-01

    Boron carbonitride films were prepared by bias-assisted hot filament chemical vapor deposition from gaseous mixtures of CH_4, B_2H_6, N_2, and H2 on polycrystalline Ni, quartz, and graphite substrates. The crystalline films with various morphologies, structures, and compositions were grown under different conditions. The electrical properties of the obtained films, including resistivity, magnetoresistance, and field emission, were investigated systematically. In addition,

  11. Energy landscape of fullerene materials: A comparion of boron to boron nitride and carbon

    NASA Astrophysics Data System (ADS)

    de, Sandip

    2012-02-01

    After the discovery of the C60 fullerene some 25 years ago, many more hollow and endohedrally doped structures made out of various elements have been proposed theoretically. However, since no other fullerenes have been synthesized up to date, the question arises whether experimentalists have just not yet found a way to synthesize these theoretically predicted fullerenes, or whether they do not exist at all in nature. Following the theoretical discovery of the B80 fullerene by Szwacki et al, various other fullereneand stuffed fullerene structures were proposed but none of them could be synthesized in the laboratory yet. Using the minima hopping global geometry optimization method on the density functional potential energy surface we show that the energy landscape of boron clusters is glass like. Medium size boron clusters exhibit many structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found. We thus present a methodology which can make predictions on the feasibility of the synthesis of new nano structures.

  12. Boron distribution in the core of Si nanowire grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, Wanghua; Dubrovskii, Vladimir G.; Liu, Xiaolong; Xu, Tao; Lardé, Rodrigue; Philippe Nys, Jean; Grandidier, Bruno; Stiévenard, Didier; Patriarche, Gilles; Pareige, Philippe

    2012-05-01

    The boron dopant distribution in Si nanowires grown by the Au-catalyzed chemical vapor deposition is characterized by laser-assisted atom probe tomography. A convenient and an effective method for performing the atom probe tomography of an individual nanowire is developed. Using this technique, we demonstrate that when Si nanowires are doped with boron at high silane partial pressure, the radial distribution of boron atoms is rather inhomogeneous. Much more boron atoms incorporate at the periphery than in the center, with the concentration increasing by an order of magnitude as the distance from the nanowire axis increases from zero to only 15 nm. A theoretical model is presented that is capable of describing the observed spatial inhomogeneity of boron dopant. We also consider different kinetic pathways of boron incorporation and discuss the values of diffusion length and diffusion coefficients obtained by fitting the experimental data.

  13. First-Principles Determination of Ultrahigh Thermal Conductivity of Boron Arsenide: A Competitor for Diamond?

    NASA Astrophysics Data System (ADS)

    Lindsay, L.; Broido, D. A.; Reinecke, T. L.

    2013-07-01

    We have calculated the thermal conductivities (?) of cubic III-V boron compounds using a predictive first principles approach. Boron arsenide is found to have a remarkable room temperature ? over 2000Wm-1K-1; this is comparable to those in diamond and graphite, which are the highest bulk values known. We trace this behavior in boron arsenide to an interplay of certain basic vibrational properties that lie outside of the conventional guidelines in searching for high ? materials, and to relatively weak phonon-isotope scattering. We also find that cubic boron nitride and boron antimonide will have high ? with isotopic purification. This work provides new insight into the nature of thermal transport at a quantitative level and predicts a new ultrahigh ? material of potential interest for passive cooling applications.

  14. First-principles determination of ultrahigh thermal conductivity of boron arsenide: a competitor for diamond?

    PubMed

    Lindsay, L; Broido, D A; Reinecke, T L

    2013-07-12

    We have calculated the thermal conductivities (?) of cubic III-V boron compounds using a predictive first principles approach. Boron arsenide is found to have a remarkable room temperature ? over 2000 W m(-1) K(-1); this is comparable to those in diamond and graphite, which are the highest bulk values known. We trace this behavior in boron arsenide to an interplay of certain basic vibrational properties that lie outside of the conventional guidelines in searching for high ? materials, and to relatively weak phonon-isotope scattering. We also find that cubic boron nitride and boron antimonide will have high ? with isotopic purification. This work provides new insight into the nature of thermal transport at a quantitative level and predicts a new ultrahigh ? material of potential interest for passive cooling applications. PMID:23889420

  15. Heated graphite cylinder electrodes

    Microsoft Academic Search

    Jian-Jun Sun; Liang Guo; De-Feng Zhang; Wen-Hui Yin; Guo-Nan Chen

    2007-01-01

    A new heated graphite cylinder electrode (HGCE) has been successfully fabricated, which arrangement is similar to that of the heated metal (Pt or Au) wire electrode invented by Grundler. The cylinders’ diameters range from ca. 95 to 300?m obtained by grinding the commercial available pencil graphite. HGCEs demonstrate rapid responses to the heating up and high thermal stability during being

  16. Graphite targets at LAMPF

    SciTech Connect

    Brown, R.D.; Grisham, D.L.

    1983-01-01

    Rotating polycrystalline and stationary pyrolytic graphite target designs for the LAMPF experimental area are described. Examples of finite element calculations of temperatures and stresses are presented. Some results of a metallographic investigation of irradiated pyrolytic graphite target plates are included, together with a brief description of high temperature bearings for the rotating targets.

  17. Characterization of pure boron depositions integrated in silicon diodes for nanometer-deep junction applications

    Microsoft Academic Search

    F. Sarubbi

    2010-01-01

    Doping technologies for formation of ultrashallow and highly-doped p+ junctions are continuously demanded to face the challenges in front-end processing that have emerged due to the aggressive downscaling of vertical dimensions for future semiconductor devices. As an alternative to implantations, current solutions are based on in-situ boron (B) doping during Si\\/SiGe chemical vapor deposition (CVD) by using diborane (B2H6) as

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

    NASA Astrophysics Data System (ADS)

    Rinaldo, Steven G.

    This thesis is divided into two parts. In Part I, we examine the properties of thin sheets of carbon and boron nitride. We begin with an introduction to the theory of elastic sheets, where the stretching and bending modes are considered in detail. The coupling between stretching and bending modes is thought to play a crucial role in the thermodynamic stability of atomically-thin 2D sheets such as graphene. In Chapter 2, we begin by looking at the fabrication of suspended, atomically thin sheets of graphene. We then study their mechanical resonances which are read via an optical transduction technique. The frequency of the resonators was found to depend on their temperature, as was their quality factor. We conclude by offering some interpretations of the data in terms of the stretching and bending modes of graphene. In Chapter 3, we look briefly at the fabrication of thin sheets of carbon and boron nitride nanotubes. We examine the structure of the sheets using transmission and scanning electron microscopy (TEM and SEM, respectively). We then show a technique by which one can make sheets suspended over a trench with adjustable supports. Finally, DC measurements of the resistivity of the sheets in the temperature range 600 -- 1400 C are presented. In Chapter 4, we study the folding of few-layer graphene oxide, graphene and boron nitride into 3D aerogel monoliths. The properties of graphene oxide are first considered, after which the structure of graphene and boron nitride aerogels is examined using TEM and SEM. Some models for their structure are proposed. In Part II, we look at synthesis techniques for boron nitride (BN). In Chapter 5, we study the conversion of carbon structures of boron nitride via the application of carbothermal reduction of boron oxide followed by nitridation. We apply the conversion to a wide variety of morphologies, including aerogels, carbon fibers and nanotubes, and highly oriented pyrolytic graphite. In the latter chapters, we look at the formation of boron nitride nanotubes (BNNTs). In Chapter 6, we look at various methods of producing BNNTs from boron droplets, and introduce a new method involving injection of boron powder into an induction furnace. In Chapter 7 we consider another useful process, where ammonia is reacted with boron vapor generated in situ, either through the reaction of boron with metal oxides or through the decomposition of metal borides.

  19. Boron Deficiency in Tea

    Microsoft Academic Search

    E. M. Chenery

    1958-01-01

    TEA must be the last commodity crop to show a need for boron. This is probably due to its low calcium requirement and to the fact that tea gardens are very rarely limed. The boron deficiency syndrome first appeared accidentally in a pot experiment testing five different soils for natural potassium uptake. All plants in two soils when they were

  20. Magnetron sputtered boron films

    DOEpatents

    Makowiecki, Daniel M. (Livermore, CA); Jankowski, Alan F. (Livermore, CA)

    1998-01-01

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence.

  1. Magnetron sputtered boron films

    DOEpatents

    Makowiecki, D.M.; Jankowski, A.F.

    1998-06-16

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence. 8 figs.

  2. Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury.

    PubMed

    Philip, Swetha Sara; John, Deepa; John, Sheeja Susan

    2012-01-01

    Reports of graphite pencil lead injuries to the eye are rare. Although graphite is considered to remain inert in the eye, it has been known to cause severe inflammation and damage to ocular structures. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies following a graphite pencil injury. PMID:22606501

  3. Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury

    PubMed Central

    Philip, Swetha Sara; John, Deepa; John, Sheeja Susan

    2012-01-01

    Reports of graphite pencil lead injuries to the eye are rare. Although graphite is considered to remain inert in the eye, it has been known to cause severe inflammation and damage to ocular structures. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies following a graphite pencil injury. PMID:22606501

  4. Microwave sintering of boron carbide

    DOEpatents

    Blake, R.D.; Katz, J.D.; Petrovic, J.J.; Sheinberg, H.

    1988-06-10

    A method for forming boron carbide into a particular shape and densifying the green boron carbide shape. Boron carbide in powder form is pressed into a green shape and then sintered, using a microwave oven, to obtain a dense boron carbide body. Densities of greater than 95% of theoretical density have been obtained. 1 tab.

  5. Electron oxidation of graphite by fluorospecies

    SciTech Connect

    Rosenthal, G.L.

    1984-09-01

    The fluoride-ion affinity (A/sub F/sup -//) of phosphorus pentafluoride was determined to be 100 kcal/mole from the heats of reaction of the Lewis bases SF/sub 4/ and ClO/sub 2/F with PF/sub 5/ near room temperature. The fluoride-ion affinity of boron trifluoride was determined to be 92 kcal/mole from the heat of reaction of ClO/sub 2/F with BF/sub 3/. The crystal structure of ClO/sub 2/BF/sub 4/ was determined and a precise lattice energy was calculated from this structure and used to determined A/sub F/sup -//. Both PF/sub 5/ and BF/sub 3/ were found to react with graphite in the presence of fluorine gas to yield a variety of non-stoichiometric compounds. The fluoride-ion affinity of silicon tetrafluoride is not known, but it does not react with graphite and F/sub 2/ except at high pressures. These and previous results suggested a threshold in oxidizing power of intercalating species below which the oxidative intercalation reaction would not occur. The reduction of C/sub x/PF/sub 6/ by PF/sub 3/ proved that the reaction is thermodynamically controlled to some extent. The displacement of PF/sub 5/ in C/sub x/PF/sub 6/ by BF/sub 3/ (with a smaller A/sub F/sup -//) suggested that two BF/sub 3/ molecules may have a larger fluoride-ion affinity than one PF/sub 5/ and that B/sub 2/F/sub 7//sup -/ may be a stable anion in graphite. Conductivity studies of PF/sub x/ and BF/sub y/ salts showed that a large drop in conductivity when the reaction reaches first stage is due in the most part to direct fluorination of carbon in graphite.

  6. Boron/aluminum graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1975-01-01

    Fabrication feasibility and potential of an adhesively bonded metal and resin matrix fiber-composite hybrid are determined as an advanced material for aerospace and other structural applications. The results show that using this hybrid concept makes possible a composite design which, when compared with nonhybrid composites, has greater transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  7. Boron/aluminum-graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1974-01-01

    An investigation was conducted to determine the fabrication feasibility and to assess the potential of adhesively-bonded metal and resin matrix fiber composite hybrids as an advanced material, for aerospace and other structural applications. The results of fabrication studies and of evaluation of physical and mechanical properties show that using this hybrid concept it is possible to design a composite which, when compared to nonhybrid composites, has improved transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  8. Boron/aluminum-graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1974-01-01

    An investigation was conducted to determine the fabrication feasibility and to assess the potential of adhesively-bonded metal and resin matrix fiber composite hybrids as an advanced material, for aerospace and other structural applications. The results of fabrication studies and of evaluation of physical and mechanical properties show that using this hybrid concept it is possible to design a composite which, when compared to nonhybrid composites, has improved transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for perdicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  9. Dose calculation from a D-D-reaction-based BSA for boron neutron capture synovectomy.

    PubMed

    Abdalla, Khalid; Naqvi, A A; Maalej, N; Elshahat, B

    2010-01-01

    Monte Carlo simulations were carried out to calculate dose in a knee phantom from a D-D-reaction-based Beam Shaping Assembly (BSA) for Boron Neutron Capture Synovectomy (BNCS). The BSA consists of a D(d,n)-reaction-based neutron source enclosed inside a polyethylene moderator and graphite reflector. The polyethylene moderator and graphite reflector sizes were optimized to deliver the highest ratio of thermal to fast neutron yield at the knee phantom. Then neutron dose was calculated at various depths in a knee phantom loaded with boron and therapeutic ratios of synovium dose/skin dose and synovium dose/bone dose were determined. Normalized to same boron loading in synovium, the values of the therapeutic ratios obtained in the present study are 12-30 times higher than the published values. PMID:19828325

  10. Molecular Structure of graphite

    NSDL National Science Digital Library

    2002-08-26

    In the the mid-16th century, a violent storm knocked over several trees in Borrowdale, England, uncovering a large deposit of a black substance that was first thought to be lead. More than 200 years later, an English scientist discovered that the substance was not actually lead, but a type of carbon instead. The substance was named graphite, after the Greek word meaning "to write," since that is how people used the substance. Graphite is a black silver with a metallic to dull luster. It has a hexagonal crystal system with crystals that are opaque. Due to its high temperature stability and chemical inertness graphite is a good candidate for a refractory material. It is used in the production of refractory bricks and in the production of Mag-carbon refractory bricks. Amorphous graphite is used in metallurgy, pencil production, and paint production.

  11. Graphite Technology Development Plan

    SciTech Connect

    W. Windes; T. Burchell; R. Bratton

    2007-09-01

    This technology development plan is designed to provide a clear understanding of the research and development direction necessary for the qualification of nuclear grade graphite for use within the Next Generation Nuclear Plant (NGNP) reactor. The NGNP will be a helium gas cooled Very High Temperature Reactor (VHTR) with a large graphite core. Graphite physically contains the fuel and comprises the majority of the core volume. Considerable effort will be required to ensure that the graphite performance is not compromised during operation. Based upon the perceived requirements the major data needs are outlined and justified from the perspective of reactor design, reatcor performance, or the reactor safety case. The path forward for technology development can then be easily determined for each data need. How the data will be obtained and the inter-relationships between the experimental and modeling activities will define the technology development for graphite R&D. Finally, the variables affecting this R&D program are discussed from a general perspective. Factors that can significantly affect the R&D program such as funding, schedules, available resources, multiple reactor designs, and graphite acquisition are analyzed.

  12. Carbon-14 Graphitization Chemistry

    NASA Astrophysics Data System (ADS)

    Miller, James; Collon, Philippe; Laverne, Jay

    2014-09-01

    Accelerator Mass Spectrometry (AMS) is a process that allows for the analysis of mass of certain materials. It is a powerful process because it results in the ability to separate rare isotopes with very low abundances from a large background, which was previously impossible. Another advantage of AMS is that it only requires very small amounts of material for measurements. An important application of this process is radiocarbon dating because the rare 14C isotopes can be separated from the stable 14N background that is 10 to 13 orders of magnitude larger, and only small amounts of the old and fragile organic samples are necessary for measurement. Our group focuses on this radiocarbon dating through AMS. When performing AMS, the sample needs to be loaded into a cathode at the back of an ion source in order to produce a beam from the material to be analyzed. For carbon samples, the material must first be converted into graphite in order to be loaded into the cathode. My role in the group is to convert the organic substances into graphite. In order to graphitize the samples, a sample is first combusted to form carbon dioxide gas and then purified and reduced into the graphite form. After a couple weeks of research and with the help of various Physics professors, I developed a plan and began to construct the setup necessary to perform the graphitization. Once the apparatus is fully completed, the carbon samples will be graphitized and loaded into the AMS machine for analysis.

  13. Graphite design handbook

    SciTech Connect

    Ho, F.H.

    1988-09-01

    The objectives of the Graphite Design Handbook (GDH) are to provide and maintain a single source of graphite properties and phenomenological model of mechanical behavior to be used for design of MHTGR graphite components of the Reactor System, namely, core support, permanent side reflector, hexagonal reflector elements, and prismatic fuel elements; to provide a single source of data and material models for use in MHTGR graphite component design, performance, and safety analyses; to present properties and equations representing material models in a form which can be directly used by the designer or analyst without the need for interpretation and is compatible with analytical methods and structural criteria used in the MHTGR project, and to control the properties and material models used in the MHTGR design and analysis to proper Quality Assurance standards and project requirements. The reference graphite in the reactor internal components is the nuclear grade 2020. There are two subgrades of interest, the cylinder nuclear grade and the large rectangular nuclear grade. The large rectangular nuclear grade is molded in large rectangular blocks. It is the reference material for the permanent side reflector and the central column support structure. The cylindrical nuclear grade is isostatically pressed and is intended for use as the core support component. This report gives the design properties for both H-451 and 2020 graphite as they apply to their respective criteria. The properties are presented in a form for design, performance, and safety calculations that define or validate the component design. 103 refs., 20 figs., 19 tabs.

  14. Boron-Based Drug Design.

    PubMed

    Ban, Hyun Seung; Nakamura, Hiroyuki

    2015-06-01

    The use of the element boron, which is not generally observed in a living body, possesses a high potential for the discovery of new biological activity in pharmaceutical drug design. In this account, we describe our recent developments in boron-based drug design, including boronic acid containing protein tyrosine kinase inhibitors, proteasome inhibitors, and tubulin polymerization inhibitors, and ortho-carborane-containing proteasome activators, hypoxia-inducible factor 1 inhibitors, and topoisomerase inhibitors. Furthermore, we applied a closo-dodecaborate as a water-soluble moiety as well as a boron-10 source for the design of boron carriers in boron neutron capture therapy, such as boronated porphyrins and boron lipids for a liposomal boron delivery system. PMID:25800654

  15. Improving Boron-Induced Retardation of Metal-Induced Lateral Crystallization Length by Hydrogen Treatment

    Microsoft Academic Search

    Shih-Fang Chen; Yuen-Kuen Fang; Ping-Chang Lin; Tsung-Han Lee; Chun-Yu Lin; Chun-Sheng Lin; Tse-Heng Chou

    2005-01-01

    In this letter, we use hydrogen treatment to improve boron-dopant-induced growth length retardation in metal-induced lateral crystallization (MILC) of amorphous silicon film (a-Si). Compared with the case without hydrogen treatment, a scanning electron microscope (SEM) micrograph shows that the grown poly-silicon length in boron-doped a-Si film can be increased from 7 to 40 mum after 6 h of MILC annealing.

  16. Minerals Yearbook, 1988. Boron

    SciTech Connect

    Lyday, P.A.

    1988-01-01

    U.S. production and sales of boron minerals and chemicals decreased during the year. Glass-fiber insulation was the largest use for borates, followed by sales to distributors, textile-grade glass fibers, and borosilicate glasses. California was the only domestic source of boron minerals. The report discusses the following: domestic data coverage; legislation and government programs; domestic production; comsumption and uses; prices; foreign trade; world capacity; world review--Argentina, Chile, France, Italy, Turkey, United Kingdom; Technology.

  17. Boron and Plants

    Microsoft Academic Search

    Munir Ozturk; Serdal Sakcali; Salih Gucel; Huseyin Tombuloglu

    \\u000a Boron is found naturally in the earth’s crust in the oxidized form as borax and colemanite, particularly in the oceans, sedimentary\\u000a rocks, coal, shale, and some soils. It is never found in the elemental form in nature possessing a complex chemistry similar\\u000a to that of silicon, with properties switching between metals and non-metals. Boron has become an important and strategic

  18. Effect of boron concentration on recombination at the p-Si-Al2O3 interface

    NASA Astrophysics Data System (ADS)

    Black, Lachlan E.; Allen, Thomas; McIntosh, Keith R.; Cuevas, Andres

    2014-03-01

    We examine the surface passivation properties of Al2O3 deposited on boron-doped planar ?100? crystalline silicon surfaces as a function of the boron concentration. Both uniformly doped and diffused surfaces are studied, with surface boron concentrations ranging from 9.2 × 1015 to 5.2 × 1019 cm-3. Atmospheric pressure chemical vapor deposition and thermal atomic layer deposition are used to deposit the Al2O3 films. The surface recombination rate of each sample is determined from photoconductance measurements together with the measured dopant profiles via numerical simulation, using the latest physical models. These values are compared with calculations based on the interface properties determined from capacitance-voltage and conductance measurements. It is found that the fundamental surface recombination velocity of electrons, Sn0, which describes the chemical passivation of the interface, is independent of the surface boron concentration Ns for Ns ? 3 × 1019 cm-3, and in excellent agreement with values calculated from the interface state density Dit and capture coefficients cn and cp measured on undiffused boron-doped surfaces. We conclude that the physical properties of the Si-Al2O3 interface are independent of the boron dopant concentration over this range.

  19. Boron Nutrition and Boron Application in Crops

    Microsoft Academic Search

    Rodrigo Marcelli Boaretto; Takashi Muraoka; Maria Fernanda Giné; Antonio Enedi Boaretto

    The application of micronutrients in citrus plants has usually been done by foliar spraying. The citrus plants are exigent\\u000a in boron, zinc, manganese, iron and deficiency of these micronutrients is common in worldwide citriculture. In Brazilian citriculture,\\u000a the B and Zn deficiencies are most frequent (Quaggio et al. 2003). For this reason, these micronutrients are routinely applied\\u000a as foliar fertilizers

  20. Boron Nutrition and Boron Application in Crops

    Microsoft Academic Search

    A. Rashid; M. Masud Mahmood; E. Rafique; K. Farooq

    Deficiencies of boron (B) and zinc (Zn) are well established in many agronomic and horticultural crops grown in calcareous\\u000a soils of Pakistan (Rashid 2006). As crop responses to B as well as to Zn are appreciable and use of their fertilizers is highly\\u000a cost–effective, application of these micronutrients is now recommended in the country. The history of Zn use in

  1. Recompressed exfoliated graphite articles

    DOEpatents

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2013-08-06

    This invention provides an electrically conductive, less anisotropic, recompressed exfoliated graphite article comprising a mixture of (a) expanded or exfoliated graphite flakes; and (b) particles of non-expandable graphite or carbon, wherein the non-expandable graphite or carbon particles are in the amount of between about 3% and about 70% by weight based on the total weight of the particles and the expanded graphite flakes combined; wherein the mixture is compressed to form the article having an apparent bulk density of from about 0.1 g/cm.sup.3 to about 2.0 g/cm.sup.3. The article exhibits a thickness-direction conductivity typically greater than 50 S/cm, more typically greater than 100 S/cm, and most typically greater than 200 S/cm. The article, when used in a thin foil or sheet form, can be a useful component in a sheet molding compound plate used as a fuel cell separator or flow field plate. The article may also be used as a current collector for a battery, supercapacitor, or any other electrochemical cell.

  2. Graphite Gamma Scan Results

    SciTech Connect

    Mark W. Drigert

    2014-04-01

    This report documents the measurement and data analysis of the radio isotopic content for a series of graphite specimens irradiated in the first Advanced Graphite Creep (AGC) experiment, AGC-1. This is the first of a series of six capsules planned as part of the AGC experiment to fully characterize the neutron irradiation effects and radiation creep behavior of current nuclear graphites. The AGC-1 capsule was irradiated in the Advanced Test Reactor (ATR) at INL at approximately 700 degrees C and to a peak dose of 7 dpa (displacements per atom). Details of the irradiation conditions and other characterization measurements performed on specimens in the AGC-1 capsule can be found in “AGC-1 Specimen Post Irradiation Data Report” ORNL/TM 2013/242. Two specimens from six different graphite types are analyzed here. Each specimen is 12.7 mm in diameter by 25.4 mm long. The isotope with the highest activity was 60Co. Graphite type NBG-18 had the highest content of 60Co with an activity of 142.89 µCi at a measurement distance of 47 cm.

  3. Two-dimensional numerical simulation of boron diffusion for pyramidally textured silicon

    NASA Astrophysics Data System (ADS)

    Ma, Fa-Jun; Duttagupta, Shubham; Shetty, Kishan Devappa; Meng, Lei; Samudra, Ganesh S.; Hoex, Bram; Peters, Ian Marius

    2014-11-01

    Multidimensional numerical simulation of boron diffusion is of great relevance for the improvement of industrial n-type crystalline silicon wafer solar cells. However, surface passivation of boron diffused area is typically studied in one dimension on planar lifetime samples. This approach neglects the effects of the solar cell pyramidal texture on the boron doping process and resulting doping profile. In this work, we present a theoretical study using a two-dimensional surface morphology for pyramidally textured samples. The boron diffusivity and segregation coefficient between oxide and silicon in simulation are determined by reproducing measured one-dimensional boron depth profiles prepared using different boron diffusion recipes on planar samples. The established parameters are subsequently used to simulate the boron diffusion process on textured samples. The simulated junction depth is found to agree quantitatively well with electron beam induced current measurements. Finally, chemical passivation on planar and textured samples is compared in device simulation. Particularly, a two-dimensional approach is adopted for textured samples to evaluate chemical passivation. The intrinsic emitter saturation current density, which is only related to Auger and radiative recombination, is also simulated for both planar and textured samples. The differences between planar and textured samples are discussed.

  4. Burning characteristics and fiber retention of graphite/resin matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1980-01-01

    Graphite fiber reinforced resin matrix composites were subjected to controlled burning conditions to determine their burning characteristics and fiber retention properties. Small samples were burned with a natural gas fired torch to study the effects of fiber orientation and structural flaws such as holes and slits that were machined into the laminates. Larger laminate samples were burned in a modified heat release rate calorimeter. Unidirectional epoxy/graphite and polyimide/graphite composites and boron powder filled samples of each of the two composite systems were burn tested. The composites were exposed to a thermal radiation of 5.3 Btu/sq ft-sec in air. Samples of each of the unfilled composite were decomposed anaerobically in the calorimeter. Weight loss data were recorded for burning and decomposition times up to thirty-five minutes. The effects of fiber orientation, flaws, and boron filler additives to the resins were evaluated. A high char forming polyimide resin was no more effective in retaining graphite fibers than a low char forming epoxy resin when burned in air. Boron powder additions to both the polyimide and the epoxy resins stabilized the chars and effectively controlled the fiber release.

  5. Irradiation Creep in Graphite

    SciTech Connect

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

    An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

  6. Status of Initial Assessment of Physical and Mechanical Properties of Graphite Grades for NGNP Appkications

    SciTech Connect

    Strizak, Joe P [ORNL; Burchell, Timothy D [ORNL; Windes, Will [Idaho National Laboratory (INL)

    2011-12-01

    Current candidate graphite grades for the core structures of NGNP include grades NBG-17, NBG-18, PCEA and IG-430. Both NBG-17 and NBG-18 are manufactured using pitch coke, and are vibrationally molded. These medium grain products are produced by SGL Carbon SAS (France). Tayo Tanso (Japan) produces IG-430 which is a petroleum coke, isostatically molded, nuclear grade graphite. And PCEA is a medium grain, extruded graphite produced by UCAR Carbon Co. (USA) from petroleum coke. An experimental program has been initiated to develop physical and mechanical properties data for these current candidate graphites. The results will be judged against the requirements for nuclear grade graphites set forth in ASTM standard D 7219-05 "Standard Specification for Isotropic and Near-isotropic Nuclear Graphites". Physical properties data including thermal conductivity and coefficient of thermal expansion, and mechanical properties data including tensile, compressive and flexural strengths will be obtained using the established test methods covered in D-7219 and ASTM C 781-02 "Standard Practice for Testing Graphite and Boronated Graphite Components for High-Temperature Gas-Cooled Nuclear Reactors". Various factors known to effect the properties of graphites will be investigated. These include specimen size, spatial location within a graphite billet, specimen orientation (ag and wg) within a billet, and billet-to-billet variations. The current status of the materials characterization program is reported herein. To date billets of the four graphite grades have been procured, and detailed cut up plans for obtaining the various specimens have been prepared. Particular attention has been given to the traceability of each specimen to its spatial location and orientation within a billet.

  7. Boronated liposome development and evaluation

    SciTech Connect

    Hawthorne, M.F. [Univ. of California, Los Angeles, CA (United States)

    1995-11-01

    The boronated liposome development and evaluation effort consists of two separate tasks. The first is the development of new boron compounds and the synthesis of known boron species with BNCT potential. These compounds are then encapsulated within liposomes for the second task, biodistribution testing in tumor-bearing mice, which examines the potential for the liposomes and their contents to concentrate boron in cancerous tissues.

  8. Improved graphite furnace atomizer

    DOEpatents

    Siemer, D.D.

    1983-05-18

    A graphite furnace atomizer for use in graphite furnace atomic absorption spectroscopy is described wherein the heating elements are affixed near the optical path and away from the point of sample deposition, so that when the sample is volatilized the spectroscopic temperature at the optical path is at least that of the volatilization temperature, whereby analyteconcomitant complex formation is advantageously reduced. The atomizer may be elongated along its axis to increase the distance between the optical path and the sample deposition point. Also, the atomizer may be elongated along the axis of the optical path, whereby its analytical sensitivity is greatly increased.

  9. An enhanced hydrogen adsorption enthalpy for fluoride intercalated graphite compounds.

    PubMed

    Cheng, Hansong; Sha, Xianwei; Chen, Liang; Cooper, Alan C; Foo, Maw-Lin; Lau, Garret C; Bailey, Wade H; Pez, Guido P

    2009-12-16

    We present a combined theoretical and experimental study on H(2) physisorption in partially fluorinated graphite. This material, first predicted computationally using ab initio molecular dynamics simulation and subsequently synthesized and characterized experimentally, represents a novel class of "acceptor type" graphite intercalated compounds that exhibit significantly higher isosteric heat of adsorption for H(2) at near ambient temperatures than previously demonstrated for commonly available porous carbon-based materials. The unusually strong interaction arises from the semi-ionic nature of the C-F bonds. Although a high H(2) storage capacity (>4 wt %) at room temperature is predicted not to be feasible due to the low heat of adsorption, enhanced storage properties can be envisaged by doping the graphitic host with appropriate species to promote higher levels of charge transfer from graphene to F(-) anions. PMID:19928879

  10. Understanding the sprayed boric acid method for bulk doping of silicon ribbons

    NASA Astrophysics Data System (ADS)

    Silva, J. A.; Pêra, David; Brito, Miguel C.; Alves, Jorge Maia; Serra, João; Vallêra, A. M.

    2011-07-01

    The sprayed boric acid (SBA) method for bulk doping of silicon ribbons is investigated. Experimental procedures and main results are reviewed. Computational fluid dynamics and experimental tests using partial spraying suggest the role of gas transported evaporated boron oxide to explain the boron incorporation profiles along the sample. The industrial applicability of the SBA method is discussed.

  11. Understanding the sprayed boric acid method for bulk doping of silicon ribbons

    Microsoft Academic Search

    J. A. Silva; David Pêra; Miguel C. Brito; Jorge Maia Alves; João Serra; A. M. Vallêra

    2011-01-01

    The sprayed boric acid (SBA) method for bulk doping of silicon ribbons is investigated. Experimental procedures and main results are reviewed. Computational fluid dynamics and experimental tests using partial spraying suggest the role of gas transported evaporated boron oxide to explain the boron incorporation profiles along the sample. The industrial applicability of the SBA method is discussed.

  12. Discharge characteristics of graphite fluoride prepared via graphite oxide

    NASA Astrophysics Data System (ADS)

    Nakajima, T.; Hagiwara, R.; Moriya, K.; Watanabe, N.

    The discharge performance of graphite fluoride, prepared by fluorinating residual carbon from the thermal decomposition of graphite oxide, has been evaluated. In most cases, the graphite fluoride was (CF) n. That prepared from flaky natural graphite gave a higher OCV and discharge potential than (C 2F) n prepared by direct fluorination; the overpotential was similar. The energy density increased by 20 - 30%. In the case of (CF) n prepared from graphitized petroleum coke, a large overpotential, which commonly appears at the beginning of discharge, was not observed, and the discharge potential gradually decreased with the progress of the discharge reaction.

  13. Stabilization of Small Boron Cage by Transition Metal Encapsulation

    NASA Astrophysics Data System (ADS)

    Zhang, Lijun; Lv, Jian; Wang, Yanchao; Ma, Yanming

    2015-03-01

    The discovery of chemically stable fullerene-like structures formed by elements other than carbon has been long-standing desired. On this aspect significant efforts have centered around boron, only one electron deficient compared with carbon. However, during the past decade a large number of experimental and theoretical studies have established that small boron clusters are either planar/quasi-planar or forming double-ring tubular structures. Until recently, two all-boron fullerenes have been independently discovered: B38 proposed by our structure searching calculations and B40 observed in a joint experimental and theoretical study. Here we extend our work to the even smaller boron clusters and propose an effective routine to stabilize them by transition metal encapsulation. By combining swarm-intelligence structure searching and first-principles calculations, we have systematically investigated the energy landscapes of transition-metal-doped MB24 clusters (M = Ti, Zr, Hf, Cr, Mo, W, Fe, Ru and Os). Two stable symmetric endohedral boron cages, MoB24 and WB24 are identified. The stability of them can be rationalized in terms of their unique 18-electron closed-shell electronic structures. Funded by Recruitment Program of Global Experts of China and China Postdoctoral Science Foundation.

  14. Boron addition to alloys

    SciTech Connect

    Coad, B. C.

    1985-08-20

    A process for addition of boron to an alloy which involves forming a melt of the alloy and a reactive metal, selected from the group consisting of aluminum, titanium, zirconium and mixtures thereof to the melt, maintaining the resulting reactive mixture in the molten state and reacting the boric oxide with the reactive metal to convert at least a portion of the boric oxide to boron which dissolves in the resulting melt, and to convert at least portion of the reactive metal to the reactive metal oxide, which oxide remains with the resulting melt, and pouring the resulting melt into a gas stream to form a first atomized powder which is subsequently remelted with further addition of boric oxide, re-atomized, and thus reprocessed to convert essentially all the reactive metal to metal oxide to produce a powdered alloy containing specified amounts of boron.

  15. Minerals Yearbook 1989: Boron

    SciTech Connect

    Lyday, P.A.

    1990-08-01

    U.S. production and sales of boron minerals and chemicals decreased during the year. Domestically, glass fiber insulation was the largest use for borates, followed by sales to distributors, textile-grade glass fibers, and borosilicate glasses. California was the only domestic source of boron minerals. The United States continued to provide essentially all of its own supply while maintaining a strong position as a source of sodium borate products and boric acid exported to foreign markets. Supplementary U.S. imports of Turkish calcium borate and calcium-sodium borate ores, borax, and boric acid, primarily for various glass uses, continued.

  16. Dislocation patterns in graphite

    Microsoft Academic Search

    P. Delavignette; S. Amelinckx

    1962-01-01

    A detailed analysis is given of the dislocation patterns observed by ; means of electron microscopy in graphite single crystal flakes. It is found that ; the dislocations are ribbons consisting of two partials of the Shockley type ; separated by a strip of stacking fault. All patterns can be interpreted in a ; consistent way on the basis of

  17. (Irradiation creep of graphite)

    SciTech Connect

    Kennedy, C.R.

    1990-12-21

    The traveler attended the Conference, International Symposium on Carbon, to present an invited paper, Irradiation Creep of Graphite,'' and chair one of the technical sessions. There were many papers of particular interest to ORNL and HTGR technology presented by the Japanese since they do not have a particular technology embargo and are quite open in describing their work and results. In particular, a paper describing the failure of Minor's law to predict the fatigue life of graphite was presented. Although the conference had an international flavor, it was dominated by the Japanese. This was primarily a result of geography; however, the work presented by the Japanese illustrated an internal program that is very comprehensive. This conference, a result of this program, was better than all other carbon conferences attended by the traveler. This conference emphasizes the need for US participation in international conferences in order to stay abreast of the rapidly expanding HTGR and graphite technology throughout the world. The United States is no longer a leader in some emerging technologies. The traveler was surprised by the Japanese position in their HTGR development. Their reactor is licensed and the major problem in their graphite program is how to eliminate it with the least perturbation now that most of the work has been done.

  18. Presolar Graphite from Murchison

    NASA Astrophysics Data System (ADS)

    Amari, S.; Zinner, E.; Gallino, R.; Lewis, R. S.

    2011-03-01

    We have analyzed 1642 graphite grains from four Murchison fractions. Many grains in lower-density fractions KE3 and KFA1 originated from supernovae. A significant number of grains in higher-density fractions KFB1 and KFC1 formed in low-metallicity AGB stars.

  19. Coatings for Graphite Fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak.

  20. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

    1986-08-27

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  1. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, Richard K. (Pleasanton, CA); Bystroff, Roman I. (Livermore, CA); Miller, Dale E. (Livermore, CA)

    1987-01-01

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  2. Boron carbonitride films deposited by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Perrone, A.; Caricato, A. P.; Luches, A.; Dinescu, M.; Ghica, C.; Sandu, V.; Andrei, A.

    1998-08-01

    Boron carbonitride (BCN) thin films were deposited on Si (100) substrates at room temperature by sequential pulsed laser ablation (PLA) of graphite and hexagonal boron nitride (h-BN) targets in vacuum and in nitrogen atmosphere in the pressure range 1-100 Pa. Different analysis techniques as transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) pointed out the synthesis of h-BCN and c-BCN. The grain size of the crystalline c-BCN phase was estimated to be in the range 30-80 nm. The size of the crystallites in h-BCN phase was 4.6 ?m, with a transversal dimension of about 30 nm. Complementary microhardness measurements evidenced the high microhardness (values up to 2.9 GPa) of the deposited films.

  3. A study of laser annealing effects in boron ion implanted polycrystalline silicon films

    E-print Network

    Suh, Inhak Harry

    1982-01-01

    of semiconductor materials including an- nealing of doped GaAs [37], and annealing of severe lattice damage in single crystal silicon [38] . Also recently, several papers on laser annealed doped polycrystalline sili- con have begun to appear [3... that the electri- cal properties of ion implanted polycrystalline silicon can be improved dramatically by thermal or laser annealing. The use of a Nd:YAG laser for annealing and. thus alter- ing the electrical properties of boron ion implanted poly...

  4. Fabrication of boron sputter targets

    DOEpatents

    Makowiecki, Daniel M. (Livermore, CA); McKernan, Mark A. (Livermore, CA)

    1995-01-01

    A process for fabricating high density boron sputtering targets with sufficient mechanical strength to function reliably at typical magnetron sputtering power densities and at normal process parameters. The process involves the fabrication of a high density boron monolithe by hot isostatically compacting high purity (99.9%) boron powder, machining the boron monolithe into the final dimensions, and brazing the finished boron piece to a matching boron carbide (B.sub.4 C) piece, by placing aluminum foil there between and applying pressure and heat in a vacuum. An alternative is the application of aluminum metallization to the back of the boron monolithe by vacuum deposition. Also, a titanium based vacuum braze alloy can be used in place of the aluminum foil.

  5. Fabrication of boron sputter targets

    DOEpatents

    Makowiecki, D.M.; McKernan, M.A.

    1995-02-28

    A process is disclosed for fabricating high density boron sputtering targets with sufficient mechanical strength to function reliably at typical magnetron sputtering power densities and at normal process parameters. The process involves the fabrication of a high density boron monolithe by hot isostatically compacting high purity (99.9%) boron powder, machining the boron monolithe into the final dimensions, and brazing the finished boron piece to a matching boron carbide (B{sub 4}C) piece, by placing aluminum foil there between and applying pressure and heat in a vacuum. An alternative is the application of aluminum metallization to the back of the boron monolithe by vacuum deposition. Also, a titanium based vacuum braze alloy can be used in place of the aluminum foil. 7 figs.

  6. Boron Nutrition of Avocados

    Microsoft Academic Search

    A. W. Whiley; I. E. Smith; B. N. Wolstenholme; J. B. Saranah

    1996-01-01

    Boron is an essential micronutrient for normal plant growth, but is deficient in many soils that support avocado cultivation. In avocado, deficiency symptoms include yellowing and deformation of leaves, thickening of nodal regions on branch es, loss of geotropism, reduced root growth, branch and trunk lesions, reduced pollen viability, and deformed and smaller fruit. Avocado trees are particularly recalcitrant in

  7. Bamboo leaf-assisted formation of carbon/nitrogen co-doped anatase TiO2 modified with silver and graphitic carbon nitride: novel and green synthesis and cooperative photocatalytic activity.

    PubMed

    Jiang, Zhifeng; Liu, Dong; Jiang, Deli; Wei, Wei; Qian, Kun; Chen, Min; Xie, Jimin

    2014-09-28

    We report a novel synthesis approach employing bamboo leaves as sources of both the C/N dopant and reductant to the formation of C/N co-doped TiO2 modified with Ag and g-C3N4 (Ag/CN-TiO2@g-C3N4). In this case, the ternary composite has a hierarchical structure and a large surface area, which increases the contact area of reactants. Degradation of rhodamine B (RhB) and hydrogen generation were carried out to evaluate the photocatalytic activity of as-prepared samples under visible light irradiation. It is found that with respect to single and binary catalysts, the Ag/CN-TiO2@g-C3N4 ternary composite shows the highest photocatalytic activity (degradation of RhB, H2 evolution from water splitting) as a result of the fast generation, separation and transportation of the photogenerated carriers, which was evidenced by photoluminescence measurements and free radical/hole scavenging experiments. At last, a possible photocatalytic mechanism under visible light irradiation was proposed. The novel and green synergistic approach presented here could provide a facile yet effective method for designing other visible light active non-metal co-doped TiO2 based photocatalysts with enhanced activity and high chemical stability. PMID:25102976

  8. Boron in Chondrules

    NASA Astrophysics Data System (ADS)

    Hoppe, P.; Goswami, J. N.; Krähenbühl, U.; Marti, K.

    2001-10-01

    Isotopic compositions and abundances of boron were measured in sixteen chondrules from seven chondrites by ion microprobe mass spectrometry. The chondrules are of the porphyritic, barred, and radial type and host meteorites include carbonaceous, ordinary, and enstatite chondrites. Boron abundances are generally low with average boron concentrations of between 80 and 500 ppb. These abundances are lower than those of bulk chondrites (0.35 to 1.2 ppm; Zhai et al., 1996), confirming earlier suggestions that boron is mostly contained in the matrix. No significant variation in the 11B/10B ratio is observed among these chondrules, outside our experimental error limits of several permil, and B-isotopic compositions agree with those reported for bulk chondrites. The lack of a significant isotope fractionation between chondrules and matrix implies that the low boron abundances are not the result of a Rayleigh fractionation during chondrule formation. Isotopic heterogeneities within individual chondrules are constrained to be < +/-20% at >95% confidence level at a spatial scale of 20-30 um, significantly lower than the value of about +/-40% previously reported for chondrules from carbonaceous and ordinary chondrites (Chaussidon and Robert, 1995, 1998). The observed B-isotopic homogeneity does not conflict with the presence of decay products from extinct 10Be, with (10Be/9Be)0 ~ 10-3, as was inferred for calcium-aluminum-rich inclusions. Extinct 10Be in chondrules would shift the abundance ratio 11B/10B at best by several permil because of their commonly observed low Be/B ratios (<2). The results show that potential B-isotopic heterogeneities in the solar nebula due to the presence of components with different B-isotopic signatures, such as boron produced by high-energy galactic cosmic rays (11B/10B ~ 2.5), or by the hypothetical low-energy particle irradiation (11B/10B ~ 3.5-11) or boron from type II supernovae (11B/10B >> 1), did not survive the chondrule formation processes to a measurable extent.

  9. Wear and friction of oxidation-resistant mechanical carbon graphites at 650 C in air

    NASA Technical Reports Server (NTRS)

    Allen, G. P.; Wisnader, D. W.

    1975-01-01

    Studies were conducted to determine the friction and wear properties of experimental carbon-graphites. Hemispherically tipped carbon-graphite rider specimens were tested in sliding contact with rotating Inconel X-750 disks in air. A surface speed of 1.33 m/sec, a load of 500 g, and a specimen temperature of 650 C were used. Results indicate: (1) hardness is not a major factor in determining friction and wear under the conditions of these studies. (2) Friction and wear as low as or lower than those observed for a good commercial seal material were attained with some of the experimental materials studied. (3) The inclusion of boron carbide (as an oxidation inhibitor) has a strong influence on wear rate. (4) Phosphate treatment reduces the friction coefficient when boron carbide is not present in the base material.

  10. Theoretical study of hydrogen atom adsorbed on carbon-doped BN nanotubes

    NASA Astrophysics Data System (ADS)

    Li, Feng; Xia, Yueyuan; Zhao, Mingwen; Liu, Xiangdong; Huang, Boda; Ji, Yanju; Song, Chen

    2006-09-01

    We have investigated the electronic structures of C-doped (9,0) boron nitride nanotubes (BNNTs) and hydrogen-decorated C-doped (9,0) BNNTs using density functional theory (DFT). It is found that the doping effect of C-doped BNNTs can be compensated by adsorption of H atom on the C sites. The adsorption energies for hydrogen atoms on different adsorption sites on BNNTs and C-doped BNNTs are obtained by using ONIOM method. The results indicate that the most favorable configuration of the adsorption structures is a hydrogen atom adsorbed on the C site of C-doped BNNT.

  11. Electrical properties of heavily doped polycrystalline silicon-germanium films

    Microsoft Academic Search

    Tsu-Jae King; James P. McVittie; Krishna C. Saraswat; James R. Pfiester

    1994-01-01

    The electrical properties of polycrystalline silicon-germanium (poly-Si1-xGex) films with germanium mole fractions up to 0.56 doped by high-dose ion implantation are presented. The resistivity of heavily doped p-type (P+) poly-Si1-x Gex is much lower than that of comparably doped poly-Si, because higher levels of boron activation and higher hole mobilities are achieved in poly-Si1-xGex. The resistivity of heavily doped n-type

  12. Boron isotopic compositions of some boron minerals

    NASA Astrophysics Data System (ADS)

    Oi, Takao; Nomura, Masao; Musashi, Masaaki; Ossaka, Tomoko; Okamoto, Makoto; Kakihana, Hidetake

    1989-12-01

    Boron minerals that have different structural formulae but are supposed to have the same geologic origin have been collected and analyzed for the 11B /10B isotopic ratio. It has been reconfirmed that minerals of marine origin have higher 11B /10B ratios than those of nonmarine origin. It has been found that the sequence of decreasing 11B /10B values among the minerals with the same geologic origin is; borax, tincal, kernite (Na borates) > ulexite ( Na/Ca borate) > colemanite, iyoite, meyerhofferite (Ca borates). This sequence is explainable on the basis of the difference in crystal structure among the minerals. That is, minerals with higher BO 3/BO 4 ratios, (the ratio of the number of the BO 3 triangle units to the number of the BO 4 tetrahedron units in the structural formula of a mineral) have higher 11B /10B ratios.

  13. Activation Behavior of Boron and Phosphorus Atoms Implanted in Polycrystalline Silicon Films by Heat Treatment at 250°C

    Microsoft Academic Search

    Toshiyuki Sameshima; Nobuyuki Andoh; Yasunori Andoh

    2005-01-01

    The activation behavior of boron and phosphorus implanted into laser-crystallized silicon films were investigated. The ratio of recrystallization of an ion-doping-induced amorphous region by heat treatment at 250°C was 0.35 for a boron concentration lower than 6.4× 1019 cm-3 and 0.5 for a phosphorus concentration lower than 2.5× 1019 cm-3. This ratio decreased as dopant concentration increased. High electrical conductivities

  14. Effect of boron segregation at grain boundaries on heat-affected zone cracking in wrought INCONEL 718

    Microsoft Academic Search

    W. Chen; M. C. Chaturvedi; N. L. Richards

    2001-01-01

    Susceptibility to heat-affected zone (HAZ) cracking during electron-beam welding was studied in two INCONEL 718-based alloys doped with different levels of boron. By lowering the carbon, sulfur, and phosphorous concentrations to be ``as low as possible,'' the occurrence of HAZ cracking was related directly to the level of segregation of boron at grain boundaries, which occurred by nonequilibrium segregation during

  15. Effect of boron segregation at grain boundaries on heat-affected zone cracking in wrought INCONEL 718

    Microsoft Academic Search

    W. Chen; M. C. Chaturvedi; N. L. Richards

    2001-01-01

    Susceptibility to heat-affected zone (HAZ) cracking during electron-beam welding was studied in two INCONEL 718-based alloys\\u000a doped with different levels of boron. By lowering the carbon, sulfur, and phosphorous concentrations to be “as low as possible,”\\u000a the occurrence of HAZ cracking was related directly to the level of segregation of boron at grain boundaries, which occurred\\u000a by nonequilibrium segregation during

  16. Impact of boron dilution accidents on low boron PWR safety

    SciTech Connect

    Papukchiev, A.; Liu, Y. [Dept. of Reactor Dynamics and Reactor Safety, Technical Univ. Munich, Walther Meissner-Str. 2, 85748 Garching (Germany); Schaefer, A. [ISaR Inst. for Safety and Reliability, Walther Meissner-Str. 2, 85748 Garching (Germany)

    2006-07-01

    In conventional pressurized water reactor (PWR) designs, soluble boron is used for reactivity control over core fuel cycle. As an inadvertent reduction of the boron concentration during a boron dilution accident could introduce positive reactivity and have a negative impact on PWR safety, design changes to reduce boron concentration in the reactor coolant are of general interest. In the framework of an investigation into the feasibility of low boron design, a PWR core configuration based on fuel with higher gadolinium (Gd) load has been developed which permits to reduce the natural boron concentration at begin of cycle (BOC) to 518 ppm. For the assessment of the potential safety advantages, a boron dilution accident due to small break loss-of-coolant-accident (SBLOCA) has been simulated with the system code ATHLET for two PWR core designs: a low boron design and a standard core design. The results from the comparative analyses showed that the impact of the boron dilution accident on the new PWR design safety is significantly lower in comparison with the standard design. The new reactor design provided at least 4, 4% higher reactivity margin to recriticality during the whole accident which is equivalent to the negative reactivity worth of additional 63% of all control rods fully inserted in to the core. (authors)

  17. Crystalline Boron Nanoribbons: Synthesis and Characterization

    E-print Network

    to its electron-deficient nature.1-3 Extensive fundamental and ap- plied research of bulk boron and boron vapor transport method using boron and iodine as precursor,12,13 and also by laser ablation of a B

  18. Multiple doping of silicon-germanium alloys for thermoelectric applications

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre; Vining, Cronin B.; Borshchevsky, Alex

    1989-01-01

    It is shown that heavy doping of n-type Si/Ge alloys with phosphorus and arsenic (V-V doping interaction) by diffusion leads to a significant enhancement of their carrier concentration and possible improvement of the thermoelectric figure of merit. High carrier concentrations were achieved by arsenic doping alone, but for a same doping level higher carrier mobilities and lower resistivities are obtained through phosphorus doping. By combining the two dopants with the proper diffusion treatments, it was possible to optimize the different properties, obtaining high carrier concentration, good carrier mobility and low electrical resistivity. Similar experiments, using the III-V doping interaction, were conducted on boron-doped p-type samples and showed the possibility of overcompensating the samples by diffusing arsenic, in order to get n-type behavior.

  19. Heterojunction diodes made from B-doped diamond grown heteroepitaxially on Si-doped c-BN

    NASA Astrophysics Data System (ADS)

    Wang, Chengxin; Zhang, Tiechen; Liu, Hongwu; Gao, Chunxiao; Zou, Guangtian

    2002-10-01

    Boron-doped p-type diamond thin film was grown heteroepitaxially on silicon-doped n-type cubic boron nitride (c-BN) bulk crystal by the conventional hot-filament chemical vapour deposition method. A diamond thin-film/c-BN heterojunction p-n diode was fabricated by the covering technique for the first time. The rectification ratio of the diode reached five orders. The threshold value is 1 V; the reverse bias voltage is 6 V. The results indicate that the device is of great importance.

  20. The polarographic microdetermination of boron 

    E-print Network

    Peacock, Dixon Williams

    1958-01-01

    LIBRARY A A M COLLEGE OF TEXAS THE POLAROGRAPHIC MICRODETERMINATION OF BORON By DIXON WILLIAMS PEACOCK A Dissertation Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in partial fulfillment................................. vi Chapter I- a. Introduction........................ 1 b. Analytical Chemistry of Boron........ 4 c. Alternative Methods................. 11 d. Objects and Methods of This Study.... 15 Chapter II- Polarography in the Determination of Boron...

  1. Effect of boron concentration on recombination at the p-Si–Al{sub 2}O{sub 3} interface

    SciTech Connect

    Black, Lachlan E., E-mail: lachlan.black@anu.edu.au; Allen, Thomas; Cuevas, Andres [Research School of Engineering, The Australian National University, Canberra, ACT 0200 (Australia); McIntosh, Keith R. [PV Lighthouse, Coledale, NSW 2515 (Australia)

    2014-03-07

    We examine the surface passivation properties of Al{sub 2}O{sub 3} deposited on boron-doped planar ?100? crystalline silicon surfaces as a function of the boron concentration. Both uniformly doped and diffused surfaces are studied, with surface boron concentrations ranging from 9.2?×?10{sup 15} to 5.2?×?10{sup 19}?cm{sup ?3}. Atmospheric pressure chemical vapor deposition and thermal atomic layer deposition are used to deposit the Al{sub 2}O{sub 3} films. The surface recombination rate of each sample is determined from photoconductance measurements together with the measured dopant profiles via numerical simulation, using the latest physical models. These values are compared with calculations based on the interface properties determined from capacitance–voltage and conductance measurements. It is found that the fundamental surface recombination velocity of electrons, S{sub n0}, which describes the chemical passivation of the interface, is independent of the surface boron concentration N{sub s} for N{sub s}???3?×?10{sup 19}?cm{sup ?3}, and in excellent agreement with values calculated from the interface state density D{sub it} and capture coefficients c{sub n} and c{sub p} measured on undiffused boron-doped surfaces. We conclude that the physical properties of the Si–Al{sub 2}O{sub 3} interface are independent of the boron dopant concentration over this range.

  2. Boron nitride nanotubes

    Microsoft Academic Search

    N. G. Chopra; R. J. Luyken; K. Cherrey; V. H. Crespi; M. L. Cohen; S. G. Louie; A. Zettl

    1995-01-01

    The successful synthesis of pure boron nitride (BN) nanotubes is reported here. Multi-walled tubes with inner diameters on the order of 1 to 3 nanometers and with lengths up to 200 nanometers were produced in a carbon-free plasma discharge between a BN-packed tungsten rod and a cooled copper electrode. Electron energy-loss spectroscopy on individual tubes yielded B:N ratios of approximately

  3. Boron carbonitride nanojunctions

    Microsoft Academic Search

    J. D. Guo; C. Y. Zhi; X. D. Bai; E. G. Wang

    2002-01-01

    Boron carbonitride (BCN) nanometric heterojunctions are controllably fabricated by bias-assisted hot-filament chemical vapor deposition with a pause-reactivation two-stage (PRTS) process. Tailored composition revulsion across the nanotube junction is obtained by simply varying the concentration of the gaseous precursor between the two stages of the PRTS process. The critical effect of the plasma power density in the reactivation process on continuous

  4. Twin structures of rhombohedral and cubic boron nitride prepared by chemical vapor deposition method

    Microsoft Academic Search

    Takeo Oku; Kenji Hiraga; Toshitsugu Matsuda; Toshio Hirai; Makoto Hirabayashi

    2003-01-01

    Nanoparticles with a rhombohedral boron nitride (r-BN) structure were synthesized by a chemical vapor deposition method from BCl3–NH3–H2 gas system at a temperature of 1600 °C and a total gas pressure of 3–5 Torr on the graphite substrates. The r-BN nanoparticles with the size of 50–1000 nm showed {101}, {113} and {001} twin structures. Cubic BN was also produced from

  5. Synthesis and field emssion behavior of highly oriented boron carbonitride nanofibers

    NASA Astrophysics Data System (ADS)

    Wang, E. G.; Bai, X. D.; Guo, J. D.; Yu, Jie; Yuan, Jun; Zhou, Wuzong

    2000-03-01

    Large-area highly oriented boron carbonitride (BCN) nanofibers have been synthesized directly on nickel substrates by bias-assisted hot filament CVD. The nanostructures and chemical composition are studied by SEM, HRTEM, and EELS, respectively. A distinct feature of the BCN fibers is that there are many small graphitic spines stand on the surface of the fibers, making the fibers cactus-like. Field electron emission of the BCN nanofibers is characterized, which implies a promising applicaiton as a new emission material.

  6. Relief of the internal stress in ternary boron carbonitride thin films

    Microsoft Academic Search

    Deyan He; Wenjuan Cheng; Juan Qin; Jinshun Yue; Erqing Xie; Guanghua Chen

    2002-01-01

    Ternary boron carbonitride (BCN) thin films were deposited by radio frequency reactive sputtering. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) absorption measurements suggested that the films are atomic-level hybrids composed of B, C and N atoms. The structure of the samples is graphitic BC2N. High compressive stresses were observed in the films deposited on silicon and fused silica

  7. Synthesis and field emssion behavior of highly oriented boron carbonitride nanofibers

    Microsoft Academic Search

    E. G. Wang; X. D. Bai; J. D. Guo; Jie Yu; Jun Yuan; Wuzong Zhou

    2000-01-01

    Large-area highly oriented boron carbonitride (BCN) nanofibers have been synthesized directly on nickel substrates by bias-assisted hot filament CVD. The nanostructures and chemical composition are studied by SEM, HRTEM, and EELS, respectively. A distinct feature of the BCN fibers is that there are many small graphitic spines stand on the surface of the fibers, making the fibers cactus-like. Field electron

  8. Effects of boron on the toughness of {gamma}-{gamma}{prime} nickel aluminium superalloys

    SciTech Connect

    Chiu, Y.L.; Ngan, A.H.W. [Univ. of Hong Kong (Hong Kong). Dept. of Mechanical Engineering] [Univ. of Hong Kong (Hong Kong). Dept. of Mechanical Engineering

    1998-12-04

    The ordered L1{sub 2}-type intermetallic Ni{sub 3}Al ({gamma}{prime}) possesses outstanding high-temperature mechanical properties. Single crystals of Ni{sub 3}Al are ductile when tested in ambient conditions, but the ductility in polycrystalline state is very poor due to grain boundary failure. This problem has been well solved with a small amount of boron addition (0.5 to {approximately}1.0 at %), which significantly toughens the material. Compared to pure Ni{sub 3}Al, the effects of boron doping on two-phase {gamma}-{gamma}{prime} alloys has not been thoroughly investigated. It has been shown that boron partitions to the grain boundaries of nickel-based superalloys and forms boride there which will stabilize the grain size at elevated temperatures, but the role of boron in influencing the toughness and grain boundary microstructures of the superalloy is not clear. In particular, it would be very interesting to know whether the toughening and nickel co-segregation behavior of boron in the pure {gamma}{prime} situation will extend to the two-phase {gamma}-{gamma}{prime} system. In this paper the authors will report some effects of boron on {gamma}-{gamma}{prime} alloys, and in order to remove any effects of other elements usually added to superalloys, boron is the only addition here.

  9. Hydrogen diffusion and induced-crystallization in intrinsic and doped hydrogenated amorphous silicon films

    Microsoft Academic Search

    F. Kail; A. Hadjadj; P. Roca i Cabarrocas

    2005-01-01

    We have studied the evolution of the structure of intrinsic and doped hydrogenated amorphous silicon films exposed to a hydrogen plasma. For this purpose, we combine in situ spectroscopic ellipsometry and secondary ion mass spectrometry measurements. We show that hydrogen diffuses faster in boron-doped hydrogenated amorphous silicon than in intrinsic samples, leading to a thicker subsurface layer from the early

  10. Raman spectroscopy of doped and compensated laser crystallized polycrystalline silicon thin films

    Microsoft Academic Search

    R. Saleh; N. H. Nickel

    2005-01-01

    The influence of dopant and the microstructure on hydrogen bonding in doped and compensated laser crystallized polycrystalline silicon (poly-Si) films were investigated using Raman backscattering spectrometry. With increasing boron and phosphorous concentration, the LO-TO phonon line in doped as well as in compensated films shifts to smaller wave numbers and broadens asymmetrically. The results are discussed in terms of resonant

  11. Molecular beam epitaxy approach to the graphitization of GaAs,,100... Paul J. Simmondsa

    E-print Network

    Woodall, Jerry M.

    thermal etching within the growth chamber. An AlAs layer beneath the carbon-doped GaAs acts as a thermal the thermally etched surfaces show that the residual surface carbon atoms form sp2 -bonded graphitic crystallites. © 2011 American Vacuum Society. DOI: 10.1116/1.3547716 I. INTRODUCTION Graphene is a sheet of sp2

  12. In situ synchrotron wide-angle X-ray scattering study on rapid lithiation of graphite anode via direct contact method for Li-ion capacitors

    NASA Astrophysics Data System (ADS)

    Park, Hyunchul; Kim, Minho; Xu, Fan; Jung, Cheolsoo; Hong, Soon Man; Koo, Chong Min

    2015-06-01

    Lithium pre-doping of graphite anode is a key process to achieve high energy density lithium-ion capacitor. In this study, in situ synchrotron wide-angle X-ray scattering examinations directly revealed that the direct contact (DC) method, simply achieved through direct physical contact between graphite electrode and sacrificial lithium metal in electrolyte, provides much faster phase transformation from stage 1? to stage 1 than conventional electronic charger (EC) and external short circuit (ESC) methods at the same doping time level. The observations indicate that DC method achieves faster pre-lithiation rate of graphite electrode than EC and ESC processes.

  13. High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

    NASA Technical Reports Server (NTRS)

    Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Lowther, Sharon E. (Inventor); Bryant, Robert George (Inventor)

    2015-01-01

    Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

  14. Graphite as a fault lubricant

    NASA Astrophysics Data System (ADS)

    Oohashi, K.; Hirose, T.; Shimamoto, T.

    2011-12-01

    Graphite is a well-known solid lubricant, and has been found in ~14 vol% of fraction from fault zones in a variety of geological settings (e.g. the Atotsugawa fault system, Japan: Oohashi et al., 2011a, submitted; the KTB borehole, Germany: Zulauf et al., 1990; and the Err nappe detachment fault, Switzerland: Manatschal, 1999). However, it received little attention even though friction of graphite gouge shows strikingly low (steady-state friction coefficient ?0.1) over seven orders of magnitude in slip rate (0.16 ?m/s to 1.3 m/s; Oohashi et al., 2011b). Thus the friction experiments were performed on mixed graphite and quartz gouges with different compositions in order to determine the minimum amount of graphite in reducing the frictional strength of faults dramatically, by using a rotary-shear low to high-velocity friction apparatus. Experimental result clearly indicates that the friction coefficient of the mixture gouge decreases with graphite content following a power-law relation irrespective of slip rate; it starts to reduce at the fraction of 5 vol% and reaches to the almost same level of pure graphite gouge at the fraction of more than 20 vol%. This result implies that the 14 vol% of graphite in natural fault rock is enough amount for reduce the shear strength to half of initial. According to the textural observation, slight weakening of 5-8 vol% of graphite mixture is associated with the development of partial connection of graphite matrix, forming a slip localized surface. On the other hand, the formation of through-going connection of diffused graphite-matrix zones along shear planes is most likely to have caused the dramatic weakening of gouge with graphite of more than 20 vol%. The non-linear power-law dependency of friction on graphite content leads to more efficient reduction of fault strength as compared with the previously reported almost linear dependency on the effects of clay minerals (e.g. Shimamoto & Logan, 1981). Hence the result demonstrates the potential importance of graphite as a weakening agent of mature faults as graphite can reduce friction efficiently as compared with other weak clay minerals. Such mechanical properties of graphite may explain the lack of pronounced heat flow in major crustal faults and the long-term fault weakening.

  15. Graphitic packing removal tool

    DOEpatents

    Meyers, Kurt Edward (Avella, PA); Kolsun, George J. (Pittsburgh, PA)

    1997-01-01

    Graphitic packing removal tools for removal of the seal rings in one piece. he packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  16. Graphitic packing removal tool

    SciTech Connect

    Meyers, K.E.; Kolsun, G.J.

    1996-12-31

    Graphitic packing removal tools are described for removal of the seal rings in one piece from valves and pumps. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  17. Formation of c-BN nanoparticles by helium, lithium and boron ion implantation

    NASA Astrophysics Data System (ADS)

    Aradi, Emily; Erasmus, Rudolph M.; Derry, Trevor E.

    2012-02-01

    Ion induced phase transformation from the soft graphitic hexagonal boron nitride ( h-BN) to ultrahard cubic boron nitride ( c-BN) nanoparticles is presented in the work herein. Ion implantation was used as a technique to introduce boron lithium and helium ions, at the energy of 150 keV and fluences ranging from 1 × 10 14 to 1 × 10 16 ions/cm 2, into hot pressed, polycrystalline h-BN. Analyses using Raman Spectroscopy showed that He +, Li + and B + led to a h-BN to c-BN phase transition, evident from the longitudinal optical (LO) Raman phonon features occurring in the implanted samples' spectra. The nature of these phonon peaks and their downshifting is explained using the spatial phonon correlation model.

  18. Spectroscopic ellipsometry of homoepitaxial diamond multilayers and delta-doped structures

    SciTech Connect

    Bousquet, J.; Chicot, G.; Eon, D.; Bustarret, E. [Univ. Grenoble Alpes, Inst. NEEL, F-38042 Grenoble (France); CNRS, Inst. NEEL, F-38042 Grenoble (France)

    2014-01-13

    The optimization of diamond-based unipolar electronic devices such as pseudo-vertical Schottky diodes or delta-doped field effect transistors relies in part on the sequential growth of nominally undoped (p{sup –}) and heavily boron doped (p{sup ++}) layers with well-controlled thicknesses and steep interfaces. Optical ellipsometry offers a swift and contactless method to characterize the thickness, roughness, and electronic properties of semiconducting and metallic diamond layers. We report ellipsometric studies carried out on delta-doped structures and other epitaxial multilayers with various boron concentrations and thicknesses (down to the nanometer range). The results are compared with Secondary Ion Mass Spectroscopy and transport measurements.

  19. Boron isotopic compositions of some boron minerals

    SciTech Connect

    Oi, Takao; Musashi, Masaaki; Ossaka, Tomoko; Kakihana, Hidetake (Sophia Univ., Tokyo (Japan)); Nomura, Masao; Okamoto, Makoto (Tokyo Institute of Technology (Japan))

    1989-12-01

    Boron minerals that have different structural formulae but are supposed to have the same geologic origin have been collected and analyzed for the {sup 11}B/{sup 10}B isotopic ratio. It has been reconfirmed that minerals of marine origin have higher {sup 11}B/{sup 10}B ratios than those of nonmarine origin. It has been found that the sequence of decreasing {sup 11}B/{sup 10}B values among the minerals with the same geologic origin is; borax, tincal, kernite (Na borates) > ulexite (Na/Ca borate) > colemanite, iyoite, meyerhofferite (Ca borates). This sequence is explainable on the basis of the difference in crystal structure among the minerals. That is, minerals with high BO{sub 3}/BO{sub 4} ratios, (the ratio of the number of the BO{sub 3} triangle units to the number of the BO{sub 4} tetrahedron units in the structural formula of a mineral) have higher {sup 11}B/{sup 10}B ratios.

  20. The Electrical Properties of Graphite

    Microsoft Academic Search

    G. H. Kinchin

    1953-01-01

    The Hall coefficient and resistivity of a range of polycrystalline graphites with different crystal sizes and a single crystal of Travancore graphite have been measured over a wide range of temperature. The number of free electrons has been found to be approximately 6 × 1018 per cm3 at room temperature; the variation with temperature cannot be accurately determined. The deficit

  1. Band gap effects of hexagonal boron nitride using oxygen plasma

    SciTech Connect

    Sevak Singh, Ram; Leong Chow, Wai [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Yingjie Tay, Roland [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Hon Tsang, Siu [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Mallick, Govind [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); Tong Teo, Edwin Hang, E-mail: htteo@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2014-04-21

    Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6?eV of pristine h-BN to 4.31?eV when exposed to oxygen plasma for 12?s. The narrowing of band gap causes the reduction in electrical resistance by ?100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

  2. Encapsulated boron as an osteoinductive agent for bone scaffolds.

    PubMed

    Gümü?derelio?lu, Menem?e; Tunçay, Ekin Ö; Kaynak, Gökçe; Demirta?, Tolga T; Ayd?n, Seda T??l?; Hakk?, Sema S

    2015-07-01

    The aim of this study was to develop boron (B)-releasing polymeric scaffold to promote regeneration of bone tissue. Boric acid-doped chitosan nanoparticles with a diameter of approx. 175nm were produced by tripolyphosphate (TPP)-initiated ionic gelation process. The nanoparticles strongly attached via electrostatic interactions into chitosan scaffolds produced by freeze-drying with approx. 100?m pore diameter. According to the ICP-OES results, following first 5h initial burst release, fast release of B from scaffolds was observed for 24h incubation period in conditioned medium. Then, slow release of B was performed over 120h. The results of the cell culture studies proved that the encapsulated boron within the scaffolds can be used as an osteoinductive agent by showing its positive effects on the proliferation and differentiation of MC3T3-E1 preosteoblastic cells. PMID:26004902

  3. Transport properties of ultrathin black phosphorus on hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Doganov, Rostislav A.; Koenig, Steven P.; Yeo, Yuting; Watanabe, Kenji; Taniguchi, Takashi; Özyilmaz, Barbaros

    2015-02-01

    Ultrathin black phosphorus, or phosphorene, is a two-dimensional material that allows both high carrier mobility and large on/off ratios. Similar to other atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer black phosphorus is expected to be affected by the underlying substrate. The properties of black phosphorus have so far been studied on the widely utilized SiO2 substrate. Here, we characterize few-layer black phosphorus field effect transistors on hexagonal boron nitride—an atomically smooth and charge trap-free substrate. We measure the temperature dependence of the field effect mobility for both holes and electrons and explain the observed behavior in terms of charged impurity limited transport. We find that in-situ vacuum annealing at 400 K removes the p-doping of few-layer black phosphorus on both boron nitride and SiO2 substrates and reduces the hysteresis at room temperature.

  4. Ultra-highly doped Si{sub 1-x}Ge{sub x}(001):B gas-source molecular-beam epitaxy: Boron surface segregation and its effect on film growth kinetics

    SciTech Connect

    Kim, H.; Glass, G.; Desjardins, P.; Greene, J. E.

    2001-01-01

    Si{sub 1-x}Ge{sub x}(001) layers doped with B concentrations C{sub B} between 2x10{sup 16} and 2x10{sup 21}cm{sup -3} were grown on Si(001)2x1 at T{sub s}=500--700{sup o}C by gas-source molecular-beam epitaxy (GS-MBE) from Si{sub 2}H{sub 6}, Ge{sub 2}H{sub 6}, and B{sub 2}H{sub 6}. Secondary-ion mass spectrometry measurements of modulation-doped structures demonstrate that B doping has no effect on the Ge incorporation probability. Steady-state B and Ge surface coverages ({theta}{sub B} and {theta}{sub Ge}) were determined as a function of C{sub B} using in situ isotopically tagged temperature-programmed desorption. Results for Si{sub 0.82}Ge{sub 0.18} layers grown at T{sub s}=500{sup o}C show that {theta}{sub Ge} remains constant at 0.63 ML while the bulk B concentration increases linearly up to 4.6x10{sup 20}cm{sup -3}, corresponding to saturation coverage at {theta}{sub B,sat}=0.5ML, with the incident precursor flux ratio {xi}=J{sub B{sub 2}H{sub 6}}/(J{sub Si{sub 2}H{sub 6}}+J{sub Ge{sub 2}H{sub 6}}). B is incorporated into substitutional electrically active sites over this entire concentration range. At higher B concentrations, C{sub B} increases faster than {xi} and there is a large decrease in the activated fraction of incorporated B. The B segregation enthalpy during Si{sub 0.82}Ge{sub 0.18}(001) growth is -0.42 eV, compared to -0.53 and -0.64 eV during Si(001):B and Ge(001):B GS-MBE, respectively. Measured segregation ratios r{sub B}={theta}{sub B}/x{sub B}, where x{sub B} is the bulk B fraction, range from 15 to 500 with a temperature dependence which is consistent with equilibrium segregation. Film deposition rates R{sub SiGe}(C{sub B}) decrease by up to a factor of 2 with increasing C{sub B}{>=}5x10{sup 19}cm{sup -3}, due primarily to a B-segregation-induced decrease in the dangling bond density. The above results were used to develop a robust model for predicting the steady-state H coverage {theta}{sub H}, {theta}{sub B}, {theta}{sub Ge}, and R{sub SiGe} as a function of {xi} and T{sub s}.

  5. Baseline Graphite Characterization: First Billet

    SciTech Connect

    Mark C. Carroll; Joe Lords; David Rohrbaugh

    2010-09-01

    The Next Generation Nuclear Plant Project Graphite Research and Development program is currently establishing the safe operating envelope of graphite core components for a very high temperature reactor design. To meet this goal, the program is generating the extensive amount of quantitative data necessary for predicting the behavior and operating performance of the available nuclear graphite grades. In order determine the in-service behavior of the graphite for the latest proposed designs, two main programs are underway. The first, the Advanced Graphite Creep (AGC) program, is a set of experiments that are designed to evaluate the irradiated properties and behavior of nuclear grade graphite over a large spectrum of temperatures, neutron fluences, and compressive loads. Despite the aggressive experimental matrix that comprises the set of AGC test runs, a limited amount of data can be generated based upon the availability of space within the Advanced Test Reactor and the geometric constraints placed on the AGC specimens that will be inserted. In order to supplement the AGC data set, the Baseline Graphite Characterization program will endeavor to provide supplemental data that will characterize the inherent property variability in nuclear-grade graphite without the testing constraints of the AGC program. This variability in properties is a natural artifact of graphite due to the geologic raw materials that are utilized in its production. This variability will be quantified not only within a single billet of as-produced graphite, but also from billets within a single lot, billets from different lots of the same grade, and across different billets of the numerous grades of nuclear graphite that are presently available. The thorough understanding of this variability will provide added detail to the irradiated property data, and provide a more thorough understanding of the behavior of graphite that will be used in reactor design and licensing. This report covers the development of the Baseline Graphite Characterization program from a testing and data collection standpoint through the completion of characterization on the first billet of nuclear-grade graphite. This data set is the starting point for all future evaluations and comparisons of material properties.

  6. Pristine graphite oxide.

    PubMed

    Dimiev, Ayrat; Kosynkin, Dmitry V; Alemany, Lawrence B; Chaguine, Pavel; Tour, James M

    2012-02-01

    Graphite oxide (GO) is a lamellar substance with an ambiguous structure due to material complexity. Recently published GO-related studies employ only one out of several existing models to interpret the experimental data. Because the models are different, this leads to confusion in understanding the nature of the observed phenomena. Lessening the structural ambiguity would lead to further developments in functionalization and use of GO. Here, we show that the structure and properties of GO depend significantly on the quenching and purification procedures, rather than, as is commonly thought, on the type of graphite used or oxidation protocol. We introduce a new purification protocol that produces a product that we refer to as pristine GO (pGO) in contrast to the commonly known material that we will refer to as conventional GO (cGO). We explain the differences between pGO and cGO by transformations caused by reaction with water. We produce ultraviolet-visible spectroscopic, Fourier transform infrared spectroscopic, solid-state nuclear magnetic resonance spectroscopic, thermogravimetric, and scanning electron microscopic analytical evidence for the structure of pGO. This work provides a new explanation for the acidity of GO solutions and allows us to add critical details to existing GO models. PMID:22239610

  7. Process for producing boron nitride

    SciTech Connect

    Parrish, L.N.; Chase, C.C.

    1988-06-07

    A process for producing boron nitride is described which comprises mixing boron oxide, orthoboric acid and melamine to form a reaction composition which comprises from about 45 to about 50 weight percent, based on the weight of the reaction composition, of melamine and from about 50 to about 55 weight percent, based on the weight of the reaction composition, of a combination of boron oxide and orthoboric acid. The weight ratio of boron oxide to orthoboric acid is from about 3:1 to about 4:1; and heating the composition to temperature of about 700/sup 0/C to about 1200/sup 0/C under a non-oxidizing atmosphere to form boron nitride.

  8. Structural investigation of graphitic foam

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, S. M.; Mahadev, N.; Joshi, P.; Roy, A. K.; Kearns, K. M.; Anderson, D. P.

    2002-03-01

    Structural and chemical characteristics of pitch-based graphitic foam have been studied using scanning electron microscopy, transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy. Chemically, the carbon atoms in these materials are found to have identical bonding states as those in pure graphite single crystals. Microstructural studies indicate that they have a cellular morphology with the cell walls made up of graphitic layers. The walls can be smooth or stepped depending upon the orientation of graphitic layers with respect to the cells. Ligaments between neighboring cells and junctions of ligaments (corners of three or more cells) distinctly show layers of graphitic planes, irregular flakes, and beam-like protruding structures made up of folded layers of graphite. The network of interconnecting pores have openings on the cell walls that have ruptured edges and sharp corners. This indicates that they were formed after hardening of the precursor, resulting in brittle fracture of the walls. The sharp cracks at pore openings may enhance mechanical failure of these structures and attempts to minimize them may improve mechanical behavior. Higher magnification studies in the TEM indicate the presence of flaky layers of graphite crystals and also long tubular structures protruding from the cell walls and ligaments. These fibrous structures (possibly rolled stacks of graphitic planes) have lengths in excess of several microns and diameters ranging between several tens of nanometers to several hundred nanometers. The walls are thick: several tens of nanometers. These structures, intermediate in size between micron size graphitic fibers and nanometer size multiwalled "nanotubes," have been discussed in light of other well investigated graphitic structures.

  9. Boron Neutron Capture Therapy for Cancer

    Microsoft Academic Search

    Rolf F. Barth; Albert H. Soloway; Ralph G. Fairchild

    1990-01-01

    Boron neutron capture therapy (BNCT) bring together two components that when kept separate have only minor effects on normal cells. The first component is a stable isotope of boron (boron 10) that can be concentrated in tumor cells. The second is a beam of low-energy neutrons that produces short-range radiation when absorbed, or captured, by the boron. The combination of

  10. Functionalized boron nitride nanotubes

    DOEpatents

    Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

    2014-04-22

    A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

  11. Adjustable boron carbonitride nanotubes

    Microsoft Academic Search

    C. Y. Zhi; J. D. Guo; X. D. Bai; E. G. Wang

    2002-01-01

    The adjustable photoluminescence (PL) and field electron emission (FEE) properties of boron carbonitride (B–C–N) nanotubes grown under well-controlled conditions are studied systematically. Large-scale highly aligned B–C–N nanotubes are synthesized directly on Ni substrates by the bias-assisted hot filament chemical vapor deposition method. Single-walled B–C–N nanotubes and nanometric B–C–N heterojunctions are obtained by the pulsed-arc-discharge technique and pause-reactivation two-stage process, respectively.

  12. Boron carbonitride nanojunctions

    NASA Astrophysics Data System (ADS)

    Guo, J. D.; Zhi, C. Y.; Bai, X. D.; Wang, E. G.

    2002-01-01

    Boron carbonitride (BCN) nanometric heterojunctions are controllably fabricated by bias-assisted hot-filament chemical vapor deposition with a pause-reactivation two-stage (PRTS) process. Tailored composition revulsion across the nanotube junction is obtained by simply varying the concentration of the gaseous precursor between the two stages of the PRTS process. The critical effect of the plasma power density in the reactivation process on continuous growth of the nanotubes is realized and controlled, leading to successful synthesis of the Y-shaped BCN nanojunctions.

  13. Adjustable boron carbonitride nanotubes

    Microsoft Academic Search

    C. Y. Zhi; J. D. Guo; X. D. Bai; E. G. Wang

    2002-01-01

    The adjustable photoluminescence (PL) and field electron emission (FEE) properties of boron carbonitride (B-C-N) nanotubes grown under well-controlled conditions are studied systematically. Large-scale highly aligned B-C-N nanotubes are synthesized directly on Ni substrates by the bias-assisted hot filament chemical vapor deposition method. Single-walled B-C-N nanotubes and nanometric B-C-N heterojunctions are obtained by the pulsed-arc-discharge technique and pause-reactivation two-stage process, respectively.

  14. Boron Diffusion In Silicon From Ultrafine Boron-Silicon Powder

    NASA Astrophysics Data System (ADS)

    Gupta, Arunava; West, Gary A.; Donlan, Jeffrey P.

    1984-06-01

    A CO2 laser pyrolysis technique has been used to prepare ultrafine (< 0.1p diameter) boron-silicon powders with different boron concentrations. These powders have been used as a spin-on boron diffusion source for silicon wafers. The spin-on colloidal suspension is prepared by mixing the powder with a thermally degradable polymer binder, polymethyl-methacrylate (PMMA), and an organic vehicle, cyclohexanone. Thin, uniform films are spun-on using a standard photoresist spinner. Two different procedures are followed in diffusing the boron from the boron-silicon powder. In the first process, the boron is diffused by heating the wafer in an argon ambient (1000-1260°C). The excess dopant layer is removed by oxidation (02) and subsequent etching (HF). In the second process, the powder is first converted to a borosilicate glass layer by oxidation, followed by diffusion in an argon ambient. Some experiments using commercially available boron nitride powder as a diffusion source are also discussed.

  15. Possible Excitonic Phase of Graphite in the Quantum Limit State

    NASA Astrophysics Data System (ADS)

    Akiba, Kazuto; Miyake, Atsushi; Yaguchi, Hiroshi; Matsuo, Akira; Kindo, Koichi; Tokunaga, Masashi

    2015-05-01

    The in-plane resistivity, Hall resistivity, and magnetization of graphite were investigated in pulsed magnetic fields applied along the c-axis. The Hall resistivity approaches zero at approximately 53 T where the in-plane and out-of-plane resistivities steeply decrease. The differential magnetization also shows an anomaly at around this field with an amplitude similar to that of de Haas-van Alphen oscillations at lower fields. This transition field appears insensitive to disorder, but reduces with hole doping. These results suggest the realization of the quantum limit states above 53 T. As a plausible explanation for the observed gapped out-of-plane conduction above 53 T, the emergence of the excitonic BCS-like state in graphite is proposed.

  16. First solar cells on silicon wafers doped using sprayed boric acid

    NASA Astrophysics Data System (ADS)

    Silva, J. A.; Brito, Miguel C.; Costa, Ivo; Alves, Jorge Maia; Serra, João; Vallêra, António

    2010-11-01

    A new method for boron bulk doping of silicon ribbons is developed. The method is based on the spraying of the ribbons with a boric acid solution and is particularly suited for silicon ribbons that require a zone-melting recrystallization step. To analyse the quality of the material thus obtained, multicrystalline silicon samples doped with this doping process were used as substrate for solar cells and compared with solar cells made on commercial multicrystalline silicon wafers. The values obtained for the diffusion length and the IV curve parameters show that the method of doping with the boric acid solution is suitable to produce p-doped silicon ribbons for solar cell applications.

  17. Low temperature coefficient of resistance and high gage factor in beryllium-doped silicon

    NASA Technical Reports Server (NTRS)

    Robertson, J. B.; Littlejohn, M. A.

    1974-01-01

    The gage factor and resistivity of p-type silicon doped with beryllium was studied as a function of temperature, crystal orientation, and beryllium doping concentration. It was shown that the temperature coefficient of resistance can be varied and reduced to zero near room temperature by varying the beryllium doping level. Similarly, the magnitude of the piezoresistance gage factor for beryllium-doped silicon is slightly larger than for silicon doped with a shallow acceptor impurity such as boron, whereas the temperature coefficient of piezoresistance is about the same for material containing these two dopants. These results are discussed in terms of a model for the piezoresistance of compensated p-type silicon.

  18. Molecular nanostructures on graphite

    NASA Astrophysics Data System (ADS)

    Riemann, Andreas; Grabill, Linda; Owens, Brandon; Krebs, Eric

    2012-02-01

    The self-assembly of different amino acids on graphite has been studied using Scanning Tunneling Microscopy. Experiments involving the amino acid methionine have shown that the molecules arrange themselves in well-ordered molecular wires with equidistant spacing tunable by the amount of adsorbate concentration on the surface. This behavior can be explained by an attractive interaction of the amino and carboxyl groups with each other, whereas the side chains exhibit repulsive interactions. Experiments using other amino acids with different side chains, like tyrosine and histidine, show adsorption behavior which lead to densely packed films of well-ordered amino acids, but no molecular wire structure. The repulsive interactions of the side chains can not be experimentally observed. This interesting phenomenon of inter-molecular interaction was further investigated using molecular mechanics calculations for these molecules.

  19. Local environment of silicon in cubic boron nitride

    NASA Astrophysics Data System (ADS)

    Murata, Hidenobu; Taniguchi, Takashi; Hishita, Shunichi; Yamamoto, Tomoyuki; Oba, Fumiyasu; Tanaka, Isao

    2013-12-01

    Si-doped cubic boron nitride (c-BN) is synthesized at high pressure and high temperature, and the local environment of Si is investigated using X-ray absorption near edge structure (XANES) and first-principles calculations. Si-K XANES indicates that Si in c-BN is surrounded by four nitrogen atoms. According to first-principles calculations, the model for substitutional Si at the B site well reproduces experimental Si-K XANES, and it is energetically more favorable than substitutional Si at the N site. Both the present experimental and theoretical results indicate that Si in c-BN prefers the B site to the N site.

  20. Local environment of silicon in cubic boron nitride

    SciTech Connect

    Murata, Hidenobu, E-mail: MURATA.Hidenobu@nims.go.jp; Taniguchi, Takashi [Advanced Key Technologies Division, National Institute for Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305–0044 (Japan); Hishita, Shunichi [Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305–0044 (Japan); Yamamoto, Tomoyuki [Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169–8555 (Japan); Oba, Fumiyasu [Department of Materials Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo, Kyoto 606–8501 (Japan); Tanaka, Isao [Department of Materials Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo, Kyoto 606–8501 (Japan); Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta, Nagoya 456–8587 (Japan)

    2013-12-21

    Si-doped cubic boron nitride (c-BN) is synthesized at high pressure and high temperature, and the local environment of Si is investigated using X-ray absorption near edge structure (XANES) and first-principles calculations. Si-K XANES indicates that Si in c-BN is surrounded by four nitrogen atoms. According to first-principles calculations, the model for substitutional Si at the B site well reproduces experimental Si-K XANES, and it is energetically more favorable than substitutional Si at the N site. Both the present experimental and theoretical results indicate that Si in c-BN prefers the B site to the N site.

  1. Bonding distances as Exact Sums of the Radii of the Constituent Atoms in Nanomaterials - Boron Nitride and Coronene

    E-print Network

    Raji Heyrovska

    2011-12-19

    This paper presents for the first time the exact structures at the atomic level of two important nanomaterials, boron nitride and coronene. Both these compounds are hexagonal layer structures similar to graphene in two dimensions and to graphite in three-dimensions. However, they have very different properties: whereas graphene is a conductor, h-BN is an electrical insulator and coronene is a polycyclic aromatic hydrocarbon of cosmological interest. The atomic structures presented here for boron nitride, coronene and graphene have been drawn to scale based on bond lengths as sums of the atomic radii.

  2. Mineral resource of the month: graphite

    USGS Publications Warehouse

    U.S. Geological Survey

    2008-01-01

    The article presents facts about graphite ideal for industrial applications. Among the characteristics of graphite are its metallic luster, softness, perfect basal cleavage and electrical conductivity. Batteries, brake linings and powdered metals are some of the products that make use of graphite. It attributes the potential applications for graphite in high-technology fields to innovations in thermal technology and acid-leaching techniques.

  3. Density of intercalated graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Slabe, Melissa E.

    1989-01-01

    The density of Amoco P-55, P-75, P-100, and P-120 pitch-based graphite fibers and their intercalation compounds with bromine, iodine monochloride, and copper (II) chloride have been measured using a density gradient column. The distribution of densities within a fiber type is found to be a sensitive indicator of the quality of the intercalation reaction. In all cases the density was found to increase, indicating that the mass added to the graphite is dominant over fiber expansion. Density increases are small (less than 10 percent) giving credence to a model of the intercalated graphite fibers which have regions which are intercalated and regions which are not.

  4. Resonating valence bonds and mean-field d -wave superconductivity in graphite

    NASA Astrophysics Data System (ADS)

    Black-Schaffer, Annica M.; Doniach, Sebastian

    2007-04-01

    We investigate the possibility of inducing superconductivity in a graphite layer by electronic correlation effects. We use a phenomenological microscopic Hamiltonian which includes nearest-neighbor hopping and an interaction term which explicitly favors nearest-neighbor spin singlets through the well-known resonance valence bond (RVB) character of planar organic molecules. Treating this Hamiltonian in mean-field theory, allowing for bond-dependent variation of the RVB order parameter, we show that both s - and d -wave superconducting states are possible. The d -wave solution belongs to a two-dimensional representation and breaks time-reversal symmetry. At zero doping there exists a quantum critical point at the dimensionless coupling J/t=1.91 and the s - and d -wave solutions are degenerate for low temperatures. At finite doping the d -wave solution has a significantly higher Tc than the s -wave solution. By using density functional theory we show that the doping induced from sulfur absorption on a graphite layer is enough to cause an electronically driven d -wave superconductivity at graphite-sulfur interfaces. We also discuss applying our results to the case of the intercalated graphites, as well as the validity of a mean-field approach.

  5. Bismaleimide-vinylpolystyrylpyridine graphite composites

    NASA Technical Reports Server (NTRS)

    Kourtides, D. A.

    1988-01-01

    Flammability, thermal, and selected mechanical properties of composites fabricated with epoxy and other thermally stable resin matrices are described. Properties which were measured included limiting-oxygen index, smoke evolution, thermal degradation products, total-heat release, heat-release rates, mass loss, flame spread, ignition resistance, thermogravimetric analysis and selected mechanical properties. This paper describes the properties of eight different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement. The resin matrices included: XU71775/H795, a blend of vinylpolystyrylpyridine and bismaleimide; H795, a bismaleimide; Cycom 6162, a phenolic; and PSP 6022M, a polystyrylpyridine. The graphite fiber used was AS-4 in the form of either tape or fabric. The properties of these composites were compared with epoxy composites. It was determined that the blend of vinylpolystyrylpyridine and bismaleimide (XU71775/H795) with the graphite tape was the optimum design giving the lowest heat release rate.

  6. Silicon carbide coatings on graphite

    Microsoft Academic Search

    A. S. Sin'kovskii; G. V. Zemskov; E. V. Smekh

    1967-01-01

    1.It was established that silicon carbide can only form on graphite in the presence of hydrogen in the gaseous mixture and at certain silicon tetrachloride to benzene concentration ratios.2.The influence of temperature and process duration on the thickness of the silicon carbide layer deposited on graphite was determined. The optimum temperature was found to be 1700–1800°C.3.The highest oxidation resistance is

  7. Graphite Fiber Reinforced Polyimide Composites

    Microsoft Academic Search

    C. E. Browning; J. A. Marshall

    1970-01-01

    Comparatively low-void content, high strength and modulus graphite fiber reinforced polyimide composites were fabricated. Utilizing matrices of Monsanto's Skybond 700 polyimide resin and TRW's P13N polyimide resin and reinforcements of ozone-treated Thornel 40 and 50 graphite fibers, these composites exhibited flexural strengths in excess of 100,000 psi, short-beam shear values in excess of 5000 psi, and void contents as low

  8. Boron isotope application for tracing sources of contamination in groundwater.

    E-print Network

    Kasher, Roni

    Boron isotope application for tracing sources of contamination in groundwater. Abstract: Boron isotope composition and concentration of sewage effluent and pristine and contaminated groundwater from. Anthropogenic boron in wastewater is isotopically distinct from natural boron in groundwater and thus can

  9. Reducing Boron Toxicity by Microbial Sequestration

    SciTech Connect

    Hazen, T.; Phelps, T.J.

    2002-01-01

    While electricity is a clean source of energy, methods of electricity-production, such as the use of coal-fired power plants, often result in significant environmental damage. Coal-fired electrical power plants produce air pollution, while contaminating ground water and soils by build-up of boron, which enters surrounding areas through leachate. Increasingly high levels of boron in soils eventually overcome boron tolerance levels in plants and trees, resulting in toxicity. Formation of insoluble boron precipitates, mediated by mineral-precipitating bacteria, may sequester boron into more stable forms that are less available and toxic to vegetation. Results have provided evidence of microbially-facilitated sequestration of boron into insoluble mineral precipitates. Analyses of water samples taken from ponds with high boron concentrations showed that algae present contained 3-5 times more boron than contained in the water in the samples. Boron sequestration may also be facilitated by the incorporation of boron within algal cells. Experiments examining boron sequestration by algae are in progress. In bacterial experiments with added ferric citrate, the reduction of iron by the bacteria resulted in an ironcarbonate precipitate containing boron. An apparent color change showing the reduction of amorphous iron, as well as the precipitation of boron with iron, was more favorable at higher pH. Analysis of precipitates by X-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectroscopy revealed mineralogical composition and biologicallymediated accumulation of boron precipitates in test-tube experiments.

  10. Boron carbonitride nanotubes.

    PubMed

    Zhi, C Y; Bai, X D; Wang, E G

    2004-01-01

    A comprehensive understanding of the design, synthesis, characterization, and properties of boron carbonitride nanotubes (BCN) is presented in this review. Distinctive structural and electronic properties are revealed in theoretical studies of the BCN nanotubes and compared with the properties of carbon nanotubes. In the experimental studies, BCN nanotubes have been synthesized by various techniques. For different purposes, controllable growth processes have been used to fabricate BCN nanotubes with novel structures, such as nanojunctions and filled nanotubes. Some interesting phenomena originating from the substitution of B and N atoms, such as the phase segregation, are considered theoretically and experimentally. Mainly the physical properties--field electron emission and photoluminescence--are discussed, which turn out to have potential applications in the industry. PMID:15112540

  11. Boron diffusion in silicon devices

    DOEpatents

    Rohatgi, Ajeet (Atlanta, GA); Kim, Dong Seop (Atlanta, GA); Nakayashiki, Kenta (Smyrna, GA); Rounsaville, Brian (Stockbridge, GA)

    2010-09-07

    Disclosed are various embodiments that include a process, an arrangement, and an apparatus for boron diffusion in a wafer. In one representative embodiment, a process is provided in which a boric oxide solution is applied to a surface of the wafer. Thereafter, the wafer is subjected to a fast heat ramp-up associated with a first heating cycle that results in a release of an amount of boron for diffusion into the wafer.

  12. The effect of dipole boron centers on the electroluminescence of nanoscale silicon p{sup +}?n junctions

    SciTech Connect

    Bagraev, Nikolay; Klyachkin, Leonid; Kuzmin, Roman; Malyarenko, Anna [Ioffe Physical-Technical Institute, Polytekhnicheskaya 26, 194021, St. Petersburg (Russian Federation); Mashkov, Vladimir [St. Petersburg State Polytechnical University, Polytekhnicheskaya 29, 195251, St. Petersburg (Russian Federation)

    2014-02-21

    Nanoscale silicon p{sup +}?;n junctions with very high concentration of boron, 5 10{sup 21} cm{sup ?3}, are found to demonstrate interesting optical properties. Emission band dominated in near-infrared electroluminescence (EL) spectra possesses high degree of the linear polarization along preferred crystallographic axis which can be controlled by the lateral voltage applied in the plane of the p{sup +}?n junction. Such behavior together with the temperature dependence of the EL intensity is attributed to the presence of the self-compensating dipole boron centers, B{sup +}-B{sup ?}, with negative correlation energy which are identified using the ESR technique in the nanoscale silicon p{sup +}?n junctions heavily doped with boron. The model of the recombination process though the negative-U dipole boron centers controlling the optical properties of the nanoscale silicon p{sup +}?n junctions is proposed.

  13. BORON--1998 13.1 By Phyllis A. Lyday

    E-print Network

    BORON--1998 13.1 BORON By Phyllis A. Lyday Domestic survey data and tables were prepared by Shantae, international data coordinator. Boron is produced domestically only in the State of California. Boron products. The United States and Turkey are the world's largest producers of boron. Boron is priced and sold

  14. Ferric chloride graphite intercalation compounds prepared from graphite fluoride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1994-01-01

    The reaction between graphite fluoride and ferric chloride was observed in the temperature range of 300 to 400 C. The graphite fluorides used for this reaction have an sp3 electronic structure and are electrical insulators. They can be made by fluorinating either carbon fibers or powder having various degrees of graphitization. Reaction is fast and spontaneous and can occur in the presence of air. The ferric chloride does not have to be predried. The products have an sp2 electronic structure and are electrical conductors. They contain first stage FeCl3 intercalated graphite. Some of the products contain FeCl2*2H2O, others contain FeF3 in concentrations that depend on the intercalation condition. The graphite intercalated compounds (GIC) deintercalated slowly in air at room temperature, but deintercalated quickly and completely at 370 C. Deintercalation is accompanied by the disappearing of iron halides and the formation of rust (hematite) distributed unevenly on the fiber surface. When heated to 400 C in pure N2 (99.99 vol %), this new GIC deintercalates without losing its molecular structure. However, when the compounds are heated to 800 C in quartz tube, they lost most of its halogen atoms and formed iron oxides (other than hematite), distributed evenly in or on the fiber. This iron-oxide-covered fiber may be useful in making carbon-fiber/ceramic-matrix composites with strong bonding at the fiber-ceramic interface.

  15. Precise isotopic analysis of boron by P-TIMS with sample preheating

    NASA Astrophysics Data System (ADS)

    Ishikawa, T.; Nagaishi, K.; Matsuoka, J.

    2010-12-01

    Precise and accurate isotopic analysis of the boron isotopic ratio (11B/10B) is required in wide areas of research. One of the recent notable applications is the use of the boron isotopic ratio in marine carbonates as a proxy of seawater pH, which provides important information for understanding seawater pH variation and atmospheric CO2 concentrations in the past. In such cases, because the precision and accuracy in boron isotopic analysis directly reflect those of the estimated pH values, the development of precise and accurate methods of boron isotopic analysis is of great importance. Positive ion thermal ionization mass spectrometry (P-TIMS) using Cs2BO2+ ions is known as one of the most precise and accurate techniques for boron isotope analysis. The high precision in this method is secured by a minimal mass fractionation effect owing to the small relative mass difference between 133Cs210B16O2+ (m/z 308) and 133Cs211B16O2+ (m/z 309). In the simplest analytical condition, in which cesium borate alone is loaded onto a graphite-coated Ta filament, an external reproducibility of ±0.1‰ (2SD) is reported for 100-3000 ng B (Xiao et al., 1988). For general analytical purposes, however, the addition of mannitol to the sample is essential for suppressing boron volatilization during acid treatments and for stabilizing boron samples on the filament. When mannitol is added, the ionization efficiency substantially decreases, and the external reproducibility for >100 ng B deteriorates (±0.2 to ±0.6 ‰: e.g. Nakano and Nakamura, 1998; Deyhle, 2001, Lemarchand et al., 2002). Here we present a new technique for improving P-TIMS by using Cs2BO2+ ions. The prepared filaments were preheated in an oven at 240 °C to eliminate the mannitol thus stabilizing the chemical species of boron on the filament and increasing the ionization efficiency of Cs2BO2+, which enabled high-precision isotopic analysis of boron with small sample sizes. Analyses of NIST SRM 951 standard showed external reproducibility (2SD) better than ±0.1‰ for 50-100 ng B and ±0.2‰ for 10 ng B. Analyses of coral and seawater standards also showed external reproducibility that was comparable to the analyses of SRM 951. The P-TIMS method developed in this study is applicable to a wide field of boron isotopic research that requires high precision and accuracy, including paleo-pH studies using marine carbonate samples, which have been predominantly carried out with N-TIMS and MC-ICPMS to date.

  16. Controllable N-Doping of Graphene Beidou Guo,,

    E-print Network

    Gong, Jian Ru

    -range -conjugation in graphene yields extraordinary thermal,1 mechanical,2 and electrical properties,3,4 an enormous for doping in graphite, carbon nanotube (CNT),18-20 but for graphene, only defect, surface charge mechanism for the introduction of defect and subsequent hetero dopant atoms into the graphene material

  17. In situ synthesis of a large area boron nitride/graphene monolayer/boron nitride film by chemical vapor deposition.

    PubMed

    Wu, Qinke; Jang, Sung Kyu; Park, Sangwoo; Jung, Seong Jun; Suh, Hwansoo; Lee, Young Hee; Lee, Sungjoo; Song, Young Jae

    2015-05-01

    We describe the successful in situ chemical vapor deposition synthesis of a graphene-based heterostructure in which a graphene monolayer is protected by top and bottom boron nitride films. The boron nitride film/graphene monolayer/boron nitride film (BGB) was found to be a mechanically robust and chemically inert heterostructure, from which the deleterious effects of mechanical transfer processes and unwanted chemical doping under air exposure were eliminated. The chemical compositions of each film layer were monitored ex situ using UV-visible absorption spectroscopy and X-ray photoelectron spectroscopy, and the crystalline structures were confirmed using transmission electron microscopy and selected-area electron diffraction measurements. The performance of the devices fabricated using the BGB film was monitored over six months and did not display large changes in the mobility or the Dirac point, unlike the conventional graphene devices prepared on a SiO2 substrate. The in situ-grown BGB film properties suggest a novel approach to the fabrication of commercial-grade graphene-based electronic devices. PMID:25864409

  18. A new boron impregnation technique of wood by vapor boron of boric acid to reduce leaching boron from wood

    Microsoft Academic Search

    Ergun Baysal; Mustafa Kemal Yalinkilic

    2005-01-01

    This study was designed to reveal impregnation ability and to enhance leaching resistance of boron from borate-treated wood. Vapor boron treatment was applied in compressed and uncompressed states at high temperatures such as 180 and 200°C for 6, 8 and 15 min. Following ten-cycle leaching periods, amounts of boron leached from vapor boron treated wood was measured by ion chromatography. According

  19. Electron tunneling through ultrathin boron nitride crystalline barriers.

    PubMed

    Britnell, Liam; Gorbachev, Roman V; Jalil, Rashid; Belle, Branson D; Schedin, Fred; Katsnelson, Mikhail I; Eaves, Laurence; Morozov, Sergey V; Mayorov, Alexander S; Peres, Nuno M R; Neto, Antonio H Castro; Leist, Jon; Geim, Andre K; Ponomarenko, Leonid A; Novoselov, Kostya S

    2012-03-14

    We investigate the electronic properties of ultrathin hexagonal boron nitride (h-BN) crystalline layers with different conducting materials (graphite, graphene, and gold) on either side of the barrier layer. The tunnel current depends exponentially on the number of h-BN atomic layers, down to a monolayer thickness. Conductive atomic force microscopy scans across h-BN terraces of different thickness reveal a high level of uniformity in the tunnel current. Our results demonstrate that atomically thin h-BN acts as a defect-free dielectric with a high breakdown field. It offers great potential for applications in tunnel devices and in field-effect transistors with a high carrier density in the conducting channel. PMID:22380756

  20. Comparison between the crystallization processes by laser and furnace annealing of pure and doped aSi:H

    Microsoft Academic Search

    R. Beserman; Yu. L Khait; A Chack; R Weil; W Beyer

    2002-01-01

    A comparison between the annealing processes is made for undoped hydrogenated amorphous Si (a-Si:H), boron and phosphorus doped amorphous silicon. It is found that in all cases the crystallization onset in the furnace always occurs at higher temperature than for the laser-annealed material. The free-carrier phonon interaction shows up in furnace-annealed doped a-Si but is not seen in laser-annealed doped