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Sample records for boron doped graphite

  1. 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.

  2. Comparison of beryllium oxide and pyrolytic graphite crucibles for boron doped silicon epitaxy

    SciTech Connect

    Ali, Dyan; Richardson, Christopher J. K.

    2012-11-15

    This article reports on the comparison of beryllium oxide and pyrolytic graphite as crucible liners in a high-temperature effusion cell used for boron doping in silicon grown by molecular beam epitaxy. Secondary ion mass spectroscopy analysis indicates decomposition of the beryllium oxide liner, leading to significant incorporation of beryllium and oxygen in the grown films. The resulting films are of poor crystal quality with rough surfaces and broad x-ray diffraction peaks. Alternatively, the use of pyrolytic graphite crucible liners results in higher quality films.

  3. Microstructure and electrochemical properties of boron-doped mesocarbon microbeads

    SciTech Connect

    Kim, C.; Fujino, T.; Miyashita, K.; Hayashi, T.; Endo, M.; Dresselhaus, M.S.

    2000-04-01

    The microstructure and electrochemical properties of pristine and boron-doped mesocarbon microbeads (MCMBs) were comparatively studied by X-ray diffraction, field-emission scanning electron microscopy, Raman spectroscopy, and electrochemical measurements. The authors examined the correlation between the boron-doping effect and the electrochemical properties of boron-doped MCMBs prepared at different heat-treatment temperatures. It was found that boron doping in MCMBs starts above 1,800 C, and then the substitution reaction proceeds with increasing heat-treatment temperature. The effect of boron doping is to accelerate graphitization of MCMBs for heat-treatment temperatures in the range from 1,800 to 2,500 C. Electrochemical lithium intercalation takes place at a higher potential in boron-doped MCMBs than in undoped MCMBs, presumably because the substitutional boron acts as an electron acceptor in the MCMBs.

  4. Boron doping a semiconductor particle

    DOEpatents

    Stevens, Gary Don; Reynolds, Jeffrey Scott; Brown, Louanne Kay

    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.

  5. Boron doping a semiconductor particle

    DOEpatents

    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.

  6. Boron doped nanostructured diamond films

    NASA Astrophysics Data System (ADS)

    Liang, Qi

    A chemical vapor deposition hydrogen/methane/nitrogen feed-gas mixture with unconventionally high methane (15% CH4 by volume) normally used to grow ultra-hard and smooth nanostructured diamond films on Ti-6Al-4V alloy substrates was modified to include diborane B2H6 for boron-doping of diamond films. The flow rates for B2H 6 and N2 were varied to investigate their effect on plasma chemistry, film structure, boron incorporation, and mechanical properties. It was found that boron atoms can easily be incorporated into diamond films and change the lattice constant and film structure. Nitrogen, on the other hand, competes with boron in the plasma and acts to prevent boron incorporation into the diamond structure. In addition, with the appropriate choice of deposition conditions, the film structure can be tailored to range from highly crystalline, well faceted diamond to nanocrystalline diamond. Glancing angle X-ray diffraction and Micro-Raman were used as the main tools to investigate the relation between processing and structure. An optimal N2/CH4 ratio of 0.4 was found to result in a film with a minimum in grain size and surface roughness, along with high boron incorporation (˜4 x 1020 cm-3). Mechanical properties and thermal stability of boron doped nanostructured diamond films were examined by means of nanoindentation, open air thermal annealing, and nanotribometry. It was found that the films have high hardness close to that of undoped nanostructured diamond films. Thermal stability of these films was evaluated by heating in an oxygen environment above 700°C. Improved thermal stability of boron doped nanostructured diamond films was observed. Tribological tests show that although both undoped and boron doped nanostructured diamond films show extremely low coefficient of friction and wear rate as compared with uncoated titanium alloys (Ti-6Al-4V) and cobalt chrome alloy (Co-Cr-Mo), a critical failure max stress of 2.2 GPa was observed for boron doped nanostructured diamond films. A FORTRAN Chemical Kinetics Package for the Analysis of Gas Phase Chemical Kinetics, gas-phase thermodynamic equilibrium calculations involving H 2/CH4/N2/B2H6 mixtures was employed to investigate the chemical interactions leading to boron incorporation and crystalline structure variations. The strong influence of the BH 3 in causing the boron incorporation and the role of CN radical in causing the nanocrystallinity are confirmed by the correlation of their modeled compositions in the gas phase with boron content and degree of nanocrystallinity as determined experimentally. A good degree of agreement was obtained between the theoretically predicted gas phase concentration of species and the experimental concentration trends as measured by the optical emission spectroscopy of the microwave plasma. Overall, high film hardness and toughness, combined with good thermal stability and low surface roughness, indicate that nanostructured boron doped diamond films can be used as wear resistant coatings that are able to withstand high temperature oxidizing environments.

  7. Development and evaluation of graphite and boron polyimide composites.

    NASA Technical Reports Server (NTRS)

    Scheck, W. G.; Stuckey, J. M.

    1972-01-01

    This paper covers the development and evaluation of the HT-S/710 graphite/polyimide system and initial evaluations of high modulus graphite and boron reinforced polyimide systems. Detail design properties of the HT-S/710 graphite/polyimide systems, test results of test sheet stringer components, and initial test evaluations of high modulus graphite and boron reinforced polyimide composites are presented. Preliminary design applications utilizing the basic processing and design data from this development program are presented as to their utilization in aircraft and space applications.

  8. Low temperature boron doped diamond

    NASA Astrophysics Data System (ADS)

    Zeng, Hongjun; Arumugam, Prabhu U.; Siddiqui, Shabnam; Carlisle, John A.

    2013-06-01

    Low temperature boron doped diamond (LT-BDD) film deposited under 600 °C (460 °C minimum) has been reported. Study reveals that the deposition temperature and boron dopant cause nanocrystalline diamond (NCD) instead of ultrananocrystalline diamond (UNCD®). Unlike conventional NCD, LT-BDD has faster renucleation rate, which ensures a low surface roughness (approximately 10 nm at 0.6 μm thickness). The overall characteristics of LT-BDD are mixed with the characteristics of conventional NCD and UNCD. Raman spectrum and electrochemical characterization prove that the quality of LT-BDD is similar to those grown under 650-900 °C. LT-BDD enables diamond applications on microelectromechanical systems, bio- and optical technologies.

  9. Ultratough single crystal boron-doped diamond

    DOEpatents

    Hemley, Russell J [Carnegie Inst. for Science, Washington, DC ; Mao, Ho-Kwang [Carnegie Inst. for Science, Washington, DC ; Yan, Chih-Shiue [Carnegie Inst. for Science, Washington, DC ; Liang, Qi [Carnegie Inst. for Science, Washington, DC

    2015-05-05

    The invention relates to a single crystal boron doped CVD diamond that has a toughness of at least about 22 MPa m.sup.1/2. The invention further relates to a method of manufacturing single crystal boron doped CVD diamond. The growth rate of the diamond can be from about 20-100 .mu.m/h.

  10. Stabilization of boron carbide via silicon doping

    NASA Astrophysics Data System (ADS)

    Proctor, J. E.; Bhakhri, V.; Hao, R.; Prior, T. J.; Scheler, T.; Gregoryanz, E.; Chhowalla, M.; Giulani, F.

    2015-01-01

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  11. Stabilization of boron carbide via silicon doping.

    PubMed

    Proctor, J E; Bhakhri, V; Hao, R; Prior, T J; Scheler, T; Gregoryanz, E; Chhowalla, M; Giulani, F

    2015-01-14

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping. PMID:25427850

  12. Method for wetting a boron alloy to graphite

    SciTech Connect

    Storms, E.K.

    1987-08-21

    A method is provided for wetting a graphite substrate and spreading a a boron alloy over the substrate. The wetted substrate may be in the form of a needle for an effective ion emission source. The method may also be used to wet a graphite substrate for subsequent joining with another graphite substrate or other metal, or to form a protective coating over a graphite substrate. A noneutectic alloy of boron is formed with a metal selected from the group consisting of nickel (Ni), palladium (Pd), and platinum (Pt) with excess boron, i.e., and atomic percentage of boron effective to precipitate boron at a wetting temperature of less than the liquid-phase boundary temperature of the alloy. The alloy is applied to the substrate and the graphite substrate is then heated to the wetting temperature and maintained at the wetting temperature for a time effective for the alloy to wet and spread over the substrate. The excess boron is evenly dispersed in the alloy and is readily available to promote the wetting and spreading action of the alloy. 1 fig.

  13. 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.

    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.

  14. Structure and functionality of bromine doped graphite

    SciTech Connect

    Hamdan, Rashid; Kemper, A. F.; Cao Chao; Cheng, H. P.

    2013-04-28

    First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br{sub 2}). However, with increased compression (decreased layer-layer separation) Br{sub 2} molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br{sub 2} molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity.

  15. Ni doping of semiconducting boron carbide

    SciTech Connect

    Hong, Nina; Liu Jing; Adenwalla, S.; Langell, M. A.; Kizilkaya, Orhan

    2010-01-15

    The wide band gap, temperature stability, high resistivity, and robustness of semiconducting boron carbide make it an attractive material for device applications. Undoped boron carbide is p type; Ni acts as a n-type dopant. Here we present the results of controlled doping of boron carbide with Ni on thin film samples grown using plasma enhanced chemical vapor deposition. The change in the dopant concentration within the thin film as a function of the dopant flow rate in the precursor gas mixture was confirmed by x-ray photoelectron spectroscopy measurements; with increasing dopant concentration, current-voltage (I-V) curves clearly establish the trend from p-type to n-type boron carbide.

  16. Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus.

    PubMed

    Kramer, Nicolaas J; Schramke, Katelyn S; Kortshagen, Uwe R

    2015-08-12

    Degenerately doped silicon nanocrystals are appealing plasmonic materials due to silicon's low cost and low toxicity. While surface plasmonic resonances of boron-doped and phosphorus-doped silicon nanocrystals were recently observed, there currently is poor understanding of the effect of surface conditions on their plasmonic behavior. Here, we demonstrate that phosphorus-doped silicon nanocrystals exhibit a plasmon resonance immediately after their synthesis but may lose their plasmonic response with oxidation. In contrast, boron-doped nanocrystals initially do not exhibit plasmonic response but become plasmonically active through postsynthesis oxidation or annealing. We interpret these results in terms of substitutional doping being the dominant doping mechanism for phosphorus-doped silicon nanocrystals, with oxidation-induced defects trapping free electrons. The behavior of boron-doped silicon nanocrystals is more consistent with a strong contribution of surface doping. Importantly, boron-doped silicon nanocrystals exhibit air-stable plasmonic behavior over periods of more than a year. PMID:26214245

  17. Theory of graphitic boron nitride nanotubes

    SciTech Connect

    Rubio, A.; Corkill, J.L.; Cohen, M.L. Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 )

    1994-02-15

    Based upon the similarities in properties between carbon- and BN-based (BN=boron nitride) materials, we propose that BN-based nanotubes can be stable and study their electronic structure. A simple Slater-Koster tight-binding scheme has been applied. All the BN nanotubes are found to be semiconducting materials. The band gaps are larger than 2 eV for most tubes. Depending on the helicity, the calculated band gap can be direct at [Gamma] or indirect. In general, the larger the diameter of the nanotube the larger the band gap, with a saturation value corresponding to the calculated local-density-approximation band gap of hexagonal BN. The higher ionicity of BN is important in explaining the electronic differences between these tubes and similar carbon nanotubes.

  18. 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.

  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. Green synthesis of boron doped graphene and its application as high performance anode material in Li ion battery

    SciTech Connect

    Sahoo, Madhumita; Sreena, K.P.; Vinayan, B.P.; Ramaprabhu, S.

    2015-01-15

    Graphical abstract: Boron doped graphene (B-G), synthesized by simple hydrogen induced reduction technique using boric acid as boron precursor, have more uneven surface as a result of smaller bonding distance of boron compared to carbon, showed high capacity and high rate capability compared to pristine graphene as an anode material for Li ion battery application. - Abstract: The present work demonstrates a facile route for the large-scale, catalyst free, and green synthesis approach of boron doped graphene (B-G) and its use as high performance anode material for Li ion battery (LIB) application. Boron atoms were doped into graphene framework with an atomic percentage of 5.93% via hydrogen induced thermal reduction technique using graphite oxide and boric acid as precursors. Various characterization techniques were used to confirm the boron doping in graphene sheets. B-G as anode material shows a discharge capacity of 548 mAh g{sup −1} at 100 mA g{sup −1} after 30th cycles. At high current density value of 1 A g{sup −1}, B-G as anode material enhances the specific capacity by about 1.7 times compared to pristine graphene. The present study shows a simplistic way of boron doping in graphene leading to an enhanced Li ion adsorption due to the change in electronic states.

  1. Boron-doped graphene and boron-doped diamond electrodes: detection of biomarkers and resistance to fouling.

    PubMed

    Tan, Shu Min; Poh, Hwee Ling; Sofer, Zdeněk; Pumera, Martin

    2013-09-01

    Doped carbon materials are of high interest as doping can change their properties. Here we wish to contrast the electrochemical behaviour of two carbon allotropes - sp(3) hybridized carbon as diamond and sp(2) hybridized carbon as graphene - doped by boron. We show that even though both materials exhibit similar heterogeneous electron transfer towards ferro/ferricyanide, there are dramatic differences towards the oxidation of biomolecules, such as ascorbic acid, uric acid, dopamine and β-nicotinamide adenine dinucleotide (NADH). The boron-doped graphene exhibits much lower oxidation potentials than boron-doped diamond. The stability of the surfaces towards NADH oxidation product fouling has been studied and in the long term, there is no significant difference among the studied materials. The proton/electron coupled reduction of dopamine and nitroaromatic explosive (TNT) takes place on boron-doped graphene, while it is not observable at boron-doped diamond. These findings show that boron-doped sp(2) graphene and sp(3) diamond behave, in many aspects, dramatically differently and this shall have a profound influence upon their applicability as electrochemical materials. PMID:23817573

  2. Boron-doped graphene as a promising anode for Na-ion batteries.

    PubMed

    Ling, Chen; Mizuno, Fuminori

    2014-06-14

    The Na-ion battery has recently gained a lot of interest as a low-cost alternative to the current Li-ion battery technology. Its feasibility strongly depends on the development of suitable electrode materials. In the present work we propose a novel anode candidate, boron-doped graphene, for the Na-ion battery. Our first-principles calculations demonstrate that the sodiation of boron-doped graphene well preserves its structural integrity. The 2D-BC3 anode has the average sodiation voltage of 0.44 V in an appropriate range to avoid the safety concerns caused by the formation of dendritic deposits. The capacity of the 2D-BC3 anode reaches ∼2.04 times that of the graphite anode in a Li-ion battery and ∼2.52 times that of hard carbon in a Na-ion battery. The high electronic mobility and Na mobility on boron-doped graphene indicates that it has a high potential to reach good rate performance. These suggest the promising potential of boron-doped graphene to serve as an anode for a rechargeable Na-ion battery. PMID:24760182

  3. Boron carbide particles formed from an amorphous boron/graphite powder mixture using a shock-wave technique

    SciTech Connect

    Yamada, Kenjiro

    1996-04-01

    Boron carbide (B{sub 4}C) particles with filamental, distorted ellipsoidal, platelike, and polyhedral shapes were formed from vapor generated from an amorphous boron/graphite powder mixture with 14% starting density using a cylindrical shock-wave technique. The crystal phases of shocked compact and microstructures of the B{sub 4}C particles were characterized by X-ray diffractometry and electron microscopy, respectively.

  4. Characteristics of deposited boron doping diamond on tungsten carbide insert by MPECVD

    NASA Astrophysics Data System (ADS)

    Kim, Jong Seok; Park, Yeong Min; Kim, Jeong Wan; Tulugan, Kelimu; Kim, Tae Gyu

    2015-03-01

    Diamond-coated cutting tools are used primarily for machining non-ferrous materials such as aluminum-silicon alloys, copper alloys, fiber-reinforced polymers, green ceramics and graphite. Because the tool life of cemented carbide cutting tool is greatly improved by diamond coating, and typically more than 10 times of the tool life is obtained. However, research of boron-doped diamond (BDD) coating tool has not been fully researched yet. In this study, we have succeeded to make boron-doped microcrystalline and nanocrystalline diamond-coated Co-cemented tungsten carbide (WC-Co) inserts. Microcrystalline BDD thin film is deposited on WC-Co insert by using microwave plasma enhanced chemical vapor deposition (MPECVD) method. Scanning electron microscope (SEM) and Raman spectroscopy are used to characterize the as-deposited diamond films.1,2

  5. Selecting boron fullerenes by cage-doping mechanisms.

    PubMed

    Boulanger, Paul; Morinière, Maxime; Genovese, Luigi; Pochet, Pascal

    2013-05-14

    So far, no boron fullerenes were synthesized: more compact sp(3)-bonded clusters are energetically preferred. To circumvent this, metallic clusters have been suggested by Pochet et al. [Phys. Rev. B 83, 081403(R) (2011)] as "seeds" for a possible synthesis which would topologically protect the sp(2) sector of the configuration space. In this paper, we identify a basic pentagonal unit which allows a balance between the release of strain and the self-doping rule. We formulate a guiding principle for the stability of boron fullerenes, which takes the form of an isolated filled pentagon rule (IFPR). The role of metallic clusters is then reexamined. It is shown that the interplay of the IFPR and the seed-induced doping breaks polymorphism and its related problems: it can effectively select between different isomers and reduce the reactivity of the boron shells. The balance between self and exterior doping represents the best strategy for boron buckyball synthesis. PMID:23676039

  6. 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

  7. C60 bonding to graphite and boron nitride surfaces

    NASA Astrophysics Data System (ADS)

    Reinke, P.; Feldermann, H.; Oelhafen, P.

    2003-12-01

    The present study focuses on the interaction of C60 with the surfaces of highly oriented pyrolitic graphite (HOPG) and sp2-bonded boron nitride (BN). The nanocrystalline BN film was deposited by mass selected ion beams and features an sp2-bonded surface layer, which covers a cubic phase BN film. The first part of the experiment is the sequential deposition of C60, which is monitored by photoelectron spectroscopy in the x-ray (XPS) and ultraviolet (UPS) regime. The growth of the C60 layer on HOPG is close to a layer-by-layer growth mode, but on the BN surface island growth is favored. No charge transfer or chemical reaction (e.g., carbide formation) between the fullerene layer, and the underlying substrate is observed in either case. In the second part of the experiment the samples are heated at a rate of 10 K/min while simultaneously recording the UPS VB spectra. The complete desorption of C60 from the HOPG surface occurs in a small temperature interval between 510-530 K. For the sp2 BN surface the majority of C60 desorbs around 493 K, about half a monolayer (ML) remains, and the C60 concentration decreases gradually with increasing temperature; less than a tenth of a ML can be detected even at 1000 K. The first desorption event at 493 K is attributable to the multilayer desorption from islands. The remaining C60 directly in contact with the BN surface is then removed in a large temperature interval between 500 and 1000 K which indicates the presence of a multitude of adsorption sites. The presence of C60 on the BN film surface also induces a band bending and related B 1s and N 1s core level shifts. An upward band bending is present in the C60 overlayer, which indicates that defects are responsible for the pinning of the Fermi level at the interface.

  8. Pairwise cobalt doping of boron carbides with cobaltocene

    NASA Astrophysics Data System (ADS)

    Ignatov, A. Yu.; Losovyj, Ya. B.; Carlson, L.; LaGraffe, D.; Brand, J. I.; Dowben, P. A.

    2007-10-01

    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 "C2B10Hx" 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±0.02Å) and are chemically bonded to the icosahedral cages of B10CHx or B9C2Hy. Pairwise Co doping occurs, with the cobalt atoms favoring sites some 5.28±0.02Å apart.

  9. Transforming chitosan into N-doped graphitic carbon electrocatalysts.

    PubMed

    Wu, T X; Wang, G Z; Zhang, X; Chen, C; Zhang, Y X; Zhao, H J

    2015-01-25

    Chitosan, the only alkaline polysaccharide in nature with rich nitrogen content, is used as the sole precursor to obtain N-doped graphitic carbon-based ORR electrocatalysts. The findings of this work demonstrate that cheap, plentiful and renewable biomasses can be transformed into high value functional carbon materials. PMID:25486248

  10. Boron-doped superlattices and Bragg mirrors in diamond

    SciTech Connect

    Fiori, A.; Bousquet, J.; Eon, D.; Omnès, F.; Bustarret, E.; Bellet-Amalric, E.

    2014-08-25

    A periodic modulation of the boron doping level of single crystal diamond multilayers over more than three orders of magnitude during epitaxial growth by microwave plasma-enhanced chemical vapor deposition is shown to yield Bragg mirrors in the visible. The thicknesses and doping level of the individual layers were controlled by in situ spectroscopic ellipsometry, enabling to tune the reflectance peak to the wavelength range of diamond color centers, such as NV{sup 0} or NV{sup −}. The crystalline quality, periodicity, and sharpness of the doping transitions in these doping superlattices over tens of periods were confirmed by high resolution X-ray diffraction.

  11. Temperature admittance spectroscopy of boron doped chemical vapor deposition diamond

    NASA Astrophysics Data System (ADS)

    Zubkov, V. I.; Kucherova, O. V.; Bogdanov, S. A.; Zubkova, A. V.; Butler, J. E.; Ilyin, V. A.; Afanas'ev, A. V.; Vikharev, A. L.

    2015-10-01

    Precision admittance spectroscopy measurements over wide temperature and frequency ranges were carried out for chemical vapor deposition epitaxial diamond samples doped with various concentrations of boron. It was found that the experimentally detected boron activation energy in the samples decreased from 314 meV down to 101 meV with an increase of B/C ratio from 600 to 18000 ppm in the gas reactants. For the heavily doped samples, a transition from thermally activated valence band conduction to hopping within the impurity band (with apparent activation energy 20 meV) was detected at temperatures 120-150 K. Numerical simulation was used to estimate the impurity DOS broadening. Accurate determination of continuously altering activation energy, which takes place during the transformation of conduction mechanisms, was proposed by numerical differentiation of the Arrhenius plot. With increase of boron doping level the gradual decreasing of capture cross section from 3 × 10-13 down to 2 × 10-17 cm2 was noticed. Moreover, for the hopping conduction the capture cross section becomes 4 orders of magnitude less (˜2 × 10-20 cm2). At T > Troom in doped samples the birth of the second conductance peak was observed. We attribute it to a defect, related to the boron doping of the material.

  12. Boron doping of diamond powder by enhanced diffusion and forced diffusion: Diffusion concentrations, mechanical, chemical and optical properties

    NASA Astrophysics Data System (ADS)

    Golshani, Fariborz

    Diamond, with its unique mechanical properties, is an excellent material for a wide range of applications. However, there exist some problems. One such problem is integration of diamond of diamond into tool's (usually tungsten-carbide) lattice matrix for the purpose of increasing its performance. The presence of cobalt in the matrix, which acts as a poison for diamond, causes graphitization and degradation of diamond. In addition, diamond graphitizes at sintering temperatures (1770 K). The results of this work suggest that boron has produced a protective layer for diamond, thus reducing the effects of annealing at high temperatures. Boron has been introduced into single crystal high pressure, high temperature diamond powder by enhanced diffusion and forced diffusion techniques. Enhanced diffusion resulted in higher concentrations of boron in diamond powder. Total boron concentrations of 500 to 600 ppm, and 10sp{20} cmsp{-3} at a depth of 0.5 micrometer, have been achieved. Hardness tests performed on doped samples reveal that diamond did not lose its strength due to diffusion at elevated temperatures. Raman spectroscopy and X-ray diffraction analysis did not show any change in the "quality" of diamond due to doping. Oxidation experiments performed on doped and undoped samples revealed that the samples with the highest boron concentrations had superior performance and resistance to oxidation. Final weight loss in these samples was much less than in undoped samples and samples with low boron concentrations. Scanning electron microscopy of these samples showed that degradation due to oxidation of heavily doped diamond samples was significantly less than other samples.

  13. Hydrogen adsorption on carbon-doped boron nitride nanotube.

    PubMed

    Baierle, Rogério J; Piquini, Paulo; Schmidt, Tomé M; Fazzio, Adalberto

    2006-10-26

    The adsorption of atomic and molecular hydrogen on carbon-doped boron nitride nanotubes is investigated within the ab initio density functional theory. The binding energy of adsorbed hydrogen on carbon-doped boron nitride nanotube is substantially increased when compared with hydrogen on nondoped nanotube. These results are in agreement with experimental results for boron nitride nanotubes (BNNT) where dangling bonds are present. The atomic hydrogen makes a chemical covalent bond with carbon substitution, while a physisorption occurs for the molecular hydrogen. For the H(2) molecule adsorbed on the top of a carbon atom in a boron site (BNNT + C(B)-H(2)), a donor defect level is present, while for the H(2) molecule adsorbed on the top of a carbon atom in a nitrogen site (BNNT + C(N)-H(2)), an acceptor defect level is present. The binding energies of H(2) molecules absorbed on carbon-doped boron nitride nanotubes are in the optimal range to work as a hydrogen storage medium. PMID:17048943

  14. Room-Temperature, Low-Barrier Boron Doping of Graphene

    NASA Astrophysics Data System (ADS)

    Du, Shixuan

    Doping graphene with boron has been difficult because of high reaction barriers. Here, we describe a low-energy reaction route derived from first-principles calculations and validated by experiments. We find that a boron atom on graphene on a ruthenium(0001) substrate can replace a carbon by pushing it through, with substrate attraction helping to reduce the barrier to only 0.1 eV, implying that the doping can take place at room temperature. High-quality graphene is grown on a Ru(0001) surface and exposed to B2H6. Scanning tunneling microscopy/spectroscopy and X-ray photoelectron spectroscopy confirmed that boron is indeed incorporated substitutionally without disturbing the graphene lattice. (L.D. Pan et al., Nano Lett. 2015, 15, 6464. In collaboration with Lida Pan, Yande Que, Hui Chen, Dongfei Wang, Jun Li, Chengmin Shen, Wende Xiao, Hongjun Gao in CAS, and S. Pantellides in Vanderbilt University.)

  15. Room-Temperature, Low-Barrier Boron Doping of Graphene.

    PubMed

    Pan, Lida; Que, Yande; Chen, Hui; Wang, Dongfei; Li, Jun; Shen, Chengmin; Xiao, Wende; Du, Shixuan; Gao, Hongjun; Pantelides, Sokrates T

    2015-10-14

    Doping graphene with boron has been difficult because of high reaction barriers. Here, we describe a low-energy reaction route derived from first-principles calculations and validated by experiments. We find that a boron atom on graphene on a ruthenium(0001) substrate can replace a carbon by pushing it through, with substrate attraction helping to reduce the barrier to only 0.1 eV, implying that the doping can take place at room temperature. High-quality graphene is grown on a Ru(0001) surface and exposed to B2H6. Scanning tunneling microscopy/spectroscopy and X-ray photoelectron spectroscopy confirmed that boron is indeed incorporated substitutionally without disturbing the graphene lattice. PMID:26348981

  16. Oxidation Resistant Graphite Studies

    SciTech Connect

    W. Windes; R. Smith

    2014-07-01

    The Very High Temperature Reactor (VHTR) Graphite Research and Development Program is investigating doped nuclear graphite grades exhibiting oxidation resistance. During a oxygen ingress accident the oxidation rates of the high temperature graphite core region would be extremely high resulting in significant structural damage to the core. Reducing the oxidation rate of the graphite core material would reduce the structural effects and keep the core integrity intact during any air-ingress accident. Oxidation testing of graphite doped with oxidation resistant material is being conducted to determine the extent of oxidation rate reduction. Nuclear grade graphite doped with varying levels of Boron-Carbide (B4C) was oxidized in air at nominal 740°C at 10/90% (air/He) and 100% air. The oxidation rates of the boronated and unboronated graphite grade were compared. With increasing boron-carbide content (up to 6 vol%) the oxidation rate was observed to have a 20 fold reduction from unboronated graphite. Visual inspection and uniformity of oxidation across the surface of the specimens were conducted. Future work to determine the remaining mechanical strength as well as graphite grades with SiC doped material are discussed.

  17. 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.

  18. 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

    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.

  19. 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.; Xue, Sha; Crunkleton, Daniel W.; Shen, Yaogen; Wang, Sanwu

    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.

  20. 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.

  1. Water dispersible, highly graphitic and nitrogen-doped carbon nanobubbles.

    PubMed

    Soll, Sebastian; Fellinger, Tim-Patrick; Wang, Xinchen; Zhao, Qiang; Antonietti, Markus; Yuan, Jiayin

    2013-12-20

    Dispersible, highly graphitic, and nitrogen-doped carbon hollow nanospheres (25-90 nm), termed 'nanobubbles', are prepared via confined carbonization through a silica nanocasting technique. Poly(ionic liquid) nanoparticles are employed as easy-to-make and multifunctional templates, which simultaneously act as both the carbon and nitrogen source. The promising potential of the nanobubbles in oxygen reduction reactions for fuel cells is demonstrated. PMID:23847129

  2. First principles modeling of boron-doped carbon nanotube sensors

    NASA Astrophysics Data System (ADS)

    Talla, Jamal A.

    2012-03-01

    We investigated the interactions between two different geometrical configurations of single-walled carbon nanotubes and boron atoms using first-principle calculations within the framework of the density functional theory. With the aid of ab initio calculations, we introduced a new type of toxic gas sensor that can detect the presence of CO, NO and H2 molecules. We proved that the dopant concentration on the surface of the nanotube plays a crucial role in the sensitivity of this device. Furthermore, we showed that small concentrations of dopants can modify the transport and electronic properties of the single-walled carbon nanotube and can lend metallic properties to the nanotube. Band-gap narrowing occurs when the nanotube is doped with boron atoms. The emerged new energy level near the Fermi level upon boron doping clearly indicates the coupling between the p orbital of the boron atom and the large p bond of the carbon nanotube. We also predicted a weak hybridization between the boron atoms and the nanotube for the valence-band edge states; this weak coupling leads to conducting states around the band gap.

  3. Selecting boron fullerenes by cage-doping mechanisms

    NASA Astrophysics Data System (ADS)

    Boulanger, Paul; Morinière, Maxime; Genovese, Luigi; Pochet, Pascal

    2013-05-01

    So far, no boron fullerenes were synthesized: more compact sp3-bonded clusters are energetically preferred. To circumvent this, metallic clusters have been suggested by Pochet et al. [Phys. Rev. B 83, 081403(R) (2011), 10.1103/PhysRevB.83.081403] as "seeds" for a possible synthesis which would topologically protect the sp2 sector of the configuration space. In this paper, we identify a basic pentagonal unit which allows a balance between the release of strain and the self-doping rule. We formulate a guiding principle for the stability of boron fullerenes, which takes the form of an isolated filled pentagon rule (IFPR). The role of metallic clusters is then reexamined. It is shown that the interplay of the IFPR and the seed-induced doping breaks polymorphism and its related problems: it can effectively select between different isomers and reduce the reactivity of the boron shells. The balance between self and exterior doping represents the best strategy for boron buckyball synthesis.

  4. Rapid carbothermal reduction of boron oxide in a graphite transport reactor

    SciTech Connect

    Weimer, A.W.; Roach, R.P.; Haney, C.N. ); Moore, W.G.; Rafaniello, W. )

    1991-05-01

    This paper reports that uniform submicron crystals of B[sub 4]C, boron-enriched boron carbide, and B[sub 4]C/TiB[sub 2] composite powders have been synthesized continuously by rapid carbothermal reduction at approximately 2,200 K in a 0.14 m ID [times] 1.68 m long pilot-scale graphite transport reactor. A unique reactor design allowed for continuous feeding of a meltable boron oxide containing precursor, rapid heating rates hat completed the carbothermal reduction reaction in seconds, and an expanded cooling that allowed for the precipitation in space of volatile excess boron oxides. Powder morphology resembled that of powder synthesized by laser pyrolysis of gaseous reactants. Rapid heating rates and minimized reaction times at high temperatures promoted nucleation and limited crystal growth. Dense parts fabricated from these powders have fine grains and extreme hardness.

  5. Annealing studies of highly doped boron superlattices

    SciTech Connect

    Jackman, T. E.; Houghton, D. C.; Jackman, J. A.; Denhoff, M. W.; Kechang, S.; McCaffrey, J.; Rockett, A.

    1989-09-01

    Coevaporation of B/sub 2/ O/sub 3/ during silicon molecular-beam epitaxy at growth temperatures (/ital T//sub /ital G// ) varying from 540 to 800 /degree/C has been used to prepare superlattice structures (/ital pipi/'s) of varying boron concentration (3/times/10/sup 18/ --3/times/10/sup 20/ B cm/sup /minus/3/). The superlattices were subsequently subjected to various annealing procedures and the layers were examined by secondary ion mass spectrometry, electrochemical profiling, and cross-sectional transmission electron microscopy. A significant redistribution of boron was observed even before annealing for /ital T//sub /ital G// /gt/700 /degree/C and high boron concentrations. In addition, significant oxygen was incorporated for /ital T//sub /ital G// /le/700 /degree/C, with a growth rate of 0.5 nm s/sup /minus/1/ and a B/sub 2/ O/sub 3/ flux of 2/times/10/sup 13/ cm/sup /minus/2/ s/sup /minus/1/. After annealing, the boron diffusion coefficients were determined for the layers and found to vary significantly with /ital T//sub /ital G//.

  6. Chemical mechanical polishing of boron-doped polycrystalline silicon

    NASA Astrophysics Data System (ADS)

    Pirayesh, Hamidreza; Cadien, Kenneth

    2014-03-01

    Chemical mechanical polishing (CMP) is a technique which helps to print a smaller depth of focus and smoother surface in micro fabrication industry. In this project, boron doped polysilicon is used as a fill material for Through Silicon Vias (TSV) creating a 3D package. It is shown that the presence of boron as dopant suppresses the polysilicon polish rate. To increase the polish rate, understanding the mechanism of polish rate retardation is essential. We believe that the electrical effects play the major role in this phenomenon and by reducing this effect we are able to increase the polish rate.

  7. Photoelectron Spectroscopy of Aluminum Doped Boron Clusters

    NASA Astrophysics Data System (ADS)

    Li, Wei-Li; Romanescu, Constantin; Wang, Lai-Sheng

    2012-06-01

    Anionic boron clusters have been shown to be planar or quasi-planar up to B21- from a series of combined photoelectron spectroscopy and theoretical studies. All these boron clusters consist of a peripheral ring characterized by strong two-center-two-electron (2c-2e) B-B bonds and one or more interior atoms. The propensity for planarity is due to σ - and π -electron delocalizations throughout the molecular plane, giving rise to concepts of σ - and π -aromaticity. The quasi-planarity, on the other hand, can be mechanical in nature - the circumference of the cluster is too small to fit the inner atoms - even for doubly aromatic clusters. Two questions arise: firstly, can isoelectronic substitution by a single aluminum atom on the outer ring enhance the planarity of quasi-planar structures, and, secondly, can the interior boron atoms be replaced by aluminum? A series of aluminum isoelectronic substitution of boron clusters have been investigated ranging from B7- to B12-. Aluminum turns out to avoid the central position in the all these clusters and enhance the planarity of AlB6- and AlB11- clusters by expanding the peripheral ring. References: [1] C. Romanescu, A. P. Sergeeva, W. L. Li, A. I. Boldyrev and L. S. Wang, {J. Am. Chem. Soc}. {133} (22), 8646-8653 (2011) [2] T. R. Galeev, C. Romanescu, W. L. Li, L. S. Wang and A. I. Boldyrev, {J. Chem. Phys.} {135}, (8) 104301 (2011) [3] W. L. Li, C. Romanescu, T. R. Galeev, L. S. Wang and A. I. Boldyrev, {J. Phys. Chem. A} {115} (38), 10391-10397 (2011)

  8. Chemical vapor deposition, doping and characterization of boron-phosphide

    NASA Astrophysics Data System (ADS)

    Garg, S. G.

    1981-08-01

    Boron phosphide was deposited on silicon and sapphire substrates using a mixture of diborane, phosphine and purified hydrogen in a pancake type epitaxial reactor. The films deposited were of high quality. Temperature of deposition and flow rates of the constituent gases were varied during the deposition. The early growth was observed. Single crystal films of high resistivity were obtained on silicon substrates. The heterostructure between BP and SI was studied. Current conduction experiments were performed. It was concluded that a tunneling mechanism was the major contributing factor. A very low value for ionicity was established. The real part of the refractive index of boron phosphide was determined the band structure is discussed, and boron phosphide compared with other III-V compounds and group 4 elements. The films was doped with zinc, beryllium, and silicon. Conductivity was determined as a function of temperature.

  9. Boronized and siliconized graphites — material processing and effects on properties

    NASA Astrophysics Data System (ADS)

    Wolf, Reinhold

    1994-09-01

    Bulk boronized graphites have been developed by using B 4C powder in portions of up to 20 wt%. Grade FU 2524 is produced according to conventional graphite technology, whereas grade FU 2373 uses self-sintering mesocarbon microbeads. The structure of the basic graphites is retained, but as heat treatment temperature is limited to about 2500 K, no distinct graphitic structure can be achieved, and thermal conductivity remains low. Two types of siliconized graphites, namely FU 2613 and SiC 30 are produced by reactive impregnation of graphite with liquid silicon at temperatures above 1800 K. Depending on the different starting materials, in case of SiC 30 a composite C/SiC/Si with SiC content of about 62 wt% is produced. In the case of FU 2613 the graphitic carbon components are still about 70 wt%. In both cases the change of the microstructure goes along with a significant increase of physical properties, especially strength, Young's modulus and thermal conductivity.

  10. Hydrogen adsorption on nitrogen and boron doped graphene.

    PubMed

    Pizzochero, Michele; Leenaerts, Ortwin; Partoens, Bart; Martinazzo, Rocco; Peeters, François M

    2015-10-28

    Hydrogen adsorption on boron and nitrogen doped graphene is investigated in detail by means of first-principles calculations. A comprehensive study is performed of the structural, electronic, and magnetic properties of chemisorbed hydrogen atoms and atom pairs near the dopant sites. The main effect of the substitutional atoms is charge doping which is found to greatly affect the adsorption process by increasing the binding energy at the sites closest to the substitutional species. It is also found that doping does not induce magnetism despite the odd number of electrons per atom introduced by the foreign species, and that it quenches the paramagnetic response of chemisorbed H atoms on graphene. Overall, the effects are similar for B and N doping, with only minor differences in the adsorption energetics due to different sizes of the dopant atoms and the accompanying lattice distortions. PMID:26439097

  11. Can doping graphite trigger room temperature superconductivity? Evidence for granular high-temperature superconductivity in water-treated graphite powder.

    PubMed

    Scheike, T; Böhlmann, W; Esquinazi, P; Barzola-Quiquia, J; Ballestar, A; Setzer, A

    2012-11-14

    Granular superconductivity in powders of small graphite grains (several tens of micrometers) is demonstrated after treatment with pure water. The temperature, magnetic field and time dependence of the magnetic moment of the treated graphite powder provides evidence for the existence of superconducting vortices with some similarities to high-temperature granular superconducting oxides but even at temperatures above 300 K. Room temperature superconductivity in doped graphite or at its interfaces appears to be possible. PMID:22949348

  12. Atomically controlled substitutional boron-doping of graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Kawai, Shigeki; Saito, Shohei; Osumi, Shinichiro; Yamaguchi, Shigehiro; Foster, Adam S.; Spijker, Peter; Meyer, Ernst

    2015-08-01

    Boron is a unique element in terms of electron deficiency and Lewis acidity. Incorporation of boron atoms into an aromatic carbon framework offers a wide variety of functionality. However, the intrinsic instability of organoboron compounds against moisture and oxygen has delayed the development. Here, we present boron-doped graphene nanoribbons (B-GNRs) of widths of N=7, 14 and 21 by on-surface chemical reactions with an employed organoboron precursor. The location of the boron dopant is well defined in the centre of the B-GNR, corresponding to 4.8 atom%, as programmed. The chemical reactivity of B-GNRs is probed by the adsorption of nitric oxide (NO), which is most effectively trapped by the boron sites, demonstrating the Lewis acid character. Structural properties and the chemical nature of the NO-reacted B-GNR are determined by a combination of scanning tunnelling microscopy, high-resolution atomic force microscopy with a CO tip, and density functional and classical computations.

  13. Atomically controlled substitutional boron-doping of graphene nanoribbons

    PubMed Central

    Kawai, Shigeki; Saito, Shohei; Osumi, Shinichiro; Yamaguchi, Shigehiro; Foster, Adam S.; Spijker, Peter; Meyer, Ernst

    2015-01-01

    Boron is a unique element in terms of electron deficiency and Lewis acidity. Incorporation of boron atoms into an aromatic carbon framework offers a wide variety of functionality. However, the intrinsic instability of organoboron compounds against moisture and oxygen has delayed the development. Here, we present boron-doped graphene nanoribbons (B-GNRs) of widths of N=7, 14 and 21 by on-surface chemical reactions with an employed organoboron precursor. The location of the boron dopant is well defined in the centre of the B-GNR, corresponding to 4.8 atom%, as programmed. The chemical reactivity of B-GNRs is probed by the adsorption of nitric oxide (NO), which is most effectively trapped by the boron sites, demonstrating the Lewis acid character. Structural properties and the chemical nature of the NO-reacted B-GNR are determined by a combination of scanning tunnelling microscopy, high-resolution atomic force microscopy with a CO tip, and density functional and classical computations. PMID:26302943

  14. Magnesium doping of boron nitride nanotubes

    DOEpatents

    Legg, Robert; Jordan, Kevin

    2015-06-16

    A method to fabricate boron nitride nanotubes incorporating magnesium diboride in their structure. In a first embodiment, magnesium wire is introduced into a reaction feed bundle during a BNNT fabrication process. In a second embodiment, magnesium in powder form is mixed into a nitrogen gas flow during the BNNT fabrication process. MgB.sub.2 yarn may be used for superconducting applications and, in that capacity, has considerably less susceptibility to stress and has considerably better thermal conductivity than these conventional materials when compared to both conventional low and high temperature superconducting materials.

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

    SciTech Connect

    Jia, Xiaoting; Dresselhaus, M; Cruz Silva, Eduardo; Munoz-Sandoval, E; Sumpter, Bobby G; Terrones Maldonado, Humberto; Terrones Maldonado, Humberto; Lopez, Florentino

    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.

  16. Laser doping of boron-doped Si paste for high-efficiency silicon solar cells

    NASA Astrophysics Data System (ADS)

    Tomizawa, Yuka; Imamura, Tetsuya; Soeda, Masaya; Ikeda, Yoshinori; Shiro, Takashi

    2015-08-01

    Boron laser doping (LD) is a promising technology for high-efficiency solar cells such as p-type passivated locally diffused solar cells and n-type Si-wafer-based solar cells. We produced a printable phosphorus- or boron-doped Si paste (NanoGram® Si paste/ink) for use as a diffuser in the LD process. We used the boron LD process to fabricate high-efficiency passivated emitter and rear locally diffused (PERL) solar cells. PERL solar cells on Czochralski Si (Cz-Si) wafers yielded a maximum efficiency of 19.7%, whereas the efficiency of a reference cell was 18.5%. Fill factors above 79% and open circuit voltages above 655 mV were measured. We found that the boron-doped area effectively performs as a local boron back surface field (BSF). The characteristics of the solar cell formed using NanoGram® Si paste/ink were better than those of the reference cell.

  17. Evidence of superconductivity in doped graphite and graphene

    NASA Astrophysics Data System (ADS)

    Larkins, Grover; Vlasov, Yuriy; Holland, Kiar

    2016-01-01

    We have observed evidence of superconductivity at temperatures in the vicinity of 260 K in phosphorus-doped graphite and graphene. This evidence includes transport current, magnetic susceptibility, Hall effect and (pancake) vortex state measurements. All of these measurements indicate a transition which is that of a type II superconductor with no type I phase until below the limits of our measurement capabilities. Vortex states are inferred from periodically repeated steps in the resistance versus temperature characteristics of highly oriented pyrolytic graphite and exfoliated doped multilayer graphene. Magnetic susceptibility measurements have shown results qualitatively similar to those expected (and experimentally observed by others) for ultra-thin (thickness ≪λ L) films. The magnetization is negative for field-cooled and zero-field-cooled measurements. The magnetization for field cooled and zero-field-cooled measurements begin to diverge at approximately 260 K. Hall effect measurements show a sign reversal in the Hall voltage as the temperature is reduced from 300 K to 78 K.

  18. Growth and characterization of boron doped graphene by Hot Filament Chemical Vapor Deposition Technique (HFCVD)

    NASA Astrophysics Data System (ADS)

    Jafari, A.; Ghoranneviss, M.; Salar Elahi, A.

    2016-03-01

    Large-area boron doped graphene was synthesized on Cu foil (as a catalyst) by Hot Filament Chemical Vapor Deposition (HFCVD) using boron oxide powder and ethanol vapor. To investigate the effect of different boron percentages, grow time and the growth mechanism of boron-doped graphene, scanning electron microscopy (SEM), Raman scattering and X-ray photoelectron spectroscopy (XPS) were applied. Also in this experiment, the I-V characteristic carried out for study of electrical property of graphene with keithley 2361 system. Nucleation of graphene domains with an average domain size of ~20 μm was observed when the growth time is 9 min that has full covered on the Cu surface. The Raman spectroscopy show that the frequency of the 2D band down-shifts with B doping, consistent with the increase of the in-plane lattice constant, and a weakening of the B-C in-plane bond strength relative to that of C-C bond. Also the shifts of the G-band frequencies can be interpreted in terms of the size of the C-C ring and the changes in the electronic structure of graphene in the presence of boron atoms. The study of electrical property shows that by increasing the grow time the conductance increases which this result in agree with SEM images and graphene grain boundary. Also by increasing the boron percentage in gas mixer the conductance decreases since doping graphene with boron creates a band-gap in graphene band structure. The XPS results of B doped graphene confirm the existence of boron in doped graphene, which indicates the boron atoms doped in the graphene lattice are mainly in the form of BC3. The results showed that boron-doped graphene can be successfully synthesized using boron oxide powder and ethanol vapor via a HFCVD method and also chemical boron doping can be change the electrical conductivity of the graphene.

  19. The boron doping of single crystal diamond for high power diode applications

    NASA Astrophysics Data System (ADS)

    Nicley, Shannon Singer

    Diamond has the potential to revolutionize the field of high power and high frequency electronic devices as a superlative electronic material. The realization of diamond electronics depends on the control of the growth process of both lightly and heavily boron doped diamond. This dissertation work is focused on furthering the state of the art of boron doped diamond (BDD) growth toward the realization of high power diamond Schottky barrier diodes (SBDs). The achievements of this work include the fabrication of a new dedicated reactor for lightly boron doped diamond deposition, the optimization of growth processes for both heavily and lightly boron doped single crystal diamond (SCD), and the proposal and realization of the corner architecture SBD. Boron doped SCD is grown in microwave plasma-assisted chemical vapor deposition (MPACVD) plasma disc bell-jar reactors, with feedgas mixtures including hydrogen, methane, carbon dioxide, and diborane. Characterization methods for the analysis of BDD are described, including Fourier-transformed infrared spectroscopy (FTIR), Secondary Ion Mass Spectroscopy (SIMS) and temperature-dependent four point probe conductivity for activation energy. The effect of adding carbon dioxide to the plasma feedgas for lightly boron doped diamond is investigated. The effect of diborane levels and other growth parameters on the incorporated boron levels are reported, and the doping efficiency is calculated over a range of boron concentrations. The presence of defects is shown to affect the doping uniformity. The substrate growth temperature dependence of the plasma gas-phase to solid-phase doping efficiency in heavily boron doped SCD deposition is investigated. The substrate temperature during growth is shown to have a significant effect on the grown sample defect morphology, and a temperature dependence of the doping efficiency is also shown. The effect of the growth rate on the doping efficiency is discussed, and the ratio of the boron concentration in the gas phase to the flux of carbon incorporated into the solid diamond phase is shown to be a more predictive measure of the resulting boron concentration than the gas phase boron to carbon ratio that is more commonly reported. The corner architecture SBD structure is proposed as an alternative vertical architecture for the realization of high power, high temperature single crystal diamond diodes. The lightly doped layer of the diode is grown in a direction perpendicular to the previous epitaxial growth of the heavily doped layer, to reduce the threading type dislocations in the active region of the fabricated diodes. The first ever corner architecture SBD is fabricated and evaluated for diode performance, using the regimes identified for high quality boron doped diamond deposition at light and heavy doping levels.

  20. Percolation exponents and thresholds obtained from the nearly ideal continuum percolation system graphite-boron nitride

    SciTech Connect

    Wu, J.; McLachlan, D.S.

    1997-07-01

    Compressed disks made from graphite and, its mechanical but not electrical isomorph, boron nitride as well as graphite-boron nitride powders, undergoing compression, are nearly ideal continuum percolation systems, as the ratio of their conductivities is nearly 10{sup {minus}18} and the scatter of the experimental points near the critical volume fraction {phi}{sub c} is very small. The following measurements, with the characteristic exponent(s) in brackets, are made on some or all of the samples in (axial) and at right angles (radial) to the direction of compression, as a function of the volume fraction of graphite ({phi}); dc conductivity (s and t), dielectric constant (s), magnetoresistivity (t{sub {perpendicular}}), and noise power (K). The noise power is also measured as function of resistance (w) and volume (b{sup {prime}}). The {phi}{sub c}{close_quote}s obtained for all measurements are consistent and explicable. The results for the exponents are less well understood but, where possible, these results are compared with theoretical predictions and previous experiments. The reasons for the nonuniversality of t are clarified. {copyright} {ital 1997} {ital The American Physical Society}

  1. Refractive index behavior of boron-doped silica films by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Horng, R. H.; Chen, F.; Wuu, D. S.; Lin, T. Y.

    1996-02-01

    The optical characterization of boron-doped silica films grown by plasma-enhanced chemical vapor deposition (PECVD) is reported. The refractive index of the deposited film is found to increase with the B 2H 6 flow rate, which is in contrast to the theoretical expectation. Infrared absorption studies show that the SiO main peak for the boron-doped sample shifts to lower wavenumber and broadens, as compared with that for the undoped sample. This suggests that the observed refractive index behavior is due to the contribution of the SiN bond. To alleviate the undesired nitrogen incorporation, the refractive index of the boron-doped film was studied as a function of deposition power. It is found that the refractive index value decreases with increasing power level. Based on the above results, a boron doping mechanism for PECVD silica films is proposed. The annealing effect on the refractive index of boron-doped silica is also described.

  2. Topological conduction of Sb films on boron-doped graphene

    NASA Astrophysics Data System (ADS)

    Yang, Chih-Kai; Lee, Chi-Hsuan

    2014-03-01

    It has been shown that thin antimony films can have topological surface states by adsorption of non-magnetic impurity atoms. Using density functional calculations, we show that Sb films placed on boron-doped graphene also have Dirac cones and can provide spin-polarized transport. The calculated binding energy indicates that it is a robust structure and thus a viable conduit for topological conduction. Supported by the National Science Council of the Republic of China under Grant No. NSC 101-2112-M-004-004-MY3.

  3. Bimolecular porous supramolecular networks deposited from solution on layered materials: graphite, boron nitride and molybdenum disulphide.

    PubMed

    Korolkov, Vladimir V; Svatek, Simon A; Allen, Stephanie; Roberts, Clive J; Tendler, Saul J B; Taniguchi, Takashi; Watanabe, Kenji; Champness, Neil R; Beton, Peter H

    2014-08-18

    A two-dimensional porous network formed from perylene tetracarboxylic diimide (PTCDI) and melamine may be deposited from solution on the surfaces of highly oriented pyrolytic graphite (HOPG), hexagonal boron nitride (hBN) and molybdenum disulphide (MoS2). Images acquired using high resolution atomic force microscopy (AFM) operating under ambient conditions have revealed that the network forms extended ordered monolayers (>1 ?m(2)) on HOPG and hBN whereas on MoS2 much smaller islands are observed. PMID:24969532

  4. Boron doped simulated graphene field effect transistor model

    NASA Astrophysics Data System (ADS)

    Sharma, Preetika; Kaur, Inderpreet; Gupta, Shuchi; Singh, Sukhbir

    2016-05-01

    Graphene based electronic devices due to its unique properties has transformed electronics. A Graphene Field Effect Transistor (GNRFET) model is simulated in Virtual Nano Lab (VNL) and the calculations are based on density functional theory (DFT). Simulations were performed on this pristine GNRFET model and the transmission spectrum was observed. The graph obtained showed a uniform energy gap of +1 to -1eV and the highest transmission peak at -1.75 eV. To this pristine model of GNRFET, doping was introduced and its effect was seen on the Fermi level obtained in the transmission spectrum. Boron as a dopant was used which showed variations in both the transmission peaks and the energy gap. In this model, first the single boron was substituted in place of carbon and Fermi level showed an energy gap of 1.5 to -0.5eV with the highest transmission peak at -1.3 eV. In another variation in the model, two carbon atoms were replaced by two boron atoms and Fermi level shifted from 2 to 0.25eV. In this observation, the highest transmission peak was observed at -1(approx.). The use of nanoelectronic devices have opened many areas of applications as GFET is an excellent building block for electronic circuits, and is being used in applications such as high-performance frequency doublers and mixers, digital modulators, phase detectors, optoelectronics and spintronics.

  5. Structural, spectroscopic, and electrochemical characterization of boron-doped diamond films from different provenances

    SciTech Connect

    Li, L.F.; Totir, D.A.; Vinokur, N.; Miller, B.; Chottiner, G.; Evans, E.A.; Angus, J.C.; Scherson, D.A.

    1998-05-01

    Morphological, spectroscopic, and electrochemical aspects of boron-doped diamond (BDD) films grown on silicon surfaces originating from three different laboratories have been examined by atomic force microscopy (AF), Raman scattering, Auger electron spectroscopy, and cyclic voltammetry in polyethylene oxide LiClO{sub 4} electrolytes in ultrahigh vacuum. All specimens displayed AFM images characteristic of diamond and Raman spectra consistent with a wide range of boron concentrations (10{sup 19} to 10{sup 21} B atom/cm{sup 3}), with no evidence for the presence of gross graphitic impurities. The cyclic voltammetry of two of the specimens (denoted as GV2 and CWRU), however, showed features at potentials positive to lithium bulk deposition attributed to lithium-ion intercalation/deintercalation phenomena in non-diamond carbon present as a surface impurity, perhaps at the grain boundaries. This finding is consistent with earlier results for a specimen of type GV2 in aqueous electrolytes for which rates of heterogeneous electron transfer for certain redox couples were found higher than those for nominally clean BDD surfaces.

  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. Enhanced diffusion of oxygen depending on Fermi level position in heavily boron-doped silicon

    SciTech Connect

    Torigoe, Kazuhisa Fujise, Jun; Ono, Toshiaki; Nakamura, Kozo

    2014-11-21

    The enhanced diffusivity of oxygen in heavily boron doped silicon was obtained by analyzing oxygen out-diffusion profile changes found at the interface between a lightly boron-doped silicon epitaxial layer and a heavily boron-doped silicon substrate by secondary ion mass spectrometry. It was found that the diffusivity is proportional to the square root of boron concentration in the range of 10{sup 18 }cm{sup −3}–10{sup 19 }cm{sup −3} at temperatures from 750 °C to 950 °C. The model based on the diffusion of oxygen dimers in double positive charge state could explain the enhanced diffusion. We have concluded that oxygen diffusion enhanced in heavily boron-doped silicon is attributed to oxygen dimers ionized depending on Fermi level position.

  8. The fabrication, testing and delivery of boron/epoxy and graphite/epoxy nondestructive test standards

    NASA Technical Reports Server (NTRS)

    Pless, W. M.; Lewis, W. H.

    1971-01-01

    A description is given of the boron/epoxy and graphite/epoxy nondestructive test standards which were fabricated, tested and delivered to the National Aeronautics and Space Administration. Detailed design drawings of the standards are included to show the general structures and the types and location of simulated defects built into the panels. The panels were laminates with plies laid up in the 0 deg, + or - 45 deg, and 90 deg orientations and containing either titanium substrates or interlayered titanium perforated shims. Panel thickness was incrementally stepped from 2.36 mm (0.093 in.) to 12.7 mm (0.500 in.) for the graphite/epoxy standards, and from 2.36 mm (0.093 in.) to 6.35 mm (0.25 in.) for the boron/epoxy standards except for the panels with interlayered shims which were 2.9 mm (0.113 in.) maximum thickness. The panel internal conditions included defect free regions, resin variations, density/porosity variations, cure variations, delaminations/disbonds at substrate bondlines and between layers, inclusions, and interlayered shims. Ultrasonic pulse echo C-scan and low-kilovoltage X-ray techniques were used to evaluate and verify the internal conditions of the panels.

  9. XPS, SIMS and FTIR-ATR characterization of boronized graphite from the thermonuclear plasma device RFX-mod

    NASA Astrophysics Data System (ADS)

    Ghezzi, F.; Laguardia, L.; Caniello, R.; Canton, A.; Dal Bello, S.; Rais, B.; Anderle, M.

    2015-11-01

    In this paper the characterization of a thin (tens of nanometers) boron layer on fine grain polycrystalline graphite substrate is presented. The boron film is used as conditioning technique for the full graphite wall of the Reversed Field eXperiment-modified (RFX-mod) experiment, a device for the magnetic confinement of plasmas of thermonuclear interest. Aim of the present analysis is to enlighten the chemical structure of the film, the trapping mechanism that makes it a getter for oxygen and hydrogen and the reason of its loss of effectiveness after exposure to about 100 s of hydrogen plasma. X-ray Photoelectron Spectroscopy (XPS), Secondary Ions Mass Spectrometry (SIMS) and Fourier Transform Infra Red spectroscopy in combination with the Attenuated Total Reflectance (FTIR-ATR) were used to obtain the structure and the chemical composition of graphitic samples as coated or coated and subsequently exposed to hydrogen plasma after boron deposition. The boron layers on the only coated samples were found to be amorphous hydrogenated boron carbide plus a variety of bonds like B-B, B-H, B-O, B-OH, C-C, C-H, C-O, C-OH. Both the thickness and the homogeneity of the layers were found to depend on the distance of the sample from the anode during the deposition. The samples contained oxygen along the layer thickness, at level of 5%, bound to boron. The gettering action of the boron is therefore already active during the deposition itself. The exposure to plasma caused erosion of the boron film and higher content of H and O bound to boron throughout the whole thickness. The interaction of the B layer with plasma is therefore a bulk phenomenon.

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

    PubMed Central

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

    2014-01-01

    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. PMID:24898033

  11. 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.

  12. Magnetic field dependent electro-conductivity of the graphite doped magnetorheological plastomers.

    PubMed

    Pang, Haoming; Xuan, Shouhu; Liu, Taixiang; Gong, Xinglong

    2015-09-14

    In this work we reported a novel graphite doped conductive magnetorheological plastomer (GMRP) with magnetic field dependent electro-conductivity. The conductivity of the GMRPs increased by increasing the content of the graphite particles, while it decreased with the graphite size. When the graphite content reached 15 wt%, the conductivity of GMRPs is approximately 10 000 times higher than the non-doped MRP. Because the iron particles in the GMRPs were magnetic, the conductivity of the GMRPs was magnetically sensitive. Upon applying a 780 mT magnetic field, the electric conductivity could increase about 1000 times larger than the one under zero magnetic field. A particle-particle resistance model was developed to investigate the influence of the magnetic field and graphite doping on the conductivity, and the fitting curve matched the experimental results very well. Finally, a magnetically controllable on-off switch based on GMRPs was proposed and its working mechanism was discussed. PMID:26235530

  13. Boron carbide-based coatings on graphite for plasma facing components

    SciTech Connect

    Valentine, P.G.; Trester, P.W.; Winter, J.; Linke, J.; Duwe, R.; Wallura, E.; Philipps, V.

    1994-01-01

    In the effort to evaluate boron-rich coatings as plasma facing surfaces in fusion devices, a new process for applying boron carbide (B{sub 4}C) coatings to graphite was developed. The process entails eutectic melting of the carbon (C) substrate surface with a precursor layer of B{sub 4}C particles. Adherent coatings were achieved which consisted of two layers: a surface layer and a graded penetration zone in the outer portion of the substrate. The surface-layer microstructure was multiphase and ranged from reaction-sintered structures of sintered B{sub 4}C particles in an eutectic-formed matrix to that of hypereutectic carbon particles in a B{sub 4}C-C eutectic matrix. Because of high surface energy, the coating generally developed a nonuniform thickness. Quantitative evaluations of the coating were performed with limiters in the TEXTOR fusion device and with coupons in electron beam tests. Test results revealed the following: good adherence of the coating even after remelting; and, during remelting, diagnostics detected a corresponding interaction of boron with the plasma.

  14. Hydrogen storage material and process using graphite additive with metal-doped complex hydrides

    DOEpatents

    Zidan, Ragaiy; Ritter, James A.; Ebner, Armin D.; Wang, Jun; Holland, Charles E.

    2008-06-10

    A hydrogen storage material having improved hydrogen absorbtion and desorption kinetics is provided by adding graphite to a complex hydride such as a metal-doped alanate, i.e., NaAlH.sub.4. The incorporation of graphite into the complex hydride significantly enhances the rate of hydrogen absorbtion and desorption and lowers the desorption temperature needed to release stored hydrogen.

  15. Chemical vapor deposition of boron-doped hydrogenated amorphous silicon

    SciTech Connect

    Ellis F.B. Jr.; Delahoy, A.E.

    1985-07-15

    Deposition conditions and film properties for a variety of boron-doped hydrogenated amorphous silicon films and silicon-carbon films produced by chemical vapor deposition (CVD) are discussed. Deposition gases include monosilane, disilane, trisilane, and acetylene. Two types of optically wide band-gap p layers are obtained. One of these window p layers (without carbon) has been extensively tested in photovoltaic devices. Remarkably, this p layer can be deposited between about 200 to 300 /sup 0/C. A typical open circuit voltage in an all CVD p-i-n device is 0.70--0.72 V, and in a hybrid device where the i and n layers are deposited by glow discharge, 0.8--0.83 V.

  16. Dirac cones in transition metal doped boron nitride

    SciTech Connect

    Feng, Min; Cao, Xuewei; Shao, Bin; Zuo, Xu

    2015-05-07

    The transition metal (TM) doped zinc blende boron nitride (c-BN) is studied by using the first principle calculation. TM atoms fill in the interstitials in c-BN and form two-dimensional honeycomb lattice. The generalized gradient approximation and projector augmented wave method are used. The calculated density of states and band structures show that d electrons of TM atoms form impurity bands in the gap of c-BN. When the TM-BN system is in ferromagnetic or non-magnetic state, Dirac cones emerge at the K point in Brillouin zone. When TM is Ti and Co, the Dirac cones are spin polarized and very close to the Fermi level, which makes them promising candidates of Dirac half-metal [H. Ishizuka and Y. Motome, Phys. Rev. Lett. 109, 237207 (2012)]. While TM is Ni and Cu, the system is non-magnetic and Dirac cones located above the Fermi level.

  17. The crystal structure of aluminum doped β-rhombohedral boron

    NASA Astrophysics Data System (ADS)

    Bykova, Elena; Parakhonskiy, Gleb; Dubrovinskaia, Natalia; Chernyshov, Dmitry; Dubrovinsky, Leonid

    2012-10-01

    A crystal structure of aluminum doped β-rhombohedral boron was studied by single-crystal X-ray diffraction at 80 K. The crystals were synthesized using high-pressure high temperature technique at 3 GPa and 2100 K. The structure is based on three-dimensional framework made of B12 icosahedra with voids occupied by the B28-B-B28 units, it has the R-3m space group with a=10.9014(3), c=23.7225(7) Å lattice dimensions in hexagonal setting. Aluminum atoms are located in A1 and D special positions of the β-B structure with occupancies of 82.7(6)% and 11.3(4)%, respectively. Additional boron atoms are located near the D-site. Their possible distribution is discussed. Finally we have found two appropriate structural models whose refinement suggests two possible chemical compositions, AlB44.8(5) and AlB37.8(5), which are in a good agreement with the chemical analysis data obtained from EDX. The crystal structure of AlB44.8(5) is described in detail.

  18. Effect of Boron doping on the electronic properties of the fullerenes of different sizes

    SciTech Connect

    Agnihotri, Deepak; Sharma, Hitesh

    2011-12-12

    We report the results of the effect of Boron doping in C{sub n}; n = 28, 32, 36, 40, 44, 50 and 60 using the first principle calculation based on density functional theory. The HOMO-LUMO gap changes significantly with the decreasing fullerene size below C{sub 60}, with maximum gap observed for C{sub 32}. The HOMO-LUMO gap of Boron doped fullerenes varies significantly w.r.t. pure fullerenes. Also, the gap decreases for C{sub n-m}B{sub m}X, the boron doped fullerenes with exohedral alkali metals for n = 28, 32, 36, 40, 44, 50 and 60; m = 1 to 4; X = Li, Na and K. The Mulliken charge transfer from the exohedral alkali metals towards the various fullerene cages is altered marginally by the boron doping in fullerenes and follows the order K>Na>Li.

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

    PubMed

    Susi, Toma; Pichler, Thomas; Ayala, Paola

    2015-01-01

    X-ray photoelectron spectroscopy (XPS) is one of the best tools for studying the chemical modification of surfaces, and in particular the distribution and bonding of heteroatom dopants in carbon nanomaterials such as graphene and carbon nanotubes. Although these materials have superb intrinsic properties, these often need to be modified in a controlled way for specific applications. Towards this aim, the most studied dopants are neighbors to carbon in the periodic table, nitrogen and boron, with phosphorus starting to emerge as an interesting new alternative. Hundreds of studies have used XPS for analyzing the concentration and bonding of dopants in various materials. Although the majority of works has concentrated on nitrogen, important work is still ongoing to identify its precise atomic bonding configurations. In general, care should be taken in the preparation of a suitable sample, consideration of the intrinsic photoemission response of the material in question, and the appropriate spectral analysis. If this is not the case, incorrect conclusions can easily be drawn, especially in the assignment of measured binding energies into specific atomic configurations. Starting from the characteristics of pristine materials, this review provides a practical guide for interpreting X-ray photoelectron spectra of doped graphitic carbon nanomaterials, and a reference for their binding energies that are vital for compositional analysis via XPS. PMID:25671162

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

    PubMed Central

    Pichler, Thomas; Ayala, Paola

    2015-01-01

    Summary X-ray photoelectron spectroscopy (XPS) is one of the best tools for studying the chemical modification of surfaces, and in particular the distribution and bonding of heteroatom dopants in carbon nanomaterials such as graphene and carbon nanotubes. Although these materials have superb intrinsic properties, these often need to be modified in a controlled way for specific applications. Towards this aim, the most studied dopants are neighbors to carbon in the periodic table, nitrogen and boron, with phosphorus starting to emerge as an interesting new alternative. Hundreds of studies have used XPS for analyzing the concentration and bonding of dopants in various materials. Although the majority of works has concentrated on nitrogen, important work is still ongoing to identify its precise atomic bonding configurations. In general, care should be taken in the preparation of a suitable sample, consideration of the intrinsic photoemission response of the material in question, and the appropriate spectral analysis. If this is not the case, incorrect conclusions can easily be drawn, especially in the assignment of measured binding energies into specific atomic configurations. Starting from the characteristics of pristine materials, this review provides a practical guide for interpreting X-ray photoelectron spectra of doped graphitic carbon nanomaterials, and a reference for their binding energies that are vital for compositional analysis via XPS. PMID:25671162

  1. Adsorption of hydrogen on boron-doped graphene: A first-principles prediction

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Gao, Fei; Nie, JL; Xiao, H. Y.

    2009-01-01

    The doping effects of boron on the atomic adsorption of hydrogen on graphene have been investigated using density functional theory calculations. The hydrogen adsorption energies and electronic structures have been considered for pristine and B-doped graphene with the adsorption of hydrogen on top of carbon or boron atom. It is found that the B-doping forms an electron-deficient structure, and decreases the hydrogen adsorption energy dramatically. For the adsorption of hydrogen on top of other sites, similar results also have been found. These results indicate that the hydrogen storage capacity is improved by the doping of B atom.

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

    SciTech Connect

    Jagannadham, K.; Butler, J. E.

    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.

  3. Phase change in terahertz waves emitted from differently doped graphite: The role of carrier drift

    SciTech Connect

    Irfan, Muhammad; Yim, Jong-Hyuk; Jho, Young-Dahl; Kim, Changyoung; Wook Lee, Sang

    2013-11-11

    We investigate characteristics of THz waves radiated from differently doped graphite samples excited by femtosecond laser pulses. Between n-type single-crystalline graphite and p-type polycrystalline graphite films, we observe the phase reversal of THz waves regardless of excitation energy variations around K-valley. In addition, variations in other parameters such as excitation fluence and azimuthal angle produce no changes in the phase of THz waves, which correlate well with the opposite dipole polarization between differently doped samples rather than unidirectional diffusive transport.

  4. 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 Ω·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)

  5. Induction annealing and subsequent quenching : effect on the thermoelectric properties of boron-doped nanographite ensembles.

    SciTech Connect

    Xie, M.; Lee, C. H.; Wang, J.; Yap, Y. K.; Bruno, P.; Gruen, D.; Singh, D.; Routbort, J.; Michigan Technological Univ.

    2010-01-01

    Boron-doped nanographite ensembles (NGEs) are interesting thermoelectric nanomaterials for high temperature applications. Rapid induction annealing and quenching has been applied to boron-doped NGEs using a relatively low-cost, highly reliable, laboratory built furnace to show that substantial improvements in thermoelectric power factors can be achieved using this methodology. Details of the design and performance of this compact induction furnace as well as results of the thermoelectric measurements will be reported here.

  6. Electrical Characterization of Diamond/Boron Doped Diamond Nanostructures for Use in Harsh Environment Applications

    NASA Astrophysics Data System (ADS)

    Gołuński, Ł.; Zwolski, K.; Płotka, P.

    2016-01-01

    The polycrystalline boron doped diamond (BDD) shows stable electrical properties and high tolerance for harsh environments (e.g. high temperature or aggressive chemical compounds) comparing to other materials used in semiconductor devices. In this study authors have designed electronic devices fabricated from non-intentionally (NiD) films and highly boron doped diamond structures. Presented semiconductor devices consist of highly boron doped structures grown on NiD diamond films. Fabricated structures were analyzed by electrical measurements for use in harsh environment applications. Moreover, the boron-doping level and influence of oxygen content on chemical composition of diamond films were particularly investigated. Microwave Plasma Enhanced Chemical Vapour Deposition (MW PE CVD) has been used for thin diamond films growth. Non-intentionally doped diamond (0 ppm [B]/[C]) films have been deposited on the Si/SiO2 wafers with different content of carbon, boron and oxygen in the gas phase. Then, the shape of the highly doped diamond structures were obtained by pyrolysis of SiO2 on NiD film and standard lithography process. The highly doped structures were obtained for different growth time and [B]/[C] ratio (4000 - 10000 ppm). The narrowest distance between two highly doped structures was 5pm. The standard Ti/Au ohmic contacts were deposited using physical vapour deposition for electrical characterization of NiD/BDD devices. The influence of diffusion boron from highly doped diamond into non-doped/low-doped diamond film was investigated. Surface morphology of designed structures was analyzed by Scanning Electron Microscope and optical microscope. The resistivity of the NiD and film was studied using four-point probe measurements also DC studies were done.

  7. 10B and 11B high-resolution NMR studies on boron-doped diamond

    NASA Astrophysics Data System (ADS)

    Murakami, M.; Shimizu, T.; Tansho, M.; Takano, Y.; Ishii, S.; Ekimov, E. A.; Sidorov, V. A.; Takegoshi, K.

    11B magic-angle spinning (MAS) NMR experiments are applied to B-doped diamond samples prepared by high-pressure and high-temperature methods. From the spectrum, we show that there are at least four boron signal components and the one at 28.5 ppm is ascribed to the substitutional boron in the diamond structure providing the carriers responsible for conductivity. We further apply two-dimensional (2D) NMR to examine 1H dipolar broadening and 11B- 11B boron spin diffusion, and candidates purported so far for the excess boron, that is, a boron + hydrogen complex and -B-B- and/or -B-C-B- clusters are negated. Furthermore, we show that 10B MAS NMR is useful to selectively observe the substitutional boron in the diamond structure appearing at 28.5 ppm, whose quadrupolar coupling is much smaller than that of the excess boron at 65.5 ppm.

  8. 10B and 11B high-resolution NMR studies on boron-doped diamond

    NASA Astrophysics Data System (ADS)

    Murakami, M.; Shimizu, T.; Tansho, M.; Takano, Y.; Ishii, S.; Ekimov, E. A.; Sidorov, V. A.; Takegoshi, K.

    2010-12-01

    11B magic-angle spinning (MAS) NMR experiments are applied to B-doped diamond samples prepared by high-pressure and high-temperature methods. From the spectrum, we show that there are at least four boron signal components and the one at 28.5 ppm is ascribed to the substitutional boron in the diamond structure providing the carriers responsible for conductivity. We further apply two-dimensional (2D) NMR to examine 1H dipolar broadening and 11B-11B boron spin diffusion, and candidates purported so far for the excess boron, that is, a boron + hydrogen complex and -B-B- and/or -B-C-B- clusters are negated. Furthermore, we show that 10B MAS NMR is useful to selectively observe the substitutional boron in the diamond structure appearing at 28.5 ppm, whose quadrupolar coupling is much smaller than that of the excess boron at 65.5 ppm.

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

    SciTech Connect

    Merabet, Souad

    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 <ρ{sub 200nm/c−Si}> < <ρ{sub 200nm/SiO2}> and <ρ{sub 520}> < <ρ{sub 605}>. 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.

  10. Electronic and optical properties of boron-doped nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Gajewski, W.; Achatz, P.; Williams, O. A.; Haenen, K.; Bustarret, E.; Stutzmann, M.; Garrido, J. A.

    2009-01-01

    We report on the electronic and optical properties of boron-doped nanocrystalline diamond (NCD) thin films grown on quartz substrates by CH4/H2 plasma chemical vapor deposition. Diamond thin films with a thickness below 350 nm and with boron concentration ranging from 1017 to 1021cm-3 have been investigated. UV Raman spectroscopy and atomic force microscopy have been used to assess the quality and morphology of the diamond films. Hall-effect measurements confirmed the expected p -type conductivity. At room temperature, the conductivity varies from 1.5×10-8Ω-1cm-1 for a nonintentionally doped film up to 76Ω-1cm-1 for a heavily B -doped film. Increasing the doping level results in a higher carrier concentration while the mobility decreases from 1.8 down to 0.2cm2V-1s-1 . For NCD films with low boron concentration, the conductivity strongly depends on temperature. However, the conductivity and the carrier concentration are no longer temperature dependent for films with the highest boron doping and the NCD films exhibit metallic properties. Highly doped films show superconducting properties with critical temperatures up to 2 K. The critical boron concentration for the metal-insulator transition is in the range from 2×1020 up to 3×1020cm-3 . We discuss different transport mechanisms to explain the influence of the grain boundaries and boron doping on the electronic properties of NCD films. Valence-band transport dominates at low boron concentration and high temperatures, whereas hopping between boron acceptors is the dominant transport mechanism for boron-doping concentration close to the Mott transition. Grain boundaries strongly reduce the mobility for low and very high doping levels. However, at intermediate doping levels where hopping transport is important, grain boundaries have a less pronounced effect on the mobility. The influence of boron and the effect of grain boundaries on the optoelectronic properties of the NCD films are examined using spectrally resolved photocurrent measurements and photothermal deflection spectroscopy. Major differences occur in the low energy range, between 0.5 and 1.0 eV, where both boron impurities and the sp2 carbon phase in the grain boundaries govern the optical absorption.

  11. 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.

  12. 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.

  13. Nitrogen-doped graphene by ball-milling graphite with melamine for energy conversion and storage

    NASA Astrophysics Data System (ADS)

    Xue, Yuhua; Chen, Hao; Qu, Jia; Dai, Liming

    2015-12-01

    N-doped graphene was prepared by ball milling of graphite with melamine. It was found that ball-milling reduced the size of graphite particles from 30 to 1 μm and facilitated the exfoliation of the resultant small particles into few-layer N-doped graphene nanosheets under ultrasonication. The as-prepared N-doped graphene nanoplatelets (NGnPs) exhibited a nitrogen content as high as 11.4 at.%, making them attractive as efficient electrode materials in supercapacitors for energy storage and as highly-active metal-free catalysts for oxygen reduction in fuel cells for energy conversion.

  14. 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. AFOSR MURI No. 105800

  15. Fabrication and characterization of boron-doped nanocrystalline diamond-coated MEMS probes

    NASA Astrophysics Data System (ADS)

    Bogdanowicz, Robert; Sobaszek, Michał; Ficek, Mateusz; Kopiec, Daniel; Moczała, Magdalena; Orłowska, Karolina; Sawczak, Mirosław; Gotszalk, Teodor

    2016-04-01

    Fabrication processes of thin boron-doped nanocrystalline diamond (B-NCD) films on silicon-based micro- and nano-electromechanical structures have been investigated. B-NCD films were deposited using microwave plasma assisted chemical vapour deposition method. The variation in B-NCD morphology, structure and optical parameters was particularly investigated. The use of truncated cone-shaped substrate holder enabled to grow thin fully encapsulated nanocrystalline diamond film with a thickness of approx. 60 nm and RMS roughness of 17 nm. Raman spectra present the typical boron-doped nanocrystalline diamond line recorded at 1148 cm-1. Moreover, the change in mechanical parameters of silicon cantilevers over-coated with boron-doped diamond films was investigated with laser vibrometer. The increase of resonance to frequency of over-coated cantilever is attributed to the change in spring constant caused by B-NCD coating. Topography and electrical parameters of boron-doped diamond films were investigated by tapping mode AFM and electrical mode of AFM-Kelvin probe force microscopy (KPFM). The crystallite-grain size was recorded at 153 and 238 nm for boron-doped film and undoped, respectively. Based on the contact potential difference data from the KPFM measurements, the work function of diamond layers was estimated. For the undoped diamond films, average CPD of 650 mV and for boron-doped layer 155 mV were achieved. Based on CPD values, the values of work functions were calculated as 4.65 and 5.15 eV for doped and undoped diamond film, respectively. Boron doping increases the carrier density and the conductivity of the material and, consequently, the Fermi level.

  16. Structure and superconductivity of isotope-enriched boron-doped diamond

    SciTech Connect

    Thompson, Joe D; Ekimov, E A; Sidorov, V A; Zoteev, A; Lebed, Y; Stishov, S M

    2008-01-01

    Superconducting boron-doped diamond samples were synthesized with isotopes of {sup 10}B, {sup 11}B, {sup 13}C and {sup 12}C. We claim the presence of a carbon isotope effect on the superconducting transition temperature, which supports the 'diamond-carbon'-related nature of superconductivity and the importance of the electron-phonon interaction as the mechanism of superconductivity in diamond. Isotope substitution permits us to relate almost all bands in the Raman spectra of heavily boron-doped diamond to the vibrations of carbon atoms. The 500 cm{sup 01} Raman band shifts with either carbon or boron isotope substitution and may be associated with vibrations of paired or clustered boron. The absence of a superconducting transition (down to 1.6 K) in diamonds synthesized in the Co-C-B system at 1900 K correlates with the small boron concentration deduced from lattice parameters.

  17. 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.

  18. Efficient electron emitter utilizing boron-doped diamond tips with sp 2 content

    NASA Astrophysics Data System (ADS)

    Wisitsora-at, A.; Kang, W. P.; Davidson, J. L.; Li, Q.; Xu, J. F.; Kerns, D. V.

    1999-05-01

    A practical technique to enhance the electron emission of diamond tips by incorporation of boron dopant and sp 2 content is reported. The effects of boron doping on electron field emission from an array of micro-patterned polycrystalline pyramidal diamond microtips with varying sp 2 content have been systematically studied. The field emission characteristics of undoped and boron-doped diamond tips are significantly improved by increasing sp 2 content of diamond tips. By increasing sp 2 content, the turn-on electric field can be reduced more than 50% for both undoped and boron-doped diamond tips. Likewise, the turn-on electric field of the diamond tips with higher sp 2 content decreases substantially with boron doping. A new field emission mechanism, that is, an increase in the field enhancement factor due to hole accumulation via the formation of cascaded sp 2-diamond-sp 2 embedded microstructures in diamond tips, is a possible explanation for the enhanced effects of boron doping and sp 2 content on the diamond field emission characteristics.

  19. 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.

  20. 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.

  1. The effect of substrate temperature and growth rate on the doping efficiency of single crystal boron doped diamond

    SciTech Connect

    Demlow, SN; Rechenberg, R; Grotjohn, T

    2014-10-01

    The substrate growth temperature dependence of the plasma gas-phase to solid-phase doping efficiency in single crystal, boron doped diamond (BDD) deposition is investigated. Single crystal diamond (SCD) is grown by microwave plasma assisted chemical vapor deposition (MPACVD) on high pressure, high temperature (HPHT) type Ib substrates. Samples are grown at substrate temperatures of 850-950 degrees C for each of five doping concentration levels, to determine the effect of the growth temperature on the doping efficiency and defect morphology. The substrate temperature during growth is shown to have a significant effect on the grown sample defect morphology, and a temperature dependence of the doping efficiency is also shown. The effect of the growth rate on the doping efficiency is discussed, and the ratio of the boron concentration in the gas phase to the flux of carbon incorporated into the solid diamond phase is shown to be a more predictive measure of the resulting boron concentration than the gas phase boron to carbon ratio that is more commonly reported. (C) 2014 Elsevier B.V. All rights reserved.

  2. Suppression of boron-oxygen defects in Czochralski silicon by carbon co-doping

    SciTech Connect

    Wu, Yichao; Yu, Xuegong He, Hang; Chen, Peng; Yang, Deren

    2015-03-09

    We have investigated the influence of carbon co-doping on the formation of boron-oxygen defects in Czochralski silicon. It is found that carbon can effectively suppress the formation of boron-oxygen defects. Based on our experiments and first-principle theoretical calculations, it is believed that this effect is attributed to the formation of more energetically favorable carbon-oxygen complexes. Moreover, the diffusion of oxygen dimers in carbon co-doped silicon also becomes more difficult. All these phenomena should be associated with the tensile stress field induced by carbon doping in silicon.

  3. Electronic and optical properties of pure and doped boron-nitride nanotube

    NASA Astrophysics Data System (ADS)

    Roknabadi, M. R.; Ghodrati, M.; Modarresi, M.; Koohjani, F.

    2013-02-01

    Band structure of the carbon doped zigzag boron nitride nanotubes (BNNTs) is calculated by a simple tight-binding model. It was found that the doping effect of B-substituted and N-substituted BNNT is different and carbon substitution for either boron or nitrogen in BNNTs reduces the band gap. Investigations show the dependence of band gap to the axial magnetic and transverse electric fields for C-doped BNNTs. The applied high electric field causes transition from semiconductor to conductor in C-doped BNNTs. The band gap of C-doped BNNTs oscillates as a function of magnetic flux with period ∅°in the magnetic fields. Influence of C-doping on the absorption spectrum is also discussed in this paper.

  4. Boron- and phosphorus-doped polycrystalline silicon thin films prepared by silver-induced layer exchange

    SciTech Connect

    Antesberger, T.; Wassner, T. A.; Jaeger, C.; Algasinger, M.; Kashani, M.; Scholz, M.; Matich, S.; Stutzmann, M.

    2013-05-27

    Intentional boron and phosphorus doping of polycrystalline silicon thin films on glass prepared by the silver-induced layer exchange is presented. A silver/(titanium) oxide/amorphous silicon stack is annealed at temperatures below the eutectic temperature of the Ag/Si system, leading to a complete layer exchange and simultaneous crystallization of the amorphous silicon. Intentional doping of the amorphous silicon prior to the exchange process results in boron- or phosphorus-doped polycrystalline silicon. Hall effect measurements show carrier concentrations between 2 Multiplication-Sign 10{sup 17} cm{sup -3} and 3 Multiplication-Sign 10{sup 20} cm{sup -3} for phosphorus and 4 Multiplication-Sign 10{sup 18} cm{sup -3} to 3 Multiplication-Sign 10{sup 19} cm{sup -3} for boron-doped layers, with carrier mobilities up to 90 cm{sup 2}/V s.

  5. 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

  6. Boron doped defective graphene as a potential anode material for Li-ion batteries.

    PubMed

    Hardikar, Rahul P; Das, Deya; Han, Sang Soo; Lee, Kwang-Ryeol; Singh, Abhishek K

    2014-08-21

    Graphene with large surface area and robust structure has been proposed as a high storage capacity anode material for Li ion batteries. While the inertness of pristine graphene leads to better Li kinetics, poor adsorption leads to Li clustering, significantly affecting the performance of the battery. Here, we show the role of defects and doping in achieving enhanced adsorption without compromising on the high diffusivity of Li. Using first principles density functional theory (DFT) calculations, we carry out a comprehensive study of diffusion kinetics of Li over the plane of the defective structures and calculate the change in the number of Li atoms in the vicinity of defects, with respect to pristine graphene. Our results show that the Li-C interaction, storage capacity and the energy barriers depend sensitively on the type of defects. The un-doped and boron doped mono-vacancy, doped di-vacancy up to two boron, one nitrogen doped di-vacancy, and Stone-Wales defects show low energy barriers that are comparable to pristine graphene. Furthermore, boron doping at mono-vacancy enhances the adsorption of Li. In particular, the two boron doped mono-vacancy graphene shows both a low energy barrier of 0.31 eV and better adsorption, and hence can be considered as a potential candidate for anode material. PMID:24986702

  7. A NMR Study of BORON-11 in Boron Nitride, Boron Phosphide, Tetraboron Carbide and Boron-Doped Silicon.

    NASA Astrophysics Data System (ADS)

    Han, Duk-Young

    1990-01-01

    Pulsed-NMR is used to investigate the atomic environments of B^{11} in various boron compounds. The B^{11} nucleus whose spin is 3/2 has a quadrupole moment which reacts to an electric field gradient present around the nucleus. If the quadrupolar interaction is strong and the electric field gradients have a random orientation, signals from sidebands will be lost, leaving a signal only from the central transition. The central transition is broadened by the quadrupolar interaction only in second order. There has been no theoretical treatment to include the line-broadening effect of the second-order quadrupolar interaction in addition to the first-order effect. It is shown that the second-order quadrupolar interaction can be easily expressed with the fictitious spin-1/2 operators. We also observed hitherto unexplained echoes whose features can be explained with the fictitious spin-1/2 operator formalism. This echo is different from the one which is due to the first-order effect of the quadrupolar interaction. Since the second-order quadrupolar interaction we observed behaves like the magnetic inhomogeneity which is responsible for the Hahn spin echo, we call it "Hahn echo in solids". The technique developed here can be applied to any half-integer nucleus under similar physical circumstances.

  8. 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

  9. 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

  10. 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.

  11. Surface passivation of heavily boron or phosphorus doped crystalline silicon utilizing amorphous silicon

    NASA Astrophysics Data System (ADS)

    Carstens, K.; Dahlinger, M.

    2016-05-01

    Excellent surface passivation of heavily boron or phosphorus doped crystalline silicon is presented utilizing undoped hydrogenated amorphous silicon (a-Si:H). For passivating boron doped crystalline silicon surfaces, amorphous silicon needs to be deposited at low temperatures 150°C ≤Tdep≤200°C , leading to a high bandgap. In contrast, low bandgap amorphous silicon causes an inferior surface passivation of highly boron doped crystalline silicon. Boron doping in crystalline silicon leads to a shift of the Fermi energy towards the valence band maximum in the undoped a-Si:H. A simulation, implementing dangling bond defects according to the defect pool model, shows this shift in the undoped a-Si:H passivation to be more pronounced if the a-Si:H has a lower bandgap. Hence, the inferior passivation of boron doped surfaces with low bandgap amorphous silicon stems from a lower silicon-hydrogen bond energy due to this shift of the Fermi energy. Hydrogen effusion and ellipsometry measurements support our interpretation.

  12. Formation of Boron-Carbon Nanosheets and Bilayers in Boron-Doped Diamond: Origin of Metallicity and Superconductivity.

    PubMed

    Polyakov, S N; Denisov, V N; Mavrin, B N; Kirichenko, A N; Kuznetsov, M S; Martyushov, S Yu; Terentiev, S A; Blank, V D

    2016-12-01

    The insufficient data on a structure of the boron-doped diamond (BDD) has frustrated efforts to fully understand the fascinating electronic properties of this material and how they evolve with doping. We have employed X-ray diffraction and Raman scattering for detailed study of the large-sized BDD single crystals. We demonstrate a formation of boron-carbon (B-C) nanosheets and bilayers in BDD with increasing boron concentration. An incorporation of two boron atoms in the diamond unit cell plays a key role for the B-C nanosheets and bilayer formation. Evidence for these B-C bilayers which are parallel to {111} planes is provided by the observation of high-order, super-lattice reflections in X-ray diffraction and Laue patterns. B-C nanosheets and bilayers minimize the strain energy and affect the electronic structure of BDD. A new shallow acceptor level associated with B-C nanosheets at ~37 meV and the spin-orbit splitting of the valence band of ~6 meV are observed in electronic Raman scattering. We identified that the superconducting transitions occur in the (111) BDD surfaces only. We believe that the origin of Mott and superconducting transitions is associated with the two-dimensional (2D) misfit layer structure of BDD. A model for the BDD crystal structure, based on X-ray and Raman data, is proposed and confirmed by density functional theoretical calculation. PMID:26754937

  13. Formation of Boron-Carbon Nanosheets and Bilayers in Boron-Doped Diamond: Origin of Metallicity and Superconductivity

    NASA Astrophysics Data System (ADS)

    Polyakov, S. N.; Denisov, V. N.; Mavrin, B. N.; Kirichenko, A. N.; Kuznetsov, M. S.; Martyushov, S. Yu; Terentiev, S. A.; Blank, V. D.

    2016-01-01

    The insufficient data on a structure of the boron-doped diamond (BDD) has frustrated efforts to fully understand the fascinating electronic properties of this material and how they evolve with doping. We have employed X-ray diffraction and Raman scattering for detailed study of the large-sized BDD single crystals. We demonstrate a formation of boron-carbon (B-C) nanosheets and bilayers in BDD with increasing boron concentration. An incorporation of two boron atoms in the diamond unit cell plays a key role for the B-C nanosheets and bilayer formation. Evidence for these B-C bilayers which are parallel to {111} planes is provided by the observation of high-order, super-lattice reflections in X-ray diffraction and Laue patterns. B-C nanosheets and bilayers minimize the strain energy and affect the electronic structure of BDD. A new shallow acceptor level associated with B-C nanosheets at 37 meV and the spin-orbit splitting of the valence band of 6 meV are observed in electronic Raman scattering. We identified that the superconducting transitions occur in the (111) BDD surfaces only. We believe that the origin of Mott and superconducting transitions is associated with the two-dimensional (2D) misfit layer structure of BDD. A model for the BDD crystal structure, based on X-ray and Raman data, is proposed and confirmed by density functional theoretical calculation.

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

    SciTech Connect

    Yin, H.; Ziemann, P.

    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.

  15. Effect of nitrogen on the growth of boron doped single crystal diamond

    SciTech Connect

    Karna, Sunil; Vohra, Yogesh

    2013-11-18

    Boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) Type Ib diamond substrates using microwave plasma assisted chemical vapor deposition. A modification in surface morphology of the film with increasing boron concentration in the plasma has been observed using atomic force microscopy. Use of nitrogen during boron doping has been found to improve the surface morphology and the growth rate of films but it lowers the electrical conductivity of the film. The Raman spectra indicated a zone center optical phonon mode along with a few additional bands at the lower wavenumber regions. The change in the peak profile of the zone center optical phonon mode and its downshift were observed with the increasing boron content in the film. Furthermore, sharpening and upshift of Raman line was observed in the film that was grown in presence of nitrogen along with diborane in process gas.

  16. Effect of nitrogen on the growth of boron doped single crystal diamond

    DOE PAGESBeta

    Karna, Sunil; Vohra, Yogesh

    2013-11-18

    Boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) Type Ib diamond substrates using microwave plasma assisted chemical vapor deposition. A modification in surface morphology of the film with increasing boron concentration in the plasma has been observed using atomic force microscopy. Use of nitrogen during boron doping has been found to improve the surface morphology and the growth rate of films but it lowers the electrical conductivity of the film. The Raman spectra indicated a zone center optical phonon mode along with a few additional bands at the lower wavenumber regions. The change in the peak profilemore » of the zone center optical phonon mode and its downshift were observed with the increasing boron content in the film. Furthermore, sharpening and upshift of Raman line was observed in the film that was grown in presence of nitrogen along with diborane in process gas.« less

  17. Silicon doped boron carbide nanorod growth via a solid-liquid-solid process

    SciTech Connect

    Han Weiqiang

    2006-03-27

    Here we report the synthesis of silicon doped boron carbide (Si-doped B{sub 4}C) nanorods via a solid reaction using activated carbon, boron, and silicon powder as reactants. These nanorods have been studied by high-resolution transmission electron microscopy, scanning electron microscopy, electron energy loss spectroscopy, and energy-dispersive x-ray spectrometry. The diameter of Si-doped B{sub 4}C nanorods ranges from 15 to 70 nm. The length of Si-doped B{sub 4}C nanorods is up to 30 {mu}m. Ni{sub x}Co{sub y}B{sub z} nanoparticles are used as catalysts for the growth of Si-doped B{sub 4}C nanorods. A solid-liquid-solid growth mechanism is proposed.

  18. Properties and electrochemical characteristics of boron-doped multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tsierkezos, Nikos G.; Ritter, Uwe; Nugraha Thaha, Yudi; Krischok, Stefan; Himmerlich, Marcel; Downing, Clive

    2015-10-01

    Boron-doped multi-walled carbon nanotubes were synthesized upon decomposition of ethyl alcohol and boric acid via chemical vapor deposition. The boron-doped nanotubes were treated with hydrochloric acid and were characterized by means of scanning electron and transmission electron microscopy in conjunction with energy-dispersive X-ray spectrometry and X-ray photoelectron spectroscopy. The electrochemistry of ferrocyanide/ferricyanide on boron-doped nanotubes was studied in temperature range of 283.15-303.15 K. The findings exhibit an improvement of films' current response and kinetics of electron transfer with the rise in temperature. The kinetics for electron transfer enhances and the redox process occurs slightly more spontaneously upon acid treatment.

  19. Critical boron-doping levels for generation of dislocations in synthetic diamond

    SciTech Connect

    Alegre, M. P. Araújo, D.; Pinero, J. C.; Lloret, F.; Villar, M. P.; Fiori, A.; Achatz, P.; Chicot, G.; Bustarret, E.; Jomard, F.

    2014-10-27

    Defects induced by boron doping in diamond layers were studied by transmission electron microscopy. The existence of a critical boron doping level above which defects are generated is reported. This level is found to be dependent on the CH{sub 4}/H{sub 2} molar ratios and on growth directions. The critical boron concentration lied in the 6.5–17.0 × 10{sup 20}at/cm{sup 3} range in the 〈111〉 direction and at 3.2 × 10{sup 21 }at/cm{sup 3} for the 〈001〉 one. Strain related effects induced by the doping are shown not to be responsible. From the location of dislocations and their Burger vectors, a model is proposed, together with their generation mechanism.

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

    SciTech Connect

    Lou, Xianchun; Zhao, Xiujian; He, Xin

    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)

  1. 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 μm 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

  2. 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.

  3. Boron-Doped Silicon Diatom Frustules as a Photocathode for Water Splitting.

    PubMed

    Chandrasekaran, Soundarrajan; Macdonald, Thomas J; Gerson, Andrea R; Nann, Thomas; Voelcker, Nicolas H

    2015-08-12

    An effective solar-powered silicon device for hydrogen production from water splitting is a priority in light of diminishing fossil fuel vectors. There is increasing demand for nanostructuring in silicon to improve its antireflective properties for efficient solar energy conversion. Diatom frustules are naturally occurring biosilica nanostructures formed by biomineralizing microalgae. Here, we demonstrate magnesiothermic conversion of boron-doped silica diatom frustules from Aulacoseira sp. into nanostructured silicon with retention of the original shape. Hydrogen production was achieved for boron-doped silicon diatom frustules coated with indium phosphide nanocrystal layers and an iron sulfur carbonyl electrocatalyst. PMID:26192101

  4. Thermal shock resistance of thick boron-doped diamond under extreme heat loads

    NASA Astrophysics Data System (ADS)

    De Temmerman, G.; Dodson, J.; Linke, J.; Lisgo, S.; Pintsuk, G.; Porro, S.; Scarsbrook, G.

    2011-05-01

    Thick free-standing boron-doped diamonds were prepared by microwave plasma assisted chemical vapour deposition. Samples with a final thickness close to 5 mm and with lateral dimensions 25 × 25 mm were produced. The thermal shock resistance of the material was tested by exposure in the JUDITH electron gun to reproduce the conditions expected in a fusion reactor during plasma instabilities. Boron-doped diamond is shown to exhibit thermal shock resistance far better than current material of choice for a fusion reactor like tungsten, with no surface damage after exposure to 100 cycles at 2.5 GW m-2 for 5 ms.

  5. Dynamics of formation of Ru, Os, Ir and Au metal nanocrystals on doped graphitic surfaces.

    PubMed

    Pitto-Barry, Anaïs; Sadler, Peter J; Barry, Nicolas P E

    2016-03-11

    The fabrication of precious metal (ruthenium, osmium, gold, and iridium) nanocrystals from single atoms has been studied in real-time. The dynamics of the first stage of the metal nanocrystallisation on a doped (B,S)-graphitic surface are identified, captured, and reported. PMID:26698913

  6. Synthesis of ultra dispersed graphite-like structures doped with nitrogen in supersonic carbon plasma flow

    NASA Astrophysics Data System (ADS)

    Sivkov, A.; Pak, A.; Shanenkov, I.; Kolganova, J.; Shatrova, K.

    2014-10-01

    In this paper the synthesis of ultra dispersed graphite-like structures doped with nitrogen by using a magneto plasma accelerator is shown. The synthesis of such structures is realized during supersonic carbon plasma jet flowing into the chamber filled with the nitrogen atmosphere. Plasma jet is generated by coaxial magneto plasma accelerator (CMPA) based on graphite electrode system. The CMPA is supplied from the pulsed capacitive energy storage with the maximum value of stored energy of 360 kJ. Electrical and energy parameters of plasma flow are recorded during experiment. According to X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) methods obtained particles with well seen triangle sectors are graphite-like carbon structures doped with nitrogen atoms. This is confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses in which carbon- nitrogen bonding configurations have been identified.

  7. New Pathways and Metrics for Enhanced, Reversible Hydrogen Storage in Boron-Doped Carbon Nanospaces

    SciTech Connect

    Pfeifer, Peter; Wexler, Carlos; Hawthorne, M. Frederick; Lee, Mark W.; Jalistegi, Satish S.

    2014-08-14

    This project, since its start in 2007—entitled “Networks of boron-doped carbon nanopores for low-pressure reversible hydrogen storage” (2007-10) and “New pathways and metrics for enhanced, reversible hydrogen storage in boron-doped carbon nanospaces” (2010-13)—is in support of the DOE's National Hydrogen Storage Project, as part of the DOE Hydrogen and Fuel Cells Program’s comprehensive efforts to enable the widespread commercialization of hydrogen and fuel cell technologies in diverse sectors of the economy. Hydrogen storage is widely recognized as a critical enabling technology for the successful commercialization and market acceptance of hydrogen powered vehicles. Storing sufficient hydrogen on board a wide range of vehicle platforms, at energy densities comparable to gasoline, without compromising passenger or cargo space, remains an outstanding technical challenge. Of the main three thrust areas in 2007—metal hydrides, chemical hydrogen storage, and sorption-based hydrogen storage—sorption-based storage, i.e., storage of molecular hydrogen by adsorption on high-surface-area materials (carbons, metal-organic frameworks, and other porous organic networks), has emerged as the most promising path toward achieving the 2017 DOE storage targets of 0.055 kg H2/kg system (“5.5 wt%”) and 0.040 kg H2/liter system. The objective of the project is to develop high-surface-area carbon materials that are boron-doped by incorporation of boron into the carbon lattice at the outset, i.e., during the synthesis of the material. The rationale for boron-doping is the prediction that boron atoms in carbon will raise the binding energy of hydro- gen from 4-5 kJ/mol on the undoped surface to 10-14 kJ/mol on a doped surface, and accordingly the hydro- gen storage capacity of the material. The mechanism for the increase in binding energy is electron donation from H2 to electron-deficient B atoms, in the form of sp2 boron-carbon bonds. Our team is proud to have demonstrated the predicted increase in binding energy experimentally, currently at ~10 kJ/mol. The synthetic route for incorporation of boron at the outset is to create appropriately designed copoly- mers, with a boron-free and a boron-carrying monomer, followed by pyrolysis of the polymer, yielding a bo- ron-substituted carbon scaffold in which boron atoms are bonded to carbon atoms by synthesis. This is in contrast to a second route (funded by DE-FG36-08GO18142) in which first high-surface area carbon is cre- ated and doped by surface vapor deposition of boron, with incorporation of the boron into the lattice the final step of the fabrication. The challenge in the first route is to create high surface areas without compromising sp2 boron-carbon bonds. The challenge in the second route is to create sp2 boron-carbon bonds without com- promising high surface areas.

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

    NASA Astrophysics Data System (ADS)

    Matsumura, Hideki; Hayakawa, Taro; Ohta, Tatsunori; Nakashima, Yuki; Miyamoto, Motoharu; Thi, Trinh Cham; Koyama, Koichi; Ohdaira, Keisuke

    2014-09-01

    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 (PH3) or diborane (B2H6) 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 1018 to 1019 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.

  9. Biocompatibility of nanostructured boron doped diamond for the attachment and proliferation of human neural stem cells

    NASA Astrophysics Data System (ADS)

    Taylor, Alice C.; Vagaska, Barbora; Edgington, Robert; Hébert, Clément; Ferretti, Patrizia; Bergonzo, Philippe; Jackman, Richard B.

    2015-12-01

    Objective. We quantitatively investigate the biocompatibility of chemical vapour deposited (CVD) nanocrystalline diamond (NCD) after the inclusion of boron, with and without nanostructuring. The nanostructuring method involves a novel approach of growing NCD over carbon nanotubes (CNTs) that act as a 3D scaffold. This nanostructuring of BNCD leads to a material with increased capacitance, and this along with wide electrochemical window makes BNCD an ideal material for neural interface applications, and thus it is essential that their biocompatibility is investigated. Approach. Biocompatibility was assessed by observing the interaction of human neural stem cells (hNSCs) with a variety of NCD substrates including un-doped ones, and NCD doped with boron, which are both planar, and nanostructured. hNSCs were chosen due to their sensitivity, and various methods including cell population and confluency were used to quantify biocompatibility. Main results. Boron inclusion into NCD film was shown to have no observable effect on hNSC attachment, proliferation and viability. Furthermore, the biocompatibility of nanostructured boron-doped NCD is increased upon nanostructuring, potentially due to the increased surface area. Significance. Diamond is an attractive material for supporting the attachment and development of cells as it can show exceptional biocompatibility. When boron is used as a dopant within diamond it becomes a p-type semiconductor, and at high concentrations the diamond becomes quasi-metallic, offering the prospect of a direct electrical device-cell interfacing system.

  10. Ultrasensitive gas detection of large-area boron-doped graphene.

    PubMed

    Lv, Ruitao; Chen, Gugang; Li, Qing; McCreary, Amber; Botello-Méndez, Andrés; Morozov, S V; Liang, Liangbo; Declerck, Xavier; Perea-López, Nestor; Cullen, David A; Feng, Simin; Elías, Ana Laura; Cruz-Silva, Rodolfo; Fujisawa, Kazunori; Endo, Morinobu; Kang, Feiyu; Charlier, Jean-Christophe; Meunier, Vincent; Pan, Minghu; Harutyunyan, Avetik R; Novoselov, Konstantin S; Terrones, Mauricio

    2015-11-24

    Heteroatom doping is an efficient way to modify the chemical and electronic properties of graphene. In particular, boron doping is expected to induce a p-type (boron)-conducting behavior to pristine (nondoped) graphene, which could lead to diverse applications. However, the experimental progress on atomic scale visualization and sensing properties of large-area boron-doped graphene (BG) sheets is still very scarce. This work describes the controlled growth of centimeter size, high-crystallinity BG sheets. Scanning tunneling microscopy and spectroscopy are used to visualize the atomic structure and the local density of states around boron dopants. It is confirmed that BG behaves as a p-type conductor and a unique croissant-like feature is frequently observed within the BG lattice, which is caused by the presence of boron-carbon trimers embedded within the hexagonal lattice. More interestingly, it is demonstrated for the first time that BG exhibits unique sensing capabilities when detecting toxic gases, such as NO2 and NH3, being able to detect extremely low concentrations (e.g., parts per trillion, parts per billion). This work envisions that other attractive applications could now be explored based on as-synthesized BG. PMID:26575621

  11. Ultrasensitive gas detection of large-area boron-doped graphene

    PubMed Central

    Lv, Ruitao; Chen, Gugang; Li, Qing; McCreary, Amber; Botello-Méndez, Andrés; Morozov, S. V.; Declerck, Xavier; Perea-López, Nestor; Cullen, David A.; Feng, Simin; Elías, Ana Laura; Cruz-Silva, Rodolfo; Fujisawa, Kazunori; Endo, Morinobu; Kang, Feiyu; Charlier, Jean-Christophe; Meunier, Vincent; Pan, Minghu; Harutyunyan, Avetik R.; Novoselov, Konstantin S.; Terrones, Mauricio

    2015-01-01

    Heteroatom doping is an efficient way to modify the chemical and electronic properties of graphene. In particular, boron doping is expected to induce a p-type (boron)-conducting behavior to pristine (nondoped) graphene, which could lead to diverse applications. However, the experimental progress on atomic scale visualization and sensing properties of large-area boron-doped graphene (BG) sheets is still very scarce. This work describes the controlled growth of centimeter size, high-crystallinity BG sheets. Scanning tunneling microscopy and spectroscopy are used to visualize the atomic structure and the local density of states around boron dopants. It is confirmed that BG behaves as a p-type conductor and a unique croissant-like feature is frequently observed within the BG lattice, which is caused by the presence of boron-carbon trimers embedded within the hexagonal lattice. More interestingly, it is demonstrated for the first time that BG exhibits unique sensing capabilities when detecting toxic gases, such as NO2 and NH3, being able to detect extremely low concentrations (e.g., parts per trillion, parts per billion). This work envisions that other attractive applications could now be explored based on as-synthesized BG. PMID:26575621

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

    SciTech Connect

    Akazawa, Housei

    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.

  13. Growth and electrical characterisation of {delta}-doped boron layers on (111) diamond surfaces

    SciTech Connect

    Edgington, Robert; Jackman, Richard B.; Sato, Syunsuke; Ishiyama, Yuichiro; Kawarada, Hiroshi; Morris, Richard

    2012-02-01

    A plasma enhanced chemical vapor deposition protocol for the growth of {delta}-doping of boron in diamond is presented, using the (111) diamond plane as a substrate for diamond growth. AC Hall effect measurements have been performed on oxygen terminated {delta}-layers and desirable sheet carrier densities ({approx}10{sup 13} cm{sup -2}) for field-effect transistor application are reported with mobilities in excess of what would expected for equivalent but thicker heavily boron-doped diamond films. Temperature-dependent impedance spectroscopy and secondary ion mass spectroscopy measurements show that the grown layers have metallic-like electrical properties with high cut-off frequencies and low thermal impedance activation energies with estimated boron concentrations of approximately 10{sup 20} cm{sup -3}.

  14. 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

  15. Visible and Infra-red Light Emission in Boron-Doped Wurtzite Silicon Nanowires

    PubMed Central

    Fabbri, Filippo; Rotunno, Enzo; Lazzarini, Laura; Fukata, Naoki; Salviati, Giancarlo

    2014-01-01

    Silicon, the mainstay semiconductor in microelectronic circuitry, is considered unsuitable for optoelectronic applications owing to its indirect electronic band gap, which limits its efficiency as a light emitter. Here we show the light emission properties of boron-doped wurtzite silicon nanowires measured by cathodoluminescence spectroscopy at room temperature. A visible emission, peaked above 1.5 eV, and a near infra-red emission at 0.8 eV correlate respectively to the direct transition at the Γ point and to the indirect band-gap of wurtzite silicon. We find additional intense emissions due to boron intra-gap states in the short wavelength infra-red range. We present the evolution of the light emission properties as function of the boron doping concentration and the growth temperature. PMID:24398782

  16. 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.

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

    DOEpatents

    Corman, Gregory Scot; Luthra, Krishan Lal

    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.

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

    DOEpatents

    Corman, Gregory Scot; Luthra, Krishan Lal

    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.

  19. 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.

  20. 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.

  1. Sulfur-doped graphene via thermal exfoliation of graphite oxide in H2S, SO2, or CS2 gas.

    PubMed

    Poh, Hwee Ling; Šimek, Petr; Sofer, Zdeněk; Pumera, Martin

    2013-06-25

    Doping of graphene with heteroatoms is an effective way to tailor its properties. Here we describe a simple and scalable method of doping graphene lattice with sulfur atoms during the thermal exfoliation process of graphite oxides. The graphite oxides were first prepared by Staudenmaier, Hofmann, and Hummers methods followed by treatments in hydrogen sulfide, sulfur dioxide, or carbon disulfide. The doped materials were characterized by scanning electron microscopy, high-resolution X-ray photoelectron spectroscopy, combustible elemental analysis, and Raman spectroscopy. The ζ-potential and conductivity of sulfur-doped graphenes were also investigated in this paper. It was found that the level of doping is more dramatically influenced by the type of graphite oxide used rather than the type of sulfur-containing gas used during exfoliation. Resulting sulfur-doped graphenes act as metal-free electrocatalysts for an oxygen reduction reaction. PMID:23656223

  2. 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

    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 (PH₃) or diborane (B₂H₆) 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 10¹⁸ to 10¹⁹cm⁻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.

  3. 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

  4. π-Ring currents in doped coronenes with nitrogen and boron: diatropic-paratropic duality.

    PubMed

    Cuesta, Inmaculada García; Pownall, Barnaby; Pelloni, Stefano; Sánchez de Merás, Alfredo M

    2015-10-14

    The change in the electronic structure of coronene upon doping with nitrogen or boron has been theoretically studied by means of its magnetic properties and magnetic field induced current density maps. The addition of two atoms of nitrogen or boron to the central ring of coronene causes a drastic variation in the delocalization of π-electrons, which does not depend on its nature but instead on its position. Then, doping in the para position makes coronene more aromatic while doping in the meta position makes it to become antiaromatic. The magnetic behavior of the pristine molecule is characterized by two concentric currents flowing in opposite senses that are converted into hemi-perimetric currents in the ortho and meta isomers, so dividing the molecule into aromatic and antiaromatic regions. The paratropic and diatropic ring currents of the coronene moiety may, therefore, be modulated through the position of the heteroatom and, consequently, also the localized/delocalized behavior. PMID:26343535

  5. Boron doping to diamond and DLC using plasma immersion ion implantation

    SciTech Connect

    Ikegami, T.; Grotjohn; Reinhard, D.; Asmussen, J.

    1997-12-31

    Controlling carriers in diamond by doping is important to realize diamond electronic devices with advanced electrical characteristics. As a doping method the Plasma Immersion Ion Implantation (PIII) has been gathering attention due to its excellence in making shallow, highly doped regions over large areas, and its high dose rate, good dose controllability and isotropic doping properties. The authors have begun to investigate boron doping of diamond, silicon and diamond-like carbon films using PIII. As a doping source they use the plasma sputtering of a solid boron carbide (B{sub 4}C) target instead of toxic gas source like diborane (B{sub 2}H{sub 6}). The B{sub 4}C target of 1-in. diameter and a substrate (Si, diamond or diamond-like carbon film) are located in the downtown region of an ECR plasma produced by the microwave plasma disc reactor (MPDR) filled with 1--5 mTorr Ar gas. In order to sputter the target a negative self bias from {minus}400V to {minus}700V is induced by applying RF (13.56 MHz) power of 50--200W to the target holder. For boron ion implantation, negative pulses of {minus}1kV to {minus}8kV, 1--5{micro}s pulse duration, 1--200Hz repetition rate are applied to the substrate holder using a voltage pulser which consists of high voltage capacitors and MOSFETs. After thermal treatment of the doped materials their electrical resistivity are measured using the four-probe method. Details of both the PIII source and substrate doping experimental results are shown at the meeting.

  6. Fabrication of vertically aligned diamond whiskers from highly boron-doped diamond by oxygen plasma etching.

    PubMed

    Terashima, Chiaki; Arihara, Kazuki; Okazaki, Sohei; Shichi, Tetsuya; Tryk, Donald A; Shirafuji, Tatsuru; Saito, Nagahiro; Takai, Osamu; Fujishima, Akira

    2011-02-01

    Conductive diamond whiskers were fabricated by maskless oxygen plasma etching on highly boron-doped diamond substrates. The effects of the etching conditions and the boron concentration in diamond on the whisker morphology and overall substrate coverage were investigated. High boron-doping levels (greater than 8.4 × 10(20) cm(-3)) are crucial for the formation of the nanosized, densely packed whiskers with diameter of ca. 20 nm, length of ca. 200 nm, and density of ca. 3.8 × 10(10) cm(-2) under optimal oxygen plasma etching conditions (10 min at a chamber pressure of 20 Pa). Confocal Raman mapping and scanning electron microscopy illustrate that the boron distribution in the diamond surface region is consistent with the distribution of whisker sites. The boron dopant atoms in the diamond appear to lead to the initial fine column formation. This simple method could provide a facile, cost-effective means for the preparation of conductive nanostructured diamond materials for electrochemical applications as well as electron emission devices. PMID:21214209

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

    NASA Astrophysics Data System (ADS)

    Koçyiğit, Serhat; Aytimur, Arda; Çınar, Emre; Uslu, İbrahim; 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.

  8. Spatial Control of Laser-Induced Doping Profiles in Graphene on Hexagonal Boron Nitride.

    PubMed

    Neumann, Christoph; Rizzi, Leo; Reichardt, Sven; Terrés, Bernat; Khodkov, Timofiy; Watanabe, Kenji; Taniguchi, Takashi; Beschoten, Bernd; Stampfer, Christoph

    2016-04-13

    We present a method to create and erase spatially resolved doping profiles in graphene-hexagonal boron nitride heterostructures. The technique is based on photoinduced doping by a focused laser beam and does neither require masks nor photoresists. This makes our technique interesting for rapid prototyping of unconventional electronic device schemes, where the spatial resolution of the rewritable, long-term stable doping profiles is limited by only the laser spot size (≈600 nm) and the accuracy of sample positioning. Our optical doping method offers a way to implement and to test different, complex doping patterns in one and the very same graphene device, which is not achievable with conventional gating techniques. PMID:26986938

  9. Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields

    NASA Astrophysics Data System (ADS)

    Kondo, Takahiro; Guo, Donghui; Shikano, Taishi; Suzuki, Tetsuya; Sakurai, Masataka; Okada, Susumu; Nakamura, Junji

    2015-11-01

    Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms.

  10. Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields

    PubMed Central

    Kondo, Takahiro; Guo, Donghui; Shikano, Taishi; Suzuki, Tetsuya; Sakurai, Masataka; Okada, Susumu; Nakamura, Junji

    2015-01-01

    Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms. PMID:26549618

  11. N-doped graphitic layer encased cobalt nanoparticles as efficient oxygen reduction catalysts in alkaline media

    NASA Astrophysics Data System (ADS)

    Han, Ce; Bo, Xiangjie; Zhang, Yufan; Li, Mian; Nsabimana, Anaclet; Guo, Liping

    2015-03-01

    Nitrogen doped graphitic layer encased cobalt (N-C@Co) nanoparticles, as novel non-precious-metal catalysts for the oxygen reduction reaction (ORR), were fabricated by a facile method using cyanamide and cobalt nitrate as precursors. The N-C@Co catalysts exhibited comparable catalytic performance, better stability and improved methanol tolerance towards the ORR than those of the commercial Pt/C catalyst.Nitrogen doped graphitic layer encased cobalt (N-C@Co) nanoparticles, as novel non-precious-metal catalysts for the oxygen reduction reaction (ORR), were fabricated by a facile method using cyanamide and cobalt nitrate as precursors. The N-C@Co catalysts exhibited comparable catalytic performance, better stability and improved methanol tolerance towards the ORR than those of the commercial Pt/C catalyst. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07571d

  12. Magnetism of Co doped graphitic ZnO layers adsorbed on Si and Ag surfaces

    NASA Astrophysics Data System (ADS)

    Fernandes, Marcelo; Schmidt, Tome M.

    2013-09-01

    The effect of the substrate on Co doped graphitic ZnO layers adsorbed on metallic and semiconductor surfaces are investigated. The first principles results reveal that the magnetic interactions are strongly affected by the substrate. While graphitic layers of ZnO:Co on the well controlled metallic Ag(111) surface present weak ferromagnetic stability, on the semiconductor Si(111) surface they are strongly ferromagnetic coupled. The presence of metallic states in ZnO:Co adsorbed on Ag(111) surface favors a superexchange mechanism, weakening the ferromagnetic interaction. On the other hand, the magnetism of few layers of ZnO:Co on Si(111) surface is governed by a direct exchange mechanism, favoring a ferromagnetic coupling. This confined II-VI system doped with transition metal on a semiconductor surface presents higher magnetic stability than III-V nanostructures, and it is desired for nanostructured oxide/semiconductor room temperature ferromagnetism, using silicon technology.

  13. Effects of hole doping by neutron irradiation of magnetic field induced electronic phase transitions in graphite

    SciTech Connect

    Singleton, John; Yaguchi, Hiroshi

    2008-01-01

    We have investigated effects of hole doping by fast-neutron irradiation on the magnetic-field induced phase transitions in graphite using specimens irradiated with fast neutrons. Resistance measurements have been done in magnetic fields of up to above 50 T and at temperatures down to about 1.5 K. The neutron irradiation creates lattice defects acting as acceptors, affecting the imbalance of the electron and hole densities and the Fermi level. We have found that the reentrant field from the field induced state back to the normal state shifts towards a lower field with hole doping, suggestive of the participation of electron subbands in the magnetic-field induced state.

  14. Boron

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Boron is an essential micronutrient element required for plant growth. Boron deficiency is wide-spread in crop plants throughout the world especially in coarse-textured soils in humid areas. Boron toxicity can also occur, especially in arid regions under irrigation. Plants respond directly to the...

  15. Catalytic doping of phosphorus and boron atoms on hydrogenated amorphous silicon films

    NASA Astrophysics Data System (ADS)

    Seto, Junichi; Ohdaira, Keisuke; Matsumura, Hideki

    2016-04-01

    We investigate the low-temperature doping of phosphorus (P) and boron (B) atoms on hydrogenated amorphous silicon (a-Si:H) films by catalytic doping (Cat-doping). The conductivity of a-Si:H films increases as catalyzer temperature (T cat) increases, and the increase in conductivity is accompanied by a significant reduction in activation energy obtained from the Arrhenius plot of the conductivity. Secondary ion mass spectrometry (SIMS) measurement reveals that Cat-doped P and B atoms exist within ˜10-15 nm from the a-Si:H film surface, indicating that the shallow doping of P and B atoms is realized on a-Si:H films similarly to the case of Cat-doping on crystalline Si (c-Si) wafers. We also confirm no additional film deposition during Cat-doping. These results suggest that decomposed species are effectively doped on a-Si:H films similarly to the case of Cat-doping on c-Si.

  16. Effects of Oxidation on Oxidation-Resistant Graphite

    SciTech Connect

    Windes, William; Smith, Rebecca; Carroll, Mark

    2015-05-01

    The Advanced Reactor Technology (ART) Graphite Research and Development Program is investigating doped nuclear graphite grades that exhibit oxidation resistance through the formation of protective oxides on the surface of the graphite material. In the unlikely event of an oxygen ingress accident, graphite components within the VHTR core region are anticipated to oxidize so long as the oxygen continues to enter the hot core region and the core temperatures remain above 400°C. For the most serious air-ingress accident which persists over several hours or days the continued oxidation can result in significant structural damage to the core. Reducing the oxidation rate of the graphite core material during any air-ingress accident would mitigate the structural effects and keep the core intact. Previous air oxidation testing of nuclear-grade graphite doped with varying levels of boron-carbide (B4C) at a nominal 739°C was conducted for a limited number of doped specimens demonstrating a dramatic reduction in oxidation rate for the boronated graphite grade. This report summarizes the conclusions from this small scoping study by determining the effects of oxidation on the mechanical strength resulting from oxidation of boronated and unboronated graphite to a 10% mass loss level. While the B4C additive did reduce mechanical strength loss during oxidation, adding B4C dopants to a level of 3.5% or more reduced the as-fabricated compressive strength nearly 50%. This effectively minimized any benefits realized from the protective film formed on the boronated grades. Future work to infuse different graphite grades with silicon- and boron-doped material as a post-machining conditioning step for nuclear components is discussed as a potential solution for these challenges in this report.

  17. Electrochemical mineralization pathway of quinoline by boron-doped diamond anodes.

    PubMed

    Wang, Chunrong; Ma, Keke; Wu, Tingting; Ye, Min; Tan, Peng; Yan, Kecheng

    2016-04-01

    Boron-doped diamond anodes were selected for quinoline mineralization, and the resulting intermediates, phenylpropyl aldehyde, phenylpropionic acid, and nonanal were identified and followed during quinoline oxidation by gas chromatography-mass spectrometry and high-performance liquid chromatography. The evolutions of formic acid, acetic acid, oxalic acid, NO2(-), NO3(-), and NH4(+) were quantified. A new reaction pathway for quinoline mineralization by boron-doped diamond anodes has been proposed, where the pyridine ring in quinoline is cleaved by a hydroxyl radical giving phenylpropyl aldehyde and NH4(+). Phenylpropyl aldehyde is quickly oxidized into phenylpropionic acid, and the benzene ring is cleaved giving nonanal. This is further oxidized to formic acid, acetic acid, and oxalic acid. Finally, these organic intermediates are mineralized to CO2 and H2O. NH4(+) is also oxidized to NO2(-) and on to NO3(-). The results will help to gain basic reference for clearing intermediates and their toxicity. PMID:26855227

  18. Detection of Several Carbohydrates Using Boron-doped Diamond Electrodes Modified with Nickel Hydroxide Nanoparticles.

    PubMed

    Teixeira, Milena E; Sedenho, Graziela C; Stradiotto, Nelson R

    2015-01-01

    In this work the electrooxidations of glucose, galactose, mannose, rhamnose, xylose and arabinose are studied at a nickel hydroxide nanoparticle modified boron-doped diamond electrode and compared to an unmodified electrode. These carbohydrates are very important in the second-generation ethanol production process. Nickel hydroxide modified boron-doped diamond was characterized by scanning electron microscopy and energy dispersive X-ray. Electrochemical impedance spectroscopy was employed to study the interface properties of surface-modified electrodes in the absence and presence of the carbohydrates. Limits of detection were 5.3 × 10(-5), 6.8 × 10(-5), 2.7 × 10(-4), 6.9 × 10(-5), 8.8 × 10(-5) and 2.6 × 10(-5) mol L(-1) for glucose, galactose, mannose, rhamnose, arabinose, xylose, respectively. PMID:26256600

  19. Communication: Towards catalytic nitric oxide reduction via oligomerization on boron doped graphene

    NASA Astrophysics Data System (ADS)

    Cantatore, Valentina; Panas, Itai

    2016-04-01

    We use density functional theory to describe a novel way for metal free catalytic reduction of nitric oxide NO utilizing boron doped graphene. The present study is based on the observation that boron doped graphene and O—N=N—O- act as Lewis acid-base pair allowing the graphene surface to act as a catalyst. The process implies electron assisted N=N bond formation prior to N—O dissociation. Two N2 + O2 product channels, one of which favoring N2O formation, are envisaged as outcome of the catalytic process. Besides, we show also that the N2 + O2 formation pathways are contrasted by a side reaction that brings to N3O3- formation and decomposition into N2O + NO2-.

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

    SciTech Connect

    Jana, Sunirmal; Vuk, Angela Surca; Mallick, Aparajita; Orel, Boris; Biswas, Prasanta Kumar

    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.

  1. Magnetic states and optical properties of single-layer carbon-doped hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    We show that carbon-doped hexagonal boron nitride (h-BN) has extraordinary properties with many possible applications. We demonstrate that the substitution-induced impurity states, associated with carbon atoms, and their interactions dictate the electronic structure and properties of C-doped h-BN. Furthermore, we show that stacking of localized impurity states in small C clusters embedded in h-BN forms a set of discrete energy levels in the wide gap of h-BN. The electronic structures of these C clusters have a plethora of applications in optics, magneto-optics, and opto-electronics.

  2. Large gauge factor of hot wire chemical vapour deposition in-situ boron doped polycrystalline silicon

    NASA Astrophysics Data System (ADS)

    Grech, David; Tarazona, Antulio; De Leon, Maria Theresa; Kiang, Kian S.; Zekonyte, Jurgita; Wood, Robert J. K.; Chong, Harold M. H.

    2016-04-01

    Polysilicon piezoresistors with a large longitudinal gauge factor (GF) of 44 have been achieved using in-situ boron doped hot-wire chemical vapour deposition (HWCVD). This GF is a consequence of a high quality p-type doped polysilicon with a crystal volume of 97% and an average grain size of 150 nm, estimated using Raman spectroscopy and atomic force microscopy (AFM) respectively. The measured minimum Hooge factor associated to the 1/f noise of the polysilicon piezoresistors is 1.4 × 10‑3. These results indicate that HWCVD polysilicon is a suitable piezoresistive material for micro-electro-mechanical systems (MEMS) applications.

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

    SciTech Connect

    Zieliński, A.; Ryl, J.; Burczyk, L.; Darowicki, K.

    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 μm 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.

  4. 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.

  5. Hydrogenation effects on carrier transport in boron-doped ultrananocrystalline diamond/amorphous carbon films prepared by coaxial arc plasma deposition

    SciTech Connect

    Katamune, Yūki Takeichi, Satoshi; Ohmagari, Shinya; Yoshitake, Tsuyoshi

    2015-11-15

    Boron-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were deposited by coaxial arc plasma deposition with a boron-blended graphite target at a base pressure of <10{sup −3} Pa and at hydrogen pressures of ≤53.3 Pa. The hydrogenation effects on the electrical properties of the films were investigated in terms of chemical bonding. Hydrogen-scattering spectrometry showed that the maximum hydrogen content was 35 at. % for the film produced at 53.3-Pa hydrogen pressure. The Fourier-transform infrared spectra showed strong absorptions by sp{sup 3} C–H bonds, which were specific to the UNCD/a-C:H, and can be attributed to hydrogen atoms terminating the dangling bonds at ultrananocrystalline diamond grain boundaries. Temperature-dependence of the electrical conductivity showed that the films changed from semimetallic to semiconducting with increasing hydrogen pressure, i.e., with enhanced hydrogenation, probably due to hydrogenation suppressing the formation of graphitic bonds, which are a source of carriers. Carrier transport in semiconducting hydrogenated films can be explained by a variable-range hopping model. The rectifying action of heterojunctions comprising the hydrogenated films and n-type Si substrates implies carrier transport in tunneling.

  6. Electrochemical properties of boron-doped ordered mesoporous carbon as electrocatalyst and Pt catalyst support.

    PubMed

    Nsabimana, Anaclet; Bo, Xiangjie; Zhang, Yufan; Li, Mian; Han, Ce; Guo, Liping

    2014-08-15

    The electrochemical properties of boron-doped ordered mesoporous carbon (BOMC) as an electrode material and Pt catalyst support were investigated. The BOMC was synthesized and its structure was examined by transmission electron microscopy (TEM), scanning electron microscopy, nitrogen adsorption-desorption, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). More defective sites were introduced into OMC by the doping of boron. Six electroactive compounds were employed to investigate their electrochemical responses on BOMC and OMC modified glassy carbon electrodes. The BOMC, with more defective sites, exhibited high activity toward the electroactive compounds. The property of BOMC of supporting platinum nanoparticle catalyst was examined. Pt nanoparticles were loaded onto BOMC and OMC, and this was confirmed by TEM, XPS and thermogravimetric analysis. Pt nanoparticles with an average diameter of 2.62 nm were deposited on BOMC. The doping of boron into OMC facilitates the dispersion of Pt nanoparticles. Pt nanoparticles supported on BOMC (Pt-BOMC) and Pt nanoparticles supported on OMC (Pt-OMC) were electrochemically characterized. The electrocatalytic activity of Pt-BOMC toward methanol oxidation reaction was compared with that of Pt-OMC and commercial Pt-C catalyst. The results show that the electrocatalytic activity of BOMC is significantly higher than that of other used catalysts. PMID:24910045

  7. Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems

    PubMed Central

    Martinez, Ulises; Dumont, Joseph H.; Holby, Edward F.; Artyushkova, Kateryna; Purdy, Geraldine M.; Singh, Akhilesh; Mack, Nathan H.; Atanassov, Plamen; Cullen, David A.; More, Karren L.; Chhowalla, Manish; Zelenay, Piotr; Dattelbaum, Andrew M.; Mohite, Aditya D.; Gupta, Gautam

    2016-01-01

    Graphitic materials are essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstrate superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Further, durability testing showed E½ retention >95% in N2- and O2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media. PMID:27034981

  8. Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems.

    PubMed

    Martinez, Ulises; Dumont, Joseph H; Holby, Edward F; Artyushkova, Kateryna; Purdy, Geraldine M; Singh, Akhilesh; Mack, Nathan H; Atanassov, Plamen; Cullen, David A; More, Karren L; Chhowalla, Manish; Zelenay, Piotr; Dattelbaum, Andrew M; Mohite, Aditya D; Gupta, Gautam

    2016-03-01

    Graphitic materials are essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstrate superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E ½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Further, durability testing showed E ½ retention >95% in N2- and O2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media. PMID:27034981

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

    SciTech Connect

    Lokhande, B.J.; Ambare, R.C.; Mane, R.S.; Bharadwaj, S.R.

    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 Ω 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.

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

    PubMed

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

    2016-08-15

    Graphitic carbon nitride (GCN) is a promising metal-free photocatalyst while suffering from low charge mobility induced inefficient photocatalysis. In this work, oxygen doping was employed to enhance the photodegradation of organic pollutants in water on graphitic carbon nitride (GCNO) under visible light. For further absorption extension, four organic dyes (Eosin-Y, Perylene, Nile-red and Coumarin) were adopted to dye-sensitize the GCNO photocatalyst. It was found that O-doping can promote dye sensitization, which was dependent on the type of dyes and influenced the photodegradation efficiencies of methylene blue (MB) and phenol. Nile-red sensitized GCNO presented the best activity in MB degradation under λ>480nm irradiations while Eosin-Y showed the best sensitization performance for phenol degradation under λ>420nm light source. However, dye sensitization was not effective for enhanced pollutant degradation on GCN without O-doping. UV-vis diffuse reflectance spectra (UV-vis DRS), photoluminescence (PL) spectra, and photocurrent analyses were applied to investigate the mechanism of carriers' transfer, which indicated that dye molecules could inject extra electrons into GCNO energy band and the energy dislocation could suppress electron/hole recombination, enhancing photocatalytic performances. PMID:27218807

  11. Lewis Basicity of Nitrogen-Doped Graphite Observed by CO2 Chemisorption

    NASA Astrophysics Data System (ADS)

    Kiuchi, Hisao; Shibuya, Riku; Kondo, Takahiro; Nakamura, Junji; Niwa, Hideharu; Miyawaki, Jun; Kawai, Maki; Oshima, Masaharu; Harada, Yoshihisa

    2016-03-01

    The characteristics of CO2 adsorption sites on a nitrogen-doped graphite model system (N-HOPG) were investigated by X-ray photoelectron and absorption spectroscopy and infrared reflection absorption spectroscopy. Adsorbed CO2 was observed lying flat on N-HOPG, stabilized by a charge transfer from the substrate. This demonstrated that Lewis base sites were formed by the incorporation of nitrogen via low-energy nitrogen-ion sputtering. The possible roles of twofold coordinated pyridinic N and threefold coordinated valley N (graphitic N) sites in Lewis base site formation on N-HOPG are discussed. The presence of these nitrogen species focused on the appropriate interaction strength of CO2 indicates the potential to fine-tune the Lewis basicity of carbon-based catalysts.

  12. Cobalt monoxide-doped porous graphitic carbon microspheres for supercapacitor application

    PubMed Central

    Yang, Zheng-Chun; Tang, Chun-Hua; Zhang, Yu; Gong, Hao; Li, Xu; Wang, John

    2013-01-01

    A novel design and facile synthesis process for carbon based hybrid materials, i.e., cobalt monoxide (CoO)-doped graphitic porous carbon microspheres (Co-GPCMs), have been developed. With the synthesis strategy, the mixture of cobalt gluconate, α-cyclodextrin and poly (ethylene oxide)106-poly (propylene oxide)70-poly (ethylene oxide)106 is treated hydrothermally, followed by pyrolysis in argon. The resultant Co-GPCMs exhibits a porous carbon matrix with localized graphitic structure while CoO nanodots are embedded in the carbon frame. Thus, the Co-GPCMs effectively combine the electric double-layer capacitance and pseudo-capacitance when used as the electrode in supercapacitor, which lead to a higher operation voltage (1.6 V) and give rise to a significantly higher energy density. This study provides a new research strategy for electrode materials in high energy density supercapacitors. PMID:24113335

  13. Lewis Basicity of Nitrogen-Doped Graphite Observed by CO2 Chemisorption.

    PubMed

    Kiuchi, Hisao; Shibuya, Riku; Kondo, Takahiro; Nakamura, Junji; Niwa, Hideharu; Miyawaki, Jun; Kawai, Maki; Oshima, Masaharu; Harada, Yoshihisa

    2016-12-01

    The characteristics of CO2 adsorption sites on a nitrogen-doped graphite model system (N-HOPG) were investigated by X-ray photoelectron and absorption spectroscopy and infrared reflection absorption spectroscopy. Adsorbed CO2 was observed lying flat on N-HOPG, stabilized by a charge transfer from the substrate. This demonstrated that Lewis base sites were formed by the incorporation of nitrogen via low-energy nitrogen-ion sputtering. The possible roles of twofold coordinated pyridinic N and threefold coordinated valley N (graphitic N) sites in Lewis base site formation on N-HOPG are discussed. The presence of these nitrogen species focused on the appropriate interaction strength of CO2 indicates the potential to fine-tune the Lewis basicity of carbon-based catalysts. PMID:26951127

  14. NMR Study of Heavily Doped SILICON:BORON

    NASA Astrophysics Data System (ADS)

    Fuller, Scott Edward

    Pulsed nuclear magnetic resonance (NMR) has been used to study the hyperfine interactions in powdered Si:B. Samples from a variety of sources were examined to confirm the generality of our results. Room temperature carrier concentrations varied from about 3.4 times 10 ^{18} to 5.1 times 10^{19} cm ^{-3}. NMR measurements were carried out on the nuclei B^{11} and Si^{29} over a temperature range from 93 K to 463 K and an applied field strength of 8.0 T and 5.5 T. The B^{11} NMR frequency shift exhibits a Curie-like temperature dependence. A strong concentration dependence to the shift was observed. Lower concentration samples showed a more rapid rise in frequency than higher concentration samples as the temperature was lowered. Shift measurements on the highest concentration sample showed a linear dependence on applied field at lower temperatures. The Si^{29} NMR frequency showed relatively no shift over the same temperature range. B^{11} NMR in cubic NaBH_4 also showed no shift, thus ruling out the probe as a source of the shift. Both the B^{11} and Si^{29} line widths increase with decreasing temperature. We attribute all of the Si^{29} temperature dependence to a distribution of paramagnetic moments localized on a small fraction of the boron sites. Part of the B ^{11} line width temperature dependence is due a similar mechanism; other parts remain unexplained. The Si^{29}^in -lattice relaxation is due to interaction with itinerant carriers and shows a Korringa enhancement ranging from 7 to 10, possibly due to disorder. The B^ {11}^in-lattice relaxation rate is not linear in temperature in the two lower concentration samples, and is presumably associated with paramagnetic fluctuations localized on the boron sites. Relaxation in the highest concentration sample is due to interaction with itinerant carriers. We suggest that the source of the paramagnetism is transitory local moments which form on every boron site with a lifetime, tau_{rm loc}, such that T_1{rm (elec)} prec tau_{rm loc} prec 1/(2Deltaomega_ {rm sep}). T_1{ rm (elec)} is the electron spin-lattice relaxation time and Deltaomega_ {rm sep} is the separation in angular frequency space between the resonance frequency of the B^0 (paramagnetic) and the B ^{-}(diamagnetic) states. The observed shift is caused by a weighted average of the local magnetic fields at the B^0 and B ^{-} sites.

  15. Amperometric glucose biosensor based on boron-doped carbon nanotubes modified electrode.

    PubMed

    Chen, Xiaoli; Chen, Jinhua; Deng, Chunyan; Xiao, Chunhui; Yang, Yanmin; Nie, Zhou; Yao, Shouzhuo

    2008-08-15

    Doped carbon nanotubes are now extremely attractive and important nanomaterials in bioanalytical applications due to their unique physicochemical properties. In this paper, the boron-doped carbon nanotubes (BCNTs) were used in amperometric biosensors. It has been found that the electrocatalytic activity of the BCNTs modified glassy carbon (GC) electrode toward the oxidation of hydrogen peroxide is much higher than that of the un-doped CNTs modified electrode due to the large amount of edge sites and oxygen-rich groups located at the defective sites induced by boron doping. Glucose oxidase (GOD) was selected as the model enzyme and immobilized on the BCNTs modified glassy carbon electrode by entrapping GOD into poly(o-aminophenol) film. The performance of the sensor was investigated by electrochemical methods. At an optimum potential of +0.60 V and pH 7.0, the biosensor exhibits good characteristics, such as high sensitivity (171.2 nA mM(-1)), low detection limit (3.6 microM), short response time (within 6s), satisfactory anti-interference ability and good stability. The apparent Michaelis-Menten constant (K(m)(app)) is 15.19 mM. The applicability to the whole blood analysis of the enzyme electrode was also evaluated. PMID:18656655

  16. 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.

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

    SciTech Connect

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

    2014-09-15

    The oxygen precipitation of highly (17.5 mΩ cm) and moderately (4.5 Ω 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 ρ is enhanced by a factor of 8 as compared to the moderately doped sample. The influence of a high B concentration on ρ 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 σ with those found at 900 °C in a previous publication.

  18. 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 mΩ cm) and moderately (4.5 Ω 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 ρ is enhanced by a factor of 8 as compared to the moderately doped sample. The influence of a high B concentration on ρ 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 σ with those found at 900 °C in a previous publication.

  19. 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.

  20. Boron-doped graphene quantum dots for selective glucose sensing based on the "abnormal" aggregation-induced photoluminescence enhancement.

    PubMed

    Zhang, Li; Zhang, Zhi-Yi; Liang, Ru-Ping; Li, Ya-Hua; Qiu, Jian-Ding

    2014-05-01

    A hydrothermal approach for the cutting of boron-doped graphene (BG) into boron-doped graphene quantum dots (BGQDs) has been proposed. Various characterizations reveal that the boron atoms have been successfully doped into graphene structures with the atomic percentage of 3.45%. The generation of boronic acid groups on the BGQDs surfaces facilitates their application as a new photoluminescence (PL) probe for label free glucose sensing. It is postulated that the reaction of the two cis-diol units in glucose with the two boronic acid groups on the BGQDs surfaces creates structurally rigid BGQDs-glucose aggregates, restricting the intramolecular rotations and thus resulting in a great boost in the PL intensity. The present unusual "aggregation-induced PL increasing" sensing process excludes any saccharide with only one cis-diol unit, as manifested by the high specificity of BGQDs for glucose over its close isomeric cousins fructose, galactose, and mannose. It is believed that the doping of boron can introduce the GQDs to a new kind of surface state and offer great scientific insights to the PL enhancement mechanism with treatment of glucose. PMID:24708154

  1. Electrocatalytic oxygen activation by carbanion intermediates of nitrogen-doped graphitic carbon.

    PubMed

    Li, Qiqi; Noffke, Benjamin W; Wang, Yilun; Menezes, Bruna; Peters, Dennis G; Raghavachari, Krishnan; Li, Liang-shi

    2014-03-01

    Nitrogen-doped graphitic carbon has been intensively studied for potential use as an electrocatalyst in fuel cells for the oxygen reduction reaction (ORR). However, the lack of a mechanistic understanding on the carbon catalysis has severely hindered the progress of the catalyst development. Herein we use a well-defined graphene nanostructure as a model system and, for the first time, reveal an oxygen activation mechanism that involves carbanion intermediates in these materials. Our work shows that the overpotential of the electrocatalytic ORR is determined by the generation of the carbanion intermediates, and the current by the rate the intermediates activate oxygen. PMID:24533901

  2. Suggestions regarding thermal diffusivity measurements on pyrolytic graphite and pyrolytic boron nitride by the laser pulse method

    NASA Astrophysics Data System (ADS)

    He, G. H.; Zhang, X. Z.; Wei, Z.; Dong, S. Q.; di, Z. Q.; Zhou, B. L.

    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 inconspicuously 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°C) and PBN (below 1000°C) are given.

  3. Carbon doping induced peculiar transport properties of boron nitride nanoribbons p-n junctions

    SciTech Connect

    Liu, N.; Gao, G. Y.; Zhu, S. C.; Ni, Y.; Wang, S. L.; Yao, K. L.; Liu, J. B.

    2014-07-14

    By applying nonequilibrium Green's function combined with density functional theory, we investigate the electronic transport properties of carbon-doped p-n nanojunction based on hexagonal boron nitride armchair nanoribbons. The calculated I-V curves show that both the center and edge doping systems present obvious negative differential resistance (NDR) behavior and excellent rectifying effect. At low positive bias, the edge doping systems possess better NDR performance with larger peak-to-valley ratio (∼10{sup 5}), while at negative bias, the obtained peak-to-valley ratio for both of the edge and center doping systems can reach the order of 10{sup 7}. Meanwhile, center doping systems present better rectifying performance than the edge doping ones, and giant rectification ratio up to 10{sup 6} can be obtained in a wide bias range. These outstanding transport properties are explained by the evolution of the transmission spectra and band structures with applied bias, together with molecular projected self-consistent Hamiltonian eigenvalues and eigenstates.

  4. Study of different thermal processes on boron-doped PERL cells

    NASA Astrophysics Data System (ADS)

    Li, Wenjia; Wang, Zhenjiao; Han, Peiyu; Lu, Hongyan; Yang, Jian; Guo, Ying; Shi, Zhengrong; Li, Guohua

    2014-08-01

    In this paper, three kinds of thermal processes for boron-doped PERL cells were investigated. These are the forming gas annealing (FGA), the rapid thermal (RTP) and the low temperature annealing processes. FGA was introduced after laser ablation and doping in order to increase minority carrier lifetime by hydrogenating the trapping centers. Subsequent evaluation revealed considerable enhancement of minority carrier lifetime (from 150 μs to 240 μs) and the implied Voc (from 660 mV to 675 mV). After aluminum sputtering, three actual peak temperatures (370 °C, 600 °C and 810 °C) of RTP (as it occurs in the compressed air environment used in our experiment) were utilized to form a contact between the metal and the semi-conductor. It is concluded that only low temperature (lower than 600 °C) firing could create boron back surface field and high quality rear reflector. Lastly, a method of improving the performance of finished PERL cells which did not experience high temperature (over 800 °C) firing was investigated. Finished cells undergone low temperature annealing in N2 atmosphere at 150 °C for 15 min produced 0.44% absolute increase in PERL cells. The enhancement of low temperature annealing originally comes from the activation of passivated boron which is deactivated during FGA.

  5. Novel band gap-tunable K-Na co-doped graphitic carbon nitride prepared by molten salt method

    NASA Astrophysics Data System (ADS)

    Zhao, Jiannan; Ma, Lin; Wang, Haoying; Zhao, Yanfeng; Zhang, Jian; Hu, Shaozheng

    2015-03-01

    Novel band gap-tunable K-Na co-doped graphitic carbon nitride was prepared by molten salt method using melamine, KCl, and NaCl as precursor. X-ray diffraction (XRD), N2 adsorption, Scanning electron microscope (SEM), UV-vis spectroscopy, Photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared catalysts. The CB and VB potentials of graphitic carbon nitride could be tuned from -1.09 and +1.55 eV to -0.29 and +2.25 eV by controlling the weight ratio of eutectic salts to melamine. Besides, ions doping inhibited the crystal growth of graphitic carbon nitride, enhanced the surface area, and increased the separation rate of photogenerated electrons and holes. The visible-light-driven Rhodamine B (RhB) photodegradation and mineralization performances were significantly improved after K-Na co-doping.

  6. 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.

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

    SciTech Connect

    Liu, Guanglong; Liao, Shuijiao; College of Basic Sciences of Huazhong Agricultural University, Wuhan 430070 ; Zhu, Duanwei; Liu, Linghua; Cheng, Dongsheng; Zhou, Huaidong

    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.

  8. Boron and hydrogen bonding in B-doped a-Si:H ? an NMR study

    NASA Astrophysics Data System (ADS)

    Greenbaum, S. G.; Carlos, W. E.; Taylor, P. C.

    1983-03-01

    11B and 1H NMR measurements performed on boron-doped films of a-Si:H prepared by glow discharge are reported. A sample containing 10 atomic % B exhibits two distinct boron sites, both of them being threefold coordinated. A second sample containing 0.7 atomic % B shows only one boron site, also threefold coordinated. Measurements of the 11B spin-spin relaxation time T 2 indicate that the boron sites are clustered in both the 10% B and 0.7% B materials. The temperature dependence of the 1H spin-lattice relaxation time T 1 in the 10% B film does not exhibit the sharp T 1 minimum commonly observed in undoped a-Si:H films prepared by glow discharge. Suppression of the T 1 minimum in the B-containing material is explained in terms of a spin diffusion bottleneck in the relaxation pathway of the Si- or B-bonded protons in the film.

  9. Boron

    MedlinePlus

    ... form of boron, inside the vagina to treat yeast infections. People also apply boric acid to the ... acid, used inside the vagina, can successfully treat yeast infections (candidiasis), including infections that do not seem ...

  10. The diffusion of hydrogen monomers on hole-doped graphitic lattices: over-barrier transition and quantum tunneling

    NASA Astrophysics Data System (ADS)

    Huang, Liang Feng; Ni, Mei Yan; Zeng, Zhi

    2011-11-01

    The diffusion of hydrogen and deuterium monomers on hole-doped graphene (a planar graphitic lattice), the outside wall and the inside wall of hole-doped (6, 0) single-walled carbon nanotubes (a curved graphitic lattice) was investigated using density functional theory and density functional perturbation theory. The jump frequencies for the over-barrier transition and phonon-assisted quantum tunneling were calculated by transition state theory and small-polaron theory, respectively. The effects of the local curvature of the surface and the hole doping on the thermodynamic and kinetic properties of a hydrogen monomer on these graphitic lattices are discussed. Our results demonstrate that it is sufficient to judge the diffusional mobility of a hydrogen monomer on graphitic lattices from just the over-barrier transition, no matter how much it is curved and hole doped, while the quantum tunneling can be safely neglected because it is significantly suppressed by the covalent bonding of hydrogen with the graphitic lattice.

  11. Synthesis of doped fullerenes

    SciTech Connect

    Compton, R.N.; Ying, Z.C.; Hettich, R.L.

    1996-12-31

    The Smalley-Haufler method of laser ablation of graphite mixed with other elements in a heated ({approximately} 1000{degrees}C) rare gas is employed to generate doped fullerenes (e.g., C{sub 56}B{sub 4}) and endohedral fullerenes (e.g., La@C{sub 60}). Laser ablation of graphite in heated nitrogen gas produces C{sub 59} N and C{sub 69} N dimers as evidence by laser desorption mass spectral studies showing C{sub 59}N{sup +} and C{sub 69}N{sup +} ions. Laser ablation of boron nitride yields elemental boron, BN tubules and BN nested fullerenes.

  12. 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.

  13. Modeling and simulation of boron-doped nanocrystalline silicon carbide thin film by a field theory.

    PubMed

    Xiong, Liming; Chen, Youping; Lee, James D

    2009-02-01

    This paper presents the application of a multiscale field theory in modeling and simulation of boron-doped nanocrystalline silicon carbide (B-SiC). The multiscale field theory was briefly introduced. Based on the field theory, numerical simulations show that intergranular glassy amorphous films (IGFs) and nano-sized pores exist in triple junctions of the grains for nanocrystalline B-SiC. Residual tensile stress in the SiC grains and compressive stress on the grain boundaries (GBs) were observed. Under tensile loading, it has been found that mechanical response of 5 wt% boron-SiC exhibits five characteristic regimes. Deformation mechanism at atomic scale has been revealed. Tensile strength and Young's modulus of nanocrystalline SiC were accurately reproduced. PMID:19441448

  14. Boron, graphite, glass, metal and aramid fiber reinforced plastics. January, 1973-May, 1981 (Citations from the Rubber and Plastics Research Association Data Base). Report for January 1973-May 1981

    SciTech Connect

    Not Available

    1981-05-01

    The citations cover information about advanced reinforced composites such as boron, graphite, glass, metal, and aramid. Topics include applications, fabrication processes, proerties, nondestructive testing, and economics of composite materials. (Contains 90 citations fully indexed and including a title list.)

  15. Bare and boron-doped cubic silicon carbide nanowires for electrochemical detection of nitrite sensitively

    PubMed Central

    Yang, Tao; Zhang, Liqin; Hou, Xinmei; Chen, Junhong; Chou, Kuo-Chih

    2016-01-01

    Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) were used to characterize SiC and boron-doped SiC NWs. As for the electrochemical behavior of both SiC NWs electrode, the cyclic voltammetric results show that both SiC electrodes exhibit wide potential window and excellent electrocatalytic activity toward nitrite oxidation. Differential pulse voltammetry (DPV) determination reveals that there exists a good linear relationship between the oxidation peak current and the concentration in the range of 50–15000 μmoL L−1 (cubic SiC NWs) and 5–8000 μmoL L−1 (B-doped cubic SiC NWs) with the detection limitation of 5 and 0.5 μmoL L−1 respectively. Compared with previously reported results, both as-prepared nitrite sensors exhibit wider linear response range with comparable high sensitivity, high stability and reproducibility. PMID:27109361

  16. Bare and boron-doped cubic silicon carbide nanowires for electrochemical detection of nitrite sensitively.

    PubMed

    Yang, Tao; Zhang, Liqin; Hou, Xinmei; Chen, Junhong; Chou, Kuo-Chih

    2016-01-01

    Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) were used to characterize SiC and boron-doped SiC NWs. As for the electrochemical behavior of both SiC NWs electrode, the cyclic voltammetric results show that both SiC electrodes exhibit wide potential window and excellent electrocatalytic activity toward nitrite oxidation. Differential pulse voltammetry (DPV) determination reveals that there exists a good linear relationship between the oxidation peak current and the concentration in the range of 50-15000 μmoL L(-1) (cubic SiC NWs) and 5-8000 μmoL L(-1) (B-doped cubic SiC NWs) with the detection limitation of 5 and 0.5 μmoL L(-1) respectively. Compared with previously reported results, both as-prepared nitrite sensors exhibit wider linear response range with comparable high sensitivity, high stability and reproducibility. PMID:27109361

  17. Thermal properties of neutron-irradiated SiC; effects of boron doping

    NASA Astrophysics Data System (ADS)

    Lee, C. W.; Pineau, F. J.; Corelli, J. C.

    1982-08-01

    The temperature dependence (25°C to 1000°C) of thermal conductivity for siliconized (reaction bonded) SiC and alpha phase (sintered) SiC irradiated to neutron fluences of 4 to 8 × 10 24n/ m2 ( E>1 MeV) were studied utilizing the heat pulse technique. The fluences are equivalent to 0.8 and 1.6 dpa and the sample temperature during irradiation was ~ 140°C. Silicon carbide exhibits a significant decrease in thermal conductivity after irradiation, specifically a factor of ~ 5 decrease is observed for siliconized SiC. Comparisons were made with SiC samples doped with 10B, 11B, and natural boron to investigate the effects of impurity doping. It was found that the presence of natural boron and 11B have no significant effect on the thermal conductivity of irradiated SiC, whereas SiC doped with 10B exhibits a slightly larger decrease in thermal conductivity due to the enhanced radiation damage (e.g., helium production) through the 10B (n, α) 7Li reaction. The lowering of the thermal conductivity after irradiation can explain the decreased resistance against thermal shcok of irradiated SiC. The decrease in thermal conductivity is due to enhanced phonon scattering by radiation-induced vacancies and dislocations. Results on annealing effects and comparison with mechanical properties are presented.

  18. Macroscopically Aligned Graphite Films Prepared from Iodine-Doped Stretchable Polyacetylene Films Using Morphology-Retaining Carbonization.

    PubMed

    Matsushita, Satoshi; Akagi, Kazuo

    2015-07-22

    We prepared graphite films using typical Shirakawa-type and stretchable polyacetylene (PA) films as precursors through a morphology-retaining carbonization. A macroscopically aligned PA film was prepared from the drawable PA film using a mechanical-stretching procedure. The degree of orientation of the aligned PA film was evaluated by measuring polarized infrared absorption spectra and an azimuthal-angle profile of a Laue X-ray diffraction (XRD) pattern. The carbonization was performed from the iodine-doped PA films as precursors at 800 °C. The carbon films were subsequently graphitized at 1400-3000 °C, yielding graphite films with almost the same surface morphology as that of the original PA films and that of the carbon films as precursors. The typical PA film graphitized at 2600 °C exhibited tensile strengths of up to 224 MPa, moduli of up to 10 GPa, and an average electrical conductivity of 2.5 × 10(2) S/cm. In contrast, the graphite film prepared from the stretched PA film presented a Laue XRD pattern in which graphitic crystal structures are aligned parallel to the direction of stretching of the PA film. The anisotropic graphite film showed an enhanced conductivity of up to 1.5 × 10(3) S/cm along the stretching direction. We demonstrated that an iodine-doped PA film is a highly efficient carbon source for producing graphite films with good mechanical and electrical properties. The total yield of a graphite film is as high as 61-74% at up to 3000 °C, which is considerably higher than that of polyacrylonitrile-based carbon fiber and polyimide-based graphite film. PMID:26102247

  19. Unraveling the formation mechanism of graphitic nitrogen-doping in thermally treated graphene with ammonia.

    PubMed

    Li, Xiao-Fei; Lian, Ke-Yan; Liu, Lingling; Wu, Yingchao; Qiu, Qi; Jiang, Jun; Deng, Mingsen; Luo, Yi

    2016-01-01

    Nitrogen-doped graphene (N-graphene) has attractive properties that has been widely studied over the years. However, its possible formation process still remains unclear. Here, we propose a highly feasible formation mechanism of the graphitic-N doing in thermally treated graphene with ammonia by performing ab initio molecular dynamic simulations at experimental conditions. Results show that among the commonly native point defects in graphene, only the single vacancy 5-9 and divacancy 555-777 have the desirable electronic structures to trap N-containing groups and to mediate the subsequent dehydrogenation processes. The local structure of the defective graphene in combining with the thermodynamic and kinetic effect plays a crucial role in dominating the complex atomic rearrangement to form graphitic-N which heals the corresponding defect perfectly. The importance of the symmetry, the localized force field, the interaction of multiple trapped N-containing groups, as well as the catalytic effect of the temporarily formed bridge-N are emphasized, and the predicted doping configuration agrees well with the experimental observation. Hence, the revealed mechanism will be helpful for realizing the targeted synthesis of N-graphene with reduced defects and desired properties. PMID:27002190

  20. Unraveling the formation mechanism of graphitic nitrogen-doping in thermally treated graphene with ammonia

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Fei; Lian, Ke-Yan; Liu, Lingling; Wu, Yingchao; Qiu, Qi; Jiang, Jun; Deng, Mingsen; Luo, Yi

    2016-03-01

    Nitrogen-doped graphene (N-graphene) has attractive properties that has been widely studied over the years. However, its possible formation process still remains unclear. Here, we propose a highly feasible formation mechanism of the graphitic-N doing in thermally treated graphene with ammonia by performing ab initio molecular dynamic simulations at experimental conditions. Results show that among the commonly native point defects in graphene, only the single vacancy 5–9 and divacancy 555–777 have the desirable electronic structures to trap N-containing groups and to mediate the subsequent dehydrogenation processes. The local structure of the defective graphene in combining with the thermodynamic and kinetic effect plays a crucial role in dominating the complex atomic rearrangement to form graphitic-N which heals the corresponding defect perfectly. The importance of the symmetry, the localized force field, the interaction of multiple trapped N-containing groups, as well as the catalytic effect of the temporarily formed bridge-N are emphasized, and the predicted doping configuration agrees well with the experimental observation. Hence, the revealed mechanism will be helpful for realizing the targeted synthesis of N-graphene with reduced defects and desired properties.

  1. Unraveling the formation mechanism of graphitic nitrogen-doping in thermally treated graphene with ammonia

    PubMed Central

    Li, Xiao-Fei; Lian, Ke-Yan; Liu, Lingling; Wu, Yingchao; Qiu, Qi; Jiang, Jun; Deng, Mingsen; Luo, Yi

    2016-01-01

    Nitrogen-doped graphene (N-graphene) has attractive properties that has been widely studied over the years. However, its possible formation process still remains unclear. Here, we propose a highly feasible formation mechanism of the graphitic-N doing in thermally treated graphene with ammonia by performing ab initio molecular dynamic simulations at experimental conditions. Results show that among the commonly native point defects in graphene, only the single vacancy 5–9 and divacancy 555–777 have the desirable electronic structures to trap N-containing groups and to mediate the subsequent dehydrogenation processes. The local structure of the defective graphene in combining with the thermodynamic and kinetic effect plays a crucial role in dominating the complex atomic rearrangement to form graphitic-N which heals the corresponding defect perfectly. The importance of the symmetry, the localized force field, the interaction of multiple trapped N-containing groups, as well as the catalytic effect of the temporarily formed bridge-N are emphasized, and the predicted doping configuration agrees well with the experimental observation. Hence, the revealed mechanism will be helpful for realizing the targeted synthesis of N-graphene with reduced defects and desired properties. PMID:27002190

  2. Thermodynamic and kinetic studies of laser thermal processing of heavily boron-doped amorphous silicon using molecular dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Liguo; Clancy, Paulette; Thompson, Michael O.; Murthy, Cheruvu S.

    2002-09-01

    Laser thermal processing (LTP) has been proposed as a means to avoid unwanted transient enhanced diffusion and deactivation of dopants, especially boron and arsenic, during the formation of ultrashallow junctions. Although experimental studies have been carried out to determine the efficacy of LTP for pure Si and lightly B-doped junctions, the effects of high concentrations of dopants (above 2% B) on the thermodynamic and kinetic properties of the regrown film are unknown. In this study, a classical interatomic potential model [Stillinger-Weber (SW)] is used with a nonequilibrium molecular dynamics computer simulation technique to study the laser thermal processing of heavily B-doped Si in the range 2-10 at. % B. We observe only a small effect of boron concentration on the congruent melting temperature of the B:Si alloy, and thus the narrowing of the "process window" for LTP is predicted to be small. No significant tendency for boron to segregate was observed at either the regrowth front or the buried c-Si interface during fast regrowth. The B-doped region regrew as defect-free crystal with full activation of the boron atoms at low boron concentrations (2%), in good agreement with experiments. As the concentration of boron increased, the number of intrinsic Si defects and boron interstitials in the regrown materials increased, with a minor amount of boron atoms in clusters (<2%). An instability limit for crystal regrowth was observed at around 8%-10% boron atoms during fast regrowth; systems with 10% B showed partial amorphization during regrowth. Comparison with tight-binding quantum mechanical calculations showed that the SW model gives similar diffusivities in the liquid and tendency to cluster, but the lifetimes of the SW clusters are considerably too long (>150 ps, compared to 5 ps in tight binding). The importance of adequate system size is discussed.

  3. The chemical durability of glass and graphite-glass composite doped with cesium oxide

    NASA Astrophysics Data System (ADS)

    Hamodi, Nasir H.; Abram, Timothy J.; Lowe, Tristan; Cernik, Robert J.; López-Honorato, Eddie

    2013-01-01

    The role of temperature in determining the chemical stability of a waste form, as well as its leach rate, is very complex. This is because the dissolution kinetics is dependent both on temperature and possibility of different rate-controlling mechanisms that appear at different temperature regions. The chemical durability of Alumina-Borosilicate Glass (ABG) and Glass-Graphite Composite (GGC), bearing Tristructural Isotropic (TRISO) fuel particles impregnated with cesium oxide, were compared using a static leach test. The purpose of this study is to examine the chemical durability of glass-graphite composite to encapsulate coated fuel particles, and as a possible alternative for recycling of irradiated graphite. The test was based on the ASTM C1220-98 methodology, where the leaching condition was set at a temperature varying from 298 K to 363 K for 28 days. The release of cesium from ABG was in the permissible limit and followed the Arrhenius's law of a surface controlled reaction; its activation energy (Ea) was 65.6 ± 0.5 kJ/mol. Similar values of Ea were obtained for Boron (64.3 ± 0.5) and Silicon (69.6 ± 0.5 kJ/mol) as the main glass network formers. In contrast, the dissolution mechanism of cesium from GGC was a rapid release, with increasing temperature, and the activation energy of Cs (91.0 ± 5 kJ/mol) did not follow any model related to carbon kinetic dissolution in water. Microstructure analysis confirmed the formation of Crystobalite SiO2 as a gel layer and Cs+1 valence state on the ABG surface.

  4. Nitrogen-Doped Carbon Nanotube/Graphite Felts as Advanced Electrode Materials for Vanadium Redox Flow Batteries.

    PubMed

    Wang, Shuangyin; Zhao, Xinsheng; Cochell, Thomas; Manthiram, Arumugam

    2012-08-16

    Nitrogen-doped carbon nanotubes have been grown, for the first time, on graphite felt (N-CNT/GF) by a chemical vapor deposition approach and examined as an advanced electrode for vanadium redox flow batteries (VRFBs). The unique porous structure and nitrogen doping of N-CNT/GF with increased surface area enhances the battery performance significantly. The enriched porous structure of N-CNTs on graphite felt could potentially facilitate the diffusion of electrolyte, while the N-doping could significantly contribute to the enhanced electrode performance. Specifically, the N-doping (i) modifies the electronic properties of CNT and thereby alters the chemisorption characteristics of the vanadium ions, (ii) generates defect sites that are electrochemically more active, (iii) increases the oxygen species on CNT surface, which is a key factor influencing the VRFB performance, and (iv) makes the N-CNT electrochemically more accessible than the CNT. PMID:26295765

  5. 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.

  6. Nanoscale Control of Rewriteable Doping Patterns in Pristine Graphene/Boron Nitride Heterostructures.

    PubMed

    Velasco, Jairo; Ju, Long; Wong, Dillon; Kahn, Salman; Lee, Juwon; Tsai, Hsin-Zon; Germany, Chad; Wickenburg, Sebastian; Lu, Jiong; Taniguchi, Takashi; Watanabe, Kenji; Zettl, Alex; Wang, Feng; Crommie, Michael F

    2016-03-01

    Nanoscale control of charge doping in two-dimensional (2D) materials permits the realization of electronic analogs of optical phenomena, relativistic physics at low energies, and technologically promising nanoelectronics. Electrostatic gating and chemical doping are the two most common methods to achieve local control of such doping. However, these approaches suffer from complicated fabrication processes that introduce contamination, change material properties irreversibly, and lack flexible pattern control. Here we demonstrate a clean, simple, and reversible technique that permits writing, reading, and erasing of doping patterns for 2D materials at the nanometer scale. We accomplish this by employing a graphene/boron nitride heterostructure that is equipped with a bottom gate electrode. By using electron transport and scanning tunneling microscopy (STM), we demonstrate that spatial control of charge doping can be realized with the application of either light or STM tip voltage excitations in conjunction with a gate electric field. Our straightforward and novel technique provides a new path toward on-demand graphene p-n junctions and ultrathin memory devices. PMID:26852622

  7. Self-compensation property of β-rhombohedral boron doped with high Li concentration

    NASA Astrophysics Data System (ADS)

    Hyodo, H.; Nezu, A.; Soga, K.; Kimura, K.

    2012-11-01

    A high concentration of Li (up to LiB5.8; 18 Li/cell) was doped into β-rhombohedral boron (β-B), which has a crystalline structure built up from B12 icosahedral clusters, by sealing the raw materials in a stainless-steel tube. The relation between the structure and the electronic properties was clarified and a self-compensation property of Li- or Mg-doped β-B was discussed. The Li concentration was analyzed by atomic absorption spectrometry. The changes in the structure and the electronic properties were investigated by X-ray diffraction using the Rietveld method and by electrical conductivity measurements, respectively. Li occupies the A1, D, E and F sites, and the occupancies of the B sites (B13, B16 and B4) decrease with increasing Li doping. In Li- or Mg-doped β-B, electron doping is compensated by the removal of interstitial B atoms at the B16 site and by the generation of vacancies at the B13 and B4 sites. There have been no reports of self-compensation in other crystalline elemental semiconductors.

  8. Photovoltaic Device Including A Boron Doping Profile In An I-Type Layer

    DOEpatents

    Yang, Liyou

    1993-10-26

    A photovoltaic cell for use in a single junction or multijunction photovoltaic device, which includes a p-type layer of a semiconductor compound including silicon, an i-type layer of an amorphous semiconductor compound including silicon, and an n-type layer of a semiconductor compound including silicon formed on the i-type layer. The i-type layer including an undoped first sublayer formed on the p-type layer, and a boron-doped second sublayer formed on the first sublayer.

  9. Raman and conductivity studies of boron doped microcrystalline diamond, facetted nanocrystalline diamond and cauliflower diamond films

    NASA Astrophysics Data System (ADS)

    May, P. W.; Ludlow, W. J.; Hannaway, M.; Heard, P. J.; Smith, J. A.; Rosser, K. N.

    2007-09-01

    We present data showing how the electrical conductivity and Raman spectra of boron-doped CVD diamond films vary with both B content and crystallite size, for microcrystalline diamond (MCD), facetted nanocrystalline diamond (f-NCD) and 'cauliflower' diamond (c-NCD). The position of the Lorentzian contribution to the 500 cm -1 Raman feature was used to estimate the B content. This underestimated the SIMS concentration of B by a factor of 5 for the f-NCD and c-NCD films, but remained reasonably accurate for MCD films. One explanation for this is that most of the B incorporates at the grain boundaries and not in substitutional sites.

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

    SciTech Connect

    Tian, Yong-Hui; Huang, Jingsong; Sumpter, Bobby G

    2015-06-18

    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.

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

    DOE PAGESBeta

    Tian, Yong-Hui; Huang, Jingsong; Sumpter, Bobby G

    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 distributedmore » 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.« less

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

    SciTech Connect

    Tian, Yong-Hui; Huang, Jingsong; Sumpter, Bobby G

    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.

  13. Effect of Boron-Doping on the Graphene Aerogel Used as Cathode for the Lithium-Sulfur Battery.

    PubMed

    Xie, Yang; Meng, Zhen; Cai, Tingwei; Han, Wei-Qiang

    2015-11-18

    A porous interconnected 3D boron-doped graphene aerogel (BGA) was prepared via a one-pot hydrothermal treatment. The BGA material was first loaded with sulfur to serve as cathode in lithium-sulfur batteries. Boron was positively polarized on the graphene framework, allowing for chemical adsorption of negative polysufide species. Compared with nitrogen-doped and undoped graphene aerogel, the BGA-S cathode could deliver a higher capacity of 994 mA h g(-1) at 0.2 C after 100 cycles, as well as an outstanding rate capability, which indicated the BGA was an ideal cathode material for lithium-sulfur batteries. PMID:26544917

  14. Structural and electronic properties of cubic boron nitride doped with zinc

    SciTech Connect

    Li, Yubo; Cheng, Tianyuan; Wang, Xiao; Jiang, Huaxing; Yang, Hangsheng; Nose, Kenji

    2014-07-28

    Structural and electronic properties of Zn-doped cubic boron nitride (cBN) were investigated via first principle calculation based on density functional theory. Our simulation suggests that Zn can substitute for both B (Zn{sub B}) and N (Zn{sub N}) atom; Zn{sub B} is energetically favorable, and Zn{sub N} can only be prepared under B-rich conditions. Zn{sub B} induced a shallow acceptor level; however, the large difference in electronegativity between Zn and N makes the acceptor level strongly localized, which reduces effective carrier density. In the case of Zn{sub N}, both deep acceptor levels within band gap and shallow acceptor levels at the top of valence band were induced, which produced more free carriers than Zn{sub B}. The calculated results account for experimental results of enhanced electric conductivity of Zn-doped cBN films prepared under B-rich conditions.

  15. Prediction of low-energy boron doping profile for ultrashallow junction formation by hybrid molecular dynamics method

    NASA Astrophysics Data System (ADS)

    Yabuhara, Hidehiko; Miyamoto, Akira

    2016-01-01

    Our original hybrid method combining tight-binding quantum chemical and classical molecular dynamics was first applied to the low-energy doping process of boron into a silicon substrate, which has a depth of more than 10 nm that is needed to evaluate an ultrashallow junction position. Tight-binding quantum chemical molecular dynamics calculation was used for an injected boron atom and surrounding silicon atoms within a sphere with a radius of 0.5 nm centered at the boron atom. This method is advantageous in treating the many-body collision effect and electron-electron interaction, which are more important in low-energy doping, compared with the Monte Carlo method with binary collision approximation. A comparison with a plasma doping experiment was also carried out. The junction positions were 6.2 nm for boron doping at an initial kinetic energy of 200 eV in the simulation results and 6.4 nm for 200 eV in the experimental results. Good agreement between simulation and experimental results indicates that our hybrid molecular dynamics method is applicable to doping profile prediction in a silicon structure with a depth of more than 10 nm that is needed to evaluate ultrashallow junction formation.

  16. Defect charge states in Si doped hexagonal boron-nitride monolayer.

    PubMed

    Mapasha, R E; Molepo, M P; Andrew, R C; Chetty, N

    2016-02-10

    We perform ab initio density functional theory calculations to investigate the energetics, electronic and magnetic properties of isolated stoichiometric and non-stoichiometric substitutional Si complexes in a hexagonal boron-nitride monolayer. The Si impurity atoms substituting the boron atom sites SiB giving non-stoichiometric complexes are found to be the most energetically favourable, and are half-metallic and order ferromagnetically in the neutral charge state. We find that the magnetic moments and magnetization energies increase monotonically when Si defects form a cluster. Partial density of states and standard Mulliken population analysis indicate that the half-metallic character and magnetic moments mainly arise from the Si 3p impurity states. The stoichiometric Si complexes are energetically unfavorable and non-magnetic. When charging the energetically favourable non-stoichiometric Si complexes, we find that the formation energies strongly depend on the impurity charge states and Fermi level position. We also find that the magnetic moments and orderings are tunable by charge state modulation q  =  -2, -1, 0, +1, +2. The induced half-metallic character is lost (retained) when charging isolated (clustered) Si defect(s). This underlines the potential of a Si doped hexagonal boron-nitride monolayer for novel spin-based applications. PMID:26760785

  17. Defect charge states in Si doped hexagonal boron-nitride monolayer

    NASA Astrophysics Data System (ADS)

    Mapasha, R. E.; Molepo, M. P.; Andrew, R. C.; Chetty, N.

    2016-02-01

    We perform ab initio density functional theory calculations to investigate the energetics, electronic and magnetic properties of isolated stoichiometric and non-stoichiometric substitutional Si complexes in a hexagonal boron-nitride monolayer. The Si impurity atoms substituting the boron atom sites SiB giving non-stoichiometric complexes are found to be the most energetically favourable, and are half-metallic and order ferromagnetically in the neutral charge state. We find that the magnetic moments and magnetization energies increase monotonically when Si defects form a cluster. Partial density of states and standard Mulliken population analysis indicate that the half-metallic character and magnetic moments mainly arise from the Si 3p impurity states. The stoichiometric Si complexes are energetically unfavorable and non-magnetic. When charging the energetically favourable non-stoichiometric Si complexes, we find that the formation energies strongly depend on the impurity charge states and Fermi level position. We also find that the magnetic moments and orderings are tunable by charge state modulation q  =  ‑2, ‑1, 0, +1, +2. The induced half-metallic character is lost (retained) when charging isolated (clustered) Si defect(s). This underlines the potential of a Si doped hexagonal boron-nitride monolayer for novel spin-based applications.

  18. The structural and mechanical behaviours of Boron-doped ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Senol, Abdulkadir; Demirozu Senol, Sevim; Ozturk, Ozgur; Asikuzun, Elif; Tasci, Ahmet Tolga; Terzioglu, Cabir

    2015-03-01

    Undoped and Boron (B)-doped Zinc Oxide (ZnO) nanopowders were synthesized by Hydrothermal method. The structural and mechanical behaviours of B doped ZnO (Zn1-xBx O, x =0, 0.05, 0.07, 0.11) were systematically examined. The crystal structure, phases, sizes and microstructure of Zn1-xBx O powder samples characterized by using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Microhardness values of all B doped ZnO powders were measured with different loads (0.245, 0.490, 0.980, 1.960 ve 2.940 N) using a digital Vickers microhardness tester. The experimental microhardness data were used to determine elastic modules, yield strength, and fracture toughness value of the samples. Additionally, the experimental results were analyzed using the various theoretical models namely, Kick's Law, Elastic/Plastic Deformation (EPD) models, Proportional Specimen Resistance (PSR), and Hays-Kendall (HK) approach. The Vickers microhardness measurements revealed that hardness of Zn1-xBx O powder samples increased with B doping. This research partially supported by Abant Izzet Baysal University Scientific Research Projects Coordination Department under the Grant No. BAP-2013.03.02.609.

  19. 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

  20. Boron δ-doped (111) diamond solution gate field effect transistors.

    PubMed

    Edgington, Robert; Ruslinda, A Rahim; Sato, Syunsuke; Ishiyama, Yuichiro; Tsuge, Kyosuke; Ono, Tasuku; Kawarada, Hiroshi; Jackman, Richard B

    2012-03-15

    A solution gate field effect transistor (SGFET) using an oxidised boron δ-doped channel on (111) diamond is presented for the first time. Employing an optimised plasma chemical vapour deposition (PECVD) recipe to deposit δ-layers, SGFETs show improved current-voltage (I-V) characteristics in comparison to previous similar devices fabricated on (100) and polycrystalline diamond, where the device is shown to operate in the enhancement mode of operation, achieving channel pinch-off and drain-source current saturation within the electrochemical window of diamond. A maximum gain and transconductance of 3 and 200μS/mm are extracted, showing comparable figures of merit to hydrogen-based SGFET. The oxidised device shows a site-binding model pH sensitivity of 36 mV/pH, displaying fast temporal responses. Considering the biocompatibility of diamond towards cells, the device's highly mutable transistor characteristics, pH sensitivity and stability against anodic oxidation common to hydrogen terminated diamond SGFET, oxidised boron δ-doped diamond SGFETs show promise for the recording of action potentials from electrogenic cells. PMID:22317833

  1. Fabrication and Characterization of N-Type Zinc Oxide/P-Type Boron Doped Diamond Heterojunction

    NASA Astrophysics Data System (ADS)

    Marton, Marián; Mikolášek, Miroslav; Bruncko, Jaroslav; Novotný, Ivan; Ižák, Tibor; Vojs, Marian; Kozak, Halyna; Varga, Marián; Artemenko, Anna; Kromka, Alexander

    2015-09-01

    Diamond and ZnO are very promising wide-bandgap materials for electronic, photovoltaic and sensor applications because of their excellent electrical, optical, physical and electrochemical properties and biocompatibility. In this contribution we show that the combination of these two materials opens up the potential for fabrication of bipolar heterojunctions. Semiconducting boron doped diamond (BDD) thin films were grown on Si and UV grade silica glass substrates by HFCVD method with various boron concentration in the gas mixture. Doped zinc oxide (ZnO:Al, ZnO:Ge) thin layers were deposited by diode sputtering and pulsed lased deposition as the second semiconducting layer on the diamond films. The amount of dopants within the films was varied to obtain optimal semiconducting properties to form a bipolar p-n junction. Finally, different ZnO/BDD heterostructures were prepared and analyzed. Raman spectroscopy, SEM, Hall constant and I-V measurements were used to investigate the quality, structural and electrical properties of deposited heterostructures, respectively. I-V measurements of ZnO/BDD diodes show a rectifying ratio of 55 at ±4 V. We found that only very low dopant concentrations for both semiconducting materials enabled us to fabricate a functional p-n junction. Obtained results are promising for fabrication of optically transparent ZnO/BDD bipolar heterojunction.

  2. 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.

  3. 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

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

    SciTech Connect

    Möller, Christian; Bartel, Til; Gibaja, Fabien; Lauer, Kevin

    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.

  5. A practical guide to using boron doped diamond in electrochemical research.

    PubMed

    Macpherson, Julie V

    2015-02-01

    Conducting, boron doped diamond (BDD), in addition to its superior material properties, offers several notable attributes to the electrochemist making it an intriguing material for electrochemical research. These include the widest solvent window of all electrode materials; low background and capacitive currents; reduced fouling compared to other electrodes and; the ability to withstand extreme potentials, corrosive and high temperature/pressure environments. However, BDD is not your typical electrode material, it is a semi-conductor doped degenerately with boron to present semi-metallic characteristics. Input from materials scientists, chemists and physicists has been required to aid understanding of how to work with this material from an electrochemical viewpoint and improve electrode quality. Importantly, depending on how the BDD has been grown and then subsequently treated, prior to electrochemical measurement, the resulting material properties can vary quite significantly from one electrode to the next. This likely explains the variability seen by different researchers working on the same experimental systems. The aim of this "protocols" article is not to provide a state-of-the-art review of diamond electrochemistry, suitable references are provided to the interested reader, but instead serves as a reference point for any researcher wishing to commence work with diamond electrodes and interpret electrochemical data. It provides information on how best to characterise the material properties of the electrode before use and outlines the interplay between boron dopant density, non-diamond-carbon content, grain morphology, surface chemistry and redox couple identity. All should ideally be considered when interpretating electrochemical data arising from the diamond electrode. This will aid the reader in making meaningful comparisons between data obtained by different researchers using different diamond electrodes. The guide also aims to help educate the researcher in choosing which form of BDD is best suited to their research application. PMID:25518988

  6. Hierarchically controlled helical graphite films prepared from iodine-doped helical polyacetylene films using morphology-retaining carbonization.

    PubMed

    Matsushita, Satoshi; Kyotani, Mutsumasa; Akagi, Kazuo

    2011-11-01

    One-handed helical graphite films with a hierarchically controlled morphology were prepared from iodine-doped helical polyacetylene (H-PA) films using the recently developed morphology-retaining carbonization method. Results from scanning electron microscopy indicate that the hierarchical helical morphology of the H-PA film remains unchanged even after carbonization at 800 °C. The weight loss of the film due to carbonization was very small; only 10-29% of the weight of the film before doping was lost. Furthermore, the graphite film prepared by subsequent heating at 2600 °C retained the same morphology as that of the original H-PA film and that of the helical carbon film prepared at 800 °C. The screwed direction, twisted degree, and vertical or horizontal alignment of the helical graphite film were well controlled by changing the helical sense, helical pitch, and orientation state of the chiral nematic liquid crystal (N*-LC) used as an asymmetric LC reaction field. X-ray diffraction and Raman scattering measurements showed that graphitic crystallization proceeds in the carbon film during heat treatment at 2600 °C. Transmission electron microscopy measurements indicate that ultrasonication of the helical graphite film in ethanol for several hours gives rise to a single helical graphite fibril. The profound potentiality of the present graphite films is exemplified in their electrical properties. The horizontally aligned helical graphite film exhibits an enhancement in electrical conductivity and an evolution of electrical anisotropy in which conductivity parallel to the helical axis of the fibril bundle is higher than that perpendicular to the axis. PMID:21970653

  7. Stability of graphitic-like zinc oxide layers under carriers doping: a first-principles study

    NASA Astrophysics Data System (ADS)

    Kan, Erjun; Deng, Kaiming; Wu, Fang

    2013-11-01

    Although theoretical works have demonstrated that (0001) polar films of wurtzite (WZ) ZnO automatically transform into graphitic-like (GP) structures, the experimental realization of GP ZnO is limited to a thickness of several atomic layers. Here, using first-principles calculations, we demonstrated that the stability of GP ZnO is closely related to the concentration of near-free carriers. Our results show that the doped carriers, originating from the rich oxygen vacancies, can effectively screen the polar field, and stabilize the WZ structure. Thus, in order to obtain GP ZnO layers with much thicker films, it is necessary to reduce the near-free carrier concentration.

  8. Boron-doped graphene as promising support for platinum catalyst with superior activity towards the methanol electrooxidation reaction

    NASA Astrophysics Data System (ADS)

    Sun, Yongrong; Du, Chunyu; An, Meichen; Du, Lei; Tan, Qiang; Liu, Chuntao; Gao, Yunzhi; Yin, Geping

    2015-12-01

    We report the synthesis of boron-doped graphene by thermally annealing the mixture of graphene oxide and boric acid, and its usage as the support of Pt catalyst towards the methanol oxidation reaction. The composition, structure and morphology of boron-doped graphene and its supported Pt nanoparticles (Pt/BG) are characterized by transmission electron microscopy, inductively coupled plasma mass spectrometry, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. It is revealed that boron atoms are doped into graphene network in the form of BC2O and BCO2 bonds, which lead to the increase in defect sites and facilitate the subsequent deposition of Pt nanoparticles. Therefore, the Pt/BG catalyst presents smaller particle size and narrower size distribution than the graphene supported Pt (Pt/G) catalyst. When evaluated as the electrocatalyst for the methanol oxidation reaction, the Pt/BG catalyst exhibits excellent electrochemical activity and stability demonstrated by cyclic voltammetry and chronoamperometry tests. The enhanced activity is mainly ascribed to the electronic interaction between boron-doped graphene and Pt nanoparticles, which lowers the d-band center of Pt and thus weakens the absorption of the poisoning intermediate CO. Our work provides an alternative approach of improving the reaction kinetics for the oxidation of small organic molecules.

  9. Electroanalysis of tetracycline using nickel-implanted boron-doped diamond thin film electrode applied to flow injection system.

    PubMed

    Treetepvijit, Surudee; Chuanuwatanakul, Suchada; Einaga, Yasuaki; Sato, Rika; Chailapakult, Orawon

    2005-05-01

    The electrochemical analysis of tetracycline was investigated using nickel-implanted boron-doped diamond thin film electrode by cyclic voltammetry and amperometry with a flow injection system. Cyclic voltammetry was used to study the electrochemical oxidation of tetracycline. Comparison experiments were carried out using as-deposited boron-doped diamond thin film electrode (BDD). Nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) provided well-resolved oxidation irreversible cyclic voltammograms. The current signals were higher than those obtained using the as-deposited BDD electrode. Results using nickel-implanted boron-doped diamond thin film electrode in flow injection system coupled with amperometric detection are presented. The optimum potential for tetracycline was 1.55 V versus Ag/AgCl. The linear range of 1.0 to 100 microM and the detection limit of 10 nM were obtained. In addition, the application for drug formulation was also investigated. PMID:15913142

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

    SciTech Connect

    Araújo, D.; Alegre, M. P.; Piñero, J. C.; Fiori, A.; Bustarret, E.; Jomard, F.

    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. Can metal-free silicon-doped hexagonal boron nitride nanosheets and nanotubes exhibit activity toward CO oxidation?

    PubMed

    Lin, Sen; Ye, Xinxin; Huang, Jing

    2015-01-14

    Si-doped hexagonal boron nitride nanosheets (Si-BNNS) and nanotubes (Si-BNNT) have been investigated by first-principle methods. The strong interaction between the silicon atom and the hexagonal boron nitride nanosheet or nanotube with a boron vacancy indicates that such nanocomposites should be very stable. The significant charge transfer from the Si-BNNS substrate to the O2 molecule, which could occupy the antibonding 2π* orbitals of O2, results in the activation of the adsorbed O2. The catalytic activity of the Si-BNNS for CO oxidation is explored and the calculated barrier (0.29 eV) of the reaction CO + O2→ CO2 + O is much lower than those on the traditional noble metals. This opens a new avenue to fabricate low cost and high activity boron nitride-based metal-free catalysts. PMID:25407885

  12. Preparation of calcium-doped boron nitride by pulsed laser deposition

    SciTech Connect

    Anzai, Atsushi; Fuchigami, Masayo; Yamanaka, Shoji; Inumaru, Kei

    2012-08-15

    Highlights: ► Ca-doped boron nitride was prepared by pulsed laser deposition. ► The films do not have long range order structure in terms of XRD. ► But the films had short-range order structure of h-BN sheets. ► Ca-free films had the same optical band gap as crystalline bulk h-BN (5.8 eV.) ► Ca-doping brought about decreases of the optical band gap by ca. 0.4 eV. -- Abstract: Calcium-doped BN thin films Ca{sub x}BN{sub y} (x = 0.05–0.1, y = 0.7–0.9) were grown on α-Al{sub 2}O{sub 3}(0 0 1) substrates by pulsed laser deposition (PLD) using h-BN and Ca{sub 3}N{sub 2} disks as the targets under nitrogen radical irradiation. Infrared ATR spectra demonstrated the formation of short range ordered structure of BN hexagonal sheets, while X-ray diffraction gave no peak indicating the absence of long-range order structure in the films. It was notable that Ca-doped film had 5.45–5.55 eV of optical band gap, while the band gap of Ca-free films was 5.80–5.85 eV. This change in the band gap is ascribed to interaction of Ca with the BN sheets; first principle calculations on h-BN structure indicated that variation of inter-plane distance between the BN layers did not affect the band gap. This study highlights that PLD could prepare BN having short-range structure of h-BN sheets and being doped with electropositive cation which varies the optical band gap of the films.

  13. The effect of surface treatment on the electrical properties of metal contacts to boron-doped homoepitaxial diamond film

    SciTech Connect

    Grot, S.A.; Gildenblat, G.S.; Hatfield, C.W.; Wronski, C.R. . Dept. of Electrical Engineering); Badzian, A.R.; Badzian, T.; Messier, R. . Materials Research Lab.)

    1990-02-01

    Both doped and undoped homoepitaxial diamond films were fabricated using microwave plasma-enhanced chemical vapor deposition (CVD). The conductivity of the diamond film is strongly affected by the surface treatment. In particular, exposure of film surface to a hydrogen plasma results in the formation of a conductive layer which can be used to obtain linear (ohmic) {ital I-V} characteristics of the Au/diamond contacts, regardless of the doping level. The proper chemical cleaning of the boron-doped homoepitaxial diamond surface allows the fabrication of Au-gate Schottky diodes with excellent rectifying characteristics at temperatures of at least 400{degrees}C.

  14. Electrical transport properties of Si-doped hexagonal boron nitride epilayers

    SciTech Connect

    Majety, S.; Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2013-12-15

    The suitability of Si as an n-type dopant in hexagonal boron nitride (hBN) wide bandgap semiconductor has been investigated. Si doped hBN epilayers were grown via in-situ Si doping by metal organic chemical vapor deposition technique. Hall effect measurements revealed that Si doped hBN epilayers exhibit n-type conduction at high temperatures (T > 800 K) with an in-plane resistivity of ∼12 Ω·cm, electron mobility of μ ∼ 48 cm{sup 2}/V·s and concentration of n ∼ 1 × 10{sup 16} cm{sup −3}. Temperature dependent resistivity results yielded a Si energy level in hBN of about 1.2 eV, which is consistent with a previously calculated value for Si substitutionally incorporated into the B sites in hBN. The results therefore indicate that Si is not a suitable dopant for hBN for room temperature device applications.

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

    SciTech Connect

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

  16. Can CO2 molecule adsorb effectively on Al-doped boron nitride single walled nanotube?

    NASA Astrophysics Data System (ADS)

    Shao, Peng; Kuang, Xiao-Yu; Ding, Li-Ping; Yang, Jing; Zhong, Ming-Min

    2013-11-01

    The adsorption of carbon dioxides (CO2) is very important in environmental and industrial applications. The boron nitride nanotube (BNNT) with large surface and polarity may be a good candidate as CO2 capture. Unfortunately, the pristine BNNT is almost inert to the highly stable CO2. To renew technical applications of BNNT for CO2 adsorption, we explore the possibility of CO2 adsorption on various (n, 0) (n = 6, 8, 10, 12 and 14) Al-doped BNNT by density functional theory (DFT) calculations. The results show that the Al-doped BNNT could be a potential CO2 adsorption material, and the CO2 adsorption energies are independent of BNNT diameters. Furthermore, the interactions between CO2 and exemplified (6, 0) Al-doped BNNT are investigated by density of states (DOS) and electron density. We found the interaction between CO2 and AlB-BNNT is stronger than that of CO2 and AlN-BNNT. The adsorption of CO2 can induce new density of state, as well as a local charge fluctuation due to more electron density redistribution on the atoms near CO2 molecule.

  17. Evaluation of freestanding boron-doped diamond grown by chemical vapour deposition as substrates for vertical power electronic devices

    SciTech Connect

    Issaoui, R.; Achard, J.; Tallaire, A.; Silva, F.; Gicquel, A.; Bisaro, R.; Servet, B.; Garry, G.; Barjon, J.

    2012-03-19

    In this study, 4 x 4 mm{sup 2} freestanding boron-doped diamond single crystals with thickness up to 260 {mu}m have been fabricated by plasma assisted chemical vapour deposition. The boron concentrations measured by secondary ion mass spectroscopy were 10{sup 18} to 10{sup 20} cm{sup -3} which is in a good agreement with the values calculated from Fourier transform infrared spectroscopy analysis, thus indicating that almost all incorporated boron is electrically active. The dependence of lattice parameters and crystal mosaicity on boron concentrations have also been extracted from high resolution x-ray diffraction experiments on (004) planes. The widths of x-ray rocking curves have globally shown the high quality of the material despite a substantial broadening of the peak, indicating a decrease of structural quality with increasing boron doping levels. Finally, the suitability of these crystals for the development of vertical power electronic devices has been confirmed by four-point probe measurements from which electrical resistivities as low as 0.26 {Omega} cm have been obtained.

  18. Decomposition of nitrous oxide on Fe-doped boron nitride nanotubes: the ligand effect.

    PubMed

    Injan, Natcha; Sirijaraensre, Jakkapan; Limtrakul, Jumras

    2014-11-14

    N2O decomposition on iron-doped boron nitride nanotubes (Fe-BNNTs) was investigated by means of the density functional theory (M06-L). Two different forms of Fe-BNNTs, which are substitutions of the Fe atom into the boron-vacancy and nitrogen-vacancy sites of BNNTs, were used as the catalyst. Influence of the support plays a crucial role in the electronic configuration and catalytic reactivity of the iron atom. With the nitrogen surrounding (Fe(B)-BNNT), the iron behaves as a Lewis acid for accepting an electron from the lone-pair orbital of the N2O oxygen atom (η(1)-O complex). The catalytic process over this one at the transition state involves a synergistic σ-donation from the HOMO of N2O into a LUMO of the catalyst and the π-back-bonding from the metal d orbital into the π* orbital of N2O, leading to the cleavage of the N-O bond. The activation for this step is 22.5 kcal mol(-1). With the boron surrounding (Fe(N)-BNNT), the iron acting as a Lewis base plays a different role as compared with the iron in the case of Fe(B)-BNNTs. The HOMO of Fe(N)-BNNTs promotes the side-on binding mode of N2O on the iron center (η(2)-O,N complex), leading to the weakening of the N-O bond at the adsorption state. As a result, the decomposition over the Fe(N)-BNNTs takes place easily without an energy barrier. PMID:25254314

  19. 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.

  20. Electronic Structure Calculations of Gas Adsorption on Boron-doped Carbon Nanotubes Sensitized with Tungsten

    SciTech Connect

    An, Wei; Turner, C. H.

    2009-11-12

    Density-functional theory methods are used to investigate the adsorption of nine prevalent gas molecules (H2, O2, CO, CO2, NO, NO2, H2O, CH3OH, and NH3) on a carbon nanotube-based support material. The support is a boron-doped, single-walled carbon nanotube, which has been sensitized by the adsorption of tungsten metal clusters. Our calculations demonstrate that this hybrid adsorbent material is able to adsorb the gas molecules with varied affinity, and these interactions are characterized by analyzing the features in the projected density-of-states for each system. These calculations represent a critical step in designing high-fidelity sensor materials, selective adsorbents, and more effective catalysts.

  1. Excitonic luminescence of SiGe/Si quantum wells δ-doped with boron

    SciTech Connect

    Bagaev, V. S.; Nikolaev, S. N.; Onishchenko, E. E.; Pruchkina, A. A.; Krivobok, V. S.; Novikov, A. V.

    2015-05-14

    Low-temperature photoluminescence of undoped and moderately δ-doped Si{sub 1−x}Ge{sub x}/Si (x < 0.1) quantum wells has been studied. The influence of boron δ-layer on the excitonic luminescence and the luminescence caused by a dense electron plasma was demonstrated. The conditions under which the luminescence spectra of quantum wells are dominated by impurity-bound excitons (BE) have been established. Some unusual properties of these BE are explained in terms of type II band-offset in Si{sub 1−x}Ge{sub x}/Si (x < 0.1) quantum wells, which favors a spatial separation of electrons and holes. It is shown that the temperature dependence of an excitonic emission in the quantum wells allows to calculate the BE-related density of states and, thus, can be used for contactless estimation of the impurity concentration in quantum wells.

  2. Relaxation of the resistive superconducting state in boron-doped diamond films

    NASA Astrophysics Data System (ADS)

    Kardakova, A.; Shishkin, A.; Semenov, A.; Goltsman, G. N.; Ryabchun, S.; Klapwijk, T. M.; Bousquet, J.; Eon, D.; Sacépé, B.; Klein, Th.; Bustarret, E.

    2016-02-01

    We report a study of the relaxation time of the restoration of the resistive superconducting state in single crystalline boron-doped diamond using amplitude-modulated absorption of (sub-)THz radiation (AMAR). The films grown on an insulating diamond substrate have a low carrier density of about 2.5 ×1021cm-3 and a critical temperature of about 2 K . By changing the modulation frequency we find a high-frequency rolloff which we associate with the characteristic time of energy relaxation between the electron and the phonon systems or the relaxation time for nonequilibrium superconductivity. Our main result is that the electron-phonon scattering time varies clearly as T-2, over the accessible temperature range of 1.7 to 2.2 K. In addition, we find, upon approaching the critical temperature Tc, evidence for an increasing relaxation time on both sides of Tc.

  3. Boron-Doped Nanocrystalline Diamond Electrodes for Neural Interfaces: In vivo Biocompatibility Evaluation

    PubMed Central

    Alcaide, María; Taylor, Andrew; Fjorback, Morten; Zachar, Vladimir; Pennisi, Cristian P.

    2016-01-01

    Boron-doped nanocrystalline diamond (BDD) electrodes have recently attracted attention as materials for neural electrodes due to their superior physical and electrochemical properties, however their biocompatibility remains largely unexplored. In this work, we aim to investigate the in vivo biocompatibility of BDD electrodes in relation to conventional titanium nitride (TiN) electrodes using a rat subcutaneous implantation model. High quality BDD films were synthesized on electrodes intended for use as an implantable neurostimulation device. After implantation for 2 and 4 weeks, tissue sections adjacent to the electrodes were obtained for histological analysis. Both types of implants were contained in a thin fibrous encapsulation layer, the thickness of which decreased with time. Although the level of neovascularization around the implants was similar, BDD electrodes elicited significantly thinner fibrous capsules and a milder inflammatory reaction at both time points. These results suggest that BDD films may constitute an appropriate material to support stable performance of implantable neural electrodes over time. PMID:27013949

  4. Boron-Doped Nanocrystalline Diamond Electrodes for Neural Interfaces: In vivo Biocompatibility Evaluation.

    PubMed

    Alcaide, María; Taylor, Andrew; Fjorback, Morten; Zachar, Vladimir; Pennisi, Cristian P

    2016-01-01

    Boron-doped nanocrystalline diamond (BDD) electrodes have recently attracted attention as materials for neural electrodes due to their superior physical and electrochemical properties, however their biocompatibility remains largely unexplored. In this work, we aim to investigate the in vivo biocompatibility of BDD electrodes in relation to conventional titanium nitride (TiN) electrodes using a rat subcutaneous implantation model. High quality BDD films were synthesized on electrodes intended for use as an implantable neurostimulation device. After implantation for 2 and 4 weeks, tissue sections adjacent to the electrodes were obtained for histological analysis. Both types of implants were contained in a thin fibrous encapsulation layer, the thickness of which decreased with time. Although the level of neovascularization around the implants was similar, BDD electrodes elicited significantly thinner fibrous capsules and a milder inflammatory reaction at both time points. These results suggest that BDD films may constitute an appropriate material to support stable performance of implantable neural electrodes over time. PMID:27013949

  5. Chemical Modification of Boron-Doped Diamond Electrodes for Applications to Biosensors and Biosensing.

    PubMed

    Svítková, Jana; Ignat, Teodora; Švorc, Ľubomír; Labuda, Ján; Barek, Jiří

    2016-05-01

    Boron-doped diamond (BDD) is a prospective electrode material that possesses many exceptional properties including wide potential window, low noise, low and stable background current, chemical and mechanical stability, good biocompatibility, and last but not least exceptional resistance to passivation. These characteristics extend its usability in various areas of electrochemistry as evidenced by increasing number of published articles over the past two decades. The idea of chemically modifying BDD electrodes with molecular species attached to the surface for the purpose of creating a rational design has found promising applications in the past few years. BDD electrodes have appeared to be excellent substrate materials for various chemical modifications and subsequent application to biosensors and biosensing. Hence, this article presents modification strategies that have extended applications of BDD electrodes in electroanalytical chemistry. Different methods and steps of surface modification of this electrode material for biosensing and construction of biosensors are discussed. PMID:26337147

  6. Optically detected cyclotron resonance in heavily boron-doped silicon nanostructures on n-Si (100)

    SciTech Connect

    Bagraev, N. T. Kuzmin, R. V.; Gurin, A. S.; Klyachkin, L. E.; Malyarenko, A. M.; Mashkov, V. A.

    2014-12-15

    Electron and hole cyclotron resonance at a frequency of 94 GHz is detected by a change in the intensity of photoluminescence lines whose positions are identical to those of dislocation luminescence lines D1 and D2 in single-crystal silicon and in heavily boron-doped silicon nanostructures on the Si (100) surface. The angular dependence of the spectrum of the optically detected cyclotron resonance corresponds to the tensor of the electron and hole effective mass in single-crystal silicon, and the resonance-line width indicates long carrier free-path times close to 100 ps. The results obtained are discussed within the framework of the interrelation of the electron-vibration coupling to charge and spin correlations in quasi-one-dimensional chains of dangling bonds in silicon.

  7. Electrochemical behavior of nitrogen gas species adsorbed onto boron-doped diamond (BDD) electrodes.

    PubMed

    Manzo-Robledo, A; Lvy-Clment, C; Alonso-Vante, N

    2007-11-01

    The adsorption of nitrogen species, in neutral electrolyte solutions, onto boron-doped diamond (BDD) electrode surfaces from dissolved NO2, NO, and N2O gases was induced at 0 V/SCE. Modified BDD electrode surfaces showed a different electrochemical response toward the hydrogen evolution reaction than did a nonmodified electrode surface in electrolyte base solution. The formation of molecular hydrogen and nitrogen gaseous species was confirmed by the online differential electrochemical mass spectrometry (DEMS) technique. Among the three nitrogen oxides gases, NO2 substantially modifies the electrolyte via hydrolysis leading to the formation of NO3- and its adsorption on the BDD electrode surface. The BDD/(NO3-) interface was the only N2O and N2 species generating system. PMID:17929845

  8. Surface Modification of Boron-Doped Diamond with Microcrystalline Copper Phthalocyanine: Oxygen Reduction Catalysis

    PubMed Central

    Gan, Patrick; Foord, John S; Compton, Richard G

    2015-01-01

    Surface modification of boron-doped diamond (BDD) with copper phthalocyanine was achieved using a simple and convenient dropcast deposition, giving rise to a microcrystalline structure. Both unmodified and modified BDD electrodes of different surface terminations (namely hydrogen and oxygen) were compared via the electrochemical reduction of oxygen in aqueous solution. A significant lowering of the cathodic overpotential by about 500 mV was observed after modification of hydrogen-terminated (hydrophobic) diamond, while no voltammetric peak was seen on modified oxidised (hydrophilic) diamond, signifying greater interaction between copper phthalocyanine and the hydrogen-terminated BDD. Oxygen reduction was found to undergo a two-electron process on the modified hydrogen-terminated diamond, which was shown to be also active for the reduction of hydrogen peroxide. The lack of a further conversion of the peroxide was attributed to its rapid diffusion away from the triple phase boundary at which the reaction is expected to exclusively occur. PMID:26491640

  9. Solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of boron in plant tissues.

    PubMed

    Resano, M; Briceño, J; Aramendía, M; Belarra, M A

    2007-01-23

    In this work, the potential of graphite furnace atomic absorption spectrometry for the direct determination of B in plant tissues has been investigated. Three certified reference materials (NIST SRM 1570a spinach leaves, NIST SRM 1573a tomato leaves and BCR CRM 679 white cabbage) were selected for this study, the goal always being to develop a fast procedure that could be robust enough to provide a satisfactory performance for all of them, without any modifications in the conditions applied. The use of a suitable chemical modifier was found to be essential for obtaining a reproducible and sufficiently sensitive signal for boron solutions. In this regard, the performance of the combination of citric acid plus W (added as a permanent modifier) was noteworthy, resulting in well-defined signal profiles, a remarkable analyte stabilization during the pyrolysis step (up to 2100 degrees C) and minimal memory effects. This mixture of modifiers provided a good performance for the direct analysis of solid samples as well, but only if a suitable temperature program, favoring the interaction between the analyte and the modifiers, was used. Thus, such a temperature program, with two pyrolysis steps and the addition of NH(4)NO(3) in order to carry out the in situ sample microdigestion, was optimized. Under these conditions, the peak areas obtained for both solid samples and aqueous standards were comparable. Finally, the analysis of the samples was carried out. In all cases, a good agreement with the certified values was obtained, while R.S.D. values ranged between 6 and 10%. It can be concluded that the method proposed shows significant advantages for the determination of this complicated element in solid samples such as the use of aqueous standards for calibration, a high sample throughput (20 min per sample), a suitable limit of detection (0.3 microg g(-1)) and reduced risk of analyte losses and contamination. PMID:17386495

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

    SciTech Connect

    Kumar, Vinod; Department of Physics, Gurukula Kangri University, Haridwar 249404 ; Singh, R.G.; Singh, Neetu; Kapoor, Avinashi; Mehra, R.M.; Purohit, L.P.

    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 (ρ), carrier concentration (n) and mobility (μ) of nanostructure films is shown in graph below. A minimum resistivity of 6.8 × 10{sup −4} Ω 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 Ω/□ 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 (ρ) of 6.8 × 10{sup −4} Ω cm in AZB films. ► Minimum sheet resistance (R{sub s}) 24 Ω/□ 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.

  11. Enhanced electrical conductivity in a substitutionally doped spiro-bis(phenalenyl)boron radical molecular solid.

    PubMed

    Pal, Sushanta K; Bag, Pradip; Itkis, Mikhail E; Tham, Fook S; Haddon, Robert C

    2014-10-22

    We report the crystallization of a subsitutionally doped organic conductor based on a host lattice composed of spiro-bis(phenalenyl)boron radicals. Co-crystallization of solutions of spiro-bis(9-oxidophenalenone)boron radical [PLY(O,O)]2B mixed with selected amounts of spiro-bis(9-oxidophenalenone)beryllium [PLY(O,O)]2Be leads to the formation of a series of solid-state solutions of composition [PLY(O,O)]2B(1-x)Be(x). The dopant molecules [PLY(O,O)]2Be serve to introduce holes into the lattice of spins provided by the [PLY(O,O)]2B radicals and lead to a systematic increase in the conductivity while decreasing the activation energy of the conduction process and leaving the solid-state structure relatively unperturbed. While the energies of the hole sites are expected to be high, the results are consistent with the interpretation of the electronic structure of [PLY(O,O)]2B in terms of the resonating valence bond model. PMID:25271884

  12. High performance optical waveguides based on boron and phosphorous doped silicon oxynitride

    NASA Astrophysics Data System (ADS)

    Sun, Fei; Driessen, Alfred; Wörhoff, Kerstin

    2010-02-01

    Silicon oxynitride (SiON) is a highly attractive material for integrated optics, due to its excellent properties such as high transparency, adjustable refractive index and good stability. In general, the growth of SiON layers by plasma enhanced chemical vapor deposition (PECVD) is followed by a high temperature annealing step in order to remove hydrogen and to achieve low propagation losses in the 1.5-μm wavelength window. The high annealing temperature (>1100°C) required for sufficient hydrogen removal induces, however, side effects like significant inter-layer diffusion and micro-cracks resulting in deterioration of the device performance. In this paper compositional and optical properties of as-deposited and annealed boron (B) and phosphorous (P) doped SiON layers were investigated. The doped layers have been fabricated by introducing PH3 and B2H6 gaseous precursors into the PECVD process. Hydrogen contents of the samples have been studied by Fourier transform infrared (FTIR) spectroscopy. Compared to undoped film, a 50% reduction of the hydrogen content was measured in as-deposited P-doped SiON layers. Further reduction down to the FTIR detection limit was achieved upon annealing at temperatures as low as 700°C. Besides hydrogen reduction the reflow properties of B and P doped SiON are also highly relevant for the realization of low-loss integrated optical circuits. Reactively ion etched channel waveguides have been reflown applying a temperature of 900°C. Significant reduction of the sidewall roughness has been confirmed by scanning electron microscopy.

  13. 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.

  14. Development of neuraminidase detection using gold nanoparticles boron-doped diamond electrodes.

    PubMed

    Wahyuni, Wulan T; Ivandini, Tribidasari A; Saepudin, Endang; Einaga, Yasuaki

    2016-03-15

    Gold nanoparticles-modified boron-doped diamond (AuNPs-BDD) electrodes, which were prepared with a self-assembly deposition of AuNPs at amine-terminated boron-doped diamond, were examined for voltammetric detection of neuraminidase (NA). The detection method was performed based on the difference of electrochemical responses of zanamivir at gold surface before and after the reaction with NA in phosphate buffer solution (PBS, pH 5.5). A linear calibration curve for zanamivir in 0.1 M PBS in the absence of NA was achieved in the concentration range of 1 × 10(-6) to 1 × 10(-5) M (R(2) = 0.99) with an estimated limit of detection (LOD) of 2.29 × 10(-6) M. Furthermore, using its reaction with 1.00 × 10(-5) M zanamivir, a linear calibration curve of NA can be obtained in the concentration range of 0-12mU (R(2) = 0.99) with an estimated LOD of 0.12mU. High reproducibility was shown with a relative standard deviation (RSD) of 1.14% (n = 30). These performances could be maintained when the detection was performed in mucin matrix. Comparison performed using gold-modified BDD (Au-BDD) electrodes suggested that the good performance of the detection method is due to the stability of the gold particles position at the BDD surface. PMID:26717895

  15. Batch fabrication of mesoporous boron-doped nickel oxide nanoflowers for electrochemical capacitors

    SciTech Connect

    Yang, Jing-He; Yu, Qingtao; Li, Yamin; Mao, Liqun; Ma, Ding

    2014-11-15

    Highlights: • A new facile liquid-phase method has been employed for synthesis boron-doped NiO nanoflowers. • The specific surface area of NiO is as high as 200 m{sup 2} g{sup −1}. • NiO nanoflowers exhibit a high specific capacitance of ∼1309 F g{sup −1} at a charge and discharge current density of 3 A g{sup −1}. • NiO nanoflowers have excellent cycling ability and even after 2500 cycles there is no significant reduction in specific capacitance. - Abstract: Boron-doped nickel oxide (B-NiO) nanoflowers are prepared by simple thermal decomposition of nickel hydroxide. B-NiO is porous sphere with a diameter of about 400 nm. B-NiO nanoflowers are composed of approximately 30 nm nanoplates and the thickness of the nanosheets is approximately 3 nm. The specific surface area of the material is as high as 200 m{sup 2} g{sup −1} and the pore size distribution curves of B-NiO has three typical peaks in the range of mesoporous (5 nm, 13 nm and 18 nm). As an electrode for supercapacitors, the crystalline B-NiO nanoflowers have favorable characteristics, for instance, a specific capacitance of 1309 F g{sup −1} at a current density of 3 A g{sup −1} and no significant reduction in Coulombic efficiency after 2500 cycles at 37.5 A g{sup −1}. This remarkable electrochemical performance will make B-NiO nanoflowers a promising electrode material for high performance supercapacitors.

  16. 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

  17. Resistance to protein adsorption and adhesion of fibroblasts on nanocrystalline diamond films: the role of topography and boron doping.

    PubMed

    Alcaide, María; Papaioannou, Stavros; Taylor, Andrew; Fekete, Ladislav; Gurevich, Leonid; Zachar, Vladimir; Pennisi, Cristian Pablo

    2016-05-01

    Boron-doped nanocrystalline diamond (BNCD) films exhibit outstanding electrochemical properties that make them very attractive for the fabrication of electrodes for novel neural interfaces and prosthetics. In these devices, the physicochemical properties of the electrode materials are critical to ensure an efficient long-term performance. The aim of this study was to investigate the relative contribution of topography and doping to the biological performance of BNCD films. For this purpose, undoped and boron-doped NCD films were deposited on low roughness (LR) and high roughness (HR) substrates, which were studied in vitro by means of protein adsorption and fibroblast growth assays. Our results show that BNCD films significantly reduce the adsorption of serum proteins, mostly on the LR substrates. As compared to fibroblasts cultured on LR BNCD films, cells grown on the HR BNCD films showed significantly reduced adhesion and lower growth rates. The mean length of fibronectin fibrils deposited by the cells was significantly increased in the BNCD coated substrates, mainly in the LR surfaces. Overall, the largest influence on protein adsorption, cell adhesion, proliferation, and fibronectin deposition was due to the underlying sub-micron topography, with little or no influence of boron doping. In perspective, BNCD films displaying surface roughness in the submicron range may be used as a strategy to reduce the fibroblast growth on the surface of neural electrodes. PMID:26975747

  18. A low-cost cementite (Fe3C) nanocrystal@N-doped graphitic carbon electrocatalyst for efficient oxygen reduction.

    PubMed

    Wu, Tianxing; Zhang, Haimin; Zhang, Xian; Zhang, Yunxia; Zhao, Huijun; Wang, Guozhong

    2015-11-01

    In this work, chitosan whiskers (CWs) were first extracted using low-cost and earth-abundant crab shells as materials by a series of chemical processes, and then assembled into chitosan whisker microspheres (CWMs) via a simple photochemical polymerization approach. Subsequently, a cementite (Fe3C) nanocrystal@N-doped graphitic carbon (Fe3C@NGC) nanocomposite was successfully fabricated by high temperature pyrolysis of CWMs adsorbed with ferric acetylacetonate (Fe(acac)3) at 900 °C. It was found that a suitable growth atmosphere generated inside CWMs during high temperature pyrolysis is critically important to form Fe3C nanocrystal cores, concurrently accompanying a structural transformation from chitosan whiskers to mesoporous graphitic carbon shells with natural nitrogen (N) doping properties, resulting in the formation of a core-shell structure Fe3C@NGC nanocomposite. The resulting samples were evaluated as electrocatalysts for oxygen reduction reaction (ORR). In comparison with sole N-doped graphitic carbon without Fe3C nanocrystals obtained by direct pyrolysis of chitosan whisker microspheres at 900 °C (CWMs-900), Fe3C@NGC showed significantly improved ORR catalytic activity. The tolerance to fuel cell molecules (e.g., methanol) and the durability of Fe3C@NGC are obviously superior to commercial Pt/C catalysts in alkaline media. The high ORR performance of Fe3C@NGC could be due to its large surface area (313.7 m(2) g(-1)), a synergistic role of Fe3C nanocrystals, N doping in graphitic carbon creating more catalytic active sites, and a porous structure of the nanocomposite facilitating mass transfer to efficiently improve the utilization of these catalytic active sites. PMID:26426862

  19. 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

  20. Boron doped g-C3N4 with enhanced photocatalytic UO22+ reduction performance

    NASA Astrophysics Data System (ADS)

    Lu, Changhai; Chen, Rongyue; Wu, Xi; Fan, Meifeng; Liu, Yunhai; Le, Zhanggao; Jiang, Shujuan; Song, Shaoqing

    2016-01-01

    Tuning the band gap and absorption intensity of visible-light by element doping is an attractive strategy to enhance the photocatalytic activity of semiconductor materials. Here we doped boron into g-C3N4 to construct highly efficient photocatalysts (B-g-C3N4) for the photocatalytic reduction of UO22+. Characterization and photocatalysis tests showed the band gap of B-g-C3N4 was narrowed, and the absorption intensity of visible-light was enhanced with increasing the formed N-B-C (BCN) of B-g-C3N4, which is consistent with the trend of the photocatalytic performance of B-g-C3N4. The optimized B-g-C3N4 photocatalyst with BCN content of 1.01 at.% exhibited excellent removal efficiency of UO22+ and good photocatalytic stability. Therefore, these results may lead to a new strategy for exploring the advanced photocatalysts based on the carbon nanomaterials with abundant BCN for the photocatalytic reduction of U(VI) pollutant.

  1. Self- and dopant diffusion in extrinsic boron doped isotopically controlled silicon multilayer structures

    SciTech Connect

    Sharp, Ian D.; Bracht, Hartmut A.; Silvestri, Hughes H.; Nicols, Samuel P.; Beeman, Jeffrey W.; Hansen, John L.; Nylandsted Larsen, Arne; Haller, Eugene E.

    2002-04-01

    Isotopically controlled silicon multilayer structures were used to measure the enhancement of self- and dopant diffusion in extrinsic boron doped silicon. {sup 30}Si was used as a tracer through a multilayer structure of alternating natural Si and enriched {sup 28}Si layers. Low energy, high resolution secondary ion mass spectrometry (SIMS) allowed for simultaneous measurement of self- and dopant diffusion profiles of samples annealed at temperatures between 850 C and 1100 C. A specially designed ion- implanted amorphous Si surface layer was used as a dopant source to suppress excess defects in the multilayer structure, thereby eliminating transient enhanced diffusion (TED) behavior. Self- and dopant diffusion coefficients, diffusion mechanisms, and native defect charge states were determined from computer-aided modeling, based on differential equations describing the diffusion processes. We present a quantitative description of B diffusion enhanced self-diffusion in silicon and conclude that the diffusion of both B and Si is mainly mediated by neutral and singly positively charged self-interstitials under p-type doping. No significant contribution of vacancies to either B or Si diffusion is observed.

  2. 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 μm 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.

  3. Electronic and optical properties of pristine and boron-nitrogen doped graphyne nanotubes.

    PubMed

    Bhattacharya, B; Singh, N B; Mondal, R; Sarkar, U

    2015-07-15

    First principle calculations with generalized gradient approximation were carried out to analyse the electronic and optical properties of armchair and zigzag graphyne nanotubes (GNTs). The possible application of these NTs in optoelectronic devices was also investigated. The GNTs were doped with boron (B) and nitrogen (N) atoms and the resulting band gap tuning was studied with respect to the B/N substitution site and increasing diameter of the NTs. The basis of this variation was examined using the partial density of states and crystal orbital Hamilton population analysis. A decreasing trend in the optical response was seen with an increase in the diameter of the NTs. The reported systems showed anisotropic behaviour in the low-energy region. The origin of the optical responses was monitored from the infrared to the UV region depending on the doping site of the B/N. As a result of the large band gap, low reflectivity and low refractive index, B/N GNTs have been established as a suitable system for novel optoelectronic devices. The strong absorption peaks in the UV region mean that they are a good choice for use in UV light protection. PMID:26138807

  4. Doping, strain engineering, and interlayer interaction in bilayer hexagonal boron nitride sheets

    NASA Astrophysics Data System (ADS)

    Saito, Susumu; Fujimoto, Yoshitaka

    We study electronic properties of bilayer hexagonal boron nitride (h-BN) sheets with different stacking sequences in the framework of the density-functional theory. The bulk h-BN material usually takes the so-called AA (or AA') stacking, corresponding to the ''non-polar'' bilayer h-BN sheet. On the other hand, the rhombohedral BN takes the ABC stacking, and the corresponding bilayer sheet has ''upper'' and ''lower'' layers which are not equivalent with each other. Interestingly, the energetics of stacking sequences for bilayer h-BN sheets is found to be different from that for bulk h-BN materials. We report that strain engineering for bilayer h-BN sheets can possess much wider possibilities than that for monolayer h-BN due to the modification of the interlayer interaction. We also study the substitutional C doping into bilayer h-BN sheets, and report the energetics and the strain effect for these C-doped sheets. Finally we discuss the similarities and differences between bilayer h-BN sheets and double-wall h-BN nanotubes. This work was partly supported by the MEXT Elements Strategy Initiative to Form Core Research Center, Grant in Aid for Scientific Research, MEXT Japan, ``Science of Atomic Layers'', and JSPS KAKENHI Grant No. 26390062.

  5. Metal-bosonic insulator-superconductor transition in boron-doped granular diamond.

    PubMed

    Zhang, Gufei; Zeleznik, Monika; Vanacken, Johan; May, Paul W; Moshchalkov, Victor V

    2013-02-15

    In a variety of superconductors, mostly in two-dimensional (2D) and one-dimensional (1D) systems, the resistive superconducting transition R(T) demonstrates in many cases an anomalous narrow R(T) peak just preceding the onset of the superconducting state R=0 at T(c). The amplitude of this R(T) peak in 1D and 2D systems ranges from a few up to several hundred percent. In three-dimensional (3D) systems, however, the R(T) peak close to T(c) is rarely observed, and it reaches only a few percent in amplitude. Here we report on the observation of a giant (∼1600%) and very narrow (∼1  K) resistance peak preceding the onset of superconductivity in heavily boron-doped diamond. This anomalous R(T) peak in a 3D system is interpreted in the framework of an empirical model based on the metal-bosonic insulator-superconductor transitions induced by a granularity-correlated disorder in heavily doped diamond. PMID:25166395

  6. Dibenzothiophene adsorption at boron doped carbon nanoribbons studied within density functional theory

    SciTech Connect

    López-Albarrán, P.; Navarro-Santos, P.; Garcia-Ramirez, M. A.; Ricardo-Chávez, J. L.

    2015-06-21

    The adsorption of dibenzothiophene (DBT) on bare and boron-doped armchair carbon nanoribbons (ACNRs) is being investigated in the framework of the density functional theory by implementing periodic boundary conditions that include corrections from dispersion interactions. The reactivity of the ACNRs is characterized by using the Fukui functions as well as the electrostatic potential as local descriptors. Non-covalent adsorption mechanism is found when using the local Perdew-Becke-Ernzerhof functional, regardless of the DBT orientation and adsorption location. The dispersion interactions addition is a milestone to describe the adsorption process. The charge defects introduced in small number (i.e., by doping with B atoms), within the ACNRs increases the selectivity towards sulfur mainly due to the charge depletion at B sites. The DBT magnitude in the adsorption energy shows non-covalent interactions. As a consequence, the configurations where the DBT is adsorbed on a BC{sub 3} island increase the adsorption energy compared to random B arrangements. The stability of these configurations can be explained satisfactorily in terms of dipole interactions. Nevertheless, from the charge-density difference analysis and the weak Bader charge-distribution interactions cannot be ruled out completely. This is why the electronic properties of the ribbons are analyzed in order to elucidate the key role played by the B and DBT states in the adsorbed configurations.

  7. Binary and ternary doping of nitrogen, boron, and phosphorus into carbon for enhancing electrochemical oxygen reduction activity.

    PubMed

    Choi, Chang Hyuck; Park, Sung Hyeon; Woo, Seong Ihl

    2012-08-28

    N-doped carbon, a promising alternative to Pt catalyst for oxygen reduction reactions (ORRs) in acidic media, is modified in order to increase its catalytic activity through the additional doping of B and P at the carbon growth step. This additional doping alters the electrical, physical, and morphological properties of the carbon. The B-doping reinforces the sp(2)-structure of graphite and increases the portion of pyridinic-N sites in the carbon lattice, whereas P-doping enhances the charge delocalization of the carbon atoms and produces carbon structures with many edge sites. These electrical and physical alternations of the N-doped carbon are more favorable for the reduction of the oxygen on the carbon surface. Compared with N-doped carbon, B,N-doped or P,N-doped carbon shows 1.2 or 2.1 times higher ORR activity at 0.6 V (vs RHE) in acidic media. The most active catalyst in the reaction is the ternary-doped carbon (B,P,N-doped carbon), which records -6.0 mA/mg of mass activity at 0.6 V (vs RHE), and it is 2.3 times higher than that of the N-doped carbon. These results imply that the binary or ternary doping of B and P with N into carbon induces remarkable performance enhancements, and the charge delocalization of the carbon atoms or number of edge sites of the carbon is a significant factor in deciding the oxygen reduction activity in carbon-based catalysts. PMID:22769428

  8. 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

  9. 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.

  10. Highly-dispersed Boron-doped Graphene Nanosheets Loaded with TiO2 Nanoparticles for Enhancing CO2 Photoreduction

    NASA Astrophysics Data System (ADS)

    Xing, Mingyang; Shen, Fan; Qiu, Bocheng; Zhang, Jinlong

    2014-09-01

    Boron doped graphene nanosheets (B-GR) as a p-type semiconductor, provides much more edges to facilitate the loading of TiO2 nanoparticles (P25). Highly-dispersed P25/B-GR nanosheets with the size of 20-50 nm, are successfully synthesized by the vacuum activation and ultraphonic method. The nanosized morphology can decrease the local density of defects which are induced by the boron substitutional doping, and make the B-GR keeping excellent conductivity and p-type transport property. Ti-O-C bonds are formed during the mixing process, which could efficiently transfer the electrons from TiO2 to B-GR and the holes from B-GR to TiO2. The tunable bandgap of B-GR determines the large potential application of P25/B-GR in the photoreduction of CO2 and other gaseous organic pollutants.

  11. 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.

  12. Spin-polarized electron current from carbon-doped open armchair boron nitride nanotubes: Implication for nano-spintronic devices

    NASA Astrophysics Data System (ADS)

    Zhou, Gang; Duan, Wenhui

    2007-03-01

    Spin-polarized density functional calculations show that the substitutional doping of carbon (C) atom at the mouth changes the atomic and spin configurations of open armchair boron nitride nanotubes (BNNTs). The occupied/unoccupied deep gap states are observed with the significant spin-splitting. The structures and spin-polarized properties are basically stable under the considerable electric field, which is important for practical applications. The magnetization mechanism is attributed to the interactions of s, p states between the C and its neighboring B or N atoms. Ultimately, advantageous geometrical and electronic effects mean that C-doped open armchair BNNTs would have promising applications in nano-spintronic devices.

  13. Boron/nitrogen co-doped helically unzipped multiwalled carbon nanotubes as efficient electrocatalyst for oxygen reduction.

    PubMed

    Zehtab Yazdi, Alireza; Fei, Huilong; Ye, Ruquan; Wang, Gunuk; Tour, James; Sundararaj, Uttandaraman

    2015-04-15

    Bamboo structured nitrogen doped multiwalled carbon nanotubes have been helically unzipped, and nitrogen doped graphene oxide nanoribbons (CNx-GONRs) with a multifaceted microstructure have been obtained. CNx-GONRs have then been codoped with nitrogen and boron by simultaneous thermal annealing in ammonia and boron oxide atmospheres, respectively. The effects of the codoping time and temperature on the concentration of the dopants and their functional groups have been extensively investigated. X-ray photoelectron spectroscopy results indicate that pyridinic and BC3 are the main nitrogen and boron functional groups, respectively, in the codoped samples. The oxygen reduction reaction (ORR) properties of the samples have been measured in an alkaline electrolyte and compared with the state-of-the-art Pt/C (20%) electrocatalyst. The results show that the nitrogen/boron codoped graphene nanoribbons with helically unzipped structures (CNx/CBx-GNRs) can compete with the Pt/C (20%) electrocatalyst in all of the key ORR properties: onset potential, exchange current density, four electron pathway selectivity, kinetic current density, and stability. The development of such graphene nanoribbon-based electrocatalyst could be a harbinger of precious metal-free carbon-based nanomaterials for ORR applications. PMID:25793636

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

    NASA Astrophysics Data System (ADS)

    Kořínek, 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.

  15. 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 μg 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

  16. Feedback-amplified electrochemical dual-plate boron-doped diamond microtrench detector for flow injection analysis.

    PubMed

    Lewis, Grace E M; Gross, Andrew J; Kasprzyk-Hordern, Barbara; Lubben, Anneke T; Marken, Frank

    2015-08-01

    An electrochemical flow cell with a boron-doped diamond dual-plate microtrench electrode has been developed and demonstrated for hydroquinone flow injection electroanalysis in phosphate buffer pH 7. Using the electrochemical generator-collector feedback detector improves the sensitivity by one order of magnitude (when compared to a single working electrode detector). The diffusion process is switched from an analyte consuming "external" process to an analyte regenerating "internal" process with benefits in selectivity and sensitivity. PMID:25735831

  17. 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

  18. Anodic oxidation of wastewater containing the Reactive Orange 16 Dye using heavily boron-doped diamond electrodes.

    PubMed

    Migliorini, F L; Braga, N A; Alves, S A; Lanza, M R V; Baldan, M R; Ferreira, N G

    2011-09-15

    Boron-doped diamond (BDD) films grown on the titanium substrate were used to study the electrochemical degradation of Reactive Orange (RO) 16 Dye. The films were produced by hot filament chemical vapor deposition (HFCVD) technique using two different boron concentrations. The growth parameters were controlled to obtain heavily doped diamond films. They were named as E1 and E2 electrodes, with acceptor concentrations of 4.0 and 8.0 × 10(21)atoms cm(-3), respectively. The boron levels were evaluated from Mott-Schottky plots also corroborated by Raman's spectra, which characterized the film quality as well as its physical property. Scanning Electron Microscopy showed well-defined microcrystalline grain morphologies with crystal orientation mixtures of (111) and (100). The electrode efficiencies were studied from the advanced oxidation process (AOP) to degrade electrochemically the Reactive Orange 16 azo-dye (RO16). The results were analyzed by UV/VIS spectroscopy, total organic carbon (TOC) and high-performance liquid chromatography (HPLC) techniques. From UV/VIS spectra the highest doped electrode (E2) showed the best efficiency for both, the aromaticity reduction and the azo group fracture. These tendencies were confirmed by the TOC and chromatographic measurements. Besides, the results showed a direct relationship among the BDD morphology, physical property, and its performance during the degradation process. PMID:21803493

  19. Low temperature boron and phosphorous doped SiGe for recessed and raised sources and drains

    NASA Astrophysics Data System (ADS)

    Hartmann, J. M.; Py, M.; Barnes, J. P.; Prévitali, B.; Batude, P.; Billon, T.

    2011-07-01

    We have first of all studied the growth kinetics of boron and phosphorous doped, 20-30 nm thick Si 0.65Ge 0.35 layers, the aim being their integration in recessed and raised sources and drains. Those layers have been grown at low pressure (20 Torr) and low temperature (650 °C) with a heavily chlorinated chemistry (in order to be selective versus SiO 2 (isolation) and Si 3N 4 (sidewall spacers)). We have quantified the impact of the diborane and phosphine flow on (i) the SiGe crystalline quality and strain state, (ii) the amount of boron or phosphorous atoms incorporated in it and (iii) the SiGe:B or SiGe:P growth kinetics. As the diborane flow increases, the SiGe:B growth rate definitely increases, while the real Ge concentration (from Time-Of-Flight Secondary Ions Mass Spectrometry) is more or less steady. B atoms, being much smaller than Si or Ge, partially compensate the compressive strain in the SiGe:B layers, leading to a decrease in the apparent Ge concentration (from X-ray diffraction). Opposite trends are observed for SiGe:P. There is indeed a definite decrease in the SiGe:P growth rate together with a definite increase in both the apparent and real Ge concentration as the phosphine flow increases. The Boron atomic concentration increases linearly with the diborane flow, with however a practical limit around 3.5×10 20 cm -3 in order to stay monocrystalline. Meanwhile, the phosphorous atomic concentration saturates quite rapidly at values close to 8-9×10 19 cm -3 as the phosphine flow increases (most likely due to surface segregation). In the second part we have highlighted some of the difficulties encountered when trying to selectively grow intrinsic SiGe raised S/Ds at 650 °C on patterned, extra-thin Silicon-On-Insulator wafers and some of the solutions identified in order to obtain 2D thick films. Amongst those, we can mention the 750 °C deposition of a thin Si buffer or the in-situ high HCl partial pressure etch at 650 °C of a few nm of Si prior to SiGe Selective Epitaxial Growth (SEG), the drastic reduction of the incoming HCl flow during SiGe SEG, etc.

  20. Determination of trace impurities in boron nitride by graphite furnace atomic absorption spectrometry and electrothermal vaporization inductively coupled plasma optical emission spectrometry using solid sampling

    NASA Astrophysics Data System (ADS)

    Barth, P.; Hassler, J.; Kudrik, I.; Krivan, V.

    2007-09-01

    Two digestion-free methods for trace analysis of boron nitride based on graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma spectrometry optical emission (ETV-ICP-OES) using direct solid sampling have been developed and applied to the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Si, Ti and Zr in four boron nitride materials in concentration intervals of 1-23, 54-735, 0.05-21, 0.005-1.3, 1.6-112, 4.5-20, 0.03-1.8, 6-46, 38-170 and 0.4-2.3 μg g - 1 , respectively. At optimized experimental conditions, with both methods, effective in-situ analyte/matrix separation was achieved and calibration could be performed using calibration curves measured with aqueous standard solutions. In solid sampling GFAAS, before sampling, the platform was covered with graphite powder and, for determination of Si, also the Pd/Mg(NO 3) 2 modifier was used. In the determination of all analyte elements by solid sampling ETV-ICP-OES, Freon R12 was added to argon carrier gas. For solid sampling GFAAS and ETV-ICP-OES, the achievable limits of detection were within 5 (Cu)-130 (Si) ng g - 1 and 8 (Cu)-200 (Si) ng g - 1 , respectively. The results obtained by these two methods for four boron nitride materials of different purity grades are compared each with the other and with those obtained in analysis of digests by ICP-OES. The performance of the two solid sampling methods is compared and discussed.

  1. Boron doped nanostructure ZnO films deposited by ultrasonic spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Karakaya, Seniye; Ozbas, Omer

    2015-02-01

    ZnO is an II-VI compound semiconductor with a wide direct band gap of 3.3 eV at room temperature. Doped with group III elements (B, Al or Ga), it becomes an attractive candidate to replace tin oxide (SnO2) or indium tin oxide (ITO) as transparent conducting electrodes in solar cell devices and flat panel display due to competitive electrical and optical properties. In this work, ZnO and boron doped ZnO (ZnO:B) films have been deposited onto glass substrates at 350 ± 5 °C by a cost-efficient ultrasonic spray pyrolysis technique. The optical, structural, morphological and electrical properties of nanostructure undoped and ZnO:B films have been investigated. Electrical resistivity of films has been analyzed by four-probe technique. Optical properties and thicknesses of the films have been examined in the wavelength range 1200-1600 nm by using spectroscopic ellipsometry (SE) measurements. The optical constants (refractive index (n) and extinction coefficient (k)) and the thicknesses of the films have been fitted according to Cauchy model. The optical method has been used to determine the band gap value of the films. Transmission spectra have been taken by UV spectrophotometer. It is found that both ZnO and ZnO:B films have high average optical transmission (≥80%). X-ray diffraction (XRD) patterns indicate that the obtained ZnO has a hexagonal wurtzite type structure. The morphological properties of the films were studied by atomic force microscopy (AFM). The surface morphology of the nanostructure films is found to depend on the concentration of B. As a result, ZnO:B films are promising contender for their potential use as transparent window layer and electrodes in solar cells.

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

    PubMed

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

    2014-04-01

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

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

    PubMed Central

    2014-01-01

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

  4. Osmium Atoms and Os2 Molecules Move Faster on Selenium-Doped Compared to Sulfur-Doped Boronic Graphenic Surfaces.

    PubMed

    Barry, Nicolas P E; Pitto-Barry, Anaïs; Tran, Johanna; Spencer, Simon E F; Johansen, Adam M; Sanchez, Ana M; Dove, Andrew P; O'Reilly, Rachel K; Deeth, Robert J; Beanland, Richard; Sadler, Peter J

    2015-07-28

    We deposited Os atoms on S- and Se-doped boronic graphenic surfaces by electron bombardment of micelles containing 16e complexes [Os(p-cymene)(1,2-dicarba-closo-dodecarborane-1,2-diselenate/dithiolate)] encapsulated in a triblock copolymer. The surfaces were characterized by energy-dispersive X-ray (EDX) analysis and electron energy loss spectroscopy of energy filtered TEM (EFTEM). Os atoms moved ca. 26× faster on the B/Se surface compared to the B/S surface (233 ± 34 pm·s(-1) versus 8.9 ± 1.9 pm·s(-1)). Os atoms formed dimers with an average Os-Os distance of 0.284 ± 0.077 nm on the B/Se surface and 0.243 ± 0.059 nm on B/S, close to that in metallic Os. The Os2 molecules moved 0.83× and 0.65× more slowly than single Os atoms on B/S and B/Se surfaces, respectively, and again markedly faster (ca. 20×) on the B/Se surface (151 ± 45 pm·s(-1) versus 7.4 ± 2.8 pm·s(-1)). Os atom motion did not follow Brownian motion and appears to involve anchoring sites, probably S and Se atoms. The ability to control the atomic motion of metal atoms and molecules on surfaces has potential for exploitation in nanodevices of the future. PMID:26525180

  5. Osmium Atoms and Os2 Molecules Move Faster on Selenium-Doped Compared to Sulfur-Doped Boronic Graphenic Surfaces

    PubMed Central

    2015-01-01

    We deposited Os atoms on S- and Se-doped boronic graphenic surfaces by electron bombardment of micelles containing 16e complexes [Os(p-cymene)(1,2-dicarba-closo-dodecarborane-1,2-diselenate/dithiolate)] encapsulated in a triblock copolymer. The surfaces were characterized by energy-dispersive X-ray (EDX) analysis and electron energy loss spectroscopy of energy filtered TEM (EFTEM). Os atoms moved ca. 26× faster on the B/Se surface compared to the B/S surface (233 ± 34 pm·s–1versus 8.9 ± 1.9 pm·s–1). Os atoms formed dimers with an average Os–Os distance of 0.284 ± 0.077 nm on the B/Se surface and 0.243 ± 0.059 nm on B/S, close to that in metallic Os. The Os2 molecules moved 0.83× and 0.65× more slowly than single Os atoms on B/S and B/Se surfaces, respectively, and again markedly faster (ca. 20×) on the B/Se surface (151 ± 45 pm·s–1 versus 7.4 ± 2.8 pm·s–1). Os atom motion did not follow Brownian motion and appears to involve anchoring sites, probably S and Se atoms. The ability to control the atomic motion of metal atoms and molecules on surfaces has potential for exploitation in nanodevices of the future. PMID:26525180

  6. QUANTIFICATION OF MERCURY IN FLUE GAS EMISSION USING BORON-DOPED DIAMOND ELECTROCHEMISTRY

    SciTech Connect

    A. Manivannan; M.S. Seehra

    2003-08-19

    In this project, we have attempted to develop a new technique utilizing Boron-doped diamond (BDD) films to electrochemically detect mercury dissolved in solution via the initial deposition of metallic mercury, followed by anodic linear sweep voltammetry in the range from 10-10{sup -10} M to 10{sup -5} M. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were employed. The extremely low background current for BDD electrodes compared to glassy carbon (GC) provides a strong advantage in trace metal detection. CV peak currents showed good linearity in the micromolar range. A detection level of 6.8 x 10{sup -10} M was achieved with DPV in 0.1 M KNO{sub 3} (pH = 1) for a deposition time of 20 minutes. Reproducible stripping peaks were obtained, even for the low concentration range. A comparison with GC shows that BDD is superior. Linear behavior was also obtained in the mercury concentration range from 10{sup -10} M to 10{sup -9} M.

  7. 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

  8. Electrochemical grafting of boron-doped single-crystalline chemical vapor deposition diamond with nitrophenyl molecules.

    PubMed

    Uetsuka, Hiroshi; Shin, Dongchan; Tokuda, Norio; Saeki, Kazuhiko; Nebel, Christoph E

    2007-03-13

    The growth of covalently bonded nitrophenyl layers on atomically smooth boron-doped single-crystalline diamond surfaces is characterized using cyclic voltammetric attachment and constant-potential grafting by electrochemical reduction of aryl diazonium salts. We apply atomic force microscopy (AFM) in contact mode to remove phenyl layers and measure phenyl layer thicknesses by oscillatory AFM. Angle-resolved X-ray photoelectron spectroscopy is applied to reveal the bonding arrangement of phenyl molecules, and transient current measurements during the grafting are used to investigate the dynamics of chemical bonding. Nitrophenyl groups at an initial stage of attachment grow three-dimensional (3D), forming layers of varying heights and densities. Layer thicknesses of up to 80 A are detected for cyclic voltammetry attachment after five cycles, whereas the layer becomes denser and only about 25 A thick in the case of constant-potential attachment. No monomolecular closed layer can be detected. The data are discussed taking into account established growth models. Redox systems such as Fe(CN)63-/4- and Ru(NH3)62+/3+ are used to probe the electrochemical barrier properties of nitrophenyl groups grafted onto diamond. PMID:17291021

  9. Ordering mechanisms of periodic stripe arrays on boron-doped Si(100)

    NASA Astrophysics Data System (ADS)

    Ermanoski, Ivan; Kellogg, Gary; Bartelt, Norman

    2009-03-01

    We have used low energy electron microscopy to determine the factors that control the degree of order in self-assembled periodic stripe arrays on the atomically flat Si(100) with high boron doping. The stripes consist of extremely elongated vacancy islands of single atomic height, formed at ˜900C, confined in micrometer-sized pits. ``Perfect'' arrays of parallel stripes (in pits of up to ˜10um in size) were formed by allowing various defects to heal over relatively long periods of time. Sublimation was compensated for by an external Si doser, allowing observation of stripe evolution over the course of hours, with no net loss or gain of Si from the area of interest. Stripe formation and ordering mechanisms include spontaneous nucleation and growth of new islands, longitudinal splitting, as well as coarsening due to surface diffusion. Stripe periodicity depends on temperature, allowing for control of this property. Stripes are stable in a range of ˜100C, outside of which they assume the familiar shape of elongated islands, shaped by the anisotropy in step energy. Stripe order can be preserved to room temperature by quenching. References: [1] J.-F. Nielsen et al., Appl. Phys. Lett. 79 (2001) 3857

  10. Structural modification of boron-doped ZnO layers caused by hydrogen outgassing

    NASA Astrophysics Data System (ADS)

    Lovics, R.; Csik, A.; Takáts, V.; Hakl, J.; Vad, K.

    2015-07-01

    Results of annealing experiments of boron-doped zinc oxide (ZnO:B) layers prepared by low pressure chemical vapor deposition method on polished Si, soda-lime glass for windows, and AF45 Schott alkali free thin glass substrates are presented. It is shown that short annealing of samples at 150 °C and 300 °C in air causes serious surface degradation of samples prepared on Si and soda-lime glass substrate. The characteristic feature of degradation is the creation of bubbles and craters on the sample surface which fully destroy the continuity of zinc oxide layers. The results of depth distribution mapping of elements indicate that the formation of bubbles is linked to increase in hydrogen concentration in the layer. The surface degradation was not noticed on samples deposited on AF45 Schott alkali free thin glass which has a SiO2 diffusion barrier layer on the surface, only much fewer and smaller bubbles were visible. The results indicate the important role of hydrogen outgassing from the substrate induced by a thermal shock.

  11. 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

  12. 3D-nanostructured boron-doped diamond for microelectrode array neural interfacing.

    PubMed

    Piret, Gaëlle; Hébert, Clément; Mazellier, Jean-Paul; Rousseau, Lionel; Scorsone, Emmanuel; Cottance, Myline; Lissorgues, Gaelle; Heuschkel, Marc O; Picaud, Serge; Bergonzo, Philippe; Yvert, Blaise

    2015-06-01

    The electrode material is a key element in the design of long-term neural implants and neuroprostheses. To date, the ideal electrode material offering high longevity, biocompatibility, low-noise recording and high stimulation capabilities remains to be found. We show that 3D-nanostructured boron doped diamond (BDD), an innovative material consisting in a chemically stable material with a high aspect ratio structure obtained by encapsulation of a carbon nanotube template within two BDD nanolayers, allows neural cell attachment, survival and neurite extension. Further, we developed arrays of 20-μm-diameter 3D-nanostructured BDD microelectrodes for neural interfacing. These microelectrodes exhibited low impedances and low intrinsic recording noise levels. In particular, they allowed the detection of low amplitude (10-20 μV) local-field potentials, single units and multiunit bursts neural activity in both acute whole embryonic hindbrain-spinal cord preparations and long-term hippocampal cell cultures. Also, cyclic voltammetry measurements showed a wide potential window of about 3 V and a charge storage capacity of 10 mC.cm(-2), showing high potentiality of this material for neural stimulation. These results demonstrate the attractiveness of 3D-nanostructured BDD as a novel material for neural interfacing, with potential applications for the design of biocompatible neural implants for the exploration and rehabilitation of the nervous system. PMID:25890717

  13. 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.

  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. Hydrogen passivation of interstitial iron in boron-doped multicrystalline silicon during annealing

    SciTech Connect

    Liu, AnYao; Sun, Chang; Macdonald, Daniel

    2014-11-21

    Effective hydrogenation of interstitial iron in boron-doped multicrystalline silicon wafers is reported. The multicrystalline silicon wafers were annealed with plasma-enhanced chemical vapour deposited silicon nitride films, at temperatures of 400 °C – 900 °C and for times from minutes to hours. At low temperatures where a combined effect of hydrogenation and precipitation of dissolved Fe is expected, results show that the hydrogenation process dominates the effect of precipitation. The concentrations of dissolved interstitial iron reduce by more than 90% after a 30-min anneal at temperatures between 600 and 900 °C. The most effective reduction occurs at 700 °C, where 99% of the initial dissolved iron is hydrogenated after 30 min. The results show that the observed reductions in interstitial Fe concentrations are not caused by the internal gettering of Fe at structural defects or by an enhanced diffusivity of Fe due to the presence of hydrogen. The hydrogenation process is conjectured to be the pairing of positively charged iron with negatively charged hydrogen, forming less recombination active Fe-H complexes in silicon.

  16. Boron-doped diamond anodic treatment of olive mill wastewaters: statistical analysis, kinetic modeling and biodegradability.

    PubMed

    Chatzisymeon, Efthalia; Xekoukoulotakis, Nikolaos P; Diamadopoulos, Evan; Katsaounis, Alexandros; Mantzavinos, Dionissios

    2009-09-01

    The electrochemical treatment of olive mill wastewaters (OMW) over boron-doped diamond (BDD) electrodes was investigated. A factorial design methodology was implemented to evaluate the statistically important operating parameters, amongst initial COD load (1000-5000 mg/L), treatment time (1-4h), current intensity (10-20A), initial pH (4-6) and the use of 500 mg/L H(2)O(2) as an additional oxidant, on treatment efficiency; the latter was assessed in terms of COD, phenols, aromatics and color removal. Of the five parameters tested, the first two had a considerable effect on COD removal. Hence, analysis was repeated at more intense conditions, i.e. initial COD values up to 10,000 mg/L and reaction times up to 7h and a simple model was developed and validated to predict COD evolution profiles. The model suggests that the rate of COD degradation is zero order regarding its concentration and agrees well with an electrochemical model for the anodic oxidation of organics over BDD developed elsewhere. The treatability of the undiluted effluent (40,000 mg/L COD) was tested at 20A for 15h yielding 19% COD and 36% phenols' removal respectively with a specific energy consumption of 96 kWh/kg COD removed. Aerobic biodegradability and ecotoxicity assays were also performed to assess the respective effects of electrochemical treatment. PMID:19423147

  17. Semiconducting polymers with nanocrystallites interconnected via boron-doped carbon nanotubes.

    PubMed

    Yu, Kilho; Lee, Ju Min; Kim, Junghwan; Kim, Geunjin; Kang, Hongkyu; Park, Byoungwook; Ho Kahng, Yung; Kwon, Sooncheol; Lee, Sangchul; Lee, Byoung Hun; Kim, Jehan; Park, Hyung Il; Kim, Sang Ouk; Lee, Kwanghee

    2014-12-10

    Organic semiconductors are key building blocks for future electronic devices that require unprecedented properties of low-weight, flexibility, and portability. However, the low charge-carrier mobility and undesirable processing conditions limit their compatibility with low-cost, flexible, and printable electronics. Here, we present significantly enhanced field-effect mobility (μ(FET)) in semiconducting polymers mixed with boron-doped carbon nanotubes (B-CNTs). In contrast to undoped CNTs, which tend to form undesired aggregates, the B-CNTs exhibit an excellent dispersion in conjugated polymer matrices and improve the charge transport between polymer chains. Consequently, the B-CNT-mixed semiconducting polymers enable the fabrication of high-performance FETs on plastic substrates via a solution process; the μFET of the resulting FETs reaches 7.2 cm(2) V(-1) s(-1), which is the highest value reported for a flexible FET based on a semiconducting polymer. Our approach is applicable to various semiconducting polymers without any additional undesirable processing treatments, indicating its versatility, universality, and potential for high-performance printable electronics. PMID:25372930

  18. Non-enzymatic electrochemical detection of glycerol on boron-doped diamond electrode.

    PubMed

    Pop, Aniela; Manea, Florica; Radovan, Ciprian; Dascalu, Dana; Vaszilcsin, Nicolae; Schoonman, Joop

    2012-02-01

    A non-enzymatic direct electrochemical glycerol detection method at a commercial boron-doped diamond (BDD) electrode in 0.1 M NaOH supporting electrolyte was developed. All the used electrochemical techniques proved useful features for the oxidation and direct amperometric determination of glycerol at a BDD electrode in 0.1 M NaOH aqueous solution. It was found that the direct electrooxidation of glycerol on the BDD electrode requires both adsorbed glycerol and hydroxyls at the electrode surface. Also, the sp(2) carbon did not allow enhancement of the glycerol oxidation process. The electronalytical sensitivity for the determination of glycerol at the BDD electrode ranged from 0.040 to 0.226 μA mM(-1) as a function of the technique used. The highest electroanalytical sensitivity for the determination of glycerol at the BDD electrode was reached in batch system amperometric quantification under stirring conditions. Performed recovery studies indicated that it is possible to determine glycerol in real samples, and the proposed batch system analysis-based methodology can be a valuable tool for practical glycerol analysis. PMID:22159176

  19. Boron-doped diamond nano/microelectrodes for bio-sensing and in vitro measurements

    PubMed Central

    Dong, Hua; Wang, Shihua; Galligan, James J.; Swain, Greg M.

    2015-01-01

    Since the fabrication of the first diamond electrode in the mid 1980s, repid progress has been made on the development and application of this new type of electrode material. Boron-doped diamond (BDD) electrodes exhibit outstanding properties compared to oxygen-containing sp2 carbon electrodes. These properties make BDD electrodes an ideal choice for use in complex samples. In recent years, BDD microelectrodes have been applied to in vitro and in vivo measurements of biological molecules in animals, tissues and cells. This review will summarize recent progress in the development and applications of BDD electrodes in bio-sensing and in vitro measurements of biomolecules. In the first section, the methods for BDD nanocrystalline diamond film deposition and BDD microelectrodes preparation are described. This is followed by a description and discussion of several approaches for characterization of the BDD electrode surface structure, morphology, and electrochemical activity. Further, application of BDD microelectrodes for use in the in vitro analysis of norepinephrine (NE), serotonin (5-HT), nitric oxide (NO), histamine, and adenosine from tissues are summarized and finally some of the remaining challenges are discussed. PMID:21196394

  20. Magnetism of single-walled silicon carbide nanotubes doped by boron, nitrogen and oxygen

    NASA Astrophysics Data System (ADS)

    Maghnaoui, Ahmed; Boufelfel, Ahmed

    2012-09-01

    We calculated, using spin polarized density functional theory, the electronic properties of zigzag (10,0) and armchair (6,6) semiconductor silicon carbide nanotubes (SiCNTs) doped once at the time with boron, nitrogen, and oxygen. We have looked at the two possible scenarios where the guest atom X (B, N, O), replaces the silicon XSi, or the carbon atom XC, in the unit cell. We found that in the case of one atom B @ SiCNT replacing a carbon atom position annotated by BC exhibits a magnetic moment of 1 μB/cell in both zigzag and armchair nanotubes. Also, B replacing Si, (BSi), induce a magnetic moment of 0.46 μB/cell in the zigzag (10,0) but no magnetic moment in armchair (6,6). For N substitution; (NC) and (NSi) each case induce a magnetic moment of 1 μB/cell in armchair (6,6), while NSi give rise to 0.75 μB/cell in zigzag (10,0) and no magnetic moment for NC. In contrast the case of OC and OSi did not produce any net magnetic moment in both zigzag and armchair geometries.

  1. Electrochemical treatment of cork boiling wastewater with a boron-doped diamond anode.

    PubMed

    Fernandes, Annabel; Santos, Diana; Pacheco, Maria José; Ciríaco, Lurdes; Simões, Rogério; Gomes, Arlindo C; Lopes, Ana

    2015-01-01

    Anodic oxidation at a boron-doped diamond anode of cork boiling wastewater was successfully used for mineralization and biodegradability enhancement required for effluent discharge or subsequent biological treatment, respectively. The influence of the applied current density (30-70 mA/cm2) and the background electrolyte concentration (0-1.5 g/L Na2SO4) on the performance of the electrochemical oxidation was investigated. The supporting electrolyte was required to achieve conductivities that enabled anodic oxidation at the highest current intensities applied. The results indicated that pollutant removal increased with the applied current density, and after 8 h, reductions greater than 90% were achieved for COD, dissolved organic carbon, total phenols and colour. The biodegradability enhancement was from 0.13 to 0.59 and from 0.23 to 0.72 for the BOD/COD ratios with BOD of 5 and 20 days' incubation period, respectively. The tests without added electrolyte were performed at lower applied electrical charges (15 mA/cm2 or 30 V) with good organic load removal (up to 80%). For an applied current density of 30 mA/cm2, there was a minimum of electric conductivity of 1.9 mS/cm (corresponding to 0.75 g/L of Na2SO4), which minimized the specific energy consumption. PMID:25409580

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

    PubMed

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

    2013-07-28

    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 π-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. PMID:23902005

  3. Microfluidic platform for environmental contaminants sensing and degradation based on boron-doped diamond electrodes.

    PubMed

    Medina-Snchez, Mariana; Mayorga-Martinez, CarmenC; Watanabe, Takeshi; Ivandini, TribidasariA; Honda, Yuki; Pino, Flavio; Nakata, Kazuya; Fujishima, Akira; Einaga, Yasuaki; Merkoi, Arben

    2016-01-15

    We have developed a lab-on-a-chip (LOC) platform for electrochemical detection and degradation of the pesticide atrazine (Atz). It is based on boron-doped diamond (BDD) electrodes and a competitive magneto-enzyme immunoassay (EIA) that enables high sensitivity. To detect the enzymatic reaction, we employed a BDD electrode modified with platinum nanoparticles (PtNPs), as a highly conductive catalytic transducer. Chronoamperometry revealed a limit of detection (LOD) of 3.5 pM for atrazine, which, to the best of our knowledge, is one of the lowest value published to date. Finally, we degraded Atz in the same platform, using a bare BDD electrode that features remarkable corrosion stability, a wide potential window, and much higher O2 overvoltage as compared to conventional electrodes. These characteristics enable the electrode to produce a greater amount of HO on the anode surface than do conventional electrodes and consequently, to destroy the pollutant more rapidly. Our new LOC platform might prove interesting as a smart system for detection and remediation of diverse pesticides and other contaminants. PMID:26339934

  4. 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.

  5. Thin layer of ordered boron-doped TiO2 nanotubes fabricated in a novel type of electrolyte and characterized by remarkably improved photoactivity

    NASA Astrophysics Data System (ADS)

    Siuzdak, Katarzyna; Szkoda, Mariusz; Lisowska-Oleksiak, Anna; Grochowska, Katarzyna; Karczewski, Jakub; Ryl, Jacek

    2015-12-01

    This paper reports a novel method of boron doped titania nanotube arrays preparation by electrochemical anodization in electrolyte containing boron precursor - boron trifluoride diethyl etherate (BF3 C4H10O), simultaneously acting as an anodizing agent. A pure, ordered TiO2 nanotubes array, as a reference sample, was also prepared in solution containing a standard etching compound: ammonium fluoride. The doped and pure titania were characterized by scanning electron microscopy, UV-vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, photoluminescence emission spectroscopy and by means of electrochemical methods. The B-doping decidedly shifts the absorption edge of TiO2 nanotubes towards the visible light region and significantly inhibits the radiative recombination processes. Despite the fact that the doped sample is characterized by 4.6 lower real surface area when compared to pure titania, it leads to the decomposition of methylene blue in 93%, that is over 2.3 times higher than the degradation efficiency exhibited by the undoped material. The formation rate of hydroxyl radicals (rad OH) upon illumination significantly favours boron doped titania as a photocatalytic material. Moreover, the simple doping of TiO2 nanotubes array results in the enhancement of generated photocurrent from 120 μA/cm2 to 350 μA/cm2 registered for undoped and doped electrode, respectively.

  6. Hard magnetic property enhancement of Co{sub 7}Hf-based ribbons by boron doping

    SciTech Connect

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

    2014-11-10

    Hard magnetic property enhancement of melt spun Co{sub 88}Hf{sub 12} ribbons by boron doping is demonstrated. B-doping could not only remarkably enhance the magnetic properties from energy product ((BH){sub max}) of 2.6 MGOe and intrinsic coercivity ({sub i}H{sub c}) of 1.5 kOe for B-free Co{sub 88}Hf{sub 12} ribbons to (BH){sub max} = 7.7 MGOe and {sub i}H{sub c} = 3.1 kOe for Co{sub 85}Hf{sub 12}B{sub 3} ribbons but also improve the Curie temperature (T{sub C}) of 7:1 phase. The (BH){sub max} value achieved in Co{sub 85}Hf{sub 12}B{sub 3} ribbons is the highest in Co-Hf alloy ribbons ever reported, which is about 15% higher than that of Co{sub 11}Hf{sub 2}B 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 Co{sub 7}Hf (7:1) crystal structure as interstitial atoms, forming Co{sub 7}HfB{sub x}, 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 (B{sub r}) and improves the squareness of demagnetization curve. The formation of interstitial-atom-modified Co{sub 7}HfB{sub x} phase and the microstructure refinement are the main reasons to give rise to the enhancement of hard magnetic properties in the B-containing Co{sub 7}Hf-based ribbons.

  7. Investigation of Boron-doping Effect on Photoluminescence Properties of CdNb2O6: Eu(3+) Phosphors.

    PubMed

    Ba?ak, Ali Sadi; Ekmeki, Mete Kaan; Erdem, Murat; Ilhan, Mustafa; Mergen, Ayhan

    2016-03-01

    Pure, Eu(3+)-doped and Eu(3+),B(3+) co-doped CdNb2O6 powders have been prepared by a molten salt synthesis method using Li2SO4/Na2SO4 salt mixture as a flux at a relatively low temperatures as compared to solid state reaction. X-ray diffraction patterns of pure CdNb2O6 samples indicated orthorhombic single phase. Photoluminescence investigations of CdNb2O6 samples showed a strong blue emission band centered at 460nm. For Eu-doped CdNb2O6 samples, the luminescence of Eu(3+) was observed with the host red emission varying with the Eu-doping concentrations. This PL characteristic of the doped samples may be attributed to the energy transfer between Eu(3+) and niobate groups (NbO6). Boron incorporation has remarkably increased the luminescence of Eu(3+)-doped CdNb2O6. PMID:26753755

  8. Empirical determination of the energy band gap narrowing in p{sup +} silicon heavily doped with boron

    SciTech Connect

    Yan, Di Cuevas, Andres

    2014-11-21

    In the analysis of highly doped silicon, energy band gap narrowing (BGN) and degeneracy effects may be accounted for separately, as a net BGN in conjunction with Fermi-Dirac statistics, or lumped together in an apparent BGN used with Boltzmann statistics. This paper presents an experimental study of silicon highly doped with boron, with the aim of evaluating the applicability of previously reported BGN models. Different boron diffusions covering a broad range of dopant densities were prepared, and their characteristic recombination current parameters J{sub 0} were measured using a contactless photoconductance technique. The BGN was subsequently extracted by matching theoretical simulations of carrier transport and recombination in each of the boron diffused regions and the measured J{sub 0} values. An evaluation of two different minority carrier mobility models indicates that their impact on the extraction of the BGN is relatively small. After considering possible uncertainties, it can be concluded that the BGN is slightly larger in p{sup +} silicon than in n{sup +} silicon, in qualitative agreement with theoretical predictions by Schenk. Nevertheless, in quantitative terms that theoretical model is found to slightly underestimate the BGN in p{sup +} silicon. With the two different parameterizations derived in this paper for the BGN in p{sup +} silicon, both statistical approaches, Boltzmann and Fermi-Dirac, provide a good agreement with the experimental data.

  9. 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.

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

    SciTech Connect

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

    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.

  11. 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

  12. Improved electrochemical performance of boron-doped SiO negative electrode materials in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Woo, Jihoon; Baek, Seong-Ho; Park, Jung-Soo; Jeong, Young-Min; Kim, Jae Hyun

    2015-12-01

    We introduce a one-step process that consists of thermal disproportionation and impurity doping to enhance the reversible capacity and electrical conductivity of silicon monoxide (SiO)-based negative electrode materials in Li-ion batteries. Transmission electron microscope (TEM) results reveal that thermally treated SiO at 900 °C (H-SiO) consists of uniformly dispersed nano-crystalline Si (nc-Si) in an amorphous silicon oxide (SiOx) matrix. Compared to that of prinstine SiO, the electrochemical performance of H-SiO shows improved specific capacity, due mainly to the increased reversible capacity by nc-Si and to the reduced volume expansion by thermally disproportionated SiOx matrix. Further electrochemical improvements can be obtained by boron-doping on SiO (HB-SiO) using solution dopant during thermal disproportionation. HB-SiO electrode without carbon coating exhibits significantly enhanced specific capacity superior to that of undoped H-SiO electrode, having 947 mAh g-1 at 0.5C rate and excellent capacity retention of 93.3% over 100 cycles. Electrochemical impedance spectroscopy (EIS) measurement reveals that the internal resistance of the HB-SiO electrode is significantly reduced by boron doping.

  13. Sulfate-mediated electrooxidation of X-ray contrast media on boron-doped diamond anode.

    PubMed

    Radjenovic, Jelena; Petrovic, Mira

    2016-05-01

    Recently, electrochemical activation of sulfate ions to sulfate radical species and nonradically activated persulfate has been demonstrated at boron-doped diamond (BDD) anode, which enhanced the electrooxidation kinetics of several persistent contaminants. In this study, we investigated the transformation pathways of two X-ray contrast media (ICM), diatrizoate and iopromide, in electrooxidation at BDD anode using sulfate and inert nitrate anolyte. Sulfate anolyte yielded a seven-fold increase in apparent rate constants for ICM oxidation compared to inert nitrate anolyte, and a two-fold increase for the removal of organic carbon. Higher iodine release was observed in electrooxidation of diatrizoate compared to iopromide. In the case of diatrizoate, around 80% of deiodination efficiency was achieved in both anolytes. Deiodination efficiency of iopromide was somewhat lower in nitrate anolyte (≤75%) and significantly reduced in sulfate anolyte (≤46%) due to a larger steric hindrance of alkyl side chains. Moreover, a considerable lag phase of iopromide deiodination was observed in sulfate anolyte, indicating that initial oxidation reactions took place almost exclusively at the alkyl side chains. Several transformation products (TPs) of ICM were identified in electrooxidation in sulfate anolyte, and only three TPs in the case of nitrate anolyte. The main mechanistic steps in the oxidation of iopromide were H-abstraction and bond cleavage in the alkyl side chains. Diatrizoate was mainly transformed through oxidative cleavage of iodine substituent and inter-molecular cyclization. Two hydroxylamine derivatives of iopromide and a nitro-derivative of diatrizoate were observed in sulfate anolyte. These products have not been reported previously for hydroxyl radical-mediated oxidation of ICM. Given that electron-transfer mechanism is more typical for sulfate than for hydroxyl radicals, formation of hydroxylamine and nitro-derivatives of ICM was assigned to one-electron charge transfer to sulfate radical species and formation of N-centered radicals. PMID:26938498

  14. Kinetics of the electrochemical mineralization of perfluorooctanoic acid on ultrananocrystalline boron doped conductive diamond electrodes.

    PubMed

    Urtiaga, Ane; Fernández-González, Carolina; Gómez-Lavín, Sonia; Ortiz, Inmaculada

    2015-06-01

    This work deals with the electrochemical degradation and mineralization of perfluorooctanoic acid (PFOA). Model aqueous solutions of PFOA (100mg/L) were electro-oxidized under galvanostatic conditions in a flow-by undivided cell provided with a tungsten cathode and an anode formed by a commercial ultrananocrystalline boron doped diamond (BDD) coating on a niobium substrate. A systematic experimental study was conducted in order to analyze the influence of the following operation variables: (i) the supporting electrolyte, NaClO4 (1.4 and 8.4g/L) and Na2SO4 (5g/L); (ii) the applied current density, japp, in the range 50-200 A/m(2) and (iii) the hydrodynamic conditions, in terms of flowrate in the range 0.4×10(-4)-1.7×10(-4)m(3)/s and temperature in the range 293-313K. After 6h of treatment and at japp 200A/m(2), PFOA removal was higher than 93% and the mineralization ratio, obtained from the decrease of the total organic carbon (TOC) was 95%. The electrochemical generation of hydroxyl radicals in the supporting electrolyte was experimentally measured based on their reaction with dimethyl sulfoxide. The enhanced formation of hydroxyl radicals at higher japp was related to the faster kinetics of PFOA removal. The fitting of experimental data to the proposed kinetic model provided the first order rate constants of PFOA degradation, kc(1) that moved from 2.06×10(-4) to 15.58×10(-4)s(-1), when japp varied from 50 to 200A/m(2). PMID:24981910

  15. Toward a Boron-Doped Ultrananocrystalline Diamond Electrode-Based Dielectrophoretic Preconcentrator.

    PubMed

    Zhang, Wenli; Radadia, Adarsh D

    2016-03-01

    This paper presents results on immunobeads-based isolation of rare bacteria and their capture at a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode in a microfluidic dielectrophoretic preconcentrator. We systematically vary the bead surface chemistry and the BD-UNCD surface chemistry and apply dielectrophoresis to improve the specific and the nonspecific capture of bacteria or beads. Immunobeads were synthesized by conjugating antibodies to epoxy-/sulfate, aldehyde-/sulfate, or carboxylate-modified beads with or without poly(ethylene glycol) (PEG) coimmobilization. The carboxylate-modified beads with PEG provided the highest capture efficiency (∼65%) and selectivity (∼95%) in isolating live Escherichia coli O157:H7 from cultures containing 1000 E. coli O157:H7 colony-forming units (cfu)/mL, or ∼500 E. coli O157:H7 and ∼500 E. coli K12 cfu/mL. Higher specificity was achieved with the addition of PEG to the antibody-functionalized bead surface, highest with epoxy-/sulfate beads (85-86%), followed by carboxylate-modified beads (76-78%) and aldehyde-/sulfate beads (74-76%). The bare BD-UNCD electrodes of the preconcentrator successfully withstood 240 kV/m for 100 min that was required for the microfluidic dielectrophoresis of 1 mL of sample. As expected, the application of dielectrophoresis increased the specific and the nonspecific capture of immunobeads at the BD-UNCD electrodes; however, the capture specificity remained unaltered. The addition of PEG to the antibody-functionalized BD-UNCD surface had little effect on the specificity in immunobeads capture. These results warrant the fabrication of electrical biosensors with BD-UNCD so that dielectrophoretic preconcentration can be performed directly at the biosensing electrodes. PMID:26829879

  16. In Situ Activation of Nitrogen-Doped Graphene Anchored on Graphite Foam for a High-Capacity Anode.

    PubMed

    Ji, Junyi; Liu, Jilei; Lai, Linfei; Zhao, Xin; Zhen, Yongda; Lin, Jianyi; Zhu, Yanwu; Ji, Hengxing; Zhang, Li Li; Ruoff, Rodney S

    2015-08-25

    We report the fabrication of a three-dimensional free-standing nitrogen-doped porous graphene/graphite foam by in situ activation of nitrogen-doped graphene on highly conductive graphite foam (GF). After in situ activation, intimate "sheet contact" was observed between the graphene sheets and the GF. The sheet contact produced by in situ activation is found to be superior to the "point contact" obtained by the traditional drop-casting method and facilitates electron transfer. Due to the intimate contact as well as the use of an ultralight GF current collector, the composite electrode delivers a gravimetric capacity of 642 mAh g(-1) and a volumetric capacity of 602 mAh cm(-3) with respect to the whole electrode mass and volume (including the active materials and the GF current collector). When normalized based on the mass of the active material, the composite electrode delivers a high specific capacity of up to 1687 mAh g(-1), which is superior to that of most graphene-based electrodes. Also, after ∼90 s charging, the anode delivers a capacity of about 100 mAh g(-1) (with respect to the total mass of the electrode), indicating its potential use in high-rate lithium-ion batteries. PMID:26258909

  17. Graphite nanosheets doped with Fe, Ni, and N, synthesized in one step, and their unique magnetic performance

    NASA Astrophysics Data System (ADS)

    Xu, Zhanwei; Li, Hejun; Luo, Huijuan; Sun, Huihui; Zhang, Qinglin; Cao, Gaoxiang; Li, Kezhi

    2011-04-01

    Graphite nanosheets (GNs) doped with N, Fe, or Ni were synthesized by pyrolysis of metal tetrapyridinoporphyrazine (MPTpz, M=Fe 2+, and Ni 2+) and a mixture of MPTpzs in a chemical vapor deposition furnace. The products obtained were characterized by scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy. The magnetic properties of the GNs obtained were investigated at room temperature using a vibrating sample magnetometer with an applied field of -10 000-10 000 Gs. The results show the GNs obtained are terrace-like and ultra-thin, with very high aspect ratio. Fe, Ni and N atoms have been doped to the GNs successfully. There are two types of N atom that are introduced into pure carbon systems: pyrinidic and graphitic N atoms. The GNs obtained exhibit ferromagnetic behavior at room temperature. Sample S1, obtained by pyrolysis of a mixture of MPTpzs (M=Fe 2+ and Ni 2+), have the highest coercivity force. The saturation magnetization ( Ms), remanent magnetization ( Mr), and coercivity ( Hc) values of sample S1 are 24.51 emu g -1, 3.95 emu g -1, and 207.34 Gs, respectively.

  18. Use of B{sub 2}O{sub 3} films grown by plasma-assisted atomic layer deposition for shallow boron doping in silicon

    SciTech Connect

    Kalkofen, Bodo Amusan, Akinwumi A.; Bukhari, Muhammad S. K.; Burte, Edmund P.; Garke, Bernd; Lisker, Marco; Gargouri, Hassan

    2015-05-15

    Plasma-assisted atomic layer deposition (PALD) was carried for growing thin boron oxide films onto silicon aiming at the formation of dopant sources for shallow boron doping of silicon by rapid thermal annealing (RTA). A remote capacitively coupled plasma source powered by GaN microwave oscillators was used for generating oxygen plasma in the PALD process with tris(dimethylamido)borane as boron containing precursor. ALD type growth was obtained; growth per cycle was highest with 0.13 nm at room temperature and decreased with higher temperature. The as-deposited films were highly unstable in ambient air and could be protected by capping with in-situ PALD grown antimony oxide films. After 16 weeks of storage in air, degradation of the film stack was observed in an electron microscope. The instability of the boron oxide, caused by moisture uptake, suggests the application of this film for testing moisture barrier properties of capping materials particularly for those grown by ALD. Boron doping of silicon was demonstrated using the uncapped PALD B{sub 2}O{sub 3} films for RTA processes without exposing them to air. The boron concentration in the silicon could be varied depending on the source layer thickness for very thin films, which favors the application of ALD for semiconductor doping processes.

  19. Feedback-amplified electrochemical dual-plate boron-doped diamond microtrench detector for flow injection analysis

    PubMed Central

    Lewis, Grace E M; Gross, Andrew J; Kasprzyk-Hordern, Barbara; Lubben, Anneke T; Marken, Frank

    2015-01-01

    An electrochemical flow cell with a boron-doped diamond dual-plate microtrench electrode has been developed and demonstrated for hydroquinone flow injection electroanalysis in phosphate buffer pH 7. Using the electrochemical generator-collector feedback detector improves the sensitivity by one order of magnitude (when compared to a single working electrode detector). The diffusion process is switched from an analyte consuming “external” process to an analyte regenerating “internal” process with benefits in selectivity and sensitivity. PMID:25735831

  20. Insight into the effect of boron doping on sulfur/carbon cathode in lithium-sulfur batteries.

    PubMed

    Yang, Chun-Peng; Yin, Ya-Xia; Ye, Huan; Jiang, Ke-Cheng; Zhang, Juan; Guo, Yu-Guo

    2014-06-11

    To exploit the high energy density of lithium-sulfur batteries, porous carbon materials have been widely used as the host materials of the S cathode. Current studies about carbon hosts are more frequently focused on the design of carbon structures rather than modification of its properties. In this study, we use boron-doped porous carbon materials as the host material of the S cathode to get an insightful investigation of the effect of B dopant on the S/C cathode. Powder electronic conductivity shows that the B-doped carbon materials exhibit higher conductivity than the pure analogous porous carbon. Moreover, by X-ray photoelectron spectroscopy, we prove that doping with B leads to a positively polarized surface of carbon substrates and allows chemisorption of S and its polysulfides. Thus, the B-doped carbons can ensure a more stable S/C cathode with satisfactory conductivity, which is demonstrated by the electrochemical performance evaluation. The S/B-doped carbon cathode was found to deliver much higher initial capacity (1300 mA h g(-1) at 0.25 C), improved cyclic stability, and rate capability when compared with the cathode based on pure porous carbon. Electrochemical impedance spectra also indicate the low resistance of the S/B-doped C cathode and the chemisorption of polysulfide anions because of the presence of B. These features of B doping can play the positive role in the electrochemical performance of S cathodes and help to build better Li-S batteries. PMID:24764111

  1. Oxidative synthesis of highly fluorescent boron/nitrogen co-doped carbon nanodots enabling detection of photosensitizer and carcinogenic dye.

    PubMed

    Jahan, Shanaz; Mansoor, Farrukh; Naz, Shagufta; Lei, Jianping; Kanwal, Shamsa

    2013-11-01

    Current research efforts have demonstrated the facile hydrothermal oxidative synthetic route to develop highly fluorescent boron/nitrogen co-doped carbon nanodots (CNDs). During this process, N-(4-hydroxyphenyl)glycine served as a source of N doping and a carbon precursor as well, while boric acid H3BO3 is used as an oxidizing agent in the N2 environment. Surface passivation through ultrasonic treatment of CNDs was performed to induce modifications by using various surface passivating agents. Polyethyleneimine (PEI) remarkably enhanced the fluorescence performance and monodispersity of polymerized carbon nanodots (P-CNDs) in aqueous phase with an enhanced quantum yield of 23.71%, along with an increase in size from ~3 nm to ~200 nm. For characterization of CNDs and P-CNDs, UV, infrared, photoluminescence, transmission electron microscopy, x-ray photoelectron spectra, and atomic force microscopy techniques were utilized. Application potentials of synthesized P-CNDs were developed via introduction of protoporphyrin (PPD, a photosensitizer) which has great doping affinity with polymer PEI to switch-off the fluorescence of P-CNDs, leading to the production of dye-doped nanoprobes. Fluorescence resonance energy transfer (FRET) was also observed during dye-doping, and PPD was detected with a limit of detection (LOD, 3σ) of 15 pM. The fluorescence recovery of this switched-off nanoprobe was made possible by using Sudan red III (carcinogenic dye), which was oxidized by PPD doped in P-CNDs. Sudan red III was detected in the concentration range of 9.9 pM-0.37 nM. Meanwhile, it was also confirmed that the dye-doped nanoprobe is highly selective and exceptionally sensitive to detect this carcinogenic agent in commercial products with a LOD (3σ) of 90 fM. PMID:24083490

  2. Boron- and nitrogen-doped graphene quantum dots/graphene hybrid nanoplatelets as efficient electrocatalysts for oxygen reduction.

    PubMed

    Fei, Huilong; Ye, Ruquan; Ye, Gonglan; Gong, Yongji; Peng, Zhiwei; Fan, Xiujun; Samuel, Errol L G; Ajayan, Pulickel M; Tour, James M

    2014-10-28

    The scarcity and high cost of platinum-based electrocatalysts for the oxygen reduction reaction (ORR) has limited the commercial and scalable use of fuel cells. Heteroatom-doped nanocarbon materials have been demonstrated to be efficient alternative catalysts for ORR. Here, graphene quantum dots, synthesized from inexpensive and earth-abundant anthracite coal, were self-assembled on graphene by hydrothermal treatment to form hybrid nanoplatelets that were then codoped with nitrogen and boron by high-temperature annealing. This hybrid material combined the advantages of both components, such as abundant edges and doping sites, high electrical conductivity, and high surface area, which makes the resulting materials excellent oxygen reduction electrocatalysts with activity even higher than that of commercial Pt/C in alkaline media. PMID:25251218

  3. Boron-doped bismuth oxybromide microspheres with enhanced surface hydroxyl groups: Synthesis, characterization and dramatic photocatalytic activity.

    PubMed

    Liu, ZhangSheng; Liu, JinLong; Wang, HaiYang; Cao, Gang; Niu, JiNan

    2016-02-01

    B-doped BiOBr photocatalysts were successfully synthesized via a facile solvothermal method with boric acid used as boron source. As-obtained products consist of novel hierarchical microspheres, whose nanosheet building units were formed by nanoparticles splicing. They showed dramatic photocatalytic efficiency toward the degradation of Rhodamine B (RhB) and phenol under the visible-light irradiation and the highest activity was achieved by 0.075B-BiOBr. The enhanced photocatalytic activity could be attributed to the enriched surface hydroxyl groups on B-doped BiOBr samples, which not only improved the adsorption of pollutant on the photocatalyst but also promoted the separation of photogenerated electron-hole pairs. In addition, it was found that the main reactive species responsible for the degradation of organic pollutant were h(+) and O2(-) radicals, instead of OH radicals. PMID:26590875

  4. Strain-induced programmable half-metal and spin-gapless semiconductor in an edge-doped boron nitride nanoribbon

    NASA Astrophysics Data System (ADS)

    Zhu, Shuze; Li, Teng

    2016-03-01

    The search for half-metals and spin-gapless semiconductors has attracted extensive attention in material design for spintronics. Existing progress in such a search often requires peculiar atomistic lattice configuration and also lacks active control of the resulting electronic properties. Here we reveal that a boron nitride nanoribbon with a carbon-doped edge can be made a half-metal or a spin-gapless semiconductor in a programmable fashion. The mechanical strain serves as the on/off switches for functions of half-metal and spin-gapless semiconductor to occur. Our findings shed light on how the edge doping combined with strain engineering can affect electronic properties of two-dimensional materials.

  5. 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; Barnes, Jean-Paul

    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 mΩ-cm. Four probe measurements show that it is possible to dope Si{sub 1−x}Ge{sub x} alloy nanowires with diborane.

  6. A Drude model analysis of conductivity and free carriers in boron-doped diamond films and investigations of their internal stress and strain

    PubMed Central

    Manciu, Marian; Durrer, William G.; Salazar, Jessica G.; Lee, Kendall H.; Bennet, Kevin E.

    2014-01-01

    Boron-doped diamond (BDD) has seen a substantial increase in interest for use as electrode coating material for electrochemistry and studies of deep brain stimulation mechanism. In this study, we present an alternative method for determining important characteristics, including conductivity, carrier concentration, and time constant, of such material by the signature of Drude-like metallic behavior in the far-infrared (IR) spectral range. Unlike the direct determination of conductivity from the four-point probe method, using far-IR transmittance provides additional information, such as whether the incorporation of boron results in a large concentration of carriers or in inducing defects in the diamond lattice. The slightly doped to medium-doped BDD samples that were produced using chemical vapor deposition and analyzed in this work show conductivities ranging between 5.5 and 11 (Ω cm)−1. Different growth conditions demonstrate that increasing boron concentration results in an increase in the carrier concentration, with values between 7.2 × 1016 and 2.5 × 1017 carriers/cm3. Addition of boron, besides leading to a decrease in the resistivity, also resulted in a decrease in the time constant, limiting BDD conductivity. Investigations, by confocal Raman mapping, of the induced stress in the material due to interaction with the substrate or to the amount of doping are also presented and discussed. The induced tensile stress, which was distributed closer to the film-substrate interface decreased slightly with doping. PMID:25328245

  7. Dissolution Mediated Boron and Carbon Storage during Exhumation of HP Metapelites: Examples from New Hampshire Tourmaline-Graphite Intergrowths

    NASA Astrophysics Data System (ADS)

    Galvez, M.; Rumble, D.; Cody, G. D.; Sverjensky, D. A.

    2013-12-01

    The dynamic of light elements (e.g. C,B) in subduction zones is a complex process ultimately governed by variables such as P, T, fH2 and pH. Interface phenomena at scales from the outcrop to intergranular surfaces play key chemical and mechanical roles on this dynamic (e.g. Galvez et al. 2013). We report here a petrological study of hydrated borosilicate tourmaline intergrown with graphite formed at the contact between igneous intrusives and high grade micaschists in New Hampshire graphite deposits (Rumble and Hoering, 1986). Our study includes Raman scattering, SEM, microprobe analysis and thermodynamic modeling, focusing on the Franklin Pierce and Walpole outcrops. Both localities experienced HP-HT metamorphism during the Acadian orogeny as well as complex metasomatic process during exhumation. The tourmaline-graphite intergrowths are structurally localized at and around contacts between an aplite sill and micaschists - biotite-muscovite-garnet-sillimanite-plagioclase-quartz-ilmenite - (Franklin Pierce), or along shear zones (Walpole) in veins. Tourmalines are dravitic in composition (i.e. Na, Mg rich with minor vacancy and Li content 0.2/0.1 a.p.f.u) and contain multiple primary tubular mixed fluid-solid inclusions containing graphite, quartz and gaseous CO2 and CH4. Sharp optical and compositional radial zonations are observed from core to rim in sections along and perpendicular to the c-axis. Blue-green cores are enriched in Mg and Ca (1.5/0.1 a.p.f.u respectively) whereas rims are enriched in Fe, Na and Ti (0.9/0.6/0.1 a.p.f.u respectively). Alternative interpretations in terms of sector zoning or compositional variability of the mineralizing fluid will be discussed. The carbonaceous material (CM) occurs primarily as flakes directly replacing biotite present in wall rocks. The structural ordering of CM, of unambiguous abiotic origin, reveals a material possessing the 3 dimensional structure of hexagonal graphite. Our results are critically compared to measurements done on other metasomatic or biogenic graphite displaying high structural ordering. Other textural habit of graphite are radiating crystals of graphite preferentially growing along crystalline planes of wall rock minerals (e.g. plagioclases) and at the interface between grain edge. We test whether a C and B(OH)3° (×As, Cu) rich acidic vapor unmixing from a salt-rich aqueous fluid exsolved from crystallizing igneous bodies can account for some geochemical and textural greisen-type metasomatic features of these outcrops. Other mechanical and geochemical processes participating in the process will be discussed. This work is direct evidence that respeciation and/or fluid-rock interaction at varying P,T,fH2,pH conditions of fluids during exhumation, as well as interaction between magmatic bodies and metasedimentary units play a key role in the cycling of light elements during exhumation. Rumble, D., III, and Hoering, T.C., 1986, Carbon isotope geochemistry of graphite vein deposits from New Hampshire, U.S.A: Geochimica et Cosmochimica Acta, v. 50, p. 1239-1247. Galvez ME, Beyssac O, Martinez I, Benzerara K, Chaduteau C, Malvoisin B, Malavieille J (2013) Graphite formation by carbonate reduction during subduction. Nature Geoscience 6 (6):473-477

  8. Pure and carbon-doped boron phosphide (6,0) zigzag nanotube: Acomputational NMR study

    NASA Astrophysics Data System (ADS)

    Arshadi, S.; Bekhradnia, A. R.; Alipour, F.; Abedini, S.

    2015-11-01

    Calculations were performed for investigation of the properties of the electronic structure of Carbon- Doped Boron Phosphide Nanotube (CDBPNT). Pristine and three models of C-doped structures of (6,0) zigzag BPNT were studied at density functional theory (DFT) in combination with 6-311G* basis set using Gaussian package of program. The calculated parameters reveal that various 11B and 31P nuclei are divided into some layers with equivalent electrostatic properties. The electronic structure properties are highly influenced by replacement of 11B and 31P atoms by 12C atoms in pristine model. Furthermore, the HOMO-LUMO gap energy for suggested doped models (I), (II) and (III) were lower than pure BPNT pristine systems. The dipole moment values of models (II) and (III) were decreased to 1.788and 1.789, respectively while the dipole moments of model (I) were enhanced to 4.373, in compare to pure pristine one (2.586). The magnitude of changes in Chemical Shielding (CS) tensor parameters revealed that the electron density at the site of 31P was higher than that at the site of 11B due to carbon doping.

  9. CE with a boron-doped diamond electrode for trace detection of endocrine disruptors in water samples.

    PubMed

    Browne, Damien J; Zhou, Lin; Luong, John H T; Glennon, Jeremy D

    2013-07-01

    Off-line SPE and CE coupled with electrochemical detection have been used for the determination of bisphenol A (BPA), bisphenol F, 4-ethylphenol, and bisphenol A diglycidyl ether in bottled drinking water. The use of boron-doped diamond electrode as an electrochemical detector in amperometric mode that provides a favorable analytical performance for detecting these endocrine-disrupting compounds, such as lower noise levels, higher peak resolution with enhanced sensitivity, and improved resistance against electrode passivation. The oxidative electrochemical detection of the endocrine-disrupting compounds was accomplished by boron-doped diamond electrode poised at +1.4 V versus Ag/AgCl without electrode pretreatment. An off-line SPE procedure (Bond Elut® C18 SPE cartridge) was utilized to extract and preconcentrate the compounds prior to separation and detection. The minimum concentration detectable for all four compounds ranged from 0.01 to 0.06 μM, having S/N equal to three. After exposing the plastic bottle water container under sunlight for 7 days, the estimated concentration of BPA in the bottled drinking water was estimated to be 0.03 μM. This proposed approach has great potential for rapid and effective determination of BPA content present in water packaging of plastic bottles that have been exposed to sunlight for an extended period of time. PMID:23172695

  10. High-pressure high-temperature phase diagram of gadolinium studied using a boron-doped heater anvil

    NASA Astrophysics Data System (ADS)

    Montgomery, J. M.; Samudrala, G. K.; Velisavljevic, N.; Vohra, Y. K.

    2016-04-01

    A boron-doped designer heater anvil is used in conjunction with powder x-ray diffraction to collect structural information on a sample of quasi-hydrostatically loaded gadolinium metal up to pressures above 8 GPa and 600 K. The heater anvil consists of a natural diamond anvil that has been surface modified with a homoepitaxially grown chemical-vapor-deposited layer of conducting boron-doped diamond, and is used as a DC heating element. Internally insulating both diamond anvils with sapphire support seats allows for heating and cooling of the high-pressure area on the order of a few tens of seconds. This device is then used to scan the phase diagram of the sample by oscillating the temperature while continuously increasing the externally applied pressure and collecting in situ time-resolved powder diffraction images. In the pressure-temperature range covered in this experiment, the gadolinium sample is observed in its hcp, αSm, and dhcp phases. Under this temperature cycling, the hcp → αSm transition proceeds in discontinuous steps at points along the expected phase boundary. From these measurements (representing only one hour of synchrotron x-ray collection time), a single-experiment equation of state and phase diagram of each phase of gadolinium is presented for the range of 0-10 GPa and 300-650 K.

  11. High-pressure high-temperature phase diagram of gadolinium studied using a boron-doped heater anvil

    DOE PAGESBeta

    Montgomery, J. M.; Samudrala, G. K.; Velisavljevic, N.; Vohra, Y. K.

    2016-04-07

    A boron-doped designer heater anvil is used in conjunction with powder x-ray diffraction to collect structural information on a sample of quasi-hydrostatically loaded gadolinium metal up to pressures above 8GPa and 600K. The heater anvil consists of a natural diamond anvil that has been surface modified with a homoepitaxially grown chemical-vapor-deposited layer of conducting boron-doped diamond, and is used as a DC heating element. Internally insulating both diamond anvils with sapphire support seats allows for heating and cooling of the high-pressure area on the order of a few tens of seconds. This device is then used to scan the phasemore » diagram of the sample by oscillating the temperature while continuously increasing the externally applied pressure and collecting in situ time-resolved powder diffraction images. In the pressure-temperature range covered in this experiment, the gadolinium sample is observed in its hcp, αSm, and dhcp phases. Under this temperature cycling, the hcp → αSm transition proceeds in discontinuous steps at points along the expected phase boundary. From these measurements (representing only one hour of synchrotron x-ray collection time), a single-experiment equation of state and phase diagram of each phase of gadolinium is presented for the range of 0–10GPa and 300–650K« less

  12. Laser heated boron doped diamond electrodes: effect of temperature on outer sphere electron transfer processes.

    PubMed

    Meng, Lingcong; Iacobini, James G; Joseph, Maxim B; Macpherson, Julie V; Newton, Mark E

    2014-01-01

    Thermoelectrochemical experiments can reveal significant information about electrochemical processes compared to ambient only measurements. Typical thermoelectrochemistry is performed using resistively heated wires or laser heated electrodes, both of which can suffer drawbacks associated with the electrode material employed. Boron doped diamond (BDD) is ideal for thermoelectrochemical investigations due to its extremely high thermal conductivity and diffusivity, extreme resistance to thermal ablation (can withstand laser power densities, Pd, of GW cm(-2) for nanosecond pulses) and excellent electrochemical properties (low background currents and wide potential window). In this paper we describe the use of a pulsed laser technique to heat the rear of a 1 mm diameter conducting BDD disc electrode, which drives electrochemical solution reactions at the front face. Maximum electrode temperatures of 90.0 °C were recorded experimentally and confirmed by finite element modelling (FEM). The effect of laser pulsed heating (maximum 3.8 kW cm(-2); 10 ms on and 90 ms off) on the cyclic voltammetric response of two fast (reversible) outer sphere electron transfer redox mediators (Ru(NH3)6(3+/2+) and IrCl6(2-/3-)) are investigated. In particular, we observe pulsed increases in the current, which increase with increasing Pd. The potential of the peak current is shifted positively for the Ru(NH3)6(3+/2+) couple (in accordance with a positive temperature coefficient, β, +0.68 mV K(-1)) and negatively for the IrCl6(3-/2-) couple (β = -0.48 mV K(-1)). Scanning backwards, in contrast to that observed for a macrodisc electrode in ambient solution, a cathodic peak is again observed for Ru(NH3)6(3+/2+) and an anodic peak for IrCl6(3-/2-) couple. We attribute this response to the entropy of the redox reaction and the time-dependant change in mass transport due to the induced thermal gradients at the electrode/electrolyte interface. The observed responses are in qualitative agreement with FEM simulations. PMID:25427195

  13. Chirality-dependent boron-mediated growth of nitrogen-doped single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wiltshire, Joseph G.; Li, Lain-Jong; Herz, Laura M.; Nicholas, Robin J.; Glerup, Marianne; Sauvajol, Jean-Louis; Khlobystov, Andrei N.

    2005-11-01

    A change in the relative abundance of single-walled carbon nanotubes, due to the presence of both nitrogen and boron during synthesis, has been identified through Raman and absorption spectroscopy. Raman spectroscopy shows that for two specific branches boron mediates the growth of smaller-diameter zigzag or near-zigzag nanotubes. We combine our experimental results with an improved Kataura model to identify two of the preferentially grown species as (16,0) and (14,1).

  14. Effect of doping by boron, carbon, and nitrogen atoms on the magnetic and photocatalytic properties of anatase

    NASA Astrophysics Data System (ADS)

    Zainullina, V. M.; Zhukov, V. P.; Korotin, M. A.; Polyakov, E. V.

    2011-07-01

    The effect of doping of titanium dioxide with the anatase structure by boron, carbon, and nitrogen atoms on the magnetic and optical properties and the electronic spectrum of this compound has been investigated using the ab initio tight-binding linear muffin-tin orbital (TB-LMTO) band-structure method in the local spin density approximation explicitly including Coulomb correlations (LSDA + U) in combination with the semiempirical extended Hückel theory (EHT) method. The LSDA + U calculations of the electronic structure, the imaginary part of the dielectric function, the total magnetic moments, and the magnetic moments at the impurity atoms have been carried out. The diagrams of the molecular orbitals of the clusters Ti3 X ( X = B, C, N) have been calculated and the pseudo-space images of the molecular orbitals of the clusters have been constructed. The effect of doping on the nature and origin of photocatalytic activity in the visible spectral range and the specific features of the generation of ferromagnetic interactions in doped anatase have been discussed based on the analysis of the obtained data. It has been shown that, in the sequence TiO2 - y N y → TiO2 - y C y → TiO2 - y B y ( y = 1/16), the photocatalytic activity can increase with the generation of electronic excitations with the participation of impurity bands. The calculated magnetic moments for boron and nitrogen atoms are equal to 1 μB, whereas the impurity carbon atoms are nonmagnetic.

  15. 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

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

    SciTech Connect

    Velusamy, P. Babu, R. Ramesh; Ramamurthi, K.

    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.

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

    NASA Astrophysics Data System (ADS)

    Velusamy, P.; Babu, R. Ramesh; Ramamurthi, K.

    2014-04-01

    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.

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

    SciTech Connect

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

    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.

  19. Molecular dynamics investigation of separation of hydrogen sulfide from acidic gas mixtures inside metal-doped graphite micropores.

    PubMed

    Huang, Pei-Hsing

    2015-09-21

    The separation of poisonous compounds from various process fluids has long been highly intractable, motivating the present study on the dynamic separation of H2S in acidic-gas-mixture-filled micropores. The molecular dynamics approach, coupled with the isothermal-isochoric ensemble, was used to model the molecular interactions and adsorption of H2S/CO2/CO/H2O mixtures inside metal-doped graphite slits. Due to the difference in the adsorption characteristics between the two distinct adsorbent materials, the metal dopant in the graphitic micropores leads to competitive adsorption, i.e. the Au and graphite walls compete to capture free adsorbates. The effects of competitive adsorption, coupled with changes in the gas temperature, concentration, constituent ratio and slit width on the constituent separation of mixtures were systematically studied. The molecule-wall binding energies calculated in this work (those of H2S, H2O and CO on Au walls and those of H2O, CO and CO2 on graphite walls) show good agreement with those obtained using density functional theory (DFT) and experimental results. The z-directional self-diffusivities (Dz) for adsorbates inside the slit ranged from 10(-9) to 10(-7) m(2) s(-1) as the temperature was increased from 10 to 500 K. The values are comparable with those for a typical microporous fluid (10(-8)-10(-9) m(2) s(-1) in a condensed phase and 10(-6)-10(-7) m(2) s(-1) in the gaseous state). The formation of H-bonding networks and hydrates of H2S is disadvantageous for the separation of mixtures. The results indicate that H2S can be efficiently separated from acidic gas mixtures onto the Au(111) surface by (i) reducing the mole fraction of H2S and H2O in the mixtures, (ii) raising the gas temperature to the high temperature limit (≥400 K), and (iii) lowering the slit width to below the threshold dimension (≤23.26 Å). PMID:26256825

  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.

    2012-10-24

    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. 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 MΩ (undoped films) to 55 kΩ, 0.6 kΩ, and 0.3 kΩ (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

  2. 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.

  3. Modification of the surface morphology of the silicon substrate for boron-doped diamond electrodes in electrochemical wastewater treatment applications

    NASA Astrophysics Data System (ADS)

    Bak, Ji-Yoon; Lee, Choong-Hyun; Kim, Jung-Do; Lim, Dae-Soon

    2016-01-01

    For electrochemical wastewater treatment applications, textured boron-doped diamond (BDD) electrodes were fabricated by using a simple and cost-effective etching process. On the basis of the surface area measurement, the etching time was optimized in order to achieve higher electrochemical wastewater treatment performance. The surface structure, electrochemical properties, and electrochemical oxidation performance of the electrodes were characterized by using Raman spectroscopy and atomic force microscopy, in addition to electrochemical techniques. The textured BDD electrode demonstrated a dense and large surface area with no change in the film's properties. The effective surface area of the textured BDD electrode was approximately twice as large as that of the planar BDD electrode. The electrochemical results clearly demonstrate that the enhanced surface area of the BDD electrode achieves a higher current efficiency and much lower energy consumption in the electrochemical oxidation of methyl-orange.

  4. Photochromism-induced amplification of critical current density in superconducting boron-doped diamond with an azobenzene molecular layer.

    PubMed

    Natsui, Keisuke; Yamamoto, Takashi; Akahori, Miku; Einaga, Yasuaki

    2015-01-14

    A key issue in molecular electronics is the control of electronic states by optical stimuli, which enables fast and high-density data storage and temporal-spatial control over molecular processes. In this article, we report preparation of a photoswitchable superconductor using a heavily boron-doped diamond (BDD) with a photochromic azobenzene (AZ) molecular layer. BDDs electrode properties allow for electrochemical immobilization, followed by copper(I)-catalyzed alkyne-azide cycloaddition (a "click" reaction). Superconducting properties were examined with magnetic and electrical transport measurements, such as field-dependent isothermal magnetization, temperature-dependent resistance, and the low-temperature voltage-current response. These measurements revealed reversible amplification of the critical current density by 55% upon photoisomerization. This effect is explained as the reversible photoisomerization of AZ inducing an inhomogeneous electron distribution along the BDD surface that renormalizes the surface pinning contribution to the critical current. PMID:25494096

  5. Chemometric study on the electrochemical incineration of nitrilotriacetic acid using platinum and boron-doped diamond anode.

    PubMed

    Zhang, Chunyong; He, Zhenzhu; Wu, Jingyu; Fu, Degang

    2015-07-01

    This study investigated the electrochemical incineration of nitrilotriacetic acid (NTA) at boron-doped diamond (BDD) and platinum (Pt) anodes. Trials were performed in the presence of sulfate electrolyte media under recirculation mode. The parameters that influence the degradation efficiency were investigated, including applied current density, flow rate, supporting electrolyte concentration and reaction time. To reduce the number of experiments, the system had been managed under chemometric technique named Doehlert matrix. As a consequence, the mineralization of NTA demonstrated similar behavior upon operating parameters on these two anodes. Further kinetic study indicated that the degradations followed pseudo-first-order reactions for both BDD and Pt anodes, and the reaction rate constant of the former was found to be higher than that of the latter. Such difference could be interpreted by results from fractal analysis. In addition, a reaction sequence for NTA mineralization considering all the detected intermediates was also proposed. PMID:25747300

  6. Adsorption of SO2 molecule on doped (8, 0) boron nitride nanotube: A first-principles study

    NASA Astrophysics Data System (ADS)

    Deng, Zun-Yi; Zhang, Jian-Min; Xu, Ke-Wei

    2016-02-01

    Adsorptions of SO2 on Al-, Ca-, Co-, Cu-, Ge-, Ni-, and Si-doped (8, 0) boron nitride nanotube (BNNT) have been studied using first-principles approach based on density functional theory in order to exploit their potential applications as SO2 gas sensors. The electronic properties of the BNNT-molecule adsorption adducts are strongly dependent on the dopants. The most stable adsorption geometries, adsorption energies, charge transfers, and density of states of these systems are thoroughly discussed. This work reveals that the sensitivity of (8, 0) BNNT based chemical gas sensors for SO2 can be drastically improved by introducing appropriate dopant. Si is found to be the best choice among all the dopants.

  7. Enhanced field emission characteristics of boron doped diamond films grown by microwave plasma assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Koinkar, Pankaj M.; Patil, Sandip S.; Kim, Tae-Gyu; Yonekura, Daisuke; More, Mahendra A.; Joag, Dilip S.; Murakami, Ri-ichi

    2011-01-01

    Boron doped diamond films were synthesized on silicon substrates by microwave plasma chemical vapor deposition (MPCVD) technique. The effect of B 2O 3 concentration varied from 1000 to 5000 ppm on the field emission characteristics was examined. The surface morphology and quality of films were characterized by scanning electron microscope (SEM) and Raman spectroscopy. The surface morphology obtained by SEM showed variation from facetted microcrystal covered with nanometric grains to cauliflower of nanocrystalline diamond (NCD) particles with increasing B 2O 3 concentration. The Raman spectra confirm the formation of NCD films. The field emission properties of NCD films were observed to improve upon increasing boron concentration. The values of the onset field and threshold field are observed to be as low as 0.36 and 0.08 V/μm, respectively. The field emission current stability investigated at the preset value of ˜1 μA is observed to be good, in each case. The enhanced field emission properties are attributed to the better electrical conductivity coupled with the nanometric features of the diamond films.

  8. Effect of reaction conditions on methyl red degradation mediated by boron and nitrogen doped TiO2

    NASA Astrophysics Data System (ADS)

    Galenda, A.; Crociani, L.; Habra, N. El; Favaro, M.; Natile, M. M.; Rossetto, G.

    2014-09-01

    Nowadays the employment of renewable and sustainable energy sources, and solar light as main option, becomes an urgent need. Photocatalytic processes received great attention in wastewater treatment due to their cheapness, environmental compatibility and optimal performances. Despite the general low selectivity of the photocatalysts, an accurate optimisation of the operational parameters needs to be carried out in order to maximise the process yield. Because of this reason, the present contribution aims to deepen either the knowledge in boron and/or nitrogen doped TiO2-based systems and their employment in methyl red removal from aqueous solutions. The samples were obtained by coprecipitation and characterised by XRD, SEM, BET specific surface area, UV-vis and XPS techniques. The catalytic activity was for the first time carefully evaluated with respect to methyl red photodegradation in different conditions as a function of working pH, counter-ions and pre-adsorption time. An ad-hoc study was performed on the importance of the pre-adsorption of the dye, suggesting that an extended adsorption is useless for the catalyst photoactivity, while a partial coverage is preferable. The photocatalytic tests demonstrate the positive influence of boron doping in photo-activated reactions and the great importance of the operational parameters with respect to the simple methyl red bleaching rather than the overall pollutant mineralisation. It is proved, indeed, that different working pH, acidifying means and substrate pre-adsorption time can enhance or limit the catalyst performances with respect to the complete pollutant degradation rather than its partial breakage.

  9. Ultra-long zinc oxide nanowires and boron doping based on ionic liquid assisted thermal chemical vapor deposition growth

    NASA Astrophysics Data System (ADS)

    Menzel, Andreas; Komin, Kris; Yang, Yang; Güder, Firat; Trouillet, Vanessa; Werner, Peter; Zacharias, Margit

    2014-11-01

    Ionic liquid assisted growth of ultra-long ZnO nanowires from thermal chemical vapor deposition and the incorporation of dopants into the ZnO lattice have been investigated. We find that decomposed components of the ionic liquid at higher temperatures facilitate ultra-long vapor-liquid-solid ZnO nanowires that exhibit an unusual a-axis orientation. In particular, the ionic liquid BMImBF4 has been studied and the mechanism of the nanowire growth model in response to the use of the ionic liquid has been explained. We show that boron which is part of the investigated ionic liquid incorporates into the ZnO lattice and serves as a donor source. Electrical measurements were conducted and have shown an enhanced electrical conductivity (ρ = 0.09 Ω cm) when using the ionic liquid assisted growth approach. This work represents a step towards the controlled doping for designing future nanowire devices.Ionic liquid assisted growth of ultra-long ZnO nanowires from thermal chemical vapor deposition and the incorporation of dopants into the ZnO lattice have been investigated. We find that decomposed components of the ionic liquid at higher temperatures facilitate ultra-long vapor-liquid-solid ZnO nanowires that exhibit an unusual a-axis orientation. In particular, the ionic liquid BMImBF4 has been studied and the mechanism of the nanowire growth model in response to the use of the ionic liquid has been explained. We show that boron which is part of the investigated ionic liquid incorporates into the ZnO lattice and serves as a donor source. Electrical measurements were conducted and have shown an enhanced electrical conductivity (ρ = 0.09 Ω cm) when using the ionic liquid assisted growth approach. This work represents a step towards the controlled doping for designing future nanowire devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05426a

  10. First-principles study on the adsorption properties of phenylalanine on carbon graphitic structures

    NASA Astrophysics Data System (ADS)

    Kang, Seoung-Hun; Kwon, Dae-Gyeon; Park, Sora; Kwon, Young-Kyun

    2015-12-01

    Using ab-initio density functional theory, we investigate the binding properties of phenylalanine, an amino acid, on graphitic carbon structures, such as graphene, nanotubes, and their modified structures. We focus especially on the effect of the adsorbate on the geometrical and the electronic structures of the absorbents. The phenylalanine molecule is found to bind weakly on pristine graphitic structures with a binding energy of 40-70 meV and not to change the electronic configuration of the graphitic structures, implying that the phenylalanine molecule may not be detected on pristine graphitic structures. On the other hand, the phenylalanine molecule exhibits a substantial increase in its binding energy up to ~2.60 eV on the magnesium-decorated boron-doped graphitic structures. We discover that the Fermi level of the system, which was shifted below the Dirac point of the graphitic structures due to p-doping by boron substitution, can be completely restored to the Dirac point because of the amino acid adsorption. This behavior implies that such modified structures can be utilized to detect phenylalanine molecules.

  11. 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.

  12. Control of Rewriteable Doping Patterns in Graphene/Boron Nitride Heterostructures

    NASA Astrophysics Data System (ADS)

    Kahn, Salman; Velasco, Jairo, Jr.; Wong, Dillon; Lee, Juwon; Tsai, Hsin Zon; Ju, Long; Jiang, Lili; Shi, Zhiwen; Ashby, Paul; Taniguchi, Takashi; Watanabe, Kenji; Zettl, Alex; Wang, Feng; Crommie, Michael

    Spatial control of charge doping in 2D materials is a promising technique for designing future electronic devices and understanding novel physics. Electrostatic gating and chemical doping are common methods to achieve control of charge doping in 2D materials. However, these approaches suffer from complicated fabrication processes that introduce impurities, change material properties irreversibly, and lack flexibility. Here, we introduce a new method for patterning rewriteable doping profiles with local interface charge transfer from defects in a tunable BN substrate into an adjacent layer of graphene. We characterize these spatial doping patterns through local probe and transport techniques. This technique enables many novel device designs for 2D materials, including atomically thin p-n junctions and rewriteable memory devices.

  13. Boron-nitrogen doped carbon scaffolding: organic chemistry, self-assembly and materials applications of borazine and its derivatives.

    PubMed

    Bonifazi, Davide; Fasano, Francesco; Lorenzo-Garcia, M Mercedes; Marinelli, Davide; Oubaha, Hamid; Tasseroul, Jonathan

    2015-10-25

    Discovered by Stock and Pohland in 1926, borazine is the isoelectronic and isostructural inorganic analogue of benzene, where the C[double bond, length as m-dash]C bonds are substituted by B-N bonds. The strong polarity of such heteroatomic bonds widens the HOMO-LUMO gap of the molecule, imparting strong UV-emitting/absorption and electrical insulating properties. These properties make borazine and its derivatives valuable molecular scaffolds to be inserted as doping units in graphitic-based carbon materials to tailor their optoelectronic characteristics, and specifically their semiconducting properties. By guiding the reader through the most significant examples in the field, in this feature paper we describe the past and recent developments in the organic synthesis and functionalisation of borazine and its derivatives. These boosted the production of a large variety of tailored derivatives, broadening their use in optoelectronics, H2 storage and supramolecular functional architectures, to name a few. PMID:26411675

  14. Interaction between Glycine/ Glycine Radicals and Intrinsic/Boron-doped (8, 0) Single-walled Carbon Nanotubes: A Density Functional Theory Study

    PubMed Central

    Sun, Wenming; Bu, Yuxiang

    2008-01-01

    The adsorptions of a glycine molecule as well as dehydrogenated radicals on the side walls of both intrinsic and boron-doped (B-doped) single-walled (8,0) carbon nanotubes (SWCNTs) were investigated by a density functional theory. A glycine molecule tends to physically adsorb on intrinsic SWCNT, yet chemically adsorb on B-doped SWCNT as a result of a somewhat chemical bond between the electron-rich nitrogen atom of the glycine molecule and the electron-scarce boron atom of the doped SWCNT. Opposite to the previous report (J. Phys. Chem. B 2006, 110, 6048-6050), it is found in the present study that both the N-centered and C-centered glycine radicals can form quite stable complexes with intrinsic as well as B-doped (8, 0) SWCNTs. When the B-doped SWCNT interacts with glycine radicals, although there is a competition between B and the neighbor C in the nanotube axis direction, glycine radicals preferentially bind to the C site. The encapsulations of a glycine molecule into SWCNTs with various diameters are also discussed. We find that the encapsulation process is endothermic for (8, 0) and (9, 0) SWCNTs, while it is exothermic for (10,0) SWCNT, indicating that the critical diameter of the zigzag SWCNT for the encapsulation is 7.83 Å, the diameter of (10,0). PMID:19006275

  15. Control of Rewriteable Doping Patterns in Graphene/Boron Nitride Heterostructures

    NASA Astrophysics Data System (ADS)

    Kahn, Salman; Velasco, Jairo, Jr.; Wong, Dillon; Lee, Juwon; Tsai, Hsin Zon; Ju, Long; Jiang, Lili; Shi, Zhiwen; Ashby, Paul; Taniguchi, Takashi; Watanabe, Kenji; Zettl, Alex; Wang, Feng; Crommie, Michael

    Spatial control of charge doping in 2D materials is a prerequisite for designing future electronic devices and understanding novel physics. Electrostatic gating and chemical doping are two of the most common methods to achieve this. However, these approaches suffer from complicated fabrication processes that introduce impurities, change material properties irreversibly, and lack flexibility. Here we introduce a new method for patterning rewriteable doping profiles using an STM tip by way of local tip-voltage-induced ionization of defects in a BN substrate. We characterize these spatial doping patterns through local probe and transport techniques. This technique enables many novel device designs for 2D materials, including atomically thin p-n junctions and rewriteable memory devices.

  16. Hydrogenation kinetics in oxidized boron-doped silicon irradiated by keV electrons

    NASA Astrophysics Data System (ADS)

    Lin, Wallace Wan-Li; Sah, Chih-Tang

    1988-08-01

    Hydrogenation kinetics of boron acceptors in oxidized silicon during and after repeated 8-keV electron irradiation (225-2700-μC/cm2 stresses and 10-168-h interirradiation anneals) at room temperature are reported. Hydrogenation proceeds rapidly during irradiation but continues for many hours after the 8-keV electron beam is removed. Postoxidation process dependencies show that postoxidation and postmetallization annealing processes reduce the hydrogenation effect during the 8-keV electron irradiation, while exposure of the oxide to water prior to aluminum electrode deposition enhances it. The data can be interpreted by our two-reaction model consisting of the hydrogen capture reaction by the boron acceptor and the hydrogen recombination reaction to form hydrogen molecule.

  17. Electrical properties and hyperfine interactions of boron doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Amir, Md; Ünal, B.; Geleri, M.; Güngüneş, H.; Shirsath, Sagar E.; Baykal, A.

    2015-12-01

    The single spinel phase nano-structured particles of FeBxFe2-xO4 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by the glycothermal method and the effect of B3+ substitution on structural and dielectric properties of Fe3O4 were studied. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on B3+ substitution have been determined. The hyperfine field values at B- and A-sites gradually decrease with increasing B3+ ion concentration (x). The cation distributions obtained from Bertaut method are in line with Mössbauer results. Complex impedance analysis of boron-substituted spinel ferrites have been made extensively in order to investigate the significant changes in ac and dc conductivity as well as complex permittivity when the boron composition ratio varies from 0.1 to 0.5. It is found that both ac and dc conductivity are also dependent on the boron content in addition to both temperature and applied frequency. The dc conductivity tendency does not purely obey the Arrhenius plots. The dielectric constant and loss of complex permittivity, in general, show similar attitudes as seen in some nanocomposites containing spinel ferrites except for some fluctuations and shifts along the characteristics of the curves. Furthermore, their imaginary components of both permittivity and modulus are almost found to obey the power law with any exponent values varying between 0.5 and 2 in accordance with the level of boron concentrations.

  18. Boron Doped Nanocrystalline Film with Improved Work Function as a Buffer Layer in Thin Film Silicon Solar Cells.

    PubMed

    Park, Jinjoo; Shin, Chonghoon; Park, Hyeongsik; Jung, Junhee; Lee, Youn-Jung; Bong, Sungjae; Dao, Vinh Ai; Balaji, Nagarajan; Yi, Junsin

    2015-03-01

    We investigated thin film silicon solar cells with boron doped hydrogenated nanocrystalline silicon/ hydrogenated amorphous silicon oxide [p-type nc-Si:H/a-SiOx:H] layer. First, we researched the bandgap engineering of diborane (B2H6) doped wide bandgap hydrogenated nanocryslline silicon (p-type nc-Si:H) films, which have excellent electrical properties of high dark conductivity, and low activation energy. The films prepared with lower doping ratio and higher hydrogen dilution ratio had higher optical gap (Eg), with higher dark conductivity (σ(d)), and lower activation energy (Ea). We controlled Eg from 2.10 eV to 1.75 eV, with σ(d) from 1.1 S/cm to 7.59 x 10(-3) S/cm, and Ea from 0.040 eV to 0.128 eV. Next, we focused on the fabrication of thin film silicon solar cells. By inserting p-type nc-Si:H film into the thin film silicon solar cells, we achieved a remarkable increase in the built-in potential from 0.803 eV to 0.901 eV. By forming p-type nc-Si:H film between SnO2:F/ZnO:Al (30 nm) and p-type a-SiOx:H layer, the solar cell properties of open circuit voltage (Voc), short circuit current density (Jsc), and efficiency (η) were improved by 3.7%, 9.2%, and 9.8%, respectively. PMID:26413646

  19. Nitrogen-Doped Hollow Amorphous Carbon Spheres@Graphitic Shells Derived from Pitch: New Structure Leads to Robust Lithium Storage.

    PubMed

    Ma, Qingtao; Wang, Luxiang; Xia, Wei; Jia, Dianzeng; Zhao, Zongbin

    2016-02-01

    Nitrogen-doped mesoporous hollow carbon spheres (NHCS) consisting of hybridized amorphous and graphitic carbon were synthesized by chemical vapor deposition with pitch as raw material. Treatment with HNO3 vapor was performed to incorporate oxygen-containing groups on NHCS, and the resulting NHCS-O showed excellent rate capacity, high reversible capacity, and excellent cycling stability when tested as the anode material in lithium-ion batteries. The NHCS-O electrode maintained a reversible specific capacity of 616 mAh g(-1) after 250 cycles at a current rate of 500 mA g(-1) , which is an increase of 113 % compared to the pristine hollow carbon spheres. In addition, the NHCS-O electrode exhibited a reversible capacity of 503 mAh g(-1) at a high current density of 1.5 A g(-1) . The superior electrochemical performance of NHCS-O can be attributed to the hybrid structure, high N and O contents, and rich surface defects. PMID:26751009

  20. Adsorption of diazinon and hinosan molecules on the iron-doped boron nitride nanotubes surface in gas phase and aqueous solution: A computational study

    NASA Astrophysics Data System (ADS)

    Farmanzadeh, Davood; Rezainejad, Hamid

    2016-02-01

    In this study, the geometric structures and electronic properties of two widely used organophosphorus pesticides, diazinon and hinosan, boron nitride nanotubes (BNNTs) and Fe doped boron nitride nanotubes (FeBNNTs) as adsorbents of these pesticides are studied by density functional theory calculation as well as dispersion correction by Grimme method. The results show that Fe doping in boron nitride nanotubes structures increases the potency of nanotubes to adsorb mentioned pesticides, especially when Fe atom located instead of N atom. Comparing the adsorption energies of diazinon on FeBNNTs with ones for hinosan demonstrate that the adsorption of hinosan is energetically more favorable by FeBNNTs. Assessment of adsorption energies in aqueous solution confirmed significant decrease in their values compared to ones in gaseous phase. However, the adsorption of diazinon and hinosan on both BNNTs and FeBNNTs are exothermic. So, BNNTs and FeBNNTs may be promising candidates as appropriate adsorbents for adsorbing diazinon and hinosan. Also, the results of calculations have revealed that van der Waals interaction energies are remarkably large in adsorption of diazinon and hinosan on all boron nitride nanotubes.

  1. Improvement of epitaxial channel quality on heavily arsenic- and boron-doped Si surfaces and impact on performance of tunnel field-effect transistors

    NASA Astrophysics Data System (ADS)

    Morita, Yukinori; Mori, Takahiro; Migita, Shinji; Mizubayashi, Wataru; Fukuda, Koichi; Matsukawa, Takashi; Endo, Kazuhiko; O'uchi, Shin-ichi; Liu, Yongxun; Masahara, Meishoku; Ota, Hiroyuki

    2015-11-01

    We evaluate the impact of tunnel junction quality on the performance of tunnel field-effect transistors (TFETs). The interface between epitaxially grown channel and source surface was used as tunnel junctions. Performing a sequential surface cleaning procedure prior to epitaxial channel growth for heavily arsenic- and boron-doped Si surfaces improved the interface quality both for p- and n-TFETs. Simultaneously, the subthreshold swing (SS) values of the TFETs improved step-by-step with interface quality.

  2. An intensified π-hole in beryllium-doped boron nitride meshes: its determinant role in CO2 conversion into hydrocarbon fuels.

    PubMed

    Azofra, Luis Miguel; MacFarlane, Douglas R; Sun, Chenghua

    2016-02-28

    DFT investigations on beryllium-doped boron nitride meshes or sheets (BNs) predict the existence of a very reactive kind of novel material capable of spontaneously reducing the first hydrogenation step in the CO2 conversion mechanism. This impressive behaviour appears as a result of the very deep π-hole generated by the beryllium moieties, and also determines its selectivity towards the production of CH4. PMID:26841973

  3. Synthesis, Characterization, and Tribological Evaluation of TiO2-Reinforced Boron and Nitrogen co-Doped Reduced Graphene Oxide Based Hybrid Nanomaterials as Efficient Antiwear Lubricant Additives.

    PubMed

    Jaiswal, Vinay; Kalyani; Umrao, Sima; Rastogi, Rashmi B; Kumar, Rajesh; Srivastava, Anchal

    2016-05-11

    The microwave-synthesized reduced graphene oxide (MRG), boron-doped reduced graphene oxide (B-MRG), nitrogen-doped reduced graphene oxide (N-MRG), boron-nitrogen-co-doped reduced graphene oxide (B-N-MRG), and TiO2-reinforced B-N-MRG (TiO2-B-N-MRG) nanomaterials have been synthesized and characterized by various state-of-the-art techniques, like Raman spectroscopy, powder X-ray diffraction, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the tribological properties of prepared nanomaterials as antiwear additives in neutral paraffin oil have been evaluated using a four-ball machine at an optimized additive concentration (0.15% w/v). The tribological parameters, like mean wear scar diameter, coefficient of friction, and wear rates, revealed that these nanomaterials have potential to be developed as environmentally friendly sulfated-ash-, phosphorus-, and sulfur-free antiwear lubricant additives. The friction- and wear-reducing behavior of MRG increased upon successive doping of nitrogen, boron, and both nitrogen and boron. Among these additives, B-N-co-doped MRG shows superior tribological behavior in paraffin base oil. Besides this, the load-carrying properties of B-N-co-doped MRG have significantly improved after its reinforcement with TiO2 nanoparticles. A comparative study of the surface morphology of a lubricated track in the presence of various additives has been assessed by SEM and contact-mode atomic force microscopy. The X-ray photoelectron spectroscopy studies have proved that the excellent lubrication properties of TiO2-B-N-MRG are due to the in situ formation of a tribofilm composed of boron nitride, adsorbed graphene layers, and tribosintered TiO2 nanoparticles during the tribocontact. Being sulfur-, halogen-, and phosphorus-free, these graphene-based nanomaterials act as green antiwear additives, protecting interacting surfaces significantly from wear and tear. PMID:27097308

  4. Effects of glucose doping on the MgB2 superconductors using cheap crystalline boron

    NASA Astrophysics Data System (ADS)

    Parakkandy, Jafar Meethale; Shahabuddin, Mohammed; Shah, M. Shahabuddin; Alzayed, Nasser S.; Qaid, Salem A. S.; Madhar, Niyaz Ahmad; Ramay, Shahid M.; Shar, Muhammad Ali

    2015-12-01

    We report the effect of glucose (C6H12O6) doping on the structural and electromagnetic properties of MgB2 superconductor fabricated by dry mixing using planetary ball milling. Herein, as-prepared bulk polycrystalline Mg (B1-xCx) 2 samples with different doping levels (x = 0, 2, 4, and 6 at. %) were systematically studied by X-ray diffraction, magnetic and resistivity measurements, and microstructure analysis. When carbon doped, the reduction in critical transition temperature and shrinkage in a-lattice were obviously observed. This resulted in structural distortion of the MgB2 lattice, and thereby, enhanced an impurity scattering. In addition to these, upper critical field and high-field critical current densities were also enhanced. On the other hand, both pinning force and low-field critical current density are decreased. The high field enhancement and low field degradation are due to increase in impurity scattering and decrease in pinning force respectively.

  5. Ion blistering of boron-doped silicon: The critical role of defect passivation

    SciTech Connect

    Desrosiers, N.; Giguere, A.; Moutanabbir, O.; Terreault, B.

    2005-12-05

    The microscopic mechanism of hydrogen ion blistering of silicon was investigated using Raman scattering spectroscopy and thermal desorption spectrometry. The data in B-doped Si({approx}10{sup -3}/{omega} cm) are particularly worth noting, since B doping at this level strongly reduces both the ion dose and the thermal budget required for blistering. In that case the Si-H stretch mode is found to be shifted markedly towards higher frequencies characteristic of highly passivated vacancies and internal surfaces. It is deduced that the degree of defect passivation is a most critical factor for blistering.

  6. Layered structure of anodic SiO{sub 2} films doped with phosphorus or boron

    SciTech Connect

    Mileshko, L. P.

    2009-12-15

    It is shown that anodic silicon oxide films deposited by reanodization (repeated anodic oxidation) of p- and n-type silicon in phosphate (1.5 M H{sub 3}PO{sub 4}), borate (1.5 M H{sub 3}BO{sub 3}), and nitrate (0.04 M NH{sub 4}NO{sub 3}) electrolytes based on tetrahydrofurfuryl alcohol have a three- or four-layer structure both before and after high-temperature annealing. It is assumed that this circumstance accounts for the nonuniform distribution of phosphorus and boron across the thickness of anodic SiO{sub 2}.

  7. Thermodynamical study of boron doped CeX3 (X=Pd, Rh)

    NASA Astrophysics Data System (ADS)

    Sharma, Ramesh; Dwivedi, Shalini; Sharma, Yamini

    2016-05-01

    The structural, electronic, thermal, and optical properties of cubic non magnetic CeX3(X=Pd, Rh) compounds which crystallize in the Au3Cu structure have been studied using the projected augmented wave (PAW) method within the density functional theory (DFT) with generalized gradient approximation (GGA) for exchange correlation potential. In this paper we have calculated the band structure which are interpreted using the density of states. The optical properties such as extinction coefficients clearly illustrate the changes in CeX3 due to intercalation of boron. Lattice instability is observed in CePd3B from the calculated dynamical properties.

  8. Brazing graphite to graphite

    DOEpatents

    Peterson, George R.

    1976-01-01

    Graphite is joined to graphite by employing both fine molybdenum powder as the brazing material and an annealing step that together produce a virtually metal-free joint exhibiting properties similar to those found in the parent graphite. Molybdenum powder is placed between the faying surfaces of two graphite parts and melted to form molybdenum carbide. The joint area is thereafter subjected to an annealing operation which diffuses the carbide away from the joint and into the graphite parts. Graphite dissolved by the dispersed molybdenum carbide precipitates into the joint area, replacing the molybdenum carbide to provide a joint of virtually graphite.

  9. 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.

    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.

  10. Electron and photon degradation in aluminum, gallium and boron doped float zone silicon solar cells

    NASA Technical Reports Server (NTRS)

    Rahilly, W. P.; Scott-Monck, J.; Anspaugh, B.; Locker, D.

    1976-01-01

    Solar cells fabricated from Al, Ga and B doped Lopex silicon over a range of resistivities were tested under varying conditions of 1 MeV electron fluence, light exposures and thermal cycling. Results indicate that Al and Ga can replace B as a P type dopant to yield improved solar cell performance.

  11. 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.

  12. Effective catalytic media using graphitic nitrogen-doped site in graphene for a non-aqueous Li-O2 battery: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Yun, Kyung-Han; Hwang, Yubin; Chung, Yong-Chae

    2015-03-01

    The cell performance of lithium-oxygen batteries using nitrogen doped graphene as a catalytic cathode has been validated in recent research, but the cathode reaction mechanism of lithium and oxygen still remains unclear. Since the oxygen reduction reaction (ORR) mechanism by ionic lithium and catalytic surface is predicted to be distinct for different defective sites such as graphitic, pyridinic, and pyrrolic, it is necessary to observe the behavior of ionic lithium and oxygen gas at each defective site in nitrogen doped graphene. In this study, density functional theory (DFT) calculations are adopted to analyze at an atomic scale how effectively each defective site acts as a catalytic cathode. Interestingly, unlike pyridinic or pyrrolic N is known to be the most effective catalytic site for ORR in fuel cells. Among the other defective sites, it is found that the graphitic N site is the most effective catalytic media activating ORR by ionic lithium in lithium-oxygen batteries due to the electron accepting the reaction of Li-O formation by the graphitic N site.

  13. Optical Properties and Boron Doping-Induced Conduction-Type Change in SnO2 Thin Films

    NASA Astrophysics Data System (ADS)

    Tran, Quang-Phu; Fang, Jau-Shiung; Chin, Tsung-Shune

    2016-01-01

    Boron-doped tin oxide (BTO) films, 0-5 at.% B, were prepared by sol-gel dip coating on a glass substrate. Dried precursor films were post-annealed at a temperature between 400°C and 750°C for 2 h. The obtained BTO thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible light (UV-Vis) spectrometry, a four-point probe, and Hall-effect and Seebeck-effect measurements. Optimal optical transmittance was achieved for post-annealed BTO thin film at 700°C. XRD results show a rutile SnO2 structure with a preferred (110) orientation for all the films. The grain size is 47-21 nm, which reduces with increasing B contents. The optical transmittance is 84.6-88.5% at a wavelength of 550 nm and optical band gap of 3.52-3.75 eV. Electrical resistivity is (3.4-8.2) × 10-3 Ω cm, and figure of merit (0.9-4.3) × 10-3 Ω-1. Carrier concentration is (0.97-7.4) × 1020 cm-3 and mobility (2.5-7.8) cm2 V-1 s-1. BTO film with 4 at.% B shows an optimal combination of properties. Conduction type changes from n- (undoped) to p- (1-4 at.% B), then to n-types (5 at.% B), as evidenced from Hall-effect and Seebeck-effect measurements. This is explained by doping-generated defects and phase separations of Sn3O4 and B2O3.

  14. Assessments of the Effect of Increasingly Severe Cathodic Pretreatments on the Electrochemical Activity of Polycrystalline Boron-Doped Diamond Electrodes.

    PubMed

    Brocenschi, Ricardo F; Hammer, Peter; Deslouis, Claude; Rocha-Filho, Romeu C

    2016-05-17

    The electrochemical response of many redox species on boron-doped diamond (BDD) electrodes can be strongly dependent on the type of chemical termination on their surface, hydrogen (HT-BDD) or oxygen (OT-BDD). For instance, on an HT-BDD electrode the [Fe(CN)6](3-/4-) redox system presents a reversible voltammetric behavior, whereas the oxidation overpotential of ascorbic acid (AA) is significantly decreased. Moreover, the electrochemical activity of BDD electrodes can be significantly affected by electrochemical pretreatments, with cathodic pretreatments (CPTs) leading to redox behaviors associated with HT-BDD. Here we report on the effect of increasingly severe CPTs on the electrochemical activity of a highly doped BDD electrode, assessed with the [Fe(CN)6](3-/4-) and AA redox probes, and on the atomic bonding structure on the BDD surface, assessed by XPS. The hydrogenation level of the BDD surface was increased by CPTs, leading to decreases of the total relative level of oxidation of the BDD surface of up to 36%. Contrary to what is commonly assumed, we show that BDD surfaces do not need to be highly hydrogenated to ensure that a reversible voltammetric behavior is obtained for Fe(CN)6](3-/4-); after a CPT, this was attained even when the total relative level of oxidation on the BDD surface was about 15%. At the same time, the overpotential for AA oxidation was confirmed as being very sensitive to the level of oxidation of the BDD surface, a behavior that might allow the use of AA as a secondary indicator of the relative atomic bonding structure on the BDD surface. PMID:27101534

  15. Effects of Doping Ratio and Thermal Annealing on Structural and Electrical Properties of Boron-Doped ZnO Thin Films by Spray Pyrolysis

    NASA Astrophysics Data System (ADS)

    Yu, Cheng-Chang; Hsu, Yu-Ting; Lee, Shao-Yi; Lan, Wen-How; Kuo, Hsin-Hui; Shih, Ming-Chang; Jui-Yang Feng, David; Huang, Kai-Feng

    2013-06-01

    Boron-doped zinc oxide (BZO) thin films have been fabricated by spray pyrolysis on a glass substrate. The morphology and electrical properties of the thin films were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed. It was found that [B]/[Zn] ratio altered both the microstructure and concentration of the BZO thin films. The film grain size was reduced by increasing the [B]/[Zn] ratio. The highest Hall mobility was 3.65 cm2 V-1 s-1 for the undoped ZnO thin film, and the highest carrier concentration of 1.0×1019 cm-3 was achieved for the as-deposited BZO thin film with [B]/[Zn] = 1.5 at. %. Conductivity was determined at different measurement temperatures and shallow donors provided the dominate conduction mechanism for the as-deposited BZO thin films. After 600 °C annealing, shallow level reduction and donors with a high activation energy of 129+/-6 meV in the BZO thin films were characterized, and the shallow donors that dominate the carrier concentration for the as-deposited spray-pyrolized BZO thin film were eliminated.

  16. 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.

  17. Comparative study of the effects of phosphorus and boron doping in vapor-liquid-solid growth with fixed flow of silicon gas

    NASA Astrophysics Data System (ADS)

    Islam, Md. Shofiqul; Mehedi, Ibrahim Mustafa

    2016-04-01

    This work was carried out to investigate the comparative effects of phosphorus and boron doing in vapor-liquid-solid (VLS) growth. Doped Si microneedles were grown by VLS mechanism at the temperature of 700 °C or less using Au as the catalyst. VLS growth using in-situ doping with the mixed gas of Si2H6 and PH3 produced phosphorus doped n-Si microneedles at Au dot sites, whereas, the mixed gas of Si2H6 and B2H6 produced boron doped p-Si microneedles. The variation of growth rate, diameter, resistivity, impurity concentration and carrier (electron, hole) mobility of these n-Si and p-Si microneeedles were investigated and compared with the variation of dopant gas (PH3 or B2H6) flow, with a fixed flow of Si gas (Si2H6). This comparative study shall be helpful while fabricating devices by growing n-Si and p-Si microneedles one above another by multistep (2-step or 3-step) VLS growth.

  18. Lithium decoration of three dimensional boron-doped graphene frameworks for high-capacity hydrogen storage

    SciTech Connect

    Wang, Yunhui; Meng, Zhaoshun; Liu, Yuzhen; You, Dongsen; Wu, Kai; Lv, Jinchao; Wang, Xuezheng; Deng, Kaiming; Lu, Ruifeng E-mail: rflu@njust.edu.cn; Rao, Dewei E-mail: rflu@njust.edu.cn

    2015-02-09

    Based on density functional theory and the first principles molecular dynamics simulations, a three-dimensional B-doped graphene-interconnected framework has been constructed that shows good thermal stability even after metal loading. The average binding energy of adsorbed Li atoms on the proposed material (2.64 eV) is considerably larger than the cohesive energy per atom of bulk Li metal (1.60 eV). This value is ideal for atomically dispersed Li doping in experiments. From grand canonical Monte Carlo simulations, high hydrogen storage capacities of 5.9 wt% and 52.6 g/L in the Li-decorated material are attained at 298 K and 100 bars.

  19. Optically transparent boron-doped nanocrystalline diamond films for spectroelectrochemical measurements on different substrates

    NASA Astrophysics Data System (ADS)

    Sobaszek, M.; Siuzdak, K.; Skowroński, Ł.; Bogdanowicz, R.; Pluciński, J.

    2016-01-01

    Fabrication process of optically transparent boron nanocrystalline diamond (B- NCD) electrode on silicon and quartz substrate was shown. The B-NCD films were deposited on the substrates using Microwave Plasma Assisted Chemical Vapor Deposition (MWPACVD) at glass substrate temperature of 475 °C. A homogenous, continuous and polycrystalline surface morphology with high sp3 content in B-NCD films and film thickness depending from substrate in the range of 60-300 nm was obtained. The high refraction index and transparency in visible (VIS) wavelength range was achieved. Moreover, cyclic voltammograms (CV) were recorded to determine reaction reversibility at the B-NCD electrode. CV measurements in aqueous media consisting of 1 mM K3[Fe(CN)6] in 0.5 M Na2SO4 demonstrated relatively fast kinetics expressed by a redox peak splitting below 503 mV for B-NCD/silicon and 110 mv for B-NCD/quartz.

  20. Synthesis of Low-Density, Carbon-Doped, Porous Hexagonal Boron Nitride Solids.

    PubMed

    Gautam, Chandkiram; Tiwary, Chandra Sekhar; Jose, Sujin; Brunetto, Gustavo; Ozden, Sehmus; Vinod, Soumya; Raghavan, Prasanth; Biradar, Santoshkumar; Galvao, Douglas Soares; Ajayan, Pulickel M

    2015-12-22

    Here, we report the scalable synthesis and characterization of low-density, porous, three-dimensional (3D) solids consisting of two-dimensional (2D) hexagonal boron nitride (h-BN) sheets. The structures are synthesized using bottom-up, low-temperature (∼300 °C), solid-state reaction of melamine and boric acid giving rise to porous and mechanically stable interconnected h-BN layers. A layered 3D structure forms due to the formation of h-BN, and significant improvements in the mechanical properties were observed over a range of temperatures, compared to graphene oxide or reduced graphene oxide foams. A theoretical model based on Density Functional Theory (DFT) is proposed for the formation of h-BN architectures. The material shows excellent, recyclable absorption capacity for oils and organic solvents. PMID:26580810

  1. High-Quality Carbon-Doped Boron Nitride Membrane for X-Ray Lithography Mask

    NASA Astrophysics Data System (ADS)

    Kishimoto, Akihiko; Sakakihara, Masahiko; Kawai, Tetsurou; Oizumi, Hiroaki; Kuniyoshi, Shinji; Yamaguchi, Sadae; Mochiji, Kozo

    1992-06-01

    Carbon-doped BN (BNC) membrane was fabricated by low pressure chemical vapor deposition (LPCVD) at a high temperature (750°C). Here, CH3NH2 was used as the reactive gas instead of NH3. The newly developed BNC has tensile stress and is transparent to visible light. A very small hydrogen content (3.3%) leads to the construction of strong atomic networks of B, N, and C, as well as to highly improved radiation stability.

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

    SciTech Connect

    Saini, Viney; Li, Zhongrui; Bourdo, Shawn; Kunets, Vasyl P.; Trigwell, Steven; Couraud, Arthur; Rioux, Julien; Boyer, Cyril; Nteziyaremye, Valens; Dervishi, Enkeleda; Biris, Alexandru R.; Salamo, Gregory J.; Viswanathan, Tito; Biris, Alexandru S.

    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.

  3. Transport Properties of p-n Junctions Formed in Boron/Nitrogen Doped Carbon Nanotubes and Graphene Nanoribbons

    NASA Astrophysics Data System (ADS)

    Hammouri, Mahmoud; Vasiliev, Igor

    2014-03-01

    We apply ab initio computational methods based on density functional theory to study the transport properties of p-n junctions made of single-walled carbon nanotubes and graphene nanoribbons. The p-n junctions are formed by doping the opposite ends of carbon nanostructures with boron and nitrogen atoms. Our calculations are carried out using the SIESTA electronic structure code combined with the generalized gradient approximation for the exchange-correlation functional. The transport properties are calculated using a self-consistent nonequilibrium Green's function method implemented in the TranSIESTA package. The modeled nanoscale p-n junctions exhibit linear I-V characteristics in the forward bias and nonlinear I-V characteristics with a negative differential resistance in the reverse bias. The computed transmission spectra and the I-V characteristics of the p-n junctions are compared to the results of other theoretical studies and to the available experimental data. Supported by NMSU GREG Award and by NSF CHE-1112388.

  4. Oxidation of carbon monoxide, hydrogen peroxide and water at a boron doped diamond electrode: the competition for hydroxyl radicals.

    PubMed

    Kisacik, Izzet; Stefanova, Ana; Ernst, Siegfried; Baltruschat, Helmut

    2013-04-01

    Boron doped diamond (BDD) electrodes have an extremely high over-voltage for oxygen evolution from water, which favours its use in oxidation processes of other compounds at high potentials. We used a rotating ring disc (RRDE) assembly and differential electrochemical mass spectrometry (DEMS) in order to monitor the consumption or the production of species in the course of the electrode processes. By intercepting the intermediate of the electrochemical water oxidation with chemical reactions we demonstrate clearly, albeit indirectly, that in the water oxidation process at BDD above 2.5 V the first step is the formation of ˙OH radicals. The electro-oxidation of CO to CO2 at BDD electrodes proceeds only via a first attack by ˙OH radicals followed by a further electron transfer to the electrode. At potentials below the onset of oxygen evolution from water, H2O2 is oxidised by a direct electron transfer to the BDD electrode, while at higher potentials, two different reactions paths compete for the ˙OH radicals formed in the first electron transfer from water: one, where these ˙OH radicals react with each other followed by further electron transfers leading to O2 on the one hand and one, where ˙OH radicals react with other species like H2O2 or CO with subsequent electron transfers on the other hand. PMID:23422949

  5. 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

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

    SciTech Connect

    McClintock, Carlee; Hettich, Robert {Bob} L

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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.

  8. Electrochemical oxidation of ampicillin antibiotic at boron-doped diamond electrodes and process optimization using response surface methodology.

    PubMed

    Körbahti, Bahadır K; Taşyürek, Selin

    2015-03-01

    Electrochemical oxidation and process optimization of ampicillin antibiotic at boron-doped diamond electrodes (BDD) were investigated in a batch electrochemical reactor. The influence of operating parameters, such as ampicillin concentration, electrolyte concentration, current density, and reaction temperature, on ampicillin removal, COD removal, and energy consumption was analyzed in order to optimize the electrochemical oxidation process under specified cost-driven constraints using response surface methodology. Quadratic models for the responses satisfied the assumptions of the analysis of variance well according to normal probability, studentized residuals, and outlier t residual plots. Residual plots followed a normal distribution, and outlier t values indicated that the approximations of the fitted models to the quadratic response surfaces were very good. Optimum operating conditions were determined at 618 mg/L ampicillin concentration, 3.6 g/L electrolyte concentration, 13.4 mA/cm(2) current density, and 36 °C reaction temperature. Under response surface optimized conditions, ampicillin removal, COD removal, and energy consumption were obtained as 97.1 %, 92.5 %, and 71.7 kWh/kg CODr, respectively. PMID:24906830

  9. Evidence for the role of hydrogen in the stabilization of minority carrier lifetime in boron-doped Czochralski silicon

    SciTech Connect

    Nampalli, N. Hallam, B.; Chan, C.; Abbott, M.; Wenham, S.

    2015-04-27

    This study demonstrates that the presence of a hydrogen source during fast-firing is critical to the regeneration of B-O defects and that is it not a pure thermally based mechanism or due to plasma exposure. Boron-doped p-type wafers were fired with and without hydrogen-rich silicon nitride (SiN{sub x}:H) films present during the fast-firing process. After an initial light-induced degradation step, only wafers fired with the SiN{sub x}:H films present were found to undergo permanent and complete recovery of lifetime during subsequent illuminated annealing. In comparison, wafers fired bare, i.e., without SiN{sub x}:H films present during firing, were found to demonstrate no permanent recovery in lifetime. Further, prior exposure to hydrogen-rich plasma processing was found to have no impact on permanent lifetime recovery in bare-fired wafers. This lends weight to a hydrogen-based model for B-O defect passivation and casts doubt on the role of non-hydrogen species in the permanent passivation of B-O defects in commercial-grade p-type Czochralski silicon wafers.

  10. Structural, Electronic, and Magnetic Features of Platinum Alloy Strings Templated on A Boron-Doped Carbon Nanotube

    SciTech Connect

    An, Wei; Turner, C. H.

    2010-05-25

    We present density-functional-theory calculations of structural, electronic, and magnetic properties of platinum-alloy strings templated on a boron-doped single-wall carbon nanotube (6,6) model, B-SWCNT(6,6). Our calculations show that the alloy strings demonstrate strong molecular recognition, forming well-defined covalent bonds with the substrate and lead to the self-assembly of stable monatomic chains. The electronic and magnetic features of the Pt-alloy string/B-SWCNT(6,6)composite systems are mainly controlled by the presence of a magnetic alloying element (i.e., Fe, Co, and Ru). By changing the composition of the Pt alloy, the easy magnetization axis of the system can oscillate between the directions parallel and perpendicular to the tube axis. Our studies suggest that pure transition-metal (TM) or TM-alloy strings anchored on a substrate via strong molecular interactions can still possess sizable magnetic anisotropy due to spin-orbital coupling effects.

  11. Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.

    PubMed

    Lütke Eversloh, Christian; Schulz, Manoj; Wagner, Manfred; Ternes, Thomas A

    2015-04-01

    The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 μM) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed. PMID:25660808

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

    PubMed Central

    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

  13. Determination of vanillin in commercial food product by adsorptive stripping voltammetry using a boron-doped diamond electrode.

    PubMed

    Yardım, Yavuz; Gülcan, Mehmet; Şentürk, Zühre

    2013-12-01

    A method for the determination of food additive vanillin was developed by adsorptive stripping voltammetry. Its determination was carried out at the anodically pre-treated boron-doped diamond electrode in aqueous solutions. Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in phosphate buffer, pH 2.5 at +1.14 V (vs. Ag/AgCl) (a pre-concentration step being carried out at open-circuit condition for 60s). A linear calibration graph was obtained in the concentration range of 0.5-15.0 μg mL(-1) (3.3×10(-6)-9.8×10(-5) mol L(-1)) with a detection limit of 0.024 μg mL(-1) (1.6×10(-7) mol L(-1)). As an example, the practical applicability of the proposed method was tested for the determination of this flavouring agent in commercial pudding powder of Keshkule (Turkish milk pudding with almond flour). PMID:23870896

  14. Sensitive voltammetric determination of thymol in essential oil of Carum copticum seeds using boron-doped diamond electrode.

    PubMed

    Stanković, Dalibor M

    2015-10-01

    Essential oil of Carum copticum seeds, obtained from a local shop, was extracted and content of thymol was analyzed using square-wave voltammetry at boron-doped diamond electrode. The effect of various parameters, such as pH of supporting electrolyte and square-wave voltammetric parameters (modulation amplitude and frequency), was examined. In Britton-Robinson buffer solution (pH 4), thymol provided a single and oval-shaped irreversible oxidation peak at +1.13 V versus silver/silver chloride potassium electrode (3M). Under optimal experimental conditions, a plot of peak height against concentration of thymol was found to be linear over the range of 4 to 100μM consisting of two linear ranges: from 4 to 20μM (R(2)=0.9964) and from 20 to 100μM (R(2)=0.9993). The effect of potential interferences such as p-cymene and γ-terpinene (major components in essential oil of C. copticum seeds) was evaluated. Thus, the proposed method displays a sufficient selectivity toward thymol with a detection limit of 3.9μM, and it was successfully applied for the determination of thymol in essential oil of C. copticum seeds. The Prussian blue method was used for validation of the proposed electroanalytical method. PMID:26119334

  15. SEMICONDUCTOR MATERIALS: Stress and resistivity controls on in situ boron doped LPCVD polysilicon films for high-Q MEMS applications

    NASA Astrophysics Data System (ADS)

    Jing, Xie; Yunfei, Liu; Jinling, Yang; Longjuan, Tang; Fuhua, Yang

    2009-08-01

    The simultaneous control of residual stress and resistivity of polysilicon thin films by adjusting the deposition parameters and annealing conditions is studied. In situ boron doped polysilicon thin films deposited at 520 °C by low pressure chemical vapor deposition (LPCVD) are amorphous with relatively large compressive residual stress and high resistivity. Annealing the amorphous films in a temperature range of 600-800 °C gives polysilicon films nearly zero-stress and relatively low resistivity. The low residual stress and low resistivity make the polysilicon films attractive for potential applications in micro-electro-mechanical-systems (MEMS) devices, especially in high resonance frequency (high-f) and high quality factor (high-Q) MEMS resonators. In addition, polysilicon thin films deposited at 570 °C and those without the post annealing process have low resistivities of 2-5 mΩ dot m cm. These reported approaches avoid the high temperature annealing process (> 1000 °C), and the promising properties of these films make them suitable for high-Q and high-f MEMS devices.

  16. Electrochemical Sensing and Assessment of Parabens in Hydro-Alcoholic Solutions and Water Using a Boron-Doped Diamond Electrode

    PubMed Central

    Radovan, Ciprian; Cinghiță, Dan; Manea, Florica; Mincea, Manuela; Cofan, Codruța; Ostafe, Vasile

    2008-01-01

    In this paper, the electrochemical behaviour of several parabens preservatives, i.e. esters of p-hydroxybenzoic acid, methyl-, ethyl- and propyl-4-hydroxybenzoates as methyl-, ethyl- and propyl-parabens (MB, EB, and PB), has been investigated at a commercial boron-doped diamond electrode (BDDE), especially in the anodic potential range, in both hydro-alcoholic and aqueous media. The cyclic voltammetric and chronoamperometric measurements yielded calibration plots with very good linearity (R2 between 0.990 and 0.998) and high sensitivity, useful for detection and analytical applications. The determination of the characteristics of individual compounds, of an “overall paraben index”, the assessment of the stability and the saturation solubility in water, and the amperometric sensing and determination in double distilled, tap and river water matrix of the relatively slightly soluble investigated parabens have been carried out using electrochemical alternative. Estimated water solubility was correlated with the octanol-water partition coefficient. Several ideas regarding stability and persistence of the presumptive eco-toxic investigated preservatives in the environment or water systems have been adjacently discussed.

  17. 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

  18. 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

  19. Highly Sensitive Measurement of Bio-Electric Potentials by Boron-Doped Diamond (BDD) Electrodes for Plant Monitoring.

    PubMed

    Ochiai, Tsuyoshi; Tago, Shoko; Hayashi, Mio; Fujishima, Akira

    2015-01-01

    We describe a sensitive plant monitoring system by the detection of the bioelectric potentials in plants with boron-doped diamond (BDD) electrodes. For sensor electrodes, we used commercially available BDD, Ag, and Pt plate electrodes. We tested this approach on a hybrid species in the genus Opuntia (potted) and three different trees (ground-planted) at different places in Japan. For the Opuntia, we artificially induced bioelectric potential changes by the surface potential using the fingers. We detected substantial changes in bioelectric potentials through all electrodes during finger touches on the surface of potted Opuntia hybrid plants, although the BDD electrodes were several times more sensitive to bioelectric potential change compared to the other electrodes. Similarly for ground-planted trees, we found that both BDD and Pt electrodes detected bioelectric potential change induced by changing environmental factors (temperature and humidity) for months without replacing/removing/changing electrodes, BDD electrodes were 5-10 times more sensitive in this detection than Pt electrodes. Given these results, we conclude that BDD electrodes on live plant tissue were able to consistently detect bioelectrical potential changes in plants. PMID:26512663

  20. Properties of boron-doped ZnO thin films deposited by pulsed DC magnetron sputtering at different substrate temperatures

    NASA Astrophysics Data System (ADS)

    Wen, B.; Liu, C. Q.; Wang, N.; Wang, H. L.; Liu, S. M.; Jiang, W. W.; Ding, W. Y.; Fei, W. D.; Chai, W. P.

    2015-11-01

    By pulsed DC magnetron sputtering, boron-doped ZnO (BZO) thin films were deposited on normal glass substrates at different substrate temperatures. The effect of substrate temperature on the properties of the BZO films was systematically investigated. Based on XRD data, the crystallization behaviors and the grain growth kinetics of the BZO films were analyzed. It was found that the substrate temperature of 300 °C is a critical temperature in the grain growth process of the BZO films. That is to say, the grain growth mechanism of the BZO films was different at the substrate temperature range of exceeding 300 °C or not. The morphological, electrical, and optical properties of the BZO films were studied by atomic force microscopy, Hall effect measurement system, and UV-Vis transmission spectroscopy, respectively. With increasing the substrate temperature, the carrier concentration and the carrier mobility increase, and the minimum resistivity (3.4 × 10-3 Ω cm) is observed at the substrate temperature of 400 °C. Moreover, the transmittance for every film is over 90 % in the visible range, and the optical band edge of the BZO films exhibits blueshift with increasing the substrate temperature.

  1. 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

    2015-01-01

    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

  2. Sensitive and Rapid Voltammetric Determination of Phenothiazine and Azaphenothiazine Derivatives in Pharmaceuticals Using a Boron-doped Diamond Electrode.

    PubMed

    Mielech-Łukasiewicz, Katarzyna; Staśkowska, Elżbieta

    2015-01-01

    Novel, sensitive and rapid electrochemical methods for the determination of phenothiazine and azaphenothiazine derivatives were developed. A boron-doped diamond (BDD) electrode was used for electrochemical oxidation of levomepromazine, promazine and prothipendyl. The electrooxidation of these substances demonstrated reversible peaks of oxidation at the potential range 0.55 - 0.75 V vs. SCE. Examining the influence of scan rate allowed is to demonstrate that the currents registered typical of the diffusion-controlled process. Determinations of the studied analytes were carried out by means of a square wave voltammetry (SWV) method and a differential pulse voltammetry (DPV) method. Linear ranges of determination with the use of the BDD electrode and the SWV method were obtained in the ranges: from 4 × 10(-7) to 1.38 × 10(-4) mol L(-1) for levomepromazine, from 4 × 10(-7) to 1.17 × 10(-5) mol L(-1) for promazine and from 4.95 × 10(-7) to 4.54 × 10(-5) mol L(-1) for prothipendyl. The influence of interferences on the voltammetric signal of the studied analytes was also checked. The proposed procedures were used for quantitative determination of the studied compounds in pharmaceutical preparations. The measurements showed high accuracy. The recovery values obtained ranged from 98.52 to 99.57%. The developed procedures were compared with pharmacopoeial reference methods. PMID:26460359

  3. Photocarrier Radiometry Investigation of Light-Induced Degradation of Boron-Doped Czochralski-Grown Silicon Without Surface Passivation

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Li, Bincheng

    2016-04-01

    Light-induced degradation (LID) effects of boron-doped Cz silicon wafers without surface passivation are investigated in details by photocarrier radiometry (PCR). The resistivity of all samples is in the range of 0.006 Ω {\\cdot } {cm} to 38 Ω {\\cdot } {cm}. It is found that light-induced changes in surface state occupation have a great effect on LID under illumination. With the increasing contribution of light-induced changes in surface state occupation, the generation rate of the defect decreases. The light-induced changes in surface state occupation and light-induced degradation dominate the temporal behaviors of the excess carrier density of high- and low-resistivity Si wafers, respectively. Moreover, the temporal behaviors of PCR signals of these samples under laser illumination with different powers, energy of photons, and multiple illuminations were also analyzed to understand the light-induced change of material properties. Based on the nonlinear dependence of PCR signal on the excitation power, a theoretical model taking into account both light-induced changes in surface state occupation and LID processes was proposed to explain those temporal behaviors.

  4. Surface Roughness and Critical Exponent Analyses of Boron-Doped Diamond Films Using Atomic Force Microscopy Imaging: Application of Autocorrelation and Power Spectral Density Functions

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Vierkant, G. P.

    2014-09-01

    The evolution of the surface roughness of growing metal or semiconductor thin films provides much needed information about their growth kinetics and corresponding mechanism. While some systems show stages of nucleation, coalescence, and growth, others exhibit varying microstructures for different process conditions. In view of these classifications, we report herein detailed analyses based on atomic force microscopy (AFM) characterization to extract the surface roughness and growth kinetics exponents of relatively low boron-doped diamond (BDD) films by utilizing the analytical power spectral density (PSD) and autocorrelation function (ACF) as mathematical tools. The machining industry has applied PSD for a number of years for tool design and analysis of wear and machined surface quality. Herein, we present similar analyses at the mesoscale to study the surface morphology as well as quality of BDD films grown using the microwave plasma-assisted chemical vapor deposition technique. PSD spectra as a function of boron concentration (in gaseous phase) are compared with those for samples grown without boron. We find that relatively higher boron concentration yields higher amplitudes of the longer-wavelength power spectral lines, with amplitudes decreasing in an exponential or power-law fashion towards shorter wavelengths, determining the roughness exponent ( α ≈ 0.16 ± 0.03) and growth exponent ( β ≈ 0.54), albeit indirectly. A unique application of the ACF, which is widely used in signal processing, was also applied to one-dimensional or line analyses (i.e., along the x- and y-axes) of AFM images, revealing surface topology datasets with varying boron concentration. Here, the ACF was used to cancel random surface "noise" and identify any spatial periodicity via repetitive ACF peaks or spatially correlated noise. Periodicity at shorter spatial wavelengths was observed for no doping and low doping levels, while smaller correlations were observed for relatively higher boron concentration. These semiquantitative spatial analyses may prove useful in comparing synthesis techniques and varying compositional makeups of diamond films and other technologically important electronic materials. These findings in terms of critical exponents are also correlated with traditional Raman spectroscopy and x-ray diffraction structural properties, thus helping to provide insight into the growth kinetics, albeit in reverse manner.

  5. The influence of Cu-doping on aluminum nitride, silicon carbide and boron nitride nanotubes’ ability to detect carbon dioxide; DFT study

    NASA Astrophysics Data System (ADS)

    Mahdavifar, Zabiollah; Abbasi, Nasibeh

    2014-02-01

    In this research, the potential use of Cu-functionalized [4,4] silicon carbide (SiC), aluminum nitride (AlN) and boron nitride (BN) single-walled nanotubes as nanodevices for CO2 monitoring is investigated. It is found that Cu-doping the different sites of the considered nanotubes and combining these nanotubes with CO2 gas molecules are both exothermic processes, and the relaxed geometries are stable. Our results reveal that the CO2 gas molecules can be strongly physisorbed on the Cu-doped nanotubes, accompanied by large adsorption energy. Compared with the weak adsorption of CO2 molecule onto pristine BNNT and SiCNT, the CO2 molecule tends to be strongly physisorbed onto Cu-decorated BNNT and SiCNT with an appreciable adsorption energy. Furthermore, the results indicate that Cu-functionalized SiCNT is more favorable than Cu-doped BNNT and AlNNT structures for CO2 adsorption. Natural bond orbital analysis indicates that the adsorption of a CO2 molecule onto Cu-doped nanotubes is influenced by the electronic conductance and mechanical properties of the nanotube, which could serve as a signal for a gas sensor. It appears that the considerable charge transfer from the Cu-doped nanotubes to a CO2 molecule reduces the energy gap. These observations suggest that the Cu-doped-SiCNT, -BNNT and -AlNNT can be introduced as promising candidates for gas sensor devices that detect CO2 molecules.

  6. Ultrathin graphitic carbon nitride nanosheets: a novel peroxidase mimetic, Fe doping-mediated catalytic performance enhancement and application to rapid, highly sensitive optical detection of glucose.

    PubMed

    Tian, Jingqi; Liu, Qian; Asiri, Abdullah M; Qusti, Abdullah H; Al-Youbi, Abdulrahman O; Sun, Xuping

    2013-12-01

    In this article, we demonstrate for the first time that ultrathin graphitic carbon nitride nanosheets (g-C3N4) possess peroxidase activity. Fe doping of the nanosheets leads to peroxidase mimetics with greatly enhanced catalytic performance and the mechanism involved is proposed. We further demonstrate the novel use of such Fe-g-C3N4 as a cheap nanosensor for simple, rapid, highly selective and sensitive optical detection of glucose with a pretty low detection limit of 0.5 μM. PMID:24121798

  7. A novel method to make boron-doped microcrystalline silicon thin films with optimal crystalline volume fraction for thin films solar cell applications.

    PubMed

    Shin, Chonghoon; Park, Jinjoo; Kim, Sangho; Park, Hyeongsik; Jung, Junhee; Bong, Sungjae; Lee, Youn-Jung; Yi, Junsin

    2014-12-01

    Highly conducting boron-doped microcrystalline silicon (p-type ?c-Si:H) thin films have been prepared by radio frequency plasma-enhanced chemical-vapor deposition (RF-PECVD). In this work, the effects of hydrogen dilution, doping ratio, plasma power, deposition pressure and substrate temperature on the growth and the properties of boron-doped microcrystalline silicon (p-type ?c-Si:H) thin films are investigated. The electrical, chemical and structural properties are improved with increasing crystallite, which depends on the plasma conditions. For various plasma parameters, the crystalline volume fraction (X(c)), dark conductivity (?(d)), activation energy (E(a)), hydrogen content (C(H)), surface roughness (S(r)), and micro void fraction (R*) were measured, and they were 0-72%, 4.17-10(-4) S/cm-1.1 S/cm, 0.041-0.113 eV, 3.8-11.5 at.%, 3.2 nm-12.2 nm, and 0.47-0.80, respectively. The film with R* of 0.47 and C(H) of about 5 at.% belonged to a region of low disorder, and acted as a good passivation layer. PMID:25971071

  8. Simultaneous electrochemical determination of nitrate and nitrite in aqueous solution using Ag-doped zeolite-expanded graphite-epoxy electrode.

    PubMed

    Manea, Florica; Remes, Adriana; Radovan, Ciprian; Pode, Rodica; Picken, Stephen; Schoonman, Joop

    2010-11-15

    In this work a new electrochemical sensor based on an Ag-doped zeolite-expanded graphite-epoxy composite electrode (AgZEGE) was evaluated as a novel alternative for the simultaneous quantitative determination of nitrate and nitrite in aqueous solutions. Cyclic voltammetry was used to characterize the electrochemical behavior of the electrode in the presence of individual or mixtures of nitrate and nitrite anions in 0.1M Na(2)SO(4) supporting electrolyte. Linear dependences of current versus nitrate and nitrite concentrations were obtained for the concentration ranges of 1-10mM for nitrate and 0.1-1mM for nitrite using cyclic voltammetry (CV), chronoamperometry (CA), and multiple-pulsed amperometry (MPA) procedures. The comparative assessment of the electrochemical behavior of the individual anions and mixtures of anions on this modified electrode allowed determining the working conditions for the simultaneous detection of the nitrite and nitrate anions. Applying MPA allowed enhancement of the sensitivity for direct and indirect nitrate detection and also for nitrite detection. The proposed sensor was applied in tap water samples spiked with known nitrate and nitrite concentrations and the results were in agreement with those obtained by a comparative spectrophotometric method. This work demonstrates that using multiple-pulse amperometry with the Ag-doped zeolite-expanded graphite-epoxy composite electrode provides a real opportunity for the simultaneous detection of nitrite and nitrate in aqueous solutions. PMID:21035645

  9. CO catalytic oxidation on Pt-doped single wall boron nitride nanotube: first-principles investigations

    NASA Astrophysics Data System (ADS)

    Abdel Aal, S.

    2016-02-01

    The catalytic oxidation of CO at Pt-doped BNNT (5,5) has been investigated theoretically using density functional theory. The electronic structures and thermochemical properties of CO and O2 that adsorbed on Pt embedded at the B- and N-vacancy sites of BNNTs are analyzed. It is demonstrated that the different BNNT substrates can modify the electronic structure of the Pt catalysts and cause different effects in the catalytic activities. With the N-vacancy (Pt(N)-BNNT), the Pt behaves as a Lewis acid for accepting an electron from the substrate, thus O2 binds stronger than CO molecules, thus alleviating the CO poisoning of the platinum catalysts. Coadsorption of CO and O2 on Pt(N)-BNNT results in additional charge transfer to O2. CO oxidation proceeds via the Eley-Rideal (ER) mechanism entails lower activation barrier and higher reaction rate than that of Langmuir-Hinshelwood (LH) mechanism suggesting the superiority of the ER mechanism for CO oxidation at Pt(N)-BNNT. Therefore, Pt(N)-BNNT might be a good candidate for low-cost, highly active, and stable catalysts for CO oxidation.

  10. A First Principles study on Boron-doped Graphene decorated by Ni-Ti-Mg atoms for Enhanced Hydrogen Storage Performance

    PubMed Central

    Nachimuthu, Santhanamoorthi; Lai, Po-Jung; Leggesse, Ermias Girma; Jiang, Jyh-Chiang

    2015-01-01

    We proposed a new solid state material for hydrogen storage, which consists of a combination of both transition and alkaline earth metal atoms decorating a boron-doped graphene surface. Hydrogen adsorption and desorption on this material was investigated using density functional theory calculations. We find that the diffusion barriers for H atom migration and desorption energies are lower than for the previously designed mediums and the proposed medium can reach the gravimetric capacity of ~6.5 wt % hydrogen, which is much higher than the DOE target for the year 2015. Molecular Dynamics simulations show that metal atoms are stably adsorbed on the B doped graphene surface without clustering, which will enhance the hydrogen storage capacity. PMID:26577659

  11. Improved fiber retention by the use of fillers in graphite fiber/resin matrix composites

    NASA Technical Reports Server (NTRS)

    Gluyas, R. E.; Bowles, K. J.

    1980-01-01

    A variety of matrix fillers were tested for their ability to prevent loss of fiber from graphite fiber/PMR polyimide and graphite fiber/epoxy composites in a fire. The fillers tested included powders of boron, boron carbide lime glass, lead glass, and aluminum. Boron was the most effective and prevented any loss of graphite fiber during burning. Mechanical properties of composites containing boron filler were measured and compared to those of composites containing no filler.

  12. Nitrogen-doped Co/Co9S8/partly-graphitized carbon as durable catalysts for oxygen reduction in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Rui; Dai, Ying; Chen, Baibing; Zou, Jinlong; Jiang, BaoJiang; Fu, Honggang

    2016-03-01

    Durability of catalysts for oxygen reduction reaction (ORR) is the key factor for governing the performance of microbial fuel cells (MFCs). The cobalt (Co) chelated polyaniline (PANI) is used as the nitrogen and carbon sources to prepare the N-doped Co/Co9S8/partly-graphitized carbon (Co/Co9S8/NPGC) catalysts. Structure-activity correlations for Co/Co9S8/NPGC are explored by tuning the heating temperature (600-1000 °C) to investigate how the active components (Co/Co9S8) and N-doped functionalities (N-species) influence the ORR activity. As temperature increases, the gradual crystallization of Co originating from the reduction of Co9S8 is conducted to form the Co/Co9S8 heterojunction. MFCs with Co/Co9S8/NPGC (800 °C) cathode obtain the highest power density (1156 mW m-2) and the lowest charge transfer resistance (11.1 Ω) after 75 d running, which are better than commercial Pt/C (10 wt.%). Although the sole Co9S8 plays a limited role in ORR, the resulting Co/Co9S8 is found to be indispensable to achieve high activity and durability in MFCs cathodes. The dominant ORR pathways of Co/Co9S8/NPGC (800 and 900 °C) are the four-electron O2 reduction, which are attributed to the co-existence of pyridinic N, graphitic N and Co-Nx species. These new N-doped metal sulfide/PGC composites show promise for applications in MFCs.

  13. The nitrogen-boron paramagnetic center in visible light sensitized N-B co-doped TiO(2). Experimental and theoretical characterization.

    PubMed

    Czoska, A M; Livraghi, S; Paganini, M C; Giamello, E; Di Valentin, C; Pacchioni, G

    2011-01-01

    Nitrogen boron co-doped TiO(2) prepared via sol-gel synthesis and active under visible light, contains two types of paramagnetic extrinsic defects, both exhibiting a well resolved EPR spectrum. The first center is the well characterized [N(i)O]˙ species (i = interstitial) also present in N-doped TiO(2), while the second one involves both N and B. This latter center (labeled [NOB]˙) exhibits well resolved EPR spectra obtained using either (14)N or (15)N which show a high spin density in a N 2p orbital. The structure of the [NOB]˙ species is different from that previously proposed in the literature and is actually based on the presence of interstitial N and B atoms both bound to the same lattice oxygen ion. The interstitial B is also linked to two other lattice oxygen ions reproducing the trigonal planar structure typical of boron compounds. The energy level of the [NOB]˙ center lies near the edge of the valence band of TiO(2) and, as such, does not contribute to the visible light absorption. However, [NOB]˙ can easily trap one electron generating the [NOB](-) diamagnetic center which introduces a gap state at about 0.4 eV above the top of the valence band. This latter species can contribute to the visible light activity. PMID:21038048

  14. 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 Wakabayashi, Yuki; Akiyama, Ryota; Nakane, Ryosho; Tanaka, Masaaki

    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.

  15. Structure, electronic and magnetic properties of hexagonal boron nitride sheets doped by 5d transition metal atoms: First-principles calculations and molecular orbital analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaofu; Geng, Zhaohui; Cai, Danyun; Pan, Tongxi; Chen, Yixin; Dong, Liyuan; Zhou, Tiege

    2015-01-01

    A first-principles calculation based on density functional theory is carried out to reveal the geometry, electronic structures and magnetic properties of hexagonal boron nitride sheets (h-BNSs) doped by 5d transitional mental atoms (Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg) at boron-site (B5d) and nitrogen-site (N5d). Results of pure h-BNS, h-BNS with B vacancy (VB) and N vacancy (VN) are also given for comparison. It is shown that all the h-BNSs doped with 5d atoms possess a C3v local symmetry except for NLu and NHg which have a clear deviation. For the same 5d dopant, the binding energy of B5d is larger than that of N5d, which indicates the substitution of a 5d atom for B is preferred. The total densities of states are presented, where impurity energy levels exist. Besides, the total magnetic moments (TMMs) change regularly with the increment of the 5d atomic number. Theoretical analyses by molecular orbital under C3v symmetry explain the impurity energy levels and TMMs.

  16. Electrochemical oxidation of reverse osmosis concentrate on boron-doped diamond anodes at circumneutral and acidic pH.

    PubMed

    Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Gernjak, Wolfgang; Joll, Cynthia; Radjenovic, Jelena

    2012-11-15

    Electrochemical processes have been widely investigated for degrading organic contaminants present in wastewater. This study evaluated the performance of electrochemical oxidation using boron-doped diamond (BDD) electrodes by forming OH() for the treatment of reverse osmosis concentrate (ROC) from secondary-treated wastewater effluents. Since oxidation by OH() and active chlorine species (HClO/ClO(-)) is influenced by pH, the electrochemical oxidation of ROC was evaluated at controlled pH 6-7 and at pH 1-2 (no pH adjustment). A high concentration of chloride ions in the ROC enhanced the oxidation, and 7-11% of Coulombic efficiency for chemical oxygen demand (COD) removal was achieved with 5.2 Ah L(-1) of specific electrical charge. Complete COD removal was observed after 5.2 and 6.6 Ah L(-1), yet the corresponding dissolved organic carbon (DOC) removal was only 48% (at acidic pH) and 59% (at circumneutral pH). Although a higher operating pH seemed to enhance the participation of OH() in oxidation mechanisms, high concentrations of chloride resulted in the formation of significant concentrations of adsorbable organic chlorine (AOCl) after electrochemical oxidation at both pH. While adsorbable organic bromine (AOBr) was degraded at a higher applied electrical charge, a continuous increase in AOCl concentration (up to 0.88 mM) was observed until the end of the experiments (i.e. 10.9 Ah L(-1)). In addition, total trihalomethanes (tTHMs) and total haloacetic acids (tHAAs) were further degraded with an increase in electrical charge under both pH conditions, to final total concentrations of 1 and 4 μM (tTHMs), and 12 and 22 μM (tHAAs), at acidic and circumneutral pH, respectively. In particular, tHAAs were still an order of magnitude above their initial concentration in ROC after further electrooxidation. Where high chloride concentrations are present, it was found to be necessary to separate chloride from ROC prior to electrochemical oxidation in order to avoid the formation of chlorinated by-products. PMID:22995242

  17. Undoped and boron doped diamond nanoparticles as platinum and platinum-ruthenium catalyst support for direct methanol fuel cell application

    NASA Astrophysics Data System (ADS)

    La Torre Riveros, Lyda

    Nanoparticular diamond is a promising material that can be used as a robust and chemically stable catalytic support. It has been studied and characterized physically and electrochemically, in its powder and thin film forms. This thesis work intends to demonstrate that undoped diamond nanoparticles (DNPs) and boron-doped diamond nanoparticles (BDDNPs) can be used as an electrode and a catalytic support material for platinum and ruthenium catalysts. The electrochemical properties of diamond nanoparticle electrodes, fabricated using the ink paste method, were investigated. As an initial step, we carried out chemical purification of commercially available undoped DNPs by refluxing in aqueous HNO3 as well as of BDDNPs which were doped through a collaborative work with the University of Missouri. The purified material was characterized by spectroscopic and surface science techniques. The reversibility of reactions such as ferricyanide/ferrocyanide (Fe(CN) 63-/Fe(CN)64-) and hexaamineruthenium (III) chloride complexes as redox probes were evaluated by cyclic voltammetry at the undoped DNPs and BDDNPs surface. These redox probes showed limited peak currents and presented linear relationships between current (i) and the square root of the potential scan rate (v1/2). However, compared to conventional electrodes, the peak currents were smaller. BDDNPs show an improvement in charge transfer currents when compared to undoped DNPs. Platinum and ruthenium nanoparticles were chemically deposited on undoped DNPs and BDDNPs through the use of the excess of a mild reducing agent such NaBH4. In order to improve the nanoparticle dispersion sodium dodecyl benzene sulfonate (SDBS), a surfactant agent, was used. Percentages of platinum and ruthenium metals were varied as well as the stoichiometric amount of the reducing agent to determine adequate parameters for optimum performance in methanol oxidation. Both before and after the reducing process the samples were characterized by scanning electron microscopy (SEM), energy dispersive analysis (EDX), infrared spectroscopy (IR), transmission electron microscopy (TEM), X-ray diffraction (XRD), prompt gamma neutron activation analysis (PGNAA), and X-ray photoelectron spectroscopy (XPS). In order to demonstrate the utility of the catalyst obtained, the samples were tested in an electrochemical cell using methanol as a probe solution. As was performed with the undoped DNPs and BDDNPs, the ink paste method was used to prepare the electrodes with Pt/DNP, Pt-Ru/DNP, Pt/BDDNP and Pt-Ru/BDDNP catalytic systems, to perform the electrochemical experiments. The Pt and Pt-Ru modified diamond electrodes were tested with cyclic voltammetry in 0.5 M H2SO4 as electrolyte support showing hydrogen adsorption/desorption at platinum surfaces. CO gas adsorption/desorption experiments were also performed to determine the active surface area of Pt when Ru is present. Methanol oxidation current peaks were obtained when the electrodes were tested in a 1.0 M methanol/0.5 M H2SO4 solution. The experimental results demonstrated that diamond nanoparticles are useful as an electrode material. A fuel cell is a device which transforms the chemical energy of a fuel directly into electrical energy. As previously mentioned, the aim of this research is to demonstrate the utility of undoped DNPs and BDDNPs as catalytic supports, which was performed by testing the catalytic systems obtained in a single fuel cell station at different temperatures to observe the cell performance.

  18. 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.

  19. A simple synthesis of nitrogen doped porous graphitic carbon: Electrochemical determination of paracetamol in presence of ascorbic acid and p-aminophenol.

    PubMed

    Biswas, Sudip; Chakraborty, Dipanjan; Das, Rashmita; Bandyopadhyay, Rajib; Pramanik, Panchanan

    2015-08-26

    Graphite paste electrode modified with nitrogen doped porous carbon (NDPC) is used for the detections of paracetamol (PCM), ascorbic acid (AA) and p-aminophenol (PAP) at relatively low concentration. NDPC is synthesized by direct carbonization of Zn(OAc)2 incorporated melamine-formaldehyde resin microsphere. The NDPC shows small pore diameters centered at 3.14 nm and 8.12 nm and has a pseudo graphitic structure with reasonable porous matrix. The lower limit of detections (S/N = 3) for PCM, AA, and PAP are found to be 30 nM, 720 nM and 10 nM respectively. Under optimized experimental condition, the linear ranges of determination for PCM and AA are 1-400 μM, 10-2700 μM respectively in mixture. Similarly for PCM and PAP mixture, the linear ranges of determination are found to be 1-90 μM. It is also used for the analysis of urine and pharmaceutical products with better sensitivity. PMID:26347171

  20. The sonication of graphite in various solvents and surfactants to synthesize high quality graphene as well as the nitrogen doping of graphene

    NASA Astrophysics Data System (ADS)

    Soden, Daniel R.; Bai, Jincheng; Dong, Lifeng

    2014-03-01

    The emergence of graphene in the scientific community has been the cause of much excitement among material scientists due to its unusual physical and photovoltaic properties. However, the much sought after monolayer graphene has proven to be difficult to produce in sufficient quantities This experiment aims to correct some of these problems, concerning itself with the synthesis of high quality graphene through continuous sonication with surfactant or solvent added throughout, as well as the issue of graphene quality as a function of sonication time. This was accomplished through the creation and addition of a solvent or surfactant solution to a graphite suspension during sonication lasting for 50, 80, 110,140, 170, and 200 minutes. The resulting suspension was then filtrated to separate out the graphene. Following this, the graphene was then doped through various methods with nitrogen to alter its properties. This completely physical method of graphene synthesis and doping provides a much simpler and more environmentally safe way to achieve the highly desired few layer graphene, and will hopefully allow for greater use of the substance in industry and its implementation into new technology. L. F. Dong acknowledges the support of the National Science Foundation (DMR-1126375 and DMR-1126375), the Faculty Research Grant and the Sabbatical Leave Award from Missouri State University.

  1. Direct assessment of the mechanical modulus of graphene co-doped with low concentrations of boron-nitrogen by a non-contact approach

    NASA Astrophysics Data System (ADS)

    Pan, Shun-Hsien; Medina, Henry; Wang, Sheng-Bo; Chou, Li-Jen; Wang, Zhiming M.; Chen, Kuei-Hsien; Chen, Li-Chyong; Chueh, Yu-Lun

    2014-07-01

    Boron and nitrogen co-doping has been shown to be an effective way to induce a band gap in graphene for electrical applications but only a few theoretical studies have been done to understand the elastic and mechanical properties of the modified graphene. Until now, no experimental assessment of the mechanical modulus of boron-nitrogen-doped graphene (BNG) has been reported in the literature. Here, we demonstrate a novel non-contact approach to determine the in-plane stiffness of BNG at low BN concentrations. The in-plane stiffness of BNG with 2 at% BN concentration was estimated to be about 309 N m-1, which is lower than that of pristine graphene, in good agreement with some theoretical studies. Moreover, we correlated the conductivity of BNG with induced strain and found the BNG to be more sensitive than pristine graphene in response to externally applied strain. This result indicates that BNG is a more suitable material than graphene for strain sensor applications.Boron and nitrogen co-doping has been shown to be an effective way to induce a band gap in graphene for electrical applications but only a few theoretical studies have been done to understand the elastic and mechanical properties of the modified graphene. Until now, no experimental assessment of the mechanical modulus of boron-nitrogen-doped graphene (BNG) has been reported in the literature. Here, we demonstrate a novel non-contact approach to determine the in-plane stiffness of BNG at low BN concentrations. The in-plane stiffness of BNG with 2 at% BN concentration was estimated to be about 309 N m-1, which is lower than that of pristine graphene, in good agreement with some theoretical studies. Moreover, we correlated the conductivity of BNG with induced strain and found the BNG to be more sensitive than pristine graphene in response to externally applied strain. This result indicates that BNG is a more suitable material than graphene for strain sensor applications. Electronic supplementary information (ESI) available: Actual strain applied on pristine graphene and 2BNG; Raman spectra of CVD graphene and 2BNG transferred onto PDMS substrates; schematic of the atomic model; I2D/IG Raman ratio as a function of the PDMS strain for pristine graphene in the reversible deformation region; Raman information of the I2D/IG ratio for pristine graphene in the irreversible deformation region; Raman G band for graphene before and under applied strain; I2D/IG Raman ratio as a function of the PDMS strain for the 2BNG film in the reversible deformation region; Raman information of the I2D/IG ratio for 2BNG in the irreversible deformation region; Raman G band for 2BNG before and under applied strain; the schematic diagram of the deposition process for a strain sensor device; schematic diagram of the 2D stress applied to graphene and BNG films; actual strain on graphene and BNG measured by Raman versus PDMS strain; schematic diagrams of the strain distribution. See DOI: 10.1039/c4nr00495g

  2. Low-Temperature Softening Due to Vacancy Orbital with Γ8 Quartet Ground State in Boron-Doped Floating Zone Silicon

    NASA Astrophysics Data System (ADS)

    Baba, Shotaro; Akatsu, Mitsuhiro; Mitsumoto, Keisuke; Komatsu, Satoru; Horie, Kunihiko; Nemoto, Yuichi; Yamada-Kaneta, Hiroshi; Goto, Terutaka

    2013-08-01

    We have carried out low-temperature ultrasonic measurements using shear-mode ultrasound to clarify the quantum state of a vacancy orbital in boron-doped silicon grown by the floating zone (FZ) method. The elastic constants (C11-C12)/2 and C44 of the transverse mode exhibit considerable softening below 2 and 5 K down to the base temperature of 30 mK, respectively. The elastic constant C44 measured by the three ultrasonic modes (kx,uy), (kz,ux), and (kx,uz) shows the different magnetic field dependences among the configurations under applied magnetic fields along the z-axis. The elastic softening and the magnetic field dependence of the elastic constants are accounted for by the quadrupole susceptibility based on the energy level scheme of the vacancy orbital with a Γ8 quartet ground state and Γ7 doublet excited state located at an energy of 1 K. The difference in C44 between the two ultrasonic modes (kz,ux) and (kx,uz) at fields along the z-axis indicates that the Γ8 quartet ground state is slightly split by local strain in the silicon sample. The quantum state of the vacancy orbital is expected to be sensitive to strain because of the extremely large quadrupole-strain coupling energy of gΓ≈ 105 K due to the extensively spreading orbital radius of r≈ 1 nm. The differences in variation of the low-temperature softening and magnetic field dependence among eight samples cut out from different locations of the present boron-doped FZ silicon ingot evidence the inhomogeneous distribution of the vacancy concentration.

  3. Coatings for graphite fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature.

  4. Bulk-bronzied graphites for plasma-facing components in ITER (International Thermonuclear Experimental Reactor)

    SciTech Connect

    Hirooka, Y.; Conn, R.W.; Doerner, R.; Khandagle, M. . Inst. of Plasma and Fusion Research); Causey, R.; Wilson, K. ); Croessmann, D.; Whitley, J. ); Holland, D.; Smolik, G. ); Matsuda, T.; Sogabe, T. (Toyo Tanso Co. Ltd., O

    1990-06-01

    Newly developed bulk-boronized graphites and boronized C-C composites with a total boron concentration ranging from 1 wt % to 30 wt % have been evaluated as plasma-facing component materials for the International Thermonuclear Experimental Reactor (ITER). Bulk-boronized graphites have been bombarded with high-flux deuterium plasmas at temperatures between 200 and 1600{degree}C. Plasma interaction induced erosion of bulk-boronized graphites is observed to be a factor of 2--3 smaller than that of pyrolytic graphite, in regimes of physical sputtering, chemical sputtering and radiation enhanced sublimation. Postbombardment thermal desorption spectroscopy indicates that bulk-boronized graphites enhance recombinative desorption of deuterium, which leads to a suppression of the formation of deuterocarbon due to chemical sputtering. The tritium inventory in graphite has been found to decrease by an order of magnitude due to 10 wt % bulk-boronization at temperatures above 1000{degree}C. The critical heat flux to induce cracking for bulk-boronized graphites has been found to be essentially the same as that for non-boronized graphites. Also, 10 wt % bulk-boronization of graphite hinders air oxidation nearly completely at 800{degree}C and reduces the steam oxidation rate by a factor of 2--3 at around 1100 and 1350{degree}C. 38 refs., 5 figs.

  5. Initial boronization of PBX-M using ablation from solid boronized probes

    SciTech Connect

    Kugel, H.W.; Timberlake, J.; Bell, R.; Kaita, R.; Kaye, S.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; Von Goeler, S. )

    1994-07-01

    Boronization was performed by plasma ablation of two solid boronized target probes. Probe-1, in a mushroom shape, consisted of a 10.7% boronized two-dimensional carbon-carbon composite containing 3.6 g of boron in a B[sub 4]C binder. Probe-2, in a rectangular shape, consisted of an 86% boronized graphite felt composite containing 19.5 g of 40-[mu]m boron particles. Probe-1 boronization deposited [approximately]26 monolayers of boron. After boronization with Probe-1, the loop voltage in 1-MW neutral-beam-heated plasmas decreased 27%, and volt-second consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of [approximately]5. The central oxygen density decreased 15 to 20%. Carbon levels initially increased during boronization but were significantly reduced after boronization. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization deposited [approximately]70 monolayers. Probe-2 boronization exhibited similar improved plasma conditions, but for some parameters, a smaller percentage change occurred because of the previous boronization with Probe-1. The ablation rates of both probes were consistent with front-face temperatures above the boron melting point. The results demonstrate the performance of two different boronized probe materials and the relative simplicity and effectiveness of solid target boronization as a convenient, real-time impurity control technique. 20 refs., 10 figs., 1 tab.

  6. Effect of nitrogen as co-dopant in carbon and boron-doped ZnO clusters

    NASA Astrophysics Data System (ADS)

    Kapila, Neha; Sharma, Gaurav; Mudahar, Isha; Sharma, Hitesh

    2016-05-01

    The effect of N as co-dopant have been investigated on magnetic properties of C and B-doped (ZnO)n clusters (n = 1 - 16) using spin-polarized density functional theory. Total energy calculations show that C and N more stable when substituted at O site, whereas B is more stable at the Zn site. The B:N co-doping is energetically more stable than C:N which is more stable than N:N doping. C and N atoms do not show tendency to form clusters when doped separately. The magnetic moment (MM) of C-doped ZnO clusters is enhanced significantly with N co-doping. The MM of 2 μB, 1 μB and 1 μB per atom is induced due to C, N and B respectively. The MM of 3 μB or 5 μB and 2 μB or 4 μB are observed for co-doping of 2C:N and C:2N respectively. In contrary, the MM in 2B:N and B:2N co-doped (ZnO)n remains 1 μB for n=2-4, 12 and 16. The results are in agreement with the available theoretical results.

  7. Metal-doped graphene layers composed with boron nitride-graphene as an insulator: a nano-capacitor.

    PubMed

    Monajjemi, Majid

    2014-11-01

    A model of a nanoscale dielectric capacitor composed of a few dopants has been investigated in this study. This capacitor includes metallic graphene layers which are separated by an insulating medium containing a few h-BN layers. It has been observed that the elements from group IIIA of the periodic table are more suitable as dopants for hetero-structures of the {metallic graphene/hBN/metallic graphene} capacitors compared to those from groups IA or IIA. In this study, we have specifically focused on the dielectric properties of different graphene/h-BN/graphene including their hetero-structure counterparts, i.e., Boron-graphene/h-BN/Boron-graphene, Al-graphene/h-BN/Al-graphene, Mg-graphene/h-BN/Mg-graphene, and Be-graphene/h-BN/Be-graphene stacks for monolayer form of dielectrics. Moreover, we studied the multi dielectric properties of different (h-BN)n/graphene hetero-structures of Boron-graphene/(h-BN)n/Boron-graphene. PMID:25359456

  8. Boron, bismuth co-doping of gallium arsenide and other compounds for photonic and heterojunction bipolar transistor devices

    DOEpatents

    Mascarenhas, Angelo

    2015-07-07

    Isoelectronic co-doping of semiconductor compounds and alloys with acceptors and deep donors is sued to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. For example, Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, B and Bi, to customize solar cells, and other semiconductor devices. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  9. Precipitation control and activation enhancement in boron-doped p{sup +}-BaSi{sub 2} films grown by molecular beam epitaxy

    SciTech Connect

    Khan, M. Ajmal; Nakamura, K.; Du, W.; Toko, K.; Usami, N.; Suemasu, T.

    2014-06-23

    Precipitation free boron (B)-doped as-grown p{sup +}-BaSi{sub 2} layer is essential for the BaSi{sub 2} p-n junction solar cells. In this article, B-doped p-BaSi{sub 2} layers were grown by molecular beam epitaxy on Si(111) substrates, and the influence of substrate growth temperature (T{sub S}) and B temperature (T{sub B}) in the Knudsen cell crucible were investigated on the formation of B precipitates and the activation efficiency. The hole concentration, p, reached 1.0 × 10{sup 19 }cm{sup −3} at room temperature for T{sub S} = 600 and T{sub B} = 1550 °C. However, the activation rate of B was only 0.1%. Furthermore, the B precipitates were observed by transmission electron microscopy (TEM). When the T{sub S} was raised to 650 °C and the T{sub B} was decreased to 1350 °C, the p reached 6.8 × 10{sup 19 }cm{sup −3}, and the activation rate increased to more than 20%. No precipitation of B was also confirmed by TEM.

  10. First-principles study of SO2 molecule adsorption on the pristine and Mn-doped boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Deng, Zun-Yi; Zhang, Jian-Min; Xu, Ke-Wei

    2015-08-01

    To exploit the potential application of nitride nanotube (BNNT), the adsorption of sulfur dioxide (SO2) on pristine and Mn-doped BNNT was theoretically studied using first-principles approach based on density functional theory (DFT). The most stable adsorption geometry, adsorption energy, magnetic moment, charge transfer and density of states of these systems are discussed. SO2 molecule is weakly adsorbed on the pristine BNNT. The Mn-doped BNNT show high reactivity toward SO2 regardless of the MnB site or MnN site adsorption. The larger formation energies and analysis of density of states show the SO2 molecules are chemically bonded to Mn-doped BNNT and the covalent interaction between the SO2 molecule and Mn atom can be formed. Therefore, the Mn-doped BNNT can be used as SO2 gas sensor manufacturing raw materials, and it may be a potential material for nanodevice applications.

  11. Monte Carlo simulation of boron doping profile of fin and trench structures by plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Shahsenov, Izat S.; Miakonkikh, Andrey V.; Rudenko, Kostantin V.

    2014-12-01

    Plasma immersion ion implantation into fins and trenches at elevated pressures is simulated. In the present work we calculate boron concentration distribution in the sample accounting for ion scattering in plasma sheath and geometric shadowing effects (ions at certain angle of incidence couldn't achieve shadowed part of trench wall and bottom). First, energy and angle distribution of ions passed through the plasma sheath to the sample surface is obtained. These data are used to calculate boron concentration distribution in the sample. Pressure range is 30-300 mTorr, plasma electron temperature 5 eV, plasma density 1010-1012 cm-3. The degree of conformity increases with the pressure raises and decreases with the density of plasma.

  12. Intercorrelated Superhybrid of AgBr Supported on Graphitic-C3N4-Decorated Nitrogen-Doped Graphene: High Engineering Photocatalytic Activities for Water Purification and CO2 Reduction.

    PubMed

    Li, Hongyan; Gan, Shiyu; Wang, Haoyu; Han, Dongxue; Niu, Li

    2015-11-18

    AgBr nanoparticles supported on graphitic-C3N4-decorated nitrogen-doped graphene intercorrelated ternary superhybrid composites (ACNNG-x) acting as a novel visible-light driven photocatalyst are reported. Because of the fast interfacial charge separation and photoelectrochemical performance, the representative of ACNNG-50 superhybrid structure achieves high efficiency and stable photocatalytic capability for organic contaminant degradation and CO2 reduction. PMID:26422111

  13. Structural and electronic properties of Li- and Cu-doped β-rhombohedral boron constructed from icosahedral and truncated icosahedral clusters

    NASA Astrophysics Data System (ADS)

    Matsuda, H.; Nakayama, T.; Kimura, K.; Murakami, Y.; Suematsu, H.; Kobayashi, M.; Higashi, I.

    1995-08-01

    This study performs dc conductivity and static magnetic-susceptibility measurements on Li- and Cu-doped β-rhombohedral boron (β-rhombohedral B), which is a unique polymorphic semiconducting (group III) material composed of B12 icosahedral clusters. dc conductivity results show a variable-range-hopping (VRH)-type temperature dependence with a typical localization length of about ~1 Å. In addition, the density of states (DOS) at the Fermi energy, which is calculated from fitted parameters of VRH conduction, was found to have a peak with respect to metal concentration, such that at the highest concentration (Li7.9B105 and Cu4.2B105), metal-doped β-rhombohedral B appears to revert back to an insulator, instead of showing insulator-to-metal transition. Corresponding static magnetic-susceptibility results, however, show a contribution from Pauli paramagnetism in the temperature-independent component χ0, where a similar concentration dependence is shows to that in the DOS of VRH conduction. Based on these properties, we discuss the possibility of filling the intrinsic acceptor band, which originates from the uppermost molecular bonding orbital of the B12 icosahedral cluster that is split by the Jahn-Teller effect. β-rhombohedral B's crystalline structure can also be viewed as a slightly distorted face-centered cubic (fcc) packing of B84 soccer-ball-shaped clusters covalently bound to each other and containing a relatively large number of large-size interstitial doping sites. This structure is considered to be topologically similar to that of fcc C60, although the bonding mechanisms of their clusters are different, and therefore we also describe the similarities and differences between them.

  14. 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 Ω 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.

  15. A Taiji-principle-designed magnetic porous C-doped graphitic carbon nitride for environment-friendly solid phase extraction of pollutants from water samples.

    PubMed

    Wang, Man; Yuan, Hao; Deng, Wenjing; Bi, Wentao; Yang, Xiaodi

    2015-09-18

    A new magnetic porous carbon-doped graphitic carbon nitride nanocomposite and experimental strategies were environment-friendly designed for solid phase extraction of brominated flame retardants from water sample. The easily synthesized and low cost nanocomposite was characterized using techniques, including Fourier transform infrared spectroscopy, X-ray diffraction spectrometry, elemental analysis, and transmission electron microscopy. The large surface area and enhanced interactions of this nanocomposite with its adsorption behavior in Taiji principle (a balance of hydrophilicity and hydrophobicity) in aqueous phase benefit the extraction. Magnetic solid phase extraction has advantages such as low solvent consumption and reusability of the sorbent, and was therefore employed in this study. In addition, a quicker and less laborious statistical method, known as response surface methodology, was used to investigate and optimize some crucial factors that affected the adsorption. The combined use of this new nanocomposite and experimental strategy showed excellent precision (2.7-5.2%) and sensitivity (limits of detection (S/N=3): 0.1-0.2 μg L(-1)). This method was successfully applied to the analysis of real water samples giving good spiked recoveries over the range of 92.4-99.8%. This research provides an environment-friendly strategy to prepare suitable sorbents for extraction or adsorption of various compounds within different matrices. PMID:26278354

  16. Substrate and method for the formation of continuous magnesium diboride and doped magnesium diboride wire

    DOEpatents

    Suplinskas, Raymond J.; Finnemore, Douglas; Bud'ko, Serquei; Canfield, Paul

    2007-11-13

    A chemically doped boron coating is applied by chemical vapor deposition to a silicon carbide fiber and the coated fiber then is exposed to magnesium vapor to convert the doped boron to doped magnesium diboride and a resultant superconductor.

  17. The effect of boron doping on crystal structure, magnetic properties and magnetocaloric effect of DyCo2

    NASA Astrophysics Data System (ADS)

    Wang, C. L.; Liu, J.; Mudryk, Y.; Gschneidner, K. A.; Long, Y.; Pecharsky, V. K.

    2016-05-01

    The magnetic properties and magnetic entropy changes of DyCo2Bx (x=0, 0.05, 0.1, and 0.2) alloys were investigated. The Curie temperature (TC) increases with increasing B concentration. The frequency dependence of ac magnetic susceptibility of DyCo2 caused by the narrow domain wall pinning effect is depressed by B doping, but the coercivity and the magnetic viscosity are prominently increased in the B doped alloys. The magnetic transition nature of DyCo2Bx changes from the first-order to the second-order with increasing x, which leads to the decrease of the maximum magnetic entropy change. However, the relative cooling power (RCP) of DyCo2 and the B doped alloys remains nearly constant.

  18. The effect of boron doping on crystal structure, magnetic properties and magnetocaloric effect of DyCo2

    DOE PAGESBeta

    Wang, C. L.; Liu, J.; Mudryk, Y.; Gschneidner, Jr., K. A.; Long, Y.; Pecharsky, V. K.

    2015-12-19

    The magnetic properties and magnetic entropy changes of DyCo2Bx (x=0, 0.05, 0.1, and 0.2) alloys were investigated. The Curie temperature (TC) increases with increasing B concentration. The frequency dependence of ac magnetic susceptibility of DyCo2 caused by the narrow domain wall pinning effect is depressed by B doping, but the coercivity and the magnetic viscosity are prominently increased in the B doped alloys. The magnetic transition nature of DyCo2Bx changes from the first-order to the second-order with increasing x, which leads to the decrease of the maximum magnetic entropy change. Furthermore, the relative cooling power (RCP) of DyCo2 and themore » B doped alloys remains nearly constant.« less

  19. The effect of boron doping on crystal structure, magnetic properties and magnetocaloric effect of DyCo2

    SciTech Connect

    Wang, C. L.; Liu, J.; Mudryk, Y.; Gschneidner, Jr., K. A.; Long, Y.; Pecharsky, V. K.

    2015-12-19

    The magnetic properties and magnetic entropy changes of DyCo2Bx (x=0, 0.05, 0.1, and 0.2) alloys were investigated. The Curie temperature (TC) increases with increasing B concentration. The frequency dependence of ac magnetic susceptibility of DyCo2 caused by the narrow domain wall pinning effect is depressed by B doping, but the coercivity and the magnetic viscosity are prominently increased in the B doped alloys. The magnetic transition nature of DyCo2Bx changes from the first-order to the second-order with increasing x, which leads to the decrease of the maximum magnetic entropy change. Furthermore, the relative cooling power (RCP) of DyCo2 and the B doped alloys remains nearly constant.

  20. The effect of boron doping on crystal structure, magnetic properties and magnetocaloric effect of DyCo2

    DOE PAGESBeta

    Wang, C. L.; Liu, J.; Mudryk, Y.; Gschneidner, Jr., K. A.; Long, Y.; Pecharsky, V. K.

    2015-12-19

    In this study, the magnetic properties and magnetic entropy changes of DyCo2Bx (x=0, 0.05, 0.1, and 0.2) alloys were investigated. The Curie temperature (TC) increases with increasing B concentration. The frequency dependence of ac magnetic susceptibility of DyCo2 caused by the narrow domain wall pinning effect is depressed by B doping, but the coercivity and the magnetic viscosity are prominently increased in the B doped alloys. The magnetic transition nature of DyCo2Bx changes from the first-order to the second-order with increasing x, which leads to the decrease of the maximum magnetic entropy change. However, the relative cooling power (RCP) ofmore » DyCo2 and the B doped alloys remains nearly constant.« less

  1. The effect of boron doping on crystal structure, magnetic properties and magnetocaloric effect of DyCo2

    SciTech Connect

    Wang, C. L.; Liu, J.; Mudryk, Y.; Gschneidner, Jr., K. A.; Long, Y.; Pecharsky, V. K.

    2015-12-19

    In this study, the magnetic properties and magnetic entropy changes of DyCo2Bx (x=0, 0.05, 0.1, and 0.2) alloys were investigated. The Curie temperature (TC) increases with increasing B concentration. The frequency dependence of ac magnetic susceptibility of DyCo2 caused by the narrow domain wall pinning effect is depressed by B doping, but the coercivity and the magnetic viscosity are prominently increased in the B doped alloys. The magnetic transition nature of DyCo2Bx changes from the first-order to the second-order with increasing x, which leads to the decrease of the maximum magnetic entropy change. However, the relative cooling power (RCP) of DyCo2 and the B doped alloys remains nearly constant.

  2. Process for producing electrodes from carbonaceous particles and a boron source

    SciTech Connect

    Sara, R.V.

    1988-09-13

    A method is described of making an electric arc furnace graphite electrode comprising: (a) calcining a carbonaceous material selected form the group consisting of anthracite coal, bituminous coal, lignites, and nos. 2 and 3 cokes; (b) mixing the calcined carbonaceous material with pitch, a lubricant, and a boron source selected from the group consisting of elemental boron, boron carbide, silicon tetraboride, and iron boride, in an amount such that the boron content is from about 0.1 to about 5.0 percent by weight of the graphite electrode to form a mixture; (c) extruding the mixture into an electrode form; (d) and graphitizing the electrode form to provide a graphite electrode.

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

    PubMed Central

    2015-01-01

    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 μm) 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

  4. Pre-irradiation spatial distribution and stability of boride particles in rapidly solidified boron-doped stainless steels

    SciTech Connect

    Kanani, N.; Arnberg, L.; Harling, O.K.

    1981-01-01

    The time temperature behavior of boride particles has been studied in rapidly solidified ultra low carbon and nitrogen modified 316 stainless steel with 0.088% boron and 0.45% zirconium. The results show that the as-splat-cooled specimens exhibit precipitates at the grain boundaries and triple junctions. For temperatures up to about 750/sup 0/C no significant microstructural changes occur for short heat treatment times. In the temperature range of 750 to 950/sup 0/C, however, particles typically 100 to 500 A in diameter containing Zr and B are formed within the grains. Higher temperatures enhance the formation of such particles and give rise to particle networks. The results show that a fine and uniform distribution of the boride particles almost exclusively within the grains can be achieved if proper annealing conditions are chosen. This type of distribution is an important requirement for the homogeneous production of helium during neutron irradiation in fast reactors.

  5. 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

  6. Simultaneous determination of eleven compounds related to metabolism of bioamines in rat cortex and hippocampus by HPLC-ECD with boron-doped diamond working electrode.

    PubMed

    Zhang, Lu; Yang, Jun-qing; Luo, Ying; Shang, Jing-chuan; Jiang, Xin-hui

    2016-01-25

    A simple and rapid high-performance liquid chromatography method with electrochemical detection employing boron-doped diamond electrode (BDD) was established for simultaneous determination of eleven bioamines with their precursor amino acids and metabolites, including two precursors (tyrosine and tryptophan), three catecholamines (dopamine, norepinephrine and epinephrine) and their four metabolites (3,4-dihydroxyphenylacetic acid, 3-methoxytyramine, homovanillic acid, and 3-methoxy-4-hydroxyphenylglycol), as well as serotonin and its metabolite (5-hydroxyindoleacetic acid), in a single run of 20 min using vanillic acid as internal standard. The separation was performed on an ODS2 column (250 mm × 4.6 mm, 5.0 μm) with column oven temperature of 30 °C. Quantification was accomplished at an oxidation potential of 700 mV vs Ag/AgCl reference electrode after a range of applied voltages were tested. Several parameters of this new chromatographic method were validated after optimizaton of the analytical conditions. The new method was successfully applied to test cortex and hippocampus samples from Sprague-Dawley rats with good separation. These eleven compounds in cortices and hippocampi were compared, which was used for monitoring their variations in neuroscience research. PMID:26512998

  7. Selective detection of dopamine using a combined permselective film of electropolymerized (poly-tyramine and poly-pyrrole-1-propionic acid) on a boron-doped diamond electrode.

    PubMed

    Shang, Fengjun; Liu, Yali; Hrapovic, Sabahudin; Glennon, Jeremy D; Luong, John H T

    2009-03-01

    An effective and robust electrochemical approach has been developed for selective detection of dopamine in the presence of 3,4-dihydroxyphenylalanine (l-DOPA), ascorbic acid, uric acid and other dopamine metabolites. A 'layer-by-layer' film of tyramine and pyrrole-1-propionic acid (PPA) was formed by subsequent electropolymerization on a boron-doped diamond (BDD) electrode with an overall thickness of approximately 33 nm as estimated by AFM. The formation of the electropolymerized homogeneous film was also confirmed by SEM and Raman spectroscopy. The modified BDD electrode exhibited rapid response to dopamine within 6 s and a detection limit of 50 nM with excellent reproducibility. The stable electropolymerized film was capable of excluding electroactive interference from 20 microM l-DOPA, 20 microM 3,4-dihydroxyphenylacetic acid (DOPAC), and ascorbic and uric acids at normal physiological conditions (100 microM each). The modified electrode could be used for several repeated analyses of dopamine at 5 microM, without noticeable surface fouling. A plausible mechanism for permselectivity was suggested and supported by pertinent experimental data. PMID:19238289

  8. Electronic Structure and Thermochemical Parameters of the Silicon-Doped Boron Clusters BnSi, with n = 8-14, and Their Anions.

    PubMed

    Mai, Dang Thi Tuyet; Duong, Long Van; Tai, Truong Ba; Nguyen, Minh Tho

    2016-05-26

    We performed a systematic investigation on silicon-doped boron clusters BnSi (n = 8-14) in both neutral and anionic states using quantum chemical methods. Thermochemical properties of the lowest-lying isomers of BnSi(0/-) clusters such as total atomization energies, heats of formation at 0 and 298 K, average binding energies, dissociation energies, etc. were evaluated by using the composite G4 method. The growth pattern for BnSi(0/-) with n = 8-14 is established as follows: (i) BnSi(0/-) clusters tend to be constructed by substituting B atom by Si-atom or adding one Si-impurity into the parent Bn clusters with n to be even number, and (ii) Si favors an external position of the Bn frameworks. Our theoretical results reveal that B8Si, B9Si(-), B10Si and B13Si(-) are systems with enhanced stability due to having high average binding energies, second-order difference in energies and dissociation energies. Especially, by analyzing the MOs, ELF, and ring current maps, the enhanced stability of B8Si can be rationalized in terms of a triple aromaticity. PMID:27128361

  9. Direct electrochemistry of Shewanella loihica PV-4 on gold nanoparticles-modified boron-doped diamond electrodes fabricated by layer-by-layer technique.

    PubMed

    Wu, Wenguo; Xie, Ronggang; Bai, Linling; Tang, Zuming; Gu, Zhongze

    2012-05-01

    Microbial Fuel Cells (MFCs) are robust devices capable of taping biological energy, converting pollutants into electricity through renewable biomass. The fabrication of nanostructured electrodes with good bio- and electrochemical activity, play a profound role in promoting power generation of MFCs. Au nanoparticles (AuNPs)-modified Boron-Doped Diamond (BDD) electrodes are fabricated by layer-by-layer (LBL) self-assembly technique and used for the direct electrochemistry of Shewanella loihica PV-4 in an electrochemical cell. Experimental results show that the peak current densities generated on the Au/PAH multilayer-modified BDD electrodes increased from 1.25 to 2.93 microA/cm(-2) as the layer increased from 0 to 6. Different cell morphologies of S. loihica PV-4 were also observed on the electrodes and the highest density of cells was attached on the (Au/PAH)6/BDD electrode with well-formed three-dimensional nanostructure. The electrochemistry of S. loihica PV-4 was enhanced on the (Au/PAH)4/BDD electrode due to the appropriate amount of AuNPsand thickness of PAH layer. PMID:22852323

  10. Serial coupling of RP and zwitterionic hydrophilic interaction LC-MS: suspects screening of diclofenac transformation products by oxidation with a boron-doped diamond electrode.

    PubMed

    Rajab, Mohamad; Greco, Giorgia; Heim, Carolin; Helmreich, Brigitte; Letzel, Thomas

    2013-09-01

    The presence of pollutants and their transformation products (TPs) in the water system is a big concern because of possible adverse effects on the aquatic environment. Their identification is still a challenge that requires the combination of different chromatographic techniques. In the current research, serial coupling of RPLC and zwitterionic hydrophilic interaction LC with TOF-MS was investigated as a single separation technique for the screening of suspected TPs from electrochemical oxidation of diclofenac using a boron-doped diamond electrode. Diclofenac oxidation was performed in three water matrices in order to study its transformation in different chemical contexts. 47 TPs resulting from similar oxidation methods were selected from the literature. As in most cases standards were not available, an identification procedure based on accurate mass data and chromatographic behavior was proposed. According to this procedure, 11 suspected TPs, previously analyzed by LC, GC, or ion chromatography, were detected in a single injection. The method was proved to be reliable and versatile and it could be efficiently employed as a comprehensive analytical tool for the simultaneous analysis of compounds in a wide polarity range. PMID:23857646

  11. Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis.

    PubMed

    Read, Tania L; Macpherson, Julie V

    2016-01-01

    Boron doped diamond (BDD) electrodes have shown considerable promise as an electrode material where many of their reported properties such as extended solvent window, low background currents, corrosion resistance, etc., arise from the catalytically inert nature of the surface. However, if during the growth process, non-diamond-carbon (NDC) becomes incorporated into the electrode matrix, the electrochemical properties will change as the surface becomes more catalytically active. As such it is important that the electrochemist is aware of the quality and resulting key electrochemical properties of the BDD electrode prior to use. This paper describes a series of characterization steps, including Raman microscopy, capacitance, solvent window and redox electrochemistry, to ascertain whether the BDD electrode contains negligible NDC i.e. negligible sp(2) carbon. One application is highlighted which takes advantage of the catalytically inert and corrosion resistant nature of an NDC-free surface i.e. stable and quantifiable local proton and hydroxide production due to water electrolysis at a BDD electrode. An approach to measuring the local pH change induced by water electrolysis using iridium oxide coated BDD electrodes is also described in detail. PMID:26779959

  12. Observation of a carbon-based protective layer on the sidewalls of boron doped ultrananocrystalline diamond-based MEMS during in situ tribotests

    NASA Astrophysics Data System (ADS)

    Buja, Federico; Kokorian, Jaap; Gulotty, Richard; Sumant, Anirudha V.; Merlijn van Spengen, W.

    2015-12-01

    We have fabricated dedicated MEMS tribotesters made from boron doped ultrananocrystalline diamond (B-UNCD) as the structural material, and carried out comprehensive nano-tribological measurements when two B-UNCD sidewall surfaces underwent sliding interaction in a micro-electromechanical systems (MEMS) in a humid and dry atmosphere. We have investigated the evolution of tribological contacts during sliding interactions and corresponding surface modification under repeated cyclic sliding conditions, while measuring displacement and lateral force with 4 nm and 64 nN resolution, respectively. We have observed the formation of carbon-based ultra-thin protective layer at the sliding interface as characterized by Raman spectroscopy and scanning electron microscopy. Interestingly, the formation of this protective layer occurs in both a dry and wet atmosphere, albeit at different rates when the energy dissipated due to friction reaches a plateau, starting from 200 000 and 400 000 cycles, respectively. Once this layer is formed, we do not observe any measurable wear indicating stable operation for an extended time period. Our results demonstrate that B-UNCD is a very promising material to overcome the wear-related reliability problems in MEMS.

  13. 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

  14. Electro-fenton and photoelectro-fenton degradation of sulfanilic acid using a boron-doped diamond anode and an air diffusion cathode.

    PubMed

    El-Ghenymy, Abdellatif; Garrido, José Antonio; Centellas, Francesc; Arias, Conchita; Cabot, Pere Lluís; Rodríguez, Rosa María; Brillas, Enric

    2012-04-01

    The mineralization of sulfanilic acid has been studied by electro-Fenton (EF) and photoelectro-Fenton (PEF) reaction with UVA light using an undivided electrochemical cell with a boron-doped diamond (BDD) anode and an air diffusion cathode able to generate H(2)O(2). Organics were then oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between generated H(2)O(2) and added Fe(2+). The UVA irradiation in PEF enhanced the production of hydroxyl radicals in the bulk, accelerating the removal of organics and photodecomposed intermediates like Fe(III)-carboxylate complexes. Partial decontamination of 1.39 mM sulfanilic acid solutions was achieved by EF until 100 mA cm(-2) at optimum conditions of 0.4 mM Fe(2+) and pH 3.0. The increase in current density and substrate content led to an almost total mineralization. In contrast, the PEF process was more powerful, yielding almost complete mineralization in less electrolysis time under comparable conditions. The kinetics for sulfanilic acid decay always followed a pseudo-first-order reaction. Hydroquinone and p-benzoquinone were detected as aromatic intermediates, whereas acetic, maleic, formic, oxalic, and oxamic acids were identified as generated carboxylic acids. NH(4)(+) ion was preferentially released in both treatments, along with NO(3)(-) ion in smaller proportion. PMID:22404230

  15. Electrochemical Imprinted Polycrystalline Nickel-Nickel Oxide Half-Nanotube-Modified Boron-Doped Diamond Electrode for the Detection of L-Serine.

    PubMed

    Dai, Wei; Li, Hongji; Li, Mingji; Li, Cuiping; Wu, Xiaoguo; Yang, Baohe

    2015-10-21

    This paper presents a novel and versatile method for the fabrication of half nanotubes (HNTs) using a flexible template-based nanofabrication method denoted as electrochemical imprinting. With use of this method, polycrystalline nickel and nickel(II) oxide (Ni-NiO) HNTs were synthesized using pulsed electrodeposition to transfer Ni, deposited by radio frequency magnetron sputtering on a porous polytetrafluoroethylene template, onto a boron-doped diamond (BDD) film. The Ni-NiO HNTs exhibited semicircular profiles along their entire lengths, with outer diameters of 50-120 nm and inner diameters of 20-50 nm. The HNT walls were formed of Ni and NiO nanoparticles. A biosensor for the detection of L-serine was fabricated using a BDD electrode modified with Ni-NiO HNTs, and the device demonstrated satisfactory analytical performance with high sensitivity (0.33 μA μM(-1)) and a low limit of detection (0.1 μM). The biosensor also exhibited very good reproducibility and stability, as well as a high anti-interference ability against amino acids such as L-leucine, L-tryptophan, L-cysteine, L-phenylalanine, L-arginine, and L-lysine. PMID:26421883

  16. 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 H₂O₂ 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. NH₄(+) ion is released in SPEF, while NO₃⁻ 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

  17. A novel paper-based device coupled with a silver nanoparticle-modified boron-doped diamond electrode for cholesterol detection.

    PubMed

    Nantaphol, Siriwan; Chailapakul, Orawon; Siangproh, Weena

    2015-09-01

    A novel paper-based analytical device (PAD) coupled with a silver nanoparticle-modified boron-doped diamond (AgNP/BDD) electrode was first developed as a cholesterol sensor. The AgNP/BDD electrode was used as working electrode after modification by AgNPs using an electrodeposition method. Wax printing was used to define the hydrophilic and hydrophobic areas on filter paper, and then counter and reference electrodes were fabricated on the hydrophilic area by screen-printing in house. For the amperometric detection, cholesterol and cholesterol oxidase (ChOx) were directly drop-cast onto the hydrophilic area, and H2O2 produced from the enzymatic reaction was monitored. The fabricated device demonstrated a good linearity (0.39mgdL(-1) to 270.69mgdL(-1)), low detection limit (0.25mgdL(-1)), and high sensitivity (49.61?AmM(-1)cm(-2)). The precision value for ten replicates was 3.76% RSD for 1mM H2O2. In addition, this biosensor exhibited very high selectivity for cholesterol detection and excellent recoveries for bovine serum analysis (in the range of 99.6-100.8%). The results showed that this new sensing platform will be an alternative tool for cholesterol detection in routine diagnosis and offers the advantages of low sample/reagent consumption, low cost, portability, and short analysis time. PMID:26388372

  18. Investigation of the synergistic effects for p-nitrophenol mineralization by a combined process of ozonation and electrolysis using a boron-doped diamond anode.

    PubMed

    Qiu, Cuicui; Yuan, Shi; Li, Xiang; Wang, Huijiao; Bakheet, Belal; Komarneni, Sridhar; Wang, Yujue

    2014-09-15

    Electrolysis and ozonation are two commonly used technologies for treating wastewaters contaminated with nitrophenol pollutants. However, they are often handicapped by their slow kinetics and low yields of total organic carbon (TOC) mineralization. To improve TOC mineralization efficiency, we combined electrolysis using a boron-doped diamond (BDD) anode with ozonation (electrolysis-O3) to treat a p-nitrophenol (PNP) aqueous solution. Up to 91% TOC was removed after 60 min of the electrolysis-O3 process. In comparison, only 20 and 44% TOC was respectively removed by individual electrolysis and ozonation treatment conducted under similar reaction conditions. The result indicates that when electrolysis and ozonation are applied simultaneously, they have a significant synergy for PNP mineralization. This synergy can be mainly attributed to (i) the rapid degradation of PNP to carboxylic acids (e.g., oxalic acid and acetic acid) by O3, which would otherwise take a much longer time by electrolysis alone, and (ii) the effective mineralization of the ozone-refractory carboxylic acids to CO2 by OH generated from multiple sources in the electrolysis-O3 system. The result suggests that combining electrolysis with ozonation can provide a simple and effective way to mutually compensate the limitations of the two processes for degradation of phenolic pollutants. PMID:25218262

  19. Boron Doped diamond films as electron donors in photovoltaics: An X-ray absorption and hard X-ray photoemission study

    SciTech Connect

    Kapilashrami, M.; Zegkinoglou, I.; Conti, G.; Nemšák, S.; Conlon, C. S.; Fadley, C. S.; Törndahl, T.; Fjällström, V.; Lischner, J.; Louie, Steven G.; Hamers, R. J.; Zhang, L.; Guo, J.-H.; Himpsel, F. J.

    2014-10-14

    Highly boron-doped diamond films are investigated for their potential as transparent electron donors in solar cells. Specifically, the valence band offset between a diamond film (as electron donor) and Cu(In,Ga)Se₂ (CIGS) as light absorber is determined by a combination of soft X-ray absorption spectroscopy and hard X-ray photoelectron spectroscopy, which is more depth-penetrating than standard soft X-ray photoelectron spectroscopy. In addition, a theoretical analysis of the valence band is performed, based on GW quasiparticle band calculations. The valence band offset is found to be small: VBO=VBM{sub CIGS} – VBM{sub diamond}=0.3 eV±0.1 eV at the CIGS/Diamond interface and 0.0 eV±0.1 eV from CIGS to bulk diamond. These results provide a promising starting point for optimizing the band offset by choosing absorber materials with a slightly lower valence band maximum.

  20. Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells

    SciTech Connect

    Kim, Soo Min; Chun, Seungju; Bae, Suhyun; Park, Seungeun; Lee, Hae-seok Kim, Donghwan; Kang, Min Gu; Song, Hee-eun; Kang, Yoonmook

    2014-08-25

    Solar cells fabricated from boron-doped p-type Czochralski silicon suffer from light-induced degradation that can lower the conversion efficiency by up to 10% relative. When solar cells are exposed to temperatures between 100 °C and 200 °C under illumination, regeneration, in which the minority carrier lifetime is gradually recovered, occurs after the initial light-induced degradation. We studied the light-induced degradation and regeneration process using carrier injection within a design chamber and observed open-circuit voltage trends at various sample temperatures. We proposed a cyclic reaction kinetics model to more precisely analyze the degradation and recovery phenomenon. Our model incorporated the reaction paths that were not counted in the original model between the three states (annealed, degradation, and regeneration). We calculated a rate constant for each reaction path based on the proposed model, extracted an activation energy for each reaction using these rate constants at various temperatures, and calculated activation energies of redegradation and the stabilization reaction.

  1. Analysis of the electron density features of small boron clusters and the effects of doping with C, P, Al, Si, and Zn: Magic B7P and B8Si clusters

    NASA Astrophysics Data System (ADS)

    Saha, P.; Rahane, A. B.; Kumar, V.; Sukumar, N.

    2016-05-01

    Boron atomic clusters show several interesting and unusual size-dependent features due to the small covalent radius, electron deficiency, and higher coordination number of boron as compared to carbon. These include aromaticity and a diverse array of structures such as quasi-planar, ring or tubular shaped, and fullerene-like. In the present work, we have analyzed features of the computed electron density distributions of small boron clusters having up to 11 boron atoms, and investigated the effect of doping with C, P, Al, Si, and Zn atoms on their structural and physical properties, in order to understand the bonding characteristics and discern trends in bonding and stability. We find that in general there are covalent bonds as well as delocalized charge distribution in these clusters. We associate the strong stability of some of these planar/quasiplanar disc-type clusters with the electronic shell closing with effectively twelve delocalized valence electrons using a disc-shaped jellium model. {{{{B}}}9}-, B10, B7P, and B8Si, in particular, are found to be exceptional with very large gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, and these are suggested to be magic clusters.

  2. Adsorption of carbon monoxide on boroxol-ring-doped zigzag boron nitride nanotube: Electronic study via DFT

    NASA Astrophysics Data System (ADS)

    Zahedi, Ehsan; Yari, Maryam; Bahmanpour, Hooman

    2016-04-01

    Previous works have already demonstrated that reactivity and sensitivity of boron nitride nanotubes (BNNTs) toward gas molecules can be modified by impurity. In this work, three nitrogen atoms of BNNT (7,0) are replaced with oxygen to study the adsorption of CO molecule through the surface of boroxol ring with different adsorption patterns, including side-on and end-on. All calculations have been done using the DFT-B3LYP/6-31G * level of theory, and their electronic energies are corrected by gCP and D3 correction terms. The calculated binding energies are large, which indicates that CO molecule undergoes chemical adsorption. NBO results showed that the charge transfer occurs from the tube to the gas molecule, which can slightly change the electronic properties of the tube. Density of state (DOS) and partial DOS (PDOS) analysis revealed that adsorption of CO molecule on the boroxol ring position is covalent in nature. The Laplacian of electron density, Lagrangian kinetic energy density, Hamiltonian kinetic energy density, and potential energy density at bond critical points between the tube and CO indicate that the interaction between the tube and CO molecule is covalent in nature. Topological analysis of the electron localization function shows that electrons in the new formed bonds are approximately localized, meaning that the nature of the adsorption process is chemical covalent.

  3. GRAPHITE EXTRUSIONS

    DOEpatents

    Benziger, T.M.

    1959-01-20

    A new lubricant for graphite extrusion is described. In the past, graphite extrusion mixtures have bcen composed of coke or carbon black, together with a carbonaceous binder such as coal tar pitch, and a lubricant such as petrolatum or a colloidal suspension of graphite in glycerin or oil. Sinee sueh a lubricant is not soluble in, or compatible with the biiider liquid, such mixtures were difficult to extrude, and thc formed pieees lacked strength. This patent teaches tbe use of fatty acids as graphite extrusion lubricants and definite improvemcnts are realized thereby since the fatty acids are soluble in the binder liquid.

  4. 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.

  5. Boron- and phosphorus-doped silicon germanium alloy nanocrystals—Nonthermal plasma synthesis and gas-phase thin film deposition

    SciTech Connect

    Rowe, David J. E-mail: kortshagen@umn.edu; Kortshagen, Uwe R. E-mail: kortshagen@umn.edu

    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.

  6. Boronic acid functionalized N-doped carbon quantum dots as fluorescent probe for selective and sensitive glucose determination

    NASA Astrophysics Data System (ADS)

    Jiang, Guohua; Jiang, Tengteng; Li, Xia; Wei, Zheng; Du, Xiangxiang; Wang, Xiaohong

    2014-04-01

    Nitrogen doped carbon quantum dots (NCQDs) of about 10 nm in diameter have been obtained by hydrothermal reaction from collagen. Because of the superiority of water dispersion, low toxicity and ease of functionlization, the NCQDs were designed as a glucose sensor after covalent grafting by 3-aminophenylboronic (APBA) (APBA-NCQDs). The as-prepared APBA-NCQDs were imparted with glucose sensitivity and selectivity from other saccharides via fluorescence (FL) quenching effect at physiological pH and at room temperature, which show high sensitivity and specificity for glucose determination with a wide range from 1 mM to 14 mM. FL quenching mechanism of APBA-NCQDs was also investigated by adding an external quencher. The APBA-NCQDs-based platform is an environmentally friendly way to substitute inorganic quantum dots containing heavy metals which offer a facile and low cost detection method.

  7. First-Principles Investigation on Boron Nanostructures

    NASA Astrophysics Data System (ADS)

    Tang, Hui

    2011-12-01

    First-principles calculations based on density functional theory are employed to study and predict the properties of boron and Mg boride nanostructures. For boron nanostructures, two-dimensional boron sheets are found to be metallic and made of mixtures of triangles and hexagons which benefit from the balance of two-center bonding and three-center bonding. This unusual bonding in boron sheets results in a self-doping picture where adding atoms to the hexagon centers does not change the number of bonding states but merely increases the electron count. Boron sheets can be either flat or buckled depending on the ratio between hexagons and triangles. Formed by stacking two identical boron sheets, double-layered boron sheets can form interlayer bonds, and the most stable one is semiconducting. Built from single-layered boron sheets, single-walled boron nanotubes have smaller curvature energies than carbon nanotubes and undergo a metal-to-semiconductor transition once the diameter is smaller than ˜20 A. Optimal double-walled boron nanotubes with inter-walled bonds formed are metallic and always more stable than single-walled ones. For Mg boride nanostructures, certain Mg boride sheets prefer to curve themselves into nanotubes, which is explained via Mg-Mg interactions governed by the charge state of Mg. In addition, optimal Mg boride sheet structures are explored with a genetic algorithm. Phase diagrams for Mg boride sheet structures are constructed and stable phases under boron-rich environments are identified. Curvature effects on the phase diagram of Mg boride nanotubes are also discussed. As a natural extension to boron sheets, layered boron crystals based on boron sheets are then presented and are shown to be stable under high pressure. Finally, this thesis ends with an investigation of hydrogen-storage properties of pristine and metal doped boron nanostructures.

  8. Controlled sp(2) Functionalization of Boron Doped Diamond as a Route for the Fabrication of Robust and Nernstian pH Electrodes.

    PubMed

    Ayres, Zoë J; Borrill, Alexandra J; Newland, Jonathan C; Newton, Mark E; Macpherson, Julie V

    2016-01-01

    The development of a voltammetric boron doped diamond (BDD) pH sensor is described. To obtain pH sensitivity, laser micromachining (ablation) is utilized to introduce controlled regions of sp(2) carbon into a high quality polycrystalline BDD electrode. The resulting sp(2) carbon is activated to produce electrochemically reducible quinone groups using a high temperature acid treatment, followed by anodic polarization. Once activated, no further treatment is required. The quinone groups show a linear (R(2) = 0.999) and Nernstian (59 mV/(pH unit)) pH-dependent reductive current-voltage response over a large analyzable pH range, from pH 2 to pH 12. Using the laser approach, it is possible to optimize sp(2) coverage on the BDD surface, such that a measurable pH response is recorded, while minimizing background currents arising from oxygen reduction reactions on sp(2) carbon in the potential region of interest. This enables the sensor to be used in aerated solutions, boding well for in situ analysis. The voltammetric response of the electrode is not compromised by the presence of excess metal ions such as Pb(2+), Cd(2+), Cu(2+), and Zn(2+). Furthermore, the pH sensor is stable over a 3 month period (the current time period of testing), can be stored in air between measurements, requires no reactivation of the surface between measurements, and can be reproducibly fabricated using the proposed approach. The efficacy of this pH sensor in a real-world sample is demonstrated with pH measurements in U.K. seawater. PMID:26638677

  9. 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; Singh, Neetu; Kapoor, Avinashi; Ntwaeaborwa, Odireleng M.; Swart, Hendrik C.

    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 ϕ{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.

  10. Preparation of TiO2/boron-doped diamond/Ta multilayer films and use as electrode materials for supercapacitors

    NASA Astrophysics Data System (ADS)

    Shi, Chao; Li, Hongji; Li, Cuiping; Li, Mingji; Qu, Changqing; Yang, Baohe

    2015-12-01

    We report nanostructured TiO2/boron-doped diamond (BDD)/Ta multilayer films and their electrochemical performances as supercapacitor electrodes. The BDD films were grown on Ta substrates using electron-assisted hot filament chemical vapor deposition. Ti metal layers were deposited on the BDD surfaces by radio frequency magnetron sputtering, and nanostructured TiO2/BDD/Ta thin films were prepared by electrochemical etching and thermal annealing. The successful formation of TiO2 and Ta layered nanostructures was demonstrated using scanning electron and transmission electron microscopies. The electrochemical responses of these electrodes were evaluated by examining their use as electrical double-layer capacitors, using cyclic voltammetry, and galvanostatic charge/discharge and impedance measurements. When the TiO2/BDD/Ta film was used as the working electrode with 0.1 M Na2SO4 as the electrolyte, the capacitor had a specific capacitance of 5.23 mF cm-2 at a scan rate of 5 mV s-1 for a B/C ratio of 0.1% w/w. Furthermore, the TiO2/BDD/Ta film had improved electrochemical stability, with a retention of 89.3% after 500 cycles. This electrochemical behavior is attributed to the quality of the BDD, the surface roughness and electrocatalytic activities of the TiO2 layer and Ta nanoporous structures, and the synergies between them. These results show that TiO2/BDD/Ta films are promising as capacitor electrodes for special applications.

  11. Radial furnace shows promise for growing straight boron carbide whiskers

    NASA Technical Reports Server (NTRS)

    Feingold, E.

    1967-01-01

    Radial furnace, with a long graphite vaporization tube, maintains a uniform thermal gradient, favoring the growth of straight boron carbide whiskers. This concept seems to offer potential for both the quality and yield of whiskers.

  12. Initial boronization of PBX-M using ablation of solid boronized probes

    SciTech Connect

    Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. . Inst. of Plasma and Fusion Research); Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P. ); Jones, S. )

    1993-05-01

    The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B[sub 4]C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 [mu] boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

  13. Initial boronization of PBX-M using ablation of solid boronized probes

    SciTech Connect

    Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M.; Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P.; Jones, S.

    1993-05-01

    The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B{sub 4}C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 {mu} boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

  14. Microstructure and superconducting properties of nanocarbon-doped internal Mg diffusion-processed MgB2 wires fabricated using different boron powders

    NASA Astrophysics Data System (ADS)

    Xu, Da; Wang, Dongliang; Li, Chen; Yuan, Pusheng; Zhang, Xianping; Yao, Chao; Dong, Chiheng; Huang, He; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-04-01

    MgB2/Nb/Monel monofilament wires were fabricated using four different boron powders by an internal Mg diffusion (IMD) process. The microstructure, morphology and the critical current density (J c) of the used boron powders and the formative MgB2 layers were analyzed and compared. It was found that the purity and particle size of the boron powder influence the superconducting properties of MgB2 wires; further that the optimized heat-treatment condition also depends on the quality of the boron powder. The highest J c was obtained in the MgB2 layer made using amorphous boron (AB) powder, although a certain amount of voids existed in the superconducting layer. The IMD-processed MgB2 layer fabricated using high-purity boron (HB) powder had also a high J c compared with the powder-in-tube (PIT) process and a few unreacted boron particles remained in it. MgB2 wire fabricated using low-purity boron (LB) powder had a high cost-performance ratio compared with the others, which is expected to allow the fabrication of large-scale and low-cost superconducting wires for practical application. However, the enhancement of the J c was not found in the MgB2 layer manufactured using the ball-milled LB (MLB) powder as expected due to the increased percentage of impurity.

  15. Boron cosmochemistry

    NASA Technical Reports Server (NTRS)

    Curtis, D. B.; Gladney, E. S.

    1984-01-01

    The assumption that boron is a moderately volatile element is examined. It was demonstrated that interior pieces of chondrites contain significantly less boron than had been thought to be indigenous to this type of meteorite. The mean and range of boron abundances in 16 internal pieces of 10 chondrites were significantly smaller than in 126 pieces of 40 chondrites with unknown terrestrial histories. A new value of the cosmic abundance of boron was determined using the geometric average of the results from interior pieces of 10 chondrites. Based upon the thermodynamic assessment of the cosmochemical properties of boron by Cameron, et al. Anders and Ebihara assumed that boron was a moderately volatile element. They renormalized the data of Curtis et al. to a chondrule free basis and thus inferred that the cosmic abundance of boron was about 3 times greater than that proposed by Curtis, et al. To resolve these differences in data, the relative abundances of several elements including boron were measured in 38 carefully prepared interior pieces of 26 different chondrites. Correlation between boron and sulfur abundances, indicate that, contrary to the conclusions of Cameron, et al., boron is not a moderately volatile element.

  16. Deposition, characterization, reflow and analysis of undoped and boron trioxide/phosphorus pentoxide-doped germanosilicate glass films

    NASA Astrophysics Data System (ADS)

    Simpson, Darrell Lorenza

    Plasma Enhanced Chemical Vapor Deposition (PECVD) of undoped mixed GeO 2-SiO2 glass films in a horizontal tube reactor using germane, silane and oxygen has been studied. Doped films of the mixed GeO2-SiO 2 glass using diborane and phosphine have been studied as well. The glass films offer the potential for both trench etch-refill and interlevel dielectric applications. Film synthesis was carried out at 200°C using a dual coil inductively coupled plasma system. It was determined that the presence SiH4 was not necessary to catalyze the decomposition of GeH4 as required in a strictly thermal environment. Oxide film composition has been determined using Energy Dispersive X-Ray Spectroscopy (EDS) and Auger Energy Spectroscopy (AES). Charging effects usually observed in non-conducting films have been eliminated in the EDS analysis with the use of an Environmental Scanning Electron Microscope (N-SEM) operating at a partial pressure of 150 mTorr of oxygen. EDS and AES results indicate that the on-wafer and wafer-to-wafer compositional uniformity was +/-5% in a caged boat using 4 inch silicon wafers. Cross-sectional Scanning Electron Microscopy has been employed to study the compositional dependency of the flow behavior of the mixed GeO2-SiO2, P2O 5-GeO2-SiO2, B2O 3-GeO2-SiO2, and P2O5-B 2O3-GeO2-SiO2, glass films over silicon trenches under various ambient atmospheres. Reflows were performed at temperatures ranging from 500°C to 1050°C in various gas ambient atmospheres. As result of the work, a low temperature (˜600°C) reflow process was developed resulting in fully planar dielectric film. This process may have application for planarization of interlevel dielectric for ULSI integrated circuits, and is the subject of a patent application.

  17. New approach to obtain boron selective emitters

    SciTech Connect

    Moehlecke, A.; Luque, A.

    1994-12-31

    Selective emitters, used in high efficiency solar cells, need a series of oxidations and photolithographic steps that render the process more expensive. In this paper, a new way to make selective emitters using boron is presented. The main feature of this approach is to save oxide growths and photolithographic processes and it is based on the property of boron doped silicon surfaces to be resistant to anisotropic etchings like the one performed during the texturization. Using this characteristic of boron emitter surfaces, the authors can obtain a highly doped emitter under metal grid and simultaneously a shield to avoid texture on these surfaces. First cells were processed and short wavelength response of p{sup +}nn{sup +} solar cells was enhanced by using lightly doped boron emitters in the uncovered area.

  18. Very low temperature (450 °C) selective epitaxial growth of heavily in situ boron-doped SiGe layers

    NASA Astrophysics Data System (ADS)

    Aubin, J.; Hartmann, J. M.; Veillerot, M.; Essa, Z.; Sermage, B.

    2015-11-01

    We have investigated the feasibility of selectively growing SiGe:B layers at 450 °C, 20 Torr in a 300 mm industrial reduced pressure chemical vapor deposition tool. A reduced H2 carrier gas mass-flow has been used in order to have acceptable growth rates at such a temperature, which is very low indeed. We have first of all studied on blanket Si wafers the in situ boron doping of SiGe with Si2H6, GeH4 and B2H6. A growth rate increase by a factor close to 7 together with a Ge concentration decrease from 53% down to 32% occurred as the diborane mass-flow increased. Very high B+ ion concentrations were obtained in layers that were single crystalline and smooth. Their concentration increased almost linearly with the B2H6 mass-flow, from 1.8 up to 8.3 × 1020 cm-3. The associated resistivity dropped from 0.43 down to 0.26 mΩ cm. We have then tested whether or not selectivity versus SiO2 could be achieved by adding various amounts of HCl to Si2H6 + GeH4 +B2H6. Single crystalline growth rates of intrinsic SiGe(:B) on Si were very similar to poly-crystalline growth rates on SiO2-covered substrates irrespective of the HCl flow. Straightforward selectivity was thus not feasible with a co-flow approach. As a consequence, a 450 °C deposition/etch (DE) process was evaluated. Growth occurred at 20 Torr with the above-mentioned chemistry, while the selective etch of poly-SiGe:B versus c-SiGe:B was conducted at 740 Torr with a medium HCl mass-flow (F(HCl)/F(H2) = 0.2) and a high H2 flow. A 2.2 etch selectivity was achieved while retaining single crystalline if slightly rough SiGe:B layers.

  19. 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.

  20. Boron doped Si rich oxide/SiO2 and silicon rich nitride/SiNx bilayers on molybdenum-fused silica substrates for vertically structured Si quantum dot solar cells

    NASA Astrophysics Data System (ADS)

    Lin, Ziyun; Wu, Lingfeng; Jia, Xuguang; Zhang, Tian; Puthen-Veettil, Binesh; Yang, Terry Chien-Jen; Conibeer, Gavin; Perez-Wurfl, Ivan

    2015-07-01

    Vertically structured Si quantum dots (QDs) solar cells with molybdenum (Mo) interlayer on quartz substrates would overcome current crowding effects found in mesa-structured cells. This study investigates the compatibility between boron (B) doped Si QDs bilayers and Mo-fused silica substrate. Both Si/SiO2 and Si/SiNx based QDs bilayers were studied. The material compatibility under high temperature treatment was assessed by examining Si crystallinity, microstress, thin film adhesion, and Mo oxidation. It was observed that the presence of Mo interlayer enhanced the Si QDs size confinement, crystalline fraction, and QDs size uniformity. The use of B doping was preferred compared to phosphine (PH3) doping studied previously in terms of better surface and interface properties by reducing oxidized spots on the film. Though crack formation due to thermal mismatch after annealing remained, methods to overcome this problem were proposed in this paper. Schematic diagram to fabricate full vertical structured Si QDs solar cells was also suggested.

  1. Boron carbide morphology changing under purification

    NASA Astrophysics Data System (ADS)

    Rahmatullin, I. A.; Sivkov, A. A.

    2015-10-01

    Boron carbide synthesized by using coaxial magnetoplasma accelerator with graphite electrodes was purified by two different ways. XRD-investigations showed content changing and respectively powder purification. Moreover TEM-investigations demonstrated morphology changing of product under purification that was discussed in the work.

  2. Doped graphene supercapacitors.

    PubMed

    Kumar, Nanjundan Ashok; Baek, Jong-Beom

    2015-12-11

    Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed. PMID:26574192

  3. Doped graphene supercapacitors

    NASA Astrophysics Data System (ADS)

    Ashok Kumar, Nanjundan; Baek, Jong-Beom

    2015-12-01

    Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.

  4. Boron Doped Plastic Scintillator Efficiency

    NASA Astrophysics Data System (ADS)

    Mahl, Adam; Chouinard-Dussault, Pascale; Pecinovsky, Cory; Potter, Andrew; Remedes, Tyler; Dorgan, John; Greife, Uwe

    2013-04-01

    This talk will describe the progress made in an interdisciplinary development project aimed at cost-effective, neutron sensitive, plastic scintillator. Colorado School of Mines researchers with backgrounds in Physics, Chemistry, and Chemical Engineering have worked on the incorporation of ^10B in plastics through extrusion. First results on transparent samples using fluorescent spectroscopy and beta excitation will be presented.

  5. Electroextraction of boron from boron carbide scrap

    SciTech Connect

    Jain, Ashish; Anthonysamy, S.; Ghosh, C.; Ravindran, T.R.; Divakar, R.; Mohandas, E.

    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.

  6. Proceedings of the conference on electrochemistry of carbon allotropes: Graphite, fullerenes and diamond

    SciTech Connect

    Kinoshita, K.; Scherson, D.

    1998-02-01

    This conference provided an opportunity for electrochemists, physicists, materials scientists and engineers to meet and exchange information on different carbon allotropes. The presentations and discussion among the participants provided a forum to develop recommendations on research and development which are relevant to the electrochemistry of carbon allotropes. The following topics which are relevant to the electrochemistry of carbon allotropes were addressed: Graphitized and disordered carbons, as Li-ion intercalation anodes for high-energy-density, high-power-density Li-based secondary batteries; Carbons as substrate materials for catalysis and electrocatalysis; Boron-doped diamond film electrodes; and Electrochemical characterization and electrosynthesis of fullerenes and fullerene-type materials. Abstracts of the presentations are presented.

  7. Highly sensitive electrochemical biosensor for bisphenol A detection based on a diazonium-functionalized boron-doped diamond electrode modified with a multi-walled carbon nanotube-tyrosinase hybrid film.

    PubMed

    Zehani, Nedjla; Fortgang, Philippe; Saddek Lachgar, Mohamed; Baraket, Abdoullatif; Arab, Madjid; Dzyadevych, Sergei V; Kherrat, Rochdi; Jaffrezic-Renault, Nicole

    2015-12-15

    A highly sensitive electrochemical biosensor for the detection of Bisphenol A (BPA) in water has been developed by immobilizing tyrosinase onto a diazonium-functionalized boron doped diamond electrode (BDD) modified with multi-walled carbon nanotubes (MWCNTs). The fabricated biosensor exhibits excellent electroactivity towards o-quinone, a product of this enzymatic reaction of BPA oxidation catalyzed by tyrosinase. The developed BPA biosensor displays a large linear range from 0.01 nM to 100 nM, with a detection limit (LOD) of 10 pM. The feasibility of the proposed biosensor has been demonstrated on BPA spiked water river samples. Therefore, it could be a promising and reliable analytical tool for on-site monitoring of BPA in waste water. PMID:26232678

  8. Crystallography, semiconductivity, thermoelectricity, and other properties of boron and its compounds, especially B6O

    NASA Astrophysics Data System (ADS)

    Slack, G. A.; Morgan, K. E.

    2015-09-01

    Electron deficient and non-deficient boron compounds are discussed as potential thermoelectric generator materials. Particular attention is paid to carbon-doped beta-boron, high-carbon boron carbide, and the alpha-boron derivative compound boron suboxide. Stoichiometric B6O shows some promise, and may have a higher ZT than the other two compounds. Carbon saturated beta-boron appears to have a higher ZT than undoped samples. Carbon saturated boron carbide at B12C3 does exist. Its thermoelectric behavior is unknown.

  9. Influence of crystalline boron powders on superconducting properties of C-doped internal Mg diffusion processed MgB2 wires

    NASA Astrophysics Data System (ADS)

    Wang, Dongliang; Zhang, Xianping; Tang, Shaopu; Xu, Da; Yao, Chao; Dong, Chiheng; Xu, Zhongtang; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2015-10-01

    Monofilament MgB2/Fe wires or tapes were fabricated with two different purity crystalline boron powders, using internal magnesium diffusion (IMD) and in situ powder-in-tube (PIT) processes. To evaluate which method was more insensitive to the purity of the boron powders, a sensitivity factor was used. It was found that the IMD process was less sensitive to the purity of the boron powders, compared to the PIT method. Furthermore, J c values of the IMD-processed wires were higher than those of the PIT-processed samples. The reduced porosity and hence the increased density in the IMD-processed samples was thought to be the main reason. Although a number of B-rich particles remained in the MgB2 region, a layer J c as high as 4.8 × 104 A cm-2 at 4.2 K and 10 T was still obtained in the IMD-processed wire, which was comparable to that of IMD-processed wires fabricated using amorphous boron powders.

  10. Fabrication and characterization of carbon and boron carbide nanostructured materials

    NASA Astrophysics Data System (ADS)

    Reynaud, Sara

    Carbon is present in nature in a variety of allotropes and chemical compounds. Due to reduced dimensionality, nanostructured carbon materials, i.e. single walled carbon nanotubes (SWNTs), are characterized by unique physical and chemical properties. There is a potential for SWNTs use as biological probes and assists for tunable tissue growth in biomedical applications. However, the presumed cytotoxicity of SWNTs requires investigation of the risks of their incorporation into living systems. Boron is not found in nature in elementary form. Boron based materials are chemically complex and exist in various polymorphic forms, i.e. boron carbide (BC). Because BC is a lightweight material with exceptional mechanical and elastic properties, it is the ideal candidate for armor and ballistic applications. However, practical use of BC as armor material is limited because of its anomalous glass-like behaviour at high velocity impacts, which has been linked to stress-induced structural instability in one of BC polymorphs, B12(CCC). Theoretical calculations suggest that formation of B12(CCC) in BC could be suppressed by silicon doping. In the first part of this thesis, biocompatibility of SWNTs is investigated. It is shown that under normal cell implantation conditions, the electrical conductivity of the SWNTs decreases due to an increase in structural disorder. This research suggests that SWNTs can be functionalized by protein and biological cells reducing the risk of cytotoxicity. In the second part of this thesis, boron carbide nanostructured materials are synthesized and investigated. Radio frequency sputtering deposition technique is employed for fabrication of BC (Si free) and BC:Si thin films. Variation of plasma conditions and temperature are found to affect chemical composition, adhesion to the substrate and morphology of the films. It is shown that BC films are predominantly amorphous and a small addition of Si largely improves their mechanical properties. In addition, nanostructured BC compounds are fabricated by arc discharge technique using graphite or boron carbide electrodes submerged in liquid nitrogen, de-ionised water, or argon gas. Microscopic and spectroscopic investigation of the synthesized material confirms formation of various BC and carbon nanostructures. Specifically, arc discharge initiated in inert environment by applying low current leads to the formation of nanostructured BC without contaminants.

  11. 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

  12. Antimony-doped graphene nanoplatelets.

    PubMed

    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 (Sb(3+) and Sb(5+)) 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

  13. 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.

  14. 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.

  15. GUM Analysis for TIMS and SIMS Isotopic Ratios in Graphite

    SciTech Connect

    Heasler, Patrick G.; Gerlach, David C.; Cliff, John B.; Petersen, Steven L.

    2007-04-01

    This report describes GUM calculations for TIMS and SIMS isotopic ratio measurements of reactor graphite samples. These isotopic ratios are used to estimate reactor burn-up, and currently consist of various ratios of U, Pu, and Boron impurities in the graphite samples. The GUM calculation is a propagation of error methodology that assigns uncertainties (in the form of standard error and confidence bound) to the final estimates.

  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. 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.

  18. 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.

  19. Microwave-Assisted Synthesis of Boron and Nitrogen co-doped Reduced Graphene Oxide for the Protection of Electromagnetic Radiation in Ku-Band.

    PubMed

    Umrao, Sima; Gupta, Tejendra K; Kumar, Shiv; Singh, Vijay K; Sultania, Manish K; Jung, Jung Hwan; Oh, Il-Kwon; Srivastava, Anchal

    2015-09-01

    The electromagnetic interference (EMI) shielding of reduced graphene oxide (MRG), B-doped MRG (B-MRG), N-doped MRG (N-MRG), and B-N co-doped MRG (B-N-MRG) have been studied in the Ku-band frequency range (12.8-18 GHz). We have developed a green, fast, and cost-effective microwave assisted route for synthesis of doped MRG. B-N-MRG shows high electrical conductivity in comparison to MRG, B-MRG and N-MRG, which results better electromagnetic interference (EMI) shielding ability. The co-doping of B and N significantly enhances the electrical conductivity of MRG from 21.4 to 124.4 Sm(-1) because N introduces electrons and B provides holes in the system and may form a nanojunction inside the material. Their temperature-dependent electrical conductivity follows 2D-variable range hopping (2D-VRH) and Efros-Shklovskii-VRH (ES-VRH) conduction model in a low temperature range (T<50 K). The spatial configuration of MRG after doping of B and N enhances the space charge polarization, natural resonance, dielectric polarization, and trapping of EM waves by internal reflection leading to a high EMI shielding of -42 dB (∼99.99% attenuation) compared to undoped MRG (-28 dB) at a critical thickness of 1.2 mm. Results suggest that the B-N-MRG has great potential as a candidate for a new type of EMI shielding material useful in aircraft, defense industries, communication systems, and stealth technology. PMID:26287816

  20. Novel mesoporous P-doped graphitic carbon nitride nanosheets coupled with ZnIn2S4 nanosheets as efficient visible light driven heterostructures with remarkably enhanced photo-reduction activity.

    PubMed

    Chen, Wei; Liu, Tian-Yu; Huang, Ting; Liu, Xiao-Heng; Yang, Xu-Jie

    2016-02-14

    In this report, we rationally designed and fabricated P-C3N4/ZnIn2S4 nanocomposites by in situ immobilizing ZnIn2S4 nanosheets onto the surface of mesoporous P-doped graphite carbon nitrogen (P-C3N4) nanosheets in a mixed solvothermal environment; their application to the photoreduction of 4-nitroaniline was used to estimate the photocatalytic performance. Different to the template route, here the mesoporous P-C3N4 nanosheets were prepared with a template-free strategy. The as-fabricated P-C3N4/ZnIn2S4 nanocomposites were systematically characterized by analyzing the phase structure, chemical components, electronic and optical properties and separation of charge carrier pairs. More importantly, these P-C3N4/ZnIn2S4 heterostructures have been proven to be highly efficient visible light responsive photocatalysts for photo-reduction, and meanwhile exhibit excellent photo-stability during recycling runs. The sufficient evidence reveals that the significantly improved photocatalytic performance is mainly attributed to the more efficient charge carrier separation based on the construction of a close heterogeneous interface. This work may provide new insights into the utilization of P-C3N4/ZnIn2S4 nanocomposites as visible light driven photocatalysts for comprehensive organic transformations in the field of fine chemical engineering. PMID:26815611