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1

Friction anisotropy in boronated graphite  

NASA Astrophysics Data System (ADS)

Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1-0.35 in the direction of basal plane and becomes high 0.2-0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

Kumar, N.; Radhika, R.; Kozakov, A. T.; Pandian, R.; Chakravarty, S.; Ravindran, T. R.; Dash, S.; Tyagi, A. K.

2015-01-01

2

Boron doped nanostructured diamond films  

NASA Astrophysics Data System (ADS)

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.

Liang, Qi

3

Stabilization of boron carbide via silicon doping  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

4

Stabilization of boron carbide via silicon doping.  

PubMed

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

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

2015-01-14

5

Structure and functionality of bromine doped graphite  

SciTech Connect

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.

Hamdan, Rashid; Kemper, A. F.; Cao Chao; Cheng, H. P. [Department of Physics and Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States)

2013-04-28

6

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

E-print Network

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

Gao, Hongjun

7

Ground-state properties of boron-doped diamond  

SciTech Connect

Boron-doped diamond undergoes an insulator-metal or even a superconducting transition at some critical value of the dopant concentration. We study the equilibrium lattice parameter and bulk modulus of boron-doped diamond experimentally and in the framework of the density functional method for different levels of boron doping. We theoretically consider the possibility for the boron atoms to occupy both substitutional and interstitial positions and investigate their influence on the electronic structure of the material. The data suggest that boron softens the lattice, but softening due to substitutions of carbon with boron is much weaker than due to incorporation of boron into interstitial positions. Theoretical results obtained for substitution of carbon are in very good agreement with our experiment. We present a concentration dependence of the lattice parameter in boron-doped diamond, which can be used for to identify the levels of boron doping in future experiments.

Zarechnaya, E. Yu., E-mail: ezarechnaya@yahoo.com; Isaev, E. I. [Moscow State Institute of Steel and Alloys (Technological University) (Russian Federation)], E-mail: eyvaz_isaev@yahoo.com; Simak, S. I. [Linkoeping University, Department of Physics, Chemistry, and Biology (IFM) (Sweden); Vekilov, Yu. Kh. [Moscow State Institute of Steel and Alloys (Technological University) (Russian Federation); Dubrovinsky, L. S. [University of Bayreuth, Bayerisches Geoinstitut (Germany); Dubrovinskaia, N. A. [University of Heidelberg, Mineralogisches Institut (Germany); Abrikosov, I. A. [Linkoeping University, Department of Physics, Chemistry, and Biology (IFM) (Sweden)

2008-04-15

8

Structural analysis of the B-doped mesophase pitch-based graphite fibers by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Milled B-doped mesophase pitch-based carbon fibers (mMPCF's) prepared from a melt-blown petroleum mesophase pitch precursor material have been developed for enhanced Li uptake capacity in Li ion batteries. Raman spectroscopy has been used to investigate the structure of graphitized and B-doped mMPCF's using 632.8-nm HeNe laser excitation. The B-doped mMPCF's show a strong Raman peak near 1330 cm-1, a well-defined peak at 1620 cm-1, and the disappearance of the second-order 2660 cm-1 band. Furthermore, it is shown that the E2g2 graphite Raman band at 1580 cm-1 is shifted to 1590 cm-1 due to B doping. The appearance of a new weak Raman band in the B-doped mMPCF's near 1320 cm-1 is closely related to the B-C stretching mode in the graphite lattice. These results are associated with the breakdown of the k=0 selection rules by a local distortion of the graphite lattice due to substitutional boron doping. On the basis of the integrated intensity ratio R of the disorder-induced line near 1330 cm-1 to the Raman line near 1590 cm-1 after 2.66 at. % boron doping, it is suggested that the substitutional boron in the mMPCF's is homogeneously distributed within the graphene layer in the fiber form. The crystallite domain size La parallel and perpendicular to the fiber axis on the surface of the fiber is estimated to be about 60 Å, which could correspond to the distance between boron atoms substituted for C atoms in a graphene layer of the fibers.

Endo, M.; Kim, C.; Karaki, T.; Tamaki, T.; Nishimura, Y.; Matthews, M. J.; Brown, S. D. M.; Dresselhaus, M. S.

1998-10-01

9

Electrochemical behavior of high-pressure synthetic boron doped diamond powder electrodes  

Microsoft Academic Search

Boron doped diamond (BDD) was synthesized under high pressure and high temperature using B-doped graphite intercalation compositions (GICs) as carbon sources. The electrochemical characteristics of high-pressure synthetic BDD powder electrodes were investigated by measuring the cyclic voltammetry curves and AC impedance spectrum. For the [Fe(CN)6]3?\\/4? redox couple, the electrode reaction process is reversible or quasi-reversible at the scan rates of

J. B. Zang; Y. H. Wang; H. Huang; W. Tang

2007-01-01

10

Ni doping of semiconducting boron carbide  

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

11

Boron Doping Carbon Structures Using Decaborane? A Theoretical Study  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

12

Theory of graphitic boron nitride nanotubes  

Microsoft Academic Search

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

Angel Rubio; Jennifer Corkill; Marvin Cohen

1994-01-01

13

Doping and Raman Characterization of Boron and Phosphorus Atoms in  

E-print Network

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

Wang, Zhong L.

14

Anode performance of a Li ion battery based on graphitized and B-doped milled mesophase pitch-based carbon fibers  

Microsoft Academic Search

The structures and anode performance of graphitized and boron-doped milled mesophase pitch-based carbon fibers (mMPCFs) have been comparatively studied and the results obtained by X-ray diffraction (XRD), SEM, Raman spectroscopy and electrochemical measurements are discussed. The boron doping at the level of 2.66 at.% (2.4 wt.%) enhances the growth of the crystallite thickness, Lc(002), of the host mMPCF. The B-doped

M. Endo; C. Kim; T. Karaki; Y. Nishimura; M. J. Matthews; S. D. M. Brown; M. S. Dresselhaus

1999-01-01

15

Transport properties of polycrystalline boron doped diamond  

NASA Astrophysics Data System (ADS)

The influence of doping level in the electronic conductivity and resistivity properties of synthetic diamond films grown by hot filament chemical vapor deposition (HFCVD) was investigated. Eight different doping level concentrations varied from 500 to 30,000 ppm were considered. The polycrystalline morphology observed by scanning electron microscopy and Raman spectra was strongly affected by the addition of boron. The electric characterization by Hall effect as a function of temperature and magnetic field showed that at sufficiently low temperatures, electrical conduction is dominated by variable range hopping (VRH) conducting process. The resistivity was also investigated by temperature-dependent transport measurements in order to investigate the conduction mechanism in the doped samples. The samples exhibited the VRH (m = 1/4) mechanism in the temperature range from 77 to 300 K. The interface between metal, and our HFCVD diamond was also investigated for the lower doped samples.

de Oliveira, J. R.; Berengue, O. M.; Moro, J.; Ferreira, N. G.; Chiquito, A. J.; Baldan, M. R.

2014-08-01

16

Superconductivity in polycrystalline boron-doped diamond synthesized at 20 GPa and 2700 K  

NASA Astrophysics Data System (ADS)

Bulk sample (~7.5 mm3) of boron-doped diamond containing 2.6(0.6) at.% B was synthesized by means of direct reaction between boron carbide and graphite in multianvil apparatus at 20 GPa and 2700 K. Electrical resistance of the sample of B-doped polycrystalline diamond was measured in the temperature interval from 10 mK to 300 K and revealed a transition to superconducting state at 2.4-1.4 K. Our results imply that increase of synthesis pressure from 8-9 GPa [Ekimov et al., Nature 428, 542 (2004)] to 20 GPa does not significantly affect boron content in diamond but decreases the temperature of the transition to superconducting state. We observed sharpening of the temperature interval of the transition to superconducting state in magnetic field that may suggest that superconductivity in our samples could arise from filaments of zero-resistant material.

Dubrovinskaia, Natalia; Eska, Georg; Sheshin, Grigorii A.; Braun, Hans

2006-02-01

17

Homoepitaxial deposition of boron-doped single crystal diamond  

NASA Astrophysics Data System (ADS)

The boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) Type Ib diamond substrates using a microwave plasma assisted chemical vapor deposition. The optical transmittance of the films was observed to change with the increasing boron content in the film. The effect of boron and nitrogen on the surface morphology of the film has been studied using atomic force microscopy. Use of nitrogen in process gas during boron doping improves the surface topography as well as gives rise to an increase in growth rate of diamond film. However, presence of nitrogen in the process gas significantly lowers the electrical conductivity of the film. Raman spectra showed a few additional bands at the lower wavenumber regions along with the zone center optical phonon mode for doped diamond. 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. The sharpening and increase in intensity of the Raman line has been also observed in boron doped diamond film when grown in the presence of nitrogen. Temperature dependent electrical measurement between 90 to 680 K indicates two different conduction mechanisms were responsible for the semiconducting behavior of the film. The observed growth rate for homoepitaxial boron-doped diamond films were in the range of 5-16 microm / hour. Various level of boron doping (1018 to 1020 cm-3) was achieved during this study. The lowest resistivity of one of the boron doped samples at room temperature was calculated to be 0.12 ?cm. The potential of boron-doped single crystal diamond in electronic devices is discussed.

Karna, Sunil Kumar Lal

18

Measured Enthalpies of Adsorption of Boron-Doped Activated Carbons  

NASA Astrophysics Data System (ADS)

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.

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

19

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

PubMed

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

Ling, Chen; Mizuno, Fuminori

2014-06-14

20

Superconductivity in Boron-doped SiC  

NASA Astrophysics Data System (ADS)

We report superconductivity in heavily boron-doped bulk silicon carbide related to the diamond structure. The compound exhibits zero resistivity and diamagnetic susceptibility below a critical temperature Tc of ˜1.4 K, and an effective boron doping concentration higher than 1021 cm-3. We present the H-T phase diagram of this new superconducting compound determined from AC susceptibility. In finite DC magnetic fields a clear hysteresis was observed between cooling and subsequent warming runs. This indicates, in contrast with the type-II superconductivity in boron-doped diamond and silicon, that a type-I superconductivity with a critical field Hc(0) of about 100 Oe is realized in boron-doped SiC. Moreover, the specific-heat shows a clear jump at Tc, demonstrating bulk nature of the superconductivity.

Ren, Zhi-An; Kato, Junya; Muranaka, Takahiro; Akimitsu, Jun; Kriener, Markus; Maeno, Yoshiteru

2007-10-01

21

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

Microsoft Academic Search

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 10-18 and the scatter of the experimental points near the critical volume fraction phic is very small. The following measurements, with the characteristic exponent(s)

Junjie Wu; D. S. McLachlan

1997-01-01

22

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

E-print Network

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

Paris-Sud XI, Université de

23

Boron-doped carbon prepared from PFO as a lithium-ion battery anode  

NASA Astrophysics Data System (ADS)

A petroleum-based Li-ion battery anode was prepared by thermal condensation of pyrolysis fuel oil (PFO) and a subsequent carbonization process. H3BO3 was used as a catalyst for efficient thermal condensation, carbonization and battery performance. The influence of the carbonization temperature on the carbon structure and battery performance was also investigated. Notably, H3BO3 promoted thermal condensation and formation of a graphitic carbon structure and acted as a boron doping agent. Boron-doping attenuated the highly active sites in carbon and effectively controlled formation of the SEI layer, which resulted in an increase in the initial efficiency of the anode. For the sample carbonized at 900 °C, a reversible capacity of 301 mAh/g and an initial efficiency of 78.6% were obtained. In addition, the samples obtained at different carbonization temperatures were all highly stable over 50 cycles, with capacity retentions greater than 90%.

Kim, Jong Gu; Liu, Fei; Lee, Chul-Wee; Lee, Young-Seak; Im, Ji Sun

2014-08-01

24

O2 Reduction on Graphite and Nitrogen-Doped Graphite: Experiment and Theory Reyimjan A. Sidik and Alfred B. Anderson*  

E-print Network

O2 Reduction on Graphite and Nitrogen-Doped Graphite: Experiment and Theory Reyimjan A. Sidik carbon. Quantum calculations on cluster models of nitrided and un-nitrided graphite sheets show that carbon radical sites formed adjacent to substitutional N in graphite are active for O2 electroreduction

Popov, Branko N.

25

Atomic hydrogen adsorption on lithium-doped graphite surfaces  

SciTech Connect

The effects of lithium doping of pristine and defective graphite surfaces on hydrogen adsorption are studied by the first-principles Plane-Wave Density Functional Theory. The surface defects are simulated by a single atomic vacancy. The DFT calculation is corrected for long-range effects through semi-empirical London terms for each constituent of the system. The lithium doping of the graphite surfaces notably reinforces hydrogen atom binding. Qualitative comparison with experimental results is given using the lithium 1s energy level shifts induced by the atomic vacancy and/or hydrogen trapping.

Allouche, Alain [CNRS/Univ. de Provence (France); Krstic, Predrag S [ORNL

2012-01-01

26

FIELD EMISSION FROM BORON-DOPING POLYCRYSTALLINE DIAMOND FILMS ON SILICON  

E-print Network

FIELD EMISSION FROM BORON-DOPING POLYCRYSTALLINE DIAMOND FILMS ON SILICON J. A. N. Gonçalves, G. M Campos, SP, Brazi Abstract This work deals with the study and development of the boron-doped diamond material fail. The field emission current from boron-doped polycrystalline diamond films grown by hot

27

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

E-print Network

Magnetic states and optical properties of single-layer carbon-doped hexagonal boron nitride://apl.aip.org/authors #12;Magnetic states and optical properties of single-layer carbon-doped hexagonal boron nitride-doped hexagonal boron nitride (h-BN) has extraordinary properties with many possible applications. We demonstrate

Wilkins, John

28

Nitrogen- and boron-doped double-walled carbon nanotubes.  

PubMed

Double-walled carbon nanotubes (DWNTs) doped with nitrogen and boron have been prepared by the decomposition of a CH(4) + Ar mixture along with pyridine (or NH(3)) and diborane, respectively, over a Mo(0.1)Fe(0.9)Mg(13)O catalyst, prepared by the combustion route. The doped DWNTs bave been characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, electron energy loss spectroscopy, and Raman spectroscopy. The dopant concentration is around 1 atom % for both boron and nitrogen. The radial breathing modes in the Raman spectra have been employed along with TEM to obtain the inner and outer diameters of the DWNTs. The diameter ranges for the undoped, N-doped (pyridine), N-doped (NH(3)), and B-doped DWNTs are 0.73-2.20, 0.74-2.30, 0.73-2.32, and 0.74-2.36 nm, respectively, the boron-doped DWNTs giving rise to a high proportion of the large diameter DWNTs. Besides affecting the G-band in the Raman spectra, N- and B-doping affect the proportion of semiconducting nanotubes. PMID:19206671

Panchakarla, L S; Govindaraj, A; Rao, C N R

2007-12-01

29

Transforming chitosan into N-doped graphitic carbon electrocatalysts.  

PubMed

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

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

2014-12-23

30

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

NASA Astrophysics Data System (ADS)

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.

Golshani, Fariborz

31

Superconductivity in heavily boron-doped silicon carbide  

NASA Astrophysics Data System (ADS)

The discoveries of superconductivity in heavily boron-doped diamond in 2004 and silicon in 2006 have renewed the interest in the superconducting state of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a metallic phase from which upon further doping superconductivity can emerge. Recently, we discovered superconductivity in a closely related system: heavily boron-doped silicon carbide. The sample used for that study consisted of cubic and hexagonal SiC phase fractions and hence this led to the question which of them participated in the superconductivity. Here we studied a hexagonal SiC sample, free from cubic SiC phase by means of x-ray diffraction, resistivity, and ac susceptibility.

Kriener, Markus; Muranaka, Takahiro; Kato, Junya; Ren, Zhi-An; Akimitsu, Jun; Maeno, Yoshiteru

2008-12-01

32

Synthesis and thermoluminescence of boron-doped germanium nanowires  

NASA Astrophysics Data System (ADS)

Boron doped germanium nanowires were synthesized using chemical vapor deposition (CVD) with Au nanoparticles as nucleating centers, germanium tetrachloride as the source of germanium and B 2H 6 gas as source of boron impurity. Au nanoparticles were deposited on Si using 3-aminopropyltriethylsilane (APTES). The single crystal Ge nanowires with diameters ranging from 19 to 200 nm were grown in a controllable manner. Effects of Au nanoparticle size, argon gas flow, temperature and duration of growth on diameter and length of nanowires were investigated. This is the first report on thermoluminescence (TL) properties of boron doped germanium nanowires. Glow curves were fitted using computerized glow curve deconvolution program and seven overlapped peaks were obtained. Further the response of synthesized nanowires to different dose levels of UV was studied and linear response regime was determined.

Zahedifar, M.; Hosseinmardi, F.; Eshraghi, L.; Ganjipour, B.

2011-03-01

33

Oxidation Resistant Graphite Studies  

SciTech Connect

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.

W. Windes; R. Smith

2014-07-01

34

Mechanisms of Postsynthesis Doping of Boron Nitride Nanostructures with Carbon from First-Principles Simulations  

E-print Network

Mechanisms of Postsynthesis Doping of Boron Nitride Nanostructures with Carbon from First May 2011; published 11 July 2011) Electron-beam-mediated postsynthesis doping of boron-nitride in nanoelectronics. Concurrently with the studies of gra- phene, individual flakes of hexagonal boron-nitride (h

Krasheninnikov, Arkady V.

35

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

SciTech Connect

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.

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

2014-03-03

36

Growth morphology of boron doped single crystal diamond  

NASA Astrophysics Data System (ADS)

The growing demand of wide band semiconductors entice researcher to investigate electronic properties in diamond. The chemical vapor deposition (CVD) method has shown that various level of doping can be possible in diamond films. The purpose of this study was to investigate the growth morphology and quality of boron doped diamond film with deposition parameters. Various level of boron doped diamond films were synthesized epitaxially on synthetic (100) ib type diamond substrate using microwave plasma assisted CVD. The structural, optical and electrical characterizations were made to study effect of deposition parameters and pretreatment of substrates on surface morphology and growth quality. Raman spectra showed shape modification of the zone center optical phonon line and its downshift with the increasing boron content in the film. Additional bands were also observed in lower wavelength region below optical phonon line. Surface modification of films with increasing boron content has been observed in atomic force microscopy. High growth rate and high quality films were obtained with the addition of a few ppm of nitrogen in feed gas during deposition with little compromise on conductivity. Electrical measurement showed carriers have been transported via two different conduction mechanisms.

Karna, Sunil; Vohra, Yogesh

2013-03-01

37

Direct determination of boron in a cobalt-based alloy by graphite furnace-atomic absorption spectrometry.  

PubMed

A matrix modifier composed of nickel and zirconium, and a graphite tube treated with zirconium solution were proposed for the determination of boron in cobalt-based alloys by graphite furnace-atomic absorption spectrometry. The effects of this matrix modifier and the treated graphite tube were studied, and the combination of 60 mug of nickel and 20 mug of zirconium as matrix modifier, and a graphite tube soaked with 10 g 1(-1) of zirconium solution were found to give the highest analytical sensitivity. The interference effects of major components (cobalt) and eight minor components (chromium, nickel, tungsten, iron, tantalum, molybdenum, titanium, aluminium and manganese) were studied. Boron in four cobalt-based alloys was determined by graphite furnace-atomic absorption spectrometry employing the proposed matrix modifier and the treated graphite tube, without the preseparation of matrix. The relative standard deviation was 3.3% for 0.048% of boron. A characteristic mass was 500 pg. PMID:18966371

Gong, B; Liu, Y; Xu, Y; Li, Z; Lin, T

1995-10-01

38

Carrier doping into boron nanobelts by neutron transmutation  

SciTech Connect

We report the effects of a neutron-capture reaction of isotope {sup 10}B on the structure and electrical transport of {sup 10}B-enriched single-crystalline boron nanobelts. Partial amorphization, particularly at the surface of the nanobelt, was observed after thermal neutron irradiation with a dose of 2x10{sup 19} cm{sup -2}. Carrier doping into the nanobelts by neutron transmutation is expected after postannealing. The change in conductance is discussed based on the distribution of localized states in the band gap of {alpha}-tetragonal boron.

Kirihara, Kazuhiro; Shimizu, Yoshiki; Sasaki, Takeshi; Koshizaki, Naoto [Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565 (Japan); Yamada, Yoichi [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Esaka, Fumitaka [Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Yamamoto, Hiroyuki; Shamoto, Shin-ichi [Quantum Beam Science Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Kimura, Kaoru [Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba 277-8561 (Japan)

2010-11-22

39

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

E-print Network

Spatially-Correlated Microstructure and Superconductivity in Polycrystalline Boron-Doped Diamond F tunneling spectroscopies are performed below 100 mK on nano-crystalline boron-doped diamond films been discovered in heavily doped group IV covalent semicon- ductors [1], in particular diamond [2

40

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

41

Effect of boron doping on the structural transformations and properties of low manganese steels  

Microsoft Academic Search

1.Doping of temper hardened steels containing 0.15–0.25% C with boron improves their bulk hardenability. As a result, the strength of boron containing low manganese steels attain the level of boronless steels with high manganese content. At the same time impact toughness and ductility remain practically unchanged.2.In the investigated steels doped with boron, boron containing inclusions may segregate; their composition and

G. Z. Koval'chuk; V. N. Yarmosh

1988-01-01

42

Study of helium embrittlement in boron doped EUROFER97 steels  

NASA Astrophysics Data System (ADS)

To simulate helium effects in Reduced Activation Ferritic/Martensitic steels, experimental heats ADS2, ADS3 and ADS4 with the basic composition of EUROFER97 (9%Cr-WVTa) were doped with different contents of natural boron and separated 10B-isotope (0.008-0.112 wt.%) and irradiated in High Flux Reactor (HFR) Petten up to 16.3 dpa at 250-450 °C and in Bor-60 fast reactor in Dimitrovgrad up to 31.8 dpa at 332-338 °C. The embrittlement and hardening are investigated by instrumented Charpy-V tests with subsize specimens. Complete burn-up of 10B isotope under neutron irradiation in HFR Petten led to generation of 84, 432 and 5580 appm He and partial boron-to-helium transformation in Bor-60 led to generation of 9, 46, 880 appm He in ADS2, ADS3 and ADS4 heats, respectively. At low irradiation temperatures Tirr ? 340 °C the boron doped steels show progressive embrittlement with increasing helium amount. Irradiation induced DBTT shift of EUROFER97 based heat doped with 1120 wppm separated 10B isotope could not be quantified due to large embrittlement found in the investigated temperature range. At Tirr ? 340 °C helium induced extra embrittlement is attributed to material hardening induced by helium bubbles and described in terms of phenomenological model.

Gaganidze, E.; Petersen, C.; Aktaa, J.

2009-04-01

43

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

SciTech Connect

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

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

1993-11-01

44

Electrostatic doping of graphene through ultrathin hexagonal boron nitride films.  

PubMed

When combined with graphene, hexagonal boron nitride (h-BN) is an ideal substrate and gate dielectric with which to build metal|h-BN|graphene field-effect devices. We use first-principles density functional theory (DFT) calculations for Cu|h-BN|graphene stacks to study how the graphene doping depends on the thickness of the h-BN layer and on a potential difference applied between Cu and graphene. We develop an analytical model that describes the doping very well, allowing us to identify the key parameters that govern the device behavior. A predicted intrinsic doping of graphene is particularly prominent for ultrathin h-BN layers and should be observable in experiment. It is dominated by novel interface terms that we evaluate from DFT calculations for the individual materials and for interfaces between h-BN and Cu or graphene. PMID:21936569

Bokdam, Menno; Khomyakov, Petr A; Brocks, Geert; Zhong, Zhicheng; Kelly, Paul J

2011-11-01

45

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

46

PHYSICAL REVIEW B 87, 035404 (2013) Electronic structure of boron nitride sheets doped with carbon from first-principles calculations  

E-print Network

PHYSICAL REVIEW B 87, 035404 (2013) Electronic structure of boron nitride sheets doped with carbon quasiparticle (GW) approach, we study the electronic structure of hexagonal boron nitride (h-BN) sheets, both and doped h-BN and should further help to optimize the postsynthesis doping of boron nitride nanostructures

Krasheninnikov, Arkady V.

47

QSPR Study of Passivation by Phenolic Compounds at Platinum and Boron-Doped Diamond Electrodes  

E-print Network

QSPR Study of Passivation by Phenolic Compounds at Platinum and Boron-Doped Diamond Electrodes Campinas, 13083-852 Campinas, SP, Brazil Blocking polycrystalline platinum Pt and boron-doped diamond BDD-bonding complexes with fluoride ion were modeled and geometry optimized with the B3LYP method and the 6-31G** basis

Ferreira, Márcia M. C.

48

Porous Boron-Doped Diamond/Carbon Nanotube Electrodes H. Zanin,*,  

E-print Network

INTRODUCTION The exceptional set of physical properties possessed by synthetic diamond films grown by chemicalPorous Boron-Doped Diamond/Carbon Nanotube Electrodes H. Zanin,*, P. W. May, D. J. Fermin, D. Plana Jose dos Campos, Sao Paulo 12227-010, Brazil ABSTRACT: Nanostructuring boron-doped diamond (BDD) films

Bristol, University of

49

Ohmic contacts to boron-doped diamond  

NASA Astrophysics Data System (ADS)

Two types of contacts, namely Au and Au/Ta, were fabricated on B-doped diamond films by rf sputtering deposition. I- V measurements show that our Au and Au/Ta contacts have exhibited good ohmic characteristics in their as-deposited states. Upon annealing, their ohmic behaviors were improved to different extent. Compared with Au contact, Au/Ta contact has lower specific contact resistance value and better adhesion. X-ray photoelectron spectroscopy (XPS) analyses indicate that there is an obvious interdiffusion between Au and diamond film in Au contact. The interdiffusion was enhanced by annealing. This interdiffusion layer may be the reason why Au contacts are ohmic in the as-deposited and annealed states. As for Au/Ta contacts, XPS analyses show the formation of TaC at the interface between Ta and diamond film in the as-deposited state, there is an increase of TaC in the annealed contact. The presence of TaC promotes our Au/Ta contacts to have better ohmic characteristic.

Zhen, Congmian; Wang, Yinyue; He, Shanhu; Guo, Qiufen; Yan, Zhijun; Pu, Yuejiao

2003-07-01

50

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

PubMed

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

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

51

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

52

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

PubMed Central

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

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

2014-01-01

53

Stable p-and n-type doping of few-layer graphene/graphite Xiuqing Meng a  

E-print Network

Stable p- and n-type doping of few-layer graphene/graphite Xiuqing Meng a , Sefaattin Tongay b were intercalated in graphite and the presence of such molecules between the graphene sheets results- and n-type doping, respectively. For higher intercalation times, the intercalated graphite turns back

Wu, Junqiao

54

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

NASA Technical Reports Server (NTRS)

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.

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

1971-01-01

55

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

DOEpatents

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.

Zidan, Ragaiy (Aiken, SC); Ritter, James A. (Lexington, SC); Ebner, Armin D. (Lexington, SC); Wang, Jun (Columbia, SC); Holland, Charles E. (Cayce, SC)

2008-06-10

56

Porous boron-doped diamond/carbon nanotube electrodes.  

PubMed

Nanostructuring boron-doped diamond (BDD) films increases their sensitivity and performance when used as electrodes in electrochemical environments. We have developed a method to produce such nanostructured, porous electrodes by depositing BDD thin film onto a densely packed "forest" of vertically aligned multiwalled carbon nanotubes (CNTs). The CNTs had previously been exposed to a suspension of nanodiamond in methanol causing them to clump together into "teepee" or "honeycomb" structures. These nanostructured CNT/BDD composite electrodes have been extensively characterized by scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Not only do these electrodes possess the excellent, well-known characteristics associated with BDD (large potential window, chemical inertness, low background levels), but also they have electroactive areas and double-layer capacitance values ?450 times greater than those for the equivalent flat BDD electrodes. PMID:24392640

Zanin, H; May, P W; Fermin, D J; Plana, D; Vieira, S M C; Milne, W I; Corat, E J

2014-01-22

57

Electrochemical oxidation of benzene on boron-doped diamond electrodes.  

PubMed

This work presents an electrochemical investigation of the benzene oxidation process in aqueous solution on boron-doped diamond (BDD) electrodes. Additionally, in order to determine the main products generated during the oxidation process, electrolysis and high performance liquid chromatography experiments were carried out. The complete degradation of this compound was performed aiming to a further application in waste water treatment. The cyclic voltammetry studies indicate that benzene is irreversibly oxidized in acid medium (H2SO4 0.5 M) on the BDD electrode surface at 2.0 V versus Ag/AgCl in a diffusion controlled process. During the cycling, other products are generated, and a pair of peaks was observed that can be associated with the oxi-reduction of anyone of the following species: hydroquinone, benzoquinone, resorcinol or catechol. The electrolysis experiments were carried out at 2.4 and 2.5 V on the BDD electrode surface in a solution containing 1x10(-2) M of benzene (below the saturation concentration in aqueous solution), for 3 and 5 h, respectively. The main products measured were: hydroquinone, resorcinol, p-benzoquinone, catechol and phenol. The complete electrochemical benzene degradation was performed in the electrolysis experiments using a rotating BDD disc electrode (2.5 V for 5 h) and the main products detected were all measured at concentrations lower than 10(-5) M in this condition. The boron-doped diamond electrode had proved to be a valuable tool for the electrochemical degradation of the benzene, a very stable chemical compound. PMID:17126378

Oliveira, Robson T S; Salazar-Banda, Giancarlo R; Santos, Mauro C; Calegaro, Marcelo L; Miwa, Douglas W; Machado, Sergio A S; Avaca, Luis A

2007-02-01

58

INFLUENCE OF GERMANIUM CONCENTRATION AND HOMOGENEOUS BORON DOPING ON MICROSTRUCTURE, KINETICS, AND SHEET RESISTANCE OF NICKEL  

E-print Network

1 INFLUENCE OF GERMANIUM CONCENTRATION AND HOMOGENEOUS BORON DOPING ON MICROSTRUCTURE, KINETICS..............................................................................15 1.2 Silicon-Germanium in Semiconductor Technologies.................................................................................................................25 2.1.1 Silicon-Germanium Binary System

Florida, University of

59

Boron-Doped Diamond Film Electrodes—New Tool for Voltammetric Determination of Organic Substances  

Microsoft Academic Search

This review with 194 references summarizes the recent progress in the development and applications of boron-doped diamond film electrodes in electroanalysis of organic compounds. It is based on the survey of 106 papers listed in a comprehensive table devoted to batch voltammetric and liquid flow amperometric methods using boron-doped diamond electrodes. The varieties in their construction, surface pre-treatment and electroanalytical

Karolina Pecková; Jana Musilová; Ji?í Barek

2009-01-01

60

Development of finely dispersed Ti- and Zr-doped isotropic graphites for the divertor of next step fusion devices  

NASA Astrophysics Data System (ADS)

Finely dispersed Ti- and Zr-doped isotropic graphites have been manufactured using three different starting raw materials. The aim is to obtain doped fine grain isotropic graphites with reduced chemical erosion, high thermal shock resistance and low cost, which aim to be competitive with present carbon-based candidate materials for next step fusion devices. First ITER relevant thermal shock loads were applied on test specimens of these materials. The brittle destruction behaviour of graphite is greatly improved by doping with Ti or Zr, most probably due to a significant increase of thermal conductivity related to the catalytic effect of TiC and ZrC on the graphitization. Doped graphites manufactured with the synthetic mesophase pitch 'AR' as raw material showed the best performance from the three investigated raw materials due to its higher graphitability. The eroded surfaces of doped graphites exhibit a thin solidified carbide layer, probably caused by the segregation of liquid carbide during the thermal shot.

López-Galilea, I.; García-Rosales, C.; Pintsuk, G.; Linke, J.

2007-03-01

61

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

PubMed

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

Susi, Toma; Pichler, Thomas; Ayala, Paola

2015-01-01

62

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

PubMed Central

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.

Pichler, Thomas; Ayala, Paola

2015-01-01

63

Laser annealing of neutron irradiated boron-10 isotope doped diamond  

SciTech Connect

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.

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

2011-01-01

64

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

SciTech Connect

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.

Irfan, Muhammad; Yim, Jong-Hyuk; Jho, Young-Dahl, E-mail: jho@gist.ac.kr [School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)] [School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Kim, Changyoung [Institute of Physics and Applied physics, Yonsei University, Seoul 120-749 (Korea, Republic of)] [Institute of Physics and Applied physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Wook Lee, Sang [Division of Quantum Phases and Devices, School of Physics, Konkuk University, Seoul 143-701 (Korea, Republic of)] [Division of Quantum Phases and Devices, School of Physics, Konkuk University, Seoul 143-701 (Korea, Republic of)

2013-11-11

65

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

66

Nitrogen-doped holey graphitic carbon from 2D covalent organic polymers for oxygen reduction.  

PubMed

Using covalent organic polymer pre-cursors, we have developed a new strategy for location control of N-dopant heteroatoms in the graphitic porous carbon, which otherwise is impossible to achieve with conventional N-doping techniques. The electrocatalytic activities of the N-doped holey graphene analogues are well correlated to the N-locations, showing possibility for tailoring the structure and property of N-doped carbon nanomaterials. PMID:24664790

Xiang, Zhonghua; Cao, Dapeng; Huang, Ling; Shui, Jianglan; Wang, Min; Dai, Liming

2014-05-28

67

First principle investigations on Boron doped Fe2VAl Heusler alloy  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

68

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

NASA Technical Reports Server (NTRS)

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

Weller, T.

1977-01-01

69

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

NASA Technical Reports Server (NTRS)

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.

Weller, T.

1977-01-01

70

CHARACTERIZATION OF BORON SURFACE DOPING EFFECTS ON PECVD SILICON NITRIDE PASSIVATION  

E-print Network

CHARACTERIZATION OF BORON SURFACE DOPING EFFECTS ON PECVD SILICON NITRIDE PASSIVATION N. M. Nursam of positive charge within PECVD silicon nitride (SiNx) films is widely believed to contribute to the generally, surface doping) and the charge density in the PECVD nitride film, has not been explored in detail. Recent

71

Electrochemically modulated liquid chromatography using a boron-doped diamond particle stationary phase  

PubMed Central

This paper reports on preliminary tests of the performance of boron-doped diamond powder (BDDP) as a stationary phase in electrochemically modulated liquid chromatography (EMLC). EMLC manipulates retention through changes in the potential applied (Eappl) to a conductive packing. Porous graphitic carbon (PGC) has routinely been utilized as a material in EMLC separations. Herein the utility of BDDP as a stationary phase in EMLC was investigated and its stability, both compositionally and microstructurally, relative to PGC was compared. The results show that BDDP is stable over a wide range of Eappl values (i.e., ?1.2 to +1.2 V vs. Ag/AgCl, sat’d NaCl). The data also reveal that electrostatics play a key role in the adsorption of the aromatic sulfonates on the BDDP stationary phase, and that these analytes are more weakly retained in comparison to the PGC support. The potential for this methodology to provide a means to advance the understanding of molecular adsorption and retention mechanisms on carbonaceous materials is briefly discussed. PMID:18922535

Muna, Grace W.; Swope, Vernon M.; Swain, Greg M.; Porter, Marc D.

2011-01-01

72

Extreme dielectric strength in boron doped homoepitaxial diamond Pierre-Nicolas Volpe, Pierre Muret, Julien Pernot, Franck Omns, Tokuyuki Teraji et al.  

E-print Network

Extreme dielectric strength in boron doped homoepitaxial diamond Pierre-Nicolas Volpe, Pierre Muret dielectric strength in boron doped homoepitaxial diamond Pierre-Nicolas Volpe,1,a Pierre Muret,1 Julien

Paris-Sud XI, Université de

73

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

PubMed

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

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

2014-08-21

74

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

NASA Astrophysics Data System (ADS)

Boron-doping of activated carbons has been shown to increase the enthalpies of adsorption for hydrogen as compared to their respective undoped precursors (>10kJ/mol compared to ca. 5kJ/mol). This has brought significant interest to boron-doped carbons for their potential to improve hydrogen storage. Boron-doped activated carbons have been produced using a process involving the deposition of decaborane (B10H14) and high-temperature annealing resulting in boron contents up to 15%. In this talk, we will present a systematic study of the effect that boron content has on the samples' structure, hydrogen sorption, and surface chemistry. Measurements have shown a significant increase in the areal hydrogen excess adsorption and binding energy. Experimental enthalpies of adsorption will be presented for comparison to theoretical predictions. Additionally, samples have been characterized by thermal gravimetric analysis, gas chromatography-mass spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. TGA and GC-MS results investigated the decomposition of the decaborane in the carbon. Boron-carbon bonds are shown in the FTIR and XPS spectra, indicating that boron has been incorporated into the carbon matrix.

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

2013-03-01

75

Polyoxometalate-Modified Boron-Doped Diamond Electrodes  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

76

Tribological properties of undoped and boron-doped nanocrystalline diamond films  

PubMed Central

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

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

2009-01-01

77

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

NASA Astrophysics Data System (ADS)

The changes in hole concentration of heavily boron (B)-doped Czochralski silicon subjected to high temperature rapid thermal anneal (RTA) and following conventional furnace anneal (CFA) have been investigated. It is found that decrease in hole concentration, namely, B deactivation, is observed starting from 1050 °C and increases with RTA temperature. The following CFA at 300-500 °C leads to further B deactivation, while that at 600-800 °C results in B reactivation. It is supposed that the interaction between B atoms and silicon interstitials (I) thus forming BI pairs leads to the B deactivation during the high temperature RTA, and, moreover, the formation of extended B2I complexes results in further B deactivation in the following CFA at 300-500 °C. On the contrary, the dissociation of BI pairs during the following CFA at 600-800 °C enables the B reactivation. Importantly, the first-principles calculation results can soundly account for the above-mentioned supposition.

Gao, Chao; Lu, Yunhao; Dong, Peng; Yi, Jun; Ma, Xiangyang; Yang, Deren

2014-01-01

78

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

SciTech Connect

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

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

2014-01-20

79

Ti-doped isotropic graphite: A promising armour material for plasma-facing components  

NASA Astrophysics Data System (ADS)

Finely dispersed Ti-doped isotropic graphites with 4 at.% Ti have been manufactured using synthetic mesophase pitch 'AR' as raw material. These new materials show a thermal conductivity at room temperature of ˜200 W/mK and flexural strength close to 100 MPa. Measurement of the total erosion yield by deuterium bombardment at ion energies and sample temperatures for which pure carbon shows maximum values, resulted in a reduction of at least a factor of 4, mainly due to dopant enrichment at the surface caused by preferential erosion of carbon. In addition, ITER relevant thermal shock loads were applied with an energetic electron beam at the JUDITH facility. The results demonstrated a significantly improved performance of Ti-doped graphite compared to pure graphite. Finally, Ti-doped graphite was successfully brazed to a CuCrZr block using a Mo interlayer. These results let assume that Ti-doped graphite can be a promising armour material for divertor plasma-facing components.

García-Rosales, C.; López-Galilea, I.; Ordás, N.; Adelhelm, C.; Balden, M.; Pintsuk, G.; Grattarola, M.; Gualco, C.

2009-04-01

80

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

NASA Astrophysics Data System (ADS)

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

Yin, H.; Ziemann, P.

2014-06-01

81

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

SciTech Connect

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.

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

2014-06-23

82

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

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

83

Formation of nitrogen-doped mesoporous graphitic carbon with the help of melamine.  

PubMed

An efficient and facile synthesis method of nitrogen-doped mesoporous graphitic carbon (NMGC) was reported with melamine as a nitrogen source and citric acid as a carbon source. By taking advantage of the functional groups on melamine and citric acid, a uniform mixture of these two components was obtained via a self-assembly process. Accordingly, the nitrogen-doped mesoporous graphitic carbon (NMGC) can be obtained by means of the high temperature treatment. This as-prepared NMGC showed a promising potential as an anode material in lithium-ion batteries. PMID:25361052

Li, Ruimin; Cao, Anmin; Zhang, Yanjun; Li, Gen; Jiang, Feng; Li, Shumu; Chen, Daiqin; Wang, Chunru; Ge, Jiechao; Shu, Chunying

2014-12-10

84

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

SciTech Connect

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)

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

2009-12-15

85

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

NASA Astrophysics Data System (ADS)

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 CH4/H2 molar ratios and on growth directions. The critical boron concentration lied in the 6.5-17.0 × 1020at/cm3 range in the ?111? direction and at 3.2 × 1021 at/cm3 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.

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

2014-10-01

86

Electrochemical inactivation of triclosan with boron doped diamond film electrodes.  

PubMed

This research investigated an electrochemical method for inactivating contaminated stockpiles of the biocidal agent, triclosan. The goal of the electrolysis was to produce products that were amenable to treatment in conventional activated sludge treatment systems. Triclosan oxidation in electrochemical cells with boron doped diamond (BDD) film anodes was investigated in aqueous solutions at a pH value of 12. Chronoamperometry experiments showed that direct oxidation of triclosan occurred at potentials below those for H2O, Cl-, or OH- oxidation. Measurable rates of triclosan oxidation began at potentials above 0.4 V with respect to the standard hydrogen electrode (SHE), while potentials of 0.5, 1.3, and 1.8 V were required to obtain measurable oxidation rates of H2O, Cl-, and OH-, respectively. At anode potentials below 2 V, the dominant electrode reaction involved direct triclosan oxidation, while indirect oxidation was the dominant pathway at higher potentials. However, cyclic voltammetry experiments showed that direct oxidation of triclosan resulted in the formation of a passivating film on the electrode that could only be removed by oxidation at potentials above 3 V. Direct triclosan oxidation showed a very weak potential dependence, suggesting that its oxidation was limited by chemical dependent factors rather than by an outer-sphere electron transfer reaction. Organic triclosan oxidation products consisted primarily of chlorinated acetic acids and chlorinated phenolic compounds. Although the byproducts of triclosan oxidation became increasingly less reactive with increasing electrolysis time, triclosan could be completely oxidized to CO2 at current densities above 2 mA/cm2. Microtox testing indicated that residual triclosan accounted for nearly all the toxicity in the treated water, despite the fact that chlorinated byproduct concentrations were significantly higher than those of triclosan itself. PMID:15506222

Wang, Jiankang; Farrell, James

2004-10-01

87

Interfacial Reaction between Aluminum Metal and Boron-Doped Polysilicon in a Planar Type Antifuse Device  

NASA Astrophysics Data System (ADS)

The interfacial reaction between Al metal and boron-doped polysilicon was investigated to understand the mechanism of link formation in the planar type antifuse with a polysilicon pad and two Al electrodes. In the antifuse, the Si Al alloy filament with a low resistance was formed only on the boron-doped polysilicon pad, not on the phosphorus-doped or undoped polysilicon pads. After annealing Al/boron-doped polysilicon at 400°C for 20 min, an Al-B compound (AlB2) was found by the reaction between Al metal and solute borons at the grain boundaries of polysilicon using Auger electron spectroscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy. In the planar type antifuse device, the formation of AlB2 at the grain boundaries might act as a seed for the conductive filament formation by supplying Al from the positive electrode. After forming a low resistance Si Al alloy filament, it grows toward the negative electrode by the reaction between supplied Al and highly reactive solute borons segregated at the grain boundaries.

Baek, Jong; Park, Hyung-Ho; Ahn, Byung; Jun, Chi; Kim, Youn; Song, Yoon; Kim, Jongdae

1998-05-01

88

Boron Nitride Thin Films Grown on Graphitized 6H-SiC Substrates by Metalorganic Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

The growth of thin boron nitride (BN) films on graphitized 6H-SiC substrates was investigated in an attempt to reduce the large lattice mismatch between 6H-SiC and BN, which would improve the three-dimensional ordering in BN thin films grown by metalorganic vapor phase epitaxy (MOVPE). BN thin films were grown by low-pressure (300 Torr) MOVPE using triethylboron and ammonia on graphitized 6H-SiC substrates with surfaces displaying (1× 1) reconstruction as determined by low energy electron diffraction (LEED). The (1× 1) surfaces were formed by annealing at 1500 °C in ultrahigh vacuum with a base pressure of 10-10 Torr. The LEED patterns showed that the surfaces were covered with single-crystal graphite several monolayers thick. X-ray diffraction revealed that the c-axis lattice constant of the BN was 6.72 Å, which is close to the 6.66 Å of bulk hexagonal BN. In contrast, BN films grown on non-graphitized 6H-SiC substrates by MOVPE under the same conditions were mostly amorphous. Use of a graphitized 6H-SiC substrate covered with graphite several monolayers thick improves the degree of three-dimensional ordering in BN thin films grown by MOVPE.

Kobayashi, Yasuyuki; Hibino, Hiroki; Nakamura, Tomohiro; Akasaka, Tetsuya; Makimoto, Toshiki; Matsumoto, Nobuo

2007-04-01

89

Improvement of the thermo-mechanical properties of fine grain graphite by doping with different carbides  

NASA Astrophysics Data System (ADS)

The possibilities for optimization of doped fine grain graphites with high thermal conductivity and high thermal shock resistance are demonstrated at laboratory scale. A mixture of MCMB powder and different carbides (B 4C, TiC, VC, ZrC and WC) was used as starting material. VC acts as catalyst of the graphitization at the lowest temperature, and ZrC is the most effective catalyst of all investigated carbides. A direct proportionality between the mean crystallite height, Lc, and the thermal conductivity at room temperature was found for all materials except for the B 4C- and the ZrC-doped graphites. With increasing graphitization temperature the open porosity of all doped materials becomes gradually closed, suggesting the existence of a diffusion mechanism responsible for both the catalytic effect and the closing of the open porosity. The addition of carbides does not strongly influence the mechanical properties of pure graphite. A high ratio flexural strength to Young's modulus was achieved.

García-Rosales, C.; Ordás, N.; Oyarzabal, E.; Echeberria, J.; Balden, M.; Lindig, S.; Behrisch, R.

2002-12-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

91

Synthesis of ultra dispersed graphite–like structures doped with nitrogen in supersonic carbon plasma flow  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

92

BORON  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

93

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

SciTech Connect

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.

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

2014-08-14

94

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

95

Intergranular fracture tendency in NiAl doped with boron and carbon  

SciTech Connect

Near-stoichiometric NiAl alloys produced by powder metallurgy, or by conventional casting and fabrication, exhibit mainly intergranular fracture at ambient temperatures. NiAl doped with 300 wt ppm C also shows grain boundary fracture at room temperature, whereas NiAl doped with 300 wt ppm B exhibits mainly transgranular fracture. George and Liu concluded that boron segregation increases grain boundary cohesion and suppresses intergranular fracture in near-stoichiometric NiAl. In addition to suppressing intergranular fracture, boron additions dramatically increase the yield strength and reduce plastic deformation in NiAl at room temperature. The purpose of this study is to further examine these two factors, i.e., enhancement of grain boundary cohesion and reduction of strain incompatibility, by compression tests of near-stoichiometric NiAl alloys doped separately with 300 wt ppm B and C at room temperature. These alloys were chosen because both carbon and boron increase strength significantly, but only boron suppresses grain boundary fracture. Compression tests were used in this study to obtain plastic deformation beyond yielding and thus ensure strain incompatibility at the grain-boundary region. The results obtained so far provide additional evidence that grain boundaries in NiAl are relatively weak and that boron segregation increases grain boundary cohesion in NiAl.

Liu, C.T.; Lee, E.H.; George, E.P.; Duncan, A.J. (Oak Ridge National Lab., TN (United States))

1994-02-15

96

Effect of nitrogen addition on the morphology and structure of boron-doped nanostructured diamond films  

NASA Astrophysics Data System (ADS)

A chemical vapor deposition hydrogen/methane/nitrogen feedgas mixture with unconventional high methane (15% CH4 by volume) normally used to grow ultrahard and smooth nanostructured diamond films on Ti-6Al-4V alloy substrates was modified to include diborane (10% B2H6 in hydrogen) for boron doping. The flow rates of N2 were varied to investigate its effect on plasma chemistry, film morphology, and mechanical properties. As expected, boron is readily incorporated into the diamond film and results in a change in the lattice parameter. Nitrogen, on the other hand, competes with boron in the plasma and acts to prevent boron incorporation into the diamond structure. Glancing angle x-ray diffraction indicates a decrease of diamond lattice parameter with increasing N2/CH4 flow rate ratio. A critical 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 (˜4×1020 cm-3). As shown from this critical limit, experimental conditions can be optimized to produce ultrahard, boron doped nanostructured diamond films with the potential for high temperature applications.

Liang, Qi; Catledge, Shane A.; Vohra, Yogesh K.

2003-12-01

97

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

E-print Network

of thin heavily boron-doped Ge quantum dot lay- ers sandwiched with two 6 nm undoped Si films. The sche in the range of 10­20 m,11 respectively. Mid-infrared photoconductivity at around 3 m has also been studied

98

Platinum particles deposited on synthetic boron-doped diamond surfaces. Application to methanol oxidation  

Microsoft Academic Search

Two methods have been used for the deposition of Pt particles on synthetic boron-doped diamond (BDD) surfaces: chemical deposition and electrodeposition under potentiostatic conditions. However, electrodeposition leads much higher platinum dispersion than chemical deposition. The mechanism of nucleation and growing of the electrodeposited platinum was investigated by means of chronoamperometric studies in acid medium. The electrodeposition on diamond surfaces shows

F. Montilla; E. Morallon; I. Duo; Ch. Comninellis; J. L. Vazquez

2003-01-01

99

Boosting activation of oxygen molecules on c60 fullerene by boron doping.  

PubMed

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

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

2015-02-01

100

Boron Undoped and Doped Europium-Bismuth Oxide Nanocomposites via the Polymeric Precursor Technique  

NASA Astrophysics Data System (ADS)

Boron-undoped and -doped europium-bismuth oxide nanocomposites were synthesized by the polymeric precursor technique. The solutions were calcined and sintered to prepare nanocomposite powders. The nanocomposites were characterized by the Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscope, and Brauner-Emmett-Teller techniques. According to Fourier transform infrared spectroscopy results, the shape, the range, and the intensity of the peaks for the calcined and sintered samples changed with the addition of boron content. Furthermore, the reaction path, resulting crystal size, and crystal morphology were all altered by boron additions. A decrease in porosity, brought about by boron additions, also altered the N2 absorption/desorption characteristics.

Aytimur, Arda; Koçyi?it, Serhat; Temel, Sinan; Uslu, Ibrahim

2014-08-01

101

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

PubMed

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 ?-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

Poh, Hwee Ling; Šimek, Petr; Sofer, Zden?k; Pumera, Martin

2013-06-25

102

Induced polarization and electronic properties of carbon-doped boron nitride nanoribbons  

NASA Astrophysics Data System (ADS)

The electronic properties of boron nitride nanoribbons (BNNRs) doped with a line of carbon atoms are investigated using density functional calculations. By replacing a line of alternating B and N atoms with carbons, three different configurations are possible depending on the type of the atoms which bond to the carbons. We found very different electronic properties for these configurations: (i) the NCB arrangement is strongly polarized with a large dipole moment having an unexpected direction, (ii) the BCB and NCN arrangements are nonpolar with zero dipole moment, (iii) the doping by a carbon line reduces the band gap regardless of the local arrangement of the borons and the nitrogens around the carbon line, and (iv) the polarization and energy gap of the carbon-doped BNNRs can be tuned by an electric field applied parallel to the carbon line. Similar effects were found when either an armchair or zigzag line of carbon was introduced.

Beheshtian, J.; Sadeghi, A.; Neek-Amal, M.; Michel, K. H.; Peeters, F. M.

2012-11-01

103

Transport properties of boron-doped single-walled silicon carbide nanotubes  

NASA Astrophysics Data System (ADS)

The doped boron (B) atom in silicon carbide nanotube (SiCNT) can substitute carbon or silicon atom, forming two different structures. The transport properties of both B-doped SiCNT structures are investigated by the method combined non-equilibrium Green’s function with density functional theory (DFT). As the bias ranging from 0.8 to 1.0 V, the negative differential resistance (NDR) effect occurs, which is derived from the great difficulty for electrons tunneling from one electrode to another with the increasing of localization of molecular orbital. The high similar transport properties of both B-doped SiCNT indicate that boron is a suitable impurity for fabricating nano-scale SiCNT electronic devices.

Yang, Y. T.; Ding, R. X.; Song, J. X.

2011-01-01

104

Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament  

NASA Astrophysics Data System (ADS)

Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

Malik, R. J.; Nottenberg, R. N.; Schubert, E. F.; Walker, J. F.; Ryan, R. W.

1988-12-01

105

Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament  

NASA Technical Reports Server (NTRS)

Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

Malik, R. J.; Nottenberg, R. N.; Schubert, E. F.; Walker, J. F.; Ryan, R. W.

1988-01-01

106

Potential rare earth free permanent magnet: interstitial boron doped FeCo  

NASA Astrophysics Data System (ADS)

Using the full potential linearized augmented plane wave method, we investigated the structural and the magnetic properties of boron doped FeCo. After fully relaxing the lattice structure, the interatomic distances between boron and Fe atoms were found to be greatly enhanced and the tetragonal distortion was realized due to this increased interatomic distance. Nonetheless, both the unit cell volume and the total magnetic moment of the tetragonally distorted FeCo structure were weakly suppressed compared with those of ideal bulk FeCo. We found a magnetocrystalline anisotropy constant of 0.8 MJ m-3 and this was mainly due to the tetragonal distortion induced by boron impurity, not from the hybridization effect with Fe or Co, because no essential change in the magnetocrystalline anisotropy constant was found even without boron impurity in the lattice distorted system. Additionally, the estimated maximum energy product and coercive field were 100 MGOe and 745 kA m-1, respectively. These results may imply that the interstitial boron doped FeCo can be used for a potential rare earth free permanent magnet although those values are likely to be suppressed in real samples due to micromagnetic factors.

Khan, Imran; Hong, Jisang

2014-10-01

107

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

SciTech Connect

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.

Singleton, John [Los Alamos National Laboratory; Yaguchi, Hiroshi [TOKYO UNIV

2008-01-01

108

The synthesis and structural characterization of boron-doped silicon-nanocrystals with enhanced electroconductivity  

NASA Astrophysics Data System (ADS)

Boron (B)-doped silicon-nanocrystals (Si-NCs) with wavelength-tunable photoluminescence (PL) properties in the visible region are successfully prepared for the first time, leading to significant enhancement of electroconductivities. The B-doped Si-NCs are prepared on a p-type Si(100) substrate by co-deposition of p-type Si(100) chips/boron chips/silica disk targets. As the number of the B chips used as the target is increased, the amount of doped B content increases gradually. Here the amount of doped B content in the Si-NCs is controlled from 0 to 0.4, 0.7, 2.3 at.%. The B elemental states, compositional ratios, and surface condition of the obtained Si-NCs are fully characterized by high-resolution transmission electron microscopy (HRTEM) observations, micro-Raman scattering spectroscopic analysis, etc. Our B-doped Si-NCs possess both the continuous luminescence property in the visible region and enhanced electroconductivity. The red-shift of the PL peak is confirmed by the increase of the amount of doped B content. This paper should be very important from the viewpoint of application to optoelectronic devices and electroluminescent (EL) displays.

Sato, Keisuke; Niino, Kazuki; Fukata, Naoki; Hirakuri, Kenji; Yamauchi, Yusuke

2009-09-01

109

Electrocatalytic characteristics of uric acid oxidation at graphite–zeolite-modified electrode doped with iron (III)  

Microsoft Academic Search

A new method is developed for the catalytic oxidation of uric acid at graphite–zeolite-modified electrode doped with iron (III) (Fe3+Y\\/ZCME). Iron (III) exchanged in zeolite Y act as catalyst to oxidize uric acid. First, the electrochemical behavior of iron (III) incorporated in the zeolite Y-modified electrode was studied. The results illustrate that diffusion controls the ferric\\/ferrous redox process at the

M. Mazloum Ardakani; Z. Akrami; H. Kazemian; H. R. Zare

2006-01-01

110

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...

111

Gallium doped in armchair and zigzag models of boron phosphide nanotubes (BPNTs): A NMR study  

NASA Astrophysics Data System (ADS)

The electrical properties and NMR parameters of the pristine and Ga-doped structures of two representative (8, 0) zigzag and (4, 4) armchair of boron phosphide nanotubes (BPNTs) have been investigated. The structural geometries of above nanotubes have been allowed to relax by optimization and then the isotropic and anisotropic chemical shielding parameters (CSI and CSA) of 11B and 31P have been calculated based on DFT theory. The results reveal that the influence of Ga-doping was more significant on the geometries of the zigzag model than the armchair one. The difference of band gap energies between the pristine and Ga-doped armchair BPNTs was larger than the zigzag model. Significant differences of NMR parameters of those nuclei directly contributed to the Ga-doping atoms have been observed.

Rezaei-Sameti, M.

2012-09-01

112

Analysis of Hybrid Type Boron-Doped Carbon Stripper Foils in J-PARC RCS  

NASA Astrophysics Data System (ADS)

J-PARC (Japan-Proton Accelerator Research Complex) requires a carbon stripper foil to strip electrons from the H- beam supplied by the linac before injection into the Rapid Cycling Synchrotron (RCS) [1]. The foil thickness is about ?m (200?g/cm2) corresponding to conversion efficiency of 99.7% from the primary H- beams of 181MeV energy to H+. We have successfully developed the Hybrid type thick Boron-doped Carbon (HBC) stripper foil, which showed a drastic improvement the lifetime without thickness reduction and shrinkage at the irradiated area. We started to study carbon stripper foils microscopically why carbon foils have considerable endurance for the beam impact by boron-doped. At first step, we made a comparison of ion irradiation effect between normal carbon and HBC by the electric microscope, ion-induced analysis. In particular, it seems that grain size of boron-rich area became much larger by irradiation for HBC. It was also observed that the boron-rich grain grew up by taking around material and generated pinholes more than 100 nm near itself consequently.

Yamazaki, Y.; Yoshimoto, M.; Takeda, O.; Kinsho, M.; Taguchi, T.; Yamamoto, S.; Kurihara, T.; Sugai, I.

2013-03-01

113

Effects of boron-doping on the morphology and magnetic property of carbon nanotubes  

Microsoft Academic Search

Boron carbide nanotubes (nano-fibers) was prepared by B powder and carbon nanotubes (CNTs) at high temperature in a vacuumed\\u000a quartz tube. The morphology, microstructure, component and magnetic property of samples were characterized by transmission\\u000a electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetic property measurement\\u000a system (MPMS) controller. The results showed that B-doping CNTs have great difference

Qi Jiang; Lan Qian; Jing Yi; Xiaotong Zhu; Yong Zhao

2007-01-01

114

Electrochemical oxidation of water on synthetic boron-doped diamond thin film anodes  

Microsoft Academic Search

Electrolysis in aqueous 1 M HClO4 and 1 M H2SO4 solutions has been carried out under galvanostatic conditions using boron-doped diamond electrodes (BDD). Analyses of the oxidation products have shown that in 1 M HClO4 the main reaction is oxygen evolution, while in H2SO4 the main reaction is the formation of H2S2O8. In both electrolytes small amounts of O3 and

P. A. Michaud; M. Panizza; L. Ouattara; T. Diaco; G. Foti; Ch. Comninellis

2003-01-01

115

Transport of heavily boron-doped synthetic semiconductor diamond in the hopping regime  

Microsoft Academic Search

We report electrical transport measurements of synthetic diamonds doped with boron about 100 ppm. The resistivity has been measured in the temperature range 20-300 K by the van der Pauw method. We have also investigated infrared absorption coefficient at room temperature. Furthermore, we have studied the effect of P+9 ion irradiations with 150 MeV which introduce donor defects and also

Toshimaro Sato; Kazutoshi Ohashi; Hiroyuki Sugai; Takashi Sumi; Katsuji Haruna; Hiroshi Maeta; Norimasa Matsumoto; Hideo Otsuka

2000-01-01

116

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

PubMed

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

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

2008-10-22

117

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

PubMed

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

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

2014-08-15

118

Effects of boron doping in TiO2 nanotubes and the performance of dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

Titanium nanotubes doped with boron used as the photoelectrode for dye-sensitized solar cells were investigated. The materials were characterized by SEM, XRD, and UV-vis spectroscopy and their photoconversion efficiencies were evaluated. The chemical compositions of TiO2 nanotubes (TNA) and boron doped TNA (B-TNA) were identified by the energy dispersive X-ray spectroscopy (EDS). XRD evidenced the presence of anatase as the main phase and presented the existence of boron elements at interstitial sites between the TiO2 lattices. The UV-vis spectra indicated the narrowing of band gap upon doping boron into titanium nanotubes. The photovoltaic properties were measured by a current-voltage meter under AM1.5 simulated light radiation. The boron-doped TiO2 nanotube arrays showed an enhanced performance with a photocurrent density of 7.85 ± 0.20 mA/cm2 and an overall conversion efficiency (?) of 3.44 ± 0.10%. The enhanced performance was attributed to the enhanced electron injection rate and retardation of the charge recombination, which could be due to perfect matching between the LUMO of dye molecules and the conduction band of TiO2. Electrochemical impedance spectroscopy (EIS) measurement indicated the longer electron lifetime and reduced TiO2/dye/electrolyte interface resistance for boron doped TiO2 nanotubes than that of undoped TiO2 nanotubes.

Subramanian, Alagesan; Wang, Hong-Wen

2012-06-01

119

Boron-doped carbon-iron nanocomposites as efficient oxygen reduction electrocatalysts derived from carbon dioxide.  

PubMed

Developing cost-effective oxygen reduction reaction (ORR) catalysts is pivotal for development of fuel cells. While Fe-N-C catalysts were proposed for ORR, Fe-B-C catalysts have not been explored. This work introduces the B-doped carbon catalysts encapsulating iron cores using CO2 as a carbon source. The Fe-B-C catalysts show enhanced ORR activity and durability due to the iron core within the graphitic layers. PMID:24797546

Zhang, Junshe; Byeon, Ayeong; Lee, Jae W

2014-06-18

120

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

PubMed

Band gap-tunable potassium doped graphitic carbon nitride with enhanced mineralization ability was prepared using dicyandiamide monomer and potassium hydrate as precursors. X-ray diffraction (XRD), N2 adsorption, UV-Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared catalysts. The CB and VB potentials of graphitic carbon nitride could be tuned from -1.09 and +1.56 eV to -0.31 and +2.21 eV by controlling the K concentration. Besides, the addition of potassium inhibited the crystal growth of graphitic carbon nitride, enhanced the surface area and increased the separation rate for photogenerated electrons and holes. The visible-light-driven Rhodamine B (RhB) photodegradation and mineralization performances were significantly improved after potassium doping. A possible influence mechanism of the potassium concentration on the photocatalytic performance was proposed. PMID:25409884

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

2015-01-21

121

Effect of diborane on the microstructure of boron-doped silicon nanowires  

NASA Astrophysics Data System (ADS)

Boron-doped silicon (Si) nanowires, with nominal diameters of 80 nm, were grown via the vapor-liquid-solid (VLS) mechanism using gold (Au) as a catalyst and silane (SiH 4) and diborane (B 2H 6) as precursors. The microstructure of the nanowires was studied by scanning electron microscopy, transmission electron microscopy and electron energy-loss spectroscopy. At lower B 2H 6 partial pressure and thus lower doping levels (?1×10 18 cm -3), most of the boron-doped Si nanowires exhibited high crystallinity. At higher B 2H 6 partial pressure (˜2×10 19 cm -3 doping level), the majority of the wires exhibited a core-shell structure with an amorphous Si shell (20-30 nm thick) surrounding a crystalline Si core. Au nanoparticles on the outer surface of the nanowires were also observed in structures grown with high B/Si gas ratios. The structural changes are believed to result from an increase in the rate of Si thin-film deposition on the outer surface of the nanowire at high B 2H 6 partial pressure, which produces the amorphous coating and also causes an instability at the liquid/solid interface resulting in a loss of Au during nanowire growth.

Pan, Ling; Lew, Kok-Keong; Redwing, Joan M.; Dickey, Elizabeth C.

2005-04-01

122

Cobalt monoxide-doped porous graphitic carbon microspheres for supercapacitor application  

PubMed Central

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, ?-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

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

2013-01-01

123

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

SciTech Connect

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

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

2014-09-15

124

Study of different thermal processes on boron-doped PERL cells  

NASA Astrophysics Data System (ADS)

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 ?s to 240 ?s) 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.

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

2014-08-01

125

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

E-print Network

WITH BORON AND PHOSPHORUS Bianca Lim1 , Karsten Bothe1 , Vladimir Voronkov2 , Robert Falster2 , and Jan in oxygen-rich boron-doped crystalline silicon degrades under illumination at room temperature, both in p as the fast forming recombination-center observed in p-Si. Keywords: Czochralski silicon, boron, phosphorus

126

Molecular chemisorption on passivated and defective boron doped silicon surfaces: a "forced" dative bond.  

PubMed

We investigate the adsorption mechanism of a single trans 4-pyridylazobenzene molecule (denoted by PAB) on a doped boron Si(111)?3×?3R30° surface (denoted by SiB) with or without boron-defects, by means of density functional theory calculations. The semiempirical approach proposed by Grimme allows us to take the dispersion correction into account. The role of the van der Waals correction in the adsorption geometries and energies is presented. In particular, two adsorption configurations are electronically studied. In the first one, the molecule is parallel to the surface and interacts with the SiB surface via the -N=N- bond. In the presence of a boron-defect, a Si-N chemical bond between the molecule and the surface is then formed, while electrostatic or/and van der Waals interactions are observed in the defectless surface. In the second adsorption configuration, the molecule presents different orientations with respect to the surface and interacts via the nitrogen atom of the pyridyl part of the PAB molecule. If the molecule is perpendicular to the perfect SiB surface, the lone-pair electrons associated with the heterocyclic nitrogen atom fill the empty dangling bond of a silicon adatom via a dative bond. Finally, in the presence of one boron-defect, the possibility of a "forced" dative bond, corresponding to a chemical bond formation between the PAB molecule and the silicon electron occupied dangling bond, is emphasized. PMID:25318974

Boukari, Khaoula; Duverger, Eric; Sonnet, Philippe

2014-12-01

127

Photovoltaic feature of boron-doped nanocrystalline carbon films on silicon  

NASA Astrophysics Data System (ADS)

Boron-doped diamond-like carbon (B-DLC) thin films were deposited on n-type silicon (100) substrates by arc-discharge plasma chemical vapor deposition (arc-PCVD) technique, followed by a deposition of TiNx (0.8 < x < 1.1) mark on top of the carbon films to form heterojunction devices. The crystallinity of the carbon film was confirmed to be a mixing of sp3/sp2 coordination with nanocrystalline diamond grains embedded in the amorphous network. The performance of TiNx / p-C (B) / n-Si / AuSb heterojunction cells has been evaluated under dark I-V rectifying curve and I-V working curve with a proper illumination. At higher boron content the films exhibited a high internal conductivity and an overall phase-related character. The TiNx exhibited an excellent ohmic contact behavior as a metallic electrode of the devices.

Ma, Z. Q.; Zhang, Q.

2004-12-01

128

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

NASA Astrophysics Data System (ADS)

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, ?) 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.

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

1982-08-01

129

Irradiation and penetration tests of boron-doped low activation concrete using 2.45 and 14 MeV neutron sources  

Microsoft Academic Search

The neutron penetration and the activation characteristics of the boron-doped low activation concrete were investigated for irradiation of 2.45 and 14 MeV neutrons. The shielding property of the 2 wt% boron-doped low activation concrete is superior to that of the 1 wt% boron for the thermal neutron, on the contrary to no clear difference for the fast neutron. The total

Atsuhiko Morioka; Satoshi Sato; Masaharu Kinno; Akira Sakasai; Junichi Hori; Kentaro Ochiai; Michinori Yamauchi; Takeo Nishitani; Atsushi Kaminaga; Kei Masaki; Shinji Sakurai; Takao Hayashi; Makoto Matsukawa; Hiroshi Tamai; Shinichi Ishida

2004-01-01

130

Deposition of boron doped zinc oxide films and their electrical and optical properties  

NASA Astrophysics Data System (ADS)

Boron doped zinc oxide films were deposited by atmospheric-pressure CVD in a laminar flow reactor from diethyl zinc, tert-butanol, and diborane in the temperature range from 300 to 420 C. When the deposition temperature was above 320 C, both doped and undoped films have highly oriented crystallites with their c-axes perpendicular to the substrate plane. Films deposited from 0.07 percent diethyl zinc and 2.4 percent tert-butanol have electron densities from 3.5 to 5.5 x 10 exp 20/cu cm, conductivities from 250 to 2500/ohm per cm, and mobilities from 2.5 to 35.0 sq cm/V-s, depending on dopant concentration, film thickness, and deposition temperature. Optical measurements show that the maximum infrared reflectance of the doped films is close to 90 percent, compared to about 20 percent for undoped films. Visible absorption and conductivity were found to increase with thickness. The ratio of conductivity to visible absorption coefficient for doped films was from 0.1 to 1.1/ohm. The bandgap of the film changes from 3.3 to 3.7 eV when the film is doped with 0.012-percent diborane.

Hu, Jianhua; Gordon, Roy G.

1992-07-01

131

Density functional theory study on boron- and phosphorus-doped hydrogen-passivated silicene.  

PubMed

When silicene is passivated by hydrogen, a bandgap occurs so that it becomes a semiconductor. Analogous to all the other semiconductors, doping is highly desired to realize the potential of hydrogen-passivated silicene (H-silicene). In the framework of density functional theory (DFT), we have studied the doping of H-silicene with boron (B) and phosphorus (P). The concentration of B or P ranges from 1.4% to 12.5%. It is found that the doping of B or P enables the indirect-bandgap H-silicene to be a semiconductor with a direct bandgap. With the increase of the concentration of B or P, both the valence band and the conduction band shift to lower energies, while the bandgap decreases. Both B- and P-doping lead to the decrease of the effective mass of holes and electrons in H-silicene. For both B- and P-doped H-silicene a subband absorption peak may appear, which blueshifts with the increase of the dopant concentration. PMID:25564050

Pi, Xiaodong; Ni, Zhenyi; Liu, Yong; Ruan, Zhichao; Xu, Mingsheng; Yang, Deren

2015-01-28

132

A FeCl2-graphite sandwich composite with Cl doping in graphite layers: a new anode material for high-performance Li-ion batteries  

NASA Astrophysics Data System (ADS)

A composite with FeCl2 nanocrystals sandwiched between Cl-doped graphite layers has been created via a space-confined nanoreactor strategy. This composite can be used as a new type of anode material for Li-ion batteries, which exhibit high reversible capacity and superior rate capability with excellent cycle life.A composite with FeCl2 nanocrystals sandwiched between Cl-doped graphite layers has been created via a space-confined nanoreactor strategy. This composite can be used as a new type of anode material for Li-ion batteries, which exhibit high reversible capacity and superior rate capability with excellent cycle life. Electronic supplementary information (ESI) available: Experimental section and Fig. S1-S8. See DOI: 10.1039/c4nr05070c

Wang, Lili; Guo, Cong; Zhu, Yongchun; Zhou, Jianbin; Fan, Long; Qian, Yitai

2014-11-01

133

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

SciTech Connect

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

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

2014-01-27

134

Visible-light sensitization of boron-doped nanocrystalline diamond through non-covalent surface modification.  

PubMed

A novel simple and versatile synthetic strategy is developed for the surface modification of boron-doped diamond. In a two-step procedure, polyethyleneimine is adsorbed on the hydrogenated diamond surface and subsequently modified with a model light-harvesting donor-?-bridge-acceptor molecule (coded P1). The sensitized diamond exhibits stable cathodic photocurrents under visible-light illumination in aqueous electrolyte solution with dimethylviologen serving as an electron mediator. In spite of the simplicity of the surface sensitization protocol, the photoelectrochemical performance is similar to or better than that of other sensitized diamond electrodes which were reported in previous studies (2008-2014). PMID:25418375

Krysova, Hana; Vlckova-Zivcova, Zuzana; Barton, Jan; Petrak, Vaclav; Nesladek, Milos; Cigler, Petr; Kavan, Ladislav

2015-01-14

135

Boron and Nitrogen Doped Single walled Carbon Nanotubes as Possible Dilute Magnetic Semiconductors  

PubMed Central

The structure of single walled armchair and zig-zag carbon nanotubes having 70 atoms and two carbons replaced by boron or nitrogen is obtained at minium energy using HF/6-31G* molecular orbital theory. The calculations show that the ground state of the zig-zag tubes is a triplet state while for the armchair tubes it is a singlet. In the zig-zag tubes the density of states at the Fermi level is greater for the spin down states compared to the spin up state indicating that the doped tubes could be ferromagnetic.

2007-01-01

136

Low Critical Concentration of Metal--Insulator Transition of Vanadium Doped Amorphous Boron  

Microsoft Academic Search

The metal--insulator transition (MIT) of V- and Zr-doped amorphous boron films (VxB100-x, ZrxB100-x) was studied. The temperature dependences of the electrical conductivity, the X-ray diffraction patterns and the X-ray absorption fine structures were measured for the samples. The compositional boundary of the metal--insulator transition is found between x = 2.9 and 3.7 in VxB100-x, and between x = 11 and

Kenji Tanabe; Kohei Soga; Shizuka Hosoi; Kazuaki Osumi; Hideshi Yamaguchi; Tomoya Uruga; Kaoru Kimura

2011-01-01

137

Electrochemical "read-write" microscale patterning of boron doped diamond electrodes.  

PubMed

Scanning electrochemical cell microscopy is utilised as a read-write pipette-based probe to both electrochemically modify the local surface chemistry of boron doped diamond and "read" the resulting modification, at the micron scale. In this specific application, localised electrochemical oxidation results in conversion of the H-terminated surface to -O, electrochemically visualised by monitoring the current change for reduction of Ru(NH3)6(3+). This methodology, in general, provides a platform for read-write analysis of electrodes, opening up new analytical avenues, particularly as the pipette can be viewed as a microfluidic device. PMID:25387408

Patten, Hollie V; Hutton, Laura A; Webb, Jennifer R; Newton, Mark E; Unwin, Patrick R; Macpherson, Julie V

2015-01-01

138

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

DOEpatents

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.

Yang, Liyou (Lawrenceville, NJ)

1993-10-26

139

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

NASA Astrophysics Data System (ADS)

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.

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

2007-09-01

140

Influence of boron doping and hydrogen dilution on p-type microcrystalline silicon carbide thin films prepared by photochemical vapor deposition  

Microsoft Academic Search

Boron doped ?c-SiC:H films have been prepared by low power (10 mW\\/cm2) photochemical vapor decomposition of SiH4, C2H2, and B2H6 gases diluted with hydrogen. The effect of boron doping and hydrogen dilution on structural and opto-electronic properties have been studied. The microstructure consists of Si crystallites while carbon remains at the grain boundaries and amorphous parts. Diborane doping beyond an

Sukriti Ghosh; Arup Dasgupta; Swati Ray

1995-01-01

141

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

Microsoft Academic Search

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

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

2011-01-01

142

Modal interferometric sensor based in a birefringent boron-doped microstructured fiber  

NASA Astrophysics Data System (ADS)

Microstructured optical fibers (MOFs) have been widely studied owing to their potential for obtaining novel transmission, nonlinear and sensing characteristics. Sensing applications of MOFs cover various types of devices for measurements of different physical and specific chemical compounds in gases and liquids employing evanescent field techniques. Such fibers can also be used as active and passive elements in fiber-optic polarimetric and interferometric sensors. We present an in-line fiber modal interferometer fabricated in boron-doped highly birefringent microstructured fiber. The boron-doped region located in the middle of the core decreases the effective index of the fundamental mode and facilitates coupling between the fundamental and the first order mode. The coupling regions have the form of fiber narrowings fabricated using CO2 laser and are distant by a few millimeters. The spectral intensity at the sensor output is modulated only by intermodal interference produced by a short piece of fiber between the two coupling points. Moreover, as the fiber is highly birefringence, each pair of polarization modes produces its own intermodal fringes, which results in the contrast modulation of the overall interference signal observed at the fiber output, and provides an additional degree of freedom to measure simultaneously a pair of measurands.

Statkiewicz-Barabach, G.; Carvalho, J. P.; Frazão, O.; Olszewski, J.; Mergo, P.; Santos, J. L.; Urbanczyk, W.

2011-05-01

143

Amperometric Determination of Sulfite by Gas Diffusion-Sequential Injection with Boron-Doped Diamond Electrode  

PubMed Central

A gas diffusion sequential injection system with amperometric detection using a boron-doped diamond electrode was developed for the determination of sulfite. A gas diffusion unit (GDU) was used to prevent interference from sample matrices for the electrochemical measurement. The sample was mixed with an acid solution to generate gaseous sulfur dioxide prior to its passage through the donor channel of the GDU. The sulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution of 0.1M phosphate buffer (pH 8)/0.1% sodium dodecyl sulfate in the acceptor channel of the GDU and turned to sulfite. Then the sulfite was carried to the electrochemical flow cell and detected directly by amperometry using the boron-doped diamond electrode at 0.95 V (versus Ag/AgCl). Sodium dodecyl sulfate was added to the carrier solution to prevent electrode fouling. This method was applicable in the concentration range of 0.2-20 mg SO32?/L and a detection limit (S/N = 3) of 0.05 mg SO32?/L was achieved. This method was successfully applied to the determination of sulfite in wines and the analytical results agreed well with those obtained by iodimetric titration. The relative standard deviations for the analysis of sulfite in wines were in the range of 1.0-4.1 %. The sampling frequency was 65 h?1.

Chinvongamorn, Chakorn; Pinwattana, Kulwadee; Praphairaksit, Narong; Imato, Toshihiko; Chailapakul, Orawon

2008-01-01

144

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

PubMed

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

Macpherson, Julie V

2015-02-01

145

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

PubMed

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

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

2005-05-01

146

Variational method for tensile stress evaluation and application to heavily boron-doped square-shaped silicon diaphragms  

Microsoft Academic Search

Motivated by the need for tensile stress evaluation in ultrathin diaphragms, and especially in heavily boron-doped silicon membranes, a new approach for the determination of this physical property is proposed. The technique employs equipment common to most IC laboratories. It combines deflection measurements and an appropriate theoretical relation between deflection and mechanical tension. Condenser microphones incorporating 0.8 ?m thick p+

T. Bourouina; C. Vauge; H. Mekki

1995-01-01

147

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

E-print Network

Surface characteristics of boron-doped diamond exposed to high-temperature annealing: Effect at the same temperature in high vacuum for 5 hours and analyzed. Surface analysis by X-ray photoelectron of energy-distributed electronic states, as revealed by AC-impedance spectroscopy in 0.1M H2SO4 electrolyte

Pfeifer, Holger

148

High-temperature point-contact transistors and Schottky diodes formed on synthetic boron-doped diamond  

Microsoft Academic Search

Point-contact transistors and Schottky diodes have been formed on synthetic boron-doped diamond. This is the first report of diamond transistors that have power gain. Further, the transistors exhibited power gain at 510°C and the Schottky diodes were operational at 700°C.

M. W. Geis; D. D. Rathman; D. J. Ehrlich; R. A. Murphy; W. T. Lindley

1987-01-01

149

Effect of test environment on ductility and fracture behavior of boron-doped Ni3Al at 600C  

Microsoft Academic Search

The work reported here was a preliminary effort to identify the factors responsible for the marked difference between ductility reported by Liu and Taub in the temperature range above 400 degrees C. The authors found that tensile ductility of boron-doped Ni3Al alloys is a strong function of test environment at 600 degrees C, with much lower ductilities observed in air

C. T. Liu; E. H. Lee; C. L. White

1985-01-01

150

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

PubMed

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 2?* 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

Lin, Sen; Ye, Xinxin; Huang, Jing

2014-12-10

151

Preparation of calcium-doped boron nitride by pulsed laser deposition  

SciTech Connect

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 ?-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.

Anzai, Atsushi; Fuchigami, Masayo; Yamanaka, Shoji [Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527 (Japan)] [Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527 (Japan); Inumaru, Kei, E-mail: inumaru@hiroshima-u.ac.jp [Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527 (Japan)] [Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527 (Japan)

2012-08-15

152

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

154

Atmospheric pressure chemical vapour deposition of boron doped titanium dioxide for photocatalytic water reduction and oxidation.  

PubMed

Boron-doped titanium dioxide (B-TiO2) films were deposited by atmospheric pressure chemical vapour deposition of titanium(iv) chloride, ethyl acetate and tri-isopropyl borate on steel and fluorine-doped-tin oxide substrates at 500, 550 and 600 °C, respectively. The films were characterised using powder X-ray diffraction (PXRD), which showed anatase phase TiO2 at lower deposition temperatures (500 and 550 °C) and rutile at higher deposition temperatures (600 °C). X-ray photoelectron spectroscopy (XPS) showed a dopant level of 0.9 at% B in an O-substitutional position. The ability of the films to reduce water was tested in a sacrificial system using 365 nm UV light with an irradiance of 2 mW cm(-2). Hydrogen production rates of B-TiO2 at 24 ?L cm(-2) h(-1) far exceeded undoped TiO2 at 2.6 ?L cm(-2) h(-1). The B-TiO2 samples were also shown to be active for water oxidation in a sacrificial solution. Photocurrent density tests also revealed that B-doped samples performed better, with an earlier onset of photocurrent. PMID:23999866

Carmichael, Penelope; Hazafy, David; Bhachu, Davinder S; Mills, Andrew; Darr, Jawwad A; Parkin, Ivan P

2013-10-21

155

Fabrication, structure, and photocatalytic activities of boron-doped ZnO nanorods hydrothermally grown on CVD diamond film  

NASA Astrophysics Data System (ADS)

The boron (B)-doped zinc oxide nanorods (ZnO NRs) have been fabricated on chemical vapor deposited (CVD) diamond film by hydrothermal technique. The mean diameter of the B-doped ZnO NRs is larger than that of the undoped NRs. The results of X-ray diffraction and first-principles calculations demonstrate that the boron atoms prefer to occupy the octahedral interstice positions of ZnO, which lead to the lattice expansion and band gap shrinkage. The rectifying B-doped ZnO NRs/p-diamond heterojunction structure has been performed to degrade reactive yellow 15 solution, showing a high performance photocatalysis. The photocatalysis mechanism based on the pn heterojunction is discussed.

Yu, Qi; Li, Jia; Li, Hongdong; Wang, Qiliang; Cheng, Shaoheng; Li, Liuan

2012-06-01

156

Effects of boron and glass hybrid epoxy-composites on graphite-fiber release in an aircraft fire  

NASA Technical Reports Server (NTRS)

Recent studies have shown that the benefits gained by using graphite-epoxy composite structures may not be realized without some risk. The graphite fibers are very good electrical conductors and fibers released into the environment during a fire create a possible hazard to electrical equipment. Several graphite-epoxy hybrids were exposed to a fire and simulated explosion and their graphite fiber retention characteristics were examined. Several low melting-temperature glasses which wet and clump graphite-fibers and a glass/graphite fabric which reduced impact damage were identified as promising hybridizing components to minimize graphite fiber release.

Tompkins, S. S.; Brewer, W. D.

1979-01-01

157

Electron spin-polarization and spin lattices in the boron- and nitrogen-doped organic framework COF-5.  

PubMed

Covalent organic frameworks (COFs) hold great promise in several applications, such as sieves, catalytic supports and gas storage because of their unique structures and electronic properties. However, most of these metal-free COFs are nonmagnetic and cannot be directly used in spintronics. Here, based on first-principles calculations, we predict that substitutional doping of COF-5 with nitrogen and boron atoms can modify the electronic structures, inducing stable electron spin-polarization in the framework. The preferability of the different doping sites is checked. The electronic structures of the doped COF-5 are dependent on the doping sites and doping atoms, which offer high degrees of freedom to tune the electronic properties. Kagome lattices of S = 1/2 spins can be achieved in the COF-5, suggesting a promising candidate for spin-liquid materials. PMID:25255699

Liu, Xiaobiao; Tan, Jie; Wang, Aizhu; Zhang, Xiaoming; Zhao, Mingwen

2014-11-14

158

Neutral and charged boron-doped fullerenes for CO2 adsorption  

PubMed Central

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

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

2014-01-01

159

Simultaneous detection of iodine and iodide on boron doped diamond electrodes.  

PubMed

Individual and simultaneous electrochemical detection of iodide and iodine has been performed via cyclic voltammetry on boron doped diamond (BDD) electrodes in a 1M NaClO(4) (pH 8) solution, representative of typical environmental water conditions. It is feasible to compute accurate calibration curve for both compounds using cyclic voltammetry measurements by determining the peak current intensities as a function of the concentration. A lower detection limit of about 20 ?M was obtained for iodide and 10 ?M for iodine. Based on the comparison between the peak current intensities reported during the oxidation of KI, it is probable that iodide (I(-)) is first oxidized in a single step to yield iodine (I(2)). The latter is further oxidized to obtain IO(3)(-). This technique, however, did not allow for a reasonably accurate detection of iodate (IO(3)(-)) on a BDD electrode. PMID:23200355

Fierro, Stéphane; Comninellis, Christos; Einaga, Yasuaki

2013-01-15

160

Fabrication of cone-shaped boron doped diamond and gold nanoelectrodes for AFM-SECM.  

PubMed

We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes. PMID:21368355

Avdic, A; Lugstein, A; Wu, M; Gollas, B; Pobelov, I; Wandlowski, T; Leonhardt, K; Denuault, G; Bertagnolli, E

2011-04-01

161

Fabrication of cone-shaped boron doped diamond and gold nanoelectrodes for AFM-SECM  

NASA Astrophysics Data System (ADS)

We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes.

Avdic, A.; Lugstein, A.; Wu, M.; Gollas, B.; Pobelov, I.; Wandlowski, T.; Leonhardt, K.; Denuault, G.; Bertagnolli, E.

2011-04-01

162

Fabrication of boron-doped diamond ultramicroelectrodes for use in scanning electrochemical microscopy experiments.  

PubMed

Boron-doped diamond (BDD) ultramicroelectrode (UME) tips were fabricated by the growth of BDD films by chemical vapor deposition onto sharpened tungsten wires. Both nanocrystalline and microcrystalline forms of diamond coatings were examined. The diamond-coated wires were selectively insulated with nail varnish, electrophoretic paint, or fast-setting epoxy to form UME tips of critical dimensions of 1-25 microm. The geometry of the exposed electrode area was disk or hemispherical in most cases. Cyclic voltammetry and chronoamperometry were used to assess exposed electrode area and integrity of the insulation. BDD UMEs were used to obtain SECM approach curves to an insulating and a conducting substrate, which were fitted to the theory appropriate for the observed tip geometry. The tips were used to obtain SECM images of immobilized respiring E. coli, illustrating the suitability of BDD UMEs for electrochemical imaging in biological media. PMID:17295447

Holt, Katherine B; Hu, Jingping; Foord, John S

2007-03-15

163

Conductive polymer-modified boron-doped diamond for DNA hybridization analysis  

NASA Astrophysics Data System (ADS)

In this paper, we study the immobilization of DNA on boron-doped diamond (BDD) thin films for DNA hybridization analysis. Taking advantage of the conducting nature of the BDD film, a thin layer of polyaniline/poly (acrylic acid) (PANI/PAA) composite polymer film could be readily electropolymerized onto the diamond surface. The carboxylic acid residues in the polymer film act as the binding sites for DNA attachment, whilst the conductive polymer matrix enhances the electron-transfer between DNA and the diamond surface. Fluorescence microscopy and cyclic voltammetry measurements indicate that the polymer-modified BDD has minimal non-specific DNA adsorption, and provides a stable transduction platform for DNA sensing.

Gu, Huiru; Su, Xiaodi; Loh, Kian Ping

2004-04-01

164

In vivo assessment of cancerous tumors using boron doped diamond microelectrode  

PubMed Central

The in vitro and in vivo electrochemical detection of the reduced form of glutathione (L-?-glutamyl-L-cysteinyl-glycine, GSH) using boron doped diamond (BDD) microelectrode for potential application in the assessment of cancerous tumors is presented. Accurate calibration curve for the determination of GSH could be obtained by the in vitro electrochemical measurements. Additionally, it was shown that it was possible to separate the detection of GSH from the oxidized form of glutathione (GSSG) using chronoamperometry measurements. In vivo GSH detection measurements have been performed in human cancer cells inoculated in immunodeficient mice. These measurements have shown that the difference of GSH level between cancerous and normal tissues can be detected. Moreover, GSH detection measurements carried out before and after X-ray irradiation have proved that it is possible to assess in vivo the decrease in GSH concentration in the tumor after a specific treatment. PMID:23198091

Fierro, Stéphane; Yoshikawa, Momoko; Nagano, Osamu; Yoshimi, Kenji; Saya, Hideyuki; Einaga, Yasuaki

2012-01-01

165

Observation of conduction electron spin resonance in boron-doped diamond  

NASA Astrophysics Data System (ADS)

We observe the electron spin resonance of conduction electrons in boron-doped (6400 ppm) superconducting diamond (Tc=3.8K). We clearly identify the benchmarks of conduction electron spin resonance (CESR): the nearly temperature independent electron spin resonance signal intensity and its magnitude, which is in good agreement with that expected from the density of states through the Pauli spin susceptibility. The temperature dependent CESR linewidth weakly increases with increasing temperature, which can be understood in the framework of the Elliott-Yafet theory of spin relaxation. An anomalous and yet unexplained relation is observed between the g-factor, CESR linewidth, and the resistivity using the empirical Elliott-Yafet relation.

Szirmai, Péter; Fábián, Gábor; Koltai, János; Náfrádi, Bálint; Forró, László; Pichler, Thomas; Williams, Oliver A.; Mandal, Soumen; Bäuerle, Christopher; Simon, Ferenc

2013-05-01

166

Boron-doped nanocrystalline silicon germanium thin films for uncooled infrared bolometer applications  

NASA Astrophysics Data System (ADS)

In this paper, boron-doped nanocrystalline Si0.78Ge0.22:H thin film is assessed for use as resistive sensing layer in uncooled infrared bolometer applications. The silicon germanium thin films were deposited by PECVD (plasma enhanced chemical vapor deposition) through decomposition of silane, germane and diborane diluted with argon at substrate temperature of 230 °C. Under optimum deposition parameters, the sensing films with modulate electrical resistivity (<104 ? cm) and high temperature coefficient of resistance (TCR) (>-3%/K) were obtained at room temperature. 1/f noise character in the form of the normalized Hooge parameter was measured in the frequency range of 1-64 Hz, resulting in a lower 1/f noise compared to other materials currently used for device application.

Xu, Rui; Li, Wei; He, Jian; Sun, Yan; Jiang, Ya-Dong

2013-05-01

167

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

SciTech Connect

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.

Bagraev, N. T., E-mail: Bagraev@mail.ioffe.ru; Kuzmin, R. V.; Gurin, A. S.; Klyachkin, L. E.; Malyarenko, A. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Mashkov, V. A. [Saint Petersburg State Polytechnical University (Russian Federation)

2014-12-15

168

Pulsed-laser crystallized highly conductive boron-doped microcrystalline silicon  

SciTech Connect

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.

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

1997-07-01

169

In vivo assessment of cancerous tumors using boron doped diamond microelectrode  

NASA Astrophysics Data System (ADS)

The in vitro and in vivo electrochemical detection of the reduced form of glutathione (L-?-glutamyl-L-cysteinyl-glycine, GSH) using boron doped diamond (BDD) microelectrode for potential application in the assessment of cancerous tumors is presented. Accurate calibration curve for the determination of GSH could be obtained by the in vitro electrochemical measurements. Additionally, it was shown that it was possible to separate the detection of GSH from the oxidized form of glutathione (GSSG) using chronoamperometry measurements. In vivo GSH detection measurements have been performed in human cancer cells inoculated in immunodeficient mice. These measurements have shown that the difference of GSH level between cancerous and normal tissues can be detected. Moreover, GSH detection measurements carried out before and after X-ray irradiation have proved that it is possible to assess in vivo the decrease in GSH concentration in the tumor after a specific treatment.

Fierro, Stéphane; Yoshikawa, Momoko; Nagano, Osamu; Yoshimi, Kenji; Saya, Hideyuki; Einaga, Yasuaki

2012-11-01

170

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

SciTech Connect

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.

An, Wei; Turner, C. H.

2009-11-12

171

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

SciTech Connect

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

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

2013-02-15

172

Superconductivity in Bulk, Hole-Doped Diamond  

NASA Astrophysics Data System (ADS)

Diamonds, synthesized at high pressure (9 GPa) and high temperature (2500-2800 K) in the systems boron carbide-graphite and boron-graphite, are heavily hole-doped by incorporation of boron into the diamond lattice. These diamonds were characterized by: X-ray diffraction, Raman scattering, NMR, SQUID magnetometry, calorimetry, Hall effect, resistivity and magnetic susceptibility measurements. They show an expanded (˜1 % in volume) lattice with a softened zone-centre optical phonon mode and reduced Debye temperature, and exhibit bulk superconductivity below Tc ˜4 K. Upper critical field, specific heat and resistivity measurements provide a consistent set of materials parameters that favor a conventional, weak coupling electron-phonon interpretation of the superconducting mechanism at high hole doping. Preliminary measurements of conductance spectra, obtained with contacts fabricated at the surface of these hole-doped diamonds, indicate the appearance of superconducting gap below Tc.

Sidorov, Vladimir

2005-03-01

173

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

PubMed

TiO2/graphene (TiO2-x/GR) composites, which are Ti(3+) 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 Ti(3+) self-doping on TiO2 nanorods and boron doping on graphene. PMID:24974890

Xing, Mingyang; Li, Xiao; Zhang, Jinlong

2014-01-01

174

Theoretical study of intermolecular interactions in nanoporous networks on boron doped silicon surface  

NASA Astrophysics Data System (ADS)

Supramolecular networks on a doped boron silicon surface under ultra high vacuum (UHV) have been recently obtained (Makoudi et al., 2013). The used molecule contains different end-groups, bearing either bromine, iodine or hydrogen atoms denoted 1,3,5-tri(4?-bromophenyl)benzene (TBB), 1,3,5-tri(4-iodophenyl)benzene (TIB) and 1,3,5-triphenyl-benzene (THB). To explain the formation of the nanoporous structures, interactions of the type aryl-X⋯H hydrogen bonds (X being a halogen atom) have been proposed. In order to obtain a complete insight of the stabilizing interaction in these networks adsorbed on the Si(1 1 1)?3x?3R30°-boron surface, we present a full density-functional-theory study taking the van der Waals interactions into account. We investigated the energetic and structural properties of three different nanoporous networks constituted by TBB, TIB and THB molecules. The electronic studies allow us to identify hydrogen bond and dipole-dipole intermolecular interactions in the supramolecular halogen networks, whereas only dipole-dipole interactions are present in the 1,3,5-triphenyl-benzene nanoporous network.

Boukari, Khaoula; Duverger, Eric; Hanf, Marie-Christine; Stephan, Régis; Sonnet, Philippe

2014-11-01

175

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

PubMed

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

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

2014-10-22

176

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

NASA Astrophysics Data System (ADS)

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-?m 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.

Sun, Fei; Driessen, Alfred; Wörhoff, Kerstin

2010-02-01

177

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

178

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

E-print Network

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

Nominanda, Helinda

2012-06-07

179

Electronic properties and dopant pairing behavior of manganese in boron-doped silicon  

NASA Astrophysics Data System (ADS)

Boron-doped silicon wafers implanted with low doses of manganese have been analyzed by means of deep-level transient spectroscopy (DLTS), injection-dependent lifetime spectroscopy, and temperature-dependent lifetime spectroscopy. While DLTS measurements allow the defect levels and majority carrier capture cross sections to be determined, the lifetime spectroscopy techniques allow analysis of the dominant recombination levels and the corresponding ratios of the capture cross sections. Interstitial manganese and manganese-boron pairs were found to coexist, and their defect parameters have been investigated. In good agreement with the literature, this study identifies the defect level of manganese-boron pairs to be located in the lower half of the band gap at an energy level of Ev+0.55 eV with a majority carrier capture cross section of ?p=3.5×10-13 cm2. The capture cross-section ratio was found to be k=?n/?p=6.0. This implies that the previously unknown minority carrier capture cross section is ?n=2.1×1012 cm2. Concerning the defect related to interstitial manganese, this study identifies the most recombination-active level to be located in the upper half of the band gap at EC-0.45 eV with a corresponding ratio of the capture cross sections of k =9.4. In addition, the temperature-dependent association time constant of manganese-boron pairs is determined to be ?assoc,Mn=8.3×105 K-1 cm-3(T /Ndop)exp(0.67 eV/kBT) and found to differ from that for iron by a factor of 3 at room temperature, allowing this association time constant to be used as a fingerprint for a possible contamination with manganese. Also, the diffusion coefficient of interstitial manganese in silicon is determined from these experiments in a temperature range from 70 to 120 °C. It can be represented by the expression DMn=6.9×10-4 cm2 s-1 exp(-0.67 eV/kBT).

Roth, T.; Rosenits, P.; Diez, S.; Glunz, S. W.; Macdonald, D.; Beljakowa, S.; Pensl, G.

2007-11-01

180

Homoepitaxial Boron Doped Diamond Anvil as Heating Element in a Diamond Anvil Cell  

NASA Astrophysics Data System (ADS)

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 ˜ 10^20/cm^3) 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 spatial 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 initial experiments with these diamond anvils we report on the measurement of the thermal conductivity of copper-beryllium using a single diamond heater and two thermocouples. We augment these measurements with measurements of sample pressure via ruby fluorescence and electrical resistance of the sample and diamond heater.

Montgomery, Jeffrey; Samudrala, Gopi; Vohra, Yogesh

2012-02-01

181

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

SciTech Connect

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.

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

182

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

183

Highly selective electrosynthesis of biphenols on graphite electrodes in fluorinated media.  

PubMed

The direct and selective phenol coupling reaction that provides biphenols still represents a challenge in organic synthesis. The recently developed electrosynthesis on boron-doped diamond anodes with fluorinated additives was developed further to allow the application to less-expensive electrodes and fluorinated media. This advanced protocol allows the highly selective anodic phenol coupling reaction on graphite with a broad scope. PMID:22109730

Kirste, Axel; Hayashi, Shotaro; Schnakenburg, Gregor; Malkowsky, Itamar M; Stecker, Florian; Fischer, Andreas; Fuchigami, Toshio; Waldvogel, Siegfried R

2011-12-01

184

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

PubMed

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

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

2014-10-01

185

Synthetic semiconductor diamond electrodes: The comparative study of the electrochemical behaviour of polycrystalline and single crystal boron-doped films  

Microsoft Academic Search

Capacitance and potentiodynamic measurements were conducted on single crystal (homoepitaxial) and polycrystalline boron-doped diamond thin-film electrodes. The impedance characteristics and kinetic data in the Ce3+\\/4+ redox system, even if having a great deal of variability, appeared to be similar for the two kinds of diamond electrodes, whereas the kinetics of redox reactions on crystalline diamond and amorphous diamond-like carbon films

Yu. V. Pleskov; Yu. E. Evstefeeva; M. D. Krotova; V. V. Elkin; V. M. Mazin; V. Ya. Mishuk; V. P. Varnin; I. G. Teremetskaya

1998-01-01

186

Effect of test environment on ductility and fracture behavior of boron-doped Ni3Al at 600C  

SciTech Connect

The work reported here was a preliminary effort to identify the factors responsible for the marked difference between ductility reported by Liu and Taub in the temperature range above 400 degrees C. The authors found that tensile ductility of boron-doped Ni3Al alloys is a strong function of test environment at 600 degrees C, with much lower ductilities observed in air than in vacuum.

Liu, C.T.; Lee, E.H.; White, C.L.

1985-10-01

187

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

188

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

PubMed Central

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

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

2010-01-01

189

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

PubMed

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

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

2011-09-15

190

Carbon doping of MBE GaAs and Ga 0.7Al 0.3As films using a graphite filament  

NASA Astrophysics Data System (ADS)

Carbon doped GaAs and Ga 0.7Al 0.3As films have been grown by molecular beam epitaxy using a resistively heated graphite filament. At moderate doping levels, the effect on carbon doping of the {V}/{III} flux ratio and the nature of the arsenic species was found to be minor. The GaAs films were doped from 1X10 15 to 5X10 19 cm -3 and the resulting hole mobilities were equivalent to beryllium doped films. Excellent doping uniformity was obtained for 3-inch diameter films. Ga 0.7Al 0.3As films were also doped from 9X10 17 to 3.4X10 19 cm -3. For the highest carbon doped films, lattice contractions were observed which were greater than for beryllium doping. The lattice contractions were analyzed with a model using tetrahedral covalent radii.

Hoke, W. E.; Lemonias, P. J.; Lyman, P. S.; Hendriks, H. T.; Weir, D.; Colombo, P.

1991-05-01

191

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

NASA Astrophysics Data System (ADS)

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.

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

2011-07-01

192

Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells.  

PubMed

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

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

2014-04-01

193

Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells  

PubMed Central

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

2014-01-01

194

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

PubMed

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

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

2014-06-21

195

Comparison of electrocatalytic characterization of boron-doped diamond and SnO2 electrodes  

NASA Astrophysics Data System (ADS)

Boron-doped diamond (BDD) and SnO2 electrodes were prepared by direct current plasma chemical vapor deposition (DC-PCVD) and sol-gel method, respectively. Electrochemical characterization of the two electrodes were investigated by phenol electrochemical degradation, accelerated service life test, cyclic voltammetry (CV) in phenol solution, polarization curves in H2SO4. The surface morphology and crystal structure of two electrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The results showed a considerable difference between the two electrodes in their electrocatalytic activity, electrochemical stability and surface properties. Phenol was readily mineralized to CO2 at BDD electrode, favoring electrochemical combustion, but its degradation was much slower at SnO2 electrode. The service life of BDD electrode was 10 times longer than that of SnO2. Higher electrocatalytic activity and electrochemical stability of BDD electrode arise from its high oxygen evolution potential and the physically absorbed hydroxyl radicals (rad OH) on electrode surface.

Lv, Jiangwei; Feng, Yujie; Liu, Junfeng; Qu, Youpeng; Cui, Fuyi

2013-10-01

196

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

PubMed Central

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

Cofan, Codru?a; Radovan, Ciprian

2008-01-01

197

Reusable platinum nanoparticle modified boron doped diamond microelectrodes for oxidative determination of arsenite.  

PubMed

Boron doped diamond (BDD) macro- and microelectrodes were modified by electrodeposition of platinum nanoparticles using a multipotential step electrodeposition technique and used for the oxidative determination of arsenite, As(III). The formation of Pt nanoparticles was evident from cyclic voltammetry measurement, whereas AFM and SEM revealed the size and size distribution of deposited Pt nanoparticles. Raman spectroscopy illustrated a correlation between the typical BDD signature and the number of platinum deposition cycles. Linear sweep voltammetry performed with the modified BDD microelectrode outperformed its macrocounterpart and resulted in very low detecting currents with enhanced signal-to-noise ratios. With linearity up to 100 ppb and a detection limit of 0.5 ppb, the electrochemical system was applicable for processing tap and river water samples. Over 150 repetitive runs could be performed, and electrochemical etching of platinum allowed the reuse of the BDD microelectrode. The presence of copper and chloride ions, the two most severe interferents at levels commonly found in groundwater, did not interfere with the assay. PMID:17222013

Hrapovic, Sabahudin; Liu, Yali; Luong, John H T

2007-01-15

198

Multichannel boron doped nanocrystalline diamond ultramicroelectrode arrays: design, fabrication and characterization.  

PubMed

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 (k(0)) 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)(6)(4-) ion at 100 mV·s(-1)) of 1.8 nA. The UMEAs are targeted for electrophysiological as well as analytical applications. PMID:22969367

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

2012-01-01

199

Boron Doped p-type Hydrogenated Nanocrystalline Silicon Films Grown by Hot Wire Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

In this paper we report on the effect of diborane (B2H6) flow rate on the microstructural and opto-electrical properties of p-type nc-Si:H films grown by HW-CVD method. An attempt has been made to elucidate the boron doping mechanism of the p-type nc-Si:H films. The correlation between B2H6 gas flow rate (FB2H6) and material properties including crystalline volume fraction (XRaman), crystallite size (dRaman), band gap (Eg) and hydrogen content (CH) has been established. We obtained p-type nc-Si:H films with high dark conductivity (?0.2 S/cm), high Eg (>2 eV) at low CH (<3.6 at. %). The employment of these films in nc-Si:H based p-i-n solar cell as a p-type window layer could have better collection of charge carriers when illuminated from p-side.

Pramod, M. R.; Kamble, M. M.; Waman, V. S.; Funde, A. M.; Sathe, V. G.; Gosavi, S. W.; Jadkar, S. R.

2011-10-01

200

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

PubMed Central

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

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

2015-01-01

201

Effect of ultraviolet light exposure to boron doped hydrogenated amorphous silicon oxide thin film  

NASA Astrophysics Data System (ADS)

We have investigated the effect of ultraviolet (UV) light exposure to boron doped (p-type) hydrogenated amorphous silicon oxide (p-a-SiO:H) thin semiconductor films by measuring changes in its structural, electrical and optical properties. After a 50 h of UV light soaking (LS) of the films, that have 1.2, 6.9, 15.2, 25.3 at.% oxygen content (C(O)) and optical gap (E04) of 1.897, 2.080, 2.146 and 2.033 eV, show a relative increase in the C(O) by 28.0%, 9.8%, 2.0%, 3.1%, a relative increase in the Urbach energy (Eu) by 42%, 24%, 8%, 0%, decrease in the E04 by 66, 2, 12, 19 meV and the gap state defect density (Nd) show an increase by 6.5%, 3.4%, 0.7%, 0.1%. At higher oxygen content the observed UV light induced degradation (LID) is relatively less than that for films with lower oxygen content, indicating that higher oxides face less changes under the UV light.

Baek, Seungsin; Iftiquar, S. M.; Jang, Juyeon; Lee, Sunhwa; Kim, Minbum; Jung, Junhee; Park, Hyeongsik; Park, Jinjoo; Kim, Youngkuk; Shin, Chonghoon; Lee, Youn-Jung; Yi, Junsin

2012-11-01

202

Electrochemical incineration of sulfanilic acid at a boron-doped diamond anode.  

PubMed

The anodic oxidation of sulfanilic acid solutions has been studied in acidic medium using a divided cell with a boron-doped diamond (BDD) anode and a stainless steel cathode. Overall mineralization was achieved under all experimental conditions tested due to the efficient destruction of sulfanilic acid and all its by-products with hydroxyl radicals generated at the BDD anode from water oxidation. The alternative use of an undivided cell with the same electrodes gave rise to the coating of the cathode with polymeric compounds, thus preventing the complete electrochemical incineration of sulfanilic acid. The solutions treated in the anodic compartment of the divided cell were degraded at similar rate under pH regulation within the pH interval 2.0-6.0. The mineralization current efficiency was enhanced when the applied current decreased and the initial substrate concentration increased. The decay of sulfanilic acid was followed by reversed-phase HPLC, showing a pseudo first-order kinetics. Hydroquinone and p-benzoquinone were identified as aromatic intermediates by gas chromatography-mass spectrometry and/or reversed-phase HPLC. Maleic, acetic, formic, oxalic and oxamic acids were detected as generated carboxylic acids by ion-exclusion HPLC. Ionic chromatographic analysis of electrolyzed solutions revealed that the N content of sulfanilic acid was mainly released as NH(4)(+) ion and in much smaller proportion as NO(3)(-) ion. PMID:22365277

El-Ghenymy, Abdellatif; Arias, Conchita; Cabot, Pere Lluís; Centellas, Francesc; Garrido, José Antonio; Rodríguez, Rosa María; Brillas, Enric

2012-06-01

203

Kinetic study of electro-Fenton oxidation of azo dyes on boron-doped diamond electrode.  

PubMed

The present work compares electrochemical degradation of red and blue azo textile dyes in single- and two-compartment electrochemical cells in the presence of Fenton reagent (Fe2+) and using a boron-doped diamond anode. Degradation of both dyes was related to the concentration of dye, applied current density and the concentration of FeSO4 catalyst. Complete colour removal and approximately 91% of organic matter oxidation was achieved in a two-compartment electrochemical cell at an applied current density of 20 mA x cm(-2), pH of 3 and Fe(2+) ion concentration of 0.02 mM. Higher current density and reaction time were required to achieve the same removals in a one-compartment electrochemical cell. Dye degradation kinetics as well as chemical oxygen demand removal rate were successfully modelled to pseudo first-order kinetics. The apparent first-order rate constants (k(o)) for degradation of red dye with an initial concentration of 20, 40 and 60 ppm were found to be 2.67 +/- 0.16, 2.19 +/- 0.09 and 1.5 +/- 0.03 min(-1), and for blue dye at the same initial concentrations were 1.99 +/- 0.2, 0.95 +/- 0.02 and 0.71 +/- 0.030 min(-1), respectively. PMID:24191481

Almomani, Fares; Baranova, Elena A

2013-01-01

204

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

SciTech Connect

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.

A. Manivannan; M.S. Seehra

2003-08-19

205

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

PubMed Central

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

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

2012-01-01

206

Anodic oxidation of textile dyehouse effluents on boron-doped diamond electrode.  

PubMed

The electrochemical oxidation of textile effluents over a boron-doped diamond anode was investigated in the present study. Experiments were conducted with a multi-component synthetic solution containing seventeen dyes and other auxiliary inorganics, as well as an actual effluent from a textile dyeing process. The effect of varying operating parameters, such as current density (4-50 mA/cm2), electrolyte concentration (0.1-0.5 M HClO4), initial solution pH (1-12.3) and temperature (22-43 °C), on process efficiency was investigated following changes in total organic carbon (TOC), chemical oxygen demand (COD) and color. Complete decolorization accompanied by significant mineralization (up to 85% depending on the conditions) could be achieved after 180 min of treatment. Performance was improved at higher electrolyte concentrations and lower pH values, while the effect of temperature was marginal. Energy consumption per unit mass of COD removed was favored at lower current densities, since energy was unnecessarily wasted to side reactions at higher densities. PMID:21530081

Tsantaki, Eleni; Velegraki, Theodora; Katsaounis, Alexandros; Mantzavinos, Dionissios

2012-03-15

207

Electrochemical oxidation and electroanalytical determination of xylitol at a boron-doped diamond electrode.  

PubMed

Xylitol is a reduced sugar with anticariogenic properties used by insulin-dependent diabetics, and which has attracted great attention of the pharmaceutical, cosmetics, food and dental industries. The detection of xylitol in different matrices is generally based on separation techniques. Alternatively, in this paper, the application of a boron-doped diamond (BDD) electrode allied to differing voltammetric techniques is presented to study the electrochemical behavior of xylitol, and to develop an analytical methodology for its determination in mouthwash. Xylitol undergoes two oxidation steps in an irreversible diffusion-controlled process (D=5.05 × 10(-5)cm(2)s(-1)). Differential pulse voltammetry studies revealed that the oxidation mechanism for peaks P1 (3.4 ? pH ? 8.0), and P2 (6.0 ? pH ? 9.0) involves transfer of 1H(+)/1e(-), and 1e(-) alone, respectively. The oxidation process P1 is mediated by the (•)OH generated at the BDD hydrogen-terminated surface. The maximum peak current was obtained at a pH of 7.0, and the electroanalytical method developed, (employing square wave voltammetry) yielded low detection (1.3 × 10(-6) mol L(-1)), and quantification (4.5 × 10(-6) mol L(-1)) limits, associated with good levels of repeatability (4.7%), and reproducibility (5.3%); thus demonstrating the viability of the methodology for detection of xylitol in biological samples containing low concentrations. PMID:24401449

Lourenço, Anabel S; Sanches, Fátima A C; Magalhães, Renata R; Costa, Daniel J E; Ribeiro, Williame F; Bichinho, Kátia M; Salazar-Banda, Giancarlo R; Araújo, Mário C U

2014-02-01

208

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

NASA Astrophysics Data System (ADS)

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.

Liu, AnYao; Sun, Chang; Macdonald, Daniel

2014-11-01

209

Influence of Ball-Milling Treatment of B Original Powder on the Phase Formation and Critical Current Density of Graphite Doped MgB  

NASA Astrophysics Data System (ADS)

In present work, the sintering process and superconducting properties of graphite doped MgB prepared with milled B original powder were investigated. It is found that ball milling treatment of B original powder obviously suppresses the solid-solid reaction between Mg and B, whereas it enhances their liquid-solid reaction during the subsequent sintering process of these graphite doped MgB bulks. Ball milling treatment of B original powder can also promote C substitution for B sites in MgB crystal lattice in the graphite-doped samples, and thus obviously increase their values of at high fields. Moreover, ball milling also refines MgB grains, enhancing grain boundary pinning and at high fields.

Su, Xiaocheng; Jiang, Qingguo; Zuo, Anying

2014-10-01

210

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

SciTech Connect

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.

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

2014-03-28

211

High-rate oxygen electroreduction over graphitic-N species exposed on 3D hierarchically porous nitrogen-doped carbons.  

PubMed

Nitrogen-doped species (NDs) are theoretically accepted as a determinant of the catalytic activity of metal-free N-doped carbon (NC) catalysts for oxygen reduction reaction (ORR). However, direct relationships between ND type and ORR activity have been difficult to extract because the complexity of carbon matrix impairs efforts to expose specific NDs. Herein, we demonstrate the fabrication of a 3D hierarchically porous NC catalyst with micro-, meso-, and macroporosity in one structure, in which sufficient exposure and availability of inner-pore catalytic sites can be achieved due to its super-high surface area (2191?cm(2) ?g(-1) ) and interconnected pore system. More importantly, in-situ formation of graphitic-N species (GNs) on the surface of NC stimulated by KOH activation enables us to experimentally reveal the catalytic nature of GNs for ORR, which is of great significance for the design and development of advanced metal-free NC electrocatalysts. PMID:25044805

He, Wenhui; Jiang, Chunhuan; Wang, Jiabo; Lu, Lehui

2014-09-01

212

Comparison of Lateral Resolution of Fine Stripes Beryllium and Boron Implanted by Focused Ion Beam in Si-Doped AlGaAs/GaAs Multiquantum Wells  

NASA Astrophysics Data System (ADS)

Using impurity controlled Al-Ga intermixing in Si-doped Multi-Quantum Wells (MQW), a highly anisotropic Be diffusion after Focused Ion Beam (FIB) implantation and thermal annealing was measured by Auger Al profiles analysis, with a Be lateral diffusion dependent on the scan speed of ion beam. Then, after the demonstration of Al-Ga intermixing suppression by Boron FIB implantation, an improved lateral pattern resolution was obtained with Boron implantation in Sidoped MQW.

Brillouet, Francois; Ishida, Koji; Morita, Tetsuo; Miyauchi, Eizo; Takamori, Takeshi; Nakashima, Hisao

1987-08-01

213

Fullerene-like boron clusters stabilized by an endohedrally doped iron atom: BnFe with n = 14, 16, 18 and 20.  

PubMed

Stabilized fullerene and tubular forms can be produced in boron clusters Bn in small sizes from n? 14 to 20 upon doping by transition metal atoms. B14Fe and B16Fe are stable tubes whereas B18Fe and B20Fe are stable fullerenes. Their formation and stability suggest the use of dopants to induce different growth paths leading to larger cages, fullerenes and tubes of boron. PMID:25557191

Tam, Nguyen Minh; Pham, Hung Tan; Duong, Long Van; Pham-Ho, My Phuong; Nguyen, Minh Tho

2015-02-01

214

Enhanced capacitance of composite TiO2 nanotube/boron-doped diamond electrodes studied by impedance spectroscopy  

NASA Astrophysics Data System (ADS)

We report on novel composite nanostructures based on boron-doped diamond thin films grown on top of TiO2 nanotubes. The nanostructures made of BDD-modified titania nanotubes showed an increase in activity and performance when used as electrodes in electrochemical environments. The BDD thin films (~200-500 nm) were deposited using microwave plasma assisted chemical vapor deposition (MW PA CVD) onto anodically fabricated TiO2 nanotube arrays. The influence of boron-doping level, methane admixture and growth time on the performance of the Ti/TiO2/BDD electrode was studied in detail. Scanning electron microscopy (SEM) was applied to investigate the surface morphology and grain size distribution. Moreover, the chemical composition of TiO2/BDD electrodes was investigated by means of micro-Raman spectroscopy. The composite electrodes TiO2/BDD are characterized by a significantly higher capacitive current compared to BDD films deposited directly onto a Ti substrate. The novel composite electrode of TiO2 nanotube arrays overgrown by boron-doped diamond (BDD) immersed in 0.1 M NaNO3 can deliver a specific capacitance of 2.10, 4.79, and 7.46 mF cm-2 at a scan rate of 10 mV s-1 for a [B]/[C] ratio of 2k, 5k and 10k, respectively. The substantial improvement of electrochemical performance and the excellent rate capability could be attributed to the synergistic effect of TiO2 treatment in CH4 : H2 plasma and the high electrical conductivity of BDD layers. The analysis of electrochemical impedance spectra using an electric equivalent circuit allowed us to determine the surface area on the basis of the value of constant phase element.

Siuzdak, K.; Bogdanowicz, R.; Sawczak, M.; Sobaszek, M.

2014-12-01

215

Enhanced capacitance of composite TiO2 nanotube/boron-doped diamond electrodes studied by impedance spectroscopy.  

PubMed

We report on novel composite nanostructures based on boron-doped diamond thin films grown on top of TiO2 nanotubes. The nanostructures made of BDD-modified titania nanotubes showed an increase in activity and performance when used as electrodes in electrochemical environments. The BDD thin films (?200-500 nm) were deposited using microwave plasma assisted chemical vapor deposition (MW PA CVD) onto anodically fabricated TiO2 nanotube arrays. The influence of boron-doping level, methane admixture and growth time on the performance of the Ti/TiO2/BDD electrode was studied in detail. Scanning electron microscopy (SEM) was applied to investigate the surface morphology and grain size distribution. Moreover, the chemical composition of TiO2/BDD electrodes was investigated by means of micro-Raman spectroscopy. The composite electrodes TiO2/BDD are characterized by a significantly higher capacitive current compared to BDD films deposited directly onto a Ti substrate. The novel composite electrode of TiO2 nanotube arrays overgrown by boron-doped diamond (BDD) immersed in 0.1 M NaNO3 can deliver a specific capacitance of 2.10, 4.79, and 7.46 mF cm(-2) at a scan rate of 10 mV s(-1) for a [B]/[C] ratio of 2k, 5k and 10k, respectively. The substantial improvement of electrochemical performance and the excellent rate capability could be attributed to the synergistic effect of TiO2 treatment in CH4?:?H2 plasma and the high electrical conductivity of BDD layers. The analysis of electrochemical impedance spectra using an electric equivalent circuit allowed us to determine the surface area on the basis of the value of constant phase element. PMID:25413987

Siuzdak, K; Bogdanowicz, R; Sawczak, M; Sobaszek, M

2014-12-11

216

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

SciTech Connect

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

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

2011-01-15

217

Electrochemical oxidation of underivatized-nucleic acids at highly boron-doped diamond electrodes.  

PubMed

Boron-doped diamond (BDD) electrodes have been examined for the electrochemical oxidation of underivatized-nucleic acids in terms of single stranded and double stranded DNA. Cyclic voltammetry and square wave voltammetry have been used to study the oxidation reactions and to detect DNA without derivatization or hydrolysis steps. At the diamond electrode, at least two well-defined voltammetric peaks were observed for both single stranded and double stranded DNA. Diamond electrode is the first material to show a well-defined voltammetric peaks for adenine group oxidation directly in the helix structure of nucleic acid due to its wide potential window. For single stranded DNA, a third peak, related to the pyrimidine group oxidation was also observed. As-deposited diamond film with predominantly hydrogen-terminated surface exhibited superior performance over oxygen-terminated diamond in terms of sensitivity. However, by optimizing the ionic strength, sensitivity of O-terminated films could be improved. Linear calibration results have shown linearity of current with concentration in the range 0.1-8 microg mL(-1) for both guanine and adenine residues at as-deposited BDD. Detection limits (S/N = 3) of 3.7 and 10 ng mL(-1) for adenine and guanine residue in single stranded DNA, respectively, and 5.2 and 10 ng mL(-1) for adenine and guanine residue in double stranded DNA, respectively, were observed. This work shows the promising use of diamond as an electrochemical detector for direct detection of nucleic acids. The results also show the possibility of using the oxidation peak current of adenine group that is more sensitive for the direct detection of nucleicacids. PMID:12894832

Ivandini, T A; Sarada, B V; Rao, T N; Fujishima, A

2003-07-01

218

Facet-selective platinum electrodeposition at free-standing polycrystalline boron-doped diamond films.  

PubMed

In the present investigation, electrochemical deposition of platinum particles was carried out on boron doped diamond (BDD) films by using cyclic voltammetry at different potential sweep rates while maintaining the Pt concentration and number of potential cycles during the deposition as constant for all samples. The BDD film surfaces were studied using Raman spectroscopy, X-ray diffraction, and scanning electrochemical microscopy. The deposited particles were characterized by scanning electron microscopy/X-ray energy dispersive analysis, X-ray photoelectron spectroscopy, and cyclic voltammetry before and after methanol oxidation. The platinum nanoparticles are found to be selectively electrodeposited on the (111) facets of the BDD. In addition, the location of the Pt particles on the diamond facets was affected by the potential sweep rate. For higher sweep rates, the particle size was dependent on the facet on which the particles are electrodeposited with smooth (110) facets exhibiting a smaller number of particles but with a larger particle diameter. After methanol oxidation studies using cyclic voltammetry and controlled potential electrolysis for several hours, the platinum particles remained attached to the (111) facets of the BDD, while the particles on the (110) facets of the BDD became agglomerated along grain boundaries. Functional groups present on the (111) facet of the diamond surface play an important role on the stability of the particles attached to the diamond surface. After methanol oxidation, the particles deposited on other facets appeared to lose their adhesion leading to agglomeration on the grain boundaries. BDD appears to be a promising electrocatalyst support material that can help to resist platinum nanoparticle agglomeration in direct methanol and other low temperature fuel cell applications. PMID:19634868

González-González, Ileana; Fachini, Estevão Rosim; Scibioh, M Aulice; Tryk, Donald A; Tague, Michele; Abruña, Héctor D; Cabrera, Carlos R

2009-09-01

219

Electrochemical detection of tyrosine derivatives and protein tyrosine kinase activity using boron-doped diamond electrodes.  

PubMed

In this report, we determined protein tyrosine kinase (PTKs) activity in human epidermoid carcinoma cells (A431) by employing a novel electrochemical method using boron-doped diamond (BDD) electrodes that enables the electrochemical oxidation of tyrosine (Tyr), phosphorylated Tyr (Tyr-P) and sulfated Tyr (Tyr-S) in water-based solutions. Cyclic voltammetry for Tyr, Tyr-P and Tyr-S showed well-defined oxidation peaks at 0.8 V for Tyr, 1.4V for Tyr-P and 1.7 V for Tyr-S, respectively. Very little work has been reported previously on the detection of Tyr-P and Tyr-S, probably due to their high oxidation potentials. We utilized electrochemical methods for the detection of kinase activity in connection with poly(Glu-Tyr) modified magnetic beads. Linear-sweep voltammograms for the electrochemical detection of PTKs activity were carried out using BDD electrodes consisting of peptide-modified magnetic beads. Without phosphorylation of the peptide-modified magnetic beads using PTKs, we observed clear oxidation peaks for Tyr oxidation and no significant electrochemical responses for Tyr-P oxidation at 1.4V for the background. On the other hand, with phosphorylation of the beads using PTKs, the peak oxidation current at 1.4V clearly increased, while the peak oxidation current for Tyr oxidation decreased. This indicates that PTKs activity could be successfully detected by using electrochemical methods employing BDD electrodes. This method was utilized for the in vitro kinase activity detection of human cell lysate, and the electrochemical measurements were compatible with the Enzyme-Linked ImmunoSorbent Assay based method. Our results indicate that the electrochemical method can be applied to real samples such as cell lysate. PMID:20634053

Chiku, Masanobu; Horisawa, Kenichi; Doi, Nobuhide; Yanagawa, Hiroshi; Einaga, Yasuaki

2010-09-15

220

Electrochemical detection of sugar-related compounds using boron-doped diamond electrodes.  

PubMed

Electrochemical detection of sugar-related compounds was conducted using a boron-doped diamond (BDD) electrode as a detector for flow-injection analysis (FIA). Sugar-related compounds oxidize at high applied potentials, for which the BDD electrode is suitable for electrochemical measurements. Conditions for an FIA system with a BDD detector were optimized, and the following detection limits were achieved for sugar-related compounds: monosaccharides, 25-100 pmol; sugar alcohols, 10 pmol; and oligosaccharides, 10 pmol. The detection limit for monosaccharide D-glucose (Glu) was 105 pmol (S/N = 3). A linear range was acquired from the detection limit to 50 nmol, and the relative standard deviation was 0.65% (20 nmol, n = 6). A high-performance liquid chromatography (HPLC) column was added to the system between the sample injector and the detector and detection limits to the picomole level were achieved, which is the same for the HPLC system and the FIA system. The electrochemical oxidation reaction of Glu was examined using cyclic voltammetry with the BDD detector. The reaction proved to be irreversible, and proceeded according to the following two-step mechanism: (1) application of a high potential (2.00 V vs. Ag/AgCl) to the electrode causes water to electrolyze on the electrode surface with the simultaneous generation of a hydroxyl radical on the surface, and (2) the hydroxyl radical indirectly oxidizes Glu. Thus, Glu can be detected by an increase in the oxidation current caused by reactions with hydroxy radicals. PMID:22322804

Hayashi, Tomohisa; Sakurada, Ikuo; Honda, Kensuke; Motohashi, Shigeyasu; Uchikura, Kazuo

2012-01-01

221

Development of amperometric immunosensor using boron-doped diamond with poly(o-aminobenzoic acid).  

PubMed

An alternative method of a protein immunosensor has been developed at boron-doped diamond (BDD) electrode material. In order to construct the base of the immunosensor, o-aminobenzoic acid (o-ABA) was electropolymerized at an electrode by cyclic voltammetry. The poly-o-ABA-modified BDD was characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The XPS result found that carboxyl groups were formed at the electrode surface. The carboxyl groups were then used to covalently attach protein probes. The amperometric sensing of mouse IgG (MIgG) was selected as the model at the poly-o-ABA-modified BDD to compare to the poly-o-ABA-modified glassy carbon (GC) at the same condition. An antimouse IgG from goat (GaMIgG) was covalently immobilized at a poly-o-ABA-modified BDD electrode which used a sandwich-type alkaline phosphatase (ALP) catalyzing amperometric immunoassay with 2-phospho-L-ascorbic acid (AAP) as substrate. The ALP enzyme conjugated at the immunosensor can generate AAP to the electroactive species of ascorbic acid (AA), which can be determined by amperometric detection. The signal was found to be proportional with the quantity of MIgG. The limits of detection (LODs) of 0.30 (3 SD) and 3.50 ng mL(-1) (3 SD) for MIgG at BDD and GC electrodes were obtained. It also was found that the dynamic range of 3 orders of magnitude (1-1000 ng mL(-1)) was obtained at BDD, whereas at GC, the dynamic range was more narrow (10-500 ng mL(-1)). The method was applied to a real mouse serum sample that contains MIgG. PMID:18271566

Preechaworapun, Anchana; Ivandini, Tribidasari A; Suzuki, Akane; Fujishima, Akira; Chailapakul, Orawon; Einaga, Yasuaki

2008-03-15

222

Mechanism of perchlorate formation on boron-doped diamond film anodes.  

PubMed

This research investigated the mechanism of perchlorate (ClO(4)(-)) formation from chlorate (ClO(3)(-)) on boron-doped diamond (BDD) film anodes by use of a rotating disk electrode reactor. Rates of ClO(4)(-) formation were determined as functions of the electrode potential (2.29-2.70 V/standard hydrogen electrode, SHE) and temperature (10-40 °C). At all applied potentials and a ClO(3)(-) concentration of 1 mM, ClO(4)(-) production rates were zeroth-order with respect to ClO(4)(-) concentration. Experimental and density functional theory (DFT) results indicate that ClO(3)(-) oxidation proceeds via a combination of direct electron transfer and hydroxyl radical oxidation with a measured apparent activation energy of 6.9 ± 1.8 kJ·mol(-1) at a potential of 2.60 V/SHE. DFT simulations indicate that the ClO(4)(-) formation mechanism involves direct oxidation of ClO(3)(-) at the BDD surface to form ClO(3)(•), which becomes activationless at potentials > 0.76 V/SHE. Perchloric acid is then formed via the activationless homogeneous reaction between ClO(3)(•) and OH(•) in the diffuse layer next to the BDD surface. DFT simulations also indicate that the reduction of ClO(3)(•) can occur at radical sites on the BDD surface to form ClO(3)(-) and ClO(2), which limits the overall rate of ClO(4)(-) formation. PMID:22029642

Azizi, Orchideh; Hubler, David; Schrader, Glenn; Farrell, James; Chaplin, Brian P

2011-12-15

223

Effect of select organic compounds on perchlorate formation at boron-doped diamond film anodes.  

PubMed

Rates of ClO4(-) formation from ClO3(-) oxidation were investigated in batch experiments as a function of organic compounds (p-nitrophenol, p-benzoquinone, p-methoxyphenol, and oxalic acid) and current density using boron-doped diamond film anodes. Excluding organics, ClO4(-) formation rates ranged from 359 to 687 ?moles m(-2) min(-1) for current densities of 1-10 mA cm(-2). The presence of p-substituted phenols inhibited ClO4(-) formation rates between 13.0 and 99.6%. Results from a reactive-transport model of the diffuse layer adjacent to the anode surface indicate that competition between organics and ClO3(•) for OH(•) within a reaction zone (0.02-0.96 ?m) adjacent to the anode controls ClO4(-) formation. Under kinetic-limited conditions (1.0 mA cm(-2)), organics reach the anode surface and substrates with higher OH(•) reaction rates demonstrate greater inhibition of perchlorate formation (IPF). At higher current densities (10 mA cm(-2)), organic compound oxidation becomes mass transfer-limited and compounds degrade a small distance from the anode surface (? 0.26 ?m for p-methoxyphenol). Therefore, OH(•) scavenging does not occur at the anode surface and IPF values decrease. Results provide evidence for the existence of desorbed OH(•) near the anode surface and highlight the importance of controlling reactor operating conditions to limit ClO4(-) production during anodic treatment of organic compounds. PMID:24066803

Donaghue, Adrienne; Chaplin, Brian P

2013-11-01

224

Boron-doped diamond electrodes for the electrochemical oxidation and cleavage of peptides.  

PubMed

Electrochemical oxidation of peptides and proteins is traditionally performed on carbon-based electrodes. Adsorption caused by the affinity of hydrophobic and aromatic amino acids toward these surfaces leads to electrode fouling. We compared the performance of boron-doped diamond (BDD) and glassy carbon (GC) electrodes for the electrochemical oxidation and cleavage of peptides. An optimal working potential of 2000 mV was chosen to ensure oxidation of peptides on BDD by electron transfer processes only. Oxidation by electrogenerated OH radicals took place above 2500 mV on BDD, which is undesirable if cleavage of a peptide is to be achieved. BDD showed improved cleavage yield and reduced adsorption for a set of small peptides, some of which had been previously shown to undergo electrochemical cleavage C-terminal to tyrosine (Tyr) and tryptophan (Trp) on porous carbon electrodes. Repeated oxidation with BDD electrodes resulted in progressively lower conversion yields due to a change in surface termination. Cathodic pretreatment of BDD at a negative potential in an acidic environment successfully regenerated the electrode surface and allowed for repeatable reactions over extended periods of time. BDD electrodes are a promising alternative to GC electrodes in terms of reduced adsorption and fouling and the possibility to regenerate them for consistent high-yield electrochemical cleavage of peptides. The fact that OH-radicals can be produced by anodic oxidation of water at elevated positive potentials is an additional advantage as they allow another set of oxidative reactions in analogy to the Fenton reaction, thus widening the scope of electrochemistry in protein and peptide chemistry and analytics. PMID:23763302

Roeser, Julien; Alting, Niels F A; Permentier, Hjalmar P; Bruins, Andries P; Bischoff, Rainer

2013-07-16

225

Square-wave voltammetric determination of propranolol and atenolol in pharmaceuticals using a boron-doped diamond electrode  

Microsoft Academic Search

The independent determination of two ?-blocker agents, namely propranolol (PROP) and atenolol (ATN), in pharmaceutical formulations using square-wave voltammetry and a cathodically pretreated boron-doped diamond electrode is described. These electroanalytical determinations of propranolol or atenolol were carried out in 0.1molL?1 H2SO4 or 0.5molL?1 NaNO3 (pH 1.0, adjusted with concentrated HNO3), respectively. Excellent linear calibration curves, ranging from 0.20 to 9.0?molL?1

Elen Romão Sartori; Roberta Antigo Medeiros; Romeu C. Rocha-Filho; Orlando Fatibello-Filho

2010-01-01

226

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

PubMed

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

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

2014-06-11

227

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

PubMed

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

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

228

Non-enzymatic glucose detection using as-prepared boron-doped diamond thin-film electrodes.  

PubMed

Electrochemical oxidation of glucose in alkaline solution at as-prepared boron-doped microcrystalline diamond (BDMD) and nanocrystalline diamond (BDND) thin-film electrodes is investigated by cyclic voltammetry. The results demonstrate that glucose can be directly oxidized at as-prepared boron-doped diamond (BDD) thin-film electrodes and the curve of the negative scan traces onto the positive scan. The effect of sodium hydroxide concentration on the response of glucose is also studied in the range of 0.02-0.6 M and the optimum concentration of sodium hydroxide is found to be 0.1 M. The voltammetric signal of glucose and the mixture of ascorbic acid (AA) and uric acid (UA) can be observed well-separated at as-prepared BDD thin-film electrodes in 0.1 M sodium hydroxide solution. The peak current is proportional to the glucose concentration in the range 0.25-10 mM with a correlation coefficient of 0.9993 in the presence of AA and UA. Furthermore, the experiment results also show that the non-enzymatic glucose sensor based on as-prepared BDD thin-film electrodes has high sensitivity, good reproducibility and stability. PMID:19305932

Zhao, Jianwen; Wu, Liangzhuan; Zhi, Jinfang

2009-04-01

229

The electrochemical oxidation of homocysteine at boron-doped diamond electrodes with application to HPLC amperometric detection.  

PubMed

The electrochemical oxidation of homocysteine was studied at as-deposited and anodized (oxidized) boron-doped diamond (BDD) thin film electrodes with cyclic voltammetry, flow injection analysis and high-pressure liquid chromatography with amperometric detection. At anodized boron-doped diamond electrodes, highly reproducible, well-defined cyclic voltammograms for homocysteine oxidation were obtained in acidic media, while as-deposited diamond did not provide a detectable signal. In alkaline media, however, the oxidation response was obtained both at as-deposited and anodized diamond electrodes. The potential sweep rate dependence of homocysteine oxidation (peak currents for 1 mM homocysteine linearly proportional to v(1/2), within the range of 0.01 to 0.3 V s(-1)) indicates that the oxidation involves a diffusing species, with negligible adsorption on the BDD surface at this concentration. In the flow system, BDD exhibited a highly reproducible amperometric response, with a peak variation less than 2%. An extremely low detection limit (1 nM) was obtained at 1.6 V vs. Ag/AgCl. In addition, the determination of homocysteine in a standard mixture with aminothiols and disulfide compounds by means of isocratic reverse-phase HPLC with amperometric detection at diamond electrodes has been investigated. The results showed excellent separation, with a detection limit of 1 pmol and a linear range of three orders of magnitude. PMID:12375837

Chailapakul, O; Siangproh, W; Sarada, B V; Terashima, C; Rao, Tata N; Tryk, D A; Fujishima, A

2002-09-01

230

Retention of enzyme activity with a boron-doped diamond electrode in the electro-oxidative nitration of lysozyme  

PubMed Central

In this paper we report the successful use of a non-metallic electrode material, boron-doped diamond (BDD), for the anodic electro-oxidative modification of hen egg white lysozyme (HEWL). Platinum electrodes can give rise to loss of activity of HEWL in electrosynthetic studies, whereas activity is retained on boron-doped diamond which is proposed as an effective substitute material for this purpose. We also compare literature methods of electrode pre-treatment to determine the most effective in electrosynthesis. Our findings show a decrease in total nitroprotein yield with decreasing nitrite concentration and an increase with increasing solution pH, confirming that, at a BDD electrode, the controlling factor remains the concentration of tyrosine phenolate anion. Purification of mono- and bis-nitrated HEWL and assay of enzymic activity showed better retention of activity at BDD electrode surfaces when compared to platinum. The products from electro-oxidation of HEWL at BDD were confirmed by electrospray ionization Fourier transform ion cyclotron resonance (ESI-FT-ICR) mass spectrometry, which revealed unique mass increases of +45 and +90 Da for the mono- and bis-nitrated lysozyme, respectively, corresponding to nitration at tyrosine residues. The nitration sites were confirmed as Tyr23 and Tyr20. PMID:21760652

Iniesta, Jesús; Esclapez-Vicente, María Deseada; Heptinstall, John; Walton, David J.; Peterson, Ian R.; Mikhailov, Victor A.; Cooper, Helen J.

2010-01-01

231

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

PubMed

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 ?M, 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 ?M. 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

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

2013-07-01

232

Catalytic activity of platinum nanoparticles on highly boron-doped and 100-oriented epitaxial diamond towards HER and HOR.  

PubMed

Platinum nanoparticles supported on boron-doped single-crystalline diamond surfaces were used as a model system to investigate the catalytic activity with respect to the influence of particle morphology, particle density and surface preparation of the diamond substrates. We report on the preparation, characterization and activity regarding hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) of these Pt/diamond electrodes. Two kinds of diamond layers with boron doping above 10(20) cm(-3) were grown epitaxially on (100)-oriented diamond substrates; post-treatments of wet chemical oxidation and radio frequency (rf) oxygen plasma treatments were applied. Electrochemical deposition of Pt was performed using a potentiostatic double-pulse technique, which allowed variation of the particle size in the range between 1 nm and 15 nm in height and 5 nm and 50 nm in apparent radius, while keeping the particle density constant. Higher nucleation densities on the plasma processed surface at equal deposition parameters could be related to the plasma-induced surface defects. Electrochemical characterization shows that the platinum particles act as nanoelectrodes and form an ohmic contact with the diamond substrate. The catalytic activity regarding HER and HOR of the platinum nanoparticles exhibits no dependence on the particle size down to particle heights of ?1 nm. The prepared Pt on diamond(100) samples show a similar platinum-specific activity as bulk platinum. Therefore, while keeping the activity constant, the well-dispersed particles on diamond offer an optimized surface-to-material ratio. PMID:21687867

Brülle, Tine; Denisenko, Andrej; Sternschulte, Hadwig; Stimming, Ulrich

2011-07-28

233

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

PubMed

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, ?, +0.68 mV K(-1)) and negatively for the IrCl6(3-/2-) couple (? = -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

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

2014-01-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

235

Growth kinetics and boron doping of very high Ge content SiGe for source/drain engineering  

NASA Astrophysics Data System (ADS)

We have studied the in-situ boron doping of high Ge content Si 1-xGe x layers ( x=0.3, 0.4 and 0.5). These layers have been grown at low pressure (20 Torr) and low temperature (600-650 °C) with a heavily chlorinated chemistry on blanket Si(0 0 1) substrates. Such a chemistry yields a full selectivity versus SiO 2 (isolation) and Si 3N 4 (sidewall spacers) on patterned wafers with gate stacks. We have quantified the impact of the diborane flow on the SiGe layer crystalline quality, its resistivity, the SiGe:B growth rate and the apparent Ge concentration. Resistivity values lower than 1 m? cm are easily achieved, all the more so for high Ge content layers. The SiGe growth rate increases and the apparent Ge concentration (from X-ray diffraction) decreases as the diborane flow increases. B atoms (much smaller than Si or Ge) indeed partially compensate the compressive strain in the SiGe:B layers. We have also probed the in-situ boron and phosphorus doping of Si at 750 °C, 20 Torr with a heavily chlorinated chemistry. The B ions concentration increases linearly with the diborane flow, then saturates at a value close to 4×10 19 cm -3. By contrast, the P ions concentration increases sub-linearly with the phosphine flow, with a maximum value close to 9×10 18 cm -3. Adding diborane (phosphine) to the gaseous mixture leads to a sharp increase (decrease) of the Si:B (the Si:P) growth rates, which has to be taken into account in device layers. All the know-how acquired will be most handy for the formation of in-situ doped recessed or raised sources and drains in metal-oxide semiconductor devices.

Hartmann, J. M.; Gonzatti, F.; Fillot, F.; Billon, T.

2008-01-01

236

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

Microsoft Academic Search

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

Andrea C. Ferrari

2007-01-01

237

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

238

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

SciTech Connect

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.

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

2014-04-24

239

In Vitro Evaluation of the Tribological Response of Mo-Doped Graphite-like Carbon Film in Different Biological Media.  

PubMed

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

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

2015-02-01

240

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

PubMed Central

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

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

2011-01-01

241

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

SciTech Connect

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.

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

2012-01-01

242

Size dependence rectification performances induced by boron and nitrogen co-doping in rhombic graphene nanoribbons  

NASA Astrophysics Data System (ADS)

Rectification performances of rhombic graphene nanoribbons coupled to gold electrodes through thiolate bonds with left and right vertical carbon atoms substituted by one nitrogen or boron atom are analyzed by performing theoretical calculations using a self-consistent ab initio approach that combines the density functional theory with the non-equilibrium Green's function formalism. Increasing the size of graphene nanoribbon markedly improves the rectification effect because of the asymmetric potential profile distribution in rhombic graphene for polarization near the boron and nitrogen atoms.

Wang, Li-hua; Zhang, Zi-zhen; Ding, Bing-jun; Guo, Yong

2014-02-01

243

Electrochemical oxidation of phenol at boron-doped diamond electrode. Application to electro-organic synthesis and wastewater treatment.  

PubMed

The electrochemical behaviour of a synthetic boron-doped diamond thin film electrode (BDD) has been studied in acid media containing phenol using cyclic voltammetry and bulk electrolysis. The results have shown that in the potential region of water stability direct electron transfers can occur on BDD surface resulting in electrode fouling due to the formation of a polymeric film on its surface. During electrolysis in the potential region of oxygen evolution, complex oxidation reactions can take place due to electrogenerated hydroxyl radicals. Electrode fouling is inhibited under these conditions. Depending on the experimental conditions, the electrogenerated hydroxyl radicals can lead to the combustion of phenol or to the selective oxidation of phenol to benzoquinone. The experimental results have also been compared to a theoretical model that permits the prediction of the evolution with time of phenol concentration, during its combustion, or during its selective oxidation to benzoquinone. PMID:12489265

Panizza, Marco; Michaud, Pierre-Alain; Iniesta, Jesus; Comninellis, Christos; Cerisola, Giacomo

2002-10-01

244

Experimental and theoretical investigations on the adsorption of 2'-deoxyguanosine oxidation products at oxidized boron-doped diamond electrodes.  

PubMed

Electrochemical oxidation of 2'-deoxyguanosine has been performed on boron-doped diamond (BDD) electrodes, resulting in a strong adsorption of the formed oxidized products onto the BDD surface. The adsorption behavior has been investigated by studying the electrochemical behavior of a redox probe ([IrCl6]3-) using cyclic voltammetry. The most probable situations are the formation of (A) an insulating adsorbed film resulting in a partially blocked electrode behavior, (B) a porous film, or (C) an overall conductive film. Different parameters such as the standard rate constant, the charge-transfer coefficient, the electrode/adsorbed products/solution interface resistance, and the formal potential of the redox couple were determined. Through comparison of theoretical current-potential curves obtained by analytical calculations with experimental cyclic voltammograms, we found that the oxidized products of 2'-deoxyguanosine form a continuous conductive film on BDD. PMID:17411007

Fortin, Elodie; Vieil, Eric; Mailley, Pascal; Szunerits, Sabine; Livache, Thierry

2007-05-15

245

Voltammetric determination of mixtures of caffeine and chlorogenic acid in beverage samples using a boron-doped diamond electrode.  

PubMed

Herein, a boron-doped diamond (BDD) electrode that is anodically pretreated was used for the simultaneous determination of caffeine (CAF) and chlorogenic acid (CGA) by cyclic and adsorptive stripping voltammetry. The dependence of peak current and potential on pH, scan rate, accumulation parameters and other experimental variables were studied. By using square-wave stripping mode after 60 s accumulation under open-circuit voltage, the BDD electrode was able to separate the oxidation peak potentials of CAF and CGA present in binary mixtures by about 0.4V in Britton-Robinson buffer at pH 1.0. The limits of detection were 0.107 µg mL(-1) (5.51×10(-7) M) for CAF, and 0.448 µg mL(-1) (1.26×10(-6) M) for CGA. The practical applicability of this methodology was tested in commercially available beverage samples. PMID:24148509

Yard?m, Yavuz; Keskin, Ertugrul; ?entürk, Zühre

2013-11-15

246

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

PubMed

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

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

2015-01-14

247

Simultaneous voltammetric determination of synthetic colorants in food using a cathodically pretreated boron-doped diamond electrode.  

PubMed

Differential pulse voltammetry (DPV) and a cathodically pretreated boron-doped diamond (BDD) electrode were used to simultaneously determine two pairs of synthetic food colorants commonly found mixed in food products: tartrazine (TT) and sunset yellow (SY) or brilliant blue (BB) and sunset yellow (SY). In the DPV measurements using the BDD electrode, the reduction peak potentials of TT and SY or BB and SY were separated by about 150 mV. The detection limit values obtained for the simultaneous determination of TT and SY or BB and SY were 62.7 nmol L(-1) and 13.1 nmol L(-1) or 143 nmol L(-1) and 25.6 nmol L(-1), respectively. The novel proposed voltammetric method was successfully applied in the simultaneous determination of these synthetic colorants in food products, with results similar to those obtained using a HPLC method at 95% confidence level. PMID:22841082

Medeiros, Roberta A; Lourencao, Bruna C; Rocha-Filho, Romeu C; Fatibello-Filho, Orlando

2012-08-15

248

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

NASA Astrophysics Data System (ADS)

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/?m, respectively. The field emission current stability investigated at the preset value of ˜1 ?A 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.

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

2011-01-01

249

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

250

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

NASA Astrophysics Data System (ADS)

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 (? = 0.09 ? 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 (? = 0.09 ? 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

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

2014-11-01

251

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

SciTech Connect

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.

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

1997-07-01

252

Comparative study on the localized surface plasmon resonance of boron- and phosphorus-doped silicon nanocrystals.  

PubMed

Localized surface plasmon resonance (LSPR) of doped Si nanocrystals (NCs) is critical to the development of Si-based plasmonics. We now experimentally show that LSPR can be obtained from both B- and P-doped Si NCs in the mid-infrared region. Both experiments and calculations demonstrate that the Drude model can be used to describe the LSPR of Si NCs if the dielectric screening and carrier effective mass of Si NCs are considered. When the doping levels of B and P are similar, the LSPR energy of B-doped Si NCs is higher than that of P-doped Si NCs because B is more efficiently activated to produce free carriers than P in Si NCs. We find that the plasmonic coupling between Si NCs is effectively blocked by oxide at the NC surface. The LSPR quality factors of B- and P-doped Si NCs approach those of traditional noble metal NCs. We demonstrate that LSPR is an effective means to gain physical insights on the electronic properties of doped Si NCs. The current work on the model semiconductor NCs, i.e., Si NCs has important implication for the physical understanding and practical use of semiconductor NC plasmonics. PMID:25551330

Zhou, Shu; Pi, Xiaodong; Ni, Zhenyi; Ding, Yi; Jiang, Yingying; Jin, Chuanhong; Delerue, Christophe; Yang, Deren; Nozaki, Tomohiro

2015-01-27

253

Investigation of film formation properties during electrochemical oxidation of serotonin (5-HT) at polycrystalline boron doped diamond.  

PubMed

The change in surface morphology of oxygen-terminated polycrystalline boron doped diamond (pBDD) during electrochemical oxidation of the neurotransmitter serotonin (5-HT), resulting in a corresponding deterioration of the current signal, is investigated for the first time using both high resolution ex situ and in situ microscopy under a range of different electrochemical conditions. In situ electrochemical-atomic force microscopy (EC-AFM) reveals the formation of a granular film over the surface, which grows faster at higher-doped regions of the electrode surface and increases in thickness with repetitive potential cycles. The film properties were investigated using both cyclic voltammetry, with a range of redox species varying in charge, and conducting-AFM. These studies reveal the film to be positively charged and electrically insulating. The extent to which the film forms during 5-HT oxidation could be significantly minimised using different electrochemical procedures, as verified by voltammetry and in situ EC-AFM. Finally, even after extensive film formation, the original current signal could be recovered simply by leaving the electrode at open circuit potential for a short period of time, highlighting the suitability of BDD electrodes for neurotransmitter detection. PMID:24060971

Patel, Anisha N; Unwin, Patrick R; Macpherson, Julie V

2013-11-01

254

Precipitation control and activation enhancement in boron-doped p+-BaSi2 films grown by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Precipitation free boron (B)-doped as-grown p+-BaSi2 layer is essential for the BaSi2 p-n junction solar cells. In this article, B-doped p-BaSi2 layers were grown by molecular beam epitaxy on Si(111) substrates, and the influence of substrate growth temperature (TS) and B temperature (TB) in the Knudsen cell crucible were investigated on the formation of B precipitates and the activation efficiency. The hole concentration, p, reached 1.0 × 1019 cm-3 at room temperature for TS = 600 and TB = 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 TS was raised to 650 °C and the TB was decreased to 1350 °C, the p reached 6.8 × 1019 cm-3, and the activation rate increased to more than 20%. No precipitation of B was also confirmed by TEM.

Khan, M. Ajmal; Nakamura, K.; Du, W.; Toko, K.; Usami, N.; Suemasu, T.

2014-06-01

255

Evidence for substitutional boron in doped single-walled carbon nanotubes  

SciTech Connect

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

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

2010-05-03

256

Response of Soil and Plant to Boron-Doped Aluminum Hydroxide  

Microsoft Academic Search

The aims of this work are to test whether boron (B) may alleviate soil acidification and aluminum (Al) phytotoxicity to rape (Brassica napus L.) in acidic soil. The Al hydroxide that reacted with borax was called ad-B-Al hydroxide. Point of zero charge (PZC) of Al hydroxide (pH 4.86) was greater than that of ad-B-Al hydroxide (pH 4.68). Compared with the

Shuijiao Liao; Liying Ren; Duanwei Zhu; Wenbing Zhou; Jingzhen Cui; Guanglong Liu

2011-01-01

257

Effective visible light-active boron and europium co-doped BiVO4 synthesized by sol-gel method for photodegradion of methyl orange.  

PubMed

Eu-B co-doped BiVO4 visible-light-driven photocatalysts have been synthesized using the sol-gel method. The resulting materials were characterized by a series of joint techniques, including XPS, XRD, SEM, BET, and UV-vis DRS analyses. Compared with BiVO4 and B-BiVO4 photocatalysts, the Eu-B-BiVO4 photocatalysts exhibited much higher photocatalytic activity for methyl orange (MO) degradation under visible light irradiation. The optimal Eu doping content is 0.8 mol%. It was revealed that boron and europium were doped into the lattice of BiVO4 and this led to more surface oxygen vacancies, high specific surface areas, small crystallite size, a narrower band gap and intense light absorbance in the visible region. The doped Eu(III) cations can help in the separation of photogenerated electrons. The synergistic effects of boron and europium in doped BiVO4 were the main reason for improving visible light photocatalytic activity. PMID:24076480

Wang, Min; Che, Yinsheng; Niu, Chao; Dang, Mingyan; Dong, Duo

2013-11-15

258

Rotating ring–disk electrode studies of the oxidation of p-methoxyphenol and hydroquinone at boron-doped diamond electrodes  

Microsoft Academic Search

The stepwise electrochemical oxidation of p-methoxyphenol and hydroquinone at boron-doped diamond (BDD) electrodes was investigated in perchloric acid media using rotating ring–disk electrode (RRDE) and hydrodynamic modulation techniques. Initial oxidation of these compounds to p-benzoquinone at the disk may be confirmed by reduction of the quinone at the ring electrode. Further oxidation, ultimately to CO2, can be followed by the

David Sopchak; Barry Miller; Yitzhak Avyigal; Rafi Kalish

2002-01-01

259

Synthetic semiconductor diamond electrodes: a study of electrochemical behavior of boron-doped single crystals grown at a high temperature and high pressure  

Microsoft Academic Search

Impedance spectroscopy and electrochemical kinetics in Fe(CN)63?\\/4? and Ce3+\\/4+ redox solutions are investigated for boron-doped `high temperature, high pressure' diamond single crystals of moderate resistivity. The comparison with thin-film chemical-vapor-deposited diamond electrodes studied earlier proved both types of diamond electrode to behave in a similar manner. In particular, a constant phase element is characteristic of their impedance behavior. Redox reactions

Yu. V Pleskov; Yu. E Evstefeeva; M. D Krotova; A. V Laptev

1999-01-01

260

Simultaneous voltammetric determination of paracetamol and ascorbic acid using a boron-doped diamond electrode modified with Nafion and lead films.  

PubMed

The paper describes the fabrication and application of a novel sensor (a boron-doped diamond electrode modified with Nafion and lead films) for the simultaneous determination of paracetamol and ascorbic acid by differential pulse voltammetry. The main advantage of the lead film and polymer covered boron-doped diamond electrode is that the sensitivity of the stripping responses is increased and the separation of paracetamol and ascorbic acid signals is improved due to the modification of the boron-doped diamond surface by the lead layer. Additionally, the repeatability of paracetamol and ascorbic acid signals is improved by the application of the Nafion film coating. In the presence of oxygen, linear calibration curves were obtained in a wide concentration range from 5×10(-7) to 2×10(-4) mol L(-1) for paracetamol and from 1×10(-6) to 5×10(-4) mol L(-1) for ascorbic acid. The analytical utility of the differential pulse voltammetric method elaborated was tested in the assay of paracetamol and ascorbic acid in commercially available pharmaceutical formulations and the method was validated by high performance liquid chromatography coupled with diode array detector. PMID:25127609

Tyszczuk-Rotko, Katarzyna; B?czkowska, Ilona; Wójciak-Kosior, Magdalena; Sowa, Ireneusz

2014-11-01

261

A new assisted molecular cycloaddition on boron doped silicon surfaces: a predictive DFT-D study.  

PubMed

In the framework of the Density Functional Theory (DFT-D), we investigate the phthalocyanine (H2Pc) molecule adsorption on SiC(0001)3 × 3 and Si(111)?3 × ?3R30°-B (SiB) surfaces, and particularly compare the involved molecular adsorptions. In the H2Pc-SiC(0001)3 × 3 system, the molecular adsorption can be ascribed to a [10+2] cycloaddition. The H2Pc-SiB system is considered in three cases: defectless SiB surface (denoted SiB-0D) and SiB surfaces presenting one or two boron defects (denoted SiB-1D and SiB-2D respectively). The SiB-0D surface is passivated by a charge transfer from the Si adatoms to the boron atoms and therefore no chemical bond between the molecule and the substrate is observed. A similar molecular adsorption as already evidenced in the H2Pc-SiC(0001)3 × 3 system is involved in the SiB-2D case. In the case of the SiB-1D surface, two Si-N bonds (Si1-N1 and Si2-N2) are observed. One of them, Si1-N1, is nearly similar to that found in the H2Pc-SiB-2D system, but the Si2-N2 bond is unexpected. The Bader charge analysis suggests that, in the presence of the H2Pc molecule, the boron atoms behave like an electron reservoir whose availability varies following the involved molecular adsorption process. In the SiB-1D case, charges are transferred from the substrate to the molecule, allowing the Si2-N2 bond formation. Such a kind of molecular adsorption, not yet observed, could be designed by "assisted pseudo cycloaddition". PMID:24817040

Boukari, Khaoula; Duverger, Eric; Stauffer, Louise; Sonnet, Philippe

2014-06-28

262

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

263

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)

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.

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

2015-03-01

264

Toward high-throughput screening of NAD(P)-dependent oxidoreductases using boron-doped diamond microelectrodes and microfluidic devices.  

PubMed

Although oxidoreductases are widely used in many applications, such as biosensors and biofuel cells, improvements in the function of existing oxidoreductases or the discovery of novel oxidoreductases with greater activities is desired. To increase the activity of oxidoreductases by directed evolution, a powerful screening technique for oxidoreductases is required. In this study, we demonstrate the utility of boron-doped diamond (BDD) microelectrodes for quantitative and potentially high-throughput measurement of the activity of NAD(P)-dependent oxidoreductases. We first confirmed that BDD microelectrodes can quantify the activity of low concentrations (10-100 pM) of glucose-6-phosphate dehydrogenase and alcohol dehydrogenase with a measuring time of 1 ms per sample. In addition, we found that poisoning of BDD microelectrodes can be repressed by optimizing the pH and by adding l-arginine to the enzyme solution as an antiaggregation agent. Finally, we fabricated a microfluidic device containing a BDD electrode for the first time and observed the elevation of the oxidation current of NADH with increasing flow rate. These results imply that the combination of a BDD microelectrode and microfluidics can be used for high-throughput screening of an oxidoreductase library containing a large number (>10(6)) of samples, each with a small (nanoliter) sample volume. PMID:25211652

Oyobiki, Ryo; Kato, Taisuke; Katayama, Michinobu; Sugitani, Ai; Watanabe, Takeshi; Einaga, Yasuaki; Matsumoto, Yoshinori; Horisawa, Kenichi; Doi, Nobuhide

2014-10-01

265

Electrochemical analysis of chloramphenicol using boron-doped diamond electrode applied to a flow-injection system.  

PubMed

The electrochemical properties of chloramphenicol at a boron-doped diamond thin-film (BDD) electrode were studied using cyclic voltammetry. The highest current response of chloramphenicol was obtained with phosphate buffer, pH 6 (0.1 M) in 1% ethanol. The relationship between the concentration of chloramphenicol and the current response was linear over the range of 0.1-10 mM (R2=0.9990). The amount of chloramphenicol was analyzed by flow-injection analysis. A thin-layer flow cell equipped with a BDD electrode was used as an amperometric detector, and experiments were carried out at -0.7 V (vs. Ag/AgCl). The linear relationship between the current response and the concentration of chloramphenicol in the range of 0.1-50 microM (R2=0.9948) and the limit of detection of 0.03 microM (S/N=3) were obtained. This method has been successfully applied to the determination of chloramphenicol in sterile eye drops and milk sample by the standard addition method. The average recoveries of chloramphenicol in eye drops were 98.0%, and the average recoveries of chloramphenicol from spiked milk were 93.9-103%. PMID:18403841

Chuanuwatanakul, Suchada; Chailapakul, Orawon; Motomizu, Shoji

2008-04-01

266

Electrochemical analysis of acetaminophen using a boron-doped diamond thin film electrode applied to flow injection system.  

PubMed

The electrochemistry of acetaminophen in phosphate buffer solution (pH 8) was studied at a boron-doped diamond (BDD) thin film electrode using cyclic voltammetry, hydrodynamic voltammetry, and flow injection with amperometric detection. Cyclic voltammetry was used to study the reaction as a function of concentration of analyte. Comparison experiments were performed using a polished glassy carbon (GC) electrode. Acetaminophen undergoes quasi-reversible reaction at both of these two electrodes. The BDD and GC electrodes provided well-resolved cyclic voltammograms but the voltammetric signal-to-background ratios obtained from the diamond electrode were higher than those obtained from the GC electrode. The diamond electrode provided a linear dynamic range from 0.1 to 8 mM and a detection of 10 microM (S/B approximately 3) for voltammetric measurement. The flow injection analysis results at the diamond electrode indicated a linear dynamic range from 0.5 to 50 microM and a detection limit of 10 nM (S/N approximately 4). Acetaminophen in syrup samples has also been investigated. The results obtained in the recovery study (24.68+/-0.26 mg/ml) were comparable to those labeled (24 mg/ml). PMID:12039625

Wangfuengkanagul, Nattakarn; Chailapakul, Orawon

2002-06-01

267

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

PubMed

The mineralization of ketoprofen (KP) by anodic oxidation was studied by employing boron doped diamond (BDD) and Pt electrodes. The redox behavior of KP molecule, fouling of electrodes, generation of oxygen and active chlorine species were studied by cyclic voltammetry. The effect of electrolyte, pH of aqueous medium and applied current density on the mineralization behavior of KP was also investigated. The degradation and mineralization were monitored by UV-vis spectrophotometer and total organic carbon analyzer, respectively. The results were explained in terms of in situ generation of hydroxyl radical (OH), peroxodisulfate (S(2)O(8)(2-)), and active chlorine species (Cl(2), HOCl, OCl(-)). The physisorbed OH on BDD was observed to trigger the combustion of KP in to CO(2) and H(2)O. The poor mineralization at both BDD and Pt anodes in the presence of NaCl as supporting electrolyte was ascribed to the formation of chlorinated organic compounds which are refractory. Complete mineralization of KP molecule was achieved using Na(2)SO(4) as supporting electrolyte. PMID:20488617

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

2010-08-15

268

Flow-injection determination of iodide ion in nuclear emergency tablets, using boron-doped diamond thin film electrode.  

PubMed

The electrochemical determination of iodide was studied at boron-doped diamond thin film electrodes (BDD) using cyclic voltammetry (CV) and flow-injection (FI) analysis, with amperometric detection. Cyclic voltammetry of iodide was conducted in a phosphate buffer pH 5. Experiments were performed using glassy carbon (GC) electrode as a comparison. Well-defined oxidation waves of the quasi-reversible cyclic voltammograms were observed at both electrodes. Voltammetric signal-to-background ratios (S/B) were comparable. However, the GC electrode gives much greater in the background current as usual. The potential sweep rate dependence exhibited that the peak current of iodide oxidation at 1mM varied linearly (r(2) = 0.998) with the square root of the scan rate, from 0.01 to 0.30Vs(-1). This result indicates that the reaction is a diffusion-controlled process with negligible adsorption on BDD surface, at this iodide concentration. Results of the flow-injection analysis show a highly reproducible amperometric response. The linear working range was observed up to 200muM (r(2) = 0.999). The detection limit, as low as 0.01muM (3sigma of blank), was obtained. This method was successfully applied for quantification of iodide contents in nuclear emergency tablets. PMID:18969738

Chailapakul, O; Amatatongchai, M; Wilairat, P; Grudpan, K; Nacapricha, D

2004-12-15

269

Quasi-real time quantification of uric acid in urine using boron doped diamond microelectrode with in situ cleaning.  

PubMed

We report herein an innovative electrochemical (EC) technique based on boron doped diamond (BDD) microelectrodes which enable the fast determination of uric acid (UA) concentrations in urine. On the basis of fast cyclic voltammetry (CV), the technique was assessed in human urine samples and compared successfully using routine spectrophotometric diagnosis. The approach relies on the use of BDD's superior properties such as low background current, low adsorption of species, long-term stability, and antifouling capabilities using electrochemical reactivation. Moreover, the article also describes an in situ activation technique, where the electrodes were reactivated within human urine, thereby opening the way toward automatic quantification of UA with in situ cleaning. The time taken to quantify UA concentration and cleaning remains below 0.5 s. Two analytic models were derived, based on different concentrations of ascorbic acid (AA) and uric acid, consisting of 2 s order calibration curves. Solving the second order equation enables the direct estimation of UA concentration, and values demonstrated good accuracy when compared with spectrophotometric measurements. PMID:23126450

Kiran, Raphael; Scorsone, Emmanuel; Mailley, Pascal; Bergonzo, Philippe

2012-12-01

270

Use of nickel implanted boron-doped diamond thin film electrode coupled to HPLC system for the determination of tetracyclines.  

PubMed

The electrochemical analysis of tetracyclines was investigated using nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) by cyclic voltammetry and high performance liquid chromatographic with amperometry. Cyclic voltammetry was used to study the electrochemical oxidation of tetracyclines. Comparison experiments were carried out utilizing as-deposited BDD and glassy carbon electrodes. Ni-DIA electrode provided well-resolved oxidative irreversible cyclic voltammograms and the highest current signals among the electrode studied. High performance liquid chromatography (HPLC) with amperometric detection was also studied. The chromatography was performed using a commercially available Inertsil C18 column, with the mobile phase being: 80% phosphate buffer (pH 2.5)-20% acetonitrile and detected at 1.55V. The methods were validated over the concentration range 0.05-100ppm with the overall average recoveries from 83.3 to 102.5% and R.S.D. of less than 10%. The proposed method was further applied to analyse shrimp samples. PMID:18970468

Treetepvijit, Surudee; Preechaworapun, Anchana; Praphairaksit, Narong; Chuanuwatanakul, Suchada; Einaga, Yasuaki; Chailapakul, Orawon

2006-02-15

271

XPS study of ruthenium tris-bipyridine electrografted from diazonium salt derivative on microcrystalline boron doped diamond.  

PubMed

Boron doped diamond (BDD) functionalization has received an increasing interest during the last few years. Such an infatuation comes from the original properties of BDD, including chemical stability or an electrochemical window, that opens the way for the design of (bio)sensors or smart interfaces. In such a context, diazonium salts appear to be well suited for BDD functionalization as they enable covalent immobilization of functional entities such as enzymes or DNA. In this study we report microcrystalline BDD functionalization with a metallic complex, ruthenium tris(bipyridine), using the p-(tris(bipyridine)Ru(2+))phenyl diazonium salt. Electrografting using cyclic voltammetry (CV) allowed the formation of a ruthenium complex film that was finely characterized using electrochemistry and X-ray photoelectron spectroscopy (XPS). Moreover, we showed that chronopotentiometry (CP) is a convenient tool to monitor Ru complex film deposition through the control of the electrochemical pulse parameters (i.e. current density and pulse duration). Finally, such a control was demonstrated through the correlation between electrochemical and XPS characterizations. PMID:20024438

Agnès, Charles; Arnault, Jean-Charles; Omnès, Franck; Jousselme, Bruno; Billon, Martial; Bidan, Gérard; Mailley, Pascal

2009-12-28

272

Electrochemical analysis of d-penicillamine using a boron-doped diamond thin film electrode applied to flow injection system.  

PubMed

The electroanalysis of d-penicillamine in 0.1 phosphate buffer (pH 7) was studied at a boron-doped diamond thin film (BDD) electrode using cyclic voltammetry as a function of concentration of analyte and pH of analyte solution. Comparison experiments were performing using a glassy carbon (GC) electrode. The BDD electrode exhibited a well-resolved and irreversible oxidation voltammogram, but the GC electrode provided only an ill-defined response. The BDD electrode provided a linear dynamic range from 0.5 to 10 mM and a detection limit of 25 muM (S/B>/=3) in voltammetric measurement. It was also found that the peak potentials were decreased when the pH of the analyte solution was increased. In addition, penicillamine has been studied by hydrodynamic voltammetry and flow injection analysis with amperometric detection using the BDD electrode. The flow injection analysis results at the diamond electrode indicated a linear dynamic range from 0.5 to 50 muM and a detection limit of 10 nM (S/N approximately 4). The proposed method was applied to determine d-penicillamine in dosage form (capsules), the results obtained in the recovery study (255+/-2.50 mg per tablet) were comparable to those labeled (250 mg per tablet). PMID:18968859

Wangfuengkanagul, Nattakarn; Chailapakul, Orawon

2002-12-01

273

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

PubMed

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

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

2014-08-01

274

Highly Conductive Boron Doped Microcrystalline Si Films Deposited by Hot Wire Cell Method and its Application to Solar Cells  

NASA Astrophysics Data System (ADS)

Boron doped microcrystalline silicon (p-?c-Si) films were successfully deposited by the Hot Wire Cell method using a gas mixture of pure silane (SiH4) and diborane (0.5% B2H6 in H2). The influence of various deposition parameters on the structural and electrical properties of the films was investigated to obtain highly conductive p-?c-Si films. A high dark conductivity (?d) of 84.6 S/cm and a low activation energy of 0.02 eV were achieved for 550-nm-thick films. For thin films with a thickness of 15 nm, a ?d of 4× 10-2 S/cm was obtained. The thin p-?c-Si was incorporated into p-i-n amorphous silicon (a-Si) and microcrystalline silicon (?c-Si) solar cells, in which intrinsic layers were deposited by photo chemical vapor deposition (photo-CVD). The initial conversion efficiencies of 9.04% and 6.17% were obtained for a-Si and ?c-Si solar cells, respectively.

Miyajima, Shinsuke; Kim, Mingyu; Ide, Yoshinori; Yamada, Akira; Konagai, Makoto

2003-06-01

275

Boron Doped nc-Si:H Window Layer Prepared by Hw-Cvd for Solar Cell Applications  

NASA Astrophysics Data System (ADS)

In this work, we report on synthesis of boron doped hydrogenated nanocrystalline silicon (p-nc-Si:H) films by HW-CVD method. Films were prepared at low substrate temperature (165 °C) and low process pressure (20 mTorr) by varying diborane gas phase ratio [defined as RB2H6 = (FB2H6/FSiH4)×100%]. The material properties of these films are studied using micro-Raman spectroscopy, low angle X-ray diffraction, X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, dark conductivity measurements etc. The correlation between RB2H6 and resulting material properties such as crystalline volume fraction, crystallite size, band gap and hydrogen content has been established. We have obtained high band gap ( 2.48 eV) p-nc-Si:H films having dark conductivity ( 0.6 S/cm) with low hydrogen content ( 1.8 at. %) at high deposition rate ( 19.2 Å/s). The employment of these films in a-Si:H based p-i-n solar cell as a p-type window layer could have low absorption losses thereby enhancing the current density which in turn would enhance the conversion efficiency of solar cell.

Pramod, M. R.; Kamble, M. M.; Waman, V. S.; Gore, S. P.; Funde, A. M.; Sathe, V. G.; Patil, K. R.; Gosavi, S. W.; Jadkar, S. R.

276

Electron-energy-loss investigation of hole-plasmon excitation due to thermal indiffusion boron doping of Si(111) surfaces  

NASA Astrophysics Data System (ADS)

High-resolution electron-energy-loss-spectroscopy (HREELS) measurements have been performed on Si(111) surfaces heavily p-doped by the decomposition of adsorbed decaborane with subsequent diffusion more than ~1000 Å below the surface. After thermal decomposition of the decaborane to produce B atoms on the surface the low-energy-electron-diffraction pattern shows a ?3 × ?3 periodicity due to 1/3 ML of boron in the second complete layer. The HREELS data have two strong features: (1) the B-Si dipole vibrational mode at 96 meV and a broad electronic surface-plasmon mode at ~100 meV loss energy due to the free carriers in the region below the B-reconstructed surface layer. We have investigated the energy dependence of the plasmon mode in order to determine the possibility of using HREELS to determine the depth profile of the free carriers due to B diffusion into the region ~50-500 Å below the surface. Unexpectedly, we find that kinematic factors play an important role in the energy range used, 1.5-28 eV, and thus limit the degree of quantitative information that can be obtained about the carrier depth profile from HREELS data in this low-energy range. An approximate depth profile is deduced from the well-established three-layer model (vacuum-surface-bulk layers) after correcting the plasmon peak position for the kinematic factors.

Chen, P. J.; Rowe, J. E.; Yates, J. T., Jr.

1994-12-01

277

Anodic stripping voltammetry of gold nanoparticles at boron-doped diamond electrodes and its application in immunochromatographic strip tests.  

PubMed

Anodic stripping voltammetry (ASV) of colloidal gold-nanoparticles (AuNPs) was investigated at boron-doped diamond (BDD) electrodes in 50mM HClO4. A deposition time of 300s at-0.2V (vs. Ag/AgCl) was fixed as the condition for the ASV. The voltammograms showed oxidation peaks that could be attributed to the oxidation of gold. These oxidation peaks were then investigated for potential application in immunochromatographic strip tests for the selective and quantitative detection of melamine, in which AuNPs were used as the label for the antibody of melamine. Linear regression of the oxidation peak currents appeared in the concentration range from 0.05-0.6?g/mL melamine standard, with an estimated LOD of 0.069?g/mL and an average relative standard deviation of 8.0%. This indicated that the method could be considered as an alternative method for selective and quantitative immunochromatographic applications. The validity was examined by the measurements of melamine injected into milk samples, which showed good recovery percentages during the measurements. PMID:25618650

Ivandini, Tribidasari A; Wicaksono, Wiyogo P; Saepudin, Endang; Rismetov, Bakhadir; Einaga, Yasuaki

2015-03-01

278

Electrochemical treatment of reverse osmosis concentrate on boron-doped electrodes in undivided and divided cell configurations.  

PubMed

An undivided electrolytic cell may offer lower electrochlorination through reduction of chlorine/hypochlorite at the cathode. This study investigated the performance of electrooxidation of reverse osmosis concentrate using boron-doped diamond electrodes in membrane-divided and undivided cells. In both cell configurations, similar extents of chemical oxygen demand and dissolved organic carbon removal were obtained. Continuous formation of chlorinated organic compounds was observed regardless of the membrane presence. However, halogenation of the organic matter did not result in a corresponding increase in toxicity (Vibrio fischeri bioassay performed on extracted samples), with toxicity decreasing slightly until 10AhL(-1), and generally remaining near the initial baseline-toxicity equivalent concentration (TEQ) of the raw concentrate (i.e., ?2mgL(-1)). The exception was a high range toxicity measure in the undivided cell (i.e., TEQ=11mgL(-1) at 2.4AhL(-1)), which rapidly decreased to 4mgL(-1). The discrepancy between the halogenated organic matter and toxicity patterns may be a consequence of volatile and/or polar halogenated by-products formed in oxidation by OH electrogenerated at the anode. The undivided cell exhibited lower energy compared to the divided cell, 0.25kWhgCOD(-1) and 0.34kWhgCOD(-1), respectively, yet it did not demonstrate any improvement regarding by-products formation. PMID:25048621

Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Escher, Beate I; Joll, Cynthia; Radjenovic, Jelena

2014-08-30

279

Electrochemical oxidation of ampicillin antibiotic at boron-doped diamond electrodes and process optimization using response surface methodology.  

PubMed

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

Körbahti, Bahad?r K; Ta?yürek, Selin

2014-06-01

280

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

PubMed

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

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

2015-02-11

281

Square-wave voltammetric determination of propranolol and atenolol in pharmaceuticals using a boron-doped diamond electrode.  

PubMed

The independent determination of two beta-blocker agents, namely propranolol (PROP) and atenolol (ATN), in pharmaceutical formulations using square-wave voltammetry and a cathodically pretreated boron-doped diamond electrode is described. These electroanalytical determinations of propranolol or atenolol were carried out in 0.1molL(-1) H(2)SO(4) or 0.5molL(-1) NaNO(3) (pH 1.0, adjusted with concentrated HNO(3)), respectively. Excellent linear calibration curves, ranging from 0.20 to 9.0micromolL(-1) for PROP and from 2.0 to 41micromolL(-1) for ATN, with detection limits of 0.18 and 0.93micromolL(-1), respectively, were obtained. The obtained recoveries range from 93.9% to 105.0%, for PROP, and from 92.5% to 106.0%, for ATN. The proposed method was successfully applied in the determination of both beta-blockers in several pharmaceutical formulations (tablets), with results in close agreement at a 95% confidence level with those obtained using official spectrophotometric methods. PMID:20441917

Sartori, Elen Romão; Medeiros, Roberta Antigo; Rocha-Filho, Romeu C; Fatibello-Filho, Orlando

2010-06-15

282

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

PubMed

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

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

2015-02-01

283

Photoconductivity of undoped, nitrogen- and boron-doped CVD and synthetic diamond  

Microsoft Academic Search

Nitrogen-doped CVD- and synthetic type IIa and Ib diamonds were investigated by the constant photocurrent method (CPM). Nominally undoped CVD-films containing nitrogen show broad absorption bands with threshold energies at 1, 2.3, 3 and 4.2 eV. The typical nitrogen donor absorption band with a threshold at 1.7 eV is partially masked by the 1 eV band in CVD-films. The absorption

E. Rohrer; C. E. Nebel; M. Stutzmann; A. Flöter; R. Zachai; X. Jiang; C.-P. Klages

1998-01-01

284

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)

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 ( ? ? 0.16 ± 0.03) and growth exponent ( ? ? 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.

Gupta, S.; Vierkant, G. P.

2014-09-01

285

Line defects and induced doping effects in graphene, hexagonal boron nitride and hybrid BNC.  

PubMed

Effects on the atomic structure and electronic properties of two-dimensional graphene (G) and h-BN sheets related to the coexistence of dopants and defects are investigated by using density functional theory based methods. Two types of extended line defects are considered for pristine G and h-BN sheets. In these sheets, the presence of individual doping increases the charge transport character. The coexistence of dopants and defects tunes the band gap towards lower values and causes the direct-indirect band gap change. The relative stability and the electronic properties of various BxNyCz systems are analyzed in detail. We find that the structural properties of these types of systems strongly depend on the orientation of grain boundaries and whether these are parallel or perpendicular to the extended line defects. The electronic structure analysis of the different systems evidences the shift of absorption to the visible region. PMID:25182411

Ansari, Narjes; Nazari, Fariba; Illas, Francesc

2014-10-21

286

Simultaneous detection of purine and pyrimidine at highly boron-doped diamond electrodes by using liquid chromatography.  

PubMed

Highly boron-doped diamond (BDD) electrode, have been examined for simultaneous detection of purine and pyrimidine bases in mild acidic media by using HPLC with amperometric detection. Cyclic voltammetry at as-deposited (AD) and anodically oxidized (AO) BDD were used to study the electrochemistry and to optimize the condition for HPLC applications. At AO BDD electrode, due to its higher overpotential of oxygen evolution reaction, well-defined anodic peaks were observed for the oxidation of purine and pyrimidine bases in acid medium, whereas at AD BDD the oxidation peak of thymine was overlapped with the anodic current of oxygen evolution. The chromatograms of adenine, guanine, cytosine, thymine and 5-methylcytosine mixture were well resolved by using a silica-based column and a solution of 5% acetonitrile in 100mM ammonium acetate buffer (pH 4.25) as the mobile phase. The detection was carried out at AO BDD electrode at an applied potential of 1.6V versus Ag/AgCl. Linear calibration curves were obtained within the concentration range from 0.1 to 10microM with the limits of detection (S/N=3) ranging from 26.3 to 162.1nM, resulting in an order of magnitude higher sensitivities than those at conventional electrodes. HPLC analysis with diamond amperometric detector was successfully applied for determination of 5-methylcytosine in real DNA samples with high reproducibility. No deactivation of the electrode was found during cyclic voltammetric and HPLC measurements, indicating the high stability for analysis of biological samples. PMID:19071355

Ivandini, Tribidasari A; Honda, Kensuke; Rao, Tata N; Fujishima, Akira; Einaga, Yasuaki

2007-02-15

287

Mineralization of the recalcitrant oxalic and oxamic acids by electrochemical advanced oxidation processes using a boron-doped diamond anode.  

PubMed

Oxalic and oxamic acids are the ultimate and more persistent by-products of the degradation of N-aromatics by electrochemical advanced oxidation processes (EAOPs). In this paper, the kinetics and oxidative paths of these acids have been studied for several EAOPs using a boron-doped diamond (BDD) anode and a stainless steel or an air-diffusion cathode. Anodic oxidation (AO-BDD) in the presence of Fe(2+) (AO-BDD-Fe(2+)) and under UVA irradiation (AO-BDD-Fe(2+)-UVA), along with electro-Fenton (EF-BDD), was tested. The oxidation of both acids and their iron complexes on BDD was clarified by cyclic voltammetry. AO-BDD allowed the overall mineralization of oxalic acid, but oxamic acid was removed much more slowly. Each acid underwent a similar decay in AO-BDD-Fe(2+) and EF-BDD, as expected if its iron complexes were not attacked by hydroxyl radicals in the bulk. The faster and total mineralization of both acids was achieved in AO-BDD-Fe(2+)-UVA due to the high photoactivity of their Fe(III) complexes that were continuously regenerated by oxidation of their Fe(II) complexes. Oxamic acid always released a larger proportion of NH(4)(+) than NO(3)(-) ion, as well as volatile NO(x) species. Both acids were independently oxidized at the anode in AO-BDD, but in AO-BDD-Fe(2+)-UVA oxamic acid was more slowly degraded as its content decreased, without significant effect on oxalic acid decay. The increase in current density enhanced the oxidation power of the latter method, with loss of efficiency. High Fe(2+) contents inhibited the oxidation of Fe(II) complexes by the competitive oxidation of Fe(2+) to Fe(3+). Low current densities and Fe(2+) contents are preferable to remove more efficiently these acids by the most potent AO-BDD-Fe(2+)-UVA method. PMID:21477836

Garcia-Segura, Sergi; Brillas, Enric

2011-04-01

288

Direct electron transfer of glucose oxidase-boron doped diamond interface: a new solution for a classical problem.  

PubMed

A planar boron-doped diamond (BDD) electrode was treated with KOH and functionalized with 3-aminopropyltriethoxysilane (APTES) to serve as a biosensing platform for biomolecule immobilization with glucose oxidase (GOx) as a test model. The free amino groups of GOx and APTES were cross-linked by glutaraldehyde (X), a bifunctional chemical to form a stable enzyme layer (GOx-X-APTES) on BDD. Micrographs obtained by scanning electron microscopy revealed that a mesoporous structure uniformly covered the BDD surface. Cyclic voltammetry of GOx immobilized showed a pair of well-defined redox peaks in neutral phosphate buffer solution, corresponding to the direct electron transfer of GOx. The apparent heterogeneous electron transfer rate constant of the immobilized GOx was estimated to be 8.85 ± 0.47 s(-1), considerably higher than the literature reported values. The determination of glucose was carried out by amperometry at -0.40 V, and the developed biosensor showed good reproducibility and stability with a detection limit of 20 ?M. Both ascorbic and uric acids at normal physiological conditions did not provoke any signals. The dynamic range of glucose detection was further extended by covering the enzyme electrode with a thin Nafion layer. The Nafion/GOx-X-APTES/BDD biosensor showed excellent stability, a detection limit of 30 ?M, a linear range between 35 ?M and 8 mM, and a dynamic range up to 14 mM. Such analytical performances were compared favorably with other complicated sensing schemes using nanomaterials, redox polymers, and nanowires. The APTES-functionalized BDD could be easily extended to immobilize other redox enzymes or proteins of interests. PMID:24766419

Bai, Yan-Feng; Xu, Tai-Bin; Luong, John H T; Cui, Hui-Fang

2014-05-20

289

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

NASA Astrophysics Data System (ADS)

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

Yin, Hong; Pongrac, Ivan; Ziemann, Paul

2008-07-01

290

Improved fiber retention by the use of fillers in graphite fiber/resin matrix composites  

NASA Technical Reports Server (NTRS)

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.

Gluyas, R. E.; Bowles, K. J.

1980-01-01

291

Boron-Doped Diamond Microelectrodes Reveal Reduced Serotonin Uptake Rates in Lymphocytes from Adult Rhesus Monkeys Carrying the Short Allele of the 5-HTTLPR  

PubMed Central

Uptake resolved by high-speed chronoamperometry on a second-by-second basis has revealed important differences in brain serotonin transporter function associated with genetic variability. Here, we use chronoamperometry to investigate variations in serotonin transport in primary lymphocytes associated with the rhesus serotonin transporter gene-linked polymorphism (rh5-HTTLPR), a promoter polymorphism whose orthologues occur only in higher order primates including humans. Serotonin clearance by lymphocytes is Na+-dependent and inhibited by the serotonin-selective reuptake inhibitor paroxetine (Paxil), indicative of active uptake by serotonin transporters. Moreover, reductions in serotonin uptake rates are evident in lymphocytes from monkeys with one or two copies of the short ‘s’ allele of the rh5-HTTLPR (s/s < s/l < l/l). These findings illustrate that rh5-HTTLPR-related alterations in serotonin uptake are present during adulthood in peripheral blood cells natively expressing serotonin transporters. Moreover, they suggest that lymphocytes can be used as peripheral biomarkers for investigating genetic or pharmacologic alterations in serotonin transporter function. Use of boron-doped diamond microelectrodes for measuring serotonin uptake, in contrast to carbon fiber microelectrodes used previously in the brain, enabled these high-sensitivity and high-resolution measurements. Boron-doped diamond microelectrodes show excellent signal-to-noise and signal-to-background ratios due mainly to low background currents and are highly resistant to fouling when exposed to lymphocytes or high concentrations of serotonin. PMID:20352073

2009-01-01

292

Amperometric detection of ultra trace amounts of Hg(I) at the surface boron doped diamond electrode modified with iridium oxide.  

PubMed

Iridium oxide (IrOx) films formed electrochemically on the surface boron doped diamond electrode by potential cycling in the range -0.2 to 1.2V from a saturated solution of alkaline iridium(III) solution. A strongly adherent deposit of iridium oxide is formed after 5-10 potential scans. The properties, stability and electrochemical behavior of iridium oxide layers were investigated by atomic force microscopy and cyclic voltammetry. The boron doped diamond (BDD) electrode modified with electrodeposition of a thin film, exhibited an excellent catalytic activity for oxidation of Hg(I) over a wide pH range. The modified electrode shows excellent analytical performance for Hg(I) amperometric detection. The detection limit, sensitivity, response time and dynamic concentration ranges are 3.2nM, 77nAmuM(-1), 100ms and 5nM-5muM. These analytical parameters compare favorably with those obtained with modern analytical techniques and recently published electrochemical methods. PMID:18970505

Salimi, Abdollah; Alizadeh, Vali; Hallaj, Rahman

2006-02-28

293

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

SciTech Connect

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.

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

2014-09-15

294

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)

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.

Zhang, Zhaofu; Geng, Zhaohui; Cai, Danyun; Pan, Tongxi; Chen, Yixin; Dong, Liyuan; Zhou, Tiege

2015-01-01

295

Electrochemical oxidation of reverse osmosis concentrate on boron-doped diamond anodes at circumneutral and acidic pH.  

PubMed

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 ?M (tTHMs), and 12 and 22 ?M (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

Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Gernjak, Wolfgang; Joll, Cynthia; Radjenovic, Jelena

2012-11-15

296

Fillers for improved graphite fiber retention by polymer matrix composites  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

297

BiFeO3 nanodots prepared via dip-pen lithography on Nb-doped SrTiO3 and highly ordered pyrolytic graphite substrates  

NASA Astrophysics Data System (ADS)

Ferroelectric BiFeO3 (BFO) nanodots were prepared on two substrate types, a Nb-doped SrTiO3 (Nb:STO) and a highly ordered pyrolytic graphite (HOPG), using elaborately controllable dip-pen nanolithography (DPN) technology. The lateral dimension and thickness of the formed BFO nanodots exhibited the substrate dependency, resulting in higher aspect ratio with smaller lateral dimension and higher thickness on the hydrophobic HOPG substrate than that of the Nb:STO substrate. Based on piezoelectric force microscope (PFM) measurements, superior ferroelectricity in d33 hysteresis loop of the BFO nanodots on the HOPG was demonstrated by significant reduction in the substrate clamping effect, compared to that on the Nb:STO.

Kim, Woo-Hee; Yeog Son, Jong

2013-07-01

298

Electroanalysis of sulfonamides by flow injection system/high-performance liquid chromatography coupled with amperometric detection using boron-doped diamond electrode.  

PubMed

Sulfonamides (SAs) were electrochemically investigated using cyclic voltammetry at a boron-doped diamond (BDD) electrode. Comparison experiments were carried out using a glassy carbon electrode. The BDD electrode provided well-resolved oxidation, irreversible cyclic voltammograms and higher current signals when compared to the glassy carbon electrode. Results obtained from using the BDD electrode in a flow injection system coupled with amperometric detection were illustrated. The optimum potential from a hydrodynamic voltammogram was found to be 1100mV versus Ag/AgCl, which was chosen for the HPLC-amperometric system. Excellent results of linear range and detection limit were obtained. This method was also used for determination of sulfonamides in egg samples. The standard solutions of 5, 10, and 15ppm were spiked in a real sample, and percentage of recoveries was found to be between 90.0 and 107.7. PMID:18970521

Preechaworapun, Anchana; Chuanuwatanakul, Suchada; Einaga, Yasuaki; Grudpan, Kate; Motomizu, Shoji; Chailapakul, Orawon

2006-02-28

299

Initial boronization of PBX-M using ablation from solid boronized probes  

SciTech Connect

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.

Kugel, H.W.; Timberlake, J.; Bell, R.; Kaita, R.; Kaye, S.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; Von Goeler, S. (Princeton Univ., NJ (United States)) (and others)

1994-07-01

300

Metal-doped graphene layers composed with boron nitride-graphene as an insulator: a nano-capacitor.  

PubMed

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

Monajjemi, Majid

2014-11-01

301

Coatings for graphite fibers  

NASA Technical Reports Server (NTRS)

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.

Galasso, F. S.; Scola, D. A.; Veltri, R. D.

1980-01-01

302

Nuclear Graphite -Fission Reactor Brief Outline of Experience and  

E-print Network

· Physical Changes ­ to Polycrystalline Graphite due to Fast Neutron Damage and Radiolytic Oxidation ­ Provided channels for control rods and coolant gas · Neutron Shield ­ Boronated graphite · Thermal columns · Irradiation Creep #12;Use of Graphite in the Nuclear Industry · Moderator ­ Slow down neutrons by scattering

McDonald, Kirk

303

Carbon doping of precursor boron powder for control of normal resistance of MgB2 bulks for specific use in fault current limiter applications  

NASA Astrophysics Data System (ADS)

Magnesium Diboride (MgB2) bulk superconductor has been manufactured in order to study the enhancement of the normal resistivity for application to superconducting fault current limiters (SFCLs). SFCLs have proven to be a viable means for limiting surge currents by dissipating fault energy as the superconductor quenches. As the current limiting behaviour is determined by the normal resistivity (?n), research has been conducted to evaluate an effective means to increase ?n for bulk superconducting MgB2, which is intrinsically much lower than for high temperature superconductors. Intragranular carbon doping has been confirmed as a means to increase ?n, and was implemented by chemical vapour deposition (CVD) on the boron precursor powder by ethylene gas at 600 °C for durations up to 6 hours in a tubular furnace apparatus. In situ manufacturing of MgB2 bulk was performed using the reactive liquid magnesium infiltration technique. Overall, carbon doping provided a factor of 11.00 increase in the residual resistivity, ?0, which provides the initial limiting action to fault currents, for an accompanying decrease in the critical temperature, Tc, of 2 K.

Archer, J.; Jarvis, A. L. L.

2014-05-01

304

Precipitation control and activation enhancement in boron-doped p{sup +}-BaSi{sub 2} films grown by molecular beam epitaxy  

SciTech Connect

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.

Khan, M. Ajmal; Nakamura, K.; Du, W.; Toko, K. [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Usami, N. [Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Japan Science and Technology Agency, Core Research for Evolutionary Science and Technology, Tokyo 102-0075 (Japan); Suemasu, T. [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Japan Science and Technology Agency, Core Research for Evolutionary Science and Technology, Tokyo 102-0075 (Japan)

2014-06-23

305

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

SciTech Connect

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

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

2012-04-15

306

MODELING THE GENERATION AND DISSOCIATION OF THE BORON-OXYGEN COMPLEX IN B-DOPED CZ-SI  

E-print Network

for the light-induced deg- radation of Czochralski silicon solar cells can be deacti- vated by simultaneous lifetime of B- doped Cz-Si [4]. A complete reversal of this lifetime deg- radation can be achieved

307

Monte Carlo simulation of boron doping profile of fin and trench structures by plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

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.

Shahsenov, Izat S.; Miakonkikh, Andrey V.; Rudenko, Kostantin V.

2014-12-01

308

Boron-doped peroxo-zirconium oxide dielectric for high-performance, low-temperature, solution-processed indium oxide thin-film transistor.  

PubMed

We developed a solution-processed indium oxide (In2O3) thin-film transistor (TFT) with a boron-doped peroxo-zirconium (ZrO2:B) dielectric on silicon as well as polyimide substrate at 200 °C, using water as the solvent for the In2O3 precursor. The formation of In2O3 and ZrO2:B films were intensively studied by thermogravimetric differential thermal analysis (TG-DTA), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT IR), high-resolution X-ray diffraction (HR-XRD), and X-ray photoelectron spectroscopy (XPS). Boron was selected as a dopant to make a denser ZrO2 film. The ZrO2:B film effectively blocked the leakage current at 200 °C with high breakdown strength. To evaluate the ZrO2:B film as a gate dielectric, we fabricated In2O3 TFTs on the ZrO2:B dielectrics with silicon substrates and annealed the resulting samples at 200 and 250 °C. The resulting mobilities were 1.25 and 39.3 cm(2)/(V s), respectively. Finally, we realized a flexible In2O3 TFT with the ZrO2:B dielectric on a polyimide substrate at 200 °C, and it successfully operated a switching device with a mobility of 4.01 cm(2)/(V s). Our results suggest that aqueous solution-processed In2O3 TFTs on ZrO2:B dielectrics could potentially be used for low-cost, low-temperature, and high-performance flexible devices. PMID:23883390

Park, Jee Ho; Yoo, Young Bum; Lee, Keun Ho; Jang, Woo Soon; Oh, Jin Young; Chae, Soo Sang; Lee, Hyun Woo; Han, Sun Woong; Baik, Hong Koo

2013-08-28

309

Fermi level position and density of states of intrinsic, phosphorus-doped, and boron-doped a-Si:H deposited on stainless steel  

SciTech Connect

We have made photoemission, Auger spectroscopy, and surface photovoltage measurements on a-Si:H films prepared by rf plasma decomposition of SiH/sub 4/ and doped SiH/sub 4/ onto substrates at 270 /sup 0/C. The density of gap states of intrinsic films, determined by photoemission, is less than 10/sup 19/ eV/sup -1/ cm/sup -3/. 2.8% P doping produced an additional 2.8 x 10/sup 19/ states cm/sup -3/. Reducing the P concentration to 0.2% only reduces the excess density to 2 x 10/sup 19/ states cm/sup -3/. The surface Fermi energy is 0.4 eV from the nearest band edge in both P- and B-doped a-Si:H, but thermopower and conductivity activation energy indicate the bulk E/sub F/ is about 0.25 eV from the nearest band edge. The variation with thickness of the surface E/sub F/ in intrinsic films deposited on P- and B-doped films indicates the existence of surface states above the equilibrium E/sub F/ at a density of about 2.6 x 10/sup 12/ eV/sup -1/ cm/sup -2/, and possibly states below E/sub F/ at a density of 8.6 x 10/sup 11/ eV/sup -1/ cm/sup -2/. These surface state densities explain the difference between bulk and surface E/sub F/ in doped films.

Nielsen, P.; Gredin, R.

1983-04-01

310

Properties of hybridized DNA arrays on single-crystalline undoped and boron-doped (100) diamonds studied by atomic force microscopy in electrolytes.  

PubMed

Properties of hybridized deoxyribonucleic acid (DNA) arrays on single-crystalline undoped and boron-doped diamonds are studied at the microscopic level by atomic force microscopy (AFM) in buffered electrolytic solutions. DNA is linked to diamond via aminodecene molecules (TFAAD) that are attached to undoped diamonds by a photochemical reaction and via nitrophenyl-diazonium molecules attached electrochemically to boron-doped diamonds. Both H-terminated and oxidized diamond surfaces are used in this process. On H-terminated surfaces, AFM measurements detect compact DNA layers. By analyzing phase and height contrast in AFM, a DNA layer height of 76 A is determined on the photochemically functionalized diamonds and a DNA layer height of up to 92 A is determined on the electrochemically functionalized diamonds. Based on the layer thickness, the DNA chains are tilted under the angle of 31 degrees . The morphology of the DNA layers exhibits long-range (30-50 nm) undulations of 20 A in height and a nanoroughness of 8 A. Using Hertz's model for calculating the contact area of the AFM tip on a DNA layer and a geometrical model of DNA arrangement on diamond yields the DNA density on diamonds of 6 x 10(12) cm(-2) on both photochemically and electrochemically functionalized diamonds. The structure of these dense DNA layers is not significantly influenced by variations in buffer salinity of 1-300 mM NaCl. DNA molecules can be removed from the diamond surface by contact-mode AFM with forces >or= 45 nN and >or= 76 nN on photochemically and electrochemically functionalized diamonds, respectively, indicating that DNA is bonded covalently and stronger on diamond than on gold substrates. The DNA arrangement and bonding strength are similar on oxidized diamond surfaces when using an electrochemical process. On oxidized surfaces after photochemical processing, DNA is bonded noncovalently as deduced from the removal force < 6 nN. The presence of hybridized DNA as well as the selective removal of DNA by AFM scanning are corroborated by fluorescence microscopy. PMID:17547423

Rezek, Bohuslav; Shin, Dongchan; Nebel, Christoph E

2007-07-01

311

Electrochemical behaviors of native and thermally denatured fish DNA in the presence of cytosine derivatives and porphyrin by cyclic voltammetry using boron-doped diamond electrode.  

PubMed

The electrochemical behaviors of native and thermally denatured fish DNA was investigated using boron-doped diamond (BDD) film electrode by cyclic voltammetry. The BDD electrode afforded us to measure weak current less than muA for the DNA solution in 100 microl. The mixture of acetic acid and sodium acetate solution (0.2 M) was used as a supporting electrolyte. Two oxidation peaks were observed at about +1.1 V and +1.3 V at pH 4.6 for thermally denatured fish DNA. This is due to the oxidation of guanine and adenine in the denatured fish DNA, respectively. In contrast, the native fish DNA showed ill-defined peaks at +1.1 V. Furthermore, the electrochemical behaviors of thermally denatured fish DNA were studied in the presence of cytosine, cytidine, cytidine-5-monophosphate, tetrakis(1-methypyridinium-4-yl)porphyrin (H(2)(TMPyP)(4+)) and Ru(II)(TMPyP)(4+). The oxidation peak intensity at +1.1 V gradually decreased with the increase of the concentrations of the above compounds. Based on the above studies, electrochemical behaviors of the thermally denatured fish DNA at BDD electrode is discussed. PMID:16950664

Apilux, Amara; Tabata, Masaaki; Chailapakul, Orawon

2007-05-01

312

A flow injection method for the analysis of tetracycline antibiotics in pharmaceutical formulations using electrochemical detection at anodized boron-doped diamond thin film electrode.  

PubMed

A method using flow injection (FI) with amperometric detection at anodized boron-doped diamond (BDD) thin films has been developed and applied for the determination of tetracycline antibiotics (tetracycline, chlortetracycline, oxytetracycline and doxycycline). The electrochemical oxidation of the tetracycline antibiotics was studied at various carbon electrodes including glassy carbon (GC), as-deposited BDD and anodized BDD electrodes using cyclic voltammetry. The anodized BDD electrode exhibited well-defined irreversible cyclic voltammograms for the oxidation of tetracycline antibiotics with the highest current signals compared to the as-deposited BDD and glassy carbon electrodes. Low detection limit of 10nM (signal-to-noise ratio = 3) was achieved for each drug when using flow injection analysis with amperometric detection at anodized BDD electrodes. Linear calibrations were obtained from 0.1 to 50mM for tetracycline and 0.5-50mM for chlortetracycline, oxytetracycline and doxycycline. The proposed method has been successfully applied to determine the tetracycline antibiotics in some drug formulations. The results obtained in percent found (99.50-103.01%) were comparable to dose labeled. PMID:18969727

Wangfuengkanagul, N; Siangproh, W; Chailapakul, O

2004-12-15

313

Electrochemical measurements of serotonin (5-HT) release from the guinea pig mucosa using continuous amperometry with a boron-doped diamond microelectrode  

PubMed Central

Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder characterized by chronic abdominal discomfort, including pain, bloating and changes in bowel habits. The exact cause of IBS is not entirely understood. Recent studies have shown that IBS may be associated with altered serotonin (5-hydroxytryptamine, 5-HT) levels within the GI tract. About 90% of 5-HT in the human body is produced and stored in enterochromaffin (EC) cells that reside in the mucosal layer of the intestine. Measurements of serotonin availability locally in the mucosa can provide insight on the functionality of these cells and potentially the pathophysiology of the disease. In this study, we used continuous amperometry with a diamond microelectrode to record serotonin levels in vitro in the ileum mucosa as an oxidation current. The boron-doped diamond (BDD) microelectrode is quite practical for these measurements because if its low background signal, low sensitivity to solution pH changes, and excellent resistance to fouling by adsorbed serotonin oxidation reaction products. In fact, the measurements are only possible because of the unique properties of diamond. We present electrochemical data that demonstrate the diamond microelectrode’s utility for assessment of enterochromaffin cell function. Confirmation that the oxidation current was associated with indogenous serotonin release came from pharmacological studies. We are hopeful that these types of in vitro electrochemical measurements will lead to a better understanding of the pathophysiology of IBS. PMID:20209031

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

2009-01-01

314

Investigation of the synergistic effects for p-nitrophenol mineralization by a combined process of ozonation and electrolysis using a boron-doped diamond anode.  

PubMed

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

Qiu, Cuicui; Yuan, Shi; Li, Xiang; Wang, Huijiao; Bakheet, Belal; Komarneni, Sridhar; Wang, Yujue

2014-09-15

315

Flow injection simultaneous determination of synthetic colorants in food using multiple pulse amperometric detection with a boron-doped diamond electrode.  

PubMed

A single-line flow injection system and multiple pulse amperometric detection using a boron-doped diamond electrode were employed to develop and optimize a simple, low-cost, and rapid method for the simultaneous determination of two pairs of food colorants: tartrazine and sunset yellow (TT-SY) or brilliant blue and SY (BB-SY). A dual-potential waveform was used: E(det.1)=-150 mV (400 ms duration) and E(det.2)=-450 mV (100 ms duration) vs. Ag/AgCl (3.0 mol L(-1) KCl). Polarization at E(det.1) or E(det.2) causes reduction of SY or the respective pair of colorants, TT-SY or BB-SY; hence, with proper current correction, both colorants in each pair can be determined. The obtained linear response ranges (detection limits) were 5.0-60.0 (2.5) and 1.0-50.0 (0.80) ?mol L(-1), for TT and SY, or 5.0-60.0 (3.5) and 1.0-50.0 (0.85) ?mol L(-1), for BB and SY, respectively. Investigation of possible interferents (other food colorants or additives) showed no significant interference with the methods here proposed, which were then used to simultaneously determine the pairs of colorants in industrialized food samples, with results that showed good agreement with those obtained using a comparative HPLC method. PMID:22967638

Medeiros, Roberta A; Lourencao, Bruna C; Rocha-Filho, Romeu C; Fatibello-Filho, Orlando

2012-09-15

316

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

PubMed

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

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

2014-01-01

317

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

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

Rajab, Mohamad; Greco, Giorgia; Heim, Carolin; Helmreich, Brigitte; Letzel, Thomas

2013-09-01

318

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

Microsoft Academic Search

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

G. E. Wade; F. J. Kempf

1963-01-01

319

Boronic acid functionalized N-doped carbon quantum dots as fluorescent probe for selective and sensitive glucose determination  

NASA Astrophysics Data System (ADS)

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.

Jiang, Guohua; Jiang, Tengteng; Li, Xia; Wei, Zheng; Du, Xiangxiang; Wang, Xiaohong

2014-04-01

320

Boron- and phosphorus-doped silicon germanium alloy nanocrystals—Nonthermal plasma synthesis and gas-phase thin film deposition  

SciTech Connect

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.

Rowe, David J., E-mail: rowex108@umn.edu, E-mail: kortshagen@umn.edu; Kortshagen, Uwe R., E-mail: rowex108@umn.edu, E-mail: kortshagen@umn.edu [Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2014-02-01

321

Cost-effective flow cell for the determination of malachite green and leucomalachite green at a boron-doped diamond thin-film electrode.  

PubMed

An electrooxidation and a cost-effective flow-based analysis of malachite green (MG) and leucomalachite green (LMG) were investigated at a boron-doped diamond thin-film (BDD) electrode. Cyclic voltammetry as a function of the pH of the supporting electrolyte solution was studied. Comparison experiments were performed with a glassy carbon electrode. A well-defined cyclic voltammogram, providing the highest peak current, was obtained when using phosphate buffer at pH 2. The potential sweep-rate dependence of MG and LMG oxidation (peak currents for 1 mM MG and LMG linearly proportional to v 1/2, within the range of 0.01 to 0.3 V/s) indicates that the oxidation current is a diffusion-controlled process on the BDD surface. In addition, hydrodynamic voltammetry and amperometric detection using the BDD electrode combined with a flow injection analysis system was also studied. A homemade flow cell was used, and the results were compared with a commercial flow cell. A detection potential of 0.85 V was selected when using a commercial flow cell, at which MG and LMG exhibited the highest signal-to-background ratios. For the homemade flow cell, a detection potential of 1.1 V was chosen because MG and LMG exhibited a steady response. The flow analysis results showed linear concentration ranges of 1-100 microM and 4-80 microM for MG and LMG, respectively. The detection limit for both compounds was 50 nM. PMID:16429784

Ngamukot, Passapol; Charoenraks, Thiraporn; Chailapakul, Orawon; Motomizu, Shoji; Chuanuwatanakul, Suchada

2006-01-01

322

Gradient liquid chromatography of leucine-enkephalin peptide and its metabolites with electrochemical detection using highly boron-doped diamond electrode.  

PubMed

Boron-doped diamond thin film (BDD) electrodes have been used to study the oxidation reactions and to detect leucine-enkephalinamide (LEA) and its metabolites, tyrosine (T), tyrosyl-alanine (TA), tyrosyl-alanine-glycine (TAG) and leucine-enkephalin (LE) using cyclic voltammetry (CV), flow-injection analysis (FIA), and gradient liquid chromatography (LC) with amperometric detection. At diamond electrodes, well-defined and highly reproducible cyclic voltammograms were obtained with signal-to-background (S/B) ratios 5-10 times higher than those observed for glassy carbon (GC) electrodes. The analytical peaks of LC for LEA and its metabolites were well resolved. No deactivation of BDD electrodes was found after several experiments with standard as well as plasma samples, indicating high stability of the electrode. Calibration curves were linear over a wide range from 0.06 to 30 microM with regression coefficients of 0.999 for all compounds. The limits of detection obtained based on a signal-to-noise ratio of 3:1 were 3, 2.2, 2.7, 20 and 11 nM for T, TA, TAG, LE and LEA, respectively. These values were at least one order lower than those obtained at GC electrodes, which has given limits of detection of 22.88, 20.64, 89.57, 116.04 and 75.67 for T, TA, TAG, LE and LEA, respectively. Application of this method to real samples was demonstrated and validated using rabbit serum samples. This work shows the promising use of conducting diamond as an amperometric detector in gradient LC, especially for the analysis of enkephalinamide and its metabolites. PMID:12798166

Ivandini, T A; Sarada, B V; Terashima, C; Rao, T N; Tryk, D A; Ishiguro, H; Kubota, Y; Fujishima, A

2003-07-01

323

Diclofenac on boron-doped diamond electrode: from electroanalytical determination to prediction of the electrooxidation mechanism with HPLC-ESI/HRMS and computational simulations.  

PubMed

Using square-wave voltammetry coupled to the boron-doped diamond electrode (BDDE), it was possible to develop an analytical methodology for identification and quantification of diclofenac (DCL) in tablets and synthetic urine. The electroanalytical procedure was validated, with results being statistically equal to those obtained by chromatographic standard method, showing linear range of 4.94 × 10(-7) to 4.43 × 10(-6) mol L(-1), detection limit of 1.15 × 10(-7) mol L(-1), quantification limit of 3.85 × 10(-7) mol L(-1), repeatability of 3.05% (n = 10), and reproducibility of 1.27% (n = 5). The association of electrochemical techniques with UV-vis spectroscopy, computational simulations and HPLC-ESI/HRMS led us to conclude that the electrooxidation of DCL on the BDDE involved two electrons and two protons, where the products are colorful and easily hydrolyzable dimers. Density functional theory calculations allowed to evaluate the stability of dimers A, B, and C, suggesting dimer C was more stable than the other two proposed structures, ca. 4 kcal mol(-1). The comparison of the dimers stabilities with the stabilities of the molecular ions observed in the MS, the compounds that showed retention time (RT) of 15.53, 21.44, and 22.39 min were identified as the dimers B, C, and A, respectively. Corroborating the observed chromatographic profile, dimer B had a dipole moment almost twice higher than that of dimers A and C. As expected, dimer B has really shorter RT than dimers A and C. The majority dimer was the A (71%) and the C (19.8%) should be the minority dimer. However, the minority was the dimer B, which was formed in the proportion of 9.2%. This inversion between the formation proportion of dimer B and dimer C can be explained by preferential conformation of the intermediaries (cation-radicals) on the surface. PMID:24806390

Lucas, Francisco Willian de S; Mascaro, Lucia H; Fill, Taicia P; Rodrigues-Filho, Edson; Franco-Junior, Edison; Homem-de-Mello, Paula; de Lima-Neto, Pedro; Correia, Adriana N

2014-05-20

324

Initial boronization of PBX-M using ablation of solid boronized probes  

SciTech Connect

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.

Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. (California Univ., Los Angeles, CA (United States). 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. (Oak Ridge National Lab., TN (United States)); Jones, S. (Massachusetts Inst. of Tech., Cambridge, MA (United States))

1993-05-01

325

Initial boronization of PBX-M using ablation of solid boronized probes  

SciTech Connect

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.

Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. [California Univ., Los Angeles, CA (United States). 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. [Oak Ridge National Lab., TN (United States); Jones, S. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1993-05-01

326

Reduction of tail state on boron doped hydrogenated amorphous silicon oxide films prepared at high hydrogen dilution.  

PubMed

In this report, we have investigated on the defect state of diborane (B2H6) doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiO:H) films prepared using silane (SiH4), hydrogen (H2) and nitrous oxide (N2O) in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system with different hydrogen dilutions. The films prepared with higher hydrogen dilution show lower Urbach energy (Eu), lower microstructure (R*), lower short and medium range disorder (omegaTO, Gamma(TO), I(TA)/I(TO), I(LA)/I(TO)), higher dark conductivity (sigma d) and higher refractive index (n) with high optical gap (Eg). Eu decreases from 248 meV to 153 meV, and R* decreases from 0.46 to 0.26, Raman peak omegaTO-TO mode position shifts from 480.24 to 483.28, GammaTO-full width half maximum of omegaTO decreases from 78.16 to 63.87, I(TA)/I(TO)-the ratio of integrated area of TA and TO mode decreases from 0.624 to 0.474, I(LA)/I(TO)-the ratio of integrated area of LA and TO mode deceases from 0.272 to 0.151, sigma d increases from 4.6 x 10(-7) S/cm to 1.1 x 10(-6) S/cm, n increases from 3.70 to 3.86. Reduced Nd, Eu and R* at wide Eg indicates that the films are more useful for solar cell window layer. Applying this layer to a single junction solar cell shows open circuit voltage (Voc) = 0.80 V, short circuit current density (Jsc) = 16.3 mA/cm2, fill factor (FF) = 72%, efficiency (eta) = 9.4%. PMID:24266147

Park, Jinjoo; Iftiquar, S M; Lee, Sunwha; Park, Hyeongsik; Shin, Chonghoon; Jung, Junhee; Lee, Youn-Jung; Balaji, Nagarajan; Yi, Junsin

2013-12-01

327

Deposition, characterization, reflow and analysis of undoped and boron trioxide/phosphorus pentoxide-doped germanosilicate glass films  

NASA Astrophysics Data System (ADS)

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.

Simpson, Darrell Lorenza

328

Boronated mesophase pitch coke for lithium insertion  

NASA Astrophysics Data System (ADS)

Boronated carbons from mesophase pitch have been used as materials for lithium storage in Li/carbon cells. Doping by boron has been realized by co-pyrolysis of coal tar pitch with the pyridine-borane complex. Amount of boron in mesocarbon microbeads (MCMB) varied from 1.4 to 1.8 wt.% affecting the texture of carbon. Optical microscopy and X-ray diffractograms have shown tendency to more disordered structure for boron-doped carbon. The values of specific reversible capacity ( x) varied from 0.7 to 1.1 depending significantly on the final temperature of pyrolysis (700-1150°C). The optimal charge/discharge performance was observed for boronated carbon heated at 1000°C.

Frackowiak, E.; Machnikowski, J.; Kaczmarska, H.; Béguin, F.

329

Exfoliation of graphite  

Microsoft Academic Search

The exfoliation of graphite is a phase transition involving the vaporization of the intercalate in the graphite. Exfoliated graphite is an expanded graphite with a low density. This paper reviews the process of the exfoliation of graphite and the exfoliated graphite material. It surveys the applications of exfoliated graphite, covers both reversible and irreversible exfoliation and reviews the methods and

D. D. L. Chung

1987-01-01

330

Doping effect on the metal-induced lateral crystallization rate  

NASA Astrophysics Data System (ADS)

The effects of phosphorus doping and boron doping on the metal-induced lateral crystallization (MILC) rate have been studied. In the case of phosphorus doping, the MILC rate is very sensitive to the sequence of nickel deposition and doping. Phosphorous doping before the nickel deposition reduced the MILC rate much more than the vice versa. When the nickel removal was between the nickel deposition and phosphorus doping, the doping effect on the MILC rate turned out to be in the between of the two cases which are phosphorus doping before nickel deposition and nickel deposition before phosphorus doping. Boron doping results in the crystallization of a-Si at a lower temperature (550°C) compared with that of the solid phase crystallization (SPC). The sheet resistance of boron doped Si remained high because the boron dopants were segregated at the grain boundaries during crystallization of a-Si.

Yang, Gui Fu; Lee, Yong Woo; Byun, Chang Woo; Son, Se Wan; Joo, Seung Ki

2012-04-01

331

Boron nitride as a lubricant additive  

Microsoft Academic Search

Hexagonal boron nitride (BN) has a graphite-like lamellar structure, but has been considered less effective than other solid lubricants except for high-temperature applications. The present paper describes a series of sliding experiments which show somewhat curious behavior of BN when added to lubricating oil, and discusses their results by comparing with the results of observation and analysis of sliding surfaces.

Yoshitsugu Kimura; Toshiaki Wakabayashi; Kazumi Okada; Tetsuya Wada; Hiroshi Nishikawa

1999-01-01

332

Magneto-Resistance in thin film boron carbides  

NASA Astrophysics Data System (ADS)

Chromium doped semiconducting boron carbide devices were fabricated based on a carborane icosahedra (B10C2H12) precursor via plasma enhanced chemical vapor deposition, and the transition metal atoms found to dope pairwise on adjacent icosahedra site locations. Models spin-polarized electronic structure calculations of the doped semiconducting boron carbides indicate that some transition metal (such as Cr) doped semiconducting boron carbides may act as excellent spin filters when used as the dielectric barrier in a magnetic tunnel junction structure. In the case of chromium doping, there may be considerable enhancements in the magneto-resistance of the heterostructure. To this end, current to voltage curves and magneto-transport measurements were performed in various semiconducting boron carbide both in and out plane. The I-V curves as a function of external magnetic field exhibit strong magnetoresistive effects which are enhanced at liquid Nitrogen temperatures. The mechanism for these effects will be discussed in the context of theoretical calculations.

Echeverria, Elena; Luo, Guangfu; Liu, J.; Mei, Wai-Ning; Pasquale, F. L.; Colon Santanta, J.; Dowben, P. A.; Zhang, Le; Kelber, J. A.

2013-03-01

333

Oxygen-assisted low-pressure chemical vapor deposition for the low-temperature direct growth of graphitic nanofibers on fluorine-doped tin oxide glass as a counter electrode for dye-sensitized solar cell  

NASA Astrophysics Data System (ADS)

In this paper, we report an oxygen-assisted low-pressure chemical vapor deposition (LPCVD) method for the direct growth of graphitic nanofibers (GNFs) on a fluorine-doped tin oxide (FTO) glass substrate at a low temperature (550 °C). By adding moderate concentrations of oxygen in a gas mixture of argon, ethylene, and hydrogen during LPCVD, an extremely dense GNF forest can be obtained on a nickel-coated FTO glass substrate. Though this process, the graphitic nanofibers are grown homogenously on a large area of FTO glass. It was observed that oxygen-assisted LPCVD leads to the direct growth of high-quality GNFs as a counter electrode for dye-sensitized solar cells (DSSCs). In combination with an N719 dye-sensitized TiO2 working electrode and an iodine-based electrolyte, the DSSC with a GNF counter electrode showed a power conversion efficiency of 5.51% under AM 1.5 (100 mW cm?2) illumination, which approached that of the DSSC with a Pt counter electrode (5.44%). The results demonstrated that our directly grown GNFs could be promising candidates for counter electrodes to achieve high performance in DSSCs.

Chen, Chih-Sheng; Hsieh, Chien-Kuo

2014-11-01

334

Electroextraction of boron from boron carbide scrap  

SciTech Connect

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.

Jain, Ashish [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Anthonysamy, S., E-mail: sas@igcar.gov.in [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ghosh, C. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ravindran, T.R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Divakar, R.; Mohandas, E. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India)

2013-10-15

335

Fabrication and testing of non-graphitic superhybrid composites  

NASA Technical Reports Server (NTRS)

A study was conducted to determine the fabrication feasibility and the mechanical properties of adhesively-bonded boron aluminum/titanium and non-graphitic fiber/epoxy resin superhybrid (NGSH) composite laminates for potential aerospace applications. The major driver for this study was the elimination of a potential graphite fiber release problem in the event of a fire. The results of the study show that non-graphitic fibers, such as S-glass and Kevlar 49, may be substituted for the graphite fibers used in superhybrid (SH) composites for some applications. As is to be expected, however, the non-graphitic superhybrids have lower stiffness properties than the graphitic superhybrids. In-plane and flexural moduli of the laminates studied in this program can be predicted reasonably well using linear laminate theory while nonlinear laminate theory is required for strength predictions.

Lark, R. F.; Sinclair, J. H.; Chamis, C. C.

1979-01-01

336

GUM Analysis for TIMS and SIMS Isotopic Ratios in Graphite  

SciTech Connect

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.

Heasler, Patrick G.; Gerlach, David C.; Cliff, John B.; Petersen, Steven L.

2007-04-01

337

Raman Spectrum of Graphite  

Microsoft Academic Search

Raman spectra are reported from single crystals of graphite and other graphite materials. Single crystals of graphite show one single line at 1575 cm?1. For the other materials like stress-annealed pyrolitic graphite, commercial graphites, activated charcoal, lampblack, and vitreous carbon another line is detected at 1355 cm?1. The Raman intensity of this band is inversely proportional to the crystallite size

F. Tuinstra; J. L. Koenig

1970-01-01

338

Thermally exfoliated graphite oxide  

NASA Technical Reports Server (NTRS)

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.

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

2011-01-01

339

Electropolymerization kinetics of pyrrole in aqueous solution on graphite felt electrodes  

E-print Network

Electropolymerization kinetics of pyrrole in aqueous solution on graphite felt electrodes I electrogenerated on graphite felt supporting electrodes by applying an anodic potential of 0.9 V versus Ag; Electropolymerization; Kinetics; Doping level; Graphite felt 1. Introduction It is well known that many properties

Otero, Toribio Fernández

340

Density Functional Study of Interaction of Atomic Pt with Pristine and Stone-Wales-Defective Single-Walled Boron Nitride Nanotubes  

E-print Network

-Walled Boron Nitride Nanotubes Ya Kun Chen, Lei Vincent Liu, and Yan Alexander Wang* Department of Chemistry or Stone-Wales-defective (5,5) single-walled boron nitride nanotubes (BNNTs) were studied using density are extended to form layered hexagonal boron nitride (hBN) and carbon graphite networks, their very different

Wang, Yan Alexander

341

Method for sputtering a PIN microcrystalline/amorphous silicon semiconductor device with the P and N-layers sputtered from boron and phosphorous heavily doped targets  

DOEpatents

A silicon PIN microcrystalline/amorphous silicon semiconductor device is constructed by the sputtering of N, and P layers of silicon from silicon doped targets and the I layer from an undoped target, and at least one semi-transparent ohmic electrode.

Moustakas, Theodore D. (Annandale, NJ); Maruska, H. Paul (Annandale, NJ)

1985-04-02

342

III 1 BORON  

Technology Transfer Automated Retrieval System (TEKTRAN)

Boron chemistry, analysis, environmental exposure, metabolism, anthropomorphic sources, beneficial physiological effects, and toxicity are reviewed. Boron is widely distributed in nature and always occurs bound to oxygen. Boron biochemistry is essentially that of boric acid, which forms ester comple...

343

LEO degradation of graphite and carbon-based composites aboard Space Shuttle Flight STS-46  

SciTech Connect

Six different types of carbon and carbon-boron nitride composites were exposed to low Earth orbit aboard Space Shuttle flight STS-46. The samples received a nominal atomic oxygen fluence of 2.2 x 10(exp 20) atoms/sq cm in 42 hours of exposure. Pyrolytic graphite and highly oriented pyrolytic graphite showed significant degradation, and the measured erosion yield was within a factor of two of published values. The erosion yield of pyrolytic boron nitride was found to be 2.6 x 10(exp 26) cu cm/atom in plasma asher exposure, over 42 times lower than that of pyrolytic graphite. This low erosion yield makes graphite plus boron nitride mixtures quite resistant to low Earth orbit exposure. Evidence suggests that the graphitic component was preferentially etched, leaving the surface boron nitride rich. Degradation resistance increases with boron nitride composition. Carbon fiber/carbon composites degraded in low Earth orbit, and the carbon pitch binder was found to etch more easily than the graphite fibers which have much higher degradation resistance.

Spady, B.R.; Synowicki, R.A.; Hale, J.S.; Devries, M.J.; Woollam, J.A.; Moore, A.W.; Lake, M. [Union Carbide Corp., Parma, OH (United States); [Applied Sciences, Inc., Cedarville, OH (United States)

1995-02-01

344

LEO degradation of graphite and carbon-based composites aboard Space Shuttle Flight STS-46  

NASA Technical Reports Server (NTRS)

Six different types of carbon and carbon-boron nitride composites were exposed to low Earth orbit aboard Space Shuttle flight STS-46. The samples received a nominal atomic oxygen fluence of 2.2 x 10(exp 20) atoms/sq cm in 42 hours of exposure. Pyrolytic graphite and highly oriented pyrolytic graphite showed significant degradation, and the measured erosion yield was within a factor of two of published values. The erosion yield of pyrolytic boron nitride was found to be 2.6 x 10(exp 26) cu cm/atom in plasma asher exposure, over 42 times lower than that of pyrolytic graphite. This low erosion yield makes graphite plus boron nitride mixtures quite resistant to low Earth orbit exposure. Evidence suggests that the graphitic component was preferentially etched, leaving the surface boron nitride rich. Degradation resistance increases with boron nitride composition. Carbon fiber/carbon composites degraded in low Earth orbit, and the carbon pitch binder was found to etch more easily than the graphite fibers which have much higher degradation resistance.

Spady, Blaine R.; Synowicki, R. A.; Hale, Jeffrey S.; Devries, M. J.; Woollam, John A.; Moore, Arthur W.; Lake, Max

1995-01-01

345

Synthesis of boron and nitrogen co-doped graphene nano-platelets using a two-step solution process and catalytic properties for oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

Chemically modified graphenes (CMGs) show great promise for various applications owing to the feasibility of their low-cost mass production and good solution processability. Recently, hetero-atom-doped CMGs have been suggested as good candidate materials for electrochemical catalysts in oxygen reduction reaction (ORR). In this study, we synthesized B, N co-doped graphene nano-platelets (BN-rG-O) using a two-step solution process with sequential reaction of graphene oxide with borane tetrahydrofuran and hydrazine monohydrate. In the ORR measured in a basic medium (0.1 M KOH), BN-rG-O exhibits an onset potential of 0.81 V (vs. reversible hydrogen electrode), follows near four electron pathway, and shows excellent stability against methanol poisoning and during durability tests.

Han, Jongwoo; Cheon, Jae Yeong; Joo, Sang Hoon; Park, Sungjin

2014-07-01

346

Boron and sulfur co-doped TiO2 nanofilm as effective photoanode for high efficiency CdS quantum-dot-sensitized solar cells  

NASA Astrophysics Data System (ADS)

A modified polysulfide redox couple, (CH3)4N)2S/((CH3)4N)2Sn, was employed in CdS quantum dots (QDs) sensitized B/S co-doped TiO2 solar cell with NiS as counter electrode, followed by chemical bath deposition (CBD) in an organic solution to prepare the QDs-cell to ensure high wettability and superior penetration ability of the B/S co-doped TiO2 films, with the co-doping of B/S in TiO2, its band-gap was narrowed and significantly extended the light capture range, and an enhanced energy conversion efficiency of up to 3.6% was observed under AM 1.5 G illuminations, with a significantly high Voc of 1.217 V, a high ff of 88.2% and a short-circuit photocurrent (Jsc) of 3.35 mA cm-2.

Li, Ling; Yang, Xichuan; Zhang, Wenming; Zhang, Huayan; Li, Xiaowei

2014-12-01

347

Boron nitride substrates for high-quality graphene electronics  

NASA Astrophysics Data System (ADS)

Graphene devices on standard SiO2 substrates are highly disordered, exhibiting characteristics that are far inferior to the expected intrinsic properties of graphene. Although suspending the graphene above the substrate leads to a substantial improvement in device quality, this geometry imposes severe limitations on device architecture and functionality. There is a growing need, therefore, to identify dielectrics that allow a substrate-supported geometry while retaining the quality achieved with a suspended sample. Hexagonal boron nitride (h-BN) is an appealing substrate, because it has an atomically smooth surface that is relatively free of dangling bonds and charge traps. It also has a lattice constant similar to that of graphite, and has large optical phonon modes and a large electrical bandgap. Here we report the fabrication and characterization of high-quality exfoliated mono- and bilayer graphene devices on single-crystal h-BN substrates, by using a mechanical transfer process. Graphene devices on h-BN substrates have mobilities and carrier inhomogeneities that are almost an order of magnitude better than devices on SiO2. These devices also show reduced roughness, intrinsic doping and chemical reactivity. The ability to assemble crystalline layered materials in a controlled way permits the fabrication of graphene devices on other promising dielectrics and allows for the realization of more complex graphene heterostructures.

Dean, C. R.; Young, A. F.; Meric, I.; Lee, C.; Wang, L.; Sorgenfrei, S.; Watanabe, K.; Taniguchi, T.; Kim, P.; Shepard, K. L.; Hone, J.

2010-10-01

348

Ultralow Contact Resistivity for a Metal/p-Type Silicon Interface by High-Concentration Germanium and Boron Doping Combined with Low-Temperature Annealing  

NASA Astrophysics Data System (ADS)

A contact resistivity of 6.9×10-9 ?.cm2 has been obtained in an AlSi (1 wt %)-Cu (0.5 wt %) alloy/silicon system by using heavy-dose ion implantations of germanium and boron combined with low-temperature annealing. The analysis of the combined state showed that B12 cluster was incorporated and the supersaturation activation layer was formed into the region where germanium separated. Separated germanium is expected to have high interface state density. It is considered that this interface state density also has a Fermi level, and in order to reduce the difference from the Fermi level of the substrate, the charge moves to interface state density from the substrate. As a result, it is not based on a metallic material but a work function becomes small because pinning by which a Fermi level is fixed to interface state density occurs owing to the substrate/metal interface. It is considered to be attributable to the existence of a Ge-rich layer formed by low-temperature annealing, and a supersaturation activation layer that lowers contact resistance was formed.

Murakoshi, Atsushi; Iwase, Masao; Niiyama, Hiromi; Koike, Mitsuo; Suguro, Kyoichi

2013-07-01

349

Friction and wear of carbon-graphite materials for high-energy brakes  

NASA Technical Reports Server (NTRS)

Caliper type brake simulation experiments were conducted on seven different carbon graphite materials formulations against a steel disk material and against a carbon graphite disk material. The effects of binder level, boron carbide (B4C) additions, SiC additions, graphite fiber additions, and graphite cloth reinforcement on friction and wear behavior were investigated. Reductions in binder level, additions of B4C, and additions of SiC each resulted in increased wear. The wear rate was not affected by the addition of graphite fibers. Transition to severe wear and high friction was observed in the case of graphite-cloth-reinforced carbon sliding against a disk of similar composition. The transition was related to the disruption of a continuous graphite shear film that must form on the sliding surfaces if low wear is to occur.

Bill, R. C.

1978-01-01

350

Friction and wear of carbon-graphite materials for high energy brakes  

NASA Technical Reports Server (NTRS)

Caliper-type brakes simulation experiments were conducted on seven different carbon-graphite material formulations against a steel disk material and against a carbon-graphite disk material. The effects of binder level, boron carbide (B4C) additions, graphite fiber additions, and graphite cloth reinforcement on friction and wear behavior were investigated. Reductions in binder level and additions of B4C each resulted in increased wear. The wear rate was not affected by the addition of graphite fibers. Transition to severe wear and high friction was observed in the case of graphite-cloth-reinforced carbon sliding against a disk of similar composition. This transition was related to the disruption of a continuous graphite shear film that must form on the sliding surfaces if low wear is to occur. The exposure of the fiber structure of the cloth constituent is believed to play a role in the shear film disruption.

Bill, R. C.

1975-01-01

351

Chapter 20: Graphite  

SciTech Connect

Graphite is truly a unique material. Its structure, from the nano- to the millimeter scale give it remarkable properties that lead to numerous and diverse applications. Graphite bond anisotropy, with strong in-plane covalent bonds and weak van der Waals type bonding between the planes, gives graphite its unique combination of properties. Easy shear of the crystal, facilitated by weak interplaner bonds allows graphite to be used as a dry lubricant, and is responsible for the substances name! The word graphite is derived from the Greek to write because of graphites ability to mark writing surfaces. Moreover, synthetic graphite contains within its structure, porosity spanning many orders of magnitude in size. The thermal closure of these pores profoundly affects the properties for example, graphite strength increases with temperature to temperatures in excess of 2200 C. Consequently, graphite is utilized in many high temperature applications. The basic physical properties of graphite are reviewed here. Graphite applications include metallurgical; (aluminum and steel production), single crystal silicon production, and metal casting; electrical (motor brushes and commutators); mechanical (seals, bearings and bushings); and nuclear applications, (see Chapter 91, Nuclear Graphite). Here we discuss the structure, manufacture, properties, and applications of Graphite.

Burchell, Timothy D [ORNL

2012-01-01

352

Covalent functionalization based heteroatom doped graphene nanosheet as a metal-free electrocatalyst for oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

Oxygen reduction reaction (ORR) is an important reaction in energy conversion systems such as fuel cells and metal-air batteries. Carbon nanomaterials doped with heteroatoms are highly attractive materials for use as electrocatalysts by virtue of their excellent electrocatalytic activity, high conductivity, and large surface area. This study reports the synthesis of highly efficient electrocatalysts based on heteroatom-doped graphene nanosheets prepared through covalent functionalization using various small organic molecules and a subsequent thermal treatment. A series of nitrogen-doped reduced graphene oxide (NRGOn) nanosheets exhibited varying degrees and configurations of nitrogen atoms within the graphitic framework depending on the type of precursors used. On the basis of the rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) experiments, NRGO3, with a high degree of pyridinic-N content, displayed the desired one-step, quasi-four-electron transfer pathway during ORR, similar to commercial Pt/C. We also demonstrated the potential of covalent functionalization of sulfur and boron-doped graphene nanosheets.Oxygen reduction reaction (ORR) is an important reaction in energy conversion systems such as fuel cells and metal-air batteries. Carbon nanomaterials doped with heteroatoms are highly attractive materials for use as electrocatalysts by virtue of their excellent electrocatalytic activity, high conductivity, and large surface area. This study reports the synthesis of highly efficient electrocatalysts based on heteroatom-doped graphene nanosheets prepared through covalent functionalization using various small organic molecules and a subsequent thermal treatment. A series of nitrogen-doped reduced graphene oxide (NRGOn) nanosheets exhibited varying degrees and configurations of nitrogen atoms within the graphitic framework depending on the type of precursors used. On the basis of the rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) experiments, NRGO3, with a high degree of pyridinic-N content, displayed the desired one-step, quasi-four-electron transfer pathway during ORR, similar to commercial Pt/C. We also demonstrated the potential of covalent functionalization of sulfur and boron-doped graphene nanosheets. Electronic supplementary information (ESI) available: UV-vis spectra of all NGOn, tables of atomic composition and nitrogen configurations from high-resolution XPS, RDE, and stability data are provided. See DOI: 10.1039/c3nr03581f

Park, Minju; Lee, Taemin; Kim, Byeong-Su

2013-11-01

353

The Graphite Page  

NSDL National Science Digital Library

John A. Jaszczak at Michigan Technological University presents the characteristics of graphite at this website. Students can find concise descriptions and helpful images about graphite properties, spirals, and structures. The website offers images and descriptions of graphite found all over the world. Using Macromedia Flash Player, students can observe graphite levitating due to its diamagnetic susceptibility. The website also offers an interactive applet presenting the atom positions for nano-tubes and nano-cones.

Jaszczak, John A.

354

Photoinduced graphitization of diamond  

NASA Astrophysics Data System (ADS)

The accumulative regime of diamond graphitization by a sequence of sub-threshold (for single impulse) femtosecond laser pulses has been studied. The model describing accumulative graphitization as gradual growth of graphite centers embedded into a diamond matrix is presented. The experimental data suggest that both the laser heating of these centers and the direct photodamage of the diamond lattice are involved in the process of diamond–graphite transformation.

Kononenko, V. V.; Gololobov, V. M.; Kononenko, T. V.; Konov, V. I.

2015-01-01

355

Pulsed laser evaporation of boron/carbon pellets: Infrared spectra and quantum chemical structures and frequencies for BCp  

E-print Network

Pulsed laser evaporation of boron/carbon pellets: Infrared spectra and quantum chemical structures March 1993) Pulsed laser evaporation of pellets pressed from boron and graphite powder gave a new 1 by pulsed laser evaporation3 and the formation of small carbon clusters including C3, Cs , Cg, and C

Martin, Jan M.L.

356

Graphite ionization vacuum gauge  

NASA Technical Reports Server (NTRS)

Triode gauge with electron source, electron collector, and positive ion collector made from either graphite or carbon material extends low-pressure ranges of existing gauges by changing only materials used in construction. Advantages of graphite gauge stem from physical properties of graphite (or carbon).

Beitel, G. A.; Benson, D. K.

1974-01-01

357

Study of high resistance inorganic coatings on graphite fibers. [for graphite-epoxy composite materials  

NASA Technical Reports Server (NTRS)

Coatings made of boron, silicon carbide, silica, and silica-like materials were studied to determine their ability to increase resistance of graphite fibers. The most promising results were attained by chemical vapor depositing silicon carbide on graphite fiber followed by oxidation, and drawing graphite fiber through ethyl silicate followed by appropriate heat treatments. In the silicon carbide coating studies, no degradation of the graphite fibers was observed and resistance values as high as three orders of magnitude higher than that of the uncoated fiber was attained. The strength of a composite fabricated from the coated fiber had a strength which compared favorably with those of composites prepared from uncoated fiber. For the silica-like coated fiber prepared by drawing the graphite fiber through an ethyl silicate solution followed by heating, coated fiber resistances about an order of magnitude greater than that of the uncoated fiber were attained. Composites prepared using these fibers had flexural strengths comparable with those prepared using uncoated fibers, but the shear strengths were lower.

Galasso, F. S.; Veltri, R. D.; Scola, D. A.

1979-01-01

358

Electron-phonon interactions in graphene, bilayer graphene, and graphite.  

PubMed

Using first-principles techniques, we calculate the renormalization of the electron Fermi velocity and the vibrational lifetimes arising from electron-phonon interactions in doped bilayer graphene and in graphite and compare the results with the corresponding quantities in graphene. For similar levels of doping, the Fermi velocity renormalization in bilayer graphene and in graphite is found to be approximately 30% larger than that in graphene. In the case of bilayer graphene, this difference is shown to arise from the interlayer interaction. We discuss our findings in the light of recent photoemission and Raman spectroscopy experiments. PMID:19368001

Park, Cheol-Hwan; Giustino, Feliciano; Cohen, Marvin L; Louie, Steven G

2008-12-01

359

Optimizing the boron effect  

Microsoft Academic Search

The effects of boron content varying from 0.0001 to 0.0110 wt pct were studied to determine the optimum boron range for commercially desirable combinations of hardenability and notch toughness in 11\\/4 in. thick steel plate made from grade ASTM A514-J. Increasing boron content up to 0.0025 pct resulted in a gradually increasing boron hardenability factor which reached a maximum value

G. F. Melloy; P. R. Summon; P. P. Podgursky

1973-01-01

360

Optimizing the boron effect  

Microsoft Academic Search

The effects of boron content varying from 0.0001 to 0.0110 wt pct were studied to determine the optimum boron range for commercially\\u000a desirable combinations of hardenability and notch toughness in 11\\/4 in. thick steel plate made from grade ASTM A514-J. Increasing\\u000a boron content up to 0.0025 pct resulted in a gradually increasing boron hardenability factor which reached a maximum value

G. F. Melloy; P. R. Summon; P. P. Podgursky

1973-01-01

361

Boron Ion Implantation into Silicon by Use of the Boron Vacuum-Arc Plasma Generator  

SciTech Connect

This paper continues with presentation of experimental work pertaining to use of the boron vacuum arc (a.k.a. cathodic arc) plasma generator for boron doping in semiconductor silicon, particularly with a view to the problems associated with shallow junction doping. Progress includes development of an excellent and novel macroparticle filter and subsequent ion implantations. An important perceived issue for vacuum arc generators is the production of copious macroparticles from cathode material. This issue is more important for cathodes of materials such as carbon or boron, for which the particles are not molten or plastic, but instead are elastic, and tend to recoil from baffles used in particle filters. The present design starts with two vanes of special orientation, so as to back reflect the particles, while steering the plasma between the vanes by use of high countercurrents in the vanes. Secondly, behind and surrounding the vanes is a complex system of baffles that has been designed by a computer-based strategy to ultimately trap the particles for multiple bounces. The statistical transmittance of particles is less than 5 per coulomb of boron ions transmitted at a position just a few centimeters outside the filter. This value appears adequate for the silicon wafer application, but improvement is easily visualized as wafers will be situated much further away when they are treated in systems. A total of 11 silicon samples, comprising an area of 250 cm2, have been implanted. Particles were not detected. Sample biases ranged from 60 to 500 V. Boron doses ranged from 5 x 1014 to 5 x 1015/cm2. Exposure times ranged from 20 to 200 ms for average transmitted boron current values of about 125 mA. SIMS concentration profiles from crystalline material are presented. The results appear broadly favorable in relation to competitive techniques and will be discussed. It is concluded that doubly charged boron ions are not present in the plume.

Williams, J. M. [Brontek Delta Corporation, 6580 Valley Center Drive, Radford, VA 24141 (United States); Klepper, C. C. [Brontek Delta Corporation, 6580 Valley Center Drive, Radford, VA 24141 (United States); HY-Tech Research Corporation, 105 Centre Court, Radford, VA 24141 (United States); Chivers, D. J. [Ion Links Int. Ltd., 32 St. Mary's Place, Bathgate, Scotland (United Kingdom); Hazelton, R. C.; Moschella, J. J.; Keitz, M. D. [HY-Tech Research Corporation, 105 Centre Court, Radford, VA 24141 (United States)

2006-11-13

362

Raman spectroscopic characterization of the core-rim structure in reaction bonded boron carbide ceramics  

NASA Astrophysics Data System (ADS)

Raman spectroscopy was used to characterize the microstructure of reaction bonded boron carbide ceramics. Compositional and structural gradation in the silicon-doped boron carbide phase (rim), which develops around the parent boron carbide region (core) due to the reaction between silicon and boron carbide, was evaluated using changes in Raman peak position and intensity. Peak shifting and intensity variation from the core to the rim region was attributed to changes in the boron carbide crystal structure based on experimental Raman observations and ab initio calculations reported in literature. The results were consistent with compositional analysis determined by energy dispersive spectroscopy. The Raman analysis revealed the substitution of silicon atoms first into the linear 3-atom chain, and then into icosahedral units of the boron carbide structure. Thus, micro-Raman spectroscopy provided a non-destructive means of identifying the preferential positions of Si atoms in the boron carbide lattice.

Jannotti, Phillip; Subhash, Ghatu; Zheng, James Q.; Halls, Virginia; Karandikar, Prashant G.; Salamone, S.; Aghajanian, Michael K.

2015-01-01

363

GUM Analysis for SIMS Isotopic Ratios in BEP0 Graphite Qualification Samples, Round 2  

SciTech Connect

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.

Gerlach, David C.; Heasler, Patrick G.; Reid, Bruce D.

2009-01-01

364

Producing graphite with desired properties  

NASA Technical Reports Server (NTRS)

Isotropic or anisotropic graphite is synthesized with precise control of particle size, distribution, and shape. The isotropic graphites are nearly perfectly isotropic, with thermal expansion coefficients two or three times those of ordinary graphites. The anisotropic graphites approach the anisotropy of pyrolytic graphite.

Dickinson, J. M.; Imprescia, R. J.; Reiswig, R. D.; Smith, M. C.

1971-01-01

365

Investigation of chemical modifiers for the determination of boron by electrothermal atomic absorption spectrometry  

NASA Astrophysics Data System (ADS)

A fast and efficient method for the determination of boron in aqueous solutions is described, using electrothermal atomic absorption spectrometry with a transversely heated graphite tube atomizer. The investigations were carried out with calcium chloride, zirconium chloride, and with mixtures of both reagents as chemical modifiers. Furthermore, the influence of zirconium treated graphite tubes on the sensitivity and stability of the analytical results was investigated. The developed method is suitable for the determination of boron over a concentration range from 0.1 to 2.0 mg/l without any additional dilution or enrichment steps. The atomization temperature could be lowered to 2550°C, and the best characteristic mass for boron of 0.19 ng was obtained for a zirconium-treated graphite tube and the addition of calcium chloride as a chemical modifier to the measurement solution. Sensitivity and precision of the measurement did not change significantly over an 8-h working day under these conditions.

Nowka, René; Eichardt, Klaus; Welz, Bernhard

2000-05-01

366

Radiation Effects in Graphite  

SciTech Connect

The requirements for a solid moderator are reviewed and the reasons that graphite has become the solid moderator of choice discussed. The manufacture and properties of some currently available near-isotropic and isotropic grades are described. The major features of a graphite moderated reactors are briefly outlined. Displacement damage and the induced structural and dimensional changes in graphite are described. Recent characterization work on nano-carbons and oriented pyrolytic graphites that have shed new light on graphite defect structures are reviewed, and the effect of irradiation temperature on the defect structures is highlighted. Changes in the physical properties of nuclear graphite caused by neutron irradiation are reported. Finally, the importance of irradiation induced creep is presented, along with current models and their deficiencies.

Burchell, Timothy D [ORNL

2012-01-01

367

Doping effects on metallic and semiconductor single-wall carbon nanotubes  

Microsoft Academic Search

In this paper we investigate nitrogen- and boron-doped zigzag and armchair single-wall carbon nanotubes (SWNTs) with theoretical models based on the density functional theory. We take into account nitrogen and boron doping for two isomers in which substitutive atoms are on opposite sides of the tube, but only in one isomer the impurity sites are symmetrical with respect to the

F. Buonocore

2007-01-01

368

Synthesis and Characterization of Boron Carbonitride Thin Films  

NASA Astrophysics Data System (ADS)

Boron carbonitride films were prepared by bias-assisted hot filament chemical vapor deposition from gaseous mixtures of CH_4, B_2H_6, N_2, and H2 on polycrystalline Ni, quartz, and graphite substrates. The crystalline films with various morphologies, structures, and compositions were grown under different conditions. The electrical properties of the obtained films, including resistivity, magnetoresistance, and field emission, were investigated systematically. In addition, it is believed that this type of films might have a higher hardness, which is important to cold cathode application. Therefore, the desired boron carbonitrides by varying the structure and composition should be listed as one of the candidates for field emitting materials.

Wang, E. G.; Yu, Jie; Xu, Guichang

1998-03-01

369

Covalent functionalization based heteroatom doped graphene nanosheet as a metal-free electrocatalyst for oxygen reduction reaction.  

PubMed

Oxygen reduction reaction (ORR) is an important reaction in energy conversion systems such as fuel cells and metal-air batteries. Carbon nanomaterials doped with heteroatoms are highly attractive materials for use as electrocatalysts by virtue of their excellent electrocatalytic activity, high conductivity, and large surface area. This study reports the synthesis of highly efficient electrocatalysts based on heteroatom-doped graphene nanosheets prepared through covalent functionalization using various small organic molecules and a subsequent thermal treatment. A series of nitrogen-doped reduced graphene oxide (NRGOn) nanosheets exhibited varying degrees and configurations of nitrogen atoms within the graphitic framework depending on the type of precursors used. On the basis of the rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) experiments, NRGO3, with a high degree of pyridinic-N content, displayed the desired one-step, quasi-four-electron transfer pathway during ORR, similar to commercial Pt/C. We also demonstrated the potential of covalent functionalization of sulfur and boron-doped graphene nanosheets. PMID:24146109

Park, Minju; Lee, Taemin; Kim, Byeong-Su

2013-12-21

370

Macroscopic Properties of Restacked, Redox-Liquid Exfoliated Graphite and Graphite Mimics Produced in Bulk Quantities  

SciTech Connect

The excellent properties exhibited by monolayer graphene have spurred the development of exfoliation techniques using bulk graphite to produce large quantities of pristine monolayer sheets. Development of simple chemistry to exfoliate and intercalate graphite and graphite mimics in large quantities is required for numerous applications. To determine the macroscopic behavior of restacked, exfoliated bulk materials, a systematic approach is presented using a simple, redox-liquid sonication process along to obtain large quantities of 2D and 3D hexagonally layered graphite, molybdenum disulfi de, and boron nitride, which are subsequently characterized to observe chemical and structural changes. For MoS 2 sonicated with the antioxidant sodium bisulfi te, results from Raman spectroscopy, X-ray diffraction, and electron microscopy indicate the presence of distorted phases from different polymorphs, and apparent nanotube structures in the bulk, restacked powder. Furthermore, using thermograviemtric analysis, the antioxidant enhances the resistance to oxidative degradation of MoS 2 , upon thermal treatment up to 900 C. The addition of the ionic antioxidant decreased dispersion stability in non-polar solvent, suggesting decreased compatibility with non-polar systems. Using simple chemical methods, the ability to generate tailored multidimensional layered materials with unique macroscopic properties is critical for numerous applications, including electrical devices, reinforced polymer composites, lithium ion capacitors, and chemical sensing.

Srivastava, Vikram K [ORNL; Quinlan, Ronald [ORNL; Agapov, Alexander L [ORNL; Dunlap, John R [ORNL; Nelson, Kimberly M [ORNL; Duranty, Edward R [ORNL; Sokolov, Alexei P [ORNL; Bhat, Gajanan [ORNL; Mays, Jimmy [ORNL

2014-01-01

371

Method for producing dustless graphite spheres from waste graphite fines  

DOEpatents

A method for producing graphite spheres from graphite fines by charging a quantity of spherical media into a rotatable cylindrical overcoater, charging a quantity of graphite fines into the overcoater thereby forming a first mixture of spherical media and graphite fines, rotating the overcoater at a speed such that the first mixture climbs the wall of the overcoater before rolling back down to the bottom thereby forming a second mixture of spherical media, graphite fines, and graphite spheres, removing the second mixture from the overcoater, sieving the second mixture to separate graphite spheres, charging the first mixture back into the overcoater, charging an additional quantity of graphite fines into the overcoater, adjusting processing parameters like overcoater dimensions, graphite fines charge, overcoater rotation speed, overcoater angle of rotation, and overcoater time of rotation, before repeating the steps until graphite fines are converted to graphite spheres.

Pappano, Peter J (Oak Ridge, TN); Rogers, Michael R (Clinton, TN)

2012-05-08

372

Performance of a diamond x-ray sensor fabricated with metal-less graphitic contacts  

NASA Astrophysics Data System (ADS)

We report the x-ray photocurrent response of a coplanar chemical vapor deposition diamond detector fabricated using a metal-less graphitic ohmic contact. Ion implantation of 70 keV boron ions to a dose of 2×1016cm-2 was performed through a patterned photoresist to produce a coplanar graphitic contact structure. The device photocurrent showed a fast response to pulsed x-ray irradiation, and showed no evidence of photocurrent persistence that is observed in devices fabricated using metal Schottky contacts. The graphite-contact device also showed no extrinsic photoconductivity when illuminated with white light.

Sellin, P. J.; Galbiati, A.

2005-08-01

373

Synthesis and structure of chemically vapour-deposited boron nitride  

Microsoft Academic Search

Chemically vapour-deposited boron nitride (CVD-BN) plates have been synthesized on a graphite substrate by the reaction of the BCl3-NH3-H2 gas system in a deposition temperature (Tdep) range from 1200 to 2000° C, with a total gas pressure (Ptot) which was varied from 5 to 60 torr. The effects ofPtot andTdep on the crystal structure and the microstructure of the CVD-BN

Toshitsugu Matsuda; Naoki Uno; Hiroyuki Nakae; Toshio Hirai

1986-01-01

374

Plant Availability of Boron Adsorbed or Occulted on Goethite to Rape (Brassica napus L.) Seedling  

Microsoft Academic Search

The purpose of the study was to determine plant availability of boron (B) and relaxation of soil acid to rape seedling exhibited by B-doped goethite in acidic soil. For this purpose, two kinds of B-doped goethite were synthesized: one was goethite with adsorbed B prepared by reacting goethite with borax solution, and the other was goethite with occluded B by

Liying Ren; Jingzhen Cui; Yuliang Dong; Duanwei Zhu; Shuijiao Liao; Mingjian Geng; David Hamilton

2010-01-01

375

Structural Modification in Carbon Nanotubes by Boron Incorporation  

PubMed Central

We have synthesized boron-incorporated carbon nanotubes (CNTs) by decomposition of ferrocene and xylene in a thermal chemical vapor deposition set up using boric acid as the boron source. Scanning and transmission electron microscopy studies of the synthesized CNT samples showed that there was deterioration in crystallinity and improvement in alignment of the CNTs as the boron content in precursor solution increased from 0% to 15%. Raman analysis of these samples showed a shift of ~7 cm?1in wave number to higher side and broadening of the G band with increasing boron concentration along with an increase in intensity of the G band. Furthermore, there was an increase in the intensity of the D band along with a decrease in its wave number position with increase in boron content. We speculate that these structural modifications in the morphology and microstructure of CNTs might be due to the charge transfer from boron to the graphite matrix, resulting in shortening of the carbon–carbon bonds. PMID:20596333

2009-01-01

376

Energy landscape of fullerene materials: A comparion of boron to boron nitride and carbon  

NASA Astrophysics Data System (ADS)

After the discovery of the C60 fullerene some 25 years ago, many more hollow and endohedrally doped structures made out of various elements have been proposed theoretically. However, since no other fullerenes have been synthesized up to date, the question arises whether experimentalists have just not yet found a way to synthesize these theoretically predicted fullerenes, or whether they do not exist at all in nature. Following the theoretical discovery of the B80 fullerene by Szwacki et al, various other fullereneand stuffed fullerene structures were proposed but none of them could be synthesized in the laboratory yet. Using the minima hopping global geometry optimization method on the density functional potential energy surface we show that the energy landscape of boron clusters is glass like. Medium size boron clusters exhibit many structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found. We thus present a methodology which can make predictions on the feasibility of the synthesis of new nano structures.

de, Sandip

2012-02-01

377

Effective Control of the Charge and Magnetic States of Transition-Metal Atoms on Single-Layer Boron Nitride  

E-print Network

-metal (TM) doped single-layer boron-nitride (SLBN) systems can be easily controlled by the (internal) defect layers. Single-layer boron-nitride (SLBN) or other III­V (e.g., AlN and GaN) and II­VI (e.g., ZnO and ZnEffective Control of the Charge and Magnetic States of Transition-Metal Atoms on Single-Layer Boron

Gong, Xingao

378

Single-walled B-doped carbon, B\\/N-doped carbon and BN nanotubes synthesized from single-walled carbon nanotubes through a substitution reaction  

Microsoft Academic Search

Bundles of single-walled boron-doped carbon (BxC1?x), boron- and nitrogen-doped carbon (BxC1?x?yNy) and boron nitride (BN) nanotubes were prepared by thermal treatment of a mixture of boron trioxide and bundles of single-walled carbon nanotubes at 1523–1623 K in a nitrogen flow. The (BxC1?x+BxC1?x?yNy)\\/BN nanotube yield ratio increased with decreasing temperature in the reaction zone. The nanotubes were characterised by using high-resolution

D. Golberg; Y Bando; W Han; K Kurashima; T Sato

1999-01-01

379

Boron arsenide thin film solar cell development. Final report  

SciTech Connect

Pyrolytic decomposition of diborane and arsine has been used in attempts to grow polycrystalline BAs films. This method, however, produced only amorphous films for deposition temperatures below 920/sup 0/C and polycrystalline boron subarsenide (B/sub 12/As/sub 2/) flms for deposition temperatures above this value. The amorphous films have been determined to have a significant arsenic content but the actual stoichiometry was not obtained. The films were adherent on single crystal sapphire (0001), (111) silicon, (0001) SiC, and polycrystalline SiC but were found not to be adherent to substrates of fused quartz, tungsten, and molybdenum. It was also found that all films deposited above 650/sup 0/C were p-type while those deposited below 600/sup 0/C were usually n-type. Polycrystalline BAs and B/sub 12/As/sub 2/ was produced by reaction of the elements in a closed tube. The amorphous films showed an indirect or non-direct optical bandgap from 1.0 to 1.7 eV with the most probable values between 1.2 to 1.4 eV. The crystalline BAs powder shows a bandgap near 1.0 eV. Photoconductance time constants have been measured for films deposited on (0001) sapphire and (0001) SiC. Attempts at doping the amorphous films were generally unsuccessful. A polycrystalline powder sample was successfully doped with sulfur. Attempts were made to produce a Schottky barrier diode by evaporating Al dots onto an amorphous film on graphite without a post-evaporation anneal. An MIS structure was also attempted by baking an amorphous film in air at 280/sup 0/C before evaporation of aluminum. Although nonlinear characteristics were obtained, none of the devices showed any photovoltaic response. A p-type amorphous film was deposited on an n-type silicon substrate to form a p-n heterojunction. This device did exhibit a photovoltaic response but it is believed that the photogeneration was occurring primarily in the silicon substrate.

Boone, J.L.; Van Doren, T.P.

1980-09-01

380

Intercalation compounds of graphite  

Microsoft Academic Search

A broad review of recent research work on the preparation and the remarkable properties of intercalation compounds of graphite, covering a wide range of topics from the basic chemistry, physics and materials science to engineering applications.

M. S. Dresselhaus; G. Dresselhaus

1981-01-01

381

Intercalation compounds of graphite  

Microsoft Academic Search

A broad review of recent research work on the preparation and the remarkable properties of intercalation compounds of graphite, covering a wide range of topics from the basic chemistry, physics and materials science to engineering applications.

M. S. Dresselhaus; G. Dresselhaus

2002-01-01

382

Structure, Mechanics and Synthesis of Nanoscale Carbon and Boron Nitride  

NASA Astrophysics Data System (ADS)

This thesis is divided into two parts. In Part I, we examine the properties of thin sheets of carbon and boron nitride. We begin with an introduction to the theory of elastic sheets, where the stretching and bending modes are considered in detail. The coupling between stretching and bending modes is thought to play a crucial role in the thermodynamic stability of atomically-thin 2D sheets such as graphene. In Chapter 2, we begin by looking at the fabrication of suspended, atomically thin sheets of graphene. We then study their mechanical resonances which are read via an optical transduction technique. The frequency of the resonators was found to depend on their temperature, as was their quality factor. We conclude by offering some interpretations of the data in terms of the stretching and bending modes of graphene. In Chapter 3, we look briefly at the fabrication of thin sheets of carbon and boron nitride nanotubes. We examine the structure of the sheets using transmission and scanning electron microscopy (TEM and SEM, respectively). We then show a technique by which one can make sheets suspended over a trench with adjustable supports. Finally, DC measurements of the resistivity of the sheets in the temperature range 600 -- 1400 C are presented. In Chapter 4, we study the folding of few-layer graphene oxide, graphene and boron nitride into 3D aerogel monoliths. The properties of graphene oxide are first considered, after which the structure of graphene and boron nitride aerogels is examined using TEM and SEM. Some models for their structure are proposed. In Part II, we look at synthesis techniques for boron nitride (BN). In Chapter 5, we study the conversion of carbon structures of boron nitride via the application of carbothermal reduction of boron oxide followed by nitridation. We apply the conversion to a wide variety of morphologies, including aerogels, carbon fibers and nanotubes, and highly oriented pyrolytic graphite. In the latter chapters, we look at the formation of boron nitride nanotubes (BNNTs). In Chapter 6, we look at various methods of producing BNNTs from boron droplets, and introduce a new method involving injection of boron powder into an induction furnace. In Chapter 7 we consider another useful process, where ammonia is reacted with boron vapor generated in situ, either through the reaction of boron with metal oxides or through the decomposition of metal borides.

Rinaldo, Steven G.

383

The structure of boron in boron fibres  

NASA Technical Reports Server (NTRS)

The structure of noncrystalline, chemically vapour-deposited boron fibres was investigated by computer modelling the experimentally obtained X-ray diffraction patterns. The diffraction patterns from the models were computed using the Debye scattering equation. The modelling was done utilizing the minimum nearest-neighbour distance, the density of the model, and the broadening and relative intensity of the various peaks as boundary conditions. The results suggest that the fibres consist of a continuous network of randomly oriented regions of local atomic order, about 2 nm in diameter, containing boron atoms arranged in icosahedra. Approximately half of these regions have a tetragonal structure and the remaining half a distorted rhombohedral structure. The model also indicates the presence of many partial icosahedra and loose atoms not associated with any icosahedra. The partial icosahedra and loose atoms indicated in the present model are in agreement with the relaxing sub-units which have been suggested to explain the anelastic behavior of fibre boron and the loosely bound boron atoms which have been postulated to explain the strengthening mechanism in boron fibres during thermal treatment.

Bhardwaj, J.; Krawitz, A. D.

1983-01-01

384

Carbon nanotube core graphitic shell hybrid fibers.  

PubMed

A carbon nanotube yarn core graphitic shell hybrid fiber was fabricated via facile heat treatment of epoxy-based negative photoresist (SU-8) on carbon nanotube yarn. The effective encapsulation of carbon nanotube yarn in carbon fiber and a glassy carbon outer shell determines their physical properties. The higher electrical conductivity (than carbon fiber) of the carbon nanotube yarn overcomes the drawbacks of carbon fiber/glassy carbon, and the better properties (than carbon nanotubes) of the carbon fiber/glassy carbon make up for the lower thermal and mechanical properties of the carbon nanotube yarn via synergistic hybridization without any chemical doping and additional processes. PMID:24224730

Hahm, Myung Gwan; Lee, Jae-Hwang; Hart, Amelia H C; Song, Sung Moo; Nam, Jaewook; Jung, Hyun Young; Hashim, Daniel Paul; Li, Bo; Narayanan, Tharangattu N; Park, Chi-Dong; Zhao, Yao; Vajtai, Robert; Kim, Yoong Ahm; Hayashi, Takuya; Ku, Bon-Cheol; Endo, Morinobu; Barrera, Enrique; Jung, Yung Joon; Thomas, Edwin L; Ajayan, Pulickel M

2013-12-23

385

Characterization of pure boron depositions integrated in silicon diodes for nanometer-deep junction applications  

Microsoft Academic Search

Doping technologies for formation of ultrashallow and highly-doped p+ junctions are continuously demanded to face the challenges in front-end processing that have emerged due to the aggressive downscaling of vertical dimensions for future semiconductor devices. As an alternative to implantations, current solutions are based on in-situ boron (B) doping during Si\\/SiGe chemical vapor deposition (CVD) by using diborane (B2H6) as

F. Sarubbi

2010-01-01

386

Graphite Technology Development Plan  

SciTech Connect

This technology development plan is designed to provide a clear understanding of the research and development direction necessary for the qualification of nuclear grade graphite for use within the Next Generation Nuclear Plant (NGNP) reactor. The NGNP will be a helium gas cooled Very High Temperature Reactor (VHTR) with a large graphite core. Graphite physically contains the fuel and comprises the majority of the core volume. Considerable effort will be required to ensure that the graphite performance is not compromised during operation. Based upon the perceived requirements the major data needs are outlined and justified from the perspective of reactor design, reatcor performance, or the reactor safety case. The path forward for technology development can then be easily determined for each data need. How the data will be obtained and the inter-relationships between the experimental and modeling activities will define the technology development for graphite R&D. Finally, the variables affecting this R&D program are discussed from a general perspective. Factors that can significantly affect the R&D program such as funding, schedules, available resources, multiple reactor designs, and graphite acquisition are analyzed.

W. Windes; T. Burchell; R. Bratton

2007-09-01

387

Passivation effects in B doped self-assembled Si nanocrystals  

NASA Astrophysics Data System (ADS)

Doping of semiconductor nanocrystals has enabled their widespread technological application in optoelectronics and micro/nano-electronics. In this work, boron-doped self-assembled silicon nanocrystal samples have been grown and characterised using Electron Spin Resonance and photoluminescence spectroscopy. The passivation effects of boron on the interface dangling bonds have been investigated. Addition of boron dopants is found to compensate the active dangling bonds at the interface, and this is confirmed by an increase in photoluminescence intensity. Further addition of dopants is found to reduce the photoluminescence intensity by decreasing the minority carrier lifetime as a result of the increased number of non-radiative processes.

Puthen Veettil, B.; Wu, Lingfeng; Jia, Xuguang; Lin, Ziyun; Zhang, Tian; Yang, Terry; Johnson, Craig; McCamey, Dane; Conibeer, Gavin; Perez-Würfl, Ivan

2014-12-01

388

Electrical Characterization of Boron-Carbon Thin Films  

NASA Astrophysics Data System (ADS)

P-N junction diodes of boron-carbide and silicon have been previously fabricated and used in thermal neutron detection [1, 2]. However, the relation between the structure and electronic behavior of the boron-carbon layer are not fully understood. Thin films of p-type boron-carbon were deposited on Al2O3 substrates using plasma-enhanced chemical vapor deposition (PECVD), approximately 300 nm thick. The precursor compound used was Orthocarborane (closo-1,2-dicarbadodecaborane; C_2B_10H_12). Transport measurements of boron-carbon films on Al_2O3 were performed over a wide range of temperatures (20 K to 500 K). The resistivity at room temperature was found to be approximately 10000 ohm cm, and the temperature dependence showed a linear increase with temperature Analysis of the resistivity revealed the boron-carbon films to be a highly-doped degenerate semiconductor [2]. We discuss the relationship between structure and doping levels in this semiconducting material. [1] Adenwalla, S; Welsch, P; Harken A; Brand, JI; Sezer, A; Robertson, BW; Applied Physics Letters 79(26): 4357-4359 (2001) [2] Robertson, BW; Adenwalla, S; Harken A; Welsch, P; Brand, JI; Dowben, PA; Claasen, JP; Applied Physics Letters 80(19): 3644-3646 (2002) [3] Ashcroft, Neil W., & Mermin, N. David 1976, in Solid State Physics, ed. Thomson (New York: Thomson), 561-585

Diaz, Manuel; Adenwalla, Shireen

2004-03-01

389

Electrical Activity of Boron and Phosphorus in Hydrogenated Amorphous Silicon  

NASA Astrophysics Data System (ADS)

Using realistic models of hydrogenated amorphous silicon and density functional methods, we explore doping and transport with the most popular impurities: boron and phosphorous. We discuss conventional analogies of doping based upon shallow acceptors and donors in a crystalline matrix and highlight the limitations of such an approach. We show that B enters the network always with considerable strain, whereas P is much more "substitutional" in a tetrahedral site. We show that H is attracted to strained centers, especially for B, which increases the likelihood of H passivation effects on B impurities. We elucidate doping and nondoping static configurations in doped a -Si ?H , and the role of H passivation as a partial explanation for the well-known low doping efficiency the material exhibits. We show that thermal fluctuations (that induce both network motion and H hopping) can also significantly impact conduction. We draw comparisons to experimental work.

Pandey, A.; Cai, B.; Podraza, N.; Drabold, D. A.

2014-11-01

390

Control of work function of graphene by plasma assisted nitrogen doping  

NASA Astrophysics Data System (ADS)

Nitrogen doping is expected to provide several intriguing properties to graphene. Nitrogen plasma treatment to defect-free and defective highly oriented pyrolytic graphite (HOPG) samples causes doping of nitrogen atom into the graphene layer. Nitrogen atoms are initially doped at a graphitic site (inside the graphene) for the defect-free HOPG, while doping to a pyridinic or a pyrrolic site (edge of the graphene) is dominant for the defective HOPG. The work function of graphene correlates strongly with the site and amount of doped nitrogen. Nitrogen atoms doped at a graphitic site lower the work function, while nitrogen atoms at a pyridinic or a pyrrolic site increase the work function. Control of plasma treatment time and the amount of initial defect could change the work function of graphite from 4.3 eV to 5.4 eV, which would open a way to tailor the nature of graphene for various industrial applications.

Akada, Keishi; Terasawa, Tomo-o.; Imamura, Gaku; Obata, Seiji; Saiki, Koichiro

2014-03-01

391

Control of work function of graphene by plasma assisted nitrogen doping  

SciTech Connect

Nitrogen doping is expected to provide several intriguing properties to graphene. Nitrogen plasma treatment to defect-free and defective highly oriented pyrolytic graphite (HOPG) samples causes doping of nitrogen atom into the graphene layer. Nitrogen atoms are initially doped at a graphitic site (inside the graphene) for the defect-free HOPG, while doping to a pyridinic or a pyrrolic site (edge of the graphene) is dominant for the defective HOPG. The work function of graphene correlates strongly with the site and amount of doped nitrogen. Nitrogen atoms doped at a graphitic site lower the work function, while nitrogen atoms at a pyridinic or a pyrrolic site increase the work function. Control of plasma treatment time and the amount of initial defect could change the work function of graphite from 4.3?eV to 5.4?eV, which would open a way to tailor the nature of graphene for various industrial applications.

Akada, Keishi; Terasawa, Tomo-o; Imamura, Gaku; Obata, Seiji; Saiki, Koichiro, E-mail: saiki@k.u-tokyo.ac.jp [Department of Complexity Science and Engineering, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8561 (Japan)

2014-03-31

392

Dose calculation from a D-D-reaction-based BSA for boron neutron capture synovectomy.  

PubMed

Monte Carlo simulations were carried out to calculate dose in a knee phantom from a D-D-reaction-based Beam Shaping Assembly (BSA) for Boron Neutron Capture Synovectomy (BNCS). The BSA consists of a D(d,n)-reaction-based neutron source enclosed inside a polyethylene moderator and graphite reflector. The polyethylene moderator and graphite reflector sizes were optimized to deliver the highest ratio of thermal to fast neutron yield at the knee phantom. Then neutron dose was calculated at various depths in a knee phantom loaded with boron and therapeutic ratios of synovium dose/skin dose and synovium dose/bone dose were determined. Normalized to same boron loading in synovium, the values of the therapeutic ratios obtained in the present study are 12-30 times higher than the published values. PMID:19828325

Abdalla, Khalid; Naqvi, A A; Maalej, N; Elshahat, B

2010-01-01

393

Graphite Gamma Scan Results  

SciTech Connect

This report documents the measurement and data analysis of the radio isotopic content for a series of graphite specimens irradiated in the first Advanced Graphite Creep (AGC) experiment, AGC-1. This is the first of a series of six capsules planned as part of the AGC experiment to fully characterize the neutron irradiation effects and radiation creep behavior of current nuclear graphites. The AGC-1 capsule was irradiated in the Advanced Test Reactor (ATR) at INL at approximately 700 degrees C and to a peak dose of 7 dpa (displacements per atom). Details of the irradiation conditions and other characterization measurements performed on specimens in the AGC-1 capsule can be found in “AGC-1 Specimen Post Irradiation Data Report” ORNL/TM 2013/242. Two specimens from six different graphite types are analyzed here. Each specimen is 12.7 mm in diameter by 25.4 mm long. The isotope with the highest activity was 60Co. Graphite type NBG-18 had the highest content of 60Co with an activity of 142.89 µCi at a measurement distance of 47 cm.

Mark W. Drigert

2014-04-01

394

Irradiation Creep in Graphite  

SciTech Connect

An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

Ubic, Rick; Butt, Darryl; Windes, William

2014-03-13

395

Channeling studies in graphite  

SciTech Connect

The channeling characteristics of helium ions in the polycrystalline semimetal graphite have been studied using Rutherford Backscattering Spectrometry in the 1.2--2.4 MeV energy range. Axial channeling is investigated in the geometry where the ion beam is parallel to the highly preferred c-axis direction of a sample of highly-oriented pyrolytic graphite (HOPG). Assuming a Gaussian distribution of crystallite orientations and measuring the energy and angular dependencies of the backscattering yield, it was possible to extract the minimum yield and the critical angle for channeling in single-crystal graphite, and the standard deviation for the spread in c-axis crystallite orientations. An unusual increase of the measured angular width for channeling with depth was observed, and is attributed to the polycrystalline nature of HOPG.

Elman, B.S.; Braunstein, G.; Dresselhaus, M.S.; Dresselhaus, G.; Venkatesan, T.; Wilkens, B.

1984-10-01

396

Interlayer interactions in graphites  

PubMed Central

Based on ab initio calculations of both the ABC- and AB-stacked graphites, interlayer potentials (i.e., graphene-graphene interaction) are obtained as a function of the interlayer spacing using a modified Möbius inversion method, and are used to calculate basic physical properties of graphite. Excellent consistency is observed between the calculated and experimental phonon dispersions of AB-stacked graphite, showing the validity of the interlayer potentials. More importantly, layer-related properties for nonideal structures (e.g., the exfoliation energy, cleave energy, stacking fault energy, surface energy, etc.) can be easily predicted from the interlayer potentials, which promise to be extremely efficient and helpful in studying van der Waals structures. PMID:24192753

Chen, Xiaobin; Tian, Fuyang; Persson, Clas; Duan, Wenhui; Chen, Nan-xian

2013-01-01

397

Cesium diffusion in graphite  

SciTech Connect

Experiments on diffusion of /sup 137/Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of /sup 137/Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000/sup 0/C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ..delta..E of the equation D/epsilon = (D/epsilon)/sub 0/ exp (-..delta..E/RT) are about 4 x 10/sup -2/ cm/sup 2//s and 30 kcal/mole, respectively.

Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

1980-05-01

398

Enhancement of electrical conductivity and electrochemical activity of hydrogenated amorphous carbon by incorporating boron atoms  

NASA Astrophysics Data System (ADS)

Conductive boron-doped hydrogenated amorphous carbon (B-DLC) thin films were successfully synthesized with RF plasma-enhanced CVD method. By incorporating boron atoms in amorphous carbon, conduction types were changed from n- to p-type, and volume resistivity was decreased from 30.4 (non-doped) to 6.36 × 10-2 ? cm (B/C = 2.500 atom%). B-DLC film with sp2/(sp2 + sp3) carbons of 75 atom% exhibited high resistance to electrochemically-induced corrosion in strong acid solution. Furthermore, it was clarified that boron atoms in DLC could enhance kinetics of hydrogen evolution during water electrolysis at B-DLC surface. B-DLC is, therefore, a promising electrode material for hydrogen production by increasing the concentration of boron atoms in B-DLC and enhancing the reactivity of H2 evolution.

Naragino, Hiroshi; Yoshinaga, Kohsuke; Nakahara, Akira; Tanaka, Sakuya; Honda, Kensuke

2013-06-01

399

Improved graphite furnace atomizer  

DOEpatents

A graphite furnace atomizer for use in graphite furnace atomic absorption spectroscopy is described wherein the heating elements are affixed near the optical path and away from the point of sample deposition, so that when the sample is volatilized the spectroscopic temperature at the optical path is at least that of the volatilization temperature, whereby analyteconcomitant complex formation is advantageously reduced. The atomizer may be elongated along its axis to increase the distance between the optical path and the sample deposition point. Also, the atomizer may be elongated along the axis of the optical path, whereby its analytical sensitivity is greatly increased.

Siemer, D.D.

1983-05-18

400

Burning characteristics and fiber retention of graphite/resin matrix composites  

NASA Technical Reports Server (NTRS)

Graphite fiber reinforced resin matrix composites were subjected to controlled burning conditions to determine their burning characteristics and fiber retention properties. Small samples were burned with a natural gas fired torch to study the effects of fiber orientation and structural flaws such as holes and slits that were machined into the laminates. Larger laminate samples were burned in a modified heat release rate calorimeter. Unidirectional epoxy/graphite and polyimide/graphite composites and boron powder filled samples of each of the two composite systems were burn tested. The composites were exposed to a thermal radiation of 5.3 Btu/sq ft-sec in air. Samples of each of the unfilled composite were decomposed anaerobically in the calorimeter. Weight loss data were recorded for burning and decomposition times up to thirty-five minutes. The effects of fiber orientation, flaws, and boron filler additives to the resins were evaluated. A high char forming polyimide resin was no more effective in retaining graphite fibers than a low char forming epoxy resin when burned in air. Boron powder additions to both the polyimide and the epoxy resins stabilized the chars and effectively controlled the fiber release.

Bowles, K. J.

1980-01-01

401

Graphite-based photovoltaic cells  

DOEpatents

The present invention uses lithographically patterned graphite stacks as the basic building elements of an efficient and economical photovoltaic cell. The basic design of the graphite-based photovoltaic cells includes a plurality of spatially separated graphite stacks, each comprising a plurality of vertically stacked, semiconducting graphene sheets (carbon nanoribbons) bridging electrically conductive contacts.

Lagally, Max (Madison, WI); Liu, Feng (Salt Lake City, UT)

2010-12-28

402

Status of Initial Assessment of Physical and Mechanical Properties of Graphite Grades for NGNP Appkications  

SciTech Connect

Current candidate graphite grades for the core structures of NGNP include grades NBG-17, NBG-18, PCEA and IG-430. Both NBG-17 and NBG-18 are manufactured using pitch coke, and are vibrationally molded. These medium grain products are produced by SGL Carbon SAS (France). Tayo Tanso (Japan) produces IG-430 which is a petroleum coke, isostatically molded, nuclear grade graphite. And PCEA is a medium grain, extruded graphite produced by UCAR Carbon Co. (USA) from petroleum coke. An experimental program has been initiated to develop physical and mechanical properties data for these current candidate graphites. The results will be judged against the requirements for nuclear grade graphites set forth in ASTM standard D 7219-05 "Standard Specification for Isotropic and Near-isotropic Nuclear Graphites". Physical properties data including thermal conductivity and coefficient of thermal expansion, and mechanical properties data including tensile, compressive and flexural strengths will be obtained using the established test methods covered in D-7219 and ASTM C 781-02 "Standard Practice for Testing Graphite and Boronated Graphite Components for High-Temperature Gas-Cooled Nuclear Reactors". Various factors known to effect the properties of graphites will be investigated. These include specimen size, spatial location within a graphite billet, specimen orientation (ag and wg) within a billet, and billet-to-billet variations. The current status of the materials characterization program is reported herein. To date billets of the four graphite grades have been procured, and detailed cut up plans for obtaining the various specimens have been prepared. Particular attention has been given to the traceability of each specimen to its spatial location and orientation within a billet.

Strizak, Joe P [ORNL; Burchell, Timothy D [ORNL; Windes, Will [Idaho National Laboratory (INL)

2011-12-01

403

Structure of the B Si(100) surface at low boron coverage studied by scanning tunnelling microscopy  

Microsoft Academic Search

Scanning tunnelling microscopy is used to study the structure of the BSi(100) surface at low boron coverage, the surface being prepared by high-temperature annealing of heavily B-doped Si(100) samples. The surface reproducibly shows features which are identified as being induced by boron atoms. Based on high-resolution scanning tunnelling microscopy measurements performed at different tip-sample biases, a structural model of the

M. A Kulakov; Z Zhang; A. V Zotov; B Bullemer; I Eisele

1996-01-01

404

Development of seal ring carbon-graphite materials (tasks 8, 9, and 10)  

NASA Technical Reports Server (NTRS)

A screening study was conducted to develop improved carbon-graphite materials for use in self-acting seals at air temperatures to 1300 F (704 C). Property measurements on materials prepared during this study have shown that: (1) The mechanical properties of a carbon-graphite material were significantly improved by using a fine milled artificial graphite filler material and including intensive mixing, warm molding, and pitch impregnation in the processing; and (2) the oxidation resistance of a carbon-graphite material was improved by including fine milled boron carbide as an oxidation-inhibiting additive. These techniques were employed to develop a material that has 10 times more oxidation resistance than that of a widely used commercial grade and mechanical properties that approach those of the commercial grade.

Fechter, N. J.; Petrunich, P. S.

1973-01-01

405

SiliconPV: 17-20 April 2011, Freiburg, Germany Electrical properties of boron, phosphorus and gallium  

E-print Network

and gallium co-doped silicon Erwann Fourmonda , Maxime Forstera,b , Roland Einhausb , Hubert Lauvrayb , Jed from solar grade poly Silicon, to which Boron, Phosphorous and Gallium were added as dopants. The introduction of Gallium as a third dopant allowed for a better control of the resistivity and the doping type

Paris-Sud XI, Université de

406

(Irradiation creep of graphite)  

SciTech Connect

The traveler attended the Conference, International Symposium on Carbon, to present an invited paper, Irradiation Creep of Graphite,'' and chair one of the technical sessions. There were many papers of particular interest to ORNL and HTGR technology presented by the Japanese since they do not have a particular technology embargo and are quite open in describing their work and results. In particular, a paper describing the failure of Minor's law to predict the fatigue life of graphite was presented. Although the conference had an international flavor, it was dominated by the Japanese. This was primarily a result of geography; however, the work presented by the Japanese illustrated an internal program that is very comprehensive. This conference, a result of this program, was better than all other carbon conferences attended by the traveler. This conference emphasizes the need for US participation in international conferences in order to stay abreast of the rapidly expanding HTGR and graphite technology throughout the world. The United States is no longer a leader in some emerging technologies. The traveler was surprised by the Japanese position in their HTGR development. Their reactor is licensed and the major problem in their graphite program is how to eliminate it with the least perturbation now that most of the work has been done.

Kennedy, C.R.

1990-12-21

407

Copper intercalation into graphite  

NASA Astrophysics Data System (ADS)

An electric brush is necessary for an electric motor to function. The purpose of this thesis is to propose a technique to improve electric brush properties in an effort to produce a more proficient electric motor by creating a new brush material with improved properties and performance. There are many applications for electric motors and each application would benefit from overall, increased proficiency. Understanding the role an electric brush plays within an electric motor is crucial to improving functionality. The proposed technique to create a novel graphite-copper material involves a two-step procedure that will intercalate CuCl2 into the graphite structure, and then by chemical reduction, will reduce the CuCl2 and result in the final products of copper and graphite. The proposed technique seeks to successfully increase the conductivity and wear properties of an electric brush by incorporating copper into graphite which will also enhance the properties of an electric motor. This thesis will detail the procedures of data collection and how to analyze results of the proposed technique. Expected results will also be discussed utilizing preliminary data collected utilizing XRD, SEM, TGA, and BET equipment. Finally, struggles and challenges of such a technique will also be discussed as well as plans for future work on the proposed technique.

Kalbus, Kyle

408

Coatings for Graphite Fibers  

NASA Technical Reports Server (NTRS)

Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak.

Galasso, F. S.; Scola, D. A.; Veltri, R. D.

1980-01-01

409

Structural graphitic carbon foams  

SciTech Connect

Graphitic carbon foams are a unique material form with very high structural and thermal properties at a light weight. A process has been developed to produce microcellular, open-celled graphitic foams. The process includes heating a mesophase pitch preform above the pitch melting temperature in a pressurized reactor. At the appropriate time, the pressure is released, the gas nucleates bubbles, and these bubbles grow forming the pitch into the foam structure. The resultant foamed pitch is then stabilized in an oxygen environment. At this point a rigid structure exists with some mechanical integrity. The foam is then carbonized to 800 C followed by a graphitization to 2700 C. The shear action from the growing bubbles aligns the graphitic planes along the foam struts to provide the ideal structure for good mechanical properties. Some of these properties have been characterized for some of the foam materials. It is known that variations of the blowing temperature, blowing pressure and saturation time result in foams of variously sized with mostly open pores; however, the mechanism of bubble nucleation is not known. Therefore foams were blown with various gases to begin to determine the nucleation method. These gases are comprised of a variety of molecular weights as well as a range of various solubility levels. By examining the resultant structures of the foam, differences were noted to develop an explanation of the foaming mechanism.

Kearns, K.M.; Anderson, H.J. [Air Force Lab., Wright-Patterson AFB, OH (United States). Materials and Mfg. Directorate

1998-12-31

410

Graphite criteria peer review  

SciTech Connect

This report documents a review of the stress criteria proposed for the graphite components of the modular high temperature gas-cooled reactor (MHTGR) core. The review was conducted by a panel of six independent consultants, chosen for their expertise over a range of relevant disciplines.

NONE

1986-09-01

411

BAND STRUCTURE OF GRAPHITE  

Microsoft Academic Search

Tight-binding calculations, using a two-dimensional model of the ; graphite lattice, lead to a point of contact of of valence and conduction bands ; at the corner of the reduced Brillouin zone. A perturbation calculation which ; starts with wave functions of the two-dimensional lattice and is applied to the ; three-dimensional lattice is described. Some general features of the

J. C. Slonczewski; P. R. Weiss

1958-01-01

412

Chemical Analysis of Impurity Boron Atoms in Diamond Using Soft X-ray Emission Spectroscopy  

SciTech Connect

To analyze the local structure and/or chemical states of boron atoms in boron-doped diamond, which can be synthesized by the microwave plasma-assisted chemical vapor deposition method (CVD-B-diamond) and the temperature gradient method at high pressure and high temperature (HPT-B-diamond), we measured the soft X-ray emission spectra in the CK and BK regions of B-diamonds using synchrotron radiation at the Advanced Light Source (ALS). X-ray spectral analyses using the fingerprint method and molecular orbital calculations confirm that boron atoms in CVD-B-diamond substitute for carbon atoms in the diamond lattice to form covalent B-C bonds, while boron atoms in HPT-B-diamond react with the impurity nitrogen atoms to form hexagonal boron nitride. This suggests that the high purity diamond without nitrogen impurities is necessary to synthesize p-type B-diamond semiconductors.

Muramatsu, Yasuji; Iihara, Junji; Takebe, Toshihiko; Denlinger, Jonathan D.

2008-03-29

413

Boron-Based Layered Structures for Energy Storage  

SciTech Connect

Based on Density Functional Theory simulations, we have studied the boron-based graphite-like materials, i.e., LiBC and MgB2 for energy storage. First, when half of the Li-ions in the LiBC are removed, the BC layered structure is still preserved. The Li intercalation potential (equilibrium lithium-insertion voltage of 2.3-2.4 V relative to lithium metal) is significantly higher than that in graphite, allowing Li0.5BC to function as a cathode material. The reversible electrochemical reaction, LiBC = Li0.5BC + 0.5Li, enables a specific energy density of 1088 Wh/kg and a volumetric energy density of 2463 Wh/L. Second, 75% of the Mg ions in MgB2 can be removed and reversibly inserted with the layered boron structures being preserved through an in-plane topological transformation between the hexagonal lattice domains and triangular domains. The mechanism of such a charge-driven transformation originates from the versatile valence state of boron in its planar form.

Zhao, Y.; Wei, S. H.

2012-01-01

414

Novel semiconducting boron carbide/pyridine polymers for neutron detection at zero bias  

NASA Astrophysics Data System (ADS)

Thin films containing aromatic pyridine moieties bonded to boron, in the partially dehydrogenated boron-rich icosahedra (B10C2HX), prove to be an effective material for neutron detection applications when deposited on n-doped (100) silicon substrates. The characteristic I-V curves for the heterojunction diodes exhibit strong rectification and largely unperturbed normalized reverse bias leakage currents with increasing pyridine content. The neutron capture generated pulses from these heterojunction diodes were obtained at zero bias voltage although without the signatures of complete electron-hole collection. These results suggest that modifications to boron carbide may result in better neutron voltaic materials.

Echeverría, Elena; James, Robinson; Chiluwal, Umesh; Pasquale, Frank L.; Colón Santana, Juan A.; Gapfizi, Richard; Tae, Jae-Do; Driver, M. Sky; Enders, A.; Kelber, Jeffry A.; Dowben, P. A.

2015-01-01

415

Piezoresistance and hole transport in beryllium-doped silicon.  

NASA Technical Reports Server (NTRS)

The resistivity and piezoresistance of p-type silicon doped with beryllium have been studied as a function of temperature, crystal orientation, and beryllium doping concentration. It is shown that the temperature coefficient of resistance can be varied and reduced to zero near room temperature by varying the beryllium doping level. Similarly, the magnitude of the piezoresistance gauge factor for beryllium-doped silicon is slightly larger than for silicon doped with a shallow acceptor impurity such as boron, while the temperature coefficient of piezoresistance is about the same for material containing these two dopants. These results are discussed in terms of a model for the piezoresistance of compensated p-type silicon.

Littlejohn, M. A.; Robertson, J. B.

1972-01-01

416

Two-dimensional numerical simulation of boron diffusion for pyramidally textured silicon  

NASA Astrophysics Data System (ADS)

Multidimensional numerical simulation of boron diffusion is of great relevance for the improvement of industrial n-type crystalline silicon wafer solar cells. However, surface passivation of boron diffused area is typically studied in one dimension on planar lifetime samples. This approach neglects the effects of the solar cell pyramidal texture on the boron doping process and resulting doping profile. In this work, we present a theoretical study using a two-dimensional surface morphology for pyramidally textured samples. The boron diffusivity and segregation coefficient between oxide and silicon in simulation are determined by reproducing measured one-dimensional boron depth profiles prepared using different boron diffusion recipes on planar samples. The established parameters are subsequently used to simulate the boron diffusion process on textured samples. The simulated junction depth is found to agree quantitatively well with electron beam induced current measurements. Finally, chemical passivation on planar and textured samples is compared in device simulation. Particularly, a two-dimensional approach is adopted for textured samples to evaluate chemical passivation. The intrinsic emitter saturation current density, which is only related to Auger and radiative recombination, is also simulated for both planar and textured samples. The differences between planar and textured samples are discussed.

Ma, Fa-Jun; Duttagupta, Shubham; Shetty, Kishan Devappa; Meng, Lei; Samudra, Ganesh S.; Hoex, Bram; Peters, Ian Marius

2014-11-01

417

The effects of boron and hydrogen on the room temperature ductility and fracture behavior of Ni(3)Al and FeAl  

NASA Astrophysics Data System (ADS)

The effects of molecular hydrogen on the ductility and fracture behavior of polycrystalline Nisb3Al and FeAl were investigated using high purity hydrogen gas. Pressures ranging from ˜7 × 10sp{-8} Pa were employed. Since small amounts of boron, on the order of a few hundred weight parts per million (wppm), are known to improve the room temperature ductilities of polycrystalline FeAl and Nisb3Al, both boron-doped (B-doped) and boron-free (B-free) samples were studied to determine the role of boron in gaseous hydrogen environments. The ductility of B-free Nisb3Al (23.4 at.% Al) was found to be nearly independent of the presence of molecular hydrogen at pressures $10% ductility in UHV showed a decrease in ductility as the hydrogen pressure increased. This suggests that Hsb2 is dissociating on the surfaces of FeAl alloys, both B-free and B-doped. Boron-free FeAl with an aluminum concentration of 37 at.% failed with near 100% transgranular cleavage over the entire pressure range investigated with a maxi?m ductility of sim17% in UHV. Boron-free samples containing either 40 or 45 at.% Al failed by a mixed mode of fracture, with ductilities not exceeding 6%. Boron-doped Fe-40Al samples failed with transgranular cleavage. The B-doped Fe-45Al failed with a mixed mode of fracture of which transgranular cleavage was in the majority. The B-doped Fe-40Al possessed the best ductility in UHV of sim18%. Boron-free FeAl with 48 at.% Al failed intergranularly with no detectable plasticity. FeAl with 48 at.% Al and doped with boron failed in an intergranular fashion with elongation to fracture not exceeding sim$6%.

Cohron, Jonathan William

418

Boron nitride housing cools transistors  

NASA Technical Reports Server (NTRS)

Boron nitride ceramic heat sink cools transistors in r-f transmitter and receiver circuits. Heat dissipated by the transistor is conducted by the boron nitride housing to the metal chassis on which it is mounted.

1965-01-01

419

All-vanadium redox flow batteries with graphite felt electrodes treated by atmospheric pressure plasma jets  

NASA Astrophysics Data System (ADS)

Graphite felts modified with atmospheric pressure plasma jets (APPJs) are applied as electrodes in an all-vanadium redox flow battery (VRFB). APPJ flow penetrates deeply into the graphite felt, improving significantly the wettability of the graphite felt inside out and, thereby, enhancing graphite fiber-electrolyte contact during battery operation. The energy efficiency of a VRFB was improved from 62% (untreated) to 76% (APPJ-treated with the scan mode) at a current density of 80 mA cm-2, an improvement of 22%. The efficiency improvement is attributed to the oxygen-containing groups and nitrogen doping introduced by N2 APPJs on the fiber surfaces of graphite felt, both of which enhance electrochemical reactivity.

Chen, Jian-Zhang; Liao, Wei-Yang; Hsieh, Wen-Yen; Hsu, Cheng-Che; Chen, Yong-Song

2015-01-01

420

Mineral of the month: boron  

USGS Publications Warehouse

What does boron have to do with baseball, apple pie, motherhood and Chevrolet? Boron minerals and chemicals are used in the tanning of leather baseballs and gloves; in micro-fertilizer to grow apples and in the glass and enamels of bakewares to cook apple pie; in boron detergents for soaking baby clothes and diapers; and in fiberglass parts for the Chevrolet Corvette.

Lyday, Phyllis A.

2005-01-01

421

Structural and electrical properties of trimethylboron-doped silicon nanowires  

NASA Astrophysics Data System (ADS)

Trimethylboron (TMB) was investigated as a p-type dopant source for the vapor-liquid-solid growth of boron-doped silicon nanowires (SiNWs). The boron concentration in the nanowires was measured using secondary ion mass spectrometry and results were compared for boron-doping using TMB and diborane (B2H6) sources. Boron concentrations ranging from 1×1018 to 4×1019cm-3 were obtained by varying the inlet dopant/SiH4 gas ratio. TEM characterization revealed that the B2H6-doped SiNWs consisted of a crystalline core with a thick amorphous Si coating, while the TMB-doped SiNWs were predominantly single crystal even at high boron concentrations. The difference in structural properties was attributed to the higher thermal stability and reduced reactivity of TMB compared to B2H6. Four-point resistivity and gate-dependent conductance measurements were used to confirm p-type conductivity in the TMB-doped nanowires and to investigate the effect of dopant concentration on nanowire resistivity.

Lew, Kok-Keong; Pan, Ling; Bogart, Timothy E.; Dilts, Sarah M.; Dickey, Elizabeth C.; Redwing, Joan M.; Wang, Yanfeng; Cabassi, Marco; Mayer, Theresa S.; Novak, Steven W.

2004-10-01

422

In Vivo Boron Uptake Determination for Boron Neutron Capture Synovectomy  

SciTech Connect

Boron neutron capture synovectomy (BNCS) has been proposed as a new application of the boron neutron capture reaction for the treatment of rheumatoid arthritis. In BNCS, a boron compound is injected into the joint space, where it is taken up by the synovium. The joint is then irradiated with neutrons of a desired energy range, inducing the boron neutron capture reaction in boron-loaded cells. Boron uptake by the synovium is an important parameter in the assessment of the potential of BNCS and in the determination of whether to proceed to animal irradiations for the testing of therapeutic efficacy. We present results from an investigation of boron uptake in vivo by the synovium.

Binello, Emanuela; Shortkroff, Sonya; Yanch, Jacquelyn C.

1999-06-06

423

Ultrahard nanotwinned cubic boron nitride.  

PubMed

Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall-Petch effect--the tendency for hardness to increase with decreasing grain size. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as ?14?nm (refs 1, 2, 4, 5). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness ?3.8?nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100?GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (?1,294?°C) and a large fracture toughness (>12?MPa?m(1/2), well beyond the toughness of commercial cemented tungsten carbide, ?10?MPa?m(1/2)). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall-Petch effect below a critical grain size or the twin thickness of ?10-15?nm found in metals and alloys. PMID:23325219

Tian, Yongjun; Xu, Bo; Yu, Dongli; Ma, Yanming; Wang, Yanbin; Jiang, Yingbing; Hu, Wentao; Tang, Chengchun; Gao, Yufei; Luo, Kun; Zhao, Zhisheng; Wang, Li-Min; Wen, Bin; He, Julong; Liu, Zhongyuan

2013-01-17

424

Homoepitaxial {111}-oriented diamond pn junctions grown on B-doped Ib synthetic diamond  

Microsoft Academic Search

Boron- and phosphorus-doped diamond layers were grown successively by microwave plasma-assisted chemical vapour deposition on {111}-oriented boron-doped Ib substrates. The resulting diodes were studied electrically with and without metallization. Although cathodoluminescence results showed that the material quality of the p-type {111} layer could still be improved, Electron Beam Induced Current imaging (EBIC) provided evidence for a space charge region. At

A. Tajani; C. Tavares; M. Wade; C. Baron; E. Gheeraert; E. Bustarret; S. Koizumi; D. Araujo

2004-01-01

425

Boron hydride polymer coated substrates  

DOEpatents

A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

1986-08-27

426

Wear and friction of oxidation-resistant mechanical carbon graphites at 650 C in air  

NASA Technical Reports Server (NTRS)

Studies were conducted to determine the friction and wear properties of experimental carbon-graphites. Hemispherically tipped carbon-graphite rider specimens were tested in sliding contact with rotating Inconel X-750 disks in air. A surface speed of 1.33 m/sec, a load of 500 g, and a specimen temperature of 650 C were used. Results indicate: (1) hardness is not a major factor in determining friction and wear under the conditions of these studies. (2) Friction and wear as low as or lower than those observed for a good commercial seal material were attained with some of the experimental materials studied. (3) The inclusion of boron carbide (as an oxidation inhibitor) has a strong influence on wear rate. (4) Phosphate treatment reduces the friction coefficient when boron carbide is not present in the base material.

Allen, G. P.; Wisnader, D. W.

1975-01-01

427

Graphite based Schottky diodes formed on Si, GaAs, and 4H-SiC S. Tongay, T. Schumann, and A. F. Hebarda  

E-print Network

the formation of semimetal graphite/semiconductor Schottky barriers where the semiconductor is either silicon Si to assure that the Schottky barrier height SBH B is small compared to temperature i.e., B kBT . Semimetal and doping.3 Here we report on the use of highly oriented pyrolytic graphite HOPG as the semimetal

Hebard, Arthur F.

428

CMB-13 research on carbon and graphite  

NASA Technical Reports Server (NTRS)

Preliminary results of the research on carbon and graphite accomplished during this report period are presented. Included are: particle characteristics of Santa Maria fillers, compositions and density data for hot-molded Santa Maria graphites, properties of hot-molded Santa Maria graphites, and properties of hot-molded anisotropic graphites. Ablation-resistant graphites are also discussed.

Smith, M. C.

1972-01-01

429

Graphite fiber reinforced thermoplastic resins  

NASA Technical Reports Server (NTRS)

The results of a program designed to optimize the fabrication procedures for graphite thermoplastic composites are described. The properties of the composites as a function of temperature were measured and graphite thermoplastic fan exit guide vanes were fabricated and tested. Three thermoplastics were included in the investigation: polysulfone, polyethersulfone, and polyarylsulfone. Type HMS graphite was used as the reinforcement. Bending fatigue tests of HMS graphite/polyethersulfone demonstrated a gradual shear failure mode which resulted in a loss of stiffness in the specimens. Preliminary curves were generated to show the loss in stiffness as a function of stress and number of cycles. Fan exit guide vanes of HMS graphite polyethersulfone were satisfactorily fabricated in the final phase of the program. These were found to have stiffness and better fatigue behavior than graphite epoxy vanes which were formerly bill of material.

Navak, R. C.

1977-01-01

430

Impedance of electrochemically modified graphite.  

PubMed

Electrochemical impedance spectroscopy, EIS, has been applied for characterization of electrochemically modified graphite electrodes in the sulphuric acid solution. Graphite modifications were performed by potential cyclization between potentials of graphite oxide formation/reduction, different number of cycles, and prolonged reduction steps after cyclization. Impedance spectra measured at two potential points within double-layer region of graphite have been successfully modeled using the concept of porous electrodes involving two different electrolyte diffusion paths, indicating existence of two classes of pores. The evaluated impedance parameter values show continuous changes with stages of graphite modification, indicating continuous structural changes of pores by number of potential cycles applied. Differences of impedance parameter values at two potential values indicate the potential induced changes of solution properties within the pores of modified graphite. PMID:25125120

Magdi?, Katja; Kvastek, Krešimir; Horvat-Radoševi?, Višnja

2014-01-01

431

Investigation of Isotopically Tailored Boron in Advanced Fission and Fusion Reactor Systems.  

NASA Astrophysics Data System (ADS)

This research examines the use of B^ {11}, in the form of metallic boron and boron carbide, as a moderating and reflecting material. An examination of the neutronic characteristics of the B ^{11} isotope of boron has revealed that B^{11} has neutron scattering and absorption cross sections favorably comparable to those of Be^9 and C^ {12}. Preliminary analysis of the neutronics of B ^{11} were performed by conducting one dimensional transport calculations on an infinite slab of varying thickness. Beryllium is the best of the three materials in reflecting neutrons due primarily to the contribution from (n,2n) reactions. Tailored neutron energy beam transmission experiments were carried out to experimentally verify the predicted neutronic characteristics of B^{11 }. To further examine the neutron moderating and reflecting characteristics of B^{11 }, the energy dependent neutron flux was measured as a function of position in an exponential pile constructed of B_4C isotopically enriched to 98.5 percent B^{11}. After the experimental verification of the neutronic behavior of B^{11}, further design studies were conducted using metallic boron and boron carbide enriched in the B^{11 } isotope. The use of materials isotopically enriched in B^{11} as a liner in the first wall/blanket of a magnetic confinement fusion reactor demonstrated acceptable tritium regeneration in the lithium blanket. Analysis of the effect of contaminant levels of B^{10} showed that B^{10} contents of less than 1 percent in metallic boron produced negligible adverse effects on the tritium breeding. A comparison of the effectiveness of graphite and B^{11}_4C when used as moderators in a reactor fueled with natural uranium has shown that the maximum k_infty for a given fuel rod design is approximately the same for both materials. Approximately half the volume of the moderator is required when B^{11 }_4C is substituted for graphite to obtain essentially the same K_infty . An analysis of the effectiveness of various materials as reflector control elements for a compact space reactor has shown that B^{11} is neutronically superior to graphite in these applications. Metallic boron and boron carbide isotopically enriched in B^{11} have been demonstrated to be neutronically acceptable for varied applications in advanced reactor systems. B^ {11} has