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1

Structure and electrochemical applications of boron-doped graphitized carbon nanofibers  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

2

Adsorption, diffusion, and recombination of hydrogen on pure and boron-doped graphite surfaces  

NASA Astrophysics Data System (ADS)

Boron inserted as impurity by substitution of carbon atoms in graphite is known to modify the reactivity of the surface in interaction with hydrogen. Boron induces a better H retention capability in graphite while it makes easier the recombination into molecular hydrogen under heating in thermal-desorption experimental conditions. It has already been calculated that boron modifies the electronic structure of the surface, which results in an increase of the adsorption energy for H. This result seems in good agreement with the better retention for H in doped graphite, but contradictory with the easier recombination observed. The aim of this work is to dismiss this contradiction by elucidating the modifications induced by boron in the recombination mechanism. We studied the diffusion of H on pure and boron-doped graphite in the density functional theory framework. We determined a diffusionlike mechanism leading to molecular hydrogen formation. Finally, we have shown the fundamental modifications induced by boron on the [0001] graphite surface reactivity. From these calculations it stands out that recombination is the result of desorption on pure graphite and diffusion on B-doped surfaces, while the activation energy for the rate limiting step is half reduced by boron. The results are compared to experimental observations. The connection between the cluster and periodic quantum modes for graphite is also discussed.

Ferro, Y.; Marinelli, F.; Jelea, A.; Allouche, A.

2004-06-01

3

Local structure analysis of boron-doped graphite by soft x-ray emission and absorption spectroscopy using synchrotron radiation  

NASA Astrophysics Data System (ADS)

The local structure of boron-doped highly oriented graphite films was determined via soft x-ray emission and absorption spectroscopy using synchrotron radiation. Analysis of the BK and CK x-ray emission spectra using the discrete variational-X? molecular orbital method clarified that boron atoms are chemisorbed onto graphite by substituting for carbon atoms in the carbon hexagonal rings. Compared to graphite, boron-doped graphite exhibits spectral differences in the higher edge of the CK x-ray emission spectrum and the CK x-ray absorption edge. Such a spectral profile of boron-doped graphite, which reflects the band structure, is well explained by the chemisorbed boron structure.

Hanafusa, Atsushi; Muramatsu, Yasuji; Kaburagi, Yutaka; Yoshida, Akira; Hishiyama, Yoshihiro; Yang, Wanli; Denlinger, Jonathan D.; Gullikson, Eric M.

2011-09-01

4

Photovoltaic characteristics of boron doped amorphous carbon films deposited by pulsed laser deposition using graphite target  

Microsoft Academic Search

This paper reports on the successful deposition of boron (B) doped carbon films (p-C(B)) and fabrication of p-C(B)\\/n-Si solar cells by pulsed laser deposition (PLD) technique at room temperature using graphite target. The B content in the film was determined by X-ray photoelectron spectroscopy (XPS) to be in the range of 0.2-1.7 atomic percentage. The photovoltaic values of the device,

X. M. Tian; M. Rusop; Y. Hayashi; T. Soga; T. Jimbo; M. Umeno

2002-01-01

5

Direct detection of uric acid in body fluid samples by using boron doped graphite nano particles as the working electrode.  

PubMed

Boron doped graphite nano particles were used as functioning elements for creation of electrodes for the detection of uric acid in biological samples. The electrode obtained in this manner was capable of oxidizing ascorbic acid at lower potentials. This provided a desirable solution to the interfering problem encountered in the detection of uric acid in biological samples caused by ascorbic acid. The detectable concentrations for uric acid ranged from 5.0 to 130 µM. The applicability of the electrode was experimentally demonstrated by the successful direct detection of uric acid in real urine samples. PMID:21478610

He, Jianjun; Fugetsu, Bunshi; Tanaka, Shunitz

2011-01-01

6

First-principles investigations of the magnetic properties of graphite boron nitride sheet induced by Fe doping.  

PubMed

The first-principles spin polarization method is used to investigate the magnetic properties of graphite boron nitride (g-BN) sheet induced by Fe doping. We find that a nitrogen or boron atom substituted by Fe can induce a magnetic moment. From standard Mulliken population analysis, we also find that the magnetic moment is mainly dominated by Fe 3d states. Using Heisenberg exchange coupling theory, we study the exchange coupling mechanisms by constructing two-Fe centers in g-BN. The results show the presence of relatively strong exchange coupling for two-Fe substituted two-B atoms and the coupling is ferromagnetic. For the case of two-Fe substituted two-N atoms, the coupling is antiferromagnetic and the exchange coupling is very weak. The paper enriches recent molecular magnetic investigations. PMID:21393706

Deng, Xiaohui; Wang, Wenwei; Zhang, Dengyu; Lu, Wei; Fan, Bingbing

2010-05-26

7

Microstructure and electrochemical properties of boron-doped mesocarbon microbeads  

SciTech Connect

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

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

2000-04-01

8

Boron doping a semiconductor particle  

SciTech Connect

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

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

1998-06-09

9

Boron doping a semiconductor particle  

DOEpatents

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

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

1998-06-09

10

Characterisation of graphite using boron as a marker element  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

11

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

PubMed

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

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

2014-04-22

12

Structure and functionality of bromine doped graphite.  

PubMed

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 (Br2). However, with increased compression (decreased layer-layer separation) Br2 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 Br2 molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity. PMID:23635160

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

2013-04-28

13

Local atomic and electronic structure of boron chemical doping in monolayer graphene.  

PubMed

We use scanning tunneling microscopy and X-ray spectroscopy to characterize the atomic and electronic structure of boron-doped and nitrogen-doped graphene created by chemical vapor deposition on copper substrates. Microscopic measurements show that boron, like nitrogen, incorporates into the carbon lattice primarily in the graphitic form and contributes ~0.5 carriers into the graphene sheet per dopant. Density functional theory calculations indicate that boron dopants interact strongly with the underlying copper substrate while nitrogen dopants do not. The local bonding differences between graphitic boron and nitrogen dopants lead to large scale differences in dopant distribution. The distribution of dopants is observed to be completely random in the case of boron, while nitrogen displays strong sublattice clustering. Structurally, nitrogen-doped graphene is relatively defect-free while boron-doped graphene films show a large number of Stone-Wales defects. These defects create local electronic resonances and cause electronic scattering, but do not electronically dope the graphene film. PMID:24032458

Zhao, Liuyan; Levendorf, Mark; Goncher, Scott; Schiros, Theanne; Pálová, Lucia; Zabet-Khosousi, Amir; Rim, Kwang Taeg; Gutiérrez, Christopher; Nordlund, Dennis; Jaye, Cherno; Hybertsen, Mark; Reichman, David; Flynn, George W; Park, Jiwoong; Pasupathy, Abhay N

2013-10-01

14

Boron-doped manganese dioxide for supercapacitors.  

PubMed

The addition of boron as a dopant during the reaction between carbon fiber and permanganate led to significant enhancement of the growth-rate and formation of the porous framework. The doped MnO2 was superior to the pristine sample as electrode materials for supercapacitors in terms of the specific capacitance and rate capability. PMID:25232909

Chi, Hong Zhong; Li, Yuwei; Xin, Yingxu; Qin, Haiying

2014-11-11

15

Ni doping of semiconducting boron carbide  

SciTech Connect

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; Liu Jing; Adenwalla, S. [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0511 (United States); Langell, M. A. [Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0304 (United States); Kizilkaya, Orhan [Center for Advanced Microstructures and Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, Louisiana 70806 (United States)

2010-01-15

16

Encapsulation of crystalline boron carbide into graphitic nanoclusters from the arc-discharge soot  

NASA Astrophysics Data System (ADS)

Boron carbide crystals were encapsulated into multiwalled graphitic carbon clusters that were prepared from a boron-containing composite anode by utilizing arc-discharge. The encapsulants are compounds of the lightest element that has yet been encapsulated, and the first of the non-metallic. The encapsulated multiwalled clusters are predominantly observed in the soot, a location where rarely graphitic multiwalled structures have ever been found before. The known tendency of boron to catalyze graphitization can possibly explain this observation.

Zhou, D.; Seraphin, S.; Withers, J. C.

1995-03-01

17

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

18

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

PubMed

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

Tan, Shu Min; Poh, Hwee Ling; Sofer, Zden?k; Pumera, Martin

2013-09-01

19

Synthesis and characterization of boron doped alumina stabilized zirconia fibers  

Microsoft Academic Search

Boron doped PVA\\/Zr-Al acetate nanofibers were prepared by electrospinning using PVA as a precursor. The effect of calcination\\u000a temperature on morphology and crystal structure was investigated at 250, 500, and 800 °C. The study also establishes the effect\\u000a of boron doping on the morphology of PVA\\/Zr-Al acetate nanofibers at various calcination temperatures. The measurements showed\\u000a that the conductivity, pH, viscosity

?. Uslu; T. Tunç; S. Keskin; M. K. Öztürk

2011-01-01

20

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

21

Selecting boron fullerenes by cage-doping mechanisms.  

PubMed

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

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

2013-05-14

22

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

23

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

24

Hydrogen adsorption on boron doped graphene: an ab initio study.  

PubMed

(i) The electronic and structural properties of boron doped graphene sheets, and (ii) the chemisorption processes of hydrogen adatoms on the boron doped graphene sheets have been examined by ab initio total energy calculations. In (i) we find that the structural deformations are very localized around the boron substitutional sites, and in accordance with previous studies (Endo et al 2001 J. Appl. Phys. 90 5670) there is an increase of the electronic density of states near the Fermi level. Our simulated scanning tunneling microscope (STM) images, for occupied states, indicate the formation of bright (triangular) spots lying on the substitutional boron (center) and nearest-neighbor carbon (edge) sites. Those STM images are attributed to the increase of the density of states within an energy interval of 0.5 eV below the Fermi level. For a boron concentration of ?2.4%, we find that two boron atoms lying on the opposite sites of the same hexagonal ring (B1-B2 configuration) represents the energetically most stable configuration, which is in contrast with previous theoretical findings. Having determined the energetically most stable configuration for substitutional boron atoms on graphene sheets, we next considered the hydrogen adsorption process as a function of the boron concentration, (ii). Our calculated binding energies indicate that the C-H bonds are strengthened near boron substitutional sites. Indeed, the binding energy of hydrogen adatoms forming a dimer-like structure on the boron doped B1-B2 graphene sheet is higher than the binding energy of an isolated H(2) molecule. Since the formation of the H dimer-like structure may represent the initial stage of the hydrogen clustering process on graphene sheets, we can infer that the formation of H clusters is quite likely not only on clean graphene sheets, which is in consonance with previous studies (Hornekær et al 2006 Phys. Rev. Lett. 97 186102), but also on B1-B2 boron doped graphene sheets. However, for a low concentration of boron atoms, the formation of H dimer structures is not expected to occur near a single substitutional boron site. That is, the formation (or not) of H clusters on graphene sheets can be tuned by the concentration of substitutional boron atoms. PMID:21825632

Miwa, R H; Martins, T B; Fazzio, A

2008-04-16

25

Boron-doped superlattices and Bragg mirrors in diamond  

NASA Astrophysics Data System (ADS)

A periodic modulation of the boron doping level of single crystal diamond multilayers over more than three orders of magnitude during epitaxial growth by microwave plasma-enhanced chemical vapor deposition is shown to yield Bragg mirrors in the visible. The thicknesses and doping level of the individual layers were controlled by in situ spectroscopic ellipsometry, enabling to tune the reflectance peak to the wavelength range of diamond color centers, such as NV0 or NV-. The crystalline quality, periodicity, and sharpness of the doping transitions in these doping superlattices over tens of periods were confirmed by high resolution X-ray diffraction.

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

2014-08-01

26

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

Microsoft Academic Search

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 ?g of nickel and 20 ?g of zirconium as matrix modifier,

Benling Gong; Yongming Liu; Yuli Xu; Zhuanhe Li; Tiezheng Lin

1995-01-01

27

Electrochemical oxidation of benzene on boron-doped diamond electrodes  

Microsoft Academic Search

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

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

2007-01-01

28

APPLICATION OF BORON-DOPED DIAMOND ELECTRODES FOR WASTEWATER TREATMENT  

Microsoft Academic Search

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

Marco Panizza; Enric Brillas; Christos Comninellis

29

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

SciTech Connect

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

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

2012-03-05

30

Benzene adsorption on basal planes of boron nitride; comparison with the benzene-graphite system  

NASA Astrophysics Data System (ADS)

A set of adsorption isotherms of benzene on boron nitride have been determined between 198 and 268 K. Just as in the case of the benzene-graphite system, the isotherms do not present the shape of the stepped isotherm. The benzene layer appears more mobile with a weaker adsorption energy on boron nitride than on graphite. The monolayer defined at the point B presents an important negative thermal expansion coefficient. It is proposed that the first layer might be unstable at high coverage and transform into clusters leaving some bare surface of boron nitride. Thus the observed isotherms might be considered as a combination of type I and III according to the Brunauer classification.

Delachaume, J. C.; Coulon, M.; Bonnetain, L.

1983-10-01

31

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

32

Characterization of boron-doped diamond epitaxial films  

NASA Astrophysics Data System (ADS)

boron-doped diamond epitaxial films were characterized on the dependence of boron concentration by an optical microscope, reflection high-energy electron diffraction, secondary ion mass spectrometry, Hall effect measurement, and metal contacts. These films were grown on synthesized single-crystal diamonds (100) by microwave plasma chemical vapor deposition (CVD) using H2, CH4 and B2H6 at a CH4 oncentration of CH 4/H2 = 6 percent and at doping gas ratios of B2H6/CH4 = 0.83 ppm, and 167 ppm. They were all epitaxially grown and had smooth surfaces. Hall effect measurements were performed in the temperature range of 300 K to 773 K. They indicated that there existed acceptorlike centers other than boron in the films synthesized in the vapor phase. Fermi degeneracy was found to occur at a boron concentration of 3 x 10 to the 20th/cu cm. Schottky diodes were fabricated using Al for Schottky contacts and Ti for ohmic contacts. Rectifying properties were degraded at high boron concentration.

Shiomi, Hiromu; Nishibayashi, Yoshiki; Fujimori, Naoji

1991-07-01

33

Carrier doping into boron nanobelts by neutron transmutation  

NASA Astrophysics Data System (ADS)

We report the effects of a neutron-capture reaction of isotope B10 on the structure and electrical transport of B10-enriched single-crystalline boron nanobelts. Partial amorphization, particularly at the surface of the nanobelt, was observed after thermal neutron irradiation with a dose of 2×1019 cm-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 ?-tetragonal boron.

Kirihara, Kazuhiro; Shimizu, Yoshiki; Yamada, Yoichi; Esaka, Fumitaka; Sasaki, Takeshi; Koshizaki, Naoto; Yamamoto, Hiroyuki; Shamoto, Shin-ichi; Kimura, Kaoru

2010-11-01

34

Chemical mechanical polishing of boron-doped polycrystalline silicon  

NASA Astrophysics Data System (ADS)

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

Pirayesh, Hamidreza; Cadien, Kenneth

2014-03-01

35

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

36

Infrared luminescence from silicon nanostructures heavily doped with boron  

SciTech Connect

Intense highly polarized radiation from silicon nanostructures heavily doped with boron to 5 Multiplication-Sign 10{sup 21} cm{sup -3} is studied as a function of temperature, forward current, and an additional lateral electric field. The features of the radiation intensity and degree of polarization suggest that an important role in the formation of the luminescence spectra is played by the ordered system of B{sup +}-B{sup -} dipoles, formed as a result of the reconstruction of shallow boron acceptors as centers with negative correlation energy. The results obtained are interpreted within a proposed model based on two-electron adiabatic potentials, according to which radiation results from donor-acceptor recombination via boron dipole center states, involving shallow phosphorus donors.

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

2012-03-15

37

Electrochemical hydrogen termination of boron-doped diamond  

SciTech Connect

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

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

2010-08-02

38

Direct cytochrome c electrochemistry at boron-doped diamond electrodes  

Microsoft Academic Search

Highly boron-doped diamond electrodes are characterized voltammetrically employing Ru(NH3)63+\\/2+, Fe(CN)63?\\/4?, benzoquinone\\/hydroquinone, and cytochrome c redox systems. The diamond electrodes, which are polished to nanometer finish, are initially `activated' electrochemically and then pretreated by oxidation, reduction, or polishing. All electrodes give reversible cyclic voltammetric responses for the reduction of Ru(NH3)63+ in aqueous solution.Redox systems other than Ru(NH3)63+\\/2+ show characteristic electrochemical behavior

Frank Marken; Christopher A Paddon; Dhinesh Asogan

2002-01-01

39

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

40

High-pressure, high-temperature processing of low-nitrogen boron-doped diamond  

Microsoft Academic Search

We have studied high-pressure, high-temperature processing (7.0 GPa, 2000–2100°C) of low-nitrogen boron-doped synthetic diamonds\\u000a grown in the Fe-Ni-C system (5.5–6.0 GPa, 1350–1450°C) with boron and titanium additions. The results indicate that, during\\u000a the growth of low-nitrogen boron-doped diamonds, there is a competition between different acceptors (boron and nickel). The\\u000a system of point defects and their distribution over the crystal are

A. I. Chepurov; A. P. Yelisseyev; E. I. Zhimulev; V. M. Sonin; I. I. Fedorov; A. A. Chepurov

2008-01-01

41

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

42

Determination of boron in silicon-doped gallium arsenide by electrothermal atomic absorption spectrometry and ultraviolet-visible spectrophotometry.  

PubMed

Two methods have been developed for the determination of boron impurities in silicon-doped gallium arsenide (GaAs) for electronics. The first method employs the electrothermal atomic absorption spectrometry (ETAAS), the second, the UV-Vis molecular absorption spectrophotomety. In both cases the GaAs sample is decomposed with aqua regia (1+1). To prevent Ga(III) interference on the ETAAS determination of boron, a double extraction of the chlorogallic acid (HGaCl4) in diethyl ether is performed. To improve the overall ETAAS performance, the graphite tubes were pre-treated with iridium(III) and tungsten(IV). A mixed chemical modifier containing Ni(II), Sr(II) and citric acid was also used. The characteristic mass (m0) is 301 +/- 47 pg and the detection limit (3sB) is 2.4 microg g(-1). The classic UV-Vis spectrophotometric procedure using curcumin was also extended to the determination of boron in GaAs. By masking Ga(III) with EDTA and a preliminary extraction of boron with 2-ethyl-hexane 1,3-diol, performed on a semi-micro scale, a detection limit of 0.6 microg g(-1) was achieved. Both methods were applied to the analysis of two Si-doped GaAs samples which were suspected of being boron-contaminated. Results are compared with those obtained by direct analysis of the decomposed sample solution using the inductively coupled plasma atomic emission spectrometry (ICP-AES). PMID:12556028

Taddia, Marco; Cerroni, Maria Grazia; Morelli, Elio; Musiani, Andrea

2002-01-01

43

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-layer graphite. Our study has pro- vided a new route to produce stable and functional graphite intercalation

Wu, Junqiao

44

Effect of the doping level on the biological stability of hydrogenated boron doped diamond electrodes.  

PubMed

Fouling of electrode surfaces by electrode reaction products or by biological spectator species is known to inactivate electrochemical sensors and thus limit their use in biological conditions. Here we present an investigation on the stability of boron doped diamond (BDD) electrodes with different levels of doping. Three different doping levels were used (0.1, 1 and 5% in the carbon phase). The highly doped (5%) BDD is of particular interest as it is here used for the first time for biological applications. Three different redox reactions were examined based on their electrode reaction characteristics: ruthenium(III) hexaammine (outer sphere), ferrocyanide (surface dependent), dopamine (adsorption mediated). The effect of albumin at blood concentration was studied. All results were compared with glassy carbon. There were no significant differences for the outer sphere electrochemistry, but all the BDDs showed improved resistance to fouling for the ferrocyanide oxidation. The electrocatalytic activity of BBD towards dopamine oxidation increased with increased boron content. However, this appears to be due to a larger number of defect sites which also increases the vulnerability to fouling by albumin and by electrode reaction products and the 5% BDD had similar properties to glassy carbon in this regard. These results suggest that it is possible to optimise the BDD performance for specific applications and that the large potential window for BDD may be due, at least in part, to its relatively poor electrocatalytic activity. PMID:21380425

Trouillon, Raphaël; O'Hare, Danny; Einaga, Yasuaki

2011-03-28

45

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

46

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

SciTech Connect

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

Agnihotri, Deepak [Department of Applied Sciences, Rayat and Bahra Institute of Engg. and Biotechnology, Sahauran, Mohali, Punjab 140104 (India); Sharma, Hitesh [Department of Physics, Punjab Technical University, Jalandhar, Punjab 144601 (India)

2011-12-12

47

Raman spectroscopy study of heat-treated and boron-doped double wall carbon nanotubes  

E-print Network

We performed Raman spectroscopy experiments on undoped and boron-doped double walled carbon nanotubes (DWNTs) that exhibit the “coalescence inducing mode” as these DWNTs are heat treated to temperatures between 1200 °C ...

Villalpando Paez, Federico

48

Effect of boron-doping on structure and some properties of carbon-carbon composite  

Microsoft Academic Search

Boron-doped carbon-carbon composites with boron concentration around 11–15 mass % were prepared from a carbon fibre felt with dispersed boron carbide powder by infiltration of pyrolytic carbon. The composite was heat treated at several different temperatures from 2000–2800 °C. The highest bending strength was obtained for the composite at a heat treatment temperature (HTT) of 2200 °C. Carbon fibre began

T. Sogabe; K. Nakajima; M. Inagaki

1996-01-01

49

Structure and Mn 2+ adsorption properties of boron-doped goethite  

Microsoft Academic Search

Two kinds of boron-doped goethites were synthesized, one was called ad-B-goethite prepared by reacting the original goethite with borax solution and the other called oc-B-goethite prepared in the presence of boric acid solution. The goethites were characterized by IR and XRD. The IR bands of FeOHFe in-plane bending and free OH of the boron-doped goethites were weak compared with the

Shuijiao Liao; Juan Wang; Duanwei Zhu; Liying Ren; Jianwei Lu; Mingjian Geng; Alan Langdon

2007-01-01

50

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

NASA Astrophysics Data System (ADS)

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

Xie, Ming; Lee, Chee Huei; Wang, Jiesheng; Yap, Yoke Khin; Bruno, Paola; Gruen, Dieter; Singh, Dileep; Routbort, Jules

2010-04-01

51

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

Microsoft Academic Search

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

Ming Xie; Chee Huei Lee; Jiesheng Wang; Yoke Khin Yap; Paola Bruno; Dieter Gruen; Dileep Singh; Jules Routbort

2010-01-01

52

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

SciTech Connect

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

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

2010-01-01

53

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

54

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

55

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

NASA Astrophysics Data System (ADS)

Electrodes based on carbon nanomaterials (carbon nanotubes or graphitic nanopetals) have been modified with boron (B) and nitrogen (N) through a facile microwave heating cycle. During the microwave heating, the electrodes are immersed in a precursor solution consisting of urea and boric acid dissolved in either water or methanol. After microwave heating and overnight vacuum drying, the electrodes are again heated in nitrogen to remove unreacted chemicals and to form CxBN. Hydrogen plasma was then used to remove any residual boron oxide from the surface of the electrodes. Carbon nanotubes modified with B and N exhibited higher lithium storage capacity as compared to pure carbon nanotube electrodes. We note that the modification appears to produce a highly unexpected and substantial cycle-to-cycle improvement in battery capacity as the electrode cycles through hundreds of charge-discharge iterations. This process can be applied to other carbon-based electrodes, which themselves are recognized for their high performance, to add further improvements.

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

2013-03-01

56

Mineralization of paracetamol in aqueous medium by anodic oxidation with a boron-doped diamond electrode.  

PubMed

The degradation of 100ml of solutions with paracetamol (N-(4-hydroxyphenyl)acetamide) up to 1 g l(-1) in the pH range 2.0-12.0 has been studied by anodic oxidation in a cell with a boron-doped diamond (BDD) anode and a graphite cathode, both of 3-cm2 area, by applying a current of 100, 300 and 450 mA between 25 and 45 degrees C. Complete mineralization is always achieved due to the great concentration of hydroxyl radical (*OH) generated at the BDD surface, with release of NH4+ and NO3- ions. The mineralization rate is pH-independent, increases with increasing applied current and temperature, but decreases when drug concentration raises from 315 mg l(-1). Reversed-phase chromatography revealed a similar complex paracetamol decay in acid and alkaline media. Ion-exclusion chromatography allowed the detection of oxalic and oxamic acids as ultimate carboxylic acids. When the same solutions have been comparatively treated with a Pt anode, a quite poor mineralization is found because of the production of much lower *OH concentration. Under these conditions, the degradation rate is enhanced in alkaline medium and polymerization of intermediates is favored in concentrated solutions. Paracetamol can be completely destroyed with Pt and its kinetics follows a pseudo-first-order reaction with a constant rate independent of pH. PMID:15620731

Brillas, Enric; Sirés, Ignasi; Arias, Conchita; Cabot, Pere Lluís; Centellas, Francesc; Rodríguez, Rosa María; Garrido, José Antonio

2005-01-01

57

Ex situ vapor phase boron doping of silicon nanowires using BBr3.  

PubMed

An ex situ vapor phase technique for doping vapor-liquid-solid grown silicon nanowires (NWs) based on the reduction of BBr(3) by H(2) has been demonstrated. Electron microscope images show that the excellent crystal quality of the nanowires is preserved with minimal alteration of their surface morphology. Fano resonance in the Raman spectra for single nanowires indicates that active boron concentrations over two orders of magnitude and as high as 10(20) cm(-3) are achievable in a well-controlled manner, with excellent axial uniformity. Electrical resistance measurements from single nanowires confirm that incorporated boron is electrically active, and doping of epitaxial bridging Si NWs is successfully demonstrated. By avoiding the pitfalls of nonuniform concentration profiles and drastic morphological changes that often accompany in situ boron doping, this technique provides a valuable alternative doping route for the development of single Si NW devices in a reliable manner. PMID:20648344

Doerk, Gregory S; Lestari, Gabriella; Liu, Fang; Carraro, Carlo; Maboudian, Roya

2010-07-01

58

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

NASA Astrophysics Data System (ADS)

Intentional boron and phosphorus doping of polycrystalline silicon thin films on glass prepared by the silver-induced layer exchange is presented. A silver/(titanium) oxide/amorphous silicon stack is annealed at temperatures below the eutectic temperature of the Ag/Si system, leading to a complete layer exchange and simultaneous crystallization of the amorphous silicon. Intentional doping of the amorphous silicon prior to the exchange process results in boron- or phosphorus-doped polycrystalline silicon. Hall effect measurements show carrier concentrations between 2×1017 cm-3 and 3×1020 cm-3 for phosphorus and 4×1018 cm-3 to 3×1019 cm-3 for boron-doped layers, with carrier mobilities up to 90 cm2/V s.

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

2013-05-01

59

Nitrogen-doped graphene nanosheets from bulk graphite using microwave irradiation.  

PubMed

Using simple microwave irradiation under the presence of sodium amide as a nitrogen source, preparation of nitrogen-doped graphene nanosheets has been successfully demonstrated. It is notable that exfoliation and nitrogen doping of graphite to nitrogen-doped graphene simultaneously occurred during the microwave irradiation within a minute, and nitrogen content of the doped graphene could reach up to 8.1%. It was also found that the binding configuration of nitrogen atom on graphitic layer consisted of various nitrogen-containing moieties such as pyridine-N, pyrrolic-N, and quaternary-N, and their composition was changed as a function of irradiation power. Although formation of undoped reduced graphene oxide by microwave irradiation resulted in slight increase of electrical conductivity because of the reductive recovery of oxidized graphite to graphene, nitrogen doping involved during irradiation induced much more notable increase of electrical conductivity more than 300 S cm(-1). Furthermore, nitrogen-doped graphene showed highly enhanced capacitive performance than that of undoped reduced graphene oxide, the specific capacitance of 200 F/g (current density of 0.5 A/g), which ascribes the pseudocapacitive effect from the incorporation of nitrogen atom on graphitic layer. PMID:24597537

Lee, Kwang Hoon; Oh, Jinwoo; Son, Jeong Gon; Kim, Heesuk; Lee, Sang-Soo

2014-05-14

60

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

61

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

62

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

63

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

64

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

65

Atomistic boron-doped graphene field-effect transistors: a route toward unipolar characteristics.  

PubMed

We report fully quantum simulations of realistic models of boron-doped graphene-based field-effect transistors, including atomistic details based on DFT calculations. We show that the self-consistent solution of the three-dimensional (3D) Poisson and Schrödinger equations with a representation in terms of a tight-binding Hamiltonian manages to accurately reproduce the DFT results for an isolated boron-doped graphene nanoribbon. Using a 3D Poisson/Schrödinger solver within the non-equilibrium Green's function (NEGF) formalism, self-consistent calculations of the gate-screened scattering potentials induced by the boron impurities have been performed, allowing the theoretical exploration of the tunability of transistor characteristics. The boron-doped graphene transistors are found to approach unipolar behavior as the boron concentration is increased and, by tuning the density of chemical dopants, the electron-hole transport asymmetry can be finely adjusted. Correspondingly, the onset of a mobility gap in the device is observed. Although the computed asymmetries are not sufficient to warrant proper device operation, our results represent an initial step in the direction of improved transfer characteristics and, in particular, the developed simulation strategy is a powerful new tool for modeling doped graphene nanostructures. PMID:22876866

Marconcini, Paolo; Cresti, Alessandro; Triozon, François; Fiori, Gianluca; Biel, Blanca; Niquet, Yann-Michel; Macucci, Massimo; Roche, Stephan

2012-09-25

66

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

67

Shallow donor induced n-type conductivity in deuterated boron-doped diamond  

Microsoft Academic Search

We show that deuteration of a series of boron-doped (100) diamond epitaxial layers can lead to a p-type to n-type conversion. The n-type diamond epilayers have electrical conductivities of a few S\\/cm at 300 K. These values are a factor 103-105 higher than the n-type conductivities achieved with phosphorus doping. This is a consequence of the shallow donor character of

J. Chevallier; Z. Teukam; C. Saguy; R. Kalish; C. Cytermann; F. Jomard; M. Barbé; T. Kociniewski; J. E. Butler; C. Baron; A. Deneuville

2004-01-01

68

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

69

Delta-doping of boron atoms by photoexcited chemical vapor deposition  

SciTech Connect

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

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

2012-03-15

70

Boron Delta-Doping Dependence on Si\\/SiGe Resonant Interband Tunneling Diodes Grown by Chemical Vapor Deposition  

Microsoft Academic Search

Si\\/SiGe resonant interband tunnel diodes (RITD) were fabricated using CVD on 200-mm silicon wafers. The RITD devices consist of a $\\\\hbox{p}^{+}\\\\hbox{-i-n}^{+}$ structure with $\\\\delta$-doped quantum wells providing resonant interband tunneling through a nominally intrinsic Si\\/SiGe region. The vapor-phase doping technique was used to obtain abrupt degenerate doping profiles. The boron doping in the $\\\\delta$ -doped region was varied, and its

Anisha Ramesh; Tyler A. Growden; Paul R. Berger; Roger Loo; Wilfried Vandervorst; Bastien Douhard; Matty Caymax

2012-01-01

71

Comparison of glassy carbon and boron doped diamond electrodes: Resistance to biofouling  

Microsoft Academic Search

Carbon based electrodes are widely used for in vivo and in vitro electrochemical studies. In particular, monoamine neurochemistry has been investigated using carbon microfibre electrodes. Similarly, glassy carbon (GC) is the preferred material for many biochemical applications, such as electrochemical detection in chromatography. More recently, boron doped diamond (BDD) has been utilized for biosensing, as its carbon sp3 structure is

Raphael Trouillon; Danny O’Hare

2010-01-01

72

Electrochemical Modification of Boron-Doped Chemical Vapor Deposited Diamond Surfaces with Covalently Bonded Monolayers  

Microsoft Academic Search

Electrochemical reduction of phenyl diazonium salts in acetonitrile at boron-doped diamond electrodes yielded covalent bonding of aromatic groups to the sp 3 carbon surface. Diamond surfaces modified with nitrophenyl, trifluoromethylphenyl, and nitroa- zobenzene showed strong X-ray photoelectron spectroscopy (XPS) signals for surface nitrogen or fluorine, which were stable to exposure to air or solvents. Raman spectra of chemisorbed nitroazobenzene on

Tzu-Chi Kuo; Richard L. McCreery; Greg M. Swainb

1999-01-01

73

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

Microsoft Academic Search

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

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

2008-01-01

74

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

PubMed Central

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

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

2014-01-01

75

Boron-doped diamond films on silicon studied by Raman and infrared spectroscopies  

NASA Astrophysics Data System (ADS)

Boron doped diamond films were deposited onto (100) orientated Si substrates using a thermal filament CVD method. Boron trioxide was used as a doping source and samples with boron to carbon (B/C) ratios of 0, 10, 100, and 1000 ppm were prepared for the optical measurements. The infrared (IR) results reveal the formation of an ultrathin SiC layer at the interface between Si and diamond. Furthermore, the IR data confirm the resistivity data obtained from electrical measurements. Raman spectroscopy was used to probe the quality and homogeneity of the diamond films. Upon increasing B/C ratio the diamond phonon line shifts to lower frequency and is also broadened revealing a softening of the diamond. In addition, the optical absorption was found to increase strongly with increasing B/c ratio.

Okano, Ken; Kurosu, Tateki; Iida, Masamori; Eickhoff, Thomas; Wilhelm, Hans; Zahn, Dietrich R. T.

1990-08-01

76

Dependence of RF power on the phase transformation for boron nitride films deposited on graphite at room temperature  

NASA Astrophysics Data System (ADS)

Cubic boron nitride (cBN) thick films deposited on mainly c-axis-oriented graphite substrate at room temperature and zero bias by radio frequency (RF) magnetron sputtering were studied. In the growth process, RF power plays a key role in determining the content of cubic phase in films, while the conventional substrate heating and biasing have been neglected. With increase in RF power, the dominated content of films converts from explosion boron nitride (eBN) to cBN. The transformation mechanism has been discussed. The unique structural properties of the "soft" graphite are favorable to propose simple conditions for growing "hard" cBN films. Furthermore, the optical band gap of BN films having ˜90% cubic phase is of ˜5.8 eV obtained from ultraviolet-visible optical transmission measurement. The electron field emission examination shows that cBN film on graphite has a high emission current density of 2.8×10 -5 A/cm 2 at an applied field of ˜30 V/?m.

Yang, Xuxin; Li, Hongdong; Li, Yingai; Lü, Xianyi; Gao, Shiyong; Zhu, Pinwen; Zhang, Qing; Zhang, Tiechen; Zou, Guangtian

2009-07-01

77

Synthesis and characterization of boron-doped NiO thin films produced by spray pyrolysis  

NASA Astrophysics Data System (ADS)

Boron-doped NiO thin films were prepared on glass substrates at 400°C by airbrush spraying method using a solution of nickel nitrate hexahydrate. Their physical properties were investigated as a function of dopant concentration. From X-ray diffraction patterns, it is observed that the films have cubic structure with lattice parameters varying with boron concentration. The morphologies of the films were examined by using scanning electron microscopy, and the grain sizes were measured to be around 30-50 nm. Optical measurements show that the band gap energies of the films first decrease then increase with increasing boron concentration. The resistivities of the films were determined by four point probe method, and the changes in resistivity with boron concentration were investigated.

Alver, U.; Yayka?l?, H.; Kerli, S.; Tanr?verdi, A.

2013-11-01

78

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

79

Carbon doping induced giant low bias negative differential resistance in boron nitride nanoribbon  

NASA Astrophysics Data System (ADS)

By applying nonequilibrium Green's function combined with density functional theory, we investigated the electronic transport properties of carbon-doped armchair boron nitride nanoribbons. Obvious negative differential resistance (NDR) behavior with giant peak-to-valley ratio up to the order of 104-106 is found by tuning the doping position and concentration. Especially, with the reduction of doping concentration, NDR peak position can enter into mV bias range and even can be expected lower than mV bias. The negative differential resistance behavior is explained by the evolution of the transmission spectra and band structures with applied bias.

Liu, N.; Liu, J. B.; Gao, G. Y.; Yao, K. L.

2014-06-01

80

Transition-Metal Strings Templated on Boron-Doped Carbon Nanotubes: A DFT Investigation  

SciTech Connect

The binding nature, magnetic, and electronic properties of transition-metal (TM) monatomic chains anchored on boron-doped single-walled carbon nanotubes (B-SWCNTs) are studied using density-functional theory. The TM systems studied here include Au, Pt, Ru, Pd, Ag, Co, Ni, Cu, W, and Ti, which are well-known for their technical importance. In conjunction, prototype semiconducting SWCNT(8,0) and metallic SWCNT(6,6) were chosen to model the general features of B-doped SWCNTs. It is found that the TM-strings exhibit well-defined covalent bonds with the boron-doped SWCNTs, in contrast to the pristine SWCNTs. The TMstring/ B-SWCNT composites exhibit high stability and unexpected electronic properties, which are relevant to applications in nanoelectronics, spintronics, nanocatalysis, and sensor devices.

An, Wei; Turner, C. H.

2009-08-27

81

Continuation calculations of boron- (aluminum-, titanium-, and nickel-) doped La13 clusters.  

PubMed

In this work, we have calculated boron-, aluminum-, titanium-, and nickel-doped La13 clusters by DMOL method based on the density-functional theory. Two doping modes are employed: surface and center doping. The boron, aluminum, and nickel atoms prefer to occupy the surface sites while the titanium atom prefers to occupy the center site. The doped La13 clusters with these four kinds of atoms have lower binding energy than pure La13 clusters. The icosahedral isomers are of lower binding energy than cubotahedral and decahedral isomers for La12B(-1), La12Al(-1), and La12Ni, while doping makes the cubotahedral La12Ti stable with a binding energy a little lower than icosahedral La12Ti. There are electronic shell effects in icosahedral La12B(-1) and La12Al(-1). The icosahedral La12B(-1) is promising to be formed during the doped process experimentally. Furthermore, we have also discussed the distorted structures of center doping by bond lengths, density of states, and charge transfers. PMID:16252954

Zhang, Dong-Bo; Shen, Jiang; Chen, Nan-Xian

2005-10-15

82

Defect-induced Symmetry Distortions in Doped Cubic Boron Nitride  

NASA Astrophysics Data System (ADS)

We have studied the substitution of silicon and beryllium for boron in cubic boron nitride with several first-principles methods. The Be and Si defects are proto-typical p- and n-type dopants respectively.(O. Mishima, S. Yamoka, and O. Fukunaga, Science 238), 181 (1987). The substitutionals have orbitally degenerate ground states leading to symmetry-lowering distortions of the Td point-group symmetry about the boron sites. Calculated IR absorption modes associated with the defects are compared with recent experimental determination of bulk modes.(M. I. Eremets, M. Gauthier, A. Polian, J. C. Chervin, J. M. Besson, G. A. Dubitskii, and Y. Y. Semenova, Phys. Rev. B 52), 8854 (1995). Changes in Fermi contact interaction terms as an effect of the distortions are discussed as a possible way of characterizing the distortions experimentally.

Patton, David C.; Harrison, Joseph G.

1996-03-01

83

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

84

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

85

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

PubMed

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

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

2014-02-18

86

Solar cells on low-resistivity boron-doped Czochralski-grown silicon with stabilized efficiencies of 20%  

Microsoft Academic Search

Recently, it was shown that the boron-oxygen complex responsible for the light-induced lifetime degradation in oxygen-rich boron-doped silicon can be permanently deactivated by illumination at elevated temperatures. Since the degradation is particularly harmful in low-resistivity Czochralski silicon (Cz-Si), we apply the deactivation procedure to a high-efficiency rear interdigitated single evaporation emitter wrap-through solar cell made on 1.4 Omega cm B-doped

Bianca Lim; Sonja Hermann; Karsten Bothe; Jan Schmidt; Rolf Brendel

2008-01-01

87

Controlled electrochemical intercalation, exfoliation and in situ nitrogen doping of graphite in nitrate-based protic ionic liquids.  

PubMed

Few-layer nitrogen-doped graphene has been prepared via fast and controlled electrochemical exfoliation of graphite in a protic ionic liquid ethylammonium nitrate. The method presents a potentially scalable approach for preparation of metal-free, N-doped graphene for use as electrocatalysts for oxygen reduction reactions. PMID:24169792

Lu, Xunyu; Zhao, Chuan

2013-12-14

88

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

SciTech Connect

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

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

2011-12-15

89

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

SciTech Connect

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

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

2013-03-25

90

Properties of boron-doped ZnO thin films grown by using MOCVD  

NASA Astrophysics Data System (ADS)

Boron-doped ZnO thin films were prepared by using metal organic chemical-vapor deposition (MOCVD) with diethyl zinc and water as precursors and B2H6 as the dopant gas. The effects of the flow rates of H2O and B2H6 on the growth and the electrical properties of boron-doped ZnO thin film were investigated. The maximum carrier concentration and mobility and the minimum resistivity obtained under these experimental conditions were 7 × 1020 /cm3, 42 cm2 /V·sec and 4 × 10-4 ?·cm, respectively, at room temperature. The electrical properties, growth rates, transmittances, and surface morphologies of the ZnO:B films grown using MOCVD are strongly affected by growth conditions such as the relative flow rates of the precursors and dopant gases and the chamber pressure, and these effects are discussed in detail in this article.

Choi, In-Hwan

2013-11-01

91

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

PubMed

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. PMID:25338171

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

2014-11-01

92

Enhancement of ultrafast nonlinear optical response of silicon nanocrystals by boron-doping.  

PubMed

Nonlinear optical responses of boron (B)-doped silicon nanocrystals (Si-ncs) embedded in borosilicate glass were studied by z-scan and optical Kerr gate methods under femtosecond excitation at 780 nm. The nonlinear refractive index (n(2)) and the two photon absorption coefficients (?) of B-doped Si-ncs were found to be 3 times enhanced, compared to those of intrinsic Si-ncs. The response time was faster than 100 fs even at 5 K. The origin of the large nonlinear optical response was discussed, based on the experimental data of n(2), electron spin resonance spectra, and linear absorption spectra. PMID:22660059

Imakita, Kenji; Ito, Masahiko; Naruiwa, Ryo; Fujii, Minoru; Hayashi, Shinji

2012-06-01

93

Local impedance imaging of boron-doped polycrystalline diamond thin films  

NASA Astrophysics Data System (ADS)

Local impedance imaging (LII) was used to visualise surficial deviations of AC impedances in polycrystalline boron-doped diamond (BDD). The BDD thin film electrodes were deposited onto the highly doped silicon substrates via microwave plasma-enhanced CVD. The studied boron dopant concentrations, controlled by the [B]/[C] ratio in plasma, ranged from 1 × 1016 to 2 × 1021 atoms cm-3. The BDD films displayed microcrystalline structure, while the average size of crystallites decreased from 1 to 0.7 ?m with increasing [B]/[C] ratios. The application of LII enabled a direct and high-resolution investigation of local distribution of impedance characteristics within the individual grains of BDD. Such an approach resulted in greater understanding of the microstructural control of properties at the grain level. We propose that the obtained surficial variation of impedance is correlated to the areas of high conductance which have been observed at the grain boundaries by using LII. We also postulate that the origin of high conductivity is due to either preferential boron accumulation, the presence of defects, or sp2 regions in the intragrain regions. The impedance modulus recorded by LII was in full agreement with the bulk impedance measurements. Both variables showed a decreasing trend with increasing [B]/[C] ratios, which is consistent with higher boron incorporation into BDD film.

Zieli?ski, A.; Bogdanowicz, R.; Ryl, J.; Burczyk, L.; Darowicki, K.

2014-09-01

94

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

95

Role of grain size in superconducting boron-doped nanocrystalline diamond thin films grown by CVD  

NASA Astrophysics Data System (ADS)

The grain size dependence of the superconducting transition, the normal state resistivity, and the insulating behavior at high magnetic fields are studied on a series of boron-doped nanocrystalline diamond (B:NCD) thin films with different grain sizes. The systematic change of the grain size is achieved by varying the methane-to-hydrogen ratio (C/H ratio) for the growth of different B:NCD films. Even though a fixed trimethylboron- (TMB) to-methane gas ratio is supposed to induce the identical boron-doping level in all the B:NCD films, the boron concentration and the carrier density are found to be a decreasing function of the grain size. Another consequence of the increase in grain size is the decreasing grain boundary density. These two concurrent consequences of the chemical vapor deposition mode of B:NCD are responsible for the grain size dependence of the critical temperature TC, the localization radius aH at the boron site, the normal state resistivity ?norm, the Hall mobility ?H, the Ioffe-Regel product kFl, the HC2-T phase boundary, and the coherence length ?GL.

Zhang, Gufei; Janssens, S. D.; Vanacken, J.; Timmermans, M.; Vacík, J.; Ataklti, G. W.; Decelle, W.; Gillijns, W.; Goderis, B.; Haenen, K.; Wagner, P.; Moshchalkov, V. V.

2011-12-01

96

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

97

Amperometric determination of chemical oxygen demand using boron-doped diamond (BDD) sensor  

Microsoft Academic Search

A new application of boron-doped diamond (BDD) electrode was developed for detecting chemical oxygen demand (COD) by amperometric method. The effects of some basic experimental parameters including pH and applied potential on the response of the BDD electrode were investigated and the optimal operating conditions were obtained. In the COD tests of standard samples, a wide linear range of 20–9000mgl?1

Hongbin Yu; Hua Wang; Xie Quan; Shuo Chen; Yaobin Zhang

2007-01-01

98

Boron doped amorphous carbon thin films grown by r.f. PECVD under different partial pressure  

Microsoft Academic Search

Boron doped hydrogenated amorphous carbon (a-C) thin films have been deposited by r.f.-plasma CVD with a frequency of 13.56 MHz at room temperature using pure methane as a precursor of carbon source mixed with hydrogen (H2) as a carrier gas. The films were prepared by varying the r.f. power, different flow rates of CH4, and partial pressure of mixed gas

J. Podder; M. Rusop; T. Soga; T. Jimbo

2005-01-01

99

Electrochemical characteristics and applications of boron-doped polycrystalline diamond film electrodes  

Microsoft Academic Search

The electrochemical characteristics of boron-doped polycrystalline diamond thin film (BDF) electrode 4 ? 4 mm2 in size were studied using cyclic voltammetry and potentiostatic method. The diamond clectrode exhibits adequate electrochemical\\u000a activity and its response current changes linearly with K3Fe(CN)6 concentrations. The response current is proportional to the square root of the scan rate, reflecting mass transport controlled\\u000a by planar

Zhu Jianzhong; Lu Deren; Zhang Guoxiong

1998-01-01

100

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

101

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

E-print Network

Journal of Crystal Growth 241 (2002) 45�50 Boron doping of silicon layers grown by liquid phase film solar cell applications as it allows the growth of a back surface field and a lightly doped bulk in a single growth step. r 2002 Elsevier Science B.V. All rights reserved. Keywords: A3. Liquid phase epitaxy

102

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

103

Radiation tolerance of boron doped dendritic web silicon solar cells  

NASA Technical Reports Server (NTRS)

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

Rohatgi, A.

1980-01-01

104

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

NASA Astrophysics Data System (ADS)

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

2014-09-01

105

Electrical transport properties of Si-doped hexagonal boron nitride epilayers  

SciTech Connect

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

Majety, S.; Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX 79409 (United States)

2013-12-15

106

Capacitance performance enhancement of TiO 2 doped with Ni and graphite  

Microsoft Academic Search

Nano-amorphous TiO2 was prepared by a sol-gel method. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that\\u000a the composite electrode material (TiO2-NiO-C) is made of powder with a grain size of 36.2 nm. Doping of nickel and graphite can increase the electrical conductivity\\u000a and the specific surface area of nano-amorphous TiO2. The electrochemical properties of TiO2-NiO-C,

Hong Wang; Zhiyuan Tang; Lei Sun; Yanbing He; Yaxian Wu; Zhongyan Li

2009-01-01

107

Electronic level scheme in boron- and phosphorus-doped silicon nanowires.  

PubMed

We report the first observation of the electronic level scheme in boron (B)- and phosphorus (P)-doped nanowires (NWs). The NWs' morphology dramatically depends on the doping impurity while a few deep electronic levels appear in both kinds of nanowires, independently of the doping type. We demonstrate that the doping impurities induce the same shallow levels as in bulk silicon. The presence of two donor levels in the lower half-bandgap is also revealed. In both kinds of NWs, B- and P-doped, the donor level (0/+) at E(v) + 0.36 eV of the gold-hydrogen complex is observed. This means that the gold diffusion from the NW tip introduces an electronically active level, which might negatively affects the electrical characteristics of the NWs. In P-doped NWs, we observed a further donor level at 0.26 eV above the valence band due to the phosphorus-vacancy pairs, the E-center, well-known in bulk silicon. These findings seriously question both diffusion modeling of impurities in NWs and the technological aspects arising from this. PMID:22545949

Sato, Keisuke; Castaldini, Antonio; Fukata, Naoki; Cavallini, Anna

2012-06-13

108

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

109

Exploration of gas sensing possibilities with edge plane pyrolytic graphite electrodes: nitrogen dioxide detection.  

PubMed

The voltammetric response of nitrogen dioxide in aqueous sulfuric acid using an edge plane pyrolytic graphite electrode has been explored and contrasted with that from basal plane pyrolytic graphite, glassy carbon or boron-doped diamond electrodes. Edge plane graphite electrode is found to produce an excellent voltammetric signal in comparison with other carbon-based electrodes exhibiting a well-defined analytically useful voltammetric redox couple in 2.5 M sulfuric acid which is absent on the alternative electrodes. PMID:15724153

Banks, Craig E; Goodwin, Alexander; Heald, Charles G R; Compton, Richard G

2005-03-01

110

Theoretical study on Si-doped hexagonal boron nitride (h-BN) sheet: Electronic, magnetic properties, and reactivity  

NASA Astrophysics Data System (ADS)

The properties and reactivity of Si-doped hexagonal boron nitride (h-BN) sheets were studied using density functional theory (DFT) methods. We find that Si impurity is more likely to substitute the boron site (SiB) due to the low formation energy. Si-doping severely deforms h-BN sheet, resulting in the local curvature changes of h-BN sheet. Moreover, Si-doping introduces two spin localized states within the band gap of h-BN sheet, thus rendering the two doped systems exhibit acceptor properties. The band gap of h-BN sheet is reduced from ˜4.70 eV to 1.24 (for SiB) and 0.84 eV (for SiN), respectively. In addition, Si-doped one exhibits higher activity than pristine one, endowing them wider application potential.

Liu, Yue-jie; Gao, Bo; Xu, Duo; Wang, Hong-mei; Zhao, Jing-xiang

2014-08-01

111

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

E-print Network

in oxygen-rich boron-doped crystalline silicon degrades under illumination at room temperature, both in p, lifetime, recombination, defects 1 INTRODUCTION Degradation of the carrier lifetime in boron-doped oxygen-rich studies on compensated p-type Czochralski-grown silicon (Cz-Si) revealed that the dependence of the defect

112

Pros and cons of nickel- and boron-doping to study helium effects in ferritic\\/martensitic steels  

Microsoft Academic Search

In the absence of a 14 MeV neutron source, the effect of helium on structural materials for fusion must be simulated using fission reactors. Helium effects in ferritic\\/martensitic steels have been studied by adding nickel and boron and irradiating in a mixed-spectrum reactor. Although the nickel- and boron-doping techniques have limitations and difficulties to estimate helium effects on the ferritic\\/martensitic

N. Hashimoto; R. L. Klueh; K. Shiba

2002-01-01

113

Elucidation of coordination structure around Ce3+ in doped SiO2 glasses using pulsed electron paramagnetic resonance: Effect of phosphorus, boron, and phosphorus-boron codoping  

NASA Astrophysics Data System (ADS)

Effects of codoping of phosphorus and/or boron on the coordination sphere of a Ce3+ in SiO2 glasses were examined by applying pulsed electron paramagnetic resonance (EPR) electron spin echo envelope modulation (ESEEM) spectroscopy. Simulation of the observed ESEEM pattern revealed a striking difference in the solvation shell structure between the P-doped and the P-free glasses, i.e., the P doping is very effective for the formation of the solvation shell, while no such an effect was observed for the B doping. When P and B are simultaneously doped, the solvation shell structure is close to that in the P-doped samples. Photoluminescence properties of Ce3+ in these samples were found to be classified into two categories corresponding to the solvation shell structures.

Saitoh, Akira; Matsuishi, Satoru; Oto, Masanori; Miura, Taisuke; Hirano, Masahiro; Hosono, Hideo

2005-12-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

115

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

116

Plasma Synthesized Doped Boron Nanopowder for MgB2 Superconductors  

SciTech Connect

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

James V. Marzik

2012-03-26

117

Isoelectronic doping of graphdiyne with boron and nitrogen: stable configurations and band gap modification.  

PubMed

Graphdiyne, consisting of sp- and sp(2)-hybridized carbon atoms, is a new member of carbon allotropes which has a natural band gap ~1.0 eV. Here, we report our first-principles calculations on the stable configurations and electronic structures of graphdiyne doped with boron-nitrogen (BN) units. We show that BN unit prefers to replace the sp-hybridized carbon atoms in the chain at a low doping rate, forming linear BN atomic chains between carbon hexagons. At a high doping rate, BN units replace first the carbon atoms in the hexagons and then those in the chains. A comparison study indicates that these substitution reactions may be easier to occur than those on graphene which composes purely of sp(2)-hybridized carbon atoms. With the increase of BN component, the band gap increases first gradually and then abruptly, corresponding to the transition between the two substitution motifs. The direct-band gap feature is intact in these BN-doped graphdiyne regardless the doping rate. A simple tight-binding model is proposed to interpret the origin of the band gap opening behaviors. Such wide-range band gap modification in graphdiyne may find applications in nanoscaled electronic devices and solar cells. PMID:22435915

Bu, Hongxia; Zhao, Mingwen; Zhang, Hongyu; Wang, Xiaopeng; Xi, Yan; Wang, Zhenhai

2012-04-19

118

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

119

A Comparison of Bulk Lifetime, Efficiency, and Light-Induced Degradation in Boron and Gallium-Doped Cast mc-Si Solar Cells  

Microsoft Academic Search

High-efficiency boron- and gallium-doped multicrystalline silicon (mc-Si) cells were fabricated and compared in this paper. The quality of three different boron-doped mc-Si ingots and one gallium-doped mc-Si ingot was investigated and compared by means of lifetime measurements and solar cell efficiencies. Untextured screen printed 4-cm2 cell efficiencies in excess of 16% were achieved in this paper when the lifetime after

Manav Sheoran; Ajay Upadhyaya; Ajeet Rohatgi

2006-01-01

120

Optoelectronic surface-related properties in boron-doped and irradiated diamond thin films  

NASA Astrophysics Data System (ADS)

Elucidation of microscopic properties of synthetic diamond films, such as formation and evolution of bulk and surface defects, chemistry of dopants, is necessary for a reliable quality control and reproducibility in applications. Surface photovoltage (SPV) spectroscopy and photoluminescence (PL) spectroscopy were employed to study diamond thin films grown on silicon by microwave plasma-assisted chemical vapor deposition and hot-filament chemical vapor deposition with different levels of boron doping in conjunction with gamma irradiation. SPV experiments showed that while the increase of boron concentration leads to a semiconductor-metal transition, subsequent gamma irradiation reverts quasi-metallic samples back to a semiconducting state by compensating electrical activity of boron possibly via hydrogen. One of the most pronounced common transitions observed at ˜3.1-3.2 eV in the SPV spectra was also present in all of the PL spectra. It is likely that this is a signature of the sp2-hybridized carbon clusters in or in the vicinity of grain boundaries.

Nemashkalo, A.; Chapagain, P. R.; Peters, R. M.; Farmer, J.; Gupta, S.; Strzhemechny, Y. M.

2012-01-01

121

Photovoltaic characteristics of amorphous silicon solar cells using boron doped tetrahedral amorphous carbon films as p-type window materials  

Microsoft Academic Search

Boron doped tetrahedral amorphous carbon (ta-C:B) was prepared by filtered cathodic vacuum arc deposition. A band gap of 2.0 eV and a conductivity of 1.42×10-7 S\\/cm were obtained at the doping ratio of 2.13 at. %. A device structure was deduced from the conventional amorphous silicon (a-Si:H) solar cell using the ta-C:B window layer. Photovoltaic parameters of the cells were

Jiecai Han; Manlin Tan; Jiaqi Zhu; Songhe Meng; Binsheng Wang; Shaojun Mu; Dawei Cao

2007-01-01

122

Raman studies of ultra-clean graphene on hexagonal boron nitride with controlled doping  

NASA Astrophysics Data System (ADS)

Graphene prepared by exfoliation on hexagonal boron nitride (h-BN) provides an ideal platform for studies of the intrinsic properties of Dirac electrons because of its unprecedented charge homogeneity. With this system, many of the fascinating phenomena hidden by charge inhomogeneity in conventional graphene samples have recently been revealed. Here we describe progress in examining both electron-phonon and electron-electron interactions by means of Raman scattering by the G- and the 2D-modes. In our studies, we were able to observe a symmetric energy shift in the Raman 2D peak at low doping levels when the Fermi level was tuned from the electron side to the hole side. This shift is understood as a change in the double-resonance condition induced by the renormalization of the electron and phonon band structures. At the same time, the 2D peak is broadened under electron or hole doping. Additionally, we observed very weak doping dependence of the G peak (both position and width) at Fermi energies less than half of the phonon energy and the subsequent usual removal of non-adiabatic Kohn anomaly with increased doping, which reflects again the extremely homogeneous charge distribution in our samples.

Li, Yilei; Meric, Inanc; Mak, Kin Fai; Malard, Leandro; Dean, Cory; Kim, Philip; Shepard, Kenneth; Heinz, Tony

2012-02-01

123

Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes.  

PubMed

The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was study by differential pulse voltammetry over a wide pH range. The hydrolysis products are 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA. PMID:20402644

Enache, Teodor Adrian; Fatibello-Filho, Orlando; Oliveira-Brett, Ana Maria

2010-08-01

124

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

125

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

126

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) College of Staten Island, City University of New York, USA (3) Inst. Surface Chemistry and Catalysis, Ulm

Pfeifer, Holger

127

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

128

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

129

Scanning tunneling microscopy simulations of nitrogen- and boron-doped graphene and single-walled carbon nanotubes.  

PubMed

We report on studies of electronic properties and scanning tunneling microscopy (STM) of the most common configurations of nitrogen- or boron-doped graphene and carbon nanotubes using density functional theory. Charge transfer, shift of the Fermi level, and localized electronic states are analyzed as a function of the doping configurations and concentrations. The theoretical STM images show common fingerprints for the same doping type for graphene, and metallic or semiconducting nanotubes. In particular, nitrogen is not imaged in contrast to boron. STM patterns are mainly shaped by local density of states of the carbon atoms close to the defect. STM images are not strongly dependent on the bias voltage when scanning the defect directly. However, the scanning of the defect-free side of the tube displays a perturbation compared to the pristine tube depending on the applied bias. PMID:20552993

Zheng, Bing; Hermet, Patrick; Henrard, Luc

2010-07-27

130

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

131

Preparation and characterization of vertically columnar boron doped diamond array electrode  

NASA Astrophysics Data System (ADS)

A vertically columnar boron doped diamond (BDD) array electrode was fabricated by microwave plasma chemical vapor deposition. Observed by scanning electron microscopy, the fabricated samples were structured with aligned columns whose diameter and height was 8 ?m and 12 ?m, respectively, and the minimum interval of neighboring columns was 2 ?m. The results of electrochemistry measurement showed that the columnar BDD array electrode possessed high oxygen evolution potential and low background current. Besides that, comparing with flat BDD electrode, the columnar BDD array electrode showed higher electrochemical activity (due to its inner active surface being up to 4.25 cm2), lower impedance of electric double layer, and especially enhanced electrical response signal (2.12 ?A/?M, 4 times of flat BDD in glucose detection as a sample). These excellent performances may open the door for the BDD materials to be applied in wide areas including electrochemical detection, electrochemistry degradation, electrochemical synthesis, and so on.

Zhao, Yang; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

2014-06-01

132

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

SciTech Connect

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

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

1993-12-31

133

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)Bex. 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

134

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

135

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

PubMed

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

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

2007-01-23

136

Boron and boron carbide coatings by vapor deposition  

Microsoft Academic Search

The Bureau of Mines investigated the formation of boron and boron-carbide coatings by vaporphase reactions. Optimum parameters\\u000a were determined for hydrogen reduction of boron trichloride and for the formation of boron-carbide coatings on graphite by\\u000a reaction with the deposited boron. At 1300°C, about 85 pct of the boron was deposited. Tungsten substrates did not react with\\u000a the boron deposit; other

Andrew A. Cochran; James B. Stephenson

1970-01-01

137

Electronic structure and ferromagnetism of boron doped bulk and surface CdSe: By generalized gradient approximation and generalized gradient approximation plus modified Becke and Johnson calculations  

NASA Astrophysics Data System (ADS)

Using the full potential linearized augment plane wave method with the generalized gradient approximation (GGA) and GGA plus modified Becke and Johnson (GGA+mBJ) potential, the electronic structures and ferromagnetism for the boron doped bulk and surface CdSe are investigated. Calculations show that the substitutional boron for selenium in CdSe could induce spin polarized localized states in the gap and generate local magnetic moments 3.00 ?B with one dopant atom. Energy difference between the antiferromagnetic and ferromagnetic phase suggests that BSe favors the ferromagnetic ground state. Electronic structures indicate the magnetic moments mainly provided by the doped boron atoms, and carriers mediated double exchange mechanism plays crucial role in forming the ferromagnetism. Ferromagnetic boron doped CdSe (100) films could be realized by using the high energy boron ions injection to form the non-surface doped configurations. The cadmium vacancy would reduce the ferromagnetism and lead the boron doped CdSe to magnetic metallicity. Formation energy for the four high symmetry doped configurations indicates BSe could be realized by using Cd-rich condition.

Fan, S. W.; Ding, L. J.; Yao, K. L.

2013-09-01

138

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

139

Homoepitaxial Boron Doped Diamond Anvils as Heating Elements 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 ^oC 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 lateral gradient in temperature occurs across the culet area. Since a thermocouple can easily be attached anywhere on the diamond surface, we can also measure diamond temperatures directly. With two such heaters, one can raise sample temperatures uniformly, or with any desired gradient along the pressure axis while preserving optical access. In our continuing set of benchmark experiments, we use two newly created matching heater anvils with 500?m culets to analyze the various fluorescence emission lines of ruby microspheres, which show more complicated behavior than traditional ruby chips. We also report on the temperature dependence of the high-pressure Raman modes of paracetamol (C8H9NO2) up to 20 GPa.

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

2013-03-01

140

Performance of Graphite Pastes Doped with Various Materials as Back Contact for CdS/CdTe Solar Cell  

NASA Astrophysics Data System (ADS)

To date the problem of developing a suitable back contact for CdS/CdTe solar cells has yet to be resolved. The Cu-doped graphite paste that is widely used as a back contact is associated with degradation problems due to possible Cu diffusion across the CdS/CdTe junction. This study was designed to find ways to improve the graphite paste for superior electrical contacts. Mixtures of graphite paste with various material constituents and dopants consisting of silver-, lead-, nickel-, antimony-, bismuth-, or phosphor-based compounds, were studied. Results show that the performances of solar cells fabricated from these graphite pastes vary with the change in the composition. In the cases of Ag2Te and Ni2P, we studied their relationship with the solar cell characteristics with regard to dopant quantity, and furthermore in the case of Ag2Te, with regard to the sintering temperature of the graphite electrode. A fill factor (F.F.) of over 0.65 and efficiencies over 13% were obtained with Ag2Te, Ag3PO4, Ag2MoO4, and NiTe, and efficiencies over 12% were obtained with AgF, AgCl, Ni2P, and Ni3P.

Hanafusa, Akira; Aramoto, Tetsuya; Morita, Akikatsu

2001-12-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

142

Analysis of laser doping of silicon using different boron dopant sources  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

143

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

145

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

146

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

Microsoft Academic Search

Boron doped microcrystalline silicon (p-muc-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-muc-Si films. A high dark conductivity (sigmad) of 84.6 S\\/cm

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

2003-01-01

147

Detection of the Pseudomonas Quinolone Signal (PQS) by cyclic voltammetry and amperometry using a boron doped diamond electrode.  

PubMed

2-Heptyl-3-hydroxy-4-quinolone, known as the Pseudomonas Quinolone Signal, is a key regulator of bacterial cooperative behaviour known as quorum sensing. A simple electrochemical strategy was employed for its sensitive detection using a bare boron-doped diamond electrode by cyclic voltammetry and amperometry. PQS (and potentially other quinolones) was then detected in cultures of P. aeruginosa pqsL(-) mutant strains. PMID:21853180

Zhou, Lin; Glennon, Jeremy D; Luong, John H T; Reen, F Jerry; O'Gara, Fergal; McSweeney, Christina; McGlacken, Gerard P

2011-10-01

148

Shallow donors with high n-type electrical conductivity in homoepitaxial deuterated boron-doped diamond layers  

Microsoft Academic Search

Diamond is a unique semiconductor for the fabrication of electronic and opto-electronic devices because of its exceptional physical and chemical properties. However, a serious obstacle to the realization of diamond-based devices is the lack of n-type diamond with satisfactory electrical properties. Here we show that high-conductivity n-type diamond can be achieved by deuteration of particularly selected homo-epitaxially grown (100) boron-doped

Zéphirin Teukam; Jacques Chevallier; Cécile Saguy; Rafi Kalish; Dominique Ballutaud; Michel Barbé; François Jomard; Annie Tromson-Carli; Catherine Cytermann; James E. Butler; Mathieu Bernard; Céline Baron; Alain Deneuville

2003-01-01

149

Hall Mobility and Scattering Mechanism of Holes in Boron-Doped Homoepitaxial Chemical Vapor Deposition Diamond Thin Films  

Microsoft Academic Search

The temperature dependence of the Hall mobility muH has been measured from 140 to 870 K for nine boron-doped homoepitaxial chemical vapor deposition (CVD) diamond thin films. The experimental muH data are compared with their theoretical muH values that are calculated by an iterative technique, assuming scattering by ionized impurities, acoustic deformation potential and nonpolar optical phonons. The donor concentration

Kunio Tsukioka; Hideyo Okushi

2006-01-01

150

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

151

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

Microsoft Academic Search

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

Nattakarn Wangfuengkanagul; Orawon Chailapakul

2002-01-01

152

Preparation of boron-doped porous titania networks containing gold nanoparticles with enhanced visible-light photocatalytic activity.  

PubMed

The ability to decrease the electron/hole recombination rate, and decrease the band gap of titania to allow photoactivity on irradiation with visible light is attracting more and more attention. Here, boron doping of the titania, the deposition of gold nanoparticles, along with a meso-macroporous structure were obtained using a facile agarose gel templating process combined with sol-gel chemistry. The Au/B/TiO(2) nanocomposites were characterized using SEM, TEM, XRD, N(2) gas sorption, diffuse UV-vis, photoluminescence, and SIMS. The photocatalytic activity was assessed by degradation of an organic probe molecule (methylene blue) under visible light (? > 420 nm). The resulting materials achieved photocatalytic activities up to 50% greater than the commercial Degussa P25 under visible light. The enhancement in photocatalytic activity was primarily attributed to the decrease in band gap as a result of the boron doping and its influence on the anatase to rutile phase formation: The doped materials were highly crystalline and an optimum anatase to rutile ratio (3:1) was obtained with 0.25 wt % boron in the sample calcined at 650 °C. In addition, the presence of the gold nanoparticles decreased recombination between the photoexcited electrons and holes, which further improved the photocatalytic activity. PMID:22242543

Wang, Xingdong; Blackford, Mark; Prince, Kathryn; Caruso, Rachel A

2012-01-01

153

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

154

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

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

155

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

156

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

157

Electrochemical degradation of PNP at boron-doped diamond and platinum electrodes.  

PubMed

The electrochemical degradation of p-nitrophenol (PNP) at boron-doped diamond (BDD) and platinum (Pt) anodes was studied by varying the parameters such as Cl(-) concentration, pH of aqueous medium and applied current density. The results obtained were explained in terms of in situ concomitant generation of hydroxyl radicals and chloride based oxidant species. The degradation of PNP was highly promoted in low concentration of NaCl electrolyte (less than 0.10 M), on contrary, the mineralization efficiency was poor at both BDD and Pt anodes with the NaCl concentration up to 0.20 M, which was ascribed to the formation of refractory chlorinated organic compounds. A maximum of 100% and 70% of COD removal was achieved in 5h of electrolysis period using both BDD and Pt anodes under similar experimental conditions. Kinetic study indicated that the degradation of PNP at BDD and Pt anodes followed pseudo-first-order reactions, and the reaction rate constant (k(s)) of the former was observed to be higher than that of the latter. Besides COD, conversion of PNP into various intermediate compounds and their degradations were also monitored. The mechanisms for PNP degradation at BDD and Pt anodes were proposed separately by considering the nature of respective intermediate species and their concentrations. PMID:23270953

Zhang, Yanrong; Yang, Nan; Murugananthan, Muthu; Yoshihara, Sachio

2013-01-15

158

Sub-bandgap analysis of boron doped InSe single crystals by constant photocurrent method  

NASA Astrophysics Data System (ADS)

Sub-bandgap absorption properties of indium selenide doped with boron atoms within a range of [B] = 0-1.8 at.% have been investigated. From the absorption coefficient spectra measured by using constant photocurrent method (CPM) at 300 K, we observed that the disorder in the structure increases. The calculated Urbach parameters, quantifying the disorder, vary from 17 to 53 meV, as [B] is increased from 0 to 1 at.%. Also the calculated optical gaps decrease from 1.28 eV to 1.17 eV for the same range of [B]. From temperature dependent dark conductivity measurements, the characteristic activation energies are calculated to range from 0.25 to 0.18 eV for vertical (to c-axis) direction; to stay almost constant for parallel (c-axis) direction. At a temperature of 12 K, the absorption coefficient spectra by using CPM and the radiative recombination spectra by photoluminescence (PL) have been taken for the samples with [B] = 0 and 0.5 at.%. Three main PL bands are observed at photon energies of ?1.24, 1.306 and 1.337 eV. The PL bands are interpreted by corresponding absorption bands detected at 12 K and at the photon energies of ?1.24, ?1.31 and ?1.35 eV.

Bac?o?lu, A.; Ertap, H.; Karabulut, M.; Mamedov, G. M.

2014-11-01

159

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

PubMed

Anodic oxidation of bisphenol A (BPA), a representative endocrine disrupting chemical, was carried out using boron-doped diamond (BDD) electrode at galvanostatic mode. The electro-oxidation behavior of BPA at BDD electrode was investigated by means of cyclic voltammetric technique. The extent of degradation and mineralization of BPA were monitored by HPLC and total organic carbon (TOC) value, respectively. The results obtained, indicate that the BPA removal at BDD depends on the applied current density (Iappl), initial concentration of BPA, pH of electrolyte and supporting medium. Galvanostatic electrolysis at BDD anode cause concomitant generation of hydroxyl radical that leads to the BPA destruction. The kinetics for the BPA degradation follows a pseudo-first order reaction with a higher rate constant 12.8x10(-5) s(-1) for higher Iappl value 35.7 mA cm(-2), indicating that the oxidation reaction is limited by Iappl control. Complete mineralization of BPA was achieved regardless of the variables and accordingly the mineralization current efficiency was calculated from the TOC removal measurements. Considering global oxidation process, the effect of supporting electrolytes has been discussed in terms of the electro generated inorganic oxidants. The better performance of BDD anode was proved on a comparative study with Pt and glassy carbon under similar experimental conditions. A possible reaction mechanism for BPA degradation involving three main aromatic intermediates, identified by GC-MS analysis, was proposed. PMID:18023975

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

2008-06-15

160

Microchip capillary electrophoresis coupled with a boron-doped diamond electrode-based electrochemical detector.  

PubMed

The attractive behavior and advantages of a diamond electrode detector for a micromachined capillary electrophoresis (CE) system are discussed. A chemically vapor-deposited boron-doped diamond (BDD) film band (0.3 x 6.0 mm) electrode is used for end-column amperomettic detection. The favorable performance of the diamond electrode microchip detector is indicated from comparison to a commonly used thick-film carbon detector. The diamond electrode offers enhanced sensitivity, lower noise levels, and sharper peaks for several groups of important anaytes (nitroaromatic explosives, organophosphate nerve agents, phenols). The favorable signal-to-background characteristics of the BDD-based CE detector are coupled with a greatly improved resistance to surface fouling and greater isolation from high separation voltages. The enhanced stability is indicated from a RSD of 0.8% for 60 repetitive measurements of 5 ppm 2,4,6-trinitrotoluene (vs RSD of 10.8% at the thick-film carbon electrode). A highly linear response is obtained for the explosives 1,3-dinitrobenzene and 2,4-dinitrotoluene over the 200-1,400 ppb range, with detection limits of 70 and 110 ppb, respectively. Factors influencing the performance of the BDD detector are assessed and optimized. The attractive properties of BDD make it very promising material for electrochemical detection in CE microchip systems and other micromachined flow analyzers. PMID:12622387

Wang, Joseph; Chen, Gang; Chatrathi, Madhu Prakash; Fujishima, Akira; Tryk, Donald A; Shin, Dongchan

2003-02-15

161

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

PubMed

Anodic oxidation at a boron-doped diamond anode of cork boiling wastewater was successfully used for mineralization and biodegradability enhancement required for effluent discharge or subsequent biological treatment, respectively. The influence of the applied current density (30-70 mA/cm(2)) and the background electrolyte concentration (0-1.5 g/L Na2SO4) on the performance of the electrochemical oxidation was investigated. The supporting electrolyte was required to achieve conductivities that enabled anodic oxidation at the highest current intensities applied. The results indicated that pollutant removal increased with the applied current density, and after 8 h, reductions greater than 90% were achieved for COD, dissolved organic carbon, total phenols and colour. The biodegradability enhancement was from 0.13 to 0.59 and from 0.23 to 0.72 for the BOD/COD ratios with BOD of 5 and 20 days' incubation period, respectively. The tests without added electrolyte were performed at lower applied electrical charges (15 mA/cm(2) or 30 V) with good organic load removal (up to 80%). For an applied current density of 30 mA/cm(2), there was a minimum of electric conductivity of 1.9 mS/cm (corresponding to 0.75 g/L of Na2SO4), which minimized the specific energy consumption. PMID:25409580

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

2015-01-01

162

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

PubMed

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

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

2008-02-27

163

Oxidative destruction of perfluorooctane sulfonate using boron-doped diamond film electrodes.  

PubMed

This research investigated the oxidative destruction of perfluorooctane sulfonate at boron-doped diamond film electrodes. Experiments measuring oxidation rates of PFOS were performed over a range in current densities and temperatures using a rotating disk electrode (RDE) reactor and a parallel plate flow-through reactor. The oxidation of PFOS yielded sulfate, fluoride, carbon dioxide, and trace levels of trifluoroacetic acid. Reaction rates in the RDE reactor were zeroth order in PFOS concentration. Reaction rates in the flow-through reactor were mass-transfer-limited and were pseudo-first-order in PFOS concentration, with a half-life of 5.3 min at a current density of 20 mA/cm2. Eyring analysis of the zeroth order rate constants at a fixed electrode potential yielded an apparent activation energy of 4.2 kJ/mol for PFOS oxidation. Density functional theory (DFT) simulations were used to calculate activation barriers for different possible reaction mechanisms, including oxidation by hydroxyl radicals at different sites on the PFOS molecule, and direct electron transfer. A comparison of the experimentally measured apparent activation energy with those calculated using DFT indicated that the most likely rate-limiting step for PFOS oxidation was direct electron transfer. PMID:18767674

Carter, Kimberly E; Farrell, James

2008-08-15

164

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

165

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

166

Growth of n-Si layers by molecular-beam epitaxy on the substrates heavily doped with boron  

SciTech Connect

Epitaxial n-Si layers doped with phosphorus or erbium have been grown by sublimation molecularbeam epitaxy at 500{sup o}C on heavily boron-doped p{sup +}-type substrates with resistivity {rho} = 0.005 {omega} cm. Distribution profiles of the B, Er, and O impurity concentrations in the samples were determined by secondary-ion mass spectrometry. A thermal annealing of the substrate in vacuum at 1300{sup o}C for 10 min and growth at a very low substrate temperature made it possible to obtain an extremely abrupt profile for doping impurities at the layer-substrate interface. This method for growth of n-p{sup +} junctions considerably improves their electrical and luminescent characteristics.

Shengurov, V. G.; Chalkov, V. Yu. [Lobachevsky State University, Research Physicotechnical Institute (Russian Federation)], E-mail: chalkov@nifti.unn.ru; Shengurov, D. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Denisov, S. A. [Lobachevsky State University, Research Physicotechnical Institute (Russian Federation)

2009-02-15

167

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

168

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

NASA Astrophysics Data System (ADS)

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

Xu, Jishou

2000-10-01

169

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

170

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

171

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

172

Boron-Proton Nuclear-Fusion Enhancement Induced in Boron-Doped Silicon Targets by Low-Contrast Pulsed Laser  

NASA Astrophysics Data System (ADS)

We show that a spatially well-defined layer of boron dopants in a hydrogen-enriched silicon target allows the production of a high yield of alpha particles of around 109 per steradian using a nanosecond, low-contrast laser pulse with a nominal intensity of approximately 3×1016 W cm-2. This result can be ascribed to the nature of the long laser-pulse interaction with the target and with the expanding plasma, as well as to the optimal target geometry and composition. The possibility of an impact on future applications such as nuclear fusion without production of neutron-induced radioactivity and compact ion accelerators is anticipated.

Picciotto, A.; Margarone, D.; Velyhan, A.; Bellutti, P.; Krasa, J.; Szydlowsky, A.; Bertuccio, G.; Shi, Y.; Mangione, A.; Prokupek, J.; Malinowska, A.; Krousky, E.; Ullschmied, J.; Laska, L.; Kucharik, M.; Korn, G.

2014-07-01

173

Solar photoelectro-Fenton degradation of cresols using a flow reactor with a boron-doped diamond anode  

Microsoft Academic Search

The solar photoelectro-Fenton degradation of 2.5l of acidic solutions containing o-cresol, m-cresol and p-cresol up to ca. 1gl?1, 0.05M Na2SO4 and Fe2+ as catalyst has been studied using a flow plant with a one-compartment filter-press electrolytic reactor with a boron-doped diamond (BDD) anode and an O2-diffusion cathode, both of 20-cm2 area, coupled to a solar photoreactor. In this environmentally friendly

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

2007-01-01

174

Electrochemical treatment of wastewater polluted by nitrate: selective reduction to N2 on boron-doped diamond cathode.  

PubMed

Electrochemical tests of nitrate reduction on Boron-Doped Diamond cathode are investigated through a Design of Experiments (DOE) method. The results show good reduction of nitrate into almost exclusively N2. In the studied domain, the best experimental conditions are high initial nitrate content, low acidic pH values and low working current densities. The application of DOE conclusions on an agro-industrial wastewater gives really satisfying results: final nitrate contents lower than 50 mg/L without nitrite or ammonium formation, and with low energy consumption (under 25 kWh/kgNO3). PMID:21252421

Georgeaud, V; Diamand, A; Borrut, D; Grange, D; Coste, M

2011-01-01

175

Simultaneous voltammetric determination of paracetamol and caffeine in pharmaceutical formulations using a boron-doped diamond electrode  

Microsoft Academic Search

A simple and highly selective electrochemical method was developed for the single or simultaneous determination of paracetamol (N-acetyl-p-aminophenol, acetaminophen) and caffeine (3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) in aqueous media (acetate buffer, pH 4.5) on a boron-doped diamond (BDD) electrode using square wave voltammetry (SWV) or differential pulse voltammetry (DPV). Using DPV with the cathodically pre-treated BDD electrode, a separation of about 550mV between the

Bruna Cláudia Lourenção; Roberta Antigo Medeiros; Romeu C. Rocha-Filho; Luiz Henrique Mazo; Orlando Fatibello-Filho

2009-01-01

176

Gas-assisted growth of boron-doped nickel nanotube arrays: rapid synthesis, growth mechanisms, tunable magnetic properties, and super-efficient reduction of 4-nitrophenol  

NASA Astrophysics Data System (ADS)

Highly ordered noncrystalline boron-doped nickel nanotube arrays are rapidly synthesized within 150 s by template-based electroless deposition. The as-prepared nanotubes have tunable magnetic properties and exhibit super efficient catalytic activity (~70 s) for the reduction of 4-nitrophenol.Highly ordered noncrystalline boron-doped nickel nanotube arrays are rapidly synthesized within 150 s by template-based electroless deposition. The as-prepared nanotubes have tunable magnetic properties and exhibit super efficient catalytic activity (~70 s) for the reduction of 4-nitrophenol. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00411b

Li, Xiang-Zi; Wu, Kong-Lin; Ye, Yin; Wei, Xian-Wen

2013-04-01

177

Tailoring of boron-doped MnTe semiconductor-sensitized TiO2 photoelectrodes as near-infrared solar cell devices  

NASA Astrophysics Data System (ADS)

We studied the photovoltaic performance of a new tailoring of boron-doped MnTe semiconductor-sensitized solar cells (B-doped MnTe SSCs). The B-doped MnTe semiconductor was grown on TiO2 using two-stages of the successive ionic layer adsorption and reaction (SILAR) technique as a photoelectrode. The phase of the boron-doped MnTe and MnTe2 semiconductor as sensitizers were characterized with ˜20-50 nm in diameter. The B-doped MnTe(5) exhibited the best efficiency of 0.04%, compared to that of the undoped sample of 0.006%. In addition, the band gaps of 1.30 and 1.26 eV were determined for the undoped and B-doped MnTe NPs, respectively. The change in the band gap after boron doping was performed due to crystal quality improvement and the larger size of the MnTe NPs, leading to a broader absorption of the sensitizer and a noticeable improvement in the photovoltaic performance. This kind of semiconductor and synthesis procedure can be applied for further improvement in a higher efficiency and more stability in SSCs.

Tubtimtae, Auttasit; Hongto, Timakorn; Hongsith, Kritsada; Choopun, Supab

2014-02-01

178

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

PubMed

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

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

2013-11-01

179

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

180

Photovoltaic characteristics of boron-doped hydrogenated amorphous carbon on n-Si substrate prepared by r.f. plasma-enhanced CVD using trimethylboron  

Microsoft Academic Search

An attempt has been made on the device fabrication with boron-doped hydrogenated amorphous carbon (a-C:H) thin film deposited on n-type Si (100) by r.f. plasma-enhanced CVD. In order to identify the optimal doping condition, the various CH4 partial pressure has been examined. a-C:H\\/n-Si heterojunction solar cells with a conversion efficiency as high as 0.04% have been fabricated. The spectral response

Y. Hayashi; S. Ishikawa; T. Soga; M. Umeno; T. Jimbo

2003-01-01

181

Synthesis of highly conductive boron-doped p-type hydrogenated microcrystalline silicon (?c-Si:H) by a hot-wire chemical vapor deposition (HWCVD) technique  

Microsoft Academic Search

Boron-doped hydrogenated microcrystalline silicon (?c-Si:H) films were prepared using hot-wire chemical vapor deposition (HWCVD) technique. Structural, electrical and optical properties of these thin films were systematically studied as a function of B2H6 gas (diborane) phase ratio (Variation in B2H6 gas phase ratio, dopant gas being diluted in hydrogen, affected the film properties through variation in doping level and hydrogen dilution).

S. R Jadkar; Jaydeep V Sali; M. G Takwale; D. V Musale; S. T Kshirsagar

2000-01-01

182

Phosphorous and boron doping of nc-Si:H thin films deposited on plastic substrates at 150 °C by Hot-Wire Chemical Vapor Deposition  

Microsoft Academic Search

Gas-phase phosphorous and boron doping of hydrogenated nanocrystalline thin films deposited by HWCVD at a substrate temperature of 150 °C on flexible-plastic (polyethylene naphthalate, polyimide) and rigid-glass substrates is reported. The influence of the substrate, hydrogen dilution, dopant concentration and film thickness on the structural and electrical properties of the films was investigated. The dark conductivity of B- and P-doped films

S. A. Filonovich; M. Ribeiro; A. G. Rolo; P. Alpuim

2008-01-01

183

Assessment of Electrodes Prepared from Wafers of Boron-doped Diamond for the Electrochemical Oxidation of Waste Lubricants  

SciTech Connect

Electrochemical oxidation using boron-doped diamond electrodes is being investigated as a treatment process for radioactively contaminated oily wastes. Previously, it was shown that electrodes coated with a thin film of diamond were able to oxidise a cutting oil but not a mineral oil. These tests were inconclusive, because the electrodes lost their diamond coating during operation. Accordingly, an electrode prepared from a 'solid' wafer of boron-doped diamond is being investigated to determine whether it will oxidise mineral oils. The electrode has been tested with sucrose, a cutting oil and an emulsified mineral oil. Before and after each test, the state of the electrode was assessed by cyclic voltammetry with the ferro/ferricyanide redox couple. Analysis of the cyclic voltammogram suggested that material accumulated on the surface of the electrode during the tests. The magnitude of the effect was in the order: - emulsified mineral oil > cutting oil > sucrose. Despite this, the results indicated that the electrode was capable of oxidising the emulsified mineral oil. Confirmatory tests were undertaken in the presence of alkali to trap the carbon dioxide, but they had to be abandoned when the adhesive holding the diamond in the electrode was attacked by the alkali. Etching of the diamond wafer was also observed at the end of the tests. Surface corrosion is now regarded as an intrinsic part of the electrochemical oxidation on diamond, and it is expected that the rate of attack will determine the service life of the electrodes. (authors)

Taylor, G.T.; Sullivan, I.A.; Newey, A.W.E. [AWE, Aldermaston, Reading, RG7 4PR (United Kingdom)

2006-07-01

184

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

185

Thermal evolution of high-purity and boron-doped sub-microcrystalline Ni{sub 3}Al produced by severe plastic deformation  

SciTech Connect

The influence of boron on the structural stability of sub-microcrystalline Ni{sub 3}Al intermetallic compounds was investigated by comparing a high-purity material with a boron-doped (0.1 wt%) compound. The nanocrystalline structure was obtained by severe shear deformation under quasi-hydrostatic pressure. Residual electrical resistivity, Vickers microhardness, X-ray diffraction and transmission electron microscopy were used to characterize the material evolution during thermal treatments in the temperature range 293--1,313 K. After severe deformation the materials were disordered, with a small crystallite size of about 20 nm, similar in both materials. During isochronal anneals, the evolution of the microstructure, the long-range ordering and the recovery of the investigated properties took place at higher temperatures in the boron-doped compound, i.e. the thermal stability of the cold-worked structure was higher.

Korznikov, A.V.; Korznikova, G.F.; Idrisova, S.R. [Russian Academy of Sciences, Ufa (Russian Federation). Inst. of Metals Superplasticity Problems] [Russian Academy of Sciences, Ufa (Russian Federation). Inst. of Metals Superplasticity Problems; Dimitrov, O.; Dallas, J.P.; Faudot, F. [CNRS, Vitry-sur-Seine (France)] [CNRS, Vitry-sur-Seine (France); Valiev, R.Z. [Ufa State Aviation Univ. (Russian Federation). Inst. of Physics of Advanced Materials] [Ufa State Aviation Univ. (Russian Federation). Inst. of Physics of Advanced Materials

1999-09-08

186

Geometric, electronic, and optical properties of a boron-doped aluminum cluster of B2Al21-: A density functional theory study  

NASA Astrophysics Data System (ADS)

We present the physicochemical properties for the lowest-energy isomer of a boron-doped aluminum cluster of B2Al21-. The isomer was obtained by basin-hopping minimization based on the density functional theory, starting from a face-sharing bi-icosahedral structure in which two boron atoms were endohedrally doped to each icosahedron. The lowest-energy isomer is a triangular form in which an aluminum cage encapsulates two boron atoms endohedrally. The electronic structure was analyzed by projecting Kohn-Sham orbitals onto the spherical harmonics; occupied and unoccupied frontier orbitals are dominantly G- and H-symmetries, respectively. Optical absorption is mainly assigned to G to H transitions.

Iwasa, Takeshi; Nakajima, Atsushi

2013-09-01

187

Capacitance of p- and n-doped graphenes is dominated by structural defects regardless of the dopant type.  

PubMed

Graphene materials possess attractive properties that can be used for the fabrication of supercapacitors with enhanced energy-storage performance. It has been shown that both boron and nitrogen doping of graphene can improve the intrinsic capacitance of the material relative to the undoped precursor. We address the question of whether p-doping (using boron as dopant) or n-doping (using nitrogen as dopant) leads to increased capacitance relative to undoped graphene materials. Using thermal exfoliation we synthesized both boron- and nitrogen-doped graphene materials and measured capacitance relative to the undoped material. After a full characterization by SEM analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, gamma-ray activation analysis, Brunauer-Emmett-Teller analysis, and electrochemical techniques we demonstrate that the doping process does not lead to enhancement of capacitive behavior and that the main characteristic influencing capacitance is the presence of structural defects within the graphitic structure, independent of doping level. PMID:24591401

Ambrosi, Adriano; Poh, Hwee Ling; Wang, Lu; Sofer, Zdenek; Pumera, Martin

2014-04-01

188

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

NASA Astrophysics Data System (ADS)

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

Zhu, J.; Oliveira, L.; Podila, R.; Neeleshwar, S.; Chen, Y. Y.; He, J.; Skove, M.; Rao, A. M.

2013-03-01

189

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

190

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

192

Large deep-ultraviolet photocurrent in metal-semiconductor-metal structures fabricated on as-grown boron-doped diamond  

NASA Astrophysics Data System (ADS)

Metal-semiconductor-metal planar devices have been fabricated on as-grown boron-doped homoepitaxial diamond thin films. They consist of two Schottky barriers connected back to back. The metal employed was a thin titanium (Ti) layer (5nm) followed by a gold (Au) cap layer (50nm), respectively. The structure shows a high ultraviolet photocurrent at 220nm, which is seven orders of magnitude higher than the reverse dark current (<1pA) for at least an applied voltage of ±0.4V. In addition, anomalous photoconductivity gain is observed. A plausible explanation could be the modification of the Schottky barrier under band-to-band illumination. The spectral photoresponse displays over six orders of magnitude discrimination between deep-ultraviolet (210nm) and visible light (630nm), and reveals a shoulder with an onset at 4.6eV.

Alvarez, Jose; Liao, Meiyong; Koide, Yasuo

2005-09-01

193

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

PubMed

This study presents the in vivo electrochemical monitoring of pH using boron doped diamond (BDD) microelectrode and silver needles for potential application in medical diagnosis. Accurate calibration curve for pH determination were obtained through in vitro electrochemical measurements. The increase induced in stomach pH by treatment with pantoprazole was used to demonstrate that it is possible to monitor the pH in vivo using the simple and noninvasive system proposed herein. Using the results of the in vivo and in vitro experiments, a quantitative analysis of the increase in stomach pH is also presented. It is proposed that the catheter-free pH monitoring system presented in this study could be potentially employed in any biological environment. PMID:24247214

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

2013-01-01

194

Electrocatalytic and photocatalytic activity of Pt-TiO2 films on boron-doped diamond substrate  

NASA Astrophysics Data System (ADS)

In the present work boron-doped diamond (BDD) polycrystalline films were used as support for direct anodic deposition of hydrous titanium oxide, and continuous TiO2 coatings were obtained by appropriately adjusting the deposition charge. The photoelectrochemical activity of the TiO2/BDD electrodes was investigated and it was found that, in terms of charge carriers separation efficiency, conductive diamond is a much better support for TiO2, compared to traditional carbonaceous materials such as glassy carbon. Further electrochemical deposition of platinum particles on the oxide-coated conductive diamond enabled the formation of a composite with enhanced electrochemically active surface area. The electrocatalytic and photocatalytic properties of the Pt/TiO2/BDD electrodes thus obtained were also scrutinized and it appeared that these hybrid systems also exhibit promising features for methanol anodic oxidation.

Sp?taru, Tan?a; Marcu, Maria; Sp?taru, Nicolae

2013-03-01

195

Influence of boron on microstructural evolution of silicon carbide derived from preceramic polymers  

NASA Astrophysics Data System (ADS)

It is well known that the addition of boron to Si-C based materials remarkably influences their microstructure evolution. This study focused on two different preceramic polymer systems: polycarbosilane (Si-C) and polycarbosilazane (Si-C-N). The influence of boron introduced in each of the two systems is investigated. Polymers were heat treated to 1400, 1600, 1800 and in some cases 2000°C in UHP argon and the polymer-to-ceramic transition and subsequent microstructural development was evaluated. It was found that boron has a significant influence on graphitization behavior of carbon in polycarbosilane (Si-C based) systems. For material derived from polycarbosilane containing 0.7 wt% boron, it is suggested that boron is doped within disordered sites of the basic structural units of graphite. These graphene layers are the building units of all carbon structures. The presence of substitutional boron increases the thermal and mechanical stability of graphite layers. Therefore, the presence of boron within graphene layers stabilizes these and thus prevents SiC nucleation and growth. A higher concentration of boron (4.4wt% at 1800°C) leads to a partial graphitization of the free carbon. This is connected to an increase of organization of graphene layers which makes SiC crystallites less connected to the surrounding matrix. This explains the larger SiC crystallite sizes observed for this case as compared to the material with 0.7 wt% boron. If no boron is incorporated in the polycarbosilane, uncontrolled and inhomogeneous SiC crystallite growth is observed and a very broad crystallite distribution (20--300 nm) results. The incorporation of boron in (Si-C) based polycarbosilane systems, therefore, gives the possibility to indirectly tailor SiC crystallite sizes by controlling the evolution of graphite structure surrounding each SiC crystal. For the polycarbosilazane (Si-C-N based) system, such trend was not found. The carbon phase in both systems (with boron as well as without) exhibits orientation to a large degree. This is attributed to the effect of nitrogen which is present in both systems. There fore, nitrogen itself substitutes for carbon, and thus aids in the elimination of structural defects which ultimately results in a large orientation of carbon cages. However, unlike boron, nitrogen leaves the material rapidly with increasing temperature (e.g. ˜2wt% nitrogen left at 1800°C) which results in the degradation of oriented carbon structures.

Eber-Koyuncu, Manuela

196

Cathodic and anodic pre-treated boron doped diamond with different sp2 content: Morphological, structural, and impedance spectroscopy characterizations  

NASA Astrophysics Data System (ADS)

In this work, the influence of cathodic (Red) and anodic (Ox) pre-treatment on boron doped diamond (BDD) films grown with different sp2/sp3 ratios was systematically studied. The sp2/sp3 ratios were controlled by the addition of CH4 of 1,3,5 and 7 sccm in the gas inlet during the growth process. The electrodes were treated in 0.5 mol L-1 H2SO4 at -3 and 3 V vs Ag/AgCl, respectively, for 30 min. The electrochemical response of BDD films was investigated using electrochemical impedance spectroscopy (EIS) and Mott-Schottky Plot (MSP) measurements. Four film sample sets were produced in a hot filament chemical vapor deposition reactor. During the growth process, an additional H2 line passing through a bubbler containing the B2O3 dissolved in methanol was used to carry the boron. The scanning electron microscopy morphology showed well faced films with a small decrease in their grain size as the CH4 concentration increased. The Raman spectra depicted a pronounced sp2 band, mainly for films with 5 and 7 sccm of CH4. MSP showed a decrease in the acceptor concentration as the CH4 increased indicating the CH4 influence on the doping process for Red-BDD and Ox-BDD samples. Nonetheless, an apparent increase in the acceptor concentrations for both Ox-BDD samples was observed compared to that for Red-BDD samples, mainly attributed to the surface conductive layer (SCL) formation after this strong oxidation process. The EIS Nyquist plots for Red-BDD showed a capacitance increase for the films with higher sp2 content (5 and 7 sccm). On the other hand, the Nyquist plots for Ox-BDD can be described as semicircles near the origin, at high frequencies, where their charge transfer resistance strongly varied with the sp2 increase in such films.

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

2013-12-01

197

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

198

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

PubMed Central

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

Sun, Wenming; Bu, Yuxiang

2008-01-01

199

Hall Mobility and Scattering Mechanism of Holes in Boron-Doped Homoepitaxial Chemical Vapor Deposition Diamond Thin Films  

NASA Astrophysics Data System (ADS)

The temperature dependence of the Hall mobility ?H has been measured from 140 to 870 K for nine boron-doped homoepitaxial chemical vapor deposition (CVD) diamond thin films. The experimental ?H data are compared with their theoretical ?H values that are calculated by an iterative technique, assuming scattering by ionized impurities, acoustic deformation potential and nonpolar optical phonons. The donor concentration ND, the acoustic deformation potential constant E1 and the coupling constant of nonpolar optical phonons Dnpo are used as fitting parameters. The experimental data of the hole concentration p are also analyzed by a fitting procedure. The acceptor concentration NA, the donor concentration ND, and the acceptor ionization energy EA are used as fitting parameters. The fitting analyses of ?H yielded an average Dnpo=(1.2± 0.2)× 1012 eV/m. Considerable differences were observed between ND values estimated from the fitting analyses of ?H and those from the p-analyses. The average E1 for the samples with little difference between the two types of ND is 14.5 eV, which is in agreement with that of a natural diamond of high quality. The average EA for the samples with a low or medium doping level is 0.365 eV, which is in good agreement with those in the literature. Some indications of the contribution of hopping conduction in the low-temperature range were observed.

Tsukioka, Kunio; Okushi, Hideyo

2006-11-01

200

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

E-print Network

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. ...

Zhang, Qian

201

On the 0.34 eV hole trap in irradiated boron-doped silicon  

Microsoft Academic Search

A detailed deep level transient spectroscopy (DLTS) study has been carried out on a prominant hole trap at 0.34 eV above the valence band in irradiated p-type silicon. The boron concentration in the float zone and Czochralski-grown samples varied between 10 and 10 cm, and irradiations with 2.0 MeV electrons have been performed at nominal room temperature to total fluences

O. O. Awaldekarim; S. A. Suliman; B. Monemar

1989-01-01

202

Effective reduction of the metastable defect concentration in boron-doped Czochralski silicon for solar cells  

Microsoft Academic Search

Different approaches to reduce the light-induced degradation of Czochralski silicon (Cz-Si) solar cells are investigated. In the first part of this paper the very promising possibility of using overcompensated oxygen-rich n-type silicon with residual boron as solar cell substrate material is demonstrated. Stable bulk carrier lifetimes in the millisecond range are achievable in this material. The second part of this

K. Bothe; J. Schmidt; R. Hezel

2002-01-01

203

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

NASA Astrophysics Data System (ADS)

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

Lin, Yung-Hsiang; Lin, Gong-Ru

2012-06-01

204

Glass Structure Changes in CO Laser Writing of Long-Period Fiber Gratings in Boron-Doped Single-Mode Fibers  

Microsoft Academic Search

We investigate in detail the process of CO2-laser writing of long-period fiber gratings (LPFGs) in unannealed and annealed boron-doped fiber samples by using repeated scanning of CO2-laser pulses. We find that the writing dynamics depends strongly on the CO2-laser energy density and the annealing temperature of the fiber. Our results from analyzing the writing dynamics reveal the relative importance of

Yunqi Liu; Ho Wai Lee; Kin Seng Chiang; Tao Zhu; Yun Jiang Rao

2009-01-01

205

High-performance liquid chromatographic method with amperometric detection employing boron-doped diamond electrode for the determination of sildenafil, vardenafil and their main metabolites in plasma  

Microsoft Academic Search

A simple, fast and sensitive HPLC method with electrochemical detection employing boron-doped diamond electrode (BDD) for the determination of sildenafil (Viagra™), vardenafil (Levitra™) and their main metabolites, N-desmethyl sildenafil and N-desethyl vardenafil in human plasma is presented. The assay involved drug extraction by tert-butyl methyl ether and isocratic reversed-phase liquid chromatography with amperometric detection. Complete separation of all analytes was

Zdenka Bartošová; David Jirovský; Aleš Horna

2011-01-01

206

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

207

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

NASA Astrophysics Data System (ADS)

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

Nishida, S.; Funashima, H.; Sato, K.; Katayama-Yoshida, H.

2013-12-01

208

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

SciTech Connect

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

Mileshko, L. P., E-mail: mil@fib.tsure.ru [Southern Federal University, Technological Institute (Russian Federation)

2009-12-15

209

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

Microsoft Academic Search

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

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

2011-01-01

210

Structural evolution of small gold clusters doped by one and two boron atoms.  

PubMed

The potential energy surfaces (PES) of a series of gold-boron clusters with formula Aun B (n?=?1-8) and Aum B2 (m?=?1-7) have been explored using a modified stochastic search algorithm. Despite the complexity of the PES of these clusters, there are well-defined growth patterns. The bonding of these clusters is analyzed using the adaptive natural density partitioning and the natural bonding orbital analyses. Reactivity is studied in terms of the molecular electrostatic potential. © 2014 Wiley Periodicals, Inc. PMID:25284009

Grande-Aztatzi, Rafael; Martínez-Alanis, Paulina R; Cabellos, José Luis; Osorio, Edison; Martínez, Ana; Merino, Gabriel

2014-12-15

211

Theory of boron doping in a-Si:H P. A. Fedders  

E-print Network

is created near the valence-band edge and there is one fewer electron to fill the electronic states. Thus is incorporated into threefold coordinated sites and that B is inert or nondoping in this configuration. Using ab initio molecular dynamics, we have studied the energetics and electronic structure doping consequences

Drabold, David

212

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

PubMed

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

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

2014-12-01

213

Tuning Hydrogen Storage in Lithium-Functionalized BC2 N Sheets by Doping with Boron and Carbon.  

PubMed

First-principles calculations are used to explore the strong binding of lithium to boron- and carbon-doped BC2 N monolayers (BC2 NBC and BC2 NCN , respectively) without the formation of lithium clusters. In comparison to BC2 N and BC2 NCB , lithium-decorated BC2 NBC and BC2 NCN systems possess stronger s-p and p-p hybridization and, hence, the binding energy is higher. Lithium becomes partially positively charged by donating electron density to the more electronegative atoms of the sheet. Attractive van der Waals interactions are responsible for binding hydrogen molecules around the lithium atoms. Each lithium atom can adsorb three hydrogen molecules on both sides of the sheet, with an average hydrogen binding energy of approximately 0.2 eV, which is in the range required for practical applications. The BC2 NBC -Li and BC2 NCN -Li complexes can serve as high-capacity hydrogen-storage media with gravimetric hydrogen capacities of 9.88 and 9.94 wt?%, respectively. PMID:25056204

Qiu, Nian-Xiang; Zhang, Cheng-Hua; Xue, Ying

2014-10-01

214

Comparative study of oxidation ability between boron-doped diamond (BDD) and lead oxide (PbO2) electrodes  

NASA Astrophysics Data System (ADS)

The electrochemical oxidation capabilities of two high-performance electrodes, the boron-doped diamond film on Ti (Ti/BDD) and the lead oxide film on Ti (Ti/PbO2), were discussed. Hydroxyl radicals (·HO) generated on the electrode surface were detected by using p-nitrosodimethylaniline (RNO) as the trapping reagent. Electrochemical oxidation measurements, including the chemical oxygen demand (COD) removal and the current efficiency (CE), were carried out via the degradation of p-nitrophenol (PNP) under the galvanostatic condition. The results indicate that an indirect reaction, which is attributed to free hydroxyl radicals with high activation, conducts on the Ti/BDD electrode, while the absorbed hydroxyl radicals generated at the Ti/PbO2 surface results in low degradation efficiency. Due to quick mineralization which combusts PNP to CO2 and H2O absolutely by the active hydroxyl radical directly, the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO2 electrode, notwithstanding the number of hydroxyl radicals produced on PbO2 is higher than that on the BDD surface.

Wei, Jun-Jun; Zhu, Xiu-Ping; Lü, Fan-Xiu; Ni, Jin-Ren

2011-10-01

215

Deposition temperature independent excellent passivation of highly boron doped silicon emitters by thermal atomic layer deposited Al2O3  

NASA Astrophysics Data System (ADS)

In this work, we demonstrate that by using H2O based thermal atomic layer deposited (ALD) Al2O3 films, excellent passivation (emitter saturation current density of ˜28 fA/cm2) on industrial highly boron p+-doped silicon emitters (sheet resistance of ˜62 ?/sq) can be achieved. The surface passivation of the Al2O3 film is activated by a fast industrial high-temperature firing step identical to the one used for screen printed contact formation. Deposition temperatures in the range of 100-300 °C and peak firing temperatures of ˜800 °C (set temperature) are investigated, using commercial-grade 5? Cz silicon wafers (˜5 ? cm n-type). It is found that the level of surface passivation after activation is excellent for the whole investigated deposition temperature range. These results are explained by advanced computer simulations indicating that the obtained emitter saturation current densities are quite close to their intrinsic limit value where the emitter saturation current is solely ruled by Auger recombination. The process developed is industrially relevant and robust.

Liao, Baochen; Stangl, Rolf; Ma, Fajun; Hameiri, Ziv; Mueller, Thomas; Chi, Dongzhi; Aberle, Armin G.; Bhatia, Charanjit S.; Hoex, Bram

2013-09-01

216

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

217

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

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

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

2011-01-13

218

Study on Optical Properties and Structure of Sm 2O 3 Doped Boron-Aluminosilicate Glass  

Microsoft Academic Search

Sm3+ doped B2O3-Al2O3-SiO2 glasses were prepared by high temperature solid-state method. The absorption spectrum, excitation spectrum, emission spectrum and the effect on concentrations of Sm3+ were investigated at room temperature. The results indicated that, under the excitation of 472 nm, the glass gane visible (VIS) and near infra-red (NIR) emissions at 596, 641, 561, 1075, 1118 and 1177 nm, respectively.

Ni Yaru; Lu Chunhua; Zhang Yan; Zhang Qitu; Xu Zhongzi

2007-01-01

219

Connections between magnetism and superconductivity in UBe13 doped with thorium or boron  

SciTech Connect

Magnetism and superconductivity appear to be intimately connected in the heavy electron (HE) superconductors. For example, it has been conjectured but not proven that the exchange of antiferromagnetic spin fluctuations are responsible for pairing in HE superconductors. In this paper we review recent results in U{sub 1-x}Th{sub x}Be{sub 13}, where specific heat, lower critical field and zero-field {mu}SR measurements reveal another second-order phase transition to a state which possesses small-moment magnetic correlations for 0.019 {le} {times} {le} 0.043. We present a new phase diagram for (U,Th)Be{sub 13} which indicates that the superconducting and magnetic order parameters are closely coupled. A discussion of the nature of the lower phase is presented, including the consideration of a possible magnetic superconducting state. When UBe{sub 13} is doped with B (UBe{sub 12.97}B{sub 0.03}) the Kondo temperature is decreased and the specific heat jump at the superconducting transition temperature is significantly enhanced. However, {mu}SR measurements reveal no magnetic signature in UBe{sub 12.97}B{sub 0.03}, unlike the case for Th doping. The correlation between changes in the Kondo temperature and changes in the superconducting properties induced by B doping provide evidence for the importance of magnetic excitations in the superconducting pairing interaction in UBe{sub 13}.

Heffner, R.H.; Ott, H.R.; Schenck, A.; Mydosh, J.A.; MacLaughlin, D.E. (Los Alamos National Lab., NM (USA))

1991-06-01

220

The influence of Cu-doping on aluminum nitride, silicon carbide and boron nitride nanotubes’ ability to detect carbon dioxide; DFT study  

NASA Astrophysics Data System (ADS)

In this research, the potential use of Cu-functionalized [4,4] silicon carbide (SiC), aluminum nitride (AlN) and boron nitride (BN) single-walled nanotubes as nanodevices for CO2 monitoring is investigated. It is found that Cu-doping the different sites of the considered nanotubes and combining these nanotubes with CO2 gas molecules are both exothermic processes, and the relaxed geometries are stable. Our results reveal that the CO2 gas molecules can be strongly physisorbed on the Cu-doped nanotubes, accompanied by large adsorption energy. Compared with the weak adsorption of CO2 molecule onto pristine BNNT and SiCNT, the CO2 molecule tends to be strongly physisorbed onto Cu-decorated BNNT and SiCNT with an appreciable adsorption energy. Furthermore, the results indicate that Cu-functionalized SiCNT is more favorable than Cu-doped BNNT and AlNNT structures for CO2 adsorption. Natural bond orbital analysis indicates that the adsorption of a CO2 molecule onto Cu-doped nanotubes is influenced by the electronic conductance and mechanical properties of the nanotube, which could serve as a signal for a gas sensor. It appears that the considerable charge transfer from the Cu-doped nanotubes to a CO2 molecule reduces the energy gap. These observations suggest that the Cu-doped-SiCNT, -BNNT and -AlNNT can be introduced as promising candidates for gas sensor devices that detect CO2 molecules.

Mahdavifar, Zabiollah; Abbasi, Nasibeh

2014-02-01

221

Ultrathin graphitic carbon nitride nanosheets: a novel peroxidase mimetic, Fe doping-mediated catalytic performance enhancement and application to rapid, highly sensitive optical detection of glucose.  

PubMed

In this article, we demonstrate for the first time that ultrathin graphitic carbon nitride nanosheets (g-C3N4) possess peroxidase activity. Fe doping of the nanosheets leads to peroxidase mimetics with greatly enhanced catalytic performance and the mechanism involved is proposed. We further demonstrate the novel use of such Fe-g-C3N4 as a cheap nanosensor for simple, rapid, highly selective and sensitive optical detection of glucose with a pretty low detection limit of 0.5 ?M. PMID:24121798

Tian, Jingqi; Liu, Qian; Asiri, Abdullah M; Qusti, Abdullah H; Al-Youbi, Abdulrahman O; Sun, Xuping

2013-12-01

222

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

PubMed Central

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

Xia, Kang; Zhan, Haifei; Wei, Ye

2014-01-01

223

Observation of d-p hybridized aromaticity in lanthanum-doped boron clusters.  

PubMed

The concept of aromaticity has been advanced beyond the framework of organic chemistry, and multiple aromaticity (?, ?, and ?) has been observed to account for the highly symmetric structures or unusual stability of the clusters. In the present study, the electronic structures and chemical bonding of small monolanthanum boride clusters are investigated using photoelectron imaging spectroscopy and first principles electronic structure calculations. Accurate electron affinities of 1.32 ± 0.04 and 1.13 ± 0.06 eV for the neutral LaB2 and LaB3 clusters are obtained by the vibrationally-resolved photoelectron spectra of the LaB2(-) and LaB3(-) clusters, respectively. It is shown that LaB2(-) and LaB3 exhibit enhanced stability in their respective cluster series, as evidenced from the calculated removal energies and HOMO-LUMO gaps. Molecular orbital analysis discloses that these two clusters possess doubly aromatic characters (? and ?), responsible for their enhanced stability. Interestingly, unlike conventional ?-, ?-, and ?-aromaticity formed by the delocalization of unhybridized p or d orbitals, the ? and ? delocalized molecular orbitals shown here are formed through the effective overlap between the 5d atomic orbital of the La atom and the p orbitals of the remaining boron atoms, representing an intriguing d-p hybridized aromaticity. PMID:24141329

Cheng, Shi-Bo; Berkdemir, Cuneyt; Castleman, A W

2014-01-14

224

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

225

Comparing atrazine and cyanuric acid electro-oxidation on mixed oxide and boron-doped diamond electrodes.  

PubMed

The breakdown of pesticides has been promoted by many methods for clean up of contaminated soil and wastewaters. The main goal is to decrease the toxicity of the parent compound to achieve non-toxic compounds or even, when complete mineralization occurs, carbon dioxide and water. Therefore, electrochemical degradation (potentiostatic and galvanostatic) of both the pesticide atrazine and cyanuric acid (CA) at boron-doped diamond (BDD) and Ti/Ru0.3Ti0.7O2 dimensionally stable anode (DSA) electrodes, in different supporting electrolytes (NaCl and Na2SO4), is presented with the aim of establishing the influence of the operational parameters on the process efficiency. The results demonstrate that both the electrode material and the supporting electrolyte have a strong influence on the rate of atrazine removal. In the chloride medium, the rate of atrazine removal is always greater than in sulfate under all conditions employed. Furthermore, in the sulfate medium, atrazine degradation was significant only at the BDD electrode. The total organic carbon (TOC) load decreased by 79% and 56% at the BDD and DSA electrodes, respectively, in the chloride medium. This trend was maintained in the sulfate medium but the TOC removal was lower (i.e. 33% and 13% at BDD and DSA electrodes, respectively). CA, a stable atrazine degradation intermediate, was also studied and it is efficiently removed using the BDD electrode in both media, mainly when high current densities are employed. The use of the BDD electrode in the chloride medium not only degrades atrazine but also mineralized cyanuric acid leading to the higher TOC removal. PMID:23837356

Malpass, Geoffroy R P; Salazar-Banda, Giancarlo R; Miwa, Douglas W; Machado, Sérgio A S; Motheo, Artur J

2013-01-01

226

Simultaneous electrochemical determination of nitrate and nitrite in aqueous solution using Ag-doped zeolite-expanded graphite-epoxy electrode.  

PubMed

In this work a new electrochemical sensor based on an Ag-doped zeolite-expanded graphite-epoxy composite electrode (AgZEGE) was evaluated as a novel alternative for the simultaneous quantitative determination of nitrate and nitrite in aqueous solutions. Cyclic voltammetry was used to characterize the electrochemical behavior of the electrode in the presence of individual or mixtures of nitrate and nitrite anions in 0.1M Na(2)SO(4) supporting electrolyte. Linear dependences of current versus nitrate and nitrite concentrations were obtained for the concentration ranges of 1-10mM for nitrate and 0.1-1mM for nitrite using cyclic voltammetry (CV), chronoamperometry (CA), and multiple-pulsed amperometry (MPA) procedures. The comparative assessment of the electrochemical behavior of the individual anions and mixtures of anions on this modified electrode allowed determining the working conditions for the simultaneous detection of the nitrite and nitrate anions. Applying MPA allowed enhancement of the sensitivity for direct and indirect nitrate detection and also for nitrite detection. The proposed sensor was applied in tap water samples spiked with known nitrate and nitrite concentrations and the results were in agreement with those obtained by a comparative spectrophotometric method. This work demonstrates that using multiple-pulse amperometry with the Ag-doped zeolite-expanded graphite-epoxy composite electrode provides a real opportunity for the simultaneous detection of nitrite and nitrate in aqueous solutions. PMID:21035645

Manea, Florica; Remes, Adriana; Radovan, Ciprian; Pode, Rodica; Picken, Stephen; Schoonman, Joop

2010-11-15

227

Structure and stability of Al-doped boron clusters by the density-functional theory.  

PubMed

The geometries, stabilities, and electronic properties of Bn and AlBn clusters, up to n=12, have been systematically investigated by using the density-functional approach. The results of Bn clusters are in good agreement with previous conclusions. When the Al atom is doped in Bn clusters, the lowest-energy structures of the AlBn clusters favor two-dimensional and can be obtained by adding one Al atom on the peripheral site of the stable Bn when n

Feng, Xiao-Juan; Luo, You-Hua

2007-03-29

228

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

229

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

230

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

231

Ex situ variable angle spectroscopic ellipsometry studies on chemical vapor deposited boron-doped diamond films: Layered structure and modeling aspects  

NASA Astrophysics Data System (ADS)

We report the optical property measurements on boron-doped diamond (BDD) films which were synthesized by microwave plasma-assisted chemical vapor deposition technique on Si (100) using methane in high hydrogen dilution and trimethylboron as precursors with varying boron concentration such that [B]/[C]gas=100, 500, 1000, 2000, 4000, and 6467ppm. These BDD films were investigated using a rotating analyzer variable angle spectroscopic ellipsometry (SE) from the near IR to UV range (830-193nm). By applying the conventional Bruggeman effective medium approximation and linear regression analyses to the raw SE data that is, [?(?i),?(?i)] and pseudodielectric function (??r(?i)?,??i(?i)?), we determined the most appropriate model fit. The SE modeling was performed through the normal and point-by-point fit methods combined with the coupled and uncoupled bulk and surface layer approaches providing the details about the thin films' microstructure in terms of the (a) multilayer (component and surface) structure and component layer thickness of the films, (b)volume fraction of constituents [fsp3C, fsp2C and void (fv) in the component layer], (c) inhomogeneity of the structure along the growth axis and its variation with boron concentration, and (iv) surface roughness layer thickness (ds) with dimensions less than the optical wavelength that is not otherwise available. A simplified three-layer structural model consisting of an interfacial layer, an intermediate (or bulk) layer, and a top surface roughness layer has been proposed, which simulates the ellipsometry data reasonably well with coupled point-by-point method. An estimator, i.e., mean squared error (?2), is used to assess the accuracy of the model fit. The results (surface roughness and constituents' fraction) obtained through SE modeling are also compared with those from atomic force microscopy (AFM) and Raman spectroscopy to validate the layered model employed. Typically, high surface roughness values around 6nm were found for films grown under different boron concentrations which is almost five times smaller than determined from AFM. In this context, we determined an approximate linear relationship between these two variables. The relatively smaller surface roughness for BDD films indicates the combined role of boron-hydrogen (B, H) in diamond (C) while keeping the substrate temperature constant. We also discussed the variation of (fv and fnd) for the bulk and surface layers with increasing boron concentration.

Gupta, S.; Dudipala, A.; Williams, O. A.; Haenen, K.; Bohannan, E.

2008-10-01

232

Undoped and boron doped diamond nanoparticles as platinum and platinum-ruthenium catalyst support for direct methanol fuel cell application  

NASA Astrophysics Data System (ADS)

Nanoparticular diamond is a promising material that can be used as a robust and chemically stable catalytic support. It has been studied and characterized physically and electrochemically, in its powder and thin film forms. This thesis work intends to demonstrate that undoped diamond nanoparticles (DNPs) and boron-doped diamond nanoparticles (BDDNPs) can be used as an electrode and a catalytic support material for platinum and ruthenium catalysts. The electrochemical properties of diamond nanoparticle electrodes, fabricated using the ink paste method, were investigated. As an initial step, we carried out chemical purification of commercially available undoped DNPs by refluxing in aqueous HNO3 as well as of BDDNPs which were doped through a collaborative work with the University of Missouri. The purified material was characterized by spectroscopic and surface science techniques. The reversibility of reactions such as ferricyanide/ferrocyanide (Fe(CN) 63-/Fe(CN)64-) and hexaamineruthenium (III) chloride complexes as redox probes were evaluated by cyclic voltammetry at the undoped DNPs and BDDNPs surface. These redox probes showed limited peak currents and presented linear relationships between current (i) and the square root of the potential scan rate (v1/2). However, compared to conventional electrodes, the peak currents were smaller. BDDNPs show an improvement in charge transfer currents when compared to undoped DNPs. Platinum and ruthenium nanoparticles were chemically deposited on undoped DNPs and BDDNPs through the use of the excess of a mild reducing agent such NaBH4. In order to improve the nanoparticle dispersion sodium dodecyl benzene sulfonate (SDBS), a surfactant agent, was used. Percentages of platinum and ruthenium metals were varied as well as the stoichiometric amount of the reducing agent to determine adequate parameters for optimum performance in methanol oxidation. Both before and after the reducing process the samples were characterized by scanning electron microscopy (SEM), energy dispersive analysis (EDX), infrared spectroscopy (IR), transmission electron microscopy (TEM), X-ray diffraction (XRD), prompt gamma neutron activation analysis (PGNAA), and X-ray photoelectron spectroscopy (XPS). In order to demonstrate the utility of the catalyst obtained, the samples were tested in an electrochemical cell using methanol as a probe solution. As was performed with the undoped DNPs and BDDNPs, the ink paste method was used to prepare the electrodes with Pt/DNP, Pt-Ru/DNP, Pt/BDDNP and Pt-Ru/BDDNP catalytic systems, to perform the electrochemical experiments. The Pt and Pt-Ru modified diamond electrodes were tested with cyclic voltammetry in 0.5 M H2SO4 as electrolyte support showing hydrogen adsorption/desorption at platinum surfaces. CO gas adsorption/desorption experiments were also performed to determine the active surface area of Pt when Ru is present. Methanol oxidation current peaks were obtained when the electrodes were tested in a 1.0 M methanol/0.5 M H2SO4 solution. The experimental results demonstrated that diamond nanoparticles are useful as an electrode material. A fuel cell is a device which transforms the chemical energy of a fuel directly into electrical energy. As previously mentioned, the aim of this research is to demonstrate the utility of undoped DNPs and BDDNPs as catalytic supports, which was performed by testing the catalytic systems obtained in a single fuel cell station at different temperatures to observe the cell performance.

La Torre Riveros, Lyda

233

PERMANENT DEACTIVATION OF THE BORON-OXYGEN RECOMBINATION CENTER IN SILICON SOLAR CELLS  

E-print Network

of solar cells made on oxygen-rich boron-doped silicon, such as B-doped Czochralski silicon (Cz-circuit voltage of solar cells made on low-resistivity boron-doped Cz-Si by simultaneously illuminating Interdigitated Single Evaporation Emitter Wrap-Through) solar cells [7] made on low- resistivity boron-doped Cz

234

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

235

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

236

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

237

Electronic structures and thermochemical properties of the small silicon-doped boron clusters B(n)Si (n=1-7) and their anions.  

PubMed

We perform a systematic investigation on small silicon-doped boron clusters B(n)Si (n=1-7) in both neutral and anionic states using density functional (DFT) and coupled-cluster (CCSD(T)) theories. The global minima of these B(n)Si(0/-) clusters are characterized together with their growth mechanisms. The planar structures are dominant for small B(n)Si clusters with n?5. The B(6)Si molecule represents a geometrical transition with a quasi-planar geometry, and the first 3D global minimum is found for the B(7)Si cluster. The small neutral B(n)Si clusters can be formed by substituting the single boron atom of B(n+1) by silicon. The Si atom prefers the external position of the skeleton and tends to form bonds with its two neighboring B atoms. The larger B(7)Si cluster is constructed by doping Si-atoms on the symmetry axis of the B(n) host, which leads to the bonding of the silicon to the ring boron atoms through a number of hyper-coordination. Calculations of the thermochemical properties of B(n)Si(0/-) clusters, such as binding energies (BE), heats of formation at 0 K (?H(f)(0)) and 298 K (?H(f)([298])), adiabatic (ADE) and vertical (VDE) detachment energies, and dissociation energies (D(e)), are performed using the high accuracy G4 and complete basis-set extrapolation (CCSD(T)/CBS) approaches. The differences of heats of formation (at 0 K) between the G4 and CBS approaches for the B(n)Si clusters vary in the range of 0.0-4.6 kcal mol(-1). The largest difference between two approaches for ADE values is 0.15 eV. Our theoretical predictions also indicate that the species B(2)Si, B(4)Si, B(3)Si(-) and B(7)Si(-) are systems with enhanced stability, exhibiting each a double (? and ?) aromaticity. B(5)Si(-) and B(6)Si are doubly antiaromatic (? and ?) with lower stability. PMID:21984168

Tai, Truong Ba; Kad?uba?ski, Pawe?; Roszak, Szczepan; Majumdar, Devashis; Leszczynski, Jerzy; Nguyen, Minh Tho

2011-11-18

238

The positive influence of boron-doped graphene for its supported Au clusters: enhancement of SERS and oxygen molecule adsorption.  

PubMed

The interactions between Au clusters and graphene sheets with and without doping have been studied systematically. It is found that B-doped graphene is a good support for Au clusters, not only because of the charge transfer from the graphene sheet to its supported Au clusters, but also due to its stronger interaction at the interface resulting from the doped B atom, which will facilitate more electrons being transferred to the upper surface of the Au cluster. This is good for surface-enhanced Raman scattering (SERS) and molecule oxygen adsorption, beneficial to the material preparation and apparatus design for high active SERS substrates and nano-catalysts. PMID:22955956

Kong, Xiangkai; Sun, Zhiyuan; Chen, Qianwang

2012-10-21

239

n-type diamond with high room temperature electrical conductivity by deuteration of boron doped diamond layers  

Microsoft Academic Search

The conversion of the conductivity of B-doped homoepitaxially grown diamond layers from p- to n-type upon deuteration and its reconversion to p-type following annealing is extensively studied. Several B doped samples have been converted to n-type when exposed to a deuterium plasma at approximately 500 °C. The n-type features are related to D uptake of the samples. The donors, thus

C. Saguy; R. Kalish; C. Cytermann; Z. Teukam; J. Chevallier; F. Jomard; A. Tromson-Carli; J. E. Butler; C. Baron; A. Deneuville

2004-01-01

240

Substrate and method for the formation of continuous magnesium diboride and doped magnesium diboride wire  

DOEpatents

A chemically doped boron coating is applied by chemical vapor deposition to a silicon carbide fiber and the coated fiber then is exposed to magnesium vapor to convert the doped boron to doped magnesium diboride and a resultant superconductor.

Suplinskas, Raymond J. (Haverhill, MA); Finnemore, Douglas (Ames, IA); Bud'ko, Serquei (Ames, IA); Canfield, Paul (Ames, IA)

2007-11-13

241

Non-covalent doping of graphitic carbon nitride with ultrathin graphene oxide and molybdenum disulfide nanosheets: an effective binary heterojunction photocatalyst under visible light irradiation.  

PubMed

A proof of concept integrating binary p-n heterojunctions into a semiconductor hybrid photocatalyst is demonstrated by non-covalent doping of graphite-like carbon nitride (g-C3N4) with ultrathin GO and MoS2 nanosheets using a facile sonochemical method. In this unique ternary hybrid, the layered MoS2 and GO nanosheets with a large surface area enhance light absorption to generate more photoelectrons. On account of the coupling between MoS2 and GO with g-C3N4, the ternary hybrid possesses binary p-n heterojunctions at the g-C3N4/MoS2 and g-C3N4/GO interfaces. The space charge layers created by the p-n heterojunctions not only enhance photogeneration, but also promote charge separation and transfer of electron-hole pairs. In addition, the ultrathin MoS2 and GO with high mobility act as electron mediators to facilitate separation of photogenerated electron-hole pairs at each p-n heterojunction. As a result, the ternary hybrid photocatalyst exhibits improved photoelectrochemical and photocatalytic activity under visible light irradiation compared to other reference materials. The results provide new insights into the large-scale production of semiconductor photocatalysts. PMID:24980624

Hu, S W; Yang, L W; Tian, Y; Wei, X L; Ding, J W; Zhong, J X; Chu, Paul K

2014-10-01

242

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

243

Exploring the electrocatalytic sites of carbon nanotubes for NADH detection: an edge plane pyrolytic graphite electrode study.  

PubMed

The electrocatalytic properties of multi-walled carbon nanotube modified electrodes toward the oxidation of NADH are critically evaluated. Carbon nanotube modified electrodes are examined and compared with boron-doped diamond and glassy carbon electrodes, and most importantly, edge plane and basal pyrolytic graphite electrodes. It is found that CNT modified electrodes are no more reactive than edge plane pyrolytic graphite electrodes with the comparison with edge plane and basal plane pyrolytic graphite electrodes allowing the electroactive sites for the electrochemical oxidation of NADH to be unambiguously determined as due to edge plane sites. Using these highly reactive edge plane sites, edge plane pyrolytic graphite electrodes are examined with cyclic voltammetry and amperometry for the electroanalytical determination of NADH. It is demonstrated that a detection limit of 5 microM is possible with cyclic voltammetry or 0.3 microM using amperometry suggesting that edge plane pyrolytic graphite electrodes can conveniently replace carbon nanotube modified glassy carbon electrodes for biosensing applications with the relative advantages of reactivity, cost and simplicity of preparation. We advocate the routine use of edge plane and basal plane pyrolytic graphite electrodes in studies utilising carbon nanotubes particularly if 'electrocatalytic' properties are claimed for the latter. PMID:16096667

Banks, Craig E; Compton, Richard G

2005-09-01

244

Hydrogen storage capacity of Ti-doped boron-nitride and B/Be -substituted carbon nanotubes  

NASA Astrophysics Data System (ADS)

We investigate the hydrogen absorption capacity of two tubular structures, namely, B/Be -substituted single-wall carbon nanotube (SWNT) and Ti covered single-wall boron nitride nanotube (SWBNT) using first-principles plane wave method. The interaction of H2 molecules with the outer surface of bare SWBNT, which is normally very weak, can be significantly enhanced upon functionalization by Ti atoms. Each Ti atom adsorbed on SWBNT can bind up to four H2 molecules with an average binding energy suitable for room temperature storage. While the substitution process of Be atom on SWNT is endothermic, the substituted Be strengthens the interaction between tube surface and H2 to hold one H2 molecule.

Durgun, E.; Jang, Y.-R.; Ciraci, S.

2007-08-01

245

The evolution of bonding and thermodynamic properties of boron-doped small carbon clusters: an ab initio study.  

PubMed

Theoretical studies on BC(n) (n=1-6) clusters are carried out using density functional theory, Møller-Plesset second-order perturbation theory (MP2), coupled-cluster calculations including up to triple excitations (CCSD(T)), and higher-level approaches. All possible isomers depending on the positions of the boron atom are generated and the lowest-energy isomers are determined for doublet and quartet electronic states. The three potential evolution paths of the clusters are determined as a function of their size. The energetic and electronic consequences for the increased size of structures differ significantly, which leads to representatives of the ground electronic state from different structural groups. The ab initio calculated thermal functions allow enhancements to the available atomization energies and improve the agreement between the calculated and experimental heat content. PMID:21488139

Saloni, Julia; Kad?uba?ski, Pawe?; Roszak, Szczepan; Majumdar, D; Hill, Glake; Leszczynski, Jerzy

2011-05-01

246

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

PubMed

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

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

2011-01-01

247

Study of degradation intermediates formed during electrochemical oxidation of pesticide residue 2,6-dichlorobenzamide (BAM) at boron doped diamond (BDD) and platinum-iridium anodes.  

PubMed

Electrochemical oxidation is a promising technique for degradation of otherwise recalcitrant organic micropollutants in waters. In this study, the applicability of electrochemical oxidation was investigated concerning the degradation of the groundwater pollutant 2,6-dichlorobenzamide (BAM) through the electrochemical oxygen transfer process with two anode materials: Ti/Pt90-Ir10 and boron doped diamond (Si/BDD). Besides the efficiency of the degradation of the main pollutant, it is also of outmost importance to control the formation and fate of stable degradation intermediates. These were investigated quantitatively with HPLC-MS and TOC measurements and qualitatively with a combined HPLC-UV and HPLC-MS protocol. 2,6-Dichlorobenzamide was found to be degraded most efficiently by the BDD cell, which also resulted in significantly lower amounts of intermediates formed during the process. The anodic degradation pathway was found to occur via substitution of hydroxyl groups until ring cleavage leading to carboxylic acids. For the BDD cell, there was a parallel cathodic degradation pathway that occurred via dechlorination. The combination of TOC with the combined HPLC-UV/MS was found to be a powerful method for determining the amount and nature of degradation intermediates. PMID:24873711

Madsen, Henrik Tækker; Søgaard, Erik Gydesen; Muff, Jens

2014-08-01

248

Direct electrochemistry of Shewanella loihica PV-4 on gold nanoparticles-modified boron-doped diamond electrodes fabricated by layer-by-layer technique.  

PubMed

Microbial Fuel Cells (MFCs) are robust devices capable of taping biological energy, converting pollutants into electricity through renewable biomass. The fabrication of nanostructured electrodes with good bio- and electrochemical activity, play a profound role in promoting power generation of MFCs. Au nanoparticles (AuNPs)-modified Boron-Doped Diamond (BDD) electrodes are fabricated by layer-by-layer (LBL) self-assembly technique and used for the direct electrochemistry of Shewanella loihica PV-4 in an electrochemical cell. Experimental results show that the peak current densities generated on the Au/PAH multilayer-modified BDD electrodes increased from 1.25 to 2.93 microA/cm(-2) as the layer increased from 0 to 6. Different cell morphologies of S. loihica PV-4 were also observed on the electrodes and the highest density of cells was attached on the (Au/PAH)6/BDD electrode with well-formed three-dimensional nanostructure. The electrochemistry of S. loihica PV-4 was enhanced on the (Au/PAH)4/BDD electrode due to the appropriate amount of AuNPsand thickness of PAH layer. PMID:22852323

Wu, Wenguo; Xie, Ronggang; Bai, Linling; Tang, Zuming; Gu, Zhongze

2012-05-01

249

Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells  

NASA Astrophysics Data System (ADS)

Solar cells fabricated from boron-doped p-type Czochralski silicon suffer from light-induced degradation that can lower the conversion efficiency by up to 10% relative. When solar cells are exposed to temperatures between 100 °C and 200 °C under illumination, regeneration, in which the minority carrier lifetime is gradually recovered, occurs after the initial light-induced degradation. We studied the light-induced degradation and regeneration process using carrier injection within a design chamber and observed open-circuit voltage trends at various sample temperatures. We proposed a cyclic reaction kinetics model to more precisely analyze the degradation and recovery phenomenon. Our model incorporated the reaction paths that were not counted in the original model between the three states (annealed, degradation, and regeneration). We calculated a rate constant for each reaction path based on the proposed model, extracted an activation energy for each reaction using these rate constants at various temperatures, and calculated activation energies of redegradation and the stabilization reaction.

Kim, Soo Min; Chun, Seungju; Bae, Suhyun; Park, Seungeun; Kang, Min Gu; Song, Hee-eun; Kang, Yoonmook; Lee, Hae-seok; Kim, Donghwan

2014-08-01

250

Propham mineralization in aqueous medium by anodic oxidation using boron-doped diamond anode: influence of experimental parameters on degradation kinetics and mineralization efficiency.  

PubMed

This study aims the removal of a carbamate herbicide, propham, from aqueous solution by direct electrochemical advanced oxidation process using a boron-doped diamond (BDD) anode. This electrode produces large quantities of hydroxyl radicals from oxidation of water, which leads to the oxidative degradation of propham up to its total mineralization. Effect of operational parameters such as current, temperature, pH and supporting electrolyte on the degradation and mineralization rate was studied. The applied current and temperature exert a prominent effect on the total organic carbon (TOC) removal rate of the solutions. The mineralization of propham can be performed at any pH value between 3 and 11 without any loss in oxidation efficiency. The propham decay and its overall mineralization reaction follows a pseudo-first-order kinetics. The apparent rate constant value of propham oxidation was determined as 4.8 x 10(-4)s(-1) at 100 mA and 35 degrees C in the presence of 50mM Na(2)SO(4) in acidic media (pH: 3). A general mineralization sequence was proposed considering the identified oxidation intermediates. PMID:18377944

Ozcan, Ali; Sahin, Yücel; Koparal, A Sava?; Oturan, Mehmet A

2008-06-01

251

Degradation of Acid Orange 7 by electrochemically generated (*)OH radicals in acidic aqueous medium using a boron-doped diamond or platinum anode: a mechanistic study.  

PubMed

A comparative study of the degradation of Acid Orange 7 (AO 7) aqueous solutions in acidic medium of pH 3.0 by electro-Fenton process using Pt or boron-doped diamond (BDD) anode was reported. The oxidative degradation of AO 7 by electrochemically generated hydroxyl radicals follows a pseudo-first order kinetic with a similar rate constant with BDD or Pt anode. The absolute rate constant of the AO 7 hydroxylation reaction was determined as (1.10+/-0.04)x10(10)M(-1)s(-1) by using the competition kinetic method. The comparative study of TOC measurements during electro-Fenton treatment showed a higher mineralization rate with BDD than Pt anode at the first hours of electrolysis because of the higher oxidizing power of this anode. The electro-Fenton degradation of AO 7 was followed by monitoring the formation and evolution of aromatic intermediates which are oxidized to aliphatic carboxylic acids before mineralization (transformation to CO(2) and inorganic ions, i.e. sulphate, nitrate and ammonium). The follow-up of the solution toxicity evolution shows the formation of intermediates more toxic than AO 7 and the connection between toxicity and aromaticity. A mineralization reaction pathway of AO 7 by electro-Fenton degradation involving all the intermediates identified was proposed. PMID:18760822

Hammami, Samiha; Bellakhal, Nizar; Oturan, Nihal; Oturan, Mehmet A; Dachraoui, Mohamed

2008-10-01

252

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

PubMed Central

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

McClintock, Carlee S; Hettich, Robert L.

2012-01-01

253

Degradation of tetracycline at a boron-doped diamond anode: influence of initial pH, applied current intensity and electrolyte.  

PubMed

The anodic oxidation of tetracycline was performed in an up-flow reactor, operating in batch mode with recirculation, using as anode a boron-doped diamond electrode. The influence on the degradation rate of solution initial pH (2 to 12), applied current intensity (25 to 300 A m(-2)) and type of electrolyte (sodium sulphate or sodium chloride) were investigated. For the assays run at equal current density, with sodium sulphate as electrolyte, the solution's initial pH of 2 presented the highest absorbance and chemical oxygen demand removals. Regarding the influence of current density, for equal charge passed, the organic load removal rate decreased with the increase in applied current. When sodium sulphate was used as an electrolyte, high-performance liquid chromatography (HPLC) results have shown an almost complete removal of tetracycline after a 2-h assay. HPLC results have also shown the presence of oxamic acid as one of the intermediates of tetracycline anodic oxidation. The complete removal of tetracycline was much faster in the presence of chloride ions that promoted the complete degradation of this antibiotic in 30 min. However, in the presence of chloride ions, the tetracycline mineralization is slower, as observed by the lower organic carbon removal rate when compared to that of the tetracycline degradation in the presence of sulphate. PMID:24664638

Brinzila, C I; Monteiro, N; Pacheco, M J; Ciríaco, L; Siminiceanu, I; Lopes, A

2014-07-01

254

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 60min 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

255

Electro-fenton and photoelectro-fenton degradation of sulfanilic acid using a boron-doped diamond anode and an air diffusion cathode.  

PubMed

The mineralization of sulfanilic acid has been studied by electro-Fenton (EF) and photoelectro-Fenton (PEF) reaction with UVA light using an undivided electrochemical cell with a boron-doped diamond (BDD) anode and an air diffusion cathode able to generate H(2)O(2). Organics were then oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between generated H(2)O(2) and added Fe(2+). The UVA irradiation in PEF enhanced the production of hydroxyl radicals in the bulk, accelerating the removal of organics and photodecomposed intermediates like Fe(III)-carboxylate complexes. Partial decontamination of 1.39 mM sulfanilic acid solutions was achieved by EF until 100 mA cm(-2) at optimum conditions of 0.4 mM Fe(2+) and pH 3.0. The increase in current density and substrate content led to an almost total mineralization. In contrast, the PEF process was more powerful, yielding almost complete mineralization in less electrolysis time under comparable conditions. The kinetics for sulfanilic acid decay always followed a pseudo-first-order reaction. Hydroquinone and p-benzoquinone were detected as aromatic intermediates, whereas acetic, maleic, formic, oxalic, and oxamic acids were identified as generated carboxylic acids. NH(4)(+) ion was preferentially released in both treatments, along with NO(3)(-) ion in smaller proportion. PMID:22404230

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

2012-04-01

256

The p-to-n-type conversion of boron-doped diamond layers by deuteration: New findings  

Microsoft Academic Search

The p-to-n-type conversion of particular B-doped homoepitaxially grown diamond layers upon deuterium plasma treatment was discovered three years ago. However, many questions regarding the reproducibility of the effect for samples of different origins remain unanswered up to now, in particular the role of the electrical contacts and the possibility of a surface inversion layer being responsible for the n-type conductivity,

C. Saguy; R. Kalish; J. Chevallier; F. Jomard; C. Cytermann; B. Philosoph; T. Kociniewski; D. Ballutaud; C. Baron; A. Deneuville

2007-01-01

257

20% Efficient Passivated Large-Area Metal Wrap Through Solar Cells on Boron-Doped Cz Silicon  

Microsoft Academic Search

We present metal wrap through passivated emitter and rear solar cells (MWT-PERC) on monocrystalline p-type silicon featuring laser-doped selective emitter structures in com- bination with either screen-printed (SP) or more advanced dis- pensed front side contacts. Thermally grown silicon oxide layers serve as emitter and rear surface passivation. Laser-fired contacts connect the SP aluminum rear contact to the silicon base.

E. Lohmuller; B. Thaidigsmann; M. Pospischil; U. Jager; S. Mack; J. Specht; J. Nekarda; M. Retzlaff; A. Krieg; F. Clement; A. Wolf; D. Biro; R. Preu

2011-01-01

258

Boron nanotubes.  

PubMed

A survey of novel classes of nanotubular materials based on boron is presented. Pure boron nanotubes are a consequence of a general Aufbau principle for boron clusters and solid boron phases, which postulates various novel boron materials besides the well-known bulk phases of boron based on boron icosahedra. Furthermore, several numerical studies suggest the existence of a large family of compound nanotubular materials derived from crystalline AlB2. We compare these novel boron-based nanotubular materials to standard nanotubular systems built from carbon, and point out a number of remarkable structural and electronic properties that make boron-based nanotubular materials an ideal component for composite nanodevices and extended nanotubular networks. PMID:16208735

Quandt, Alexander; Boustani, Ihsan

2005-10-14

259

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

260

Micro Extrinsic Fiber-Optic Fabry-Perot Interferometric Sensor Based on Erbium- and Boron-Doped Fibers  

NASA Astrophysics Data System (ADS)

Micro extrinsic Fabry-Perot interferometers (MEFPIs), with cavity lengths of up to ~ 9 ?m and maximum fringe contrast of ~ 19 dB, are fabricated by chemically etching Er- and B-doped optical fibers and then splicing the etched fiber to a single-mode fiber, for the first time to the best of our knowledge. The strain and temperature responses of the MEFPI sensors are investigated experimentally. Good linearity and high sensitivity are achieved. Such a type of MEFPI sensor is cost-effective and suitable for mass production, indicating its great potential for a wide range of applications.

Rao, Yun-Jiang; Xu, Bing; Ran, Zeng-Ling; Gong, Yuan

2010-02-01

261

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

262

First-Principles Investigation on Boron Nanostructures  

NASA Astrophysics Data System (ADS)

First-principles calculations based on density functional theory are employed to study and predict the properties of boron and Mg boride nanostructures. For boron nanostructures, two-dimensional boron sheets are found to be metallic and made of mixtures of triangles and hexagons which benefit from the balance of two-center bonding and three-center bonding. This unusual bonding in boron sheets results in a self-doping picture where adding atoms to the hexagon centers does not change the number of bonding states but merely increases the electron count. Boron sheets can be either flat or buckled depending on the ratio between hexagons and triangles. Formed by stacking two identical boron sheets, double-layered boron sheets can form interlayer bonds, and the most stable one is semiconducting. Built from single-layered boron sheets, single-walled boron nanotubes have smaller curvature energies than carbon nanotubes and undergo a metal-to-semiconductor transition once the diameter is smaller than ˜20 A. Optimal double-walled boron nanotubes with inter-walled bonds formed are metallic and always more stable than single-walled ones. For Mg boride nanostructures, certain Mg boride sheets prefer to curve themselves into nanotubes, which is explained via Mg-Mg interactions governed by the charge state of Mg. In addition, optimal Mg boride sheet structures are explored with a genetic algorithm. Phase diagrams for Mg boride sheet structures are constructed and stable phases under boron-rich environments are identified. Curvature effects on the phase diagram of Mg boride nanotubes are also discussed. As a natural extension to boron sheets, layered boron crystals based on boron sheets are then presented and are shown to be stable under high pressure. Finally, this thesis ends with an investigation of hydrogen-storage properties of pristine and metal doped boron nanostructures.

Tang, Hui

263

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

264

Electrochemical incineration of omeprazole in neutral aqueous medium using a platinum or boron-doped diamond anode: degradation kinetics and oxidation products.  

PubMed

The electrochemical incineration of omeprazole, a widely prescribed gastrointestinal drug which is detected in natural waters, has been studied in a phosphate buffer of pH 7.0 by anodic oxidation with electrogenerated H(2)O(2) (AO-H(2)O(2)) operating at constant current density (j). The experiments were carried out in a cell equipped with either a Pt or a boron-doped diamond (BDD) anode and an air-diffusion cathode to continuously produce H(2)O(2). In these systems, organics are mainly oxidized by hydroxyl radicals formed at the Pt or BDD surface from water oxidation. A partial total organic carbon (TOC) abatement close to 78% for omeprazole was achieved by AO-H(2)O(2) with a BDD anode after consumption of 18 Ah L(-1) at 100 mA cm(-2), whereas the alternative use of Pt did not allow mineralizing the drug. However, the drug was totally removed using both anodes, although it decayed more rapidly using BDD. In this latter system, increasing j accelerated the degradation process, but lowering the mineralization current efficiency. Greater drug content also enhanced the degradation rate with higher mineralization degree and current efficiency. The kinetics for omeprazole decay always followed a pseudo-first-order reaction and its rate constant increased with increasing j and with decreasing its concentration. Seven heteroaromatic intermediates and four hydroxylated derivatives were detected by LC-MS, while nine short-linear carboxylic acids were identified and quantified by ion-exclusion HPLC. These acids were largely accumulated using Pt and rapidly removed using BDD, thus explaining the partial mineralization of omeprazole achieved by AO-H(2)O(2) with the latter anode. The release of inorganic ions such as NO(3)(-), NH(4)(+) and SO(4)(2-) was followed by ionic chromatography. A plausible reaction sequence for omeprazole mineralization involving all intermediates detected is proposed. PMID:23351432

Cavalcanti, Eliane Bezerra; Garcia-Segura, Sergi; Centellas, Francesc; Brillas, Enric

2013-04-01

265

The effect of boron implant energy on transient enhanced diffusion J. Liu and V. Krishnamoorthy  

E-print Network

sources of TED for boron implants B-I: short time component that decays rapidly consistent with nonvisibleThe effect of boron implant energy on transient enhanced diffusion in silicon J. Liu and V after low energy boron implantation and annealing was investigated using boron-doping superlattices DSLs

Florida, University of

266

The effect of boron implant energy on transient enhanced diffusion J. Liu and V. Krishnamoorthy  

E-print Network

sources of TED for boron implants B-I : short time component that decays rapidly consistentThe effect of boron implant energy on transient enhanced diffusion in silicon J. Liu and V after low energy boron implantation and annealing was investigated using boron-doping superlattices DSLs

Florida, University of

267

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

268

Generation and annihilation of boron-oxygen-related recombination centers in compensated p- and n-type silicon  

Microsoft Academic Search

The impact of boron-oxygen-related recombination centers as well as their defect kinetics have been intensely studied in boron-doped oxygen-rich p-type crystalline silicon. Experimental data for the defect in simultaneously boron- and phosphorus-doped compensated p- and n-type silicon, however, is sparse. In this study, we present time-resolved carrier lifetime measurements on Czochralski-grown silicon (Cz-Si) doped with both boron and phosphorus under

Bianca Lim; Fiacre Rougieux; Daniel MacDonald; Karsten Bothe; Jan Schmidt

2010-01-01

269

Global transport of light elements boron and carbon in the full-W ASDEX Upgrade  

NASA Astrophysics Data System (ADS)

Transport of carbon and boron has been investigated in the full-W ASDEX Upgrade after experimental campaigns with (2008) and without (2007) boronizations. For this purpose, poloidal deposition profiles of the two elements on tungsten and graphite regions of lower-divertor tiles have been determined. Carbon is mainly deposited in the inner divertor - 80-90% of the determined 12C and 13C inventories on W - while boron shows a much more symmetric deposition profile. In the unboronized machine, the boron inventories are a factor of 10 smaller than in the boronized case and result from residual boron atoms left in the torus prior to the 2007 campaign. Both carbon and boron are deposited more efficiently and/or show less erosion on graphite than on tungsten, particularly in the outer divertor. For 13C, the difference is 10-100 in favor of graphite. This is most probably caused by a higher re-erosion from tungsten surfaces.

ASDEX Upgrade Team; Hakola, A.; Likonen, J.; Koivuranta, S.; Krieger, K.; Mayer, M.; Neu, R.; Rohde, V.; Sugiyama, K.

2011-08-01

270

Mesophase Graphite.  

National Technical Information Service (NTIS)

This report contains results and discussions related to the investigation of the materials and process parameters associated with the development of the mesophase- graphite process. Three starting materials are investigated as precursors for preparing mes...

M. P. Whittaker, H. P. Gilliam

1973-01-01

271

New approach to obtain boron selective emitters  

SciTech Connect

Selective emitters, used in high efficiency solar cells, need a series of oxidations and photolithographic steps that render the process more expensive. In this paper, a new way to make selective emitters using boron is presented. The main feature of this approach is to save oxide growths and photolithographic processes and it is based on the property of boron doped silicon surfaces to be resistant to anisotropic etchings like the one performed during the texturization. Using this characteristic of boron emitter surfaces, the authors can obtain a highly doped emitter under metal grid and simultaneously a shield to avoid texture on these surfaces. First cells were processed and short wavelength response of p{sup +}nn{sup +} solar cells was enhanced by using lightly doped boron emitters in the uncovered area.

Moehlecke, A.; Luque, A. [ETSI Telecomunicacion, Madrid (Spain). Inst. de Energia Solar

1994-12-31

272

Boron reclamation  

SciTech Connect

A process to recover high purity /sup 10/B enriched crystalline boron powder from a polymeric matrix was developed on a laboratory basis and ultimately scaled up to production capacity. The process is based on controlled pyrolysis of boron-filled scrap followed by an acid leach and dry sieving operation to return the powder to the required purity and particle size specifications. Typically, the recovery rate of the crystalline powder is in excess of 98.5 percent, and some of the remaining boron is recovered in the form of boric acid. The minimum purity requirement of the recovered product is 98.6 percent total boron.

Smith, R.M.

1980-07-01

273

Analogies between boron and carbon.  

PubMed

The structural connections between the compounds of boron and carbon are extended using the mno rule beyond the borane-carbocation continuum, the lithium boride-polycarbyne analogy, and the magnesium boride (MgB(2))-graphite equivalence to beta-rhombohedral boron and fullerenes. The structural similarity of the pentagonal pyramidal C(6)H(6)(2+) and MgB(4) is established. An interesting electronic structural relationship between the B(84) fragment of the beta-rhombohedral boron and the fulleride anion, C(60)(12-), is derived by replacing the 12 pentagonal pyramidal B(6)(4-) units by isoelectronic C(5)(-) units and removing the central B(12) from the electron-deficient B(84) unit. This relationship is well supported by the experimental realization of C(60)M(12) (M = Li, K) and C(48)N(12). PMID:14622028

Jemmis, Eluvathingal D; Jayasree, Elambalassery G

2003-11-01

274

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

275

Boron Clusters  

NSDL National Science Digital Library

The May featured molecules are discussed in the Viewpoints article "Boron Clusters Come of Age". The review paper by Russell N. Grimes on boron clusters reminds us both of the past impact that these interesting structures have had on the development of our understanding of cluster chemistry and on the future development of what one might refer to as "post-fullerene" clusters. The wide range of structures found in this paper admirably illustrate the structural flexibility arising from clusters of a variety of symmetries and degrees of boron replacement with carbon and other atoms.

276

Boron mullite: Formation and basic characterization  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? Decrease of B-mullite formation temperature with increasing boron content. ? Decrease of lattice parameters b and c with increasing boron content. ? Significant reduction of thermal expansion (?15%) due to incorporation of boron. ? Decomposition of B-mullite at 1400 °C, long-term stability at 800 °C. -- Abstract: A series of boron doped mullites (B-mullite) was prepared from single-phase gels with initial compositions based on a 1:1 isomorphous substitution of Si by B, starting from a 3:2 mullite composition (Al{sub 4.5}Si{sub 1.5}O{sub 9.75}). A high amount of boron (>10 mol.%) can be incorporated into the crystal structure of mullite where it most likely replaces Si. In situ phase formation of B-mullites was studied with high temperature X-ray diffraction and thermal analysis. A decrease of the formation temperature for B-mullite with increasing boron content was observed. With increasing boron content lattice parameters b and c significantly decrease, while no systematic evolution of a is observed. Long annealing at 1400 °C results in decomposition of B-mullite to boron free mullite and ?-alumina. At 800 °C B-mullite appears to be stable over a period of at least 12 days. The mean thermal expansion coefficient was reduced by 15% upon incorporation of boron which makes the material technologically interesting.

Lührs, Hanna, E-mail: hanna.luehrs@uni-bremen.de [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany)] [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany); Fischer, Reinhard X. [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany)] [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany); Schneider, Hartmut [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany) [Universität Bremen, FB 5 Geowissenschaften, Klagenfurter Straße, D-28359 Bremen (Germany); Universität Köln, Institut für Kristallographie, Greinstraße 6, D-50939 Kölm (Germany)

2012-12-15

277

Development and fabrication of a graphite polyimide box beam  

NASA Technical Reports Server (NTRS)

The state-of-the-art of graphite/polyimide structures was evaluated and key design and fabrication issues to be considered in future hardware programs are defined. The fabrication and testing at 500 F of a graphite/polyimide center wing box beam using OV-10A aircraft criteria was accomplished. The baseline design of this box was developed in a series of studies of other advanced composite materials: glass/epoxy, boron/epoxy, and boron/polyimide. The use of this basic design permits ready comparison of the performance of graphite/polyimide with these materials. Modifications to the baseline composite design were made only in those areas effected by the change of materials. Processing studies of graphite fiber polyimide resins systems resulted in the selection of a Modmor II/Gemon L material.

Nadler, M. A.; Darms, F. J.

1972-01-01

278

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

279

Bridged graphite oxide materials  

NASA Technical Reports Server (NTRS)

Bridged graphite oxide material comprising graphite sheets bridged by at least one diamine bridging group. The bridged graphite oxide material may be incorporated in polymer composites or used in adsorption media.

Herrera-Alonso, Margarita (Inventor); McAllister, Michael J. (Inventor); Aksay, Ilhan A. (Inventor); Prud'homme, Robert K. (Inventor)

2010-01-01

280

Spectrographic analysis of boron nitride for trace impurities.  

PubMed

A d.c. arc emission spectrographic method has been developed for the determination of nine trace impurities in boron nitride. The charge for exciting the sample contains equal quantities of boron nitride and graphite (containing 2% NaF as carrier and 1% La(2)O(3) as an internal standard). The method is useful in the determination of impurities in the range 2-1000 ppm, with a mean relative standard deviation of 13%. PMID:18961750

Vengsarkar, B R; Machado, I J; Malhotra, S K

281

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

282

Deposition and Tribology of Carbon and Boron Nitride Super Lattice Solid Lubricant Films  

Microsoft Academic Search

Carbon and boron nitride super lattice films were deposited by RF sputtering using two semicircular targets. Super lattice (C\\/BN)n films were deposited by control of the opposing time of substrate to each graphite and boron nitride semicircular targets respectively. Micro Vickers hardness, nanoindentation hardness and nanoscratch properties of these films were evaluated. Both micro Vickers and nanoindentation hardness of 4nm

Shojiro Miyake; Yukio Sekine; Shuichi Watanabe

2004-01-01

283

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

284

On the nature of boron-carbon-nitrogen compounds synthesised from organic precursors  

Microsoft Academic Search

Three compounds were prepared through pyrolysis of organic precursors, namely pyridine-borane, piperazine-borane, poly(acrylonitrile)-BCl3, following the routes proposed in the literature for the synthesis of single-phase boron carbonitrides of various compositions. X-ray diffraction and MAS NMR studies performed on the powders obtained suggest that the resulting compounds are mixtures of amorphous boron and turbostratically distorted hexagonal boron nitride and graphite rather

Yuri G. Andreev; Torsten Lundström; Robin K. Harris; Se-Woung Oh; David C. Apperley; Derek P. Thompson

1995-01-01

285

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

286

Boron nitride substrates for high-quality graphene electronics.  

PubMed

Graphene devices on standard SiO(2) 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 SiO(2). 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. PMID:20729834

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

287

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

288

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

289

Optical properties and electrical resistivity of boron-doped ZnO thin films grown by sol-gel dip-coating method  

NASA Astrophysics Data System (ADS)

Sol-gel dip-coating was used to grow ZnO thin films doped with various concentrations of B ranging from 0 to 2.5 at.% on quartz substrates. The effects of B doping on the absorption coefficient (?), optical band gap (Eg), Urbach energy (EU), refractive index (n), refractive index at infinite wavelength (n?), extinction coefficient (k), single-oscillator energy (Eo), dispersion energy (Ed), average oscillator strength (So), average oscillator wavelength (?o), moments M-1 and M-3, dielectric constant (?), optical conductivity (?), and electrical resistivity (?) of the BZO thin films were investigated. The transmittance spectra of the ZnO and BZO thin films show that the transmittance of the BZO thin films was significantly higher than that of the ZnO thin films in the visible region of the spectrum and that the absorption edge of the BZO thin films was blue-shifted. The BZO thin films exhibited higher Eg, EU, and Eo and lower Ed, ?o, M-1 and M-3 moments, So, n?, and ? than the ZnO thin films.

Kim, Soaram; Yoon, Hyunsik; Kim, Do Yeob; Kim, Sung-O.; Leem, Jae-Young

2013-10-01

290

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

291

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

292

Development and validation of a method to determine the boron isotopic composition of crop plants.  

PubMed

We present a comprehensive chemical and mass spectrometric method to determine boron isotopic compositions of plant tissue. The method including dry ashing, a three-step ion chromatographic boron-matrix separation, and (11)B/(10)B isotope ratio determinations using the Cs(2)BO(2)(+) graphite technique has been validated using certified reference and quality control materials. The developed method is capable to determine ?(11)B values in plant tissue down to boron concentrations of 1 mg/kg with an expanded uncertainty of ?1.7‰ (k = 2). The determined ?(11)B values reveal an enormous isotopic range of boron in plant tissues covering three-quarters of the natural terrestrial occurring variation in the boron isotopic composition. As the local environment and anthropogenic activity mainly control the boron intake of plants, the boron isotopic composition of plants can be used for food provenance studies. PMID:21401079

Rosner, Martin; Pritzkow, Wolfgang; Vogl, Jochen; Voerkelius, Susanne

2011-04-01

293

Boron Nitride Nanotubes  

NASA Technical Reports Server (NTRS)

Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

Smith, Michael W. (Inventor); Jordan, Kevin (Inventor); Park, Cheol (Inventor)

2012-01-01

294

Exfoliated soluble graphite  

Microsoft Academic Search

Reduction of graphite by lithium in liquid ammonia yields graphite salts that can be reacted with dodecyl iodide to yield soluble dodecylated graphite. The height of the soluble graphite nanoplatelets was determined by scanning tunneling microscopy (STM) to be 3.5nm, corresponding to approximately 10 layers of graphene. Solubility in organic solvents was determined to be 20mg\\/L in chloroform and 70mg\\/L

Jayanta Chattopadhyay; Arnab Mukherjee; Soma Chakraborty; JungHo Kang; Peter J. Loos; Kevin F. Kelly; Howard K. Schmidt; W. E. Billups

2009-01-01

295

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

296

Electronic structure and thermochemical properties of small neutral and cationic lithium clusters and boron-doped lithium clusters: Li(n)(0/+) and Li(n)B(0/+) (n = 1-8).  

PubMed

The stability, electronic structure, and thermochemical properties of the pure Li(n) and boron-doped Li(n)B (n = 1-8) clusters in both neutral and cationic states are studied using electronic structure methods. The global equilibrium structures are established, and their heats of formation are evaluated using the G3B3 and CCSD(T)/CBS methods based on the density functional theory geometries. Theoretical adiabatic ionization energies (IE(a)) for the Li(n) clusters are in good agreement with experiment: Li(2) (G3B3, 5.21 eV; CCSD(T), 5.14 eV; expt, 5.1127 ± 0.0003 eV), Li(3) (4.16, 4.11, 4.08 ± 0.10), Li(4) (4.76, 4.68, 4.70 ± 0.05), Li(5) (4.11, 4.06, 4.02 ± 0.10), Li(6) (4.46, 4.32, 4.20 ± 0.10), Li(7) (4.07, 3.99, 3.94 ± 0.10), and Li(8) (4.49, 4.31, 4.16 ± 0.10). The Li(4) experimental IE(a) has been revised on the basis of the Franck-Condon simulations. Species Li(5)B, Li(6)B(+), Li(7)B, and Li(8)B(+) exhibit high stability as compared to their neighbors, which can be understood by considering the magic numbers of the phenomenological shell model (PSM). PMID:21671620

Tai, Truong Ba; Nhat, Pham Vu; Nguyen, Minh Tho; Li, Shenggang; Dixon, David A

2011-07-01

297

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.

298

Enhanced optical and electrical properties of boron-doped zinc-oxide thin films prepared by using the sol-gel dip-coating method  

NASA Astrophysics Data System (ADS)

Undoped ZnO and B-dopoed ZnO (BZO) thin films with 0 to 2.5 at.% B were prepared by using sol-gel synthesis. Their optical and electrical properties and surface morphology were investigated using scanning electron microscopy, photoluminescence (PL), and van der Pauw Hall-effect measurements. All of the thin films were deposited appropriately onto quartz substrates; they exhibited a fibrous root morphology, with structures that changed in size with increasing B concentration. The PL spectra showed near-band-edge (NBE) emissions and deep-level emissions (DLE). The NBE emission and the DLE for the BZO thin films were more blue-shifted than those for the undoped ZnO thin film, and the blue shift increased the efficiency of the NBE emission of the BZO thin films. The Hall-effect data suggested that B doping also improved the electrical properties, such as the carrier concentration, Hall mobility, and resistivity, of the thin films. The resistivity and the Hall mobility decreased with increasing B concentration and were inversely proportional to the carrier concentration.

Lee, Sang-heon; Kim, MinSu; Jung, YuJin; Jung, Jae Hak; Kim, Soaram; Leem, Jae-Young; Kim, Howoon

2013-11-01

299

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

300

New quasi-planar surfaces of bare boron  

NASA Astrophysics Data System (ADS)

New very stable quasi-planar clusters of bare boron are found by systematic ab initio density functional and quantum chemical methods. They are composed of dove-tailed hexagonal pyramids different from the classical forms of ?- or ?-rhombohedral boron crystallines. The quasi-planar structures are considered to be fragments of quasi-planar surfaces, which can easily be obtained and constructed from a basic unit of hexagonal pyramids. A new investigation on double layers of boron quasi-planar surfaces shows an increase in the stability of the system which can be related to the overlap of ?-orbitals between the layers. Therefore, we predict the existence of a series of parallel boron layers, as in graphite. These proposed surfaces can serve as lightweight protective armor, as a neutron-absorber material in fission reactions, or as very high temperature semiconductors.

Boustani, Ihsan

1997-01-01

301

Superconductivity in doped cubic silicon  

NASA Astrophysics Data System (ADS)

Although the local resistivity of semiconducting silicon in its standard crystalline form can be changed by many orders of magnitude by doping with elements, superconductivity has so far never been achieved. Hybrid devices combining silicon's semiconducting properties and superconductivity have therefore remained largely underdeveloped. Here we report that superconductivity can be induced when boron is locally introduced into silicon at concentrations above its equilibrium solubility. For sufficiently high boron doping (typically 100p.p.m.) silicon becomes metallic. We find that at a higher boron concentration of several per cent, achieved by gas immersion laser doping, silicon becomes superconducting. Electrical resistivity and magnetic susceptibility measurements show that boron-doped silicon (Si:B) made in this way is a superconductor below a transition temperature Tc~0.35K, with a critical field of about 0.4T. Ab initio calculations, corroborated by Raman measurements, strongly suggest that doping is substitutional. The calculated electron-phonon coupling strength is found to be consistent with a conventional phonon-mediated coupling mechanism. Our findings will facilitate the fabrication of new silicon-based superconducting nanostructures and mesoscopic devices with high-quality interfaces.

Bustarret, E.; Marcenat, C.; Achatz, P.; Ka?mar?ik, J.; Lévy, F.; Huxley, A.; Ortéga, L.; Bourgeois, E.; Blase, X.; Débarre, D.; Boulmer, J.

2006-11-01

302

Surface protection of graphite fabric/PMR-15 composites subjected to thermal oxidation  

NASA Technical Reports Server (NTRS)

Graphite fabric/PMR-15 laminates develop matrix cracks during long-term exposure in air at temperatures in the range of 500 to 600 F. This study was performed to demonstrate the effectiveness of incorporating graphite mat surface plies as a means of reducing the developing of matrix cracks. Celion 3000 graphite fabric/PMR-15 laminates were fabricated with graphite or graphite mat/325-mesh boron powder surface plies. Laminates without mat surface plies were also fabricated for control purposes. Composite flexural strength, flexural modulus, and interlaminar shear strength were determined at 288 C before and after long-term exposure (up to 1500 hr) in air at 316 C. The results of this study showed that the incorporation of graphite mat surface plies reduces matrix cracking and improves the elevated temperature mechanical property retention characteristics of the composites.

Hanson, M. P.; Serafini, T. T.

1985-01-01

303

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

304

Boron Fixation by Illites  

Microsoft Academic Search

The mechanism of boron uptake by clays, especially illitic clays, and the factors which control such uptake have long been debated issues. In an attempt to answer some of the questions of the controversy, three illites were treated in solutions containing boron. In the study, boron concen- tration, salinity, temperature, and time were varied independently over rather wide ranges. For

Elton L. Couch; RALPH E. GRIM

1968-01-01

305

Tuning electronic eigenvalues of benzene via doping  

NASA Astrophysics Data System (ADS)

Using variable atomic numbers within molecular grand-canonical ensemble theory, the highest occupied Kohn-Sham eigenvalue of isoelectronic benzene derivatives is tuned. The performed transmutational changes correspond to the iterative doping with boron and nitrogen. The molecular Fukui function proves to be a reliable index in order to predict the changes in the highest occupied molecular orbital eigenvalue due to doping.

Marcon, Valentina; von Lilienfeld, O. Anatole; Andrienko, Denis

2007-08-01

306

The structure and bonding of solid solutions of transition and p-elements in ?-rhombohedral boron  

NASA Astrophysics Data System (ADS)

Recent research on the structure and bonding of solid solutions in ?-rhombohedral boron is reviewed. The structure of ?-rhombohedral boron consists mainly of boron icosahedra, which form an open although rigid three-dimensional network. The interstices between the icosahedra accommodate atoms of the transition elements (Sc, Cr, Mn, Fe, Ni, Cu, Zr) and atoms with partially filled p-levels (Si, Ge, Se). The structure accommodates up to 5 atomic percent interstitial atoms. In a few cases substitutional replacements of boron by metal or non-metal atoms have been estalished. The interstitial positions are never completely occupied by the dissolved atoms. Pure ?-rhombohedral boron is an electron-deficient covalent solid. It is in pure, single-crystalline form a p-type semiconductor due to electron-deficiency and the fact that two of the boron positions are invariably only partially occupied. By doping ?-rhombohedral boron with three atomic percent iron an n-type semiconductor can be prepared.

Lundström, Torsten

1986-04-01

307

Intercalated graphite electrical conductors  

Microsoft Academic Search

For years NASA has wanted to reduce the weight of spacecraft and aircraft. Experiments are conducted to find a lightweight synthetic metal to replace copper. The subject of this paper, intercalated graphite, is such a material. Intercalated graphite is made by heating petroleum or coal to remove the hydrogen and to form more covalent bonds, thus increasing the molecular weight.

B. A. Banks

1983-01-01

308

Intercalated graphite fiber conductor  

Microsoft Academic Search

Lightweight electrical conductors were developed from graphitic fibers intercalated with highly electrophilic intercalants. Conductance increases of 30-36 times over the unintercalated fibers were observed. This corresponds to about 45% of the specific conductivity of copper at room temperature. Unlike copper, the intercalated graphite fibers exhibit a nearly zero temperature coefficient of conductance. The intercalated yarn did not change its resistance

I. L. Kalnin

1980-01-01

309

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

310

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

311

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

312

Properties of boron/boron-nitride multilayers  

SciTech Connect

Boron-Nitride films are of interest for their high hardness and wear resistance. Large intrinsic stresses and poor adhesion which often accompany high hardness materials can be moderated through the use of a layered structure. Alternate layers of boron (B) and boron-nitride (BN) are formed by modulating the composition of the sputter gas during deposition from a pure B target. The thin films are characterized with TEM to evaluate the microstructure and with nanoindentation to determine hardness. Layer pair spacing and continuity effects on hardness are evaluated for the B/BN films.

Jankowski, A.F.; Wall, M.A.; Hayes, J.P. [Lawrence Livermore National Lab., CA (United States); Alexander, K.B. [Oak Ridge National Lab., TN (United States)

1996-06-01

313

Growth of crystals of several boron-carbon compositions by chemical vapor deposition  

NASA Technical Reports Server (NTRS)

Boron-carbon compounds have been deposited by the flow of carbon tetrachloride and boron trichloride, in the presence of a large excess of hydrogen, over a graphite surface maintained at 1000-1300 C. Deposits were formed on either an RF-heated disc or a tube or insert heated by a resistance furnace. Crystalline materials ranging in composition from B2C to B17C have been obtained.

Kevill, D. N.; Rissmann, T. J.; Brewe, D.; Wood, C.

1986-01-01

314

Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury  

PubMed Central

Reports of graphite pencil lead injuries to the eye are rare. Although graphite is considered to remain inert in the eye, it has been known to cause severe inflammation and damage to ocular structures. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies following a graphite pencil injury. PMID:22606501

Philip, Swetha Sara; John, Deepa; John, Sheeja Susan

2012-01-01

315

Investigation of Hard Boron Rich Solids: Osmium Diboride and ?-Rhombohedral Boron  

NASA Astrophysics Data System (ADS)

Recently, we succeeded in synthesizing three osmium borides, i.e., OsB1.1, Os2B3 and OsB2. Up to date, almost nothing is known about the physical properties of these materials. Microhardness measurements show that OsB2 is extremely hard. Ab initio calculations show that it is due to formation of covalent bonds between boron atoms. OsB2 is also a low compressibility material. It can be used for hard coatings. The ?-rhombohedral polymorph of boron is the second hardest elemental crystal (H ? 33 GPa). It is also very light and a p-type semiconductor. In early 1970s, it has been shown that the doping of boron with 3d transition elements enhances its hardness by about 25%. We predict that, in general, heavily doped samples MBx, with x ? 31 or equivalently a dopant concentration larger than 3.2 at.%, should be ultrahard, i.e., H > 43 GPa. The relevant dopants M are Al, Cu, Sc, Mn, Mg and Li. In addition to these properties, boron-rich materials have a very low volatility, a high chemical inertness and high melting point. They are suitable for applications under extreme conditions and thermoelectric equipment.

Hebbache, M.; Živkovi?, D.

316

Laser nanoablation of graphite  

NASA Astrophysics Data System (ADS)

Experimental data on laser ablation of highly oriented pyrolitic graphite by nanosecond pulsed UV ( nm) and green ( nm) lasers are presented. It was found that below graphite vaporization threshold 1 J/cm, the nanoablation regime can be realized with material removal rates as low as 10 nm/pulse. The difference between physical (vaporization) and physical-chemical (heating + oxidation) ablation regimes is discussed. Special attention is paid to the influence of laser fluence and pulse number on ablation kinetics. Possibility of laser-induced graphite surface nanostructuring has been demonstrated. Combination of tightly focused laser beam and sharp tip of scanning probe microscope was applied to improve material nanoablation.

Frolov, V. D.; Pivovarov, P. A.; Zavedeeev, E. V.; Komlenok, M. S.; Kononenko, V. V.; Konov, V. I.

2014-01-01

317

Fabricating graphene devices from graphite intercalation compounds  

NASA Astrophysics Data System (ADS)

We report a method of making few-layer graphene flakes by mechanically exfoliating SbCl5-graphite intercalation compounds (GICS). The number of exfoliated graphene flakes had a peculiar distribution relevant to the stage structure of GICs. The carrier doping of the few-layer graphene flakes was about two orders of magnitude smaller than that expected from the stoichiometry of the GICs. The measured electric mobility was comparable to that made from pristine graphite. The EPMA measurement showed that inhomogeneous distribution of dopant near the surface of GIC was responsible for obtaining the virtually undoped graphene. Deintercalation of dopant would expand interlayer distance of each graphene layer, and thereby layer-number of exfoliated graphene depended stage number of GIC.

Yagi, Ryuta; Shimomura, Midori; Tahara, Fumiya; Fukada, Seiya

2013-03-01

318

Boron: elementary challenge for experimenters and theoreticians.  

PubMed

Many of the fundamental questions regarding the solid-state chemistry of boron are still unsolved, more than 200 years after its discovery. Recently, theoretical work on the existence and stability of known and new modifications of the element combined with high-pressure and high-temperature experiments have revealed new aspects. A lot has also happened over the last few years in the field of reactions between boron and main group elements. Binary compounds such as B(6)O, MgB(2), LiB(1-x), Na(3)B(20), and CaB(6) have caused much excitement, but the electron-precise, colorless boride carbides Li(2)B(12)C(2), LiB(13)C(2), and MgB(12)C(2) as well as the graphite analogue BeB(2)C(2) also deserve special attention. Physical properties such as hardness, superconductivity, neutron scattering length, and thermoelectricity have also made boron-rich compounds attractive to materials research and for applications. The greatest challenges to boron chemistry, however, are still the synthesis of monophasic products in macroscopic quantities and in the form of single crystals, the unequivocal identification and determination of crystal structures, and a thorough understanding of their electronic situation. Linked polyhedra are the dominating structural elements of the boron-rich compounds of the main group elements. In many cases, their structures can be derived from those that have been assigned to modifications of the element. Again, even these require a critical revision and discussion. PMID:19830749

Albert, Barbara; Hillebrecht, Harald

2009-01-01

319

CRITICAL MEASUREMENTS ON INTERMEDIATE-ENERGY GRAPHITE-U²³⁵ SYSTEMS  

Microsoft Academic Search

A system for the measurement of near-homogeneous carbon-U²³⁵ ; critical masses is described. Cores are constructed with thin, enriched-uranium ; foils spaced between graphite blocks. Fuel density is variable by use ef ; different foil thicknesses and spacings. Reactivity is controlled by boron rods; ; standard reactor instrumentation permits critical operation at low power. ; Results of critical measurements on

J. E. Schwager; F. A. Kloverstrom; W. S. Gilbert

1957-01-01

320

Structural Modification in Carbon Nanotubes by Boron Incorporation.  

PubMed

We have synthesized boron-incorporated carbon nanotubes (CNTs) by decomposition of ferrocene and xylene in a thermal chemical vapor deposition set up using boric acid as the boron source. Scanning and transmission electron microscopy studies of the synthesized CNT samples showed that there was deterioration in crystallinity and improvement in alignment of the CNTs as the boron content in precursor solution increased from 0% to 15%. Raman analysis of these samples showed a shift of ~7 cm(-1) in wave number to higher side and broadening of the G band with increasing boron concentration along with an increase in intensity of the G band. Furthermore, there was an increase in the intensity of the D band along with a decrease in its wave number position with increase in boron content. We speculate that these structural modifications in the morphology and microstructure of CNTs might be due to the charge transfer from boron to the graphite matrix, resulting in shortening of the carbon-carbon bonds. PMID:20596333

Handuja, Sangeeta; Srivastava, P; Vankar, V D

2009-01-01

321

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

322

Boron implantation\\/in situ annealing procedure for optimal p -type properties of diamond  

Microsoft Academic Search

Boron is a p-type dopant in diamond. It can be intro- duced into the diamond crystal or into polycrystalline ~CVD! diamond films by ion-implantation or during CVD growth. However, the doping efficiencies and carrier mobilities are limited, for CVD diamond, by the presence of compensating impurities and defects introduced during CVD growth, or for implantation doped single crystals, by residual

F. Fontaine; C. Uzan-Saguy; B. Philosoph; R. Kalish

1996-01-01

323

Electron oxidation of graphite by fluorospecies  

SciTech Connect

The fluoride-ion affinity (A/sub F/sup -//) of phosphorus pentafluoride was determined to be 100 kcal/mole from the heats of reaction of the Lewis bases SF/sub 4/ and ClO/sub 2/F with PF/sub 5/ near room temperature. The fluoride-ion affinity of boron trifluoride was determined to be 92 kcal/mole from the heat of reaction of ClO/sub 2/F with BF/sub 3/. The crystal structure of ClO/sub 2/BF/sub 4/ was determined and a precise lattice energy was calculated from this structure and used to determined A/sub F/sup -//. Both PF/sub 5/ and BF/sub 3/ were found to react with graphite in the presence of fluorine gas to yield a variety of non-stoichiometric compounds. The fluoride-ion affinity of silicon tetrafluoride is not known, but it does not react with graphite and F/sub 2/ except at high pressures. These and previous results suggested a threshold in oxidizing power of intercalating species below which the oxidative intercalation reaction would not occur. The reduction of C/sub x/PF/sub 6/ by PF/sub 3/ proved that the reaction is thermodynamically controlled to some extent. The displacement of PF/sub 5/ in C/sub x/PF/sub 6/ by BF/sub 3/ (with a smaller A/sub F/sup -//) suggested that two BF/sub 3/ molecules may have a larger fluoride-ion affinity than one PF/sub 5/ and that B/sub 2/F/sub 7//sup -/ may be a stable anion in graphite. Conductivity studies of PF/sub x/ and BF/sub y/ salts showed that a large drop in conductivity when the reaction reaches first stage is due in the most part to direct fluorination of carbon in graphite.

Rosenthal, G.L.

1984-09-01

324

Molecular Structure of graphite  

NSDL National Science Digital Library

In the the mid-16th century, a violent storm knocked over several trees in Borrowdale, England, uncovering a large deposit of a black substance that was first thought to be lead. More than 200 years later, an English scientist discovered that the substance was not actually lead, but a type of carbon instead. The substance was named graphite, after the Greek word meaning "to write," since that is how people used the substance. Graphite is a black silver with a metallic to dull luster. It has a hexagonal crystal system with crystals that are opaque. Due to its high temperature stability and chemical inertness graphite is a good candidate for a refractory material. It is used in the production of refractory bricks and in the production of Mag-carbon refractory bricks. Amorphous graphite is used in metallurgy, pencil production, and paint production.

2002-08-26

325

Intercalated graphite electrical conductors  

NASA Technical Reports Server (NTRS)

For years NASA has wanted to reduce the weight of spacecraft and aircraft. Experiments are conducted to find a lightweight synthetic metal to replace copper. The subject of this paper, intercalated graphite, is such a material. Intercalated graphite is made by heating petroleum or coal to remove the hydrogen and to form more covalent bonds, thus increasing the molecular weight. The coal or petroleum eventually turns to pitch, which can then be drawn into a fiber. With continued heating the pitch-based fiber releases hydrogen and forms a carbon fiber. The carbon fiber, if heated sufficiently, becomes more organized in parallel layers of hexagonally arranged carbon atoms in the form of graphite. A conductor of intercalated graphite is potentially useful for spacecraft or aircraft applications because of its low weight.

Banks, B. A.

1983-01-01

326

Brominated graphitized carbon fibers  

NASA Technical Reports Server (NTRS)

Low cost, high break elongation graphitized carbon fibers having low degree of graphitization are inert to bromine at room or higher temperatures, but are brominated at -7 to 20 C, and then debrominated at ambient. Repetition of this bromination-debromination process can bring the bromine content to 18 percent. Electrical conductivity of the brominated fibers is three times of the before-bromination value.

Hung, Ching-Cheh (inventor)

1991-01-01

327

Nitrogen-doped graphene and its electrochemical applications Yuyan Shao,a  

E-print Network

mechanical exfoliation of graphite with scotch tape,33 mild exfoliation of graphite,34 chemical vaporNitrogen-doped graphene and its electrochemical applications Yuyan Shao,a Sheng Zhang,a Mark Hst March 2010, Accepted 4th June 2010 DOI: 10.1039/c0jm00782j Nitrogen-doped graphene (N-graphene

Aksay, Ilhan A.

328

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

329

First-principles determination of ultrahigh thermal conductivity of boron arsenide: a competitor for diamond?  

PubMed

We have calculated the thermal conductivities (?) of cubic III-V boron compounds using a predictive first principles approach. Boron arsenide is found to have a remarkable room temperature ? over 2000 W m(-1) K(-1); this is comparable to those in diamond and graphite, which are the highest bulk values known. We trace this behavior in boron arsenide to an interplay of certain basic vibrational properties that lie outside of the conventional guidelines in searching for high ? materials, and to relatively weak phonon-isotope scattering. We also find that cubic boron nitride and boron antimonide will have high ? with isotopic purification. This work provides new insight into the nature of thermal transport at a quantitative level and predicts a new ultrahigh ? material of potential interest for passive cooling applications. PMID:23889420

Lindsay, L; Broido, D A; Reinecke, T L

2013-07-12

330

First-Principles Determination of Ultrahigh Thermal Conductivity of Boron Arsenide: A Competitor for Diamond?  

NASA Astrophysics Data System (ADS)

We have calculated the thermal conductivities (?) of cubic III-V boron compounds using a predictive first principles approach. Boron arsenide is found to have a remarkable room temperature ? over 2000Wm-1K-1; this is comparable to those in diamond and graphite, which are the highest bulk values known. We trace this behavior in boron arsenide to an interplay of certain basic vibrational properties that lie outside of the conventional guidelines in searching for high ? materials, and to relatively weak phonon-isotope scattering. We also find that cubic boron nitride and boron antimonide will have high ? with isotopic purification. This work provides new insight into the nature of thermal transport at a quantitative level and predicts a new ultrahigh ? material of potential interest for passive cooling applications.

Lindsay, L.; Broido, D. A.; Reinecke, T. L.

2013-07-01

331

Minerals Yearbook 1989: Boron  

Microsoft Academic Search

U.S. production and sales of boron minerals and chemicals decreased during the year. Domestically, glass fiber insulation was the largest use for borates, followed by sales to distributors, textile-grade glass fibers, and borosilicate glasses. California was the only domestic source of boron minerals. The United States continued to provide essentially all of its own supply while maintaining a strong position

Lyday

1990-01-01

332

Boron in the Environment  

Microsoft Academic Search

Boron has recently come to the attention of the U.S. Environmental Protection Agency as a possible contaminant worthy of regulation, but questions must still be addressed before a regulatory determination can take place. This article reviews current knowledge about boron as it pertains to water treatment and the environment so that informed decisions can be made regarding regulations and direction

JEFFREY L. PARKS; MARC EDWARDS

2005-01-01

333

Magnetron sputtered boron films  

DOEpatents

A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence. 8 figs.

Makowiecki, D.M.; Jankowski, A.F.

1998-06-16

334

Magnetron sputtered boron films  

DOEpatents

A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence.

Makowiecki, Daniel M. (Livermore, CA); Jankowski, Alan F. (Livermore, CA)

1998-01-01

335

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

336

Pt/C trapped in activated graphitic carbon layers as a highly durable electrocatalyst for the oxygen reduction reaction.  

PubMed

A thin nitrogen-doped graphitic carbon layer is elaborately introduced into the Pt/C surface to not only inhibit migration and dissolution of Pt nanoparticles, but also impart activity to the integral catalyst without blocking the inner Pt catalytic active sites. The corrosion of the carbon support can also be alleviated due to the outer graphitic coverage. PMID:25351928

Nie, Yao; Chen, Siguo; Ding, Wei; Xie, Xiaohong; Zhang, Yun; Wei, Zidong

2014-12-18

337

Curvature effects of nitrogen on graphitic sheets: Structures and energetics  

NASA Astrophysics Data System (ADS)

A correlation of the nitrogen concentration on graphitic sheets with structural deformations is presented using the density functional based tight binding method (DFTB). Graphite sheets of various sizes were doped by nitrogen at different sites; either a local deviation from planarity or negative curvature is obtained. In addition, we derive a formula for constructing two sets of isomer series namely methylene cyclopentadiene and benzene to study nitrogen's role in positive curvature formation. Comparing these structures, the exact energy difference to convert a fully hexagonal network to a pentagon centered hexagonal network can be predicted systematically for infinitely large structures.

Mandumpal, Jestin; Gemming, Sibylle; Seifert, Gotthard

2007-10-01

338

Interlayer interactions in graphites  

NASA Astrophysics Data System (ADS)

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.

Chen, Xiaobin; Tian, Fuyang; Persson, Clas; Duan, Wenhui; Chen, Nan-Xian

2013-11-01

339

Interlayer interactions in graphites.  

PubMed

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

340

Boron nitride nanotubes and nanosheets.  

PubMed

Hexagonal boron nitride (h-BN) is a layered material with a graphite-like structure in which planar networks of BN hexagons are regularly stacked. As the structural analogue of a carbon nanotube (CNT), a BN nanotube (BNNT) was first predicted in 1994; since then, it has become one of the most intriguing non-carbon nanotubes. Compared with metallic or semiconducting CNTs, a BNNT is an electrical insulator with a band gap of ca. 5 eV, basically independent of tube geometry. In addition, BNNTs possess a high chemical stability, excellent mechanical properties, and high thermal conductivity. The same advantages are likely applicable to a graphene analogue-a monatomic layer of a hexagonal BN. Such unique properties make BN nanotubes and nanosheets a promising nanomaterial in a variety of potential fields such as optoelectronic nanodevices, functional composites, hydrogen accumulators, electrically insulating substrates perfectly matching the CNT, and graphene lattices. This review gives an introduction to the rich BN nanotube/nanosheet field, including the latest achievements in the synthesis, structural analyses, and property evaluations, and presents the purpose and significance of this direction in the light of the general nanotube/nanosheet developments. PMID:20462272

Golberg, Dmitri; Bando, Yoshio; Huang, Yang; Terao, Takeshi; Mitome, Masanori; Tang, Chengchun; Zhi, Chunyi

2010-06-22

341

Boron isotopic compositions of some boron minerals  

Microsoft Academic Search

Boron minerals that have different structural formulae but are supposed to have the same geologic origin have been collected and analyzed for the 11 B \\/ 10 B isotopic ratio. It has been reconfirmed that minerals of marine origin have higher 11 B \\/ 10 B ratios than those of nonmarine origin. It has been found that the sequence of

Takao Oi; Masao Nomura; Masaaki Musashi; Tomoko Ossaka; Makoto Okamoto; Hidetake Kakihana

1989-01-01

342

Improved graphite furnace atomizer  

SciTech Connect

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

343

Observation of inter-sub-level transitions in modulation-doped Ge quantum dots  

E-print Network

Observation of inter-sub-level transitions in modulation-doped Ge quantum dots J. L. Liu,a) W. G-doped Ge quantum dots are observed. The dot structure is grown by molecular-beam epitaxy, and consists of 30 periods of Ge quantum dots sandwiched by two 6 nm boron-doped Si layers. An absorption peak

344

Direct current sputtering of boron from boron/coron mixtures  

DOEpatents

A method for coating a substrate with boron by sputtering includes lowering the electrical resistance of a boron-containing rod to allow electrical conduction in the rod; placing the boron-containing rod inside a vacuum chamber containing substrate material to be coated; applying an electrical potential between the boron target material and the vacuum chamber; countering a current avalanche that commences when the conduction heating rate exceeds the cooling rate, and until a steady equilibrium heating current is reached; and, coating the substrate material with boron by sputtering from the boron-containing rod.

Timberlake, John R. (Allentown, NJ); Manos, Dennis (Williamsburg, VA); Nartowitz, Ed (Edison, NJ)

1994-01-01

345

Direct current sputtering of boron from boron/carbon mixtures  

SciTech Connect

A method for coating a substrate with boron by sputtering includes lowering the electrical resistance of a boron-containing rod to allow electrical conduction in the rod; placing the boron-containing rod inside a vacuum chamber containing substrate material to be coated; applying an electrical potential between the boron target material and the vacuum chamber; countering a current avalanche that commences when the conduction heating rate exceeds the cooling rate, and until a steady equilibrium heating current is reached and coating the substrate material with boron by sputtering from the boron-containing rod.

Timberlake, J.R.; Manos, D.; Nartowitz, E.

1993-12-31

346

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

347

Graphite technology development plan  

SciTech Connect

This document presents the plan for the graphite technology development required to support the design of the 350 MW(t) Modular HTGR within the US National Gas-Cooled Reactor Program. Besides descriptions of the required technology development, cost estimates, and schedules, the plan also includes the associated design functions and design requirements.

NONE

1986-07-01

348

(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

349

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

350

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

351

Molecular Structure of boron  

NSDL National Science Digital Library

Boron was founded in 1808 by Sir Humphry Davy and Gay-Lussac and Thenard. It occurs as orthoboric acid in volcanic spring waters and as borates in Boron and colematic. Some sources can also be found in the Mohave Desert. It is used when making glass to keep the glass from breaking under temperature stress. Also if combined with sodium hydroxide and hydrogen peroxide it makes bleach.

2002-08-26

352

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

353

Strain-induced delamination of edge-grafted graphite.  

PubMed

Edge-selectively grafted graphite (EGG) with poly(ether-ketone) was prepared by the Friedel-Crafts acylation in a mild polyphosphoric acid (PPA)-phosphorous pentoxide (P(2)O(5)) mixture. The homogeneous reaction dope was coagulated in air moisture at different temperatures. The morphology of expanded EGG was changed from balls, balls/rods and rods with respect to coagulation temperatures of 80, 60, 40 and 25 °C, respectively. PMID:23041764

Choi, Eun-Kyung; Jeon, In-Yup; Shin, Yeon-Ran; Baek, Jong-Beom

2012-11-21

354

Synthesizability of Superhard Carbon by Cold Compression of Graphite  

NASA Astrophysics Data System (ADS)

We present an efficient scheme combining Monte Carlo walk in the space of transition pathways with molecular dynamics simulations for predicting matter modification under high pressure. If crystal structure prediction is a top-interest field for science and technology, the quest is even more exciting for elements such as boron and carbon. While under pressure above 15 GPa and at high temperatures (1600-2500 K) graphite is converted into diamond, room temperature compression gives a new superhard modification of carbon. Its nature remained unresolved until recent theoretical investigations predicted two candidate structures, M-Carbon and BCT4. Both structures have comparable physical properties and refine well the XRD data. To elucidate the nature of the final product of graphite cold compression we performed molecular dynamics transition path sampling simulations and we determined the energy profile of each transition (graphite to M-carbon and graphite to BCT4). The intrinsic mechanism of the reconstruction and the reasons of the favoring of one structure over the other have been determined. A detailed picture of events of nucleation and growth during the transition is finely reproduced. Our procedure do not only determine the nature of a transition final product but predicts its synthesizability under given conditions of pressure and temperature.

Eddine Boulfelfel, Salah; Oganov, Artem; Leoni, Stefano

2011-03-01

355

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

356

Chemical analysis of impurity boron atoms in diamond using soft X-ray emission spectroscopy.  

PubMed

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. PMID:18614820

Muramatsu, Yasuji; Iihara, Junji; Takebe, Toshihiko; Denlinger, Jonathan D

2008-07-01

357

Fabrication of Metal–Oxide–Diamond Field-Effect Transistors with Submicron-Sized Gate Length on Boron-Doped (111) H-Terminated Surfaces Using Electron Beam Evaporated SiO 2 and Al 2 O 3  

Microsoft Academic Search

A H-terminated surface conductive layer of B-doped diamond on a (111) surface was used to fabricate a metal–oxide–semiconductor\\u000a field-effect transistor (MOSFET) using an electron beam evaporated SiO2 or Al2O3 gate insulator and a Cu-metal stacked gate. When the bulk carrier concentration was approximately 1015\\/cm3 and the B-doped diamond layer was 1.5 ?m thick, the surface carrier mobility of the H-terminated surface

Takeyasu Saito; Kyung-Ho Park; Kazuyuki Hirama; Hitoshi Umezawa; Mitsuya Satoh; Hiroshi Kawarada; Zhi-Quan Liu; Kazutaka Mitsuishi; Kazuo Furuya; Hideyo Okushi

2011-01-01

358

Effect of microstructure of graphite on the nonreductive thermal ion emission in thermal ionization mass spectrometry.  

PubMed

The emission behavior of polyatomic ions in the ionization source of thermal ionization mass spectrometry (TIMS) was investigated. The results suggest that the presence of a graphite promoter plays a key role for the formation and stable emission of polyatomic ions, such as M(2)X(+), M(2)BO(2)(+), Cs(2)NO(2)(+), and Cs(2)CNO(+). Our data further implied that the intensity of M(2)X(+) and M(2)BO(2)(+) increases and the emission temperature decreases with increasing cationic and anionic radius. During the boron isotopic measurement using the Cs(2)BO(2)(+)-graphite-PTIMS method, the isobaric interference ion Cs(2)CNO(+) cannot be transformed from nitrate or organic compounds containing an amide group but can be induced by the existence of trace amounts of boron because of its special electron-deficiency property (B(3+)). Characterization on the planar crystalline structure of various graphite samples with SEM, TEM, and Raman spectroscopy confirmed the relationship of the emission capacity of polyatomic ions and the crystal microstructure of graphite and provides direct evidence that graphite with a perfect parallel and equidistant layer orientation shows a beneficial effect on the emission of polyatomic ions in TIMS. The mechanism study on the formation of polyatomic ions opens the possibility to establish high precision methods for isotopic composition analysis of more nonmetal elements with the TIMS technique. PMID:20112900

Wei, H Z; Jiang, S Y; Xiao, Y K

2010-02-25

359

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.

2014-09-01

360

Process for making boron nitride using sodium cyanide and boron  

DOEpatents

This a very simple process for making boron nitride by mixing sodium cyanide and boron phosphate and heating the mixture in an inert atmosphere until a reaction takes place. The product is a white powder of boron nitride that can be used in applications that require compounds that are stable at high temperatures and that exhibit high electrical resistance.

Bamberger, Carlos E. (Oak Ridge, TN)

1990-01-01

361

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

362

Boronated liposome development and evaluation  

SciTech Connect

The boronated liposome development and evaluation effort consists of two separate tasks. The first is the development of new boron compounds and the synthesis of known boron species with BNCT potential. These compounds are then encapsulated within liposomes for the second task, biodistribution testing in tumor-bearing mice, which examines the potential for the liposomes and their contents to concentrate boron in cancerous tissues.

Hawthorne, M.F. [Univ. of California, Los Angeles, CA (United States)

1995-11-01

363

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

364

Bamboo leaf-assisted formation of carbon/nitrogen co-doped anatase TiO2 modified with silver and graphitic carbon nitride: novel and green synthesis and cooperative photocatalytic activity.  

PubMed

We report a novel synthesis approach employing bamboo leaves as sources of both the C/N dopant and reductant to the formation of C/N co-doped TiO2 modified with Ag and g-C3N4 (Ag/CN-TiO2@g-C3N4). In this case, the ternary composite has a hierarchical structure and a large surface area, which increases the contact area of reactants. Degradation of rhodamine B (RhB) and hydrogen generation were carried out to evaluate the photocatalytic activity of as-prepared samples under visible light irradiation. It is found that with respect to single and binary catalysts, the Ag/CN-TiO2@g-C3N4 ternary composite shows the highest photocatalytic activity (degradation of RhB, H2 evolution from water splitting) as a result of the fast generation, separation and transportation of the photogenerated carriers, which was evidenced by photoluminescence measurements and free radical/hole scavenging experiments. At last, a possible photocatalytic mechanism under visible light irradiation was proposed. The novel and green synergistic approach presented here could provide a facile yet effective method for designing other visible light active non-metal co-doped TiO2 based photocatalysts with enhanced activity and high chemical stability. PMID:25102976

Jiang, Zhifeng; Liu, Dong; Jiang, Deli; Wei, Wei; Qian, Kun; Chen, Min; Xie, Jimin

2014-09-28

365

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

366

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

367

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

368

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

369

Minerals Yearbook 1989: Boron  

SciTech Connect

U.S. production and sales of boron minerals and chemicals decreased during the year. Domestically, glass fiber insulation was the largest use for borates, followed by sales to distributors, textile-grade glass fibers, and borosilicate glasses. California was the only domestic source of boron minerals. The United States continued to provide essentially all of its own supply while maintaining a strong position as a source of sodium borate products and boric acid exported to foreign markets. Supplementary U.S. imports of Turkish calcium borate and calcium-sodium borate ores, borax, and boric acid, primarily for various glass uses, continued.

Lyday, P.A.

1990-08-01

370

Structure of Liquid Boron  

NASA Astrophysics Data System (ADS)

The structure factor S\\(Q\\) and the pair distribution function g\\(r\\) has been measured for liquid boron in the temperature range 2600-2000 K, extending over both the normal and supercooled liquid states. The bond length and coordination number of the first coordination shell are similar to those reported for the crystalline and amorphous solid forms, but the second and third coordination shells are broader and shifted to higher distances. The insulator-metal transition that takes place in boron upon melting is associated with a relatively small change in both volume and short-range order.

Krishnan, S.; Ansell, S.; Felten, J. J.; Volin, K. J.; Price, D. L.

1998-07-01

371

Structure of Liquid Boron  

SciTech Connect

The structure factor S(Q) and the pair distribution function g(r) has been measured for liquid boron in the temperature range 2600{endash}2000thinspthinspK, extending over both the normal and supercooled liquid states. The bond length and coordination number of the first coordination shell are similar to those reported for the crystalline and amorphous solid forms, but the second and third coordination shells are broader and shifted to higher distances. The insulator-metal transition that takes place in boron upon melting is associated with a relatively small change in both volume and short-range order. {copyright} {ital 1998} {ital The American Physical Society}

Krishnan, S.; Felten, J.J. [Containerless Research, Inc., 906 University Place, Evanston, Illinois 60201 (United States)] [Containerless Research, Inc., 906 University Place, Evanston, Illinois 60201 (United States); Ansell, S.; Volin, K.J.; Price, D.L. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

1998-07-01

372

Boron Nanowires for Flexible Electronics and Field Emission  

NASA Astrophysics Data System (ADS)

Development of a rational synthetic method of flexible nanomaterials may enable exciting avenues in both fundamental research and novel device applications. In this paper, flexible boron nanowires have been successfully synthesized on both Si (111) and scanning tunneling microscope (STM) tungsten (W) tips via thermoreduction of boron-oxygen compounds with active metal (magnesium). These as-prepared nanowires, which are structurally uniform and single crystalline, represent good semiconductor at high temperature. Electrical conductivity of these intrinsic nanowires can be improved two orders by introducing doping atoms. Tensile stress measurements demonstrate excellent mechanical property of as-synthesized boron nanowires as well as resistance to mechanical fracture even under a strain of 3%. Importantly, simultaneous electrical measurement reveals that the corresponding electrical conductance is very robust and remains constant under mechanical strain. Our results can be briefly explained by Mott's variable range hopping (VRH) model. A stable field emission current was also observed from a single boron nanowire. Boron nanostructures with excellent controllability, remarkable mechanical flexibility and field emission characteristics represent promising candidates for flexible nanoelectronic circuits as well as electron emission nanodevices.

Tian, Jifa; Cai, Jinming; Hui, Chao; Li, Chen; Tian, Yuan; Shen, Chengmin; Gao, Hongjun

2009-09-01

373

Understanding the sprayed boric acid method for bulk doping of silicon ribbons  

NASA Astrophysics Data System (ADS)

The sprayed boric acid (SBA) method for bulk doping of silicon ribbons is investigated. Experimental procedures and main results are reviewed. Computational fluid dynamics and experimental tests using partial spraying suggest the role of gas transported evaporated boron oxide to explain the boron incorporation profiles along the sample. The industrial applicability of the SBA method is discussed.

Silva, J. A.; Pêra, David; Brito, Miguel C.; Alves, Jorge Maia; Serra, João; Vallêra, A. M.

2011-07-01

374

Boron Requirement in Cyanobacteria 1  

PubMed Central

The effect of boron on heterocystous and nonheterocystous dinitrogen fixing Cyanobacteria was examined. The absence of boron in culture media inhibited growth and nitrogenase activity in Nodularia sp., Chlorogloeopsis sp., and Nostoc sp. cultures. Examinations of boron-deficient cultures showed changes in heterocyst morphology. However, cultures of nonheterocystous Cyanobacteria, Gloeothece sp. and Plectonema sp., grown in the absence of boron did not show any alteration in growth or nitrogenase activity. These results suggest a requirement of boron only by heterocystous Cyanobacteria. A possible role for this element in the early evolution of photosynthetic organisms is proposed. Images Figure 4 Figure 5 Figure 6 PMID:16667889

Bonilla, Ildefonso; Garcia-Gonzalez, Mercedes; Mateo, Pilar

1990-01-01

375

Electronic structures of boron nanoribbons  

NASA Astrophysics Data System (ADS)

Using first principles calculations, we investigate the electronic properties of boron nanoribbons. The boron nanoribbons are constructed from the stable boron sheet. The bare boron nanoribbons with different edges are metals. The boron nanoribbons with two-hydrogen passivated on the zigzag edges become semiconductors and are more stable than the one-hydrogen passivated ones. The band gaps are within the range of 0.5eV and there is an oscillatory variation in the band gaps with the change of widths due to the even-odd number of nanoribbon widths.

Ding, Yi; Yang, Xiaobao; Ni, Jun

2008-07-01

376

Fabrication of boron sputter targets  

DOEpatents

A process for fabricating high density boron sputtering targets with sufficient mechanical strength to function reliably at typical magnetron sputtering power densities and at normal process parameters. The process involves the fabrication of a high density boron monolithe by hot isostatically compacting high purity (99.9%) boron powder, machining the boron monolithe into the final dimensions, and brazing the finished boron piece to a matching boron carbide (B.sub.4 C) piece, by placing aluminum foil there between and applying pressure and heat in a vacuum. An alternative is the application of aluminum metallization to the back of the boron monolithe by vacuum deposition. Also, a titanium based vacuum braze alloy can be used in place of the aluminum foil.

Makowiecki, Daniel M. (Livermore, CA); McKernan, Mark A. (Livermore, CA)

1995-01-01

377

Fabrication of boron sputter targets  

DOEpatents

A process is disclosed for fabricating high density boron sputtering targets with sufficient mechanical strength to function reliably at typical magnetron sputtering power densities and at normal process parameters. The process involves the fabrication of a high density boron monolithe by hot isostatically compacting high purity (99.9%) boron powder, machining the boron monolithe into the final dimensions, and brazing the finished boron piece to a matching boron carbide (B{sub 4}C) piece, by placing aluminum foil there between and applying pressure and heat in a vacuum. An alternative is the application of aluminum metallization to the back of the boron monolithe by vacuum deposition. Also, a titanium based vacuum braze alloy can be used in place of the aluminum foil. 7 figs.

Makowiecki, D.M.; McKernan, M.A.

1995-02-28

378

Boron nitride as desalting material in combination with phosphopeptide enrichment in shotgun proteomics.  

PubMed

Hydrophilic peptides in shotgun proteomics have been shown to be problematic in conventional chromatography. Typically, C18 solid phase extraction or peptide traps are used for desalting the sample prior to mass spectrometry analysis, but the capacity to retain hydrophilic peptides is not very high, causing a bias toward more hydrophobic peptides. This is particularly problematic in phosphoproteomic studies. We tested the compatibility of commercially available boron nitride as a novel material for peptide desalting. Boron nitride can be used to recover a wide range of peptides with different physicochemical properties comparable to combined C18 and graphite carbon material. PMID:24462817

Furuhashi, Takeshi; Nukarinen, Ella; Ota, Shigenori; Weckwerth, Wolfram

2014-05-01

379

Graphitic packing removal tool  

SciTech Connect

Graphitic packing removal tools are described for removal of the seal rings in one piece from valves and pumps. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

Meyers, K.E.; Kolsun, G.J.

1996-12-31

380

Sublimation of Boron.  

National Technical Information Service (NTIS)

Torsion-effusion and mass spectrometric techniques were used to study the vaporization of beta -rhombohedral boron over the temperature range 1823 to 2253 exp 0 K. The pressure-temperature data were fitted by the equation ln P(Pa) = -(66.8 +- 1.4) 10 exp ...

R. W. Mar, R. G. Bedford

1976-01-01

381

Process for microwave sintering boron carbide  

DOEpatents

A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

Holcombe, C.E.; Morrow, M.S.

1993-10-12

382

Process for microwave sintering boron carbide  

DOEpatents

A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

Holcombe, Cressie E. (440 Sugarwood Dr., Knoxville, TN 37922); Morrow, Marvin S. (Rte. #3, Box 113, Kingston, TN 37763)

1993-01-01

383

Effects of carbon doping on superconductivity in magnesium diboride  

Microsoft Academic Search

We introduce carbon onto boron sites in MgB2. The resulting changes in crystal lattice constants and superconducting transition temperature Tc are characterized by x-ray-diffraction, magnetic susceptibility, and electrical resistance measurements. The consequence of approximately 10% carbon doping of boron sites is a 1% contraction of the intraplane lattice dimension (with no appreciable change in the interplane dimension) and a lowering

William Mickelson; John Cumings; W. Q. Han; A. Zettl

2002-01-01

384

Doping of graphene during chemical exfoliation  

NASA Astrophysics Data System (ADS)

Graphene provides a perfect platform to explore the unique electronic properties in two-dimensions. However, most electronic applications are handicapped by the absence of a semiconducting gap in pristine graphene. To control the semiconducting properties of graphene, doping is regarded as one of the most feasible methods. Here we demonstrate that graphene can be effectively doped during chemical exfoliation of highly ordered pyrolitic graphite in organic solvents. Layered structure of graphene sheets was confirmed by confocal Raman spectroscopy and doping was probed by analyzing shift in Raman peak positions and transistor transfer (IDS-VGS) characteristics.

Srivastava, Pawan Kumar; Yadav, Premlata; Ghosh, Subhasis

2013-02-01

385

Cleavage of graphite to graphene  

Microsoft Academic Search

Graphite intercalation compounds (GICs) are of interest to chemists and physicists because of their unusual properties. Much attention has been focused on the preparation and the properties of GICs themselves and on their utilization. In recent years, there have been attempts to intercalate two guest species together into graphite to study the behavior of the first intercalated component towards the

H. Shioyama

2001-01-01

386

Baseline Graphite Characterization: First Billet  

SciTech Connect

The Next Generation Nuclear Plant Project Graphite Research and Development program is currently establishing the safe operating envelope of graphite core components for a very high temperature reactor design. To meet this goal, the program is generating the extensive amount of quantitative data necessary for predicting the behavior and operating performance of the available nuclear graphite grades. In order determine the in-service behavior of the graphite for the latest proposed designs, two main programs are underway. The first, the Advanced Graphite Creep (AGC) program, is a set of experiments that are designed to evaluate the irradiated properties and behavior of nuclear grade graphite over a large spectrum of temperatures, neutron fluences, and compressive loads. Despite the aggressive experimental matrix that comprises the set of AGC test runs, a limited amount of data can be generated based upon the availability of space within the Advanced Test Reactor and the geometric constraints placed on the AGC specimens that will be inserted. In order to supplement the AGC data set, the Baseline Graphite Characterization program will endeavor to provide supplemental data that will characterize the inherent property variability in nuclear-grade graphite without the testing constraints of the AGC program. This variability in properties is a natural artifact of graphite due to the geologic raw materials that are utilized in its production. This variability will be quantified not only within a single billet of as-produced graphite, but also from billets within a single lot, billets from different lots of the same grade, and across different billets of the numerous grades of nuclear graphite that are presently available. The thorough understanding of this variability will provide added detail to the irradiated property data, and provide a more thorough understanding of the behavior of graphite that will be used in reactor design and licensing. This report covers the development of the Baseline Graphite Characterization program from a testing and data collection standpoint through the completion of characterization on the first billet of nuclear-grade graphite. This data set is the starting point for all future evaluations and comparisons of material properties.

Mark C. Carroll; Joe Lords; David Rohrbaugh

2010-09-01

387

Boron isotopic compositions of some boron minerals  

NASA Astrophysics Data System (ADS)

Boron minerals that have different structural formulae but are supposed to have the same geologic origin have been collected and analyzed for the 11B /10B isotopic ratio. It has been reconfirmed that minerals of marine origin have higher 11B /10B ratios than those of nonmarine origin. It has been found that the sequence of decreasing 11B /10B values among the minerals with the same geologic origin is; borax, tincal, kernite (Na borates) > ulexite ( Na/Ca borate) > colemanite, iyoite, meyerhofferite (Ca borates). This sequence is explainable on the basis of the difference in crystal structure among the minerals. That is, minerals with higher BO 3/BO 4 ratios, (the ratio of the number of the BO 3 triangle units to the number of the BO 4 tetrahedron units in the structural formula of a mineral) have higher 11B /10B ratios.

Oi, Takao; Nomura, Masao; Musashi, Masaaki; Ossaka, Tomoko; Okamoto, Makoto; Kakihana, Hidetake

1989-12-01

388

Impact of boron dilution accidents on low boron PWR safety  

SciTech Connect

In conventional pressurized water reactor (PWR) designs, soluble boron is used for reactivity control over core fuel cycle. As an inadvertent reduction of the boron concentration during a boron dilution accident could introduce positive reactivity and have a negative impact on PWR safety, design changes to reduce boron concentration in the reactor coolant are of general interest. In the framework of an investigation into the feasibility of low boron design, a PWR core configuration based on fuel with higher gadolinium (Gd) load has been developed which permits to reduce the natural boron concentration at begin of cycle (BOC) to 518 ppm. For the assessment of the potential safety advantages, a boron dilution accident due to small break loss-of-coolant-accident (SBLOCA) has been simulated with the system code ATHLET for two PWR core designs: a low boron design and a standard core design. The results from the comparative analyses showed that the impact of the boron dilution accident on the new PWR design safety is significantly lower in comparison with the standard design. The new reactor design provided at least 4, 4% higher reactivity margin to recriticality during the whole accident which is equivalent to the negative reactivity worth of additional 63% of all control rods fully inserted in to the core. (authors)

Papukchiev, A.; Liu, Y. [Dept. of Reactor Dynamics and Reactor Safety, Technical Univ. Munich, Walther Meissner-Str. 2, 85748 Garching (Germany); Schaefer, A. [ISaR Inst. for Safety and Reliability, Walther Meissner-Str. 2, 85748 Garching (Germany)

2006-07-01

389

Study on the structural evolution of modified phenol formaldehyde resin adhesive for the high-temperature bonding of graphite  

NASA Astrophysics Data System (ADS)

A novel adhesive for carbon materials composed of phenol-formaldehyde resin, boron carbide and fumed silica, was prepared. The adhesive property of graphite joints bonded by the above adhesive treated at high-temperatures was tested. Results showed that the adhesive was found to have outstanding high-temperature bonding properties for graphite. The adhesive structure was dense and uniform even after the graphite joints were heat-treated at 1500 °C. Bonding strength was 17.1 MPa. The evolution of adhesive structure was investigated. The results indicated that the addition of the secondary additive, fumed silica, improved the bonding performance greatly. Borosilicate phase with better stability was formed during the heat-treatment process, and the volume shrinkage was restrained effectively, which was responsible for the satisfactory high-temperature bonding performance of graphite.

Wang, Jigang; Jiang, Nan; Guo, Quangui; Liu, Lang; Song, Jinren

2006-01-01

390

Hypervelocity impacts into graphite  

NASA Astrophysics Data System (ADS)

Studies have been conducted into the characterisation of the behaviour of commercial graphite (brittle) when subjected to hypervelocity impacts by a range of projectiles. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6kms-1 at right angles into target plates. The damage caused is quantified by measurements of the crater depth and diameters. From the experimental data collected, scaling laws were derived which correlate the crater dimensions to the velocity and the density of the projectile. It was found that for moderate projectile densities the crater dimensions obey the '2/3 power law' which applies to ductile materials.

Latunde-Dada, S.; Cheesman, C.; Day, D.; Harrison, W.; Price, S.

2011-03-01

391

Effect of boron segregation at grain boundaries on heat-affected zone cracking in wrought INCONEL 718  

Microsoft Academic Search

Susceptibility to heat-affected zone (HAZ) cracking during electron-beam welding was studied in two INCONEL 718-based alloys\\u000a doped with different levels of boron. By lowering the carbon, sulfur, and phosphorous concentrations to be “as low as possible,”\\u000a the occurrence of HAZ cracking was related directly to the level of segregation of boron at grain boundaries, which occurred\\u000a by nonequilibrium segregation during

W. Chen; M. C. Chaturvedi; N. L. Richards

2001-01-01

392

Effect of boron segregation at grain boundaries on heat-affected zone cracking in wrought INCONEL 718  

Microsoft Academic Search

Susceptibility to heat-affected zone (HAZ) cracking during electron-beam welding was studied in two INCONEL 718-based alloys doped with different levels of boron. By lowering the carbon, sulfur, and phosphorous concentrations to be ``as low as possible,'' the occurrence of HAZ cracking was related directly to the level of segregation of boron at grain boundaries, which occurred by nonequilibrium segregation during

W. Chen; M. C. Chaturvedi; N. L. Richards

2001-01-01

393

Deposition and tribology of carbon and boron nitride nanoperiod multilayer solid lubricating films  

Microsoft Academic Search

The solid lubricating properties of nanoperiod multilayer (C\\/BN)n films are discussed in this article. Nanoperiod multilayer films composed of carbon and boron nitride layers, which have a structure expected to provide solid lubrication such as the h-BN and graphite structures were deposited, and their nanoindentation and tribological properties were evaluated. The nanoindentation hardness and modulus of dissipation of the nanoperiod

Shojiro Miyake; Tsuyoshi Hashizume; Wataru Kurosaka; Masatoshi Sakurai; Mei Wang

2007-01-01

394

High Performance Plasma Operation on DIII-D During Extended Periods Without Boronization  

SciTech Connect

High performance plasmas, including both hybrid and advanced tokamak (AT) bench-mark discharges, were shown to be highly repeatable in DIII-D over 6000 plasma-seconds of operation during the 2006 campaign with no intervening boron depositions or high temperature bakes. Hybrid and AT discharges with identical control targets were repeated after the initial boronization at the beginning of the 2006 campaign, and again just before and after a second boronization near the end of the 2006 campaign. After a long entry vent between the 2006 and 2007 campaigns, similar discharges were again repeated after the standard high temperature baking and plasma cleanup, but prior to a boronization. Performance metrics, such as {beta}, confinement quality, and density control, were extremely well repeated. A low performance daily reference shot (DRS) was also established as a routine monitor of impurity influx. Over the 2006 campaign, the DRS database indicated little to no secular increase in impurity content. Oxygen content and Ni line emission were higher after the intervening vent, but were still minor contributors to plasma contamination. This indicates that erosion of boron films used for wall conditioning will not be a limitation to establishing long pulse high performance discharges in the new generation of superconducting tokamaks if graphite is used as the primary plasma facing material. These results contrast with recent work in devices using high-Z metallic plasma facing materials, where very frequent refreshing of boron films is required for high performance plasma operation.

West, W P; Groth, M; Hyatt, A W; Jackson, G L; Wade, M R; Greenfield, C M; Politzer, P A

2007-06-27

395

Multiple doping of silicon-germanium alloys for thermoelectric applications  

NASA Technical Reports Server (NTRS)

It is shown that heavy doping of n-type Si/Ge alloys with phosphorus and arsenic (V-V doping interaction) by diffusion leads to a significant enhancement of their carrier concentration and possible improvement of the thermoelectric figure of merit. High carrier concentrations were achieved by arsenic doping alone, but for a same doping level higher carrier mobilities and lower resistivities are obtained through phosphorus doping. By combining the two dopants with the proper diffusion treatments, it was possible to optimize the different properties, obtaining high carrier concentration, good carrier mobility and low electrical resistivity. Similar experiments, using the III-V doping interaction, were conducted on boron-doped p-type samples and showed the possibility of overcompensating the samples by diffusing arsenic, in order to get n-type behavior.

Fleurial, Jean-Pierre; Vining, Cronin B.; Borshchevsky, Alex

1989-01-01

396

Spent graphite fuel element processing  

SciTech Connect

The Department of Energy currently sponsors two programs to demonstrate the processing of spent graphite fuel elements. General Atomic in San Diego operates a cold pilot plant to demonstrate the processing of both US and German high-temperature reactor fuel. Exxon Nuclear Idaho Company is demonstrating the processing of spent graphite fuel elements from Rover reactors operated for the Nuclear Rocket Propulsion Program. This work is done at Idaho National Engineering Laboratory, where a hot facility is being constructed to complete processing of the Rover fuel. This paper focuses on the graphite combustion process common to both programs.

Holder, N.D.; Olsen, C.W.

1981-07-01

397

Effect of boron segregation at grain boundaries on heat-affected zone cracking in wrought INCONEL 718  

NASA Astrophysics Data System (ADS)

Susceptibility to heat-affected zone (HAZ) cracking during electron-beam welding was studied in two INCONEL 718-based alloys doped with different levels of boron. By lowering the carbon, sulfur, and phosphorous concentrations to be “as low as possible,” the occurrence of HAZ cracking was related directly to the level of segregation of boron at grain boundaries, which occurred by nonequilibrium segregation during a preweld heat treatment. The study has demonstrated a direct correlation between the amount of boron segregated at grain boundaries and their susceptibility to HAZ cracking, in terms of the total crack length and number of cracks observed in the HAZ. The analysis of results suggests that both the melting and resolidification temperatures of the boron-segregated grain boundaries can be about 100 °C to 200 °C lower than those of the grain boundaries that were susceptible to constitutional liquation of Nb carbides on them, making boron more deleterious in causing HAZ cracking.

Chen, W.; Chaturvedi, M. C.; Richards, N. L.

2001-04-01

398

Effects of boron on the toughness of {gamma}-{gamma}{prime} nickel aluminium superalloys  

SciTech Connect

The ordered L1{sub 2}-type intermetallic Ni{sub 3}Al ({gamma}{prime}) possesses outstanding high-temperature mechanical properties. Single crystals of Ni{sub 3}Al are ductile when tested in ambient conditions, but the ductility in polycrystalline state is very poor due to grain boundary failure. This problem has been well solved with a small amount of boron addition (0.5 to {approximately}1.0 at %), which significantly toughens the material. Compared to pure Ni{sub 3}Al, the effects of boron doping on two-phase {gamma}-{gamma}{prime} alloys has not been thoroughly investigated. It has been shown that boron partitions to the grain boundaries of nickel-based superalloys and forms boride there which will stabilize the grain size at elevated temperatures, but the role of boron in influencing the toughness and grain boundary microstructures of the superalloy is not clear. In particular, it would be very interesting to know whether the toughening and nickel co-segregation behavior of boron in the pure {gamma}{prime} situation will extend to the two-phase {gamma}-{gamma}{prime} system. In this paper the authors will report some effects of boron on {gamma}-{gamma}{prime} alloys, and in order to remove any effects of other elements usually added to superalloys, boron is the only addition here.

Chiu, Y.L.; Ngan, A.H.W. [Univ. of Hong Kong (Hong Kong). Dept. of Mechanical Engineering] [Univ. of Hong Kong (Hong Kong). Dept. of Mechanical Engineering

1998-12-04

399

Formation of c-BN nanoparticles by helium, lithium and boron ion implantation  

NASA Astrophysics Data System (ADS)

Ion induced phase transformation from the soft graphitic hexagonal boron nitride ( h-BN) to ultrahard cubic boron nitride ( c-BN) nanoparticles is presented in the work herein. Ion implantation was used as a technique to introduce boron lithium and helium ions, at the energy of 150 keV and fluences ranging from 1 × 10 14 to 1 × 10 16 ions/cm 2, into hot pressed, polycrystalline h-BN. Analyses using Raman Spectroscopy showed that He +, Li + and B + led to a h-BN to c-BN phase transition, evident from the longitudinal optical (LO) Raman phonon features occurring in the implanted samples' spectra. The nature of these phonon peaks and their downshifting is explained using the spatial phonon correlation model.

Aradi, Emily; Erasmus, Rudolph M.; Derry, Trevor E.

2012-02-01

400

Intercalated hybrid graphite fiber composite  

NASA Technical Reports Server (NTRS)

The invention is directed to a highly conductive lightweight hybrid material and methods of producing the same. The hybrid composite is obtained by weaving strands of a high strength carbon or graphite fiber into a fabric-like structure, depositing a layer of carbon onto the structure, heat treating the structure to graphitize the carbon layer, and intercalating the graphitic carbon layer structure. A laminate composite material useful for protection against lightning strikes comprises at least one layer of the hybrid material over at least one layer of high strength carbon or graphite fibers. The composite material of the present invention is compatible with matrix compounds, has a coefficient of thermal expansion which is the same as underlying fiber layers, and is resistant to galvanic corrosion in addition to being highly conductive. These materials are useful in the aerospace industry, in particular as lightning strike protection for airplanes.

Gaier, James R. (inventor)

1993-01-01

401

Graphite for the nuclear industry  

SciTech Connect

Graphite finds applications in both fission and fusion reactors. Fission reactors harness the energy liberated when heavy elements, such as uranium or plutonium, fragment or fission''. Reactors of this type have existed for nearly 50 years. The first nuclear fission reactor, Chicago Pile No. 1, was constructed of graphite under a football stand at Stagg Field, University of Chicago. Fusion energy devices will produce power by utilizing the energy produced when isotopes of the element hydrogen are fused together to form helium, the same reaction that powers our sun. The role of graphite is very different in these two reactor systems. Here we summarize the function of the graphite in fission and fusion reactors, detailing the reasons for their selection and discussing some of the challenges associated with their application in nuclear fission and fusion reactors. 10 refs., 15 figs., 1 tab.

Burchell, T.D.; Fuller, E.L.; Romanoski, G.R.; Strizak, J.P.

1991-01-01

402

Europium doping of cBN and taC thin films  

Microsoft Academic Search

We investigated the doping of thin films of tetrahedral amorphous carbon (ta-C) and cubic boron nitride (c-BN) with europium. The films were grown by mass selected ion beam deposition and doped with europium during growth. Analysis was performed in vacuo using photoelectron spectroscopy and ex vacuo with conversion electron Mössbauer, Fourier transform infrared and cathodoluminescence spectroscopy. Successful incorporation of europium

U. Vetter; P. Reinke; C. Ronning; H. Hofsäss; P. Schaaf; K. Bharuth-Ram; T. Taniguchi

2003-01-01

403

Influence of electron-phonon interaction in doped silicon crystals on the root-mean-square dynamic displacement of atoms  

Microsoft Academic Search

The root-mean-square dynamic displacements (begin{array}{*{20}c} - \\\\ {u^2 } \\\\ _{dyn} ) of silicon atoms in single-crystals doped with phosphorus, arsenic, antimony, boron, gallium, and indium are determined experimentally. Characteristic concentration dependences ofbegin{array}{*{20}c} - \\\\ {u^2 } \\\\ _{dyn} are obtained for boron- and phosphorus-doped silicon. A number of experimental facts indicating the existence of electron-phonon interaction in comparison with

M. D. Kapustina; V. A. Panteleev; T. Yu. Markova

1977-01-01

404

Doped zinc oxide window layers for dye sensitized solar cells  

NASA Astrophysics Data System (ADS)

The present paper reports the fabrication of dye sensitized solar cell (DSSC), where boron doped ZnO (BZO) and aluminum-boron co-doped ZnO (AZB) thin films were used as front window electrodes. The highly crystalline zinc oxide (ZnO) nanoparticles (NPs) synthesized by the sol-gel route were used as host material for the dye. The efficiencies of the DSSCs formed using the BZO and AZB as window layers were obtained to be 1.56 and 1.84%, respectively. The enhanced efficiency in the case of an AZB window layer based DSSC is attributed to the increase in conductivity induced by co-doping of Al and B and an increase in the number of conducting pathways between the window layer and NPs provided by the nanorods. This facilitates a new approach in the window layer (doped ZnO) for DSSC application.

Kumar, Vinod; Singh, Neetu; Kumar, Vijay; Purohit, L. P.; Kapoor, Avinashi; Ntwaeaborwa, Odireleng M.; Swart, Hendrik C.

2013-10-01

405

THERMAL NEUTRON SPECTRA IN GRAPHITE  

Microsoft Academic Search

A pulsed, high-current, electron linear accelerator is used to excite ; thermal-neutron spectra in a graphite asemmbly. The steady-state energy spectra ; of neutrons are measured at several temperatures by pulsed-beam time-of-flight ; techniques. The measured spectra are compared with theoretical predictions which ; use free- and bound-carbon scattering kernels. The scattering kernel for carbon ; bound in graphite is

D. E. Parks; J. R. Beyster; N. F. Wikner

1962-01-01

406

Ioninduced modification of graphite coatings  

Microsoft Academic Search

Burnished graphite powders and physical vapor-deposition (PVD) coatings of layered crystalline materials such as MoSx have often been used as solid lubricants. This letter will report on a novel ion-induced modification of a graphite-powder coating on a silicon surface. Even at very low ion doses, the bombardment results in structural modifications observed as a considerable reduction in x rays reflected

B. K. Gupta; J. Janting; U. M. Jensen; G. N. Pedersen

1992-01-01

407

Boron Clusters Come of Age  

ERIC Educational Resources Information Center

Boron is the only element other than carbon that can build molecules of unlimited size by covalently boding to itself, a property known as catenation. In contrast to the chains and rings favored by carbon, boron arguably adopts a cluster motif that is reflected in the various forms of the pure element and in the huge area of polyhedral borane…

Grimes, Russell N.

2004-01-01

408

Anthraquinonedisulfonate electrochemistry:? a comparison of glassy carbon, hydrogenated glassy carbon, highly oriented pyrolytic graphite, and diamond electrodes.  

PubMed

The electrochemistry of anthraquinone-2,6-disulfonate (2,6-AQDS) at glassy carbon (GC), hydrogenated glassy carbon (HGC), the basal plane of highly oriented pyrolytic graphite (HOPG), and boron-doped diamond was investigated by cyclic voltammetry and chronocoulometry. Quantitative determination of the surface coverage and qualitative assessment of the physisorption strength of 2,6-AQDS adsorption on each of these electrodes were done. The diamond and HGC surfaces are nonpolar and relatively oxygen-free, with the surface carbon atoms terminated by hydrogen. The polar 2,6-AQDS does not adsorb on these surfaces, and the electrolysis proceeds by a diffusion-controlled reaction. Conversely, the GC and HOPG surfaces are polar, with the exposed defect sites terminated by carbon-oxygen functionalities. 2,6-AQDS strongly physisorbs on both of these surfaces at near monolayer or greater coverages, such that the electrolysis proceeds through a surface-confined state. Less than 40% of the initial surface coverage can be removed by rinsing and solution replacement, reflective of strong physisorption. The results show the important role of the surface carbon-oxygen functionalities in promoting strong dipole-dipole and ion-dipole interactions with polar and ionic molecules such as 2,6-AQDS. The results also support the theory that diamond electrodes may be less subject to fouling by polar adsorbates, as compared to GC, leading to improved response stability in electroanalytical measurements. The relationship between the 2,6-AQDS surface coverage, the double-layer capacitance, and the heterogeneous electron-transfer rate constant for Fe(CN)(6)(3)(-)(/4)(-) for these four carbon electrodes is presented. PMID:21644653

Xu, J; Chen, Q; Swain, G M

1998-08-01

409

Band gap effects of hexagonal boron nitride using oxygen plasma  

NASA Astrophysics Data System (ADS)

Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6 eV of pristine h-BN to 4.31 eV when exposed to oxygen plasma for 12 s. The narrowing of band gap causes the reduction in electrical resistance by ˜100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

Sevak Singh, Ram; Yingjie Tay, Roland; Leong Chow, Wai; Hon Tsang, Siu; Mallick, Govind; Tong Teo, Edwin Hang

2014-04-01

410

First-principles investigation of B- and N-doped fluorographene  

NASA Astrophysics Data System (ADS)

The effect of substitutional doping of fluorographene with boron and nitrogen atoms on its electronic and magnetic properties is investigated using first-principles calculations. It is found that boron dopants can be readily incorporated in the fluorographene crystal where they act as shallow acceptors and cause hole doping, but no changes in the magnetic properties are observed. Nitrogen dopants act as deep donors and give rise to a magnetic moment, but the resulting system becomes chemically unstable. These results are opposite to what was found for substitutional doping of graphane, i.e., hydrogenated graphene, in which case B substituents induce magnetism and N dopants do not.

Leenaerts, O.; Sahin, H.; Partoens, B.; Peeters, F. M.

2013-07-01

411

Boron Neutron Capture Therapy for Cancer  

Microsoft Academic Search

Boron neutron capture therapy (BNCT) bring together two components that when kept separate have only minor effects on normal cells. The first component is a stable isotope of boron (boron 10) that can be concentrated in tumor cells. The second is a beam of low-energy neutrons that produces short-range radiation when absorbed, or captured, by the boron. The combination of

Rolf F. Barth; Albert H. Soloway; Ralph G. Fairchild

1990-01-01

412

Ferrix Chloride-Graphite Intercalation Compounds Prepared From Graphite Flouride  

NASA Technical Reports Server (NTRS)

The reaction between graphite fluoride and ferric chloride was observed in the temperature range of 300 to 400 C. The graphite fluorides used for this reaction have an sp(sup 3) electronic structure and are electrical insulators. They can be made by fluorinating either carbon fibers or powder having various degrees of graphitization. Reaction is fast and spontaneous and can occur in the presence of air. The ferric chloride does not have to be predried. The products have an sp(sup 2) electronic structure and are electrical conductors. They contain first-stage FeCl3 intercalated graphite. Some of the products contain FeCl2 (center dot) 2H2O, others contain FeF3, in concentrations that depend on the intercalation condition. The graphite intercalated compounds (GIC) deintercalated slowly in air at room temperature, but deintercalated quickly and completely at 370 C. Deintercalation is accompanied by the disappearance of iron halides and the formation of rust (hematite) distributed unevenly on the fiber surface. When heated to 400 C in pure N2 (99.99 vol%), this new GIC deintercalates without losing its molecular structure. However, when the compounds are exposed to 800 C N2, in a quartz tube, they lost most of their halogen atoms and formed iron oxides (other than hematite), distributed evenly in or on the fiber.

Hung, Ching-Cheh

1995-01-01

413

Ferric chloride graphite intercalation compounds prepared from graphite fluoride  

NASA Technical Reports Server (NTRS)

The reaction between graphite fluoride and ferric chloride was observed in the temperature range of 300 to 400 C. The graphite fluorides used for this reaction have an sp3 electronic structure and are electrical insulators. They can be made by fluorinating either carbon fibers or powder having various degrees of graphitization. Reaction is fast and spontaneous and can occur in the presence of air. The ferric chloride does not have to be predried. The products have an sp2 electronic structure and are electrical conductors. They contain first stage FeCl3 intercalated graphite. Some of the products contain FeCl2*2H2O, others contain FeF3 in concentrations that depend on the intercalation condition. The graphite intercalated compounds (GIC) deintercalated slowly in air at room temperature, but deintercalated quickly and completely at 370 C. Deintercalation is accompanied by the disappearing of iron halides and the formation of rust (hematite) distributed unevenly on the fiber surface. When heated to 400 C in pure N2 (99.99 vol %), this new GIC deintercalates without losing its molecular structure. However, when the compounds are heated to 800 C in quartz tube, they lost most of its halogen atoms and formed iron oxides (other than hematite), distributed evenly in or on the fiber. This iron-oxide-covered fiber may be useful in making carbon-fiber/ceramic-matrix composites with strong bonding at the fiber-ceramic interface.

Hung, Ching-Cheh

1994-01-01

414

Differences in interfacial bond strengths of graphite fiber-epoxy resin composites  

NASA Technical Reports Server (NTRS)

The effect of epoxy-size and degree of cure on the interfacial bonding of an epoxy-amine-graphite fiber composite system is examined. The role of the fiber-resin interface in determining the overall mechanical properties of composites is poorly understood. A good interfacial adhesive bond is required to achieve maximum stress transfer to the fibers in composites, but at the same time some form of energy absorbing interfacial interaction is needed to achieve high fracture toughening. The incompatibility of these two processes makes it important to understand the nature and basic factors involved at the fiber-resin interface as stress is applied. The mechanical properties including interlaminar shear values for graphite fiber-resin composites are low compared to glass and boron-resin composites. These differences have been attributed to poor fiber-matrix adhesion. Graphite fibers are commonly subjected to post-treatments including application of organic sizing in order to improve their compatibility with the resin matrix and to protect the fiber tow from damage during processing and lay-up. In such processes, sized graphite fiber tow is impregnated with epoxy resin and then layed-up i nto the appropriate configuration. Following an extended ambient temperature cure, the graphite-resin composite structure is cured at elevated temperature using a programmed temperature sequence to cure and then cool the product.

Needles, H. L.

1985-01-01

415

Carbon doping of superconducting magnesium diboride  

Microsoft Academic Search

We present details of synthesis optimization and physical properties of nearly single phase carbon doped MgB2 with a nominal stoichiometry of Mg(B0.8C0.2)2 synthesized from magnesium and boron carbide (B4C) as starting materials. The superconducting transition temperature is ?22 K (?17 K lower than in pure MgB2). The temperature dependence of the upper critical field is steeper than in pure MgB2

R. A. Ribeiro; S. L. Bud’ko; C. Petrovic; P. C. Canfield

2003-01-01

416

PtSi/Si LWIR Detectors Made With p+ Doping Spikes  

NASA Technical Reports Server (NTRS)

PtSi/Si Schottky-barrier devices detecting long-wavelength infrared (LWIR) photons demonstrated. Essential feature of one of these devices is p+ "doping spike"; layer of Si about 10 Angstrom thick, located at PtSi/Si interface, and doped with electron acceptors (boron atoms) at concentration between 5 x 10(19) and 2 x 10(20) cm(-3). Doping spikes extend cutoff wavelengths of devices to greater values than otherwise possible.

Lin, True-Lon; Park, Jin S.; George, Thomas; Fathauer, Robert W.; Jones, Eric W.; Maserjian, Joseph

1996-01-01

417

Texture of Graphitized Films Prepared from Polyimide  

NASA Astrophysics Data System (ADS)

A high-temperature heat treatment of polyimide (Kapton) film yielded a highly oriented graphite film, composed of thin graphite layers with 6-7nm in thickness. The hexagonal lattice formation of graphite depends on the heat treated temperature (HTT), and the orientation of the graphite layer preferentially proceeds from the surface of the film. As the results, the orientation of the graphite layer at the surface is superior than inner parts. The graphite films are particularly suitable for constituting optical components for X-ray monochromater.

Nishiki, Naomi; Take, Hiroyoshi; Watanabe, Kazuhiro; Murakami, Mutsuaki; Yoshimura, Susumu; Yoshino, Katsumi

418

Electrochemical and solid-state lithiation of graphitic C3N4  

SciTech Connect

Lithium reacted graphitic carbon nitride (C3N4) was fabricated by electrochemical and solid-state reactions. The data show the addition of Li to C3N4 results in a reaction between the Li and the graphite like C3N species in C3N4. This reaction leads to the formation of Li-CH=NR and Li-N=CR2 species which are likely detrimental to anode properties. From these experiments suitable nitrogen doped carbon structures for anode applications are predicted to need high concentrations of C-N-C terminal bonds and low concentrations of quaternary C3N species to boost electronic conductivity.

Veith, Gabriel M [ORNL; Baggetto, Loic [ORNL; Dudney, Nancy J [ORNL; Adamczyk, Leslie A [ORNL; Guo, Bingkun [ORNL; Brown, Suree [ORNL; Albert, Austin A [ORNL; Humble, James R [University of Tennessee, Knoxville (UTK); Barnes, Craig E. [University of Tennessee, Knoxville (UTK); Bojdys, Michael J [University of Liverpool; Dai, Sheng [ORNL

2013-01-01

419

Sulfonate pseudohalides of boron subphthalocyanine.  

PubMed

The crystal structures of three sulfonate pseudohalide derivatives of boron subphthalocyanine (BsubPc) are described and compared with four structures of three published sulfonate derivatives. Benzenesulfonate boron subphthalocyanine [(benzenesulfonato)(subphthalocyaninato)boron, C(30)H(17)BN(6)O(3)S, (I)] crystallizes in the space group P-1 with Z = 2. The structure contains two centrosymmetric ?-stacking interactions between the concave faces of the isoindoline units in the BsubPc ligands. 3-Nitrobenzenesulfonate boron subphthalocyanine [(3-nitrobenzenesulfonato)(subphthalocyaninato)boron, C(30)H(16)BN(7)O(5)S, (II)] crystallizes in the space group P2(1)/c with Z = 4. The structure contains an intermolecular S-O···? interaction from the sulfonate group to a five-membered N-containing ring of an isoindoline unit on the concave side of a neighbouring BsubPc ligand, at a distance of 3.151 (3) Å. The crystal of methanesulfonate boron subphthalocyanine [(methanesulfonato)(subphthalocyaninato)boron, C(25)H(15)BN(6)O(3)S, (III)] was produced via sublimation and it is not a solvate, in contrast with two previously published structures of the same compound. Compound (III) crystallizes in the space group P2(1)/n with Z = 2, and its structure is similar to that of the more common compound Cl-BsubPc. PMID:23124463

Paton, Andrew S; Lough, Alan J; Bender, Timothy P

2012-11-01

420

Diamond Lattice Defects Caused by P-doping  

NASA Astrophysics Data System (ADS)

Two sets of diamond films prepared using two different techniques were studied using electron paramagnetic resonance (EPR). Phosphorous was the intended dopant in both sets of films. The first set was doped using fast ion implantation while the second set was doped by introducing a P_2O_2/MeOH solution with the CVD gasses. We found that the lattice defect density, characterized by an isotropic single-line EPR spectrum at about g = 2.002, increases with the phosphorous doping level and is much larger for P-doped samples than for boron-doped samples. Since lattice defects have a large effect on diamond electrical and optical properties, EPR characterization proves to be very useful tool for quick, non-perturbing evaluation of diamond quality. We thank SI Diamond Technology and NAWC, China Lake for doped diamond films.

Zhang, Shigang; Zvanut, M. E.

1996-03-01

421

Low temperature coefficient of resistance and high gage factor in beryllium-doped silicon  

NASA Technical Reports Server (NTRS)

The gage factor and resistivity of p-type silicon doped with beryllium was studied as a function of temperature, crystal orientation, and beryllium doping concentration. It was shown that the temperature coefficient of resistance can be varied and reduced to zero near room temperature by varying the beryllium doping level. Similarly, the magnitude of the piezoresistance gage factor for beryllium-doped silicon is slightly larger than for silicon doped with a shallow acceptor impurity such as boron, whereas the temperature coefficient of piezoresistance is about the same for material containing these two dopants. These results are discussed in terms of a model for the piezoresistance of compensated p-type silicon.

Robertson, J. B.; Littlejohn, M. A.

1974-01-01

422

First solar cells on silicon wafers doped using sprayed boric acid  

NASA Astrophysics Data System (ADS)

A new method for boron bulk doping of silicon ribbons is developed. The method is based on the spraying of the ribbons with a boric acid solution and is particularly suited for silicon ribbons that require a zone-melting recrystallization step. To analyse the quality of the material thus obtained, multicrystalline silicon samples doped with this doping process were used as substrate for solar cells and compared with solar cells made on commercial multicrystalline silicon wafers. The values obtained for the diffusion length and the IV curve parameters show that the method of doping with the boric acid solution is suitable to produce p-doped silicon ribbons for solar cell applications.

Silva, J. A.; Brito, Miguel C.; Costa, Ivo; Alves, Jorge Maia; Serra, João; Vallêra, António

2010-11-01

423

Local environment of silicon in cubic boron nitride  

SciTech Connect

Si-doped cubic boron nitride (c-BN) is synthesized at high pressure and high temperature, and the local environment of Si is investigated using X-ray absorption near edge structure (XANES) and first-principles calculations. Si-K XANES indicates that Si in c-BN is surrounded by four nitrogen atoms. According to first-principles calculations, the model for substitutional Si at the B site well reproduces experimental Si-K XANES, and it is energetically more favorable than substitutional Si at the N site. Both the present experimental and theoretical results indicate that Si in c-BN prefers the B site to the N site.

Murata, Hidenobu, E-mail: MURATA.Hidenobu@nims.go.jp; Taniguchi, Takashi [Advanced Key Technologies Division, National Institute for Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305–0044 (Japan); Hishita, Shunichi [Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305–0044 (Japan); Yamamoto, Tomoyuki [Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169–8555 (Japan); Oba, Fumiyasu [Department of Materials Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo, Kyoto 606–8501 (Japan); Tanaka, Isao [Department of Materials Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo, Kyoto 606–8501 (Japan); Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta, Nagoya 456–8587 (Japan)

2013-12-21

424

Development of polyphenylquinoxaline graphite composites.  

NASA Technical Reports Server (NTRS)

The potential of polyphenylquinoxaline (PPQ)/graphite composites to serve as structural material at 316 C (600 F) has been demonstrated using a block copolymer, BICo(1:3), PPQ derivative. Initially, 13 polyphenylquinoxalines were evaluated. From this work, four candidate polymers were selected for preliminary evaluation as matrices for HMS graphite fiber reinforced composites. The preliminary composite evaluation enabled selection of one of the four polymers for advanced composite preparation and testing. Using an experimentally established cure schedule for each of the four polymers, preliminary laminates of 50% resin volume content, prepared without postcure, were tested for flexure strength and modulus, interlaminar shear strength (short beam), tensile strength, and modulus of ambient temperature. The potential of PPQ/graphite laminates to serve as short term structural materials at temperatures up to 371 C (700 F) was demonstrated through weight loss experiments.

Shdo, J. G.; Hoggatt, J. T.

1973-01-01

425

Graphite-Graphene Contact Resistance  

NASA Astrophysics Data System (ADS)

Exploiting the exceptional electronic properties of graphene has been attempted in several applications. However, graphene based applications still lag behind conventional electronics due, in part, to the highly resistive metal-graphene junction. For example, graphene based RF transistors suffer a diminished (fmax) due to highly resistive source-drain contacts (>200 ?- ?m). Reducing this paracistic resistance can yield substantial improvement in device performance for transistors and many other applications. To achieve this, we create an electrical contact to graphene using mesoscopic, exfoliated graphite (10 - 20 nm thick). We fabricate graphite-graphene contacts by transferring pre-defined graphite contacts to graphene on silicon dioxide. Experimental measurement has shown the contact resistance to be <50 ?- ?m, a four-fold improvement over conventional contacts to graphene.

Chari, Tarun; Dean, Cory; Meric, Inanc; Wang, Lei; Shepard, Ken

2013-03-01

426

Graphite fiber reinforced thermoplastic resins  

NASA Technical Reports Server (NTRS)

Mechanical properties of neat resin samples and graphite fiber reinforced samples of thermoplastic resins were characterized with particular emphasis directed to the effects of environmental exposure (humidity, temperature and ultraviolet radiation). Tensile, flexural, interlaminar shear, creep and impact strengths were measured for polysulfone, polyarylsulfone and a state-of-the-art epoxy resin samples. In general, the thermoplastic resins exhibited environmental degradation resistance equal to or superior to the reference epoxy resin. Demonstration of the utility and quality of a graphite/thermoplastic resin system was accomplished by successfully thermoforming a simulated compressor blade and a fan exit guide vane.

Novak, R. C.

1975-01-01

427

Pyrolytic graphite collector development program  

NASA Technical Reports Server (NTRS)

Pyrolytic graphite promises to have significant advantages as a material for multistage depressed collector electrodes. Among these advantages are lighter weight, improved mechanical stiffness under shock and vibration, reduced secondary electron back-streaming for higher efficiency, and reduced outgassing at higher operating temperatures. The essential properties of pyrolytic graphite and the necessary design criteria are discussed. This includes the study of suitable electrode geometries and methods of attachment to other metal and ceramic collector components consistent with typical electrical, thermal, and mechanical requirements.

Wilkins, W. J.

1982-01-01

428

Preferential sliding directions on graphite  

NASA Astrophysics Data System (ADS)

The anisotropy of friction on graphitic surfaces is investigated by a combined friction force microscopy and modeling study. Friction vectors deviate up to 15° from pulling directions. The strongest deviations are found for pulling directions which lie almost along one zigzag direction of the honeycomb structure, the preferred sliding direction on graphite surfaces and epitaxial graphene grown on SiC(0001). Atomic stick-slip events along and across molecular rows determine direction and magnitude of friction. Simulation and modeling reveal the role of temperature and of the two-dimensional character of the surface potential for the friction anisotropy.

Balakrishna, S. G.; de Wijn, Astrid S.; Bennewitz, Roland

2014-06-01

429

Graphite: A Distributed Parallel Simulator for Multicores  

E-print Network

This paper introduces the open-source Graphite distributed parallel multicore simulator infrastructure. Graphite is designed from the ground up for exploration of future multicore processors containing dozens, hundreds, ...

Beckmann, Nathan

2009-11-09

430

Second harmonic generation from exfoliated graphitic films  

Microsoft Academic Search

Optical SHG is observed from graphene, and few-layer graphite on an oxidized (001)Si substrate. The SHG signal from graphene is rotationally isotropic but shows 3-fold anisotropy from bi-layer graphene and graphite.

Jesse Dean; Henry M. van Driel

2010-01-01

431

Purification and Processing of Graphitic Carbons  

E-print Network

Exfoliation of graphite 20 Figure 1.14: Graphenesolubilize graphene sheets. 12, 13 Exfoliation of graphitegraphene is desirable to achieve facile manipulation of the material for device applications although the exfoliation of graphite

Worsley, Kimberly Anne

2010-01-01

432

Composition and method for brazing graphite to graphite  

DOEpatents

The present invention is directed to a brazing material for joining graphite structures that can be used at temperatures up to about 2800.degree. C. The brazing material formed of a paste-like composition of hafnium carbide and uranium oxide with a thermosetting resin. The uranium oxide is converted to uranium dicarbide during the brazing operation and then the hafnium carbide and uranium dicarbide form a liquid phase at a temperature about 2600.degree. C. with the uranium diffusing and vaporizing from the joint area as the temperature is increased to about 2800.degree. C. so as to provide a brazed joint consisting essentially of hafnium carbide. This brazing temperature for hafnium carbide is considerably less than the eutectic temperature of hafnium carbide of about 3150.degree. C. The brazing composition also incorporates the thermosetting resin so that during the brazing operation the graphite structures may be temporarily bonded together by thermosetting the resin so that machining of the structures to final dimensions may be completed prior to the completion of the brazing operation. The resulting brazed joint is chemically and thermally compatible with the graphite structures joined thereby and also provides a joint of sufficient integrity so as to at least correspond with the strength and other properties of the graphite.

Taylor, Albert J. (Ten Mile, TN); Dykes, Norman L. (Oak Ridge, TN)

1984-01-01

433

Graphitic platelets prepared by electrochemical exfoliation of graphite and their application for Li energy storage  

Microsoft Academic Search

Electrochemical exfoliation of graphite in the flame-retarded electrolyte is used for the preparation of novel carbon materials for the first time. Graphitic platelets with submicron thickness are prepared by an electrochemical graphite exfoliation route in the trimethyl phosphate (TMP) based electrolyte. The morphology and size of the graphitic platelets can be controlled by adjusting the reaction temperature and current density.

H. F. Xiang; J. Y. Shi; X. Y. Feng; X. W. Ge; H. H. Wang; C. H. Chen

2011-01-01

434

Reducing Boron Toxicity by Microbial Sequestration  

SciTech Connect

While electricity is a clean source of energy, methods of electricity-production, such as the use of coal-fired power plants, often result in significant environmental damage. Coal-fired electrical power plants produce air pollution, while contaminating ground water and soils by build-up of boron, which enters surrounding areas through leachate. Increasingly high levels of boron in soils eventually overcome boron tolerance levels in plants and trees, resulting in toxicity. Formation of insoluble boron precipitates, mediated by mineral-precipitating bacteria, may sequester boron into more stable forms that are less available and toxic to vegetation. Results have provided evidence of microbially-facilitated sequestration of boron into insoluble mineral precipitates. Analyses of water samples taken from ponds with high