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Sample records for boron 14

  1. Boron

    USDA-ARS?s Scientific Manuscript database

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

  2. Boron

    MedlinePlus

    ... body handles other minerals such as magnesium and phosphorus. It also seems to increase estrogen levels in ... happens in men.PhosphorusSupplemental boron might reduce blood phosphorus levels in some people.

  3. Transition metal-boron complexes BnM: from bowls (n = 8-14) to tires (n = 14).

    PubMed

    Li, Si-Dian; Miao, Chang-Qing; Guo, Jin-Chang; Ren, Guang-Ming

    2006-11-30

    Transition metal-boron complexes BnM have been predicted at density functional theory level to be molecular bowls (n = 8-14) hosting a transition metal atom (M) inside or molecular tires (n = 14) centered with a transition metal atom. Small Bn clusters prove to be effective inorganic ligands to all the VB-VIIIB transition metal elements in the periodic table. Density functional evidences obtained in this work strongly suggest that bowl-shaped fullerene analogues of Bn units exist in small BnM complexes and the bowl-to-tire structural transition occur to the first-row transition metal complexes BnM (M = Mn, Fe, Co) at n = 14, a size obviously smaller than n = 20 where the 2D-3D structural transition occurs to bare Bn. The half-sandwich-type B12Cr (C3v), full sandwich-type (B12)2Cr (D3d), bowl-shaped B14Fe (C2), and tire-shaped B14Fe (D7d) and B14Fe- (C7v) are the most interesting prototypes to be targeted in future experiments. These BnM complexes may serve as building blocks to form extended boron-rich BnMm tubes or cages (m > or = 2) or as structural units to be placed inside carbon nanotubes with suitable diameters. Copyright 2006 Wiley Periodicals, Inc.

  4. Three-chain B{sub 6n+14} cages as possible precursors for the syntheses of boron fullerenes

    SciTech Connect

    Lu, Haigang Li, Si-Dian

    2013-12-14

    Using the first principle methods, we proposed a series of three-chain boron cages B{sub 6n+14} (n = 1–12) which are mainly built by fusing three boron semi-double-rings. Their simple geometric structures (approximate D{sub 3} or C{sub 3} symmetry) facilitate their bottom-up syntheses from the hexagonal B{sub 7} and the double-chain boron clusters, such as B{sub 2}, B{sub 4}, B{sub 6}, B{sub 8}H{sub 2}, B{sub 10}H{sub 2}, B{sub 12}H{sub 2}, and the double ring B{sub 20}. The spherical shapes of these three-chain boron cages show that they could be taken as the possible precursors to further synthesize the boron fullerenes, such as B{sub 80}. Therefore, these three-chain boron cages provide a possible synthesis pathway of the boron fullerenes from the experimentally synthesized small planar boron clusters.

  5. Structure of boron clusters revisited, Bn with n = 14-20

    NASA Astrophysics Data System (ADS)

    Tai, Truong Ba; Tam, Nguyen Minh; Nguyen, Minh Tho

    2012-03-01

    We reinvestigate the structures of neutral boron clusters Bn, with n = 14-20. G3B3 calculations confirm that a transition between 2D and 3D shape occurs at B20, which has a tubular form. In disagreement with Boustani et al. (Phys. Rev. B, 83 (2011) 193405), we find a planar B19 cluster. Standard heats of formation are obtained and used to evaluate the clusters stability. The average binding energy tends to increase with increasing size toward a limit. Higher stability is found B14, B16, B18 and B20. All Bn have negative NICS-values. The bonding nature and electron delocalization of B20 are re-examined using CMO and LOL.

  6. Comet assay study of DNA damage and repair of tumour cells following boron neutron capture irradiation with fast d(14) + Be neutrons.

    PubMed

    Pöller, F; Bauch, T; Sauerwein, W; Böcker, W; Wittig, A; Streffer, C

    1996-11-01

    We compared the amount of radiation-induced DNA damage and the extent of DNA repair in human melanoma cells (MeWo) using the 'comet assay' after neutron, boron neutron capture and X-irradiation. Using a colony-forming assay it was shown earlier that lethal effects in tumour cells treated with fast neutrons may be increased by the neutron capture reaction 10B(n, alpha)7Li. The effectiveness of boron neutron capture in killing tumour cells depends on the number of 10B atoms delivered to the tumour, the subcellular distribution of 10B and the thermal neutron fluence at the side of the tumour. Using the 'comet assay' the DNA damage of fast neutrons (mean energy 5.8 MeV) was shown to be significantly greater than for the same absorbed dose of X-rays. The presence of 600 ppm 10B (boric acid H5 10BO3) in the cell medium during irradiation with d(14) + Be neutrons in a phantom enhances the DNA damage by 20% compared with neutron irradiation alone. After DNA damage induction by neutrons and neutron capture of boron, the DNA repair capacity of the MeWo cells is significantly reduced in comparison with X-irradiation resulting in proportionally more residual DNA damage after 180 min of repair time.

  7. (Z)-1,4-diamino-2-butene as a vector of boron, fluorine, or iodine for cancer therapy and imaging: synthesis and biological evaluation.

    PubMed

    Martin, Bénédicte; Possémé, Françoise; Le Barbier, Caroline; Carreaux, François; Carboni, Bertrand; Seiler, Nikolaus; Moulinoux, Jacques-Philippe; Delcros, Jean-Guy

    2002-09-01

    Polyamine vectors are attractive for tumor targeting. We envisaged (Z)-1,4-diamino-2-butene (Z-DAB), an unsaturated analogue of putrescine as vector of (10)B, (18)F and (131)I for boron neutron capture therapy (BNCT), and tumor imaging by positron emission tomography or scintigraphy respectively. In the present work, the synthesis and characterization of new derivatives of Z-DAB were reported. Z-DAB was actively transported in cells via the polyamine transport system and converted into the spermidine analogue.(E)-2-iodo-1,4-diamino-2-butene (E-I-DAB) was not taken up by the polyamine transport system and may not be suitable for tumor imaging. In contrast, (Z)-2-[4-(5,5-dimethyl-dioxaborinan-2-yl)phenyl]methyl-1,4-diamino-2-butene (Z-4-Bbz-DAB) was a substrate of the transport system and allowed significant boron accumulation in 3LL cells. Its potential in BNCT will be evaluated.

  8. Boron cosmochemistry

    NASA Technical Reports Server (NTRS)

    Curtis, D. B.; Gladney, E. S.

    1985-01-01

    The abundances of boron, silicon, sulfur, and sodium were determined in 50 pieces of 28 chondritic meteorites. Boron abundances are found to define compositionally distinct domains within type C2M carbonaceous chondrites and petrologic type 5 and 6 ordinary chondrites. These domains may manifest the redistribution of boron within meteorites in response to low-temperature hydrous processes in C2M chondrites and high-temperature metamorphic processes in high petrologic type ordinary chondrites. Assuming that the redistribution was limited to regions comparable in size to the mass of the available meteorites, the boron abundance in unaltered material is determined. The depletion factors for boron in chondritic subgroups correlate with those for sulfur in the same subgroups. This correlation indicates that boron, like sulfur, is a moderately volatile element with a condensation temperature between 400 and 900 K.

  9. Boron supercapacitors

    DOE PAGES

    Zhan, Cheng; Zhang, Pengfei; Dai, Sheng; ...

    2016-11-16

    Supercapacitors based on the electric double-layer mechanism use porous carbons or graphene as electrodes. To move beyond this paradigm, we propose boron supercapacitors to leverage two-dimensional (2D) boron sheets’ metallicity and low weight. Six 2D boron sheets from both previous theoretical design and experimental growth are chosen as test electrodes. By applying joint density functional theory (JDFT) to the electrode–electrolyte system, we examine how the 2D boron sheets charge up against applied potential. JDFT predicts that these 2D boron sheets exhibit specific capacitance on the order of 400 F/g, about four times that of graphene. As a result, our workmore » suggests that 2D boron sheets are promising electrodes for supercapacitor applications.« less

  10. Boron supercapacitors

    SciTech Connect

    Zhan, Cheng; Zhang, Pengfei; Dai, Sheng; Jiang, De -en

    2016-11-16

    Supercapacitors based on the electric double-layer mechanism use porous carbons or graphene as electrodes. To move beyond this paradigm, we propose boron supercapacitors to leverage two-dimensional (2D) boron sheets’ metallicity and low weight. Six 2D boron sheets from both previous theoretical design and experimental growth are chosen as test electrodes. By applying joint density functional theory (JDFT) to the electrode–electrolyte system, we examine how the 2D boron sheets charge up against applied potential. JDFT predicts that these 2D boron sheets exhibit specific capacitance on the order of 400 F/g, about four times that of graphene. As a result, our work suggests that 2D boron sheets are promising electrodes for supercapacitor applications.

  11. Boron reclamation

    SciTech Connect

    Smith, R.M.

    1980-07-01

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

  12. Clinical evaluation of neodymium-iron-boron (Ne2Fe14B) rare earth magnets in the treatment of mid line diastemas.

    PubMed

    Prasad, Mandava; Manoj-Kumar, Mitta; Gowri-Sankar, Singaraju; Chaitanya, Nellore; Vivek-Reddy, Ganugapanta; Venkatesh, Nettam

    2016-04-01

    To evaluate the closure of midline diastema using the Neodymium-Iron-Boron magnets and to compare the treatment duration of midline diastemas with the use of magnets compared to regular orthodontic treatment. Thirty patients with age group 12 to 30 years with the midline diastema ranging from 0.5 to 3mm were selected. These patients were divided into two groups. Diastema closure in one group was accomplished by conventional method, in other group was done with Ne2Fe14B magnets. These magnets were fitted to the labial surfaces of the maxillary central incisors such a way that the opposite poles of the magnets face each other. At each appointment, study models and radiographs were taken for study subjects and the midline diastema was measured using digital vernier calipers on the study models obtained. Descriptive statistics carried out using Paired t-test. Subjects treated with Ne2Fe14B magnets showed a significant difference compared to fixed orthodontic appliance subjects with respect to time of closure, rate of space closure and incisal inclination. Significant difference between 2 groups with reduction of 64.6 days in time to diastema closure in subjects treated with Ne2Fe14B magnets (P<0.05). Ne2Fe14B magnets more efficient in complete closure of mid line diastema in less duration of time. Midline diastema, Ne2Fe14B magnets, rare earth magnets, space closure.

  13. Clinical evaluation of neodymium-iron-boron (Ne2Fe14B) rare earth magnets in the treatment of mid line diastemas

    PubMed Central

    Manoj-Kumar, Mitta; Gowri-Sankar, Singaraju; Chaitanya, Nellore; Vivek-Reddy, Ganugapanta; Venkatesh, Nettam

    2016-01-01

    Background To evaluate the closure of midline diastema using the Neodymium-Iron-Boron magnets and to compare the treatment duration of midline diastemas with the use of magnets compared to regular orthodontic treatment. Material and Methods Thirty patients with age group 12 to 30 years with the midline diastema ranging from 0.5 to 3mm were selected. These patients were divided into two groups. Diastema closure in one group was accomplished by conventional method, in other group was done with Ne2Fe14B magnets. These magnets were fitted to the labial surfaces of the maxillary central incisors such a way that the opposite poles of the magnets face each other. At each appointment, study models and radiographs were taken for study subjects and the midline diastema was measured using digital vernier calipers on the study models obtained. Descriptive statistics carried out using Paired t-test. Results Subjects treated with Ne2Fe14B magnets showed a significant difference compared to fixed orthodontic appliance subjects with respect to time of closure, rate of space closure and incisal inclination. Significant difference between 2 groups with reduction of 64.6 days in time to diastema closure in subjects treated with Ne2Fe14B magnets (P<0.05). Conclusions Ne2Fe14B magnets more efficient in complete closure of mid line diastema in less duration of time. Key words:Midline diastema, Ne2Fe14B magnets, rare earth magnets, space closure. PMID:27034757

  14. Electroextraction of boron from boron carbide scrap

    SciTech Connect

    Jain, Ashish; Anthonysamy, S.; Ghosh, C.; Ravindran, T.R.; Divakar, R.; Mohandas, E.

    2013-10-15

    Studies were carried out to extract elemental boron from boron carbide scrap. The physicochemical nature of boron obtained through this process was examined by characterizing its chemical purity, specific surface area, size distribution of particles and X-ray crystallite size. The microstructural characteristics of the extracted boron powder were analyzed by using scanning electron microscopy and transmission electron microscopy. Raman spectroscopic examination of boron powder was also carried out to determine its crystalline form. Oxygen and carbon were found to be the major impurities in boron. Boron powder of purity ∼ 92 wt. % could be produced by the electroextraction process developed in this study. Optimized method could be used for the recovery of enriched boron ({sup 10}B > 20 at. %) from boron carbide scrap generated during the production of boron carbide. - Highlights: • Recovery of {sup 10}B from nuclear grade boron carbide scrap • Development of process flow sheet • Physicochemical characterization of electroextracted boron • Microscopic examination of electroextracted boron.

  15. Boron behavior induced lamellar structure and anisotropic magnetic properties of Nd2Fe14B during HDDR process

    NASA Astrophysics Data System (ADS)

    Choi, Moonhee; Cho, Seungchan; Jo, Ilguk; Song, Yeonghwan; Kim, Chiho; Yu, Jihun; Kim, Yangdo

    2017-08-01

    The anisotropy of the Nd2Fe14B powder is originated during the creation of a fine Fe2B lamellar structure in the disproportionation step. The aspect ratio (A/R) of Fe2B structure increased from 3.37 ± 1.5 to 6.69 ± 3.2 during phase decomposition for 0 60 min at 820 ° C (P H2 = 10 kPa). The Fe2B having high A/R ratio recombined Nd2Fe14B, which is close to the single domain, and the magnetic properties are also improved with increasing A/R ratio.

  16. Direct current sputtering of boron from boron/boron mixtures

    DOEpatents

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

    1994-12-13

    A method for coating a substrate with boron by sputtering includes lowering the electrical resistance of a boron-containing rod to allow electrical conduction in the rod; placing the boron-containing rod inside a vacuum chamber containing substrate material to be coated; applying an electrical potential between the boron target material and the vacuum chamber; countering a current avalanche that commences when the conduction heating rate exceeds the cooling rate, and until a steady equilibrium heating current is reached; and, coating the substrate material with boron by sputtering from the boron-containing rod. 2 figures.

  17. ET-14OPTIMISATION OF BORONOPHENYLALANINE (BPA) DELIVERY AND LAT1 EXPRESSION FOR THE CLINICAL APPLICATION OF BORON NEUTRON CAPTURE THERAPY (BNCT) IN GLIOBLASTOMA

    PubMed Central

    Cruickshank, Garth; Detta, Allah; Green, Stuart; Lockyer, Nick; Ngoga, Desire; Ghani, Zahir; Phoenix, Ben

    2014-01-01

    BNCT is a biologically targeted radiotherapy where preferential boron uptake interacts with a neutron beam in cancerous cells causing irreparable alpha DNA damage. This requires the delivery of at least 30 parts per million (ppm) of 10B into tumour tissue and <10ppm 10B in healthy tissue. Renewed interest arises from the advent of ‘accelerator’ technology and the recognition of specific uptake transporter in tumour cells. We report an optimising pharmacokinetic and tissue uptake study in glioblastoma patients to determine the route of delivering a new formulation of (p-boronophenylalanine, BPA), its pharmacokinetics, toxicity profile, and LAT1 dependent cellular uptake for a clinical trial. Using inductively-coupled plasma mass spectrometry (ICP-MS), secondary ion mass spectrometry (SIMS) and immunohistochemistry (IHC), boron was measured in blood, urine, cerebrospinal fluid (CSF), extracellular fluid (ECFmicrodialysis), and tissue prior to, during and post BPA infusions in newly-diagnosed patients (n = 10). Tumour and brain-around tumour (BAT) tissue were sampled at 2.5h and 3.5h post-infusion. Tumour and BAT, IHC expression levels of the BPA transporter L-amino acid transporter 1 (LAT-1) were recorded, and cellular boron levels, estimated in SIMS images.LAT1 dependent BPA uptake was also determined. There was no toxicity with BPA given at 375mg/kg as a 2h intravenous or intracarotid infusion with or without pre-infusion mannitol-induced BBB disruption. The Pk profile indicates highest plasma-to-brain concentration gradient from intracarotid infusion and BBB manipulation,with high boron concentrations in the brain compartment. SIMS boron ratio in tumour vs BAT was 0.96 intravenous,1.85 IV + mannitol BBB-D and 2.40 intracarotid cohorts, confirming improved delivery of boron. Tumour and BAT uptake varied, but sustained uptake in BAT (>30ppm boron) indicates potential BNCT targeting after surgery. Tumour boron uptake is governed by LAT-1 behaviour rather than BBB

  18. Crystalline boron nitride aerogels

    DOEpatents

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

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  19. Boron Nitride Nanotubes

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  20. Boron nitride nanotubes

    DOEpatents

    Smith, Michael W [Newport News, VA; Jordan, Kevin [Newport News, VA; Park, Cheol [Yorktown, VA

    2012-06-06

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

  1. Boron nitride composites

    DOEpatents

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

    2017-02-21

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

  2. Boron Derivatives of 3-Methylpyrazole.

    DTIC Science & Technology

    1984-12-01

    AD-A14$ 988 BORON DERIVRTIYES OF 3 -IETHYLPYRRZOLECU) KENTUCKY UNIV i/i LEXINGTON DEPT OF CHEMISTRY K NIEDENZU ET AL. DEC 84 UK/DC/TR- 5 N8@814-83-K...REPORT DOCUMENTATION PAGE BEFORE CO.!?OVE~r;G FORM UK/DC/TR- 5 I - -_ E. ’and Subtitle) OF 21-P R & PZRIOD COVER=~ BORON DERIVATIVES OF 3 -METHYLPYRAZOLE...pathways for the latter process. In addition, the compounds 4 ,4 ,8,8-tetrabromo- and 4 ,4 ,8 ,8-tetrakis( 3 -methylpyrazole-l-yl)-l, 5 (7)-dimethyl

  3. Boronated mesophase pitch coke for lithium insertion

    NASA Astrophysics Data System (ADS)

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

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

  4. Methods of forming boron nitride

    DOEpatents

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

    2015-03-03

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

  5. Boron-enhanced diffusion of boron from ultralow-energy boron implantation

    SciTech Connect

    Agarwal, A.; Eaglesham, D.J.; Gossmann, H.J.; Pelaz, L.; Herner, S.B.; Jacobson, D.C.; Haynes, T.E.; Erokhin, Y.E.

    1998-05-03

    The authors have investigated the diffusion enhancement mechanism of BED (boron enhanced diffusion), wherein the boron diffusivity is enhanced three to four times over the equilibrium diffusivity at 1,050 C in the proximity of a silicon layer containing a high boron concentration. It is shown that BED is associated with the formation of a fine-grain polycrystalline silicon boride phase within an initially amorphous Si layer having a high B concentration. For 0.5 keV B{sup +}, the threshold implantation dose which leads to BED lies between 3 {times} 10{sup 14} and of 1 {times} 10{sup 15}/cm{sup {minus}2}. Formation of the shallowest possible junctions by 0.5 keV B{sup +} requires that the implant dose be kept lower than this threshold.

  6. Cosmic abundance of boron.

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.; Colgate, S. A.; Grossman, L.

    1973-01-01

    All abundances are expressed relative to a million atoms of Si. An average abundance of boron in ordinary chondrites is 6.2. The boron abundance in meteorites is highly variable. It has been found that the abundances in carbonaceous chondrites are very much higher than those in ordinary chondrites. The condensation of boron and beryllium from a cooling, low-pressure gas of solar composition is discussed together with the occurrence of boron in the interstellar medium, questions of element abundances in the sun, problems of boron production by cosmic rays, and boron production from supernovae.

  7. High intrinsic coercivities in iron-rare earth-carbon-boron alloys through the carbide or boro-carbide Fe14R2X (X=BxC1-x)

    NASA Astrophysics Data System (ADS)

    Liu, N. C.; Stadelmaier, H. H.; Schneider, G.

    1987-04-01

    In the phase Fe14R2X, where R is a lanthanide and X is either boron or carbon, or a mixture of the two, the extent of stability of the carbides and their miscibility with the borides is traced for the lighter rare-earth metals. Like the borides, the carbides are magnetically hard, but unlike them, they do not normally crystallize from the melt, and this property is exploited to produce intrinsic coercivities above 12 kOe in cast materials without the added special processing step of sintering or melt spinning. The high coercivity is related to a cellular microstructure of Fe14R2X in which the cell size is approximately 1 μm. The cell structure, which originates in a peritectoidlike transformation from primary Fe17R2, is quite stable and does not change during prolonged annealing. The coercivity is sensitive to variations in composition.

  8. Boron nitride converted carbon fiber

    SciTech Connect

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

    2016-04-05

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

  9. Effects of chronic boron exposure on semen profile.

    PubMed

    Korkmaz, Mehmet; Yenigün, Mehmet; Bakırdere, Sezgin; Ataman, Osman Yavuz; Keskin, Sıddık; Müezzinoğlu, Talha; Lekili, Murat

    2011-11-01

    The possible changes in semen quality were studied in men living in a boron mining area. The subjects in the boron group had exposure to boron at an average level of 6.5 mg/day, as determined by urinary analysis. The results obtained by the boron group were compared to those obtained for the control group whose subjects were living in the same geographical area but away from the boron region; average exposure level was 1.4 mg/day for this group. The semen samples were analyzed according to the recommendations of the World Health Organization. Boron levels were established in the water samples obtained from various locations in the study region. In the boron mining fields where the subjects in the boron group live, water samples contained boron in the range of 1.4-6.5 mg/L, while the values were <0.01 mg/L for the water samples obtained from the region where the subjects of the control group reside. No negative effects were found in the sperm samples obtained from the subjects of the boron group.

  10. Electronic structure of the boron fullerene B14 and its silicon derivatives B13Si(+), B13Si(-) and B12Si2: a rationalization using a cylinder model.

    PubMed

    Van Duong, Long; Nguyen, Minh Tho

    2016-06-29

    Geometric and electronic structures of the boron cluster B14 and its silicon derivatives B13Si(+), B13Si(-), and B12Si2 were determined using DFT calculations (TPSSh/6-311+G(d)). The B12Si2 fullerene, which is formed by substituting two B atoms at two apex positions of the B14 fullerene by two Si atoms, was also found as the global minimum structure. We demonstrated that the electronic structure and orbital configuration of these small fullerenes can be predicted by the wavefunctions of a particle on a cylinder. The early appearance of high angular node MOs in B14 and B12Si2 can be understood by this simple model. Replacement of one B atom at a top position of B14 by one Si atom, followed by the addition or removal of one electron does not lead to a global minimum fullerene structure for the anion B13Si(-) and cation B13Si(+). The early appearance of the 5σ1 orbital in B13Si(+) causes a lower stability for the fullerene-type structure.

  11. Properties of boron/boron-nitride multilayers

    SciTech Connect

    Jankowski, A.F.; Wall, M.A.; Hayes, J.P.; Alexander, K.B.

    1996-06-01

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

  12. Fabrication of boron articles

    DOEpatents

    Benton, Samuel T.

    1976-01-01

    This invention is directed to the fabrication of boron articles by a powder metallurgical method wherein the articles are of a density close to the theoretical density of boron and are essentially crackfree. The method comprises the steps of admixing 1 to 10 weight percent carbon powder with amorphous boron powder, cold pressing the mixture and then hot pressing the cold pressed compact into the desired article. The addition of the carbon to the mixture provides a pressing aid for inhibiting the cracking of the hot pressed article and is of a concentration less than that which would cause the articles to possess significant concentrations of boron carbide.

  13. The structure of boron in boron fibres

    NASA Technical Reports Server (NTRS)

    Bhardwaj, J.; Krawitz, A. D.

    1983-01-01

    The structure of noncrystalline, chemically vapour-deposited boron fibres was investigated by computer modelling the experimentally obtained X-ray diffraction patterns. The diffraction patterns from the models were computed using the Debye scattering equation. The modelling was done utilizing the minimum nearest-neighbour distance, the density of the model, and the broadening and relative intensity of the various peaks as boundary conditions. The results suggest that the fibres consist of a continuous network of randomly oriented regions of local atomic order, about 2 nm in diameter, containing boron atoms arranged in icosahedra. Approximately half of these regions have a tetragonal structure and the remaining half a distorted rhombohedral structure. The model also indicates the presence of many partial icosahedra and loose atoms not associated with any icosahedra. The partial icosahedra and loose atoms indicated in the present model are in agreement with the relaxing sub-units which have been suggested to explain the anelastic behavior of fibre boron and the loosely bound boron atoms which have been postulated to explain the strengthening mechanism in boron fibres during thermal treatment.

  14. Magnetron sputtered boron films

    DOEpatents

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

    1998-06-16

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

  15. Magnetron sputtered boron films

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1998-01-01

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

  16. Microwave sintering of boron carbide

    DOEpatents

    Blake, R.D.; Katz, J.D.; Petrovic, J.J.; Sheinberg, H.

    1988-06-10

    A method for forming boron carbide into a particular shape and densifying the green boron carbide shape. Boron carbide in powder form is pressed into a green shape and then sintered, using a microwave oven, to obtain a dense boron carbide body. Densities of greater than 95% of theoretical density have been obtained. 1 tab.

  17. The investigation of physical conditions of boron uptake region in proton boron fusion therapy (PBFT)

    NASA Astrophysics Data System (ADS)

    Jung, Joo-Young; Yoon, Do-Kun; Lee, Heui Chang; Lu, Bo; Suh, Tae Suk

    2016-09-01

    We conducted a quantitative study to identify the effectiveness of proton boron fusion therapy (PBFT). Four simulation scenarios were designed to investigate the escalation in total dose with the proton boron reaction using a Monte Carlo n-particle extended (MCNPX 2.6.0) simulation. The peak integrated dose was obtained for three different physical conditions (i.e., boron uptake region (BUR) thickness, BUR location, and boron concentration) with differing proton beam energy (60-90 MeV). We found that the peak integrated dose was increased by up to 96.62% compared to the pristine proton Bragg-peak. For the synergetic effect to take place with 60-70 MeV proton beam, the BUR had to be at least 0.3 cm thick while spanning the Bragg-peak. Similarly to the thickness, the BUR location needed to be within 0.3 cm from the Bragg-peak when the thickness was maintained at 0.9 cm. An effective proton boron reaction required the boron concentration to be equal to or greater than 14.4 mg/g. These results demonstrate the impact of various physical and beam conditions of the PBFT, which are critical environmental factors for the treatment planning. We envision that this study will advance our understanding of the PBFT, which can be an invaluable treatment method for maximizing the potential of proton therapy.

  18. Boron and the kidney.

    PubMed

    Pahl, Madeleine V; Culver, B Dwight; Vaziri, Nosratola D

    2005-10-01

    Boron, the fifth element in the periodic table, is ubiquitous in nature. It is present in food and in surface and ocean waters, and is frequently used in industrial, cosmetic, and medical settings. Exposure to boron and related compounds has been recently implicated as a potential cause of chronic kidney disease in Southeast Asia. This observation prompted the present review of the published data on the effects of acute and chronic exposure to boron on renal function and structure in human beings and in experimental animals.

  19. Innovative method for boron extraction from iron ore containing boron

    NASA Astrophysics Data System (ADS)

    Wang, Guang; Wang, Jing-song; Yu, Xin-yun; Shen, Ying-feng; Zuo, Hai-bin; Xue, Qing-guo

    2016-03-01

    A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-rich slag, and elucidation of the boron extraction behavior of boron-rich slag by acid leaching, were performed at the laboratory. The results indicated that 95.7% of the total boron could be enriched into the slag phase, thereby forming a boron-rich slag during the iron and slag melting separation process. Suanite and kotoite were observed to be the boron-containing crystalline phases, and the boron extraction properties of the boron-rich slag depended on the amounts and grain sizes of these minerals. When the boron-rich slag was slowly cooled to 1100°C, the slag crystallized well and the efficiency of extraction of boron (EEB) of the slag was the highest observed in the present study. The boron extraction property of the slow-cooled boron-rich slag obtained in this study was much better than that of szaibelyite ore under the conditions of 80% of theoretical sulfuric acid amount, leaching time of 30 min, leaching temperature of 40°C, and liquid-to-solid ratio of 8 mL/g.

  20. Fluorine-enhanced boron diffusion in germanium-preamorphized silicon

    SciTech Connect

    Jacques, J.M.; Jones, K.S.; Robertson, L.S.; Li-Fatou, A.; Hazelton, C.M.; Napolitani, E.; Rubin, L.M.

    2005-10-01

    Silicon wafers were preamorphized with 60 keV Ge{sup +} or 70 keV Si{sup +} at a dose of 1x10{sup 15} atoms/cm{sup 2}. F{sup +} was then implanted into some samples at 6 keV at doses ranging from 1x10{sup 14} to 5x10{sup 15} atoms/cm{sup 2}, followed by {sup 11}B{sup +} implants at 500 eV, 1x10{sup 15} atoms/cm{sup 2}. Secondary-ion-mass spectrometry confirmed that fluorine enhances boron motion in germanium-preamorphized materials in the absence of annealing. The magnitude of boron diffusion scales with increasing fluorine dose. Boron motion in as-implanted samples occurs when fluorine is concentrated above 1x10{sup 20} atoms/cm{sup 3}. Boron atoms are mobile in as-implanted, amorphous material at concentrations up to 1x10{sup 19} atoms/cm{sup 3}. Fluorine directly influences boron motion only prior to activation annealing. During the solid-phase epitaxial regrowth process, fluorine does not directly influence boron motion, it simply alters the recrystallization rate of the silicon substrate. Boron atoms can diffuse in germanium-amorphized silicon during recrystallization at elevated temperatures without the assistance of additional dopants. Mobile boron concentrations up to 1x10{sup 20} atoms/cm{sup 3} are observed during annealing of germanium-preamorphized wafers.

  1. Direct current sputtering of boron from boron/coron mixtures

    DOEpatents

    Timberlake, John R.; Manos, Dennis; Nartowitz, Ed

    1994-01-01

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

  2. Boron-Based Drug Design.

    PubMed

    Ban, Hyun Seung; Nakamura, Hiroyuki

    2015-06-01

    The use of the element boron, which is not generally observed in a living body, possesses a high potential for the discovery of new biological activity in pharmaceutical drug design. In this account, we describe our recent developments in boron-based drug design, including boronic acid containing protein tyrosine kinase inhibitors, proteasome inhibitors, and tubulin polymerization inhibitors, and ortho-carborane-containing proteasome activators, hypoxia-inducible factor 1 inhibitors, and topoisomerase inhibitors. Furthermore, we applied a closo-dodecaborate as a water-soluble moiety as well as a boron-10 source for the design of boron carriers in boron neutron capture therapy, such as boronated porphyrins and boron lipids for a liposomal boron delivery system.

  3. Boron nitride composites

    DOEpatents

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

    2016-02-16

    According to one embodiment, a composite product includes hexagonal boron nitride (hBN), and a plurality of cubic boron nitride (cBN) particles, wherein the plurality of cBN particles are dispersed in a matrix of the hBN. According to another embodiment, a composite product includes a plurality of cBN particles, and one or more borate-containing binders.

  4. Zeolitic Boron Imidazolate Frameworks**

    PubMed Central

    Zhang, Jian; Wu, Tao; Zhou, Cong; Chen, Shumei; Feng, Pingyun; Bu, Xianhui

    2009-01-01

    From porous AlPO4 to porous BIFs Reported here are a family of crystalline materials based on boron imidazolate frameworks (BIFs). It is demonstrated that the synthetic method, which is based on the crosslinking of various pre-synthesized boron imidazolates by monovalent cations (Li+ and Cu+), is capable of generating a large variety of open frameworks ranging from the 4-connected zeolitic sodalite type to the 3-connected chiral (10,3)-a type. PMID:19241428

  5. Characterization of a boron carbide-based polymer neutron sensor

    NASA Astrophysics Data System (ADS)

    Tan, Chuting; James, Robinson; Dong, Bin; Driver, M. Sky; Kelber, Jeffry A.; Downing, Greg; Cao, Lei R.

    2015-12-01

    Boron is used widely in thin-film solid-state devices for neutron detection. The film thickness and boron concentration are important parameters that relate to a device's detection efficiency and capacitance. Neutron depth profiling was used to determine the film thicknesses and boron-concentration profiles of boron carbide-based polymers grown by plasma enhanced chemical vapor deposition (PECVD) of ortho-carborane (1,2-B10C2H12), resulting in a pure boron carbide film, or of meta-carborane (1,7-B10C2H12) and pyridine (C5H5N), resulting in a pyridine composite film, or of pyrimidine (C4H4N2) resulting in a pure pyrimidine film. The pure boron carbide film had a uniform surface appearance and a constant thickness of 250 nm, whereas the thickness of the composite film was 250-350 nm, measured at three different locations. In the meta-carborane and pyridine composite film the boron concentration was found to increase with depth, which correlated with X-ray photoelectron spectroscopy (XPS)-derived atomic ratios. A proton peak from 14N (n,p)14C reaction was observed in the pure pyrimidine film, indicating an additional neutron sensitivity to nonthermal neutrons from the N atoms in the pyrimidine.

  6. Boron neutron capture therapy for malignant melanoma: An experimental approach

    SciTech Connect

    Larsson, B.S.; Larsson, B.; Roberto, A. )

    1989-07-01

    Previous studies have shown that some thioamides, e.g., thiouracil, are incorporated as false precursors into melanin during its synthesis. If boronated analogs of the thioamides share this property, the melanin of melanotic melanomas offers a possibility for specific tumoural uptake and retention of boron as a basis for neutron capture therapy. We report on the synthesis of boronated 1H-1,2,4-triazole-3-thiol (B-TZT), boronated 5-carboxy-2-thiouracil (B-CTU), and boronated 5-diethylaminomethyl-2-thiouracil (B-DEAMTU) and the localization of these substances in melanotic melanomas transplanted to mice. The distribution in the mice was studied by boron neutron capture radiography. B-TZT and B-CTU showed the highest tumour:normal tissue concentration ratios, with tumour:liver ratios of about 4 and tumour:muscle ratios of about 14; B-DEAMTU showed corresponding ratios of 1.4 and 5, respectively. The absolute concentration of boron in the tumours, however, was more than three times higher in the mice injected with B-TZT, compared with B-CTU. The results suggest that B-TZT may be the most promising compound of the three tested with regard to possible therapy of melanotic melanomas.

  7. Boron-based nanostructures: Synthesis, functionalization, and characterization

    NASA Astrophysics Data System (ADS)

    Bedasso, Eyrusalam Kifyalew

    Boron-based nanostructures have not been explored in detail; however, these structures have the potential to revolutionize many fields including electronics and biomedicine. The research discussed in this dissertation focuses on synthesis, functionalization, and characterization of boron-based zero-dimensional nanostructures (core/shell and nanoparticles) and one-dimensional nanostructures (nanorods). The first project investigates the synthesis and functionalization of boron-based core/shell nanoparticles. Two boron-containing core/shell nanoparticles, namely boron/iron oxide and boron/silica, were synthesized. Initially, boron nanoparticles with a diameter between 10-100 nm were prepared by decomposition of nido-decaborane (B10H14) followed by formation of a core/shell structure. The core/shell structures were prepared using the appropriate precursor, iron source and silica source, for the shell in the presence of boron nanoparticles. The formation of core/shell nanostructures was confirmed using high resolution TEM. Then, the core/shell nanoparticles underwent a surface modification. Boron/iron oxide core/shell nanoparticles were functionalized with oleic acid, citric acid, amine-terminated polyethylene glycol, folic acid, and dopamine, and boron/silica core/shell nanoparticles were modified with 3-(amino propyl) triethoxy silane, 3-(2-aminoethyleamino)propyltrimethoxysilane), citric acid, folic acid, amine-terminated polyethylene glycol, and O-(2-Carboxyethyl)polyethylene glycol. A UV-Vis and ATR-FTIR analysis established the success of surface modification. The cytotoxicity of water-soluble core/shell nanoparticles was studied in triple negative breast cancer cell line MDA-MB-231 and the result showed the compounds are not toxic. The second project highlights optimization of reaction conditions for the synthesis of boron nanorods. This synthesis, done via reduction of boron oxide with molten lithium, was studied to produce boron nanorods without any

  8. Process for making boron nitride using sodium cyanide and boron

    DOEpatents

    Bamberger, Carlos E.

    1990-02-06

    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.

  9. Process for making boron nitride using sodium cyanide and boron

    DOEpatents

    Bamberger, Carlos E.

    1990-01-01

    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.

  10. Boronated liposome development and evaluation

    SciTech Connect

    Hawthorne, M.F.

    1995-11-01

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

  11. Method for separating boron isotopes

    DOEpatents

    Rockwood, Stephen D.

    1978-01-01

    A method of separating boron isotopes .sup.10 B and .sup.11 B by laser-induced selective excitation and photodissociation of BCl.sub.3 molecules containing a particular boron isotope. The photodissociation products react with an appropriate chemical scavenger and the reaction products may readily be separated from undissociated BCl.sub.3, thus effecting the desired separation of the boron isotopes.

  12. Status of Boron Combustion Research

    DTIC Science & Technology

    1984-10-01

    layer . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5 Vaporization of boron oxide drops In wet and dry .-. environments. From Turns et al . ([1...19 10 SEN photographs of boron slurry agglomerates: a. Oxide layer present: b. Oxide layer absent.From Turns et al . [7...21 -- f- 11 Ignition of boron agglomerates as a function of particle and agglomerate diameters. From Shevahuk et al . [26

  13. Mineral of the month: boron

    USGS Publications Warehouse

    Lyday, Phyllis A.

    2005-01-01

    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.

  14. Boron-enhanced diffusion of boron from ultralow-energy ion implantation

    SciTech Connect

    Agarwal, A.; Gossmann, H.; Eaglesham, D.J.; Herner, S.B.; Fiory, A.T.; Haynes, T.E.

    1999-04-01

    We have investigated the diffusion enhancement mechanism of boron-enhanced diffusion (BED), wherein boron diffusivity is enhanced four to five times over the equilibrium diffusivity at 1050&hthinsp;{degree}C in the proximity of a silicon layer containing a high boron concentration. It is demonstrated that BED is driven by excess interstitials injected from the high boron concentration layer during annealing. For evaporated layers, BED is observed above a threshold boron concentration between 1{percent} and 10{percent}, though it appears to be closer to 1{percent} for B-implanted layers. For sub-keV B implants above the threshold, BED dominates over the contribution from transient-enhanced diffusion to junction depth. For 0.5 keV B, this threshold implantation dose lies between 3{times}10{sup 14} and 1{times}10{sup 15} cm{sup {minus}2}. It is proposed that the excess interstitials responsible for BED are produced during the formation of a silicon boride phase in the high B concentration layers. {copyright} {ital 1999 American Institute of Physics.}

  15. In Vivo Boron Uptake Determination for Boron Neutron Capture Synovectomy

    SciTech Connect

    Binello, Emanuela; Shortkroff, Sonya; Yanch, Jacquelyn C.

    1999-06-06

    Boron neutron capture synovectomy (BNCS) has been proposed as a new application of the boron neutron capture reaction for the treatment of rheumatoid arthritis. In BNCS, a boron compound is injected into the joint space, where it is taken up by the synovium. The joint is then irradiated with neutrons of a desired energy range, inducing the boron neutron capture reaction in boron-loaded cells. Boron uptake by the synovium is an important parameter in the assessment of the potential of BNCS and in the determination of whether to proceed to animal irradiations for the testing of therapeutic efficacy. We present results from an investigation of boron uptake in vivo by the synovium.

  16. Boron isotope exchange in a heterogeneous boron-boron fluoride system

    SciTech Connect

    Begak, O.Yu.; Fedorov, V.V.

    1988-11-01

    Studies have been made on exchange between /sup 10/B and /sup 11/B in heterogeneous systems containing finely divided amorphous boron and BF/sub 3/ gas. The kinetic and thermodynamic parameters have been examined. The self-diffusion coefficient for boron in amorphous boron has been determined at 973-1273 K.

  17. Minerals Yearbook 1989: Boron

    SciTech Connect

    Lyday, P.A.

    1990-08-01

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

  18. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, Richard K.; Bystroff, Roman I.; Miller, Dale E.

    1987-01-01

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  19. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

    1986-08-27

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  20. Fabrication of boron sputter targets

    DOEpatents

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

    1995-02-28

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

  1. Fabrication of boron sputter targets

    DOEpatents

    Makowiecki, Daniel M.; McKernan, Mark A.

    1995-01-01

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

  2. Determination of phase stability of elemental boron.

    PubMed

    White, Mary Anne; Cerqueira, Anthony B; Whitman, Catherine A; Johnson, Michel B; Ogitsu, Tadashi

    2015-03-16

    Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (α or β) is stable at ambient conditions. Through experiment, we quantify the relative stability of α-boron and β-boron as a function of temperature. The ground-state energies of α-boron and β-boron are nearly identical. For all temperatures up to 2000 K, the complicated β-boron structure is more stable than the simpler α-boron structure at ambient pressure. Below 1000 K, β-boron is entropically stabilized with respect to α-boron owing to its partially occupied sites, whereas at higher temperatures β-boron is enthalpically stabilized with respect to α-boron. We show that α-boron only becomes stable on application of pressure.

  3. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, Cressie E.; Morrow, Marvin S.

    1993-01-01

    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.

  4. Process for microwave sintering boron carbide

    DOEpatents

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

    1993-10-12

    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.

  5. Methods of producing continuous boron carbide fibers

    SciTech Connect

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  6. Boron and Compounds

    Integrated Risk Information System (IRIS)

    EPA 635 / 04 / 052 www.epa.gov / iris TOXICOLOGICAL REVIEW OF BORON AND COMPOUNDS ( CAS No . 7440 - 42 - 8 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) June 2004 U.S . Environmental Protection Agency Washington , DC DISCLAIMER This document has been reviewed

  7. Nothing Boring About Boron.

    PubMed

    Pizzorno, Lara

    2015-08-01

    The trace mineral boron is a micronutrient with diverse and vitally important roles in metabolism that render it necessary for plant, animal, and human health, and as recent research suggests, possibly for the evolution of life on Earth. As the current article shows, boron has been proven to be an important trace mineral because it (1) is essential for the growth and maintenance of bone; (2) greatly improves wound healing; (3) beneficially impacts the body's use of estrogen, testosterone, and vitamin D; (4) boosts magnesium absorption; (5) reduces levels of inflammatory biomarkers, such as high-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor α (TNF-α); (6) raises levels of antioxidant enzymes, such as superoxide dismutase (SOD), catalase, and glutathione peroxidase; (7) protects against pesticide-induced oxidative stress and heavy-metal toxicity; (8) improves the brains electrical activity, cognitive performance, and short-term memory for elders; (9) influences the formation and activity of key biomolecules, such as S-adenosyl methionine (SAM-e) and nicotinamide adenine dinucleotide (NAD(+)); (10) has demonstrated preventive and therapeutic effects in a number of cancers, such as prostate, cervical, and lung cancers, and multiple and non-Hodgkin's lymphoma; and (11) may help ameliorate the adverse effects of traditional chemotherapeutic agents. In none of the numerous studies conducted to date, however, do boron's beneficial effects appear at intakes > 3 mg/d. No estimated average requirements (EARs) or dietary reference intakes (DRIs) have been set for boron-only an upper intake level (UL) of 20 mg/d for individuals aged ≥ 18 y. The absence of studies showing harm in conjunction with the substantial number of articles showing benefits support the consideration of boron supplementation of 3 mg/d for any individual who is consuming a diet lacking in fruits and vegetables or who is at risk for or has osteopenia; osteoporosis; osteoarthritis (OA

  8. Effect of fluorine implantation dose on boron thermal diffusion in silicon

    SciTech Connect

    El Mubarek, H.A.W.; Bonar, J.M; Dilliway, G.D.; Ashburn, P.; Karunaratne, M.; Willoughby, A.F.; Wang, Y.; Hemment, P.L.F.; Price, R.; Zhang, J.; Ward, P.

    2004-10-15

    This paper investigates how the thermal diffusion of boron in silicon is influenced by a high energy fluorine implant with a dose in the range 5x10{sup 14}-2.3x10{sup 15} cm{sup -2}. Secondary Ion Mass Spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine profiles to establish the conditions under which thermal boron diffusion is suppressed. The (SIMS) profiles show significantly reduced boron thermal diffusion above a critical F{sup +} dose of 0.9-1.4x10{sup 15} cm{sup -2}. Fitting of the measured boron profiles gives suppressions of the boron thermal diffusion coefficient by factors of 1.9 and 3.7 for F{sup +} implantation doses of 1.4x10{sup 15} and 2.3x10{sup 15} cm{sup -2}, respectively. The suppression of boron thermal diffusion above the critical fluorine dose correlates with the appearance of a shallow fluorine peak on the (SIMS) profile in the vicinity of the boron marker layer. This shallow fluorine peak is present in samples with and without boron marker layers, and hence it is not due to a chemical interaction between the boron and the fluorine. Analysis of the (SIMS) profiles and cross-section Transmission Electron Microscope micrographs suggests that it is due to the trapping of fluorine at vacancy-fluorine clusters, and that the suppression of the boron thermal diffusion is due to the effect of the clusters in suppressing the interstitial concentration in the vicinity of the boron profile.

  9. Impact of boron dilution accidents on low boron PWR safety

    SciTech Connect

    Papukchiev, A.; Liu, Y.; Schaefer, A.

    2006-07-01

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

  10. Boronizing protects metals against wear

    SciTech Connect

    Stewart, K.

    1997-03-01

    Boronizing is a thermochemical surface treatment that involves diffusion of boron into a base metal at a high temperature. The resulting metallic boride provides high hardness and resistance to acid corrosion, and lengthens service life by a factor of three to ten. Boronizing fills a gap between conventional surface treatments and the more exotic chemical and physical vapor deposition. In a number of applications, boronizing has replaced such processes as carburizing, nitriding, and nitrocarburizing. It has even replaced hard chrome plating in some cases, while achieving similar service life improvements. Boron can be uniformly applied to irregular surfaces, and can be applied to specific areas of a surface. It is also suitable for high-volume production applications, as first demonstrated in the European automotive industry. This article describes the boronizing process, provides material selection/preparation criteria, and lists industrial applications.

  11. Suppression of oxidation enhanced boron diffusion in silicon by carbon implantation and characterization of MOSFETs with carbon implanted channels

    SciTech Connect

    Ban, I.; Oeztuerk, M.C.; Demirlioglu, E.

    1996-12-31

    Scaling of MOSFETs into the deep submicron regime requires shallow doping profiles with abrupt doping transitions in the MOSFET active region. In NMOS transistors with boron doped channels, oxidation enhanced diffusion is a key contributor to boron profile broadening. Starting from the arguments presented in several recent reports on the role of carbon in silicon as a sink for self-interstitials, we have explored the feasibility of using carbon in the MOSFET in the active region to retard boron diffusion during gate oxidation. MOSFETs with carbon and boron implanted channels have been fabricated. Boron diffusion, activation, and critical electrical parameters such as subthreshold swing, threshold voltage, and off-state leakage current have been evaluated as a function of the carbon dose. We have shown that carbon can effectively suppress boron diffusion during gate oxidation. However, at dose levels around 10{sup 14}cm{sup -2} carbon results in poor boron activation and degradation in MOSFET performance.

  12. Microstructure Analysis of Boron Nanotubes

    DTIC Science & Technology

    2012-05-01

    figure 1 2 3 High resolution TEM showing very small elongated BNT filaments 3 4 SAED from an area in figure 3 showing exactly the same kind of...scattered large numbers of BNT 4 7 EDAX analyses of boron nitride nano powder showing boron and oxygen 5 8 Low magnification SEM picture of folded 600...Picatinny Arsenal, New Jersey. INTRODUCTION Boron nanotubes ( BNT ) have never been produced in a reliable manner, yet they remain a promising

  13. Structures, stability, mechanical and electronic properties of α-boron and α∗-boron

    NASA Astrophysics Data System (ADS)

    He, Chaoyu; Zhong, J. X.

    2013-04-01

    The structures, stability, mechanical and electronic properties of α-boron and a promising metastable boron phase (α*-boron) have been studied by first-principles calculations. α-boron and α*-boron consist of equivalent icosahedra B12 clusters in different connecting configurations of "3S-6D-3S" and "2S-6D-4S", respectively. The total energy calculations show that α*-boron is less stable than α-boron but more favorable than the well-known β-boron and γ-boron at zero pressure. Both α-boron and α*-boron are confirmed dynamically and mechanically stable. The mechanical and electronic properties of α-boron and α*-boron indicate that they are potential superhard semiconducting phases of element boron.

  14. Boron nitride nanotubes.

    PubMed

    Chopra, N G; Luyken, R J; Cherrey, K; Crespi, V H; Cohen, M L; Louie, S G; Zettl, A

    1995-08-18

    The successful synthesis of pure boron nitride (BN) nanotubes is reported here. Multi-walled tubes with inner diameters on the order of 1 to 3 nanometers and with lengths up to 200 nanometers were produced in a carbon-free plasma discharge between a BN-packed tungsten rod and a cooled copper electrode. Electron energy-loss spectroscopy on individual tubes yielded B:N ratios of approximately 1, which is consistent with theoretical predictions of stable BN tube structures.

  15. Validation of the scanning γ-ray telescope for in vivo dosimetry and boron measurements during BNCT

    NASA Astrophysics Data System (ADS)

    Verbakel, W. F. A. R.

    2001-12-01

    γ-ray telescope scans of a box phantom with inhomogeneous boron concentrations have proven the feasibility of in vivo measurements of different boron distributions in the head of a patient during boron neutron capture therapy (BNCT). Small structures with enhanced boron concentration can be reconstructed in a head phantom, even if the brain compartment of the phantom is surrounded by a skin layer with a ten times higher boron concentration. The motor-controlled telescope can scan the head/phantom, detecting boron and hydrogen prompt γ-rays emitted at neutron capture reactions with a two-dimensional spatial resolution of 14 mm full width at half maximum. For reconstruction of the boron concentrations from the measured γ-ray detection rates, a mathematical reconstruction algorithm is derived and discussed. Proper reconstruction requires position-dependent γ-ray measurements combined with treatment planning programme calculations of the thermal neutron distribution. In a head phantom, in which the brain and the skull (bulk) were represented using a homogeneous boron distribution of 5.2 +/- 0.5 ppm 10B, surrounded by a skin layer with a ten times higher boron concentration, the bulk concentration was reconstructed to 4.7 +/- 0.3 ppm 10B. Telescope scans along and perpendicular to the beam axis showed the influence of inhomogeneities with a high boron concentration such as skin and a simulated blood vessel, respectively with a low boron concentration such as white matter. The profiles of the boron and hydrogen γ-ray detection rates indicate how future patient measurements can be interpreted. In clinical trials, the telescope can then be used to investigate the averaged boron concentration in the bulk of a patient and local enhanced boron concentrations (e.g. in tumour tissue) in order to relate the measured boron dose distributions to the clinical effects of BNCT. Simultaneously, it can serve as quality control of the dosimetry during the irradiation.

  16. The loss of boron in ultra-shallow boron implanted Si under heavy ion irradiation

    NASA Astrophysics Data System (ADS)

    Pelicon, P.; El Bouanani, M.; Prasad, G. V. R.; Razpet, A.; Simcic, J.; Guo, B. N.; Birt, D.; Duggan, J. L.; McDaniel, F. D.

    2006-08-01

    Heavy ion impact has been known to cause a loss of light elements from the near-surface region of the irradiated sample. One of the possible approaches to a better understanding of the processes responsible for the release of specific elements is to irradiate shallow-implanted samples, which exhibit a well-known depth distribution of the implanted species. In this work, the samples studied were produced by implantation of Si wafers with 11 B at implantation energies of 250 and 500 eV and fluence of 1.0x10(15) atoms/cm 2 . Elastic Recoil Detection Analysis was applied to monitor the remnant boron fluence in the sample. Irradiation of the samples by a 14.2 (MeVF4+)-F-19 beam resulted in a slow decrease of boron remnant fluence with initial loss rates of the order of 0.05 B atom per impact ion. Under irradiation with 12 (MeVS3+)-S-32 ions, the remnant boron fluence in Si decreased exponentially with a much faster loss rate of boron and became constant after a certain heavy ion irradiation dose. A simple model, which assumes a finite desorption range and corresponding depletion of the near-surface region, was used to describe the observations. The depletion depths under the given irradiation conditions were calculated from the measured data.

  17. Method of fabricating boron containing coatings

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1999-01-01

    Hard coatings are fabricated from boron nitride, cubic boron nitride, and multilayer boron/cubic boron nitride, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron is formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/cubic boron nitride, is produced by depositing alternate layers of boron and cubic boron nitride, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be discrete or of a blended or graded composition.

  18. Method of fabricating boron containing coatings

    DOEpatents

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

    1999-04-27

    Hard coatings are fabricated from boron nitride, cubic boron nitride, and multilayer boron/cubic boron nitride, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron is formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/cubic boron nitride, is produced by depositing alternate layers of boron and cubic boron nitride, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be discrete or of a blended or graded composition. 3 figs.

  19. Boron isotopic compositions of some boron minerals

    SciTech Connect

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

    1989-12-01

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

  20. Boron containing multilayer coatings and method of fabrication

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1997-01-01

    Hard coatings are fabricated from multilayer boron/boron carbide, boron carbide/cubic boron nitride, and boron/boron nitride/boron carbide, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron and boron carbide used in forming the multilayers are formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/boron carbide, and boron carbide/cubic boron nitride is produced by depositing alternate layers of boron, cubic boron nitride or boron carbide, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be of a discrete or a blended or graded composition.

  1. Boron Clusters Come of Age

    ERIC Educational Resources Information Center

    Grimes, Russell N.

    2004-01-01

    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…

  2. Boron Clusters Come of Age

    ERIC Educational Resources Information Center

    Grimes, Russell N.

    2004-01-01

    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…

  3. Temporally and Spatially Resolved Plasma Spectroscopy in Pulsed Laser Deposition of Ultra-Thin Boron Nitride Films (Postprint)

    DTIC Science & Technology

    2015-04-24

    in the plasma plume. Boron, being the lighter of the two species ( atomic weights: B¼ 10.81, N¼ 14.01), will escape the Knudsen layer of plasma plume...AFRL-RX-WP-JA-2016-0196 TEMPORALLY AND SPATIALLY RESOLVED PLASMA SPECTROSCOPY IN PULSED LASER DEPOSITION OF ULTRA-THIN BORON NITRIDE...AND SPATIALLY RESOLVED PLASMA SPECTROSCOPY IN PULSED LASER DEPOSITION OF ULTRA-THIN BORON NITRIDE FILMS (POSTPRINT) 5a. CONTRACT NUMBER FA8650

  4. Functionalized boron nitride nanotubes

    DOEpatents

    Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

    2014-04-22

    A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

  5. New Carbonate Standard Reference Materials for Boron Isotope Geochemistry

    NASA Astrophysics Data System (ADS)

    Stewart, J.; Christopher, S. J.; Day, R. D.

    2015-12-01

    The isotopic composition of boron (δ11B) in marine carbonates is well established as a proxy for past ocean pH. Yet, before palaeoceanographic interpretation can be made, rigorous assessment of analytical uncertainty of δ11B data is required; particularly in light of recent interlaboratory comparison studies that reported significant measurement disagreement between laboratories [1]. Well characterised boron standard reference materials (SRMs) in a carbonate matrix are needed to assess the accuracy and precision of carbonate δ11B measurements throughout the entire procedural chemistry; from sample cleaning, to ionic separation of boron from the carbonate matrix, and final δ11B measurement by multi-collector inductively coupled plasma mass spectrometry. To date only two carbonate reference materials exist that have been value-assigned by the boron isotope measurement community [2]; JCp-1 (porites coral) and JCt-1 (Giant Clam) [3]. The National Institute of Standards and Technology (NIST) will supplement these existing standards with new solution based inorganic carbonate boron SRMs that replicate typical foraminiferal and coral B/Ca ratios and δ11B values. These new SRMs will not only ensure quality control of full procedural chemistry between laboratories, but have the added benefits of being both in abundant supply and free from any restrictions associated with shipment of biogenic samples derived from protected species. Here we present in-house δ11B measurements of these new boron carbonate SRM solutions. These preliminary data will feed into an interlaboratory comparison study to establish certified values for these new NIST SRMs. 1. Foster, G.L., et al., Chemical Geology, 2013. 358(0): p. 1-14. 2. Gutjahr, M., et al., Boron Isotope Intercomparison Project (BIIP): Development of a new carbonate standard for stable isotopic analyses. Geophysical Research Abstracts, EGU General Assembly 2014, 2014. 16(EGU2014-5028-1). 3. Inoue, M., et al., Geostandards and

  6. METHOD OF COATING SURFACES WITH BORON

    DOEpatents

    Martin, G.R.

    1949-10-11

    A method of forming a thin coating of boron on metallic, glass, or other surfaces is described. The method comprises heating the article to be coated to a temperature of about 550 d C in an evacuated chamber and passing trimethyl boron, triethyl boron, or tripropyl boron in the vapor phase and under reduced pressure into contact with the heated surface causing boron to be deposited in a thin film.

  7. Boron implanted strontium titanate

    NASA Astrophysics Data System (ADS)

    Cooper, C. J. M.

    Single crystals of strontium titanate implanted with boron were found to have highly conductive surface layers. The effects of varying dose from 10 to the 16th power to 10 to the 17th power ions/sq cm, implantation voltage from 50 to 175 keV and annealing conditions on the room temperature surface resistance and Hall mobility are presented. Variation of the implantation voltage did not have a major effect on the sheet resistances obtained by boron implantation of strontium titanate, while dose and annealing conditions have major effects. Doses of 5 x 10 to the 16th power ions/sq cm required annealing on the order of one hour at 500 K for maximum reduction of the room temperature resistance in the implanted layer. Samples implanted with a dose of 1 x 10 to the 17th power ions/sq cm required slightly higher temperatures (approximately 575 K) to obtain a minimum resistance at room temperature. Long term (several weeks) room temperature annealing was found to occur in high dose samples. After one to two months at room temperature followed by an anneal to 575 K, the surface resistances were found to be lower than those produced by the annealing of a freshly implanted sample to 575 K.

  8. Effects of Boron on Proton Transport and Membrane Properties of Sunflower (Helianthus annuus L.) Cell Microsomes.

    PubMed Central

    Ferrol, N.; Belver, A.; Roldan, M.; Rodriguez-Rosales, M. P.; Donaire, J. P.

    1993-01-01

    Boron deficiency and toxicity inhibit ATP-dependent H+ pumping and vanadate-sensitive ATPase activity in sunflower roots and cell suspensions. The effects of boron on H+ pumping and on passive H+ conductance, as well as on fluorescence anisotropy in KI-washed microsomes isolated from sunflower (Helianthus annuus L. cv Enano) cell suspensions, have been investigated. Boron deficiency reduced the total and vanadate-sensitive ATPase activities as well as the vanadate-sensitive ATP-dependent H+ pumping without affecting the amount of antigenic ATPase protein as measured by immunoblotting with an Arabidopsis thaliana plasma membrane anti-H+-ATPase polyclonal antibody. Kinetic studies revealed that boron deficiency reduced Vmax of vanadate-sensitive ATPase activity with little change in the apparent Km for Mg2+-ATP. Proton leakage was greater in microsomal vesicles isolated from cells grown without boron and incubated in reaction medium without added boron, and this effect was reversed by addition of boron to the reaction medium. Fluorescence anisotropy indicated that diphenyl hexatriene and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene probes were immobilized to a greater extent in microsomes from cells grown without boron than in those from cells grown with 100 [mu]M H3BO3. The apparent decrease of membrane fluidity in microsomes from cells grown without boron was reversed by the addition of boron to the reaction medium. Taken together these data suggest that inhibition of H+ gradient formation in microsomes from sunflower cells grown in the absence of boron could be due to the combined effects of reduced H+-ATPase activity and increased passive conductance across the membrane, possibly resulting from increased membrane rigidity. PMID:12231978

  9. Boron transient enhanced diffusion in heavily phosphorus doped silicon

    SciTech Connect

    Huang, M.B.; Myler, U.; Simpson, T.W.; Simpson, P.J.; Mitchell, I.V.

    1997-11-01

    A study has been made of B transient enhanced diffusion (TED) in heavily P-doped Si using secondary ion mass spectroscopy (SIMS) and positron annihilation spectroscopy (PAS). The P-doped silicon was implanted with boron ions of 40 keV energy to a dose of 3 {times} 10{sup 14} cm{sup {minus}2}, and then annealed at temperatures ranging from 700--1,000 C in a N{sub 2} ambient for varying durations. As P doping concentration increased from 3 {times} 10{sup 19} to 1 {times} 10{sup 20} cm{sup {minus}3}, boron diffusivity and the immobile boron fraction decreased. The experimental results are inconsistent with the predictions of the Fermi-level model and suggest that the clustering between B atoms and Si interstitials should be invoked in order to explain the immobile portion of the B peak during TED.

  10. Iron-Catalyzed Boron Removal from Molten Silicon in Ammonia

    NASA Astrophysics Data System (ADS)

    Chen, Zhiyuan; Morita, Kazuki

    2016-12-01

    A high-temperature process of refining metallurgical-grade silicon to solar-grade silicon was developed. In this gas purging treatment, boron impurity in silicon reacts with ammonia and the products are removed as volatiles at high temperature. 1 mass pct metallic iron was added to molten silicon as a catalyst, improving the boron removal ratio from 14 to 80 pct at 1723 K (1450 °C). At 1823 K (1550 °C), this reaction could reduce boron concentration from more than 120 ppmw to <1 ppmw within 6 hours, meeting the purity requirement of solar-grade silicon. Nickel was tested in place of iron but showed no catalytic effect on boron removal. The result confirmed the catalytic role of iron in boron removal from molten silicon in ammonia. Possible mechanisms of catalysis, influence from iron concentration, and temperature effect on the catalytic reaction were explored. An apparent activation energy of 329 ± 129 kJ mol-1 was calculated from experimental data.

  11. Atomically controlled substitutional boron-doping of graphene nanoribbons

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  12. Entropy of gaseous boron monobromide

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Feng; Peng, Xiao-Long; Zhang, Lie-Hui; Wang, Chao-Wen; Jia, Chun-Sheng

    2017-10-01

    We present an explicit representation of molar entropy for gaseous boron monobromide in terms of experimental values of only three molecular constants. Fortunately, through comparison of theoretically calculated results and experimental data, we find that the molar entropy of gaseous boron monobromide can be well predicted by employing the improved Manning-Rosen oscillator to describe the internal vibration of boron monobromide molecule. The present approach provides also opportunities for theoretical predictions of molar entropy for other gases with no use of large amounts of experimental spectroscopy data.

  13. A new and effective approach to boron removal by using novel boron-specific fungi isolated from boron mining wastewater.

    PubMed

    Taştan, Burcu Ertit; Çakir, Dilara Nur; Dönmez, Gönül

    2016-01-01

    Boron-resistant fungi were isolated from the wastewater of a boron mine in Turkey. Boron removal efficiencies of Penicillium crustosum and Rhodotorula mucilaginosa were detected in different media compositions. Minimal Salt Medium (MSM) and two different waste media containing molasses (WM-1) or whey + molasses (WM-2) were tested to make this process cost effective when scaled up. Both isolates achieved high boron removal yields at the highest boron concentrations tested in MSM and WM-1. The maximum boron removal yield by P. crustosum was 45.68% at 33.95 mg l(-1) initial boron concentration in MSM, and was 38.97% at 42.76 mg l(-1) boron for R. mucilaginosa, which seemed to offer an economically feasible method of removing boron from the effluents.

  14. Boron and Boron-Rich Solids at High Pressures

    NASA Astrophysics Data System (ADS)

    Polian, Alain; Ovsyannikov, Sergey V.; Gauthier, Michel; Munsch, Pascal; Chervin, Jean-Claude; Lemarchand, Gilles

    Boron seems to be the indispensable ingredient to obtain materials with high hardness. It exists under many different structures. The simplest member of the family, α-boron is based on an arrangement of slightly distorted B12 icosahedra in a rhombohedral unit cell. B12X2 compounds, with X = O, P, As, are based on the α-boron structure, with the X atoms in the inter-icosahedra space. The stability of α-boron has been studied by x-ray diffraction and Raman scattering up to 100 GPa, showing no sign of phase transformation, and by Raman scattering for B12P2 and B12As2 with the observation of phase transformation in the 80 GPa range.

  15. Boron removal from aqueous solutions using alginate gel beads in fixed-bed systems

    PubMed Central

    Demey-Cedeño, Hary; Ruiz, Montserrat; Barron-Zambrano, Jesús Alberto; Sastre, Ana Maria

    2014-01-01

    Background A column sorption study was carried out using calcium alginate gel beads as adsorbent for the removal of boron from aqueous solutions. The breakthrough curve was obtained as a function of pH, initial concentration of boron, feed flow rate, adsorbent mass and column diameter. The breakthrough capacity values and adsorption percentage of calcium alginate gel for boron were calculated. Column data obtained at different conditions were described using the Adams–Bohart model and bed-depth service time (BDST), derived from the Adams–Bohart equation to predict breakthrough curves and to determine the characteristic column parameters required for process design. Results The maximum adsorption percentage of boron on calcium alginate gel beads using an initial concentration of boron of 50 mg L−1 at pH 11 and room temperature (20±1°C) was calculated to be 55.14%. Conclusion The results indicated that calcium alginate can be used in a continuous packed-bed column for boron adsorption. The optimal conditions for boron adsorption were obtained at high pH, higher initial boron concentration, increased column depth and lower flow velocity. © 2014 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. PMID:25821332

  16. Copper passivation of boron in silicon and boron reactivation kinetics

    NASA Astrophysics Data System (ADS)

    Aboelfotoh, M. O.; Svensson, B. G.

    1991-12-01

    Copper passivation of substitutional boron in single-crystal silicon and the reactivation kinetics of the passivated boron have been investigated with the use of Schottky-barrier structures formed by the deposition of copper on boron-doped silicon at room temperature. It is found that passivation of the boron acceptors occurs after copper deposition. The results suggest that the fast-diffusing interstitial Cu+ passivates the boron acceptors by forming neutral B-Cu complexes, rather than by direct compensation. No compensating donor levels associated with Cu are observed. These results are consistent with recent theoretical predictions. The reactivation kinetics are first order with an activation energy of 0.89 eV, and the annealing process is found to be controlled by long-range diffusion, rather than by pure dissociation. The thermal dissociation of the B-Cu complexes is driven by the formation of the copper silicide η'-Cu3Si, indicating the importance of silicide formation in the reactivation of the boron acceptors.

  17. Nothing Boring About Boron

    PubMed Central

    Pizzorno, Lara

    2015-01-01

    The trace mineral boron is a micronutrient with diverse and vitally important roles in metabolism that render it necessary for plant, animal, and human health, and as recent research suggests, possibly for the evolution of life on Earth. As the current article shows, boron has been proven to be an important trace mineral because it (1) is essential for the growth and maintenance of bone; (2) greatly improves wound healing; (3) beneficially impacts the body’s use of estrogen, testosterone, and vitamin D; (4) boosts magnesium absorption; (5) reduces levels of inflammatory biomarkers, such as high-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor α (TNF-α); (6) raises levels of antioxidant enzymes, such as superoxide dismutase (SOD), catalase, and glutathione peroxidase; (7) protects against pesticide-induced oxidative stress and heavy-metal toxicity; (8) improves the brains electrical activity, cognitive performance, and short-term memory for elders; (9) influences the formation and activity of key biomolecules, such as S-adenosyl methionine (SAM-e) and nicotinamide adenine dinucleotide (NAD+); (10) has demonstrated preventive and therapeutic effects in a number of cancers, such as prostate, cervical, and lung cancers, and multiple and non-Hodgkin’s lymphoma; and (11) may help ameliorate the adverse effects of traditional chemotherapeutic agents. In none of the numerous studies conducted to date, however, do boron’s beneficial effects appear at intakes > 3 mg/d. No estimated average requirements (EARs) or dietary reference intakes (DRIs) have been set for boron—only an upper intake level (UL) of 20 mg/d for individuals aged ≥ 18 y. The absence of studies showing harm in conjunction with the substantial number of articles showing benefits support the consideration of boron supplementation of 3 mg/d for any individual who is consuming a diet lacking in fruits and vegetables or who is at risk for or has osteopenia; osteoporosis

  18. Reducing Boron Toxicity by Microbial Sequestration

    SciTech Connect

    Hazen, T.; Phelps, T.J.

    2002-01-01

    While electricity is a clean source of energy, methods of electricity-production, such as the use of coal-fired power plants, often result in significant environmental damage. Coal-fired electrical power plants produce air pollution, while contaminating ground water and soils by build-up of boron, which enters surrounding areas through leachate. Increasingly high levels of boron in soils eventually overcome boron tolerance levels in plants and trees, resulting in toxicity. Formation of insoluble boron precipitates, mediated by mineral-precipitating bacteria, may sequester boron into more stable forms that are less available and toxic to vegetation. Results have provided evidence of microbially-facilitated sequestration of boron into insoluble mineral precipitates. Analyses of water samples taken from ponds with high boron concentrations showed that algae present contained 3-5 times more boron than contained in the water in the samples. Boron sequestration may also be facilitated by the incorporation of boron within algal cells. Experiments examining boron sequestration by algae are in progress. In bacterial experiments with added ferric citrate, the reduction of iron by the bacteria resulted in an ironcarbonate precipitate containing boron. An apparent color change showing the reduction of amorphous iron, as well as the precipitation of boron with iron, was more favorable at higher pH. Analysis of precipitates by X-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectroscopy revealed mineralogical composition and biologicallymediated accumulation of boron precipitates in test-tube experiments.

  19. Nano boron nitride flatland.

    PubMed

    Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

    2014-02-07

    Recent years have witnessed many breakthroughs in research on two-dimensional (2D) nanomaterials, among which is hexagonal boron nitride (h-BN), a layered material with a regular network of BN hexagons. This review provides an insight into the marvellous nano BN flatland, beginning with a concise introduction to BN and its low-dimensional nanostructures, followed by an overview of the past and current state of research on 2D BN nanostructures. A comprehensive review of the structural characteristics and synthetic routes of BN monolayers, multilayers, nanomeshes, nanowaves, nanoflakes, nanosheets and nanoribbons is presented. In addition, electronic, optical, thermal, mechanical, magnetic, piezoelectric, catalytic, ecological, biological and wetting properties, applications and research perspectives for these novel 2D nanomaterials are discussed.

  20. Boron diffusion in silicon devices

    DOEpatents

    Rohatgi, Ajeet; Kim, Dong Seop; Nakayashiki, Kenta; Rounsaville, Brian

    2010-09-07

    Disclosed are various embodiments that include a process, an arrangement, and an apparatus for boron diffusion in a wafer. In one representative embodiment, a process is provided in which a boric oxide solution is applied to a surface of the wafer. Thereafter, the wafer is subjected to a fast heat ramp-up associated with a first heating cycle that results in a release of an amount of boron for diffusion into the wafer.

  1. Neutron detectors comprising boron powder

    DOEpatents

    Wang, Zhehui; Morris, Christopher; Bacon, Jeffrey Darnell; Makela, Mark F; Spaulding, Randy Jay

    2013-05-21

    High-efficiency neutron detector substrate assemblies comprising a first conductive substrate, wherein a first side of the substrate is in direct contact with a first layer of a powder material comprising .sup.10boron, .sup.10boron carbide or combinations thereof, and wherein a conductive material is in proximity to the first layer of powder material; and processes of making said neutron detector substrate assemblies.

  2. Characterization of electrodeposited elemental boron

    SciTech Connect

    Jain, Ashish; Anthonysamy, S. Ananthasivan, K.; Ranganathan, R.; Mittal, Vinit; Narasimhan, S.V.; Vasudeva Rao, P.R.

    2008-07-15

    Elemental boron was produced through electrowinning from potassium fluoroborate dissolved in a mixture of molten potassium fluoride and potassium chloride. The characteristics of the electrodeposited boron (raw boron) as well as the water and acid-leached product (processed boron) were studied. The chemical purity, specific surface area, size distribution of particles and X-ray crystallite size of the boron powders were investigated. The morphology of the deposits was examined using scanning electron microscopy (SEM). The chemical state of the matrix, as well as the impurity phases present in them, was established using X-ray photoelectron spectroscopy (XPS). In order to interpret and understand the results obtained, a thermodynamic analysis was carried out. The gas-phase corrosion in the head space as well as the chemistry behind the leaching process were interpreted using this analysis. The ease of oxidation of these powders in air was investigated using differential thermal analysis (DTA) coupled with thermogravimetry (TG). From the results obtained in this study it was established that elemental boron powder with a purity of 95-99% could be produced using a high temperature molten salt electrowinning process. The major impurities were found to be oxygen, carbon, iron and nickel.

  3. The Oxidation Products of Aluminum Hydride and Boron Aluminum Hydride Clusters

    DTIC Science & Technology

    2016-01-04

    AFRL-AFOSR-VA-TR-2016-0075 The Oxidation Products of Aluminum Hydride and Boron Aluminum Hydride Clusters KIT BOWEN JOHNS HOPKINS UNIV BALTIMORE MD...Hydride and Boron Aluminum Hydride Clusters 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-14-1-0324 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) KIT...of both Aluminum Hydride Cluster Anions and Boron Aluminum Hydride Cluster Anions with Oxygen: Anionic Products The anionic products of reactions

  4. Tomographic image of prompt gamma ray from boron neutron capture therapy: A Monte Carlo simulation study

    SciTech Connect

    Yoon, Do-Kun; Jung, Joo-Young; Suk Suh, Tae; Jo Hong, Key

    2014-02-24

    Purpose of paper is to confirm the feasibility of acquisition of three dimensional single photon emission computed tomography image from boron neutron capture therapy using Monte Carlo simulation. Prompt gamma ray (478 keV) was used to reconstruct image with ordered subsets expectation maximization method. From analysis of receiver operating characteristic curve, area under curve values of three boron regions were 0.738, 0.623, and 0.817. The differences between length of centers of two boron regions and distance of maximum count points were 0.3 cm, 1.6 cm, and 1.4 cm.

  5. Thermionic emission and surface composition of the lanthanum-boron and yttrium-boron systems

    SciTech Connect

    Jaskie, J.E.

    1981-12-01

    At thermionic temperatures, a difference between bulk and surface composition will exist unless the interior happens to be at the congruently vaporizing composition (CVC). Vaporization rates from the surface compete with diffusion rates in the bulk to cause this difference. The surface composition will tend toward the congruently vaporizing composition which is YB/sub 4/ in the yttrium-Boron system and LaB/sub 6/ in the Lanthanum-Boron system. The CVC is also a function of temperature and may vary slightly for the same bulk composition at different temperature. Four Yttrium-Boron (Y-B) compounds, YB/sub 2/ /sub 5/, YB/sub 5/, YB/sub 6/ /sub 4/, YB/sub 14/ and three Lanthanum-Boron (La-B) compounds, LaB/sub 6/ /sub 01/, LaB/sub 8/ /sub 5/ and LaB/sub 5/ /sub 9/ were tested in a variable spacing vacuum emission system with a guard assembly. Emitted current measurements were made with interelctrode potentials between 250 and 1400 volts. Schottky plots were used to extrapolate the zero field currents. When a sample is taken from equilibrium to a new temperature, a definite time lag appears while vaporization rates change to bring about a new equilibrium surface composition. This manifests itself in the recorded emission currents. After thermal equilibrium is reached a distinct change is seen in emission currents. A higher density is measured, reflecting the emission of a surface that has been raised to a higher temperature. But with time, at this temperature, the surface reacts through vaporization and a new composition appears that is closer to the congruently vaporizing composition, and hence, has a work function nearer that of the CVC.

  6. Coprecipitation and isotopic fractionation of boron in modern biogenic carbonates

    SciTech Connect

    Vengosh, A. Hebrew Univ., Jerusalem ); Chivas, A.R.; McCulloch, M.T. ); Kolodny, Y.; Starinsky, A. )

    1991-10-01

    The abundances and isotopic composition of boron in modern, biogenic calcareous skeletons from the Gulf of Elat, Israel, the Great Barrier Reef, Australia, and in deep-sea sediments have been examined by negative thermal-ionization mass spectrometry. The selected species (Foraminifera, Pteropoda, corals, Gastropoda, and Pelecypoda) yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals. The variations of {delta}{sup 11}B may be controlled by isotopic exchange of boron species in which {sup 10}B is preferentially partitioned into the tetrahedral species, and coprecipitation of different proportions of trigonal and tetrahedral species in the calcium carbonates. The B content and {delta}{sup 11}B values of deep-sea sediments, Foraminifera tests, and corals are used to estimate the global oceanic sink of elemental boron by calcium carbonate deposition. As a result of enrichment of B in corals, a substantially higher biogenic sink of 6.4 {plus minus} 0.9 {times} 10{sup 10} g/yr is calculated for carbonates. This is only slightly lower than the sink for desorbable B in marine sediments (10 {times} 10{sup 10} g/yr) and approximately half that of altered oceanic crust (14 {times} 10{sup 10} g/yr). Thus, carbonates are an important sink for B in the oceans being {approximately}20% of the total sinks. The preferential incorporation of {sup 10}B into calcium carbonate results in oceanic {sup 11}B-enrichment, estimated as 1.2 {plus minus} 0.3 {times} 10{sup 12} per mil {center dot} g/yr. The boron-isotope composition of authigenic, well-preserved carbonate skeletons may provide a useful tool to record secular boron-isotope variations in seawater at various times in the geological record.

  7. Plasma-induced highly efficient synthesis of boron doped reduced graphene oxide for supercapacitors.

    PubMed

    Li, Shaobo; Wang, Zhaofeng; Jiang, Hanmei; Zhang, Limei; Ren, Jingzheng; Zheng, Mingtao; Dong, Lichun; Sun, Luyi

    2016-09-21

    In this work, we presented a novel route to synthesize boron doped reduced graphene oxide (rGO) by using the dielectric barrier discharge (DBD) plasma technology under ambient conditions. The doping of boron (1.4 at%) led to a significant improvement in the capacitance of rGO and supercapacitors based on the as-synthesized B-rGO exhibited an outstanding specific capacitance.

  8. Boronated porhyrins and methods for their use

    DOEpatents

    Miura, Michiko; Shelnutt, John A.; Slatkin, Daniel N.

    1999-03-02

    The present invention covers boronated porphyrins containing multiple carborane cages which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies such as boron neutron capture therapy and photodynamic therapy.

  9. Boronated porhyrins and methods for their use

    DOEpatents

    Miura, M.; Shelnutt, J.A.; Slatkin, D.N.

    1999-03-02

    The present invention covers boronated porphyrins containing multiple carborane cages which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies such as boron neutron capture therapy and photodynamic therapy. 3 figs.

  10. Synthesis and Utility of Dihydropyridine Boronic Esters**

    PubMed Central

    Panda, Santanu; Coffin, Aaron; Nguyen, Q. Nhu; Tantillo, Dean; Ready, Joseph M.

    2016-01-01

    When activated by an acylating agent, pyridine boronic esters react with organometallic reagents to form a dihydropyridine boronic ester. This intermediate allows access to a number of valuable substituted pyridine, dihydropyridine and piperidine products. PMID:26694785

  11. Synthesis and Utility of Dihydropyridine Boronic Esters.

    PubMed

    Panda, Santanu; Coffin, Aaron; Nguyen, Q Nhu; Tantillo, Dean J; Ready, Joseph M

    2016-02-05

    When activated by an acylating agent, pyridine boronic esters react with organometallic reagents to form a dihydropyridine boronic ester. This intermediate allows access to a number of valuable substituted pyridine, dihydropyridine, and piperidine products.

  12. Processing of boron carbide

    NASA Astrophysics Data System (ADS)

    Cho, Namtae

    The processing of boron carbide powder including sintering optimization, green body optimization and sintering behavior of nano-sized boron carbide was investigated for the development of complex shaped body armor. Pressureless sintered B4C relative densities as high as 96.7% were obtained by optimizing the soak temperature, and holding at that temperature for the minimum time required to reach terminal density. Although the relative densities of pressureless sintered specimens were lower than that of commercially produced hot-pressed B4C, their (Vickers) hardness values were comparable. For 4.45 cm dia. 1.35 cm height disk-shaped specimens, pressureless sintered to at least 93.0% relative density, post-hot isostatic pressing resulted in vast increases in relative densities (e.g. 100.0%) and hardness values significantly greater than that of commercially produced hot-pressed B 4C. The densification behavior of 20-40nm graphite-coated B4C nano-particles was studied using dilatometry, x-ray diffraction and electron microscopy. The higher than expected sintering onset from a nano-scale powder (˜1500°C) was caused by remnant B2O3 not removed by methanol washing, keeping particles separated until volatilization, and the carbon coatings, which imposed particle to particle contact of a substance more refractory than B4C. Solid state sintering (1500-1850°C) was followed by an arrest in contraction attributed to formation of eutectic liquid droplets of size more than 10X the original nano-particles. These droplets, induced to form well below known B4C-graphite eutectic temperatures by the high surface energy of nanoparticles, are interpreted to have quickly solidified to form a vast number of voids in particle packing, which in turn, impeded continued solid state sintering. Starting at 2200°C, a permanent liquid phase formed which facilitated a rapid measured contraction by liquid phase sintering and/or compact slumping.

  13. Ultrahard nanotwinned cubic boron nitride.

    PubMed

    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

    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.

  14. Methods for boron delivery to mammalian tissue

    DOEpatents

    Hawthorne, M. Frederick; Feaks, Debra A.; Shelly, Kenneth J.

    2003-01-01

    Boron neutron capture therapy can be used to destroy tumors. This treatment modality is enhanced by delivering compounds to the tumor site where the compounds have high concentrations of boron, the boron compounds being encapsulated in the bilayer of a liposome or in the bilayer as well as the internal space of the liposomes. Preferred compounds, include carborane units with multiple boron atoms within the carborane cage structure. Liposomes with increased tumor specificity may also be used.

  15. Methods and compositions for boronizing metallic surfaces

    SciTech Connect

    Reid, D. K.

    1985-11-26

    The present disclosure is directed to methods and compositions for boronizing metal and in particular ferrous surfaces. It has been discovered that if hydrocarbons are processed in metallic equipment which have been previously boronized, that coke formation and deposition which is commonly experienced at high temperatures can be minimized if not totally eliminated. The compositions utilized for this purpose are comprised of boron or boron compounds contained in an organic solvent or carrier together with specific activating materials.

  16. Diffusion of boron in alloys

    SciTech Connect

    Wang, W.; Zhang, S; He, X.

    1995-04-01

    By means of particle tracking autoradiography (PTA), the diffusion coefficients of boron between 900 and 1,200 C were measured in 04MnNbB steel, 25MnTiB steel, Ni-B, Fe-30%Ni-B and Fe-3%Si-B alloys, and the frequency factor D{sub 0} and activation energy Q were obtained respectively. The experiment results indicated that there was an obvious difference between the present result and the result obtained by Busby (in 1953). It was found that the boron diffusivity in {gamma}-Fe increased as Ni was added. The diffusivity of boron in Fe-3%Si-B alloy with b.c.c. structure was much slower than one obtained by Busby in {alpha}-Fe (1954), which, however, was much faster than the results obtained in {gamma}-Fe (with f.c.c. structure). Based on the present data of boron diffusion coefficients, the mechanism of segregation of boron to grain boundaries is discussed.

  17. Wettability of boron carbide

    SciTech Connect

    Torvund, T.; Akselsen, O.M.; Ulvensoeen, J.H.; Grong, O.

    1994-12-31

    The wettability of boron carbide has been examined by means of the sessile drop method, using the following candidate alloys: (96wt%AG-4wt%Ti), (Ag-26.5wt%Cu-3wt%Ti), (Sn-10wt%Ag-4wt%Ti), Sn(99.95wt%) and Al(99.99wt%). The results show that B{sub 4}C is completely wetted by the Ag-based alloys. Sn-10wt%Ag-4wt%Ti alloy and pure Al partly wet the B{sub 4}C surface, while pure Sn does not wet B{sub 4}C at all. For all the alloys used, except pure Sn, a reaction layer was observed at the interface between the ceramic part and the metal drop. Although the spreading kinetics of the Al-drop was much slower compared with the Ti-containing alloys, the reaction rate was considerably higher in the former case. This suggests that aluminium is an attractive candidate material for brazing of B{sub 4}C. Formation of the low melting B{sub 2}O{sub 3} at the B{sub 4}C surface may cause oxidation of the filler metal during joining, which, in turn, leads to a low bond strength.

  18. Boron intake and prostate cancer risk.

    PubMed

    Gonzalez, Alejandro; Peters, Ulrike; Lampe, Johanna W; White, Emily

    2007-12-01

    Experimental studies suggest that boron may prevent prostate cancer. Only one small epidemiological study has been conducted of boron, which found that those in the highest quartile of boron intake had less than half the risk of prostate cancer versus those in the lowest quartile. We evaluated the association between boron intake and prostate cancer within the VITamins And Lifestyle (VITAL) cohort. A total of 35,244 men completed the baseline supplement and food frequency questionnaire (FFQ) in 2000-2002. A boron database was constructed from published sources to estimate boron intake from the FFQ and from multivitamins. A total of 832 men developed prostate cancer from baseline to 31 December 2004. Dietary boron intake and total boron intake from diet plus multivitamins were not associated with prostate cancer risk. The hazard ratio of prostate cancer for those in the highest versus lowest quartile of total boron intake was 1.17 (95% CI 0.85, 1.61). This risk did not vary by prostate cancer stage or Gleason score. Furthermore, none of the foods high in boron content was associated with a decreased risk of prostate cancer. This cohort study provides no evidence for a preventive role of boron intake on prostate cancer. Since few studies exist on this topic, future research is needed to better elucidate any role that boron may play in the prevention of prostate cancer.

  19. Mineral resource of the month: boron

    USGS Publications Warehouse

    Lyday, Phyllis A.

    2005-01-01

    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.

  20. Techniques for increasing boron fiber fracture strain

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1977-01-01

    Improvement in the strain-to-failure of chemical-vapor-deposition boron fibers is shown possible by contracting the tungsten boride core region and its inherent flaws. Results of three methods are presented in which etching and thermal-processing techniques were employed to achieve core flaw contraction by internal stresses available in the boron sheath. After commercially and treatment-induced surface flaws were removed from 203-micron (8-mil) fibers, the core flaw was observed to be essentially the only source of fiber fracture. Thus, fiber strain-to-failure was found to improve by an amount equal to the treatment-induced contraction on the core flaw. To date, average fracture strains and stresses greater than 1.4% and 5.5 GN/sq m (800 ksi), respectively, have been achieved. Commercial feasibility considerations suggest as the most cost-effective technique that method in which as-produced fibers are given a rapid heat treatment above 700 C. Preliminary results concerning the contraction kinetics and fracture behavior observed with this technique are presented and discussed for both high-vacuum and argon-gas heat-treatment environments.

  1. Electrochemical Corrosion Behavior of Spray-Formed Boron-Modified Supermartensitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Zepon, Guilherme; Nogueira, Ricardo P.; Kiminami, Claudio S.; Botta, Walter J.; Bolfarini, Claudemiro

    2017-04-01

    Spray-formed boron-modified supermartensitic stainless steel (SMSS) grades are alloys developed to withstand severe wear conditions. The addition of boron to the conventional chemical composition of SMSS, combined with the solidification features promoted by the spray forming process, leads to a microstructure composed of low carbon martensitic matrix reinforced by an eutectic network of M2B-type borides, which considerably increases the wear resistance of the stainless steel. Although the presence of borides in the microstructure has a very beneficial effect on the wear properties of the alloy, their effect on the corrosion resistance of the stainless steel was not comprehensively evaluated. The present work presents a study of the effect of boron addition on the corrosion resistance of the spray-formed boron-modified SMSS grades by means of electrochemical techniques. The borides fraction seems to have some influence on the repassivation kinetics of the spray-formed boron-modified SMSS. It was shown that the Cr content of the martensitic matrix is the microstructural feature deciding the corrosion resistance of this sort of alloys. Therefore, if the Cr content in the alloy is increased to around 14 wt pct to compensate for the boron consumed by the borides formation, the corrosion resistance of the alloy is kept at the same level of the alloy without boron addition.

  2. Early-life exposure to lithium and boron from drinking water.

    PubMed

    Harari, Florencia; Ronco, Ana María; Concha, Gabriela; Llanos, Miguel; Grandér, Margaretha; Castro, Francisca; Palm, Brita; Nermell, Barbro; Vahter, Marie

    2012-12-01

    The transfer of lithium and boron from exposed mothers to fetuses and breast-fed infants was investigated in areas in northern Argentina and Chile with up to 700 μg lithium/L and 5-10 mg boron/L in drinking water. Maternal and cord blood concentrations were strongly correlated and similar in size for both lithium (47 and 70 μg/L, respectively) and boron (220 and 145 μg/L, respectively). The first infant urine produced after birth contained the highest concentrations (up to 1700 μg lithium/L and 14,000 μg boron/L). Breast-milk contained 40 and 60% of maternal blood concentrations of lithium and boron, respectively (i.e. about 30 and 250 μg/L, respectively, in high exposure areas), and infant urine concentrations decreased immediately after birth (120 μg lithium/L and 920 μg boron/L). We conclude that lithium and boron easily passed the placenta to the fetus, and that exclusively breast-fed infants seemed to have lower exposure than formula-fed infants.

  3. SU-E-T-656: Quantitative Analysis of Proton Boron Fusion Therapy (PBFT) in Various Conditions

    SciTech Connect

    Yoon, D; Jung, J; Shin, H; Kim, M; Suh, T; Jang, H

    2015-06-15

    Purpose: Three alpha particles are concomitant of proton boron interaction, which can be used in radiotherapy applications. We performed simulation studies to determine the effectiveness of proton boron fusion therapy (PBFT) under various conditions. Methods: Boron uptake regions (BURs) of various widths and densities were implemented in Monte Carlo n-particle extended (MCNPX) simulation code. The effect of proton beam energy was considered for different BURs. Four simulation scenarios were designed to verify the effectiveness of integrated boost that was observed in the proton boron reaction. In these simulations, the effect of proton beam energy was determined for different physical conditions, such as size, location, and boron concentration. Results: Proton dose amplification was confirmed for all proton beam energies considered (< 96.62%). Based on the simulation results for different physical conditions, the threshold for the range in which proton dose amplification occurred was estimated as 0.3 cm. Effective proton boron reaction requires the boron concentration to be equal to or greater than 14.4 mg/g. Conclusion: We established the effects of the PBFT with various conditions by using Monte Carlo simulation. The results of our research can be used for providing a PBFT dose database.

  4. Electrochemical Corrosion Behavior of Spray-Formed Boron-Modified Supermartensitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Zepon, Guilherme; Nogueira, Ricardo P.; Kiminami, Claudio S.; Botta, Walter J.; Bolfarini, Claudemiro

    2017-01-01

    Spray-formed boron-modified supermartensitic stainless steel (SMSS) grades are alloys developed to withstand severe wear conditions. The addition of boron to the conventional chemical composition of SMSS, combined with the solidification features promoted by the spray forming process, leads to a microstructure composed of low carbon martensitic matrix reinforced by an eutectic network of M2B-type borides, which considerably increases the wear resistance of the stainless steel. Although the presence of borides in the microstructure has a very beneficial effect on the wear properties of the alloy, their effect on the corrosion resistance of the stainless steel was not comprehensively evaluated. The present work presents a study of the effect of boron addition on the corrosion resistance of the spray-formed boron-modified SMSS grades by means of electrochemical techniques. The borides fraction seems to have some influence on the repassivation kinetics of the spray-formed boron-modified SMSS. It was shown that the Cr content of the martensitic matrix is the microstructural feature deciding the corrosion resistance of this sort of alloys. Therefore, if the Cr content in the alloy is increased to around 14 wt pct to compensate for the boron consumed by the borides formation, the corrosion resistance of the alloy is kept at the same level of the alloy without boron addition.

  5. The effect of boron implant energy on transient enhanced diffusion in silicon

    SciTech Connect

    Liu, J.; Krishnamoorthy, V.; Gossman, H.; Rubin, L.; Law, M.E.; Jones, K.S.

    1997-02-01

    Transient enhanced diffusion (TED) of boron in silica after low energy boron implantation and annealing was investigated using boron-doping superlattices (DSLs) grown by low temperature molecular beam epitaxy. Boron ions were implanted at 5, 10, 20, and 40 keV at a constant dose of 2{times}10{sup 14}/cm{sup 2}. Subsequent annealing was performed at 750{degree}C for times of 3 min, 15 min, and 2 h in a nitrogen ambient. The broadening of the boron spikes was measured by secondary ion mass spectroscopy and simulated. Boron diffusivity enhancement was quantified as a function of implant energy. Transmission electron microscopy results show that {l_angle}311{r_angle} defects are only seen for implant energies {ge}10 keV at this dose and that the density increases with energy. DSL studies indicate the point defect concentration in the background decays much slower when {l_angle}311{r_angle} defects are present. These results imply there are at least two sources of TED for boron implants (B-I): short time component that decays rapidly consistent with nonvisible B-I pairs and a longer time component consistent with interstitial release from the {l_angle}311{r_angle} defects. {copyright} {ital 1997 American Institute of Physics.}

  6. Hemorrhage in mouse tumors induced by dodecaborate cluster lipids intended for boron neutron capture therapy.

    PubMed

    Schaffran, Tanja; Jiang, Nan; Bergmann, Markus; Küstermann, Ekkehard; Süss, Regine; Schubert, Rolf; Wagner, Franz M; Awad, Doaa; Gabel, Detlef

    2014-01-01

    The potential of boron-containing lipids with three different structures, which were intended for use in boron neutron capture therapy, was investigated. All three types of boron lipids contained the anionic dodecaborate cluster as the headgroup. Their effects on two different tumor models in mice following intravenous injection were tested; for this, liposomes with boron lipid, distearoyl phosphatidylcholine, and cholesterol as helper lipids, and containing a polyethylene glycol lipid for steric protection, were administered intravenously into tumor-bearing mice (C3H mice for SCCVII squamous cell carcinoma and BALB/c mice for CT26/WT colon carcinoma). With the exception of one lipid (B-THF-14), the lipids were well tolerated, and no other animal was lost due to systemic toxicity. The lipid which led to death was not found to be much more toxic in cell culture than the other boron lipids. All of the lipids that were well tolerated showed hemorrhage in both tumor models within a few hours after administration. The hemorrhage could be seen by in vivo magnetic resonance and histology, and was found to occur within a few hours. The degree of hemorrhage depended on the amount of boron administered and on the tumor model. The observed unwanted effect of the lipids precludes their use in boron neutron capture therapy.

  7. Graphene on hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Yankowitz, Matthew; Xue, Jiamin; LeRoy, B. J.

    2014-07-01

    The field of graphene research has developed rapidly since its first isolation by mechanical exfoliation in 2004. Due to the relativistic Dirac nature of its charge carriers, graphene is both a promising material for next-generation electronic devices and a convenient low-energy testbed for intrinsically high-energy physical phenomena. Both of these research branches require the facile fabrication of clean graphene devices so as not to obscure its intrinsic physical properties. Hexagonal boron nitride has emerged as a promising substrate for graphene devices as it is insulating, atomically flat and provides a clean charge environment for the graphene. Additionally, the interaction between graphene and boron nitride provides a path for the study of new physical phenomena not present in bare graphene devices. This review focuses on recent advancements in the study of graphene on hexagonal boron nitride devices from the perspective of scanning tunneling microscopy with highlights of some important results from electrical transport measurements.

  8. Boron doping a semiconductor particle

    DOEpatents

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

    1998-06-09

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

  9. Boron doping a semiconductor particle

    DOEpatents

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

    1998-06-09

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

  10. Energetics and electronic structure of double-walled boron nanotubes

    NASA Astrophysics Data System (ADS)

    Tang, Hui; Ismail-Beigi, Sohrab

    2010-03-01

    Single-walled boron nanotubes have been studied extensively since their first successful fabrication in experiments. On the other hand, double-walled or multi-walled boron nanotubes have not yet been discussed in literature. Here, using density functional theory, we present a stable semiconducting two-dimensional double-layered boron sheet, which is 0.14 eV/atom more stable than the most stable single-layered α-sheet [1]. This double-layered sheet is stabilized due to the formation of inter-layer bonds. We show that double-walled boron nanotubes made from this double-layered sheet are all semiconducting. These double-walled nanotubes are more stable than single-walled ones for large nanotubes, but become less energetically favorable when the tube radius is smaller than 20 å due to their large curvature energies. To reduce the large curvature energies, we construct double-walled nanotubes whose inner and outer walls have different number of atoms around their circumference. The resulting nanotubes are more stable than single-walled ones for all radii.[4pt] [1] H. Tang, and S. Ismail-Beigi, PRL 99, 115501 (2007).

  11. Boron oxygen complexes in Si

    NASA Astrophysics Data System (ADS)

    Sanati, M.; Estreicher, S. K.

    2006-04-01

    The carrier lifetime in boron-doped Czochralski Si is strongly reduced by irradiation (space-based solar cells) or illumination (terrestrial cells). The culprits are believed to be boron-oxygen complexes. We use first-principles theory to predict the structure, electrical activity, and stability of complexes involving substitutional or interstitial B and interstitial O or oxygen dimers. Four complexes with comparable binding energies and thermodynamic gap levels are identified and their local vibrational modes predicted. Replacing B with Ga yields complexes with much smaller binding energies.

  12. Analytical boron diffusivity model in silicon for thermal diffusion from boron silicate glass film

    NASA Astrophysics Data System (ADS)

    Kurachi, Ikuo; Yoshioka, Kentaro

    2015-09-01

    An analytical boron diffusivity model in silicon for thermal diffusion from a boron silicate glass (BSG) film has been proposed in terms of enhanced diffusion due to boron-silicon interstitial pair formation. The silicon interstitial generation is considered to be a result of the silicon kick-out mechanism by the diffused boron at the surface. The additional silicon interstitial generation in the bulk silicon is considered to be the dissociation of the diffused pairs. The former one causes the surface boron concentration dependent diffusion. The latter one causes the local boron concentration dependent diffusion. The calculated boron profiles based on the diffusivity model are confirmed to agree with the actual diffusion profiles measured by secondary ion mass spectroscopy (SIMS) for a wide range of the BSG boron concentration. This analytical diffusivity model is a helpful tool for p+ boron diffusion process optimization of n-type solar cell manufacturing.

  13. Boron Nitride Nanoribbons from Exfoliation of Boron Nitride Nanotubes

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Hurst, Janet; Santiago, Diana

    2017-01-01

    Two types of boron nitride nanotubes (BNNTs) were exfoliated into boron nitride nanoribbons (BNNR), which were identified using transmission electron microscopy: (1) commercial BNNTs with thin tube walls and small diameters. Tube unzipping was indicated by a large decrease of the sample's surface area and volume for pores less than 2 nm in diameter. (2) BNNTs with large diameters and thick walls synthesized at NASA Glenn Research Center. Here, tube unraveling was indicated by a large increase in external surface area and pore volume. For both, the exfoliation process was similar to the previous reported method to exfoliate commercial hexagonal boron nitride (hBN): Mixtures of BNNT, FeCl3, and NaF (or KF) were sequentially treated in 250 to 350 C nitrogen for intercalation, 500 to 750 C air for exfoliation, and finally HCl for purification. Property changes of the nanosized boron nitride throughout this process were also similar to the previously observed changes of commercial hBN during the exfoliation process: Both crystal structure (x-ray diffraction data) and chemical properties (Fourier-transform infrared spectroscopy data) of the original reactant changed after intercalation and exfoliation, but most (not all) of these changes revert back to those of the reactant once the final, purified products are obtained.

  14. Computational Studies of Nanostructures of Boron

    NASA Astrophysics Data System (ADS)

    Tandy, P.; Yu, M.; Leahy, C.; Tian, W. Q.; Wu, S. Y.; Jayanthi, C. S.

    2009-03-01

    The goal of this work is to develop a reliable semi-empirical Hamiltonian for boron that may be used to predict nanostructures of boron. It is well known that bonding in boron is complicated as it may form three-center, two-electron bonds. The semi-empirical Hamiltonian used here was recently developed by Leahy et al. in the framework of linear combination of atomic orbitals[1]. The salient feature of this Hamiltonian is that it treats environment dependency and charge redistributions on equal footing. It will be shown that such a parameterized Hamiltonian can predict the B80 cage structure with C1 symmetry as found in a recent first-principles study [2]. Having validated our semi-empirical Hamiltonian for boron with small boron clusters and the B80 cage, we have performed a systematic study of other boron nanostructures: (i) larger cage structures (e.g., B215), (ii) boron clusters cut from the bulk alpha boron, and (iii) boron sheets (triangular sheets with and without holes). We will discuss the ground state structures of these boron nanostructures as well as the energetics and HOMO-LUMO gaps of different families of boron clusters as a function their diameters. 1. C. Leahy et al. Phys. Rev. B74, 155408 (2006). 2. N. G. Szwacki et al. PRL 100, 159901 (2008).

  15. Thermionic properties of the molybdenum boron system

    SciTech Connect

    Storms, E.K.

    1980-01-01

    The thermionic work function has been measured as a function of composition within the various two phase regions between Mo and MoB/sub 2/. Values at the low boron and high boron phase boundaries for the various compounds were obtained by extrapolation. The following effective work functions were obtained: Mo/sub 2/B (low boron) = 3.08 eV; Mo/sub 2/B (high boron) = 3.63 eV; ..cap alpha..-MoB (low boron) = 3.38 eV; ..cap alpha..-MoB (high boron) = 4.30 eV; ..beta..-MoB (low boron) = 2.83 eV; ..beta..-MoB (high boron) = 3.92; Mo/sub 2/B/sub 3/ (low boron) = 4.65 eV; Mo/sub 2/B/sub 3/ (high boron) = 3.85 eV; and MoB/sub 2/ (low boron) = 3.52 eV. Because the composition range of these compounds is very narrow, the work function is very sensitive to the composition within the single phase regions.

  16. Boron analysis and boron imaging in biological materials for Boron Neutron Capture Therapy (BNCT).

    PubMed

    Wittig, Andrea; Michel, Jean; Moss, Raymond L; Stecher-Rasmussen, Finn; Arlinghaus, Heinrich F; Bendel, Peter; Mauri, Pier Luigi; Altieri, Saverio; Hilger, Ralf; Salvadori, Piero A; Menichetti, Luca; Zamenhof, Robert; Sauerwein, Wolfgang A G

    2008-10-01

    Boron Neutron Capture Therapy (BNCT) is based on the ability of the stable isotope 10B to capture neutrons, which leads to a nuclear reaction producing an alpha- and a 7Li-particle, both having a high biological effectiveness and a very short range in tissue, being limited to approximately one cell diameter. This opens the possibility for a highly selective cancer therapy. BNCT strongly depends on the selective uptake of 10B in tumor cells and on its distribution inside the cells. The chemical properties of boron and the need to discriminate different isotopes make the investigation of the concentration and distribution of 10B a challenging task. The most advanced techniques to measure and image boron are described, both invasive and non-invasive. The most promising approach for further investigation will be the complementary use of the different techniques to obtain the information that is mandatory for the future of this innovative treatment modality.

  17. High fluence boron implantation into polyimide

    NASA Astrophysics Data System (ADS)

    Vacík, J.; Hnatowicz, V.; Červená, J.; Peřina, V.; Popok, V.; Odzhaev, V.; Fink, D.

    1999-01-01

    100 keV B + ions are implanted at high fluences into polyimide and the boron depth distributions are measured by the neutron depth profiling technique. Subsequently the implanted samples are annealed isochronally to determine the diffusional, trapping and detrapping behaviour of the boron atoms. The boron depth profiles of as-implanted samples differ significantly from those predicted by TRIM code. Pronounced inward and outward profile tails point at increased mobility and redistribution of boron atoms after implantation. Thermal annealing to the temperatures below 150°C does not change the total boron content in 1 μm thick surface layer and the boron depth profiles as well. For higher annealing temperatures a continuous desorption and significant redistribution of boron atoms is observed.

  18. [Boron neutron capture therapy of human gastric cancer by boron-containing immunoliposomes under thermal neutron irradiation].

    PubMed

    Xu, L

    1991-10-01

    Boron neutron capture therapy (BNCT) is based on the nuclear reaction yielding high LET Li-7 and alpha particles when boron-10 is irradiated with thermal neutrons. (Et4N)2(10)B10H10 was entrapped in 40 nm liposomes coating the monoclonal antibody, MGb 2, against human gastric cancer. There were 1.4 x 10(4) 10B atoms encapsulated and 20 molecules of MGb 2 incorporated per liposomes ELISA indicated that the immunoreactivity of antibodies on liposomes retained 80%. Preferred binding to human gastric cancer cell line SGC-7901 was observed as many as 15.1 x 10(9) 10B atoms/tumor cell, 38-fold more than that to normal human embryonic lung cell line SL 7. The fluorescent immunoliposome-stained tumor cells showed membrane-fluorescence while SL 7 cells showed no obvious fluorescence. Irradiated with thermal neutrons (0.025 eV, 3.12 x 10(11)n/cm2, gamma-ray 0.84 Gy), 10B-containing immunoliposomes pretreated SGC-7901 cells survived 27%, significantly lower than non-irradiated cells or non-pretreated cells with irradiation (P less than 0.001). The results demonstrated that boron-containing immunoliposomes could bind selectively and deliver sufficient amount of boron-10 to the target tumor cells.

  19. Structure of boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Buranova, Yu. S.; Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

    2015-01-01

    The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

  20. Boron trifluoride coatings for plastics

    NASA Technical Reports Server (NTRS)

    Kubacki, R. M.

    1978-01-01

    Tough, durable coatings of boron triflouride can be deposited on plastic optical components to protect them from destructive effects of abrasion, scratching, and environment. Coating material can be applied simultaneously with organic polymers, using plasma glow-discharge methods, or it can be used as base material for other coatings to increase adhesion.

  1. Method of separating boron isotopes

    DOEpatents

    Jensen, R.J.; Thorne, J.M.; Cluff, C.L.

    1981-01-23

    A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)-dichloroborane as the feed material. The photolysis can readily by achieved with CO/sub 2/ laser radiation and using fluences significantly below those required to dissociate BCl/sub 3/.

  2. Method of separating boron isotopes

    DOEpatents

    Jensen, Reed J.; Thorne, James M.; Cluff, Coran L.; Hayes, John K.

    1984-01-01

    A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)dichloroborane as the feed material. The photolysis can readily be achieved with CO.sub.2 laser radiation and using fluences significantly below those required to dissociate BCl.sub.3.

  3. Structure of boron nitride nanotubes

    SciTech Connect

    Buranova, Yu. S. Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

    2015-01-15

    The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

  4. Method of separating boron isotopes

    SciTech Connect

    Jensen, R.J.; Cluff, C.L.; Hayes, J.K.; Thorne, J.M.

    1984-05-08

    A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)dichloroborane as the feed material. The photolysis can readily be achieved with CO/sub 2/ laser radiation and using fluences significantly below those required to dissociate BCl/sub 3/.

  5. Periodic trends and index of boron LEwis acidity.

    PubMed

    Plumley, Joshua A; Evanseck, Jeffrey D

    2009-05-21

    Lewis acidity is customarily gauged by comparing the relative magnitude of coordinate covalent bonding energies, where the Lewis acid moiety is varied and the Lewis base is kept constant. However, the prediction of Lewis acidity from first principles is sometimes contrary to that suggested by experimental bond energies. Specifically, the order of boron trihalide Lewis acidities predicted from substituent electronegativity arguments is opposite to that inferred by experiment. Contemporary explanations for the divergence between theory, computation, and experiment have led to further consternation. Due to the fundamental importance of understanding the origin of Lewis acidity, we report periodic trends for 21 boron Lewis acids, as well as their coordinate covalent bond strengths with NH(3), utilizing ab initio, density functional theory, and natural bond orbital analysis. Coordinate covalent bond dissociation energy has been determined to be an inadequate index of Lewis acid strength. Instead, acidity is measured in the manner originally intended by Lewis, which is defined by the valence of the acid of interest. Boron Lewis acidity is found to depend upon substituent electronegativity and atomic size, differently than for known Brønsted-Lowry periodic trends. Across the second period, stronger substituent electronegativity correlates (R(2) = 0.94) with increased Lewis acidity. However, across the third period, an equal contribution from substituent electronegativity and atomic radii is correlated (R(2) = 0.98) with Lewis acidity. The data suggest that Lewis acidity depends upon electronegativity solely down group 14, while equal contribution from both substituent electronegativity and atomic size are significant down groups 16 and 17. Originally deduced from Pauling's electronegativities, boron's substituents determine acidity by influencing the population of its valence by withdrawing electron density. However, size effects manifest differently than previously

  6. Chronic boron exposure and human semen parameters.

    PubMed

    Robbins, Wendie A; Xun, Lin; Jia, Juan; Kennedy, Nola; Elashoff, David A; Ping, Liu

    2010-04-01

    Boron found as borates in soil, food, and water has important industrial and medical applications. A panel reviewing NTP reproductive toxicants identified boric acid as high priority for occupational studies to determine safe versus adverse reproductive effects. To address this, we collected boron exposure/dose measures in workplace inhalable dust, dietary food/fluids, blood, semen, and urine from boron workers and two comparison worker groups (n=192) over three months and determined correlations between boron and semen parameters (total sperm count, sperm concentration, motility, morphology, DNA breakage, apoptosis and aneuploidy). Blood boron averaged 499.2 ppb for boron workers, 96.1 and 47.9 ppb for workers from high and low environmental boron areas (p<0.0001). Boron concentrated in seminal fluid. No significant correlations were found between blood or urine boron and adverse semen parameters. Exposures did not reach those causing adverse effects published in animal toxicology work but exceeded those previously published for boron occupational groups.

  7. Boron neutron capture therapy for cancer

    SciTech Connect

    Barth, R.E.; Soloway, A.H. ); Fairchild, R.G. State Univ. of New York, Stony Brook )

    1990-10-01

    Boron neutron capture therapy (BNCT) bring together two components that when kept separate have only minor effects on normal cells. The first component is a stable isotope of boron (boron 10) that can be concentrated in tumor cells. The second is a beam of low-energy neutrons that produces short-range radiation when absorbed, or captured, by the boron. The combination of these two conditions at the site of a tumor releases intense radiation that can destroy malignant tissues. BNCT is based on the nuclear reaction that occurs when boron 10 is irradiated with an absorbs neutrons. The neutrons that it takes up are called thermal, or slow, neutrons. They are of such low energy that they cause little tissue damage as compared with other forms of radiation such as protons, gamma rays and fast neutrons. When an atom of boron 10 captures a neutron, an unstable isotope, boron 11, forms. The boron 11 instantly fissions, yielding lithium 7 nuclei and energetic alpha particles. These heavy particles, which carry 2.79 million electron volts of energy, are a highly lethal form of radiation. If the treatment proceeds as intended, the destructive effects of the capture reaction would occur primarily in those cancer cells that have accumulated boron 10. Normal cells with low concentrations of boron would be spared.

  8. Ferromagnetism and semiconducting of boron nanowires

    PubMed Central

    2012-01-01

    More recently, motivated by extensively technical applications of carbon nanostructures, there is a growing interest in exploring novel non-carbon nanostructures. As the nearest neighbor of carbon in the periodic table, boron has exceptional properties of low volatility and high melting point and is stronger than steel, harder than corundum, and lighter than aluminum. Boron nanostructures thus are expected to have broad applications in various circumstances. In this contribution, we have performed a systematical study of the stability and electronic and magnetic properties of boron nanowires using the spin-polarized density functional calculations. Our calculations have revealed that there are six stable configurations of boron nanowires obtained by growing along different base vectors from the unit cell of the bulk α-rhombohedral boron (α-B) and β-rhombohedral boron (β-B). Well known, the boron bulk is usually metallic without magnetism. However, theoretical results about the magnetic and electronic properties showed that, whether for the α-B-based or the β-B-based nanowires, their magnetism is dependent on the growing direction. When the boron nanowires grow along the base vector [001], they exhibit ferromagnetism and have the magnetic moments of 1.98 and 2.62 μB, respectively, for the α-c [001] and β-c [001] directions. Electronically, when the boron nanowire grows along the α-c [001] direction, it shows semiconducting and has the direct bandgap of 0.19 eV. These results showed that boron nanowires possess the unique direction dependence of the magnetic and semiconducting behaviors, which are distinctly different from that of the bulk boron. Therefore, these theoretical findings would bring boron nanowires to have many promising applications that are novel for the boron bulk. PMID:23244063

  9. Pharmacokinetics of core-polymerized, boron-conjugated micelles designed for boron neutron capture therapy for cancer.

    PubMed

    Sumitani, Shogo; Oishi, Motoi; Yaguchi, Tatsuya; Murotani, Hiroki; Horiguchi, Yukichi; Suzuki, Minoru; Ono, Koji; Yanagie, Hironobu; Nagasaki, Yukio

    2012-05-01

    Core-polymerized and boron-conjugated micelles (PM micelles) were prepared by free radical copolymerization of a PEG-b-PLA block copolymer bearing an acetal group and a methacryloyl group (acetal-PEG-b-PLA-MA), with 1-(4-vinylbenzyl)-closo-carborane (VB-carborane), and the utility of these micelles as a tumor-targeted boron delivery system was investigated for boron neutron capture therapy (BNCT). Non-polymerized micelles (NPM micelles) that incorporated VB-carborane physically showed significant leakage of VB-carborane (ca. 50%) after 12 h incubation with 10% fetal bovine serum (FBS) at 37 °C. On the other hand, no leakage from the PM micelles was observed even after 48 h of incubation. To clarify the pharmacokinetics of the micelles, (125)I (radioisotope)-labeled PM and NPM micelles were administered to colon-26 tumor-bearing BALB/c mice. The (125)I-labeled PM micelles showed prolonged blood circulation (area under the concentration curve (AUC): 943.4) than the (125)I-labeled NPM micelles (AUC: 495.1), whereas tumor accumulation was similar for both types of micelles (AUC(PM micelle): 249.6, AUC(NPM micelle): 201.1). In contrast, the tumor accumulation of boron species in the PM micelles (AUC: 268.6) was 7-fold higher than the NPM micelles (AUC: 37.1), determined by ICP-AES. Thermal neutron irradiation yielded tumor growth suppression in the tumor-bearing mice treated with the PM micelles without reduction in body weight. On the basis of these data, the PM micelles represent a promising approach to the creation of boron carrier for BNCT. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Boron neutron capture therapy demonstrated in mice bearing EMT6 tumors following selective delivery of boron by rationally designed liposomes

    PubMed Central

    Kueffer, Peter J.; Maitz, Charles A.; Khan, Aslam A.; Schuster, Seth A.; Shlyakhtina, Natalia I.; Jalisatgi, Satish S.; Brockman, John D.; Nigg, David W.; Hawthorne, M. Frederick

    2013-01-01

    The application of boron neutron capture therapy (BNCT) following liposomal delivery of a 10B-enriched polyhedral borane and a carborane against mouse mammary adenocarcinoma solid tumors was investigated. Unilamellar liposomes with a mean diameter of 134 nm or less, composed of an equimolar mixture of cholesterol and 1,2-distearoyl-sn-glycero-3-phosphocholine and incorporating Na3[1-(2′-B10H9)-2-NH3B10H8] in the aqueous interior and K[nido-7-CH3(CH2)15-7,8-C2B9H11] in the bilayer, were injected into the tail veins of female BALB/c mice bearing right flank EMT6 tumors. Biodistribution studies indicated that two identical injections given 24 h apart resulted in tumor boron levels exceeding 67 µg/g tumor at 54 h—with tumor/blood boron ratios being greatest at 96 h (5.68:1; 43 µg boron/g tumor)—following the initial injection. For BNCT experiments, tumor-bearing mice were irradiated 54 h after the initial injection for 30 min with thermal neutrons, resulting in a total fluence of 1.6 × 1012 neutrons per cm2 (±7%). Significant suppression of tumor growth was observed in mice given BNCT vs. control mice (only 424% increase in tumor volume at 14 d post irradiation vs. 1551% in untreated controls). In a separate experiment in which mice were given a second injection/irradiation treatment 7 d after the first, the tumor growth was vastly diminished (186% tumor volume increase at 14 d). A similar response was obtained for mice irradiated for 60 min (169% increase at 14 d), suggesting that neutron fluence was the limiting factor controlling BNCT efficacy in this study. PMID:23536304

  11. Boron neutron capture therapy demonstrated in mice bearing EMT6 tumors following selective delivery of boron by rationally designed liposomes.

    PubMed

    Kueffer, Peter J; Maitz, Charles A; Khan, Aslam A; Schuster, Seth A; Shlyakhtina, Natalia I; Jalisatgi, Satish S; Brockman, John D; Nigg, David W; Hawthorne, M Frederick

    2013-04-16

    The application of boron neutron capture therapy (BNCT) following liposomal delivery of a (10)B-enriched polyhedral borane and a carborane against mouse mammary adenocarcinoma solid tumors was investigated. Unilamellar liposomes with a mean diameter of 134 nm or less, composed of an equimolar mixture of cholesterol and 1,2-distearoyl-sn-glycero-3-phosphocholine and incorporating Na3[1-(2'-B10H9)-2-NH3B10H8] in the aqueous interior and K[nido-7-CH3(CH2)15-7,8-C2B9H11] in the bilayer, were injected into the tail veins of female BALB/c mice bearing right flank EMT6 tumors. Biodistribution studies indicated that two identical injections given 24 h apart resulted in tumor boron levels exceeding 67 µg/g tumor at 54 h--with tumor/blood boron ratios being greatest at 96 h (5.68:1; 43 µg boron/g tumor)--following the initial injection. For BNCT experiments, tumor-bearing mice were irradiated 54 h after the initial injection for 30 min with thermal neutrons, resulting in a total fluence of 1.6 × 10(12) neutrons per cm(2) (±7%). Significant suppression of tumor growth was observed in mice given BNCT vs. control mice (only 424% increase in tumor volume at 14 d post irradiation vs. 1551% in untreated controls). In a separate experiment in which mice were given a second injection/irradiation treatment 7 d after the first, the tumor growth was vastly diminished (186% tumor volume increase at 14 d). A similar response was obtained for mice irradiated for 60 min (169% increase at 14 d), suggesting that neutron fluence was the limiting factor controlling BNCT efficacy in this study.

  12. Reductive Insertion of Elemental Chalcogens into Boron-Boron Multiple Bonds.

    PubMed

    Braunschweig, Holger; Dellermann, Theresa; Ewing, William C; Kramer, Thomas; Schneider, Christoph; Ullrich, Stefan

    2015-08-24

    The syntheses of sulfur- and selenium-bridged cyclic compounds containing boron stabilized by N-heterocyclic carbenes (NHCs) have been achieved by the reductive insertion of elemental chalcogens into boron-boron multiple bonds. The three pairs of bonding electrons between the boron atoms in the triply bonded diboryne enabled six-electron reduction reactions, resulting in the formation of [2.2.1]-bicyclic systems wherein bridgehead boron atoms are spanned by three chalcogen bridges. A similar reaction using a diborene (boron-boron double bond) resulted in the reductive transfer of both pairs of bonding electrons to three sulfur atoms, yielding a NHC-stabilized trisulfidodiborolane. The demonstration of these six- and four-electron reductions lends support to the presence of three and two pairs of bonding electrons between the boron atoms of the diboryne and diborene, respectively, a fact that may be useful in future discussions on bond order.

  13. Jaguar Procedures for Detonation Behavior of Explosives Containing Boron

    NASA Astrophysics Data System (ADS)

    Stiel, L. I.; Baker, E. L.; Capellos, C.

    2009-12-01

    The Jaguar product library was expanded to include boron and boron containing products by analysis of Available Hugoniot and static volumetric data to obtain constants of the Murnaghan relationships for the components. Experimental melting points were also utilized to obtain the constants of the volumetric relationships for liquid boron and boron oxide. Detonation velocities for HMX—boron mixtures calculated with these relationships using Jaguar are in closer agreement with literature values at high initial densities for inert (unreacted) boron than with the completely reacted metal. These results indicate that the boron does not react near the detonation front or that boron mixtures exhibit eigenvalue detonation behavior (as shown by some aluminized explosives), with higher detonation velocities at the initial points. Analyses of calorimetric measurements for RDX—boron mixtures indicate that at high boron contents the formation of side products, including boron nitride and boron carbide, inhibits the detonation properties of the formulation.

  14. Synthesis of boron nitride nanotubes by boron ink annealing

    NASA Astrophysics Data System (ADS)

    Li, Lu Hua; Chen, Ying; Glushenkov, Alexey M.

    2010-03-01

    Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). We report that the method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing gas to form nanotubes. The new method greatly enhances the yield of BNNTs, giving a higher density of nanotubes. These improvements are caused by the addition of metal nitrate and ethanol, both of which can strongly boost the nitriding reaction, as revealed by thermogravimetric analysis. The size and structure of BNNTs can be controlled by varying the annealing conditions. This high-yield production of BNNTs in large quantities enables the large-scale application of BNNTs.

  15. Synthesis of boron nitride nanotubes by boron ink annealing.

    PubMed

    Li, Lu Hua; Chen, Ying; Glushenkov, Alexey M

    2010-03-12

    Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). We report that the method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing gas to form nanotubes. The new method greatly enhances the yield of BNNTs, giving a higher density of nanotubes. These improvements are caused by the addition of metal nitrate and ethanol, both of which can strongly boost the nitriding reaction, as revealed by thermogravimetric analysis. The size and structure of BNNTs can be controlled by varying the annealing conditions. This high-yield production of BNNTs in large quantities enables the large-scale application of BNNTs.

  16. Longitudinal Splitting of Boron Nitride Nanotubes for the Facile Synthesis of High Quality Boron Nitride Nanoribbons

    DTIC Science & Technology

    2011-05-24

    Boron Nitride Nanotubes for the Facile Synthesis of High Quality Boron Nitride Nanoribbons Kris J. Erickson,†,‡,§ Ashley...We report the synthesis of BNNRs through the potassium-intercalation-induced longitudinal splitting of boron nitride nanotubes (BNNTs). This facile...COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Longitudinal Splitting of Boron Nitride Nanotubes for the Facile Synthesis of High

  17. Mapping Boron Dioxide (BO2) Light Emission During Ballistic Initiation of Boron

    DTIC Science & Technology

    2016-03-03

    ARL-TN-0738 ● FEB 2016 US Army Research Laboratory Mapping Boron Dioxide (BO2) Light Emission During Ballistic Initiation of...ARL-TN-0738 ● FEB 2016 US Army Research Laboratory Mapping Boron Dioxide (BO2) Light Emission During Ballistic Initiation of Boron...Technical Note 3. DATES COVERED (From - To) February 2013–February 2015 4. TITLE AND SUBTITLE Mapping Boron Dioxide (BO2) Light Emission During

  18. Behavior of Boron Doped Graphites and Boron Carbide under Ion Beam and Plasma Irradiation

    NASA Astrophysics Data System (ADS)

    Begrambekov, L. B.; Buzhinsky, O. I.; Zakharovi, A.

    The paper shortly describes the methods of boron carbide coating deposition and presents the experimental results characterizing the properties of boron carbide coatings and of boron doped graphites important to their application as the plasma facing materials of fusion devices and other plasma apparatus dealing with dense and high temperature plasma. Conclusion is made that thick renewable boron carbide coating can successfully be used as the protecting coating of plasma facing elements of ITER.

  19. Prediction of boron carbon nitrogen phase diagram

    NASA Astrophysics Data System (ADS)

    Yao, Sanxi; Zhang, Hantao; Widom, Michael

    We studied the phase diagram of boron, carbon and nitrogen, including the boron-carbon and boron-nitrogen binaries and the boron-carbon-nitrogen ternary. Based on the idea of electron counting and using a technique of mixing similar primitive cells, we constructed many ''electron precise'' structures. First principles calculation is performed on these structures, with either zero or high pressures. For the BN binary, our calculation confirms that a rhmobohedral phase can be stablized at high pressure, consistent with some experimental results. For the BCN ternary, a new ground state structure is discovered and an Ising-like phase transition is suggested. Moreover, we modeled BCN ternary phase diagram and show continuous solubility from boron carbide to the boron subnitride phase.

  20. Method for preparing boron-carbide articles

    DOEpatents

    Benton, S.T.; Masters, D.R.

    1975-10-21

    The invention is directed to the preparation of boron carbide articles of various configurations. A stoichiometric mixture of particulate boron and carbon is confined in a suitable mold, heated to a temperature in the range of about 1250 to 1500$sup 0$C for effecting a solid state diffusion reaction between the boron and carbon for forming the boron carbide (B$sub 4$C), and thereafter the resulting boron-carbide particles are hot-pressed at a temperature in the range of about 1800 to 2200$sup 0$C and a pressure in the range of about 1000 to 4000 psi for densifying and sintering the boron carbide into the desired article.

  1. A new class of boron nanotube.

    PubMed

    Wang, Jing; Liu, Ying; Li, You-Cheng

    2009-12-07

    The configurations, stability and electronic structures of a new class of boron sheet and related boron nanotubes are predicted within the framework of density functional theory. This boron sheet is sparser than those of recent proposals. Our theoretic results show that the stable boron sheet remains flat and is metallic. There are bands similar to the pi-bands in graphite near the Fermi level. Stable nanotubes with various diameters and chiral vectors can be rolled from the sheet. Within our study, only the thin (8, 0) nanotube with a band gap of 0.44 eV is semiconducting, while all the other thicker boron nanotubes are metallic, independent of their chirality. It indicates the possibility, in the design of nanodevices, to control the electronic transport properties of the boron nanotube through the diameter.

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

    SciTech Connect

    Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M.; Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P.; Jones, S.

    1993-05-01

    The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B{sub 4}C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 {mu} boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

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

    SciTech Connect

    Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. . Inst. of Plasma and Fusion Research); Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P. ); Jones, S. )

    1993-05-01

    The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B[sub 4]C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 [mu] boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

  4. Evaluation of two hybrid poplar clones as constructed wetland plant species for treating saline water high in boron and selenium, or waters only high in boron

    USDA-ARS?s Scientific Manuscript database

    Wetland mesocosms were constructed to assess two salt- and B-tolerant hybrid poplar clones (Populus trichocarpa ×P. deltoides×P. nigra '345-1' and '347-14') for treating saline water high in boron (B) and selenium (Se). In addition, a hydroponic experiment was performed to test the B tolerance and B...

  5. Probing the interactions between boronic acids and cis-diol-containing biomolecules by affinity capillary electrophoresis.

    PubMed

    Lü, Chenchen; Li, Hengye; Wang, Heye; Liu, Zhen

    2013-02-19

    The affinity of boronic acids to cis-diol-containing biomolecules has found wide applications in many fields, such as sensing, separation, drug delivery, and functional materials. A sound understanding of the binding interactions will greatly facilitate exquisite applications of this chemistry. Although a few analytical tools have been available for the characterization of the interactions, these techniques are associated with some apparent drawbacks, so they are only applicable to a limited range of boronic acids and cis-diol-containing biomolecules. Therefore, a widely applicable method is still greatly needed. In this work, an affinity capillary electrophoresis (ACE) method was established and validated to probe the interactions between boronic acids and cis-diol-containing biomolecules. The method was proven to be applicable to almost all types of cis-diol-containing biomolecules and boronic acids. Based on this method, a quantitative, comparative study on the interactions between 14 boronic acids that have important potentials for application with 5 typical monosaccharides of biological importance was carried out. The findings provided new insights into boronate affinity interactions, particularly the relationship between the binding strength with the molecular structures of the binding species. Besides, effects of pH and temperature on the binding strength were also investigated. This method exhibited several significant advantages, including (1) possibility of simultaneous study of multiple interactions, (2) low requirement on the purity of the binding species, (3) wide applicability, and (4) high accuracy and precision.

  6. Dietary boron, brain function, and cognitive performance.

    PubMed Central

    Penland, J G

    1994-01-01

    Although the trace element boron has yet to be recognized as an essential nutrient for humans, recent data from animal and human studies suggest that boron may be important for mineral metabolism and membrane function. To investigate further the functional role of boron, brain electrophysiology and cognitive performance were assessed in response to dietary manipulation of boron (approximately 0.25 versus approximately 3.25 mg boron/2000 kcal/day) in three studies with healthy older men and women. Within-subject designs were used to assess functional responses in all studies. Spectral analysis of electroencephalographic data showed effects of dietary boron in two of the three studies. When the low boron intake was compared to the high intake, there was a significant (p < 0.05) increase in the proportion of low-frequency activity, and a decrease in the proportion of higher-frequency activity, an effect often observed in response to general malnutrition and heavy metal toxicity. Performance (e.g., response time) on various cognitive and psychomotor tasks also showed an effect of dietary boron. When contrasted with the high boron intake, low dietary boron resulted in significantly poorer performance (p < 0.05) on tasks emphasizing manual dexterity (studies II and III); eye-hand coordination (study II); attention (all studies); perception (study III); encoding and short-term memory (all studies); and long-term memory (study I). Collectively, the data from these three studies indicate that boron may play a role in human brain function and cognitive performance, and provide additional evidence that boron is an essential nutrient for humans. PMID:7889884

  7. Synthesis, Properties, and Applications Of Boron Nitride

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Alterovitz, Samuel A.

    1993-01-01

    Report describes synthesis, properties, and applications of boron nitride. Especially in thin-film form. Boron nitride films useful as masks in x-ray lithography; as layers for passivation of high-speed microelectronic circuits; insulating films; hard, wear-resistant, protective films for optical components; lubricants; and radiation detectors. Present status of single-crystal growth of boron nitride indicates promising candidate for use in high-temperature semiconductor electronics.

  8. Toxic effects of boron on mallard reproduction

    USGS Publications Warehouse

    Smith, G.J.; Anders, V.P.

    1989-01-01

    Boron, a naturally occurring trace element generally considered environmentally innocuous, was documented to severely impair mallard reproduction. Boron is leached from irrigated agricultural soils and transported in drainage water that contaminates wetlands. Until now, only the selenium accumulated in aquatic food chains has been documented to pose a toxic hazard to wildlife in drainage water wetlands. Management of drainage water-contaminated environments must now also consider the adverse effects of boron, as well as the possible interactions of drainage water contaminants.

  9. Stereodivergent Olefination of Enantioenriched Boronic Esters

    PubMed Central

    Armstrong, Roly J.; García‐Ruiz, Cristina; Myers, Eddie L.

    2016-01-01

    Abstract A stereodivergent coupling reaction between vinyl halides and boronic esters is described. This coupling process proceeds without a transition‐metal catalyst, instead proceeding by electrophilic selenation or iodination of a vinyl boronate complex followed by stereospecific syn or anti elimination. Chiral, nonracemic boronic esters could be coupled with complete enantiospecificity. The process enables the highly stereoselective synthesis of either the E or Z alkene from a single isomer of a vinyl coupling partner. PMID:27958668

  10. Synthesis, Properties, and Applications Of Boron Nitride

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Alterovitz, Samuel A.

    1993-01-01

    Report describes synthesis, properties, and applications of boron nitride. Especially in thin-film form. Boron nitride films useful as masks in x-ray lithography; as layers for passivation of high-speed microelectronic circuits; insulating films; hard, wear-resistant, protective films for optical components; lubricants; and radiation detectors. Present status of single-crystal growth of boron nitride indicates promising candidate for use in high-temperature semiconductor electronics.

  11. Boron and Coumaphos Residues in Hive Materials Following Treatments for the Control of Aethina tumida Murray

    PubMed Central

    Valdovinos-Flores, Cesar; Gaspar-Ramírez, Octavio; Heras–Ramírez, María Elena; Dorantes-Ugalde, José Antonio; Saldaña-Loza, Luz María

    2016-01-01

    In the search of alternatives for controlling Aethina tumida Murray, we recently proposed the BAA trap which uses boric acid and an attractant which mimics the process of fermentation caused by Kodamaea ohmeri in the hive. This yeast is excreted in the feces of A. tumida causing the fermentation of pollen and honey of infested hives and releasing compounds that function as aggregation pheromones to A. tumida. Since the boron is the toxic element in boric acid, the aim of this article is to assess the amount of boron residues in honey and beeswax from hives treated with the BAA trap. For this aim, the amount of bioaccumulated boron in products of untreated hives was first determined and then compared with the amount of boron of products from hives treated with the BAA trap in two distinct climatic and soil conditions. The study was conducted in the cities of Padilla, Tamaulipas, and Valladolid, Yucatan (Mexico) from August 2014 to March 2015. The quantity of boron in honey was significantly less in Yucatan than in Tamaulipas; this agrees with the boron deficiency among Luvisol and Leptosol soils found in Yucatan compared to the Vertisol soil found in Tamaulipas. In fact, the honey from Yucatan has lower boron levels than those reported in the literature. The BAA treatment was applied for four months, results show that the BAA trap does not have any residual effect in either honey or wax; i.e., there is no significant difference in boron content before and after treatment. On the other hand, the organophosphate pesticide coumaphos was found in 100% of wax samples and in 64% of honey samples collected from Yucatan. The concentration of coumaphos in honey ranges from 0.005 to 0.040 mg/kg, which are below Maximum Residue Limit (MRL) allowed in the European Union (0.1 mg/kg) but 7.14% of samples exceeded the MRL allowed in Canada (0.02 mg/kg). PMID:27092938

  12. Boron and Coumaphos Residues in Hive Materials Following Treatments for the Control of Aethina tumida Murray.

    PubMed

    Valdovinos-Flores, Cesar; Gaspar-Ramírez, Octavio; Heras-Ramírez, María Elena; Lara-Álvarez, Carlos; Dorantes-Ugalde, José Antonio; Saldaña-Loza, Luz María

    2016-01-01

    In the search of alternatives for controlling Aethina tumida Murray, we recently proposed the BAA trap which uses boric acid and an attractant which mimics the process of fermentation caused by Kodamaea ohmeri in the hive. This yeast is excreted in the feces of A. tumida causing the fermentation of pollen and honey of infested hives and releasing compounds that function as aggregation pheromones to A. tumida. Since the boron is the toxic element in boric acid, the aim of this article is to assess the amount of boron residues in honey and beeswax from hives treated with the BAA trap. For this aim, the amount of bioaccumulated boron in products of untreated hives was first determined and then compared with the amount of boron of products from hives treated with the BAA trap in two distinct climatic and soil conditions. The study was conducted in the cities of Padilla, Tamaulipas, and Valladolid, Yucatan (Mexico) from August 2014 to March 2015. The quantity of boron in honey was significantly less in Yucatan than in Tamaulipas; this agrees with the boron deficiency among Luvisol and Leptosol soils found in Yucatan compared to the Vertisol soil found in Tamaulipas. In fact, the honey from Yucatan has lower boron levels than those reported in the literature. The BAA treatment was applied for four months, results show that the BAA trap does not have any residual effect in either honey or wax; i.e., there is no significant difference in boron content before and after treatment. On the other hand, the organophosphate pesticide coumaphos was found in 100% of wax samples and in 64% of honey samples collected from Yucatan. The concentration of coumaphos in honey ranges from 0.005 to 0.040 mg/kg, which are below Maximum Residue Limit (MRL) allowed in the European Union (0.1 mg/kg) but 7.14% of samples exceeded the MRL allowed in Canada (0.02 mg/kg).

  13. Boron containing multilayer coatings and method of fabrication

    DOEpatents

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

    1997-09-23

    Hard coatings are fabricated from multilayer boron/boron carbide, boron carbide/cubic boron nitride, and boron/boron nitride/boron carbide, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron and boron carbide used in forming the multilayers are formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/boron carbide, and boron carbide/cubic boron nitride is produced by depositing alternate layers of boron, cubic boron nitride or boron carbide, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be of a discrete or a blended or graded composition. 6 figs.

  14. Boron-10 ABUNCL Active Testing

    SciTech Connect

    Kouzes, Richard T.; Ely, James H.; Lintereur, Azaree T.; Siciliano, Edward R.

    2013-07-09

    The Department of Energy Office of Nuclear Safeguards and Security (NA-241) is supporting the project Coincidence Counting With Boron-Based Alternative Neutron Detection Technology at Pacific Northwest National Laboratory (PNNL) for the development of a 3He proportional counter alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a system based upon 10B-lined proportional tubes in a configuration typical for 3He-based coincidence counter applications. This report provides results from testing of the active mode of the General Electric Reuter-Stokes Alternative Boron-Based Uranium Neutron Coincidence Collar (ABUNCL) at Los Alamos National Laboratory using sources and fuel pins.

  15. Low temperature boron doped diamond

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  16. Mineral resource of the month: boron

    USGS Publications Warehouse

    Crangle, Robert D.

    2012-01-01

    The article offers information on the mineral, boron. Boron compounds, particularly borates, have more commercial applications than its elemental relative which is a metalloid. Making up the 90% of the borates that are used worldwide are colemanite, kernite, tincal, and ulexite. The main borate deposits are located in the Mojave Desert of the U.S., the Tethyan belt in southern Asia, and the Andean belt of South America. Underground and surface mining are being used in gathering boron compounds. INSETS: Fun facts;Boron production and consumption.

  17. Premixed Combustion Model for Boron Clouds

    NASA Astrophysics Data System (ADS)

    Wang, Mengze; Han, Wang; Chen, Zheng

    2015-11-01

    Boron particle is an ideal additive in solid propellants and fuels due to its very high volumetric heat release. In this study, a premixed combustion model for boron clouds is developed based on a previous combustion model for single boron particle. The flame structure is assumed to be composed of three zones: the preheat zone, the ignition zone, and the reaction zone, and analytical solutions are derived from the governing equations. Consequently the influence of the boron clouds' physical properties on the flame propagation process is investigated.

  18. Producing carbon stripper foils containing boron

    SciTech Connect

    Stoner, J. O. Jr.

    2012-12-19

    Parameters being actively tested by the accelerator community for the purpose of extending carbon stripper foil lifetimes in fast ion beams include methods of deposition, parting agents, mounting techniques, support (fork) materials, and inclusion of alloying elements, particularly boron. Specialized production apparatus is required for either sequential deposition or co-deposition of boron in carbon foils. A dual-use vacuum evaporator for arc evaporation of carbon and electron-beam evaporation of boron and other materials has been built for such development. Production of both carbon and boron foils has begun and improvements are in progress.

  19. Boron removal from geothermal waters by electrocoagulation.

    PubMed

    Yilmaz, A Erdem; Boncukcuoğlu, Recep; Kocakerim, M Muhtar; Yilmaz, M Tolga; Paluluoğlu, Cihan

    2008-05-01

    Most of the geothermal waters in Turkey contain extremely high concentration of boron when they are used for irrigation. The use of geothermal waters for irrigation can results in excess amount deposition of boron in soil. On the other hand, a minimal boron concentration is required for irrigational waters. In this study, electrocoagulation (EC) was selected as a treatment process for the removal of boron from thermal waters obtained from Ilica-Erzurum in Turkey. Current density (CD), pH of solution and temperature of solution were selected as operational parameters. The results showed that boron removal efficiency increased from pH 4.0 to 8.0 and decreased at pH 10.0. Although boron removal efficiency was highest at pH 8.0, energy consumption was very high at this pH value compared to other pH intervals. Boron removal efficiency reached to 95% with increasing current density from 1.5 to 6.0 mA/cm(2), but energy consumption was also increased in this interval. At higher temperatures of solution, such as 313 and 333 K, boron removal efficiency increased. At optimum conditions, boron removal efficiency in geothermal water reached up to 95%.

  20. Boron deposition from fused salts. Final report

    SciTech Connect

    Smith, M.L.

    1980-08-01

    A partial evaluation of the feasibility of a process to electrodeposit pure coherent coatings of elemental boron from molten fluorides has been performed. The deposit produced was powdery and acicular, unless the fluoride melt was purified to have very low oxygen concentration. When the oxygen activity was reduced in the melt by addition of crystalline elemental boron, dense, amorphous boron deposit was produced. The boron deposits produced had cracks but were otherwise pure and dense and ranged up to 0.35 mm thick. Information derived during this project suggests that similar deposits might be obtained crack-free up to 1.00 mm thick by process modifications and improvements.

  1. METHOD OF PREPARING POLONIUM-BORON SOURCES

    DOEpatents

    Birden, J.H.

    1959-08-01

    An improved technique is described for preparation of a polonium-boron neutron source. A selected amount of Po-210 is vaporized into a thin walled nickel container, then the desired amcunt of boron powder is added. After sealing the container, it is heated quickly by induction heating to vaporize the Po-210 and deposit it in the still cool boron powder. The unit is then quickly cooled to prevent revaporization of the Po-210 from the boron. The build-up of neutron emission may be followed by means of a neutron counter in order to terminate the heating at the optimum level of neutron yield.

  2. Making Microscopic Cubes Of Boron

    NASA Technical Reports Server (NTRS)

    Faulkner, Joseph M.

    1993-01-01

    Production of finely divided cubes of boron involves vacuum-deposition technology and requires making of template. Template supports pattern of checkered squares 25 micrometers on side, which are etched 25 micrometers into template material. Template coasted uniformly with paralyene or some similar vacuum coating with low coefficient of adhesion. Intended application to solid rocket fuels, explosives, and pyrotechnics; process used for other applications, from manufacture of pharmaceuticals to processing of nuclear materials.

  3. Conduction mechanism in boron carbide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  4. Making Microscopic Cubes Of Boron

    NASA Technical Reports Server (NTRS)

    Faulkner, Joseph M.

    1993-01-01

    Production of finely divided cubes of boron involves vacuum-deposition technology and requires making of template. Template supports pattern of checkered squares 25 micrometers on side, which are etched 25 micrometers into template material. Template coasted uniformly with paralyene or some similar vacuum coating with low coefficient of adhesion. Intended application to solid rocket fuels, explosives, and pyrotechnics; process used for other applications, from manufacture of pharmaceuticals to processing of nuclear materials.

  5. Conduction mechanism in boron carbide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  6. Boronization in DIII-D

    SciTech Connect

    Jackson, G.L.; Burrell, K.H.; DeBoo, J.C.; Greenfield, C.M.; Groebner, R.J.; Hodapp, T.; Kellman, A.G.; Lee, R.; Lippman, S.I.; Phillips, J.; Taylor, T.S.; West, W.P.; Winter, J.; Moyer, R.; Watkins, J.

    1992-05-01

    A thin boron film has been applied to the DIII-D tokamak plasma facing surfaces to reduce impurity influx, particularly oxygen and carbon. A direct result of this surface modification was the observation of a regime of very high energy confinement, VH-mode, with confinement times from 1.5 to 2 times greater than predicted by H-mode scaling relation for the same set of parameters. VH-mode discharges are characterized by low ohmic target densities, low edge neutral pressure, and reduced cycling. These conditions have reduced the collisionality, {nu}*, in the edge region producing a higher edge pressure gradient and a significant bootstrap current, up to 30% of the total current. We will describe the edge plasma properties after boronization including reductions in recycling inferred from measurements of {tau}{sup p}*. In particular we will discuss the edge plasma conditions necessary for access to VH-mode including the boronization process and properties of the deposited film.

  7. Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Durmazuçar, Hasan H.; Gündüz, Güngör

    2000-12-01

    Uranium dioxide-only and uranium dioxide-gadolinium oxide (5% and 10%) ceramic nuclear fuel pellets which were already coated with boron nitride were coated with thin boron layer by chemical vapor deposition to increase the burn-up efficiency of the fuel during reactor operation. Coating was accomplished from the reaction of boron trichloride with hydrogen at 1250 K in a tube furnace, and then sintering at 1400 and 1525 K. The deposited boron was identified by infrared spectrum. The morphology of the coating was studied by using scanning electron microscope. The plate, grainy and string (fiber)-like boron structures were observed.

  8. Energy Landscape of Fullerene Materials: A Comparison of Boron to Boron Nitride and Carbon

    NASA Astrophysics Data System (ADS)

    de, Sandip; Willand, Alexander; Amsler, Maximilian; Pochet, Pascal; Genovese, Luigi; Goedecker, Stefan

    2011-06-01

    Using the minima hopping global geometry optimization method on the density functional potential energy surface we show that the energy landscape of boron clusters is glasslike. Larger boron clusters have many structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found. We thus present a methodology which can make predictions on the feasibility of the synthesis of new nanostructures.

  9. The noble gases adsorption on boron-rich boron nitride nanotubes: A theoretical investigation

    NASA Astrophysics Data System (ADS)

    Wang, Chong; Guo, Chen

    2017-07-01

    In this work, using density functional theory (DFT) calculations, we have systematically explored the noble gases (Ng = He, Ne, Ar, Kr) adsorption on boron-rich boron nitride nanotubes (BNNTs) surface with antisite boron atom. One or two nitrogen atoms of BNNTs are replaced by boron atoms, which are considered as boron-rich BNNTs for Ng adsorption. It is found that the boron-rich BNNTs can adsorb Ng in exothermic process, and the adsorption energies increase in order from He to Kr. The quantum theory of atoms in molecules (QTAIM) and noncovalent interactions (NCIs) calculations show that the interactions between boron-rich BNNTs and Ng are noncovalent, and the interactions for Ar and Kr are obviously larger than those for He and Ne. The charge transfer from Ng to boron-rich BNNTs and the changes of energy gap caused by Ng adsorption demonstrate that the boron-rich BNNTs are expected to become the Ng adsorption and sensing materials. Moreover, the 2B-BNNTs do not decrease the Ng adsorption interactions on boron-rich BNNTs, compared with 1B-BNNTs. It is expected that the present results will provide a useful guide to develop novel boron nitride nanomaterials for storage and application of Ng.

  10. The symmetry of the boron buckyball and a related boron nanotube

    NASA Astrophysics Data System (ADS)

    Gonzalez Szwacki, N.; Tymczak, C. J.

    2010-07-01

    We investigate the symmetry of the boron buckyball and a related boron nanotube. Using large-scale ab initio calculations up to second-order Møller-Plesset perturbation theory, we have determined unambiguously the equilibrium geometry/symmetry of two structurally related boron clusters: the B 80 fullerene and the finite-length (5 0) boron nanotube. The B 80 cluster was found to have the same symmetry, Ih, as the C 60 molecule since its 20 additional boron atoms are located exactly at the centers of the 20 hexagons. Additionally, we also show that the (5 0) boron nanotube does not suffer from atomic buckling and its symmetry is D5d instead of C5v as has been described by previous calculations. Therefore, we predict that all the boron nanotubes rolled from the α-sheet will be free from structural distortions, which has a significant impact on their electronic properties.

  11. Boron neutron capture synovectomy (BNCS) as a potential therapy for rheumatoid arthritis: boron biodistribution study in a model of antigen-induced arthritis in rabbits.

    PubMed

    Trivillin, Verónica A; Abramson, David B; Bumaguin, Gaston E; Bruno, Leandro J; Garabalino, Marcela A; Monti Hughes, Andrea; Heber, Elisa M; Feldman, Sara; Schwint, Amanda E

    2014-11-01

    Boron neutron capture synovectomy (BNCS) is explored for the treatment of rheumatoid arthritis (RA). The aim of the present study was to perform boron biodistribution studies in a model of antigen-induced arthritis (AIA) in female New Zealand rabbits, with the boron carriers boronophenylalanine (BPA) and sodium decahydrodecaborate (GB-10) to assess the potential feasibility of BNCS for RA. Rabbits in chronic phase of AIA were used for biodistribution studies employing the following protocols: intra-articular (ia) (a) BPA-f 0.14 M (0.7 mg (10)B), (b) GB-10 (5 mg (10)B), (c) GB-10 (50 mg (10)B) and intravenous (iv), (d) BPA-f 0.14 M (15.5 mg (10)B/kg), (e) GB-10 (50 mg (10)B/kg), and (f) BPA-f (15.5 mg (10)B/kg) + GB-10 (50 mg (10)B/kg). At different post-administration times (13-85 min for ia and 3 h for iv), samples of blood, pathological synovium (target tissue), cartilage, tendon, muscle, and skin were taken for boron measurement by inductively coupled plasma mass spectrometry. The intra-articular administration protocols at <40 min post-administration both for BPA-f and GB-10, and intravenous administration protocols for GB-10 and [GB-10 + BPA-f] exhibited therapeutically useful boron concentrations (>20 ppm) in the pathological synovium. Dosimetric estimations suggest that BNCS would be able to achieve a therapeutically useful dose in pathological synovium without exceeding the radiotolerance of normal tissues in the treatment volume, employing boron carriers approved for use in humans. Radiobiological in vivo studies will be necessary to determine the actual therapeutic efficacy of BNCS to treat RA in an experimental model.

  12. Boron in chondritic meteorites

    NASA Astrophysics Data System (ADS)

    Shaw, D. M.; Higgins, M. D.; Hinton, R. W.; Truscott, M. G.; Middleton, T. A.

    1988-09-01

    The B and Li content and distribution in 14 chondrites are investigated experimentally by means of prompt gamma neutron activation on bulk samples, EMPA, and alpha-track imaging of thin polished sections attached to neutron-irradiated cellulose nitrate films. Alpha-track and transmitted-light images are shown, and numerical results are presented in extensive tables. Chondrites of lower equilibration grades are found to contain practically no Li or B in chondrules, inclusions, sulfides, or metal, so that bulk B/Li content represents material from the matrix. Weathering products in Antarctic meteorites are shown to be significantly enriched in B and Cl, and the bulk B content in carbonaceous and ordinary chondrites is found to range from 0.2 to 1 ppm (mean 0.55 ppm).

  13. Boron Discovered in Ancient Habitable Mars Groundwater

    SciTech Connect

    Gasda, Patrick

    2016-12-13

    Boron was recently discovered in calcium-sulfate veins on Mars using the ChemCam instrument on NASA’s Curiosity Mars Rover. This is the first Mars mission to detect boron on the Red Planet. Los Alamos Post-Doctoral Student Patrick Gasda explains how this discovery helps us better understand the timescale of habitability on Mars.

  14. Boron Carbides As Thermo-electric Materials

    NASA Technical Reports Server (NTRS)

    Wood, Charles

    1988-01-01

    Report reviews recent theoretical and experimental research on thermoelectric materials. Recent work with narrow-band semiconductors demonstrated possibility of relatively high thermoelectric energy-conversion efficiencies in materials withstanding high temperatures needed to attain such efficiencies. Among promising semiconductors are boron-rich borides, especially boron carbides.

  15. Boron chemicals in diagnosis and therapeutics

    PubMed Central

    Das, Bhaskar C; Thapa, Pritam; Karki, Radha; Schinke, Caroline; Das, Sasmita; Kambhampati, Suman; Banerjee, Sushanta K; Van Veldhuizen, Peter; Verma, Amit; Weiss, Louis M; Evans, Todd

    2013-01-01

    Advances in the field of boron chemistry have expanded the application of boron from material use to medicine. Boron-based drugs represent a new class of molecules that possess several biomedical applications including use as imaging agents for both optical and nuclear imaging as well as therapeutic agents with anticancer, antiviral, antibacterial, antifungal and other disease-specific activities. For example, bortezomib (Velcade®), the only drug in clinical use with boron as an active element, was approved in 2003 as a proteasome inhibitor for the treatment of multiple myeloma and non-Hodgkin’s lymphoma. Several other boron-based compounds are in various phases of clinical trials, which illustrates the promise of this approach for medicinal chemists working in the area of boron chemistry. It is expected that in the near future, several boron-containing drugs should become available in the market with better efficacy and potency than existing drugs. This article discusses the current status of the development of boron-based compounds as diagnostic and therapeutic agents in humans. PMID:23617429

  16. Boron chemicals in diagnosis and therapeutics.

    PubMed

    Das, Bhaskar C; Thapa, Pritam; Karki, Radha; Schinke, Caroline; Das, Sasmita; Kambhampati, Suman; Banerjee, Sushanta K; Van Veldhuizen, Peter; Verma, Amit; Weiss, Louis M; Evans, Todd

    2013-04-01

    Advances in the field of boron chemistry have expanded the application of boron from material use to medicine. Boron-based drugs represent a new class of molecules that possess several biomedical applications including use as imaging agents for both optical and nuclear imaging as well as therapeutic agents with anticancer, antiviral, antibacterial, antifungal and other disease-specific activities. For example, bortezomib (Velcade(®)), the only drug in clinical use with boron as an active element, was approved in 2003 as a proteasome inhibitor for the treatment of multiple myeloma and non-Hodgkin's lymphoma. Several other boron-based compounds are in various phases of clinical trials, which illustrates the promise of this approach for medicinal chemists working in the area of boron chemistry. It is expected that in the near future, several boron-containing drugs should become available in the market with better efficacy and potency than existing drugs. This article discusses the current status of the development of boron-based compounds as diagnostic and therapeutic agents in humans.

  17. Porphyrins for boron neutron capture therapy

    DOEpatents

    Miura, Michiko; Gabel, Detlef

    1990-01-01

    Novel compounds for treatment of brain tumors in Boron Neutron Capture Therapy are disclosed. A method for preparing the compounds as well as pharmaceutical compositions containing said compounds are also disclosed. The compounds are water soluble, non-toxic and non-labile boronated porphyrins which show significant uptake and retention in tumors.

  18. Ultratough single crystal boron-doped diamond

    DOEpatents

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

    2015-05-05

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

  19. 14. DETAIL SHOWING HYDROGEN (LEFT) AND OXYGEN (RIGHT) PREVALVES. Looking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. DETAIL SHOWING HYDROGEN (LEFT) AND OXYGEN (RIGHT) PREVALVES. Looking southeast. - Edwards Air Force Base, Air Force Rocket Propulsion Laboratory, Test Stand 1-A, Test Area 1-120, north end of Jupiter Boulevard, Boron, Kern County, CA

  20. 14. LOOKING WEST INTO THE EAST PURSUIT PLANE BAY OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. LOOKING WEST INTO THE EAST PURSUIT PLANE BAY OF AR-9. LOW WALLED CREW SHELTER AT RIGHT. - Edwards Air Force Base, South Base, Rammed Earth Aircraft Dispersal Revetments, Western Shore of Rogers Dry Lake, Boron, Kern County, CA

  1. Primitive boron isotope composition of the mantle.

    PubMed

    Chaussidon, M; Marty, B

    1995-07-21

    Boron isotope ratios are homogeneous in volcanic glasses of oceanic island basalts [-9.9 +/- 1.3 per mil, relative to standard NBS 951 (defined by the National Bureau of Standards)], whereas mid-oceanic ridge basalts (MORBs) and back-arc basin basalts (BABBs) show generally higher and more variable ratios. Melts that have assimilated even small amounts of altered basaltic crust show significant variations in the boron isotope ratios. Assimilation may thus account for the higher boron ratios of MORBs and BABBs. A budget of boron between mantle and crust implies that the primitive mantle had a boron isotope ratio of -10 +/- 2 per mil and that this ratio was not fractionated significantly during the differentiation of the mantle.

  2. Stabilization of boron carbide via silicon doping.

    PubMed

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

    2015-01-14

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

  3. Stabilization of boron carbide via silicon doping

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  4. Recombination Activity of Iron in Boron Doped Silicon

    NASA Astrophysics Data System (ADS)

    Yli-Koski, M.; Palokangas, M.; Sokolov, V.; Storgårds, J.; Väinölä, H.; Holmberg, H.; Sinkkonen, J.

    The charge carrier lifetime in iron contaminated boron doped silicon wafers was determined by surface photovoltage, SPV, and microwave photoconductive decay, µPCD, techniques. Our results show that the charge carrier lifetime in boron doped silicon wafers depends on the boron concentration when the lifetime is limited by iron-boron pairs.

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

    SciTech Connect

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

    2014-08-14

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

  6. Boron enrichment in martian clay.

    PubMed

    Stephenson, James D; Hallis, Lydia J; Nagashima, Kazuhide; Freeland, Stephen J

    2013-01-01

    We have detected a concentration of boron in martian clay far in excess of that in any previously reported extra-terrestrial object. This enrichment indicates that the chemistry necessary for the formation of ribose, a key component of RNA, could have existed on Mars since the formation of early clay deposits, contemporary to the emergence of life on Earth. Given the greater similarity of Earth and Mars early in their geological history, and the extensive disruption of Earth's earliest mineralogy by plate tectonics, we suggest that the conditions for prebiotic ribose synthesis may be better understood by further Mars exploration.

  7. Boron Enrichment in Martian Clay

    PubMed Central

    Nagashima, Kazuhide; Freeland, Stephen J.

    2013-01-01

    We have detected a concentration of boron in martian clay far in excess of that in any previously reported extra-terrestrial object. This enrichment indicates that the chemistry necessary for the formation of ribose, a key component of RNA, could have existed on Mars since the formation of early clay deposits, contemporary to the emergence of life on Earth. Given the greater similarity of Earth and Mars early in their geological history, and the extensive disruption of Earth's earliest mineralogy by plate tectonics, we suggest that the conditions for prebiotic ribose synthesis may be better understood by further Mars exploration. PMID:23762242

  8. Boron foils for RDDS experiment

    NASA Astrophysics Data System (ADS)

    Lipski, A. R.; Rainovski, G.; Pietralla, N.; Dewald, A.

    2008-06-01

    Application of the deposition method based on the vibrational motion of micro particles in an electrostatic field [I. Sugai, Nucl. Instr. and Meth. A 397 (1997) 81] is described for the production of isotopic 11B foils. The method proved suitable for target production of this typically brittle material when a very flat target surface was required. The goal to produce 11B targets of 160-350 μg/cm 2 was achieved by depositing the boron on a thin foil substrate, such as Nb and Sn. The coated foil was stretched flat before it was mounted on a frame.

  9. Improved Boron for Enhanced Combustion

    DTIC Science & Technology

    1990-06-01

    2, p. 74F - 80F, 1955. 11. Perry and Chilton, " Chemical Engineer ’ Handbook," McGraw-Hill, 5th Edition, 1973, and 6th Edition, 1986. 12. Levenspiel ...0., " Chemical Reaction Engineering ," Wiley & Sons, 2nd Edition, 1972. 13. Hern, R. B, and R. G. Sidall, M. W. Thring, "Flow Patterns in a Phase Change...wet chemical method, allows the use of higher solution concentrations of boron than AAS, provides better precision, and allows us to simultaneously

  10. Hydrocarbon analogues of boron clusters - planarity, aromaticity and antiaromaticity

    NASA Astrophysics Data System (ADS)

    Zhai, Hua-Jin; Kiran, Boggavarapu; Li, Jun; Wang, Lai-Sheng

    2003-12-01

    An interesting feature of elemental boron and boron compounds is the occurrence of highly symmetric icosahedral clusters. The rich chemistry of boron is also dominated by three-dimensional cage structures. Despite its proximity to carbon in the periodic table, elemental boron clusters have been scarcely studied experimentally and their structures and chemical bonding have not been fully elucidated. Here we report experimental and theoretical evidence that small boron clusters prefer planar structures and exhibit aromaticity and antiaromaticity according to the Hückel rules, akin to planar hydrocarbons. Aromatic boron clusters possess more circular shapes whereas antiaromatic boron clusters are elongated, analogous to structural distortions of antiaromatic hydrocarbons. The planar boron clusters are thus the only series of molecules other than the hydrocarbons to exhibit size-dependent aromatic and antiaromatic behaviour and represent a new dimension of boron chemistry. The stable aromatic boron clusters may exhibit similar chemistries to that of benzene, such as forming sandwich-type metal compounds.

  11. First-principles simulations of boron diffusion in graphite.

    PubMed

    Suarez-Martinez, I; El-Barbary, A A; Savini, G; Heggie, M I

    2007-01-05

    Boron strongly modifies electronic and diffusion properties of graphite. We report the first ab initio study of boron interaction with the point defects in graphite, which includes structures, thermodynamics, and diffusion. A number of possible diffusion mechanisms of boron in graphite are suggested. We conclude that boron diffuses in graphite by a kick-out mechanism. This mechanism explains the common activation energy, but large magnitude difference, for the rate of boron diffusion parallel and perpendicular to the basal plane.

  12. First-Principles Simulations of Boron Diffusion in Graphite

    SciTech Connect

    Suarez-Martinez, I.; El-Barbary, A. A.; Savini, G.; Heggie, M. I.

    2007-01-05

    Boron strongly modifies electronic and diffusion properties of graphite. We report the first ab initio study of boron interaction with the point defects in graphite, which includes structures, thermodynamics, and diffusion. A number of possible diffusion mechanisms of boron in graphite are suggested. We conclude that boron diffuses in graphite by a kick-out mechanism. This mechanism explains the common activation energy, but large magnitude difference, for the rate of boron diffusion parallel and perpendicular to the basal plane.

  13. Autoionizing states of atomic boron

    NASA Astrophysics Data System (ADS)

    Argenti, Luca; Moccia, Roberto

    2016-04-01

    We present a B -spline K -matrix method for three-active-electron atoms in the presence of a polarizable core, with which it is possible to compute multichannel single-ionization scattering states with good accuracy. We illustrate the capabilities of the method by computing the parameters of several autoionizing states of the boron atom, with S2e, 2,o2P and D2e symmetry, up to at least the 2 p2(1S) excitation threshold of the B ii parent ion, as well as selected portions of the photoionization cross section from the ground state. Our results exhibit remarkable gauge consistency, they significantly extend the existing sparse record of data for the boron atom, and they are in good agreement with the few experimental and theoretical data available in the literature. These results open the way to extend to three-active-electron systems the spectral analysis of correlated wave packets in terms of accurate scattering states that has already been demonstrated for two-electron atoms in Argenti and Lindroth [Phys. Rev. Lett. 105, 053002 (2010), 10.1103/PhysRevLett.105.053002].

  14. Composite boron nitride neutron detectors

    NASA Astrophysics Data System (ADS)

    Roth, M.; Mojaev, E.; Khakhan, O.; Fleider, A.; Dul`kin, E.; Schieber, M.

    2014-09-01

    Single phase polycrystalline hexagonal boron nitride (BN) or mixed with boron carbide (BxC) embedded in an insulating polymeric matrix acting as a binder and forming a composite material as well as pure submicron size polycrystalline BN has been tested as a thermal neutron converter in a multilayer thermal neutron detector design. Metal sheet electrodes were covered with 20-50 μm thick layers of composite materials and assembled in a multi-layer sandwich configuration. High voltage was applied to the metal electrodes to create an interspacing electric field. The spacing volume could be filled with air, nitrogen or argon. Thermal neutrons were captured in converter layers due to the presence of the 10B isotope. The resulting nuclear reaction produced α-particles and 7Li ions which ionized the gas in the spacing volume. Electron-ion pairs were collected by the field to create an electrical signal proportional to the intensity of the neutron source. The detection efficiency of the multilayer neutron detectors is found to increase with the number of active converter layers. Pixel structures of such neutron detectors necessary for imaging applications and incorporation of internal moderator materials for field measurements of fast neutron flux intensities are discussed as well.

  15. High fluence boron implantation into polymers

    NASA Astrophysics Data System (ADS)

    Vacik, J.; Cervena, J.; Fink, D.; Klett, R.; Hnatowicz, V.; Popok, V.; Odzhaev, V.

    100 keV B+ ions are implanted at high fluence into three polymers of technological importance and into a polymeric mixture, respectively. The boron depth distributions are measured by the neutron depth profiling technique. It is shown that the boron atoms redistribute after their implantation according to the nuclear (collisional) energy transfer distribution. This contrasts to low fluence implantation, where the boron atoms redistribute according to their electronic energy transfer distributions. Subsequently, the samples are annealed isochronally. The change of the boron depth profiles with annealing temperature is then evaluated to determine the diffusional, trapping and detrapping behavior of the boron atoms. At, or slightly above room temperature, intrinsic boron impurities of the examined polymer foils become mobile and getter in the ion-implanted region. At higher temperatures, the thermal desorption spectra show a nearly continuous desorption of both the implanted and gettered boron, with no pronounced desorption peaks. Due to the high polymeric destruction yield, the different polymers show little difference in their desorption behavior.

  16. Atomistic study of boron-doped silicon

    SciTech Connect

    Fearn, M.; Pettifor, D.G.; Jefferson, J.H.

    1996-12-31

    Atomistic simulations using both tight-binding and density-functional approaches have been performed to investigate boron-related defects in silicon. In agreement with experiment, the boron interstitial is shown to be a negative-U center in the sense that its neutral charge state, with an associated Jahn-Teller distortion off the ideal tetrahedral site, is never the ground state for any value of the chemical potential in the gap. The possible consequences for an electron-assisted migration of the interstitial are discussed. The authors also find the boron substitutional defect to be a next-nearest neighbor of a silicon vacancy in agreement with EPR spectra. A semi-empirical tight-binding model of the boron-silicon system is validated by direct comparison with the accurate density-functional results and is then used to perform molecular dynamics simulations of boron diffusion at high temperatures. The mobility of the interstitial is found to be strongly charge-state dependent. Termination of the boron interstitial migration path by recombination with a silicon vacancy is shown to be a very likely process with a number of configurations having no barrier to capture when the boron is a near-neighbor of the vacancy.

  17. Where Boron? Mars Rover Detects It

    NASA Image and Video Library

    2016-12-13

    This map shows the route driven by NASA's Curiosity Mars rover (blue line) and locations where the rover's Chemistry and Camera (ChemCam) instrument detected the element boron (dots, colored by abundance of boron according to the key at right). The main map shows the traverse from landing day (Sol 0) in August 2012 to the rover's location in September 2016, with boron detections through September 2015. The inset at upper left shows a magnified version of the most recent portion of that traverse, with boron detections during that portion. Overlapping dots represent cases when boron was detected in multiple ChemCam observation points in the same target and non-overlapping dots represent cases where two different targets in the same location have boron. Most of the mission's detections of boron have been made in the most recent seven months (about 200 sols) of the rover's uphill traverse. The base image for the map is from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. North is up. The scale bar at lower right represents one kilometer (0.62 mile). http://photojournal.jpl.nasa.gov/catalog/PIA21150

  18. Properties of vacuum-evaporated boron films

    NASA Technical Reports Server (NTRS)

    Feakes, F.

    1973-01-01

    The work on the properties of thin boron films made by vacuum evaporation of elemental boron using an electron beam as the energy source is reported. The program aimed at characterizing the properties of vacuum evaporated films. The work was directed toward those variables considered to be important in affecting the tensile strength of the boron films. In general, the thickness of the films was less than 0.002 in. The temperature of the substrate on which the boron was condensed was found to be most important. Three distinctly different forms of boron deposit were produced. Although the transition temperature was not sharply defined, at substrate temperatures of less than approximately 600 deg C the boron deposits were amorphous to X-ray. If the substrate were highly polished, the deposits were black and mirror-like. For substrates with coefficients of thermal expansion close to that of boron, the deposits were then continuous and uncracked. The studies suggest that the potential continues to exist for film-type composites to have both high strength and high modulus.

  19. Combustion synthesis of novel boron carbide

    NASA Astrophysics Data System (ADS)

    Harini, R. Saai; Manikandan, E.; Anthonysamy, S.; Chandramouli, V.; Eswaramoorthy, D.

    2013-02-01

    The solid-state boron carbide is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. Boron carbide (BxCx) enriched in the 10B isotope is used as a control rod material in the nuclear industry due to its high neutron absorption cross section and other favorable physico-chemical properties. Conventional methods of preparation of boron carbide are energy intensive processes accompanied by huge loss of boron. Attempts were made at IGCAR Kalpakkam to develop energy efficient and cost effective methods to prepare boron carbide. The products of the gel combustion and microwave synthesis experiments were characterized for phase purity by XRD. The carbide formation was ascertained using finger-print spectroscopy of FTIR. Samples of pyrolized/microwave heated powder were characterized for surface morphology using SEM. The present work shows the recent advances in understanding of structural and chemical variations in boron carbide and their influence on morphology, optical and vibrational property results discussed in details.

  20. Boron-Loaded Silicone Rubber Scintillators

    SciTech Connect

    Bell, Z.W.; Maya, L.; Brown, G.M.; Sloop, F.V.Jr

    2003-05-12

    Silicone rubber received attention as an alternative to polyvinyltoluene in applications in which the scintillator is exposed to high doses because of the increased resistance of the rubber to the formation of blue-absorbing color centers. Work by Bowen, et al., and Harmon, et al., demonstrated their properties under gamma/x-ray irradiation, and Bell, et al. have shown their response to thermal neutrons. This last work, however, provided an example of a silicone in which both the boron and the scintillator were contained in the rubber as solutes, a formulation which led to the precipitation of solids and sublimation of the boron component. In the present work we describe a scintillator in which the boron is chemically bonded to the siloxane and so avoids the problem of precipitation and loss of boron to sublimation. Material containing up to 18% boron, by weight, was prepared, mounted on photomultipliers, and exposed to both neutron and gamma fluxes. Pulse height spectra showing the neutron and photon response were obtained, and although the light output was found to be much poorer than from samples in which boron was dissolved, the higher boron concentrations enabled essentially 100% neutron absorption in only a few millimeters' thickness of rubber.

  1. Conductivity of boron-doped polycrystalline diamond films: influence of specific boron defects

    NASA Astrophysics Data System (ADS)

    Ashcheulov, P.; Šebera, J.; Kovalenko, A.; Petrák, V.; Fendrych, F.; Nesládek, M.; Taylor, A.; Vlčková Živcová, Z.; Frank, O.; Kavan, L.; Dračínský, M.; Hubík, P.; Vacík, J.; Kraus, I.; Kratochvílová, I.

    2013-10-01

    The resistivity of boron doped polycrystalline diamond films changes with boron content in a very complex way with many unclear factors. From the large number of parameters affecting boron doped polycrystalline diamond film's conductivity we focused on the role of boron atoms inside diamond grains in terms of boron contribution to the continuum of diamond electronic states. Using a combination of theoretical and experimental techniques (plane-wave Density Functional Theory, Neutron Depth Profiling, resistivity and Hall effect measurements, Atomic Force Microscopy and Raman spectroscopy) we studied a wide range of B defect parameters - the boron concentration, location, structure, free hole concentration and mobility. The main goal and novelty of our work was to find the influence of B defects (structure, interactions, charge localisation and spins) in highly B-doped diamonds - close or above the metal-insulator transition - on the complex material charge transport mechanisms.

  2. JAGUAR Procedures for Detonation Behavior of Explosives Containing Boron

    NASA Astrophysics Data System (ADS)

    Stiel, Leonard; Baker, Ernest; Capellos, Christos

    2009-06-01

    The JAGUAR product library was expanded to include boron and boron containing products. Relationships of the Murnaghan form for molar volumes and derived properties were implemented in JAGUAR. Available Hugoniot and static volumertic data were analyzed to obtain constants of the Murnaghan relationship for solid boron, boron oxide, boron nitride, boron carbide, and boric acid. Experimental melting points were also utilized with optimization procedures to obtain the constants of the volumetric relationships for liquid boron and boron oxide. Detonation velocities for HMX - boron mixtures calculated with these relationships using JAGUAR are in closer agreement with literature values at high initial densities for inert (unreacted) boron than with the completely reacted metal. These results indicate that boron mixtures may exhibit eigenvalue detonation behavior, as observed by aluminized combined effects explosives, with higher detonation velocities than would be achieved by a classical Chapman-Jouguet detonation. Analyses of calorimetric measurements for RDX - boron mixtures indicate that at high boron contents the formation of side products, including boron nitride and boron carbide, inhibits the energy output obtained from the detonation of the formulation.

  3. Thermodynamic limitation on boron energy realization in ramjet propulsion

    NASA Astrophysics Data System (ADS)

    Gany, Alon

    2014-05-01

    This study addresses a specific boron combustion aspect, revealing that thermodynamic conditions associated with highly boron-loaded ramjet combustors, may lead to blockage of the reaction between boron and air, causing termination of the combustion process, incomplete chemical reaction, and only partial realization of the potential boron combustion energy. Sustained boron combustion may take place when the evaporation rate of the protective liquid boron oxide layer B2O3(l) on the boron particles exceeds its generation rate by the oxidation reaction, typically at temperatures above 1900-2000 K. However, if the actual partial pressure of gaseous boron oxide B2O3(g) produced in the combustion process attains the equilibrium vapor pressure of boron oxide at the conditions existing in the combustion chamber, condensation of the boron oxide to form a liquid layer on the boron particle surfaces may take place, extinguishing the particle combustion by blocking the reaction between the boron and the surrounding oxidizing gas. The study predicts conditions for blockage and incomplete boron combustion over a range of chamber pressures and temperatures. This effect may be characteristic to combustors employing boron-containing fuels, but may not be encountered in the combustion of individual boron particles in air.

  4. X-ray diffraction study of boron produced by pyrolysis of boron tribromide

    NASA Astrophysics Data System (ADS)

    Rosenberg, David

    The goal of this research was to determine the composition of boron deposits produced by pyrolysis of boron tribromide, and to use the results to (a) determine the experimental conditions (reaction temperature, etc.) necessary to produce alpha-rhombohedral boron and (b) guide the development/refinement of the pyrolysis experiments such that large, high purity crystals of alpha-rhombohedral boron can be produced with consistency. Developing a method for producing large, high purity alpha-rhombohedral boron crystals is of interest because such crystals could potentially be used to achieve an alpha-rhombohedral boron based neutron detector design (a solid-state detector) that could serve as an alternative to existing neutron detector technologies. The supply of neutron detectors in the United States has been hampered for a number of years due to the current shortage of helium-3 (a gas used in many existing neutron detector technologies); the development of alternative neutron detector technology such as an alpha-rhombohedral boron based detector would help provide a more sustainable supply of neutron detectors in this country. In addition, the prospect/concept of an alpha-rhombohedral boron based neutron detector is attractive because it offers the possibility of achieving a design that is smaller, longer life, less power consuming, and potentially more sensitive than existing neutron detectors. The main difficulty associated with creating an alpha-rhombohedral boron based neutron detector is that producing large, high purity crystals of alpha-rhombohedral boron is extremely challenging. Past researchers have successfully made alpha-rhombohedral boron via a number of methods, but no one has developed a method for consistently producing large, high purity crystals. Alpha-rhombohedral boron is difficult to make because it is only stable at temperatures below around 1100-1200 °C, its formation is very sensitive to impurities, and the conditions necessary for its

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  6. Boron Nitride and Silicon Nitride Systems

    DTIC Science & Technology

    1991-02-01

    2381.43 [85VilJ 13-B a=1098.B6 [SiCre) at 2.4atCr c=2385.14 Cr aB oF40 a=1470.6 (879mi) 򒼎* Fddd b= 741.33 o -Kn ZB o = 425.35 CrwBq t132 a= 546.40...2095* CMOs b= 788.89 CrB 0: 293.33 Cr vB4 0114 a= 298.58 [879miJ * 2075* Iam b=1302.2 TaB94 o = 295.25 135 CraBs oC20 a= 302.84 [870kaJ Cues b=1811.5...1-2x)*+13700(1-2x)’) 0.3632 Cr 20 o ., AtG : -30663.4+15.22 T (78Fro] 138 Fig.l: The binary system Cr 8 ; based on [7lPra,BBMasJ and Chromium - Boron

  7. Crystallization of Beryllium-Boron Metallic Glasses

    SciTech Connect

    Jankowski, A F; Wall, M A; Nieh, T G

    2002-02-14

    Prior studies of evaporation and sputter deposition show that the grain size of pure beryllium can be dramatically refined through the incorporation of metal impurities. Recently, the addition of boron at a concentration greater than 11% is shown to serve as a glassy phase former in sputter deposited beryllium. Presently, thermally induced crystallization of the beryllium-boron metallic glass is reported. The samples are characterized during an in-situ anneal treatment with bright field imaging and electron diffraction using transmission electron microscopy. A nanocrystalline structure evolves from the annealed amorphous phase and the crystallization temperature is affected by the boron concentration.

  8. Boron-10 Lined Proportional Counter Wall Effects

    SciTech Connect

    Siciliano, Edward R.; Kouzes, Richard T.

    2012-05-01

    The Department of Energy Office of Nuclear Safeguards (NA-241) is supporting the project 'Coincidence Counting With Boron-Based Alternative Neutron Detection Technology' at Pacific Northwest National Laboratory (PNNL) for development of an alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a boron-lined proportional tube based system in the configuration of a coincidence counter. This report provides information about how variations in proportional counter radius and gas pressure in a typical coincident counter design might affect the observed signal from boron-lined tubes. A discussion comparing tubes to parallel plate counters is also included.

  9. Boron Nitride Nanoribbons: Synthesis and Future Directions

    NASA Astrophysics Data System (ADS)

    Gibb, Ashley; Erikson, Kris; Sinitskii, Alex; Rousseas, Michael; Alem, Nasim; Tour, James; Zettl, Alex

    2012-02-01

    Boron Nitride Nanoribbons (BNNR) have been theorized to have many interesting electrical and magnetic properties and edge states, but these characteristics have not been experimentally verified due to challenges in synthesis and purification. We have produced BNNRs by longitudinally splitting boron nitride nanotubes (BNNT) using potassium vapor as an intercalant. Due to the strong interactions between boron nitride sheets, separation of nanoribbons from their parent tubes is challenging. We have used various solvent systems to assist with separation of the ribbons with the goal of probing their properties.

  10. Boron distribution in sintered silicon carbide

    SciTech Connect

    Carter, W.D.; Holloway, P.H. ); White, C.; Clausing, R. )

    1988-01-01

    Boron concentrations on intergranular and transgranular fracture areas in sintered SiC were measured; {alpha}-SiC grains oriented parallel to the fracture surface would fracture at the {alpha}-{beta} interphase boundary. Auger electron spectroscopy showed that boron does not segregate to these boundaries in sintered SiC. This conclusion was generalized to include the other types of SiC grain boundaries. The absence of boron at grain boundaries suggests that its role in sintering is not to enhance diffusion rates. Chemical reactions and free surface segregation, which may explain the increased densification of SiC when B is present, are discussed.

  11. Boron Fullerenes: An Electronic Structure Study

    NASA Astrophysics Data System (ADS)

    Sadrzadeh, Arta; Pupysheva, Olga; Boustani, Ihsan; Yakobson, Boris

    2008-03-01

    Using ab initio calculations, we study electronic structure and frequency modes of B80, a member of boron fullerene family made from boron isomorphs of carbon fullerenes with additional atoms in the centers of hexagons. We also investigate geometrical and electronic structural properties of double-rings with various diameters, which are important as building blocks of boron nanotubes, and as the most stable clusters among the studied isomers with no more than 36 atoms. Double-rings also appear as building blocks of B80. Furthermore, we investigate the possibility of further stabilizing some of fullerenes by depleting them.

  12. Developments in boron magnetic resonance imaging (MRI)

    SciTech Connect

    Schweizer, M.

    1995-11-01

    This report summarizes progress during the past year on maturing Boron-11 magnetic resonance imaging (MRI) methodology for noninvasive determination of BNCT agents (BSH) spatially in time. Three major areas are excerpted: (1) Boron-11 MRI of BSH distributions in a canine intracranial tumor model and the first human glioblastoma patient, (2) whole body Boron-11 MRI of BSH pharmacokinetics in a rat flank tumor model, and (3) penetration of gadolinium salts through the BBB as a function of tumor growth in the canine brain.

  13. Characterization of boron tolerant bacteria isolated from a fly ash dumping site for bacterial boron remediation.

    PubMed

    Edward Raja, Chellaiah; Omine, Kiyoshi

    2013-08-01

    Boron is an essential micronutrient for plants, but can above certain concentrations be toxic to living organisms. A major environmental concern is the removal of boron from contaminated water and fly ash. For this purpose, the samples were collected from a fly ash dumping site, Nagasaki prefecture, Japan. The chemical characteristics and heavy metal concentration of the samples were performed by X-ray fluorescent analysis and leaching test. For bacterial analysis, samples were collected in sterile plastic sheets and isolation was carried out by serial dilution method. The boron tolerant isolates that showed values of maximum inhibitory concentration toward boron ranging from 100 to 260 mM level were screened. Based on 16S rRNA sequencing and phylogenetic analysis, the isolates were most closely related to the genera Bacillus, Lysinibacillus, Microbacterium and Ralstonia. The boron tolerance of these strains was also associated with resistant to several heavy metals, such as As (III), Cr (VI), Cd, Cu, Pb, Ni, Se (III) and Zn. Indeed, these strains were arsenic oxidizing bacteria confirmed by silver nitrate test. These strains exhibited their salt resistances ranging from 4 to 15 % were determined in Trypticase soy agar medium. The boron tolerant strains were capable of removing 0.1-2.0 and 2.7-3.7 mg l(-1) boron from the medium and fly ash at 168 h. Thus, we have successfully identified the boron tolerant and removal bacteria from a fly ash dumping site for boron remediation.

  14. Mathematical modeling of boron diffusion from boron oxide glass film sources

    SciTech Connect

    Yeckel, A.; Middleman, S.

    1988-09-01

    Mathematical models are developed to examine two alternative means of boron doping from boron-rich glass films. For the planar source diffusion system, in which boron diffusion and glass film growth occur simultaneously at high temperature (900-1200/sup 0/C), glass film growth rates and the degree of doping achieved are predicted. In most cases, the solubility limit of boron in silicon is attained at the silicon surface. It is found that depletion of the boron source wafers used in this process may be slowed considerably by their removal from the reactor after a short time. Model predictions for an alternative method, in which the glass film is pregrown at low temperature (300/sup 0/C) and the diffusion subsequently performed at high temperature, demonstrate a strong dependence of the boron surface concentration on the initial boron content in the pregrown glass film, for concentrations of boron near the solubility limit. The conditions for which a masking film of SiO/sub 2/ is insufficient to prevent boron diffusion into silicon, known as mask failure, are also predicted by the models.

  15. Borocaptate sodium: a potential boron delivery compound for boron neutron capture therapy evaluated in dogs with spontaneous intracranial tumors.

    PubMed Central

    Kraft, S L; Gavin, P R; DeHaan, C E; Leathers, C W; Bauer, W F; Miller, D L; Dorn, R V

    1992-01-01

    Borocaptate sodium (Na2B12H11SH) is a boron-carrying compound under consideration for use in boron neutron capture therapy. The biodistribution of boron from borocaptate sodium administration will partly determine boron neutron capture therapy efficacy and normal tissue radiation tolerance. The biodistribution of boron was determined in 30 dogs with spontaneous intracranial tumors at 2, 6, or 12 hr after intravenous borocaptate sodium infusion. Blood and tissue boron concentrations were measured using inductively coupled plasma atomic emission spectroscopy. Mean tumor boron concentration (mean +/- standard error) was 35.9 +/- 4.6 (n = 15), 22.5 +/- 6.0 (n = 9), and 7.0 +/- 1.1 micrograms of boron per g (n = 6) at 2, 6, and 12 hr, respectively, after borocaptate sodium infusion. Peritumor boron concentrations were elevated above that of normal brain in half of the dogs. Normal brain boron concentration (mean +/- standard error) was 4.0 +/- 0.5, 2.0 +/- 0.4, and 2.0 +/- 0.3 micrograms of boron per g at 2, 6, and 12 hr after infusion, respectively. Some cranial and systemic tissues, and blood, had high boron concentration relative to tumor tissue. Geometric dose sparing should partly offset these relatively high normal tissue and blood concentrations. Borocaptate sodium biodistribution is favorable because tumor boron concentrations of recommended magnitude for boron neutron capture therapy were obtained and there was a high tumor-to-normal brain boron concentration ratio. PMID:1465427

  16. Fragment approach to the electronic structure of τ -boron allotrope

    NASA Astrophysics Data System (ADS)

    Karmodak, Naiwrit; Jemmis, Eluvathingal D.

    2017-04-01

    The presence of nonconventional bonding features is an intriguing part of elemental boron. The recent addition of τ boron to the family of three-dimensional boron allotropes is no exception. We provide an understanding of the electronic structure of τ boron using a fragment molecular approach, where the effect of symmetry reduction on skeletal bands of B12 and the B57 fragments are examined qualitatively by analyzing the projected density of states of these fragments. In spite of the structural resemblance to β boron, the reduction of symmetry from a rhombohedral space group to the orthorhombic one destabilizes the bands and reduces the electronic requirements. This suggests the presence of the partially occupied boron sites, as seen for a β boron unit cell, and draws the possibility for the existence of different energetically similar polymorphs. τ boron has a lower binding energy than β boron.

  17. Boron dose determination for BNCT using Fricke and EPR dosimetry

    SciTech Connect

    Wielopolski, L.; Ciesielski, B.

    1995-02-01

    In Boron Neutron Capture Therapy (BNCT) the dominant dose delivered to the tumor is due to {alpha} and {sup 7}Li charged particles resulting from a neutron capture by {sup 10}B and is referred to herein as the boron dose. Boron dose is directly attributable to the following two independent factors, one boron concentration and the neutron capture energy dependent cross section of boron, and two the energy spectrum of the neutrons that interact with boron. The neutron energy distribution at a given point is dictated by the incident neutron energy distribution, the depth in tissue, geometrical factors such as beam size and patient`s dimensions. To account for these factors can be accommodated by using Monte Carlo theoretical simulations. However, in conventional experimental BNCT dosimetry, e.g., using TLDs or ionization chambers, it is only possible to estimate the boron dose. To overcome some of the limitations in the conventional dosimetry, modifications in ferrous sulfate dosimetry (Fricke) and Electron Paramagnetic Resonance (EPR) dosimetry in alanine, enable to measure specifically boron dose in a mixed gamma neutron radiation fields. The boron dose, in either of the dosimeters, is obtained as a difference between measurements with boronated and unboronated dosimeters. Since boron participates directly in the measurements, the boron dosimetry reflects the true contribution, integral of the neutron energy spectrum with boron cross section, of the boron dose to the total dose. Both methods are well established and used extensively in dosimetry, they are presented briefly here.

  18. Boron-Filled Hybrid Carbon Nanotubes.

    PubMed

    Patel, Rajen B; Chou, Tsengming; Kanwal, Alokik; Apigo, David J; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-07-27

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs.

  19. Boron-Filled Hybrid Carbon Nanotubes

    PubMed Central

    Patel, Rajen B.; Chou, Tsengming; Kanwal, Alokik; Apigo, David J.; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-01-01

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs. PMID:27460526

  20. Ni doping of semiconducting boron carbide

    SciTech Connect

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

    2010-01-15

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

  1. Bipolaron Hopping Conduction in Boron Carbides

    SciTech Connect

    ASELAGE, TERRENCE L.; EMIN, D.; MCCREADY, STEVEN S.

    1999-09-20

    The electrical conductivities of boron carbides, B{sub 12+x}C{sub 3{minus}x} with 0.1 < x < 1.7, between 300 and 1200K suggest the hopping of a nearly temperature-independent density of small (bi)polarons. The activation energies of the nobilities are low, {approx} 0.16 eV, and are nearly independent of the composition. At lower temperatures, conductivities have non-Arrhenius temperature dependencies and strong sensitivity to carbon concentration. Percolative aspects of low-temperature hopping are evident in this sensitivity to composition. Boron carbides' Seebeck coefficients are anomalous in that (1) they are much larger than expected from boron carbides' large carrier densities and (2) they depend only weakly on the carrier density. Carrier-induced softening of local vibrations gives contributions to the Seebeck coefficient that mirror the magnitudes and temperature dependencies found in boron carbides.

  2. Boron Neutron Capture Therapy - A Literature Review

    PubMed Central

    Nedunchezhian, Kavitaa; Thiruppathy, Manigandan; Thirugnanamurthy, Sarumathi

    2016-01-01

    Boron Neutron Capture Therapy (BNCT) is a radiation science which is emerging as a hopeful tool in treating cancer, by selectively concentrating boron compounds in tumour cells and then subjecting the tumour cells to epithermal neutron beam radiation. BNCT bestows upon the nuclear reaction that occurs when Boron-10, a stable isotope, is irradiated with low-energy thermal neutrons to yield α particles (Helium-4) and recoiling lithium-7 nuclei. A large number of 10 Boron (10B) atoms have to be localized on or within neoplastic cells for BNCT to be effective, and an adequate number of thermal neutrons have to be absorbed by the 10B atoms to maintain a lethal 10B (n, α) lithium-7 reaction. The most exclusive property of BNCT is that it can deposit an immense dose gradient between the tumour cells and normal cells. BNCT integrates the fundamental focusing perception of chemotherapy and the gross anatomical localization proposition of traditional radiotherapy. PMID:28209015

  3. Boron strengthening in FeAl

    SciTech Connect

    Baker, I.; Li, X.; Xiao, H.; Klein, O.; Nelson, C.; Carleton, R.L.; George, E.P.

    1998-11-01

    The effect of boron on the strength of B2-structured FeAl is considered as a function of composition, grain size and temperature. Boron does not affect the concentrations of antisite atoms or vacancies present, with the former increasing and the latter decreasing with increasing deviation from the stoichiometric composition. When vacancies are absent, the strength increase per at. % B per unit lattice strain, {Delta}{sigma}/({Delta}c x {epsilon}) increases with increasing aluminum concentration, but when vacancies are present (>45 at. % Al), {Delta}{sigma}/({Delta}c x {epsilon}) decreases again. Boron increases grain size strengthening in FeAl. B strengthening is roughly independent of temperature up to the yield strength peak but above the point, when diffusion-assisted deformation occurs, boron strengthening increases dramatically.

  4. New approach to obtain boron selective emitters

    SciTech Connect

    Moehlecke, A.; Luque, A.

    1994-12-31

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

  5. Neutron dosimetry in boron neutron capture therapy

    SciTech Connect

    Fairchild, R.G.; Miola, U.J.; Ettinger, K.V.

    1981-01-01

    The recent development of various borated compounds and the utilization of one of these (Na/sub 2/B/sub 12/H/sub 11/SH) to treat brain tumors in clinical studies in Japan has renewed interest in neutron capture therapy. In these procedures thermal neutrons interact with /sup 10/B in boron containing cells through the /sup 10/B(n,..cap alpha..)/sup 7/Li reaction producing charged particles with a maximum range of approx. 10..mu..m in tissue. Borated analogs of chlorpromazine, porphyrin, thiouracil and deoxyuridine promise improved tumor uptake and blood clearance. The therapy beam from the Medical Research Reactor in Brookhaven contains neutrons from a modified and filtered fission spectrum and dosimetric consequences of the use of the above mentioned compounds in conjunction with thermal and epithermal fluxes are discussed in the paper. One of the important problems of radiation dosimetry in capture therapy is determination of the flux profile and, hence, the dose profile in the brain. This has been achieved by constructing a brain phantom made of TE plastic. The lyoluminescence technique provides a convenient way of monitoring the neutron flux distributions; the detectors for this purpose utilize /sup 6/Li and /sup 10/B compounds. Such compounds have been synthesized specially for the purpose of dosimetry of thermal and epithermal beams. In addition, standard lyoluminescent phosphors, like glutamine, could be used to determine the collisional component of the dose as well as the contribution of the /sup 14/N(n,p)/sup 14/C reaction. Measurements of thermal flux were compared with calculations and with measurements done with activation foils.

  6. Large diameter carbon-boron fiber

    NASA Technical Reports Server (NTRS)

    Veltri, R. D.; Jacob, B. A.; Galasso, F. S.

    1975-01-01

    Investigations concerned with a development of large-diameter carbon fibers are considered, taking into account the employment of vapor deposition techniques. In the experiments a carbon monofilament substrate is used together with reacting gases which consist of combinations of hydrogen, methane, and boron trichloride. It is found that the described approach can be used to obtain a large-diameter carbon filament containing boron. The filament has reasonable strength and modulus properties.

  7. Formose reaction controlled by boronic acid compounds

    PubMed Central

    Imai, Toru; Michitaka, Tomohiro

    2016-01-01

    Formose reactions were carried out in the presence of low molecular weight and macromolecular boronic acid compounds, i.e., sodium phenylboronate (SPB) and a copolymer of sodium 4-vinylphenylboronate with sodium 4-styrenesulfonate (pVPB/NaSS), respectively. The boronic acid compounds provided different selectivities; sugars of a small carbon number were formed favorably in the presence of SPB, whereas sugar alcohols of a larger carbon number were formed preferably in the presence of pVPB/NaSS. PMID:28144337

  8. Boronate-tau mediated uptake in neurons.

    PubMed

    Pérez, Mar; Cuadros, Raquel; Pallas-Bazarra, Noemi; García, Carlos; Langa, Elena; Jurado-Arjona, Jerónimo; Hernández, Félix; Avila, Jesús

    2014-01-01

    We modified tau protein with boronic acid to facilitate its delivery into non neural or neural cultured cells lacking tau protein. Our results indicate that the incorporated tau promotes the formation of cytoplasmic extensions in non-neuronal cells, as well as the appearance of neurites in cultured tau knockout hippocampal neurons. In addition, boronated tau is incorporated into hippocampal neurons of tau knockout mice after intracranial injection in vivo. These findings describe a novel method to deliver exogenous tau protein into cells.

  9. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, E.L.

    1984-11-29

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  10. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, Edward L.

    1985-01-01

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  11. Boron

    SciTech Connect

    Cozen, L.F. )

    1991-05-01

    This paper reports that borate minerals and refined borates are used extensively for the manufacture of vitreous materials such as insulation and textile fiberglasses, borosilicate glass, and porcelain enamels and frits. In North America, these applications are estimated to account for over 54% of the borate consumption. Other substantial uses are in soaps and detergents, metallurgy, fire retardants, industrial biocides, agriculture, and various miscellaneous applications. Reported domestic borate consumption in 1990 was estimated by the U.S. Bureau of Mines to be 320 000 metric tons B{sub 2}O{sub 3} versus 354 000 metric tons B{sub 2}O{sub 3} in 1989. Consumption is projected to remain essentially static in 1991. Imports were estimated by the Bureau to be 50 000 metric tons B{sub 2}O{sub 3} in 1990. Exports of boric acid and refined borates were approximately 650 000 metric tons of product, a 15 000 metric ton increase from the 1989 level. This increase partially offsets the drop in the 1990 consumption level.

  12. Boronization on NSTX using Deuterated Trimethylboron

    SciTech Connect

    W.R. Blanchard; R.C. Gernhardt; H.W. Kugel; P.H. LaMarche

    2002-01-28

    Boronization on the National Spherical Torus Experiment (NSTX) has proved to be quite beneficial with increases in confinement and density, and decreases in impurities observed in the plasma. The boron has been applied to the interior surfaces of NSTX, about every 2 to 3 weeks of plasma operation, by producing a glow discharge in the vacuum vessel using deuterated trimethylboron (TMB) in a 10% mixture with helium. Special NSTX requirements restricted the selection of the candidate boronization method to the use of deuterated boron compounds. Deuterated TMB met these requirements, but is a hazardous gas and special care in the execution of the boronization process is required. This paper describes the existing GDC, Gas Injection, and Torus Vacuum Pumping System hardware used for this process, the glow discharge process, and the automated control system that allows for remote operation to maximize both the safety and efficacy of applying the boron coating. The administrative requirements and the detailed procedure for the setup, operation and shutdown of the process are also described.

  13. Amorphous boron nitride at high pressure

    NASA Astrophysics Data System (ADS)

    Durandurdu, Murat

    2016-06-01

    The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions.

  14. Synthesis of Borophene: Anisotropic, Two-Dimensional Boron Allotrope

    SciTech Connect

    Mannix, Andrew J.; Zhou, Xiang-Feng; Kiraly, Brian T.; Wood, Joshua D.; Alducin, Diego; Meyers, Benjamin; Liu, Xiaolong; Fisher, Brandon L.; Santiago, Ulises; Guest, Jeffrey R.; Yacaman, Miguel; Ponce, Artura; oganov, artem R; Hersam, Mark C.; Guisinger, N. P.

    2015-12-18

    At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes. Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal.

  15. Development of magnetic resonance technology for noninvasive boron quantification

    SciTech Connect

    Bradshaw, K.M.

    1990-11-01

    Boron magnetic resonance imaging (MRI) and spectroscopy (MRS) were developed in support of the noninvasive boron quantification task of the Idaho National Engineering Laboratory (INEL) Power Burst Facility/Boron Neutron Capture Therapy (PBF/BNCT) program. The hardware and software described in this report are modifications specific to a GE Signa{trademark} MRI system, release 3.X and are necessary for boron magnetic resonance operation. The technology developed in this task has been applied to obtaining animal pharmacokinetic data of boron compounds (drug time response) and the in-vivo localization of boron in animal tissue noninvasively. 9 refs., 21 figs.

  16. The effect of boron supplementation on lean body mass, plasma testosterone levels, and strength in male bodybuilders

    NASA Technical Reports Server (NTRS)

    Ferrando, A. A.; Green, N. R.

    1993-01-01

    The effect of boron supplementation was investigated in 19 male bodybuilders ages 20-27 years. Ten were given a 2.5-mg boron supplement while 9 were given a placebo every day for 7 weeks. Plasma total and free testosterone, plasma boron, lean body mass, and strength measurements were determined on Days 1 and 49 of the study. Plasma boron values were significantly (p < 0.05) different as the experimental group increased from (+/- SD) 20.1 +/- 7.7 ppb pretest to 32.6 +/- 27.6 ppb posttest, while the control group mean decreased from 15.1 +/- 14.4 ppb pretest to 6.3 +/- 5.5 ppb posttest. Analysis of variance indicated no significant effect of boron supplementation on any of the dependent variables. Both groups demonstrated significant increases in total testosterone, lean body mass, 1-RM squat, and 1-RM bench press. The findings suggest that 7 weeks of bodybuilding can increase total testosterone, lean body mass, and strength in lesser trained bodybuilders, and that boron supplementation had no effect on these measures.

  17. The effect of boron supplementation on lean body mass, plasma testosterone levels, and strength in male bodybuilders

    NASA Technical Reports Server (NTRS)

    Ferrando, A. A.; Green, N. R.

    1993-01-01

    The effect of boron supplementation was investigated in 19 male bodybuilders ages 20-27 years. Ten were given a 2.5-mg boron supplement while 9 were given a placebo every day for 7 weeks. Plasma total and free testosterone, plasma boron, lean body mass, and strength measurements were determined on Days 1 and 49 of the study. Plasma boron values were significantly (p < 0.05) different as the experimental group increased from (+/- SD) 20.1 +/- 7.7 ppb pretest to 32.6 +/- 27.6 ppb posttest, while the control group mean decreased from 15.1 +/- 14.4 ppb pretest to 6.3 +/- 5.5 ppb posttest. Analysis of variance indicated no significant effect of boron supplementation on any of the dependent variables. Both groups demonstrated significant increases in total testosterone, lean body mass, 1-RM squat, and 1-RM bench press. The findings suggest that 7 weeks of bodybuilding can increase total testosterone, lean body mass, and strength in lesser trained bodybuilders, and that boron supplementation had no effect on these measures.

  18. The effect of boron deficiency on gene expression and boron compartmentalization in sugarbeet

    USDA-ARS?s Scientific Manuscript database

    NIP5, BOR1, NIP6, and WRKY6 genes were investigated for their role in boron deficiency in sugar beet, each with a proposed role in boron use in model plant species. All genes showed evidence of polymorphism in fragment size and gene expression in the target genomic DNA and cDNA libraries, with no co...

  19. Spectromicroscopy of boron for the optimization of boron neutron capture therapy (BNCT) for cancer

    NASA Astrophysics Data System (ADS)

    Gilbert, B.; Redondo, J.; Baudat, P.-A.; Lorusso, G. F.; Andres, R.; Van Meir, E. G.; Brunet, J.-F.; Hamou, M.-F.; Suda, T.; Mercanti, Delio; Ciotti, M. Teresa; Droubay, T. C.; Tonner, B. P.; Perfetti, P.; Margaritondo, M.; DeStasio, Gelsomina

    1998-10-01

    We used synchrotron spectromicroscopy to study the microscopic distribution of boron in rat brain tumour and healthy tissue in the field of boron neutron capture therapy (BNCT). The success of this experimental cancer therapy depends on the preferential uptake of ? in tumour cells after injection of a boron compound (in our case ?, or BSH). With the Mephisto (microscope à emission de photoélectrons par illumination synchrotronique de type onduleur) spectromicroscope, high-magnification imaging and chemical analysis was performed on brain tissue sections from a rat carrying an implanted brain tumour and the results were compared with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) detection of boron in bulk tissue. Boron was found to have been taken up more favourably by regions of tumour rather than healthy tissue, but the resulting boron distribution in the tumour was inhomogeneous. The results demonstrate that Mephisto can perform microchemical analysis of tissue sections, detect and localize the presence of boron with submicron spatial resolution. The application of this technique to boron in brain tissue can therefore be used to evaluate the current efforts to optimize BNC therapy.

  20. Boron site preference in ternary Ta and Nb boron silicides

    SciTech Connect

    Khan, Atta U.; Nunes, Carlos A.; Coelho, Gilberto C.; Suzuki, Paulo A.; Grytsiv, Andriy; Bourree, Francoise; Rogl, Peter F.

    2012-06-15

    X-ray single crystal (XSC) and neutron powder diffraction data (NPD) were used to elucidate boron site preference for five ternary phases. Ta{sub 3}Si{sub 1-x}B{sub x} (x=0.112(4)) crystallizes with the Ti{sub 3}P-type (space group P4{sub 2}/n) with B-atoms sharing the 8g site with Si atoms. Ta{sub 5}Si{sub 3-x} (x=0.03(1); Cr{sub 5}B{sub 3}- type) crystallizes with space group I4/mcm, exhibiting a small amount of vacancies on the 4a site. Both, Ta{sub 5}(Si{sub 1-x}B{sub x}){sub 3}, x=0.568(3), and Nb{sub 5}(Si{sub 1-x}B{sub x}){sub 3}, x=0.59(2), are part of solid solutions of M{sub 5}Si{sub 3} with Cr{sub 5}B{sub 3}-type into the ternary M-Si-B systems (M=Nb or Ta) with B replacing Si on the 8h site. The D8{sub 8}-phase in the Nb-Si-B system crystallizes with the Ti{sub 5}Ga{sub 4}-type revealing the formula Nb{sub 5}Si{sub 3}B{sub 1-x} (x=0.292(3)) with B partially filling the voids in the 2b site of the Mn{sub 5}Si{sub 3} parent type. - Graphical abstract: The crystal structures of a series of compounds have been solved from X-ray single crystal diffractometry revealing details on the boron incorporation. Highlights: Black-Right-Pointing-Pointer Structure of a series of compounds have been solved by X-ray single crystal diffractometry. Black-Right-Pointing-Pointer Ta{sub 3}(Si{sub 1-x}B{sub x}) (x=0.112) crystallizes with the Ti{sub 3}P-type, B and Si atoms randomly share the 8g site. Black-Right-Pointing-Pointer Structure of Nb{sub 5}Si{sub 3}B{sub 1-x} (x=0.292; Ti{sub 5}Ga{sub 4}-type) was solved from NPD.

  1. Enhanced diffusion of boron by oxygen precipitation in heavily boron-doped silicon

    NASA Astrophysics Data System (ADS)

    Torigoe, Kazuhisa; Ono, Toshiaki

    2017-06-01

    The enhanced diffusion of boron has been investigated by analyzing out-diffusion profiles in the vicinity of the interface between a lightly boron-doped silicon epitaxial layer and a heavily boron-doped silicon substrate with a resistivity of 8.2 mΩ cm and an oxide precipitate (O.P.) density of 108-1010 cm-3. It is found that the boron diffusion during annealing at 850-1000 °C is enhanced with the increase of the oxide precipitate density. On the basis of a model for boron diffusion mediated by silicon self-interstitials, we reveal that the enhanced diffusion is attributed to self-interstitials supersaturated as a result of the emission from oxide precipitates and the absorption by punched-out dislocations. In addition, the temperature dependence of the fraction of the self-interstitial emission obtained analyzing the diffusion enhancement well explains the morphology changes of oxide precipitates reported in literature.

  2. Ceramic silicon-boron-carbon fibers from organic silicon-boron-polymers

    NASA Technical Reports Server (NTRS)

    Riccitiello, Salvatore R. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    1993-01-01

    Novel high strength ceramic fibers derived from boron, silicon, and carbon organic precursor polymers are discussed. The ceramic fibers are thermally stable up to and beyond 1200 C in air. The method of preparation of the boron-silicon-carbon fibers from a low oxygen content organosilicon boron precursor polymer of the general formula Si(R2)BR(sup 1) includes melt-spinning, crosslinking, and pyrolysis. Specifically, the crosslinked (or cured) precursor organic polymer fibers do not melt or deform during pyrolysis to form the silicon-boron-carbon ceramic fiber. These novel silicon-boron-carbon ceramic fibers are useful in high temperature applications because they retain tensile and other properties up to 1200 C, from 1200 to 1300 C, and in some cases higher than 1300 C.

  3. Feasibility of a boron loaded scintillation detector for dose measurements related to boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Kim, Don-Soo; Egan, James J.; Kegel, Gunter H. R.; Desimone, David

    2002-04-01

    The feasibility of the use of a boron loaded scintillation detector in a head phantom for boron neutron capture therapy dose estimates was evaluated. Several monoenergetic neutron groups were produced via the ^7Li(p,n)^7Be reaction in a metallic lithium target using the Van de Graaff accelerator at University of Massachusetts Lowell. The pulse-height spectra were taken from a natural boron loaded (10205-, 304-, 407-, 507-, 570-, 702-, and 780-keV incident neutrons. The results shows that a boron loaded scintillator could be used to distinguish the doses from different radiation sources in boron neutron capture therapy. This detector may be used in the estimation of doses due to fast neutrons, alpha particles and recoil lithium from ^10B(n,α)^7Li, and photons at the same time during neutron irradiation procedures.

  4. Atmospheric contribution to boron enrichment in aboveground wheat tissues.

    PubMed

    Wang, Cheng; Ji, Junfeng; Chen, Mindong; Zhong, Cong; Yang, Zhongfang; Browne, Patrick

    2017-05-01

    Boron is an essential trace element for all organisms and has both beneficial and harmful biological functions. A particular amount of boron is discharged into the environment every year because of industrial activities; however, the effects of environmental boron emissions on boron accumulation in cereals has not yet been estimated. The present study characterized the accumulation of boron in wheat under different ecological conditions in the Yangtze River Delta (YRD) area. This study aimed to estimate the effects of atmospheric boron that is associated with industrial activities on boron accumulation in wheat. The results showed that the concentrations of boron in aboveground wheat tissues from the highly industrialized region were significantly higher than those from the agriculture-dominated region, even though there was no significant difference in boron content in soils. Using the model based on the translocation coefficients of boron in the soil-wheat system, we estimated that the contribution of atmosphere to boron accumulation in wheat straw in the highly industrialized region exceeded that in the agriculture-dominated region by 36%. In addition, from the environmental implication of the model, it was estimated that the development of boron-utilizing industries had elevated the concentration of boron in aboveground wheat tissues by 28-53%. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Effects of supplemental boron on growth performance and meat quality in African ostrich chicks.

    PubMed

    Wang, Wei; Xiao, Ke; Zheng, Xinting; Zhu, Daiyun; Yang, Zhi; Tang, Juan; Sun, Pengpeng; Wang, Jing; Peng, Kemei

    2014-11-19

    To investigate the effects of boron on growth performance and meat quality, 10-day-old Africa ostrich chicks were randomly divided into 6 groups with 6 replicates in each group. For 80 days, birds in the treatments were fed the same basal diet but given different concentrations of boron-supplemented water. The highest final BW (33.4 ± 0.30 kg), ADFI (376 ± 1.83 g), and ADG (224 ± 1.01 g) appeared in the group receiving 160 mg/L boron (group 4). 160 mg/L boron also decreased drip loss (2.20 ± 0.59), cooking loss (35.3 ± 1.14), and elevated pH value (6.13 ± 0.28) of meat (P < 0.05). Ostrich chicks in the 640 mg/L treatment group (group 6) had the lowest final BW (30.8 ± 1.05 kg) and ADG (208 ± 0.74 g) (P < 0.05). The highest ash (1.35 ± 0.01%) and pH (6.18 ± 0.03) and the lowest protein (20.4 ± 1.74%), drip loss (2.10 ± 0.76%), cooking loss (35.0 ± 0.41%), C18:1 (28.2 ± 0.65%), and C18:3ω3 (2.60 ± 0.51%) appeared in group 6 (P < 0.05) as well. Overall, the optimum concentration of 160 mg/L supplemental boron improved ostrich growth performance and meat quality; however, high concentrations of boron decreased both performance and meat quality.

  6. Boronic acids as probes for investigation of allosteric modulation of the chemokine receptor CXCR3.

    PubMed

    Bernat, Viachaslau; Admas, Tizita Haimanot; Brox, Regine; Heinemann, Frank W; Tschammer, Nuska

    2014-11-21

    The chemokine receptor CXCR3 is a G protein-coupled receptor, which conveys extracellular signals into cells by changing its conformation upon agonist binding. To facilitate the mechanistic understanding of allosteric modulation of CXCR3, we combined computational modeling with the synthesis of novel chemical tools containing boronic acid moiety, site-directed mutagenesis, and detailed functional characterization. The design of boronic acid derivatives was based on the predictions from homology modeling and docking. The choice of the boronic acid moiety was dictated by its unique ability to interact with proteins in a reversible covalent way, thereby influencing conformational dynamics of target biomolecules. During the synthesis of the library we have developed a novel approach for the purification of drug-like boronic acids. To validate the predicted binding mode and to identify amino acid residues responsible for the transduction of signal through CXCR3, we conducted a site-directed mutagenesis study. With the use of allosteric radioligand RAMX3 we were able to establish the existence of a second allosteric binding pocket in CXCR3, which enables different binding modes of structurally closely related allosteric modulators of CXCR3. We have also identified residues Trp109(2.60) and Lys300(7.35) inside the transmembrane bundle of the receptor as crucial for the regulation of the G protein activation. Furthermore, we report the boronic acid 14 as the first biased negative allosteric modulator of the receptor. Overall, our data demonstrate that boronic acid derivatives represent an outstanding tool for determination of key receptor-ligand interactions and induction of ligand-biased signaling.

  7. Boron nitride fibers from polymer precursors

    SciTech Connect

    Wade, B.E.

    1992-12-31

    Conversion of polymer precursors to high performance boron nitride fibers as explored through a fundamental study of the mutually dependent chemical, morphological, and processing requirements in precursor polymer synthesis, formation of continuous precursor fibers, and finally thermochemical conversion to oriented boron nitride fibers. Polyborate and polyborazylene precursors were investigated. method of incorporating polyborazine in polyborate were also explored in order to stabilize the shape of polyborate fibers and to help initiate an orientable boron nitride structure. Polyborazylene, a polyborazine of fused borazine polycyclic structures was chosen for study as a precursor for boron nitride fibers because of the closeness of its structure to that of the desired turbostratic boron nitride. Both poly(ethylene oxide) and poly(methyl methacrylate) were found to be compatible with the monomer, borazine, and polyborazylenesolutions with monoglyme. They could be used to build the viscosity of solutions. However, fibers that were hand-drawn from these solutions were very sticky and quickly hydrolyzed in room atmosphere. Conversion of polyborazylene to oriented boron nitride fibers was not realized. Processable polyborates were produced by polycondensation of trimethoxyboroxine and boric acid and also by disproportionation or trimethyoxyboraxine. It was shown that the rheological characteristics of the polyborate formed could be controlled by an appropriate combination of the conversion of the monomer to polymer and the addition of a linear organic polymer as a rheological aid. Poly(methyl methacrylate) was found to be a suitable rheological aid, with a decomposition temperature that is high enough to facilitate its incorporation in the polymerizing system and low energy to be fugitive during thermochemical conversion of the polyborate to boron nitride.

  8. Boron removal in radioactive liquid waste by forward osmosis membrane

    SciTech Connect

    Doo Seong Hwang; Hei Min Choi; Kune Woo Lee; Jei Kwon Moon

    2013-07-01

    This study investigated the treatment of boric acid contained in liquid radioactive waste using a forward osmosis membrane. The boron permeation through the membrane depends on the type of membrane, membrane orientation, pH of the feed solution, salt and boron concentration in the feed solution, and osmotic pressure of the draw solution. The boron flux begins to decline from pH 7 and increases with an increase of the osmotic driving force. The boron flux decreases slightly with the salt concentration, but is not heavily influenced by a low salt concentration. The boron flux increases linearly with the concentration of boron. No element except for boron was permeated through the FO membrane in the multi-component system. The maximum boron flux is obtained in an active layer facing a draw solution orientation of the CTA-ES membrane under conditions of less than pH 7 and high osmotic pressure. (authors)

  9. Method of manufacture of atomically thin boron nitride

    DOEpatents

    Zettl, Alexander K

    2013-08-06

    The present invention provides a method of fabricating at least one single layer hexagonal boron nitride (h-BN). In an exemplary embodiment, the method includes (1) suspending at least one multilayer boron nitride across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure. The present invention also provides a method of fabricating single layer hexagonal boron nitride. In an exemplary embodiment, the method includes (1) providing multilayer boron nitride suspended across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure.

  10. [Minimally invasive cytoselective radiation therapy using boron neutron capture reaction].

    PubMed

    Nakamura, Hiroyuki

    2010-12-01

    The cell-killing effect of boron neutron capture therapy (BNCT) is due to the nuclear reaction of two essentially nontoxic species, boron-10 ((10)B) and thermal neutrons, whose destructive effect is well observed in boron-loaded tissues. High accumulation and selective delivery of boron into tumor tissue are the most important requirements to achieve efficient neutron capture therapy of cancers. This review focuses on liposomal boron delivery system (BDS) as a recent promising approach that meet these requirements for BNCT. BDS involves two strategies: (1) encapsulation of boron in the aqueous core of liposomes and (2) accumulation of boron in the liposomal bilayer. In this review, recent development of liposomal boron delivery system is summarized.

  11. Epoxy resin composition containing metal tetrafluoroborate and boron ester

    SciTech Connect

    Morehead, G.T.

    1990-06-12

    This patent describes a curable composition. It comprises: a polyepoxide; a metal tetrafluoroborate; and at least one boron ester selected from the group consisting of triesters of boric acid and diesters of boronic acid.

  12. Fatigue of boron-aluminum composites bonds and joints

    NASA Technical Reports Server (NTRS)

    Hersh, M. S.

    1973-01-01

    Study examines effects of boron filament diameter on bonds and joints in boron-aluminum composite. Data include static strength, fatigue, and dynamic moduli of elasticity. Manson-Coffin analyses and metallurgical and fracture surface evaluation were also performed.

  13. Boron toxicity in the rare serpentine plant, Streptanthus morrisonii.

    PubMed

    Sage, R F; Ustin, S L; Manning, S J

    1989-01-01

    The release of boron-laden mist from the cooling towers of some geothermal power stations in northern California potentially threatens nearby populations of the rare serpentine plant, Streptanthus morrisonii F. W. Hoffm. To assess the tolerance of S. morrisonii to high levels of boron, the effect of boron on leaf condition, life history, germination rate, growth rate, allocation and photosynthesis was measured on plants grown in a greenhouse. Relative to other species, S. morrisonii was tolerant of excess boron. On serpentine soil, mild to moderate toxicity symptoms (older leaves exhibiting chlorosis and necrosis, but few leaves killed) were apparent when the boron concentration in applied nutrient solutions was 240-650 microm. Severe toxicity symptoms (significant leaf loss, young leaves with toxicity symptoms) were apparent when the applied solution was over 1000 microm boron. Above 1000 microm boron, S. morrisonii appeared unable to complete its life cycle. On a tissue basis, boron toxicity was first observed when leaf boron content was 40-90 micromol g(-1) dry weight. In leaves with severe boron toxicity (> 35% injury), the boron content was generally above 130 micromol g(-1) dry weight. These levels were an order of magnitude above the tissue boron content of plants in the field. Prior to the onset of pronounced boron toxicity symptoms, growth rate, allocation patterns, and photosynthesis were unaffected by high boron. These results indicate that inhibition of growth and photosynthesis occurred because of a loss of viable tissue due to boron injury, rather than a progressive decline as leaf boron levels increased.

  14. Polyethylene/Boron Composites for Radiation Shielding Applications

    SciTech Connect

    Harrison, Courtney; Grulke, Eric; Burgett, Eric; Hertel, Nolan

    2008-01-21

    Multifunctional composites made with boron are absorbers of low energy nuetrons, and could be used for structural shielding materials. Polyethylene/boron carbide composites were fabricated using conventional polymer processing techniques, and were evaluated for mechanical and radiation shielding properties. Addition of neat boron carbide (powder and nanoparticles) to an injection molding grade HPDE showed superior mechanical properties compared to neat HDPE. Radiation shielding measurements of a 2 wt% boron carbide composite were improved over those of the neat polyethylene.

  15. Update on human health effects of boron.

    PubMed

    Nielsen, Forrest H

    2014-10-01

    In vitro, animal, and human experiments have shown that boron is a bioactive element in nutritional amounts that beneficially affects bone growth and central nervous system function, alleviates arthritic symptoms, facilitates hormone action and is associated with a reduced risk for some types of cancer. The diverse effects of boron suggest that it influences the formation and/or activity of substances that are involved in numerous biochemical processes. Several findings suggest that this influence is through the formation of boroesters in biomolecules containing cis-hydroxyl groups. These biomolecules include those that contain ribose (e.g., S-adenosylmethionine, diadenosine phosphates, and nicotinamide adenine dinucleotide). In addition, boron may form boroester complexes with phosphoinositides, glycoproteins, and glycolipids that affect cell membrane integrity and function. Both animal and human data indicate that an intake of less than 1.0mg/day inhibits the health benefits of boron. Dietary surveys indicate such an intake is not rare. Thus, increasing boron intake by consuming a diet rich in fruits, vegetables, nuts and pulses should be recognized as a reasonable dietary recommendation to enhance health and well-being. Published by Elsevier GmbH.

  16. Unilamellar liposomes with enhanced boron content.

    PubMed

    Li, Tiejun; Hamdi, Julie; Hawthorne, M Frederick

    2006-01-01

    A new type of boron-rich, DSPC-free, unilamellar liposomes was formed using the novel dual-chain, ionic, nido-carborane lipid, K[nido-7-(C16H33OCH2)2CHOCH2-7,8-C2B9H11] (DAC-16), and cholesterol for encapsulation of an aqueous buffer core. Since DSPC was not necessary for the formation of stable DAC-16 liposomes, the boron concentration of these vesicles was increased dramatically to approximately 8.8 wt % in the dry lipid; these liposomes had a high bilayer boron incorporation efficiency of 98%. DSPC-free liposomes exhibited a size distribution pattern of 40-60 nm, which was in the range normally associated with selective tumor uptake. This size distribution was maintained throughout storage at room temperature for several months. Additionally, optimized liposome formulations incorporating DAC-16, DSPC, and cholesterol were identified having stable size distribution patterns after storage for more than two months at a variety of temperatures. Although animal studies indicate that DAC-16 liposomes are toxic, this new ionic nido-carborane lipid allows the formation of liposomes of high boron content for in vitro applications that require the delivery of large amounts of boron.

  17. Boron nitride nanotubes and nanosheets.

    PubMed

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

    2010-06-22

    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.

  18. Screening of Wheat Genotypes for Boron Efficiency in Bangladesh

    USDA-ARS?s Scientific Manuscript database

    A number of Bangladeshi wheat genotypes (varieties and advanced lines) have been tested for boron efficiency through sand culture experiments over two years (2007-08 & 2008-09) against two Thai check varieties ‘Fang 60’ (boron efficient) and ‘SW41’ (boron inefficient). Performances of the genotypes ...

  19. Dietary boron: possible roles in human and animal physiology

    USDA-ARS?s Scientific Manuscript database

    Boron is a bioactive element of low molecular weight. Since discovery of the first boron biomolecule, boromycin, in 1967, several other similar biomolecules are now well-characterized. Most recently described was a bacterial cell-to-cell communication signal that requires boron, autoinducer-II. Boro...

  20. Colorimetric Sugar Sensing Using Boronic Acid-Substituted Azobenzenes.

    PubMed

    Egawa, Yuya; Miki, Ryotaro; Seki, Toshinobu

    2014-02-14

    In association with increasing diabetes prevalence, it is desirable to develop new glucose sensing systems with low cost, ease of use, high stability and good portability. Boronic acid is one of the potential candidates for a future alternative to enzyme-based glucose sensors. Boronic acid derivatives have been widely used for the sugar recognition motif, because boronic acids bind adjacent diols to form cyclic boronate esters. In order to develop colorimetric sugar sensors, boronic acid-conjugated azobenzenes have been synthesized. There are several types of boronic acid azobenzenes, and their characteristics tend to rely on the substitute position of the boronic acid moiety. For example, o-substitution of boronic acid to the azo group gives the advantage of a significant color change upon sugar addition. Nitrogen-15 Nuclear Magnetic Resonance (NMR) studies clearly show a signaling mechanism based on the formation and cleavage of the B-N dative bond between boronic acid and azo moieties in the dye. Some boronic acid-substituted azobenzenes were attached to a polymer or utilized for supramolecular chemistry to produce glucose-selective binding, in which two boronic acid moieties cooperatively bind one glucose molecule. In addition, boronic acid-substituted azobenzenes have been applied not only for glucose monitoring, but also for the sensing of glycated hemoglobin and dopamine.

  1. Boron-containing amino carboxylic acid compounds and uses thereof

    DOEpatents

    Kabalka, George W.; Srivastava, Rajiv R.

    2000-03-14

    Novel compounds which are useful for boron neutron capture therapy (BNCT) are disclosed. The compounds comprise a stable boron-containing group and an aminocycloalkane carboxylic acid group or a boronated acyclic hydrocarbon-linked amino carboxylic acid. Methods for synthesis of the compounds and for use of the compounds in BNCT are disclosed.

  2. Mechanical and physical properties of modern boron fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1978-01-01

    Measurements of the Young's modulus, flexural modulus, shear modulus and Poisson's ratio for boron fibers prepared by modern deposition techniques are reported. Physical properties of the boron fibers, including density, thermal expansion and resistance, are also surveyed. In addition, prediction of the total deformation strain in an anelastic boron fiber subjected to tensile or flexural stress is discussed.

  3. X-ray diffraction investigation of ultrafine boron nitride powders

    SciTech Connect

    Gurov, S.V.; Chukalin, V.I.; Rezchikova, T.V.; Torbov, V.J.; Troitskii, V.N.

    1986-01-01

    This paper presents an x-ray diffraction analysis of ultrafine boron nitride powders of different mean particle sizes. Diffraction spectra of the ultrafine boron nitride powders were obtained using a DRON-1 apparatus. The experimental facts are indicative of a turbostratic character of deformation of the hexagonal lattice of ultrafinely divided boron nitride.

  4. Reverse annealing and low-temperature diffusion of boron in boron-implanted silicon

    SciTech Connect

    Huang, J.; Fan, D.; Jaccodine, R.J.

    1988-06-01

    Low-temperature annealing (525 /sup 0/C--800 /sup 0/C) of 50-keV, 1 x 10/sup 15/-cm/sup -2/, boron-implanted silicon was studied with the emphasis on the mechanisms responsible for the reverse annealing as well as the enhanced diffusion of the implanted boron. The electrical properties of boron-implanted silicon were analyzed with Hall measurement. Boron depth profiles were also measured using secondary-ion mass spectrometry. These results were then correlated with cross-section transmission electron microscopy studies and deep-level transient spectroscopy studies. It is shown that reverse annealing is possibly due to boron-silicon interstitial complexes, rather than the formation of the commonly observed rodlike defects or precipitates. On the other hand, the enhanced tail diffusion of boron is found to be most likely associated with self-interstitials. Consequently, vacancy trapping of the silicon interstitial component may account for both the charge carrier recovery and the ending of the enhanced tail diffusion of implanted boron.

  5. Distinct surface hydration behaviors of boron-rich boride thin film coatings

    NASA Astrophysics Data System (ADS)

    Lu, Xinhong; Liu, Wei; Ouyang, Jun; Tian, Yun

    2014-08-01

    In this work, the surface boron chemical states and surface hydration behaviors of the as-deposited and annealed boron-rich boride thin film coatings, including AlMgB14, TiB2 and AlMgB14-TiB2, were systematically studied by use of X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The XPS results indicate that boron at annealed AlMgB14 film surface can be oxidized; surprisingly, such oxidation does not lead to the formation of boric acid in ambient air. Instead, boric acid can be produced at the surface of annealed TiB2 film and AlMgB14-TiB2 film. It is shown, via the water contact angle measurements, that these boride films exhibit distinct surface wettability characteristics, which are believed to result in the observed surface hydration processes. Furthermore, we found anatase TiO2 formation plays a major role in the surface wetting behaviors for these boride films.

  6. Electron spin relaxation of a boron-containing heterocyclic radical

    NASA Astrophysics Data System (ADS)

    Eaton, Sandra S.; Huber, Kirby; Elajaili, Hanan; McPeak, Joseph; Eaton, Gareth R.; Longobardi, Lauren E.; Stephan, Douglas W.

    2017-03-01

    Preparation of the stable boron-containing heterocyclic phenanthrenedione radical, (C6F5)2B(O2C14H8), by frustrated Lewis pair chemistry has been reported recently. Electron paramagnetic resonance measurements of this radical were made at X-band in toluene:dichloromethane (9:1) from 10 to 293 K, in toluene from 180 to 293 K and at Q-band at 80 K. In well-deoxygenated 0.1 mM toluene solution at room temperature hyperfine splittings from 11B, four pairs of 1H, and 5 pairs of 19F contribute to an EPR spectrum with many resolved lines. Observed hyperfine couplings were assigned based on DFT calculations and account for all of the fluorines and protons in the molecule. Rigid lattice g values are gx = 2.0053, gy = 2.0044, and gz = 2.0028. Near the melting point of the solvent 1/Tm is enhanced due to motional averaging of g and A anisotropy. Increasing motion above the melting point enhances 1/T1 due to contributions from tumbling-dependent processes. The overall temperature dependence of 1/T1 from 10 to 293 K was modeled with the sum of contributions of a process that is linear in T, a Raman process, spin rotation, and modulation of g anisotropy by molecular tumbling. The EPR measurements are consistent with the description of this compound as a substituted aromatic radical, with relatively small spin density on the boron.

  7. Effect of boron particle size on microstructure and superconducting properties of in-situ Cu addition MgB2 multifilamentary wire

    NASA Astrophysics Data System (ADS)

    Hishinuma, Y.; Kikuchi, A.; Shimada, Y.; Hata, S.; Takeuchi, T.; Yamada, S.; Sagara, A.

    2014-05-01

    In previous studies, the secondary (impurity and non-reactive) phase and voids were observed in MgB2 matrix after the heat treatment, and then these are the lowering factors of critical current density (Jc) property. In order to improve Jc property by microstructure control of MgB2 matrix, the fine elemental boron powder as the raw material was carried out using the high-speed vibrated milling with tungsten carbide (WC) jar. The average particle size of metal boron powder was decreased from 1.14 μm to 0.20 μm by the high-speed vibrated milling. The various fine particle boron powders as the function of milling time were also prepared, and in-situ Cu addition MgB2 multifilamentary wires using these fine boron powders were fabricated. Critical transition temperature (Tc) value of Cu addition MgB2 wire using fine boron powder obtained to about 37 K. No change of the Tc property by the different particle sized boron powders was confirmed. In this paper, the comparisons of microstructure and superconducting properties between the different boron particle sizes were investigated.

  8. Cubic boron nitride thin film growth by boron and nitrogen ion implantation

    SciTech Connect

    Eyhusen, S.; Ronning, C.; Hofsaess, H.

    2005-08-01

    Cubic boron nitride (c-BN) thin films were deposited on silicon substrates using mass separated ion beam deposition (MSIBD). In order to investigate the influence of the ion energy on the growth of c-BN films, {sup 11}B{sup +} and {sup 14}N{sup +} ions were implanted into c-BN with ion energies ranging from 5 keV to 43 keV and substrate temperatures (T{sub S}) from room temperature (RT) to 250 deg. C. A systematic study on the interplay of E{sub ion} and T{sub S} has revealed a characteristic energy-dependent temperature threshold for c-BN growth. This behavior is explained by dynamic annealing of defects caused by a penetrating ion in a collision cascade. In this picture, the suppression of defect accumulation that is crucial for maintaining cubic phase formation is attributed to temperature-driven back diffusion and subsequent annihilation of B and N interstitial recoils. The model is confirmed by analyzing the depth profile of implanted, isotopically pure {sup 10}B, and its application for both c-BN nucleation and growth is discussed.

  9. Longitudinal splitting of boron nitride nanotubes for the facile synthesis of high quality boron nitride nanoribbons.

    PubMed

    Erickson, Kris J; Gibb, Ashley L; Sinitskii, Alexander; Rousseas, Michael; Alem, Nasim; Tour, James M; Zettl, Alex K

    2011-08-10

    Boron nitride nanoribbons (BNNRs), the boron nitride structural equivalent of graphene nanoribbons (GNRs), are predicted to possess unique electronic and magnetic properties. We report the synthesis of BNNRs through the potassium-intercalation-induced longitudinal splitting of boron nitride nanotubes (BNNTs). This facile, scalable synthesis results in narrow (down to 20 nm), few sheet (typically 2-10), high crystallinity BNNRs with very uniform widths. The BNNRs are at least 1 μm in length with minimal defects within the ribbon plane and along the ribbon edges.

  10. Biological Evaluation of Boronated Unnatural Amino Acids as New Boron Carriers

    PubMed Central

    Kabalka, G.W.; Yao, M.-L.; Marepally, S.R.; Chandra, S.

    2010-01-01

    There is a pressing need for new and more efficient boron delivery agents to tumor cells for use in boron neutron capture therapy (BNCT). A class of boronated unnatural cyclic amino acids has demonstrated a remarkable selectivity toward tumors in animal and cell culture models, far superior to currently used agents in clinical BNCT. One of these amino acids, 1-amino-3-boronocyclopentanecarboxylic acid (ABCPC), has shown a tumor to blood ratio of 8 and a tumor to normal brain ratio of nearly 21 in a melanoma bearing mouse model. This work represents further biological characterization of this compound for tumor targeting in an EMT6 murine mammary carcinoma mouse model and a T98G human glioblastoma cell line. Female BALB/c mice bearing EMT6 tumors were injected with the fructose complex form of racemic mixtures of cis- and trans isomers of ABCPC in identical concentrations. Boron concentrations were measured in the tumor, blood, brain, skin, and liver tissues at 1, 3, and 5 hr post injection. These observations revealed a remarkable difference in racemic mixtures of cis and trans isomers in tumor targeting by boron. This implies that further separation of the L and D forms of this compound may enhance tumor targeting to an even higher degree than that provided by the racemic mixtures. Since the uptake measurements were made in homogenized tumor and normal tissues, little is known about the subcellular location of the boron arising from the various isomeric forms of the amino acid. To study subcellular delivery of boron from ABCPC in T98G human glioblastoma cells, we employed secondary ion mass spectrometry (SIMS) based technique of ion microscopy, which is capable of quantitatively imaging isotopic (elemental) gradients in cells and tissues at 500 nm spatial resolution. The T98G cells were exposed to the nutrient medium containing 100 ppm boron equivalent of a mixture of both L and D isomers of ABCPC in the form of a fructose complex for 1 hr. Following this

  11. Conducting Boron Sheets Formed by the Reconstruction of the α-Boron (111) Surface

    NASA Astrophysics Data System (ADS)

    Amsler, Maximilian; Botti, Silvana; Marques, Miguel A. L.; Goedecker, Stefan

    2013-09-01

    Systematic ab initio structure prediction was applied for the first time to predict low energy surface reconstructions by employing the minima hopping method on the α-boron (111) surface. Novel reconstruction geometries were identified and carefully characterized in terms of structural and electronic properties. Our calculations predict the formation of a planar, monolayer sheet at the surface, which is responsible for conductive surface states. Furthermore, the isolated boron sheet is shown to be the ground state 2D structure in vacuum at a hole density of η=1/5 and is therefore a potential candidate as a precursor for boron nanostructures.

  12. Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Singh, Bikramjeet; Singh, Paviter; Kumar, Manjeet; Thakur, Anup; Kumar, Akshay

    2015-05-01

    Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H3BO3). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT).

  13. Infiltration processing of boron carbide-, boron-, and boride-reactive metal cermets

    DOEpatents

    Halverson, Danny C.; Landingham, Richard L.

    1988-01-01

    A chemical pretreatment method is used to produce boron carbide-, boron-, and boride-reactive metal composites by an infiltration process. The boron carbide or other starting constituents, in powder form, are immersed in various alcohols, or other chemical agents, to change the surface chemistry of the starting constituents. The chemically treated starting constituents are consolidated into a porous ceramic precursor which is then infiltrated by molten aluminum or other metal by heating to wetting conditions. Chemical treatment of the starting constituents allows infiltration to full density. The infiltrated precursor is further heat treated to produce a tailorable microstructure. The process at low cost produces composites with improved characteristics, including increased toughness, strength.

  14. A system to deposit boron films (boronization) in the DIII-D tokamak

    SciTech Connect

    Hodapp, T.R.; Jackson, G.L.; Phillips, J.; Holtrop, K.L.; Petersen, P.I. ); Winter, J. . Inst. fuer Plasmaphysik)

    1991-09-01

    A system has been added to the D3-D tokamak to coat its plasma facing surfaces with a film of boron using diborane gas. The system includes special health and safety equipment for handling the diborane gas which is toxic and inflammable. The purpose of the boron film is to reduce the levels of impurity atoms in the D3-D plasmas. Experiments following the application of the boron film in D3-D have led to significant reductions in plasma impurity levels and the observation of a new, very high confinement regime. 9 refs., 1 fig.

  15. Formation of cubic boron-nitride by the reactive sputter deposition of boron

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; Makowiecki, D.W.; McKeman, M.A.

    1997-03-01

    Boron-nitride films are synthesized by RF magnetron sputtering boron targets where the deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are analyzed using Auger electron spectroscopy, transmission electron microscopy, nanoindentation, Raman spectroscopy and x-ray absorption spectroscopy. These techniques provide characterization of film composition, crystalline structure, hardness and chemical bonding, respectively. Reactive, rf-sputtering process parameters are established which lead to the growth of crystalline BN phases. The deposition of stable and adherent boron nitride coatings consisting of the cubic phase requires 400 `C substrate heating and the application of a 300 V negative bias.

  16. Enhancement and retardation of thermal boron diffusion in silicon from atmospheric pressure chemical vapor deposited boron silicate glass film

    NASA Astrophysics Data System (ADS)

    Kurachi, Ikuo; Yoshioka, Kentaro

    2014-03-01

    Thermal boron diffusion into silicon from boron silicate glass (BSG) prepared by atmospheric pressure CVD (AP-CVD) has been investigated in terms of the BSG boron concentration dependence on diffusion mechanism for N-type solar cell applications. With thermal diffusion at 950 °C in N2 for 20 min, the sheet resistance of the boron-diffused layer decreases with BSG boron concentration up to approximately 4 × 1021 cm-3 at which a boron-rich layer (BRL) is formed at the surface. However, the resistance increases with BSG boron concentration when the BSG boron concentration is higher than 4 × 1021 cm-3. It is also confirmed that the diffusion depth decreases with increasing BSG boron concentration within this BSG concentration region. To clarify this mechanism, the BSG boron concentration dependence on boron diffusivity has also been studied. From extracted diffusivities, the anomalous diffusion can be explained by silicon interstitials formed owing to kick-out by diffused boron atoms and by silicon interstitial generation-degradation due to BRL formation.

  17. Accelerator-driven boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Edgecock, Rob

    2014-05-01

    Boron Neutron Capture Therapy is a binary treatment for certain types of cancer. It works by loading the cancerous cells with a boron-10 carrying compound. This isotope has a large cross-section for thermal neutrons, the reaction producing a lithium nucleus and alpha particle that kill the cell in which they are produced. Recent studies of the boron carrier compound indicate that the uptake process works best in particularly aggressive cancers. Most studied is glioblastoma multiforme and a trial using a combination of BNCT and X-ray radiotherapy has shown an increase of nearly a factor of two in mean survival over the state of the art. However, the main technical problem with BNCT remains producing a sufficient flux of neutrons for a reasonable treatment duration in a hospital environment. This paper discusses this issue.

  18. Oxygen radical functionalization of boron nitride nanosheets.

    PubMed

    Sainsbury, Toby; Satti, Amro; May, Peter; Wang, Zhiming; McGovern, Ignatius; Gun'ko, Yurii K; Coleman, Jonathan

    2012-11-14

    The covalent chemical functionalization of exfoliated hexagonal boron-nitride nanosheets (BNNSs) is achieved by the solution-phase oxygen radical functionalization of boron atoms in the h-BN lattice. This involves a two-step procedure to initially covalently graft alkoxy groups to boron atoms and the subsequent hydrolytic defunctionalization of the groups to yield hydroxyl-functionalized BNNSs (OH-BNNSs). Characterization of the functionalized-BNNSs using HR-TEM, Raman, UV-vis, FTIR, NMR, and TGA was performed to investigate both the structure of the BNNSs and the covalent functionalization methodology. OH-BNNSs were used to prepare polymer nanocomposites and their mechanical properties analyzed. The influence of the functional groups grafted to the surface of the BNNSs is investigated by demonstrating the impact on mechanical properties of both noncovalent and covalent bonding at the interface between the nanofiller and polymer matrixes.

  19. On the Mechanism of Boron Ignition

    NASA Technical Reports Server (NTRS)

    Keil, D. G.; Dreizin, E. L.; Felder, W.; Vicenzi, E. P.

    1997-01-01

    Boron filaments were electrically heated in air and argon/oxygen mixtures while their resistance, temperature, and radiation at the wavelengths of BO and BO2 bands were monitored. The filaments 'burned' in two distinct stages. Samples of the filaments were quenched at different times before and during the burning and analyzed using electron microscopy. The beginning of the first stage combustion characterized by a local resistance minimum, a sharp spike in boron oxide radiation emission, and a rapid rise in temperature, occurred at 1500 +/- 70 deg. C, independent of pre-heating history and oxygen content (540%) in the gas environment. The data suggest that a phase transition occurs in the filaments at this temperature that triggers stage one combustion. Significant amounts of oxygen were found inside quenched filaments. Large spherical voids formed in the boron filaments during their second stage combustion which is interpreted to indicate a crucial role for the gas dissolution processes in the combustion scenario.

  20. A small, insertable oven for boronization

    SciTech Connect

    Brouchous, D.A.; Diebold, D.A.; Doczy, M.L.

    1996-04-01

    A small insertable oven for benchmarking the boronizing characteristics of solid compounds, such as decaborane and carborane, has been developed for the Phaedrus-T tokamak. Assembly and installation of the oven are relatively easy as the oven design utilizes a Langmuir probe drive assembly, which is standard equipment on most tokamaks and allows the oven to be inserted into the tokamak without requiring a vent. Films deposited by heating carborane into the vapor state with the oven are found to be spatially nonuniform in both thickness and in the ratio of boron to carbon as compared to films deposited with trimethylboron, a gaseous compound. Overall plasma performance is not found to be greatly affected by whether decaborane, carborane or trimethylboron is used for boronization in Phaedrus-T. {copyright} {ital 1996 American Institute of Physics.} {lt}ii;010512{gt}

  1. Metallicity of boron carbides at high pressure

    NASA Astrophysics Data System (ADS)

    Dekura, Haruhiko; Shirai, Koun; Yanase, Akira

    2010-03-01

    Electronic structure of semiconducting boron carbide at high pressure has been theoretically investigated, because of interests in the positive pressure dependence of resistivity, in the gap closure, and in the phase transition. The most simplest form B12(CCC) is assumed. Under assumptions of hydrostatic pressure and neglecting finite-temperature effects, boron carbide is quite stable at high pressure. The crystal of boron carbide is stable at least until a pressure higher than previous experiments showed. The gap closure occurs only after p=600 GPa on the assumption of the original crystal symmetry. In the low pressure regime, the pressure dependence of the energy gap almost diminishes, which is an exceptional case for semiconductors, which could be one of reasons for the positive pressure dependence of resistivity. A monotonous increase in the apex angle of rhombohedron suggests that the covalent bond continues to increase. The C chain inserted in the main diagonal of rhombohedral structure is the chief reason of this stability.

  2. On the Mechanism of Boron Ignition

    NASA Technical Reports Server (NTRS)

    Keil, D. G.; Dreizin, E. L.; Felder, W.; Vicenzi, E. P.

    1997-01-01

    Boron filaments were electrically heated in air and argon/oxygen mixtures while their resistance, temperature, and radiation at the wavelengths of BO and BO2 bands were monitored. The filaments 'burned' in two distinct stages. Samples of the filaments were quenched at different times before and during the burning and analyzed using electron microscopy. The beginning of the first stage combustion characterized by a local resistance minimum, a sharp spike in boron oxide radiation emission, and a rapid rise in temperature, occurred at 1500 +/- 70 deg. C, independent of pre-heating history and oxygen content (540%) in the gas environment. The data suggest that a phase transition occurs in the filaments at this temperature that triggers stage one combustion. Significant amounts of oxygen were found inside quenched filaments. Large spherical voids formed in the boron filaments during their second stage combustion which is interpreted to indicate a crucial role for the gas dissolution processes in the combustion scenario.

  3. Boron-10 Lined Proportional Counter Model Validation

    SciTech Connect

    Lintereur, Azaree T.; Siciliano, Edward R.; Kouzes, Richard T.

    2012-06-30

    The Department of Energy Office of Nuclear Safeguards (NA-241) is supporting the project “Coincidence Counting With Boron-Based Alternative Neutron Detection Technology” at Pacific Northwest National Laboratory (PNNL) for the development of an alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a boron-lined proportional tube-based alternative system in the configuration of a coincidence counter. This report discusses the validation studies performed to establish the degree of accuracy of the computer modeling methods current used to simulate the response of boron-lined tubes. This is the precursor to developing models for the uranium neutron coincidence collar under Task 2 of this project.

  4. Boron Nanotubes/Nanofibers in Propellant Material Formulations: Testing and Characterization for Gun Barrel Protection

    DTIC Science & Technology

    2011-01-13

    synthesis of boron nanostructures comprising of a mixture of boron nanotubes ( BNTs ) and nanofibers (BNFs) was developed under this contract. A method of...nitrogen doping the BNTs and BNFs was also demonstrated. A key feature of this work is the use of a solid instead of a gaseous boron precursor for the...synthesis of boron nanotubes and boron nanofibers. A solid boron precursor was chosen for BNT /BNF synthesis because typical gaseous boron precursors

  5. Chemical and mechanical analysis of boron-rich boron carbide processed via spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Munhollon, Tyler Lee

    Boron carbide is a material of choice for many industrial and specialty applications due to the exceptional properties it exhibits such as high hardness, chemical inertness, low specific gravity, high neutron cross section and more. The combination of high hardness and low specific gravity makes it especially attractive for high pressure/high strain rate applications. However, boron carbide exhibits anomalous behavior when high pressures are applied. Impact pressures over the Hugoniot elastic limit result in catastrophic failure of the material. This failure has been linked to amorphization in cleavage planes and loss of shear strength. Atomistic modeling has suggested boron-rich boron carbide (B13C2) may be a better performing material than the commonly used B4C due to the elimination of amorphization and an increase in shear strength. Therefore, a clear experimental understanding of the factors that lead to the degradation of mechanical properties as well as the effects of chemistry changes in boron carbide is needed. For this reason, the goal of this thesis was to produce high purity boron carbide with varying stoichiometries for chemical and mechanical property characterization. Utilizing rapid carbothermal reduction and pressure assisted sintering, dense boron carbides with varying stoichiometries were produced. Microstructural characteristics such as impurity inclusions, porosity and grain size were controlled. The chemistry and common static mechanical properties that are of importance to superhard materials including elastic moduli, hardness and fracture toughness of the resulting boron-rich boron carbides were characterized. A series of six boron carbide samples were processed with varying amounts of amorphous boron (up to 45 wt. % amorphous boron). Samples with greater than 40 wt.% boron additions were shown to exhibit abnormal sintering behavior, making it difficult to characterize these samples. Near theoretical densities were achieved in samples with

  6. Boron neutron capture therapy of intracerebral rat gliosarcomas.

    PubMed Central

    Joel, D D; Fairchild, R G; Laissue, J A; Saraf, S K; Kalef-Ezra, J A; Slatkin, D N

    1990-01-01

    The efficacy of boron neutron capture therapy (BNCT) for the treatment of intracerebrally implanted rat gliosarcomas was tested. Preferential accumulation of 10B in tumors was achieved by continuous infusion of the sulfhydryl borane dimer, Na4(10)B24H22S2, at a rate of 45-50 micrograms of 10B per g of body weight per day from day 11 to day 14 after tumor initiation (day 0). This infusion schedule resulted in average blood 10B concentrations of 35 micrograms/ml in a group of 12 gliosarcoma-bearing rats and 45 micrograms/ml in a group of 10 similar gliosarcoma-bearing rats treated by BNCT. Estimated tumor 10B levels in these two groups were 26 and 34 micrograms/g, respectively. On day 14, boron-treated and non-boron-treated rats were exposed to 5.0 or 7.5 MW.min of radiation from the Brookhaven Medical Research Reactor that yielded thermal neutron fluences of approximately 2.0 x 10(12) or approximately 3.0 x 10(12) n/cm2, respectively, in the tumors. Untreated rats had a median postinitiation survival time of 21 days. Reactor radiation alone increased median postinitiation survival time to 26 (5.0 MW.min) or 28 (7.5 MW.min) days. The 12 rats that received 5 MW.min of BNCT had a median postinitiation survival time of 60 days. Two of these animals survived greater than 15 months. In the 7.5 MW.min group, the median survival time is not calculable since 6 of the 10 animals remain alive greater than 10 months after BNCT. The estimated radiation doses to tumors in the two BNCT groups were 14.2 and 25.6 Gy equivalents, respectively. Similar gliosarcoma-bearing rats treated with 15.0 or 22.5 Gy of 250-kilovolt peak x-rays had median survival times of only 26 or 31 days, respectively, after tumor initiation. Images PMID:2263630

  7. Liposomal boron delivery for neutron capture therapy.

    PubMed

    Nakamura, Hiroyuki

    2009-01-01

    Tumor cell destruction in boron neutron capture therapy (BNCT) is due to the nuclear reaction between (10)B and thermal neutrons. The thermal neutrons have an energy of 0.025 eV, clearly below the threshold energy required to ionize tissue components. However, neutron capture by (10)B produces lithium ion and helium (alpha-particles), which are high linear energy transfer (LET) particles, and dissipate their kinetic energy before traveling one cell diameter (5-9 microm) in biological tissues, ensuring their potential for precise cell killing. BNCT has been applied clinically for the treatment of malignant brain tumors, malignant melanoma, head and neck cancer, and hepatoma using two boron compounds: sodium borocaptate (Na(2)(10)B(12)H(11)SH; Na(2)(10)BSH) and l-p-boronophenylalanine (l-(10)BPA). These low molecular weight compounds are cleared easily from the cancer cells and blood. Therefore, high accumulation and selective delivery of boron compounds into tumor tissues are most important to achieve effective BNCT and to avoid damage of adjacent healthy cells. Much attention has been focused on the liposomal drug delivery system (DDS) as an attractive, intelligent technology of targeting and controlled release of (10)B compounds. Two approaches have been investigated for incorporation of (10)B into liposomes: (1) encapsulation of (10)B compounds into liposomes and (2) incorporation of (10)B-conjugated lipids into the liposomal bilayer. Our laboratory has developed boron ion cluster lipids for application of the latter approach. In this chapter, our boron lipid liposome approaches as well as recent developments of the liposomal boron delivery system are summarized.

  8. Boron removal by electrocoagulation and recovery.

    PubMed

    Isa, Mohamed Hasnain; Ezechi, Ezerie Henry; Ahmed, Zubair; Magram, Saleh Faraj; Kutty, Shamsul Rahman Mohamed

    2014-03-15

    This work investigated the removal of boron from wastewater and its recovery by electrocoagulation and hydrothermal mineralization methods respectively. The experimental design was developed using Box-Behnken Model. An initial study was performed based on four preselected variables (pH, current density, concentration and time) using synthetic wastewater. Response surface methodology (RSM) was used to evaluate the effect of process variables and their interaction on boron removal. The optimum conditions were obtained as pH 6.3, current density 17.4 mA/cm(2), and time 89 min. At these applied optimum conditions, 99.7% boron removal from an initial concentration of 10.4 mg/L was achieved. The process was effectively optimized by RSM with a desirability value of 1.0. The results showed that boron removal efficiency enhanced with increase in current density and treatment time. Removal efficiency also increased when pH was increased from 4 to 7 and subsequently decreased at pH 10. Adsorption kinetics study revealed that the reaction followed pseudo second order kinetic model; evidenced by high correlation and goodness of fit. Thermodynamics study showed that mechanism of boron adsorption was chemisorption and the reaction was endothermic in nature. Furthermore, the adsorption process was spontaneous as indicated by negative values of the adsorption free energy. Treatment of real produced water using electrocoagulation resulted in 98% boron removal. The hydrothermal mineralization study showed that borate minerals (Inyoite, Takadaite and Nifontovite) can be recovered as recyclable precipitate from electrocoagulation flocs of produced water. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

    SciTech Connect

    Dang, Hongli; Liu, Yingdi; Xue, Wenhua; Anderson, Ryan S.; Sewell, Cody R.; Xue, Sha; Crunkleton, Daniel W.; Shen, Yaogen; Wang, Sanwu

    2014-03-03

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

  10. Thermal conductivity behavior of boron carbides

    NASA Technical Reports Server (NTRS)

    Wood, C.; Zoltan, A.; Emin, D.; Gray, P. E.

    1983-01-01

    Knowledge of the thermal conductivity of boron carbides is necessary to evaluate its potential for high temperature thermoelectric energy conversion applications. The thermal diffusivity of hot pressed boron carbide B/sub 1-x/C/sub x/ samples as a function of composition, temperature and temperature cycling was measured. These data in concert with density and specific heat data yield the thermal conductivities of these materials. The results in terms of a structural model to explain the electrical transport data and novel mechanisms for thermal conduction are discussed.

  11. Proton linacs for boron neutron capture therapy

    SciTech Connect

    Lennox, A.J. |

    1993-08-01

    Recent advances in the ability to deliver boron-containing drugs to brain tumors have generated interest in {approximately}4 MeV linacs as sources of epithermal neutrons for radiation therapy. In addition, fast neutron therapy facilities have been studying methods to moderate their beams to take advantage of the high cross section for epithermal neutrons on boron-10. This paper describes the technical issues involved in each approach and presents the motivation for undertaking such studies using the Fermilab linac. the problems which must be solved before therapy can begin are outlined. Status of preparatory work and results of preliminary measurements are presented.

  12. Boron Nitride Nanotubes-Reinforced Glass Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam; Hurst, Janet B.; Choi, Sung R.

    2005-01-01

    Boron nitride nanotubes of significant lengths were synthesized by reaction of boron with nitrogen. Barium calcium aluminosilicate glass composites reinforced with 4 weight percent of BN nanotubes were fabricated by hot pressing. Ambient-temperature flexure strength and fracture toughness of the glass-BN nanotube composites were determined. The strength and fracture toughness of the composite were higher by as much as 90 and 35 percent, respectively, than those of the unreinforced glass. Microscopic examination of the composite fracture surfaces showed pullout of the BN nanotubes. The preliminary results on the processing and improvement in mechanical properties of BN nanotube reinforced glass matrix composites are being reported here for the first time.

  13. Tight-Binding study of Boron structures

    NASA Astrophysics Data System (ADS)

    McGrady, Joseph W.; Papaconstantopoulos, Dimitrios A.; Mehl, Michael J.

    2014-10-01

    We have performed Linearized Augmented Plane Wave (LAPW) calculations for five crystal structures (alpha, dhcp, sc, fcc, bcc) of Boron which we then fitted to a non-orthogonal tight-binding model following the Naval Research Laboratory Tight-Binding (NRL-TB) method. The predictions of the NRL-TB approach for complicated Boron structures such as R105 (or β-rhombohedral) and T190 are in agreement with recent first-principles calculations. Fully utilizing the computational speed of the NRL-TB method we calculated the energy differences of various structures, including those containing vacancies using supercells with up to 5000 atoms.

  14. Phenylene bridged boron-nitrogen containing dendrimers.

    PubMed

    Proń, Agnieszka; Baumgarten, Martin; Müllen, Klaus

    2010-10-01

    The synthesis and characterization of novel phenylene bridged boron-nitrogen containing π-conjugated dendrimers N3B6 and N3B3, with peripheral boron atoms and 1,3,5-triaminobenzene moiety as a core, are presented. UV-vis absorption and emission measurements reveal that the optical properties of the resulting compounds can be controlled by changing the donor/acceptor ratio: a 1:1 ratio results in a more efficient charge transfer than the 1:2 ratio. This was proven by the red shift of the emission maxima and the stronger solvatochromic effect in N3B3 compared to N3B6.

  15. Reactive sputter deposition of boron nitride

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; McKernan, M.A.; Makowiecki, D.M.

    1995-10-01

    The preparation of fully dense, boron targets for use in planar magnetron sources has lead to the synthesis of Boron Nitride (BN) films by reactive rf sputtering. The deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are characterized for composition using Auger electron spectroscopy, for chemical bonding using Raman spectroscopy and for crystalline structure using transmission electron microscopy. The deposition conditions are established which lead to the growth of crystalline BN phases. In particular, the growth of an adherent cubic BN coating requires 400--500 C substrate heating and an applied {minus}300 V dc bias.

  16. Can Two-Dimensional Boron Superconduct?

    PubMed

    Penev, Evgeni S; Kutana, Alex; Yakobson, Boris I

    2016-04-13

    Two-dimensional boron is expected to exhibit various structural polymorphs, all being metallic. Additionally, its small atomic mass suggests strong electron-phonon coupling, which in turn can enable superconducting behavior. Here we perform first-principles analysis of electronic structure, phonon spectra, and electron-phonon coupling of selected 2D boron polymorphs and show that the most stable structures predicted to feasibly form on a metal substrate should also exhibit intrinsic phonon-mediated superconductivity, with estimated critical temperature in the range of Tc ≈ 10-20 K.

  17. Titanium reinforced boron-polyimide composite

    NASA Technical Reports Server (NTRS)

    Clark, G. A.; Clayton, K. I.

    1969-01-01

    Processing techniques for boron polyimide prepreg were developed whereby composites could be molded under vacuum bag pressure only. A post-cure cycle was developed which resulted in no loss in room temperature mechanical properties of the composite at any time during up to 16 hours at 650 F. A design utilizing laminated titanium foil was developed to achieve a smooth transition of load from the titanium attachment points into the boron-reinforced body of the structure. The box beam test article was subjected to combined bending and torsional loads while exposed to 650 F. Loads were applied incrementally until failure occurred at 83% design limit load.

  18. Low pressure growth of cubic boron nitride films

    NASA Technical Reports Server (NTRS)

    Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)

    1997-01-01

    A method for forming thin films of cubic boron nitride on substrates at low pressures and temperatures. A substrate is first coated with polycrystalline diamond to provide a uniform surface upon which cubic boron nitride can be deposited by chemical vapor deposition. The cubic boron nitride film is useful as a substitute for diamond coatings for a variety of applications in which diamond is not suitable. any tetragonal or hexagonal boron nitride. The cubic boron nitride produced in accordance with the preceding example is particularly well-suited for use as a coating for ultra hard tool bits and abrasives, especially those intended to use in cutting or otherwise fabricating iron.

  19. Magnetron sputtered boron films and TI/B multilayer structures

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1993-01-01

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

  20. Magnetron sputtered boron films and TI/B multilayer structures

    DOEpatents

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

    1993-04-20

    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 ultra-thin band pass filters as well as the low Z element in low Z/high Z mirrors which enhance reflectivity from grazing to normal incidence.

  1. Magnetron sputtered boron films and Ti/B multilayer structures

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1995-01-01

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

  2. Magnetron sputtered boron films and Ti/B multilayer structures

    DOEpatents

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

    1995-02-14

    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 ultra-thin band pass filters as well as the low Z element in low Z/high Z mirrors which enhance reflectivity from grazing to normal incidence. 6 figs.

  3. Dietary boron: progress in establishing essential roles in human physiology.

    PubMed

    Hunt, Curtiss D

    2012-06-01

    This review summarizes the progress made in establishing essential roles for boron in human physiology and assesses that progress in view of criteria for essentiality of elements. The evidence to date suggests that humans and at least some higher animals may use boron to support normal biological functions. These include roles in calcium metabolism, bone growth and maintenance, insulin metabolism, and completion of the life cycle. The biochemical mechanisms responsible for these effects are poorly understood but the nature of boron biochemistry suggests further characterization of the cell signaling molecules capable of complexing with boron. Such characterization may provide insights into the biochemical function(s) of boron in humans.

  4. Boron Nitride Nanotubes for Spintronics

    PubMed Central

    Dhungana, Kamal B.; Pati, Ranjit

    2014-01-01

    With the end of Moore's law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR) effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT), which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics. PMID:25248070

  5. Boron nitride nanotubes for spintronics.

    PubMed

    Dhungana, Kamal B; Pati, Ranjit

    2014-09-22

    With the end of Moore's law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR) effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT), which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics.

  6. Aerolization During Boron Nanoparticle Multi-Component Fuel Group Burning Studies

    DTIC Science & Technology

    2014-02-03

    fuel burner assembly system with a Phase-Doppler-Particle Analyzer ( PDPA ) to investigate the effect of specific nanoparticle addition (boron, CeO2...variable fuel and gas supply, and Aerometrics Phase-Doppler-Particle Analyzer ( PDPA ). …………………… 14 Figure 3. Schematic diagram of the group...gas supply showing optimal control flame rates, adjustable stage, and Aerometrics Phase-Doppler-Particle Analyzer ( PDPA ). Position 1, 2, 3, and 4

  7. Chemical Behaviors of Energetic Deuterium Implanted into Boron Coatings

    SciTech Connect

    Kodama, H.; Morimoto, Y.; Sasaki, M.; Oyaidu, M.; Oya, Y.; Sagara, A.; Noda, N.; Okuno, K.

    2003-09-15

    To study chemical behaviors of energetic deuterium implanted into boron coating deposited by boronization in fusion devices, two types of boron coating film deposited on silicon and IG-430U were prepared by Plasma Chemical Vapor Deposition (PCVD) technique. Boron polycrystal was used as the reference sample. The chemical behavior of deuterium was investigated by XPS (X-ray photoelectron spectroscopy) and TDS (Thermal adsorption spectroscopy).The 1.0 keV D{sub 2}{sup +} ions were implanted into the samples and the deuterium desorption behavior was studied by TDS. The TDS spectra showed that there were two deuterium release peaks at around 550 and 750 K, which were attributed to the release from deuterium trapped by boron and carbon, respectively. It was also found that most of implanted deuterium was trapped in carbon trapping site compared with boron one.In XPS measurements, the chemical shift of B-1s towards positive side was observed in the film on IG-430U after D{sub 2}{sup +} ion implantation. However, no chemical shifts were found in the film on silicon and boron polycrystal. In highly concentrated boron materials, even if deuterium was implanted into the boron materials, the amount of B-D bond was too low to be measured by XPS. This suggests that deuterium implanted into highly pure boron materials wasn't almost trapped, so that the retention of deuterium in the boron materials would be reduced, compared that in carbon materials.

  8. Cell cycle dependence of boron uptake from two boron compounds used for clinical neutron capture therapy.

    PubMed

    Yoshida, F; Matsumura, A; Shibata, Y; Yamamoto, T; Nakauchi, H; Okumura, M; Nose, T

    2002-12-10

    In neutron capture therapy, it is important that the boron is selectively uptaken by tumor cells. In the present study, we used flow cytometry to sort the cells in the G0/G1 phase and those in the G2/M phase, and the boron concentration in each fraction was measured with inductively coupled plasma atomic emission spectroscopy. The results revealed that sodium borocaptate and boronophenylalanine (BPA), were associated with higher rates of boron uptake in the G2/M than in the G0/G1 phase. However, the difference was more prominent in the case of BPA. The G2/M:G0/G1 ratio decreased as a function of exposure time in BPA containing culture medium, thereby indicating the cell cycle dependency of BPA uptake. Such heterogeneity of boron uptake by tumor cells should be considered for microdosimetry.

  9. Hollow boron nitride nanospheres as boron reservoir for prostate cancer treatment

    NASA Astrophysics Data System (ADS)

    Li, Xia; Wang, Xiupeng; Zhang, Jun; Hanagata, Nobutaka; Wang, Xuebin; Weng, Qunhong; Ito, Atsuo; Bando, Yoshio; Golberg, Dmitri

    2017-01-01

    High global incidence of prostate cancer has led to a focus on prevention and treatment strategies to reduce the impact of this disease in public health. Boron compounds are increasingly recognized as preventative and chemotherapeutic agents. However, systemic administration of soluble boron compounds is hampered by their short half-life and low effectiveness. Here we report on hollow boron nitride (BN) spheres with controlled crystallinity and boron release that decrease cell viability and increase prostate cancer cell apoptosis. In vivo experiments on subcutaneous tumour mouse models treated with BN spheres demonstrated significant suppression of tumour growth. An orthotopic tumour growth model was also utilized and further confirmed the in vivo anti-cancer efficacy of BN spheres. Moreover, the administration of hollow BN spheres with paclitaxel leads to synergetic effects in the suppression of tumour growth. The work demonstrates that hollow BN spheres may function as a new agent for prostate cancer treatment.

  10. Hollow boron nitride nanospheres as boron reservoir for prostate cancer treatment.

    PubMed

    Li, Xia; Wang, Xiupeng; Zhang, Jun; Hanagata, Nobutaka; Wang, Xuebin; Weng, Qunhong; Ito, Atsuo; Bando, Yoshio; Golberg, Dmitri

    2017-01-06

    High global incidence of prostate cancer has led to a focus on prevention and treatment strategies to reduce the impact of this disease in public health. Boron compounds are increasingly recognized as preventative and chemotherapeutic agents. However, systemic administration of soluble boron compounds is hampered by their short half-life and low effectiveness. Here we report on hollow boron nitride (BN) spheres with controlled crystallinity and boron release that decrease cell viability and increase prostate cancer cell apoptosis. In vivo experiments on subcutaneous tumour mouse models treated with BN spheres demonstrated significant suppression of tumour growth. An orthotopic tumour growth model was also utilized and further confirmed the in vivo anti-cancer efficacy of BN spheres. Moreover, the administration of hollow BN spheres with paclitaxel leads to synergetic effects in the suppression of tumour growth. The work demonstrates that hollow BN spheres may function as a new agent for prostate cancer treatment.

  11. Hollow boron nitride nanospheres as boron reservoir for prostate cancer treatment

    PubMed Central

    Li, Xia; Wang, Xiupeng; Zhang, Jun; Hanagata, Nobutaka; Wang, Xuebin; Weng, Qunhong; Ito, Atsuo; Bando, Yoshio; Golberg, Dmitri

    2017-01-01

    High global incidence of prostate cancer has led to a focus on prevention and treatment strategies to reduce the impact of this disease in public health. Boron compounds are increasingly recognized as preventative and chemotherapeutic agents. However, systemic administration of soluble boron compounds is hampered by their short half-life and low effectiveness. Here we report on hollow boron nitride (BN) spheres with controlled crystallinity and boron release that decrease cell viability and increase prostate cancer cell apoptosis. In vivo experiments on subcutaneous tumour mouse models treated with BN spheres demonstrated significant suppression of tumour growth. An orthotopic tumour growth model was also utilized and further confirmed the in vivo anti-cancer efficacy of BN spheres. Moreover, the administration of hollow BN spheres with paclitaxel leads to synergetic effects in the suppression of tumour growth. The work demonstrates that hollow BN spheres may function as a new agent for prostate cancer treatment. PMID:28059072

  12. Mechanisms implicated in the effects of boron on wound healing.

    PubMed

    Nzietchueng, Rosine Mayap; Dousset, Brigitte; Franck, Patricia; Benderdour, Mohamed; Nabet, Pierre; Hess, Ketsia

    2002-01-01

    Recently, we demonstrated that boron modulates the turnover of the extracellular matrix and increases TNFalpha release. In the present study, we used an in vitro test to investigate the direct effect of boron on specific enzymes (elastase, trypsin-like enzymes, collagenase and alkaline phosphatase) implicated in extracellular matrix turnover. Boron decreased the elastase and alkaline phosphatase activity, but had no effect on trypsin and collagenase activities. The effect of boron on the enzyme activities was also tested in fibroblasts considered as an in vivo test. In contrast to the results obtained in vitro, boron enhanced the trypsin-like, collagenase, and cathepsin D activities in fibroblasts. Boron did not modify the generation of free radicals compared to the control and did not seem to act on the intracellular alkaline phosphatase activity, However, as it did enhance phosphorylation, it can be hypothesized that boron may affect living cells via a mediator, which could be TNFalpha whose transduction signal involves a cascade of phosphorylations.

  13. Annealing behaviour of boron atoms implanted into polyethyleneterephtalate

    NASA Astrophysics Data System (ADS)

    Vacík, J.; Hnatowicz, V.; Červená, J.; Peřina, V.; Popok, V.; Odzhaev, V.; Švorčík, V.; Rybka, V.; Arenholz, E.; Fink, D.

    2000-05-01

    Hundred keV B+ ions were implanted at high fluences into polyethyleneterephtalate (PET, Mylar) and the boron depth distributions were measured by the neutron depth profiling technique (NDP). Subsequently the implanted samples were annealed isochronally to determine the diffusional, trapping and detrapping behaviour of the boron atoms. The boron depth profiles of as-implanted samples differ significantly from those predicted by TRIM code. Pronounced inward and outward profile tails point at increased mobility and redistribution of boron atoms during the implantation. Thermal annealing to the temperatures below 100°C does not change the total boron content in the 1 μm thick surface layer and the boron depth profiles as well. For higher annealing temperatures a significant redistribution of boron atoms is observed.

  14. Process of Making Boron-Fiber Reinforced Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

    2002-01-01

    The invention is an apparatus and method for producing a hybrid boron reinforced polymer matrix composition from powder pre-impregnated fiber tow bundles and a linear array of boron fibers. The boron fibers are applied onto the powder pre-impregnated fiber tow bundles and then are processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the powder pre-impregnated fiber tow bundles with the boron fibers become a hybrid boron reinforced polymer matrix composite tape. A driving mechanism pulls the powder pre-impregnated fiber tow bundles with boron fibers through the processing line of the apparatus and a take-up spool collects the formed hybrid boron-fiber reinforced polymer matrix composite tape.

  15. The versatility of boron in biological target engagement

    NASA Astrophysics Data System (ADS)

    Diaz, Diego B.; Yudin, Andrei K.

    2017-08-01

    Boron-containing molecules have been extensively used for the purposes of chemical sensing, biological probe development and drug discovery. Due to boron's empty p orbital, it can coordinate to heteroatoms such as oxygen and nitrogen. This reversible covalent mode of interaction has led to the use of boron as bait for nucleophilic residues in disease-associated proteins, culminating in the approval of new therapeutics that work by covalent mechanisms. Our analysis of a wide range of covalent inhibitors with electrophilic groups suggests that boron is a unique electrophile in its chameleonic ability to engage protein targets. Here we review boron's interactions with a range of protein side-chain residues and reveal that boron's properties are nuanced and arise from its uncommon coordination preferences. These mechanistic and structural insights should serve as a guide for the development of selective boron-based bioactive molecules.

  16. Process of Making Boron-Fiber Reinforced Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

    2002-01-01

    The invention is an apparatus and method for producing a hybrid boron reinforced polymer matrix composition from powder pre-impregnated fiber tow bundles and a linear array of boron fibers. The boron fibers are applied onto the powder pre-impregnated fiber tow bundles and then are processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the powder pre-impregnated fiber tow bundles with the boron fibers become a hybrid boron reinforced polymer matrix composite tape. A driving mechanism pulls the powder pre-impregnated fiber tow bundles with boron fibers through the processing line of the apparatus and a take-up spool collects the formed hybrid boron-fiber reinforced polymer matrix composite tape.

  17. Boron gettering on cavities induced by helium implantation in Si

    NASA Astrophysics Data System (ADS)

    Roqueta, F.; Alquier, D.; Ventura, L.; Dubois, Ch.; Jérisian, R.

    2001-10-01

    In this paper, we shed light on the strong interaction between the cavity layer induced by helium implantation and boron. First of all, we evidence the impact of He gettering step on a boron-diffused profile. In order to study the boron-cavity interaction, we had used uniformly boron-doped wafers implanted with helium at high dose and anneal using usual furnace annealing (FA) as well as rapid thermal annealing. Then, to avoid any precipitation phenomena, conditions were chosen to not exceed the boron solid solubility value. Our experimental results exhibit a large trapping of boron within the cavity layer. This trapping occurs since the early stage of the annealing. These results enable us to have better understanding of this He gettering step as well as its interaction with boron atoms, which are of great interest for device.

  18. Reproductive toxicity parameters and biological monitoring in occupationally and environmentally boron-exposed persons in Bandirma, Turkey.

    PubMed

    Duydu, Yalçın; Başaran, Nurşen; Üstündağ, Aylin; Aydin, Sevtap; Ündeğer, Ülkü; Ataman, Osman Yavuz; Aydos, Kaan; Düker, Yalçın; Ickstadt, Katja; Waltrup, Britta Schulze; Golka, Klaus; Bolt, Hermann M

    2011-06-01

    Boric acid and sodium borates have been considered as being "toxic to reproduction and development", following results of animal studies with high doses. Experimentally, a NOAEL (no observed adverse effect level) of 17.5 mg B/kg-bw/day has been identified for the (male) reproductive effects of boron in a multigeneration study of rats, and a NOAEL for the developmental effects in rats was identified at 9.6 mg B/kg-bw/day. These values are being taken as the basis of current EU safety assessments. The present study was conducted to investigate the reproductive effects of boron exposure in workers employed in boric acid production plant in Bandirma, Turkey. In order to characterize the external and internal boron exposures, boron was determined in biological samples (blood, urine, semen), in workplace air, in food, and in water sources. Unfavorable effects of boron exposure on the reproductive toxicity indicators (concentration, motility, morphology of the sperm cells and blood levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and total testosterone) were not observed. The mean calculated daily boron exposure (DBE) of the highly exposed group was 14.45 ± 6.57 (3.32-35.62) mg/day. These human exposures represent worst-case exposure conditions to boric acid/borates in Turkey. These exposure levels are considerably lower than exposures, which have previously led to reproductive effects in experimental animals. In conclusion, this means that dose levels of boron associated with developmental and reproductive toxic effects in animals are by far not reachable for humans under conditions of normal handling and use.

  19. A DLTS study of 4H-SiC-based p-n junctions fabricated by boron implantation

    SciTech Connect

    Ivanov, P. A. Potapov, A. S.; Samsonova, T. P.; Korol'kov, O.; Sleptsuk, N.

    2011-10-15

    Deep-level transient spectroscopy (DLTS) has been used to study p-n junctions fabricated by implantation of boron into epitaxial 4H-SiC films with n-type conductivity and the donor concentration (8-9) Multiplication-Sign 10{sup 14} cm{sup -3}. A DLTS signal anomalous in sign is observed; this signal is related to recharging of deep compensating boron-involved centers in the n-type region near the metallurgical boundary of the p-n junction.

  20. Effect of low temperature oxidation (LTO) in reducing boron skin in boron spin on dopant diffused emitter

    SciTech Connect

    Singha, Bandana; Solanki, Chetan Singh

    2016-05-06

    Formation of boron skin is an unavoidable phenomenon in p-type emitter formation with boron dopant source. The boron skin thickness is generally less than 100 nm and difficult to remove by chemical and physical means. Low temperature oxidation (LTO) used in this work is useful in removing boron skin thickness up to 30 nm and improves the emitter performance. The effective minority carrier lifetime gets improved by more than 30% after using LTO and leakage current of the emitter gets lowered by 100 times thereby showing the importance of low temperature oxidation in boron spin on dopant diffused emitters.

  1. The geochemical cycle of boron: Constraints from boron isotope partitioning experiments between mica and fluid

    NASA Astrophysics Data System (ADS)

    Wunder, Bernd; Meixner, Anette; Romer, Rolf L.; Wirth, Richard; Heinrich, Wilhelm

    2005-10-01

    The fractionation of boron isotopes between synthetic boromuscovite and fluid was experimentally determined at 3.0 GPa/500 °C and 3.0 GPa/700 °C. For near-neutral fluids Δ 11B (mica-fluid) = δ 11B (mica) - δ 11B (fluid) is - 10.9 ± 1.3‰ at 500 °C, and - 6.5 ± 0.4‰ at 700 °C. This supports earlier assumptions that the main fractionation effect is due to the change from trigonal coordination of boron in neutral fluids to tetrahedrally coordinated boron in micas, clays and melts. The T-dependence of this effect is approximated by the equation Δ 11B (mica,clay,melt-neutral fluid) = - 10.69 · (1000/ T [K]) + 3.88; R2 = 0.992, valid from 25 °C for fluid-clay up to about 1000 °C for fluid-silicate melt. Experiments at 0.4 GPa that used strongly basic fluids produced significantly lower fractionations with Δ 11B (mica-fluid) of - 7.4 ± 1.0‰ at 400 °C, and - 4.8 ± 1.0‰ at 500 °C, showing the reduced fractionation effect when large amounts of boron in basic fluids are tetrahedrally coordinated. Field studies have shown that boron concentrations and 11B/ 10B-ratios in volcanic arcs systematically decrease across the arc with increasing distance from the trench, thus reflecting the thermal structure of the subducting slab. Our experiments show that the boron isotopic signature in volcanic arcs probably results from continuous dehydration of micas along a distinct P- T range. Continuous slab dehydration and boron transport via fluid into the mantle wedge is responsible for the boron isotopic signature in volcanic arcs.

  2. Boron uptake measurements in a rat model for Boron Neutron Capture Therapy of lung tumours.

    PubMed

    Bortolussi, S; Bakeine, J G; Ballarini, F; Bruschi, P; Gadan, M A; Protti, N; Stella, S; Clerici, A; Ferrari, C; Cansolino, L; Zonta, C; Zonta, A; Nano, R; Altieri, S

    2011-02-01

    Lung carcinoma is the leading cause of cancer mortality in the Western countries. Despite the introduction over the last few years of new therapeutic agents, survival from lung cancer has shown no discernible improvement in the last 20 years. For these reasons any efforts to find and validate new effective therapeutic procedures for lung cancer are very timely. The selective boron uptake in the tumour with respect to healthy tissues makes Boron Neutron Capture Therapy a potentially advantageous option in the treatment of tumours that affect whole vital organs, and that are surgically inoperable. To study the possibility of applying BNCT to the treatment of diffuse pulmonary tumours, an animal model for boron uptake measurements in lung metastases was developed. Both healthy and tumour-bearing rats were infused with Boronophenylalanine (BPA) and sacrificed at different time intervals after drug administration. The lungs were extracted, and prepared for boron analysis by neutron autoradiography and α-spectroscopy. The boron concentrations in tumour and normal lung were plotted as a function of the time elapsed after BPA administration. The concentration in tumour is almost constant within the error bars for all the time intervals of the experiment (1-8 h), while the curve in normal lung decreases after 4 h from BPA infusion. At 4 h, the ratio of boron concentration in tumour to boron concentration in healthy lung is higher than 3, and it stays above this level up to 8 h. Also the images of boron distribution in the samples, obtained by neutron autoradiography, show a selective absorption in the metastases. Copyright © 2010 Elsevier Ltd. All rights reserved.

  3. In vitro and in vivo studies of boron neutron capture therapy: boron uptake/washout and cell death.

    PubMed

    Ferrari, C; Bakeine, J; Ballarini, F; Boninella, A; Bortolussi, S; Bruschi, P; Cansolino, L; Clerici, A M; Coppola, A; Di Liberto, R; Dionigi, P; Protti, N; Stella, S; Zonta, A; Zonta, C; Altieri, S

    2011-04-01

    Boron neutron capture therapy (BNCT) is a binary radiotherapy based on thermal-neutron irradiation of cells enriched with (10)B, which produces α particles and (7)Li ions of short range and high biological effectiveness. The selective uptake of boron by tumor cells is a crucial issue for BNCT, and studies of boron uptake and washout associated with cell survival studies can be of great help in developing clinical applications. In this work, boron uptake and washout were characterized both in vitro for the DHDK12TRb (DHD) rat colon carcinoma cell line and in vivo using rats bearing liver metastases from DHD cells. Despite a remarkable uptake, a large boron release was observed after removal of the boron-enriched medium from in vitro cell cultures. However, analysis of boron washout after rat liver perfusion in vivo did not show a significant boron release, suggesting that organ perfusion does not limit the therapeutic effectiveness of the treatment. The survival of boron-loaded cells exposed to thermal neutrons was also assessed; the results indicated that the removal of extracellular boron does not limit treatment effectiveness if adequate amounts of boron are delivered and if the cells are kept at low temperature. Cell survival was also investigated theoretically using a mechanistic model/Monte Carlo code originally developed for radiation-induced chromosome aberrations and extended here to cell death; good agreement between simulation outcomes and experimental data was obtained. © 2011 by Radiation Research Society

  4. Identification of a Novel System for Boron Transport: Atr1 Is a Main Boron Exporter in Yeast▿ †

    PubMed Central

    Kaya, Alaattin; Karakaya, Huseyin C.; Fomenko, Dmitri E.; Gladyshev, Vadim N.; Koc, Ahmet

    2009-01-01

    Boron is a micronutrient in plants and animals, but its specific roles in cellular processes are not known. To understand boron transport and functions, we screened a yeast genomic DNA library for genes that confer resistance to the element in Saccharomyces cerevisiae. Thirty boron-resistant transformants were isolated, and they all contained the ATR1 (YML116w) gene. Atr1 is a multidrug resistance transport protein belonging to the major facilitator superfamily. C-terminal green fluorescent protein-tagged Atr1 localized to the cell membrane and vacuole, and ATR1 gene expression was upregulated by boron and several stress conditions. We found that atr1Δ mutants were highly sensitive to boron treatment, whereas cells overexpressing ATR1 were boron resistant. In addition, atr1Δ cells accumulated boron, whereas ATR1-overexpressing cells had low intracellular levels of the element. Furthermore, atr1Δ cells showed stronger boron-dependent phenotypes than mutants deficient in genes previously reported to be implicated in boron metabolism. ATR1 is widely distributed in bacteria, archaea, and lower eukaryotes. Our data suggest that Atr1 functions as a boron efflux pump and is required for boron tolerance. PMID:19414602

  5. High-pressure behavior of superconducting boron-doped diamond

    NASA Astrophysics Data System (ADS)

    Abdel-Hafiez, Mahmoud; Kumar, Dinesh; Thiyagarajan, R.; Zhang, Q.; Howie, R. T.; Sethupathi, K.; Volkova, O.; Vasiliev, A.; Yang, W.; Mao, H. K.; Rao, M. S. Ramachandra

    2017-05-01

    This work investigates the high-pressure structure of freestanding superconducting (Tc=4.3 K) boron-doped diamond (BDD) and how it affects the electronic and vibrational properties using Raman spectroscopy and x-ray diffraction in the 0-30 GPa range. High-pressure Raman scattering experiments revealed an abrupt change in the linear pressure coefficients, and the grain boundary components undergo an irreversible phase change at 14 GPa. We show that the blueshift in the pressure-dependent vibrational modes correlates with the negative pressure coefficient of Tc in BDD. The analysis of x-ray diffraction data determines the equation of state of the BDD film, revealing a high bulk modulus of B0=510 ±28 GPa. The comparative analysis of high-pressure data clarified that the s p2 carbons in the grain boundaries transform into hexagonal diamond.

  6. Prediction of Boron-Boron Triple-Bond Polymers Stabilized by Janus-Type Bis(N-heterocyclic) Carbenes.

    PubMed

    Fantuzzi, Felipe; Chaer Nascimento, Marco A

    2015-05-18

    A class of polymeric compounds containing boron-boron triple bonds stabilized by N-heterocyclic biscarbenes is proposed. Since a triply bonded B2 is related to its third excited state, the predicted macromolecule would be composed by several units of an electronically excited first-row homonuclear dimer. Moreover, it is shown that the replacement of biscarbene with N2 or CO as spacers could change the bonding profile of the boron-boron units to a cumulene-like structure. Based on these results, different types of diboryne polymers are proposed, which could lead to an unprecedented set of boron materials with distinct physical properties. The novel diboryne macromolecules could be synthesized by the reaction of Janus-type biscarbenes with tetrabromodiborane, B2 Br4 , and sodium naphthalenide, [Na(C10 H8 )], similarly to Braunschweig's work on the room temperature stable boron-boron triple bond compounds (Science, 2012, 336, 1420).

  7. Biological activity of N(4)-boronated derivatives of 2'-deoxycytidine, potential agents for boron-neutron capture therapy.

    PubMed

    Nizioł, Joanna; Uram, Łukasz; Szuster, Magdalena; Sekuła, Justyna; Ruman, Tomasz

    2015-10-01

    Boron-neutron capture therapy (BNCT) is a binary anticancer therapy that requires boron compound for nuclear reaction during which high energy alpha particles and lithium nuclei are formed. Unnatural, boron-containing nucleoside with hydrophobic pinacol moiety was investigated as a potential BNCT boron delivery agent. Biological properties of this compound are presented for the first time and prove that boron nucleoside has low cytotoxicity and that observed apoptotic effects suggest alteration of important functions of cancer cells. Mass spectrometry analysis of DNA from cancer cells proved that boron nucleoside is inserted into nucleic acids as a functional nucleotide derivative. NMR studies present very high degree of similarity of natural dG-dC base pair with dG-boron nucleoside system. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. NEW ADVANCES IN BORON SOIL CHEMISTRY

    EPA Science Inventory

    Boron is an essential plant micronutrient for which the range between deficiency and toxicity is narrower than for any other nutrient element. Plants respond directly to the amount of B in soil solution and only indirectly to the amount of B adsorbed on soil particle surfaces. ...

  9. NEW ADVANCES IN BORON SOIL CHEMISTRY

    EPA Science Inventory

    Boron is an essential plant micronutrient for which the range between deficiency and toxicity is narrower than for any other nutrient element. Plants respond directly to the amount of B in soil solution and only indirectly to the amount of B adsorbed on soil particle surfaces. ...

  10. New insight into pecan boron nutrition

    USDA-ARS?s Scientific Manuscript database

    Alternate bearing by individual pecan [Carya illinoinensis (Wangenh.) K. Koch] trees is problematic for nut producers and processors. There are many unknowns regarding alternate bearing physiology, such as the relationship between boron and fruit set, nutmeat quality, and kernel maladies. Evidence...

  11. Boron nitride solid state neutron detector

    DOEpatents

    Doty, F. Patrick

    2004-04-27

    The present invention describes an apparatus useful for detecting neutrons, and particularly for detecting thermal neutrons, while remaining insensitive to gamma radiation. Neutrons are detected by direct measurement of current pulses produced by an interaction of the neutrons with hexagonal pyrolytic boron nitride.

  12. Boron Nitride Nanotubes for Engineering Applications

    NASA Technical Reports Server (NTRS)

    Hurst, Janet; Hull, David; Gorican, Daniel

    2005-01-01

    Boron nitride nanotubes (BNNT) are of significant interest to the scientific and technical communities for many of the same reasons that carbon nanotubes (CNT) have attracted wide attention. Both materials have potentially unique and important properties for structural and electronic applications. However of even more consequence than their similarities may be the complementary differences between carbon and boron nitride nanotubes While BNNT possess a very high modulus similar to CNT, they also possess superior chemical and thermal stability. Additionally, BNNT have more uniform electronic properties, with a uniform band gap of 5.5 eV while CNT vary from semi-conductive to highly conductive behavior. Boron nitride nanotubes have been synthesized both in the literature and at NASA Glenn Research Center, by a variety of methods such as chemical vapor deposition, arc discharge and reactive milling. Consistent large scale production of a reliable product has proven difficult. Progress in the reproducible synthesis of 1-2 gram sized batches of boron nitride nanotubes will be discussed as well as potential uses for this unique material.

  13. Tetrahedral boron in naturally occurring tourmaline

    SciTech Connect

    Tagg, S.L.; Cho, H.; Dyar, M.D.; Grew, E.S.

    1999-09-01

    Evidence for boron in both trigonal and tetrahedral coordination has been found in {sup 11}B magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectra of natural, inclusion-free specimens of aluminum-rich lithian tourmaline from granitic pregmatites.

  14. Axial residual stresses in boron fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1978-01-01

    The axial residual stress distribution as a function of radius was determined from the fiber surface to the core including the average residual stress in the core. Such measurements on boron on tungsten (B/W) fibers show that the residual stresses for 102, 142, 203, and 366 micron diameter fibers were similar, being compressive at the surface and changing monotonically to a region of tensile within the boron. At approximately 25 percent of the original radius, the stress reaches a maximum tensile stress of about 860 mn/sq.m and then decreases to a compressive stress near the tungsten boride core. Data were presented for 203 micron diameter B/W fibers that show annealing above 900 C reduces the residual stresses. A comparison between 102 micron diameter B/W and boron on carbon (b/C) shows that the residual stresses were similar in the outer regions of the fibers, but that large differences near and in the core were observed. The effects of these residual stresses on the fracture of boron fibers were discussed.

  15. Intrinsic ferromagnetism in hexagonal boron nitride nanosheets

    SciTech Connect

    Si, M. S.; Gao, Daqiang E-mail: xueds@lzu.edu.cn; Yang, Dezheng; Peng, Yong; Zhang, Z. Y.; Xue, Desheng E-mail: xueds@lzu.edu.cn; Liu, Yushen; Deng, Xiaohui; Zhang, G. P.

    2014-05-28

    Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

  16. Intrinsic ferromagnetism in hexagonal boron nitride nanosheets.

    PubMed

    Si, M S; Gao, Daqiang; Yang, Dezheng; Peng, Yong; Zhang, Z Y; Xue, Desheng; Liu, Yushen; Deng, Xiaohui; Zhang, G P

    2014-05-28

    Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

  17. Intrinsic ferromagnetism in hexagonal boron nitride nanosheets

    NASA Astrophysics Data System (ADS)

    Si, M. S.; Gao, Daqiang; Yang, Dezheng; Peng, Yong; Zhang, Z. Y.; Xue, Desheng; Liu, Yushen; Deng, Xiaohui; Zhang, G. P.

    2014-05-01

    Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

  18. Investigating the Boron Requirement of Plants.

    ERIC Educational Resources Information Center

    Bohnsack, Charles W.

    1991-01-01

    This article describes a simple and rapid method for using summer squash to investigate born deficiency in plants. Author asserts that students are likely to feel challenged by laboratory exercises and projects that focus on the role boron plays in plant growth because it is an unresolved problem in biology. (PR)

  19. Annealing studies of highly doped boron superlattices

    SciTech Connect

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

    1989-09-01

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

  20. NEW ADVANCES IN BORON SOIL CHEMISTRY - Paper

    EPA Science Inventory

    Boron is an essential plant micronutrient for which the range between deficiency and toxicity is narrower than for any other nutrient element. Plants respond directly to the amount of B in soil solution and only indirectly to the amount of B adsorbed on soil particle surfaces. ...

  1. Powdered Hexagonal Boron Nitride Reducing Nanoscale Wear

    NASA Astrophysics Data System (ADS)

    Chkhartishvili, L.; Matcharashvili, T.; Esiava, R.; Tsagareishvili, O.; Gabunia, D.; Margiev, B.; Gachechiladze, A.

    2013-05-01

    A morphology model is suggested for nano-powdered hexagonal boron nitride that can serve as an effective solid additive to liquid lubricants. It allows to estimate the specific surface, that is a hard-to-measure parameter, based on average size of powder particles. The model can be used also to control nanoscale wear processes.

  2. Composite Reinforcement using Boron Nitride Nanotubes

    DTIC Science & Technology

    2014-05-09

    while retaining the nanotube structure. This project involves the use of computational quantum chemistry to study interactions of aluminium (Al...small clusters of 1–4 metal atoms. The effect of varying the radius of the nanotubes and the size of aluminium and titanium clusters was considered...15. SUBJECT TERMS Boron Nitride Nanotubes, composite materials, Aluminum Alloys , Titanium Alloy , Theoretical Chemistry 16. SECURITY

  3. Monolayer boron-aluminum compacted sheet material

    NASA Technical Reports Server (NTRS)

    Sumner, E. V.

    1973-01-01

    The manufacturing techniques, basic materials used, and equipment required to produce monolayer boron-aluminum composites are described. Tentative materials and process specifications are included. Improvements in bonding and filament spacing obtained through use of brazing powder in the fugitive binder are discussed.

  4. Advances in boronization on NSTX-Upgrade

    NASA Astrophysics Data System (ADS)

    Skinner, C. H.; Blanchard, W.; Cai, D.; Jaworski, M.; Bedoya, F.; Allain, J. P.; Scotti, F.; Koel, B. E.

    2016-10-01

    Boronization has been effective in reducing plasma impurities and enabling access to higher density, higher confinement plasmas in many magnetic fusion devices. The National Spherical Torus eXperiment, NSTX, has recently undergone a major upgrade to NSTX-U in order to develop the physics basis for a ST-based Fusion Nuclear Science Facility (FNSF) with capability for double the toroidal field, plasma current, and NBI heating power and increased pulse duration from 1 - 1.5 s to 5 - 8 s. A new deuterated tri-methyl boron conditioning system was implemented together with a novel surface analysis diagnostic (MAPP). We report on the spatial distribution of the boron deposition versus discharge pressure, gas injection and electrode location. The oxygen concentration of the plasma facing surface was measured by in-vacuo XPS and increased both with plasma exposure and with exposure to trace residual gases. This increase was correlated with the rise of oxygen emission from the plasma. A dedicated experiment is planned to optimize the boronization process including XPS measurements of the plasma facing surface under specific plasma conditions. We will report on the results. Support was provided through DOE Contract Number DE-AC02-09CH11466.

  5. Investigating the Boron Requirement of Plants.

    ERIC Educational Resources Information Center

    Bohnsack, Charles W.

    1991-01-01

    This article describes a simple and rapid method for using summer squash to investigate born deficiency in plants. Author asserts that students are likely to feel challenged by laboratory exercises and projects that focus on the role boron plays in plant growth because it is an unresolved problem in biology. (PR)

  6. Assessment of Boron Steels for Army Use

    DTIC Science & Technology

    1978-11-01

    transform the microstructure from austenite to the lower tempera- ture transformation product martensite (lower bainite may also be satisfactory for... bainite , carbides, or pearlite. Thus, as long as low tem- perature transformation products are desired (martensite and lower bainite ), boron 13

  7. NEW ADVANCES IN BORON SOIL CHEMISTRY - Paper

    EPA Science Inventory

    Boron is an essential plant micronutrient for which the range between deficiency and toxicity is narrower than for any other nutrient element. Plants respond directly to the amount of B in soil solution and only indirectly to the amount of B adsorbed on soil particle surfaces. ...

  8. Energetics of Boron Doping of Carbon Pores

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  9. Influence of the order of boron and phosphorus diffusion on the fabrication of thin bifacial silicon solar cells

    NASA Astrophysics Data System (ADS)

    da Conceição Osório, Vanessa; Moehlecke, Adriano; Zanesco, Izete

    2016-10-01

    The aim of this paper is to analyze the fabrication process of thin bifacial silicon solar cells concerning the order of diffusions to form p+ and n+ regions. The n+pp+ structure with the p+ selective region was implemented by using thin solar grade Czochralski silicon wafers. The whole rear face was doped with boron deposited by spin-on and thermally diffused and an Al metal grid was screen-printed and diffused. The phosphorus diffusion after the boron one produced the thinner n+ emitter and thinner dead layer, which allow the manufacturing of more efficient solar cells. Furthermore, the phosphorus diffusion at the end of processing promoted gettering, enhancing the minority charge carrier lifetime. Solar cells with the phosphorus diffusion after the boron one reached front and rear efficiencies of 14.0% and 10.4%, respectively, without any surface passivation.

  10. Boron carbide nanowires: Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Guan, Zhe

    Bulk boron carbide has been widely used in ballistic armored vest and the property characterization has been heavily focused on mechanical properties. Even though boron carbides have also been projected as a promising class of high temperature thermoelectric materials for energy harvesting, the research has been limited in this field. Since the thermal conductivity of bulk boron carbide is still relatively high, there is a great opportunity to take advantage of the nano effect to further reduce it for better thermoelectric performance. This dissertation work aims to explore whether improved thermoelectric performance can be found in boron carbide nanowires compared with their bulk counterparts. This dissertation work consists of four main parts. (1) Synthesis of boron carbide nanowires. Boron carbide nanowires were synthesized by co-pyrolysis of diborane and methane at low temperatures (with 879 °C as the lowest) in a home-built low pressure chemical vapor deposition (LPCVD) system. The CVD-based method is energy efficient and cost effective. The as-synthesized nanowires were characterized by electron microscopy extensively. The transmission electron microscopy (TEM) results show the nanowires are single crystalline with planar defects. Depending on the geometrical relationship between the preferred growth direction of the nanowire and the orientation of the defects, the as-synthesized nanowires could be further divided into two categories: transverse fault (TF) nanowires grow normal to the defect plane, while axial fault (AF) ones grow within the defect plane. (2) Understanding the growth mechanism of as-synthesized boron carbide nanowires. The growth mechanism can be generally considered as the famous vapor-liquid-solid (VLS) mechanism. TF and AF nanowires were found to be guided by Ni-B catalysts of two phases. A TF nanowire is lead by a hexagonal phase catalyst, which was proved to be in a liquid state during reaction. While an AF nanowires is catalyzed by a

  11. Boron: elementary challenge for experimenters and theoreticians.

    PubMed

    Albert, Barbara; Hillebrecht, Harald

    2009-01-01

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

  12. Microstructural characterization of superalloy 718 with boron and phosphorus additions

    SciTech Connect

    Horton, J.A.; McKamey, C.G.; Miller, M.K.; Cao, W.D.; Kennedy, R.L.

    1997-06-01

    Boron and phosphorus additions are known to improve the stress rupture properties of IN-718. One possible mechanism to explain this property improvement relies on the boron and phosphorus additions slowing down the growth of {gamma}{double_prime} and {gamma}{prime} precipitates during high temperature service or aging. However, atom probe analysis found no segregation of boron and phosphorus to {gamma}-{gamma}{double_prime} or to {gamma}-{gamma}{prime} interfaces in the alloys with the high boron and high phosphorus levels. No difference in growth rates were found by transmission electron microscopy in the sizes of the {gamma}{double_prime} or {gamma}{prime} in alloys with high phosphorus and high boron as compared to commercial alloys and to alloys with even lower levels of phosphorus and boron. Atom probe analysis further found that much of the phosphorus, boron, and carbon segregated to grain boundaries. Creep curves comparing the alloys with high levels of phosphorus and boron and alloys with low levels of phosphorus and boron show a large difference in strain rate in the first hours of the test. These results suggest that the boron and phosphorus may have a direct effect on dislocation mobility by some pinning mechanism.

  13. Investigations on boron levels in drinking water sources in China.

    PubMed

    Xu, Ren-ji; Xing, Xiao-ru; Zhou, Qun-fang; Jiang, Gui-bin; Wei, Fu-sheng

    2010-06-01

    To evaluate boron contamination of public drinking water in China, both dissolved and total boron contents in 98 public drinking water sources from 49 cities, 42 brands of bottled water samples from supermarkets in several cities, and 58 water samples from boron industrial area were measured by inductively coupled plasma-mass spectrometry (ICP-MS). Our experimental results showed that boron existed in public drinking water sources mainly in dissolved status with total concentrations ranging from 0.003 to 0.337 mg/L (mean = 0.046 mg/L). The mean boron concentrations in mineral and pure bottled water were 0.052 and 0.028 mg/L, respectively. The results obtained in this work showed that there was no health risk on view of boron in public drinking water sources and bottled water. In boron industrial area, boron concentrations in surface water and ground water were 1.28 mg/L (range = 0.007-3.8 mg/L) and 18.3 mg/L (range = 0.015-140 mg/L), respectively, which indicated that boron industry caused boron pollution in local water system.

  14. Boron-enriched streptavidin potentially useful as a component of boron carriers for neutron capture therapy of cancer.

    PubMed

    Sano, T

    1999-01-01

    A boron-enriched streptavidin has been prepared by chemical conjugation of a boron-rich compound, B(12)H(11)SH(2)(-) (BSH), to a genetically engineered streptavidin variant. The streptavidin variant used has 20 cysteine residues per molecule, derived from a C-terminal cysteine stretch consisting of five cysteine residues per subunit. Because natural streptavidin has no cysteine residues, the reactive sulfhydryl groups of the cysteine stretch serve as unique conjugation sites for sulfhydryl chemistry. BSH was conjugated irreversibly to the sulfhydryl groups of the streptavidin variant via a sulfhydryl-specific homobifunctional chemical cross-linker. Quantitative boron analysis indicates that the resulting streptavidin-BSH conjugate carries approximately 230 boron atoms/molecule. This indicates that the chemical conjugation of BSH to the streptavidin variant was highly specific and efficient because this method should allow the conjugation of a maximum of 240 boron atoms/streptavidin molecule. This boron-enriched streptavidin retained both full biotin-binding ability and tetrameric structure, suggesting that the conjugation of BSH has little, if any, effect on the fundamental properties of streptavidin. This boron-enriched streptavidin should be very useful as a component of targetable boron carriers for neutron capture therapy of cancer. For example, a monoclonal antibody against a tumor-associated antigen can be attached tightly to the boron-enriched streptavidin upon simple biotinylation, and the resulting conjugate could be used to target boron to tumor cells on which the tumor-associated antigen is overexpressed.

  15. Boron Arsenide and Boron Phosphide for High Temperature and Luminescent Devices. [semiconductor devices - crystal growth/crystal structure

    NASA Technical Reports Server (NTRS)

    Chu, T. L.

    1975-01-01

    The crystal growth of boron arsenide and boron phosphide in the form of bulk crystals and epitaxial layers on suitable substrates is discussed. The physical, chemical, and electrical properties of the crystals and epitaxial layers are examined. Bulk crystals of boron arsenide were prepared by the chemical transport technique, and their carrier concentration and Hall mobility were measured. The growth of boron arsenide crystals from high temperature solutions was attempted without success. Bulk crystals of boron phosphide were also prepared by chemical transport and solution growth techniques. Techniques required for the fabrication of boron phosphide devices such as junction shaping, diffusion, and contact formation were investigated. Alloying techniques were developed for the formation of low-resistance ohmic contacts to boron phosphide. Four types of boron phosphide devices were fabricated: (1) metal-insulator-boron phosphide structures, (2) Schottky barriers; (3) boron phosphide-silicon carbide heterojunctions; and (4) p-n homojunctions. Easily visible red electroluminescence was observed from both epitaxial and solution grown p-n junctions.

  16. From Boron Cluster to Two-Dimensional Boron Sheet on Cu(111) Surface: Growth Mechanism and Hole Formation

    PubMed Central

    Liu, Hongsheng; Gao, Junfeng; Zhao, Jijun

    2013-01-01

    As attractive analogue of graphene, boron monolayers have been theoretically predicted. However, due to electron deficiency of boron atom, synthesizing boron monolayer is very challenging in experiments. Using first-principles calculations, we explore stability and growth mechanism of various boron sheets on Cu(111) substrate. The monotonic decrease of formation energy of boron cluster BN with increasing cluster size and low diffusion barrier for a single B atom on Cu(111) surface ensure continuous growth of two-dimensional (2D) boron cluster. During growth process, hexagonal holes can easily arise at the edge of a 2D triangular boron cluster and then diffuse entad. Hence, large-scale boron monolayer with mixed hexagonal-triangular geometry can be obtained via either depositing boron atoms directly on Cu(111) surface or soft landing of small planar BN clusters. Our theoretical predictions would stimulate further experiments of synthesizing boron sheets on metal substrates and thus enrich the variety of 2D monolayer materials. PMID:24241341

  17. Nominal effective radiation doses delivered during clinical trials of boron neutron capture therapy

    SciTech Connect

    Capala, J.; Diaz, A.Z.; Chanana, A.D.

    1997-12-31

    Boron neutron capture therapy (BNCT) is a binary system that, in theory, should selectively deliver lethal, high linear energy transfer (LET) radiation to tumor cells dispersed within normal tissues. It is based on the nuclear reaction 10-B(n, {alpha})7-Li, which occurs when the stable nucleus of boron-10 captures a thermal neutron. Due to the relatively high cross-section of the 10-B nucleus for thermal neutron capture and short ranges of the products of this reaction, tumor cells in the volume exposed to thermal neutrons and containing sufficiently high concentration of 10-B would receive a much higher radiation dose than the normal cells contained within the exposed volume. Nevertheless, radiation dose deposited in normal tissue by gamma and fast neutron contamination of the neutron beam, as well as neutron capture in nitrogen, 14-N(n,p)14-C, hydrogen, 1-H(n,{gamma})2-H, and in boron present in blood and normal cells, limits the dose that can be delivered to tumor cells. It is, therefore, imperative for the success of the BNCT the dosed delivered to normal tissues be accurately determined in order to optimize the irradiation geometry and to limit the volume of normal tissue exposed to thermal neutrons. These are the major objectives of BNCT treatment planning.

  18. Determination of nitrogen in boron carbide by instrumental photon activation analysis.

    PubMed

    Merchel, Silke; Berger, Achim

    2007-05-01

    Boron carbide is widely used as industrial material, because of its extreme hardness, and as a neutron absorber. As part of a round-robin exercise leading to certification of a new reference material (ERM-ED102) which was demanded by the industry we analysed nitrogen in boron carbide by inert gas fusion analysis (GFA) and instrumental photon activation analysis (IPAA) using the 14N(gamma,n)13N nuclear reaction. The latter approach is the only non-destructive method among all the methods applied. By using photons with energy below the threshold of the 12C(gamma,n)11C reaction, we hindered activation of matrix and other impurities. A recently installed beam with a very low lateral activating flux gradient enabled us to homogeneously activate sample masses of approximately 1 g. Taking extra precautions, i.e. self-absorption correction and deconvolution of the complex decay curves, we calculated a nitrogen concentration of 2260+/-100 microg g-1, which is in good agreement with our GFA value of 2303+/-64 microg g-1. The values are the second and third highest of a rather atypical (non-S-shape) distribution of data of 14 round-robin participants. It is of utmost importance for the certification process that our IPAA value is the only one not produced by inert gas fusion analysis and, therefore, the only one which is not affected by a possible incomplete release of nitrogen from high-melting boron carbide.

  19. A study of boron adsorption onto activated sludge.

    PubMed

    Fujita, Yuichiro; Hata, Takayosi; Nakamaru, Makoto; Iyo, Toru; Yoshino, Tsuneo; Shimamura, Tadashi

    2005-08-01

    Boron adsorption onto activated sludge was investigated using bench-scale reactors under simulated wastewater treatment conditions. Two experiments, continuous flow and batch, were performed. Boron concentrations were determined by means of inductively coupled plasma mass spectrometry. The results of the continuous-flow experiment indicated that a small amount of boron accumulated on the activated sludge and its concentration in the sludge depended on the nature of the biota in the sludge. Freundlich and Langmuir isotherm plots generated using the data from the batch experiment indicated that boron was adsorbed onto rather than absorbed into the sludge. The Freundlich constants, k and 1/n, were determined to be 26 mg/kg and 0.87. These values indicate that activated sludge has a limited capacity for boron adsorption and thus utilization of the excess sludge for farmland may not be toxic to plant at least boron concern.

  20. Combined effect of boron and salinity on water transport

    PubMed Central

    del Carmen Martínez-Ballesta, Maria; Bastías, Elizabeth

    2008-01-01

    Boron toxicity is an important disorder that can limit plant growth on soils of arid and semi arid environments throughout the world. Although there are several reports about the combined effect of salinity and boron toxicity on plant growth and yield, there is no consensus about the experimental results. A general antagonistic relationship between boron excess and salinity has been observed, however the mechanisms for this interaction is not clear and several options can be discussed. In addition, there is no information, concerning the interaction between boron toxicity and salinity with respect to water transport and aquaporins function in the plants. We recently documented in the highly boron- and salt-tolerant the ecotype of Zea mays L. amylacea from Lluta valley in Northern Chile that under salt stress, the activity of specific membrane components can be influenced directly by boron, regulating the water uptake and water transport through the functions of certain aquaporin isoforms. PMID:19704850

  1. Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs.

    PubMed

    Mannix, Andrew J; Zhou, Xiang-Feng; Kiraly, Brian; Wood, Joshua D; Alducin, Diego; Myers, Benjamin D; Liu, Xiaolong; Fisher, Brandon L; Santiago, Ulises; Guest, Jeffrey R; Yacaman, Miguel Jose; Ponce, Arturo; Oganov, Artem R; Hersam, Mark C; Guisinger, Nathan P

    2015-12-18

    At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes. Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal. Copyright © 2015, American Association for the Advancement of Science.

  2. One-dimensional boron nanostructures: Prediction, synthesis, characterizations, and applications.

    PubMed

    Tian, Jifa; Xu, Zhichuan; Shen, Chengmin; Liu, Fei; Xu, Ningsheng; Gao, Hong-Jun

    2010-08-01

    One-dimensional (1D) boron nanostructures are very potential for nanoscale electronic devices since their physical properties including electric transport and field emission have been found very promising as compared to other well-developed 1D nanomaterials. In this article, we review the current progress that has been made on 1D boron nanostructures in terms of theoretical prediction, synthetic techniques, characterizations and potential applications. To date, the synthesis of 1D boron nanostructures has been well-developed. The popular structures include nanowires, nanobelts, and nanocones. Some of these 1D nanostructures exhibited improved electric transport properties over bulk boron materials as well as promising field emission properties. By current experimental findings, 1D boron nanostructures are promising to be one of core materials for future nanodevices. More efforts are expected to be made in future on the controlled growth of 1D boron nanostructures and tailoring their physical properties.

  3. Isothermal superplastic boronizing of high carbon and low alloy steels

    SciTech Connect

    Xu, C.H.; Gao, W.; Xi, J.K.

    1996-02-01

    Superplasticity has been developed rapidly since the 1960`s. Superplasticity and superplastic deformation technique of steel and ferrous alloys offer a new method of forming complex parts for industrial applications, such as dies and gears. On the other hand, boronizing has long been used to improve the surface properties of dies and tools because boride has high hardness, good wear resistance, and good corrosion and oxidation resistance. Superplastic boronizing, a new technique, is the processes that combines boronizing with superplastic deformation. Because two processes become one, energy and time can be saved. In the present paper, the superplastic boronizing processes for commercial 0.9C-1Si-1Cr-Fe and 1C-1Cr-Fe steels are described first. Then, the microstructure and properties of specimens produced by using superplastic and conventional boronizing are compared. Finally, a physical model for superplastic boronizing processes is suggested.

  4. Influence of dopants, particularly carbon, on β-rhombohedral boron

    NASA Astrophysics Data System (ADS)

    Werheit, H.; Flachbart, K.; Pristáš, G.; Lotnyk, D.; Filipov, V.; Kuhlmann, U.; Shitsevalova, N.; Lundström, T.

    2017-09-01

    Due to the high affinity of carbon to boron, the preparation of carbon-free boron is problematic. Even high-purity (6 N) β-rhombohedral boron contains 30-60 ppm of C. Hence, carbon affects the boron physical properties published so far more or less significantly. We studied well-defined carbon-doped boron samples based on pure starting material carefully annealed with up to about 1% C, thus assuring homogeneity. We present and discuss their electrical conductivity, optical absorption, luminescence and phonon spectra. Earlier attempts of other authors to determine the conductivity of C-doped boron are revised. Our results allow estimating the effects of oxygen and iron doping on the electrical conductivity using results taken from literature. Discontinuities at low T impair the electronic properties.

  5. Boron nitride - Composition, optical properties, and mechanical behavior

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

    1987-01-01

    A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at. percent. The carbon and oxygen impurities were in the 5 to 8 at. percent range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

  6. Boron nitride: Composition, optical properties and mechanical behavior

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

    1987-01-01

    A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at %. The carbon and oxygen impurities were in the 5 to 8 at % range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

  7. Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs

    PubMed Central

    Mannix, Andrew J.; Zhou, Xiang-Feng; Kiraly, Brian; Wood, Joshua D.; Alducin, Diego; Myers, Benjamin D.; Liu, Xiaolong; Fisher, Brandon L.; Santiago, Ulises; Guest, Jeffrey R.; Yacaman, Miguel Jose; Ponce, Arturo; Oganov, Artem R.; Hersam, Mark C.; Guisinger, Nathan P.

    2016-01-01

    At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes.Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal. PMID:26680195

  8. Marine corrosion protective coatings of hexagonal boron nitride thin films on stainless steel.

    PubMed

    Husain, Esam; Narayanan, Tharangattu N; Taha-Tijerina, Jose Jaime; Vinod, Soumya; Vajtai, Robert; Ajayan, Pulickel M

    2013-05-22

    Recently, two-dimensional, layered materials such as graphene and hexagonal boron nitride (h-BN) have been identified as interesting materials for a range of applications. Here, we demonstrate the corrosion prevention applications of h-BN in marine coatings. The performance of h-BN/polymer hybrid coatings, applied on stainless steel, were evaluated using electrochemical techniques in simulated seawater media [marine media]. h-BN/polymer coating shows an efficient corrosion protection with a low corrosion current density of 5.14 × 10(-8) A/cm(2) and corrosion rate of 1.19 × 10(-3) mm/year and it is attributed to the hydrofobic, inert and dielectric nature of boron nitride. The results indicated that the stainless steel with coatings exhibited improved corrosion resistance. Electrochemical impedance spectroscopy and potentiodynamic analysis were used to propose a mechanism for the increased corrosion resistance of h-BN coatings.

  9. Boron atomic-scale mapping in advanced microelectronics by atom probe tomography

    NASA Astrophysics Data System (ADS)

    Estivill, Robert; Juhel, Marc; Servanton, Germain; Gregoire, Magali; Lorut, Fréderic; Clement, Laurent; Chevalier, Pascal; Grenier, Adeline; Blavette, Didier

    2017-06-01

    Two types of industrial transistor technologies have been studied using atom probe tomography (APT). Both 14 nm node high-K metal-oxide-semiconductor field effect transistors (MOSFETs) on ultrathin body and buried oxide and 320 GHz Ft Si/SiGe Heterojunction Bipolar Transistors (HBT) embedded in a 55-nm BiCMOS chip have been analysed and their atomic distribution has been mapped. Due to the limitations of routine characterisation techniques, boron can remain invisible in such nanometric sized structures. Also, size effects can induce differences between the actual device and larger test zones used for monitoring these technologies. This paper presents results obtained by APT from two advanced nodes, in contrast to complementary techniques. Using different methodologies, including specific APT-friendly test structures and multiple-impact data filtering, the dopant behaviour in these structures can be better understood. An unexpected boron distribution in both the MOSFET source/drain and HBT base regions has been highlighted.

  10. Effect of fiber diameter and matrix alloys on impact-resistant boron/aluminum composites

    NASA Technical Reports Server (NTRS)

    Mcdanels, D. L.; Signorelli, R. A.

    1976-01-01

    Efforts to improve the impact resistance of B/Al are reviewed and analyzed. Nonstandard thin-sheet charpy and Izod impact tests and standard full-size Charpy impact tests were conducted on composites containing unidirectional 0.10mm, 0.14mm, and 0.20mm diameter boron fibers in 1100, 2024, 5052, and 6061 Al matrices. Impact failure modes of B/Al are proposed in an attempt to describe the mechanisms involved and to provide insight for maximizing impact resistance. The impact strength of B/Al was significantly increased by proper selection of materials and processing. The use of a ductile matrix and large diameter boron fibers gave the highest impact strengths. This combination resulted in improved energy absorption through matrix shear deformation and multiple fiber breakage.

  11. An ultrathin high-performance heat spreader fabricated with hydroxylated boron nitride nanosheets

    NASA Astrophysics Data System (ADS)

    Fu, Li; Wang, Ting; Yu, Jinhong; Dai, Wen; Sun, Hongyan; Liu, Zhiduo; Sun, Rong; Jiang, Nan; Yu, Aimin; Lin, Cheng-Te

    2017-06-01

    An ultrathin, highly thermally conductive heat spreader has been fabricated by layer-by-layer stacking of hydroxylated boron nitride nanosheets (HBNNS) for the first time. HBNNS were prepared by a molten hydroxide-assisted liquid exfoliation from hexagonal boron nitride powder. The as-prepared heat spreader of HBNNS exhibits a high thermal conductivity of 51.1 W m-1 K-1 along the in-plane direction, and can be further enhanced 14% by annealing for de-hydroxylation. This heat spreader with 10-30 µm in thickness possessed excellent thermal stability with negligible weight loss at wide temperature range up to 700 °C, resulting in promising applications for heat dissipation in electronic components operated at high working temperature.

  12. Structural analysis of pyridine-imino boronic esters involving secondary interactions on solid state

    NASA Astrophysics Data System (ADS)

    Sánchez-Portillo, Paola; Arenaza-Corona, Antonino; Hernández-Ahuactzi, Irán F.; Barba, Victor

    2017-04-01

    Twelve boronic esters (1a-1l) synthesized from 4-halo- substituted arylboronic acids (halo = F, Cl, Br, I and CF3) with 2-amino-2- alkyl (H, Me) -1,3-propanediol in presence of (3- or 4)-pyridine carboxaldehyde are described. A solvent mixture toluene/methanol 1:4 ratio was used. All compounds include both donor/acceptor functional groups, which are the necessary elements to self-assembly of the molecular species. Several secondary interactions as I⋯N, Br⋯Br, Br⋯B, F⋯B, Csbnd H⋯N, Csbnd H⋯O, Br⋯π and Csbnd H⋯π support the 1D and 2D polymeric frameworks in solid state. The coordination of the nitrogen atom from the pyridine moiety with the boron atom was not observed in either solution or solid state.

  13. Early clinical experience of boron neutron capture therapy for glioblastoma multiforme

    SciTech Connect

    Joel, D.D.; Bergland, R.; Capala, J.

    1995-12-31

    Boron neutron capture therapy (BNCT) is a binary treatment modality that can selectively irradiate tumor tissue. BNCT uses drugs containing a stable isotope of boron. {sup 10}B, to sensitize tumor cells to irradiation by low energy (thermal) neutrons. The interaction of the {sup 10}B with a thermal neutron (neutron capture) causes the {sup 10}B nucleus to split, releasing an alpha particle and a lithium nucleus. These products of the {sup 10}B(n, {alpha}){sup 7}Li reaction are very damaging to cells but have a combined path length in tissue of approximately 14 {mu}m, or roughly the diameter of one or two cells. Thus, most of the ionizing energy imparted to tissue is localized to {sup 10}B-loaded cells.

  14. Double aromaticity in transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8)

    NASA Astrophysics Data System (ADS)

    Xu, Chang; Cheng, Longjiu; Yang, Jinlong

    2014-09-01

    It is well known that double-ring boron clusters have got the special double aromaticity with delocalized π orbitals in two directions (tangential and radial), which are potential ligands centered by a transition metal. In this article, the transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8) are theoretically investigated by density functional theory calculations. These endohedral compounds have also got double aromaticity in both tangential and radial directions. Interestingly, the tangential delocalized π orbitals of boron ligands following the Huckle's (4n + 2) rule do not interact with the central metal, while the radial π orbitals of boron ligands are bonded with the central mental to form spd-π endohedral bonding. The spd-π endohedral bonding follows the 18e-principle in Ni@B14 and Fe@B16. However, due to the flat shape of the compounds, 14e (Cr@B14) and 16e (Ni@B12) can also be electronically very stable where the energy levels of the spd-π orbitals delocalized in z-direction rise up. This intriguing bonding model makes sense in further study of the boron chemistry.

  15. Strongly Phosphorescent Transition Metal π-Complexes of Boron-Boron Triple Bonds.

    PubMed

    Braunschweig, Holger; Dellermann, Theresa; Dewhurst, Rian D; Hupp, Benjamin; Kramer, Thomas; Mattock, James D; Mies, Jan; Phukan, Ashwini K; Steffen, Andreas; Vargas, Alfredo

    2017-03-27

    Herein are reported the first π-complexes of compounds with boron-boron triple bonds with transition metals, in this case Cu(I). Three different compounds were isolated that differ in the number of copper atoms bound to the BB unit. Metalation of the B-B triple bonds causes lengthening of the B-B and B-C(NHC) bonds, as well as large upfield shifts of the (11)B NMR signals, suggesting greater orbital interactions between the boron and transition metal atoms than those observed with recently published diboryne/alkali metal cation complexes. In contrast to previously reported fluorescent copper(I) π-complexes of boron-boron double bonds, the Cun-π-diboryne compounds (n = 2, 3) show intense phosphorescence in the red to near-IR region from their triplet excited states, according to their microsecond lifetimes, with quantum yields of up to 58%. While the Cu diborene bond is dominated by electrostatic interactions, giving rise to S1 and T1 states of pure IL(π-π*) nature, DFT studies show that the Cu(I) π-complexes of diborynes reported herein exhibit enhanced metal d orbital contributions to HOMO and HOMO-1, which results in S1 and T1 having significant MLCT character, enabling strong spin-orbit coupling for highly efficient intersystem-crossing S1 → Tn and phosphorescence T1 → S0.

  16. Potential of using boric acid as a boron drug for boron neutron capture therapy for osteosarcoma.

    PubMed

    Hsu, C F; Lin, S Y; Peir, J J; Liao, J W; Lin, Y C; Chou, F I

    2011-12-01

    Osteosarcoma is a malignant tumor commonly found in human and animals. The ability of boric acid (BA) to accumulate in osteosarcoma due to the mechanism of the bone formation of cancer cells would make boron neutron capture therapy (BNCT) an alternative therapy for osteosarcoma. This study evaluated the feasibility of using BA as the boron drug for BNCT of bone cancer. The cytotoxicity of BA to L929 cells exceeded that of UMR-106 cells. With 25 μg (10)B/mL medium of BA treatment, the boron concentration in UMR-106 cells was higher than that in L929 cells. The biodistribution and pharmacokinetics of BA in Sprague-Dawley (SD) rats were studied by administrating 25 mg (10)B/kg body weight to SD rats. Blood boron level decreased rapidly within one hour after BA injection. Boron concentration in the long bone was 4-6 time higher than that of blood. Results of this study suggest that BA may be a potential drug for BNCT for osteosarcoma.

  17. Receptor-mediated uptake of boron-rich neuropeptide y analogues for boron neutron capture therapy.

    PubMed

    Ahrens, Verena M; Frank, René; Boehnke, Solveig; Schütz, Christian L; Hampel, Gabriele; Iffland, Dorothée S; Bings, Nicolas H; Hey-Hawkins, Evamarie; Beck-Sickinger, Annette G

    2015-01-01

    Peptidic ligands selectively targeting distinct G protein-coupled receptors that are highly expressed in tumor tissue represent a promising approach in drug delivery. Receptor-preferring analogues of neuropeptide Y (NPY) bind and activate the human Y1 receptor subtype (hY1 receptor), which is found in 90% of breast cancer tissue and in all breast-cancer-derived metastases. Herein, novel highly boron-loaded Y1 -receptor-preferring peptide analogues are described as smart shuttle systems for carbaboranes as (10) B-containing moieties. Various positions in the peptide were screened for their susceptibility to carbaborane modification, and the most promising positions were chosen to create a multi-carbaborane peptide containing 30 boron atoms per peptide with excellent activation and internalization patterns at the hY1 receptor. Boron uptake studies by inductively coupled plasma mass spectrometry revealed successful uptake of the multi-carbaborane peptide into hY1 -receptor-expressing cells, exceeding the required amount of 10(9) boron atoms per cell. This result demonstrates that the NPY/hY receptor system can act as an effective transport system for boron-containing moieties.

  18. Oxidation of boron nitride in an arc heated jet.

    NASA Technical Reports Server (NTRS)

    Buckley, J. D.

    1971-01-01

    Two grades of hot pressed boron nitride and a boron nitride composite were subjected to oxidation tests in a 2.5 megawatt atmospheric arc jet. The results showed that fabrication and/or composition influenced thermal shock and oxidation resistance. Changes in surface structure and recession due to oxidation suggest correlation with specimen composition. The boron nitride composite reacted with the oxygen in the hot subsonic airstream to produce a glassy coating on the hot face surface.

  19. Low-loss binder for hot pressing boron nitride

    DOEpatents

    Maya, Leon

    1991-01-01

    Borazine derivatives used as low-loss binders and precursors for making ceramic boron nitride structures. The derivative forms the same composition as the boron nitride starting material, thereby filling the voids with the same boron nitride material upon forming and hot pressing. The derivatives have a further advantage of being low in carbon thus resulting in less volatile byproduct that can result in bubble formation during pressing.

  20. Boron compounds as anion binding agents for nonaqueous battery electrolytes

    DOEpatents

    Lee, Hung Sui; Yang, Xia-Oing; McBreen, James; Xiang, Caili

    2000-02-08

    Novel fluorinated boron-based compounds which act as anion receptors in non-aqueous battery electrolytes are provided. When added to non-aqueous battery electrolytes, the fluorinated boron-based compounds of the invention enhance ionic conductivity and cation transference number of non-aqueous electrolytes. The fluorinated boron-based anion receptors include borane and borate compounds bearing different fluorinated alkyl and aryl groups.

  1. First Principles Atomistic Model for Carbon-Doped Boron Suboxide

    DTIC Science & Technology

    2014-09-01

    First Principles Atomistic Model for Carbon-Doped Boron Suboxide by Amol B Rahane, Jennifer S Dunn, and Vijay Kumar ARL-TR-7106...2014 First Principles Atomistic Model for Carbon-Doped Boron Suboxide Amol B Rahane Dr Vijay Kumar Foundation 1969 Sector 4 Gurgaon...Final 3. DATES COVERED (From - To) October 2013–July 2014 4. TITLE AND SUBTITLE First Principles Atomistic Model for Carbon-Doped Boron Suboxide

  2. Apparatus for the production of boron nitride nanotubes

    DOEpatents

    Smith, Michael W; Jordan, Kevin

    2014-06-17

    An apparatus for the large scale production of boron nitride nanotubes comprising; a pressure chamber containing; a continuously fed boron containing target; a source of thermal energy preferably a focused laser beam; a cooled condenser; a source of pressurized nitrogen gas; and a mechanism for extracting boron nitride nanotubes that are condensed on or in the area of the cooled condenser from the pressure chamber.

  3. Techniques for increasing boron fiber fracture strain

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1977-01-01

    Improvement in the strain-to-failure of CVD boron fibers is shown possible by contracting the tungsten boride core region and its inherent flaws. The results of three methods are presented in which etching and thermal processing techniques were employed to achieve core flaw contraction by internal stresses available in the boron sheath. After commercially and treatment induced surface flaws were removed from 203 micrometers (8 mil) fibers, the core flaw was observed to be essentially the only source of fiber fracture. Thus, fiber strain-to-failure was found to improve by an amount equal to the treatment induced contraction on the core flaw. Commercial feasibility considerations suggest as the most cost effective technique that method in which as-produced fibers are given a rapid heat treatment above 700 C. Preliminary results concerning the contraction kinetics and fracture behavior observed are presented and discussed both for high vacuum and argon gas heat treatment environments.

  4. Boron Nitride Nanotube: Synthesis and Applications

    NASA Technical Reports Server (NTRS)

    Tiano, Amanda L.; Park, Cheol; Lee, Joseph W.; Luong, Hoa H.; Gibbons, Luke J.; Chu, Sang-Hyon; Applin, Samantha I.; Gnoffo, Peter; Lowther, Sharon; Kim, Hyun Jung; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Kang, Jin Ho; Sauti, Godfrey; Thibeault, Sheila A.; Yamakov, Vesselin; Wise, Kristopher E.; Su, Ji; Fay, Catharine C.

    2014-01-01

    Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800 C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

  5. Boron nitride encapsulated graphene infrared emitters

    SciTech Connect

    Barnard, H. R.; Zossimova, E.; Mahlmeister, N. H.; Lawton, L. M.; Luxmoore, I. J.; Nash, G. R.

    2016-03-28

    The spatial and spectral characteristics of mid-infrared thermal emission from devices containing a large area multilayer graphene layer, encapsulated using hexagonal boron nitride, have been investigated. The devices were run continuously in air for over 1000 h, with the emission spectrum covering the absorption bands of many important gases. An approximate solution to the heat equation was used to simulate the measured emission profile across the devices yielding an estimated value of the characteristic length, which defines the exponential rise/fall of the temperature profile across the device, of 40 μm. This is much larger than values obtained in smaller exfoliated graphene devices and reflects the device geometry, and the increase in lateral heat conduction within the devices due to the multilayer graphene and boron nitride layers.

  6. Boron nitride nanotube: synthesis and applications

    NASA Astrophysics Data System (ADS)

    Tiano, Amanda L.; Park, Cheol; Lee, Joseph W.; Luong, Hoa H.; Gibbons, Luke J.; Chu, Sang-Hyon; Applin, Samantha; Gnoffo, Peter; Lowther, Sharon; Kim, Hyun Jung; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Kang, Jin Ho; Sauti, Godfrey; Thibeault, Sheila A.; Yamakov, Vesselin; Wise, Kristopher E.; Su, Ji; Fay, Catharine C.

    2014-04-01

    Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA/JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800°C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

  7. Boron-10 ABUNCL Models of Fuel Testing

    SciTech Connect

    Siciliano, Edward R.; Lintereur, Azaree T.; Kouzes, Richard T.; Ely, James H.

    2013-10-01

    The Department of Energy Office of Nuclear Safeguards and Security (NA-241) is supporting the project Coincidence Counting With Boron-Based Alternative Neutron Detection Technology at Pacific Northwest National Laboratory (PNNL) for the development of a 3He proportional counter alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a system based upon 10B-lined proportional tubes in a configuration typical for 3He-based coincidence counter applications. This report provides results from MCNP simulations of the General Electric Reuter-Stokes Alternative Boron-Based Uranium Neutron Coincidence Collar (ABUNCL) active configuration model with fuel pins previously measured at Los Alamos National Laboratory. A comparison of the GE-ABUNCL simulations and simulations of 3He based UNCL-II active counter (the system for which the GE-ABUNCL was targeted to replace) with the same fuel pin assemblies is also provided.

  8. Method for fabricating boron carbide articles

    DOEpatents

    Ardary, Zane L.; Reynolds, Carl D.

    1980-01-01

    The present invention is directed to the fabrication of boron carbide articles having length-to-diameter or width ratios greater than 2 to 1. The process of the present invention is practiced by the steps comprising hot pressing boron carbide powder into article segments or portions in which the segments have a length-to-diameter or width ratio less than 1.5, aligning a plurality of the initially hot-pressed segments in a hot-pressing die with the end surfaces of the segments placed in intimate contact with one another, and then hot pressing the aligned segments into an article of the desired configuration. The resulting article exhibits essentially uniform density throughout the structure with the bonds between the segments being equivalent in hardness, strength, and density to the remainder of the article.

  9. Boron nitride encapsulated graphene infrared emitters

    NASA Astrophysics Data System (ADS)

    Barnard, H. R.; Zossimova, E.; Mahlmeister, N. H.; Lawton, L. M.; Luxmoore, I. J.; Nash, G. R.

    2016-03-01

    The spatial and spectral characteristics of mid-infrared thermal emission from devices containing a large area multilayer graphene layer, encapsulated using hexagonal boron nitride, have been investigated. The devices were run continuously in air for over 1000 h, with the emission spectrum covering the absorption bands of many important gases. An approximate solution to the heat equation was used to simulate the measured emission profile across the devices yielding an estimated value of the characteristic length, which defines the exponential rise/fall of the temperature profile across the device, of 40 μm. This is much larger than values obtained in smaller exfoliated graphene devices and reflects the device geometry, and the increase in lateral heat conduction within the devices due to the multilayer graphene and boron nitride layers.

  10. Natural Radioactivity of Boron Added Clay Samples

    SciTech Connect

    Akkurt, I.; Guenoglu, K.; Canakcii, H.; Mavi, B.

    2011-12-26

    Clay, consisting fine-grained minerals, is an interesting materials and can be used in a variety of different fields especially in dermatology application. Using clay such a field it is important to measure its natural radioactivity. Thus the purpose of this study is to measure {sup 226}Ra, {sup 232}Th and {sup 40}K concentration in clay samples enriched with boron. Three different types of clay samples were prepared where boron is used in different rate. The measurements have been determined using a gamma-ray spectrometry consists of a 3''x3'' NaI(Tl) detector. From the measured activity the radium equivalent activities (Ra{sub eq}), external hazard index (H{sub ex}), absorbed dose rate in air (D) and annual effective dose (AED) have also been obtained.

  11. Nonlinear response of unidirectional boron/aluminum

    NASA Technical Reports Server (NTRS)

    Pindera, M.-J.; Herakovich, C. T.; Becker, W.; Aboudi, J.

    1990-01-01

    Experimental results obtained for unidirectional boron/aluminum subjected to combined loading using off-axis tension, compression and Iosipescu shear specimens are correlated with a nonlinear micromechanics model. It is illustrated that the nonlinear response in the principal material directions is markedly influenced by the different loading modes and different ratios of the applied stress components. The observed nonlinear response under pure and combined loading is discussed in terms of initial yielding, subsequent hardening, stress-interaction effects and unloading-reloading characteristics. The micromechanics model is based on the concept of a repeating unit cell representative of the composite-at-large and employs the unified theory of Bodner and Partom to model the inelastic response of the matrix. It is shown that the employed micromechanics model is sufficiently general to predict the observed nonlinear response of unidirectional boron/aluminum with good accuracy.

  12. Asymmetric twins in rhombohedral boron carbide

    SciTech Connect

    Fujita, Takeshi Guan, Pengfei; Madhav Reddy, K.; Hirata, Akihiko; Guo, Junjie; Chen, Mingwei

    2014-01-13

    Superhard materials consisting of light elements have recently received considerable attention because of their ultrahigh specific strength for a wide range of applications as structural and functional materials. However, the failure mechanisms of these materials subjected to high stresses and dynamic loading remain to be poorly known. We report asymmetric twins in a complex compound, boron carbide (B{sub 4}C), characterized by spherical-aberration-corrected transmission electron microscopy. The atomic structure of boron-rich icosahedra at rhombohedral vertices and cross-linked carbon-rich atomic chains can be clearly visualized, which reveals unusual asymmetric twins with detectable strains along the twin interfaces. This study offers atomic insights into the structure of twins in a complex material and has important implications in understanding the planar defect-related failure of superhard materials under high stresses and shock loading.

  13. Nonlinear response of unidirectional boron/aluminum

    NASA Technical Reports Server (NTRS)

    Pindera, M.-J.; Herakovich, C. T.; Becker, W.; Aboudi, J.

    1990-01-01

    Experimental results obtained for unidirectional boron/aluminum subjected to combined loading using off-axis tension, compression and Iosipescu shear specimens are correlated with a nonlinear micromechanics model. It is illustrated that the nonlinear response in the principal material directions is markedly influenced by the different loading modes and different ratios of the applied stress components. The observed nonlinear response under pure and combined loading is discussed in terms of initial yielding, subsequent hardening, stress-interaction effects and unloading-reloading characteristics. The micromechanics model is based on the concept of a repeating unit cell representative of the composite-at-large and employs the unified theory of Bodner and Partom to model the inelastic response of the matrix. It is shown that the employed micromechanics model is sufficiently general to predict the observed nonlinear response of unidirectional boron/aluminum with good accuracy.

  14. Natural Radioactivity of Boron Added Clay Samples

    NASA Astrophysics Data System (ADS)

    Akkurt, I.; ćanakciı, H.; Mavi, B.; Günoǧlu, K.

    2011-12-01

    Clay, consisting fine-grained minerals, is an interesting materials and can be used in a variety of diferent fields especially in dermatology application. Using clay such a field it is important to measure its natural radioacitivty. Thus the purpose of this study is to measure 226Ra, 232Th and 40K concentration in clay samples enriched with boron. Three different types of clay samples were prepared where boron is used in different rate. The measurements have been determined using a gamma-ray spectrometry consists of a 3″×3″ NaI(Tl) detector. From the measured activity the radium equivalent activities (Raeq), external hazard index (Hex), absorbed dose rate in air (D) and annual effective dose (AED) have also been obtained.

  15. Concentrations of Arsenic and Boron in Water, Sediment and the Tissues of Fish in Emet Stream (Turkey).

    PubMed

    Benzer, Semra

    2017-06-01

    In this study, the concentrations of arsenic and boron were determined in the water and the sediment, as well as in the muscle tissues of Squalius cephalus, Alburnoides bipunctatus, Barbus plebejus and Capoeta tinca from Emet Stream. The fish samples were caught in May 2011 and September 2012. The metal concentrations in the water samples were as follows: arsenic was 137.1-1002 µg L(-1), and boron was 2421-14490 µg L(-1). The metal concentrations in the sediment samples were as follows: arsenic was 14.51-3317.1 mg kg(-1), and boron was 14.22-1014.01 mg kg(-1). The mean tissue concentration of arsenic was lower than the TFC and WHO limits. Boron has been identified in fish tissues at concentrations between 0.26 and 2.96 mg kg(-1). The bioaccumulation in the muscle tissues of all fish species caught from Emet Stream did not exceed the limit values.

  16. Effect of dietary boron on the aging process.

    PubMed

    Massie, H R

    1994-11-01

    Total boron concentrations in Drosophila changed during development and aging. The highest concentration of boron was found during the egg stage, followed by a decline during the larval stages. Newly emerged flies contained 35.5 ppm boron. During the adult stage the boron concentration increased by 52% by 9 weeks of age. Adding excess dietary boron during the adult stage decreased the median life span by 69% at 0.01 M sodium borate and by 21% at 0.001 M sodium borate. Lower concentrations gave small but significant increases in life span. Supplementing a very low boron diet with 0.00025 M sodium borate improved life span by 9.5%. The boron contents of young and old mouse tissues were similar to those of Drosophila and human samples. Boron supplements of 4.3 and 21.6 ppm in the drinking water, however, did not significantly change the life span of old mice fed a diet containing 31.1 ppm boron.

  17. The prospects for composites based on boron fibers

    NASA Technical Reports Server (NTRS)

    Naslain, R.

    1978-01-01

    The fabrication of boron filaments and the production of composite materials consisting of boron filaments and organic or metallic matrices are discussed. Problem involving the use of tungsten substrates in the filament fabrication process, the protection of boron fibers with diffusion barrier cladings, and the application of alloy additives in the matrix to lessen the effects of diffusion are considered. Data on the kinetics of the boron fiber/matrix interaction at high temperatures, and the influence of the fiber/matrix interaction on the mechanical properties of the composite are presented.

  18. Ecological risk assessment of a wetland exposed to boron

    SciTech Connect

    Powell, R.L.; Kimerle, R.A.; Coyle, G.T.; Best, G.R.

    1997-11-01

    A wetland located in the southeastern portion of the United States was the site of an investigation to determine the potential ecological risk of elevated boron concentrations to the flora and fauna living in the wetland. The conceptual model identified the vegetation as the primary receptor of concern, and thus the vegetation is the focus of this article. Samples of surface water, sediments, and selected vegetation were collected from the study wetland and several nearby reference sites and were analyzed for boron. Concentrations of boron in all three media exceeded reference site concentrations. Boron concentrations were highest near the suspected source but decreased almost to reference-site concentrations near the outer perimeter of the wetland. Some plants appeared stressed with yellowing and necrotic leaves; however, a correlation between tissue boron concentrations and the plant`s visual appearance was not apparent for all species studied. Modeling of the fate of boron indicated that the wetland has likely been at a steady state for many years and that boron concentrations were not expected to increase. It was concluded that no observable adverse ecological impacts to the vegetation could be attributed to boron, nor is it likely that the boron poses an unacceptable risk to the surrounding areas.

  19. Annealing effects on the optical properties of semiconducting boron carbide

    SciTech Connect

    Billa, R. B.; Robertson, B. W.; Hofmann, T.; Schubert, M.

    2009-08-01

    Infrared vibrations of as-deposited and annealed semiconducting boron carbide thin films were investigated by midinfrared spectroscopic ellipsometry. The strong boron-hydrogen resonance at approx2560 cm{sup -1} in as-deposited films reveals considerable hydrogen incorporation during plasma-enhanced chemical vapor deposition. Extended annealing at 600 deg. C caused significant reduction in film thickness, substantial reduction of boron-hydrogen bond resonance absorption, and development of distinct blue-shifted boron-carbon and icosahedral vibration mode resonances. Our findings suggest that annealing results in substantial loss of hydrogen and in development of icosahedral structure, accompanied by strain relaxation and densification.

  20. Laser Boronizing of Stainless Steel with Direct Diode Laser

    NASA Astrophysics Data System (ADS)

    Kusuhara, Takayoshi; Morimoto, Junji; Abe, Nobuyuki; Tsukamoto, Masahiro

    Boronizing is a thermo-chemical surface treatment in which boron atoms are diffused into the surface of a work piece to form borides with the base material. When applied to the metallic materials, boronizing provides wear and abrasion resistance comparable to sintered carbides. However conventional boronizing is carried out at temperatures ranging from 800°C to 1050°C and takes from one to several hours. The structure and properties of the base material is influenced considerably by the high temperature and long treatment time. In order to avoid these drawbacks of conventional boronizing, laser-assisted boronizing is investigated which activates the conventional boronizing material and the work piece with a high density laser power. In this study, effect of laser characteristics was examined on the laser boronizing of stainless steel. After laser boronizing, the microstructure of the boride layer was analyzed with an optical microscope, electron probe micro analyser(EPMA) and X-ray diffractometer (XRD). The mechanical properties of borided layer were evaluated using Vickers hardness tester and sand erosion tester. Results showed that the boride layer was composed of NiB, CrB, FeB and Fe2B, and get wear resistance.

  1. Switchable Surface Wettability by Using Boronic Ester Chemistry.

    PubMed

    Taleb, Sabri; Noyer, Elisabeth; Godeau, Guilhem; Darmanin, Thierry; Guittard, Frédéric

    2016-01-18

    Here, we report for the first time the use of a boronic ester as an efficient tool for reversible surface post-functionalization. The boronic ester bond allows surfaces to be reversibly switched from hydrophilic to hydrophobic. Based on the well-known boronic acid/glycol affinity, this strategy offers the opportunity to play with surface hydrophobic properties by adding various boronic acids onto substrates bearing glycol groups. The post-functionalization can then be reversed to regenerate the starting glycol surface. This pathway allows for the preparation of various switchable surfaces for a large range of applications in biosensors, liquid transportation, and separation membranes.

  2. Boron diffusion in silicon from metal boride sources

    SciTech Connect

    Ryan, J.G.

    1988-01-01

    Thin films of titanium and lanthanum borides were investigated as potential boron diffusion sources. TiB{sub x} and LaB{sub 6} films exhibited room-temperature film stresses and resistivity values similar to refractory-metal silicides, and acted as boron diffusion sources, producing diffusions with high surface concentrations. The source of boron from TiB{sub x} films appears to be the excess boron present in the metal boride or at the metal boride-silicon substrate interface. Boron surface concentration increases with increasing mole fraction of boron in the metal boride source. Boron surface concentration peaks at 1000{degree}C for furnace-annealed TiB{sub 2.2}, but rises until a plateau is reached at 1050{degree}C for rapid-annealed samples of the same composition. The concentration of electrically active boron was consistently lower than the chemical concentration in these studies. The stability of the boride films on silicon substrates was found to be dependent on boride source composition. LaB{sub 6} and TiB films reacted with the silicon substrate. Although the TiB{sub 2.1}, TiB{sub 2.2}, and TiB{sub 2.9} films did not decompose or allow Si to diffuse into them, a silicon boride surface layer was formed in the silicon substrate caused by boron out-diffusing from these sources during furnace annealing.

  3. Electronic structures and transport properties of fluorinated boron nitride nanoribbons.

    PubMed

    Zeng, Jing; Chen, Ke-Qiu; Sun, Chang Q

    2012-06-14

    By applying the nonequilibrium Green's functions and the density-functional theory, we investigate the electronic structures and transport properties of fluorinated zigzag-edged boron nitride nanoribbons. The results show that the transition between half-metal and semiconductor in zigzag-edged boron nitride nanoribbons can be realized by fluorination at different sites or by the change of the fluorination level. Moreover, the negative differential resistance and varistor-type behaviors can also be observed in such fluorinated zigzag-edged boron nitride nanoribbon devices. Therefore, the fluorination of zigzag-edged boron nitride nanoribbons will provide the possibilities for a multifunctional molecular device design.

  4. Lateral gas phase diffusion length of boron atoms over Si/B surfaces during CVD of pure boron layers

    SciTech Connect

    Mohammadi, V. Nihtianov, S.

    2016-02-15

    The lateral gas phase diffusion length of boron atoms, L{sub B}, along silicon and boron surfaces during chemical vapor deposition (CVD) using diborane (B{sub 2}H{sub 6}) is reported. The value of L{sub B} is critical for reliable and uniform boron layer coverage. The presented information was obtained experimentally and confirmed analytically in the boron deposition temperature range from 700 °C down to 400 °C. For this temperature range the local loading effect of the boron deposition is investigated on the micro scale. A L{sub B} = 2.2 mm was determined for boron deposition at 700 °C, while a L{sub B} of less than 1 mm was observed at temperatures lower than 500 °C.

  5. Lateral gas phase diffusion length of boron atoms over Si/B surfaces during CVD of pure boron layers

    NASA Astrophysics Data System (ADS)

    Mohammadi, V.; Nihtianov, S.

    2016-02-01

    The lateral gas phase diffusion length of boron atoms, LB, along silicon and boron surfaces during chemical vapor deposition (CVD) using diborane (B2H6) is reported. The value of LB is critical for reliable and uniform boron layer coverage. The presented information was obtained experimentally and confirmed analytically in the boron deposition temperature range from 700 °C down to 400 °C. For this temperature range the local loading effect of the boron deposition is investigated on the micro scale. A LB = 2.2 mm was determined for boron deposition at 700 °C, while a LB of less than 1 mm was observed at temperatures lower than 500 °C.

  6. Explorations of mechanisms regulating ectomycorrhizal colonization of boron-fertilized pine: Quarterly report, January 1, 1988 to March 31, 1988

    SciTech Connect

    Garrett, H.E.; Reid, R.K.; Sword, M.A.

    1988-01-01

    This study was undertaken to determine if boron and IAA applied in combination to the roots of nonmycorrhizal shortleaf pine seedlings results in a greater downward flux of sucrose than when each is applied independently. Carbon 14 content of pine root systems were analysed as a complet randomized block experiment with 5 blocks, 4 IBA levels, and 4 boron levels. Originally, two time periods were included and analyzed as a split plot, but no difference in /sup 14/C content was found between the two times, and time was dropped as a effect and data combined for further analysis. The only effect on /sup 14/C transport to the roots was due to IAA concentration, but that effect was not as expected

  7. Production and Coating of Pure Boron Powders

    DTIC Science & Technology

    1990-03-30

    usually supersonic ; and causing that stream to impinge upon a surface, producing a shock wave, such that the aerosol particles strike the surface...McGraw-Hill, New York, 1960). 20. Donaldson, C.D., Snedeker, R.S., and Margolis, D.P., "A Study of Free Jet Impingement . Part 2. Free Jet Turbulent...products expanded through a supersonic nozzle, in which titanium tetrachloride is added to produce titanium. The titanium coats the boron particle. The

  8. Anomalous thermal conductivity of monolayer boron nitride

    SciTech Connect

    Tabarraei, Alireza Wang, Xiaonan

    2016-05-02

    In this paper, we use nonequilibrium molecular dynamics modeling to investigate the thermal properties of monolayer hexagonal boron nitride nanoribbons under uniaxial strain along their longitudinal axis. Our simulations predict that hexagonal boron nitride shows an anomalous thermal response to the applied uniaxial strain. Contrary to three dimensional materials, under uniaxial stretching, the thermal conductivity of boron nitride nanoribbons first increases rather than decreasing until it reaches its peak value and then starts decreasing. Under compressive strain, the thermal conductivity of monolayer boron nitride ribbons monolithically reduces rather than increasing. We use phonon spectrum and dispersion curves to investigate the mechanism responsible for the unexpected behavior. Our molecular dynamics modeling and density functional theory results show that application of longitudinal tensile strain leads to the reduction of the group velocities of longitudinal and transverse acoustic modes. Such a phonon softening mechanism acts to reduce the thermal conductivity of the nanoribbons. On the other hand, a significant increase in the group velocity (stiffening) of the flexural acoustic modes is observed, which counteracts the phonon softening effects of the longitudinal and transverse modes. The total thermal conductivity of the ribbons is a result of competition between these two mechanisms. At low tensile strain, the stiffening mechanism overcomes the softening mechanism which leads to an increase in the thermal conductivity. At higher tensile strain, the softening mechanism supersedes the stiffening and the thermal conductivity slightly reduces. Our simulations show that the decrease in the thermal conductivity under compressive strain is attributed to the formation of buckling defects which reduces the phonon mean free path.

  9. Immobilization of proteins on boron nitride nanotubes.

    PubMed

    Zhi, Chunyi; Bando, Yoshio; Tang, Chengchun; Golberg, Dmitri

    2005-12-14

    We report for the first time that proteins are immobilized on boron nitride nanotubes. It is found that there is a natural affinity of a protein to BNNT; this means that it can be immobilized on BNNT directly, without usage of an additional coupling reagent. For the most effective immobilization, noncovalently functionalized BNNTs should be used. The effect of immobilization was studied using high-resolution transmission electron microscopy and energy dispersion spectroscopy.

  10. Fuel-Solid Propellant Boron Combustion.

    DTIC Science & Technology

    1986-08-15

    vessels with differing initial oxygen levels, resulting in data with an unusably low signal-to-noise ratio. A burner and two-dimensional nozzle deice...were designed (and the burner constructed) for study of condensation of boron oxides and hydroxides (all to boric oxide, with elimination of hydrogen...composed of the burner /plenum/nozzle assembly developed during this investigation, and a test section, diffuser, heat-exchanger, particle scrubber and

  11. Anomalous thermal conductivity of monolayer boron nitride

    NASA Astrophysics Data System (ADS)

    Tabarraei, Alireza; Wang, Xiaonan

    2016-05-01

    In this paper, we use nonequilibrium molecular dynamics modeling to investigate the thermal properties of monolayer hexagonal boron nitride nanoribbons under uniaxial strain along their longitudinal axis. Our simulations predict that hexagonal boron nitride shows an anomalous thermal response to the applied uniaxial strain. Contrary to three dimensional materials, under uniaxial stretching, the thermal conductivity of boron nitride nanoribbons first increases rather than decreasing until it reaches its peak value and then starts decreasing. Under compressive strain, the thermal conductivity of monolayer boron nitride ribbons monolithically reduces rather than increasing. We use phonon spectrum and dispersion curves to investigate the mechanism responsible for the unexpected behavior. Our molecular dynamics modeling and density functional theory results show that application of longitudinal tensile strain leads to the reduction of the group velocities of longitudinal and transverse acoustic modes. Such a phonon softening mechanism acts to reduce the thermal conductivity of the nanoribbons. On the other hand, a significant increase in the group velocity (stiffening) of the flexural acoustic modes is observed, which counteracts the phonon softening effects of the longitudinal and transverse modes. The total thermal conductivity of the ribbons is a result of competition between these two mechanisms. At low tensile strain, the stiffening mechanism overcomes the softening mechanism which leads to an increase in the thermal conductivity. At higher tensile strain, the softening mechanism supersedes the stiffening and the thermal conductivity slightly reduces. Our simulations show that the decrease in the thermal conductivity under compressive strain is attributed to the formation of buckling defects which reduces the phonon mean free path.

  12. New nanoforms of carbon and boron nitride

    NASA Astrophysics Data System (ADS)

    Pokropivny, V. V.; Ivanovskii, A. L.

    2008-10-01

    Data on new carbon nanostructures including those based on fullerenes, nanotubes as well monolithic diamond-like nanoparticles, nanofibres, various nanocomposites, etc., published in the last decade are generalised. The experimental and theoretical data on their atomic and electronic structures, the nature of chemical bonds and physicochemical properties are discussed. These data are compared with the results obtained in studies of nanoforms of boron nitride, an isoelectronic analogue of carbon. Potential fields of applications of the new nanostructures are considered.

  13. Electron-Spin Resonance in Boron Carbide

    NASA Technical Reports Server (NTRS)

    Wood, Charles; Venturini, Eugene L.; Azevedo, Larry J.; Emin, David

    1987-01-01

    Samples exhibit Curie-law behavior in temperature range of 2 to 100 K. Technical paper presents studies of electron-spin resonance of samples of hot pressed B9 C, B15 C2, B13 C2, and B4 C. Boron carbide ceramics are refractory solids with high melting temperatures, low thermal conductives, and extreme hardnesses. They show promise as semiconductors at high temperatures and have unusually large figures of merit for use in thermoelectric generators.

  14. Boron-containing aptamers to ATP

    PubMed Central

    Lato, Susan M.; Ozerova, Nicole D. S.; He, Kaizhang; Sergueeva, Zinaida; Shaw, Barbara Ramsay; Burke, Donald H.

    2002-01-01

    Boron neutron capture therapy (BNCT), an experimental treatment for certain cancers, destroys only cells near the boron; however, there is a need to develop highly specific delivery agents. As nucleic acid aptamers recognize specific molecular targets, we investigated the influence of boronated nucleotide analogs on RNA function and on the systematic evolution of ligands by exponential enrichment (SELEX) process. Substitution of guanosine 5′-(α-P-borano) triphosphate (bG) for GTP or uridine 5′-(α-P-borano) triphosphate (bU) for UTP in several known aptamers diminished or eliminated target recognition by those RNAs. Specifically, ATP-binding aptamers containing the ζ-fold, which appears in several selections for adenosine aptamers, became inactive upon bG substitution but were only moderately affected by bU substitution. Selections were carried out using the bG or bU analogs with C8-linked ATP agarose as the binding target. The selections with bU and normal NTP yielded some ζ-fold aptamers, while the bG selection yielded none of this type. Non-ζ aptamers from bU and bG populations tolerated the borano substitution and many required it. The borano nucleotide requirement is specific; bU could not be used in bG-dependent aptamers nor vice versa. The borano group plays an essential role, as yet undefined, in target recognition or RNA structure. We conclude that the bG and bU nucleotides are fully compatible with SELEX, and that these analogs could be used to make boronated aptamers as therapeutics for BNCT. PMID:11884639

  15. Composite Reinforcement using Boron Nitride Nanotubes

    DTIC Science & Technology

    2016-11-15

    known to have desirable properties for use as a structural material. Metal atoms , tetra- atomic metal clusters and metal surfaces comprising Al, Ti...nitride nanotubes change with the presence of atomic oxygen were also carried out. 15.  SUBJECT TERMS Nanotubes, Boron Nitride, Composites, Theoretical...copper alloys are known to have desirable properties for use as a structural material. Metal atoms , tetra- atomic metal clusters and metal surfaces

  16. Photoelectron Spectroscopy of Aluminum Doped Boron Clusters

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  17. Catalytic Asymmetric Synthesis of Phosphine Boronates.

    PubMed

    Hornillos, Valentín; Vila, Carlos; Otten, Edwin; Feringa, Ben L

    2015-06-26

    The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of α,β-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good yields and high enantiomeric excess. The synthetic utility of the products is demonstrated through stereospecific transformations into multifunctional optically active compounds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

  19. Computational study of boron nitride nanotube synthesis: How catalyst morphology stabilizes the boron nitride bond

    NASA Astrophysics Data System (ADS)

    Riikonen, S.; Foster, A. S.; Krasheninnikov, A. V.; Nieminen, R. M.

    2009-10-01

    In an attempt to understand why catalytic methods for the growth of boron nitride nanotubes work much worse than for their carbon counterparts, we use first-principles calculations to study the energetics of elemental reactions forming N2 , B2 , and BN molecules on an iron catalyst. We observe that the local morphology of a step edge present in our nanoparticle model stabilizes the boron nitride molecule with respect to B2 due to the ability of the step edge to offer sites with different coordination simultaneously for nitrogen and boron. Our results emphasize the importance of atomic steps for a high yield chemical vapor deposition growth of BN nanotubes and may outline new directions for improving the efficiency of the method.

  20. Boron-carbide-aluminum and boron-carbide-reactive metal cermets

    DOEpatents

    Halverson, Danny C.; Pyzik, Aleksander J.; Aksay, Ilhan A.

    1986-01-01

    Hard, tough, lightweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidation step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modulus of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi.sqroot.in. These composites and methods can be used to form a variety of structural elements.

  1. Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

    SciTech Connect

    Singh, Bikramjeet; Singh, Paviter; Kumar, Akshay; Kumar, Manjeet; Thakur, Anup

    2015-05-15

    Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H{sub 3}BO{sub 3}). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT)

  2. Nanotwins soften boron-rich boron carbide (B13C2)

    NASA Astrophysics Data System (ADS)

    An, Qi; Goddard, William A.

    2017-03-01

    Extensive studies of metals and alloys have observed that nanotwins lead to strengthening, but the role of nanotwins in ceramics is not well established. We compare here the shear strength and the deformation mechanism of nanotwinned boron-rich boron carbide (B13C2) with the perfect crystal under both pure shear and biaxial shear deformations. We find that the intrinsic shear strength of crystalline B13C2 is higher than that of crystalline boron carbide (B4C). But nanotwins in B13C2 lower the strength, making it softer than crystalline B4C. This reduction in strength of nanotwinned B13C2 arises from the interaction of the twin boundary with the C-B-C chains that connect the B12 icosahedra.

  3. Synthesis of Sugar-Boronic Acid Derivatives: A Class of Potential Agents for Boron Neutron Capture Therapy.

    PubMed

    Imperio, Daniela; Del Grosso, Erika; Fallarini, Silvia; Lombardi, Grazia; Panza, Luigi

    2017-04-07

    To date, sugar analogues that contain boronic acids as substitutes for hydroxyl groups are a class of compounds nearly unknown in the literature. The challenging synthesis of two sugar-boronic acid analogues is described, and data are retrieved on their solution behavior, stability, and toxicity. As these compounds were expected to mimic the behavior of carbohydrates, they were tested in regards to their future development as potential boron neutron capture therapy agents.

  4. Synthesis and Characterization of a Boron-Nitrogen-Boron Zigzag-Edged Benzo[fg]tetracene Motif.

    PubMed

    Fingerle, Michael; Maichle-Mössmer, Cäcilia; Schundelmeier, Simon; Speiser, Bernd; Bettinger, Holger F

    2017-09-01

    The boron-nitrogen-boron (BNB) zigzag edged benzo[fg]tetracene is accessible from 4-butyl-2,6-diphenylaniline in four steps in good yields. The two mesityl groups stabilize the boron centers toward nucleophilic attack and result in two enantiomeric forms in the solid state. The title compound has a large optical gap, shows blue fluorescence, and is quite resistant toward oxidation and reduction.

  5. Boron impregnation treatment of Eucalyptus grandis wood.

    PubMed

    Dhamodaran, T K; Gnanaharan, R

    2007-08-01

    Eucalyptus grandis is suitable for small timber purposes, but its wood is reported to be non-durable and difficult to treat. Boron compounds being diffusible, and the vacuum-pressure impregnation (VPI) method being more suitable for industrial-scale treatment, the possibility of boron impregnation of partially dry to green timber was investigated using a 6% boric acid equivalent (BAE) solution of boric acid and borax in the ratio 1:1.5 under different treatment schedules. It was found that E. grandis wood, even in green condition, could be pressure treated to desired chemical dry salt retention (DSR) and penetration levels using 6% BAE solution. Up to a thickness of 50mm, in order to achieve a DSR of 5 kg/m(3) boron compounds, the desired DSR level as per the Indian Standard for perishable timbers for indoor use, it was found that neither the moisture content of wood nor the treatment schedule posed any problem as far as the treatability of E. grandis wood was concerned.

  6. ANALYSIS OF BORON DILUTION TRANSIENTS IN PWRS.

    SciTech Connect

    DIAMOND,D.J.BROMLEY,B.P.ARONSON,A.L.

    2004-02-04

    A study has been carried out with PARCS/RELAP5 to understand the consequences of hypothetical boron dilution events in pressurized water reactors. The scenarios of concern start with a small-break loss-of-coolant accident. If the event leads to boiling in the core and then the loss of natural circulation, a boron-free condensate can accumulate in the cold leg. The dilution event happens when natural circulation is re-established or a reactor coolant pump (RCP) is restarted in violation of operating procedures. This event is of particular concern in B&W reactors with a lowered-loop design and is a Generic Safety Issue for the U.S. Nuclear Regulatory Commission. The results of calculations with the reestablishment of natural circulation show that there is no unacceptable fuel damage. This is determined by calculating the maximum fuel pellet enthalpy, based on the three-dimensional model, and comparing it with the criterion for damage. The calculation is based on a model of a B&W reactor at beginning of the fuel cycle. If an RCP is restarted, unacceptable fuel damage may be possible in plants with sufficiently large volumes of boron-free condensate in the cold leg.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  8. Formation of boron nitride and boron carbide composite by nitrogen implantation at elevated temperature

    NASA Astrophysics Data System (ADS)

    Yu, N.; Romero-Borja, F.; Zhang, Z. H.; Cui, X. T.; Liu, J. R.; Wood, L. T.; Chu, W. K.; Marton, D.; Rabalais, J. W.; Forster, K. M.; Reeber, R. R.

    1993-09-01

    Boron carbide (B4C) is a wear resistant material with hardness slightly less than that of diamond. It has an excellent strength to weight ratio and relatively high toughness under controlled processing. These essential mechanical properties make B4C an ideal candidate for cutting tool and bearing applications. We will demonstrate that hexagonal boron nitride (h-BN), a good solid lubricant, can be formed on B4C surfaces through high temperature (850 °C) nitrogen ion implantation. The formation of composite B4C and h-BN on the B4C surface can potentially reduce surface friction coefficients, making the material more attractive for tribological applications.

  9. Roles of ATR1 paralogs YMR279c and YOR378w in boron stress tolerance.

    PubMed

    Bozdag, Gonensin Ozan; Uluisik, Irem; Gulculer, Gulce Sila; Karakaya, Huseyin C; Koc, Ahmet

    2011-06-17

    Boron is a necessary nutrient for plants and animals, however excess of it causes toxicity. Previously, Atr1 and Arabidopsis Bor1 homolog were identified as the boron efflux pump in yeast, which lower the cytosolic boron concentration and help cells to survive in the presence of toxic amount of boron. In this study, we analyzed ATR1 paralogs, YMR279c and YOR378w, to understand whether they participate in boron stress tolerance in yeast. Even though these genes share homology with ATR1, neither their deletion rendered cells boron sensitive nor their expression was significantly upregulated by boron treatment. However, expression of YMR279, but not YOR378w, from the constitutive GAPDH promoter on a high copy plasmid provided remarkable boron resistance by decreasing intracellular boron levels. Thus our results suggest the presence of a third boron exporter, YMR279c, which functions similar to ATR1 and provides boron resistance in yeast.

  10. Chemical disposition of boron in animals and humans.

    PubMed Central

    Moseman, R F

    1994-01-01

    Elemental boron was isolated in 1808. It typically occurs in nature as borates hydrated with varying amounts of water. Important compounds are boric acid and borax. Boron compounds are also used in the production of metals, enamels, and glasses. In trace amounts, boron is essential for the growth of many plants, and is found in animal and human tissues at low concentrations. Poisoning in humans has been reported as the result of accidental ingestion or use of large amounts in the treatment of burns. Boron as boric acid is fairly rapidly absorbed and excreted from the body via urine. The half-life of boric acid in humans is on the order of 1 day. Boron does not appear to accumulate in soft tissues of animals, but does accumulate in bone. Normal levels of boron in soft tissues, urine, and blood generally range from less than 0.05 ppm to no more than 10 ppm. In poisoning incidents, the amount of boric acid in brain and liver tissue has been reported to be as high as 2000 ppm. Recent studies at the National Institute of Environmental Health Sciences have indicated that boron may contribute to reduced fertility in male rodents fed 9000 ppm of boric acid in feed. Within a few days, boron levels in blood and most soft tissues quickly reached a plateau of about 15 ppm. Boron in bone did not appear to plateau, reaching 47 ppm after 7 days on the diet. Cessation of exposure to dietary boron resulted in a rapid drop in bone boron.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7889870

  11. Model studies directed toward the boron neutron-capture therapy of cancer: boron delivery to murine tumors with liposomes.

    PubMed Central

    Shelly, K; Feakes, D A; Hawthorne, M F; Schmidt, P G; Krisch, T A; Bauer, W F

    1992-01-01

    The successful treatment of cancer by boron neutron-capture therapy (BNCT) requires the selective concentration of boron-10 within malignant tumors. The potential of liposomes to deliver boron-rich compounds to tumors has been assessed by the examination of the biodistribution of boron delivered by liposomes in tumor-bearing mice. Small unilamellar vesicles with mean diameters of 70 nm or less, composed of a pure synthetic phospholipid (distearoyl phosphatidylcholine) and cholesterol, have been found to stably encapsulate high concentrations of water-soluble ionic boron compounds. The hydrolytically stable borane anions B10H10(2-), B12H11SH2-, B20H17OH4-, B20H19(3-), and the normal form and photoisomer of B20H18(2-) were encapsulated in liposomes as their soluble sodium salts. The tissue concentration of boron in tumor-bearing mice was measured at several time points over 48 h after i.v. injection of emulsions of liposomes containing the borane anions. Although the boron compounds used do not exhibit an affinity for tumors and are normally rapidly cleared from the body, liposomes were observed to selectively deliver the borane anions to tumors. The highest tumor concentrations achieved reached the therapeutic range (greater than 15 micrograms of boron per g of tumor) while maintaining high tumor-boron/blood-boron ratios (greater than 3). The most favorable results were obtained with the two isomers of B20H18(2-). These boron compounds have the capability to react with intracellular components after they have been deposited within tumor cells by the liposome, thereby preventing the borane ion from being released into blood. PMID:1409600

  12. Interactions of ion-implantation-induced interstitials with boron at high concentrations in silicon

    SciTech Connect

    Haynes, T.E.; Eaglesham, D.J.; Stolk, P.A.; Gossmann, H.; Jacobson, D.C.; Poate, J.M.

    1996-09-01

    Ion implantation of Si (60 keV, 1{times}10{sup 14}/cm{sup 2}) has been used to introduce excess interstitials into silicon predoped with high background concentrations of B, which were varied between 1{times}10{sup 18} and 1{times}10{sup 19}/cm{sup 3}. Following post-implantation annealing at 740{degree}C for 15 min to allow agglomeration of the available interstitials into elongated {l_brace}311{r_brace} defects, the density of the agglomerated interstitials was determined by plan-view transmission electron microscopy observation of the defects. We report a significant reduction in the fraction of excess interstitials trapped in {l_brace}311{r_brace} defects as a function of boron concentration, up to nearly complete disappearance of the {l_brace}311{r_brace} defects at boron concentrations of 1{times}10{sup 19}/cm{sup 3}. The reduction of the excess interstitial concentration is interpreted in terms of boron-interstitial clustering, and implications for transient-enhanced diffusion of B at high concentrations are discussed. {copyright} {ital 1996 American Institute of Physics.}

  13. Thermodynamic stability of boron: the role of defects and zero point motion.

    PubMed

    van Setten, Michiel J; Uijttewaal, Matthé A; de Wijs, Gilles A; de Groot, Robert A

    2007-03-07

    Its low weight, high melting point, and large degree of hardness make elemental boron a technologically interesting material. The large number of allotropes, mostly containing over a hundred atoms in the unit cell, and their difficult characterization challenge both experimentalists and theoreticians. Even the ground state of this element is still under discussion. For over 30 years, scientists have attempted to determine the relative stability of alpha- and beta-rhombohedral boron. We use density functional calculations in the generalized gradient approximation to study a broad range of possible beta-rhombohedral structures containing interstitial atoms and partially occupied sites within a 105 atoms framework. The two most stable structures are practically degenerate in energy and semiconducting. One contains the experimental 320 atoms in the hexagonal unit cell, and the other contains 106 atoms in the triclinic unit cell. When populated with the experimental 320 electrons, the 106 atom structure exhibits a band gap of 1.4 eV and an in-gap hole trap at 0.35 eV above the valence band, consistent with known experiments. The total energy of these two structures is 23 meV/B lower than the original 105 atom framework, but it is still 1 meV/B above the alpha phase. Adding zero point energies finally makes the beta phase the ground state of elemental boron by 3 meV/B. At finite temperatures, the difference becomes even larger.

  14. Boron diffusion across the dialysis membrane during hemodialysis.

    PubMed

    Usuda, K; Kono, K; Nishiura, K; Miyata, K; Nishiura, H; Saito, M; Goto, E; Nakaya, H

    1997-01-01

    To investigate the movement of boron across the dialysis membrane, serum and dialysate boron levels of long-term hemodialysis (HD) patients (n = 17) were determined using inductively coupled plasma emission spectrometry in both the inlet and the outlet side of the dialyzer. Results revealed that 77.8% of the serum boron in the inlet side of the dialyzer was filterable and 94.4% of filterable boron was actually filtered during HD. Boron dialysance was found to be 138.6 +/- 16.1 ml/min, and this value was higher than the clearance value of blood urea nitrogen (not significant), phosphorus and creatinine (p < 0.001). It is concluded that HD is effective in eliminating serum boron even at low concentrations, and boron can be classified as an element that is easily diffusible across the dialysis membrane. There seems to be relatively little relation of boron to serum constituents of macromolecules that are reported to have a major impact on the diffusion of trace elements across the HD membrane.

  15. Growing evidence for human health benefits of boron

    USDA-ARS?s Scientific Manuscript database

    Growing evidence from numerous laboratories using a variety of experimental models shows that boron is a bioactive beneficial, perhaps essential, element for humans. Reported beneficial actions of boron include arthritis alleviation or risk reduction; bone growth and maintenance; central nervous sys...

  16. Boron containing amino acid compounds and methods for their use

    DOEpatents

    Glass, John D.; Coderre, Jeffrey A.

    2000-01-01

    The present invention provides new boron containing amino acid compounds and methods for making these compounds by contacting melphalan or another nitrogen mustard derivative and sodium borocaptate. The present invention also provides a method of treating a mammal having a tumor by administering to the mammal a therapeutically effective amount of the new boron containing amino acid compounds.

  17. RADIATION PROTECTION THROUGH BORON-CONTAINING CEMENTS AND CONCRETES

    DTIC Science & Technology

    WATER-SOLUBLE BORON COMPOUNDS, SUCH AS BORIC ACID OR BORAX , RETARDS THE SETTING OF CEMENT AND IMPAIRS THE MECHANICAL STRENGTH OF CONCRETE. The...deterioration was found to depend on the quantity of boron introduced, regardless of whether it is in the acid form ( boric acid ) or the alkaline form ( borax

  18. Boron diffusion in nanocrystalline 3C-SiC

    SciTech Connect

    Schnabel, Manuel; Weiss, Charlotte; Rachow, Thomas; Löper, Philipp; Janz, Stefan; Canino, Mariaconcetta; Summonte, Caterina; Mirabella, Salvo; Wilshaw, Peter R.

    2014-05-26

    The diffusion of boron in nanocrystalline silicon carbide (nc-SiC) films with a grain size of 4–7 nm is studied using a poly-Si boron source. Diffusion is found to be much faster than in monocrystalline SiC as it takes place within the grain boundary (GB) network. Drive-in temperatures of 900–1000°C are suitable for creating shallow boron profiles up to 100 nm deep, while 1100°C is sufficient to flood the 200 nm thick films with boron. From the resulting plateau at 1100 °C a boron segregation coefficient of 28 between nc-SiC and the Si substrate, as well as a GB boron solubility limit of 0.2 nm{sup −2} is determined. GB diffusion in the bulk of the films is Fickian and thermally activated with D{sub GB}(T)=(3.1−5.6)×10{sup 7}exp(−5.03±0.16  eV/k{sub B}T) cm{sup 2}s{sup −1}. The activation energy is interpreted in terms of a trapping mechanism at dangling bonds. Higher boron concentrations are present at the nc-SiC surface and are attributed to immobilized boron.

  19. Modelling boron-lined proportional counter response to neutrons.

    PubMed

    Shahri, A; Ghal-Eh, N; Etaati, G R

    2013-09-01

    The detailed Monte Carlo simulation of a boron-lined proportional counter response to a neutron source has been presented. The MCNP4C and experimental data on different source-moderator geometries have been given for comparison. The influence of different irradiation geometries and boron-lining thicknesses on the detector response has been studied.

  20. Boron as a tracer of aerosol from combustion of coal

    NASA Astrophysics Data System (ADS)

    Fogg, Thomas R.; Rahn, Kenneth A.

    1984-09-01

    Atmospheric boron was found to be predominantly gaseous in ambient samples and in stacks of coal-fired power plants. Typical gas/particulate ratios ranged from 20 to more than 100, with stack ratios above 100 and ambient ratios generally below 100. In the stacks, B/SO2 ratios were lower than expected from bulk U.S. coals, consistent with volatilization of 20-80 percent of the boron during combustion. Midwestern ambient B/SO2 ratios were at or above stack values, with the lowest ratios associated with highest concentrations. SO2 was always more variable than gaseous boron. These observations are consistent with coal combustion as the major source of atmospheric boron (and SO2) in the Midwest. In northern Vermont, concentrations of gaseous boron and SO2 were several times lower than in the Midwest, but the B/SO2 ratio was several times higher. Both species passed through quasiweekly in-phase cycles of concentration with the relative amplitudes being greater for SO2 than for gaseous boron. All major pulses of boron and SO2 came from the direction of the Midwest, on the backsides of high-pressure areas. Since the ocean is also a source of gaseous boron, its anthropogenic tracer potential for acid deposition studies will be most useful in the interior of continents.

  1. Method for removal of phosgene from boron trichloride

    DOEpatents

    Freund, S.M.

    1983-09-20

    Selective ultraviolet photolysis using an unfiltered mercury arc lamp has been used to substantially reduce the phosgene impurity in a mixture of boron trichloride and phosgene. Infrared spectrophotometric analysis of the sample before and after irradiation shows that it is possible to highly purify commercially available boron trichloride with this method. 5 figs.

  2. Determination of boron in silicates after ion exchange separation

    USGS Publications Warehouse

    Kramer, H.

    1955-01-01

    Existing methods for the determination of boron in silicates are not entirely satisfactory. Separation as the methyl ester is lengthy and frequently erratic. An accurate and rapid method applicable to glass, mineral, ore, and water samples uses ion exchange to remove interfering cations, and boron is determined titrimetrically in the presence of mannitol, using a pH meter to indicate the end point.

  3. Low-dimensional boron structures based on icosahedron B12

    NASA Astrophysics Data System (ADS)

    Kah, C. B.; Yu, M.; Tandy, P.; Jayanthi, C. S.; Wu, S. Y.

    2015-10-01

    One-dimensional icosahedral boron chains and two-dimensional icosahedral boron sheets (icosahedral α, δ6, and δ4 sheets) that contain icosahedra B12 as their building units have been predicted in a computer simulation study using a state-of-the-art semi-empirical Hamiltonian. These novel low-dimensional icosahedral structures exhibit interesting bonding and electronic properties. Specifically, the three-center, two-electron bonding between icosahedra B12 of the boron bulk (rhombohedral boron) transforms into a two-center bonding in these new allotropes of boron sheets. In contrast to the previously reported stable buckled α and triangular boron monolayer sheets, these new allotropes of boron sheets form a planar network. Calculations of electronic density of states (DOS) reveal a semiconducting nature for both the icosahedral chain and the icosahedral δ6 and δ4 sheets, as well as a nearly gapless (or metallic-like) feature in the DOS for the icosahedral α sheet. The results for the energy barrier per atom between the icosahedral δ6 and α sheets (0.17 eV), the icosahedral δ6 and δ4 sheets (0.38 eV), and the icosahedral α and δ4 sheets (0.27 eV), as indicated in the respective parentheses, suggest that these new allotropes of boron sheets are relatively stable.

  4. Predicted phase diagram of boron-carbon-nitrogen

    NASA Astrophysics Data System (ADS)

    Zhang, Hantao; Yao, Sanxi; Widom, Michael

    2016-04-01

    Noting the structural relationships between phases of carbon and boron carbide with phases of boron nitride and boron subnitride, we investigate their mutual solubilities using a combination of first-principles total energies supplemented with statistical mechanics to address finite temperatures. Thus we predict the solid-state phase diagram of boron-carbon-nitrogen (B-C-N). Owing to the large energy costs of substitution, we find that the mutual solubilities of the ultrahard materials diamond and cubic boron nitride are negligible, and the same for the quasi-two-dimensional materials graphite and hexagonal boron nitride. In contrast, we find a continuous range of solubility connecting boron carbide to boron subnitride at elevated temperatures. An electron-precise ternary compound B13CN consisting of B12 icosahedra with NBC chains is found to be stable at all temperatures up to melting. It exhibits an order-disorder transition in the orientation of NBC chains at approximately T =500 K. We also propose that the recently discovered binary B13N2 actually has composition B12.67N2 .

  5. Progress in preparation, properties and application of boron nitride nanomaterials

    NASA Astrophysics Data System (ADS)

    Wang, Youjun; Han, Jiaqi; Li, Yanjiao; Chen, Hao

    2017-08-01

    Boron nitride nanomaterials have attracted much and more interest in scientific research workers because of their excellent physical and chemical properties. They have become an important research hotspot in today's materials field. In this paper, boron nitride nanoparticles, "fullerenes", nanotubes, nanoribbons and Nano sheets were reviewed in terms of preparation methods, properties and potential applications.

  6. Boron as a platform for new drug design.

    PubMed

    Ciani, Laura; Ristori, Sandra

    2012-11-01

    Boron lies on the borderline between metals and non-metals in the periodic table. As such, it possesses peculiarities which render it suitable for a variety of applications in chemistry, technology and medicine. However, boron's peculiarities have been exploited only partially so far. In this review, the authors highlight selected areas of research which have witnessed new uses of boron compounds in recent times. The examples reported illustrate how difficulties in the synthesis and physicochemical characterization of boronated molecules, encountered in past years, can be overcome with positive effects in different fields. Many potentialities of boron-based systems reside in the peculiar properties of both boron atoms (the ability to replace carbon atoms, electron deficiency) and of boronated compounds (hydrophobicity, lipophilicity, versatile stereochemistry). Taken in conjunction, these properties can provide innovative drugs. The authors highlight the need to further investigate the assembly of boronated compounds, in terms of drug design, since the mechanisms required to obtain supramolecular structures may be unconventional compared with the more standard molecules used. Furthermore, the authors propose that computational methods are a valuable tool for assessing the role of multicenter, quasi-aromatic bonds and its peculiar geometries.

  7. Method for removal of phosgene from boron trichloride

    SciTech Connect

    Freund, Samuel M.

    1983-01-01

    Selective ultraviolet photolysis using an unfiltered mercury arc lamp has been used to substantially reduce the phosgene impurity in a mixture of boron trichloride and phosgene. Infrared spectrophotometric analysis of the sample before and after irradiation shows that is is possible to highly purify commercially available boron trichloride with this method.

  8. Boron trichloride purification with a KrF excimer laser

    SciTech Connect

    Hyer, R.C.; Hartford, A. Jr.; Atencio, J.H.

    1980-01-01

    Selective ultraviolet photolysis using a KrF excimer laser has been used to substantially reduce the phosgene impurity in a binary mixture of boron trichloride and phosgene. Infrared spectroscopic analysis of the sample before and after irradiation shows that it is possible to highly purify commercially available boron trichloride with this technique.

  9. Boron Diffusion in Surface-Treated Framing Lumber

    Treesearch

    Patricia K. Lebow; Stan T. Lebow; Steven A. Halverson

    2013-01-01

    The extent of boron penetration in framing lumber treated by spray applications during construction is not well quantified. This study evaluated the effect of formulation and concentration on diffusion of boron in lumber specimens that were equilibrated in conditions that produced wood moisture contents of 18 to 21 percent. One set of specimens was pressure treated...

  10. Effect of boron on carbon-fiber microstructure and reactivity

    SciTech Connect

    Jones, L.E.

    1987-01-01

    A mesophase pitch P55 and a PAN T-300 carbon filter were substitutionally doped with boron at concentration levels ranging from 4 x 10/sup -5/ to 0.05 B/C atom ratio. Boron enhanced graphitization in these fibers at concentrations greater than 2 x 10/sup -4/ B/C. Below this concentration level, the microstructure of the pitch P55 fiber was unaffected. High concentrations of boron were found to modulate the (001) diffraction profiles in both fibers. This indicated the presence of two separate graphite fractions in the same fiber (one fraction was much more turbostratic than the other). The presence of boron was also found to increase the L/sub c/ and decrease the L/sub a/ dimensions of the more graphitic fractions of the fiber structure. The decrease in the L/sub a/ is the result of an increase in tilt boundaries along the a direction, parallel to the fiber axis. The presence of boron inhibits fiber gasification. The cause of gasification inhibition at high boron concentrations is related to changes in the fiber microstructure; however, there is a pronounced effect of specific-site blockage by an oxide of boron that develops on the surface during gasification. At relatively low boron concentrations, decrease in the reactivity of the fiber was correlated to changes in fiber electronic structure which, in turn, influences the chemistry of the active surface sites.

  11. BORON NITRIDE CAPACITORS FOR ADVANCED POWER ELECTRONIC DEVICES

    SciTech Connect

    N. Badi; D. Starikov; C. Boney; A. Bensaoula; D. Johnstone

    2010-11-01

    This project fabricates long-life boron nitride/boron oxynitride thin film -based capacitors for advanced SiC power electronics with a broad operating temperature range using a physical vapor deposition (PVD) technique. The use of vapor deposition provides for precise control and quality material formation.

  12. Synthesis, characterization, and antifungal activity of boron-containing thiosemicarbazones.

    PubMed

    Hicks, Justin W; Kyle, Christian B; Vogels, Christopher M; Wheaton, Susan L; Baerlocher, Felix J; Decken, Andreas; Westcott, Stephen A

    2008-11-01

    Addition of thiosemicarbazide, 4-allylthiosemicarbazide, and 4-phenylthiosemicarbazide to (formylphenyl)boronic acids affords a series of thiosemicarbazones containing boronic acids. Addition of 2-formylphenylboronic acid to the thiosemicarbazides gave the corresponding cyclic 2,3,1-benzodiazaborines. All new compounds have been investigated for potential antifungal activity.

  13. Predicting Boron, Molybdenum, Selenium, and Arsenic Adsorption in Soil Systems

    USDA-ARS?s Scientific Manuscript database

    A chemical surface complexation model was applied to boron, molybdenum, selenium, and arsenic adsorption on up to 49 soils selected for variation in soil properties. The surface complexation model was able to fit boron, molybdenum, selenite, and arsenate adsorption on the soils. General regression...

  14. Boron containing amino acid compounds and methods for their use

    SciTech Connect

    Glass, J.D.; Coderre, J.A.

    2000-01-25

    The present invention provides new boron containing amino acid compounds and methods for making these compounds by contacting melphalan or another nitrogen mustard derivative and sodium borocaptate. The present invention also provides a method of treating a mammal having a tumor by administering to the mammal a therapeutically effective amount of the new boron containing amino acid compounds.

  15. Boron Investigation Survey, March Air Force Base, California

    DTIC Science & Technology

    1992-07-01

    for boron recommend 0.75 mg/l for long-term irrigation on sensitive crops(5). A common source of boron is soap containing sodium borate or perborate ...Sodium perborate (Eodium metaborate peroxyhvdrate--NaB0 2 3H20) is a bleaching powder found in many soaps. It is frequently listed as a perborate bleach

  16. Ionic high-pressure form of elemental boron.

    PubMed

    Oganov, Artem R; Chen, Jiuhua; Gatti, Carlo; Ma, Yanzhang; Ma, Yanming; Glass, Colin W; Liu, Zhenxian; Yu, Tony; Kurakevych, Oleksandr O; Solozhenko, Vladimir L

    2009-02-12

    Boron is an element of fascinating chemical complexity. Controversies have shrouded this element since its discovery was announced in 1808: the new 'element' turned out to be a compound containing less than 60-70% of boron, and it was not until 1909 that 99% pure boron was obtained. And although we now know of at least 16 polymorphs, the stable phase of boron is not yet experimentally established even at ambient conditions. Boron's complexities arise from frustration: situated between metals and insulators in the periodic table, boron has only three valence electrons, which would favour metallicity, but they are sufficiently localized that insulating states emerge. However, this subtle balance between metallic and insulating states is easily shifted by pressure, temperature and impurities. Here we report the results of high-pressure experiments and ab initio evolutionary crystal structure predictions that explore the structural stability of boron under pressure and, strikingly, reveal a partially ionic high-pressure boron phase. This new phase is stable between 19 and 89 GPa, can be quenched to ambient conditions, and has a hitherto unknown structure (space group Pnnm, 28 atoms in the unit cell) consisting of icosahedral B(12) clusters and B(2) pairs in a NaCl-type arrangement. We find that the ionicity of the phase affects its electronic bandgap, infrared adsorption and dielectric constants, and that it arises from the different electronic properties of the B(2) pairs and B(12) clusters and the resultant charge transfer between them.

  17. Boron distribution and the effect of lime on boron uptake by pansy, petunia, and gerbera plants

    USDA-ARS?s Scientific Manuscript database

    Reports of boron (B) deficiency have become more prevalent in pansy (Viola ×wittrockiana), petunia (Petunia ×hybrida), and gerbera (Gerbera jamesonii) plug production. When symptoms are observed in production the presence and severity of symptoms have no pattern, symptomatic plants can be located a...

  18. Isotopic Enrichment of Boron in the Sputtering of Boron Nitride with Xenon Ions

    NASA Technical Reports Server (NTRS)

    Ray, P. K.; Shutthanandan, V.

    1998-01-01

    An experimental study is described to measure the isotopic enrichment of boron. Xenon ions from 100 eV to 1.5 keV were used to sputter a boron nitride target. An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 microA/sq cm. Xenon ions impinged on the target surface at 50 deg angle to the surface normal. Since boron nitride is an insulator, a flood electron gun was used in our experiments to neutralize the positive charge buildup on the target surface. The sputtered secondary ions of boron were detected by a quadrupole mass spectrometer. The spectrometer entrance aperture was located perpendicular to the ion beam direction and 10 mm away from the target surface. The secondary ion flux was observed to be enriched in the heavy isotopes at lower ion energies. The proportion of heavy isotopes in the sputtered secondary ion flux was found to decrease with increasing primary ion energy from 100 to 350 eV. Beyond 350 eV, light isotopes were sputtered preferentially. The light isotope enrichment factor was observed to reach an asymptotic value of 1.27 at 1.5 keV. This trend is similar to that of the isotopic enrichment observed earlier when copper was sputtered with xenon ions in the same energy range.

  19. Isotopic Enrichment of Boron in the Sputtering of Boron Nitride with Xenon Ions

    NASA Technical Reports Server (NTRS)

    Ray, P. K.; Shutthanandan, V.

    1998-01-01

    An experimental study is described to measure the isotopic enrichment of boron. Xenon ions from 100 eV to 1.5 keV were used to sputter a boron nitride target. An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 microA/sq cm. Xenon ions impinged on the target surface at 50 deg angle to the surface normal. Since boron nitride is an insulator, a flood electron gun was used in our experiments to neutralize the positive charge buildup on the target surface. The sputtered secondary ions of boron were detected by a quadrupole mass spectrometer. The spectrometer entrance aperture was located perpendicular to the ion beam direction and 10 mm away from the target surface. The secondary ion flux was observed to be enriched in the heavy isotopes at lower ion energies. The proportion of heavy isotopes in the sputtered secondary ion flux was found to decrease with increasing primary ion energy from 100 to 350 eV. Beyond 350 eV, light isotopes were sputtered preferentially. The light isotope enrichment factor was observed to reach an asymptotic value of 1.27 at 1.5 keV. This trend is similar to that of the isotopic enrichment observed earlier when copper was sputtered with xenon ions in the same energy range.

  20. Elastic properties of various boron-nitride structures

    NASA Astrophysics Data System (ADS)

    Oh, Eun-Suok

    2011-02-01

    The stress-deformation behaviors derived from the continuum-lattice thermodynamic approach were applied to estimate the elastic properties of various boron-nitride crystals, such as boron-nitride sheets and nanotubes as well as cubic boron-nitride. The Tersoff and Tersoff-like potentials were used to describe the interatomic bond potential for the boron-nitride crystals. In this study, three sets of the Tersoff potential parameters and two sets of the Tersoff-like potential parameters from the literature were employed. Both the Tersoff potential parameters proposed by Matsunaga et al. and the Tersoff-like potential parameters proposed by Oh were best for estimating the elastic properties of boron-nitride nanotubes, including a sheet. Meanwhile, the elastic constants of c-BN calculated by the Tersoff potential parameters proposed by Sekkal et al. and the Tersofflike potential parameters proposed by Albe and Moller were in good agreement with experimental and other quantumistic calculation results.

  1. Boron Partitioning Coefficient above Unity in Laser Crystallized Silicon

    PubMed Central

    Lill, Patrick C.; Dahlinger, Morris; Köhler, Jürgen R.

    2017-01-01

    Boron pile-up at the maximum melt depth for laser melt annealing of implanted silicon has been reported in numerous papers. The present contribution examines the boron accumulation in a laser doping setting, without dopants initially incorporated in the silicon wafer. Our numerical simulation models laser-induced melting as well as dopant diffusion, and excellently reproduces the secondary ion mass spectroscopy-measured boron profiles. We determine a partitioning coefficient kp above unity with kp=1.25±0.05 and thermally-activated diffusivity DB, with a value DB(1687K)=(3.53±0.44)×10−4 cm2·s−1 of boron in liquid silicon. For similar laser parameters and process conditions, our model predicts the anticipated boron profile of a laser doping experiment. PMID:28772548

  2. Boron Carbide Deposition on Urania and Urania-Gadolinia Fuels

    SciTech Connect

    Disbudak, H.; Uslu, I.; Bilgesu, A.Y.; Guenduez, G.

    2001-09-15

    Pure uranium dioxide and uranium dioxide-gadolinium oxide (5 and 10%) fuels used in this study were prepared by the solution-gelation (sol-gel) technique. The fuels were then coated with boron carbide by chemical vapor deposition. Boron carbide was produced from the reaction of carbon tetrachloride and boron trichloride with excess hydrogen, in a tube furnace at 1000, 1100, and 1175 deg. C. The Fourier transform infrared data of boron carbide deposited on a silica glass were in agreement with the ones in the literature. The experiments showed that the composition of the coating changed with deposition temperature. There was boron-rich coating at low-temperature deposition, and carbon-rich coating at high-temperature deposition. The morphology and the thickness of the coating have been investigated by using scanning electron microscopy and X-ray diffraction spectroscopy.

  3. Advancements in Tumor Targeting Strategies for Boron Neutron Capture Therapy.

    PubMed

    Luderer, Micah John; de la Puente, Pilar; Azab, Abdel Kareem

    2015-09-01

    Boron neutron capture therapy (BNCT) is a promising cancer therapy modality that utilizes the nuclear capture reaction of epithermal neutrons by boron-10 resulting in a localized nuclear fission reaction and subsequent cell death. Since cellular destruction is limited to approximately the diameter of a single cell, primarily only cells in the neutron field with significant boron accumulation will be damaged. However, the emergence of BNCT as a prominent therapy has in large part been hindered by a paucity of tumor selective boron containing agents. While L-boronophenylalanine and sodium borocaptate are the most commonly investigated clinical agents, new agents are desperately needed due to their suboptimal tumor selectivity. This review will highlight the various strategies to improve tumor boron delivery including: nucleoside and carbohydrate analogs, unnatural amino acids, porphyrins, antibody-dendrimer conjugates, cationic polymers, cell-membrane penetrating peptides, liposomes and nanoparticles.

  4. Enhanced boron diffusion in excimer laser preannealed Si

    SciTech Connect

    Monakhov, E.V.; Svensson, B.G.; Linnarsson, M.K.; La Magna, A.; Spinella, C.; Bongiorno, C.; Privitera, V.; Fortunato, G.; Mariucci, L.

    2005-04-11

    We have investigated boron diffusion during rapid thermal annealing in Si implanted with boron using an energy of 1 keV and a dose of 1x10{sup 16} cm{sup -2}. Two types of samples have been studied: As-implanted and pretreated with excimer laser annealing. For both types an enhanced diffusion of boron has been observed with an enhancement by a factor of 3-5 over the 'standard' diffusion. It is suggested that the high concentration of implanted boron is a dominant factor for the diffusion enhancement as compared to the effect of implantation-induced damage. The data indicate that the proximity of the surface can also affect the boron diffusion enhancement.

  5. Model of boron diffusion from gas phase in silicon carbide

    SciTech Connect

    Aleksandrov, O. V.; Mokhov, E. N.

    2011-06-15

    Boron diffusion from the gas phase in silicon carbide is described on the basis of a two-component model. 'Shallow' boron, i.e., boron at silicon sites, is a slow component with a high surface concentration. Its diffusivity is proportional to the concentration of positively charged intrinsic point defects, which are presumably interstitial silicon atoms. 'Deep' boron, i.e., impurity-defect pairs of boron-carbon vacancy, is a fast component with lower surface concentration. The ratio between the surface concentrations of the components depends on the pressure of silicon or carbon vapors in the gas phase. The diffusion and interaction of components are described by the set of diffusion-reaction equations. The diffusion retardation observed on the concentration-profile tail is related to the capture of impurity-defect pairs and excess vacancies by traps of background impurities and defects.

  6. Elemental Boron for Efficient Carbon Dioxide Reduction under Light Irradiation.

    PubMed

    Liu, Guigao; Meng, Xianguang; Zhang, Huabin; Zhao, Guixia; Pang, Hong; Wang, Tao; Li, Peng; Kako, Tetsuya; Ye, Jinhua

    2017-03-24

    The photoreduction of CO2 is attractive for the production of renewable fuels and the mitigation of global warming. Herein, we report an efficient method for CO2 reduction over elemental boron catalysts in the presence of only water and light irradiation through a photothermocatalytic process. Owing to its high solar-light absorption and effective photothermal conversion, the illuminated boron catalyst experiences remarkable self-heating. This process favors CO2 activation and also induces localized boron hydrolysis to in situ produce H2 as an active proton source and electron donor for CO2 reduction as well as boron oxides as promoters of CO2 adsorption. These synergistic effects, in combination with the unique catalytic properties of boron, are proposed to account for the efficiency of the CO2 reduction. This study highlights the promise of photothermocatalytic strategies for CO2 conversion and also opens new avenues towards the development of related solar-energy utilization schemes.

  7. Safety Assessment of Boron Nitride as Used in Cosmetics.

    PubMed

    Fiume, Monice M; Bergfeld, Wilma F; Belsito, Donald V; Hill, Ronald A; Klaassen, Curtis D; Liebler, Daniel C; Marks, James G; Shank, Ronald C; Slaga, Thomas J; Snyder, Paul W; Andersen, F Alan

    2015-01-01

    The Cosmetic Ingredient Review Expert Panel (Panel) assessed the safety of boron nitride which functions in cosmetics as a slip modifier (ie, it has a lubricating effect). Boron nitride is an inorganic compound with a crystalline form that can be hexagonal, spherical, or cubic; the hexagonal form is presumed to be used in cosmetics. The highest reported concentration of use of boron nitride is 25% in eye shadow formulations. Although boron nitride nanotubes are produced, boron nitride is not listed as a nanomaterial used in cosmetic formulations. The Panel reviewed available chemistry, animal data, and clinical data and concluded that this ingredient is safe in the present practices of use and concentration in cosmetic formulations. © The Author(s) 2015.

  8. A computational study of carbon dioxide adsorption on solid boron.

    PubMed

    Sun, Qiao; Wang, Meng; Li, Zhen; Du, Aijun; Searles, Debra J

    2014-07-07

    Capturing and sequestering carbon dioxide (CO2) can provide a route to partial mitigation of climate change associated with anthropogenic CO2 emissions. Here we report a comprehensive theoretical study of CO2 adsorption on two phases of boron, α-B12 and γ-B28. The theoretical results demonstrate that the electron deficient boron materials, such as α-B12 and γ-B28, can bond strongly with CO2 due to Lewis acid-base interactions because the electron density is higher on their surfaces. In order to evaluate the capacity of these boron materials for CO2 capture, we also performed calculations with various degrees of CO2 coverage. The computational results indicate CO2 capture on the boron phases is a kinetically and thermodynamically feasible process, and therefore from this perspective these boron materials are predicted to be good candidates for CO2 capture.

  9. pH dependent salinity-boron interactions impact yield, biomass, evapotranspiration and boron uptake in broccoli (Brassica oleracea L.)

    USDA-ARS?s Scientific Manuscript database

    Soil pH is known to influence many important biochemical processes in plants and soils, however its role in salinity - boron interactions affecting plant growth and ion relations has not been examined. The purpose of this research was to evaluate the interactive effects of salinity, boron and soil ...

  10. Thermodynamic Behavior and Mass Transfer Kinetics of Boron Between Ferrosilicon and CaO-SiO2 Slag

    NASA Astrophysics Data System (ADS)

    Krystad, Egil; Jakobsson, Lars K.; Tang, Kai; Tranell, Gabriella

    2017-06-01

    Equilibrium distribution and transport kinetics of boron between ferrosilicon and calcium silicate slag were investigated through experimental study. A 50 pct CaO-50 pct SiO2 slag (by weight) was held for different durations at 1873 K (1600 °C) in a graphite tube furnace together with boron-doped ferrosilicon alloys in the range 50 to 85 wt pct Fe. The results indicate that the equilibrium partition ratio of boron between slag and metal is 2.4 ± 0.7 and largely independent of ferrosilicon alloy composition below 85 wt pct Fe. At 85 wt pct Fe, the equilibrium partition ratio is measured to be 6.2 ± 1.4. Although reported with a significant standard deviation, it is also found that the mass transfer rate of boron between ferrosilicon alloy and slag increases slightly with increasing iron content in ferrosilicon. These findings are discussed in terms of slag-metal bulk and interfacial properties.

  11. Thermodynamic Behavior and Mass Transfer Kinetics of Boron Between Ferrosilicon and CaO-SiO2 Slag

    NASA Astrophysics Data System (ADS)

    Krystad, Egil; Jakobsson, Lars K.; Tang, Kai; Tranell, Gabriella

    2017-10-01

    Equilibrium distribution and transport kinetics of boron between ferrosilicon and calcium silicate slag were investigated through experimental study. A 50 pct CaO-50 pct SiO2 slag (by weight) was held for different durations at 1873 K (1600 °C) in a graphite tube furnace together with boron-doped ferrosilicon alloys in the range 50 to 85 wt pct Fe. The results indicate that the equilibrium partition ratio of boron between slag and metal is 2.4 ± 0.7 and largely independent of ferrosilicon alloy composition below 85 wt pct Fe. At 85 wt pct Fe, the equilibrium partition ratio is measured to be 6.2 ± 1.4. Although reported with a significant standard deviation, it is also found that the mass transfer rate of boron between ferrosilicon alloy and slag increases slightly with increasing iron content in ferrosilicon. These findings are discussed in terms of slag-metal bulk and interfacial properties.

  12. Mechanical properties of particulate composites based on a body-centered-cubic Mg-Li alloy containing boron

    NASA Technical Reports Server (NTRS)

    Whalen, R. T.; Gonzalez-Doncel, G.; Robinson, S. L.; Sherby, O. D.

    1989-01-01

    The effect of substituting the Mg metal in Mg-B composites by a Mg-14 wt pct Li solid solution on the ductility of the resulting composite was investigated using elastic modulus measurements on the P/M composite material prepared with a dispersion of B particles (in a vol pct range of 0-30) in a matrix of Mg-14 wt pct Li-1.5 wt pct Al. It was found that the elastic modulus of the composites increased rapidly with increasing boron, with specific stiffness values reaching about two times that of most structural materials. The values of the compression and tensile strengths increased significantly with boron additions. Good tensile ductility was achieved at the level of 10 vol pct B. However, at 20 vol pct B, the Mg-Li composite exhibited only limited tensile ductility (about 2 percent total elongation).

  13. Novel α- and β-type boron sheets: Theoretical insight into their structures, thermodynamic stability, and work functions

    NASA Astrophysics Data System (ADS)

    Zheng, Bing; Yu, Hai-tao; Lian, Yong-fu; Xie, Ying

    2016-03-01

    In this study, we report the quantum-mechanical characterization of two novel α- and β-type 2D pure boron sheets, i.e., α6- and β14-sheets, constructed from the experimentally available B36 and B35 building blocks. Ten isomeric configurations were located. Using the calculated binding energies, the thermodynamic stability of these structures was considered in detail. Additionally, we calculated the work functions of α6- and β14-sheets. The results clearly demonstrate that their work functions (approximately 4.6 eV) are the highest among all of the reported mixed triangular-hexagonal type 2D boron sheets and are very similar to that of graphene.

  14. Mechanical properties of particulate composites based on a body-centered-cubic Mg-Li alloy containing boron

    NASA Technical Reports Server (NTRS)

    Whalen, R. T.; Gonzalez-Doncel, G.; Robinson, S. L.; Sherby, O. D.

    1989-01-01

    The effect of substituting the Mg metal in Mg-B composites by a Mg-14 wt pct Li solid solution on the ductility of the resulting composite was investigated using elastic modulus measurements on the P/M composite material prepared with a dispersion of B particles (in a vol pct range of 0-30) in a matrix of Mg-14 wt pct Li-1.5 wt pct Al. It was found that the elastic modulus of the composites increased rapidly with increasing boron, with specific stiffness values reaching about two times that of most structural materials. The values of the compression and tensile strengths increased significantly with boron additions. Good tensile ductility was achieved at the level of 10 vol pct B. However, at 20 vol pct B, the Mg-Li composite exhibited only limited tensile ductility (about 2 percent total elongation).

  15. Compositions for boron delivery to mammalian tissue

    DOEpatents

    Hawthorne, M. Frederick; Feaks, Debra Arlene; Shelly, Kenneth John

    2001-01-01

    Boron neutron capture therapy can utilize X.sub.y B.sub.20 H.sub.17 L where X is an alkali metal, y is 1 to 4, and L is a two electron donor such as NH.sub.3, and Na.sub.2 B.sub.10 H.sub.9 NCO, among others. These borane salts may be used free or encapsulated in liposomes. Liposomes may also have embedded within their bilayers carboranes to increase the amount of delivered .sup.10 B and/or to increase the tumor specificity of the liposome.

  16. Recent advancements in boron nitride nanotubes.

    PubMed

    Wang, Jiesheng; Lee, Chee Huei; Yap, Yoke Khin

    2010-10-01

    This article provides a concise review of the recent research advancements in boron nitride nanotubes (BNNTs) with a comprehensive list of references. As the motivation of the field, we first summarize some of the attractive properties and potential applications of BNNTs. Then, latest discoveries on the properties, applications, and synthesis of BNNTs are discussed. In particular, we focus on low-temperature and patterned growth, and mass production of BNNTs, since these are the major challenges that have hindered investigation of the properties and application of BNNTs for the past decade. Finally, perspectives of future research on BNNTs are discussed.

  17. Fe nanowire encapsulated in boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Koi, Naruhiro; Oku, Takeo; Nishijima, Masahiko

    2005-11-01

    Boron nitride (BN) nanotubes, nanohorns, nanocoils were synthesized by annealing Fe 4N and B powders at 1000 °C for 1 h in nitrogen gas atmosphere. Especially, Fe-filled BN nanotubes were produced, and investigated by high-resolution electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, electron diffraction and energy dispersive X-ray spectroscopy, which indicates that the [110] of Fe is parallel to the BN nanotube axis. Formation mechanism of Fe-filled BN nanotube was speculated based on these results.

  18. Recent advancements in boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Jiesheng; Lee, Chee Huei; Yap, Yoke Khin

    2010-10-01

    This article provides a concise review of the recent research advancements in boron nitride nanotubes (BNNTs) with a comprehensive list of references. As the motivation of the field, we first summarize some of the attractive properties and potential applications of BNNTs. Then, latest discoveries on the properties, applications, and synthesis of BNNTs are discussed. In particular, we focus on low-temperature and patterned growth, and mass production of BNNTs, since these are the major challenges that have hindered investigation of the properties and application of BNNTs for the past decade. Finally, perspectives of future research on BNNTs are discussed.

  19. Large fracture toughness boron-epoxy composites

    NASA Technical Reports Server (NTRS)

    Atkins, A. G.

    1975-01-01

    The high tensile strengths of strong interfacial bonding may be combined with the large fracture toughness of weak interfacial bonding in brittle fiber/brittle matrix composites by intermittently coating the filaments before layup so as to have random alternate weak and strong regions. Appropriate coating materials enable Cook-Gordon Mode I interfacial debonding to take place, which produces very long pull-out lengths with an associated large contribution to toughness. Unidirectional boron-epoxy composites have been so made which have toughnesses greater than 200 kJ/sq m while retaining rule of mixtures tensile strengths. Similar trends have been observed for crossply layups.

  20. Boron nitride nanomaterials for thermal management applications.

    PubMed

    Meziani, Mohammed J; Song, Wei-Li; Wang, Ping; Lu, Fushen; Hou, Zhiling; Anderson, Ankoma; Maimaiti, Halidan; Sun, Ya-Ping

    2015-05-18

    Hexagonal boron nitride nanosheets (BNNs) are analogous to their two-dimensional carbon counterparts in many materials properties, in particular, ultrahigh thermal conductivity, but also offer some unique attributes, including being electrically insulating, high thermal stability, chemical and oxidation resistance, low color, and high mechanical strength. Significant recent advances in the production of BNNs, understanding of their properties, and the development of polymeric nanocomposites with BNNs for thermally conductive yet electrically insulating materials and systems are highlighted herein. Major opportunities and challenges for further studies in this rapidly advancing field are also discussed.