Method of chemical vapor deposition of boron nitride using polymeric cyanoborane

DOEpatents

Maya, Leon

1994-01-01

Polymeric cyanoborane is volatilized, decomposed by thermal or microwave plasma energy, and deposited on a substrate as an amorphous film containing boron, nitrogen and carbon. Residual carbon present in the film is removed by ammonia treatment at an increased temperature, producing an adherent, essentially stoichiometric boron nitride film.

Method of chemical vapor deposition of boron nitride using polymeric cyanoborane

DOEpatents

Maya, L.

1994-06-14

Polymeric cyanoborane is volatilized, decomposed by thermal or microwave plasma energy, and deposited on a substrate as an amorphous film containing boron, nitrogen and carbon. Residual carbon present in the film is removed by ammonia treatment at an increased temperature, producing an adherent, essentially stoichiometric boron nitride film. 11 figs.

Mechanical behavior enhancement of defective graphene sheet employing boron nitride coating via atomistic study

NASA Astrophysics Data System (ADS)

Setoodeh, A. R.; Badjian, H.

2017-12-01

The most stable form of boron nitride polymorph naming hexagonal boron nitride sheet has recently been widely concerned like graphite due to its interesting features such as electrical insulation and high thermal conductivity. In this study, the molecular dynamic simulations are implemented to investigate the mechanical properties of single-layer graphene sheets under tensile and compressive loadings in the absence and presence of boron-nitride coating layers. In this introduced hybrid nanostructure, the benefit of combining both individual interesting features of graphene and boron-nitride sheets such as exceptional mechanical and electrical properties can be simultaneously achieved for future potential application in nano devices. The influences of chiral indices, boundary conditions and presence of mono-atomic vacancy defects as well as coating dimension on the mechanical behavior of the resulted hybrid structure are reported. The interatomic forces between the atoms are modeled by employing the AIREBO and Tersoff-Brenner potentials for carbon-carbon and boron-nitrogen atoms in each layer, respectively. Furthermore, the van der Waal interlayer forces of carbon-boron and carbon-nitrogen are estimated by the Lennard-Jones potential field. Besides the potential improvement in electrical and physical properties of the nanostructure, it is demonstrated that the buckling load capacity of the fully coated graphene sheet with 3% concentration of mono-atomic vacancy defects noticeably enhances by amounts of 24.1%.

Synthesis of Boron Nitride Nanotubes for Engineering Applications

NASA Technical Reports Server (NTRS)

Hurst, Janet; Hull, David; Gorican, Dan

2005-01-01

Boron Nitride nanotubes (BNNT) are of interest to the scientific and technical communities for many of the same reasons that carbon nanotubes (CNT) have attracted large amounts of attention. Both materials have potentially unique and significant properties which may have important structural and electronic applications in the future. However of even more interest than their similarities may be the differences between carbon and boron nanotubes. Whilt boron nitride nanotubes possess a very high modulus similaar to CNT, they are also more chemically and thermally inert. Additionally BNNT possess more uniform electronic properties, having a uniform band gap of approximately 5.5 eV while CNT vary from semi-conductin to conductor behavior. Boron Nitride nanotubes have been synthesized by a variety of methods such as chemical vapor deposition, arc discharge and reactive milling. Consistently producing a reliable product has proven difficult. Progress in synthesis of 1-2 gram sized batches of Boron Nitride nanotubes will be discussed as well as potential uses for this unique material.

Hybridized boron-carbon nitride fibrous nanostructures on Ni substrates

NASA Astrophysics Data System (ADS)

Yap, Yoke Khin; Yoshimura, Masashi; Mori, Yusuke; Sasaki, Takatomo

2002-04-01

Stoichiometric BC2N films can be deposited on Si (100) at 800 °C, however, they are phase separated as pure carbon and BN phases. Likewise, hybridized boron-carbon nitride (BCN) films can be synthesized on Ni substrates. On Ni, the carbon and BN phases are hybridized through carbon nitride and boron carbide bonds. These films appeared as fibrous nanostructures. Evidence indicates that the Ni substrate acts as a sink for the carbon and forces the carbon composites to grow on top of the B and N atoms. However, as these films are grown thicker, phase separation occurs again. These results indicate that hybridized BCN phases should now be regarded as semiconducting or superhard nanostructures. High-temperature deposition on Ni substrates might be a solution to the obstacle of preparing hybridized BCN phases.

High quality boron carbon nitride/ZnO-nanorods p-n heterojunctions based on magnetron sputtered boron carbon nitride films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, J. C.; Department of Engineering Physics, Polytechnique Montréal, Montreal, Quebec H3A 3A7; Jha, S. K., E-mail: skylec@gmail.com, E-mail: apwjzh@cityu.edu.hk

2014-11-10

Boron carbon nitride (BCN) films were synthesized on Si (100) and fused silica substrates by radio-frequency magnetron sputtering from a B{sub 4}C target in an Ar/N{sub 2} gas mixture. The BCN films were amorphous, and they exhibited an optical band gap of ∼1.0 eV and p-type conductivity. The BCN films were over-coated with ZnO nanorod arrays using hydrothermal synthesis to form BCN/ZnO-nanorods p-n heterojunctions, exhibiting a rectification ratio of 1500 at bias voltages of ±5 V.

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.

Alginic Acid-Aided Dispersion of Carbon Nanotubes, Graphene, and Boron Nitride Nanomaterials for Microbial Toxicity Testing

PubMed Central

Chang, Chong Hyun

2018-01-01

Robust evaluation of potential environmental and health risks of carbonaceous and boron nitride nanomaterials (NMs) is imperative. However, significant agglomeration of pristine carbonaceous and boron nitride NMs due to strong van der Waals forces renders them not suitable for direct toxicity testing in aqueous media. Here, the natural polysaccharide alginic acid (AA) was used as a nontoxic, environmentally relevant dispersant with defined composition to disperse seven types of carbonaceous and boron nitride NMs, including multiwall carbon nanotubes, graphene, boron nitride nanotubes, and hexagonal boron nitride flakes, with various physicochemical characteristics. AA’s biocompatibility was confirmed by examining AA effects on viability and growth of two model microorganisms (the protozoan Tetrahymena thermophila and the bacterium Pseudomonas aeruginosa). Using 400 mg·L−1 AA, comparably stable NM (200 mg·L−1) stock dispersions were obtained by 30-min probe ultrasonication. AA non-covalently interacted with NM surfaces and improved the dispersibility of NMs in water. The dispersion stability varied with NM morphology and size rather than chemistry. The optimized dispersion protocol established here can facilitate preparing homogeneous NM dispersions for reliable exposures during microbial toxicity testing, contributing to improved reproducibility of toxicity results. PMID:29385723

Alginic Acid-Aided Dispersion of Carbon Nanotubes, Graphene, and Boron Nitride Nanomaterials for Microbial Toxicity Testing.

PubMed

Wang, Ying; Mortimer, Monika; Chang, Chong Hyun; Holden, Patricia A

2018-01-30

Robust evaluation of potential environmental and health risks of carbonaceous and boron nitride nanomaterials (NMs) is imperative. However, significant agglomeration of pristine carbonaceous and boron nitride NMs due to strong van der Waals forces renders them not suitable for direct toxicity testing in aqueous media. Here, the natural polysaccharide alginic acid (AA) was used as a nontoxic, environmentally relevant dispersant with defined composition to disperse seven types of carbonaceous and boron nitride NMs, including multiwall carbon nanotubes, graphene, boron nitride nanotubes, and hexagonal boron nitride flakes, with various physicochemical characteristics. AA's biocompatibility was confirmed by examining AA effects on viability and growth of two model microorganisms (the protozoan Tetrahymena thermophila and the bacterium Pseudomonas aeruginosa ). Using 400 mg·L -1 AA, comparably stable NM (200 mg·L -1 ) stock dispersions were obtained by 30-min probe ultrasonication. AA non-covalently interacted with NM surfaces and improved the dispersibility of NMs in water. The dispersion stability varied with NM morphology and size rather than chemistry. The optimized dispersion protocol established here can facilitate preparing homogeneous NM dispersions for reliable exposures during microbial toxicity testing, contributing to improved reproducibility of toxicity results.

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.

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.

Probing carbon impurities in hexagonal boron nitride epilayers

NASA Astrophysics Data System (ADS)

Uddin, M. R.; Li, J.; Lin, J. Y.; Jiang, H. X.

2017-05-01

Carbon doped hexagonal boron nitride epilayers have been grown by metal organic chemical vapor deposition. Photocurrent excitation spectroscopy has been utilized to probe the energy levels associated with carbon impurities in hexagonal boron nitride (h-BN). The observed transition peaks in photocurrent excitation spectra correspond well to the energy positions of the bandgap, substitutional donors (CB, carbon impurities occupying boron sites), and substitutional acceptors (CN, carbon impurities occupying nitrogen sites). From the observed transition peak positions, the derived energy level of CB donors in h-BN is ED ˜ 0.45 eV, which agrees well with the value deduced from the temperature dependent electrical resistivity. The present study further confirms that the room temperature bandgap of h-BN is about 6.42-6.45 eV, and the CN deep acceptors have an energy level of about 2.2-2.3 eV. The results also infer that carbon doping introduces both shallow donors (CB) and deep acceptors (CN) via self-compensation, and the energy level of carbon donors appears to be too deep to enable carbon as a viable candidate as an n-type dopant in h-BN epilayers.

Dispersion toughened silicon carbon ceramics

DOEpatents

Wei, G.C.

1984-01-01

Fracture resistant silicon carbide ceramics are provided by incorporating therein a particulate dispersoid selected from the group consisting of (a) a mixture of boron, carbon and tungsten, (b) a mixture of boron, carbon and molybdenum, (c) a mixture of boron, carbon and titanium carbide, (d) a mixture of aluminum oxide and zirconium oxide, and (e) boron nitride. 4 figures.

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.

Microplasma Processed Ultrathin Boron Nitride Nanosheets for Polymer Nanocomposites with Enhanced Thermal Transport Performance.

PubMed

Zhang, Ri-Chao; Sun, Dan; Lu, Ai; Askari, Sadegh; Macias-Montero, Manuel; Joseph, Paul; Dixon, Dorian; Ostrikov, Kostya; Maguire, Paul; Mariotti, Davide

2016-06-01

This Research Article reports on the enhancement of the thermal transport properties of nanocomposite materials containing hexagonal boron nitride in poly(vinyl alcohol) through room-temperature atmospheric pressure direct-current microplasma processing. Results show that the microplasma treatment leads to exfoliation of the hexagonal boron nitride in isopropyl alcohol, reducing the number of stacks from >30 to a few or single layers. The thermal diffusivity of the resulting nanocomposites reaches 8.5 mm(2) s(-1), 50 times greater than blank poly(vinyl alcohol) and twice that of nanocomposites containing nonplasma treated boron nitride nanosheets. From TEM analysis, we observe much less aggregation of the nanosheets after plasma processing along with indications of an amorphous carbon interfacial layer, which may contribute to stable dispersion of boron nitride nanosheets in the resulting plasma treated colloids.

Environmental Electrometry with Luminescent Carbon Nanotubes.

PubMed

Noé, Jonathan C; Nutz, Manuel; Reschauer, Jonathan; Morell, Nicolas; Tsioutsios, Ioannis; Reserbat-Plantey, Antoine; Watanabe, Kenji; Taniguchi, Takashi; Bachtold, Adrian; Högele, Alexander

2018-06-25

We demonstrate that localized excitons in luminescent carbon nanotubes can be utilized to study electrostatic fluctuations in the nanotube environment with sensitivity down to the elementary charge. By monitoring the temporal evolution of the cryogenic photoluminescence from individual carbon nanotubes grown on silicon oxide and hexagonal boron nitride, we characterize the dynamics of charge trap defects for both dielectric supports. We find a one order of magnitude reduction in the photoluminescence spectral wandering for nanotubes on extended atomically flat terraces of hexagonal boron nitride. For nanotubes on hexagonal boron nitride with pronounced spectral fluctuations, our analysis suggests proximity to terrace ridges where charge fluctuators agglomerate to exhibit areal densities exceeding those of silicon oxide. Our results establish carbon nanotubes as sensitive probes of environmental charge fluctuations and highlight their potential for applications in electrometric nanodevices with all-optical readout.

Cu and Boron Doped Carbon Nitride for Highly Selective Oxidation of Toluene to Benzaldehyde.

PubMed

Han, Hongling; Ding, Guodong; Wu, Tianbin; Yang, Dexin; Jiang, Tao; Han, Buxing

2015-07-13

A novel Cu and boron doped graphitic carbon nitride catalyst (Cu-CNB) was synthesized using cheap precursors and systematically characterized. The selective oxidation of toluene proceeded very smoothly over the catalyst at 70 °C using tert-butyl hydroperoxide (TBHP) as the oxidant to exclusively afford benzaldehyde. The catalyst can be used for at least five cycles without decrease in activity and selectivity.

Thermal conduction mechanisms in isotope-disordered boron nitride and carbon nanotubes

NASA Astrophysics Data System (ADS)

Savic, Ivana; Mingo, Natalio; Stewart, Derek

2009-03-01

We present first principles studies which determine dominant effects limiting the heat conduction in isotope-disordered boron nitride and carbon nanotubes [1]. Using an ab initio atomistic Green's function approach, we demonstrate that localization cannot be observed in the thermal conductivity measurements [1], and that diffusive scattering is the dominant mechanism which reduces the thermal conductivity [2]. We also give concrete predictions of the magnitude of the isotope effect on the thermal conductivities of carbon and boron nitride single-walled nanotubes [2]. We furthermore show that intershell scattering is not the main limiting mechanism for the heat flow through multi-walled boron nitride nanotubes [1], and that heat conduction restricted to a few shells leads to the low thermal conductivities experimentally measured [1]. We consequently successfully compare the results of our calculations [3] with the experimental measurements [1]. [1] C. W. Chang, A. M. Fennimore, A. Afanasiev, D. Okawa, T. Ikuno, H. Garcia, D. Li, A. Majumdar, A. Zettl, Phys. Rev. Lett. 2006, 97, 085901. [2] I. Savic, N. Mingo, D. A. Stewart, Phys. Rev. Lett. 2008, 101, 165502. [3] I. Savic, D. A. Stewart, N. Mingo, to be published.

High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Park, Cheol (Inventor); Bryant, Robert George (Inventor); Lowther, Sharon E. (Inventor)

2015-01-01

Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

Origin of band gaps in graphene on hexagonal boron nitride

PubMed Central

Jung, Jeil; DaSilva, Ashley M.; MacDonald, Allan H.; Adam, Shaffique

2015-01-01

Recent progress in preparing well-controlled two-dimensional van der Waals heterojunctions has opened up a new frontier in materials physics. Here we address the intriguing energy gaps that are sometimes observed when a graphene sheet is placed on a hexagonal boron nitride substrate, demonstrating that they are produced by an interesting interplay between structural and electronic properties, including electronic many-body exchange interactions. Our theory is able to explain the observed gap behaviour by accounting first for the structural relaxation of graphene’s carbon atoms when placed on a boron nitride substrate, and then for the influence of the substrate on low-energy π-electrons located at relaxed carbon atom sites. The methods we employ can be applied to many other van der Waals heterojunctions. PMID:25695638

Improved Dental Implant Drill Durability and Performance Using Heat and Wear Resistant Protective Coatings.

PubMed

Er, Nilay; Alkan, Alper; Ilday, Serim; Bengu, Erman

2018-06-01

The dental implant drilling procedure is an essential step for implant surgery, and frictional heat in bone during drilling is a key factor affecting the success of an implant. The aim of this study was to increase the dental implant drill lifetime and performance by using heat- and wear-resistant protective coatings to decrease the alveolar bone temperature caused by the dental implant drilling procedure. Commercially obtained stainless steel drills were coated with titanium aluminum nitride, diamond-like carbon, titanium boron nitride, and boron nitride coatings via magnetron-sputter deposition. Drilling was performed on bovine femoral cortical bone under the conditions mimicking clinical practice. Tests were performed under water-assisted cooling and under the conditions when no cooling was applied. Coated drill performances and durabilities were compared with those of three commonly used commercial drills with surfaces made from zirconia, black diamond. and stainless steel. Protective coatings with boron nitride, titanium boron nitride, and diamond-like carbon have significantly improved drill performance and durability. In particular, boron nitride-coated drills have performed within safe bone temperature limits for 50 drillings even when no cooling is applied. Titanium aluminium nitride coated drills did not show any improvement over commercially obtained stainless steel drills. Surface modification using heat- and wear-resistant coatings is an easy and highly effective way to improve implant drill performance and durability, which can improve the surgical procedure and the postsurgical healing period. The noteworthy success of different types of coatings is novel and likely to be applicable to various other medical systems.

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.

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.

Bias in bonding behavior among boron, carbon, and nitrogen atoms in ion implanted a-BN, a-BC, and diamond like carbon films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genisel, Mustafa Fatih; Uddin, Md. Nizam; Say, Zafer

2011-10-01

In this study, we implanted N{sup +} and N{sub 2}{sup +} ions into sputter deposited amorphous boron carbide (a-BC) and diamond like carbon (DLC) thin films in an effort to understand the chemical bonding involved and investigate possible phase separation routes in boron carbon nitride (BCN) films. In addition, we investigated the effect of implanted C{sup +} ions in sputter deposited amorphous boron nitride (a-BN) films. Implanted ion energies for all ion species were set at 40 KeV. Implanted films were then analyzed using x-ray photoelectron spectroscopy (XPS). The changes in the chemical composition and bonding chemistry due to ion-implantationmore » were examined at different depths of the films using sequential ion-beam etching and high resolution XPS analysis cycles. A comparative analysis has been made with the results from sputter deposited BCN films suggesting that implanted nitrogen and carbon atoms behaved very similar to nitrogen and carbon atoms in sputter deposited BCN films. We found that implanted nitrogen atoms would prefer bonding to carbon atoms in the films only if there is no boron atom in the vicinity or after all available boron atoms have been saturated with nitrogen. Implanted carbon atoms also preferred to either bond with available boron atoms or, more likely bonded with other implanted carbon atoms. These results were also supported by ab-initio density functional theory calculations which indicated that carbon-carbon bonds were energetically preferable to carbon-boron and carbon-nitrogen bonds.« less

Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells

PubMed Central

2014-01-01

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

Boron Nitride Nanotubes Synthesized by Pressurized Reactive Milling Process

NASA Technical Reports Server (NTRS)

Hurst, Janet B.

2004-01-01

Nanotubes, because of their very high strength, are attractive as reinforcement materials for ceramic matrix composites (CMCs). Recently there has been considerable interest in developing and applying carbon nanotubes for both electronic and structural applications. Although carbon nanotubes can be used to reinforce composites, they oxidize at high temperatures and, therefore, may not be suitable for ceramic composites. Boron nitride, because it has a higher oxidation resistance than carbon, could be a potential reinforcement material for ceramic composites. Although boron nitride nanotubes (BNnT) are known to be structurally similar to carbon nanotubes, they have not undergone the same extensive scrutiny that carbon nanotubes have experienced in recent years. This has been due to the difficulty in synthesizing this material rather than lack of interest in the material. We expect that BNnTs will maintain the high strength of carbon nanotubes while offering superior performance for the high-temperature and/or corrosive applications of interest to NASA. At the NASA Glenn Research of preparing BN-nTs were investigated and compared. These include the arc jet process, the reactive milling process, and chemical vapor deposition. The most successful was a pressurized reactive milling process that synthesizes BN-nTs of reasonable quantities.

Tuning electronic properties of boron nitride nanoplate via doping carbon for enhanced adsorptive performance.

PubMed

Pang, Jingyu; Chao, Yanhong; Chang, Honghong; Li, Hongping; Xiong, Jun; He, Minqiang; Zhang, Qi; Li, Huaming; Zhu, Wenshuai

2017-12-15

In this paper, the carbon-doped boron nitride nanoplate (C-BNNP) was prepared by pyrolyzing the precursor under N 2 and served as an excellent adsorbent for removal of Rhodamine B (RhB). The structure and composition of C-BNNP were characterized and its adsorption behavior for RhB was investigated. Compared with boron nitride nanoplate (BNNP) which was synthesized under NH 3 , C-BNNP displayed an enhancement of the adsorption capacity for RhB (833mg/g). The adsorption activity was comprehensibly studied by kinetics, isotherm and thermodynamics. The adsorption kinetics followed pseudo-second-order model. The equilibrium adsorption data agreed well with the Langmuir isotherm. And the thermodynamics indicated that the adsorption process was a spontaneous, exothermic and physisorption process. In addition, the density functional theory was proposed that doping carbon in the BNNP decreased the chemical hardness of the adsorbent and enhanced the adsorption capacity of C-BNNP for RhB. Copyright © 2017 Elsevier Inc. All rights reserved.

Structural transformations of carbon and boron nitride nanoscrolls at high impact collisions.

PubMed

Woellner, C F; Machado, L D; Autreto, P A S; de Sousa, J M; Galvao, D S

2018-02-14

The behavior of nanostructures under high strain-rate conditions has been the object of theoretical and experimental investigations in recent years. For instance, it has been shown that carbon and boron nitride nanotubes can be unzipped into nanoribbons at high-velocity impacts. However, the response of many nanostructures to high strain-rate conditions is still unknown. In this work, we have investigated the mechanical behavior of carbon (CNS) and boron nitride nanoscrolls (BNS) colliding against solid targets at high velocities, using fully atomistic reactive (ReaxFF) molecular dynamics (MD) simulations. CNS (BNS) are graphene (boron nitride) membranes rolled up into papyrus-like structures. Their open-ended topology leads to unique properties not found in their close-ended analogs, such as nanotubes. Our results show that collision products are mainly determined by impact velocities and by two orientation angles, which define the position of the scroll (i) axis and (ii) open edge relative to the target. Our MD results showed that for appropriate velocities and orientations, large-scale deformations and nanoscroll fractures could occur. We also observed unscrolling (scrolls going back to quasi-planar membranes), scroll unzipping into nanoribbons, and significant reconstruction due to breaking and/or formation of new chemical bonds. For particular edge orientations and velocities, conversion from open to close-ended topology is also possible, due to the fusion of nanoscroll walls.

Structural transformations of carbon and boron nitride nanoscrolls at high impact collisions

NASA Astrophysics Data System (ADS)

Woellner, C. F.; Machado, L. D.; Autreto, P. A. S.; de Sousa, J. M.; Galvao, D. S.

The behavior of nanostructures under high strain-rate conditions has been object of theoretical and experimental investigations in recent years. For instance, it has been shown that carbon and boron nitride nanotubes can be unzipped into nanoribbons at high velocity impacts. However, the response of many nanostructures to high strain-rate conditions is still not completely understood. In this work we have investigated through fully atomistic reactive (ReaxFF) molecular dynamics (MD) simulations the mechanical behavior of carbon (CNS) and boron nitride nanoscrolls (BNS) colliding against solid targets at high velocities,. CNS (BNS) nanoscrolls are graphene (boron nitride) membranes rolled up into papyrus-like structures. Their open-ended topology leads to unique properties not found in close-ended analogues, such as nanotubes. Our results show that the collision products are mainly determined by impact velocities and by two impact angles, which define the position of the scroll (i) axis and (ii) open edge relative to the target. Our MD results showed that for appropriate velocities and orientations large-scale deformations and nanoscroll fracture can occur. We also observed unscrolling (scrolls going back to quasi-planar membranes), scroll unzipping into nanoribbons, and significant reconstruction due to breaking and/or formation of new chemical bonds. For particular edge orientations and velocities, conversion from open to close-ended topology is also possible, due to the fusion of nanoscroll walls.

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

PubMed

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

2014-05-01

Hydrophilic peptides in shotgun proteomics have been shown to be problematic in conventional chromatography. Typically, C18 solid phase extraction or peptide traps are used for desalting the sample prior to mass spectrometry analysis, but the capacity to retain hydrophilic peptides is not very high, causing a bias toward more hydrophobic peptides. This is particularly problematic in phosphoproteomic studies. We tested the compatibility of commercially available boron nitride as a novel material for peptide desalting. Boron nitride can be used to recover a wide range of peptides with different physicochemical properties comparable to combined C18 and graphite carbon material. Copyright © 2014. Published by Elsevier Inc.

Structural, electronic and magnetic properties of carbon doped boron nitride nanowire: Ab initio study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jalilian, Jaafar, E-mail: JaafarJalilian@gmail.com; Kanjouri, Faramarz, E-mail: kanjouri@khu.ac.ir

2016-11-15

Using spin-polarized density functional theory calculations, we demonstrated that carbon doped boron nitride nanowire (C-doped BNNW) has diverse electronic and magnetic properties depending on position of carbon atoms and their percentages. Our results show that only when one carbon atom is situated on the edge of the nanowire, C-doped BNNW is transformed into half-metal. The calculated electronic structure of the C-doped BNNW suggests that doping carbon can induce localized edge states around the Fermi level, and the interaction among localized edge states leads to semiconductor to half-metal transition. Overall, the bond reconstruction causes of appearance of different electronic behavior suchmore » as semiconducting, half-metallicity, nonmagnetic metallic, and ferromagnetic metallic characters. The formation energy of the system shows that when a C atom is doped on surface boron site, system is more stable than the other positions of carbon impurity. Our calculations show that C-doped BNNW may offer unique opportunities for developing nanoscale spintronic materials.« less

A comparative study on carbon, boron-nitride, boron-phosphide and silicon-carbide nanotubes based on surface electrostatic potentials and average local ionization energies.

PubMed

Esrafili, Mehdi D; Behzadi, Hadi

2013-06-01

A density functional theory study was carried out to predict the electrostatic potentials as well as average local ionization energies on both the outer and the inner surfaces of carbon, boron-nitride (BN), boron-phosphide (BP) and silicon-carbide (SiC) single-walled nanotubes. For each nanotube, the effect of tube radius on the surface potentials and calculated average local ionization energies was investigated. It is found that SiC and BN nanotubes have much stronger and more variable surface potentials than do carbon and BP nanotubes. For the SiC, BN and BP nanotubes, there are characteristic patterns of positive and negative sites on the outer lateral surfaces. On the other hand, a general feature of all of the systems studied is that stronger potentials are associated with regions of higher curvature. According to the evaluated surface electrostatic potentials, it is concluded that, for the narrowest tubes, the water solubility of BN tubes is slightly greater than that of SiC followed by carbon and BP nanotubes.

The elevated temperature mechanical properties of silicon nitride/boron nitride fibrous monoliths

NASA Astrophysics Data System (ADS)

Trice, Rodney Wayne

A unique, all-ceramic material capable of non-brittle fracture via crack deflection has been characterized from 25sp°C through 1400sp°C. This material, called fibrous monoliths (FMs), was comprised of unidirectionally aligned 250 mum diameter cells of silicon nitride surrounded by 10 mum thick cell boundaries of boron nitride. Six weight percent yttria and two weight percent alumina were added to the silicon nitride to aid in densification. TEM experiments revealed that the sintering aids used to densify the silicon nitride cells were migrating into the boron nitride cell boundary during hot-pressing and that a fine network of micro-cracks existed between basal planes of boron nitride. Elevated temperature four point bending tests were performed on fibrous monolith ceramics from room temperature through 1400sp°C. Peak strengths of FMs averaged 510 MPa for specimens tested at room temperature through 176 MPa at 1400sp°C. Work of fractures ranged from 7300 J/msp2 to 3200 J/msp2 under the same temperature conditions. The interfacial fracture energy of boron nitride, GammasbBN, as a function of temperature has been determined using the Charalambides method. The fracture energy of boron nitride is approximately 40 J/msp2 and remained constant from 25sp°C through 950sp°C. A sharp increase in GammasbBN, to about 60 J/msp2, was observed at 1000sp°C-1050sp°C. This increase in GammasbBN was attributed to interactions of the crack tip with the cell boundary glassy phase. Subsequent measurements at 1075sp°C indicated a marked decrease in GammasbBN to near 40 J/msp2 before plateauing at 17-20 J/msp2 in the 1200sp°C-1300sp°C regime. The Mode I fracture toughness of silicon nitride was also determined using the single edge precracked beam method as a function of temperature. The He and Hutchinson model relating crack deflection at an interface to the Dundurs' parameter was applied to the current data set using the temperature dependent fracture energies of the boron nitride and the silicon nitride. A more refractory fibrous monolith was fabricated in an effort to extend the high temperature properties of SN/BN fibrous monoliths. Only 4 wt.% yttria was added to the silicon nitride to aid in densification. The presence of residual carbon following binder burnout was proposed to be responsible for the formation of melilite, a phase known to undergo severe oxidation between 900sp°C-1100sp°C. When residual carbon was removed prior to hot-pressing with a post-binder burnout heat treatment at 400sp°C in air this phase was not present. A room temperature strength of 553 MPa and a work of fracture of 6700 J/msp2 was observed. A strength of 293 MPa was measured at 1400sp°C.

Adsorption of nucleic acid bases and amino acids on single-walled carbon and boron nitride nanotubes: a first-principles study.

PubMed

Zheng, Jiaxin; Song, Wei; Wang, Lu; Lu, Jing; Luo, Guangfu; Zhou, Jing; Qin, Rui; Li, Hong; Gao, Zhengxiang; Lai, Lin; Li, Guangping; Mei, Wai Ning

2009-11-01

We study the adsorptions of nucleic acid bases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) and four amino acids phenylalanine, tyrosine, tryptophan, alanine on the single-walled carbon nanotubes (SWCNTs) and boron nitride nanotubes (SWBNNTs) by using density functional theory. We find that the aromatic content plays a critical role in the adsorption. The adsorptions of nucleic acid bases and amino acids on the (7, 7) SWBNNT are stronger than those on the (7, 7) SWCNT. Oxidative treatment of SWCNTs favors the adsorption of biomolecules on nanotubes.

Hybrid-PIC Simulation of Backsputtered Carbon Transport in the Near-Field Plume of a Hall Thruster

NASA Technical Reports Server (NTRS)

Choi, Maria; Yim, John T.; Williams, George J.; Herman, Daniel A.; Gilland, James H.

2017-01-01

Magnetic shielding has eliminated boron nitride erosion as the life limiting mechanism in a Hall thruster but has resulted in erosion of the front magnetic field pole pieces. Recent experiments show that the erosion of graphite pole covers, which are added to protect the magnetic field pole pieces, causes carbon to redeposit on other surfaces, such as boron nitride discharge channel and cathode keeper surfaces. As a part of the risk-reduction activities for AEPS thruster development, this study models transport of backsputtered carbon from the graphite front pole covers and vacuum facility walls. Fluxes, energy distributions, and redeposition rates of backsputtered carbon on the anode, discharge channel, and graphite cathode keeper surfaces are predicted.

Structural stability and electronic properties of an octagonal allotrope of two dimensional boron nitride.

PubMed

Takahashi, Lauren; Takahashi, Keisuke

2017-03-27

An octagonal allotrope of two dimensional boron nitride is explored through first principles calculations. Calculations show that two dimensional octagonal boron nitride can be formed with a binding energy comparable to two dimensional hexagonal boron nitride. In addition, two dimensional octagonal boron nitride is found to have a band gap smaller than two dimensional hexagonal boron nitride, suggesting the possibility of semiconductive attributes. Two dimensional octagonal boron nitride also has the ability to layer through physisorption. Defects present within two dimensional octagonal boron nitride also lead toward the introduction of a magnetic moment through the absence of boron atoms. The presence of defects is also found to render both hexagonal and octagonal boron nitrides reactive against hydrogen, where greater reactivity is seen in the presence of nitrogen. Thus, two dimensional octagonal boron nitride is confirmed with potential to tailor properties and reactivity through lattice shape and purposeful introduction of defects.

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.

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.

The mechanical design of hybrid graphene/boron nitride nanotransistors: Geometry and interface effects

NASA Astrophysics Data System (ADS)

Einalipour Eshkalak, Kasra; Sadeghzadeh, Sadegh; Jalaly, Maisam

2018-02-01

From electronic point of view, graphene resembles a metal or semi-metal and boron nitride is a dielectric material (band gap = 5.9 eV). Hybridization of these two materials opens band gap of the graphene which has expansive applications in field-effect graphene transistors. In this paper, the effect of the interface structure on the mechanical properties of a hybrid graphene/boron nitride was studied. Young's modulus, fracture strain and tensile strength of the models were simulated. Three likely types (hexagonal, octagonal and decagonal) were found for the interface of hybrid sheet after relaxation. Although Csbnd B bonds at the interface were indicated to result in more promising electrical properties, nitrogen atoms are better choice for bonding to carbon for mechanical applications.

Hybrid-Particle-In-Cell Simulation of Backsputtered Carbon Transport in the Near-Field Plume of a Hall Thruster

NASA Technical Reports Server (NTRS)

Choi, Maria; Yim, John T.; Williams, George J.; Herman, Daniel A.; Gilland, James H.

2018-01-01

Magnetic shielding has eliminated boron nitride erosion as the life limiting mechanism in a Hall thruster but has resulted in erosion of the front magnetic field pole pieces. Recent experiments show that the erosion of graphite pole covers, which are added to protect the magnetic field pole pieces, causes carbon to redeposit on other surfaces, such as boron nitride discharge channel and cathode keeper surfaces. As a part of the risk-reduction activities for Advanced Electric Propulsion System thruster development, this study models transport of backsputtered carbon from the graphite front pole covers and vacuum facility walls. Fluxes, energy distributions, and redeposition rates of backsputtered carbon on the anode, discharge channel, and graphite cathode keeper surfaces are predicted.

Boron Nitride Obtained from Molecular Precursors: Aminoboranes Used as a BN Source for Coatings, Matrix, and Si 3N 4-BN Composite Ceramic Preparation

NASA Astrophysics Data System (ADS)

Thévenot, F.; Doche, C.; Mongeot, H.; Guilhon, F.; Miele, P.; Cornu, D.; Bonnetot, B.

1997-10-01

Aminoboranes, pure or partially converted into aminoborazines using thermal or aminolysis polymerization, have been used as boron nitride precursors. An amorphous BN preceramic is obtained when pyrolysed up to 1000°C that can be stabilized using further annealing up to 1400°C or crystallized into h-BN above 1700°C. These molecular precursors have been used to prepare carbon fiber/BN matrix microcomposites to get an efficient BN coating on graphite and as a BN source in Si3N4/BN composite ceramic. The properties of these new types of samples have been compared with those obtained by classical processes. The boron nitride obtained from these precursors is a good sintering agent during the hot-pressing of the samples. However, the crystallinity of BN, even sintered up to 1800°C, remains poor. In fact, most of the mechanical properties of the composite ceramic (density, porosity, hardness) are clearly improved and the aminoboranes can be considered as convenient boron nitride sources and helpful sintering agents in hot-pressing technology.

Graphite carbon nitride/boron-doped graphene hybrid for efficient hydrogen generation reaction.

PubMed

Yang, Liang; Wang, Xin; Wang, Juan; Cui, Guomin; Liu, Daoping

2018-08-24

Metal-free carbon materials, with tuned surface chemical and electronic properties, hold great potential for the hydrogen evolution reaction (HER). We designed and synthesized a CN/BG hybrid electrocatalytic system with a porous and active graphite carbon nitride (CN) layer on boron-doped graphene (BG). A porous CN layer on graphene could provide exposed defects and edges that act as active sites for proton adsorption and reduction. The composition, structure, surface electronics, and chemical properties of this CN/BG hybrid system were tuned to obtain excellent HER activity and stability. Detailed surface chemical, morphological, and structural analyses demonstrated the synergetic effect arising from the electronic interaction between CN and BG, which contributed to the enhanced electrocatalytic performances.

Hydrogen adsorption capacities of multi-walled boron nitride nanotubes and nanotube arrays: a grand canonical Monte Carlo study.

PubMed

Ahadi, Zohreh; Shadman, Muhammad; Yeganegi, Saeed; Asgari, Farid

2012-07-01

Hydrogen adsorption in multi-walled boron nitride nanotubes and their arrays was studied using grand canonical Monte Carlo simulation. The results show that hydrogen storage increases with tube diameter and the distance between the tubes in multi-walled boron nitride nanotube arrays. Also, triple-walled boron nitride nanotubes present the lowest level of hydrogen physisorption, double-walled boron nitride nanotubes adsorb hydrogen better when the diameter of the inner tube diameter is sufficiently large, and single-walled boron nitride nanotubes adsorb hydrogen well when the tube diameter is small enough. Boron nitride nanotube arrays adsorb hydrogen, but the percentage of adsorbed hydrogen (by weight) in boron nitride nanotube arrays is rather similar to that found in multi-walled boron nitride nanotubes. Also, when the Langmuir and Langmuir-Freundlich equations were fitted to the simulated data, it was found that multi-layer adsorptivity occurs more prominently as the number of walls and the tube diameter increase. However, in single-walled boron nitride nanotubes with a small diameter, the dominant mechanism is monolayer adsorptivity.

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.

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.

Excellent electrical conductivity of the exfoliated and fluorinated hexagonal boron nitride nanosheets.

PubMed

Xue, Yafang; Liu, Qian; He, Guanjie; Xu, Kaibing; Jiang, Lin; Hu, Xianghua; Hu, Junqing

2013-01-24

The insulator characteristic of hexagonal boron nitride limits its applications in microelectronics. In this paper, the fluorinated hexagonal boron nitride nanosheets were prepared by doping fluorine into the boron nitride nanosheets exfoliated from the bulk boron nitride in isopropanol via a facile chemical solution method with fluoboric acid; interestingly, these boron nitride nanosheets demonstrate a typical semiconductor characteristic which were studied on a new scanning tunneling microscope-transmission electron microscope holder. Since this property changes from an insulator to a semiconductor of the boron nitride, these nanosheets will be able to extend their applications in designing and fabricating electronic nanodevices.

Band gap engineering of BC2N for nanoelectronic applications

NASA Astrophysics Data System (ADS)

Lim, Wei Hong; Hamzah, Afiq; Ahmadi, Mohammad Taghi; Ismail, Razali

2017-12-01

The BC2N as an example of boron-carbon-nitride (BCN), has the analogous structure as the graphene and boron nitride. It is predicted to have controllable electronic properties. Therefore, the analytical study on the engineer-able band gap of the BC2N is carried out based on the schematic structure of BC2N. The Nearest Neighbour Tight Binding (NNTB) model is employed with the dispersion relation and the density of state (DOS) as the main band gap analysing parameter. The results show that the hopping integrals having the significant effect on the band gap, band structure and DOS of BC2N nanowire (BC2NNW) need to be taken into consideration. The presented model indicates consistent trends with the published computational results around the Dirac points with the extracted band gap of 0.12 eV. Also, it is distinguished that wide energy gap of boron nitride (BN) is successfully narrowed by this carbon doped material which assures the application of BC2N on the nanoelectronics and optoelectronics in the near future.

Chemical reaction of hexagonal boron nitride and graphite nanoclusters in mechanical milling systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muramatsu, Y.; Grush, M.; Callcott, T.A.

1997-04-01

Synthesis of boron-carbon-nitride (BCN) hybrid alloys has been attempted extensively by many researchers because the BCN alloys are considered an extremely hard material called {open_quotes}super diamond,{close_quotes} and the industrial application for wear-resistant materials is promising. A mechanical alloying (MA) method of hexagonal boron nitride (h-BN) with graphite has recently been studied to explore the industrial synthesis of the BCN alloys. To develop the MA method for the BCN alloy synthesis, it is necessary to confirm the chemical reaction processes in the mechanical milling systems and to identify the reaction products. Therefore, the authors have attempted to confirm the chemical reactionmore » process of the h-BN and graphite in mechanical milling systems using x-ray absorption near edge structure (XANES) methods.« less

Massive radius-dependent flow slippage in carbon nanotubes

NASA Astrophysics Data System (ADS)

Siria, Alessandro; Secchi, Eleonora; Marbach, Sophie; Niguès, Antoine; Stein, Derek; Bocquet, Lydéric

2016-11-01

Nanofluidics is the frontier where the continuum picture of fluid mechanics confronts the atomic nature of matter. Recent reports indicate that carbon nanotubes exhibit exceptional water transport properties due to nearly frictionless interfaces and this has stimulated interest in nanotube-based membranes for desalination, nano-filtration, and energy harvesting. However, the fundamental mechanisms of water transport inside nanotubes and at water-carbon interfaces remain controversial, as existing theories fail to provide a satisfying explanation for the limited experimental results. We report a study of water jets emerging from single nanotubes made of carbon and boron-nitride materials. Our experiments reveal extensive and radius-dependent surface slippage in carbon nanotubes (CNT). In stark contrast, boron-nitride nanotubes (BNNT), which are crystallographically similar to CNTs but electronically different, exhibit no slippage. This shows that slippage originates in subtle atomic-scale details of the solid-liquid interface. ERC StG - NanoSOFT.

Viscoelastic Behavior of PDMS Filled with Boron Nitrides

NASA Astrophysics Data System (ADS)

Bian, J. F.; Weinkauf, D. H.; Jeon, H. S.

2004-03-01

The addition of high thermal conductive filler particles such as boron nitride, aluminum nitride, or carbon fiber is an effective way to increase the thermal conductivity of polymeric materials for the industrial applications such as electronic packaging materials, encapsulants, and thermal fluids among others. The effects of particle dispersions, concentrations, and the interactions between BN and polymer matrix on the viscoelastic properties of the boron nitride (BN)/polydimethylsiloxane (PDMS) composites prepared by mechanical mixing are investigated using oscillatory shear rheology. Both untreated and plasma treated boron nitride (BNP) particles with hexafluoropropylene oxide monomers have been used in this study. The addition of the plasma treated BN particles to the PDMS matrix decrease significantly the complex viscosity as well as storage and loss modulus of the composites due to the reduced interfacial energy between the surface of BNP and PDMS chains. For the PDMS/BN and PDMS/BNP composites, the maximum volume packing fraction ( ˜0.4) of the particles has been determined from the complex viscosity as a function of the frequency. Additionally, the shear-induced alignment of the BN particles dispersed in the PDMS matrix decreases the viscoelastic properties of the composites with the irregular oscillations which is related to the network formation of dispersed BN particles at the higher volume fractions (> ˜0.2).

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

NASA Astrophysics Data System (ADS)

Zhou, Gang; Duan, Wenhui

2007-03-01

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

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.

In Situ Mechanical Property Measurements of Amorphous Carbon-Boron Nitride Nanotube Nanostructures

NASA Technical Reports Server (NTRS)

Kim, Jae-Woo; Lin, Yi; Nunez, Jennifer Carpena; Siochi, Emilie J.; Wise, Kristopher E.; Connell, John W.; Smith, Michael W.

2011-01-01

To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

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.

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.

Ultrasound exfoliation of inorganic analogues of graphene

PubMed Central

2014-01-01

High-intensity ultrasound exfoliation of a bulk-layered material is an attractive route for large-scale preparation of monolayers. The monolayer slices could potentially be prepared with a high yield (up to 100%) in a few minutes. Exfoliation of natural minerals (such as tungstenite and molybdenite) or bulk synthetic materials (including hexagonal boron nitride (h-BN), hexagonal boron carbon nitride (h-BCN), and graphitic carbon nitride (g-C3N4)) in liquids leads to the breakdown of the 3D graphitic structure into a 2D structure; the efficiency of this process is highly dependent upon the physical effects of the ultrasound. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were employed to verify the quality of the exfoliation. Herein, this new method of exfoliation with ultrasound assistance for application to mono- and bilayered materials in hydrophobic and hydrophilic environments is presented. PMID:24708572

Ultrasound exfoliation of inorganic analogues of graphene.

PubMed

Stengl, Václav; Henych, Jiří; Slušná, Michaela; Ecorchard, Petra

2014-04-05

High-intensity ultrasound exfoliation of a bulk-layered material is an attractive route for large-scale preparation of monolayers. The monolayer slices could potentially be prepared with a high yield (up to 100%) in a few minutes. Exfoliation of natural minerals (such as tungstenite and molybdenite) or bulk synthetic materials (including hexagonal boron nitride (h-BN), hexagonal boron carbon nitride (h-BCN), and graphitic carbon nitride (g-C3N4)) in liquids leads to the breakdown of the 3D graphitic structure into a 2D structure; the efficiency of this process is highly dependent upon the physical effects of the ultrasound. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were employed to verify the quality of the exfoliation. Herein, this new method of exfoliation with ultrasound assistance for application to mono- and bilayered materials in hydrophobic and hydrophilic environments is presented.

Oven rack having integral lubricious, dry porcelain surface

DOEpatents

Ambrose, Jeffrey A; Mackiewicz-Ludtka, Gail; Sikka, Vinod K; Qu, Jun

2014-06-03

A lubricious glass-coated metal cooking article capable of withstanding repeated heating and cooling between room temperature and at least 500.degree. F. without chipping or cracking the glass coating, wherein the glass coating includes about 0.1 to about 20% by weight of a homogeneously distributed dry refractory lubricant material having a particle size less than about 200 .mu.m. The lubricant material is selected from the group consisting of carbon; graphite; boron nitride; cubic boron nitride; molybdenum (FV) sulfide; molybdenum sulfide; molybdenum (IV) selenide; molybdenum selenide, tungsten (IV) sulfide; tungsten disulfide; tungsten sulfide; silicon nitride (Si.sub.3N.sub.4); TiN; TiC; TiCN; TiO.sub.2; TiAlN; CrN; SiC; diamond-like carbon; tungsten carbide (WC); zirconium oxide (ZrO.sub.2); zirconium oxide and 0.1 to 40 weight % aluminum oxide; alumina-zirconia; antimony; antimony oxide; antimony trioxide; and mixtures thereof.

Wafer-Scale and Wrinkle-Free Epitaxial Growth of Single-Orientated Multilayer Hexagonal Boron Nitride on Sapphire.

PubMed

Jang, A-Rang; Hong, Seokmo; Hyun, Chohee; Yoon, Seong In; Kim, Gwangwoo; Jeong, Hu Young; Shin, Tae Joo; Park, Sung O; Wong, Kester; Kwak, Sang Kyu; Park, Noejung; Yu, Kwangnam; Choi, Eunjip; Mishchenko, Artem; Withers, Freddie; Novoselov, Kostya S; Lim, Hyunseob; Shin, Hyeon Suk

2016-05-11

Large-scale growth of high-quality hexagonal boron nitride has been a challenge in two-dimensional-material-based electronics. Herein, we present wafer-scale and wrinkle-free epitaxial growth of multilayer hexagonal boron nitride on a sapphire substrate by using high-temperature and low-pressure chemical vapor deposition. Microscopic and spectroscopic investigations and theoretical calculations reveal that synthesized hexagonal boron nitride has a single rotational orientation with AA' stacking order. A facile method for transferring hexagonal boron nitride onto other target substrates was developed, which provides the opportunity for using hexagonal boron nitride as a substrate in practical electronic circuits. A graphene field effect transistor fabricated on our hexagonal boron nitride sheets shows clear quantum oscillation and highly improved carrier mobility because the ultraflatness of the hexagonal boron nitride surface can reduce the substrate-induced degradation of the carrier mobility of two-dimensional materials.

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;

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.

Tribological properties of boron nitride synthesized by ion beam deposition

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Spalvins, T.

1985-01-01

The adhesion and friction behavior of boron nitride films on 440 C bearing stainless steel substrates was examined. The thin films containing the boron nitride were synthesized using an ion beam extracted from a borazine plasma. Sliding friction experiments were conducted with BN in sliding contact with itself and various transition metals. It is indicated that the surfaces of atomically cleaned BN coating film contain a small amount of oxides and carbides, in addition to boron nitride. The coefficients of friction for the BN in contact with metals are related to the relative chemical activity of the metals. The more active the metal, the higher is the coefficient of friction. The adsorption of oxygen on clean metal and BN increases the shear strength of the metal - BN contact and increases the friction. The friction for BN-BN contact is a function of the shear strength of the elastic contacts. Clean BN surfaces exhibit relatively strong interfacial adhesion and high friction. The presence of adsorbates such as adventitious carbon contaminants on the BN surfaces reduces the shear strength of the contact area. In contrast, chemically adsorbed oxygen enhances the shear strength of the BN-BN contact and increases the friction.

BN Bonded BN fiber article and method of manufacture

DOEpatents

Hamilton, Robert S.

1981-08-18

A boron nitride bonded boron nitride fiber article and the method for its manufacture which comprises forming a shaped article with a composition comprising a bonding compound selected from boron oxide and boric acid and a structural fiber selected from the group consisting of boron oxide, boron nitride and partially nitrided boron oxide fibers, heating the composition in an anhydrous gas to a temperature above the melting point of the compound and nitriding the resulting article in ammonia gas.

Rich interfacial chemistry and properties of carbon-doped hexagonal boron nitride nanosheets revealed by electronic structure calculations

NASA Astrophysics Data System (ADS)

Xie, Wei; Tamura, Takahiro; Yanase, Takashi; Nagahama, Taro; Shimada, Toshihiro

2018-04-01

The effect of C doping to hexagonal boron nitride (h-BN) to its electronic structure is examined by first principles calculations using the association from π-electron systems of organic molecules embedded in a two-dimensional insulator. In a monolayered carbon-doped structure, odd-number doping with carbon atoms confers metallic properties with different work functions. Various electronic interactions occur between two layers with odd-number carbon substitution. A direct sp3 covalent chemical bond is formed when C replaces adjacent B and N in different layers. A charge transfer complex between layers is found when C replaces B and N in the next-neighboring region, which results in narrower band gaps (e.g., 0.37 eV). Direct bonding between C and B atoms is found when two C atoms in different layers are at a certain distance.

Interlayer interaction and mechanical properties in multi-layer graphene, Boron-Nitride, Aluminum-Nitride and Gallium-Nitride graphene-like structure: A quantum-mechanical DFT study

NASA Astrophysics Data System (ADS)

Ghorbanzadeh Ahangari, Morteza; Fereidoon, A.; Hamed Mashhadzadeh, Amin

2017-12-01

In present study, we investigated mechanical, electronic and interlayer properties of mono, bi and 3layer of Boron-Nitride (B-N), Aluminum-Nitride (Al-N) and Gallium-Nitride (Ga-N) graphene sheets and compared these results with results obtained from carbonic graphenes (C-graphenes). For reaching this purpose, first we optimized the geometrical parameters of these graphenes by using density functional theory (DFT) method. Then we calculated Young's modulus of graphene sheet by compressing and then elongating these sheets in small increment. Our results indicates that Young's modulus of graphenes didn't changed obviously by increasing the number of layer sheet. We also found that carbonic graphene has greatest Young's modulus among another mentioned sheets because of smallest equilibrium distance between its elements. Next we modeled the van der Waals interfacial interaction exist between two sheets with classical spring model by using general form of Lennard-Jones (L-J) potential for all of mentioned graphenes. For calculating L-J parameters (ε and σ), the potential energy between layers of mentioned graphene as a function of the separation distance was plotted. Moreover, the density of states (DOS) are calculated to understand the electronic properties of these systems better.

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.

Synthesis of thin films in boron-carbon-nitrogen ternary system by microwave plasma enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kukreja, Ratandeep Singh

The Boron Carbon Nitorgen (B-C-N) ternary system includes materials with exceptional properties such as wide band gap, excellent thermal conductivity, high bulk modulus, extreme hardness and transparency in the optical and UV range that find application in most fields ranging from micro-electronics, bio-sensors, and cutting tools to materials for space age technology. Interesting materials that belong to the B-C-N ternary system include Carbon nano-tubes, Boron Carbide, Boron Carbon Nitride (B-CN), hexagonal Boron Nitride ( h-BN), cubic Boron Nitride (c-BN), Diamond and beta Carbon Nitride (beta-C3N4). Synthesis of these materials requires precisely controlled and energetically favorable conditions. Chemical vapor deposition is widely used technique for deposition of thin films of ceramics, metals and metal-organic compounds. Microwave plasma enhanced chemical vapor deposition (MPECVD) is especially interesting because of its ability to deposit materials that are meta-stable under the deposition conditions, for e.g. diamond. In the present study, attempt has been made to synthesize beta-carbon nitride (beta-C3N4) and cubic-Boron Nitride (c-BN) thin films by MPECVD. Also included is the investigation of dependence of residual stress and thermal conductivity of the diamond thin films, deposited by MPECVD, on substrate pre-treatment and deposition temperature. Si incorporated CNx thin films are synthesized and characterized while attempting to deposit beta-C3N4 thin films on Si substrates using Methane (CH4), Nitrogen (N2), and Hydrogen (H2). It is shown that the composition and morphology of Si incorporated CNx thin film can be tailored by controlling the sequence of introduction of the precursor gases in the plasma chamber. Greater than 100mum size hexagonal crystals of N-Si-C are deposited when Nitrogen precursor is introduced first while agglomerates of nano-meter range graphitic needles of C-Si-N are deposited when Carbon precursor is introduced first in the deposition chamber. Hexagonal -- BN thin films are successfully deposited using Diborane (B2H6) (5% in H2), Ammonia (NH3) and H2 as precursor gases in the conventional MPECVD mode with and without the negative DC bias. The quality of h-BN in the films improved with pressure and when NH3 used as the first precursor gas in the deposition chamber. c-BN thin films are successfully deposited using Boron-Trifluoride (BF3) (10% in Argon (Ar)), N2, H2, Ar and Helium (He) gases in the electron cyclotron resonance (ECR) mode of the MPECVD system with negative DC bias. Up-to 66% c-BN in the films is achieved under deposition conditions of lower gas flow rates and higher deposition pressures than that reported in the literature for film deposited by ECR-MPECVD. It is shown that the percentage c-BN in the films correlates with the deposition pressure, BF3/H2 ratio and, negative DC bias during nucleation and growth. Diamond thin films are deposited using 60%Ar, 39% H2 and, 1%CH4 at 600°C, 700°C and 800°C substrate temperatures, measured by an IR pyrometer, on Si substrates pre-treated with 3-6nm diamond sol and 20-40mum diamond slurry. Raman spectroscopy, FTIR, X-Ray diffraction (XRD) and, photo-thermal reflectivity methods are used to characterize the thin films. Residual stresses observed for the diamond thin films deposited in this study are tensile in nature and increased with deposition temperature. Better quality diamond films with lower residual stresses are obtained for films deposited on Si substrate pre-treated with 3-6nm diamond sol. Preliminary results on thermal conductivity, k, suggest that k is directly dependent on the deposition temperature and independent of substrate pre-treatment signifying that the nano-seeding technique can be used to replace conventional surface activation technique for diamond seeding where needed.

Dispersible shortened boron nitride nanotubes with improved molecule-loading capacity.

PubMed

Zhi, Chunyi; Hanagata, Nobutaka; Bando, Yoshio; Golberg, Dmitri

2011-09-05

The oxidation process of boron nitride nanotubes was thoroughly investigated, and a slow oxidation characteristic was clearly revealed. Subsequently, the controllable oxidation process was utilized to break the sturdy structure of the boron nitride nanotubes to fabricate shortened nanotubes. The shortened boron nitride nanotubes were found to possess good solubility in water and many organic solvents. Further experiments demonstrated remarkably improved molecule-loading capacity of the shortened boron nitride nanotubes. These dispersible shortened boron nitride nanotubes might have the potential to be developed as effective delivery systems for various molecules, which may find applications in bio-related fields. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of graphitic carbon nitride and boron carbon nitride film on sapphire substrate

NASA Astrophysics Data System (ADS)

Kosaka, Maito; Urakami, Noriyuki; Hashimoto, Yoshio

2018-02-01

As a novel production method of boron carbon nitride (BCN) films, in this paper, we present the incorporation of B into graphitic carbon nitride (g-C3N4). First, we investigated the formation of g-C3N4 films via chemical vapor deposition (CVD) using melamine powder as the precursor. The formation of g-C3N4 films on a c-plane sapphire substrate was confirmed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy measurements. The deposition temperature of g-C3N4 films was found to be suitable between 550 and 600 °C since the degradation and desorption of hexagonal C-N bonds should be suppressed. As for BCN films, we prepared BCN films via two-zone extended CVD using ammonia borane as the B precursor. Several XPS signals from B, C, and N core levels were detected from B-incorporated g-C3N4 films. While the N composition was almost constant, the marked tendencies for increasing B composition and decreasing C composition were achieved with the increase in the B incorporation, indicating the incorporation of B atoms by the substitution for C atoms. Optical absorptions were shifted to the high-energy side by B incorporation, which indicates the successful formation of BCN films using melamine and ammonia borane powders as precursors.

Nanotube phonon waveguide

DOEpatents

Chang, Chih-Wei; Zettl, Alexander K.

2013-10-29

Disclosed are methods and devices in which certain types of nanotubes (e.g., carbon nanotubes and boron nitride nanotubes conduct heat with high efficiency and are therefore useful in electronic-type devices.

Friction and transfer behavior of pyrolytic boron nitride in contact with various metals

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1976-01-01

Sliding friction experiments were conducted with pyrolytic boron nitride in sliding contact with itself and various metals. Auger emission spectroscopy was used to monitor transfer of pyrolytic boron nitride to metals and metals to pyrolytic boron nitride. Results indicate that the friction coefficient for pyrolytic boron nitride in contact with metals can be related to the chemical activity of the metals and more particularly to the d valence bond character of the metal. Transfer was found to occur to all metals except silver and gold and the amount of transfer was less in the presence than in the absence of metal oxide. Friction was less for pyrolytic boron nitride in contact with a metal in air than in vacuum.

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.

Novel 3D metallic boron nitride containing only sp2 bonds

NASA Astrophysics Data System (ADS)

Wang, Hao; Zhang, Wei; Huai, Ping

2017-09-01

As the closest isoelectronic analogue of carbon, boron nitride (BN) shares a similar structure with carbon from 1D nanotubes, 2D nanosheets, and 3D diamond structures. However, most BN structures are insulators, which limits their application. In this work, under the inspiration of the sp2 hybridized carbon honeycomb, we propose a hexagonal phase of BN consisting of only sp2 bonds, which exhibits intriguingly intrinsic metallicity. First-principles calculations confirm that this phase is both thermally and dynamically stable. Moreover, the calculations on the band structure, partial density states and electron localization function suggest that the metallic behavior is attributable to the delocalized B-2p electrons, leading to second-neighbor interaction between the p z states of sp2-bonded B atoms in adjacent layers. Our findings not only enrich the BN allotrope family with 3D structures but also stimulate further experimental interest in applications of metallic BN in electronic devices.

In Situ Formation of Carbon Nanotubes Encapsulated within Boron Nitride Nanotubes via Electron Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arenal, Raul; Lopez-Bezanilla, Alejandro

2014-07-25

We report experimental evidence of the formation by in situ electron-irradiation of single-walled carbon nanotubes (C NT) confined within boron nitride nanotubes (BN-NT). The electron radiation stemming from the microscope supplies the energy required by the amorphous carbonaceous structures to crystallize in a tubular form in a catalyst free procedure, at room temperature and high vacuum. The structural defects resulting from the interaction of the shapeless carbon with the BN nanotube are corrected in a self-healing process throughout the crystallinization. Structural changes developed during the irradiation process such as defects formation and evolution, shrinkage, and shortness of the BN-NT weremore » in situ monitored. The outer BN wall provides a protective and insulating shell against environmental Perturbations to the inner C-NT without affecting their electronic properties, as demonstrated by first principles calculations.« less

Boron Nitride Coated Carbon Nanotube Arrays with Enhanced Compressive Mechanical Property

NASA Astrophysics Data System (ADS)

Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Tan, Dunlin; Zhang, Bowei; Tok, Alfred Iing Yoong; Teo, Edwin Hang Tong

Vertically aligned carbon nanotube (CNT) array is one of the most promising energy dissipating materials due to its excellent temperature invariant mechanical property. However, the CNT arrays with desirable recoverability after compression is still a challenge. Here, we report on the mechanical enhancement of the CNT arrays reinforced by coating with boron nitride (BN) layers. These BN coated CNT (BN/CNT) arrays exhibit excellent compressive strength and recoverability as compared to those of the as-prepared CNT arrays which totally collapsed after compression. In addition, the BN coating also provides better resistance to oxidation due to its intrinsic thermal stability. This work presented here opens a new pathway towards tuning mechanical behavior of any arbitrary CNT arrays for promising potential such as damper, vibration isolator and shock absorber applications.

Effect of MoO3 on the synthesis of boron nitride nanotubes over Fe and Ni catalysts.

PubMed

Nithya, Jeghan Shrine Maria; Pandurangan, Arumugam

2012-05-01

Synthesis of boron nitride nanotubes at reduced temperature is important for industrial manufactures. In this study boron nitride nanotubes were synthesized by thermal evaporation method using B/Fe2O3/MoO3 and B/Ni2O3/MoO3 mixtures separately with ammonia as the nitrogen source. The growth of boron nitride nanotubes occurred at 1100 degrees C, which was relatively lower than other metal oxides assisted growth processes requiring higher than 1200 degrees C. MoO3 promoted formation of B2O2 and aided boron nitride nanotubes growth at a reduced temperature. The boron nitride nanotubes with bamboo shaped, nested cone structured and straight tubes like forms were evident from the high resolution transmission electron microscopy. Metallic Fe and Ni, formed during the process, were the catalysts for the growth of boron nitride nanotubes. Their formation was established by X-ray diffraction. FT Raman showed a peak due to B-N vibration of BNNTs close to 1370 cm(-1). Hence MoO3 assisted growth of boron nitride nanotubes is advantageous, as it significantly reduced the synthesis temperature.

Spherical boron nitride particles and method for preparing them

DOEpatents

Phillips, Jonathan; Gleiman, Seth S.; Chen, Chun-Ku

2003-11-25

Spherical and polyhedral particles of boron nitride and method of preparing them. Spherical and polyhedral particles of boron nitride are produced from precursor particles of hexagonal phase boron nitride suspended in an aerosol gas. The aerosol is directed to a microwave plasma torch. The torch generates plasma at atmospheric pressure that includes nitrogen atoms. The presence of nitrogen atoms is critical in allowing boron nitride to melt at atmospheric pressure while avoiding or at least minimizing decomposition. The plasma includes a plasma hot zone, which is a portion of the plasma that has a temperature sufficiently high to melt hexagonal phase boron nitride. In the hot zone, the precursor particles melt to form molten particles that acquire spherical and polyhedral shapes. These molten particles exit the hot zone, cool, and solidify to form solid particles of boron nitride with spherical and polyhedral shapes. The molten particles can also collide and join to form larger molten particles that lead to larger spherical and polyhedral particles.

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers

PubMed Central

Domun, Nadiim; Paton, Keith R.; Sainsbury, Toby; Zhang, Tao; Mohamud, Hibaaq

2017-01-01

In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs) was used as single filler, increased the critical strain energy release rate, GIC, by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS) were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs) and boron nitride nanotubes (BNNTs) were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly. PMID:29048345

Efficient Gate-tunable light-emitting device made of defective boron nitride nanotubes: from ultraviolet to the visible

PubMed Central

Attaccalite, Claudio; Wirtz, Ludger; Marini, Andrea; Rubio, Angel

2013-01-01

Boron nitride is a promising material for nanotechnology applications due to its two-dimensional graphene-like, insulating, and highly-resistant structure. Recently it has received a lot of attention as a substrate to grow and isolate graphene as well as for its intrinsic UV lasing response. Similar to carbon, one-dimensional boron nitride nanotubes (BNNTs) have been theoretically predicted and later synthesised. Here we use first principles simulations to unambiguously demonstrate that i) BN nanotubes inherit the highly efficient UV luminescence of hexagonal BN; ii) the application of an external perpendicular field closes the electronic gap keeping the UV lasing with lower yield; iii) defects in BNNTS are responsible for tunable light emission from the UV to the visible controlled by a transverse electric field (TEF). Our present findings pave the road towards optoelectronic applications of BN-nanotube-based devices that are simple to implement because they do not require any special doping or complex growth. PMID:24060843

Interaction of Boron Nitride Nanosheets with Model Cell Membranes.

PubMed

Hilder, Tamsyn A; Gaston, Nicola

2016-06-03

Boron nitride nanomaterials have attracted attention for biomedical applications, due to their improved biocompatibility when compared with carbon nanomaterials. Recently, graphene and graphene oxide nanosheets have been shown, both experimentally and computationally, to destructively extract phospholipids from Escherichia coli. Boron nitride nanosheets (BNNSs) have exciting potential biological and environmental applications, for example the ability to remove oil from water. These applications are likely to increase the exposure of prokaryotes and eukaryotes to BNNSs. Yet, despite their promise, the interaction between BNNSs and cell membranes has not yet been investigated. Here, all-atom molecular dynamics simulations were used to demonstrate that BNNSs are spontaneously attracted to the polar headgroups of the lipid bilayer. The BNNSs do not passively cross the lipid bilayer, most likely due to the large forces experienced by the BNNSs. This study provides insight into the interaction of BNNSs with cell membranes and may aid our understanding of their improved biocompatibility. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers.

PubMed

Domun, Nadiim; Paton, Keith R; Hadavinia, Homayoun; Sainsbury, Toby; Zhang, Tao; Mohamud, Hibaaq

2017-10-19

In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs) was used as single filler, increased the critical strain energy release rate, G IC , by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS) were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs) and boron nitride nanotubes (BNNTs) were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly.

Transition-metal dispersion on carbon-doped boron nitride nanostructures: Applications for high-capacity hydrogen storage

NASA Astrophysics Data System (ADS)

Chen, Ming; Zhao, Yu-Jun; Liao, Ji-Hai; Yang, Xiao-Bao

2012-07-01

Using density-functional theory calculations, we investigated the adsorption of transition-metal (TM) atoms (TM = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) on carbon doped hexagonal boron nitride (BN) sheet and the corresponding cage (B12N12). With carbon substitution of nitrogen, Sc, V, Cr, and Mn atoms were energetically favorable to be dispersed on the BN nanostructures without clustering or the formation of TM dimers, due to the strong binding between TM atoms and substrate, which contains the half-filled levels above the valence bands maximum. The carbon doped BN nanostructures with dispersed Sc could store up to five and six H2, respectively, with the average binding energy of 0.3 ˜ 0.4 eV, indicating the possibility of fabricating hydrogen storage media with high capacity. We also demonstrated that the geometrical effect is important for the hydrogen storage, leading to a modulation of the charge distributions of d levels, which dominates the binding between H2 and TM atoms.

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.

Chemical Sharpening, Shortening, and Unzipping of Boron Nitride Nanotubes

NASA Technical Reports Server (NTRS)

Liao, Yunlong; Chen, Zhongfang; Connell, John W.; Fay, Catharine C.; Park, Cheol; Kim, Jae-Woo; Lin, Yi

2014-01-01

Boron nitride nanotubes (BNNTs), the one-dimensional member of the boron nitride nanostructure family, are generally accepted to be highly inert to oxidative treatments and can only be covalently modifi ed by highly reactive species. Conversely, it is discovered that the BNNTs can be chemically dispersed and their morphology modifi ed by a relatively mild method: simply sonicating the nanotubes in aqueous ammonia solution. The dispersed nanotubes are significantly corroded, with end-caps removed, tips sharpened, and walls thinned. The sonication treatment in aqueous ammonia solution also removes amorphous BN impurities and shortened BNNTs, resembling various oxidative treatments of carbon nanotubes. Importantly, the majority of BNNTs are at least partially longitudinally cut, or "unzipped". Entangled and freestanding BN nanoribbons (BNNRs), resulting from the unzipping, are found to be approximately 5-20 nm in width and up to a few hundred nanometers in length. This is the fi rst chemical method to obtain BNNRs from BNNT unzipping. This method is not derived from known carbon nanotube unzipping strategies, but is unique to BNNTs because the use of aqueous ammonia solutions specifi cally targets the B-N bond network. This study may pave the way for convenient processing of BNNTs, previously thought to be highly inert, toward controlling their dispersion, purity, lengths, and electronic properties.

Oxygen- and Lithium-Doped Hybrid Boron-Nitride/Carbon Networks for Hydrogen Storage.

PubMed

Shayeganfar, Farzaneh; Shahsavari, Rouzbeh

2016-12-20

Hydrogen storage capacities have been studied on newly designed three-dimensional pillared boron nitride (PBN) and pillared graphene boron nitride (PGBN). We propose these novel materials based on the covalent connection of BNNTs and graphene sheets, which enhance the surface and free volume for storage within the nanomaterial and increase the gravimetric and volumetric hydrogen uptake capacities. Density functional theory and molecular dynamics simulations show that these lithium- and oxygen-doped pillared structures have improved gravimetric and volumetric hydrogen capacities at room temperature, with values on the order of 9.1-11.6 wt % and 40-60 g/L. Our findings demonstrate that the gravimetric uptake of oxygen- and lithium-doped PBN and PGBN has significantly enhanced the hydrogen sorption and desorption. Calculations for O-doped PGBN yield gravimetric hydrogen uptake capacities greater than 11.6 wt % at room temperature. This increased value is attributed to the pillared morphology, which improves the mechanical properties and increases porosity, as well as the high binding energy between oxygen and GBN. Our results suggest that hybrid carbon/BNNT nanostructures are an excellent candidate for hydrogen storage, owing to the combination of the electron mobility of graphene and the polarized nature of BN at heterojunctions, which enhances the uptake capacity, providing ample opportunities to further tune this hybrid material for efficient hydrogen storage.

Radio Frequency Plasma Synthesis of Boron Nitride Nanotubes (BNNTs) for Structural Applications: Part I

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Alexa, Joel A.; Jensen, Brian J.; Thomsen, Donald L.

2016-01-01

It is evident that nanotubes, such as carbon, boron nitride and even silicon, offer great potential for many aerospace applications. The opportunity exists to harness the extremely high strength and stiffness exhibited by high-purity, low-defect nanotubes in structural materials. Even though the technology associated with carbon nanotube (CNT) development is mature, the mechanical property benefits have yet to be fully realized. Boron nitride nanotubes (BNNTs) offer similar structural benefits, but exhibit superior chemical and thermal stability. A broader range of potential structural applications results, particularly as reinforcing agents for metal- and ceramic- based composites. However, synthesis of BNNTs is more challenging than CNTs mainly because of the higher processing temperatures required, and mass production techniques have yet to emerge. A promising technique is radio frequency plasma spray (RFPS), which is an inductively coupled, very high temperature process. The lack of electrodes and the self- contained, inert gas environment lend themselves to an ultraclean product. It is the aim of this White Paper to survey the state of the art with regard to nano-material production by analyzing the pros and cons of existing methods. The intention is to combine the best concepts and apply the NASA Langley Research Center (LaRC) RFPS facility to reliably synthesize large quantities of consistent, high-purity BNNTs.

Boron nitride housing cools transistors

NASA Technical Reports Server (NTRS)

1965-01-01

Boron nitride ceramic heat sink cools transistors in r-f transmitter and receiver circuits. Heat dissipated by the transistor is conducted by the boron nitride housing to the metal chassis on which it is mounted.

Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity.

PubMed

Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

2016-01-19

Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets' interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation.

Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity

PubMed Central

Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

2016-01-01

Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets’ interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation. PMID:26783258

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.

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.

Growth of single-layer boron nitride dome-shaped nanostructures catalysed by iron clusters.

PubMed

Torre, A La; Åhlgren, E H; Fay, M W; Ben Romdhane, F; Skowron, S T; Parmenter, C; Davies, A J; Jouhannaud, J; Pourroy, G; Khlobystov, A N; Brown, P D; Besley, E; Banhart, F

2016-08-11

We report on the growth and formation of single-layer boron nitride dome-shaped nanostructures mediated by small iron clusters located on flakes of hexagonal boron nitride. The nanostructures were synthesized in situ at high temperature inside a transmission electron microscope while the e-beam was blanked. The formation process, typically originating at defective step-edges on the boron nitride support, was investigated using a combination of transmission electron microscopy, electron energy loss spectroscopy and computational modelling. Computational modelling showed that the domes exhibit a nanotube-like structure with flat circular caps and that their stability was comparable to that of a single boron nitride layer.

Packing C60 in Boron Nitride Nanotubes

NASA Astrophysics Data System (ADS)

Mickelson, W.; Aloni, S.; Han, Wei-Qiang; Cumings, John; Zettl, A.

2003-04-01

We have created insulated C60 nanowire by packing C60 molecules into the interior of insulating boron nitride nanotubes (BNNTs). For small-diameter BNNTs, the wire consists of a linear chain of C60 molecules. With increasing BNNT inner diameter, unusual C60 stacking configurations are obtained (including helical, hollow core, and incommensurate) that are unknown for bulk or thin-film forms of C60. C60 in BNNTs thus presents a model system for studying the properties of dimensionally constrained ``silo'' crystal structures. For the linear-chain case, we have fused the C60 molecules to form a single-walled carbon nanotube inside the insulating BNNT.

Continuous Growth of Hexagonal Graphene and Boron Nitride In-Plane Heterostructures by Atmospheric Pressure Chemical Vapor Deposition

PubMed Central

Han, Gang Hee; Rodríguez-Manzo, Julio A.; Lee, Chan-Woo; Kybert, Nicholas J.; Lerner, Mitchell B.; Qi, Zhengqing John; Dattoli, Eric N.; Rappe, Andrew M.; Drndic, Marija; Charlie Johnson, A. T.

2013-01-01

Graphene-boron nitride monolayer heterostructures contain adjacent electrically active and insulating regions in a continuous, single-atom thick layer. To date structures were grown at low pressure, resulting in irregular shapes and edge direction, so studies of the graphene-boron nitride interface were restricted to microscopy of nano-domains. Here we report templated growth of single crystalline hexagonal boron nitride directly from the oriented edge of hexagonal graphene flakes by atmospheric pressure chemical vapor deposition, and physical property measurements that inform the design of in-plane hybrid electronics. Ribbons of boron nitride monolayer were grown from the edge of a graphene template and inherited its crystallographic orientation. The relative sharpness of the interface was tuned through control of growth conditions. Frequent tearing at the graphene-boron nitride interface was observed, so density functional theory was used to determine that the nitrogen-terminated interface was prone to instability during cool down. The electronic functionality of monolayer heterostructures was demonstrated through fabrication of field effect transistors with boron nitride as an in-plane gate dielectric. PMID:24182310

Continuous growth of hexagonal graphene and boron nitride in-plane heterostructures by atmospheric pressure chemical vapor deposition.

PubMed

Han, Gang Hee; Rodríguez-Manzo, Julio A; Lee, Chan-Woo; Kybert, Nicholas J; Lerner, Mitchell B; Qi, Zhengqing John; Dattoli, Eric N; Rappe, Andrew M; Drndic, Marija; Johnson, A T Charlie

2013-11-26

Graphene-boron nitride monolayer heterostructures contain adjacent electrically active and insulating regions in a continuous, single-atom thick layer. To date structures were grown at low pressure, resulting in irregular shapes and edge direction, so studies of the graphene-boron nitride interface were restricted to the microscopy of nanodomains. Here we report templated growth of single crystalline hexagonal boron nitride directly from the oriented edge of hexagonal graphene flakes by atmospheric pressure chemical vapor deposition, and physical property measurements that inform the design of in-plane hybrid electronics. Ribbons of boron nitride monolayer were grown from the edge of a graphene template and inherited its crystallographic orientation. The relative sharpness of the interface was tuned through control of growth conditions. Frequent tearing at the graphene-boron nitride interface was observed, so density functional theory was used to determine that the nitrogen-terminated interface was prone to instability during cool down. The electronic functionality of monolayer heterostructures was demonstrated through fabrication of field effect transistors with boron nitride as an in-plane gate dielectric.

Direct growth of graphene on in situ epitaxial hexagonal boron nitride flakes by plasma-assisted molecular beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza

2015-11-23

Hexagonal boron nitride (h-BN) single-crystal domains were grown on cobalt (Co) substrates at a substrate temperature of 850–900 °C using plasma-assisted molecular beam epitaxy. Three-point star shape h-BN domains were observed by scanning electron microscopy, and confirmed by Raman and X-ray photoelectron spectroscopy. The h-BN on Co template was used for in situ growth of multilayer graphene, leading to an h-BN/graphene heterostructure. Carbon atoms preferentially nucleate on Co substrate and edges of h-BN and then grow laterally to form continuous graphene. Further introduction of carbon atoms results in layer-by-layer growth of graphene on graphene and lateral growth of graphene on h-BNmore » until it may cover entire h-BN flakes.« less

Electric heater for nuclear fuel rod simulators

DOEpatents

McCulloch, Reginald W.; Morgan, Jr., Chester S.; Dial, Ralph E.

1982-01-01

The present invention is directed to an electric cartridge-type heater for use as a simulator for a nuclear fuel pin in reactor studies. The heater comprises an elongated cylindrical housing containing a longitudinally extending helically wound heating element with the heating element radially inwardly separated from the housing. Crushed cold-pressed preforms of boron nitride electrically insulate the heating element from the housing while providing good thermal conductivity. Crushed cold-pressed preforms of magnesia or a magnesia-15 percent boron nitride mixture are disposed in the cavity of the helical heating element. The coefficient of thermal expansion of the magnesia or the magnesia-boron nitride mixture is higher than that of the boron nitride disposed about the heating element for urging the boron nitride radially outwardly against the housing during elevated temperatures to assure adequate thermal contact between the housing and the boron nitride.

Additive Manufacturing of Dense Hexagonal Boron Nitride Objects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marquez Rossy, Andres E.; Armstrong, Beth L.; Elliott, Amy M.

The feasibility of manufacturing hexagonal boron nitride objects via additive manufacturing techniques was investigated. It was demonstrated that it is possible to hot-extrude thermoplastic filaments containing uniformly distributed boron nitride particles with a volume concentration as high as 60% and that these thermoplastic filaments can be used as feedstock for 3D-printing objects using a fused deposition system. Objects 3D-printed by fused deposition were subsequently sintered at high temperature to obtain dense ceramic products. In a parallel study the behavior of hexagonal boron nitride in aqueous solutions was investigated. It was shown that the addition of a cationic dispersant to anmore » azeotrope enabled the formulation of slurries with a volume concentration of boron nitride as high as 33%. Although these slurries exhibited complex rheological behavior, the results from this study are encouraging and provide a pathway for manufacturing hexagonal boron nitride objects via robocasting.« less

Carbon Coated Boron Nitride Nanosheets for Polymer Nanocomposites with Enhanced Dielectric Performance

PubMed Central

Yang, Minhao; Zhao, Hang; He, Delong; Hu, Chaohe; Chen, Haowei; Bai, Jinbo

2017-01-01

Carbon coated boron nitride nanosheets (BNNSs@C) hybrids with different carbon contents were synthesized by a chemical vapor deposition (CVD) method. The content of carbon in as-obtained BNNSs@C hybrids could be precisely adjusted from 2.50% to 22.62% by controlling the carbon deposition time during the CVD procedure. Afterward, the BNNSs@C hybrids were subsequently incorporated into the polyvinylidene fluoride (PVDF) matrix to fabricate the BNNSs@C/PVDF nanocomposites through a combination of solution and melting blending methods. The dielectric properties of the as-obtained BNNSs@C/PVDF nanocomposites could be accurately tuned by adjusting the carbon content. The resultant nanocomposites could afford a high dielectric constant about 39 (103 Hz) at BNNSs@C hybrids loading of 30 vol %, which is 4.8 times larger than that of pristine BNNSs-filled ones at the same filler loading, and 3.5 times higher than that of pure PVDF matrix. The largely enhanced dielectric performance could be ascribed to the improved interfacial polarizations of BNNSs/carbon and carbon/PVDF interfaces. The approach reported here offers an effective and alternative method to fabricate high-performance dielectric nanocomposites, which could be potentially applied to the embedded capacitors with high dielectric performance. PMID:28773105

Preliminary study on preparation of BCNO phosphor particles using citric acid as carbon source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nuryadin, Bebeh W.; Pratiwi, Tripuspita; Faryuni, Irfana D.

A citric acid was used as a carbon source in the preparation of boron carbon oxy-nitride (BCNO) phosphor particles by a facile process. The preparation process was conducted at relatively low temperature 750 °C and at ambient pressure. The prepared BCNO phosphors showed a high photoluminescence (PL) performance at peak emission wavelength of 470 nm under excitation by a UV light 365 nm. The effects of carbon/boron and nitrogen/boron molar ratios on the PL properties were also investigated. The result showed that the emission spectra with a wavelength peak ranging from 444 nm to 496 nm can be obtained bymore » varying carbon/boron ratios from 0.1 to 0.9. In addition, the observations showed that the BCNO phosphor material has two excitation peaks located at the 365 nm (UV) and 420 nm (blue). Based on these observations, we believe that the citric acid derived BCNO phosphor particles can be a promising inexpensive material for phosphor conversion-based white LED.« less

Boron Nitride Nanotubes

NASA Technical Reports Server (NTRS)

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

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.

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

DTIC Science & Technology

2015-04-24

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...distributions within a PVD plasma plume ablated from a boron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated

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.

Formation of boron nitride coatings on silicon carbide fibers using trimethylborate vapor

NASA Astrophysics Data System (ADS)

Yuan, Mengjiao; Zhou, Tong; He, Jing; Chen, Lifu

2016-09-01

High quality boron nitride (BN) coatings have been grown on silicon carbide (SiC) fibers by carbothermal nitridation and at atmospheric pressure. SiC fibers were first treated in chlorine gas to form CDC (carbide-derived carbon) film on the fiber surface. The CDC-coated SiC fibers were then reacted with trimethylborate vapor and ammonia vapor at high temperature, forming BN coatings by carbothermal reduction. The FT-IR, XPS, XRD, SEM, TEM and AES were used to investigate the formation of the obtained coatings. It has been found that the obtained coatings are composed of phase mixture of h-BN and amorphous carbon, very uniform in thickness, have smooth surface and adhere well with the SiC fiber substrates. The BN-coated SiC fibers retain ∼80% strength of the as-received SiC fibers and show an obvious interfacial debonding and fiber pullout in the SiCf/SiOC composites. This method may be useful for the large scale production of high quality BN coating on silicon carbide fiber.

Predicting the structural and electronic properties of two-dimensional single layer boron nitride sheets

NASA Astrophysics Data System (ADS)

Li, Xiao-Dong; Cheng, Xin-Lu

2018-02-01

Three two-dimensional (2D) single layer boron nitride sheets have been predicted based on the first-principles calculations. These 2D boron nitride sheets are comprised of equivalent boron atoms and nitride atoms with sp2 and sp bond hybridization. The geometry optimization reflects that they all possess stable planar crystal structures with the space group P 6 bar 2 m (D3h3) symmetry. The charge density distribution manifests that the B-N bonds in these boron nitride sheets are covalent in nature but with ionic characteristics. The tunable band gaps indicate their potential applications in nanoscale electronic and optoelectronic devices by changing the length of sp-bonded Bsbnd N linkages.

Boron nitride nanowires synthesis via a simple chemical vapor deposition at 1200 °C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Pervaiz; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd

2015-04-24

A very simple chemical vapor deposition technique is used to synthesize high quality boron nitride nanowires at 1200 °C within a short growth duration of 30 min. FESEM micrograph shows that the as-synthesized boron nitride nanowires have a clear wire like morphology with diameter in the range of ∼20 to 150 nm. HR-TEM confirmed the wire-like structure of boron nitride nanowires, whereas XPS and Raman spectroscopy are used to find out the elemental composition and phase of the synthesized material. The synthesized boron nitride nanowires have potential applications as a sensing element in solid state neutron detector, neutron capture therapy and microelectronicmore » devices with uniform electronic properties.« less

Extreme-UV electrical discharge source

DOEpatents

Fornaciari, Neal R.; Nygren, Richard E.; Ulrickson, Michael A.

2002-01-01

An extreme ultraviolet and soft x-ray radiation electric capillary discharge source that includes a boron nitride housing defining a capillary bore that is positioned between two electrodes one of which is connected to a source of electric potential can generate a high EUV and soft x-ray radiation flux from the capillary bore outlet with minimal debris. The electrode that is positioned adjacent the capillary bore outlet is typically grounded. Pyrolytic boron nitride, highly oriented pyrolytic boron nitride, and cubic boron nitride are particularly suited. The boron nitride capillary bore can be configured as an insert that is encased in an exterior housing that is constructed of a thermally conductive material. Positioning the ground electrode sufficiently close to the capillary bore outlet also reduces bore erosion.

Photoinduced doping in heterostructures of graphene and boron nitride.

PubMed

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

2014-05-01

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

Shock induced polymorphic transition in quartz, carbon, and boron nitride

NASA Technical Reports Server (NTRS)

Tan, Hua; Ahrens, Thomas J.

1990-01-01

The model proposed by Ahrens (1988) to explain the mechanism of the polymorphism in silicates is revised, and the revised model is applied to the quartz/stishovite, graphite/diamond, and graphite-boron nitride (g-BN) phase transformations. In this model, a key assumption is that transformation to a high-density amorphous or possibly liquid phase which rapidly crystallized to the high-pressure phase is triggered by the high temperatures in the shear band and upon crossing the metastable extension of a melting curve. Good agreement between the calcualted results and published data is obtained. The present theory predicts the standard entropy for cubic BN to be 0.4-0.5 J/g K.

Improved high modulus carbon fibers. [elimination of hazards due to electrical properties

NASA Technical Reports Server (NTRS)

Ansell, G. S.; Chen, S. H.; Diffendorf, R. J.; Kim, C. M.; Lemaistre, C. W.; Lyman, C. E.; Shen, T. H.; Wang, J. J. H.

1979-01-01

Carbon fibers which are electrically insulating but still maintain the mechanical properties of the original carbon fibers were investigated. Three approaches were taken to increase the electrical resistance of carbon fibers: (1) boron nitride (BN) coatings; (2) doping of carbon fibers to alter their electrical properties; and (3) low temperature final heat treatment. The structure of carbon fibers and its effect upon properties was also studied. Results are presented.

Enhanced optoelectronic performances of vertically aligned hexagonal boron nitride nanowalls-nanocrystalline diamond heterostructures

NASA Astrophysics Data System (ADS)

Sankaran, Kamatchi Jothiramalingam; Hoang, Duc Quang; Kunuku, Srinivasu; Korneychuk, Svetlana; Turner, Stuart; Pobedinskas, Paulius; Drijkoningen, Sien; van Bael, Marlies K.; D' Haen, Jan; Verbeeck, Johan; Leou, Keh-Chyang; Lin, I.-Nan; Haenen, Ken

2016-07-01

Field electron emission (FEE) properties of vertically aligned hexagonal boron nitride nanowalls (hBNNWs) grown on Si have been markedly enhanced through the use of nitrogen doped nanocrystalline diamond (nNCD) films as an interlayer. The FEE properties of hBNNWs-nNCD heterostructures show a low turn-on field of 15.2 V/μm, a high FEE current density of 1.48 mA/cm2 and life-time up to a period of 248 min. These values are far superior to those for hBNNWs grown on Si substrates without the nNCD interlayer, which have a turn-on field of 46.6 V/μm with 0.21 mA/cm2 FEE current density and life-time of 27 min. Cross-sectional TEM investigation reveals that the utilization of the diamond interlayer circumvented the formation of amorphous boron nitride prior to the growth of hexagonal boron nitride. Moreover, incorporation of carbon in hBNNWs improves the conductivity of hBNNWs. Such a unique combination of materials results in efficient electron transport crossing nNCD-to-hBNNWs interface and inside the hBNNWs that results in enhanced field emission of electrons. The prospective application of these materials is manifested by plasma illumination measurements with lower threshold voltage (370 V) and longer life-time, authorizing the role of hBNNWs-nNCD heterostructures in the enhancement of electron emission.

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.

Engineering and Localization of Quantum Emitters in Large Hexagonal Boron Nitride Layers.

PubMed

Choi, Sumin; Tran, Toan Trong; Elbadawi, Christopher; Lobo, Charlene; Wang, Xuewen; Juodkazis, Saulius; Seniutinas, Gediminas; Toth, Milos; Aharonovich, Igor

2016-11-02

Hexagonal boron nitride is a wide-band-gap van der Waals material that has recently emerged as a promising platform for quantum photonics experiments. In this work, we study the formation and localization of narrowband quantum emitters in large flakes (up to tens of micrometers wide) of hexagonal boron nitride. The emitters can be activated in as-grown hexagonal boron nitride by electron irradiation or high-temperature annealing, and the emitter formation probability can be increased by ion implantation or focused laser irradiation of the as-grown material. Interestingly, we show that the emitters are always localized at the edges of the flakes, unlike most luminescent point defects in three-dimensional materials. Our results constitute an important step on the roadmap of deploying hexagonal boron nitride in nanophotonics applications.

On the buckling of hexagonal boron nitride nanoribbons via structural mechanics

NASA Astrophysics Data System (ADS)

Giannopoulos, Georgios I.

2018-03-01

Monolayer hexagonal boron nitride nanoribbons have similar crystal structure as graphene nanoribbons, have excellent mechanical, thermal insulating and dielectric properties and additionally present chemical stability. These allotropes of boron nitride can be used in novel applications, in which graphene is not compatible, to achieve remarkable performance. The purpose of the present work is to provide theoretical estimations regarding the buckling response of hexagonal boron nitride monolayer under compressive axial loadings. For this reason, a structural mechanics method is formulated which employs the exact equilibrium atomistic structure of the specific two-dimensional nanomaterial. In order to represent the interatomic interactions appearing between boron and nitrogen atoms, the Dreiding potential model is adopted which is realized by the use of three-dimensional, two-noded, spring-like finite elements of appropriate stiffness matrices. The critical compressive loads that cause the buckling of hexagonal boron nitride nanoribbons are computed with respect to their size and chirality while some indicative buckled shapes of them are illustrated. Important conclusions arise regarding the effect of the size and chirality on the structural stability of the hexagonal boron nitride monolayers. An analytical buckling formula, which provides good fitting of the numerical outcome, is proposed.

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.

Interface formation in monolayer graphene-boron nitride heterostructures.

PubMed

Sutter, P; Cortes, R; Lahiri, J; Sutter, E

2012-09-12

The ability to control the formation of interfaces between different materials has become one of the foundations of modern materials science. With the advent of two-dimensional (2D) crystals, low-dimensional equivalents of conventional interfaces can be envisioned: line boundaries separating different materials integrated in a single 2D sheet. Graphene and hexagonal boron nitride offer an attractive system from which to build such 2D heterostructures. They are isostructural, nearly lattice-matched, and isoelectronic, yet their different band structures promise interesting functional properties arising from their integration. Here, we use a combination of in situ microscopy techniques to study the growth and interface formation of monolayer graphene-boron nitride heterostructures on ruthenium. In a sequential chemical vapor deposition process, boron nitride grows preferentially at the edges of existing monolayer graphene domains, which can be exploited for synthesizing continuous 2D membranes of graphene embedded in boron nitride. High-temperature growth leads to intermixing near the interface, similar to interfacial alloying in conventional heterostructures. Using real-time microscopy, we identify processes that eliminate this intermixing and thus pave the way to graphene-boron nitride heterostructures with atomically sharp interfaces.

Template-Free Synthesis of Highly Porous Boron Nitride: Insights into Pore Network Design and Impact on Gas Sorption.

PubMed

Marchesini, Sofia; McGilvery, Catriona M; Bailey, Josh; Petit, Camille

2017-10-24

Production of biocompatible and stable porous materials, e.g., boron nitride, exhibiting tunable and enhanced porosity is a prerequisite if they are to be employed to address challenges such as drug delivery, molecular separations, or catalysis. However, there is currently very limited understanding of the formation mechanisms of porous boron nitride and the parameters controlling its porosity, which ultimately prevents exploiting the material's full potential. Herein, we produce boron nitride with high and tunable surface area and micro/mesoporosity via a facile template-free method using multiple readily available N-containing precursors with different thermal decomposition patterns. The gases are gradually released, creating hierarchical pores, high surface areas (>1900 m 2 /g), and micropore volumes. We use 3D tomography techniques to reconstruct the pore structure, allowing direct visualization of the mesopore network. Additional imaging and analytical tools are employed to characterize the materials from the micro- down to the nanoscale. The CO 2 uptake of the materials rivals or surpasses those of commercial benchmarks or other boron nitride materials reported to date (up to 4 times higher), even after pelletizing. Overall, the approach provides a scalable route to porous boron nitride production as well as fundamental insights into the material's formation, which can be used to design a variety of boron nitride structures.

Chemical and Bandgap Engineering in Monolayer Hexagonal Boron Nitride

PubMed Central

Ba, Kun; Jiang, Wei; Cheng, Jingxin; Bao, Jingxian; Xuan, Ningning; Sun, Yangye; Liu, Bing; Xie, Aozhen; Wu, Shiwei; Sun, Zhengzong

2017-01-01

Monolayer hexagonal boron nitride (h-BN) possesses a wide bandgap of ~6 eV. Trimming down the bandgap is technically attractive, yet poses remarkable challenges in chemistry. One strategy is to topological reform the h-BN’s hexagonal structure, which involves defects or grain boundaries (GBs) engineering in the basal plane. The other way is to invite foreign atoms, such as carbon, to forge bizarre hybrid structures like hetero-junctions or semiconducting h-BNC materials. Here we successfully developed a general chemical method to synthesize these different h-BN derivatives, showcasing how the chemical structure can be manipulated with or without a graphene precursor, and the bandgap be tuned to ~2 eV, only one third of the pristine one’s. PMID:28367992

BN Bonded BN fiber article from boric oxide fiber

DOEpatents

Hamilton, Robert S.

1978-12-19

A boron nitride bonded boron nitride fiber article and the method for its manufacture which comprises forming a shaped article with a composition comprising boron oxide fibers and boric acid, heating the composition in an anhydrous gas to a temperature above the melting point of the boric acid and nitriding the resulting article in ammonia gas.

Multi-Functional BN-BN Composite

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Bryant, Robert G. (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Gibbons, Luke (Inventor); Lowther, Sharon (Inventor); Thibeault, Sheila A. (Inventor); Fay, Catharine C. (Inventor)

2017-01-01

Multifunctional Boron Nitride nanotube-Boron Nitride (BN-BN) nanocomposites for energy transducers, thermal conductors, anti-penetrator/wear resistance coatings, and radiation hardened materials for harsh environments. An all boron-nitride structured BN-BN composite is synthesized. A boron nitride containing precursor is synthesized, then mixed with boron nitride nanotubes (BNNTs) to produce a composite solution which is used to make green bodies of different forms including, for example, fibers, mats, films, and plates. The green bodies are pyrolized to facilitate transformation into BN-BN composite ceramics. The pyrolysis temperature, pressure, atmosphere and time are controlled to produce a desired BN crystalline structure. The wholly BN structured materials exhibit excellent thermal stability, high thermal conductivity, piezoelectricity as well as enhanced toughness, hardness, and radiation shielding properties. By substituting with other elements into the original structure of the nanotubes and/or matrix, new nanocomposites (i.e., BCN, BCSiN ceramics) which possess excellent hardness, tailored photonic bandgap and photoluminescence, result.

Method of enhancing the wettability of boron nitride for use as an electrochemical cell separator

DOEpatents

McCoy, L.R.

1981-01-23

A felt or other fabric of boron nitride suitable for use as an interelectrode separator within an electrochemical cell is wetted with a solution containing a thermally decomposable organic salt of an alkaline earth metal. An aqueous solution of magnesium acetate is the preferred solution for this purpose. After wetting the boron nitride, the solution is dried by heating at a sufficiently low temperature to prevent rapid boiling and the creation of voids within the separator. The dried material is then calcined at an elevated temperature in excess of 400/sup 0/C to provide a coating of an oxide of magnesium on the surface of the boron nitride fibers. A fabric or felt of boron nitride treated in this manner is easily wetted by molten electrolytic salts, such as the alkali metal halides or alkaline earth metal halides, that are used in high temperature, secondary electrochemical cells.

Method of enhancing the wettability of boron nitride for use as an electrochemical cell separator

DOEpatents

McCoy, Lowell R.

1982-01-01

A felt or other fabric of boron nitride suitable for use as an interelecte separator within an electrochemical cell is wetted with a solution containing a thermally decomposable organic salt of an alkaline earth metal. An aqueous solution of magnesium acetate is the preferred solution for this purpose. After wetting the boron nitride, the solution is dried by heating at a sufficiently low temperature to prevent rapid boiling and the creation of voids within the separator. The dried material is then calcined at an elevated temperature in excess of 400.degree. C. to provide a coating of an oxide of magnesium on the surface of the boron nitride fibers. A fabric or felt of boron nitride treated in this manner is easily wetted by molten electrolytic salts, such as the alkali metal halides or alkaline earth metal halides, that are used in high temperature, secondary electrochemical cells.

Vertical transport in graphene-hexagonal boron nitride heterostructure devices

PubMed Central

Bruzzone, Samantha; Logoteta, Demetrio; Fiori, Gianluca; Iannaccone, Giuseppe

2015-01-01

Research in graphene-based electronics is recently focusing on devices based on vertical heterostructures of two-dimensional materials. Here we use density functional theory and multiscale simulations to investigate the tunneling properties of single- and double-barrier structures with graphene and few-layer hexagonal boron nitride (h-BN) or hexagonal boron carbon nitride (h-BC2N). We find that tunneling through a single barrier exhibit a weak dependence on energy. We also show that in double barriers separated by a graphene layer we do not observe resonant tunneling, but a significant increase of the tunneling probability with respect to a single barrier of thickness equal to the sum of the two barriers. This is due to the fact that the graphene layer acts as an effective phase randomizer, suppressing resonant tunneling and effectively letting a double-barrier structure behave as two single-barriers in series. Finally, we use multiscale simulations to reproduce a current-voltage characteristics resembling that of a resonant tunneling diode, that has been experimentally observed in single barrier structure. The peak current is obtained when there is perfect matching between the densities of states of the cathode and anode graphene regions. PMID:26415656

Preparation of boron nitride fiber by organic precursor method

NASA Astrophysics Data System (ADS)

Zhou, Yingying; Sun, Runjun; Zhang, Zhaohuan; Fan, Wei; Zhou, Dan; Sheng, Cuihong

In this paper, boron nitride polymer precursor was made by boric acid, melamine, twelve sodium alkyl sulfate as raw materials and pure water as medium which is heated to 70 °C. Boron nitride precursor polymer was soluble in formic acid solution. The boron nitride precursor can be electrostatically spun at the voltage in 23 kV and the distance between the positive and negative poles is 15 cm. The formed fiber is very uniform. The properties of the precursors were analyzed through electron microscope, infrared spectrum, X-ray and ultraviolet spectrum. The aim of the job is to got the precursor of BN and spun it.

Characterization and manipulation of individual defects in insulating hexagonal boron nitride using scanning tunnelling microscopy.

PubMed

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

2015-11-01

Defects play a key role in determining the properties and technological applications of nanoscale materials and, because they tend to be highly localized, characterizing them at the single-defect level is of particular importance. Scanning tunnelling microscopy has long been used to image the electronic structure of individual point defects in conductors, semiconductors and ultrathin films, but such single-defect electronic characterization remains an elusive goal for intrinsic bulk insulators. Here, we show that individual native defects in an intrinsic bulk hexagonal boron nitride insulator can be characterized and manipulated using a scanning tunnelling microscope. This would typically be impossible due to the lack of a conducting drain path for electrical current. We overcome this problem by using a graphene/boron nitride heterostructure, which exploits the atomically thin nature of graphene to allow the visualization of defect phenomena in the underlying bulk boron nitride. We observe three different defect structures that we attribute to defects within the bulk insulating boron nitride. Using scanning tunnelling spectroscopy we obtain charge and energy-level information for these boron nitride defect structures. We also show that it is possible to manipulate the defects through voltage pulses applied to the scanning tunnelling microscope tip.

Efficient FEM simulation of static and free vibration behavior of single walled boron nitride nanotubes

NASA Astrophysics Data System (ADS)

Giannopoulos, Georgios I.; Kontoni, Denise-Penelope N.; Georgantzinos, Stylianos K.

2016-08-01

This paper describes the static and free vibration behavior of single walled boron nitride nanotubes using a structural mechanics based finite element method. First, depending on the type of nanotube under investigation, its three dimensional nanostructure is developed according to the well-known corresponding positions of boron and nitride atoms as well as boron nitride bonds. Then, appropriate point masses are assigned to the atomic positions of the developed space frame. Next, these point masses are suitably interconnected with two-noded, linear, spring-like, finite elements. In order to simulate effectively the interactions observed between boron and nitride atoms within the nanotube, appropriate potential energy functions are introduced for these finite elements. In this manner, various atomistic models for both armchair and zigzag nanotubes with different aspect ratios are numerically analyzed and their effective elastic modulus as well as their natural frequencies and corresponding mode shapes are obtained. Regarding the free vibration analysis, the computed results reveal bending, breathing and axial modes of vibration depending on the nanotube size and chirality as well as the applied boundary support conditions. The longitudinal stiffness of the boron nitride nanotubes is found also sensitive to their geometric characteristics.

Single photon emitters in boron nitride: More than a supplementary material

NASA Astrophysics Data System (ADS)

Koperski, M.; Nogajewski, K.; Potemski, M.

2018-03-01

We present comprehensive optical studies of recently discovered single photon sources in boron nitride, which appear in form of narrow lines emitting centres. Here, we aim to compactly characterise their basic optical properties, including the demonstration of several novel findings, in order to inspire discussion about their origin and utility. Initial inspection reveals the presence of narrow emission lines in boron nitride powder and exfoliated flakes of hexagonal boron nitride deposited on Si/SiO2 substrates. Generally rather stable, the boron nitride emitters constitute a good quality visible light source. However, as briefly discussed, certain specimens reveal a peculiar type of blinking effects, which are likely related to existence of meta-stable electronic states. More advanced characterisation of representative stable emitting centres uncovers a strong dependence of the emission intensity on the energy and polarisation of excitation. On this basis, we speculate that rather strict excitation selectivity is an important factor determining the character of the emission spectra, which allows the observation of single and well-isolated emitters. Finally, we investigate the properties of the emitting centres in varying external conditions. Quite surprisingly, it is found that the application of a magnetic field introduces no change in the emission spectra of boron nitride emitters. Further analysis of the impact of temperature on the emission spectra and the features seen in second-order correlation functions is used to provide an assessment of the potential functionality of boron nitride emitters as single photon sources capable of room temperature operation.

Heteroepitaxial Growth of Single-Walled Carbon Nanotubes from Boron Nitride

PubMed Central

Tang, Dai-Ming; Zhang, Li-Li; Liu, Chang; Yin, Li-Chang; Hou, Peng-Xiang; Jiang, Hua; Zhu, Zhen; Li, Feng; Liu, Bilu; Kauppinen, Esko I.; Cheng, Hui-Ming

2012-01-01

The growth of single-walled carbon nanotubes (SWCNTs) with predefined structure is of great importance for both fundamental research and their practical applications. Traditionally, SWCNTs are grown from a metal catalyst with a vapor-liquid-solid mechanism, where the catalyst is in liquid state with fluctuating structures, and it is intrinsically unfavorable for the structure control of SWCNTs. Here we report the heteroepitaxial growth of SWCNTs from a platelet boron nitride nanofiber (BNNF), which is composed of stacked (002) planes and is stable at high temperatures. SWCNTs are found to grow epitaxially from the open (002) edges of the BNNFs, and the diameters of the SWCNTs are multiples of the BN (002) interplanar distance. In situ transmission electron microscopy observations coupled with first principles calculations reveal that the growth of SWCNTs from the BNNFs follows a vapor-solid-solid mechanism. Our work opens opportunities for the control over the structure of SWCNTs by hetero-crystallographic epitaxy. PMID:23240076

Influence of oxygen impurity on electronic properties of carbon and boron nitride nanotubes: A comparative study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Ram Sevak, E-mail: singh915@gmail.com

2015-11-15

Influence of oxygen impurity on electronic properties of carbon and boron nitride nanotubes (CNTs and BNNTs) is systematically studied using first principle calculations based on density functional theory. Energy band structures and density of states of optimized zigzag (5, 0), armchair (3, 3), and chiral (4, 2) structures of CNT and BNNT are calculated. Oxygen doping in zigzag CNT exhibits a reduction in metallicity with opening of band gap in near-infrared region while metallicity is enhanced in armchair and chiral CNTs. Unlike oxygen-doped CNTs, energy bands are drastically modulated in oxygen-doped zigzag and armchair BNNTs, showing the nanotubes to havemore » metallic behaviour. Furthermore, oxygen impurity in chiral BNNT induces narrowing of band gap, indicating a gradual modification of electronic band structure. This study underscores the understanding of different electronic properties induced in CNTs and BNNTs under oxygen doping, and has potential in fabrication of various nanoelectronic devices.« less

STIR: Novel Electronic States by Gating Strongly Correlated Materials

DTIC Science & Technology

2016-03-01

plan built on my group’s recent demonstration of electrolyte gating in Strontium Titanate, using an atomically thin hexagonal Boron Nitride barrier to...demonstration of electrolyte gating in Strontium Titanate, using an atomically thin hexagonal Boron Nitride barrier to prevent disorder and chemical...techniques and learned to apply thin hexagonal Boron Nitride to single crystals of materials expected to show some of the most exciting correlated

Ordering of lipid membranes altered by boron nitride nanosheets.

PubMed

Zhang, Yonghui; Li, Zhen; Chan, Chun; Ma, Jiale; Zhi, Chunyi; Cheng, Xiaolin; Fan, Jun

2018-02-07

Boron nitride nanosheets are novel promising nanomaterials with a lower cytotoxicity than graphene making them a better candidate for biomedical applications. However, there is no systematic study on how they interact with cell membranes. Here we employed large scale all-atom molecular dynamics simulations to provide molecular details of the structure and properties of membranes after the insertion of boron nitride nanosheets. Our results reveal that the boron nitride nanosheet can extract phospholipids from the lipid bilayers and is enveloped by the membrane. Afterwards, the acyl chains of lipid molecules re-orient and become more ordered. As a result, a fluid to gel phase transition occurs in the 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer. Consequently, the bending moduli of the bilayers increase, and the diffusivity of the individual lipid molecule decreases. These changes will affect relevant cellular activities, such as endocytosis and signal transduction. Our study provides novel insights into the biocompatibility and cytotoxicity of boron nitride nanosheets, which may facilitate the design of safer nanocarriers, antibiotics and other bio-nanotechnology applications.

Intrinsic ferromagnetism in hexagonal boron nitride nanosheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Si, M. S.; Gao, Daqiang, E-mail: gaodq@lzu.edu.cn, E-mail: xueds@lzu.edu.cn; Yang, Dezheng

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 demonstratemore » 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.« less

Hydrolytic Unzipping of Boron Nitride Nanotubes in Nitric Acid.

PubMed

Kim, Dukeun; Muramatsu, Hiroyuki; Kim, Yoong Ahm

2017-12-01

Boron nitride nanoribbons (BNNRs) have very attractive electrical and optical properties due to their unique edge states and width-related properties. Herein, for the first time, BNNRs were produced by a simple reflux of boron nitride nanotubes (BNNTs) in nitric acid containing water, which had led to unzipped sidewalls through hydrolysis. Their high reactivity that originated from edges was verified via a strong interaction with methylene blue.

Inexpensive Method for Coating the Interior of Silica Growth Ampoules with Pyrolytic Boron Nitride

NASA Technical Reports Server (NTRS)

Wang, Jianbin; Regel, Liya L.; Wilcox, William R.

2003-01-01

An inexpensive method was developed for coating the interior of silica ampoules with hexagonal boron nitride. An aqueous solution of boric acid was used to coat the ampoule prior to drying in a vacuum at 200 C. This coating was converted to transparent boron nitride by heating in ammonia at 1000 C. Coated ampoules were used to achieve detached solidification of indium antimonide on earth.

Dimensional Analysis and Extended Hydrodynamic Theory Applied to Long-Rod Penetration of Ceramics

DTIC Science & Technology

2016-07-01

thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron carbide. Test...of confined thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron ...since the mid 20th century. Popular candidate ceramics for such systems include alumina, aluminum nitride, boron carbide, silicon carbide, and titanium

A Combination of Boron Nitride Nanotubes and Cellulose Nanofibers for the Preparation of a Nanocomposite with High Thermal Conductivity.

PubMed

Zeng, Xiaoliang; Sun, Jiajia; Yao, Yimin; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

2017-05-23

With the current development of modern electronics toward miniaturization, high-degree integration and multifunctionalization, considerable heat is accumulated, which results in the thermal failure or even explosion of modern electronics. The thermal conductivity of materials has thus attracted much attention in modern electronics. Although polymer composites with enhanced thermal conductivity are expected to address this issue, achieving higher thermal conductivity (above 10 W m -1 K -1 ) at filler loadings below 50.0 wt % remains challenging. Here, we report a nanocomposite consisting of boron nitride nanotubes and cellulose nanofibers that exhibits high thermal conductivity (21.39 W m -1 K -1 ) at 25.0 wt % boron nitride nanotubes. Such high thermal conductivity is attributed to the high intrinsic thermal conductivity of boron nitride nanotubes and cellulose nanofibers, the one-dimensional structure of boron nitride nanotubes, and the reduced interfacial thermal resistance due to the strong interaction between the boron nitride nanotubes and cellulose nanofibers. Using the as-prepared nanocomposite as a flexible printed circuit board, we demonstrate its potential usefulness in electronic device-cooling applications. This thermally conductive nanocomposite has promising applications in thermal interface materials, printed circuit boards or organic substrates in electronics and could supplement conventional polymer-based materials.

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.

Methods of repairing a substrate

NASA Technical Reports Server (NTRS)

Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

2011-01-01

A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium boride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

Theory-Guided Innovation of Noncarbon Two-Dimensional Nanomaterials

DTIC Science & Technology

2016-05-24

unique structures and exceptional properties, such as Be5C2 monolayers with quasi -planaer pentacoordinate carbon, FeB6 monolayers hypercoordinate...properties, such as Be5C2 monolayers with quasi -planaer pentacoordinate carbon, FeB6 monolayers hypercoordinate transition metal, semiconducting Group 15...theoretical and experimental studies, we have developed a convenient chemical approach to etch hexagonal boron nitride monolayers to achieve holes

Composite treatment of ceramic tile armor

DOEpatents

Hansen, James G. R. [Oak Ridge, TN; Frame, Barbara J [Oak Ridge, TN

2010-12-14

An improved ceramic tile armor has a core of boron nitride and a polymer matrix composite (PMC) facing of carbon fibers fused directly to the impact face of the tile. A polyethylene fiber composite backing and spall cover are preferred. The carbon fiber layers are cured directly onto the tile, not adhered using a separate adhesive so that they are integral with the tile, not a separate layer.

Composite treatment of ceramic tile armor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, James G. R.; Frame, Barbara J

An improved ceramic tile armor has a core of boron nitride and a polymer matrix composite (PMC) facing of carbon fibers fused directly to the impact face of the tile. A polyethylene fiber composite backing and spall cover are preferred. The carbon fiber layers are cured directly onto the tile, not adhered using a separate adhesive so that they are integral with the tile, not a separate layer.

Process development for the manufacture of an integrated dispenser cathode assembly using laser chemical vapor deposition

NASA Astrophysics Data System (ADS)

Johnson, Ryan William

2005-07-01

Laser Chemical Vapor Deposition (LCVD) has been shown to have great potential for the manufacture of small, complex, two or three dimensional metal and ceramic parts. One of the most promising applications of the technology is in the fabrication of an integrated dispenser cathode assembly. This application requires the deposition of a boron nitride-molybdenum composite structure. In order to realize this structure, work was done to improve the control and understanding of the LCVD process and to determine experimental conditions conducive to the growth of the required materials. A series of carbon fiber and line deposition studies were used to characterize process-shape relationships and study the kinetics of carbon LCVD. These studies provided a foundation for the fabrication of the first high aspect ratio multi-layered LCVD wall structures. The kinetics studies enabled the formulation of an advanced computational model in the FLUENT CFD package for studying energy transport, mass and momentum transport, and species transport within a forced flow LCVD environment. The model was applied to two different material systems and used to quantify deposition rates and identify rate-limiting regimes. A computational thermal-structural model was also developed using the ANSYS software package to study the thermal stress state within an LCVD deposit during growth. Georgia Tech's LCVD system was modified and used to characterize both boron nitride and molybdenum deposition independently. The focus was on understanding the relations among process parameters and deposit shape. Boron nitride was deposited using a B3 N3H6-N2 mixture and growth was characterized by sporadic nucleation followed by rapid bulk growth. Molybdenum was deposited from the MoCl5-H2 system and showed slow, but stable growth. Each material was used to grow both fibers and lines. The fabrication of a boron nitride-molybdenum composite was also demonstrated. In sum, this work served to both advance the general science of Laser Chemical Vapor Deposition and to elucidate the practicality of fabricating ceramic-metal composites using the process.

Plasma induced sp 2 to sp 3 transition in boron nitride

NASA Astrophysics Data System (ADS)

Zhang, J.; Cui, Q.; Li, X.; He, Z.; Li, W.; Ma, Y.; Guan, Q.; Gao, W.; Zou, G.

2004-12-01

The transition from sp 2 to sp 3 hybridization in boron nitride has been induced in plasma. Nano-crystals of cubic boron nitride (cBN) have been synthesized by direct current arc discharge method using hexagonal boron nitride (hBN) as the starting material. The characterization of the as-grown powders is carried out by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. It has been shown that cBN and hBN grains with 20-60 nm in size co-exist in the powders. A reaction route of sublimation - re-hybridization - crystallization had been put forward to explain the mechanism of the hybridization transition and the growth of cBN by this method.

Dissolution and Characterization of Boron Nitride Nanotubes in Superacid.

PubMed

Kleinerman, Olga; Adnan, Mohammed; Marincel, Daniel M; Ma, Anson W K; Bengio, E Amram; Park, Cheol; Chu, Sang-Hyon; Pasquali, Matteo; Talmon, Yeshayahu

2017-12-19

Boron nitride nanotubes (BNNTs) are of interest for their unique combination of high tensile strength, high electrical resistivity, high neutron cross section, and low reactivity. The fastest route to employing these properties in composites and macroscopic articles is through solution processing. However, dispersing BNNTs without functionalization or use of a surfactant is challenging. We show here by cryogenic transmission electron microscopy that BNNTs spontaneously dissolve in chlorosulfonic acid as disentangled individual molecules. Electron energy loss spectroscopy of BNNTs dried from the solution confirms preservation of the sp 2 hybridization for boron and nitrogen, eliminating the possibility of BNNT functionalization or damage. The length and diameter of the BNNTs was statistically calculated to be ∼4.5 μm and ∼4 nm, respectively. Interestingly, bent or otherwise damaged BNNTs are filled by chlorosulfonic acid. Additionally, nanometer-sized synthesis byproducts, including boron nitride clusters, isolated single and multilayer hexagonal boron nitride, and boron particles, were identified. Dissolution in superacid provides a route for solution processing BNNTs without altering their chemical structure.

Method for forming hermetic coatings for optical fibers

DOEpatents

Michalske, Terry A.; Rye, Robert R.; Smith, William L.

1993-01-01

A method for forming hermetic coatings on optical fibers by hot filament assisted chemical vapor deposition advantageously produces a desirable coating while maintaining the pristine strength of the pristine fiber. The hermetic coatings may be formed from a variety of substances, such as, for example, boron nitride and carbon.

Free vibration analysis of single-walled boron nitride nanotubes based on a computational mechanics framework

NASA Astrophysics Data System (ADS)

Yan, J. W.; Tong, L. H.; Xiang, Ping

2017-12-01

Free vibration behaviors of single-walled boron nitride nanotubes are investigated using a computational mechanics approach. Tersoff-Brenner potential is used to reflect atomic interaction between boron and nitrogen atoms. The higher-order Cauchy-Born rule is employed to establish the constitutive relationship for single-walled boron nitride nanotubes on the basis of higher-order gradient continuum theory. It bridges the gaps between the nanoscale lattice structures with a continuum body. A mesh-free modeling framework is constructed, using the moving Kriging interpolation which automatically satisfies the higher-order continuity, to implement numerical simulation in order to match the higher-order constitutive model. In comparison with conventional atomistic simulation methods, the established atomistic-continuum multi-scale approach possesses advantages in tackling atomic structures with high-accuracy and high-efficiency. Free vibration characteristics of single-walled boron nitride nanotubes with different boundary conditions, tube chiralities, lengths and radii are examined in case studies. In this research, it is pointed out that a critical radius exists for the evaluation of fundamental vibration frequencies of boron nitride nanotubes; opposite trends can be observed prior to and beyond the critical radius. Simulation results are presented and discussed.

Surface Chemistry, Microstructure, and Tribological Properties of Cubic Boron Nitride Films

NASA Technical Reports Server (NTRS)

Watanabe, Shuichi; Wheeler, Donald R.; Abel, Phillip B.; Street, Kenneth W.; Miyoshi, Kazuhisa; Murakawa, Masao; Miyake, Shojiro

1998-01-01

This report deals with the surface chemistry, microstructure, bonding state, morphology, and friction and wear properties of cubic boron nitride (c-BN) films that were synthesized by magnetically enhanced plasma ion plating. Several analytical techniques - x-ray photoelectron spectroscopy, transmission electron microscopy and electron diffraction, Fourier transform infrared spectroscopy, atomic force microscopy, and surface profilometry - were used to characterize the films. Sliding friction experiments using a ball-on-disk configuration were conducted for the c-BN films in sliding contact with 440C stainless-steel balls at room temperature in ultrahigh vacuum (pressure, 10(exp -6), in ambient air, and under water lubrication. Results indicate that the boron-to-nitrogen ratio on the surface of the as-deposited c-BN film is greater than 1 and that not all the boron is present as boron nitride but a small percentage is present as an oxide. Both in air and under water lubrication, the c-BN film in sliding contact with steel showed a low wear rate, whereas a high wear rate was observed in vacuum. In air and under water lubrication, c-BN exhibited wear resistance superior to that of amorphous boron nitride, titanium nitride, and titanium carbide.

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).

Cellulose nanobiocomposites with reinforcement of boron nitride: study of thermal, oxygen barrier and chemical resistant properties.

PubMed

Swain, Sarat K; Dash, Satyabrata; Behera, Chandini; Kisku, Sudhir K; Behera, Lingaraj

2013-06-20

A series of cellulose based nanobiocomposites (cellulose/BN) were prepared with incorporation of various percentage of nano boron nitride (BN). The interaction between cellulose and boron nitride was studied by Fourier transform infrared spectroscopy (FTIR). The structure of cellulose/BN nanobiocomposites was investigated by XRD, FESEM, and HRTEM. It was observed that the boron nitride nanoparticles were dispersed within cellulose matrix due to intercalation and partial exfoliation. The quantitative identification of nanobiocomposites was investigated by selected area electron diffraction (SAED). Thermal stabilities of the prepared nanobiocomposites were measured by thermo gravimetric analysis (TGA) and it was found that thermal stability of the nanobiocomposites was higher than the virgin cellulose. The oxygen barrier property of cellulose/BN nanobiocomposites was measured using a gas permeameter and a substantial reduction in oxygen permeability due to increase in boron nitride loading was observed. Further it was noticed that the chemical resistance of the nanobiocomposites was more than the virgin cellulose. Hence, the prepared nanobiocomposite may be widely used for insulating and temperature resistant packaging materials. Copyright © 2013 Elsevier Ltd. All rights reserved.

Boron nitride nanotube as a delivery system for platinum drugs: Drug encapsulation and diffusion coefficient prediction.

PubMed

Khatti, Zahra; Hashemianzadeh, Seyed Majid

2016-06-10

Molecular dynamics (MD) simulation has been applied to investigate a drug delivery system based on boron nitride nanotubes, particularly the delivery of platinum-based anticancer drugs. For this propose, the behavior of carboplatin drugs inserted in boron nitride nanotubes (BNNT) as a carrier was studied. The diffusion rate of water molecules and carboplatin was investigated inside functionalized and pristine boron nitride nanotubes. The penetration rate of water and drug in functionalized BNNT was higher than that in pristine BNNT due to favorable water-mediated hydrogen bonding in hydroxyl edge-functionalized BNNT. Additionally, the encapsulation of multiple carboplatin drugs inside functionalized boron nitride nanotubes with one to five drug molecules confined inside the nanotube cavity was examined. At high drug loading, the hydrogen bond formation between adjacent drugs and the non-bonded van der Waals interaction between carboplatin and functionalized BNNT inner surface were found to be influential in drug displacement within the functionalized BNNT cavity for higher drug-loading capacity. Copyright © 2016 Elsevier B.V. All rights reserved.

Platinum Nanoparticle Loading of Boron Nitride Aerogel and Its Use as a Novel Material for Low-Power Catalytic Gas Sensing

DOE PAGES

Harley-Trochimczyk, Anna; Pham, Thang; Chang, Jiyoung; ...

2015-12-09

We report that a high-surface-area, highly crystalline boron nitride aerogel synthesized with nonhazardous reactants has been loaded with crystalline platinum nanoparticles to form a novel nanomaterial that exhibits many advantages for use in a catalytic gas sensing application. The platinum nanoparticle-loaded boron nitride aerogel integrated onto a microheater platform allows for calorimetric propane detection. The boron nitride aerogel exhibits thermal stability up to 900 °C and supports disperse platinum nanoparticles, with no sintering observed after 24 h of high-temperature testing. The high thermal conductivity and low density of the boron nitride aerogel result in an order of magnitude faster responsemore » and recovery times (<2 s) than reported on alumina support and allow for 10% duty cycling of the microheater with no loss in sensitivity. Lastly, the resulting 1.5 mW sensor power consumption is two orders of magnitude less than commercially available catalytic gas sensors and unlocks the potential for wireless, battery-powered catalytic gas sensing.« less

Electrostatic-Assisted Liquefaction of Porous Carbons

DOE PAGES

Li, Peipei; Schott, Jennifer A.; Zhang, Jinshui; ...

2017-10-10

Porous liquids are a newly developed porous material that combine unique fluidity with permanent porosity, which exhibit promising functionalities for a variety of applications. However, the apparent incompatibility between fluidity and permanent porosity makes the stabilization of porous nanoparticle with still empty pores in the dense liquid phase a significant challenging. For this study, by exploiting the electrostatic interaction between carbon networks and polymerized ionic liquids, we demonstrate that carbon-based porous nanoarchitectures can be well stabilized in liquids to afford permanent porosity, and thus opens up a new approach to prepare porous carbon liquids. Furthermore, we hope this facile synthesismore » strategy can be widely applicated to fabricate other types of porous liquids, such as those (e.g., carbon nitride, boron nitride, metal–organic frameworks, covalent organic frameworks etc.) also having the electrostatic interaction with polymerized ionic liquids, evidently advancing the development and understanding of porous liquids.« less

Effects of ultraviolet radiation on lattice imperfections in pyrolytic boron nitride.

NASA Technical Reports Server (NTRS)

Buckley, J. D.; Cooley, J. A.

1971-01-01

Pyrolitic boron nitride was exposed to 310 equivalent sun hours of ultraviolet radiation in a space environment simulator with the objective to evaluate its applicability as a pigment for a thermal control coating and to identify radiation damage using X-ray diffraction techniques. Lattice parameter comparisons show a definite increase in lattice imperfections in the crystal structure resulting from the ultraviolet irradiation. This sensitivity to radiation damage makes pyrolitic boron nitride unsuitable as a pigment for thermal control coating.

High Temperature Oxidation of Boron Nitride. Part 1; Monolithic Boron Nitride

NASA Technical Reports Server (NTRS)

Jacobson, Nathan; Farmer, Serene; Moore, Arthur; Sayir, Haluk

1997-01-01

High temperature oxidation of monolithic boron nitride (BN) is examined. Hot pressed BN and both low and high density CVD BN were studied. It is shown that oxidation rates are quite sensitive to microstructural factors such as orientation, porosity, and degree of crystallinity. In addition small amounts of water vapor lead to volatilization of the B2O3 oxide as H(x)B(y)O(z). For these reasons, very different oxidation kinetics were observed for each type of BN.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Bikramjeet; Singh, Paviter; Kumar, Akshay, E-mail: akshaykumar.tiet@gmail.com

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 asmore » well boron neutron capture therapy (BNCT)« less

Process for producing wurtzitic or cubic boron nitride

DOEpatents

Holt, J.B.; Kingman, D.D.; Bianchini, G.M.

1992-04-28

Disclosed is a process for producing wurtzitic or cubic boron nitride comprising the steps of: [A] preparing an intimate mixture of powdered boron oxide, a powdered metal selected from the group consisting of magnesium or aluminum, and a powdered metal azide; [B] igniting the mixture and bringing it to a temperature at which self-sustaining combustion occurs; [C] shocking the mixture at the end of the combustion thereof with a high pressure wave, thereby forming as a reaction product, wurtzitic or cubic boron nitride and occluded metal oxide; and, optionally [D] removing the occluded metal oxide from the reaction product. Also disclosed are reaction products made by the process described.

Process for producing wurtzitic or cubic boron nitride

DOEpatents

Holt, J. Birch; Kingman, deceased, Donald D.; Bianchini, Gregory M.

1992-01-01

Disclosed is a process for producing wurtzitic or cubic boron nitride comprising the steps of: [A] preparing an intimate mixture of powdered boron oxide, a powdered metal selected from the group consisting of magnesium or aluminum, and a powdered metal azide; [B] igniting the mixture and bringing it to a temperature at which self-sustaining combustion occurs; [C] shocking the mixture at the end of the combustion thereof with a high pressure wave, thereby forming as a reaction product, wurtzitic or cubic boron nitride and occluded metal oxide; and, optionally [D] removing the occluded metal oxide from the reaction product. Also disclosed are reaction products made by the process described.

Effect of boron and phosphorus codoping on the electronic and optical properties of graphitic carbon nitride monolayers: First-principle simulations

NASA Astrophysics Data System (ADS)

Yousefi, Mahdieh; Faraji, Monireh; Asgari, Reza; Moshfegh, Alireza Z.

2018-05-01

We study the effect of boron (B) and phosphorous (P) doping and B/P codoping on electronic and optical properties of graphitic carbon nitride (g-C3N4 or GCN) monolayers using density functional simulations. The energy band structure indicates that the incorporation of both B and P into a hexagonal lattice of GCN reduces the energy band gap from 3.1 for pristine GCN to 1.9 eV, thus extending light absorption toward the visible region. Moreover, on the basis of calculating absorption spectra and dielectric function, the codoped system exhibits an improved absorption intensity in the visible region and more electronic transitions, which named π* electronic transitions that occurred and were prohibited in the pristine GCN. These transitions can be attributed to charge redistribution upon doping, caused by distorted configurable B/P-codoped GCN confirmed by both electron density and Mulliken charge population. Therefore, B/P-codoped GCN is expected to be an auspicious candidate to be used as a promising photoelectrode in photoelectrochemical water splitting reactions leading to efficient solar H2 production.

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.

Improvement in interfacial characteristics of low-voltage carbon nanotube thin-film transistors with solution-processed boron nitride thin films

NASA Astrophysics Data System (ADS)

Jeon, Jun-Young; Ha, Tae-Jun

2017-08-01

In this article, we demonstrate the potential of solution-processed boron nitride (BN) thin films for high performance single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) with low-voltage operation. The use of BN thin films between solution-processed high-k dielectric layers improved the interfacial characteristics of metal-insulator-metal devices, thereby reducing the current density by three orders of magnitude. We also investigated the origin of improved device performance in SWCNT-TFTs by employing solution-processed BN thin films as an encapsulation layer. The BN encapsulation layer improves the electrical characteristics of SWCNT-TFTs, which includes the device key metrics of linear field-effect mobility, sub-threshold swing, and threshold voltage as well as the long-term stability against the aging effect in air. Such improvements can be achieved by reduced interaction of interfacial localized states with charge carriers. We believe that this work can open up a promising route to demonstrate the potential of solution-processed BN thin films on nanoelectronics.

Evaluation of boron nitride nanotubes and hexagonal boron nitrides as nanocarriers for cancer drugs.

PubMed

Emanet, Melis; Şen, Özlem; Çulha, Mustafa

2017-04-01

Boron nitride nanotubes (BNNTs) and hexagonal boron nitrides (hBNs) are novel nanostructures with high mechanical strengths, large surface areas and excellent biocompatibilities. Here, the potential use of BNNTs and hBNs as nanocarriers was comparatively investigated for use with cancer drugs. Doxorubicin (Dox) and folate are used as model drugs and targeting agents, respectively. The obtained results indicate that BNNTs have about a threefold higher Dox loading capacity than hBNs. It was also found that cellular uptake of folate-Dox-BNNTs was much higher when compared with Dox-BNNTs for HeLa cells, due to the presence of folate receptors on the cell surface, leading to increased cancer cell death. In summary, folate and Dox conjugated BNNTs are promising agents in nanomedicine and may have potential drug delivery applications.

Structure and Growth of Hexagonal Boron Nitride on Ir(111).

PubMed

Farwick Zum Hagen, Ferdinand H; Zimmermann, Domenik M; Silva, Caio C; Schlueter, Christoph; Atodiresei, Nicolae; Jolie, Wouter; Martínez-Galera, Antonio J; Dombrowski, Daniela; Schröder, Ulrike A; Will, Moritz; Lazić, Predrag; Caciuc, Vasile; Blügel, Stefan; Lee, Tien-Lin; Michely, Thomas; Busse, Carsten

2016-12-27

Using the X-ray standing wave method, scanning tunneling microscopy, low energy electron diffraction, and density functional theory, we precisely determine the lateral and vertical structure of hexagonal boron nitride on Ir(111). The moiré superstructure leads to a periodic arrangement of strongly chemisorbed valleys in an otherwise rather flat, weakly physisorbed plane. The best commensurate approximation of the moiré unit cell is (12 × 12) boron nitride cells resting on (11 × 11) substrate cells, which is at variance with several earlier studies. We uncover the existence of two fundamentally different mechanisms of layer formation for hexagonal boron nitride, namely, nucleation and growth as opposed to network formation without nucleation. The different pathways are linked to different distributions of rotational domains, and the latter enables selection of a single orientation only.

Synthesis of boron nitride nanostructures from catalyst of iron compounds via thermal chemical vapor deposition technique

NASA Astrophysics Data System (ADS)

da Silva, Wellington M.; Ribeiro, Hélio; Ferreira, Tiago H.; Ladeira, Luiz O.; Sousa, Edésia M. B.

2017-05-01

For the first time, patterned growth of boron nitride nanostructures (BNNs) is achieved by thermal chemical vapor deposition (TCVD) technique at 1150 °C using a mixture of FeS/Fe2O3 catalyst supported in alumina nanostructured, boron amorphous and ammonia (NH3) as reagent gas. This innovative catalyst was synthesized in our laboratory and systematically characterized. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The X-ray diffraction profile of the synthesized catalyst indicates the coexistence of three different crystal structures showing the presence of a cubic structure of iron oxide and iron sulfide besides the gamma alumina (γ) phase. The results show that boron nitride bamboo-like nanotubes (BNNTs) and hexagonal boron nitride (h-BN) nanosheets were successfully synthesized. Furthermore, the important contribution of this work is the manufacture of BNNs from FeS/Fe2O3 mixture.

Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

NASA Technical Reports Server (NTRS)

Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

2009-01-01

A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

Shear-Assisted Production of Few-Layer Boron Nitride Nanosheets by Supercritical CO2 Exfoliation and Its Use for Thermally Conductive Epoxy Composites.

PubMed

Tian, Xiaojuan; Li, Yun; Chen, Zhuo; Li, Qi; Hou, Liqiang; Wu, Jiaye; Tang, Yushu; Li, Yongfeng

2017-12-19

Boron nitride nanosheets (BNNS) hold the similar two-dimensional structure as graphene and unique properties complementary to graphene, which makes it attractive in application ranging from electronics to energy storage. The exfoliation of boron nitride (BN) still remains challenge and hinders the applications of BNNS. In this work, the preparation of BNNS has been realized by a shear-assisted supercritical CO 2 exfoliation process, during which supercritical CO 2 intercalates and diffuses between boron nitride layers, and then the exfoliation of BN layers is obtained in the rapid depressurization process by overcoming the van der Waals forces. Our results indicate that the bulk boron nitride has been successfully exfoliated into thin nanosheets with an average 6 layers. It is found that the produced BNNS is well-dispersed in isopropyl alcohol (IPA) with a higher extinction coefficient compared with the bulk BN. Moreover, the BNNS/epoxy composite used as thermal interface materials has been prepared. The introduction of BNNS results in a 313% enhancement in thermal conductivity. Our results demonstrate that BNNS produced by supercritical CO 2 exfoliation show great potential applications for heat dissipation of high efficiency electronics.

Investigation of the Kinetic Energy Characterization of Advanced Ceramics

DTIC Science & Technology

2015-04-01

of Science, under a US Army International Technology Center contract. These ceramic formulations were compared with standard armor-grade boron ...Experimental Methodology 1 3. Results and Discussion 4 3.1 Aluminum Performance Baseline 4 3.2 Ceramic Inspection 6 3.3 Boron Carbide 6 3.4 Silicon...Carbide 7 3.5 Boron Carbide–Aluminum Nitride 7 3.6 Boron Carbide–Vanadium Diboride 7 3.7 Titanium Nitride–Aluminum Nitride 8 3.8 Comparative

Integrated rig for the production of boron nitride nanotubes via the pressurized vapor-condenser method

DOEpatents

Smith, Michael W; Jordan, Kevin C

2014-03-25

An integrated production apparatus for production of boron nitride nanotubes via the pressure vapor-condenser method. The apparatus comprises: a pressurized reaction chamber containing a continuously fed boron containing target having a boron target tip, a source of pressurized nitrogen and a moving belt condenser apparatus; a hutch chamber proximate the pressurized reaction chamber containing a target feed system and a laser beam and optics.

Integrated Rig for the Production of Boron Nitride Nanotubes via the Pressurized Vapor-Condenser Method

NASA Technical Reports Server (NTRS)

Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor)

2014-01-01

An integrated production apparatus for production of boron nitride nanotubes via the pressure vapor-condenser method. The apparatus comprises: a pressurized reaction chamber containing a continuously fed boron containing target having a boron target tip, a source of pressurized nitrogen and a moving belt condenser apparatus; a hutch chamber proximate the pressurized reaction chamber containing a target feed system and a laser beam and optics.

Cytocompatibility evaluation of gum Arabic-coated ultra-pure boron nitride nanotubes on human cells.

PubMed

Ciofani, Gianni; Del Turco, Serena; Rocca, Antonella; de Vito, Giuseppe; Cappello, Valentina; Yamaguchi, Maho; Li, Xia; Mazzolai, Barbara; Basta, Giuseppina; Gemmi, Mauro; Piazza, Vincenzo; Golberg, Dmitri; Mattoli, Virgilio

2014-05-01

Boron nitride nanotubes (BNNTs) are tubular nanoparticles with a structure analogous to that of carbon nanotubes, but with B and N atoms that completely replace the C atoms. Many favorable results indicate BNNTs as safe nanomaterials; however, important concerns have recently been raised about ultra-pure, long (~10 µm) BNNTs tested on several cell types. Here, we propose additional experiments with the same BNNTs, but shortened (~1.5 µm) with a homogenization/sonication treatment that allows for their dispersion in gum Arabic aqueous solutions. Obtained BNNTs are tested on human endothelial and neuron-like cells with several independent biocompatibility assays. Moreover, for the first time, their strong sum-frequency generation signal is exploited to assess the cellular uptake. Our data demonstrate no toxic effects up to concentrations of 20 µg/ml, once more confirming biosafety of BNNTs, and again highlighting that nanoparticle aspect ratio plays a key role in the biocompatibility evaluation.

N2O reduction over a fullerene-like boron nitride nanocage: A DFT study

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.

2017-07-01

We study, for the first time, the adsorption and catalytic decomposition of N2O molecule over a fullerene-like boron nitride nanocage (B12N12) using density functional theory calculations. It is found that the electron donating property of the cage plays an important role in the adsorption and activation of N2O. By the incorporation of a carbon atom into B12N12 cluster, our results indicate that the adsorption of N2O over B11N12C or B12N11C is more stronger than over pristine B12N12. The decomposition of N2O into N2 and O species over the C-doped clusters is energetically more favorable than that on B12N12. Moreover, the C-doping plays an important role in reducing the activation barrier for the CO + O* reaction over B12N12 surface.

Ultrahigh interlayer friction in multiwalled boron nitride nanotubes.

PubMed

Niguès, A; Siria, A; Vincent, P; Poncharal, P; Bocquet, L

2014-07-01

Friction at the nanoscale has revealed a wealth of behaviours that depart strongly from the long-standing macroscopic laws of Amontons-Coulomb. Here, by using a 'Christmas cracker'-type of system in which a multiwalled nanotube is torn apart between a quartz-tuning-fork-based atomic force microscope (TF-AFM) and a nanomanipulator, we compare the mechanical response of multiwalled carbon nanotubes (CNTs) and multiwalled boron nitride nanotubes (BNNTs) during the fracture and telescopic sliding of the layers. We found that the interlayer friction for insulating BNNTs results in ultrahigh viscous-like dissipation that is proportional to the contact area, whereas for the semimetallic CNTs the sliding friction vanishes within experimental uncertainty. We ascribe this difference to the ionic character of the BN, which allows charge localization. The interlayer viscous friction of BNNTs suggests that BNNT membranes could serve as extremely efficient shock-absorbing surfaces.

BN-C Hybrid Nanoribbons as Gas Sensors

NASA Astrophysics Data System (ADS)

Darvishi Gilan, Mahdi; Chegel, Raad

2018-02-01

The effects of carbon monoxide (CO) and ammonia (NH3) molecules adsorption on the various composites of boron nitride and graphene BN-C hybrid nanoribbons are investigated using the non-equilibrium Green's function (NEGF) technique based on density functional theory (DFT). The effects of adsorption with possible random configurations on the average of the density of states (DOS), transmission coefficient, and the current-voltage ( I- V) characteristics are calculated. The results indicate that, by embedding armchair graphene nanoribbon (AGNR) with boron nitride nanoribbon (BNNR), the various electronic properties can be observed after gas molecule adsorption. The electronic structure and gap of hybrids system is modified due to gas adsorption, and the systems act like the n-type semiconductor by NH3 molecule adsorption. The hybrid structures due to their tunable band gap are better candidates for gas detecting compared to the pristine BNNRs and AGNRs.

Tubes of rhombohedral boron nitride

NASA Astrophysics Data System (ADS)

Bourgeois, L.; Bando, Y.; Sato, T.

2000-08-01

The structure of boron nitride bamboo-like tubular whiskers grown from boron nitride powder is investigated by high-resolution transmission electron microscopy. Despite the relatively small size of the tubes (20-200 nm in diameter), they all exhibit rhombohedral-like ordering in their layer stacking. The tubular sheets also tend to have their [10 bar 1 0] direction parallel to the fibre axis. Particles of iron alloys are commonly found encapsulated inside or at the end of the filaments. It is suggested that iron plays an active role in the growth of the fibres.

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.

Ion beam modification of the structure and properties of hexagonal boron nitride: An infrared and X-ray diffraction study

NASA Astrophysics Data System (ADS)

Aradi, E.; Naidoo, S. R.; Billing, D. G.; Wamwangi, D.; Motochi, I.; Derry, T. E.

2014-07-01

The vibrational mode for the cubic symmetry of boron nitride (BN) has been produced by boron ion implantation of hexagonal boron nitride (h-BN). The optimum fluence at 150 keV was found to be 5 × 1014 ions/cm2. The presence of the c-BN phase was inferred using glancing incidence XRD (GIXRD) and Fourier Transform Infrared Spectroscopy (FTIR). After implantation, Fourier Transform Infrared Spectroscopy indicated a peak at 1092 cm-1 which corresponds to the vibrational mode for nanocrystalline BN (nc-BN). The glancing angle XRD pattern after implantation exhibited c-BN diffraction peaks relative to the implantation depth of 0.4 μm.

Test study of boron nitride as a new detector material for dosimetry in high-energy photon beams.

PubMed

Poppinga, D; Halbur, J; Lemmer, S; Delfs, B; Harder, D; Looe, H K; Poppe, B

2017-09-05

The aim of this test study is to check whether boron nitride (BN) might be applied as a detector material in high-energy photon-beam dosimetry. Boron nitride exists in various crystalline forms. Hexagonal boron nitride (h-BN) possesses high mobility of the electrons and holes as well as a high volume resistivity, so that ionizing radiation in the clinical range of the dose rate can be expected to produce a measurable electrical current at low background current. Due to the low atomic numbers of its constituents, its density (2.0 g cm -3 ) similar to silicon and its commercial availability, h-BN appears as possibly suitable for the dosimetry of ionizing radiation. Five h-BN plates were contacted to triaxial cables, and the detector current was measured in a solid-state ionization chamber circuit at an applied voltage of 50 V. Basic dosimetric properties such as formation by pre-irradiation, sensitivity, reproducibility, linearity and temporal resolution were measured with 6 MV photon irradiation. Depth dose curves at quadratic field sizes of 10 cm and 40 cm were measured and compared to ionization chamber measurements. After a pre-irradiation with 6 Gy, the devices show a stable current signal at a given dose rate. The current-voltage characteristic up to 400 V shows an increase in the collection efficiency with the voltage. The time-resolved detector current behavior during beam interrupts is comparable to diamond material, and the background current is negligible. The measured percentage depth dose curves at 10 cm  ×  10 cm field size agreed with the results of ionization chamber measurements within  ±2%. This is a first study of boron nitride as a detector material for high-energy photon radiation. By current measurements on solid ionization chambers made from boron nitride chips we could demonstrate that boron nitride is in principle suitable as a detector material for high-energy photon-beam dosimetry.

Test study of boron nitride as a new detector material for dosimetry in high-energy photon beams

NASA Astrophysics Data System (ADS)

Poppinga, D.; Halbur, J.; Lemmer, S.; Delfs, B.; Harder, D.; Looe, H. K.; Poppe, B.

2017-09-01

The aim of this test study is to check whether boron nitride (BN) might be applied as a detector material in high-energy photon-beam dosimetry. Boron nitride exists in various crystalline forms. Hexagonal boron nitride (h-BN) possesses high mobility of the electrons and holes as well as a high volume resistivity, so that ionizing radiation in the clinical range of the dose rate can be expected to produce a measurable electrical current at low background current. Due to the low atomic numbers of its constituents, its density (2.0 g cm-3) similar to silicon and its commercial availability, h-BN appears as possibly suitable for the dosimetry of ionizing radiation. Five h-BN plates were contacted to triaxial cables, and the detector current was measured in a solid-state ionization chamber circuit at an applied voltage of 50 V. Basic dosimetric properties such as formation by pre-irradiation, sensitivity, reproducibility, linearity and temporal resolution were measured with 6 MV photon irradiation. Depth dose curves at quadratic field sizes of 10 cm and 40 cm were measured and compared to ionization chamber measurements. After a pre-irradiation with 6 Gy, the devices show a stable current signal at a given dose rate. The current-voltage characteristic up to 400 V shows an increase in the collection efficiency with the voltage. The time-resolved detector current behavior during beam interrupts is comparable to diamond material, and the background current is negligible. The measured percentage depth dose curves at 10 cm  ×  10 cm field size agreed with the results of ionization chamber measurements within  ±2%. This is a first study of boron nitride as a detector material for high-energy photon radiation. By current measurements on solid ionization chambers made from boron nitride chips we could demonstrate that boron nitride is in principle suitable as a detector material for high-energy photon-beam dosimetry.

Exceptionally large migration length of carbon and topographically-facilitated self-limiting molecular beam epitaxial growth of graphene on hexagonal boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plaut, Annette S.; Wurstbauer, Ulrich; Wang, Sheng

We demonstrate growth of single-layer graphene (SLG) on hexagonal boron nitride (h-BN) by molecular beam epitaxy (MBE), only limited in area by the finite size of the h-BN flakes. Using atomic force microscopy and micro-Raman spectroscopy, we show that for growth over a wide range of temperatures (500 °C – 1000 °C) the deposited carbon atoms spill off the edge of the h-BN flakes. We attribute this spillage to the very high mobility of the carbon atoms on the BN basal plane, consistent with van der Waals MBE. The h-BN flakes vary in size from 30 μm to 100 μm,more » thus demonstrating that the migration length of carbon atoms on h-BN is greater than 100 μm. When sufficient carbon is supplied to compensate for this loss, which is largely due to this fast migration of the carbon atoms to and off the edges of the h-BN flake, we find that the best growth temperature for MBE SLG on h-BN is ~950 °C. Self-limiting graphene growth appears to be facilitated by topographic h-BN surface features: We have thereby grown MBE self-limited SLG on an h-BN ridge. This opens up future avenues for precisely tailored fabrication of nano- and hetero-structures on pre-patterned h-BN surfaces for device applications.« less

Theoretical study of ozone adsorption on the surface of Fe, Co and Ni doped boron nitride nanosheets

NASA Astrophysics Data System (ADS)

Farmanzadeh, Davood; Askari Ardehjani, Nastaran

2018-06-01

In this work, the adsorption of ozone molecule on Fe, Co and Ni doped boron nitride nanosheets (BNNSs) were investigated using density functional theory. The most stable adsorption configurations, charge transfer and adsorption energy of ozone molecule on pure and doped BNNSs are calculated. It is shown that ozone molecule has no remarkable interaction with pure boron nitride nanosheet, it tends to be chemisorbed on Fe, Co and Ni doped BNNSs with adsorption energy in the range of -249.4 to -686.1 kJ/mol. In all configurations, the adsorption of ozone molecule generates a semiconductor by reducing Eg in the pure and Fe, Co and Ni doped boron nitride nanosheet. It shows that the conductance of BNNSs change over the adsorption of ozone molecule. The obtained results in this study can be used in developing BN-based sheets for ozone molecule removal.

Single-Photon Emitters in Boron Nitride Nanococoons.

PubMed

Ziegler, Joshua; Blaikie, Andrew; Fathalizadeh, Aidin; Miller, David; Yasin, Fehmi S; Williams, Kerisha; Mohrhardt, Jordan; McMorran, Benjamin J; Zettl, Alex; Alemán, Benjamín

2018-04-11

Quantum emitters in two-dimensional hexagonal boron nitride (hBN) are attractive for a variety of quantum and photonic technologies because they combine ultra-bright, room-temperature single-photon emission with an atomically thin crystal. However, the emitter's prominence is hindered by large, strain-induced wavelength shifts. We report the discovery of a visible-wavelength, single-photon emitter (SPE) in a zero-dimensional boron nitride allotrope (the boron nitride nanococoon, BNNC) that retains the excellent optical characteristics of few-layer hBN while possessing an emission line variation that is lower by a factor of 5 than the hBN emitter. We determined the emission source to be the nanometer-size BNNC through the cross-correlation of optical confocal microscopy with high-resolution scanning and transmission electron microscopy. Altogether, this discovery enlivens color centers in BN materials and, because of the BN nanococoon's size, opens new and exciting opportunities in nanophotonics, quantum information, biological imaging, and nanoscale sensing.

Untangling the Energetics and Dynamics of Boron Monoxide Radical Reactions (11BO; X2Sigma+)

DTIC Science & Technology

2015-04-15

Reaction products of isoelectronic boron monoxide (BO), cyano (CN), ethynyl (CCH), and silicon nitride (SiN) radicals with acetylene and ethylene. 3.10...Isoelectronicity in the Reactions of the Cyano (CN), Boron Monoxide (BO), Silicon Nitride (SiN), and Ethynyl (C2H) Radicals with Unsaturated Hydrocarbons...AFRL-OSR-VA-TR-2015-0111 Untangling the Energetics and Dynamics of Boron Monoxide Radical Reactions Ralf Kaiser UNIVERSITY OF HAWAII SYSTEMS HONOLULU

Concepts for smart nanocomposite materials

NASA Astrophysics Data System (ADS)

Pammi, SriLaxmi; Brown, Courtney; Datta, Saurabh; Kirikera, Goutham R.; Schulz, Mark J.

2003-10-01

This paper explores concepts for new smart materials that have extraordinary properties based on nanotechnology. Carbon and boron nitride nanotubes in theory can be used to manufacture fibers that have piezoelectric, pyroelectric, piezoresistive, and electrochemical field properties. Smart nanocomposites designed using these fibers will sense and respond to elastic, thermal, and chemical fields in a positive human-like way to improve the performance of structures, devices, and possibly humans. Remarkable strength, morphing, cooling, energy harvesting, strain and temperature sensing, chemical sensing and filtering, and high natural frequencies and damping will be the properties of these new materials. Synthesis of these unique atomically precise nanotubes, fibers, and nanocomposites is at present challenging and expensive, however, there is the possibility that we can synthesize the strongest and lightest actuators and most efficient sensors man has ever made. A particular advantage of nanotube transducers is their very high load bearing capability. Carbon nanotube electrochemical actuators have a predicted energy density at low frequencies that is thirty times greater than typical piezoceramic materials while boron nitride nanotubes are insulators and can operate at high temperatures, but they have a predicted piezoelectric induced stress constant that is about twenty times smaller than piezoceramic materials. Carbon nanotube fibers and composites exhibit a change in electrical conductivity due to strain that can be used for sensing. Some concepts for nanocomposite material sensors are presented and initial efforts to fabricate carbon nanocomposite load sensors are discussed.

Preparation and characterization of boron nitride coatings on carbon fibers from borazine by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Li, Jun-Sheng; Zhang, Chang-Rui; Li, Bin

2011-06-01

Boron nitride (BN) coatings were deposited on carbon fibers by chemical vapor deposition (CVD) using borazine as single source precursor. The deposited coatings were characterized by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The effect of temperatures on growth kinetics, morphology, composition and structure of the coatings was investigated. In the low temperature range of 900 °C-1000 °C, the growth rate increased with increasing temperature complying with Arrhenius law, and an apparent active energy of 72 kJ/mol was calculated. The coating surface was smooth and compact, and the coatings uniformly deposited on individual fibers of carbon fiber bundles. The growth was controlled by surface reaction. At 1000 °C, the deposition rate reached a maximum (2.5 μm/h). At the same time, the limiting step of the growth translated to be mass-transportation. Above 1100 °C, the growth rate decreased drastically due to the occurrence of gas-phase nucleation. Moreover, the coating surface became loose and rough. Composition and structure examinations revealed that stoichiometric BN coatings with turbostratic structure were obtained below 1000 °C, while hexagonal BN coatings were deposited above 1100 °C. A penetration of carbon element from the fibers to the coatings was observed.

Super-hard cubic BN layer formation by nitrogen ion implantation

NASA Astrophysics Data System (ADS)

Komarov, F. F.; Pilko, V. V.; Yakushev, V. A.; Tishkov, V. S.

1994-11-01

Microcrystalline and amorphous boron thin films were implanted with nitrogen ions at energies from 25 to 125 keV and with doses from 2 × 10 17 to 1 × 10 18 at.cm 2 at temperatures below 200°C. The structure of boron nitride phases after ion implantation, formation of phases and phase transformations were investigated by TEM and TED methods. The cubic boron nitride phase is revealed. The microhardness of the formed films was satisfactorily explained in terms of chemical compound formation by polyenergetic ion implantation. The influence of the copper impurity on the formation of the cubic boron nitride phase is demonstrated. It has also been shown that low concentrations of copper promote cubic BN boundary formation.

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.

The redox potential of boron nitride and implications for its use as a crucible material in experimental petrology

NASA Technical Reports Server (NTRS)

Wendlandt, R. F.; Huebner, J. S.; Harrison, W. J.

1982-01-01

The suitability of boron nitride for use as a crucible material in silicate and oxygen-bearing metal sulfide systems has been investigated. Boron nitride is unsatisfactory for use with many silicate systems because its presence in combination with a source of oxygen establishes the oxygen fugacity at values below that of the assemblage quartz + fayalite + iron, reducing transition metal ions such as Ni(2+) and Fe(2+) to the metallic state. B2O3, resulting from the oxidation of BN, acts as a flux to promote formation of melt.

Communication: Water on hexagonal boron nitride from diffusion Monte Carlo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Hamdani, Yasmine S.; Ma, Ming; Michaelides, Angelos, E-mail: angelos.michaelides@ucl.ac.uk

2015-05-14

Despite a recent flurry of experimental and simulation studies, an accurate estimate of the interaction strength of water molecules with hexagonal boron nitride is lacking. Here, we report quantum Monte Carlo results for the adsorption of a water monomer on a periodic hexagonal boron nitride sheet, which yield a water monomer interaction energy of −84 ± 5 meV. We use the results to evaluate the performance of several widely used density functional theory (DFT) exchange correlation functionals and find that they all deviate substantially. Differences in interaction energies between different adsorption sites are however better reproduced by DFT.

Anisotropic Nanomechanics of Boron Nitride Nanotubes: Nanostructured "Skin" Effect

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Menon, Madhu; Cho, KyeongJae

2000-01-01

The stiffness and plasticity of boron nitride nanotubes are investigated using generalized tight-binding molecular dynamics and ab-initio total energy methods. Due to boron-nitride BN bond buckling effects, compressed zigzag BN nanotubes are found to undergo novel anisotropic strain release followed by anisotropic plastic buckling. The strain is preferentially released towards N atoms in the rotated BN bonds. The tubes buckle anisotropically towards only one end when uniaxially compressed from both. A "skin-effect" model of smart nanocomposite materials is proposed which will localize the structural damage towards the 'skin' or surface side of the material.

Isotope engineering of van der Waals interactions in hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Vuong, T. Q. P.; Liu, S.; van der Lee, A.; Cuscó, R.; Artús, L.; Michel, T.; Valvin, P.; Edgar, J. H.; Cassabois, G.; Gil, B.

2018-02-01

Hexagonal boron nitride is a model lamellar compound where weak, non-local van der Waals interactions ensure the vertical stacking of two-dimensional honeycomb lattices made of strongly bound boron and nitrogen atoms. We study the isotope engineering of lamellar compounds by synthesizing hexagonal boron nitride crystals with nearly pure boron isotopes (10B and 11B) compared to those with the natural distribution of boron (20 at% 10B and 80 at% 11B). On the one hand, as with standard semiconductors, both the phonon energy and electronic bandgap varied with the boron isotope mass, the latter due to the quantum effect of zero-point renormalization. On the other hand, temperature-dependent experiments focusing on the shear and breathing motions of adjacent layers revealed the specificity of isotope engineering in a layered material, with a modification of the van der Waals interactions upon isotope purification. The electron density distribution is more diffuse between adjacent layers in 10BN than in 11BN crystals. Our results open perspectives in understanding and controlling van der Waals bonding in layered materials.

Isotope engineering of van der Waals interactions in hexagonal boron nitride.

PubMed

Vuong, T Q P; Liu, S; Van der Lee, A; Cuscó, R; Artús, L; Michel, T; Valvin, P; Edgar, J H; Cassabois, G; Gil, B

2018-02-01

Hexagonal boron nitride is a model lamellar compound where weak, non-local van der Waals interactions ensure the vertical stacking of two-dimensional honeycomb lattices made of strongly bound boron and nitrogen atoms. We study the isotope engineering of lamellar compounds by synthesizing hexagonal boron nitride crystals with nearly pure boron isotopes ( 10 B and 11 B) compared to those with the natural distribution of boron (20 at% 10 B and 80 at% 11 B). On the one hand, as with standard semiconductors, both the phonon energy and electronic bandgap varied with the boron isotope mass, the latter due to the quantum effect of zero-point renormalization. On the other hand, temperature-dependent experiments focusing on the shear and breathing motions of adjacent layers revealed the specificity of isotope engineering in a layered material, with a modification of the van der Waals interactions upon isotope purification. The electron density distribution is more diffuse between adjacent layers in 10 BN than in 11 BN crystals. Our results open perspectives in understanding and controlling van der Waals bonding in layered materials.

Synthesis of Continuous Boron Nitride Nanofibers by Electrospinning

NASA Astrophysics Data System (ADS)

Li, Xia; Wen, G.; Zhang, Tao; Xia, Long; Zhong, Bo; Fan, Shaoyu

Continuous boron nitride nanofibers (BNNFs) have been gotten by electrospinning. The appropriate precursor of BNNFs was electrospinned to green born nitride nanofibers (GBNNFs) with temperatures from 80°C to 100°C in the protection of N2. By successive heat treatments in N2, the organics in GBNNFs disappeared and BN ceramics nanofibers came into being. The average diameters of BNNFs by electrospinning are less than 10 μm

Magnetic-Field-Assisted Assembly of Ordered Multifunctional Ceramic Nanocomposites for Extreme Environments

DTIC Science & Technology

2016-04-01

SUBJECT TERMS carbon nanotubes, composite, electromagnetic shielding , extreme environments, magnetism , fibers, woven composite, boron nitride...AFRL-AFOSR-VA-TR-2016-0158 Magnetic -Field-Assisted Assembly of Ordered Multifunctional Ceramic Nanocomposites for Extreme Environments Konstantin...From - To) 15 Sep 2012 to 14 Nov 2017 4. TITLE AND SUBTITLE Magnetic -Field-Assisted Assembly of Ordered Multifunctional Ceramic Nanocomposites for

Structural impact on the eigenenergy renormalization for carbon and silicon allotropes and boron nitride polymorphs

NASA Astrophysics Data System (ADS)

Tutchton, Roxanne; Marchbanks, Christopher; Wu, Zhigang

2018-05-01

The phonon-induced renormalization of electronic band structures is investigated through first-principles calculations based on the density functional perturbation theory for nine materials with various crystal symmetries. Our results demonstrate that the magnitude of the zero-point renormalization (ZPR) of the electronic band structure is dependent on both crystal structure and material composition. We have performed analysis of the electron-phonon-coupling-induced renormalization for two silicon (Si) allotropes, three carbon (C) allotropes, and four boron nitride (BN) polymorphs. Phonon dispersions of each material were computed, and our analysis indicates that materials with optical phonons at higher maximum frequencies, such as graphite and hexagonal BN, have larger absolute ZPRs, with the exception of graphene, which has a considerably smaller ZPR despite having phonon frequencies in the same range as graphite. Depending on the structure and material, renormalizations can be comparable to the GW many-body corrections to Kohn-Sham eigenenergies and, thus, need to be considered in electronic structure calculations. The temperature dependence of the renormalizations is also considered, and in all materials, the eigenenergy renormalization at the band gap and around the Fermi level increases with increasing temperature.

Effects of nano-sized boron nitride (BN) reinforcement in expandable graphite based in-tumescent fire retardant coating

NASA Astrophysics Data System (ADS)

Zulkurnain, E. S.; Ahmad, F.; Gillani, Q. F.

2016-08-01

The purpose of in-tumescent fire retardant coating (IFRC) is to protect substrate from fire attack by limiting heat transfer. A range of coating formulations have been prepared using Bisphenol A epoxy resin BE-188 and polyamide solidifier H-2310 as two-part binder, ammonium polyphosphate (APP) as acid source, melamine (MEL) as the blowing agent, expandable graphite (EG) as carbon source and nano-boron nitride (BN) as inorganic nano filler. The filler was used to improve the performances of the APP-EG-MEL coating. The effects of nano-BN on the char morphology and thermal degradation were investigated by fire test, thermo gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X- ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). The results showed that by substituting or reinforcing of 4% weight percentage of nano-BN, residual weight of the char increases by 23.82% compared to APP-EG-MEL coating without filler. Higher carbon content was obtained in the char and a more compact char was produced. The results indicated that nano-BN could be used as a filler to improve thermal stability of the APP-EG-MEL coating.

Polymer-Derived Boron Nitride: A Review on the Chemistry, Shaping and Ceramic Conversion of Borazine Derivatives

PubMed Central

Bernard, Samuel; Miele, Philippe

2014-01-01

Boron nitride (BN) is a III-V compound which is the focus of important research since its discovery in the early 19th century. BN is electronic to carbon and thus, in the same way that carbon exists as graphite, BN exists in the hexagonal phase. The latter offers an unusual combination of properties that cannot be found in any other ceramics. However, these properties closely depend on the synthesis processes. This review states the recent developments in the preparation of BN through the chemistry, shaping and ceramic conversion of borazine derivatives. This concept denoted as Polymer-Derived Ceramics (PDCs) route allows tailoring the chemistry of precursors to elaborate complex BN shapes which cannot be obtained by conventional process. The effect of the chemistry of the molecular precursors, i.e., borazine and trichloroborazine, and their polymeric derivatives i.e., polyborazylene and poly[tri(methylamino)borazine], in which the specific functional groups and structural motifs determine the shaping potential by conventional liquid-phase process and plastic-forming techniques is discussed. Nanotubes, nano-fibers, coatings, monoliths and fiber-reinforced matrix composites are especially described. This leads to materials which are of significant engineering interest. PMID:28788257

Delivery of Cisplatin Anti-Cancer Drug from Carbon, Boron Nitride, and Silicon Carbide Nanotubes Forced by Ag-Nanowire: A Comprehensive Molecular Dynamics Study.

PubMed

Mehrjouei, Esmat; Akbarzadeh, Hamed; Shamkhali, Amir Nasser; Abbaspour, Mohsen; Salemi, Sirous; Abdi, Pooya

2017-07-03

In this work, liberation of cisplatin molecules from interior of a nanotube due to entrance of an Ag-nanowire inside it was simulated by classical molecular dynamics method. The aim of this simulation was investigation on the effects of diameter, chirality, and composition of the nanotube, as well as the influence of temperature on this process. For this purpose, single walled carbon, boron nitride, and silicon carbide nanotube were considered. In order for a more concise comparison of the results, a new parameter namely efficiency of drug release, was introduced. The results demonstrated that the efficiency of drug release is sensitive to its adsorption on outer surface of the nanotube. Moreover, this efficiency is also sensitive to the nanotube composition and its diameter. For the effect of nanotube composition, the results indicated that silicon carbide nanotube has the least efficiency for drug release, due to its strong drug-nanotube. Also, the most important acting forces on drug delivery are van der Waals interactions. Finally, the kinetic of drug release is fast and is not related to the structural parameters of the nanotube and temperature, significantly.

Polymer-Derived Boron Nitride: A Review on the Chemistry, Shaping and Ceramic Conversion of Borazine Derivatives.

PubMed

Bernard, Samuel; Miele, Philippe

2014-11-21

Boron nitride (BN) is a III-V compound which is the focus of important research since its discovery in the early 19th century. BN is electronic to carbon and thus, in the same way that carbon exists as graphite, BN exists in the hexagonal phase. The latter offers an unusual combination of properties that cannot be found in any other ceramics. However, these properties closely depend on the synthesis processes. This review states the recent developments in the preparation of BN through the chemistry, shaping and ceramic conversion of borazine derivatives. This concept denoted as Polymer-Derived Ceramics (PDCs) route allows tailoring the chemistry of precursors to elaborate complex BN shapes which cannot be obtained by conventional process. The effect of the chemistry of the molecular precursors, i.e. , borazine and trichloroborazine, and their polymeric derivatives i.e. , polyborazylene and poly[tri(methylamino)borazine], in which the specific functional groups and structural motifs determine the shaping potential by conventional liquid-phase process and plastic-forming techniques is discussed. Nanotubes, nano-fibers, coatings, monoliths and fiber-reinforced matrix composites are especially described. This leads to materials which are of significant engineering interest.

Defective boron nitride nanotubes: mechanical properties, electronic structures and failure behaviors

NASA Astrophysics Data System (ADS)

Wang, Huan; Ding, Ning; Zhao, Xian; Wu, Chi-Man Lawrence

2018-03-01

Due to their excellent physical and chemical characteristics, boron nitride nanotubes (BNNTs) are regarded as a complementary addition to carbon nanotubes. Pioneer studies have demonstrated that defects in carbon nanotubes are considered tools for tuning the physical properties of these materials. In the present work, investigation on the mechanical and electronic properties of pristine and defective BNNTs was performed using the density functional theory method. The analysis on the intrinsic strength, stiffness, and failure critical strain of different types of BNNTs was conducted systematically. The computing results showed that the intrinsic strength of BNNTs decreased linearly with the increased Stone-Wales (SW) defect density around the axis. The SW defect density along the axis played a minor role on the changing of mechanical properties of BNNTs. The BNNT with a B vacancy expressed higher intrinsic strength than that of the N vacancy model. The final failure of the pristine BNNTs was due to the fracture of the Type1 bonds under the mechanical strain. Defects like SW or vacancy are served as the initial break site of BNNTs. Applying strain or creating defects are both effective methods for reducing the band gap of BNNTs.

Nano-solenoid: helicoid carbon-boron nitride hetero-nanotube

NASA Astrophysics Data System (ADS)

Zhang, Zi-Yue; Miao, Chunyang; Guo, Wanlin

2013-11-01

As a fundamental element of a nanoscale passive circuit, a nano-inductor is proposed based on a hetero-nanotube consisting of a spiral carbon strip and a spiral boron nitride strip. It is shown by density functional theory associated with nonequilibrium Green function calculations that the nanotube exhibits attractive transport properties tunable by tube chirality, diameter, component proportion and connection manner between the two strips, with excellent `OFF' state performance and high current on the order of 10-100 μA. All the hetero-nanotubes show negative differential resistance. The transmission peaks of current are absolutely derived from the helicoid carbon strips or C-BN boundaries, giving rise to a spiral current analogous with an energized nano-solenoid. According to Ampere's Law, the energized nano-solenoid can generate a uniform and tremendous magnetic field of more than 1 tesla, closing to that generated by the main magnet of medical nuclear magnetic resonance. Moreover, the magnitude of magnetic field can be easily modulated by bias voltage, providing great promise for a nano-inductor to realize electromagnetic conversion at the nanoscale.As a fundamental element of a nanoscale passive circuit, a nano-inductor is proposed based on a hetero-nanotube consisting of a spiral carbon strip and a spiral boron nitride strip. It is shown by density functional theory associated with nonequilibrium Green function calculations that the nanotube exhibits attractive transport properties tunable by tube chirality, diameter, component proportion and connection manner between the two strips, with excellent `OFF' state performance and high current on the order of 10-100 μA. All the hetero-nanotubes show negative differential resistance. The transmission peaks of current are absolutely derived from the helicoid carbon strips or C-BN boundaries, giving rise to a spiral current analogous with an energized nano-solenoid. According to Ampere's Law, the energized nano-solenoid can generate a uniform and tremendous magnetic field of more than 1 tesla, closing to that generated by the main magnet of medical nuclear magnetic resonance. Moreover, the magnitude of magnetic field can be easily modulated by bias voltage, providing great promise for a nano-inductor to realize electromagnetic conversion at the nanoscale. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02914j

Defects in Ceramic Matrix Composites and Their Impact on Elastic Properties (Postprint)

DTIC Science & Technology

2013-07-01

numerically modeled. The composite under investigation was a 10 layer T300 carbon/ SiC composite in which carbon fabric was impregnated using a polymer ...fraction. (3) Melt Infiltrated in situ BN SiC / SiC composite comprising a stochiometric SiC (Sylramic™) fiber, with an in situ boron nitride treatment...SiNC composite is listed in Table 4. Polymer derived SiC and SiNC matrix material do not ex- hibit a major change in their elastic properties at

Bridgman Growth of GeSi Alloys in a Static Magnetic Field

NASA Technical Reports Server (NTRS)

Volz, M. P.; Szofran, F. R.; Vujisic, L.; Motakef, S.

1998-01-01

Ge(0.95)Si(0.050 alloy crystals have been grown by the vertical Bridgman technique, both with and without an axial 5 Tesla magnetic field. The crystals were processed in a constant axial thermal gradient and the effects of graphite, hot pressed boron nitride, and pyrolitic boron nitride ampoule materials on interface shapes and macrosegregation profiles were investigated. The sample grown in a graphite ampoule at 5 Tesla exhibited a macroscopic axial concentration profile close to that of complete mixing and strong striation patterns. In samples grown in boron nitride ampoules, both with and without a 5 Tesla magnetic field applied, measured macroscopic axial concentration profiles were intermediate between those expected for a completely mixed melt and diffusion-controlled growth, and striation patterns were also observed. Possible explanations for the apparent inability of the magnetic field to reduce the flow velocities to below the growth velocities are discussed, and results of growth experiments in pyrolitic boron nitride ampoules are also described.

The different adsorption mechanism of methane molecule onto a boron nitride and a graphene flakes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seyed-Talebi, Seyedeh Mozhgan; Neek-Amal, M., E-mail: neekamal@srttu.edu

2014-10-21

Graphene and single layer hexagonal boron-nitride are two newly discovered 2D materials with wonderful physical properties. Using density functional theory, we study the adsorption mechanism of a methane molecule over a hexagonal flake of single layer hexagonal boron-nitride (h-BN) and compare the results with those of graphene. We found that independent of the used functional in our ab-initio calculations, the adsorption energy in the h-BN flake is larger than that for graphene. Despite of the adsorption energy profile of methane over a graphene flake, we show that there is a long range behavior beyond minimum energy in the adsorption energymore » of methane over h-BN flake. This result reveals the higher sensitivity of h-BN sheet to the adsorption of a typical closed shell molecule with respect to graphene. The latter gives insight in the recent experiments of graphene over hexagonal boron nitride.« less

Preparation of Boron Nitride Nanoparticles with Oxygen Doping and a Study of Their Room-Temperature Ferromagnetism.

PubMed

Lu, Qing; Zhao, Qi; Yang, Tianye; Zhai, Chengbo; Wang, Dongxue; Zhang, Mingzhe

2018-04-18

In this work, oxygen-doped boron nitride nanoparticles with room-temperature ferromagnetism have been synthesized by a new, facile, and efficient method. There are no metal magnetic impurities in the nanoparticles analyzed by X-ray photoelectron spectroscopy. The boron nitride nanoparticles exhibit a parabolic shape with increase in the reaction time. The saturation magnetization value reaches a maximum of 0.2975 emu g -1 at 300 K when the reaction time is 12 h, indicating that the Curie temperature ( T C ) is higher than 300 K. Combined with first-principles calculation, the coupling between B 2p orbital, N 2p orbital, and O 2p orbital in the conduction bands is the main origin of room-temperature ferromagnetism and also proves that the magnetic moment changes according the oxygen-doping content change. Compared with other room temperature ferromagnetic semiconductors, boron nitride nanoparticles have widely potential applications in spintronic devices because of high temperature oxidation resistance and excellent chemical stability.

Enhanced mechanical properties of epoxy nanocomposites by mixing noncovalently functionalized boron nitride nanoflakes.

PubMed

Lee, Dongju; Song, Sung Ho; Hwang, Jaewon; Jin, Sung Hwan; Park, Kwang Hyun; Kim, Bo Hyun; Hong, Soon Hyung; Jeon, Seokwoo

2013-08-12

The influence of surface modifications on the mechanical properties of epoxy-hexagonal boron nitride nanoflake (BNNF) nanocomposites is investigated. Homogeneous distributions of boron nitride nanoflakes in a polymer matrix, preserving intrinsic material properties of boron nitride nanoflakes, is the key to successful composite applications. Here, a method is suggested to obtain noncovalently functionalized BNNFs with 1-pyrenebutyric acid (PBA) molecules and to synthesize epoxy-BNNF nanocomposites with enhanced mechanical properties. The incorporation of noncovalently functionalized BNNFs into epoxy resin yields an elastic modulus of 3.34 GPa, and 71.9 MPa ultimate tensile strength at 0.3 wt%. The toughening enhancement is as high as 107% compared to the value of neat epoxy. The creep strain and the creep compliance of the noncovalently functionalized BNNF nanocomposite is significantly less than the neat epoxy and the nonfunctionalized BNNF nanocomposite. Noncovalent functionalization of BNNFs is effective to increase mechanical properties by strong affinity between the fillers and the matrix. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-Pressure Design of Advanced BN-Based Materials.

PubMed

Kurakevych, Oleksandr O; Solozhenko, Vladimir L

2016-10-20

The aim of the present review is to highlight the state of the art in high-pressure design of new advanced materials based on boron nitride. Recent experimental achievements on the governing phase transformation, nanostructuring and chemical synthesis in the systems containing boron nitride at high pressures and high temperatures are presented. All these developments allowed discovering new materials, e.g., ultrahard nanocrystalline cubic boron nitride (nano-cBN) with hardness comparable to diamond, and superhard boron subnitride B 13 N₂. Thermodynamic and kinetic aspects of high-pressure synthesis are described based on the data obtained by in situ and ex situ methods. Mechanical and thermal properties (hardness, thermoelastic equations of state, etc.) are discussed. New synthetic perspectives, combining both soft chemistry and extreme pressure-temperature conditions are considered.

Influence of point defects on the near edge structure of hexagonal boron nitride

NASA Astrophysics Data System (ADS)

McDougall, Nicholas L.; Partridge, Jim G.; Nicholls, Rebecca J.; Russo, Salvy P.; McCulloch, Dougal G.

2017-10-01

Hexagonal boron nitride (hBN) is a wide-band-gap semiconductor with applications including gate insulation layers in graphene transistors, far-ultraviolet light emitting devices and as hydrogen storage media. Due to its complex microstructure, defects in hBN are challenging to identify. Here, we combine x-ray absorption near edge structure (XANES) spectroscopy with ab initio theoretical modeling to identify energetically favorable defects. Following annealing of hBN samples in vacuum and oxygen, the B and N K edges exhibited angular-dependent peak modifications consistent with in-plane defects. Theoretical calculations showed that the energetically favorable defects all produce signature features in XANES. Comparing these calculations with experiments, the principle defects were attributed to substitutional oxygen at the nitrogen site, substitutional carbon at the boron site, and hydrogen passivated boron vacancies. Hydrogen passivation of defects was found to significantly affect the formation energies, electronic states, and XANES. In the B K edge, multiple peaks above the major 1 s to π* peak occur as a result of these defects and the hydrogen passivated boron vacancy produces the frequently observed doublet in the 1 s to σ* transition. While the N K edge is less sensitive to defects, features attributable to substitutional C at the B site were observed. This defect was also calculated to have mid-gap states in its band structure that may be responsible for the 4.1-eV ultraviolet emission frequently observed from this material.

Program for the development of high temperature electrical materials and components

NASA Technical Reports Server (NTRS)

Neff, W. S.; Lowry, L. R.

1972-01-01

Evaluation of high temperature, space-vacuum performance of selected electrical materials and components, high temperature capacitor development, and evaluation, construction, and endurance testing of compression sealed pyrolytic boron nitride slot insulation are described. The first subject above covered the aging evaluation of electrical devices constructed from selected electrical materials. Individual materials performances were also evaluated and reported. The second subject included study of methods of improving electrical performance of pyrolytic boron nitride capacitors. The third portion was conducted to evaluate the thermal and electrical performance of pyrolytic boron nitride as stator slot liner material under varied temperature and compressive loading. Conclusions and recommendations are presented.

Inter-layer potential for hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Leven, Itai; Azuri, Ido; Kronik, Leeor; Hod, Oded

2014-03-01

A new interlayer force-field for layered hexagonal boron nitride (h-BN) based structures is presented. The force-field contains three terms representing the interlayer attraction due to dispersive interactions, repulsion due to anisotropic overlaps of electron clouds, and monopolar electrostatic interactions. With appropriate parameterization, the potential is able to simultaneously capture well the binding and lateral sliding energies of planar h-BN based dimer systems as well as the interlayer telescoping and rotation of double walled boron-nitride nanotubes of different crystallographic orientations. The new potential thus allows for the accurate and efficient modeling and simulation of large-scale h-BN based layered structures.

Thermal conductivity of ultra-thin chemical vapor deposited hexagonal boron nitride films

NASA Astrophysics Data System (ADS)

Alam, M. T.; Bresnehan, M. S.; Robinson, J. A.; Haque, M. A.

2014-01-01

Thermal conductivity of freestanding 10 nm and 20 nm thick chemical vapor deposited hexagonal boron nitride films was measured using both steady state and transient techniques. The measured value for both thicknesses, about 100 ± 10 W m-1 K-1, is lower than the bulk basal plane value (390 W m-1 K-1) due to the imperfections in the specimen microstructure. Impressively, this value is still 100 times higher than conventional dielectrics. Considering scalability and ease of integration, hexagonal boron nitride grown over large area is an excellent candidate for thermal management in two dimensional materials-based nanoelectronics.

Auger electron spectroscopy analysis for growth interface of cubic boron nitride single crystals synthesized under high pressure and high temperature

NASA Astrophysics Data System (ADS)

Lv, Meizhe; Xu, Bin; Cai, Lichao; Guo, Xiaofei; Yuan, Xingdong

2018-05-01

After rapid cooling, cubic boron nitride (c-BN) single crystals synthesized under high pressure and high temperature (HPHT) are wrapped in the white film powders which are defined as growth interface. In order to make clear that the transition mechanism of c-BN single crystals, the variation of B and N atomic hybrid states in the growth interface is analyzed with the help of auger electron spectroscopy in the Li-based system. It is found that the sp2 fractions of B and N atoms decreases, and their sp3 fractions increases from the outer to the inner in the growth interface. In addition, Lithium nitride (Li3N) are not found in the growth interface by X-ray diffraction (XRD) experiment. It is suggested that lithium boron nitride (Li3BN2) is produced by the reaction of hexagonal boron nitride (h-BN) and Li3N at the first step, and then B and N atoms transform from sp2 into sp3 state with the catalysis of Li3BN2 in c-BN single crystals synthesis process.

First principles study of electronic and structural properties of single walled zigzag boron nitride nanotubes doped with the elements of group IV

NASA Astrophysics Data System (ADS)

Bahari, Ali; jalalinejad, Amir; Bagheri, Mosahhar; Amiri, Masoud

2017-11-01

In this paper, structural and electronic properties and stability of (10, 0) born nitride nanotube (BNNT) are considered within density functional theory by doping group IV elements of the periodic table. The HOMO-LUMO gap has been strongly modified and treated a dual manner by choosing B or N sites for dopant atoms. Formation energy calculation shows that B site doping is more stable than N site doping. Results also show that all dopants turn the pristine BNNT into a p-type semiconductor except for carbon-doped BNNT at B site.

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.

Magnetic, electronic and optical properties of different graphene, BN and BC2N nanoribbons

NASA Astrophysics Data System (ADS)

Guerra, T.; Leite, L.; Azevedo, S.; de Lima Bernardo, B.

2017-04-01

Graphene nanoribbons are predicted to be essential components in future nanoelectronics. The size, edge type, form, arrangement of atoms and width of nanoribbons drastically change their properties. However, magnetic, electronic and optical properties of armchair, chevron and sawtooth of graphene, BN and BC2N nanoribbons are not fully understood so far. Here, we make use of first-principles calculations based on the density functional theory (DFT) to investigate the structural, magnetic, electronic and optical properties of nanoribbons of graphene, boron nitride and BC2N with armchair edge, chevron-type and sawtooth forms. The lowest formation energies were found for the armchair and chevron nanoribbons of graphene and boron nitride. We have shown that the imbalance of carbon atoms between different sublattices generates a net magnetic moment. Chevron-type nanoribbons of BC2N and graphene showed a band gap comparable with silicon, and a high light absorption in the visible spectrum when compared to the other configurations.

Superhard nanocomposite of dense polymorphs of boron nitride: Noncarbon material has reached diamond hardness

NASA Astrophysics Data System (ADS)

Dubrovinskaia, Natalia; Solozhenko, Vladimir L.; Miyajima, Nobuyoshi; Dmitriev, Vladimir; Kurakevych, Oleksandr O.; Dubrovinsky, Leonid

2007-03-01

The authors report a synthesis of unique superhard aggregated boron nitride nanocomposites (ABNNCs) showing the enhancement of hardness up to 100% in comparison with single crystal c-BN. Such a great hardness increase is due to the combination of the Hall-Petch and the quantum confinement effects. The decrease of the grain size down to 14nm and the simultaneous formation of the two dense BN phases with hexagonal and cubic structures within the grains at nano- and subnanolevel result in enormous mechanical property enhancement with maximum hardness of 85(5)GPa. Thus, ABNNC is the first non-carbon-based bulk material with the value of hard-ness approaching that of single crystal and polycrystalline diamond and aggregated diamond nanorods. ABNNC also has an unusually high fracture toughness for superhard materials (K1C=15MPam0.5) and wear resistance (WH=11; compare, for industrial polycrystalline diamond, WH=3-4), in combination with high thermal stability (above 1600K in air), making it an exceptional superabrasive.

Boron nitride nanotubes matrix for signal enhancement in infrared laser desorption postionization mass spectrometry.

PubMed

Lu, Qiao; Hu, Yongjun; Chen, Jiaxin; Li, Yujian; Song, Wentao; Jin, Shan; Liu, Fuyi; Sheng, Liusi

2018-09-01

The nanomaterials function as the substrate to trap analytes, absorb energy from the laser irradiation and transfer energy to the analytes to facilitate the laser desorption process. In this work, the signal intensity and reproducibility of analytes with nanomaterials as matrices were explored by laser desorption postionization mass spectrometry (LDPI-MS). Herein, the desorbed neutral species were further ionized by vacuum ultraviolet (VUV, 118 nm) and analyzed by mass spectrometer. Compared with other nanomaterial matrices such as graphene and carbon nanotubes (CNTs), boron nitride nanotubes (BNNTs) exhibited much higher desorption efficiency under infrared (IR) light and produced no background signal in the whole mass range by LDPI-MS. Additionally, this method was successfully and firstly exploited to in situ detection and imaging for drugs of low concentration in intact tissues, which proved the utility, facility and convenience of this method applied in drug discovery and biomedical research. Copyright © 2018 Elsevier B.V. All rights reserved.

Core-level photoabsorption study of defects and metastable bonding configurations in boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jimenez, I.; Jankowski, A.F.; Terminello, L.J.

1997-04-01

Boron nitride is an interesting material for technological applications and for fundamental solid state physics investigations. It is a compound isoelectronic with carbon and, like carbon can possess sp{sup 2} and sp{sup 3} bonded phases resembling graphite and diamond. BN crystallizes in the sp{sup 2}-bonded hexagonal (h-BN), rhombohedral (r-BN) and turbostratic phases, and in the sp{sup 3}-bonded cubic (c-BN) and wurtzite (w-BN) phases. A new family of materials is obtained when replacing C-C pairs in graphite with isoelectronic B-N pairs, resulting in C{sub 2}BN compounds. Regarding other boron compounds, BN is exceptional in the sense that it has standard two-centermore » bonds with conventional coordination numbers, while other boron compounds (e.g. B{sub 4}C) are based on the boron icosahedron unit with three-center bonds and high coordination numbers. The existence of several allotropic forms and fullerene-like structures for BN suggests a rich variety of local bonding and poses the questions of how this affects the local electronic structure and how the material accommodates the stress induced in the transition regions between different phases. One would expect point defects to play a crucial role in stress accommodation, but these must also have a strong influence in the electronic structure, since the B-N bond is polar and a point defect will thus be a charged structure. The study of point defects in relationship to the electronic structure is of fundamental interest in these materials. Recently, the authors have shown that Near-Edge X-ray Absorption Fine Structure (NEXAFS) is sensitive to point defects in h-BN, and to the formation of metastable phases even in amorphous materials. This is significant since other phase identification techniques like vibrational spectroscopies or x-ray diffraction yield ambiguous results for nanocrystalline and amorphous samples. Serendipitously, NEXAFS also combines chemical selectivity with point defect sensitivity.« less

Carbon nanotube, graphene and boron nitride nanotube reinforced bioactive ceramics for bone repair.

PubMed

Gao, Chengde; Feng, Pei; Peng, Shuping; Shuai, Cijun

2017-10-01

The high brittleness and low strength of bioactive ceramics have severely restricted their application in bone repair despite the fact that they have been regarded as one of the most promising biomaterials. In the last few years, low-dimensional nanomaterials (LDNs), including carbon nanotubes, graphene and boron nitride nanotubes, have gained increasing attention owing to their favorable biocompatibility, large surface specific area and super mechanical properties. These qualities make LDNs potential nanofillers in reinforcing bioactive ceramics. In this review, the types, characteristics and applications of the commonly used LDNs in ceramic composites are summarized. In addition, the fabrication methods for LDNs/ceramic composites, such as hot pressing, spark plasma sintering and selective laser sintering, are systematically reviewed and compared. Emphases are placed on how to obtain the uniform dispersion of LDNs in a ceramic matrix and maintain the structural stability of LDNs during the high-temperature fabrication process of ceramics. The reinforcing mechanisms of LDNs in ceramic composites are then discussed in-depth. The in vitro and in vivo studies of LDNs/ceramic in bone repair are also summarized and discussed. Finally, new developments and potential applications of LDNs/ceramic composites are further discussed with reference to experimental and theoretical studies. Despite bioactive ceramics having been regarded as promising biomaterials, their high brittleness and low strength severely restrict their application in bone scaffolds. In recent years, low-dimensional nanomaterials (LDNs), including carbon nanotubes, graphene and boron nitride nanotubes, have shown great potential in reinforcing bioactive ceramics owing to their unique structures and properties. However, so far it has been difficult to maintain the structural stability of LDNs during fabrication of LDNs/ceramic composites, due to the lengthy, high-temperature process involved. This review presents a comprehensive overview of the developments and applications of LDNs in bioactive ceramics. The newly-developed fabrication methods for LDNs/ceramic composites, the reinforcing mechanisms and the in vitro and in vivo performance of LDNs are also summarized and discussed in detail. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Nonlinear vibration of double-walled boron nitride and carbon nanopeapods under multi-physical fields with consideration of surface stress effects

NASA Astrophysics Data System (ADS)

Ghorbanpour Arani, A.; Sabzeali, M.; BabaAkbar Zarei, H.

2017-12-01

In this study, the nonlinear thermo-electro vibrations of double-walled boron nitride nanopeapods (DWBNNPPs) and double-walled carbon nanopeapods (DWCNPPs) under magnetic field embedded in an elastic medium is investigated. DWBNNPPs are made of piezoelectric and smart materials therefore, electric field is effective on them; meanwhile, DWCNPPs are made of carbon thus, magnetic field can be useful to control them. The Pasternak model is used to simulate the effects of elastic medium which surrounds the system. Nanotubes are modeled with assumption of the Euler-Bernoulli beam (EBB) theory and the surface effects are considered to achieve accurate response of the system. Moreover, interaction between two layers is modeled by van der Waals (vdW) forces. The equations of motion are derived using the energy method and the Hamilton principle. Then the governing equations are solved by using Galerkin's method and incremental harmonic balance method (IHBM). The influences of various parameters such as the magnetic field, different types of DWCNPPs and DWBNNPPs, elastic medium, existence of fullerene and surface effect on the vibration behavior of the system are investigated. The results demonstrate that DWBNNPPs have more influence on the frequency of the system than DWCNPPs. In addition, the presence of fullerene in nanotubes has a negative impact on the frequency behavior of revisionthe system.

High density hexagonal boron nitride prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1992-01-01

Boron nitride powder with less than or equal to the oxygen content of starting powder (down to 0.5% or less) is hot isostatically pressed in a refractory metal container to produce hexagonal boron nitride with a bulk density greater than 2.0 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1800.degree. C. and 30 KSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.21 g/cc. Complex shapes can be made.

Phonon-Assisted Resonant Tunneling of Electrons in Graphene-Boron Nitride Transistors.

PubMed

Vdovin, E E; Mishchenko, A; Greenaway, M T; Zhu, M J; Ghazaryan, D; Misra, A; Cao, Y; Morozov, S V; Makarovsky, O; Fromhold, T M; Patanè, A; Slotman, G J; Katsnelson, M I; Geim, A K; Novoselov, K S; Eaves, L

2016-05-06

We observe a series of sharp resonant features in the differential conductance of graphene-hexagonal boron nitride-graphene tunnel transistors over a wide range of bias voltages between 10 and 200 mV. We attribute them to electron tunneling assisted by the emission of phonons of well-defined energy. The bias voltages at which they occur are insensitive to the applied gate voltage and hence independent of the carrier densities in the graphene electrodes, so plasmonic effects can be ruled out. The phonon energies corresponding to the resonances are compared with the lattice dispersion curves of graphene-boron nitride heterostructures and are close to peaks in the single phonon density of states.

Tunable Ultrafast Photon Source and Imaging System for Studying Carrier Dynamics in Graphene Devices

DTIC Science & Technology

2015-07-23

structure systems (for example of graphene and boron nitride ). Figure 2 shows the homebuilt Raman spectroscopy setup in our lab which uses two...pseudo-Dirac points in the band structure. In a run up to these studies, we have also developed a technique to optically image boron nitride flakes with...2) Dheeraj Golla, K. Chattrakun, K. Watanabe, T. Taniguchi, Brian J. LeRoy, Arvinder Sandhu, “Optical thickness determination of hexagonal boron

Single-step synthesis of crystalline h-BN quantum- and nanodots embedded in boron carbon nitride films

NASA Astrophysics Data System (ADS)

Matsoso, Boitumelo J.; Ranganathan, Kamalakannan; Mutuma, Bridget K.; Lerotholi, Tsenolo; Jones, Glenn; Coville, Neil J.

2017-03-01

Herein we report on the synthesis and characterization of novel crystalline hexagonal boron nitride (h-BN) quantum- and nanodots embedded in large-area boron carbon nitride (BCN) films. The films were grown on a Cu substrate by an atmospheric pressure chemical vapour deposition technique. Methane, ammonia, and boric acid were used as precursors for C, N and B to grow these few atomic layer thick uniform films. We observed that both the size of the h-BN quantum/nanodots and thickness of the BCN films were influenced by the vaporization temperature of boric acid as well as the H3BO3 (g) flux over the Cu substrate. These growth conditions were easily achieved by changing the position of the solid boric acid in the reactor with respect to the Cu substrate. Atomic force microscope (AFM) and TEM analyses show a variation in the h-BN dot size distribution, ranging from nanodots (˜224 nm) to quantum dots (˜11 nm) as the B-source is placed further away from the Cu foil. The distance between the B-source and the Cu foil gave an increase in the C atomic composition (42 at% C-65 at% C) and a decrease in both B and N contents (18 at% B and 14 at% N to 8 at% B and 7 at% N). UV-vis absorption spectra showed a higher band gap energy for the quantum dots (5.90 eV) in comparison with the nanodots (5.68 eV) due to a quantum confinement effect. The results indicated that the position of the B-source and its reaction with ammonia plays a significant role in controlling the nucleation of the h-BN quantum- and nanodots. The films are proposed to be used in solar cells. A mechanism to explain the growth of h-BN quantum/nanodots in BCN films is reported.

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

DOEpatents

Corman, Gregory Scot; Luthra, Krishan Lal

2002-01-01

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

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

DOEpatents

Corman, Gregory Scot; Luthra, Krishan Lal

1999-01-01

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

Friction of water on graphene and hexagonal boron nitride from ab initio methods: very different slippage despite very similar interface structures.

PubMed

Tocci, Gabriele; Joly, Laurent; Michaelides, Angelos

2014-12-10

Friction is one of the main sources of dissipation at liquid water/solid interfaces. Despite recent progress, a detailed understanding of water/solid friction in connection with the structure and energetics of the solid surface is lacking. Here, we show for the first time that ab initio molecular dynamics can be used to unravel the connection between the structure of nanoscale water and friction for liquid water in contact with graphene and with hexagonal boron nitride. We find that although the interface presents a very similar structure between the two sheets, the friction coefficient on boron nitride is ≈ 3 times larger than that on graphene. This comes about because of the greater corrugation of the energy landscape on boron nitride arising from specific electronic structure effects. We discuss how a subtle dependence of the friction on the atomistic details of a surface, which is not related to its wetting properties, may have a significant impact on the transport of water at the nanoscale, with implications for the development of membranes for desalination and for osmotic power harvesting.

Oxidative Unzipping and Transformation of High Aspect Ratio Boron Nitride Nanotubes into “White Graphene Oxide” Platelets

PubMed Central

Nautiyal, Pranjal; Loganathan, Archana; Agrawal, Richa; Boesl, Benjamin; Wang, Chunlei; Agarwal, Arvind

2016-01-01

Morphological and chemical transformations in boron nitride nanotubes under high temperature atmospheric conditions is probed in this study. We report atmospheric oxygen induced cleavage of boron nitride nanotubes at temperatures exceeding 750 °C for the first time. Unzipping is then followed by coalescence of these densely clustered multiple uncurled ribbons to form stacks of 2D sheets. FTIR and EDS analysis suggest these 2D platelets to be Boron Nitride Oxide platelets, with analogous structure to Graphene Oxide, and therefore we term them as “White Graphene Oxide” (WGO). However, not all BNNTs deteriorate even at temperatures as high as 1000 °C. This leads to the formation of a hybrid nanomaterial system comprising of 1D BN nanotubes and 2D BN oxide platelets, potentially having advanced high temperature sensing, radiation shielding, mechanical strengthening, electron emission and thermal management applications due to synergistic improvement of multi-plane transport and mechanical properties. This is the first report on transformation of BNNT bundles to a continuous array of White Graphene Oxide nanoplatelet stacks. PMID:27388704

Oxidative Unzipping and Transformation of High Aspect Ratio Boron Nitride Nanotubes into “White Graphene Oxide” Platelets

NASA Astrophysics Data System (ADS)

Nautiyal, Pranjal; Loganathan, Archana; Agrawal, Richa; Boesl, Benjamin; Wang, Chunlei; Agarwal, Arvind

2016-07-01

Morphological and chemical transformations in boron nitride nanotubes under high temperature atmospheric conditions is probed in this study. We report atmospheric oxygen induced cleavage of boron nitride nanotubes at temperatures exceeding 750 °C for the first time. Unzipping is then followed by coalescence of these densely clustered multiple uncurled ribbons to form stacks of 2D sheets. FTIR and EDS analysis suggest these 2D platelets to be Boron Nitride Oxide platelets, with analogous structure to Graphene Oxide, and therefore we term them as “White Graphene Oxide” (WGO). However, not all BNNTs deteriorate even at temperatures as high as 1000 °C. This leads to the formation of a hybrid nanomaterial system comprising of 1D BN nanotubes and 2D BN oxide platelets, potentially having advanced high temperature sensing, radiation shielding, mechanical strengthening, electron emission and thermal management applications due to synergistic improvement of multi-plane transport and mechanical properties. This is the first report on transformation of BNNT bundles to a continuous array of White Graphene Oxide nanoplatelet stacks.

Thin Refractory Films on Fused Silica Crucibles

DTIC Science & Technology

1988-07-01

9 4.1.4 Iridium 11 4.1.5 Boron Nitride (BN) 11 4.2 Adherence Testing 13 4.3 Metallography 13 5.0 Conclusions and Recommendations 16 Accession For...Chamber 4 2. Schematic of Crucible Coating Apparatus (SiC, NbN, and TiB 2) 6 3. Schematic of CVD Apparatus for Iridium 7 4. Schematic of Apparatus for...ultrahigh-purity coatings of silicon carbide (SiC), niobium nitride (NbN), titanium diboride (TiB2), iridium , and boron nitride (BN) onto the interior

Optical Boron Nitride Insulator Erosion Characterization of a 200 W Xenon Hall Thruster

DTIC Science & Technology

2005-05-01

Hall thruster boron nitride insulator is evaluated as a diagnostic for real-time evaluation of thruster insulator erosion. Three Hall thruster plasma control variables are examined: ion energy (discharge potential), ion flux (propellant flow), and plasma conductivity (magnetic field strength). The boron emission, and hence the insulator erosion rate, varies linearly with ion energy and ion flux. A minimum erosion rate appears at intermediate magnetic field strengths. This may indicate that local plasma conductivity significantly affects the divergence

Rolling contact fatigue of surface modified 440C using a 'Ge-Polymet' type disc rod test rig

NASA Technical Reports Server (NTRS)

Thom, Robert L.

1989-01-01

Through hardened 440 C martensitic stainless steel test specimens were surface modified and tested for changes in rolling contact fatigue using a disc on rod test rig. The surface modifications consisted of nitrogen, boron, titanium, chromium, tantalum, carbon, or molybdenum ion implantation at various ion fluences and energies. Tests were also performed on specimens reactively sputtered with titanium nitride.

Tribological Characteristics and Applications of Superhard Coatings: CVD Diamond, DLC, and c-BN

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Murakawa, Masao; Watanabe, Shuichi; Takeuchi, Sadao; Wu, Richard L. C.

1999-01-01

Results of fundamental research on the tribological properties of chemical-vapor-deposited (CVD) diamond, diamondlike carbon, and cubic boron nitride films in sliding contact with CVD diamond in ultrahigh vacuum, dry nitrogen, humid air, and water are discussed. Furthermore, the actual and potential applications of the three different superhard coatings in the field of tribology technology, particularly for wear parts and tools, are reviewed.

Castable cements to prevent corrosion of metals in molten salts

DOE PAGES

Gomez-Vidal, Judith C.; Morton, E.

2016-04-22

Castable cements on metals form a protective barrier that is able to prevent permeation of molten salts towards metallic surfaces. Silica-based castable cements are capable of protecting containment metallic alloys from the corrosive attack of molten chlorides at temperatures as high as 650 °C. Boron nitride (BN) blocking the pores in the cured cement prevents permeation of the molten chloride towards the metal surface. The cements tested are not chemically stable in molten carbonates, because the bonding components dissolved into molten carbonates salt. The corrosion rate is 7.72±0.32 mm/year for bare stainless steel 347 in molten eutectic NaCl – 65.58more » wt% LiCl at 650 °C, which is the baseline used for determining how well the cement protects the metallic surfaces from corrosion. In particular the metal fully encapsulated with Aremco 645-N with pores filled with boron nitride immersed in molten eutectic NaCl – 65.58 wt% LiCl at 650 °C shows a corrosion rate of 9E-04 mm/year. Here, the present study gives initial corrosion rates. Long-term tests are required to determine if Aremco 645-N with BN coating on metal has long term chemical stability for blocking salt permeation through coating pores.« less

Ultralight boron nitride aerogels via template-assisted chemical vapor deposition

PubMed Central

Song, Yangxi; Li, Bin; Yang, Siwei; Ding, Guqiao; Zhang, Changrui; Xie, Xiaoming

2015-01-01

Boron nitride (BN) aerogels are porous materials with a continuous three-dimensional network structure. They are attracting increasing attention for a wide range of applications. Here, we report the template-assisted synthesis of BN aerogels by catalyst-free, low-pressure chemical vapor deposition on graphene-carbon nanotube composite aerogels using borazine as the B and N sources with a relatively low temperature of 900 °C. The three-dimensional structure of the BN aerogels was achieved through the structural design of carbon aerogel templates. The BN aerogels have an ultrahigh specific surface area, ultralow density, excellent oil absorbing ability, and high temperature oxidation resistance. The specific surface area of BN aerogels can reach up to 1051 m2 g−1, 2-3 times larger than the reported BN aerogels. The mass density can be as low as 0.6 mg cm−3, much lower than that of air. The BN aerogels exhibit high hydrophobic properties and can absorb up to 160 times their weight in oil. This is much higher than porous BN nanosheets reported previously. The BN aerogels can be restored for reuse after oil absorption simply by burning them in air. This is because of their high temperature oxidation resistance and suggests broad utility as water treatment tools. PMID:25976019

Ultralight boron nitride aerogels via template-assisted chemical vapor deposition.

PubMed

Song, Yangxi; Li, Bin; Yang, Siwei; Ding, Guqiao; Zhang, Changrui; Xie, Xiaoming

2015-05-15

Boron nitride (BN) aerogels are porous materials with a continuous three-dimensional network structure. They are attracting increasing attention for a wide range of applications. Here, we report the template-assisted synthesis of BN aerogels by catalyst-free, low-pressure chemical vapor deposition on graphene-carbon nanotube composite aerogels using borazine as the B and N sources with a relatively low temperature of 900 (°)C. The three-dimensional structure of the BN aerogels was achieved through the structural design of carbon aerogel templates. The BN aerogels have an ultrahigh specific surface area, ultralow density, excellent oil absorbing ability, and high temperature oxidation resistance. The specific surface area of BN aerogels can reach up to 1051 m(2) g(-1), 2-3 times larger than the reported BN aerogels. The mass density can be as low as 0.6 mg cm(-3), much lower than that of air. The BN aerogels exhibit high hydrophobic properties and can absorb up to 160 times their weight in oil. This is much higher than porous BN nanosheets reported previously. The BN aerogels can be restored for reuse after oil absorption simply by burning them in air. This is because of their high temperature oxidation resistance and suggests broad utility as water treatment tools.

A template-free solvent-mediated synthesis of high surface area boron nitride nanosheets for aerobic oxidative desulfurization.

PubMed

Wu, Peiwen; Zhu, Wenshuai; Chao, Yanhong; Zhang, Jinshui; Zhang, Pengfei; Zhu, Huiyuan; Li, Changfeng; Chen, Zhigang; Li, Huaming; Dai, Sheng

2016-01-04

Hexagonal boron nitride nanosheets (h-BNNs) with rather high specific surface area (SSA) are important two-dimensional layer-structured materials. Here, a solvent-mediated synthesis of h-BNNs revealed a template-free lattice plane control strategy that induced high SSA nanoporous structured h-BNNs with outstanding aerobic oxidative desulfurization performance.

Toward achieving flexible and high sensitivity hexagonal boron nitride neutron detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maity, A.; Grenadier, S. J.; Li, J.

Hexagonal boron nitride (h-BN) detectors have demonstrated the highest thermal neutron detection efficiency to date among solid-state neutron detectors at about 51%. We report here the realization of h-BN neutron detectors possessing one order of magnitude enhancement in the detection area but maintaining an equal level of detection efficiency of previous achievement.

Toward achieving flexible and high sensitivity hexagonal boron nitride neutron detectors

DOE PAGES

Maity, A.; Grenadier, S. J.; Li, J.; ...

2017-07-17

Hexagonal boron nitride (h-BN) detectors have demonstrated the highest thermal neutron detection efficiency to date among solid-state neutron detectors at about 51%. We report here the realization of h-BN neutron detectors possessing one order of magnitude enhancement in the detection area but maintaining an equal level of detection efficiency of previous achievement.

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.

N-Doped Hybrid Graphene and Boron Nitride Armchair Nanoribbons As Nonmagnetic Semiconductors with Widely Tunable Electronic Properties

NASA Astrophysics Data System (ADS)

Habibpour, Razieh; Kashi, Eslam; Vazirib, Raheleh

2018-03-01

The electronic and chemical properties of N-doped hybrid graphene and boron nitride armchair nanoribbons (N-doped a-GBNNRs) in comparison with graphene armchair nanoribbon (pristine a-GNR) and hybrid graphene and boron nitride armchair nanoribbon (C-3BN) are investigated using the density functional theory method. The results show that all the mentioned nanoribbons are nonmagnetic direct semiconductors and all the graphitic N-doped a-GBNNRs are n-type semiconductors while the rest are p-type semiconductors. The N-doped graphitic 2 and N-doped graphitic 3 structures have the lowest work function and the highest number of valence electrons (Lowdin charges) which confirms that they are effective for use in electronic device applications.

Large-area few-layer hexagonal boron nitride prepared by quadrupole field aided exfoliation

NASA Astrophysics Data System (ADS)

Lun Lu, Han; Zhi Rong, Min; Qiu Zhang, Ming

2018-03-01

A quadrupole electric field-mediated exfoliation method is proposed to convert micron-sized hexagonal boron nitride (h-BN) powder into few-layer hexagonal boron nitride nanosheets (h-BNNS). Under optimum conditions (400 Hz, 40 V, 32 μg ml-1, sodium deoxycholate, TAE medium), the h-BN powders (thickness >200 nm, horizontal scale ˜10 μm) are successfully exfoliated into 0.5-4 nm (1-10 layers) thick h-BNNS with the same horizontal scale. Dynamic laser scattering and atomic force microscope data show that the yield is 47.6% (for the portion with the thickness of 0.5-6 nm), and all of the vertical sizes are reduced to smaller than 18 nm (45 layers).

Electrically dependent bandgaps in graphene on hexagonal boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaplan, D., E-mail: daniel.b.kaplan.civ@mail.mil; Swaminathan, V.; Recine, G.

2014-03-31

We present first-principles calculations on the bandgap of graphene on a layer of hexagonal boron nitride in three different stacking configurations. Relative stability of the configurations is identified and bandgap tunability is demonstrated through the application of an external, perpendicularly applied electric field. We carefully examine the bandgap's sensitivity to both magnitude of the applied field as well as separation between the graphene and hexagonal boron nitride layers. Features of the band structure are examined and configuration-dependent relationships between the field and bandgap are revealed and elucidated through the atom-projected density of states. These findings suggest the potential for openingmore » and modulating a bandgap in graphene as high as several hundred meV.« less

Interaction of carbohydrate modified boron nitride nanotubes with living cells.

PubMed

Emanet, Melis; Şen, Özlem; Çobandede, Zehra; Çulha, Mustafa

2015-10-01

Boron nitride nanotubes (BNNTs) are composed of boron and nitrogen atoms and they show significantly different properties from their carbon analogues (carbon nanotubes, CNTs). Due to their unique properties including low electrical conductivity, and imaging contrast and neutron capture properties; they can be used in biomedical applications. When their use in biological fields is considered, the route of their toxic effect should be clarified. Therefore, the study of interactions between BNNTs and living systems is important in envisaging biological applications at both cellular and sub-cellular levels to fully gain insights of their potential adverse effects. In this study, BNNTs were modified with lactose, glucose and starch and tested for their cytotoxicity. First, the interactions and the behavior of BNNTs with bovine serum albumin (BSA), Dulbecco's Modified Eagle's Medium (DMEM) and DMEM/Nutrient Mixture F-12Ham were investigated. Thereafter, their cellular uptake and the cyto- and genotoxicity on human dermal fibroblasts (HDFs) and adenocarcinoma human alveolar basal epithelial cells (A549) were evaluated. HDFs and A549 cells internalized the modified and unmodified BNNTs, and BNNTs were found to not cause significant viability change and DNA damage. A higher uptake rate of BNNTs by A549 cells compared to HDFs was observed. Moreover, a concentration-dependent cytotoxicity was observed on A549 cells while they were safer for HDFs in the same concentration range. Based on these findings, it can be concluded that BNNTs and their derivatives made with biomacromolecules might be good candidates for several applications in medicine and biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Anomalous thermal conductivity of monolayer boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tabarraei, Alireza, E-mail: atabarra@uncc.edu; Wang, Xiaonan

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 themore » 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.« less

Covalent coupling via dehalogenation on Ni(111) supported boron nitride and graphene.

PubMed

Morchutt, Claudius; Björk, Jonas; Krotzky, Sören; Gutzler, Rico; Kern, Klaus

2015-02-11

Polymerization of 1,3,5-tris(4-bromophenyl)benzene via dehalogenation on graphene and hexagonal boron nitride is investigated by scanning tunneling microscopy experiments and density functional theory calculations. This work reveals how the interactions between molecules and graphene or h-BN grown on Ni(111) govern the surface-confined synthesis of polymers through C-C coupling.

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

Polymer/boron nitride nanocomposite materials for superior thermal transport performance.

PubMed

Song, Wei-Li; Wang, Ping; Cao, Li; Anderson, Ankoma; Meziani, Mohammed J; Farr, Andrew J; Sun, Ya-Ping

2012-06-25

Boron nitride nanosheets were dispersed in polymers to give composite films with excellent thermal transport performances approaching the record values found in polymer/graphene nanocomposites. Similarly high performance at lower BN loadings was achieved by aligning the nanosheets in poly(vinyl alcohol) matrix by simple mechanical stretching (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A template-free solvent-mediated synthesis of high surface area boron nitride nanosheets for aerobic oxidative desulfurization

DOE PAGES

Wu, Peiwen; Zhu, Wenshuai; Chao, Yanhong; ...

2015-10-16

Hexagonal boron nitride nanosheets (h-BNNs) with rather high specific surface area (SSA) are important two-dimensional layer-structured materials. Here in this study, a solvent-mediated synthesis of h-BNNs revealed a template-free lattice plane control strategy that induced high SSA nanoporous structured h-BNNs with outstanding aerobic oxidative desulfurization performance.

Mid-infrared polaritonic coupling between boron nitride nanotubes and graphene.

PubMed

Xu, Xiaoji G; Jiang, Jian-Hua; Gilburd, Leonid; Rensing, Rachel G; Burch, Kenneth S; Zhi, Chunyi; Bando, Yoshio; Golberg, Dmitri; Walker, Gilbert C

2014-11-25

Boron nitride (BN) is considered to be a promising substrate for graphene-based devices in part because its large band gap can serve to insulate graphene in layered heterostructures. At mid-infrared frequencies, graphene supports surface plasmon polaritons (SPPs), whereas hexagonal-BN (h-BN) is found to support surface phonon polaritons (SPhPs). We report on the observation of infrared polaritonic coupling between graphene SPPs and boron nitride nanotube (BNNT) SPhPs. Infrared scattering type scanning near-field optical microscopy is used to obtain spatial distribution of the two types of polaritons at the nanoscale. The observation suggests that those polaritons interact at the nanoscale in a one-dimensional/two-dimensional (1D/2D) geometry, exchanging energy in a nonplanar configuration at the nanoscale. Control of the polaritonic interaction is achieved by adjustment of the graphene Fermi level through voltage gating. Our observation suggests that boron nitride nanotubes and graphene can interact at mid-infrared frequencies and coherently exchange their energies at the nanoscale through the overlap of mutual electric near field of surface phonon polaritons and surface plasmon polaritons. Such interaction enables the design of nano-optical devices based on BNNT-graphene polaritonics in the mid-infrared range.

Ab initio study of boron nitride lines on graphene

NASA Astrophysics Data System (ADS)

Mata-Carrizal, Berenice; Sanginés-Mendoza, Raúl; Martinez, Edgar

2013-03-01

Graphene has unusual electronic properties which make it a promising material for electronic devices. Neverthless, the absence of a band gap sets limitations on its practical applications. Thus, it is crucial to find methods to create and tune the band gap of systems based on graphene. In this way, we explore the modulation of the electronic properties of graphene through doping with boron nitride lines. In particular, we studied the electronic structure of graphene sheets doped with boron nitride lines armchair and zigzag type. The calculations were performed using the pseudopotential LCAO method with a Generalized Gradient Approximation (GGA) for the exchange-correlation energy functional. We found that both doping lines type induce a bandgap and that the energy gap increases as the length of doping lines increases. Accordingly to our DFT calculations, we found that the energy gap on graphene doped with armchair and zigzag lines is due to a two different mechanisms to drain charge from pi- to sigma- orbitals. Thus, we found that doping graphene with boron nitride lines is a useful way to induce and modulate the bandgap on graphene. This research was supported by Consejo Nacional de Ciencia y Tecnología (Conacyt) under Grant No. 133022.

Adsorption of sugars on Al- and Ga-doped boron nitride surfaces: A computational study

NASA Astrophysics Data System (ADS)

Darwish, Ahmed A.; Fadlallah, Mohamed M.; Badawi, Ashraf; Maarouf, Ahmed A.

2016-07-01

Molecular adsorption on surfaces is a key element for many applications, including sensing and catalysis. Non-invasive sugar sensing has been an active area of research due to its importance to diabetes care. The adsorption of sugars on a template surface study is at the heart of matter. Here, we study doped hexagonal boron nitride sheets (h-BNNs) as adsorbing and sensing template for glucose and glucosamine. Using first principles calculations, we find that the adsorption of glucose and glucosamine on h-BNNs is significantly enhanced by the substitutional doping of the sheet with Al and Ga. Including long range van der Waals corrections gives adsorption energies of about 2 eV. In addition to the charge transfer occurring between glucose and the Al/Ga-doped BN sheets, the adsorption alters the size of the band gap, allowing for optical detection of adsorption. We also find that Al-doped boron nitride sheet is better than Ga-doped boron nitride sheet to enhance the adsorption energy of glucose and glucosamine. The results of our work can be potentially utilized when designing support templates for glucose and glucosamine.

Boron nitride encapsulated graphene infrared emitters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnard, H. R.; Zossimova, E.; Mahlmeister, N. H.

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 devicesmore » and reflects the device geometry, and the increase in lateral heat conduction within the devices due to the multilayer graphene and boron nitride layers.« less

Method and device to synthesize boron nitride nanotubes and related nanoparticles

DOEpatents

Zettl, Alexander K.

2016-07-19

Methods and apparatus for producing chemical nanostructures having multiple elements, such as boron and nitride, e.g. boron nitride nanotubes, are disclosed. The method comprises creating a plasma jet, or plume, such as by an arc discharge. The plasma plume is elongated and has a temperature gradient along its length. It extends along its length into a port connector area having ports for introduction of feed materials. The feed materials include the multiple elements, which are introduced separately as fluids or powders at multiple ports along the length of the plasma plume, said ports entering the plasma plume at different temperatures. The method further comprises modifying a temperature at a distal portion of or immediately downstream of said plasma plume; and collecting said chemical nanostructures after said modifying.

Shock-induced reaction synthesis of cubic boron nitride

NASA Astrophysics Data System (ADS)

Beason, M. T.; Pauls, J. M.; Gunduz, I. E.; Rouvimov, S.; Manukyan, K. V.; Matouš, K.; Son, S. F.; Mukasyan, A.

2018-04-01

Here, we report ultra-fast (0.1-5 μs) shock-induced reactions in the 3B-TiN system, leading to the direct synthesis of cubic boron nitride, which is extremely rare in nature and is the second hardest material known. Composite powders were produced through high-energy ball milling to provide intimate mixing and subsequently shocked using an explosive charge. High-resolution transmission electron microscopy and X-ray diffraction confirm the formation of nanocrystalline grains of c-BN produced during the metathetical reaction between boron and titanium nitride. Our results illustrate the possibility of rapid reactions enabled by high-energy ball milling possibly occurring in the solid state on incredibly short timescales. This process may provide a route for the discovery and fabrication of advanced compounds.

Ultra-sensitive Hall sensors based on graphene encapsulated in hexagonal boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dauber, Jan; Stampfer, Christoph; Peter Grünberg Institute

2015-05-11

The encapsulation of graphene in hexagonal boron nitride provides graphene on substrate with excellent material quality. Here, we present the fabrication and characterization of Hall sensor elements based on graphene boron nitride heterostructures, where we gain from high mobility and low charge carrier density at room temperature. We show a detailed device characterization including Hall effect measurements under vacuum and ambient conditions. We achieve a current- and voltage-related sensitivity of up to 5700 V/AT and 3 V/VT, respectively, outpacing state-of-the-art silicon and III/V Hall sensor devices. Finally, we extract a magnetic resolution limited by low frequency electric noise of less than 50more » nT/√(Hz) making our graphene sensors highly interesting for industrial applications.« less

Large Area Few Layers Hexagonal Boron Nitride Prepared by Quadrupole Field Aided Exfoliation.

PubMed

Hanlun, Lu; Rong, Min Zhi; Zhang, Ming Qiu

2018-01-16

A quadrupole electric field mediated exfoliation method is proposed to convert micron sized hexagonal boron nitride (hBN) powders into few layers hexagonal boron nitride nano-sheets (h-BNNS). Under the optimum conditions (400 Hz, 40 V, 32μg/mL, sodium deoxycholate, TAE medium), the hBN powders (thickness > 200 nm, horizontal scale ~ 10 μm) are successfully exfoliated into 0.5-4 nm (1-10 layers) thick h-BNNS with the same horizontal scale. Dynamic laser scattering (DLS) and atomic force microscope (AFM) statistics show that the yield is 47.6 % (for the portion with the thickness of 0.5-6 nm), and all of the vertical sizes are reduced to smaller than 18 nm (45 layers). © 2018 IOP Publishing Ltd.

Determination of the optical band-gap energy of cubic and hexagonal boron nitride using luminescence excitation spectroscopy

NASA Astrophysics Data System (ADS)

Evans, D. A.; McGlynn, A. G.; Towlson, B. M.; Gunn, M.; Jones, D.; Jenkins, T. E.; Winter, R.; Poolton, N. R. J.

2008-02-01

Using synchrotron-based luminescence excitation spectroscopy in the energy range 4-20 eV at 8 K, the indirect Γ-X optical band-gap transition in cubic boron nitride is determined as 6.36 ± 0.03 eV, and the quasi-direct band-gap energy of hexagonal boron nitride is determined as 5.96 ± 0.04 eV. The composition and structure of the materials are self-consistently established by optically detected x-ray absorption spectroscopy, and both x-ray diffraction and Raman measurements on the same samples give independent confirmation of their chemical and structural purity: together, the results are therefore considered as providing definitive measurements of the optical band-gap energies of the two materials.

Solid state thermal rectifier

DOEpatents

None

2016-07-05

Thermal rectifiers using linear nanostructures as core thermal conductors have been fabricated. A high mass density material is added preferentially to one end of the nanostructures to produce an axially non-uniform mass distribution. The resulting nanoscale system conducts heat asymmetrically with greatest heat flow in the direction of decreasing mass density. Thermal rectification has been demonstrated for linear nanostructures that are electrical insulators, such as boron nitride nanotubes, and for nanostructures that are conductive, such as carbon nanotubes.

Hot isostatic pressing of silicon nitride with boron nitride, boron carbide, and carbon additions

NASA Technical Reports Server (NTRS)

Mieskowski, Diane M.; Sanders, William A.

1989-01-01

Si3N4 test bars containing additions of BN, B4C, and C, were hot isostatically pressed in Ta cladding at 1900 and 2050 C to 98.9 percent to 99.5 percent theoretical density. Room-temperature strength data on specimens containing 2 wt pct BN and 0.5 wt pct C were comparable to data obtained for Si3N4 sintered with Y2O3, Y2O3 and Al2O3, or ZrO2. The 1370 C strengths were less than those obtained for additions of Y2O3 or ZrO2 but greater than those obtained from a combination of Y2O3 and Al2O3. SEM fractography indicated that, as with other types of Si3N4, room-temperature strength was controlled by processing flaws. The decrease in strength at 1370 C was typical of Si3N4 having an amorphous grain-boundary phase. The primary advantage of nonoxide additions appears to be in facilitating specimen removal from the Ta cladding.

Accurate atomistic potentials and training sets for boron-nitride nanostructures

NASA Astrophysics Data System (ADS)

Tamblyn, Isaac

Boron nitride nanotubes exhibit exceptional structural, mechanical, and thermal properties. They are optically transparent and have high thermal stability, suggesting a wide range of opportunities for structural reinforcement of materials. Modeling can play an important role in determining the optimal approach to integrating nanotubes into a supporting matrix. Developing accurate, atomistic scale models of such nanoscale interfaces embedded within composites is challenging, however, due to the mismatch of length scales involved. Typical nanotube diameters range from 5-50 nm, with a length as large as a micron (i.e. a relevant length-scale for structural reinforcement). Unlike their carbon-based counterparts, well tested and transferable interatomic force fields are not common for BNNT. In light of this, we have developed an extensive training database of BN rich materials, under conditions relevant for BNNT synthesis and composites based on extensive first principles molecular dynamics simulations. Using this data, we have produced an artificial neural network potential capable of reproducing the accuracy of first principles data at significantly reduced computational cost, allowing for accurate simulation at the much larger length scales needed for composite design.

Penetration Resistance of Armor Ceramics: Dimensional Analysis and Property Correlations

DTIC Science & Technology

2015-08-01

been reported in experimental studies. Particular ceramics analyzed here are low- and high-purity alumina, aluminum nitride, boron carbide, silicon...analyzed here are low- and high-purity alumina, aluminum nitride, boron carbide, silicon carbide, and titanium diboride. Data for penetration depth...include high hardness, high elastic stiffness, high strengths (static/dynamic compressive, shear, and bending), and low density relative to armor steels

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

Ambient Carbon Dioxide Capture Using Boron-Rich Porous Boron Nitride: A Theoretical Study.

PubMed

Li, Lanlan; Liu, Yan; Yang, Xiaojing; Yu, Xiaofei; Fang, Yi; Li, Qiaoling; Jin, Peng; Tang, Chengchun

2017-05-10

The development of highly efficient sorbent materials for CO 2 capture under ambient conditions is of great importance for reducing the impact of CO 2 on the environment and climate change. In this account, strong CO 2 adsorption on a boron antisite (B N ) in boron-rich porous boron nitrides (p-BN) was developed and studied. The results indicated that the material achieved larger adsorption energies of 2.09 eV (201.66 kJ/mol, PBE-D). The electronic structure calculations suggested that the introduction of B N in p-BN induced defect electronic states in the energy gap region, which strongly impacted the adsorption properties of the material. The bonding between the B N defect and the CO 2 molecule was clarified, and it was found that the electron donation first occurred from CO 2 to the B N double-acceptor state then, followed by electron back-donation from B N to CO 2 accompanied by the formation of a B N -C bond. The thermodynamic properties indicated that the adsorption of CO 2 on the B N defect to form anionic CO 2 δ- species was spontaneous at temperatures below 350 K. Both the large adsorption energies and the thermodynamic properties ensured that p-BN with a B N defect could effectively capture CO 2 under ambient conditions. Finally, to evaluate the energetic stability, the defect formation energies were estimated. The formation energy of the B N defects was found to strongly depend on the chemical environment, and the selection of different reactants (B or N sources) would achieve the goal of reducing the formation energy. These findings provided a useful guidance for the design and fabrication of a porous BN sorbent for CO 2 capture.

Alloy Design of Martensitic 9Cr-Boron Steel for A-USC Boiler at 650 °C — Beyond Grades 91, 92 and 122

NASA Astrophysics Data System (ADS)

Abe, Fujio; Tabuchi, M.; Tsukamoto, S.

Boundary hardening is shown to be the most important strengthening mechanism in creep of tempered martensitic 9% Cr steel base metal and welded joints at 650 °C. The enrichment of soluble boron near prior austenite grain boundaries (PAGBs) by the GB segregation is essential for the reduction of coarsening rate of M23C6 carbides near PAGBs, enhancing the boundary and sub-boundary hardening near PAGBs, and also for the change in α/γ transformation behavior in heat-affected-zone (HAZ) of welded joints during heating of welding, producing the same microstructure in HAZ as in the base metal. Excess addition of nitrogen to the 9Cr-boron steel promotes the formation of boron nitrides during normalizing heat treatment, which consumes most of soluble boron and degrades the creep strength. A NIMS 9Cr steel (MARBN; Martensitic 9Cr steel strengthened by boron and MX nitrides) with 120-150 ppm boron and 60-90 ppm nitrogen, where no boron nitride forms during normalizing heat treatment, exhibits not only much higher creep strength of base metal than Grades 91, 92 and 122 but also substantially no degradation in creep strength due to Type IV fracture in HAZ of welded joints at 650°C. The protective Cr2O3-rich scale forms on the surface of 9Cr steel by pre-oxidation treatment in Ar gas, which significantly improves the oxidation resistance in steam at 650°C.

Performance, Stability, and Plume Characterization of the HERMeS Thruster with Boron Nitride Silica Composite Discharge Channel

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Huang, Wensheng; Gilland, James H.; Haag, Thomas W.; Mackey, Jonathan; Yim, John; Pinero, Luis; Williams, George; Peterson, Peter; Herman, Daniel

2017-01-01

NASA's Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5kW Technology Demonstration Unit-3 (TDU-3) has been the subject of extensive technology maturation in preparation for flight system development. Detailed performance, stability, and plume characterization tests of the thruster were performed at NASA GRC's Vacuum Facility 5 (VF-5). The TDU-3 thruster implements a magnetic topology that is identical to TDU-1. The TDU-3 boron nitride silica composite discharge channel material is different than the TDU-1 heritage boron nitride discharge channel material. Performance and stability characterization of the TDU-3 thruster was performed at discharge voltages between 300V and 600V and at discharge currents between 5A and 21.8A. The thruster performance and stability were assessed for varying magnetic field strength, cathode flow fractions between 5% and 9%, varying harness inductance, and for reverse magnet polarity. Performance characterization test results indicate that the TDU-3 thruster performance is in family with the TDU-1 levels. TDU-3's thrust efficiency of 65% and specific impulse of 2,800sec at 600V and 12.5kW exceed performance levels of SOA Hall thrusters. Thruster stability regimes were characterized with respect to the thruster discharge current oscillations (discharge current peak-to-peak and root mean square magnitudes), discharge current waveform power spectral density analysis, and maps of the current-voltage-magnetic field. Stability characterization test results indicate a stability profile similar to TDU-1. Finally, comparison of the TDU-1 and TDU-3 plume profiles found that there were negligible differences in the plasma plume characteristics between the TDU with heritage boron nitride versus the boron nitride silica composite discharge channel.

Effect of polymer residues on the electrical properties of large-area graphene–hexagonal boron nitride planar heterostructures

DOE PAGES

Voyloy, Dimitry; Lassiter, Matthew G.; Sokolov, Alexei P.; ...

2017-06-19

Polymer residue plays an important role in the performance of 2D heterostructured materials. Herein, we study the effect of polymer residual impurities on the electrical properties of graphene–boron nitride planar heterostructures. Large-area graphene (Gr) and hexagonal boron nitride (h-BN) monolayers were synthesized using chemical vapor deposition techniques. Atomic van-der-Waals heterostructure layers based on varied configurations of Gr and h-BN layers were assembled. The average interlayer resistance of the heterojunctions over a 1 cm 2 area for several planar heterostructure configurations was assessed by impedance spectroscopy and modeled by equivalent electrical circuits. As a result, conductive AFM measurements showed that themore » presence of polymer residues on the surface of the Gr and h-BN monolayers resulted in significant resistance deviations over nanoscale regions.« less

A new class of boron nitride fibers with tunable properties by combining an electrospinning process and the polymer-derived ceramics route

NASA Astrophysics Data System (ADS)

Salles, Vincent; Bernard, Samuel; Brioude, Arnaud; Cornu, David; Miele, Philippe

2010-02-01

Novel boron nitride (BN) fibers have been developed with diameters ranging from the nano- to microscale by thermal conversion of as-electrospun fibers from polyacrylonitrile and poly[B-(methylamino)borazine] blend solutions. Such a new class of ceramic fibers is seen as potential candidate for thermal management applications and filtration systems in harsh environments.Novel boron nitride (BN) fibers have been developed with diameters ranging from the nano- to microscale by thermal conversion of as-electrospun fibers from polyacrylonitrile and poly[B-(methylamino)borazine] blend solutions. Such a new class of ceramic fibers is seen as potential candidate for thermal management applications and filtration systems in harsh environments. Electronic supplementary information (ESI) available: Experimental details and EDX results. See DOI: 10.1039/b9nr00185a

Extraction of Boron Nitride Nanotubes and Fabrication of Macroscopic Articles Using Chlorosulfonic Acid.

PubMed

Adnan, Mohammed; Marincel, Daniel M; Kleinerman, Olga; Chu, Sang-Hyon; Park, Cheol; Hocker, Samuel J A; Fay, Catharine; Arepalli, Sivaram; Talmon, Yeshayahu; Pasquali, Matteo

2018-03-14

Due to recent advances in high-throughput synthesis, research on boron nitride nanotubes (BNNTs) is moving toward applications. One future goal is the assembly of macroscopic articles of high-aspect-ratio, pristine BNNTs. However, these articles are presently unattainable because of insufficient purification and fabrication methods. We introduce a solution process for extracting BNNTs from synthesis impurities without sonication or the use of surfactants and proceed to convert the extracted BNNTs into thin films. The solution process can also be used to convert as-synthesized material-which contains significant amounts of hexagonal boron nitride ( h-BN)-into mats and aerogels with controllable structure and dimension. The solution extraction method, combined with further advances in synthesis and purification, contributes to the development of all-BNNT macroscopic articles, such as fibers and 3-D structures.

Oriented graphene nanoribbons embedded in hexagonal boron nitride trenches

PubMed Central

Chen, Lingxiu; He, Li; Wang, Hui Shan; Wang, Haomin; Tang, Shujie; Cong, Chunxiao; Xie, Hong; Li, Lei; Xia, Hui; Li, Tianxin; Wu, Tianru; Zhang, Daoli; Deng, Lianwen; Yu, Ting; Xie, Xiaoming; Jiang, Mianheng

2017-01-01

Graphene nanoribbons (GNRs) are ultra-narrow strips of graphene that have the potential to be used in high-performance graphene-based semiconductor electronics. However, controlled growth of GNRs on dielectric substrates remains a challenge. Here, we report the successful growth of GNRs directly on hexagonal boron nitride substrates with smooth edges and controllable widths using chemical vapour deposition. The approach is based on a type of template growth that allows for the in-plane epitaxy of mono-layered GNRs in nano-trenches on hexagonal boron nitride with edges following a zigzag direction. The embedded GNR channels show excellent electronic properties, even at room temperature. Such in-plane hetero-integration of GNRs, which is compatible with integrated circuit processing, creates a gapped channel with a width of a few benzene rings, enabling the development of digital integrated circuitry based on GNRs. PMID:28276532

Effect of polymer residues on the electrical properties of large-area graphene–hexagonal boron nitride planar heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voyloy, Dimitry; Lassiter, Matthew G.; Sokolov, Alexei P.

Polymer residue plays an important role in the performance of 2D heterostructured materials. Herein, we study the effect of polymer residual impurities on the electrical properties of graphene–boron nitride planar heterostructures. Large-area graphene (Gr) and hexagonal boron nitride (h-BN) monolayers were synthesized using chemical vapor deposition techniques. Atomic van-der-Waals heterostructure layers based on varied configurations of Gr and h-BN layers were assembled. The average interlayer resistance of the heterojunctions over a 1 cm 2 area for several planar heterostructure configurations was assessed by impedance spectroscopy and modeled by equivalent electrical circuits. As a result, conductive AFM measurements showed that themore » presence of polymer residues on the surface of the Gr and h-BN monolayers resulted in significant resistance deviations over nanoscale regions.« less

Fluid synthesis and structure of a new polymorphic modification of boron nitride

NASA Astrophysics Data System (ADS)

Pokropivny, V. V.; Smolyar, A. S.; Ovsiannikova, L. I.; Pokropivny, A. V.; Kuts, V. A.; Lyashenko, V. I.; Nesterenko, Yu. V.

2013-04-01

A new previously unknown phase of boron nitride with a hardness of 0.41-0.63 GPa has been pre-pared by the supercritical fluid synthesis. The presence of a new phase is confirmed by the X-ray spectra and IR absorption spectra, where new reflections and bands are distinguished. The fundamental reflection of the X-ray diffraction pattern is d = 0.286-0.291 nm, and the characteristic band in the infrared absorption spectrum is observed at 704 cm-1. The X-ray diffraction pattern and the experimental and theoretical infrared absorption spectra show that a new synthesized boron nitride phase can be a cluster crystal (space group 211) with a simple cubic lattice. Cage clusters of a fullerene-like morphology B24N24 with point symmetry O are arranged in lattice sites.

Boron nitride microfibers grown by plasma-assisted laser chemical vapor deposition without a metal catalyst

NASA Astrophysics Data System (ADS)

Komatsu, Shojiro; Kazami, Daisuke; Tanaka, Hironori; Shimizu, Yoshiki; Moriyoshi, Yusuke; Shiratani, Masaharu; Okada, Katsuyuki

2006-04-01

Boron nitride fibers were found to grow on polycrystalline nickel and Si (100) substrates by plasma-assisted laser chemical vapor deposition from B2H6+NH3 using an excimer laser at 193nm. Their diameter was typically a few hundreds of nanometers, while the length was a few tens of micrometers. They were stoichiometric or boron-rich BN in chemical composition. When the substrate was rotated during deposition, spiral fibers were found to grow. We conclude that they grew with the help of laser light by other than the vapor - liquid - solid mechanism.

Graphene-like 2D nanomaterial-based biointerfaces for biosensing applications.

PubMed

Zhu, Chengzhou; Du, Dan; Lin, Yuehe

2017-03-15

Due to their unique structures and multifunctionalities, two-dimensional (2D) nanomaterials have aroused increasing interest in the construction of the novel biointerfaces for biosensing applications. Efforts in constructing novel biointerfaces led to exploit the more versatile and tunable graphene-like 2D nanomaterials (e.g. graphitic carbon nitride, boron nitride, transition metal dichalcogenides, and transition metal oxides) with various structural and compositional characteristics. This review highlights recent efforts in the design of graphene-like 2D nanomaterials and their derived biointerfaces and exploitation of their research on fluorescent sensors and a series of electrochemical sensors, including amperometric, electrochemiluminescence, photoelectrochemical and field-effect transistor sensors. Finally, we discuss some critical challenges and future perspectives in this field. Copyright © 2016. Published by Elsevier B.V.

Carbon-doped BN nanosheets for metal-free photoredox catalysis

PubMed Central

Huang, Caijin; Chen, Cheng; Zhang, Mingwen; Lin, Lihua; Ye, Xinxin; Lin, Sen; Antonietti, Markus; Wang, Xinchen

2015-01-01

The generation of sustainable and stable semiconductors for solar energy conversion by photoredox catalysis, for example, light-induced water splitting and carbon dioxide reduction, is a key challenge of modern materials chemistry. Here we present a simple synthesis of a ternary semiconductor, boron carbon nitride, and show that it can catalyse hydrogen or oxygen evolution from water as well as carbon dioxide reduction under visible light illumination. The ternary B–C–N alloy features a delocalized two-dimensional electron system with sp2 carbon incorporated in the h-BN lattice where the bandgap can be adjusted by the amount of incorporated carbon to produce unique functions. Such sustainable photocatalysts made of lightweight elements facilitate the innovative construction of photoredox cascades to utilize solar energy for chemical conversion. PMID:26159752

Atomically Thin Hexagonal Boron Nitride Nanofilm for Cu Protection: The Importance of Film Perfection.

PubMed

Khan, Majharul Haque; Jamali, Sina S; Lyalin, Andrey; Molino, Paul J; Jiang, Lei; Liu, Hua Kun; Taketsugu, Tetsuya; Huang, Zhenguo

2017-01-01

Outstanding protection of Cu by high-quality boron nitride nanofilm (BNNF) 1-2 atomic layers thick in salt water is observed, while defective BNNF accelerates the reaction of Cu toward water. The chemical stability, insulating nature, and impermeability of ions through the BN hexagons render BNNF a great choice for atomic-scale protection. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Method for forming monolayer graphene-boron nitride heterostructures

DOEpatents

Sutter, Peter Werner; Sutter, Eli Anguelova

2016-08-09

A method for fabricating monolayer graphene-boron nitride heterostructures in a single atomically thin membrane that limits intermixing at boundaries between graphene and h-BN, so as to achieve atomically sharp interfaces between these materials. In one embodiment, the method comprises exposing a ruthenium substrate to ethylene, exposing the ruthenium substrate to oxygen after exposure to ethylene and exposing the ruthenium substrate to borazine after exposure to oxygen.

Effect of the hexagonal phase interlayer on rectification properties of boron nitride heterojunctions to silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teii, K., E-mail: teii@asem.kyushu-u.ac.jp; Ito, H.; Katayama, N.

2015-02-07

Rectification properties of boron nitride/silicon p-n heterojunction diodes fabricated under low-energy ion impact by plasma-enhanced chemical vapor deposition are studied in terms of the resistive sp{sup 2}-bonded boron nitride (sp{sup 2}BN) interlayer. A two-step biasing technique is developed to control the fraction of cubic boron nitride (cBN) phase and, hence, the thickness of the sp{sup 2}BN interlayer in the films. The rectification ratio at room temperature is increased up to the order of 10{sup 4} at ±10 V of biasing with increasing the sp{sup 2}BN thickness up to around 130 nm due to suppression of the reverse leakage current. The variation ofmore » the ideality factor in the low bias region is related to the interface disorders and defects, not to the sp{sup 2}BN thickness. The forward current follows the Frenkel-Poole emission model in the sp{sup 2}BN interlayer at relatively high fields when the anomalous effect is assumed. The transport of the minority carriers for reverse current is strongly limited by the high bulk resistance of the thick sp{sup 2}BN interlayer, while that of the major carriers for forward current is much less affected.« less

Catalyst-free one step synthesis of large area vertically stacked N-doped graphene-boron nitride heterostructures from biomass source.

PubMed

Esteve-Adell, Ivan; He, Jinbao; Ramiro, Fernando; Atienzar, Pedro; Primo, Ana; García, Hermenegildo

2018-03-01

A procedure for the one-step preparation of films of few-layer N-doped graphene on top of nanometric hexagonal boron nitride sheets ((N)graphene/h-BN) based on the pyrolysis at 900 °C under an inert atmosphere of a film of chitosan containing about 20 wt% of ammonium borate salt as a precursor is reported. During the pyrolysis a spontaneous segregation of (N)graphene and boron nitride layers takes place. The films were characterized by optical microscopy that shows a thin graphene overlayer covering the boron nitride layer, the latter showing characteristic cracks, and by XPS measurements at different monitoring angles from 0° to 50° where an increase in the proportion of C vs. B and N was observed. The resulting (N)graphene/h-BN films were also characterized by Raman, HRTEM, SEM, FIB-SEM and AFM. The thickness of the (N)graphene and h-BN layers can be controlled by varying the concentration of precursors and the spin coating rate and is typically below 5 nm. Electrical conductivity measurements using microelectrodes can cause the burning of the graphene layer at high intensities, while lower intensities show that (N)graphene/h-BN films behave as capacitors in the range of positive voltages.

Sputtering Erosion in Ion and Plasma Thrusters

NASA Technical Reports Server (NTRS)

Ray, Pradosh K.

1996-01-01

Low energy sputtering of molybdenum, tantalum and boron nitride with xenon ions are being studied using secondary neutral and secondary ion mass spectrometry (SNMS/SIMS). An ultrahigh vacuum chamber was used to conduct the experiment at a base pressure of 1x10(exp -9) torr. The primary ion beam is generated by an ion gun which is capable of delivering ion currents in the range of 20 to 500 nA. The ion beam can be focused to a spot size of approximately 1 mm in diameter. The mass spectrometer is positioned 10 mm from the target and 90 deg to the primary ion beam direction. SNMS and SIMS spectra were collected at various incident angles and different ion energies. For boron nitride sputtering, the target was flooded with an electron beam to neutralize the charge buildup on the surface. In the SNMS mode, sputtering of Mo and Ta can be detected at an ion energy as low as 100 eV whereas in boron nitride the same was observed up to an energy of 300 eV. However, in the positive-SIMS mode, the sputtering of Mo was observed at 10 eV incident ion energy. The SIMS spectra obtained for boron nitride clearly identifies the two isotopes of boron as well as cluster ions such as B2(sup +) and molecular ions such as BN(sup +). From the angle versus yields measurements, it was found that the maximum SNMS yield shifts towards lower incident angles at low ion energies for all three samples.

Tension-Compression Fatigue of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature in Air and Steam Environments

DTIC Science & Technology

2015-03-26

method has been successfully used with several materials such as silicon carbide fiber - silicon carbide matrix ( SiC / SiC ) CMCs with carbon and boron...elements [14]. These advanced ceramics include oxides, nitrides and carbides of silicon , aluminum, titanium, and zirconium [12]. One of the most...oxides over silicon carbide and other non-oxide materials. In fact, it is the inherent stability of oxides in oxidizing environments which originally

High-Efficiency Silicon Carbide (SiC) Converters. Delivery Order 0001: Development of High-Temperature, High-Power, High-Efficiency, High-Voltage Converters Using Silicon Carbide

DTIC Science & Technology

2004-03-01

32 Silicon Dioxide as a Mask ......................................................... 34 Silicon Nitride as a Mask...phosphorous (P), and arsenic (As) for n-type material and aluminum (Al), boron (B), beryllium (Be), gallium (Ga), oxygen (O), and scandium (Sc) for...O2 in carbon tetrafluoride (CF4), nitrogen trifluoride (NF3), and sulfur hexafluoride (SF6) were observed because these gases produce high fluorine

Multifunctional fiber reinforced polymer composites using carbon and boron nitride nanotubes

NASA Astrophysics Data System (ADS)

Ashrafi, Behnam; Jakubinek, Michael B.; Martinez-Rubi, Yadienka; Rahmat, Meysam; Djokic, Drazen; Laqua, Kurtis; Park, Daesun; Kim, Keun-Su; Simard, Benoit; Yousefpour, Ali

2017-12-01

Recent progress in nanotechnology has made several nano-based materials available with the potential to address limitations of conventional fiber reinforced polymer composites, particularly in reference to multifunctional structures. Carbon nanotubes (CNTs) are the most prevalent case and offer amazing properties at the individual nanotube level. There are already a few high-profile examples of the use of CNTs in space structures to provide added electrical conductivity for static dissipation and electromagnetic shielding. Boron nitride nanotubes (BNNTs), which are structurally analogous to CNTs, also present a range of attractive properties. Like the more widely explored CNTs, individual BNNTs display remarkable mechanical properties and high thermal conductivity but with contrasting functional attributes including substantially higher thermal stability, high electrical insulation, polarizability, high neutron absorption and transparency to visible light. This presents the potential of employing either or both BNNTs and CNTs to achieve a range of lightweight, functional composites for space structures. Here we present the case for application of BNNTs, in addition to CNTs, in space structures and describe recent advances in BNNT production at the National Research Council Canada (NRC) that have, for the first time, provided sufficiently large quantities to enable commercialization of high-quality BNNTs and accelerate development of chemistry, composites and applications based on BNNTs. Early demonstrations showing the fabrication and limited structural testing of polymer matrix composites, including glass fiber-reinforced composite panels containing BNNTs will be discussed.

Multifunctional Electroactive Nanocomposites Based on Piezoelectric Boron Nitride Nanotubes.

PubMed

Kang, Jin Ho; Sauti, Godfrey; Park, Cheol; Yamakov, Vesselin I; Wise, Kristopher E; Lowther, Sharon E; Fay, Catharine C; Thibeault, Sheila A; Bryant, Robert G

2015-12-22

Space exploration missions require sensors and devices capable of stable operation in harsh environments such as those that include high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation. However, conventional or state-of-the-art electroactive materials like lead zirconate titanate, poly(vinylidene fluoride), and carbon nanotube (CNT)-doped polyimides have limitations on use in those extreme applications. Theoretical studies have shown that boron nitride nanotubes (BNNTs) have strength-to-weight ratios comparable to those of CNTs, excellent high-temperature stability (to 800 °C in air), large electroactive characteristics, and excellent neutron radiation shielding capability. In this study, we demonstrated the experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites. Upon application of an external electric field, the 2 wt % BNNT/polyimide composite was found to exhibit electroactive strain composed of a superposition of linear piezoelectric and nonlinear electrostrictive components. When the BNNTs were aligned by stretching the 2 wt % BNNT/polyimide composite, electroactive characteristics increased by about 460% compared to the nonstretched sample. An all-nanotube actuator consisting of a BNNT buckypaper layer between two single-walled carbon nanotube buckypaper electrode layers was found to have much larger electroactive properties. The additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions.

Carbon-doped boron nitride nanosheet as a promising catalyst for N2O reduction by CO or SO2 molecule: A comparative DFT study

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.; Saeidi, Nasibeh

2018-06-01

We report for the first time, the catalytic activity of the experimentally available carbon-doped boron nitride nanosheet (C-BNNS) towards the reduction of N2O in the presence of CO or SO2 molecule. According to our density functional theory calculations, C-doping can introduce high spin density into BN monolayer which is mainly localized over the C and its neighboring N atoms. The Hirshfeld charge density analysis reveals that the electron-rich C-BNNS acts as an electron donating support to activate N2O molecule which is an important step in the reduction of N2O. The N2O reduction reaction starts with the dissociative adsorption of N2O over the C-BNNS surface, yielding the N2 molecule and an activated oxygen moiety (Oads) adsorbed over the C atom. The reaction then proceeds via the elimination of Oads by a CO or SO2 molecule. The obtained low activation energies clearly indicate that the metal-free C-BNNS surface can be regarded as a highly active catalyst for the reduction of N2O. The results of this study may open new avenues in searching low cost and highly active BN-based catalysts for low temperature reduction of N2O.

Multifunctional Electroactive Nanocomposites Based on Piezoelectric Boron Nitride Nanotubes

NASA Technical Reports Server (NTRS)

Kang, Jin Ho; Sauti, Godfrey; Park, Cheol; Yamakov, Vesselin I.; Wise, Kristopher E.; Lowther, Sharon E.; Fay, Catharine C.; Thibeault, Sheila A.; Bryant, Robert G.

2015-01-01

Space exploration missions require sensors and devices capable of stable operation in harsh environments such as those that include high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation. However, conventional or state-of-the-art electroactive materials like lead zirconate titanate, poly(vinylidene fluoride), and carbon nanotube (CNT)-doped polyimides have limitations on use in those extreme applications. Theoretical studies have shown that boron nitride nanotubes (BNNTs) have strength-to-weight ratios comparable to those of CNTs, excellent high-temperature stability (to 800 C in air), large electroactive characteristics, and excellent neutron radiation shielding capability. In this study, we demonstrated the experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites. Upon application of an external electric field, the 2 wt % BNNT/polyimide composite was found to exhibit electroactive strain composed of a superposition of linear piezoelectric and nonlinear electrostrictive components. When the BNNTs were aligned by stretching the 2 wt % BNNT/polyimide composite, electroactive characteristics increased by about 460% compared to the nonstretched sample. An all-nanotube actuator consisting of a BNNT buckypaper layer between two single-walled carbon nanotube buck-paper electrode layers was found to have much larger electroactive properties. The additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions. utilizing the unique characteristics of BNNTs.

JPRS Report, Science & Technology, USSR: Materials Science

DTIC Science & Technology

1988-07-11

MATERIALY, No 2, Mar-Apr 88) , 19 Formation of Multilayer Polytypes Based on Diamond or Sphaleritic Boron Nitride Under High Pressures at High...in Compact Modifications of Boron Nitride (V. B, Shipilo, et al,; SVERKHTVERDYYE MATERIALY, No 2, Mar-Apr 88) 20 Change in Electrical...25CrMnNiMoTi alloy steel were first refined by heat treatment and then, covered with a heat-absorbent MnP04 coating , treated with a laser beam

Gate-dependent Pseudospin Mixing in Graphene/boron Nitride Moire Superlattices

DTIC Science & Technology

2014-08-31

LETTERS PUBLISHED ONLINE: 31 AUGUST 2014 | DOI : 10.1038/NPHYS3075 Gate-dependent pseudospin mixing in graphene/boron nitride moiré superlattices... Dirac –Weyl spinors with a two-component pseudospin1–12. The unique pseudospin structure of Dirac electrons leads to emerging phenomena such as the...massless Dirac cone2, anomalous quantum Hall eect2,3, and Klein tunnelling4,5 in graphene. The capability to manipulate electron pseudospin is highly

Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy.

PubMed

Jobst, Johannes; van der Torren, Alexander J H; Krasovskii, Eugene E; Balgley, Jesse; Dean, Cory R; Tromp, Rudolf M; van der Molen, Sense Jan

2016-11-29

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the 'chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of.

Purification of boron nitride nanotubes via polymer wrapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Jin-Hyuk; Kim, Jaewoo; WCI Quantum Beam based Radiation Research Center, Korea Atomic Energy Research Institute, 1045 Daedukdaero, Daejeon 305-353

2013-03-15

Highlights: ► Surface modification of boron nitride nanotubes using polymeric materials. ► Surface-modified BNNT was purified with a simple dilution-centrifugation step. ► Surface-modified BNNT can be directly used for polymer composite fabrication ► Degree of purification was analyzed by Raman spectroscopy. - Abstract: Boron nitride nanotubes (BNNT) synthesized by a ball milling-annealing were surface-modified using three different types of polymeric materials. Those materials were chosen depending on future applications especially in polymer nanocomposite fabrications. We found that the surface-modified BNNT can be purified with a simple dilution-centrifugation step, which would be suitable for large-scale purification. Degree of purification was monitoredmore » by means of the center peak position and FWHM of E{sub 2g} mode of BNNT in Raman spectra. As the purification of BNNT develops, the peak position was up-shifted while FWHM of the peak was narrowed.« less

Simulation of STM technique for electron transport through boron-nitride nanotubes

NASA Astrophysics Data System (ADS)

Ganji, M. D.; Mohammadi-nejad, A.

2008-06-01

We report first-principles calculations on the electrical transport properties of boron-nitrid nanotubes (BNNTs). We consider a single walled (5,0) boron-nitrid nanotube sandwiched between an Au(1 0 0) substrate and a monatomic Au scanning tunneling microscope (STM) tip. Lateral motion of the tip over the nanotube wall cause it to change from one conformation class to the others and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity these Au/BNNT/Au nanowires are shown to be a convenient switch. Experiments with a conventional STM are proposed to test these predictions. The projection of the density of states (PDOS) and the transmission coefficients T(E) of the two-probe systems at zero bias are analyzed, and it suggests that the variation of the coupling between the wire and the electrodes leads to switching behaviour.

UV absorption in metal decorated boron nitride flakes: a theoretical analysis of excited states

NASA Astrophysics Data System (ADS)

Chopra, Siddheshwar; Plasser, Felix

2017-10-01

The excited states of single metal atom (X = Co, Al and Cu) doped boron nitride flake (MBNF) B15N14H14-X and pristine boron nitride (B15N15H14) are studied by time-dependent density functional theory. The immediate effect of metal doping is a red shift of the onset of absorption from about 220 nm for pristine BNF to above 300 nm for all metal-doped variants with the biggest effect for MBNF-Co, which shows appreciable intensity even above 400 nm. These energy shifts are analysed by detailed wavefunction analysis protocols using visualisation methods, such as the natural transition orbital analysis and electron-hole correlation plots, as well as quantitative analysis of the exciton size and electron-hole populations. The analysis shows that the Co and Cu atoms provide strong contributions to the relevant states whereas the aluminium atom is only involved to a lesser extent.

Raman spectroscopy measurement of bilayer graphene's twist angle to boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Bin; Wang, Peng; Pan, Cheng

2015-07-20

When graphene is placed on hexagonal boron nitride with a twist angle, new properties develop due to the resulting moiré superlattice. Here, we report a method using Raman spectroscopy to make rapid, non-destructive measurements of the twist angle between bilayer graphene and hexagonal boron nitride. The lattice orientation is determined by using flakes with both bilayer and monolayer regions, and using the known Raman signature for the monolayer to measure the twist angle of the entire flake. The widths of the second order Raman peaks are found to vary linearly in the superlattice period and are used to determine themore » twist angle. The results are confirmed by using transport measurements to infer the superlattice period by the charge density required to reach the secondary resistance peaks. Small twist angles are also found to produce a significant modification of the first order Raman G band peak.« less

Lattice-Matched Epitaxial Graphene Grown on Boron Nitride.

PubMed

Davies, Andrew; Albar, Juan D; Summerfield, Alex; Thomas, James C; Cheng, Tin S; Korolkov, Vladimir V; Stapleton, Emily; Wrigley, James; Goodey, Nathan L; Mellor, Christopher J; Khlobystov, Andrei N; Watanabe, Kenji; Taniguchi, Takashi; Foxon, C Thomas; Eaves, Laurence; Novikov, Sergei V; Beton, Peter H

2018-01-10

Lattice-matched graphene on hexagonal boron nitride is expected to lead to the formation of a band gap but requires the formation of highly strained material and has not hitherto been realized. We demonstrate that aligned, lattice-matched graphene can be grown by molecular beam epitaxy using substrate temperatures in the range 1600-1710 °C and coexists with a topologically modified moiré pattern with regions of strained graphene which have giant moiré periods up to ∼80 nm. Raman spectra reveal narrow red-shifted peaks due to isotropic strain, while the giant moiré patterns result in complex splitting of Raman peaks due to strain variations across the moiré unit cell. The lattice-matched graphene has a lower conductance than both the Frenkel-Kontorova-type domain walls and also the topological defects where they terminate. We relate these results to theoretical models of band gap formation in graphene/boron nitride heterostructures.

Synergic nitrogen source route to inorganic fullerene-like boron nitride with vessel, hollow sphere, onion, and peanut nanostructures.

PubMed

Xu, Fen; Xie, Yi; Zhang, Xu; Zhang, Shuyuan; Liu, Xianming; Tian, Xiaobo

2004-01-26

In this paper we describe the large-scale synthesis of inorganic fullerene-like (IF-like) hexagonal boron nitride with vessel, hollow sphere, peanut, and onion structures by reacting BBr(3) with the synergic nitrogen sources NaNH(2) and NH(4)Cl at 400-450 degrees C for 6-12 h. The composition of products could be confirmed to be pure boron nitride with hexagonal structures by the XRD patterns and FT-IR, XPS, and EDXA spectra. The representative HRTEM images clearly reveal the layerlike features of the products. Here, the peanut-like structure of the IF-like BN is reported for the first time, and added to the list as one kind of new morphology of BN nanomaterials. The similarity in the structure between h-BN and graphite is responsible for the formation of IF-like BN with nanostructures of vessels, hollow spheres, peanuts, and onions.

Shock compression behavior of a mixture of cubic and hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Hu, Xiaojun; Yang, Gang; Zhao, Bin; Li, Peiyun; Yang, Jun; Leng, Chunwei; Liu, Hanyu; Huang, Haijun; Fei, Yingwei

2018-05-01

We report Hugoniot measurements on a mixture of cubic boron nitride (cBN) and hexagonal boron nitride (hBN, ˜10% in weight) to investigate the shock compression behavior of BN at Hugoniot stresses up to 110 GPa. We observed a discontinuity at ˜77 GPa along the Hugoniot and interpreted it as the manifestation of the shock-induced phase transition of hBN to cBN. The experimental stress at 77-110 GPa shows significant deviation from the hydrodynamic Hugoniot of cBN calculated using the Mie-Grüneisen model coupled with the reported 300 K-isotherms of cBN. Our investigation reveals that material strength in cBN increases with the experimental stress at least up to 110 GPa. The material strength might be preserved at higher stress if we consider the previously reported high stress data.

Synthesis of Hexagonal Boron Nitride Mono layer: Control of Nucleation and Crystal Morphology

DOE PAGES

Stehle, Yijing Y.; Meyer, III, Harry M.; Unocic, Raymond R.; ...

2015-11-10

Mono layer hexagonal boron nitride (hBN) attracts significant attention due to the potential to be used as a complementary two-dimensional dielectric in fabrication of functional 2D heterostructures. Here we investigate the growth stages of the hBN single crystals and show that hBN crystals change their shape from triangular to truncated triangular and further to hexagonal depending on copper substrate distance from the precursor. We suggest that the observed hBN crystal shape variation is affected by the ratio of boron to nitrogen active species concentrations on the copper surface inside the CVD reactor. Strong temperature dependence reveals the activation energies formore » the hBN nucleation process of similar to 5 eV and crystal growth of similar to 3.5 eV. We also show that the resulting h-BN film morphology is strongly affected by the heating method of borazane precursor and the buffer gas. Elucidation of these details facilitated synthesis of high quality large area monolayer hexagonal boron nitride by atmospheric pressure chemical vapor deposition on copper using borazane as a precursor.« less

Computational Nanomechanics of Carbon Nanotubes and Composites

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Wei, Chenyu; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)

2002-01-01

Nanomechanics of individual carbon and boron-nitride nanotubes and their application as reinforcing fibers in polymer composites has been reviewed with interplay of theoretical modeling, computer simulations and experimental observations. The emphasis in this work is on elucidating the multi-length scales of the problems involved, and of different simulation techniques that are needed to address specific characteristics of individual nanotubes and nanotube polymer-matrix interfaces. Classical molecular dynamics simulations are shown to be sufficient to describe the generic behavior such as strength and stiffness modulus but are inadequate to describe elastic limit and nature of plastic buckling at large strength. Quantum molecular dynamics simulations are shown to bring out explicit atomic nature dependent behavior of these nanoscale materials objects that are not accessible either via continuum mechanics based descriptions or through classical molecular dynamics based simulations. As examples, we discus local plastic collapse of carbon nanotubes under axial compression and anisotropic plastic buckling of boron-nitride nanotubes. Dependence of the yield strain on the strain rate is addressed through temperature dependent simulations, a transition-state-theory based model of the strain as a function of strain rate and simulation temperature is presented, and in all cases extensive comparisons are made with experimental observations. Mechanical properties of nanotube-polymer composite materials are simulated with diverse nanotube-polymer interface structures (with van der Waals interaction). The atomistic mechanisms of the interface toughening for optimal load transfer through recycling, high-thermal expansion and diffusion coefficient composite formation above glass transition temperature, and enhancement of Young's modulus on addition of nanotubes to polymer are discussed and compared with experimental observations.

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.

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.

A Survey of the Use of Ceramics in Battery and Fuel Cell Applications

DTIC Science & Technology

1977-06-01

Company is looking at step IV, spray drying, to obtain powders with these desirable properties . At the University of (41) Utah the "zeta" process ...porous carbon matrix. As with other developments in high-temperature batteries a lithium alloy (Li- Al ) is used as the anode material, while the...with Li- Al alloys , where the activity of lithium is reduced, a longer life is obtained than with pure lithium anodes. Boron nitride felt or paper

High Purity and Yield of Boron Nitride Nanotubes Using Amorphous Boron and a Nozzle-Type Reactor

PubMed Central

Kim, Jaewoo; Seo, Duckbong; Yoo, Jeseung; Jeong, Wanseop; Seo, Young-Soo; Kim, Jaeyong

2014-01-01

Enhancement of the production yield of boron nitride nanotubes (BNNTs) with high purity was achieved using an amorphous boron-based precursor and a nozzle-type reactor. Use of a mixture of amorphous boron and Fe decreases the milling time for the preparation of the precursor for BNNTs synthesis, as well as the Fe impurity contained in the B/Fe interdiffused precursor nanoparticles by using a simple purification process. We also explored a nozzle-type reactor that increased the production yield of BNNTs compared to a conventional flow-through reactor. By using a nozzle-type reactor with amorphous boron-based precursor, the weight of the BNNTs sample after annealing was increased as much as 2.5-times with much less impurities compared to the case for the flow-through reactor with the crystalline boron-based precursor. Under the same experimental conditions, the yield and quantity of BNNTs were estimated as much as ~70% and ~1.15 g/batch for the former, while they are ~54% and 0.78 g/batch for the latter. PMID:28788161

High Purity and Yield of Boron Nitride Nanotubes Using Amorphous Boron and a Nozzle-Type Reactor.

PubMed

Kim, Jaewoo; Seo, Duckbong; Yoo, Jeseung; Jeong, Wanseop; Seo, Young-Soo; Kim, Jaeyong

2014-08-11

Enhancement of the production yield of boron nitride nanotubes (BNNTs) with high purity was achieved using an amorphous boron-based precursor and a nozzle-type reactor. Use of a mixture of amorphous boron and Fe decreases the milling time for the preparation of the precursor for BNNTs synthesis, as well as the Fe impurity contained in the B/Fe interdiffused precursor nanoparticles by using a simple purification process. We also explored a nozzle-type reactor that increased the production yield of BNNTs compared to a conventional flow-through reactor. By using a nozzle-type reactor with amorphous boron-based precursor, the weight of the BNNTs sample after annealing was increased as much as 2.5-times with much less impurities compared to the case for the flow-through reactor with the crystalline boron-based precursor. Under the same experimental conditions, the yield and quantity of BNNTs were estimated as much as ~70% and ~1.15 g/batch for the former, while they are ~54% and 0.78 g/batch for the latter.

Tribo-mechanical and electrical properties of boron-containing coatings

NASA Astrophysics Data System (ADS)

Qian, Jincheng

The development of new hard protective coatings with advanced performance is very important for progress in a variety of scientific and industrial fields. Application of hard protective coatings can significantly improve the performance of parts and components, extend their service life, and save energy in many industrial applications including aerospace, automotive, manufacturing, and other industries. In addition, the multifunctionality of protective coatings is also required in many other application fields such as optics, microelectronics, biomedical, magnetic storage media, etc. Therefore, protective coatings with enhanced tribo-mechanical and corrosion properties as well as other functions are in demand. The coating characteristics can be adjusted by controlling the microstructure at different scales. For example, films with nanostructures, such as superlattice, nanocolumn, and nanocomposite systems, exhibit distinctive characteristics compared to single-phase materials. They show superior tribo-mechanical properties due to the presence of strong interfaces, and different functions can be achieved due to the multi-phase characteristics. Boron-containing materials with their excellent mechanical properties and interesting electronic characteristics are good candidates for functional hard protective coatings. For instance, cubic boron nitride (c-BN), boron carbide (B1-xCx), and titanium diboride (TiB 2) are well known for their high hardness, high thermal stability, and high chemical inertness. An interesting example is the boron carbon nitride (BCN) compound that possesses many attractive properties because its structure is similar to that of carbon (graphite and diamond) and of boron nitride (BN in hexagonal and cubic phases). The main goal of this work is to further develop the family of Boron-containing films including B1-xCx, Ti-B-C, and BCN films fabricated by magnetron sputtering, and to enhance their performance by controlling their microstructure on the nanoscale. Their tribo-mechanical, corrosion, and electrical properties are studied in relation to the composition and microstructure, aiming at enhancing their performance for multi-functional protective coating applications via microstructural design. First, B1-xCx (0 < x < 1) films with tailored tribo-mechanical properties were deposited by magnetron sputtering using one graphite and two boron targets. The hardness of the B1-xC x films was found to reach 25 GPa both for boron-rich and carbon-rich films, and the friction coefficient and wear rate can be adjusted from 0.66 to 0.13 and from 6.4x10-5 mm3/Nm to 1.3x10 -7 mm3/Nm, respectively, by changing the carbon content from 19 to 76 at.%. The hardness variation is closely related to the microstructure, and the low friction and wear rate of the B0.24C0.76 film are due to the high portion of an amorphous carbon phase. Moreover, application of the B0.81C0.19 film improves the corrosion resistance of the M2 steel substrate significantly, indicated by the decrease of the corrosion current by almost four orders of magnitude. Based on the optimization of the B1-xCx films, nanostructured Ti-B-C films with different compositions were deposited by adding titanium by simultaneously sputtering a titanium diboride target. We found that the film microstructure features TiB2 nanocrystallites embedded in an amorphous boron carbide matrix. The film hardness varies from 33 to 42 GPa with different titanium contents, which is related to the changes in microstructure, namely, the size and concentration of the TiB2 nanocrystallites. The friction coefficient and wear rate are in the ranges of 0.37-0.73 and of 3.3x10-6-5.7x10-5 mm3/Nm, respectively, which are affected by the mechanical properties and the surface chemical states of the films. By applying the Ti-B-C films, the corrosion resistance of the M2 steel substrate is significantly enhanced as documented by a reduction of the corrosion current density by two orders of magnitude. BCN films were synthesized by magnetron sputtering using a single B 4C target in an N2: Ar gas mixture. The BCN films exhibit an amorphous structure and contain a mixture of B-C, B-N, and C-N bonds. The films show p-type conductivity with an optical band gap of 1.0 eV. Subsequently, ZnO nanorods were grown on the BCN films using hydrothermal synthesis to form BCN/ZnO nanorods p-n heterojunctions. The performance of the junctions is evaluated by the I-V characterization, which shows a rectification behavior with a rectification ratio of 1500 at the bias voltages of +/-5 V.

Electronic transport in heterostructures of chemical vapor deposited graphene and hexagonal boron nitride.

PubMed

Qi, Zhengqing John; Hong, Sung Ju; Rodríguez-Manzo, Julio A; Kybert, Nicholas J; Gudibande, Rajatesh; Drndić, Marija; Park, Yung Woo; Johnson, A T Charlie

2015-03-25

CVD graphene devices on stacked CVD hexagonal boron nitride (hBN) are demonstrated using a novel low-contamination transfer method, and their electrical performance is systematically compared to devices on SiO(2). An order of magnitude improvement in mobility, sheet resistivity, current density, and sustained power is reported when the oxide substrate is covered with five-layer CVD hBN. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Edge-Hydroxylated Boron Nitride Nanosheets as an Effective Additive to Improve the Thermal Response of Hydrogels.

PubMed

Xiao, Feng; Naficy, Sina; Casillas, Gilberto; Khan, Majharul H; Katkus, Tomas; Jiang, Lei; Liu, Huakun; Li, Huijun; Huang, Zhenguo

2015-11-25

Upon flowing hot steam over hexagonal boron nitride (h-BN) bulk powder, efficient exfoliation and hydroxylation of BN occur simultaneously. Through effective hydrogen bonding with water and N-isopropylacrylamide, edge-hydroxylated BN nanosheets dramatically improve the dimensional change and dye release of this temperature-sensitive hydrogel and thereby enhance its efficacy in bionic, soft robotic, and drug-delivery applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nucleobases-decorated boron nitride nanoribbons for electrochemical biosensing: a dispersion-corrected DFT study.

PubMed

Dabhi, Shweta D; Roondhe, Basant; Jha, Prafulla K

2018-03-28

Understanding the interactions between biomolecules and boron nitride nanostructures is key for their use in nanobiotechnology and medical engineering. In this study, we investigated the adsorption of nucleobases adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U) over armchair and zigzag boron nitride nanoribbons (BNNR) using density functional theory to define the applicability of BNNR for the sensing of nucleobases and DNA sequencing. To appropriately account for dispersion, the van der Waals forces (DFT-D2)-type method developed by Grimme was also included in the calculations. The calculated adsorption energy suggests the following order of adsorption for A-BNNR and Z-BNNR with the nucleobases: G > T > A > U > C and G > C > A > T > U, respectively. The origin of the binding of the different nucleobases with BNNR was analysed and π-π stacking was found to be responsible. In addition, the electronic properties, density of states and work function significantly vary after adsorption. These analyses indicate different binding natures for different nucleobases and BNNRs. Thus, this study demonstrates that BNNR can be applied as biosensors for the detection of nucleobases, which are constituents of DNA and RNA. Furthermore, analysis of electronic properties and adsorption energies will play a key role in targeted drug delivery, enzyme activities and genome sequencing. Our results indicate that BNNRs have better adsorption capacity than graphene and boron nitride nanotubes.

The influence of metal Mg on micro-morphology and crystallinity of spherical hexagonal boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ning, E-mail: zhangning5832@163.com; Liu, Huan; Kan, Hongmin

2015-08-15

Highlights: • The action mechanism of Mg to the synthesis of spherical BN was explored. • The influence of Mg content on the crystallinity of h-BN powders was studied. • Even if not added any template, the spherical h-BN could be prepared. - Abstract: This search used the boric acid and borax as a source of boron, urea as a nitrogen source, Mg as metal catalyst, and thus prepared different micro-morphology and crystallinity hexagonal boron nitride powders under a flowing ammonia atmosphere at a nitriding temperature of 750 °C. The effect of Mg content on the crystallinity and micro-morphology ofmore » hexagonal boron nitride powders was studied, and the Mg action mechanism was explored. Without the added surfactant, the graphitization index (GI) was 6.87, and the diameter of the spherical h-BN was bigger. When the added Mg were 0.1 g, 0.3 g, 0.5 g and 0.7 g, the (GI) decreased to 6.04, 5.67, 4.62 and 4.84, respectively. When the Mg content was higher (0.9 g), GI value increased rapidly, and the crystallinity became bad. When the Mg content was 0.5 g, the dispersion of h-BN powders was at its optimum and refinement apparently, and the crystallinity at its highest.« less

Defect mediated van der Waals epitaxy of hexagonal boron nitride on graphene

NASA Astrophysics Data System (ADS)

Heilmann, M.; Bashouti, M.; Riechert, H.; Lopes, J. M. J.

2018-04-01

Van der Waals heterostructures comprising of hexagonal boron nitride and graphene are promising building blocks for novel two-dimensional devices such as atomically thin transistors or capacitors. However, demonstrators of those devices have been so far mostly fabricated by mechanical assembly, a non-scalable and time-consuming method, where transfer processes can contaminate the surfaces. Here, we investigate a direct growth process for the fabrication of insulating hexagonal boron nitride on high quality epitaxial graphene using plasma assisted molecular beam epitaxy. Samples were grown at varying temperatures and times and studied using atomic force microscopy, revealing a growth process limited by desorption at high temperatures. Nucleation was mostly commencing from morphological defects in epitaxial graphene, such as step edges or wrinkles. Raman spectroscopy combined with x-ray photoelectron measurements confirm the formation of hexagonal boron nitride and prove the resilience of graphene against the nitrogen plasma used during the growth process. The electrical properties and defects in the heterostructures were studied with high lateral resolution by tunneling current and Kelvin probe force measurements. This correlated approach revealed a nucleation apart from morphological defects in epitaxial graphene, which is mediated by point defects. The presented results help understanding the nucleation and growth behavior during van der Waals epitaxy of 2D materials, and point out a route for a scalable production of van der Waals heterostructures.

Effect of Adventitious Carbon on the Environmental Degradation of SiC/BN/SiC Composites

NASA Technical Reports Server (NTRS)

Ogbuji, L. U. J. T.; Yun, H. M.; DiCarlo, J.

2002-01-01

Pesting remains a major obstacle to the application of SiC/SiC composites in engine service and selective degradation of the boron nitride interphase at intermediate temperatures is of primary concern. However, significant progress has been made on interphase improvement recently and we now know more about the phenomenon and ways to suppress it. By screening SiC/BN/SiC materials through characterization of strength and microstructures after exposure in a burner rig, some factors that control pesting in these composites have been determined. A key precaution is careful control of elemental carbon presence in the interphase region.

A Porous Ceramic Interphase for SiC/Si(sub 3)N(sub 4) Composites

NASA Technical Reports Server (NTRS)

Ogbuji, Linus U. J. T.

1995-01-01

A suitable interphase material for non-oxide ceramic-matrix composites must be resistant to oxidation. This means it must exhibit a slow rate of oxidation, and its oxidation product must be such as to ensure that the system survives oxidation when it does occur. Because the current benchmark interphase materials, carbon and boron nitride, lack these qualities, a porous fiber coating was developed to satisfy both the mechanical and oxidative requirements of an interphase for the SiC/SiC and SiC/Si2N4 composites that are of interest to NASA. This report presents the interphase microstructure achieved and the resulting characteristics of fiber push-out from a matrix of reaction-bonded silicon nitride (RBSN), both as-fabricated and after substantial annealing and oxidation treatments.

Synthesis and Investigation of Millimeter-Scale Vertically Aligned Boron Nitride Nanotube Arrays

NASA Astrophysics Data System (ADS)

Tay, Roland; Li, Hongling; Tsang, Siu Hon; Jing, Lin; Tan, Dunlin; Teo, Edwin Hang Tong

Boron nitride nanotubes (BNNTs) have shown potential in a wide range of applications due to their superior properties such as exceptionally high mechanical strength, excellent chemical and thermal stabilities. However, previously reported methods to date only produced BNNTs with limited length/density and insufficient yield at high temperatures. Here we present a facile and effective two-step synthesis route involving template-assisted chemical vapor deposition at a relatively low temperature of 900 degree C and subsequent annealing process to fabricate vertically aligned (VA) BN coated carbon nanotube (VA-BN/CNT) and VA-BNNT arrays. By using this method, we achieve the longest VA-BN/CNTs and VA-BNNTs to date with lengths of over millimeters (exceeding two orders of magnitude longer than the previously reported length of VA-BNNTs). In addition, the morphology, chemical composition and microstructure of the resulting products, as well as the mechanism of coating process are systematically investigated. This versatile BN coating technique and the synthesis of millimeter-scale BN/CNT and BNNT arrays pave a way for new applications especially where the aligned geometry of the NTs is essential such as for field-emission, interconnects and thermal management.

Folate-conjugated boron nitride nanospheres for targeted delivery of anticancer drugs.

PubMed

Feng, Shini; Zhang, Huijie; Yan, Ting; Huang, Dandi; Zhi, Chunyi; Nakanishi, Hideki; Gao, Xiao-Dong

With its unique physical and chemical properties and structural similarity to carbon, boron nitride (BN) has attracted considerable attention and found many applications. Biomedical applications of BN have recently started to emerge, raising great hopes in drug and gene delivery. Here, we developed a targeted anticancer drug delivery system based on folate-conjugated BN nanospheres (BNNS) with receptor-mediated targeting. Folic acid (FA) was successfully grafted onto BNNS via esterification reaction. In vitro cytotoxicity assay showed that BNNS-FA complexes were non-toxic to HeLa cells up to a concentration of 100 μg/mL. Then, doxorubicin hydrochloride (DOX), a commonly used anticancer drug, was loaded onto BNNS-FA complexes. BNNS-FA/DOX complexes were stable at pH 7.4 but effectively released DOX at pH 5.0, which exhibited a pH sensitive and sustained release pattern. BNNS-FA/DOX complexes could be recognized and specifically internalized by HeLa cells via FA receptor-mediated endocytosis. BNNS-FA/DOX complexes exhibited greater cytotoxicity to HeLa cells than free DOX and BNNS/DOX complexes due to the increased cellular uptake of DOX mediated by the FA receptor. Therefore, BNNS-FA complexes had strong potential for targeted cancer therapy.

Nanoporous Boron Nitride as Exceptionally Thermally Stable Adsorbent: Role in Efficient Separation of Light Hydrocarbons.

PubMed

Saha, Dipendu; Orkoulas, Gerassimos; Yohannan, Samuel; Ho, Hoi Chun; Cakmak, Ercan; Chen, Jihua; Ozcan, Soydan

2017-04-26

In this work, nanoporous boron nitride sample was synthesized with a Brunauer-Emmett-Teller (BET) surface area of 1360 m 2 /g and particle size 5-7 μm. The boron nitride was characterized with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electron microscopy (TEM and SEM). Thermogravimetric analysis (TGA) under nitrogen and air and subsequent analysis with XPS and XRD suggested that its structure is stable in air up to 800 °C and in nitrogen up to 1050 °C, which is higher than most of the common adsorbents reported so far. Nitrogen and hydrocarbon adsorption at 298 K and pressure up to 1 bar suggested that all hydrocarbon adsorption amounts were higher than that of nitrogen and the adsorbed amount of hydrocarbon increases with an increase in its molecular weight. The kinetics of adsorption data suggested that adsorption becomes slower with the increase in molecular weight of hydrocarbons. The equilibrium data suggested that that boron nitride is selective to paraffins in a paraffin-olefin mixture and hence may act as an "olefin generator". The ideal adsorbed solution theory (IAST)-based selectivity for CH 4 /N 2 , C 2 H 6 /CH 4 , and C 3 H 8 /C 3 H 6 was very high and probably higher than the majority of adsorbents reported in the literature. IAST-based calculations were also employed to simulate the binary mixture adsorption data for the gas pairs of CH 4 /N 2 , C 2 H 6 /CH 4 , C 2 H 6 /C 2 H 4 , and C 3 H 8 /C 3 H 6 . Finally, a simple mathematical model was employed to simulate the breakthrough behavior of the above-mentioned four gas pairs in a dynamic column experiment. The overall results suggest that nanoporous boron nitride can be used as a potential adsorbent for light hydrocarbon separation.

Measurement of the elastic modulus of a multi-wall boron nitride nanotube

NASA Astrophysics Data System (ADS)

Chopra, Nasreen G.; Zettl, A.

1998-02-01

We have experimentally determined the elastic properties of an individual multi-wall boron nitride (BN) nanotube. From the thermal vibration amplitude of a cantilevered BN nanotube observed in a transmission electron microscope, we find the axial Young's modulus to be 1.22 ± 0.24 TPa, a value consistent with theoretical estimates. The observed Young's modulus exceeds that of all other known insulating fibers. Our elasticity results confirm that BN nanotubes are highly crystalline with very few defects.

Laser sintered thin layer graphene and cubic boron nitride reinforced nickel matrix nanocomposites

NASA Astrophysics Data System (ADS)

Hu, Zengrong; Tong, Guoquan

2015-10-01

Laser sintered thin layer graphene (Gr)-cubic boron nitride (CBN)-Ni nanocomposites were fabricated on AISI 4140 plate substrate. The composites fabricating process, composites microstructure and mechanical properties were studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were employed to study the micro structures and composition of the composites. XRD and Raman tests proved that graphene and CBN were dispersed in the nanocomposites. Nanoindentation test results indicate the significant improvements were achieved in the composites mechanical properties.

Method for exfoliation of hexagonal boron nitride

NASA Technical Reports Server (NTRS)

Lin, Yi (Inventor); Connell, John W. (Inventor)

2012-01-01

A new method is disclosed for the exfoliation of hexagonal boron nitride into mono- and few-layered nanosheets (or nanoplatelets, nanomesh, nanoribbons). The method does not necessarily require high temperature or vacuum, but uses commercially available h-BN powders (or those derived from these materials, bulk crystals) and only requires wet chemical processing. The method is facile, cost efficient, and scalable. The resultant exfoliated h-BN is dispersible in an organic solvent or water thus amenable for solution processing for unique microelectronic or composite applications.

The Physics and Chemistry of carbides, Nitrides and Borides. Volume 185

DTIC Science & Technology

1990-01-01

and C-B-C chains [15,17]. Clearly, the use of boron-rich solids as electronic materials will place new demands on the quality of materials. In this...first heated in a pyrolytic boron nitride (PBN) crucible ( Union Carbide Corp.) under high vacuum (< 50 mTorr) to 1900°C. This removed surface...contamination of the sample. The powders were loaded into a graphite die with a high-purity BN die liner ( Union Carbide Grade HBC) with inner diameter of 3/8

Wettability of Pyrolytic Boron Nitride by Aluminum

NASA Technical Reports Server (NTRS)

Chiaramonte, Francis P.; Rosenthal, Bruce N.

1991-01-01

The wetting of pyrolytic boron nitride by molten 99.9999 percent pure aluminum was investigated by using the sessile drop method in a vacuum operating at approximately 660 micro-Pa at temperatures ranging from 700 to 1000 C. The equilibrium contact angle decreased with an increase in temperature. For temperatures at 900 C or less, the equilibrium contact angle was greater than 90 deg. At 1000 C a nonwetting-to-wetting transition occurred and the contact angle stabilized at 49 deg.

Anomalous Insulator-Metal Transition in Boron Nitride-Graphene Hybrid Atomic Layers

DTIC Science & Technology

2012-08-13

REPORT Anomalous insulator-metal transition in boron nitride-graphene hybrid atomic layers 14 . ABSTRACT 16. SECURITY CLASSIFICATION OF: The study of...from the DFT calculation. The calculated transmission through a N terminated zigzag edged h-BN nanodomain embedded in graphene is shown in Fig. 14 , with...Energy ε − ε F (eV) 0 0.5 1 1.5 2 Tr an sm is si on FIG. 14 . (Color online) Transmission through a N terminated zigzag edged h-BN nanodomain embedded in

Surface Design and Engineering Toward Wear-Resistant, Self-Lubricant Diamond Films and Coatings. Chapter 10

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1999-01-01

This chapter describes three studies on the surface design, surface engineering, and tribology of chemical-vapor-deposited (CVD) diamond films and coatings toward wear-resistant, self-lubricating diamond films and coatings. Friction mechanisms and solid lubrication mechanisms of CVD diamond are stated. Effects of an amorphous hydrogenated carbon on CVD diamond, an amorphous, nondiamond carbon surface layer formed on CVD diamond by carbon and nitrogen ion implantation, and a materials combination of cubic boron nitride and CVD diamond on the adhesion, friction, and wear behaviors of CVD diamond in ultrahigh vacuum are described. How surface modification and the selected materials couple improved the tribological functionality of coatings, giving low coefficient of friction and good wear resistance, is explained.

Acute in vitro and in vivo toxicity of a commercial grade boron nitride nanotube mixture.

PubMed

Kodali, Vamsi K; Roberts, Jenny R; Shoeb, Mohammad; Wolfarth, Michael G; Bishop, Lindsey; Eye, Tracy; Barger, Mark; Roach, Katherine A; Friend, Sherri; Schwegler-Berry, Diane; Chen, Bean T; Stefaniak, Aleksandr; Jordan, Kevin C; Whitney, Roy R; Porter, Dale W; Erdely, Aaron D

2017-10-01

Boron nitride nanotubes (BNNTs) are an emerging engineered nanomaterial attracting significant attention due to superior electrical, chemical and thermal properties. Currently, the toxicity profile of this material is largely unknown. Commercial grade BNNTs are composed of a mixture (BNNT-M) of ∼50-60% BNNTs, and ∼40-50% impurities of boron and hexagonal boron nitride. We performed acute in vitro and in vivo studies with commercial grade BNNT-M, dispersed by sonication in vehicle, in comparison to the extensively studied multiwalled carbon nanotube-7 (MWCNT-7). THP-1 wild-type and NLRP3-deficient human monocytic cells were exposed to 0-100 µg/ml and C57BL/6 J male mice were treated with 40 µg of BNNT-M for in vitro and in vivo studies, respectively. In vitro, BNNT-M induced a dose-dependent increase in cytotoxicity and oxidative stress. This was confirmed in vivo following acute exposure increase in bronchoalveolar lavage levels of lactate dehydrogenase, pulmonary polymorphonuclear cell influx, loss in mitochondrial membrane potential and augmented levels of 4-hydroxynonenal. Uptake of this material caused lysosomal destabilization, pyroptosis and inflammasome activation, corroborated by an increase in cathepsin B, caspase 1, increased protein levels of IL-1β and IL-18 both in vitro and in vivo. Attenuation of these effects in NLRP3-deficient THP-1 cells confirmed NLRP3-dependent inflammasome activation by BNNT-M. BNNT-M induced a similar profile of inflammatory pulmonary protein production when compared to MWCNT-7. Functionally, pretreatment with BNNT-M caused suppression in bacterial uptake by THP-1 cells, an effect that was mirrored in challenged alveolar macrophages collected from exposed mice and attenuated with NLRP3 deficiency. Analysis of cytokines secreted by LPS-challenged alveolar macrophages collected after in vivo exposure to dispersions of BNNT-M showed a differential macrophage response. The observed results demonstrated acute inflammation and toxicity in vitro and in vivo following exposure to sonicated BNNT-M was in part due to NLRP3 inflammasome activation.

Acetylene chain reaction on hydrogenated boron nitride monolayers: a density functional theory study.

PubMed

Ponce-Pérez, R; Cocoletzi, Gregorio H; Takeuchi, Noboru

2017-11-28

Spin-polarized first-principles total-energy calculations have been performed to investigate the possible chain reaction of acetylene molecules mediated by hydrogen abstraction on hydrogenated hexagonal boron nitride monolayers. Calculations have been done within the periodic density functional theory (DFT), employing the PBE exchange correlation potential, with van der Waals corrections (vdW-DF). Reactions at two different sites have been considered: hydrogen vacancies on top of boron and on top of nitrogen atoms. As previously calculated, at the intermediate state of the reaction, when the acetylene molecule is attached to the surface, the adsorption energy is of the order of -0.82 eV and -0.20 eV (measured with respect to the energy of the non interacting molecule-substrate system) for adsorption on top of boron and nitrogen atoms, respectively. After the hydrogen abstraction takes place, the system gains additional energy, resulting in adsorption energies of -1.52 eV and -1.30 eV, respectively. These results suggest that the chain reaction is energetically favorable. The calculated minimum energy path (MEP) for hydrogen abstraction shows very small energy barriers of the order of 5 meV and 22 meV for the reaction on top of boron and nitrogen atoms, respectively. Finally, the density of states (DOS) evolution study helps to understand the chain reaction mechanism. Graphical abstract Acetylene chain reaction on hydrogenated boron nitride monolayers.

Emerging Carbon and Post-Carbon Nanomaterial Inks for Printed Electronics.

PubMed

Secor, Ethan B; Hersam, Mark C

2015-02-19

Carbon and post-carbon nanomaterials present desirable electrical, optical, chemical, and mechanical attributes for printed electronics, offering low-cost, large-area functionality on flexible substrates. In this Perspective, recent developments in carbon nanomaterial inks are highlighted. Monodisperse semiconducting single-walled carbon nanotubes compatible with inkjet and aerosol jet printing are ideal channels for thin-film transistors, while inkjet, gravure, and screen-printable graphene-based inks are better-suited for electrodes and interconnects. Despite the high performance achieved in prototype devices, additional effort is required to address materials integration issues encountered in more complex systems. In this regard, post-carbon nanomaterial inks (e.g., electrically insulating boron nitride and optically active transition-metal dichalcogenides) present promising opportunities. Finally, emerging work to extend these nanomaterial inks to three-dimensional printing provides a path toward nonplanar devices. Overall, the superlative properties of these materials, coupled with versatile assembly by printing techniques, offer a powerful platform for next-generation printed electronics.

Metal-free spin and spin-gapless semiconducting heterobilayers: monolayer boron carbonitrides on hexagonal boron nitride.

PubMed

Pan, Hongzhe; Zhang, Hongyu; Sun, Yuanyuan; Ding, Yingchun; Chen, Jie; Du, Youwei; Tang, Nujiang

2017-06-07

The interfaces between monolayer boron carbonitrides and hexagonal boron nitride (h-BN) play an important role in their practical applications. Herein, we respectively investigate the structural and electronic properties of two metal-free heterobilayers constructed by vertically stacking two-dimensional (2D) spintronic materials (B 4 CN 3 and B 3 CN 4 ) on a h-BN monolayer from the viewpoints of lattice match and lattice mismatch models using density functional calculations. It is found that both B 4 CN 3 and B 3 CN 4 monolayers can be stably adsorbed on the h-BN monolayer due to the van der Waals interactions. Intriguingly, we demonstrate that the bipolar magnetic semiconductor (BMS) behavior of the B 4 CN 3 layer and the spin gapless semiconductor (SGS) property of the B 3 CN 4 layer can be well preserved in the B 4 CN 3 /BN and B 3 CN 4 /BN heterobilayers, respectively. The magnetic moments and spintronic properties of the two systems originate mainly from the 2p z electrons of the carbon atoms in the B 4 CN 3 and B 3 CN 4 layers. Furthermore, the BMS behavior of the B 4 CN 3 /BN bilayer is very robust while the electronic property of the B 3 CN 4 /BN bilayer is sensitive to interlayer couplings. These theoretical results are helpful both in understanding the interlayer coupling between B 4 CN 3 or B 3 CN 4 and h-BN monolayers and in providing a possibility of fabricating 2D composite B 4 CN 3 /BN and B 3 CN 4 /BN metal-free spintronic materials theoretically.

Dynamic consolidation of cubic boron nitride and its admixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, H.; Ahrens, T.J.

1988-09-01

Cubic boron nitride (C-BN) powders admixed with graphite-structured boron nitride powder (g-BN), silicon carbide whisker (SCW), or silicon nitride whisker (SNW) were shock compacted to pressures up to 22 GPa. Unlike previous work with diamond and graphite (D. K. Potter and T. J. Ahrens, J. Appl. Phys. 63, 910 (1987)) it was found that the addition of g-BN inhibited dynamic consolidation. Good consolidation was achieved with a 4--8 ..mu..m particle size C-BN powder admixed with 15 wt.% SNW or 20 wt.% SCW. Whereas a 37--44 ..mu..m particle size C-BN mixture was only poorly consolidated. Scanning electron microscopy (SEM) analysis demonstratemore » that SCW and SNW in the mixtures were highly deformed and indicated melt textures. A skin heating model was used to describe the physics of consolidation. Model calculations are consistent with SEM analysis images that indicate plastic deformation of SCW and SNW. Micro-Vickers hardness values as high as 50 GPa were obtained for consolidated C-BN and SNW mixtures. This compares to 21 GPa for single-crystal Al/sub 2/O/sub 3/ and 120 GPa for diamond.« less

Radio Frequency Plasma Synthesis of Boron Nitride Nanotubes (BNNTs) for Structural Applications. Part II

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Alexa, Joel A.; Jensen, Brian J.

2016-01-01

Boron nitride nanotubes (BNNTs) are more thermally and chemically compatible with metal- and ceramic-matrix composites than carbon nanotubes (CNTs). The lack of an abundant supply of defect-free, high-aspect-ratio BNNTs has hindered development as reinforcing agents in structural materials. Recent activities at the National Research Council - Canada (NRC-C) and the University of California - Berkeley (UC-B) have resulted in bulk synthesis of few-walled, small diameter BNNTs. Both processes employ induction plasma technology to create boron vapor and highly reactive nitrogen species at temperatures in excess of 8000 K. Subsequent recombination under controlled cooling conditions results in the formation of BNNTs at a rate of 20 g/hr and 35 g/hr, respectively. The end product tends to consist of tangled masses of fibril-, sheet-, and cotton candy-like materials, which accumulate within the processing equipment. The radio frequency plasma spray (RFPS) facility at NASA Langley (LaRC), developed for metallic materials deposition, has been re-tooled for in-situ synthesis of BNNTs. The NRC-C and UC-B facilities comprise a 60 kW RF torch, a reactor with a stove pipe geometry, and a filtration system. In contrast, the LaRC facility has a 100 kW torch mounted atop an expansive reaction chamber coupled with a cyclone separator. The intent is to take advantage of both the extra power and the equipment configuration to simultaneously produce and gather BNNTs in a macroscopic form amenable to structural material applications.

Defect charge states in Si doped hexagonal boron-nitride monolayer

NASA Astrophysics Data System (ADS)

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

2016-02-01

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

Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy

PubMed Central

Jobst, Johannes; van der Torren, Alexander J. H.; Krasovskii, Eugene E.; Balgley, Jesse; Dean, Cory R.; Tromp, Rudolf M.; van der Molen, Sense Jan

2016-01-01

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the ‘chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of. PMID:27897180

Taming interfacial electronic properties of platinum nanoparticles on vacancy-abundant boron nitride nanosheets for enhanced catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Wenshuai; Wu, Zili; Foo, Guo Shiou

Taming interfacial electronic effects on Pt nanoparticles modulated by their concomitants has emerged as an intriguing approach to optimize Pt catalytic performance. Here, we report Pt nanoparticles assembled on vacancy-abundant hexagonal boron nitride nanosheets and their use as a model catalyst to embrace an interfacial electronic effect on Pt induced by the nanosheets with N-vacancies and B-vacancies for superior CO oxidation catalysis. Experimental results indicate that strong interaction exists between Pt and the vacancies. Bader charge analysis shows that with Pt on B-vacancies, the nanosheets serve as a Lewis acid to accept electrons from Pt, and on the contrary, whenmore » Pt sits on N-vacancies, the nanosheets act as a Lewis base for donating electrons to Pt. The overall-electronic effect demonstrates an electron-rich feature of Pt after assembling on hexagonal boron nitride nanosheets. Such an interfacial electronic effect makes Pt favour the adsorption of O 2, alleviating CO poisoning and promoting the catalysis.« less

Taming interfacial electronic properties of platinum nanoparticles on vacancy-abundant boron nitride nanosheets for enhanced catalysis

DOE PAGES

Zhu, Wenshuai; Wu, Zili; Foo, Guo Shiou; ...

2017-06-09

Taming interfacial electronic effects on Pt nanoparticles modulated by their concomitants has emerged as an intriguing approach to optimize Pt catalytic performance. Here, we report Pt nanoparticles assembled on vacancy-abundant hexagonal boron nitride nanosheets and their use as a model catalyst to embrace an interfacial electronic effect on Pt induced by the nanosheets with N-vacancies and B-vacancies for superior CO oxidation catalysis. Experimental results indicate that strong interaction exists between Pt and the vacancies. Bader charge analysis shows that with Pt on B-vacancies, the nanosheets serve as a Lewis acid to accept electrons from Pt, and on the contrary, whenmore » Pt sits on N-vacancies, the nanosheets act as a Lewis base for donating electrons to Pt. The overall-electronic effect demonstrates an electron-rich feature of Pt after assembling on hexagonal boron nitride nanosheets. Such an interfacial electronic effect makes Pt favour the adsorption of O 2, alleviating CO poisoning and promoting the catalysis.« less

Hole polarons and p -type doping in boron nitride polymorphs

NASA Astrophysics Data System (ADS)

Weston, L.; Wickramaratne, D.; Van de Walle, C. G.

2017-09-01

Boron nitride polymorphs hold great promise for integration into electronic and optoelectronic devices requiring ultrawide band gaps. We use first-principles calculations to examine the prospects for p -type doping of hexagonal (h -BN ), wurtzite (w z -BN ), and cubic (c -BN ) boron nitride. Group-IV elements (C, Si) substituting on the N site result in a deep acceptor, as the atomic levels of the impurity species lie above the BN valence-band maximum. On the other hand, group-II elements (Be, Mg) substituting on the B site do not give impurity states in the band gap; however, these dopants lead to the formation of small hole polarons. The tendency for polaron formation is far more pronounced in h -BN compared to w z -BN or c -BN . Despite forming small hole polarons, Be acceptors enable p -type doping, with ionization energies of 0.31 eV for w z -BN and 0.24 eV for c -BN ; these values are comparable to the Mg ionization energy in GaN.

Impact of tensile strain on the thermal transport of zigzag hexagonal boron nitride nanoribbon: An equilibrium molecular dynamics study

NASA Astrophysics Data System (ADS)

Navid, Ishtiaque Ahmed; Intisar Khan, Asir; Subrina, Samia

2018-02-01

The thermal conductivity of single layer strained hexagonal boron nitride nanoribbon (h-BNNR) has been computed using the Green—Kubo formulation of Equilibrium Molecular Dynamics (EMD) simulation. We have investigated the impact of strain on thermal transport of h-BNNR by varying the applied tensile strain from 1% upto 5% through uniaxial loading. The thermal conductivity of h-BNNR decreases monotonically with the increase of uniaxial tensile strain keeping the sample size and temperature constant. The thermal conductivity can be reduced upto 86% for an applied uniaxial tensile strain of 5%. The impact of temperature and width variation on the thermal conductivity of h-BNNR has also been studied under different uniaxial tensile strain conditions. With the increase in temperature, the thermal conductivity of strained h-BNNR exhibits a decaying characteristics whereas it shows an opposite pattern with the increasing width. Such study would provide a good insight on the strain tunable thermal transport for the potential device application of boron nitride nanostructures.

Corrosion resistance of inconel 690 to borax, boric acid, and boron nitride at 1100{degrees}C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imrich, K.J.

1996-12-12

Significant general and localized corrosion was observed on Inconel 690 coupons following exposure to borax, boric acid and boron nitride at 1100{degrees}C. Severe localized attack at and below the melt line was observed on coupons exposed to borax. An intergranular attack at and below the melt line was observed on coupons exposed to borax. An intergranular attack (IGA) of the Inconel 690 was also observed. Severe internal void formation and IGA (30 mils penetration after 3 days) was observed in the coupon exposed to boric acid. Both borax and boric acid remove the protective chromium oxide; however, this layer canmore » be reestablished by heating the Inconel 690 to 975 {degrees}C in air for several hours. Inconel 690 in direct contact with boron nitride resulted in the formation of a thick chromium borate layer, a general corrosion rate of 50 to 90 mils per year, and internal void formation of 1 mil per day.« less

Multifunctional cyanate ester nanocomposites reinforced by hexagonal boron nitride after noncovalent biomimetic functionalization.

PubMed

Wu, Hongchao; Kessler, Michael R

2015-03-18

Boron nitride (BN) reinforced polymer nanocomposites have attracted a growing research interest in the microelectronic industry for their uniquely thermal conductive but electrical insulating properties. To overcome the challenges in surface functionalization, in this study, hexagonal boron nitride (h-BN) nanoparticles were noncovalently modified with polydopamine in a solvent-free aqueous condition. The strong π-π interaction between the hexagonal structural BN and aromatic dopamine molecules facilitated 15 wt % polydopamine encapsulating the nanoparticles. High-performance bisphenol E cyanate ester (BECy) was incorporated by homogeneously dispersed h-BN at different loadings and functionalities to investigate their effects on thermo-mechanical, dynamic-mechanical, and dielectric properties, as well as thermal conductivity. Different theoretical and empirical models were successfully applied to predict thermal and dielectric properties of h-BN/BECy nanocomposites. Overall, the prepared h-BN/BECy nanocomposites exhibited outstanding performance in dimensional stability, dynamic-mechanical properties, and thermal conductivity, together with the controllable dielectric property and preserved thermal stability for high-temperature applications.

Chemisorption of Hydroxide on 2D Materials From DFT Calculations: Graphene Versus Hexagonal Boron Nitride

PubMed Central

Grosjean, Benoit; Pean, Clarisse; Siria, Alessandro; Bocquet, Lyderic; Vuilleumier, Rodolphe; Bocquet, Marie-Laure

2017-01-01

Recent nanofluidic measurements revealed strongly different surface charge measurements for boron-nitride and graphitic nanotubes when in contact with saline and alkaline water. 1,2 These observations contrast with the similar reactivity of a graphene layer and its boron nitride counterpart, using Density Functional Theory (DFT) framework, for intact and dissociative adsorption of gaseous water molecules. Here, we investigate, by DFT in implicit water, single and multiple adsorption of anionic hydroxide on single layers. A differential adsorption strength is found in vacuum for the first ionic adsorption on the two materials – chemisorbed on BN while physisorbed on graphene. The effect of implicit solvation reduces all adsorption values resulting in a favorable (non-favorable) adsorption on BN (graphene). We also calculate a pKa ≃ 6 for BN in water, in good agreement with experiments. Comparatively, the unfavorable results for graphene in water echoes the weaker surface charge measurements, but points to an alternative scenario. PMID:27809540

Enhancement of thermal conductive pathway of boron nitride coated polymethylsilsesquioxane composite.

PubMed

Kim, Gyungbok; Ryu, Seung Han; Lee, Jun-Tae; Seong, Ki-Hun; Lee, Jae Eun; Yoon, Phil-Joong; Kim, Bum-Sung; Hussain, Manwar; Choa, Yong-Ho

2013-11-01

We report here in the fabrication of enhanced thermal conductive pathway nanocomposites of boron nitride (BN)-coated polymethylsilsesquioxane (PMSQ) composite beads using isopropyl alcohol (IPA) as a mixing medium. Exfoliated and size-reduced boron nitride particles were successfully coated on the PMSQ beads and explained by surface charge differences. A homogeneous dispersion and coating of BN on the PMSQ beads using IPA medium was confirmed by SEM. Each condition of the composite powder was carried into the stainless still mould and then hot pressed in an electrically heated hot press machine. Three-dimensional percolation networks and conductive pathways created by exfoliated BN were precisely formed in the nanocomposites. The thermal conductivity of nanocomposites was measured by multiplying specific gravity, specific heat, and thermal diffusivity, based upon the laser flash method. Densification of the composite resulted in better thermal properties. For an epoxy reinforced composite with 30 vol% BN and PMSQ, a thermal conductivity of nine times higher than that of pristine PMSQ was observed.

Thermal transport in boron nitride nanotorus—towards a nanoscopic thermal shield

NASA Astrophysics Data System (ADS)

Loh, G. C.; Baillargeat, D.

2013-11-01

Nanotori, or nanorings, are topological variants of nanotubes and are conceived to have different properties from their tubular form. In this study, the toroidal arrangement of boron nitride is introduced. Using classical molecular dynamics simulations, the thermal behaviour (thermal conductivity and thermal stability) of the boron nitride nanotorus and its relationship with the structural characteristics are investigated. Its circumferential thermal rectification strength displays a linear dependence on the bending coefficient of the nanostructure. Surface kinks are relatively inconsequential on its circumferential mode of conduction, as compared to its axial sense. The circumferential conductivity in the diffusive regime is calculated to be approximately 10 W/m K, while the axial conductivity is more than tenfold of this value. All nanotori with different toroidal characters show excellent thermal stability at extremely high temperatures approaching 3400 K. With consideration to its favourable properties, a thermal shield made up of a parallel row of nanotori is proposed as a nanoscale thermal insulation device.

Detection of boron nitride radicals by emission spectroscopy in a laser-induced plasma

NASA Astrophysics Data System (ADS)

Dutouquet, C.; Acquaviva, S.; Hermann, J.

2001-06-01

Several vibrational bands of boron nitride radicals have been observed in a plasma produced by pulsed-laser ablation of a boron nitride target in low-pressure nitrogen or argon atmospheres. Using time- and space-resolved emission spectroscopic measurements with a high dynamic range, the most abundant isotopic species B 11N have been detected. The emission bands in the spectral range from 340 to 380 nm belong to the Δυ =-1, 0, +1 sequences of the triplet system (transition A 3Π-X 3Π). For positive identification, the molecular emission bands have been compared with synthetic spectra obtained by computer simulations. Furthermore, B 10N emission bands have been reproduced by computer simulation using molecular constants which have been deduced from the B 11N constants. Nevertheless, the presence of the lower abundant isotopic radical B 10N was not proved due the noise level which masked the low emission intensity of the B 10N band heads.

Boron Nitride Nanotubes and Nanoplatelets as Reinforcing Agents of Polymeric Matrices for Bone Tissue Engineering

PubMed Central

Farshid, Behzad; Lalwani, Gaurav; Mohammadi, Meisam Shir; Simonsen, John; Sitharaman, Balaji

2016-01-01

This study investigates the mechanical properties and in vitro cytotoxicity of one- and two-dimensional boron nitride nanomaterials-reinforced biodegradable polymeric nanocomposites. Poly(propylene fumarate) (PPF) nanocomposites were fabricated using crosslinking agent N-vinyl pyrrolidone (NVP) and inorganic nanomaterials: boron nitride nanotubes (BNNTs) and boron nitride nanoplatelets (BNNPs) dispersed at 0.2 wt.% in the polymeric matrix. The incorporation of BNNPs and BNNTs resulted in a ~38% and ~15% increase in compressive (young's) modulus, and ~31% and ~6% increase in compressive yield strength compared to PPF control, respectively. The nanocomposites showed a time-dependent increased protein adsorption for only collagen-I protein. The cytotoxicity evaluation of aqueous BNNT and BNNP dispersions (at 1-100 μg/mL concentrations) using a representative murine MC3T3 preosteoblast cell line showed cytocompatibility of BNNTs and BNNPs (~73-99% viability). The cytotoxicity evaluation of media extracts of nanocomposites prior to crosslinking, after crosslinking and upon degradation (using 1X-100X dilutions) showed dose-dependent cytotoxicity responses. Crosslinked nanocomposites showed excellent (~79-100%) cell viability, cellular attachment (~57-67%), and spreading similar to cells grown on the surface of tissue culture polystyrene (TCPS) control. The media extracts of degradation products showed a dose-dependent cytotoxicity. The favorable cytocompatibility results in combination with improved mechanical properties of BNNT and BNNP nanocomposites opens new avenues for further in vitro and in vivo safety and efficacy studies for their bone tissue engineering applications. PMID:26526153

Synthesis and Electronic Transport in Single-Walled Carbon Nanotubes of Known Chirality

NASA Astrophysics Data System (ADS)

Caldwell, Robert Victor

Since their discovery in 1991, carbon nanotubes have proven to be a very interesting material for its physical strength, originating from the pure carbon lattice and strong covalent sp2 orbital bonds, and electronic properties which are derived from the lattice structure lending itself to either a metallic or semiconducting nature among its other properties. Carbon nanotubes have been researched with an eye towards industry applications ranging from use as an alloy in metals and plastics to improve physical strength of the resulting materials to uses in the semiconductor industry as either an interconnect or device layer for computer chips to chemical or biological sensors. This thesis focuses on both the synthesis of individual single-walled carbon nanotubes as well as the electrical properties of those tubes. What makes the work herein different from that of other thesis is that the research has been performed on carbon nanotubes of known chirality. Having first grown carbon nanotubes with a chemical vapor deposition growth in a quartz tube using ethanol vapor as a feedstock to grow long individual single-walled carbon nanotubes on a silicon chip that is also compatible with Rayleigh scattering spectroscopy to identify the chiral indices of the carbon nanotubes in question, those tubes were then transferred with a mechanical transfer process specially designed in our research lab onto a substrate of our choosing before an electrical device was made out of those tubes using standard electron beam lithography. The focus in this thesis is on the work that went into designing and testing this process as well as the initial results of the electronic properties of those carbon nanotubes of known chirality, such as the first known electrical measurements on single individual armchair carbon nanotubes as well as the first known electrical measurements of a single semiconducting carbon nanotube on thin hexagonal boron nitride to study the effects of the surface optical phonons from the boron nitride on the electrical properties of the carbon nanotube. Finally a few research projects are discussed in which carbon nanotubes of known chirality were used in conjunction with first electrical tests on molecules, secondly on a prefabricated complementary metal-oxide-semiconductor integrated circuit as an inverter and lastly to study the photoconductivity generated by a synchrotron laser source to identify the values for the low energy excitonic peak.

High-Speed Imaging Optical Pyrometry for Study of Boron Nitride Nanotube Generation

NASA Technical Reports Server (NTRS)

Inman, Jennifer A.; Danehy, Paul M.; Jones, Stephen B.; Lee, Joseph W.

2014-01-01

A high-speed imaging optical pyrometry system is designed for making in-situ measurements of boron temperature during the boron nitride nanotube synthesis process. Spectrometer measurements show molten boron emission to be essentially graybody in nature, lacking spectral emission fine structure over the visible range of the electromagnetic spectrum. Camera calibration experiments are performed and compared with theoretical calculations to quantitatively establish the relationship between observed signal intensity and temperature. The one-color pyrometry technique described herein involves measuring temperature based upon the absolute signal intensity observed through a narrowband spectral filter, while the two-color technique uses the ratio of the signals through two spectrally separated filters. The present study calibrated both the one- and two-color techniques at temperatures between 1,173 K and 1,591 K using a pco.dimax HD CMOS-based camera along with three such filters having transmission peaks near 550 nm, 632.8 nm, and 800 nm.

A series of BCN nanosheets with enhanced photoelectrochemical performances

NASA Astrophysics Data System (ADS)

Li, Junqi; Lei, Nan; Hao, Hongjuan; Zhou, Jian

2017-03-01

A series of flake-like BCN compounds were produced by calcination at different reaction temperatures via thermal substitution of C atoms with B atoms of boric acid substructures in graphitic carbon nitrides (g-C3N4). The structural and optical properties of the samples were characterized by XRD, TEM, HRTEM, XPS and UV-vis absorption. The photoelectrochemical (PEC) performance of all samples were characterized through photocurrent and electrochemical impedance spectroscopy (EIS) measurement. The test results demonstrated that BCN nanosheets exhibited higher PEC performance with increasing substituted amount of boron.

Corrosion resistance of monolayer hexagonal boron nitride on copper

PubMed Central

Mahvash, F.; Eissa, S.; Bordjiba, T.; Tavares, A. C.; Szkopek, T.; Siaj, M.

2017-01-01

Hexagonal boron nitride (hBN) is a layered material with high thermal and chemical stability ideal for ultrathin corrosion resistant coatings. Here, we report the corrosion resistance of Cu with hBN grown by chemical vapor deposition (CVD). Cyclic voltammetry measurements reveal that hBN layers inhibit Cu corrosion and oxygen reduction. We find that CVD grown hBN reduces the Cu corrosion rate by one order of magnitude compared to bare Cu, suggesting that this ultrathin layer can be employed as an atomically thin corrosion-inhibition coating. PMID:28191822

Near-Field Infrared Pump-Probe Imaging of Surface Phonon Coupling in Boron Nitride Nanotubes.

PubMed

Gilburd, Leonid; Xu, Xiaoji G; Bando, Yoshio; Golberg, Dmitri; Walker, Gilbert C

2016-01-21

Surface phonon modes are lattice vibrational modes of a solid surface. Two common surface modes, called longitudinal and transverse optical modes, exhibit lattice vibration along or perpendicular to the direction of the wave. We report a two-color, infrared pump-infrared probe technique based on scattering type near-field optical microscopy (s-SNOM) to spatially resolve coupling between surface phonon modes. Spatially varying couplings between the longitudinal optical and surface phonon polariton modes of boron nitride nanotubes are observed, and a simple model is proposed.

A simple method to synthesize polyhedral hexagonal boron nitride nanofibers

NASA Astrophysics Data System (ADS)

Lin, Liang-xu; Zheng, Ying; Li, Zhao-hui; shen, Xiao-nv; Wei, Ke-mei

2007-12-01

Hexagonal boron nitride (h-BN) fibers with polyhedral morphology were synthesized with a simple-operational, large-scale and low-cost method. The sample obtained was studied by X-ray photoelectron spectrometer (XPS), electron energy lose spectroscopy (EELS), X-ray powder diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), etc., which matched with h-BN. Environment scanning electron microscopy (ESEM) and transmission electron microscope (TEM) indicated that the BN fibers possess polyhedral morphology. The diameter of the BN fibers is mainly in the range of 100-500 nm.

Electron tunneling through atomically flat and ultrathin hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Lee, Gwan-Hyoung; Yu, Young-Jun; Lee, Changgu; Dean, Cory; Shepard, Kenneth L.; Kim, Philip; Hone, James

2011-12-01

Electron tunneling through atomically flat and ultrathin hexagonal boron nitride (h-BN) on gold-coated mica was investigated using conductive atomic force microscopy. Low-bias direct tunneling was observed in mono-, bi-, and tri-layer h-BN. For all thicknesses, Fowler-Nordheim tunneling (FNT) occurred at high bias, showing an increase of breakdown voltage with thickness. Based on the FNT model, the barrier height for tunneling (3.07 eV) and dielectric strength (7.94 MV/cm) of h-BN are obtained; these values are comparable to those of SiO2.

Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications.

PubMed

Lee, Chee Huei; Bhandari, Shiva; Tiwari, Bishnu; Yapici, Nazmiye; Zhang, Dongyan; Yap, Yoke Khin

2016-07-15

A comprehensive overview of current research progress on boron nitride nanotubes (BNNTs) is presented in this article. Particularly, recent advancements in controlled synthesis and large-scale production of BNNTs will first be summarized. While recent success in mass production of BNNTs has opened up new opportunities to implement the appealing properties in various applications, concerns about product purity and quality still remain. Secondly, we will summarize the progress in functionalization of BNNTs, which is the necessary step for their applications. Additionally, selected potential applications in structural composites and biomedicine will be highlighted.

Thermal neutron scintillators using unenriched boron nitride and zinc sulfide

NASA Astrophysics Data System (ADS)

McMillan, J. E.; Cole, A. J.; Kirby, A.; Marsden, E.

2015-06-01

Thermal neutron detectors based on powdered zinc sulfide intimately mixed with a neutron capture compound have a history as long as scintillation technique itself. We show that using unenriched boron nitride powder, rather than the more commonly used enriched lithium fluoride, results in detection screens which produce less light but which are very considerably cheaper. Methods of fabricating large areas of this material are presented. The screens are intended for the production of large area low cost neutron detectors as a replacement for helium-3 proportional tubes.

Very Long Single and Few-Walled Boron Nitride Nanotubes via the Pressurized Vapor/Condenser Method

NASA Technical Reports Server (NTRS)

Smith, Michael W.; Jordan, Kevin C.; Park, Cheol; Kim, Jae-Woo; Lillehei, Peter T.; Crooks, Roy; Harrison, Joycelyn S.

2009-01-01

A new method for producing long, small diameter, single and few-walled, boron nitride nanotubes (BNNTs) in macroscopic quantities is reported. The pressurized vapor/condenser (PVC) method produces, without catalysts, highly crystalline, very long, small diameter, BNNTs. Palm-sized, cotton-like masses of BNNT raw material were grown by this technique and spun directly into centimeters-long yarn. Nanotube lengths were observed to be 100 times that of those grown by the most closely related method. Self-assembly and growth models for these long BNNTs are discussed.

High temperature solar energy absorbing surfaces

DOEpatents

Schreyer, J.M.; Schmitt, C.R.; Abbatiello, L.A.

A solar collector having an improved coating is provided. The coating is a plasma-sprayed coating comprising a material having a melting point above 500/sup 0/C at which it is stable and selected from the group of boron carbide, boron nitride, metals and metal oxides, nitrides, carbides, borides, and silicates. The coatings preferably have a porosity of about 15 to 25% and a thickness of less than 200 micrometers. The coatings can be provided by plasma-spraying particles having a mean diameter of about 10 to 200 micrometers.

Magnesium doping of boron nitride nanotubes

DOEpatents

Legg, Robert; Jordan, Kevin

2015-06-16

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

Scaling Behavior for Ionic Transport and its Fluctuations in Individual Carbon Nanotubes.

PubMed

Secchi, Eleonora; Niguès, Antoine; Jubin, Laetitia; Siria, Alessandro; Bocquet, Lydéric

2016-04-15

In this Letter, we perform an experimental study of ionic transport and current fluctuations inside individual carbon nanotubes (CNTs). The conductance exhibits a power law behavior at low salinity, with an exponent close to 1/3 versus the salt concentration in this regime. This behavior is rationalized in terms of a salinity dependent surface charge, which is accounted for on the basis of a model for hydroxide adsorption at the (hydrophobic) carbon surface. This is in contrast to boron nitride nanotubes which exhibit a constant surface conductance. Further, we measure the low frequency noise of the ionic current in CNTs and show that the amplitude of the noise scales with the surface charge, with data collapsing on a master curve for the various studied CNTs at a given pH.

Scaling Behavior for Ionic Transport and its Fluctuations in Individual Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Secchi, Eleonora; Niguès, Antoine; Jubin, Laetitia; Siria, Alessandro; Bocquet, Lydéric

2016-04-01

In this Letter, we perform an experimental study of ionic transport and current fluctuations inside individual carbon nanotubes (CNTs). The conductance exhibits a power law behavior at low salinity, with an exponent close to 1 /3 versus the salt concentration in this regime. This behavior is rationalized in terms of a salinity dependent surface charge, which is accounted for on the basis of a model for hydroxide adsorption at the (hydrophobic) carbon surface. This is in contrast to boron nitride nanotubes which exhibit a constant surface conductance. Further, we measure the low frequency noise of the ionic current in CNTs and show that the amplitude of the noise scales with the surface charge, with data collapsing on a master curve for the various studied CNTs at a given p H .

Chemical Interaction-Guided, Metal-Free Growth of Large-Area Hexagonal Boron Nitride on Silicon-Based Substrates.

PubMed

Behura, Sanjay; Nguyen, Phong; Debbarma, Rousan; Che, Songwei; Seacrist, Michael R; Berry, Vikas

2017-05-23

Hexagonal boron nitride (h-BN) is an ideal platform for interfacing with two-dimensional (2D) nanomaterials to reduce carrier scattering for high-quality 2D electronics. However, scalable, transfer-free growth of hexagonal boron nitride (h-BN) remains a challenge. Currently, h-BN-based 2D heterostructures require exfoliation or chemical transfer of h-BN grown on metals resulting in small areas or significant interfacial impurities. Here, we demonstrate a surface-chemistry-influenced transfer-free growth of large-area, uniform, and smooth h-BN directly on silicon (Si)-based substrates, including Si, silicon nitride (Si 3 N 4 ), and silicon dioxide (SiO 2 ), via low-pressure chemical vapor deposition. The growth rates increase with substrate electronegativity, Si < Si 3 N 4 < SiO 2 , consistent with the adsorption rates calculated for the precursor molecules via atomistic molecular dynamics simulations. Under graphene with high grain density, this h-BN film acts as a polymer-free, planar-dielectric interface increasing carrier mobility by 3.5-fold attributed to reduced surface roughness and charged impurities. This single-step, chemical interaction guided, metal-free growth mechanism of h-BN for graphene heterostructures establishes a potential pathway for the design of complex and integrated 2D-heterostructured circuitry.

An Assessment of the Potential Use of BNNTs for Boron Neutron Capture Therapy.

PubMed

Ferreira, Tiago H; Miranda, Marcelo C; Rocha, Zildete; Leal, Alexandre S; Gomes, Dawidson A; Sousa, Edesia M B

2017-04-12

Currently, nanostructured compounds have been standing out for their optical, mechanical, and chemical features and for the possibilities of manipulation and regulation of complex biological processes. One of these compounds is boron nitride nanotubes (BNNTs), which are a nanostructured material analog to carbon nanotubes, but formed of nitrogen and boron atoms. BNNTs present high thermal stability along with high chemical inertia. Among biological applications, its biocompatibility, cellular uptake, and functionalization potential can be highlighted, in addition to its eased utilization due to its nanometric size and tumor cell internalization. When it comes to new forms of therapy, we can draw attention to boron neutron capture therapy (BNCT), an experimental radiotherapy characterized by a boron-10 isotope carrier inside the target and a thermal neutron beam focused on it. The activation of the boron-10 atom by a neutron generates a lithium atom, a gamma ray, and an alpha particle, which can be used to destroy tumor tissues. The aim of this work was to use BNNTs as a boron-10 carrier for BNCT and to demonstrate its potential. The nanomaterial was characterized through XRD, FTIR, and SEM. The WST-8 assay was performed to confirm the cell viability of BNNTs. The cells treated with BNNTs were irradiated with the neutron beam of a Triga reactor, and the apoptosis caused by the activation of the BNNTs was measured with a calcein AM/propidium iodide test. The results demonstrate that this nanomaterial is a promising candidate for cancer therapy through BNCT.

Manual modification and plasma exposure of boron nitride ceramic to study Hall effect thruster plasma channel material erosion

NASA Astrophysics Data System (ADS)

Satonik, Alexander J.

Worn Hall effect thrusters (HET) show a variety of unique microstructures and elemental compositions in the boron nitride thruster channel walls. Worn thruster channels are typically created by running test thrusters in vacuum chambers for hundreds of hours. Studies were undertaken to manually modify samples of boron nitride without the use of a hall effect thruster. Samples were manually abraded with an abrasive blaster and sandpaper, in addition to a vacuum heater. Some of these samples were further exposed to a xenon plasma in a magnetron sputter device. Sandpaper and abrasive blaster tests were used to modify surface roughness values of the samples from 10,000 A to 150,000 A, matching worn thruster values. Vacuum heat treatments were performed on samples. These treatments showed the ability to modify chemical compositions of boron nitride samples, but not in a manner matching changes seen in worn thruster channels. Plasma erosion rate was shown to depend on the grade of the BN ceramic and the preparation of the surface prior to plasma exposure. Abraded samples were shown to erode 43% more than their pristine counterparts. Unique surface features and elemental compositions on the worn thruster channel samples were overwritten by new surface features on the ceramic grains. The microscope images of the ceramic surface show that the magnetron plasma source rounded the edges of the ceramic grains to closely match the worn HET surface. This effect was not as pronounced in studies of ion beam bombardment of the surface and appears to be a result of the quasi-neutral plasma environment.

Sensing properties of pristine boron nitride nanostructures towards alkaloids: A first principles dispersion corrected study

NASA Astrophysics Data System (ADS)

Roondhe, Basant; Dabhi, Shweta D.; Jha, Prafulla K.

2018-05-01

To understand the underlying physics behind the interaction of biomolecules with the nanomaterials to use them practically as bio-nanomaterials is very crucial. A first principles calculation under the frame work of density functional theory is executed to investigate the electronic structures and binding properties of alkaloids (Caffeine and Nicotine) over single walled boron nitride nanotube (BNNT) and boron nitride nanoribbon (BNNR) to determine their suitability towards filtration or sensing of these molecules. We have also used GGA-PBE scheme with the inclusion of Van der Waals (vdW) interaction based on DFT-D2. Increase in the accuracy by incorporating the dispersion correction in the calculation is observed for the long range Van der Waals interaction. Binding energy range of BNNT and BNNR with both alkaloids have been found to be -0.35 to -0.76 eV and -0.45 to -0.91 eV respectively which together with the binding distance shows physisorption binding of these molecules to the both nanostructures. The transfer of charge between the BN nanostructures and the adsorbed molecule has also been analysed by using Lowdin charge analysis. The sensitivity of both nanostructures BNNT and BNNR towards both alkaloids is observed through electronic structure calculations, density of states and quantum conductance. The binding of both alkaloids with BNNR is stronger. The analysis of the calculated properties suggests absence of covalent interaction between the considered species (BNNT/BNNR) and alkaloids. The study may be useful in designing the boron nitride nanostructure based sensing device for alkaloids.

Boron nitride nanotubes and nanoplatelets as reinforcing agents of polymeric matrices for bone tissue engineering.

PubMed

Farshid, Behzad; Lalwani, Gaurav; Shir Mohammadi, Meisam; Simonsen, John; Sitharaman, Balaji

2017-02-01

This study investigates the mechanical properties and in vitro cytotoxicity of one- and two-dimensional boron nitride nanomaterials-reinforced biodegradable polymeric nanocomposites. Poly(propylene fumarate) (PPF) nanocomposites were fabricated using crosslinking agent N-vinyl pyrrolidone and inorganic nanomaterials: boron nitride nanotubes (BNNTs) and boron nitride nanoplatelets (BNNPs) dispersed at 0.2 wt % in the polymeric matrix. The incorporation of BNNPs and BNNTs resulted in a ∼38 and ∼15% increase in compressive (Young's) modulus, and ∼31 and ∼6% increase in compressive yield strength compared to PPF control, respectively. The nanocomposites showed a time-dependent increased protein adsorption for collagen I protein. The cytotoxicity evaluation of aqueous BNNT and BNNP dispersions (at 1-100 μg/mL concentrations) using murine MC3T3 preosteoblast cells showed ∼73-99% viability. The cytotoxicity evaluation of media extracts of nanocomposites before crosslinking, after crosslinking, and upon degradation (using 1×-100× dilutions) showed dose-dependent cytotoxicity responses. Crosslinked nanocomposites showed excellent (∼79-100%) cell viability, cellular attachment (∼57-67%), and spreading similar to cells grown on the surface of tissue culture polystyrene control. The media extracts of degradation products showed a dose-dependent cytotoxicity. The favorable cytocompatibility results in combination with improved mechanical properties of BNNT and BNNP nanocomposites opens new avenues for further in vitro and in vivo safety and efficacy studies towards bone tissue engineering applications. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 406-419, 2017. © 2015 Wiley Periodicals, Inc.

All-nanotube stretchable supercapacitor with low equivalent series resistance.

PubMed

Gilshteyn, Evgenia P; Amanbayev, Daler; Anisimov, Anton S; Kallio, Tanja; Nasibulin, Albert G

2017-12-12

We report high-performance, stable, low equivalent series resistance all-nanotube stretchable supercapacitor based on single-walled carbon nanotube film electrodes and a boron nitride nanotube separator. A layer of boron nitride nanotubes, fabricated by airbrushing from isopropanol dispersion, allows avoiding problem of high internal resistance and short-circuiting of supercapacitors. The device, fabricated in a two-electrode test cell configuration, demonstrates electrochemical double layer capacitance mechanism and retains 96% of its initial capacitance after 20 000 electrochemical charging/discharging cycles with the specific capacitance value of 82 F g -1 and low equivalent series resistance of 4.6 Ω. The stretchable supercapacitor prototype withstands at least 1000 cycles of 50% strain with a slight increase in the volumetric capacitance from 0.4 to 0.5 mF cm -3 and volumetric power density from 32 mW cm -3 to 40 mW cm -3 after stretching, which is higher than reported before. Moreover, a low resistance of 250 Ω for the as-fabricated stretchable prototype was obtained, which slightly decreased with the strain applied up to 200 Ω. Simple fabrication process of such devices can be easily extended making the all-nanotube stretchable supercapacitors, presented here, promising elements in future wearable devices.

Hexagonal boron nitride nanoparticles decorated halloysite clay nanotubes as a potential hydrogen storage medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muthu, R. Naresh, E-mail: rnaresh7708@gmail.com; Rajashabala, S.; Kannan, R.

2016-05-23

The light weight and compact hydrogen storage materials is still prerequisite for the carbon free hydrogen fuel cell technology. In this work, the hydrogen storage performance of acid treated halloysite clay nanotubes (A-HNTs) and hexagonal boron nitride (h-BN) nanoparticles decorated acid treated halloysite nanoclay composite (A-HNT-h-BN) are demonstrated, where facile ultrasonic technique is adopted for the synthesis of A-HNT-h-BN nanoclay composite. Hydrogen storage studies were carried out using Sieverts-like hydrogenation setup. The A-HNTs and A-HNT-h-BN nanoclay composite were analyzed by XRD, FTIR, HRTEM, EDX, CHNS-elemental analysis and TGA. The A-HNT-h-BN nanoclay composite shows superior storage capacity of 2.19 wt% atmore » 50 °C compared to the A-HNTs (0.58 wt%). A 100% desorption of stored hydrogen is noted in the temperature range of 138–175 °C. The average binding energy of hydrogen was found to be 0.34 eV for the prepared A-HNT-h-BN nanoclay composite. The excellent storage capability of A-HNT-h-BN nanoclay composite towards hydrogen at ambient temperature may find bright perspective in hydrogen fuel cell technology in near future.« less

Origin and roles of oxygen impurities in hexagonal boron nitride epilayers

NASA Astrophysics Data System (ADS)

Grenadier, S. J.; Maity, A.; Li, J.; Lin, J. Y.; Jiang, H. X.

2018-04-01

Photoluminescence emission spectroscopy and electrical transport measurements have been employed to study the origin and roles of oxygen impurities in hexagonal boron nitride (h-BN) epilayers grown on sapphire substrates. The temperature dependence of the electrical resistivity revealed the presence of a previously unnoticed impurity level of about 0.6 eV in h-BN epilayers grown at high temperatures. The results suggested that in addition to the common nitrogen vacancy (VN) shallow donors in h-BN, oxygen impurities diffused from sapphire substrates during high temperature growth also act as substitutional donors (ON). The presence of ON gives rise to an additional emission peak in the photoluminescence spectrum, corresponding to a donor-acceptor pair recombination involving the ON donor and the CN (carbon occupying nitrogen site) deep level acceptor. Moreover, due to the presence of ON donors, the majority charge carrier type changed to electrons in epilayers grown at high temperatures, in contrast to typical h-BN epilayers which naturally exhibit "p-type" character. The results provided a more coherent picture for common impurities/defects in h-BN as well as a better understanding of the growth mediated impurities in h-BN epilayers, which will be helpful for finding possible ways to further improve the quality and purity of this emerging material.

Folate-conjugated boron nitride nanospheres for targeted delivery of anticancer drugs

PubMed Central

Feng, Shini; Zhang, Huijie; Yan, Ting; Huang, Dandi; Zhi, Chunyi; Nakanishi, Hideki; Gao, Xiao-Dong

2016-01-01

With its unique physical and chemical properties and structural similarity to carbon, boron nitride (BN) has attracted considerable attention and found many applications. Biomedical applications of BN have recently started to emerge, raising great hopes in drug and gene delivery. Here, we developed a targeted anticancer drug delivery system based on folate-conjugated BN nanospheres (BNNS) with receptor-mediated targeting. Folic acid (FA) was successfully grafted onto BNNS via esterification reaction. In vitro cytotoxicity assay showed that BNNS-FA complexes were non-toxic to HeLa cells up to a concentration of 100 μg/mL. Then, doxorubicin hydrochloride (DOX), a commonly used anticancer drug, was loaded onto BNNS-FA complexes. BNNS-FA/DOX complexes were stable at pH 7.4 but effectively released DOX at pH 5.0, which exhibited a pH sensitive and sustained release pattern. BNNS-FA/DOX complexes could be recognized and specifically internalized by HeLa cells via FA receptor-mediated endocytosis. BNNS-FA/DOX complexes exhibited greater cytotoxicity to HeLa cells than free DOX and BNNS/DOX complexes due to the increased cellular uptake of DOX mediated by the FA receptor. Therefore, BNNS-FA complexes had strong potential for targeted cancer therapy. PMID:27695318

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes

NASA Astrophysics Data System (ADS)

O'Brien, S. A.; Harvey, A.; Griffin, A.; Donnelly, T.; Mulcahy, D.; Coleman, J. N.; Donegan, J. F.; McCloskey, D.

2017-11-01

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter—the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes.

PubMed

O'Brien, S A; Harvey, A; Griffin, A; Donnelly, T; Mulcahy, D; Coleman, J N; Donegan, J F; McCloskey, D

2017-11-24

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter-the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Single photon emission from plasma treated 2D hexagonal boron nitride.

PubMed

Xu, Zai-Quan; Elbadawi, Christopher; Tran, Toan Trong; Kianinia, Mehran; Li, Xiuling; Liu, Daobin; Hoffman, Timothy B; Nguyen, Minh; Kim, Sejeong; Edgar, James H; Wu, Xiaojun; Song, Li; Ali, Sajid; Ford, Mike; Toth, Milos; Aharonovich, Igor

2018-05-03

Artificial atomic systems in solids are becoming increasingly important building blocks in quantum information processing and scalable quantum nanophotonic networks. Amongst numerous candidates, 2D hexagonal boron nitride has recently emerged as a promising platform hosting single photon emitters. Here, we report a number of robust plasma and thermal annealing methods for fabrication of emitters in tape-exfoliated hexagonal boron nitride (hBN) crystals. A two-step process comprising Ar plasma etching and subsequent annealing in Ar is highly robust, and yields an eight-fold increase in the concentration of emitters in hBN. The initial plasma-etching step generates emitters that suffer from blinking and bleaching, whereas the two-step process yields emitters that are photostable at room temperature with emission wavelengths greater than ∼700 nm. Density functional theory modeling suggests that the emitters might be associated with defect complexes that contain oxygen. This is further confirmed by generating the emitters via annealing hBN in air. Our findings advance the present understanding of the structure of quantum emitters in hBN and enhance the nanofabrication toolkit needed to realize integrated quantum nanophotonic circuits.

Ultrathin-shell boron nitride hollow spheres as sorbent for dispersive solid-phase extraction of polychlorinated biphenyls from environmental water samples.

PubMed

Fu, Meizhen; Xing, Hanzhu; Chen, Xiangfeng; Chen, Fan; Wu, Chi-Man Lawrence; Zhao, Rusong; Cheng, Chuange

2014-11-21

Boron nitride hollow spheres with ultrathin-shells were synthesized and used as sorbents for dispersive solid-phase extraction of aromatic pollutants at trace levels from environmental water samples. Polychlorinated biphenyls (PCBs) were selected as target compounds. Sample quantification and detection were performed by gas chromatography-tandem mass spectrometry. Extraction parameters influencing the extraction efficiency were optimized through response surface methodology using the Box-Behnken design. The proposed method achieved good linearity within the concentration range of 0.15-250 ng L(-1) PCBs, low limits of detection (0.04-0.09 ng L(-1), S/N=3:1), good repeatability of the extractions (relative standard deviation, <12%, n=6), and satisfactory recoveries between 84.9% and 101.0% under optimal conditions. Real environmental samples collected from rivers, local lakes, rain and spring waters were analyzed using the developed method. Results demonstrated that the hexagonal boron nitride-based material has significant potential as a sorbent for organic pollutant extraction from environmental water samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Novel Composite Proton Exchange Membrane with Connected Long-Range Ionic Nanochannels Constructed via Exfoliated Nafion-Boron Nitride Nanocomposite.

PubMed

Jia, Wei; Tang, Beibei; Wu, Peiyi

2017-05-03

Nafion-boron nitride (NBN) nanocomposites with a Nafion-functionalized periphery are prepared via a convenient and ecofriendly Nafion-assisted water-phase exfoliation method. Nafion and the boron nitride nanosheet present strong interactions in the NBN nanocomposite. Then the NBN nanocomposites were blended with Nafion to prepare NBN Nafion composite proton exchange membranes (PEMs). NBN nanocomposites show good dispersibility and have a noticeable impact on the aggregation structure of the Nafion matrix. Connected long-range ionic nanochannels containing exaggerated (-SO 3 - ) n ionic clusters are constructed during the membrane-forming process via the hydrophilic and H-bonding interactions between NBN nanocomposites and Nafion matrix. The addition of NBN nanocomposites with sulfonic groups also provides additional proton transportation spots and enhances the water uptake of the composite PEMs. The proton conductivity of the NBN Nafion composite PEMs is significantly increased under various conditions relative to that of recast Nafion. At 80 °C-95% relative humidity, the proton conductivity of 0.5 NBN Nafion is 0.33 S·cm -1 , 6 times that of recast Nafion under the same conditions.

Improving performance of armchair graphene nanoribbon field effect transistors via boron nitride doping

NASA Astrophysics Data System (ADS)

Goharrizi, A. Yazdanpanah; Sanaeepur, M.; Sharifi, M. J.

2015-09-01

Device performance of 10 nm length armchair graphene nanoribbon field effect transistors with 1.5 nm and 4 nm width (13 and 33 atoms in width respectively) are compared in terms of Ion /Ioff , trans-conductance, and sub-threshold swing. While narrow devices suffer from edge roughness wider devices are subject to more substrate surface roughness and reduced bandgap. Boron Nitride doping is employed to compensate reduced bandgap in wider devices. Simultaneous effects of edge and substrate surface roughness are considered. Results show that in the presence of both the edge and substrate surface roughness the 4 nm wide device with boron nitride doping shows improved performance with respect to the 1.5 nm one (both of which incorporate the same bandgap AGNR as channel material). Electronic simulations are performed via NEGF method along with tight-binding Hamiltonian. Edge and surface roughness are created by means of one and two dimensional auto correlation functions respectively. Electronic characteristics are averaged over a large number of devices due to statistic nature of both the edge and surface roughness.

The role of boron nitride nanotube as a new chemical sensor and potential reservoir for hydrogen halides environmental pollutants

NASA Astrophysics Data System (ADS)

Yoosefian, Mehdi; Etminan, Nazanin; Moghani, Maryam Zeraati; Mirzaei, Samaneh; Abbasi, Shima

2016-10-01

Density functional theory (DFT) studies on the interaction of hydrogen halides (HX) environmental pollutants and the boron nitride nanotubes (BNNTs) have been reported. To exploit the possibility of BNNTs as gas sensors, the adsorption of hydrogen fluoride (HF), hydrogen chloride (HCl) and hydrogen bromide (HBr) on the side wall of armchair (5,5) boron nitride nanotubes have been investigated. B3LYP/6-31G (d) level were used to analyze the structural and electronic properties of investigate sensor. The adsorption process were interpreted by highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO), quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO) and molecular electrostatic potential (MEP) analysis. Topological parameters of bond critical points have been used to calculate as measure of hydrogen bond (HB) strength. Stronger binding energy, larger charge transfer and charge density illustrate that HF gas possesses chemisorbed adsorption process. The obtained results also show the strongest HB in HF/BNNT complex. We expect that results could provide helpful information for the design of new BNNTs based sensing devices.

Stable synthesis of few-layered boron nitride nanotubes by anodic arc discharge.

PubMed

Yeh, Yao-Wen; Raitses, Yevgeny; Koel, Bruce E; Yao, Nan

2017-06-08

Boron nitride nanotubes (BNNTs) were successfully synthesized by a dc arc discharge using a boron-rich anode as synthesis feedstock in a nitrogen gas environment at near atmospheric pressure. The synthesis was achieved independent of the cathode material suggesting that under such conditions the arc operates in so-called anodic mode with the anode material being consumed by evaporation due to the arc heating. To sustain the arc current by thermionic electron emission, the cathode has to be at sufficiently high temperature, which for a typical arc current density of ~100 A/cm 2 , is above the boron melting point (2350 K). With both electrodes made from the same boron-rich alloy, we found that the arc operation unstable due to frequent sticking between two molten electrodes and formation of molten droplets. Stable and reliable arc operation and arc synthesis were achieved with the boron-rich anode and the cathode made from a refractory metal which has a melting temperature above the melting point of boron. Ex-situ characterization of synthesized BNNTs with electron microscopy and Raman spectroscopy revealed that independent of the cathode material, the tubes are primarily single and double walled. The results also show evidence of root-growth of BNNTs produced in the arc discharge.

Conductive Boron-Doped Graphene as an Ideal Material for Electrocatalytically Switchable and High-Capacity Hydrogen Storage.

PubMed

Tan, Xin; Tahini, Hassan A; Smith, Sean C

2016-12-07

Electrocatalytic, switchable hydrogen storage promises both tunable kinetics and facile reversibility without the need for specific catalysts. The feasibility of this approach relies on having materials that are easy to synthesize, possessing good electrical conductivities. Graphitic carbon nitride (g-C 4 N 3 ) has been predicted to display charge-responsive binding with molecular hydrogen-the only such conductive sorbent material that has been discovered to date. As yet, however, this conductive variant of graphitic carbon nitride is not readily synthesized by scalable methods. Here, we examine the possibility of conductive and easily synthesized boron-doped graphene nanosheets (B-doped graphene) as sorbent materials for practical applications of electrocatalytically switchable hydrogen storage. Using first-principle calculations, we find that the adsorption energy of H 2 molecules on B-doped graphene can be dramatically enhanced by removing electrons from and thereby positively charging the adsorbent. Thus, by controlling charge injected or depleted from the adsorbent, one can effectively tune the storage/release processes which occur spontaneously without any energy barriers. At full hydrogen coverage, the positively charged BC 5 achieves high storage capacities up to 5.3 wt %. Importantly, B-doped graphene, such as BC 49 , BC 7 , and BC 5 , have good electrical conductivity and can be easily synthesized by scalable methods, which positions this class of material as a very good candidate for charge injection/release. These predictions pave the route for practical implementation of electrocatalytic systems with switchable storage/release capacities that offer high capacity for hydrogen storage.

Largely enhanced dielectric properties of carbon nanotubes/polyvinylidene fluoride binary nanocomposites by loading a few boron nitride nanosheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Minhao; Zhao, Hang; He, Delong

2016-08-15

The ternary nanocomposites of boron nitride nanosheets (BNNSs)/carbon nanotubes (CNTs)/polyvinylidene fluoride (PVDF) are fabricated via a combination of solution casting and extrusion-injection processes. The effects of BNNSs on the electrical conductivity, dielectric behavior, and microstructure changes of CNTs/PVDF binary nanocomposites are systematically investigated. A low percolation value (f{sub c}) for the CNTs/PVDF binary system is obtained due to the integration of solution and melting blending procedures. Two kinds of CNTs/PVDF binary systems with various CNTs contents (f{sub CNTs}) as the matrix are discussed. The results reveal that compared with CNTs/PVDF binary systems at the same f{sub CNTs}, the ternary BNNSs/CNTs/PVDFmore » nanocomposites exhibit largely enhanced dielectric properties due to the improvement of the CNTs dispersion state and the conductive network. The dielectric constant of CNTs/PVDF binary nanocomposite with 6 vol. % CNTs (f{sub CNTs} < f{sub c}) shows a 79.59% enhancement from 49 to 88 after the incorporation of 3 vol. % BNNSs. For the other CNTs/PVDF system with 8 vol. % CNTs (f{sub CNTs} > f{sub c}), it displays a 43.32% improvement from 1325 to 1899 after the addition of 3 vol. % BNNSs. The presence of BNNSs facilitates the formation of the denser conductive network. Meanwhile, the ternary BNNSs/CNTs/PVDF systems exhibit a low dielectric loss. The adjustable dielectric properties could be obtained by employing the ternary systems due to the microstructure changes of nanocomposites.« less

Bottom-Up Syntheses and Characterization of One Dimensional Nanomaterials

NASA Astrophysics Data System (ADS)

Yeh, Yao-Wen

Nanomaterials, materials having at least one dimension below 100 nm, have been creating exciting opportunities for fundamental quantum confinement studies and applications in electronic devices and energy technologies. One obvious and important aspect of nanomaterials is their production. Although nanostructures can be obtained by top-down reductive e-beam lithography and focused ion beam processes, further development of these processes is needed before these techniques can become practical routes to large scale production. On the other hand, bottom-up syntheses, with advantages in material diversity, throughput, and the potential for large volume production, may provide an alternative strategy for creating nanostructures. In this work, we explore syntheses of one dimensional nanostructures based on hydrothermal and arc discharge methods. The first project presented in this thesis involves syntheses of technologically important nanomaterials and their potential application in energy harvesting. In particular, it was demonstrated that single crystal ferroelectric lead magnesium niobate lead titanate (PMN-PT) nanowires can be synthesized by a hydrothermal route. The chemical composition of the synthesized nanowires is near the rhombohedral-monoclinic boundary of PMN-PT, which leads to a high piezoelectric coefficient of 381 pm/V. Finally, the potential use of PMN-PT nanowires in energy harvesting applications was also demonstrated. The second part of this thesis involves the synthesis of carbon and boron nitride nanotubes by dc arc discharges. In particular, we investigated how local plasma related properties affected the synthesis of carbon nanostructures. Finally, we investigated the anodic nature of the arc and how a dc arc discharge can be applied to synthesize boron nitride nanotubes.

Electronic and transport properties of zigzag carbon nanotubes with the presence of periodical antidot and boron/nitride doping defects

NASA Astrophysics Data System (ADS)

Zoghi, Milad; Yazdanpanah Goharrizi, Arash; Mirjalili, Seyed Mohammad; Kabir, M. Z.

2018-06-01

Electronic and transport properties of Carbon nanotubes (CNTs) are affected by the presence of physical or chemical defects in their structures. In this paper, we present novel platforms of defected zigzag CNTs (Z-CNTs) in which two topologies of antidot and Boron/Nitride (BN) doping defects are periodically imposed throughout the length of perfect tubes. Using the tight binding model and the non-equilibrium Green’s function method, it is realized that the quantum confinement of Z-CNTs is modified by the presence of such defects. This new quantum confinement results in the appearance of mini bands and mini gaps in the transmission spectra, as well as a modified band structure and band gap size. The modified band gap could be either larger or smaller than the intrinsic band gap of a perfect tube, which is determined by the category of Z-CNT. The in-depth analysis shows that the size of the modified band gap is the function of several factors consisting of: the radii of tube (D r), the distance between adjacent defects (d d), the utilized defect topology, and the kind of defect (antidot or BN doping). Furthermore, taking advantage of the tunable band gap size of Z-CNT with the presence of periodical defects, new platforms of defect-based Z-CNT resonant tunneling diode (RTD) are proposed for the first time. Our calculations demonstrate the apparition of resonances in transmission spectra and the negative differential resistance in the I-V characteristics for such RTD platforms.

Epitaxial growth of hexagonal boron nitride monolayers by a three-step boration-oxidation-nitration process

NASA Astrophysics Data System (ADS)

Müller, Frank; Hüfner, Stefan; Sachdev, Hermann; Gsell, Stefan; Schreck, Matthias

2010-08-01

The formation of well-ordered monolayers of hexagonal boron nitride on the surface of a Rh/YSZ/Si(111) multilayer substrate via a three-step boration-oxidation-nitration process was investigated by x-ray photoelectron spectroscopy (XPS), x-ray photoelectron diffraction (XPD) and low-energy electron diffraction (LEED). The chemical vapor deposition (CVD) of trimethylborate B(OCH3)3 results in a selective decomposition of the precursor, leading to a dilute distribution of boron within the interstitials of the Rh lattice. After oxidation, the layer of a boron oxygen species of about 1 nm thickness can be transformed into a hexagonal monolayer of BN by annealing in NH3 atmosphere. The results of the present study clearly show that the formation of BN monolayers is also possible when boron and nitrogen are provided successively from separate sources. This procedure represents an alternative routine for the preparation of well-ordered BN monolayers, which benefits from a strong reduction of hazardous potential and economic costs compared to the use of borazine as the current standard precursor.

Identification of B-K near edge x-ray absorption fine structure peaks of boron nitride thin films prepared by sputtering deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niibe, Masahito; Miyamoto, Kazuyoshi; Mitamura, Tohru

2010-09-15

Four {pi}{sup *} resonance peaks were observed in the B-K near edge x-ray absorption fine structure spectra of boron nitride thin films prepared by magnetron sputtering. In the past, these peaks have been explained as the K-absorption of boron atoms, which are present in environment containing nitrogen vacancies, the number of which is 1-3 corresponding to the three peaks at higher photon energy. However, the authors found that there was a strong correlation between the intensities of these three peaks and that of O-K absorption after wide range scanning and simultaneous measurement of nitrogen and oxygen K-absorptions of the BNmore » films. Therefore, the authors conclude that these three peaks at the higher energy side correspond to boron atoms bound to one-to-three oxygen atoms instead of three nitrogen atoms surrounding the boron atom in the h-BN structure. The result of the first-principles calculation with a simple cluster model supported the validity of this explanation.« less

Lithium Nitride Synthesized by in situ Lithium Deposition and Ion Implantation for Boron Neutron Capture Therapy

NASA Astrophysics Data System (ADS)

Ishitama, Shintaro; Baba, Yuji; Fujii, Ryo; Nakamura, Masaru; Imahori, Yoshio

Li3N synthesis on Li deposition layer was conducted without H2O and O2 by in situ lithium deposition in high vacuum chamber of 10-6 Pa and ion implantation techniques and the thermo-chemical stability of the Li3N/Li/Cu tri-layered target for Boron Neutron Capture Therapy (BNCT) under laser heating and air exposure was characterized by X-ray photoelectron spectroscopy (XPS). Following conclusions were derived; (1) Li3N/Li/Cu tri-layered target with very low oxide and carbon contamination was synthesized by in situ lithium vacuum deposition and N2+ ion implantation without H2O and O2 additions, (2) The starting temperature of evaporation of Li3N/Li/Cu tri-layered target increased by 120K compared to that of the Li/Cu target and (3) Remarkable oxidation and carbon contamination were observed on the surface of Li3N/Li/Cu after air exposure and these contaminated compositions was not removed by Ar+ heavy sputtering.

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kharlamov, Alexey; Bondarenko, Marina, E-mail: mebondarenko@ukr.net; Kharlamova, Ganna

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists ofmore » weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets. - Graphical abstract: XRD pattern and schematic atomic model of one layer of reduced carbon nitride, carbon nitride oxide and synthesized carbon nitride. For the first time at the reduction by hydroquinone of the water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O is obtained the reduced carbon nitride (or reduced multi-layer azagraphene). Display Omitted - Highlights: • First the reduced carbon nitride (RCN) at the reduction of the carbon nitride oxide was obtained. • Water-soluble carbon nitride oxide was reduced by hydroquinone. • The chemical bonds in a heteroatomic plane of RCN correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. • Reduced carbon nitride consists of poorly connected heteroatomic azagraphene layers.« less

Synthesis of boron nitride nanotubes and their applications

PubMed Central

Kalay, Saban; Yilmaz, Zehra; Sen, Ozlem; Emanet, Melis; Kazanc, Emine

2015-01-01

Summary Boron nitride nanotubes (BNNTs) have been increasingly investigated for use in a wide range of applications due to their unique physicochemical properties including high hydrophobicity, heat and electrical insulation, resistance to oxidation, and hydrogen storage capacity. They are also valued for their possible medical and biomedical applications including drug delivery, use in biomaterials, and neutron capture therapy. In this review, BNNT synthesis methods and the surface modification strategies are first discussed, and then their toxicity and application studies are summarized. Finally, a perspective for the future use of these novel materials is discussed. PMID:25671154

Large Excitonic Reflectivity of Monolayer MoSe2 Encapsulated in Hexagonal Boron Nitride

NASA Astrophysics Data System (ADS)

Scuri, Giovanni; Zhou, You; High, Alexander A.; Wild, Dominik S.; Shu, Chi; De Greve, Kristiaan; Jauregui, Luis A.; Taniguchi, Takashi; Watanabe, Kenji; Kim, Philip; Lukin, Mikhail D.; Park, Hongkun

2018-01-01

We demonstrate that a single layer of MoSe2 encapsulated by hexagonal boron nitride can act as an electrically switchable mirror at cryogenic temperatures, reflecting up to 85% of incident light at the excitonic resonance. This high reflectance is a direct consequence of the excellent coherence properties of excitons in this atomically thin semiconductor. We show that the MoSe2 monolayer exhibits power-and wavelength-dependent nonlinearities that stem from exciton-based lattice heating in the case of continuous-wave excitation and exciton-exciton interactions when fast, pulsed laser excitation is used.

Measurement of the Elastic Modulus of a Single Boron Nitride Nanotube

NASA Astrophysics Data System (ADS)

Chopra, Nasreen G.; Cohen, Marvin L.; Louie, Steven G.; Zettl, A.

1997-03-01

In situ transmission electron microscope (TEM) measurements of thermally-excited vibrational characteristics of boron nitride (BN) nanotubes are used to extract the elastic modulus. We find BN nanotubes to have a higher axial Young's modulus, 1.2 TPa, than any other insulating fiber. This value is consistent with theoretical predictions and confirms previous TEM observations of the high degree of crystallinity of these structures. This work was supported by the U. S. Department of Energy under contract No. DE-AC03-76-SF00098 and the Office of Naval Research, Order No. N00014-95-F-0099

Synthesis of boron nitride nanofibers and measurement of their hydrogen uptake capacity

NASA Astrophysics Data System (ADS)

Ma, Renzhi; Bando, Yoshio; Sato, Tadao; Golberg, Dmitri; Zhu, Hongwei; Xu, Cailu; Wu, Dehai

2002-12-01

High-purity boron nitride (BN) nanofibers with diameters ranging from 30 to 100 nm were synthesized. Electron energy loss spectroscopy revealed that they have stoichiometric BN composition. The hydrogen uptake capacity measurements showed that the fibers could adsorb 2.9 wt % hydrogen under ˜10 MPa at room temperature. This hydrogen uptake capacity was compared with those of BN multiwalled or bamboo-like nanotubes under the same experimental conditions. It was suggested that the unique morphology of nanofibers, namely open-ended BN edge layers on the exterior surface, might facilitate hydrogen adsorption.

A platform for large-scale graphene electronics--CVD growth of single-layer graphene on CVD-grown hexagonal boron nitride.

PubMed

Wang, Min; Jang, Sung Kyu; Jang, Won-Jun; Kim, Minwoo; Park, Seong-Yong; Kim, Sang-Woo; Kahng, Se-Jong; Choi, Jae-Young; Ruoff, Rodney S; Song, Young Jae; Lee, Sungjoo

2013-05-21

Direct chemical vapor deposition (CVD) growth of single-layer graphene on CVD-grown hexagonal boron nitride (h-BN) film can suggest a large-scale and high-quality graphene/h-BN film hybrid structure with a defect-free interface. This sequentially grown graphene/h-BN film shows better electronic properties than that of graphene/SiO2 or graphene transferred on h-BN film, and suggests a new promising template for graphene device fabrication. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atomistic modeling of BN nanofillers for mechanical and thermal properties: a review.

PubMed

Kumar, Rajesh; Parashar, Avinash

2016-01-07

Due to their exceptional mechanical properties, thermal conductivity and a wide band gap (5-6 eV), boron nitride nanotubes and nanosheets have promising applications in the field of engineering and biomedical science. Accurate modeling of failure or fracture in a nanomaterial inherently involves coupling of atomic domains of cracks and voids as well as a deformation mechanism originating from grain boundaries. This review highlights the recent progress made in the atomistic modeling of boron nitride nanofillers. Continuous improvements in computational power have made it possible to study the structural properties of these nanofillers at the atomistic scale.

Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaskell, J.; Fromhold, T. M.; Greenaway, M. T.

We assess the potential of two-terminal graphene-hexagonal boron nitride-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit impedances. Our results indicate that current oscillations with frequencies of up to several hundred GHz should be achievable.

Lattice mismatch induced ripples and wrinkles in planar graphene/boron nitride superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nandwana, Dinkar; Ertekin, Elif, E-mail: ertekin@illinois.edu; International Institute for Carbon Neutral Energy Research

A continuum theory to describe periodic ripple formation in planar graphene/boron nitride superlattices is formulated. Due to the lattice mismatch between the two materials, it is shown that flat superlattices are unstable with respect to ripple formation of appropriate wavelengths. A competition between bending energy and transverse stretching energy gives rise to an optimal ripple wavelength that depends on the superlattice pitch. The optimal wavelengths predicted by the continuum theory are in good agreement with atomic scale total energy calculations previously reported by Nandwana and Ertekin [Nano Lett. 15, 1468 (2015)].

Low-Energy Sputtering Studies of Boron Nitride with Xenon Ions

NASA Technical Reports Server (NTRS)

Ray, P. K.; Shutthanandan, V.

1999-01-01

Sputtering of boron nitride with xenon ions was investigated using secondary ion (SIMS) and secondary neutral (SNMS) mass spectrometry. The ions generated from the ion gun were incident on the target at an angle of 50' with respect to the surface'normal. The energy of ions ranged from 100 eV to 3 keV. A flood electron gun was used to neutralize the positive charge build-up on the target surface. The intensities of sputtered neutral and charged particles, including single atoms, molecules, and clusters, were measured as a function of ion energy. Positive SIMS spectra were dominated by the two boron isotopes whereas BN- and B- were the two major constituents of the negative SIMS spectra. Nitrogen could be detected only in the SNMS spectra. The intensity-energy curves of the sputtered particles were similar in shape. The knees in P-SIMS and SNMS intensity-energy curves appear at around I keV which is significantly higher that 100 to 200 eV energy range at which knees appear in the sputtering of medium and heavy elements by ions of argon and xenon. This difference in the position of the sputter yield knee between boron nitride and heavier targets is due to the reduced ion energy differences. The isotopic composition of secondary ions of boron were measured by bombarding boron nitride with xenon ions at energies ranging from 100 eV to 1.5 keV using a quadrupole mass spectrometer. An ion gun was used to generate the ion beam. A flood electron gun was used to neutralize the positive charge buildup on the target surface. The secondary ion flux was found to be enriched in heavy isotopes at lower incident ion energies. The heavy isotope enrichment was observed to decrease with increasing primary ion energy. Beyond 350 eV, light isotopes were sputtered preferentially with the enrichment increasing to an asymptotic value of 1.27 at 1.5 keV. The trend is similar to that of the isotopic enrichment observed earlier when copper was sputtered with xenon ions in the same energy range.

Modified carbon fibers to improve composite properties. [sizing fibers for reduced electrical conductivity and adhesion during combustion

NASA Technical Reports Server (NTRS)

Shepler, R. E.

1979-01-01

Thin coatings, 5 to 10 wt. percent, were applied to PAN-based carbon fibers. These coatings were intended to make the carbon fibers less electrically conductive or to cause fibers to stick together when a carbon fiber/epoxy composite burned. The effectiveness of the coatings in these regards was evaluated in burn tests with a test rig designed to simulate burning, impact and wind conditions which might release carbon fibers. The effect of the coatings on fiber and composite properties and handling was also investigated. Attempts at sizing carbon fibers with silicon dioxide, silicon carbide and boron nitride meet with varying degrees of success; however, none of these materials provided an electrically nonconductive coating. Coatings intended to stick carbon fibers together after a composite burned were sodium silicate, silica gel, ethyl silicate, boric acid and ammonium borate. Of these, only the sodium silicate and silica gel provided any sticking together of fibers. The amount of sticking was insufficient to achieve the desired objectives.

First-principles engineering of charged defects for two-dimensional quantum technologies

NASA Astrophysics Data System (ADS)

Wu, Feng; Galatas, Andrew; Sundararaman, Ravishankar; Rocca, Dario; Ping, Yuan

2017-12-01

Charged defects in two-dimensional (2D) materials have emerging applications in quantum technologies such as quantum emitters and quantum computation. The advancement of these technologies requires a rational design of ideal defect centers, demanding reliable computation methods for the quantitatively accurate prediction of defect properties. We present an accurate, parameter-free, and efficient procedure to evaluate the quasiparticle defect states and thermodynamic charge transition levels of defects in 2D materials. Importantly, we solve critical issues that stem from the strongly anisotropic screening in 2D materials, that have so far precluded the accurate prediction of charge transition levels in these materials. Using this procedure, we investigate various defects in monolayer hexagonal boron nitride (h -BN ) for their charge transition levels, stable spin states, and optical excitations. We identify CBVN (nitrogen vacancy adjacent to carbon substitution of boron) to be the most promising defect candidate for scalable quantum bit and emitter applications.

Layer speciation and electronic structure investigation of freestanding hexagonal boron nitride nanosheets

NASA Astrophysics Data System (ADS)

WangEqual Contribution To This Work., Jian; Wang, Zhiqiang; Cho, Hyunjin; Kim, Myung Jong; Sham, T. K.; Sun, Xuhui

2015-01-01

Chemical imaging, thickness mapping, layer speciation and polarization dependence have been performed on single and multilayered (up to three layers and trilayered nanosheets overlapping to form 6 and 9 layers) hexagonal boron nitride (hBN) nanosheets by scanning transmission X-ray microscopy. Spatially-resolved XANES directly from freestanding regions of different layers has been extracted and compared with sample normal and 30° tilted configurations. Notably a double feature σ* excitonic state and a stable high energy σ* state were observed at the boron site in addition to the intense π* excitonic state. The boron projected σ* DOS, especially the first σ* exciton, is sensitive to surface modification, particularly in the single layered hBN nanosheet which shows more significant detectable contaminants and defects such as tri-coordinated boron/nitrogen oxide. The nitrogen site has shown very weak or no excitonic character. The distinct excitonic effect on boron and nitrogen was interpreted to the partly ionic state of hBN. Bulk XANES of hBN nanosheets was also measured to confirm the spectro-microscopic STXM result. Finally, the unoccupied electronic structures of hBN and graphene were compared.Chemical imaging, thickness mapping, layer speciation and polarization dependence have been performed on single and multilayered (up to three layers and trilayered nanosheets overlapping to form 6 and 9 layers) hexagonal boron nitride (hBN) nanosheets by scanning transmission X-ray microscopy. Spatially-resolved XANES directly from freestanding regions of different layers has been extracted and compared with sample normal and 30° tilted configurations. Notably a double feature σ* excitonic state and a stable high energy σ* state were observed at the boron site in addition to the intense π* excitonic state. The boron projected σ* DOS, especially the first σ* exciton, is sensitive to surface modification, particularly in the single layered hBN nanosheet which shows more significant detectable contaminants and defects such as tri-coordinated boron/nitrogen oxide. The nitrogen site has shown very weak or no excitonic character. The distinct excitonic effect on boron and nitrogen was interpreted to the partly ionic state of hBN. Bulk XANES of hBN nanosheets was also measured to confirm the spectro-microscopic STXM result. Finally, the unoccupied electronic structures of hBN and graphene were compared. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04445b

Effects of Fiber Coatings on Tensile Properties of Hi-Nicalon SiC/RBSN Tow Composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Hull, David R.

1997-01-01

Uncoated Hi-Nicalon silicon carbide (SiC) fiber tows and those coated with a single surface layer of pyrolytic boron nitride (PBN), double layers of PBN/Si-rich PBN, and boron nitride (BN)/SiC coatings deposited by chemical vapor deposition (CVD) method were infiltrated with silicon slurry and then exposed to N2, for 4 hr at 1200 and 1400 C. Room temperature ultimate tensile fracture loads and microstructural characterization of uncoated and CVD coated Hi-Nicalon SiC fiber reinforced reaction-bonded silicon nitride (RBSN) tow composites were measured to select suitable interface coating(s) stable under RBSN processing conditions. Results indicate that room temperature ultimate fracture loads of the uncoated Hi-Nicalon SiC/RBSN tow composites nitrided at both temperatures were significantly lower than those of the uncoated Hi-Nicalon tows without slurry infiltration. In contrast, all CVD coated Hi-Nicalon SiC/RBSN tow composites retained a greater fraction of the dry tow fracture load after nitridation at 1200 C, but degraded significantly after nitridation at 1400 C. Reaction between metal impurities (Fe and Ni) present in the attrition milled silicon powder and uncoated regions of SiC fibers appears to be the probable cause for fiber degradation.

Scaling Behavior for Ionic Transport and its Fluctuations in Individual Carbon Nanotubes

PubMed Central

Secchi, Eleonora; Niguès, Antoine; Jubin, Laetitia; Siria, Alessandro; Bocquet, Lydéric

2016-01-01

In this Letter, we perform an experimental study of ionic transport and current fluctuations inside individual carbon nanotubes (CNTs). The conductance exhibits a power law behavior at low salinity, with an exponent close to 1/3 versus the salt concentration in this regime. This behavior is rationalized in terms of a salinity dependent surface charge, which is accounted for on the basis of a model for hydroxide adsorption at the (hydrophobic) carbon surface. This is in contrast to boron nitride nanotubes which exhibit a constant surface conductance. Further, we measure the low frequency noise of the ionic current in CNTs and show that the amplitude of the noise scales with the surface charge, with data collapsing on a master curve for the various studied CNTs at a given pH. PMID:27127970

Gap discrete breathers in strained boron nitride

NASA Astrophysics Data System (ADS)

Barani, Elham; Korznikova, Elena A.; Chetverikov, Alexander P.; Zhou, Kun; Dmitriev, Sergey V.

2017-11-01

Linear and nonlinear dynamics of hexagonal boron nitride (h-BN) lattice is studied by means of molecular dynamics simulations with the use of the Tersoff interatomic potentials. It is found that sufficiently large homogeneous elastic strain along zigzag direction opens a wide gap in the phonon spectrum. Extended vibrational mode with boron and nitrogen sublattices vibrating in-plane as a whole in strained h-BN has frequency within the phonon gap. This fact suggests that a nonlinear spatially localized vibrational mode with frequencies in the phonon gap, called discrete breather (also often termed as intrinsic localized mode), can be excited. Properties of the gap discrete breathers in strained h-BN are contrasted with that for analogous vibrational mode found earlier in strained graphene. It is found that h-BN modeled with the Tersoff potentials does not support transverse discrete breathers.

Boron nitride nanotube-enhanced osteogenic differentiation of mesenchymal stem cells.

PubMed

Li, Xia; Wang, Xiupeng; Jiang, Xiangfen; Yamaguchi, Maho; Ito, Atsuo; Bando, Yoshio; Golberg, Dmitri

2016-02-01

The interaction between boron nitride nanotubes (BNNTs) layer and mesenchymal stem cells (MSCs) is evaluated for the first time in this study. BNNTs layer supports the attachment and growth of MSCs and exhibits good biocompatibility with MSCs. BNNTs show high protein adsorption ability, promote the proliferation of MSCs and increase the secretion of total protein by MSCs. Especially, BNNTs enhance the alkaline phosphatase (ALP) activity as an early marker of osteoblasts, ALP/total protein and osteocalcin (OCN) as a late marker of osteogenic differentiation, which shows that BNNTs can enhance osteogenesis of MSCs. The release of trace boron and the stress on cells exerted by BNNTs with a fiber structure may account for the enhanced differentiation of MSCs into osteoblasts. Therefore BNNTs are potentially useful for bone regeneration in orthopedic applications. © 2015 Wiley Periodicals, Inc.

Epitaxial hexagonal boron nitride on Ir(111): A work function template

NASA Astrophysics Data System (ADS)

Schulz, Fabian; Drost, Robert; Hämäläinen, Sampsa K.; Demonchaux, Thomas; Seitsonen, Ari P.; Liljeroth, Peter

2014-06-01

Hexagonal boron nitride (h-BN) is a prominent member in the growing family of two-dimensional materials with potential applications ranging from being an atomically smooth support for other two-dimensional materials to templating growth of molecular layers. We have studied the structure of monolayer h-BN grown by chemical vapor deposition on Ir(111) by low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) experiments and state-of-the-art density functional theory (DFT) calculations. The lattice mismatch between the h-BN and Ir(111) surface results in the formation of a moiré superstructure with a periodicity of ˜29 Å and a corrugation of ˜0.4 Å. By measuring the field emission resonances above the h-BN layer, we find a modulation of the work function within the moiré unit cell of ˜0.5 eV. DFT simulations for a 13-on-12 h-BN/Ir(111) unit cell confirm our experimental findings and allow us to relate the change in the work function to the subtle changes in the interaction between boron and nitrogen atoms and the underlying substrate atoms within the moiré unit cell. Hexagonal boron nitride on Ir(111) combines weak topographic corrugation with a strong work function modulation over the moiré unit cell. This makes h-BN/Ir(111) a potential substrate for electronically modulated thin film and heterosandwich structures.

Stable synthesis of few-layered boron nitride nanotubes by anodic arc discharge

DOE PAGES

Yeh, Yao-Wen; Raitses, Yevgeny; Koel, Bruce E.; ...

2017-06-08

Boron nitride nanotubes (BNNTs) were successfully synthesized by a dc arc discharge using a boron-rich anode as synthesis feedstock in a nitrogen gas environment at near atmospheric pressure. The synthesis was achieved independent of the cathode material suggesting that under such conditions the arc operates in so-called anodic mode with the anode material being consumed by evaporation due to the arc heating. In order to sustain the arc current by thermionic electron emission, the cathode has to be at sufficiently high temperature, which for a typical arc current density of similar to 100 A/cm 2, is above the boron meltingmore » point (2350 K). With both electrodes made from the same boron-rich alloy, we found that the arc operation unstable due to frequent sticking between two molten electrodes and formation of molten droplets. We achieved a stable and reliable arc operation and arc synthesis with the boronrich anode and the cathode made from a refractory metal which has a melting temperature above the melting point of boron. Ex-situ characterization of synthesized BNNTs with electron microscopy and Raman spectroscopy revealed that independent of the cathode material, the tubes are primarily single and double walled. Our results also show evidence of root-growth of BNNTs produced in the arc discharge.« less

Design of the magnetic homonuclear bonds boron nitride nanosheets using DFT methods.

PubMed

Anota, E Chigo; Hernández, A Bautista; Morales, A Escobedo; Castro, M

2017-06-01

Design and characterization of the structural, electronic, and magnetic properties of armchair boron-nitride, BN (B 27 N 27 H 18 ), nanosheets were performed by means of density functional theory all-electron calculations. The HSEh1PBE-GGA method together with 6-31G(d) basis sets were used. Non-stoichiometric B 30 N 24 H 18 and B 24 N 30 H 18 compositions: rich in boron or nitrogen atoms, forming homonuclear B or N bonds, respectively, were chosen. The obtained results reveal that these BN nanosheets reach structural stability in the anionic form, where semiconductor and magnetic behaviors are promoted. Effectively, the HOMO-LUMO gap is of 2.03 and 2.39eV, respectively and the magnetic moments are of 1.0 magneton bohrs, coming from the boron atoms in both systems. The rich in boron nanosheets present high-polarity, either in the gas phase or embedded in aqueous mediums like water, as well as low chemical reactivity, signifying potential applicability in the transportation of pharmaceutical species in biological mediums. These systems are also promising for the design of electronic devices, because they possess low-work functions, mainly arising from the homonuclear boron or nitrogen bond formation. Copyright © 2017 Elsevier Inc. All rights reserved.

Stable synthesis of few-layered boron nitride nanotubes by anodic arc discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yeh, Yao-Wen; Raitses, Yevgeny; Koel, Bruce E.

Boron nitride nanotubes (BNNTs) were successfully synthesized by a dc arc discharge using a boron-rich anode as synthesis feedstock in a nitrogen gas environment at near atmospheric pressure. The synthesis was achieved independent of the cathode material suggesting that under such conditions the arc operates in so-called anodic mode with the anode material being consumed by evaporation due to the arc heating. In order to sustain the arc current by thermionic electron emission, the cathode has to be at sufficiently high temperature, which for a typical arc current density of similar to 100 A/cm 2, is above the boron meltingmore » point (2350 K). With both electrodes made from the same boron-rich alloy, we found that the arc operation unstable due to frequent sticking between two molten electrodes and formation of molten droplets. We achieved a stable and reliable arc operation and arc synthesis with the boronrich anode and the cathode made from a refractory metal which has a melting temperature above the melting point of boron. Ex-situ characterization of synthesized BNNTs with electron microscopy and Raman spectroscopy revealed that independent of the cathode material, the tubes are primarily single and double walled. Our results also show evidence of root-growth of BNNTs produced in the arc discharge.« less

Ceramic-bonded abrasive grinding tools

DOEpatents

Holcombe, C.E. Jr.; Gorin, A.H.; Seals, R.D.

1994-11-22

Abrasive grains such as boron carbide, silicon carbide, alumina, diamond, cubic boron nitride, and mullite are combined with a cement primarily comprised of zinc oxide and a reactive liquid setting agent and solidified into abrasive grinding tools. Such grinding tools are particularly suitable for grinding and polishing stone, such as marble and granite.

Ceramic-bonded abrasive grinding tools

DOEpatents

Holcombe, Jr., Cressie E.; Gorin, Andrew H.; Seals, Roland D.

1994-01-01

Abrasive grains such as boron carbide, silicon carbide, alumina, diamond, cubic boron nitride, and mullite are combined with a cement primarily comprised of zinc oxide and a reactive liquid setting agent and solidified into abrasive grinding tools. Such grinding tools are particularly suitable for grinding and polishing stone, such as marble and granite.

Valley Physics in Non-Hermitian Artificial Acoustic Boron Nitride

NASA Astrophysics Data System (ADS)

Wang, Mudi; Ye, Liping; Christensen, J.; Liu, Zhengyou

2018-06-01

The valley can serve as a new degree of freedom in the manipulation of particles or waves in condensed matter physics, whereas systems containing combinations of gain and loss elements constitute rich building units that can mimic non-Hermitian properties. By introducing gain and loss in artificial acoustic boron nitride, we show that the acoustic valley states and the valley-projected edge states display exotic behaviors in that they sustain either attenuated or amplified wave propagation. Our findings show how non-Hermiticity introduces a mechanism in tuning topological protected valley transports, which may have significance in advanced wave control for sensing and communication applications.

Phase stability limit of c-BN under hydrostatic and non-hydrostatic pressure conditions

NASA Astrophysics Data System (ADS)

Xiao, Jianwei; Du, Jinglian; Wen, Bin; Melnik, Roderick; Kawazoe, Yoshiyuki; Zhang, Xiangyi

2014-04-01

Phase stability limit of cubic boron nitride (c-BN) has been investigated by the crystal structure search technique. It indicated that this limit is ˜1000 GPa at hydrostatic pressure condition. Above this pressure, c-BN turns into a metastable phase with respect to rocksalt type boron nitride (rs-BN). However, rs-BN cannot be retained at 0 GPa owing to its instability at pressure below 250 GPa. For non-hydrostatic pressure conditions, the phase stability limit of c-BN is substantially lower than that under hydrostatic pressure conditions and it is also dramatically different for other pressure mode.

One-pot synthesis of reduced graphene oxide@boron nitride nanosheet hybrids with enhanced oxidation-resistant properties

NASA Astrophysics Data System (ADS)

Sun, Guoxun; Bi, Jianqiang; Wang, Weili; Zhang, Jingde

2017-12-01

Reduced graphene oxide@boron nitride nanosheet (RGO@BNNS) hybrids were prepared for the first time using template-assisted autoclave pyrolysis technique at the temperature as low as 600 °C. The developed method can be scaled into gram-scale synthesis of the material. The BNNSs combine with RGO through van der Waals interplanar interaction without damaging the structures of RGO. Such ultrathin BNNSs on the surface of RGO can serve as high-performance oxidation-resistant coatings in oxidizing atmospheres at high temperatures. The RGO@BNNS hybrids can sustain up to 800 °C over a relatively long period of time.

Utilization of multiwalled boron nitride nanotubes for the reinforcement of lightweight aluminum ribbons

PubMed Central

2013-01-01

Multiwalled boron nitride nanotubes (BNNTs) have very attractive mechanical and thermal properties, e.g., elasticity, tensile strength, and high resistance to oxidation, and may be considered as ideal reinforcing agents in lightweight metal matrix composites. Herein, for the first time, Al-BNNT ribbons with various BNNT contents (up to 3 wt.%) were fabricated via melt spinning in an argon atmosphere. BNNTs were randomly dispersed within a microcrystalline Al matrix under ribbon casting and led to more than doubling of room-temperature ultimate tensile strength of the composites compared to pure Al ribbons produced at the similar conditions. PMID:23279813

Cellulose nanofibrils (CNF) filled boron nitride (BN) nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sulaiman, Hanisah Syed; Hua, Chia Chin; Zakaria, Sarani

In this study, nanocomposite using cellulose nanofibrils filled with different percentage of boron nitride (CNF-BN) were prepared. The objective of this research is to study the effect of different percentage of BN to the thermal conductivity of the nanocomposite produced. The CNF-BN nanocomposite were characterization by FT-IR, SEM and thermal conductivity. The FT-IR analysis of the CNF-BN nanocomposite shows all the characteristic peaks of cellulose and BN present in all samples. The dispersion of BN in CNF were seen through SEM analysis. The effect of different loading percentage of BN to the thermal conductivity of the nanocomposite were also investigated.

Submicron cubic boron nitride as hard as diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Guoduan; Kou, Zili, E-mail: kouzili@scu.edu.cn, E-mail: yanxz@hpstar.ac.cn; Lei, Li

Here, we report the sintering of aggregated submicron cubic boron nitride (sm-cBN) at a pressure of 8 GPa. The sintered cBN compacts exhibit hardness values comparable to that of single crystal diamond, fracture toughness about 5-fold that of cBN single crystal, in combination with a high oxidization temperature. Thus, another way has been demonstrated to improve the mechanical properties of cBN besides reducing the grain size to nano scale. In contrast to other ultrahard compacts with similar hardness, the sm-cBN aggregates are better placed for potential industrial application, as their relative low pressure manufacturing perhaps be easier and cheaper.

Phase stability limit of c-BN under hydrostatic and non-hydrostatic pressure conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Jianwei; Du, Jinglian; Wen, Bin, E-mail: wenbin@ysu.edu.cn

2014-04-28

Phase stability limit of cubic boron nitride (c-BN) has been investigated by the crystal structure search technique. It indicated that this limit is ∼1000 GPa at hydrostatic pressure condition. Above this pressure, c-BN turns into a metastable phase with respect to rocksalt type boron nitride (rs-BN). However, rs-BN cannot be retained at 0 GPa owing to its instability at pressure below 250 GPa. For non-hydrostatic pressure conditions, the phase stability limit of c-BN is substantially lower than that under hydrostatic pressure conditions and it is also dramatically different for other pressure mode.

Robust half-metallic ferromagnetism and curvature dependent magnetic coupling in fluorinated boron nitride nanotubes.

PubMed

Guo, Chunsheng; Zhou, Yu; Shi, Xin-Qiang; Gan, Li-Yong; Jiang, Hong; Zhao, Yong

2016-04-28

The fluorinated boron nitride (F-BN) nanostructures are found to be fully spin polarized and half-metallic by means of first-principles calculations based on the Heyd-Scuseria-Ernzerhof hybrid functional. It is found that the full spin polarization and 1 μB local moment in F-BN nanotubes are independent of tube radius and it is also robust in planar ribbons and sheets. The long-ranged ferromagnetic coupling between local moments decreases with decreasing tube radius. This suggests that F-BN systems with small local curvatures could be more easily experimentally observed and have greater potential applications in spin devices.

Superior thermal conductivity in suspended bilayer hexagonal boron nitride

PubMed Central

Wang, Chengru; Guo, Jie; Dong, Lan; Aiyiti, Adili; Xu, Xiangfan; Li, Baowen

2016-01-01

We reported the basal-plane thermal conductivity in exfoliated bilayer hexagonal boron nitride h-BN that was measured using suspended prepatterned microstructures. The h-BN sample suitable for thermal measurements was fabricated by dry-transfer method, whose sample quality, due to less polymer residues on surfaces, is believed to be superior to that of PMMA-mediated samples. The measured room temperature thermal conductivity is around 484 Wm−1K−1(+141 Wm−1K−1/ −24 Wm−1K−1) which exceeds that in bulk h-BN, providing experimental observation of the thickness-dependent thermal conductivity in suspended few-layer h-BN. PMID:27142571

Thermally conductive tough flexible elastomers as composite of slide-ring materials and surface modified boron nitride particles via plasma in solution

NASA Astrophysics Data System (ADS)

Goto, Taku; Iida, Masaki; Tan, Helen; Liu, Chang; Mayumi, Koichi; Maeda, Rina; Kitahara, Koichi; Hatakeyama, Kazuto; Ito, Tsuyohito; Shimizu, Yoshiki; Yokoyama, Hideaki; Kimura, Kaoru; Ito, Kohzo; Hakuta, Yukiya; Terashima, Kazuo

2018-03-01

We have developed a thermally conductive flexible elastomer as a composite material with slide-ring (SR) materials and boron nitride (BN) particles surface-modified via plasma in solution. This composite shows excellent properties as a flexible insulator for thermal management. Surface modification of BN particles using plasma in solution increases the tensile strength, extension ratio at break, toughness, and rubber characteristics of the composites, compared to SR and non-modified BN, while the Young's modulus values are identical. Furthermore, the thermal conductivity also improved as a result of plasma surface modification.

Computational simulation of subatomic-resolution AFM and STM images for graphene/hexagonal boron nitride heterostructures with intercalated defects

NASA Astrophysics Data System (ADS)

Lee, Junsu; Kim, Minjung; Chelikowsky, James R.; Kim, Gunn

2016-07-01

Using ab initio density functional calculations, we predict subatomic-resolution atomic force microscopy (AFM) and scanning tunneling microscopy (STM) images of vertical heterostructures of graphene/hexagonal boron nitride (h-BN) with an intercalated metal atom (Li, K, Cr, Mn, Co, or Cu), and study the effects of the extrinsic metal defect on the interfacial coupling. We find that the structural deformation of the graphene/h-BN layer caused by the metal defect strongly affects the AFM images, whereas orbital hybridization between the metal defect and the graphene/h-BN layer characterizes the STM images.

Search for giant magnetic anisotropy in transition-metal dimers on defected hexagonal boron nitride sheet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J.; Wang, H.; Wu, R. Q., E-mail: wur@uci.edu

2016-05-28

Structural and magnetic properties of many transition-metal dimers embedded in a defected hexagonal boron nitride monolayer are investigated through density functional calculations to search for systems with magnetic anisotropy energies (MAEs) larger than 30meV. In particular, Ir–Ir@Dh–BN is found to have both large MAE (∼126 meV) and high structural stability against dissociation and diffusion, and it hence can serve as magnetic unit in spintronics and quantum computing devices. This giant MAE mainly results from the spin orbit coupling and the magnetization of the upper Ir atom, which is in a rather isolated environment.

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.

Spring Constants for Stacks of Curved Leaves of Pyrolytic Boron Nitride

NASA Technical Reports Server (NTRS)

Kaforey, M. L.; Deeb, C. W.; Matthiesen, D. H.

1999-01-01

Stacks of curved leaves of pyrolytic boron nitride (PBN) were deflected and the force versus deflection data was recorded. From this data, the spring constant for a given spring geometry (radius of curvature of a leaf, width of a leaf, thickness of a leaf, and number of leaves in the stack) was determined. These experiments were performed at room temperature, 500 C and 1000 C. However, temperature was not found to affect the spring constant. The measured values were generally within one order of magnitude of predictions made using a previously derived equation for a simply supported cylindrical section with a line force at the center.

Experimental identification of p-type conduction in fluoridized boron nitride nanotube

NASA Astrophysics Data System (ADS)

Zhao, Jing; Li, Wuxia; Tang, Chengchun; Li, Lin; Lin, Jing; Gu, Changzhi

2013-04-01

The transport properties of F-doped boron nitride nanotube (BNNT) top-gate field effect devices were investigated to demonstrate the realization of p-type BNNTs by F-doping. The drain current was found to increase substantially with the applied negative gate voltage, suggesting these devices persist significant field effect with holes predominated; it also suggests that F-doping remarkably modified the band gap with F atoms preferred to be absorbed on B sites. Parameters, including the resistivity, charge concentration, and mobility, were further retrieved from the I-V curves. Our results indicate that device characterization is an effective method to reveal the specific properties of BNNTs.

Electron transport in polycyclic aromatic hydrocarbons/boron nitride hybrid structures: density functional theory combined with the nonequilibrium Green's function.

PubMed

Panahi, S F K S; Namiranian, Afshin; Soleimani, Maryam; Jamaati, Maryam

2018-02-07

We investigate the electronic transport properties of two types of junction based on single polyaromatic hydrocarbons (PAHs) and PAHs embedded in boron nitride (h-BN) nanoribbons, using nonequilibrium Green's functions (NEGF) and density functional theory (DFT). In the PAH junctions, a Fano resonance line shape at the Fermi energy in the transport feature can be clearly seen. In hybrid junctions, structural asymmetries enable interactions between the electronic states, leading to observation of interface-based transport. Our findings reveal that the interface of PAH/h-BN strongly affects the transport properties of the structures.

Adsorption of cyanogen chloride on the surface of boron nitride nanotubes for CNCl sensing

NASA Astrophysics Data System (ADS)

Movlarooy, Tayebeh; Fadradi, Mahboobeh Amiri

2018-05-01

The adsorption of CNCl gas, on the surface of boron nitride nanotubes in pure form, as well as doped with Al and Ga, based on the density functional theory (DFT) has been studied. The electron and structural properties of pristine and doped nanotubes have been investigated. By calculating the adsorption energy, the most stable positions and the equilibrium distance are obtained, and charge transferred and electronic properties have been calculated. The most stable molecule adsorption position for pure nanotube is obtained at the center of the hexagon and for doped nanotube above the impurity atom from N side.

Hall effects on peristalsis of boron nitride-ethylene glycol nanofluid with temperature dependent thermal conductivity

NASA Astrophysics Data System (ADS)

Abbasi, F. M.; Gul, Maimoona; Shehzad, S. A.

2018-05-01

Current study provides a comprehensive numerical investigation of the peristaltic transport of boron nitride-ethylene glycol nanofluid through a symmetric channel in presence of magnetic field. Significant effects of Brownian motion and thermophoresis have been included in the energy equation. Hall and Ohmic heating effects are also taken into consideration. Resulting system of non-linear equations is solved numerically using NDSolve in Mathematica. Expressions for velocity, temperature, concentration and streamlines are derived and plotted under the assumption of long wavelength and low Reynolds number. Influence of various parameters on heat and mass transfer rates have been discussed with the help of bar charts.

Signatures of Phonon and Defect-Assisted Tunneling in Planar Metal-Hexagonal Boron Nitride-Graphene Junctions.

PubMed

Chandni, U; Watanabe, K; Taniguchi, T; Eisenstein, J P

2016-12-14

Electron tunneling spectroscopy measurements on van der Waals heterostructures consisting of metal and graphene (or graphite) electrodes separated by atomically thin hexagonal boron nitride tunnel barriers are reported. The tunneling conductance, dI/dV, at low voltages is relatively weak, with a strong enhancement reproducibly observed to occur at around |V| ≈ 50 mV. While the weak tunneling at low energies is attributed to the absence of substantial overlap, in momentum space, of the metal and graphene Fermi surfaces, the enhancement at higher energies signals the onset of inelastic processes in which phonons in the heterostructure provide the momentum necessary to link the Fermi surfaces. Pronounced peaks in the second derivative of the tunnel current, d 2 I/dV 2 , are observed at voltages where known phonon modes in the tunnel junction have a high density of states. In addition, features in the tunneling conductance attributed to single electron charging of nanometer-scale defects in the boron nitride are also observed in these devices. The small electronic density of states of graphene allows the charging spectra of these defect states to be electrostatically tuned, leading to "Coulomb diamonds" in the tunneling conductance.

Thin-film preparation by back-surface irradiation pulsed laser deposition using metal powder targets

NASA Astrophysics Data System (ADS)

Kawasaki, Hiroharu; Ohshima, Tamiko; Yagyu, Yoshihito; Ihara, Takeshi; Yamauchi, Makiko; Suda, Yoshiaki

2017-01-01

Several kinds of functional thin films were deposited using a new thin-film preparation method named the back-surface irradiation pulsed laser deposition (BIPLD) method. In this BIPLD method, powder targets were used as the film source placed on a transparent target holder, and then a visible-wavelength pulsed laser was irradiated from the holder side to the substrate. Using this new method, titanium oxide and boron nitride thin films were deposited on the silicon substrate. Surface scanning electron microscopy (SEM) images suggest that all of the thin films were deposited on the substrate with some large droplets irrespective of the kind of target used. The deposition rate of the films prepared by using this method was calculated from film thickness and deposition time to be much lower than that of the films prepared by conventional PLD. X-ray diffraction (XRD) measurement results suggest that rutile and anatase TiO2 crystal peaks were formed for the films prepared using the TiO2 rutile powder target. Crystal peaks of hexagonal boron nitride were observed for the films prepared using the boron nitride powder target. The crystallinity of the prepared films was changed by annealing after deposition.

Effects of deposition temperature and ammonia flow on metal-organic chemical vapor deposition of hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Rice, Anthony; Allerman, Andrew; Crawford, Mary; Beechem, Thomas; Ohta, Taisuke; Spataru, Catalin; Figiel, Jeffrey; Smith, Michael

2018-03-01

The use of metal-organic chemical vapor deposition at high temperature is investigated as a means to produce epitaxial hexagonal boron nitride (hBN) at the wafer scale. Several categories of hBN films were found to exist based upon precursor flows and deposition temperature. Low, intermediate, and high NH3 flow regimes were found to lead to fundamentally different deposition behaviors. The low NH3 flow regimes yielded discolored films of boron sub-nitride. The intermediate NH3 flow regime yielded stoichiometric films that could be deposited as thick films. The high NH3 flow regime yielded self-limited deposition with thicknesses limited to a few mono-layers. A Langmuir-Hinshelwood mechanism is proposed to explain the onset of self-limited behavior for the high NH3 flow regime. Photoluminescence characterization determined that the intermediate and high NH3 flow regimes could be further divided into low and high temperature behaviors with a boundary at 1500 °C. Films deposited with both high NH3 flow and high temperature exhibited room temperature free exciton emission at 210 nm and 215.9 nm.

Boron Nitride-supported Sub-nanometer Pd 6 Clusters for Formic Acid Decomposition: A DFT Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schimmenti, Roberto; Cortese, Remedios; Duca, Dario

A periodic, self-consistent planewave DFT study was carried out to explore the potential use of Pd 6 clusters supported on a boron nitride sheet as a catalyst for the selective decomposition of formic acid (HCOOH) to CO 2 and H 2. The competition between formate (HCOO) and carboxyl (COOH) paths on catalytic sites, with different proximities to the support, was studied. Based on energetics alone, the reaction may mainly follow the HCOO route. Slightly lower activation energies were found at the lateral sites of the cluster as compared to top face sites. This is particularly true for the bidentate tomore » monodentate HCOO conversion. Through comparison of results with similar studies on HCOOH decomposition on extended Pd surfaces, it was demonstrated that the existence of undercoordinated sites in the sub-nanometer cluster could play a key role in preferentially stabilizing HCOO over COOH, which is a common CO precursor in this reaction. A hydrogen spillover mechanism was also investigated; migration toward the boron nitride support is not favorable, at least in the early stages of the reaction. However, hydrogen diffusion on the cluster has low barriers compared to those involved in formic acid decomposition.« less

Boron Nitride-supported Sub-nanometer Pd 6 Clusters for Formic Acid Decomposition: A DFT Study

DOE PAGES

Schimmenti, Roberto; Cortese, Remedios; Duca, Dario; ...

2017-04-25

A periodic, self-consistent planewave DFT study was carried out to explore the potential use of Pd 6 clusters supported on a boron nitride sheet as a catalyst for the selective decomposition of formic acid (HCOOH) to CO 2 and H 2. The competition between formate (HCOO) and carboxyl (COOH) paths on catalytic sites, with different proximities to the support, was studied. Based on energetics alone, the reaction may mainly follow the HCOO route. Slightly lower activation energies were found at the lateral sites of the cluster as compared to top face sites. This is particularly true for the bidentate tomore » monodentate HCOO conversion. Through comparison of results with similar studies on HCOOH decomposition on extended Pd surfaces, it was demonstrated that the existence of undercoordinated sites in the sub-nanometer cluster could play a key role in preferentially stabilizing HCOO over COOH, which is a common CO precursor in this reaction. A hydrogen spillover mechanism was also investigated; migration toward the boron nitride support is not favorable, at least in the early stages of the reaction. However, hydrogen diffusion on the cluster has low barriers compared to those involved in formic acid decomposition.« less

Toward Edge-Defined Holey Boron Nitride Nanosheets

NASA Technical Reports Server (NTRS)

Lin, Yi; Liao, Yunlong; Chen, Zhongfan; Connell, John W.

2015-01-01

"Holey" two-dimensional (2D) nanosheets with well-defined holy morphology and edge chemistry are highly desirable for applications such as energy storage, catalysis, sensing, transistors, and molecular transport/separation. For example, holey grapheme is currently under extensive investigation for energy storage applications because of the improvement in ion transport due to through the thickness pathways provided by the holes. Without the holes, the 2D materials have significant limitations for such applications in which efficient ion transport is important. As part of an effort to apply this approach to other 2D nanomaterials, a method to etch geometrically defined pits or holes on the basal plane surface of hexagonal boron nitride (h-BN) nanosheets has been developed. The etching, conducted via heating in ambient air using metal nanoparticles as catalysts, was facile, controllable, and scalable. Starting h-BN layered crystals were etched and subsequently exfoliated into boron nitride nanosheets (BNNSs). The as-etched and exfoliated h-BN nanosheets possessed defined pit and hole shapes that were comprised of regulated nanostructures at the edges. The current finding are the first step toward the bulk preparation of holey BNNSs with defined holes and edges.

Nanostructured Boron Nitride With High Water Dispersibility For Boron Neutron Capture Therapy

PubMed Central

Singh, Bikramjeet; Kaur, Gurpreet; Singh, Paviter; Singh, Kulwinder; Kumar, Baban; Vij, Ankush; Kumar, Manjeet; Bala, Rajni; Meena, Ramovatar; Singh, Ajay; Thakur, Anup; Kumar, Akshay

2016-01-01

Highly water dispersible boron based compounds are innovative and advanced materials which can be used in Boron Neutron Capture Therapy for cancer treatment (BNCT). Present study deals with the synthesis of highly water dispersible nanostructured Boron Nitride (BN). Unique and relatively low temperature synthesis route is the soul of present study. The morphological examinations (Scanning/transmission electron microscopy) of synthesized nanostructures showed that they are in transient phase from two dimensional hexagonal sheets to nanotubes. It is also supported by dual energy band gap of these materials calculated from UV- visible spectrum of the material. The theoretically calculated band gap also supports the same (calculated by virtual nano lab Software). X-ray diffraction (XRD) analysis shows that the synthesized material has deformed structure which is further supported by Raman spectroscopy. The structural aspect of high water disperse ability of BN is also studied. The ultra-high disperse ability which is a result of structural deformation make these nanostructures very useful in BNCT. Cytotoxicity studies on various cell lines (Hela(cervical cancer), human embryonic kidney (HEK-293) and human breast adenocarcinoma (MCF-7)) show that the synthesized nanostructures can be used for BNCT. PMID:27759052

Ammonium-tungstate-promoted growth of boron nitride nanotubes

NASA Astrophysics Data System (ADS)

E, Songfeng; Li, Chaowei; Li, Taotao; Geng, Renjie; Li, Qiulong; Lu, Weibang; Yao, Yagang

2018-05-01

Ammonium tungstate ((NH4)10W12O41 · xH2O) is a kind of oxygen-containing ammonium salt. The following study proves that it can be successfully used as a metal oxide alternative to produce boron oxide (B2O2) by oxidizing boron (B) in a traditional boron oxide chemical vapor deposition (BOCVD) process. This special oxidant promotes the simplistic fabrication of boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace, an outcome which may have resulted from its strong oxidizability. The experimental results demonstrate that the mole ratio of B and (NH4)10W12O41 · xH2O is a key parameter in determining the formation, quality and quantity of BNNTs when stainless steel is employed as a catalyst. We also found that Mg(NO3)2 and MgO nanoparticles (NPs) can be used as catalysts to grow BNNTs with the same precursor. The BNNTs obtained from the Mg(NO3)2 catalyst were straighter than those obtained from the MgO NP catalyst. This could have been due to the different physical forms of the catalysts that were used.

Ammonium-tungstate-promoted growth of boron nitride nanotubes.

PubMed

E, Songfeng; Li, Chaowei; Li, Taotao; Geng, Renjie; Li, Qiulong; Lu, Weibang; Yao, Yagang

2018-05-11

Ammonium tungstate ((NH 4 ) 10 W 12 O 41  · xH 2 O) is a kind of oxygen-containing ammonium salt. The following study proves that it can be successfully used as a metal oxide alternative to produce boron oxide (B 2 O 2 ) by oxidizing boron (B) in a traditional boron oxide chemical vapor deposition (BOCVD) process. This special oxidant promotes the simplistic fabrication of boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace, an outcome which may have resulted from its strong oxidizability. The experimental results demonstrate that the mole ratio of B and (NH 4 ) 10 W 12 O 41  · xH 2 O is a key parameter in determining the formation, quality and quantity of BNNTs when stainless steel is employed as a catalyst. We also found that Mg(NO 3 ) 2 and MgO nanoparticles (NPs) can be used as catalysts to grow BNNTs with the same precursor. The BNNTs obtained from the Mg(NO 3 ) 2 catalyst were straighter than those obtained from the MgO NP catalyst. This could have been due to the different physical forms of the catalysts that were used.

Nanostructured Boron Nitride With High Water Dispersibility For Boron Neutron Capture Therapy

NASA Astrophysics Data System (ADS)

Singh, Bikramjeet; Kaur, Gurpreet; Singh, Paviter; Singh, Kulwinder; Kumar, Baban; Vij, Ankush; Kumar, Manjeet; Bala, Rajni; Meena, Ramovatar; Singh, Ajay; Thakur, Anup; Kumar, Akshay

2016-10-01

Highly water dispersible boron based compounds are innovative and advanced materials which can be used in Boron Neutron Capture Therapy for cancer treatment (BNCT). Present study deals with the synthesis of highly water dispersible nanostructured Boron Nitride (BN). Unique and relatively low temperature synthesis route is the soul of present study. The morphological examinations (Scanning/transmission electron microscopy) of synthesized nanostructures showed that they are in transient phase from two dimensional hexagonal sheets to nanotubes. It is also supported by dual energy band gap of these materials calculated from UV- visible spectrum of the material. The theoretically calculated band gap also supports the same (calculated by virtual nano lab Software). X-ray diffraction (XRD) analysis shows that the synthesized material has deformed structure which is further supported by Raman spectroscopy. The structural aspect of high water disperse ability of BN is also studied. The ultra-high disperse ability which is a result of structural deformation make these nanostructures very useful in BNCT. Cytotoxicity studies on various cell lines (Hela(cervical cancer), human embryonic kidney (HEK-293) and human breast adenocarcinoma (MCF-7)) show that the synthesized nanostructures can be used for BNCT.

Modeling of Laser Vaporization and Plume Chemistry in a Boron Nitride Nanotube Production Rig

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.; Fay, Catharine C.

2012-01-01

Flow in a pressurized, vapor condensation (PVC) boron nitride nanotube (BNNT) production rig is modeled. A laser provides a thermal energy source to the tip of a boron ber bundle in a high pressure nitrogen chamber causing a plume of boron-rich gas to rise. The buoyancy driven flow is modeled as a mixture of thermally perfect gases (B, B2, N, N2, BN) in either thermochemical equilibrium or chemical nonequilibrium assuming steady-state melt and vaporization from a 1 mm radius spot at the axis of an axisymmetric chamber. The simulation is intended to define the macroscopic thermochemical environment from which boron-rich species, including nanotubes, condense out of the plume. Simulations indicate a high temperature environment (T > 4400K) for elevated pressures within 1 mm of the surface sufficient to dissociate molecular nitrogen and form BN at the base of the plume. Modifications to Program LAURA, a finite-volume based solver for hypersonic flows including coupled radiation and ablation, are described to enable this simulation. Simulations indicate that high pressure synthesis conditions enable formation of BN vapor in the plume that may serve to enhance formation of exceptionally long nanotubes in the PVC process.

Hard carbon nitride and method for preparing same

DOEpatents

Haller, Eugene E.; Cohen, Marvin L.; Hansen, William L.

1992-01-01

Novel crystalline .alpha. (silicon nitride-like)-carbon nitride and .beta. (silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate.

Hard carbon nitride and method for preparing same

DOEpatents

Haller, E.E.; Cohen, M.L.; Hansen, W.L.

1992-05-05

Novel crystalline [alpha](silicon nitride-like)-carbon nitride and [beta](silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate. 1 figure.

Phonon Transport at the Interfaces of Vertically Stacked Graphene and Hexagonal Boron Nitride Heterostructures

DOE PAGES

Yan, Zhequan; Chen, Liang; Yoon, Mina; ...

2016-01-12

Hexagonal boron nitride (h-BN) is a substrate for graphene based nano-electronic devices. We investigate the ballistic phonon transport at the interface of vertically stacked graphene and h-BN heterostructures using first principles density functional theory and atomistic Green's function simulations considering the influence of lattice stacking. We compute the frequency and wave-vector dependent transmission function and observe distinct stacking-dependent phonon transmission features for the h-BN/graphene/h-BN sandwiched systems. We find that the in-plane acoustic modes have the dominant contributions to the phonon transmission and thermal boundary conductance (TBC) for the interfaces with the carbon atom located directly on top of the boronmore » atom (C–B matched) because of low interfacial spacing. The low interfacial spacing is a consequence of the differences in the effective atomic volume of N and B and the difference in the local electron density around N and B. For the structures with the carbon atom directly on top of the nitrogen atom (C–N matched), the spatial distance increases and the contribution of in-plane modes to the TBC decreases leading to higher contributions by out-of-plane acoustic modes. We find that the C–B matched interfaces have stronger phonon–phonon coupling than the C–N matched interfaces, which results in significantly higher TBC (more than 50%) in the C–B matched interface. The findings in this study will provide insights to understand the mechanism of phonon transport at h-BN/graphene/h-BN interfaces, to better explain the experimental observations and to engineer these interfaces to enhance heat dissipation in graphene based electronic devices.« less

Investigation on stabilization of CO2 foam by ionic and nonionic surfactants in presence of different additives for application in enhanced oil recovery

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Mandal, Ajay

2017-10-01

Application of foam in upstream petroleum industry specifically in enhanced oil recovery (EOR) has gained significant interest in recent years. In view of this, an attempt has been paid to design the suitable foaming agents (foamer) by evaluating the influence of three surfactants, five nanoparticles and several additives. Experimental investigations have been carried out in order to examine the mechanism of foam generation in presence of sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and polysorbate 80 (Tween 80) as anionic, cationic and nonionic surfactants by using the CO2 as gaseous component. It has been found that ionic surfactants show the higher foam life compared to nonionic surfactant. Out of different nano particles used, namely alumina (Al2O3) zirconium oxide (ZrO2), calcium carbonate (CaCO3), boron nitride (BN) and silica (SiO2), boron nitride shows the maximum improvement of foam stability. The foam stability of surfactant-nanoparticles foam is further increased by addition of different additives viz. polymer, alcohol and alkali. The results show that, the designed foaming solution have nearly 2.5 times higher half-decay time (t1/2) compared to the simple surfactant system. Finally, it has been found that gas injection rate plays an important role in obtaining a uniform and stabilized foam.

Preparation of nanocrystalline TiN coated cubic boron nitride powders by a sol-gel process.

PubMed

Park, Hee S; Umer, M Adeel; Ryu, Ho J; Hong, Soon H

2011-01-01

Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO2, followed by nitridation with NH3 gas at 900 degrees C. Coating of TiO2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO(x) layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO2 phase through calcination in air at 400 degrees C. The crystallized TiO2 layer was 50 nm in thickness, and the size of TiO2 particles comprising the layer was nearly 10 nm. The TiO2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH3 gas.

Molecular dynamics simulations of trihalomethanes removal from water using boron nitride nanosheets.

PubMed

Azamat, Jafar; Khataee, Alireza; Joo, Sang Woo

2016-04-01

Molecular dynamics simulations were performed to investigate the separation of trihalomethanes (THMs) from water using boron nitride nanosheets (BNNSs). The studied systems included THM molecules and a functionalized BNNS membrane immersed in an aqueous solution. An external pressure was applied to the z axis of the systems. Two functionalized BNNSs with large fluorinated-hydrogenated pore (F-H-pores) and small hydrogen-hydroxyl pore (H-OH-pores) were used. The pores of the BNNS membrane were obtained by passivating each nitrogen and boron atoms at the pore edges with fluorine and hydrogen atoms in the large pore or with hydroxyl and hydrogen atoms in the small pore. The results show that the BNNS with a small functionalized pore was impermeable to THM molecules, in contrast to the BNNS with a large functionalized pore. Using these membranes, water contaminants can be removed at lower cost.

Introducing Overlapping Grain Boundaries in Chemical Vapor Deposited Hexagonal Boron Nitride Monolayer Films

PubMed Central

2017-01-01

We demonstrate the growth of overlapping grain boundaries in continuous, polycrystalline hexagonal boron nitride (h-BN) monolayer films via scalable catalytic chemical vapor deposition. Unlike the commonly reported atomically stitched grain boundaries, these overlapping grain boundaries do not consist of defect lines within the monolayer films but are composed of self-sealing bilayer regions of limited width. We characterize this overlapping h-BN grain boundary structure in detail by complementary (scanning) transmission electron microscopy techniques and propose a catalytic growth mechanism linked to the subsurface/bulk of the process catalyst and its boron and nitrogen solubilities. Our data suggest that the overlapping grain boundaries are comparatively resilient against deleterious pinhole formation associated with grain boundary defect lines and thus may reduce detrimental breakdown effects when polycrystalline h-BN monolayer films are used as ultrathin dielectrics, barrier layers, or separation membranes. PMID:28410557

Nanoscale adhesion interactions in carbon nanotube based systems and experimental study of the mechanical properties of carbon and boron nitride nanotubes

NASA Astrophysics Data System (ADS)

Zheng, Meng

Part I: Carbon nanotubes (CNTs) are a type of 1D nanostructures, which possess extraordinary mechanical, electrical, thermal, and chemical properties and are promising for a number of applications. For many of their applications, CNTs will be assembled into micro or macro-scale structures (e.g. thin-films and yarns), or integrated with other bulk materials to form heterogeneous material systems and devices (e.g. nanocomposites and solid-state electronics). The interfaces formed among CNTs themselves and between the CNT and other material surfaces play crucial roles in the functioning and performance of CNT-based material systems and devices. Therefore, characterization of the interfacial interaction in CNT-based systems is a critical step to understand the nanoscale interface and tune the system and device design and manufacturing for optimal functioning and performance. In this part of dissertation, a combination of both mechanical and theoretical methods was employed to study the adhesion interactions in CNT-based systems. Part II: Both CNTs and boron nitride nanotubes (BNNTs) possess superb mechanical properties and are promising for a great many applications. They can be used in similar applications, such as reinforcing fibers in polymer composites based on their similar mechanical and thermal properties. CNTs are promising for electronics and sensors while BNNTs can be used as electrical insulators due to the tremendous differences of the electrical property. Furthermore, BNNTs can survive in high temperature and hazardous environments because of their resistant to oxidation and harsh chemicals. In order to optimize their applications, their mechanical properties should be fully understood. In this part of the dissertation research, first, the radial elasticity of single-walled CNTs and BNNTs was investigated by means of atomic force microscopy (AFM); secondly, the engineering radial deformations in single walled CNTs and BNNTs covered by monolayer grapheme oxide (GO) is presented.

Finding the Stable Structures of WxN1-x with an ab-initio High-Throughput Approach

DTIC Science & Technology

2014-03-13

cubic boron nitride[4], carbonitrides,[5] and transition metal borides .[6, 7] Over the past several years there has been considerable theoretical...include ionic and covalent structures which seem chemically similar to W-N. These include borides , carbides, oxides, and other nitrides. In this paper we...metallic alloys, [23–27] we extended it to include over fifty new structures. These include nitrides, oxides, borides , and carbides. The important

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O

NASA Astrophysics Data System (ADS)

Kharlamov, Alexey; Bondarenko, Marina; Kharlamova, Ganna; Fomenko, Veniamin

2016-09-01

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C3N4. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists of weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets.

Investigation of the Optical, Electronic, and Structural Properties of Fiber Optic Glasses

DTIC Science & Technology

1993-06-01

H. Kawarada, and A. Hiraki , Proc. of MRS: Symp. in Diamond, Boron Nitride, Silicon Carbide and Related Wide Bandgap Semiconductors, eds. J.F. Glass...vacancy emission. This ,5Y. Yokota, H. Kawarada, and A. Hiraki , in Diamond, Boron Ni- observation is in accord with the interpretation of the tride

Synthesis and Characterization of Three Dimensional Nanostructures Based on Interconnected Carbon Nanomaterials

NASA Astrophysics Data System (ADS)

Koizumi, Ryota

This thesis addresses various types of synthetic methods for novel three dimensional nanomaterials and nanostructures based on interconnected carbon nanomaterials using solution chemistry and chemical vapor deposition (CVD) methods. Carbon nanotube (CNT) spheres with porous and scaffold structures consisting of interconnected CNTs were synthesized by solution chemistry followed by freeze-drying, which have high elasticity under nano-indentation tests. This allows the CNT spheres to be potentially applied to mechanical dampers. CNTs were also grown on two dimensional materials--such as reduced graphene oxide (rGO) and hexagonal boron nitride (h-BN)--by CVD methods, which are chemically interconnected. CNTs on rGO and h-BN interconnected structures performed well as electrodes for supercapacitors. Furthermore, unique interconnected flake structures of alpha-phase molybdenum carbide were developed by a CVD method. The molybdenum carbide can be used for a catalyst of hydrogen evolution reaction activity as well as an electrode for supercapacitors.

Consolidation of cubic and hexagonal boron nitride composites

DOE PAGES

Du Frane, W. L.; Cervantes, O.; Ellsworth, G. F.; ...

2015-12-08

When we Consolidate cubic boron nitride (cBN) it typically requires either a matrix of metal bearing materials that are undesirable for certain applications, or very high pressures within the cBN phase stability field that are prohibitive to manufacturing size and cost. We present new methodology for consolidating high stiffness cBN composites within a hexagonal boron nitride (hBN) matrix (15–25 vol%) with the aid of a binder phase (0–6 vol%) at moderate pressures (0.5–1.0 GPa) and temperatures (900–1300 °C). The composites are demonstrated to be highly tailorable with a range of compositions and resulting physical/mechanical properties. Ultrasonic measurements indicate that inmore » some cases these composites have elastic mechanical properties that exceed those of the highest strength steel alloys. Moreover, two methods were identified to prevent phase transformation of the metastable cBN phase into hBN during consolidation: 1. removal of hydrocarbons, and 2. increased cBN particle size. Lithium tetraborate worked better as a binder than boron oxide, aiding consolidation without enhancing cBN to hBN phase transformation kinetics. These powder mixtures consolidated within error of their full theoretical mass densities at 1 GPa, and had only slightly lower densities at 0.5 GPa. This shows potential for consolidation of these composites into larger parts, in a variety of shapes, at even lower pressures using more conventional manufacturing methods, such as hot-pressing.« less

Design of improved ceramic/polymeric composites

NASA Astrophysics Data System (ADS)

Seghi, Steven Monte

This thesis describes an optimized approach for fabrication of boron nitride matrix composites reinforced with carbon fibers. The boron nitride was introduced via liquid infiltration of borazine oligomer to obtain high density (rho ˜ 1.75g/cc) composites and d002 spacings of 3.35A, which afforded excellent hydrolytic stability. The friction and wear properties were explored using an inertial dynamometer for potential replacement of current C/C in aircraft brakes. One set of tested composites provided outstanding wear resistance, incurring nearly zero wear across the entire range tested. In contrast to C/C, the coefficient of friction (COF) was relatively stable with respect to energy level, varying only 0.2 to 0.3. The wear surface morphologies were examined and it was found that low volume BN composites wore by a mechanism similar to C/C. The wear rates were controlled by the formation of a friction film from the wear debris. In the case of BN composites, this film incurred wear via an abrasive and brittle fracture mechanism while C/C exhibited only abrasive wear. As the BN content increased, a film still formed from the debris but large particles of BN emerged that limited direct contact of the surfaces thus effectively eliminating abrasive wear so the underlying film wore via brittle fracture. The removed wear debris was easily reincorporated into the film, with the suspected aid of boron oxide, thus keeping the wear rates low. The last chapter deals with the design, fabrication, and evaluation of a new coupling agent for glass fiber/epoxy matrix composites. This interface consisted of a thin coating of activated carbon (ACI) with high surface area to take advantage of mechanical interlocking. Furthermore, the surface chemistry was modified to provide varying degrees of bonding to the resin. These ACI provided equivalent moduli when compared to similar composites using commercial coupling agents. Hygrothermal aging showed the basic surface chemistry ACI to be extremely resistant to mechanical property degradation. The ACI systems displayed two distinct failure modes, fiber/matrix fracture and fiber debonding, controlled by the interface strength and thus the surface chemistry. These different failure modes led to a damage evolution study via thermoelastic stress analysis.

Effect of Silica Nanoparticles on the Photoluminescence Properties of BCNO Phosphor

NASA Astrophysics Data System (ADS)

Nuryadin, Bebeh W.; Faryuni, Irfana Diah; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal, Khairurrijal

2011-12-01

Effect of additional silica nanoparticles on the photoluminescence (PL) performance of boron carbon oxy-nitride (BCNO) phosphor was investigated. As a precursor, boric acid and urea were used as boron and nitrogen sources, respectively. The carbon sources was polyethylene glycol (PEG) with average molecule weight 20000 g/mol.. Precursor solutions were prepared by mixing these raw materials in pure water, followed by stirring to achieve homogeneous solutions. In this precursor, silica nanoparticles were added at various mass ratio from 0 to 7 %wt in the solution. The precursors were then heated at 750 °C for 60 min in a ceramic crucible under atmospheric pressure. The photoluminescence (PL) spectrum that characterized by spectrophotometer showed a single, distinct, and broad emission band varied from blue to near red color, depend on the PEG, boric acid and urea ratio in the precursor. The addition of silica nanoparticles caused the increasing of PL intensity as well as the shifting of peak wavelength of PL spectrum. The peak shifting of PL was affected by the concentration of silica nanoparticles that added into the precursor. We believe that the BCNO-silica composite phosphor becomes a promising material for the phosphor conversion-based white light-emitting diodes.

Rebar graphene from functionalized boron nitride nanotubes.

PubMed

Li, Yilun; Peng, Zhiwei; Larios, Eduardo; Wang, Gunuk; Lin, Jian; Yan, Zheng; Ruiz-Zepeda, Francisco; José-Yacamán, Miguel; Tour, James M

2015-01-27

The synthesis of rebar graphene on Cu substrates is described using functionalized boron nitride nanotubes (BNNTs) that were annealed or subjected to chemical vapor deposition (CVD) growth of graphene. Characterization shows that the BNNTs partially unzip and form a reinforcing bar (rebar) network within the graphene layer that enhances the mechanical strength through covalent bonds. The rebar graphene is transferrable to other substrates without polymer assistance. The optical transmittance and conductivity of the hybrid rebar graphene film was tested, and a field effect transistor was fabricated to explore its electrical properties. This method of synthesizing 2D hybrid graphene/BN structures should enable the hybridization of various 1D nanotube and 2D layered structures with enhanced mechanical properties.

Electronic structure and optical properties of boron nitride nanotube bundles from first principles

NASA Astrophysics Data System (ADS)

Behzad, Somayeh

2015-06-01

The electronic and optical properties of bundled armchair and zigzag boron nitride nanotubes (BNNTs) are investigated by using density functional theory. Owing to the inter-tube coupling, the dispersions along the tube axis and in the plane perpendicular to the tube axis of BNNT bundles are significantly varied, which are characterized by the decrease of band gap, the splitting of the doubly degenerated states, the expansions of valence and conduction bands. The calculated dielectric functions of the armchair and zigzag bundles are similar to that of the isolated tubes, except for the appearance of broadened peaks, small shifts of peak positions about 0.1 eV and increasing of peak intensities.

Ultra-bright emission from hexagonal boron nitride defects as a new platform for bio-imaging and bio-labelling

NASA Astrophysics Data System (ADS)

Elbadawi, Christopher; Tran, Trong Toan; Shimoni, Olga; Totonjian, Daniel; Lobo, Charlene J.; Grosso, Gabriele; Moon, Hyowan; Englund, Dirk R.; Ford, Michael J.; Aharonovich, Igor; Toth, Milos

2016-12-01

Bio-imaging requires robust ultra-bright probes without causing any toxicity to the cellular environment, maintain their stability and are chemically inert. In this work we present hexagonal boron nitride (hBN) nanoflakes which exhibit narrowband ultra-bright single photon emitters1. The emitters are optically stable at room temperature and under ambient environment. hBN has also been noted to be noncytotoxic and seen significant advances in functionalization with biomolecules2,3. We further demonstrate two methods of engineering this new range of extremely robust multicolour emitters across the visible and near infrared spectral ranges for large scale sensing and biolabeling applications.

Phase controlled homodyne infrared near-field microscopy and spectroscopy reveal inhomogeneity within and among individual boron nitride nanotubes.

PubMed

Xu, Xiaoji G; Tanur, Adrienne E; Walker, Gilbert C

2013-04-25

We propose a practical method to obtain near-field infrared absorption spectra in apertureless near-field scanning optical microscopy (aNSOM) through homodyne detection with a specific choice of reference phase. The underlying mechanism of the method is illustrated by theoretical and numeric models to show its ability to obtain absorptive rather than dispersive profiles in near-field infrared vibrational microscopy. The proposed near-field nanospectroscopic method is applied to obtain infrared spectra from regions of individual multiwall boron nitride nanotubes (BNNTs) in spatial regions smaller than the diffraction limit of the light source. The spectra suggest variations in interwall spacing within the individual tubes probed.

Evidence for Defect-Mediated Tunneling in Hexagonal Boron Nitride-Based Junctions.

PubMed

Chandni, U; Watanabe, K; Taniguchi, T; Eisenstein, J P

2015-11-11

We investigate electron tunneling through atomically thin layers of hexagonal boron nitride (hBN). Metal (Cr/Au) and semimetal (graphite) counter-electrodes are employed. While the direct tunneling resistance increases nearly exponentially with barrier thickness as expected, the thicker junctions also exhibit clear signatures of Coulomb blockade, including strong suppression of the tunnel current around zero bias and step-like features in the current at larger biases. The voltage separation of these steps suggests that single-electron charging of nanometer-scale defects in the hBN barrier layer are responsible for these signatures. We find that annealing the metal-hBN-metal junctions removes these defects and the Coulomb blockade signatures in the tunneling current.

Elastic deformation of helical-conical boron nitride nanotubes

NASA Astrophysics Data System (ADS)

Xu, F. F.; Bando, Y.; Golberg, D.; Ma, R. Z.; Li, Y. B.; Tang, C. C.

2003-08-01

Boron nitride nanotubes with hollow conical-helix geometry have exhibited striking flexibility and elasticity comparable to metals. During an electron-beam induced deformation at room temperature, the nanotubes can be bent by a maximum angle as high as 180° and then retrieve the starting morphology without any evidence of structural failure. The outstanding low-temperature elasticity in this nano-material is interpreted by a theoretical model, displaying deformation processes dominated by slide of filaments along with changes in apex angles stepwise. The specific tubular geometry is believed to take advantages of both high stiffness and extraordinary flexibility of BN filaments, and easiness of interlayer slide in graphitic structure, hence leading to high resistance to fracture.

Thickness determination of few-layer hexagonal boron nitride films by scanning electron microscopy and Auger electron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutter, P., E-mail: psutter@bnl.gov; Sutter, E.

2014-09-01

We assess scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) for thickness measurements on few-layer hexagonal boron nitride (h-BN), the layered dielectric of choice for integration with graphene and other two-dimensional materials. Observations on h-BN islands with large, atomically flat terraces show that the secondary electron intensity in SEM reflects monolayer height changes in films up to least 10 atomic layers thickness. From a quantitative analysis of AES data, the energy-dependent electron escape depth in h-BN films is deduced. The results show that AES is suitable for absolute thickness measurements of few-layer h-BN of 1 to 6 layers.

Magnetic tunnel junctions with monolayer hexagonal boron nitride tunnel barriers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piquemal-Banci, M.; Galceran, R.; Bouzehouane, K.

We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.

Scanning Tunneling Spectroscopy of Potassium on Graphene

NASA Astrophysics Data System (ADS)

Cormode, Daniel; Leroy, Brian; Yankowitz, Matthew

2012-02-01

We investigate the effect of charged impurities on the electronic properties of large single crystal CVD grown graphene using scanning tunneling microscopy. Mono- and multilayer crystals were prepared by transferring graphene from copper onto exfoliated boron nitride flakes on 300 nm SiO2 substrates. The boron nitride provides an ultra flat surface for the graphene. Potassium atoms are controllably deposited on the graphene at low temperature by heating a nearby getter source. Scanning tunneling spectroscopy and transport measurements were performed in ultra high vacuum at 4.5 K. Transport measurements demonstrate the shifting of the Dirac point as the samples are doped, while STM measurements demonstrate the size, arrangement and local electronic influence of the potassium atoms.

Interface amorphization in hexagonal boron nitride films on sapphire substrate grown by metalorganic vapor phase epitaxy

NASA Astrophysics Data System (ADS)

Yang, Xu; Nitta, Shugo; Pristovsek, Markus; Liu, Yuhuai; Nagamatsu, Kentaro; Kushimoto, Maki; Honda, Yoshio; Amano, Hiroshi

2018-05-01

Hexagonal boron nitride (h-BN) films directly grown on c-plane sapphire substrates by pulsed-mode metalorganic vapor phase epitaxy exhibit an interlayer for growth temperatures above 1200 °C. Cross-sectional transmission electron microscopy shows that this interlayer is amorphous, while the crystalline h-BN layer above has a distinct orientational relationship with the sapphire substrate. Electron energy loss spectroscopy shows the energy-loss peaks of B and N in both the amorphous interlayer and the overlying crystalline h-BN layer, while Al and O signals are also seen in the amorphous interlayer. Thus, the interlayer forms during h-BN growth through the decomposition of the sapphire at elevated temperatures.

Study of electronic and magnetic properties of h-BN on Ni surfaces: A DFT approach

NASA Astrophysics Data System (ADS)

Sahoo, M. R.; Sahu, S.; Kushwaha, A. K.; Nayak, S.

2018-04-01

Hexagonal boron nitride (h-BN) is a promising material for implementation in spintronics due to large band gap, low spin-orbit coupling, and a small lattice mismatch to graphene and close-packedsurfaces of fcc-Ni(111). Electronic and magnetic properties of single layer hexagonal Boron Nitride (h-BN) on Ni (111) surface have been studied with density functional calculation. Since lattice constants of nickel surfaces are very close to that of h-BN, nickel acts as a good substrate. We found that the interaction between 2Pz - 3dz2 orbitals leads to change in electronic band structure as well as density of states which results spin polarization in h-BN.

Adhesion, friction, and deformation of ion-beam-deposited boron nitride films

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Buckley, Donald H.; Alterovitz, Samuel A.; Pouch, John J.; Liu, David C.

1987-01-01

The tribological properties and mechanical strength of boron nitride films were investigated. The BN films were predominantly amorphous and nonstoichiometric and contained small amounts of oxides and carbides. It was found that the yield pressure at full plasticity, the critical load to fracture, and the shear strength of interfacial adhesive bonds (considered as adhesion) depended on the type of metallic substrate on which the BN was deposited. The harder the substrate, the greater the critical load and the adhesion. The yield pressures of the BN film were 12 GPa for the 440C stainless steel substrate, 4.1 GPa for the 304 stainless steel substrate, and 3.3 GPa for the titanium substrate.

Adhesion, friction and deformation of ion-beam-deposited boron nitride films

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Alterovitz, S. A.; Pouch, J. J.; Liu, D. C.

1987-01-01

The tribological properties and mechanical strength of boron nitride films were investigated. The BN films were predominantly amorphous and nonstoichiometric and contained small amounts of oxides and carbides. It was found that the yield pressure at full plasticity, the critical load to fracture, and the shear strength of interfacial adhesive bonds (considered as adhesion) depended on the type of metallic substrate on which the BN was deposited. The harder the substrate, the greater the critical load and the adhesion. The yield pressures of the BN film were 12 GPa for the 440C stainless steel substrate, 4.1 GPa for the 304 stainless steel substrate, and 3.3 GPa for the titanium substrate.

Adhesion and friction of transition metals in contact with nonmetallic hard materials

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1981-01-01

Sliding friction experiments were conducted with the metals yttrium, titanium, tantalum, zirconium, vanadium, neodymium, iron, cobalt, nickel, tungsten, platinum, rhenium, ruthenium, and rhodium in sliding contact with single crystal diamond, silicon carbide, pyrolytic boron nitride, and ferrite. Auger electron spectroscopy analysis was conducted with the metals and nonmetals to determine the surface chemistry and the degree of surface cleanliness. The results of the investigation indicate the adhesion and friction of the transition metals in contact with diamond, silicon carbide, boron nitride, and ferrite are related to the relative chemical activity of the metals. The more chemically active the metal, the higher the coefficient of friction and the greater amount of transfer to the nonmetals.

Energetics and formation mechanism of borders between hexagonal boron nitride and graphene

NASA Astrophysics Data System (ADS)

Sawahata, Hisaki; Yamanaka, Ayaka; Maruyama, Mina; Okada, Susumu

2018-06-01

We studied the energetics of two-dimensional heterostructures consisting of hexagonal boron nitride (h-BN) and graphene with respect to the border structure and heterobond species using density functional theory. A BC heterobond is energetically preferable at the border between h-BN and graphene. We also found that the polarization at the zigzag border increases the total energy of the heterostructures. Competition between the bond formation energy and the polarization energy leads to chiral borders at which BC heterobonds are dominant. By taking the formation process of the heterostructures into account, the zigzag border with BC heterobonds is found to be preferentially synthesized from graphene edges under hydrogen-rich conditions.

Intraband Raman laser gain in a boron nitride coupled quantum well

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moorthy, N. Narayana; Peter, A. John, E-mail: a.john.peter@gmail.com

2016-05-23

On-centre impurity related electronic and optical properties are studied in a Boron nitride coupled quantum well. Confined energies for the intraband transition are investigated by studying differential cross section of electron Raman scattering taking into consideration of spatial confinement in a B{sub 0.3}Ga{sub 0.7}N/BN coupled quantum well. Raman gain as a function of incident optical pump intensity is computed for constant well width. The enhancement of Raman gain is observed with the application of pump power. The results can be applied for the potential applications for fabricating some optical devices such as optical switches, infrared photo-detectors and electro-optical modulator.

Static tensile and tensile creep testing of four boron nitride coated ceramic fibers at elevated temperatures

NASA Technical Reports Server (NTRS)

Coguill, Scott L.; Adams, Donald F.; Zimmerman, Richard S.

1989-01-01

Six types of uncoated ceramic fibers were static tensile and tensile creep tested at various elevated temperatures. Three types of boron nitride coated fibers were also tested. Room temperature static tensile tests were initially performed on all fibers, at gage lengths of 1, 2, and 4 inches, to determine the magnitude of end effects from the gripping system used. Tests at one elevated temperature, at gage lengths of 8 and 10 inches, were also conducted, to determine end effects at elevated temperatures. Fiber cross sectional shapes and areas were determined using scanning electron microscopy. Creep testing was typically performed for 4 hours, in an air atmosphere.

Structure of Boron Nitride Nanotubes: Tube Closing Vs. Chirality

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Menon, Madhu

1998-01-01

The structure of boron nitride nanotubes is investigated using a generalized tight-binding molecular dynamics method. It is shown that dynamic relaxation results in a wavelike or "rippled" surface in which the B atoms rotate inward and the N atoms move outward, reminiscent of the surface relaxation of the III-V semiconductors. More importantly, the three different morphologies of the tube closing with flat, conical and amorphous ends, as observed in experiments, are shown to be directly related to the tube chiralities. The abundance of flat end tubes observed in experiments is, thus, shown to be an indication of the greater stability of "zig-zag" BN tubes over the "arm-chair" tubes under experimental conditions.

Diamond Nucleation of Surfaces Using Carbon Clusters

DTIC Science & Technology

1993-05-01

8217 den lotafC 0, OAF e ol (*(.Pt 01If CZ.,,C :A 4 C.d,^; flt.0"$ j .n to, thl 0..eftC TO 440?.NqtOn -44sca.’lie’l eon Ofttlo tt 0( tl O Af~tO o0V614...is used to keep the sample in place. The cap is made of either graphite, quartz, or boron nitride depending on the particular experiment. In this...John, P., Alvarez, M.M., Diederich, F., and Whetten, R.L., J. Phys. Chem. in press (1991). 40 44. Zhang, Q.L., 0’ Brien , S.C., Heath, J.R., Liu, Y

Generation of ultrashort pulses with minimum duration of 90\\ {\\text{fs}} in a hybrid mode-locked erbium-doped all-fibre ring laser

NASA Astrophysics Data System (ADS)

Dvoretskiy, D. A.; Sazonkin, S. G.; Voropaev, V. S.; Negin, M. A.; Leonov, S. O.; Pnev, A. B.; Karasik, V. E.; Denisov, L. K.; Krylov, A. A.; Davydov, V. A.; Obraztsova, E. D.

2016-11-01

Regimes of ultrashort pulse generation in an erbium-doped all-fibre ring laser with hybrid mode locking based on single-wall carbon - boron nitride nanotubes and the nonlinear Kerr effect in fibre waveguides are studied. Stable dechirped ultrashort pulses are obtained with a duration of ˜ 90 {\\text{fs}}, a repetition rate of ˜ 42.2 {\\text{MHz}}, and an average output power of ˜ 16.7 {\\text{mW}}, which corresponds to a pulse energy of ˜ 0.4 {\\text{nJ}} and a peak laser power of ˜ 4.4 {\\text{kW}}.

The first true inorganic fullerenes?

NASA Astrophysics Data System (ADS)

Parilla, P. A.; Dillon, A. C.; Jones, K. M.; Riker, G.; Schulz, D. L.; Ginley, D. S.; Heben, M. J.

1999-01-01

Boron nitride and materials of composition MX2, where M is molybdenum or tungsten and X is sulphur or selenium, can form fullerene-like structures such as nested polyhedra or nanotubes. However, the analogy to the carbon fullerene family falls short because no small preferred structure akin to C60(ref. 5) has been found. We have discovered nano-octahedra of MoS2of discrete sizes in soots that we prepared by laser ablation of pressed MoS2targets. These nano-octahedra are much larger than C60structures, having edge lengths of about 4.0 and 5.0 nanometres, and may represent the first `inorganic fullerenes'.

Bulk superhard B-C-N nanocomposite compact and method for preparing thereof

DOEpatents

Zhao, Yusheng; He, Duanwei

2004-07-06

Bulk, superhard, B-C-N nanocomposite compact and method for preparing thereof. The bulk, superhard, nanocomposite compact is a well-sintered compact and includes nanocrystalline grains of at least one high-pressure phase of B-C-N surrounded by amorphous diamond-like carbon grain boundaries. The bulk compact has a Vicker's hardness of about 41-68 GPa. It is prepared by ball milling a mixture of graphite and hexagonal boron nitride, encapsulating the ball-milled mixture, and sintering the encapsulated ball-milled mixture at a pressure of about 5-25 GPa and at a temperature of about 1000-2500 K.

Transition metal carbides, nitrides and borides, and their oxygen containing analogs useful as water gas shift catalysts

DOEpatents

Thompson, Levi T.; Patt, Jeremy; Moon, Dong Ju; Phillips, Cory

2003-09-23

Mono- and bimetallic transition metal carbides, nitrides and borides, and their oxygen containing analogs (e.g. oxycarbides) for use as water gas shift catalysts are described. In a preferred embodiment, the catalysts have the general formula of M1.sub.A M2.sub.B Z.sub.C O.sub.D, wherein M1 is selected from the group consisting of Mo, W, and combinations thereof; M2 is selected from the group consisting of Fe, Ni, Cu, Co, and combinations thereof; Z is selected from the group consisting of carbon, nitrogen, boron, and combinations thereof; A is an integer; B is 0 or an integer greater than 0; C is an integer; O is oxygen; and D is 0 or an integer greater than 0. The catalysts exhibit good reactivity, stability, and sulfur tolerance, as compared to conventional water shift gas catalysts. These catalysts hold promise for use in conjunction with proton exchange membrane fuel cell powered systems.

High-purity production of ultrathin boron nitride nanosheets via shock chilling and their enhanced mechanical performance and transparency in nanocomposite hydrogels.

PubMed

Sun, Zemin; Lin, Liu; Yuan, Mengwei; Li, Huifeng; Sun, Genban; Ma, Shulan; Yang, Xiaojing

2018-05-25

A simple, highly efficient, and eco-friendly method is prepared to divide bulk boron nitride (BN) into boron nitride nanosheets (BNNSs). Due to the anisotropy of the hexagonal BN expansion coefficient, bulk BN is exfoliated utilizing the rapid and tremendous change in temperature, the extreme gasification of water, and ice thermal expansion pressure under freeze drying. The thickness of most of the BNNSs was less than ∼3 nm with a yield of 12-16 wt%. The as-obtained BNNS/polyacrylamide (PAAm) composite hydrogels exhibited outstanding mechanical properties. The tensile strength is fives times the bulk of the BN/PAAm composite hydrogels and the elongations are more than nine-fold the bulk of the BN/PAAm composite hydrogels. The BNNS/PAAm nanocomposite hydrogels also exhibited excellent elastic recovery, and the hysteresis of the BNNS nanocomposite hydrogels was negligible even after 30 cycles with a maximum tensile strain (ε max ) of 700%. This work provides new insight into the fabrication of BN/polymer nanocomposites utilizing the excellent mechanical properties and transparency of BN. The results confirm that a few layers of BNNSs can also efficiently and directly improve the mechanical properties of composite polymer due to its stronger surface free energy and better wettability.

Shockwave Processing of Composite Boron and Titanium Nitride Powders

NASA Astrophysics Data System (ADS)

Beason, Matthew T.; Gunduz, I. Emre; Mukasyan, Alexander S.; Son, Steven F.

2015-06-01

Shockwave processing of powders has been shown to initiate reactions between condensed phase reactants. It has been observed that these reactions can occur at very short timescales, resulting in chemical reactions occurring at a high pressure state. These reactions have the potential to produce metastable phases. Kinetic limitations prevent gaseous reactants from being used in this type of synthesis reaction. To overcome this limitation, a solid source of gaseous reactants must be used. An example of this type of reaction is the nitrogen exchange reaction (e.g. B + TiN, B + Si3N4 etc.). In these reactions nitrogen is ``carried'' by a material that can be then reduced by the second reactant. This work explores the possibility of using nitrogen exchange reactions to synthesize the cubic phase of boron nitride (c-BN) through shockwave processing of ball milled mixtures of boron and titanium nitride. The heating from the passage of the shock wave (pore collapse, plastic work, etc.) combined with thermochemical energy from the reaction may provide a means to synthesize c-BN. This material is based upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number(s) DE-NA0002377. National Defense Science & Engineering Graduate Fellowship (NDSEG), 32 CFR 168a.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope.

PubMed

Govyadinov, Alexander A; Konečná, Andrea; Chuvilin, Andrey; Vélez, Saül; Dolado, Irene; Nikitin, Alexey Y; Lopatin, Sergei; Casanova, Fèlix; Hueso, Luis E; Aizpurua, Javier; Hillenbrand, Rainer

2017-07-21

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

High-purity production of ultrathin boron nitride nanosheets via shock chilling and their enhanced mechanical performance and transparency in nanocomposite hydrogels

NASA Astrophysics Data System (ADS)

Sun, Zemin; Lin, Liu; Yuan, Mengwei; Li, Huifeng; Sun, Genban; Ma, Shulan; Yang, Xiaojing

2018-05-01

A simple, highly efficient, and eco-friendly method is prepared to divide bulk boron nitride (BN) into boron nitride nanosheets (BNNSs). Due to the anisotropy of the hexagonal BN expansion coefficient, bulk BN is exfoliated utilizing the rapid and tremendous change in temperature, the extreme gasification of water, and ice thermal expansion pressure under freeze drying. The thickness of most of the BNNSs was less than ∼3 nm with a yield of 12–16 wt%. The as-obtained BNNS/polyacrylamide (PAAm) composite hydrogels exhibited outstanding mechanical properties. The tensile strength is fives times the bulk of the BN/PAAm composite hydrogels and the elongations are more than nine-fold the bulk of the BN/PAAm composite hydrogels. The BNNS/PAAm nanocomposite hydrogels also exhibited excellent elastic recovery, and the hysteresis of the BNNS nanocomposite hydrogels was negligible even after 30 cycles with a maximum tensile strain (ε max) of 700%. This work provides new insight into the fabrication of BN/polymer nanocomposites utilizing the excellent mechanical properties and transparency of BN. The results confirm that a few layers of BNNSs can also efficiently and directly improve the mechanical properties of composite polymer due to its stronger surface free energy and better wettability.

Toxicity evaluation of boron nitride nanospheres and water-soluble boron nitride in Caenorhabditis elegans

PubMed Central

Wang, Ning; Wang, Hui; Tang, Chengchun; Lei, Shijun; Shen, Wanqing; Wang, Cong; Wang, Guobin; Wang, Zheng; Wang, Lin

2017-01-01

Boron nitride (BN) nanomaterials have been increasingly explored for potential biological applications. However, their toxicity remains poorly understood. Using Caenorhabditis elegans as a whole-animal model for toxicity analysis of two representative types of BN nanomaterials – BN nanospheres (BNNSs) and highly water-soluble BN nanomaterial (named BN-800-2) – we found that BNNSs overall toxicity was less than soluble BN-800-2 with irregular shapes. The concentration thresholds for BNNSs and BN-800-2 were 100 µg·mL−1 and 10 µg·mL−1, respectively. Above this concentration, both delayed growth, decreased life span, reduced progeny, retarded locomotion behavior, and changed the expression of phenotype-related genes to various extents. BNNSs and BN-800-2 increased oxidative stress levels in C. elegans by promoting reactive oxygen species production. Our results further showed that oxidative stress response and MAPK signaling-related genes, such as GAS1, SOD2, SOD3, MEK1, and PMK1, might be key factors for reactive oxygen species production and toxic responses to BNNSs and BN-800-2 exposure. Together, our results suggest that when concentrations are lower than 10 µg·mL−1, BNNSs are more biocompatible than BN-800-2 and are potentially biocompatible material. PMID:28860759

Toxicity evaluation of boron nitride nanospheres and water-soluble boron nitride in Caenorhabditis elegans.

PubMed

Wang, Ning; Wang, Hui; Tang, Chengchun; Lei, Shijun; Shen, Wanqing; Wang, Cong; Wang, Guobin; Wang, Zheng; Wang, Lin

2017-01-01

Boron nitride (BN) nanomaterials have been increasingly explored for potential biological applications. However, their toxicity remains poorly understood. Using Caenorhabditis elegans as a whole-animal model for toxicity analysis of two representative types of BN nanomaterials - BN nanospheres (BNNSs) and highly water-soluble BN nanomaterial (named BN-800-2) - we found that BNNSs overall toxicity was less than soluble BN-800-2 with irregular shapes. The concentration thresholds for BNNSs and BN-800-2 were 100 µg·mL -1 and 10 µg·mL -1 , respectively. Above this concentration, both delayed growth, decreased life span, reduced progeny, retarded locomotion behavior, and changed the expression of phenotype-related genes to various extents. BNNSs and BN-800-2 increased oxidative stress levels in C. elegans by promoting reactive oxygen species production. Our results further showed that oxidative stress response and MAPK signaling-related genes, such as GAS1 , SOD2 , SOD3 , MEK1 , and PMK1 , might be key factors for reactive oxygen species production and toxic responses to BNNSs and BN-800-2 exposure. Together, our results suggest that when concentrations are lower than 10 µg·mL -1 , BNNSs are more biocompatible than BN-800-2 and are potentially biocompatible material.

Synergistic Behavior of Tubes, Junctions, and Sheets Imparts Mechano-Mutable Functionality in 3D Porous Boron Nitride Nanostructures

PubMed Central

2015-01-01

One-dimensional (1D) boron nitride nanotube (BNNT) and 2D hexagonal BN (h-BN) are attractive for demonstrating fundamental physics and promising applications in nano-/microscale devices. However, there is a high anisotropy associated with these BN allotropes as their excellent properties are either along the tube axis or in-plane directions, posing an obstacle in their widespread use in technological and industrial applications. Herein, we report a series of 3D BN prototypes, namely, pillared boron nitride (PBN), by fusing single-wall BNNT and monolayer h-BN aimed at filling this gap. We use density functional theory and molecular dynamics simulations to probe the diverse mechano-mutable properties of PBN prototypes. Our results demonstrate that the synergistic effect of the tubes, junctions, and sheets imparts cooperative deformation mechanisms, which overcome the intrinsic limitations of the PBN constituents and provide a number of superior characteristics including 3D balance of strength and toughness, emergence of negative Poisson’s ratio, and elimination of strain softening along the armchair orientation. These features, combined with the ultrahigh surface area and lightweight structure, render PBN as a 3D multifunctional template for applications in graphene-based nanoelectronics, optoelectronics, gas storage, and functional composites with fascinating in-plane and out-of-plane tailorable properties. PMID:25289114

Enhancement of the water flow velocity through carbon nanotubes resulting from the radius dependence of the friction due to electron excitations

NASA Astrophysics Data System (ADS)

Sokoloff, J. B.

2018-03-01

Secchi et al. [Nature (London) 537, 210 (2016), 10.1038/nature19315] observed a large enhancement of the permeability and slip length in carbon nanotubes when the tube radius is of the order of 15 nm, but not in boron nitride nanotubes. It will be pointed out that none of the parameters that appear in the usual molecular dynamics treatments of water flow in carbon nanotubes have a length scale comparable to 15 nm, which could account for the observed flow velocity enhancement. It will be demonstrated here, however, that if the friction force between the water and the tube walls in carbon nanotubes is dominated by friction due to electron excitations in the tube walls, the enhanced flow can be accounted for by a reduction in the contribution to the friction due to electron excitations in the wall, resulting from the dependence of the electron energy band gap on the tube radius.

High-Yield Synthesis of Stoichiometric Boron Nitride Nanostructures

DOE PAGES

Nocua, José E.; Piazza, Fabrice; Weiner, Brad R.; ...

2009-01-01

Boron nimore » tride (BN) nanostructures are structural analogues of carbon nanostructures but have completely different bonding character and structural defects. They are chemically inert, electrically insulating, and potentially important in mechanical applications that include the strengthening of light structural materials. These applications require the reliable production of bulk amounts of pure BN nanostructures in order to be able to reinforce large quantities of structural materials, hence the need for the development of high-yield synthesis methods of pure BN nanostructures. Using borazine ( B 3 N 3 H 6 ) as chemical precursor and the hot-filament chemical vapor deposition (HFCVD) technique, pure BN nanostructures with cross-sectional sizes ranging between 20 and 50 nm were obtained, including nanoparticles and nanofibers. Their crystalline structure was characterized by (XRD), their morphology and nanostructure was examined by (SEM) and (TEM), while their chemical composition was studied by (EDS), (FTIR), (EELS), and (XPS). Taken altogether, the results indicate that all the material obtained is stoichiometric nanostructured BN with hexagonal and rhombohedral crystalline structure.« less

Atomic oxygen effects on boron nitride and silicon nitride: A comparison of ground based and space flight data

NASA Technical Reports Server (NTRS)

Cross, J. B.; Lan, E. H.; Smith, C. A.; Whatley, W. J.

1990-01-01

The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si3N4) were evaluated in a low Earth orbit (LEO) flight experiment and in a ground based simulation facility. In both the inflight and ground based experiments, these materials were coated on thin (approx. 250A) silver films, and the electrical resistance of the silver was measured in situ to detect any penetration of atomic oxygen through the BN and Si3N4 materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the inflight and ground based experiments. In contrast, no permeation of atomic oxygen through Si3N4 was observed in either the inflight or ground based experiments. The ground based results show good qualitative correlation with the LEO flight results, indicating that ground based facilities such as the one at Los Alamos National Lab can reproduce space flight data from LEO.

A comparison of ground-based and space flight data: Atomic oxygen reactions with boron nitride and silicon nitride

NASA Technical Reports Server (NTRS)

Cross, J. B.; Lan, E. H.; Smith, C. A.; Whatley, W. J.; Koontz, S. L.

1990-01-01

The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si3N4) have been studied in low Earth orbit (LEO) flight experiments and in a ground-based simulation facility at Los Alamos National Laboratory. Both the in-flight and ground-based experiments employed the materials coated over thin (approx 250 Angstrom) silver films whose electrical resistance was measured in situ to detect penetration of atomic oxygen through the BN and Si3N4 materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the in-flight and ground-based experiments. In contrast, no permeation of atomic oxygen through Si3N4 was observed in either the in-flight or ground-based experiments. The ground-based results show good qualitative correlation with the LEO flight results, thus validating the simulation fidelity of the ground-based facility in terms of reproducing LEO flight results.

Defect-Based Modulation of Optoelectronic Properties for Biofunctionalized Hexagonal Boron Nitride Nanosheets.

PubMed

Shakourian-Fard, Mehdi; Heydari, Hadiseh; Kamath, Ganesh

2017-09-06

Defect engineering potentially allows for dramatic tuning of the optoelectronic properties of two-dimensional materials. With the help of DFT calculations, a systematic study of DNA nucleobases adsorbed on hexagonal boron-nitride nanoflakes (h-BNNFs) with boron (V B ) and nitrogen (V N ) monovacancies is presented. The presence of V N and V B defects increases the binding strength of nucleobases by 9 and 34 kcal mol -1 , respectively (h-BNNF-V B >h-BNNF-V N >h-BNNF). A more negative electrostatic potential at the V B site makes the h-BNNF-V B surface more reactive than that of h-BNNF-V N , enabling H-bonding interactions with nucleobases. This binding energy difference affects the recovery time-a significant factor for developing DNA biosensors-of the surfaces in the order h-BNNF-V B >h-BNNF-V N >h-BNNF. The presence of V B and V N defect sites increases the electrical conductivity of the h-BNNF surface, V N defects being more favorable than V B sites. The blueshift of absorption peaks of the h-BNNF-V B -nucleobase complexes, in contrast to the redshift observed for h-BNNF-V N -nucleobase complexes, is attributed to their observed differences in binding energies, the HOMO-LUMO energy gap and other optoelectronic properties. Time-dependent DFT calculations reveal that the monovacant boron-nitride-sheet-nucleobase composites absorb visible light in the range 300-800 nm, thus making them suitable for light-emitting devices and sensing nucleobases in the visible region. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Boron carbon nitride nanostructures from salt melts: tunable water-soluble phosphors.

PubMed

Lei, Weiwei; Portehault, David; Dimova, Rumiana; Antonietti, Markus

2011-05-11

A simple, high yield, chemical process is developed to fabricate layered h-BN nanosheets and BCNO nanoparticles with a diameter of ca. 5 nm at 700 °C. The use of the eutectic LiCl/KCl salt melt medium enhances the kinetics of the reaction between sodium borohydride and urea or guanidine as well as the dispersion of the nanoparticles in water. The carbon content can be tuned from 0 to 50 mol % by adjusting the reactant ratio, thus providing precise control of the light emission of the particles in the range 440-528 nm while reaching a quantum yield of 26%. Because of their green synthesis, low toxicity, small size, and stability against aggregation in water, the as-obtained photoluminescent BCNO nanoparticles show promise for diagnostics and optoelectronics. © 2011 American Chemical Society