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Sample records for boron nitrides

  1. Boron nitride composites

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Boron nitride converted carbon fiber

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-04-05

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

  3. Determination of boron content in boron carbide, boron nitride and amorphous boron

    International Nuclear Information System (INIS)

    In the present article an analyzing method of determination of boron content in boron carbide, boron nitride and amorphous boron described. Examined samples were digested with potassium hydroxide and potassium nitrate in nickel crucible and the boron contents determined subsequently by an alcalimetric titration of boric acid in presence of mannite resp. sorbite. (author)

  4. Innovative boron nitride-doped propellants

    OpenAIRE

    Thelma Manning; Richard Field; Kenneth Klingaman; Michael Fair; John Bolognini; Robin Crownover; Carlton P. Adam; Viral Panchal; Eugene Rozumov; Henry Grau; Paul Matter; Michael Beachy; Christopher Holt; Samuel Sopok

    2016-01-01

    The U.S. military has a need for more powerful propellants with balanced/stoichiometric amounts of fuel and oxidants. However, balanced and more powerful propellants lead to accelerated gun barrel erosion and markedly shortened useful barrel life. Boron nitride (BN) is an interesting potential additive for propellants that could reduce gun wear effects in advanced propellants (US patent pending 2015-026P). Hexagonal boron nitride is a good lubricant that can provide wear resistance and lower ...

  5. Innovative boron nitride-doped propellants

    Directory of Open Access Journals (Sweden)

    Thelma Manning

    2016-04-01

    Full Text Available The U.S. military has a need for more powerful propellants with balanced/stoichiometric amounts of fuel and oxidants. However, balanced and more powerful propellants lead to accelerated gun barrel erosion and markedly shortened useful barrel life. Boron nitride (BN is an interesting potential additive for propellants that could reduce gun wear effects in advanced propellants (US patent pending 2015-026P. Hexagonal boron nitride is a good lubricant that can provide wear resistance and lower flame temperatures for gun barrels. Further, boron can dope steel, which drastically improves its strength and wear resistance, and can block the formation of softer carbides. A scalable synthesis method for producing boron nitride nano-particles that can be readily dispersed into propellants has been developed. Even dispersion of the nano-particles in a double-base propellant has been demonstrated using a solvent-based processing approach. Stability of a composite propellant with the BN additive was verified. In this paper, results from propellant testing of boron nitride nano-composite propellants are presented, including closed bomb and wear and erosion testing. Detailed characterization of the erosion tester substrates before and after firing was obtained by electron microscopy, inductively coupled plasma and x-ray photoelectron spectroscopy. This promising boron nitride additive shows the ability to improve gun wear and erosion resistance without any destabilizing effects to the propellant. Potential applications could include less erosive propellants in propellant ammunition for large, medium and small diameter fire arms.

  6. Innovative boron nitride-doped propellants

    Institute of Scientific and Technical Information of China (English)

    Thelma MANNING; Henry GRAU; Paul MATTER; Michael BEACHY; Christopher HOLT; Samuel SOPOK; Richard FIELD; Kenneth KLINGAMAN; Michael FAIR; John BOLOGNINI; Robin CROWNOVER; Carlton P. ADAM; Viral PANCHAL; Eugene ROZUMOV

    2016-01-01

    The U.S. military has a need for more powerful propellants with balanced/stoichiometric amounts of fuel and oxidants. However, balanced and more powerful propellants lead to accelerated gun barrel erosion and markedly shortened useful barrel life. Boron nitride (BN) is an interesting potential additive for propellants that could reduce gun wear effects in advanced propellants (US patent pending 2015-026P). Hexagonal boron nitride is a good lubricant that can provide wear resistance and lower flame temperatures for gun barrels. Further, boron can dope steel, which drastically improves its strength and wear resistance, and can block the formation of softer carbides. A scalable synthesis method for producing boron nitride nano-particles that can be readily dispersed into propellants has been developed. Even dispersion of the nano-particles in a double-base propellant has been demonstrated using a solvent-based processing approach. Stability of a composite propellant with the BN additive was verified. In this paper, results from propellant testing of boron nitride nano-composite propellants are presented, including closed bomb and wear and erosion testing. Detailed characterization of the erosion tester substrates before and after firing was obtained by electron microscopy, inductively coupled plasma and x-ray photoelectron spectroscopy. This promising boron nitride additive shows the ability to improve gun wear and erosion resistance without any destabilizing effects to the propellant. Potential applications could include less erosive propellants in propellant ammunition for large, medium and small diameter fire arms.

  7. Boron Nitride Nanotubes for Spintronics

    Directory of Open Access Journals (Sweden)

    Kamal B. Dhungana

    2014-09-01

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

  8. Boron nitride nanosheets reinforced glass matrix composites

    Czech Academy of Sciences Publication Activity Database

    Saggar, Richa; Porwal, H.; Tatarko, P.; Dlouhý, Ivo; Reece, M. J.

    2015-01-01

    Roč. 114, SEP (2015), S26-S32. ISSN 1743-6753 R&D Projects: GA MŠk(CZ) 7AMB14SK155 EU Projects: European Commission(XE) 264526 Institutional support: RVO:68081723 Keywords : Boron nitride nanosheets * Borosilicate glass * Mechanical properties Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.163, year: 2014

  9. Thermal conductivity of boron carbide-boron nitride composites

    International Nuclear Information System (INIS)

    This paper reports that because of their preferred orientation, the addition of boron nitride dispersions to hot-pressed boron carbide was found to result in a considerable degree of anisotropy in thermal conductivity of the resulting composite, indicated by an increase in the thermal conductivity perpendicular to the hot-pressing direction by as much as a factor of 3 at the highest boron nitride volume fractions of this study, and a decrease in the thermal conductivity parallel to the hot-pressing direction by as much as a factor of 2. The composite data were found to be below the values expected from composite theory, which may represent indirect evidence for the existence of an interfacial thermal barrier

  10. Reactive sputter deposition of boron nitride

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2010-03-12

    Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). We report that the method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing gas to form nanotubes. The new method greatly enhances the yield of BNNTs, giving a higher density of nanotubes. These improvements are caused by the addition of metal nitrate and ethanol, both of which can strongly boost the nitriding reaction, as revealed by thermogravimetric analysis. The size and structure of BNNTs can be controlled by varying the annealing conditions. This high-yield production of BNNTs in large quantities enables the large-scale application of BNNTs. PMID:20154372

  12. Synthesis of boron nitride nanotubes by boron ink annealing

    International Nuclear Information System (INIS)

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

  13. Boron Nitride Nanosheets for Metal Protection

    OpenAIRE

    Li, Lu Hua; Xing, Tan; Chen, Ying; Jones, Rob

    2015-01-01

    Although the high impermeability of graphene makes it an excellent barrier to inhibit metal oxidation and corrosion, graphene can form a galvanic cell with the underlying metal that promotes corrosion of the metal in the long term. Boron nitride (BN) nanosheets which have a similar impermeability could be a better choice as protective barrier, because they are more thermally and chemically stable than graphene and, more importantly, do not cause galvanic corrosion due to their electrical insu...

  14. Anomalous thermal conductivity of monolayer boron nitride

    Science.gov (United States)

    Tabarraei, Alireza; Wang, Xiaonan

    2016-05-01

    In this paper, we use nonequilibrium molecular dynamics modeling to investigate the thermal properties of monolayer hexagonal boron nitride nanoribbons under uniaxial strain along their longitudinal axis. Our simulations predict that hexagonal boron nitride shows an anomalous thermal response to the applied uniaxial strain. Contrary to three dimensional materials, under uniaxial stretching, the thermal conductivity of boron nitride nanoribbons first increases rather than decreasing until it reaches its peak value and then starts decreasing. Under compressive strain, the thermal conductivity of monolayer boron nitride ribbons monolithically reduces rather than increasing. We use phonon spectrum and dispersion curves to investigate the mechanism responsible for the unexpected behavior. Our molecular dynamics modeling and density functional theory results show that application of longitudinal tensile strain leads to the reduction of the group velocities of longitudinal and transverse acoustic modes. Such a phonon softening mechanism acts to reduce the thermal conductivity of the nanoribbons. On the other hand, a significant increase in the group velocity (stiffening) of the flexural acoustic modes is observed, which counteracts the phonon softening effects of the longitudinal and transverse modes. The total thermal conductivity of the ribbons is a result of competition between these two mechanisms. At low tensile strain, the stiffening mechanism overcomes the softening mechanism which leads to an increase in the thermal conductivity. At higher tensile strain, the softening mechanism supersedes the stiffening and the thermal conductivity slightly reduces. Our simulations show that the decrease in the thermal conductivity under compressive strain is attributed to the formation of buckling defects which reduces the phonon mean free path.

  15. Formation and Structure of Boron Nitride Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Jiang ZHANG; Zongquan LI; Jin XU

    2005-01-01

    Boron nitride (BN) nanotubes were simply synthesized by heating well-mixed boric acid, urea and iron nitrate powders at 1000℃. A small amount of BN nanowires was also obtained in the resultants. The morphological and structural characters of the BN nanostructures were studied using transmission electron microscopy. Other novel BN nanostructures, such as Y-junction nanotubes and bamboo-like nanotubes, were simultaneously observed. The growth mechanism of the BN nanotubes was discussed briefly.

  16. Thermal conductivity of nanostructured boron nitride materials.

    Science.gov (United States)

    Tang, Chengchun; Bando, Yoshio; Liu, Changhong; Fan, Shoushan; Zhang, Jun; Ding, Xiaoxia; Golberg, Dmitri

    2006-06-01

    We have measured the thermal conductivity of bulky pellets made of various boron nitride (BN)-based nanomaterials, including spherical nanoparticles, perfectly structured, bamboo-like nanotubes, and collapsed nanotubes. The thermal conductivity strongly depends on the morphology of the BN nanomaterials, especially on the surface structure. Spherical BN particles have the lowest thermal conductivity while the collapsed BN nanotubes possess the best thermoconductive properties. A model was proposed to explain the experimental observations based on the heat percolation passage considerations. PMID:16722739

  17. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    Science.gov (United States)

    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.

  18. Composition and microhardness of CAE boron nitride films

    International Nuclear Information System (INIS)

    The paper deals with boron nitride produced by cathodic arc evaporation techniques.The films were applied on titanium and cemented carbide substrates. Their characterization was carried out using X-ray diffraction and Knoop microhardness tests. Demonstrated are the high properties of two-phase films, containing β (cubic) and γ (wurtzitic) modifications of boron nitride. (author). 7 refs., 1 fig., 3 tabs

  19. Synthesis and characterization of boron nitrides nanotubes

    International Nuclear Information System (INIS)

    This paper presents a new synthesis for the production of boron nitride nanotubes (BNNT) from boron powder, ammonium nitrate and hematite tube furnace CVD method. The samples were subjected to some characterization techniques as infrared spectroscopy, thermal analysis, X-ray diffraction and scanning electron microscopy and transmission. By analyzing the results can explain the chemical reactions involved in the process and confirm the formation of BNNT with several layers and about 30 nanometers in diameter. Due to excellent mechanical properties and its chemical and thermal stability this material is promising for various applications. However, BNNT has received much less attention than carbon nanotubes, it is because of great difficulty to synthesize appreciable quantities from the techniques currently known, and this is one of the main reasons this work.(author)

  20. Ballistic thermoelectric properties in boron nitride nanoribbons

    Science.gov (United States)

    Xie, Zhong-Xiang; Tang, Li-Ming; Pan, Chang-Ning; Chen, Qiao; Chen, Ke-Qiu

    2013-10-01

    Ballistic thermoelectric properties (TPs) in boron nitride nanoribbons (BNNRs) are studied using the nonequilibrium Green's function atomistic simulation of electron and phonon transport. A comparative analysis for TPs between BNNRs and graphene nanoribbons (GNRs) is made. Results show that the TPs of BNNRs are better than those of GNRs stemming from the higher power factor and smaller thermal conductance of BNNRs. With increasing the ribbon width, the maximum value of ZT (ZTmax) of BNNRs exhibits a transformation from the monotonic decrease to nonlinear increase. We also show that the lattice defect can enhance the ZTmax of these nanoribbons strongly depending on its positions and the edge shape.

  1. Magnesium doping of boron nitride nanotubes

    Science.gov (United States)

    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.

  2. Boron nitride nanomaterials for thermal management applications.

    Science.gov (United States)

    Meziani, Mohammed J; Song, Wei-Li; Wang, Ping; Lu, Fushen; Hou, Zhiling; Anderson, Ankoma; Maimaiti, Halidan; Sun, Ya-Ping

    2015-05-18

    Hexagonal boron nitride nanosheets (BNNs) are analogous to their two-dimensional carbon counterparts in many materials properties, in particular, ultrahigh thermal conductivity, but also offer some unique attributes, including being electrically insulating, high thermal stability, chemical and oxidation resistance, low color, and high mechanical strength. Significant recent advances in the production of BNNs, understanding of their properties, and the development of polymeric nanocomposites with BNNs for thermally conductive yet electrically insulating materials and systems are highlighted herein. Major opportunities and challenges for further studies in this rapidly advancing field are also discussed. PMID:25652360

  3. Low-dimensional boron nitride nanomaterials

    Directory of Open Access Journals (Sweden)

    Amir Pakdel

    2012-06-01

    Full Text Available In this review, a concise research history of low-dimensional boron nitride (BN nanomaterials followed by recent developments in their synthesis, morphology, properties, and applications are presented. Seventeen years after the initial synthesis of BN nanotubes, research on BN nanomaterials has developed far enough to establish them as one of the most promising inorganic nanosystems. In this regard, it is envisaged that the unique properties of low-dimensional BN systems, such as superb mechanical stiffness, high thermal conductivity, wide optical bandgap, strong ultraviolet emission, thermal stability and chemical inertness will play a key role in prospective developments.

  4. Optical absorption of boron nitride nanomaterials

    International Nuclear Information System (INIS)

    Optical absorption spectra have been measured for hexagonal boron nitride (h-BN), rhombohedral BN(rh-BN), and material obtained by laser vaporization of BN target under a nitrogen atmosphere and contained single-wall BN-nanotubes. Band gap of the BN materials was found to have a value of 6.0-6.3 eV. The spectra of h -BN and vaporized material exhibited a peak at ∝5.5 eV, moreover, the latter sample showed an absorption band around 4.5 eV. The vaporized material has been fractionated to the BN-platelets and single-wall BN-nanotubes. Absorption peaks, located bellow the bottom of the conductance band, were found to be characteristics of thin BN-platelets and they could be attributed to defects in BN network. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Quantum emission from hexagonal boron nitride monolayers.

    Science.gov (United States)

    Tran, Toan Trong; Bray, Kerem; Ford, Michael J; Toth, Milos; Aharonovich, Igor

    2016-01-01

    Artificial atomic systems in solids are widely considered the leading physical system for a variety of quantum technologies, including quantum communications, computing and metrology. To date, however, room-temperature quantum emitters have only been observed in wide-bandgap semiconductors such as diamond and silicon carbide, nanocrystal quantum dots, and most recently in carbon nanotubes. Single-photon emission from two-dimensional materials has been reported, but only at cryogenic temperatures. Here, we demonstrate room-temperature, polarized and ultrabright single-photon emission from a colour centre in two-dimensional hexagonal boron nitride. Density functional theory calculations indicate that vacancy-related defects are a probable source of the emission. Our results demonstrate the unprecedented potential of van der Waals crystals for large-scale nanophotonics and quantum information processing. PMID:26501751

  6. Quantum emission from hexagonal boron nitride monolayers

    Science.gov (United States)

    Tran, Toan Trong; Bray, Kerem; Ford, Michael J.; Toth, Milos; Aharonovich, Igor

    2016-01-01

    Artificial atomic systems in solids are widely considered the leading physical system for a variety of quantum technologies, including quantum communications, computing and metrology. To date, however, room-temperature quantum emitters have only been observed in wide-bandgap semiconductors such as diamond and silicon carbide, nanocrystal quantum dots, and most recently in carbon nanotubes. Single-photon emission from two-dimensional materials has been reported, but only at cryogenic temperatures. Here, we demonstrate room-temperature, polarized and ultrabright single-photon emission from a colour centre in two-dimensional hexagonal boron nitride. Density functional theory calculations indicate that vacancy-related defects are a probable source of the emission. Our results demonstrate the unprecedented potential of van der Waals crystals for large-scale nanophotonics and quantum information processing.

  7. Boron nitride: A new photonic material

    Energy Technology Data Exchange (ETDEWEB)

    Chubarov, M., E-mail: mihcu@ifm.liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Pedersen, H., E-mail: henke@ifm.liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Högberg, H., E-mail: hanho@ifm.liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Filippov, S., E-mail: stafi@ifm.liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.za [Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); O' Connel, J., E-mail: jacques.oconnell@gmail.com [Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Henry, A., E-mail: anne.henry@liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden)

    2014-04-15

    Rhombohedral boron nitride (r-BN) layers were grown on sapphire substrate in a hot-wall chemical vapor deposition reactor. Characterization of these layers is reported in details. X-ray diffraction (XRD) is used as a routine characterization tool to investigate the crystalline quality of the films and the identification of the phases is revealed using detailed pole figure measurements. Transmission electron microscopy reveals stacking of more than 40 atomic layers. Results from Fourier Transform InfraRed (FTIR) spectroscopy measurements are compared with XRD data showing that FTIR is not phase sensitive when various phases of sp{sup 2}-BN are investigated. XRD measurements show a significant improvement of the crystalline quality when adding silicon to the gas mixture during the growth; this is further confirmed by cathodoluminescence which shows a decrease of the defects related luminescence intensity.

  8. Hexagonal boron nitride and water interaction parameters.

    Science.gov (United States)

    Wu, Yanbin; Wagner, Lucas K; Aluru, Narayana R

    2016-04-28

    The study of hexagonal boron nitride (hBN) in microfluidic and nanofluidic applications at the atomic level requires accurate force field parameters to describe the water-hBN interaction. In this work, we begin with benchmark quality first principles quantum Monte Carlo calculations on the interaction energy between water and hBN, which are used to validate random phase approximation (RPA) calculations. We then proceed with RPA to derive force field parameters, which are used to simulate water contact angle on bulk hBN, attaining a value within the experimental uncertainties. This paper demonstrates that end-to-end multiscale modeling, starting at detailed many-body quantum mechanics and ending with macroscopic properties, with the approximations controlled along the way, is feasible for these systems. PMID:27131542

  9. Hexagonal boron nitride and water interaction parameters

    Science.gov (United States)

    Wu, Yanbin; Wagner, Lucas K.; Aluru, Narayana R.

    2016-04-01

    The study of hexagonal boron nitride (hBN) in microfluidic and nanofluidic applications at the atomic level requires accurate force field parameters to describe the water-hBN interaction. In this work, we begin with benchmark quality first principles quantum Monte Carlo calculations on the interaction energy between water and hBN, which are used to validate random phase approximation (RPA) calculations. We then proceed with RPA to derive force field parameters, which are used to simulate water contact angle on bulk hBN, attaining a value within the experimental uncertainties. This paper demonstrates that end-to-end multiscale modeling, starting at detailed many-body quantum mechanics and ending with macroscopic properties, with the approximations controlled along the way, is feasible for these systems.

  10. Boron nitride: A new photonic material

    International Nuclear Information System (INIS)

    Rhombohedral boron nitride (r-BN) layers were grown on sapphire substrate in a hot-wall chemical vapor deposition reactor. Characterization of these layers is reported in details. X-ray diffraction (XRD) is used as a routine characterization tool to investigate the crystalline quality of the films and the identification of the phases is revealed using detailed pole figure measurements. Transmission electron microscopy reveals stacking of more than 40 atomic layers. Results from Fourier Transform InfraRed (FTIR) spectroscopy measurements are compared with XRD data showing that FTIR is not phase sensitive when various phases of sp2-BN are investigated. XRD measurements show a significant improvement of the crystalline quality when adding silicon to the gas mixture during the growth; this is further confirmed by cathodoluminescence which shows a decrease of the defects related luminescence intensity.

  11. Pure and doped boron nitride nanotubes

    Directory of Open Access Journals (Sweden)

    M. Terrones

    2007-05-01

    Full Text Available More than ten years ago, it was suggested theoretically that boron nitride (BN nanotubes could be produced. Soon after, various reports on their synthesis appeared and a new area of nanotube science was born. This review aims to cover the latest advances related to the synthesis of BN nanotubes. We show that these tubes can now be produced in larger amounts and, in particular, that the chemistry of BN tubes appears to be very important to the production of reinforced composites with insulating characteristics. From the theoretical standpoint, we also show that (BN-C heteronanotubes could have important implications for nanoelectronics. We believe that BN nanotubes (pure and doped could be used in the fabrication of novel devices in which pure carbon nanotubes do not perform very efficiently.

  12. Method for determination of boron carbide in wurtzite-like boron nitride

    International Nuclear Information System (INIS)

    A technique for increase of sensitivity and analysis accuracy while boron carbide determination in wurtzite-like boron nitride is proposed. Boron nitride with an addition of boron carbide is bjected to treatment by the mixture of concentrated sulphuric acid and 0.1-0.5 N of porassium bichromate solution at ratio of (2-1):1 at the temperature of mixture boiling. Boron carboide content is calculated according to the quantity of restored Cr(3+), which is determined by titration of Cr(6+) excess with the Mohr's salt solution

  13. Burnup performances of boron nitride and boron coated nuclear fuels

    International Nuclear Information System (INIS)

    The nuclear fuels of urania (UOV) and 5% and 10% gadolinia (Gd2O3) containing UO2 previously produced by sol-gel technique were coated with first boron nitride (BN) then boron (B) thin layer by chemical vapor deposition (CVD) and also by plasma enhanced chemical vapor deposition (PECVD) techniques to increase the fuel cycle length and to improve the physical properties. From the cross-sectional view of BN and B layers taken from scanning electron microscope (SEM), the excellent adherence of BN onto fuel and B onto BN layer was observed in both cases. The behavior of fuel burnup, depletion of BN and B, the effect of coating thickness and also Gd2O3 content on the burnup performances of the fuels were identified by using the code WIMS-D/4 for Pressurized Water Reactor (PWR) and Boiling Water Reactor (BWR) cores. The optimum thickness ratio of B to BN was found as 4 and their thicknesses were chosen as 40 mm and 10 mm respectively in both reactor types to get extended cycle length. The assemblies consisting of fuels with 5% Gd2O3 and also coated with 10 mm BN and 40 mm B layers were determined as candidates for getting higher burnup in both types of reactors

  14. Cubic boron nitride- a new material for ultracold neutron application

    International Nuclear Information System (INIS)

    For the first time, the Fermi potential of cubic boron nitride (cBN) was measured at the ultra cold neutron source at the TRIGA reactor, Mainz using the time of flight method (TOF). The investigated samples have a Fermi potential of about 300 neV. Because of its good dielectric characteristics, cubic boron nitride could be used as suitable coating for insulator in storage chambers of future EDM projects. This talk presents recent results and an outlook on further investigations.

  15. Research of nanocomposite structure of boron nitride at proton radiation

    OpenAIRE

    Borodin, Yuri Viktorovich; Ermolaev, D. S.; Pak, V.; Zhang, K.

    2016-01-01

    Using roentgen diffraction and electron microscopy, the influence of nanosecond irradiation by ion beams of high energy on forming of self-organized nanoblocks in near surface's layers of boron nitride (BN) has been studied. It was shown that low temperature transitions from hexagonal to wrutz boron nitrides is associated with changes of shape and sizes of self-organized particles consisting the nanoblocks. We have calculated the parameters of nanoblocks using the meanings of interplane dista...

  16. Vertical transport in graphene-hexagonal boron nitride heterostructure devices

    OpenAIRE

    Samantha Bruzzone; Demetrio Logoteta; Gianluca Fiori; Giuseppe Iannaccone

    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...

  17. Boron-nitride coated nuclear fuels

    Energy Technology Data Exchange (ETDEWEB)

    Guenduez, G. [Orta Dogu Teknik Univ., Ankara (Turkey); Uslu, I. [Tuerkiye Atom Enerjisi Kurumu, Ankara (Turkey); Durmazucar, H.H. [Cumhuriyet Univ., Sivas (Turkey)

    1996-10-01

    Pure urania- and urania-gadolinia-containing fuel pellets were coated with boron nitride (BN) to improve the physical and neutronic properties of the fuel. The BN coating seems to have a technological advantage over zirconium-diboride coating. The BN is chemically inert, corrosion resistant, withstands rapid temperature changes, and has a high thermal conductivity. Since gadolinia fuel has low thermal conductivity. Since gadolinia fuel has low thermal conductivity, the gadolinia content can be lowered in the fuel by coating it with BN. In fact, the existence of two burnable absorbers in a fuel introduces desired nuclear properties since gadolinia is a fast-burning and boron a slow-burning element. The BN was deposited on fuel from two different sources, (a) from the reaction of boron trichloride (BCl{sub 3}) and ammonia (NH{sub 3}) at 875 K and (b) from the decomposition of trimethylamine borate complex at 1200 K. The infrared and X-ray diffraction (XRD) spectra of BN from both precursors agreed with the available data in the literature. However BN powder from borane complex had a shifted XRD peak due to the presence of carbonaceous material in the structure. The BN powder-coated fuels were heated to 1400, 1525, and 1600 K to sinter the BN. The examination under scanning electron microscope showed that grainy, rod-shaped and layered BN coatings were achieved. Rod-shaped structures were usually seen on gadolinia fuels. The increased thickness of coating favors the formation of a glassy looking layer. The BN from a borane complex seems to form a layered structure more easily than the BN from BCl{sub 3}. The BN coated the surface of the fuels, and it did not penetrate into the fuels.

  18. Boron-nitride coated nuclear fuels

    International Nuclear Information System (INIS)

    Pure urania- and urania-gadolinia-containing fuel pellets were coated with boron nitride (BN) to improve the physical and neutronic properties of the fuel. The BN coating seems to have a technological advantage over zirconium-diboride coating. The BN is chemically inert, corrosion resistant, withstands rapid temperature changes, and has a high thermal conductivity. Since gadolinia fuel has low thermal conductivity. Since gadolinia fuel has low thermal conductivity, the gadolinia content can be lowered in the fuel by coating it with BN. In fact, the existence of two burnable absorbers in a fuel introduces desired nuclear properties since gadolinia is a fast-burning and boron a slow-burning element. The BN was deposited on fuel from two different sources, (a) from the reaction of boron trichloride (BCl3) and ammonia (NH3) at 875 K and (b) from the decomposition of trimethylamine borate complex at 1200 K. The infrared and X-ray diffraction (XRD) spectra of BN from both precursors agreed with the available data in the literature. However BN powder from borane complex had a shifted XRD peak due to the presence of carbonaceous material in the structure. The BN powder-coated fuels were heated to 1400, 1525, and 1600 K to sinter the BN. The examination under scanning electron microscope showed that grainy, rod-shaped and layered BN coatings were achieved. Rod-shaped structures were usually seen on gadolinia fuels. The increased thickness of coating favors the formation of a glassy looking layer. The BN from a borane complex seems to form a layered structure more easily than the BN from BCl3. The BN coated the surface of the fuels, and it did not penetrate into the fuels

  19. BORON NITRIDE CAPACITORS FOR ADVANCED POWER ELECTRONIC DEVICES

    Energy Technology Data Exchange (ETDEWEB)

    N. Badi; D. Starikov; C. Boney; A. Bensaoula; D. Johnstone

    2010-11-01

    This project fabricates long-life boron nitride/boron oxynitride thin film -based capacitors for advanced SiC power electronics with a broad operating temperature range using a physical vapor deposition (PVD) technique. The use of vapor deposition provides for precise control and quality material formation.

  20. Structure, Mechanics and Synthesis of Nanoscale Carbon and Boron Nitride

    Science.gov (United States)

    Rinaldo, Steven G.

    This thesis is divided into two parts. In Part I, we examine the properties of thin sheets of carbon and boron nitride. We begin with an introduction to the theory of elastic sheets, where the stretching and bending modes are considered in detail. The coupling between stretching and bending modes is thought to play a crucial role in the thermodynamic stability of atomically-thin 2D sheets such as graphene. In Chapter 2, we begin by looking at the fabrication of suspended, atomically thin sheets of graphene. We then study their mechanical resonances which are read via an optical transduction technique. The frequency of the resonators was found to depend on their temperature, as was their quality factor. We conclude by offering some interpretations of the data in terms of the stretching and bending modes of graphene. In Chapter 3, we look briefly at the fabrication of thin sheets of carbon and boron nitride nanotubes. We examine the structure of the sheets using transmission and scanning electron microscopy (TEM and SEM, respectively). We then show a technique by which one can make sheets suspended over a trench with adjustable supports. Finally, DC measurements of the resistivity of the sheets in the temperature range 600 -- 1400 C are presented. In Chapter 4, we study the folding of few-layer graphene oxide, graphene and boron nitride into 3D aerogel monoliths. The properties of graphene oxide are first considered, after which the structure of graphene and boron nitride aerogels is examined using TEM and SEM. Some models for their structure are proposed. In Part II, we look at synthesis techniques for boron nitride (BN). In Chapter 5, we study the conversion of carbon structures of boron nitride via the application of carbothermal reduction of boron oxide followed by nitridation. We apply the conversion to a wide variety of morphologies, including aerogels, carbon fibers and nanotubes, and highly oriented pyrolytic graphite. In the latter chapters, we look at the

  1. Process for producing wurtzitic or cubic boron nitride

    International Nuclear Information System (INIS)

    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

  2. Homogeneous dispersion of gallium nitride nanoparticles in a boron nitride matrix by nitridation with urea.

    Science.gov (United States)

    Kusunose, Takafumi; Sekino, Tohru; Ando, Yoichi

    2010-07-01

    A Gallium Nitride (GaN) dispersed boron nitride (BN) nanocomposite powder was synthesized by heating a mixture of gallium nitrate, boric acid, and urea in a hydrogen atmosphere. Before heat treatment, crystalline phases of urea, boric acid, and gallium nitrate were recognized, but an amorphous material was produced by heat treatment at 400 degrees C, and then was transformed into GaN and turbostratic BN (t-BN) by further heat treatment at 800 degrees C. TEM obsevations of this composite powder revealed that single nanosized GaN particles were homogeneously dispersed in a BN matrix. Homogeneous dispersion of GaN nanoparticles was thought to be attained by simultaneously nitriding gallium nitrate and boric acid to GaN and BN with urea. PMID:21128417

  3. Ceramic processing of boron nitride insulators

    International Nuclear Information System (INIS)

    Fuel pin simulators (FPS) are the prime elements of several test facilities at the Oak Ridge National Laboratory (ORNL). These experimental facilities are used to conduct out-of-reactor thermal-hydraulic and mechanical interaction safety tests for both light-water and breeder reactor programs. The FPS units simulate the geometry, heat flux profiles, and operational capabilities of a reactor core element under steady-state and transient conditions. They are subjected to temperatures as high as 16000C (29000F) and power levels as high as 57.5 kW/m (17.5 kW/ft) as well as severe thermal stresses during transient tests. The insulating material in the narrow annulus between the heating coil and the FPS sheath is subjected to very rigorous conditions. Accuracy of the reactor safety test information and validity of the test data depend on the heat flux uniformity under all test conditions and on the reliable operation of all fuel pin simulators and their internal thermocouples. Boron nitride (BN), because of its high degree of chemical inertness combined with its relatively unique properties of high thermal conductivity and low electrical conductivity, is the most suitable insulating material for FPS. The important BN properties, thermal conductivity and electrical resistance, are strongly influenced by crystallite orientation and by impurities. The article describes new BN powder processing techniques, which optimize these properties

  4. Hyperbolic phonon polaritons in hexagonal boron nitride

    Science.gov (United States)

    Dai, Siyuan

    2015-03-01

    Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. While hyperbolic responses are normally achieved with metamaterials, hexagonal boron nitride (hBN) naturally possesses this property due to the anisotropic phonons in the mid-infrared. Using scattering-type scanning near-field optical microscopy, we studied polaritonic phenomena in hBN. We performed infrared nano-imaging of highly confined and low-loss hyperbolic phonon polaritons in hBN. The polariton wavelength was shown to be governed by the hBN thickness according to a linear law persisting down to few atomic layers [Science, 343, 1125-1129 (2014)]. Additionally, we carried out the modification of hyperbolic response in heterostructures comprised of a mononlayer graphene deposited on hBN. Electrostatic gating of the top graphene layer allows for the modification of wavelength and intensity of hyperbolic phonon polaritons in bulk hBN. The physics of the modification originates from the plasmon-phonon coupling in the hyperbolic medium. Furthermore, we demonstrated the ``hyperlens'' for subdiffractional imaging and focusing using a slab of hBN.

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

    Energy Technology Data Exchange (ETDEWEB)

    Durmazucar, Hasan H.; Guenduez, Guengoer E-mail: ggunduz@metu.edu.tr

    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.

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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)

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

    Science.gov (United States)

    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).

  9. Experimental core electron density of cubic boron nitride

    DEFF Research Database (Denmark)

    Wahlberg, Nanna; Bindzus, Niels; Bjerg, Lasse;

    boron nitride we may obtain a deeper understanding of the effect of bonding on the total density. We report here a thorough investigation of the charge density of cubic boron nitride with a detailed modelling of the inner atom charge density. By combining high resolution powder X-ray diffraction data...... has been obtained. The displacement parameters reported here are significantly lower than those previously reported, stressing the importance of an adequate description of the core density. The charge transfer from boron to nitrogen clearly affects the inner electron density, which is evident from...... theoretical as well as experimental result. The redistribution of electron density will, if not accounted for, result in increased thermal parameters. It is estimated that 1.7-2 electrons is transferred from boron to nitrogen. [1]: N. Bindzus, T. Straasø, N. Wahlberg, J. Becker, L. Bjerg, N. Lock, A...

  10. Thin boron nitride nanotubes formed during annealing in ammonia gas

    International Nuclear Information System (INIS)

    Full text: We present a mechano-thermal process to synthesis thin boron nitride nanotubes of diameter around 7 nanometers. They were produced by mechanical milling of amorphous boron powder at ambient temperature, followed by thermal annealing in ammonia gas. High energy ball milling creates a precursor containing a high density of nanocrystalline BN seeds and fine particles of metal catalyst. Nanotubes grow out from the milled boron powder during subsequent annealing. The novelty of this approach lies in the formation of the thin BN nanotubes by annealing in ammonia gas instead of nitrogen gas. The boron nitride nanotubes produced have a well-defined crystalline structure and there is no iron within them. If nitrogen gas is used, thicker nanotubes of diameter in the range of 20-100 nm were obtained and iron was more likely to be found inside the nanotubes. Copyright (2005) Australian Institute of Physics

  11. Communication: Water on hexagonal boron nitride from diffusion Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hamdani, Yasmine S.; Ma, Ming; Michaelides, Angelos, E-mail: angelos.michaelides@ucl.ac.uk [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Alfè, Dario [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT (United Kingdom); Lilienfeld, O. Anatole von [Institute of Physical Chemistry and National Center for Computational Design and Discovery of Novel Materials, Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland); Argonne Leadership Computing Facility, Argonne National Laboratories, 9700 S. Cass Avenue Argonne, Lemont, Illinois 60439 (United States)

    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.

  12. Inter-layer potential for hexagonal boron nitride

    Science.gov (United States)

    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.

  13. Communication: Water on hexagonal boron nitride from diffusion Monte Carlo

    International Nuclear Information System (INIS)

    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

  14. Synthesis of Boron Nitride Nanotubes for Engineering Applications

    Science.gov (United States)

    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.

  15. Microstructure of boron nitride coated on nuclear fuels by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Three nuclear fuels, pure urania, 5% and 10% gadolinia containing fuels were coated with boron nitride to improve nuclear and physical properties. Coating was done by plasma enhanced chemical vapor deposition technique by using boron trichloride and ammonia. The specimens were examined under a scanning electron microscope. Boron nitride formed a grainy structure on all fuels. Gadolinia decreased the grain size of boron nitride. The fractal dimensions of fragmentation and of area-perimeter relation were determined. (orig.)

  16. Microstructure of boron nitride coated on nuclear fuels by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Durmazucar, H.H. [Cumhuriyet Univ., Sivas (Turkey). Kimya Muehendisligi Boeluemue; Guenduez, G. [Kimya Muehendisligi Boeluemue, Orta Dogu Teknik Ueniversitesi, Ankara 06531 (Turkey); Toker, C. [Elektrik-Elektronik Muehendisligi Boeluemue, Orta Dogu Teknik Ueniversitesi, Ankara 06531 (Turkey)

    1998-08-03

    Three nuclear fuels, pure urania, 5% and 10% gadolinia containing fuels were coated with boron nitride to improve nuclear and physical properties. Coating was done by plasma enhanced chemical vapor deposition technique by using boron trichloride and ammonia. The specimens were examined under a scanning electron microscope. Boron nitride formed a grainy structure on all fuels. Gadolinia decreased the grain size of boron nitride. The fractal dimensions of fragmentation and of area-perimeter relation were determined. (orig.) 19 refs.

  17. Graphene and Boron Nitride: Members of Two Dimensional Material Family

    OpenAIRE

    Riaz, Ibtsam

    2012-01-01

    Name of University: University of ManchesterCandidate full name: Ibtsam RiazDegree Title: Doctor of Philosophy in the Faculty of Engineering and Physical sciencesThesis Title: Graphene and Boron Nitride: Members of Two Dimensional Material FamilyDate: 18-JAN-2012

  18. Boron nitride elastic and thermal properties. Irradiation effects

    International Nuclear Information System (INIS)

    The anisotropy of boron nitride (BN) and especially thermal and elastic properties were studied. Specific heat and thermal conductivity between 1.2 and 300K, thermal conductivity between 4 and 350K and elastic constants C33 and C44 were measured. BN was irradiated with electrons at 77K and with neutrons at 27K to determine properties after irradiation

  19. Nanodefects in ultrahard crystalline cubic boron nitride

    International Nuclear Information System (INIS)

    Cubic boron nitride (cBN), the second hardest known material after diamond, exhibits high thermal conductivity and an excellent ability to be n or p doped, which makes it a strong candidate for the next generation of high-temperature micro optical and micro electronic devices. According to recent studies, cBN exhibits a better resistance to radiation damage than diamond, which suggests potential applications in extreme radiation environments. Crystalline cBN powders of up to 0.5 mm linear size is obtained in a similar way as diamond, by catalytic conversion of hexagonal BN (hBN) to cBN at even higher pressures (> 5GPa) and temperatures (∼ 1900 K). Considering the essential role played by the nanodefects (point defects and impurities) in determining its physical properties, it is surprising how limited is the amount of published data concerning the properties of nanodefects in this material, especially by Electron Paramagnetic Resonance (EPR) spectroscopy, the most powerful method for identification and characterization of nanodefects in both insulators and semiconductors. This seems to be due mainly to the absence of natural cBN gems and the extreme difficulties in producing even mm3 sized synthetic crystals. We shall present our recent EPR studies on cBN crystalline powders, performed in a broad temperature range from room temperature (RT) down to 1.2 K on several sorts of large size cBN powder grits of yellow and amber color for industrial applications. Previous multifrequency (9.3 GHz and 95 GHz) EPR studies of brown to black cBN crystallites prepared with excess of boron, resulted in the discovery of two new types of paramagnetic point defects with different spectral properties, called the D1 and D2 centers. Our X(9.3 GHz)-band EPR investigations resulted in the observation in amber cBN crystalline powders of a spectrum with a strong temperature dependence of the lineshape. It was found that for high and low temperatures, respectively, the numerical

  20. Investigations on the characterization of ion implanted hexagonal boron nitride

    Science.gov (United States)

    Aradi, E.; Naidoo, S. R.; Erasmus, R. M.; Julies, B.; Derry, T. E.

    2013-07-01

    The effect of ion implantation on hexagonal boron nitride (h-BN) is studied herein. We use boron as an ion of choice to introduce radiation damage into h-BN, at fluences ranging from 1 × 1014-1 × 1016 ions/cm2 and implantation energy ranges from 40 to 160 keV. The thermal dependence is also investigated by varying the annealing temperature from room temperature to 400 °C after implantation. Raman spectroscopy showed Raman active defects one of which is possibly related to the formation of cubic boron nitride nanocrystals (nc-BN) within the implanted range. The relationship of these defect induced Raman active peaks was investigated by varying the implantation parameters. The preliminary Transmission Electron Microscopy (TEM) results also are reported briefly.

  1. Grain refinement by boron nitride; Gefuegemodifizierung durch Bornitrid

    Energy Technology Data Exchange (ETDEWEB)

    Bach, F.W.; Guenther, A.; Phan-Tan, T.; Kruessel, T.; Wilk, P. [Institut fuer Werkstoffkunde der Universitaet Hannover, Struktur- und Biomedizinwerkstoffe, Garbsen (Germany)

    2005-01-01

    Grain refinement of magnesium alloys aims at better deformation behaviour, higher strength and improved corrosion resistance. Besides mechanical treatment like pressing, it is possible to refine the grainsize by using nucleation materials. Whereas calcium and rare earth elements are already widely used, the use of boron nitride offers a cheap alternative to refine grains of magnesium aluminum alloys. The effect is achieved by the reaction of boron nitride with aluminum which cracks the chemical compound to form aluminum nitride with the nitrogen while boron is forming different magnesium borides. These two compounds both exhibit very high melting points and are stable in this environment so that they can act as seed crystals. Because boron nitride shows a bad wettability to metal molds, it would float on top of the mold. Therefore, it is necessary to produce pellets out of boron nitride and aluminum powder to improve contact to the mold and enhance reaction velocity. (Abstract Copyright [2005], Wiley Periodicals, Inc.) [German] Durch die Kornfeinung von Magnesiumlegierungen wird das Ziel einer Festigkeitssteigerung, einer verbesserten Umformbarkeit und einer erhoehten Korrosionsbestaendigkeit verfolgt. Neben mechanischen Loesungswegen (Strangpressen etc.) besteht die Moeglichkeit legierungstechnisch durch den Einsatz keimbildender Stoffe eine Kornfeinung zu erzielen. Neben dem Einsatz von Kalzium oder Seltenen Erden bietet Bornitrid eine kostenguenstige Moeglichkeit eine Kornfeinung fuer aluminiumhaltige Magnesiumlegierungen zu erzeugen. Die Kornfeinung beruht dabei auf der Reaktion des Bornitrids mit dem Aluminium in der Schmelze, durch welche das Bornitrid zersetzt wird und mit dem freiwerdenden Stickstoff zu Aluminiumnitrid reagiert, waehrend sich das Bor mit Magnesium zu Magnesiumboriden verbindet. Bei beiden Produkten handelt es sich um hochschmelzende, in dieser Umgebung stabile Verbindungen, die als Kristallisationskeime wirken koennen. Die Zugabe des

  2. The structure and local chemical properties of boron-terminated tetravacancies in hexagonal boron-nitride

    OpenAIRE

    Cretu, Ovidiu; Lin, Yung-Chang; Koshino, Masanori; Tizei, Luiz H. G.; Liu, Zheng; Suenaga, Kazutomo

    2014-01-01

    Imaging and spectroscopy performed in a low-voltage scanning transmission electron microscope (LV-STEM) are used to characterize the structure and chemical properties of boron-terminated tetravacancies in hexagonal boron nitride (h-BN). We confirm earlier theoretical predictions about the structure of these defects and identify new features in the electron energy-loss spectra (EELS) of B atoms using high resolution chemical maps, highlighting differences between these areas and pristine sampl...

  3. Amorphous boron nitride at high pressure

    Science.gov (United States)

    Durandurdu, Murat

    2016-06-01

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

  4. Preparation and characterization of boron nitride/carbon fiber composite with high specific surface area

    International Nuclear Information System (INIS)

    Boron nitride can be used as a good catalyst carrier because of its high thermal conductivity and chemical stability. However, a high specific surface area of boron nitride is still desirable. In this work, a carbon fiber composite coated with boron nitride villous nano-film was prepared, and was also characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The results indicated that the carbon fibers were covered by uniform villous boron nitride films whose thickness was about 150 - 200 nm. The specific surface area of the boron nitride/carbon fiber composite material was 96 m2 g-1, which was markedly improved compared with conventional boron nitride materials. (orig.)

  5. boron and boron nitride coated nuclear fuel production in plasma atmosphere

    International Nuclear Information System (INIS)

    In these study uranium dioxide (UO2) and 5, 10 % gadolinium oxide (Gd2O3) containing UO2 nuclear fuel pellets were coated with first boron nitride (BN) then boron (B) layers as the results of the reactions between boron trichloride (BCl3) with ammonia (NH3) and BCl3 with hydrogen (H2) in the medium of argon (Ar) plasma created at 650 W and 500 W and 27.12 MHz to increase the fuel burnup efficiency and reactor core life by the method of plasma enhanced chemical vapor deposition (PECVD). Grainy BN and B structures were observed on the photographs taken from scanning electron microscope (SEM)

  6. Modelling structure and properties of amorphous silicon boron nitride ceramics

    OpenAIRE

    Johann Christian Schön; Alexander Hannemann; Guneet Sethi; Ilya Vladimirovich Pentin; Martin Jansen

    2011-01-01

    Silicon boron nitride is the parent compound of a new class of high-temperature stable amorphous ceramics constituted of silicon, boron, nitrogen, and carbon, featuring a set of properties that is without precedent, and represents a prototypical random network based on chemical bonds of predominantly covalent character. In contrast to many other amorphous materials of technological interest, a-Si3B3N7 is not produced via glass formation, i.e. by quenching from a melt, the reason being that th...

  7. Substrate-induced bandgap in graphene on hexagonal boron nitride

    OpenAIRE

    Giovannetti, Gianluca; Khomyakov, Petr A.; Brocks, Geert; Paul J. Kelly; Brink, Jeroen van den

    2007-01-01

    We determine the electronic structure of a graphene sheet on top of a lattice-matched hexagonal boron nitride (h-BN) substrate using ab initio density functional calculations. The most stable configuration has one carbon atom on top of a boron atom, the other centered above a BN ring. The resulting inequivalence of the two carbon sites leads to the opening of a gap of 53 meV at the Dirac points of graphene and to finite masses for the Dirac fermions. Alternative orientations of the graphene s...

  8. Efficient boron nitride nanotube formation via combined laser-gas flow levitation

    Energy Technology Data Exchange (ETDEWEB)

    Whitney, R. Roy; Jordan, Kevin; Smith, Michael

    2014-03-18

    A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B.sub.xC.sub.yN.sub.z. The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B.sub.xC.sub.yN.sub.z.

  9. Efficient Boron Nitride Nanotube Formation via Combined Laser-Gas Flow Levitation

    Science.gov (United States)

    Whitney, R. Roy (Inventor); Jordan, Kevin (Inventor); Smith, Michael W. (Inventor)

    2014-01-01

    A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B(sub x)C(sub y)N(sub z) The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B(sub x)C(sub y)N(sub z).

  10. Tunable Band Gap of Boron Nitride Interfaces under Uniaxial Pressure

    Science.gov (United States)

    Moraes, Elizane; Manhabosco, Taise; de Oliveira, Alan; Batista, Ronaldo

    2013-03-01

    In this work we show, by means of a density functional theory formalism, that the interaction between hydrogen terminated boron nitride surfaces gives rise to a metallic interface with free carries of opposite sign at each surface. A band gap can be induced by decreasing the surface separation. The size of the band gap changes continuously from zero up to 4.4 eV with decreasing separation, which is understood in terms of the interaction between surface states.Due to the high thermal conductivity of cubic boron nitride and the coupling between band gap and applied pressure, such tunable band gap interfaces may be used in high stable electronic and electromechanical devices. In addition, the spacial separation of charge carries at the interface may lead to photovoltaic applications. The authors thank tha brazilian agencies Fapemig, CNPq and Capes

  11. Preparation of high-pressure phase boron nitride films by physical vapor deposition

    CERN Document Server

    Zhu, P W; Zhao, Y N; Li, D M; Liu, H W; Zou Guang Tian

    2002-01-01

    The high-pressure phases boron nitride films together with cubic, wurtzic, and explosive high-pressure phases, were successfully deposited on the metal alloy substrates by tuned substrate radio frequency magnetron sputtering. The percentage of cubic boron nitride phase in the film was about 50% as calculated by Fourier transform infrared measurements. Infrared peak position of cubic boron nitride at 1006.3 cm sup - sup 1 , which is close to the stressless state, indicates that the film has very low internal stress. Transition electron microscope micrograph shows that pure cubic boron nitride phase exits on the surface of the film. The growth mechanism of the BN films was also discussed.

  12. Boron nitride nanotubes as a reinforcement for brittle matrices

    Czech Academy of Sciences Publication Activity Database

    Tatarko, Peter; Grasso, S.; Porwal, H.; Saggar, Richa; Chlup, Zdeněk; Dlouhý, Ivo; Reece, M.J.

    2014-01-01

    Roč. 34, č. 14 (2014), s. 3339-3349. ISSN 0955-2219 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 EU Projects: European Commission(XE) 264526 - GLACERCO Institutional support: RVO:68081723 Keywords : Amorphous borosilicate glass * Boron nitride nanotubes * Composite * Toughening mechanisms * Scratch resistance Subject RIV: JH - Ceramic s, Fire-Resistant Materials and Glass Impact factor: 2.947, year: 2014

  13. Delamination of hexagonal boron nitride in a stirred media mill

    International Nuclear Information System (INIS)

    A scalable process for delamination of hexagonal boron nitride in an aqueous solution of the non-ionic surfactant TWEEN85 using a stirred media mill is presented. The size of the ZrO2 beads used as grinding media governs the dimensions of the ground boron nitride particles as atomic force microscopic investigations (AFM) reveal: the mean flakes thickness decreases from 3.5 to 1.5 nm and the ratio between mean flake area and mean flake thickness increases from 2,200 to 5,800 nm if the grinding media size is reduced from 0.8 to 0.1 mm. This result shows that a high number of stress events in combination with low stress energy (small grinding media) facilitate delamination of the layered material whereas at high stress energies in combination with a low number of stress events (large grinding media) breakage of the layers dominates over delamination. The results of particle height analyses by AFM show that few-layer structures have been formed by stirred media milling. This result is in agreement with the layer thickness dependence of the delamination energy for hexagonal boron nitride. The concentration of nanoparticles remaining dispersed after centrifugation of the ground suspension increases with grinding time and with decreasing grinding media size. After 5 h of grinding using 0.1 mm ZrO2 grinding media the yield of nanoparticle formation is about 5 wt%. The nanoparticles exhibit the typical Raman peak for hexagonal boron nitride at 1,366 cm−1 showing that the in-plane order in the milled platelets is remained.

  14. Method for forming monolayer graphene-boron nitride heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Effect of boron nitride coating on fiber-matrix interactions

    International Nuclear Information System (INIS)

    Coatings can modify fiber-matrix reactions and consequently interfacial bond strengths. Commercially available mullite, silicon carbide, and carbon fibers were coated with boron nitride via low pressure chemical vapor deposition and incorporated into a mullite matrix by hot-pressing. The influence of fiber-matrix interactions for uncoated fibers on fracture morphologies was studied. These observations are related to the measured values of interfacial shear strengths

  16. Phonon spectrum of single-walled boron nitride nanotubes

    Institute of Scientific and Technical Information of China (English)

    Xiao Yang; Yan Xiao-Hong; Cao Jue-Xian; Mao Yu-Liang; Xiang Jun

    2004-01-01

    Based on a force constant model, we investigated the phonon spectrum and then specific heat of single-walled boron nitride nanotubes. The results show that the frequencies of Raman and infrared active modes decrease with increasing diameter in the low frequency, which is consistent with the results calculated by density functional theory.The fitting formulae for diameter and chirality dependence of specific heat at 300K are given.

  17. Tribological properties of cubic, amorphous and hexagonal boron nitride films

    International Nuclear Information System (INIS)

    Cubic boron nitride (c-BN), amorphous boron nitride (a-BN) and hexagonal boron nitride (h-BN) films were deposited onto a silicon substrate using a magnetically enhanced plasma ion plating method which has a hot cathode plasma discharge in a parallel magnetic field. A reciprocating tribometer was used to examine friction and wear properties for these three BN films, whose crystal structures were identified by IR spectroscopy. The tribological properties were revealed to be highly dependent on the films' crystal structures. The c-BN film showed the highest wear and peeling resistance of the tested films. The lubricating performance of the c-BN film proved significant with a long lubricating life and low friction. In contrast, the a-BN and h-BN films showed short lubricating endurance lives and large friction changes in spite of the fact that they are good in general as solid lubricants. These unexpected results are speculated to reflect the premature debonding of the h-BN and a-BN films during sliding and the subsequent discharge of their flakes out of the nip between the substrate and the ball indenter, owing to their lower adhesion to the substrate. (orig.)

  18. Boron carbide nitride derived from amine-boranes

    International Nuclear Information System (INIS)

    This paper reports that amine-boranes such as pyridine- or piperazine-borane can be converted into infusible polymers by thermal crosslinking at temperatures up to 420 degrees C. Further rise of the temperature up to 1050 degrees C in argon results in transformation of the polymers into black residues. Microstructural (TEM/EELS, ESCA) and chemical investigations indicate the presence of single phase boron carbide nitrides which exhibit a graphite-like, turbostratic structure with a homogeneous distribution of the elements B, N, and C. Subsequent annealing at 2200 degrees C in argon gives rise to crystallization of the pyrolytic material generating the thermodynamically stable phases BN, C, and B4C. The semiconducting properties of the X-ray amorphous boron carbide nitride synthesized at 1050 degrees C depend on the B/N/C-ratio which can be influenced by the type of amine-borane-precursor and by the applied atmosphere (Ar or NH3) during pyrolysis. The amine-boranes can be converted into boron carbide nitride- and BN-monoliths at 1050 degrees C under argon or reactive gas (NH3), respectively. The monoliths are transformed into composites with 91% rel. density containing BN, C, and B4C when heated up to 2200 degrees C

  19. Study the gas sensing properties of boron nitride nanosheets

    Energy Technology Data Exchange (ETDEWEB)

    Sajjad, Muhammad; Feng, Peter, E-mail: p.feng@upr.edu

    2014-01-01

    Graphical abstract: - Highlights: • We synthesized boron nitride nanosheets (BNNSs) on silicon substrate. • We analyzed gas sensing properties of BNNSs-based gas-sensor device. • CH{sub 4} gas is used to measure gas-sensing properties of the device. • Quick response and recovery time of the device is recorded. • BNNSs showed excellent sensitivity to the working gas. - Abstract: In the present communication, we report on the synthesis of boron nitride nanosheets (BNNSs) and study of their gas sensing properties. BNNSs are synthesized by irradiating pyrolytic hexagonal boron nitride (h-BN) target using CO{sub 2} laser pulses. High resolution transmission electron microscopic measurements (HRTEM) revealed 2-dientional honeycomb crystal lattice structure of BNNSs. HRTEM, electron diffraction, XRD and Raman scattering measurements clearly identified h-BN. Gas sensing properties of synthesized BNNSs were analyzed with prototype gas sensor using methane as working gas. A systematic response curve of the sensor is recorded in each cycle of gas “in” and “out”; suggesting excellent sensitivity and high performance of BNNSs-based gas-sensor.

  20. Ab initio study of boron nitride lines on graphene

    Science.gov (United States)

    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.

  1. Synthesis of hexagonal boron nitride graphene-like few layers

    Science.gov (United States)

    Yuan, S.; Toury, B.; Journet, C.; Brioude, A.

    2014-06-01

    Self-standing highly crystallized hexagonal boron nitride (h-BN) mono-, bi- and few-layers have been obtained for the first time via the Polymer Derived Ceramics (PDCs) route by adding lithium nitride (Li3N) micropowders to liquid-state polyborazylene (PBN). Incorporation of Li3N as a crystallization promoter allows the onset of crystallization of h-BN at a lower temperature (1200 °C) than under classical conditions (1800 °C). The hexagonal structure was confirmed by both electron and X-ray diffraction.Self-standing highly crystallized hexagonal boron nitride (h-BN) mono-, bi- and few-layers have been obtained for the first time via the Polymer Derived Ceramics (PDCs) route by adding lithium nitride (Li3N) micropowders to liquid-state polyborazylene (PBN). Incorporation of Li3N as a crystallization promoter allows the onset of crystallization of h-BN at a lower temperature (1200 °C) than under classical conditions (1800 °C). The hexagonal structure was confirmed by both electron and X-ray diffraction. Electronic supplementary information (ESI) available: See DOI: 10.1039/c4nr01017e

  2. High Temperature Characteristic in Electrical Breakdown and Electrical Conduction of Epoxy/Boron-nitride Composite

    Science.gov (United States)

    Takenaka, Yutaka; Kurimoto, Muneaki; Murakami, Yoshinobu; Nagao, Masayuki

    The power module for the electrical vehicle needs electrical insulation material with high thermal conductivity. Recently, the epoxy insulating material filled with boron-nitride particles (epoxy/boron-nitride composite) is focused as an effective solution. However, the insulation performance of epoxy/boron-nitride composite was not investigated enough especially at the high temperature in which the power module was used, i.e. more than 100°C. In this paper, we investigated high temperature characteristics in electrical breakdown and conduction current of epoxy/boron-nitride composite. Breakdown test under the application of DC lamp voltage and impulse voltage clarified that the epoxy/boron-nitride composite had the constant breakdown strength even in the high temperature. Comparison of the epoxy/boron-nitride composite with previous material, which was epoxy/alumina composite, indicated that the breakdown voltage of the epoxy/boron-nitride composite in the high temperature was found to be higher than that of epoxy/alumina composite under the same thermal-transfer quantity among them. Furthermore, conduction current measurement of epoxy/boron-nitride composite in the high temperature suggested the possibility of the ionic conduction mechanism.

  3. Salt rejection and water transport through boron nitride nanotubes.

    Science.gov (United States)

    Hilder, Tamsyn A; Gordon, Daniel; Chung, Shin-Ho

    2009-10-01

    Nanotube-based water-purification devices have the potential to transform the field of desalination and demineralization through their ability to remove salts and heavy metals without significantly affecting the fast flow of water molecules. Boron nitride nanotubes have shown superior water flow properties compared to carbon nanotubes, and are thus expected to provide a more efficient water purification device. Using molecular dynamics simulations it is shown that a (5, 5) boron nitride nanotube embedded in a silicon nitride membrane can, in principle, obtain 100% salt rejection at concentrations as high as 1 M owing to a high energy barrier while still allowing water molecules to flow at a rate as high as 10.7 water molecules per nanosecond (or 0.9268 L m(-2) h(-1)). Furthermore, ions continue to be rejected under the influence of high hydrostatic pressures up to 612 MPa. When the nanotube radius is increased to 4.14 A the tube becomes cation-selective, and at 5.52 A the tube becomes anion-selective. PMID:19582727

  4. Structure and local chemical properties of boron-terminated tetravacancies in hexagonal boron nitride.

    Science.gov (United States)

    Cretu, Ovidiu; Lin, Yung-Chang; Koshino, Masanori; Tizei, Luiz H G; Liu, Zheng; Suenaga, Kazutomo

    2015-02-20

    Imaging and spectroscopy performed in a low-voltage scanning transmission electron microscope are used to characterize the structure and chemical properties of boron-terminated tetravacancies in hexagonal boron nitride. We confirm earlier theoretical predictions about the structure of these defects and identify new features in the electron energy-loss spectra of B atoms using high resolution chemical maps, highlighting differences between these areas and pristine sample regions. We correlate our experimental data with calculations which help explain our observations. PMID:25763963

  5. Synthesis of multiwall boron nitride nanotubes dependent on crystallographic structure of boron

    International Nuclear Information System (INIS)

    Synthesis and growth of multiwall boron nitride nanotubes (BNNTs) under the B and ZrO2 seed system in the milling–annealing process were investigated. BNNTs were synthesized by annealing a mechanically activated boron powder under nitrogen environment. We explored the aspects of the mechanical activation energy transferred to milled crystalline boron powder producing structural disorder and borothermal reaction of the ZrO2 seed particles on the synthesis of BNNTs during annealing. Under these circumstances, the chemical reaction of amorphous boron coated on the seed nanoparticles with nitrogen synthesizing amorphous BN could be enhanced. It was found that amorphous BN was crystallized to the layer structure and then grown to multiwall BNNTs during annealing. Especially, bamboo-type multiwall BNNTs were mostly produced and grown to the tail-side of the nanotube not to the round head-side. Open gaps with ∼0.3 nm of the bamboo side walls of BNNTs were also observed. Based on these understandings, it might be possible to produce bamboo-type multiwall BNNTs by optimization of the structure and shape of boron coat on the seed nanoparticles. -- Highlights: ► Structure of B is a key factor for BNNT synthesis for milling–annealing method. ► Amorphous boron is coated on the seed during milling of crystalline boron. ► Amorphous BN nanoclusters are crystallized during annealing. ► Growing of bamboo BNNTs is not to the round head-side but to the tail-side.

  6. Physical vapor deposition of cubic boron nitride thin films

    International Nuclear Information System (INIS)

    Cubic boron nitride was successfully deposited using physical vapor-deposition methods. RF-sputtering, magnetron sputtering, dual-ion-beam deposition, and ion-beam-assisted evaporation were all used. The ion-assisted evaporation, using boron evaporation and bombardment by nitrogen and argon ions, led to successful cubic boron nitride growth over the widest and most controllable range of conditions. It was found that two factors were important for c-BN growth: bombardment of the growing film and the presence of argon. A systematic study of the deposition conditions was carried out. It was found that the value of momentum transferred into the growing from by the bombarding ions was critical. There was a very narrow transition range in which mixed cubic and hexagonal phase films were prepared. Momentum-per-atom value took into account all the variables involved in ion-assisted deposition: deposition rate, ion energy, ion flux, and ion species. No other factor led to the same control of the process. The role of temperature was also studied; it was found that at low temperatures only mixed cubic and hexagonal material are deposited

  7. Turbostratic boron nitride coated on high-surface area metal oxide templates

    DEFF Research Database (Denmark)

    Klitgaard, Søren Kegnæs; Egeblad, Kresten; Brorson, M.;

    2007-01-01

    Boron nitride coatings on high-surface area MgAl2O4 and Al2O3 have been synthesized and characterized by transmission electron microscopy and by X-ray powder diffraction. The metal oxide templates were coated with boron nitride using a simple nitridation in a flow of ammonia starting from ammonium...... borate adsorbed on MgAl2O4 or gamma-Al2O3. This procedure resulted in the formation of a turbostratic boron nitride film with a thickness of a few individual BN layers....

  8. Deposition of hexagonal boron nitride thin films on silver nanoparticle substrates and surface enhanced infrared absorption

    International Nuclear Information System (INIS)

    Silver nanoparticle thin films with different average particle diameters are grown on silicon substrates. Boron nitride thin films are then deposited on the silver nanoparticle interlayers by radio frequency (RF) magnetron sputtering. The boron nitride thin films are characterized by Fourier transform infrared spectra. The average particle diameters of silver nanoparticle thin films are 126.6, 78.4, and 178.8 nm. The results show that the sizes of the silver nanoparticles have effects on the intensities of infrared spectra of boron nitride thin films. An enhanced infrared absorption is detected for boron nitride thin film grown on silver nanoparticle thin film. This result is helpful to study the growth mechanism of boron nitride thin film. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  9. Ultrathin high-temperature oxidation-resistant coatings of hexagonal boron nitride

    Science.gov (United States)

    Liu, Zheng; Gong, Yongji; Zhou, Wu; Ma, Lulu; Yu, Jingjiang; Idrobo, Juan Carlos; Jung, Jeil; MacDonald, Allan H.; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M.

    2013-10-01

    Hexagonal boron nitride is a two-dimensional layered material that can be stable at 1,500 °C in air and will not react with most chemicals. Here we demonstrate large-scale, ultrathin, oxidation-resistant coatings of high-quality hexagonal boron nitride layers with controlled thicknesses from double layers to bulk. We show that such ultrathin hexagonal boron nitride films are impervious to oxygen diffusion even at high temperatures and can serve as high-performance oxidation-resistant coatings for nickel up to 1,100 °C in oxidizing atmospheres. Furthermore, graphene layers coated with a few hexagonal boron nitride layers are also protected at similarly high temperatures. These hexagonal boron nitride atomic layer coatings, which can be synthesized via scalable chemical vapour deposition method down to only two layers, could be the thinnest coating ever shown to withstand such extreme environments and find applications as chemically stable high-temperature coatings.

  10. Synthesis of boron nitride from boron containing poly(vinyl alcohol) as ceramic precursor

    Indian Academy of Sciences (India)

    M Das; S Ghatak

    2012-02-01

    A ceramic precursor, prepared by condensation reaction from poly(vinyl alcohol) (PVA) and boric acid (H3BO3) in 1:1, 2:1 and 4:1 molar ratios, was synthesized as low temperature synthesis route for boron nitride ceramic. Samples were pyrolyzed at 850°C in nitrogen atmosphere followed by characterization using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).

  11. Low-Cost Preparation of Boron Nitride Ceramic Powders

    Institute of Scientific and Technical Information of China (English)

    LI Duan; ZHANG Changrui; LI Bin; CAO Feng; WANG Siqing; LIU Kun; FANG Zhenyu

    2012-01-01

    The amorphous boron nitride ceramic powders were prepared at 750-950 ℃ by the lowcost urea route,and the effects of preparation temperatures,molar ratios of the raw materials and oxidation treatment on the composition,structure and surface morphology of the products were investigated through FTIR,XRD and SEM.The results show that the products ceramize and crystallize gradually with the increase of the temperature.When the molar ratio and reaction temperature are 3:2 and 850 ℃,respectively,the products have high purity,compact structure and nice shape.The oxidation treatment at 450 ℃ will not impair the composition and structure of boron nitfide but effectively remove the impurities.

  12. Research on the Cutting Performance of Cubic Boron Nitride Tools

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    There were only two kinds of superhard tool material at the past, i.e. diamond and cubic boron nitride (CBN). Manmade diamond and CBN are manufactured by the middle of 20th century. Various manufacturing methods and manmade superhard materials were developed later. They were widely used in different industry and science areas. Recently, a new kind of superhard tool material, C 3N 4 coating film, had been developed. American physical scientists, A. M. Liu and M. L. Cohen, designed a new kind of inorganic c...

  13. Boron nitride nanosheets as oxygen-atom corrosion protective coatings

    International Nuclear Information System (INIS)

    The research of two-dimensional nanomaterials for anticorrosion applications is just recently burgeoning. Herein, we demonstrate the boron nitride nanosheets (BNNSs) coatings for protecting polymer from oxygen-atom corrosion. High-quality BNNSs, which are produced by an effective fluid dynamics method with multiple exfoliation mechanisms, can be assembled into coatings with controlled thickness by vacuum filtration. After exposed in atom oxygen, the naked polymer is severely corroded with remarkable mass loss, while the BNNSs-coated polymer remains intact. Barrier and bonding effects of the BNNSs are responsible for the coating's protective performance. These preliminary yet reproducible results pave a way for resisting oxygen-atom corrosion

  14. Cellulose nanofibrils (CNF) filled boron nitride (BN) nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Sulaiman, Hanisah Syed; Hua, Chia Chin; Zakaria, Sarani [School of Applied Physic, Faculty of Science and Technology, Universiti Kebangsaan Malaysia.43600 Bangi, Selangor (Malaysia)

    2015-09-25

    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.

  15. Superior thermal conductivity in suspended bilayer hexagonal boron nitride

    Science.gov (United States)

    Wang, Chengru; Guo, Jie; Dong, Lan; Aiyiti, Adili; Xu, Xiangfan; Li, Baowen

    2016-05-01

    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.

  16. Cellulose nanofibrils (CNF) filled boron nitride (BN) nanocomposites

    Science.gov (United States)

    Sulaiman, Hanisah Syed; Hua, Chia Chin; Zakaria, Sarani

    2015-09-01

    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.

  17. Cathodoluminescence of boron nitride nanotubes doped by ytterbium

    International Nuclear Information System (INIS)

    Boron nitride nanotubes (BNNTs) are wide band gap semiconducting material with super thermal and chemical stabilities, which make them an ideal nano-sized host for luminescent ions. In this work, we report an in situ synthesis of Ytterbium (Yb) doped BNNTs using a ball milling and annealing approach. Yb doped BNNTs show more red-light emissions in the cathodoluminescent (CL) spectrum in comparison with pure BNNTs. The light emission is due to the insertion of Yb ions into the nanotube wall as the BNNTs serve as a host and contribute directly to the light emission. The cathodoluminescent image demonstrates strong cathodoluminescent emission of whole Yb doped BNNTs.

  18. Aqueous compatible boron nitride nanosheets for high-performance hydrogels

    Science.gov (United States)

    Hu, Xiaozhen; Liu, Jiahui; He, Qiuju; Meng, Yuan; Cao, Liu; Sun, Ya-Ping; Chen, Jijie; Lu, Fushen

    2016-02-01

    Hexagonal boron nitride nanosheets (BNNSs) possess ultimate thermal and chemical stabilities and mechanical strengths. However, the unmodified BNNSs are hydrophobic and insoluble in water, which hinders their use in many technological areas requiring aqueous compatibility. In this work, h-BN was treated with molten citric acid to produce aqueous dispersible boron nitride sheets (ca-BNNSs). The resultant ca-BNNSs were used to fabricate ca-BNNS/polyacrylamide (i.e., BNNS2.5/PAAm) nanocomposite hydrogels, targeting high water retentivity and flexibility. The BNNS2.5/PAAm hydrogel (initially swollen in water) largely remained swollen (water content ~94 wt%) even after one-year storage under ambient conditions. Importantly, the swollen BNNS2.5/PAAm hydrogel (water content ~95 wt%) was highly flexible. Its elongation and compressive strength exceeded 10 000% and 8 MPa at 97% strain, respectively. Moreover, the aforementioned hydrogel recovered upon the removal of compression force, without obvious damage. The substantially improved water retentivity and flexibility revealed that BNNSs can serve as a promising new platform in the development of high-performance hydrogels.Hexagonal boron nitride nanosheets (BNNSs) possess ultimate thermal and chemical stabilities and mechanical strengths. However, the unmodified BNNSs are hydrophobic and insoluble in water, which hinders their use in many technological areas requiring aqueous compatibility. In this work, h-BN was treated with molten citric acid to produce aqueous dispersible boron nitride sheets (ca-BNNSs). The resultant ca-BNNSs were used to fabricate ca-BNNS/polyacrylamide (i.e., BNNS2.5/PAAm) nanocomposite hydrogels, targeting high water retentivity and flexibility. The BNNS2.5/PAAm hydrogel (initially swollen in water) largely remained swollen (water content ~94 wt%) even after one-year storage under ambient conditions. Importantly, the swollen BNNS2.5/PAAm hydrogel (water content ~95 wt%) was highly flexible. Its

  19. Preparation and characterization of thick cubic boron nitride films

    International Nuclear Information System (INIS)

    Cubic boron nitride (c-BN) films are prepared by the radio frequency magnetron sputtering technique. The stresses and crystallinities of the films are estimated by the Fourier transform infrared spectroscopy of c-BN samples, including the peak shifts and varieties of full widths at half maximum. The effects of the B—C—N interlayer and the two-stage deposition method on the c-BN films are investigated. Then the thick and stable c-BN films are prepared by a combination of the two methods. The properties of the interlayer and film are also characterized

  20. Carbon nanotube quantum dots on hexagonal boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Baumgartner, A., E-mail: andreas.baumgartner@unibas.ch; Abulizi, G.; Gramich, J.; Schönenberger, C. [Institute of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Watanabe, K.; Taniguchi, T. [National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)

    2014-07-14

    We report the fabrication details and low-temperature characteristics of carbon nanotube (CNT) quantum dots on flakes of hexagonal boron nitride (hBN) as substrate. We demonstrate that CNTs can be grown on hBN by standard chemical vapor deposition and that standard scanning electron microscopy imaging and lithography can be employed to fabricate nanoelectronic structures when using optimized parameters. This proof of concept paves the way to more complex devices on hBN, with more predictable and reproducible characteristics and electronic stability.

  1. Tuning the optical response in carbon doped boron nitride nanodots

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-09-04

    Time dependent density functional theory and the hybrid B3LYP functional are used to investigate the structural and optical properties of pristine and carbon doped hexagonal boron nitride nanodots. In agreement with recent experiments, the embedded carbon atoms are found to favor nucleation. Our results demonstrate that carbon clusters of different shapes promote an early onset of absorption by generating in-gap states. The nanodots are interesting for opto-electronics due to their tunable optical response in a wide energy window. We identify cluster sizes and shapes with optimal conversion efficiency for solar radiation and a wide absorption range form infrared to ultraviolet. This journal is

  2. Electronic structure of superlattices of graphene and hexagonal boron nitride

    KAUST Repository

    Kaloni, Thaneshwor P.

    2011-11-14

    We study the electronic structure of superlattices consisting of graphene and hexagonal boron nitride slabs, using ab initio density functional theory. We find that the system favors a short C–B bond length at the interface between the two component materials. A sizeable band gap at the Dirac point is opened for superlattices with single graphene layers but not for superlattices with graphene bilayers. The system is promising for applications in electronic devices such as field effect transistors and metal-oxide semiconductors.

  3. Synthesis of boron nitride nanotubes and their applications

    Directory of Open Access Journals (Sweden)

    Saban Kalay

    2015-01-01

    Full Text Available 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.

  4. Van der Waals interaction in a boron nitride bilayer

    International Nuclear Information System (INIS)

    We have carried out quantum Monte Carlo (QMC) calculations to study the interlayer interaction in a boron nitride (BN) bilayer. The binding energy, 81 meV/2BN after finite-size corrections, was found to be larger than that obtained by density functional theory (DFT) with local density approximation, and smaller than those using van der Waals density functionals, both by considerable amounts. The QMC calculated interaction beyond the equilibrium interlayer separation was found to have a longer-range behavior than all the available DFT schemes. (paper)

  5. Pressure effects on dynamics behavior of multiwall boron nitride nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Talebian, Taha [Faculty of Engineering, Neyshabur Branch, Islamic Azad University, Neyshabur (Iran, Islamic Republic of)

    2016-01-15

    The dynamic behavior of Multiwall boron nitride nanotubes (MWBNNTs) is investigated by employing multiple elastic shells model. The influences of van der Waals interactions on layers are shown as nonlinear functions of the interlayer distance of MWBNNTs. Governing equations are solved by using the developed finite element method and by employing time history diagrams. The radial wave speed from the outermost layer to the innermost layer is computed. The effects of geometrical factors such as diameter-to-thickness ratio on dynamic behavior of MWBNNTs are determined. The magnification aspects of MWBNNTs are computed, and the effects of surrounding pressures on wave speed and magnification aspect of MWBNNTs are discussed.

  6. INFLUENCE OF ANNEALING TEMPERATURE ON SOME PHYSICAL PROPERTIES OF CUBIC BORON NITRIDES OBTAINED FROM PYROLITIC BORON NITRIDE

    Directory of Open Access Journals (Sweden)

    N. D. Bayluk

    2010-01-01

    Full Text Available The paper presents results of investigations on dependence of dielectric, electromechanical and elastic properties of BNпсф  polycrystals (sphalerite with texture axis [111]сф, obtained from pyrolitic boron nitride  BNпг on annealing temperature up to 2173 К. Peculiar features concerning changes of the given properties in the zone of low-temperature annealing 700–773 К and phase transformation BNпг — BNпсф  are shown in the paper.

  7. Fabrication and characterization of hexagonal boron nitride powder by spray drying and calcining-nitriding technology

    International Nuclear Information System (INIS)

    Hexagonal boron nitride (hBN) powder was fabricated prepared by the spray drying and calcining-nitriding technology. The effects of nitrided temperature on the phases, morphology and particle size distribution of hBN powder, were investigated. The synthesized powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transformed infrared spectrum, ultraviolet-visible (UV-vis) spectrum and photoluminescence (PL) spectrum. UV-vis spectrum revealed that the product had one obvious band gap (4.7 eV) and PL spectrum showed that it had a visible emission at 457 nm (λex=230 nm). FESEM image indicated that the particle size of the synthesized hBN was mainly in the range of 0.5-1.5 μm in diameter, and 50-150 nm in thickness. The high-energy ball-milling process following 900 deg. C calcining process was very helpful to obtain fully crystallized hBN at lower temperature. - Graphical abstract: hBN powder was fabricated prepared by spray drying and calcining-nitriding technology. The results indicated that spray drying and calcining-nitriding technology assisted with high-energy ball-milling process following calcined process was a hopeful way to manufacture hBN powder with high crystallinity in industrial scale

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

    Science.gov (United States)

    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. PMID:27120101

  9. Facile preparation and multifunctional applications of boron nitride quantum dots

    Science.gov (United States)

    Lei, Zhouyue; Xu, Shengjie; Wan, Jiaxun; Wu, Peiyi

    2015-11-01

    Boron nitride quantum dots are obtained by a facile sonication-solvothermal technique. They are proven to be promising fluorescent bioimaging probes for bioimaging with remarkably low cytotoxicity and easily integrated into high-performance proton exchange membranes. This work will probably trigger research interest in BN and its new applications in a variety of fields.Boron nitride quantum dots are obtained by a facile sonication-solvothermal technique. They are proven to be promising fluorescent bioimaging probes for bioimaging with remarkably low cytotoxicity and easily integrated into high-performance proton exchange membranes. This work will probably trigger research interest in BN and its new applications in a variety of fields. Electronic supplementary information (ESI) available: AFM images of BN nanosheets, TEM, HRTEM and AFM images of BN QDs prepared in DMSO, digital photographs of DMF, DMSO, DMF with the addition of BN raw materials and DMSO with the addition of BN raw materials, UV-vis and FTIR spectra of the BN QDs, cell viability of the BN QDs, a summary of cell viabilities of different fluorescent QDs, digital photographs and CLSM images of the as-prepared PEMs, TGA and DSC curves of the PEMs, and AFM images of the PEMs. See DOI: 10.1039/c5nr05960g

  10. Band gap effects of hexagonal boron nitride using oxygen plasma

    International Nuclear Information System (INIS)

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

  11. Chemical Sharpening, Shortening, and Unzipping of Boron Nitride Nanotubes

    Science.gov (United States)

    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.

  12. Dimensional Crossover of Thermal Transport in Hybrid Boron Nitride Nanostructures.

    Science.gov (United States)

    Sakhavand, Navid; Shahsavari, Rouzbeh

    2015-08-26

    Although boron nitride nanotubes (BNNT) and hexagonal-BN (hBN) are superb one-dimensional (1D) and 2D thermal conductors respectively, bringing this quality into 3D remains elusive. Here, we focus on pillared boron nitride (PBN) as a class of 3D BN allotropes and demonstrate how the junctions, pillar length and pillar distance control phonon scattering in PBN and impart tailorable thermal conductivity in 3D. Using reverse nonequilibrium molecular dynamics simulations, our results indicate that although a clear phonon scattering at the junctions accounts for the lower thermal conductivity of PBN compared to its parent BNNT and hBN allotropes, it acts as an effective design tool and provides 3D thermo-mutable features that are absent in the parent structures. Propelled by the junction spacing, while one geometrical parameter, e.g., pillar length, controls the thermal transport along the out-of-plane direction of PBN, the other parameter, e.g., pillar distance, dictates the gross cross-sectional area, which is key for design of 3D thermal management systems. Furthermore, the junctions have a more pronounced effect in creating a Kapitza effect in the out-of-plane direction, due to the change in dimensionality of the phonon transport. This work is the first report on thermo-mutable properties of hybrid BN allotropes and can potentially impact thermal management of other hybrid 3D BN architectures. PMID:26158661

  13. Vertical transport in graphene-hexagonal boron nitride heterostructure devices

    Science.gov (United States)

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

    2015-09-01

    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.

  14. Electronic structure of carbon-boron nitride nanotubes

    Science.gov (United States)

    Sanginés-Mendoza, Raúl; Martinez, Edgar

    2013-03-01

    Structures of carbon and boron nitride nanotubes (CNTs, BNNTs) are quite similar, conversely, electronic properties are radically different from each other. Carbon nanotubes, whose electronic properties can be either metallic or semiconducting depending on their chiral structure, boron nitride nanotubes are always semiconductors with bandgaps over 4 eV. We have looked to hybrid systems, to predict a new kind of nanostructures with novel electronic properties. In this way, we explore the electronic properties of C-BN nanotubes. In particular, we studied the electronic structure of armchair C-BN nanotubes. The calculations were performed using the pseudopotential LCAO method with a Generalized Gradient Approximation for the exchange-correlation energy functional. The band structure of most of these systems have semiconductor character with an indirect gap smaller than its analogous BNNTs. In addition, the most prominent feature of these systems is the existence of flat bands both at the valence band top and at the conduction band minimum. Such flat bands results in sharp and narrow peaks on the total density of states. The behavior of these flat bands mainly indicates that electrons are largely localized. Thus, a detailed analysis on the electronic band structure shows that hybridization between those orbitals on the interfaces is responsible to exhibit localization effects on the hybrid systems.This research was supported by Conacyt under Grant No. 133022.

  15. Shockwave Processing of Composite Boron and Titanium Nitride Powders

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  19. Thermally activated reactions of boron nitride nanotubes with C60 fullerene: a Raman study of boron nitride-carbon nanotube composites

    International Nuclear Information System (INIS)

    Full text: Boron nitride nanotubes (BNNT) are topological analogues to single wall carbon nanotubes (SWCNT). LiKEX the latter one expects that boron nitride nanotubes can be filled with fullerenes to maKEX BN-carbon peapods. This opens new possibilities of generating nanostructures with interesting physical properties. BNNTs were first heat treated in air to open the ends and to remove excess boron particles. We analysed and refined the filling process for SWCNTs and applied it to the BNNTs. For the carbon system critical conditions were determined for opening of tube ends. Filling with C60 fullerene via vapour phase was applied. Subsequently high temperature treatment was performed to transform the fullerenes in a carbon nanotube. We performed multi-frequency Raman spectroscopy to follow the process. Some spectral features of the reaction product in the low frequency range may be assigned to small diameter carbon nanotubes inside the boron nitride nanotubes. (author)

  20. Hydrogen Storage in Boron Nitride and Carbon Nanomaterials

    Directory of Open Access Journals (Sweden)

    Takeo Oku

    2014-12-01

    Full Text Available Boron nitride (BN nanomaterials were synthesized from LaB6 and Pd/boron powder, and the hydrogen storage was investigated by differential thermogravimetric analysis, which showed possibility of hydrogen storage of 1–3 wt%. The hydrogen gas storage in BN and carbon (C clusters was also investigated by molecular orbital calculations, which indicated possible hydrogen storage of 6.5 and 4.9 wt%, respectively. Chemisorption calculation was also carried out for B24N24 cluster with changing endohedral elements in BN cluster to compare the bonding energy at nitrogen and boron, which showed that Li is a suitable element for hydrogenation to the BN cluster. The BN cluster materials would store H2 molecule easier than carbon fullerene materials, and its stability for high temperature would be good. Molecular dynamics calculations showed that a H2 molecule remains stable in a C60 cage at 298 K and 0.1 MPa, and that pressures over 5 MPa are needed to store H2 molecules in the C60 cage.

  1. Growth of atomically thin hexagonal boron nitride films by diffusion through a metal film and precipitation

    International Nuclear Information System (INIS)

    Atomically thin hexagonal boron nitride films were grown on both the top and bottom surfaces of a polycrystalline Co or Ni film by annealing a Co (Ni)/amorphous boron nitride/SiO2 structure in vacuum. This method of growing hexagonal boron nitride is much simpler than other methods, such as thermal chemical vapour deposition. B and N atoms diffuse through the metal film, although N is almost completely insoluble in both Co and Ni, and precipitation occurs at the topmost surface. The mass transport is considered to be caused by grain boundary diffusion.

  2. Charge carrier transport properties in layer structured hexagonal boron nitride

    Science.gov (United States)

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

    2014-10-01

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0)-α with α = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  3. Charge carrier transport properties in layer structured hexagonal boron nitride

    Directory of Open Access Journals (Sweden)

    T. C. Doan

    2014-10-01

    Full Text Available Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV, hexagonal boron nitride (hBN has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K. The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0−α with α = 3.02, satisfying the two-dimensional (2D carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm-1, which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  4. Beryllium decorated armchair boron nitride nanoribbon: A new planar tetracoordinate nitride containing system with enhanced conductivity

    Science.gov (United States)

    Xiao, Bo; Yu, Xuefang; Hu, Hong; Ding, Yihong

    2014-07-01

    In this Letter, a new kind of planar tetracoordinate nitride (ptN) structure is obtained via Be-decorated armchair boron nitride nanoribbon (aBNNR). The high stability of such a ptN system is confirmed by both global minimization and molecular dynamical simulation at 1500 K. The results suggest that this Be-decorated aBNNR will be a thermally stable material. The electronic property of aBNNR is significantly increased after the addition of Be atoms to the edges and the band gap decreases as the width of the ribbon decreases. Our Letter posits a new and potentially stable and useful BNNR and augments the literature on ptN.

  5. Modelling structure and properties of amorphous silicon boron nitride ceramics

    Directory of Open Access Journals (Sweden)

    Johann Christian Schön

    2011-06-01

    Full Text Available Silicon boron nitride is the parent compound of a new class of high-temperature stable amorphous ceramics constituted of silicon, boron, nitrogen, and carbon, featuring a set of properties that is without precedent, and represents a prototypical random network based on chemical bonds of predominantly covalent character. In contrast to many other amorphous materials of technological interest, a-Si3B3N7 is not produced via glass formation, i.e. by quenching from a melt, the reason being that the binary components, BN and Si3N4, melt incongruently under standard conditions. Neither has it been possible to employ sintering of μm-size powders consisting of binary nitrides BN and Si3N4. Instead, one employs the so-called sol-gel route starting from single component precursors such as TADB ((SiCl3NH(BCl2. In order to determine the atomic structure of this material, it has proven necessary to simulate the actual synthesis route.Many of the exciting properties of these ceramics are closely connected to the details of their amorphous structure. To clarify this structure, it is necessary to employ not only experimental probes on many length scales (X-ray, neutron- and electron scattering; complex NMR experiments; IR- and Raman scattering, but also theoretical approaches. These address the actual synthesis route to a-Si3B3N7, the structural properties, the elastic and vibrational properties, aging and coarsening behaviour, thermal conductivity and the metastable phase diagram both for a-Si3B3N7 and possible silicon boron nitride phases with compositions different from Si3N4: BN = 1 : 3. Here, we present a short comprehensive overview over the insights gained using molecular dynamics and Monte Carlo simulations to explore the energy landscape of a-Si3B3N7, model the actual synthesis route and compute static and transport properties of a-Si3BN7.

  6. Phase and property studies of boron carbide-boron nitride composites

    International Nuclear Information System (INIS)

    This paper reports on boron carbide-boron nitride particulate composites that were fabricated by vacuum hot-pressing. Near-theoretical densities of B4C were obtained, but percent theoretical densities decreased with increasing amounts of BN. The grain size of B4C and BN was not affected by composition, but the amount of twinning in B4C decreased with increasing BN content. No third phase was found at the B4C-BN interface by analytical STEM analysis. Lattice parameter measurements indicated slight solubility of B4C in BN, but no solubility of BN in B4C for samples hot-pressed at 2250 degrees C. Room-temperature flexural strength measurements revealed a sharply decreasing strength with increasing BN content up to 40% BN, and then relatively constant values with greater amounts of BN

  7. Nitrogen implantation effects on the chemical bonding and hardness of boron and boron nitride coatings

    Energy Technology Data Exchange (ETDEWEB)

    Anders, S; Felter, T; Hayes, J; Jankowski, A F; Patterson, R; Poker, D; Stamler, T

    1999-02-08

    Boron nitride (BN) coatings are deposited by the reactive sputtering of fully dense, boron (B) targets utilizing an argon-nitrogen (Ar-N{sub 2}) reactive gas mixture. Near-edge x-ray absorption fine structure analysis reveals features of chemical bonding in the B 1s photoabsorption spectrum. Hardness is measured at the film surface using nanoindentation. The BN coatings prepared at low, sputter gas pressure with substrate heating are found to have bonding characteristic of a defected hexagonal phase. The coatings are subjected to post-deposition nitrogen (N{sup +} and N{sub 2}{sup +}) implantation at different energies and current densities. The changes in film hardness attributed to the implantation can be correlated to changes observed in the B 1s NEXAFS spectra.

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

    International Nuclear Information System (INIS)

    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 microelectronic devices with uniform electronic properties

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

    Science.gov (United States)

    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. PMID:27153343

  10. Dynamic response of multiwall boron nitride nanotubes subjected to impact

    Indian Academy of Sciences (India)

    S T Talebian; M Tahani

    2015-12-01

    Dynamic behaviours of multiwall boron nitride nanotubes (MWBNNTs) with finite length were studied by employing continuum structure. Multiple elastic shells with nonlinear model of van der Waals interactions were used for developing an inclusive and inexpensive dynamical model of MWBNNTs. The systems of coupled partial differential equations were solved by applying the finite element method. Whole or part of thin and bulky MWBNNTs were exposed to external pressure impact and dynamical treatment were investigated and precision of results were checked by evaluating the answers with those found by other methods. Both deflection and stress studies were carried out for tubes of MWBNNTs and the influences of longitudinal wave caused by external pressure impact were considered in MWBNNTs. Also, time history diagrams of MWBNNTs with impact of initial longitudinal deflection were investigated and the extension of the longitudinal waves through the length of layers were shown and so, wave speed was determined.

  11. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    International Nuclear Information System (INIS)

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO2, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications

  12. High thermal conductivity of hexagonal boron nitride laminates

    Science.gov (United States)

    Zheng, Jin-Cheng; Zhang, Liang; Kretinin, A. V.; Morozov, S. V.; Wang, Yi Bo; Wang, Tun; Li, Xiaojun; Ren, Fei; Zhang, Jingyu; Lu, Ching-Yu; Chen, Jia-Cing; Lu, Miao; Wang, Hui-Qiong; Geim, A. K.; Novoselov, K. S.

    2016-03-01

    Two-dimensional materials are characterised by a number of unique physical properties which can potentially make them useful to a wide diversity of applications. In particular, the large thermal conductivity of graphene and hexagonal boron nitride (hBN) has already been acknowledged and these materials have been suggested as novel core materials for thermal management in electronics. However, it was not clear if mass produced flakes of hBN would allow one to achieve an industrially-relevant value of thermal conductivity. Here we demonstrate that laminates of hBN exhibit thermal conductivity of up to 20 W/m·K, which is significantly larger than that currently used in thermal management. We also show that the thermal conductivity of laminates increases with the increasing volumetric mass density, which creates a way of fine tuning its thermal properties.

  13. Phonon wave interference in graphene and boron nitride superlattice

    Science.gov (United States)

    Chen, Xue-Kun; Xie, Zhong-Xiang; Zhou, Wu-Xing; Tang, Li-Ming; Chen, Ke-Qiu

    2016-07-01

    The thermal transport properties of the graphene and boron nitride superlattice (CBNSL) are investigated via nonequilibrium molecular dynamics simulations. The simulation results show that a minimum lattice thermal conductivity can be achieved by changing the period length of the superlattice. Additionally, it is found that the period length at the minimum shifts to lower values at higher temperatures, and that the depth of the minimum increases with decreasing temperature. In particular, at 200 K, the thermal conductivities of CBNSLs with certain specific period lengths are nearly equal to the corresponding values at 300 K. A detailed analysis of the phonon spectra shows that this anomalous thermal conductivity behavior is a result of strong phonon wave interference. These observations indicate a promising strategy for manipulation of thermal transport in superlattices.

  14. Thermal conductivity of vertically aligned boron nitride nanotubes

    Science.gov (United States)

    Essedik Belkerk, Boubakeur; Achour, Amine; Zhang, Dongyan; Sahli, Salah; Djouadi, M.-Abdou; Khin Yap, Yoke

    2016-07-01

    For the first time, we report the thermal conductivity of vertically aligned boron nitride nanotube (BNNT) films produced by catalytic chemical vapor deposition. High-quality BNNTs were synthesized at 1200 °C on fused silica substrates precoated with Pt thin-film thermometers. The thermal conductivity of the BNNTs was measured at room temperature by using a pulsed photothermal technique. The apparent thermal conductivity of the BNNT coatings increased from 55 to 170 W m‑1 K‑1 when the thickness increased from 10 to 28 µm, while the thermal conductivity attained a value as high as 2400 W m‑1 K‑1. These results suggested that BNNTs, which are highly thermally conductive, but electrically insulating, are promising materials with unique properties.

  15. Modelling heat conduction in polycrystalline hexagonal boron-nitride films

    Science.gov (United States)

    Mortazavi, Bohayra; Pereira, Luiz Felipe C.; Jiang, Jin-Wu; Rabczuk, Timon

    2015-08-01

    We conducted extensive molecular dynamics simulations to investigate the thermal conductivity of polycrystalline hexagonal boron-nitride (h-BN) films. To this aim, we constructed large atomistic models of polycrystalline h-BN sheets with random and uniform grain configuration. By performing equilibrium molecular dynamics (EMD) simulations, we investigated the influence of the average grain size on the thermal conductivity of polycrystalline h-BN films at various temperatures. Using the EMD results, we constructed finite element models of polycrystalline h-BN sheets to probe the thermal conductivity of samples with larger grain sizes. Our multiscale investigations not only provide a general viewpoint regarding the heat conduction in h-BN films but also propose that polycrystalline h-BN sheets present high thermal conductivity comparable to monocrystalline sheets.

  16. Transverse electric surface mode in atomically thin Boron-Nitride.

    Science.gov (United States)

    Merano, Michele

    2016-06-01

    The spatial confinement and the propagation length of surface waves in a single-layer two-dimensional atomic crystal are analyzed in terms of its surface susceptibility and its surface conductivity. Based on the values of these macroscopic parameters, extracted from experimental observations, it is confirmed that graphene supports a transverse magnetic nonradiating surface mode in the ultraviolet spectral region while a single-layer hexagonal Boron-Nitride is predicted to support a transverse electric nonradiating surface mode in the visible spectrum. This last mode, at a vacuum wavelength of 633 nm, has a spatial confinement of 15 μm and an intensity-propagation distance greater than 2 cm. PMID:27244441

  17. A molecular dynamics study of nanofracture in monolayer boron nitride

    International Nuclear Information System (INIS)

    In this paper, we use molecular dynamics (MD) modeling to study the fracture properties of monolayer hexagonal boron nitride (h-BN) under mixed mode I and II loading. We investigate the impact of crack edge chirality, crack tip configuration and loading phase angle on the crack propagation path and critical stress intensity factors. The MD results predict that under all the loading phase angles cracks prefer to propagate along a zigzag direction and the critical stress intensity factors of zigzag cracks are higher than those of armchair cracks. Under mixed mode loading, the h-BN sheets can undergo out-of-plane deformations due to the buckling induced by compressive stresses. The out-of-plane deformations can be significant when mode II loading is dominant. An excessive amount of out-of-plane deformation can induce buckling cracks. Depending on the loading phase angle and crack configurations, buckling cracks can nucleate before or after the propagation of the original cracks

  18. Submicron cubic boron nitride as hard as diamond

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Guoduan; Kou, Zili, E-mail: kouzili@scu.edu.cn, E-mail: yanxz@hpstar.ac.cn; Lei, Li; Peng, Fang; Wang, Qiming; Wang, Kaixue; Wang, Pei; Li, Liang; Li, Yong; Wang, Yonghua [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Yan, Xiaozhi, E-mail: kouzili@scu.edu.cn, E-mail: yanxz@hpstar.ac.cn; Li, Wentao [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Bi, Yan [Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physic, China Academy of Engineering Physics, Mianyang 621900 (China); Leng, Yang [Department of Mechanical Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong (China); He, Duanwei [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physic, China Academy of Engineering Physics, Mianyang 621900 (China)

    2015-03-23

    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.

  19. Nanocrystalline-graphene-tailored hexagonal boron nitride thin films.

    Science.gov (United States)

    Lee, Kang Hyuck; Shin, Hyeon-Jin; Kumar, Brijesh; Kim, Han Sol; Lee, Jinyeong; Bhatia, Ravi; Kim, Sang-Hyeob; Lee, In-Yeal; Lee, Hyo Sug; Kim, Gil-Ho; Yoo, Ji-Beom; Choi, Jae-Young; Kim, Sang-Woo

    2014-10-20

    Unintentionally formed nanocrystalline graphene (nc-G) can act as a useful seed for the large-area synthesis of a hexagonal boron nitride (h-BN) thin film with an atomically flat surface that is comparable to that of exfoliated single-crystal h-BN. A wafer-scale dielectric h-BN thin film was successfully synthesized on a bare sapphire substrate by assistance of nc-G, which prevented structural deformations in a chemical vapor deposition process. The growth mechanism of this nc-G-tailored h-BN thin film was systematically analyzed. This approach provides a novel method for preparing high-quality two-dimensional materials on a large surface. PMID:25204810

  20. Mechanical strength of boron nitride nanotube-polymer interfaces

    International Nuclear Information System (INIS)

    We investigate the mechanical strength of boron nitride nanotube (BNNT) polymer interfaces by using in situ electron microscopy nanomechanical single-tube pull-out techniques. The nanomechanical measurements show that the shear strengths of BNNT-epoxy and BNNT-poly(methyl methacrylate) interfaces reach 323 and 219 MPa, respectively. Molecular dynamics simulations reveal that the superior load transfer capacity of BNNT-polymer interfaces is ascribed to both the strong van der Waals interactions and Coulomb interactions on BNNT-polymer interfaces. The findings of the extraordinary mechanical strength of BNNT-polymer interfaces suggest that BNNTs are excellent reinforcing nanofiller materials for light-weight and high-strength polymer nanocomposites

  1. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)

    2016-01-04

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  2. Preparation of ohmic n-type cubic boron nitride contacts

    CERN Document Server

    Wang Cheng Xin; Li Xun; Zhang Tie Chen; Han Yong; Luo Ji Feng; Shen Cai Xia; Gao Chun Xi; Zou Guang Tian

    2002-01-01

    Ohmic electrodes in the form of n-type (Si-doped) cubic boron nitride (c-BN) bulk crystals were fabricated by utilizing a covering technique, depositing Ti(10 nm)/Mo/(20 nm)/Pt-Au(200 nm) ohmic contact metal on both the sides of the c-BN substrate. The size of the specimen electrode was 100 x 100 mu m sup 2 on one side and 300 x 300 mu m sup 2 on the other side. Measurements on the specimen were made using a specially made device. Linear current-voltage characteristics were obtained. It is considered that the contact between the Ti-and Si-doped c-BN was ohmic.

  3. Transverse electric surface mode in atomically thin Boron-Nitride

    CERN Document Server

    Merano, Michele

    2016-01-01

    The spatial confinement and the propagation length of surface waves in a single-layer two-dimensional atomic crystal are analysed in term of its surface susceptibility and its surface conductivity. Based on the values of these macroscopic parameters, extracted from experimental observations, it is confirmed that graphene supports a transverse magnetic non-radiating surface mode in the ultraviolet spectral region while a single-layer hexagonal Boron-Nitride is predicted to support a transverse electric non-radiating surface mode in the visible spectrum. This last mode, at a vacuum wavelength of 633 nm, has a spatial confinement of 15 microns and an intensity-propagation distance greater than 2 cm.

  4. Etched graphene quantum dots on hexagonal boron nitride

    Science.gov (United States)

    Engels, S.; Epping, A.; Volk, C.; Korte, S.; Voigtländer, B.; Watanabe, K.; Taniguchi, T.; Trellenkamp, S.; Stampfer, C.

    2013-08-01

    We report on the fabrication and characterization of etched graphene quantum dots (QDs) on hexagonal boron nitride (hBN) and SiO2 with different island diameters. We perform a statistical analysis of Coulomb peak spacings over a wide energy range. For graphene QDs on hBN, the standard deviation of the normalized peak spacing distribution decreases with increasing QD diameter, whereas for QDs on SiO2 no diameter dependency is observed. In addition, QDs on hBN are more stable under the influence of perpendicular magnetic fields up to 9 T. Both results indicate a substantially reduced substrate induced disorder potential in graphene QDs on hBN.

  5. Photoresponsive memory device based on Graphene/Boron Nitride heterostructure

    Science.gov (United States)

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

    2015-03-01

    Recent technological advancements have allowed the stacking of two dimensional layered material in order to create van der Waals heterostructures (VDH), enabling the design of novel properties by exploiting the proximal interaction between layers with different electronic properties. We report the creation of an optoelectronic memory device using a Graphene/Boron Nitride (hBN) heterostructure. Using the photo-induced doping phenomenon, we are able to spatially ``write'' a doping profile on graphene and ``read'' the profile through electrical transport and local probe techniques. We then utilize defect engineering to enhance the optoelectronic response of graphene and explore the effect of defects in hBN. Our work introduces a simple device architecture to create an optoelectronic memory device and contributes towards understanding the proximal effects of hBN on Graphene.

  6. Functionalized hexagonal boron nitride nanomaterials: emerging properties and applications.

    Science.gov (United States)

    Weng, Qunhong; Wang, Xuebin; Wang, Xi; Bando, Yoshio; Golberg, Dmitri

    2016-07-11

    Functionalization is an important way to breed new properties and applications for a material. This review presents an overview of the progresses in functionalized hexagonal boron nitride (h-BN) nanomaterials. It begins with an introduction of h-BN structural features, physical and chemical properties, followed by an emphasis on the developments of BN functionalization strategies and its emerging properties/applications, and ends with the research perspectives. Different functionalization methods, including physical and chemical routes, are comprehensively described toward fabrication of various BN derivatives, hetero- and porous structures, etc. Novel properties of functionalized BN materials, such as high water solubility, excellent biocompatibility, tunable surface affinities, good processibility, adjustable band gaps, etc., have guaranteed wide applications in biomedical, electronic, composite, environmental and "green" energy-related fields. PMID:27173728

  7. Hexagonal-boron nitride substrates for electroburnt graphene nanojunctions

    Science.gov (United States)

    Sadeghi, Hatef; Sangtarash, Sara; Lambert, Colin

    2016-08-01

    We examine the effect of a hexagonal boron nitride (hBN) substrate on electron transport through graphene nanojunctions just before gap formation. Junctions in vacuum and on hBN are formed using classical molecular dynamics to create initial structures, followed by relaxation using density functional theory. We find that the hBN only slightly reduces the current through the junctions at low biases. Furthermore due to quantum interference at the last moments of breaking, the current though a single carbon filament spanning the gap is found to be higher than the current through two filaments spanning the gap in parallel. This feature is present both in the presence of absence of hBN.

  8. Ultraviolet dielectric hyperlens with layered graphene and boron nitride

    CERN Document Server

    Wang, Junxia; Zhang, Baile

    2012-01-01

    The concept of hyperlens, as a novel transformation optics device, is a promising real-time super-resolution lens that can effectively transform evanescent waves into propagating waves and thus break the diffraction limit. However, previous hyperlens implementations usually adopted metal which would absorb most energy during light transmission and thus deteriorate imaging efficiency. Here we propose a novel hyperlens design based on dielectric layered graphene and h-boron nitride (h-BN) whose performance can surpass the counterpart design with metal. Our first-principle and Kramers-Kronig relation calculation shows that both layered graphene and layered h-BN exhibit strong anisotropic properties in ultraviolet spectrum regions, where their permittivity components perpendicular to the optic axis can be negative while the components parallel to the optic axis can be positive. Based on the anisotropic properties, flat and cylindrical hyperlenses are designed and numerically verified with layered graphene at 1200...

  9. A new monoclinic structure for compressed hexagonal boron nitride

    International Nuclear Information System (INIS)

    A prominent contraction of the interplanar spacing between sp2 sheets from 3.33 to 3.10 angstrom in so-called compressed h-BN, which appears on the phase transition from h(hexagonal)- to c(cubic)-boron nitride (BN) under high pressure (7.7 GPa) at high temperature (1,800 C), is examined by high-resolution transmission electron microscopy (HRTEM). It is attributable to a monoclinic lattice distortion of the residual h-BN, which originates from the difference in the compressibility as well as the thermal expansion between adjoining h- and c-BN grains. The parameters of the monoclinic unit-cell are am = 4.33, bm = 2.50, cm = 3.1--3.3 angstrom and β = 92--95 degree. Thin plates of h-BN are often folded and the folding also causes the monoclinic structure

  10. Piezoelectricity in planar boron nitride via a geometric phase

    Science.gov (United States)

    Droth, Matthias; Burkard, Guido; Pereira, Vitor M.

    2016-08-01

    Due to their low surface mass density, two-dimensional materials with a strong piezoelectric response are interesting for nanoelectromechanical systems with high force sensitivity. Unlike graphene, the two sublattices in a monolayer of hexagonal boron nitride (hBN) are occupied by different elements, which breaks inversion symmetry and allows for piezoelectricity. This has been confirmed with density functional theory calculations of the piezoelectric constant of hBN. Here, we formulate an entirely analytical derivation of the electronic contribution to the piezoelectric response in this system based on the concepts of strain-induced pseudomagnetic vector potential and the modern theory of polarization that relates the polar moment to the Berry curvature. Our findings agree with the symmetry restrictions expected for the hBN lattice and reproduce well the magnitude of the piezoelectric effect previously obtained ab initio.

  11. Mechanical strength of boron nitride nanotube-polymer interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiaoming; Ke, Changhong, E-mail: xqwang@uga.edu, E-mail: cke@binghamton.edu [Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, New York 13902 (United States); Zhang, Liuyang; Wang, Xianqiao, E-mail: xqwang@uga.edu, E-mail: cke@binghamton.edu [College of Engineering, University of Georgia, Athens, Georgia 30602 (United States); Park, Cheol [NASA Langley Research Center, Hampton, Virginia 23681 (United States); Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Fay, Catharine C. [NASA Langley Research Center, Hampton, Virginia 23681 (United States)

    2015-12-21

    We investigate the mechanical strength of boron nitride nanotube (BNNT) polymer interfaces by using in situ electron microscopy nanomechanical single-tube pull-out techniques. The nanomechanical measurements show that the shear strengths of BNNT-epoxy and BNNT-poly(methyl methacrylate) interfaces reach 323 and 219 MPa, respectively. Molecular dynamics simulations reveal that the superior load transfer capacity of BNNT-polymer interfaces is ascribed to both the strong van der Waals interactions and Coulomb interactions on BNNT-polymer interfaces. The findings of the extraordinary mechanical strength of BNNT-polymer interfaces suggest that BNNTs are excellent reinforcing nanofiller materials for light-weight and high-strength polymer nanocomposites.

  12. Thermal conductivity of polymer composites with oriented boron nitride

    International Nuclear Information System (INIS)

    Highlights: • Thermal conductivity depended on the orientation of BN in the polymer matrices. • Hexagonal boron nitride (BN) particles were treated by C27H27N3O2 and C14H6O8. • Amphiphilic-agent-treated BN particles are more easily oriented in the composite. • BN/PVA composites with C14H6O8-treated BN showed the highest thermal conductivity. • Thermal conductivity of the composites was compared with several theoretical models. - Abstract: Thermal conductivity of boron nitride (BN) with polyvinyl alcohol (PVA) and/or polyvinyl butyral (PVB) was investigated as a function of the degree of BN orientation, the numbers of hydroxyl groups in the polymer matrices and the amphiphilic agents used. The composites with in-plane orientation of BN showed a higher thermal conductivity than the composites with out-of-plane orientation of BN due to the increase of thermal pathway. For a given BN content, the composites with in-plane orientation of BN/PVA showed higher thermal conductivity than the composites with in-plane orientation of BN/PVB. This result could be attributed to the improved degree of orientation of BN, caused by a larger number of hydroxyl groups being present. Those treated with C14H6O8 amphiphilic agent demonstrated a higher thermal conductivity than those treated by C27H27N3O2. The measured thermal conductivity of the composites was compared with that predicted by the several theoretical models

  13. Reduced stability of copper interconnects due to wrinkles and steps on hexagonal boron nitride substrates

    Science.gov (United States)

    Gao, Jian; Chow, Philippe K.; Thomas, Abhay V.; Lu, Toh-Ming; Borca-Tasciuc, Theodorian; Koratkar, Nikhil

    2014-09-01

    There is great scientific and technological interest in the use of chemical-vapor-deposition grown hexagonal boron nitride dielectric substrates for microelectronics applications. This interest stems from its superior heat spreading capability compared to silicon dioxide as well as the lack of surface dangling bonds or charge traps in hexagonal boron nitride which results in superior performance for graphene based electronics devices. However, surface heterogeneities, such as wrinkles or steps, are ubiquitous in such devices due to the fabrication and processing of chemical vapor deposition grown hexagonal boron nitride. In this study, we characterize the effect of such surface heterogeneities on the stability of copper interconnects used in microelectronics devices. Based on the theoretical thermo-physical properties of the constituent thin film layers, our simulations predict that copper interconnects deposited on hexagonal boron nitride can withstand ˜1.9 times more power than on a silicon dioxide substrate, due to its superior in-plane thermal conductivity. However, our electrical measurements reveal that copper wires melt and fail at consistently lower current densities on hexagonal boron nitride than on silicon dioxide. This was verified by testing in air as well as under vacuum. Scanning electron microscopy and atomic force microscopy characterization of the hexagonal boron nitride surface indicates that this contradictory result is due to nanoscale surface non-uniformities (i.e., wrinkles and steps) which are omnipresent in chemical-vapor-deposition grown and transferred hexagonal boron nitride films. Our results highlight the critical need for improved processing methods before large-scale microelectronics applications of chemical vapor deposition grown hexagonal boron nitride can be realized.

  14. Computer-aided analytical control of diamond and cubic boron nitride grits

    International Nuclear Information System (INIS)

    Methodical and information aspects of the superhard materials powder uniformity as a characteristics of the powder quality are discussed. Computer-aided analytical methods of the rapid diagnostics of the sieve granulometric composition and the external specific surface of diamond and cubic boron nitride grits are described. The results of the application of the developed methods and software to standard powders of synthetic diamond and cubic boron nitride are given

  15. Electronic properties of Mn-decorated silicene on hexagonal boron nitride

    KAUST Repository

    Kaloni, Thaneshwor P.

    2013-12-17

    We study silicene on hexagonal boron nitride, using first-principles calculations. Since hexagonal boron nitride is semiconducting, the interaction with silicene is weaker than for metallic substrates. It therefore is possible to open a 50 meV band gap in the silicene. We further address the effect of Mn decoration by determining the onsite Hubbard interaction parameter, which turns out to differ significantly for decoration at the top and hollow sites. The induced magnetism in the system is analyzed in detail.

  16. Hexagonal boron nitride for deep ultraviolet photonic devices

    International Nuclear Information System (INIS)

    This paper provides a brief overview on recent advances in tackling the doping and optical polarization issues involved in the development of high performance deep ultraviolet (DUV) light emitting devices. In particular, recent developments in the exploitation of a novel DUV emitter layer structure based on a hexagonal boron nitride (hBN) and AlGaN p–n junction and doping engineering to potentially overcome the intrinsic problem of low p-type conductivity (or low free hole concentration) in Al-rich AlGaN are summarized. By implementing the wide bandgap and highly conductive hBN p-type layer strategy in nitride DUV emitters, p-type conductivities and DUV transparency of the electron blocking layer and p-type contact layer will be dramatically increased. This will significantly improve the free hole injection and quantum efficiency, reduce the operating voltage and heat generation, and increase the device operating lifetime. The growth of undoped and Mg-doped p-type hBN via a metal organic chemical vapor deposition technique has been studied. Furthermore, p-hBN/n-AlGaN p–n junctions have been fabricated and characterized to demonstrate the feasibility and potential of p-hBN/n-AlGaN p–n heterostructure based DUV light emitting devices. Further improvements in material quality, p-type conductivity control and device processing procedures would enhance the properties of these p–n structures, which could ultimately pave the way towards the realization of high efficiency nitride DUV photonic devices. (invited article)

  17. Transport properties of ultrathin black phosphorus on hexagonal boron nitride

    International Nuclear Information System (INIS)

    Ultrathin black phosphorus, or phosphorene, is a two-dimensional material that allows both high carrier mobility and large on/off ratios. Similar to other atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer black phosphorus is expected to be affected by the underlying substrate. The properties of black phosphorus have so far been studied on the widely utilized SiO2 substrate. Here, we characterize few-layer black phosphorus field effect transistors on hexagonal boron nitride—an atomically smooth and charge trap-free substrate. We measure the temperature dependence of the field effect mobility for both holes and electrons and explain the observed behavior in terms of charged impurity limited transport. We find that in-situ vacuum annealing at 400 K removes the p-doping of few-layer black phosphorus on both boron nitride and SiO2 substrates and reduces the hysteresis at room temperature

  18. Effects of heat treatment on properties of boron nitride fiber

    Institute of Scientific and Technical Information of China (English)

    LI Duan; ZHANG ChangRui; LI Bin; CAO Feng; WANG SiQing

    2012-01-01

    The boron nitride fibers were heated at the range of 600-1400°C in flowing nitrogen and air,respectively,and the effects of heat treatment on the structure,composition and morphology of BN fibers were studied.The results showed that BN fibers exhibited smooth surfaces,and that t-BN was the main phase with a little B2O3 included.After heat treatment at 1400°C in nitrogen atmosphere,the fibers displayed rough surfaces with little change in mass.Better crystallinity was obtained with the increasing temperature.During heat treatment in air,the fibers were oxidized severely as the temperature went up,especially at 1400°C.The volatilization of B2O3,HBO2 and H3BO3 led to the pores on the surfaces of the fibers,while the boron oxide glaze and nitrogen gas produced during the oxidation process protected the fibers from further oxidation.

  19. Transport properties of ultrathin black phosphorus on hexagonal boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Doganov, Rostislav A.; Özyilmaz, Barbaros [Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore (Singapore); Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, 28 Medical Drive, 117456 Singapore (Singapore); Koenig, Steven P.; Yeo, Yuting [Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore (Singapore); Watanabe, Kenji; Taniguchi, Takashi [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)

    2015-02-23

    Ultrathin black phosphorus, or phosphorene, is a two-dimensional material that allows both high carrier mobility and large on/off ratios. Similar to other atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer black phosphorus is expected to be affected by the underlying substrate. The properties of black phosphorus have so far been studied on the widely utilized SiO{sub 2} substrate. Here, we characterize few-layer black phosphorus field effect transistors on hexagonal boron nitride—an atomically smooth and charge trap-free substrate. We measure the temperature dependence of the field effect mobility for both holes and electrons and explain the observed behavior in terms of charged impurity limited transport. We find that in-situ vacuum annealing at 400 K removes the p-doping of few-layer black phosphorus on both boron nitride and SiO{sub 2} substrates and reduces the hysteresis at room temperature.

  20. Preparation and properties of unidirectional boron nitride fibre reinforced boron nitride matrix composites via precursor infiltration and pyrolysis route

    International Nuclear Information System (INIS)

    Highlights: → BN fibres degrade little when exposed at elevated temperatures. → Precursor infiltration and pyrolysis route is useful to prepare BNf/BN composites. → Few reports have related to the preparation and properties of BNf/BN composites. → BNf/BN composites have desirable high-temperature mechanical properties. → BNf/BN composites have excellent dielectric properties at 2-18 GHz. - Abstract: The unidirectional boron nitride fibre reinforced boron nitride matrix (BNf/BN) composites were prepared via the precursor infiltration and pyrolysis (PIP) route, and the structure, composition, mechanical and dielectric properties were studied. The composites have a high content and fine crystallinity of BN. The density is 1.60 g cm-3 with a low open porosity of 4.66%. The composites display good mechanical properties with the average flexural strength, elastic modulus and fracture toughness being 53.8 MPa, 20.8 GPa and 6.88 MPa m1/2, respectively. Lots of long fibres pull-out from the fracture surface, suggesting a good fibre/matrix interface. As temperature increases, both of the flexural strength and elastic modulus exhibit a decreasing trend, with the lowest values being 36.2 MPa and 8.6 GPa at 1000 deg. C, respectively. The desirable residual ratios of the flexural strength and elastic modulus at 1000 deg. C are 67.3% and 41.3%, respectively. The composites have excellent dielectric properties, with the average dielectric constant and loss tangent being 3.07 and 0.0044 at 2-18 GHz, respectively.

  1. Optical Spectroscopy of Two Dimensional Graphene and Boron Nitride

    Science.gov (United States)

    Ju, Long

    This dissertation describes the use of optical spectroscopy in studying the physical properties of two dimensional nano materials like graphene and hexagonal boron nitride. Compared to bulk materials, atomically thin two dimensional materials have a unique character that is the strong dependence of physical properties on external control. Both electronic band structure and chemical potential can be tuned in situ by electric field-which is a powerful knob in experiment. Therefore the optical study at atomic thickness scale can greatly benefit from modern micro-fabrication technique and electric control of the material properties. As will be shown in this dissertation, such control of both gemometric and physical properties enables new possibilities of optical spectroscopic measurement as well as opto-electronic studies. Other experimental techniques like electric transport and scanning tunneling microscopy and spectroscopy are also combined with optical spectroscopy to reveal the physics that is beyond the reach of each individual technique. There are three major themes in the dissertation. The first one is focused on the study of plasmon excitation of Dirac electrons in monolayer graphene. Unlike plasmons in ordinary two dimensional electron gas, plasmons of 2D electrons as in graphene obey unusual scaling laws. We fabricate graphene micro-ribbon arrays with photolithography technique and use optical absorption spectroscopy to study its absorption spectrum. The experimental result demonstrates the extraordinarily strong light-plasmon coupling and its novel dependence on both charge doping and geometric dimensions. This work provides a first glance at the fundamental properties of graphene plasmons and forms the basis of an emerging subfield of graphene research and applications such as graphene terahertz metamaterials. The second part describes the opto-electronic response of heterostructures composed of graphene and hexagonal boron nitride. We found that there is

  2. Interaction of carbohydrate modified boron nitride nanotubes with living cells.

    Science.gov (United States)

    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. PMID:26222410

  3. The Adhesion Improvement of Cubic Boron Nitride Film on High Speed Steel Substrate Implanted by Boron Element

    Institute of Scientific and Technical Information of China (English)

    CAI Zhi-hai; ZHANG Ping; TAN Jun

    2005-01-01

    Cubic boron nitride(c-BN) films were deposited on W6Mo5Cr4V2 high speed steel(HSS) substrate implanted with boron ion by RF-magnetron sputtering. The films were analyzed by the bending beam method, scratch test, XPS and AFM. The experimental results show that the implantation of boron atom can reduce the in ternal stress and improve the adhesion strength of the films. The critical load of scratch test rises to 27.45 N, compared to 1.75 N of c-BN film on the unimplanted HSS. The AFM shows that the surface of the c-BN film on the implanted HSS is low in roughness and small in grain size. Then the composition of the boron implanted layer was analyzed by the XPS. And the influence of the boron implanted layer on the internal stress and adhesion strength of c-BN films were investigated.

  4. Graphene on hexagonal boron nitride as a tunable hyperbolic metamaterial

    Science.gov (United States)

    Dai, S.; Ma, Q.; Liu, M. K.; Andersen, T.; Fei, Z.; Goldflam, M. D.; Wagner, M.; Watanabe, K.; Taniguchi, T.; Thiemens, M.; Keilmann, F.; Janssen, G. C. A. M.; Zhu, S.-E.; Jarillo-Herrero, P.; Fogler, M. M.; Basov, D. N.

    2015-08-01

    Hexagonal boron nitride (h-BN) is a natural hyperbolic material, in which the dielectric constants are the same in the basal plane (ɛt ≡ ɛx = ɛy) but have opposite signs (ɛtɛz phonon polaritons—collective modes that originate from the coupling between photons and electric dipoles in phonons. However, control of these hyperbolic phonon polaritons modes has remained challenging, mostly because their electrodynamic properties are dictated by the crystal lattice of h-BN. Here we show, by direct nano-infrared imaging, that these hyperbolic polaritons can be effectively modulated in a van der Waals heterostructure composed of monolayer graphene on h-BN. Tunability originates from the hybridization of surface plasmon polaritons in graphene with hyperbolic phonon polaritons in h-BN, so that the eigenmodes of the graphene/h-BN heterostructure are hyperbolic plasmon-phonon polaritons. The hyperbolic plasmon-phonon polaritons in graphene/h-BN suffer little from ohmic losses, making their propagation length 1.5-2.0 times greater than that of hyperbolic phonon polaritons in h-BN. The hyperbolic plasmon-phonon polaritons possess the combined virtues of surface plasmon polaritons in graphene and hyperbolic phonon polaritons in h-BN. Therefore, graphene/h-BN can be classified as an electromagnetic metamaterial as the resulting properties of these devices are not present in its constituent elements alone.

  5. One-dimensional surface phonon polaritons in boron nitride nanotubes.

    Science.gov (United States)

    Xu, Xiaoji G; Ghamsari, Behnood G; Jiang, Jian-Hua; Gilburd, Leonid; Andreev, Gregory O; Zhi, Chunyi; Bando, Yoshio; Golberg, Dmitri; Berini, Pierre; Walker, Gilbert C

    2014-01-01

    Surface polaritons, which are electromagnetic waves coupled to material charge oscillations, have enabled applications in concentrating, guiding and harvesting optical energy below the diffraction limit. Surface plasmon polaritons involve oscillations of electrons and are accessible in noble metals at visible and near-infrared wavelengths, whereas surface phonon polaritons (SPhPs) rely on phonon resonances in polar materials, and are active in the mid-infrared. Noble metal surface plasmon polaritons have limited applications in the mid-infrared. SPhPs at flat interfaces normally possess long polariton wavelengths and provide modest field confinement/enhancement. Here we demonstrate propagating SPhPs in a one-dimensional material consisting of a boron nitride nanotube at mid-infrared wavelengths. The observed SPhP exhibits high field confinement and enhancement, and a very high effective index (neff~70). We show that the modal and propagation length characteristics of the SPhPs may be controlled through the nanotube size and the supporting substrates, enabling mid-infrared applications. PMID:25154586

  6. Efficient gating of epitaxial boron nitride monolayers by substrate functionalization

    Science.gov (United States)

    Fedorov, A.; Praveen, C. S.; Verbitskiy, N. I.; Haberer, D.; Usachov, D.; Vyalikh, D. V.; Nefedov, A.; Wöll, C.; Petaccia, L.; Piccinin, S.; Sachdev, H.; Knupfer, M.; Büchner, B.; Fabris, S.; Grüneis, A.

    2015-09-01

    Insulating hexagonal boron nitride monolayers (h BN ) are best known for being resistant to chemical functionalization. This property makes h BN an excellent substrate for graphene heterostructures, but limits its application as an active element in nanoelectronics where tunable electronic properties are needed. Moreover, the two-dimensional-materials' community wishes to learn more about the adsorption and intercalation characteristics of alkali metals on h BN , which have direct relevance to several electrochemistry experiments that are envisioned with layered materials. Here we provide results on ionic functionalization of h BN /metal interfaces with K and Li dopants. By combining angle-resolved photoemission spectroscopy (ARPES), x-ray photoelectron spectroscopy, and density functional theory calculations, we show that the metallic substrate readily ionizes the alkali dopants and exposes h BN to large electric fields and band-energy shifts. In particular, if h BN is in between the negatively charged substrate and the positive alkali ion, this allows us to directly study, using ARPES, the effects of large electric fields on the electron energy bands of h BN .

  7. Highly thermally conductive papers with percolative layered boron nitride nanosheets.

    Science.gov (United States)

    Zhu, Hongli; Li, Yuanyuan; Fang, Zhiqiang; Xu, Jiajun; Cao, Fangyu; Wan, Jiayu; Preston, Colin; Yang, Bao; Hu, Liangbing

    2014-04-22

    In this work, we report a dielectric nanocomposite paper with layered boron nitride (BN) nanosheets wired by one-dimensional (1D) nanofibrillated cellulose (NFC) that has superior thermal and mechanical properties. These nanocomposite papers are fabricated from a filtration of BN and NFC suspensions, in which NFC is used as a stabilizer to stabilize BN nanosheets. In these nanocomposite papers, two-dimensional (2D) nanosheets form a thermally conductive network, while 1D NFC provides mechanical strength. A high thermal conductivity has been achieved along the BN paper surface (up to 145.7 W/m K for 50 wt % of BN), which is an order of magnitude higher than that in randomly distributed BN nanosheet composites and is even comparable to the thermal conductivity of aluminum alloys. Such a high thermal conductivity is mainly attributed to the structural alignment within the BN nanosheet papers; the effects of the interfacial thermal contact resistance are minimized by the fact that the heat transfer is in the direction parallel to the interface between BN nanosheets and that a large contact area occurs between BN nanosheets. PMID:24601534

  8. Adhesion and size dependent friction anisotropy in boron nitride nanotubes

    International Nuclear Information System (INIS)

    The frictional properties of individual multiwalled boron nitride nanotubes (BN-NTs) synthesized by chemical vapour deposition (CVD) and deposited on a silicon substrate are investigated using an atomic force microscope tip sliding along (longitudinal sliding) and across (transverse sliding) the tube’s principal axis. Because of the tube’s transverse deformations during the tip sliding, a larger friction coefficient is found for the transverse sliding as compared to the longitudinal sliding. Here, we show that the friction anisotropy in BN-NTs, defined as the ratio between transverse and longitudinal friction forces per unit area, increases with the nanotube–substrate contact area, estimated to be proportional to (LNTRNT)1/2, where LNT and RNT are the length and the radius of the nanotube, respectively. Larger contact area denotes stronger surface adhesion, resulting in a longitudinal friction coefficient closer to the value expected in the absence of transverse deformations. Compared to carbon nanotubes (C-NTs), BN-NTs display a friction coefficient in each sliding direction with intermediate values between CVD and arc discharge C-NTs. CVD BN-NTs with improved tribological properties and higher oxidation temperature might be a better candidate than CVD C-NTs for applications in extreme environments. (paper)

  9. Large-area monolayer hexagonal boron nitride on Pt foil.

    Science.gov (United States)

    Park, Ji-Hoon; Park, Jin Cheol; Yun, Seok Joon; Kim, Hyun; Luong, Dinh Hoa; Kim, Soo Min; Choi, Soo Ho; Yang, Woochul; Kong, Jing; Kim, Ki Kang; Lee, Young Hee

    2014-08-26

    Hexagonal boron nitride (h-BN) has recently been in the spotlight due to its numerous applications including its being an ideal substrate for two-dimensional electronics, a tunneling material for vertical tunneling devices, and a growth template for heterostructures. However, to obtain a large area of h-BN film while maintaining uniform thickness is still challenging and has not been realized. Here, we report the systematical study of h-BN growth on Pt foil by using low pressure chemical vapor deposition with a borazine source. The monolayer h-BN film was obtained over the whole Pt foil (2 × 5 cm(2)) under film. The total pressure and orientation of the Pt lattice plane are crucial parameters for thickness control. At high pressure (∼0.5 Torr), thick film was grown on Pt (111), and in contrast, thin film was grown on Pt (001). Our advances in monolayer h-BN growth will play an important role to further develop a high quality h-BN film that can be used for vertical tunneling, optoelectronic devices and growth templates for a variety of heterostructures. PMID:25094030

  10. Thermal transport across graphene and single layer hexagonal boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jingchao, E-mail: zhang@unl.edu, E-mail: yyue@whu.edu.cn [Holland Computing Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States); Hong, Yang [Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States); Yue, Yanan, E-mail: zhang@unl.edu, E-mail: yyue@whu.edu.cn [School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072 (China)

    2015-04-07

    As the dimensions of nanocircuits and nanoelectronics shrink, thermal energies are being generated in more confined spaces, making it extremely important and urgent to explore for efficient heat dissipation pathways. In this work, the phonon energy transport across graphene and hexagonal boron-nitride (h-BN) interface is studied using classic molecular dynamics simulations. Effects of temperature, interatomic bond strength, heat flux direction, and functionalization on interfacial thermal transport are investigated. It is found out that by hydrogenating graphene in the hybrid structure, the interfacial thermal resistance (R) between graphene and h-BN can be reduced by 76.3%, indicating an effective approach to manipulate the interfacial thermal transport. Improved in-plane/out-of-plane phonon couplings and broadened phonon channels are observed in the hydrogenated graphene system by analyzing its phonon power spectra. The reported R results monotonically decrease with temperature and interatomic bond strengths. No thermal rectification phenomenon is observed in this interfacial thermal transport. Results reported in this work give the fundamental knowledge on graphene and h-BN thermal transport and provide rational guidelines for next generation thermal interface material designs.

  11. Hydrothermal Synthesis and Photoluminescence of Boron Nitride Quantum Dots

    Science.gov (United States)

    Li, Hongling; Tay, Roland Yingjie; Tsang, Siu Hon; Teo, Edwin Hang Tong

    Boron nitride quantum dots (BNQDs), as a new member of heavy metal-free quantum dots, have attracted great interest owing to its unique structure as well as fascinating physical/chemical properties. However, it is still a challenge to controllably synthesize high quality BNQDs with high quantum yield (QY), uniform size and strong luminescence. Here we present a facile and effective approach to controllablly fabricate BNQDs by snoication-solvothermal technique. Encouragingly, the as-prepared BNQDs possess strong blue luminescence with high QY of up to 19.5%, which can be attributed to the synergic effect of size, surface chemistry and edge defects. In addition, the size of the BNQDs could be controlled with a narrow size distribution of 1.32 nm and the smallest average size achieved is 2.62 nm with an average thickness of ~3 atomic layers. Furthermore, the as-prepared BNQDs are non-toxic to cells and show nanosecond-scaled lifetimes and little photobleaching effect. Therefore, it is believed that BNQDs are promising as one of the novel heavy metal-free QDs for multi-purpose applications in a range of fields. Moreover, this synthesis concept is expected to open a new window to controllably prepare other heavy metal-free QDs, as well as to understand their luminescence mechanism.

  12. Controllable Synthesis of Highly Luminescent Boron Nitride Quantum Dots.

    Science.gov (United States)

    Li, Hongling; Tay, Roland Yingjie; Tsang, Siu Hon; Zhen, Xu; Teo, Edwin Hang Tong

    2015-12-22

    Boron nitride quantum dots (BNQDs), as a new member of heavy metal-free quantum dots, have aroused great interest in fundamental research and practical application due to their unique physical/chemical properties. However, it is still a challenge to controllably synthesize high-quality BNQDs with high quantum yield (QY), uniform size and strong fluorescent. In this work, BNQDs have been successfully fabricated by the liquid exfoliation and the subsequent solvothermal process with respect to its facileness and easy large scale up. Importantly, BNQDs with high-quality can be controllably obtained by adjusting the synthetic parameters involved in the solvothermal process including filling factor, synthesis temperature, and duration time. Encouragingly, the as-prepared BNQDs possess strong blue luminescence with QY as high as 19.5%, which can be attributed to the synergetic effect of size, surface chemistry and edge defects. In addition, this strategy presented here provides a new reference for the controllable synthesis of other heavy metal-free QDs. Furthermore, the as-prepared BNQDs are non-toxic to cells and exhibit nanosecond-scaled lifetimes, suggesting they have great potential biological and optoelectronic applications. PMID:26574683

  13. Boron nitride ceramics from molecular precursors: synthesis, properties and applications.

    Science.gov (United States)

    Bernard, Samuel; Salameh, Chrystelle; Miele, Philippe

    2016-01-21

    Hexagonal boron nitride (h-BN) attracts considerable interest because its structure is similar to that of carbon graphite while it displays different properties which are of interest for environmental and green technologies. The polar nature of the B-N bond in sp(2)-bonded BN makes it a wide band gap insulator with different chemistry on its surface and particular physical and chemical properties such as a high thermal conductivity, a high temperature stability, a high resistance to corrosion and oxidation and a strong UV emission. It is chemically inert and nontoxic and has good environmental compatibility. h-BN also has enhanced physisorption properties due to the dipolar fields near its surface. Such properties are closely dependent on the processing method. Bottom-up approaches consist of transforming molecular precursors into non-oxide ceramics with retention of the structural units inherent to the precursor molecule. The purpose of the present review is to give an up-to-date overview on the most recent achievements in the preparation of h-BN from borazine-based molecular single-source precursors including borazine and 2,4,6-trichloroborazine through both vapor phase syntheses and methods in the liquid/solid state involving polymeric intermediates, called the Polymer-Derived Ceramics (PDCs) route. In particular, the effect of the chemistry, composition and architecture of the borazine-based precursors and derived polymers on the shaping ability as well as the properties of h-BN is particularly highlighted. PMID:26646607

  14. Precursor design of vapour deposited cubic boron nitride versus diamond

    International Nuclear Information System (INIS)

    The similarities and dissimilarities in the growth of diamond vs. cubic boron nitride (c-BN) were studied using quantum mechanical calculations. Great similarities were observed when considering the surface stabilization by H atoms. Very great similarities were recorded when considering the adsorption of various growth species to these materials. It was found necessary to avoid mixtures of B- and N-containing species in the gas phase during c-BN growth, since they should most probably result in a mixture of these species also on the surfaces. Greater dissimilarities were observed when studying the surface migrations on the diamond and c-BN surfaces and nucleation of the cubic phases on the corresponding hexagonal ones. Nucleation of diamond/c-BN on graphite/h-BN was found to be energetically feasible. This was calculated to be especially the situation for the armchair edge of the basal plane of h-BN and of the zigzag edge of the basal plane of graphite. These theoretical results can be used as guidelines in the strive towards thin film deposition of c-BN using gentle chemical vapour deposition methods like atomic layer deposition. (author)

  15. Boron nitride nanotubes enhance properties of chitosan-based scaffolds.

    Science.gov (United States)

    Emanet, Melis; Kazanç, Emine; Çobandede, Zehra; Çulha, Mustafa

    2016-10-20

    With their low toxicity, high mechanical strength and chemical stability, boron nitride nanotubes (BNNTs) are good candidates to enhance the properties of polymers, composites and scaffolds. Chitosan-based scaffolds are exhaustively investigated in tissue engineering because of their biocompatibility and antimicrobial activity. However, their spontaneous degradation prevents their use in a range of tissue engineering applications. In this study, hydroxylated BNNTs (BNNT-OH) were included into a chitosan scaffold and tested for their mechanical strength, swelling behavior and biodegradability. The results show that inclusion of BNNTs-OH into the chitosan scaffold increases the mechanical strength and pore size at values optimal for high cellular proliferation and adhesion. The chitosan/BNNT-OH scaffold was also found to be non-toxic to Human Dermal Fibroblast (HDF) cells due to its slow degradation rate. HDF cell proliferation and adhesion were increased as compared to the chitosan-only scaffold as observed by scanning electron microscopy (SEM) and fluorescent microscopy images. PMID:27474572

  16. Periodic buckling patterns of graphene/hexagonal boron nitride heterostructure

    International Nuclear Information System (INIS)

    Graphene/hexagonal boron nitride (h-BN) heterostructure has showed great potential to improve the performance of a graphene device. A graphene on an h-BN substrate may buckle due to the thermal expansion mismatch between the graphene and h-BN. We used an energy method to investigate the periodic buckling patterns including one-dimensional, square checkerboard, hexagonal, equilateral triangular and herringbone mode in a graphene/h-BN heterostructure under equi-biaxial compression. The total energy, consisting of cohesive energy, graphene membrane energy and graphene bending energy, for each buckling pattern is obtained analytically. At a compression slightly larger than the critical strain, all buckling patterns have the same total energies, which suggests that any buckling pattern may occur. At a compression much larger than the critical strain, the herringbone mode has the lowest total energy by significantly reducing the membrane energy of graphene at the expense of a slight increase of the bending energy of graphene and cohesive energy. These results may serve as guidelines for strain engineering in graphene/h-BN heterostructures. (paper)

  17. Mechanical properties of hybrid boron nitride-carbon nanotubes

    Science.gov (United States)

    Zhang, Jin; Wang, Chengyuan

    2016-04-01

    Hybrid boron nitride-carbon nanotubes (BN-CNTs) have attracted considerable attention in recent research. In this effort, molecular dynamics simulations were performed to study the fundamentals of BN-CNTs in tensile tests, i.e. Young’s modulus and fracture strength (strain). Particular attention was paid to the influence of the atomic structure, hybrid style, and BN concentration on the tensile properties. The morphological changes were also investigated for the BN-CNTs at the onset of fracture. It is noted that the Young’s modulus of BN-CNTs decreases almost linearly with increasing the BN concentration with a rate of change independent of the hybrid style. In contrast, the sensitivity of the fracture strength and fracture strain to the variation of BN concentration depends strongly on the hybrid style of BN-CNTs. These results are expected to significantly expand the knowledge of the elastic and fracture properties of novel nanostructures and facilitate their applications in bandgap-engineering.

  18. Real time ellipsometric study of boron nitride thin film growth

    International Nuclear Information System (INIS)

    The authors present an in situ study of the growth of boron nitride thin films by real time ellipsometry. Films were produced in a PEVCD reactor by rf glow discharge decomposition of ammonia (pure) and diborane (1% in hydrogen), on in-Cr coated c-Si substrates placed either on the powered electrode or on the grounded electrode of the reactor. A fast phase-modulated ellipsometer performed the real time monitoring of the growth processes at 350 nm. The ellipsometric angle trajectories were obtained through an autocalibrated method, especially suitable for the in situ optical analysis of transparent thin films. The authors applied several thin film growth optical models (homogeneous, two-layer, surface roughness) to analyze parameters of the films such as refractive index, extinction coefficient, roughness and deposition rate. In all the cases studied, the two-layer model fits well with the ellipsometric measurements, but a more sophisticated model considering a variable refractive index could better describe these films

  19. Boron nitride hollow nanospheres: Synthesis, formation mechanism and dielectric property

    International Nuclear Information System (INIS)

    Highlights: • BN hollow nanospheres are fabricated in large scale via a new CVD method. • Morphology and structure are elucidated by complementary analytical techniques. • Formation mechanism is proposed based on experimental observations. • Dielectric properties are investigated in the X-band microwave frequencies. • BN hollow nanospheres show lower dielectric loss than regular BN powders. - Abstract: Boron nitride (BN) hollow nanospheres have been successfully fabricated by pyrolyzing vapors decomposed from ammonia borane (NH3BH3) at 1300 °C. The final products have been extensively characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The BN hollow nanospheres were ranging from 100 to 300 nm in diameter and around 30–100 nm in thickness. The internal structure of the products was found dependent on the reaction temperatures. A possible formation mechanism of the BN hollow nanospheres was proposed on the basis of the experimental observations. Dielectric measurements in the X-band microwave frequencies (8–12 GHz) showed that the dielectric loss of the paraffin filled by the BN hollow nanospheres was lower than that filled by regular BN powders, which indicated that the BN hollow nanospheres could be potentially used as low-density fillers for microwave radomes

  20. Thermal vibration characteristics of armchair boron-nitride nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Anirban [Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Patra, Puneet Kumar [Advanced Technology Development Center, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Bhattacharya, Baidurya, E-mail: baidurya@civil.iitkgp.ernet.in [Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2015-12-21

    A nanomechanical resonator based sensor works by detecting small changes in the natural frequency of the device in presence of external agents. In this study, we address the length and the temperature-dependent sensitivity of precompressed armchair Boron-Nitride nanotubes towards their use as sensors. The vibrational data, obtained using molecular dynamics simulations, are analyzed for frequency content through the fast Fourier transformation. As the temperature of the system rises, the vibrational spectrum becomes noisy, and the modal frequencies show a red-shift irrespective of the length of the nanotube, suggesting that the nanotube based sensors calibrated at a particular temperature may not function desirably at other temperatures. Temperature-induced noise becomes increasingly pronounced with the decrease in the length of the nanotube. For the shorter nanotube at higher temperatures, we observe multiple closely spaced peaks near the natural frequency, that create a masking effect and reduce the sensitivity of detection. However, longer nanotubes do not show these spurious frequencies, and are considerably more sensitive than the shorter ones.

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

    Science.gov (United States)

    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.

  2. The prospects of using boron nitride in nuclear reactors as an absorbant and decelerator of neutrons

    International Nuclear Information System (INIS)

    Full text: The given work tells us that there are a widespread materials having an ability of amorphism, magnezation, hightemperature stability, wear resistance and corrosion resisting. To special requests which being presented to modern materials by some spheres of science and technics concern an ability of materials to work not only within the conditions of radioactive irradiation nor also capture heating neutrons. Hexagonal boron nitride has the most of these features. Boron nitride is used by the aircraft industry, because of its hightemperature resistance for a long time in extreme conditions. That is why the given material had been suggested as a neutron immerse material during production of containers for radioactive wastes long-lived storage. Using of enriched boron nitride in the first wall of thermonuclear reactor gives an oppotunity of refining nuclear and physical characteristics of reactor installation as a whole. Boron nitride has feeble activation in reactor neutron shell and high radiation resistance. All abovementioned boron nitride features, also its lower atmoic weight are very important for application in plasma devices, such as for using in installations of thermonuclear synthesis.

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

    Science.gov (United States)

    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.

  4. Anisotropic Hexagonal Boron Nitride Nanomaterials - Synthesis and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Han,W.Q.

    2008-08-01

    Boron nitride (BN) is a synthetic binary compound located between III and V group elements in the Periodic Table. However, its properties, in terms of polymorphism and mechanical characteristics, are rather close to those of carbon compared with other III-V compounds, such as gallium nitride. BN crystallizes into a layered or a tetrahedrally linked structure, like those of graphite and diamond, respectively, depending on the conditions of its preparation, especially the pressure applied. Such correspondence between BN and carbon readily can be understood from their isoelectronic structures [1, 2]. On the other hand, in contrast to graphite, layered BN is transparent and is an insulator. This material has attracted great interest because, similar to carbon, it exists in various polymorphic forms exhibiting very different properties; however, these forms do not correspond strictly to those of carbon. Crystallographically, BN is classified into four polymorphic forms: Hexagonal BN (h-BN) (Figure 1(b)); rhombohedral BN (r-BN); cubic BN (c-BN); and wurtzite BN (w-BN). BN does not occur in nature. In 1842, Balmain [3] obtained BN as a reaction product between molten boric oxide and potassium cyanide under atmospheric pressure. Thereafter, many methods for its synthesis were reported. h-BN and r-BN are formed under ambient pressure. c-BN is synthesized from h-BN under high pressure at high temperature while w-BN is prepared from h-BN under high pressure at room temperature [1]. Each BN layer consists of stacks of hexagonal plate-like units of boron and nitrogen atoms linked by SP{sup 2} hybridized orbits and held together mainly by Van der Waals force (Fig 1(b)). The hexagonal polymorph has two-layered repeating units: AA'AA'... that differ from those in graphite: ABAB... (Figure 1(a)). Within the layers of h-BN there is coincidence between the same phases of the hexagons, although the boron atoms and nitrogen atoms are alternatively located along the c

  5. Preparation and characterization of sputtered boron nitride and boron carbide films and their modification by ion implantation

    International Nuclear Information System (INIS)

    Nanocrystalline cubic boron nitride and boron carbide films have been synthesized using sputtering. The relationship between the structures and properties as well as the influence of the deposition parameters, such as rf power, bias voltage, substrate temperature, composition and flow rate of the sputtering gas, on the structures and properties have been studied. The influence of the ion bombardment could be described by the specific ion momentum P*=[ion momentum.(ion flux/atom flux)]. The specific ion momentum was found to be proportional to the rf power and to the 1.5th power of the bias voltage. Two phases have been identified in our boron nitride films: hexagonal boron nitride (h-BN) and cubic boron nitride (c-BN); the films were either single phase or contained a mixture of these two phases. Nanocrystalline boron films have been grown with a deposition rate of 2 nm/s not only on Si but also on hard metal (WC-6%Co) substrates. Stoichiometric and crystalline films have already been grown at room temperature (about 0.1 Tm, Tm=melting point-3900 K). All the films contained about 8 at% carbon and 6 at% oxygen as impurities, which come mainly from the targt. The concentration of the impurities is independent of the deposition paramters. The growth of c-BN appears after the specific ion momentum larger than a threshold value, which is dependent on the substrate temperature, composition and on the flow rate of the sputtering gas. The volume content of c-BN runs through a maximum value with increasing specific ion momentum. (orig.)

  6. A comparative study of the thermal interface materials with graphene and boron nitride fillers

    Science.gov (United States)

    Kargar, F.; Salgado, R.; Legedza, S.; Renteria, J.; Balandin, A. A.

    2014-09-01

    We report the results of an experimental study that compares the performance of graphene and boron nitride flakes as fillers in the thermal interface materials. The thickness of both fillers varied from a single atomic plane to about a hundred. The measurements have been conducted using a standard TIM tester. Our results show that the addition of a small fraction of graphene (f=4 wt%) to a commercial thermal interface material increases the resulting apparent thermal conductivity substantially stronger than the addition of boron nitride. The obtained data suggest that graphene and fewlayer graphene flakes couple better to the matrix materials than the boron nitride fillers. A combination of both fillers can be used to increase the thermal conductivity while controlling the electrical conduction.

  7. Phase transitions to 120 GPa for shock-compressed pyrolytic and hot-pressed boron nitride

    International Nuclear Information System (INIS)

    Shock-compression characteristics of two types of hexagonal graphitelike boron nitride have been investigated. Highly oriented very pure pyrolytic boron nitride exhibits shock-velocity versus particle-velocity discontinuities that appear to be manifestations of the initiation of a sluggish phase transition. This transition begins at 20 GPa and is driven to completion (melting) at 75 GPa. Discontinuities in the plot for impure hot-pressed boron nitride indicate initiation at 10 GPa and completion at 20 GPa. The (U/sub s/, U/sub p/) plots follow essentially the same paths for 4.0 < U/sub p/ < 5.2 km/sec. No evidence for a transition to a metalliclike state was seen. Temperature calculations indicate that the material is liquid above approx.80 GPa

  8. Growth of cubic boron nitride on diamond particles by microwave plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Saitoh, H.; Yarbrough, W. A.

    1991-06-01

    The nucleation and growth of cubic boron nitride (c-BN) onto diamond powder using solid NaBH4 in low pressure gas mixtures of NH3 and H2 by microwave plasma enhanced chemical vapor deposition has been studied. Boron nitride was deposited on submicron diamond seed crystals scattered on (100) silicon single crystal wafers and evidence was found for the formation of the cubic phase. Diamond powder surfaces appear to preferentially nucleate c-BN. In addition, it was found that the ratio of c-BN to turbostratic structure boron nitride (t-BN) deposited increases with decreasing NH3 concentration in H2. It is suggested that this may be due to an increased etching rate for t-BN by atomic hydrogen whose partial pressure may vary with NH3 concentration.

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

    Energy Technology Data Exchange (ETDEWEB)

    Seyed-Talebi, Seyedeh Mozhgan [Shahid Chamran University, Golestan boulevard, Ahvaz, Khouzestan (Iran, Islamic Republic of); Neek-Amal, M., E-mail: neekamal@srttu.edu [Shahid Rajaee Teacher Training University, Lavizan, Tehran (Iran, Islamic Republic of)

    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 energy 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.

  10. Thermodynamic approach to boron nitride nanotube solubility and dispersion

    Science.gov (United States)

    Tiano, A. L.; Gibbons, L.; Tsui, M.; Applin, S. I.; Silva, R.; Park, C.; Fay, C. C.

    2016-02-01

    Inadequate dispersion of nanomaterials is a critical issue that significantly limits the potential properties of nanocomposites and when overcome, will enable further enhancement of material properties. The most common methods used to improve dispersion include surface functionalization, surfactants, polymer wrapping, and sonication. Although these approaches have proven effective, they often achieve dispersion by altering the surface or structure of the nanomaterial and ultimately, their intrinsic properties. Co-solvents are commonly utilized in the polymer, paint, and art conservation industries to selectively dissolve materials. These co-solvents are utilized based on thermodynamic interaction parameters and are chosen so that the original materials are not affected. The same concept was applied to enhance the dispersion of boron nitride nanotubes (BNNTs) to facilitate the fabrication of BNNT nanocomposites. Of the solvents tested, dimethylacetamide (DMAc) exhibited the most stable, uniform dispersion of BNNTs, followed by N,N-dimethylformamide (DMF), acetone, and N-methyl-2-pyrrolidone (NMP). Utilizing the known Hansen solubility parameters of these solvents in comparison to the BNNT dispersion state, a region of good solubility was proposed. This solubility region was used to identify co-solvent systems that led to improved BNNT dispersion in poor solvents such as toluene, hexane, and ethanol. Incorporating the data from the co-solvent studies further refined the proposed solubility region. From this region, the Hansen solubility parameters for BNNTs are thought to lie at the midpoint of the solubility sphere: 16.8, 10.7, and 9.0 MPa1/2 for δd, δp, and δh, respectively, with a calculated Hildebrand parameter of 21.8 MPa1/2.Inadequate dispersion of nanomaterials is a critical issue that significantly limits the potential properties of nanocomposites and when overcome, will enable further enhancement of material properties. The most common methods used to

  11. Nanostructured Boron Nitride: From Molecular Design to Hydrogen Storage Application

    Directory of Open Access Journals (Sweden)

    Georges Moussa

    2014-07-01

    Full Text Available The spray-pyrolysis of borazine at 1400 °C under nitrogen generates boron nitride (BN nanoparticles (NPs. The as-prepared samples form elementary blocks containing slightly agglomerated NPs with sizes ranging from 55 to 120 nm, a Brunauer-Emmett-Teller (BET-specific surface area of 34.6 m2 g−1 and a helium density of 1.95 g cm−3. They are relatively stable in air below 850 °C in which only oxidation of the NP surface proceeds, whereas under nitrogen, their lower size affects their high temperature thermal behavior in the temperature range of 1450–2000 °C. Nitrogen heat-treated nanostructures have been carefully analyzed using X-ray diffraction, electron microscopy and energy-dispersive X-ray spectroscopy. The high temperature treatment (2000 °C gives hollow-cored BN-NPs that are strongly facetted, and after ball-milling, hollow core-mesoporous shell NPs displaying a BET-specific surface area of 200.5 m2·g−1 and a total pore volume of 0.287 cm3·g−1 were produced. They have been used as host material to confine, then destabilize ammonia borane (AB, thus improving its dehydrogenation properties. The as-formed AB@BN nanocomposites liberated H2 at 40 °C, and H2 is pure in the temperature range 40–80 °C, leading to a safe and practical hydrogen storage composite material.

  12. Nanomechanical cutting of boron nitride nanotubes by atomic force microscopy

    Science.gov (United States)

    Zheng, Meng; Chen, Xiaoming; Park, Cheol; Fay, Catharine C.; Pugno, Nicola M.; Ke, Changhong

    2013-12-01

    The length of nanotubes is a critical structural parameter for the design and manufacture of nanotube-based material systems and devices. High-precision length control of nanotubes by means of mechanical cutting using a scriber has not materialized due to the lack of the knowledge of the appropriate cutting conditions and the tube failure mechanism. In this paper, we present a quantitative nanomechanical study of the cutting of individual boron nitride nanotubes (BNNTs) using atomic force microscopy (AFM) probes. In our nanotube cutting measurements, a nanotube standing still on a flat substrate was laterally scribed by an AFM tip. The tip-tube collision force deformed the tube, and eventually fractured the tube at the collision site by increasing the cutting load. The mechanical response of nanotubes during the tip-tube collision process and the roles of the scribing velocity and the frictional interaction on the tip-tube collision contact in cutting nanotubes were quantitatively investigated by cutting double-walled BNNTs of 2.26-4.28 nm in outer diameter. The fracture strength of BNNTs was also quantified based on the measured collision forces and their structural configurations using contact mechanics theories. Our analysis reports fracture strengths of 9.1-15.5 GPa for the tested BNNTs. The nanomechanical study presented in this paper demonstrates that the AFM-based nanomechanical cutting technique not only enables effective control of the length of nanotubes with high precision, but is also promising as a new nanomechanical testing technique for characterizing the mechanical properties of tubular nanostructures.

  13. Electron affinity of cubic boron nitride terminated with vanadium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yu; Sun, Tianyin; Shammas, Joseph; Hao, Mei; Nemanich, Robert J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Kaur, Manpuneet [School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287-6106 (United States)

    2015-10-28

    A thermally stable negative electron affinity (NEA) for a cubic boron nitride (c-BN) surface with vanadium-oxide-termination is achieved, and its electronic structure was analyzed with in-situ photoelectron spectroscopy. The c-BN films were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition employing BF{sub 3} and N{sub 2} as precursors. Vanadium layers of ∼0.1 and 0.5 nm thickness were deposited on the c-BN surface in an electron beam deposition system. Oxidation of the metal layer was achieved by an oxygen plasma treatment. After 650 °C thermal annealing, the vanadium oxide on the c-BN surface was determined to be VO{sub 2}, and the surfaces were found to be thermally stable, exhibiting an NEA. In comparison, the oxygen-terminated c-BN surface, where B{sub 2}O{sub 3} was detected, showed a positive electron affinity of ∼1.2 eV. The B{sub 2}O{sub 3} evidently acts as a negatively charged layer introducing a surface dipole directed into the c-BN. Through the interaction of VO{sub 2} with the B{sub 2}O{sub 3} layer, a B-O-V layer structure would contribute a dipole between the O and V layers with the positive side facing vacuum. The lower enthalpy of formation for B{sub 2}O{sub 3} is favorable for the formation of the B-O-V layer structure, which provides a thermally stable surface dipole and an NEA surface.

  14. C60 bonding to graphite and boron nitride surfaces

    Science.gov (United States)

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

    2003-12-01

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

  15. Electron affinity of cubic boron nitride terminated with vanadium oxide

    International Nuclear Information System (INIS)

    A thermally stable negative electron affinity (NEA) for a cubic boron nitride (c-BN) surface with vanadium-oxide-termination is achieved, and its electronic structure was analyzed with in-situ photoelectron spectroscopy. The c-BN films were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition employing BF3 and N2 as precursors. Vanadium layers of ∼0.1 and 0.5 nm thickness were deposited on the c-BN surface in an electron beam deposition system. Oxidation of the metal layer was achieved by an oxygen plasma treatment. After 650 °C thermal annealing, the vanadium oxide on the c-BN surface was determined to be VO2, and the surfaces were found to be thermally stable, exhibiting an NEA. In comparison, the oxygen-terminated c-BN surface, where B2O3 was detected, showed a positive electron affinity of ∼1.2 eV. The B2O3 evidently acts as a negatively charged layer introducing a surface dipole directed into the c-BN. Through the interaction of VO2 with the B2O3 layer, a B-O-V layer structure would contribute a dipole between the O and V layers with the positive side facing vacuum. The lower enthalpy of formation for B2O3 is favorable for the formation of the B-O-V layer structure, which provides a thermally stable surface dipole and an NEA surface

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

    Science.gov (United States)

    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.

  17. Influence of disorder on thermal transport properties of boron nitride nanostructures

    Science.gov (United States)

    Sevik, Cem; Kinaci, Alper; Haskins, Justin B.; Çaǧın, Tahir

    2012-08-01

    The impact of isotopes on thermal transport in boron nitride nanotubes (BNNTs) and boron nitride white graphene is systematically studied via molecular dynamic simulations. By varying the concentration of the 10B isotope in these materials, we find that thermal conductivity ranges from 340 to 500 W/m-1 K-1, closely agreeing with experimental observations for isotopically pure and natural (19.9% 10B) BNNTs. Further, we investigate the interplay between dimension and isotope disorder in several C-based materials. Our results show a general trend of decreasing influence of isotope disorder with dimension of these materials.

  18. Investigation of tensile response and thermal conductivity of boron-nitride nanosheets using molecular dynamics simulations

    Science.gov (United States)

    Mortazavi, Bohayra; Rémond, Yves

    2012-06-01

    In this paper, we employed classical molecular dynamics simulations using the Tersoff potential for the evaluation of thermal conductivity and tensile response of single-layer boron-nitride sheets (SBNS). By carrying out uniaxial tension simulations, the elastic moduli of SBNS structures are predicted to be close to those of boron-nitride nanotubes in a range between 0.8 and 0.85 TPa for different chirality directions. Performing non-equilibrium molecular dynamics simulations, the thermal conductivity of SBNS is predicted to be around 80 W/m-K, which is shown to be independent of chirality directions.

  19. Deep levels of nitrogen vacancies complexes in graphite-like boron nitride

    CERN Document Server

    Grinyaev, S N; Lopatin, V V

    2002-01-01

    Paper presents results of theoretical studies using methods of model pseudopotential and of extended elementary cell of deep levels of nitrogen vacancies, small clusters from di- and trivacancies of nitrogen covering nearest defects in one layer of graphite-like boron nitride. On the basis of calculated spectra and intensities of oscillators one interpreted local bands of optical absorption, luminescence, photoconductivity in pyrolytic boron nitride prior to and subsequent to irradiation by fast neutrons, protons and ions of carbon (50-150 keV). One identified not deep levels of activation of thermally stimulated luminescence and conductivity prior to and subsequent to irradiation

  20. Non-linear excitation of quantum emitters in two-dimensional hexagonal boron nitride

    CERN Document Server

    Schell, Andreas W; Takashima, Hideaki; Takeuchi, Shigeki; Aharonovich, Igor

    2016-01-01

    Two-photon absorption is an important non-linear process employed for high resolution bio-imaging and non-linear optics. In this work we realize two-photon excitation of a quantum emitter embedded in a two-dimensional material. We examine defects in hexagonal boron nitride and show that the emitters exhibit similar spectral and quantum properties under one-photon and two-photon excitation. Furthermore, our findings are important to deploy two-dimensional hexagonal boron nitride for quantum non-linear photonic applications.

  1. Quasi free-standing silicene in a superlattice with hexagonal boron nitride

    KAUST Repository

    Kaloni, T. P.

    2013-11-12

    We study a superlattice of silicene and hexagonal boron nitride by first principles calculations and demonstrate that the interaction between the layers of the superlattice is very small. As a consequence, quasi free-standing silicene is realized in this superlattice. In particular, the Dirac cone of silicene is preserved. Due to the wide band gap of hexagonal boron nitride, the superlattice realizes the characteristic physical phenomena of free-standing silicene. In particular, we address by model calculations the combined effect of the intrinsic spin-orbit coupling and an external electric field, which induces a transition from a semimetal to a topological insulator and further to a band insulator.

  2. Cubic boron nitride: a new prospective material for ultracold neutron application

    CERN Document Server

    Sobolev, Yu; Borisov, Yu; Daum, M; Fresne, N du; Goeltl, L; Hampel, G; Heil, W; Knecht, A; Keunecke, M; Kratz, J V; Lang, T; Meister, M; Plonka-Spehr, Ch; Pokotilovski, Yu; Reichert, P; Schmidt, U; Krist, Th; Wiehl, N; Zenner, J

    2009-01-01

    For the first time, the neutron optical wall-potential of natural cubic boron nitride (cBN) was measured at the ultracold neutron (UCN) source of the research reactor TRIGA Mainz using the time-of-flight method (TOF). The samples investigated had a wall-potential of (305 +/- 15) neV. This value is in good agreement with the result extracted from neutron reflectometry data and theoretical expectations. Because of its high critical velocity for UCN and its good dielectric characteristics, cubic boron nitride coatings (isotopically enriched) will be useful for a number of applications in UCN experiments.

  3. The preparation of high-adsorption, spherical, hexagonal boron nitride by template method

    International Nuclear Information System (INIS)

    Highlights: • The high-adsorption, spherical, hexagonal boron nitride powders were prepared. • The influence mechanism of template content on the micro-morphology and adsorption was explored. • At appropriate synthesis temperature, higher adsorption mesoporous spheres h-BN began to form. - Abstract: This research used low-cost boric acid and borax as a source of boron, urea as a nitrogen source, dodecyl-trimethyl ammonium chloride (DTAC) as a template, and thus prepared different micro-morphology hexagonal boron nitride powders under a flowing ammonia atmosphere at different nitriding temperatures. The effects of the template content and nitriding temperature on the micro-morphology of hexagonal boron nitride were studied and the formation mechanism analysed. The influences of the template content and nitriding temperature on adsorption performance were also explored. The results showed that at a nitriding temperature of 675 °C, the micro-morphologies of h-BN powder were orderly, inhomogeneous spherical, uniform spherical, beam, and pie-like with increasing template content. The micro-morphology was inhomogeneous spherical at a DTAC dose of 7.5%. The micro-morphology was uniform spherical at a DTAC dose of 10%. At a DTAC dose of 12%, the micro-morphology was a mixture of beam and pie-like shapes. At a certain template content (DTAC at 10%) and at lower nitriding temperatures (625 °C and 650 °C), spherical shell structures with surface subsidence began to form. The porous spheres would appear at a nitriding temperature of 675 °C, and the ball diameter thus formed was approximately 500–600 nm. The ball diameter was about 600–700 nm when the nitriding temperature was 700 °C. At a nitriding temperature of 725 °C, the ball diameter was between 800 and 1000 nm and sintering necking started to form. When the relative pressure was higher, previously closed pores opened and connected with the outside world: the adsorption then increased significantly. The

  4. The preparation of high-adsorption, spherical, hexagonal boron nitride by template method

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ning, E-mail: zhangning5832@163.com; Liu, Huan; Kan, Hongmin; Wang, Xiaoyang; Long, Haibo; Zhou, Yonghui

    2014-11-15

    Highlights: • The high-adsorption, spherical, hexagonal boron nitride powders were prepared. • The influence mechanism of template content on the micro-morphology and adsorption was explored. • At appropriate synthesis temperature, higher adsorption mesoporous spheres h-BN began to form. - Abstract: This research used low-cost boric acid and borax as a source of boron, urea as a nitrogen source, dodecyl-trimethyl ammonium chloride (DTAC) as a template, and thus prepared different micro-morphology hexagonal boron nitride powders under a flowing ammonia atmosphere at different nitriding temperatures. The effects of the template content and nitriding temperature on the micro-morphology of hexagonal boron nitride were studied and the formation mechanism analysed. The influences of the template content and nitriding temperature on adsorption performance were also explored. The results showed that at a nitriding temperature of 675 °C, the micro-morphologies of h-BN powder were orderly, inhomogeneous spherical, uniform spherical, beam, and pie-like with increasing template content. The micro-morphology was inhomogeneous spherical at a DTAC dose of 7.5%. The micro-morphology was uniform spherical at a DTAC dose of 10%. At a DTAC dose of 12%, the micro-morphology was a mixture of beam and pie-like shapes. At a certain template content (DTAC at 10%) and at lower nitriding temperatures (625 °C and 650 °C), spherical shell structures with surface subsidence began to form. The porous spheres would appear at a nitriding temperature of 675 °C, and the ball diameter thus formed was approximately 500–600 nm. The ball diameter was about 600–700 nm when the nitriding temperature was 700 °C. At a nitriding temperature of 725 °C, the ball diameter was between 800 and 1000 nm and sintering necking started to form. When the relative pressure was higher, previously closed pores opened and connected with the outside world: the adsorption then increased significantly. The

  5. Theory of thermal transport in multilayer hexagonal boron nitride and nanotubes

    Science.gov (United States)

    Lindsay, L.; Broido, D. A.

    2012-01-01

    We present a theory for the lattice thermal conductivity κL of single-walled boron nitride nanotubes (BNNTs) and multilayer hexagonal boron nitride (MLBN), which is based on an exact numerical solution of the phonon Boltzmann equation. Coupling between layers in MLBN and nanotube curvature in BNNTs each break a phonon scattering selection rule found in single-layer hexagonal boron nitride (SLBN), which reduces κL in these systems. We show that out-of-plane flexural phonons in MLBN and out-of-tube phonons in BNNTs provide large contributions to κL, qualitatively similar to multilayer graphene (MLG) and single-walled carbon nanotubes (SWCNTs). However, we find that the κL's in BNNTs and MLBN are considerably smaller compared to similar SWCNTs and MLG structures because of stronger anharmonic phonon scattering in the former. A large and strongly temperature-dependent isotope effect is found reflecting the interplay between anharmonic and isotope scattering phonons. Finally, we also demonstrate convergence of BNNTs into SLBN for large-diameter nanotubes and MLBN to bulk hexagonal boron nitride within a few layers.

  6. A method to manufacture a core catcher of boron nitride, protecting against melt-through

    International Nuclear Information System (INIS)

    A method to manufacture a protective layer made of boron nitride to be placed under the reactor and collect molten material in case of a meltdown accident. The layer is made from hexagonal boronnitride and is isostatically pressed at a temperature of at least 1600 degrees C and a pressure of at least 50 MPa. (L.E.)

  7. Synthesis and radiation response of BCON: a graphene oxide and hexagonal boron nitride hybrid

    Science.gov (United States)

    Bhimanapati, Ganesh R.; Wetherington, Maxwell; Mahabir, Shawn; Robinson, Joshua A.

    2016-06-01

    Since graphene, there has been a focus on several two-dimensional material systems (e.g. boron nitride, borocarbon nitride (BCN), transition-metal dichalcogenides) that provide an even wider array of unique chemistries and properties to explore future applications. Specifically, tailoring graphene/boron nitride heterostructures—which can theoretically retain the character of a single-atom thick sheet, withstand large physical strains, are easily functionalized, and have entirely different optical and mechanical properties compared to graphene—can provide the foundation for entirely new research avenues. In recent years, it has been shown that because of the similar crystal structure, carbon, boron, and nitrogen can co-exist as atomic sheets in a layered structure. We have developed a facile method of integrating boron nitride (hBN) and graphene oxide (GO) via chemical exfoliation which we refer to as BCON. The study of the stability of this material at different pH conditions indicates a stable and a uniform solution is achievable at pH 4–8. X-Ray Photoelectron Spectroscopy helped to identify the new bonds which indicated the formation of BCON linkage. Further, an in situ XPS technique was used to understand the chemical changes while exposing it to ionization radiation specially focusing on the C/O ratio. It was observed that even with a very low energy source, this material is highly sensitive to ionizing radiation, such as neutron, alpha and beta particles.

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

    Science.gov (United States)

    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. PMID:23648034

  9. Quantifying the Solubility of Boron Nitride Nanotubes and Sheets with Static Light Scattering and Refractometry

    Energy Technology Data Exchange (ETDEWEB)

    Mutz, M [The University of Tennessee; Eastwood, Eric Allen [ORNL; Dadmun, Mark D [ORNL

    2013-01-01

    The dissolution of nanoparticles, particularly those containing boron, is an important area of interest for polymer nanocomposite formation and material development. In this work, the solubility of boron nitride nanotubes (BNNT), functionalized boron nitride nanotubes (FBNNT), and boron nitride sheets (BNZG) is quantified in toluene and THF with static light scattering, refractometry, UV vis spectroscopy, and physical observations. UV vis spectroscopy provides a method to determine the concentration and solubility limits of the solutions tested. Using light scattering, the second virial coefficient, A2, is determined and used to calculate , the solute solvent interaction parameter. The Hildebrand solubility parameter, , is then extracted from this data using the Hildebrand Scatchard Solution Theory. A list of potential good solvents based on the estimated value is provided for each nanoparticle. Single-walled carbon nanotubes (SWNTs) and prepolymers (EN4 and EN8) used to synthesize polyurethanes were also tested, because the published and molar attraction constants of these materials provided a selfconsistent check. The dn/dc of SWNTs and boron-containing particles was measured for the first time in this work. A solvent screen for BN-ZG provides additional information that supports the obtained and . Three systems were found to have values below 0.5 and were thermodynamically soluble: BNNT in THF, EN8 in THF, and EN8 in toluene.

  10. Effect of heat conditions on the mechanical properties of boron nitride polycrystals

    International Nuclear Information System (INIS)

    This paper examines the effect of various types of heat treatment on the mechanical and service properties of polycrystals of boron nitride. Quantitative phase analysis was carried out using the methods described when using a DRON-2.0 x-ray diffractometer. The mechanical characteristics were determined by the method of local loading using the standard nitride polycrystals in the initial state are quite high. On the basis of the results it may be concluded that the heat treatment conditions examined (annealing, hf heating, annealing and hf heating) lead to the same changes in the structural state as those taking place in thermal cycling thus causing the corresponding reduction of the level of the strength properties of the boron nitride polycrystals

  11. Fabrication of particular structures of hexagonal boron nitride and boron-carbon-nitrogen layers by anisotropic etching

    Science.gov (United States)

    Vishwakarma, Riteshkumar; Sharma, Subash; Shinde, Sachin M.; Sharma, Kamal P.; Thangaraja, Amutha; Kalita, Golap; Tanemura, Masaki

    2016-05-01

    Anisotropic etching of hexagonal boron nitride (h-BN) and boron-carbon-nitrogen (BCN) basal plane can be an exciting platform to develop well-defined structures with interesting properties. Here, we developed an etching process of atomically thin h-BN and BCN layers to fabricate nanoribbons (NRs) and other distinct structures by annealing in H2 and Ar gas mixture. BCN and h-BN films are grown on Cu foil by chemical vapor deposition (CVD) using solid camphor and ammonia borane as carbon, nitrogen and boron source, respectively. Formation of micron size well-defined etched holes and NRs are obtained in both h-BN and BCN layers by the post growth annealing process. The etching process of h-BN and BCN basal plane to fabricate NRs and other structures with pronounced edges can open up new possibilities in 2D hybrid materials.

  12. Synthesis and anti-oxidation performance of nanoflake-decorated boron nitride hollow microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Li, Juan [College of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Lin, Hong [Department of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084 (China); Chen, Yongjun, E-mail: chenyj99@163.com [College of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); College of Material and Chemical Engineering, Hainan University, Haikou 570228 (China); Su, Qiaoqiao; Bi, Xiaofan [College of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China)

    2013-02-15

    Highlights: Black-Right-Pointing-Pointer A novel boron nitride (BN) composite structure composed of nanoflake and hollow microspheres was synthesized. Black-Right-Pointing-Pointer The raw materials are simple precursors of boron and Fe(NO{sub 3}){sub 3}{center_dot}9H{sub 2}O ethanol solution. Black-Right-Pointing-Pointer The structures have a high anti-oxidation temperature of 900 Degree-Sign C. Black-Right-Pointing-Pointer The growth mechanism consists of a combined vapor-liquid-solid (VLS) and vapor-solid (VS) model. - Abstract: In this study, a novel boron nitride composite structure composed of nanoflake-decorated hollow microspheres is demonstrated. A paste-like mixture is firstly prepared by mixing amorphous boron with ferric nitrate ethanol solution, followed by heating at 1300 Degree-Sign C in a flowing ammonia atmosphere for 5 h. Both the nanoflakes and microspheres are composed of crystalline hexagonal boron nitride. The hollow spheres have outer diameters of 0.8-3 {mu}m with thickness of about 300 nm, while the nanoflakes have thicknesses of 2-7 nm and lengths of 10-100 nm. Heating temperature is found to be crucial for the formation of this composite structure. The growth process consists of a vapor-liquid-solid growth stage of smooth hollow microspheres at lower temperature and a vapor-solid growth stage of nanoflakes on the surface of the microspheres at higher temperature. The boron nitride composite structure exhibits excellent anti-oxidation performance up to 900 Degree-Sign C.

  13. Folate Functionalized Boron Nitride Nanotubes and their Selective Uptake by Glioblastoma Multiforme Cells: Implications for their Use as Boron Carriers in Clinical Boron Neutron Capture Therapy

    Science.gov (United States)

    2009-01-01

    Boron neutron capture therapy (BNCT) is increasingly being used in the treatment of several aggressive cancers, including cerebral glioblastoma multiforme. The main requirement for this therapy is selective targeting of tumor cells by sufficient quantities of10B atoms required for their capture/irradiation with low-energy thermal neutrons. The low content of boron targeting species in glioblastoma multiforme accounts for the difficulty in selective targeting of this very malignant cerebral tumor by this radiation modality. In the present study, we have used for the first time boron nitride nanotubes as carriers of boron atoms to overcome this problem and enhance the selective targeting and ablative efficacy of BNCT for these tumors. Following their dispersion in aqueous solution by noncovalent coating with biocompatible poly-l-lysine solutions, boron nitride nanotubes were functionalized with a fluorescent probe (quantum dots) to enable their tracking and with folic acid as selective tumor targeting ligand. Initial in vitro studies have confirmed substantive and selective uptake of these nanovectors by glioblastoma multiforme cells, an observation which confirms their potential clinical application for BNCT therapy for these malignant cerebral tumors. PMID:20596476

  14. Evaluation of Synthesis & Processing Routes for the High K- Boron Nitride Nano Tubes (BNNTS) for Thermal Management Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The purpose of this proposal is to develop and demonstrate the feasibility of processing the High Thermal Conductivity Boron Nitride Nano Tubes (High-K BNNTs) that...

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

    Science.gov (United States)

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

  16. The effect of the boron source composition ratio on the adsorption performance of hexagonal boron nitride without a template

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ning, E-mail: zhangning5832@163.com; Zhang, Tong; Kan, Hongmin; Wang, Xiaoyang; Long, Haibo; Cui, Xingyu

    2015-08-01

    An inexpensive boric acid (H{sub 3}BO{sub 3}) and borax (Na{sub 2}B{sub 4}O{sub 7}·10H{sub 2}O) mix was used as a source of boron with different composition ratios, and urea was used as a nitrogen source, in flowing ammonia atmosphere, for the preparation of hexagonal boron nitride (h-BN) with different micro-morphologies. Under a certain synthesis process, the effects of the molar ratio of borax and boric acid (or simply the boron source composition ratio for short) on the phase composition of the sample were studied; the work also explored the effect of boron source composition ratio on the micro-morphology, adsorption desorption isotherm and specific surface area of the h-BN powder. The main purpose of this work was to determine the optimum composition ratio of preparing spherical mesoporous h-BN and ensure that the micro-mechanism underpinning the formation of spherical mesoporous h-BN was understood. The results showed that at the optimum boron source composition ratio of 1:1, globular mesoporous spheres with a diameter of approximately 600–800 nm could be obtained with the highest pore volume and specific surface area (230.2 m{sup 2}/g). - Graphical abstract: Display Omitted - Highlights: • Spherical h-BN was synthesized by controlling the boron source composition ratio. • Without extra spherical template, solid Na{sub 2}O was equal to a spherical template. • At boron source composition ratio of 1:1, h-BN had best adsorption performance.

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

    International Nuclear Information System (INIS)

    Boron carbon nitride (BCN) films were synthesized on Si (100) and fused silica substrates by radio-frequency magnetron sputtering from a B4C target in an Ar/N2 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

  18. Applicability of carbon and boron nitride nanotubes as biosensors: Effect of biomolecular adsorption on the transport properties of carbon and boron nitride nanotubes

    Science.gov (United States)

    Zhong, Xiaoliang; Mukhopadhyay, Saikat; Gowtham, S.; Pandey, Ravindra; Karna, Shashi P.

    2013-04-01

    The effect of molecular adsorption on the transport properties of single walled carbon and boron nitride nanotubes (CNTs and BNNTs) is investigated using density functional theory and non-equilibrium Green's function methods. The calculated I-V characteristics predict noticeable changes in the conductivity of semiconducting BNNTs due to physisorption of nucleic acid base molecules. Specifically, guanine which binds to the side wall of BNNT significantly enhances its conductivity by introducing conduction channels near the Fermi energy of the bioconjugated system. For metallic CNTs, a large background current masks relatively small changes in current due to the biomolecular adsorption. The results therefore suggest the suitability of BNNTs for biosensing applications.

  19. Enhanced thermal-mechanical properties of polymer composites with hybrid boron nitride nanofillers

    Science.gov (United States)

    Yan, Haiyan; Tang, Yanxia; Su, Juling; Yang, Xiaoyan

    2014-02-01

    The present work focuses on the investigation of the thermal-mechanical properties of the epoxy composites with hybrid boron nitride nanotubes (BNNTs) and boron nitride nanosheets (BNNSs). The stable dispersions of BNNTs-BNNSs were achieved by a noncovalent functionalization with pyrene carboxylic acid. The resulting epoxy/BNNTs-BNNSs composites exhibited homogeneously dispersed BNNTs-BNNSs and a strong filler-matrix interface interaction. The composites showed a 95 % increase in thermal conductivity and a 57 % improvement in Young's modulus by addition of only 1 vol. % BNNTs-BNNSs. Meanwhile, the composites also retained a high electrical resistance of pure epoxy. Our study thus shows the potential for hybrid BNNTs-BNNSs to be successfully used as the nanofillers of polymer composites for applications in electrically insulating thermal interface materials.

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

    Science.gov (United States)

    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.

  1. Boundary scattering in quasi-ballistic graphene/hexagonal boron nitride mesoscopic wires

    Science.gov (United States)

    Iguchi, Kazuyuki; Masubuchi, Satoru; Yamaguchi, Takehiro; Ohnuki, Masahiro; Watanabe, Kenji; Taniguchi, Takashi; Machida, Tomoki

    2012-02-01

    In a quasi-ballistic transport regime where the mean free path is larger than the width of conduction channel, diffusive boundary scattering results in an anomalous positive magnetoresistance due to a megnetic commensurability effect between cyclotron motion and sample width. In this work, we fabricate a high-mobility two terminal graphene mesoscopic wire on hexagonal boron nitride with a mean free path comparable to sample width ˜ 1 μm. Magnetoresistance of the graphene mesoscopic wire shows a peak structure at a magnetic field which scales with the ratio of the cyclotron radius Rc to the wire width w. The peak field increases with back-gate voltage as a consequence that the ratio w/Rc is modified due to the change in Rc. These results indicate the quasi-ballistic transport and diffusive boundary scattering in graphene on hexagonal boron nitride.

  2. Hyperbolic phonon-polaritons in boron nitride for near-field optical imaging and focusing

    Science.gov (United States)

    Li, Peining; Lewin, Martin; Kretinin, Andrey V.; Caldwell, Joshua D.; Novoselov, Kostya S.; Taniguchi, Takashi; Watanabe, Kenji; Gaussmann, Fabian; Taubner, Thomas

    2015-06-01

    Hyperbolic materials exhibit sub-diffractional, highly directional, volume-confined polariton modes. Here we report that hyperbolic phonon polaritons allow for a flat slab of hexagonal boron nitride to enable exciting near-field optical applications, including unusual imaging phenomenon (such as an enlarged reconstruction of investigated objects) and sub-diffractional focusing. Both the enlarged imaging and the super-resolution focusing are explained based on the volume-confined, wavelength dependent propagation angle of hyperbolic phonon polaritons. With advanced infrared nanoimaging techniques and state-of-art mid-infrared laser sources, we have succeeded in demonstrating and visualizing these unexpected phenomena in both Type I and Type II hyperbolic conditions, with both occurring naturally within hexagonal boron nitride. These efforts have provided a full and intuitive physical picture for the understanding of the role of hyperbolic phonon polaritons in near-field optical imaging, guiding, and focusing applications.

  3. A quantum chemistry study of curvature effects on boron nitride nanotubes/nanosheets for gas adsorption.

    Science.gov (United States)

    Sha, Haoyan; Faller, Roland

    2016-07-20

    Quantum chemistry calculations were performed to investigate the effect of the surface curvature of a Boron Nitride (BN) nanotube/nanosheet on gas adsorption. Curved boron nitride layers with different curvatures interacting with a number of different gases including noble gases, oxygen, and water on both their convex and concave sides of the surface were studied using density functional theory (DFT) with a high level dispersion corrected functional. Potential energy surfaces of the gas molecules interacting with the selected BN surfaces were investigated. In addition, the charge distribution and electrostatic potential contour of the selected BN surfaces are discussed. The results reveal how the curvature of the BN surfaces affects gas adsorption. In particular, small curvatures lead to a slight difference in the physisorption energy, while large curvatures present distinct potential energy surfaces, especially for the short-range repulsion. PMID:27399852

  4. Ultrafast optical nonlinearity and photoacoustic studies on chitosan-boron nitride nanotube composite films

    Science.gov (United States)

    Kuthirummal, Narayanan; Philip, Reji; Mohan, Athira; Jenks, Cassidy; Levi-Polyachenko, Nicole

    2016-07-01

    Ultrafast optical nonlinearity in chitosan (CS) films doped with multi-walled boron nitride nanotubes (MWBN) has been investigated using 800 nm, 100 fs laser pulses, employing the open aperture Z-scan technique. Two-photon absorption coefficients (β) of CS-MWBN films have been measured at 800 nm by Z-scan. While chitosan with 0.01% MWBN doping gives a β value of 0.28×10-13 m/W, 1% doping results in a higher β value of 1.43×10-13 m/W, showing nonlinearity enhancement by a factor of 5. These nonlinearity coefficients are comparable to those reported for silver nanoclusters in glass matrix and Pt-PVA nanocomposites, indicating potential photonic applications for MWBN doped chitosan films. Characterization of the synthesized films using Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) reveals significant interactions between the NH and CO groups of chitosan with boron nitride.

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

    International Nuclear Information System (INIS)

    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 the 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Muramatsu, Y.; Grush, M.; Callcott, T.A. [Univ. of Tennessee, Knoxville, TN (United States)] [and others

    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 reaction process of the h-BN and graphite in mechanical milling systems using x-ray absorption near edge structure (XANES) methods.

  7. The electronic transport behavior of hybridized zigzag graphene and boron nitride nanoribbons

    International Nuclear Information System (INIS)

    In this present work, we have investigated the electronic transport properties of the hybridized structure constructed by the zigzag graphene and boron-nitride (BN) nanoribbons (Z-BnNmCp, n + m + p = 16) through employing nonequilibrium Green's functions in combination with the density-functional theory. The results demonstrate that the electronic transport properties of the hybridized Z-BnNmCp nanoribbons are strongly dependent on the width of boron-nitride or graphene nanoribbons. When the numbers of n and m are not equal, the negative differential resistance behavior is observed, which can be modulated by varying the width of BN nanoribbons. The conductance of the hybridized Z-BnNmCp nanoribbons with odd numbers of zigzag carbon chains also increases by the width of BN nanoribbons

  8. Giant magnetoresistance and spin-filtering effects in zigzag graphene and hexagonal boron nitride based heterojunction

    International Nuclear Information System (INIS)

    The spin-dependent electronic transport properties of heterojunction constructed by bare zigzag graphene nanoribbon and hexagonal boron nitride nanoribbon are investigated by the non-equilibrium Green's function method in combination with the density functional theory. The results show that the giant magnetoresistance effect can be realized in the heterojunction, and the magnetoresistance ratio can reach to 106. Moreover, it is found that the heterojunction is a good spin-filtering device with nearly 100% spin filtering efficiency at a wide bias voltage region in both ferromagnetic and antiferromagnetic magnetic configurations. - Highlights: • The spin-dependent electronic transport of ZGNR and boron nitride based heterojunction. • The magnetoresistance ratio can reach to 106. • The perfect spin-filtering device with nearly 100% spin filtering efficiency

  9. The structure evolution process and the electronic properties of armchair boron nitride nanotubes

    Science.gov (United States)

    Yao, Chengpeng; Tang, Yuchao; Liu, Denghui; Zhu, Hengjiang

    2016-04-01

    We report the results of density functional calculations on the structural evolution and electronic properties of armchair boron nitride nanotubes (BNNTs), including SWBNNTs and DWBNNTs. Our results show that the initial structural configuration of the BNNTs was determined by the small boron nitride clusters. The evolution process of the BNNTs is through forming tubular clusters with a global reconstruction from structure of the double-rings. Then, it elongates through the layer-by-layer growth process with local reconstructions. Eventually, the infinite BNNTs can be constructed with corresponding repeat unit, designed by the periodic characteristics on the basis of tubular clusters. From the band structure of armchair BNNTs, it can be found the gap slightly increases with increasing diameter of the tube, decrease with the increasing of the walls. Moreover, the evolution process provides a better way to understand the growth mechanism of armchair BNNTs in atomic-level and guide the production of armchair BNNTs in industrial.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ganji, M.D. [Department of Chemistry, Azad University, Ghaemshahr Branch, Mazandaran (Iran, Islamic Republic of)], E-mail: ganji_md@yahoo.com; Mohammadi-nejad, A. [Department of Computer Engineering, Olom Fonon University of Mazandaran, Babol (Iran, Islamic Republic of)

    2008-06-30

    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.

  11. Biophysical response of living cells to boron nitride nanoparticles: uptake mechanism and bio-mechanical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Rasel, Md. Alim Iftekhar; Li, Tong; Nguyen, Trung Dung; Singh, Sanjleena [Queensland University of Technology (QUT), School of Chemistry, Physics and Mechanical Engineering (Australia); Zhou, Yinghong; Xiao, Yin [Queensland University of Technology (QUT), Institute of Health and Biomedical Innovation (Australia); Gu, YuanTong, E-mail: yuantong.gu@qut.edu.au [Queensland University of Technology (QUT), School of Chemistry, Physics and Mechanical Engineering (Australia)

    2015-11-15

    Boron nitride nanomaterials have attracted significant interest due to their superior chemical and physical properties. Despite these novel properties, investigation on the interaction between boron nitride nanoparticle (BN NP) and living systems has been limited. In this study, BN NP (100–250 nm) is assessed as a promising biomaterial for medical applications. The toxicity of BN NP is evaluated by assessing the cells behaviours both biologically (MTT assay, ROS detection etc.) and physically (atomic force microscopy). The uptake mechanism of BN NP is studied by analysing the alternations in cellular morphology based on cell imaging techniques. The results demonstrate in vitro cytocompatibility of BN NP with immense potential for use as an effective nanoparticle for various bio-medical applications.

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

    Energy Technology Data Exchange (ETDEWEB)

    Dauber, Jan; Stampfer, Christoph [JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen (Germany); Peter Grünberg Institute (PGI-8/9), Forschungszentrum Jülich, 52425 Jülich (Germany); Sagade, Abhay A.; Neumaier, Daniel [Advanced Microelectronic Center Aachen (AMICA), AMO GmbH, 52074 Aachen (Germany); Oellers, Martin [JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen (Germany); Watanabe, Kenji; Taniguchi, Takashi [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)

    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 50 nT/√(Hz) making our graphene sensors highly interesting for industrial applications.

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

    Science.gov (United States)

    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

    2016-05-01

    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. PMID:27203338

  14. Electron beam machining of nanometer-sized tips from multiwalled boron nitride nanotubes

    Science.gov (United States)

    Celik-Aktas, Ayten; Stubbins, James F.; Zuo, Jian-Min

    2007-07-01

    We report here that high energy electron irradiation of multiwalled boron nitride nanotubes can be used to form sharp, crystalline, conical tips, or to cut boron nitride nanotubes by controlling the electron beam size. Electron beam cutting is observed when a focused electron beam with a diameter much smaller than the tube diameter is used. The tip formation is observed when a shaped, disklike, electron beam is used to irradiate the tube; the diameter of the beam in this case is similar to the tube diameter. In situ electron microscopy observation shows that the tip formation effect is driven by layer peeling and the collapse of the inner walls of the nanotube. This is very different from the formation of nanoarches observed during cutting. The combination of shaping and cutting can be used to fabricate atomically sharp tips for field emitters, nanoimaging, and manipulations.

  15. Biophysical response of living cells to boron nitride nanoparticles: uptake mechanism and bio-mechanical characterization

    International Nuclear Information System (INIS)

    Boron nitride nanomaterials have attracted significant interest due to their superior chemical and physical properties. Despite these novel properties, investigation on the interaction between boron nitride nanoparticle (BN NP) and living systems has been limited. In this study, BN NP (100–250 nm) is assessed as a promising biomaterial for medical applications. The toxicity of BN NP is evaluated by assessing the cells behaviours both biologically (MTT assay, ROS detection etc.) and physically (atomic force microscopy). The uptake mechanism of BN NP is studied by analysing the alternations in cellular morphology based on cell imaging techniques. The results demonstrate in vitro cytocompatibility of BN NP with immense potential for use as an effective nanoparticle for various bio-medical applications

  16. Thermal reduction reactions in the exothermal processes of boron nitride synthesis by CVD

    International Nuclear Information System (INIS)

    Thermodynamic analysis of adiabatic heat-up of reactions and equilibrium composition of products in the systems BCl3-N2-M (M = Li, Na, Cs), BCl3-M, BCl3-N2-H2, BCl3-H2 has been carried out to fit the preparation of boron nitride on the basis of exothermal CVD-processes, based on chemical deposition from vapor phase. In temperature range 300-3000 K and at atmospheric pressure optimal regions of boron nitride yield are determined and general mechanism of the process is suggested. Strong effect of chemical heat release on equilibrium products composition and mechanism of their formation has been detected. 7 refs.; 4 figs

  17. Method and device to synthesize boron nitride nanotubes and related nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    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.

  18. Edge Chemistry Effects on the Structural, Electronic, and Electric Response Properties of Boron Nitride Quantum Dots

    OpenAIRE

    Krepel, Dana; Kalikhman-Razvozov, Lena; Hod, Oded

    2014-01-01

    The effects of edge hydrogenation and hydroxylation on the relative stability and electronic properties of hexagonal boron nitride quantum dots (h-BNQDs) are investigated. Zigzag edge hydroxylation is found to result in considerable energetic stabilization of h-BNQDs as well as a reduction of their electronic gap with respect to their hydrogenated counterparts. The application of an external in-plane electric field leads to a monotonous decrease of the gap. When compared to their edge-hydroge...

  19. Effects of Edge Oxidation on the Structural, Electronic, and Magnetic Properties of Zigzag Boron Nitride Nanoribbons

    OpenAIRE

    Krepel, Dana; Hod, Oded

    2013-01-01

    The effects of edge chemistry on the relative stability and electronic properties of zigzag boron nitride nanoribbons (ZBNNRs) are investigated. Among all functional groups considered, fully hydroxylated ZBNNRs are found to be the most energetically stable. When an in-plane external electric field is applied perpendicular to the axis of both hydrogenated and hydroxylated ZBNNRs, a spin-polarized half-metallic state is induced, whose character is different than that predicted for ZGNRs. The on...

  20. Amplitude- and phase-resolved nano-spectral imaging of phonon polaritons in hexagonal boron nitride

    OpenAIRE

    Shi, Zhiwen; Bechte, Hans A.; Berweger, Samuel; Sun, Yinghui; Zeng, Bo; Jin, Chenhao; Chang, Henry; Martin, Michael C.; Raschke, Markus B.; Wang, Feng

    2015-01-01

    Phonon polaritons are quasiparticles resulting from strong coupling of photons with optical phonons. Excitation and control of these quasiparticles in 2D materials offer the opportunity to confine and transport light at the nanoscale. Here, we image the phonon polariton (PhP) spectral response in thin hexagonal boron nitride (hBN) crystals as a representative 2D material using amplitude- and phase-resolved near-field interferometry with broadband mid-IR synchrotron radiation. The large spectr...

  1. Hyperbolic phonon-polaritons in boron nitride for near-field optical imaging and focusing

    OpenAIRE

    Li, Peining; Lewin, Martin; Kretinin, Andrey V.; Caldwell, Joshua D.; Novoselov, Kostya S.; Taniguchi, Takashi; Watanabe, Kenji; Gaussmann, Fabian; Taubner, Thomas

    2015-01-01

    Hyperbolic materials exhibit sub-diffractional, highly directional, volume-confined polariton modes. Here we report that hyperbolic phonon polaritons allow for a flat slab of hexagonal boron nitride to enable exciting near-field optical applications, including unusual imaging phenomenon (such as an enlarged reconstruction of investigated objects) and sub-diffractional focusing. Both the enlarged imaging and the super-resolution focusing are explained based on the volume-confined, wavelength d...

  2. Ion-induced stress relaxation during the growth of cubic boron nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Abendroth, B.E.

    2004-08-01

    in this thesis the deposition of cubic boron nitride films by magnetron sputtering is described. The deposition process is analyzed by Langmuir-probe measurement and energy resolved mass spectroscopy. the films are studied by stress measurement, spectroscopic ellipsometry, infrared spectroscopy, elastic recoil detection analysis, Rutherford backscattering spectroscopy, X-ray absorption near edge spectroscopy, X-ray diffraction, and transmission electron microscopy. Discussed are the stress relaxation and the microstructure and bonding characteristics together with the effects of ion bombardement. (HSI)

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

    OpenAIRE

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

    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...

  4. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers

    OpenAIRE

    Wang, Zifeng; Fu, Yuqiao; Meng, Wenjun; Zhi, Chunyi

    2014-01-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal...

  5. Charged defects in graphene and the ionicity of hexagonal boron nitride in direct images

    OpenAIRE

    Meyer, Jannik C.; Kurasch, Simon; Park, Hye Jin; Skakalova, Viera; Künzel, Daniela; Groß, Axel; Chuvilin, Andrey; Algara-Siller, Gerardo; Roth, Siegmar; Iwasaki, Takayuki; Starke, Ulrich; Smet, Jürgen; Kaiser, Ute

    2010-01-01

    We report on the detection and charge distribution analysis for nitrogen substitutional dopants in single layer graphene membranes by aberration-corrected high-resolution transmission electron microscopy (HRTEM). Further, we show that the ionicity of single-layer hexagonal boron nitride can be confirmed from direct images. For the first time, we demonstrate by a combination of HRTEM experiments and first-principles electronic structure calculations that adjustments to the atomic potentials du...

  6. Asymmetric energy transport in defected boron nitride nanoribbons: Implications for thermal rectification

    Directory of Open Access Journals (Sweden)

    Krishna Muralidharan

    2011-12-01

    Full Text Available Using molecular dynamics simulations, the thermal transport properties of boron nitride nanoribbons (BNNR containing geometrically-asymmetric triangular nano-vacancies were investigated. By suitably interpreting the time-evolution of spatially decomposed heat-current autocorrelation function in terms of phonon propagation characteristics, we have demonstrated the possibility of observing defect induced direction-dependent thermal transport in BNNR. This was further confirmed by appropriate analysis of direction dependent thermal diffusivity estimations in BNNR.

  7. Picosecond laser structuration under high pressures: observation of boron nitride nanorods

    OpenAIRE

    Museur, L.; Petitet, J. P.; Michel, J.P.; Marine, V.; Anglos, D.; Fotakis, C.; Kanaev, A.V.

    2008-01-01

    We report on picosecond UV-laser processing of hexagonal boron nitride (hBN) at moderately high pressures above 500 bar. The main effect is specific to the ambient gas and laser pulse duration in the ablation regime: when samples are irradiated by 5 ps or 0.45 ps laser pulses in nitrogen gas environment, multiple nucleation of a new crystalline product - BN nanorods - takes place. This process is triggered on structural defects, which number density strongly decreases upon recrystallization. ...

  8. Influence of Biofield Treatment on Physical, Structural and Spectral Properties of Boron Nitride

    OpenAIRE

    Trivedi, Mahendra; Nayak, Gopal

    2015-01-01

    Boron nitride (BN) is known for high hardness, thermal stability, thermal conductivity, and catalytic action. The aim of this study was to investigate the effect of biofield treatment on physical, structural and spectral properties of BN powder. The control and treated sample of BN powder were characterized by X-ray diffraction (XRD), surface area analysis and Fourier transform infrared spectroscopy (FT-IR). XRD results indicated that biofield treatment had substantially changed the crystalli...

  9. Preparation of boron nitride (BN) coatings onto different substrates using the polymer derived ceramics (PDCs) approach.

    OpenAIRE

    Termoss, Hussein

    2009-01-01

    The aim of this work was to prepare boron nitride coatings onto different substrates using the Polymers Derived Ceramics (PDCs) approach. In that way, BN coatings were obtained onto graphite, pure silica and metal especially titanium. The first part of this thesis was to study parameters (of the solution used and of the dip-coating process), to obtain the best coatings in terms of morphology, cristallinity and chemical composition. The second part was dedicated to BN coatings obtained onto me...

  10. Ion-induced stress relaxation during the growth of cubic boron nitride thin films

    International Nuclear Information System (INIS)

    in this thesis the deposition of cubic boron nitride films by magnetron sputtering is described. The deposition process is analyzed by Langmuir-probe measurement and energy resolved mass spectroscopy. the films are studied by stress measurement, spectroscopic ellipsometry, infrared spectroscopy, elastic recoil detection analysis, Rutherford backscattering spectroscopy, X-ray absorption near edge spectroscopy, X-ray diffraction, and transmission electron microscopy. Discussed are the stress relaxation and the microstructure and bonding characteristics together with the effects of ion bombardement. (HSI)

  11. Water-dispersed thermo-responsive boron nitride nanotubes: synthesis and properties

    Czech Academy of Sciences Publication Activity Database

    Kalay, S.; Stetsyshyn, Y.; Lobaz, Volodymyr; Harhay, K.; Ohar, H.; Ҫulha, M.

    2016-01-01

    Roč. 27, č. 3 (2016), 035703_1-035703_8. ISSN 0957-4484 R&D Projects: GA ČR(CZ) GA13-08336S; GA MPO(CZ) FR-TI4/625 Institutional support: RVO:61389013 Keywords : boron nitride nanotubes * thermo-responsive polymer brushes * poly(N-isopropylacrylamide) Subject RIV: CA - Inorganic Chemistry Impact factor: 3.821, year: 2014

  12. A new stepwise-pressing reaction method for synthesizing pure turbostractic boron nitride

    International Nuclear Information System (INIS)

    A new stepwise-pressing reaction method is proposed, by which pure and near monodisperse turbostractic boron nitride (tBN) nano-particles with high yield (higher than 92%) are selectively synthesized via reacting BBr3 and (CH3)3N at 260 oC in benzene. The obtained sample emits a strong photoluminescence band at 346 nm (under a excitation of 215 nm), making tBN a promising candidate for fabricating UV photoelectronic devices.

  13. Facile fabrication of boron nitride nanosheets-amorphous carbon hybrid film for optoelectronic applications

    KAUST Repository

    Wan, Shanhong

    2015-01-01

    A novel boron nitride nanosheets (BNNSs)-amorphous carbon (a-C) hybrid film has been deposited successfully on silicon substrates by simultaneous electrochemical deposition, and showed a good integrity of this B-C-N composite film by the interfacial bonding. This synthesis can potentially provide the facile control of the B-C-N composite film for the potential optoelectronic devices. This journal is

  14. Graphene quantum dot on boron nitride: Dirac cone replica and Hofstadter butterfly

    OpenAIRE

    Chizhova, L. A.; Libisch, F.; Burgdörfer, J.

    2014-01-01

    Graphene flakes placed on hexagonal boron nitride feature in the presence of a magnetic field a complex electronic structure due to a hexagonal moir\\'e potential resulting from the van der Waals interaction with the substrate. The slight lattice mismatch gives rise to a periodic supercell potential. Zone folding is expected to create replica of the original Dirac cone and Hofstadter butterflies. Our large-scale tight binding simulation reveals an unexpected coexistence of a relativistic and n...

  15. Growth Feature of Cubic Boron Nitride on c-BN Crystal Substrates

    Institute of Scientific and Technical Information of China (English)

    YANG Da-Peng; SU Zuo-Peng; DU Yong-Hui; JI Xiao-Rui; YANG Xu-Xin; GONG Xi-Liang; ZHANG Tie-Chen

    2006-01-01

    @@ Cubic boron nitride (c-BN) films were deposited on highly-oriented (111) bulk c-BN crystal by using the rf magnetron sputtering method. The growth films are characterized by micro-Raman spectroscopy (μ-RS) and scanning electron microscopy (SEM). The results show that the high crystallization electron transparent c-BN films in thickness of about 10μm are obtained. Island and step growth models are clearly shown.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, S.; Funashima, H.; Sato, K.; Katayama-Yoshida, H. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

    2013-12-04

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

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

    Science.gov (United States)

    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. PMID:25365544

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ning, E-mail: zhangning5832@163.com; Liu, Huan; Kan, Hongmin; Wang, Xiaoyang; Long, Haibo; Zhou, Yonghui

    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 of 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.

  19. Feasibility study of Boron Nitride coating on Lithium-ion battery casing

    International Nuclear Information System (INIS)

    Increasing in public awareness about global warming and exhaustion of energy resources has led to a flourishing electric vehicle industry that would help realize a zero-emission society. The thermal management of battery packs, which is an essential issue closely linked to a number of challenges for electric vehicles including cost, safety, reliability and lifetime, has been extensively studied. However, relatively little is known about the thermal effect of polymer insulation on the Lithium-ion battery casing. This study investigates the feasibility of replacing the polymer insulation with a Boron Nitride coating on the battery casing using the Taguchi experimental method. The effect of casing surface roughness, coating thickness and their interaction were examined using orthogonal array L9 (34). Nominal the best is chosen for the optimization process to achieve optimum adhesion strength. In addition, the thermal improvements of the coating as compared to conventional polymer insulator on the battery are further investigated. - Highlights: • We studied the Boron Nitride coating on battery casing using Taguchi method. • We investigated the effect of surface roughness and coating thickness on adhesion strength. • We compared the effect of coating and polymer insulator in heat transfer. • The Boron Nitride coating could enhance the thermal management of the battery

  20. Kinetics and film properties of boron nitride derived from trimethoxyborane/ammonia by chemical vapor deposition

    International Nuclear Information System (INIS)

    The kinetics of the CVD of boron nitride from trimethoxyborane (TMOB) and ammonia (NH3) under atmospheric pressure was investigated by varying the following process parameters: temperature, residence time of the reactants, molar fraction of TMOB, and the NH3/TMOB ratio, γ. A kinetic power law equation was derived, that describes the experimental results with good accuracy. The reaction order with respect to TMOB is found to be 0.9 and -0.2 with respect to NH3. Between 800 C and 950 C, the deposition rate is controlled by the surface reaction kinetics with apparent activation energy of 115.1 kJ mol-1. The deposited BN films were characterized by IR spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The microstructure of the deposits depends on the nature of the substrates used. Turbostratic boron nitride (t-BN) was deposited on graphite, and hexagonal boron nitride (h-BN) on alumina substrates. X-ray photoelectron spectroscopy (XPS) analyses show nearly stoichiometric BN films for deposition temperatures in the range 850-950 C for high amounts of ammonia (100< γ <150) in the feed gas. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

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

    International Nuclear Information System (INIS)

    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 sp2-bonded boron nitride (sp2BN) interlayer. A two-step biasing technique is developed to control the fraction of cubic boron nitride (cBN) phase and, hence, the thickness of the sp2BN interlayer in the films. The rectification ratio at room temperature is increased up to the order of 104 at ±10 V of biasing with increasing the sp2BN thickness up to around 130 nm due to suppression of the reverse leakage current. The variation of the ideality factor in the low bias region is related to the interface disorders and defects, not to the sp2BN thickness. The forward current follows the Frenkel-Poole emission model in the sp2BN 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 sp2BN interlayer, while that of the major carriers for forward current is much less affected

  2. Molecular dynamics study of the torsional vibration characteristics of boron-nitride nanotubes

    International Nuclear Information System (INIS)

    In recent years, synthesizing inorganic nanostructures such as boron nitride nanotubes (BNNTs) has led to extensive studies on their exceptional properties. In this study, the torsional vibration behavior of boron-nitride nanotubes (BNNTs) is explored on the basis of molecular dynamics (MD) simulation. The results show that the torsional frequency is sensitive to geometrical parameters such as length and boundary conditions. The axial vibration is found to be induced by torsional vibration of nanotubes which can cause instability in the nanostructure. It is also observed that the torsional frequency of BNNTs is higher than that of their carbon counterpart. Moreover, the shear modulus is predicted by incorporating MD simulation numerical results into torsional vibration frequency obtained through continuum-based model of tubes. Finally, it is seen that the torsional frequency of double-walled boron-nitride nanotubes (DWBNNTs) is between the frequencies of their constituent inner and outer tubes. - Highlights: • Molecular dynamics study of the torsional vibration behavior of BNNTs • Torsional vibration frequency are found to be dependent to geometrical parameters • The shear modulus of BNNTs are calculated through the continuum model • Torsional frequency of BNNTs are bigger than that of their carbon counterpart

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

    International Nuclear Information System (INIS)

    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 of 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

  4. Molecular dynamics study of the torsional vibration characteristics of boron-nitride nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ansari, R.; Ajori, S., E-mail: Shahram_ajori1366@yahoo.com

    2014-08-01

    In recent years, synthesizing inorganic nanostructures such as boron nitride nanotubes (BNNTs) has led to extensive studies on their exceptional properties. In this study, the torsional vibration behavior of boron-nitride nanotubes (BNNTs) is explored on the basis of molecular dynamics (MD) simulation. The results show that the torsional frequency is sensitive to geometrical parameters such as length and boundary conditions. The axial vibration is found to be induced by torsional vibration of nanotubes which can cause instability in the nanostructure. It is also observed that the torsional frequency of BNNTs is higher than that of their carbon counterpart. Moreover, the shear modulus is predicted by incorporating MD simulation numerical results into torsional vibration frequency obtained through continuum-based model of tubes. Finally, it is seen that the torsional frequency of double-walled boron-nitride nanotubes (DWBNNTs) is between the frequencies of their constituent inner and outer tubes. - Highlights: • Molecular dynamics study of the torsional vibration behavior of BNNTs • Torsional vibration frequency are found to be dependent to geometrical parameters • The shear modulus of BNNTs are calculated through the continuum model • Torsional frequency of BNNTs are bigger than that of their carbon counterpart.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Teii, K., E-mail: teii@asem.kyushu-u.ac.jp; Ito, H.; Katayama, N. [Department of Applied Science for Electronics and Materials, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Matsumoto, S. [Department of Applied Science for Electronics and Materials, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Exploratory Materials Research Laboratory for Energy and Environment, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    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 of 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.

  8. Radio-frequency sputter deposition of boron nitride based thin films

    International Nuclear Information System (INIS)

    Thin films (∼2 μm) of boron nitride, titanium boron nitride, and titanium aluminum boron nitride have been grown on molybdenum, niobium, and cemented carbide substrates employing nonreactive as well as reactive rf magnetron sputter deposition from either a BN, a TiN-BN, or a TiN--AlN--BN target. Substrates have been rf biased, with dc potentials up to -200 V. By means of nonreactive sputtering mixed-phase structures with dominant phases B48B2N2 (using a BN target), or B48B2N2 and hexagonal Ti--B--N (using a TiN--BN or a TiN--AlN--BN target) are formed. Reactive deposition leads to the existence of hexagonal BN in all deposition modes. In the cases of Ti--B--N and Ti--Al--B--N films this phase is accompanied by fcc Ti--B--N. SEM cross sections revealed very fine grained to fracture-amorphous film structures. Hardness measurements gave the following maximum HV 0.02 values: B--N films 2800, Ti--B--N films 2750, and Ti--Al--B--N films 1650

  9. The mechanism for low temperature growth of vertically aligned boron nitride nanotubes

    Science.gov (United States)

    Wang, Jiesheng; Xie, Ming; Khin Yap, Yoke

    2006-03-01

    Boron nitride nanotubes (BNNTs) are well recognized as the candidate that will complement the uses of carbon nanotubes (CNTs) in nanotechnology. However, high growth temperatures (>1100 ^oC), low production yield, and impurities have prevented effective synthesis and applications of boron nitride nanotubes (BNNTs) in the past ten years. For the first time, we have succeeded on the growth of pure BNNTs on substrates [1, 2]. This has been realized based on our experiences of growing CNTs and boron nitride (BN) phases (cubic phase BN, hexagonal phase BN). According to our hypothetical model, energetic growth species play an important role on controlling the phases of BN solids. We have experimentally verified that BNNTs can be grown by energetic growth species by a plasma-enhanced pulsed laser deposition (PEPLD) technique. These BNNTs can be grown vertically aligned into arrays of regular patterns at 600 ^oC, and can be used for applications without purification. The growth mechanism of thee BNNTs will be discussed. [1]. Yap et al., Bull APS Vol 50, 1346-1347 (March 2005). [2]. Wang et al., nano Letters (2005) ASAP, DOI: 10.1021/nl051859n.

  10. Laser-initiated primary and secondary nuclear reactions in Boron-Nitride

    Science.gov (United States)

    Labaune, C.; Baccou, C.; Yahia, V.; Neuville, C.; Rafelski, J.

    2016-02-01

    Nuclear reactions initiated by laser-accelerated particle beams are a promising new approach to many applications, from medical radioisotopes to aneutronic energy production. We present results demonstrating the occurrence of secondary nuclear reactions, initiated by the primary nuclear reaction products, using multicomponent targets composed of either natural boron (B) or natural boron nitride (BN). The primary proton-boron reaction (p + 11B → 3 α + 8.7 MeV), is one of the most attractive aneutronic fusion reaction. We report radioactive decay signatures in targets irradiated at the Elfie laser facility by laser-accelerated particle beams which we interpret as due to secondary reactions induced by alpha (α) particles produced in the primary reactions. Use of a second nanosecond laser beam, adequately synchronized with the short laser pulse to produce a plasma target, further enhanced the reaction rates. High rates and chains of reactions are essential for most applications.

  11. Characterization of bulk hexagonal boron nitride single crystals grown by the metal flux technique

    Science.gov (United States)

    Edgar, J. H.; Hoffman, T. B.; Clubine, B.; Currie, M.; Du, X. Z.; Lin, J. Y.; Jiang, H. X.

    2014-10-01

    The optical and physical properties of hexagonal boron nitride single crystals grown from a molten metal solution are reported. The hBN crystals were grown by precipitation from a nickel-chromium flux with a boron nitride source, by slowly cooling from 1500 °C at 2-4 °C/h under a nitrogen flow at atmospheric pressure. The hBN crystals formed on the surface of the flux with an apparent crystal size up to 1-2 mm in diameter. Individual grains were as large as 100-200 μm across. Typically, the flakes removed from the metal were 6-20 μm thick. Optical absorption measurements suggest a bandgap of 5.8 eV by neglecting the binding energy of excitons in hBN. The highest energy photoluminescence peak was at 5.75 eV at room temperature. The hBN crystals typically had a pit density of 5×106 cm-2 after etching in a molten eutectic mixture of potassium hydroxide and sodium hydroxide. The quality of these crystals suggests they are suitable as substrates for two dimensional materials such as graphene and gallium nitride based devices.

  12. Plasma deposition of cubic boron nitride films from non-toxic material at low temperatures

    International Nuclear Information System (INIS)

    Boron nitride has become the focus of a considerable amount of interest because of its properties which relate closely to those of carbon. In particular, the cubic nitride phase has extreme hardness and very high thermal conductivity similar to the properties of diamond. The conventional methods of synthesis use the highly toxic and inflammable gas diborane (B2H6) as the reactant material. A study has been made of the deposition of thin films of boron nitride (BN) using non-toxic material by the plasma-assisted chemical vapour deposition technique. The source material was borane-ammonia (BH3-NH3) which is a crystalline solid at room temperature with a high vapour pressure. The BH3-NH3 vapour was decomposed in a 13.56 MHz nitrogen plasma coupled either inductively or capacitively with the system. The composition of the films was assessed by measuring their IR absorption when deposited on silicon and KBr substrates. The hexagonal (graphitic) and cubic (diamond-like) allotropes can be distinguished by their characteristic absorption bands which occur at 1365 and 780 cm-1 (hexagonal) and 1070 cm-1 (cubic). We have deposited BN films consisting of a mixture of hexagonal and cubic phases; the relative content of the cubic phase was found to be directly dependent on r.f. power and substrate bias. (orig.)

  13. Microstructure and spectroscopy studies on cubic boron nitride synthesized under high-pressure conditions

    CERN Document Server

    Nistor, L C; Dinca, G; Georgeoni, P; Landuyt, J V; Manfredotti, C; Vittone, E

    2002-01-01

    High-resolution electron microscopy (HREM) studies of the microstructure and specific defects in hexagonal boron nitride (h-BN) precursors and cubic boron nitride (c-BN) crystals made under high-pressure high-temperature conditions revealed the presence of half-nanotubes at the edges of the h-BN particles. Their sp sup 3 bonding tendency could strongly influence the nucleation rates of c-BN. The atomic resolution at extended dislocations was insufficient to allow us to determine the stacking fault energy in the c-BN crystals. Its mean value of 191 pm, 15 mJ m sup - sup 2 is of the same order of magnitude as that of diamond. High-frequency (94 GHz) electron paramagnetic resonance studies on c-BN single crystals have produced new data on the D1 centres associated with the boron species. Ion-beam-induced luminescence measurements have indicated that c-BN is a very interesting luminescent material, which is characterized by four luminescence bands and exhibits a better resistance to ionizing radiation than CVD di...

  14. Mechanisms of the boron carbide and boron nitride preferred sputtering by low energy ions bombardment

    International Nuclear Information System (INIS)

    The ion irradiation of BN and B4C leads to enriching of the materials with the lighter component - borons as the experiment shows . With a view to explain this effect sputtering of BN and B4C under the irradiation by the He+ and Ar+ ions with the energy E0=0,5-5 keV has been calculated with computer modelling and the real structure of BN has been considered. In the case of B4C the calculations have been carried with Monte-Carlo code. It was shown that enriching of BN by boron may be accounted for building up the molecules N2 on the irradiated surface and their desorbing. The enriching of B4C with boron results from the difference of the binding energy of the B and C atoms. (author). 10 refs., 5 tabs

  15. XPS analysis for cubic boron nitride crystal synthesized under high pressure and high temperature using Li3N as catalysis

    International Nuclear Information System (INIS)

    Highlights: • The cBN was synthesized by Li3N as catalyst under high pressure and high temperature (HPHT). • The film coated on the as-grown cBN crystals was studied by XPS. • The electronic structure variation in the film was investigated. • The growth mechanism of cubic boron nitride crystal was analyzed briefly. - Abstract: Cubic boron nitride (cBN) single crystals are synthesized with lithium nitride (Li3N) as catalyst under high pressure and high temperature. The variation of electronic structures from boron nitride of different layers in coating film on the cBN single crystal has been investigated by X-ray photoelectron spectroscopy. Combining the atomic concentration analysis, it was shown that from the film/cBN crystal interface to the inner, the sp2 fractions are decreasing, and the sp3 fractions are increasing in the film at the same time. Moreover, by transmission electron microscopy, a lot of cBN microparticles are found in the interface. For there is no Li3N in the film, it is possible that Li3N first reacts with hexagonal boron nitride to produce Li3BN2 during cBN crystals synthesis under high pressure and high temperature (HPHT). Boron and nitrogen atoms, required for cBN crystals growth, could come from the direct conversion from hexagonal boron nitride with the catalysis of Li3BN2 under high pressure and high temperature, but not directly from the decomposition of Li3BN2

  16. Electron beam generation and structure of defects in carbon and boron nitride nano-tubes

    International Nuclear Information System (INIS)

    The nature and role of defects is of primary importance to understand the physical properties of C and BN (boron nitride) single walled nano-tubes (SWNTs). Transmission electron microscopy (TEM) is a well known powerful tool to study the structure of defects in materials. However, in the case of SWNTs, the electron irradiation of the TEM may knock out atoms. This effect may alter the native structure of the tube, and has also been proposed as a potential tool for nano-engineering of nano-tubular structures. Here we develop a theoretical description of the irradiation mechanism. First, the anisotropy of the emission energy threshold is obtained via density functional based calculations. Then, we numerically derive the total Mott cross section for different emission sites of carbon and boron nitride nano-tubes with different chiralities. Using a dedicated STEM (Scanning Transmission Electron Microscope) microscope with experimental conditions optimised on the basis of derived cross-sections, we are able to control the generation of defects in nano-tubular systems. Either point or line defects can be obtained with a spatial resolution of a few nanometers. The structure, energetics and electronics of point and line defects in BN systems have been investigated. Stability of mono- and di- vacancy defects in hexagonal boron nitride layers is investigated, and their activation energies and reaction paths for diffusion have been derived using the nudged elastic band method (NEB) combined with density functional based techniques. We demonstrate that the appearance of extended linear defects under electron irradiation is more favorable than a random distribution of point defects and this is due to the existence of preferential sites for atom emission in the presence of pre-existing defects, rather than thermal vacancy nucleation and migration. (author)

  17. Electron beam generation and structure of defects in carbon and boron nitride nano-tubes

    Energy Technology Data Exchange (ETDEWEB)

    Zobelli, A

    2007-10-15

    The nature and role of defects is of primary importance to understand the physical properties of C and BN (boron nitride) single walled nano-tubes (SWNTs). Transmission electron microscopy (TEM) is a well known powerful tool to study the structure of defects in materials. However, in the case of SWNTs, the electron irradiation of the TEM may knock out atoms. This effect may alter the native structure of the tube, and has also been proposed as a potential tool for nano-engineering of nano-tubular structures. Here we develop a theoretical description of the irradiation mechanism. First, the anisotropy of the emission energy threshold is obtained via density functional based calculations. Then, we numerically derive the total Mott cross section for different emission sites of carbon and boron nitride nano-tubes with different chiralities. Using a dedicated STEM (Scanning Transmission Electron Microscope) microscope with experimental conditions optimised on the basis of derived cross-sections, we are able to control the generation of defects in nano-tubular systems. Either point or line defects can be obtained with a spatial resolution of a few nanometers. The structure, energetics and electronics of point and line defects in BN systems have been investigated. Stability of mono- and di- vacancy defects in hexagonal boron nitride layers is investigated, and their activation energies and reaction paths for diffusion have been derived using the nudged elastic band method (NEB) combined with density functional based techniques. We demonstrate that the appearance of extended linear defects under electron irradiation is more favorable than a random distribution of point defects and this is due to the existence of preferential sites for atom emission in the presence of pre-existing defects, rather than thermal vacancy nucleation and migration. (author)

  18. Transport properties through hexagonal boron nitride clusters embedded in graphene nanoribbons

    Science.gov (United States)

    Silva, F. W. N.; Cruz-Silva, E.; Terrones, M.; Terrones, H.; Barros, E. B.

    2016-05-01

    First-principles calculations are employed in the study of the electronic and quantum transport properties of hexagonally shaped boron nitride (h-BN) clusters embedded in either zigzag or armchair graphene nanoribbons. Chemical doping of the h-BN cluster was taken into consideration by using carbon atoms to replace either the boron ({{{B}}}24{{{N}}}27{{{C}}}3) or the nitrogen ({{{B}}}27{{{N}}}24{{{C}}}3) sites in the central ring. While the quantum conductance of the system with zigzag edges is found to be spin-dependent, it was observed that the system with an armchair edge requires an electron imbalance in order to show a spin-dependent conductance. Furthermore, the possibility of molecular adsorption onto these doped systems is studied. The effects of the attached molecules to the quantum conductance shows the potential of these hybrid systems for molecular sensing applications.

  19. DFT study on the structural and electronic properties of Pt-doped boron nitride nanotubes

    Science.gov (United States)

    Vessally, E.; Dehbandi, B.; Edjlali, Ladan

    2016-06-01

    First-principles calculations based on density functional theory were carried out to investigate the structural and electronic properties of Pt substitution-doped boron nitride (BN) nanotubes. The electronic and structural properties were studied for substituted Pt in the boron and the nitrogen sites of the (BN) nanotube. The band gap significantly diminishes to 2.095 eV for Pt doping at the B site while the band gap diminishes to 2.231 eV for Pt doping at the N site. The band density increases in both the valence band and the conduction band after doping. The effects of the hardness and softness group 17 (halogen elements) were calculated by density functional theory (DFT).

  20. The production, characterization, and neutronic performance of boron nitride coated uranium dioxide fuel

    International Nuclear Information System (INIS)

    The fuel pellets produced by sol-gel technique were coated with boron nitride (BN). This was achieved through chemical vapor deposition (CVD) using boron trichloride and ammonia. Mixing and chemical reaction take place at a temperature around 875 K. The coated samples were then sintered at 1600 K. Thermal reactor physics lattice-cell code WIMS-D/4 was used in the neutronic analysis of CANDU fuel bundle to observe the neutronic performance of the coated fuel. Three types of fuel were considered; fuel made of natural uranium, slightly enriched uranium (SEU, enrichment: 0.82 % U-235), and SEU with various BN coatings. The burnup calculations showed that feasible coating thickness is between 1 to 2 μm. (author)

  1. Transport properties through hexagonal boron nitride clusters embedded in graphene nanoribbons.

    Science.gov (United States)

    Silva, F W N; Cruz-Silva, E; Terrones, M; Terrones, H; Barros, E B

    2016-05-01

    First-principles calculations are employed in the study of the electronic and quantum transport properties of hexagonally shaped boron nitride (h-BN) clusters embedded in either zigzag or armchair graphene nanoribbons. Chemical doping of the h-BN cluster was taken into consideration by using carbon atoms to replace either the boron ([Formula: see text]) or the nitrogen ([Formula: see text]) sites in the central ring. While the quantum conductance of the system with zigzag edges is found to be spin-dependent, it was observed that the system with an armchair edge requires an electron imbalance in order to show a spin-dependent conductance. Furthermore, the possibility of molecular adsorption onto these doped systems is studied. The effects of the attached molecules to the quantum conductance shows the potential of these hybrid systems for molecular sensing applications. PMID:27004996

  2. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers

    Science.gov (United States)

    Wang, Zifeng; Fu, Yuqiao; Meng, Wenjun; Zhi, Chunyi

    2014-11-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal stability well preserved.

  3. Atomic Resolution Transmission Electron Microscopy of Defects in Hexagonal Boron Nitride and Graphene

    Science.gov (United States)

    Gibb, Ashley; Alem, Nasim; Song, Chengyu; Ciston, Jim; Zettl, Alex

    2014-03-01

    Monolayer sheets of sp2-bonded materials such as graphene and hexagonal boron nitride (h-BN) have been studied extensively due to their properties including high mechanical strength, thermal conductivity, stability, interesting electronic properties, and potential for integration into novel devices. Understanding the atomic scale structure of defects in these materials is important because defects can significantly affect the physical properties in these materials. In particular, understanding the dynamics of these defects explains much about the material's stability. We have synthesized h-BN and graphene using low pressure chemical vapor deposition and imaged defects using atomic resolution aberration corrected transmission electron microscopy.

  4. Carbon nanotubes with atomic impurities on boron nitride sheets under applied electric fields

    OpenAIRE

    Kang, Seoung-Hun; Kim, Gunn; Kwon, Young-Kyun

    2013-01-01

    We perform first-principles calculations to investigate the structural and electronic properties of metal-doped (10, 0) carbon nanotubes (CNTs) on a single hexagonal boron nitride (hBN) sheet in the presence of an external electric field. We consider K, Cl and Ni atoms as dopants to study the dependence of the electronic properties of the CNT on doping polarity and concentration. The electric field strength is varied from -0.2 V/\\AA to +0.2 V/\\AA to explore the effects of an external electric...

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

    Science.gov (United States)

    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. PMID:26727539

  6. Orthorhombic BN: A novel superhard sp{sup 3} boron nitride allotrope

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhiguo [College of Physics, Beihua University, Jilin 132013 (China); Lu, Mingchun [Department of Aeronautical Engineering Professional Technology, Jilin Institute of Chemical Technology, Jilin 132102 (China); Zhu, Li; Zhu, Lili; Li, Yadan [College of Physics, Beihua University, Jilin 132013 (China); Zhang, Miao, E-mail: zhangmiaolmc@126.com [College of Physics, Beihua University, Jilin 132013 (China); College of Materials Science and Engineering, National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Li, Quan, E-mail: liquan777@jlu.edu.cn [College of Materials Science and Engineering, National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)

    2014-02-07

    Here, a novel superhard orthorhombic allotrope of boron nitride (O-BN) with the space group of Pbam has been predicted using first-principles calculations. Our results revealed that O-BN simultaneously posses incompressible with a high bulk modulus of 397.38 GPa, and superhard properties with a high Vickers hardness of 65 GPa. Further phonon calculations show O-BN structure is dynamically stable. Moreover, it is thermodynamics energetically more preferable than previous proposed BN allotropes and a transparent insulator with an indirect band gap of about 4.85 eV. Our researches represent a significant step toward the exploration of superhard materials.

  7. Static tensile and tensile creep testing of four boron nitride coated ceramic fibers at elevated temperatures

    Science.gov (United States)

    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.

  8. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers.

    Science.gov (United States)

    Wang, Zifeng; Fu, Yuqiao; Meng, Wenjun; Zhi, Chunyi

    2014-01-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal stability well preserved. PMID:25489292

  9. Science and technology in the recent development of boron nitride materials

    CERN Document Server

    Fukunaga, O

    2002-01-01

    In this paper, we review recent developments relating to cubic boron nitride (cBN) abrasive grains and sintered cutting tools. The demand for high-speed machining and the ecological benefits of using ferrous materials have led to developments in the area of heavy-duty dry cutting and grinding processes in recent years. Optimization of the process of manufacturing cBN materials is an important issue, both fundamentally and as regards applications. We review recent developments in cBN applications and discuss the challenges arising from new processes encountered in basic cBN study at high pressure and high temperature.

  10. Molecular dynamics investigation into the oscillatory behavior of double-walled boron-nitride nanotubes

    Science.gov (United States)

    Ansari, R.; Ajori, S.

    2016-05-01

    In this paper, the oscillatory behavior of double-walled boron-nitride nanotubes is investigated based on the molecular dynamics (MD) simulations. The MD simulations are performed using the Lennard-Jones and Tersoff-like potential functions. The influences of friction between the walls of inner and outer tubes, flexibility, velocity and outer length-to-inner length ratio on the frequency of oscillations are studied. The results show that the flexibility increases the frequency during the simulation. Furthermore, it is observed that by increasing the initial velocity, the frequency decreases.

  11. Effect of reaction time on the characteristics of catalytically grown boron nitride nanotubes

    International Nuclear Information System (INIS)

    The paper reports on the growth of boron nitride nanotube (BNNTs) on Si substrate by catalytic chemical vapor deposition technique and the effect of reaction time and temperature on the size and purity were investigated. Scanning electron microscopy image revealed the bamboo-like BNNTs of multiwalled type with interlayer spacing of 0.34 nm. EDX analysis described the presence of a small percentage of Mg in the sample, indicating the combination of base-tip growth model for the sample synthesized at 1200°C. The reaction time has an effect of extending the length of the BNNTs until the catalyst is oxidized or covered by growth precursor

  12. Science and technology in the recent development of boron nitride materials

    Energy Technology Data Exchange (ETDEWEB)

    Fukunaga, Osamu [Ace - Tech Co. Ltd, 1-167-1Higashi-Ome, Ome 198-0042 (Japan)

    2002-11-11

    In this paper, we review recent developments relating to cubic boron nitride (cBN) abrasive grains and sintered cutting tools. The demand for high-speed machining and the ecological benefits of using ferrous materials have led to developments in the area of heavy-duty dry cutting and grinding processes in recent years. Optimization of the process of manufacturing cBN materials is an important issue, both fundamentally and as regards applications. We review recent developments in cBN applications and discuss the challenges arising from new processes encountered in basic cBN study at high pressure and high temperature.

  13. Utilization of multiwalled boron nitride nanotubes for the reinforcement of lightweight aluminum ribbons.

    Science.gov (United States)

    Yamaguchi, Maho; Pakdel, Amir; Zhi, Chunyi; Bando, Yoshio; Tang, Dai-Ming; Faerstein, Konstantin; Shtansky, Dmitry; Golberg, Dmitri

    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

  14. Deposition of diamond and boron nitride films by plasma chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Albella, J.M. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.; Gomez-Aleixandre, C. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.; Sanchez-Garrido, O. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.; Vazquez, L. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.; Martinez-Duart, J.M. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.

    1995-01-01

    The deposition problems of diamond and cubic boron nitride (c-BN) by chemical vapour deposition techniques are reviewed, with major emphasis on the nucleation and reaction mechanisms. A discussion is made of the main deposition parameters (i.e. gas mixture, substrate conditioning, plasma discharges etc.) which favour the formation of the cubic phase. Most of the work is devoted to diamond owing to the large progress attained in this material. In fact, the use of diamond as a hard protective coating is now on a commercial scale. By contrast, the preparation of c-BN layers with good characteristics still needs of further research. ((orig.))

  15. Synthesis of boron nitride nanofibers and measurement of their hydrogen uptake capacity

    International Nuclear Information System (INIS)

    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

  16. Synthesis and characterization of bamboo-like turbostratic boron nitride tubes

    International Nuclear Information System (INIS)

    The bamboo-like turbostratic boron nitride (tBN) tubes were synthesized by chemical vapor deposition method. The as-prepared tBN tubes were characterized by X-ray diffraction, field emission scanning electron microscope (FESEM), field emission transmission electron microscope, Fourier transformed infrared spectrum, ultraviolet-visible (UV-vis) spectrum and photoluminescence (PL) spectrum. UV-vis spectrum revealed that the product had one broad band gap (4.5-4.7 eV) and PL spectrum showed that it had a visible emission at 457 nm (λex = 230 nm)

  17. Opening of triangular hole in triangular-shaped chemical vapor deposited hexagonal boron nitride crystal

    OpenAIRE

    Sharma, Subash; Kalita, Golap; Vishwakarma, Riteshkumar; Zulkifli, Zurita; Tanemura, Masaki

    2015-01-01

    In-plane heterostructure of monolayer hexagonal boron nitride (h-BN) and graphene is of great interest for its tunable bandgap and other unique properties. Here, we reveal a H2-induced etching process to introduce triangular hole in triangular-shaped chemical vapor deposited individual h-BN crystal. In this study, we synthesized regular triangular-shaped h-BN crystals with the sizes around 2-10 μm on Cu foil by chemical vapor deposition (CVD). The etching behavior of individual h-BN crystal w...

  18. Formation of hexagonal Boron Nitride on Graphene-covered Copper Surfaces

    OpenAIRE

    Gopalan, Devashish P.; Mende, Patrick C.; de la Barrera, Sergio C.; Dhingra, Shonali; Jun LI; Zhang, Kehao; Simonson, Nicholas A.; Robinson, Joshua A.; Lu, Ning; Wang, Qingxiao; Kim, Moon J.; D'Urso, Brian; Feenstra, Randall M.

    2015-01-01

    Graphene-covered copper surfaces have been exposed to borazine, (BH)3(NH)3, with the resulting surfaces characterized by low-energy electron microscopy. Although the intent of the experiment was to form hexagonal boron nitride (h-BN) on top of the graphene, such layers were not obtained. Rather, in isolated surface areas, h-BN is found to form micrometer-size islands that substitute for the graphene. Additionally, over nearly the entire surface, the properties of the layer that was originally...

  19. Single Crystalline Film of Hexagonal Boron Nitride Atomic Monolayer by Controlling Nucleation Seeds and Domains

    OpenAIRE

    Qinke Wu; Ji-Hoon Park; Sangwoo Park; Seong Jun Jung; Hwansoo Suh; Noejung Park; Winadda Wongwiriyapan; Sungjoo Lee; Young Hee Lee; Young Jae Song

    2015-01-01

    A monolayer hexagonal boron nitride (h-BN) film with controllable domain morphology and domain size (varying from less than 1 μm to more than 100 μm) with uniform crystalline orientation was successfully synthesized by chemical vapor deposition (CVD). The key for this extremely large single crystalline domain size of a h-BN monolayer is a decrease in the density of nucleation seeds by increasing the hydrogen gas flow during the h-BN growth. Moreover, the well-defined shape of h-BN flakes can ...

  20. High-quality, faceted cubic boron nitride films grown by chemical vapor deposition

    Science.gov (United States)

    Zhang, W. J.; Jiang, X.; Matsumoto, S.

    2001-12-01

    Thick cubic boron nitride (cBN) films showing clear crystal facets were achieved by chemical vapor deposition. The films show the highest crystallinity of cBN films ever achieved from gas phase. Clear evidence for the growth via a chemical route is obtained. A growth mechanism is suggested, in which fluorine preferentially etches hBN and stabilizes the cBN surface. Ion bombardment of proper energy activates the cBN surface bonded with fluorine so as to enhance the bonding probability of nitrogen-containing species on the F-stabilized B (111) surface.

  1. Ab Initio Investigations of Thermoelectric Effects in Graphene – Boron Nitride Nanoribbons

    Directory of Open Access Journals (Sweden)

    Visan Camelia

    2016-01-01

    Full Text Available Thermoelectric effects of graphene – hexagonal boron nitride (hBN nanoribbons have been investigated by density functional theory (DFT calculations. Pristine zig-zag nanoribbons are not suited to achieve high thermopower as the transmission function is flat around the chemical potential. By introducing hBN inclusions, the nanoribbon systems exhibit enhanced thermopower, due to the asymmetries introduced in the spin dependent transmission functions. Finite temperature differences between the two contacts are considered. The possibility of a good integration of hBN into graphene, makes the hybrid systems suitable for thermoelectric applications, which may be subject to further optimizations.

  2. Effect of Structural Relaxation on the Electronic Structure of Graphene on Hexagonal Boron Nitride.

    Science.gov (United States)

    Slotman, G J; van Wijk, M M; Zhao, Pei-Liang; Fasolino, A; Katsnelson, M I; Yuan, Shengjun

    2015-10-30

    We performed calculations of electronic, optical, and transport properties of graphene on hexagonal boron nitride with realistic moiré patterns. The latter are produced by structural relaxation using a fully atomistic model. This relaxation turns out to be crucially important for electronic properties. We describe experimentally observed features such as additional Dirac points and the "Hofstadter butterfly" structure of energy levels in a magnetic field. We find that the electronic structure is sensitive to many-body renormalization of the local energy gap. PMID:26565485

  3. Phonon-assisted resonant tunneling of electrons in graphene-boron nitride transistors

    OpenAIRE

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

    2015-01-01

    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 $\\sim$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...

  4. The unique Raman fingerprint of boron nitride substitution patterns in graphene.

    Science.gov (United States)

    Maschio, Lorenzo; Lorenz, Marco; Pullini, Daniele; Sgroi, Mauro; Civalleri, Bartolomeo

    2016-07-27

    Boron nitride-substituted graphene (BNsG) two-dimensional structures are new materials of wide technological interest due to the rich variety of electronic structures and properties they can exploit. The ability to accurately characterize them is key to their future success. Here we show, by means of ab initio simulations, that the vibrational Raman spectra of such compounds are extremely sensitive to substitution motifs and concentration, and that each structure has unique and distinct features. This result can be useful as a guide for the optimization of production processes. PMID:27406407

  5. Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators

    International Nuclear Information System (INIS)

    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

  6. Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Gaskell, J.; Fromhold, T. M.; Greenaway, M. T. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Eaves, L. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Novoselov, K. S.; Mishchenko, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Geim, A. K. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-09-07

    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.

  7. Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators

    Science.gov (United States)

    Gaskell, J.; Eaves, L.; Novoselov, K. S.; Mishchenko, A.; Geim, A. K.; Fromhold, T. M.; Greenaway, M. T.

    2015-09-01

    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.

  8. Coaxial nanocable: silicon carbide and silicon oxide sheathed with boron nitride and carbon

    Science.gov (United States)

    Zhang; Suenaga; Colliex; Iijima

    1998-08-14

    Multielement nanotubes comprising multiple phases, with diameters of a few tens of nanometers and lengths up to 50 micrometers, were successfully synthesized by means of reactive laser ablation. The experimentally determined structure consists of a beta-phase silicon carbide core, an amorphous silicon oxide intermediate layer, and graphitic outer shells made of boron nitride and carbon layers separated in the radial direction. The structure resembles a coaxial nanocable with a semiconductor-insulator-metal (or semiconductor-insulator-semiconductor) geometry and suggests applications in nanoscale electronic devices that take advantage of this self-organization mechanism for multielement nanotube formation. PMID:9703508

  9. Effect of reaction time on the characteristics of catalytically grown boron nitride nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mohamed, Norani Muti, E-mail: noranimuti-mohamed@petronas.com.my, E-mail: pervaiz-pas@yahoo.com, E-mail: shuaib-penang@yahoo.com, E-mail: zainabh@petronas.com.my; Ahmad, Pervaiz, E-mail: noranimuti-mohamed@petronas.com.my, E-mail: pervaiz-pas@yahoo.com, E-mail: shuaib-penang@yahoo.com, E-mail: zainabh@petronas.com.my; Saheed, Mohamed Shuaib Mohamed, E-mail: noranimuti-mohamed@petronas.com.my, E-mail: pervaiz-pas@yahoo.com, E-mail: shuaib-penang@yahoo.com, E-mail: zainabh@petronas.com.my; Burhanudin, Zainal Arif, E-mail: noranimuti-mohamed@petronas.com.my, E-mail: pervaiz-pas@yahoo.com, E-mail: shuaib-penang@yahoo.com, E-mail: zainabh@petronas.com.my [Center of Innovative Nanostructures and Nanodevices (COINN), Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750, Tronoh, Perak (Malaysia)

    2014-10-24

    The paper reports on the growth of boron nitride nanotube (BNNTs) on Si substrate by catalytic chemical vapor deposition technique and the effect of reaction time and temperature on the size and purity were investigated. Scanning electron microscopy image revealed the bamboo-like BNNTs of multiwalled type with interlayer spacing of 0.34 nm. EDX analysis described the presence of a small percentage of Mg in the sample, indicating the combination of base-tip growth model for the sample synthesized at 1200°C. The reaction time has an effect of extending the length of the BNNTs until the catalyst is oxidized or covered by growth precursor.

  10. Cubic boron nitride: a new prospective material for ultracold neutron application

    OpenAIRE

    Sobolev, Yu.; Lauer, Th.; Borisov, Yu.; Daum, M.; Fresne, N. du; Goeltl, L.; Hampel, G.; Heil, W.; Knecht, A.; Keunecke, M.; Kratz, J.V.; Lang, T.; Meister, M.; Plonka-Spehr, Ch.; Pokotilovski, Yu.

    2009-01-01

    For the first time, the neutron optical wall-potential of natural cubic boron nitride (cBN) was measured at the ultracold neutron (UCN) source of the research reactor TRIGA Mainz using the time-of-flight method (TOF). The samples investigated had a wall-potential of (305 +/- 15) neV. This value is in good agreement with the result extracted from neutron reflectometry data and theoretical expectations. Because of its high critical velocity for UCN and its good dielectric characteristics, cubic...

  11. Simulation of single-electron state density for one-wall nanotubes from carbon and boron nitride

    International Nuclear Information System (INIS)

    The single-electron density is calculated for all possible geometrical configurations of the one-wall nanotubes from carbon and boron nitride. The calculation is accomplished through the numerical differentiation of the two-dimensional dispersion ratios for the graphite and hexagonal boron nitride by all permitted values of the wave vector. The π-electron approximation was applied. Good agreement of the energy gaps between the symmetrical singularities in the density of the single-electron states and experimental data obtained through the method of the resonance combination light scattering is demonstrated by the example of the concrete carbon nanotubes

  12. Kinetic modelling of PECVD of boron nitride films

    International Nuclear Information System (INIS)

    Using PECVD for BN deposition more than hundred reaction equations must be taken into account and the reaction paths are very complex in a system with the educts B/H/X/N/Ar (X=F,Cl,Br,I). Therefore it takes advantage if modelling of the processes can be performed parallel to experimental investigations. In the paper following reactions are considered: neutral-neutral-, electron-neutral- and ion-neutral-processes in the volume as well as on the surface. Modelling was performed with the Plasma-PSR-module of the software Chemkin-Pro. It allows the introduction of different temperatures for the species in the description of plasma initiated reactions. For comparison of data resulting from our own experiments and from kinetic modelling we started with the simple system B/N/Ar at different plasma conditions. While at equilibrium conditions the influence of plasma can be neglected up to temperatures of 2500 K in kinetic modelling dissociation, ionisation and excitation play an important role. From analysis of results of kinetic modelling, the main process in BN deposition in the system B/N/Ar seems to be the dissociation of nitrogen molecules by electron impact and the reaction of atomic nitrogen with boron on the surface.

  13. Superior thermal conductivity of polymer nanocomposites by using graphene and boron nitride as fillers

    Science.gov (United States)

    Liem, H.; Choy, H. S.

    2013-06-01

    We report a significant enhancement of thermal conductivity in polymer nanocomposites with graphene and boron nitride as fillers. Strong variations in the Raman spectra for different single-layer graphene flakes are related to the measured thermal conductivity in polymer nanocomposites. In the absence of doping, variations in the Raman parameters are most common, suggesting the presence of excess charges in the samples. Graphene has a Raman D-peak that indicates structural disorder is present, causing the large variations in Raman G peaks. Using this type of graphene and boron nitride for preparing the polymer nanocomposites, the thermal conductivities of the polymer nanocomposites are measured to be in the range of 6.2-9.5 W/mK. The absence of Raman D peaks suggests that structural defects are infinitesimal and the graphene is pristine. Polymer nanocomposites filled with graphene without a D-peak exhibit thermal conductivities as high as ˜21.6 W/mK. As a thermal management material, thermal imaging shows that the polymer nanocomposite can effectively lower the surface mounted LED temperature by 21.1 °C. The existence of Raman D peaks can be used to distinguish two different types of graphenes, establishing the primary prerequisite for achieving a higher thermal conductivity.

  14. A Comparative Study of Ab-Initio Thermal Conductivity Approaches: The Case of Cubic Boron Nitride

    Science.gov (United States)

    Mukhopadhyay, Saikat; Lindsay, Lucas; Broido, David; Stewart, Derek

    2013-03-01

    Given its high strength and large thermal conductivity, cubic boron nitride (cBN) provides an important complement to diamond films for heat spreading applications. However, cBN, in contrast to diamond, is a polar material with significant LO-TO splitting in the phonon dispersion. In this talk, we examine the lattice thermal conductivity of cBN using several approaches based on first principles calculations. These approaches include: (1) an analytic modified Callaway-Debye model that relies on parameters from ab-initio harmonic force constants, (2) a fully self-consistent calculation of the thermal conductivity that links an iterative solution of the phonon Boltzmann transport equation (BTE) with harmonic and anharmonic interatomic force constants. The force constants for the BTE are calculated using two approaches: density functional perturbation theory and a real-space supercell approach. We will compare the results from these approaches, highlight the role of normal phonon-phonon scattering, and also examine the impact of optical modes and LO-TO splitting. In addition, we will discuss how isotope scattering affects thermal conductivity and compare this to other boron nitride structures (hexagonal BN, BN sheets and BN nanotubes).

  15. Boron nitride nanotube-mediated stimulation of cell co-culture on micro-engineered hydrogels.

    Directory of Open Access Journals (Sweden)

    Leonardo Ricotti

    Full Text Available In this paper, we describe the effects of the combination of topographical, mechanical, chemical and intracellular electrical stimuli on a co-culture of fibroblasts and skeletal muscle cells. The co-culture was anisotropically grown onto an engineered micro-grooved (10 µm-wide grooves polyacrylamide substrate, showing a precisely tuned Young's modulus (∼ 14 kPa and a small thickness (∼ 12 µm. We enhanced the co-culture properties through intracellular stimulation produced by piezoelectric nanostructures (i.e., boron nitride nanotubes activated by ultrasounds, thus exploiting the ability of boron nitride nanotubes to convert outer mechanical waves (such as ultrasounds in intracellular electrical stimuli, by exploiting the direct piezoelectric effect. We demonstrated that nanotubes were internalized by muscle cells and localized in both early and late endosomes, while they were not internalized by the underneath fibroblast layer. Muscle cell differentiation benefited from the synergic combination of topographical, mechanical, chemical and nanoparticle-based stimuli, showing good myotube development and alignment towards a preferential direction, as well as high expression of genes encoding key proteins for muscle contraction (i.e., actin and myosin. We also clarified the possible role of fibroblasts in this process, highlighting their response to the above mentioned physical stimuli in terms of gene expression and cytokine production. Finally, calcium imaging-based experiments demonstrated a higher functionality of the stimulated co-cultures.

  16. The effect of temperature on the compressive buckling of boron nitride nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Shokuhfar, Ali; Ebrahimi-Nejad, Salman [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, 19991-43344 Tehran (Iran, Islamic Republic of); Hosseini-Sadegh, Amin [Faculty of Petroleum Engineering, Petroleum University of Technology, 14539-53153 Tehran (Iran, Islamic Republic of); Zare-Shahabadi, Abolfazl [Department of Mechanical Engineering, Yazd Branch, Islamic Azad University, Yazd (Iran, Islamic Republic of)

    2012-07-15

    Inspired by the stability at high temperature and the high mechanical strength of boron nitride nanotubes (BNNTs), the effect of temperature on the compressive buckling of BNNTs has been investigated in this paper. Molecular dynamics (MD) simulations of BNNTs subjected to high temperatures (up to 3000 K) were performed and their structures were analyzed by studying their optimized structures at different temperatures through the radial distribution function (RDF). Then, the structural stability and compressive resistance properties of these nanotubes were investigated and the critical buckling loads and critical buckling strains of the nanotubes and their susceptibility to high temperatures were determined. The gradual decrease in the sharpness of the peaks of RDF plots of non-loaded nanotubes implies that at higher temperatures the structure displays greater deviations from that at room temperature. Results of buckling simulations also indicate a general weakening of the nanotubes and lower critical buckling loads and critical buckling strains at increased temperatures. The decrease in the critical buckling load is more significant for the longer nanotube (L {proportional_to} 6 nm) than the shorter one (L {proportional_to} 3 nm). The critical buckling strain experienced a drop of about 35-50% at temperatures higher than 1500 K. A transitional behavior was observed between T = 1000 and 2000 K. Temperature-dependent axial buckling behavior of boron nitride nanotubes. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

    Science.gov (United States)

    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.

  18. Dielectric response of carbon and boron nitride nanotubes from first-principles calculations

    Science.gov (United States)

    Kozinsky, Boris; Marzari, Nicola

    2007-03-01

    We present a complete characterization of the dielectric response of isolated single- and multi-wall carbon (CNT) and boron-nitride nanotubes (BNNT) using first-principles calculations and density-functional theory. The longitudinal polarizability of a nanotube is sensitive to the band gap and its radius, and in multi-wall nanotubes and bundles it is trivially given by the sum of the polarizabilities of the constituent tubes. The transverse polarizability of both types of nanotubes is insensitive to band gap and chirality and depends only on the radius. However, the transverse response and screening properties of BNNTs are qualitatively different from those of metallic and semiconducting CNTs. The fundamental differences in electronic properties of the two materials are inherited from the corresponding two-dimensional sheets - graphene and boron-nitride. The screening of the external field in CNTs is stronger than in BNNTs and has a different radius dependence. The transverse response in BNNTs is found to be that of an insulator, while in CNTs it is intermediate between metallic and semiconducting. Our results have practical implications for selective growth of different types of nanotubes using aligning electric fields and for Raman characterization of nanotubes.

  19. Mechanically activated catalyst mixing for high-yield boron nitride nanotube growth.

    Science.gov (United States)

    Li, Ling; Li, Lu Hua; Chen, Ying; Dai, Xiujuan J; Xing, Tan; Petravic, Mladen; Liu, Xiaowei

    2012-01-01

    Boron nitride nanotubes (BNNTs) have many fascinating properties and a wide range of applications. An improved ball milling method has been developed for high-yield BNNT synthesis, in which metal nitrate, such as Fe(NO3)3, and amorphous boron powder are milled together to prepare a more effective precursor. The heating of the precursor in nitrogen-containing gas produces a high density of BNNTs with controlled structures. The chemical bonding and structure of the synthesized BNNTs are precisely probed by near-edge X-ray absorption fine structure spectroscopy. The higher efficiency of the precursor containing milling-activated catalyst is revealed by thermogravimetric analyses. Detailed X-ray diffraction and X-ray photoelectron spectroscopy investigations disclose that during ball milling the Fe(NO3)3 decomposes to Fe which greatly accelerates the nitriding reaction and therefore increases the yield of BNNTs. This improved synthesis method brings the large-scale production and application of BNNTs one step closer. PMID:22827911

  20. Dislocations in stacking and commensurate-incommensurate phase transition in bilayer graphene and hexagonal boron nitride

    Science.gov (United States)

    Lebedeva, Irina V.; Lebedev, Alexander V.; Popov, Andrey M.; Knizhnik, Andrey A.

    2016-06-01

    Dislocations corresponding to a change of stacking in two-dimensional hexagonal bilayers, graphene and boron nitride, and associated with boundaries between commensurate domains are investigated using the two-chain Frenkel-Kontorova model on top of ab initio calculations. Structural transformations of bilayers in which the bottom layer is stretched and the upper one is left to relax freely are considered for gradually increased elongation of the bottom layer. Formation energies of dislocations, dislocation width, and orientation of the boundary between commensurate domains are analyzed depending on the magnitude and direction of elongation. The second-order phase transition from the commensurate phase to the incommensurate one with multiple dislocations is predicted to take place at some critical elongation. The order parameter for this transition corresponds to the density of dislocations, which grows continuously upon increasing the elongation of the bottom layer above the critical value. In graphene and metastable boron nitride with the layers aligned in the same direction, where elementary dislocations are partial, this transition, however, is preceded by formation of the first dislocation at the elongation smaller than the critical one. The phase diagrams including this intermediate state are plotted in coordinates of the magnitude and direction of elongation of the bottom layer.

  1. Variations in Crystalline Structures and Electrical Properties of Single Crystalline Boron Nitride Nanosheets.

    Science.gov (United States)

    Aldalbahi, Ali; Zhou, Andrew Feng; Feng, Peter

    2015-01-01

    We report the studies of (1) the basic mechanism underlying the formation of defect-free, single crystalline boron nitride nanosheets (BNNSs) synthesized using pulsed laser plasma deposition (PLPD) technique, (2) the variation in the crystalline structure at the edges of the hexagonal boron nitride (h-BN) nanosheets, and (3) the basic electrical properties related to the BNNSs tunneling effect and electrical breakdown voltage. The nanoscale morphologies of BNNSs are characterized using scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The results show that each sample consisted of a number of transparent BNNSs that partially overlapped one another. Varying the deposition duration yielded different thicknesses of sample but did not affect the morphology, structure, and thickness of individual BNNSs pieces. Analysis of the SEM and HRTEM data revealed changes in the spatial period of the B3-N3 hexagonal structures and the interlayer distance at the edge of the BNNSs, which occurred due to the limited number of atomic layers and was confirmed further by x-ray diffraction (XRD) study. The experimental results clearly indicate that the values of the electrical conductivities of the super-thin BNNSs and the effect of temperature relied strongly on the direction of observation. PMID:26563901

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

    Science.gov (United States)

    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. PMID:24245317

  3. Two-dimensional hexagonal boron nitride as lateral heat spreader in electrically insulating packaging

    Science.gov (United States)

    Bao, Jie; Edwards, Michael; Huang, Shirong; Zhang, Yong; Fu, Yifeng; Lu, Xiuzhen; Yuan, Zhichao; Jeppson, Kjell; Liu, Johan

    2016-07-01

    The need for electrically insulating materials with a high in-plane thermal conductivity for lateral heat spreading applications in electronic devices has intensified studies of layered hexagonal boron nitride (h-BN) films. Due to its physicochemical properties, h-BN can be utilised in power dissipating devices such as an electrically insulating heat spreader material for laterally redistributing the heat from hotspots caused by locally excessive heat flux densities. In this study, two types of boron nitride based heat spreader test structures have been assembled and evaluated for heat dissipation. The test structures separately utilised a few-layer h-BN film with and without graphene enhancement drop coated onto the hotspot test structure. The influence of the h-BN heat spreader films on the temperature distribution across the surface of the hotspot test structure was studied at a range of heat flux densities through the hotspot. It was found that the graphene-enhanced h-BN film reduced the hotspot temperature by about 8–10 °C at a 1000 W cm‑2 heat flux density, a temperature decrease significantly larger than for h-BN film without graphene enhancement. Finite element simulations of the h-BN film predict that further improvements in heat spreading ability are possible if the thermal contact resistance between the film and test chip are minimised.

  4. Catalytic growth of vertically aligned neutron sensitive 10Boron nitride nanotubes

    International Nuclear Information System (INIS)

    10Boron nitride nanotubes (10BNNTs) are a potential neutron sensing element in a solid-state neutron detector. The aligned 10BNNT can be used for its potential application without any further purification. Argon-supported thermal CVD is used to achieve vertically aligned 10BNNT with the help of nucleation sites produced in a thin layer of magnesium–iron alloy deposited at the top of Si substrate. FESEM shows vertically aligned 10BNNTs with ball-like catalytic tips at top. EDX reveals magnesium (Mg) contents in the tips that refer to catalytic growth of 10BNNT. HR-TEM shows tubular morphology of the synthesized 10BNNT with lattice fringes on its outer part having an interlayer spacing of ∼0.34 nm. XPS shows B 1 s and N 1 s peaks at 190.5 and 398 eV that correspond to hexagonal 10Boron nitride (10h-BN) nature of the synthesized 10BNNT, whereas the Mg kll auger peaks at ∼301 and ∼311 eV represents Mg contents in the sample. Raman spectrum has a peak at 1390 (cm−1) that corresponds to E2g mode of vibration in 10h-BN

  5. Flexible band gap tuning of hexagonal boron nitride sheets interconnected by acetylenic bonds.

    Science.gov (United States)

    Zhang, Hongyu; Luo, Youhua; Feng, Xiaojuan; Zhao, Lixia; Zhang, Meng

    2015-08-21

    The energetic and electronic properties of acetylenic-bond-interconnected hexagonal boron nitride sheets (BNyne), in which the number of rows of BN hexagonal rings (denoted as BN width) between neighboring arrays of acetylenic linkages increases consecutively, have been explored using first-principles calculations. Depending on the spatial position of B/N atoms with respect to the acetylenic linkages, there are two different types of configurations. The band structure features and band gap evolutions of BNyne structures as a function of the BN width can be categorized into two families, corresponding to two distinct types of configurations. In particular, for both types of BNyne structures, the band gap variations exhibit odd-even oscillating behavior depending on the BN width, which is related to the different symmetries of acetylenic chains in the unit cell. These results suggest that the embedded linear acetylenic chains can provide more flexibility for manipulation of the atomic and electronic properties of hexagonal boron nitride. These sp-sp(2) hybrid structures might promise importantly potential applications for developing nanoscale electronic and optoelectronic devices. PMID:26194068

  6. Catalytic growth of vertically aligned neutron sensitive {sup 10}Boron nitride nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Pervaiz, E-mail: pervaizahmad@siswa.um.edu.my, E-mail: Pervaiz-pas@yahoo.com; Khandaker, Mayeen Uddin, E-mail: mu-khandaker@yahoo.com, E-mail: mu-khandaker@um.edu.my; Amin, Yusoff Mohd [University of Malaya, Department of Physics, Faculty of Science (Malaysia); Khan, Ghulamullah [University of Malaya, Department of Mechanical Engineering (Malaysia); Ramay, Shahid M. [King Saud University, Department of Physics and Astronomy, College of Science (Saudi Arabia); Mahmood, Asif [King Saud University, Department of Chemical Engineering, College of Engineering (Saudi Arabia); Amin, Muhammad [University of the Punjab, Department of Physics (Pakistan); Muhammad, Nawshad [Interdisciplinary Research Centre in Biomedical Materials (IRCBM) COMSATS Institute of Information Technology (Pakistan)

    2016-01-15

    {sup 10}Boron nitride nanotubes ({sup 10}BNNTs) are a potential neutron sensing element in a solid-state neutron detector. The aligned {sup 10}BNNT can be used for its potential application without any further purification. Argon-supported thermal CVD is used to achieve vertically aligned {sup 10}BNNT with the help of nucleation sites produced in a thin layer of magnesium–iron alloy deposited at the top of Si substrate. FESEM shows vertically aligned {sup 10}BNNTs with ball-like catalytic tips at top. EDX reveals magnesium (Mg) contents in the tips that refer to catalytic growth of {sup 10}BNNT. HR-TEM shows tubular morphology of the synthesized {sup 10}BNNT with lattice fringes on its outer part having an interlayer spacing of ∼0.34 nm. XPS shows B 1 s and N 1 s peaks at 190.5 and 398 eV that correspond to hexagonal {sup 10}Boron nitride ({sup 10}h-BN) nature of the synthesized {sup 10}BNNT, whereas the Mg kll auger peaks at ∼301 and ∼311 eV represents Mg contents in the sample. Raman spectrum has a peak at 1390 (cm{sup −1}) that corresponds to E{sub 2g} mode of vibration in {sup 10}h-BN.

  7. boron nitride coating of uranium dioxide and uranium dioxide-gadolinium oxide fuels by chemical precipitation method

    International Nuclear Information System (INIS)

    In this research pure urania and urania-gadolinia (5 and 10 %) fuels were coated with boron nitride (BN). This is achieved through chemical vapor deposition (CVD) using boron tricloride BCl3) and ammonia (NH3) at 600 C.Boron tricloride and ammonia are carried to tubular furnace using hydrogen as carrier gas. The coated samples were sintered at 1600 K. The properties of the coated samples were observed using BET surface area analysis, infrared spectra (IR), X-Ray Diffraction and Scanning Electron Microscope (SEM) techniques

  8. Encapsulation of cisplatin as an anti-cancer drug into boron-nitride and carbon nanotubes: Molecular simulation and free energy calculation.

    Science.gov (United States)

    Roosta, Sara; Hashemianzadeh, Seyed Majid; Ketabi, Sepideh

    2016-10-01

    Encapsulation of cisplatin anticancer drug into the single walled (10, 0) carbon nanotube and (10, 0) boron-nitride nanotube was investigated by quantum mechanical calculations and Monte Carlo Simulation in aqueous solution. Solvation free energies and complexation free energies of the cisplatin@ carbon nanotube and cisplatin@ boron-nitride nanotube complexes was determined as well as radial distribution functions of entitled compounds. Solvation free energies of cisplatin@ carbon nanotube and cisplatin@ boron-nitride nanotube were -4.128kcalmol(-1) and -2457.124kcalmol(-1) respectively. The results showed that cisplatin@ boron-nitride nanotube was more soluble species in water. In addition electrostatic contribution of the interaction of boron- nitride nanotube complex and solvent was -281.937kcalmol(-1) which really more than Van der Waals and so the electrostatic interactions play a distinctive role in the solvation free energies of boron- nitride nanotube compounds. On the other hand electrostatic part of the interaction of carbon nanotube complex and solvent were almost the same as Van der Waals contribution. Complexation free energies were also computed to study the stability of related structures and the free energies were negative (-374.082 and -245.766kcalmol(-1)) which confirmed encapsulation of drug into abovementioned nanotubes. However, boron-nitride nanotubes were more appropriate for encapsulation due to their larger solubility in aqueous solution. PMID:27287103

  9. Nonlocal piezoelastic surface effect on the vibration of visco-Pasternak coupled boron nitride nanotube system under a moving nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Ghorbanpour Arani, A., E-mail: aghorban@kashanu.ac.ir [Faculty of Mechanical Engineering, University of Kashan, Kashan (Iran, Islamic Republic of); Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan (Iran, Islamic Republic of); Roudbari, M.A. [Faculty of Mechanical Engineering, University of Kashan, Kashan (Iran, Islamic Republic of)

    2013-09-02

    In this article, the nonlocal longitudinal and transverse vibrations of coupled boron nitride nanotube (BNNT) system under a moving nanoparticle using piezoelastic theory and surface stress based on Euler–Bernoulli beam are developed. BNNTs are coupled by visco-Pasternak medium and single-walled zigzag structure BNNT is selected in this study. Hamilton's principle is employed to derive the corresponding higher order equations of motion for both nanotubes. The detailed parametric study is conducted, focusing on the remarkable effects of the small scale parameter, aspect ratio, surface stress and visco-Pasternak coefficients on the vibration behavior of the coupled BNNT system. Also it is demonstrated that the normalized dynamic deflections obtained by using the classical beam theory are smaller than those obtained by the nonlocal beam theory. The influence of the smart controller is proved on the nondimensional fundamental longitudinal frequency. The result of this study can be useful to manufacture of smart microelectromechanical system and nanoelectromechanical system in advanced biomechanics applications with electric field as a parametric controller. - Highlights: • Vibration of coupled boron nitride nanotube system is studied. • Boron nitride nanotubes are coupled by a visco-Pasternak medium. • Single-walled zigzag boron nitride nanotube structure is considered. • The applied electric potential effect on the longitudinal vibration is studied. • The results may be useful to design of micro/nanoelectromechanical systems.

  10. Nonlocal piezoelastic surface effect on the vibration of visco-Pasternak coupled boron nitride nanotube system under a moving nanoparticle

    International Nuclear Information System (INIS)

    In this article, the nonlocal longitudinal and transverse vibrations of coupled boron nitride nanotube (BNNT) system under a moving nanoparticle using piezoelastic theory and surface stress based on Euler–Bernoulli beam are developed. BNNTs are coupled by visco-Pasternak medium and single-walled zigzag structure BNNT is selected in this study. Hamilton's principle is employed to derive the corresponding higher order equations of motion for both nanotubes. The detailed parametric study is conducted, focusing on the remarkable effects of the small scale parameter, aspect ratio, surface stress and visco-Pasternak coefficients on the vibration behavior of the coupled BNNT system. Also it is demonstrated that the normalized dynamic deflections obtained by using the classical beam theory are smaller than those obtained by the nonlocal beam theory. The influence of the smart controller is proved on the nondimensional fundamental longitudinal frequency. The result of this study can be useful to manufacture of smart microelectromechanical system and nanoelectromechanical system in advanced biomechanics applications with electric field as a parametric controller. - Highlights: • Vibration of coupled boron nitride nanotube system is studied. • Boron nitride nanotubes are coupled by a visco-Pasternak medium. • Single-walled zigzag boron nitride nanotube structure is considered. • The applied electric potential effect on the longitudinal vibration is studied. • The results may be useful to design of micro/nanoelectromechanical systems

  11. Increased charge storage capacity of titanium nitride electrodes by deposition of boron-doped nanocrystalline diamond films

    DEFF Research Database (Denmark)

    Meijs, Suzan; McDonald, Matthew; Sørensen, Søren; Rechendorff, Kristian; Petrak, Vaclav; Nesladek, Milos; Rijkhoff, Nico; Pennisi, Cristian P.

    The aim of this study was to investigate the feasibility of depositing a thin layer of boron-doped nanocrystalline diamond (B-NCD) on titanium nitride (TiN) coated electrodes and the effect this has on charge injection properties. The charge storage capacity increased by applying the B-NCD film, ...

  12. Phase formation and microstructure of boron nitride thin layers deposited using Nd:YAG and KrF

    Czech Academy of Sciences Publication Activity Database

    Mroz, W.; Kosydar, R.; Jelínek, Miroslav; Kocourek, Tomáš; Major, B.

    2006-01-01

    Roč. 200, - (2006), s. 6438-6443. ISSN 0257-8972 Grant ostatní: Polish Ministry of Science and Informatization(PL) PBZ-KBN-100/T08/2003 Institutional research plan: CEZ:AV0Z10100522 Keywords : boron nitride * pulsed laser deposition * coating Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.559, year: 2006

  13. First principle study of structural, electronic and magnetic properties of zigzag boron nitride nanoribbon: Role of vacancies

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Arun [Department of Physics, Govt. College Banjar, Kullu, Himanchal Pradesh, 175123 India (India); Bahadur, Amar, E-mail: abr.phys@gmail.com [Department of Physics, Kamla Nehru Institute of Physical and Social Sciences, Sultanpur, Uttar Pradesh, 228118 India (India); Mishra, Madhukar [Department of Physics, Birla Institute of Technology and Science, Pilani, Rajasthan, 333031 India (India); Vasudeva, Neena [Department of Physics, S. V. G. College, Ghumarwin, Bilaspur, Himanchal Pradesh, 1714021 India (India)

    2015-05-15

    We study the effect of vacancies on the structural, electronic and magnetic properties of zigzag boron nitride nanoribbon (ZBNNR) by using first principle calculations. We find that the shift of the vacancies with respect to the ribbon edges causes change in the structural geometry, electronic structure and magnetization of ZBNNR. These vacancies also produce band gap modulation and consequently results the magnetization of ZBNNR.

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

    Science.gov (United States)

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

    2016-01-01

    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. PMID:26502800

  15. Synthesis of few-layer, large area hexagonal-boron nitride by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Glavin, Nicholas R. [Nanoelectronic Materials Branch, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH 45433 (United States); School of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 (United States); Jespersen, Michael L. [Nanoelectronic Materials Branch, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH 45433 (United States); University of Dayton Research Institute, 300 College Park, Dayton, OH 45469 (United States); Check, Michael H. [Nanoelectronic Materials Branch, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH 45433 (United States); Hu, Jianjun [Nanoelectronic Materials Branch, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH 45433 (United States); University of Dayton Research Institute, 300 College Park, Dayton, OH 45469 (United States); Hilton, Al M. [Nanoelectronic Materials Branch, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH 45433 (United States); Wyle Laboratories, Dayton, OH 45433 (United States); Fisher, Timothy S. [School of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 (United States); Voevodin, Andrey A. [Nanoelectronic Materials Branch, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH 45433 (United States)

    2014-12-01

    Pulsed laser deposition (PLD) has been investigated as a technique for synthesis of ultra-thin, few-layer hexagonal boron nitride (h-BN) thin films on crystalline highly ordered pyrolytic graphite (HOPG) and sapphire (0001) substrates. The plasma-based processing technique allows for increased excitations of deposited atoms due to background nitrogen gas collisional ionizations and extended resonance time of the energetic species presence at the condensation surface. These processes permit growth of thin, polycrystalline h-BN at 700 °C, a much lower temperature than that required by traditional growth methods. Analysis of the as-deposited films reveals epitaxial-like growth on the nearly lattice matched HOPG substrate, resulting in a polycrystalline h-BN film, and amorphous BN (a-BN) on the sapphire substrates, both with thicknesses of 1.5–2 nm. Stoichiometric films with boron-to-nitrogen ratios of unity were achieved by adjusting the background pressure within the deposition chamber and distance between the target and substrate. The reduction in deposition temperature and formation of stoichiometric, large-area h-BN films by PLD provide a process that is easily scaled-up for two-dimensional dielectric material synthesis and also present a possibility to produce very thin and uniform a-BN. - Highlights: • PLD was used to synthesize boron nitride thin films on HOPG and sapphire substrates. • Lattice matched substrate allowed for formation of polycrystalline h-BN. • Nitrogen gas pressure directly controlled film chemistry and structure. • Technique allows for ultrathin, uniform films at reduced processing temperatures.

  16. EPR observation of first point defects in cubic boron nitride crystalline powders

    Science.gov (United States)

    Nistor, S. V.; Stefan, M.; Schoemaker, D.; Dinca, G.

    2000-05-01

    An X-band electron paramagnetic resonance (EPR) study of nominally pure, diamond-like cubic boron nitride (c-BN) crystalline powders, has led to the first identification of a spectrum attributed to two related paramagnetic species. The composite EPR spectrum can be observed only in dark brown colored powders known to contain excess of boron. It consists of two superimposed lorentzian components, called D1 and D2, centered at g1=2.0063 and g2=2.0084, with peak-to-peak linewidths of 3.3 and 17.9 mT, respectively. The temperature dependence of the integrated intensities, their linewidths and intensity ratio D2/D1 allows one to conclude that the narrow line D1 originates from EPR transitions inside a S=1/2 ground doublet and the broad line D2 from transitions inside the excited levels of another center. Evidence suggests that both centers are boron related paramagnetic species.

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

    Science.gov (United States)

    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.

  18. Photoluminescence of hexagonal boron nitride: effect of surface oxidation under UV-laser irradiation

    CERN Document Server

    Museur, Luc; Petitet, Jean-Pierre; Michel, Jean Pierre; Kanaev, Andrei V

    2008-01-01

    We report on the UV laser induced fluorescence of hexagonal boron nitride (h-BN) following nanosecond laser irradiation of the surface under vacuum and in different environments of nitrogen gas and ambient air. The observed fluorescence bands are tentatively ascribed to impurity and mono (VN), or multiple (m-VN with m = 2 or 3) nitrogen vacancies. A structured fluorescence band between 300 nm and 350 nm is assigned to impurity-band transition and its complex lineshape is attributed to phonon replicas. An additional band at 340 nm, assigned to VN vacancies on surface, is observed under vacuum and quenched by adsorbed molecular oxygen. UV-irradiation of h-BN under vacuum results in a broad asymmetric fluorescence at ~400 nm assigned to m-VN vacancies; further irradiation breaks more B-N bonds enriching the surface with elemental boron. However, no boron deposit appears under irradiation of samples in ambient atmosphere. This effect is explained by oxygen healing of radiation-induced surface defects. Formation o...

  19. 机械法合成BN纳米管%Mechanosynthesis of Boron Nitride Nanotubes

    Institute of Scientific and Technical Information of China (English)

    籍凤秋; 曹传宝; 徐红; 杨子光

    2006-01-01

    Boron nitride nanotubes (BN-NTs) with pure hexagonal BN phase have been synthesized by heating ball-milled boron powders in flowing ammonia gas at a temperature of 1200℃. The as-synthesized products were characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron energy loss spectroscopy (EELS). The diameters of nanotubes are in the rage of 40120nm and the lengths are more than 10μm. EELS result identifies that the ratio of boron and nitrogen is almost 1:1. The growth temperature is a crucial growth parameter in controlling the structure and crystalline of BN-NTs. The nanotubes grown at 1100℃ possesses of a bamboo-like structure, while as the temperature increased to 1200℃, most of the nanotubes exhibited a cylindrical structure. In addition, changing the heating time can control the size of the nanotubes. The gas atmosphere has influence on the yield of BN-NTs during heating process. When heating atmosphere was replaced by nitrogen, the yield of nanotubes was remarkably decreased.

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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

  2. Application of nitriding to electroless nickel–boron coatings: Chemical and structural effects; mechanical characterization; corrosion resistance

    International Nuclear Information System (INIS)

    Highlights: ► Nitriding of electroless nickel–boron coatings is possible and improves properties. ► Nitrided electroless nickel–boron coatings are harder than heat treated coatings. ► Nitrided electroless nickel–boron coatings have a good scratch test resistance. ► Nitrided Ni–B coatings have a better corrosion resistance than untreated coatings. -- Abstract: Electroless nickel–boron coatings, synthesized on mild steel, were submitted to nitridation treatments in varying conditions of pressure, temperature and atmosphere composition. One treatment was carried out under a reduced pressure of a nitrogen-based gas, the other under ambient pressure in a ammonia-based atmosphere. The modifications of the samples’ chemistry after those treatments were investigated by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy), GD-OES (Glow Discharge-Optical Emission Spectroscopy) and ToF-SIMS (Time of flight-Secondary Ions Mass Spectroscopy) analysis. Their structures and morphology were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy. The mechanical properties of the samples were investigated by micro- and nanohardness measurements successively on the free surface of the sample and on polished cross-sections; their roughness and resistance to scratch test were measured. Electrochemical corrosion tests were also carried out. The effects of both treatments were then compared: after the treatment carried out under lowered pressure, the coatings are dense, present signs of solution hardening and are characterized by a high hardness (close to 1600 hv100). A combination layer is observable on the samples treated under an ammonia-based atmosphere. This outer layer possesses poorer mechanical properties but the inner layer of the coating presents properties similar to those of vacuum nitrided coatings. The corrosion resistance of the coatings is as good as that of heat treated coatings.

  3. Enhancing Thermal Conductivity of Hexagonal Boron Nitride Filled Thermoplastics for Thermal Interface Management

    Science.gov (United States)

    Prindl, John

    Hexagonal Boron Nitride has been shown to enhance thermal conductivity in polymer composites more so than conventional ceramic fillers. However, to see a significant increase in thermal conductivity a high loading level of the advanced ceramic is often needed which can have an adverse effect on the mechanical behavior of the composite part. Applications for thermal management using thermal interface materials (TIM) continue to grow with thermoplastic injection molded parts emerging as an area for market growth. There is a growing need for published technical data in this particular area of application. In the current study, the thermal conductivity and mechanical behavior of hexagonal Boron Nitride (hBN) loaded thermoplastic composites is investigated. The main objectives of this work is produce a novel data package which illustrates the effects of hBN, loaded at high concentrations, across several different thermoplastic resins with the ultimate goal being to find a desirable formulation for specific thermal management applications. The desired properties for such applications being high thermal conductivity and high electrical resistivity with a minimal decrease in mechanical properties. Hexagonal BN cooling filler agglomerates were compounded into polypropylene (PP), nylon-6 (PA-6), and thermoplastic elastomer (TPE) via twin-screw extruder at 3 different loading levels. Injection molded samples were produced and characterized to show varying degrees of thermal conductivity and mechanical strength. Results from this research showed that in all cases, the thermal conductivity increased with increasing levels of hBN addition. The largest increases in thermal conductivity were seen in the PA-6 and TPE systems with the possible indication of exceeding the percolation threshold in the TPE system. This is hypothesized to occur due to the preferential migration of hBN to form conduction pathways around the elastomeric domains in the TPE matrix. Though TPE produced

  4. Effects of domains in phonon conduction through hybrid boron nitride and graphene sheets

    Science.gov (United States)

    Sevinçli, H.; Li, W.; Mingo, N.; Cuniberti, G.; Roche, S.

    2011-11-01

    We theoretically investigate the phonon propagation and thermal conductivity κ in hybrid boron nitride and graphene sheets. By using a real-space Kubo-computational transport scheme, large and disordered graphene structures are simulated, introducing disk-shaped domains with varying sizes of 2 to 8 nm and concentrations ranging from 0% to 100%. A strong influence of the domain size and concentration on the transport properties is obtained. The mean free paths are minimized at 50% domain concentration, and stronger suppression of κ is achieved with smaller domains. It is found to decrease by up to 65% at room temperature when the domain size is 2 nm. These results are beyond the scope of any effective medium approximation.

  5. Thermal Conductivity and Phonon Transport in Suspended Few-Layer Hexagonal Boron Nitride

    Science.gov (United States)

    Jo, Insun; Pettes, Michael Thompson; Kim, Jaehyun; Watanabe, Kenji; Taniguchi, Takashi; Yao, Zhen; Shi, Li

    2013-02-01

    The thermal conductivity of suspended few-layer hexagonal boron nitride (h-BN) was measured using a micro-bridge device with built-in resistance thermometers. Based on the measured thermal resistance values of 11-12 atomic layer h-BN samples with suspended length ranging between 3 and 7.5 um, the room-temperature thermal conductivity of a 11-layer sample was found to be about 360 Wm-1K-1, approaching the basal plane value reported for bulk h-BN. The presence of a polymer residue layer on the sample surface was found to decrease the thermal conductivity of a 5-layer h-BN sample to be about 250 Wm-1K-1 at 300 K. Thermal conductivities for both the 5 layer and the 11 layer samples are suppressed at low temperatures, suggesting increasing scattering of low frequency phonons in thin h-BN samples by polymer residue.

  6. The interaction between hexagonal boron nitride and water from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yanbin; Aluru, Narayana R., E-mail: aluru@illinois.edu [Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Wagner, Lucas K. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080 (United States)

    2015-06-21

    The use of hexagonal boron nitride (h-BN) in microfluidic and nanofluidic applications requires a fundamental understanding of the interaction between water and the h-BN surface. A crucial component of the interaction is the binding energy, which is sensitive to the treatment of electron correlation. In this work, we use state of the art quantum Monte Carlo and quantum chemistry techniques to compute the binding energy. Compared to high-level many-body theory, we found that the second-order Møller-Plesset perturbation theory captures the interaction accurately and can thus be used to develop force field parameters between h-BN and water for use in atomic scale simulations. On the contrary, density functional theory with standard dispersion corrections tends to overestimate the binding energy by approximately 75%.

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

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ram Sevak, E-mail: singh915@gmail.com [Department of Physics, National Institute of TechnologyKurukshetra 136119 (Haryana) (India)

    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 have 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.

  8. Utilizing boron nitride sheets as thin supports for high resolution imaging of nanocrystals

    International Nuclear Information System (INIS)

    We demonstrate the use of thin BN sheets as supports for imaging nanocrystals using low voltage (80 kV) aberration-corrected high resolution transmission electron microscopy. This provides an alternative to the previously utilized 2D crystal supports of graphene and graphene oxide. A simple chemical exfoliation method is applied to get few layer boron nitride (BN) sheets with micrometer-sized dimensions. This generic approach of using BN sheets as supports is shown by depositing Mn doped ZnSe nanocrystals directly onto the BN sheets and resolving the atomic structure from both the ZnSe nanocrystals and the BN support. Phase contrast images reveal moire patterns of interference between the beams diffracted by the nanocrystals and the BN substrate that are used to determine the relative orientation of the nanocrystals with respect to the BN sheets and interference lattice planes. Double diffraction is observed and has been analyzed.

  9. Mass spectroscopic analysis of a plume induced by laser ablation of pyrolytic boron nitride

    CERN Document Server

    Chae, H B; Lee, I H; Park, S M

    1998-01-01

    The laser ablation of a pyrolytic boron nitride (pBN) target was investigated by time-of- flight quadrupole mass spectroscopy. According to the laser-correlated ion mass spectra, B sup + and B sub 2 sup + ions were produced, but neither N sup + , N sub 2 sup + , or BN sup + ions were observed at laser fluences below 1 J/cm sup 2. Instead, neutral N sub 2 molecules were found to be formed. The mean velocities and kinetic energies of the B sup + ions were obtained by time-of-flight analysis. Also, reactive laser ablation under a N sub 2 atmosphere was attempted by using a pulsed valve synchronized with the laser pulse.

  10. Emission and propagation of hyperbolic phonon polaritons in hexagonal boron nitride

    Science.gov (United States)

    Dai, Siyuan; Ma, Qiong; Yang, Yafang; Rosenfeld, Jeremy; Goldflam, Michael; McLeod, Alex; Andersen, Trond; Fei, Zhe; Liu, Mengkun; Sun, Zhiyuan; Shao, Yinming; Watanabe, Kenji; Taniguchi, Takashi; Thiemens, Mark; Keilmann, Fritz; Jarillo-Herrero, Pablo; Fogler, Michael; Basov, D. N.

    Using scattering-type scanning near-field optical microscope (s-SNOM), we studied various kinds of emission and propagation of hyperbolic phonon polaritons (HP2s) in hexagonal boron nitride (hBN). The systematic study via real-space nano-imaging reveals the emission mechanisms and propagating properties of HP2s excited by crystal edges, artificial structures, surface defects and impurities. Compared with traditional s-SNOM tip emitter, the polaritons from new emitters reported in this work possess longer propagation length and can be artificially manipulated on the hBN surface. Our work may benefit the future applications and engineering of HP2s using convenient emitters which are analogous to collective modes in other materials.

  11. Imaging of Anomalous Internal Reflections of Hyperbolic Phonon-Polaritons in Hexagonal Boron Nitride

    Science.gov (United States)

    Giles, Alexander J.; Dai, Siyuan; Glembocki, Orest J.; Kretinin, Andrey V.; Sun, Zhiyuan; Ellis, Chase T.; Tischler, Joseph G.; Taniguchi, Takashi; Watanabe, Kenji; Fogler, Michael M.; Novoselov, Kostya S.; Basov, Dimitri. N.; Caldwell, Joshua D.

    2016-06-01

    We use scanning near-field optical microscopy to study the response of hexagonal boron nitride nanocones at infrared frequencies, where this material behaves as a hyperbolic medium. The obtained images are dominated by a series of hot rings that occur on the sloped sidewalls of the nanocones. The ring positions depend on the incident laser frequency and the nanocone shape. Both dependences are consistent with directional propagation of hyperbolic phonon polariton rays that are launched at the edges and zigzag through the interior of the nanocones, sustaining multiple internal reflections off the sidewalls. Additionally, we observe a strong overall enhancement of the near-field signal at discrete resonance frequencies. These resonances attest to low dielectric losses that permit coherent standing waves of the sub-diffractional polaritons to form. We comment on potential applications of such shape-dependent resonances and the field concentration at the hot rings.

  12. Spintronics with graphene-hexagonal boron nitride van der Waals heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kamalakar, M. Venkata, E-mail: venkata.mutta@chalmers.se; Dankert, André; Bergsten, Johan; Ive, Tommy; Dash, Saroj P., E-mail: saroj.dash@chalmers.se [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg (Sweden)

    2014-11-24

    Hexagonal boron nitride (h-BN) is a large bandgap insulating isomorph of graphene, ideal for atomically thin tunnel barrier applications. In this letter, we demonstrate large area chemical vapor deposited (CVD) h-BN as a promising spin tunnel barrier in graphene spin transport devices. In such structures, the ferromagnetic tunnel contacts with h-BN barrier are found to show robust tunneling characteristics over a large scale with resistances in the favorable range for efficient spin injection into graphene. The non-local spin transport and precession experiments reveal spin lifetime ≈500 ps and spin diffusion length ≈1.6 μm in graphene with tunnel spin polarization ≈11% at 100 K. The electrical and spin transport measurements at different injection bias current and gate voltages confirm tunnel spin injection through h-BN barrier. These results open up possibilities for implementation of large area CVD h-BN in spintronic technologies.

  13. Boron nitride nanosheets decorated with silver nanoparticles through mussel-inspired chemistry of dopamine

    International Nuclear Information System (INIS)

    Boron nitride nanosheet (BNNS) decorated with silver nanoparticles (AgNPs) was successfully synthesized via mussel-inspired chemistry of dopamine. Poly(dopamine)-functionalized BNNS (PDA-BNNS) was prepared by adding dopamine into the aqueous dispersion of hydroxylated BNNS (OH-BNNS) at alkaline condition. AgNPs were decorated on PDA-BNNS through spontaneous reduction of silver cations by catechol moieties of a PDA layer on BNNS, resulting in AgNP-BNNS with good dispersion stability. Incorporation of PDA on BNNS not only played a role as a surface functionalization method of BNNS, but also provided a molecular platform for creating very sophisticated two-dimensional (2D) BNNS-based hybrid nanomaterials such as metal nanoparticle-decorated BNNS. (paper)

  14. The thermal conductivity in hybridised graphene and boron nitride nanoribbons modulated with strain

    Science.gov (United States)

    Chen, Xue-Kun; Xie, Zhong-Xiang; Zhou, Wu-Xing; Chen, Ke-Qiu

    2016-03-01

    Thermal transport properties in hybridised graphene and boron nitride ribbons (HGBNRs) under different strains are studied by using reverse nonequilibrium molecular dynamics simulations. It is found that the effect of strains on the thermal conductivity is different for different types of strains. When the tensile and shear strains are applied, the thermal conductivity can be modulated at least up to 50% at room temperature as the strain ε ranges from 0 to 0.2. However, when the compressive and flexural strains are respectively applied, the thermal conductivity is insensitive to the variation of the strain. In addition, it is also found that the thermal conductivity of HGBNRs depends sensitively on the dimension of the hybridised ribbon and the relative amount of h-BN to graphene. A brief analysis of these results is given.

  15. Electro-Orientation of Boron-Nitride Nanotubes in Aqueous Solution

    Science.gov (United States)

    Cetindag, Semih; Kim, Sangil; Tiwari, Bishnu; Bhandari, Shiva; Zhang, Dongyan; Yap, Yoke Khin; Shan, Jerry

    2015-11-01

    Boron-nitride nanotubes (BNNTs), which have similar structure to carbon nanotubes but very different electronic properties, are of interest for a variety of applications, including hydrogen storage, water desalination, mechanical reinforcement and improving the thermal conductivity of composites. Many potential applications would benefit from alignment of BNNTs. We demonstrate, for the first time, the ability to align BNNTs, which are insulating at room temperature, with spatially uniform AC fields in aqueous solution. Electro-orientation rates are experimentally found to decline as the frequency of the AC field is increased. The behavior of the cross-over frequency with varying solution conductivity is suggestive of induced-charge-electro-osmotic (ICEO) alignment, despite the extremely low electrical conductivity of BNNTs. We further discuss electro-orientation with DNA-wrapped BNNTs and compare with pristine nanotubes.

  16. Thermal transport across few-layer boron nitride encased by silica

    Science.gov (United States)

    Ni, Yuxiang; Jiang, Jiechao; Meletis, Efstathios; Dumitric, Traian

    2015-07-01

    Two dimensional hexagonal boron nitride (h-BN) attracted attention for use in applications. Using equilibrium molecular dynamics, we examine the phonon transport in few-layer h-BN encased by silica (SiO2). We report large interfacial thermal resistances, of about 2.2 × 10-8 m2 K W-1, which are not sensitive to the number of h-BN layers or the SiO2 crystallinity. The h-BN/SiO2 superlattices exhibit ultra-low thermal conductivities across layers, as low as 0.3 W/m K. They are structurally stable up to 2000 K while retaining the low-thermal conductivity attributes. Our simulations indicate that incorporation of h-BN layers and nanoparticles in silica could establish thermal barriers and heat spreading paths, useful for high performance coatings and electronic device applications.

  17. Synthesis and Characterization of Hexagonal Boron Nitride as a Gate Dielectric

    Science.gov (United States)

    Jang, Sung Kyu; Youn, Jiyoun; Song, Young Jae; Lee, Sungjoo

    2016-07-01

    Two different growth modes of large-area hexagonal boron nitride (h-BN) film, a conventional chemical vapor deposition (CVD) growth mode and a high-pressure CVD growth mode, were compared as a function of the precursor partial pressure. Conventional self-limited CVD growth was obtained below a critical partial pressure of the borazine precursor, whereas a thick h-BN layer (thicker than a critical thickness of 10 nm) was grown beyond a critical partial pressure. An interesting coincidence of a critical thickness of 10 nm was identified in both the CVD growth behavior and in the breakdown electric field strength and leakage current mechanism, indicating that the electrical properties of the CVD h-BN film depended significantly on the film growth mode and the resultant film quality.

  18. Enhancement of thermoelectric efficiency by embedding hexagonal boron-nitride cells in zigzag graphene nanoribbons

    International Nuclear Information System (INIS)

    We study thermoelectric properties of zigzag graphene nanoribbon (ZGNR)–boron nitride (BN) junctions coupled to square electrodes using nonequilibrium Green function formalism in the linear response regime. The embedding of hexagonal BN cells into the ZGNR results in the change of the thermoelectric properties with the length and position of BN cells. The influence of the width variation on the electrical conductance and the Seebeck coefficient of the ZGNR–BN junctions is examined. Also, the coupling of asymmetric electrodes to the ZGNR–BN junctions and the pristine ZGNR is considered. It is observed that the asymmetric electrodes lead to the increase of the Seebeck coefficients of both structures, while the phonon thermal conductance is decreased because of the reduction of the phonon transport in inhomogeneous structures. Our results predict that the thermoelectric efficiency of the system is increased by embedding the hexagonal BN cells, as well as coupling to the asymmetric electrodes. (paper)

  19. Enhancement of thermoelectric efficiency by embedding hexagonal boron-nitride cells in zigzag graphene nanoribbons

    Science.gov (United States)

    Izadi Vishkayi, Sahar; Bagheri Tagani, Meysam; Rahimpour Soleimani, Hamid

    2015-06-01

    We study thermoelectric properties of zigzag graphene nanoribbon (ZGNR)-boron nitride (BN) junctions coupled to square electrodes using nonequilibrium Green function formalism in the linear response regime. The embedding of hexagonal BN cells into the ZGNR results in the change of the thermoelectric properties with the length and position of BN cells. The influence of the width variation on the electrical conductance and the Seebeck coefficient of the ZGNR-BN junctions is examined. Also, the coupling of asymmetric electrodes to the ZGNR-BN junctions and the pristine ZGNR is considered. It is observed that the asymmetric electrodes lead to the increase of the Seebeck coefficients of both structures, while the phonon thermal conductance is decreased because of the reduction of the phonon transport in inhomogeneous structures. Our results predict that the thermoelectric efficiency of the system is increased by embedding the hexagonal BN cells, as well as coupling to the asymmetric electrodes.

  20. Molecular dynamics simulation of nano-indentation of (111) cubic boron nitride with optimized Tersoff potential

    Science.gov (United States)

    Zhao, Yinbo; Peng, Xianghe; Fu, Tao; Huang, Cheng; Feng, Chao; Yin, Deqiang; Wang, Zhongchang

    2016-09-01

    We conduct molecular dynamics simulation of nanoindentation on (111) surface of cubic boron nitride and find that shuffle-set dislocations slip along direction on {111} plane at the initial stage of the indentation. The shuffle-set dislocations are then found to meet together, forming surfaces of a tetrahedron. We also find that the surfaces are stacking-fault zones, which intersect with each other, forming edges of stair-rod dislocations along direction. Moreover, we also calculate the generalized stacking fault (GSF) energies along various gliding directions on several planes and find that the GSF energies of the {111} and {111} systems are relatively smaller, indicating that dislocations slip more easily along and directions on the {111} plane.

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

    International Nuclear Information System (INIS)

    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 have 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

  2. High performance vertical tunneling diodes using graphene/hexagonal boron nitride/graphene hetero-structure

    International Nuclear Information System (INIS)

    A tunneling rectifier prepared from vertically stacked two-dimensional (2D) materials composed of chemically doped graphene electrodes and hexagonal boron nitride (h-BN) tunneling barrier was demonstrated. The asymmetric chemical doping to graphene with linear dispersion property induces rectifying behavior effectively, by facilitating Fowler-Nordheim tunneling at high forward biases. It results in excellent diode performances of a hetero-structured graphene/h-BN/graphene tunneling diode, with an asymmetric factor exceeding 1000, a nonlinearity of ∼40, and a peak sensitivity of ∼12 V−1, which are superior to contending metal-insulator-metal diodes, showing great potential for future flexible and transparent electronic devices

  3. High performance vertical tunneling diodes using graphene/hexagonal boron nitride/graphene hetero-structure

    Energy Technology Data Exchange (ETDEWEB)

    Hwan Lee, Seung; Lee, Jia; Ho Ra, Chang; Liu, Xiaochi; Hwang, Euyheon [Samsung-SKKU Graphene Center (SSGC), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Department of Nano Science and Technology, SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Sup Choi, Min [Department of Nano Science and Technology, SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Hee Choi, Jun [Frontier Research Laboratory, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd., Yongin, Gyeonggi-do 446-711 (Korea, Republic of); Zhong, Jianqiang; Chen, Wei [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore); Jong Yoo, Won, E-mail: yoowj@skku.edu [Samsung-SKKU Graphene Center (SSGC), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Department of Nano Science and Technology, SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of)

    2014-02-03

    A tunneling rectifier prepared from vertically stacked two-dimensional (2D) materials composed of chemically doped graphene electrodes and hexagonal boron nitride (h-BN) tunneling barrier was demonstrated. The asymmetric chemical doping to graphene with linear dispersion property induces rectifying behavior effectively, by facilitating Fowler-Nordheim tunneling at high forward biases. It results in excellent diode performances of a hetero-structured graphene/h-BN/graphene tunneling diode, with an asymmetric factor exceeding 1000, a nonlinearity of ∼40, and a peak sensitivity of ∼12 V{sup −1}, which are superior to contending metal-insulator-metal diodes, showing great potential for future flexible and transparent electronic devices.

  4. Current-voltage characteristics of Co-fired cubic boron nitride

    International Nuclear Information System (INIS)

    Pellets of two phase ceramics consisting of cubic boron nitride as the base material and a secondary glass phase with high wetting characteristics to the primary phase, have been prepared. The results of a parametric study of the current voltage characteristics of such structures, fired at 850 oC in five millimeter diameter dies under mild retention pressure, are reported. Specimen variation resulted primarily from changes in concentration of the secondary phase and from the types of c-BN used. The results of experimental work has enabled a preliminary analysis of the conduction mechanisms in structures consisting of pellets held between metal electrodes, so far at room temperature. The second objective of the study, to determine the feasibility of using pellets in lieu of more time consuming and more costly circuits in evaluating c-BN based thick films, yielded the result that favors the use of pellets in most cases. (author)

  5. Exploring carrier transport phenomena in a CVD-assembled graphene FET on hexagonal boron nitride

    International Nuclear Information System (INIS)

    The supporting substrate plays a crucial role in preserving the superb electrical characteristics of an atomically thin 2D carbon system. We explore carrier transport behavior in a chemical-vapor-deposition- (CVD-) assembled graphene monolayer on hexagonal boron nitride (h-BN) substrate. Graphene-channel field-effect transistors (GFETs) were fabricated on ultra-thin h-BN multilayers to screen out carrier scattering from the underlying SiO2 substrate. To explore the transport phenomena, we use three different approaches to extract carrier mobility, namely, effective carrier mobility (μeff), intrinsic carrier mobility (μ), and field-effect mobility (μFE). A comparative study has been conducted based on the electrical characterization results, uncovering the impacts of supporting substrate material and device geometry scaling on carrier mobility in GFETs with CVD-assembled graphene as the active channel. (paper)

  6. Patterning monolayer graphene with zigzag edges on hexagonal boron nitride by anisotropic etching

    Science.gov (United States)

    Wang, Guole; Wu, Shuang; Zhang, Tingting; Chen, Peng; Lu, Xiaobo; Wang, Shuopei; Wang, Duoming; Watanabe, Kenji; Taniguchi, Takashi; Shi, Dongxia; Yang, Rong; Zhang, Guangyu

    2016-08-01

    Graphene nanostructures are potential building blocks for nanoelectronic and spintronic devices. However, the production of monolayer graphene nanostructures with well-defined zigzag edges remains a challenge. In this paper, we report the patterning of monolayer graphene nanostructures with zigzag edges on hexagonal boron nitride (h-BN) substrates by an anisotropic etching technique. We found that hydrogen plasma etching of monolayer graphene on h-BN is highly anisotropic due to the inert and ultra-flat nature of the h-BN surface, resulting in zigzag edge formation. The as-fabricated zigzag-edged monolayer graphene nanoribbons (Z-GNRs) with widths below 30 nm show high carrier mobility and width-dependent energy gaps at liquid helium temperature. These high quality Z-GNRs are thus ideal structures for exploring their valleytronic or spintronic properties.

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

    Directory of Open Access Journals (Sweden)

    Ram Sevak Singh

    2015-11-01

    Full Text Available 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 have 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.

  8. Contact-induced spin polarization of monolayer hexagonal boron nitride on Ni(111)

    International Nuclear Information System (INIS)

    Hexagonal boron nitride (h-BN) is a promising barrier material for graphene spintronics. In this Letter, spin-polarized metastable de-excitation spectroscopy (SPMDS) is employed to study the spin-dependent electronic structure of monolayer h-BN/Ni(111). The extreme surface sensitivity of SPMDS enables us to elucidate a partial filling of the in-gap states of h-BN without any superposition of Ni 3d signals. The in-gap states are shown to have a considerable spin polarization parallel to the majority spin of Ni. The positive spin polarization is attributed to the π-d hybridization and the effective spin transfer to the nitrogen atoms at the h-BN/Ni(111) interface

  9. Tubular Shape Fullerenes Inside Single Wall Boron Nitride Nanotubes: A Theoretical Simulation.

    Science.gov (United States)

    Ma, Fengxian; Yao, Zhen; Yao, Mingguang; Liu, Ran; Cui, Tian; Liu, Bingbing

    2016-06-01

    The orientations of fullerene molecules filled in nanotubes have important influence on the electronic properties of the formed peapods and their transformations such as polymerization under certain conditions. Here we present a investigation on the preferable orientations of tubular C70, C80 and C90 fullerenes confined inside single-walled boron nitride nanotubes (SWBNNTs) by calculating the van der Waals energy between the encapsulated molecule and the hosting nanotube. The minimum entering radius and the energetically favorable radius for encapsulating C70, C80 and C90 have been determined by the reaction energy calculation. We also show that the three studied molecules filled in SWBNNTs exhibit a transition from lying (five-fold axis) orientation to tilted orientation and then to standing orientation (two-fold axis) with increasing the tube radius. The preferable orientations of the encapsulated fullerenes are irrelevant on the tube chirality, but are dependent on the radius. PMID:27427630

  10. Nanoscale structure and superhydrophobicity of sp(2)-bonded boron nitride aerogels.

    Science.gov (United States)

    Pham, Thang; Goldstein, Anna P; Lewicki, James P; Kucheyev, Sergei O; Wang, Cheng; Russell, Thomas P; Worsley, Marcus A; Woo, Leta; Mickelson, William; Zettl, Alex

    2015-06-21

    Aerogels have much potential in both research and industrial applications due to their high surface area, low density, and fine pore size distribution. Here we report a thorough structural study of three-dimensional aerogels composed of highly crystalline sp(2)-bonded boron nitride (BN) layers synthesized by a carbothermic reduction process. The structure, crystallinity and bonding of the as-prepared BN aerogels are elucidated by X-ray diffraction, (11)B nuclear magnetic resonance, transmission electron microscopy, and resonant soft X-ray scattering. The macroscopic roughness of the aerogel's surface causes it to be superhydrophobic with a contact angle of ∼155° and exhibit high oil uptake capacity (up to 1500 wt%). The oil can be removed from the BN aerogel by oxidizing in air without damaging the crystalline porous structure of the aerogel or diminishing its oil absorption capacity. PMID:26007693

  11. Spintronics with graphene-hexagonal boron nitride van der Waals heterostructures

    International Nuclear Information System (INIS)

    Hexagonal boron nitride (h-BN) is a large bandgap insulating isomorph of graphene, ideal for atomically thin tunnel barrier applications. In this letter, we demonstrate large area chemical vapor deposited (CVD) h-BN as a promising spin tunnel barrier in graphene spin transport devices. In such structures, the ferromagnetic tunnel contacts with h-BN barrier are found to show robust tunneling characteristics over a large scale with resistances in the favorable range for efficient spin injection into graphene. The non-local spin transport and precession experiments reveal spin lifetime ≈500 ps and spin diffusion length ≈1.6 μm in graphene with tunnel spin polarization ≈11% at 100 K. The electrical and spin transport measurements at different injection bias current and gate voltages confirm tunnel spin injection through h-BN barrier. These results open up possibilities for implementation of large area CVD h-BN in spintronic technologies

  12. The electrical properties of sulfur-implanted cubic boron nitride thin films

    Institute of Scientific and Technical Information of China (English)

    Deng Jin-Xiang; Qin Yang; Kong Le; Yang Xue-Liang; Li Ting; Zhao Wei-Ping; Yang Ping

    2012-01-01

    Cubic boron nitride (c-BN) thin films are deposited on p-type Si wafers using radio frequency (RF) sputtering and then doped by implanting S ions.The implantation energy of the ions is 19 keV,and the implantation dose is between 1015 ions/cm2 and 1016 ions/cm2.The doped c-BN thin films are then annealed at a temperature between 400 ℃ and 800 ℃.The results show that the surface resistivity of doped and annealed c-BN thin films is lowered by two to three orders,and the activation energy of c-BN thin films is 0.18 eV.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-06-23

    Phase pure cubic boron nitride (c-BN) films have been epitaxially grown on (001) diamond substrates at 900 °C. The n-type doping of c-BN epitaxial films relies on the sequential growth of nominally undoped (p-) and Si doped (n-) layers with well-controlled thickness (down to several nanometer range) in the concept of multiple delta doping. The existence of nominally undoped c-BN overgrowth separates the Si doped layers, preventing Si dopant segregation that was observed for continuously doped epitaxial c-BN films. This strategy allows doping of c-BN films can be scaled up to multiple numbers of doped layers through atomic level control of the interface in the future electronic devices. Enhanced electronic transport properties with higher hall mobility (10{sup 2} cm{sup 2}/V s) have been demonstrated at room temperature as compared to the normally continuously Si doped c-BN films.

  14. Boron Nitride Coated Carbon Nanotube Arrays with Enhanced Compressive Mechanical Property

    Science.gov (United States)

    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.

  15. Engineering and localization of quantum emitters in large hexagonal boron nitride layers

    CERN Document Server

    Choi, Sumin; ElBadawi, Christopher; Lobo, Charlene; Wang, Xuewen; Juodkazis, Saulius; Seniutinas, Gediminas; Toth, Milos; Aharonovich, Igor

    2016-01-01

    Hexagonal boron nitride (hBN) is a wide bandgap van der Waals material that has recently emerged as 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 microns wide) of hBN. The emitters can be activated in as-grown hBN 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 edges of the flakes, unlike most luminescent point defects in 3D materials. Our results constitute an important step on the road map of deploying hBN in nanophotonics applications.

  16. Boron nitride-MWCNT/epoxy hybrid nanocomposites: Preparation and mechanical properties

    International Nuclear Information System (INIS)

    Highlights: • We studied the effects of BN nanoplatelets on tensile strength and elasticity modulus for polymer composites. • We investigated the synergetic effects of BN nanoplatelets and MWCNTs on tensile strength and elasticity modulus for polymer composites. • Fracture surfaces were examined by SEM analysis. - Abstract: In this study, production and mechanical properties of hybrid nanocomposites have been investigated. Hybrid nanocomposites are consisting of boron nitride nanoplatelets (BN) and multiwall carbon nanotubes (MWCNT) embedded in epoxy resin. The BN and MWCNT were mixed to epoxy resin in different weight fractions and mixtures were utilized for tensile test specimen production. The synthesized BN and produced hybrid nanocomposites were characterized by SEM, TEM, XRD, FT-IR and TGA analyses. The elasticity modulus and tensile strength values were obtained via tensile tests. The fracture morphologies were investigated after tensile test by means of scanning electron microscopy

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

    Science.gov (United States)

    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.

  18. Synthesis and characterization of boron nitride sponges as a novel support for metal nanoparticles

    Institute of Scientific and Technical Information of China (English)

    ZHENG MingTao; LIU YingLiang; GU YunLe; XU ZiLin

    2008-01-01

    This paper describes a simple synthetic route for the synthesis of hexagonal boron nitride (h-BN) powders with high specific surface area, in which BBr3, NH4Cl and Al powders are used as starting materials. The structure and composition of the powders were characterized by electron diffraction, Fourier transformation infrared spectroscopy and X-ray photoelectron spectroscopy in the selected area. X-ray diffraction shows wide peaks of crystalline h-BN with the particle size on the nanometer scale, and transmission electron microscopy reveals that the products have a novel spongy morphol-ogy. Silver nanoparticles loaded h-BN sponges were prepared via a one-step synthesis method. Dif-ferent reaction conditions for the formation of h-BN sponges were also investigated.

  19. Synthesis and characterization of boron nitride sponges as a novel support for metal nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This paper describes a simple synthetic route for the synthesis of hexagonal boron nitride (h-BN) powders with high specific surface area, in which BBr3, NH4Cl and Al powders are used as starting materials. The structure and composition of the powders were characterized by electron diffraction, Fourier transformation infrared spectroscopy and X-ray photoelectron spectroscopy in the selected area. X-ray diffraction shows wide peaks of crystalline h-BN with the particle size on the nanometer scale, and transmission electron microscopy reveals that the products have a novel spongy morphology. Silver nanoparticles loaded h-BN sponges were prepared via a one-step synthesis method. Different reaction conditions for the formation of h-BN sponges were also investigated.

  20. Fringe structures and tunable bandgap width of 2D boron nitride nanosheets.

    Science.gov (United States)

    Feng, Peter; Sajjad, Muhammad; Li, Eric Yiming; Zhang, Hongxin; Chu, Jin; Aldalbahi, Ali; Morell, Gerardo

    2014-01-01

    We report studies of the surface fringe structures and tunable bandgap width of atomic-thin boron nitride nanosheets (BNNSs). BNNSs are synthesized by using digitally controlled pulse deposition techniques. The nanoscale morphologies of BNNSs are characterized by using scanning electron microscope (SEM), and transmission electron microscopy (TEM). In general, the BNNSs appear microscopically flat in the case of low temperature synthesis, whereas at high temperature conditions, it yields various curved structures. Experimental data reveal the evolutions of fringe structures. Functionalization of the BNNSs is completed with hydrogen plasma beam source in order to efficiently control bandgap width. The characterizations are based on Raman scattering spectroscopy, X-ray diffraction (XRD), and FTIR transmittance spectra. Red shifts of spectral lines are clearly visible after the functionalization, indicating the bandgap width of the BNNSs has been changed. However, simple treatments with hydrogen gas do not affect the bandgap width of the BNNSs. PMID:25161852

  1. Controlled Synthesis of ZrS2 Monolayer and Few Layers on Hexagonal Boron Nitride.

    Science.gov (United States)

    Zhang, Mei; Zhu, Yiming; Wang, Xinsheng; Feng, Qingliang; Qiao, Shanlin; Wen, Wen; Chen, Yanfeng; Cui, Menghua; Zhang, Jin; Cai, Congzhong; Xie, Liming

    2015-06-10

    Group IVB transition metal (Zr and Hf) dichalcogenide (TMD) monolayers can have higher carrier mobility and higher tunneling current density than group VIB (Mo and W) TMD monolayers. Here we report the synthesis of hexagonal ZrS2 monolayer and few layers on hexagonal boron nitride (BN) using ZrCl4 and S as precursors. The domain size of ZrS2 hexagons is around 1-3 μm. The number of layers of ZrS2 was controlled by tuning the evaporation temperature of ZrCl4. The stacking angle between ZrS2 and BN characterized by transmission electron microscopy shows a preferred stacking angle of near 0°. Field-effect transistors (FETs) fabricated on ZrS2 flakes showed n-type transport behavior with an estimated mobility of 0.1-1.1 cm(2) V(-1) s(-1). PMID:25996159

  2. A cohesive law for interfaces in graphene/hexagonal boron nitride heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chenxi [Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, Florida 33146 (United States); Lou, Jun [Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77251 (United States); Song, Jizhou, E-mail: jzsong@gmail.com [Department of Engineering Mechanics and Soft Matter Research Center, Zhejiang University, Hangzhou 310027 (China)

    2014-04-14

    Graphene/hexagonal boron nitride (h-BN) heterostructure has showed great potential to improve the performance of graphene device. We have established the cohesive law for interfaces between graphene and monolayer or multi-layer h-BN based on the van der Waals force. The cohesive energy and cohesive strength are given in terms of area density of atoms on corresponding layers, number of layers, and parameters in the van der Waals force. It is found that the cohesive law in the graphene/multi-layer h-BN is dominated by the three h-BN layers which are closest to the graphene. The approximate solution is also obtained to simplify the expression of cohesive law. These results are very useful to study the deformation of graphene/h-BN heterostructure, which may have significant impacts on the performance and reliability of the graphene devices especially in the areas of emerging applications such as stretchable electronics.

  3. Decoupled electron and phonon transports in hexagonal boron nitride-silicene bilayer heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yongqing; Pei, Qing-Xiang, E-mail: peiqx@ihpc.a-star.edu.sg, E-mail: zhangg@ihpc.a-star.edu.sg; Zhang, Gang, E-mail: peiqx@ihpc.a-star.edu.sg, E-mail: zhangg@ihpc.a-star.edu.sg; Zhang, Yong-Wei [Institute of High Performance Computing, A*STAR, Singapore 138632 (Singapore)

    2016-02-14

    Calculations based on the density functional theory and empirical molecular dynamics are performed to investigate interlayer interaction, electronic structure and thermal transport of a bilayer heterostructure consisting of silicene and hexagonal boron nitride (h-BN). In this heterostructure, the two layers are found to interact weakly via a non-covalent binding. As a result, the Dirac cone of silicene is preserved with the Dirac cone point being located exactly at the Fermi level, and only a small amount of electrons are transferred from h-BN to silicene, suggesting that silicene dominates the electronic transport. Molecular dynamics calculation results demonstrate that the heat current along h-BN is six times of that along silicene, suggesting that h-BN dominates the thermal transport. This decoupled role of h-BN and silicene in thermal and electronic transport suggests that the BN-silicene bilayer heterostructure is promising for thermoelectric applications.

  4. Evidence for Defect-Mediated Tunneling in Hexagonal Boron Nitride-Based Junctions.

    Science.gov (United States)

    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. PMID:26509431

  5. In silico rational design of ionic liquids for the exfoliation and dispersion of boron nitride nanosheets.

    Science.gov (United States)

    García, Gregorio; Atilhan, Mert; Aparicio, Santiago

    2016-01-14

    A requirement for exploiting most of the unique properties of boron-nitride (BN) nanosheets is their isolation from the bulk material. A rational design of task-specific ionic liquids (ILs) through DFT simulations is reported in this work. The applied computational protocol allowed the screening of large IL families, which was carried out bearing in mind the achievement of strong π-π stacking between the anions and BN nanosheets as well as a negative charge transfer from the anion to the surface. The selected ionic liquids yielded strong interaction energies with BN nanosheets and high charge transfer values, while the main features of the ionic liquid are not affected in the presence of nanosheets. DFT simulations provided a detailed picture of the interaction mechanism and useful structure-property relationships in the search of a new ionic liquid for BN exfoliation. PMID:26658819

  6. Two-level spatial modulation of vibronic conductance in conjugated oligophenylenes on boron nitride.

    Science.gov (United States)

    Palma, Carlos-Andres; Joshi, Sushobhan; Hoh, Tobias; Ecija, David; Barth, Johannes V; Auwärter, Willi

    2015-04-01

    Intramolecular current-induced vibronic excitations are reported in highly ordered monolayers of quaterphenylene dicarbonitriles at an electronically patterned boron nitride on copper platform (BN/Cu(111)). A first level of spatially modulated conductance at the nanometer-scale is induced by the substrate. Moreover, a second level of conductance variations at the molecular level is found. Low temperature scanning tunneling microscopy studies in conjunction with molecular dynamics calculations reveal collective amplification of the molecule's interphenylene torsion angles in the monolayer. Librational modes influencing these torsion angles are identified as initial excitations during vibronic conductance. Density functional theory is used to map phenylene breathing modes and other vibrational excitations that are suggested to be at the origin of the submolecular features during vibronic conductance. PMID:25756645

  7. The structural and dynamical aspects of boron nitride nanotubes under high velocity impacts.

    Science.gov (United States)

    Machado, Leonardo D; Ozden, Sehmus; Tiwary, ChandraSekhar; Autreto, Pedro A S; Vajtai, Robert; Barrera, Enrique V; Galvao, Douglas S; Ajayan, Pulickel M

    2016-06-01

    This communication report is a study on the structural and dynamical aspects of boron nitride nanotubes (BNNTs) shot at high velocities (∼5 km s(-1)) against solid targets. The experimental results show unzipping of BNNTs and the formation of hBN nanoribbons. Fully atomistic reactive molecular dynamics simulations were also carried out to gain insights into the BNNT fracture patterns and deformation mechanisms. Our results show that longitudinal and axial tube fractures occur, but the formation of BN nanoribbons from fractured tubes was only observed for some impact angles. Although some structural and dynamical features of the impacts are similar to the ones reported for CNTs, because BNNTs are more brittle than CNTs this results in a larger number of fractured tubes but with fewer formed nanoribbons. PMID:27189765

  8. In situ mechanical property measurements of amorphous carbon-boron nitride nanotube nanostructures

    Science.gov (United States)

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

    2012-01-01

    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.

  9. Boron nitride colloidal solutions, ultralight aerogels and freestanding membranes through one-step exfoliation and functionalization

    Science.gov (United States)

    Lei, Weiwei; Mochalin, Vadym N.; Liu, Dan; Qin, Si; Gogotsi, Yury; Chen, Ying

    2015-11-01

    Manufacturing of aerogels and membranes from hexagonal boron nitride (h-BN) is much more difficult than from graphene or graphene oxides because of the poor dispersibility of h-BN in water, which limits its exfoliation and preparation of colloidal solutions. Here, a simple, one-step mechano-chemical process to exfoliate and functionalize h-BN into highly water-dispersible, few-layer h-BN containing amino groups is presented. The colloidal solutions of few-layer h-BN can have unprecedentedly high concentrations, up to 30 mg ml-1, and are stable for up to several months. They can be used to produce ultralight aerogels with a density of 1.4 mg cm-3, which is ~1,500 times less than bulk h-BN, and freestanding membranes simply by cryodrying and filtration, respectively. The material shows strong blue light emission under ultraviolet excitation, in both dispersed and dry state.

  10. Investigation of hexagonal boron nitride as an atomically thin corrosion passivation coating in aqueous solution

    Science.gov (United States)

    Zhang, Jing; Yang, Yingchao; Lou, Jun

    2016-09-01

    Hexagonal boron nitride (h-BN) atomic layers were utilized as a passivation coating in this study. A large-area continuous h-BN thin film was grown on nickel foil using a chemical vapor deposition method and then transferred onto sputtered copper as a corrosion passivation coating. The corrosion passivation performance in a Na2SO4 solution of bare and coated copper was investigated by electrochemical methods including cyclic voltammetry (CV), Tafel polarization and electrochemical impedance spectroscopy (EIS). CV and Tafel analysis indicate that the h-BN coating could effectively suppress the anodic dissolution of copper. The EIS fitting result suggests that defects are the dominant leakage source on h-BN films, and improved anti-corrosion performances could be achieved by further passivating these defects.

  11. Boron nitride nanotubes included thermally cross-linked gelatin-glucose scaffolds show improved properties.

    Science.gov (United States)

    Şen, Özlem; Culha, Mustafa

    2016-02-01

    Boron nitride nanotubes (BNNTs) are increasingly investigated for their medical and biomedical applications due to their unique properties such as resistance to oxidation, thermal and electrical insulation, and biocompatibility. BNNTs can be used to enhance mechanical strength of biomedical structures such as scaffolds in tissue engineering applications. In this study, we report the use of BNNTs and hydroxylated BNNTs (BNNT-OH) to improve the properties of gelatin-glucose scaffolds prepared with electrospinning technique. Human dermal fibroblast (HDF) cells are used for the toxicity assessment and cell seeding studies. It is found that the addition of BNNTs into the scaffold does not influence cell viability, decreases the scaffold degradation rate, and improves cell attachment and proliferation compared to only-gelatin scaffold. PMID:26642075

  12. Role of hexagonal boron nitride in protecting ferromagnetic nanostructures from oxidation

    Science.gov (United States)

    Zihlmann, Simon; Makk, Péter; Vaz, Carlos A. F.; Schönenberger, Christian

    2016-03-01

    Ferromagnetic contacts are widely used to inject spin polarized currents into non-magnetic materials such as semiconductors or 2-dimensional materials like graphene. In these systems, oxidation of the ferromagnetic materials poses an intrinsic limitation on device performance. Here we investigate the role of ex situ transferred chemical vapour deposited hexagonal boron nitride (hBN) as an oxidation barrier for nanostructured cobalt and permalloy electrodes. The chemical state of the ferromagnets was investigated using x-ray photoemission electron microscopy because of its high sensitivity and lateral resolution. We have compared the oxide thickness formed on ferromagnetic nanostructures covered by hBN to uncovered reference structures. Our results show that hBN reduces the oxidation rate of ferromagnetic nanostructures suggesting that it could be used as an ultra-thin protection layer in future spintronic devices.

  13. Surface functionalization of hexagonal boron nitride and its effect on the structure and performance of composites

    Science.gov (United States)

    Jin, Wenqin; Zhang, Wei; Gao, Yuwen; Liang, Guozheng; Gu, Aijuan; Yuan, Li

    2013-04-01

    A new organized hexagonal boron nitride (OhBN) with significantly increased amount of amine groups was synthesized, and characterized by Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric (TG) analysis, UV-vis Transmittance Spectra, Transmission Electron Microscope (TEM) and the potentiometric titration. The content of amine groups for OhBN is about 5 times of that for original hexagonal boron nitride (hBN). Based on the preparation of OhBN, new composites consisting of OhBN and bismaleimide (BD) resin were developed, which show greatly improved integrated performance (including dynamic mechanical, dielectric and thermal properties) compared with BD resin and the hBN/BD composites. In the case of the OhBN/BD composite with 15 wt% OhBN, its storage modulus, dielectric loss, thermal conductivity and coefficient of thermal expansion are about 1.2, 0.56, 1.11 and 0.92 times of the corresponding values of hBN/BD composite, respectively; moreover, the glass transition temperature of the former is 15 °C higher than that of the latter. These interesting results suggest that the integrated performance of the composites is closely related to the surface nature of the fillers because the change in the surface nature not only varies the chemical structure, free volume and crosslinking density of the composite, but also determines the interfacial nature between inorganic fillers and the resin matrix. This investigation demonstrates that the method proposed herein provides a new approach to prepare organized inorganic fillers as well as corresponding composites with controlled structure and expected performances for cutting-edge industries.

  14. Large quantity production of carbon and boron nitride nanotubes by mechano-thermal process

    International Nuclear Information System (INIS)

    Full text: Nanotube materials including carbon and boron nitride have excellent properties compared with bulk materials. The seamless graphene cylinders with a high length to diameter ratio make them as superstrong fibers. A high amount of hydrogen can be stored into nanotubes as future clean fuel source. Theses applications require large quantity of nanotubes materials. However, nanotube production in large quantity, fully controlled quality and low costs remains challenges for most popular synthesis methods such as arc discharge, laser heating and catalytic chemical decomposition. Discovery of new synthesis methods is still crucial for future industrial application. The new low-temperature mechano-thermal process discovered by the current author provides an opportunity to develop a commercial method for bulk production. This mechano-thermal process consists of a mechanical ball milling and a thermal annealing processes. Using this method, both carbon and boron nitride nanotubes were produced. I will present the mechano-thermal method as the new bulk production technique in the conference. The lecture will summarise main results obtained. In the case of carbon nanotubes, different nanosized structures including multi-walled nanotubes, nanocells, and nanoparticles have been produced in a graphite sample using a mechano-thermal process, consisting of I mechanical milling at room temperature for up to 150 hours and subsequent thermal annealing at 1400 deg C. Metal particles have played an important catalytic effect on the formation of different tubular structures. While defect structure of the milled graphite appears to be responsible for the formation of small tubes. It is found that the mechanical treatment of graphite powder produces a disordered and microporous structure, which provides nucleation sites for nanotubes as well as free carbon atoms. Multiwalled carbon nanotubes appear to grow via growth of the (002) layers during thermal annealing. In the case of BN

  15. Large-scale fabrication of boron nitride nanotubes with high purity via solid-state reaction method

    Science.gov (United States)

    2014-01-01

    An effective solid-state reaction method is reported for synthesizing boron nitride nanotubes (BNNTs) in large scale and with high purity by annealing amorphous boron powder and ferric chloride (FeCl3) catalyst in ammonia atmosphere at elevated temperatures. FeCl3 that has rarely been utilized before is introduced not only as a catalyst but also as an efficient transforming agent which converts boron powder into boron chloride (BCl3) vapor in situ. The nanotubes are bamboo in shape and have an average diameter of about 90 nm. The effect of synthetic temperatures on nanotube morphology and yield is investigated. The photoluminescence (PL) measurement shows emission bands of the nanotubes at 354, 423, 467, and 666 nm. A combined growth mechanism of vapor–liquid-solid (VLS) and solid–liquid-solid (SLS) model is proposed for the formation of the BNNTs. PMID:25313303

  16. Powder metallurgy routes toward aluminum boron nitride nanotube composites, their morphologies, structures and mechanical properties

    International Nuclear Information System (INIS)

    Aluminum/boron nitride nanotube (BNNT) composites with up to 5 wt% (i.e., 9.7 vol%) nanotube fractions were prepared via spark plasma sintering (SPS) and high-pressure torsion (HPT) methods. Various microscopy techniques, X-ray diffraction, and energy dispersive X-ray analysis confirmed the integration of the two phases into decently dense and compact composites. No other phases, like Al borides or nitrides, formed in the Al–BNNTs macrocomposites of the two series. The BNNTs were found to be preferentially located along Al grain boundaries in SPS samples (grain size was 10–20 μm) creating micro-discontinuities and pores which were found to be detrimental for the sample hardness, whereas in HPT samples, the tubes were rather evenly distributed within a fine-grained Al matrix (grain size of several hundred nm). Therefore, the hardness of HPT samples was drastically increased with increasing BNNTs content in Al pellets. The value for Al–BNNT 3.0 wt% sample was more than doubled (190 MPa) compared to a pure Al–HPT compact (90 MPa). And the room temperature ultimate tensile strength of Al–BNNTs HPT samples containing 3.0 wt% BNNT (∼300 MPa) became ∼1.5 times larger than that of a BNNT-free HPT–Al compact (∼200 MPa)

  17. Powder metallurgy routes toward aluminum boron nitride nanotube composites, their morphologies, structures and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, Maho [Nanotube Unit, World Premier International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 3050044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1, Tsukuba, Ibaraki 3050005 (Japan); Meng, Fanqiang [Research Center for Strategic Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 3050044 (Japan); Firestein, Konstantin [Laboratory of Inorganic Nanomaterials, National University of Science and Technology “MISIS”, Leninsky pr. 4, Moscow 119049 (Russian Federation); Tsuchiya, Koichi [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1, Tsukuba, Ibaraki 3050005 (Japan); Research Center for Strategic Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 3050044 (Japan); Golberg, Dmitri, E-mail: GOLBERG.Dmitri@nims.go.jp [Nanotube Unit, World Premier International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 3050044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1, Tsukuba, Ibaraki 3050005 (Japan)

    2014-05-01

    Aluminum/boron nitride nanotube (BNNT) composites with up to 5 wt% (i.e., 9.7 vol%) nanotube fractions were prepared via spark plasma sintering (SPS) and high-pressure torsion (HPT) methods. Various microscopy techniques, X-ray diffraction, and energy dispersive X-ray analysis confirmed the integration of the two phases into decently dense and compact composites. No other phases, like Al borides or nitrides, formed in the Al–BNNTs macrocomposites of the two series. The BNNTs were found to be preferentially located along Al grain boundaries in SPS samples (grain size was 10–20 μm) creating micro-discontinuities and pores which were found to be detrimental for the sample hardness, whereas in HPT samples, the tubes were rather evenly distributed within a fine-grained Al matrix (grain size of several hundred nm). Therefore, the hardness of HPT samples was drastically increased with increasing BNNTs content in Al pellets. The value for Al–BNNT 3.0 wt% sample was more than doubled (190 MPa) compared to a pure Al–HPT compact (90 MPa). And the room temperature ultimate tensile strength of Al–BNNTs HPT samples containing 3.0 wt% BNNT (∼300 MPa) became ∼1.5 times larger than that of a BNNT-free HPT–Al compact (∼200 MPa)

  18. Synthesis and characterization of nanocrystalline hexagonal boron carbo-nitride under high temperature and high pressure

    International Nuclear Information System (INIS)

    A study of the synthesis of hexagonal boron carbo-nitride (h-BCN) compounds via a two-step high-temperature and high-pressure (HTHP) technique using melamine (C3N6H6) and boron oxide (B2O3) as raw materials is presented. An amorphous BCN precursor was prepared at 1000 K under vacuum in a resistance furnace and then single-phase h-BCN nanocrystalline was synthesized at 1600 K and 5.1 GPa in a multi-anvil apparatus. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the final products were pure h-BCN crystals with the lattice constants a 0.2510 nm and c = 0.6690 nm. The average grain size was about 150 nm. X-ray photoelectron spectroscopy (XPS) results confirmed the occurrence of bonding between C-C, C-N, C-B and N-B atoms. Raman scattering analysis suggested that there were three strong Raman bands centered at 1359, 1596 and 1617 cm-1, respectively. The band at 1617 cm-1 was considered to be consistent with the characteristic Raman peak of h-BCN

  19. Manipulation and functionalization of nano-tubes: application to boron nitride nano-tubes

    International Nuclear Information System (INIS)

    This PhD work is divided into two parts dealing with boron nitride (BNNT) and carbon nano-tubes. The first part is about synthesis, purification and chemical functionalization of BNNT. Single-walled BNNT are synthesized by LASER ablation of a hBN target. Improving the synthesis parameters first allowed us to limit the byproducts (hBN, boric acid). A specific purification process was then developed in order to enrich the samples in nano-tubes. Purified samples were then used to develop two new chemical functionalization methods. They both involve chemical molecules that present a high affinity towards the BN network. The use of long chain-substituted quinuclidines and borazines actually allowed the solubilization of BNNT in organic media. Purification and functionalization were developed for single-walled BNNT and were successfully applied to multi-walled BNNT. Sensibility of boron to thermic neutrons finally gave birth to a study about covalent functionalization possibilities of the network. The second part of the PhD work deals with separation of carbon nano-tubes depending on their properties. Microwave irradiation of carbon nano-tubes first allowed the enrichment of initially polydisperse samples in large diameter nano-tubes. A second strategy involving selective interaction between one type of tubes and fullerene micelles was finally envisaged to selectively solubilize carbon nano-tubes with specific electronic properties. (author)

  20. Directional anisotropy, finite size effect and elastic properties of hexagonal boron nitride

    Science.gov (United States)

    Thomas, Siby; Ajith, K. M.; Valsakumar, M. C.

    2016-07-01

    Classical molecular dynamics simulations have been performed to analyze the elastic and mechanical properties of two-dimensional (2D) hexagonal boron nitride (h-BN) using a Tersoff-type interatomic empirical potential. We present a systematic study of h-BN for various system sizes. Young’s modulus and Poisson’s ratio are found to be anisotropic for finite sheets whereas they are isotropic for the infinite sheet. Both of them increase with system size in accordance with a power law. It is concluded from the computed values of elastic constants that h-BN sheets, finite or infinite, satisfy Born’s criterion for mechanical stability. Due to the the strong in-plane sp2 bonds and the small mass of boron and nitrogen atoms, h-BN possesses high longitudinal and shear velocities. The variation of bending rigidity with system size is calculated using the Foppl–von Karman approach by coupling the in-plane bending and out-of-plane stretching modes of the 2D h-BN.

  1. Electron cyclotron resonance plasma deposition of cubic boron nitride using N-trimethylborazine

    International Nuclear Information System (INIS)

    N-Trimethylborazine has been used as precursor in a downstream electron cyclotron resonance (ECR) plasma process to deposit cubic boron nitride (c-BN). N-Trimethylborazine ((CH3-N-B-H)3) is a non-corrosive and non-explosive liquid with a low toxicity. As plasma gas an argon-nitrogen mixture was used and N-trimethylborazine vapour was fed into the downstream region of the ECR plasma source. BN deposits on silicon (111) were characterized by IR spectroscopy, electron probe microanalysis and X-ray diffraction. The formation of nanocrystalline c-BN depends strongly on the process parameters and requires a substrate temperature of above 800 C. Furthermore, the application of a negative substrate bias-in our experiments achieved with a low frequency (100-450 kHz) generator-is essential to increase the c-BN fraction of the deposit. As shown by IR spectroscopy, a stepwise transition from hexagonal BN into wurtzite-type BN and finally into c-BN takes place by changing the deposition conditions. From these observations some conclusions concerning the growth mechanism of c-BN can be derived. Owing to the merits of N-trimethylborazine, its processing-compared with that of diborane or boron trihalides-is uncomplicated and promising for future applications of c-BN. (orig.)

  2. Research on the direct doping effect of silicon on cubic boron nitride ceramics by UV-VIS diffuse reflectance

    International Nuclear Information System (INIS)

    Cubic boron nitride (cBN) micro-powders mixed with 1 wt% silicon were sintered at 1450 deg. C under a pressure of 5.0 GPa. The grain boundaries and silicon distribution in Si-cBN ceramics were studied by scanning electronic microscope (SEM) and energy-dispersive spectrometer (EDS). Optical properties of the ceramics were investigated by UV-VIS diffuse reflectance and photoluminescence spectra at room temperature. Some important parameters of studied ceramics such as absorption coefficient and defect levels were identified from reflection spectra by intercept method. The experimental results indicated the direct n-doped effect of silicon on cubic boron nitride ceramics. With a direct forbidden transition characteristic, the donor energy level of Si in forbidden zone of cBN ceramics was found to be 2.82 eV. The phonon energy related to the direct forbidden transition was 0.235 eV.

  3. The Tunable Hybrid Surface Phonon and Plasmon Polariton Modes in Boron Nitride Nanotube and Graphene Monolayer Heterostructures

    OpenAIRE

    SUN, Yu; Zheng, Zheng; Cheng, Jiangtao; Liu, Jiansheng

    2014-01-01

    The hybrid modes incorporating surface phonon polariton (SPhP) modes in boron nitride nanotubes (BNNTs) and surface plasmon polariton (SPP) modes in graphene monolayers are theoretically studied. The combination of the 1D BNNTs and 2D graphene monolayer further improves the modal characteristics with electrical tunability. Superior to the graphene monolayers, the proposed heterostructures supports single mode transmission with lateral optical confinement. The modal characteristics can be shif...

  4. Bonding distances as Exact Sums of the Radii of the Constituent Atoms in Nanomaterials - Boron Nitride and Coronene

    OpenAIRE

    Heyrovska, Raji

    2010-01-01

    This paper presents for the first time the exact structures at the atomic level of two important nanomaterials, boron nitride and coronene. Both these compounds are hexagonal layer structures similar to graphene in two dimensions and to graphite in three-dimensions. However, they have very different properties: whereas graphene is a conductor, h-BN is an electrical insulator and coronene is a polycyclic aromatic hydrocarbon of cosmological interest. The atomic structures presented here for bo...

  5. Controlling Electronic and Geometrical Structure of Honeycomb-Lattice Materials Supported on Metal Substrates : Graphene and Hexagonal Boron Nitride

    OpenAIRE

    Vinogradov, Nikolay

    2013-01-01

    The present thesis is focused on various methods of controlling electronic and geometrical structure of two-dimensional overlayers adsorbed on metal surfaces exemplified by graphene and hexagonal boron nitride (h-BN) grown on transition metal (TM) substrates. Combining synchrotron-radiation-based spectroscopic and various microscopic techniques with in situ sample preparation, we are able to trace the evolution of overlayer electronic and geometrical properties in overlayer/substrate systems,...

  6. Dielectric Engineering of a Boron Nitride/Hafnium Oxide Heterostructure for High-Performance 2D Field Effect Transistors.

    Science.gov (United States)

    Zou, Xuming; Huang, Chun-Wei; Wang, Lifeng; Yin, Long-Jing; Li, Wenqing; Wang, Jingli; Wu, Bin; Liu, Yunqi; Yao, Qian; Jiang, Changzhong; Wu, Wen-Wei; He, Lin; Chen, Shanshan; Ho, Johnny C; Liao, Lei

    2016-03-01

    A unique design of a hexagonal boron nitride (h-BN)/HfO2 dielectric heterostructure stack is demonstrated, with few-layer h-BN to alleviate the surface optical phonon scattering, followed by high-κ HfO2 deposition to suppress Coulombic impurity scattering so that high-performance top-gated two-dimensional semiconductor transistors are achieved. Furthermore, this dielectric stack can also be extended to GaN-based transistors to enhance their performance. PMID:26762171

  7. Wafer-scale CVD Growth of Monolayer Hexagonal Boron Nitride with Large Domain Size by Cu Foil Enclosure Approach

    OpenAIRE

    Song, Xiuju; Gao, Junfeng; Gao, Teng; Nie, Yufeng; Sun, Jingyu; Chen, Yubin; Jin, Chuanhong; Ding, Feng; Zhang, Yanfeng; Liu, Zhongfan

    2015-01-01

    Chemical vapor deposition synthesis of large domain hexagonal boron nitride (h-BN) with uniform thickness on Cu foils is of great challenge, originating from the extremely high nucleation densities and the reverse hydrogen etching competition reaction. We report herein the successful growth of wafer-scale high-quality h-BN monolayer film with the largest single crystalline domain sizes up to 72 micrometer in edge length using a folded Cu enclosure approach. The highly-confined growth space wi...

  8. Reply to Comment on ‘Molecular structure-dependent deformations in boron nitride nanostructures subject to an electrical field’

    Science.gov (United States)

    Zhang, Jin; Wang, Chengyuan; Adhikari, Sondipon

    2016-03-01

    A large scattering of effective atomic charge distribution was found in the literature for hexagonal boron nitride nanostructures (BNNSs). In our paper (Zhang J, Wang C Y and Sondipon A 2013 J. Phys. D: Appl. Phys. 46 235303) ‘±3e’ was chosen as a rough approximation for the effective atomic charge in BNNSs as it gave the piezoelectric coefficient of BNNSs close to the values in the literature.

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

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, I.; Jankowski, A.F.; Terminello, L.J. [Lawrence Berkeley National Lab., CA (United States)] [and others

    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-center 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.

  10. Implementation of Outstanding Electronic Transport in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour

    Science.gov (United States)

    Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan

    2016-01-01

    A theoretical investigation of the unique electronic transport properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through non-equilibrium Green’s function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic electronic devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the transport properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias. PMID:27211110

  11. Implementation of Outstanding Electronic Transport in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour

    Science.gov (United States)

    Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan

    2016-05-01

    A theoretical investigation of the unique electronic transport properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through non-equilibrium Green’s function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic electronic devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the transport properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias.

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

    Science.gov (United States)

    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

  13. Synthesis of hollow boron nitride nanoboxes with ultrathin walls from cube-like LaB6.

    Science.gov (United States)

    Wang, Liancheng; Si, Lulu; Qian, Yitai

    2013-07-01

    In this study, cube-like LaB6 was synthesized by Mg coreduction of LaCl3 and B20,3. Then, boron nitride nanoboxes (BNNBs) were produced by nitriding cube-like LaB6, and the latter is not only played as boron source, but also as hard template. The results of characterization (transmission electron microscopy and scanning electron microscopy) indicate that the BN products are hollow structures, the diameter of the nanoboxes is in the range of 200-1000 nm, and the wall thickness of the BN nanoboxes is 16 nm. The specific surface area of BN nanoboxes is 45 m2/g, the pore size is mainly located at 10 nm, and the total pore volume is 0.16 cm3/g. The nitriding of cube-like LaB6 into hollow BNNBs here would provide an alternative route for the synthesis of other hollow BN architectures by other boron-containing materials. PMID:23901485

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

    Science.gov (United States)

    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

  15. Vertically self-ordered orientation of nanocrystalline hexagonal boron nitride thin films for enhanced thermal characteristics

    Science.gov (United States)

    Cometto, Olivier; Sun, Bo; Tsang, Siu Hon; Huang, Xi; Koh, Yee Kan; Teo, Edwin Hang Tong

    2015-11-01

    Vertically self-ordered hexagonal boron nitride (ordered h-BN) is a highly ordered turbostratic BN (t-BN) material similar to hexagonal BN, with its planar structure perpendicularly oriented to the substrate. The ordered h-BN thin films were grown using a High Power Impulse Magnetron Sputtering (HiPIMS) system with a lanthanum hexaboride (LaB6) target reactively sputtered in nitrogen gas. The best vertical alignment was obtained at room temperature, with a grounded bias and a HiPIMS peak power density of 60 W cm-2. Even though the film contains up to 7.5 at% lanthanum, it retains its highly insulative properties and it was observed that an increase in compressive stress is correlated to an increase in film ordering quality. Importantly, the thermal conductivity of vertically ordered h-BN is considerably high at 5.1 W m-1 K-1. The favourable thermal conductivity coupled with the dielectric properties of this novel material and the low temperature growth could outperform SiO2 in high power density electronic applications.Vertically self-ordered hexagonal boron nitride (ordered h-BN) is a highly ordered turbostratic BN (t-BN) material similar to hexagonal BN, with its planar structure perpendicularly oriented to the substrate. The ordered h-BN thin films were grown using a High Power Impulse Magnetron Sputtering (HiPIMS) system with a lanthanum hexaboride (LaB6) target reactively sputtered in nitrogen gas. The best vertical alignment was obtained at room temperature, with a grounded bias and a HiPIMS peak power density of 60 W cm-2. Even though the film contains up to 7.5 at% lanthanum, it retains its highly insulative properties and it was observed that an increase in compressive stress is correlated to an increase in film ordering quality. Importantly, the thermal conductivity of vertically ordered h-BN is considerably high at 5.1 W m-1 K-1. The favourable thermal conductivity coupled with the dielectric properties of this novel material and the low temperature

  16. Nanoscale structure and superhydrophobicity of sp2-bonded boron nitride aerogels

    Science.gov (United States)

    Pham, Thang; Goldstein, Anna P.; Lewicki, James P.; Kucheyev, Sergei O.; Wang, Cheng; Russell, Thomas P.; Worsley, Marcus A.; Woo, Leta; Mickelson, William; Zettl, Alex

    2015-06-01

    Aerogels have much potential in both research and industrial applications due to their high surface area, low density, and fine pore size distribution. Here we report a thorough structural study of three-dimensional aerogels composed of highly crystalline sp2-bonded boron nitride (BN) layers synthesized by a carbothermic reduction process. The structure, crystallinity and bonding of the as-prepared BN aerogels are elucidated by X-ray diffraction, 11B nuclear magnetic resonance, transmission electron microscopy, and resonant soft X-ray scattering. The macroscopic roughness of the aerogel's surface causes it to be superhydrophobic with a contact angle of ~155° and exhibit high oil uptake capacity (up to 1500 wt%). The oil can be removed from the BN aerogel by oxidizing in air without damaging the crystalline porous structure of the aerogel or diminishing its oil absorption capacity.Aerogels have much potential in both research and industrial applications due to their high surface area, low density, and fine pore size distribution. Here we report a thorough structural study of three-dimensional aerogels composed of highly crystalline sp2-bonded boron nitride (BN) layers synthesized by a carbothermic reduction process. The structure, crystallinity and bonding of the as-prepared BN aerogels are elucidated by X-ray diffraction, 11B nuclear magnetic resonance, transmission electron microscopy, and resonant soft X-ray scattering. The macroscopic roughness of the aerogel's surface causes it to be superhydrophobic with a contact angle of ~155° and exhibit high oil uptake capacity (up to 1500 wt%). The oil can be removed from the BN aerogel by oxidizing in air without damaging the crystalline porous structure of the aerogel or diminishing its oil absorption capacity. Electronic supplementary information (ESI) available: High resolution TEM images of different portions of sample, photos of aerogels in oil bath over time, thermal gravimetric analysis data of the aerogels, and

  17. Valence and conduction band offsets at amorphous hexagonal boron nitride interfaces with silicon network dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    King, Sean W., E-mail: sean.king@intel.com; Brockman, Justin; Bielefeld, Jeff; French, Marc; Kuhn, Markus [Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124 (United States); Paquette, Michelle M.; Otto, Joseph W.; Caruso, A. N. [Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States); French, Benjamin [Ocotillo Materials Laboratory, Intel Corporation, Chandler, Arizona 85248 (United States)

    2014-03-10

    To facilitate the design of heterostructure devices employing hexagonal/sp{sup 2} boron nitride, x-ray photoelectron spectroscopy has been utilized in conjunction with prior reflection electron energy loss spectroscopy measurements to determine the valence and conduction band offsets (VBOs and CBOs) present at interfaces formed between amorphous hydrogenated sp{sup 2} boron nitride (a-BN:H) and various low- and high-dielectric-constant (k) amorphous hydrogenated silicon network dielectric materials (a-SiX:H, X = O, N, C). For a-BN:H interfaces formed with wide-band-gap a-SiO{sub 2} and low-k a-SiOC:H materials (E{sub g} ≅ 8.2−8.8 eV), a type I band alignment was observed where the a-BN:H band gap (E{sub g} = 5.5 ± 0.2 eV) was bracketed by a relatively large VBO and CBO of ∼1.9 and 1.2 eV, respectively. Similarly, a type I alignment was observed between a-BN:H and high-k a-SiC:H where the a-SiC:H band gap (E{sub g} = 2.6 ± 0.2 eV) was bracketed by a-BN:H with VBO and CBO of 1.0 ± 0.1 and 1.9 ± 0.2 eV, respectively. The addition of O or N to a-SiC:H was observed to decrease the VBO and increase the CBO with a-BN:H. For high-k a-SiN:H (E{sub g} = 3.3 ± 0.2 eV) interfaces with a-BN:H, a slightly staggered type II band alignment was observed with VBO and CBO of 0.1 ± 0.1 and −2.3 ± 0.2 eV, respectively. The measured a-BN:H VBOs were found to be consistent with those deduced via application of the commutative and transitive rules to VBOs reported for a-BN:H, a-SiC:H, a-SiN:H, and a-SiO{sub 2} interfaces with Si (100)

  18. Phonon transport at the interfaces of vertically stacked graphene and hexagonal boron nitride heterostructures

    Science.gov (United States)

    Yan, Zhequan; Chen, Liang; Yoon, Mina; Kumar, Satish

    2016-02-01

    Hexagonal boron nitride (h-BN) is a promising 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 boron 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.

  19. Phonon transport at the interfaces of vertically stacked graphene and hexagonal boron nitride heterostructures.

    Science.gov (United States)

    Yan, Zhequan; Chen, Liang; Yoon, Mina; Kumar, Satish

    2016-02-21

    Hexagonal boron nitride (h-BN) is a promising 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 boron 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. PMID:26817419

  20. Deposition of thin layers of boron nitrides and hydrogenated microcrystalline silicon assisted by high current direct current arc plasma

    International Nuclear Information System (INIS)

    In the frame of this thesis, a high current direct current arc (HCDCA) used for the industrial deposition of diamond, has been adapted to study the deposition of two types of coatings: a) boron nitride, whose cubic phase is similar to diamond, for tribological applications, b) hydrogenated microcrystalline silicon, for applications in the semiconductor fields (flat panel displays, solar cells,...). For the deposition of these coatings, the substrates were placed in the diffusion region of the arc. The substrate heating is mainly due to atomic species recombining on its surface. The deposition temperature, varying from 300 to 900 oC according to the films deposited, is determined by the substrate position, the arc power and the injected gas fluxes, without the use of any external heating or cooling system. Measurements performed on the arc plasma show that the electronic temperature is around 2 eV (23'000 K) while the gas temperature is lower than 5500 K. Typical electronic densities are in the range of 1012-101'3 cm-3. For the deposition of boron nitride films, different boron precursors were used and a wide parameter range was investigated. The extreme difficulty of synthesising cubic boron nitride films by chemical vapour deposition (CVD) did not allow to stabilize the cubic phase of boron nitride in HCDCA. Coatings resulted in hexagonal or amorphous boron nitride with a chemical composition close to stoichiometric. The presence of hydrogen leads to the deposition of rough and porous films. Negative biasing of the samples, for positive ion bombardment, is commonly used to stabilize the cubic phase. In HCDCA and in our biasing range, only a densification of the films could be observed. A boron nitride deposition plasma study by infrared absorption spectroscopy in a capacitive radio frequency reactor has demonstrated the usefulness of this diagnostic for the understanding of the various chemical reactions which occur in this kind of plasma. Diborane dissociation

  1. Phonon transport on two-dimensional graphene/boron nitride superlattices

    Science.gov (United States)

    Zhu, Taishan; Ertekin, Elif

    2014-11-01

    Using nonequilibrium molecular dynamics and lattice dynamics, we investigate phonon conduction on two-dimensional graphene/boron nitride superlattices with varying periods and interface structures. As the period of superlattice increases to a critical value near 5 nm the lattice thermal conductivity drops sharply to a minimum, and beyond that it smoothly increases with the period. We show that the minimum in the thermal conductivity arises from a competition between lattice dispersion and anharmonic effects such as interface scattering. The initial reduction of thermal conductivity can partially be accounted for by harmonic wave effects induced by interfacial modulation, such as the opening of phononic band gaps and reduction of group velocity. Beyond the minimum, reduced inelastic interface scattering is responsible for the recovery. The overall range of thermal conductivity exhibited by the superlattices is substantially reduced with respect to the parent materials. A universal scaling of the thermal conductivity with total superlattice length is found, suggesting that the critical period is independent of total length and that long-wavelength phonons are dominant carriers. Furthermore, we demonstrate the ultrasensitivity of thermal conductivity to interfacial defects and superlattice periodicity disorder.

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

    Science.gov (United States)

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

    2014-07-01

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

  3. Enhanced thermal conductivity and isotope effect in single-layer hexagonal boron nitride

    Science.gov (United States)

    Broido, David; Lindsay, Lucas

    2012-02-01

    We have calculated the lattice thermal conductivity, k, of both naturally occurring and isotopically enriched single layers of hexagonal boron nitride (h-BN) as well as bulk h-BN using an exact numerical solution of the Boltzmann transport equation for phonons [1]. Good agreement is obtained with measured bulk h-BN data [2], and the stronger phonon-phonon scattering identified in these systems explains why their k values are significantly lower than those in graphene and graphite. A reduction in such scattering in the single layer arising mainly from a symmetry-based selection rule leads to a substantial increase in k, with calculated room temperature values of more than 600 W/m-K. Additional enhancement is obtained from isotopic enrichment, which exhibits a strong peak as a function of temperature, with magnitude growing rapidly with crystallite size. [1] L. Lindsay and D. A. Broido, Phys. Rev. B 84, 155421 (2011). [2] E. K. Sichel, R. E. Miller, M. S. Abrahams, and C. J. Buiocchi, Phys. Rev. B 13, 4607 (1976).

  4. Local charge states in hexagonal boron nitride with Stone-Wales defects.

    Science.gov (United States)

    Wang, Rui; Yang, Jiali; Wu, Xiaozhi; Wang, Shaofeng

    2016-04-14

    A Stone-Wales (SW) defect is the simplest topological defect in graphene-like materials and can be potentially employed to design electronic devices . In this paper, we have systematically investigated the formation, structural, and electronic properties of the neutral and charged SW defects in hexagonal boron nitride (BN) using first-principles calculations. The transition states and energy barrier for the formation of SW defects demonstrate that the defected BN is stable. Our calculations show that there are two in-gap defect levels, which originate from the asymmetrical pentagon-heptagon pairs. The local defect configurations and electronic properties are sensitive to their charge states induced by the defect levels. The electronic band structures show that the negative and positive charged defects are mainly determined by shifting the conduction band minimum (CBM) and valence band maximum (VBM) respectively, and the SW-defected BN can realize -1 and +1 spin-polarized charge states. The effects of carbon (C) substitution on neutral and charged SW-defected BN have also been studied. Our results indicate that the C substitution of B in BN is in favour of the formation of SW defects. Structural and electronic calculations show rich charge-dependent properties of C substitutions in SW-defected BN, thus our theoretical study is important for various applications in the design of BN nanostructure-based devices. PMID:27030259

  5. Synthesis and Characterization of Nano Boron Nitride Reinforced Magnesium Composites Produced by the Microwave Sintering Method

    Directory of Open Access Journals (Sweden)

    Manoj Gupta

    2013-05-01

    Full Text Available In this study, magnesium composites with nano-size boron nitride (BN particulates of varying contents were synthesized using the powder metallurgy (PM technique incorporating microwave-assisted two-directional sintering followed by hot extrusion. The effect of nano-BN addition on the microstructural and the mechanical behavior of the developed Mg/BN composites were studied in comparison with pure Mg using the structure-property correlation. Microstructural characterization revealed uniform distribution of nano-BN particulates and marginal grain refinement. The coefficient of thermal expansion (CTE value of the magnesium matrix was improved with the addition of nano-sized BN particulates. The results of XRD studies indicate basal texture weakening with an increase in nano-BN addition. The composites showed improved mechanical properties measured under micro-indentation, tension and compression loading. While the tensile yield strength improvement was marginal, a significant increase in compressive yield strength was observed. This resulted in the reduction of tension-compression yield asymmetry and can be attributed to the weakening of the strong basal texture.

  6. MOCVD of hexagonal boron nitride thin films on Si(100) using new single source precursors

    CERN Document Server

    Boo, J H; Yu, K S; Kim, Y S; Kim, Y S; Park, J T

    1999-01-01

    We have been carried out the growth of hexagonal boron nitride (h-BN) thin films on Si(100) substrates by low pressure metal-organic chemical vapor deposition (LPMOCVD) method using triethylborane tert-butylamine complex (TEBTBA), Et sub 3 BNH sub 2 ( sup t Bu), and triethylborane isopropylamine complex (TEBIPA), Et sub 3 BNH sub 2 ( sup t Pr) as a new single molecular precursors in the temperature range of 850 approx 1000 .deg. C. polycrystalline, crack-free h-BN film was successfully grown on Si(100) substrate at 850 .deg. C using TEBTBA. This growth temperature is very lower than those in previous reports. Carbon-rich polycrystalline BN was also obtained at 900 .deg. C from TEBIPA. With increasing substrate temperature to 1000 .deg. C, however, BC sub 4 N-like species are strongly formed along with h-BN and the BN films obtained from both TEBTBA and TEBIPA but almost polycrystalline. To our best knowledge, this is the first report of the growth of h-BN films formed with the new single source precursors of ...

  7. Effects of Polydopamine Functionalization on Boron Nitride Nanotube Dispersion and Cytocompatibility.

    Science.gov (United States)

    Fernandez-Yague, Marc A; Larrañaga, Aitor; Gladkovskaya, Olga; Stanley, Alanna; Tadayyon, Ghazal; Guo, Yina; Sarasua, Jose-Ramon; Tofail, Syed A M; Zeugolis, Dimitrios I; Pandit, Abhay; Biggs, Manus J

    2015-10-21

    Boron nitride nanotubes (BNNTs) have unique physical properties, of value in biomedical applications; however, their dispersion and functionalization represent a critical challenge in their successful employment as biomaterials. In the present study, we report a process for the efficient disentanglement of BNNTs via a dual surfactant/polydopamine (PD) process. High-resolution transmission electron microscopy (HR-TEM) indicated that individual BNNTs become coated with a uniform PD nanocoating, which significantly enhanced dispersion of BNNTs in aqueous solutions. Furthermore, the cytocompatibility of PD-coated BNNTs was assessed in vitro with cultured human osteoblasts (HOBs) at concentrations of 1, 10, and 30 μg/mL and over three time-points (24, 48, and 72 h). In this study it was demonstrated that PD-functionalized BNNTs become individually localized within the cytoplasm by endosomal escape and that concentrations of up to 30 μg/mL of PD-BNNTs were cytocompatible in HOBs cells following 72 h of exposure. PMID:26282841

  8. Structure and Electronic Properties of Edge-Functionalized Armchair Boron Nitride Nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Benzanilla, Alejandro [Oak Ridge National Laboratory (ORNL); Huang, Jingsong [ORNL; Terrones Maldonado, Humberto [ORNL; Sumpter, Bobby G [ORNL

    2012-01-01

    We report a quantum mechanical description based on the density functional theory of the structures and electronic properties of armchair boron nitride nanoribbons (BNNRs) edge-terminated with O atoms and OH groups. The O edge termination was found to give a peroxide-like structure that is nonmagnetic and semiconducting with a bandgap of Eg= 2.8 eV. The O-terminated BNNR ribbon was stabilized bythe reduction of the peroxide groups with H atoms leading to a polyol-like structure. The two chains of hydrogen bonds created along the edges lead to alternating 5- and 7-membered rings and cause the ribbon to become nonplanar with rippled edges. Three configurations of different ripple periods and amplitudes were found with energy differences up to 2 eV per unit cell but with virtually the same bandgap of Eg = 4.2 eV. The hydrogen bond mediated ripples are characterized through the lone pair orbitals showing a local separation and a pair of rabbit-ears on the acceptor O atoms in 5- and 7-membered rings respectively dictated by the hydrogen bond lengths. Energy bands and total and projected density of states are discussed for both functionalizations to show their effects on altering the electronic properties of armchair BNNRs.

  9. Coherent phonon transport in short-period two-dimensional superlattices of graphene and boron nitride

    Science.gov (United States)

    da Silva, Carlos; Saiz, Fernan; Romero, David A.; Amon, Cristina H.

    2016-03-01

    Promoting coherent transport of phonons at material interfaces is a promising strategy for controlling thermal transport in nanostructures and an alternative to traditional methods based on structural defects. Coherent transport is particularly relevant in short-period heterostructures with smooth interfaces and long-wavelength heat-carrying phonons, such as two-dimensional superlattices of graphene and boron nitride. In this work, we predict phonon properties and thermal conductivities in these superlattices using a normal mode decomposition approach. We study the variation of the frequency dependence of these properties with the periodicity and interface configuration (zigzag and armchair) for superlattices with period lengths within the coherent regime. Our results showed that the thermal conductivity decreases significantly from the first period length (0.44 nm) to the second period length (0.87 nm), 13% across the interfaces and 16% along the interfaces. For greater periods, the conductivity across the interfaces continues decreasing at a smaller rate of 11 W/mK per period length increase (0.43 nm), driven by changes in the phonon group velocities (coherent effects). In contrast, the conductivity along the interfaces slightly recovers at a rate of 2 W/mK per period, driven by changes in the phonon relaxation times (diffusive effects). By changing the interface configuration from armchair to zigzag, the conductivities for all period lengths increase by approximately 7% across the interfaces and 19% along the interfaces.

  10. Growth and spectroscopic characterization of monolayer and few-layer hexagonal boron nitride on metal substrates

    Science.gov (United States)

    Feigelson, Boris N.; Bermudez, Victor M.; Hite, Jennifer K.; Robinson, Zachary R.; Wheeler, Virginia D.; Sridhara, Karthik; Hernández, Sandra C.

    2015-02-01

    Atomically thin two dimensional hexagonal boron nitride (2D h-BN) is one of the key materials in the development of new van der Waals heterostructures due to its outstanding properties including an atomically smooth surface, high thermal conductivity, high mechanical strength, chemical inertness and high electrical resistance. The development of 2D h-BN growth is still in the early stages and largely depends on rapid and accurate characterization of the grown monolayer or few layers h-BN films. This paper demonstrates a new approach to characterizing monolayer h-BN films directly on metal substrates by grazing-incidence infrared reflection absorption spectroscopy (IRRAS). Using h-BN films grown by atmospheric-pressure chemical vapor deposition on Cu and Ni substrates, two new sub-bands are found for the A2u out-of-plane stretching mode. It is shown, using both experimental and computational methods, that the lower-energy sub-band is related to 2D h-BN coupled with substrate, while the higher energy sub-band is related to decoupled (or free-standing) 2D h-BN. It is further shown that this newly-observed fine structure in the A2u mode can be used to assess, quickly and easily, the homogeneity of the h-BN-metal interface and the effects of metal surface contamination on adhesion of the layer.

  11. Thermal diffusivity of hexagonal boron nitride composites based on cross-linked liquid crystalline polyimides.

    Science.gov (United States)

    Shoji, Yu; Higashihara, Tomoya; Tokita, Masatoshi; Morikawa, Junko; Watanabe, Junji; Ueda, Mitsuru

    2013-04-24

    Hexagonal boron nitride (h-BN) composites with the oriented cross-linked liquid crystalline (LC) polyimide have been developed as high thermally conductive materials. Well-dispersed h-BN composite films were obtained, as observed by scanning electron microscopy. The morphology of the composite films was further investigated in detail by the wide-angle X-ray diffraction. The obtained composite films based on the cross-linked LC polyimide showed that the polymer chains vertically aligned in the direction parallel to the films, while those based on the amorphous polyimide showed an isotropic nature. Moreover, the alignment of the cross-linked LC polyimides was maintained, even after increasing the volume fraction of h-BN. This alignment plays an important role in the effective phonon conduction between h-BN and the matrices. Indeed, the thermal diffusivity in the thickness direction of the composite films based on the LC polyimide measured by a temperature wave analysis method was increased to 0.679 mm(2) s(-1) at a 30 vol % h-BN loading, which was higher than that based on the amorphous polyimide. PMID:23506319

  12. Thermal stability of boron nitride/silicon p-n heterojunction diodes

    Science.gov (United States)

    Teii, Kungen; Mizusako, Yusei; Hori, Takuro; Matsumoto, Seiichiro

    2015-10-01

    Heterojunctions of p-type cubic boron nitride (cBN) and n-type silicon with sp2-bonded BN (sp2BN) interlayers are fabricated under low-energy ion impact by plasma-enhanced chemical vapor deposition, and their rectification properties are studied at temperatures up to 573 K. The rectification ratio is increased up to the order of 105 at room temperature by optimizing the thickness of the sp2BN interlayer and the cBN fraction for suppressing the reverse leakage current. A highly rectifying p-type cBN/thick sp2BN/n-type silicon junction diode shows irreversible rectification properties mainly characterized by a marked decrease in reverse current by an order of magnitude in an initial temperature ramp/down cycle. This irreversible behavior is much more reduced by conducting the cycle twice or more. The temperature-dependent properties confirm an overall increase in effective barrier heights for carrier injection and conduction by biasing at high temperatures, which consequently increases the thermal stability of the diode performance.

  13. Synthesis and applications of two-dimensional hexagonal boron nitride in electronics manufacturing

    Science.gov (United States)

    Bao, Jie; Jeppson, Kjell; Edwards, Michael; Fu, Yifeng; Ye, Lilei; Lu, Xiuzhen; Liu, Johan

    2016-01-01

    In similarity to graphene, two-dimensional (2D) hexagonal boron nitride (hBN) has some remarkable properties, such as mechanical robustness and high thermal conductivity. In addition, hBN has superb chemical stability and it is electrically insulating. 2D hBN has been considered a promising material for many applications in electronics, including 2D hBN based substrates, gate dielectrics for graphene transistors and interconnects, and electronic packaging insulators. This paper reviews the synthesis, transfer and fabrication of 2D hBN films, hBN based composites and hBN-based van der Waals heterostructures. In particular, this review focuses on applications in manufacturing electronic devices where the insulating and thermal properties of hBN can potentially be exploited. 2D hBN and related composite systems are emerging as new and industrially important materials, which could address many challenges in future complex electronics devices and systems. [Figure not available: see fulltext.

  14. Effects of hexagonal boron nitride on dry compression mixture of Avicel DG and Starch 1500.

    Science.gov (United States)

    Uğurlu, Timuçin; Halaçoğlu, Mekin Doğa

    2016-06-01

    The objective of this study was to investigate the lubrication properties of hexagonal boron nitride (HBN) on a (1:1) binary mixture of Avicel DG and Starch 1500 after using the dry granulation-slugging method and compare it with conventional lubricants, such as magnesium stearate (MGST), glyceryl behenate (COMP) and stearic acid (STAC). MGST is one of the most commonly used lubricants in the pharmaceutical industry. However, it has several adverse effects on tablet properties. In our current study, we employed various methods to eradicate the work hardening phenomenon in dry granulation, and used HBN as a new lubricant to overcome the adverse effects of other lubricants on tablet properties. HBN was found to be as effective as MGST and did not show any significant adverse effects on the crushing strength or work hardening. From the scanning electron microscope (SEM) images, it was concluded that HBN distributed better than MGST. As well as showing better distribution, HBN's effect on disintegration was the least pronounced. Semi-quantitative weight percent distribution of B and N elements in the tablets was obtained using EDS (energy dispersive spectroscopy). Based on atomic force microscope (AFM) surface roughness images, formulations prepared with 1% HBN showed better plastic character than those prepared with MGST. PMID:25716058

  15. Boron nitride nanotubes coated with organic hydrophilic agents: Stability and cytocompatibility studies

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Tiago Hilário; Soares, Daniel Crístian Ferreira; Moreira, Luciana Mara Costa; Ornelas da Silva, Paulo Roberto [Serviço de Nanotecnologia, Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN, Avenida Presidente Antônio Carlos, 6.627, Campus da UFMG, Pampulha, CEP 31270-901 Belo Horizonte, Minas Gerais (Brazil); Gouvêa dos Santos, Raquel [Laboratório de Radiobiologia, Centro de Desenvolvimento da Tecnologia Nuclear CNEN/CDTN, Av. Presidente Antônio Carlos 6.627, Campus da UFMG, Pampulha, 31270-901 Belo Horizonte, Minas Gerais (Brazil); Barros de Sousa, Edésia Martins, E-mail: sousaem@cdtn.br [Serviço de Nanotecnologia, Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN, Avenida Presidente Antônio Carlos, 6.627, Campus da UFMG, Pampulha, CEP 31270-901 Belo Horizonte, Minas Gerais (Brazil)

    2013-12-01

    In the present study, Boron Nitride Nanotubes (BNNTs) were synthesized and functionalized with organic hydrophilic agents constituted by glucosamine (GA), polyethylene glycol (PEG){sub 1000}, and chitosan (CH) forming new singular systems. Their size, distribution, and homogeneity were determined by photon correlation spectroscopy, while their surface charge was determined by laser Doppler anemometry. The morphology and structural organization were evaluated by Transmission Electron Microscopy. The functionalization was evaluated by Thermogravimetry analysis and Fourier Transformer Infrared Spectroscopy. The results showed that BNNTs were successfully obtained and functionalized, reaching a mean size and dispersity deemed adequate for in vitro studies. The in vitro stability tests also revealed a good adhesion of functionalized agents on BNNT surfaces. Finally, the in vitro cytocompatibility of functionalized BNNTs against MCR-5 cells was evaluated, and the results revealed that none of the different functionalization agents disturbed the propagation of normal cells up to the concentration of 50 μg/mL. Furthermore, in this concentration, no significantly chromosomal or morphologic alterations or increase in ROS (Reactive Oxygen Species) could be observed. Thus, findings from the present study reveal an important stability and cytocompatibility of functionalized BNNTs as new potential drugs or radioisotope nanocarriers to be applied in therapeutic procedures. - Highlights: • BNNTs were synthesized and functionalized with organic hydrophilic agents. • Hydrophilic molecules do not alter the biocompatibility profile of BNNTs. • No significantly chromosomal or morphologic alterations in ROS could be observed.

  16. Doping and electrical properties of cubic boron nitride thin films: A critical review

    International Nuclear Information System (INIS)

    Cubic boron nitride (c-BN) is a promising material for high-power and high-temperature electronic devices operating in harsh environments due to its outstanding properties including a wide band-gap, good chemical stability, high thermal conductivity, and high breakdown field. The electronic applications of c-BN have received considerable attention, benefiting from the progress in c-BN thin film deposition techniques during the last few years. The present article reviews the latest developments in doping and electrical properties of c-BN thin films. Following a brief introduction on film growth, we present calculated theoretical results on electronic structure as well as the energies of native defects and impurity dopants in c-BN. In recent experimental research, several dopants, including Be, Mg, Zn, S, and Si, have been incorporated into c-BN thin films during deposition or by post ion implantation, resulting in both n- and p-type conduction. These results are summarized and discussed in Section 3. In addition, results on c-BN/metal-contacts and p–n junctions based on intrinsic or doped c-BN thin films are discussed in Section 4. Finally, current status and future prospects for doping and electrical properties of c-BN thin films are discussed

  17. Oscillatory motion in layered materials: graphene, boron nitride, and molybdenum disulfide.

    Science.gov (United States)

    Ye, Zhijiang; Otero-de-la-Roza, Alberto; Johnson, Erin R; Martini, Ashlie

    2015-04-24

    Offset-driven self-retraction and oscillatory motion of bilayer graphene has been observed experimentally and is potentially relevant for nanoscale technological applications. In a previous article, we showed that friction between laterally offset graphene layers is controlled by roughness and proposed a simple reduced-order model based on density-functional theory (DFT) and molecular dynamics (MD) data, with which predictions on the experimental size-scale could be made. In this article, we extend our study to other layered materials, with emphasis on boron nitride (BN) and molybdenum disulfide (MoS2). Using MD and DFT simulations of these systems and a generalized version of the reduced-order model, we predict that BN will exhibit behavior similar to graphene (heavily-damped oscillation with a decay rate that increases with roughness) and that MoS2 shows no oscillatory behavior even in the absence of roughness. This is attributed to the higher energy barrier for sliding in MoS2 as well as the surface structure. Our generalized reduced-order model provides a guide to predicting and tuning experimental oscillation behavior using a few parameters that can be derived from simulation data. PMID:25815685

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

    Science.gov (United States)

    Muthu, R. Naresh; Rajashabala, S.; Kannan, R.

    2016-05-01

    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% at 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.

  19. High-Responsivity Graphene-Boron Nitride Photodetector and Autocorrelator in a Silicon Photonic Integrated Circuit

    CERN Document Server

    Shiue, Ren-Jye; Wang, Yifei; Peng, Cheng; Robertson, Alexander D; Efetov, Dimitri; Assefa, Solomon; Koppens, Frank H L; Hone, James; Englund, Dirk

    2015-01-01

    Graphene and other two-dimensional (2D) materials have emerged as promising materials for broadband and ultrafast photodetection and optical modulation. These optoelectronic capabilities can augment complementary metal-oxide-semiconductor (CMOS) devices for high-speed and low-power optical interconnects. Here, we demonstrate an on-chip ultrafast photodetector based on a two-dimensional heterostructure consisting of high-quality graphene encapsulated in hexagonal boron nitride. Coupled to the optical mode of a silicon waveguide, this 2D heterostructure-based photodetector exhibits a maximum responsivity of 0.36 A/W and high-speed operation with a 3 dB cut-off at 42 GHz. From photocurrent measurements as a function of the top-gate and source-drain voltages, we conclude that the photoresponse is consistent with hot electron mediated effects. At moderate peak powers above 50 mW, we observe a saturating photocurrent consistent with the mechanisms of electron-phonon supercollision cooling. This nonlinear photorespo...

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

    Science.gov (United States)

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

    2015-05-01

    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.

  1. Bilayer Graphene-Hexagonal Boron Nitride Heterostructure Negative Differential Resistance Interlayer Tunnel FETs

    Science.gov (United States)

    Kang, Sangwoo; Fallahazad, Babak; Lee, Kayoung; Movva, Hema; Kim, Kyounghwan; Corbet, Chris; Taniguchi, Takashi; Watanabe, Kenji; Colombo, Luigi; Register, Leonard; Tutuc, Emanuel; Banerjee, Sanjay

    2015-03-01

    We present the operation of a vertical tunneling field effect transistor using a stacked double bilayer graphene (BLG) and hexagonal boron nitride (hBN) heterostructure. The device is fabricated with the so-called Van der Waals transfer method with the edges of the top and bottom BLG flakes being rotationally aligned to roughly 60°. The device shows multiple negative differential resistance (NDR) peaks which can be adjusted through the gate bias. Temperature dependent measurements show that the peak width of the differential conductance broadens and the height lowered when the temperature is increased, which is indicative of resonant tunneling. Through electrostatic calculations, it is shown that the multiple peaks occur when the two conduction bands at the K-point of the top and bottom bilayer graphene become aligned at certain bias conditions. It is also shown that by adjusting the rotational alignment of the bands of the top and bottom BLG through an in-plane magnetic field, the conductance peaks can be broadened. In addition, utilizing the NDR characteristic of the device, one-transistor latch or SRAM operation is demonstrated.

  2. Platinum nanoparticle modified polyaniline-functionalized boron nitride nanotubes for amperometric glucose enzyme biosensor.

    Science.gov (United States)

    Wu, Jianmin; Yin, Longwei

    2011-11-01

    A novel amperometric biosensor based on the BNNTs-Pani-Pt hybrids with Pt nanoparticle homogeneously decorated on polyaniline (Pani)-wrapped boron nitride nanotubes (BNNTs), was developed. It is shown that π interactions take place between BNNTs and polyaniline (Pani) located at N atoms from BNNTs and C atoms from Pani, resulting in the water solubility for the Pani wrapped BNNTs hybrids. The developed glucose biosensor displayed high sensitivity and stability, good reproducibility, anti-interference ability, especially excellent acid stability and heat resistance. The resulted BNNTs-Pani-Pt hybrid amperometric glucose biosensor exhibited a fast response time (within 3 s) and a linear calibration range from 0.01 to 5.5 mM with a high sensitivity and low detection limit of 19.02 mA M(-1) cm(-2) and 0.18 μM glucose (S/N = 3). Surprisedly, the relative activity of the GC/BNNTs-Pani-Pt-GOD electrode keeps almost no change in a range from pH 3 to 7. Futhermore, the BNNTs-Pani-Pt hybrid biosensor maintains a high GOD enzymatic activity even at a relatively high temperature of 60 °C. This might be attributed to the effect of electrostatic field and hydrophobia of BNNTs. The unique acid stability and heat resistance of this sensor indicate great promising application in numerous industrial and biotechnological operations involving harsh conditions. PMID:22013877

  3. The defect-induced fracture behaviors of hexagonal boron-nitride monolayer nanosheets under uniaxial tension

    International Nuclear Information System (INIS)

    Due to its excellent mechanical and electrical insulating properties, the hexagonal boron-nitride (h-BN) monolayer nanosheet is regarded as a complementary addition to graphene. However, its mechanical strength can be significantly affected by various defects pre-existing in it, such as a Stone–Wales defect, a vacancy defect, an atomic anti-site defect, etc. In this work, the influences of various pre-existing defects on the fracture behaviors of an h-BN monolayer nanosheet are investigated carefully using molecular dynamics simulation. The results show that the nucleation and evolution of a fracture induced by defects in the h-BN monolayer nanosheet are directional, and that the crack always starts from the location which has a weak bond energy. An unexpected observation is that the defect propagates mostly in the zigzag direction but occasionally in the armchair direction. The fracture strength and the fracture strain of the h-BN monolayer nanosheet are reduced at different extents due to the various pre-existing defects. Additionally, for the defective h-BN monolayer nanosheets, the fracture strength and strain measured in the armchair direction is much higher than the strength found in the zigzag direction. However, the strengths measured in the armchair and zigzag directions for the defect-free h-BN monolayer nanosheets almost are identical which implies that the armchair direction has a stronger ability to resist various defects compared to the zigzag direction. (paper)

  4. Surface adhesion between hexagonal boron nitride nanotubes and silicon based on lateral force microscopy

    International Nuclear Information System (INIS)

    This study presents the surface adhesion between hexagonal boron nitride nanotube (BNNT) and silicon based on lateral manipulation in an atomic force microscope (AFM). The BNNT was mechanically manipulated by the lateral force of an AFM pyramidal silicon probe using the scan mechanism in the imaging mode. With a controlled normal force of the AFM probe and the lateral motion, the lateral force applied to the BNNT could overcome the surface adhesion between BNNT and silicon surface. The individual BNNT is forced to slide and rotate on the silicon surface. Based on the recorded force curve, the calculated shear stress due to surface adhesion is 0.5 GPa. And the specific sliding energy loss is 0.2 J/m2. Comparing BNNTs and carbon nanotube (CNT), the shear stress and specific sliding energy loss of BNNT are an order of magnitude larger than that of CNT. Therefore, the results show that the surface adhesion between BNNT and silicon surface is higher than that of CNT.

  5. High-Responsivity Graphene-Boron Nitride Photodetector and Autocorrelator in a Silicon Photonic Integrated Circuit.

    Science.gov (United States)

    Shiue, Ren-Jye; Gao, Yuanda; Wang, Yifei; Peng, Cheng; Robertson, Alexander D; Efetov, Dmitri K; Assefa, Solomon; Koppens, Frank H L; Hone, James; Englund, Dirk

    2015-11-11

    Graphene and other two-dimensional (2D) materials have emerged as promising materials for broadband and ultrafast photodetection and optical modulation. These optoelectronic capabilities can augment complementary metal-oxide-semiconductor (CMOS) devices for high-speed and low-power optical interconnects. Here, we demonstrate an on-chip ultrafast photodetector based on a two-dimensional heterostructure consisting of high-quality graphene encapsulated in hexagonal boron nitride. Coupled to the optical mode of a silicon waveguide, this 2D heterostructure-based photodetector exhibits a maximum responsivity of 0.36 A/W and high-speed operation with a 3 dB cutoff at 42 GHz. From photocurrent measurements as a function of the top-gate and source-drain voltages, we conclude that the photoresponse is consistent with hot electron mediated effects. At moderate peak powers above 50 mW, we observe a saturating photocurrent consistent with the mechanisms of electron-phonon supercollision cooling. This nonlinear photoresponse enables optical on-chip autocorrelation measurements with picosecond-scale timing resolution and exceptionally low peak powers. PMID:26372880

  6. Structural, energetic and electrical properties of boron nitride nanotubes interacting with DMMP chemical agent

    International Nuclear Information System (INIS)

    Highlights: • ab initio DFT calculations were used for interaction of DMMP with BNNTs. • Full structural optimization was performed for several possible active sites. • Electronic structure of the energetically favorable complexes was analyzed. • The stability of the most stable complex was evaluated at ambient condition. • First-principles calculations showed that DMMP is strongly bound to the small diameter BNNTs. - Abstract: The adsorption of DMMP as an intoxicating chemical warfare agent onto the boron nitride nanotube has been investigated by using density functional theory calculations. Several active sites were considered for both interacting systems and full structural optimization was performed to accurately find the energetically favorable state. It is found that DMMP molecule prefers to be adsorbed strongly on the top site above the B atom of a (5, 0) BNNT with a binding energy of about −103.24 kJ mol−1 and an O–B binding distance of 1.641 Å. We have performed a comparative investigation of BNNTs with different diameters and the results indicate that the DMMP adsorption ability for the side wall of the tubes significantly decreases for higher diameters BNNTs. Furthermore, the adsorption properties of DMMP molecule onto the BNNT have been investigated using the ab initio MD simulation at room temperature. Our result showed that BNNTs facilitates the DMMP detection at ambient conditions for practical applications

  7. Boron nitride nanosheets as improved and reusable substrates for gold nanoparticles enabled surface enhanced Raman spectroscopy

    KAUST Repository

    Cai, Qiran

    2015-01-01

    Atomically thin boron nitride (BN) nanosheets have been found to be excellent substrates for noble metal particles enabled surface enhanced Raman spectroscopy (SERS), thanks to their good adsorption of aromatic molecules, high thermal stability and weak Raman scattering. Faceted gold (Au) nanoparticles have been synthesized on BN nanosheets using a simple but controllable and reproducible sputtering and annealing method. The size and density of the Au particles can be controlled by sputtering time, current and annealing temperature etc. Under the same sputtering and annealing conditions, the Au particles on BN of different thicknesses show various sizes because the surface diffusion coefficients of Au depend on the thickness of BN. Intriguingly, decorated with similar morphology and distribution of Au particles, BN nanosheets exhibit better Raman enhancements than silicon substrates as well as bulk BN crystals. Additionally, BN nanosheets show no noticeable SERS signal and hence cause no interference to the Raman signal of the analyte. The Au/BN substrates can be reused by heating in air to remove the adsorbed analyte without loss of SERS enhancement. This journal is © the Owner Societies 2015.

  8. Temperature dependent structural properties and bending rigidity of pristine and defective hexagonal boron nitride

    Science.gov (United States)

    Thomas, Siby; Ajith, K. M.; Chandra, Sharat; Valsakumar, M. C.

    2015-08-01

    Structural and thermodynamical properties of monolayer pristine and defective boron nitride sheets (h-BN) have been investigated in a wide temperature range by carrying out atomistic simulations using a tuned Tersoff-type inter-atomic empirical potential. The temperature dependence of lattice parameter, radial distribution function, specific heat at constant volume, linear thermal expansion coefficient and the height correlation function of the thermally excited ripples on pristine as well as defective h-BN sheet have been investigated. Specific heat shows considerable increase beyond the Dulong-Petit limit at high temperatures, which is interpreted as a signature of strong anharmonicity present in h-BN. Analysis of the height fluctuations, , shows that the bending rigidity and variance of height fluctuations are strongly temperature dependent and this is explained using the continuum theory of membranes. A detailed study of the height-height correlation function shows deviation from the prediction of harmonic theory of membranes as a consequence of the strong anharmonicity in h-BN. It is also seen that the variance of the height fluctuations increases with defect concentration.

  9. Magnetism and transport properties of zigzag graphene nanoribbons/hexagonal boron nitride heterostructures

    International Nuclear Information System (INIS)

    Results of ab initio study of magnetism and transport properties of charge carriers in zigzag graphene nanoribbons (ZGNR) on hexagonal boron nitride (h-BN(0001)) substrate are presented within the density functional theory framework. Peculiarities of the interface band structure and its role in the formation of magnetism and transport properties of the ZGNR/h-BN(0001) heterostructure have been studied using two different density functional approximations. The effect of the substrate and graphene nanoribbons width on the low-energy spectrum of π-electrons, local magnetic moments on atoms of interface, and charge carriers mobility in the ZGNR/h-BN(0001) heterostructures have been established for the first time. The regularity consisting in the charge carrier mobility growth with decrease of dimers number in nanoribbon was also established. It is found that the charge carriers mobility in the N-ZGNR/h-BN(0001) (N—number of carbon (C) dimers) heterostructures is 5% higher than in freestanding ZGNR

  10. Magnetism and transport properties of zigzag graphene nanoribbons/hexagonal boron nitride heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ilyasov, V. V., E-mail: viily@mail.ru, E-mail: chuongnguyen11@gmail.com; Meshi, B. C.; Nguyen, V. C., E-mail: viily@mail.ru, E-mail: chuongnguyen11@gmail.com; Ershov, I. V. [Don State Technical University, 1 Gagarin Sq, 344000 Rostov on Don (Russian Federation); Nguyen, D. C. [Department of Electronic Materials, School of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Rd, 10000 Hanoi (Viet Nam)

    2014-02-07

    Results of ab initio study of magnetism and transport properties of charge carriers in zigzag graphene nanoribbons (ZGNR) on hexagonal boron nitride (h-BN(0001)) substrate are presented within the density functional theory framework. Peculiarities of the interface band structure and its role in the formation of magnetism and transport properties of the ZGNR/h-BN(0001) heterostructure have been studied using two different density functional approximations. The effect of the substrate and graphene nanoribbons width on the low-energy spectrum of π-electrons, local magnetic moments on atoms of interface, and charge carriers mobility in the ZGNR/h-BN(0001) heterostructures have been established for the first time. The regularity consisting in the charge carrier mobility growth with decrease of dimers number in nanoribbon was also established. It is found that the charge carriers mobility in the N-ZGNR/h-BN(0001) (N—number of carbon (C) dimers) heterostructures is 5% higher than in freestanding ZGNR.

  11. Radiolabeling and physicochemical characterization of boron nitride nanotubes functionalized with glycol chitosan polymer

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Daniel Cristian Ferreira; Ferreira, Tiago Hilario; Ferreira, Carolina de Aguiar; Sousa, Edesia Martins Barros de, E-mail: sousaem@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG) Belo Horizonte, MG (Brazil). Lab. de Materiais Nanoestruturados para Bioaplicacoes; Cardoso, Valbert Nascimento, E-mail: cardosov@farmacia.ufmg.b [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Fac. de Farmacia

    2011-07-01

    In the last years, some nanostructured systems has proposed as new drugs and radioisotopes delivery systems, aiming the diagnosis and treatment of many diseases, including the cancer. Among these systems, the Boron Nitride Nanotubes (BNNTs) showed adequate characteristics to be applied in biomedical area, due to its high stability and considerable biocompatibility. However, due to its hydrophobic characteristics, these applications are limited and its behavior in vivo (guinea pigs) is unexplored yet. Seeking to overcome this problems, in the present work, we functionalized the BNNTs (noncovalent wrapped) with glycol chitosan (GC), a biocompatible and stable polymer, in order to disperse it in water. The results showed that BNNTs were well dispersed in water with mean size and polydispersity index suitable to conduct biodistribution studies in mice. The nanostructures were physicochemical and morphologically characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Raman Spectroscopy. The results revealed that the functionalization process with glycol chitosan was obtained with successfully on BNNTs surface. Furthermore, we developed a radiolabeling protocol with {sup 99m}Tc radioisotope in functionalized BNNTs, aiming in future, to conduct image biodistribution studies in mice. The results revealed that the nanotubes were radiolabeled with radiochemical purity above of 90%, being considered suitable to scintigraphic image acquisition. (author)

  12. Synthesis of large single-crystal hexagonal boron nitride grains on Cu-Ni alloy

    Science.gov (United States)

    Lu, Guangyuan; Wu, Tianru; Yuan, Qinghong; Wang, Huishan; Wang, Haomin; Ding, Feng; Xie, Xiaoming; Jiang, Mianheng

    2015-01-01

    Hexagonal boron nitride (h-BN) has attracted significant attention because of its superior properties as well as its potential as an ideal dielectric layer for graphene-based devices. The h-BN films obtained via chemical vapour deposition in earlier reports are always polycrystalline with small grains because of high nucleation density on substrates. Here we report the successful synthesis of large single-crystal h-BN grains on rational designed Cu-Ni alloy foils. It is found that the nucleation density can be greatly reduced to 60 per mm2 by optimizing Ni ratio in substrates. The strategy enables the growth of single-crystal h-BN grains up to 7,500 μm2, approximately two orders larger than that in previous reports. This work not only provides valuable information for understanding h-BN nucleation and growth mechanisms, but also gives an effective alternative to exfoliated h-BN as a high-quality dielectric layer for large-scale nanoelectronic applications.

  13. Growth and Contrast of Hexagonal Boron Nitride: From Submonolayer Islands to Multilayer Films

    Science.gov (United States)

    Koepke, Justin; Wood, Joshua; Pop, Eric; Lyding, Joseph

    2013-03-01

    Strong interest in hexagon boron nitride (h-BN) as a substrate for graphene devices or as a template for growth of other layered compounds has motivated recent attempts to synthesize large scale h-BN by chemical vapor deposition (CVD). We synthesize h-BN by low pressure CVD on polycrystalline Cu foil in a hot wall tube furnace with a heated ammonia borane precursor carried downstream by Ar and H2 gas. Transmission electron microscopy (TEM) diffraction patterns show that the resulting growths are highly crystalline, with several layers obtained for longer growth times. Short growth times show that the h-BN nucleates in triangular islands at a higher precursor temperature than previously reported in and a lower temperature than reported in. In-air calcination of the Cu foils after partial h-BN growth allows optical contrast of the previously transparent h-BN islands on the Cu foil. This observed resistance to oxidation suggests that grown h-BN films can serve as an insulating anti-corrosion layer.

  14. Direct growth of nanocrystalline hexagonal boron nitride films on dielectric substrates

    International Nuclear Information System (INIS)

    Atomically thin hexagonal-boron nitride (h-BN) films are primarily synthesized through chemical vapor deposition (CVD) on various catalytic transition metal substrates. In this work, a single-step metal-catalyst-free approach to obtain few- to multi-layer nanocrystalline h-BN (NCBN) directly on amorphous SiO2/Si and quartz substrates is demonstrated. The as-grown thin films are continuous and smooth with no observable pinholes or wrinkles across the entire deposited substrate as inspected using optical and atomic force microscopy. The starting layers of NCBN orient itself parallel to the substrate, initiating the growth of the textured thin film. Formation of NCBN is due to the random and uncontrolled nucleation of h-BN on the dielectric substrate surface with no epitaxial relation, unlike on metal surfaces. The crystallite size is ∼25 nm as determined by Raman spectroscopy. Transmission electron microscopy shows that the NCBN formed sheets of multi-stacked layers with controllable thickness from ∼2 to 25 nm. The absence of transfer process in this technique avoids any additional degradation, such as wrinkles, tears or folding and residues on the film which are detrimental to device performance. This work provides a wider perspective of CVD-grown h-BN and presents a viable route towards large-scale manufacturing of h-BN substrates and for coating applications

  15. Direct growth of nanocrystalline hexagonal boron nitride films on dielectric substrates

    Energy Technology Data Exchange (ETDEWEB)

    Tay, Roland Yingjie [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore); Temasek Laboratories@NTU, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore); Tsang, Siu Hon [Temasek Laboratories@NTU, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore); Loeblein, Manuela; Chow, Wai Leong [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore); CNRS-International NTU Thales Research Alliance CINTRA UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Singapore, Singapore 637553 (Singapore); Loh, Guan Chee [Institue of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632 (Singapore); Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States); Toh, Joo Wah; Ang, Soon Loong [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore); Teo, Edwin Hang Tong, E-mail: htteo@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore)

    2015-03-09

    Atomically thin hexagonal-boron nitride (h-BN) films are primarily synthesized through chemical vapor deposition (CVD) on various catalytic transition metal substrates. In this work, a single-step metal-catalyst-free approach to obtain few- to multi-layer nanocrystalline h-BN (NCBN) directly on amorphous SiO{sub 2}/Si and quartz substrates is demonstrated. The as-grown thin films are continuous and smooth with no observable pinholes or wrinkles across the entire deposited substrate as inspected using optical and atomic force microscopy. The starting layers of NCBN orient itself parallel to the substrate, initiating the growth of the textured thin film. Formation of NCBN is due to the random and uncontrolled nucleation of h-BN on the dielectric substrate surface with no epitaxial relation, unlike on metal surfaces. The crystallite size is ∼25 nm as determined by Raman spectroscopy. Transmission electron microscopy shows that the NCBN formed sheets of multi-stacked layers with controllable thickness from ∼2 to 25 nm. The absence of transfer process in this technique avoids any additional degradation, such as wrinkles, tears or folding and residues on the film which are detrimental to device performance. This work provides a wider perspective of CVD-grown h-BN and presents a viable route towards large-scale manufacturing of h-BN substrates and for coating applications.

  16. Enhanced deposition of cubic boron nitride films on roughened silicon and tungsten carbide-cobalt surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Teii, K., E-mail: teii@asem.kyushu-u.ac.j [Department of Applied Science for Electronics and Materials, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Hori, T. [Department of Applied Science for Electronics and Materials, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Matsumoto, S. [Exploratory Materials Research Laboratory for Energy and Environment, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Ceramic Forum Co. Ltd., 1-6-6 Taitoh, Taitoh-ku, Tokyo 110-0016 (Japan)

    2011-01-03

    We report the influence of substrate surface roughness on cubic boron nitride (cBN) film deposition under low-energy ion bombardment in an inductively coupled plasma. Silicon and cemented tungsten carbide-cobalt (WC-Co) surfaces are roughened by low-energy ion-assisted etching in a hydrogen plasma, followed by deposition in a fluorine-containing plasma. Infrared absorption coefficients are measured to be 22,000 cm{sup -1} and 17,000 cm{sup -1} for sp{sup 2}-bonded BN and cBN phases, respectively, for our films. For the silicon substrates, the film growth rate and the cBN content in the film increase with increasing the surface roughness, while the amount of sp{sup 2}BN phase in the film shows only a small increase. A larger surface roughness of the substrate results in a smaller contact angle of water, indicating that a higher surface free energy of the substrate contributes to enhancing growth of the cBN film. For the WC-Co substrates, the film growth rate and the cBN content in the film increase similarly by roughening the surface.

  17. Direct deposition of cubic boron nitride films on tungsten carbide-cobalt.

    Science.gov (United States)

    Teii, Kungen; Matsumoto, Seiichiro

    2012-10-24

    Thick cubic boron nitride (cBN) films in micrometer-scale are deposited on tungsten carbide-cobalt (WC-Co) substrates without adhesion interlayers by inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD) using the chemistry of fluorine. The residual film stress is reduced because of very low ion-impact energies (a few eV to ∼25 eV) controlled by the plasma sheath potential. Two types of substrate pretreatment are used successively; the removal of surface Co binder using an acid solution suppresses the catalytic effect of Co and triggers cBN formation, and the surface roughening using mechanical scratching and hydrogen plasma etching increases both the in-depth cBN fraction and deposition rate. The substrate surface condition is evaluated by the wettability of the probe liquids with different polarities and quantified by the apparent surface free energy calculated from the contact angle. The surface roughening enhances the compatibility in energy between the cBN and substrate, which are bridged by the interfacial sp(2)-bonded hexagonal BN buffer layer, and then, the cBN overlayer is nucleated and evolved easier. PMID:22950830

  18. Enhanced deposition of cubic boron nitride films on roughened silicon and tungsten carbide-cobalt surfaces

    International Nuclear Information System (INIS)

    We report the influence of substrate surface roughness on cubic boron nitride (cBN) film deposition under low-energy ion bombardment in an inductively coupled plasma. Silicon and cemented tungsten carbide-cobalt (WC-Co) surfaces are roughened by low-energy ion-assisted etching in a hydrogen plasma, followed by deposition in a fluorine-containing plasma. Infrared absorption coefficients are measured to be 22,000 cm-1 and 17,000 cm-1 for sp2-bonded BN and cBN phases, respectively, for our films. For the silicon substrates, the film growth rate and the cBN content in the film increase with increasing the surface roughness, while the amount of sp2BN phase in the film shows only a small increase. A larger surface roughness of the substrate results in a smaller contact angle of water, indicating that a higher surface free energy of the substrate contributes to enhancing growth of the cBN film. For the WC-Co substrates, the film growth rate and the cBN content in the film increase similarly by roughening the surface.

  19. Hexagonal boron nitride thin film thermal neutron detectors with high energy resolution of the reaction products

    International Nuclear Information System (INIS)

    Hexagonal boron nitride (h-BN) is highly promising for solid-state thermal neutron detector applications due to its many outstanding physical properties, especially its very large thermal neutron capture cross-section (~3840 barns for 10B), which is several orders of magnitude larger than those of most other isotopes. The focus of the present work is to carry out studies on h-BN thin film and detector properties to lay the foundation for the development of a direct-conversion solid-state thermal neutron detector with high sensitivity. The measured carrier mobility-lifetime (μτ) product of h-BN thin films grown on sapphire substrates is 2.83×10−7 cm2/V for electrons and holes, which is comparable to the value of about 10−7 cm2/V for GaN thin films grown on sapphire. Detectors based on h-BN thin films were fabricated and the nuclear reaction product pulse height spectra were measured. Under a bias of 20 V, very narrow individual peaks corresponding to the reaction product energies of α and Li particles as well as the sum peaks have been clearly resolved in the pulse height spectrum for the first time by a B-based direct-conversion semiconductor neutron detector. Our results indicate that h-BN thin film detectors possess unique advantages including small size, low weight, portability, low voltage operation and high energy resolution of specific reaction products

  20. Hexagonal boron nitride thin film thermal neutron detectors with high energy resolution of the reaction products

    Science.gov (United States)

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

    2015-05-01

    Hexagonal boron nitride (h-BN) is highly promising for solid-state thermal neutron detector applications due to its many outstanding physical properties, especially its very large thermal neutron capture cross-section (~3840 barns for 10B), which is several orders of magnitude larger than those of most other isotopes. The focus of the present work is to carry out studies on h-BN thin film and detector properties to lay the foundation for the development of a direct-conversion solid-state thermal neutron detector with high sensitivity. The measured carrier mobility-lifetime (μτ) product of h-BN thin films grown on sapphire substrates is 2.83×10-7 cm2/V for electrons and holes, which is comparable to the value of about 10-7 cm2/V for GaN thin films grown on sapphire. Detectors based on h-BN thin films were fabricated and the nuclear reaction product pulse height spectra were measured. Under a bias of 20 V, very narrow individual peaks corresponding to the reaction product energies of α and Li particles as well as the sum peaks have been clearly resolved in the pulse height spectrum for the first time by a B-based direct-conversion semiconductor neutron detector. Our results indicate that h-BN thin film detectors possess unique advantages including small size, low weight, portability, low voltage operation and high energy resolution of specific reaction products.

  1. High-temperature stability of polycrystalline cubic boron nitride cutting tool materials in air

    International Nuclear Information System (INIS)

    Highlights: ► Oxidation of cBN–TiC composites is not passive within 550–1100 °C, obeying a linear rate law. ► Outward diffusion of Ti, Al and C, and inward diffusion of O2 controlled this oxidation. ► Ultimately, the oxidation scale is made of a porous outer layer (TiO2 and Al2O3 sub-layers) and an inner layer. ► Constitution and morphology of the inner layer vary with temperature. ► Formation and evaporation of B2O3 keeps the porosity within the oxidation scale. - Abstract: Thermal stability of cubic boron nitride (cBN)–TiC cutting tool material in air was analyzed using TGA and oxidation tests in a muffle furnace within the temperature range 550–1100 °C for a holding time of 60 min. A scanning electron microscope equipped with an energy dispersive X-ray spectroscopy analysis system was particularly used for the characterization of the oxidation scales obtained thereafter. The significance of the results obtained was discussed in terms of oxidation kinetics law, oxidation mechanisms as well as variation of constitution and morphology of the oxidation scale with temperature, keeping focus on the machining context.

  2. Mobility enhancement in graphene transistors on low temperature pulsed laser deposited boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, Md Ahsan, E-mail: uddin2@email.sc.edu, E-mail: gkoley@clemson.edu; Koley, Goutam, E-mail: uddin2@email.sc.edu, E-mail: gkoley@clemson.edu [Department of Electrical and Computer Engineering and Advanced Materials Research Laboratory, Clemson University, Clemson, South Carolina 29634 (United States); Department of Electrical Engineering, University of South Carolina, Columbia, South Carolina 29208 (United States); Glavin, Nicholas [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States); School of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Singh, Amol [Department of Electrical Engineering, University of South Carolina, Columbia, South Carolina 29208 (United States); Naguy, Rachel; Jespersen, Michael; Voevodin, Andrey [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States)

    2015-11-16

    Low temperature pulsed laser deposited (PLD) ultrathin boron nitride (BN) on SiO{sub 2} was investigated as a dielectric for graphene electronics, and a significant enhancement in electrical transport properties of graphene/PLD BN compared to graphene/SiO{sub 2} has been observed. Graphene synthesized by chemical vapor deposition and transferred on PLD deposited and annealed BN exhibited up to three times higher field effect mobility compared to graphene on the SiO{sub 2} substrate. Graphene field effect transistor devices fabricated on 5 nm BN/SiO{sub 2} (300 nm) yielded maximum hole and electron mobility of 4980 and 4200 cm{sup 2}/V s, respectively. In addition, significant improvement in carrier homogeneity and reduction in extrinsic doping in graphene on BN has been observed. An average Dirac point of 3.5 V and residual carrier concentration of 7.65 × 10{sup 11 }cm{sup −2} was observed for graphene transferred on 5 nm BN at ambient condition. The overall performance improvement on PLD BN can be attributed to dielectric screening of charged impurities, similar crystal structure and phonon modes, and reduced substrate induced doping.

  3. In Vivo Biodistribution and Toxicity of Highly Soluble PEG-Coated Boron Nitride in Mice

    Science.gov (United States)

    Liu, Bo; Qi, Wei; Tian, Longlong; Li, Zhan; Miao, Guoying; An, Wenzhen; Liu, Dan; Lin, Jing; Zhang, Xiaoyong; Wu, Wangsuo

    2015-12-01

    The boron nitride (BN) nanoparticles, as the structural analogues of graphene, are the potential biomedicine materials because of the excellent biocompatibility, but their solubility and biosafety are the biggest obstacle for the clinic application. Here, we first synthesized the highly soluble BN nanoparticles coated by PEG (BN-PEG) with smaller size (~10 nm), then studied their biodistribution in vivo through radioisotope (Tc99mO4 -) labeling, and the results showed that BN-PEG nanoparticles mainly accumulated in the liver, lung, and spleen with the less uptake by the brain. Moreover, the pathological changes induced by BN-PEG could be significantly observed in the sections of the liver, lung, spleen, and heart, which can be also supported by the test of biochemical indexes in serum. More importantly, we first observed the biodistribution of BN-PEG in the heart tissues with high toxicity, which would give a warning about the cardiovascular disease, and provide some opportunities for the drug delivery and treatment.

  4. Vertically aligned boron nitride nanosheets: chemical vapor synthesis, ultraviolet light emission, and superhydrophobicity.

    Science.gov (United States)

    Yu, Jie; Qin, Li; Hao, Yufeng; Kuang, Shengyong; Bai, Xuedong; Chong, Yat-Ming; Zhang, Wenjun; Wang, Enge

    2010-01-26

    Boron nitride (BN) is a promising semiconductor with a wide band gap ( approximately 6 eV). Here, we report the synthesis of vertically aligned BN nanosheets (BNNSs) on silicon substrates by microwave plasma chemical vapor deposition from a gas mixture of BF(3)-N(2)-H(2). The size, shape, thickness, density, and alignment of the BNNSs were well-controlled by appropriately changing the growth conditions. With changing the gas flow rates of BF(3) and H(2) as well as their ratio, the BNNSs evolve from three-dimensional with branches to two-dimensional with smooth surface and their thickness changes from 20 to below 5 nm. The growth of the BNNSs rather than uniform granular films is attributed to the particular chemical properties of the gas system, mainly the strong etching effect of fluorine. The alignment of the BNNSs is possibly induced by the electrical field generated in plasma sheath. Strong UV light emission with a broad band ranging from 200 to 400 nm and superhydrophobicity with contact angles over 150 degrees were obtained for the vertically aligned BNNSs. The present BNNSs possess the properties complementary to carbon nanosheets such as intrinsically semiconducting, high temperature stability, and high chemical inertness and may find applications in ultraviolet nanoelectronics, catalyst supports, electron field emission, and self-cleaning coatings, etc., especially those working at high temperature and in harsh environments. PMID:20047271

  5. Dry etching techniques for active devices based on hexagonal boron nitride epilayers

    International Nuclear Information System (INIS)

    Hexagonal boron nitride (hBN) has emerged as a fundamentally and technologically important material system owing to its unique physical properties including layered structure, wide energy bandgap, large optical absorption, and neutron capture cross section. As for any materials under development, it is necessary to establish device processing techniques to realize active devices based on hBN. The authors report on the advancements in dry etching techniques for active devices based on hBN epilayers via inductively coupled plasma (ICP). The effect of ICP radio frequency (RF) power on the etch rate and vertical side wall profile was studied. The etching depth and angle with respect to the surface were measured using atomic force microscopy showing that an etching rate ∼1.25 μm/min and etching angles >80° were obtained. Profilometer data and scanning electron microscope images confirmed these results. This work demonstrates that SF6 is very suitable for etching hBN epilayers in RF plasma environments and can serve as a guide for future hBN device processing

  6. Dry etching techniques for active devices based on hexagonal boron nitride epilayers

    Energy Technology Data Exchange (ETDEWEB)

    Grenadier, Samuel; Li, Jing; Lin, Jingyu; Jiang, Hongxing [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2013-11-15

    Hexagonal boron nitride (hBN) has emerged as a fundamentally and technologically important material system owing to its unique physical properties including layered structure, wide energy bandgap, large optical absorption, and neutron capture cross section. As for any materials under development, it is necessary to establish device processing techniques to realize active devices based on hBN. The authors report on the advancements in dry etching techniques for active devices based on hBN epilayers via inductively coupled plasma (ICP). The effect of ICP radio frequency (RF) power on the etch rate and vertical side wall profile was studied. The etching depth and angle with respect to the surface were measured using atomic force microscopy showing that an etching rate ∼1.25 μm/min and etching angles >80° were obtained. Profilometer data and scanning electron microscope images confirmed these results. This work demonstrates that SF{sub 6} is very suitable for etching hBN epilayers in RF plasma environments and can serve as a guide for future hBN device processing.

  7. Photoluminescence spectroscopy of electron-irradiation induced defects in cubic boron nitride (cBN)

    International Nuclear Information System (INIS)

    Cubic boron nitride is an ultra-hard material that is widely used in industrial applications where its specific mechanical properties make it the material of choice. Compared to diamond, which has similar applications, relatively little is known about the defects in cBN, their structure, electronic properties and their possible effects on the mechanical properties. We present results of photoluminescence spectroscopy at low temperature (<10 K) of two types of cBN irradiated at ambient temperature with 1.9 MeV electrons. All the samples were small (<1 mm diameter) single crystals of cBN. Three defect centres (with narrow lines at 2.28 eV, 2.15 eV and 1.98 eV) are introduced in both the amber-coloured and black-brown coloured samples by the irradiation. The amber coloured sample also shows a defect centre (at 1.65 eV) that is present before and after irradiation. Line shape analysis of the zero phonon lines of all three irradiation-induced centres shows that the lines are predominantly Gaussian in character, suggesting that line-type defects such as dislocations are a prevalent characteristic of these crystals. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Subangstrom Edge Relaxations Probed by Electron Microscopy in Hexagonal Boron Nitride

    Science.gov (United States)

    Alem, Nasim; Ramasse, Quentin M.; Seabourne, Che R.; Yazyev, Oleg V.; Erickson, Kris; Sarahan, Michael C.; Kisielowski, Christian; Scott, Andrew J.; Louie, Steven G.; Zettl, A.

    2012-11-01

    Theoretical research on the two-dimensional crystal structure of hexagonal boron nitride (h-BN) has suggested that the physical properties of h-BN can be tailored for a wealth of applications by controlling the atomic structure of the membrane edges. Unexplored for h-BN, however, is the possibility that small additional edge-atom distortions could have electronic structure implications critically important to nanoengineering efforts. Here we demonstrate, using a combination of analytical scanning transmission electron microscopy and density functional theory, that covalent interlayer bonds form spontaneously at the edges of a h-BN bilayer, resulting in subangstrom distortions of the edge atomic structure. Orbital maps calculated in 3D around the closed edge reveal that the out-of-plane bonds retain a strong π* character. We show that this closed edge reconstruction, strikingly different from the equivalent case for graphene, helps the material recover its bulklike insulating behavior and thus largely negates the predicted metallic character of open edges.

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

    Science.gov (United States)

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

    2016-03-01

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

  10. Evolution of Moiré Profiles from van der Waals Superstructures of Boron Nitride Nanosheets.

    Science.gov (United States)

    Liao, Yunlong; Cao, Wei; Connell, John W; Chen, Zhongfang; Lin, Yi

    2016-01-01

    Two-dimensional (2D) van der Waals (vdW) superstructures, or vdW solids, are formed by the precise restacking of 2D nanosheet lattices, which can lead to unique physical and electronic properties that are not available in the parent nanosheets. Moiré patterns formed by the crystalline mismatch between adjacent nanosheets are the most direct features for vdW superstructures under microscopic imaging. In this article, transmission electron microscopy (TEM) observation of hexagonal Moiré patterns with unusually large micrometer-sized lateral areas (up to ~1 μm(2)) and periodicities (up to ~50 nm) from restacking of liquid exfoliated hexagonal boron nitride nanosheets (BNNSs) is reported. This observation was attributed to the long range crystallinity and the contaminant-free surfaces of these chemically inert nanosheets. Parallel-line-like Moiré fringes with similarly large periodicities were also observed. The simulations and experiments unambiguously revealed that the hexagonal patterns and the parallel fringes originated from the same rotationally mismatched vdW stacking of BNNSs and can be inter-converted by simply tilting the TEM specimen following designated directions. This finding may pave the way for further structural decoding of other 2D vdW superstructure systems with more complex Moiré images. PMID:27188697

  11. Negative differential resistance in boron nitride graphene heterostructures: physical mechanisms and size scaling analysis.

    Science.gov (United States)

    Zhao, Y; Wan, Z; Xu, X; Patil, S R; Hetmaniuk, U; Anantram, M P

    2015-01-01

    Hexagonal boron nitride (hBN) is drawing increasing attention as an insulator and substrate material to develop next generation graphene-based electronic devices. In this paper, we investigate the quantum transport in heterostructures consisting of a few atomic layers thick hBN film sandwiched between graphene nanoribbon electrodes. We show a gate-controllable vertical transistor exhibiting strong negative differential resistance (NDR) effect with multiple resonant peaks, which stay pronounced for various device dimensions. We find two distinct mechanisms that are responsible for NDR, depending on the gate and applied biases, in the same device. The origin of first mechanism is a Fabry-Pérot like interference and that of the second mechanism is an in-plane wave vector matching when the Dirac points of the electrodes align. The hBN layers can induce an asymmetry in the current-voltage characteristics which can be further modulated by an applied bias. We find that the electron-phonon scattering suppresses the first mechanism whereas the second mechanism remains relatively unaffected. We also show that the NDR features are tunable by varying device dimensions. The NDR feature with multiple resonant peaks, combined with ultrafast tunneling speed provides prospect for the graphene-hBN-graphene heterostructure in the high-performance electronics. PMID:25991076

  12. Mobility enhancement in graphene transistors on low temperature pulsed laser deposited boron nitride

    International Nuclear Information System (INIS)

    Low temperature pulsed laser deposited (PLD) ultrathin boron nitride (BN) on SiO2 was investigated as a dielectric for graphene electronics, and a significant enhancement in electrical transport properties of graphene/PLD BN compared to graphene/SiO2 has been observed. Graphene synthesized by chemical vapor deposition and transferred on PLD deposited and annealed BN exhibited up to three times higher field effect mobility compared to graphene on the SiO2 substrate. Graphene field effect transistor devices fabricated on 5 nm BN/SiO2 (300 nm) yielded maximum hole and electron mobility of 4980 and 4200 cm2/V s, respectively. In addition, significant improvement in carrier homogeneity and reduction in extrinsic doping in graphene on BN has been observed. An average Dirac point of 3.5 V and residual carrier concentration of 7.65 × 1011 cm−2 was observed for graphene transferred on 5 nm BN at ambient condition. The overall performance improvement on PLD BN can be attributed to dielectric screening of charged impurities, similar crystal structure and phonon modes, and reduced substrate induced doping

  13. Adsorption properties of boroxol ring doped zigzag boron nitride nanotube toward NO molecule using DFT

    Science.gov (United States)

    Zahedi, Ehsan; Babaie, Mahsa; Bahmanpour, Hooman

    2016-05-01

    In previous researches it is demonstrated that reactivity and sensitivity of boron nitride nanotubes (BNNTs) toward gas molecules can be modified by impurity. In this work, oxygen defect for three nitrogen sites was used to study the adsorption of NO molecule through the surface of boroxol ring of oxygen doped BNNT (7,0) with different adsorption patterns, including side-on and end-on. All calculations are performed using the DFT-B3LYP/6-31G∗ level of theory, and their electronic energies are corrected by gCP and D3 correction terms. High binding energies indicate that NO molecule undergoes chemical adsorption with large charge transfer from the tube which can significantly change electronic properties of the tube. Density of state (DOS) and partial DOS (PDOS) analyses revealed that adsorption of NO molecule on the boroxol ring position is covalent in nature with significant effect on the electronic properties of tube. The Laplacian of electron density, Lagrangian kinetic energy density, Hamiltonian kinetic energy density and potential energy density at bond critical points between the tube and NO indicate that the interaction between the tube and NO molecule is covalent in nature. Topological analysis of the electron localization function shows that electrons in the new formed bonds are approximately localized, meaning that the nature of adsorption process is chemical covalent. The studied nanotube is a suitable candidate to filter and eliminate NO gas molecule.

  14. Theoretical investigation of methane adsorption onto boron nitride and carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Masoud Darvish Ganji, Amir Mirnejad and Ali Najafi

    2010-01-01

    Full Text Available Methane adsorption onto single-wall boron nitride nanotubes (BNNTs and carbon nanotubes (CNTs was studied using the density functional theory within the generalized gradient approximation. The structural optimization of several bonding configurations for a CH4 molecule approaching the outer surface of the (8,0 BNNT and (8,0 CNT shows that the CH4 molecule is preferentially adsorbed onto the CNT with a binding energy of −2.84 kcal mol−1. A comparative study of nanotubes with different diameters (curvatures reveals that the methane adsorptive capability for the exterior surface increases for wider CNTs and decreases for wider BNNTs. The introduction of defects in the BNNT significantly enhances methane adsorption. We also examined the possibility of binding a bilayer or a single layer of methane molecules and found that methane molecules preferentially adsorb as a single layer onto either BNNTs or CNTs. However, bilayer adsorption is feasible for CNTs and defective BNNTs and requires binding energies of −3.00 and −1.44 kcal mol−1 per adsorbed CH4 molecule, respectively. Our first-principles findings indicate that BNNTs might be an unsuitable material for natural gas storage.

  15. Ab-Initio Calculations of the Electronic Properties of Boron Nitride

    Science.gov (United States)

    Stewart, Anthony; Khamala, Bethuel; Hart, Daniel; Bagayoko, Diola

    2014-03-01

    The potential of Boron Nitride (BN) in nanotechnology is tremendous. BN in its bulk form has a wide band gap with excellent thermal and chemical stability. BN structures can be tailored using various techniques in order to obtain desired materials properties. The State-of-the-art Proton Exchange Membrane Fuel Cell (PEMFCs) technology exploits graphitized carbon as a support for platinum-type catalysts. However, some forms of carbon are susceptible to long-term durability issues such as corrosion which is a detriment to fuel cell performance and viability. Novel non-carbon supports such as BN may provide a pathway for addressing the durability and performance issues associated with carbon support materials. We present preliminary theoretical studies, using an linear combination of atomic orbital (LCAO) quantum chemistry package from Ames Laboratory, of the electronic properties of this potentially important material. Our calculated band gap of 6.48 eV for the cubic structure, obtained with an LDA potential and the BZW-EF method, is in agreement with experiment. LASIGMA/ NNSA_MSIP.

  16. Synthesis of Large and Few Atomic Layers of Hexagonal Boron Nitride on Melted Copper

    Science.gov (United States)

    Khan, Majharul Haque; Huang, Zhenguo; Xiao, Feng; Casillas, Gilberto; Chen, Zhixin; Molino, Paul J.; Liu, Hua Kun

    2015-01-01

    Hexagonal boron nitride nanosheets (h-BNNS) have been proposed as an ideal substrate for graphene-based electronic devices, but the synthesis of large and homogeneous h-BNNS is still challenging. In this contribution, we report a facile synthesis of few-layer h-BNNS on melted copper via an atmospheric pressure chemical vapor deposition process. Comparative studies confirm the advantage of using melted copper over solid copper as a catalyst substrate. The former leads to the formation of single crystalline h-BNNS that is several microns in size and mostly in mono- and bi-layer forms, in contrast to the polycrystalline and mixed multiple layers (1-10) yielded by the latter. This difference is likely to be due to the significantly reduced and uniformly distributed nucleation sites on the smooth melted surface, in contrast to the large amounts of unevenly distributed nucleation sites that are associated with grain boundaries and other defects on the solid surface. This synthesis is expected to contribute to the development of large-scale manufacturing of h-BNNS/graphene-based electronics.

  17. Strain-Engineered Graphene Grown on Hexagonal Boron Nitride by Molecular Beam Epitaxy

    Science.gov (United States)

    Summerfield, Alex; Davies, Andrew; Cheng, Tin S.; Korolkov, Vladimir V.; Cho, YongJin; Mellor, Christopher J.; Foxon, C. Thomas; Khlobystov, Andrei N.; Watanabe, Kenji; Taniguchi, Takashi; Eaves, Laurence; Novikov, Sergei V.; Beton, Peter H.

    2016-01-01

    Graphene grown by high temperature molecular beam epitaxy on hexagonal boron nitride (hBN) forms continuous domains with dimensions of order 20 μm, and exhibits moiré patterns with large periodicities, up to ~30 nm, indicating that the layers are highly strained. Topological defects in the moiré patterns are observed and attributed to the relaxation of graphene islands which nucleate at different sites and subsequently coalesce. In addition, cracks are formed leading to strain relaxation, highly anisotropic strain fields, and abrupt boundaries between regions with different moiré periods. These cracks can also be formed by modification of the layers with a local probe resulting in the contraction and physical displacement of graphene layers. The Raman spectra of regions with a large moiré period reveal split and shifted G and 2D peaks confirming the presence of strain. Our work demonstrates a new approach to the growth of epitaxial graphene and a means of generating and modifying strain in graphene. PMID:26928710

  18. Ab initio investigation of the SCN− chemisorption of single-walled boron nitride nanotubes

    International Nuclear Information System (INIS)

    Highlights: ► We explored the adsorption behavior of the SCN− on outer surface BNNTs via DFT. ► We reported the NBO charge distribution of SCN− on BNNTs surface. ► Chemisorptions are observed for SCN− on Al- and Ga-doped BNNTs. ► Notable changes are observed in the electronic properties of BNNT after doping. - Abstract: The thiocyanate anion (SCN−) adsorption capacity of zigzag single-walled boron nitride nanotubes (SWBNNTs) is studied via first-principles theory. Binding energy corresponding to the most stable configuration of SCN−/BNNT is found to be −148.42 kJ mol−1, which is typical for the chemisorptions. Our results indicate that both aluminum and gallium doping can significantly enhance the adsorption energy of SCN−/BNNTs complexes. Our electronic results reveal that there is a significant orbital hybridization between two species in adsorption process being an evidence of strong interaction. Thus, we arrive at the prediction that the BNNTs nanocage can be implemented as suitable sensor for practical applications.

  19. Hexagonal Boron Nitride assisted transfer and encapsulation of large area CVD graphene.

    Science.gov (United States)

    Shautsova, Viktoryia; Gilbertson, Adam M; Black, Nicola C G; Maier, Stefan A; Cohen, Lesley F

    2016-01-01

    We report a CVD hexagonal boron nitride (hBN-) assisted transfer method that enables a polymer-impurity free transfer process and subsequent top encapsulation of large-area CVD-grown graphene. We demonstrate that the CVD hBN layer that is utilized in this transfer technique acts as a buffer layer between the graphene film and supporting polymer layer. We show that the resulting graphene layers possess lower doping concentration, and improved carrier mobilities compared to graphene films produced by conventional transfer methods onto untreated SiO2/Si, SAM-modified and hBN covered SiO2/Si substrates. Moreover, we show that the top hBN layer used in the transfer process acts as an effective top encapsulation resulting in improved stability to ambient exposure. The transfer method is applicable to other CVD-grown 2D materials on copper foils, thereby facilitating the preparation of van der Waals heterostructures with controlled doping. PMID:27443219

  20. Quasiparticle Band Gaps of Graphene and Graphone on Hexagonal Boron Nitride Substrate

    Science.gov (United States)

    Kharche, Neerav; Nayak, Saroj

    2012-02-01

    Graphene holds great promise for post-silicon electronics; however, it faces two main challenges: opening up a band gap and finding a suitable substrate material. Graphene on hexagonal boron nitride (hBN) substrate provides a potential system to overcome these challenges. While theoretical studies suggested a possibility of a finite band gap of graphene on hBN, recent experimental studies find no band gap. We have studied graphene-hBN system using the first-principles density functional method and the many-body perturbation theory within GW approximation [1]. A Bernal stacked graphene on hBN has a band gap on the order of 0.1 eV, which disappears when graphene is misaligned with respect to hBN. The latter is the likely scenario in realistic devices. In contrast, if graphene supported on hBN is hydrogenated, the resulting system (graphone) exhibits band gaps larger than 2.5 eV. The graphone band gap is due to chemical functionalization and is robust in the presence of misalignment, however, it reduces by about 1 eV due to the polarization effects at the graphone/hBN interface.[4pt] [1] N. Kharche and S. K. Nayak, Nano Lett., DOI: 10.1021/nl202725w, (2011).

  1. Theoretical studies of urea adsorption on single wall boron-nitride nanotubes

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • DFT base investigations of urea molecule with various type of armchair BNNTs studied. • The adsorption of urea molecule is observed to be exothermic and physical in nature. • The most effective interaction occurs when urea located inside of BNNTs. • The electronic analysis indicated ΔEg values changed after urea adsorption. - Abstract: Surface modification of a boron nitride nanotube (BNNT) with urea molecule was investigated in terms of its energetic, geometric, and electronic properties using B3LYP and PW91 density functionals. In this investigation, various armchair (n,n) nanotubes, where n = 5, 6, 7 have been used. Two different interaction modes, including interaction with outer layer and inner layer of tube were studied. The results indicated that the adsorption of single urea molecule in all of its configurations is observed to be exothermic and physical in nature. Interestingly, the adsorption energy for the most stable configuration of urea was observed when the molecule located inside of the nanotube. Besides, the adsorption of urea on BNNTs changes the conductivity of nanotube

  2. Antenna-coupled photon emission from hexagonal boron nitride tunnel junctions

    Science.gov (United States)

    Parzefall, M.; Bharadwaj, P.; Jain, A.; Taniguchi, T.; Watanabe, K.; Novotny, L.

    2015-12-01

    The ultrafast conversion of electrical signals to optical signals at the nanoscale is of fundamental interest for data processing, telecommunication and optical interconnects. However, the modulation bandwidths of semiconductor light-emitting diodes are limited by the spontaneous recombination rate of electron-hole pairs, and the footprint of electrically driven ultrafast lasers is too large for practical on-chip integration. A metal-insulator-metal tunnel junction approaches the ultimate size limit of electronic devices and its operating speed is fundamentally limited only by the tunnelling time. Here, we study the conversion of electrons (localized in vertical gold-hexagonal boron nitride-gold tunnel junctions) to free-space photons, mediated by resonant slot antennas. Optical antennas efficiently bridge the size mismatch between nanoscale volumes and far-field radiation and strongly enhance the electron-photon conversion efficiency. We achieve polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling and establish a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields.

  3. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties.

    Science.gov (United States)

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

    2016-06-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ∼4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (∼60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications. PMID:27227818

  4. Tuning dissociation using isoelectronically doped graphene and hexagonal boron nitride: Water and other small molecules

    Science.gov (United States)

    Al-Hamdani, Yasmine S.; Alfè, Dario; von Lilienfeld, O. Anatole; Michaelides, Angelos

    2016-04-01

    Novel uses for 2-dimensional materials like graphene and hexagonal boron nitride (h-BN) are being frequently discovered especially for membrane and catalysis applications. Still however, a great deal remains to be understood about the interaction of environmentally and industrially relevant molecules such as water with these materials. Taking inspiration from advances in hybridising graphene and h-BN, we explore using density functional theory, the dissociation of water, hydrogen, methane, and methanol on graphene, h-BN, and their isoelectronic doped counterparts: BN doped graphene and C doped h-BN. We find that doped surfaces are considerably more reactive than their pristine counterparts and by comparing the reactivity of several small molecules, we develop a general framework for dissociative adsorption. From this a particularly attractive consequence of isoelectronic doping emerges: substrates can be doped to enhance their reactivity specifically towards either polar or non-polar adsorbates. As such, these substrates are potentially viable candidates for selective catalysts and membranes, with the implication that a range of tuneable materials can be designed.

  5. Ultra-thin epitaxial films of graphite and hexagonal boron nitride on solid surfaces

    CERN Document Server

    Oshima, C

    1997-01-01

    In this article, we have reviewed the recent progress of the experimental studies on ultra-thin films of graphite and hexagonal boron nitride (h-BN) by using angle-resolved electron spectroscopy together with other techniques. The fundamental properties of these high-quality films are discussed on the basis of the data on dispersion relations of valence electrons, phonon dispersion etc. The interfacial orbital mixing of the pi-state of the monolayer graphite (MG) with the d states of the reactive substrates is the origin for the phonon softening, expansion of the nearest-neighbour C-C distance, modification of the pi-band, low work function, and two-dimensional plasmons with high electron density, etc. In the cases of weak mixing at the interface between the MG and relatively inert substrates, the observed properties of the MG are very close to the bulk ones. In contrast to the case for MG, the interfacial interaction between the h-BN monolayer and the substrate is weak. (author)

  6. Low pressure synthesis of boron nitride with(C2H5)2O·BF3 and Li3N precursor

    Institute of Scientific and Technical Information of China (English)

    WANG Shao-bo; XU Xiao-wei; FAN Hui-li; LI Yu-ping

    2005-01-01

    Cubic boron nitride(c-BN) was synthesized through benzene thermal method at a lower temperature of 300 ℃ by selecting liquid(C2H5)2O·BF3 and Li3N as reactants. Hexagonal boron nitride(h-BN) and orthorhombic boron nitride(o-BN) were also obtained. The samples were characterized by X-ray powder diffractometry and Fourier transformation infrared spectroscopy. The results show that all the BF3, BCl3 and BBr3 in the same family compounds can react with Li3N to synthesize BN since the strongest bond of B-F can be broken. Compared with BBr3, liquid (C2H5)2O·BF3 is cheaper, less toxic and more convenient to operate. Li3N not only provides nitrogen source but also has catalytic effect on accelerating the formation of c-BN at low temperature and pressure.

  7. The Influence of Surface-Active Agent on the Micro-Morphology and Crystallinity of Spherical Hexagonal Boron Nitride.

    Science.gov (United States)

    Zhang, Ning; Liu, Huan; Kan, Hongmin; Wang, Xiaoyang; Long, Haibo; Zhou, Yonghui

    2015-08-01

    This search used the low-cost boric acid and borax as a source of boron, urea as a nitrogen source, surface-active agent Dodecyl benzenesulfonic acid (SDBS) as a dispersant, and thus prepared different micro-morphology and crystallinity hexagonal boron nitride powders under a flowing ammonia atmosphere at a nitriding temperature of 900 °C. The effect of the surface-active agent (SDBS) content on the crystallinity and micro-morphology of hexagonal boron nitride powders was studied, and the corresponding relationship between micro-morphology and crystallinity was explored. The results showed that under a certain synthetic process (900 °C for 3 h), the surfactant content had affected the crystallinity and micro-morphology of h-BN powders. Without the added surfactant, the graphitization index (GI) was 3.61, and micro-morphology of h-BN powders. was spherical, the distribution of ball diameters was uneven, and there was also significant particle agglomeration, with some particles even exhibiting adhesion, sintering necks, and high sphericity and diameter. When the added SDBS percentages were 2%, 4% and 6%, the graphitization index (GI) decreased to 2.98, 2.58 and 2.41 respectively: the corresponding crystallinity improved significantly. When the surfactant SDBS content was higher (10%), the diameter distribution of the h-BN powders was even, but there was evidence of agglomeration of particles and particle adhesion. The crystallinity decreased when the GI value was increased to 4. When the surfactant SDBS content was 6%, the dispersion of h-BN powders was at its optimum, and the particle size distribution was at its most uniform. Meanwhile the GI value was at its lowest, and the crystallinity at its highest. PMID:26369229

  8. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties

    Science.gov (United States)

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

    2016-05-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ~4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (~60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications.Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability

  9. A model of the gas-phase chemistry of boron nitride CVD from BCl3 and NH3

    International Nuclear Information System (INIS)

    The kinetics of gas-phase reactions occurring during the CVD of boron nitride (BN) from BCl3 and NH3 are investigated using an elementary reaction mechanism whose rate constants were obtained from theoretical predictions and literature sources. Plug-flow calculations using this mechanism predict that unimolecular decomposition of BCl3 is not significant under typical CVD conditions, but that some NH3 decomposition may occur, especially for deposition occurring at atmospheric pressure. Reaction of BCl3 with NH3 is rapid under CVD conditions and yields species containing both boron and nitrogen. One of these compounds, Cl2BNH2, is predicted to be a key gas-phase precursor to BN

  10. Bonding distances as Exact Sums of the Radii of the Constituent Atoms in Nanomaterials - Boron Nitride and Coronene

    CERN Document Server

    Heyrovska, Raji

    2010-01-01

    This paper presents for the first time the exact structures at the atomic level of two important nanomaterials, boron nitride and coronene. Both these compounds are hexagonal layer structures similar to graphene in two dimensions and to graphite in three-dimensions. However, they have very different properties: whereas graphene is a conductor, h-BN is an electrical insulator and coronene is a polycyclic aromatic hydrocarbon of cosmological interest. The atomic structures presented here are based on bond lengths as the sums of the atomic radii.

  11. Excitation wavelength dependence of water-window line emissions from boron-nitride laser-produced plasmas

    OpenAIRE

    Crank, M.; Harilal, S. S.; S.M. Hassan; Hassanein, A.

    2012-01-01

    We investigated the effects of laser excitation wavelength on water-window emission lines of laser-produced boron-nitride plasmas. Plasmas are produced by focusing 1064 nm and harmonically generated 532 and 266 nm radiation from a Nd:YAG laser on BN target in vacuum. Soft x-ray emission lines in the water-window region are recorded using a grazing-incidence spectrograph. Filtered photodiodes are used to obtain complementary data for water-window emission intensity and angular dependence. Spec...

  12. Ion beam-assisted deposition of boron nitride from a condensed layer of diborane and ammonia at 78 K

    International Nuclear Information System (INIS)

    This paper examines the ion beam-assisted deposition (IBAD) of thin boron nitride films using cryogenically condensed precursors. Low energy (1100 eV) argon ad (2000 eV) deuterated ammonia beams with currents of 600--850 nA were used to mix and initiate reactions in frozen (90 K) layers of diborane (B2H6 and ammonia (NH3) or only B2H6, respectively. The resulting film is shown to be an amorphous BN coating approximately 30 Angstrom thick

  13. Investigation of wear and tool life of coated carbide and cubic boron nitride cutting tools in high speed milling

    OpenAIRE

    Twardowski, P.; Legutko, S.; G. Krolczyk; S. Hloch

    2015-01-01

    The objective of the investigation was analysis of the wear of milling cutters made of sintered carbide and of boron nitride. The article presents the life period of the cutting edges and describes industrial conditions of the applicability of tools made of the materials under investigation. Tests have been performed on modern toroidal and ball-end mill cutters. The study has been performed within a production facility in the technology of high speed machining of 55NiCrMoV6 and X153CrMoV1...

  14. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ULTRAFINE WC/Co CEMENTED CARBIDES WITH CUBIC BORON NITRIDE AND Cr₃C₂ ADDITIONS

    OpenAIRE

    Genrong Zhang; Haiyan Chen; Dong Lihua; Yin,; Li Kun

    2016-01-01

    This study investigates the microstructure and mechanical properties of ultrafine tungsten carbide and cobalt (WC/Co) cemented carbides with cubic boron nitride (CBN) and chromium carbide (Cr₃C₂) fabricated by a hot pressing sintering process. This study uses samples with 8 wt% Co content and 7.5 vol% CBN content, and with different Cr₃C₂ content ranging from 0 to 0.30 wt%. Based on the experimental results, Cr₃C₂ content has a significant influence on inhibiting abnormal grain growth and dec...

  15. Configurable three-dimensional boron nitride-carbon architecture and its tunable electronic behavior with stable thermal performances.

    Science.gov (United States)

    Loeblein, Manuela; Tay, Roland Yingjie; Tsang, Siu Hon; Ng, Wei Beng; Teo, Edwin Hang Tong

    2014-08-13

    Recent developments of 3D-graphene and 3D-boron-nitride have become of great interest owing to their potential for ultra-light flexible electronics. Here we demonstrate the first synthesis of novel 3D-BNC hybrids. By specifically controlling the compositions of C and BN, new fascinating properties are observed, such as highly tunable electrical conductivity, controllable EMI shielding properties, and stable thermal conductivity. This ultra-light hybrid opens up many new applications such as for electronic packaging and thermal interface materials (TIMs). PMID:24789084

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

    OpenAIRE

    Samuel Bernard; Philippe Miele

    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 che...

  17. Damage effects from medium-energy ion bombardment during the growth of cubic-boron nitride films

    International Nuclear Information System (INIS)

    Cubic-boron nitride (c-BN) films with low stress have been produced by simultaneous 35 keV N+ ion implantation during growth by ion assisted sputtering. The stress release is achieved at the lost of a decrease in the c-BN content. Despite this fact, films with a high c-BN content and relatively large thickness (∼0.4 μm) have been produced. The decrease on the c-BN content is discussed in terms of the damage induced by the medium-energy ion implantation

  18. Polar Effects on the Thermal Conductivity of Cubic Boron Nitride under Pressure

    Science.gov (United States)

    Mukhopadhyay, Saikat; Stewart, Derek A.

    2014-07-01

    We report the lattice thermal conductivity (κ) of cubic boron nitride (c-BN) under pressure calculated using density functional theory. Pressure was used to manipulate the c-BN phonon dispersion and study its effect on thermal conductivity. These results were compared to c-BN's mass-equivalent, nonpolar counterpart, diamond, in order to isolate the effect of polar bonds on thermal conductivity. Unlike diamond, the variation of κ at room temperature (κRT) with applied pressure in c-BN is nonlinear in the low-pressure regime followed by a transition to a linear regime with a distinct change in the slope at P >114 GPa. We find that the change in κ with pressure cannot be described with power law expressions commonly used for Earth mantle materials. The nonlinearity in the low-pressure regime can be related to the nonlinear change in LO-TO gap, group velocities, and specific heat with increasing pressure. In addition, we find that, although optical branch contributions to thermal conductivity are small (˜2% at RT), the rise in κRT for P >114 GPa is due to (1) the decoupling of the longitudinal acoustic branch from the optical branches and (2) depopulation of the optical branches. These lead to a sharp reduction in acoustic-acoustic-optic (a-a-o) scattering and a discrete change in the acoustic phonon mean free paths. This study illustrates the importance of optical branches and their interactions with acoustic branches in determining the total thermal conductivity of polar materials. This finding is also relevant for current research in geologic minerals under pressure and the design of thermoelectrics.

  19. Nucleation and growth of cubic boron nitride films produced by ion-assisted pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Friedmann, T.A.; Medlin, D.L.; Mirkarimi, P.B.; McCarty, K.F.; Klaus, E.J.; Boehme, D.R.; Johnsen, H.A.; Mills, M.J.; Ottesen, D.K. [Sandia National Labs., Livermore, CA (United States)

    1993-12-31

    We are studying the boron nitride system using a pulsed excimer laser to ablate from hexagonal BN (cBN) targets to form cubic BN (cBN) films. We are depositing BN films on heated (25--800C) Si (100) surfaces and are using a broad-beam ion source operated with Ar and N{sub 2} source gases to produce BN films with a high percentage of sp{sup 3}-bonded cBN. In order to optimize growth and nucleation of cBN films, parametric studies of the growth parameters have been performed. The best films to date show >85% sp{sup 3}-bonded BN as determined from Fourier-transform infrared (FTIR) reflection spectroscopy. High resolution transmission electron microscopy (TEM) and selected area electron diffraction confirm the presence of cBN in these samples. The films are polycrystalline and show grain sizes up to 30--40 mn. We find from both the FTIR and TEM analyses that the cBN content in these films evolves with growth time. Initially, the films are deposited as hBN and the cBN nucleates on this hBN underlayer. Importantly, the position of the cBN IR phonon also changes with growth time. Initially this mode appears near 1130 cm{sup {minus}1} and the position decreases with growth time to a constant value of 1085 cm{sup {minus}1}. Since in bulk cBN this IR mode appears at 1065 cm{sup {minus}1}, a large compressive stress induced by the ion bombardment is suggested. In addition, we report on the variation in cBN percentage with temperature.

  20. Thermal Conductance at the 2D MoS2-hexagonal Boron Nitride Interface

    Science.gov (United States)

    Liu, Yi; Hippalgaonkar, Kedar; Ong, Zhun Yong; Thong, John Tl; Qiu, Chengwei

    In recent years, a number of 2D heterostructure devices have emerged, including graphene/hexagonal boron nitride (h-BN), graphene/MoS2 and MoS2/ h-BN. Among them, MoS2/ h-BN field-effect transistors with MoS2 channels and h-BN dielectric have been reported to have higher carrier mobility and reduced hysteresis compared to MoS2 on SiO2. Despite relatively high in-plane thermal conductivity of MoS2 and h-BN, heat dissipation from these 2D devices is mainly limited by heat transfer in the vertical direction. Consequently, their operating temperatures are strongly influenced by the interface thermal conductance. In this work, we demonstrate the measurement of interface thermal conductance between MoS2 and h-BN. This is realized by electrically heating MoS2 and monitoring their temperatures through Raman spectroscopy. The obtained interface thermal conductance between MoS2 and h-BN is 1.77 MW/m2K, smaller than the reported value for the graphene/ h-BN interface, due to the weak coupling of phonon modes between MoS2 and h-BN based on our NEGF calculation. The low interface thermal conductance value suggests this interface is not favorable for heat dissipation, and should be considered carefully for the design of electronic and optoelectronic devices based on MoS2/ h-BN heterostructures.