- A room-temperature approach to boron nitride hollow spheres
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Boron nitride hollow spheres were synthesized by the reaction of BBr 3 and NaNH2 at room temperature; X-ray powder diffraction pattern could be indexed as hexagonal BN with the lattice constants of a=2.482 and c=6.701?; high-resolution transmission electron microscopy image showed the hollow spheres consisted of BN nanoparticles, with diameter between 80 and 300 nm; a possible formation mechanism of BN hollow spheres was discussed.
- Chen, Luyang,Gu, Yunle,Shi, Liang,Yang, Zeheng,Ma, Jianhua,Qian, Yitai
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- A novel precursor for synthesis of pure boron nitride nanotubes
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A novel precursor, a mixture of B2O2 and Mg which is generated in situ by reacting B and MgO at 1300°C, can be used to effectively synthesize bulk amounts of pure BN nanotubes with Mg evaporated from the final product; transmission electron microscope observation for the synthesized BN nanotubes indicates that defects present strongly depend on the tube diameter.
- Tang, Chengchun,Bando, Yoshio,Sato, Tadao,Kurashima, Keiji
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- One pot synthesis of ultrathin boron nitride nanosheet-supported nanoscale zerovalent iron for rapid debromination of polybrominated diphenyl ethers
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To minimize the aggregation and size effects of nanoscale zerovalent iron (nZVI), nZVI/boron nitride nanosheets (BNNSs) composites were fabricated via a one pot autoclave route on a gram-scale. BNNSs (1-6 nm) supported nZVI (4-40 nm) was prepared by heating NaBH4, FeCl3 and NaN3 at 400 °C. The BNNSs matrixes benefit the retention of the activity for nZVI. The high specific surface area (182 m2 g -1) and density of structural defects allows enrichment of the pollutants, leading to a relatively high conversion by the nearby supported nZVI. Meanwhile, the gram-scale bifunctional nZVI/BNNSs have both reductive and magnetic properties, which make them highly reactive towards the test polybromodiphenyl ethers (PBDEs) and also easy to separate. The reaction rate of nZVI/BNNSs is almost twice that of the nZVI made in our lab. This study indicates that gram-scale nZVI/BNNSs are highly efficient and effective materials that can be utilized to treat PBDEs-contaminated sites, followed by the sequential magnetic separation. The Royal Society of Chemistry 2013.
- Wang, Liancheng,Ni, Shou-Qing,Guo, Chunli,Qian, Yitai
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- Insight into carbon nanotubes-template reaction at high temperature
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Different types of carbon nanotubes (CNTs), including multi-walled CNTs, single-walled CNTs bundles, isolated single- or double-walled CNTs and nano-bamboo structured CNTs, were used as the templates to synthesize SiC and BN one-dimensional nanostructures
- Hu, Long,Li,Ding,Tang,Qi
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- New Phase of sp3-Bonded BN: The 5H Polytype
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A new phase of sp3-bonded BN, that is, 5H polytype, has been found. The representative lattice parameters a and c were determined to be 2.528 and 10.407 Angstroem, respectively. The new BN phase was prepared by chemical vapor deposition assisted with 193 nm laser irradiation of the surface. Source gases were diborane and ammonia diluted in argon and hydrogen. The substrate temperature was 850 degC.
- Komatsu, Shojiro,Okada, Katsuyuki,Shimizu, Yoshiki,Moriyoshi, Yusuke
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- X-ray absorption near edge structure study of BN nanotubes and nanothorns
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Two boron nitride (BN) nanostructures, the bamboo-like nanotubes and nanothoms where the nanosize h-BN layers are randomly stacked looking like thorns, were synthesized selectively via thermal chemical vapor deposition of B/B2O3 under the NH3 flow at 1200?°C. Electron energy-loss spectroscopy reveals the N-rich h-BN layers with a ratio of B/N = 0.75-0.85. Angle-resolved X-ray absorption near edge structure of these two N-rich nanostructures has been compared with that of h-BN microcrystals. The ??* transition in the N K-edge shifts to the lower energy by 0.8-1.0 eV from that of h-BN microcrystals, and the second-order signals of N ls electrons become significant. We suggest that the N enrichment would decrease the band gap of nanostructures from that of h-BN microcrystals. The Raman spectrum shows the peak broadening due to the defects of N-rich h-BN layers. ? 2005 American Chemical Society.
- Choi, Hyun Chul,Bae, Seung Yong,Jang, Woo Sung,Park, Jeunghee,Song, Ha Jin,Shin, Hyun-Joon
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- Characterization of boron nitride films deposited from BCl3-NH3-H2 mixtures in chemical vapour infiltration conditions
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Boron nitride (BN) thin films deposited by isopressure and isothermal chemical vapour infiltration (ICVI) from BCl3-NH3-N2 mixtures have been characterized from a physicochemical point of view as functions of both the deposition conditions and the destabilizing action of moisture. As-deposited (deposited at 773 K and post-treated at 1273 K), the BN films are turbostractic (d002 = 0.36 nm, Lc = 1.5 nm), have a low density (1.4 g cm-3) and contain oxygen (about 20 at%). A first oxygen content (191.5 eV by XPS) is inserted in the films during the CVI step in relation to the hygroscopy of intermediate solid products and the quasi-equilibrium between the formation of BN and B2O3. A second oxygen content (192.5 eV) is due to the hydrolysis of BN by moisture which induces a very drastic transformation of BN. This destabilization affects both boron and nitrogen atoms and leads to the formation of ammonium borate hydrates. Different post-treatments have been investigated to stabilize the BN films and it appears that nitriding under ammonia is the most efficient.
- Cholet, V.,Vandenbulcke, L.,Rouan, J. P.,Baillif, P.,Erre, R.
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- Formation of B, Al, Ga, and Si nitrides from their oxides: A reactive laser ablation study
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Nitrides such as Si3N4 and GaN are made by the reaction of the respective oxide with N2 or NH3. In order to understand the mechanism of formation of nitrides, reactive laser ablation of B2O3, Al2O3, Ga2O 3, and SiO2 in pure form, as well as in mixture with carbon, has been carried out in an atmosphere of nitrogen or ammonia in a pulsed supersonic jet. The reaction of N2 with SiO2 gives nitridic species such as Si2Ny (y≤5) in the vapor phase. On reaction with N2 in the presence of carbon, B 2O3 and Ga2O3 yield species of the type BxNy and GaNy, respectively. Nitridic species are preponderant in the reaction with ammonia only in the case of SiO2. Al2O3 predominantly gives oxynitridic species under the reaction conditions examined.
- Raina,Kulkarni,Rao
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- A low-temperature coreduction route to boron nitride flakes and hollow spheres
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Boron nitride flakes and hollow spheres were synthesized by coreduction of NH4Cl and BBr3 using sodium as reductant. X-ray powder diffraction (XRD) pattern could be indexed as hexagonal BN. The X-ray photoelectron spectra (XPS) were used to determine the composition ratio, which is B:N = 1:1.05. The transmission electron microscopy (TEM) images showed flake-like and hollow spherical morphology.
- Chen, Luyang,Gu, Yunle,Shi, Liang,Yang, Zeheng,Ma, Jianhua,Qian, Yitai
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- Composition and microstructure of chemically vapor-deposited boron nitride, aluminum nitride, and boron nitride + aluminum nitride composites
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The composition and microstructure of dispersed-phase ceramic composites containing BN and AlN as well as BN and AlN single-phase ceramics prepared by chemical vapor deposition have been characterized using X-ray diffraction, scanning electron microscopy, electron microprobe, and transmission electron microscopy techniques. Under certain processing conditions, the codeposited coating microstructure consists of small single-crystal AlN fibers (whiskers) surrounded by a turbostatic BN matrix. Other processing conditions resulted in single-phase films of AlN with a fibrous structure. The compositions of the codeposits range from 2 to 50 mol% BN, 50 to 80 mol% AlN with 7% to 25% oxygen impurity as determined by electron microprobe analysis.
- Hanigofsky,More,Lackey,Lee,Freeman
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- Large-scale fabrication of boron nitride nanohorn
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Boron nitride nanohorns (BNNHs) are synthesized in large scale. Their morphology and structure were investigated by scanning electron microscopy and transmission electron microscopy. The hollow conical structure and particular aggregation behavior are rev
- Zhi, Chunyi,Bando, Yoshio,Tang, Chengchun,Golberg, Dmitri,Xie, Rongguo,Sekiguchi, Takashi
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- Infrared response of multiwalled boron nitride nanotubes
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We report the infrared (IR) response of bulk samples of multiwalled boron nitride nanotubes, produced by a substitution reaction from single walled carbon nanotubes, which is dominated by two characteristic BN-vibrations at 800 and 1372 cm-1.
- Borowiak-Palen,Pichler,Fuentes,Bendjemil,Liu,Graff,Behr,Kalenczuk,Knupfer,Fink
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- Boron nitride microfibers grown by plasma-assisted laser chemical vapor deposition without a metal catalyst
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Boron nitride fibers were found to grow on polycrystalline nickel and Si(100) substrates by plasma-assisted laser chemical vapor deposition from B2 H6 + NH3 using an excimer laser at 193 nm. Their diameter was typically a few hundreds of nanometers, while the length was a few tens of micrometers. They were stoichiometric or boron-rich BN in chemical composition. When the substrate was rotated during deposition, spiral fibers were found to grow. We conclude that they grew with the help of laser light by other than the vapor - liquid - solid mechanism.
- Komatsu, Shojiro,Kazami, Daisuke,Tanaka, Hironori,Shimizu, Yoshiki,Moriyoshi, Yusuke,Shiratani, Masaharu,Okada, Katsuyuki
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- Br?nsted and Lewis Base Behavior of Sodium Amidotrihydridoborate (NaNH2BH3)
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The reactivity of sodium amidoborane (NaNH2BH3) as a Br?nsted and Lewis base was studied systematically. The [NH2BH3]– anion can act as a proton acceptor or a hydride donor in different types of reactions. In reactions with very weak Br?nsted acids such as cyclopentadiene, ammonia, and pyrazole, the [NH2BH3]– anion acts as a proton acceptor through the lone pair on N. The reactions of [NH2BH3]– with stronger Br?nsted acids are complicated. In the reaction with ammonium chloride or acetic acid, [NH2BH3]– accepts a proton, reforming NH3BH3. However, in the reaction with HCl or methanol, N–B bond cleavage occurs. [NH2BH3]– can also donate hydride in some reactions. The possible mechanisms of these reactions are discussed.
- Chen, Xi-Meng,Li, Huizhen,Yang, Qiu-Yu,Wang, Rui-Rui,Hamilton, Ewan J. M.,Zhang, Jie,Chen, Xuenian
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- Band gap and chemically ordered domain structure of a graphene analogue BxCyNz
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Chemically synthesized few layer graphene analogues of BxC yNz are characterized by aberration corrected transmission electron microscopy and high resolution electron energy loss spectroscopy (HREELS) to determine the local phase, electronic structure and band gap. HREELS band gap studies of a BxCyNz composition reveal absorption edges at 2.08, 3.43 and 6.01 eV, indicating that the B xCyNz structure may consist of domains of different compositions. The K-absorption edge energy position of the individual elements in BxCyNz is determined and compared with h-BN and graphite. An understanding of these experimental findings is developed with complementary first-principles based calculations of the various ordered configurations of BxCyNz.
- Venu,Kanuri,Raidongia,Hembram,Waghmare,Datta
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- Catalytic synthesis of bamboo-like multiwall BN nanotubes via SHS-annealing process
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Bamboo-like multiwall boron nitride (BN) nanotubes were synthesized via annealing porous precursor prepared by self-propagation high temperature synthesis (SHS) method. The as-synthesized BN nanotubes were characterized by the field emission scanning elec
- Zhang,Gu,Wang,Zhao,Qian,Li,Pan,Zhang
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- Reaction of Diborane and Ammonia Gas Mixtures in a Chemical Vapor Deposition Hot-Wall Reactor
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Boron nitride has been deposited by chemical vapor deposition from diborane and ammonia gas mixtures, in the form of either films of powders depending on the pressure in the reactor.IR analysis of the boron nitride deposits has been used to obtain the composition of the films.In the temperature range studied, 600-850 deg C, the effect of the deposition temperature on the reaction kinetics has been interpreted by assuming the change in the relative concentration of activated species arising from diborane and ammonia molecules.This change modifies the reaction path followed in the boron nitride synthesis through the formation of different intermediate compounds: aminodiborane in the low-temperature range (= 775 deg C).The presence of either of these intermediate compounds determines the deposition rate and the final composition of the boron nitride films.
- Gomez-Aleixandre, Cristina,Diaz, Domingo,Orgaz, Felipe,Albella, Jose M.
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- Electronic and optical properties of boron nitride nanotubes
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Boron nitride (BN) nanotubes were fabricated, and their electronic and optical properties were investigated by scanning tunneling microscopy (STM) and optical absorption at room temperature. STM images showed atomic arrangements of BN nanotubes, and its chirality was directly observed. The current-voltage characteristics of the BN nanotubes showed onset voltage at 5.0 V, and the optical absorption spectrum of BN nanotubes showed a peak at 4.8 eV.
- Oku, Takeo,Koi, Naruhiro,Suganuma, Katsuaki
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- Synthesis, characterization, and explosive properties of the nitrogen-rich borazine [H3N3B3(N3)3]
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[Me3N3B2(Me)2B(N3 )] and [H3N3B3(N3)3] were prepared from the combination of Me3SiN3 and the chloroborazines [Me3N3B2(Me)2BCl] and (H3N3B3Cl3). The compounds have been characterized by analytical and spectroscopic methods. The molecular structure of [H3N3B3(N3)3] has been confirmed by single-crystal X-ray diffraction techniques: triclinic space group P1 with a = 8.579(1) A?, b = 9.182(1) A?, c = 12.043(1) A?, a = 104.62(1)°, β= 90.26(1)°, γ = 110.74(1)°, and Z = 4. The thermal behavior of the azides have been examined by TGA/DTA. The explosion sensitivity of [H3N3B3(N3)3], which contains 82.58percent nitrogen by weight, has been accessed by drop weight impact, spark, and friction tests. These measurements indicate that [H3N3B3(N3)3] is a relatively sensitive explosive. The Staudinger reactivity of the azides with Ph3P was examined, and [H3N3B3(N3)3] was found to produce [Ph3P=NH2](N3). The molecular structure of this compound was determined by single-crystal X-ray diffraction techniques: orthorhombic space group P212121 with a = 10.649(2) A?, b = 11.737(3) A?, c = 13.364(4) A?, α = β= γ = 90°, Z = 4.
- Paine, Robert T.,Koestle, Wolfgang,Borek, Theodore T.,Wood, Gary L.,Pruss, Eugene A.,Duesler, Eileen N.,Hiskey, Michael A.
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- Formation, structure, and structural properties of a new filamentary tubular form: Hollow conical-helix of graphitic boron nitride
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A novel tubular form of graphitic boron nitride (BN) displaying a hollow conical-helix was discovered. It was generated via wrapping a single beltlike filament according to the geometry of an Archimedes spiral. Cone apex angles of helical-conical nanotubes (HCNTs) were found to exhibit specific values, each of which refers to a certain coincidence site lattice. A unique structural property of HCNTs was observed, displaying the transformation of apex angles during the annealing process. The observed apex angles were reduced with decreasing annealing temperature, which is in accordance with an estimated HCNT strain energy decrease for a given tubular radius. It is suggested that the curvature and apex angle of a HCNT are determined by a sole dynamic element, that is, enthalpy (ΔH), whereas the HCNT disclination configuration changes through helical sliding of the filament.
- Xu, Fang-Fang,Bando, Yoshio,Ma, Renzhi,Golberg, Dmitri,Li, Yubao,Mitome, Masanori
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- Annealing improvement on the localized states of plasma grown boron nitride film assessed through admittance measurements
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Boron nitride (BN) thin film was grown by plasma enhanced chemical vapor deposition (PECVD) technique and was investigated by UV-Visible transmission, Fourier transform infrared (FTIR) and ac conductance spectroscopies. Mainly the density of electronic lo
- ?zdemir, Orhan,Anutgan, Mustafa,Aliyeva-Anutgan, Tamila,Atilgan, Ismail,Katircio?lu, Bayram
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- Synthesis of nitrogen-rich B-C-N materials from melamine and boron trichloride
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Nitrogen-rich B C N materials have been prepared by the reaction between melamine and boron trichloride at different temperatures. The composition of the materials was dependent on the synthesis and annealing temperatures: C6N10.8-11H9.4B1.5-1.7 (for products synthesized and annealed at 673 K), C6N9.3-9.4H3.8-3.9B2.2-2.5 (for those synthesized at 673 K and annealed at 873 K) and C6N9.2H3.6B1.2-1.3 (for those synthesized and annealed at 873 K). Fourier transform infrared spectroscopy and 13C nuclear magnetic resonance showed that the s-triazine rings from the melamine molecules were preserved in materials synthesized and annealed at 673 and 873 K. The sample obtained at 873 K had a graphite-like structure as suggested by X-ray and electron diffraction studies. The s-triazine rings were decomposed in the materials synthesized or annealed at 1223 K and the main product obtained was turbostratic boron nitride.
- Popov, Cyril,Saito, Kimitsugu,Yamamoto, Kazuhiro,Ouchi, Akihiko,Nakamura, Takako,Ohana, Yoritsugu,Koga, Yoshinori
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- High-resolution electron microscopy of boron nitride nanotube with yttrium nanowire
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Boron nitride (BN) nanotubes were investigated by high-resolution electron microscopy (HREM) and image processing. From the HREM image, a BN nanotube encapsulating yttrium nanowire was confirmed by comparing calculated diffraction and a nanostructure model. The present work indicated that yttrium elements could be confined in BN nanotube with large energy gap.
- Oku, Takeo,Narita, Ichihito
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- Over 1.0 mm-long boron nitride nanotubes
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Over 1.0 mm boron nitride nanotubes (BNNTs) were successfully synthesized by an optimized ball milling and annealing method. The annealing temperature of 1100 °C is crucial for the growth of the long BNNTs because at this temperature there is a fast nitrogen dissolution rate in Fe and the B/N ratio in Fe is 1. Such long BNNTs enable a reliable single tube configuration for electrical property characterization and consequently the average resistivity of the long BNNTs is determined to be 7.1 ± 0.9 × 104 Ω cm. Therefore, these BNNTs are promising insulators for three dimensional microelectromechanical system.
- Chen, Hua,Chen, Ying,Liu, Yun,Fu, Lan,Huang, Cheng,Llewellyn, David
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- Turbostratic boron nitride coated on high-surface area metal oxide templates
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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 MgAl2O 4 or γ-Al2O3. This procedure resulted in the formation of a turbostratic boron nitride film with a thickness of a few individual BN layers. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Klitgaard, Soren K.,Egeblad, Kresten,Brorson, Michael,Herbst, Konrad,Christensen, Claus H.
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- Attempts of boron nitride deposition on different substrates under the influence of the electric field present in the reaction zone
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Attempts were undertaken to obtain deposits of hexagonal boron nitride under the influence of either the electric field or current of various frequency flowing through the substrate. It was demonstrated that magnetic field as well as electrical potential difference created in the reaction zone both influence the way BN layers are formed. The layers grow with the formation of fine crystallites in the center of the substrate with their size increasing while moving from the center of the substrate to its edges. Distinct correlation between the electric fields line density and the sizes of the crystallites was observed. The distribution of the crystallites depends on current frequency used. It was found that there is an optimal current frequency for which the substrate is covered with the homogeneous layer of BN. The adhesion of this deposit depends strongly on the kind of the substrate used.
- Pawlas-Foryst, Ewa,Przybylo, Witold,Kopyto, Marek,Fitzner, Krzysztof
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- Synthesis of mono-, Di-, and triaminoborazines: Pyrolysis of triaminoborazines
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The B-triamino-, B-tris-(methylamino)-, and B-tris-(dimethylamino)- derivatives of N-trimethyl- and N-triphenylborazine have been prepared and characterized. The compounds were pyrolyzed at temperatures to 400° and the volatile products examined. Ring ope
- Toeniskoetter, Richard H.,Hall, Frances R.
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- Phase identification of boron nitride thin films by polarized infrared reflection spectroscopy
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Six different types of boron nitride films were investigated by polarized infrared reflection spectroscopy. Films with a highly cubic, mixed cubic and noncubic, and exclusively noncubic phase composition were synthesized using ion beam assisted deposition. Additionally, postdeposition argon ion irradiated cubic and noncubic boron nitride films as well as a nitrogen implanted boron sample were analyzed. Using this technique, besides the cubic phase, two different noncubic modifications, layered anisotropic and amorphous, could be distinguished. A preferential orientation of the normal axis of the sp2-bonded basal planes parallel to the substrate surface was observed.
- Plass,Fukarek,Maendl,Moeller
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- Hydrogen storage in boron nitride nanomaterials studied by TG/DTA and cluster calculation
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BN nanotubes, nanocages and nanocapsules were synthesized from LaB 6 and Pd with boron powder by using an arc melting method. Thermogravimetry/differential thermogravimetric analysis of BN nanomaterials produced from LaB6 and Pd/boron powder showed possibility of hydrogen storage of 1-3wt%. Conditions of H2 gas storage in B 36N36 cluster, which was considered as a cap structure of B99N99 nanotube, were predicted by first principle single point energy calculations. H2 molecules would be introduced from hexagonal rings of the cage structure. BN fullerene materials would store H 2 molecule easier than carbon fullerene materials, and its stability for high temperature would be good.
- Oku, Takeo,Kuno, Masaki,Narita, Ichihito
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- Influence of Diborane Flow Rate on the Structure and Stability of CVD Boron Nitride Films
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CVD boron nitride films have been deposited at 800 deg C from diborane, ammonia, and hydrogen gas mixtures, using different B2H6 flow rates.The effect of the / ratio in the gas mixture on the structure, composition, and the stability of the lay
- Gomez-Aleixandre, C.,Essafti, A.,Fernandez, M.,Fierro, J. L. G.,Albella, J. M.
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- Structure of boron nitride nanoscale cones: Ordered stacking of 240° and 300° disclinations
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Recently discovered boron nitride (BN) nanoscale cone particles are shown to consist of an ordered stacking of seamless conical shells. High-resolution transmission electron microscopy and nanobeam electron diffraction allowed the orientation of the BN hexagonal rings to be determined. In all but one case, the results conformed with a model of orderly stacked 240° disclinations, which is the smallest cone geometry ensuring the presence of B-N bonds only. One case of a nanoscale cone constituted of 300° disclinations was found, implying that structures containing line defects of non-B-N bonds may form. 2000 The American Physical Society.
- Bourgeois,Bando,Han,Sato
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- One convenient synthesis route to boron nitride nanotube
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We describe one convenient synthesis route to boron nitride (BN) nanotube by the reaction of boron powder, iron oxide, and ammonium chloride at 600 °C for 12 h. Characterized by XRD, FTIR, XPS, TEM and SAED, the composition and morphology of the products are confirmed. The possible reaction mechanism is also discussed.
- Cai, Peijun,Chen, Luyang,Shi, Liang,Yang, Zeheng,Zhao, Aiwu,Gu, Yunle,Huang, Tao,Qian, Yitai
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- Syntheses of metal nitrides, metal carbides and rare-earth metal dioxymonocarbodiimides from metal oxides and dicyandiamide
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We design a facile and efficient solid-state reaction method by selecting an organic reagent dicyandiamide and metal oxides as precursors to prepare metal nitrides, carbides and rare-earth metal dioxymonocarbodiimides in sealed ampoules. Some fine divided nitride and carbide nanoparticles with small and uniform size can be easily obtained at the relatively low temperatures. It is interesting to find that dicyandiamide is not only a highly efficient nitridation reagent but also a highly efficient carburization reagent, and can be used as a precursor to directly synthesize rare-earth metal dioxymonocarbodiimides. A possible mechanism is proposed to explain the results of the reactions between the organic reagent and metal oxides.
- Lei,Zhao,Yang,Song,Cao,Li,Tang
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- DENSITY AND DEPOSITION RATE OF CHEMICAL-VAPOUR-DEPOSITED BORON NITRIDE.
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A study was made on the density and deposition rate characteristics of chemical vapour deposited boron nitride (CVD-BN) plates synthesized by use of the BCl//3-NH//3-H//2 system at a deposition temperature (T//d//e//p) of 1200 to 2000 degree C and a total gas pressure (P//t//o//t) of 5 to 60 torr. At a P//t//o//t of 5 torr, all the CVD-BN plates synthesized at each T//d//e//p above 1300 degree C had a density greater than 2. 0 g cm** minus **3 and showed no noticeable dependence on T//d//e//p. Over the P//t//o//t range from 10 to 60 torr, the density reached a maximum of 2. 08 g cm** minus **3 at a T//d//e//p of 2000 degree C. As T//d//e//p was lowered, density decreased to a minimum of 1. 40 g cm** minus **3. The deposition rate varied with both T//d//e//p and P//t//o//t and showed a maximum value under a certain P//t//o//t at a given T//d//e//p. The value of P//t//o//t where the deposition rate becomes maximum changed depending on the T//d//e//p. The maximum deposition rate was 0. 6 mm h** minus **1 for the CVD-BN plates when the density was less than 2. 0 g cm** minus **3 and 0. 4 mm h** minus **1 when the density was above 2. 0 g cm** minus **3. The effects of deposition conditions on the characteristics of density and deposition rate are discussed in terms of the structure and deposition mechanism.
- Matsuda, Toshitsugu,Nakae, Hiroyuki,Hirai, Toshio
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- CVD synthesis of boron nitride nanotubes without metal catalysts
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An efficient CVD synthetic route for bulk quantities of boron nitride nanotubes (BN-NTs) was developed, where a B-N-O precursor generated from melamine diborate (C3N6H6·2H3BO3) was employed as the precursor and no metal catalyst was used. The resultant tubes all show remarkable ordering of the concentric atomic layers and exhibit stoichiometric BN composition. It is commonly found that the nanotubes have bulbous tips showing B-N-O amorphous clusters encapsulated in BN cages. The amorphous clusters might play the catalytic role in the nanotube 'tip-growth' process as the metal catalysts do in the metal-catalyzed CVD method.
- Ma,Bando,Sato
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- Influence of isothermal chemical vapor deposition and chemical vapor infiltration conditions on the deposition kinetics and structure of boron nitride
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An experimental study has been performed to gain some insight into the correlations between the deposition conditions and the structure of boron nitride (BN) coatings that are used in ceramic-matrix composites. BN has been deposited at 700°C from BCl3-NH3-H2 mixtures on various substrates, by using chemical vapor deposition (CVD) and isothermal-isobaric chemical vapor infiltration (ICVI) processes, simultaneously in the same reactor. A kinetic study has shown that the CVD process is governed either by a combination of mass transfer with chemical kinetics at low flow rates or by the heterogeneous kinetics only at high flow velocities. In contrast, the limiting contribution of mass transfer always is observed for the ICVI process. The influence of diffusion cages that are positioned around the fibrous preforms is reported. The structure of BN deposits has been studied as a function of the various deposition conditions via transmission electron microscopy. The chosen CVD conditions lead to a poor organization of the BN deposits. Fairly well-organized BN coatings are deposited on all fibers of a fibrous preform via ICVI. The results are discussed in terms of supersaturation and deposition yields. The use of diffusion cages and the adjustment of the inlet composition and mass flow rate seem to be very important to obtain the best BN organization and thickness uniformity.
- Leparoux, Marc,Vandenbulcke, Lionel,Clinard, Christian
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- MOCVD Growth of Boron Nitride Films from Single Source III-V Precursor
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The sp2 and sp3 phases of boron nitride (BN) have been deposited on Si and Ni substrates by low pressure MO-CVD (metal organic chemical vapour deposition) at 450 deg C from diethylaminoborane and the films were characterised by Fourier transform infrared (FTIR) and X-ray diffraction (XRD); a plausible mechanism of CVD is proposed from gas-phase decomposition studies, and to our knowlege this is the first report of the growth of BN by MO-CVD using a single source.
- Phani, A. Ratna,Devi, G. Sarala,Roy, Sujit,Rao, V. J.
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- Formation and atomic structure of boron nitride nanotubes with a cup-stacked structure
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Boron nitride (BN) nanotubes were synthesized by annealing Fe4N/B powder at 1000?{ring operator}C for 1 h in a nitrogen gas atmosphere, and large amounts of BN nanotubes with a cup-stacked structure were obtained after a purification process. The atomic structures of the cup-stacked BN nanotubes were investigated by high-resolution electron microscopy as well as molecular mechanics calculations, and compared with double walled BN nanotubes. The present results indicate that the cup-stacked structure with a cone angle of 20{ring operator} is more stable than the structure with an angle of 38{ring operator} and ordinary nanotube structures.
- Oku, Takeo,Koi, Naruhiro,Suganuma, Katsuaki,Belosludov, Rodion V.,Kawazoe, Yoshiyuki
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- Nanocages of layered BN: Super-high-pressure nanocells for formation of solid nitrogen
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High nitrogen contents inside boron nitride fullerene like multilayered nanocages formed by reacting CNx nanotubes (x≤0.1) and B2O3 in a nitrogen atmosphere at 1985-2113 K was observed. Various studies suggested that the super high pressures were generated inside nanocages, which were responsible for crystallizing gaseous nitrogen trapped within the BN shells. High pressure induced phase transformation of graphitic-like BN into diamond like cubic BN occurs inside the nanocages.
- Golberg,Bando,Sato,Grobert,Reyes-Reyes,Terrones,Terrones
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Read Online
- Reductive dechlorination of BCl3 for efficient ammonia borane regeneration
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This paper reports a complete ammonia borane (AB) regeneration process in which Bu3SnH was utilized as a reductant for the reductive dechlorination of BCl3, and Et2PhN was selected as a 'helper ligand' to generate Et2PhN·BH3, which gives rise to a high yield of AB by a base-exchange reaction at ambient temperature.
- Tan, Yingbin,Zhang, Lijun,Chen, Xiaowei,Yu, Xuebin
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Read Online
- Purification of boron nitride nanotubes
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A purification process was developed for the first time for boron nitride (BN) nanotubes. BN nanotubes, prepared using a ball milling and annealing method, contain a high yield of nanotubes and a small amount of BN and metal catalyst particles. The metal particles can be dissolved in an HCl solution. Fine BN nanoparticles and thin layers were first converted to water soluble B2O3 via a partial oxidation treatment at 800 °C. The oxide particles and layers can then be dissolved in hot water. Thermogravimetric analysis has been used to determine an adequate oxidation temperature at which fine BN particles were oxidized.
- Chen, Hua,Chen, Ying,Yu, Jun,Williams, James S.
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Read Online
- SYNTHESIS OF BN USING BPO4 AS THE BORON SOURCE.
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The reaction of BPO//4 with different amounts of NaCN to yield BN and sodium phosphates was studied, mainly as a function of temperature and of the ratio NaCN/BPO//4. Gravimetric data, together with analytical results, allowed us to postulate and confirm that the yield of reaction products is dependent on the initial ratio NaCN/BPO//4.
- Bamberger,Begun
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- Synthesis and structure of BN coatings on SiC nanofibers
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The Gibbs potential has been calculated as a function of temperature for a number of BN synthesis reactions. Detailed studies of BN chemical vapor deposition on SiC nanofibers were used to develop a technique for BN coating production from nontoxic precur
- Silenko,Shlapak,Pilipchuk,D'Yachkov,Solonin
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Read Online
- Synthesis of boron nitride nanotubes from carbon nanotubes by a substitution reaction
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A method involving carbon nanotubes substituted reaction was developed for the synthesis of mass quantities of boron nitride nanotubes. Boron oxide vapor was reacted with nitrogen gas in the presence of carbon nanotubes to form boron nitride nanotubes, whose diameters and lengths are similar to those of the starting carbon nanotubes. It is proposed that carbon atoms of carbon nanotubes can be fully substituted by boron and nitrogen atoms through a general chemical reaction. The results suggest that the synthesis methodology developed here may also be extended to form nanotubes from other novel materials.
- Han, Weiqiang,Bando, Yoshio,Kurashima, Keiji,Sato, Tadao
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Read Online
- Cu-Catalyzed Chemoselective Reduction of N-Heteroaromatics with NH3·BH3 in Aqueous Solution
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An efficient catalytic system was successfully developed on reduction of N-heteroaromatics with H3N?BH3 as hydrogen source in CuSO4 solution, featuring excellent chemoselectivity as well as very broad functional group tolerance. Various challenging substrates, such as OH-, NH2-, Cl-, Br-, etc., contained quinolines, quinoxalines, 1,5-naphthyridines and quinazolines were all reduced smoothly. Mechanistic studies suggested that [Cu-H] intermediate might be generated from NH3?BH3, which was believed to form with H3N?BH3 in CuSO4 solution.
- Gao, Chao,Xuan, Qingqing,Song, Qiuling
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supporting information
p. 2504 - 2508
(2021/07/31)
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- Photocatalytic performance of visible active boron nitride supported ZnFe2O4 (ZnFe2O4/BN) nanocomposites for the removal of aqueous organic pollutants
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Visible active novel ZnFe2O4/BN heterostructured nanocomposites with different wt% of BN nanosheets were prepared using a solvothermal method. Their structural, morphological and optical properties were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), Fourier-Transform Infrared Spectroscopy (FT-IR), UV-Visible spectrophotometry, Photoluminescence (PL) and X-ray Photoelectron Spectroscopy (XPS) techniques. The photocatalytic performance of ZnFe2O4/BN hybrid nanocomposites was evaluated towards oxidative degradation of organic pollutants such as Congo red (CR) and tetracycline (TC) under visible light irradiation. The porous BN nanosheets act as a catalytic support and enhance the photoactivity of ZnFe2O4 in the nanocomposite. The results also indicated that the presence of BN nanosheets lowers the recombination rate and shows significantly improved separation of the photo-induced electron-hole pairs in ZnFe2O4/BN when compared to bare ZnFe2O4. Among the different ZnFe2O4/BN nanocomposites, 9.3 wt% of BN loaded ZnFe2O4 hybrid was found to show the most efficient photocatalytic activity towards the degradation of Congo Red and tetracycline under visible light irradiation. The apparent rate constant values of ZnFe2O4/9.3% BN were found to be three and five times higher than that of bare ZnFe2O4 in the degradation of CR and TC respectively.
- Durai, Mani,Erusappan, Elangovan,Kumaravel, Sakthivel,Thiripuranthagan, Sivakumar,Vembuli, Thanigaivel
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p. 7758 - 7770
(2020/06/17)
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- Boron-hyperdoped silicon for the selective oxidative dehydrogenation of propane to propylene
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Boron containing catalysts have great potential in the oxidative dehydrogenation of propane. Herein, a series of 15, 25 and 42 atpercent boron-hyperdoped silicon catalysts synthesized by laser pyrolysis was studied. Boron-hyperdoped silicon samples showed >6 times higher propylene productivity than commercial h-BN at 450 °C.
- Chen, Junjie,Karakalos, Stavros G.,Kyriakidou, Eleni A.,Lance, Michael J.,Rohani, Parham,Swihart, Mark T.,Toops, Todd J.
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supporting information
p. 9882 - 9885
(2020/09/09)
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- Mechanisms of the Reactions of B-Substituted Amine Boranes with THF·BH3
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The reactions of NH3BH2R (R = Me, Ph and Cl) with THFBH3 have been investigated and it was found that different substituents on the B atom help to proceed the reactions in different ways. The expected doubly-bridged B-substituted aminodiborane products, similar to aminodiborane (ADB, BH2(μ-H)(μ-NH2)BH2) via the reaction of ammonia borane (AB, NH3BH3) and tetrahydrofuran borane (THFBH3), are not obtained. Two competitive reactions occurred with the change of R = Me or Ph. When R is a Me group, an “open“ version of B-substituted μ-aminodiborane, THFBH(Me)(μ-NH2)BH3, is formed as a major product; when R is a Ph group, AB and THFBH2Ph are formed as main products via the intermolecular NH3–THF exchange reaction. However, if R is Cl, then NH3BH2Cl reacts with THFBH3 through reversible intermolecular Cl–H exchange mechanism. Furthermore, DFT calculations are performed to elucidate the formation mechanism of THFBH(Me)(μ-NH2)BH3 via the reaction of NH3BH2Me and THFBH3 as well as the exchange mechanism of Cl–H in the reaction of NH3BH2Cl and THFBH3.
- Guo, Yu,Wang, Xinghua,Ma, Nana,Cao, Yilin,Hussain, Sajjad,Zhang, Jie,Wei, Donghui,Chen, Xuenian
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p. 4994 - 4999
(2019/12/24)
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- OPEN-FLASK HYDROBORATION AND THE USE THEREOF
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The present disclosure generally relates to a process for hydroboration of an alkene or alkyne using ammonia borane (AB). In particular, the present invention relates to hydroboration of an alkene or alkyne in the presence of air or moisture, and a clean process for facile preparation of an alcohol by oxidizing the organoborane so formed with hydrogen peroxide. The products, including aminodialkylboranes, ammonia trialkylborane complexes, as well as various alcohols so prepared, are within the scope of this disclosure.
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Paragraph 0042
(2018/03/25)
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- Edge-hydroxylated Boron Nitride for Oxidative Dehydrogenation of Propane to Propylene
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Oxidative dehydrogenation of propane to olefins is a promising alternative route to industrialized direct dehydrogenation, but encounters the difficulty in selectivity control for olefins because of the overoxidation reactions that produce a substantial amount of undesired CO2. Here we report edge-hydroxylated boron nitride, a metal-free catalyst, that efficiently catalyzed dehydrogenation of propane to propylene with superior selectivity (80.2 %) but with only negligible CO2 formation (0.5 %) at a given propane conversion of 20.6 %. Remarkable stability was evidenced by the operation of a 300 h test with steady conversion and product selectivity. The active BNO. site, generated dynamically through hydrogen abstraction of B?OH groups by molecular oxygen, triggered propane dehydrogenation by selectively breaking the C?H bond but simultaneously shut off the pathway of propylene overoxidation towards CO2.
- Shi, Lei,Wang, Dongqi,Song, Wei,Shao, Dan,Zhang, Wei-Ping,Lu, An-Hui
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p. 1788 - 1793
(2017/05/26)
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- Preparation of hexagonal BN whiskers synthesized at low temperature and their application in fabricating an electrochemical nitrite sensor
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Hexagonal boron nitride (h-BN) whiskers were synthesized via the polymeric precursor method using boric acid (H3BO3) and melamine (C3H6N6) as raw materials at 1073-1273 K in flowing nitrogen/hydrogen (5% hydrogen). The phase and morphology of the obtained products were characterized using XRD, FTIR, SEM, TEM and BET techniques. The results show that h-BN wishers can be successfully fabricated at 1073-1273 K with 0.5-3 μm diameters and 50-200 μm lengths. They possess micropores and mesopores. Moreover, the as-prepared BN whiskers can be used as a sensing electrode for detection of nitrite (NO2-). Compared with other electrodes for nitrite detection, the h-BN wishers electrode shows a much higher sensitivity in the wider range from 10 to 1000 μM, with a detection limit of 0.089 μM (10-400 μM) and 0.412 μM (400-6300 μM) (S/N = 3), respectively. The oxidation process of NO2- on the h-BN whiskers electrode is controlled by a diffusion process.
- Luo, Wenpo,Yang, Tao,Su, Lei,Chou, Kuo-Chih,Hou, Xinmei
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p. 27767 - 27774
(2016/04/04)
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- Design of 3D h-BN architecture as Ag3VO4 enhanced photocatalysis stabilizer and promoter
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Hexagonal boron nitride (h-BN), with a band gap of ～5.5 eV, is commonly excluded photocatalysis and photovoltaic conversion application. Herein, we rationally designed 3D h-BN hierarchical architecture with an interconnected network of graphene-analogue h-BN nanosheets and wrapped Ag3VO4 by in-situ precipitation at room temperature. After hybridization, stabilized Ag3VO4 with enhanced photocatalytic activity was obtained and the enhanced activity was fluctuated by the varied addition of h-BN. The 3 wt% h-BN/Ag3VO4 composite exhibited the highest photocatalytic activity for the degradation of RhB under visible light, which was 6.2 times that of bare Ag3VO4. Meanwhile, it showed higher photocurrent responses, which was about 4 times that of pure Ag3VO4. More interestingly, their absorbance intensity were enhanced obviously both in visible and UV light region after hybridization. Structure characterization, as well as the radical trapping experiments were further explored to reveal mechanism of the enhanced activity and stability of h-BN/Ag3VO4 composite. The results provided an alternative simple and convenient route to stabilize photocatalysts prone to photocorrosion with enhanced performance.
- Lv, Xiaomeng,Wang, Jiaxi,Yan, Zaoxue,Jiang, Deli,Liu, Jun
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p. 146 - 153
(2016/04/19)
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- Facile Green Synthesis of BCN Nanosheets as High-Performance Electrode Material for Electrochemical Energy Storage
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Two-dimensional hexagonal boron carbon nitride (BCN) nanosheets (NSs) were synthesized by new approach in which a mixture of glucose and an adduct of boric acid (H3BO3) and urea (NH2CONH2) is heated at 900 °C. The method is green, scalable and gives a high yield of BCN NSs with average size of about 1 μm and thickness of about 13 nm. Structural characterization of the as-synthesized material was carried out by several techniques, and its energy-storage properties were evaluated electrochemically. The material showed excellent capacitive behaviour with a specific capacitance as high as 244 F g-1 at a current density of 1 A g-1. The material retains up to 96 % of its initial capacity after 3000 cycles at a current density of 5 A g-1.
- Karbhal, Indrapal,Devarapalli, Rami Reddy,Debgupta, Joyashish,Pillai, Vijayamohanan K.,Ajayan, Pulickel M.,Shelke, Manjusha V.
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p. 7134 - 7140
(2016/05/19)
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- Porous boron nitride coupled with CdS for adsorption-photocatalytic synergistic removal of RhB
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Porous boron nitride (a-BN) modified by uniformly dispersed CdS photocatalysts was successfully prepared using a facile hydrothermal method, and probed by electron microscopy, X-ray diffraction and UV-vis diffuse reflection spectroscopy. Adsorption and photocatalytic activities were evaluated using high concentration Rhodamine B (RhB) as a target organic pollutant. The results show that after adding a small amount of CdS nanoparticles, the absorbent can self-regenerate with the assistance of visible light irradiation to photocatalytically degrade the organic pollutants adsorbed on the surface of a-BN/CdS. During the adsorption and photocatalytic process, boron nitride could supply a concentrated pollutant environment around CdS photocatalyst active sites. The optimal loading amount of CdS was observed to be 0.5 wt% with the best adsorption-photocatalytic synergistic efficiency, which was probably due to the better dispersion of CdS on a-BN support and the separation of photogenerated electron-hole pairs by negatively charged a-BN. The photocatalytic mechanism of the a-BN/CdS composite was also investigated by radical trapping experiments.
- Li, Xiaopeng,Qi, Feng,Xue, Yanming,Yu, Chao,Jia, Huichao,Bai, Yinghao,Wang, Sai,Liu, Zhenya,Zhang, Jun,Tang, Chengchun
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p. 99165 - 99171
(2016/11/02)
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- An ultrasound-assisted wet-chemistry approach towards uniform Mg(BH4)2·6NH3 nanoparticles with improved dehydrogenation properties
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Metal borohydride ammoniates are a novel family of high-capacity hydrogen storage materials. However, high dehydrogenation temperature and low hydrogen purity retard their practical applications. Reducing the particle size to the nanometre range is an eff
- Li, You,Liu, Yongfeng,Zhang, Xin,Zhou, Di,Lu, Yunhao,Gao, Mingxia,Pan, Hongge
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p. 8366 - 8373
(2016/06/09)
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- Catalysis and Mechanism of H2 Release from Amine-Boranes by Diiron Complexes
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Studies focused on the dehydrogenation of amine-borane by diiron complexes that serve as well-characterized rudimentary models of the diiron subsite in [FeFe]-hydrogenase are reported. Complexes of formulation (μ-SCH2XCH2S)[Fe(CO)su
- Lunsford, Allen M.,Blank, Jan H.,Moncho, Salvador,Haas, Steven C.,Muhammad, Sohail,Brothers, Edward N.,Darensbourg, Marcetta Y.,Bengali, Ashfaq A.
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p. 964 - 973
(2016/02/03)
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- The role of ammonia in promoting ammonia borane synthesis
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Ammonia promotes the synthesis of pure ammonia borane (AB) in excellent yields from sodium borohydride and ammonium sulfate in tetrahydrofuran under ambient conditions. An examination of the influence of added ammonia reveals that it is incorporated into the product AB, contrary to its perceived function as a catalyst or a co-solvent. Mechanistic studies point to a nucleophilic attack by ammonia on ammonium borohydride with concurrent dehydrogenation to yield AB.
- Ramachandran, P. Veeraraghavan,Kulkarni, Ameya S.
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p. 16433 - 16440
(2016/10/31)
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- Free-standing membranes made of activated boron nitride for efficient water cleaning
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Developing membranes with excellent mechanical strength and chemical stability is a practically important issue for efficient removal of pollutants from wastewater. In this work, we report on a free-standing membrane fabrication from an activated boron nitride (ABN) micro-ribbon. The membrane techniques we used, combine the intrinsic active adsorption competence of ABN and the mechanical advantages of conventional membrane filtration. The obtained membranes show an excellent removal ability of water pollutants through a simple filtration adsorption process. The examined pollutants include toxic metallic ions and organics. We showed that the dye (like methylene blue) removal ability significantly exceeded that of activated carbon by an order of magnitude at least; lead ions (Pb2+) in wastewater can be nearly fully removed, the starting 5 mg L-1 concentration was reduced to less than 0.01 mg L-1 after the 600 μm-thickness membrane adsorption filtration. Moreover, the membranes can be stacked together to further improve the adsorption capacity because of their high permeability. The excellent reusable performance of the filtration membranes was also confirmed. We believe that the reported work should open the way toward the practical application of ABN membranes in the field of wastewater purification.
- Li, Jie,Jia, Huichao,Lin, Jing,Luo, Han,Liu, Zhenya,Xu, Xuewen,Huang, Yang,Jin, Peng,Zhang, Jun,Abbas, Saleem,Tang, Chengchun
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p. 71537 - 71543
(2015/09/08)
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- Synthesis and characterization of BN/Bi2WO6 composite photocatalysts with enhanced visible-light photocatalytic activity
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Bi2WO6 modified with few-layer BN was synthesized by an impregnation method. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflection spectroscopy (DRS) and Fourier transform infrared spectroscopy (FT-IR). The as-prepared BN/Bi2WO6 photocatalysts exhibited a higher photocatalytic activity for the degradation of Rhodamine B (RhB) than the pure Bi2WO6. The 3 wt% BN/Bi2WO6 photocatalyst showed the best photocatalytic activity and high stability after five runs under visible light irradiation. The enhanced visible-light photocatalytic activity could be attributed to the synergetic effect of few-layer BN and Bi2WO6.
- Li, Weibin,Wang, Qi,Huang, Liying,Li, Yeping,Xu, Yuanguo,Song, Yanhua,Zhang, Qi,Xu, Hui,Li, Huaming
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p. 88832 - 88840
(2015/11/09)
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- Open-Flask Synthesis of Amine-Boranes via Tandem Amine-Ammonium Salt Equilibration-Metathesis
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An amine-ammonium salt equilibration-metathesis sequence provides high-purity amine-boranes in excellent yields from sodium borohydride in refluxing reagent-grade tetrahydrofuran in an open flask.
- Ramachandran, P. Veeraraghavan,Kulkarni, Ameya S.
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p. 5618 - 5620
(2015/06/25)
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- Preparation of boron nitride and polystyrene/boron nitride composite particles by dehydrogenation in ionic liquids
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Boron nitride (BN) was prepared by the dehydrogenation of ammonia borane (AB) in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim][BF4]) at 300 °C, which is lower than the temperature of the general preparation method of BN and below the decomposition temperature of polystyrene (PS). The reaction was performed at 120 °C for 10 h under atmospheric pressure, and the product material was subsequently heated at 300 °C for 24 h under reduced pressure in [Bmim][BF4]. The reaction rate and final conversion increased when [Bmim][BF4] was used as the medium as compared to those observed in the bulk system (in the absence of the solvent system). Moreover, PS/BN composite particles were successfully prepared by dehydrogenation in [Bmim][BF4] in the presence of cross-linked PS seed particles. Transmission electron microscopy images of ultrathin cross-sections of the composite particles confirmed the core-shell morphology of the particles with a PS core and a BN shell. The Royal Society of Chemistry.
- Kinoshita,Matsunaga,Hiraoka,Yanagimoto,Minami
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p. 8605 - 8611
(2014/03/21)
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- Graphene-analogue boron nitride/Ag3PO4 composite for efficient visible-light-driven photocatalysis
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Graphene-analogues BN modified Ag3PO4 photocatalysts were successfully prepared. The composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning e
- Song, Yanhua,Xu, Hui,Wang, Cheng,Chen, Jiajia,Yan, Jia,Xu, Yuanguo,Li, Yeping,Liu, Chengbao,Li, Huaming,Lei, Yucheng
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p. 56853 - 56862
(2015/01/09)
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- Reaction of a P/Al-based frustrated lewis pair with ammonia, borane, and amine-boranes: Adduct formation and catalytic dehydrogenation
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Open wide! The geminal P/Al-based frustrated Lewis pair (Mes 2P)(tBu2Al)Ci￡C(H)Ph forms stable Lewis adducts with BH3 and NH3. This compound facilitates the dehydrocoupling of the ammonia-borane adduct by unusual N-H bond activation and elimination of dihydrogen at the boron center, and it is a very active main-group-based FLP catalyst for the dehydrogenation of amine-borane H 3B×NMe2H. Mes=mesityl. Copyright
- Appelt, Christian,Slootweg, J. Chris,Lammertsma, Koop,Uhl, Werner
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supporting information
p. 4256 - 4259
(2013/05/09)
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- Synthesis of vertically aligned boron nitride nanosheets using CVD method
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Boron nitride nanosheets (BNNSs) protruding from boron nitride (BN) films were synthesized on silicon substrates by chemical vapor deposition technique from a gas mixture of BCl3-NH3-H2-N 2. Parts of the as-grown nanosheets were vertically aligned on the BN films. The morphology and structure of the synthesized BNNSs were characterized by scanning electron microscopy, transmission electron microscopy, and Fourier transformation infrared spectroscopy. The chemical composition was studied by energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Cathodoluminescence spectra revealed that the product emitted strong UV light with a broad band ranging from 250 to 400 nm. Field-emission characteristic of the product shows a low turn-on field of 6.5 V μm-1.
- Zhang, Chao,Hao, Xiaopeng,Wu, Yongzhong,Du, Miao
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p. 2277 - 2281
(2012/09/22)
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- Synthetic and mechanistic studies of metal-free transfer hydrogenations applying polarized olefins as hydrogen acceptors and amine borane adducts as hydrogen donors
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Metal-free transfer hydrogenation of polarized olefins (RR′ CCEE′: R, R′ = H or organyl, E, E′ = CN or CO2Me) using amine borane adducts RR′NH-BH3 (R = R′ = H, AB; R = Me, R′ = H, MAB; R = tBu, R′ = H, tBAB; R = R′ = Me, DMAB) as hydrogen donors, were studied by means of in situ NMR spectroscopy. Deuterium kinetic isotope effects and the traced hydroboration intermediate revealed that the double H transfer process occurred regio-specifically in two steps with hydride before proton transfer characteristics. Studies on substituent effects and Hammett correlation indicated that the rate determining step of the HN transfer is in agreement with a concerted transition state. The very reactive intermediate [NH2BH2] generated from AB was trapped by addition of cyclohexene into the reaction mixture forming Cy2BNH2. The final product borazine (BHNH)3 is assumed to be formed by dehydrocoupling of [NH2BH2] or its solvent stabilized derivative [NH2BH2]-(solvent), rather than by dehydrogenation of cyclotriborazane (BH2NH 2)3 which is the trimerization product of [NH 2BH2].
- Yang, Xianghua,Fox, Thomas,Berke, Heinz
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p. 852 - 860
(2012/02/05)
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- Convert graphene sheets to boron nitride and boron nitride-carbon sheets via a carbon-substitution reaction
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Here we discuss our synthesis of highly crystalline pure boron nitride (BN) and BN-carbon (BN-C) sheets by using graphene sheets as templates via a carbon-substitution reaction. Typically, these sheets are several micrometers wide and have a few layers. The composition ratios of BN-C sheets can be controlled by the post-treatment (remove carbon by oxidation) temperature. We also observed pure BN and BN-C nanoribbons. We characterized the BN-C sheets via Raman spectroscopy and density functional theory calculations. The results reveal that BN-C sheets with an armchair C-BN chain, and embedded C2 or C6 units in BN-dominated regions energetically are the most favorable.
- Han, Wei-Qiang,Yu, Hua-Gen,Liu, Zhenxian
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- Low-temperature solid state synthesis and in situ phase transformation to prepare nearly pure cBN
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Cubic boron nitride (cBN) is synthesized by a low-temperature solid state synthesis and in situ phase transformation route with NH4BF 4, B, NaBH4 and KBH4 as the boron sources and NaN3 as the nitrogen
- Lian, Gang,Zhang, Xiao,Tan, Miao,Zhang, Shunjie,Cui, Deliang,Wang, Qilong
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p. 6961 - 6967
(2011/09/13)
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- Thin film growth of boron nitride on α-Al2O3 (0 0 1) substrates by reactive sputtering
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Boron nitride thin films were grown on α-Al2O3 (0 0 1) substrates by reactive magnetron sputtering. Infrared attenuated total reflection (ATR) spectra of the films gave an intense signal associated with in-plane B-N stretching TO mode of short range ordered structure of BN hexagonal sheets. X-ray diffraction for the film prepared at a low working pressure (ca. 1 × 10-3 Torr) gave a diffraction peak at slightly lower angle than that corresponding to crystal plane h-BN (0 0 2). It is notable that crystal thickness calculated from X-ray peak linewidth (45 nm) was close to film thickness (53 nm), revealing well developed sheet stacking along the direction perpendicular to the substrate surface. When the substrates of MgO (0 0 1) and Si (0 0 1) were used, the short-range ordered structure of h-BN sheet was formed but the films gave no X-ray diffraction. The film showed optical band gap of 5.9 eV, being close to that for bulk crystalline h-BN.
- Anzai, Atsushi,Nishiyama, Fumitaka,Yamanaka, Shoji,Inumaru, Kei
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p. 2230 - 2234
(2012/01/04)
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- Facile synthesis and characterization of hexagonal boron nitride nanoplates by two-step route
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Large quantities of hexagonal boron nitride (h-BN) nanoplates with hexagonal morphologies have been successfully synthesized by a simple two-step route without using any template or catalyst, including combustion synthesis and then annealing processes. Th
- Zhao, Zhengyan,Yang, Zhigang,Wen, Yan,Wang, Yuhua
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p. 4496 - 4501
(2012/03/08)
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- Epitaxially grown semiconducting hexagonal boron nitride as a deep ultraviolet photonic material
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Hexagonal boron nitride (hBN) has emerged as an important material for various device applications and as a template for graphene electronics. Low-dimensional hBN is expected to possess rich physical properties, similar to graphene. The synthesis of wafer-scale semiconducting hBN epitaxial layers with high crystalline quality and electrical conductivity control has not been achieved but is highly desirable. Large area hBN epitaxial layers (up to 2 in. in diameter) were synthesized by metal organic chemical vapor deposition. P-type conductivity control was attained by in situ Mg doping. Compared to Mg-doped wurtzite AlN, which possesses a comparable energy band gap (～6 eV), dramatic reductions in Mg acceptor energy level and P-type resistivity (by about six to seven orders of magnitude) have been realized in hBN epilayers. The ability of conductivity control and wafer-scale production of hBN opens up tremendous opportunities for emerging applications, ranging from revolutionizing p-layer approach in III-nitride deep ultraviolet optoelectronics to graphene electronics.
- Dahal,Li,Majety,Pantha,Cao,Lin,Jiang
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- A simple thermal decomposition-nitridation route to nanocrystalline boron nitride (BN) from a single N and B source precursor
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Nanocrystalline boron nitride (BN) was synthesized via a simple thermal decomposition-nitridation route by the reaction of hydrated ammonium tetraborate (NH4HB4O7·3H2O) and metallic magnesium powders in an autoc
- Zhang, Hong,Chen, Youjian,Ma, Jianhua,Tong, Hanxuan,Yang, Jiang,Ni, Danwei,Hu, Huiming,Zheng, Fangqing
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p. 6616 - 6620
(2011/08/04)
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- Simple synthesis of mesoporous boron nitride with strong cathodoluminescence emission
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Mesoporous BN was prepared at 550 °C for 10 h or so via a simple reaction between NaBH4 and CO(NH2)2. X-ray diffraction demonstrates the formation of t-BN with lattice constants a=2.46 and c=6.67 A. High-resolution transmi
- Meng, Xiang-Lin,Lun, Ning,Qi, Yong-Xin,Zhu, Hui-Ling,Han, Fu-Dong,Yin, Long-Wei,Fan, Run-Hua,Bai, Yu-Jun,Bi, Jian-Qiang
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p. 859 - 862
(2011/05/06)
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- Dehydrogenation performance of NH3BH3 with Mg 2NiH4 addition
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The dehydrogenation performance of NH3BH3 destabilized by Mg2NiH4 was investigated. It was found that the onset dehydrogenation temperature was reduced, and no gaseous by-products were released during the whole decomposition process. This enhanced dehydrogenation performance could be attributed to the destabilization effect of Mg2NiH4. In comparison with the 2NH3BH 3/MgH2 sample, the dehydrogenation behavior and destabilization mechanism are different. 4NH3BH3/Mg 2NiH4 composite exhibits a three-step decomposition feature. NH3BH3 and Mg2NiH4 decomposed separately. The destabilization effect of Mg2NiH 4 on the chemical bonds of NH3BH3 plays a crucial role in the enhanced dehydrogenation performance. Our results provide a new insight on destabilized dehydrogenation behavior of NH3BH 3 after metal hydrides addition.
- Weng, Baicheng,Wu, Zhu,Li, Zhilin,Leng, Haiyan
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- An investigation on the synthesis of borazine
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Borazine is a promising precursor for boron nitride. A detailed investigation on the reaction of sodium borohydride and ammonium sulfate from 40 °C to 120 °C for synthesis of borazine was performed. The reaction was monitored by means of 11B nuclear magnetic resonance (11B NMR) and Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mass spectroscopy (MS). The reaction produces mainly ammonia borane (AB), but not borazine at temperatures below 60 °C. Increases of temperature promote yield of borazine, which reaches the maximum around 110 °C. Whereas further increased temperature causes severe polymerization of borazine, and hence holds back yields of borazine.
- Li, Jun-Sheng,Zhang, Chang-Rui,Li, Bin,Cao, Feng,Wang, Si-Qing
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p. 173 - 176
(2011/03/21)
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- Reactions of organyl and silyl alane with 1.3.4.5.6-pentamethyl-2- aminoborazine
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The reactions of (Me3Si)3Al, Me3Al, Et3Al, and i-Bu3Al with 1,3,4,5,6-pentamethyl-2- aminoborazine have been examined. An amine alane adduct (Me3Si) 3Al NH2B3/su
- Fan, Maomin,Duesler, Eileen N.,Noeth, Heinrich,Paine, Robert T.
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p. 2983 - 2989
(2010/06/13)
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- Synthesis of hexagonal boron nitride with the presence of representative metals
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Hexagonal boron nitride (h-BN) samples were prepared using the modified O'Connor method with KNO3 and Ca(NO3)2 at different temperatures (1050, 1250, and 1450 °C). The samples were characterized by FTIR, XRD, and SEM techniques. Usage of representative metals exhibited a positive effect on the crystallization of h-BN and they caused the formation of nano-scale products at relatively low temperature. XRD results indicated that there was an increase in interlayer spacing due to the dπ interaction. The calculated lattice constants were very close to the reported value for h-BN.
- Budak, Erhan,Bozkurt, ?etin
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p. 4702 - 4705
(2011/01/06)
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- Synthesis of rose-like boron nitride particles with a high specific surface area
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Novel rose-like BN nanostructures were synthesized on a large scale via a two-step procedure. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometer and nitrogen porosimetry. The results show that the obtained rose-like nanostructures are composed of a large amount of h-BN crystalline flakes and have a surface area of 90.31 m2/g. A mechanism was proposed to explain the formation process of the rose-like BN nanostructures.
- Yu, Hongming,Huang, Xiaoxiao,Wen, Guangwu,Zhong, Bo,Zhang, Tao,Bai, Hongwei
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p. 1013 - 1016
(2010/10/02)
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- Sulfur-assisted synthesis of nitride nanocrystals
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A series of nitrides (TiN, ZrN, BN, AlN) were prepared by using the corresponding elements (Ti, Zr, B, Al), NaN3 and sulfur as starting materials in a stainless steel autoclave at 250 °C. Sulfur was used to facilitate the exothermic reaction between NaN3 and sulfur (at 250 °C) and the final formation of nitrides. The treatment temperature affected the growth of the nitride crystals, for example, diversified morphologies of TiN nanocrystals were formed in different temperature ranges: grain and truncated octahedron (250 °C), octahedron (>300 °C), and dendrite (>400 °C). Through similar processes, other nitrides (for example, TiN, AlN, Si3N4) could also be produced by employing NaNH 2 and additives (such as iodine or N-aminothiourea instead of sulfur) in low temperatures.
- Yang, Lishan,Yu, Hongxiao,Xu, Liqiang,Ma, Qiang,Qian, Yitai
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p. 2855 - 2860
(2010/06/19)
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- Metal chloride-doped ammonia borane thermolysis: Positive effect on induction period as well as hydrogen and borazine release
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In this work we studied the effect of metal chlorides (CoCl2, FeCl3 and AlCl3) on thermal decomposition of ammonia borane NH3BH3 (AB). The chlorides were chosen because they are simple and cost-effective. They showed promising performances as the onset temperature of AB decomposition decreased. Temperatures of 52, 65 and 85 °C were determined for CoCl2-, FeCl3- and AlCl 3-doped AB whereas it was 99 °C for AB. The induction period of AB dehydrogenation has been reduced. The relative mass losses were found as being 11.9, 12.3 and 10.4 wt% at about 110 °C but at 85 °C they were 4.5, 4.5 and 1.6 wt%, respectively. The gaseous side-products were analyzed and traces of borazine B3N3H6 were detected. It was found that the CoCl2 presence has a positive effect on the B 3N3H6 evolution. The solid by-products were characterized by XRD and IR: [NH2BH2]x forms after the first decomposition of AB and [BNHx]z forms after the second decomposition. The IR-print of [BNHx]z resembles that of BN, what suggests high dehydrogenation extent. These results are analyzed and discussed in the present paper.
- Benzouaa,Demirci,Chiriac,Toche,Miele
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- Nano Au-decorated boron nitride nanotubes: Conductance modification and field-emission enhancement
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This letter reports the electrical and field-emission properties of Au-decorated boron nitride nanotubes (Au-BNNTs). The insulating BNNTs become metallic after Au coating as the Au coverage exceeds a critical value. The Au decoration modifies the work function of the BNNTs and, as a consequence, the field-emission current densities of Au-BNNTs are significantly enhanced. Correspondingly, the turn-on field of the Au-BNNTs is reduced to one third and the emission current density is increased by four orders in contrast to pure BNNTs. The experimental results demonstrate that such Au-BNNTs are promising electron field emitters.
- Chen, Hua,Zhang, Hongzhou,Fu, Lan,Chen, Ying,Williams, James S.,Yu, Chao,Yu, Dapeng
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- Electron field emission from nanostructured cubic boron nitride islands
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Nanocrystal-assembled cubic boron nitride (cBN) islands are formed by using low-energy (～20 eV) ion irradiation in an inductively coupled fluorine-containing plasma. The temporal evolution of surface morphology and roughness reveals three-dimensional island growth for initial s p2 -bonded BN and subsequent cBN, accompanied by a high frequency of renucleation. The formation of cBN islands enhances the field emission and reduces the turn-on field down to around 9 Vμm due to an increase in the island-related field. The results demonstrate the high potential of cBN for field emitters, comparable to other wide band gap semiconductors.
- Teii, Kungen,Matsumoto, Seiichiro,Robertson, John
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- High-temperature chemistry and oxidation of ZrB2 ceramics containing SiC, Si3N4, Ta5Si3, and TaSi2
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The effect of Si3N4, Ta5Si3, and TaSi2 additions on the oxidation behavior of ZrB2 was characterized at 1200°-1500°C and compared with both ZrB2 and ZrB2/SiC. Significantly improved oxidation resistance of all Si-containing compositions relative to ZrB2 was a result of the formation of a protective layer of borosilicate glass during exposure to the oxidizing environment. Oxidation resistance of the Si3N 4-modified ceramics increased with increasing Si3N 4 content and was further improved by the addition of Cr and Ta diborides. Chromium and tantalum oxides induced phase separation in the borosilicate glass, which lead to an increase in liquidus temperature and viscosity and to a decrease in oxygen diffusivity and of boria evaporation from the glass. All tantalum silicide-containing compositions demonstrated phase separation in the borosilicate glass and higher oxidation resistance than pure ZrB2, with the effect increasing with temperature. The most oxidation-resistant ceramics contained 15 vol% Ta5Si3, 30 vol% TaSi2, 35 vol% Si3N4, or 20 vol% Si 3N4 with 10 mol% CrB2. These materials exceeded the oxidation resistance of the ZrB2/SiC ceramics below 1300°-1400°C. However, the ZrB2/SiC ceramics showed slightly superior oxidation resistance at 1500°C.
- Talmy, Inna G.,Zaykoski, James A.,Opeka, Mark M.
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p. 2250 - 2257
(2009/09/30)
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- A convenient catalytic approach to synthesize straight boron nitride nanotubes using synergic nitrogen source
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Straight boron nitride nanotubes (BNNTs) with pure hexagonal phase were conveniently prepared by heating the mixture of Mg(BO2)2 · H2O, NH4Cl, NaN3 and Mg powder in an autoclave at 600 °C for 20-60 h. These BNNTs had diameters mainly ranging 30-300 nm and lengths up to ～5 μm, and a majority of them had at least one closed end. Besides the traditional end tips, additional cone-like tips were frequently found to be attached on the BNNTs. The effects of temperature, reactants and the possible mechanism of the catalytic formation of the BNNTs are discussed.
- Dai, Jun,Xu, Liqiang,Fang, Zengli,Sheng, Daopeng,Guo, Qingfeng,Ren, Zeyu,Wang, Kang,Qian, Yitai
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p. 253 - 258
(2008/10/09)
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