Boron Carbonitride Research Articles

Size-dependent electronic structures of boron carbonitride (BC 2N) nanotubes. A DFT approach

The electronic structures and physical properties of zigzag BC 2N ( n,0; n = 4–10) and armchair BC 2N ( n, m; n = m = 4–10) nanotubes (type III) are studied by using density functional theory with the generalized gradient approximation. From a comparison of the binding energies, it is inferred that in the large diameter BC 2N nanotubes, the zigzag form is thermally more stable than the armchair form. BC 2N nanotubes (with the exception of (4,0) which is conductor) are gapless semiconductors. Depend on the chirality index, the zigzag forms of BC 2N nanotubes have narrower band gap than the armchair form. Semiconductor character in the studied BC 2N nanotubes is due to contribution of p electrons in the Fermi level. Mulliken population analyses show that significant amounts of electron charge are transferred between atoms; which suggests the existence of polar covalent bonds in the BC 2N nanotubes.

Thermal properties of hyperbranched polyborate functionalized multiwall carbon nanotube/polybenzoxazine composites

Using a noncovalent functionalization strategy, hyperbranched polyborate (HBb) acts as a solubilizer for carbon nanotubes (CNTs), and a stable HBb-CNT dispersion in N-methyl-pyrrolidone was produced. The thermal properties of the resulting HBb-CNT/polybenzoxazine (B-BOZ) composites and their carbonized structures were investigated. Scanning electron microscopy demonstrated that the fracture surface of HBb-CNT/B-BOZ composites was rather rough and plenty of plastic deformation was exhibited. Thermogravimetric analysis indicates an improvement in the thermal stability of the composite with CNTs, especially that of 2.0 wt% CNT modified composite. The increase in the thermal stability is due to the good nanotube dispersion and the effective polymer-CNT interaction. Graphite-like boron carbonitride ceramic compounds were found after the composites were carbonized at 1,100°C for 2 h, and there was more B-C, B-N, and C-N bonds in the carbonized HBb-CNT/B-BOZ composite than that of HBb/B-BOZ composite. The result implied that CNTs can promote the ceramic process of HBb/B-BOZ composite, and the strategy of introducing ceramic precursor into polymer composites may be useful to improve their ablation properties. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Effect of silicon-containing additives on the phase constitution and properties of boron carbonitride composites

The phase constitution and properties of BNC composites (with SiC and SiO2 (quartz glass) additives) are studied as functions of hot pressing temperature. The developed BNC composites have higher mechanical strength and oxidation resistance than hot-pressed BNC without additives and retain high insulating properties, thermal and chemical resistance, and good machinability.

The effect of C atom concentration on the electronic properties of boron carbonitride alloy nanotube in zig-zag form

Electronic properties of single-walled boron nitride nanotube in zig-zag form are numerically investigated by replacing B atoms with C atoms. Using a tight-binding Hamiltonian, the methods based on Green’s function theory, Landauer formalism and Dyson equation, the electronic density of states and electronic conductance in boron nitride nanotube and boron carbonitride nanotube are calculated. Our calculations indicate that in a boron nitride nanotube, the localized states associated with C impurities appear as the concentration of C atoms increases. The boron carbonitride nanotube thus behaves like a semiconductor. Also, by increasing the C atom concentration, the voltage in the first step on the I–V characteristics decreases, whereas the corresponding current increases.

Optical characterization of BCN films deposited at various N2/Ar gas flow ratios by RF magnetron sputtering

Abstract We present the deposition and optical characterization of amorphous thin films of boron carbonitride (BCN). The BCN thin films were deposited in a radio frequency magnetron sputtering system using a B4C target. Films of different compositions were deposited by varying the ratio of argon and nitrogen gas in the sputtering ambient. X-ray photoelectron spectroscopy was used to perform surface characterization of the deposited films and a change in composition with nitrogen flow ratio was observed. The effect of gas flow ratios on the optical properties of the films was also investigated. It was found that the transmittance of the films increases with nitrogen incorporation. The optical band gap of the films ranged from 2.0 eV to 3.1 eV and increased with N2/Ar gas flow ratio except at the highest ratio.

Synthesis and growth mechanism of BCN nanowires

The synthesis of ternary boron carbonitride (BCN) nanowires was reported in this study through a simple approach, by the reactions among a novel precursor boron triiodide (BI 3), ammonia and water-free alcohol at 1100 °C. The product was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectrometer (EDS) and electron energy loss spectroscopy (EELS), respectively. The results show that the BCN nanowires are structurally disordered and possess a uniform diameter of about 30 nm. The elemental mapping shows that B and N elements are distributed homogeneously within the nanowires, while C element is enriched in the outer layer of the nanowires. The formation of these nanowires is believed to be governed by a vapor–solid (VS) growth model.

Mechanical properties and density of BCxNy films grown by low-pressure chemical vapor deposition from triethylamine borane

Boron carbonitride (BCxNy) films of different compositions have been grown by low-pressure chemical vapor deposition using triethylamine borane as a single-source precursor and ammonia as an additional nitrogen source. Experiments were performed at various initial vapor compositions. The resultant films have been characterized by ellipsometry, IR spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, nanoindentation, and surface acoustic wave spectroscopy. The mechanical properties of the films are shown to correlate with their density and chemical composition. With increasing initial ammonia partial pressure in the vapor phase, the elemental composition of the films moves away from boron carbide, approaching boron nitride, which is accompanied by a reduction in the Young’s modulus, hardness, and density of the films.

Elaboration and quantitative investigation of BCN‐type films by dynamic SIMS using the MCsx+ mode

AbstractA quantitative SIMS approach using MCs+ mode has been tested on boron carbonitride type films (BCN). Thick amorphous BxCyNz films of different stoichiometries (0.46 ≤ x ≤ 0.68; 0.07 ≤ y ≤ 0.43; 0.01 ≤ z ≤ 0.26), deposited by thermal chemical vapour deposition, were used as standard samples to establish calibration curves between secondary ion intensities derived from in‐depth secondary ion mass spectroscopy analyses and compositions determined by X‐ray photoelectron spectroscopy. The matrix intensity ratios I(CCs+)/I(BCs+) and I(CCs2+)/I(BCs2+) appear linear with the concentration ratios CC:CB; ratios of I(NCs+)/I(BCs+) and I(NCs2+)/I(BCs2+) appear linear with the concentration ratio CN:CB as well. These calibration curves allow the quantification of matrix species in BCN films, in the range of studied stoichiometries and can be employed for compositional determination of unknown BCN films. Copyright © 2010 John Wiley & Sons, Ltd.

Fabrication of boron carbonitride (BCN) nanotubes and giant fullerene cages

Boron carbonitride (BCN) nanotubes have been successfully prepared using NH4Cl, KBH4, and ZnBr2 as the reactants at 480 °C for 12 h by a new benzene-thermal approach in a N2 atmosphere. As its by-product, a new form of carbon regular hexagonal nanocages are observed. The samples are characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), transmission electron diffraction (TED), electron energy loss spectroscopy (EELS), and high-resolution transmission electron microscopy (HRTEM). The prepared nanotubes have uniform outer diameters in the range of 150 to 500 nm and a length of up to several micrometerss. The novel carbon hexagonal nanocages have a typical size ranging from 100 nm to 1.5 µm, which could be the giant fullerene cages of [Formula: see text] (N = 17∼148). So, high fullerenes are observed for the first time. The influences of reaction temperature and ZnBr2 on products and the formation mechanism of BCN nanotubes are discussed.

Orientation of B–C–N hybrid films deposited on Ni (111) and polycrystalline Ti substrates explored by X-ray absorption spectroscopy

Orientation of sp2-bonded boron carbonitride (BCN) hybrid films has been investigated. The films were synthesized on Ni (111) and polycrystalline Ti substrates by radio frequency plasma enhanced chemical vapor deposition using tris–dimethylamino borane as a single-source molecular precursor. The deposition was performed at the radiofrequency power 400–800W at the working pressure 2.6Pa. Formation of sp2-BCN hybrids in the samples was confirmed by X-ray diffraction (XRD). In the XRD profile, the peak at 26.3° revealed formation of crystalline phase in the samples in which the lattice planes are separated from each other by around 3.5Å. The D band at ~1350cm−1 and the G band at ~1570cm−1 in Raman spectra also suggested presence of graphite-like sp2-B–C–N hybrid bonds. The films were composed of different B–N, B–C, and C–N bonds to form sp2-BCN atomic hybrids confirmed by X-ray photoelectron spectra. Orientation and local structures of the films were studied by near-edge X-ray absorption fine structure (NEXAFS) measurements. The dominant presence of π* and σ* resonance peaks of the sp2 hybrid orbitals in B K-edge NEXAFS spectra revealed preferred formation of sp2-BCN atomic hybrids around B atoms like-BN3 configuration in respect to the plane of Ni (111) substrate. Different orientations were suggested on the basis of polarization dependence of B K-edge and NK-edge of the NEXAFS spectra.

Composites of Oxidized Boron Carbonitride Nanotubes with Polyaniline: Preparation and Conductivity Studies

Five precursors of boron carbonitride nanotubes with different B/N ratios were synthesized. Oxidation with nitric acid afforded oxidized boron carbonitride nanotubes (o-BCNNTs), with which composites with polyaniline (o-BCNNTs/PANI) were prepared by in situ oxidative polymerization. For one of the o-BCNNTs, composites were synthesized with a varying amount of the nanotube (up to 30 wt %), while for the rest the nanotube content was maintained at 30 wt % in each case. It has been found that the conductivity of the oxidized boron carbonitride nanotubes decreases with an increasing B/N ratio and that of the composites increases with an increasing percentage of the o-BCNNTs.

Elastic constants and anisotropy of β-BC 2N under pressure

Structural, elastic constants and anisotropy of the potential superhard orthorhombic structure boron carbonitride β-BC 2N under hydrostatic pressure up to 100 GPa have been studied using density functional theory within the local density approximation (LDA) as well as the generalized gradient approximation (GGA) for exchange and correlation. The results are in excellent agreement with available experimental data and other theoretical results. Changes of lattice constants, the cell volume, elastic constants, and elastic anisotropy of β-BC 2N under hydrostatic loading are examined, and the bulk modulus B 0 and its pressure derivative B ′ 0 are fitted from the volume–pressure relation. It is concluded that β-BC 2N is a brittle and hard material in nature up to 100 GPa and is next to diamond in hardness. An analysis for the calculated elastic constant has been made to reveal the mechanical stability of β-BC 2N up to 100 GPa.

Solid-state reaction synthesis of boron carbonitride nanotubes

In this study, a simple route for synthesis of ternary boron carbonitride (B-C-N) nanotubes was demonstrated, by heating ball-milled mixture powders of amorphous boron and activated charcoal with a small amount of iron oxide (Fe(2)O(3)) at 1000-1200A degrees C under a mixture gas flow of nitrogen (N(2)) and hydrogen (H(2)). The reduction of Fe(2)O(3) by H(2) at 650A degrees C produced Fe nanoparticles, playing the role of a catalyst during the nanotube growth. The nanotubes synthesized at 1100A degrees C exhibit two morphologies. One is a bamboo-like structure with thick compartments. The other is a quasi-cylindrical structure with thin or disappearing compartments. The average diameter of the nanotubes is about 80 nm. It is found that the reaction temperature has a great influence on the morphology, diameter and yield of the B-C-N nanotubes. Higher temperature (1200A degrees C) is favorable for the formation of quasi-cylindrical nanotubes with larger diameters, while lower temperature (1000A degrees C) enhances the formation of bamboo-like nanotubes with smaller diameters; the yield of nanotubes decreases with the rise of reaction temperature. The nanotubes grow via a combination mechanism of solid-liquid-solid (SLS) and vapor-liquid-solid (VLS) models.

Properties of BC x N y films grown by plasma-enhanced chemical vapor deposition from N-trimethylborazine-nitrogen mixtures

Boron carbonitride films of various compositions have been grown by plasma-enhanced chemical vapor deposition using N-trimethylborazine as a single-source precursor and nitrogen as a plasma gas and an additional nitrogen source. Experiments were performed at various deposition temperatures and rf powers. The films were characterized by ellipsometry, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, IR and Raman spectroscopies, synchrotron X-ray diffraction, energy dispersive X-ray microanalysis, and spectrophotometry. The results demonstrate that, under the conditions of this study, the growth kinetics and physicochemical properties of boron carbonitride layers are influenced by both the substrate temperature and rf power. Conditions are found for producing boron carbonitride films transparent in the UV through visible spectral region.

Boron-nitride and boron-carbonitride nanotubes: synthesis, characterization and theory

We present in this review a joint experimental and theoretical overview of the synthesis techniques and properties of boron-nitride (BN) and boron-carbonitride (BCN) nanotubes. While their tubular structure is similar to that of their carbon analogues, we show that their electronic properties are significantly different. BN tubes are wide band gap insulators while BCN systems can be semiconductors with a band gap in the visible range.

Growth and characterization of stoichiometric BCN films on highly oriented pyrolytic graphite by radiofrequency plasma enhanced chemical vapor deposition

Hexagonal boron carbonitride (h-BCN) hybrid films have been synthesized on highly oriented pyrolytic graphite by radiofrequency plasma enhanced chemical vapor deposition using tris-(dimethylamino)borane as a single-source molecular precursor. The films were characterized by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopic measurements. XPS measurement showed that the B atoms were bonded to C and N atoms to form the sp 2–B–C–N atomic hybrid chemical environment. The atomic composition estimated from the XPS of the typical sample was found to be almost B 1C 1N 1. NEXAFS spectra of the B K-edge and the N K-edge had the peaks due to the π* and σ* resonances of sp 2 hybrid orbitals implying the existence of the sp 2 hybrid configurations of h-BCN around the B atoms. The G band at 1592 and D band at 1352 cm − 1 in the Raman spectra also suggested the presence of the graphite-like sp 2–B–C–N atomic hybrid bonds. The films consisted of micrometer scale crystalline structure of around 10 µm thick has been confirmed by the field emission scanning electron microscopy.

Electrical characteristics of thin boron carbonitride films on Ge(100) and Si(100)

Metal insulator semiconductor structures were fabricated from n-Si(100) and n-Ge(100) wafers passivated with thin (4.5–5 nm) films of N-rich BCxNy (0.09≤x≤0.15, 0.38≤y≤0.52) and with atomic layer deposition HfO2 (10 nm) as the gate dielectric. C-V and I-V characteristics of devices with BCxNy films grown at 275–400 °C by chemical vapor deposition showed that lower deposition temperatures resulted in improved electrical characteristics, including decreased hysteresis, lower VFB shift, lower leakage current, and less C-V stretch out. The electrical improvement is attributed to decreased bulk and interfacial defects in lower temperature deposited BCxNy films, which also had a higher optical bandgap [Eg=3.55 eV at 275 °C on Ge(100)], lower subbandgap absorption, lower index of refraction [n(633 nm)=1.84 at 275 °C on Ge(100)], reduced O uptake during ambient exposure, and increased percentage of B. Even for the lowest growth temperature studied (275 °C), BCxNy-passivated Ge(100) devices had considerable hysteresis (1.05 V), and electrical characteristics worsened after a postmetallization anneal. BCxNy-passivated Si(100) devices outperformed similar Ge(100) devices likely due to the higher interface state densities at the BCxNy–Ge(100) interface associated with the higher relative inertness of Ge(100) to thermal nitridation. C-rich BC0.61N0.08 films were also investigated but large amounts of hysteresis and fixed negative charge motivated the abandonment of these films.

PECVD BCxNy Films from Mixtures of N-trimethylborazine with Hydrogen and Ammonia: Modelling, Synthesis and Characterization

Thin boron carbonitride films were grown by plasma enhanced chemical vapour deposition using mixture of N-trimethylborazine with ammonia or hydrogen. The thermodynamic analysis of the chemical vapour deposition in B-C-N-H system was carried out for temperatures from 300 to 1300 K, a total pressure from 1.33 to 1333 Pa and a wide range of values of H2:B3N3H3(CH3)3 and NH3:B3N3H3(CH3)3 ratios. The effect of the gas phase composition and substrate temperature on the chemical composition and optical properties of the deposits was studied by ellipsometry, scanning electron microscopy, IR-spectroscopy, and optical transmittance spectrophotometry. The low temperature boron carbonitride films were demonstrated to exhibit high optical transparency in the region of 400-2000 nm (transmittance up to 93 %).

Effect of hot-pressing temperature on the phase formation and properties of boron carbonitride composite

The dependence of the phase composition and properties of a boron carbonitride (BCN) composite on hot-pressing temperature is studied. It is established that the composite forms with the synthesis of new reinforcing phases in reaction sintering under pressure. The optimum conditions to obtain the BCN composite are determined. The BCN composite has high thermal strength, oxidation resistance, and electrical insulating properties.

Facile Synthesis of Ternary Boron Carbonitride Nanotubes.

In this study, a novel and facile approach for the synthesis of ternary boron carbonitride (B–C–N) nanotubes was reported. Growth occurred by heating simple starting materials of boron powder, zinc oxide powder, and ethanol absolute at 1150 °C under a mixture gas flow of nitrogen and hydrogen. As substrate, commercial stainless steel foil with a typical thickness of 0.05 mm played an additional role of catalyst during the growth of nanotubes. The nanotubes were characterized by SEM, TEM, EDX, and EELS. The results indicate that the synthesized B–C–N nanotubes exhibit a bamboo-like morphology and B, C, and N elements are homogeneously distributed in the nanotubes. A catalyzed vapor–liquid–solid (VLS) mechanism was proposed for the growth of the nanotubes.