Carbonitride Nanotubes Research Articles

First-principles study of the adsorption of atomic and molecular hydrogen onBC2Nnanotubes

The adsorption of atomic and molecular hydrogen on armchair and zigzag boron carbonitride nanotubes is investigated within the ab initio density functional theory. The adsorption of atomic H on the $\mathrm{B}{\mathrm{C}}_{2}\mathrm{N}$ nanotubes presents properties which are promising for nanoelectronic applications. Depending on the adsorption site for the H, the Fermi energy moves toward the bottom of the conduction band or toward the top of the valence band, leading the system to exhibit donor or acceptor characteristics, respectively. The ${\mathrm{H}}_{2}$ molecules are physisorbed on the $\mathrm{B}{\mathrm{C}}_{2}\mathrm{N}$ surface for both chiralities. The binding energies for the ${\mathrm{H}}_{2}$ molecules are slightly dependent on the adsorption site, and they are near to the range to work as a hydrogen storage medium.

Multiwall Boron Carbonitride/Carbon Nanotube Junction and Its Rectification Behavior

Theoretical calculations have predicted that the band gap of boron carbonitride (BCN) nanotubes can be tailored over a wide range by chemical composition rather than by geometrical structure. The following attempts toward the fabrication of BCN nanotube devices should be of great importance both to further understand their electronic properties and to develop their prospective applications for nanoscale electronic and photonic devices. Here, the direct synthesis of massive BCN/C nanotube junctions has been realized via a bias-assisted hot-filament chemical vapor deposition method. The electrical transport measurements of individual nanotube junctions were performed on a conductive atomic force microscopy. It is found that the BCN/C nanotube junction shows a typical rectifying diode behavior.

Large-scale aligned silicon carbonitride nanotube arrays: Synthesis, characterization, and field emission property

Large-scale aligned silicon carbonitride (SiCN) nanotube arrays have been synthesized by microwave-plasma-assisted chemical vapor deposition using SiH4, CH4, and N2 as precursors. The three elements of Si, C, and N are chemically bonded with each other and the nanotube composition can be adjusted by varying the SiH4 concentration, as revealed by electron energy loss spectroscopy and x-ray photoelectron spectroscopy. The evolution of microstructure of the SiCN nanotubes with different Si concentrations was characterized by high-resolution transmission electron microscopy and Raman spectroscopy. The dependence of field emission characteristics of the SiCN nanotubes on the composition has been investigated. With the increasing Si concentration, the SiCN nanotube exhibits more favorable oxidation resistance, which suggests that SiCN nanotube is a promising candidate as stable field emitter.

X-ray Photoelectron Spectroscopy and First Principles Calculation of BCN Nanotubes

Multiwalled boron carbonitride (BCN) nanotubes with two different structures were synthesized via thermal chemical vapor deposition; one has 10% C atoms homogeneously doped into BN nanotubes (B0.45C0.1N0.45 NTs), and the other has BN layers sheathed with 5-nm-thick C outerlayers (BN-C NTs). The electronic structures of the B, C, and N atoms were thoroughly probed by synchrotron X-ray photoelectron spectroscopy and the X-ray absorption near-edge structure method. The B0.45C0.1N0.45 NTs contain a significant amount of B-C and C-N bonding with a pyridine-like structure (hole structure), which reduces the pi bonding states of the B and N atoms. From the XPS valence band spectrum, the band gap was estimated to be about 2.8 eV. In the BN-C NTs, the C and BN domains are separated without forming the pyridine-like structure. Using the first principles method, we investigated the relative stabilities and electronic structures of the various isomers of the double-walled (12,0)@(20,0) BCN NTs. The C-outerlayer BN nanotube structure is the most stable isomer, when there exist no defects in the tubes with B/N = 1.0 (i.e., graphite-like structure). In addition, a reasonable model, which is characterized by the motives consisted of three pyridine-like rings around a hollow site, is presented for the local structure of C atoms in the B0.45N0.45C0.1 NTs. A considerable decrease of the band gap due to the 10% C doping was predicted, which was consistent with the experimental results.

Formation of boron carbonitride nanotubes from in situ grown carbon nanotubes

Boron carbonitride nanotubes (BCNNTs) were grown with high yield by DC arc discharge without catalyst particles or pre-grown template nanostructures. Two types of nanotubes (NTs) were formed: thin NTs with diameters of 10–15 nm and thick NTs with diameters of 25–50 nm. Transmission electron microscopy, electron energy loss spectroscopy, and Raman spectroscopy analyses indicate that the thin NTs are carbon NTs (CNTs) while the thick NTs are BCNNTs wrapped around CNTs. The growth kinetic appears to be faster for CNTs than for BCNNTs. Through the concerted substitution of B and N for C in the in situ grown CNTs, template growth of BCNNTs follows the CNTs growth without causing topological changes.

Analytical TEM investigations on boron carbonitride nanotubes grown via chemical vapour deposition

A systematic microstructure investigation on the boron carbonitride (BCN) nanotubes, synthesized by bias-assisted hot-filament chemical vapour deposition, is reported. The BCN nanotubes were found to be well-crystallized with uniform diameters and transverse connections inside. Their lengths can be over a few tens of micrometres. Transmission electron microscopy (TEM) analyses indicate that the BCN nanotubes have near zigzag graphic-layered structures with helical angles of less than 30°. Spatial-resolved electron energy loss spectroscopy (EELS) demonstrates typical sp2 bonding configuration of the nanotubes with pronounced characteristic π* and σ* peaks of boron and carbon and characteristic K-shell ionization edges of nitrogen. EELS and energy-filtered TEM analyses reveal that the inner layer of the nanotube contains mass of carbon and some amount of boron, and the outer layer and the connections across the inner walls are rich in boron. The nitrogen is found distributing in the nanotube dispersedly and traceable amount of oxygen is measured existing in the shell of the nanotube.

Resonance Raman scattering of boron carbonitride nanotubes

Resonance Raman spectra of boron carbonitride (BCN) nanotubes synthesized by hot-filament chemical vapor deposition were investigated. The intensity of the D band is insensitive to laser excitation energy (Elaser), while the intensity of the G and G′ bands increases as Elaser increases, and saturates at Elaser=2.67 eV. This particular resonance behavior is ascribed to an electronic transition process different from the π–π* transition that occurs in carbon materials. The dispersive behavior of the D-related bands also shows an inflection at Elaser=2.67 eV and different ∂ω/∂Elaser compared to carbon materials. These results indicate there are special electronic and phonon structures in BCN nanotubes.

The effect of hydrogen and nitrogen on the growth of boron carbonitride nanotubes

On the basis of the study of different temperature and catalyst, the effect of hydrogen and nitrogen on the morphology and yield of boron carbonitride(BCN) nanotubes produced by thermal decomposition at 860℃ was studied. It is found that nitrogen has a little effect on the growth of BCN nanotubes. Different from nitrogen, transmission electron microscopy(TEM) images reveal that hydrogen is important to the growth of BCN nanotube. Bamboo-shaped thinner wall nanotubes with higher yield are produced with hydrogen flow rate of 40 sccm, whereas curved nanotubes with lower yield and are generated with hydrogen flow rate of 0 sccm. BCN nanotubes with some holes on were produced with the flow rate of 80 sccm. Basic on previous analysis, we think that the appropriate range of N2 should be 150—210 sccm, and that of H2 should be about 40 sccm. At last, the reasons were also analysised.

Boron carbonitride nanotubes.

A comprehensive understanding of the design, synthesis, characterization, and properties of boron carbonitride nanotubes (BCN) is presented in this review. Distinctive structural and electronic properties are revealed in theoretical studies of the BCN nanotubes and compared with the properties of carbon nanotubes. In the experimental studies, BCN nanotubes have been synthesized by various techniques. For different purposes, controllable growth processes have been used to fabricate BCN nanotubes with novel structures, such as nanojunctions and filled nanotubes. Some interesting phenomena originating from the substitution of B and N atoms, such as the phase segregation, are considered theoretically and experimentally. Mainly the physical properties--field electron emission and photoluminescence--are discussed, which turn out to have potential applications in the industry.

Formation of boron carbonitride nanotubes from in situ grown carbon nanotubes for space applications

ABSTRACTBoron carbonitride nanotubes (BCNNTs) were grown with high yield by arc discharge without catalyst particles or pre-grown template nanostructures. Two types of nanotubes (NTs) were formed: thin NTs with diameters of 10–15 nm and thick NTs with diameters of 25–50 nm, all multiwall. Transmission electron microscopy, electron energy loss spectroscopy, and Raman spectroscopy analyses indicate that the thin NTs are carbon NTs (CNTs) while the thick NTs are BCNNTs wrapped around CNTs. The growth kinetic appears to be faster for CNTs than for BCNNTs. Through the concerted substitution of B and N for C in the in situ grown CNTs, template growth of BCNNTs follows the CNTs growth without causing topological changes.

The effect of different catalysts on the growth of boron carbonitride nanotubes by thermal decomposition

The effect of cobalt, nickel, cobalt/nickel, cobalt/ferrocene, nickel/ferrocene and ferrocene catalysts on the morphology and yield of boron carbonitride(BCN) nanotubes produced by thermal decomposition at 860℃ was studied. It is found that the catalysts have a strong effect on the growth of BCN nanotubes. Transmission electron microscopy images reveal that bamboo-shaped thinner wall nanotubes with a higher yield are produced with nickel/ferrocene and cobalt/ferrocene as catalysts, whereas thicker wall nanotubes with a lower yield are generated with cobalt, nickel and cobalt/nickel as catalysts. BCN nanotubes cannot be produced with ferrocene alone as catalyst. Catalyst particles were found together with the BCN nanotubes. The morphology and yield of BCN nanotubes depend on the catalysts in the following order: nickel/ferrocene≈cobalt/ferrocene>cobalt≈nickel>cobalt/nickelferrocene. Their Raman spectroscopies were also studied.

Raman characterization of boron carbonitride nanotubes

A systematic Raman study of boron carbonitride (BCN) nanotubes, synthesized by bias-assisted hot filament chemical vapor deposition, is reported. Raman spectra up to the fourth order are observed from the BCN nanotubes. Comparing with pure carbon nanotubes, the Raman bands in BCN nanotubes are broadened and the relative intensity of the D mode with respect to the G mode varies with increasing B and N atomic concentrations. The underlying mechanism has been studied on the basis of the microstructures obtained by high-resolution transmission electron microscopy.

Adjustable boron carbonitride nanotubes

The adjustable photoluminescence (PL) and field electron emission (FEE) properties of boron carbonitride (B–C–N) nanotubes grown under well-controlled conditions are studied systematically. Large-scale highly aligned B–C–N nanotubes are synthesized directly on Ni substrates by the bias-assisted hot filament chemical vapor deposition method. Single-walled B–C–N nanotubes and nanometric B–C–N heterojunctions are obtained by the pulsed-arc-discharge technique and pause-reactivation two-stage process, respectively. It is found that the microstructures, orientations, and chemical compositions of the nanotubes can be controlled by varying growth parameters. The mechanism of the controllable growth is also investigated. Intense and stable PL from the nanotubes is observed in both blue-violet (photon energies 3.14–2.55 eV) and yellow-green bands (photon energies 2.13–2.34 eV) and the emission bands are adjusted by varying the compositions of the nanotubes. FEE properties are also studied and optimized by varying the B or N atomic concentrations in the nanotubes. All these results verify the controllability of the electronic band structure of the B–C–N nanotubes.