Fracture Patterns of Boron Nitride Nanotubes

This paper concerns the vibrational behavior of concentric double-walled and triple-walled carbon and boron nitride nanotubes using the finite element method. Armchair and zigzag nanotubes with different lengths and diameters are considered. Moreover, different boundary conditions are applied on the nanotubes. It is observed that in double-walled nanotubes, when the inner and outer layers are respectively from boron nitride and carbon, the frequencies are larger than those in the reverse arrangement. Investigating the effect of diameter on the first 10 natural frequencies of double-walled and triple-walled nanotubes showed that nanotubes with larger diameters possess smaller frequencies. The effect of diameter is more significant for higher modes. Finally, comparisons are made between the vibrational behavior of concentric carbon and boron nitride double-walled and triple-walled nanotubes. Considering the effect of vacancy defect on the vibrational characteristics of the nanotubes revealed that when all of the walls of the nanotubes are defective, the largest diminish occurs for the fundamental natural frequencies.

In the present work, an extensive study for predicting efficiency parameters (ji) of various simulated nanocomposites including Polymethyl methacrylate (PMMA) as matrix and different structures including various sizes of graphene platelets (GPLs), single, double, and multi-walled carbon nanotubes (SWCNTs-DWCNTs-MWCNTs), and single and double-walled boron nitride nanotubes (SWBNNTs-DWBNNTs) are investigated. It should be stated that GPLs, carbon and boron nitride nanotubes (CNTs, BNNT) with different chiralities (5, 0), (5, 5), (10, 0), and (10, 10) as reinforcements are considered. In this research, molecular dynamics (MDs) method with Materials studio software is applied to examine the mechanical properties (Young's modulus) of simulated nanocomposite boxes and calculate i of each nanocomposite boxes. Then, it is noteworthy that by changing length (6.252, 10.584, and 21.173 nm) and width (7.137, 10.515, and 19.936) of GPLs, j1, j2, and j3 approximately becomes (0.101, 0.114, and 0.124), (1.15, 1.22, and 1.26), (1.04, 1.05, and 1.07) respectively. After that efficiency parameters of SWCNTs, DWCNTs, and MWCNTs are calculated and discussed separately. Finally efficiency parameters of SWBNNTs and DWBNNTs with different chiralities by PMMA as matrix are determined by MD and discussed separately. It is known that the accurate efficiency parameters helps a lot to calculate the properties of nanocomposite analytically. In particular, the obtained results from this research can be used for analytical work based on the extended rule of mixture (ERM) in bending, buckling and vibration analysis of structure in future study.

Nanotubes represent a unique class of materials in which all atoms are located near the surface. Since electrons flowing through nanotubes are confined near the surface, nanotubes are attractive for sensing biological and chemical molecules. In addition, their tubular structures enable nanofluidic devices that are useful for novel sensing applications. In this paper, we will discuss current applications and the latest advancements on the growth of carbon nanotubes (CNTs), boron nitride nanotubes (BNNTs), and ZnO nanotubes (ZnONTs). First, CNT growth is highly controlled by regulating the effective catalysts and the dissociative adsorption of the hydrocarbon molecules during chemical-vapor deposition growth. Second, we have achieved low temperature growth of vertically aligned BNNTs at 600 degC , the first success of growing pure BNNTs directly on substrates at temperatures about half of those reported so far. Finally, we have developed an original approach for growing ZnONTs without catalyst or template. Robust, controllable growth techniques for nanotubes are necessary in order to fully realize their sensing potential.

The production and storage of the ultimate clean fuel hydrogen has received tremendous interest recently. Among the suggested hydrogen storage media for on-board applications are carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs). The present research investigated the mechanical and thermal properties of hydrogen encapsulated CNTs, BNNTs, and their hybrid structures using molecular dynamics simulations in conjunction with advanced interatomic potentials. The results suggest distinctly different bonding interactions of hydrogen with carbon, boron, and nitrogen atoms in the host that may, depending on the nanotube composition, adversely impact the mechanical robustness and thermal conductivity with increasing amounts of entrapped hydrogen.

This work presents a theoretical study of the interaction between carbon nanotubes (CNT), boron nitride nanotubes and gallium nitride nanotubes with pollutant diamines cadaverine and putrescine using density functional theory (DFT) implemented using SIESTA.

The interaction between H(2) molecules and boron nitride (BN) single-walled nanotubes with BN divacancies is investigated with density-functional theory. Our calculations reveal that H(2) molecules adsorb physically outside defective BN nanotubes, and cannot enter into BN nanotubes through bare BN divacancies because the energy barrier is as high as 4.62 eV. After the defects are saturated by hydrogen atoms, the physisorption behavior of H(2) molecules is not changed, but the energy barrier of H(2) molecules entering into BN nanotubes through the defects is reduced to 0.58 eV. This phenomenon is ascribed to hydrogen saturation induced reduction of electrostatic potential around the defects.

Investigations on gas adsorption in nanostructures are important for potential applications such as fuel cell, gas sensor, hydrogen storage etc. Of all nanomaterials, carbon (CNTs) and boron nitride nanotubes (BNNTs) are analyzed widely, since they are porous, having large surface area and high thermal stability. It is interesting to note that while CNTs exhibit both semiconducting and metallic behaviour, BNNTs show only semiconducting nature. Factors like topological defects, doping and functionalization are observed to enhance the effect of adsorption in these nanotubes. We have considered physisorption of H2, N2 and O2 in armchair (5,5) nanotubes of both carbon and boron nitride and estimated the binding energies through simulation. To study the role of defects, we have introduced a combination of an octagon and a pair of pentagon (5-8-5) called divacancy defect in the hexagonal structure and calculated adsorption binding energy (Eads) of gas molecules at the defected site. We could observe 59.72% increment in Eads in defected CNTs and 122.7% enhancement in defected BNNTs compared to defect-free tubes for hydrogen. With nitrogen molecule as adsorbate, we found 58.49% and 84.13% increase in Eads in defected CNTs and BNNTs respectively. The results lead to the conclusion that defects plays a vital role on physisorption in both carbon and boron nitride nanotubes.

Boron nitride nanotubes (BNNTs) are structurally similar to carbon nanotubes (CNTs), but exhibit completely different physical and chemical properties. Thus, BNNTs with various interesting properties may be complementary to CNTs and provide an alternative perspective to be useful in different applications. However, synthesis of high quality of BNNTs is still challenging. Hence, the major goals of this research work focus on the fundamental study of synthesis, characterizations, functionalization, and explorations of potential applications. In this work, we have established a new growth vapor trapping (GVT) approach to produce high quality and quantity BNNTs on a Si substrate, by using a conventional tube furnace. This chemical vapor deposition (CVD) approach was conducted at a growth temperature of 1200 °C. As compared to other known approaches, our GVT technique is much simpler in experimental setup and requires relatively lower growth temperatures. The as-grown BNNTs are fully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), Energy Filtered Mapping, Raman spectroscopy, Fourier Transform Infra Red spectroscopy (FTIR), UV-Visible (UV-vis) absorption spectroscopy, etc. Following this success, the growth of BNNTs is now as convenient as growing CNTs and ZnO nanowires. Some important parameters have been identified to produce high-quality BNNTs on Si substrates. Furthermore, we have identified a series of effective catalysts for patterned growth of BNNTs at desirable or pre-defined locations. This catalytic CVD technique is achieved based on our finding that MgO, Ni or Fe are the good catalysts for the growth of BNNTs. The success of patterned growth not only explains the role of catalysts in the formation of BNNTs, this technique will also become technologically important for future device fabrication of BNNTs. Following our success in controlled growth of BNNTs on substrates, we have discovered the superhydrophobic behavior of these partially vertically aligned BNNTs. Since BNNTs are chemically inert, resistive to oxidation up to ~1000°C, and transparent to UV-visible light, our discovery suggests that BNNTs could be useful as self-cleaning, insulating and protective coatings under rigorous chemical and thermal conditions. We have also established various approaches to functionalize BNNTs with polymeric molecules and carbon coatings. First, we showed that BNNTs can be functionalized by mPEG-DSPE (Polyethylene glycol-1,2-distearoyl-sn-glycero-3-phosphoethanolamine), a bio-compatible polymer that helps disperse and dissolve BNNTs in water solution. Furthermore, well-dispersed BNNTs in water can be cut from its original length of >10µm to(>20hrs). This success is an essential step to implement BNNTs in

Adsorption of transition atoms on a (8,0) zigzag single-walled boron nitride (BN) nanotube has been investigated using density-functional theory methods. Main focuses have been placed on configurations corresponding to the located minima of the adsorbates, the corresponding binding energies, and the modified electronic properties of the BN nanotubes due to the adsorbates. We have systemically studied a series of metal adsorbates including all 3d transition-metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) and two group-VIIIA transition-metal elements (Pd and Pt). We found that many transition-metal atoms can be chemically adsorbed on the outer surface of the BN nanotubes and that the adsorption process is typically exothermic. Upon adsorption, the binding energies of the Sc, Ti, Ni, Pd, and Pt atoms are relatively high (>1.0 eV), while those of V, Fe, and Co atoms are modest, ranging from 0.62 to 0.92 eV. Mn atom forms a weak bond with the BN nanotube, while Zn atom cannot be chemically adsorbed on the BN nanotube. In most cases, the adsorption of transition-metal atoms can induce certain impurity states within the band gap of the pristine BN nanotube, thereby reducing the band gap. Most metal-adsorbed BN nanotubes exhibit nonzero magnetic moments, contributed largely by the transition-metal atoms.

With the density-functional theory and nudged elastic band method, the adsorption and dissociation of the hydrogen molecule on the boron nitride (BN) nanotubes with and without defects are studied theoretically. Hydrogen molecule physically adsorbs on the surface of the BN layer and nanotubes. The dissociation of the hydrogen molecule on the surface of the perfect BN layer and nanotubes is endothermic, and the energy barrier reduces with the decrease of the diameter of the tubes, while it is still larger than 2.0 eV for the (7,0) BN nanotube. Antisite, carbon substitutional, vacancy, and Stone-Wales 5775 defects on the wall of the tube are considered. With the presence of the defects, the dissociation of the hydrogen molecule becomes exothermic and the dissociation barrier can be reduced to about 0.67 eV.

Epoxy resin is widely used in various industrial fields due to its good adhesion, corrosion resistance and the like, but its thermal conductivity is low and it is difficult to meet the heat dissipation requirements. In order to obtain epoxy composites with high thermal conductivity and excellent electrical insulation, an effective method for functionalizing boron nitride (BN) and multi-walled carbon nanotubes (CNTs) is proposed. The BN and CNTs were first ultrasonically mixed, and then functionalized by a simple dip coating procedure with polydopamine (PDA) coating (named as m(BN/CNT)). Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy analysis demonstrated the successful functionalization of PDA on BN and CNTs surfaces. Adding 20 vol% m(BN10/CNT1) increased the thermal conductivity of the epoxy composite by 231% compared to pure epoxy matrix, while still maintained a volume resistivity above 1014 Ω·cm. Dynamic mechanical analysis and scanning electron microscopy showed that PDA functionalization improved the interfacial interaction between BN, CNTs and the matrix, thus ensuring the improved thermal and mechanical properties.

Rapid developments of the silicon electronics industry have close to the physical limits and nanotube materials are the ideal materials to replace silicon for the preparation of next generation electronic devices. Boron-carbon-nitrogen nanotubes (BCNNT) can be formed by joining carbon nanotube (CNT) and boron nitride nanotube (BNNT) segments, and BC2N nanotubes have been widely and deeply studied. Here, we employed first-principles calculations based on density function theory (DFT) to study the structure, stability, and electronic properties of ultra thin (4Å diameter) BC2N nanotubes. Our results showed that the cross sections of BC2N nanotubes can transform from round to oval when CNT and BNNT segments are parallel to the tube axis. It results when the curvature of BNNT segments become larger than CNT segments. Further, we found the stability of BC2N nanotubes is sensitive to the number of B-N bonds, and the phase segregation of BNNT and CNT segments is energetically favored. We also obtained that all (3,3) BC2N nanotubes are semiconductor, whereas (5,0) BC2N nanotubes are conductor when CNT and BNNT segments are perpendicular to the tube axis; and semiconductor when CNT and BNNT segments are parallel to the tube axis. These electronic properties are abnormal when compared to the relative big ones.

Nanotube (such as carbon and boron nitride nanotubes) is a key component of modern technology applications of nanostructures due to their unique mechanical, electrical, and physical characteristics such as high elasticity modulus, suitable heat transfer, and electrical conductivity. Carbon and boron nitride nanotubes are among the promising choices in nano-fluidic, gas storage, and drug delivery systems due to their hollow cylindrical shape and appropriate chemical, mechanical, and physical properties. Thermal vibration assessment should be conducted on fluid-conveying carbon nanotubes since the effect of thermal fluctuations on the mechanical characteristics of nanostructure are significant. Previous studies have revealed that when thermal vibration is taken into account, quantum effects can become extremely important in nanoscale electronics and structures. Hence, the present review focuses mostly on previous work on fluid-conveying nanotubes and the dynamical characteristics of size-dependent vibration and non-local strain gradient theory of fluid-conveying nanotubes. Furthermore, a special effort is made to address recent and rare investigations on the vibration of fluid-conveying nanotubes in thermal environment, as well as thermal vibration concerns of carbon nanotubes.

This study explores the effects of doping by carbon (C) atoms on electronic properties of (10,10) and (16,0) boron nitride (BN) nanotubes (NTs). We exploit the random tight-binding model with Green’s function technique and coherent potential approximation to show that the C dopant causes a decrease in the bandgap of the BN NTs, and their matching Van Hove singularities (VHS) in the density of states (DOS) are broadened. When the impurity concentration is large enough, the form of the DOS of the BN NTs becomes similar to that of metallic (10,10) and semiconducting (16,0) C NTs and their VHS get sharpened. This work might provide opportunities for creating new optoelectronic devices based on BN honeycomb nanosystems.

Boron nitride (BN) nanotubes were synthesized through chemical vapor deposition over a wafer made by a LaNi5/B mixture and nickel powder at 1473 K. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were performed to characterize the microstructure and composition of BN nanotubes. It was found that the obtained BN nanotubes were straight with a diameter of 30-50 nm and a length of up to several microns. We first verify that the BN nanotubes can storage hydrogen by means of an electrochemical method, though its capacity is low at present. The hydrogen desorption of nonelectrochemical recombination in cyclic voltammograms, which is considered as the slow reaction at BN nanotubes, suggests the possible existence of strong chemisorption of hydrogen, and it may lead to the lower discharge capacity of BN nanotubes. It is tentatively concluded that the improvement of the electrocatalytic activity by surface modification with metal or alloy would enhance the electrochemical hydrogen storage capacity of BN nanotubes.