Non-carbon Nanotubes Research Articles

Enhancement behaviours of carbon nanotubes reinforced cement based grouting materials under dynamic loading

Carbon nanotubes (CNTs) reinforced cement based grouting material is an important part of green manufacturing industry. Our previous research showed that this material can effectively enhance the impact resistance of rock matrix. In this study, We conducted a comprehensive study and quantitative analysis of the changes in pore structure of this material under impact conditions. Dynamic impact testing and computed tomography (CT) revealed that CNTs significantly increased the cement content in the sample by 79.11 %. The CNTs group exhibited higher internal pore density and uniformity, effectively suppressing the formation of dynamic cracks in the sample. Compared to Non-carbon nanotubes (Non-CNTs) cement-based materials, the peak dynamic stress of the CNTs group increased by 4.76–21.54 %, while the porosity decreased by 57.26 %.This study further refined the enhancement behaviors of carbon nanotubes reinforced cement based, and making outstanding contributions to engineering practice.

On the Determination of Elastic Properties of Single-Walled Nitride Nanotubes Using Numerical Simulation.

In recent years, tubular nanostructures have been related to immense advances in various fields of science and technology. Considerable research efforts have been centred on the theoretical prediction and manufacturing of non-carbon nanotubes (NTs), which meet modern requirements for the development of novel devices and systems. In this context, diatomic inorganic nanotubes formed by atoms of elements from the 13th group of the periodic table (B, Al, Ga, In, Tl) and nitrogen (N) have received much research attention. In this study, the elastic properties of single-walled boron nitride, aluminium nitride, gallium nitride, indium nitride, and thallium nitride nanotubes were assessed numerically using the nanoscale continuum modelling approach (also called molecular structural mechanics). The elastic properties (rigidities, surface Young's and shear moduli, and Poisson's ratio) of nitride nanotubes are discussed with respect to the bond length of the corresponding diatomic hexagonal lattice. The results obtained contribute to a better understanding of the mechanical response of nitride compound-based nanotubes, covering a broad range, from the well-studied boron nitride NTs to the hypothetical thallium nitride NTs.

Static analysis and vibration characteristics of some noncarbon nanotubes through atomistic continuum coupled modelling

Static analysis and vibration characteristics of some noncarbon nanotubes through atomistic continuum coupled modelling

Elastic Properties of Single-Walled Phosphide Nanotubes: Numerical Simulation Study.

After a large-scale investigation into carbon nanotubes, significant research efforts have been devoted to discovering and synthesizing other nanotubes formed by chemical elements other than carbon. Among them, non-carbon nanotubes based on compounds of the elements of the 13th group of the periodic table and phosphorus. These inorganic nanotubes have proved to be more suitable candidates than carbon nanotubes for the construction of novel electronic and optical-electronic nano-devices. For this reason, until recently, mainly the structural and electrical properties of phosphide nanotubes were investigated, and studies to understand their mechanical behavior are infrequent. In the present work, the elastic properties of single-walled boron phosphide, aluminum phosphide, gallium phosphide and indium phosphide nanotubes were numerically evaluated using a nanoscale continuum modelling (also called molecular structural mechanics) approach. The force field constants required to assess the input parameters for numerical simulations were calculated for boron phosphide, aluminum phosphide, gallium phosphide and indium phosphide nanostructures using two different methods. The influence of input parameters on the elastic properties evaluated by numerical simulation was studied. A robust methodology to calculate the surface elastic moduli of phosphide nanotubes is proposed.

Overview on the Evaluation of the Elastic Properties of Non-Carbon Nanotubes by Theoretical Approaches.

Low-dimensional structures, such as nanotubes, have been the focus of research interest for approximately three decades due to their potential for use in numerous applications in engineering and technology. In addition to extensive investigation of carbon nanotubes, those composed of elements other than carbon, the so-called non-carbon nanotubes, have also begun to be studied, since they can be more suitable for electronic and optical nano-devices than their carbon counterparts. As in the case of carbon nanotubes, theoretical (numerical and analytical) approaches have been established predominantly to study non-carbon nanotubes. So far, most of work has dealt with the investigation of the structural and electrical properties of non-carbon nanotubes, paying less attention to the evaluation of their mechanical properties. As the understanding of the mechanical behaviour of the constituents is fundamental to ensure the effective performance of nanotube-based devices, this overview aims to analyse and systematize the literature results on the elastic properties of inorganic non-carbon nanotubes.

Imogolite: Curvature‐Induced Hospitality for Trivalent Dopants

Imogolite—a congregation of aluminosilicate nanotubes—has shown a great promise for fabrication of advanced materials. Imogolite nanotubes hold the record narrow diameters distribution and demonstrate one of the highest curvatures among noncarbon nanotubes. Current experimental and theoretical prospects for their modification are related mostly to surface functionalization or to progressive Si substitution on Ge, whereas a doping of Al sublattice is steadily neglected. The empirical rules of Hume–Rothery disallow such doping due to a large size mismatch between Al3+ and the majority of metal cations. Using the quantum‐chemical calculations, herein, the difference in coordination environment is unveiled for 12 sorts of trivalent cations at octahedral Al sites in both a highly curved imogolite layer and the flat gibbsite layer. The curvature of natural imogolite acts provoking for violation of the Hume–Rothery rules, sterically promoting the doping of Al sublattice by cations with radii 1.0–1.2 Å typical for rare‐earth elements. Theoretically, the synthesis of a metal‐doped imogolite is restricted only by the overlap of the phase stability fields for precursor reactants or by kinetic factors. This study might be inciting for the synthesis of chemically modified imogolite and related Ge‐imogolites.

Acoustical characteristics of single-walled noncarbon nanotubes: Longitudinal and torsional waves

A study based on nonlocal continuum elastic theory is presented on the acoustic properties of single-walled noncarbon nanotubes, including boron nitride (BN), aluminum nitride (AlN), gallium nitride (GaN), aluminum phosphide (AlP), gallium phosphide (GaP), and boron (B) nanotubes. Elastic characteristics of the noncarbon nanotubes needed to describe the elastic waves propagation correctly have been defined previously. Two-dimensional densities (2D densities) for each type of noncarbon nanotubes are calculated. The values of propagation velocities of longitudinal and torsional elastic waves for proposed nanotubes with different diameter and chirality are obtained. Specific result is that in boron nanotubes sound propagates at a speed equal 54 km/s.

Elastic properties of noncarbon nanotubes as compared to carbon nanotubes

A comparative study of stability, structural, and elastic properties of single-wall noncarbon nanotubes, including BN, AlN, GaN, AlP, GaP, and B nanotubes using ab initio simulation is presented. The proposed nanotubes can be found in nature, which is confirmed by calculation of their binding energy. The values of Young's modulus and Poisson's ratio for (0,$n$) and ($n,n$) proposed nanotubes with $n=3\ensuremath{\cdots}20$ are obtained. The conception of two-dimensional (2D) Young's modulus of planar and tubular materials was developed. The calculations show that stable forms of boron nitride nanotubes have the 2D Young's modulus almost similar to carbon nanotubes. At the same time, it is stated that boron nanotubes have a higher 2D Young's modulus than any other known carbon and noncarbon nanostructures.

Investigation of the sorption properties of carbon nanotubes with different boron impurity contents

DOI 10.17586/2220-8054-2016-7-1-93-98 Since their discovery in the early 1990’s, carbon nanotubes (CNTs) have become the subject of numerous investigations into their electronic structure and energy spectrum parameters as well as their physico-chemical properties. Due to their high surface activity, nanotubes can be used as base components for the fabrication of various types of composites. However, along with carbon nanotubes, current research also focuses on theoretical and experimental investigation of non-carbon nanotubes, namely recently discovered boron-carbon nanotubes with different concentrations of boron in them (25 % or 50 %). This article presents the results of theoretical research into the properties of boron-carbon nanotubes (BCNTs) within the framework of an ionic-built covalent-cyclic cluster model and an appropriately modified MNDO quantum chemical scheme, as well as DFT method. The authors studied mechanism of Cl and O atoms sorption onto the external surface of single-walled armchair nanotubes. As result of the study, geometrical optimization of the sorption complexes was defined, and sorption energy values were obtained.

Submerged arc discharge technique to explore novel non-carbon nanotubes: Syntheses of nanotubes from ZnO and BaTiO3

A unique reaction field using arc discharge in water can create novel nanostructures, where an extreme temperature drop is observed in bubbles around a hot arc plasma zone. Here, a Mo anode had a hole at its tip, into which ZnO or BaTiO3 powder was stuffed. The cathode received film products on its surface. It was revealed that BaTiO3 nanotubes were firstly synthesized as novel nanotubes when BaTiO3 powder was stuffed in the anode hole. When ZnO powder was stuffed in the anode hole, narrow ZnO nanotubes were synthesized. The diameter of the ZnO nanotubes synthesized was the smallest ever reported.

ChemInform Abstract: Atom‐Decorated Nanotubes

AbstractReview: 332 refs.

Magnetic properties of model non-carbon nanotubes with macroscopic value of ground state spin

The spin model of “ferrimagnetic” nanotube is proposed and some theoretical predictions concerning the ground state and low energy excitations of the model are given. In particular, the spin–wave structure of the exact ground state of bipartite magnets is proven. For tubes formed by weakly interacted cyclic fragments we show: first, the existence of gapless excitations with decreasing total spin; and second, gapped excitations. This leads to an intermediate plateau in field dependence of tube magnetization. Numerical calculations show the strong effect of frustrations on the magnetization of anisotropic spin tubes at low temperatures which may lead to the creation of an additional fractional magnetization plateau.

Boron Nitride Nanotubes and Nanosheets

Hexagonal boron nitride (h-BN) is a layered material with a graphite-like structure in which planar networks of BN hexagons are regularly stacked. As the structural analogue of a carbon nanotube (CNT), a BN nanotube (BNNT) was first predicted in 1994; since then, it has become one of the most intriguing non-carbon nanotubes. Compared with metallic or semiconducting CNTs, a BNNT is an electrical insulator with a band gap of ca. 5 eV, basically independent of tube geometry. In addition, BNNTs possess a high chemical stability, excellent mechanical properties, and high thermal conductivity. The same advantages are likely applicable to a graphene analogue-a monatomic layer of a hexagonal BN. Such unique properties make BN nanotubes and nanosheets a promising nanomaterial in a variety of potential fields such as optoelectronic nanodevices, functional composites, hydrogen accumulators, electrically insulating substrates perfectly matching the CNT, and graphene lattices. This review gives an introduction to the rich BN nanotube/nanosheet field, including the latest achievements in the synthesis, structural analyses, and property evaluations, and presents the purpose and significance of this direction in the light of the general nanotube/nanosheet developments.

Linear augmented cylindrical wave method and its applications to nanotubes electronic structure

A linear augmented cylindrical wave method for calculating an electronic structure of the single-wall, double-wall, and embedded nanotubes is developed. The approximations are made in the sense of muffin-tin potentials and local-density-functional theory only. The method is implemented as a program package and applied to determine the total band structures and densities of states of the chiral and achiral, semiconducting and metallic both pure and copper intercalated tubules. The effect of As impurities on the electronic structure of the BN nanotubes demonstrates application of method to the non-carbon nanotubes.

Linearized augmented cylindrical wave method for chiral nanotubes

The linearized augmented cylindrical wave (LACW) method has been developed for calculation of the electronic structure of carbon nanotubes [1‐3]. The LACW method is an extension of the well-known linearized augmented plane wave method (LAPW), one of the most exact methods in the band theory of crystals [4‐6], to cylindrical molecules. The major argument for the use of cylindrical waves to describe nanotubes is that such a choice of a basis set allows explicit consideration of the cylindrical geometry of nanotubes, which, in particular, ensures fast convergence of a computational procedure. However, all previous calculations of single- and double-walled carbon and non-carbon nanotubes by the LACW method dealt only with achiral nanotubes, ( n , n ) armchair and ( n , 0 ) zigzag nanotubes with a small number of atoms per translational unit cell [1‐3, 7‐12]. For even small-diameter chiral nanotubes, the number of atoms in the translational unit cell can be very large. For example, the translational cell of the achiral (10,10) nanotube comprises 40 atoms, whereas the translational cell of the chiral (10,9) tube of somewhat smaller diameter comprises 1084 atoms. As is known, the basis set required for convergence rapidly increases with an increase in the number of atoms in the unit cell, which renders impracticable calculations of chiral tubes. It is worth noting that alternative ab initio quantum-chemical calculations of the electronic structure of nanotubes, such as the tight binding method with an atomic basis set and the pseudopotential method with a basis set of plane waves, face the same problem as the LACW method. Therefore, all ab initio band calculations of nanotubes have been restricted to armchair and zigzag tubes or, at best, have dealt with some of the simplest chiral tubes of the smallest diameter and, thus, with a minimal number of atoms in the translational cell. These facts indicate that all rather than only translational symmetry properties of nanotubes should be considered in development of the theory of their electronic structure.

Energy and electronic properties of non-carbon nanotubes based on silicon dioxide

The geometric, energy, and electronic characteristics of new non-carbon nanotubes based on silicon dioxide are investigated in the framework of the local electron density functional formalism. Nanotubes are classified according to the type of rolling-up of the SiO2 sheet. It is shown that, among the entire set of considered nanotubes with different symmetries, the (6, 0) nanotubes are energetically more favorable. The densities of states for nanotubes are calculated. It is established that all nanotubes are dielectrics with a wide band gap. The band gap varies over a wide range with a change in the longitudinal strain of the nanotube.

New class of non-carbon AlP nanotubes: Structure and electronic properties

A new class of non-carbon nanotubes based on Group III and Group V elements (aluminum and phosphorus, respectively) is considered. The equilibrium geometry, energy characteristics, and electronic structure of the AlP nanotubes were calculated using the density functional theory. These calculations demonstrated that the AlP nanotubes are energetically stable structures. It was found that a low strain energy (approximately 0.01–0.07 eV) is required for rolling a two-dimensional hexagonal AlP structure into a tube. The AlP nanotubes are found to be wide-band-gap semiconductors with a band gap of 2.05–3.73 eV with direct (for the zigzag type) or indirect (for the armchair type) transitions between the top of the valence band and the bottom of the conduction band. The band gap of these nanotubes increases with the tube diameter, approaching the band gap of a two-dimensional hexagonal AlP layer.

Optimization of the Calculations of the Electronic Structure of Carbon Nanotubes

A method is proposed for calculating the electronic structure and physical properties (in particular, Young’s modulus) of nanotubes, including single-walled carbon nanotubes. This method explicitly accounts for the periodic boundary conditions for the geometric structure of nanotubes and makes it possible to decrease considerably (by a factor of 10–103) the time needed to calculate the electronic structure with minimum error. In essence, the proposed method consists in changing the geometry of the structure by partitioning nanotubes into sectors with the introduction of the appropriate boundary conditions. As a result, it becomes possible to reduce substantially the size of the unit cell of the nanotube in two dimensions, so that the number of atoms in a new unit cell of the modified nanotube is smaller than the number of atoms in the initial unit cell by a factor equal to an integral number. A decrease in the unit cell size and the corresponding decrease in the number of atoms provide a means for drastically reducing the computational time, which, in turn, substantially decreases with an increase in the degree of partition, especially for nanotubes with large diameters. The results of the calculations performed for carbon and non-carbon (boron nitride) nanotubes demonstrate that the electronic structures, densities of states, and Young’s moduli determined within the proposed approach differ insignificantly from those obtained by conventional computational methods.

Recent Advances in Hydrogen Storage in Metal‐Containing Inorganic Nanostructures and Related Materials

AbstractFor Abstract see ChemInform Abstract in Full Text.

Nanostructured superconductors: from granular through wire towards high-T<SUB align=right>c nanotubular 2D composites

Superconductivity in nanostructured materials, nanowires, nanotubes and their 2D crystals is briefly reviewed. Experimental data show both the decrease of a critical superconducting temperature Tc under transition from polycrystalline to nanogranular ceramics, and the increase of Tc under transition to one-dimensional (1D) nanowires, nanotubes and their 2D crystals. Theoretical requirements for ideal room-Tc superconductor is shown to point out on 2D crystals built from noncarbon nanotubes of superconducting layered material as the ideal media. Analysis of superconductivity in MgBE2 is presented which point out on a key role of E2g-vibrations of boron ions resulted in the mechanism of two-gap two-phonon superconductivity. Connected with the author's concept of nanotubular superconductivity, this model lay off a bridge for the novel joint model of a nanotubular multi-phonon multi-gap room-Tc superconductivity on base of gallery of whispering circular zero-points phonon modes (twistons, rotons), in particular E2g-mode, resulting in resonant electron-phonon coupling. From a structural engineering point of view, a novel route in high-Tc and room-Tc superconductivity is advanced based on 2D crystals built from noncarbon MgB2, NbSe2, Sn, Bi or other superconducting nanotubes with expected record Tc. The suggested original model is in accordance with some recent experimental data confirming the effect of nanotubular superconductivity. Recent progress in synthesis of 2D nanochannel membrane and nanowire-brush templates, aligned nanotube arrays and nanotubular crystals are briefly reviewed as promising routes to fabricate these record nanotubular superconductors.