On the Mechanical Properties of Chiral Carbon Nanotubes

Carbon nanotubes (CNTs) are specific structures with valuable characteristics. In general, the structure of each nanotube is defined by a unique chiral vector. In this paper, different structures of short single-walled CNTs are simulated and their mechanical properties are determined using finite element method. For this aim, a simple algorithm is presented which is able to model the geometry of single-walled CNTs with any desired structure based on nano-scale continuum mechanics approach. By changing the chiral angle from 0 to 30 degree for constant length to radius ratio, the effect of nanotube chirality on its mechanical properties is evaluated. It is observed that the tensile modulus of CNTs changes between 0.93-1.02 TPa for different structures, and it can be higher for chiral structures than zigzag and armchair ones. Also, for different chiral angles, the bending modulus changes between 0.76-0.82 TPa, while the torsional modulus varies in the range of 0.283-0.301TPa

Improving the dispersion of SWNT in epoxy resin through a simple Multi-Stage method

This paper presents a new, univariate and improved Multi-Stage approach for dispersing of nanoparticles as well as nanotubes (CNTs) in polymeric resin. Unlike other old methods, the proposed improved technique is not dependent on various parameters and it is safer than old methods. This Multi-Stage approach includes functionalization of CNTs, mechanical dispersion and ultra-sonication (bath and probe). The quality of dispersion obtained by the proposed method, unlike the probe sonication method, is not affected by different variables such as frequency, cross-section and suspension's temperature. Because during the process, all these parameters are kept constant and linked to the time of process (Univariate system). In the planned tactic, the time of process is determined by a visual test in macro scale.In the next, in order to verify the presented method, Scanning electron microscopy (SEM) and viscosity tests were used. These tests were employed to examine and compare the quality of Single-wall carbon nanotubes (SWNT) distribution. This comparison was between the new presented approach and one of the known conventional methods (dispersion of functionalized nanotube via Ultra-sonic Probe). Also before these tests, FT-IR test was carryout for investigation of functionalized carbon nanotubes.The comparison between the results of the new proposed model and applied traditional method showed that the output quality achieved by the new method not only is not lower than the quality achieved by the traditional method but also sometimes is preferable. In addition, for validation, mechanical bending tests on samples made by the presented method showed that the proposed approach improves the mechanical properties of the nanocomposite. This increment was consistent with the results of previous researches that were based on the traditional method. Also, the proposed method was used for dispersing of another nanoparticle named Graphene Oxide, and the accuracy of the proposed method was re-confirmed. Finally, transmission electron microscopy (TEM) was used to show the full dispersion of SWNT based on the new proposed method. Keywords: Multi-Stage method, Carbon nanotube, Epoxy resin, Dispersion, Functionalizing, Sonication, Mechanical propertie

A Study on Equivalent Spherical Structure of Buckyball-C 60 Based on Continuum Shell Model

Abstract The main goal of this research is to extract a suitable continuum modeling of buckyball-C60. For this purpose, firstly the lattice structure of buckyball-C60 is modelled and subsequently a spherical structure equivalent to fullerene structure is considered. The fullerene structure modeled with shell elements is under internal pressure and in the continuum shell modeling process. The results of simulation demonstrate that the fullerene structure can be modelled using spherical structure. The comparison between strain energies of the equivalent fullerene spherical model and molecular mechanics model under radial displacement, shows that C60-fullerene spherical structures can be modeled using a shell with 0.665 Å thickness, 5.07 TPa elastic modulus and 0.165 Poisson's ratio or a shell with 0.75 Å thickness, 4.84 TPa elastic modulus and 0.19 Poisson's ratio. Moreover, the applied elliptical strain is used to demonstrate that the performance of the continuum spherical shell model of C60 is faultless

Three new records of Collembola (Hexapoda) from Birjand (South Khorasan, Iran)

During samplings were performed during 2019 in Birjand area located in South Khorasan province, three species are identified from families Entomobryidae and Bourletiellidae. Drepanura tuxeni Nosek, 1964, Drepanosira gisini Nosek, 1964 and Cassagnaudiella c.f. gamae (Bretfeld, 1994) are newly reported for the Iranian fauna of Collembola. The material examined, brief description and some illustration were given. Cassagnaudiella c.f. gamae represents the second species record of the family Bourletiellidae from Iran