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Content available remote Probabilistic mechanical properties and reliability of carbon nanotubes
Carbon nanotubes (CNTs) and their products such as polymer nanocomposite (PNC) are an undeniable part of future materials. To use such future materials, it is necessary to have an accurate evaluation of their properties. Several uncertainties such as structural defects and their distributions cause change in the properties of CNTs that could be considered probabilistic variables. A novel procedure is presented for evaluating CNTs’ probabilistic fracture properties and structural reliability using stochastic finite element methods. By employing two dimensionless parameters, both types of Stone–Wales 5-7-7-5 defects are randomly applied to CNTs. Section defect density and critical section defect density are defined and used to manage the distribution and geometrical configuration of CNTs’ structural defects. A probabilistic method is used to evaluate the effect of defects’ distribution on Young's modulus, ultimate strain, and ultimate stress. It has been observed that normal and Weibull distribution functions are suitable for describing Young's modulus distribution and ultimate stress distribution, respectively. Defect density ratio is defined and, using this parameter, the effect of aggregated defects on mechanical properties is evaluated. It is demonstrated that the defects out of critical section have an unavoidable effect on Young's modulus and ultimate strain; but they have an insignificant effect on ultimate stress. A reliability analysis is performed on armchair (15,15) CNTs and it is investigated that the reliability of CNTs depends on critical defect density significantly. In addition, the reliability is equal to one for the stress of less than 50 GPa and this value is equal to zero for the stress of higher than 100 GPa, independent from the changes of critical defect density. Eventually, a procedure is described to estimate the reliability of armchair CNTs using critical defect density and the results’ accuracy is discussed and evaluated.
Content available remote Nanocomposites consisting of SWCNTs/DWCNTs decorated with Re nanoparticles
Purpose: The main aim of this work is to present a method for manufacturing nanocomposite consisting of single and double-walled carbon nanotubes and rhenium nanoparticles. A decoration process was started with functionalization of CNTs, then placed CNTs in a medium containing rhenium precursors, inserted it in quartz vessel and finally heating wet material in the atmosphere of H2 and in the shield of inert gas Ar. Design/methodology/approach: The microscope examinations of single- and double walled carbon nanotubes decorated with Re were carried out with the TEM and STEM mode using an HAADF detector. An energy dispersive spectroscope (EDS) was employed to determine chemical composition of the material. Findings: This paper shows the fabrications of SWCNTs/DWCNTs–Re hybrid nanostructures. The researches has found that rhenium nanocrystals are located in the outer walls and in the core of the carbon nanotubes. Research limitations/implications: The development of CNTs decorated with metal nanoparticles has concerned intensive interest in the last decade because of their outstanding sensing properties. CNTs-based gas sensors are attractive because of their small size, low weight, low power consumption, ultra sensitivity (high and prompt response). Originality/value: Rhenium is a heavy metals, possesses very high melting and boiling point, good electrical and thermal properties, and is used in the developing industries such as space, electrical, petrochemicals, chemicals. Searching for new uses of Re, including as a component of nanocomposites composed of CNTs is purposeful and interesting.
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