Search

Influence of hydrocarbon partial pressure on single carbon nanotube (CNT) growth in chemical vapor deposition is investigated by a new theoretical model based on kinetic theory of gases and, phonon vibrations of carbon nanotube on catalyst. Results show that CNTs with larger diameter grow lesser owing to higher damping factors and CNT inertia. In addition, an optimum temperature for the growth is obtained for a CNT with a specific diameter and catalyst. Also it is shown that the optimum temperature is changed by using different catalysts. Finally effect of the partial pressure on the growth is also discussed. It is demonstrated that increasing partial pressure leads to the longest CNTs and also, influence of partial pressure on CNTs with smaller diameters is stronger. All results of the presented mechanism are in good agreement with reported experimental results. [ABSTRACT FROM AUTHOR]

One of the important phenomena influencing the resistivity behavior of nanotubes based on the change of their radius is a physical effect called "pinch effect". In this paper, according to the experimental results, the electrical resistivity behavior of carbon nanotubes is modeled as a function of the radius in the radius range of 3–10 nm. The pinch effect is not observed for weak current, but if the radius of carbon nanotube is very small, this effect will be considerable and affects carbon nanotube resistivity. The deviations observed in ρ – R (resistivity as a function of nanotube radius) diagrams for individual carbon nanotube are justified with different parameters such as pinch effect phenomenon. The results show an acceptable theoretical model for the behavior of electrical resistivity relative to radius reduction. The theory diagram of the electrical resistivity behavior of carbon nanotubes in terms of radius reduction is predicted in very small radii. These results are consistent with the experimental results. It is consistent and generalizable. [ABSTRACT FROM AUTHOR]

Experimental results show that there are unpredicted phenomena in the resistivity behavior of nanotubes as a function of their diameter. In this paper, the electrical resistivity behavior of carbon nanotubes (CNTs) is modeled as a function of diameter (at constant temperature) based on nanotube chirality. The effect of overlap of chirality surfaces on the resistivity of individual CNTs has been investigated and showed that if the windows of hexagonal lattice of individual CNTs face each other, the CNT resistivity increases. This effect becomes weaker if the diameter of nanotube increases. The proposed theoretical model explains the behavior of electrical resistivity of CNTs as a function of their diameters caused by chirality surface overlapping effect, and the obtained results are compared with the experimental reports. [ABSTRACT FROM AUTHOR]