Mechanical and Electrical Properties of Nanotubes

Abstract

We review the recent progress in our understanding of the mechanical and electrical properties of carbon nanotubes, emphasizing the theoretical aspects. Nanotubes are the strongest materials known, but the ultimate limits of their strength have yet to be reached experimentally. Modeling of nanotube-reinforced composites indicates that the addition of small numbers of nanotubes may lead to a dramatic increase in the modulus, with only minimal crosslinking. Deformations in nanotube structures lead to novel structural transformations, some of which have clear electrical signatures that can be utilized in nanoscale sensors and devices. Chemical reactivity of nanotube walls is facilitated by strain, which can be used in processing and functionalization. Scanning tunneling microscopy and spectroscopy have provided a wealth of information about the structure and electronic properties of nanotubes, especially when coupled with appropriate theoretical models. Nanotubes are exceptional ballistic conductors, which can be used in a variety of nanodevices that can operate at room temperature. The quantum transport through nanotube structures is reviewed at some depth, and the critical roles played by band structure, one-dimensional confinement, and coupling to nanoscale contacts are emphasized. Because disorder or point defect-induced scattering is effectively averaged over the circumference of the nanotube, electrons can propagate ballistically over hundreds of nanometers. However, severe deformations or highly resistive contacts isolate nanotube segments and lead to the formation of quantum dots, which exhibit Coulomb blockade effects, even at room temperature. Metal-nanotube and nanotube-nanotube contacts range from highly transmissive to very resistive, depending on the symmetry of two structures, the charge transfer, and the detailed rehybridization of the wave functions. The progress in terms of nanotube applications has been extraordinarily rapid, as evidenced by the development of several nanotube-based prototypical devices, including memory and logic circuits, chemical sensors, electron emitters and electromechanical actuators.

Buckling of double-walled carbon nanotubes modeled by solid shell elements

“…[1][2][3][4][5] CNTs may be classified as single-walled carbon nanotube ͑SWCNT͒, double-walled carbon nanotube ͑DWCNT͒, and multiwalled carbon nanotube ͑MWCNT͒. Recently, it was reported that the physical properties of purely produced DWCNTs are superior to those of SWCNTs and MWCNTs.…”

The Separation Power of Nanotubes in Membranes: A Review

“…Nanotubes are the strongest materials known, but the ultimate limits of their strength have yet to be reached experimentally [40]. Because nanotubes can be viewed as "rolled-up" graphene sheets, and because graphite is exceptionally strong with respect to inplane deformations, nanotubes possess extraordinary mechanical properties.…”

“…Because nanotubes can be viewed as "rolled-up" graphene sheets, and because graphite is exceptionally strong with respect to inplane deformations, nanotubes possess extraordinary mechanical properties. An extensive discussion of bending and elastic deformation and the tensile strength of nanotubes, including modeling of nanotubes-based composites, is given by Bernholc et al [40]. This also allows their use as additives for reinforcement of composite materials based on polymers [41].…”

Directed nucleation assembly of DNA tile complexes for barcode-patterned lattices

“…If the molecular and supramolecular world can be controlled at will, then it may be possible to achieve vastly better performance for computers and memories, and it might open up a host of other applications in materials science, medicine, and biology. Because of this promise, numerous research teams have embarked on the development of various detailed aspects of nanotechnology, such as the use of physically strong and electrically active fullerene materials (1), and organic molecules that have electrical switching properties (2). The construction of molecular-scale structures is one of the key challenges facing science and technology in the 21st century.…”