This paper investigates the effective wall thickness of a single-walled carbon nanotube, a critical quantity for any research in mechanics and property characterization of carbon nanotubes. To this end, the response of a bundle of single-walled carbon nanotubes to external hydrostatic pressure was modeled using the ring theory of continuum mechanics. The model predicted that the equivalent thickness should be 0.617 Å. This in turn clarified the dilemma of the inconsistent Young's modulus of carbon nanotubes reported in the literature.

This letter investigates the structural changes in monocrystalline silicon caused by microindentation with the aid of the high-resolution transmission electron microscopy. It shows that the transformation zone is amorphous when the maximum indentation load, P max , is low, but a crystalline phase of high-pressure R8/BC8 can appear when P max increases. The nanodeformation of the pristine silicon outside the transformation zone proceeds with the mechanical bending and distortion of the crystalline planes. Certain extent of plastic deformation took place due to dislocation slipping. The results seem to indicate that the shear stress component played an important role in the deformation of the transformation zone.

This study discusses the behavior of high-pressure phases of monocrystalline silicon when subjected to cyclic indentations with a spherical indenter. It was found that specific phases form in the second and subsequent indentation cycles under low maximum loads. An increase of the maximum indentation load causes changes of subsequent indentation cycles of the phase transformation events to occur earlier on both loading and unloading. The repeated indentations result in the formation of a multiphase structure in the deformed zone, featuring a nonhysteresis behavior. After a critical stage, the properties of the transformed material are stabilized and further indentations can no longer alter the load–displacement curve. It was also found that the greater the maximum load, the faster the occurence of property stabilization.

The study presents evidence of the microstructural evolution during cyclic indentation of monocrystalline silicon with a spherical indenter. Transmission electron microscopy examination of microindentation on cross-section view samples showed that the structure change in the transformation zone features a decomposition of the amorphous phase to R8/BC8 crystals. Outside the zone, cyclic loading gives rise to bending of pristine silicon, slip penetration, and radial cracking. The development of the load–displacement curves during consecutive indentations is justified in terms of the phase transformation events observed.

To make full use of the strength of carbon nanotubes in a composite, it is important to have a high-stress transfer at the matrix−nanotube interface via strong chemical bonding. This paper investigates the possible polyethylene−nanotube bonding with the aid of a quantum mechanics analysis. The polyethylene chains were represented by alkyl segments, and the nanotubes were modeled by nanotube segments with H atoms added to the dangling bonds of the perimeter carbons. The study predicts that covalent bonding between an alkyl radical and a nanotube is energetically favorable, and that the tubes of smaller diameters have higher binding energies. Hence, a high-stress transfer can be realized in polyethylene-based carbon nanotube composites in the presence of free-radical generators.