The rate-dependent interfacial behavior between a carbon nanotube (CNT) and a polyethylene (PE) matrix is investigated using molecular dynamics (MD) simulations. Various MD simulations were set up to determine the “size” effects on the interfacial properties, such as the molecular weight, or the length of the polymer, the diameter of the CNT, and the simulation model size. The interfacial rate-dependency was probed by applying various relative sliding velocities between the CNT and the polymer. Two quantities, directly obtained from the MD simulations, described the interfacial properties: the critical interfacial shear stress (CISS) and the steady interfacial shear stress (SISS). The simulations show that the SISS was not sensitive to the simulation size. In addition, the CISS was dependent upon the combined factors of the variation in PE stiffness, induced by simulation size changes and the effect of the fixed boundaries of the simulation models. The CISS increases almost linearly with the relative sliding velocity of CNTs. Also, a linear relationship between the SISS and the CNT-sliding velocity is observed when the SISS drops below a critical value. A clear size scaling is observed as the CISS and SISS decrease with increasing CNT radius and increase with the increasing polymer chain length.

The effects of water filling and electric field on the mechanical property of carbon nanotubes (CNTs) are investigated with molecular dynamics simulations. The simulation results indicate that the water filling and electric field could enhance the elastic modulus but reduce the Poisson’s ratio of the CNTs. As for the buckling behaviors, a significant enhancement could be observed in the yield stress and average post-buckling stress of the CNTs. In particular, the enhancement in the yield stress induced by the water filling and electric field could be even higher than that resulted from the solid filling. Moreover, a transition mechanism from the rod instability to shell buckling is shown to explain the nonmonotonic variation of yield stress, and the critical diameter can be tuned through filling the water molecules and applying the electric field. The present findings provide a valuable route for the optimized design and application of the nanoscale functional devices based on the water-filled CNTs.

electric field. The distributions of the dipole orientations of water molecules along the CNTs are utilized to elucidate the stretching mechanism. Our findings provide a feasible route for the design and fabrication of nanoscale switch and controller.

Carbon nanotubes have a significant application in nanotechnology as nanopipes conveying fluids. In this letter, a pressure control model for transport of liquid mercury through carbon nanotubes using classical molecular dynamics simulations in conjunction with an atomistic model is presented. Wetting of single-walled carbon nanotubes by mercury occurs above a threshold pressure of liquid mercury. The liquid mercury can be transported through carbon nanotubes with the continuous increase of its internal pressure. Also, the authors show that single-walled carbon nanotubes can transport liquid mercury discontinuously when a periodical pressure is applied on the liquid.