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This paper uses the molecular dynamics method to investigate the influence of chemical bonds on the mechanical behaviour of nanotube–polyethylene composites subjected to nano-particle impacts. In the analysis, carbon nanotubes (CNTs) were incorporated into the polyethylene (PE) matrix in two ways, with and without radical centres, so that the resulting nano-composites had two corresponding properties, i.e., with and without chemical bonds at the CNT–PE interfaces. A spherical diamond nano-particle was used to impact and penetrate into the composites with a high velocity. It was found that the interface chemical bonds play an important role in the composite reinforcement.

This paper presents both experimental and theoretical studies on the atomic structure changes of monocrystalline silicon brought about by surface nano-modification. The experiment revealed amorphous transformations with boundaries featuring faceting along {111} planes near the sample surface, which were altered to a random nature at the bottom of the transformation zone. The deformation outside the zone was minor near the surface, but advanced to heavy bending, extensive dislocations and plane shifting in the depth of the samples. Theoretical analysis closely reproduced this deformation, highlighting some scaling effects.

This paper discusses the phase transformation of diamond cubic silicon under nano-indentation with the aid of molecular dynamics analysis using the Tersoff potential. By monitoring the positions of atoms within the model, the microstructural changes as silicon transforms from its diamond cubic structure to other phases were identified. The simulation showed that diamond cubic silicon transforms into a body-centred tetragonal form (β-silicon) upon loading of the indentor. The change of structure is accomplished by the flattening of the tetrahedron structure in diamond cubic silicon. Upon unloading, the body-centred tetragonal form transforms into an amorphous phase accompanied by the loss of long-range order of the silicon atoms. By performing a second indentation on the amorphous zone, it was found that the body-centred-tetragonal-to-amorphous phase transformation could be a reversible process.

Molecular dynamics simulations of ZnO nanowires under tensile loading were performed and compared with simulations of TiO(2) wires to present size-dependent mechanical properties and super ductility of metal oxide wires. It is shown that while large surface-to-volume ratio is responsible for their size effects, ZnO and TiO(2) wires displayed opposite trends. Although the stiffness of both wires converged monotonically to their bulk stiffness values as diameter increases, bulk stiffness represented the upper bound for ZnO nanowires as opposed to the lower bound for TiO(2) wires. ZnO nanowires relaxed to either completely amorphous or completely crystalline states depending on wire thickness, whereas a thin amorphous shell is always present in TiO(2) nanowires. It was also found that when crystalline ZnO nanowires are stretched, necking initiated at localized amorphous regions to eventually form single-atom chains which can sustain strains above 100%. Such large elongations are not observed in TiO(2) nanowires. Using the analogy of a clothesline, an explanation is offered for the necessary conditions leading to super ductility.

The mechanisms governing the tensile behavior of TiO(2) nanowires were studied by molecular dynamics simulations. Nanowires below a threshold diameter of about 10 A transformed into a completely disordered structure after thermodynamic equilibration, whereas thicker nanowires retained their crystalline core. Initial elastic tensile deformation was effected by the reconfiguration of surface atoms while larger elongations resulted in continuous cycles of Ti-O bond straightening, bond breakage, inner atomic distortion, and necking until rupture. Nanowires have much better mechanical properties than bulk TiO(2). Nanowires below the threshold diameter exhibit extraordinarily high stiffness and toughness and are more sensitive to strain rate.