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This study adopts a classical molecular dynamics (MD) simulation with the realistic Tersoff many-body potential model to investigate the mechanical properties of gallium nitride (GaN) nanotubes. The investigation focuses primarily on the mechanical properties of (n,0) and (n,n) GaN nanotubes since these particular nanotubes represent two extreme cases. The present results indicate that under small strain conditions, mechanical properties such as Young’s modulus are insensitive to the wrapping angle. Conversely, the wrapping angle has a significant influence upon these mechanical properties under large strain conditions. It is demonstrated that (9,0) GaN nanotubes are far less resistant to bond rotation. Under large tensile strain conditions, due to the unfavourable bond orientations induced by Stone–Wales (SW) transformation, the bonds in (n,0) GaN tubes quickly degenerate. Moreover, the present results suggest that the tensile strength of a nanotube is strongly sensitive to the temperature and strain rate. Regarding the fatigue test, this study uses a standard theoretical model to derive curves of amplitude stress versus number of cycles for the current nanotubes. The results demonstrate that the fatigue limit of GaN nanotubes increases with increasing temperature.

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An experimental investigation is performed into the tribological properties of mineral oil lubricants containing carbon nanocapsules (CNCs) additives with various concentrations (wt.%). Friction characteristics and wear behaviors at contact interfaces are examined by the block-on-ring tests, high-resolution transmission electron microscopy (HRTEM), and mapping (MAP) analysis. The results suggest that the addition of CNCs to the mineral oil yields an effective reduction in the friction coefficient at the contact interface. Molecular dynamics (MD) simulations clarify the lubrication mechanism of CNCs at the sliding system, indicating the tribological properties are essentially sensitive to the structural evolutions of CNCs.

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