Carbon Trends (Jun 2023)
Local buckling behavior of multi-walled carbon nanotubes encapsulating C60 fullerenes
Abstract
Carbon nanotubes (CNTs) have a hollow structure and high aspect ratio. Generally, buckling under axial compression is dependent on the dimensions and chirality of the CNT and materials encapsulated in the hollow space. In this study, we performed compressive molecular dynamics simulations of (10,10), (17,17), and (28,28) single-walled CNTs (SWCNTs) and counterpart five-walled CNTS (5WCNTs) with each of these SWCNT as the innermost layer, with and without an encapsulated C60. We found that the buckling stress decreased as the CNT diameter increased. After inserting a C60, the buckling stress decreased for models with (17,17) and (28,28) but remained unchanged for models with (10,10). By analyzing the distributions of atomic stress and atomic elastic stiffness coefficient, we found that the stress distribution became non-uniform in the circumferential direction of CNTs due to the bias of C60 in models with (17,17) and (28,28). This stress heterogeneity decreased the buckling strength in both SWCNTs and 5WCNTs. We also investigated SWCNTs to 5WCNTs with (10,10) as the innermost layer and with multiple C60s at equal intervals. Cyclic shell buckling occurred in SWCNT and 2WCNT without C60. When the interval between C60s differed from the wavelength of cyclic shell buckling, the buckling stress increased due to a change in the buckling mode to local buckling. In models with three or less layers, local buckling occurred in the oblique vicinity of C60, where attractive interactions between CNTs and C60s overlapped. In 4WCNTs and 5WCNTs, the presence of C60 did not affect the buckling behavior. In the case of a peapod structure with no circumferential bias for materials in the hollow space, such as four- or more walled CNTs with encapsulated C60s, it is likely that the encapsulated material does not affect the buckling behavior of multi-walled CNTs.
