Coalescence of double-walled carbon nanotubes: Formation of novel carbon bicables

Here, we demonstrate that by coalescing double-walled carbon nanotubes (DWNTs), a novel and stable structure consisting of flattened tubules containing two single-walled tubes (SWNTs) is created. The process occurs due to the coalescence and reconstruction of the outer shells of DWNTs, leaving the inner cylinders almost intact, the latter being encapsulated inside the large diameter coalesced tube (bicable). We propose that the coalescence process is due to: (1) the thermal activity of the outer shells, which is driven by a surface energy minimization process, and (2) a zipping mechanism followed by atom reconstruction, in which two outer shells interact and anneal.