©  Copyright 2013 Multi-walled CNT  Multi-walled nanotubes (MWCNTs) consist of multiple rolled layers (concentric tubes) of graphite.  There are two models which can be used to describe the structures of multi-walled nanotubes. In  the Russian Doll model, sheets of graphite are arranged in concentric cylinders, e.g. a (0,8) single-  walled nanotube (SWNT) within a larger (0,10) single-walled nanotube. In the Parchment model, a  single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled  newspaper. The interlayer distance in multi-walled nanotubes is close to the distance between  graphene layers in graphite, approximately 3.3 Å (330 pm). Conceptual diagrams of single-walled  carbon nanotube (SWCNT) and multiwalled carbon nanotube (MWCNT)  delivery systems showing  typical dimensions of length, width, and separation distance between graphene layers in MWCNTs.  Chemical Engineering & Gas Processing