The Formation Mechanism And Related Characteristics Of Carbon Nanovolumes

With special open edge,Carbon nanoscroll(CNS)rolled up by a single graphene sheet shows different structures compared with multi-walled carbon nanotube(MWCNT).In the preparative process of nanotubes,CNSs are more common and have more yield than MWCNT.At the same time,CNSs even have similar application to hydrogen storage,drug carrier and so on.This material has attracted the attention of many researchers,while the formation mechanism of CNS is not clear.We used molecular dynamics method to simulate the spontaneous process of forming a helical graphene nanoribbon(GNR)structure into a single-walled carbon nanotube(SWCNT),and then the process of evolution into CNS was simulated.As analyzed in this work:1.In this paper,we used AIREBO potential function to study the deformation process of GNR into SWCNT and found:(1)GNR can enter the SWCNT and form helical structure spontaneously.The distance between the adjacent helical rings is always 3.5A,which is independent of the width of GNR.(2)The distance between the helical nanoribbon and the inner wall of SWCNT is always 3.5 A,which is independent of the type of tube and the size of GNR.(3)The oscillatory frequency of GNR is around dozens of gigahertz.(4)In order to form the perfect helical structure in a SWCNT with diameter of L and length of D,the length of GNR l needs to satisfied the following conditions:(?)A.(w?4.27A,D?23.05A)2.On the base of the formation of helical nanoribbon into the SWCNT,we tried to sperate the two by moving the tube or helical nanoribbon.Under certain conditions,helical nanoribbons can deform into the CNS after the separation.Once the nanoscroll was formed by nanoribbon with the same size,its shape is independent of the carbon tube's type and size.The diameter of its central circle oscillates near 20A.The length of nanoribbon only influences the winding number of CNS.This result could bring great convenience to the manufacture of CNS with specific size.3.According to the simulation process,we put forward a possible mechanism of CNS.During the process of producing CNSs by arc discharge,some GNRs with suitable size entered into the SWCNTs and deformed into helical structure.These helical nanoribbons were pushed out of the tube due to the thermal motion,which lead to the spontaneous deformation of nanoribbons into nanoscrolls.Thus,we can observe the compound of nanotubes and nanoscrolls through transmission electron microscopy(TEM).