Nanoinstability And Nanoprocessing Of Multi-walled Carbon Nanotubes With Different Configurations Under E-beam Athermal Irradiation

With the continuous development of nanoscience and technology,low dimensional nanostructure have attracted more and more attention,among which carbon nanotube has lots of promising applications in nanodevice along with its fabrication.This,a great deal of effort has be devoted to study on the nanostructure instability and transformation of carbon nanotube under energetic beam irradiation.Among these studies,the classical knock-on mechanism and related molecular dynamics simulation are nornally used to explain and predict the nanostructure instability and transformation of carbon nanotube under energetic beam irradiation.However,the knock-on mechanism and related molecular dynamics simulation are established on the basis of equilibrium,symmetry,periodicity and linearity nature of bulk crystalline structure or its approximation.They cannot accurately explain the phenomenon of low-dimensional nanostructure instability or transformation under the irradiation of energetic beam which is intrinsically of non equilibrium,disordered or nonlinear nature.Therefore,the effect of low-dimensional nanostructure nanocurvature and the effect of beam-induced athermal activation are not well understood or their key roles in the process of nanoinstability transformation of low dimensional nanostructure are normally neglected.In order to further reveal the effect of low-dimensional nanostructure and the effect of beam-induced athermal activation,in this thesis,using in-situ TEM electron beam irradiation technique at room temperature,we systematically investigated the nanoinstability and nanoprocessing of multi-walled carbon nanotube(MWCNT)with different configuration and under different electron beam irradiation.The specific investigations are detailed as following:(1)"necking"of MWCNT under focused electron beam irradiation;(2)elongation/contraction of MWCNT under uniform electron beam irradiation;(3)structural transformation of MWCNT fixed in both ends;(4)structural transformation of axial-curved MWCNT with"V"shape under uniform electron beam irradiation;(5)structural transformation of axial-curved MWCNT with"U" shape under uniform electron beam irradiation.The experimental results showed that at room temperature:(1)with focused electron beam irradiation,the"necking"appeared in the irradiated structure with wall atom plastic flow and wetting,leading to a gradual decrease of the number of wall,tranformation to single walled carbon nanotube and final breakage of the tube at the centre of the beam spot:(2)with uniform electron beam irradiation,the MWCNT demonstrated a homogeneous plastic elongation and radial shrinkage with wall atom plastic flow;(3)under uniform electron beam irradiation,different structural transformation of"V" and"U" shaped"MWCNTs appeared due to the non uniform distribution of nanocurvature over the surafce of the MWCNTs.The above beam-induced nanoinstabilities of MWCNTs with different configurations were driven by the MWCNT nanocurvature effect and beam athermal activation effect with the induced carbon atom"diffusion"and"evaporation".The investigation provides a reliable theoretical basis for the design,fabrication and nanoprocessing of a new generation of MWCNT-based nanodevices.At the same time,the investigationconfirmed that the nanocurvature effect and the enegetic beam athermal activation effect are universal comcepts,which can be used to predict and explain the nanoinstability and nanoprocessing of different low dimensional structures under enegetic beam irradiation.