Study On Dynamic Behaviors Of Double Walled Carbon Nanotubes System

Since their discovery, carbon nanotubes (CNTs) have attracted extensive attention due totheir excellent properties. The unique physical properties between interlayer of multiwalledcarbon nanotubes (MWNTs) make them the perfect candidate in nano-electramechanicalsystems (NEMS), including bearing, oscillator and motor. There are lots of research works oninterlayer fiction of MWNTs. It is generally believed that the interlayer friction of MWNTswith open ends is generated by van der Waals effects and end effects. In the present study,molecular dynamics (MD) simulation is adopted to investigate the dynamic behaviors ofdouble-walled carbon nanotubes (DWNTs). The results show that the end effects andinterlayer action will excite oscillatory and rotational behavior when the outer tube of DWNTsis fixed. The thesis is organized as follows:First, a simple introduction on CNTs is given, which includes their basic configurations,classification, methods of preparation, properties and applications. Then the research progresson mechanical properties, such as tension and compression performance and interlayerfriction, is reviewed. Hence, the necessary of the present study on dynamic behaviors ofDWNTs is raised.Second, the research methods of mechanical properties about CNTs are introduced. AsMD simulation approach is used in the present work, the principles and techniques on MDsimulation are specifically described.Third, the dynamic behaviors of DWNTs with different length differences between innerand outer tubes are investigated. The results show that higher length difference between theinner and outer tubes leads to the oscillation of inner tube at one side. In addition, the higherlength difference between inner and outer tubes, the faster approaching of the stable rotationof inner tube, and the bigger steady rotational velocity of inner tube.Fourth, the dynamic behaviors of DWNTs with different constraint on the degrees offreedom of outer tube are studied by MD simulation. It is revealed that the oscillatoryregularities of inner tubes are similar when the outer tubes are either entirely or partly fixed.However, when outer tube is entirely fixed, the shorter time for both of the excited rotation ofthe inner tube and the steady rotation approaching is required as comparing with that of theouter tube partly fixed. But the steady rotational velocity of the inner tube in a bitube system with entirely fixed outer tube is less than that of the outer tube partly fixed.Final, the dynamic behaviors of DWNTs with different interlayer gaps are investigated.The smaller interlayer gap, the higher end effect of the bitube system. Smaller inter layer gapalso leads to the earlier appearing of excited, the faster of the steady rotational velocity ofinner tube achieving and the higher steady rotational velocity of inner tube.The main contributions of the dissertation are concluded and some future works arepreviewed.