We use molecular dynamics (MD) simulations to study the effects of vacancies on tube diameters and interwall spacings of multi-walled carbon nanotubes (MWCNTs). Two types of vacancies, double vacancy and three danglin...We use molecular dynamics (MD) simulations to study the effects of vacancies on tube diameters and interwall spacings of multi-walled carbon nanotubes (MWCNTs). Two types of vacancies, double vacancy and three dangling-bond (3DB) single vacancy, are identified to have opposite effects on the tube size change, which explains the inconsistency of the experimentally measured interwall spacings of MWCNTs after electron beam irradiation. A theoretical model to quantitatively predict the shrunk structures of the irradiated MWCNTs is further developed. We also discuss the fabrications of prestressed MWCNTs, in which reduced interwall spacings are desired to enhance the overall elastic modulus and strength.展开更多
Strengthening in metals is traditionally achieved through the controlled creation of various grain boundaries(GBs),such as low-angle GBs,high-angle GBs,and twin boundaries(TBs).In the present study,a series of large-s...Strengthening in metals is traditionally achieved through the controlled creation of various grain boundaries(GBs),such as low-angle GBs,high-angle GBs,and twin boundaries(TBs).In the present study,a series of large-scale molecular dynamics simulations with spherical nanoindentation and carefully designed model were conducted to investigate and compare the strengthening effects of various GBs with nano-spacing as barriers of dislocation motion.Simulation results showed that high-angle twist GBs and TBs are similar barriers and low-angle twist GBs are less effective in obstructing dislocation motion.Corresponding atomistic mechanisms were also given.At a certain indentation depth,dislocation transmission and dislocation nucleation from the other side of boundaries were observed for low-angle twist GBs,whereas dislocations were completely blocked by high-angle twist GBs and TBs at the same indentation depth.The current findings should provide insights for comprehensive understanding of the strengthening effects of various GBs at nanoscale.展开更多
基金Project supported by the National Basic Research Program (973) of China (No 2007CB936803)the National High-Tech R&D Program (863) of China (No 2008AA03Z302)+1 种基金the National Natural Science Foundation of China (No 10832005)the Joint Research Scheme of the National Natural Science Foundation of China and Research Grants Council of Hong Kong (No 50518003)
文摘We use molecular dynamics (MD) simulations to study the effects of vacancies on tube diameters and interwall spacings of multi-walled carbon nanotubes (MWCNTs). Two types of vacancies, double vacancy and three dangling-bond (3DB) single vacancy, are identified to have opposite effects on the tube size change, which explains the inconsistency of the experimentally measured interwall spacings of MWCNTs after electron beam irradiation. A theoretical model to quantitatively predict the shrunk structures of the irradiated MWCNTs is further developed. We also discuss the fabrications of prestressed MWCNTs, in which reduced interwall spacings are desired to enhance the overall elastic modulus and strength.
基金supported by the National Natural Science Foundation of China(Grant Nos.11472286,and 11672313)the National Key Basic Research Program of China(Grants Nos.2012CB932203,and 2012CB937500)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB22040503)
文摘Strengthening in metals is traditionally achieved through the controlled creation of various grain boundaries(GBs),such as low-angle GBs,high-angle GBs,and twin boundaries(TBs).In the present study,a series of large-scale molecular dynamics simulations with spherical nanoindentation and carefully designed model were conducted to investigate and compare the strengthening effects of various GBs with nano-spacing as barriers of dislocation motion.Simulation results showed that high-angle twist GBs and TBs are similar barriers and low-angle twist GBs are less effective in obstructing dislocation motion.Corresponding atomistic mechanisms were also given.At a certain indentation depth,dislocation transmission and dislocation nucleation from the other side of boundaries were observed for low-angle twist GBs,whereas dislocations were completely blocked by high-angle twist GBs and TBs at the same indentation depth.The current findings should provide insights for comprehensive understanding of the strengthening effects of various GBs at nanoscale.
