Carbon nanotubes （CNTs） having pristine structure （i.e., structure without any defect） hold very high mechanical properties. However, CNTs suffer from defects ＇which can appear at production stage, purification s...Carbon nanotubes （CNTs） having pristine structure （i.e., structure without any defect） hold very high mechanical properties. However, CNTs suffer from defects ＇which can appear at production stage, purification stage or be deliberately introduced by irradiation with energetic particles or by chemical treatment. In this article, mechanical properties of single-walled nanotubes with defects are studied under both compressive and tensile loads using molecular dynamics （MD） simulations. Two types of defectStone-Wales and vacancy defects with different defect densities are considered for present investigation. Molecular simulations are carried out using the classical MD method. The Brenner potential is used for carbon-carbon interaction in the CNT. Temperature of the system is controlled by velocity scaling. Simulation results show that the defects have negligible effect on the modulus of elasticity of nanotubes. However, they have significant effect on the failure stress and strain of the nanotubes.展开更多
The thermal conductivity of carbon nanotubes with certain defects （doping, Stone-Wales, and vacancy） is investigated by using the non-equilibrium molecular dynamics method. The defective carbon nanotubes （CNTs） ar...The thermal conductivity of carbon nanotubes with certain defects （doping, Stone-Wales, and vacancy） is investigated by using the non-equilibrium molecular dynamics method. The defective carbon nanotubes （CNTs） are compared with perfect tubes. The influences of type and concentration of the defect, length, diameter, and chirality of the tube, and the ambient temperature are taken into consideration. It is demonstrated that defects result in a dramatic reduction of thermal conductivity. Doping and Stone-Wales （SW） defects have greater effect on armchair tubes, while vacancy affects the zigzag ones more. Thermal conductivity of the nanotubes increases, reaches a peak, and then decreases with increasing temperature. The temperature at which the thermal conductivity peak occurs is dependent on the defect type. Different from SW or vacancy tubes, doped tubes are similar to the perfect ones with a sharp peak at the same temperature. Thermal conductivity goes up when the tube length grows or diameter declines. It seems that the length of thermal conductivity convergence for SW tubes is much shorter than perfect or vacancy ones. The SW or vacancy tubes are less sensitive to the diameter change, compared with perfect ones.展开更多
Axial buckling behavior of perfect and defective zigzag single-walled carbon nanotubes(SWCNTs) is studied by molecular dynamics(MD) simulations.Different effects of three typical categories of defect on the axial buck...Axial buckling behavior of perfect and defective zigzag single-walled carbon nanotubes(SWCNTs) is studied by molecular dynamics(MD) simulations.Different effects of three typical categories of defect on the axial buckling properties of SWCNTs are investigated.MD simulation results show that the buckling behavior of defective tubes is quite different from the perfect tube.The critical buckling load of zigzag SWCNTs is significantly reduced with different defect appeared in the tube wall,and the effective elastic modulus are also slightly but distinguishingly influenced by individual defect.It is revealed that an Stone-Thrower-Wales defect could induce greater decrease of the rigidity a single vacancy defect or a double vacancies one.The harmful effects of defects do not depend simply on the size of the defective area,but related strongly to the buckling modes of the defective SWCNTs which specifically differ from each other due to the different defect structures.展开更多
基金support of this research by the DAERS division of Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
文摘Carbon nanotubes （CNTs） having pristine structure （i.e., structure without any defect） hold very high mechanical properties. However, CNTs suffer from defects ＇which can appear at production stage, purification stage or be deliberately introduced by irradiation with energetic particles or by chemical treatment. In this article, mechanical properties of single-walled nanotubes with defects are studied under both compressive and tensile loads using molecular dynamics （MD） simulations. Two types of defectStone-Wales and vacancy defects with different defect densities are considered for present investigation. Molecular simulations are carried out using the classical MD method. The Brenner potential is used for carbon-carbon interaction in the CNT. Temperature of the system is controlled by velocity scaling. Simulation results show that the defects have negligible effect on the modulus of elasticity of nanotubes. However, they have significant effect on the failure stress and strain of the nanotubes.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50876010 and 51176011)the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-08-0721)
文摘The thermal conductivity of carbon nanotubes with certain defects （doping, Stone-Wales, and vacancy） is investigated by using the non-equilibrium molecular dynamics method. The defective carbon nanotubes （CNTs） are compared with perfect tubes. The influences of type and concentration of the defect, length, diameter, and chirality of the tube, and the ambient temperature are taken into consideration. It is demonstrated that defects result in a dramatic reduction of thermal conductivity. Doping and Stone-Wales （SW） defects have greater effect on armchair tubes, while vacancy affects the zigzag ones more. Thermal conductivity of the nanotubes increases, reaches a peak, and then decreases with increasing temperature. The temperature at which the thermal conductivity peak occurs is dependent on the defect type. Different from SW or vacancy tubes, doped tubes are similar to the perfect ones with a sharp peak at the same temperature. Thermal conductivity goes up when the tube length grows or diameter declines. It seems that the length of thermal conductivity convergence for SW tubes is much shorter than perfect or vacancy ones. The SW or vacancy tubes are less sensitive to the diameter change, compared with perfect ones.
基金the National Natural Science Foundation of China(No.11272123)the China Postdoctoral Science Foundation(No.2011M500132)+1 种基金the Fundamental Research Funds for the Central UniversitiesSouth China University of Technology (No.2012ZB0023)
文摘Axial buckling behavior of perfect and defective zigzag single-walled carbon nanotubes(SWCNTs) is studied by molecular dynamics(MD) simulations.Different effects of three typical categories of defect on the axial buckling properties of SWCNTs are investigated.MD simulation results show that the buckling behavior of defective tubes is quite different from the perfect tube.The critical buckling load of zigzag SWCNTs is significantly reduced with different defect appeared in the tube wall,and the effective elastic modulus are also slightly but distinguishingly influenced by individual defect.It is revealed that an Stone-Thrower-Wales defect could induce greater decrease of the rigidity a single vacancy defect or a double vacancies one.The harmful effects of defects do not depend simply on the size of the defective area,but related strongly to the buckling modes of the defective SWCNTs which specifically differ from each other due to the different defect structures.
