基于应力梯度理论修正的Timoshenko(铁木辛柯)梁模型,结合管间Van der Waals(范德华)力,研究了非局部效应对双壁碳纳米管中弹性波各阶模态的相速度、频率、临界频率、内外管振幅比等频散特性的影响.数值模拟结果表明:在应力梯度理论修...基于应力梯度理论修正的Timoshenko(铁木辛柯)梁模型,结合管间Van der Waals(范德华)力,研究了非局部效应对双壁碳纳米管中弹性波各阶模态的相速度、频率、临界频率、内外管振幅比等频散特性的影响.数值模拟结果表明:在应力梯度理论修正模型下,对应同一波数,4阶模态的相速度、频率均随剪力非局部因子的增大而减小,且随着剪力非局部因子的等幅增加,相速度、频率的减小并没有明显的等幅规律;值得注意的是,3、4阶模态的内外管振幅比并不是随着剪力非局部因子的增加依次减小;在波数较高阶段,剪力非局部因子对双壁碳纳米管中波的相速度、频率、渐近频率、内外管振幅比等频散特性均有显著影响.展开更多
Nanoscale defects in the outer tube to preserve the electrical and optical features of the inner tube can be engineered to exploit the intrinsic properties of double walled carbon nanotubes (DWCNTs) for various promis...Nanoscale defects in the outer tube to preserve the electrical and optical features of the inner tube can be engineered to exploit the intrinsic properties of double walled carbon nanotubes (DWCNTs) for various promising applications. We demonstrated a selective way to make defects in the outer tube by the fluorination of DWCNTs followed by the thermal detachment of the F atoms at 1000 °C in argon. Fluorinated DWCNTs with different amounts of F atoms were prepared by reacting with fluorine gas at 25, 200, and 400 °C that gave the stoichiometry of CF0.20, CF0.30, and CF0.43, respectively. At the three different temperatures used, we observed preservation of the coaxial morphology in the fluorinated DWCNTs. For the DWCNTs fluorinated at 25 and 200 °C, the strong radial breathing modes (RBMs) of the inner tube and weakened RBMs of the outer tube indicated selective fluorine attachment onto the outer tube. However, the disappearance of the RBMs in the Raman spectrum of the DWCNTs fluorinated at 400 °C showed the introduction of F atoms onto both inner and outer tubes. There was no significant change in the morphology and optical properties when the DWCNTs fluorinated at 25 and 200 °C were thermally treated at 1000 °C in argon. However, in the case of the DWCNTs fluorinated at 400 °C, the recovery of strong RBMs from the inner tube and weakened RBMs from the outer tube indicated the selective introduction of substantial defects on the outer tube while preserving the original tubular shape. The thermal detachment of F atoms from fluorinated DWCNTs is an efficient way to make highly defective outer tubes for preserving the electrical conduction and optical activity of the inner tubes.展开更多
文摘基于应力梯度理论修正的Timoshenko(铁木辛柯)梁模型,结合管间Van der Waals(范德华)力,研究了非局部效应对双壁碳纳米管中弹性波各阶模态的相速度、频率、临界频率、内外管振幅比等频散特性的影响.数值模拟结果表明:在应力梯度理论修正模型下,对应同一波数,4阶模态的相速度、频率均随剪力非局部因子的增大而减小,且随着剪力非局部因子的等幅增加,相速度、频率的减小并没有明显的等幅规律;值得注意的是,3、4阶模态的内外管振幅比并不是随着剪力非局部因子的增加依次减小;在波数较高阶段,剪力非局部因子对双壁碳纳米管中波的相速度、频率、渐近频率、内外管振幅比等频散特性均有显著影响.
基金support from JSPS KAKENHI (24710115)Y.A.K. and K.S.Y. acknowledge the support from Global Research Laboratory (K2090300202412E010004010) through the National Research Foundation of Korea funded by the Ministry of Science, Information and Communication Technologies and Future Planning, KoreaY.C.J. and C.M.Y. acknowledge the support from the Institutional Program of Korea Institute of Science and Technology (2Z04250)
文摘Nanoscale defects in the outer tube to preserve the electrical and optical features of the inner tube can be engineered to exploit the intrinsic properties of double walled carbon nanotubes (DWCNTs) for various promising applications. We demonstrated a selective way to make defects in the outer tube by the fluorination of DWCNTs followed by the thermal detachment of the F atoms at 1000 °C in argon. Fluorinated DWCNTs with different amounts of F atoms were prepared by reacting with fluorine gas at 25, 200, and 400 °C that gave the stoichiometry of CF0.20, CF0.30, and CF0.43, respectively. At the three different temperatures used, we observed preservation of the coaxial morphology in the fluorinated DWCNTs. For the DWCNTs fluorinated at 25 and 200 °C, the strong radial breathing modes (RBMs) of the inner tube and weakened RBMs of the outer tube indicated selective fluorine attachment onto the outer tube. However, the disappearance of the RBMs in the Raman spectrum of the DWCNTs fluorinated at 400 °C showed the introduction of F atoms onto both inner and outer tubes. There was no significant change in the morphology and optical properties when the DWCNTs fluorinated at 25 and 200 °C were thermally treated at 1000 °C in argon. However, in the case of the DWCNTs fluorinated at 400 °C, the recovery of strong RBMs from the inner tube and weakened RBMs from the outer tube indicated the selective introduction of substantial defects on the outer tube while preserving the original tubular shape. The thermal detachment of F atoms from fluorinated DWCNTs is an efficient way to make highly defective outer tubes for preserving the electrical conduction and optical activity of the inner tubes.
