Zhu Chunzhang, Guo Wanlin, Yu Tongxi
Department of Material Engineering, Nanjing Institute of Technology, Nanjing, People's Republic of China. Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China.
Nanotechnology. 2008 Nov 19;19(46):465703. doi: 10.1088/0957-4484/19/46/465703. Epub 2008 Oct 22.
The behavior of nanobearings constructed from double-walled carbon nanotubes (DWCNTs) is investigated with molecular dynamics simulations. The results show that the (5, 5)/(10, 10) DWCNTs can work as stable and reliable nanobearings to a speed as high as ∼2.65 r ps(-1) with an inner tube as rotator. When the speed is lower than ∼0.75 r ps(-1), the nanobearings remain in an ultrasmooth state, beyond which the intertube friction increases and fluctuates sharply. The rotational friction is sensitive to many factors such as rotation speed, radial size, and flexibility of CNTs. Increase in rotation speed and the radial sizes of CNTs leads to increase of centrifugal force and decrease of intertube distance, thus, increases the intertube friction. As a result, both the critical speed for ultrasmooth rotation and the ultimate speed decrease with increasing radius of the inner tube with constant intertube distance. The centrifugal force and thermal motion of atoms will stimulate flexile deformation of CNTs, namely waving tube axis and distorting cross-section, which will lead to an increase in rotational friction. When the outer tube serves as the rotator, the DWCNT nanobearing becomes more easily damaged.
利用分子动力学模拟研究了由双壁碳纳米管（DWCNT）构建的纳米轴承的行为。结果表明，（5,5）/（10,10）双壁碳纳米管可以作为稳定可靠的纳米轴承，以内管作为转子时，转速高达约2.65转每秒（r ps⁻¹）。当转速低于约0.75转每秒时，纳米轴承保持超光滑状态，超过该转速后，管间摩擦力增加并急剧波动。旋转摩擦力对许多因素敏感，如转速、碳纳米管的径向尺寸和柔韧性。转速和碳纳米管径向尺寸的增加会导致离心力增加和管间距离减小，从而增加管间摩擦力。因此，在管间距离恒定的情况下，随着内管半径的增加，超光滑旋转的临界速度和极限速度都会降低。原子的离心力和热运动会刺激碳纳米管的柔性变形，即管轴摆动和横截面扭曲，这将导致旋转摩擦力增加。当外管作为转子时，双壁碳纳米管纳米轴承更容易损坏。
