College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, People's Republic of China. Research School of Engineering, the Australian National University, ACT, 2601, Commonwealth of Australia.
Nanotechnology. 2017 Apr 18;28(15):155701. doi: 10.1088/1361-6528/aa622d.
In recent years, carbon-nanotube (CNT)-based gigahertz oscillators have been widely used in numerous areas of practical engineering such as high-speed digital, analog circuits, and memory cells. One of the major challenges to practical applications of the gigahertz oscillator is generating a stable oscillation process from the gigahertz oscillators and then maintaining the stable process for a specified period of time. To address this challenge, an oscillator from a triple-walled CNT-based rotary system is proposed and analyzed numerically in this paper, using a molecular dynamics approach. In this system, the outer tube is fixed partly as a stator. The middle tube, with a constant rotation, is named Rotor 2 and runs in the stator. The inner tube acts as Rotor 1, which can rotate freely in Rotor 2. Due to the friction between the two rotors when they have relative motion, the rotational frequency of Rotor 1 increases continuously and tends to converge with that of Rotor 2. During rotation, the oscillation of Rotor 1 may be excited owing to both a strong end barrier at Rotor 2 and thermal vibration of atoms in the tubes. From the discussion on the effects of length of Rotor 1, temperature, and input rotational frequency of Rotor 2 on the dynamic response of Rotor 1, an effective way to control the oscillation of Rotor 1 is found. Being much longer than Rotor 2, Rotor 1 will have perfect oscillation, i.e., with both stable (or nearly constant) period and amplitude-especially at relatively low temperature. This discovery can be taken as a useful guidance for the design of an oscillator from CNTs.
近年来，基于碳纳米管（CNT）的千兆赫兹振荡器在高速数字、模拟电路和存储单元等众多实际工程领域得到了广泛应用。千兆赫兹振荡器实际应用的主要挑战之一是从千兆赫兹振荡器产生稳定的振荡过程，然后在指定的时间段内保持稳定的过程。为了解决这一挑战，本文提出并通过分子动力学方法对基于三壁 CNT 的旋转系统的振荡器进行了数值分析。在该系统中，外管部分固定作为定子。中间管以恒定的转速旋转，称为转子 2，并在定子中运行。内管作为转子 1，可在转子 2 中自由旋转。由于两个转子在相对运动时存在摩擦，转子 1 的旋转频率会不断增加，并趋于与转子 2 的旋转频率收敛。在旋转过程中，由于转子 2 上的强端壁和管内原子的热振动，转子 1 的振荡可能会被激发。通过讨论转子 1 的长度、温度和转子 2 的输入旋转频率对转子 1 动态响应的影响，找到了控制转子 1 振荡的有效方法。转子 1 比转子 2 长得多，将具有完美的振荡，即具有稳定（或几乎恒定）的周期和幅度——特别是在相对较低的温度下。这一发现可以作为 CNT 振荡器设计的有用指导。
