Nanomechanics of carbon nanotubes based nanoscale devices

• Main Author: Shenai, Prathamesh Mahesh.
• Other Authors: Zhao Yang
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Materials::Nanostructured materials; DRNTU::Engineering::Nanotechnology; DRNTU::Engineering::Mechanical engineering::Mechanics and dynamics
• Online Access: http://hdl.handle.net/10356/52488
• Institution: Nanyang Technological University

Owing to their exceptional mechanical properties, carbon nanotubes have recently emerged as promising candidates to construct nearly wear-less nanomechanical devices that can operate at ultra-high gigahertz frequencies. In this work, we specifically focus on simple machine components such as linear nano-oscillators and rotational nanobearings based on double-walled carbon nanotubes (DWNTs) and investigate those with the help of molecular dynamics (MD) simulations. This thesis aims at a comprehensive study of nanomechanics of DWNTs based nanomachines along three major aspects - performance, driving mechanisms and non-linear dynamics. We have first carried out an extensive study of factors affecting the performance of rotational nanobearings. An interesting operational regime for a short-sleeved rotational bearing constructed with (4,4)/(9,9) DWNT exhibiting a peculiar dependence on the rotational speed was uncovered. When initiated with an intermediately high angular speed, such bearing may undergo energy dissipation and enter stable operational regimes at certain specific lower angular velocity ranges. We successfully identified the energy transfer pathways between different modes that may lead to such energy dissipation. The translational motion of the sleeve was found to serve as the channeling mode that funnels a part of its rotational kinetic energy to the dissipative modes such as wavy modes of the long inner tube. As the axial translation comes to a halt, the decay channel gets closed leading to stable rotation. We then used this principle of the energy leakage channel blocking to propose a novel design scheme of a rotational nanobearing with improved performance. In the proposed structure called the `flanged nanobearing', a DWNT is structurally modified by connecting to both of its ends, another DWNT with slightly larger tube diameters. The flanged nanobearing near-completely inhibits the axial sliding of the rotor thereby resulting in an improved bearing operation at both the high angular velocity and at high temperature regimes.