Our Publications

  • Formation of sp3 Bonding in Nanoindented Carbon Nanotubes and Graphite. Wanlin Guo, C.Z. Zhu, T.X. Yu, C.H. Woo, B. Zhang, and Y.T. Dai. Phys. Rev. Lett., 2004, 93, 245502.

    Wanlin Guo1,*, C. Z. Zhu1,2, T. X. Yu2, C. H. Woo3, B. Zhang1, and Y. T. Dai1

    1. Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
    2. Department of Mechanical Engineering, Hong Kong University of Science and Technology, Hong Kong, China
    3. Department of Electronic and Information Engineering, Hong Kong Polytechnic University, Hong Kong, China

    Phys. Rev. Lett. 93, 245502 (2004) [4 pages]

    Received 19 April 2004; published 8 December 2004

    Nanoindentation-induced interlayer bond switching and phase transformation in carbon nanotubes (CNTs) and graphite are simulated by molecular dynamics. Both graphite and CNTs experience a soft-to-hard phase transformation at room temperature at compressive stresses of 12 and 16 GPa, respectively. Further penetration leads to the formation of interlayer sp3 bonds, which are reversible upon unloading if the compressive stress is under about 70 GPa, beyond which permanent interlayer sp3 bonds form. During nanoindentation, the maximum nanohardness of graphite can reach 109 GPa, and CNTs 120 GPa, which is comparable to that of diamond.

  • The coupled effects of mechanical deformation and electronic properties in carbon nanotubes. Wanlin Guo, and Yufeng Guo. Acta Mechanica Sinica, 2004, 20(2), 192-198.

    Wanlin Guo, and Yufeng Guo.

    Acta Mechanica Sinica, 2004, 20(2), 192-198.

    Coupled effects of mechanical and electronic behavior in single walled carbon nanotubes are investigated by using quantum mechanics and quantum molecular dynamics. It is found that external applied electric fields can cause charge polarization and significant geometric deformation in metallic and semi-metallic carbon nanotubes. The electric induced axial tension ratio can be up to 10% in the armchair tube and 8.5% in the zigzag tube. Pure external applied load has little effect on charge distribution, but indeed influences the energy gap. Tensile load leads to a narrower energy gap and compressive load increases the gap. When the CNT is tensioned under an external electric field, the effect of mechanical load on the electronic structures of the CNT becomes significant, and the applied electric field may reduce the critical mechanical tension load remarkably. Size effects are also discussed.

    Keywords: quantum mechanics, quantum-molecular dynamics, single-walled carbon nanotube, coupled effect, mechanical-electronic property

  • Structural Transition of Copper Nanowires Confined in Single-Walled Carbon Nanotubes. Yufeng Guo, Yong Kong, Wanlin Guo, and Huajian Gao. Journal of Computational and Theoretical Nanoscience, 2004, 1(1), 93-98.

    Yufeng Guo,1,2 Yong Kong,1, Wanlin Guo,2, and Huajian Gao,1

    1. Max-Planck Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany
    2. Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China

    Journal of Computational and Theoretical Nanoscience, 2004, 1(1), 93-98.

    Structural transition of Cu-nanowires confined in single-walled carbon nanotubes (SWNTs) was investigated using classical molecular dynamics simulations. The nanowires were assumed to have an fcc structure with axis in the (100) direction before being encapsulated into the SWNTs. With increasing temperature, the initial fcc structure of the confined nanowires was found to transform into a coaxial cylindrical multi-shell structure within the SWNTs. Due to larger thermal expansion coefficient of the Cu-nanowire, the confining pressure inside SWNT increases with rising temperature. The combined effect of pressure and the cylindrical geometry of SWNTs are believed to play a dominant role in the structural transformation of the encapsulated Cu-nanowires. The transition temperature of the nanowire under conditions of varying degrees of confining pressure and geometry templating was investigated.