Thermal-mechanical properties of carbon nanotubes: molecular dynamics simulation

We determine single-wall carbon nanotube (SWCNT) thermal conductivity and tunable flattening dynamics at heat flux ranging from 0.01 to 0.3 W/m 2 subject to different thermal loading of 5 to 50 K/nm, using a nonequilibrium molecular dynamics (MD) simulation with true carbon potentials. The numerical model adopts Morse bending, a harmonic cosine, and a torsion potential. The applied Nose-Hoover thermostate describes atomic interactions taking place between the atoms. Hot and cold temperature reservoirs are respectively imposed on both computational domain sides to establish the temperature gradient along the carbon nanotube. Atoms at the interface exhibit transient behavior and undergo an exponential type decay with exerted temperature gradient. The thermal impact causes system fluctuation in the initial 3 ps leading to a transport region temperature as high as 600 K. The thermal relaxation process reduces impact energy influence after 30 ps and leads to Maxwell's distribution. Steady-state constant heat flux is observed after thermal equilibrium. Furthermore, the temperature curves show distinct high disturbance at initial time and linear distribution along the tube axial direction after steady state. Results suggest that thermal conductivity value increases with increasing CNTs subjected to thermal loading up to a temperature gradient of at least ~41.3 K/A, representing thermal gradient convergence at heat conduction value 1258 W/mK. Simulation results yield precise understanding of nanoscale transient heat transfer characteristics in a single-wall carbon nanotube. Last, it is shown that given a thermal loading of sufficient intensity, the initial round cross section of the hot end of the nanotube transits through a series of triangular-like states to a flattened, rectangular configuration. As time elapses, the cross section oscillates between two fully perpendicular flattened states at a frequency that increases linearly with the intensity of the applied thermal load. (Cont'd.)