Ming-Shan Jeng

I nfluence of biphenyl chemisorption on the thermal properties of single-walled carbon nanotube

Non-equilibrium molecular dynamics simulations are performed to investigate the influences of chemisorption biphenyl rings under axial thermal loadings of 1.65 K/Å. This investigation determines carbon nanotube thermal conductivity at biphenyl rings sorption density ranging from 0%~30%, using a non-equilibrium molecular dynamics simulation with true carbon potentials. The thermal impact causes system fluctuation in the initial 3 ps leading to a transport region temperature as high as 400K. The thermal relaxation process reduces impact energy influence after 30 ps and leads to Maxwells 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. Simulations are performed on pristine CNTs and CNTs on which 0.25%, 1%, 5%, 10%, 15%, 20%, 25% and 30% of the carbon atoms have a bonded biphenyl group. The case where biphenyl groups are attached to 0.25% of the atoms on a nanotube is illustrated in the left panel of Figure 1. Results suggest that thermal conductivity value increases with increasing CNT subjected to thermal loading up to a temperature gradient of ~ 20 K/Å representing rapidly thermal conductivity drop at sorption density of 10%. The functionalized CNTs all show significantly smaller thermal conductivities. Simulation results yield precise understanding of nano-scale transient heat transfer characteristics in a single-wall carbon nanotube.

Influence of Thermal Loading on the Thermal Conductivity of Single-Wall Carbon Nanotube

This investigation determines carbon nanotube thermal conductivity at heat flux ranging from 0.01 to 0.3 subject to different thermal loading of 5 ∼ 50 K/nm, using a non-equilibrium molecular dynamics 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 600K. 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 CNT 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. Simulation results yield precise understanding of nano-scale transient heat transfer characteristics in a single-wall carbon nanotube.Copyright