Water filling and electric field-induced enhancement in the mechanical property of carbon nanotubes.
Bottom Line:
The effects of water filling and electric field on the mechanical property of carbon nanotubes (CNTs) are investigated with molecular dynamics simulations.The simulation results indicate that the water filling and electric field could enhance the elastic modulus but reduce the Poisson's ratio of the CNTs.The present findings provide a valuable route for the optimized design and application of the nanoscale functional devices based on the water-filled CNTs.
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Affiliation: State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China.
ABSTRACT
The effects of water filling and electric field on the mechanical property of carbon nanotubes (CNTs) are investigated with molecular dynamics simulations. The simulation results indicate that the water filling and electric field could enhance the elastic modulus but reduce the Poisson's ratio of the CNTs. As for the buckling behaviors, a significant enhancement could be observed in the yield stress and average post-buckling stress of the CNTs. In particular, the enhancement in the yield stress induced by the water filling and electric field could be even higher than that resulted from the solid filling. Moreover, a transition mechanism from the rod instability to shell buckling is shown to explain the nonmonotonic variation of yield stress, and the critical diameter can be tuned through filling the water molecules and applying the electric field. The present findings provide a valuable route for the optimized design and application of the nanoscale functional devices based on the water-filled CNTs. No MeSH data available. Related in: MedlinePlus |
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Mentions: The MD method is adopted to study the mechanical property of water-filled CNTs under the compressive load. Fig. 6 illustrates the computational models. Five capped armchair CNTs, i.e., (6, 6), (8, 8), (10, 10), (12, 12) and (16, 16) CNTs, are chosen as the water carriers. The bottom end of the water-filled CNTs is fixed on a rigid substance, and the top end is compressed by a spring. The spring is gradually compressed as 0.1 Å/ps and its length change is used to calculate the applied compressive force. Moreover, to examine the effect of loading rate, the stress-strain curves with a small spring velocity of 0.05 Å/ps is also extracted and presented in Supplementary Fig. S1 online. The consistent results demonstrate the rationality of the present loading rate. Without considering the boundary section, the effective lengths of the water-filled CNTs are about 100 Å. The filling density of water inside the CNTs is 1.0 g/cm3. The mechanical property of the CNTs is described by the reactive empirical bond-order (REBO) potential28. The water molecules are simulated by the TIP4P-EW model29, in which the bond lengths and angle degrees are constrained by the SHAKE algorithm to the initial values of 0.9572 Å and 104.52°, respectively. The atomic interactions between the carbon atoms of CNTs and the oxygen atoms of water molecules are calculated by the Lennard-Jones (LJ) potential, and the corresponding parameters are σCO = 3.28218 Å and εCO = 0.11831 = kcal/mol30. The particle-particle-particle-mesh method is adopted to compute the long-range Coulomb interactions between the polar water molecules. The cutoff distances of the LJ and Coulomb interactions are 12 Å and 10 Å, respectively. The position and velocity are updated through the canonical ensemble (NVT) with the integration time-step of 1 fs. The system temperature is maintained at room temperature (298 = K) by the Nosé-Hoover thermostat. In the present research, the effect of the electric field on the mechanical property of water-filled CNTs is also explored through applying an axial electric field along the CNTs. The electric field intensity is 0.5 V/Å, which is comparable to the average local electric field within the condensed phase of water31. Moreover, it can be found that this intensity is still in the range of high-intensity electric field in laboratories32333435. Initially, the relaxation times for the hollow and the water-filled CNTs are 100 and 300 ps, respectively. Subsequently, the spring is compressed by 1 Å and the system is equilibrated for 100 ps. To eliminate the influences of the initial configuration and velocity, the results below are the averages of six independent simulations for each case. The MD simulations are carried out by LAMMPS package36. |
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Affiliation: State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China.
No MeSH data available.