The Controlling Mechanism Of The Deformation Behavior Of Liquid-Filled Carbon Nanotubes Under Electric Field

Carbon nanotubes(CNTs)are considered as ideal materials for structural units and functional devices in micro-electromechanical systems because of their superior mechanical,electrical and optical properties.Due to the one-dimensional hollow structure,the CNT performance could be further enhanced through the internal filling.Hence,based on the understanding of the effects of internal fillings on CNTs,the effective and accurate control of the property and behavior of CNTs would extend the function and application of CNTs.In this paper,the deformation behaviors of water and salt water-filled CNTs under the electric field are systematically studied,respectively.Firstly,the bending deformations of water-filled CNTs under electric field with two mutually orthogonal components are investigated by molecular dynamics simulations.The effects of the CNT diameters,the intensity and direction of electric field on the bending deformation of the water-filled CNTs are examined.The numerical results show that the bending of the water-filled CNTs is resulted from the cooperative effect of the axial and transverse electric field,while the water-filled CNTs slightly deformed under the unidirectional electric field.The water-filled CNTs could bend to the opposite direction by changing the direction of axial electric field,and the bending deformation could be enhanced by increasing the intensity of transverse electric field.Moreover,the theoretical models of the bending deformation of water-filled CNTs under the coupling loads of the bending moment and the shearing force with the axial force are constructed,respectively.The results show that the bending deflection curve obtained from the theoretical model based on the shearing force could well describe the numerical simulation results.Secondly,the tensile and bending deformations of salt water-filled CNTs under the longitudinal electric field and the electric field with two components are studied by molecular dynamics simulations,respectively.The effects of the CNT diameters,the intensity of electric field and ionic concentration on the bending deformation of the salt water-filled CNTs are investigated.The numerical results show that the elongation of the salt water-filled CNTs is proportional to the ion concentration and the diameter of CNTs.The tensile deformations of the salt water-filled CNTs with small-diameter show a linear trend with the electric field intensity,while the electric field and the deformations of the large-diameter CNTs show a nonlinear trend.Moreover,the bending deflection of salt water-filled CNTs is basically proportional to the intensity of transverse electric field,and the ionic concentration could further influence the relationship between the bending deformation and the diameter.In addition,the theoretical model for the tensile and bending deformation behaviors of salt water-filled CNTs under the electric field are established.The results show that the tensile and bending deformation of the salt water-filled CNTs could be described by the axial force and the combined effects of the axial force and shearing force,respectively.In this dissertation,based on molecular dynamics simulation,we reveal the relationship between the deformation of liquid-filled CNTs and the CNT diameters,the ionic concentration,the intensity and direction of electric field.Moreover,the theoretical models are established to clarify the mechanism of the deformation behaviors of liquid-filled CNTs are clarified.The present study provides guidances for the design and application of the water and salt water-filled CNTs in nanoscale controllable devices.