The Research Of Structural Control And Adhesion Properties Of Vertically Aligned Carbon Nanotube Arrays

Vertically aligned carbon nanotube?VACNT?arrays are a highly promising gecko inspired dry adhesive material.In this paper,the introduction of hydrogen in the preparation process was studied to synthesis VACNT with different structural parameters were obtained.And by changing the atmospheric pressure,we synthesized VACNT with strong substrate bonding strengths,which can realize repeated adhesion applications.In addition,the adhesion performance of VACNT in high temperature environments was studied,which laid the foundation for its application in extreme environments.The main results and conclusions of this paper are as follows:1.By changing the beginning temperature of inducing during chemical vapor deposition,a series of parameters such as the diameter,wall number and density of the synthesized VACNT were controlled.The rise of H₂ introduce temperature means the pretreatment time of H₂ is shortened,resulting in the increase of surface roughness.The density of VACNT increases,and the outer diameter and wall number almost unchanged.And too short pretreatment time will lead to a decrease in catalyst activity and slow down the growth rate of VACNT.2.By changing the gas pressure during chemical vapor deposition,VACNT with controlled bond strength to the substrate were obtained.The binding strength of the synthesized VACNT to the substrate was in the range of 2.63-11.05 N/cm² in the pressure range of 100-700 torr.When the gas pressure is increased,the concentration of C in the reaction chamber becomes larger,and the generated more amorphous carbon.Amorphous carbon weakening the activity of particles by covering on their surfaces.The carbon nanotubes corresponding to the deactivated Fe particles stopped growing,which decrease the density of VACNT.The mass density is proportional to the contact area of the VACNT and the substrate,so the gas pressure adjusts the bonding strength by changing the density of the VACNT.3.The adhesion properties of VACNT under high temperature conditions were also investigated.When temperature is raised from 25°C to 150°C,the sheer adhesive strength of VACNT arrays decreased from 12.04 N/cm² to 6.08 N/cm².At high temperature,the van der Waals force between the sidewalls of VACNT is reduced,and with the drag during sheer adhesion test,cracks generated in the VACNT,causing wrinkles on the surface of the arrays.The wrinkles damage the interface which weaken the adhesion.