Influence Of Structure Property Of Carbon Nanotubes On Adhesion Strength

Carbon nanotubes(CNTs)are seamless hollow tubular one-dimensional nanomaterials made of single or multilayer graphene,which was rolling around a central axis and along a specific helix angle.CNTs have excellent mechanical,electrical and thermal properties due to their special structural characteristics.Based on these excellent comprehensive properties,macroscopic forms of vertical aligned CNTs can exhibit excellent adhesion strength in some specific fields(e.g.high and low temperatures).In this study,we optimize the structural properties and surface morphology of the aligned CNT arrays with the ultra-high purity.The mechanical properties of these aligned CNTs have been measured and their influences on the adhesion strength also have been investigated.The main research content and results are listed as follows:(1)The catalyst systems of Al OX / Fe are prepared by magnetron sputtering method.Then,the aligned CNTs with ultra-high purity and uniform diameter distribution are prepared through the water assisted chemical vapor deposition(CVD).By adjusting the growth time,gas flow and growth temperature,the structure properties of aligned CNTs are tailored including the height range from 150 to 850 ?m and the density from15 to 50mg/cm~3.The influence of structure properties on adhesion has been studied and the adhesion strength on both smooth surfaces(e.g.glass,silicon)and rough surfaces(e.g.sand paper and copper)are optimized.The maximum adhesion strength on the smooth surface is up to 26 N/cm~2 with the CNT height within 250-350 ?m,which is higher than the adhesion on the rough surface(only the 1/2 of adhesion on the smooth surface).The underlying reason for the decrease of the adhesion strength on rough substrates has also been explored by observing the morphology of the adhesion surface through SEM.(2)The adhesion strength of CNT dry adhesives on rough surfaces has been improved through plasma etching.The surface morphologies of aligned CNTs have been tailored by adjusting the power and treatment time of plasma etching.Theoptimal plasma condition is fixed by reaction gas of O2 with the etching power of18 W,gas pressure of 1000 m Torr and etching time of 3min.Then,the adhesion strength can be improved to 60 N/cm~2 on Cu foils.It has been found that the adhesion strength showed almost a linear increase from 25 N/cm~2 to 60 N/cm~2 with the increasing of CNT density from 15 mg/cm~3 to 50 mg/cm~3.(3)The CNT adhesive has been applied to double-sided adhesion by adhering two surfaces with different roughness such as Cu foil and Si wafer.The variation of adhesion strength with temperature has been studied.It has been found that the CNT double-sided adhesive can be sustained up to 350 ? with the adhesion strength maintained at 30 N/cm~2.As comparison,the commercial double-sided tape failed at80 ?.Meanwhile,the mechanism of the double-sided adhesion at high temperatures has been studied by observing the surface morphologies through SEM and AFM.