Laser Processing Technology Of NiTi Surface With Special Wettability And Its Property Investigation

Inspired by natural lives such as lotus,rice leaves,rose petals,research efforts on the modification of solid material surface wettability attract more and more attention recently.These bio-inspired surfaces with special wettabilities have significant potential applications in scientific research and practical production such as microfluidic devices,biomemitic materials manufacturing,lab on chip and so on.Shape Memory Alloys(SMAs)including AgCd?AuCd?CuZn?NiTi gain a lot of interests in daily life and production.This dissertation introduces a simple but effective method of fabricating nano/micro-structures and low surface energy coatings on the nitinol alloy wafer surface through nano-second laser beam irradiation and silanization process by fluoride.With this method,surface with tunable anisotropic wetting and high adhesive ability and superhydrophobic surface can be produced successively.In order to investigate the influences of laser processing and silanization process on surface wettability,the chemical composition,anisotropic wetting ability were assessed by Scanning Electron Microscope(SEM),white light confocal microscope,X-Ray Photoelectron Spectroscope(XPS)and contact angle measurement respectively.What's more,the relationship between the water volume and the surface anisotropic wetting is also investigated.To thoroughly investigate the property of the superhydrophobic surface,the thermal stability and chemical stability were all assessed in detail.By a serious of experiments and analyzing the results,it can be known that by changing the processing characteristics,the two-dimensional anisotropic wetting ability ranges from 0°to 20.3°,which is far beyond the range of the anisotropic wetting ability on natural rice leaves.The detected water sliding angles(WSAs)kept stable at a value of180°,successfully mimicking the adhesive ability of natural rose petals.For the relationship between the silanization process and anisotropic wetting ability,the results also indicated the strengthening effect and the weakening effect of silanization process on hydrophobicity and anisotropic wetting respectively.Among all the superhydrophobic sample surfaces,g80 surface has the largest WCA with a value of154.42°±2.1°,and g60 sample has the smallest WCA of 152.16°±1.25°.The treated superhydrophobic samples also show strong anti corrosion stability on acid solutions,organic solvents and salt water,but slightly weak durability when they are dipped into alkaline solutions.Furthermore,the modified surfaces can keep excellent superhydrophobicity under 150?,and hydrophobicity under 350? but becomes hydrophilicity when the temperature exceeds 550 ?.In addition,the influences of carbon ion implantation process on superhydrophobic surfaces have also been studied here.The results show that the effects of carbon ion implantation process on the superhydrophobic surface modification of NiTi are closely related to the process of silane modification.The carbon ion implantation process will change the color of the surfaces due to the chemical actions,but the surface structures do not change.What's more,the effect of carbon ion implantation process on the surface carbon content is very weak.