The Preparation And Properties Of Zirconium Oxide Thin Films On316L Stainless Steel

With the improvement of people’s material life and the lifestyle changes,cardiovascular disease has been growing more and more, which is known as "themost powerful killer". Stent implantation is a vital means for the treatment andprevention of cardiovascular disease.316L stainless steel stents are the most widelyused stents. After those stents implanted in human body, there will be two aspects ofproblems with restenosis along with thrombosis and toxicity caused by corrosion,which are related to the hemocompatibility and corrosion resistance of stent materials.This thesis prepared zirconium oxide thin films on316L stainless steel by sol-gelmethod. The effect of process parameters (annealing temperature and vertical liftingspeed) on the microstructure and properties of films was researched, and the optimalprocess parameter was obtained. Graphene doped zirconia thin films were preparedwith the optimal process parameter, and the effect of doping percentage on theproperties of films was evaluated, and the rules between them were summarized. Themain results of this thesis are as follows.Firstly, the TG-DTA curve of zirconia thin film between20℃and600℃wasdivided into three stages; XRD showed that the films annealed at400,500and600℃had crystallized to tetragonal structure, and graphene doping did not affect thecrystallization. SEM showed that the film annealed at500℃with lifting speed at7cm/min was symmetrical and dense, and had small grain size about25nm. It can beachieved to prepare symmetrical and dense zirconia nano thin films with theprocedure of this thesis.Secondly, the hemocompatibility of316L stainless steel was improved bydeposition of zirconia films, and the film annealed at500℃had the besthemocompatibility. The film annealed at500℃with lifting speed at7cm/min hadstronger corrosion resistance. Therefore, the optimal process parameter of zirconiafilms was lifting speed of7cm/min and annealing of500℃.Thirdly, the interfacial tension sbccurves between graphene doped zirconia thinfilms and four blood component performed the same regular pattern. Doped filmsimproved the hemocompatibility of316L stainless steel, and ζ=5wt.%,7.5wt.%,10wt.%,15wt.%and20wt.%doped films improved the hemocompatibility of undoped zirconia films.Finally, graphene doped zirconia thin films improved the corrosion resistance of316L stainless steel, andζ=10wt.%doped films had the most favorable corrosionresistant.ζ=7.5wt.%andζ=10wt.%doped films improved the corrosion resistanceof undoped zirconia films. The corrosion pore distribution was not symmetrical, andhole shape was irregular. The depth of hole wall and hole bottom surface were uneven,and the maximum depth was57.7907μm of the cross sections.This thesis belongs to the basic applied research, and the work can providetechnical guidances to surface modification of316L stainless steel and relevantmaterials choosing.