Influence of Alkali Treatment on Ti6Al4V Alloy and the HA Coating Deposited by Hydrothermal-Electrochemical Methods

摘要:

Ti6Al4V基体经NaOH溶液恒温预处理不同的时间（12、24、36、48、60 h），然后分析了不同的碱预处理时间对Ti6Al4V基体及羟基磷灰石（HA）形态、物相的影响。经碱预处理后Ti6Al4V表面呈现三维网状结构，并检测到了钛酸钠凝胶的存在。随后采用水热电化学方法得到了HA涂层，水热反应电解质包括NaCl、K2HPO4·3H2O、CaCl2，在恒温120 ℃、电流密度为1.25 mA/cm2的条件下保持120 min。结果表明：HA的生长模式及形态均受预处理时间的影响：当基体经过12 h的预处理后，水热反应形成一层针状HA及少量蒲公英状HA。而蒲公英状HA的数量随预处理时间的增加而增多。但预处理时间大于48 h时，其数量稍有减小。HA在（002）晶面的取向指数、结晶度在预处理时间为48 h时分别达到了最小值、最大值。

Abstract:

The aim of this work is to investigate the influence of NaOH pretreatment time on the phases and morphologies of Ti6Al4V substrates and hydroxyapatite (HA) coatings. Ti6Al4V substrates were pretreated with a sodium hydroxide (NaOH) solution for different amounts of time (12, 24, 36, 48, and 60 h). After NaOH pretreatment, a three-dimensional porous network of sodium titanate gel was observed on the Ti6Al4V surface. Subsequently, HA deposition was achieved using the hydrothermal-electrochemical methods, while the electrolyte solution containing NaCl, K2HPO4·3H2O, and CaCl2, was maintained at 120 °C and applied by a constant current density of 1.25 mA/cm2 for 120 min. The results indicate that the growth pattern and micromorphology of the HA coating are all influenced by different pretreatment time. After pretreating Ti6Al4V substrates with NaOH for 12 h, needle-like structures are primarily formed on the HA coating, and some dandelion-like morphologies are presented. During 48 h NaOH solution pretreatment, the dandelion-like structures increase with the increase of time. However, the amount of the dandelion-shaped HA drops slightly, when pretreatment time is longer than 48 h. The orientation index of the (002) plane of HA reaches the minimum when Ti6Al4V substrates are pretreated for 48 h, whereas the crystallinity is the highest for this pretreatment time.