阴极电沉积法在钛表面制备生物陶瓷涂层的研究

【作者】 张刚；

【导师】 赵中伟；

【作者基本信息】 中南大学 ， 有色金属冶金， 2004， 硕士

【摘要】 随着老龄化社会的到来，在外科矫形手术、齿填充材料、人体硬组织的修复领域对于生物活性材料的需求量日益增长。金属基生物活性陶瓷涂层由于具有金属和生物活性陶瓷的综合优势，被认为是目前最有前途的一种承重骨替换材料。 目前众多陶瓷涂层制备技术中，阴极电沉积工艺因低温操作、适合各种形状基体而具有独特优势。但其缺点在于沉积过程中，电极表面剧烈析氢，影响沉积和结晶，致使膜层疏松、易脱落，成为亟待解决的问题。 考虑到H₂O₂的阴极还原电位比H₂O正得多，容易在阴极被还原，本研究中使用H₂O₂修饰电解质溶液，以期抑制H₂析出，改善涂层质量。研究了电沉积方法在基体钛表面制备生物活性陶瓷涂层过程中电解液pH值、添加H₂O₂量、沉积温度、沉积时间，以及阴极电位和阴极电流密度等影响因素。通过采用XRD和FTIR对涂层的化学组成进行了分析，用SEM观察了涂层的表面形貌。 试验表明： 较高的初始电解液pH值有利于羟基磷灰石涂层的生长，pH为5.5与2.5时比较，所得涂层更加致密，XRD射线谱上的特征衍射强度增强； 延长沉积时间，羟基磷灰石膜层逐渐生长，相应衍射峰的强度不断加强，SEM图像也显示涂层覆盖率不断提高，晶体结构由0.015μm左右的长柱状晶体转变为0.4～0.5μm的片状结构； 阴极电流密度随沉积温度的提高而逐渐升高，所得晶体尺寸变小，但仍维持片状晶体形貌，晶体互相交错成为网状结构。但是温度高至70℃时，溶液不稳定，反而不利沉积； H₂O₂的用量由1％逐渐增加到9％，电流密度不断增大，羟基磷灰石晶体的形貌先由团絮结构转变为较大片状结构，又进一步转变为较小片状结构。随H₂O₂用量增加，衍射峰的强度总体增强； 阴极的恒电位极化增强时，电流密度增大。羟基磷灰石的晶体由片状转变为针状结构，涂层变得致密。恒电流极化时也有类似现象； 本研究得到的最佳工艺条件是：溶液pH值为5.5，H₂O₂为添加量6％，温度为70℃，阴极电位ψ=-0.6V（vs SCE），沉积时间t=2000s，上述条件下可制备出较好的羟基磷灰石涂层，其结合力可达到12.73MPa。更多还原

【Abstract】 With the aged population increasing, the need for artificial biomaterials increasingly enhanced in orthopedic, dental surgery and hard-tissue repaired areas. Bioactive ceramic-coated metal has the predominance of both metal and ceramics, so it is considered as a kind of the most promising bone replacement material.At present, many methods have been applied to prepare bioactive coatings. Among which, the cathodic electrodeposition has its special advantages, such as low operation temperature and high ability to coat on irregular objects. But the main problem of the electrodeposition, the coating being loose and prone to desquamat, is caused by the violent evolution of H2 bubbles from reduction of water on the surface of the substrate.The reduction potential of H2O2 is more positive than that of water. In our work, H2O2 was used to modify electrolyte in order to inhibited H2 evolution and improve the quality of the coatings. The influences of pH value, the amount of H2O2, electrolyte temperature, loading time, cathodic potential and cathodic current density on depositing calcium phosphate coating were investigated. The coating is tested by XRD?SEM and FTIR technology.The results showed that:High initial pH value is beneficial for depositing hydroxyapatite (HAp) coatings. The coating prepared at pH=5.5 is denser and the intensity of XRD diffraction peaks of hydroxyapatite is stronger than those at pH=2.5.The intensity of diffraction peaks of hydroxyapatite increases with the loading time, and SEM photos indicate coverage also increases. At the same time, the claval crystals of about 0.015 um turn into the flake-shaped crystals of about 0.5 Mm.With the rising of electrolyte temperatures, the cathodic current density increases gradually. The crystals, which form a network structure, keeps flake-shaped while the crystal size reduced. But when the electrolyte temperature exceeds 70, the electrolyte becomes unstableand, accordingly, the deposition process becomes difficulty to conduct.When the amount of H2O2 addition increases from 1% to 9%, the current density increases gradually, and the morphology of hydroxyapatite crystal change greatly from amorphous to larger flake crystals, eventually to small ones. Increased H2O2 addition causes an increase in HAp XRD diffraction intensity.A high constant cathodic potential causes a high current density and produces a dense coatings. The irregular flake-shaped crystals also turn into needle ones. When a constant cathodic current is applied, the similar phenomena appear.The results showed that the high quality coatings can be deposited under such conditions: T=70, pH=5.5, =-0.8V (vs SCE), and H2O2 addition=6%. The adhesion strength between coatings and substrate reaches 12.73MPa.更多还原