【作者】 王勇；

【导师】 高家诚；

【作者基本信息】 重庆大学 ， 材料学， 2002， 博士

【摘要】 在钛合金基体上涂覆以羟基磷灰石（HA）为主的生物陶瓷涂层制成的复合生物材料，既有优良的力学性能，又有优良的生物相容性，被认为是最有希望的新型生物骨替换材料之一，因此成为近年来生物材料领域研究最为活跃的方向之一。本文依据 HA 可以通过适当的含钙、磷盐的混合物在烧结过程中反应合成，以及激光技术已广泛用于涂层制备的事实，提出通过激光处理在钛合金表面同步合成及熔覆以HA 为主的生物陶瓷复合涂层，可以节约成本，并缩短生产周期。同时，在涂层中添加了少量Y₂O₃，获得了良好的效果。 试验证明，在经过激光重熔预处理的TC4表面，预涂敷80％CaHPO₄，·2H₂O、20％CaCO₃以及另加1％Y₂O₃的混合粉末，以较低的功率密度（13～15W／mm²）和较高的扫描速度（630mm／min）进行激光处理，实现了 HA 的同步合成与熔覆，获得的稀土生物陶瓷复合涂层的物相组成为：Ca₁₀（PO₄）₆（OH）₂（HA）、β-Ca₃（PO₄）₂（β-TCP）、α-Ca₃（PO₄）₂、Ca₂P₂O₇、Ca₂Y₂O₄和CaY₄O₇。该涂层晶粒细小、表面呈多孔状，形貌与自然骨十分相似，并且其成分、组织和性能都具有梯度分布。涂层复合材料具有良好的综合力学性能，其强度和硬度高于自然骨，并具有一定的塑性和韧性，由于涂层的弹性模量介于基体与自然骨之间，所以植入体的生物力学相容性也能得到改善。 生物学试验表明，涂层材料对肌肉、红系细胞及成纤维细胞均无毒副作用，大剂量地注入动物体内也未引起明显的急性毒性反应，表明其具有较好的血液相容性和组织相容性。动物植入试验证实，钛合金与涂层在生物体内均有良好的生物相容性。但钛合金属生物惰性材料，植入较长时间后，被纤维组织包裹而与活体硬组织隔离；稀土生物陶瓷复合涂层则具有一定的生物活性，它不影响破骨细胞与成骨细胞的活性，在体内有细胞介导的降解，植入60天后，新骨生长直接发生于涂层表面，表现出较好的骨传导性。 稀土元素可以显著改善涂层的相组成、组织和性能。温度场计算表明，在激光加热过程中，Y₂O₃并未完全熔化，又因为其密度较大，所以倾向于下沉，使钇元素富集于界面，这一点也为成分分析所证实。富集于界面的钇阻碍了基体元素向涂层的迁移，降低了涂层的稀释度，有利于 HA 等生物陶瓷相的合成。同时，热分析试验证明，Y₂O₃对 HA 的合成具有催化作用，并且钇可以提高 HA 和β-TCP 的高温稳定性，所以涂层中产生了较多的生物活性陶瓷相。残留于涂层中的钇多具有细化晶粒的作用，可以提高其力学性能。含稀土的涂层与基体的界面结合强度为42.76MPa，比不含稀土者提高了两倍以上；同时，钇还提高了涂层在酸、碱和生理盐液中的耐腐蚀性能。更多还原

【Abstract】 The composites of titanium alloy with bioceramics coating, mainly containing hydroxyapatite (HA), have been developed for the hard tissue implant for their superior bioactivity and mechanical properties. Because these composites are thought to be the most promising substitute of hard tissues, many efforts are made to develop new cladding techniques, improve their properties and so on. Based on those facts that HA can be synthesized during sintering the proper mixture of some Ca-P-containing salts, and laser beam is widely used in coating techniques, a new method was proposed to synthesize and clad the HA-based bioceramic coatings on titanium alloy with laser beam. Additionally, a few amount of Y2C>3 were added into the coating.The surface of titanium alloy (TC4) was remelted with laser beam beforehand, then mixed powders of 80%CaHPO4’2H2O and 20%CaCO3 with 1% Y2O3 in addition were preplaced on it. During laser-treated once more, HA was surely synthesized and a RE-containing bioceramic coating was cladded on the substrate at the same time. The phases in this coating are: Ca10 (P04), (OH) ^ 0 -Ca3(PO4)^ a -Ca3(PO4)2> Ca2P207 ^ Ca2Y2O4 and CaY4O7. The optimal laser processing parameters recommended in this paper are: power density=13~15W/mm2, scanning rate=630mm/min. With fine grains and porous top, the morphologies of the coating are similar to that of natural bone. The compositions, microstructures and mechanical properties graded vary along the depth direction. And the mechanical properties of this bioceramic-TC4 composite are excellent. Compared with natural hard tissues, its strength and hardness are much higher, and it exhibits some ductility and toughness as well. Furthermore, the biomechanical compatibility of the implant made of the composite can be improved for the coating possesses an elastic modulus between TC4 and natural bones.As illustrated by biocomparability experiment in vitro, the coating has not toxic effects on muscles, red cells and fibroblasts. And acute toxic reactions were not observed in experimental mice having been injected the coating material in large dose. So its excellent compatibility with blood and tissue was well proved. Implanting experiments were also performed in dogs. It was found that both the substrate and coating are biocomparable in vivo. The substrate TC4 is bioinert, so it will wholly packed with connective tissues after a certain period in vivo. Whereas, the coating is bioactive, it doesn’t affect the activity of osteoblasts and osteoclasts, and it isbiodegradable induced by cells. 60 days later in vivo, new bones were found to form on the coating, which means it is osteoconduct.Yttrium is helpful to improve phase compositions, microstructures and properties. During laser heating, Y2O3 didn’t melt as discovered by numerical simulation of the laser temperature field. So they are apt to sink in the laser pool for their larger density, and Y mainly segregate in interface area as a result, which was ascertained by chemical composition analysis. These yttrium can restrain the substrate elements from moving to coating, and decrease the dilute of coating, which is beneficial to the forming of HA and other calcium phosphate bioceramics. Moreover, DSC analysis confirmed that Y2O3 could catalyze the forming reaction of HA, i.e., decreasing its forming temperature, and that Y could increase the stability of HA and P -TCP at elevated temperature. Those Y retaining in coating make the grains finer so increase its mechanical properties. The Y-containing coating has an interface bonding strength of 42.76MPa with substrate, more than three times as high as that of Y-free coating. Additionally, yttrium can also improve corrosion-resistance of the coating in acid, alkali and salt mediums.更多还原