Fabrication of Biodegradable Fiber Reinforced Ti Functionally Graded Materials and Their Wear Properties

钛及钛合金是一种极具吸引力的金属植入材料。这是因为这些合金具有较低的剪切模数，与骨具有良好的生物相容性。然而，骨与钛合金的界面粘结能力较低。作为改善界面粘附性的方法，羟基磷灰石等生物亲和性材料被涂覆在钛合金表面。然而，这种生物亲和性材料的强度和耐磨性较低。本研究采用放电等离子烧结法制备了含可生物降解的聚L乳酸纤维的钛复合材料。PLLA纤维在钛基体中起到增强的作用，并随着时间的推移在体内逐渐分解。通过PLLA的分解，在钛基质中产生气孔，骨同时穿透到气孔中。因此，骨与钛基质之间的紧密结合是可以预期的。采用SPS法制备了Ti-PLLA复合材料，并进行了显微组织观察和力学性能测试。结果表明，Ti-PLLA复合材料具有片状PLLA的层状结构。由于Ti-PLLA复合材料的组织结构，其硬度和磨损行为具有各向异性。然而，由于钛基体的烧结不完善，使得钛-聚乳酸复合材料的强度较低。由于改变SPS的温度可以改善钛基的烧结性，因此SPS法可以得到力学性能各向异性的Ti-PLLA复合材料。

Ti and Ti alloys are particularly attractive materials as the metallic implant-material. This is because that these alloys have low shear modulus and the good biological compatibility with bone. However, interfacial adhesion ability of bone and Ti alloy is low. As improvement method of the interfacial adhesion ability, bioaffinity material like hydroxyapatite has been coated on surface of the Ti alloys. However, such bioaffinity materials have low strength and wear resistance. In this study, Ti composites containing biodegradable poly-L-lactic-acid (PLLA) fiber were fabricated by spark plasma sintering (SPS) method. The PLLA fiber plays a role as reinforcement in Ti matrix, and can be gradually decomposed inside body with progress of time. By the decomposition of PLLA, pore is generated in Ti matrix, and bone simultaneously penetrates into the pore. Therefore, tightly bond between bone and Ti matrix can be expected. Using the Ti-PLLA composites fabricated by SPS method, microstructural observation and mechanical tests were performed. It was found that Ti-PLLA composite has laminate-layer structure with plate-like shape PLLA. Hardness and wear behavior of Ti-PLLA composite has anisotropy due to its structure. However, strength of the Ti-PLLA composite is low because of the imperfect sintering of Ti matrix. Since sintering of Ti matrix can be improved by changing the temperature of SPS, Ti-PLLA composite with anisotropic mechanical properties can be expected by SPS method.