导　　师： 张新平

学科专业： 080503

授予学位： 硕士

作　　者： ;

机构地区： 华南理工大学

摘　　要： 本论文对多孔NiTi形状记忆合金进行了高温氧化、化学氧化以及化学氧化与后续高温氧化相结合的表面改性研究,采用扫描电子显微镜/(SEM/)、能谱分析/(EDS/)及X射线衍射/(XRD/)等分析方法系统研究了表面改性后多孔NiTi记忆合金的表面组织结构特征,并将表面改性后的多孔NiTi记忆合金在生理盐水/(0.9/%NaCl/)中进行浸泡/(悬挂/)和电化学腐蚀试验,表征了其耐蚀性能的变化和Ni离子释出行为。 研究结果表明,高温氧化温度升高时多孔NiTi记忆合金表面膜经历了由低结晶度Ti的过渡氧化物向锐钛矿型TiO2相的转变,同时膜层中Ni含量逐渐下降。但获得锐钛矿型TiO2相的同时,过高的氧化温度/(>500 oC/)导致了氧化膜内部出现因热应力而产生的微裂纹,并对基体//氧化层界面的结合强度造成不利影响。腐蚀性能的测试结果表明,与氧化层的相结构相比它的均匀、完整性是提高合金耐蚀能力的关键。 经H2O2+HCl溶液体系化学氧化处理后多孔NiTi记忆合金表面生成了以Ti的非晶氧化物为主且相对贫镍的完整氧化层,因而多孔NiTi记忆合金的耐蚀能力明显提高,Ni离子释出速率大幅减小,这对改善合金的生物相容性十分有益。氧化动力学的初步研究表明,化学氧化过程中合金的质量变化即反应过程中的氧化和溶解反应的平衡受到HCl浓度和氧化时间的协同作用。 研究还表明,经过化学氧化处理后的多孔NiTi记忆合金再进行后续高温氧化处理时,在较低温度下/(400oC/)其表面的非晶氧化物即转变为锐钛矿型TiO2相,虽然后续高温处理仍对氧化层原有的组织结构及基体//氧化层界面的结合强度产生影响,但所获得的锐钛矿型TiO2相将为后续沉积生物活性更高的羟基磷灰石层提供了可能。 In this thesis, surface modification of porous NiTi shape memory alloys were performed through high temperature oxidation, chemical oxidation and the combination of the above two precesses /(i.e., the initial chemical oxidation followed by a high temperature treatment/). The surface microstructures of the surface-modified porous NiTi alloys were characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The Ni ion release behavior and corrosion resistance of the surface-modified porous NiTi alloys immersed in physiological saline and electrochemical solution were evaluated. The results have shown that the oxide film mainly composed of anatase TiO2 and depleted in Ni formed on porous NiTi surface by high temperature oxidation. The content of anatase TiO2 phase increases with the oxidation temperature. However, an over high temperature /(e.g., >500 oC/) tends to induce cracking of the surface film caused by internal thermal stress and thus deteriorate the interface strength between the oxide film and NiTi substrate. The results of corrosion resistance tests indicate that the uniformity and integrity of the protective oxide film play a key in improving corrosion resistance of porous NiTi alloy. After a chemical oxidation in H2O2+HCl solution, the oxide film composed of the amorphous oxide and depleted in Ni formed on porous NiTi surface. The defect-free oxide film can significantly enhance corrosion resistance of the substrate and reduce Ni ion release, thus would greatly improve biocompatibility of porous NiTi alloys. The preliminary study of oxidation kinetics has shown that the mass variation of porous NiTi substrate, determined by the HCl concentration and oxidation time, depends on the balance of the kinetics between the oxidation and dissolution reactions during the chemical oxidation process. It has been shown that the amorphous titanium oxide formed through chemical oxidation followed by high temperature oxidation. At a relatively low temperature of 400oC, the amorphous titanium oxide changed into crystalline anatase TiO2. Although the follow-up high temperature treatment had an adverse influence on interface strength between the oxide film and NiTi substrate, the anatase TiO2 phase provides the possibility for the deposition of HA.

关 键 词： 多孔 形状记忆合金 高温氧化 化学氧化 表面改性 耐蚀性能

分 类 号： [TG139.6 TG174.4]

领　　域： [金属学及工艺] [一般工业技术] [金属学及工艺] [金属学及工艺] [金属学及工艺]