Undisz A, Schrempel F, Wesch W, Rettenmayr M
Institute of Materials Science and Technology, Metallic Materials, FSU-Jena, Loebdergraben 32, 07743 Jena, Germany.
J Biomed Mater Res A. 2009 Mar 15;88(4):1000-9. doi: 10.1002/jbm.a.31946.
Medical grade Ni-Ti alloys with shape memory or pseudo-elastic behavior exhibit good biocompatibility because of an electrochemically passive oxide layer on the surface. In this work, the mechanical stability of surface oxide layers is investigated during reversible pseudo-elastic deformation of commonly applied medical grade Ni-Ti wires. Surface oxide layers with varying thickness were generated by varying annealing times under air atmosphere. The thicknesses of the surface oxide layers were determined by means of Rutherford backscattering spectrometry. In situ scanning electron microscopy investigations reveal a damage mechanism, which is assumed to have a significant influence on the biocompatibility of the material. The conditions that lead to the appearance of cracks in the surface oxide layer or to the flaking of surface oxide layer particles are identified. The influence of the thickness of the surface oxide layer on the damage mode is characterized. The possible impact of the damaged surface oxide layer on the material's biocompatibility and the potentials to reduce or avoid the damage are discussed.
具有形状记忆或伪弹性行为的医用级镍钛合金由于其表面存在电化学钝化氧化层而表现出良好的生物相容性。在这项工作中，研究了常用医用级镍钛丝在可逆伪弹性变形过程中表面氧化层的机械稳定性。通过在空气气氛下改变退火时间来生成不同厚度的表面氧化层。表面氧化层的厚度通过卢瑟福背散射光谱法测定。原位扫描电子显微镜研究揭示了一种损伤机制，该机制被认为对材料的生物相容性有重大影响。确定了导致表面氧化层出现裂纹或表面氧化层颗粒剥落的条件。表征了表面氧化层厚度对损伤模式的影响。讨论了受损表面氧化层对材料生物相容性的可能影响以及减少或避免损伤的潜力。
