Defect formation in thin polyelectrolyte films on polycrystalline NiTi substrates.
Defect formation in thin polyelectrolyte films on polycrystalline NiTi substrates.
复制标题
多晶镍钛基板上聚电解质薄膜中的缺陷形成。
DOI：
10.1016/j.jmbbm.2010.03.008
复制
发表时间：
2010
影响因子：
3.9
通讯作者：
H. Maier
中科院分区：
文献类型：
--
作者：
J. Lackmann;R. Regenspurger;M. Maxisch;G. Grundmeier;H. Maier
本文报道了在多晶镍钛合金（NiTi）基体上采用逐层沉积技术制备的聚丙烯酸/聚烯丙基胺盐酸盐（PAAA/PAH）纳米复合薄膜的力学性能。由于薄的纳米薄膜是潜在的合适的涂层，以减少在生物医学应用中的Ni释放，薄膜的机械性能通过施加单调和循环拉伸应变的5%和3%，分别确定。虽然高达5%的单一拉伸应变揭示了所施加涂层的惊人应变失效，但循环应变导致聚电解质内的缺陷形成。为了更好地理解确定缺陷形成的机制，通过数字图像相关和EBSD（电子背散射衍射）技术确定宏观和微观缺陷定位。特别是在局部应变差升高的区域内出现缺陷，并且主要在晶界附近观察到缺陷。为了将这些发现与考虑应变局部化和晶间约束的多晶NiTi的转变行为相关联，将从EBSD测量获得的晶体学数据与缺陷分布相关联。EBSD数据揭示了一个明显的依赖于相邻晶粒的取向差的缺陷形成。
This paper reports on the mechanical properties of ultrathin PAA/PAH (polyacrylic acid/polyallylamine hydrochloride) polyelectrolyte films deposited by a layer-by-layer technique on a polycrystalline Nickel–Titanium (NiTi) substrate. Since thin polyelectrolyte films are potentially suitable coatings to reduce the Ni release in biomedical applications, the mechanical properties of the thin films were determined by applying monotonic and cyclic tensile strains of 5% and 3%, respectively. While single tensile strains up to 5% revealed the amazing strain to failure of the applied coating, cyclic strains resulted in defect formation within the polyelectrolytes. To provide a better understanding of the mechanisms that are determining the defect formation, macroscopic and microscopic defect localizations were determined by digital image correlation–and EBSD (electron back-scattered diffraction)–techniques. Defects emerged particularly within areas of elevated local strain differences and were predominantly observed in the vicinity of grain boundaries. To relate these findings to the transformation behavior of polycrystalline NiTi considering strain localizations and intergranular constraints, crystallographic data obtained from the EBSD measurements were correlated with the defect distribution. EBSD data revealed a distinct dependence of defect formation on misorientation of neighboring grains.