Tarnowski Michał, Witkowska Justyna, Morgiel Jerzy, Jakubowski Witold, Walkowiak Bogdan, Borowski Tomasz, Wierzchoń Tadeusz
Faculty of Materials Science and Engineering, Warsaw University of Technology, 141 Wołoska St., 02-507 Warsaw, Poland.
Polish Academy of Sciences, Institute of Metallurgy and Materials Science, 25 Reymonta St., 30-059 Cracow, Poland.
Materials (Basel). 2021 Mar 23;14(6):1575. doi: 10.3390/ma14061575.
NiTi shape memory alloys are increasingly being used as bone and cardiac implants. The oxide layer of nanometric thickness spontaneously formed on their surface does not sufficiently protect from nickel transition into surrounding tissues, and its presence, even in a small amount, can be harmful to the human organism. In order to limit this disadvantageous phenomenon, there are several surface engineering techniques used, including oxidation methods. Due to the usually complex shapes of implants, one of the most prospective methods is low-temperature plasma oxidation. This article presents the role of cathode sputtering in the formation of a titanium dioxide surface layer, specifically rutile. The surface of the NiTi shape memory alloy was modified using low-temperature glow discharge plasma oxidation processes, which were carried out in two variants: oxidation using an argon + oxygen (80% vol.) reactive atmosphere and the less chemically active argon + air (80% vol.), but with a preliminary cathode sputtering process in the Ar + N (1:1) plasma. This paper presents the structure (STEM), chemical composition (EDS, SIMS), surface topography (optical profilometer, Atomic Force Microscopy-AFM) and antibacterial properties of nanocrystalline TiO diffusive surface layers. It is shown that prior cathodic sputtering in argon-nitrogen plasma almost doubled the thickness of the produced nitrogen-doped titanium dioxide layers despite using air instead of oxygen. The (TiON) diffusive surface layer showed a high level of resistance to colonization in comparison with NiTi, which indicates the possibility of using this surface layer in the modification of NiTi implants' properties.
镍钛形状记忆合金越来越多地被用作骨骼和心脏植入物。在其表面自发形成的纳米级厚度的氧化层并不能充分防止镍向周围组织的转移，即使其含量很少，也可能对人体有害。为了限制这种不利现象，人们使用了多种表面工程技术，包括氧化方法。由于植入物通常形状复杂，最有前景的方法之一是低温等离子体氧化。本文介绍了阴极溅射在二氧化钛表面层（特别是金红石型）形成过程中的作用。使用低温辉光放电等离子体氧化工艺对镍钛形状记忆合金的表面进行了改性，该工艺分两种变体进行：在氩气 + 氧气（80% 体积）反应气氛中进行氧化，以及在化学活性较低的氩气 + 空气（80% 体积）中进行氧化，但在氩气 + 氮气（1:1）等离子体中进行初步阴极溅射工艺。本文介绍了纳米晶TiO扩散表面层的结构（扫描透射电子显微镜）、化学成分（能谱分析、二次离子质谱）、表面形貌（光学轮廓仪、原子力显微镜）和抗菌性能。结果表明，尽管使用空气代替氧气，但在氩气 - 氮气等离子体中进行的预阴极溅射使所制备的氮掺杂二氧化钛层的厚度几乎增加了一倍。与镍钛相比，（TiON）扩散表面层显示出对定植的高抗性，这表明该表面层可用于改性镍钛植入物的性能。
