Abstract A crucial property for implants is their biocompatibility. To ensure biocompatibility, thin coatings of hydroxyapatite (HA) are deposited on the actual implant. In this study, we investigate the effects of the addition of silicate anions to the structure of hydroxyapatite coatings on their adhesion strength via a scratch test and ab initio calculations. We find that both the grain size and adhesion strength decrease with the increase in the silicon content in the HA coating (SiHA). The increase in the silicon content to 1.2 % in the HA coating leads to a decrease in the average crystallite size from 28 to 21 nm, and in the case of 4.6 %, it leads to the formation of an amorphous or nanocrystalline film. The decreases in the grain and crystallite sizes lead to peeling and destruction of the coating from the titanium substrate at lower loads. Further, our ab initio simulations demonstrate an increased number of molecular bonds at the amorphous SiHA-TiO2 interface. However, the experimental results revealed that the structure and grain size have more pronounced effects on the adhesion strength of the coatings. In conclusion, based on the results of the ab initio simulations and the experimental results, we suggest that the presence of Si in the form of silicate ions in the HA coating has a significant impact on the structure, grain size, and number of molecular bonds at the interface and on the adhesion strength of the SiHA coating to the titanium substrate.

中文翻译：

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射频磁控溅射沉积羟基磷灰石和含硅羟基磷灰石涂层的从头算计算和划痕试验研究

摘要 植入物的一个关键特性是其生物相容性。为了确保生物相容性，羟基磷灰石 (HA) 的薄涂层沉积在实际植入物上。在这项研究中，我们通过划痕测试和从头计算来研究将硅酸盐阴离子添加到羟基磷灰石涂层的结构中对其粘附强度的影响。我们发现晶粒尺寸和粘附强度都随着 HA 涂层 (SiHA) 中硅含量的增加而降低。HA 涂层中硅含量增加到 1.2% 导致平均微晶尺寸从 28 nm 减小到 21 nm，在 4.6% 的情况下，它导致非晶或纳米晶膜的形成。晶粒和微晶尺寸的减小导致涂层在较低负载下从钛基材上剥离和破坏。此外，我们的 ab initio 模拟表明无定形 SiHA-TiO2 界面处的分子键数量增加。然而，实验结果表明，结构和晶粒尺寸对涂层的附着强度有更显着的影响。总之，基于 ab initio 模拟的结果和实验结果，我们认为在 HA 涂层中以硅酸盐离子形式存在的 Si 对结构、晶粒尺寸和分子键数有显着影响在界面和 SiHA 涂层与钛基材的附着强度上。我们的 ab initio 模拟表明无定形 SiHA-TiO2 界面上的分子键数量增加。然而，实验结果表明，结构和晶粒尺寸对涂层的附着强度有更显着的影响。总之，基于 ab initio 模拟的结果和实验结果，我们认为在 HA 涂层中以硅酸盐离子形式存在的 Si 对结构、晶粒尺寸和分子键数有显着影响在界面和 SiHA 涂层与钛基材的附着强度上。我们的 ab initio 模拟表明无定形 SiHA-TiO2 界面上的分子键数量增加。然而，实验结果表明，结构和晶粒尺寸对涂层的附着强度有更显着的影响。总之，基于 ab initio 模拟的结果和实验结果，我们认为在 HA 涂层中以硅酸盐离子形式存在的 Si 对结构、晶粒尺寸和分子键数有显着影响在界面和 SiHA 涂层与钛基材的附着强度上。