Fatty Acid Adsorption on Several DLC Coatings Studied by Neutron Reflectometry
Fatty Acid Adsorption on Several DLC Coatings Studied by Neutron Reflectometry
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DOI：
10.1007/s11249-013-0257-0
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发表时间：
2014-01-01
影响因子：
3.2
通讯作者：
Geue, T.
中科院分区：
文献类型：
--
作者：
Simic, R.;Kalin, M.;Geue, T.
类金刚石（DLC）涂层由于其优异的摩擦学性能，在机械系统接触件上的应用越来越广泛。在过去的十年中，已经报道了许多关于DLC涂层的研究，因此，对其润滑的理解有所提高。边界润滑接触的摩擦学性能受到吸附层的显著影响;然而，由于润滑剂添加剂和涂层结构的多样性，迄今为止还没有提出DLC涂层的一般吸附机制。不幸的是，这阻碍了其润滑性能的改善。吸附层的许多基本物理性质也仍然不确定。本文用中子反射法测定了脂肪酸分子在a-C、a-C：H、a-C：H：F和a-C：H：Si涂层上的吸附层厚度和密度。结果表明，在a-C和a-C：H涂层上均存在一层0.9 nm厚的吸附层。相比之下，两种掺杂涂层，即a-C：H：F和a-C：H：Si，显示出比a-C和a-C：H更差的对脂肪酸分子的吸附能力。在a-C：H：F和a-C：H：Si上没有检测到连续的吸附层;但是，不能排除较低量吸附的可能性。
The application of diamond-like carbon (DLC) coatings on the contacts of mechanical systems is becoming widespread thanks to their excellent tribological properties. Numerous studies of DLC coatings have been reported over the past decade and, as a result, the understanding of their lubrication has improved. The tribological properties of boundary-lubricated contacts are drastically affected by adsorbed layers; however, due to the variety of lubricant additives and coating structures, no general adsorption mechanisms for DLC coatings have been put forward until now. This has, unfortunately, hindered improvements in their lubrication performance. Many of the essential physical properties of the adsorbed layers also remain undefined. In this work, we used neutron reflectometry to determine the thickness and the density of the adsorbed layers of fatty acid molecules on coatings of a-C, a-C:H, a-C:H:F and a-C:H:Si. The results showed that a 0.9-nm-thick layer adsorbed onto the a-C and a-C:H coatings. In contrast, both doped coatings, i.e. the a-C:H:F and a-C:H:Si, showed a poorer adsorption ability towards the fatty acid molecules than the a-C and a-C:H. Continuous adsorption layers were not detected on the a-C:H:F and a-C:H:Si; however, the possibility of adsorption in lower quantities cannot be ruled out.