Watanabe Seiya, Tadokoro Chiharu, Miyake Koji, Sasaki Shinya, Nakano Ken
Department of Mechanical Engineering, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo, 125-8585, Japan.
Department of Mechanical Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan.
Sci Rep. 2022 Mar 9;12(1):3870. doi: 10.1038/s41598-022-07854-5.
Adsorbed molecular films, referred to as boundary films in tribology, are widely used in various industrial products as a keyway for surface functionalisation, such as lubricity, wettability, and adhesion. Because boundary films are thin nanometre-scale molecular layers and can easily be removed, their formation process cannot be elucidated in detail. In this study, to analyse the growth dynamics of boundary films, the film thickness and molecular orientation of the boundary film of a fatty acid used as an additive in rolling contact as mechanical stimuli were measured in situ. The measurements were performed on simple test lubricants, which were composed of n-hexadecane and stearic acid, at rolling tribological condition between steel and glass (or sapphire) surfaces by ultrathin film interferometry combined with sum-frequency generation spectroscopy according to a unique protocol. The results quantitatively demonstrate shear-induced boundary film formation. The insight gained from these results is anticipated to enable the formulation of high-performance lubricant additives to further reduce friction loss and high-performance glues that can be freely designed for removability.
吸附分子膜在摩擦学中被称为边界膜，作为表面功能化的关键途径，广泛应用于各种工业产品中，如润滑性、润湿性和粘附性。由于边界膜是纳米级的薄分子层，且易于去除，其形成过程无法详细阐明。在本研究中，为了分析边界膜的生长动力学，在滚动接触中作为机械刺激的添加剂使用的脂肪酸边界膜的膜厚和分子取向通过独特的方案，采用超薄膜干涉测量法结合和频产生光谱法在钢与玻璃（或蓝宝石）表面之间的滚动摩擦条件下，对由正十六烷和硬脂酸组成的简单测试润滑剂进行了原位测量。结果定量地证明了剪切诱导边界膜的形成。从这些结果中获得的见解有望用于配制高性能润滑添加剂，以进一步减少摩擦损失，以及用于可自由设计可去除性的高性能胶水。
