Bedolla Pedro O, Feldbauer Gregor, Wolloch Michael, Gruber Christoph, Eder Stefan J, Dörr Nicole, Mohn Peter, Redinger Josef, Vernes András
Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria ; Austrian Center of Competence for Tribology, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria.
Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria.
J Phys Chem C Nanomater Interfaces. 2014 Sep 18;118(37):21428-21437. doi: 10.1021/jp504695m. Epub 2014 Sep 9.
The presence of water in biofuels poses the question of how it affects the frictional performance of additives in fuels containing organic substances. To investigate the effect of water on the adsorption of molecules present in fuel and its additives we simulated within the framework of density functional theory the adsorption of ethanol, isooctane (2,2,4-trimethylpentane), and acetic acid on a bare and a water-covered Fe(100) surface. Van der Waals interactions are taken into account in our computations. In those molecules, where dispersion forces contribute significantly to the binding mechanism, the water layer has a stronger screening effect. Additionally, this effect can be enhanced by the presence of polar functional groups in the molecule. Thus, with the introduction of a water layer, the adsorption energy of isooctane and ethanol is reduced but it is increased in the case of the acetic acid. The adsorption configuration of ethanol is changed, while the one of acetic acid is moderately, and for isooctane only very slightly altered. Therefore, the effect of a water layer in the adsorption of organic molecules on an Fe(100) surface strongly depends on the type of bond and consequently, so do the tribological properties.
生物燃料中存在的水引发了一个问题，即它如何影响含有有机物质的燃料中添加剂的摩擦性能。为了研究水对燃料及其添加剂中存在的分子吸附的影响，我们在密度泛函理论框架内模拟了乙醇、异辛烷（2,2,4 - 三甲基戊烷）和乙酸在裸露的和被水覆盖的Fe(100)表面上的吸附。我们的计算中考虑了范德华相互作用。在那些色散力对结合机制有显著贡献的分子中，水层具有更强的屏蔽作用。此外，分子中极性官能团的存在可以增强这种效应。因此，随着水层的引入，异辛烷和乙醇的吸附能降低，但乙酸的吸附能增加。乙醇的吸附构型发生了变化，而乙酸的吸附构型变化适中，异辛烷的吸附构型仅略有改变。因此，水层对有机分子在Fe(100)表面吸附的影响强烈取决于键的类型，摩擦学性质也同样如此。
