Akbulut Mustafa, Godfrey Alig Anna R, Israelachvili Jacob
Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA.
J Chem Phys. 2006 May 7;124(17):174703. doi: 10.1063/1.2184310.
The tribological and tribochemical properties of 5-10 nm thick Ag films sliding on various metal and inorganic substrates were measured using a surface forces apparatus coupled with ex situ x-ray photoelectron spectroscopy. We observed enhanced chemical reactivity in the sheared regions compared to the unsheared regions, which we attribute to significant frictional heating in agreement with two recent simulations. It is also found that the initial topography (roughness) of the films plays a significant role in determining the friction, wear, and tribochemical reactions. The larger the surface roughness, the larger are the friction coefficients. Initially smooth surfaces, forming large continuous junctions, create large wear debris particles; whereas initially rough surfaces, forming many small junctions, create many small particles. Even though initially smooth surfaces are chemically less reactive than initially rough surfaces, they are tribochemically more reactive, forming two to three times more oxides of silver during shearing than under static conditions and organometals of silver that under normal (static) conditions do not form. The chemical reactions observed cannot be explained without including the tribological processes, such as the local stresses, temperature rises, and type of wear produced by the shearing surfaces.
使用表面力仪结合非原位X射线光电子能谱，测量了在各种金属和无机基底上滑动的5-10纳米厚银膜的摩擦学和摩擦化学性质。我们观察到，与未剪切区域相比，剪切区域的化学反应性增强，我们将其归因于显著的摩擦热，这与最近的两项模拟结果一致。还发现，薄膜的初始形貌（粗糙度）在决定摩擦、磨损和摩擦化学反应中起着重要作用。表面粗糙度越大，摩擦系数越大。初始光滑的表面形成大的连续连接，产生大的磨损碎屑颗粒；而初始粗糙的表面形成许多小连接，产生许多小颗粒。尽管初始光滑表面的化学反应性比初始粗糙表面低，但它们的摩擦化学反应性更高，在剪切过程中形成的银氧化物比静态条件下多两到三倍，并且在正常（静态）条件下不会形成银有机金属化合物。如果不考虑摩擦学过程，如局部应力、温度升高和剪切表面产生的磨损类型，就无法解释所观察到的化学反应。
