ABSTRACT
The features of a solid surface as a physical object are governed by its spatial arrangement as a boundary between two phases. The atoms and molecules belonging to the surface have fewer neighbors than those in the bulk. Physical adsorption is characterized by the van der Waals interactions between the adsorbate and the solid surface. As a rule, its energy of the interaction is below 20 kJ/mol. The polymolecular films adsorbed on the surface are removed relatively easily. The boundary layer may be in a diversity of physical states, ranging from nearly gaseous to solid crystalline. Both the basic parameters and the pattern of interactions with the solid phase determine its state. When investigating the real contact, it should be remembered that machine-part surfaces deviate to various extents from design shapes that are usually designed to be geometrically due to manufacturing or other considerations.
