History and the Characteristics of Solid Surfaces

FIGURE 7.4. Schematic illustration of plastic deformation and flow under load at points of contact between asperities of a soft material and a relatively hard surface. 

In addition to local pressure effects, normal sintering temperatures will also usually allow significant amounts of diffusion, both in the bulk and in the surface. By such mechanisms, scratches on some metal surfaces will be healed if the sample is heated to a temperature well below the melting point. 

Other factors that can affect the apparent energy of a surface include the action of friction (see Chapter 18), corrosive action (which actually changes the chemical nature of the surface such as oxidation in metals), and adsorption. All of these items are pointed out because they should always be taken into account when one attempts to determine the surface energy of a solid. 

Of equal or greater importance to the nature of a surface is the question of the history of its formation (as opposed to the treatments noted above). 

TABLE 7.1. Reported Surface Energies of Commonly Encountered Solids 

---