Surface free determination

A solid, by definition, is a portion of matter that is rigid and resists stress. Although the surface of a solid must, in principle, be characterized by surface free energy, it is evident that the usual methods of capillarity are not very useful since they depend on measurements of equilibrium surface properties given by Laplace s equation (Eq. II-7). Since a solid deforms in an elastic manner, its shape will be determined more by its past history than by surface tension forces. 

Bikerman [182] criticized the derivation of Eq. X-18 out of concern for die ignored vertical component of On soft surfaces a circular ridge is raised at the periphery of a drop (see Ref. 67) on harder solids there is no visible effect, but the stress is there. It has been suggested that the contact angle is determined by the balance of surface stresses rather than one of surface free energies, the two not necessarily being the same for a... 

A number of methods have been described in earlier sections whereby the surface free energy or total energy could be estimated. Generally, it was necessary to assume that the surface area was known by some other means conversely, if some estimate of the specific thermodynamic quantity is available, the application may be reversed to give a surface area determination. This is true if the heat of solution of a powder (Section VII-5B), its heat of immersion (Section X-3A), or its solubility increase (Section X-2) are known. 

If 31/1 is small and AF is a known function of temperature, Eq. (2.3) can be used to determine the melting point and surface free energy of a lamella from experimental data. For long chain molecules there are several difficulties in choosing the relevant form for AF, Therefore we first consider the limiting case... 

Busscher, H. J., H. M. Uyen, G. A. M. ICip, and J. Arends. 1987. Adsorption of aminefluorides onto glass and the determination of surface free energy, zeta potential and adsorbed layer thickness. Colloids and Surfaces 22 161-69. 

The surface polarity of telomerized starches was determined by the contact angle technique. The surface free energy of the solid was measured from the contact angles of a drop of various probe liquids with the surface of a starch tablet (Table 16). 

Surface free energy (surface tension) of the fillers determines both matrix/filler and particle/particle interaction. The former has a pronounced effect... 

It is now well established that the structure of a thermally equilibrated surface may be quite different from that obtained by simply truncating a solid.10 Surface atoms may rearrange to form a structure according to the lowest surface free energy of that surface. The determination of the atomic structure of solid surfaces is one of the important endeavors in surface science, as the atomic structure will decide both the physical and the chemical properties of the surfaces. Surface reconstruction will also play an important role in the crystal growth and epitaxy of thin films. 

Equation (42) provides a thermodynamically valid way to determine y for an interface involving a solid. The thermodynamic approach makes it clear that curvature has an effect on activity for any curved surface. The surface free energy interpretation of y is more plausible for solids than the surface tension interpretation, which is so useful for liquid surfaces. Either interpretation is valid in both cases, and there are situations in which both are useful. From solubility studies on a particle of known size, y5 can be determined by the method of Example 6.2. 

Equation (46), one form of the Gibbs equation, is an important result because it supplies the connection between the surface excess of solute and the surface tension of an interface. For systems in which y can be determined, this measurement provides a method for evaluating the surface excess. It might be noted that the finite time required to establish equilibrium adsorption is why dynamic methods (e.g., drop detachment) are not favored for the determination of 7 for solutions. At solid interfaces, 7 is not directly measurable however, if the amount of adsorbed material can be determined, this may be related to the reduction of surface free energy through Equation (46). To understand and apply this equation, therefore, it is imperative that the significance of r2 be appreciated. 

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