Surface work reversible

The quantity Wm, represents the total reversible work obtainable in the given change this may include other forms of work, e.g., electrical or surface work, in addition to work of expansion. The latter is equal to PAV ( 3g), and so Wrav. — PAV represents the reversible work, exclusive of work of expansion, that can be obtained from a given change in state. This quantity is sometimes referred to as the net work, and is represented by so that by equation (25.10),... 

Surface Work The work required to increase the area of the surface of tension. Under reversible, isothermal conditions, the surface work (per unit surface area) equals the equilibrium or static surface tension. 

To increase the surface area of a solid, we have to bring atoms from the bulk of a solid or liquid to the surface and move the atoms that are already on the surface along the surface to accommodate the new surface atoms. Under conditions of equilibrium at constant temperature T and pressure P, the reversible surface work 6IF" required to increase the surface area OL by an amount dOL of a one-component system is given by... 

The fracture of practical adhesive joints involves two primary processes— cohesive or adhesive failure at or near the joint and work (reversible and irreversible) involved in plastic, elastic, or viscoelastic deformation of one or all of the components of the joint—one of the two solid surfaces or the adhesive (Fig. 19.4). As indicated in the preceding chapter on friction, cohesive failure of the weaker of two solids in contact is common. The same can be said for normal adhesive joints, in that actual adhesive failure (i.e., exactly at the interface) is less common that cohesive failure, of, for example, the adhesive material, near the interface. What, then, are the necessary conditions for obtaining good adhesion between two surfaces ... 

In these early studies, Frumkin not only demonstrated his remarkable experimental skills but also revealed his deep understanding of natural phenomena, which was rare for someone so young. For example, he provided a complete and rigorous analysis of electrocapillarity theory and also derived the general relationship between the surface tension (reversible work of surface formation) and the surface electric charge, valid for solutions of aU compositions. The Lippmann equation was included as a special case. He also experimentally confirmed the validity of the results by carrying out measurements on a mercury electrode. The concepts developed by Frumkin changed the established view of electrode potentials, accepted since the time of Nemst. 

We can write a different expression for the reversible work by considering the phases separately. The surface work term in Eq. (5.5-7) is added to the usual expression for fwrev for the liquid phase. 

Figure III-l depicts a hypothetical system consisting of some liquid that fills a box having a sliding cover the material of the cover is such that the interfacial tension between it and the liquid is zero. If the cover is slid back so as to uncover an amount of surface dJl, the work required to do so will he ydSl. This is reversible work at constant pressure and temperature and thus gives the increase in free energy of the system (see Section XVII-12 for a more detailed discussion of the thermodynamics of surfaces).

Shuttleworth [26] (see also Ref. 27) gives a relation between surface free energy and stretching tension as follows. For an anisotropic solid, if the area is increased in two directions by dAi and dA2, as illustrated in Fig. VII-1, then the total increase in free energy is given by the reversible work against the surface stresses, that is. 

The seminal discovery that transformed membrane separation from a laboratory to an industrial process was the development, in the early 1960s, of the Loeb-Sourirajan process for making defect-free, high flux, asymmetric reverse osmosis membranes (5). These membranes consist of an ultrathin, selective surface film on a microporous support, which provides the mechanical strength. The flux of the first Loeb-Sourirajan reverse osmosis membrane was 10 times higher than that of any membrane then avaUable and made reverse osmosis practical. The work of Loeb and Sourirajan, and the timely infusion of large sums of research doUars from the U.S. Department of Interior, Office of Saline Water (OSW), resulted in the commercialization of reverse osmosis (qv) and was a primary factor in the development of ultrafiltration (qv) and microfiltration. The development of electro dialysis was also aided by OSW funding. 

The van der Waals and other non-covalent interactions are universally present in any adhesive bond, and the contribution of these forces is quantified in terms of two material properties, namely, the surface and interfacial energies. The surface and interfacial energies are macroscopic intrinsic material properties. The surface energy of a material, y, is the energy required to create a unit area of the surface of a material in a thermodynamically reversible manner. As per the definition of Dupre [14], the surface and interfacial properties determine the intrinsic or thermodynamic work of adhesion, W, of an interface. For two identical surfaces in contact ... 

Eqs. 1-5 hold whether failure is interfacial or cohesive within the adhesive. Furthermore, Eq. 5 shows that the reversible work of adhesion directly controls the fracture energy of an adhesive joint, even if failure occurs far from the interface. This is demonstrated in Table 5, which shows the static toughness of a series of wedge test specimens with a range of adherend surface treatments. All of these samples failed cohesively within the resin, yet show a range of static toughness values of over 600%. 

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