Interphase concept

On the basis of the interphase conception, Lipatov and Privalko proposed in... 

Theoretical studies of interphase and three engineered interphase concepts... 

First theoretical interpretations of Me UPD by Rogers [3.7, 3.12], Nicholson [3.209, 3.210], and Schmidt [3.45] were based on an idealized adsorption model already developed by Herzfeld [3.211]. Later, Schmidt [3.54] used Guggenheim s interphase concept" [3.212, 3.213] to describe the thermodynamics of Me UPD processes. Schmidt, Lorenz, Staikov et al. [3.48, 3.57, 3.89-3.94, 3.100, 3.214, 3.215] and Schultze et al. [3.116-3.120, 3.216] used classical concepts to explain the kinetics of Me UPD and UPD-OPD transition processes including charge transfer, Meloiy bulk diffusion, and nucleation and growth phenomena. First and higher order phase transitions, which can participate in 2D Meads phase formation processes, were discussed controversially by various authors [3.36, 3.83, 3.84, 3.92-3.94, 3.98, 3.101, 3.110-3.114, 3.117-3.120, 3.217-3.225]. 

The thermodynamics of 2D Meads overlayers on ideally polarizable foreign substrates can be relatively simply described following the interphase concept proposed by Guggenheim [3.212, 3.213] and later applied on Me UPD systems by Schmidt [3.54] as shown in Section 8.2. A phase scheme of the electrode-electrolyte interface is given in Fig. 8.1. Thermodynamically, the chemical potential of Meads is given by eq. (8.14) as a result of a formal equilibrium between Meads and its ionized form Me in the interphase (IP). The interphase equilibrium is quantitatively described by the Gibbs adsorption isotherm, eq. (8.18). In the presence of an excess of supporting electrolyte KX, i.e., c , the chemical potential is constant and... 

It should be noticed that the model assumption in eq. (3.16) is rather arbitrary. The true state of charge of any adsorbed species is unknown from a thermodynamic point of view since a localization of electronic charge within the interphase would not change the total surface excess concentration, 7i(w), of the species i involved. According to the thermodynamic interphase concept presented here [3.54], experimentally observed deviations y z have only to be explained in terms of cosorption or competitive sorption... 

The thermodynamic description of a system consisting of a 3D Me-S bulk alloy phase (instead of an ideally polarizable substrate S) in contact with the electrolyte phase is based on an interphase concept similar to that in Section 8.2 [3.54, 3.322, 3.323). The necessary changes in the thermodynamic formalism are given in Section 8.6. The electrochemical system considered is schematically shown in Fig. 8.5. 

The main result of the thermodynamic treatment in Section 8.6 is that the interphase between a 3D Me-S bulk alloy phase and an electrolyte phase can be described by relative specific surface excess quantities, q, Tand Fi with f = IC and X, analogous to the interphase concept of an ideally polarizable substrate S in contact with the electrolyte phase (Section 8.2). 

The following discussion will therefore make but a weak attempt to review past approaches to inhibition theory. Rather, emphasis will be placed on the interphase concept. It is hoped that the reader will thus be offered a short introduction to corrosion inhibition as well as being stimulated to further investigative efforts in the field of corrosion inhibition. 

Experimental evidence now strongly favors the interphase concept. In addition to the two investigations already cited (12,13), there have been several small-angle x-ray studies (e.g., 21) which were sufficiently precise to measure the interphase thickness, and results proved to be compatible with recent thermodynamic models (8-10,22). Rheological evidence from the liquid state has also been interpreted in terms of a critical role played by the interphase (23). Finally, we will show here that data from dynamic mechanical spectroscopy can be explained only by choosing 0 and that details of G (T) and G (T) can be... 

Ishida has reported that dry coating, as often used in particnlate filler treatment, resnlts in an approximate monolayer of chemi-sorbed silane, giving imperfect coverage with the rest of the silane being weakly physisorbed [59]. Unlike the sitnation with solution coating of glass fibre, it is unusual to use more than a monolayer. Hence, the interphase concepts are less important in this case. 

Once it is recognized that particles adhere to a substrate so strongly that cohesive fracture often results upon application of a detachment force and that the contact region is better describable as an interphase [ 18J rather than a sharp demarcation or interface, the concept of treating a particle as an entity that is totally distinct from the substrate vanishes. Rather, one begins to see the substrate-particle structure somewhat as a composite material. To paraphrase this concept, one could, in many instances, treat surface roughness (a.k.a. asperities) as particles appended to the surface of a substrate. These asperities control the adhesion between two macroscopic bodies. 

The mechanism of chemical adhesion is probably best studied and demonstrated by the use of silanes as adhesion promoters. However, it must be emphasized that the formation of chemical bonds may not be the sole mechanism leading to adhesion. Details of the chemical bonding theory along with other more complex theories that particularly apply to silanes have been reviewed [48,63]. These are the Deformable Layer Hypothesis where the interfacial region allows stress relaxation to occur, the Restrained Layer Hypothesis in which an interphase of intermediate modulus is required for stress transfer, the Reversible Hydrolytic Bonding mechanism which combines the chemical bonding concept with stress relaxation through reversible hydrolysis and condensation reactions. 

The term chemistry in interphases was first introduced in the field of reverse-phase chromatography [41], In 1995 Lindner et al. transferred the concept to the area of transition metal catalysis [42] and in a recent review the concept is explained in detail [43], The interphase is defined as a region within a system in which the stationary and a mobile component penetrate on a molecular level without the formation of a homogeneous mixture. In these regions the reactive centre on the stationary phase... 

Model of a supramolecular structure of polymolecular ensembles or clusters, determined by interaction and mutual arrangement of the forming molecules. At this level, the specific mechanisms of supramolecular chemistry, including molecular recognition, self-assembly, etc. [4] can be allocated. In most cases, it is possible to limit this area to objects with the sizes under 1 to 2 nm, since further increase in the sizes admits application of statistical concepts like phase and interphase surface. 

The concept of the cell cycle (Figure 1-1-2) can be used to describe the timing of some of these events in a eukaryotic cell. The M phase (mitosis) is the time in which the cell divides to form two daughter cells. Interphase is the term used to describe the time between two cell divisions or mitoses. Gene expression occurs throughout all stages of interphase. Interphase is subdivided as follows ... 

The concept sounds attractive, but there is a flaw in the explanation. Assuming an equilibrium situation between the two bulk phases and the interphase, complex formation at the interfacial region requires the same complexes are formed also in the bulk phases. Consequently, in order to produce a considerable amount of the mixed species MA, xBx in the liquid-liquid boundary layer some B must be dissolved in the aqueous, as weU as some A in the organic phase. Since by definition this condition is not met, the relative amount of M present at the interphase region as MAn xBx must be negligible. However, now the metal ion will be distributed between MA in the aqueous phase and MBp in the organic layer (n and p are the... 

Sideridis, E. (1994). Thermal expansion coefficients of fiber composites defined by the concept of the interphase. Composites Sci. Technol. 51, 301-317. 

Third, a curious and subtle concept was explained, the concept of surface excess, r. This is not to be confused with adsorption, although the surface excess may become nearly identical to the total amount adsorbed under certain limiting conditions. The surface excess of a particular species is the excess of that species present in the surface phase relative to the amount that would have been present had there been no double layer. The surface excess, therefore, represents the accumulation or depletion of the species in the entire interphase region. Further, electrocapillaiy measurements and radiochemical experiments permit a direct experimental description of the surface excess of a species. 

Recent work has expanded the concept of the fiber-matrix interface which exists as a two-dimensional boundary into that of a fiber-matrix interphase that exists in three dimensions 2). The complexity of this interphase can best be illustrated with the use of a schematic model which allows the many different characteristics of this region to be enumerated as shown in Fig. 1 3). 

New concepts of bonding across the interphase in composites have also been explored in recent years. Plueddemann has proposed a new mechanism for bonding to thermoplastics under conditions of high shear. The property desired in the interphase region of thermoplastic composites under these conditions fits the description of commercial ionomers [38]. 

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