The Interphase Concept

To be able to control the PCM properties in the desired direction it is very important to know the relationships between the material composition and properties. Since melt viscosity is one of the most important characteristics of processability of PCM, there have naturally been a large number of equations proposed for describing the viscosity versus filler concentration relationship. For the purpose of this review it may be most interesting to discuss the numerous equations which have in common the use of the value representing the maximum possible volume filling by filler particles packed in one way or another, as the principal constant. Here are a few examples of such equations. 

It is even more difficult, relying on hydrodynamical models, to explain the frequently observed decrease, rather than increase, of viscosity when a certain quantity of filler is added [47-50]. 

It became possible to elucidate such experimental facts when it was proposed that considerable restructuring, manifesting itself in the appearance of boundary layers, occurs in the matrix under the effect of a filler [51-56]. 

The boundary layers, or interphases as they are also called, form the mesophase with properties different from those of the bulk matrix and result from the long-range effects of the solid phase on the ambient matrix regions. Even for low-molecular liquids the effects of this kind spread to liquid layers as thick as tens or hundreds or Angstrom [57, 58], As a result the liquid layers at interphases acquire properties different from properties in the bulk, e.g., higher shear strength, modified thermophysical characteristics, etc. [58, 59], The transition from the properties prevalent in the boundary layers to those in the bulk may be sharp enough and very similar in a way to the first-order phase transition [59]. 

The thickness of interphases in polymer melts and solutions may be much greater than in low-molecular matrices owing to the greater size of their macromolecules and existence in them of submolecular associates [51], 

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

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... 

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. 

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... 

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. 

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]. 

Classical treatment of mass transfer is to consider a unit, of mass transfer as a measure of the interphase equilibrium changes needed to produce a desired degree of diffusion [13], This concept is best applied to the concept of a theoretical plate in distillation [4], Defining Gm as the gas superficial molar velocity (mole/hr/ft2 of tower cross section) and dy as the change of concentration of the diffusing species, then... 

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]. 

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 large number of contemporary MC approaches for dealing with the problem of phase behaviour can usefully be categorized in terms of the the interphase path they utilize to connect the phases and the sampling strategy adopted to traverse this path. We have exemplified some of the principal concepts within the limited context of the phase behaviour of simple particle... 

An example follows that is used to illustrate some of the details of the EC analysis process and its forecasting characteristics. The general reader may skip over this technical section without loss of continuity of the subject. It involves an important and very common EC problem and illustrates the effective use of the flux concept in connecting the interphase chemical movement in a multimedia context. 

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