Effect of Composition Changes

So far we have considered only the effect of salinity on microemnlsion phase behavior. The effects of other compositional variables and temperatnre can be understood in terms of a single unifying principle. First, we summarize the results of numerous experiments by several workers in systems containing oil, brine, an anionic surfactant, and a short-chain alcohol. 

An empirical correlation describing how various compositional variables influence optimal salinity for petroleum sulfonate surfactants was developed by Salager et al. (1979)  

Schechter, and coworkers (Cash et al., 1977) proposed that mixtnres of oils and snrfactants can be described by Equation 4.20, provided that average values of ACN and a are used. 

Here is the mole fraction of component i. Further discussion of oil mixtures and of handling oils with naphthenic and aromatic groups can be found in Cayias et al. (1976) and Puerto and Reed (1983). 

For certain classes of anionic surfactants, other effects are also important. For example, changes in pH affect the degree of ionization and hence the phase behavior when the surfactants include organic adds, amines, or other pH-sensitive compounds. An increase in the degree of ionization produces a more hydrophilic surfactant film and hence, other things bdng equal, increases optimal salinity (Qumbuddin et al., 1984). 

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Figure 2. Contour sensitivity analysis illustrating the effect of compositional changes on the response around the optimal formulation.

An associated technique which links thermal properties with mechanical ones is dynamic mechanical analysis (DMA). In this, a bar of the sample is typically fixed into a frame by clamping at both ends. It is then oscillated by means of a ceramic shaft applied at the centre. The resonant frequency and the mechanical damping exhibited by the sample are sensitive measurements of the mechanical properties of a polymer which can be made over a wide range of temperatures. The effects of compositional changes and methods of preparation can be directly assessed. DMA is assuming a position of major importance in the study of the physico-chemical properties of polymers and composites. 

Davies, J. H. Ewart, F. T. "The Chemical Effects of Composition Changes in Irradiated Oxide Fuel Materials, Jour, of Nuclear Materials 1971,41,143-155. 

Figure 8.2 Relative detergency of cosmetic soil with 3 wt.% silicone resin in a series of microemulsions containing DC at 25°C. (a) Effect of DC concentration. The composition change corresponds to that from point p to q in Fig. 8.1. Concentration of ethanol is 12 wt.%. (b) Effect of ethanol concentration. The composition change corresponds to that from point r to s in Fig. 8.1. Concentration of DC is 6 wt.%. (c) Effect of composition change along the solubilisation limit from the point t to s in Fig. 8.1. Dashed lines represent the phase boundaries. (From Ref. [1 ], reprinted with permission of JOCS.)...

At constant T and p, expressing only the effect of composition change. 

In the present study, synthetic analcites having fixed Al/Si ratios of 2/3, 1/2, and 1/3 were subjected to ion exchange with a series of cations of various size, charge, and polarizability to fix limits of crystalline solubility and to determine the effects of compositional change on structure. Structure data as a function of temperature and pH2o (to be presented in a future publication) are available in a doctoral thesis by Balgord (2). 

A kinetic model, based on the FACSIMILE code, has been developed to study the effects of composition change during reactor scenarios. Vaporisation flux and vapour pressure data have been used in a preliminary study of transport of gaseous species from the external surface of the fuel and... 

The relationship of tensile properties, impact properties, and austenite stability to compositional variations is very complex. The generally desirable features of high tensile and yield strength, adequate ductility, and high impact strength at low temperatures cannot be simply related to the effect of compositional variations on the austenite stability. A detailed discussion of the effect of compositional changes follows. 

Gotze W, Voigtmann T (2003) Effect of composition changes on the structural relaxation of a binary mixture.Phys Rev E 67 021502... 

The classical theory of nucleation was developed by Volmer and Weber, and Becker and Doring" for the condensation of a pure vapour to form a liquid. The subsequent theory-- for the liquid-solid transformation was based on this earlier work. The theory considered homogeneous nucleation, ia the formation of one phase by the aggregation of components of another phase without change of composition and without being influenced ly impurities or external surfaces. Impurity particles and external surfaces are taken into account in heterogeneous nucleation theory (Section 2.3). Modifications to the classical theory are necessary to allow for the effects of compositional changes. 

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