Heterogeneities of composition

In general, lack of equilibrium during the pyro-processing stage and heterogeneity of composition make it impractical to calculate the phase content of fly ash from its chemical analysis. Two other factors, common to all types of fly ash, further complicate evaluation of the potential to use fly ash. One is the presence of unburnt carbon, which should preferably not exceed a few wt% the other is the presence of alkali-sulphates (see Groppo et al., 2004). When used in cementitious formulations, free... 

The statements sometimes seen in the literature that S-AN copolymers have maximum strength when they contain 30% AN probably can be attributed to the effects of heterogeneity of composition (15, 16). The mechanical properties of these copolymers do in fact depend on the method by which they are prepared. 

Every solid body contains flaws or points of weakness resulting from heterogeneities of composition or structure. In addition, because of the presence of sharp corners, nicks, cuts, scratches, and embedded dirt particles or other sharp inclusions, applied stresses are magnified (concentrated) in certain... 

Neglecting all other restrictions for the system under study, the mixed solvent theory of light scattering can be applied only if the solution composition is the same in the vicinity of every polymer molecules, viz., the polymer surfactant complex is homogeneous with respect to composition. In order to study the heterogeneity of composition of polymer-surfactant complex, the latter was considered as a copolymer solved in pure solvent. The polymer-surfactant molecules are built up of Myy p polymeric and Myy surfactant component, the average composition by weight is defined as... 

The second important factor is the calculation of draw ratio 2, for composites. This problem is due to heterogeneity of composite structure, consisting of two phases elasticity modulus of one of them is essentially (in some orders of value) more, than the second. Differently speaking, during composite tension process only one phase is extended, namely, rubber, owing to nominal value X not already does describe adequately composite deformation process. This effect is well known and for its quantitative accounting for there are two models. The first of them uses the equation [7] ... 

The substitution of Cr + for Al + in the AIPO4-5 framework results in a material with heterogeneity of composition and no fi"amework charge. The compositional heterogeneity affects the sorption properties generally in a similar way as do the charged centers of divalent substituted metal ions. A different influence of the neutral Cr centers can mainly be noticed for the sorbates with nonpolar molecules. It is also found that the distribution of the Cr centers throughout the crystal has the most important effect on the sorption of nonpolar sorbates (217). 

Mechanical tests for advanced composite materials conform in many respects to the conventional test typology used for traditional isotropic materials. Despite the complication associated with the heterogeneity of composite systems, the interface between fiber and matrix, and the anisotropy at the micro- and macroscopic levels, the same characteristic property definitions generally used for conventional materials can be identified for these novel materials. In some cases additional constants are required and some differences in nomenclature are introduced especially when no isotropic counterpart exists. 

The electrochemical corrosion of metals buried in wet soils is based on the creation of multiple corrosion cetts, formed by coupled anodes and cathodes. The cathodes are characterized by metal areas with a higher level of potential energy (Gibbs Free Energy) and the anodes have a lower potential energy. This energy difference between anodes and cathodes sites is usually due to the heterogeneity of composition of the metal structure. The soil in which the metal resides could also contribute to corrosion cell formation. 

A detailed account is presented of the use of scanning electron microscopy in conjunction with energy selection X-ray spectrometry to investigate features of mbbers such as heterogeneity of composition, visual defects, blooming, surface coatings, interfacial characteristics and surfaces of substrates. Diagrammatic representations of equipment. 

Actually, just as for the crystallization starting fiorn a fluid solution, it is also necessary to carry out an analysis in order to determine the tine reactants, which is, in turn, complicated by the difficrrlties inherent in the soUds minor defects, heterogeneity of composition, and difficulty in performing the online chemical analysis. 

The classification of nanosized materials is quite challenging, due to the extreme heterogeneity of compositions and shapes reported so far. A tentative classification may be based on dimensionality of the structures, as shown in Table 17.1. ... 

What has happened, in effect, is that local beam heating, following the first oxidation of the metal film and subsequent rapid quenching, has produced a more or less random heterogeneity of composition, and the phases observed reflect this. Of course, there is no question of this specimen being at equilibrium, but the important feature of the observations is that different structures with different compositions can intergrow coherently in these systems-a property known as syntaxy. This behaviour is well-documented in the literature on d-block transition metal oxides, and the term microdomain texture has been coined to describe it. 

Thus, the Curie temperature of the material (0.75Ba, OJSSrlTiOj is 25°C. This is not the only condition to fulfill with respect to the application, since relative permittivity is a highly sensitive function of the temperature around T. . A heterogenity of composition induces a statistical distribution of Curie temperatures and therefore a flattening of the curve Sj.(T). This heterogenity can be introduced on different scales ... 

These features of bimetallic catalysts, obtained by the proposed method, provide the possibility for studying the peculiarities of the catalytic action of bimetallic particles under conditions excluding segregation and sintering of metals, as well as heterogeneity of composition of mixed particles and differences of their surface composition from the bulk composition. 

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