Microstructured characteristic features

In this paper, a molecular thermodynamic approach is developed to predict the structural and compositional characteristics of microemulsions. The theory can be applied not only to oil-in-water and water-in-cil droplet-type microemulsions but also to bicontinuous microemulsions. This treatment constitutes an extension of our earlier approaches to micelles, mixed micelles, and solubilization but also takes into account the self-association of alcohol in the oil phase and the excluded-volume interactions among the droplets. Illustrative results are presented for an anionic surfactant (SDS) pentanol cyclohexane water NaCl system. Microstructur al features including the droplet radius, the thickness of the surfactant layer at the interface, the number of molecules of various species in a droplet, the size and composition dispersions of the droplets, and the distribution of the surfactant, oil, alcohol, and water molecules in the various microdomains are calculated. Further, the model allows the identification of the transition from a two-phase droplet-type microemulsion system to a three-phase microemulsion system involving a bicontinuous microemulsion. The persistence length of the bicontinuous microemulsion is also predicted by the model. Finally, the model permits the calculation of the interfacial tension between a microemulsion and the coexisting phase. 

The characteristic features of microsystems stem from the small size of the space in the microstructures. Therefore, microsystems are not necessarily small systems in total size. They can be large in total size as long as they contain microstructures that can be used for chemical reactions. This sharply contrasts with the concept of a lab-on-a-chip, which should be small in total size. It is also important to note that microsystems are normally set up as flow-type reactors with a constant flow of solutions through a microstructured reaction chamber or channel. Although the reactor s capacity at any one time is small, total production capacity over time is much greater than may be imagined. Therefore, microflow systems are not necessarily used solely to produce small quantities of chemical substances. In fact, a microfluidic device has been developed that fits in the palm of the hand but can produce several tons of a product per year (see Chapter 10). 

Stemming from the small sizes and high surface-to-volume ratio of the microstructures, microflow systems composed of microfluidic devices have the following characteristic features (Table 7.2) ... 

In regard to the copolymerization process, we have to describe the rates of incorporation of comonomers and distribution of different units in the resulting copolymer (microstructure). In this section we briefly discuss characteristic features of copolymerization of TXN with cyclic formals and then with other oxacyclic and some vinyl monomers. 

The microstructure of this compound deserves, in our opinion, a special discussion. A characteristic feature of the microstructure is the presence of strictly parallel shear lines in each grain. A similar effect is observed for grains of the main phase over the whole concentration range of silicon where it exists. In addition, striation is exhibited even after annealing an Mn4Si7 single crystal, obtained by a special method. 

In an effective properties model, the porous microstructures of the SOFC electrodes are treated as continua and microstructural properties such as porosity, tortuosity, grain size, and composition are used to calculate the effective transport and reaction parameters for the model. The microstmctural properties are determined by a number of methods, including fabrication data such as composition and mass fractions of the solid species, characteristic features extracted from micrographs such as particle sizes, pore size, and porosity, experimental measurements, and smaller meso- and nanoscale modeling. Effective transport and reaction parameters are calculated from the measured properties of the porous electrodes and used in the governing equations of the ceU-level model. For example, the effective diffusion coefficients of the porous electrodes are typically calculated from the diffusion coefficient of Eq. (26.4), and the porosity ( gas) and tortuosity I of the electrode ... 

The peculiar features of polydienes are due not only to the presence of unsaturated double bonds in the polymer chain, but also to their particular microstructural characteristics (chemo-, regio-, and stereoselectivity). Owing to the complexity of polydiene structures, before going into detail concerning the different stereoregular polymers that can be obtained from a given monomer, it is... 

The procedure to determine the grain size or microstructure of a metal or alloy is to first prepare a sample for microscopic study by grinding and polishing the surface of a specimen mounted in a plastic material. The polished surface is then corroded with a suitable etching reagent, such as those briefly described in Table 2.3, that attacks more readily the grain boundaries of a metallic microstructure to reveal its characteristic features. 

The microstnictural evolution process is calculated by substituting Eq.(22) into TDGL Eq.(21) and the results are presented in Fig.ll. The microstructure is visualized by ffay levels representing different values of /= ), +fjj +tj,. fn this calculation, the system is annealed at T = 1.6. One sees that a triple junction of APB s is formed in the later period. This is one of characteristic features of the anti-phase domain structure in Llo ordered alloy and is in marked difference with those shown in Figs.9 and 10. 

Table I demonstrates the application of the five-parameter relationship in the Interaction Matrix format. After inserting the five modified power-law parameters along the top of the vertical columns, one may then proceed to list molecular and microstructural characteristics along the left side of the horizontal rows. The list of characteristics is fairly representative of measurable features common to polymer science and technology. Individual characteristics may not be mutually independent, and additions or refinements are likely to be used for specific cases. The intersecting columns and rows may then...

As follows from the data of work [37], the characteristic feature of the microstructure of the LajcMn03+5 samples with x = 0.815 and 0.90 is the presence of simply connected domains containing a number of grains. The porosity of these samples does not exceed 7 %. In both the cases, the peak resistivity is comparable to the values which were observed in polycrystalline samples for which the negligible role of tunneling effects was proved experimentally [26,62,63]. All these facts imply that for the Lo.gis and L0.90 samples, the porosity affects the absolute value of resistivity but hardly modifies its temperature dependence. For the other samples, however, the role of porosity as well as the contribution of tunneling effects to the conductivity should be discussed separately. This will be done below while discussing the resistivity of the L0.94 sample. 

To further characterize the event it is first necessary to identify critical features of the initial configuration that will strongly influence the process. For powder compacts, the most obvious features are the morphological characteristics of the powders, their microstructures, and the porosity of the compact. For solid density samples, the grain structure, grain boundaries, defect level, impurities, and inclusions are critical features. 

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