Microscopic heterogeneous structure

Figure 3.5 Visually observaUe light trajectory due to forward scattering by microscopic heterogeneous structures in PMMA-based Gl preform.

The metallurgical characteristics of the aluminum oxide layer also depend on its physical metallurgy, such as defects and metallurgical structure included in the oxide layer. For instance, when intermetallic compound particles as secondary phases are exposed on the surface, a discontinuous oxide film with various defects is often produced at the metal-particle interface. This discontinuous oxide film is weakly or non-protective chemically and physically. Because corrosion is a chemical and electrochemical reaction on the surface, corrosion behavior is readily influenced by surface morphology. The aluminum surface is usually adsorbed or contaminated by water, gases and many kinds of micron-sized substances. Microscopic heterogeneous structures such as vacancies, steps, kinks, and dislocations, and macroscopic heterogeneous structures such as scratches, pits and other superficial blemishes influence the corrosion behavior of aluminum and its alloys to different extents. 

Texture and structure are not explicitly defined terms. Structure is usually applied to macroscopic heterogeneity due to macroscopic movement such as flow structure or foliated structure, whereas texture usually refers to microscopic heterogeneity, such as holocrystalline texture, porphyritic texture, and lamellar texture due to exsolution. 

In common with conventional surfactants, Inisurfs and Transurfs, Surfmers form micelles in aqueous solutions above the CMC. The organized monomer aggregates of colloidal dimension are microscopically heterogeneous and may affect polymerization kinetics and polymer structure and properties. 

The second approach considers the heterogeneous structure of the compact particulate reaction mixture. Since the combustion wave propagates through a mixture of powder reactants with varying particle sizes (O.l-KX) m), nonuniformity of the combustion front and variations in propagation velocity can be expected at the microscopic scale. 

Previous work has shown that gels formed from cross-linked polyacrylamide (6), alginate (6), hydrolyzed starch-polyacrylonitrile (7), and a cross-linked poly(acrylic acid) (8), consist of discontinuous structures with microregions of extremely low viscosity. Such microscopic heterogeneity has been attributed to permanent or diffusing fluctuations within the gel (i) or to a structure of closely packed, swollen microgels in a continuous water phase (2, 3). 

Understanding the effects of membrane structure, water content and water distribution on proton conductivity has to invoke additional theoretical tools. They have to bridge many length scales from molecular environments to random heterogeneous structure at macroscale. This involves phenomenological concepts and homogenization methods in order to average over microscopic details [65]. 

It is impossible to mistake man-made fibers for fibers of animal origin under the microscope. Man-made fibers are homogeneous in their fine structure. Animal hairs-7-such as wool, fiir, and human hair too—have a strongly differentiated, heterogeneous structure. 

Structural parameters of a polymer matrix. The structural microscopic heterogenity of solid samples has important kinetic implications even... 

Me/a/—composition, detailed atomic structure, microscopic and macroscopic heterogeneities, stress (tensile, compressive, cyclic), etc. 

Heterogeneities associated with a metal have been classified in Table 1.1 as atomic see Fig. 1.1), microscopic (visible under an optical microscope), and macroscopic, and their effects are considered in various sections of the present work. It is relevant to observe, however, that the detailed mechanism of all aspects of corrosion, e.g. the passage of a metallic cation from the lattice to the solution, specific effects of ions and species in solution in accelerating or inhibiting corrosion or causing stress-corrosion cracking, etc. must involve a consideration of the detailed atomic structure of the metal or alloy. 

The degradation of the matrix in a moist environment strongly dominates the material response properties under temperature, humidity, and stress fatigue tests. The intrinsic moisture sensitivity of the epoxy matrices arises directly from the resin chemical structure, such as the presence of hydrophilic polar and hydrogen grouping, as well as from microscopic defects of the network structure, such as heterogeneous crosslinking densities. 

On a microscopic scale, a microemulsion is a heterogeneous system and, depending on the relative amounts of the constituents, three main types of structures can be distinguished [69] oil in water (OAV, direct micellar structure), water in oil (W/O, reverse micellar structure) and a bicontinuous structure (B) (Figure 6.1). By adding oil in water, OAV dispersion evolves smoothly to a W/O dispersion via bicontinuous phases. 

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