Structural materials microstructural evolutions

Using the triple-ion beam irradiation apparatus, the microstructural evolution of austenitic stainless steel, which is considered as a structural material for water-cooled fusion reactors... 

Interfacial structure is known to be different from bulk structure, and in polymers filled with nanofillers possessing extremely high specific surface areas, most of the polymers is present near the interface, in spite of the small weight fraction of filler. This is one of the reasons why the nature of the reinforcement is different in nanocomposites and is manifested even at very low filler loadings (<10 wt%). Crucial parameters in determining the effect of fillers on the properties of composites are filler size, shape, aspect ratio, and filler-matrix interactions [2-5]. In the case of nanocomposites, the properties of the material are more tied to the interface. Thus, the control and manipulation of microstructural evolution is essential for the growth of a strong polymer-filler interface in such nanocomposites. 

Suction controlled oedometer tests were performed to gain insight into the characterization of the material, which exhibits a marked double structure a microstructure, which describes the dense aggregates of clay platelets and a macrostructure which includes the inter-aggregate and inter-pellet voids. An important feature of this material is the evolution of the microstructure as the mixture hydrates. 

Furthermore, the surface properties of the powders have direct effect on the densification and microstructural evolution of green bodies during the firing process. This is because the surfaces of the particles will form interfaces and grain boundaries, which are actually the sources and sinks for the diffusion of various species within the materials. Therefore, the structure and composition of the interfaces and grain boundaries will determine the behaviors of densification and... 

It is beyond the scope of this chapter to review structure and bonding in each class of engineering carbons listed in Table 5. Instead, a generic description of microstructure and bonding in these materials will be attempted. The evolution in understanding of the structure of engineering carbons and graphites has followed the initial application of X-ray diffraction and subsequent application... 

One may now ask whether natural systems have the necessary structural evolution needed to incorporate high-performance properties. An attempt is made here to compare the structure of some of the advanced polymers with a few natural polymers. Figure 1 gives the cross-sectional microstructure of a liquid crystalline (LC) copolyester, an advanced polymer with high-performance applications [33]. A hierarchically ordered arrangement of fibrils can be seen. This is compared with the microstructure of a tendon [5] (Fig. 2). The complexity and higher order of molecular arrangement of natural materi-... 

The constitutive equations use a thermodynamic framework, that in fact embodies not only purely mechanical aspects, but also transfers of masses between the phases and diffusion of matter through the extrafibrillar phase. Since focus is on the chemo-mechanical couplings, we use experimental data that display different salinities. The structure of the constitutive functions and the state variables on which they depend are briefly motivated. Calibration of material parameters is defined and simulations of confined compression tests and of tree swelling tests with a varying chemistry are described and compared with available data in [3], The evolution of internal entities entering the model, e.g. the masses and molar fractions of water and ions, during some of these tests is also documented to highlight the main microstructural features of the model. 

There is clearly a microstructural dependence, and studies on HAZs show corrosion to be appreciably more severe when the material composition and welding parameters are such that hardened structures are formed. It has been known for many years that hardened steel may corrode more rapidly in acid conditions than fully tempered material, apparently because local microcathodes on the hardened surface stimulate the cathodic hydrogen evolution reaction. (Bond)5... 

As discussed earlier, analysis of temperature profiles obtained by microthermocouple measurements have elucidated the unique conditions associated with the combustion synthesis process. However, this approach does not directly identify the composition or microstructure of the phases formed. It is important to recognize that most published investigations in the field of combustion synthesis only address the final product structure. Considerably less has been reported about the structure formation processes leading to the final product. Most results that describe the evolution from the initial reactants to the final product are inferred by the effects of processing variables (e.g., density, dilution, particle size) on the final microstructure (see Section V). To date, only a few investigations have directly identified initial product structure. As discussed earlier, identification of this structure is important since the initial structure represents the starting point for all subsequent material structure formation processes. Thus, the focus of this section is on the initial stages of the structure formation mechanisms in combustion synthesis and novel methods developed especially for this purpose. 

Interfacial structure The role of electrochemical phenomena at interfaces between ionic, electronic, photonic, and dielectric materials is reviewed. Also reviewed are opportunities for research concerning microstructure of solid surfaces, the influence of the electric field on electrochemical processes, surface films including corrosion passivity, electrocatalysis and adsorption, the evolution of surface shape, and self-assembly in supramolecular domains. 

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