Microstructural evolution

C. Charbon, S. Swaminarayan. Modeling the microstructural evolution of thermoplastic composites. Mater Sci Eng A 238A66, 1997. 

Y. Saito. The Monte Carlo simulation of microstructural evolution in metals. Mater Sci and Eng A 99 114, 1997. 

Fig. 2 illustrates the ordering process after a quench of a disordered alloy below the ordering spinodal. As it was mentioned by AC, the primary ordered domains are formed after few atomic exchanges A.t 1, while further evolution corresponds to the growth of these domains. Fig. 3 shows that in the absence of APBs the microstructure evolution under spinodal decomposition with ordering is similar to that for disordered... 

To examine replication of IPBs we made MFKEi-based simulations using the simplest 2D alloy model with the nearest-neighbor interaction. Some results are presented in Figs. 8-10. The lower row in Fig. 10 illustrates possible effects of thermal fluctuations, similar to those discussed in Sec. 3 for the replication of APBs. The figure shows that peculiar features of microstructural evolution are preserved even under rather strong thermal fluctuations used in this simulation. 

Porous ultrafine tin oxide ethanol gas sensors92 in the form of a thin film have been prepared from tin alkoxide by the sol-gel process. The microstructural evolution of the tin oxide films, which affected the ethanol gas-sensing properties of the films, was investigated as a function of firing temperature and solution concentration. Theoretically, it was expected that ethanol gas sensitivity would increase monotonically with decreasing film thickness, but experimental results showed a maximum sensitivity at about 70 nm. The sudden decrease of the sensitivity below the thickness of 70 nm seemed to be due to the sudden decrease of film porosity, i.e., the sudden decrease of the number of the available sites for the oxidation reaction of ethanol molecules. Thus, it seemed that below the thickness of 70 nm, the sensitivity was governed by microstructure rather than by film thickness. 

Mauritz, K. A., Stefanithis, I. D., Davis, S. V., Scheetz, R. W, Pope, R. K., Wilkes, G. L. and Huang, H. H. 1995. Microstructural evolution of a silicon-oxide phase in a perfluorosulfonic acid ionomer by an in situ sol-gel reaction. Journal of Applied Polymer Science 55 181-190. 

Microstructural Evolution During Milling and Subsequent Cycling of Commercial MgH Powders... 

R.A. Varin, T. Czujko, 1. Mizera, Microstructural evolution during controlled ball milling of (Mg Ni + MgNi ) intermetaUic aUoy , J. Alloys Compd. 350 (2003) 332-339. 

Figure 10.64 Schematic illustrations showing die microstructural evolution of three kinds of + 7 microstiuctures widmanstitten, type I lamellar and blocky type 2 lamellar stnictures in Ni-2SAl-(>)t8Fe, (b)lSFe and (c)13Fe alloys.

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... 

Heterogeneous catalysis is a dynamic process and gas-catalyst reactions occur at the atomic level. In gas-catalyst reactions, the dynamic atomic structure of catalysts under operating conditions therefore plays a pivotal role in catalytic properties. Direct observations of the microstructural evolution and active sites of... 

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. 

Moschakis, T., Murray, B.S., Dickinson, E. (2005). Microstructural evolution of viscoelastic emulsions stabilized by sodium caseinate and xanthan gum. Journal of Colloid and Interface Science, 284, 714-728. 

Numerical models of conserved order-parameter evolution and of nonconserved order-parameter evolution produce simulations that capture many aspects of observed microstructural evolution. These equations, as derived from variational principles, constitute the phase-field method [9]. The phase-field method depends on models for the homogeneous free-energy density for one or more order parameters, kinetic assumptions for each order-parameter field (i.e., conserved order parameters leading to a Cahn-Hilliard kinetic equation), model parameters for the gradient-energy coefficients, subsidiary equations for any other fields such as heat flow, and trustworthy numerical implementation. 

The ratio of additive combinations also influences the microstructural evolution. For instance, with decreasing ratio of Y203/Al203 the microstructure becomes finer and the aspect ratio lower [301, 302]. MgO as well as CaO additives accelerate the grain growth and increase the aspect ratio [303, 304]. 

The ability to modify the metal-ceramic interface in nanocomposites by the formation of intergranular films holds exciting prospects. From a thermodynamic point of view, the existence of a film at equilibrium indicates a lower interface energy than an interface without a film. This indicates the potential to increase the adhesion of interfaces, although experimental investigations are required to fully evaluate this effect. However, the promotion of particle occlusion due to the presence of the films has been shown,28 and this means that a new method to modify and control the microstructural evolution of nanocomposites is available, as discussed in the next section. 

For second-phase sintered ceramics, these phases control the plasticity and they are responsible for the asymmetric behaviour when deformed in tension or compression, because there is a crucial difference in the microstructure evolution associated with tension and compression creep. There are few explanations for this asymmetry. 

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