Structures spinodal

Spinodal structure is a fine homogeneous mixture of two phases that form by tie growth of composition waves in a solid solution during suitable heat treatment. The phases of a spinodal differ in composition from each other and from the parent phase, but have the same crystal structure as the parent phase. 

Spinodal Structures upon Fast Electrochemical Ordering Processes... 

K.R. Rundman, Spinodal structures. In Metals Handbook, T. Lyman, ed. American Society for Metals Metals Park, Vol. 8, 1973. 

Figure 2.6a shows that this can be achieved by rapid quenching as, for example, with binary alloys [12]. However, this possibility fails with the formation of surface nanostructures, and hence practically (with the exception of pol5uners where diffusion is slow enough) no reports for spinodal structures exist. This problem could be overcome in a study in which about 50% of the atoms of the topmost layer of a Au(l 11) surface were removed within 20 ps by an electrochemical pulse techniques [13]. The result is shown in Fig. 2.10. In the STM image of Fig. 2.10a, the dark arrow...

FIGURE 2.10. Formation of spinodal structures in the topmost monolayer of a Au(l 11) surface [13]. 

A third stage is usually observed in which the spinodal structure coarsens (Figure 3.11). This process can be described by an exponential dependence of the maximum intensity and the maximum reduced scattering angle on time, viz. 

Chu] Chuang, Y.-Y, Schmid, R., Chang, Y.A., Thermodynamic Stability of Ternary Systems and its Application to Spinodal Structures in Cu-Fe-Ni Alloys in "Noble Met. Alloys , Proc. 

When a polymer solution is allowed to evaporate from a surface, dewetting instabilities can arise, producing modulated patterns like spinodal structures (68). Section IV addresses the applicability of these interesting phenomena to making opto-electronical devices. 

The spinodal decomposition can be studied in much more detail using confocal scanning laser microscopy (CSLM). Aarts et al. [98] studied the phase separation kinetics of a PMMA colloid plus PS polymer mixture in decalin with q = 0.56. In Fig. 4.17 typical spinodal structures are observed that coarsen in time. 

Fig. 4.17 CSLM images (each side is 1,400 am) of a phase separating polystyrene polymers mixed with fluorescently labeled PMMA spheres exhibiting the typical spinodal structure. The images correspond to t = 3 s (left), 11s (middle) and 22 s (right) after homogenization. These images were kindly provided by D.G.A.L. Aarts, Oxford University, UK. See also the movies on http //www.njp.org.

Hopper R.W., "Stochastic Theory of Scattering from Idealized Spinodal Structures II. Scattering in General and for the Basic Late Stage Model," J. Non-Cryst. Solids, 70, 111—42 (1985). 

Read D J, Teixeira PIC, Duckett R A, Sweeney J and McLeish T C B (2002) Theoretical and finite-element investigation of the mechanical response of spinodal structures, Eur Phys J P 8 15-31. 

Bulk spinodal decomposition in TMPC/PS [TMPC = poly(tetramethyl-Bisphenol-A-polycarbonate)] films was also studied by Cabral et ol. [151] using AFM. These authors were able to show that the topography observed by AFM is related to the spinodal morphology, although the periodicity of the structure determined by AFM appears to be larger than expected from LS measurements. Since the AFM structure factor is obtained by Fourier transform of an image of a cross-section (2D) whereas the LS data are 3D Fourier transform of the spinodal structure, such a discrepancy between AFM and LS results is not surprising. 

Entirely different fiber topologies are obtained if nanofibers are spun from a solution of mixtures of immiscible polymers in the same solvent [53]. Phase separation occurs with the evaporation of the solvent, leading to binodal or spinodal structures, respectively, in the nanofibers depending on the system. To generate porous fibers of high overall porosity two strategies are possible [54] ... 

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