| Research Interests |
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| V. Pattern formation and dynamics of fluctuations in complex systems | ||||
Here we investigate the dynamics of phase separations in quenched binary mixtures, such as binary alloys and polymer blends. When the binary system is quenched into a two-phase metastable region from one-phase region, it undergoes a phase separation by nucleation and growth of droplets of the minority phase [1,2,3]. I. Causal motion; Growth of droplet -average droplet radius <a> and droplet size distribution function F(a/<a>). In Fig. 1 a log-log of the reduced average droplet radius <a> (t) versus reduced time t is shown. At lower volume fractions Q, there are three characteristic time stages with two crossovers after the nucleation stage; (a) early stage <a> (t) , where the droplets grow directly and independently from the supersaturated solution by diffusion <a> - t1/2, (b) intermediate stage <a> - t1/4 , where the growth is governed by the many-body interactions between droplets, (c) late stage <a> - t1/3, where the Ostwald ripening (or coarsening) dominates the growth [2]. | ||||
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| Fig. 1 |
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| In Fig. 2 the time evolution of the relative-droplet-size distribution function F(a/<a>,t) versus the relative droplet size a/<a> is shown at Q = 0.1 for different times t = 300 and 100000. The histogram indicates the simulation results and the solid lines the analytical results [2]. | ||||
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| Fig. 2 |
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| In Fig. 3(A) the theoretical results in the late stage are compared with the experimental data [4] for an Al-Li alloy with Q = 0.1 T = 448 K for various ageing times; (a) 72 ks, (b) 180 ks, and (c) 720 ks. For comparison the results of the LSW theory and the Ardell theory are also shown. In Fig. 3(B) the time evolution of the average radii is also shown. | ||||
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| II. Density fluctuations; the structure function S(k,t). In Fig. 4 the time evolution of the structure function S(k,t) is shown at Q = 0.1 for different times (a) up to 300 and (b) from 3000 to 100000. |
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 Fig. 4 |
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References [1] M. Tokuyama an K. Kawasaki, Physica A 123 (1984) 386-411. [2] M. Tokuyama and Y. Enomoto, Phys. Rev. E 47 (1993) 1156-1179. [3] Y. Enomoto, K. Kawasaki, and M. Tokuyama, Acta. metal. 35 (1987) 915-922. [4] T. Eguchi, Y. Tomokiyo, and S. Matsumura, Phase Transitions. |
