Alloy time evolution

Quantitation of components in samples is a general goal of analytical purposes. In the fields of archaeometry, conservation, and restoration, quantitation of analytes is of considerable interest in a wide variety of applications. Thus, the provenance of raw materials, alloy composition, and more, can be crucial for authentication, geographical location, or analysis of the time evolution of works of art, techniques, etc. 

Figure 2. Successive snapshots of a cluster A47B20 in the course of time evolution. The upper left is the initial configuration, and the elapsed time are imposed for each snapshot. Guest atoms are shown by black circles, while host atoms are denoted by white circles. Gray circles indicate host atoms that are initially located in the center of the cluster. In 1 ps the cluster is in alloyed state. Gray atoms are gradually moves toward the cluster surface. On the other hand, guest atoms diffuse into the inside.

In Fig. 3, time evolution of a medium-sized cluster A95B40 is displayed. Again, the temperature is controlled to T = 600 K by the AKTM. In 1 ps the alloyed state is observed near the cluster surface. However, there is no mixing... 

Gay] Gay-Sanz, N., Prieto, C., Munoz-Martin, A., de Andres, A., Vazquez, M., Yu, S.C., Time Evolution of the Stmetural Short-Range Order During the Mechanical Milling of Co-Fe-Cu Nanocrystalline Alloys , J. Mater. Res., 14(10), 3882-3888 (1999) (Abstract, Experimental, Morphology, Crys. Stracture, 13) cited from abstract... 

Bortz, A.B., Kalos, M.H., Lebowitz, J.L., and Zandejas, M.A. (1974) Time evolution of a quenched binary alloy computer simulation of a two-dimensional model system, Phys. Rev. B. 10, 535. 

Kirkendall Effect The Kirkendall effect is a phenomenon observed frequently in solid materials [38]. It refers to a vacancy counter diffusion process through an interface of two solid materials, metals in particular, to compensate the unequal material flow formation at the interface [38a]. In metals and metallic alloys, the vacancy is atomic defect, that is, empty lattice site. Combination of excess vacancies can lead to the formation of void within the fast-diffusion side of the interface [39]. While this phenomenon has been known for a very long time, synthesis of hollow nanostructures based on Kirkendall effect was realized fairly recently [40]. Ym studied the time evolution in the formation of hollow nanospheres and found that Kirkendall diffusion followed the Tick s law [41]. This means that the diffusion of atoms and vacancies is driven by the difference in atom concentration. Wu et al. synthesized hollow nanostructures of CoCuPt alloy catalyst by using Co nanoparticles as the sacrificial templates. For this trimetallic system, Co atoms diffused faster than those of Pt or Cu to form core-shell like Co CuPt hollow nanoparticles and then the CoCuPt hollow spheres (Fig. 2.10) [42]. 

Fig. 135. Time evolution of (i) resistivity and (ii) X-ray intensity of two dominant peaks [LaHjj fee (111) solid line j6-La fee (111)] in the indicated crystal structure in LaMg alloy film capped with Pd. The different region I-IV are...

Some S(Q,u)) spectra for solid fee Al close to melting are shown in Figure 8 by the dotted curves there appears to be broadly similar to spectra for fee Ar suitably scaled (16). Some interesting interference effects have been predicted (l to be observable in Al. The main interest in these metals has however, centred on the study of defects (26) and their migration by MD methods but such studies go beyond the scope of this article. Finally, the method has been extended to study localised modes of vibration associated with light impurities in alloys. The system K29Rh7i has been extensively studied (IT) and detailed results will be published in due course. The correlation with available experimental information is excellent. The time evolution of a quenched binary alloy has also been studied using MD (27.). 

Some evolution types observed in our simulations are shown in Figs. 2-7. The simulations were performed for the same 2D alloy model as that used in Refs. , on a square lattice of 128x128 sites with periodic boundary conditions. The as-quenched distribution Ci(0) was characterized by its mean value c and small random fluctuations Sci = 0.01. The intersite atomic jumps were supposed to occur only between nearest neighbors and we used the reduced time variable t = <7,m-... 

Fig. 8. Temporal evolution of q for the alloy model described in text after the quench from T = 0.9 to T = 0.61. at following times t after the quench (a) 0, (b) 120, (c) 260, and (d) 1000.

Fig. 12. Temporal evolution of q = cf (upper row) and c- (lower row) for the alloy model described in text, at T = 0.4, c = 0.35, = 0.01, and following values of the reduced time...

The spectra of silver and gold nanoclusters are intense and distinct (Table 4). They are thus particularly suitable to detect the evolution of a cluster composition during the construction of a bimetallic cluster in mixed solution. The system studied by pulse radiolysis was the radiolytic reduction of a mixed solution of two monovalent ions, the cyano-silver and the cyano-gold ions Ag(CN)2 and Au(CN)2 (Fig- 7) [66]. Actually, the time-resolved observation demonstrated a two-step process. First, the atoms Ag and Au are readily formed after the pulse and coalesce into an alloyed oligomer. However, due to... 

H2Oz was added 5 times after an interval of 5mins. The mixt was cooled and 1 drop of 1% Osmium Tetraoxide soln was added to decomp excess H202. Three hundred mg of Devarda s alloy was added and the flask quickly connected to a steam distilling app. The distillate entered 25ml N/70 HC1. Steam distillation was commenced after the H2 evolution ceased. 

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