Intermetal Coupling

According to Hush analysis the intermetal coupling is reciprocal to the intramolecular electron-transfer distance between the donor and the acceptor sites, tad. 

Reality is more complicated than this, however. By the same reasoning, CuO would be expected to be greenish-blue like Cu(H20) + in water, but is black. This is due to other types of excitations that are not included in the CFT. The black color of CuO may be due to intermetal coupling superposed on the CFT spectrum. Another possibility, also not within the CFT, is that the excitation is from the ligand levels of the 3d levels on the same metal complex. Some of these transitions, like the intermetal transitions, would have a high intensity. 

The possible formation of an alloyed or a core-shell cluster depends on the kinetic competition between, on one hand, the irreversible release of the metal ions displaced by the excess ions of the more noble metal after electron transfer and, on the other hand, the radiation-induced reduction of both metal ions, which depends on the dose rate (Table 5). The pulse radiolysis study of a mixed system [66] (Fig. 7) suggested that a very fast and total reduction by the means of a powerful and sudden irradiation delivered for instance by an electron beam (EB) should prevent the intermetal electron transfer and produce alloyed clusters. Indeed, such a decisive effect of the dose rate has been demonstrated [102]. However, the competition imposed by the metal displacement is more or less serious, because, depending on the couple of metals, the process may not occur [53], or, on the contrary, may last only hours, minutes, or even seconds [102]. 

When the diffusion couple of Cu-10 massXSn and Al-0. 5 massiliSn is heated at 773 K which is lower than the eutectic temperature of 821 K in Cu-Al system, 4 intermetal 1ic compounds are formed in the diffusion layer[3]. In this research, these compounds are judged by using CGM. 

As a new application of FGH, the identification of unknown multicomponent precipitates in the system of Cu-Al-Sn is studied. Three among four intermet-allic compounds can be identified as 7 2, n 2 and 6 in the system of Cu-Al with using the compositionally graded diffusion couple(CGDC). 

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