Zn system

Fig. 28. Isopleth in Al—Cu—Mg—Zn system where the appropriate ratio is CuMg Zn = 1 1.4 3.3.

The SME process can be illustrated by the Cu—Zn system, one of the first SMAs to be studied. A single orientation of the bcc P-phase on cooling goes through an ordering process to a B2 phase. In a disordered alloy, the lattice sites are randomly occupied by both types of atoms, but on ordering the species locate at particular atomic sites, yielding what is called a supedattice. When the B2 phase is cooled below the Mp it transforms to... 

An alloy system is all the alloys you can make with a given set of components "the Cu-Zn system" describes all the alloys you can make from copper and zinc. A binary alloy has two components a ternary alloy has three. 

TA2 mode ([IlO] polarization) visibly depends on the influence of the electrons on the lattice vibrations (see Fig. 7). Without V2, the stiffness of the TAi mode is enlarged. Therefore, we can conclude that this TA2 mode is very sensitive to changes in the electronic structure and measures the stability of the B2 phase. This may be a hint of the temperature or stress dependence of the Cu-Zn system in the martensitic region (Zn < 42 at%) close to the stoichiometric concentration CuZn... 

Because of the financial importance of this process to steel producers (about one-third of all the steel produced in the world is subsequently galvanised) a great deal of research has been carried out throughout the world to establish the true equilibrium phase boundaries in the Fe,, -Zn( system and the critical temperature of stability of the f phase. Since the AG -7 diagrams or the phase stability diagrams could not account for these discrepancies in this system, AG ,-concentration curves were used for... 

Fig. 7.87 Construction showing position of free-energy-conservation curves of T, Tj, 6i, and rf phases for the Fe j —Zn, system at 793 K (after Mackowiack )...

These three diagrams show clearly how a very small change in the relative position of the AG-concentration curves for the different phases can have a dramatic effect on the composition and stability of the solid phases in the Fe,j,-Zn( system. A detailed discussion of these diagrams can be found elsewhere In addition, Fig. 7.86 shows that any physical effects in the solid phases, which can be expressed in terms of energy, can be added to the AG -concentration curves. Thus the curves can be corrected for these effects and the resulting new equilibria from the shift of the AG-concentra-tion curves (i.e. change in composition of phase, their stability, etc.) can be predicted simply by the use of the tangency rule. 

Similar results, to the Fe-Zn system were obtained in the Ti,j,-Al(,) and Ti(j)-Al, ) system where, in the solid-liquid couples some of the expected surface layer phases were not formed, whereas in the solid-vapour system it was possible to obtain all the phases and predict from the AG -concen-tration curves the compositions at the different layer phase boundaries. 

Cu-Zn system, shape-memory effect in, 22 343. See also Copper entries CVD-deposited films, properties of,... 

A Ni(dppe)Br2-Zn system effectively catalyzes co-cydotrimerization of an allene with a propiolate. The reaction is highly regio- and chemoselective to afford a poly-substituted benzene derivative in good yield. (Scheme 16.82) [92], From the observation that no desired [2 + 2 + 2] product is obtained for the reaction of 1-hexyne and phenylacetylene with w-butylallene under similar conditions, the presence of an electron-withdrawing C02Me group in the alkyne moiety is essential for the success of the present [2 + 2 + 2]-co-cyclotrimerization. 

Figure 2.42. The Cu-Zn system phase diagram and microstructure scheme of the diffusion couple obtainable by maintaining Cu and Zn blocks in contact for several days at 400°C. Shading indicates subsequent layers, each one corresponding to a one-phase region. The two-phase regions are represented by the interfaces between the one-phase layers (adapted from Rhines 1956).

Figure 2.44 The Ti-Zn system. The calculated enthalpy of formation of the intermetallics and the resulting convex hull are shown according to Ghosh et al. (2006). Experimental values of about 22-19 kJ/mol of atoms were measured in the composition range 50-75 at.% Zn. The calculations yield a ground state convex hull defined by the following structures (1) Ti3Zn-Ll2 (2)...

Olefin dimerization (200 201) catalyzed by electrogenerated Ni(I) complexes is performed in a PC-Bu4NCl04-(Zn) system in the presence of an Ni(II)Cl2(PPh3)2... 

This is obtained via combination of the two partial electrode reactions, oxidation and reduction, reaction (9.5) and (9.6), respectively. Thus, in the displacement deposition of Cu on a Zn substrate, a layer of metallic Cu is deposited on the zinc while Zn dissolves into solution (Fig. 5.11). We stated that this reaction is possible since the Zn/Zn system has an electrode potential lower than that of the Cu/Cu system (Table 5.1 and Fig. 5.10). The overall displacement deposition reaction according to Eq. (9.7) can be considered as the reaction of the electrochemical cell... 

Incorporation of n-Si in the mixed CdS-ZnS system results in electron flow from the n-Si to the CdS conduction band, resulting in greater utilization of solar radiation as well as superior electron-hole separation [162,163]. Under direct sunlight (25 mW/cm ), a suspension of n-Si/CdS-ZnS yields 15 mL/h/g of hydrogen from an aqueous sulfite/sulfide solution [162]. Hydrogen evolution of 35 mL/h/g has been recorded for CdS-ZnS (2 1 weight ratio) prepared by coprecipitation and then loaded with n-Si (1.4 - 1.6%) [163]. 

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