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Copper-zinc system

Figure A1.19 shows the phase diagram for the copper-zinc system. It is more complicated than you have seen so far, but all the same rules apply. The Greek letters (conventionally) identify the single-phase fields. [Pg.342]

The copper-zinc system (which includes brasses) has one eutectoid reaction. Mark the eutectoid point on the phase diagram (Fig. A 1.38). [Pg.356]

The copper-zinc system shown in Fig. A1.38 has no fewer than five peritectic reactions. Locate them and ring the peritectic points. (Remember that when a single-phase field closes above at a point, the point is a peritectic point.)... [Pg.359]

Let us first consider, as an example, the copper-zinc system of alloys.1 The ordinary yellow brass of commerce is restricted in composition to the first (copper-rich) phase of the system. This phase, which has the face-centered cubic structure characteristic of copper, is followed successively, as the zinc content is increased, by the /3-phase (body-centered cubic),... [Pg.362]

Examples of non-stoicheiometric compounds are provided by the copper-zinc system. The three compounds referred to above have the following compositions at 300 °C ... [Pg.23]

In addition to the eutectic, other invariant points involving three different phases are found for some aUoy systems. One of these occurs for the copper-zinc system (Figure 9.19) at 560°C (1040°F) and 74 wt% Zn-26 wt% Cu. A portion of the phase diagram in this vicinity is enlarged in Figure 9.21. Upon coohng, a solid 8 phase transforms into two other solid phases (y and e) according to the reaction... [Pg.328]

The peritectic reaction is another invariant reaction involving three phases at equilibrium. With this reaction, upon heating, one solid phase transforms into a liquid phase and another solid phase. A peritectic exists for the copper-zinc system (Figure 9.21, point P) at 598°C (1108°F) and 78.6 wt% Zn-21.4 wt% Cu this reaction is as follows ... [Pg.328]

As you can see from the tables in Chapter 1, few metals are used in their pure state -they nearly always have other elements added to them which turn them into alloys and give them better mechanical properties. The alloying elements will always dissolve in the basic metal to form solid solutions, although the solubility can vary between <0.01% and 100% depending on the combinations of elements we choose. As examples, the iron in a carbon steel can only dissolve 0.007% carbon at room temperature the copper in brass can dissolve more than 30% zinc and the copper-nickel system - the basis of the monels and the cupronickels - has complete solid solubility. [Pg.16]

Phase diagrams have been measured for almost any alloy system you are likely to meet copper-nickel, copper-zinc, gold-platinum, or even water-antifreeze. Some... [Pg.30]

Fang et al. [661] have described a flow injection system with online ion exchange preconcentration on dual columns for the determination of trace amounts of heavy metal at pg/1 and sub-pg/1 levels by flame atomic absorption spectrometry (Fig. 5.17). The degree of preconcentration ranges from a factor of 50 to 105 for different elements, at a sampling frequency of 60 samples per hour. The detection limits for copper, zinc, lead, and cadmium are 0.07, 0.03, 0.5, and 0.05 pg/1, respectively. Relative standard deviations are 1.2-3.2% at pg/1 levels. The behaviour of the various chelating exchangers used was studied with respect to their preconcentration characteristics, with special emphasis on interferences encountered in the analysis of seawater. [Pg.238]

B. Better tools available, but no consensus on mechanism or active site—1980 to 2006. Rhodes et al.291 published a comprehensive review on the heterogeneously catalyzed water-gas shift mechanism in 1995. Included in that discussion was the copper/zinc oxide/alumina system. The conclusion was that this system appears to be constructed of small metallic islands of copper resting on a zinc oxide alumina phase. Zinc oxide may exert some impact on catalytic activity, but it was suggested in the review that the contribution is small. It was indicated that strong evidence exists to support either a formate or a redox mechanism, and the authors even suggest the possibility that both mechanisms might occur, though insufficient data exist to determine which mechanism predominates. [Pg.180]

Guanine is the most easily oxidizable natural nucleic acid base [8] and many oxidants can selectively oxidize guanine in DNA [95]. Here, we focus on the site-selective oxidation of guanine by the carbonate radical anion, COs , one of the important emerging free radicals in biological systems [96]. The mechanism of COs generation in vivo can involve one-electron oxidation of HCOs at the active site of copper-zinc superoxide dismutase [97, 98], and homolysis of the nitrosoperoxycarbonate anion (0N00C02 ) formed by the reaction of peroxynitrite with carbon dioxide [99-102]. [Pg.150]

The coupling of two azinyl halides, in the presence of an appropriate electron source, also leads to the formation of diaryl compounds. 2-Iodopyrimidine and its derivatives were converted into the symmetrical 2,2 -bipyrimidines (7.88.) using activated copper. This method was found to give superior results,111 compared to the earlier reported nickel chloride-zinc system.112... [Pg.170]

J. A Fee Copper Proteins - Systems Containing the Blue" Copper Center. - M.F.Dunn Mechanisms of Zinc Ion Catalysis in Small Molecules and Enzymes. - W. Schneider Kinetics and Mechanism of Metalloporphyrin Formation. - M. Orchin, D. M. Bollinger Hydro gen-Deuterium Exchange in Aromatic Compounds. [Pg.191]


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