Copper system

The lead—copper phase diagram (1) is shown in Figure 9. Copper is an alloying element as well as an impurity in lead. The lead—copper system has a eutectic point at 0.06% copper and 326°C. In lead refining, the copper content can thus be reduced to about 0.08% merely by cooling. Further refining requites chemical treatment. The solubiUty of copper in lead decreases to about 0.005% at 0°C. 

Tin babbitts are based on the tin—antimony—copper system and commonly contain about 3—8% copper and 5—8% antimony. Within a soft, sohd-solution matrix of antimony in tin are dispersed small hard particles of the intermetaUic copper—tin, Cu Sn [12019-69-1] (13). 

The copper system appears to behave similarly to the silver system, and it may be used here in order to illustrate the idea of "selective, naked-cluster cryophotochemistry 150,151). A typical series of optical-spectral traces that illustrate these effects for Cu atoms is given in Fig. 15, which shows the absorptions of isolated Cu atoms in the presence of small proportions of Cu2, and traces of Cus molecules. Under these concentration conditions, the outcome of 300-nm, narrow-band photoexcitation of atomic Cu is photoaggregation up to the Cus stage. The growth-decay behavior of the various cluster-absorptions allows unequivocal pinpointing of UV-visible, electronic transitions associated with Cuj and Cus 150). With the distribution of Cui,2,3 shown in Fig. 15, 370-nm, narrow-band excitation of Cu2 can be considered. Immediately apparent from these optical spectra is the growth (—10%) of the Cu atomic-resonance lines. Noticeable also is the concomitant... 

Two phase diagrams are available for lithium-copper systems. No intermetallic phases were found, but LiCu4 was later observed. Substantial solid solubility of lithium in copper approaching 20 at% at the melting point of Li has been observed. 

No phase diagram is available for the sodium-copper system. 

No compound has been reported for other alkali-metai-copper systems. 

The ruthenium-copper and osmium-copper systems represent extreme cases in view of the very limited miscibility of either ruthenium or osmium with copper. It may also be noted that the crystal structure of ruthenium or osmium is different from that of copper, the former metals possessing the hep structure and the latter the fee structure. A system which is less extreme in these respects is the rhodium-copper system, since the components both possess the face centered cubic structure and also exhibit at least some miscibility at conditions of interest in catalysis. Recent EXAFS results from our group on rhodium-copper clusters (14) are similar to the earlier results on ruthenium-copper ( ) and osmium-copper (12) clusters, in that the rhodium atoms are coordinated predominantly to other rhodium atoms while the copper atoms are coordinated extensively to both copper and rhodium atoms. Also, we conclude that the copper concentrates in the surface of rhodium-copper clusters, as in the case of the ruthenium-copper and osmium-copper clusters. 

P. Duby, The Thermodynamic Properties of Aqueous Inorganic Copper Systems, Int. Copper Res. Assoc., p. 56,1977. 

So far we have derived an expression for the overall rate constant k. As with the copper system, we should also like an expression for the first-order rate constant k, describing the passage of particles from the secondary minimum over the barrier. The equilibrium constant describing the population of the secondary minimum is given by the same expression (49) as (36), where, as in Fig. 14, xR describes the width... 

P. R. Subramanian and J. H. Perepezko, Ag-Cu (silver-copper) system, in Phase Diagrams of Binary Copper Alloys (P. R. Subramanian, D. J. Chakrabarti and D. E. Laughlin, eds.). Materials Park, OH ASM International, 1994. 

The initial screen of potential catalysts by these workers revealed that several Lewis acids are capable of effecting nitrenoid transfer to alkenes. In particular, SmLOf-Bu, a species that is unlikely to participate in redox processes, was found to work well for 7ra s-p-methylstyrene aziridination. Although the generality of this catalyst fell far short of the copper system, it raises the intriguing possibility that the Cu(II) species formed in the aziridination acts at least in part as a Lewis acid. The considerable Lewis acidity of cationic Cu(II) complexes has since been extensively exploited (cf. Section V). 

Silver-copper (Ag-Cu) ionization systems, environmental limits on, 22 652 Silver-copper system, properties of, 22 644 Silver cyanide, 22 670-671, 674-675 in electroplating, 22 685-686 Silver cyclohexanebutyrate, 22 671 Silver development, corrosion model of, 19 245... 

Promoter deposition through different mechanisms can account for different catalyst properties. In particular, chromate depositing as chromia does not easily redissolve but, zinc oxide does redissolve once the leach front passes and the pH returns to the bulk level of the lixiviant. Therefore, chromate can provide a more stable catalyst structure against aging, as observed in the skeletal copper system. Of course, promoter involvement in catalyst activity as well as structural promotion must be considered in the selection of promoters. This complexity once again highlights the dependence of the catalytic activity of these materials on the preparation conditions. 

Duby, P. "The Thermodynamic Properties of Aqueous Inorganic Copper Systems", International Copper Research Association New York, 1977. 

For the niobium-copper system different phase diagrams of the simple eutectic type (with the eutectic point very close to Cu) have been proposed, either with an S-shaped near horizontal liquidus line or with a monotectic equilibrium. It was stated that the presence of about 0.3 at.% O can induce the monotectic reaction to occur, whereas if a lesser amount of oxygen is present no immiscibility gap is observed in the liquid. 

A similar behaviour has been suggested for the vanadium-copper system. Examples of shifts of solid-solution boundaries due to small amounts of interstitial impurities have also been discussed with special reference to the Y-Th and Th-Zr alloy systems. 

Okamoto, H., Massalski, T.B., Chakrabarti, D.J. and Laughlin, D.E. (1987) The Au-Cu (gold-copper) system. In Phase Diagrams of Binary Gold Alloys, ed. Okamoto, H. and Massalski, T.B. (ASM International, Materials Park, OH). 

Other two-component systems may exhibit either limited solubility or complete insolubility in the solid state. An example with limited solubUity is the silver-copper system, of which the reduced-phase diagram is shown in Figure 13.5. Region L represents a liquid phase, with F = 2, and S and 5s represent solid-solution phases rich in Ag and Cu, respectively, so they are properly called one-phase areas. S2 is a two-phase region, with F= 1, and the curves AB and DF represent the compositions of the two solid-solution phases that are in equilibrium at any... 

Leach cap expressions on the surface reflect what could be beneath in these porphyry copper systems. 

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