Copper impurities

Figure 2.6 Photochromic glass (a) glass melt containing dissolved CuCl and AgCl (b) melt is cast into a homogeneous glass blank (c) heat treatment precipitates crystallites (much exaggerated in size here) in the blank and (d) sodium chloride structure of AgCl containing copper impurities and Frenkel defects.

The starting material for making these pigments is cadmium sulphate, which must be free from iron, nickel and copper impurities. Cadmium sulphide is precipitated from the sulphate solution by adding an alkaline solution of pure sodium sulphide under controlled conditions of pH, temperature and addition rate. The yellow product is in the cubic crystal form, which is converted into the required hexagonal form by calcination at 500-600 °C in the absence of air. 

Component Raw NaNT solution /wt-% Purified NaNT solution /wt-% Copper impurity complex /wt-%... 

Finally, think of a bar of zinc with microscopic inclusions of copper, i.e., with copper impurities, (Fig. 12.5). If this zinc bar is immersed in a solution containing Zn2+ and Cu2+ ions, the result is that the zinc will dissolve out and copper will deposit preferentially on the already existing copper areas or even form such areas by crystallization. 

Fig. 12.5. Even without copper strips, copper will deposit on a zinc bar from a cupric ion-containing electrolyte, preferably at some microscopic inclusions of copper impurities.

Polyethylene glycol in the synthesis of materials. PEG has been used as a solvent in polymerization reactions. It was found to facilitate easy removal of the metal catalyst in transition metal mediated living radical polymerization (Figure 8.10). Products from this type of polymerization are usually heavily contaminated with intensely coloured copper impurities. In the case of methyl methacrylate polymerization the reaction rate was higher than in conventional organic solvents, but for styrene the reaction was slower than in xylene. 

There are, however, several challenges with the using copper metal before it can be accepted into IC manufacturing. First, copper exhibits deep levels in the silicon band gap and copper impurities in SiOj lead to leakage. However, several materials are effective barriers to copper diffusion and their use as liner films... 

Many hydrometallurgical processes or process steps are used to upgrade concentrates, process recycled scrap metal, or purify aqueous process steams. Examples are (I) the leaching of molybdenite concentrate to remove Knpurities ,ft (2) leaching of tungsten carbide and molybdenum scrap-, (3) removal of copper impurities in nickel anolyte by cementation on metallic ruckel and (4) various methods for treating nuclear fuel elements. 

PatilR.R. and Moharil S.V. 1995b. On the role of copper impurity in LiF Mg,Cu,P phosphor, 7. Phys. Condens. Matter 1 9925-9922. 

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