Copper, zone-refined

Describe, using the copper-nickel ("monel") system as an example, the process of zone-refining. (Figure A1.51 shows a system with complete solid solubility.) Flow many phases are present in an alloy of 60 wt% Ni and 40 wt% Cu at ... 

Figure 6.3. Levitation of a molten metal in a radio-frequency field. The coil consists of water-cooled copper tubes. The counter winding above the sample stabilizes levitation. The same coils (and possibly additional ones) act as the induction heater. This technique has been applied to container-less melting and zone refining of metals and for drop calorimetry of liquid metals. It can be also used to decarburize and degas in ultrahigh vacuum mono-crystalline spheres of highly refractory metals (adapted from Brandt (1989)). The arrows indicate the instantaneous current flow directions in the inductors.

For the production of superpurity aluminum on a large scale, the Hoopes cell is used. This cell involves three layers of material. Impure (99.35 to 99.9% aluminum) metal from conventional electrolytic cells is alloyed with 33% copper (cutcctic composition) which serves as the anode of the cell A middle, fused-salt layer consists of 60% barium chloride and 40% AlF 1.5NaF (chiolite), mp 72(TC. This layer floats above the aluminum-copper alloy. The top layer consists of superpurity aluminum (99.995%). The final product usually is cast in graphite equipment because iron and other container metals readily dissolve in aluminum. For extreme-purity aluminum, zone refining is used. This process is similar to that used for the production of semiconductor chemicals and yields a product that is 99.9996% aluminum and is available in commercial quantities. 

As mentioned, there are also many other materials that fall into the category of electronic materials. Some, such as copper, gold, and other pure elements, are produced in normal ways and then subjected to methods such as zone refining and vapor deposition techniques to achieve high purity and thin layers in the construction of electronic devices. Many exotic... 

By drawing a staircase in Figure 6.17, determine what composition will result from three successive zone refining passes starting with a gold-copper solid solution of gold mole fraction equal to 0.70. What would many successive zone refining passes lead to if the curves had a maximum instead of a minimum ... 

Refined tellurium contains traces of lead, copper, iron, selenium, and other impurities. Highly pure tellurium can be obtained either by distilling refined tellurium in vacuum or by the zone melting process. The last traces of selenium can be removed as hydride by treating molten tellurium with hydrogen. 

Indium is mainly won from residues during the metallurgical treatment of indium-rich zinc and lead ores. The residues are dissolved in acid and indium chloride precipitates at the inlet of chlorine gas. The indium chloride is purified from tin, copper and lead using liquid-liquid extraction. A concentrated indium solution is obtained, from which indium is precipitated on zinc sheets. The spongy metal is scraped off, fused and cast into bars. For normal use, purification by electrolysis is satisfactory. For semiconductor purposes, repeated electrolysis and zone melting create an extreme purity. In 2001 the refined indium production was about 300 tonnes. 

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