| ArticleName |
Employment of zone melting to obtain ultrapure copper: behavioural patterns of impurity metals |
| Abstract |
The paper presents a construction of a new precision installation for zone melting and conveys the results of copper purification that contains a wide spectre of impurity metals (with a total concentration of 380 ppm). Behavioural patterns of admixture metals in different testing conditions were researched: at temperatures that exceed copper melting temperatures by 100, 150 and 200 °C, and with different exposure times of the liquid zone. With zone melting, the impurities with higher vapour pressure than copper are removed in the highest degree. The most difficult is to remove iron, manganese, chrome, nickel and cobalt, whose partial pressure is close to the partial pressure of copper. The concentration of admixtures that are hard to separate (iron, nickel and cobalt) was successfully lowered to the following levels, %: 0,0031 Fe; 0,0021 Ni; 0,0015 Co. It was shown that the concentration of these elements was lowered due to their interaction with one another as well as with other impurity metals. Such interaction contributes to forming of new stable chemical compounds in liquid phases, whilst the subsequent lowering of temperature leads to concentration of the compounds in solid phases. It was determined that a high level of copper purity is achieved when the molten zone temperature stands at 1233 °C (which exceeds the melting temperature by 150 °C) and the exposure time of the liquid zone equals 15 minutes. By conducting zone melting in these conditions the total level of impurity metals is reduced from 380 to 9,8 ppm. Based on essential characteristics and behavioural patterns of impurities, as determined in the process of deep copper purification, recommendations may be given regarding the optimal technological regimes for obtaining any given ultrapure metal. |
| References |
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