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HEAVY NON-FERROUS METALS
ArticleName Ultra-pure Cu obtaining using zone melting: influence of liquid zone width on impurities’ behavior
DOI 10.17580/nfm.2017.02.03
ArticleAuthor Dosmukhamedov N. K., Zholdasbay E. E., Nurlan G. B.
ArticleAuthorData

Kazakh National Research Technical University named after K. I. Satpayev, Almaty, Kazakhstan:

N. K. Dosmukhamedov, Professor of a Chair “Metallurgy and Dressing of Mineral Resources”, e-mail: nurdos@bk.ru
E. E. Zholdasbay, Senior Researcher of a Chair “Metallurgy and Dressing of Mineral Resources”
G. B. Nurlan, Engineer of a Chair “Metallurgy and Dressing of Mineral Resources”

Abstract

In work with the use of a new precision design of the zone melting unit, which allows to regulate the main parameters of the process (width and velocity of the molten zone), technological experiments were carried out to obtain ultrapure copper, depending on the temperature distribution. Peculiarities of the behavior of impurity metals and the laws governing their distribution between the solid and liquid phases are established under conditions of a change in the width of the molten zone and high gradients of the temperature gradients 1183, 1233 and 1283 оC. It has been found that the number of passes equal to four and the ratio of the width of the liquid zone (X) to the total length of the rod (L), X/L = 0.15, is sufficient conditions to achieve an ordered distribution of impurities along the rod within the entire range of temperature variation without the time of exposure to liquid zone. It is shown that the best results for the purification of copper from impurities are reached at a temperature of 1233 оC, exceeding the melting point of copper at 150 оC. The absolute decrease in the total concentration of impurity metals at this temperature was 371.68 ppm. The copper content in the final purified copper matrix corresponds to 5N3 (99.9993%). On the basis of a change in the concentrations of impurity metals, the distribution coefficients of impurity metals were calculated in the range of reduction of the ratio with X/L= 0.35 to X/L = 0.15. The high values of the metal distribution coefficients at Xi/L = 0.35 and their decrease in the Co, Ni, Fe, Mn and As series are established: KCo = 8.0; KNi = 6.33; KFe = 4.4; KMn = 3.0; KAs = 1.0. It is not possible to achieve deep copper purification from Co, Ni, Fe, Mn, B, and As in the production of ultrapure copper by zone melting. In this case, an increase in the copper content in the matrix of purified copper must be achieved by deeper cleaning of other impurity metals present in the initial copper to be purified. It is established that the designed design of the plant allows to regulate a number of such important parameters of zone melting as the temperature of the molten zone, the spreading of the boundaries of the liquid zone, diffusion in the liquid zone by imposing a magnetic field. Flexible regulation of these parameters makes it possible to achieve deep segregation of volatile metal impurities even at sufficiently high values of the ratio X/L = 0.35. It is shown that a sufficient degree of segregation for a number of volatile metal impurities (Pb, Bi, Ag, Sn, P, Sb, Zn) is observed at a ratio of X/L= 0.35 due to their high vapor pressure elasticity, compared to copper. A deeper degree of purification of copper from them is achieved at a ratio of X/L = 0.15. Moreover, in the range of reduction of the ratio with X/L = 0.35 to X/L = 0.15, their concentrations undergo slight changes. It has been established that a decrease in the ratio X/L in the range from X/L = 0.35 to X/L = 0.15 significantly affects the change in the concentrations of impurity metals having a distribution coefficient K > 1 (Fe, Ni, Co, Mn, As). It is shown that the behavior of this group of impurity metals under conditions of high temperature of 1233 оC is associated with their interaction with each other and the formation of a number of chemical compounds that concentrate in the solid phase and create a convective flow that prevents the equipartition of each separately taken impurity from the liquid zone in solid phase. This phenomenon reduces the degree of purification of copper from this group of metals.

keywords Purification, zone melting, temperature, width of liquid zone, impurity, concentration, segregation, ultrapure copper
References

1. Steigerwald J. M., Murarka S. P., Gutmann R. J. Chemical Mechanical Planarization of Microelectronic Materials. New York, John Wiley & Sons., 1997.
2. Torres J. Advanced Cu interconnections for Si CMOS technologies. Applied Surface Science. 1995. Vol. 91. p. 112.
3. Woo T.-G., Park I.-S., Seol K.-W. Effect of ion-beam assisted deposition оn resistivity and crystallographic structure of Cr/Cu. Electronic Materials Letters. 2009. Vol. 5. pp. 105–107.
4. Kurosaka A., Tanabe N., Kohno O., Osanai H. Proceedings of the 1st International Conference of Ultra High Purity Base Metals (UHPM-94). 1994. p. 446. Kitakyushu, Japan.
5. Dost S., Liu Y. C., Haas J., Roszmann J., Grenier S., Audet N. Effect of applied electric current on impurity transport in zone refining. Journal of Crystal Growth. 2007. Vol. 307, No. 1. pp. 211–218.
6. Cheung, T., Cheung N., Garcia A. Application of an artificial intelligence technique to improve purification in the zone refining process. Journal of Electronic Materials. 2010. Vol. 39 (1). pp. 49–55.
7. Zhu Y., Mimura K., Ishikawa Y., Isshiki M. Effect of Floating Zone Refining under Reduced Hydrogen Pressure on Cu Purification. Materials Transactions. 2002. Vol. 43, No 11. pp. 2802–2807.
8. Lalev G. M., Lim J.-W., Munirathnam N. R., Choi G.-S., Uchikoshi M., Mimura K., Isshiki M. Impurity Behavior in Cu Refined by Ar Plasma-Arc Zone Melting. Metals and Materials International. 2009. Vol. 15, No. 5. pp. 753–757.
9. Zhu Y., Mimura K., Ishikawa Y., Isshiki M. Effect of Floating Zone Refining under Reduced Hydrogen Pressure on Cu Purification. Materials Transactions. 2002. Vol. 43, No 11. pp. 2802–2807.
10. Yoon Y. O., Jo H. H., Cho H., Kim S. K., Kim Y. J. Effect of distribution coefficient in Cu purification by zone refining process. Materials Science Forum. 2004. Vol. 449–452. pp. 173–176.
11. Lim J-W., Kim M. S., Munirathnam N. R., Le M. T., Uchikoshi M., Mimura K., Isshiki М., Kwon Н. С. Choi G. S. Effect of Ar/Ar-H2 Plasma Arc Melting on Cu Purification. Materials Transactions. 2008. Vol. 49, No. 8. pp. 1826–1829.
12. Cheung T., Cheung N., Tobar C. M. T., Caram R., Garcia A. Application of a Genetic Algorithm to Optimize Purification in the Zone Refining Process. Materials and Manufacturing Processes. 2011. Vol. 26. pp. 493–500.
13. Ghosh K., Mani V. N. and Dhar S. A modeling approach for the purification of group III metals (Ga and In) by zone refining. Journal of Applied Physics. 2008. pp. 104–112.
14. Dosmukhamedov N. K., Zholdasbay E. E. Optimization of the width and speed of molten zone in the conditions of purifying Cu of impurities by zone melting. Austrian Journal of Technical and Natural Sciences. 2016. No. 3–4. Section 3. Materials Science. pp. 20–22.
15. Alieva Z. U., Trubitsyn Yu. V. Aspects of control of kinetics of vertical float zone melting during the Si purification. Novye materialy v metallurgii i mashinooborudovanii. 2011. No. 1. pp. 106–110.

16. Liu D., Engelhardt H., Li X., Loffler A., Rettenmayr M. Growth of an oriented Bi40–xInxTe60 (x = 3,7) thermoelectric material by seeding zone melting for the enhancement of chemical homogeneity. CrystEngComm. 2015. Vol. 17. pp. 3076–3081.
17. Dosmukhamedov N. K., Zholdasbay E. E., Nurlan G. B., Kurmanseitov M. B. Employment of zone melting to obtain ultrapure Cu: behavioural patterns of impurity metals. Tsvetnye Metally. 2017. No. 7. pp. 34–41.

Full content Ultra-pure Cu obtaining using zone melting: influence of liquid zone width on impurities’ behavior
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