Abstract
The effects of various electropolishing (EP) parameters such as duration, applied voltage, working temperature, mechanical prepolishing and acid volume ratio on the EP process, and surface smoothness of high purity niobium (Nb) were systematically investigated using electrochemical technique and optical profilometry. The electropolishing parameters had a significant influence on the smoothness of the Nb by controlling the current density. Prolonged EP duration caused different dissolution rates of grains. Applied voltages above the oxygen evolution potential resulted in severe pitting of the Nb. High working temperature-caused roughening of the Nb surface via different dissolution rates of grains and mechanically ground smooth surfaces were roughened by the formation of valleys on the surfaces. A lower fluoride ion concentration in the acid solution gave rise to a rougher surface of the Nb because the fluoride ions were transport-limited species during the EP process.
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References
Padamsee H, Knobloch J, Hays T (2008) RF Superconductivity for accelerators. 2nd edn. Wiley-VCH, New York
Shemelin V, Padamsee H (2008) Magnetic field enhancement at pits and bumps on the surface of superconducting cavities, TTC-Report 2008-07
Higuchi T, Saito K, Noguchi S, Ono M, Kako E, Shishido T, Funahashi Y, Inoue H, Suzuki T (1995) Proceedings of the 1995 workshop on RF superconductivity, Gif-sur-Yvette, France, pp 723–727
Padamsee H (2009) RF superconductivity: science, technology and applications, Wiley-VCH, Weinheim
Palmieri V, Stivanello F, Stark SY, Roncolato C, Valentino M (2001) Besides the standard niobium bath chemical polishing. 10th Workshop on RF superconductivity, Tsukuba
Saito K, Inouge H, Kako E, Fujino T, Noguchi S, Ono M, Shishido T (1998) Superiority of electropolishing over chemical polishing on high gradients. Part Accel 60:193
Chandra A, Sumption M, Frankel GS (2012) On the mechanism of niobium electropolishing. J Electrochem Soc 159:C485
Jacquet PA (1935) Electrolytic method for obtaining bright copper surfaces. Nature 135:1076
Landolt D (1987) Fundamental aspects of electropolishing. Electrochim Acta 32:1
Tian H, Corcoran SG, Reece CE, Kelley MJ (2008) The mechanism of electropolishing of niobium in hydrofluoric–sulfuric acid electrolyte. J Electrochem Soc 155:D563
Eozenou F, Aspart A, Antoine C, Malki B (2006) Electropolishing of niobium: best EP parameters. CARE-Report-06-010-SRF. EU contract number RII3-CT-2003-506395
Elmore WC (1939) Electrolytic polishing. J Appl Phys 10:724
Rokicki R, Hryniewicz T (2012) Enhanced oxidation-dissolution theory of electropolishing. Trans Inst Met Finish 90:188
Palmieri V (2003) Fundamentals of electrochemistry: the electrolytic polishing of metals: application to copper and niobium. 11th Workshop on RF superconductivity, Germany
Landolt D, Chauvy PF, Zinger O (2003) Electrochemical micromachining, polishing and surface structuring of metals: fundamental aspects and new developments. Electrochim Acta 48:3185
Ricker RE, Myneni GR (2010) Evaluation of the propensity of niobium to absorb hydrogen during fabrication of superconducting radio frequency cavities for particle accelerators. J Res Natl Stand Technol 115:353
Halbritter J (1987) On the oxidation and on the superconductivity of niobium. Appl Phys A 43:1
Acknowledgments
The authors gratefully acknowledge funding provided for this work by the US Dept. of Energy through grant DE-SC0004217. We also thank Lance Cooley from Fermi National Accelerator Laboratory, USA for the Nb samples.
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Khun, N.W., Sumption, M. & Frankel, G.S. Smoothening of niobium by electropolishing. J Appl Electrochem 43, 829–838 (2013). https://doi.org/10.1007/s10800-013-0574-x
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DOI: https://doi.org/10.1007/s10800-013-0574-x