http://www.surfacetreatments.it/thinfilms Literature Review of Nb Electroplating (Dmytro Chirkov - 20') Speaker: Dmytro Chirkov - Legnaro National Laboratories of INFN | Duration: 20 min. Abstract The main aim of this work is try to understand if expensive techniques of niobium coating could be replaced by cheaper electroplating method. Nowadays electrochemical surface treatment is one of the most used approaches in industry. Aqueous solutions has been the most widely used process mainly because of advantages such us low cost, non-flammability, high solubility of electrolytes, high conductivities resulting in low ohmic losses, high solubility of metal salts and high rates of mass transfer. However, despite these advantages there are several limitations in using aqueous solutions such as limited potential windows, gas evolution processes that can result in hydrogen embrittlement, passivation of substrates, electrodes and deposits, and the necessity for hazardous complex agents such as cyanide, causing environmental contamination. These are the reasons why new non-aqueous solutions to electrodeposit niobium have been researched. One of the main limitations in using aqueous solutions is their narrow electrochemical window. The major reason for carrying out electrodeposition in non-aqueous electrolytes (such as conventional organic solvents, ionic liquids and molten salts) is water and air stability and the wide electrochemical window of these media. Alternatively, also high temperature molten salts have been used extensively for niobium electrodeposition. They have wide potential windows, high conductivities and high solubility for metal salts. In fact, they have most of the advantages of aqueous solutions and overcome most of the limitations of aqueous solutions, but their one major limitation is the very high temperature (more than 750 °C). Therefore, the alternative to high temperature molten salts was an ionic substance that melts at a low temperature. Over the last few decades, room temperature ionic liquids have been widely studied in various scientific fields due to their interesting properties, such as negligible vapour pressures, high chemical and thermal stability, acceptable intrinsic ionic conductivity and wide potential window. Ionic liquids are molten salts with melting points below 100 °C and they consist entirely of cations and anions. The development of ionic liquids, especially air and water stable types, has attracted extensive attention since they have outstanding physical properties. The aim of this work will be the analysis of available literature data in order to have precise knowledge about niobium behavior in the different electrolytes and to get new information about possible electrolytes based on ionic liquids.

1. Literature Review of Nb Electroplating DmytroChirkov LNL-INFN 1

3. Non-aqueous electrolytes

4. Electrolytes with organic solvents

5. High-temperature melts

6. Ionic liquidsConclusions 2

7. Motivation The main aim of this work is try to understand if expensivetechniques for Nb coating could be replaced by cheaper electroplating method 3

8. The process of electroplating Cathode Mn+ + ne- -> M 2H+ + 2e- -> H2 Anode M -> Mn+ + ne- 2H2O -> O2 + 4H+ + 4e- 4

10. High-temperature melts

11. Ionic liquids5

12. Aqueous electrolytes Diagram E – pH for system Nb –H2O 6

13. Aqueous electrolytes Reactions which can occur on cathode in niobium salts aqueous solutions and their potentials Niobium can’t be isolated by electrolysis of aqueous solutions of its compounds, since the water would be electrolyzed preferentially 7

14. Aqueous electrolytes 8 Ajogin F.F. Galvanotechnic. Handbook. 1987

15. Aqueous electrolytes 9 Kadaner L.I., Fedchenko V.M. About electrodeposition of Ni-Nb and Fe-Nb alloys. 1987 Ni-Nb alloy

16. Aqueous electrolytes 10 Kadaner L.I., Fedchenko V.M. About electrodeposition of Ni-Nb and Fe-Nb alloys. 1987 Fe-Nb alloy

18. High-temperature melts

19. Ionic liquids11

20. Electrolytes with organic solvents Kuznetsov V. V., Grigoriev V. P., Osipov O. A. Method of electrochemical deposition of niobium. 1973 The extreme high vapor pressure, flammability and explosiveness makes these solutions dangerous 12

21. Electrolytes with organic solvents Compact bright Ni-Nb coatings with Nb content ≤1% 13 Fialkov U. Y., Grishchenko V. F. Electrodeposition of metals from non-aqueous solutions. 1985

22. High-temperature melts Electrolyzer - hermetically sealed Have been obtained pure Nb with impurities of C - 0,02wt%; O < 0,05wt%; N - 0,02wt% 14 Yagodin G.A., Technology of rare metals in atomic technique. Moscow, Atomizdat. 1974

23. High-temperature melts Outgassing the mixture under vacuum at 400 ⁰C for one week to remove adsorbed moisture. Have been obtained dense coherent deposits of Nb 15 On the electrodeposition and characterization of niobium from fused fluoride electrolytes G. P. Capsimalis, E. S. Chen. Journal of Applied ElectrochemistryV17, #2 / March, 1987

24. Ionic liquids Ionic liquids are molten salts with melting points below 100 °C 16

25. Ionic liquids Niobium Electrodeposition from Low-Valent Niobium Species Graham T. Cheek Niobium contents of 10 - 12 % in the co-deposited niobium-aluminum coatings 17

26. Ionic liquids It was confirmed that aluminium alloys containing Nb could be electrodeposited. However, niobium could not be deposited in the pure form. Niobium content in alloy – from 3 % to 13% 18 Electrochemical Behaviour of Dissolved Nb,Mo and Ta Species in MoltenChloroaluminates. Geir Martin Haarberg and Gery Stafford

27. Ionic liquids Layer of niobium deposited on Ni is not very uniform 19 Electrodeposition of Ta and Nb using ionic liquid. GuiseppinaBarbato. A thesis for the degree of Master of Applied Science

28. Ionic liquids Electrodeposition of Nb3Sn alloy film from Lewis basic NbCl5-SnCl2-EMIC melt Koura N. Electrochemistry V77, I9, September 2009, P798-800 Have been obtained Nb-Sn alloy with Nb content – 69,1wt％ 20

29. Conclusions The electrodeposition of Nb is not possible from aqueous solutions because the electrochemical potential for this metal falls outside the window of stability for water Non-aqueous solutions could be used for Nb electroplating With high-temperature melts could be obtained Nb coatings Ionic liquids are a relatively new class of materials with properties (wide potentional window, inflammability, low vapour pressure) that makes them attractive for electroplating of Nb 21

30. Thanks for your attention!!!! 22