vlada pastushenko progress on fluorine-free electropolishing
DESCRIPTION
High purity niobium (Nb) is used to make superconducting radio frequency (SRF) cavities. To improve the cavity performance it is necessary to reduce the surface resistance as much as possible. To achieve this goal each Nb cavity undergoes to a series of successive treatments (mechanical polishing, buffered chemical polishing, electropolishing, annealing). Choline Chloride-based ionic liquids are considered as a new class of electrolytes. Comparing to traditional ionic liquids, choline chloride-based ionic liquids are low toxic, biodegradable, and the price is generally low, which make them more and more attractive in green chemistry and industrial chemistry. Since it was found that, the mixture of Choline Chloride and Urea can polish Niobium every year, this solution has been improved. Was investigated the optimal ratio of Choline Chloride and Urea, studied the effect of additives, temperature and current density. When it was found suitable parameters for the polishing of planar samples, we have started to implement it to the polishing of 6 GHz Niobium cavities.TRANSCRIPT
![Page 1: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/1.jpg)
LABORATORI NAZIONALI DI LEGNARO
Progress on Fluorine-free
ElectropolishingVlada Pastushenko,
F. Stivanello, V. Palmieri6th Workshop on "Thin Films and New Ideas for SRF", Legnaro (PD) Italy, October 6-8 2014
![Page 2: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/2.jpg)
Outline Ionic liquids, their properties and application.
Electropolishing of Niobium in Fluorine-free solutions (first steps).
Study the parameters of Electropolishing in Ionic Liquids.
Procedure of standard electropolishing 6 GHz cavities.
Development the systems for Electropolishing in Ionic Liquids: Different shapes of the cathode; Vertical system for EP 6 GHz cavity; Horizontal system for EP 6 GHz cavity.
Q-factor result.
![Page 3: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/3.jpg)
DES is a type of ionic solvent with special properties composed of a mixture which forms a eutectic with a melting point much lower than either of the individual components.
The deep eutectic phenomenon was first described in 2003 for a mixture of choline chloride and urea in a 1:2 mole ratio, respectively.
Choline chloride has a melting point of 302 °C and that of urea is 133 °C. The eutectic mixture melts lower than 100 ˚C.
Deep Eutectic Solvent or DES*
*Andrew Abbott; John Barron, Karl Ryder and David Wilson (2007). "Eutectic-Based Ionic Liquids with Metal-Containing Anions and Cations". Chem. Eur. J. 13: 6495– 6501. doi:10.1002/chem.200601738.
![Page 4: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/4.jpg)
Type I Eutectic metal salt + organic salt (e.g. ZnCl2 + choline chloride)
Type II Eutectic metal salt hydrate + organic salt (e.g. CoCl2*6H2O + choline chloride)
Type III Eutectic organic salt + hydrogen bond donor (e.g. choline chloride + urea)
Type IV Eutectic metal salt (hydrate) + hydrogen bond donor (e.g. ZnCl2 + urea)
Four types of eutectic solvents:
![Page 5: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/5.jpg)
Room Temperature 120˚C
Choline Chloride – based Ionic liquids
![Page 6: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/6.jpg)
Conductivity and viscosity of a Urea : Choline chloride mixture (2:1) as a function of temperature*
*A. P. Abbott, G. Capper, D. L. Davies, R. Rasheed and V. Tambyrajah “Novel Solvent Properties of Choline Chloride/ Urea Mixtures” Chem. Commun, 2003, 70-71.
![Page 7: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/7.jpg)
Electropolishing of Niobium in
Fluorine-free solutions(first steps)
![Page 8: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/8.jpg)
Acetonitrile tetramethylammonium perchlorate tetrabutylammonium perchlorate potassium perchlorate
Dimethylformamide tetrabutylammonium perchlorate potassium perchlorate Urea
Organic solvents Ionic Liquids Choline Chloride : Urea (1:2) tetramethylammonium perchlorate tartaric acid oxalic acid ammonium chloride
Choline Chloride : Urea (1:3) ammonium chloride potassium tartrate
Choline Chloride : Urea (1:4) ammonium chloride
Choline Chloride: Ethylene Glycol (1:2) ammonium chloride
M. Ceccato, “Elettropulitura del Niobio con Elettroliti a base di Liquidi Ionici”, Master Thesis (2007) University of Padua.
![Page 9: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/9.jpg)
Optical microscopy analysis
![Page 10: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/10.jpg)
SEM analysis
![Page 11: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/11.jpg)
Sulfamic acid – first success*
*Rupp V. "Electropolishing of Niobium 6 GHz RF cavities in fluorine-free electrolyte", Master Thesis, 2009.
![Page 12: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/12.jpg)
Influence of S and N containing compounds
![Page 13: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/13.jpg)
Surface maps of different treatments
raw Nb
10 min IL
10 min classical EP
60 min IL
![Page 14: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/14.jpg)
Choline Chloride and Urea (1:4) with Sulfamic Acid (SA) and Ammonium Sulfamate (AmS)
+30 g/l SA
+50 g/l SA +75 g/l AmS +114 g/L AmS
+ 97 g/l SA
![Page 15: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/15.jpg)
The Best parameters for EP Nb samples
Choline Chloride : Urea 1 : 4
Sulfamic acid, g/l 97
Material cathode Nb
Temperature, °C Higher then 120
Current density, A/cm2 0,3
![Page 16: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/16.jpg)
Procedure of standard electropolishing
6 GHz cavities
![Page 17: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/17.jpg)
Cavity kit appearance
1 – cavity; 2 – cathode; 3 – up flange; 4 – bottom flange
1
4
2
3
![Page 18: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/18.jpg)
1 – cavity;
2 – anode contacts;
3 – cathode contact;
Blue indicator – direct flow,
red – indirect.
Stand for BCP and EP
![Page 19: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/19.jpg)
EP result obtained in 6GHz cavity
![Page 20: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/20.jpg)
Schematic diagram of an anodic polarization
![Page 21: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/21.jpg)
Automatic software for controlling potential.
![Page 22: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/22.jpg)
System for Electropolishing
in Ionic Liquids
![Page 23: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/23.jpg)
Electropolishing in Ionic Liquid (preliminary tests)
![Page 24: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/24.jpg)
Different cathode
performance
![Page 25: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/25.jpg)
Cut-offCell
“Full holed” cathode
![Page 26: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/26.jpg)
Cut-offCell
“Center holed” cathode
![Page 27: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/27.jpg)
“Two parts” cathode
1 – cathode; 2 – flange; 3 – surface of cathode which has to be
covered with Teflon ribbon; 4 – cavity; 5 – tube junction
1
23
45
![Page 28: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/28.jpg)
Vertical system for EP 6GHz
cavities in Ionic liquids
![Page 29: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/29.jpg)
Scheme of flux direction ”inside cathode” 6GHz cavities treatment procedure IL EP process
![Page 30: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/30.jpg)
Cavity after Vertical EP
![Page 31: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/31.jpg)
Horizontal system for EP
6GHz cavities in Ionic liquids
![Page 32: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/32.jpg)
SEM Analysis
Half cavity polished in horizontal position
Solution - 1:4 Choline :Urea,Sulfammic Acid - 1M/l;
T- 120°C
![Page 33: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/33.jpg)
Horizontal system for EP 6 GHz cavity*
*O. Malkova, “Study of the Electropolishing of 6GHz Niobium cavity in ionic liquids”, Master Thesis, 2013.
![Page 34: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/34.jpg)
Surface inside cavity after EP
![Page 35: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/35.jpg)
Modified system for EP in Ionic liquids
![Page 36: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/36.jpg)
Iris
Cell
Electropolishing of the Niobium: result after first try (60min)
![Page 37: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/37.jpg)
Electropolishing of the Niobium: result after 6 hours
![Page 38: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/38.jpg)
Q-factor result
![Page 39: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/39.jpg)
![Page 40: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/40.jpg)
Choline Chloride - urea based Ionic liquids are a possible alternative to the hazardous standard electropolishing electrolyte based on hydrofluoric and sulphuric acid.
The best solution that we found for Electropolishing of Niobium is Choline Chloride with Urea in ratio 1 to 4 with 1 M/l Sulfamic acid.
The electropolishing in horizontal system give us shiny surface without pitting and damages and the result is reproducible.
Summary
![Page 41: Vlada pastushenko progress on fluorine-free electropolishing](https://reader034.vdocuments.mx/reader034/viewer/2022042601/5565d69bd8b42a8a7b8b5449/html5/thumbnails/41.jpg)
Thank you for attention!