Enhanced control of electropolishing for the preparation of thin foils for transmission electron microscopy: Artificial and multiple-phase micro-electropolishing
- Univ. of Wisconsin, Madison, WI (United States)
In order to provide more routine sample preparation for superconducting composites we have developed a new method of controlling micro-electropolishing. We can set up {open_quotes}artificial{close_quotes} micro-electropolishing conditions that would normally be outside the {open_quotes}ideal{close_quotes} micro-electropolishing range (where film dissolution is balanced by film creation) by rapidly oscillating ({le}1sec/level) between low current regimes where there is film build up and high current regimes where there is film removal. The periodic removal of the film by using the high current density level limits the level of sub-film species build up. For typical electropolishing of Nb-Ti and Nb{sub 3}Sn superconductor composites with Cu matrices we use an electrolytic solution was 2 vol.% HF{sub aq}, 5 vol.% H{sub 2}SO{sub 4aq} and 93 vol.% methanol at a temperature of {approximately}-40C. We have found that extremely good specimens can be obtained by oscillating between 3-8mA mm{sup -2} and 30-32mA mm{sup -2}, even for transverese cross-sections of strand less than 0.1mm in diameter. For these specimens the oxide film can be controlled so that further surface cleaning (normally performed by ion beam thinning) is unnecessary. Balancing the polishing rates of Cu and the superconducting phase is performed by adjusting the duration at each current level, lowering the lower current level and increasing the time at that level increased the polishing rate for the superconductor and increasing the time at that level increased the polishing rate for the superconductor and increasing the upper voltage level and increasing the time at that level increased the polishing rate for the Cu. Time intervals of 10 ms for the upper current level and 20-100 ms for the lower current have provided the best results so far.
- DOE Contract Number:
- FG02-91ER40643
- OSTI ID:
- 468969
- Report Number(s):
- CONF-960877-; TRN: 97:001308-0227
- Resource Relation:
- Conference: Microscopy and microanalysis 1996, Minneapolis, MN (United States), 11-15 Aug 1996; Other Information: PBD: 1996; Related Information: Is Part Of Microscopy and microanalysis 1996; Bailey, G.W.; Corbett, J.M.; Dimlich, R.V.W.; Michael, J.R.; Zaluzec, N.J. [eds.]; PB: 1107 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Highly smooth Nb surfaces fabricated by buffered electropolishing
ELECTROPOLISHING OF SRE FUEL SLUGS