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Electropolishing is a well-known technique, mostly used to prepare (inter)metallic samples, because these materials are conducting, too soft for crushing, and easily damaged by conventional ion milling.
For instance, 3-mm discs in diameter were punched from alloy sheets of Al-1.5wt% Cu-4.0wt% Mg-0.5wt% Ag and then electropolished in a 1:2 nitric acid:methanol solution (by volume) with applied voltages between 12 and 14V at a temperature of 253K [1].
Table 4488. Examples of electropolishing for TEM sample preparation.
| Materials in TEM sample |
Electrolyte used |
Applied voltages |
Temperature |
Reference |
| Al-1.5wt% Cu-4.0wt% Mg-0.5wt% Ag |
1:2 nitric acid:methanol solution (by volume) |
Between 12 and 14V |
- 20 °C |
[1] |
| Al-Zn-Mn-Si-Fe-Mg |
8% perchloric acid in methanol |
|
|
[2] |
| C-Cr-Co-Mo-Al-Ti-Nb-V-B-Zr |
8% perchloric acid + 92% methanol |
|
-15 °C |
[3] |
However, electropolished specimen can be contaminated by residues from either the electrolyte used for thinning or the solvents used for cleaning.
[1] Harsh Deep Chopra, The structure of primary strengthening precipitates in an Al-1.5wt% Cu-4.0wt% Mg-0.5wt% Ag alloy, Philosophical Magazine Letters, 73:6, 351-358 (1996).
[2] Wim Sillekens, Sean Agnew, Neale Neelameggham, Suveen Mathaudhu, Magnesium Technology 2011.
[3] Proceedings of the 2014 Energy Materials Conference, The Minerals, Metals & Materials Society (TMS), Xi'an, Shaanxi Province.
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