Electropolishing for TEM Sample Preparation
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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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