Copper enrichment on aluminium surfaces after electropolishing and its effect on electron imaging and diffraction

Thickness profiling of electron transparent aluminium alloy foil using convergent beam electron diffraction

“…In this work it is assumed that the TEM foil was pure Al, since the alloy was aged long enough for the solute elements to be incorporated in the metastable phases and leaving enough space for the convergent beam to probe between the precipitates where the solute concentration is dilute. However, it is reported that in addition to the oxidation layer, which forms on the surface of the TEM samples, there might be solute enriched layers which segregate between the oxide layer and the matrix 17 . This will alter the structure factor and the volume of the unit cell described in the Equation (), which in turn will influence the extinctions distance and the absorbing coefficient.…”

Electropolishing and Shaping of Micro-Scale Metallic Features

“…Recently, Wenner et al [ 29 ] used electropolishing to prepare smooth and transparent TEM samples for studying the copper enrichment of aluminum alloys. The precipitate phases of Cu in Al were revealed by electropolishing discs to a thickness of around 80 um, using an electrolyte with 1/3 nitric acid in methanol at a voltage of 20 V. For mass spectrometry, a 30 kV Ga source was used with a scanning area of 100 μm × 100 μm under static conditions, while depth profiling was done at 3 keV over a 600 μm × 600 μm area for a duration of 10 s. This allowed Cu-rich layers to be observed by TEM in both alloys, the second alloy having more copper content.…”

“… ( A ) Optical images of ( a ) sample, ( b ) slice sectioned from the sample using low-speed diamond saw (isomet), ( c ) slice after punching TEM disc ( d ) TEM disc ( e ) TEM disc after grinding and electropolishing (note the shiny contrast in the central portion due to electropolishing [ 59 ] (copyrights granted by author). ( B ) Schematic of twin jet electropolishing, (copyrights granted by Elsevier) [ 163 ] ( C ) Nano-structure based optical images of TEM samples in various forms is shown, ( a ) carbon coated, ( b ) mechanically milled, ( c ) free standing ribbon processed by rapid solidification, ( d ) small ribbon bonded to a slotted copper grid, ( e ) TEM image showing the powder particles on copper grid, ( f ) optical image of iron powder particles embedded in epoxy [ 59 ] (copyrights granted by author), ( D ) TEM results showing grain orientation of electropolished Al samples at 200 kV electrons, ( a , d ) cut-outs from larger ADF-STEM images in [001] and [011], ( b , e ) Fourier transforms, ( c , f ) diffraction patterns of ( a , d ) [ 29 ], (open access article distributed under the terms of the Creative Commons CC-BY license). …”

“…Conventionally, it is a strong acid, with some surfactants or additives being used to improve the electrodes’ viscosity, wettability, and reactivity. Sulfuric and phosphoric acids are used widely to electropolish metals and alloys [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Since acidic electrolytes can be hazardous or harmful to human safety and the environment, there is a growing trend of using green electrolytes.…”

“…Moreover, electrochemical polishing is capable of removing material at controlled rates using various waveforms: pulsed current (PC) and pulse reverse pulse current (PPR) can help maintain the structural integrity of micro-scale features [ 53 , 54 , 55 , 56 , 57 ]. The critical applications for the electrochemical polishing of micro-structures include TEM sample preparation [ 29 , 58 , 59 ], AM parts [ 12 , 60 , 61 , 62 ], biomedical stents and implants [ 7 , 17 , 54 , 56 , 63 ], and RF MEMS or MOEMS [ 64 , 65 , 66 , 67 , 68 ], which will be explained later in this review. There is also potential for electropolishing to be used as a shaping and forming process in the manufacturing of micro-mold tool inserts in order to boost the performance of micro-injection molding by preventing demolding problems.…”