Preparation of Cross Sections of Diffi cult Materials for SEM Imaging
Figure 2 : Powder embedded in epoxy. (A) Surface of cured epoxy containing the powder. (B) Outline for trimming epoxy/powder block. Edge to be polished (arrow) traverses an area of high powder concentration.
Materials and Methods As the physical composition of particulates may vary, it
can be diffi cult to cleanly cut materials to examine their internal features. Below is a general procedure for preparing and polishing cross-section specimens of particulates and wires.
Materials 1. Two-part epoxy such as Devcon 5 minute epoxy gel (ITW Devcon, Danvers, Massachusetts, USA). T is epoxy does not require heating and is transparent on curing, so the embedded sample remains visible, which is not the case with some epoxies (for example, Gatan G1 epoxy cures opaque and almost black in 10 minutes at 130°C).
2. Polytetrafl uoroethylene (PTFE; Tefl on ) sheet (JEOL USA, Peabody, Massachusetts or other supplier).
3. Aclar fl uoropolymer fi lm (Ted Pella, Inc., Redding, California USA).
Procedure 1. Dispense equal amounts of the two epoxy components on a disposable surface like cardboard ( Figure 1A ). Mix gently but thoroughly with a disposable tool such
42
Figure 3 : Embedded and polished coated copper wire. (A) The Aclar ® covering has been pushed down to the surface of the wire during embedding. (B, C) Scanning electron micrographs of polished wire cross section; metallic grain structure is obvious.
as a toothpick or wooden applicator stick ( Figure 1B ). Avoid introducing air bubbles.
2. Transfer some of the epoxy to the PTFE sheet, and form a rectangular puddle about 20 mm × 10 mm × 3 mm deep. Work quickly so the epoxy does not begin to set.
3. Place a generous amount of the powder on top of the epoxy; do not mix ( Figure 1C ). T e powder should be concentrated in one area rather than dispersed.
4. Cover the epoxy/powder surface with a piece of Aclar ( Figure 1D ), which will remain attached to the sample permanently. T e Aclar should be larger than the area covered by the powder. Press down gently on the Aclar to thin the epoxy puddle to about 1–1.5 mm thickness, and submerge the powder ( Figure 1E ). T e powder grains will spread apart somewhat; the goal is to have just enough epoxy between the grains to hold them in place.
www.microscopy-today.com • 2018 May
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
