Specimen preparation of friable and brittle materials such as graphite present a microstructural preparation challenge. Proper microstructural preparation of these materials must maintain the structure of the graphite structure. This is accomplished by first mounting the graphite in a castable mounting compound such as epoxy. Initial grinding with a 320 grit or finer SiC paper is required to prevent pulling out the graphite particles, especially the smaller particles. Rough polishing is accomplished on low napped polishing cloths using diamond, with final polishing for a very short time on a high napped cloth using an alumina suspension.
SECTIONING
Diamond Wafering blade - fine grit / low concentration
MOUNTING
Castable Mounting with Epoxy or Acrylic resins
POLISHING
Abrasive/surface |
Lubricant |
Force/ sample |
Speed |
Time |
| 320 grit SiC paper 400 grit SiC paper 600 grit SiC paper 800 grit SiC paper 1200 grit SiC paper |
Water |
5-10 lbs | 200/200 rpm |
Until plane 1 minute 1 minute 1 minute 1 minute |
1 um DIAMAT diamond on ATLANTIS polishing pad |
SIAMAT colloidal silica |
5-10 lbs |
200/200 rpm |
3 minutes |
0.05 um Nanometer alumina on NAPPAD cloth |
|
5-10 lbs | 100/100 rpm |
1 minute |
 |
Graphite, magnification 1000 (B.F.), as polished |