Enhanced control of electropolishing for the preparation of thin foils for TEM: Artificial and multiple - phase micro-electropolishing

By rapidly changing voltage and current settings during electropolishing conditions can be set up for polishing otherwise difficult to polish multi-phase material. In addition a wider a more flexible range of polishing conditions can be obtained by manipulating the film build-up condition in micro-electropolishing that is normally outside the useful range of electropolishing. Electropolishing may be broken down into two distinct processes: Macro-electropolishing or “smoothing” whereby large scale asperities are removed and Mcro-electropolishing or “brightening” in which smaller (<lμm) irregularities are removed. In “bath” (immersion) electropolishing both processes take place whereas in “jet” electropolishing the polishing mechanism is primarily micro-electropolishing. For micro-polishing to occur a thin solid film must be produced at the specimen surface. In order for micro-electropolishing (sometimes called brightening or brilliance) there must be random removal of metal from the surface irrespective of features such as grain-boundaries, grain orientation and defects.