The laboratory prepares specimens (thin foils) for Transmission Electron Microscopy (TEM) using mechanical, electrolytic, and ion polishing methods. The most common form of TEM specimens is thin foils. The preparation process involves cutting a 3 mm diameter disc, mechanically thinning them using sandpaper and mechanical thinners (dimple grinders), and then final polishing them using ion, electrolytic, or mechanical polishers. Electrolytic polishing is used for electrically conductive samples. The effectiveness of this method is very high if the electrolyte, temperature, and electropolishing current conditions are carefully selected. This method is not suitable for non-conductive materials. In such cases, ion thinning is used. A disc of ground metallic material is exposed to a stream of argon ions, which causes atoms to be ejected from the sample surface. This process takes place at locally elevated temperatures, which is a limitation in the case of low-melting materials.
Workshop equipment:
- The Accutom-50 cutting machine is a precision saw used to prepare material samples for testing. The process involves precisely cutting the material using a grinding wheel appropriately selected for the hardness of the material being cut.
- Gatan 691 Ion Polisher (2 units) – the operation involves bombarding the sample with argon ions in a vacuum chamber, which slowly removes atoms from the surface, creating a thin film.
- Gatan GRINDER – mechanical thinner.
- DIMPLING GRINDER M200 – mechanical thinner is a precision device used for thinning samples. It is most often used in electron microscopy (TEM). During thinning, a concave depression is created in the center of the sample, significantly shortening the subsequent ion polishing time. The device allows for electronic control of the thinning (abrasion) speed and depth (with precision down to one micron).
- The Struers Tenu Pol-5 electropolishing machine is used for automatic electrolytic thinning of samples for transmission electron microscopy (TEM) examination. Establishing parameters for new materials and storing them in the method database is easy thanks to the built-in current-voltage curve recording function. The TenuPol-5 consists of two separate units – a control unit and a polishing unit. With the appropriate current-voltage parameters and electrolyte, a metallic TEM sample is prepared in minutes