Preparation of micro-foils for TEM/STEM analysis from metallic powders

Karl Dawson; Gordon J Tatlock

doi:10.1016/j.micron.2015.04.006

Preparation of micro-foils for TEM/STEM analysis from metallic powders

Micron. 2015 Jul:74:54-8. doi: 10.1016/j.micron.2015.04.006. Epub 2015 Apr 23.

Authors

Karl Dawson¹, Gordon J Tatlock²

Affiliations

¹ Centre for Materials and Structures, School of Engineering, University of Liverpool, UK. Electronic address: k.dawson@liverpool.ac.uk.
² Centre for Materials and Structures, School of Engineering, University of Liverpool, UK.

PMID: 25967375
DOI: 10.1016/j.micron.2015.04.006

Abstract

A technique has been developed which facilitates the preparation of electro-polished micro-foil transmission electron microscopy (TEM) specimens, which have previously been machined out of ≈100 μm diameter metallic powder particles using a Focussed Ion Beam (FIB) instrument. The technique can be used to create small volume TEM specimens from most metallic powder particles and bulk metal samples. This is especially useful when the matrices are ferritic steels, which are often difficult to image in the electron microscope, since the necessary aberration corrections change as the sample is tilted in the magnetic field of the objective lens. Small samples, such as powder particles, were attached to gold support grids using deposited platinum and were then ion milled to approximately 2 μm thickness in a focussed ion beam (FIB) instrument. Subsequently, the specimen assemblies were electropolished for short durations under standard conditions, to produce large (5 μm×5 μm) electron transparent regions of material. The specimens produced by this technique were free from FIB related artefacts and facilitated atomic resolution scanning-TEM (STEM) imaging of ferritic and nickel matrices containing, for example, yttrium rich oxide nano-dispersoids.

Keywords: Electropolished samples; Mechanically alloyed powder; Oxide dispersion strengthened steel; TEM specimen preparation.