Sample Preparation Method for Characterization of Fine Solids in Athabasca Oil Sands by Electron Microscopy

This study introduces a new sample preparation method for characterization of fine solids in Athabasca oil sands using electron microscopy. The method uses a combination of microtome and focused ion beam (FIB) techniques to produce samples for both scanning and transmission electron microscopy (SEM/TEM). In this procedure, SEM images and X-ray maps provide general microstructure and compositional information, with detailed analysis provided through TEM analysis of site-specific electron transparent sections prepared using FIB methods. The method is particularly useful for identifying low concentrations of metals and their compounds and is demonstrated for the identification of fine iron oxide particles in the froth stream of an Athabasca oil sands sample after hot-water extraction. Fine particles (<2 mu m fraction of oil sands minerals) are embedded in a polymer resin and sectioned using an ultramicrotome to prepare a fresh, flat surface for SEM analysis. An iron-rich region is located using X-ray mapping in the SEM. A thin section of the region of interest is prepared using FIB, which is then characterized using TEM imaging, electron diffraction, and X-ray microanalysis. Specifically, nanosized hematite and magnetite particles were identified in the froth stream.