Particle Characterization: Challenges Associated With Submicrometer-Sized Objects
Craig S. Schwandt
American Laboratory - April 02, 2014
Materials in the form of particulate or engineered objects are relatively easy to characterize in terms of their composition, shape, size, and size distribution, provided they are larger than 1 μm in average dimension. It is often assumed that nanometer-scale materials are just smaller versions of larger-sized materials made with the same precursors and procedures, but the chemical and physical interactions of submicrometer- or nanometer-scale materials are in fact different—offering new materials with novel properties. The very small scale of these new materials makes them very difficult to accurately characterize, and because of their unique properties, it is critical for materials scientists and engineers to conduct confirmatory analysis to verify the properties of their materials.
Fortunately, advances in analytical instrumentation, especially field emission scanning electron microscopy (FESEM), permit characterization of submicrometer-sized materials. Several challenges need to be addressed in order to successfully accomplish a comprehensive, high-quality material characterization. These include: calibrating the scalar measurement tools of the FESEM, understanding the limitations of sample handling and preparation relative to other methods, the inability to use automated methods either in terms of image analysis software or other optical size distribution methods, and using crystal structural analysis to strengthen elemental analysis when small analysis volumes preclude standards for fully quantitative analysis.