Classification of small Al-particles

Abrasion in production lines can be a source of contaminated products and/or malfunctioning machinery. Using micro-XRF it is straight-forward to classify steel particles with sizes down to 50 µm because their heavy matrix will allow a reliable quantitative analysis of the main elements. For the classification of Aluminum flakes usually heavy elements are of importance, whereas the main element is very light. Therefore, it is difficult to asses the alloy type of thin Aluminum particles. The fast mapping capabilities of the M4 TORNADO (PLUS) allow to quickly scan small Al particles and find the thickest part of the sample. This thick region is likely to give the most reliable results for a classification. The region of interest can be cut out from the Hypermap dataset and be quantified for classification.

Map of different Al flakes. The sample is thickest where the color signal is brightest. The left pictrue shows an Al particle of roughly 500 µm width. This particle is folded, whis from the optical image was not apparent. The right pictrue shows an even smaller particle which overall is thicker than the first sample. The thickness information is obtained easiest by a quick map of the whole particle.
Four different particles with diameters well below 500 µm and much lower thickness where mapped, the thickest part was selected and quantified. The Al sample holder was the piece where the flakes were abraded from. For all particles the heavy elements Pb and Bi are underestimated, because the samples are too thin. Fo the medium elements the quantification still worked for the two thicker flakes, but failed for particle 3 and 4. This way to assess the size range for a reliable classification is fast and direct. Aluminum particles that are larger (thicker) than 200 µm can be classified reliably.