Study of surface oxidation in metal powders by means of optical spectroscopy

Copper alloy powders undergo oxidation upon exposure to ambient air conditions, leading to the formation of a metastable surface layer predominantly comprised of cuprous oxide (Cu2O), which subsequently transitions to cupric oxide (CuO). Accurately quantifying the thickness of this oxide layer, typically spanning a few nanometers, presents inherent challenges. This research delves into examining the composition and extent of the surface oxide layer on CuAg3.4 alloy powder, produced via gas atomization, utilizing Raman and UV–Vis spectroscopy. The primary objective of the investigation is to introduce a straightforward and innovative approach for evaluating the oxidation status of metal powders. Specifically, the composition of the oxide layer is assessed through Raman spectroscopy, whereas its thickness is determined through UV–Vis spectroscopy using a nearest-neighbor regression model trained on simulated spectra obtained by Mie's model. Furthermore, the study reveals the limitations of X-ray diffraction measurements in providing compositional insights into the oxide layer.