Nitridation reactions in two-phase Cr(Pt) + Cr₃Pt alloys as a basis for a new synthesis route to form near-surface composite structures

Recent research has focused on studying nanoscale materials because of the novel properties and behaviors they exhibit. Nanoscale dispersions of complex ceramics are of interest for functional applications because of their potential to exhibit unique magnetic, optical, chemical, and electrical properties and behaviors, however they are difficult to make. Internal oxidation reactions in multi-phase alloys offer a possible route for the controlled synthesis of these types of functional surfaces. In support of this application, the nitridation behavior of model single-phase Cr(Pt) and Cr3Pt alloys were studied individually and in combination at 800°C and 1000°C. Results suggest that nitridation of the two-phase Cr(Pt) + Cr3Pt alloy followed the underlying two-phase microstructure, which effectively acted as a template and led to the formation of a dispersion of the Cr3PtN perovskite phase, derived from Cr3Pt metal precipitates. Interestingly, the nitridation behavior of the Cr3Pt phase differed when present as the matrix phase as opposed to as a second phase precipitate. Details of the modes of nitridation are presented.