The non-equilibrium phases in the nanostructured Cd–Ni powders and their specific formation

Abstract

The synthetic processes of nanodimensional and nanostructured intermetallic compounds, and the features of the phase diagrams of these systems were discussed in the present work with the example of the nanostructured Cd–Ni system due to their scientific novelty. The discrepancies of its phase composition to its phase diagram were determined, the scheme, experimentally reasonable and explaining these features of the Cd–Ni system with the coreduction of the water solutions of the Ni and Cd salts by hydrazine, was proposed, some of its structural and size-dependent properties were considered. By TEM, SEM, and SAXS, the three-level morphology of the particles was established including unusual to FCC structures anisometry of the composing units of the nanodimensional crystallites of a CdxNi1–x solid solution. The methods of electronic microscopy and cyclic voltamperemetry confirmed the unusual phase composition of the system. According to the results of thermogravimetry and mass-spectrometry (TMS), the surface composition of the particles was defined (sorbed H2O, O2, CO2, nanoinsular inclusions of hydroxides and carbonates) and the nature of some thermal superficial transformations. The scheme of metal products preparation (including intermetallic nanophases) was established by the element analysis of hydroxide precursors and metal products (ICP-OES) during the synthesis and by the TMS results (the reduction of hydroxide precursors in the hydrogen atmosphere) and the XRD measurements previously accomplished. Probably, this scheme of the liquid ox-redox synthesis of metal products was revealed for such kind of materials for the first time, including the features of forming nanosized intermetallic compounds.