Structural and mechanistic inferences in the mechanochemical synthesis of nanostructured Ni-Sn and Co-Sn alloys

We focus on the synthetic path of nanostructured Ni-Sn and Co-Sn systems by
mechanical alloying. A similar reaction path seems to characterize the process for both the
systems: the formation of intermediate, metastable, Sn rich phases has been evidenced, not
provided for by the corresponding equilibrium phase diagrams. Their crystallographic and
thermodynamic properties were evaluated through a structural and calorimetric investigation.
Further mechanical processing induced structural evolutions by the progressive alloys
enrichment in Ni and Co respectively, according to the stoichiometric constraints. Quantitative
assessment of relative abundance of crystallographic phases let us investigate the alloying
kinetics. By resorting to a previously developed procedure we evaluated collision frequency
and impact energy. Then the analytical solution of the kinetic curves allowed us to relate the
conversion degree to the effective collisions undergone by each powder particle.