| In this thesis, a surfactant-free synthesis of binary and ternary metal nanoparticles via co-reduction of metal chloride precursors is used to investigate the relationship between the bulk phase diagram and the formation of ordered intermetallic structures. The majority of the synthesized phases are binary materials of the formula Pt-M (M = Sn, Sb, In, Bi), because of their propensity to form single-phase regions with very narrow phase widths, known as "line phases". These line phases are thermodynamically stable according to the bulk phase diagram; however, the relationship between bulk stability and stability in the nanoparticle regime - and the implications for nanoparticle growth and ordering behavior - have not been fully explored. The 1:1 Pt-Sn phase (PtSn) forms ordered intermetallic nanoparticles with small domain sizes (4.3 nm) at room temperature, without any thermal annealing required. Pt3Sn similarly orders at low temperature (200 oC), in contrast to the three Pt-rich line phases, all of which require higher annealing temperatures to form the intermetallic phase. Other Pt-M phases show varying degrees of ordering, but none are observed to have the same low-temperature ordering as the Pt-rich Pt-Sn phases. This behavior is extremely rare, with only one other phase to our knowledge (Pt-Bi) forming the intermetallic without annealing, and only under specific conditions. It is possible to make qualitative statements concerning which phases should easily order and form phase-pure products; however, in order to more quantitatively predict these patterns, a multivariate analysis utilizing many physical properties (e.g., melting point, whether a phase melts congruently or incongruently, crystal structure, etc) was conducted. Using principal components analysis, partial least squares regression, and logistic regression techniques, a model was constructed to determine which properties would be most predictive of phases that were able to be synthesized as pure ordered intermetallics. |
