Synthesis and Study of the Phase Composition of Ni-Pt Particles Used in Carbon Composite Materials

As a result of studying the phase composition of Ni-Pt nanoalloy particles using X-ray diffraction (XRD) analysis, it has been established that during the synthesis of Ni-Pt nanoalloy particles by co-reduction of the aqueous metal precursor solutions (Ni2+ and [PtCl6]2-) with an alkaline hydrazine hydrate solution, the formation of ƒcc-type Ni-Pt solid solution particles occurs, with an average Ni content of 13 at%. These particles have ellipsoid shape with the equatorial and lateral size 6-13 and 10-28 nm, respectively. By comparing the XRD results with data obtained from high-resolution transmission electron microscopy (HRTEM) and small-angle X-ray scattering (SAXS), it has been shown that, in addition to the aforementioned Ni-Pt solid solution particles, the synthesised samples contain ultrafine Ni-rich particles: the phases of Ni-Pt intermetallides and the ƒcc-phase of individual Ni. As a result of heating the sample with total nickel content 20 at% in high vacuum to a temperature of 390 °C, the phase transformation takes place, leading to the formation of ƒcc-type Ni-Pt solid solution particles with Ni content 23 at% and average size ≈26 nm, as well as the particles of practically pure platinum with the average size ≈55 nm.