Control of the size, shape and phase composition of nanocrystalline materials is a key point in current nano-science research. Synthetic chemical methods have proved efficiency for the nanocrystals production with a tight size distribution and composition. Ru, Re and Os bulk and nanoscale solid solutions show high thermal, chemical and mechanical stability. Metals with hexagonal close packed (hcp) structures have extremely high melting points as well as Re and Os. Therefore their solid solutions are difficult to prepare. The main purpose of this work is preparation of the nanodimention solid solutions Ru – Re, Ru – Os and Re – Os and their characterization by powder X-ray diffraction and scanning electron microscope. Binary phase and Retgers diagrams were analyzed.
Ru – Re, Ru – Os and Re – Os bimetallic solid solutions were prepared by thermal decomposition under H₂ of bimetallic compounds: [M¹(NH₃)₅Cl][M²Cl₆] and [M¹(NH₃)₅Cl]₂[M²Cl₆]Cl₂ (M¹ = Ru, Os; M² = Re, Os). Precursors were prepared as described previously for isoformular compounds¹.

Preparation at 500 °C gives homogeneous hcp bimetallic solid solutions with crystallite dimensions nearly 100 Å. Additional annealing of the samples during 5 h at 800 °C does not essentially affect the unit cell parameters, but the crystallite size is doubled. The dependence of atomic volumes (V/Z) on the composition on the Ru – Re, Ru – Os and Re – Os bimetallic solid solutions is depicted here. Dependences are nearly-linear with negative deflection not more than 0.5 %. Equilibrium binary phase diagrams of given metallic systems were calculated by CALPHAD method based on an ideal solutions model. Obtained bimetallic powders are nearly equilibrium and prepared on 1/5 melting points for pure metals. It gives possibilities for the preparation of the nano-dimensional solid solutions of high melting metals for catalytic and material applications.

¹S.A. Martynova, K.V. Yusenko, I.V. Korolkov, S.A. Gromilov (2007): Russ. J. Coord. Chem., 33, 530

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