In this work, on the example of bimetallic systems FePt and FePd, an approach is developed to assessing the structural parameters of nanoscale mono-and polymetallic systems by transmission electron microscopy (TEM), in comparison with the X-ray diffraction method of analysis. The interplanar distances, average sizes and phase compositions of FePt and FePd nanosystems are calculated.

Nanoparticles of the FePt and CoPt alloys are studied. Detailed structural-phase data on the platinum-rich nanosystems has been obtained using a combination of X-ray diffraction (XRD), selected-area electron diffraction (SAED), highresolution transmission electron microscopy (HR-TEM) in a scanning transmission electron microscope, in addition with derivatography in coupled with the simultaneous mass spectrometry, and elemental analysis of the samples. The upper limits of Fe and Co solubility in Pt and their temperature dependencies have been defined. It is shown that, if Fe or Co contents are above the solubility limits, there is not only the diffraction-detectable phases of FCC solid solutions but also undetectable phases by XRD-method, probably, it is the intermetallic

Joint reduction with hydrazine from aqueous solutions of precursors produced nanostructured powders of the Fe – Pt system in three characteristic phase regions. The samples were subjected to heat treatment in the range up to 800 ° C and characterized at all stages by X-ray diffraction and high-resolution electron microscopy; the elemental composition of the samples was refined by the method of optical emission spectroscopy with inductively coupled plasma. In the initially obtained samples, only a part of the substance is detected by diffraction-the largest, platinum-rich crystals with dimensions of about 10 nm (established from TEM images and broadening of diffraction lines). The fcc-type cubic lattice parameters and the composition of the observed crystals were estimated from the distances between the regular bands in TEM images, identified with atomic rows, based on the composition dependence of the bulk characteristics of mixed iron-platinum phases (according to ICDD databases). In the course of heating, the processes of phase transformation are traced in detail, the parameters of the resulting crystal structures of intermetallic compounds are fixed, and the mechanisms of these transformations are discussed. Based on the measured lattice parameters, the thermal expansion coefficients of some mixed phases are calculated and the phase compositions are estimated at different stages of heat treatment.

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