In the paper, the particle morphology is considered and the slices of phase diagrams of nanosystems agreeable to the synthesis conditions are constructed according to the data obtained earlier by authors, as well as new results of the study of nanostructured Fe-Co, Fe-Ni, Co-Ni, Fe-Co-Ni, Fe-Pt, Cu-Ni and Ni-Cd powders. It is found that all considered polymetallic systems have common nature of the particle size spatial organization, i.e., 7-20 nm nanocrystals (for different systems) form highly compact aggregates (40-100 nm) which put together into loose porous agglomerates (up to 200-250 nm) and then into unconsolidated micron size formation of cloud type. It is classified uncovered features of nanostructured polymetallic phase diagrams in comparison with phase diagrams of bulk systems. Magnetic properties of nanosystems are studied.

Nanostructured Fe–Co–Ni powders, with crystallite sizes of 10–35 nm for different compositions, are obtained in the whole range of compositions (step change in the components content is of 10 wt.% and, in the case of near the phase boundaries, 3–5 wt.%) by the reduction of freshly co‐precipitated mixed hydroxides with hydrazine hydrate in a strongly alkaline medium. The isothermal section of the phase diagram corresponding to the synthesis temperature (363–368 K) is constructed using reflection modeling based on XRD data of the samples series with different compositions. Its features are founded, characterized, and discussed: the phase diagram of the system in the nanostructured and nonequilibrium state is compared with the phase diagram of the system in the bulk state. In the region of the FCC‐solid solution, the “lattice parameter–composition” dependence was described by the flat surface equation (three‐dimensional analog of Vegard's law). Some magnetic characteristics are measured for the Fe–Co–Ni systems containing 10 wt.% Ni and variable Co/Fe ratio. Some features of the superparamagnetic component are observed above the blocking temperature; they are related to the crystallite size and the phase composition of the samples.

<p>The influence of heating process (up to 200, 400 and 600 °C) on the phase transformation of non-equilibrium biphase Fe-Co-Ni systems was studied. The system was not changed at 200 °C, it remained nanostructured, and there were no phase transformations. At higher temperatures phase transformation BCC- into FCC-phase (high-temperature phase modification) was observed. The degree of phase transformation depended on the system composition. At 400–600 °C there was coarsening of the crystallites. In addition, there was the phenomenon of system oxidizing attended by iron outflow from phase; as a result, the lattice parameters were decreased. According to the measurements of the lattice parameters at coolingdown, parameters dependences on temperature and coefficients of thermal expansion were obtained. Changing of the system composition (due to metal oxidation) had low impact on the coefficients. The phases with different compositions and close lattice parameters had different coefficients of expansion. It was supposed that the expansion coefficients dependence from the composition was not additive. Magnetic characteristics of the samples were measured. It was found that heating changed it essentially. The main reasons of it was coarsening of grains (crystallites) and changes of the phase composition. The dependence of the magnetic properties of systems on phase composition and size of the crystallites (particles), as well as changes occurring under the temperature effect were required a more detailed study.</p>

Методом осаждения гидроксидом натрия из водных растворов солей металлов при контролируемых условиях проведения реакций синтезированы мелкодисперсные порошки смешанных гидроксидов (СГ) железа и кобальта, железа и никеля-прекурсоров наноструктурированных двухкомпонентных и трехкомпонентной систем металлов подгруппы железа. Получены наноструктурированные твердые растворы гидроксидов металлов систем: железо-кобальт, железо-никель и железо-кобальт-никель; определены фазовый состав, структурные параметры, распределение частиц по размерам СГ металлов. Ключевые слова: наноразмерные системы переходных металлов, фазовый состав, смешанные гидроксиды