Analysis of Phase Composition and CSR Sizes in Non-Equilibrium Nanostructured Systems Fe-Co and Ni-Cu Using Diffraction Maxima Simulations in a Doublet Radiation

Zakharov, Yu. A.; Пугачев, В. М.; Korchuganova, Kseniya A.; Ponomarchuk, Y V; Larichev, T. A.

doi:10.1134/s0022476620060219

Cited by 3 publications

(2 citation statements)

References 3 publications

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“…The lattice parameters (LP) and crystallite sizes, that is the coherent scattering regions (CSRs), are calculated by the Scherrer equation using the approaches discussed in [17].…”

Section: Testing Methodsmentioning

confidence: 99%

Study of the Pt-rich nanostructured FePt and CoPt alloys: oddities of phase composition

Zakharov¹,

Tikhonova²,

Zakharov³

et al. 2022

Lett. Mater.

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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

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“…The lattice parameters (LP) and crystallite sizes, that is the coherent scattering regions (CSRs), are calculated by the Scherrer equation using the approaches discussed in [17].…”

Section: Testing Methodsmentioning

confidence: 99%

Study of the Pt-rich nanostructured FePt and CoPt alloys: oddities of phase composition

Zakharov¹,

Tikhonova²,

Zakharov³

et al. 2022

Lett. Mater.

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“…The Scherrer formula was used to estimate the crystallite size from the broadening of the XRD peaks, following the procedure described in [28].…”

Section: Specimen Characterizationmentioning

confidence: 99%

Morphology and Phase Compositions of FePt and CoPt Nanoparticles Enriched with Noble Metal

Zakharov,

Popova,

Pugachev

et al. 2023

Materials

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The article reveals for the first time the features of nanoparticle morphology, phase compositions, and their changes when heating FePt and CoPt nanoalloys. Nanoparticles were obtained by co-reduction of precursor solution mixtures with hydrazine hydrate. The features were found by a complex of methods of X-ray diffraction (in situ XRD and X-ray scattering), TEM HR, and cyclic voltammetry. In addition, adsorbometry results were obtained, and the stability of different nanocluster structures was calculated by the molecular dynamics method. There were only FCC solid solutions in the X-ray patterns of the FePt and CoPt nanoalloys. According to XRD, in the case of nanoparticle synthesis with Fe and Co content less than 10 at. %, the composition of solid solutions was close to or practically equal to the composition of the as-synthesized nanoparticles quantified by inductively coupled plasma optical emission spectrometry. For systems synthesis with Fe and Co content greater than the above, the solubility limits (SLs) of Fe and Co in Pt were set 11.4 ± 0.7 at. % and 17.5 ± 0.6 at. %, respectively. Therefore, there were non-registered XRD extra-phases (XRNDPh-1) in the systems when CFe,Co ≥ SL. This statement was supported by the results of TEM HR and X-ray scattering: the smallest nanocrystals (1–2 nm) and amorphous particles were found, which qualitatively agreed with the sorbometry and SAXS results. Molecular dynamics calculations of stability for FePt and CoPt alloys claimed the structures of the most stable phase corresponded to phase diagrams (A1 and L12). Specific peculiarities of the morphology and compositions of the solid solutions of nanoalloys were established: structural blockiness (domain) and composition heterogeneity, namely, platinum enrichment of internal (deep) layers and homogenization of the nanoalloy compositions at relatively low temperatures (130–200 °C). The suggested model of the formation of nanoalloys during the synthesis, qualitatively, was compliant with the results of electrochemical deposition of FePt films on the surface of various electrodes. When nanocrystals of solid solutions (C(Fe, Co) < SL) were heated above specific temperatures, there were phase transformations with the formation of two-phase regions, with solid solutions enriched with platinum or iron (non-registered XRD phase XRNDPh-2). The newly formed phase was most likely intermetallic compounds, FePt3, CoPt3. As a result of the study, the model was developed, taking into account the nanoscale of the particles: XRDPh (A1, FeaPt1−a) → XRDPh (A1, Fem×a−xPtm−m×a+x) + XRNDPh-2 (Fen×a+yPtn−n×a−y) (here, m + n = 1, m ≤ 1, n ≤ 1).

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Phase transformations of the nanostructured iron-platinum system upon heating

Пугачев

Zakharov

Попова

et al. 2021

J. Phys.: Conf. Ser.

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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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Analysis of Phase Composition and CSR Sizes in Non-Equilibrium Nanostructured Systems Fe-Co and Ni-Cu Using Diffraction Maxima Simulations in a Doublet Radiation

Cited by 3 publications

References 3 publications

Study of the Pt-rich nanostructured FePt and CoPt alloys: oddities of phase composition

Study of the Pt-rich nanostructured FePt and CoPt alloys: oddities of phase composition

Morphology and Phase Compositions of FePt and CoPt Nanoparticles Enriched with Noble Metal

Phase transformations of the nanostructured iron-platinum system upon heating

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