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

Zakharov, N. S.; Tikhonova, Irina G.; Zakharov, Yuri D.; Попова, А. Н.; Пугачев, В. М.; Russakov, D. М.

doi:10.22226/2410-3535-2022-4-480-485

Cited by 3 publications

(14 citation statements)

References 24 publications

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“…%. When the Co content in precursors and in the samples as a whole exceeds the established limit, in addition to the FCC-type SS fixed by XRD, the formation of the phase(s) with a higher Co content in it (them) (the X-ray diffraction-undetectable phase), which we noticed earlier [18,20].…”

Section: Resultsmentioning

confidence: 67%

“…1) FCC SS Co-Pt solution is fixed as the only metallic phase. The Co content in SS was determined from the ratio (1) [20]. XPt=0.0126V 2 at-0.07845Vat-0.6874 It can be seen that on the XRD of samples with Co content above 50 at.…”

Section: Resultsmentioning

confidence: 99%

“…In the conditions of coreduction of metal ions, which are very different in the values of redox potentials, it is possible to form the so-called diffraction-unregisterable phase(s) with a higher content of Co [15-18, 20, 21]. It was shown [20,21] there were non-trivial features of phase transformations in Co-Pt system when temperature elevated that realized due to irregularity of phase compositions in Co-Pt nanoparticles as we believed.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and study of some physicochemical features of Co-Pt nanostructured system

Zakharov,

Tikhonova,

Popova

et al. 2024

BIO Web Conf.

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In the work by methods of XRD, TEM, SAED, XPS combined with mass-spectrometry of gaseous products, SAXS, and elemental analysis of samples the phase compositions and morphology of particles of nanostructured Co-Pt system synthesized by the method of reduction of hydrazine-hydrate aqueous solutions of precursors were studied (in the region rich in Pt for the first time). It was found that in the composition range up to ≈ 60 at. % Co. XRD-analysis of synthesized samples fixes as the only FCC phase of solid solution of Co in Pt, with the established upper limit of solubility %18±1 at. At the content of Co above the limit, along with it, the X-ray diffraction unregistered phases with the content of Co above the limit in solid solution are also formed. Their presence was confirmed by the SAXS method, and their metallic nature (not oxide-hydroxide) nature follows from the results of XRD, SAED. When FCC phase formed metal reduction process proceeded directly without cobalt hydroxides forming. According to results of XPS with the Ar-etching of samples there were internal platinum-rich sub-regions in Co-Pt nanoalloys.

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Section: Resultsmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis and study of some physicochemical features of Co-Pt nanostructured system

Zakharov,

Tikhonova,

Popova

et al. 2024

BIO Web Conf.

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“…An impressive body of research over the last few decades has revealed significant inconsistency between experimentally determined phase compositions (PhCs) of nanosized (NS) bimetallic alloys obtained by chemical co-reduction, and the PhCs pre-defined the phase diagrams (PhDs) of the corresponding systems [1][2][3][4][5][6][7][8]. The most significant difference is the difference in redox potential (Eh) values.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, some authors acknowledged the crucial role of the SPhT during phase formation [24,25]. Authors previously reached peculiar conclusions, based on X-ray diffraction studies, about the co-existence of a platinum-rich solid solution as the only observed phase (the X-ray detectable phase, XRDPh) and, along with it, the diffraction-unregistered phase (the X-ray non-detectable phase, XRNDPh) [1,2,26,27].…”

Section: Introductionmentioning

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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Thermal stability of equiatomic FePt nanoclusters of different habitus with ordered and disordered structure

Sadykova,

Yakubik,

Zakharov

2023

E3S Web Conf.

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In this work, the thermal stability of FePt nanoclusters of different habitus is considered using the molecular dynamics method with the multiparticle interaction potential MEAM-2NN. Three variants of determining the temperatures of structural disorder/melting of these nanoclusters are presented: by the normalised per atom total energy of clusters from temperature, with approximation of curves by linear sections, the intersection points of which were used to determine the disorder temperatures; the second by the mean-square displacement of atoms; the third by visualisation of cross sections of atomic planes perpendicular to the face <100>. It is shown that the melting of the cluster occurs layer by layer from the surface to the volume. The temperatures of structural disorder of nanoclusters determined by different methods are in good agreement with each other.

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

Cited by 3 publications

References 24 publications

Synthesis and study of some physicochemical features of Co-Pt nanostructured system

Synthesis and study of some physicochemical features of Co-Pt nanostructured system

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

Thermal stability of equiatomic FePt nanoclusters of different habitus with ordered and disordered structure

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