Natural formation of bcc Co: Initial stage of Co precipitation in supersaturated<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Au</mml:mtext></mml:mrow><mml:mrow><mml:mn>90</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>Co</mml:mtext></mml:mrow><mml:mrow><mml:mn>10</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Bauer, Rico; Bischoff, E.; Mittemeijer, E. J.

doi:10.1103/physrevb.81.094113

Cited by 8 publications

(11 citation statements)

References 27 publications

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“…Tables 1 and 2) and the peak maximum heights (see Fig. 3) could result from slight microstructural differences between the specimens, e. g. different amounts of strains induced upon quenching [11] and due to measurement errors in particular at low heating rate and at low isothermal temperature (small signals).…”

Section: Differential Scanning Calorimetrymentioning

confidence: 96%

“…2. The small exothermic valley-like signal, before the appearance of the strong exothermic signal, is ascribed to relaxation of quenched-in strains [11]. This small exothermic relaxation peak, exhibiting a heat release of about -80 J mol -1 for all heating rates applied, has been substituted by a zero heat signal in the following graphs of DSC results (see Fig.…”

Section: Differential Scanning Calorimetrymentioning

confidence: 97%

“…In the as-quenched specimens the Bragg peaks observed show a modest but significant broadening. This is due to thermal stresses and lattice defects evolving upon quenching as (i) dislocations [11] and (ii) quenched-in vacancies [32].…”

Section: X-ray Diffractometrymentioning

confidence: 99%

“…After annealing in a temperature range from 743 K to 838 K of initially homogeneous and quenched Au-Co alloys, the formation of disc-shaped Co precipitates claimed to be of fcc crystal structure was found with the platelets aligned along {001} Au planes in the majority of cases, [3 -9] but also along {111} Au planes [10]. Recently it was proven by experiment that the initially formed disc-shaped Co precipitates exhibit a bcc crystal structure [11]. Very little information on the kinetics of the Co precipitation reaction is available.…”

Section: Introductionmentioning

confidence: 99%

“…Such work is deemed timely in view of (i) the recent recognition that the initial precipitates have a bcc (rather than a fcc) crystal structure [11], and (ii) the recent availability of a modular model for transformation kinetics that is much less constrained than the classical JMA approach [13,14]. The kinetics of the Co precipitation process in a supersaturated solid solution of Au-10.12 at.% Co has been deduced from both isothermal and isochronal annealing experiments performed in a differential scanning calorimeter (DSC).…”

Section: Introductionmentioning

confidence: 99%

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Precipitation of Co from supersaturated Au₉₀Co₁₀: microstructure and kinetics

Bauer

Bischoff

Mittemeijer

2011

International Journal of Materials Research

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Precipitation of Co from supersaturated Au 90 Co 10 : microstructure and kineticsThe kinetics of the precipitation of Co from a supersaturated solid solution of Au-10.12 at.% Co was investigated by differential scanning calorimetry upon isothermal annealing at temperatures in the range from 567 K to 612 K and upon isochronal annealing at heating rates between 5 K min -1 and 40 K min -1 . The microstructural evolution during the course of precipitation was traced by (high-resolution) transmission electron microscopy, scanning electron microscopy, X-ray diffraction and hardness measurements. First, the exothermic formation of 0.5 -1 nm thin plate-like bcc Co precipitates takes place parallel to {100} habit planes of the Au-matrix. Upon continued annealing, equiaxed fcc Co particles in epitaxial orientation with the Au lattice occur by a Bain-type transformation of the Co particles from the bcc to the fcc lattice structure associated with loss of coherency. Fitting of a modular model of transformation kinetics (Liu et al., Int. Mat. Rev. 52 (2007) 193) simultaneously to the first peak of all isothermal differential scanning calorimetry runs and simultaneously to the first peak of all isochronal differential scanning calorimetry runs demonstrated that the nucleation of bcc Co plates is governed by site saturation in the case of isothermal annealing and continuous nucleation in the case of isochronal annealing, and by linear growth for both isothermal and isochronal annealing. The activation energy for growth is remarkably small due to the presence of quenched-in vacancies. Recovery prior to precipitation leads to a change of the nucleation mechanism from site saturation to continuous nucleation as well as an increase in the activation energy for growth.

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Section: Differential Scanning Calorimetrymentioning

confidence: 96%

Section: Differential Scanning Calorimetrymentioning

confidence: 97%

Section: X-ray Diffractometrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Precipitation of Co from supersaturated Au₉₀Co₁₀: microstructure and kinetics

Bauer

Bischoff

Mittemeijer

2011

International Journal of Materials Research

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Structural and magnetic properties of large cobalt clusters

2016

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We use a real-space implementation of pseudopotentials within the density-functional theory to investigate the structural and magnetic properties of cobalt clusters with up to 365 atoms. We find from structural optimization that hexagonal close-packed (hcp) and icosahedral clusters are lower in energy than body-centered cubic (bcc) and face-centered cubic (fcc) ones. We find the calculated magnetic moments generally decrease as a function of increasing cluster size. For clusters of several hundred atoms the bulk limit becomes apparent. However, the decrease is not monotonic. It depends on the details of the interior structure of the cluster and the corresponding surface geometry. By analyzing the detailed evolution of the local magnetic moment, we find the spin moment is bulk-like in the cluster interior and increases in the vicinity of the surface and can be correlated with coordination. The calculated behavior accounts for the observed variations in the measured moments.

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