The cobalt transformation

Houska, C. R.; Averbach, B.L.; Cohen, Morris

doi:10.1016/0001-6160(60)90088-2

Cited by 119 publications

(44 citation statements)

References 6 publications

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“…A hcp→ fcc phase transition is clearly visible at a temperature ϳ500Ϯ 25°C, where a sudden drop of hcp/fcc ratio is observed. The observed phase-transition temperature is higher than the previous reported 417°C for bulk Co. 1 This can be rationalized by ͑1͒ difference in particle size: the Co crystallites in this Co pow- The number is the temperature in degrees Celsius, e.g., CC200 is a sample heated to 200°C and then crash-cooled. The errors quoted refer to the errors deduced from the reproducibility of the fits from data that has undergone processing using the procedure described in the text, starting from the different sets of raw data.…”

Section: B Hcp\ Fcc Allotropic Phase Transformationmentioning

confidence: 77%

“…1 Unlike bulk Co materials, the untreated Co powder used here has an appreciable fcc phase content, approximately 20%. One would expect to observe a hcp→ fcc phase transition at a certain temperature.…”

Section: B Hcp\ Fcc Allotropic Phase Transformationmentioning

confidence: 97%

“…4 From XRD, the phase-transition temperature was found to be at 417°C, with considerable hysteresis between 390-430°C. 1 However, Kitakami et al 5 have reported that there is a close relationship between the Co crystallite size and the crystal phase. In general at room temperature, hcp is the dominant phase for Co crystallites with diameter ͑d͒ Ͼ 40 nm, fcc phase for d Յ 20 nm, and a mixture of hcp and fcc phases for d in the range of 20-40 nm.…”

Section: Introductionmentioning

confidence: 99%

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C59oNMR study of the allotropic phase transformation in small ferromagnetic cobalt particles

et al. 2009

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To demonstrate the potential of nuclear-magnetic-resonance ͑NMR͒ spectroscopy in investigating detailed structural properties in ferromagnetic materials, the allotropic phase transformation of polycrystalline cobalt with m particle size ͑Ͻ2 m͒ is characterized by internal-field 59 Co NMR. The 59 Co NMR spectra show distinct resonance bands corresponding to the different Co sites: face-centered cubic ͑fcc͒, hexagonal-close packed ͑hcp͒, and stacking faults ͑sfs͒, in Co metal powder. The hcp→ fcc phase-transition temperature is determined by systematically monitoring the signal intensity of each Co environment in a series of heat-treated Co powders. The potential limits to which absolute quantification of the different sites can be pushed are mentioned, with relative changes in intensity giving unequivocal evidence of the structural evolution. For example, the phase-transition temperature is observed to be 500Ϯ 25°C, and above this temperature, the sf Co sites were reduced by more than 10%.

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Section: B Hcp\ Fcc Allotropic Phase Transformationmentioning

confidence: 77%

Section: B Hcp\ Fcc Allotropic Phase Transformationmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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C59oNMR study of the allotropic phase transformation in small ferromagnetic cobalt particles

et al. 2009

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“…Large efforts have been devoted to the studies of adsorption of intermediates on hcp Co (0001), which is the thermodynamically most stable surface of the industrial Co catalysts at FTS condition [110][111][112][113]. The chemisorption energies of the most stable configurations for the related surface species on Co (0001) are summarized in Table 1.…”

Section: Adsorption Energies Of the Surface Speciesmentioning

confidence: 99%

Recent Progresses in Understanding of Co-Based Fischer–Tropsch Catalysis by Means of Transient Kinetic Studies and Theoretical Analysis

Yang

Chen

et al. 2014

Catal Lett

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During the last years it has been an increasing focus on fundamental studies of the Fischer-Tropsch synthesis (FTS). Steady-state isotopic transient kinetic analysis and first principles investigation have proven to be important methods in studying the reaction mechanism of FTS. The present contribution deals with recent progresses in understanding of the F-T mechanism on Co catalysts based on combined DFT calculations, in situ characterization, steady-state isotopic transient kinetic analysis and microkinetics. A brief outlook into future perspectives of the FTS for converting synthesis gas from different carbon sources to fuels and chemicals is also provided.

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“…This inhibiting effect of plastic deformation, the lowering of transformation rates, is referred to as mechanical stabilization, and has been observed in iron alloys(1-7). Plastic deformation of the parent phase is known to decrease the rates of martensitic transformations in the systems,cerium(7) and cobalt (8), as well as the iron alloys.…”

mentioning

confidence: 99%

Transformation Rates of Plastically Deformed Plutonium

Nelson¹

1966

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The cobalt transformation

Cited by 119 publications

References 6 publications

C59oNMR study of the allotropic phase transformation in small ferromagnetic cobalt particles

C59oNMR study of the allotropic phase transformation in small ferromagnetic cobalt particles

Recent Progresses in Understanding of Co-Based Fischer–Tropsch Catalysis by Means of Transient Kinetic Studies and Theoretical Analysis

Transformation Rates of Plastically Deformed Plutonium

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