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  • Mössbauer  (2)
  • iron-based catalysts  (1)
  • 1
    ISSN: 1572-9028
    Keywords: Mössbauer spectroscopy ; Fischer-Tropsch synthesis ; iron-based catalysts ; χ-carbide ; magnetite ; water-gas shift activity ; pretreatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mössbauer spectroscopy investigation of iron-based Fischer-Tropsch (FT) catalysts from the US Department of Energy's LaPorte pilot plant demonstration run (August 1992) has revealed that the ratio of iron in the octahedral site to that in the tetrahedral site in magnetite correlates with the water-gas-shift activity. Studies of the catalysts from laboratory-scale fixed-bed reactor indicate that activation of the oxide precursor with CO results in the formation of χ-carbide (Fe5C2) whose amount decreases with increasing SiO2 content in the catalyst. The Fe5C2 is converted into Fe3O4 during FT synthesis. The FT activity of the catalyst is found to follow the trend of χ-carbide variation indicating that χ-carbide is active for the FT synthesis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 10 (1976), S. 377-401 
    ISSN: 1573-4889
    Keywords: oxidation ; iron ; Mössbauer ; electron re-emission ; ERM spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The results of an electron re-emission Mössbauer (ERM) spectroscopy study of the oxidation of metallic Fe at temperatures from 150 to 500°C in pure oxygen ( $${\text{p}}_{{\text{O}}_{\text{2}} } \approx {\text{ }}10$$ Torr) are presented. The oxidized samples were prepared from a metallic Fe sample enriched to 70% in the Mössbauer isotope Fe57 and the oxidation kinetics were determined volumetrically. Scanning electron microscopy was employed to characterize the morphology of the oxide films. The hematite, magnetite, and total-oxide thicknesses were determined from the ERM spectra using a theory recently developed in this laboratory, and the results were found to agree well with the measured oxygen content of the oxide films. For Fe and Fe-base alloys it is shown that the ERM technique is most useful in the oxide-thickness range of approximately 20–3000 Å within that range, oxide-phase identifications and thickness determinations are perhaps more readily determined by ERM spectroscopy than by any competing technique. In particular, the ERM measurement is nondestructive, and no supplementary measurements (such as surface-roughness determinations) or special sample preparations (such as oxide-film stripping) are required
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4889
    Keywords: oxidation ; iron ; Mössbauer ; conversion electron ; ERM Spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A reanalysis of earlier electron reemission Mössbauer (ERM) data obtained from iron oxidized in pure oxygen at 150 to 500°C is presented. The new data analysis utilized the same theoretical method used previously, but with significantly altered values for the electron attenuation coefficients determined from recent experimental work by Graham, Mitchell, and Channing. The recalculated oxide-thickness values were found to be in much better agreement with the volumetrically measured oxygen uptake.
    Type of Medium: Electronic Resource
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