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  • 1990-1994  (6)
  • 1990  (6)
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  • 1990-1994  (6)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Mössbauer kinetics study of the clustering-ordering synergy during the ageing of high carbon Fe−C martensite (1990)
    Springer
    Hyperfine interactions 54 (1990), S. 869-876 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The kinetics of the isochronal ageing of 1.7–1.9 wt% C iron martensite made from 200 K to 450 K is done by following the Mössbauer spectra run at 10 K intervals for varying ageing times of 1, 10 and 100 hours. A new analysis, similar to that used in constant heating rate measurements of resistivity, calorimetry and dilatometry, is made here and shows that the two steps of clustering and ordering prior the in situ transformation into ε-η carbide have exactly the same activation energy of 75±2.5 and 74±1.5 kJ.mol−1, respectively. The clustering-ordering synergy is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396142
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Superparamagnetic behaviour of goethite prepared in sulphated medium (1990)
    Springer
    Hyperfine interactions 57 (1990), S. 2037-2043 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The formation of goethite is simulated by stirring up in the presence of air a mixture of FeSO4, 7H2O and NaOH in the 1∶5 ratio at different initial concentrationC of ferrous ions. Mössbauer spectra of the oxidation end products display the sextet of goethite (αFeOOH) and a paramagnetic ferric doublet increasing whenC decreases; the crystal structure of goethite is also being modified. At a critical low concentration, the orthorhombic structure is no longer justified; inactive α′-FeOOH, which has a similar X-ray diffraction pattern as δ-FeOOH is obtained. All these compounds are crystallographically related.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405761
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The substitution of chloride ions to OH−-Ions in the akaganeite beta ferric oxyhydroxide studied by Mössbauer effect (1990)
    Springer
    Hyperfine interactions 57 (1990), S. 2067-2075 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The formation of the β allotropic form of ferric oxyhydroxide is obtained by oxidation of iron when done in chlorinated aqueous media of high concentration. The Mössbauer study of samples prepared invarious conditions display three ferric ions where the intensities of two of them are always in the 2:1 ratio. One infers that it is due to the substitution of OH−ions by Cl− ions. These two iron environments differ essentially by the relative orientation of the axis of the electric field gradient with respect to the fourfold axis of symmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405765
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Mössbauer study of the hydrogen induced martensitic transformation in high carbon Fe−C martensite and its ageing behaviour (1990)
    Springer
    Hyperfine interactions 54 (1990), S. 877-881 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Cathodic hydrogen charging at low current density at room temperature in acidic medium is carried out on an austenitic 1.9 wt% C iron alloy. This induces the martensitic transformation as checked by Mössbauer spectroscopy and the spectra observed at room temperature present all the features of an already aged martensite. Further ageing at higher temperatures up to 390 K clearly demonstrates that the ageing kinetics is stopped compared to that of uncharged martensite of a similar alloy. Further, in situ transformation of extended multiplets into ε-η carbide precipitates resumes at the same temperature in both cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396143
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of formation of green rust 2 in the steady acidic sulphated medium (1990)
    Springer
    Hyperfine interactions 57 (1990), S. 2029-2035 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The kinetics of formation of green rust 2, 4Fe(OH)2.2FeOOH.FeSO4.nH2O, called “GR2, was followed by Mössbauer spectroscopy in the controlled aeration of a mixture of 0.4 M FeSO4 and 0.4 M NaOH. Mössbauer spectra run at 78 K of the reaction products taken at different time intervals display an average of seven doublets. The initial products of reaction consists of a badly crystallized ferrous hydroxide, FE(OH)2., called “FH”, which disappears first at about 1/3 of the total time of formation of GR2, and sulphated ferrous hydroxide, 4Fe(OH)2.FeSO4.nH2O, called “SFH”. The kinetics of oxidation of SFH into GR2 can be described by a linear growth reaction and the transformation is considered to be in situ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405760
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The substitution of Fe2+ ions by Ni2+ ions in the green rust 2 compound studied by Mössbauer effect (1990)
    Springer
    Hyperfine interactions 57 (1990), S. 2061-2066 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Green rust 2 is usually obtained by oxidizing an initial mixture of FeSO4 and NaOH solutions and a complete oxidation leads mainly towards γ oxyhydroxide known as lepidorocite. By adding some NiSO4 one can stop at the first stage and Mössbauer spectra reveral only ferric doublets. This implies that the initial formula 4Fe(OH)2, 2FeOOH, FeSO4 of green rust 2 must be replaced byxNi(OH)2, (6−x)FeOOH, NiSO4, wherex scans from 2 to 4. It also means that all initial ferrous ions become oxidized into the ferric state leaving the Ni2+ ions unchanged. Therefore the end product of oxidation is the nickel containing green rust 2 at the place of the usual lepidocrocite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405764
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    Paper (German National Licenses)
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