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  • 1990-1994  (38)
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  • 1
    Electronic Resource
    Electronic Resource
    Thermal stability of the unstable fcc-Fe50Cu50 phase prepared by mechanical alloying (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1056-1058 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An unstable fcc-Fe50Cu50 alloy has been prepared by milling of elemental powder blends. The structure and the decomposition behavior of the alloy were studied by x-ray diffraction and Mössbauer spectroscopy. A broad distribution of different local environments of the iron atoms was observed in the fcc-FeCu phase. This indicates that Fe and Cu are mixed on an atomic level. In the initial state of decomposition, iron atoms precipitated coherently in the fcc-FeCu matrix as fcc-Fe particles. At higher annealing temperatures the particle size increased during the thermal treatment, and the fcc-Fe precipitates transformed into the bcc-Fe structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109832
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Mössbauer investigations of mechanical alloying in the Fe-Cu system (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2768-2770 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fcc-Fe50Cu50 solid solution was prepared by mechanical alloying of elemental Fe and Cu powder blends. The alloying process was studied by using x-ray diffraction and Mössbauer spectroscopy. Initially, the milling process reduced the crystallite sizes of both elemental powders. After 20 h milling, some Fe particles transformed into the fcc structure. Due to the structural similarity of the fcc-Fe and fcc-Cu phases, composites consisting of coherent Cu and Fe regions were formed. The increasing density of interfaces during further milling resulted in an interdiffusion of Cu and Fe. The alloying process was monitored by Mössbauer investigations which showed an increasing Fe concentration in fcc Cu. After 50 h of milling, the Mössbauer spectra consisted of a broadened sextet caused by a hyperfine field distribution, which demonstrates that the Fe and Cu were alloyed on an atomic level. These observations are in agreement with a model proposed by C. Gente, M. Oehring, and R. Bormann [Phys. Rev. B 48, 13244 (1993)] describing the formation of unstable alloys by mechanical alloying.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110329
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  • 3
    Electronic Resource
    Electronic Resource
    Suppression of superparamagnetism in surface-oxidized nanocrystals (1990)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 12 (1990), S. 35-43 
    Details
    ISSN: 0392-6737
    Keywords: Diamagnetism and paramagnetism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si sono preparati nanocristalli di Fe (particelle con una dimensione di alcuni nanometri) per mezzo del metodo della condensazione di gas inerti con conseguente ossidazione. La misura media delle particelle nel fine strato di ossido è stata determinata intorno ai 30 Å. Si sono studiati i campioni attraverso la spettroscopia di Mössbauer a varie temperature. In questi esempi il supermagnetismo sembra essere soppresso. Inoltre si è osservata una diminuzione del campo medio iperfino nello strato di ossido. L'anisotropia dell'interfaccia tra ossido di Fe e Fe è proposta come causa di questo fenomeno.
    Abstract: Резюме Используя метод конденсации в инертном газе с последующим окислением, приготовляутся нанокристаллы железа (частицы с размерами порядка нанометров). Средние размеры частиц в тонком слое окисла составляют около 30 Å. Полученные образцы исследуются с помощью Мессбаузровской спектроскопии при различных температурах. Наблюдается двух-ступенчатое уменьшение среднего сверхтонного поля в слоях окисла. Предполагается, что анизотропия границы раздела между окислом железа и железом является ответственной за это явление.
    Notes: Summary Fe nanocrystals (particles with a size of some nanometers) were prepared by the inert-gas condensation method with subsequent oxidization. The average size of the particles in the thin oxide layer was determined to be about 30 Å. The samples were studied by Mössbauer spectroscopy at various temperatures. Superparamagnetism seems to be suppressed in these samples. Furthermore, a two-stage decrease of the average hyperfine field was observed in the oxide layer. The Fe oxide-Fe interface anisotropy is proposed to be responsible for this phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02453024
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  • 4
    Electronic Resource
    Electronic Resource
    57Fe Mössbauer study of YBa4Cu2.95Fe0.05O8.5+y (1991)
    Springer
    Applied physics 53 (1991), S. 426-429 
    Details
    ISSN: 1432-0630
    Keywords: 74.70.Vy ; 76.80.+y
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract 57Fe Mössbauer measurements were performed on the Fe-doped YBa4Cu3O8.5+y compound as a function of annealing temperature in vacuum. Mössbauer spectra were analyzed using three different quadrupole split doublets. The resistance measurements showed that the compound is not superconducting. The possible identification of the Cu sites with their nearest neighbor oxygen sites in this compound is suggested. Comparison of the results with data of the presence of the superconductor YBa2Cu3O7 allows us to suppose that the presence of the Cu-chain sites alone does not result in superconductivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348157
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Laser remelting of cast iron: a Mössbauer study (1991)
    Springer
    Journal of materials science 26 (1991), S. 5019-5024 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The Mössbauer spectroscopy in backscattering technique (CXMS) was used to analyse cw-CO2 laser-treated samples of cast iron. The depth profile as revealed by Mössbauer phase analysis is discussed in connection with the initial microstructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00549886
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetism of nanocrystalline materials (1990)
    Springer
    Hyperfine interactions 54 (1990), S. 591-597 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Nanocrystalline solids are materials consisting of small crystallites (typically 1–10 nanometers). These materials have a high proportion of atoms located in the interfacial regions between the crystallites. Therefore their magnetic properties are strongly determined by the interfaces. In this work we present Mössbauer studies carried out on various nanocrystalline materials. Beneath the normal crystalline component the Mössbauer spectra clearly indicate the existence of an component with modified magnetic properties which corresponds to the interfaces in this type of material. For nanocrystalline α-Fe an enhancement of the hyperfine field was observed in the interfacial component at low temperatures, whereas a decrease was found for nanocrystalline Ni.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396095
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  • 7
    Electronic Resource
    Electronic Resource
    Crystallization of Fe-B amorphous alloy powders produced by chemical reduction (1990)
    Springer
    Hyperfine interactions 55 (1990), S. 981-985 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The crystallization behaviour of the Fe−B amorphous alloy powders prepared by the chemical reduction method has been investigated by Mössbauer spectroscopy. In comparison to amorphous ribbons prepared by melt-spinning, a different crystallization behaviour has been observed. After annealing the amorphous samples entirely crystallized into three crystalline phases: α-Fe, Fe3B, and Fe2B. In the case of Fe80B20 amorphous alloy ribbons produced by melt-spinning technique eutectic crystallization is commonly observed and results in the crystalline phases: α-Fe and Fe3B. This kind of crystallization was not observed in the chemically prepared samples. The metastable tetragonal Fe3B phase transformed completely into α-Fe and Fe2B after annealing at 973 K for one hour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397110
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  • 8
    Electronic Resource
    Electronic Resource
    Correlations between hyperfine parameters of Fe−Ni-B amorphous metals (1990)
    Springer
    Hyperfine interactions 55 (1990), S. 1001-1007 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The correlations between fluctuations in the57Fe Mössbauer hyperfine parameters of the amorphous alloys (Fe0.5Ni0.5)100−x B x (x=16, 18, 20, 22 and 25 at%) and FeyNi80−y B20 (y=20, 25, 40 and 60 at%) have been determined. Values of the correlation between the fluctuations of the isomer shift and the fluctuations of magnetic hyperfine field, μN 〈ΔHΔδ〉 together with published values on similar amorphous systems are compared with correlation values for related crystalline phases. The lack of characteristic values suggests that the correlation values do not allow a link to be made between local structural units in amorphous alloy and crystalline phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397113
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  • 9
    Electronic Resource
    Electronic Resource
    Mössbauer study of the stability of Fe5Si95 produced by inert gas condensation (1992)
    Springer
    Hyperfine interactions 69 (1992), S. 655-658 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Fe5Si95 specimens with an enhanced solubility of Fe in Si by about twenty-one orders of magnitude relative to crystalline Si at room temperature were prepared by the inert gas condensation technique. The thermal stability of the Fe5Si95 sample was investigated by Mössbauer spectroscopy. The spectrum of the as-prepared Fe5Si95 exhibited a broadened many different iron sites in the sample. This material was thermal stable up to temperatures of 673k for one hour. After annealing at 773K for one hour, the intermetallic compound α-FeSi2 was formed in the annealed sample, probably via the precipitation process. The amount of the α-FeSi2 phase increased with the annealing temperature. No β-FeSi2 phase was observes in any of the annealed samples up to an annealing temperature of 1273K For one hour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02401912
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  • 10
    Electronic Resource
    Electronic Resource
    Distribution of hyperfine fields of57Fe2+ in amorphous LiNbO3: Mössbauer study at low temperatures in high magnetic fields (1992)
    Springer
    Hyperfine interactions 69 (1992), S. 667-671 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mössbauer spectra of amorphous LiNbO3 doped with57Fe2+ ions were measured atT≥4.2 K in external magnetic fields up toH=5.5 T. It was found that the oxygen octahedra around the high-spin Fe2+ ions are randomly distorted obeying no symmetry at all. The correlation of isomer shift and quadrupole splitting is probably due to T2g distortions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02401915
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