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  • 1990-1994  (38)
  • 1975-1979  (4)
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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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  • 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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  • 5
    Electronic Resource
    Electronic Resource
    Determination of cation distribution in Ti4+ and Co2+ substituted barium ferrite by Mössbauer spectroscopy (1976)
    Springer
    Applied physics 10 (1976), S. 175-180 
    Details
    ISSN: 1432-0630
    Keywords: 75.30 ; 76
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In barium ferrite, BaFe12O19, the Fe3+ ions were gradually substituted by Ti4+ and Co2+. The cation distribution of the various lattice sites is determined as a function of the degree of replacement. The preferred site population is discussed by a substitution model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00896336
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  • 6
    Electronic Resource
    Electronic Resource
    Book reviews (1976)
    Springer
    Applied physics 11 (1976), S. 310-312 
    Details
    ISSN: 1432-0630
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897073
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  • 7
    Electronic Resource
    Electronic Resource
    Photorefractive centers in LiNbO3, studied by optical-, Mössbauer- and EPR-methods (1977)
    Springer
    Applied physics 12 (1977), S. 355-368 
    Details
    ISSN: 1432-0630
    Keywords: 78.20 ; 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The photorefractive properties of LiNbO3∶Fe and LiNbO3∶Cu have been studied in combination with optical absorption-, Mössbauer- and EPR-measurements. The charge states of Fe in successively reduced LiNbO3∶Fe have been investigated with respect to the influence on the photorefractive sensitivity and saturation value of the refractive index change. The results of this experiment demonstrate clearly the close correlation between the concentration of Fe2+ impurities and the optical absorption band around 2.6 eV in LiNbO3∶Fe, which is known to give rise to an anisotropic charge transport upon optical excitation. The resulting photocurrents determine the photorefractive sensitivity mainly in the initial state of halographic exposure. With increasing conversion from Fe3+ to Fe2+ the photorefractive sensitivity saturates and the saturation value of the refractive index change decreases remarkably. In the case of LiNbO3∶Cu a similar behaviour of the photorefractive storage parameters after successive reduction treatments has been observed qualitatively. However, in contradiction to LiNbO3∶Fe the Cu2+ centers cannot be related to the photorefractive sensitivity of LiNbO3∶Cu. These results are discussed with respect to the predictions of two models concerning the microscopic nature of the photorefractive process in doped LiNbO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00886038
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  • 8
    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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  • 9
    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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  • 10
    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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