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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3365-3370 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanocrystalline Fe-Cu-Si-B alloys with grain sizes of 25–90 nm were synthesized by crystallization of the amorphous alloy. Two nanocrystalline phases of α-Fe(Si) and Fe2B were observed in all tested samples. Transmission Mössbauer spectroscopy investigation on the structure of nanocrystalline Fe-Cu-Si-B alloys showed that Si atoms are completely and substitutionally dissolved in Fe bcc lattice and the arrangement of the Si atoms in the α-Fe(Si) phase shows short range order (SRO), whereas 8.5–9.7 at. % of the B atoms were found as Fe2B and the remainder were located in the interfaces. When grains grow larger, the arrangement of the Si atoms in the α-Fe(Si) phase changes. Interestingly, x-ray diffraction results reveal that the lattice constant of α-Fe(Si) phase decreases rapidly with grain coarsening. Based on the thermodynamic analysis, the changes in the lattice constant of the α-Fe(Si) phase and SRO of Si atoms in bcc Fe lattices were attributed to the lattice expansion as a result of the variation of vacancy concentration in α-Fe(Si) solid solution. Meanwhile, owing to the interface contribution, the alloy with small grain size is found to exhibit large values of half linewidth (HLW) and isomer shift (IS) in the Mössbauer spectra. The results from electrical resistivity measurements agree and confirm the strong effects of the lattice distortion and interfaces.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6408-6414 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Grain growth and strain release processes in the electrodeposited nanocrystalline (nc) Cu specimen with a high purity were investigated by means of differential scanning calorimetry, x-ray diffraction, electrical resistance measurement, and high-resolution transmission electron microscopy. It was found that for the as-deposited nc Cu, the grain growth started at about 75 °C, at which the microstrain in (111) plane (e111) began to release, while the mean microstrain and that in (100) plane (e100) began to release at a higher temperature (150 °C). With an increment in microstrain in the nc Cu introduced by cold rolling, the grain growth onset temperature increased while the strain release onset temperature dropped obviously. These results showed an evident correlation between the grain size stability and the microstrain in the nc materials. The activation energy for the grain growth was determined by using Kissinger analysis and isothermal kinetics analysis, being about 86 kJ/mol, implying that the grain growth process is dominated by grain boundary diffusion. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5124-5129 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline Fe78B13Si9 alloys with nanoscale grain sizes prepared by the crystallization method have been studied by positron lifetime and Doppler-broadened line-shape measurements. The results obtained are different from those on amorphous or coarse-grained crystalline alloys with the same composition. When the grain sizes are clearly smaller than the mean positron diffusion length (L+(approximately-equal-to)100 nm), saturation trapping and annihilation of the positrons in the samples should occur at traps within the interfaces. There are two kinds of defects in the interfaces of the nanocrystalline FeBSi alloys, i.e., the free volumes (the size of which is slightly smaller than that of the amorphous counterpart) and the microvoids. The dependence of grain sizes on the type of interface defects and structure-sensitive properties has also been studied by positron spectroscopy. The measurements and comparison of the mean positron lifetime τ¯ and the Doppler parameter S on the nanocrystalline, amorphous, and coarse-grained crystalline alloys have given a satisfactory explanation for the relationship between the structure-sensitive properties, grain sizes, and crystalline states.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 654-656 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to clarify the formation mechanism of extremely fine-grained microstructures by crystallization of the FeBSi metallic glass, the nucleation and crystal-growth rates have been determined. The results indicate that the parabolic growth rate increases with annealing temperature, showing a maximum nucleation rate at an intermediate temperature range. Obviously it is possible to obtain nanocrystalline structures by controlling crystallization of the metallic glass on annealing at temperatures near the maximum nucleation rate.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6165-6169 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin film reactions of Cu/Al multilayer films were investigated by differential scanning calorimetry and transmission electron microscopy. Sequential intermetallic compound formation was found in the temperature range from 300 to 620 K. With excess copper present in the as-deposited trilayer and multilayer films, the observed sequence was CuAl2 and Cu9Al4, and the interfacial reactions were controlled by interfacial and grain boundary diffusion. The activation energies for the formation of CuAl2 and Cu9Al4 are 0.78±0.11 and 0.83±0.2 eV, respectively.
    Type of Medium: Electronic Resource
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