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  • 1990-1994  (19)
  • 1
    Electronic Resource
    Electronic Resource
    Mechanical Characteristics of Nanostructure Zinc (1994)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 170-172 (Oct. 1994), p. 147-152 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/00/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.170-172.147.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Perturbed Angular Correlations Studies of Alloys (1991)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 37 (Jan. 1991), p. 139-150 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/05/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.37.139.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Deuteron tunneling at electron-volt energies (1990)
    Springer
    Journal of fusion energy 9 (1990), S. 409-411 
    Details
    ISSN: 1572-9591
    Keywords: Fusion (theory) ; cold fusion ; deuteron tunneling ; nuclear reactions ; electron conversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We speculate on a new mechanism for deuteron-deuteron fusion reactions at electron-volt energies. Appealing to conservation principles, it is shown that deuteron tunneling leading to fusion is very unlikely to take place between two isolated deuterons. It is argued that in solids, however, tunneling may lead to fusion via a new reaction mechanism which populates energy levels of4He, with simultaneous energy transfer to an electron. Predictions of this theory are that d+d+e− fusion at electron-volt energies in solids should lead to copious production of tritium, protium, energetic electrons, and small quantities of4He.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01588270
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  • 4
    Electronic Resource
    Electronic Resource
    Electrolytic loading of hydrogen in metals studied by PAC (1990)
    Springer
    Hyperfine interactions 60 (1990), S. 663-666 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In previous work, we introduced hydrogen (H) into Ni and Pt metals at room temperature by electrolysis. To study H-vacancy interactions on an atomic scale, trapping of diffusing H atoms at impurity-vancancy complexes was detected using perturbed γ-γ angular correlations. Two new results are reported here: (1) Transformation rules are clarified between undecorated and H-decorated complexes which are detected after annealing Pt at 323 K. In addition, non-cubic In sites were observed to form by chargingannealed, Pt, which are attiributed either to H atoms at random in the lattice or to precursor nuclei of a Pt hydride. (2) NiH is observed to form under cathodic charging of Ni at high current densities, and detected by growth of a nonmagnetic, cubic metastable phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399840
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  • 5
    Electronic Resource
    Electronic Resource
    Laser surface-melting of metals studied by PAC (1990)
    Springer
    Hyperfine interactions 61 (1990), S. 1339-1342 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High purity Pt, Ni, Cu, Fe and Al metal foils were electroplated with carrier-free111In probe atoms and melted at 293 K using 32 ns ruby laser pulses with energy densities in the range 1–10 J cm−2. Three distinct lattice locations of the probe atoms were detected in the melted surface layers using perturbed γ-γ angular correlation spectroscopy: (i) defect-free substitutional sites, (ii) non-unique sites with broad distributions of quadrupole interactions, and (iii) a probemonovacancy complex (for Pt only). The defect-free fraction was found to approach 100% when Pt is irradiated at 9 J cm−2. The fraction of probes on defect-free sites was found to increase with the energy density of the pulse and with the solubility of In in the metals. The data are consistent with the idea that laser surface-melting produces high concentrations of vacancies and lattice sinks, although no thermal trapping of point defects was detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407620
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrogen binding in vacancy clusters in platinum (1993)
    Springer
    Hyperfine interactions 79 (1993), S. 749-753 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The binding of hydrogen in different vacancy complexes in platinum metal was investigated with atomic-scale sensitivity using perturbed angular correlations of gamma rays (PAC). Hydrogen was introduced by cathodic charging. Detrapping was monitored microscopically during desorption at 294 K by changes in site fractions of hydrogen-decorated and undecorated complexes. Analysis of desorption includes effects of retrapping of hydrogen at other sites. Assuming a trap concentration of 10−3, binding enthalpies of 0.23(2), 0.28(1), 0.24(1) and 〉0.20 eV are obtained for hydrogen atoms in 1V to 4V complexes, respectively. The small differences between the binding enthalpies demonstrate that hydrogen binding is insensitive to the detailed geometrical structure of small vacancy complexes. However, the magnitudes found here are a factor of two smaller than in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567603
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  • 7
    Electronic Resource
    Electronic Resource
    Grain boundary sites in fcc metals studied by PAC (1993)
    Springer
    Hyperfine interactions 79 (1993), S. 761-764 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Perturbed angular correlation of gamma rays (PAC) is applied to study the atomic structure of grain boundaries (gb) in fcc metals using nuclear quadrupole interactions.111In probes were diffused in samples of Au, Cu, Ni and Pt which had first been annealed to form high-angle gbs. Diffusions were carried out at such low temperatures that only gb diffusion should occur (Harrison's type-C kinetic regime), and measurements were made after removing any residual surface activity. For three Pt samples, a unique signal attributed to a gb site was detected with a site fraction of about 50%, coupling frequency ω1=80.0(2) Mrad/s and electric-field-gradient asymmetry parameter η=0. A Pt sample of 99.9995% purity exhibited much less inhomogeneous signal broadening than 99.998% pure samples, indicating the level of purity necessary to observe the gb sites via quadrupole interactions. The broadening is attributed to gb segregation. For Au, Cu and Ni, only ill-defined, non-unique signals were detected, apparently because of gb segregation. The small broadening in the high-purity Pt sample indicates a high degree of uniformity in the crystal structure of the high-angle gb sites. The large site fraction of the 80 Mrad/s signal demonstrates the dominance of a single site for Cd probes in high-angle gbs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567605
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  • 8
    Electronic Resource
    Electronic Resource
    Indium metal nanoclusters studied by PAC (1993)
    Springer
    Hyperfine interactions 80 (1993), S. 1117-1120 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The technique of perturbed angular correlations of gamma rays (PAC) is applied for the first time to study the structure of small metal clusters. Metal clusters containing111In probe atoms with 50 nm radii were synthesized by dissolving InCl3 containing111In in hexane using a surfactant, thereby creating an inverse micellar solution. The salt was then reduced to metal form by addition of NaBH4. 100% conversion efficiency of In salt to metal clusters was achieved. PAC measurements at 293 K on the111Cd daughter nuclide exhibited a nuclear quadrupole interaction with coupling frequency ω0=16.0(5) Mrad/s and a small asymmetry parameter, η=0.20(4). The frequency is as observed for bulk In crystals, but a non-zero value of η has not been previously reported. Lack of inhomogeneous signal broadening and the faceted shape of some nanoclusters suggest high crystal perfection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567473
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  • 9
    Electronic Resource
    Electronic Resource
    Application of PAC to study equilibrium point defects in intermetallic compounds (1993)
    Springer
    Hyperfine interactions 80 (1993), S. 1257-1261 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new method has been developed to measure properties of equilibrium, or thermal, defects in intermetallics using the technique of perturbed angular correlations of gamma rays (PAC). After quenching, thermal defects are detected microscopically by distinctive nuclear hyperfine interaction signals produced when they localize next to probe atoms present in high dilution. Using a Schottky defect model and applying the law of mass action to defect equilibria, a linear Arrhenius temperature dependence is predicted for a “normalized” monovacancy site fraction. We have observed such linear dependences in PAC experiments on NiAl, CoAl and TiAl using the111In probe. Features of the method are summarized, of which the most important are the abilities to discriminate between different defects and to determine absolute vacancy concentrations, formation enthalpies and entropies. Extremely large formation entropies have been obtained for NiAl, CoAl and TiAl, suggesting vacancy concentrations of ∼ 15% at the melting temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567488
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  • 10
    Electronic Resource
    Electronic Resource
    Equilibrium point defects in TiAl studied by PAC (1993)
    Springer
    Hyperfine interactions 79 (1993), S. 745-748 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Site fractions of dilute111In/111Cd probe atoms in different lattice locations in quenched, equi-atomic TiAl are measured using perturbed angular correlations of gamma rays (PAC). The vacancy-free substitutional site fraction, observed via its nuclear quadrupole interaction, is observed to decrease with increasing quenching temperature, reflecting an increase in the thermal defect concentration. Assuming that the thermal defect is the Schottky defect, the law of mass action, and a binding energy of 0.2 eV between vacancies and the In probe, the experimental temperature dependence is analysed to yield a formation enthalpy of 4.7(4) eV and entropy of 25(4)k B for the Schottky defect. The vacancy concentration on one sublattice is given in terms of these parameters by the expression [v]=exp(S F/2k B) exp(−E F/2k B T), and is found, for example, to have the value 1.4% at 1350°C, a large value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567602
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