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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
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    The martensitic phase transition in NiTi (1993)
    Springer
    Hyperfine interactions 80 (1993), S. 995-998 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The technique of perturbed angular correlation of gamma rays (PAC) was applied to study the martensitic phase transition of a shape-memory-effect alloy Ni49.9Ti50.1 doped with111In/Cd probe atoms. Spectra measured above and below the martensite starting temperature,M s ≈ 340 K, exhibit quadrupole interactions of probes at cubic and noncubic lattice sites, consistent with the respective crystal structures. Unlike spectra measured belowM s those measured above exhibit a large frequency distribution attributed to lattice displacement waves observed in diffraction studies. Analysis tentatively suggests that the waves are dynamic and not static. BelowM s, at 290 K, a static quadrupole interaction was observed with coupling frequency ω1=34 Mrad/s and asymmetry parameter η=0.18, increasing to ω1=40.5 Mrad/s and η=0.34 at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567453
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Mössbauer and PAC studies of nanocrystalline Fe (1994)
    Springer
    Hyperfine interactions 92 (1994), S. 949-953 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High-purity Fe powder was mechanically milled under argon at ambient temperature using an SPEX 8000 mill. The local atomic and magnetic structure was studied using57Co/Fe Mössbauer and111In/Cd perturbed angular correlations (PAC) spectroscopies. After 32 hours of milling, X-ray diffraction revealed effective grain diameters of 18 nm and energy-dispersive X-ray analysis indicated a Cr impurity concentration of ∼5%, presumably introduced by mechanical attrition of steel ball bearings used for milling. In addition to a spectral component very similar to bulk iron metal, the Mössbauer spectra exhibited hyperfine field shifts attributed to the Cr impurities. PAC spectra on Fe milled for 5 h, with no contamination, exhibited two components: (1) A slightly broadened magnetic interaction attributed to interior, defect-free sites of In/Cd probes with a mean hyperfine field slightly greater than in macroscopic grains. The defect-free site fraction grew appreciably during milling, even though In is essentially insoluble in Fe. (2) An indistinct signal due to mixed magnetic and quadrupole interactions attributed to probes at surface or other defect sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065717
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  • 9
    Electronic Resource
    Electronic Resource
    Formation of Ni3Fe by mechanical alloying (1994)
    Springer
    Hyperfine interactions 92 (1994), S. 955-958 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ni and Fe powders in a 75∶25 atomic proportion were mechanically alloyed using a high-energy ball mill.57Fe Mössbauer measurements were made to determine the reaction mechanism for alloy formation by means of analysis of the evolution of the Fe hyperfine fields during milling. After a latent period of 2 hours, the spectral area of an Fe-like component decreased monotonically with milling time, disappearing after 8 hours. It was replaced by a well-resolved Zeeman pattern with hyperfine fieldH=29.1 T and outer lines of width 0.75 mm/s which is attributed to Fe in disordered Ni3Fe. The evolution of hyperfine fields rules out alloy formation by dissolution of Ni in the Fe matrix or of Fe in the Ni matrix, so that formation must occur by reaction of Ni and Fe at the interfaces between their grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065718
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  • 10
    Electronic Resource
    Electronic Resource
    Cage motion of a probe atom in a vacancy complex in Pt (1990)
    Springer
    Hyperfine interactions 60 (1990), S. 651-653 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The perturbation function of a Cd probe atom bound in a hydrogen-decorated vacancy complex in Pt is found to exhibit dynamical relaxation at 294 K, as measured by the technique of perturbed γ-γ angular correlations. Based on other characteristics of the complex, a model is proposed for the structure of the complex. In the undecorated state, it consists of a probe atom at the center of a tetrahedron of vacancies in the fcc structure. In the decorated state at low temperature, the probe atom returns to one of the four vacant lattice sites. The relaxation at room temperature is attributed to motion of the probe atom in a cage formed by the four vacant sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399837
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