Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Electronic Resource  (6)
  • 1990-1994  (6)
Source
Material
  • Electronic Resource  (6)
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    A Study of FeC2 and FeC2H by Anion Photoelectron Spectroscopy (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 11814-11817 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100097a002
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Point defects in NiAl near the equiatomic composition (1990)
    Springer
    Hyperfine interactions 60 (1990), S. 655-658 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Perturbed γ-γ angular correlation spectroscopy was applied to study the structure and properties of point defects near111In probes in quenched and annealed NiAl samples with five compositions in the range cNi=48–52%. Quadrupole interaction signals are analysed in terms of near-neighbor Ni-vacancy and nextnear-neighbor Ni antisite atom defects. Large mono- and divacancy concentrations were observed in all samples after quenching. For cNi〈50%, the vacancy defects could not be annealed out (structural defects). For CNi〉50%, large quenched-in vacancy concentrations annealed out near 500°C. For cNi=50%, most vacancies annealed out near 500°C, but about 35% of the111In probes retained a trapped monovacancy. This is attributed to a very low value of the formation enthalpy of a vacancy next to the In probe, estimated to be 0.16(2) eV. A lesser annelaing stage detected at 300°C is tentatively attributed to diffusion of Al-vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399838
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Perturbed γ−γ angular correlations: A spectroscopy for point defects in metals and alloys (1990)
    Springer
    Hyperfine interactions 62 (1990), S. 1-34 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Atomic defects which migrate and trap at impurity probe atoms can be labelled by the changes they induce in the hyperfine interactions of the probe nuclei. Many studies have been made using perturbed γ−γ angular correlations (PAC) and the111In probe because of the excellent resolution of different sites. Identification of the bound states is the key problem in applying hyperfine interactions methods to point defects studies. In this study three structure-sensitive methods are applied to help identify the atomic structures of various multivacancy complexes in Pt and Au: (1) Quadrupole interaction parameters are compared with results of point-charge calculations of electric-field gradients for 20 structures containing 1–4 vacancies in the fcc lattice. (2) Hyperfine interactions induced by decorating vacancy complexes with hydrogen atoms are measured and interpreted with the assistance of point-charge calculations. (3) Transformations between complexes observed by annihilation of vacancies by mobile self-interstitials are used to test the consistency of the identifications. Using these methods in conjunction with analysis of the trapping behavior which occurs during annealing of damaged samples, structural models are presented for divacancy (2V), 3V and 4V complexes in Pt, and 3V and 4V complexes in Au. The activation temperatures of the 3V defect in Au and Pt are determined to be 162 K and 390 K, respectively, and activation temperatures of defects in Ni, Cu, Pt and Au are compared. For Pt, trapping of H at 1V and 2V complexes is observed to lead to small changes in the quadrupole interactions, consistent with well shielded protonic charges. However, trapping at 3V and 4V complexes leads to very large changes which we attribute to atomic restructuring to the defect complexes. Finally, the application of the same methodology to interpret recent experiments on NiAl, an ordered alloy, is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407659
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...