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  • American Institute of Physics (AIP)  (3)
  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Negative surface ionization of hydrogen atoms and molecules (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2896-2901 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The total yield of H− ions, Y(Ein), produced in backscattering of low-energy H+ and H+2 ions from polycrystalline gold, tungsten, and molybdenum converter surfaces was measured at normal incidence in the energy range Ein=2–30 eV per nucleus. The yield per nucleus is independent of the ion mass. This indicates that the molecular ions are dissociated before colliding with the converter surface. A universal expression for Y(Ein) was developed by combining the electron tunneling theory with atomic scattering theory. This expression agrees well with measurements. The yield is completely characterized by two parameters, Eth/RE and RNη0, which can be determined experimentally: Y=0 for Ein=Eth/RE, and Y approaches the maximum yield Rη0 as Ein increases. These parameters were determined from measured H− yields in ion beam backscattering experiments, as well as for backscattering of thermal distributions of hydrogen atoms. For beam experiments, the maximum yield of 0.3 per nucleus was obtained for Mo/Cs converters with 1.5 eV work function. A higher maximum yield of 0.42 was obtained from experiments on backscattering thermal distributions of H atoms. This is attributed to high extraction fields. The universal yield formula made it possible to compare the results of the two different types of experiments. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361285
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanical strength of the solid-HDDR treated Nd–Fe–B-type materials : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7130-7132 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hydrogenation, disproportionation, desorption, recombination (HDDR) is known as a unique process through which a noncoercive cast Nd–Fe–B-type material can be easily converted into a coercive one. Although the conventional HDDR process generally leads to a powderlike material, a solid-HDDR material can be realized if the HDDR process is properly modified (solid-HDDR). In the present study, the change of mechanical strength (compressive strength) of the Nd–Fe–B-type material during the solid-HDDR has been investigated using a sintered magnet with composition Nd13.8Dy0.7Fe78.25Si0.15Mn0.6B6.5. It has been found that the low strength of the hydrided material was improved by the subsequent disproportionation. The restoration of the strength was explained by the eutectoidlike disproportionation structure containing fine neodymium hydride rod embedded in tough iron matrix. The high strength of disproportionated material was reduced radically in an earlier stage of recombination, and this was explained by the reduction of the disproportionated phase. The reduced strength was, however, recovered by further recombination, and this was explained by the fact that as the recombination continues the recombined grains become continuous and adhere together. The optimally HDDR processed material has a comparable or even higher strength with respect to the initial sintered material prior to the solid-HDDR. The present study suggested that the mechanical strength of Nd–Fe–B-type material could be retained even after the solid-HDDR. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367542
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  • 3
    Electronic Resource
    Electronic Resource
    Recombination characteristics of the Nd–Fe(–Co)–B(–Ga–Zr)-type anisotropic hydrogenation, desorption, disproportionation, recombination alloys (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4693-4695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The recombination characteristics of the Nd–Fe–B-type isotropic and anisotropic hydrogenation, desorption, disproportionation, recombination (HDDR) alloys were investigated using three types of alloys: alloy A (Nd12.6Fe81.4B6), alloy B (Nd12.6Fe81.3B6Zr0.1), and alloy C (Nd12.6Fe68.8Co11.5B6Ga1.0Zr0.1). Alloy A is featured with the isotropic HDDR character, while alloys B and C are featured with the anisotropic HDDR character. Recombination characteristics of the alloys were examined by observing the coercivity variation as a function of recombination time. Microstructural development during the HDDR was examined by means of transmission electron microscopy, and it was correlated with the coercivity variation. The present study revealed that the intrinsic coercivities of the recombined materials rapidly increased with increasing the recombination time and then showed a peak, after which the coercivities decreased gradually as usual. However, it has been found that the degraded coercivity was recovered significantly on prolonged recombination. Compared with the isotropic HDDR alloy A, the anisotropic HDDR alloys B and C are notable for their greater recovery of coercivity. The significant recovery of coercivity was accounted for in terms of the development of a well-defined smooth grain boundary between the recombined grains on prolonged recombination. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370450
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