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  • 1990-1994  (8)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2719-2724 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Nd-Fe-B and Nd-Fe-Co-B magnet powders with the high coercivity (≥10 kOe) were obtained by the hydrogenation-decomposition-desorption-recombination (HDDR) process at temperatures between 800 °C and 900 °C. We studied magnetic properties and microstructures of the Nd-Fe-B systems during the HDDR process. The NdH2 phase produced by decomposition of Nd2Fe14BHx with hydrogenation exists in the maze-like form of the size of 10−1 μm. It was found that the size of the NdH2 phase determines the size of the Nd2Fe14B phase formed by the recombination. NdH2, Fe, and Fe2B are more stable than Nd2Fe14B at temperatures from 800 °C to 900 °C. The magnet powders produced by the HDDR process are magnetically almost isotropic.
    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 71 (1992), S. 5395-5400 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline and amorphous Si-C films were prepared by rf glow-discharge decomposition of silane-methane mixtures at 700 °C. We have demonstrated that polycrystalline SiC films with large grains grow under heavy hydrogen dilution. The bonding properties as a function of film composition and hydrogen dilution were characterized by means of x-ray diffraction and x-ray photoelectron spectroscopy. Crystallization takes place at around C content x=0.5 in Si1−xCx, accompanying some segregation of carbon atoms in grain boundaries, as a result of a preference for heteronuclear bonds. It was shown that C-C(C3−nSin) (n=0–3) bonds appear in the carbidic phase of C-rich films, leading to occurrence of compressive strain in the crystalline SiC grains. In addition, effects of hydrogen dilution were discussed in correlation with the strain.
    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 70 (1991), S. 3770-3774 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hydrogen treatment of the Nd-Fe-B alloy ingots was found to produce magnet powders with good magnetic properties. Typical magnetic properties of these powders are as follows; 4πIs = 9.5 kG, Br = 7.7 kG, iHc = 9.4 kOe, and (BH)max = 12.2 MGOe. Microstructural studies of these powders showed that they are made of fine crystalline grains of ∼0.3 μm diameter and that these crystalline grains in the individual magnet powder are not necessarily enclosed with boundary phase(s), which is quite different from previously known Nd-Fe-B magnets, i.e., the sintered magnet (the nucleation type magnet) or the amorphous ribbon magnet (the pinning type magnet). It is also noted that the size of these crystalline grains is comparable to that of the single magnetic domain of the tetragonal Nd2Fe14B intermetallic compound and the coercive force of these powders appears to be related to their fine crystalline grain size.
    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 72 (1992), S. 1374-1377 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Doped polycrystalline SiC films were deposited from a SiH4-CH4-H2-(PH3 or N2) mixture by plasma-enhanced chemical vapor deposition at 700 °C. The best crystallinity was obtained at x∼0.53 in Si1−xCx for both undoped and doped films. The crystallinity was enhanced by both P and N doping, but deteriorated again under high doping conditions. Also, better crystallinity was obtained by doping with P rather than N. Intrinsic tensile and compressive stresses were observed for P- and N-doped films, respectively. The resistivity and dangling-bond density decreased in correspondence to the enhancement in crystallinity. Origins of the dangling bonds and of a change in the crystallinity were discussed.
    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 69 (1991), S. 7945-7947 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using x-ray diffraction and electron-spin-resonance measurements, the crystal structure and bonding configurations of Si1−xCx films by plasma-enhanced chemical vapor deposition at 700 °C are shown to change abruptly at around x=0.5. At around this composition, a polycrystalline film with a cubic SiC 〈111〉 preferred orientation and an average grain size of 95 nm is grown on a fused silica substrate under high hydrogen dilution. The structural change can be attributed to an increase in the probability of occurrence of a Si- C4 tetrahedron in a chemically ordered network.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4665-4665 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hydrogen treatment of the Nd-Fe-B alloy ingots was found to produce magnet powders with good magnetic properties. Typical magnetic properties of these powders are as follows: 4πIs=9.5 kG, Br=7.7 kG, iHc=9.4 kOe, and (BH)max=12.2 MG Oe. Microstructural studies of these powders showed that they are made of fine crystalline grains of ∼0.3 μm diameter and that these crystalline grains in the individual magnet powder are not necessarily enclosed with boundary phase(s), which is quite different from previously known Nd-Fe-B magnets, i.e., the sintered magnet (the nucleation type magnet) or the amorphous ribbon magnet (the pinning type magnet). It is also noted that the size of these crystalline grains is comparable to that of the single magnetic domain of the tetragonal Nd2Fe14B intermetallic compound and the coercivity force of these powders appears to be related with their fine crystalline grain size.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In addition to being initially developed as an energy driver for an inertial confinement fusion, an intense, pulsed, light-ion beam (LIB) has been found to be applied to materials science. If a LIB is used to irradiate targets, a high-density "ablation'' plasma is produced near the surface since the range of the LIB in materials is very short. Since the first demonstration of quick preparation of thin films of ZnS by an intense, pulsed, ion-beam evaporation (IBE) using the LIB-produced ablation plasma, various thin films have been successfully prepared, such as of ZnS:Mn, YBaCuO, BaTiO3, cubic BN, SiC, ZrO2, ITO, B, C, and apatite. Some of these data will be presented in this paper, with its analytic solution derived from a one-dimensional, hydrodynamic, adiabatic expansion model for the IBE. The temperature will be deduced using ion-flux signals measured by a biased ion collector. Reasonable agreement is obtained between the experiment and the simulation. High-energy LIB implantation to make chemical compounds and the associated surface modification are also discussed.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructures of anisotropic Nd-Fe-Co-B-(Ga, or Zr) magnet powders produced by the hydrogenation-decomposition-desorption-recombination (HDDR) process and the resulting crystallographic c-axis orientation of Nd2(Fe,Co)14B crystals in the powder particles have been studied. It was found that the powder particles consist of fine Nd2(Fe,Co)14B crystals of the size of about 0.3 μm, and any boundary-layer phase between the Nd2(Fe,Co)14B crystalline grains is almost absent. The morphology of fine Nd2(Fe,Co)14B crystalline grains in anisotropic magnet powders is the same as that of isotropic magnet powders produced by the HDDR process. In anisotropic powders, it was found that there is a strong correlation among the a axes, b axes, and c axes of the fine Nd2(Fe,Co)14B crystal grains. The dispersion in solid angles made by the c-axis direction is less than ±18° in the case of Nd-Fe-Co-B-Ga magnet powder particle. The c-axis direction of fine grains in magnet powders produced by the HDDR process is associated with that of large Nd2(Fe,Co)14B grains in the original cast or the homogenized alloy. The microstructure of anisotropic magnet powders before the hydrogen desorption step in the HDDR process is very complicated. It consists of five distinct regions, and among these, two regions are made of NdH2 and Fe.
    Type of Medium: Electronic Resource
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