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  • 1
    Electronic Resource
    Electronic Resource
    Microstructures and crystallographic orientation of crystalline grains in anisotropic Nd-Fe-Co-B-(Ga or Zr) magnet powders produced by the hydrogenation-decomposition-desorption-recombination process (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 412-417 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.357091
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  • 2
    Electronic Resource
    Electronic Resource
    Anisotropic Nd–Fe–B bonded magnets made from HDDR powders (invited) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5040-5044 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Anisotropic Nd–Fe–B magnet powders can be produced by the hydrogenationdecomposition-desorption-recombination (HDDR) process from Nd–Fe–B–Co–M (M=Ga, Zr, Nb, Hf, and Ta) alloys. The present status of those HDDR powders and the bonded magnets made from them are reviewed with regards to the powder particle size dependence of their magnetic properties, their magnetic thermal stability, and their magnetization behavior. The results of a mechanistic study on the recombination step are also presented. The magnetic properties of the anisotropic HDDR powder depend relatively little on the powder particle size. Bonded magnets with a density of ∼6.20 g/cm3 and a BHmax of 18.5–20.5 MGOe can be produced from anisotropic HDDR powders with particle sizes of below 300 μm diam. The temperature coefficient of the intrinsic coercive force iHc, of the bonded magnet is −0.55%/°C in the temperature range from 25 to 100 °C. The magnetization force needed for full magnetization of the bonded magnet is about twice the coercive force of the magnet, indicating that the magnetization mechanism is different from that of the rapidly solidified isotropic Nd–Fe–B magnet. In the early stage of the recombination step of the HDDR process (1 min desorption), three phases are produced, i.e., α-(Fe,Co), spherical NdH2 and rimlike Nd2(Fe,Co)14B surrounding the NdH2 particle. Further desorption makes the Nd2(Fe,Co)14B phase grow. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361567
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  • 3
    Electronic Resource
    Electronic Resource
    Thermoelectric properties of lanthanum sulfide with Sm, Eu, and Yb additives (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2331-2336 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Seebeck coefficient and electrical resistivity have been measured for the La3−x Mx S4 alloys with the Th3 P4 -type structure for M=Sm, Eu, Yb, and x=0.1 to 0.9 in order to determine their potential as high-temperature thermoelectric energy conversion materials. An analysis of the lattice parameters of these alloys suggests that Sm has a valence of 2.2 over the entire composition range. Furthermore, the variation of the Seebeck coefficient and electrical resistivity as a function of electron concentration is different for the Sm-doped alloys than for the Eu- and Yb-doped alloys, which are all different from that of the pure binary LaSy alloys. A maximum in the electrical power factor at 1000 °C is found to occur at x (approximately-equal-to) 0.3, but when a reasonable estimate is made of the thermal conductivity the maximum in the figure-of-merit at 1000 °C shifts to larger x values (∼0.7) in all alloy systems. The long term stability of the Sm and Eu ternaries is also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341049
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation of γ-LaSy (1.33〈y〈1.50) alloys by the pressure-assisted reaction sintering method and their thermoelectric properties (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4633-4637 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pressure-assisted reaction sintering (PARS) method was used to prepare thermoelectric elements of the γ-phase lanthanum sesquisulfide solid solution alloys which exist over a wide homogeneity range: LaSy (1.33〈y〈1.5). A mixture of powders of stoichiometric lanthanum sesquisulfide (La2S3) and lanthanum trihydride (LaH3) was reaction sintered in a hot-press to make the desired composition of γ-LaSy. This method produced black dense single-phase γ-LaSy pellets with a theoretical density of 97% or better. The thermoelectric properties (electrical resistivity and Seebeck coefficient) of the samples prepared by the PARS technique were measured. The room temperature electrical resistivity and Seebeck coefficient of γ-LaSy varied in a systematic manner with the electron concentration indicating that γ-LaSy alloys behave like a simple metal. Although the current carriers appear to be quite heavy (drift mobility ∼3 cm2/V s), the temperature dependence (up to 1000 °C) of these properties of LaS1.42 were found to be linear functions, which is in accord with the above observations. The thermoelectric figure of merit based on the measured resistivity and Seebeck coefficient and an estimated thermal conductivity for LaS1.42 is 0.75×10−3 °C−1 at 1000 °C, which is comparable to those of the state-of-the-art materials such as silicon–germanium alloys at 1000 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335373
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  • 5
    Electronic Resource
    Electronic Resource
    Phosphorus and nitrogen doping into polycrystalline SiC films prepared by plasma-enhanced chemical vapor deposition at 700 °C (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1374-1377 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.351748
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  • 6
    Electronic Resource
    Electronic Resource
    Bonding properties of glow-discharge polycrystalline and amorphous Si-C films studied by x-ray diffraction and x-ray photoelectron spectroscopy (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5395-5400 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.350561
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic properties and microstructures of the Nd-Fe-B magnet powder produced by hydrogen treatment (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3770-3774 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.349232
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic properties and microstructures of the Nd-Fe-B system during the hydrogenation-decomposition-desorption-recombination process (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2719-2724 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.354666
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  • 9
    Electronic Resource
    Electronic Resource
    Crystal structure of Si1−xCx films by plasma-enhanced chemical vapor deposition at 700 °C (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7945-7947 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.347490
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic properties and microstructures of the Nd-Fe-B magnet powder produced by hydrogen treatment-(II) (abstract) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4665-4665 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.344820
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