Materials Transactions, JIM
Online ISSN : 2432-471X
Print ISSN : 0916-1821
ISSN-L : 0916-1821
Volume 39 , Issue 5
Showing 1-14 articles out of 14 articles from the selected issue
  • H. Sasajima, T. Arai, I. Yokoyama
    1998 Volume 39 Issue 5 Pages 551-556
    Published: 1998
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    In this paper, the thermodynamic entropies of the liquid rare-earth metals are explained by the statistical theory of entropy using the hypotheses about the electronic structure suggested by what is believed to be true of the corresponding solids. The pair correlation entropies are computed from measured pair correlation functions, while the triplet correlation entropies are estimated by measured structure factors with the help of the uniform fluid model for evaluation of a change in the structure factor on application of the pressure. The magnitude of the pair and triplet correlation entropies is smaller than that of the liquid 3d transition metals near the melting point. The excess entropy of a hard sphere model is discussed in relation to the correlation entropies studied.
    Download PDF (752K)
  • S. Sato, M. Saito, E. Matsubara, Y. Waseda, K. Inomata
    1998 Volume 39 Issue 5 Pages 557-561
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Two different X-ray scattering experiments of θ-2θ X-ray scattering and grazing incidence X-ray scattering (GIXS) geometries have been done for evaluating the lattice strain anisotropically formed in the Co9Fe/Cu superlattices. The magnitude of lattice strain along Cu [001] and [110] directions which are parallel to the surface was estimated using GIXS geometry. The results confirm that the lattice strain along both directions increases with decreasing Cu thickness and its degree changes with a variation in orientation. On the other hand, the magnitude of lattice strain along two directions of Cu [110] (parallel to the surface) and Cu [1\bar10] (perpendicular to the surface) is found to differ from each other by comparing the lattice strain estimated from the measurements for equivalent Cu 220 reflections. The present results clearly suggest that the lattice strain formed in the Co9Fe/Cu superlattices depends upon the lattice orientation.
    Download PDF (804K)
  • Yasuhiro Ono, Akihiro Bungo, Takashi Noji, Yoji Koike, Tsuyoshi Kajita ...
    1998 Volume 39 Issue 5 Pages 562-569
    Published: 1998
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    Detailed crystal structures of high-Tc superconductors Pb2Sr2Y0.90Sr0.10Cu3O8, Pb2Sr2Y1−xCaxCu3O8 (x=0.25 and 0.41) and Pb2Sr2Ho0.64Ca0.36Cu3O8 were successfully determined by means of single crystal X-ray diffraction at room temperature. Space symmetry changes from C2/m (x=0.10 and 0.25) to Cmmm (x=0.36 and 0.41) with increasing divalent cation concentration, x. Their electron density distributions are determined by means of the maximum entropy method (MEM). Two- or four-splitting oxygen peaks clearly appear in the electron density maps of PbO plane, which is consistent with oxygen disorder models introduced to the present structure determination. In the electron density maps of monovalent copper plane, no peak corresponding to excess oxygens was observed at the 1×103 e/nm3 contour level. In the vicinities of divalent copper in the conducting plane, some anomalous electron density distribution is represented in the yttrium compounds.
    Download PDF (1368K)
  • E. Z. Kurmaev, S. Stadler, D. L. Ederer, Yu. M. Yarmoshenko, D. A. Zat ...
    1998 Volume 39 Issue 5 Pages 570-573
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The results of measurements of S L2,3 ultra-soft X-ray emission spectra excited by synchrotron radiation at hv=163–165 eV for samples with 240 ppm S in Ni after annealing at 400–700°C are presented. It is found that S L2,3 X-ray emission spectra of S-impurity atoms in Ni show fine structure which can be simulated by a superposition of spectra of nickel sulphide and pure sulphur providing evidence that sulphur atoms are present after annealing both in solid solution and in clusters where they form S–S bonds. The variation of temperature and time of annealing (at T=400°C for 1 h and at T=700°C for 2 h) leads to some redistribution of intensity of S L2,3 X-ray emission valence spectra which can be attributed to changes in the number of S–Ni and S–S bonds in accordance with the limit of sulphur solubility at these temperatures.
    Download PDF (568K)
  • Toru Kuzumaki, Takuya Hayashi, Kun’ichi Miyazawa, Hideki Ichinos ...
    1998 Volume 39 Issue 5 Pages 574-577
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    A new carbon/carbon (C/C) composite was successfully produced at room temperature by drawing a silver tube containing carbon nanotubes as the fiber material and nanocrystalline carbon 60 (C60) as the matrix. Fine structures of the composite were examined by transmission electron microscopy (TEM) and the mechanical properties by conventional tensile tests. TEM observations have shown that the carbon nanotubes in the composite are not damaged and well aligned along the longitudinal direction of the composite wire. The stress-strain curve of the composite wire de-sheathed by the evaporation of silver through a heat treatment exhibited an approximately 20-fold increase in fracture stress over that of polycrystalline C60, and the higher fracture strain (more than 10%). The fractured surface of the wire showed that nanotubes have been pulled out but not fractured. The experiments lead us to a new concept of a ductile C/C composite.
    Download PDF (1808K)
  • Toru Kuzumaki, Takuya Hayashi, Kun’ichi Miyazawa, Hideki Ichinos ...
    1998 Volume 39 Issue 5 Pages 578-581
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The effects of the interfacial fine structure (interfacial bonding interaction) on the mechanical properties of nanotube/C60 composite were examined by high resolution transmission electron microscope (HRTEM) observations of nanotube/vapor-deposited C60 crystal interfaces and pull-out tests of high modulus carbon fiber with a vapor-deposited C60 single crystal. Interfaces between nanotube and {111}-faceted C60 crystal were observed to possess a parallel orientation relationship between the tube axis and ⟨110⟩ of the C60 crystal. The shear strength of the carbon fiber/C60 composite was estimated to be 4.4×10−2 MPa. Interfacial sliding was observed in the carbon fiber/C60 single crystal interface without deformation of the C60 matrix nor the fracture of fiber. It has been inferred that the pull-out of the carbon fiber from the C60 matrix is due to the shear sliding, which is caused by the weak bonding between graphitic basal plane and C60. The experiments have indicated that the ductility of the nanotube/C60 composite originates probably from sliding at the interface between the nanotube and the C60 matrix.
    Download PDF (1896K)
  • O. P. Modi, R. P. Yadav, B. K. Prasad, A. K. Jha, R. Dasgupta, G. Dixi ...
    1998 Volume 39 Issue 5 Pages 582-586
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    An attempt has been made to examine the influence of swaging on the microstructure, mechanical properties and sliding wear characteristics of some zinc-based alloys comprising varying concentrations of aluminium. The density of the alloys decreased with aluminium content while hardness followed a reverse trend. Further, the aluminium concentration in an intermediate range (close to 27.5%) led the alloy system to attain maximum tensile properties and sliding wear resistance. Swaged specimens exhibited properties superior to their as-cast variety irrespective of the test condition and aluminium content.
    Download PDF (1628K)
  • H. Fredriksson, Y. Arai, T. Emi, M. Haddad-Sabsevar, H. Shibata
    1998 Volume 39 Issue 5 Pages 587-595
    Published: 1998
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    Cu–Ag samples produced during rapid solidification experiments using a Planar Flow Melt Spinning Process or a levitation casting technique were rapidly heated in a mirror furnace to a variety of temperatures at rates between 100 and 1.6 K/s. The surface of each sample was observed in a confocal laser scanning microscope. Metallographic analyses were performed on the samples by optical and scanning electron microscopy. The rapidly solidified samples melted far below the equilibrium melting point.
    The melted and resolidified samples mostly consisted of structures similar to those seen in alloys with a miscible gap.
    It is proposed that this type of behaviour is a result of lattice defects formed during the rapid solidification process. The effect of these defects on the thermodynamic properties was investigated. A metastable phase diagram with a miscibility gap can be constructed below the equilibrium melting point. This could explain the observed phase structure and the melting of the alloy below the equilibrium melting point.
    Download PDF (4740K)
  • N. Shiga, F. Kogiku, S. Okabe, N. Morito
    1998 Volume 39 Issue 5 Pages 596-601
    Published: 1998
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    The building factor (B.F.) of Fe–Bi–Si amorphous alloy toroidal cores was improved by adding Mn to the alloy. The total iron loss of amorphous ribbons under bending strain was reduced by adding Mn. This reduction in total iron loss was the result of reduced hysteresis loss. The critical compressive strain, which is defined as the ratio of magnetic anisotropy energy to magnetoelastic energy, was estimated by observing domain structures, and increased as the Mn content increased. The decrease in hysteresis loss in amorphous toroidal cores by Mn addition was due to this increase in the critical compressive strain.
    Download PDF (1284K)
  • Yasutoshi Noda, Masaki Orihashi, Isao A. Nishida
    1998 Volume 39 Issue 5 Pages 602-605
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Single crystals of p-type PbTe were prepared by the Bridgman method, where either Ag2Te or K was doped as the source material of silver or potassium, respectively. Carrier concentration and Hall mobility were measured from 77 to 300 K. The hole concentration was successfully controlled in the range from 2.0×1024 to 9.0×1024 m−3 by doping 100 to 700 mol ppm Ag2Te, while the conduction type changed from p- to n-type in the region more than 1000 mol ppm Ag2Te. In the case of K-doping, the carrier concentration was controlled in the region of 8.0×1024 to 4.0×1025 m−3 with 1000 to 25000 mol ppm K. Figure of merits (Z) of p-PbTe at 300 K were 8.0×10−4 K−1 at a hole concentration of 1.34×1025 m−3 (2400 mol ppm K) and 1.38×10−3 K−1 at 2.34×1024 m−3 (200 mol ppm Ag2Te).
    Diffusion lengths of dopant elements of Ag, K and Sn for p-type and I for n-type PbTe were estimated using the literature data. The result indicates that long distance diffusion occurs in a short period in the case of Ag and K. Therefore, the stable functionally graded materials (FGM) of PbTe might be prepared by gradient I doping or Sn alloying, while those by Ag or K doping will be soon changed into non-FGM due to the rapid diffusion resulting in the decreased efficiency of thermoelectric energy conversion.
    Download PDF (628K)
  • Kaushik Datta, Pragati Mukherjee, B. K. Datta, H. S. Ray
    1998 Volume 39 Issue 5 Pages 606-608
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The role of basicity of the melt during electrodeposition of tungsten carbide from the Na2WO4–Na2O–B2O3–NaCl system using the graphite electrode has been studied by UV-vis reflectance spectroscopy of tungsten species formed. It has been shown that tungsten in the melt is predominantly found as W6+ at low basicity, as ditungstate in an intermediate basicity range and as monomeric (WO4)2− species in highly basic melts leading to deposition of W, W2C and WC during electrolysis depending upon the Na2O:B2O3 ratio of the melt. Addition of NaCl was found to play no direct role in changing the tungsten species in the melt; its role probably is to increase the electrical conductivity or to decrease the viscosity/surface tension of the melt.
    Download PDF (876K)
  • H. Nishizawa, E. Sukedai, W. Liu, H. Hashimoto
    1998 Volume 39 Issue 5 Pages 609-612
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Since ω-phase crystals in β-Ti alloys formed by aging become nucleation sites of α-phase crystals due to further or high temperature aging, it is thought that this phenomenon can be utilized to produce stronger and more ductile (β+α) duplex Ti alloys. In order to form high density ω-phase crystals, the effects of a stress-aging and hydrostatic pressurizing on the formation of ω-phase crystals in Ti–20Mo and Ti–15Mo–5Zr alloys (mass%) were investigated using high resolution electron microscopy and dark field imaging methods. The results obtained are as follows: (1) An aging under a stress of a half of the yield stress promotes the precipitation of high density ω-phase crystals. (2) Hydrostatic pressurizing also promotes the formation of ω-phase crystals, and it is recognized that a hydrostatic pressure of 0.7 GPa initiates to form ω-phase crystals in a Ti–20Mo alloy.
    Download PDF (1624K)
  • A. Kanni Raj, K. A. Padmanabhan
    1998 Volume 39 Issue 5 Pages 613-616
    Published: 1998
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    Sheets of a low nickel (1.2 mass%Ni) metastable austenitic stainless steel, developed by some members of the Indian Stainless Steel Development Association, were tested for formability. The 0.70 mm thick sheets displayed inferior formability to the 0.90 mm thick sheets in all the three regions of forming-stretching, plane strain forming and deep drawing till a minor strain of −10%. This result was traced mainly to the lower sheet thickness and reduced straininduced martensite formation that leads to reduced work hardening. The forming limit diagrams predicted by a model due to Date and Padmanabhan correlated well with the experimental plots.
    Download PDF (760K)
  • Tsuyoshi Kawashima, Masakazu Hishinuma
    1998 Volume 39 Issue 5 Pages 617-620
    Published: 1998
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The diffusion coefficient of Mn in yttria-stabilized zirconia (YSZ, 3 mol%Y2O3) and the structural change in YSZ have been investigated. The diffusion coefficients of Mn were determined to be 7×10−14 m2/s at 1573 K and 2×10−13 m2/s at 1673 K by analyzing the concentration profiles of Mn in YSZ/Mn3O4 diffusion couples. The solubilities of MnOx were 7.4 mol% and 7.6 mol% at 1573 and 1673 K, respectively. Remarkable grain growth was observed on the YSZ side near the interface. The dissolution of MnOx almost up to the solubility limit of 7.6 mol% resulted in grain growth and the phase transformation from the tetragonal phase to the fluorite-type cubic phase. These results were discussed by comparing with the previous studies on the ZrO2–Y2O3–MnOx ternary system and on the ZrO2–MnO binary system.
    Download PDF (932K)
feedback
Top