Journal of the Ceramic Association, Japan
Online ISSN : 1884-2127
Print ISSN : 0009-0255
ISSN-L : 0009-0255
Volume 88, Issue 1018
Displaying 1-12 of 12 articles from this issue
  • Takefumi MITSUHASHI, Yoichi TAKAHASHI
    1980 Volume 88 Issue 1018 Pages 305-311
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The heat capacity of a rutile (TiO2) single crystal of 99.99% purity has been measured between 80 and 1100K using the laser-flash calorimeter. The reproducibility of the data was ±0.5% below 800K, and ±1% above that. The smoothed heat capacity agrees with the values in JANAF Tables (1975) within ±0.7% up to 700K, above which the present data are lower by 0.3 to 0.7% than those in the Table. The accuracy of the data is believed to be nearly equal to the reproducibility above 130K.
    The heat capacity of rutile has been analyzed in order to estimate a contribution from anharmonic lattice vibrations. The negative anharmonic heat capacity, which decreases linearly with temperature with the coefficient of -1.24×10-3J⋅mol-1⋅K-2, was obtained from the heat capacity at constant volume by subtracting a theoretical heat capacity based on the summation of the Debye and the Einstein function; the characteristic temperature of the latter was calculated to be 607K by considering three acoustic and fifteen optical branches of the lattice vibrations. It has been argued that the anharmonic heat capacity is semi-quantitatively correlated with the temperature derivatives of frequencies of the lattice vibrations at constant volume.
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  • Ken-ichi ISHIMA, Muneyuki MOTOYAMA, Genzo HASHIZUME, Minoru TANAKA
    1980 Volume 88 Issue 1018 Pages 312-316
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The surface contaminants on the smoked rooftiles deposited during the manufacturing process were analyzed and its prevention method was discussed. The contaminants are known to reduce the silver luster of the rooftiles. Infrared spectroscopic, gas chromatographic and mass spectroscopic analyses showed that the major components of the contaminants were condensed aromatic materials and some of the 2-4 ring compounds were identified. The amount of contaminants increased with the increasing amount of hydrocarbons. The contaminants on the products were predominantly formed at about 400°C by the contact with the raw smoking gas remained in the flue. The dilution of smoking gas with inert gas prevented the formation of the contaminants.
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  • Yoshihiko SASA, Masayuki UDA
    1980 Volume 88 Issue 1018 Pages 316-321
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    X-ray diffraction intensity distribution obtained from anisotropic hexaferrite magnets with an uniaxial orientation was explained quantitatively by use of the “Texture pattern technique” developed by one of the authors. The degree of the orientation or the magnitude of the deviation from a random distribution is presented by two parameters, a Gaussian constant h and a randomness factor b. We could estimate more accurate degree of the orientation by this method than by the Lotgering's one because the diffraction peak overlapping in the case of the latter was not taken into account. Based on this method it was also concluded that the crystallite distribution even in so-called “isotropic” magnet was not completely random. A relationship between the degree of the orientation and Br/4πMs or (BH)max was linear.
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  • Masao MIZUNO, Tetsuo NOGUCHI
    1980 Volume 88 Issue 1018 Pages 322-327
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    In the phase diagram studies on the Al2O3-Yb2O3 system, the liquidus and eutectic temperatures were measured from the cooling curves of specimens by the specular reflection method with a heliostat-type solar furnace. Quenched specimens from the melt were examined by X-ray diffractometry and chemical analysis.
    Garnet-type compound, 3Yb2O3⋅5Al2O3, was obtained as a single cubic phase by heating an α-Al2O3-Yb2O3 mixture of corresponding stoichiometry at 1600°C in an electric resistance furnace and also by crystallization from the melt in the solar furnace.
    When the specimens of the 2Yb2O3⋅Al2O3 composition were quenched from 1700°C and from the melt, both specimens appeared to be the single phase with monoclinic structure.
    The freezing points of 3Yb2O3⋅5Al2O3 and 2Yb2O3⋅Al2O3 were measured as 2000±20°C and 2002±20°C, respectively.
    The lattice parameter of the garnet compound was a0=11.951Å, and the parameters of the monoclinic phase were a0=7.278Å, b0=10.310Å, c0=11.040Å and β=108.30°.
    All of the above compounds appeared to be stable phase, because they showed no phase transition in repeated heating and cooling cycles.
    The phase diagram shows three eutectic points at 1845°C, 1875°C, and 1890°C with 18, 52.5, and 82mol% of Yb2O3 composition, respectively.
    Each of cooling curves of Al2O3, 3Yb2O3⋅3Al2O3 and 2Yb2O3⋅Al2O3 showed a single exothermic peak which was assigned to solidification point, while Yb2O3 showed two exothermic peaks, corresponding to a solid state phase transformation as well as solidification point.
    A high temperature phase diagram for Al2O3-Yb2O3 system was presented.
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  • Kazunao YAMAMOTO, Ken KUMATA, Hiroshi NAMIKAWA
    1980 Volume 88 Issue 1018 Pages 327-330
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    CdO-based oxide glasses exhibit the marked photoconductivity when exposed to the light with the photon energy corresponding to the absorption edge. This leads us to expect that the dark conductivity also originated from an electronic process. In order to understand the conduction mechanism of such type of glasses electric conduction and dielectric relaxation of 47.5CdO⋅47.5SiO2⋅5Na2O glass were measured.
    The optical gap was much greater than the energy gap evaluated from the activation energy for electric conduction by assuming interband transition. The dielectric relaxation originated from ionic diffusional motion and correlated closely with the electric conduction was observed. These results and presence of Na+ ions in glass leads us to the conclusion that the electric conduction is ascribed to the transport process of the Na+ ion.
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  • State of Products at Various Temperatures
    Hajime SAITO, Iwao YAMAI
    1980 Volume 88 Issue 1018 Pages 330-336
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The vapor phase growth of β-SiC whiskers from gaseous species evolved by the reaction of fluorosilicate melts with carbon has been studied in wide temperature range with two methods, in which the reactant gases were introduced from evolution chamber to reaction zone by a carrier gas or suction. In flow method, Ar gas was used as the carrier gas of SiO, that evolved by the reaction of SiO2-NaF melt with carbon at 1350°C or 1400°C. When the SiO gas reacted with CO gas on a substrate of graphite at the temperatures ranging 1350°C to 800°C, β-SiC whiskers formed in the wide temperature range. At the same time, carbon deposited at the intermediate temperature zone and silicon at the lower temperature zone at the higher flow rate of the Ar by the disproportionation of CO and SiO respectively. Moreover, glassy material deposited in the lowest temperature range.
    In the case of suction method, SiO gas was produced by the reaction of SiO2-Na3AlF6 melt with carbon at 1450°C. In this case, AlF3 gas should have evolved above atmospheric pressure from the inside of the melt, and then might have promoted the evolution of the SiO gas. By the reaction of the SiO gas with CO gas, a large amount of β-SiC whiskers were produced in the reaction zone of the temperature range from 1350° to 1190°C under the following conditions: the molar ratio of SiO2 to Na3AlF6 was about unity, and suction was carried out with weakly reduced pressure. The results obtained have been discussed in detail from thermochemical data.
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  • Katsuaki TAKAHASHI, Yoshinari MIURA
    1980 Volume 88 Issue 1018 Pages 337-345
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    In previous papers, most of Arrhenius plots for the diffusion coefficients of Cd2+, Ni2+, Co2+ and Cr6+ ions in molten sodium borate glasses were shown to depart from the linearity. On the diffusion coefficients of Ni2+ ions in molten alkaline earth borate glasses (R2+=Ca2+, Sr2+ or Ba2+), molten lithium and potassium borate glasses, non-Arrhenius behavior was also demonstrated.
    In this paper, applications of “the modified Fulcher equation”, log (D/T1/2, η/T1/2, λT1/2)=A+B/(T-T0) (where, D: diffusion coefficient, η: viscosity, λ: equivalent conductance, T0, A, B: constants) derived from the Cohen-Turnbull free volume theory were examined to diffusion behavior. At the same time, the same applications were examined on viscosity and electrical conduction measured by Shartsis et al.
    It was ascertained that the proper T0 values giving the best linear plots of logD/T1/2 vs. 1/(T-T0) existed on diffusion of the metal ions in alkali and alkaline earth borate glasses. Moreover, the obtained T0 values were located below the respective glass transition temperatures Tg, changing almost in parallel with Tg for most of the glass systems. The Tg/T0 ratios were about 1.2 for almost all glass systems, were not necessarily dependent on the glass compositions. The T0 values obtained from diffusion of Cd2+, Ni2+, Co2+ and Cr6+ ions in the molten sodium borate glasses were equal within 40K at the corresponding glass composition.
    The T0 values giving the best linear plots against “the modified Fulcher equation” were found for viscosity and electrical conduction measured by Shartsis et al. The obtained T0 values were consistent with those of diffusion except a few cases.
    As previously discussed by Angell et al., the Tg/T0 ratio may become a criterion for “ideality” of glass. Departure from ideality in the borate systems was smaller than in the silicate systems because the former had smaller Tg/T0 values.
    Jumping distances of diffusion of Ni2+ ions calculated from “the modified Fulcher equation” in the molten alkali and alkaline earth borate glasses were within the range 5-10Å except for BaO-B2O3 systems. In the same way, jumping distances of diffusion of Cd2+, Ni2+, Co2+ and Cr6+ ions in the sodium borate glasses were within the range 5-13Å. In this case, the jumping distances did not apparently correlate on the composition of glass. The diameters of flow units calculated from viscosity in molten alkali borate glasses were about 4Å, suggesting that the flow units were relatively small such as BO3 and BO4.
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  • Tetsuro KATO, Shin-ichi HIRANO, Masahiro YOSHIMURA, Sigeyuki SOMIYA
    1980 Volume 88 Issue 1018 Pages 345-352
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Reactions and phase relations in the system Cr-B-N at 1600°C under 1atm N2 have been studied. In the region of Cr5B3-B-N, Cr or Cr2N reacted with BN to form Cr5B3, while CrB or CrB2 reacted with N2 finally to form Cr5B3+BN. The reaction processes seem to be by steps as CrB2→Cr3B4→CrB→Cr5B3. It can be concluded that Cr5B3 is an equilibrium phase at 1600°C under 1atm N2. Lattice parameters of Cr5B3 obtained from the initial composition of Cr+BN were a=5.467±0.007Å, c=10.081±0.007Å, which were equal to those from the step reactions of CrB with N2 or CrB2 with N2.
    Cr2B+Cr5B3 or Cr2N+Cr2B was produced as the final solid phases in the region of Cr2B-Cr5B3-N, or Cr-Cr2B-N respectively.
    Cr2N phase in the equilibrium state was obtained both from the nitridation of Cr and the decomposition of CrN.
    Their lattice parameters were a=4.765±0.002Å, c=4.441±0.003Å.
    The isothermal section of the system Cr-B-N at 1600°C under the above conditions was divided into 3 three-phase triangles; Cr2N+Cr2B+N2, Cr5B3+Cr2B+N2 and Cr5B3+BN+N2. No homogeneity ranges can be detected on the tie lines Cr2N-Cr2B, Cr2B-Cr5B3 and Cr5B3-BN.
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  • Yoshizo INOMATA, Hidehiko TANAKA, Zenzaburoh INOUE, Haruo KAWABATA
    1980 Volume 88 Issue 1018 Pages 353-355
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The phase relation in SiC-Al4C3-B4C system at 1800°C was studied experimentally. Three complex carbides, Al4SiC4, Al4Si2C5 and Al8B4C7 were found in the system and liquid phase was formed around Al8B4C7 at that temperature. The aluminum silicon carbide, Al4Si2C5 showed a tendency to appear clearly in a boron containing pseudo-ternary system, SiC-Al4SiC4-Al8B4C7, rather than SiC-Al4C3 binary system, and the compound is considered to be unstable in the binary system at 1800°C. Compatible triangles are supposed to be SiC-B4C-Liq., SiC-Al4SiC4-Liq. and Al4SiC4-Al4C3-Liq. The stability of Al4Si2C5 in the system leaves some uncertainty.
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  • Toshihisa MARUTA, Akihiko TAKEI, Giichi SUDOH
    1980 Volume 88 Issue 1018 Pages 356-358
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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  • Kiyoshi KASAI, Yoshitaka KUBOTA, Takaaki TSUKIDATE
    1980 Volume 88 Issue 1018 Pages 358-359
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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  • 1980 Volume 88 Issue 1018 Pages A32-A38
    Published: June 01, 1980
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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