Journal of the Ceramic Association, Japan
Online ISSN : 1884-2127
Print ISSN : 0009-0255
ISSN-L : 0009-0255
Volume 78, Issue 897
Displaying 1-7 of 7 articles from this issue
  • Toshiyasu HORIBE, Shigeru KATTO, Senzo KUWABARA
    1970 Volume 78 Issue 897 Pages 149-157
    Published: May 01, 1970
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The corundum grains of single crystal 60 to 80μm in size, which were prepared from commercial brown aluminous abrasives by removing their impurity phases, were heated in air at temperatures between 1, 200° and 1, 630°C for various hours. Phases of the precipitates given by the oxidation of Ti3+ ions in the corundum were examined by the X-ray diffraction method and by optical microscopy. Only rutile was found within the corundum crystals in any of the specimens, although β-Al2TiO5 is stable above about 1, 300°C. β-Al2TiO5 was found on the surfaces of the corundum crystals after long heat-treatments at high temperatures. The β-Al2TiO5 was given by the titanium moving out to the surfaces from the rutile which had precipitated within the corundum crystals. The cause of the fact that the rutile did not give β-Al2TiO5 within the corundum crystals was discussed. Formation of β-Al2TiO5 from a mixture of Al2O3 and TiO2 powders was found to be supressed by the addition of a small amount of CuO. A trace of Cu was contained in the corundum grains.
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  • Hironori OHTA, Morihisa HARA
    1970 Volume 78 Issue 897 Pages 158-164
    Published: May 01, 1970
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The ion-exchange process was investigated by electrolyzing potassium ions into commercial sheet glass below its strain point. The concentration of potassium ions diffused into the glass sheet under the electric field gave a rectangular profile. The analytical measurements showed that no more than 93% of sodium ions were replaced by the potassium ions.
    The apparent resistivity ρ, increased linearly with the increase of thickness ε of the ion-exchanged layer, as expressed in the equation, ρ=ρ01ε/L, where L is the thickness of the glass sheet, ρ0 and ρ1 are resistivities related to the diffusion of sodium ions and potassium ions in the sheet glass respectively. The activation energy for conductivity due to those ions was obtained from the temperature dependence of ρ0 and ρ1. The potassium diffusion coefficient in the sheet glass was estimated from the Einstein relation by use of an assumed correlation factor.
    The stress profile in the layer was measured by means of a polarization microscope with the aid of a Eerek compensator. The compressive stress increased appreciably with the depth of the ion-exchanged layer and abruptly changed into the tensile stress at the boundary of the layer. The characteristics of the stress profile were explained by the different degree of stress relaxation which is greater at the layer nearer to the surface.
    When potassium ions were diffused into one side of a glass sheet, the sheet was bent in order to balance stresses due to the ion-exchange. The stresses in the layer calculated from the curvature of the bend were not changed with the temperature of the treatment and became fairly larger than the observed values when the sheet was treated at higher temperatures, because the curvature was not affected by stress relaxation.
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  • Koichi WATANABE, Yoshiro SUMIYOSHI, Eiji ANBO
    1970 Volume 78 Issue 897 Pages 165-171
    Published: May 01, 1970
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Ternary glasses of the system SiO2-Bi2O3-Na2O were prepared by fusion in porcelain crucibles. The range of glass formation in the system was also studied.
    Thermal, optical, electrical properties for the glass prepared were investigated, and the results were obtained as follows:
    Thermal expansion coefficient and alkali soluble quantity of these glasses were increased with the increase of Na2O contents, and also specific gravity and refractive index were increased with increasing Bi2O3 contents.
    Electrical resistivity of these glasses were 101-105(Ωcm) at 350°C, and dielectric constant and dissipation factor were ε=12.7-15.8, tan δ=0.001-0.007 respectively at room temperature.
    By infrared absorption spectra, absorption bands that can be ascribed to OH-, CO32- ion and Si-O vibration were observed.
    Results of X-ray diffraction, a halo that appeared at an angle of about 30°(2 θ) was shifted toward a low diffraction angle as decreasing Na2O contents.
    A. E. Owen reported as follows:
    In glass systems where the electric current is thought to be carried by alkali ions there is an approximately linear relationship between resistivity and activation energy over a very wide range of alkali concentration. In this work, however, several samples appeared out of accordance with the linear relationship.
    Bi2O3 behaves as both of network-former and network-modifier oxide in the glass, and besides, Bi element is classed with semiconductor-metals in periodic table. By these results, it was regarded that the mechanism of electric conduction in these glasses was not only ionic conduction but also more complex mechanism including electronic conduction.
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  • Kazuo OOKA, Toru KISHII
    1970 Volume 78 Issue 897 Pages 171-173
    Published: May 01, 1970
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The mechanisms of contraction of glass structure caused by ultra-violet irradiation were explained by the authors in terms of the conversion of oxygen ions from the nonbridging to bridging state and the fixation of alkali ions near the oxygen ions. The effects of these structural changes on the electrical properties of glass were examined with the following results: DC resistivity increased by irradiation; ε″ in the low frequency region decreased suggesting the decrease of alkali ion relaxation loss; and in the frequency region of 105-106Hz ε″ increased and ε′ decreased suggesting the shift of the network deformation loss peak to the low frequency side. These results were compatible with the mechanisms proposed by the authors.
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  • Yoji KAWAMOTO, Shoji TSUCHIHASHI
    1970 Volume 78 Issue 897 Pages 173-174
    Published: May 01, 1970
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The thermal expansion of the As-S glasses has been measured and the softening temperature (At), transformation temperature (Tg), and linear coefficients of thermal expansion from room temperature to Tg and Tg to At1 and αh, respectively) were determined from the expansion curve. The relationships of composition and At, Tg or α1 are interpreted by the structural model proposed for the As-S glasses previously.
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  • Takaho TANAKA, Hiroshige SUZUKI
    1970 Volume 78 Issue 897 Pages 174-175
    Published: May 01, 1970
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The thermal diffusivity of aluminum nitride was measured within the range from 1200° to 1630°C by electron beam method. The density of samples was from 83% to 95% of theoretical density. Thermal conductivity values were calculated from the thermal diffusivity data. The values were from 0.0204 (1250°C) to 0.0165 (1630°C) cal/cm·sec·deg. Thermal conductivity data of aluminum nitride in this temperature range can not be found in the literature, however, Taylor and Lenie have reported the data only within the temperature range from 200° to 800°C. Extrapolation of their values seems to be in fair contrast to the present author's.
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  • 1970 Volume 78 Issue 897 Pages A49-A60
    Published: May 01, 1970
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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