Journal of the Ceramic Association, Japan
Online ISSN : 1884-2127
Print ISSN : 0009-0255
ISSN-L : 0009-0255
Volume 94, Issue 1088
Displaying 1-13 of 13 articles from this issue
  • Condition of Atmosphere to Produce Red Copper Glaze
    Mitsuru WAKAMATSU, Nobuyuki TAKEUCHI, Hiroki NAGAI, Yoshiki ONO, Shing ...
    1986 Volume 94 Issue 1088 Pages 387-392
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Porcelain bodies applied with copper glaze were heated to 1300°C under various atmospheres in the same firing schedule. Colors of the glaze samples obtained were classified by reflectance spectroscopy. The mode of the copper distribution and its oxidation state in the glaze were examined by EPMA, EDX and ESR. The copper glaze was grey and green for reducing and oxidizing atmospheres respectively. Red copper glaze was obtained by heating in reducing atmosphere followed by cooling in oxidizing one. From ESR analyses, it was found that the red glaze consisted of Cu2+ as well as Cu+, as was assumed from the equilibrium condition. The result denied the conventional theory that the red coloration is caused mainly by metallic copper colloid. The red chromophore in red copper glaze was assumed to be Cu2O. The copper in glazes volatilized remarkably during the reducing firing.
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  • Hiroshi YAMAMURA, Toshihiko KAKIO, Hajime HANEDA, Akio WATANABE, Shin- ...
    1986 Volume 94 Issue 1088 Pages 393-399
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Oxalate of Ni2+ and Fe2+ was co-precipitated by titrating an aqueous solution containing Ni2+ and Fe2+ (Ni/Fe=0.5) to an oxalic acid solution. The oxalate changed to nickel ferrite on firing at various temperatures from 500° to 1000°C in air. The nickel ferrite thus obtained was an Fe-deficient spinal-type phase, of which chemical composition can be written as Ni1.09Fe1.91O3.95 from the results of chemical analysis and density measurements. The analysis of X-ray diffraction line-broadening showed that the sample fired at fairly low temperatures have many crystal imperfections such as lattice strain (Δd/d) and lattice defects, which decreased with increasing firing temperature and vanished above 800°C. The nickel ferrite having such crystal imperfections has a low saturation magnetization, which increased with increasing firing temperature. In order to clarify the relation between saturation magnetization and lattice imperfections, another sample of nickel ferrite, which was prepared by solid state reaction of NiO and Fe2O3, was mechanically ground for an extended tune period to introduce lattice strain. The saturation magnetization of the nickel ferrite thus obtained also decreased linearly with increasing lattice strain, as in the sample prepared by co-precipitation method. These facts suggest that the lattice strain, regardless of its origin, lowers the saturation magnetization.
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  • Saburo HORI, Yoshio ISHII, Masahiro YOSHIMURA, Shigeyuki SOMIYA
    1986 Volume 94 Issue 1088 Pages 400-408
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Spherical ultrafine (average 30-50nm) codeposited Al2O3-TiO2 powders were prepared by the oxidation of vapor mixture of AlCl3 and TiCl4 in a combustion flame. γ-Al2O3 and anatase and rutile TiO2 were detected in the as-prepared powders, but β-Al2TiO5, which was one of the major phases in the Al2O3-TiO2 powders prepared from AlBr3 and TiCl4 by r.f. plasma or in a tubular reactor, was scarcely observed. The simultaneous deposition of Al2O3 and TiO2, leading to the formation of β-Al2TiO5, became difficult due to the adoption of less reactive AlCl3. It appeared that the anatase TiO2 particles were not accompanied by Al2O3, while the rutile TiO2 crystallites dispersed in the Al2O3 contained noticeable amounts of Al2O3 metastably. The solution of Al2O3 into TiO2 appeared to promote the phase change of TiO2 from anatase to rutile. The calcination experiment was performed to investigate the stability of phases in the codeposited powders. The TiO2 appeared to accelerate the formation of α-Al2O3 due to the solution of TiO2 into γ-(or δ-)Al2O3. An unknown phase was detected in the powders calcined at 1200°C, whose X-ray diffraction pattern was similar to that of Na2Ti2Ti6O16. The new phase was considered to be a bronze-type compound containing H+ and Al3+, possibly expressed by H2-X(AlYTi1-Y)2Ti6O16-Z.
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  • Oxidation Resistance of C-SiC-B4C Composite in Air
    Ichitaro OGAWA, Takayoshi YAMAMOTO, Tsuyoshi HAGIO, Hisayoshi YOSHIDA, ...
    1986 Volume 94 Issue 1088 Pages 409-414
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The oxidation resistance of C-SiC-B4C composite materials was determined in air and compared with that of C-B4C composites. Powder mixtures of raw coke and SiC-B4C (42:58 in weight) was ground, compacted and baked in Ar gas at 2000°C. The oxidation resistance at 800°C was improved remarkably by more than 5vol% addition of SiC-B4C. Thus, the weight loss of the composites made from the ground powder containing 30vol% SiC-B4C was 0.2, 0.6 and 6% after 1000°C-20h, 1200°C-5h and 1300°C-5h heating respectively, whereas for C-B4C composites, 6 and 30% weight loss were recorded after 1000°C-20h and 1200°C-5h heating respectively. X-ray diffraction analysis and IR spectroscopy showed that the specimens were coated with a liquid film of B2O3- or SiO2-B2O3 glass in air.
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  • Hideki ICHINOSE, Yoshizo INOMATA, Yoichi ISHIDA
    1986 Volume 94 Issue 1088 Pages 415-418
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    A grain boundary of high purity SiC bicrystal grown by sublimation recrystallization method was observed by high resolution electron microscope in order to analyze the most stable, or the most basic, structure of SiC grain boundary. The boundary was expected to realize the most stable structure because it was grown slowly without any applied external forces which may prevent from free formation of the boundary. Purity of the crystal was kept below 10-17/cm3 in donor concentration. Observed structure of the boundary was coincided with one of three models which were constructed so that the number of dangling bond was least throughout the possible atomic arrangement at that orientation relationship. The reason why only one structure was preferred among three in spite of that the number of dangling bond was same was attributed to the effect of ionic bonding component of SiC crystal.
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  • Seigen RI, Kenya HAMANO, Zenbe-e NAKAGAWA
    1986 Volume 94 Issue 1088 Pages 419-424
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The temperature dependence of Debye length of undoped and Sm2O3-doped ZnO ceramic specimens in air and the changes in electrical resistivity caused by admission of propane gas were investigated. The Debye length of the both specimens increased as temperature increased from 100° to 550°C. Especially the Debye length of undoped ZnO specimens was 0.31μm at room-temperature (27°C) and 0.4μm at 550°C. Only specimens, whose neck radii were smaller than the Debye length, showed a decrease in electrical resistivity under the admission of propane gas. This mechanism is explained by the gate action of pinch-off potential at the necks.
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  • Yoshinari MIURA, Yukinori AKIYAMA, Katsuaki TAKAHASHI
    1986 Volume 94 Issue 1088 Pages 425-431
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Though it is well recognized that the knowledge on electrolysis of glass is important to understand ionic behavior of molten glass and to operate an electric melting furnace, there have been few investigations on the decomposition voltage of molten glass. In this paper, electrolytic behavior in the molten sodium borate glass system was investigated by measuring current-potential curves on Pt electrodes. The effects of water were also studied. The products on the Pt test electrode were identified both by direct observation during electrolysis and by EPMA analysis for the electrode-glass interface after polarization. Moreover, conceivable decomposition reactions were determined by comparing with the theoretical decomposition voltages. In the system containing small amounts of water (xNa2O⋅(10-x)B2O3, x=1-5), experimental decomposition voltages were 1.3-1.6V at 1000°C, which increased with increasing Na2O. In the system introduced much water (xNa2O⋅(10-x) H3BO3, x=1-3.33), experimental decomposition voltages were around 1.6V, which decreased slightly with increasing Na2O content. In the system containing small amounts of water, at the platinum cathode, noticeable bubbles due to the discharge of sodium ions (b.p. of Na=883°C) could not be observed at any applied potentials, but occasional and small bubble formation was observed due to the liberation of hydrogen gases which were decomposition products of water as an impurity. In this case, boron elements were produced at the cathode by the discharge of borate anions. In the system introduced much water, hydrogen gas evolution was observed prior to the reduction of borate anions. On anodic polarization, oxygen gases evolved. Comparison between experimental decomposition voltages and theoretical ones indicated that the most probable decomposition reactions might be such reactions as Na2B4O7→2NaBO2+2B+3/2O2 and Na2B6O10→Na2B4O7+2B+3/2O2.
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  • Masahiro ASHIZUKA, Hideki KIYOHARA, Eiichi ISHIDA, Makoto KUWABARA, Yo ...
    1986 Volume 94 Issue 1088 Pages 432-439
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The fatigue behavior of 3mol% Y2O3-partially stabilized zirconia with average grain size of 0.4μm (Z3Y-I) and 1.0μm (Z3Y-II) was studied by measuring their strength as a function of stressing rate (dynamic fatigue) and time to failure under constant stress (static fatigue). The crack growth parameter (N) measured by the dynamic fatigue technique at 20°C was 40.8 and there was no difference between the fracture stress-stressing rate relationship of Z3Y-I and that of Z3Y-II. The N value of Z3Y-I at 250°C was 50.5 and the fracture stress-stressing rate relationship was similar to that of Z3Y-I and Z3Y-II at ambient temperature. On the other hand, the N value of Z3Y-II at 250°C was 10.2 and it was found that the fatigue resistance of Z3Y-II decreased markedly at 250°C in comparison with that at ambient temperature. Average lifetime of Z3Y-I and Z3Y-II predicted from dynamic fatigue data at 20°C was about 12 years at the applied stress of 600MPa and about 20, 000 years at 500MPa, and lifetime of Z3Y-I at 250°C was 114 days at 600MPa and 3, 000 years at 500MPa. It was found that it is possibile to use Z3Y-I and Z3Y-II below the applied stress of 600MPa at 20°C and Z3Y-I below 500MPa at 250°C over a long period of time. On the other hand, the lifetime of Z3Y-II at 250°C was about 8 minutes at 500MPa, and even if applied stress was lowered to 200MPa, the lifetime merely extended to 4.7 months. The average lifetime of Z3Y-II measured by the static fatigue technique at 250°C was 4 to 6 times the liftime predicted from dynamic fatigue data, and the N value obtained from static fatigue data was 10.7 and it was considered that its value is the same as that from dynamic fatigue. The fracture surface of Z3Y-I and Z3Y-II tested by dynamic fatigue technique at 20°C and that of Z3Y-I at 250°C showed a smooth region near the fracture origin and was followed by a rougher area being spread in a radial manner from the fracture origin. Their fracture surface features were similar to those of the typical fracture surface observed in many ceramics. The fracture surface of Z3Y-II tested at a higher stressing rate at 250°C was similar to that in ambient temperature, too. However, if the stressing rate was lowered to 0.301MPa/s, fatigue fracture surface was observed at the fracture origin, and it was followed by a smooth region and rougher area. The fracture surface of Z3Y-II tested by the static fatigue technique at 250°C showed fatigue fracture surface near tensile surface and its zone size increased with decreasing applied stress and increasing time to failure.
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  • 1986 Volume 94 Issue 1088 Pages 439
    Published: 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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  • Yoshitomo TODA, Kazuaki HASHIMOTO, Koshiro HASHIMOTO, Yasuo ARAI
    1986 Volume 94 Issue 1088 Pages 440-448
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    CO3(PO4)2⋅8H2O was treated hydrothermally under the saturated vapor pressure at temperatures between 150° and 350°C. Co3(PO4)2⋅8H2O was placed in a micro-autoclave with water and was heated under several conditions. Characteristics of the obtained crystals, such as morphology, color and thermal stability were investigated. In particular, the colors were discussed on the basis of the spectral reflectance. Co3(PO4)2⋅8H2O changed to 2Co3(PO4)2⋅7H2O (platy: 2×20μm, light bluish purple) under hydrothermal condition at 150°C for 120h, to Co3(PO4)2⋅2H2O (granular: 28-46μm, dark purplish red) at 200°C for 48h, to Co3(PO4)2⋅H2O (needle-like: 17μm, light reddish purple) at 250°C for 72h, and to Co3(PO4)2 (platy: 7×10μm, deep reddish violet) at 350°C for 120h. 2Co3(PO4)2⋅7H2O, Co3(PO4)2⋅2H2O, Co3(PO4)2⋅H2O showed endothermic peaks due to dehydration at 393°C, 470°C, and 566°C on DTA curve, respectively. Addition of ZnCl2 to the hydrothermal solution remarkably accelerated the crystal growth of the obtained crystals, and their morphologies were considerably different from those without additives
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  • Yoshinori KANNO
    1986 Volume 94 Issue 1088 Pages 449-451
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    A Method for temperature-controlling of an innert gas furnace equipped with a B4C/C thermocouple has been proposed. The thermocouple was consisted of a graphite tube and a B4C rod connected to one another by a conical fitting. In the temperature range between 1300° and 2000°C, the thermoelectric voltage rose almost linearly and at 2000°C it was at ca. 450mV. The electric resistance of the thermocouple decreased slightly with increasing furnace temperature, reached a minimum at ca. 250°C, increased remarkably with a further increase of the temperature, and at 2000°C it was at ca. 4.4kΩ. Because of the high thermoelectric voltage and the violent variation of electric resistance, the temperature controlling unit was equipped with a volte-current converter having a high impedance, additionally.
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  • Hiroyuki IKAWA, Kunio SATO, Masaharu SUZUKI, Kazuyori URABE, Shigekazu ...
    1986 Volume 94 Issue 1088 Pages 452-453
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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  • The Cl2- Center in the Microsecond Time Range
    Takashi MAEKAWA, Noriyo KOTANIGAWA, Toshio YOKOKAWA, Sadashi SAWAMURA, ...
    1986 Volume 94 Issue 1088 Pages 454-456
    Published: April 01, 1986
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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