Journal of the Ceramic Association, Japan
Online ISSN : 1884-2127
Print ISSN : 0009-0255
ISSN-L : 0009-0255
Volume 89, Issue 1027
Displaying 1-10 of 10 articles from this issue
  • Katsuaki TAKAHASHI, Yoshinari MIURA
    1981 Volume 89 Issue 1027 Pages 107-118
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The cathodic reactions of simple ions such as Cd2+, Ni2+ and Zn2+ and redox ions such as Fe3+/Fe2+, Cr6+/Cr3+ and As5+/As3+ in molten sodium borate (28.7Na2O⋅71.3B2O3) were investigated by potential sweep voltammetry with platinum electrodes. The electrolytic currents were measured when linearly changing potentials were applied to the electrodes. Potential sweep rates were selected between 10 and 0.02V/s. The electrode reactions and reversible electrode potentials of various ions were determined by analysis of the peak potential and the peak current in the current-potential curve at 950°, 900°, 850° and 790°C.
    Cadmium, zinc and nickel ions at lower temperature were reduced reversibly to metallic state with 2-electrons process without deposition on the electrode. On the other hand, lead and thallium ions were reduced reversibly to metallic state and deposited on the electrode. The latter results agree with the fact that these metals are preferentially adsorped on platinum electrode by Faradaic adsorption process in acidic aqueous solution.
    Such redox ions as Fe3+/Fe2+, Cu2+/Cu+, Sb5+/Sb3+ and As5+/As3+ were reduced stepwisely. In the cases of former two ions, 1-electron steps were followed by the second reduction steps of 2-electrons or 1-electron, respectively, while in the cases of latter two ions 2-electrons steps were followed by the second 3-electrons steps. Chromium, cerium and manganese which are expected to be reduced stepwisely, showed only one reduction step, respectively, because the second step became obscure by disturbance of the large residual current of the base glass. The reduction of tin ions shows the first step caused by adsorption phenomenon and is followed by the second step caused by the reduction of Sn4+ to Sn2+. On many ions the results obtained by potential sweep method were almost compatible with the previous studies by chronopotentiometry. Potential sweep method was found to be more suitable than chronopotentiometry in terms of detailed study on the electrode reaction.
    On the basis of these results, electrochemical series were established. For example, at 950°C the order of increase of oxidizing power was Cr6+/Cr3+>Mn3+/Mn2+≅Sb5+/Sb3+>Ce4+/Ce3+>Cu2+/Cu+>As5+/As3+>Sb3+/Sb>Sn4+/Sn2+>Fe3+/Fe2+>Pb2+/Pb>Cd2+/Cd>Tl+/Tl>Zn2+/Zn>Fe2+/Fe. The order of increase of oxidizing power among Cr, Mn and Ce ions coincided with the result by Kühl et al., but the order between As5+/As3+ and Sb5+/Sb3+ was reverse. The electrochemical series supports the results of measurement on the free energies of antimony and arsenic oxides in molten glass by Baak and Hornyak.
    Some equilibrium constants K between different redox pairs were calculated from the electrochemical series. The K value between iron and cerium ions approximately coincided with the value obtained by chemical analysis. In comparison with the results on mutual interaction of different redox pairs obtained from optical absorption measurement and chemical analysis, the reactions were shown to proceed toward the same directions in the cases of chromium-iron, manganese-arsenic and chromium-arsenic. In the case of chromium-cerium, however, the reverse direction of reaction was obtained. On manganese-cerium the K values obtained by these two different methods roughly agreed.
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  • Shigeto KANAOKA, Etsuzo KATO
    1981 Volume 89 Issue 1027 Pages 119-123
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The Izushi Toseki has been used for Kiyomizu-yaki (a porcelain product in Kyoto). A clay mineral specimen found in it was investigated by mean of chemical, thermal, IR and X-ray analysis.
    Chemical composition is: SiO2 54.48%, TiO2 0.06%, Al2O3 29.56%, Fe2O3 1.41%, CaO 0.13%, MgO 0.50%, K2O 6.15%, Na2O 0.36% and Ig. loss 7.80%. In DTA curve, three endothermic peaks at 100°C, 550°C and 680°C were found. In the X-ray diffraction pattern of oriented specimen, three peaks at 10.5Å, 5.09Å and 3.31Å and a weak shoulder at 23Å were recognized.
    In the X-ray pattern of randomly oriented specimen treated with E. G., three peaks at 14Å, 10Å and 5.09Å and a shoulder at 26Å were recognized. From these results this mineral found in the Izushi Toseki is a mica/smectite interstratified mineral having 90-70% mica layer and 10-30% smectite layer.
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  • Kazutoshi MATSUMOTO, Toshiyuki SATA
    1981 Volume 89 Issue 1027 Pages 124-129
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The effect of Ca-addition upon the vaporization of LaCrO3 has been studied in pO2 controlled atmosphere.
    Powder samples having the composition, La1-xCaxCrO3 (x=0-0.15) were synthesized at 1400°C in air from the mixture of La2O3, Cr2O3 and CaCO3, and pressed to pellets and sintered at 1700°C. The pellet was suspended by Pt·20%Rh wire in an alumina tube of a Mo-wound hydrogen furnace and heat-treated at 1650°C in atmospheres of O2-Ar or H2-CO2 mixture (pO2=10-10-1atm) at flowing rate of 60cm3/min (NTP).
    The weight loss of the specimen was almost proportional to heating time. The vaporization rates increased with increasing Ca content at any pO2, and showed a minimum value around pO2=10-2atm. The vaporization would be mainly attributed to CaCrO3 component from La1-xCaxCrO3 and the vaporization rate of CaCrO3 component would be fifty times as fast as that of LaCrO3 component.
    The surface after vaporization was found to be composed of three phases of the initial perovskite (P0), another perovskite (P1) having a smaller lattice constant than P0, and monoclinic B-type La2O3 (B-L). The P1 phase was considered to be Ca-rich LaCrO3 formed by decomposition of CaCrO3 component.
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  • Shigeki MORIMOTO, Michiharu MISHIMA
    1981 Volume 89 Issue 1027 Pages 129-134
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The precipitation of silver halide crystals, the photochromic properties and the effect of CuO were studied in aluminoborophosphate glass of the composition 33.4P2O5⋅22.2Al2O3⋅22.2B2O3⋅11.1MgO⋅2.5Na2O⋅8.6K2O (wt%) containing small amounts of Ag, Cl, Br and CuO.
    It was found that the amount of precipitated silver halide crystals showed a maximum at a certain temperature, which shifted to higher temperature with increasing Br content in glass. The maximum temperature above which silver halide crystals were not precipitated also shifted to higher temperatures with increasing Br content in glass. The ratio (Cl)/(Cl+Br) in precipitated silver halide crystals was always lower than that in glasses, decreasing gradually with increasing temperature.
    The saturation darkening increased with increasing amount of silver halide crystals precipitated. The half fading time increased with increasing crystal diameter of silver halides and with increasing Br content in glass.
    The glass containing no CuO showed no photochromism. The saturation darkening increased rapidly with increasing CuO content, reaching the maximum at about 0.05wt% CuO and decreased again with further increase in the CuO content. The half fading time decreased with increasing CuO content.
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  • Nobuhiro OHTA, Yoshinori FUJIKI
    1981 Volume 89 Issue 1027 Pages 134-139
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The moisture absorption, potassium extraction and thermal behavior of K2Ti4O9 fibers grown from various starting temperatures of slow cooling by the flux method are investigated.
    The fibers obtained from the high starting temperature of 1200°C or 1100°C have the large content of absorbed moisture, the small extractability of K+ ions in a dilute acid solution, the small amount of interlayer water and bound water which dehydrate at high temperature in comparison with them grown from the low starting temperature of 1000°C.
    The thermal behavior of hydrated titania fibers prepared by extracting K+ ions from the various K2Ti4O9 fibers mentioned above was also examined. The dehydration behavior of them resembles to that of the original K2Ti4O9 phases. In addition, during the heating of them originated from the high starting temperature, an inversion to an intermediate phase were represented by a sharp exothermic peak, and continuously, a transformation to anatase phase occurred to begin at relatively low temperature.
    The relationship between fabrication histories and the differences of chemical properties of K2Ti4O9 fibers is based on the temperature dependence of flux growth reaction, especially, on the differences of crystal size and quality.
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  • Yoko SUYAMA, Akio KATO
    1981 Volume 89 Issue 1027 Pages 140-147
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The relationship among the sinterability, the particle size and the sintering mechanism were studied by using the TiO2 powder prepared by the oxidation of TiCl4 in vapor phase.
    The relative density of sintered pellets increased with decreasing the particle size of TiO2 powder. The relative density of sintered pellet from the powder with average particle size of 0.06μm went up to 100% by sintering at 1200°C for 2h in air. The sintering of fine powder whose particle size are less than a few thousands Å proceeded via two densification processes, that is, the rapid densification by rearrangement of primary particles at above 750°C and the slow densification by diffusion mechanisms accompanying grain growth, neck growth and elimination of pores at above 900°-1000°C. For the powder which predominantly consisted of particles of above 1μm, the densification by the rearrangement was not observed and the densification proceeded slowly by diffusion mechanisms at above 1000°C. The high sinterability of fine TiO2 powder is considered to be due to (1) the densification by the rapid rearrangement and (2) the contribution of the effects of particle size on the sintering in the diffusion mechanisms.
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  • Yasutoshi T. HASEGAWA, Kazushi HIROTA, Tsuneko YAMANE, Mamoru MITOMO, ...
    1981 Volume 89 Issue 1027 Pages 148-155
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Hot-pressed β′-sialon (z=1-4) and reaction sintered β′2 “balanced” sialon were prepared from commercial grade Si3N4, SiO2 and AlN powder. Densities of sialon were 2.853 (z=1), 3.108 (z=2), 2.980 (z=2, RS), 3.095 (z=3) and 3.110g/ml (z=4). Specimens were oxidized in dry oxygen at temperature 1200° and 1300°C for up to 720h (30d), and characterized by measurements of weight gain, X-ray diffraction, EPMA, SEM and microscopy. The main oxidation products were mullite and cristobalite which formed around internal pores and surface (stage 1), and eventually as a relative dense oxidized layer (stage 2). The weight gain in each stage is proportional to (time)1/2 and erratic point between stage 1 and stage 2 appear at about 168h (7d). The rate of oxidation in each stage increases with increasing temperature. The weight gain of oxidized samples are as follows:
    β1′>β2′>β3′>β4′ But the mean thickness of oxidized layer, as contrasted with the weight gain, are as follows: β1′<β2′<β3′<β4
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  • Ryozo OYAMADA
    1981 Volume 89 Issue 1027 Pages 156-159
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Mullite formation at low temperatures from low grade kaolin (Roseki) with the addition of mineralizer (LiF) was described. Samples were sintered for 90 days at 700°-1200°C. Mullite yields of the samples were measured by X-ray internal standard powder method. Relations among mullite yields (αi) and logarithms of sintering time (t) were represented as follows:
    α1=-4.3+2.3logt (t: 72-1300h) at 700°C. α4=-0.5+3.0logt (t: 15-1000h) at 900°C. α6=2.0+3.1logt (t: 1-700h) at 1050°C. α8=8.9+4.2logt (t: 1-25h) at 1200°C.
    It becomes apparent that reaction of mullitization of low grade kaolin containing mineralizer at low temperatures proceeds through the stage of Al-Si spinel phase. Activation energies of the reactions are 10.3kcal/mol at below 950°C and 65.8kcal/mol at above 950°C.
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  • High Density β-spodumene Series Ceramics and Its Infrared Radiation Properties, Part 2
    Hirotaka YAMAMOTO, Hideaki NINOMIYA
    1981 Volume 89 Issue 1027 Pages 160-163
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Ceramics, at high temperature stage, radiates the infrared rays much more than other materials, it was reported. We confirmed it by the β-spodumene series ceramics. In the 1st report, this ceramics is more superior than actual heaters for drying from market, in the infrared radiation intensity, it was confirmed. So, in this 2nd report, the infrared radiation effect for some organic material and water by β-spodumene series ceramics heater and other material heaters is measured, through their practical temperature rising. As the result through 1st and 2nd reports, this β-spodumene series ceramics has the possibility of using as the new high temperature heater material, it was confirmed.
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  • 1981 Volume 89 Issue 1027 Pages A16-A20
    Published: March 01, 1981
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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