Journal of the Ceramic Society of Japan
Online ISSN : 1882-1022
Print ISSN : 0914-5400
ISSN-L : 0914-5400
Volume 107, Issue 1242
Displaying 1-18 of 18 articles from this issue
  • Kamilia A. El-Barawy, Samir Z. El-Tawil, Adel A. Francis
    1999 Volume 107 Issue 1242 Pages 97-102
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    Thermal reaction of Zircon with lime is studied within the temperature range 1200-1500°C for periods up to 4h. The heating products are examined physically, chemically and mineralogically. The extent of reaction is determined from the solubilized silica obtained by leaching the sintered products in hydrochloric acid. A product assaying -91% ZrO2 in monoclinic form is obtained by HCl acid leaching of the product fired at 1400°C for 2h in presence of 1.2 stoichiometry calcium oxide. The thermal reaction of decomposition at the aforementioned temperature seem to follow a diffusion kinetic model in the form of x+(1-x)In(1-x)=kt, where x is the extent of solubilized silica in time t and k is the rate constant. The apparent activation energy of the process was calculated and found to be 205kJ/mole.
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  • Jong-Won YOON, Masaru MIYAYAMA
    1999 Volume 107 Issue 1242 Pages 103-108
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
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    N-type and p-type semiconducting regions were formed on an insulating SrTiO3 single crystal by KrF excimer laser irradiation at non-treated and CuO-diffused surfaces, respectively. The n-type and p-type semiconductivity was confirmed using Hall coefficient measurement. The pn junction showed rectifying characteristics. An n-p-n structure was formed by laser-irradiation on a surface including a thin (1μm in width) CuO-diffused layer. It shows nonlinear I-V characteristics with a nonlinear coefficient of 7, as observed in semiconducting SrTiO3 ceramics with acceptor-diffused grain boundaries. This fabrication method was found to be effective for realizing the pn and n-p-n electrical properties at desired positions on insulating oxides.
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  • Yusuke OKAMOTO, Naoto HIROSAKI, Hideaki MATSUBARA
    1999 Volume 107 Issue 1242 Pages 109-114
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
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    A model is proposed for studying grain growth in silicon nitride by computer simulation. The simulation is based on the Monte Carlo method and uses the Potts model with additional features peculiar to silicon nitride ceramics, such as anisotropy of grain boundary energies and the presence of liquid phase. The simulation successfully produced self-reinforced microstructures. It was found that the self-reinforcement phenomenon occurred only within a particular range of liquid phase fractions. The influence of anisotropy in interface energy on inhomogeneous grain growth was also examined. When interface energies are isotropic, the microstructure was essentially homogeneous. The results of these simulations suggest that anisotropy in interface energy and the presence of an appropriate amount of liquid phase are two important factors controlling the self-reinforcement process in silicon nitride materials.
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  • Bok-Hee KIM, Ji-Won MOON, Jo-Young LEE, Youn-Kyu CHOI
    1999 Volume 107 Issue 1242 Pages 115-118
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
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    The synthesis of the perovskite Pb(Mg1/3Nb2/3)O3 powder by the emulsion method was investigated. Pb(NO3)2, Mg(NO3)2⋅6H2O, and Nb(HC2O4)5nH2O were used as starting materials. Span 80, kerosene and paraffin oil were used to prepare organic phase. Finely dispersed emulsions of mixed solution were prepared with the organic phase and dried using the petroleum drying method. Emulsion size distribution was in the range of 0.7-4.0μm. Mean particle size of powders as-dried at 170°C and calcined at 800°C was 0.4 and 0.3μm, respectively. A single phase of perovskite was obtained by calcination of as-dried powders at 800°C for 2h. The sintered body of emulsion-derived PMN at 1100°C showed a dielectric permittivity of over 11000.
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  • Yoshinori TAKAYAMA, Hideyuki NEGISHI, Satoshi NAKAMURA, Nobuyuki KOURA ...
    1999 Volume 107 Issue 1242 Pages 119-122
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
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    The charging behavior of various oxide particles was investigated using the zeta potential, which is affected by the electronegativity of the metal ion in an oxide and the properties of the solvents. Acetone, methylethylketone, cyclohexanone, ethanol (EtOH), 1-propanol (1-PrOH) and 1-butanol (1-BuOH) were used for the bath. In the case of the I2-added ketone bath, the H+ ion concentration increased with increasing I2 content. The zeta potential of the various oxide particles was changed to positive. The zeta potential of the oxides was large in the high H+ ion concentration bath. Accordingly, the positive charged oxide particles were attributed to the adsorption of H+ ion onto the particles. In the case of alcohol, included H2O generates H+ and OH- by electrolytic dissociation. Therefore, the zeta potential becomes large in the case when the electronegativity of the metal ion in oxide is low, and the H+ ion behaves as a potential determining ion.
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  • Kenji ITO, Yasuhiro YAGI, Shingo HIRANO, Masaru MIYAYAMA, Tetsuichi KU ...
    1999 Volume 107 Issue 1242 Pages 123-127
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    Pore size of several porous materials such as zeolites (MCM-41 and MCM-48) and highly fined grain aggregates of zirconia was estimated by means of positron annihilation lifetime measurement. Observed lifetimes of ortho-positronium (over -20ns, τ4 and τ5) correspond to the meso-pore sizes assessed by conventional porosimetries due to a nitrogen physisorption and a mercury porosimetry. The long-lived lifetime components included an unassigned lifetime component (τ5), which was not detected by the other porosimetry. The observed ortho-positronium lifetimes are correlated to the mean size of pores. A relation between relative intensities of the long-lived ortho-positronium components (I4 and I5) and specific surface areas is discussed and a variation of a numerical concentration of pores is correlated to the change of the particle sizes of the zirconia aggregates.
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  • Nobukatsu OHMICHI, Kunikazu KAMIOKA, Kuniyoshi UEDA, Koji MATSUI, Mich ...
    1999 Volume 107 Issue 1242 Pages 128-133
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
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    The tetragonal-to-monoclinic phase transformation of Y2O3-doped tetragonal ZrO2 polycrystals (Y-TZP) was investigated by annealing at 140°C in hot water. Sintered bodies of Y-TZP were prepared by sintering at temperatures ranging between 1300 and 1500°C, using a 3mol% Y-TZP fine powder, synthesized by means of the hydrolysis method, as a starting powder. X-ray diffraction measurements on the sample surfaces and Rietveld analyses revealed that the amount of cubic phase increased and the Y2O3 concentration within the tetragonal phase decreased as the sintering temperature increased. Scanning electron microscopy measurements also showed that the grain size on the sample surfaces increased as the sintering temperature increased. When the sintered bodies were subjected to annealing in hot water, the phase-transformation rate on their surfaces increased as the sintering temperature increased. This behavior can be explained by both the decrease in the Y2O3 concentration within the tetragonal phase and the increase in the grain size.
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  • Kunio HAYASHI, Mitsuhiro HASEGAWA, Hiroe KONDO, Yasunori OKAMOTO, Kenj ...
    1999 Volume 107 Issue 1242 Pages 134-139
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    Deformation behavior of four kinds of polycrystalline cordierites, fabricated by firing glass powder compacts at 1373K for 1h (heating rate of 6K/min or 20K/min) was characterized by a four-point-bending creep test. The powder compacts had a composition 2MgO⋅2Al2O3⋅5SiO2 and were eventually added with a small amount of ZrO2. The deformation of stoichiometric cordierite bodies obeyed a diffusional creep law at lower applied stresses, over the temperature range 1473-1523K. On the other hand, accelerate creep deformation was observed with increasing the applied stress and over the whole range of stress applied at 1573K, resulting from crack nucleation and coalescence. Deformation behavior, considered to be represented by the steady state creep rate over the temperature range 1423-1473K, was monitored in cordierite bodies added with 1.8mass% ZrO2 as a nucleation agent. However, this creep deformation was due to intergranular crack growth, whose opening increased proportional to time. Creep rupture of cordierite bodies added with ZrO2 occurred at lower applied stresses and temperatures as compared to stoichiometric cordierite bodies.
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  • Akira HASEGAWA
    1999 Volume 107 Issue 1242 Pages 140-146
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    Silica fibers coated with alumina layers have been prepared using a solution of aluminum nitrate dissolved in 1, 3-butanediol. Texture and crystallite structures of the alumina have been examined from a viewpoint of thermal stability of the modified silica fiber. Amorphous alumina layer could be uniformly prepared on the silica fiber by impregnating the fibers in the aluminum solution. The alumina layer transformed to crude assemblies of alumina particles after aging the alumina-modified silica fiber in deionized water at 100°C. The alumina particles were composed of fibrils with 6nm in diameter and 100-150nm in length. The phase of the alumina also changed from amorphous to boehmite by aging and to γ-alumina by reheating at 500°C. The texture of the alumina on the silica fiber was thermally stable up to 1200°C for the aged samples. The surface area, based on the weight of the alumina, of the samples calcined at 1200°C for 5h and 30h were 84m2·g-1 and 80m2·g-1, respectively. XRD analysis showed no α-alumina formation the after above treatment, indicating that the crude texture of the alumina might suppress sintering because of small contact area among the alumina fibrils. Furthermore, it was found that alumina surface was covered with silica, and the silica might also restrain the surface diffusion of alumina not to induce the sintering. Both the crude texture of alumina and silica on alumina structure might effectively improve the thermal stability of the silica fiber.
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  • Nobuyuki TOHYAMA, Byung-Nam KIM, Manabu ENOKI, Teruo KISHI
    1999 Volume 107 Issue 1242 Pages 147-152
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    The oxidation mechanisms of Si-Ti-C-O fiber-bonded ceramics had been investigated through thermogravimetric analysis, electron microscopy and X-ray diffraction. The influence of temperatures ranging from 773 to 1773K in air is discussed. The materials showed mass loss due to oxidation of the carbon interface and free carbon in the fibers at the beginning of the oxidation tests. Then, mass gain due to the formation of silica on the surface of the fibers was observed. When heat-treated below 1023K, most of the free carbon was oxidized and flexural strength decreased to almost zero. The free carbon contained in the materials was about 7.7mass% and oxidized along the fiber direction. On the other hand, upon heat treatment above 1073K, the oxidation of carbon was strongly inhibited due to a cristobalite coat formed on the surface of the specimen which maintained its initial strength even after oxidized for 100h. After the formation of the cristobalite coating, the materials showed an excellent oxidation resistance even if oxidized at 973K
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  • Toshio SHIMOO, Kei-ichiro HAYASHI, Kiyohito OKAMURA
    1999 Volume 107 Issue 1242 Pages 153-158
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    SiC-AlN powder mixture was prepared by heating a silica-alumina-graphite powder mixture in flowing nitrogen at temperatures between 1773 and 1973K. The reaction mechanism of the carbothermic reduction and nitridation has been both thermodynamically and kinetically investigated. The reaction rates were determined according to thermol balance and the reaction products were examined by X-ray diffraction. SiO2 was initially reduced into SiC and subsequently Al2O3 was reduced and nitrided into AlN. During reduction of Al2O3, AlON, Si2N2O, Si3N4 and SiAlON were produced as transitional phases. Once graphite is coated by a SiC layer, Al2O3 may also be reduced by SiC, with the consequent formation of the above transitional phases. The reaction rates of SiC and AlN formation were described by a three dimensional contracting-sphere formula for diffusion-control. The activation energies were 429kJ/mol for SiC formation and 611kJ/mol for AlN formation. The rate-determining steps of SiC and AlN formation are probably the diffusion through SiC layer formed around graphite particles and AlN layer formed around Al2O3 particles, respectively.
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  • Masayuki ARAI, Toshio SAKUMA, Uichi IWATA, Masahiro SAITOH, Tomofumi M ...
    1999 Volume 107 Issue 1242 Pages 159-165
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    Main components in gas turbine such as combustor, transition duct, first-stage nozzles and blades are coated with ceramic materials to prevent attacks by high-temperature and burnt gas environments. These coated components in service are subjected to frequent thermo-mechanical loading due to start-stop and steady operations. Recently, many damages, such as microcrack and/or delamination, have also been reported in these components. In order to comprehend mechanical properties of ceramic coating materials, we had measured Young's modulus and hardness changing with temperature and carried out 4-point bending tests. The aim of this study is to comprehend the damage process in ceramic coating layers and to propose a new strength evaluation method for crack initiation in the layer which is based on the Weibull statistical theory. As a result, it was found from continuous observations that coating damages proceeded as follows. In the elastic region of a stress-strain curve, a crack initiated at the coating surface and then propagated along the bonding interface with increasing load. An evaluation method of crack initiation in coating layer was proposed by considering a residual stress caused by the coating process. It was indicated that the proposed method could estimate with a good accuracy the crack initiation strength of coating layers from strength data of coating material.
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  • Toshiyuki SATA
    1999 Volume 107 Issue 1242 Pages 166-173
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
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    NaCl powder specimens composed of equally sized (approximately 1.8μm), cubic single crystals were prepared by additions of acetone to saturated NaCl solution at -21°C under various preparation conditions. Grain growth during storage of the powder specimens was found to be greatly influenced by moisture in the ambient atmosphere. Storage of the specimens in a furnace at 400°C prevented grain growth. Compacts of the powder specimens produced by cold pressing (CP) and cold isostatic pressing (CIP) were sintered, or the powders were directly hot-pressed (HP). Relative densities (RD) of the resulting sintered bodies depended on the compaction or sintering conditions. From these sintered bodies, appropriate equations relating bending strength with porosity and grain size were obtained. The high-temperature bending strength increased up to 300°C and then decreased at higher temperatures. Deflections observed in the bending tests incerased with sintering temperature, that is, with the increase in grain size. Observed tensile strength values (5-10MPa) were smaller than observed bending strength values (8-20MPa). Measured values of the Weibull coefficient and fracture toughness were m=5.34 and K1C=1.05MPa·m1/2, respectively. Single crystal specimens obtained from melts by the Czochralski method were also subjected to bending tests. These specimens showed large deflections above 200°C, and strain-hardening phenomena were also observed. Tension tests for single crystal whiskers prepared by condensation of vaporized NaCl in a flowing air conducted along the [100] direction, and showed that the strength incresed with the whisker cross sectional area up to a maximum value and then decreased. The highest stregth value was obtained in vacuum with lower values being obtained in dry air and moist air because of the effects of oxygen and moisture, respectively.
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  • Toyohiko SUGIYAMA, Atsushi FUJII, Tatsuro HORIUCHI, Toshihiko OSAKI, T ...
    1999 Volume 107 Issue 1242 Pages 174-180
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
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    A lot of test pieces are usually produced in glaze studies. Data base is useful for an efficient utilization of them. Construction of two data base systems was attempted for several hundred thousand glaze test pieces accumulated during many years of ceramic studies at the National Industrial Research Institute of Nagoya. One system was for filing of glaze test pieces data as a library catalogue, while the other was opened to the public on Internet WWW. The data items of the systems were reference number, glaze name, firing temperature, firing type, color, surface conditions, Seger formula, coloring element, picture of test pieces, and so on. Construction of data items, evaluation method of color, classification of glaze, and treatment of pictures were discussed in both the systems.
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  • Masahiro KATO, Minoru TAKAHASHI, Hidero UNUMA, Suguru SUZUKI
    1999 Volume 107 Issue 1242 Pages 181-183
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
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    It is known that the colors of inorganic pigments can be changed by adding of small amount of mineralizers. In this research, the effect of Mg2+ on the coloring of (Al, Cr)2O3-pigment was investigated. The Mg2+-added pigments consisted of (Al, Cr)2O3 corundum and Mg(Al, Cr)2O4 spinel. It was verified that the lattice constants of the corundum phase were not affected by the addition of Mg2+. The valence of Cr in (Al, Cr)2O3 and in Mg(Al, Cr)2O4 were trivalent as found by X-ray photoelectron spectroscopy. The color changing of the pigments was due to the content of Cr3+ in the Mg(Al, Cr)2O4.
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  • Shigeru OKADA, Toetsu SHISHIDO, Kunio KUDOU, Iwami HIGASHI, Makoto OGA ...
    1999 Volume 107 Issue 1242 Pages 184-186
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    PrRh4.8B2 single crystals were prepared from high temperature copper solutions by slow cooling method, using praseodymium tips, rhodium powders and boron powders as starting materials under helium flow. PrRh4.8B2 belongs to the orthorhombic system with the space group Fmmm; a=0.9697(4)nm, b=0.5577(2)nm and c=2.564(3)nm. Vickers microhardness and electrical resistivity of the compound were measured, and oxidation resistivity of the compound at high temperature in air was studied. Vickers microhardness (HV) and the electrical resistivity (ρ) value on (001) plane with the orthorhombic system of PrRh4.8B2 were in the range of HV=6.12-7.32GPa and ρ=670×10-6Ω·cm, respectively. The oxidation in air of PrRh4.8B2 crystals began to proceed at about 590°C. Weight gain of the sample heated up to 1200°C in air is 13% and the identified oxidation product consisted of the PrBO3 (orthorhombic) and Rh (cubic)
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  • Kazuyuki KUMEDA, Yoshihiro NAKAMURA, Atsushi TAKATA, Kozo ISHIZAKI
    1999 Volume 107 Issue 1242 Pages 187-189
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    The Pulsed Electric Current Sintering (PECS) method uses electric energy for sintering, however, the phenomenon behind this sintering process is ambiguous. The sintering of green bodies, especially insulating powders, requires Joule heat as well as other phenomena. Insulating materials can be sintered more quickly by the PECS method than by other similar processes such as the hot pressing method. We attempted to clarify why PECS facilitates sintering in a shorter period, using alumina balls as a model starting material. After sintering, the surfaces of the alumina balls were observed by scanning electron microscopy (SEM) and analyzed by electron probe micro analysis (EPMA) in an attempt to clarify the ambiguous phenomena which occurs during PECS. Crystallized alumina of excess aluminum and liquid-state bridging material were found on some parts of the surfaces of the balls, and whisker-like crystalline materials were also found on other parts of the surfaces. If the surface of alumina is exposed to an oxygen partial pressure of 5×10-12Pa at an estimated temperature of above 1880°C, which was about 380K higher than the die surface temperature, alumina can be reduced. Based on this hypothesis, it is concluded that part of the surface of the alumina balls was heated intensively during the PECS process. The high temperature at the surface promotes sintering.
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  • Xiao-Hong DU, Qing-Ming WANG, Uma BELEGUNDU, Kenji UCHINO
    1999 Volume 107 Issue 1242 Pages 190-191
    Published: February 01, 1999
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    The effective piezoelectric strain constant d33 and electromechanical coupling factor k33 of polycrystalline lead zirconate titanate (PZT) at different cutting angles have been measured by using the IEEE standard resonance method. It was found that for tetragonal PZT 48/52, the effective d33 and k33 monotonously decreases as the cutting angle canted from the poling direction increases. However, for rhombohedral PZT 54/46, the effective d33 has the maximum value along a direction which is canted about 45° away from the poling direction, while the effective electromechanical coupling factor is not sensitive to the cutting direction and remains almost constant in the cutting angle range from 0° to 45°.
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