Journal of the Ceramic Association, Japan
Online ISSN : 1884-2127
Print ISSN : 0009-0255
ISSN-L : 0009-0255
Volume 90, Issue 1044
Displaying 1-13 of 13 articles from this issue
  • Hiroshi HIRASHIMA, Minoru MITSUHASHI, Tetsuro YOSHIDA
    1982 Volume 90 Issue 1044 Pages 411-419
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The glass formation region of the system was determined. Composition- and temperature-dependence of dc conductivity of the glasses were measured in the temperature range from 100°C to the temperature which was 10°-20°C below the glass transition temperature, Tg. Density, thermal expansivity, Tg and fraction of the reduced transition metal ion were measured. Conduction mechanism of the glass was discussed from the view point of the small polaron hopping theory by N. F. Mott. The adiabatic approximation, in which the tunnelling factor, α, was assumed to be nearly zero, was roughly applicable for these glasses within the errors of about one order of phonon frequencies, ν0, but the reasonable values of α and ν0 which agreed with other experimental results were not obtained. The activation energy was the predominant factor to determine the dependence of conductivity on the composition. The dc conductivity and the activation energy for conduction of the glasses containing less than about 10mol% of Fe2O3 depend on V2O5 content predominantly as in V2O5-P2O5 glasses. Fe2+ was not found by the measurement of Mossbauer spectra of these glasses. The contribution of Fe-ion pairs to conduction was concluded to be much less than V-ion pairs. The glasses containing more than about 20mol% of Fe2O3 had higher conductivity than V2O5-P2O5 glasses. Addition of Fe2O3, or substitution of V2O5 or P2O5 with more than 20mol% of Fe2O3 increased the conductivity and decreased the activation energy. Fe-ion seemed to contribute to the conduction together with V-ion. The observed conductivities of these glasses were much higher than the calculated values from the assumption for the adiabatic equation that the conduction path was composed of V-ion pairs or Fe-ion pairs independently. It was suggested that the hopping conduction between V- and Fe-ions could take place.
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  • Mikio SUGAI, Shigeyuki SOMIYA
    1982 Volume 90 Issue 1044 Pages 420-426
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Effects of SiO2-TiO2-Al2O3 liquid phase on sintering of zircon were investigated with the compacts of zircon containing 0-30wt% additives at 1600°C. Compositions of additives used in this study were 85-100wt% SiO2-TiO2 eutectic mixture (89.5wt% SiO2, 10.5wt% TiO2) and 0-15wt% Al2O3. The liquid phase was formed from additives in the sintered bodies. The resultant liquid accelerated sintering of zircon and increased the density of the sintered zircon bodies by filling the intergranular spase of the compacts. But excess liquid prevented binding of each zircon grain, resulting in the high closed porosity. Therefore, the adequate amounts of additives for sintering of zircon were in the range of about 10 to 20wt%. The increase of Al2O3 contents in additives resulted in a faster melting of additives and in a decrease in the viscosity of liquid. Consequently, it caused a decrease in the open porosity and an increase in the closed porosity. Since the former was more significant than the latter in this study, the overall effect was favorable for densification. The use of pre-glassified additives, which contained none and 5wt% Al2O3, resulted in an acceleration of formation of liquid and of sintering of zircon with a significant decrease in the open porosity.
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  • Tetsuo MATSUO, Shigeru TOYOURA
    1982 Volume 90 Issue 1044 Pages 427-432
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Recently, various types of ceramic hard materials are being used for machine parts. The superhard abrasive grains; diamond and CBN-boron nitride, are indispensable tool material for the cutting and grinding of these hard materials. The major problem in these tools is wear, and hence, much attention are being paid to the wear research of superhard abrasive grains and wheels. In this study, a series of pin-on-disc grain wear test has been performed for six different hard abrasive grain types, including diamond and CBN, against various hard materials such as sintered carbide, sintered alumina and sintered magnesia. The wear test was made at the speeds of 300 to 1200m/min under the vertical loads of 2.5N or 4.5N. Thus, the relative wear ranking of grain was determined for each disc material. This result was discussed based on the results obtained on SEM-micrograph of worn surface of grain, frictional force measurement, disc wear volume measurement and wear debris observation. From the wear research it is evident that the relative wear ranking is independent of the disc material used. Namely, the most small wear was obtained on the diamond grain as expected, followed by the CBN grain, and the silicon carbide grain types show the largest wear, and the alumina grain types lie between the superhard grain types and the silicon carbide grain types. Increased sliding speed seems to increase wear rate. Many thermal cracks were observed on the wear surface of the grain, especially when the sintered alumina or the sintered SiC disc is used. The crack will increase the grain wear at high sliding speeds.
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  • Atsushi OHTSUKA, Mitsuaki SHIZAWA
    1982 Volume 90 Issue 1044 Pages 432-440
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    This study was concerned with the formation and color of the olivine type and the phenacite type solid solutions in (Co, Mg, Zn)2SiO4 system. Specimens were prepared by calcining the mixtures of each oxide of cobalt, zinc and silicon, and basic oxide of magnesium at 1300°C for 3h. Formation range of the olivine type and the phenacite type solid solutions in (Co, Mg, Zn)2SiO4 system were examined by X-ray analysis, and the lattice parameters of each solid solution were calculated. The color was discussed by measuring the spectral reflectance, and the stability of specimens in glazes (colored glaze test) was observed. The results were summarized as follows.
    1) The incorporation of Zn2SiO4 into Mg2SiO4 or Co2SiO4 was ca. 15mol%.
    2) The incorporation of Co2SiO4 into Zn2SiO4 was ca. 45mol%, but that of Mg2SiO4 into Zn2SiO4 was ca. 35mol%.
    3) Equal amounts of Mg2+ occupied M1 and M2 sites respectively in olivine. In the case of incorporation of Co2SiO4 into Mg2SiO4, a large portion of Co2+ occupied M1 site, and therefore, the deviation from Vegard's law was observed in olivine type solid solutions in (Co, Mg, Zn)2SiO4 system.
    4) Purple or pink developed in olivine type solid solutions in (Co, Mg, Zn)2SiO4 system, resulting from the octahedral Co2+. On the other hand, blue developed in the phenacite type solid solutions in (Co, Mg, Zn)2SiO4 system owing to the tetrahedral Co2+.
    5) The phenecite type solid solutions in (Co, Mg, Zn)2SiO4 system were stable in zinc-mat glaze, and development of blue or violet was observed.
    6) The olivine type and the phenacite type solid solutions in (Co, Mg, Zn)2SiO4 system decomposed in lime-zinc glaze and lime glaze, but in these solid solutions cobalt ions were maintained only as the divalent state, and therefore, blue or violet developed.
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  • Minoru IMAOKA, Suguru SUZUKI
    1982 Volume 90 Issue 1044 Pages 440-447
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The retarded elasticity was investigated for SiO2-Na2O and B2O3-Na2O glasses by using a compressive method in the transition range. The compliance (J) determined at the final stage of each measurement displayed a maximum as a function of viscosity of glass in both systems and was simulated by the same equation applied for As-Se glasses reported in a previous paper. J=(1-k2ηG/η)(f1[k1/η]+f2[nk1/η]) (3) where k1, k2, f1, f2 and n are parameters and ηG is the viscosity related to the retarded elasticity. The terms [k1/η] and [nk1/η] are assumed to be equal to unity for all values exceeding one. Therefore, the experimental Equation (3) is valid for the oxide glasses in the systems SiO2-Na2O and B2O3-Na2O.
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  • Tadashi SASA, Shin KOGA, Satoru KURITA
    1982 Volume 90 Issue 1044 Pages 447-458
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Pressureless-sintered or reaction-bonded silicon carbide and silicon nitride (S-SC, S-SN, RB-SC, RB-SN, respectively) were selected as the candidate materials for advanced gas-turbine combustors. Data of thermal and mechanical properties of these materials representing the present state of the manufacturing technology were evaluated. Characteristic tensile strengths corresponding to the spontaneous fracture of the materials were deduced from the available bending strength data on the basis of Weibull statistics. A simplified model of combustor tube was selected, which corresponds to the primary combustion zone without film-cooling. Computations of the steady-state temperatures and thermal stresses of the combustor wall were carried out by FEM, and the failure probabilities associated with the spontaneous fracture by thermal stress were calculated. The dependences of the results on the selection of material, wall thickness, flame temperature and Weibull modulus of the strength of the material were studied. The selection of material gave large effects on the maximum temperatures and the temperature gradients, and their trend was as RB-SN<S-SN<RB-SC≅S-SC. The change of thermal stress with the selection of material was as S-SN≅S-SC≅RB-SC<RB-SN at flame temperatures below 1600°C. The increase in flame temperature resulted in the increase in thermal stress, which was steepest in the case of S-SN because of the largest temperature dependence of the properties of that material. The failure probabilities of the ceramic combustor tubes associated with the thermal stress increased with flame temperature. Especially those of S-SN and RB-SC showed highly steep increase due to the steep decrease of the strengths of these materials with temperature. The failure probabilities were as RB-SN<RB-SC≅S-SC≥S-SN at flame temperatures>1600°C, but were as S-SN<RB-SC<RB-SN<S-SC at flame temperatures≅1800°C. The Weibull modulus associated with the strength of material had an extremely large effect on the failure probabilities of the combustor tube. Reasonably high reliabilities are not expected from materials with Weibull moduli>10.
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  • Yoshinori TANAKA, Jiro FUKUNAGA, Masahiro SETOGUCHI, Tuneyuki HIGASHI, ...
    1982 Volume 90 Issue 1044 Pages 458-463
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    A new compound was found recently in the glass forming region of K2O-Al2O3-B2O3 three component system. EPMA and chemical analyses showed that this crystal is K3AlB8O15. Single crystals up to 0.1mm were grown by the slow cooling method from a stoichiometric melt in a Pt cruicible. Unit cell dimensions and standard errors are a=10.107±0.005Å, b=11.485±0.005Å, c=12.760±0.005Å and β=91.54±0.02°. The observed and the calculated densities are 2.10 and 2.11g/cm3, respectively. The formula units in the cell is Z=4. The crystal was weakly hygroscopic and covered with collodion film. Weissenberg photographs were obtained using Cu Kα radiation for the zero to the 2nd layer on the rotation around the b-axis and for the zero layer on the rotation around the c-axis. Intensity data were collected at 3670 reciprocal lattice points with a four-circle single crystal automatic diffractometer by using Mo Kα radiation. The systematic extinctions for the reciprocal lattice points closely obey the requirements for the space group C52h-P21/c. The true space group seems to be of lower symmetry, C2s-Pc, however. So the structure was analysed for the both space groups. The structures were determined by the direct methods, using the MULTAN 78 program system. The structures were refined by the method of least-squares using a block diagonal matrix program. Atomic scattering factors corrected for dispersion were used. The structure refined to R values of 0.050 and 0.051 for space groups Pc and P21/c, respectively. As very similar structures were obtained, the space group P21/c was used for a description of the structure. The aluminoborate polyanion in this crystal is built up from three different groups, viz. the double ring pentaborate group, the single ring triborate group and a single AlO4 tetrahedron. The groups are mutually connected by sharing of oxygen atoms to an infinite two dimensional double layer, which runs almost perpendicular to the a-axis of the crystal. In this layer, upper and lower anion networks are connected by a bridge between pentaborate groups and AlO4. The average B-O bond lengths for the BO4 tetrahedra and the BO3 triangles are normal, and 1.474 and 1.364Å, respectively. The AlO4 tetrahedra are distorted, and one Al-O bond is longer than the other three Al-O bonds. The coordinating O atoms do not surround the K atoms in a symmetrical fashion. Anionic networks of oxygen polyhedron have similar configuration as β-Na2O⋅3B2O3 crystal, except for the replacement of B by Al at the tetrahedral sites. In alkaliborate glasses, introduced Al atoms often occupy tetrahedral sites just as in this crystal.
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  • Makio KINOSHITA, Kiyoshi ITATANI
    1982 Volume 90 Issue 1044 Pages 463-469
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    The sintering of MgO with γ-Ca2P2O7 addition in the concentrations of 0.1, 0.5, 1.0 and 3.0mol% has been studied at increasing temperatures up to 1400°C (heating rate: 10°C⋅min-1) and at a constant temperature of 1400°C in air. The shrinkage coefficient of specimens (5mmφ×3mm) was measured dilatometrically at increasing temperatures and the bulk density of fired specimens (originally 8mmφ×3mm) was evaluated. The microstructure of resultant specimens was examined. The results of sintering at increasing temperatures were nearly in accord with those at constant temperature. At increasing temperatures, the shrinkage process of MgO specimens was markedly different for various contents of γ-Ca2P2O7. The shrinkage was promoted in the initial stage (950°-1150°C) and delayed in the final stage (1200°-1400°C) by the addition of 0.5mol% or more γ-Ca2P2O7. At constant temperature, the densification of MgO specimens was inhibited by the addition of γ-Ca2P2O7 in all the concentrations used and was most inhibited by that of 1.0mol%. However, a liquid phase formed at 1200°C, which retarded the growth of periclase grains. The reaction products in the sintering process were β-Ca3(PO4)2, Ca3Mg3(PO4)4, and Mg3(PO4)2 at increasing temperature. The final reaction product was (Ca, Mg)3(PO4)2, at a constant temperature of 1400°C for 5h. The above products had little effects on the lattice parameter of periclase.
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  • Makoto KUWABARA
    1982 Volume 90 Issue 1044 Pages 469-476
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
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    Large PTCR (positive temperature coefficient of resistivity) effects of more than seven orders of magnitude have been observed in porous semiconducting barium titanate ceramics with small average grain sizes in the range of 2 to 5μm and porosities between 10 and 20%. It has been shown that the magnitude of the PTCR effect in the porous materials was very sensitive to both the average grain size and the degree of sintering, where densification to a high relative sintered density above 90% which was normally associated with a significant grain growth led to a drastic degradation of the PTCR effect. This paper is concerned with factors affecting the magnitude of the PTCR effect in barium titanate ceramics, in which the influences of both the inclusions and the ununiformity of grain size existing in the starting material on the effect were specifically investigated. They often cause exaggerated graingrowth leading to a small PTCR effect. Mixtures of Al2O3 and SiO2, SiO2 and TiO2 were intentionally added in the starting material as inclusions in this study.
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  • Kazuyuki HIRAO, Naohiro SOGA
    1982 Volume 90 Issue 1044 Pages 476-481
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
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    The heat capacities of several alkali aluminosilicate glasses were measured at 77 to 300K. The experimental results of these glasses were analyzed using the three-band theory. The characteristic temperatures (θ1, θ3, θE) obtained were used to determine the nature of atomic interactions in glasses. The behaviour of the Gruneisen parameter γ(T) obtained by using the result of heat capacity, thermal expansion coefficient, density and bulk modulus for alkali aluminosilicate glasses was not depending on alkali content, which was different from alkali silicate glasses. The behaviors of these parameters are considered to be due to the lack of non-bridging oxygen in aluminosilicate glasses.
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  • Ryozo OYAMADA, Kazuhiro SUMI
    1982 Volume 90 Issue 1044 Pages 481-484
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
    Effect of additives on the mullite formation reactions of North Korea kaolin was studied. Knead-formed samples containing 20mol% of LiF, Li2CO3, MgF2, MgO, CuF2 and CuO were heated at 1000°C up to 90 days and the amount of mullite formed was determine dby X-ray diffractometry. Mullite yields (%) were as follows: without additives 8.7; when Li2CO3 was added, 16.5; LiF, 18; Li2CO3 (10mol%), 19.7; MgF2, 20.7; MgO, 22.5; CuF2, 27.7 and CuO, 29.3. It has been deduced that all the reaction rate curves obtained follow the Tammann's equation, where the mullite yield increases linearly with logarithm of time and reaches to a constant value αe at a time te.
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  • Shen-tai SONG, Masahiro YOSHIMURA, Shigeyuki SOMIYA
    1982 Volume 90 Issue 1044 Pages 484-486
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
    JOURNAL FREE ACCESS
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  • 1982 Volume 90 Issue 1044 Pages A51-A54
    Published: August 01, 1982
    Released on J-STAGE: April 30, 2010
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