Journal of the Ceramic Society of Japan
Online ISSN : 1882-1022
Print ISSN : 0914-5400
ISSN-L : 0914-5400
Volume 100, Issue 1158
Displaying 1-24 of 24 articles from this issue
  • Shigeru YAMAGATA
    1992 Volume 100 Issue 1158 Pages 107-111
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
    JOURNAL FREE ACCESS
    The effects of prolonged irradiation of KrF (248nm) and ArF (193nm) lasers on the optical properties of silica glass were studied, with a glass made from a high purity silicon tetrachloride by the oxy-hydrogen flame hydrolysis method for sample. Experiments were conducted as an acceleration test for services in excimer laser apparatuses, and the results were examined in terms of solarization, i.e., degradation in transmission, T, or increase in the absorption coefficient at 5.8eV, k2, as a function of the per pulse laser energy density, ε. It was found that k2 was related to ε as in: for KrF excimer laser: k2=2.38×10-7⋅ε3.15(ε⋅p)1.31, and for ArF excimer laser: k2=8.71×10-8⋅ε1.42(ε⋅p)1.45, where p is the number of shots. It was demonstrated that these formulas were precise enough to make reasonable estimates of the service lifetime for silica glass in industrial excimer laser apparatus, where the intensity of the laser would be much smaller.
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  • Takenobu SAKAI, Izumi HIRABAYASHI, Shoji TANAKA
    1992 Volume 100 Issue 1158 Pages 112-116
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The critical current density (Jc) of superconductor with high-Tc depends on the orientation of grains highly. In order to investigate the effect of orientation, the superconducting wires were fabricated by an extrusion method and examined on superconducting properties. The Bi-based superconducting powders were mixed with the wax binder after calcining at 1113K for 200h in air, and extruded to form wires 1mm in diameter at 403K. The samples, after burned wax binder out in air, showed the poor superconductivity due to a deficiency of oxygen confirmed by an X-ray diffraction analysis. On the other hand, the good superconducting property was obtained with the samples burned wax binder out in flowing oxygen gas. It is found from magnetic susceptibility data that particles oriented approximately parallel to the extrusion direction.
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  • Satoshi IIO, Tomonori NIWA, Yo TAJIMA, Masakazu WATANABE
    1992 Volume 100 Issue 1158 Pages 117-121
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The crack propagation behavior in gas pressure sintered Si3N4 was investigated under cyclic and static loading by 3-point bending for pre-cracked specimens by indentation on the center of the mirror finished tensile surfaces. Crack propagation occurred under cyclic loading with a maximum applied stress below the applied stress at which crack propagation stagnated under static loading, showing that crack propagation velocity under cyclic loading was higher than that under static loading. Although intergranular crack propagation with crack-bridging was observed in both cases under cyclic and static loading, crack-bridging, observed after static loading, was found to be fractured by the subsequent cyclic loading. It was thought that the crack shielding force by crack-bridging, which is effective for restraining crack propagation under static loading, was decreased by cyclic loading, resulting in faster crack propagation under cyclic loading than under static loading.
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  • Preparation of Transparent Gel Monoliths of Y2O3-Doped ZrO2
    Hiroaki HAYASHI, Hisao SUZUKI, Hajime SAITO
    1992 Volume 100 Issue 1158 Pages 122-127
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Polymeric gels of Y-doped zirconia were successfully prepared by the controlled hydrolysis and polycondensation of zirconium n-propoxide and yttrium nitrate. The following parameters affected on the reaction mechanism and the microstructure of the resulting gels: (1) the kind of catalyst, (2) the water to alkoxide ratio and (3) the amount of yttrium nitrate. Acetic acid was very effective to control the alkoxide reaction under the limited water to alkoxide ratio. The complex effect of the steric hindrance by alkoxide-acetic acid chelating and the enhanced hydrolysis by the increased proton could control the polycondensation moderately. The yttrium nitrate hydrate acted as a hydrolysis accelerator, which also affected the microstructure of the resulting gel. Transparent monolithic gels of Y-doped zirconia containing up to 10mol% yttrium oxide were successfully prepared by optimizing these parameters.
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  • Hiroshi SHIGA, Hideo TSUNATORI, Mohamed G. M. U. Ismail, Keiichi KATAY ...
    1992 Volume 100 Issue 1158 Pages 128-133
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Mullite/15vol% ZrO2 composite powders doped with MgO were synthesized using sol-gel method. The effects of MgO addition on the powder characteristics, sinterability, microstructure and mechanical properties have been investigated. The addition of more than 0.3wt% MgO resulted in the formation of ZrSiO4 when calcined at 1400°C. This reaction is ascribed to the liberation of SiO2 from mullite grains due to the exsolution of MgO. ZrSiO4 decomposed to t-ZrO2 and SiO2 liquid phases during sintering process. The decomposition temperature decreased as the MgO content increased, and the lowest decomposition temperature of 1440°C was observed in the composition containing 1.0wt% MgO. The sinterability of composite powders was greatly improved by the addition of MgO. The densification temperature necessary to achieve a relative density of higher than 99% was lowered from 1630° to 1450°C by the 1.5wt% MgO addition. Although the remarkable grain growth was observed with an increased addition of MgO, the amount of t-ZrO2 in the specimens were also increased. Due to the transformation toughening, the mechanical properties were improved, such as flexural strength of 560MPa and KIC value of 5.8MPa⋅m1/2 for the 1.5wt% MgO doped composite fired at 1475°C.
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  • Shinichi KATSUDA, Yoshitaka KAWANISHI
    1992 Volume 100 Issue 1158 Pages 134-137
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Silicon nitride (SiN) thin films prepared by reactive sputtering are one of the protective layer materials for optical disks. SiN films with low internal stress have been prepared only under restricted sputtering conditions. Chemical stability of SiN films is sensitive to the sputtering conditions, especially to total (Ar+N2) gas pressures and to fraction of N2. The fraction of N2 also influences refractive indices of deposited SiN films. Sputtered SiN films with proper refractive indices and low internal stresses have been proved to have sufficient stabilities for the protective layers of the magneto-optical disks, because such SiN films showed good water proof properties against the oxidation of the magnetic layer (rare earth-transition metal alloy), of which corrosion speed is very fast.
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  • Junya NISHINO, Yuh SHIOHARA, Shoji TANAKA
    1992 Volume 100 Issue 1158 Pages 138-143
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The effect of low temperature pre-heating (LTPH) in the ranges of 350°C to 500°C was studied on the characteristics of YBa2Cu3O7-δ ceramics prepared by sintering the starting powders of mixed Y(OH)3, Cu(OH)2 and Ba-metal in ethanol solution. A critical current density of about 103A/cm2 was achieved in spite of the samples of large cross-sectional areas of 0.03-0.04cm2 by LTPH treatment of 500°C for 10-100h. It was found that the LTPH treatment removes water and other gases from the starting powder and also induces a uniform distribution of various constituent elements, especially oxygen.
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  • Ichiro TAKAHASHI, Takakazu YOSHIOKA
    1992 Volume 100 Issue 1158 Pages 144-147
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The test technique for measuring Young's modulus for ceramics at elevated temperature was studied. (1) Test technique for measuring Young's modulus at elevated temperature was developed by using the impact sound. (2) The eigenvalues increased monotonically with an increase in slenderness ratio. The difference in eigenvalues due to the slenderness ratio, was more remarkable in higher modes. The eigenvalues were not affected by the Poisson's ratio. (3) The Young's modulus of the SiC and Si3N4 did not depend upon the elevated temperature. The Young's modulus of Al2O3, AlN, ZrO2, CrC and TiN decreased with an increase in temperature. The Young's modulus of the composite ceramics Si3N4/BN increased slightly with increasing temperature.
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  • Hitoshi OHSATO, Shoji OKUDA, Masato MITSUMATSU, Iwao MAKI
    1992 Volume 100 Issue 1158 Pages 148-151
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Pseudobinary phase relations relevant to K-Al-priderite (KxAlxTi8-xO16) have been given with the incongruent melting temperature of priderite and the eutectic melting temperature between priderite and rutile. From the lattice parameter change K-Al-priderite has been proved to occur in the range of 1.47<x<1.80 at 1200°C. With increasing x the a-axis decreases from 10.064 to 10.042Å, while the c-axis expands from 2.937 to 2.939Å. The formation range becomes narrow with increasing temperature and finally converges at x=1.5. The stability of K-Al-priderite with x=1.5 was discussed in connection with the formation of a super structure.
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  • Hideaki YAGI, Michitoshi NAKATA
    1992 Volume 100 Issue 1158 Pages 152-156
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Ultra-fine paticles of Al2O3, TiO2 and SnO2 prepared by the sol-gel method for humidity sensing materials with an optimal porous structuture, a superior humidity sensing characteristics have been acquired in a humidity range of 10 to 95% RH and at an operation temperature of -20 to 100°C. The sensing mechanism of this humidity sensor utilizes the variation in proton conductivity in absorbed water. This mechanism has proved to be hard to use at temperatures above 100°C. Heat cleaning by a ceramic heater enables us to improve humidity sensors of high reliability and high precision. They are exellent in withstanding various corrosive environments over a long period.
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  • Toshio SHIMOO, Masaki SUGIMOTO, Kiyohito OKAMURA
    1992 Volume 100 Issue 1158 Pages 157-162
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The fibers containing 5% O (fiber-A) and 17% O (fiber-B) were prepared from polycarbosilane by the oxidation at 453K and 503K in O2 stream and by the heat treatment at 1473K in Ar stream, and the effect of oxygen on the mechanism of the pyrolysis of SiC fibers was studied. The rate of pyrolysis of the SiC fiber was measured with a thermo-balance in an atmosphere of Ar from 1673K to 1973K. The pyrolysis products were examined by X-ray diffraction, SEM and TEM observations. The core of the original fiber-A crystallized slightly, though its surface was amorphous. The pyrolysis proceeded rapidly in the early stage of reaction, but it was remarkably sluggish in the late stage. The SiC crystallite in the fiber coarsened only at the surface. The surface layer with high concentrations of oxygen decomposed rapidly, but the core with low concentrations of oxygen was difficult to decompose. The fiber-B, which was amorphous in the original state, decomposed to β-SiC rapidly. SiC crystallite grew and coarsened throughout the whole region of the fiber. The rate of pyrolysis was described by an Avrami-Erofeev equation. The rate-determining step changed from the crystal growth controlled by diffusion to that controlled by chemical reaction with rising pyrolysic temperature.
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  • Fumie HATAKEYAMA, Takashi MAEKAWA
    1992 Volume 100 Issue 1158 Pages 163-166
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Al2O3-SiO2 gels were synthesized by the sol-gel method using aluminium nitrate and tetraethylorthosilicate in various organic solvents. By calcining the dry gels, aluminium ion could be incorporated into SiO2 gel networks. By increasing heat treatment temperature, the coordination number of aluminium ion changed from six to four. At around 1000°C mullite crystals precipitated. The temperature of mullite precipitation should depend on the homogeneity of the dry gels. The presence of five-coordinated aluminium ions was confirmed between 400° and 800°C, as in accordance with the gels derived from silicon-aluminium alkoxide. The proportion of the five-coordinated aluminium ions was reduced by hydration in an autoclave.
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  • Kazuro KAWAMURA, Jyoji KOGA, Tomio IWATA, Seiji YAMANAKA, Mikiya ONO
    1992 Volume 100 Issue 1158 Pages 167-171
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Green sheets were made from polycarbosilane (PCS), phenol-formaldehyde resin or furfuryl alcohol resin by adding binder with the weight ratio of PCS to resin equal to 2/1 or 1/1. The two types of green sheets were heat-treated at 1200° to 1400°C under N2 gas to form SiC/C composite sheets 0.4-0.6mm thick. The SiC/C composite sheets were highly amorphous, that is, the crystallite sizes of L111 and LC of SiC and C components in the SiC/C composites were below 34Å and 25Å, respectively. As another feature, it was recognized that amorphous SiO2 was formed as a secondary product by the reaction of silicon in PCS and oxygen in resin during pyrolysis. Little difference was observed in bending strength and oxidation resistance between two SiC/C composite sheets. These features depend on the content of SiC in the composite sheet. The effective mixing ratio is PCS/resin≥2/1.
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  • Hidehiko KOBAYASHI, Miyuki KATOH, Yoshihide KAMIYAMA, Takashi MITAMURA
    1992 Volume 100 Issue 1158 Pages 172-177
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The reactivity of starting materials and heat treatment conditions for the preparation of ZrB2 fine powders using a thermite method were examined in the ZrO2-B2O3-Mg and ZrO2-B-Mg systems. The removal treatment of by-products was also investigated. In the ZrO2-B2O3-Mg and ZrO2-amorphous B-Mg systems, the reduction of ZrO2 and B2O3 by Mg and the boriding reaction of α-Zr and Mg occurred concurrently. The ZrB2 fine powders of single phase were successfully prepared at 1100°C in the ZrO2-B2O3-9Mg (molar ratio) system and at temperatures above 700°C in the ZrO2-2B-5Mg (molar ratio) system. Washing of the products with deoxidized acidic solutions in nitrogen atmosphere was effective to separate ZrB2 from MgO and MgB2, and to inhibit the oxidation of the ZrB2, too. Mg content in the powders after the acid treatment was 0.6-1.0wt%.
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  • Kinue TSUNEMATSU, Hiroshi TATEYAMA, Satoshi NISHIMURA, Kazuhiko JINNAI
    1992 Volume 100 Issue 1158 Pages 178-181
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    In order to delaminate kaolinite so as to improve its plasticity which is an essential factor as a porcelain material, intercalation of urea along with grinding was applied to kaolinite. In this process, kaolinite was ground with addition of various amounts of urea by using a ball-mill, a mechanical mortar or the combination of a mechanical mortar and a ball-mill. The ratio of intercalation was evaluated by X-ray diffractometry and the degree of delamination was estimated by the surface area and X-ray diffraction measurements. The results are summarized as follow: (1) Grinding using the mechanical mortar markedly accelerated the intercalation of urea into kaolinite. When a mixture of kaolinite and urea without the grinding treatment was stood in a humidity-controlled vessel, the urea intercalation took place, but its ratio was small. The ball-milling was ineffective in the urea intercalation. (2) The 00l and hkl reflections of kaolinite became broad after grinding a mixture of kaolinite and urea first by the mechanical mortar and then by the ball-mill. The specific surface areas of the kaolinite samples ground with addition of urea by 0, 5 and 10wt% were 20.8, 34.4 and 36.5m2/g, respectively. These results suggest that the urea intercalation accelerates the delamination of kaolinite when combined with grinding.
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  • Toshihiro ISHIKAWA, Takemi YAMAMURA, Kiyohito OKAMURA
    1992 Volume 100 Issue 1158 Pages 182-186
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The curing process for the synthesis of Si-Ti-C-O fiber was investigated in air. In curing by heat-treatment in air of polytitanocarbosilane as precursor of Si-Ti-C-O fiber, Si-H bonds, which were included in main structures of polytitanocarbosilane, were reacted with oxygen atoms to form Si-O-Si bonds between main chains of the polymer. DTA curve of polytitanocarbosilane in air showed the exothermic peak at the most suitable temperature for the curing of this polymer. The exothermic peak shifted to the higher temperature as the molecurar weight of polytitanocarbosilane increased from 1560 to 1970. The increase in gel fraction and the weight residue at 1300°C in N2 of the cured fiber was observed with a rise in curing temperature. The tensile strength of Si-Ti-C-O fiber correlated closely to these gel fraction and the weight residue. The maximum strength value of Si-Ti-C-O fiber was exhibited when the cured fiber had gel fraction of more than 70wt% and the weight residue of more than 85wt%. Young's modulus of Si-Ti-C-O fiber, which was obtained from the cured fiber with gel fraction of 60 to 75wt%, led to be maximum. Its young's modulus, however, gradually became small in the case of the gel fraction of more than 75wt%, because of the increase in oxygen content in the fiber.
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  • Shin NISHIYAMA, Osamu SAKURAI, Kazuo SHINOZAKI, Nobuyasu MIZUTANI
    1992 Volume 100 Issue 1158 Pages 187-190
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Electrical conductivity and Seebeck coefficient of La2 Cu1-xZnxO4+δ were measured as a function of temperature and oxygen partial pressure. In the temperature region from 500° to 800°C, the electrical conductivity decreased as temperature increased. This is due to decrease in excess interstitial oxygen and hole as temperature increased. Below 500°C, the semiconductive behavior was observed for the specimens containing more than 0.03 Zn. The XPS peak near the Fermi level vanished on Zn substitution. Seebeck coefficient increased as temperature increased. This is also due to the oxygen nonstoichiometry, and corresponds to the change in the electrical conductivity. Thermoelectrical efficiency of La2Cu1-xZnxO4+δ was slightly lower than that of La2CuO4.
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  • Akio NISHIDA, Shinji FUKUDA, Yasuhiko KOHTOKU, Kenji TERAI
    1992 Volume 100 Issue 1158 Pages 191-195
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Cubic- and tetragonal-ZrO2-MgO composite ceramics were prepared by the pressureless sintering at 1650°C for 4h and 1350°C for 24h respectively, and the effect of grain size and ZrO2 phase on bending strength (at room temperature and 1200°C) was investigated. The bending strength at room temperature of ZrO2-MgO composite ceramics increased with increasing ZrO2 content, because the grain size of MgO decreased with ZrO2 addition. But the effect of ZrO2 phase on the bending strength at room temperature was not recognized. In the case of bending test at 1200°C, when grain size of MgO was below 6μm, specimens deformed plastically before breakage, and the yield stress at 1200°C of c-ZrO2-MgO was larger than that of t-ZrO2-MgO, and fracture stress increased with decreasing the grain size of MgO.
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  • Shigeru AKIMOTO, Kazunori KIJIMA, Makoto KITAMURA
    1992 Volume 100 Issue 1158 Pages 196-202
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Pure and 3wt%-Y2O3 doped AlN powder compacts were sintered in an r.f. inductively coupled plasma under reduced pressure. The effects of the r.f. output power and gas pressure on their densification were investigated. AlN powder compacts doped with 3wt%-Y2O3 showed rapid densification to the theoretical density, while pure AlN densified only to 68% of the theoretical density under the experimental conditions studied. Time dependence of the densification of 3wt%-Y2O3 doped AlN was found to be divided into three stages; (1) rapid densification region occurring during insertion to plasma, (2) plateau region of constant density, (3) re-densification region with evaporation of AlN. Direct measurements of the specimen temperature showed that the densification at the first stage proceeded during rapid heating up to 1800°C, and that the re-densification at the third stage occurred as a result of elevation of the specimen temperature from 1800°C to >2000°C.
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  • Akihiro TSUCHINARI, Toshiyuki HOKII, Osamu SHIMOBAYASHI, Chikao KANAOK ...
    1992 Volume 100 Issue 1158 Pages 203-207
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Changes in the structure and physical properties of porous magnesia ceramic containing TiO2-Al2O3 matrix with TiO2/Al2O3 molar ratio 0.96 and 15wt% content were studied at different sizes and firing temperatures for controlling the pore shape. The shape of pore was complicated depending on the grain size and firing temperature, and pores were found to have a fractal nature. While the fractal dimension increased with increasing firing temperature for small grains, it decreased with increasing firing temperature for large grains. The fractal dimension of each MgO grain size tends to converge at a lower firing temperature which is close to the temperature at which the MgAl2O4-Mg2 TiO4 solid solution is formed. Specimens with small grains were found to shrink on firing, but the expansion was observed for large grained specimens. These phenomena were explained by the densification and molar volume of MgAl2O4-Mg2TiO4 solid solution and CaTiO3 formed. From the above facts, it was possible to controll the pore shape by grain size and firing temperature.
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  • Akira INOUE, Junzo FUKUTA, Yoshinori MATANO, Yoshiro MATSUMOTO
    1992 Volume 100 Issue 1158 Pages 208-210
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The relationship between the amount of anorthite (CaO⋅Al2O3⋅2SiO2) formed in the sintering process of the CaO-Al2O3-SiO2-B2O3 ceramics and the thermal expansion coefficients was studied. The results obtained are as follows: (1) The thermal expansion coefficient decreased with increasing the amount of anorthite. (2) In the case of 890°C-30min sintering, the maximum anorthite amount of 30% was produced by using a small particle α-Al2O3 of 0.9μm in size. The thermal expansion coefficient of the ceramics containing 30% anorthite was 4.7×10-6/°C, which was comparatively lower than the value of 6.2×10-6/°C for the ceramics containing no anorthite.
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  • Yoshimitsu KANKAWA, Yasunari KANEKO, Katsuyoshi SAITOU
    1992 Volume 100 Issue 1158 Pages 211-214
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Injection molding of β-TCP powder was studied. Rod like test pieces (φ6×50l) were produced by the injection molding using three powder-binder compound: (I) β-TCP and several organic binders; (II) β-TCP, alumina (3-9wt%) and several organic binders; (III) β-TCP, zirconia (3-9wt%) and several organic binders. After the binder extraction process, the test pieces were heated up to 1000°C-1400°C at a rate of 100°C/h. The relative densities and bending strength of the sintered test pieces (I) (relative density: 99%, bending strength: 130MPa, sintering temperature: 1200°C) in the absence alumina or zirconia were higher than that of the sintered test pieces (II, III) in the presence of alumina or zirconia.
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  • Akihiko KAWAHARA, Hiromichi ICHINOSE, Sachiko FURUTA, Hiroaki KATSUKI
    1992 Volume 100 Issue 1158 Pages 215-218
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    The gelation of ammonium alginate by hydrochloric acid was applied for the formation of gel-like precursor composed of alumina particles and alginic polymer. The porous alumina ceramics fired at temperatures from 1000° to 1600°C had very sharp pore size distributions. Their porosity ranged from 17 to 56%, which was 15 to 20% higher compared with that of porous alumina prepared by the slip casting method. Furthermore, the pore structure was more stable at high temperatures than that of the slip casting method. The optimum concentration of ammonium alginate for the uniform mixing of each raw material was 0.3 to 2.0wt%. The concentration of hydrochloric acid was over 0.1N for the sufficient gelation of the gel-like precursor.
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  • Junichi MATSUSHITA, Toshiyuki SUZUKI, Akira SANO
    1992 Volume 100 Issue 1158 Pages 219-222
    Published: February 01, 1992
    Released on J-STAGE: August 06, 2010
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    Wire electrical discharge machining of pressureless sintered TiB2 containing Cr and C as the sintering aids was investigated. The effects of machining conditions on the surface roughness and bending strength were discussed. The surface roughness increased with increase in the cutting speed. The bending strength remained with increase in the cutting speed to 5-40mm2/min. The bending strength of 320MPa was very close to the values for sintered body prepared by cut and polished with a diamond disc and powder.
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