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Kazuo KOTANI, Akio MAKISHIMA, Mitsuaki ASAMI
1989 Volume 97 Issue 1122 Pages
95-100
Published: February 01, 1989
Released on J-STAGE: August 06, 2010
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We have investigated the formation of the glasses containing Shirasu, yttria concentrate, calcium oxide and zinc oxide from melts. Densities, thermal expansion coefficients and Vickers hardnesses were measured for some glasses. Linear relation between some physical properties and glass composition has been discussed. The agreement between observed values of density is satisfactory. On the contrary, observed values of thermal expansion coefficient are smaller than calculated values for yttria containing glasses. In a specific compositional region, crystals with needle-like habit were observed by SEM, which were identified as Ca
4Y
6O(SiO
4)
6 by XRD. The crystallized glass was able to be machined by lathe, and it is applicable to the machinable glass ceramics. This glass ceramics has a higher Vickers hardness than usual machinable glass ceramics.
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Keijiro SHIGERU, Takashi OKU, Shigehide TAKAGI
1989 Volume 97 Issue 1122 Pages
101-106
Published: February 01, 1989
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Hydroxyapatite thermal decomposition product which is a mixture of alpha-tricalcium phosphate and tetracalcium phosphate was investigated physically, chemically and biologically as a self-hardening type biomaterial. Hardening of the decomposition product mixing with water was caused by recrystallization of hydroxyapatite. Implanting in the femoral cavity of a rabbit, the hardened body bonded to the bone directly and new bone formed in the gaps between the cortical bone and the hardened body. Addition of citric acid improved the physical properties. In this case, an amorphous phase consisted of Ca-PO
4-Cit-H
2O system was formed. But the color of marrow bone around the hardened body changed into black. The reason of the color change was thought to be owing to excess dissolution of calcium ion which is an important factor of the blood coagulation. Further addition of trisodium citrate improved the color change, because the further added citrate ion captured the excess calcium ion. The hardened body also bonded to the bone directly and new bone formed.
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Akio NISHIDA, Tuneo SHIMAMURA, Yasuhiko KOHTOKU
1989 Volume 97 Issue 1122 Pages
107-112
Published: February 01, 1989
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Magnesia powders with different particle sizes were prepared by a vapor phase oxidation process, and the effects of particle size and particle shape on their sinterabilities were investigated from a viewpoint of that densification progressed with simultaneous grain growth. For the magnesia powders with particle sizes such as 0.014 and 0.054μm, the densification began at lower temperatures, but the density of sintered bodies slightly increased at temperature above 1400°C. The rate of grain growth was higher than that of densification, because grains in sintered bodies constituted small radius of curvature of grain boundaries. On the other hand, for magnesia powders with particle sizes such as 0.126 and 0.199μm, sinterability was inferior to the small-sized powders at lower temperature, but the density of sintered bodies considerably increased up to 1650°C. The rate of grain growth was lower than that of densification, because most grains in sintered bodies were cubic. Consequently, it was found that grain growth as an integral part of controlling sintering phenomena was affected by the shape of magnesia particles.
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Chunting LI, Iwao YAMAI, Etsuro KATO
1989 Volume 97 Issue 1122 Pages
113-118
Published: February 01, 1989
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Zirconium sulfate solutions were hydrothermally treated at temperatures from 200° to 250°C for various periods of time. Crystalline phases, morphology and amount of solid products were investigated to study, especially, the formation process of zirconium oxide sulfate (ZOS), being submicron thin hexagonal crystals with a chemical composition of Zr
3O
5SO
4⋅nH
2O. Crystalline phases of the solid products varied with H
2SO
4 concentration of the solution; at 240°C for 3 days, m-ZrO
2 and t-ZrO
2, ZOS and/or a pseudo-ZOS phase (PZOS) and ZrOSO
4⋅H
2O at H
2SO
4 concentrations below 0.2mol/l, in the range of 0.2-2.0mol/l and above 2.5mol/l respectively, PZOS formed generally at lower temperature or at the early stage of the hydrothermal process, and its amount decreased with increasing H
2SO
4 concentration. Since the PZOS phase was metastable at higher temperature or higher H
2SO
4 concentration, it gradually changed to ZOS with a prolonged hydrothermal treatment time. The ZOS crystals were considered to be formed by a neucleation and crystal growth process. The crystal size of the ZOS increased with increasing H
2SO
4 concentration but was almost independent of Zr concentration. Effect of seeding and repeated treating on the crystal growth of ZOS was confirmed in a solution containing 1.6mol/l H
2SO
4 at 250°C.
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Chung Hsin LU, Kazuo SHINOZAKI, Nobuyasu MIZUTANI, Masanori KATO
1989 Volume 97 Issue 1122 Pages
119-124
Published: February 01, 1989
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The liquid-phase formation around 690°C in the system of 3PbO⋅Fe
2O
3⋅WO
3 as a raw material of low-temperature-firing PbFe
2/3W
1/3O
3 was investigated. In DTA a sharp endothermic peak was observed at 690°C on heating, and an exothermic peak was found at 670°C on cooling immediately after that endothermic peak. The endothermic peak is interpreted as to be due to the formation of the liquid-phase from a certain intermediate unknown phase, and the exothermic peak on cooling is due to solidification of the liquid-phase. A rapid shrinkage in specimens was observed by TMA, and drastic changes in microstructure were also investigated by SFM and high temperature optical microscopy. A pyrochlore phase formed from the liquid-phase was determined to be Pb:Fe:W≈2:1:1.
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Mookyung KIM, Tadahiko WATANABE, Hideki YAMAMOTO
1989 Volume 97 Issue 1122 Pages
125-130
Published: February 01, 1989
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Ti(C, N), TiC, and TiN have high melting points, high hardness and extremely good wear resistance to steel. Among them, the densification of Ti(C, N) is easiest. However, the sintered body of pure Ti(C, N) has a porosity of several volume persent. The properties of Ti(C, N)-Cr
3C
2 ceramics were studied. Also, the densification behavior of the Ti(C, N)-Cr
3C
2 system was compared with those of the TiC-Cr
3C
2, TiN-Cr
3C
2 and TiC-TiN-Cr
3C
2 systems. The main results are as follows:
(1) The Ti(C, N)-Cr
3C
2 system can be sintered at relatively low temperatures from 1873 to 1973K The Cr
3C
2 additive plays an effective role in the densification of Ti(C, N).
(2) Ti(C, N)-5%Cr
3C
2 ceramics had a porosity of 0.1vol%, a transverse rupture strength of 450MPa and a Vickers hardness of 1900.
(3) In the TiC-20%Cr
3C
2 and TiN-20%Cr
3C
2 system, the chromium carbide phase dissolves completely into TiC and TiN, and does not remain among the grains. Thus, TiC and TiN grains grow.
(4) Both Ti(C, N)-20%Cr
3C
2 and TiC-TiN-20%Cr
3C
2 ceramics had a Cr
7C
3 phase among the grains. Cr
7C
3 restrains the Ti(C, N) grain growth more effectively than TiC-TiN grain growth.
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Strengthening by Erosion in Tetragonal ZrO2 Ceramics
Shigetaka WADA, Naoyoshi WATANAHE, Hideo HASEGAWA
1989 Volume 97 Issue 1122 Pages
131-135
Published: February 01, 1989
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Strengthening tetragonal ZrO
2 ceramics by the erosion caused by iron spheres and SiC abrasives has been studied. When tetragonal ZrO
2 ceramics, TOSO: TZ-3Y, was eroded by SiC abrasives with an average particle size of 0.5mm, at 100m/s and 45deg, a surface layer about 15-20μm thick with compressive stress was formed and the bending strength increased from 850MPa to 1130MPa on the average. The surface layer acquired a large apparent K
IC. Reversion of the (002)/(200) peak height ratio, induction of a 1200MPa compressive stress in tetragonal ZrO
2, and broadening in all diffraction peaks were observed in the surface layer in X-ray diffraction analysis. Small amounts of monoclinic and rhombohedral ZrO
2 transformed from tetragonal ZrO
2 were also detected. After heat treatment at 1200°C for 2h, monoclinic and rhombohedral ZrO
2 disappeared. The crystallinity of tetragonal ZrO
2 was improved and the compressive stress became zero, but the (002)/(200) peak height ratio kept the reversion. Heat treatment decreased the bending strength of eroded specimens to 580MPa.
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Yohtaro MATSUO, Toshihiko OIDA, Katsuhisa JINBO, Kouichi YASUDA, Shius ...
1989 Volume 97 Issue 1122 Pages
136-142
Published: February 01, 1989
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A new theory was formulated for analyzing the cyclic fatigue behavior of ceramics by combining the multi-modal Weibull distribution function with slow crack growth law (S. C. G.). Using an internal pressure testing machine, static and fatigue tests were performed on cylindrical alumina specimens. Statistical data analysis showed that cyclic stress reduces the number of cycles to failure. Intergranular fracture was dominant on fatigue fractured surfaces. The semi-length of the crack at branching has been best correlated with the peak applied stress in the cyclic fatigue test. The least of the number of cycles to failure was ensured for the specimens passing through the pre-loading proof test.
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Hisanori YAMANE, Yuzuru MIYAZAKI, Toshio HIRAI
1989 Volume 97 Issue 1122 Pages
143-147
Published: February 01, 1989
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Sr
0.09Ca
0.91CuO
2 was obtained by heating a powder mixture of SrCO
3, CaCO
3, and CuO at 1000°C in flowing oxygen. The compound has a tetragonal symmetry, P4/mmm, and is characterized by a=3.8581 (1), c=3.1997 (1)Å, Z=1, D
m=4.86g/cm
3, and D
cal=4.88g/cm
3. The crystal structure was determined and refined to R
p=3.7% by the Rietveld analysis of X-ray powder diffraction data. The compound has an oxygen-deficient perovskite structure. A copper atom is in a square plane of oxygen atoms. This square plane forms a Cu-O flat sheet sharing the oxygen atoms at vertices of the square. The bond length of Cu-O is 1.929Å. Sr(0.09) and Ca(0.91) atoms are statistically in an oxygen square prism. The interatomic distance of (Ca, Sr)-O is 2.506Å. This compound is a p-type semiconductor with electric conductivity of 1.2×10
-4(Ω·cm)
-1 at 22°C.
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Yoshiyuki YASUTOMI, Kousuke NAKAMURA, Masahisa SOBUE, Yutaka KUBO
1989 Volume 97 Issue 1122 Pages
148-154
Published: February 01, 1989
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Electro-conductive Si
3N
4 bonded TiN ceramics were successfully produced by sintering green compacts composed of Si and TiN powders in nitrogen gas atmosphere. These ceramics showed little dimensional change in the sintering stage, which was very favorable to get near-net-shape ceramic components in as-sintered state. Si and TiN powders were mixed in a ball mill and molded using thermoplastic resin binder. The green body was dewaxed and then sintered in 0.88MPa nitrogen gas atmosphere. The dimensional change in the sintering stage was under 0.3%, and electrical resistivity of 26μΩm was obtained when TiN content was 70vol%. The bending strength of 460MPa was obtained for the ceramics containing 20vol% of TiN. Other properties of these ceramics, such as hardness, thermal expansion coefficient and oxidation resistance, were measured and discussed.
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AlPO4 and BaSO4
Tadashi NISHINO, Xouda WON
1989 Volume 97 Issue 1122 Pages
155-160
Published: February 01, 1989
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Dissolution rate of AlPO
4 powder with different modifications in aqueous suspension containing H-R, strongly acidic H-formed ion exchange resin, was investigated as a function of suspension concentration, temperature and stirring speed. Dissolution of BaSO
4 powder was carried out under the similar experimental conditions, for comparison. Fractional dissolution was calculated from the analytical result of liberated amounts of PO
43- and SO
42- brought about by the cation exchange reaction.
The results obtained were summarized as follows;
(1) Well-crystallized quartz-type AlPO
4 (b-AlPO
4) did not dissolve appreciably, whereas cristobalite-type AlPO
4 (c-AlPO
4), heat-treated sample of b-AlPO
4, dissolved considerably for its metastability.
(2) Dissolution of AlPO
4 did not so accelerated by suspension concentration as compared with BaSO
4.
(3) Dissolution tendency of both AlPO
4 and BaSO
4 increased with increasing temperature.
(4) Stirring increased the collision frequency between sample powder and H-R particle to enhance the dissolution rate, in general, as shown in BaSO
4. However, the increase in stirring speed hinders the dissolution tendency of AlPO
4 because of slow exchange reaction at the collision interface.
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Kazuo TORII, Takashi IWASAKI, Yoshio ONODERA, Masahiko SHIMADA
1989 Volume 97 Issue 1122 Pages
161-165
Published: February 01, 1989
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Hectorite-inorganic interlayer complexes, hydrothermally synthesized from precursory Si-Mg hydrous oxide at 125°-300°C in 2h, were studied by thermal analyses. DTA detected a broad low-temperature endotherm corresponding to a loss of loosely bound interlayer water, a small endotherm associated with dehydroxylation (ca. 700°C), and immediately followed by the two sharp exotherms corresponding to enstatite formation. The peak temperatures of two exotherms decrease drastically with increasing Li content. The peak temperature of the first exotherm correlates well with interlayer Li content (r=-0.92) and is affected by the excess amount of Na and/or Mg. Moreover, peak area of the first exotherm correlates well with the specific surface area (r=0.94). Thus, these results suggest that the first exotherm corresponds to early enstatite recrystallization of inorganic materials which exist between silicate layers and act as pillars on dehydration. As the peak temperature of the second exotherm is affected significantly by the Li content in octahedral sheet (r=-0.91), it is assumed that the second exotherm is associated with enstatite recrystallization of hectorite silicate layers. Results of DTG indicate that there are three types of water in the complexes; interlayer water (RT-300°C), less tightly bound structural water (300°-650°C) and structural water in silicate layer (650°-850°C). The amount of the structural water which is released at low temperature correlates with specific surface area (r=0.99) very well and the amount of the silicate structural water correlates well with the methylene blue adsorbed (r=0.96).
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Hiromichi TAKEBE, Tsuneji KAMEDA, Michiyasu KOMATSU, Katsutoshi KOMEYA ...
1989 Volume 97 Issue 1122 Pages
166-173
Published: February 01, 1989
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The single-phase region of AlON, a spinel type solid solution in the system Al
2O
3-AlN, has been determined. AlON was synthesized from solid phase reactions between Al
2O
3 and AlN powder in several reaction vessels. The reaction vessel of porous Al
2O
3 with AlN coating was suitable for obtaining pure AlON. The single-phase region of AlON was from 28 to 32mol% AlN at 1700°C and from 20 to 34mol% AlN at 1800°C. The lattice parameters of AlON increased from 7.926 to 7.946Å with increasing AlN content. Y
2O
3-powder was used as a sintering aid to obtain translucent AlON from synthesized AlON powder at low temperature. For 1wt% Y
2O
3 addition, the translucent AlON was obtained at 1800°C, and its relative density and flexural strength were 99% and 250MPa, respectively.
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Koji WATARI, Yoshiyuki SEKI, Kozo ISHIZAKI
1989 Volume 97 Issue 1122 Pages
174-181
Published: February 01, 1989
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Thermal diffusivity and conductivity as well as specific heat of capsule-HIPped Si
3N
4 with Y
2O
3 and Al
2O
3 6mol% in total as additives were measured at different temperatures ranging from 100 to 1300K. The isobaric specific heat C
p agreed with the isochoric specific heat C
v calculated by the Debye's theory, assuming that silicon and nitrogen atoms are lattice dynamically equivalent. The Dulong-Petit's rule applied well to sintered Si
3N
4 at high temperatures and C
v≅25J/(K·mol). The glassy phase quantity could be estimated by the difference of the measured specific heat and the calculated specific heat at low temperatures. The specimens with higher thermal diffusivity and conductivity at low temperatures were those with higher β-phase fraction, larger particle size of raw Si
3N
4 and richer Y
2O
3 additive. For these specimens the thermal diffusivity and conductivity showed a larger temperature depencence.
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Kunio TOCHI, Tomiyasu OHGAKU, Nozomu TAKEUCHI
1989 Volume 97 Issue 1122 Pages
182-186
Published: February 01, 1989
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The optimum composition for the dielectric constant and Q-value of the materials in the Ba(
1-x)Sr
x(Ni
1/3Ta
2/3)O
3 system has been experimentally determined. It was found that the materials with x=0.4 showed maximal values in both dielectric constant and Q-value, where the correction for porosity of the materials was made.
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Osami ABE, Shuzo KANZAKI
1989 Volume 97 Issue 1122 Pages
187-191
Published: February 01, 1989
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A high-temperature dilatometer was assembled for studying the densification behavior of non-oxide ceramics up to 2300°C in 1MPa innert gas atmosphere. The accuracy of shrinkage up to 2300°C was better than 17.8×10
-3% for 40mm long samples including the base line drift and probable error. The accuracy of shrinking rate was better than 3.3×10
-3%·min
-1, where the base line drift was negligibly small. The shift of base lines estimated from the drift of shrinkage was also smaller than the probable error of shrinking rate. Heating rate affected the base line drift of shrinkage, while the probable error was not influenced. The accuracy of shrinkage and shrinking rate did not depend on the kind of atmospheric gas. With decreasing gas pressure, the accuracy was improved by the damped gas convection. The densif ication behavior of some kinds of silicon nitride and silicon carbide powder compacts was measured by using this equipment. The high accuracy was maintained for silicon carbide during measurement in spite of the large shrinkage and shrinking rate. The probable error for silicon nitride increased above 1600°C, because of the thermal decomposition and vaporization. The error was diminished by a numerical smoothing.
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Kazuo OKANO, Naruyuki HOSOKAWA
1989 Volume 97 Issue 1122 Pages
192-194
Published: February 01, 1989
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For application to electronic devices, the relationship between manufacturing conditions and electrical properties of SiC was investigated. High-β phase silicon carbide powder was formed into cylindrical pellet at various pressures between 50MPa and 350MPa, and was sintered at 2100°C for 0.5h in a vacuum furnace. Electrical conductivity and relative density were measured, and microstructures were observed using a scanning electron microscope (SEM). The electrical conductivity of specimens decreased from 8×10
-5S/m to 4×10
-6S/m with increasing the forming pressure from 50MPa to 250MPa. Whereas the density and the microstructure slightly depended on the forming pressure. For the specimens formed above the pressure of 250MPa, the electrical conductivity and density showed constant value regardless of the forming pressure.
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Mikio IWASA, Makoto KINOSHITA
1989 Volume 97 Issue 1122 Pages
195-199
Published: February 01, 1989
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The ball-on-disk method was applied to measure the wear behavior of Si
3N
4 balls sliding on SiC disk at the load of 10kgf and velocity of 20cm/s. Four kinds of Si
3N
4 balls from different sources were named A, B, C, D, in increasing order of their hardness or fracture toughness. The large grain structure and large porosity of Si
3N
4 (A) will explain its low hardness and low fracture toughness. The fine fibrous structure without porosity of Si
3N
4 (D) may be the reason of its high hardness and high fracture toughness. The wear volume calculated from the wear scar on a Si
3N
4 ball sliding on the SiC disk was proportional to the weight loss and to the sliding distance. The wear of Si
3N
4 ball decreased with increasing hardness or fracture toughness, but on the contrary, the wear of SiC disk increased sharply. The Si
3N
4 (C) ball, which has crystallized grain boundary phases, showed very low wear of ball but high wear of SiC disk.
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Fumio MUNAKATA, Kazuhiko SHINOHARA, Mitsugu YAMANAKA
1989 Volume 97 Issue 1122 Pages
200-202
Published: February 01, 1989
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The temperature dependence of electrical resistance of Eu
1+xBa
2-xCu
3O
y (x=0.0, 0.2, and 0.5) was measured in N
2O and 5% N
2O-N
2. Kinks were observed in the temperature-resistance curves of EuBa
2Cu
3O
y in N
2O and 5% N
2O-N
2. This behavior was considered to be related to the order-disorder transition of oxygen vacancy (oxygen ion). Substitution of Eu ions for Ba ions affects the decomposition of N
2O and the migration of oxygen ions, that is, the local rearrangement of oxygen ions in Eu
1+xBa
2-xCu
3O
y.
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