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Volume 41, Issue 10
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[in Japanese]1994 Volume 41 Issue 10 Pages 1168
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (81K) -
Atsushi Hitomi, Kenji Koseki, Kenji Horino, Junko Yamamatsu, Takeshi N ...1994 Volume 41 Issue 10 Pages 1169-1174
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRelationships between microstructure and electrical properties of SrTiO3-based varistor have been studied. Si-rich amorphous layers(several nm thick) are found at the grain boundaries when reduced enough under much lower oxygen partial pressure(Po2) than that of firing step after sintering. Then, the sample shows a large V-I nonlinear coefficient(α). On the other hand, the sample without reducing treatment has grain boundaries of facet. structure, and then, shows a small α. Behavior of oxygen diffusion during re-oxidation is changed by the reducing treatment ; from volume diffusion controlled to grain-boundary diffusion controlled.View full abstractDownload PDF (4231K) -
Jin Hwang Hae, Atsushi Nakahira, Tohru Sekino, Koichi Niihara1994 Volume 41 Issue 10 Pages 1175-1180
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDense and fine grained BaTiO3-based composites with the nano-sized SiC particulate were successfully fabricated by hot-pressing method. Mechanical properties and fracture behavior were investigated. High resolution TEM observation revealed that there were no conspicuous reaction phases in the interface between BaTiO3 and SiC. The crystal structure was changed from ferroelectric tetragonal to paraelectric cubic phase with increasing SiC, and finally was pseudo-cubic for BaTiO3 with more than 3vol% SiC. Mechanical properties such as fracture strength, fracture toughness, Young's modulus and so on were markedly improved by the incorporation of nano-sized SiC particulates. The improvement of mechanical properties, particularly, microhardness and Young's modulus might be caused by the crystal structural change as well as SiC addition. Fracture behavior and subcritical crack growth (SCG) phenomenon were also investigated using the indentation induced flaw method (IIF).View full abstractDownload PDF (4160K) -
Citrate MethodHidemi Watanabe, Osamu Kimura1994 Volume 41 Issue 10 Pages 1181-1184
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTo improve mechanical properties, well dispersed Al2O3 / TiO2 powders are prepared by the citrate process and Al2O3 / Al2TiO5 composites are obtained by hot-pressing the powders. Hot-pressing is carried out at 1350°C for 45 minutes under a pressure of 30MPa in N2 atmosphere. Formation of Al2TiO5 is ascertained by XRD analysis for all composites. The mechanical strength decreases with increasing addition of TiO2. The composite containing 30vol% TiO2, however, exhibites 100MPa in bending strength, while it still re-taines a low thermal expansion coefficient, i. e. 4.6x10-6 from R.T. to 1000°C.View full abstractDownload PDF (176K) -
Yoshifumi Uchita, Tadashi Endo, Hirotsugu Takizawa, Masahiko Shimada1994 Volume 41 Issue 10 Pages 1185-1188
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe reported here the results of the fabrication of clay unit layers/organic molecules multilayers films using a conventional Langmuir-Blodgett technique. Smectite were ultrasonically separated by each unit layer into distilled water. Successively, octadecylamine or nonadecylamine was spread from benzene solution on the water subphases contained clay unit layers at various pH. The monolayers were deposited on an appropriate plate such as glass, silicon etc. at pressures of 25-35dyne. The preferred conditions for making the best multilayers films were systematically examined. The reasonable surface areas were obtained from the π-A curves. According to the XRD patterns, the resulting basal spacing of LB films was estimated to be about 61.3A, which corresponded to the bilayeres of alkylamines. IR spectra demonstrated the existence of hydrogen bonding between the alkylamine and silicate layers. On heating above 60°C, the conformation of alkylamines was stepwisely changed. The possible molecular arrangements within the LB film were discussed.View full abstractDownload PDF (251K) -
Yoshiaki Fukushima1994 Volume 41 Issue 10 Pages 1189-1192
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNanoscale structure control by an intercalation method was reviewed. An open ring polymerization of ε-caprolaclam in interlayer spaces of layered clay mineral; montmorillonite, caused the indefinite swelling of silicate layers to form a nanoscale composit of 6-nylon and silicate layers of clay minerals. An interaction of guest molecules with the silicate surface arranged guest molecules and controlled the structure of intercalated compounds. We also found that aggregates of guest organic cations folded silica sheets of layered polysilicate, kanemite. Calcination of the complex of the folded silicate sheet and organic cations gave highly ordered mesoporous materials with a hexagonal array of uniform channels. An intercalation would be one of the effective methods to controll nanoscale structure of materials.View full abstractDownload PDF (3262K) -
Junichi Hojo, Osamu Sagawa, Hideyoshi Kimura1994 Volume 41 Issue 10 Pages 1193-1198
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFabrication processes of metal-alumina composites were investigated with emphasis on the use of metal-coated alumina particles. Al2O3 particles (mean diameter: 250μm and 45μm) were coated with Ni powder (mean diameter: 5μm) and/or W powder (mean diameter: 1μm) by an agglomeration coating technique and the pressed compacts were sintered. The coated particles gave Ni-Al2O3 composites with more uniform microstructures compared with mechanically-mixed powders. W layer had to be localized at the surface of Al2O3 to improve adhesion of Ni. The sintered bodies were porous. Molten Ni and Cu were Basely infiltrated into the pores, giving the dense composites of Al2O3-Ni and Al2O3-Ni-Cu systems.View full abstractDownload PDF (6224K) -
Takehisa Ohno1994 Volume 41 Issue 10 Pages 1199-1202
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIron-nickel and iron-magnesium nanocomposite particles were prepared by evaporation of coat material (nickel or magnesium) onto flying iron nanoparticles, which were produced by gas-evaporation technique. They were studied by means of a transmission electron microscope (TEM) and a scanning electron microscope (SEM) equipped with an energydispersive X-ray analysis system. For the iron-nickel system, the presence of nickel atoms was confirmed only by the analysis with SEM, while for the other one, magnesium particles sticking to chain-like iron particles were observed by means of TEM.View full abstractDownload PDF (2609K) -
Tsugio Sato, Akitsugu Okuwaki1994 Volume 41 Issue 10 Pages 1203-1208
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe survey deals with the preparation of ceramic powders by crystallizing in nonaqueous solvents and supercritical drying. The sintering behaviors and mechanical properties of sintered bodies are very much sensitive to the crystallizing conditions, since hard agglomerates formed when the precipitated gels were crystallized by normal calcination in air, whereas soft agglomerates formed when they were crystallized in water or organic solvents. CeO2-ZrO2 powders crystallized in methanol and water at 250°C were sintered to full theoretical density at 1100° and 1400°C, respectively, whereas that crystallized by calcination in air at 450°C was sintered to only 95.2% of theoretical density, even at 1500°C. Sintered bodies fabricated using the powders crystallized and dried using supercritical methanol possessed excellent mechanical properties.View full abstractDownload PDF (4535K) -
Mechanical and Thermal PropertiesShigehiro Nishijima1994 Volume 41 Issue 10 Pages 1209-1214
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe composite materials for cryogenic use have been developed aiming at the application to the superconducting magnets and cryogenic fields. The properties required to the composites were surveyed considering the environments in the magnets. The mechanical and thermal properties of polymer matrix composite materials were demonstrated and the merits of the cryogenic applications were discussed. The demerits of the polymer matrix composites were also discussed based on the their characteristic at cryogenic temperatures. To overcome the difficulties the study of cryogenic application of ceramic materials and ceramic matrix composites has been started. The recent results about ceramics were also reported.View full abstractDownload PDF (291K) -
Junichi Hojo, Fumio Hongo1994 Volume 41 Issue 10 Pages 1215-1219
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTiC particles (average size: 2.1μm) were coated with Ni by a chemical plating technique and the pressed compacts were sintered at about 1300°C. The density of sintered body was 98-99%. Compared with mechanically-mixed powder, Ni-plated TiC particles gave more uniform microstructure in which TiC particles were well dispersed in Ni matrix. The composites were subjected to ductile fracture at 30vol% TiC and brittle fracture at 70vol% TiC. The flexural strength was improved by homogeneous dispersion of TiC particles. The thermal expansion coefficient decreased with an increase in TiC content, following nearly the linear law of mixture on the basis of volume fractions of pure TiC and Ni.View full abstractDownload PDF (3038K) -
Masahiro Nawa, Keiichi Yamazaki, Tohru Sekino, Koichi Niihara1994 Volume 41 Issue 10 Pages 1220-1225
Published: October 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSYttria stabilized tetragonal zirconia polycrystal (Y-TZP)/0-100 vol% molybdenum (Mo) composites were fabricated by hot-pressing a mixture of Y-TZP powder containing 3mol% yttria and a fine Mo powder in vacuum. This composite system possessed a novel microstructural feature composed of a mutual intragranular nanostructure, in which either nanometer sized Mo particles or equivalent sized zirconia particles were located within the zirconia grains or Mo grains, respectively. Both fracture strength and toughness increased with increasing Mo content. They achieved a simultaneous improvement in strength and toughness that overcame the strength-toughness tradeoff relation. A maximum fracture strength of 2100 MPa was obtained at 70 vol% Mo content. Moreover, a fracture toughness increased dramatically with increasing Mo content above 40 vol% and exhibited 18.0 MPa⋅m 1/2at above 50 vol% Mo content. The relation between microstructure and mechanical properties will be discussed.View full abstractDownload PDF (4169K) -
Hisao Ueda, Hidekazu Tsuji, Takeyoshi Takenouchi, Atsushi Nakahira, Ko ...1994 Volume 41 Issue 10 Pages 1226-1231
Published: October 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSAl2O3/TiC nanocomposites containing 5, 25 volume fraction of TiC were fabricated by pressureless sintering (PLS) technique. Al2O3/TiC mixtures consisted of 0.2μm-Al2O3, 0.2μm-TiC and sintering aids, which were mixed by ball-milling with ethanol for 24 hours. Al2O3/TiC-compacts were densified by pressureless sintering at 1500°to 1700°C in Ar atmosphere with hot isostatic pressing (post-HIP) at 1500°C under Ar pressure of 147 MPa. Al2O3/TiC nanocomposites had the microstructures, in which TiC partcles were dispersed mainly within Al2O3 grains, and showed the fracture strength of 1200 MPa and the fracture toughness of 4.3 MPa⋅m1/2. Also, Al2O3/TiC nanocomposites were approximately equal to those of hot pressing (HP). The improvement in high temperature hardness must be due to the pinning of dislocation and to the prohibitation of the grain boundary sliding by the nanosize TiC dispersion within Al2O3 matrix grains.View full abstractDownload PDF (2730K) -
Ryuichi Matsuki, Takeyoshi Takenouchi, Atsushi Nakahira, Koichi Niihar ...1994 Volume 41 Issue 10 Pages 1232-1237
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of TiC and three kinds of ZrO2(unstable, 2mol%Y2O3 doped, 3mol%Y2O3 doped) dispersions on the microstructure, fracture strength and toughness were investigated for Al2O3/TiC/ZrO2 composites. These composites were fabricated by hot-pressing the mixture of Al2O3, TiC and ZrO2 powders. X-ray diffraction analyses revealed that all composites were composed of α-Al2O3, TiC, t-ZrO2 and m-ZrO2, and another reacting phases were not detected. Transmission electron microscopic observation indicated that ZrO2 particles were located mainly at the grain boundaries of Al2O3 matrix and most of TiC particles were homogeneously dispersed not only at the grain boundaries of Al2O3 but also within Al2O3 and ZrO2 grains. The fracture strength and toughness of these composites were greatly enhanced by incorporating the TiC and ZrO2 particles. The strengthening and toughening mechanisms of Al2O3/TiC/ZrO2 composites were discussed.View full abstractDownload PDF (2240K) -
Toshihiko Nishida, You Yamamoto, Hiromi Nakano, Kazuyori Urabe1994 Volume 41 Issue 10 Pages 1238-1242
Published: October 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSCompacts of an equimolar mixture of Si and C powders were buried in an equimolar mixture of Ti and C powders, and was ignited by a tungsten heater with peassure of 1 GPa or without pressure. In the case of the processing without pressure, SiC powder with a mean particle size of 4μm was obtained by the SHS reaction which was assisted by the heat of the SHS reaction of Ti-C. The densely sintered SiC body with a relative density of 95% (maximum value) was obtained by the SHS processing with pressure. However, the reproducebility of the degree of densification was very poor. It was clarified by X-ray diffraction and high-resolution TEM observation that the SiC crystal prepared by this SHS processing was mainly composed of 3C polytype with containing a small amount of 6H, 2H and 4H polytypes as hosts.View full abstractDownload PDF (4730K) -
Takeshi Hirano, Atsushi Nakahira, Koichi Niihara1994 Volume 41 Issue 10 Pages 1243-1248
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of SiC particle dispersions with average particle size in the range of 0.04-125μm on the α-β phase transformation and room temperature mechanical properties were investigated for Si3N4/SiC composites containing a 30vol% SiC particle. All composites were fabricated by hot pressing the mixture of sub-micron sized α-Si3N4 and α or β-SiC powders using 8wt% Y2O3 as a sintering additive. Addition of finest SiC particle (40nm) affected considerably the α-β phase transformation of Si3N4 matrix and the microstructure was composed mostly of fine equiaxed grains. As increasing the size of added SiC particles, the α-β phase transformation and the grain growth of β-Si3N4 were found to be promoted up to 25μm SiC and then saturated. As decreasing the size of added SiC particles, the fracture strength was increased and then saturated. The addition of finest SiC particle, however, was found to decrease the fracture strength drastically. The fracture toughness was increased as increasing the size of added SiC particles.View full abstractDownload PDF (1700K) -
Hideto Yoshida, Noboru Miyata, Kazunari Naito, Chitake Yamagishi1994 Volume 41 Issue 10 Pages 1249-1254
Published: October 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSHigh purity β-SiC films were coated on C1/SiC composite by a chemical vapor deposition method using SiCl4, C3H8 and H2 as source gases under following conditions ; deposition temperature 1000-1500°C, total gas pressure 103-105 Pa. Oxidizing resistance of β-SiC films was measured by oxidizing test under following conditions;temperature 1450°C, keeping time 100 hr in oxidizing atomosphere. The β-SiC coated C1/SiC composite showed high oxdizing resistance and the weight loss of the composite after oxdizing test were 2mg/cm2.
The flexural strength of the composite after oxdizing test depended on the thickness of SiC coating film, and the composite with the film thickness of 50μm showed the highest flexural strength.View full abstractDownload PDF (1325K) -
Takahiro Sato, Atsuyuki Nakano, Takeshi Nomura1994 Volume 41 Issue 10 Pages 1257-1260
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe dissociation behavior of CuO1-x from NiCuZn ferrite has been studied with special reference to the oxidation state of Fe contamination introduced from ball mill. The oxidation state of Fe is greatly affected by the ambient atmosphere during ball-milling. In case of CO2 atmosphere, CuO is reduced significantly, but, in case of O2 atmosphere, CuO is not reduced. It is thought that the strong reduction of CuO is caused by the reaction with a strong reductive Fe(OH)2 which is Fe contamination introduced from ball mill.View full abstractDownload PDF (253K) -
Hao-Nien Huang, Hideo Nakae, Teruhisa Watanabe1994 Volume 41 Issue 10 Pages 1261-1264
Published: October 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn our previous papers, we presented general equations concerning infiltration through one surface and all surfaces of a model sintered skeleton based on a rectangular parallelopiped having same-radius straight-cylindrical pores crossing at right angles on three dimensions and examined them by some experiments using sintered iron skeletons and water infiltrant and pure silver infiltrant hardly alloyed to iron. The present report, by doing an experiment with sintered iron skeletons and copper base infiltrant easily alloyed reaction to iron, clarifies that these two equations are also applicable in the first half period of the infiltration time, as follows :
1) The general equation of infiltration through a single side of a skeleton is,
V=Pr⋅S1⋅(R⋅γLV⋅COSθ/18ηL)1/2⋅t1/2
2) The general equation of infiltration through all surfaces of the skeleton is,
V=Pr⋅SA⋅(R⋅γLV⋅COSθ/18ηL)1/2⋅t1/2
where, V : volume of the liquid infiltrated(cm3), P r : porosity of the skeleton, S1: infiltration area of the skeleton(cm2), γLV: surface tension of the liquid(g/s2), R :radius of the pore(cm), θ : contact angle between the skeleton and the liquid(deg), ηL: viscosity of the liquid(g/cm-s), t : infiltrating time(s), SA: 2 (S1+S2+S3)[total surface area of the skeleton] (cm2).View full abstractDownload PDF (1492K) -
Minoru Umemoto, Mamoru Kubosaka, Masamichi Udaka, Kazuhiro Kawasaki, I ...1994 Volume 41 Issue 10 Pages 1265-1269
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe application of powder interlayers to solid-state diffusion bonding was investigated. Base materials used in this investigation were pure Cu, Fe and Ni. Interlayer materials were also Cu, Fe and Ni powders. The bonding was carried out by hot pressing at bonding temperatures of 573-973K and bonding pressures of 7 or 100MPa in vacuum. The cross section of the bonded specimens obtained was observed by optical microscope and SEM. The bonding strength of the specimens was measured using a shearing test. The main results obtained were as follows : (1) When the base and powder interlayer materials are the same, the strength of the diffusion bonded powder interlayer samples was higher than that of direct bonded samples. (2)When the base and powder interlayer materials are different, the strength of diffusion bonded powder interlayer samples was found to be high when the two components are well soluble and low when they are not. (3)When the green density of the powder interlayers was low, the bonding strength of the diffusion bonded powder interlayer samples was below that of direct bonded samples, This is thougth to be due to the sintering shrinkage of powder interlayers during bonding.View full abstractDownload PDF (2793K) -
Yohtaro Yamazaki1994 Volume 41 Issue 10 Pages 1270-1275
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSStudies on the increase in the coercive forces (Hc) of Fe3O4-γFe2O3 intermediate particles and thin films have been summarized. This phenomenon was reported first by M. Namikawa in 1963 and was intermittently followed for years by many researchers. The effective experimental results to approach the origin of the coercive force increase have been pointed out, i.e., (1) increase in He at a particular region of Fe2+/Fe3+, (2) reversible increase in He for the oxidation process of Fe3O4 and for the reduction process of γFe2O3, (3) increase in He during an aging process, (4) large increase in He for thin film samples than for powder samples. It is emphasized that the two phases of cubic and tetragonal crystal structures coexist at the oxidation rate of Fe2+/Fe3+=0.10-0.15 where the coercive forces of the samples increase to their maximum values. The intermediate films are examined with the transmission electron microscopy. The result suggests that the apparent crystallites observed in the intermediate films have fine sub-structures.View full abstractDownload PDF (1812K) -
Shigemi Sato, Ryusuke Adachi, Toyoyuki Higashino, Hiroshi Koyama1994 Volume 41 Issue 10 Pages 1276-1281
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSStrength and fatigue life of a thin leaf spring, which was made of 3mol%Y2O3 partially stabilized zirconia (PSZ) and was fabricated by hot-pressing, were tested to estimate the possibility of ceramics as a spring material.
Four-point bending test, cyclic bending fatigue test at room temperature and static fatigue test at 573K were carried out for the estimation of the strength.
From the results of the tests, it is found that the PSZ has rather low heat resistivity and the wide scattering of the material strength. Therefore, the greatest care on the effect of the temperature and the scattering of the strength are required to design a PSZ spring. The fatigue life, which is important to design a spring, can be estimated by using the technique of fracture mechanics and Weibull distribution function.View full abstractDownload PDF (361K) -
F. Velasco, J.M. Ruiz-Román, L.E.G. Cambronero, J.M. Torralba, ...1994 Volume 41 Issue 10 Pages 1282-1287
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe feasibility of cast iron swarf utilization as a raw material in the powder metallurgy industry has been studied. This work derives the possibility of making steel components from cast iron swarf powder with P/M techniques. Cast iron swarfs have been used as a direct additive in the manufacturing of steels, without making any other preliminary processes different from the pulverization to the desired size distribution. In order to get a steel composition, the cast iron swarf powder has been diluted in high purity iron powder to reduce the cast iron carbon content.It has been tried not to modify the industrial conditions with the objective of simplifying the possible reuse of swarfs in the processes already existing in powder metallurgy.View full abstractDownload PDF (4626K) -
Kazuo Nishii, Hidenobu Sonoda, Hidehiro Kamiya, Masayuki Horio1994 Volume 41 Issue 10 Pages 1288-1293
Published: October 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA novel binderless granulation method, Pressure Swing Granulation (PSG) was applied to the granulation of waxed hardmetal powders in which the conventional spray drying (SD) technique has been facing difficulties to produce good granules. Properties of granules and green compacts from the PSG based process were examined and compared with those from the SD based process. Mechanical properties of sintered bodies were evaluated with a Cemented Carbide Industrial Standard of Japan Cemented Carbide Tool Manufacturers' Association.
Spherical granules of sizes ranging 0.1-1mm in diameter were obtained with a high yield. Angle of repose and relative bulk density of granule beds were much improved compared with those of original powder beds and the bed of spray dried granules. Density of green compacts with pressures of 0.5-1.5tf/cm2 (49.0-147.1MPa) was greater than 50% of theoretical density which should be sufficient for obtaining good quality of sintered products. The sintered samples of compaction at a pressure of ltf/cm2 and sintering at 1673K in vacuum for lh showed sufficient mechanical properties for industrial use.View full abstractDownload PDF (3486K)
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