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Volume 39, Issue 12
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[in Japanese]1992 Volume 39 Issue 12 Pages 1044
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (73K) -
Yoshiaki Fukushima, Arimitsu Usuki1992 Volume 39 Issue 12 Pages 1045-1049
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSStructure of intercalated compounds of montmorillonite and 6-or 12-polyamides was studied by XRD, DSC and IR. Basal spacing was increased stepwise; 1.36nm, 1.83nm and 2.30nm. Two phases; 1.36nm/1.83nm and 1.83nm/2.30nm, were coexisted in montmorillonite/6-polyamide compounds. On the other hand, random mixed-layer phases, in which two lattice units, 1.36nm/ 1.83nm or 1.83nm/2.30nm, was randomly mixed, were observed for montmorillonite/12-polyamide compounds. When polymer contents was low, an associated NH-group with polar interaction and fusion of a polyamide were not observed in IR-absorption spectra and DSC curves. As the contents was increased, the associated NH-groups in polyamide and the fusion of polyamide were observed. Results of Fourier transformations of XRD suggested that an arrangement of polyamide chains in the interlayer spacing of montmorillonite was restricted to parallel to the silicate layers. It was concluded that the weak Van der Waals interactions between silicate surface and guest molecules played an important roll to determine a structure of the intercalated compounds.View full abstractDownload PDF (321K) -
Mamoru Omori, Toshio Hirai, Akira Watanabe, Shusaku Shibata, Minoru Ma ...1992 Volume 39 Issue 12 Pages 1050-1054
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPoly(phenylsilane) soluble in hydrocarbon was synthesized from trichlorophenylsilane using 18-crown-6 as a cocatalyst. This polymer was heated in vacuum of 6.7 Pa for 2h at 1000°C to get a precursor for composites. The precursor was fired at 1450, 1600, 1800, 2000, 2200 and 2400°C and SiC-carbon composites was formed. The size of SIC crystals was less than 10 nm below 1600°C and grew several hundred nm at 1800-2200°C. The matrix of carbon was not graphitized till 2400°C.View full abstractDownload PDF (2913K) -
Hideto Yoshida, Noboru Miyata, Masaaki Sagawa, Kazunari Naito, Shigeki ...1992 Volume 39 Issue 12 Pages 1055-1059
Published: December 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSSiC composites (Cf/SiC) reinforced with unidirectionally oriented carbon fibers were fabricated by various hot-press sintering conditions. The flexural strengh of Cf/SiC composites at 1250°C (628-721MPa) was higher than that of Cf/SiC composites at room temperature (517-554MPa). The flexural strengh of Cf/SiC composites at 1250°C was increased by delaying the starting point for increasing the pressure from low temperature to high temperatures.View full abstractDownload PDF (1313K) -
Toshio Kawanami1992 Volume 39 Issue 12 Pages 1060-1066
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDevelopment of toughened zirconia parts for grinding was reviewed. This work was achieved by developing the high purity, ultra-fine zirconia powder processing and toughened Y-TZP( Y2O3 doped tetragonal ZrO2 ceramics ), and investigating the propertieswear characteristics relation. Zirconia powders prepared by the hydrolysis method, which was the lowest production cost, showed the good formability and sinterbility. Y-TZPP containing 2.5-3.0mol% Y2O3 gave higher fracture toughness and strength by the stress induced phase transformation toughening. The wear characteristics of Y-TZP grinding media depended strongly on the fracture toughness, strength and grain size, but not on hardness and density within the range of this experiment. It is considered that the excellent wear characteristic zirconia parts for grinding can be obtained by controlling the fracture toughness, strength and microstructure. To investigate these mechanism, the microstructures of worn areas were examined by SEM observations.View full abstractDownload PDF (5323K) -
Tomoko Uno, Toshihiro Kasuga, Shin Nakayama, Akira Ikushima1992 Volume 39 Issue 12 Pages 1067-1071
Published: December 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSA new type of glass-ceramic containing calcium-mica crystals, in which numerous zirconia nano-particles are dispersed, exhibits high strength (-500 MPa in bending) and good machinability. This nano-composite structure is formed by controlling the growth rates of the precipitated crystals, i.e., zirconia and mica. The precipitation of mica crystals was controlled by the amount of fluorine in the mother glasses. A glass, in which the mica crystals were precipitated by heat treatment at low temperature, was converted into a micro-composite type of glass-ceramic containing zirconia crystals with -100 nm in size. This glass-ceramic was machinable, and its bending strength and fracture toughness were 310 MPa and 3.4 MPa⋅m0.5, respectively. The formation of tetragonal zirconia in sub-micronmeter size will lead to increase in the fracture toughness. These results imply that the tough glass-ceramics with "micro/nano"-composite structure can be prepared by controlling the crystallization.View full abstractDownload PDF (2371K) -
Suguru Inamura, Kei Miyamoto, Yuzuru Takahashi, Hiroki Miyamoto1992 Volume 39 Issue 12 Pages 1072-1075
Published: December 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe mixed powder of ZrO2(3Y) and Al2O3 was ground by a bead milling method. The particle sizes of ZrO2(3Y) and Al2O3 were reduced to 10 nm and 18 nm by milling for 377 hours, respectively. Open pores in the specimen sintered at 1300°C were diminished to less than 0.1% of total volume for fine mixed powder milled for 422 hr, while open pores in the specimen sintered at the same conditions using mixed powder milled for 1 hr showed more than 17%. Therefore, it was concluded that the reduction of particle size mentioned above greatly enhanced the sinterability of the mixed powder. The relative density reached more than 99.7% of theoretical density when the pre-sintered bodies free from open pores were HIP'ed at temperatures from 1300°C to 1500°C under Ar gas pressure of 196 MPa. The bending strength of the HIP'ed specimen was 1520 MPa although that of pre-sintered specimen was 800 MPa.View full abstractDownload PDF (4551K) -
Ichiro Minato, Giuseppe Pezzotti, Koichi Niihara1992 Volume 39 Issue 12 Pages 1076-1079
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSRelationship between microstructure and fracture behavior of monolithic Si3N4 and Si3N4/25vol%SiC nanocomposites was investigated. For the Si3N4/25vo1%SiC nanocomposites, the fracture strength was increased by the nano-size SiC dispersion which allowed to control the growth of fine and uniformly elongated Si3N4 grains. Fracture toughness was also improved because of bridging and pull-out of elongated Si3N4 grains. The variation of the fracture toughness value with the indentation load, i.e. crack length, was measured by indentation fracture (IF) method, and this result was compared with that of chevron notched beam (CNB) method. In this experiment, the fracture toughness by IF method exhibited a rising with increasing the crack length. This was interpreted as due to the rising R-curve behavior also observed by the CNB method. Therefore, it is proposed that R-curve behavior can be also estimated by IF method. However, the saturated KR value observed by IF method was within ±15% of measured by CNB method.View full abstractDownload PDF (2994K) -
Hisashi Kuwano, Hiroyuki Morita, Yoshikazu Hamaguchi, Hao Ouyang, Bren ...1992 Volume 39 Issue 12 Pages 1080-1084
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThree bcc metals and an alloy (Cr, Mo, W, Cr-Fe) were ball-milled by tungsten carbide, carbon steel and stainless steel vial/balls to prepare nano-sized materials of grain sizes of 5.5-17nm. Mössbauer spectroscopy, magnetization and X-ray diffraction measurements were performed. A presence of the grain boundary component and the crystalline component of the Fe hyperfine field was confirmed for the boc nanocrystallites studied The average hyperfine fields of these two oomponents were independent of the materials studied, and independent of temperature down to about 20K A significant reduction in the magnetic moment of Fe occurred in the nano-sized Cr-20at%Fe.View full abstractDownload PDF (342K) -
Toyohisa Fujita, Kunihiko Yamaguchi, Kenji Yoshino1992 Volume 39 Issue 12 Pages 1085-1088
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWhen the relative index of reflection of dispersing particle to solvent is enough large and particle diameter is too small comparing wavelength of visible rays, Rayleigh scattering is observed and the scattering changes significantly by changing the particle diame-ter.Ultrafine barium titanate of average particle size 10nm which has been coated with surfactant shows good dispersion into insulated oil. This dielectric fluid is filled between two ITO coated glass plates to prepare thin film. When appropriate electric field to the forward direction of light is applied, particles make many long clusters of large diameter. Therefore, it becomes difficult for visible rays to pass through the thin film.As the application of this scattering, the light shutter has been considerd.View full abstractDownload PDF (1285K) -
Toshihiro Kasuga, Tomoko Uno, Masahiro Yoshida, Kinobu Osakabe, Akira ...1992 Volume 39 Issue 12 Pages 1089-1092
Published: December 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSBioactivity of zirconia-toughened glass-ceramic composites was evaluated in terms of their surface reaction in simulated body fluid. The bioactivity was degraded by introducing large amounts of zirconia TEM observation revealed that Ca in the glass-ceramic particles reacted with the zirconia during sintering, and that the decrease in Ca in the particles degraded the bioactivity of the composites. In this study, the optimum composition and preparation process are determined for high-strength and bioactive ceramics.View full abstractDownload PDF (1330K) -
Shin-ichi Hirano1992 Volume 39 Issue 12 Pages 1093-1099
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCeramic composites have received great attentions in order to improve the reliability and the mechanical properties and to create the functionalities of advanced ceramics. The control of grain boundaries exhibits the remarkable feature on developing the specific characters which cannot be predicted by the additivity of the properties derived from the two phase mixture. This review describes the concepts of the in-situ microstructure control of ceramic composites during processing. Examples are the composite powder processing of ZnO coated with MnO2 and Bi2O3 for varistor with grain boundary control, ferrite dispersed carbon composites by the pressure pyrolysis of organometallic copolymers and Ce UP composite preparation with La-β alumina platelets during sintering of consolidated powder mixture.View full abstractDownload PDF (4538K) -
Kim Seo Weon, Makoto Sasaki, Toshio Hirai1992 Volume 39 Issue 12 Pages 1100-1103
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSFor the fabrication of functionally gradient materials (FGMs) composed of titanium carbide (TiC) and carbon (C), TiC-C composites in the C/(TiC+C) from 6 to 91 mol% were prepared by the chemical vapor deposition (CVD) using a TiCl4-CH4-H2 system. The relation between microstructure and free carbon content in the TiC-C composites is necessary for the design of the TiC/C FGMs. Microstructure of the TiC-C composites was continuously changed from dense faceted to porous dome microstructure with increasing the pore volume in matrix accompanied with increasing the carbon content. The pore size was also changed from 10 nm to 105 run with increasing of the pore volume in the TiC-C composites.View full abstractDownload PDF (1604K) -
Masahiro Nawa, Tohru Sekino, Koichi Niihara1992 Volume 39 Issue 12 Pages 1104-1108
Published: December 15, 1992
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSThe Al2O3/5-20vol%Mo composites were fabricated by hot-pressing a mixture of a-Al2O3 and fine Mo powders under a vacuum. In these composites, nanometer size Mo particles were dispersed within the
Al2O3 grains and relatively large Mo particles, above 1μm, were located at the grain boundaries. Thus, it was confirmed that ceramic/metal nanocomposites could be successfully fabricated with a conventional powder metallurgical process. The addition of Mo particles resulted in the grain growth inhibition of the Al2O3 matrix. A significant improvement in fracture strength and toughness was observed, but they could not be achieved simultaneously. A fracture strength of 884MPa for the Al2O3/7.5vol%Mo composite sintered at 1400°C was obtained. The fracture toughness was improved with increasing Mo content and rising sintering temperature. It obtained a value of 7.21MPa⋅1/2 for the Al2O3/20vol%Mo composite sintered at 1700°C.View full abstractDownload PDF (2999K) -
Masayuki Ishitsuka, Masumi Tamai1992 Volume 39 Issue 12 Pages 1109-1112
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe microstructure and mechanical properties of Al2O3/SiC nanocomposites, which were prepared by pressureless-sintering of the nanocomposite powder, were investigated Nanocomposite powders were synthesized by calcination of mixtures of r-A2O3 (aveage paticle size:4nm) and SiC (average particle size:20nm). The particlesof nanocomposite powder had a two-phase structure, SiC contained within Al2O3. Transmission electron microscope observation of pressureless sintered bodies showed that SiC particles were dispersed within the Al2O3 grains and some dislocation lines were observed within the Al2O3 grains. The fracture strength of Al2O3/SiC nanocomposites was higher than that of the Al2O3 monolithic ceramics. At the same time, the fracture mode changed from intergranular to tragranular. After HiPing and annealing of the sintered bodies, the fracture strength increased up to above 1000MPa. It was also observed that the dislocation pile-up increased and the tragranular fracture surface was coarser.View full abstractDownload PDF (5563K) -
Chitake Yamagishi, Kazuyoshi Minamisawa, Tatsuya Shiogai, Kazushige Su ...1992 Volume 39 Issue 12 Pages 1113-1118
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe Relation between the high-temperature mechanical properties and the microstructure of SiC/β-sialon composites was investigated. Addition of SiC increased the flexual strength and the creep resistance of β-sialon at high temperatures. Average grain size of β-sialon in SiC/β-sialon composites was smaller than that of β-sialon ceramics. And a part of sintering aid existed at the inside of β-sialon grains in SiC/β-sialon composites. The better mechanical properties of SiC/β-sialon composites may be attributed to the decrease of the amount of liquid phase, the thickness of intergranular phase and the size of triple grain junctions. SiC particles existed both at the intergranular phase and within the matrix grains. The creep resistance was also improved probably due to inhibitation of the grain boundary sliding.View full abstractDownload PDF (2885K) -
Jin-Joo Matsui, Akira Yamakawa, Koichi Niihara1992 Volume 39 Issue 12 Pages 1119-1123
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe fabrication process and microstructure of Si3N4-based nanocomposites were investigated for the improvement in fracture toughness. The fine Si3N4 powders containing metal nitride particles such as VN, NbN, TaN and TiN were synthesized by heating the mixtures of Si3N4 and corresponding metal oxide powders in a N2 atmosphere. The obtained VN/Si3N4 and TiN/Si3N4 powders were confirmed to be very fine (20 to 30 nm in diameter). These composite powders were sintered with sintering aids. No improvement in fracture toughness for the VN/Si3N4 composites. For the TiN/Si3N4 composites, in which nano-sized TiN grains were dispersed within the Si3N4 matrix Brains, the fracture toughness was increased. This was probably due to crack propagation through intragrains of the Si3N4 matrix.View full abstractDownload PDF (4738K) -
Hisashi Kaga, Yoshihiro Taya, Hiroshi Katayama, Yoshikazu Hamaguchi1992 Volume 39 Issue 12 Pages 1124-1128
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSUsing the vacuum mechanofusion apparatus which has been reported, we tried to coat A12O3 core particles with Cu covering particles. Mechanofusion in air and low vacuum induced lower degree of coating promotion, while the mechanofusion in high vacuum and Ar atmosphere gave a higher yield. That is to say, the yield of composite particle was enhanced by decreasing the partial pressure of O2 in the atmosphere. AES analysis for the Cu covering layer of the composite particles showed that the content and the enriched depth of oxygen in the Cu covering layer increased as the pressure of the atmosphere became higher.View full abstractDownload PDF (1465K) -
Hisashi Kaga, Yoshihiro Taya, Hiroshi Katayama, Yoshikazu Hamaguchi1992 Volume 39 Issue 12 Pages 1129-1133
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSUsing the vacuum mechanofusion apparatus, we coated Al2O3 powders with Cu powders. It was found that the longer the mechanofusion processing time. the smoother the surface of the composite particles. Such grain boundaries as typically seen in an anealed Cu bulk were observed in the smooth Cu covering layer when it was chemically etched. This implies that the temperature of the composite particles during the mechanofusion processing increases as high as Cu sinterring occurs. The surface temperature of each particle during the mechanofusion processing was estimated at about 1000 K from the result of sintering behavior of cold pressed Cu compacts.View full abstractDownload PDF (3717K) -
Masaharu Tokizane, Kazuo Isonishi1992 Volume 39 Issue 12 Pages 1137-1144
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAtomization mechanism and production of atomized high quality powder by Plasma Rotating Electrode Process (PREP) were discussed. The atomization mechanism changed from direct drop formation (DDF) to film disintegration (FD), through ligament disintegration (LD) depending on either the changes in material parameters or those in the operation parameters. DDF mechanism yielded the highest quality powder particles consisting of exceedingly spherical shape, uniform size and clean without contamination. Therfore, this powder seemed to be suitable for compaction by Wing or near-net-shape forming. The results of the study were applied for producing PREPed powders of some intermetallics such as Ti-aluminides and TiNi. The compacts of those powders showed improved mechanical properties compared with the conventionally processed materials.View full abstractDownload PDF (3664K) -
Shuji Wanikawa, Tohru Takeda1992 Volume 39 Issue 12 Pages 1145-1150
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSBy using the planetary, screw disc and vibration type ball mills, mechanically activated states of Ti-C powders formed in milling were investigated with the change of their reaction temperature. The temperature decreased with increasing milling time, and its relation is characteristic of the milling methods. Especially, in case of the vibration mill, there is clear indication that the reaction temperature of milled powder was saturated at a constant value as the lapse of the milling time, and also the size of balls charged in mill influenced markedly to the reaction temperature.View full abstractDownload PDF (2109K) -
Nobujiro Tsuchiya, Masahide Fukuda, Hiroyuki Ike, Hisashi Suzuki1992 Volume 39 Issue 12 Pages 1151-1156
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe sintered WC compact was machined by electric discharge machining, and then annealed in vacuum at 800-1300°C for the time up to 80hrs. The phase change of different phases (β-WC1-x, W2C) appearing along the machining surface was studied as functions of annealing temperature and time. It was found that the different phases had a tendency to disappear and finally change to WC. Such a phase change could be explained by assuming that two sorts of eutectoid reactions, that is, β-WC1-xW2C+WC and W2CW+WC took place during annealing, and that the formed W2C or W changed to WC, because they reacted with the free carbon remaining in non-equilibrium state in the surface layer. Microstructural changes of surface layer due to annealing were in detail studied.View full abstractDownload PDF (3294K) -
Tomohiro Furukawa, Nobuya Machida, Toshihiko Shigematsu, Norihiko Naka ...1992 Volume 39 Issue 12 Pages 1157-1162
Published: December 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSSurface carbonate ion observed in YBa2Cu3Ox from a conventional ceramic method was removed during vacuum calcination up to 1200 K. No surface condensation of Y and Ba due to the formation of the Y-CO3 and Ba-CO3 bond was observed in YBa2Cu3Ox prepared by vacuum calcination and subsequent oxidation in a pure oxygen atmosphere. YBa2Cu3Ox prepared by this process had a lower ΔTc value and low temperature coefficient of electrical resistivity than those observed in the sample from the conventional ceramic method. The existence of carbonate ion at the surface and grain boundaries had adverse effects on the superconducting properties of the products.View full abstractDownload PDF (317K)
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