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Volume 47, Issue 8
Displaying 1-19 of 19 articles from this issue
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Yutaka Hiraoka, Tadayuki Fujii2000 Volume 47 Issue 8 Pages 811-818
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFor the wider utilization of single crystals of refractory metals such as molybdenum and tungsten, development of high performance and/or composite single crystals is necessary. For this purpose, first, we developed new methods to control the crystallographic orientation of the single-crystalline molybdenum and to produce a multi-layered single crystal of molybdenum by means of secondary recrystallization. Second, we established fundamental conditions to braze single-crystalline molybdenum alternatively to single-crystalline molybdenum or to carbon-ceramics, respectively, by using Mo-40%Ru alloys or by palladium.View full abstractDownload PDF (7599K) -
An Estimate by Two-dimensional Model SimulationHitoshi Hashimoto, Toshihiko Abe2000 Volume 47 Issue 8 Pages 819-823
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSBall motion in a vibratory ball mill during mechanical alloying was studied by a two-dimensional model simulation to estimate an effect of ball charge fraction on the mechanical alloying process. As a result, it was found that the ball motion changed drastically at a ball charge fraction between 0.7 and 0.8. The ball motion became so violent and the power consumed by dashpots of descrete element method model increased so much in a range of high fractions. It was found from the simulation that the range of ball movement was limited to lower parts of the mill vessel at ball charge fractions less than 0.7, while the range of ball movement spread over the vessel at fractions over 0.8, which increased the frequency of ball-to-vessel collision and also increased energy transferred from vessel to balls. However, the amplitude and frequency of vibration and the power of actual vibratory mills must decrease with an increase in the ball charge fraction because of the limitation of driving motor power. It suggests that an effective ball charge fraction should be in a range from 0.7 to 1.0.View full abstractDownload PDF (403K) -
Naoki Yosizawa, Yutaka Hiraoka, Seiji Kohi, Kazuo Iwakuma2000 Volume 47 Issue 8 Pages 824-829
Published: August 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThree-point bend tests were performed for five kinds of molybdenum-nickel alloys and three kinds of molybdenum-palladium alloys. After correcting for the grain size effect, the critical stress and critical temperature representing the low-temperature fracture strength and ductility of the material, respectively, were evaluated. First, effects of a small addition of nickel or palladium on the low-temperature fracture behaviour of molybdenum were investigated. Secondly, improvement of low-temperature ductility by nickel or palladium additions was discussed in terms of critical stress and yield strength.
The results are summarized as follows.
(1) The average grain size decreased by nickel or palladium additions.
(2) In Mo-Ni alloys and Mo-Pd alloys, the critical stress decreased with the alloy content.
(3) In Mo-Ni alloys, the yield strength decreased with the alloy content up to 610 at.ppm, but it tended to increase at the alloy content of 830 at.ppm. In Mo-Pd alloys, the yield strength decreased with the alloy content up to 500 at.ppm.
(4) In Mo-Ni alloys, the critical temperature decreased with the alloy content up to 610 at.ppm, but it tended to increase at the alloy content of 830 at.ppm. In Mo-Pd alloys, the critical temperature decreased with the alloy content up to 500 at.ppm.View full abstractDownload PDF (474K) -
Yoshikazu Suzuki, Katsuyoshi Shimokawa, Hideki Minagawa2000 Volume 47 Issue 8 Pages 830-837
Published: August 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIt is hoped that shape memory alloys (SMAs) can serve as useful materials in cold regions of the earth. It is necessary to find a means to control the shift of these alloys at temperatures lower than atmospheric temperatures.
Cupper alloys are suitable materials for controlling the constituent elements and easily treating the sampling condition.
Improvements in the characteristics of these alloys have been performed, and these advances are demonstrated in this report.
The main results can be summarized as follows: (1) When the thickness of specimen became thiner, it was clarified that the width of the hysteresis curve of load and temperature increased. This occurs due to the thermal conductivities for shape memory reactions of the specimens. (2) The effect of shape memory behavior on saddle shape specimens was revealed under lower ice-forming temperatures as increasing the slope of load/°C in the hysteresis curve of load and temperature. (3) By adding Ti to a Cu-Al-Ni alloy and B and Celements to a Cu-Al-Ni-Ti alloy, it was recognized that the fracture strength of the alloy had increased and operation temperature of the shape memory behavior had shifted to a lower temperature.View full abstractDownload PDF (5974K) -
Yoshimitsu Yachi, Shigeki Chiba, Hiroshi Osada, Hideo Oka, Kyoshiro Se ...2000 Volume 47 Issue 8 Pages 838-843
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAn approach to biochemistry of the technology on the powder metallurgy has been advanced and various biosensors have been developed. The temperature-sensitive metal oxide semiconductor thin film, TMT is prepared via process of the vacuum deposition of the transition metals and subsequent annealing treatment. The marked temperature dependent TMT has the function of detecting the minute temperature of 10-3°C in degree, so it can be used for the thermal enzyme sensor. The paper describes preparation of the TMT and the sensor system for discriminating various chemical substances by minute heat generated with an enzyme reaction.View full abstractDownload PDF (1846K) -
Ryosuke Ueyama, Tamotu Ueyama, Takashi Yamamoto, Kiyoshi Kuribayashi, ...2000 Volume 47 Issue 8 Pages 844-852
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPhysical and electrical properties of three types of Ag-Pd pastes, which consist of different metal fine powders, i.e., a coprecipitated powder, an agglomerated alloy powder made by heat treatment and a pulverized alloy powder produced by improved pulverization method, have been studied. The paste prepared from pulverized alloy powder showed a higher film packing density (6.3g/cm3) than those made of the other powders. The film consisting of pulverized alloy powder showed a lower expansion at around 500°C, a lower shrinkage from 700°C to 1100°C and a lower electric resistivity. The results indicated that the paste which consists of an pulverized Ag-Pd alloy powder was superior in performance to the other two pastes for an internal electrode material of multilayer ceramic device.View full abstractDownload PDF (5559K) -
Katsuyoshi Kondoh, Ryuzo Watanabe, Hitoshi Hashimoto2000 Volume 47 Issue 8 Pages 853-859
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of the powder particle size of rapidly solidified aluminum alloy powder on its compaction behavior was examined using Cooper-Eaton equation. The first particle rearrangement due to the filling of pores between the powder particles strongly depends on the apparent density that has a relationship with the particle distribution. The second particle rearrangement depends on the friction force between the powder particle surfaces in filling the pores and is ruled by the specific surface area. The plastic deformation of powder, which occurs at the higher compaction pressure, is related to the compaction proof strength of the sintered material. It has a relationship with a rapidly solidified microstructure which depends on the powder particle size. The calculated total volumetric compaction quantitatively corresponds to the measured density of the green compact.View full abstractDownload PDF (512K) -
Katsuyoshi Kondoh, Ryuzo Watanabe2000 Volume 47 Issue 8 Pages 860-865
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of the AIN content dispersed in the aluminum based sintered composite material on the cavitation toughness have been examined. The Al-AIN composites were prepared by two processes. One was the directly nitriding process and another was the conventional premixing process in this study. The cavitation toughness was measured by using a magnetostriction vibratory cavitation apparatus. The nitrided and sintered Al-AIN composite material showed superior cavitation toughness compared to the premixed composite. This is because AIN particles in the former have good bonding to the matrix, while AINs of the latter are mechanically held at the primary particle boundaries.View full abstractDownload PDF (3706K) -
Hiroyuki Y. Suzuki, Kenji Shinozaki, Syunzo Tashima, Hidenori Kuroki2000 Volume 47 Issue 8 Pages 866-873
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTwo types of fine (0.2μm) and pure (99.99%) alumina powders are dispersed in ion-exchanged water and compacted into a columnar shape ofφ8×60mm by the High-Speed Centrifugal Compaction Process(HCP)at 11, 500 rpm for 3 ks. Specimens are sintered at 1423-1823K for 5.4 ks.
HCP alumina shows good compactability regardless of starting powder. Its behavior is slightly affected by the dispersing condition of the slip. The sintering behavior of compacts can be evaluated by grain-size/relative-density trajectory. The optimum mechanical properties are realized at a characteristic part of the curve, where the curve starts to go upward.
Bending strength of the alumina with different starting materials obeys basically one equation. So does the Vickers hardness. Therefore, the strength-microstructure diagram has validity for HCP alumina of various powders. The powder which gives lower position for grain-size/relative-density trajectory of sintered alumina gives higher mechanical properties.View full abstractDownload PDF (4028K) -
Hiroyuki Y. Suzuki, Kenji Shinozaki, Yasuhiro Tanka, Hidenori Kuroki2000 Volume 47 Issue 8 Pages 874-881
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSResidual defects in alumina green compacts are observed by liquid-immersion technique. A high purity (of 99.99%) and fine (of 0.2μm) alumina powder is dispersed in the ion-exchanged water and compacted by High Speed Centrifugal Compaction Process (HCP) and pressure casting (PC). Green compacts are pre-sintered at 1073 K for 3.6ks and subsequently sliced into 500μm thick disks. The disk are immersed in diiodmethane and observed by optical microscopy with transmission light.
Although HCP and PC green compacts show almost the same green densities and sintered densities, only PC compacts contain many residual bubbles remaining as huge pores after pre-sintering. The residual bubbles in PC compacts become larger as the viscosity of slip increases. The de-bubbling effect of HCP is far greater than that of vacuum de-bubbling, whereas its efficiency is also affected by the condition of the compaction. In HCP, the bubbles can be removed more effectively under greater centrifugal force using a slip with low viscosity.View full abstractDownload PDF (5275K) -
Shigeru Ito, Jun Nishii, Takashi Fujii, Kazuo Akashi2000 Volume 47 Issue 8 Pages 882-886
Published: August 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe composites consisting of α-quartz crystallites and amorphous SiO2 were prepared by HIP technique, imitating the structure of natural agate. In the previous study, the KIC of the composite prepared from the mixed powder of crystallites and amorphous SiO2 was comparable to that of the natural agate (0.56 MN/m1.5). In this study, to increase the toughness of the composite, (1) the mixture of silica sol and α-quartz powder and (2) silica sol including nucleation promoter were examined as starting materials respectively. These starting materials were pressed into powder compacts with φ10×50mm in size. The Pyrex glass capsule containing the compact was hipped at 800-1200°C for 0-120 minutes under the pressure of 200MPa. The KIC of the composite obtained from the mixture of silica sol and α-quartz powder was equivalent to that obtained in the previous study, while the maximum KIC (0.63 MN/m1.5) was obtained when PbCl2 was used as a nucleation promoter. The nucleation promoter having low solubility in water was useful for the homogeneous generation of the crystallites.View full abstractDownload PDF (3836K) -
Hwan-tae Kim, Masakazu Kawahara, Masao Tokita2000 Volume 47 Issue 8 Pages 887-891
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSpecimen temperature and sintering behavior of Ni powder by spark plasma sintering (SPS) were investigated. Microstructure observation of the sintered compact revealed that the fast densification of the powder materials was due to the promotion of neck growth and plastic deformation of powder particles in the initial stage of SPS. With die temperature at 1073 K, the temperature of the specimen center was 1203 K. The temperature difference between specimen and graphite die exponentially increased with the increase of the temperature of the graphite die. When the graphite die was kept warm by a thermal insulation jacket, the temperature difference between specimen and graphite die was smaller than when using a non-insulated die, and the temperature difference lineally increased with the increase of the temperature of the graphite die.View full abstractDownload PDF (4084K) -
Yuji Yamasaki, Mari Yonetsu, Ken-ichi Takagi2000 Volume 47 Issue 8 Pages 892-896
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNi-5B-xMo-3.5Cr-11.5V (mass%) model alloys with eight levels of Mo contents corresponding to Mo/B atomic ratio ranging from 0.8 to 1.5 were prepared to study the effects of the Mo/B atomic ratio on the mechanical properties and microstructures. The results indicated that transverse rupture strength (TRS) increased with increasing the Mo/B atomic ratio and showed the maximum value of 2.95 GPa at MoB=1.2 and then decreased with increasing the atomic ratio. Hardness increased monotonically from 82 HRA to 89.9 HRA with increasing the atomic ratio up to 1.3 and then gradually increased to 90.5 HRA with the atomic ratio up to 1.5. When the Mo/B ratio was 1.1 and 1.2, excellent TRS values were obtained because tetragonal M3B2 (M: Mo, B, Ni, Cr, V) complex boride particles were finely dispersed in the alloy. When the Mo/B ratio was less than 1.0, the TRS decreased due to the appearance of coarse orthorhombic M3B2 particles in addition to the tetragonal M3B2. Above the Mo/B ratio higher than 1.3, the TRS decreased due to the appearance of coarse tetragonal M5B3 particles.View full abstractDownload PDF (3892K) -
Sachio Oki, Kouzou Tsuchida, Yoshinori Kinoshita, Kenichi Watanabe2000 Volume 47 Issue 8 Pages 897-903
Published: August 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSurface coated composite powders made by the mechanical powder modification system were prepared in order to investigate the basic sintering behavior of the composite powder, as well as the strengthening and function enhancement of the porous sintered materials made from the composite powder. The sintering behavior of fine alumina or fine titania coated alumina powder was examined. Alumina powder coated with fine alumina powder ground away from coarse alumina material powder surface during surface modification process was also examined. The results obtained were summarized as follows:
(1) It was possible to coat the alumina mother powder surface with the fine powder of alumina or titania by the mechanical powder modification system.
(2) It was possible to coat with fine alumina powders ground away from coarse alumina material powder surface during the surface modification process.
(3) The sintered compacts made from surface coated composite powders show markedly high bend strength compared with that made from untreated powder. The strength of the compact made from alumina coated powder was double, and that made from titania coated powder was 8-fold that of the compact made from untreated material powder.
(4) Porosity and pore size distribution hardly changed, even if the strength was improved by the modification of the powder.
These results show that this method is effective for the fabrication of high-strength porous sintered compacts.View full abstractDownload PDF (5591K) -
Mitsuya Hashii, Kazuto Tokumitsu2000 Volume 47 Issue 8 Pages 904-908
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe pure Fe and pure Al (25 mol%) powder mixture was mechanically alloyed for various times by a dry tumbler ball-milling. The magnetic property of the milled powder was measured by a vibrating sample magnetometer (VSM) and a 57Fe Mössbauer spectroscopy. The powder milled for an enough long time, 1800ks, had a broad Mossbauer spectrum. It was predicted that the fully milled powder was composed with both ordered and disordered Fe3Al phases. The VSM measurements showed that the saturation magnetization (Ms) of the milled powder was decreased with the milling time until 360 ks due to the solid solution of Al into α-Fe. However, after 360 ks, the Ms was contrary increased with straining by the milling. The Ms of the powder milled for 1800ks decreased by annealing.View full abstractDownload PDF (370K) -
Hisashi Kaga, E.M. Carrillo-Heian, Z.A. Munir2000 Volume 47 Issue 8 Pages 909-915
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe reactive sintered compacts of Ti-W-Cr-B mixed powders were manufactured by a pulse electric current technique. Identification and characterization of the resulting boride phase were done using EPMA, XRD and other methods.
The density of the sintered compacts rose rapidly with sintering temperature up to 1773 K, at which temperature the relative density was 94%. Above this temperature, the density rose only slightly with increasing sintering temperature. The borides of Ti and W were synthesized from mixed metal powders by this method. The type of boride formed and its composition depended on sintering temperature. Compacts sintered at lower temperatures consisted of WB2 and TiB2 phases, but at the highest sintering temperature, 2173 K, the main phase was (Ti, W, Cr)B2 solid solution, in which W and Cr were dissolved in TiB2. There was also a very small amount of β-(W, Ti, Cr)B phase. By annealing compact sintered at high temperature, the (Ti, W, Cr)B2 solid solution phase decomposed and the amount decreased.View full abstractDownload PDF (4253K) -
Chie Ando, Noriyuki Kohzu, Hirokazu Chazono, Hiroshi Kishi2000 Volume 47 Issue 8 Pages 916-920
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSBaTiO3 (BT) was synthesized by the solid state reaction of an almost equimolar mixture of BaCO3 and TiO2 in various atmospheres. The rate of reaction decreased as the CO2 partial pressure increased. There observed no Ba2TiO4 irrespective of the CO2 partial pressure in the whole temperature range studied. The morphology of BT powder calcined at 1035°C in air was spherical. However, it was angular and the particle growth was inhibited when calcined at 1035°C in the atmosphere with above 30vol% of CO2 partial pressure. Furthermore, the amount of the remained BaCO3 during the solid state reaction for angular BT was larger than that for spherical one from the X-ray diffraction analysis. It was found that BaCO3, of which decomposition was suppressed by the high CO2 partial pressure, had a considerable influence on the reaction rate, morphology of the particle, and the particle growth in the solid state synthesis of BT.View full abstractDownload PDF (3697K) -
Takenobu Yamasaki, Takeshi Yamamoto, Keiichi Ishihara, Hideo P. Shingu2000 Volume 47 Issue 8 Pages 921-926
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTi-Al-C composite materials were produced by SHS (Self-propagating High-temperature Synthesis) -Pseudo-HIP (Hot Isostatic Pressing) method. The self-propagating reaction of Ti, Al and C occurred at aluminum melting temperature (933 K). The synthesis conditions to attain high density materials with finely dispersed particles of Ti-Al-C ceramics were confirmed. The composites synthesized at atomic composition of Ti45Al45C10 consisted of TiAl matrix dispersed with the Ti2AlC fine particles of 1-5μm. The micro-hardness and yield stress of this material were, respectively, 4.6 GPa and 1.1 GPa which were much higher than those of Ti-46Al. The wear rate of this composite was approximately 80% of pure tungsten and the constanct to sliding rates.View full abstractDownload PDF (3461K) -
Makoto Nakanishi, Masaki Yoshino, Tatsuo Fujii, Jun Takada, Minoru Fuk ...2000 Volume 47 Issue 8 Pages 927-930
Published: August 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNi-Zn ferrite/SiC sintered composite was prepared as electromagnetic wave absorber through pre-ceramics method and subsequent annealing at 1273 K. Amorphous SiC particles dispersed uniformly in Ni-Zn ferrite matrix and the density of the composites decreased with increasing the amount of SiC particles. The absorption characteristics of the sintered composite were found to depend upon the amount of SiC particles. The matching frequency of the composites shifted toward higher frequency, from about 100 MHz to 1 GHz, with increasing the amount of SiC particles.View full abstractDownload PDF (1749K)
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