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Volume 50, Issue 5
Displaying 1-14 of 14 articles from this issue
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Yoshinari Kaieda2003 Volume 50 Issue 5 Pages 333-340
Published: May 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSTiNi intermetallic compound, which is the most important shape memory material, is industrially manufactured with the combustion synthesis process by using the heat of formation of Ti and Ni starting elemental powders. One kind of specimen with Ni-rich composition from stoichiometric value (Ti:Ni=1:1), 51.6 atomic%Ni, which shows the superelasticity at room temperature, is produced because the superelastic material is much in demand. In the present paper, the influence of the heat treatment conditions on the transformation temperatures of the specimen is mainly investigated from the viewpoint of practical use. The tendency of the transformation temperatures are divided into two regions, those are in the heat treatment temperatures under 800K and above 800K. The transformation temperatures decrease with the increase in heat treatment temperature up to 800K. In this case, it is not so dependent on the heat treatment time. The heat treatment temperature above 800K becomes a transition region where the transformation temperatures show a tendency to increase. In this case, the transformation temperatures show the tendency to increase with the heat treatment time. The transformation temperatures increase because Ti3Ni4 precipitates and Ni content in the matrix decreases in the heat treatment temperature region above 800K.View full abstractDownload PDF (2491K) -
Yasuharu Miyauchi, Tamotsu Ishiyama2003 Volume 50 Issue 5 Pages 341-346
Published: May 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe present paper deals with of the investigation of piezoelectric properties of xNaNbO3+(1-x)MeNb2O6 (Me=Ba, Sr, Ca) ceramics. The interesting behavior of the electromechanical coupling factor (kr) for composition was found. From the XRD analysis the structure at x=0.33 appeared single phase of Me2NaNb5O15, at x=0.4-0.9 it was observed to be double phases of Me2NaNb5O15 and NaNbO3, and at x≥0.95 it had single phase of NaNbO3. Hysteresis measurements showed that the phase of NaNbO3 was anti-ferroelectric at x=0.4-0.8 and ferroelectric at x≥0.90. 0.05NaNbO3+0.95(Ba0.4Sr0.4Ca0.2)Nb2O6 ceramics had εr=125 and θmax=86.7° (θmax is maximum phase angle between resonance point and antiresonance point). It was found that xNaNbO3+(1-x)(Ba0.4Sr0.4Ca0.2)Nb2O6 ceramics had possibility of the application for resonators.View full abstractDownload PDF (2188K) -
Masayoshi Horibe, Naoichi Yamamoto2003 Volume 50 Issue 5 Pages 347-353
Published: May 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe formation diagram of Bi-Fe-OH- system in the aqueous solution was studied using hydrothermal or "wet" method. Three kinds of bismuth-ferricoxides, Bi25FeO40 (Fe-sillenite), BiFeO3 and Bi2Fe4O9 were obtained depending on their reaction conditions. The stoichiometric Bi25FeO40 has two kinds of particle shapes, the cubic and the tetrahedral, depend on its reaction conditions, although formation mechanism of the two kinds of particle shapes is not clear yet. The precipitate obtained below 100°C from starting materials with higher ratio of Fe/Bi than 3.8mole% showed interesting feature as follows. The precipitate gave only analogous XRD spectrum of Bi25FeO40, but observations by SEM and Mossbauer effect showed the surface of the precipitate was coated homogenously with fine particles of amorphous Fe oxide. The Bi25FeO40 coated with amorphous fine particles of Fe oxide (hereafter described as pseudo Fe-sillenite) reacted with CO2 gas or CO32- in aqueous solution and easily converted to Bi2O2(CO3) at the mild reaction conditions. The gradual conversion took place even at the room temperature during the prolonged period. The phenomena may be applied to the immobilization of the CO2 in the air and in the aqueous solution.View full abstractDownload PDF (6478K) -
Masakuni Ozawa, Hisayuki Hibi, Suguru Suzuki2003 Volume 50 Issue 5 Pages 354-358
Published: May 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWe examined the preparation condition of ceria (CeO2) powders through homogeneous precipitation at 90°C and the effect of its morphology on sintering. The synthesized powder had different morphology depending on the condition in homogeneous precipitation method using hexamethylenetetramine (HMT). The coalesced spherulic powder with ca. 0.1μm size was obtained under the condition of Ce concentration of 0.05M with 0.3-0.5 M HMT. In the case of 0.1M Ce solution, the rod-like particles and fibers of CeO2 were obtained. For the synthesis of dense cerium oxide ceramics by pressureless sintering, the starting powders with spherulic shape were useful. The relative density of ceramics was 93% after sintering at 1400 °C for 1h in air. At 1500°C, the oxygen release in CeO2 was assumed. A sintering temperature of 1400°C can be applied for forming CeO2 ceramic by using the spherulic powders through the homogeneous precipitation at the concentration of 0.05 M Ce and 0.3-0.5M HMT.View full abstractDownload PDF (4271K) -
Kaduichi Kitagawa, Takeshi Toyoda, Kazuo Kitagawa, Takashi Yamamoto2003 Volume 50 Issue 5 Pages 359-364
Published: May 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical properties of PZT ceramics with small amount of Mn and Nb were investigated. The addition of 0.01mol% Mn and 0.02mol% Nb to PZT improved and stabilized their piezoelectric properties. The four point bending strengths of PZT with 0.01mol% Mn and 0.02mol% Nb addition were 85MPa and 63MPa, respectively. And the values of Weibull modulus were 9.1 and 7.8. As for the static mechanical properties, there is no large difference between 2 specimens.
But compared with 0.02mol% Nb, the addition of 0.01mol% Mn to PZT doubled the vickers hardness. As to the 0.01mol% Mn added-PZT, the crack length measured by a micro vickers diamond indentor was anisotropic, and the internal stress measured with the microindetation tecnique increased.View full abstractDownload PDF (2411K) -
[in Japanese]2003 Volume 50 Issue 5 Pages 366
Published: May 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (107K) -
Yuji Hiroki, Masaru Yoshinaka, Ken Hirota, Osamu Yamaguchi2003 Volume 50 Issue 5 Pages 367-371
Published: May 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe synthesis of single-phase CrB was succeeded by self-propagating high-temperature synthesis (SHS) in an argon atmosphere from an elemental mixed powders (Cr: ≤ 2μm and B:0.2μm) preheated at 300° to 600°C in a reduced pressure. The dense monolithic CrB ceramics ( ≥ 98% of theoretical) were obtained by hot-isostatically pressing CrB powder for 2h under 196 MPa at 1200°to 1500°C. They revealed excellent mechanical properties: Vicker's hardness Hv-23.3 GPa, bending strength σb-690 MPa and fracture toughness KIC- 6.6MPa⋅m1/2.View full abstractDownload PDF (2076K) -
Hiroyuki Motono, Masaru Yoshinaka, Ken Hirota, Osamu Yamaguchi2003 Volume 50 Issue 5 Pages 372-376
Published: May 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSChromium carbide (Cr7C3) ceramics have been synthesized and sintered simultaneously from a mixture of Cr (-2μmφ) and C (-5μmφ) powders by spark plasma sintering method. Dense ceramics were obtained and are composed of single-phase Cr7C3 with a small amount of Cr2O3, which originates from a trace amount of oxygen adsorbed on as-received starting powders. Cr7C3 ceramics sintered at 1350°C have 99.5% relative density and fine structure with 2.5μm grain size. They exhibit excellent mechanical properties: bending strength σb 540 MPa, Vicker's hardness Hv 16.9 GPa, and fracture toughness KIC 5.3 MPa⋅m1/2.View full abstractDownload PDF (4021K) -
Satoshi Kinoshita, Masaki Kobayashi, Yasuro Taniguchi, Koji Hayashi2003 Volume 50 Issue 5 Pages 377-384
Published: May 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWe have already developed a new WC-Co base cemented carbides with highly oriented plate-like triangular prismatic WC grains by using W+C+Co base mixed powder instead of usual WC+Co base mixed powder, and then proposed the mechanism for the generation of such WC grains.
In this report, the results on the effects of the starting-powder size and ball-milling time on the orientation degree of plate-like WC grains were mainly described. The orientation degree of plate-like WC grains became larger in the cases of coarser W and finer Co powders, and longer ball-milling of W, C and Co. These results could be explained, based on our previously proposed mechanism for the generation of highly oriented plate-like WC grains.View full abstractDownload PDF (8023K) -
Nobuo Hojo, Satoshi Kinoshita, Yasuro Taniguchi, Koji Hayashi2003 Volume 50 Issue 5 Pages 385-395
Published: May 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe open pore generation on the surface of Ti(C, N) base cermets by sintering was investigated as a function of the compositional and processing factors, and then its mechanism was considered. The following were obtained. (1) Phenomena: The generation occurred, when the atmosphere in the temperature-keeping stage during sintering was vacuum (7 Pa), irrespective of the kind of atmospheres (vacuum and nitrogen of 0.13 kPa) in the temperature-raising and cooling stages, and vice versa. The generation became more frequent at higher N/(C+N) atomic ratio of Ti(C, N) powder and/or at higher carbon content of cermet as far as the microstructure was without free carbon phase and (Ti, Mo)3Ni compound, i.e., θ-phase. The origin of open pore was a dent on the surface of the green compact. (2) Mechanism: The growth of open pores occurs by the net-diffusion, i.e., transport of Ti and Mo atoms mainly from the side and bottom of the dent to the edge. This diffusion is caused by the N content gradient formed due to the denitriding, which occurs more rapidly from the compact surface having lager ratio of surface-area/volume. The method for suppressing the open pore generation was also considered.View full abstractDownload PDF (12166K) -
Kusuhiko Sakagami, Shinichi Kouno, Tsutomu Yamamoto2003 Volume 50 Issue 5 Pages 396-399
Published: May 15, 2003
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSAs micrograin carbide alloys with average WC grain size below 1μm have been widely used for cutting tools and wear resistant tools, it is very important to acquire knowledge on bending fatigue characteristics of the alloys in order to estimate and improve a tool life. Therefore, in this study, the characteristics of three points bending fatigue in micrograin WC-6-15 mass%Co-0.4-1.2mass%Cr3C2 alloys with grain size of 0.8μm which were treated by HIP or Sinter-HIP process was mainly investigated in relation to a fracture origin.
The results obtained were as follows: (1) As regarding the effects of Co content on bending fatigue of the HIP-treated alloys, the fatigue life was almost same in 6-12mass%Co alloys, but it decreased in 15 mass% Co alloy. (2) The fracture origin observed on the fractured surface after bending fatigue test in the HIP-treated alloys was Co pool with the step-shaped form in all cases. (3) There was some correlation between the size of Co pool origin and the fatigue life under same applied stress. In the Sinter-HIP treated alloys, the fatigue life was considerably improved
due to the decrease of the size of Co pool defect in the microstructure.View full abstractDownload PDF (5252K) -
Kusuhiko Sakagami, Tsutomu Yamamoto2003 Volume 50 Issue 5 Pages 400-403
Published: May 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSAs WC-Co based alloys have high hardness, compressive strength and Young's modulus and excellent deformation resistance, they have been widely applied for wear and impact resistance tools. Therefore, it becomes very important to acquire knowledge on compressive fatigue characteristics of these alloys. In this study, the effects of Co content, WC grain size, HIP and coating treatment on compressive fatigue life of medium or coarse-grain WC-7-20mass% Co alloys and micrograin WC-6-l5mass%Co-0.4-1.2mass%Cr3C2 alloys were mainly investigated and discussed with the variation of coercive force during fatigue process.
The results obtained were as follows: (1) The fatigue life increased with decreasing Co content in the medium and coarse-grain alloys, but it was almost same with no relation to Co content in the micrograin alloys. The fatigue life showed an upward tendency with decreasing WC grain size. (2) The effect of HIP treatment on fatigue life was not observed at all. The fatigue life of PVD-coated alloy did not change and that of CVD-coated alloy remarkably decreased, comparing with that of non-coated alloy. (3) The coercive force of medium-grain WC-12mass%Co alloy increased with increasing applied maximum stress and repeated cycle, and it became much larger in the repeated compressive fatigue test than static compressive test. This increase of the coercive force was considered to be equivalent to the degree of toughness deterioration due to fatigue hardening in Co phase during fatigue process.View full abstractDownload PDF (334K) -
Shuichi Imasato, Shigeya Sakaguchi, Taikou Okada, Yasunori Hayashi2003 Volume 50 Issue 5 Pages 404-410
Published: May 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn the case of applying cemented carbides to mechanical seal rings or baring parts in pump, the cemented carbides sometimes corrode faster than the expected corrosion rate from the individual corrosion test. It is considered that the galvanic corrosion occurs between cemented carbides and steels as assembled parts.
In this reports, the coupled cemented carbides (WC-Co, WC-Ni-Cr3C2, WC-TiC-TaC) and steels (carbon steel and stainless steels) were immersed in both 3%NaCl and 3%NaCl+0.1NH2SO4 aqueous solutions. And their electrochemical corrosive behavior were evaluated by measuring the change of electrode potentials and the current density.
As the results, in the case of WC-Co coupled with stainless steels, WC-Co acted as anode being dissolved in either solution. On the other hand, the potential differences were small and the current hardly flowed between WC-Ni-Cr3C2 or WC-TiC-TaC and stainless steels. It was considered that the galvanic corrosion scarcely occurred in these cases.View full abstractDownload PDF (508K) -
Nobuyuki Mori, Akihiko Ikegaya2003 Volume 50 Issue 5 Pages 411-417
Published: May 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSTiebar-cut punch is a cutting tool which is attached to a mold for cutting lead frame and resin. For this tool, high wear resistant hard materials(especially cemented carbide)are widely used. It is generally known that the life-time of tiebar-cut punch depends on the wear resistance to resin, on the other hand, high toughness is required. However it is difficult for cemented carbide to increase both properties because there is a trade-off relation between wear resistance and transverse rupture strength. To overcome this problem and to improve the property of cemented carbide, we developed a new functionally graded material of cemented carbide (FGM) which coated high wear resistant cemented carbide on tough cemented carbide with pulse current pressure sintering system. We applied this FGM to tiebar-cut punch and evaluated it by cutting test. Compared with a conventional tiebar-cut punch, the FGM tiebar-cut punch revealed higher wear resistance.View full abstractDownload PDF (5072K)
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