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Volume 52, Issue 11
November
Displaying 1-14 of 14 articles from this issue
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Paper
Paper
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Kiyotaka Katou, Tsutomu Sonoda, Takahiko Yamada, Insu Jeon, Tadashi As ...2005 Volume 52 Issue 11 Pages 795-799
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIn the powder metallurgical process, porous aluminium compacts were prepared by using pure aluminium powders and resin particles as the raw materials. The resin powders classified at more than 250 μm, 110∼250 μm, and less than 110 μm mixed with pure-aluminium powder having average particle size of 20 μm, 10 μm, and 3 μm at the content of 56 vol.%. This mixtures were press-molded into column shape (d=11 mm, L=16∼17 mm). To form pores, resin particles in the green compacts were removed by heat-treatment at 380°C in Ar-gas flow, and then the compacts were sintered at 655°C for 2 hours in vacuum. Effects of particle size of raw materials on the densities and static compressive properties at room temperature for sintered compacts were mainly investigated. The relative densities of sintered compacts were within the range of 39%∼47% on the above-mentioned process conditions. Reduction in particle size of either aluminiun powder or resin particle resulted in higher density. The compressive strength increased with dcreasing the size of aluminium powder. When aluminium powder was 10 μm and 3 μm, the compressive strength increased with decreasing size of resin particle. Especially, the sintered compacts originating in resin particle less than 110 μm had much higher strength than the others regardless of size for aluminium powder.View full abstractDownload PDF (1566K) -
Eiji Yuasa, Hiroaki Sagawa, Yoshinari Oki2005 Volume 52 Issue 11 Pages 800-804
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSAtomized aluminum powder was mixed to magnesium alloy (AZ31) machined chips to realize the final composition of Mg-12, 40 and 61.5 mol% Al. Then the powder mixtures were mechanically alloyed (MA) for 54 ks. For the surface improvements of the magnesium alloy, the obtained MA powders were stacked on magnesium alloy (AZ31B) rod as the substratum, and they were bonded by hot-compressive deformation at various temperatures. After the bonding of Mg-12 mol% Al MA powder to AZ31B substratum at 673 K over, Mg17Al12 phase precipitates from super-saturated α-Mg in the bonded alloy layer. The structure of the bonded Mg-40 mol% Al MA alloy layer changes from Mg17Al12 single phase to Mg17Al12 and Mg3Al2 double phases. In the case of Mg-61.5 mol% Al MA powder, the amorphous phase formed by MA crystallizes to Mg2Al3 and MgAl phases. The hardness in the MA alloy layer becomes to higher than as-MA powder particles after the bonding. If the MA powder bonds to AZ31 alloy substratum at high temperature by the compressive deformation, the gradient of Mg and Al concentrations forms in the bonding interface by diffusion phenomenon with low activation energy.View full abstractDownload PDF (908K) -
Dense Nano-structured and Preferentially-oriented Anatase Synthesized by Pulsed High Current HeatingYukio Makino, Takanori Mori, Hisayoshi Eguchi, Takashi Yoshioka, Hiden ...2005 Volume 52 Issue 11 Pages 805-811
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSDense nano-structured bulk anatase was synthesized with pulsed high current heating (PHC) method. Nano-powder anatase compact was successfully consolidated up to 90%TD (TD; theoretical density) with preferential orientation and no transformation to rutile, with suppressing the grain growth below about 300 nm. Nearly full densification over 95%TD was attained in the condition of coexisting both anatase and rutile phases. Remarkable preferential orientation was observed in the anatase consolidated at the temperature ranging from 700°C to 850°C. The preferential orientation depended on the angle (z) of crystallographic plane of anatase to the direction of current (and pressure). Degree of the orientation linearly increased with the increase of pressure and the angle in ranging from 45° to 90°, resulting in the appearance of strong preferential orientation in the (004) and (105) XRD peaks. While preferential orientation was not found in the crystallographic planes of anatase observed at the angle z less than 45°.View full abstractDownload PDF (1082K)
Special Issue: Functionally Graded Materials
Summarization
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Takashi Goto2005 Volume 52 Issue 11 Pages 814
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSDownload PDF (114K)
Review
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Akinaga Kumakawa2005 Volume 52 Issue 11 Pages 815-819
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThe original concept of Functionally Graded Materials (FGMs) for thermal stress relaxation was proposed in Japan in 1984, and research activities on FGMs have expanded throughout the world in the last two decades. Much effort covering the design, synthesis, testing & evaluation and integration of FGMs as well as their application have been done. Two kinds of small thrusters for a reusable rocket plane were made and demonstrated their superiority. Research activities on FGMs in Japan have stimulated those of other counties and some components of rocket engines made of FGMs were recently fabricated and tested. Subjects for realizing FGMs in practical use are finally discussed.View full abstractDownload PDF (935K) -
Masayuki Niino, Katsuto Kisara, Masahiro Mori, Kazuyuki Suzuki, Seiich ...2005 Volume 52 Issue 11 Pages 820-825
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSTo raise the economics of Space Solar Power System (SSPS) that is to supply large energy from space to the ground and is expected for practical application in 20-30 years, weight reduction and improvement of the lifespan need to be sought to reduce transportation costs and life cycle costs. In relation to the SSPS research that has been conducted by JAXA, present report suggests a new vision for material development applying the Japan-developed FGMs concept and proposes some concepts of innovative materials in which the advantages of FGMs are fully utilized.View full abstractDownload PDF (1553K)
Paper
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Go Yamamoto, Yoshinori Sato, Toru Takahashi, Mamoru Omori, Akira Okubo ...2005 Volume 52 Issue 11 Pages 826-830
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIn our previous report, we have successfully prepared single-walled carbon nanotubes (SWCNTs) solids without any additives employing a spark plasma sintering (SPS) method. The effects of preparation conditions on the mechanical properties of the SWCNT solids have been investigated using a small punch (SP) testing method. It was shown from the SP test results that an indentation was formed on the specimen by the spherical puncher used for the load application, and the main fracture initiated and propagated in a cone-shaped region from the edge of the indentation. Therefore, no measurement of the fracture strength has been made on SWCNT solids prepared by the SPS method to date. In this investigation, the three-point bending tests were employed to examine the mechanical properties such as Young's modulus and fracture strength of the SWCNT solids. The compaction pressure used in the SPS method was 120 MPa, and the temperatures were 1000, 1200 and 1400°C, respectively. The mechanical properties have been found to depend on the processing temperature. The binder-free SWCNT solids had Young's modulus and fracture strength of 8.3 GPa and 52.4 MPa, respectively prepared by SPS technique.View full abstractDownload PDF (1081K) -
Go Yamamoto, Yoshinori Sato, Makoto Ohtsubo, Toru Takahashi, Mamoru Om ...2005 Volume 52 Issue 11 Pages 831-835
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThe starting materials used in this study were single-walled carbon nanotubes (SWCNTs) synthesized by an arc discharge method and multi-walled carbon nanotubes (MWCNTs) prepared by a CVD method (NanoLab, Inc.). A spark plasma sintering (SPS) method was utilized to solidify SWCNTs and MWCNTs. To facilitate the solidification, phenol resin (50 mass%) was added to the purified SWCNTs and MWCNTs. The compaction pressures used in the SPS method were 40 MPa for SWCNTs and 80 MPa for MWCNTs, and the temperature was 1000°C. The mechanical properties of the solidified SWCNTs and MWCNTs were examined using a small punch (SP) testing method. The SWCNT solids showed significant non-linear deformation response, producing quasi-ductile fracture behavior, and Young's modulus and work of fracture were 1.6 GPa and 15.8 N · mm, respectively. In contrast, the MWCNT solids showed brittle fracture behavior, and Young's modulus and work of fracture were 1.5 GPa and 4.4 N · mm, respectively. TEM observations revealed that the fracture of the SWCNT solids was characterized by pull out of SWCNT bundles, and that of the MWCNT solids was characterized by “bamboo-like” failure of MWCNTs.View full abstractDownload PDF (1306K) -
Kazuhisa Sato, Toshiyuki Hashida, Keiji Yashiro, Hiroo Yugami, Tatsuya ...2005 Volume 52 Issue 11 Pages 836-839
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSA simple fracture testing method, which was combined with acoustic-emission (AE) monitoring was developed in order to investigate the mechanical performance of solid oxide fuel cells (SOFCs) under simulated environments. The fracture testing method was applied to ceria electrolyte-supported single cells. The fracture damage process was shown to involve vertical cracking and delamination in the cathode, and vertical cracking in the electrolyte, and the fracture damages were most likely due to the chemical expansion induced stresses. It was demonstrated that the AE method enabled us to detect the above-mentioned fracture process and determine the condition for the onset of the fracture damage in the single cell.View full abstractDownload PDF (1112K) -
Kazuhisa Sato, Toshiyuki Hashida, Ken Suzuki, Hiroo Yugami, Tatsuya Ka ...2005 Volume 52 Issue 11 Pages 840-844
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThe influences of the sintering additive content of Y2O3 on elastic modulus of ceria ceramics were investigated by small punch (SP) testing method and molecular dynamics (MD) method. Y2O3 doped ceria powders with a composition of (CeO2)1-x(YO1.5)x (x=0, 0.10, 0.15, 0.20, 0.30, 0.40) were prepared by a co-precipitation method. The powders were compacted by die pressing (50 MPa) followed by cold isostatic pressing (120 MPa), and sintered at 1500°C in air for 5 h. The elastic modulus was decreased significantly with increasing additive contents of the Y2O3 oxides. Especially, it tended to exhibit a minimum value at 10∼20 mol%. However, ionic conductivity increased with increasing additive content of the Y2O3 oxides, exhibited a maximum value at 15 mol%. Calculation model and interatomic potential were shown to be useful to evaluate the elastic property.View full abstractDownload PDF (1058K) -
Teiichi Kimura, Ryan Banal, Takashi Goto2005 Volume 52 Issue 11 Pages 845-850
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSYttria films were prepared by laser CVD using an Y(dpm)3 precursor. When the laser power (PL) was less than 100 W, deposition rates were small around 10 μm/h comparable to those by conventional thermal CVD. At PL>160 W, deposition rates increased drastically to more than 200 μm/h. The highest deposition rate in this study was 270 μm/h, which is 100 times higher than that reported in literatures. Film morphologies changed from a dense isotropic structure to a (440) oriented columnar structure with increasing substrate pre-heating temperature. By changing PL during deposition, a structure-graded yttria film was obtained. Moreover, Periodically structure-graded yttria films were also prepared by periodical changing of PL.View full abstractDownload PDF (1508K) -
Takashi Goto, Hidetoshi Miyazaki, Hiroshi Masumoto2005 Volume 52 Issue 11 Pages 851-856
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSSilicon suboxide (SiOx) could be a potential material for radiative cooling due to appropriate infra-red absorption at wave-length (λ) between 8 and 13 μm. In this study, SiOx films ranging from x=0.98 to 1.7 were prepared by magnetron sputtering using a SiO sintered body target. An SiO0.98 single layer film had a relatively sharp absorption peak at λ=10 μm. The obtained SiO0.98 film showed amorphous and a black-brown color. An optical band gap (Eg) of the SiO0.98 film was 3.6 eV, and the SiOx (x>1.4) film was transparent in the UV-visible range with a wide optical band gap (>4 eV). A functionally graded SiOx layers showed broader absorption from λ=8 to 13 μm, promising for radiative cooling.View full abstractDownload PDF (743K) -
Jun Chiba, Hiroki Tamura, Shinichi Kikkawa, Yoshiaki Deyama, Kuniaki S ...2005 Volume 52 Issue 11 Pages 857-860
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIntercalation on hydrotalcite has been expected to apply for the drug delivery system. Osteoblast was cultivated in the culture solution dispersed hydrotalcite-ATP intercalation compound. The cells expanded in volume after 3 h cultivation. Hydrotalcite was not toxic and a part of it can be incorporated in the osteoblast. Fine size of hydrotalcite crystals is necessary for its endocytosis. Their fine crystals of < 50 nm were obtained in the precipitation from aqueous solution in strong magnetic field of 5 T applied vertically to the gravity. The intercalated drug should be concentrated at the diseased part. Magnetic hydrotalcite can be transferred by an external magnetic field to the part. Hydrotalcite was firmly bonded on the surface of magnetite particles by firing its coated complex at 400°C in nitrogen atmosphere.View full abstractDownload PDF (1540K) -
Takamasa Onoki, Masa-aki Tanaka, Toshiyuki Hashida2005 Volume 52 Issue 11 Pages 861-864
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSSolidification of hydroxyapatite (HA) and its coating on titanium (Ti) rod was achieved simultaneously by utilizing a hydrothermal hot-pressing (HHP) method at a low temperature of 135°C. A mixture of calcium hydrogen phosphate dehydrate (DCPD) and calcium hydroxide was used as a starting powder material for HA coating. Ti rod was treated with the alkali solution before HHP treatment. The powder mixture and the Ti rod were placed into a double layered capsule. The capsule was put into a batch type autoclave for hydrothermal treatment.
Pull-out tests were conducted to obtain an estimate of the interfacial property or the HA/Ti interface. The shear fracture strength obtained from the pull-out tests was approximately 4.0-5.5 MPa. In post-test observations after fracture tests, HA ceramics remained on Ti rod. It could be demonstrated that the fracture occurred into the HA ceramics, not into the HA/Ti interface. This observation suggests that the fracture property of the HA/Ti interface was close to or higher than that of the HA ceramics only.View full abstractDownload PDF (738K)
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