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Volume 56, Issue 7
July
Displaying 1-9 of 9 articles from this issue
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Paper
Paper
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Agus Sukarto Wismogroho, Heru Irawanto, Wahyu Bambang Widayatno, Alfia ...2009 Volume 56 Issue 7 Pages 427-432
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSIron aluminide coating of structural steel by mechanical alloying (MA) followed by annealing was examined. As starting materials, stabilized Al powders containing fat, fat-free Al powders and pure Fe powders were used. Stabilized Al-25 at% Fe powder deposited on the steel substrate from the early stage of MA and formed the coating layer. The mixing and the refinement of Al rich and Fe rich phases in the coating layer were promoted by the suppression of cold welding due to the presence of fat in the coating layer, resulting in the formation of coating layer with fine and homogeneous microstructure. In annealing for 7.2 ks after MA, Fe2Al5 was formed at 673 K, Fe2Al5 and FeAl were formed at 873 K and Fe2Al5, FeAl and Fe3Al were formed at1073 K, respectively. Thus, the formation temperature of FeAl was lower than that of the conventional hot dip coating or pack cementation. This is because interdiffusion between the steel substrate and the coating layer is enhanced by the refinement of microstructure of coating layer due to MA. By coupling annealing to MA, it is possible to improve embrittlement of iron aluminide coating layer.View full abstractDownload PDF (1334K) -
Mitsuyoshi Nagano, Shinzo Mitomi2009 Volume 56 Issue 7 Pages 433-437
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSIn this study, with a view to improve the mechanical properties, the influence of the change in the micro-structure, crystal phase and mechanical properties were evaluated, by changing the amount of one of the sintering additives, Al2O3 and the HIP sintering conditions, from the viewpoint of the micro-structure consisting of α-Si3N4, β-Si3N4 and glassy grain boundary phase.
The experimental results showed that 1) the combination of the sintering additives makes a various sorts of crystals and glassy phase formed which promotes the densification, 2) the addition of Al2O3 was effective in the densification, further, 3) as for the HIP sintering condition, N2 gas pressure higher than 60MPa greatly influences the transformation from α-Si3N4 to β-Si3N4 with densification.View full abstractDownload PDF (806K)
Rapid Communication
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Kiyoshi Mizuuchi, Kanryu Inoue, Yasuyuki Agari, Yoshiaki Morisada, Mas ...2009 Volume 56 Issue 7 Pages 438-443
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSDiamond-particle-dispersed-aluminum (Al) matrix composites were fabricated in continuous solid-liquid co-existent state by Spark Plasma Sintering (SPS) process from the mixture of diamond powders, pure Al powders and Al-5mass%Si alloy powders. The microstructures and thermal conductivities of the composites fabricated were examined. These composites were all well consolidated by heating at a temperature range between 798 K and 876 K for 1.56 ks during SPS process. No reaction at the interface between the diamond particle and the Al matrix was observed by scanning electron microscopy for the composites fabricated under the sintering conditions employed in the present study. The relative packing density of the diamond-Al composite fabricated was 99 % or higher in a volume fraction range of diamond between 45 % and 50 %. Thermal conductivity of the diamond-Al composite containing 50 vol.% diamond reached 552 W/mK, approximately 95 % the theoretical thermal conductivity estimated using Maxwell-Eucken's equation. The coefficient of thermal expansion of the composites fell in the upper line of Kerner model, indicating strong bonding between the diamond particle and the Al matrix in the composite.View full abstractDownload PDF (883K)
Paper
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Masayuki Ohshima, Toshimitsu Tetsui, Kazuhiro Hasezaki2009 Volume 56 Issue 7 Pages 444-448
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSThe NbSi2/Nb/γ-TiAl and NbSi2/Nb functionally graded materials (FGMs) were prepared and their tolerances tested by exposing them to temperatures from 1323 K to 1523 K under vacuum and in air. Oxygen resistivity was estimated from metallographic investigations. The FGM lifetime was estimated by using a diffusion equation that considers the disappearance of the NbSi2 and Nb interlayer. These occurred during NbSi2 oxidation and Si diffusion from NbSi2 to Nb and interdiffusion between Nb and γ-TiAl. The results were validated by diffusion equations. The results indicate that a coating used at 1323 K for 380 h requires a NbSi2+Nb coating thickness of more than 77 μm.View full abstractDownload PDF (910K)
Special Issue: Smart Carbon
Summarization
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Akinori Muto2009 Volume 56 Issue 7 Pages 450
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSDownload PDF (114K)
Review
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Masahiro Toyoda2009 Volume 56 Issue 7 Pages 451-455
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSExfoliated carbon fibers (ExCFs) were prepared by rapid heating of intercalation compounds of Pitch-basd and PAN-based carbon fibers. After exfoliation, a single fiber of pitch-based and PAN-based carbon fiber was found to be converted to a bundle of thin filaments and a scale-like fragments, respectively. The ExCFs were found that it have good despersibility. Size of these ExCFs was sub-micro meter to nano meter. Their ExCFs were examined as an electrode of electric double layer capacitor (EDLC) in H2SO4 electrolyte. The capacitance of ExCFs prepared form PAN-based carbon fibers reached 320 F/g in 1 mol/dm3 H2SO4 electrolyte, even though ExCFs had relativity small surface area of around 300 m2/g. On the other hands, the capacitance of ExCFs prepared form Pitc-based carbon fibers reached 550 F/g in 18 mol/dm3 H2SO4 electrolyte. Fabrication of composite using its ExCFs was also investigated. ExCFs were composited with Poly Methyl Methacrylate (PMMA) in-situ polymerization process, and them their mechanical properties were examined. Flexural strength and modulus of PMMA composite reinforced by ExCFs increased 166 % and 171 % comparison with bulk PMMA. In addition, it was better than that of PMMA composite reinforced by CNTs. ExCFs might be expected application to energy storage and nano composite, in stead of CNTs.View full abstractDownload PDF (1340K)
Paper
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Kenji Kamishima, Daisuke Miyata, Yuki Sato, Takashi Tokue, Koichi Kaki ...2009 Volume 56 Issue 7 Pages 456-460
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSWe have prepared pyrolytic carbon samples from triethylamine and investigated their yields and magnetic properties. Ferromagnetic samples were obtained from the pyrolysis products even at room temperature. The yield of the ferromagnetic sample was increased by setting a magnetic circuit on the pyrolysis chamber. The magnetic field seemed to affect the triethylamine vapor and then increased the yield and the magnetization. Also, the synchrotron X-ray diffraction experiments were performed for these pyrolytic carbon samples. Diffraction peaks of iron or iron oxides were not observed for the ferromagnetic samples, whereas the major diffraction peaks of the intermediate graphite-diamond (IGD) structure were observed for the ferromagnetic samples. The best magnetization sample also showed the diffraction peaks of the diamond-like-carbon structure. Therefore, the magnetic field may help to form a three-dimentional ferromagnetic structure in pyrolytic carbon.View full abstractDownload PDF (798K) -
Tatsuya Nakamura, Kenichi Hatakeyama, Mika Hirose, Satoshi Yoshiuchi2009 Volume 56 Issue 7 Pages 461-464
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSEM-wave absorbers were prepared by a smoked roof-tile process. The shape of the absorbers was in pyramidal form, where the height was adjusted in the range of 100 to 200 mm. The roof-tile process produced a carbon-coated surface layer on the pyramidal-shaped substrate, which exhibited good electrical conductivity and led to good EM-wave absorption in the microwave frequency range. It is possible to adjust the center frequency of the absorption by changing the height of the pyramid. In addition, the absorbers exhibited strong resistance to high-power incident EM-waves, and the environmental stability in ambient atmosphere is expected.View full abstractDownload PDF (823K) -
Akinori Muto, Nobuhisa Oyama2009 Volume 56 Issue 7 Pages 465-469
Published: 2009
Released on J-STAGE: July 29, 2009
JOURNAL OPEN ACCESSA composite of a porous carbon with magnetic and photocatalytic potential was prepared by mixing polyvinyl alcohol, titanium oxide and magnetite and heating at 500°C, 600°C and 900°C. Crystalline TiO2, metallic Fe, martensite and ilmenite were found in the composite. Removal of 4-Chlorophenol in the aqueous solution was conducted by a batch test with irradiation of black light. As a result the composite had potential for adsorption and decomposition of organic compounds in water.View full abstractDownload PDF (687K)
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