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76 巻, 4 号
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杉岡 奈穂子, 北田 正弘2012 年 76 巻 4 号 p. 223-228
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーThe microstructure of silk fiber dyed by a chrom-yellow dyeing technique imported into Japan in the last Edo period has been investigated. The silk fiber is dyed using lead acetate and potassium chromate solution. The color is measured with a spectrophotometer. The microstructures are observed with a scanning electron microscope and transmission electron microscope. The crystal structure is determined with an X-ray diffractometer. The composition is analyzed using an energy dispersive X-ray spectrometer. A thin film is prepared by the focused ion beam method to observe the nanostructures. The cross section is flattened by ion milling to reduce the damage of the surface. The absorption edge of silk thread dyed is 558 nm (2.2 eV). The edge agrees with that of PbCrO4. The dyestuff compounds, monoclinic and orthorhombic PbCrO4, are detected by X-ray diffraction analysis. The PbCrO4 crystals precipitate on the silk fiber surface; the length and width of the crystals are 0.2~1.2 µm and 0.05~0.4 nm, respectively. Preferential precipitation is observed in the fiber, and most of the precipitates align along a specific direction in the fiber. Fine PbCrO4 particles with a size of 4~170 nm are also observed in side of the silk fiber. The distribution of precipitates shows that there is a correlation between the precipitation phenomenon and the silk fiber structure. An outline of the microstructures of the silk fiber can be revealed by exploiting the preferential precipitation.
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成島 隆, 吉岡 隆幸, 宮崎 英機, 菅 育正, 佐藤 進, 米澤 徹2012 年 76 巻 4 号 p. 229-233
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーNon-oxidized metallic copper particles were prepared by plasma irradiation into aqueous solution of cupric sulfate in the presence of gelatin as a protective agent using home-made microwave induced plasma equipment. Then, two different steric structures of ascorbic acid, L-ascorbic acid and isoascorbic acid, were added as reducing auxiliaries. In the case of isoascorbic acid addition, metallic copper particles were obtained by plasma irradiation within about 5 minute. This result suggests that the reduction of copper ion from Cu2+ to metallic Cu can be succeeded by hydrogen radical generated by plasma in water combination with isoascorbic acid, and without toxic chemical agent such as hydrazine. Additionally, the diameter of copper particles can be controlled by the mount of CuSO4•5H2O and gelatin. These results were indicated that the plasma in liquid process has possibilities for high-speed and low environmental load process to prepare metallic copper particles.
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岡本 和孝, 高橋 智一, 佐々木 正登2012 年 76 巻 4 号 p. 234-239
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーCommercial magnesium alloys have a great potential for structural applications in automotive due to their significant weight saving. However, they have poor creep resistance at temperature over 125℃, thus making them inadequate for power train applications such as engine pistons, which are operated at temperature up to 300℃. Recently, creep resistant magnesium alloys with rare-earth elements and zinc have been developed and it is suggested that Mg-2Zn-10Y-5Gd-0.5Zr alloy is promising as a candidate material for the engine piston application. However, the detail strengthening mechanism is not clear, hence the detail microstructure of Mg-Zn-(Y, Gd) alloys was investigated in this paper. Gravity casting was performed with Mg-Zn-(Y, Gd)-Zr alloy, followed by T6 treatment. In the as cast condition, both Mg12(Y, Gd)Zn and Mg24(Y, Gd)5 were observed at the α-Mg grain boundaries, while metastable Mg24(Y, Gd)5 was dissolved into α-Mg matrix and surplus (Y, Gd) and Zn were precipitated on the Mg12(Y, Gd)Zn via solution heat treatment at 535℃. After the aging treatment for 24 hours at 225℃, fine β′ precipitates were formed in α-Mg matrix.
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朴 相漢, 江阪 久雄, 篠塚 計2012 年 76 巻 4 号 p. 240-245
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーIn order to investigate the mechanism for equalization of primary dendrite arm spacing, in-situ observation of solutal field using succinonitrile-H2O-dye system has been carried out. The brightness, which corresponds to the concentration of dye, has been characterized by an image analyzer along the centerline of interdendritic region. When the local primary dendrite spacings were uneven, the brightness along the centerline of interdendritic region was low in case of local primary dendrite arm spacing was large. After growth with rather long distance, the local primary dendrite arm spacings became even and the brightness along the centerline of interdendritic region became uniform. The solutal profile along the interdendritic region qualitatively agreed with the calculation results of newly developed model. A dendrite trunk is prone to grow toward the wide-spacing-region because the solute concentration of this side is lower than that of the other side. This leads to equal primary spacing.
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折橋 広樹, 満永 大輔, 廣井 政彦, 三井 好古, 高橋 弘紀, 渡辺 和雄, 小山 佳一2012 年 76 巻 4 号 p. 246-250
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーMeasurements of magnetization, electrical resistivity and high field X-ray powder diffraction (XRD) were carried out for polycrystalline Mn1.8Co0.2Sb in magnetic fields up to 5 T in 4.2-300 K temperature range, in order to investigate the structural properties affected by magnetic fields. In a zero field, the compound shows the first-order magnetic transition from the ferrimagnetic (FRI) to antiferromagnetic (AFM) states at Tt=145 K with decreasing temperature. By applying magnetic fields of 5 T, Tt decreased to 60 K with thermal hysteresis of 35 K. From the XRD measurements, not only the AFM phase but also the residual FRI phase was confirmed even at 10 K in cooling process under 5 T. Results obtained indicate that the residual FRI phase is kinetically arrested.
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柴山 淳史, 寺田 芳弘, 村田 純教, 森永 正彦2012 年 76 巻 4 号 p. 251-255
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーThe creep behavior of hypoeutectic Mg1−xCax(x=2.8, 8.7, and 14.8 mass%) cast alloys was investigated at 473 K under stresses between 30 and 60 MPa. The microstructure of the alloys is characterized by the discontinuously distributed primary α-Mg phase in a continuous eutectic fine lamellar structure consisting of α-Mg and C14-Mg2Ca phases. The creep curves of the alloys exhibit three stages: a normal transient creep stage, a minimum creep rate stage and finally an accelerating stage. The decrease in creep rate during the transient stage becomes pronounced and the onset of the accelerating stage is delayed with increasing calcium concentration. The stress exponent of the minimum creep rate is four for each alloy for stresses below the yield stress. The creep of the alloys is controlled by the high-temperature climb of dislocations. The effect of the eutectic fine lamellar structure on creep strength is prominent when the volume fraction is below 50%.
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千葉 真, 宮本 吾郎, 古原 忠2012 年 76 巻 4 号 p. 256-264
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーAustenite formation on the surface of pure iron during nitriding in a mixture of NH3 and H2 gases and surface hardening due to formation of iron-nitrogen martensite by subsequent quenching were investigated. In nitriding at 973 K at a partial pressure of NH3(fNH3) of 5% and 10%, austenite layer is formed at the surface while double-layered structures consisting ε-Fe2~3N and austenite are developed at fNH3 of 20%. In addition, at these high fNH3, voids are formed in ε-Fe2~3N nitride as well as austenite with high nitrogen content. At fNH3 of 5% and 10%, the growth rates of austenite accords with parabolic growth law and become faster with increasing fNH3. On the other hand, after prolonged treatment at fNH3 of 20%, thickness of the nitrided zone is less than that for 10% due to substantial formation of voids and resultant emission of nitrogen from the surface. The hardness of the nitrided zone is nearly the constant at 800HV in the specimen nitrided at fNH3 of 5% whereas softening near the surface occurs in the specimens nitrided at fNH3 of 10% and 20% due to formation of the retained austenite and the voids.
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田口 智子, 桐野 文良2012 年 76 巻 4 号 p. 265-271
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーThe surface structure of Mameitagin, which is a silver coin used in the Edo period, was investigated by spectrophotoscopy, X-ray diffraction (XRD), electron diffraction, electron dispersive X-ray analysis (EDS), X-ray fluorescence analysis (XRF), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The EDS analysis confirmed that Ansei Mameitagin is composed of only 13% silver and 87% copper. However, an absorption edge at 600 nm that is characteristic of copper was not observed in the reflectance spectra. A layer with high silver concentration was detected on the surfaces of Ansei and Bunsei Mameitagin. After polishing, the surface color of Ansei Mameitagin changed from silver to copper, and an absorption edge was detected at 600 nm. The microstructure analyzed by TEM revealed that Ansei Mameitagin has two surface layers. One is a 0.6-µm-thick Ag-rich layer that forms on the ground metal while the other is a 0.8-µm-thick oxide layer composed of Cu2O. These results suggest that the surface of Mameitagin had been chemically treated to form Ag-rich layer called Iroage.
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曲田 喜彦, 木庭 正貴, 荒木 俊雄, 南部 将一, 井上 純哉, 小関 敏彦2012 年 76 巻 4 号 p. 272-277
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーThe fracture toughness of Fe-Al intermetallic compound (IMC), FeAl and Fe2Al5, that forms as a thin layer on steel substrate was investigated. A model to evaluate the fracture toughness of a brittle thin layer on the elasto-plastic substrate was applied, and the fracture toughness was evaluated by the thickness of the IMC layer and crack interval in the IMC layer after uniaxial tensile testing. The phase and microstructure of the IMC layer were varied to investigate their effects on the fracture toughness of the IMC. Relation between layer thickness and crack interval was in good agreement with the theoretical model and the fracture toughness can be evaluated by the model. It was clarified that FeAl has higher fracture toughness than Fe2Al5, and that fine-grained Fe2Al5 has higher fracture toughness than coarse-grained Fe2Al5.
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結城 翔三, 榛葉 和晃, 手束 展規, 杉本 諭2012 年 76 巻 4 号 p. 278-282
発行日: 2012年
公開日: 2012/04/01
ジャーナル フリーAmorphous Fe-B particles were prepared by a direct reduction method. Resin composites were then prepared by mixing the amorphous Fe-B particles with several types of resins. The resin composites showed a relative permeability of μ′r=6.4-8.5 at 1 GHz, and exhibited good microwave absorption properties in the quasi-microwave band (1-3 GHz). In particular, the composites prepared with polyvinyl pyrrolidone or acrylic-type silicone resin had good microwave absorption properties with matching thicknesses of dm=2.0-3.7 mm and dm=2.0-3.9 mm, respectively.
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