巻号一覧
71 巻, 6 号
選択された号の論文の9件中1～9を表示しています
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小野木 哲也, 小山 佳一, 渡辺 和雄2007 年 71 巻 6 号 p. 489-493
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーMagnetization measurements of polycrystalline MnBi were carried out in magnetic fields up to 10 T and in the temperature range from 300 to 773 K, in order to clarify the magnetic properties under high magnetic fields and high temperature. The magnetic phase transition temperature (Tc) at a zero magnetic field is 633 K, which almost linearly increases by 2.3 KT-1 with increasing fields up to 10 T. Furthermore, a metamagnetic transition was observed just above Tc, indicating that the phase transition is first order. The magnetic entropy change is estimated to be 14 J kg-1 K-1 for 2 T at Tc using Clausius-Clapayron's equation, which is almost constant for magnetic fields up to 10 T.
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駒井 正雄, 吉岡 興2007 年 71 巻 6 号 p. 494-501
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーMagnesium alloy has poor formability at room temperature. It is necessary to raise its temperature to allow it to be press-formed. Thus, magnesium alloy sheets are formed at about 523 K using lubricants such as press-oil or MoS2. However, even under these conditions the formability of magnesium alloy sheet is insufficient. In a special case, the magnesium alloy sheet is press-formed by placing a PTFE-sheet between the magnesium alloy sheet and the metal mold to get better formability. However, preparing a magnesium alloy sheet for press-forming involves complicated manual work and takes time, and PTFE-sheet is very expensive. Therefore, it is very important to develop a more suitable lubricant for press-forming of magnesium alloy sheet.
The aim of this study was to develop a special surface treatment giving excellent lubricity to magnesium alloy sheet. To achieve this aim, a thin organic resin-coated magnesium alloy sheet with good press-formability even in the absence of oil has been developed. This newly developed magnesium alloy sheet given this highly lubricating pre-coat has better formability than conventional magnesium alloy sheets coated with lubricants such as press-oil, MoS2 and PTFE.
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小山 元道, 村上 雅人, 小川 一行, 菊池 武丕児, 澤口 孝宏2007 年 71 巻 6 号 p. 502-507
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーWe investigated the shape memory effect and ductility of Fe-30Mn-(6-x)Si-xAl (x=0, 1, 2 and 3, mass-%) alloys. The alloy for x=0 is known as a shape memory alloy, which shows a good shape memory effect but poor ductility. The alloys for x=2 and 3 are known as TWIP (Twinning Induced Plasticity) steels, which show a high ductility but the shape memory effect has not been reported in these alloys. In the present study, it was found that the shape memory effect is preserved for x=0 and 1, but drastically disappears when x exceeds 2. On the other hand, the ductility almost linearly increases with increasing amount of Al. As a consequence, the best combination of the shape memory effect and ductility was found in the alloy for x=1.
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長谷 泉2007 年 71 巻 6 号 p. 508-510
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーThe electronic structures of anti-perovskite-type intermetallic compound Ni3AlXy(X=B, C, H; 0<y<1) have been calculated using coherent-potential approximation (CPA) within the local-density approximation (LDA). Ferromagnetic moment in Ni3Al rapidly decreases with increasing y for every dopant X, even though the lattice is more expanded than non-doped Ni3Al.
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王 栄光, 木戸 光夫2007 年 71 巻 6 号 p. 511-516
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーAnodic polarization testing of SUS304 stainless steel with crevice was carried out in an aqueous solution of 3.5 mass%NaCl at a potential increasing at a constant rate of 0.33 mV/s. When the current density reached 10, 12 or 50 A/m2, the potential was kept at a constant value for a constant period. When an ultrasonic wave (UW) was applied to the specimen during the holding period of the potential, the current density on the specimen surface was compared to that without the application of UW. Crevice corrosion and pitting corrosion were found on the specimen after the polarization test. The corrosion of specimen was largely decreased when UW was applied to the specimen. The current density almost synchronized with the cyclic application and stop of UW. The suppression of crevice corrosion and pitting corrosion in the specimen is attributed to the decrease in the enrichment of hydrogen ions and chloride ions in the crevice or pits by the stirring effect of UW.
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野崎 潔, 伊丹 俊夫2007 年 71 巻 6 号 p. 517-521
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーThe dc electrical conductivity, σdc, of the liquid (AgI)x-(Ag2O)y-(B2O3)1-(x+y)(x=0.7~0.9; y=0.05~0.2) was measured using an ac impedance method, particularly concerned with the precipitation mechanism of the α-AgI precipitated glass. The twin-roller apparatus was applied to obtain the α-AgI precipitated glass. The σdc on cooling process exhibited two inflection points on its temperature dependence curve. This implies the existence of the two liquid phase separation, which was confirmed rigorously by measuring the dc electrical conductivity on cooling process with the use of a specially designed conductivity cell. In addition, the rapidly quenched samples were analyzed by the X-ray diffractometry (XRD) and the scanning electron microscopy (SEM). The α-AgI crystallites were precipitated in the glass matrix in the case of a higher holding temperature, whereas the β-AgI precipitated glass was obtained in the case of a lower holding temperature. These results indicate the role of two liquid phase separation on the precipitation process of nano α-AgI crystallites in the glass matrix.
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鷲尾 宏太, 棟方 泰裕, 大貫 惣明, 須田 孝徳, 伊藤 秀明, 荒島 裕信, 久保 和也, 兜森 俊樹2007 年 71 巻 6 号 p. 522-527
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーThe cyclic degradation of TiCrV hydrogen storage alloy has been studied by using SEM and TEM. Microstructural analysis indicated that the accumulation of lattice defects such as dislocations and strain field occurred due to volume expansion and shrinkage during cycles, led to a loss of the effective storage capacity. Annealing with minute particles in order to suppress the development of lattice defects during cycles resulted in increase in plateau width during hydrogenation but nothing improved during de-hydrogenation. This is probably due to beta-hydrides formed during hydrogenation, which is stable with lattice defects and strain field. Fine particles less than several hundred nano-meter in size could have a good degradation resistance due to less accumulation of lattice defects and during cycles.
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安田 敬司, 福本 倫久, 佐藤 芳幸, 原 基2007 年 71 巻 6 号 p. 528-533
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーSi diffusion layers on SUS430 and SUS304 stainless steel surfaces were formed by the pack-cementation method. Thickness of the Si diffusion layer became nearly constant value after 20 ks of the treatment time. The thickness of the diffusion layer for SUS430 steel was about 200 μm, while that for SUS304 steel was about 100 μm. For both the steels, the Si diffusion layer consisted of α-phase, and the Si concentration in the surface region was about 6 mass%. High temperature corrosion tests of these samples were carried out under a coating of molten NaCl-KCl-Na2SO4 in an 18.4 vol%O2-20 vol%H2O-1348 vol. ppm HCl-N2 atmosphere at 1173 K. As a result, it was found that for both the steels the oxidation mass gains for the pack-cementation treated samples were far lower than those for the no treated samples. Corresponding to the results, the thickness of a scale formed on the treated samples was thinner than that on the no treated samples. In the treated samples, further, the formation of SiO2 layer was observed in the interior side of the scale.
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菊地 英樹, 高橋 まさえ, 川添 良幸2007 年 71 巻 6 号 p. 534-538
発行日: 2007年
公開日: 2007/06/01
ジャーナル フリーNine isomers of Ge6, Ge62-, Ge64-, and Ge66- have been searched for by the MP2/6-31+G(d), B3LYP/6-311+G(d), and B3LYP/LANL2DZ electronic structure calculations. Totally 16 isomers are found: six Ge6, three Ge62-, five Ge64-, and two Ge66-. We discovered that the predicted stable shapes of Ge62-, Ge64-, and Ge66- are octahedral, pentagonal pyramidal, and hexagonal, respectively, which agrees well with the Wade rule. It is concluded that the electron counting rule governs the structural preference in Ge anion clusters as well as in Si anion clusters.
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