巻号一覧
69 巻, 5 号
選択された号の論文の8件中1～8を表示しています
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—電子構造による理解—竹内 恒博2005 年 69 巻 5 号 p. 403-412
発行日: 2005年
公開日: 2005/10/12
ジャーナル フリーRecently thermoelectric materials have attracted a great deal of interests because of their ability in the practical use as one of the most effective energy-saving technologies. Unfortunately, however, the guiding principle to produce a high-performance thermoelectric material has not been established yet, and the most of the efforts to improve their performance have been conducted based on the empirical ideas. This unfavorable situation is not caused by a delay in the theoretical works but by the approximations employed in the theories. In order to clarify the problems in the frequently employed approximations and the resulting formulas, new ideas to calculate the thermoelectric power in the metallic samples and the obtained rigorous formula are explained in detail on the basis of the Mott's consideration. It is stressed with a help of the resulting rigorous formula that the accurate determination of the electronic structure near the Fermi level is of great importance to quantitatively evaluate the thermoelectric power, because thermoelectric power is directly calculated from the spectral conductivity σ(ε) in which the electronic structure plays a key role as the most important parameter. A simple method using the rigorous formula with the numerical data of the electronic structure is introduced to quantitatively evaluate the magnitude and the temperature dependence of the thermoelectric power. For the electronic structure determination, two different methods are introduced; the high-resolution photoemission spectroscopy and the LMTO-ASA band calculation with reliable structure parameters determined by the Rietveld analysis. In this review paper, it is clearly demonstrated by use of some practical examples that the thermoelectric power in metallic systems can be quantitatively estimated from the electronic structure near the Fermi level, and that the method newly introduced in this paper should be employed in the material-design of the high-performance thermoelectric devices.
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西條 謹二, 吉田 一雄2005 年 69 巻 5 号 p. 413-420
発行日: 2005年
公開日: 2005/10/12
ジャーナル フリーLow temperature pressure bonding tests were carried out by surface activated bonding technique. The experiments were made in a high vacuum range from 1×10-4 to 10-3 Pa by using commercially supplied aluminum (1050), copper (C1100) and mild steel (SPC3) sheets. As the surface activating treatment, RF plasma ion etching was employed. The effects of bonding pressure and RF plasma ion etching on bonding strength were investigated. It was revealed that the tightly bonding could successfully be achieved at low temperature (335 K) when the metal surfaces were sufficiently activated by RF plasma ion etching. The bonding strengths of activated specimens were increased with increase of loading pressure. In the case of aluminum, more than 495 MPa of loading, the fracture the bonding interface was not observed by peeling test but the aluminum plate was fractured itself. For the copper bonding, more than 750 MPa of loading was sufficient enough to achieve tight bonding. The bonding pressure required to achieve tight bonding was about 3-4 times of yielding strength. However the bonding could slightly achieve by loading those of pressure without surface activating treatment. The bonding strengths were increased with the increase of the amount of RF ion etching treatment. The amount of RF ion etching for surface activation could be estimated by XPS depth-profile analysis.
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藤田 毅, 中村 展之, 占部 俊明, 奥田 金晴, 細谷 佳弘2005 年 69 巻 5 号 p. 421-428
発行日: 2005年
公開日: 2005/10/12
ジャーナル フリーThe effect of cold-rolling reductions on the recrystallization texture and planar anisotropy of the r-value (Δr) in JIS S35C high carbon cold-rolled steel sheets was investigated.
When the microstructure contained coarse cementite prior to cold rolling, Δr was large regardless of the cold-rolling reduction ratio. In particular, Δr showed its maximum value at 50% cold-rolling reduction with a secondary annealing temperature of 953 K. This is attributed to strong development of {110} grains, which correspond to the recrystallization texture in the secondary annealing process and are an impediment to planar anisotropy, thereby reducing Δr. Growth of these {110} grains reached its maximum with 50% cold-rolling reduction. Formation of {110} grains originated in the high dislocation density surrounding cementite grains. The dislocation density was high around coarse cementite.
On the other hand, when the microstructure contained fine spheroidized cementite prior to cold rolling, nucleation of {110} grains was extremely slight at 30% and 70% cold-rolling reduction, resulting in minimum values of Δr. Because dislocation was homogeneously distributed over the matrix by the fine homogeneous cementite distribution, the dislocation density around cementite grains was reduced. As a result, it is thought that these dislocations did not act as nucleation sites for {110} grains.
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岡本 尚樹, 渡辺 徹2005 年 69 巻 5 号 p. 429-432
発行日: 2005年
公開日: 2005/10/12
ジャーナル フリーIn the present study, the microstructure of substitutional-deposited Pd-Cu film was investigated. Results show that the composition of Pd-Cu substitutional-deposited film was Cu-16~18 at%Pd. High resolution TEM image and XRD measurements results shows that the Pd-Cu film consist of Cu and intermetallic compound (Cu3Pd). Cu3Pd intermetallic compound was existed at as-deposited film. The morphology of initial deposited Pd-Cu film was affected by crystallographic structure of Cu substrate.
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工東 隆夫, 中森 裕子, 折茂 慎一, ぺトラ バディカ, 戸叶 一正2005 年 69 巻 5 号 p. 433-438
発行日: 2005年
公開日: 2005/10/12
ジャーナル フリーIn this paper, we report on the effects of using LiH as a starting material or and hydrogen atmosphere on the synthesis processes and electrical resistivities of LiBC compound. We observed that, in argon atmosphere, the use of LiH was effective in synthesizing the LiBC-samples of high phase purity. In this case, the obtained LiBC phase is non-stoichiometric, Li-deficient. On the other side, samples prepared from LiH as starting material, under different hydrogen partial pressures (PH2=0.01, 0.10 and 1.00 MPa), have shown a different behavior. Namely, sample prepared under PH2=1.00 MPa has significantly lower concentration of impurity phases and the c-axis lattice parameter of LiBC is as of the stoichiometric phase (without Li-deficiency) that is usually observed and reported in the literature. The other samples prepared under lower hydrogen pressure (PH2=0.01, 0.10) have an appreciable amount of impurity phases and Li-deficiency probably caused by the Li evaporation.
Electrical resistance vs. temperature was measured for two almost single-phase LiBC samples with Li-deficiency and without Li-deficiency and it is about one order of magnitude lower for the sample with Li-deficiency, due to hole-doping effect. Both samples show semiconducting behavior and do not exhibit superconductivity down to 2.0 K, although superconductivity is predicted theoretically for the Li-deficient LiBC compound.
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西田 宏, 田中 洋, 村田 孝夫2005 年 69 巻 5 号 p. 439-443
発行日: 2005年
公開日: 2005/10/12
ジャーナル フリーA Micro Electro-Mechanical System (MEMS) consist of a movable silicon substrate and static glass substrate. Two substrates are joined using an anodic bonding technique at 693 K for 1 h. A conductive thin film is deposited on to the silicon to provide the required electrical circuit. Thin film aluminum alloy is an appropriate material for MEMS, because it has low electrical resistance and is easy to etch using conventional acid techniques.
Both electrical characteristics and mechanical characteristics of aluminum alloy film affect the MEMS device performance. Annealing at over 693 K will cause re-crystalization of the grain structure and hence the annealed aluminum alloy thin film has a large grain structure.
With the addition of nitrogen and oxygen into the aluminum alloy, the grain growth will be inhibited during annealing, resulting in a fine grain structure of the annealed thin film.
The dynamic hardness of the film with fine grain structure was approximately 1100 MPa and that of large one is 640 MPa, respectively. Both aluminum alloy thin films have been applied to yaw rate sensors. The static output of the sensors with the fine grain aluminum alloy thin film has been stable, but while those with coarse grain aluminum alloy thin film was found to be unstable.
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田口 真実, 住友 秀彦, 石橋 良, 青野 泰久2005 年 69 巻 5 号 p. 444-451
発行日: 2005年
公開日: 2005/10/12
ジャーナル フリーTargets of this study are realization of better mechanical strength and retention of toughness for ferritic stainless steel by micro-structural modification of grain refinement in the material processing by doping of an active element and mechanical alloying (MA). MA allows the introduction of large strain energy and for materials produced by MA, the formation and presence of dispersed particles in them plays an important role in the grain refinement. The authors have been interested in zirconium which has a high affinity for gaseous impurities such as oxygen, carbon etc., and they examined the effect of zirconium on grain refinement of 12 mass% chrome ferritic stainless steel by MA.
Conventional 12Cr(SUS 410) and 12Cr-1Zr ferritic stainless steels containing about 1 mass%Zr were consolidated by extrusion-forming of their powders without MA at 1073 K. They had grain diameter sizes of about 30 μm and 1 μm, respectively. On the other hand, 12Cr-1Zr steel produced through MA and the same consolidation process (designated MA-12Cr-1Zr) had a grain diameter of 0.36 μm or less. For MA-12Cr-1Zr, it seemed that Zr atoms strongly reacted with gaseous impurities such as oxygen and carbon and fixed them as oxide and carbide. These dispersed particles ranged from 5 to 30 nm in diameter. In particular, it seemed that the zirconium oxide particles were more effective in suppressing the growth of grain boundaries as TEM images showed that the particles were mainly located along them. The grain sizes obtained from the diameter and volume fraction of dispersed particles tended to support Doherty's prediction.
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吉 沢昇, 杉山 澄雄, 柳本 潤2005 年 69 巻 5 号 p. 452-456
発行日: 2005年
公開日: 2005/10/12
ジャーナル フリーThe structural changes of AZ31B in the semisolid state are clarified in terms of the responses of AZ31B to a certain heat treatment temperature, holding time, heating rate and deformation rate. Two types of test piece are adopted, namely, the heat-extruded material without predeformation and that with predeformation, resulting in a 30% height reduction at 573 K(300°C). The following are the main results. (1) The heat-extruded material without predeformation only exhibits grain growth after a long holding time. (2) The heat-extruded material with 30% predeformation shows an almost perfectly spheroidized structure in the semisolid state at a temperature of 883K, heating rate of 2 K•s-1 and holding time of 120 s. (3) The heating rate markedly affects the spheroidizing rate of grains. In the case of the heating rate is larger than the diffusion rate at a semisolid temperature, it is difficult to obtain the spheroidized semisolid structure.
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