巻号一覧
61 巻, 2 号
選択された号の論文の14件中1～14を表示しています
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李 星国, 大崎 勝久, 宇田 雅広, 千葉 晶彦, 高橋 正氣1997 年 61 巻 2 号 p. 99-104
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーThe composite ultrafine powder AlN/Al with an average size of 300 nm was synthesized by arc-plasma method. This powder was added up to 15 mass% into the two kinds of commercial AlN powders prepared by the direct nitridation of Al and the carbon reduction nitriding of Al2O3. The mixed powders with the sintering aid Eu2O3 were sintered in the temperature range from 1923 to 2123 K in a flow of N2 gas and their density and thermal diffusivity were measured at 300 K. The composite ultrafine powder AlN/Al promotes the sintering of the two kinds of AlN powders. A sintered compact of AlN with the theoretical density was obtained at 1973 K by adjusting the amounts of Eu2O3 and composite ultrafine powder AlN/Al. The thermal diffusivity of the sintered sample increases with increasing the amount of the composite ultrafine powder AlN/Al if the sintering temperature is lower than 2073 K and the amount of Eu2O3 is less than 3 mass%. Otherwise it decreases with adding the composite ultrafine powder. Compared with the case used Y2O3 as the sintering aid, the effect for the composite ultrafine powder to promote the sintering of AlN is larger, but the effect for it to raise the thermal diffusivity of AlN is smaller when the sintering aid Eu2O3 is used.抄録全体を表示PDF形式でダウンロード (1675K) -
沼田 英夫, 天野 宗幸, 富塚 功, 辻本 得蔵1997 年 61 巻 2 号 p. 105-112
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーDecomposition of hydrides formed in the surface layer of a TiAl-based alloy by an electrochemical treatment in sulfuric acid solution was studied by thermal desorption spectroscopy (TDS) combined with quadrupole mass spectroscopy (QMS), and X-ray diffractometry (XRD).
Two peaks in the TDS curve and the results of QMS supported the presence of two hydrides in the alloy which was suggested by a previous study. XRD showed that the tetragonal hydride decomposed at 400 K corresponds to the first peak in TDS curve and the hexagonal hydride decomposed at 500 K corresponds to the second peak. The lattice parameters of the tetragonal hydride are a=0.455 nm and c=0.463 nm and these of the hexagonal hydride are a=0.523 nm and c=0.448 nm. The reason why two hydrides were formed is discussed.抄録全体を表示PDF形式でダウンロード (859K) -
小隈 龍一郎, 江口 鐵男1997 年 61 巻 2 号 p. 113-119
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーA theory is displayed to describe the development of off-phase variants in the L12 ordering in alloys such as Cu3Au. In this type of order, there exist four distinct crystallographic variants, anyone of which is displaced from the other three by one of the three primitive translations of an fcc structure. In the present model, the fcc lattice is decomposed into four simple cubic sublattices, where the atomic arrangement in the long range order is represented by three independent order parameters. These parameters are related to the corresponding structure factors for superstructure reflections. The state of order of atomic arrangement in the system is defined by a point in the three dimensional Euclid space spanned by these three order parameters. The actual L12 order structure is given by anyone of the four tips of a regular tetrahedron around the origin, which represents the disordered state. A simple free energy of the Landau type is introduced as a function of these order parameters up to their fourth powers. The free energy includes two parameters depending on temperature, and the equilibrium values for the L12 order parameters are determined by those as functions of the temperature. Below the transformation temperature, the disordered state is unstable against ordering. Small disturbances in the atomic arrangement cause the system to change their state of order following a path in the order space, and to fall into one of the four minimum points of the free energy. In order to investigate the dynamical behavior of the ordering, the surface and the interfacial energies are introduced between the ordered phase and the disordered one, or between any pair of the ordered variants. The equations of motion for the space-time evolution of the order state are derived by the TDGL (time-dependent Ginzburg-Landau) method. The PC simulation for the pattern formation of ordering with multiple variants was performed successfully.抄録全体を表示PDF形式でダウンロード (818K) -
戸田 裕之, 小林 俊郎, 井上 直也1997 年 61 巻 2 号 p. 120-127
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーRecently it has been reported that PFZ layers, ranging several ten and 100 nm in thickness, and coarse interfacial equiribrium precipitates were formed around reinforcements, and that solute atoms were simultaneously segregated toward the interface. In this study, SiC whisker-reinforced 6061 Aluminum alloys are adopted as model materials. Effects of such locally-inhomogeneous microstructures of a matrix on the deformation and fracture characteristics of the MMCs are analyzed by means of the elastic-plastic finite element analysis.
Due to the ductile nature of the PFZ layers, the concentrated plastic flow within the PFZ layers increases the effective plastic strain in the whole matrix, thereby reducing the strength of the MMCs. On the other hand, the interfacial precipitates effectively retard the concentrated plastic flow within the PFZ layers and consequently suppress the reduction in strength due to the formation of the PFZ. However, the interfacial precipitates never exhibit such preferable influence when the matrix is homogeneous.
Both the axial stress within the whiskers and the initiation rate of voids due to the strain concentration around edges of the whiskers increase with extension of the PFZ layers and the interfacial precipitates. The initiation rate of the void is remarkably affected by the morphology and density of the precipitates. Since both the shear stress at the precipitate-reinforcement interface and the internal stresses within the precipitates are considerably high, the properties of the precipitates except for Young’s modulus are important.
Interphase having intermediate Young’s modulus remarkably improves the strength of the MMCs.抄録全体を表示PDF形式でダウンロード (694K) -
日比野 敦1997 年 61 巻 2 号 p. 128-134
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーThe combustion synthesis process has attracted attention as new synthesizing technology of intermetallic compounds. However, as the products tend to be porous and the process control condition is not clear, the process has not been put in practical use. To realize the production of intermetallic compounds by combustion synthesis process, fundamental mechanism or compound formation stages in the combustion reaction should be made clear. In this paper, the compound formation behavior between the Ti and the Al melt was measured, and the compound formation stages in the combustion synthesis of TiAl was investigated.
Dipping experiment which dipped a Ti wire into the Al melt was performed under various conditions of the holding time and temperature. On the other hand, the Ti/Al mixed compacts were quenched during the thermal explosion reaction. The compound formation stage of TiAl was estimated by comparison between the cross section of dipped wires and the microstructure of quenched compacts.
By the dipping experiment, it was found that the compound formation behavior in the Ti-Al system changed with temperature. At the low temperature such as 973∼1173 K, the formation reaction of TiAl3 took place, and small dispersive particles were formed around a Ti wire. However, in the dipping at high temperature as 1373 K or 1473 K, the Ti(α, β) solid solution formed in the wire. In a quenched compact, these phases were detected as well. The TiAl3 phase was found in a compact quenched at the initial stage of synthesis, and the Ti(α, β) solid solution phase was observed at the middle stage. Therefore, it was estimated that the compound formation in the TiAl combustion synthesis progressed through the formation of these phases. As the synthesis reaction was affected by the combustion temperature, the temperature control is of importance to improve the microstructure and synthesized phase of the product.抄録全体を表示PDF形式でダウンロード (1078K) -
香山 滉一郎, 前川 信行1997 年 61 巻 2 号 p. 135-139
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーThe standard Gibbs energies of formation of CoMoO4 and Co2Mo3O8 have been redetermined in the temperature range from 1119 to 1273 K by measuring electromotive forces of galvanic cells having a solid oxide electrolyte. The results are as follows:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere the standard pressure is 1 bar (100 kPa).抄録全体を表示PDF形式でダウンロード (355K) -
升田 博之1997 年 61 巻 2 号 p. 140-144
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーThe small water droplets which adhere the material surface cause corrosion and a photo catalytic reaction. So it is very important to study the behavior of water droplet. We used a graphite to obtain the atomically flat and clean surface and study the behavior of water droplets of nano meter scale by a atomic force microscope (AFM) with the non-contacting mode. A lot of nano-scale water droplets were observed on the surface freshly created by peeling then pouring pure water and sprayed with cleaner gas. The water film was formed and the water droplets moved when the surface was slowly scanned while applying a certain bias. Multi-layer water films and water droplets were observed on the surface freshly created then pouring pure water. These water film and droplets show a different behavior from ordinary water droplets.抄録全体を表示PDF形式でダウンロード (1084K) -
鈴木 裕, 荒木 弘, 野田 哲二1997 年 61 巻 2 号 p. 145-152
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーSilicon isotope separation from hexafluorodisilane (Si2F6) has been examined using CO2 pulse laser. Si2F6 containing specific isotopes was preferentially decomposed to SiF4 depending on the wavenumber of the laser. 29Si and 30Si were concentrated in the SiF4 produced at 945-955 cm−1 while the SiF4 slightly enriched with 28Si was obtained at 970-980 cm−1. The SiF4 containing 30Si and 29Si with an enrichment factor of 14.0 and 2.63, respectively, at maximum was continuously produced with a yield efficiency of 4.4% at 951.203 cm−1 and 9.6% at 956.205 cm−1, under the flow rate of 16.7 mm3s−1 and pressure of 26.6 Pa for the inlet Si2F6. These enrichment factors correspond to the isotopic oncentrations of 43.3% and 12.3% for 30Si and 29Si, respectively. A higher concentration than 97.6% with an enrichment factor of 1.06 is attained for 28Si in the residual Si2F6 after irradiating at 951.203 cm−1 followed by 956.205 cm−1. The dependence of silicon isotope enrichment on the wavenumber could be explained by the difference in apparent decomposition rate for the reaction of Si2F6+nhν→SiF4+SiF2 between six isotopic species such as 28Si28SiF6, 28Si29SiF6, 28Si30SiF6, 29Si29SiF6, 29Si30SiF6 and 30Si30SiF6 in Si2F6 from the mass balance analysis of the experimental results.抄録全体を表示PDF形式でダウンロード (643K) -
奥宮 正洋, 恒川 好樹, 近藤 浩, 吉田 憲司1997 年 61 巻 2 号 p. 153-157
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーSurface modification was carried out on aluminum substrates using pulsed electrical discharges in an air or nitrogen atmosphere. With an aluminum electrode and alumina powder applied on the substrate, formation of aluminum-oxinitride occurs on the substrate surface. The synthesized aluminum-oxinitride is composed of aluminum supplied from the electrode and substrate, oxygen from the alumina powder and nitrogen from the atmosphere. The thickness of deposition layers increases as discharged current, pulsed width or duty factor which is the ratio of pulse width to a total pulse period increases. With an electrode of iron, titanium or nickel composite layers mainly consisting of aluminum-oxinitride and aluminide intermetallic compounds are formed. In addition to the above constituents, when the electrode is aluminum or titanium, the modified layers also contain each nitride.抄録全体を表示PDF形式でダウンロード (500K) -
山内 利夫, 西田 義則, 中江 秀雄1997 年 61 巻 2 号 p. 158-165
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーPreform deformation occurs often during the infiltration when metal matrix composites are produced by squeeze casting. One of the means to overcome the problem is to make the permeability large and the infiltration easy. Then, the granulated whisker preform was developed and the pressure infiltration phenomena of molten aluminum into the preform were investigated by squeeze casting.
The aluminum borate whiskers were prepared as a reinforcement. The permeability of the granulated whisker preform was six times larger than that of the uniform preform in which whiskers were distributed randomly and homogeneously. When the pressure is applied, the molten metal first flows between the granules of whiskers to the bottom of the preform and then infiltrates into the granule of whiskers as the applied pressure increaces. The pressure infiltration phenomena were analyzed with the threshold pressure and the infiltration pressure. It became possible to suppress the preform deformation using the developed preform having larger permeability than that of the uniform preform.抄録全体を表示PDF形式でダウンロード (1107K) -
高野 英毅, 秋山 友宏, 小林 三郎, 八木 順一郎1997 年 61 巻 2 号 p. 166-170
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーOne of typical hydrogen storage alloys, Mg2Ni, was produced by combustion synthesis under five different heating conditions. The product was observed to study the reaction mechanism of this process by using scanning electron microscopy. Compressed samples of magnesium and nickel at 2:1 molar ratio were slowly or quickly heated and kept at constant temperatures for 1.8 ks. The condition of holding temperature influenced to the structure of the product, as expected. When the holding temperature was below the eutectic temperature (779 K) of Mg-Ni, the product was dense and showed a cracked structure. In contrast, under higher holding-temperature conditions, the product indicated fine particles. Moreover, at higher temperatures finer particles with a pseudo-cubic shape were formed. The results implied that the reaction mechanism of this process depends significantly on the heating rate and holding temperature. The reaction equation should obey the crystal growth model above 779 K. These results suggest the possibility of a novel production process of ultrafine powders of an inter-metallic compound.抄録全体を表示PDF形式でダウンロード (1855K) -
新家 光雄, 廣田 友昭, 長谷川 孝, 小林 俊郎, 野田 俊治1997 年 61 巻 2 号 p. 171-179
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーThe strength, ductility, toughness and microstructure of the as-cast and hot isostatic press, HIP, -treated cast TiAl with the compositions of (γ+α2) two-phase structure were investigated. The relationships between fracture mechanism and microstructure of each TiAl were then examined in the present study.
The fracture toughness, Kin, of the as-cast TiAl increases with increasing size of the lamellar grain and decreasing linearity of the lamellar grain boundary when the specimen has little porosity and dendritic structure because the grain boundary fracture is inhibited, and microcracks and secondary cracks are easy to form in these microstructures.
The microstructure of the cast TiAl changes from fully lamellar to (lamellar+γ grain) duplex structure by HIP-treatment. According to this microstructural change, the strength, ductility and fracture toughness decrease. The reductions in strength, ductility and fracture toughness caused by the formation of γ which tends to fracture in the manners of cleavage and decohesion between γ interfaces will be greater than those caused by diminishing microshrinkage and spheroidization of pores.
The cast TiAl used in this study exhibits relatively good fracture toughness and ductility (elongation) compared with those reported in polycrystal TiAl because the direction of lamella is nearly equal to that which exhibits excellent fracture toughness and ductility.抄録全体を表示PDF形式でダウンロード (1215K) -
野田 泰稔, 折橋 正樹, 西田 勲夫1997 年 61 巻 2 号 p. 180-183
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーSingle crystals of p-type PbTe were prepared by the Bridgman method, where either Ag2Te or K was doped as the source material of silver or potassium. The carrier concentration and Hall mobility were measured from 77 to 300 K. The hole concentration was successfully controlled in the range from 2.0×1024 to 9.0×1024 m−3 by doping 100 to 700 mol ppm Ag2Te, while the conduction type changed from p- to n-type in the region more than 1000 mol ppm Ag2Te. In the case of K-doping, the carrier concentration was controlled in the region 8.0×1024 to 4.0×1025 m−3 with 1000 to 20000 mol ppm K. The figures-of-merits Z of PbTe at 300 K were 8.0×10−4 K−1 for p-type at a hole concentration of 1.0×1025 m−3 (2000 mol ppm K) and 1.38×10−3 K−1 at 2.34×1024 m−3 (200 mol ppm Ag2Te).
The diffusion lengths of dopant elements of Ag and K for p-type and I for n-type PbTe were estimated using the diffusion data. The result indicates that long-distance diffusion occurs in a short period in the case of Ag and K, but not so much in the case of I. Therefore, the PbTe carrier concentration functionally graded material (FGM) prepared by doping Ag or K might be soon changed into non-FGM due to the dopant diffusion, resulting in the decreased efficiency of thermoelectric energy conversion.抄録全体を表示PDF形式でダウンロード (340K) -
樋野村 徹, 那須 三郎, 金清 裕和, 広沢 哲1997 年 61 巻 2 号 p. 184-190
発行日: 1997年
公開日: 2008/04/04
ジャーナル フリーUsing 57Fe Mössbauer spectroscopy, X-ray diffraction and magnetization measurements, the magnetic properties of the melt-spun Nd4.5Fe77B18.5 ribbon have been investigated as a function of annealing treatments which make nanocrystalline composite of various phases like Fe3B, Nd2Fe23B3, Nd2Fe14B and α-Fe. These phases have been formed by decomposition of the as-prepared amorphous phase and make a nanocrystalline composite. Magnetic properties of the nanocrystalline composite depend on the heat-treatments applied subsequently to the ribbon. By heating up to 873 K, Fe3B and Nd2Fe23B3 phases have been formed in the ribbon. Mössbauer spectra of these two phases show magnetically split-patterns with large hyperfine magnetic fields suggesting that the ribbon has a large saturation magnetization. Coercivity of this ribbon is determined to be nearly zero because of the low magnetic anisotropy of these phases. The ribbon annealed up to 943 K shows a coercivity and the Mössbauer spectrum obtained shows clearly the existence of the Nd2Fe14B component. Results obtained from the Mössbauer measurements suggest that the coercivity of the ribbon rises from the formation of hard magnetic phase, Nd2Fe14B. The ribbon which has the suitable magnetic properties for a permanent magnet consists of the mixture of Fe3B and Nd2Fe14B and the fractional amounts of these two phases have been determined to be 90%Fe3B and 10%Nd2Fe14B.抄録全体を表示PDF形式でダウンロード (675K)
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