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Volume 56, Issue 12
Displaying 1-19 of 19 articles from this issue
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Shigenori Yuhya, David J. Baar, Koichi Nakao, Tsunemi Sugimoto, Yuh Sh ...1992 Volume 56 Issue 12 Pages 1371-1377
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe superconducting properties of 5 to 300 nm thick Bi-Sr-Ca-Cu-O films prepared by MOCVD have been investigated. The zero resistance temperature (Tco) and critical current density (Jc) at 4.2 K in zero applied field for all samples were about 70 K and 1×1010 A/m2, respectively. The temperature dependences of Jc varied with film thickness. Jc(T) for a film with intermediate thickness could be modeled as a weighted average of the critical current densities for thicker and thinner films. This suggested the existence of a distinct layer in the films containing different junctions by the annealing effect during deposition.
Both Tco and Jc were nearly independent of magnetic fields up to 6 T when the fields were apllied parallel to the film surface. This results were thought to be due to the effect of the film thinness. By the calculation of the free energy for the thin film with high Ginzburg-Landau parameter, the effective lower critical field in fields parallel to the film surface (H\varparallelc1) was shown to become larger than that for a bulk superconductor. In addition, it is difficult for a vortex to move through the film because of the potential barrier near the surface of the film.View full abstractDownload PDF (1163K) -
Hideyuki Ikeda, Hidehiko Matsuda1992 Volume 56 Issue 12 Pages 1378-1384
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSComputer simulations on the spinodal decomposition processes in a bcc binary alloy with a crystal anisotropy were carried out by using a Monte Carlo method combined with the static variational method. The Johnson-type potentials were used for the interaction between the constituent elements. We assumed that the elastic modulus of solute atoms was equal to or softer than that of the solvent atoms. In the former case, the wave number (km) corresponding to the maximum in the structure functions along ⟨100⟩ direction was constant during the initial stage of decomposition, while in the latter case, km decreased with time and the structure functions showed the scaling behavior. Furthermore, a giant cluster of solute atoms was formed and the cluster created a percolative structure at the later stages of aging for the latter.View full abstractDownload PDF (1068K) -
Isamu Yamauchi, Itsuo Ohnaka, Masahiko Murata1992 Volume 56 Issue 12 Pages 1385-1391
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA new approach for the metastable phase formation based on chemical reaction was proposed. Various ternary Al3(NixFe1−x) alloys were rapidly solidified and then aluminum atoms were leached from the alloys by the hot alkaline solution. The structure of the as-leached and heat treated specimens were examined by SEM and X-ray diffraction. The results are as follows.
(1)In the as-leached state, the crystal structure varied with the value of x.
In the range of x=0 to 0.33, a metastable bcc structure (supersaturated bcc in Ni) and magnetite were formed. Fcc and magnetite were formed between 0.33 and 0.5 of x. At a high values of x (more than 0.5), only the fcc phase was observed.
(2)X-ray diffraction patterns of the fcc phase were very broad, and it was estimated that the grain size of the leached specimens were in the range of 5 and 10 nm. Since the specific surface area of the as-leached specimens was quite large, each grain might have a gap (free space) at the grain boundary.
(3)The leached specimens showed high activity and sometimes ignited spontaneously in atomosphere due to their high specific surface area.
(4)Rapidly solidified alloys were nonmagnetic, but after leaching they showed magnetism due to the formation of magnetite and ferromagnetic bcc and fcc phases.View full abstractDownload PDF (2159K) -
Eiichi Sukedai, Hatsujiro Hashimoto1992 Volume 56 Issue 12 Pages 1392-1400
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSInvestigation about the volume fraction of omega particles in Ti-20 mass%Mo alloy single crystal aged at 623 K for 12.6, 28.8 and 100.8 ks was carried out using electron diffraction, dark field and high resolution electron microscope methods. The diffraction spot due to each omega variant was identified by calculating the structure factors in the case of the incident beams parallel to the [10\bar1], [31\bar1] and [3\bar1\bar1] directions. The image of each omega variant in the same area of each specimen was taken separately by dark field technique of electron microscope, and the volume fraction of each omega variant was estimated from those images. It is found that the volume fraction of each omega variant in the specimen has a different value and the volume fractions are not equal at different places in the specimen. The volume fractions estimated for the specimens aged for three different periods are evaluated by comparing the yield strength estimated from the volume fractions by the precipitation hardening mechanism with the corresponding Vickers hardness values. And it is found that the values of volume fractions are reasonable.
It seems that the differences among the volume fractions in the same composite alloys estimated by X-ray and electron microscopy are not due to the methods for estimations but due to the differences in oxygen content of the specimens.View full abstractDownload PDF (4829K) -
Masayuki Ohashi, Taku Sakai, Takao Endo1992 Volume 56 Issue 12 Pages 1401-1407
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe process of dynamically recrystallized (DRX) band formation which takes place after the stress peak followed by its rapid drop has been studied using hot tensile testing of polycrystalline nickel, with microstructural observations being carried out by optical and transmission electron microscopy. Few DRX grains nucleated at a specimen edge and propagated easily across the cross-section during stress drop, and then developed sidewise along the specimen axis. Such processes took place repeatedly accompanied with serrations in stress at high strains. Microstructures inside DRX band showed dislocation density gradient and more ragged cellular boundaries, compared with homogeneous and recovered ones in zero-DRX region. The critical condition at which the DRX band was formed was t=D (Here t and D are the specimen thickness and the stable DRX grain size, respectively.). These results are interpreted in terms of the stability of plastic flow as well as DRX grain growth.View full abstractDownload PDF (2122K) -
Hiroaki Nakamura, Youichi Ogawa, Akira Kasahara, Satosi Iwasaki1992 Volume 56 Issue 12 Pages 1408-1413
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe electrical conductivity of a beryllium sulfide disk prepared so carefully as to avoid any contamination has been measured in the temperature range from 923 to 1073 K and in the sulfur partial pressure range from 10−10 to 103 Pa with the aid of an alternating current bridge. Because the conductivity is independent of sulfur pressure in the lower sulfur pressure range (PS2<10−4), it is concluded that BeS is an ionic conductor. The specific conductivity can be expressed as follows:
(This article is not displayable. Please see full text pdf.)
The apparent activation energy for the ionic conduction is 103.3 kJ/mol. From the comparison of this activation energy with that of other alkaline-earth sulfides it is suggested that the charge carrier of BeS is Be2+.
In the PS2 range from 10−4 to 10−1 the conductivity depends on sulfur pressure and is expressed as
(This article is not displayable. Please see full text pdf.)
The observed sulfur pressure dependence is attributed to the predominance of fully ionized beryllium vacancies or to the predominance of divalent sulfur interstitials.View full abstractDownload PDF (878K) -
Toshio Shimoo, Yasuhiro Kobayashi1992 Volume 56 Issue 12 Pages 1414-1421
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn relation to lowering silicon content of the molten pig iron in a blast furnace, the effect of CaO or MgO addition on the mechanism of the carbothermic reduction of SiO2 has been investigated. Using powdered SiO2-graphite mixtures containing CaO or MgO, the reduction rate has been determined with a thermo-balance in an argon atmosphere at 1873 K.
The solid products were SiC, Ca2SiO4 or Mg2SiO4, and the gaseous products were SiO, Ca and Mg. The small additions of CaO and MgO increased the formation rates of SiC and SiO. The formation of SiC and SiO from the mixtures with %CaO/%SiO2 or %MgO/SiO2 above 0.6 was slower than that from 100%SiO2. In the early stage of reaction, the reduction rate of SiO2 was mixed-controlled by the interfacial reactions at both graphite and the silicate particles. As the reduction proceeded, the rate-determining step was shifted to the gaseous diffusion through the Ca2SiO4 or Mg2SiO4 layer left on the surface of the silicate particles.View full abstractDownload PDF (981K) -
Sil Mook Lim, Yasushi Nakamura1992 Volume 56 Issue 12 Pages 1422-1427
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEquilibrium experiments were performed to determine thermally stable ranges of 3BaO·2FeO·12Fe2O3(BaZ) and BaO·6Fe2O3(BaM) hexa-ferrites under various oxygen partial pressures. The obtained results are summarized as follows.
(1) BaZ is found to decompose into BaM and liquid at relatively higher temperatures, and into BaM and BaO·Fe2O3 at relatively lower temperatures. The partial pressures of oxygen on the decompositions depend only on the reaction temperature as follows:
(This article is not displayable. Please see full text pdf.)
The thermally stable range of BaZ, thus, exists between the conditions given by both of the above equations.
(2) BaM is found to decompose into BaX and liquid at higher oxygen pressures, and into BaX and BaZ at lower oxygen pressures. The relations between the oxygen partial pressures and reaction temperatures on the decompositions are given by the following equations:
(This article is not displayable. Please see full text pdf.)View full abstractDownload PDF (994K) -
Yukio Inokuti, Kazuhiro Suzuki, Yasuhiro Kobayashi1992 Volume 56 Issue 12 Pages 1428-1434
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to investigate the possibility of improving the iron loss in grain oriented silicon steel sheet, ceramic coatings such as TiN, CrN and TiC were produced by ion plating on polished silicon steel sheets. The results obtained are summarized as follows.
(1) The magnetic flux density B8(T) of silicon steel sheets with the ceramic films increases moderately to 0.004∼0.015 T, while the iron loss W17⁄50(W/kg) improves dramatically to 0.12∼0.20 W/kg. The improvement in the iron loss is remarkable in silicon steel sheets with higher magnetic flux densities. For example, in the silicon steel sheet products with B8=1.93 T, W17⁄50=0.88 W/kg, the final magnetic properties containing magnetic domain refinements manifest an ultra-low iron loss of 0.55 W/kg, which corresponds to the improvement in iron loss of about 40%.
(2) Silicon steel sheets with TiN or CrN films are improved dramatically in magnetic properties, while those with TiC, SiC, SiO2, or Al2O3 films show comparatively a little improvement.
(3) The attainment of ultra-low iron loss is due to improvement of hysteresis loss arising from the use of a polished steel surface which is clean and free from impurities and to the reduced eddy current loss arising from the strong tension of the ceramic films.
(4) Silicon steel sheets with ceramic films show no deterioration in magnetic properties after strain relief annealing, superior compressive stress dependence of magnetstriction and good lamination performance.
(5) It is considered that the ceramic coatings on the polished silicon steel sheet produced by physical techniques such as the PVD and CVD methods are the best method of improving the iron loss in silicon steel sheet.View full abstractDownload PDF (2074K) -
Atsushi Hibino1992 Volume 56 Issue 12 Pages 1435-1443
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe formation mechanism of a Ni3Al intermetallic compound produced by combustion synthesis was investigated by the observation of the reaction process in premixed powder compacts of Ni and Al (Ni : Al=3 : 1, in atomic ratio). A green compact was vacuum-heated in an electric furnace to cause its thermal explosion reaction. The measurements of sample temperature and the observation of microstructural changes during the reaction process were perfomed. The synthesized products were analyzed by X-ray diffraction and EPMA. It was found that the Al eutectic melt was formed and it surrounded Ni particles at the eutectic temperature in the Ni-Al system. The synthesis reaction was initiated at the interface between the melt and Ni, and the Ni2Al3 layer was shaped in the particles during the combustion sinthesis. The reaction process has been simulated with a spherical shell model which comprises reaction kinetics and heat balance equations. The calculated value obtained by the model was in good agreement with the experimental value. Therefore, the shell model could be applied for the analysis of the present synthesis mechanism. It was evaluated by the model that in the initial stage of combustion synthesis the chemical reaction at the interface between Ni2Al3 and Ni controlled the overall reaction rate of the compound formation, and in the last stage the diffusion of Al in the Ni2Al3 layer was dominant.View full abstractDownload PDF (1695K) -
Gil Geun Lee, Hitoshi Hashimoto, Ryuzo Watanabe1992 Volume 56 Issue 12 Pages 1444-1449
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPowder premix of Mo and Si (Mo:Si=1:2) was vibratory ball milled with 12.7 mm and 25.4 mm balls to investigate the effect of ball size on the phase formation during milling. The milling process and the phase formation were monitored by X-ray diffraction analysis (XRD), optical microscopy, SEM and EPMA of the milled powders. The temperature of a milling pot was also monitored by a thermocouple attached to the milling pot.
A temperature spike was seen after 50 h of milling when milled with 25.4 mm balls. The X-ray diffraction analysis showed that intermetallic compound MoSi2 (tetragonal phase) was formed from the mixture of Mo and Si powders right after the temperature spike. On the other hand, when milled with 12.7 mm balls no temperature spike was seen and hexagonal MoSi2 was gradually formed. The hexagonal MoSi2 formed by the milling with 12.7 mm balls transformed into the thermodynamically stable tetragonal phase after annealing at 1173 K. The phase formation mechanism was discussed.View full abstractDownload PDF (1472K) -
Jing-Feng Li, Akira Kawasaki, Ryuzo Watanabe1992 Volume 56 Issue 12 Pages 1450-1456
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFully dense compacts of SiC-AlN solid solution and composite were fabricated by the combination of reaction synthesis and hot isostatic pressing (HIP). Their strength and deformation behavior were investigated from room temperature to 1773 K by a Modified Small Punch (MSP) test which has been found to be suitable for the mechanical evaluation of brittle materials.
The SiC-AlN solid solution and composite samples showed higher strength than both of the HIPed SiC (with 0.5 mass%B4C additives) and AlN compacts from room temperature to 1473 K. A decrease in the strength was then observed above 1473 K for the solid solutions containing 5, 10 and 25 mol%AlN, while the SiC, AlN and SiC-AlN composites maintained the room temperature strength up to 1773 K. Nonlinear deformation occurred at 1773 K in the solid solution samples with the composition of SiC-25 mol%AlN, being accompanied by a drastic drop in strength. Considering the fact that single-phase SiC-AlN solid solutions have a fine microstructure of uniform grain size, the nonlinear deformation is due to grain boundary sliding. On the other hand, the SiC-50, 70 mol%AlN composites maintained their high strengths up to 1773 K, probably because coarser grains with AlN-rich composition in the fine-grained matrix effectively suppressed the grain boundary sliding. For the single-phase SiC-AlN solid solutions, moderate grain growth is needed to achieve high strength at elevated temperature.View full abstractDownload PDF (1856K) -
Kazuhisa Shibue, Masaki Kumagai, Mok-Soon Kim1992 Volume 56 Issue 12 Pages 1457-1462
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe oxidation property of a Ti-33.5 mass%Al-2.5 mass%Mn intermetallic compound prepared by a reactive-sintering process was studied at 1223 K in air in comparison with that by a melt process. The reactive-sintered alloy had been found to have superior oxidation resistance to the melted one. The oxidation scale of the former was suggested to be adhesive, for example, owing to the presence of fine alumina particulates and/or pores which contribute to pegs. The fine alumina particulates were developed by breaking up of the oxide layer along prior particle boundaries during the reactive-sintering process.View full abstractDownload PDF (2505K) -
Xiang-Xu Cui, Ning Zhang, Akira Kanno, Shotaro Morozumi1992 Volume 56 Issue 12 Pages 1463-1469
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPressureless sintered SiC joints, bonded with thin Ti foil at various temperatures, have been examined for the bend strength at room and high temperatures, thermall shock resistivity, resistivity for oxidation of interfacial reaction layer, and microstructure by optical and SEM microscopies with EPMA. The results obtained are as follows:
(1) The optimum joining temperature range for the present joining process is recomended as between 1773 and 1873 K.
(2) The bend strength at room temperature is kept up to the vicinity of 1473 K.
(3) The thermal shock resistivity of the interfacial reaction layer is higher than that of SiC itself.
(4) The interfacial reaction layer is Ti3SiC2 which is (Si, Ti)O2 at the exposed surface when the joint is kept at high temperatures in ambient oxidizing atmosphere. This oxidation, however, results in strengthening of the layer by the exposure around 1473 K and contrarily in deterioating of the layer above 1673 K where the oxidation of the layer proceeds rapidly.View full abstractDownload PDF (1865K) -
Yutaka Kagawa, Teruo Kishi1992 Volume 56 Issue 12 Pages 1470-1478
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFracture toughness, defined as a starting point of the R curve, of unidirectionally-reinforced continuous SiC(Nicalon®) fiber-reinforced LAS-II matrix composites have been obtained using newly-developed electric resistance technique. Effects of the volume fraction and interfacial shear sliding strength, respectively on the initial toughness of the composite were evaluated using specially-prepared composites. The obtained results were discussed with the stress fields near the notch tip. The electric resistance technique allowed determination of the start of fracture at a tip of notch. The initial toughness calculated at the initial fracture load obtained from the electric resistance technique depends strongly on the interfacial shear sliding stress. When the interfacial shear strength was sufficiently high to prevent splitting along the interface betwen the fiber and matrix, the initial toughness increased with increasing the fiber volume fraction. However, when the interfacial shear stress was low, the splitting along the interface initiated before the tensile fracture of the matrix phase. In this case, the initial toughness was independent of the volume fraction. Theoretical prediction of the stress field near the notch tip explained this dependence of the initial toughness on the interfacial shear strength. The possibility of the improvement of initial toughness and limitations of the toughness of ceramics by the addition of fiber were discussed from a point of materials design.View full abstractDownload PDF (2599K) -
Seishi Abe, Katsumi Mochizuki, Katashi Masumoto1992 Volume 56 Issue 12 Pages 1479-1484
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLead calchogenide compound semiconductors are expected to be the tunable laser diodes which lase at mid-infrared region between 3 and 4 μm. In this study, the solubility range and the lattice constant of a new quaternary solid solution semiconductor Pb1−xCaxS1−ySey are investigated. The solubility range was determined at 1273, 973 and 773 K. The lattice constant is evaluated as a function of the compositions x and y. From the results, the suitable compositions x and y of cladding layers, Pb1−xCaxS1−ySey, necessary for the fabrication of the double-heterostructure laser, using PbS as an active layer, can be easily chosen.View full abstractDownload PDF (817K) -
Fumiyoshi Kirino, Akiko Mutou, Norio Ohta1992 Volume 56 Issue 12 Pages 1485-1494
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe film structure and optical characteristics of Al, Cr or Co-doped silicon nitride films were studied. As the relationships between producing processes and the refractive index were studied, the refractive index was larger as the substitution ratio of metal element was higher and the nitrogen mixing ratio in the sputtering gas was lower. The magneto-optical disk characteristics were measured. On the disks using the Cr or Al-doped SiNx films, the C⁄N was 1∼2 dB lower than that on the disk using the SiNx film. On the disk using the Co-doped SiNx film, the C⁄N was 9 dB lower than that on the disk using the SiNx film. These results may be explained by the light absorption of the Co-doped SiNx film. The bonding state of each element in the Al, Cr or Co-doped SiNx film whose refractive index was 2.0∼2.1 was analysed by the ESCA method. The bonding state of Si in the SiNx film was present as a mixture of 2∼3 states. The bonding state of Si in the (Si, Co)-N film was shifted to the lower bonding energy state and the higher bonding energy state. The bonding state of N in the (Si, Al)-N film showed the oxinitride peak. Cr and Al were in the nitride state, but Co existed as a mixture of nitride and metal. The section structures of these films were obtained by TEM. The SiNx films and the Cr, Al or Co-doped SiNx films were all amorphous. On the Cr-doped SiNx film, a nearprismatic structure was observed, and on the Co-doped SiNx film, corpuscles of 2∼5 nm diameter were observed. The inner streses of the SiNx film and the (Si, X)-N (X=Cr, Al, Co) films produced by the reactive sputtering method were stress free.View full abstractDownload PDF (2834K) -
Kiyoshi Watanabe, Takejiro Kaneko, Shigehiro Ohnuma1992 Volume 56 Issue 12 Pages 1495-1500
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe thermal magnetic analysis and the temperature dependence of the permanent magnet properties of CoPt, Fe-39Pt and Cr-59.2Pt alloys were investigated by using a VSM and a recording fluxmeter.
The results of the thermal magnetic analysis showed that the magnetization of these alloys have the maxima at 720 K (Co-Pt), 650 K (Fe-Pt) and 1085 K (Cr-Pt). The maximum appears to be due to the decrease in magnetic anisotropy at that temperature.
The coercivities are 820 kA/m for the CoPt, 520 kA/m for Fe-39Pt and 700 kA/m for Cr-59.2Pt alloys at 4.2 K, and decreased gradually with increasing temperature. The temperature coefficients of residual flux density are −0.04%/deg for CoPt and −0.06%/deg for Fe-39Pt alloys.
The Cr-Pt magnet alloys, which show a high coercivity in a narrow composition range from 58 to 60 at%Pt, exhibit a low magnetization but a high magnetic transition temperature. It is presumed that the mechanism of the coercivity is closely related with the enhanced magnetization, because the coercivity increase with increasing magnetization.View full abstractDownload PDF (716K) -
Motohiro Kanno, Hiroshi Okada, Goroh Itoh1992 Volume 56 Issue 12 Pages 1501-1502
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (297K)
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