MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 51 , Issue 1
Showing 1-33 articles out of 33 articles from the selected issue
  • Cheng Xu, Zenji Horita, Terence G. Langdon
    2010 Volume 51 Issue 1 Pages 2-7
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: November 26, 2009
    JOURNALS FREE ACCESS
    Measurements were taken to evaluate the evolution of homogeneity in disks of high-purity aluminum in the early stages of processing by high-pressure torsion. The results demonstrate that samples processed through 1/4 or more whole revolutions exhibit microhardness values which are generally higher in the centers of the disks than at the edges whereas after 1/8 turn the hardness is higher at the edge than in the center. It is shown that all of the hardness measurements are mutually consistent and they scatter around a unique curve when plotted against the equivalent strain. The measurements of hardness are supplemented by microstructural observations which provide evidence of a gradual evolution in the microstructure with increasing strain from an initial formation of subgrains to an array of ultrafine grains separated by boundaries having high angles of misorientation.
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  • Andrea Bachmaier, Martin Hafok, Reinhard Pippan
    2010 Volume 51 Issue 1 Pages 8-13
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    High pressure torsion (HPT) deformation enables the grain refinement of bulk materials until a saturation region is reached where no further microstructural refinement can be observed. The influence of deformation temperature, alloying and strain rate on the saturation region was examined by using pure aluminum, an Al-1 mass%Mg alloy and an Al-3 mass%Mg alloy. The deformation temperature was varied between −196°C and 450°C. Both, temperature and alloying exhibit a pronounced influence on the saturation microstructure. The measurements reveal either a rate independent behavior of the structural evolution at low temperatures and a rate dependent behavior of the structural evolution at high temperatures. Two different processes are proposed to be the reason for the saturation at low and high homologous temperatures.
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  • Octav Ciuca, Koichi Tsuchiya, Yoshihiko Yokoyama, Yoshikazu Todaka, Mi ...
    2010 Volume 51 Issue 1 Pages 14-22
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 09, 2009
    JOURNALS FREE ACCESS
    The process of grain refinement in Ni3Al by high-pressure torsion (HPT) was investigated up to 100 turns. The entire diametric sections of the deformed samples were analyzed by optical microscopy and image processing methods in order to evaluate both the spatial distribution and the volume fractions of the nanocrystalline and coarse grains. A thick band of nanocrystalline phase was formed in the middle section of the samples, and a structure containing mainly coarser ordered fragments was present in the vicinity of the top and bottom surfaces. Pseudo-twinning along {111} was observed at the boundaries of coarse-fragmented grains as well as the inside of the fragments and is put forward as a possible mechanism for disordering and nanocrystalline structure formation in Ni3Al.
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  • Kaveh Edalati, Yoshihiko Yokoyama, Zenji Horita
    2010 Volume 51 Issue 1 Pages 23-26
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 02, 2009
    JOURNALS FREE ACCESS
    Machining chips and bulk discs of an amorphous Zr50Cu30Al10Ni10 alloy were processed by high-pressure torsion (HPT). It was confirmed that the machining chips can be consolidated using HPT at room temperature to disc-shaped samples with 10 mm diameter and 0.6 mm thickness having a relative density of 96.7%. The hardness for the consolidated chips was well comparable to those obtained using the bulk samples when the imposed strain is large. No crystallization was detected after HPT processing of chips and bulk samples.
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  • Joo-Hee Kang, Tadanobu Inoue, Shiro Torizuka
    2010 Volume 51 Issue 1 Pages 27-35
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    The microstructural evolution of a low carbon steel was investigated under two different conditions with and without shear strain, using electron backscattered diffraction (EBSD) when a uniaxial compression of 67% was applied at a warm working temperature of 773 K. The equivalent strain and shear strain imposed by the compression test were calculated quantitatively by finite element analysis (FEA). As the equivalent strain was increased without any shear strain, the texture of the α and γ fibers was strongly developed, and the grain refinement was accelerated. However, as the shear strain was increased at the same equivalent strain, the thickness of the pancaked ferrite decreased and the texture was weakened. With increasing shear strain, a shear texture, such as ⟨110⟩||TD and {110}||ND, was observed and a high angle boundary over 15° developed at the expense of low and medium angle boundaries below 15°. The shear strain accelerated the subdivision of the ferrite grain and randomized the texture.
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  • Shaohua Xia, Jingtao Wang
    2010 Volume 51 Issue 1 Pages 36-38
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: November 11, 2009
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    By nanoindentation of different regions in a bimodal grain sized distribution Cu-Al eutectoid alloy, the mechanical behavior of micrometer-grained and ultrafine-grained region was investigated. And it is concluded from this study that the strain-hardening coefficient of micrometer-grained region could be critical to the ductility improvement of nanostructured material through bimodal mechanism.
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  • Tatsuya Sekiguchi, Keita Ono, Hiroshi Fujiwara, Kei Ameyama
    2010 Volume 51 Issue 1 Pages 39-45
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 16, 2009
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    Commercially pure titanium powder is subjected to mechanical milling (MM)-a severe plastic deformation process-for various periods of time. The MM powder has two different kinds of microstructure, which can be controlled by the MM conditions. They include ultra fine and coarse grain structures known as “shell” and “core”, respectively. Subsequently, these MM powder is sintered using a hot roll sintering (HRS) process. The HRS materials with the shell and the core have a network structure of continuously connected shells, which is known as a harmonic structure. The HRS materials with the harmonic structure simultaneously demonstrate both high strength and elongation. These outstanding mechanical properties are influenced by the harmonic structure characteristics such as shell and core grain sizes, and shell fraction and shell network size. Thus, the harmonic structure can be considered as a remarkable design for improving the mechanical properties of commercially pure titanium as well as other metallic materials.
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  • Seung Chae Yoon, Anumalasetty Venkata Nagasekhar, Ji Hoon Yoo, Mohamed ...
    2010 Volume 51 Issue 1 Pages 46-50
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: October 21, 2009
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    In current studies, equal channel angular pressing process (ECAP) and modified ECAP processes are simulated under ideal conditions to compare the deformation characteristics. The deformation behaviour is more complicated and the strain induced during the processes is highly non-uniform in the modified ECAP processes except in the equal channel multi-angular pressing (ECMAP) process with Route C. The strain homogeneity is more of a possibility with ECAP and ECMAP with Route C processes. The deformation stress state is widely distributed in nature in modified ECAP processes than in conventional ECAP. In addition, the load requirements are also higher in modified ECAP processes with that of the ECAP process.
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  • Masato Yoshiya, Hiroki Yoshizu
    2010 Volume 51 Issue 1 Pages 51-57
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 16, 2009
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    Dislocation-accumulated grain boundaries were systematically investigated in terms of local atomic coordinates in the vicinity of grain boundary and energetics on grain boundary evolution by first-principles calculations. Detailed numerical analyses of energy and local atomic configuration at a grain boundary with fixed misorientation angle identified the most stable configurations both for the dislocation-distinctive model and the coincident-site-lattice model with kite-shaped structural units on grain boundary planes. The energy profiles of structural optimization using both initial models indicate that the distinctive dislocations at a grain boundary can be readily converted into kite-shaped structural units without noticeable energy barrier, though they look quite different, and reverse conversion may also be realized under external stress, enabling grain boundaries functioning as dislocation sources and sinks. Systematic calculations for grain boundary with misorientation angles ranging from 5.7° to 53.1° revealed that the interaction energy between dislocation is blunted within a dislocation core region. Furthermore, the energy needed to increase the misorientation angle during severe plastic deformation is quantitatively evaluated.
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  • Juan Chen, Jifan Hu, Hongwei Qin, Zhongli Zhang, Zhangang Zhao, Bo Li
    2010 Volume 51 Issue 1 Pages 58-61
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 02, 2009
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    The Fe77.5Si13.5B9 as-cast ribbons are amorphous. Without any annealing processes, partial crystallization can be obtained in Cu-doped Fe77.5−xSi13.5B9Cux as-cast ribbons. Cu addition improves the nucleation of α-Fe(Si) in the as-cast ribbons. Some soft magnetic properties of Fe77.5−xSi13.5B9Cux as-cast ribbons are measured. Results indicate that Fe75Si13.5B9Cu2.5 as-cast ribbons exhibit a saturation magnetization μ0Ms of 1.55 T, a saturation magnetostriction λs of 1×10−6, and an effective permeability μeff (at 1 kHz) of 5000, which may be of potential applications in some fields.
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  • Raden Dadan Ramdan, Tomohiro Takaki, Kisaragi Yashiro, Yoshihiro Tomit ...
    2010 Volume 51 Issue 1 Pages 62-67
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    A morphological evolution of the growth of Fe2B boride on steel substrate has been investigated using two dimensional (2D) multi-phase-field (MPF) simulations. In order to evaluate competitive growth between boride seeds during the coating process, variations on boride seed orientation have been implemented. In addition, in order to have anisotropy growth of boride, anisotropy of interfacial energy is considered on the evaluation of phase-field evolution. It was observed that boride seed with structure orientation of 90° shows a preferential growth as compared with the growth of boride seeds at other orientations. On the other hand, competitive growth between boride seeds at different crystal orientations can also be observed, where boride seeds approaching a preferential orientation angle grow faster and suppress the growth of boride seeds at the lower orientation angle. Both of these present observations agree with previous experimental observations that boride seeds tend to grow perpendicular to the substrate surface and the growth of boride seeds in this direction suppress growth in other directions. Additionally, it was observed that the preferential growth of boride is independent of the initial size of the boride seed.
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  • L. Xia, K. C. Chan, S. K. Kwok, Y. D. Dong
    2010 Volume 51 Issue 1 Pages 68-71
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    In this work, the glass-forming ability (GFA) of Cu-Hf binary alloys was systematically studied and some metastable phases were observed in the rapidly quenched samples. The microstructure of a Cu50Hf50 as-cast rod between the surface and the central region was carefully examined, and the composition of the unknown metastable phase was identified to be about Cu42Hf58. The formation mechanism of metastable phases and their effect on the GFA of Cu-Hf binary alloys was also investigated. Taking the metastable phases into account, the parameter γ* was revised, and its prediction of the GFA of Cu-Hf binary alloys was found to be roughly in accordance with the experimental results.
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  • H. Sugimura, Y. Kaneno, T. Takasugi
    2010 Volume 51 Issue 1 Pages 72-77
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    The site preference of ternary additions in Ni3Nb (D0a) was determined from the direction of solubility lobes of the GCP phases which were available from the reported ternary phase diagrams and constructed in the present work. It was shown that Cr, Co and Cu preferred the substitution for Ni-site, Ti, V, Hf, Ta and W the substitution for Nb-site, and Fe the substitution for both sites. The thermodynamic model, which was based on the change in total bonding energy of the host compound by a small addition of ternary solute, was applied to predict the site preference of ternary additions. The bond energy of each nearest neighbor pair used in the thermodynamic calculation was derived from the heat of compound formation by Miedema’s formula. The agreement between the thermodynamic model and the experimental result was excellent. From both experimental and theoretical results, both the transition and B-subgroup elements have two possibilities, i.e., the case of substitution for Ni-site or the case of substitution for Nb-site, depending on the relative value of two interaction energies.
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  • Koji Murakami, Makoto Hino, Ryosuke Furukawa, Teruto Kanadani
    2010 Volume 51 Issue 1 Pages 78-84
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 02, 2009
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    Zincate treatment and electroless nickel-phosphorus plating for aluminum alloys of A1100, A2017, A5052 and A7075 were researched from the viewpoints of alloying elements and activation conducted prior to zincate treatment. Surface morphologies of zincated surfaces, electrochemical properties during zincate treatment and depth profiles on activated and zincated surfaces were investigated by microscopy and measurement of temporal changes of electrode potential.
    Adhesion strengths of the plated films were measured by 90° peeling test, which showed that double zincate treatment improved adhesion strength especially when ferric ion was added into the zincate solution except for the case of A7075. Temporal changes of electrode potential during zincate treatments and morphologies of the zincated surfaces showed that copper and zinc promoted uniform precipitation of zinc and resulting rapid termination of conversion reaction. Excess zinc was shown to dissolve into the plating solution and cause the formation of low-density area or gaps between plated films and substrates.
    Activation for A1100 by various conditions showed that formation of oxide film had a remarkable effect on precipitation of zinc during zincate treatment. When a mixture of nitric and hydrofluoric acid was used for activation, finer particles of zinc were formed near etch pits compared with the cases of hydrochloric or nitric acid. On the other hand, the surface was uniformly covered with fine zinc particles in the case of the activation with a solution of sodium hydroxide. This indicates that uniformity of oxide film on substrate before zincate treatment is thought to bring about uniform precipitation of zinc.
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  • Bo-In Noh, Jeong-Won Yoon, Jung-Hyun Choi, Seung-Boo Jung
    2010 Volume 51 Issue 1 Pages 85-89
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    The adhesion strength of a Cu/Cr/polyimide (PI) flexible copper clad laminate (FCCL), which was manufactured by the roll-to-roll process, was evaluated according to the thickness of the Cr seed layer using the 90° peel test. The changes in the morphology, chemical bonding and adhesion properties were characterized by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The peel strength of the FCCL decreased with increasing Cr layer thickness. The higher FCCL peel strength was attributed to the lower proportion of C-N bonds and higher proportion of C-O or carbonyl (C=O) bonds on the PI surface compared to the FCCL with the lower adhesion strength. The FCCL with the higher peel strength had a fractured PI surface with a higher surface roughness. The adhesion strength between the metal and PI was mostly attributed to the chemical interaction between the metal layer and the functional groups of the PI.
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  • Motohiro Sakamoto, Kazuki Morita
    2010 Volume 51 Issue 1 Pages 90-93
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 09, 2009
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    A β-Fe(1−x)CoxSi2 film was prepared by a cation-exchange reaction between molten NaCl-KCl-FeCl2-CoCl2 salts and a Si substrate at 1173 K. At low CoCl2 concentrations of molten salts, the β-FeSi2 phase was formed. However, when the CoCl2 concentration was higher than 0.015 mol%, α-FeSi2 and FeSi phases were formed in addition to the β-FeSi2 phase. The α-FeSi2 and FeSi phases changed to β-FeSi2 when the sample was annealed at 1123 K for 24 h. The Co content of the reaction layer increased with the CoCl2 concentration of molten salts. The electrical resistivity of β-FeSi2 was measured by the four-probe method, and the band gap (Eg) of the sample was roughly determined from the temperature dependence of electrical resistivity by using the equation ρ=ρ0exp(Eg⁄2kT). The electrical resistivity decreased and the band gap slightly decreased with the increase in the Co content of β-FeSi2.
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  • Santosh Prasad Sah, Yoshitaka Aoki, Hiroki Habazaki
    2010 Volume 51 Issue 1 Pages 94-102
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    Plasma electrolytic oxidation of AZ80 magnesium alloy in alkaline aluminate electrolytes develops MgAl2O4-based highly crystalline oxide coatings with the morphology changing largely with phosphate concentration in electrolyte. The thickness of the coatings increases with phosphate concentration from 5 μm in phosphate-free electrolyte to ∼70 μm in the electrolyte containing 0.1 mol·dm−3 phosphate after anodizing for 900 s. The formation of the latter thick coating is associated with intense sparking during anodizing. The thick coatings formed in the electrolytes containing 0.075 and 0.1 mol·dm−3 phosphate are highly cracked. In contrast, the coating formed in the electrolyte containing 0.05 mol·dm−3 phosphate is relatively uniform, showing the highest corrosion protection in 0.5 mol·dm−3 NaCl solution. The coatings consist of two layers, comprising an outer thick layer with high concentration of aluminum and an inner thin magnesium-rich layer.
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  • Haruki Itofuji, Mikio Tamura, Hiromichi Ito, Takanobu Nishimura, Yasuo ...
    2010 Volume 51 Issue 1 Pages 103-109
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 02, 2009
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    Stator flange castings were produced in our foundry as the parts for a 1 million kwh power generator at the Hekinan Plant of the Chubu Electric Company. Nonmagnetic ductile iron was applied as its material. The guarantees of their permeability and the mechanical properties were required in the trepan test samples taken from the stator flange castings using a core drill. Since the sensitivity of the wall thickness on those properties is severer than that of normal ductile iron, the precise quality control was needed. The site theory was helpful to control the graphite nodularity and to avoid the chunky graphite formation. Heat treatment was conducted to gain the austenitic matrix structure. Nondestructive tests such as VT, PT and RT were applied to prove the soundness of the castings. As the results, all the properties required could be satisfied well.
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  • Toshiaki Himemiya, Kenichi Ohsasa, Takahiro Saga
    2010 Volume 51 Issue 1 Pages 110-115
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 02, 2009
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    A cell-automaton model for a binary eutectic system has been developed. This study examines a Bridgeman-type temperature field with periodic boundary conditions. A stable operating range of lamellar spacings is obtained based on the parameters of the temperature field. The undercooling of the liquid phase ahead of the solid/liquid interface is also estimated in the calculations. The estimated lamellar spacings and undercoolings agree well with the predictions of the Jackson-Hunt model.
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  • Minh-Tung Le, Yong-Un Sohn, Jae-Won Lim, Good-Sun Choi
    2010 Volume 51 Issue 1 Pages 116-120
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    Cu thin films were deposited on Si(100) substrates using direct current (DC) magnetron sputtering. We focused on the effect of sputtering DC power on the electrical, structural properties, and the nucleation and growth of Cu films during the initial stage of sputtering. The Cu films deposited at higher sputtering power showed strong crystallinity, low electrical resistivity in comparison with the Cu films deposited at lower sputtering power. Concerning the nucleation and growth of Cu films during initial stage of magnetron sputtering, it was found that the progress of the nucleation and growth of the Cu films at higher sputtering is much faster than those of the Cu films at lower sputtering power even though they have a similar nucleation and growth mechanism, and their relation to resultant microstructure was confirmed by atomic force microscopy.
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  • Keisuke Iwata, Yoshitake Nishi
    2010 Volume 51 Issue 1 Pages 121-127
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    The effects of homogeneous irradiation of electron-beam (EB) with low voltage on the Charpy impact value (auc) of borosilicate glass were studied. When it performed in short bursts to maintain a low temperature, EB irradiation at a dosage from 0.04 to 0.22 MGy increased the auc value and enhanced its reproducibly. Based on the electron spin resonance (ESR) spectra, EB-irradiation formed apparent dangling bonds constructed with sodium atoms with high density of outer-shell electrons and terminated oxygen atoms of silica network in the borosilicate glass. When the intermolecular repulsive force generated the partial relaxation against residual and deformed strain, as well as expansion in front of crack tips near the sodium atoms, the initial auc enhancement of the borosilicate glass by the irradiation can be explained. Furthermore, the strong resistance to radiation damage of borosilicate glass was qualitatively confirmed. Although the large start point of irradiation dose to decrease the as value was 0.08 MGy for silica glass, it was 0.22 MGy for borosilicate glass. Consequently, the boron addition enhanced the resistivity to irradiation damage.
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  • Harumi Tsutsumi, Mitsuo Niinomi, Toshikazu Akahori, Masaaki Nakai, Tsu ...
    2010 Volume 51 Issue 1 Pages 128-135
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    The applicability of a calcia mold to casting a β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), was evaluated with focusing on the dimensional accuracy of the casting in this study. Pure zirconium particles were added to a calcia mold to take advantage of the expansion of oxidized zirconium during the baking process in order to compensate for the solidification shrinkage of TNTZ. The morphological characteristics of the casting surface, such as the roughness and dimensional accuracy, of the cast TNTZ were investigated.
    The dilation ratio of the calcia mold is found to increase with increasing the number of pure zirconium particles. The addition of 12 mass% or 14 mass% pure zirconium particles compensates for not only the solidification of TNTZ but also the occurrence of shrinkage of the calcia mold. In addition, the formation of a surface reaction layer in TNTZ is restrained to a larger extent by casting into a calcia mold than into a magnesia mold, which is the conventional investment mold for titanium casting. Furthermore, the volume fraction and number of casting defects are also restrained to a larger extent by casting into a calcia mold than into a magnesia mold. The results of this study should lead to enhancements in the creation of cast TNTZ for dental products.
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  • Harumi Tsutsumi, Mitsuo Niinomi, Toshikazu Akahori, Masaaki Nakai, Tsu ...
    2010 Volume 51 Issue 1 Pages 136-142
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    A calcia mold, which is stable at high temperatures for dental precision casting of β-type titanium alloys such as Ti-29Nb-13Ta-4.6Zr (TNTZ) with high melting point, has been developed. The applicability of the calcia mold to casting TNTZ was evaluated with focusing on the mechanical properties of the casting in this study. The molten TNTZ was cast into the calcia mold of which dimensional accuracy was controlled by adding pure zirconium particles. The tensile and fatigue properties of TNTZ cast into the calcia mold were examined with comparing those of TNTZ cast into the magnesia mold, which is the conventional one for casting titanium alloys.
    The tensile properties of TNTZ cast into the calcia and the magnesia molds are not markedly different. The fatigue strength of TNTZ cast into the calcia mold in the low- and high-cycle fatigue life regions is slightly higher than that of TNTZ cast into the magnesia mold. Therefore, the calcia mold is expected to be applicable to the dental precision casting of TNTZ.
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  • Koji Murakami, Masako Okano, Makoto Hino, Masao Takamizawa, Kiyomichi ...
    2010 Volume 51 Issue 1 Pages 143-151
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: November 18, 2009
    JOURNALS FREE ACCESS
    Generation and growth of whiskers and nodules from electroplated tin and tin-lead films on copper or nickel substrates were studied by scanning electron microscopy and X-ray diffraction. In the case of copper substrates, whiskers were formed in 0.3 Ms on the tin film whose thickness was 1 μm. On the other hand, tin-lead films on copper substrates showed only nodules even after 13 Ms. Residual stress of the tin film (1 μm) and the number of whiskers increased with the amount of copper-tin intermetallic compounds (Cu6Sn5) which developed between the plated film and the copper substrate. Although residual stress and the amount of Cu6Sn5 also increased in the tin-lead system, the morphology of the layer of Cu6Sn5 was more uniform compared with the case of tin films on copper substrates. When the tin-lead film was subjected to the compression testing by a ball of zirconium oxide (1 mm-diameter, 2.94 N–0.605 Ms), the edge of the indentation did not show any whiskers but diffusion of lead was observed from right under the zirconium oxide ball to the fringe, as well as Ostwald growth of lead. In the case of the tin film on the nickel substrate, whose residual stress was weakly tensional, nickel-tin intermetallic compounds (Ni3Sn, Ni3Sn2, Ni3Sn4) uniformly developed immediately after electroplating, and no whiskers were observed even after the compression testing. While growth of whiskers is considered to be due to diffusion of tin atoms induced by inhomogeneous strain field in the electroplated film, lead atoms in tin-lead system is considered to diffuse rapidly toward the free surface to release residual stress and to generate many nodules.
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  • Chinatsu Okamura, Takashi Ueda, Kazuhiro Hasezaki
    2010 Volume 51 Issue 1 Pages 152-155
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 02, 2009
    JOURNALS FREE ACCESS
    Single phase β-Zn4Sb3 was prepared by mechanical grinding (MG). Source materials for the Zn4Sb3 ingots were prepared using three different processes after the direct melting of constituent elements. The ingot was obtained by quenching the melt in water within an evacuated quartz ampoule and heat-treated for a total of 200 h in two stages at 723 K and 673 K. The resultant ingots were mechanically ground and sintered at 623 K by hot pressing. The sintered materials were obtained crack-free single phase β-Zn4Sb3 and characterized by X-ray diffraction, differential thermal analysis (DTA) and thermoelectric property measurements. The thermal conductivity of the sintered materials was 0.88 Wm−1K−1 at room temperature and this was slightly lower than that reported for the materials prepared by a conventional method. Results indicate that the β-Zn4Sb3 single phase of the dimensionless figure of merit ranged from 1.06–1.31 at 573 K.
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  • Tatsuya Oki, Taeko Hazumi, Yoko Umemiya, Mikio Kobayashi
    2010 Volume 51 Issue 1 Pages 156-164
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 02, 2009
    JOURNALS FREE ACCESS
    Gravity separation techniques such as jigging are based on the difference in the settling velocities of particles in water, which depends on the specific gravity, size, and shape of the particles. When a particle falls in stationary water, it is known that its settling velocity in the acceleration period before it reaches its terminal velocity depends on its specific gravity. Therefore, if one jigging cycle were completed before the particle reaches its terminal velocity, separation based on the difference in particle specific gravity would be promoted as the jigging frequency increases. However, there are few reports discussing whether the acceleration period in stationary water could be applied to an unsteady jigging movement. In this study, we used particles of around 1 mm, which are small particles for a jig, and investigated the relation between jigging frequency and particle movement. We have concluded from the results that although the reason is incorrect, the above classical hypothesis reflects the actual phenomenon, since the effect calculated in this study almost agrees with estimations obtained using the hypothesis developed by Gaudin.
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  • Yoshitake Nishi, Nobuaki Kunikyo, Masae Kanda, Laurent Lebrun, Daniel ...
    2010 Volume 51 Issue 1 Pages 165-170
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 09, 2009
    JOURNALS FREE ACCESS
    Copper powder dispersed acrylonitrile butadiene styrene (ABS) composites were prepared by the solution cast method. Although the addition of Cu greatly enhanced the electric conductivity at the critical volume fraction (19.0+⁄−1.0 vol%Cu) from the insulator to the electric conductor, the decrease in the Charpy impact value was gradual. Since the impact value of the ABS polymer prepared by the solution cast method was 1.75 times larger than that before treatment, it is clear that the solution casting improved the impact value. When the volume fraction of Cu powders of high electric conductive ABS composites was from 20 to 30 vol%Cu, the impact value was 7 kJm−2. The moderated impact value was not only 44% of that of pure ABS polymer before solution casting, but was also higher than that of dispersed nylon6 composites (2 kJm−2) utilizeed for practical exteriors.
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  • Wen Zeng, Tianmo Liu, Zhongchang Wang, Susumu Tsukimoto, Mitsuhiro Sai ...
    2010 Volume 51 Issue 1 Pages 171-175
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 09, 2009
    JOURNALS FREE ACCESS
    The structural, adsorptive, and electronic properties of oxygen adsorption on anatase TiO2 are investigated by first-principles calculations with special focus on two experimentally confirmed surfaces. We find that compared with (101) surface, the (001) surface exhibits lower oxygen adsorption energy, reduced band gap, and larger charge transfer, thereby holding the potential for the improvement of sensitivity to reductive gases. Moreover, the (001) surface is found to be more active in oxygen adsorption. These findings render a careful synthesis of anatase TiO2 crystals so as to form, to the largest extent, the (001) surface primarily important for further improving gas-sensing properties of TiO2-based sensors.
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  • Hiromitsu Takeda, Hiroyuki Yoneda, Kazunori Asano
    2010 Volume 51 Issue 1 Pages 176-185
    Published: January 01, 2010
    Released: December 25, 2009
    [Advance publication] Released: December 09, 2009
    JOURNALS FREE ACCESS
    Although the thinning of spheroidal graphite cast iron castings has been promoted to reduce the weight of the castings, the thinning tends to cause chilling. Due to the chilling, the required mechanical properties can not be obtained. The addition of certain elements is a way to solve this problem. In this study, the spheroidal graphite cast iron melt containing minor Bi, 3.3 to 3.7 mass%C and 2.0 to 3.2 mass%Si was poured into a stepped plate mold to obtain the thin wall castings, and observation of their graphite and matrix microstructure, thermal analysis during the solidification process of the melt in the mold and the qualitative analysis of elements inside the spheroidal graphite by FE-EPMA were carried out.
    It was found that an increase in the Si/C mass ratio in the spheroidal graphite cast iron was effective for decreasing the amount of cementite (chill) in the matrix, and the chill was further inhibited by adding 0.01 mass% Bi even for the thin wall castings of 2 mm. Amounts up to 0.01 mass%Bi promoted refinement of the graphite, increased the graphite nodule, and promoted ferritizing of the matrix. It was also found that a high Si/C mass ratio in the spheroidal graphite cast iron promoted the effects of Bi. The temperature of the eutectic start and that of the eutectic solidification end increased due to the 0.01 mass%Bi. The temperature of the eutectoid transformation start increased and the stability eutectoid transformation of the thin wall castings was promoted by containing a minor amount of Bi. It was confirmed that substances including Bi and Mg existed in the graphite containing Bi. These results lead to the conclusion that the Bi compound and the Mg compound acted as heterogeneous nuclei of the graphite, and the nuclei promoted the crystallization of the graphite, and then the graphite nodule increased.
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  • Chih-Hsien Wang, Fei-Yi Hung, Truan-Sheng Lui, Li-Hui Chen
    2010 Volume 51 Issue 1 Pages 186-191
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    Carbon materials decomposed by low temperature have a higher surface area and contain micro-holes and thus have a larger lithium storage space. In this study, the natural bamboo carbon powders were used as the experimental materials to process the hydrothermal method with the post-treatment. The results show that Fe3O4 thin films are formed on the surface of carbon particles. After charge-discharge testing, it was found that the powders not only increased the capacity, but also improved the irreversibility. With increasing the concentration (0.05∼0.25 M), the coating particles became coarse and the thickness of Fe3O4 nano thin films increased. Notably, the C-0.05Fe powder had a better charge-discharge cyclability.
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  • Byung-Koog Jang, Yoshio Sakka
    2010 Volume 51 Issue 1 Pages 192-195
    Published: January 01, 2010
    Released: December 25, 2009
    JOURNALS FREE ACCESS
    The shortening of multi-walled carbon nanotubes (CNTs) was achieved by size-reduction treatment using shear force. Special atomizing unit with double diamond disks under a higher forwarding speed of CNTs suspension was used to obtain a high shear force and to break the entangled CNTs. Tangled pristine CNTs can be shortened below 200 nm by the introduction of shear stress during repetitive size-reduction treatment. CNTs that have undergone size-reduction treatment show a lower optical transmittance than that of the original untreated CNTs, resulting in the well dispersion in aqueous suspension.
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