MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 52 , Issue 4
Showing 1-42 articles out of 42 articles from the selected issue
  • Saishun Yamazaki, Jin Nakamura, Kouji Sakaki, Yumiko Nakamura, Etsuo A ...
    2011 Volume 52 Issue 4 Pages 586-590
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    We used powder X-ray diffraction (XRD) and Rietveld refinement to study phase transformation and the lattice strain introduced into each hydride phase of Ti1.0V1.1Mn0.9 during first absorption and desorption. Hydrogenation proceeded from a solid-solution phase to a dihydride phase via a monohydride phase. Each single-phase region was observed beside two clear plateau regions on the pressure–composition (PC) isotherm. In contrast, the desorption PC isotherm showed only one clear plateau, corresponding to a two-phase region of the dihydride and the monohydride. The plateau was connected to a two-phase region of the monohydride and a solid-solution phase, and to another region of solid-solution phases. The monohydride single-phase region was not clearly observed during desorption. Isotropic lattice strain was introduced, and increased with phase transformation during the first absorption. The strain increased further in the subsequent phase transformation during desorption, particularly upon formation of a solid-solution phase.
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  • Yumiko Nakamura, Takashi Kamiyama, Etsuo Akiba
    2011 Volume 52 Issue 4 Pages 591-594
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    Hydrogen vibrational excitation was studied for CaF2-type metal hydrides synthesized from Ti-based BCC solid solution alloys using inelastic incoherent neutron scattering (IINS). Ti1.0V1.1Mn0.9H4.5 and Ti0.7V1.2Cr1.1H4.8 showed IINS spectra similar to that reported for TiH2. The first three peaks were isolated but the higher excitation peaks were not clear. Analysis of the spectra using curve-fitting with Gauss functions revealed that the hydrogen vibration of Ti1.0V1.1Mn0.9H4.5 is harmonic but that of the Ti0.7V1.2Cr1.1H4.8 is deviated from harmonic, which reflects a trumpet-type potential. The relation between metal-hydrogen distance and vibrational excitation energy for the above two hydrides and Ti1.1Cr1.4Mo0.3H∼5 was compared with a series of CaF2-type binary metal hydrides. All the hydrides of the Ti-based alloys had lower vibrational excitation energies than the binary metal hydrides for the corresponding metal-hydrogen distances.
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  • Hiroyuki Saitoh, Yuka Okajima, Yasuhiro Yoneda, Akihiko Machida, Yoshi ...
    2011 Volume 52 Issue 4 Pages 595-597
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: December 15, 2010
    JOURNALS FREE ACCESS
    The hydrogenation process of aluminum, especially pulverization of aluminum prior to the hydrogenation reaction was investigated by in situ synchrotron radiation X-ray diffraction measurements at high pressure and high temperature. Changes in the crystal grain sizes during the hydrogenation process were observed using the angle dispersive method, while weak Bragg peaks from aluminum and AlH3 with small X-ray scattering factors were detected using focused monochromatic X-rays as the incident beam. The in situ measurement system monitored the pulverization of aluminum at several pressure-temperature conditions where AlH3 was thermodynamically stable.
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  • Kazutaka Ikeda, Hidetoshi Ohshita, Naokatsu Kaneko, Junrong Zhang, Mas ...
    2011 Volume 52 Issue 4 Pages 598-601
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 02, 2011
    JOURNALS FREE ACCESS
    The structural and hydrogen/deuterium desorption properties of AlH3/AlD3 were investigated by Raman spectroscopy, high-intensity X-ray/neutron diffraction, and thermogravimetric analysis. The latter revealed that more than 9.6 mass% of hydrogen/18.1 mass% of deuterium desorbs from AlH3/AlD3, respectively. The presence of χ-Al2O3 on the surface may prevent the hydrogen/deuterium desorption reaction of AlH3/AlD3 to Al at room temperature.
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  • Hiroyuki Saitoh, Akihiko Machida, Yoshinori Katayama, Katsutoshi Aoki
    2011 Volume 52 Issue 4 Pages 602-604
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: December 01, 2010
    JOURNALS FREE ACCESS
    An Al3Ti alloy was immersed in hydrogen at high pressures and high temperatures. An anomalous expansion of the Al3Ti metal lattice was observed by in situ powder X-ray diffraction measurements at 625°C and 10 GPa, suggesting that Al3Ti is hydrogenated to form Al3TiHx. The hydrogen content is roughly estimated to be x∼0.4. However, the formed hydride phase is dehydrogenated during depressurization, and cannot be recovered at ambient conditions.
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  • Satoshi Semboshi, Tomoya Nishida, Hiroshi Numakura
    2011 Volume 52 Issue 4 Pages 605-609
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 30, 2011
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    The influence of hydrogen pressure during isothermal aging on the mechanical strength, electrical conductivity, and microstructure of Cu-3 at% Ti alloys was investigated under various hydrogen pressures from 0 to 0.8 MPa. The variation of hardness with aging time was not significantly different among all specimens aged under the hydrogen pressures. This is because the hardness is improved primarily by the precipitation strengthening of Cu4Ti particles, which is less affected by hydrogen pressure. The electrical conductivity increased more significantly for specimens aged under higher hydrogen pressure, due to a rapid reduction in the concentration of Ti dissolved in the matrix, which is attributed to the accelerated formation of TiH2. The conductivity at peak-hardness was improved by a factor of approximately 1.4 in the specimens aged at both 773 and 723 K under the highest hydrogen pressure, compared to that for the specimen aged in vacuum. Therefore, aging under high hydrogen pressure assisted in the significant improvement of both strength and electrical conductivity.
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  • H. Yukawa, T. Nambu, Y. Matsumoto
    2011 Volume 52 Issue 4 Pages 610-613
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: January 13, 2011
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    The alloying effects of tungsten on the hydrogen solubility, the resistance to hydrogen embrittlement and the hydrogen permeability are investigated for Ta-based hydrogen permeable membranes. The hydrogen solubility is found to decrease by the addition of tungsten into tantalum or by increasing the temperature. It is also found that the mechanical properties (i.e., strength and ductility) for Ta-based alloy is better than that for Nb-based alloy in hydrogen atmosphere at high temperature. It is demonstrated that the Ta-5 mol%W alloy possesses excellent hydrogen permeability without showing any hydrogen embrittlement when used under appropriate permeation conditions. For example, the hydrogen flux for Ta-5 mol%W alloy measured at 773 K under the pressure condition of inlet/outlet = 0.15/0.01 MPa is about 5 times higher than that for Pd-27 mol%Ag alloy measured at the same testing condition.
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  • Hiroshi Ogawa
    2011 Volume 52 Issue 4 Pages 614-617
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: January 13, 2011
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    Hydrogen absorption in f.c.c. nanoparticles of 1–8 nm diameter was investigated using molecular dynamics simulation with model interatomic potentials. Atomic configuration with five-fold symmetries was observed in both hydrogen-free and hydrogenated particles smaller than 2 nm. The f.c.c. structure was maintained in larger particles after hydrogenation in cases where the M–H interaction is weak. Lattice deformation was induced in cases of strong M–H interaction. A shift of critical size for icosahedral–cubic transition by hydrogenation was also inferred. The number of absorbed H atoms increased concomitantly with increasing particle size and M–H interaction. Most absorbed H atoms located at O-sites when M–H interaction was weak. The T-site occupancy increased with M–H interaction. Analysis using local atomic configuration revealed that structural variation in nanoparticles results from three factors: surface effects, icosahedral transformation, and lattice deformation attributable to M–H interaction.
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  • Xuanzhou Zhang, Wenhuai Tian, Junzhi Yang, Rong Yang, Jie Zheng, Xingg ...
    2011 Volume 52 Issue 4 Pages 618-622
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    Pure Mg2FeH6 compounds with two different morphologies have been successfully synthesized directly by mechanical milling (MM) and sintering of a mixture of 2Mg+Fe nanoparticles under an H2 atmosphere, respectively. The successful preparation of pure Mg2FeH6 can be attributed to the small particle sizes of Mg and Fe nanoparticles prepared by hydrogen plasma-metal reaction (HPMR), which provides shorter diffusion distance for hydrogen and the metals. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results show that the Mg2FeH6 synthesized by mechanical milling has larger particle size but smaller crystallite size compared with the Mg2FeH6 synthesized by sintering. The Mg2FeH6 synthesized by mechanical milling can desorb more than 4.5 mass% hydrogen in 10 min under an initial hydrogen pressure of 0.001 bar at 573 K. Compared with the Mg2FeH6 synthesized by sintering under the same conditions as the Mg2FeH6 synthesized by mechanical milling, it is suggested that decrease of crystallite size is beneficial for enhancing desorption property of Mg2FeH6.
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  • Masaharu Menjo, Yoshihiro Hyodo, Satoko Moriyama, Hai-Wen Li, Motoaki ...
    2011 Volume 52 Issue 4 Pages 623-626
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: February 09, 2011
    JOURNALS FREE ACCESS
    Cyclic hydrogenation and dehydrogenation property of LiNH2 impregnated into the Ni foam was experimentally investigated, comparing with that of conventional LiNH2 powder. The amount of dehydrogenation from the impregnated sample after activating was 4.3 mass% (without the weight of the Ni foam), and remained 3.3 mass% after the 49th cycle of hydrogenation and dehydrogenation, while the amount from the powder sample drastically decreased down to 0.5 mass% until only the 11th cycle. The main origin of the superior cyclic property of the impregnated sample was attributed to the suppression of sintering, mainly due to release of the exothermic heat during the hydrogenation supported by the frames of the Ni foam.
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  • Yongfeng Liu, Ruijun Ma, Runlai Luo, Kun Luo, Mingxia Gao, Hongge Pan
    2011 Volume 52 Issue 4 Pages 627-634
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: December 29, 2010
    JOURNALS FREE ACCESS
    Metal ammine complexes (MACs) were recently regarded as one of promising materials for reversible hydrogen storage due to their high hydrogen content. In this work, a first attempt is conducted to elucidate the hydrogen storage reversibility by combining Mg(NH3)6Cl2 with LiH. It is found that hydrogen is gradually evolved from the combined system during ball milling. After 24 h of milling, approximate 3.5 mass% of hydrogen, equivalent to 6 mol of H2 molecules, is released from the Mg(NH3)6Cl2-18LiH mixture. Additional 3.4 mass% of hydrogen is further desorbed from the combined system milled for 24 h with a two-step reaction in heating process. Totally ∼12 mol of H2 molecules are librated from the Mg(NH3)6Cl2-18LiH mixture along with the formation and consumption of Mg(NH2)2 and LiNH2 in the ball milling and subsequent heating process. The resultant products consist of Li2Mg(NH)2, Li2NH, LiH and LiCl after dehydrogenation at 310°C. Further hydrogenation experiment indicates that ∼6 mol of H2 molecules are reversibly stored in the Mg(NH3)6Cl2-12LiH mixture.
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  • Daiju Matsumura, Takahiro Ohyama, Yuka Okajima, Yasuo Nishihata, Hai-W ...
    2011 Volume 52 Issue 4 Pages 635-640
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: January 26, 2011
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    Local structure of Ti-based additives in Mg(BH4)2 was studied by X-ray absorption fine structure spectroscopy with conventional and dispersive mode in order to understand the correlation between the structure of the additives and dehydrogenation property of Mg(BH4)2. Simultaneous measurement of the dehydrogenation curve and the X-ray absorption spectroscopy by the dispersive optics revealed that a part of TiCl3 additive is converted to TixMg1−3x⁄2(BH4)2 (x=0∼0.67) just after ball milling mixture and then promptly resolved to TiB2 at 100–150°C with the first dehydrogenation peak. TiO2 additive is slowly converted to lower oxidation state in wide temperature range around the second dehydrogenation peak at 350°C where the main dehydrogenation reaction of Mg(BH4)2 occurs.
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  • Young Li, Toshihisa Izuhara, Hiroyuki T. Takeshita
    2011 Volume 52 Issue 4 Pages 641-646
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: January 13, 2011
    JOURNALS FREE ACCESS
    The effect of Al addition on the reversibility of a MgH2+2LiBH4 hydrogen storage mixture was examined in order to improve the mixture’s requirement for a hydrogen atmosphere even in dehydrogenation. The experiments using high pressure differential scanning calorimetry and X-ray powder diffraction confirmed that a MgH2+Al+4LiBH4 mixture can reversibly dehydrogenate and rehydrogenate below 773 K under mild conditions of 0.1 MPa H2 for dehydrogenation and 4.0 MPa H2 for rehydrogenation. Moreover, thermogravimetry tests revealed that this mixture starts hydrogen desorption at about 530 K, which is 80 K lower than the corresponding temperature for the MgH2+2LiBH4 mixture, and desorbs 9.5 mass% of hydrogen below 773 K. Thus, the addition of Al improves not only the reversibility of the reaction but also dehydrogenation kinetics. The hydrogen desorption of the mixture occurs by three steps, which includes the formation of Mg-Al alloys by the reaction of MgH2 and metallic Al followed by the formation of Mg1−xAlxB2 by the reaction of the Mg-Al alloys and LiBH4. Al in this mixture suppresses the formation of metallic Mg and accelerates the formation of Mg1−xAlxB2 from B produced by dehydrogenation of LiBH4. Mg1−xAlxB2 is derived from partial substitution of Al for Mg in MgB2, which contributes to reversible hydrogenation and dehydrogenation of MgH2+2LiBH4.
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  • H. Wang, H. L. Zhang, C. Luo, T. Sun, M. Zhu
    2011 Volume 52 Issue 4 Pages 647-650
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: February 23, 2011
    JOURNALS FREE ACCESS
    To improve the dehydrogenation properties of LiBH4, the MgH2 and NdCl3 were added with different modes by ball-milling, and their influences on the decomposition of LiBH4 were investigated by performing X-ray diffraction (XRD) analysis and dehydriding kinetic measurements. The results show that adding either NdCl3 or MgH2 alone could not promote the decomposition of LiBH4. But for the NdCl3 doped LiBH4-MgH2 composites, not only the decomposition of MgH2 is accelerated, but also the dehydrogenation rate and capacity of LiBH4 are greatly enhanced. The kinetic improvement is attributed to a cooperative catalytic role arising from dual addition of MgH2 and NdCl3. The NdH2 phase, resulting from reaction between MgH2 and NdCl3, might be responsible for the enhanced dehydrogenation of LiBH4.
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  • Zaixing Yang, Yan Wang, Jing Liang, Jun Chen
    2011 Volume 52 Issue 4 Pages 651-653
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    This paper reports on the preparation and hydrogen releasing of lithium amidoborane (LiNH2BH3, LiAB). LiAB is synthesized by a wet-chemical route through the direct interaction of LiH with NH3BH3 in tetrahydrofuran (THF) at room temperature. The structure of the as-prepared sample is investigated using X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. The thermal decomposition process is determined by temperature programmed desorption/mass spectrometer (TPD/MS). The results show that the as-prepared LiAB starts to release H2 at the temperature of 70.9°C, which is much lower than that of pure AB, while detectable NH3 releasing should be controlled.
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  • Yu Zhou, Motoaki Matsuo, Yohei Miura, Hitoshi Takamura, Hideki Maekawa ...
    2011 Volume 52 Issue 4 Pages 654-657
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    The electrical conductivities of complex hydrides Li2(BH4)(NH2) and Li4(BH4)(NH2)3 consisting of (BH4) and (NH2) anions are investigated focusing on their low melting temperatures (365 K for Li2(BH4)(NH2) and 490 K for Li4(BH4)(NH2)3). The two hydrides show lithium fast-ion conductivities of about 1×10−4 S·cm−1 at room temperature. After melting, the total ion conductivities of Li2(BH4)(NH2) and Li4(BH4)(NH2)3 reach 6×10−2 S·cm−1 (378 K) and 2×10−1 S·cm−1 (513 K), respectively. The crystal structure and local atomistic structures closely correlated with the lithium ion conduction before and after melting are also discussed.
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  • Shuji Harada, Yuki Nagai, Kazuya Kazama
    2011 Volume 52 Issue 4 Pages 658-662
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: February 09, 2011
    JOURNALS FREE ACCESS
    A gas handling technique of the gas controllable H2 | H+electrolyte | Pt cell has been reported in order to obtain the reproducible gas environmental condition. The small amount of dissolved hydrogen and oxygen gas in the electrolyte has been evaluated by measurements of the temperature dependence of electromotive force (EMF) of the cell. The gas controllable technique and the evaluation method of a dilute H and O gas dissolved in an electrolyte should contribute to clarify the interfacial phenomena on electrode materials.
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  • H. Sugimura, Y. Kaneno, T. Takasugi
    2011 Volume 52 Issue 4 Pages 663-671
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 02, 2011
    JOURNALS FREE ACCESS
    The atom substitution preference of ternary additions in Ni3M-type GCP (geometrically close-packed) compounds with D0a structure was determined from the direction of single-phase region of the GCP phase on the reported ternary phase diagrams. In Ni3Nb, Co and Cu preferred the substitution for Ni-site, Hf, Ta, Ti, V and W the substitution for Nb-site, and Fe the substitution for both sites. In Ni3Ta, Co, Cu, Fe, Ir, Mn and Re preferred the substitution for Ni-site, Mo and Nb the substitution for Ta-site, and Al and Cr the substitution for both sites. In Ni3Mo, Pd and W preferred the substitution for Ni-site, and Al, Nb, Ta, Ti and Zr the substitution for Mo-site. The thermodynamic model, which was based on the change in heat of formation of the host compound by a small addition of ternary solute, was applied to predict the atom substitution preference of ternary additions. The heat of compound formation used in the thermodynamic calculation was derived from Miedema’s formula. Good agreement was obtained between the thermodynamic model and the result of the literature search. For Ni3Mo, with a small negative heat of formation, a weak binding force between the constituent elements is often enhanced by the addition of the ternary elements that substitute for Mo-site.
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  • Fusanori Hamasaki, Kenji Tsuruta
    2011 Volume 52 Issue 4 Pages 672-676
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 09, 2011
    JOURNALS FREE ACCESS
    The atomic- and electronic-level structures of a dislocation loop and a stacking fault in 4H-SiC crystal are investigated by using large-scale tight-binding (TB) molecular-dynamics simulation. We employ a linear-scaling TB method implemented on a parallel computer in order to accelerate the 9,600-atoms calculation which is required for such a nanoscale simulation. We find that the initial configuration that involves unstable C-C networks around the dislocation loop is relaxed to a structure having six-membered rings, and that the distribution of electron populations is inhomogeneous on the loop. The local electronic density of states shows two peaks in the bulk band gap, where one of these peaks may correspond to the defect state observed in EBIC and CL experiments.
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  • Minho O, Masanori Kajihara
    2011 Volume 52 Issue 4 Pages 677-684
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 02, 2011
    JOURNALS FREE ACCESS
    In the wire bonding technique, a thin Au wire is interconnected with an Al layer on a Si chip. During energization heating at solid-state temperatures, however, brittle Au-Al compounds with high electrical resistivities are formed at the interconnection by the reactive diffusion between Au and Al. In order to examine the growth behavior of the Au-Al compounds, the kinetics of the reactive diffusion was experimentally observed using sandwich Al/Au/Al diffusion couples. The diffusion couple was prepared by a diffusion bonding technique and then isothermally annealed at temperatures of 623–723 K for various times up to 103 h. Under such annealing conditions, the diffusion couple is practically considered semi-infinite. Owing to annealing, compound layers consisting of AuAl2, AuAl and Au8Al3 are produced at the initial Au/Al interface in the diffusion couple. The volume fraction in the compound layers is larger for Au8Al3 than for AuAl and AuAl2 in the early stages but becomes smaller for Au8Al3 than for AuAl and AuAl2 in the late stages. However, there are no systematic dependencies of the volume fraction on the annealing time and temperature. The total thickness of the compound layers is proportional to a power function of the annealing time. The exponent of the power function is smaller than 0.5 at 673–723 K. The exponent smaller than 0.5 means that the interdiffusion across the compound layers governs the layer growth and boundary diffusion predominantly contributes to the interdiffusion. On the other hand, at 623 K, the exponent is equal to unity for annealing times shorter than 8 h but smaller than 0.5 for those longer than 8 h. The exponent of unity indicates that the layer growth is controlled by the interface reaction at the migrating interface. Thus, at T=623 K, the transition of the rate-controlling process occurs at a critical annealing time of 8 h.
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  • Yuepeng Song, Jiangtao Li, Yixiang Chen, Wenwen Ji, Chong Soo Lee, Hyo ...
    2011 Volume 52 Issue 4 Pages 685-690
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 30, 2011
    JOURNALS FREE ACCESS
    The combustion front quenching method (CFQM) combined with the temperature field simulated using the finite element method was used to investigate the microstructural aspects of the fabrication of transparent Y3Al5O12 via combustion synthesis. The simulated results indicate that there are three regions corresponding with the temperature distribution whose microstructural aspects were studied. The composite mixtures of the products cannot be separated depending only on their gravities. The filamentous profile of aluminum along with many aluminous intermediate products are detected by XRD, SEM and EDS analysis in the preheat region, which indicates that the heat-transfer can affect the mass-transfer process and the subsequent reaction process. The microstructural aspects show that the combustion reaction of the Al/NiO/Y2O3 powder mixture was initiated by the melting of Al particles.
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  • Manabu Tamura, Takuya Kumagai, Nobuhiro Miura, Yoshihiro Kondo, Kei Sh ...
    2011 Volume 52 Issue 4 Pages 691-698
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 09, 2011
    JOURNALS FREE ACCESS
    A modified 9Cr-1Mo steel was cooled to a temperature between the Ms point and room temperature from the normalizing temperature and then directly heated to the tempering temperature. It was found that the time to rupture at 650 and 700°C of the steel heat-treated by the new heat treatment increased 2–3 times longer than that of the steel conventionally normalized and tempered. The microstructure of the improved steel was tempered martensite and the size of martensite blocks was larger than for the conventional heat treatment. The hardness of the improved steel was fully recovered after tempering. This strengthening is not caused by fresh martensite, but caused by the refining of M23C6 and V(C,N) particles in addition to the increase in the martesite block size, where M denotes metallic elements.
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  • Kun Liu, Lihui Zhu, Ranran Tu
    2011 Volume 52 Issue 4 Pages 699-703
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    WC-10Co (mass pct.) cemented carbides containing plate-like WC grains were prepared by using plate-like WC single crystals as seeds. With the increase of seed addition amount, more and bigger plate-like WC grains are formed, the hardness and transverse rupture strength (TRS) increase first and then decrease. When 2.5 mass% seeds are added in WC-10Co, the density is hardly affected, whereas the hardness and TRS increase simultaneously, especially TRS increases by 12.8%. The hardening and toughening mechanisms of WC-10Co cemented carbides with plate-like WC grains were discussed.
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  • Satoshi Itoh, Yosuke Inoue
    2011 Volume 52 Issue 4 Pages 704-708
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 02, 2011
    JOURNALS FREE ACCESS
    The activity of tin in Ti-Sn alloy has been determined at 1400 K by Knudsen effusion method with electrobalance. The activity of titanium was calculated by applying the Gibbs-Duhem relation to the Ti-Sn binary system. The standard Gibbs energy of the formation of intermetallic compound such as Ti3Sn, Ti2Sn, Ti5Sn3 and Ti6Sn5 was calculated at 1400 K by using the activities of components. X-ray diffraction studies were additionally conducted for some samples after the activity measurement. The identified phases were consistent with the phase diagram reported in the literature.
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  • Sung-chul Kim, Shin-ichi Yamaura, Akihiro Makino, Akihisa Inoue
    2011 Volume 52 Issue 4 Pages 709-713
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    In this work, electro-less plating was adopted to produce a new metallic bipolar plate coated with amorphous alloy. The Ni-P amorphous alloy thin film was deposited on Al plate with a bipolar plate flow field and its corrosion resistance and contact electrical resistance were measured. As results, it was found that the electro-less plated Ni-P amorphous thin film showed much lower corrosion resistance than the Ni-Cr-P-B metallic glass because of its lack of Cr content and also found that the Ni-P film showed lower contact electrical resistance than the stainless steel SUS316L plate.
    The electricity generation tests with the single cell having the Ni-P amorphous alloy-coated bipolar plates produced in this study revealed that the single cell with the Ni-P amorphous alloy-coated bipolar plates showed excellent I-V performance as well as the cell with the carbon bipolar plates after 39th repetition. However, the I-V performance degraded gradually and was found to be much lower than that with the carbon bipolar plates after 50th repetition. Then the long time durability tests for 24 h were also conducted at the constant current density of 200 mA·cm−2. It was found that the cell voltage of the single cell with the Ni-P amorphous alloy-coated bipolar plates decreased gradually with time.
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  • Yasuhiro Michiyama, Kei Demizu
    2011 Volume 52 Issue 4 Pages 714-718
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    This paper describes the creation of a surface-hardened layer with a minimum thickness of 1.0 mm on a titanium alloy. Two layers, a soft layer and a thick surface-hardened layer, were created on the titanium alloy specimens by using different age hardening speeds caused by different conditions of solution treatment. The solution treatment used furnace heating and laser heating as heating methods. Our accelerated aging treatment was conducted at temperature 300°C for aging times 86.4–432.0 ks after the solution treatment. Changes in the titanium alloy specimens after the aging treatment were examined by hardness and wear tests and microstructure observation.
    The results revealed that the laser-heated part hardened at an early stage in aging time. Because of the difference in hardening speed, a hardened layer was formed. Except for the case of furnace heating at 700°C, the grain diameter of the laser-heated parts barely changed after furnace heating. The wear amount of the titanium alloy decreased with hardness; this decrease was remarkable especially at 450 HV and higher. For the specimens of both furnace- and laser-heated parts having the same hardness, the wear amounts were the same. The specimen that was laser heated for 259.2 ks after furnace heating at 800°C had an effective hardened layer with hardness 490–500 HV, ranging from the surface to a thickness of about 1.0 mm. The hardness of the internal unhardened layer for this specimen was 260 HV.
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  • Nobumitsu Shohoji, Fernando Almeida Costa Oliveira, Luís Guerra ...
    2011 Volume 52 Issue 4 Pages 719-727
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: February 09, 2011
    JOURNALS FREE ACCESS
    Reactions of d-group transition metals including Ti, V, Nb and Ta with N2 gas were investigated at target temperature of 2000°C under heating with concentrated solar beam at PROMES-CNRS in Odeillo (France). In the typical experimental setup using graphite crucible as the sample holder, synthesis of pure nitride with fcc (face centred cubic) structure was proved to be difficult on account of inevitable C2 radical plume with high carbon activity a(C) from the graphite components and the majority of reaction products were carbo-nitride. By insertion of Sky blue filter in the solar beam path before entering into the parabolic concentrator, C2 radical formation appeared to be efficiently suppressed and phases with high N content were synthesized. However, under conditions in which C2 radical plume yield was considerable, nitrogen content in the reaction products became suppressed and tetragonal Nb4N3 yielded in place of fcc NbN from Nb or N-deficit sub-nitride Ta2N in place of mono-nitride TaN formed.
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  • Takuya Koizumi, Kota Kido, Kazuhiko Kita, Koichi Mikado, Svyatoslav Gn ...
    2011 Volume 52 Issue 4 Pages 728-733
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    Metallic foams are commonly produced using hydride foaming agents. Carbonates are safer to handle than hydrides; however, their use in the powder metallurgy (PM) route to obtaining a fine and homogenous cell structure has not been evaluated. In this study, carbonates and hydroxides were investigated as foaming agents for the production of Al-Si-Cu alloy foams by the PM route. The thermal decomposition behavior of the foaming agents was evaluated in conjunction with the cell structure of the aluminum foams produced. From the results, it was clarified that a foaming agent that began decomposing after the matrix melted is required to obtain a fine and homogenous cell structure. The TiH2 foam formed under similar conditions was obviously different and had a coarse and rounded cell structure. MgCO3 and CaMg(CO3)2 were selected as suitable foaming agents for the Al-Si-Cu alloy. Once expanded, the CaMg(CO3)2 foam had a specific gravity of 1.19 and a homogeneous, fine and spherical cell structure.
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  • Hiroaki Takei, Michelle Salvia, Alain Vautrin, Akira Tonegawa, Yoshita ...
    2011 Volume 52 Issue 4 Pages 734-739
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 30, 2011
    JOURNALS FREE ACCESS
    Homogeneous low voltage electron beam irradiation (HLEBI) improved the elasticity indicated by both flexural modulus (Ef) and the maximum slope value ((dσ⁄dε)max) of the bending stress–strain curve of carbon fiber reinforced thermoplastic polyetheretherketone (CFRTP) composite sheets with 0.50 mm thickness, although the penetration depth estimated was from 0.14 to 0.21 mm on both side surfaces. HLEBI remarkably enhanced both Ef and (dσ⁄dε)max. The Ef at middle cumulative probability (PE) of 0.50 for CFRTP irradiated at 0.30 MGy (kJg−1) was 3.3 GPa, which was 27% higher (2.6 GPa) than for CFRTP before irradiation. Moreover, (dσ⁄dε)max at middle cumulative probability (PE=0.50) was more than 4.9 GPa for CFRTP irradiated at 0.30 MGy. The interfacial friction force, as well as the strengthening of both carbon fiber and polyetheretherketone probably contributed to the HLEBI effects to enhance both Ef and (dσ⁄dε)max in the CFRTP.
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  • Kazuaki Shimba, Kiyotaka Furuta, Nobuyuki Morimoto, Nobuki Tezuka, Sat ...
    2011 Volume 52 Issue 4 Pages 740-745
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 02, 2011
    JOURNALS FREE ACCESS
    Polymer composites of magnetic particles are widely used as microwave absorbers. An effective method for obtaining thinner microwave absorbers for device design is increasing the volume fraction of magnetic nanoparticles by enhancing the permeability of composites. In this study, composites were prepared using Ni-Zn ferrite nanoparticles surface-modified with 4-META (4-methacryloylioxyethyl trimellitate anhydride) and cross-linked with PEG-4SH (pentaerythritol tetra-polyethylene glycol ether with four thiol-modified terminals). These composites have a high volume fraction of nanoparticles (up to 72 vol%) and permeability (μr max″=5.9). In addition, the prepared composites showed good microwave absorption properties (R.L.<−20 dB) with a smaller matching thickness than conventional microwave absorber using spinel-type ferrite.
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  • Jan Pana Rabatho, William Tongamp, Atsushi Shibayama, Yasushi Takasaki ...
    2011 Volume 52 Issue 4 Pages 746-752
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    In some (Cu-Mo) mines around the world, Mo recovery is low due to poor liberation, fine dissemination in gangue minerals, and losses of Cu and Mo to tailing streams. Studies to recover these materials as a new resource will increasingly become an attractive option. In the current study, a flotation tailing sample obtained from a mine recovering only 40% Mo was re-floated to upgrade Cu and Mo. The sample containing 0.07% Cu and 0.01% Mo, was used in the study and the goal was to improve the grades to over 2.0% Cu and 0.5% Mo, to obtain an additional feed for the flotation process. Sodium aluminium silicate (NaAlSi3O8) and quartz (SiO2) were observed as the dominant mineral phases. The original samples were milled and screened to pass 105 μm screen to be used in the subsequent tests. To evaluate the efficiency of the process, both single and multi-stage flotation steps including de-sliming for the removal of fines and attrition for surface activation, together with other parameters (pH, PAX concentration, time) were performed. Based on the experimental results, a four-stage flotation process allowed the improvement of Cu and Mo grades to 1.63% and 0.24% respectively. A single-stage flotation process with de-sliming and attrition stages before flotation with PAX and MIBC concentrations of 40 g/t improved Cu and Mo grades to 2.07% and 0.64%, with a recovery of 48.60% and 65.97% respectively.
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  • Kazuhiro Matsugi, Yasuhiro Iwashita, Yong-Bum Choi, Gen Sasaki, Koji F ...
    2011 Volume 52 Issue 4 Pages 753-758
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 30, 2011
    JOURNALS FREE ACCESS
    In order to evaluate the stability in long time for the performance of AC-low voltage fuses, this study aimed to measure the changes of the specific resistivity, specific heat and thermal conductivity due to the microstructure-change, using a diffusion couple consisting of the Sn-9Zn fuse element and Cu-connector which are exposed at 443 K for 7.2 ks. The reaction area with the thickness of 5 μm consisting of Sn, Cu and Zn phases, was formed at its interface. The values in their properties were increased due to microstructure-change caused by the diffusion. The equations for the estimation of their values could be represented as a function of temperature. The good stability in long time for the un-melt down performance at 210 A of electric current, was confirmed by three-dimensional voltage and temperature calculations on fuse elements after diffusion.
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  • Yueming Wang, Xiang Xiong, Lu Xie, Xuan Xu, Xiaobing Min, Feng Zheng
    2011 Volume 52 Issue 4 Pages 759-767
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 30, 2011
    JOURNALS FREE ACCESS
    Refractory metallic thin-walled products of 95W–3.5Ni–1.5Fe (in mass%) were fabricated by plasma spray forming (PSF) in argon atmosphere at 1.01×105 Pa followed by high temperature sintering (1200, 1300, 1400 and 1465°C). Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Archimedes method, differential scanning calorimetry (DSC) and X-ray diffractometer (XRD) have been employed to study microstructure, solubilities, density, solidus and liquidus temperatures and phases of the parts. Lamellar structure consisting of vertical columnar grains and fine particles was found in PSF deposits. Supersaturated solid solutions were formed in the deposits with the relative density of 88±2%. Solidus and liquidus temperatures of γ phase were measured to be 1392 and 1412±5°C, respectively. Initial lamellar structure was remained in the tested samples after sintering at lower temperatures (1200°C/90 min, 1300°C/90 min and 1400°C/15, 90 min) and turned into granular structure at 1465°C/5, 15, 30, 90 min. In addition, the relative densities of deposits, after sintering at 1200, 1300, 1400 and 1465°C for 90 min, were increased from 88 to 90, 92, 94 and 98±2%, respectively. A five-stage sintering mechanism proposed by us previously has been re-validated and double checked by experimental results.
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  • Jong-Won Yoon, Chel-Jong Choi, Daewon Kim
    2011 Volume 52 Issue 4 Pages 768-771
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: February 23, 2011
    JOURNALS FREE ACCESS
    Pulsed laser ablation in a liquid phase was employed successfully to synthesize a calcium molybdate (CaMoO4) nanocolloidal suspension. The crystalline phase, particle morphology, particle size distribution, absorbance, optical band-gap and photoluminescence (PL) were examined. Stable colloidal suspensions consisting of well-dispersed CaMoO4 nanoparticles with a narrow size distribution could be obtained without a surfactant. The optical absorption edge located near 270 nm was blue-shifted by approximately 70 nm compared to that reported for bulk crystals. The estimated optical energy band-gap was 4.7 eV and the PL spectrum was blue-shifted at approximately 430 nm compared to the emission of bulk CaMoO4 target (525 nm). The observed band-gap widening and blue-shift of PL emission was attributed to the quantum-size effect due to the very small size of the CaMoO4 nanoparticles prepared by pulsed laser ablation in deionized water.
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  • Hajime Takada, Takafumi Ozeki
    2011 Volume 52 Issue 4 Pages 772-779
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 02, 2011
    JOURNALS FREE ACCESS
    A new ultrasonic testing technique and a new test system using a transducer array have been developed. The test system works as follows: (1) Ultrasonic waves are transmitted from all the ultrasonic transducer elements in the array at the same time; and (2) By additively synthesizing time-converted ultrasound signals transformed from echo signals received by all the ultrasonic transducer elements in the array at the same time, lines of continuously focused receiving beam (receiving needle beam) are closely formed under the transducer array (parallel receiving needle beam). Also, internal flaws in a cross-section are detected at once using the parallel receiving needle beam. The results of experiments using a 50-MHz transducer array and the developed system have proven that ultra-minute internal flaws 20 μm in diameter can be detected at a scan speed of 1000 mm/s. In addition, the focal zone formed is very long as compared with conventional point-focused beam forming. It is concluded that the system is suitable for simultaneous testing of a cross-section of a test object at high scanning speed.
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  • Yui Yamashita, Yunping Li, Hiroaki Matsumoto, Yuichiro Koizumi, Akihik ...
    2011 Volume 52 Issue 4 Pages 780-786
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 02, 2011
    JOURNALS FREE ACCESS
    The high-temperature deformation behavior of Co-29Cr-6Mo-0.23C-0.14N alloy was investigated by carrying out compression tests; the tests were carried out in the temperature range of 1000–1200°C and strain rates ranging from 0.01 to 30 s−1 with a height reduction of approximately 65%. The optimum hot-working conditions were determined from the processing map based on the dynamic materials model. Dynamic recrystallization was observed to occur over the entire temperature and strain rate range. However, uniformly sized grains were formed for strain rates higher than 1 s−1, which is considered to be the optimum hot-working condition. In addition, authors suggested that in extremely low stacking fault energy alloy, explosive and homogeneous formation of mechanical twinning should be considered to be stable state, and new processing map with more detailed description of deformation mechanism seems necessary in future.
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  • De-Chang Tsai, Weng-Sing Hwang
    2011 Volume 52 Issue 4 Pages 787-794
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    The purpose of this study is to predict the morphologies of the solidification process for brass alloys (Cu70Zn30 and Cu65Zn35) by horizontal continuous casting (HCC) and to verify its accuracy by the observed experimental results. This study was extended from previous study (predict the solidification microstructure of pure copper rod by vertical continuous casting process). In numerical simulation aspect, finite difference method (FDM) and cellular automaton (CA) model were utilized to solve the macro-temperature field and micro-nucleation and grain growth of brass alloy respectively. From the observed casting experiment, the unidirectionally solidified brass rod could be fabricated by the HCC process with using cooled mold. The cast grain morphology by CAFD model was corresponding to the result of actual casting experiment well.
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  • Chia-Hung Kuo, Hsiu-Shan Chien, Chii-Shyang Hwang, Ya-Wen Chou, Ming-S ...
    2011 Volume 52 Issue 4 Pages 795-801
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 30, 2011
    JOURNALS FREE ACCESS
    Dense fine-grained PbTe bulk materials without oxide phases are fabricated using a process that combines cryomilling (mechanical milling at cryogenic temperature) and spark plasma sintering (SPS). In the process, micro-grained PbTe powder is cryomilled into nanocrystalline powders, which are then rapidly densified into dense bulk samples with fine grains by SPS at 573 K. The effect of cryomilling on the composition ratio, microstructure, and thermoelectric properties of sintered PbTe samples is investigated. Experimental results indicate that when the grain size decreases to the nano-scale, the Seebeck coefficient increases, the thermal conductivity decreases, and the electrical conductivity only slightly changes for all sintered samples. According to the results, the combination of cryomilling and spark plasma sintering can improve the thermoelectric transport properties of PbTe bulk materials.
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  • Don Hyun Choi, Byung Wook Ahn, Shae Kwang Kim, Yun Mo Yeon, Young Jik ...
    2011 Volume 52 Issue 4 Pages 802-805
    Published: April 01, 2011
    Released: April 01, 2011
    JOURNALS FREE ACCESS
    The present study was carried out to evaluate the microstructural properties of a friction stir welded AZ91 with CaO Mg alloy. For this work, friction stir welding (FSW) was performed at a tool rotation speed of 1250 rpm and a traveling speed of 32 mm·min−1. A network of intermetallic compounds (Al2Ca) was observed in the base metal (BM). In the stir zone (SZ), fine grains and intermetallic compound particles were formed due to dynamic recrystalization and mechanical stirring. The hardness profile showed that the hardness of the SZ was higher than that of the BM, probably due to the presence of fine grains and thermally stable intermetallic compounds.
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  • Masataka Hakamada, Toshiyuki Furukawa, Tao Yamamoto, Masaki Takahashi, ...
    2011 Volume 52 Issue 4 Pages 806-809
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 02, 2011
    JOURNALS FREE ACCESS
    Hydrogen absorption/desorption properties of nanoporous Pt fabricated by dealloying were investigated. At high pressure (>1.3 MPa), the nanoporous Pt released hydrogen during hydrogen pressurization; in contrast, it absorbed hydrogen up to 3.5 atom% during hydrogen depressurization, which have not been seen in current metal/hydride systems including nanoparticles. First-principles calculations suggested that the abnormal hydrogen absorption/desorption properties are due to the relaxation/preservation of the lattice strain in Pt hydride.
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  • T. M. Yue, K. J. Huang
    2011 Volume 52 Issue 4 Pages 810-813
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 09, 2011
    JOURNALS FREE ACCESS
    To improve the wear and corrosion resistance of AZ91D magnesium alloy, Zr-based coatings were fabricated on the alloy substrate using laser forming. They were prepared from (i) Zr+Mg powders (5:1 mass%), and (ii) an undercoating of Zr+Mg powders (5:1 mass%) with a top layer of Zr powder. The Zr+Mg powder coating was found to consist primarily of Zr particles with some Zr-based intermetallic compounds in a Mg-Al matrix; while that with an extra top coating of Zr powder had an outer layer composed of Zr oxides and Zr aluminides. With regard to wear and corrosion resistance, the highest improvement was obtained for the specimen that was clad with a top layer of Zr powder. Compared to the AZ91D specimen without a laser formed coating, a fivefold decrease in weight loss and around three orders of magnitude decrease in corrosion current density respectively were obtained.
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  • Hiroshi Oikawa, Yoshio Waseda
    2011 Volume 52 Issue 4 Pages 814-815
    Published: April 01, 2011
    Released: April 01, 2011
    [Advance publication] Released: March 30, 2011
    JOURNALS FREE ACCESS
    The authors of three papers on Zr-Ti-Al-Ni-Cu amorphous alloy sheets and Zr-Al-Ni-Cu amorphous alloy wires, previously published in Materials Transaction JIM Vol. 39, No. 8 and No. 12 (1998) and Vol. 41, No. 11 (2000), are requested to explain explicitly the reason for the late corrections after more than a decade published in Materials Transaction Vol. 51, No. 8 (2010).
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