MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 43 , Issue 11
Showing 1-50 articles out of 50 articles from the selected issue
  • Kouji Sakaki, Tomoyasu Yamada, Masataka Mizuno, Hideki Araki, Yasuharu ...
    2002 Volume 43 Issue 11 Pages 2652-2655
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Lattice defects induced by hydriding in pure Pd have been studied by means of positron lifetime spectroscopy. Component analyses of positron lifetime spectra show that a surprising amount of vacancies together with dislocations are generated by the hydriding at room temperature. Vacancy migration in pure Pd after hydriding is observed around 378 K . Dislocations are much more stable and its migration is observed around 873 K . During the vacancy recovery process, secondary defects, that is, dislocation loops are formed.
    Download PDF (576K)
  • Tetsuo Mohri, W. A. Oates
    2002 Volume 43 Issue 11 Pages 2656-2661
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    By combining the Tetrahedron-Octahedron approximation of the Cluster Variation Method with a phenomenological expression for the atomic interaction energies, the phase diagram of the Pd-H system in the disordered region is calculated. A miscibility gap is confirmed. The phase separation is caused by the configuration-independent atomic interactions originating from elastic interactions. The temperature dependency of the Short Range Order Diffuse Intensity Spectrum is calculated at four special points. It is found that, with decreasing temperature, the short range order diffuse intensity at (1 1/2 0) in k-space is amplified, implying the existence of a chalcopyrite-type (I41amd) ordered phase at lower temperatures.
    Download PDF (113K)
  • Hiroshi Mizubayashi, Yasushi Ishikawa, Hisanori Tanimoto
    2002 Volume 43 Issue 11 Pages 2662-2669
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The hydrogen internal friction peak (HIFP) in amorphous (a-) Zr60Cu40−yAly (y=0,10), a-Zr50Cu50, a-Zr40Cu60 and a-Zr40Cu50−xAl10Six (x=0,1,3) are studied to pursue a high-strength and high-damping performance as well as the underlying process for the HIFP in a-alloys. The tensile strength, σf, of a-Zr60Cu30Al10, a-Zr40Cu50Al10 and a-Zr40Cu49Al10Si1 increases from about 1.5 GPa to 2 GPa with increasing hydrogen concentration, CH, to 20 at%. One part of a-Zr60Cu30Al10, a-Zr40Cu50Al10 and a-Zr40Cu49Al10Si1 specimens show a very high HIFP beyond 3×10−2 in the as hydrogen charged state, where the hydrogen induced structural relaxation (HISR) proceeds above room temperature. A maximum value of the HIFP, Qp−1, after the HISR shows a moderate increase with increasing CH, about 1×10−2 at CH of 10 at%. The combination of σf and Qp−1 data indicates that a-Zr60Cu40Al10(H), a-Zr40Cu50Al10(H) and a-Zr40Cu49Al10Si1(H) after the HISR are potential materials with a high-strength and high-damping performance. The peak temperature of the HIFP, Tp, at 10 at%H is 309 K, 270 K and 220 K with the measurement frequency of about 200 Hz for a-Zr40Cu49Al10Si1, a-Zr40Cu50Al10 and a-Zr60Cu30Al10, respectively. It is noted that Tp found for a-Zr40Cu49Al10Si1 shows a breakthrough for an elevation of Tp of the HIFP in a-alloys, and that a composite material composed of these a-alloys can serve a high-damping performance in a wide temperature range or a wide frequency range. For the underlying process of the HIFP, the Qp−1 vs.CH data shows a camel’s humps like change for a-Zr50Cu50 and a-Zr40Cu60, suggesting that only one part of hydrogen atoms can contribute to the HIFP . In contrast, Qp−1 shows a monotonous increase with increasing CH for CH below 20 at% for a-Zr60Cu40−yAly (y=0,10) and a-Zr40Cu50−xAl10Six (x=0,1,3), suggesting that most of hydrogen atoms are associated with the HIFP in the a-alloys. For the relaxation parameters of the HIFP, values of 1/τ0 fall in the range expected for a simple relaxation process for a-Zr60Cu40−yAly (y=0,10) and a-Zr40Cu50−xAl10Six (x=0,1,3), but are extremely high for a-Zr50Cu50 and a-Zr40Cu60, where τ0 denotes the pre-exponential factor of the relaxation time. These results are discussed in the light of the amorphous structures in the a-alloys.
    Download PDF (302K)
  • Makoto Arita, Hirofumi Konishi, Masataka Masuda, Yasunori Hayashi
    2002 Volume 43 Issue 11 Pages 2670-2672
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Tin-germanium oxide thin films with various Ge/Sn ratios were deposited by RF magnetron sputtering. The electrical and optical properties of these films were investigated. All the as-deposited films were transparent to visible light. No effect was observed by hydrogen ion implantation on the electrical resistivity of the Ge rich (Sn/Ge≤1) films. On the other hand, hydrogen ion implantation improved the conductivity of the Sn rich (Sn/Ge≥4) films. The enhancement of the conductivity would be attributed to the increase in carrier density by protium introduction.
    Download PDF (78K)
  • L. Y. Zhu, T. Hirae, M. Itakura, N. Kuwano, K. Machida
    2002 Volume 43 Issue 11 Pages 2673-2677
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The microstructural modification for NdFeB magnetic powders (MQP-B) after Zn vapor sorption has been investigated by transmission electron microscopy (TEM). It is found that a coating layer about 100 nm thick was formed on the surface of powder. Selected area electron diffraction (SAED) pattern and high resolution transmission electron microscopy (HRTEM) analyses show that the coating layer consists of condensed nano-scale crystallites of Fe11Zn40, NdZn5 and Zn. After the temperature for Zn vapor sorption is raised to 648 K, a thin layer has been formed on boundaries of Nd2Fe14B grains locally in the rim region of the powders. The morphology of the grain-boundary thin-layers is very similar to that in HDDR-NdFeB magnet powder after Zn vapor sorption treatment. Since the latter has a good thermal stability of magnetic property, the Zn vapor sorption treatment is expected to improve also the thermal stability of MQP-B magnet.
    Download PDF (222K)
  • Teruyuki Ikeda, Michiharu Tsukamoto, Hideo Nakajima
    2002 Volume 43 Issue 11 Pages 2678-2684
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Lotus-type porous stainless steel SUS304L has been fabricated by unidirectional solidification under mixed gases of hydrogen and argon. The atmospheric pressure dependence of porosity and pore diameter has been investigated. The porosity is lower if the partial pressure of argon is higher under a constant partial pressure of hydrogen and is higher if the partial pressure of hydrogen is higher under a constant total pressure of atmosphere composing of hydrogen and argon. Average pore diameter increases with increasing distance from the bottom chill plane. From tensile tests, the ultimate tensile strength of the porous stainless steel with porosity about 50% has been found to be about 7 times lower than nonporous alloy in the direction perpendicular to pore growth direction.
    Download PDF (463K)
  • Kiyoshi Aoki, Katsuhiko Mori, Tsuyoshi Masumoto
    2002 Volume 43 Issue 11 Pages 2685-2691
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The hydrogen pressure dependence of structural changes in C15 Laves phases TbM2 (M=Fe, Co and Ni) were investigated between 0.1 and 5.0 MPa H2 in order to elucidate conditions and the mechanism of hydrogen induced amorphization (HIA). General thermal reactions occur on heating as follows; hydrogen absorption in the crystalline state, hydrogen-induced amorphization (HIA), precipitation of TbH2 (or TbNi5Hx) and decomposition of the remaining amorphous alloys. Exceptionally, a single-phase amorphous a-TbFe2Hx was not formed below 0.2 MPa H2 in TbFe2, because HIA and precipitation of TbH2 simultaneously occurred. On the other hand, a single-phase a-TbNi2Hx was not formed below 1.0 MPa H2 because of the low hydrogen contents in c-TbNi2Hx. The present work indicates that hydrogen absorption more than 1.0 (H/M) is essential for the occurrence of HIA in the C15 Laves phases TbM2.
    Download PDF (314K)
  • Kazuhide Tanaka, Kosuke Nagai
    2002 Volume 43 Issue 11 Pages 2692-2695
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    X-ray diffraction and Auger-electron spectroscopy depth profiling experiments clearly show that an interlayer reaction in a Ni/V bilayer forming Ni3V and Ni2V takes place at a temperature around 823 K when it is annealed in vacuum. However, this reaction temperature is reduced down to around 773 K when it is annealed in 0.5 MPa H2. A similar effect has also been observed for a Ni/Nb bilayer previously. These hydrogen-enhanced reactions in the two systems are interpreted to be due to formation of abundant vacancy-hydrogen complexes in the V and Nb layers, which efficiently assist the interdiffusion of the constituent atoms across the interfaces in the two bilayers.
    Download PDF (98K)
  • Yoshiji Hashimoto, Kohta Asano, Yoshiaki Iijima
    2002 Volume 43 Issue 11 Pages 2696-2702
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The hydrogenation and dehydrogenation behavior of LaNi5−xAlx (x=0–0.5) was studied by the pressure differential scanning calorimetry (PDSC) at the hydrogen pressure range of 1 to 5 MPa in the temperature range from 323 to 573 K with the heating and cooling rates of 2 to 30 K min−1. In the heating runs of the hydride with x≤0.1 two endothermic peaks were observed. With the increase in the aluminum content, the first peak at lower temperature decreased, while the second peak at higher temperature increased. Furthermore, the difference in the temperatures of the peak top decreased with the increase in the aluminum content. In the heating runs of the hydride with x>0.1 only one endothermic peak was observed. These endothermic peaks shifted to higher temperatures with the increase in the hydrogen pressure. Using Ozawa’s method, the activation energies for dehydrogenation and hydrogenation processes were estimated. The activation energy for the dehydrogenation process of the hydrides increased with the increase in the hydrogen pressure and the aluminum content. However, the dependence of the activation energy on the aluminum concentration in the range of x≥0.1 was different from that of x<0.1. The activation energy for the hydrogenation process was estimated only in the range of x>0.1 at the hydrogen pressure of 5 MPa. The value of activation energy for the hydrogenation was lower than that for the dehydrogenation.
    Download PDF (282K)
  • Takanori Suda, Masaki Ohkawa, Shougo Sawada, Seiichi Watanabe, Somei O ...
    2002 Volume 43 Issue 11 Pages 2703-2705
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    In order to improve initial activation properties of TiFe alloy, simple ion implantation and ion mixing with the deposition of LaNi5 were carried out at room temperature. The results show that argon-ion mixing caused extensive improvement of initial activation, wherein hydrogenation was easily effected at 373 K and 1 MPa. Those results are related to several irradiation effects; the re-crystallization of amorphous film of LaNi5 and the local segregation of composed elements. Both of these irradiation effects greatly improve the initial hydrogenation process of TiFe alloy.
    Download PDF (104K)
  • Chiaki Iwakura, Hiroshi Inoue, Naoji Furukawa, Shinji Nohara
    2002 Volume 43 Issue 11 Pages 2706-2710
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Hydriding-dehydriding and charge-discharge characteristics of amorphous MgNi alloys modified by ball-milling with different carbon materials were investigated with the intention of using them in nickel-metal hydride batteries. It was found that the ball-milling with carbon materials markedly improved hydriding-dehydriding and charge-discharge characteristics of the MgNi alloy, and an optimum ball-milling time was shortened by utilization of carbon material with lower crystallinity. However, ball-milling for longer than the optimum time led to a decrease in the amount of absorbed hydrogen and the discharge capacity, which was ascribed to the formation of MgNi3C . These results indicate that the characteristics of MgNi alloy-carbon material composites greatly depend on both crystallinity of carbon material used and ball-milling time.
    Download PDF (129K)
  • Tiejun Ma, Yuji Hatano, Takayuki Abe, Kuniaki Watanabe
    2002 Volume 43 Issue 11 Pages 2711-2716
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Amorphous MgNi was modified by ball milling with perylene and its effects on the charge/discharge capacity were examined by using a conventional two-electrode cell. It was found that both the ball milling time and perylene/MgNi ratio had great influence on the discharge capacity and cycle life of MgNi. Three types of effects were identified, depending on ball-milling conditions. One of them was the increase in the discharge capacity at the first cycle, the second type was the deceleration of the degradation of the discharge capacity with charge/discharge cycle, and the last type was the reduction in the charge/discharge capacity. Chemical states of modified surfaces were analyzed by Auger electron spectroscopy (AES) as well as ab-inito calculation. Both AES and ab-initio calculations indicated that carbon atoms can form bonding with both magnesium and nickel atoms, but bonding with magnesium atoms is most preferable. The change in the charge/discharge capacity is attributed to such kind of reactions, and the three distinct effects are ascribed to the presence of different MgNi-perylene composites, formed during the ball milling on the surface, resulting in the retardation or acceleration of Mg(OH)2 formation on the electrode.
    Download PDF (569K)
  • Yasuyuki Goto, Atsunori Kamegawa, Hitoshi Takamura, Masuo Okada
    2002 Volume 43 Issue 11 Pages 2717-2720
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    A new hydride in the MgH2–YH3 system was found by using a high pressure of 5 GPa, and their crystal structure, thermal stability and hydrogen content were studied. The high-pressure synthesis was carried out at 1073 K for 2 h under 5 GPa by using an anvil-type apparatus. In the MgH2xat%YH3 system (x=33–100), novel hydride was synthesized near x=67 (MgY2Hy). This phase exhibited a FCC-type structure with a cell parameter of a=0.516 nm. This high-pressure phase was dehydrogenated at about 600 K under an Ar atmosphere of 0.05 MPa, and the FCC structure was maintained after dehydrogenation. The amount of hydrogen desorbed at about 600 K was 1.4 mass%.
    Download PDF (236K)
  • Hironobu Fujii, Koichi Higuchi, Kenichi Yamamoto, Hideshi Kajioka, Shi ...
    2002 Volume 43 Issue 11 Pages 2721-2727
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    In this paper, we review our recent results on hydrogen storage, structural and optical properties in multi-layered Pd/Mg thin films. The thin films were prepared using a RF associated magnetron sputtering method, in which the structure in Mg layer was controlled into columnar-like textures with several tens nanometer in diameter by optimizing the sputtering conditions. The results obtained indicate that hydrogen of ∼ 5 mass% absorbs at 373 K in Mg under a hydrogen pressure of 0.1 MPa in multi-layered Pd/Mg films and the hydrogen desorbs at 360 K in vacuum. Such excellent hydrogen storage properties are explained by cooperative phenomena that hydrogen displays in nano-composite interface boundary regions between the Pd and Mg films. In addition, we experimentally confirmed at the first time that the rare earth and nickel free two-layered Pd/Mg film displayed optical transparency upon hydrogenation.
    Download PDF (334K)
  • Hayato Okumura, Akihiro Matsui, Shintaro Yamagiwa, Shigeharu Kamado, Y ...
    2002 Volume 43 Issue 11 Pages 2728-2733
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    In this study, an attempt is made to form composites by mechanical alloying (MA) or pulse-electric-current-sintering (PECS) for utilization of synergy effect to acquire both high capacity and ability to absorb/desorb protium at low temperatures. The composites have well-bonded structure consisting of Mg2Ni alloy that has high hydrogenation capacity and LaNi5 alloy that is capable of protium absorption/desorption at relatively low temperatures. During the absorption process, the protium content of MA+PECS and MA specimens at 80°C is over the theoretical value corresponding to the ratio of LaNi5 phase. After absorption of the maximum protium content at 40°C by MA+PECS specimen, the desorption process was evaluated by TG/DTA analysis and the specimen starts desorbing protium at about 100°C. Consequently, the result suggests the occurrence of synergy effect during the absorption/desorption process of the obtained composites.
    Download PDF (312K)
  • Kunihiko Hashi, Kazuhiro Ishikawa, Kiyonori Suzuki, Kiyoshi Aoki
    2002 Volume 43 Issue 11 Pages 2734-2740
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Titanium aluminides [L10-TiAl (Ti0.50Al0.50 and Ti0.40Al0.60), TiAl2 and D022-TiAl3] have been mechanically ground (MG) in an argon atmosphere. In addition, hydrogen absorption and desorption properties of the MG-alloys have been investigated. Hcp- and amorphous (a-) TiAl, fcc- and a-TiAl2 and fcc-TiAl3 are formed by mechanical grinding (MG) of TiAl, TiAl2 and TiAl3, respectively. Although original Ti-aluminides do not absorb hydrogen, hcp- and a-TiAl, and fcc- and a-TiAl2, prepared by MG, having a fresh surface absorb hydrogen of the amount of 0.4−0.1 (H/M). The present work clearly demonstrates that MG is a useful technique for an emergence of the hydrogen absorption ability of intermetallic compounds containing much hydride-forming elements.
    Download PDF (934K)
  • Hirofumi Homma, Hideyuki Saitoh, Atsunori Kamegawa, Masuo Okada
    2002 Volume 43 Issue 11 Pages 2741-2747
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Hydrogenation behavior in Ti–Cr alloys with compositions around TiCr2 Laves phase has been examined by the tritium radioluminography and the PCT measurement. All of the specimens have been two-phase structure of BCC phase and Laves phase. The ratio of the BCC phase to the Laves phase has been increased as increasing the heat treatment temperature. The Ti-rich BCC phase and Cr-rich BCC phase have been formed in the Ti50Cr50 alloy and the Ti30Cr70 alloy, respectively. It is found that hydrogen easily penetrates into the Laves phase in the initial stage of hydrogen penetration. In the PCT measurements, Ti50Cr50 alloy absorbed the largest amount of hydrogen. The maximum protium storaging capacity of 3.5 mass% was obtained in the Ti50Cr50 specimen heat treated at 1400°C at the measured temperature of 150°C. The plateau of PCT curves in Ti50Cr50 alloy and Ti30Cr70 alloy appeared at low hydrogen pressure and high hydrogen pressure region, respectively. These plateaus are attributed to the Ti-rich BCC phase and the Cr-rich BCC phase, respectively.
    Download PDF (1306K)
  • Takashi Kazumi, Takuya Tamura, Atsunori Kamegawa, Hitoshi Takamura, Ma ...
    2002 Volume 43 Issue 11 Pages 2748-2752
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Ti–Cr–V alloys with a BCC structure have high protium capacities, but it is known that the cyclic properties for the alloys change with varying V content. In this paper, the cyclic properties of the Ti–Cr–V alloys are investigated in view of the crystal structure of the β protide phase, which was measured at the point after desorbing at the plateau region and the thermal stability of the γ protide phase, which was measured at the point immediately before desorbing at the desorption region. It was found that the crystal structure of the β phase was changed from BCC phase to BCT phase and the ca increased with increasing the cycle number. This difference of the crystal structure of the β phase suggests that the lattice can’t gradually contract to a-axis direction at absorbing process with increasing the cycle number. Furthermore, it was found that the absorption-desorption cycle process causes the declined slope of the ΔH plots due to existence of the different γ protides of different thermal stabilities. Namely, this result suggests that site energies of protium in the lattice have a distribution after absorption-desorption cycles.
    Download PDF (220K)
  • Takuya Tamura, Takashi Kazumi, Atsunori Kamegawa, Hitoshi Takamura, Ma ...
    2002 Volume 43 Issue 11 Pages 2753-2756
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Ti–Cr–V alloys have a higher protium (hydrogen atom) desorption capacity, but a larger hysteresis in the absorption and desorption processes than AB2 and AB5 type protium absorption alloys. It is desirable that the alloys have a smaller hysteresis for the use of hydrogen storage tanks. This paper aims to clarify the effects of protide (hydride) structures on the hysteresis in Ti–Cr–V protium absorption alloys. It was found that the β phases observed after desorbing at the desorption plateau region had the BCC structure for the alloys (Ti:Cr=2:3) containing less than 70 at%V, but the BCT structure for the alloys (Ti:Cr=2:3) containing more than 70 at%V . A major reason for the large hysteresis in the Ti–Cr–V alloys appears to be the a-axial contraction in the absorbing process and the a-axial expansion in the desorbing process as opposed to the c-axial changes.
    Download PDF (134K)
  • Hiroshi Yukawa, Daisuke Yamashita, Shigeyuki Ito, Masahiko Morinaga, S ...
    2002 Volume 43 Issue 11 Pages 2757-2762
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The alloying effects on the stability of vanadium hydrides have been investigated systematically for binary V–M and ternary V–Ti–M alloys, where M’s are various alloying elements. The PCT curves for the β phase (V2H or VH) are measured at low hydrogen pressures using an electrochemical method. On the other hand, for the γ phase (VH2), the PCT curves are measured at high hydrogen pressures using an ordinary Sieverts-type apparatus. It is found that the phase stability of vanadium hydrides is affected strongly by the presence of a small amount of elements added to vanadium metal. The alloying effects on the hydride stability are different between the γ phase and the β phase. For example, the γ phase becomes most unstable when the group 8 elements in the periodic table, Fe, Ru and Os, are added to vanadium metal. On the other hand, the stability of the β phase changes monotonously following the order of elements in the periodic table. Also, the efficiency of alloying element in modifying the hydride stability is found to be different between the β1 phase (V2H) and the β2 phase (VH). In addition, it is shown that the logarithm of the plateau pressures for the β1 and the γ phases change almost linearly with the amount of alloying element in the alloy. Using this linear relationship for the γ phase, the second plateau pressures of ternary V–Ti–Ru and V–Ti–Cr alloys can be estimated quantitatively in the wide compositional range.
    Download PDF (190K)
  • Masahiro Itoh, Masahiro Masuda, Ken-ichi Machida
    2002 Volume 43 Issue 11 Pages 2763-2767
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    A series of fine powders of Fe–MOx (M=Ce, Al, Si, Sr, and Zr) composite were prepared by the conventional coprecipitation method from their nitrate solutions. The activity of hydrogen extraction from ammonia over these composite powders as ammonia cracking catalyst was characterized. The catalytic activity for ammonia decomposition observed on the composite powders of Fe–(Ce, Zr)O2 was high because of the electron donation to the iron metal from Ce3+ due to the reduction of CeO2 through the reaction. In addition to this effect, the additive (Ce, Zr)O2 solid solution supports worked as a solid acid to enhance the ammonia adsorption and reaction probability of Fe component. These were effective to generate hydrogen through the ammonia decomposition at relatively low temperature.
    Download PDF (158K)
  • Jun Nakahigashi, Hirofumi Yoshimura
    2002 Volume 43 Issue 11 Pages 2768-2772
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Superplastic-tensile test and superplastic forming for the denture base (One of the dental parts) were carried out experimentally using an α+β two-phase type Ti–6Al–4V alloy with an ultra-fine grained structure (grain size: 0.3–0.5 \\micron) obtained through protium treatment. The ultra-fine grained material exhibited a significant superplastic elongation of over 9000% at 1123 K and a flow stress lower than that of coarse-grained material made from the same alloy without protium treatments. Superplastic forming was successfully used to fabricate a denture base without cracks on the surface. These materials may be applicable as biomaterials in medical industries.
    Download PDF (433K)
  • Keiko Sasaki, Mai Endo, Kunihiko Kurosawa, Hidetaka Konno
    2002 Volume 43 Issue 11 Pages 2773-2777
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    To apply manganese-oxidizing bacteria to waste water treatment, basic performance of the manganese-oxidizing bacterium, Leptothrix discophora, distributed by ATCC was examined. In addition, the effect of carbon fiber on the oxidation by the bacterium was also investigated, since carbon fiber was reported to accelerate the growth of activated sludge during sewage treatment. The bacterium was found to be active in the medium containing 24 ppm Mn(II) ions, the concentration being about 8 times higher than the recommended one and practically useful level. The oxidation rate was higher with the static culture than the shaking culture. This was considered to be due to physical damage to the sheath structure of bacteria which is reported to be important to oxidize Mn(II) ions. The carbon fiber did not accelerate the microbial oxidation of Mn(II) ions. This is partly attributed to the lack of contact between the bacterial cell, which floated as thin membranes, and the carbon fiber sunk in the bottom of vessels. However, oxidized Mn species precipitated on the carbon fiber, which resulted in an improvement of the transparency of water. This effect is different from the one caused by activated carbons, since the carbon fiber has very low specific surface area and no pore structure. The effect was more remarkable in the shaking culture than the static culture, indicating that organic substances originated from the bacterium play an important role in the adsorption of oxidized Mn species.
    Download PDF (176K)
  • Keiko Sasaki, Takanori Haga, Tsuyoshi Hirajima, Kunihiko Kurosawa, Mas ...
    2002 Volume 43 Issue 11 Pages 2778-2783
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The vertical distributions of heavy metals and other elements in sediment core samples in a landfill of abandoned mine tailings were examined. Core samples were analyzed by XRF and XRD, and further examined by ICP-AES measurements after acid-sequential extraction with HCl, HF, and HNO3. According to XRD, the sediments contained α-quartz as the main component, and sericite, chlorite, rhodochrosite, pyrite, jarosite, sphalerite, and galena as minor components. A complete decomposition method using sequential extraction for the mine tailings sediments was established at ambient temperatures. Acid sequential extraction was useful for the analysis of minerals in mine tailings which are difficult to detect by XRD . Rhodochrosite and chlorite were dissolved by HCl-extraction, quartz and sericite by HF-extraction, and sulfides by HNO3-extraction. Rhodochrosite was the main source of high concentrations of Mn in mine drainage, highly distributed below the −100 cm zone in the mine tailings, combined with pyrite but not with sericite and quartz. The distributions of most heavy metals were related to those of pyrite.
    Download PDF (219K)
  • Yosuke Tamura, Tadashi Haitani, Eiji Yano, Tetsuichi Motegi, Norio Kon ...
    2002 Volume 43 Issue 11 Pages 2784-2788
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Grain refining mechanisms of Fe- and Mn-free high-purity Mg–Al alloy ingots and the influence of a small addition of Fe or Mn on their cast structures are investigated. In order to prepare the alloys, distilled pure magnesium (<99.99%) and commercial high-purity aluminum (99.99%) were melted, and given amounts of Fe and Mn were added to the molten alloys. The grain size of the high-purity alloy is refined naturally without the use of a grain refiner or superheat treatment, and the addition of small amounts of Fe and Mn to the alloy coarsens the grains. In the composition range of Fe or Mn where magnesium does not crystallize from the melt as the primary crystal, both grain-coarsening and the effect of superheat treatment are remarkable. EPMA and AES analyses reveal a dispersion of fine particles composed of Mg, O, Al, and C elements in the high-purity alloy. Some combination of these elements seems to be an effective nucleation substance for magnesium crystal, and the nucleation substance is similar to those whose presence has been confirmed in AZ91E alloy to which a proper amount of carbide was added. In coarse-grained alloys, Fe and Mn elements coexist with the above-mentioned nucleation substances, and this disturbs the grain refinement.
    Download PDF (218K)
  • Kenji Matsuda, Shohei Taniguchi, Kosuke Kido, Yasuhiro Uetani, Susumu ...
    2002 Volume 43 Issue 11 Pages 2789-2795
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Morphology and crystal lattice of precipitates formed in the 6000 series Al–Mg–Si alloys containing Cu and transition metals of Cr and Fe (TM) after aging at 523 K were investigated by high-resolution transmission microscopy (HRTEM). The precipitates in the Cu-bearing alloys are more finely and densely distributed than those in the Cu-free alloys, whereas those in the TM-bearing alloys were coarser and formed inhomogeneously at the interfaces between the dispersoids and the matrix. Three kinds of metastable phases were detected by HRTEM as follows: β-phase in the balanced alloy, the TYPE-B precipitate in the excess-Si alloy, and Q-phase in the Cu-bearing alloys. No significant difference in between the precipitates in the TM-free alloys and in the TM-bearing alloys was observed. However, the Type-B precipitate in the excess-Si alloy was replaced with the β-phase by the addition of TM . This suggests that the chemical composition of the excess-Si alloy changes to the balanced composition, because the excess Si in the matrix has been consumed by the formation of the AlSi(Fe, Cr) and AlSiFe dispersoids.
    Download PDF (600K)
  • Yong-Jai Kwon, Makoto Kobashi, Takao Choh, Naoyuki Kanetake
    2002 Volume 43 Issue 11 Pages 2796-2801
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Aluminum matrix composites reinforced with TiB2 particles which were synthesized in situ by a combustion reaction between titanium and boron were fabricated from powder mixtures of Al, Ti and B . The combustion reaction was generated in the compacted powder mixtures with and without preheating by an ignitor. The influences of a powder mixing ratio, porosity and preheating of the compacted reactant on the combustion reaction for the Al–Ti–B system were experimentally investigated. The aluminum matrix composites including 30 to 60 vol%TiB2 could be fabricated by the combustion reaction without preheating, but some macroscopic cracks were occurred in the composites except for the Al–50 vol%TiB2. The relatively large porosity and preheating before the combustion reaction were effective to the self-propagation of the combustion reaction and microstructure of the synthesized composites, especially in the low volume fraction of TiB2. The reaction between titanium and boron in the Al–Ti–B system was initiated after the melting of aluminum.
    Download PDF (259K)
  • Yongfu Zhu, Kouji Mimura, Yukio Ishikawa, Minoru Isshiki
    2002 Volume 43 Issue 11 Pages 2802-2807
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Floating zone refining of copper under a reduced hydrogen pressure of 0.7 Pa has been carried out. Commercial 99.9999% pure 8-mm-diameter Cu rod was used as a starting material. The purification effect has been examined by the bulk residual resistivity ratio (RRRB) and glow discharge mass spectrometry (GDMS). The RRRB of the starting material is 3200, and that of refined copper is 22000. Almost all impurities were effectively reduced to near or below their detection limits of GDMS . The removal of S and Se is attributable to the reaction with hydrogen. The marked decrease of Al and Si is ascribed to a convective transportation of alumina and silica inclusions to the surface of the molten zone, and these inclusions are concluded to come from the starting material. This result suggests that trace amounts of Al and Si present as solid solution in starting material can be removed in the same manner by zone melting in a slight oxidizing atmosphere for the first few passes.
    Download PDF (315K)
  • Kyung Seon Min, Soo Chan Lee, Soo Woo Nam
    2002 Volume 43 Issue 11 Pages 2808-2812
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    In order to investigate the effects of TiC and Cr23C6 carbides on creep-fatigue behaviors, total strain range controlled creep-fatigue tests of TiC and Cr23C6 aged AISI 321 stainless steels with the same carbide density at the grain boundary were conducted at 600°C. It is observed that creep-fatigue life of TiC aged alloy is longer than that of Cr23C6 aged alloy in the same test conditions. To verify the origin of the difference in creep-fatigue life between the two alloys, microstructural observations are conducted by scanning electron microscope (SEM) and transmission electron microscope (TEM). It is understood to be due to the strong cavitation resistance of TiC aged alloy compared with that of Cr23C6 aged alloy. It is considered that formation and growth of cavities are retarded by strong interfacial affinity between TiC and matrix.
    Download PDF (437K)
  • Masahiro Tahashi, Kensuke Sassa, Shigeo Asai
    2002 Volume 43 Issue 11 Pages 2813-2817
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Non-magnetic materials of bismuth and zinc were deposited on glass and copper plates used as a substrate under a high magnetic field of 12 T . The substrate was set in perpendicular or parallel to the magnetic field direction at the position of the maximum magnetic field intensity. In the case with the glass substrate, no significant difference in the surface aspect of a film was observed regardless of target materials and the magnetic field direction to the substrate. On the other hand, in the case with the copper substrate, the surface aspect of the zinc film deposited under the magnetic field was different from that under no magnetic field, but no difference was observed in the bismuth film. These experimental results are discussed from the viewpoint of electric conductivity of the substrates and target materials.
    Download PDF (767K)
  • Katsuhiko Asami, Michio Kikuchi
    2002 Volume 43 Issue 11 Pages 2818-2825
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Several weathering steels and a plain carbon steel exposed to atmosphere for 17 years at Yokkaichi (at a coastal and industrial region) and Mikuni Pass (at a rural region) in Japan were analyzed and compared to find effects of environments on the formed rusts. Specimens were examined with electron probe microanalysis (EPMA), X-ray diffraction (XRD) and transmission electron microscope (TEM). Their cross-sections were also analyzed by EPMA . XRD detected mainly α-FeOOH as major rust constituent and β-FeOOH and γ-FeOOH as minor ones in the surface region. The concentration of β-FeOOH was especially high on the skyward surface of all the specimens irrespective of steel composition. EPMA results showed that Si, Na, S were abundant on the skyward surface. In the cross-section, alloying elements Cu and Cr were enriched in the inner layer of rust as well as Si, while P and Ni did not show any characteristic distribution. TEM examination of cross-section of rusts showed that α-FeOOH was also main constituent of the rust. The β-FeOOH showed no special distribution feature in the main part of rust except in the very surface region. Amorphous rust judged from electron diffraction pattern and Fe3O4 distributed mainly near the interface between steel and rust layer. The γ-FeOOH was contained much more in rust on plain carbon steel than weathering steels. A quantity ratio α⁄γ, that is, the ratio of α-FeOOH to the sum of β-FeOOH, γ-FeOOH and magnetite, is >1 for a weathering steel, and <1 for a mild steel. The Si in the inner layer was suggested in the form of SiO44− state. There was almost no difference between specimens exposed at the industrial region and the rural region because of chloride sprayed for melting snow on road during winter at the rural region.
    Download PDF (437K)
  • Hideo Nakae, Yoshio Igarashi
    2002 Volume 43 Issue 11 Pages 2826-2831
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The nuclei of spheroidal graphite (abbreviated SG) were studied using an FE-SEM and an EDS. Many kinds of SG irons with different sulfur contents were prepared for the observation of the nucleus-like core materials. The Mg-treated SG iron was cast into a thin CO2 sand mold and a chilled test piece that is usually used for chemical analysis. The core materials were observed using the chilled test piece. The number of SGs is maximum in the range from 0.010 to 0.025 mass%S of the base melt and the nucleus material is MgS. We propose that this is the most desirable S content for the production of the SG iron castings. This S level is nearly identical to that of the base melt chemical composition for commercial SG iron production. If the S content of the base melt is greater than 0.005 mass%S, the SG nucleus is a spherical MgS in the Mg-treated SG iron. On the other hand, when the S content is less than 0.0022 mass%, the nucleus is a hexagonal (Mg, Si, Al)N as reported by Skaland and Solberg et al.
    Download PDF (467K)
  • Toshimasa Wadayama, Tuyoshi Arigane, Kensho Hayamizu, Aritada Hatta
    2002 Volume 43 Issue 11 Pages 2832-2837
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Rapid thermal oxidation and quenching in liquid nitrogen (RTOQN) has been examined on anodized porous silicon (PS). The as-anodized PS samples exhibit a photoluminescence peak at 750 nm that decays instantaneously upon discontinuance of 325-nm He–Cd laser irradiation. In contrast, PS samples after RTOQN show a luminescence peak at 560 nm that decays very slowly (>1 s). In this paper some detailed RTOQN conditions leading to such a slow-decay photoluminescence are defined.
    Download PDF (268K)
  • Lihe Qian, Toshiro Kobayashi, Hiroyuki Toda, Takashi Goda, Zhong-guang ...
    2002 Volume 43 Issue 11 Pages 2838-2842
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The fracture toughness of 6061Al alloy metal matrix composite reinforced with 15 vol% fine SiC particles of 600 nm in size under a high temperature over-aged condition was studied. And the toughness of the 6061Al matrix alloy and the same matrix alloy reinforced with coarse SiC particles of 9.5 \\micron were also measured for comparison. Fracture toughness tests were conducted on a servo-hydraulic testing machine by using three point bending specimens. The results showed that the toughness of the fine particle reinforced composite was obviously higher than that of the coarse particle reinforced composite in terms of crack initiation toughness, crack propagation energy and total absorbed energy. The mechanisms controlling the fracture toughness of the two composites reinforced with fine and coarse SiC particles were discussed based upon the measured toughness data and microstructure examinations by means of an optical microscope and a scanning electron microscope.
    Download PDF (240K)
  • Takeshi Wada, Tao Zhang, Akihisa Inoue
    2002 Volume 43 Issue 11 Pages 2843-2846
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    A Zr–Al–Co ternary alloy was investigated in order to clarify the glass-forming ability, thermal stability and mechanical properties. The Zr55Al20Co25 alloy was found to be fabricated in bulk glassy alloy rods with diameters up to at least 2.5 mm. The glassy alloy rod of 2.5 mm in diameter exhibits a large supercooled liquid region of 79 K, followed by a nearly single exothermic peak due to the precipitation of ZrCo+ZrAlCo+Zr6Al2Co phases. The glassy alloy rod exhibits Young’s modulus of 114 GPa, high compressive fracture strength of 1900 MPa and total fracture elongation of 1.7%. The finding of forming the bulk glassy alloy at the new ternary composition of Zr55Al20Co25 by the copper mold casting method is encouraging for future search of a new glassy alloy composition.
    Download PDF (117K)
  • Yoshiki Mizutani, Hideyuki Yasuda, Itsuo Ohnaka, Akira Sugiyama, Satos ...
    2002 Volume 43 Issue 11 Pages 2847-2854
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    This paper presents a selection of the eutectic systems in the Al2O3–Y2O3–ZrO2 pseudo-ternary system and the production of the undercooled melt due to melting of the metastable eutectic structure at the metastable eutectic temperature. In the pseudo-ternary system, there are two eutectic systems; one is the Al2O3–YAG(Y3Al5O12)–ZrO2 equilibrium system and the other is the Al2O3–YAP(YAlO3)–ZrO2 metastable system. The eutectic system was selected by maximum melt temperature before solidification. YAG nucleation was inhibited in the melt when heated above 2250 K and consequently the metastable eutectic solidification path was selected. The selection controlled by the melt temperature before solidification was similar to that of the Al2O3–Y2O3 system. Furthermore, the undercooled melt formation was found when the Al2O3–YAP-ZrO2 metastable eutectic structure was heated up to temperatures above the metastable eutectic temperature. The addition of ZrO2 to the Al2O3–Y2O3 system inhibited the YAG nucleation remarkably and enhanced the undercooled melt formation in comparison with the Al2O3–Y2O3 pseudo-binary system. Ease of the undercooled melt formation in the pseudo-ternary system will be beneficial for the melt shaping processes.
    Download PDF (448K)
  • Bo-Ping Zhang, Hiroshi Masumoto, Yoshihiro Someno, Takashi Goto
    2002 Volume 43 Issue 11 Pages 2855-2859
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Au/SiO2 nano-composite multilayers were prepared by helicon plasma sputtering. The Au particles dispersed in the SiO2 matrix grew with increasing deposition time in the initial time less than 10 s, then changed from network-like to film-like microstructure with increasing deposition time. The optimum deposition time for preparing the Au particles was 8 s, and the size of Au particles was about 6 to 8 nm. The absorption peak due to the surface plasmon resonance of Au particles was observed at the wavelength of 560 nm in the optical absorption spectra for the as-deposited Au/SiO2 thin films containing 3.3 to 10.3 vol%Au. The intensity of the absorption peak increased with increasing Au content, and the optimum Au content was about 10.3 vol%.
    Download PDF (358K)
  • Mutsumi Takeda, Naoki Morihiro, Ryuichiro Ebara, Yoshio Harada, Ronggu ...
    2002 Volume 43 Issue 11 Pages 2860-2865
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    WC–Co thermally sprayed coating, formed by high velocity oxygen-fuel flame spraying, has had the problem of low corrosion resistance in aqueous solutions. Furthermore, much remains unknown regarding corrosion reactions on coating surfaces and the formation of passivation films. This study focused on changes of the corrosion surfaces of two thermally sprayed coatings, WC–12Co and WC–10Co–4Cr, with immersion time. The chemical composition of the corrosion surfaces was analyzed by electron spectroscopy, and the relation with passivation film stability is discussed. For WC–12Co, the thermally sprayed coating was immersed in Na2SO4 solution. The W and Co components were dissolved by extended anodic reaction. Oxides of W and Co were then formed on the surface of the thermally sprayed coating. However, these oxides appeared to have little effect on the corrosion. Passivation film, which mainly consists of Cr2O3, was formed on the surface of WC–10Co–4Cr thermally sprayed coating immediately after immersion, and limited the dissolving of coating components into the aqueous solution. However, it is suspected that this film did not completely cover the entire coating surface. It is probably a thin porous film formed as islands.
    Download PDF (337K)
  • Hidekazu Sueyoshi, Tomohito Maruno, Masahiro Asano, Yoshihiro Hirata, ...
    2002 Volume 43 Issue 11 Pages 2866-2872
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Processing of a continuous ceramic fiber/iron alloy composite by powder metallurgy was investigated. The preparation of a continuous ceramic fiber-reinforced iron alloy is feasible by mixing of continuous ceramic fibers and iron alloy powders in an ultrasonic equipment with acetone, followed by hot isostatic pressing (HIPing) or hot pressing (HPing) at 1273 K . In HPing, a volume fraction of ceramic fibers in the composite in which ceramic fibers are distributed uniformly depends upon a diameter of ceramic fibers and a mean particle size of iron alloy powders. When a volume fraction of ceramic fibers is more than an optimum value, the excess fibers aggregate, resulting in nonuniform dispersion of ceramic fibers. Nonuniform dispersion is also achieved because of the formation of ceramic fiber-free region when a volume fraction of ceramic fiber is less than the optimum value. In uniform dispersion of ceramic fibers, volume fraction of ceramic fibers in HIPed composite is higher than that in HPed composite. This is because ceramic fiber migration due to high stress occurs during HIPing. Therefore, to obtain the composite with uniform dispersion of ceramic fibers, the specimen is to be uniformly deformed during HIPing.
    Download PDF (596K)
  • Hector M. Henao, Mitsuhisa Hino, Kimio Itagaki
    2002 Volume 43 Issue 11 Pages 2873-2879
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    To provide thermodynamic data for converting the nickel matte to liquid nickel, an experimental study was conducted in the phase equilibrium between the Ni–S alloy and the CaO–Al2O3 based slag melted in a MgO or Al2O3 crucible at 1773 K under controlled PSO2 of 10.1 kPa and PO2 in a range between 5.0×10−3 and 1.6 Pa by using CO–CO2–SO2 gas mixtures. The contents of nickel in these slags at PO2 of 1.6 Pa, above which solid NiO is expected to precipitate in equilibrium state, were found to be 5.6 and 7.2 mass% for the slags melted in the MgO and Al2O3 crucibles, respectively. The contents of sulfur and oxygen in the nickel melt at PO2 of 1.6 Pa were 2 and 0.4 mass%, respectively. The CaO–Al2O3 based slag with the mass% ratio (CaO/Al2O3) of about 1 melted in the MgO crucible was homogeneous in the investigated PO2 range. While, that with the ratio of about 0.5 melted in the Al2O3 crucible formed two phases composed of a liquid and an Al2O3–NiO solid solution whose nickel content was increased with increasing PO2. The dissolutions of nickel and sulfur in the slag melted in the MgO crucible were discussed on the basis of distribution ratio and sulfide capacity, respectively.
    Download PDF (261K)
  • Tetsuro Tohma, Hiroshi Masumoto, Takashi Goto
    2002 Volume 43 Issue 11 Pages 2880-2884
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Barium titanate (BaTiO3) films were prepared on (100)Pt/(100)MgO substrates by metal-organic chemical vapor deposition (MOCVD). The effects of deposition temperature (Tdep) and O2 partial pressure (PO2) on the microstructure and dielectric properties of the films were investigated. The BaTiO3 films prepared at Tdep=873 K showed a randomly orientated granular structure, while those prepared at Tdep=973 K showed a significant (001) orientation with a columnar structure. The grain size was strongly affected by PO2 and showed the maximum at PO2=66 to 93 Pa. The dielectric constant increased from 93 to 640 with increasing grain size from 20 to 130 nm, showing a broad peak at 350 to 380 K.
    Download PDF (216K)
  • Minoru Yamasaki, Masaaki Hamano, Takayuki Kobayashi
    2002 Volume 43 Issue 11 Pages 2885-2889
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    In order to investigate the crystallization process of an α-Fe/Nd2Fe14B type nanocomposite magnet alloy, Mössbauer study has been carried out on Nd8Fe80Co4Nb1.5B6.5 alloy ribbons prepared by melt spinning and post-heat-treatment at 600, 650, 700 and 760°C. The relative mass fractions of the α-Fe, Fe3B, Nd2Fe14B and the intergranular phases, in crystallization process, were estimated from Mössbauer line-intensities. As-quenched alloys are practically amorphous states and start to crystallize at 600°C, but the crystallized grains are still so fine as to be observed with X-ray diffraction method and the Mössbauer spectroscopy. Around 650°C, α-Fe, Nd2Fe14B and metastable Fe3B phases are formed definitely and the amorphous phase decreases drastically but still remains as the intergranular phase. With increasing temperature, metastable Fe3B phase converts into α-Fe, Nd2Fe14B, and a part of the intergranular phases also crystallize to form α-Fe and Nd2Fe14B . At 760°C being the optimum heat-treating temperature to obtain the alloy with the best magnetic properties, about 10 mass% of the intergranular phases is considered to remain between the grains of α-Fe and Nd2Fe14B.
    Download PDF (163K)
  • Toshiaki Himemiya, Waldemar Wolczy\\`{n}ski
    2002 Volume 43 Issue 11 Pages 2890-2896
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    The micro-segregation of an iron-based multi-component alloy, where the liquid is assumed to be completely mixed and finite diffusion works in the solid, is calculated by a simple method. With this method, not only the solidification path in which the solute distribution ratios change as functions of the composition, but also the solute redistribution profile after solidification can be estimated. As examples, the solidification path and solute redistribution for an iron-carbon-nickel system and an iron-carbon-chromium system have been estimated and compared with the predictions given by assumptions of the equilibrium solidification for carbon and Scheil-type solidification for the metallic solute.
    Download PDF (95K)
  • Kyosuke Yoshimi, Shuji Hanada, Tomohide Haraguchi, Hidemi Kato, Takaom ...
    2002 Volume 43 Issue 11 Pages 2897-2902
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Numerous thermal vacancies are frozen into FeAl B2-ordered alloy ribbons by a conventional rapid-solidification technique. Through heat treatment at 723 K, clustering of the supersaturated vacancies generates a large number of nanopores, particulary near surfaces, thus creating nanoporous surfaces. The nanoporous surface structure was confirmed by scanning electron microscopy and atomic force microscopy. The behavior of this vacancy clustering was examined by differential scanning calorimetry. An exothermic, irreversible peak, probably due to vacancy clustering, was observed around 800 K, giving an activation evergy of about 1.17 eV . The nanopore formation was also observed by in-situ heating experiments in a transmission electron microscope. The pores have specific morphology and crystallography with pore surfaces faceting toward {100} planes. These results suggest that the vacancy clustering is a unique process which enables us to efficiently make nanoporous surfaces.
    Download PDF (403K)
  • Xian-Wei Li, Etsuro Shibata, Eiki Kasai, Takashi Nakamura
    2002 Volume 43 Issue 11 Pages 2903-2907
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    A new apparatus with Knudsen effusion method especially designed for the vapour pressure measurements of dioxin congeners and other POPs is described. Crystalline benzoic acid and anthracene were first used to test the new designed apparatus. The vapour pressure and enthalpy results of the two reference compounds were found in good agreement with accepted literature data. The vapour pressure and enthalpy results of crystalline DD, DF, OCDD and OCDF determined with the new apparatus are presented, and compared with the literature data measured with other methods.
    Download PDF (63K)
  • Kouichi Hatakeyama, Akira Sugawara, Takuya Tojyo, Keisuke Ikeda
    2002 Volume 43 Issue 11 Pages 2908-2912
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Uniform deformation of tempered copper alloy sheets is small, and their bend formability depends largely on the amount of non-uniform deformation, which is complicatedly influenced by other factors in addition to the work-hardening exponent n. In this study, it has been shown that post-uniform elongation in the tensile test can be represented by two parameters, (efeu) and f. The symbol ef is the nominal strain at the breakage point, eu the uniform elongation and f the parameter giving the degree of strain localization along the tensile axis. Good correlation between those parameters and bend formability was ascertained by experimental studies on C51900 and some other Cu alloy sheets. The experimental results showed that the introduced two parameters were not independent variables but mutually related. In addition, the nucleation and growth processes of surface wrinkles in bending, which finally led to cracking, were studied metallographically. A lot of micro necks first arose in the vicinity of grain boundaries, and part of them developed into the groove of wrinkles. Spacing between grooves appeared to correspond with the size and distribution of cube-oriented grains.
    Download PDF (249K)
  • Li-Wu Huang, Pi-Wein Wang, Teng-Shih Shih, Jenq-Hwu Liou
    2002 Volume 43 Issue 11 Pages 2913-2920
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    In melting aluminum alloys, inclusion particles suspended in melt can be effectively reduced by floatation and/or sedimentation. Nevertheless, few researchers have focused on the effect of degassing bubbles on inclusion particles entrapped in the Al melt and the poured casting as well. The degassed bubbles evolved from a diffuser, floated up and collapsed on free surface of the melt. After explosion, the splashed droplets dropped on surface and then sank into melt following the movement of convection loop induced near the free surface of melt. Consequently, after degassing treatment, Al–7Si melts increased the inclusion particle counts and foggy marks revealing on the section of chilled samples. The A356.2 melts decreased the inclusion particle counts but increased the foggy marks on the poured chilled samples.
    Download PDF (352K)
  • Akihisa Inoue, Wei Zhang
    2002 Volume 43 Issue 11 Pages 2921-2925
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    New Cu-based bulk glassy alloys with large supercooled liquid region and high mechanical strength were found to be formed in Cu–Zr–Al ternary system. The large supercooled liquid region exceeding 70 K was obtained in the composition range of 40 at%Zr at 2.5 at%Al, 37.5%Zr to 47.5%Zr at 5%Al and 42.5%Zr at 7.5%Al. The largest ΔTx was 74 K for Cu55Zr40Al5 and Cu50Zr42.5Al7.5 alloys and the highest TgTl was 0.62 for the former alloy. The alloys with large ΔTx values above 70 K were formed into a bulk glassy rod form with diameters up to 3 mm by copper mold casting and the glassy alloy rods exhibit high compressive strength of 1885 to 2210 MPa and Young’s modulus of 102 to 115 GPa combined with elastic elongation of 1.60 to 1.95% and plastic elongation of 0 to 0.4%. The addition of 2.5 to 7.5%Al to Cu–Zr alloys was very effective for the increase in glass-forming ability as well as the stabilization of supercooled liquid. The effectiveness can be interpreted on the basis of the concept of the formation of the unique glassy structure in special multi-component alloys with the three empirical component rules.
    Download PDF (141K)
  • Shanping Lu, Hidetoshi Fujii, Hiroyuki Sugiyama, Manabu Tanaka, Kiyosh ...
    2002 Volume 43 Issue 11 Pages 2926-2931
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Active flux can modify the fusion zone geometry dramatically in GTA welding (A-TIG). In the present study, in order to investigate the effect of the active flux on the Marangoni convection in the welding pool, bead-on-plate specimens are made on SUS304 stainless steel pre-placed with single active flux, Cu2O, NiO, Cr2O3, SiO2 and TiO2 by the GTA process. Weld pool cross-sections and the bead surface morphology are analyzed by optical microscopy after welding. The oxygen content in the weld metal is measured using a HORIBA EMGA-520 Oxygen/Nitrogen Analyzer. The results showed that the depth/width ratio of the weld pool was closely related to the oxygen content in the pool. The oxygen content in the weld metal increases with the quantity of fluxes, Cu2O, NiO, Cr2O3, SiO2 and TiO2. However, for the TiO2 oxide flux, the highest oxygen content in the weld metal is below 200 ppm. As the oxygen content in the weld metal is in a certain range of 70–300 ppm, the depth/width ratio increases to 1.5 to 2.0 times. Too low or too high oxygen content in the pool does not increase the depth/width ratio. The oxygen from the decomposition of the flux in the welding pool alters the surface tension gradients on the weld pool surface, and hence, changes the Marangoni convection direction and the weld pool penetration depth.
    Download PDF (340K)
  • Atsushi Yumoto, Takahisa Yamamoto, Fujio Hiroki, Ichiro Shiota, Naotak ...
    2002 Volume 43 Issue 11 Pages 2932-2934
    Published: 2002
    Released: September 06, 2005
    JOURNALS FREE ACCESS
    Ceramic coating is a very popular technology for improving the properties of structural materials. A titanium nitride (TiN) coating is a typical example and has been widely applied to cutting tools, electronic devices and many other fields utilizing its superior physical properties. This paper sought to produce a graded TiN coating on a Ti substrate by combining Supersonic Free-Jet PVD (SFJ-PVD) with a reactive plasma-metal reaction technique. The authors have developed SFJ-PVD as a new coating method in which a coating film is formed by depositing nanoparticles with very high velocity onto a substrate. SFJ-PVD can provide a high deposition rate and thick film coating. Gradually changing the nitrogen flow rate during deposition produces a graded TiN coating, in which composition changes gradually from pure Ti to TiN . A monolithic TiN coating is also produced with SFJ-PVD . XRD analysis of the graded TiN detected peaks for Ti, Ti2N and TiN, while only a TiN peak is observed in the monolithic TiN coating. EPMA analysis of a graded coating reveals a gradual compositional change from pure Ti to TiN . Few pores or cracks are observed in a graded TiN or in a monolithic TiN formed under the optimized conditions of SFJ-PVD.
    Download PDF (292K)
feedback
Top