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Volume 71, Issue 7
Displaying 1-7 of 7 articles from this issue
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Yasushi Sasajima, Tomoaki Akabane2007 Volume 71 Issue 7 Pages 539-544
Published: 2007
Released on J-STAGE: July 01, 2007
JOURNAL FREE ACCESSThe aggregation process of silicon nanocrystals was simulated using the molecular dynamics method and the stability of the nanocrystals was examined as a function of temperature and pressure. The specimens were constructed as follows: ultrafine particles of silicon with 1.6 nmφ, each of which has a diamond structure, were oriented randomly and set on the face centered lattice sites. The nanocrystal system was surrounded by perfect rigid body walls and pressed by the walls at a constant pressure. The temperature was held constant by ad hoc scaling. The Tersoff potential was assumed as the interaction mechanism of the silicon atoms, and the Morse potential was used to calculate the force between the silicon atoms and the rigid walls. After the system reached the equilibrium state, the radial distribution functions were calculated for each sample and the stability region of the silicon nanocrystal was determined. The critical temperatures for the stability were about 750 K for 1.013×105 Pa and 300 K for 1.013×109 Pa. The time change of the fraction of the coordinate number was also calculated, and it was clarified that the fraction of 4-coordinated bonds, which represents the local tetragonal structure in the diamond lattice, decreased substantially whereas the fraction of 3-coordinated bonds increased at high temperatures, and that the decrease in the fraction of 4-coordinated bonds was suppressed at high pressure.
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Masami Ueda, Yoichi Mori, Masaru Hashimoto, Shigeki Yamamuro, Shigeo T ...2007 Volume 71 Issue 7 Pages 545-552
Published: 2007
Released on J-STAGE: July 01, 2007
JOURNAL FREE ACCESSConductive amorphous carbon was coated on the stainless steel separators by using electron cyclotron resonance (ECR) plasma sputtering technique. The carbon-coating reduced contact resistance between carbon paper and stainless steel substrate by two orders of magnitude. The carbon-coating also enhanced corrosion resistance of the stainless steels. Polarization performances of the polymer electrolyte fuel Cell (PEFC) using the carbon-coated SUS316L and SUS329J4L separators were comparable with that using the conventional carbon separator.
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Kenji Hashimoto, Takeshi Kubota, Tuyoshi Mashiko, Teiko Okazaki, Yasub ...2007 Volume 71 Issue 7 Pages 553-558
Published: 2007
Released on J-STAGE: July 01, 2007
JOURNAL FREE ACCESSMechanical deformation effect on the magnetic properties in a bulk metallic glass (BMG) Fe60Co8Zr10Mo5W2B15 alloy at its glass transition temperature (Tg) was studied to investigate the possibility of some influence on the micro, nano-structure and magnetic properties of Fe-based BMG. Three different mechanical strains of 5, 10 and 20% were applied to specimens at Tg (=882 K). From the results by vibrating sample magnetometer (VSM) measurement, magnetic susceptibility (χ) and coercive force (Hc) were low in as-cast material, on the other hand, in the samples after strains of 10% and 20%, both χ and Hc increased very much. Transmission electron microscope (TEM) observation shows that very small crystalline precipitations with grain size of several nm order appeared and it's volume fraction gradually increases in the deformed samples. The morphological change seen in the selected area electron diffraction (SAED) pattern was well agreed with the changing tendency of the X-ray diffraction (XRD) analysis. Barkhausen noise (BHN) pulse voltage which is directly related to the dynamic behavior (i.e. magnetic pinning effect) of magnetic domains' movements increased with increasing the strain and BHN outbreak timing moved to higher magnetization level. These behaviors seem to correspond with the increase in Hc and χ. Therefore, a suitable deformation conditions (i.e. the amount of strain and temperature) at Tg should be chosen to maintain the excellent magnetic characteristics in Fe-BMG.
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Masami Ando, Hiroyasu Tanigawa, Kiyoyuki Shiba, Shiro Jitsukawa, Yutak ...2007 Volume 71 Issue 7 Pages 559-562
Published: 2007
Released on J-STAGE: July 01, 2007
JOURNAL FREE ACCESSThe irradiation creep behavior of F82H and several JLF-1 steels has been measured at 573 and 773 K up to 5 dpa using pressurized creep tubes irradiated in HFIR. These tubes were pressurized with high-purity helium to hoop stress levels of 0 to 400 MPa at the irradiation temperature. The results for F82H and JLF-1 with hoop stress of 400 MPa showed small creep strains (<0.25%) after irradiation at 573 K. The irradiation creep strain at 573 K in these steels is linearly dependent on the applied stress at stress levels below 250 MPa. However, at higher hoop stress levels, the creep strain is nonlinear. At 773 K, the irradiation creep strain of F82H is linearly dependent on the applied hoop stress level below 100 MPa. At higher stress levels, the creep strain increased strongly. The creep compliance co-efficient for F82H and JLF-1 is consistent with the values obtained for other steels. These data contribute to the materials database for ITER test blanket design work.
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Ichiro Daigo, Susumu Hashimoto, Yasunari Matsuno, Yoshihiro Adachi2007 Volume 71 Issue 7 Pages 563-569
Published: 2007
Released on J-STAGE: July 01, 2007
JOURNAL FREE ACCESSThe recovery of metal scrap for recycling contributes to the conservation of natural resources and the construction of a sound material cycle. A dynamic material (substance) flow analysis is useful to understand how and in what proportion materials are used, how they may dissipate into the environment, and how they partition into certain reservoirs (e.g. landfills). So, it enables us to investigate the potentials of metal scrap recovery in the designated area in the future. In this article a dynamic material flow analysis for copper and its alloys in Japan was conducted in order to estimate the stock, the amount of discarded and collected scraps in the future. There was a significant gap between the supply and the demand of scraps in statistics in Japan. The comparison between the estimation and the statistics suggested that this gap was due to the obsolete scraps which were not accounted as a supply of collected scraps. The amounts of collected copper scraps and its alloy scraps were estimated separately from 1970-2005. The results showed that approximately 300 thousand tons of high-purity copper or high copper alloys were recovered with impurities or copper-alloy scraps, which were finally consumed as copper-alloy scraps.
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Haruo Baba, Yasuyuki Katada, Hideo Kimura2007 Volume 71 Issue 7 Pages 570-577
Published: 2007
Released on J-STAGE: July 01, 2007
JOURNAL FREE ACCESSA stainless steel material was produced based on a Fe-23 mass%Cr-4 mass%Ni alloy with varying contents of N (0.7-1 mass%) and Mo (0-1 mass%), through electro-slag remelting (ESR) under high nitrogen gas pressure. The effects of nitrogen on crevice corrosion behavior in an acidic chloride solution were investigated, and the passive film of the crevice corrosion area after corrosion tests was analyzed using X-ray photoelectron spectroscopy (XPS). At the same time, the effects of nitrogen on the passivation behaviors after scratching were also investigated. During crevice corrosion at a noble potential of 0.7 V (SCE), the nitrogen in solid solution in the steel dissolves into the solution as NO3-, and its concentration increases with the nitrogen content in the steel. It was also established that the number of corrosion spots, the corrosion loss, and the maximum depth of corrosion all decrease with the increase in the amount of nitrogen present in the steel and the applied potential. Such results can be attributed to the presence of NO3- dissolved into the aqueous solution. On the other hand, results from scratch tests show that the increase in the amount of added nitrogen decreases the peak value of passivation current as well as the amount of electricity during repassivation, suggesting that nitrogen stimulates the passivation process and suppresses the occurrence of crevice corrosion. XPS analysis shows the presence of nitrogen as nitrides and NH3 in the surface layer of crevice corrosion and the internal layer of passivation films.
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Yasuko Numata, Bunei Syuto, Naoyuki Nomura, Akihiko Chiba2007 Volume 71 Issue 7 Pages 578-585
Published: 2007
Released on J-STAGE: July 01, 2007
JOURNAL FREE ACCESSThe aim of this study is to examine the cytocompatibility of new cobalt-29 chromium-6 molybdenum alloys prepared by addition of a small amount of zirconium or carbon. Four kinds of Co-based alloy, containing 0.05 mass% of zirconium (0.05Zr-CCM), 0.08 mass% of zirconium (0.08Zr-CCM), 0.09 mass% of carbon (0.09C-CCM) and 0.18 mass% of carbon (0.18C-CCM), were prepared. The tests for cell adhesion, colony formation and cell growth were carried out according to a procedure of JIS T0301 by use of L929 cells.
By addition of ziruconium to cobalt-based alloy, some cytocompatibilities were improved. in cell adhesion and colony formation in the direct contact tests.
In 0.05Zr-CCM, the rates of cell adhesion and colony formation in the direct contact tests were improved in 0.05Zr-CCM but not in the other alloys. The colony formation rate in the static extract solution was improved in 0.08Zr-CCM. In the dynamic extract solution, the rate was decreased in 0.09C-CCM and increased in 0.18C-CCM.
These results indicate that the cytocompatibility of Co-based alloy is changeable by addition of a small amount of zirconium or carbon.
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