MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 46 , Issue 12
Showing 1-50 articles out of 93 articles from the selected issue
  • Shinichiro Nakamura, Kenichi Nakajima
    2005 Volume 46 Issue 12 Pages 2550-2553
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    This paper develops a theoretical model of material flow analysis (MFA) within the framework of the Waste Input–Output model (WIO) (Nakamura and Kondo). The model is developed based on two fundamental ingredients: yield ratios and the degree of fabrication. In manufacturing process, multiplication of physical inputs by the yield ratios gives the portion that enters physical outputs, with the rest being discarded as process waste without entering outputs. In input–output analysis, the degree of fabrication can be visualized as triangularity of the input coefficients matrix (goods of lower degree of fabrication can enter those of higher fabrication, but the reverse does not hold), which is known to emerge through an appropriate reordering of sectors. Application to the Japanese IO data indicates that the model can provide accurate estimates of the weight as well as the composition of metals (Fe, Cu, Pb, Zn, and Al) used in a passenger car. The model is also used to estimate the major final use categories (household consumption, public consumption, capital investment, inventory investment, and export) of metals.
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  • Katsutoshi Yamada, Kohmei Halada, Kiyoshi Ijima
    2005 Volume 46 Issue 12 Pages 2554-2560
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    One of the gravest environmental problems facing us today is how to manage materials we use and produce as a result of the industrial development in the 20th century. The concept of ecomaterials was proposed with their full life-cycle taken into consideration in 1991 and has widely developed now. There have been many governmental activities for the creation of sustainable society in Japan such as enactments of environmental laws and regulations. Many Japanese enterprises have been also engaged in a lot of activities for environmental protection. Owing to their endeavour, ecomaterials in Japan have been developed and their number has increased yearly. The research was made on how ecomaterials are currently used in Japan. All the information was obtained from the Web-sites 2004 year version environmental reports of the organizations concerned. In this paper, ecomaterials produced by two hundred and sixty six listed companies on the stock market were researched and classified into six categories. About 3900 ecomaterials were found in the 2004 year version environmental reports of 266 companies researched, whereas the number of ecomaterials researched in the year 2001 was only 1898 in 286 companies and in the year 2003 about 3700 in 281 companies. This means the number of ecomaterials in Japan in the year 2003 nearly doubled compared to that of 2001 and increased further in 2004. It also indicates the realization on the part of Japanese companies of the importance of ecomaterials resulting in the advancement of related research activities. Higher materials efficiency products of user friendly, energy saving and high performance type, which are the results of years of engineering research and development are being promoted as newly improved and efficient products. It seems that the time is approaching when it is necessary to consider as a part of environmental problems the limited availability of natural resources and to promote a sustainable society from a broader perspective.
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  • Taeko Aoe, Takayuki Michiyasu
    2005 Volume 46 Issue 12 Pages 2561-2566
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    In order to verify the effectiveness of the “Ecological Rucksack” as an indicator on resource utilization for electrical and electronic equipments, the Ecological Rucksack of 36-inch high-definition TVs produced in 1993 and 2003 has been estimated in cooperation with the Wuppertal Institute in Germany. The Ecological Rucksack (abiotic material) of the 1993 product was 19 tons (product mass 91.0 kg) and that of the 2003 product was 7.7 tons (product mass 79.5 kg), therefore, an approximate 11 tons or 60% reduction. The breakdown of the Ecological Rucksack (abiotic material) of the 1993 product indicated that the values associated with the print circuit board mounted inc. electronic components (hereafter called PC board) represented approximately 50% of the total, followed by power consumption during use at 40%. The PC board represented less than 10% of the product mass but occupied approx 50% of the Ecological Rucksack (abiotic material). The smaller and lighter PC boards employed in the later product substantially contributed to the reduction of Ecological Rucksack. As evident in the example of the PC board, the consideration of Ecological Rucksack reveals the hidden material flow and presents a new approach to resource utilization.
    However as for the materials used over the life cycle of a high-definition TV set, the factors obtainable from the MI factors table represented only 25% of the product mass. By applying the MI factors of materials with equivalent properties, the rate of MI factors increased to 99% of the product mass, thereby enabling an estimation of the Ecological Rucksack for a TV set. The estimation made this time around underlined the fact that further examination of the data was required for the PC board, because it would strongly affect the evaluation results for determining the Ecological Rucksack of a high-definition TV set. Further enhancement of the database is therefore required for enabling applications to electric and electronic equipment.
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  • Toshio Fukushima
    2005 Volume 46 Issue 12 Pages 2567-2573
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Super environment-conscious intelligent composite materials incorporated with life-cycle program of self-repair during in service and self-collapse after designed service life are proposed. One example is carbon short-cut fiber reinforced composites (CFRC) incorporated into matrix mortar with numerous two kinds of micro capsules imbedded with two smaller capsules containing nanometer-size reacting particle (calcium oxide (CaO) or cement) and initiating one (highly water-containing resin particle). These double capsules are incorporated during mixing mortar and fiber as chemical admixture, but they are stably dispersed, not breaking during in service of composites. By triggering these double capsules by external electromagnetic wave having two different frequencies, these capsules are broken, and chemical reaction occurs. As the results, self-repair is made to occur in the crack part during in service by the rather mild hydration reaction of cement, and self-collapse after designed service life by the rapid expansive hydration reaction of CaO. These cement composites are intelligent due to the appropriate response to the controlled external electromagnetic trigger, and environment-friendly due to the elongation of service life by self-repair, and the easiness of demolition and recycling by self-collapse. The same concept is also applied to carbon continuous fiber reinforced plastic reinforced concrete (CFRPRC). Other than double microcapsules, glass optical fibers are also imbedded into matrix resin of FRP. By detecting the change of electric resistance of CFRP, we can predict the collapse. By triggering the embedded double capsules, self-repair and self-collapse are made to occur. These pseudo-biological functions of self-repair and self-collapse are also incorporated into base concrete. These CFRPRC are enough to become intelligent and environment-friendly. By using well designed these super environment-conscious intelligent composites, I try to realize environment-conscious interior planning in which non-adhesive, but joint or set-in type interior construction are considered.
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  • Hideki Kakisawa, Kazumi Minagawa, Keisuke Ida, Katsuhiro Maekawa, Kohm ...
    2005 Volume 46 Issue 12 Pages 2574-2581
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Using fine metal powders, we were able to fabricate dense P/M (powder metallurgy) products by a three-dimensional inkjet printing system. We used carbonyl nickel powder with a mean particle size of 5 μm as a raw material and examined two binder supply methods: (i) supplying a binder directly from the inkjet head (DB method), and (ii) coating the powder with a water-soluble polymer and then supplying thin polymer-dissolved water from the inkjet head (CB method). The layered green product was sintered in a hydrogen atmosphere at a temperature in the range of 1073–1623 K. Sintered samples fabricated by the CB method had non-uniform microstructure due to agglomeration of the coated powder. In samples made by the DB method, the macroscopic shape was retained after high-temperature sintering at 1623 K, and a high density of over 90% was achieved, which was attributed to uniform powder cohesion in the laminating process.
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  • Noboru Yoshikawa, Yuuya Nakano, Kentarou Sato, Shoji Taniguchi
    2005 Volume 46 Issue 12 Pages 2582-2585
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Model experiments were performed for fabricating composite materials using Al scrap and waste glasses. Significance of the fabrication using the waste matters was discussed from an environmental point of view. Al alloy having composition of the Al scrap was melted and infiltrated into a soda-lime glass beads’ bed by a vacuum process. Reaction layer was formed at the interface between the glass beads and the molten Al alloy. The layer thickness of 50 microns was obtained after 1 h reaction. The composite materials showed a strong bonding between the filler (the glass particles) and the matrix. Variation of the layer thickness was measured at various conditions of the reaction time and temperature.
    Distribution of the metal elements in the microstructure of the composite material was analyzed with SEM/EDX. It was shown that not only Si but also some elements were removed from the glass to the Al alloy matrix. Behaviors of the other elements were discussed, considering the thermodynamics. Compression test of the composite materials was performed. They fractured in a brittle manner once, however, after the fracture, they were not broken into pieces, but followed by the ductile deformation.
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  • Katsuyoshi Kondoh, Hideki Oginuma, Junko Umeda, Takateru Umeda
    2005 Volume 46 Issue 12 Pages 2586-2591
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Innovative reuse process of rice husks (RH), being one of the representative agricultural wastes, has been developed to fabricate magnesium composites by solid-state reaction to form magnesium silicide (Mg2Si) reinforcements, having high hardness and Young’s modulus. From a view point of the biomass energy, rice husks, including about 70 mass% organics, could be effectively used as environmentally benign fuels to supply electric power or biomass ethanol. Considering that the most of the rice husk wastes after absorbing organics is SiO2, the solid-state synthesis of Mg2Si compounds by reaction of SiO2 with magnesium was suggested in this study. First of all, the effect of the acid washing treatment to remove organics of rice husks on the crystallization of amorphous SiO2 was evaluated by TG-DTA and XRD analysis. The carbon content of 0.05% in the wastes was drastically reduced by using acid-washed rice husks, compared to that of non acid-washed ones (0.19%). When employing the wastes with and without the acid washing treatment, the crystallization temperature is about 1273 and 1073 K, respectively. The latter showed the lower crystallization temperature because the reaction of the alkaline contents, such as K, P, and Ca, with SiO2 during heating caused to decrease the SiO2 melting point. Rice husk wastes burned at 1273 K after the acid treatment was mixed with AZ31 magnesium alloy powder to fabricate the magnesium composites including Mg2Si dispersoids. Microscope observation and XRD analysis indicated that the amorphous SiO2 included the wastes was more effective to promote Mg2Si formation.
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  • Yasumasa Chino, Lee Jae-Seol, Yusuke Nakaura, Koichi Ohori, Mamoru Mab ...
    2005 Volume 46 Issue 12 Pages 2592-2595
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Solid-state recycling for runner scraps of Mg–Al–Ca alloy was carried out by extrusion at 673 K and mechanical properties of the recycled Mg alloy were investigated by tensile tests. At room temperature, the recycled specimen showed a good combination of high ultimate tensile strength (348 MPa), high 0.2% proof stress (305 MPa) and large elongation (9%). Additionally, the recycled specimen exhibited superplastic behavior at 573 and 673 K. The excellent mechanical properties of the recycled specimen result most likely from fine dispersion of precipitates which is attained by hot extrusion.
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  • Toshio Haga, Masaaki Ikawa, Hisaki Watari, Kenta Suzuki, Shinji Kumai
    2005 Volume 46 Issue 12 Pages 2596-2601
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    In this work, the mechanical properties of roll-cast recycled aluminum alloy were investigated. Fe was added to 6111 aluminum alloy to simulate recycled aluminum alloy. The Fe content was varied between 0.14 and 1.02 mass%. A high-speed twin roll caster was used because it exhibits better cooling characteristics than the conventional twin roll casters. The strip was cast at a speed of 60 m/min and the resulting strip microstructure was not columnar, but equiaxed or globular. When the Fe content was 0.4 mass%, the Fe content does not appear to exert any influence on the tension test results after T6 heat treatment, and after a 180-degree bending test no cracks occurred on the outer surface.
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  • Kenta Suzuki, Shinji Kumai, Yuichi Saito, Toshio Haga
    2005 Volume 46 Issue 12 Pages 2602-2608
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Thin strips of the 6063 aluminum alloy and the alloys with increased nominal Fe contents (0.7–6 mass%Fe) were fabricated directly from the molten alloys using a vertical-type high speed twin-roll strip caster equipped with a pair of water-cooled pure copper rolls. The estimated cooling rates from the DAS measurement were about 4500 and 100°C/s at the near the surface region and the mid-thickness region of the strip respectively. Refinement of Al–Fe–Si intermetallic compound particles was also successfully achieved, however, segregated coarse particles were also observed at the mid-thickness region. The cast strips were cold-rolled and heat-treated to form 0.5 mm-thick thin sheets. They were either naturally aged at room temperature (T4) or artificially aged (T6), and then subjected to bending, tensile and hardness tests. No detrimental effect of Fe was appeared concerning the bendability even in the alloy containing 3 mass%Fe. No cracking took place even in the 180° bending (hemming) test. The reduction of age-hardenability was evident for the alloy with 1 mass%Fe and more. The alloy sheet containing 0.7 mass%Fe exhibited not only a good bendability in the T4 condition but also the larger proof stress and UTS than those of the master alloy in the T6 condition. This means that the capacity of Fe impurity in a 6063 alloy (0.35 mass% according to JIS) can be doubled by using the present roll caster. Strip casting at a high cooling rate using the present roll caster is considered to be a promising method for reducing the detrimental effect of impurity iron from the scrap melt.
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  • Osamu Umezawa, Munefumi Nakamoto, Yoshiaki Osawa, Kenta Suzuki, Shinji ...
    2005 Volume 46 Issue 12 Pages 2609-2615
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Although the cascade of material flow is presently suitable for the aluminum recycling, a better utilization of secondary alloys is required. In order to establish an upgradeable recycling design for developing wrought products from secondary aluminum alloys, a fine distribution of the primary phases in hyper-eutectic Al–Si–Fe–Mn cast materials has been achieved. Two novel processes were adopted. One was repeated thermomechanical treatment (RTMT), which involves a repetition of a multi-step cold-working followed by heat treatment. The other was rapid solidification by high-speed twin-roll casting to develop a fine solidification structure in a thin sheet. By applying these processes, refined microstructures were successfully obtained. Microstructural refinement by RTMT resulted in the avoidance of early fracture that was detected in the cast material by a tensile test. The RTMT imparted good ductility; therefore, it was possible to allow greater flexibility in the cold working of Al–Si–Fe–Mn cast materials.
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  • Osamu Umezawa
    2005 Volume 46 Issue 12 Pages 2616-2623
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Tensile and high-cycle fatigue behavior of thermomechanical treated hyper-eutectic Al–Si–(Fe,Mn,Cu) materials were studied. Through the repeated thermomechanical treatment (RTMT) which is a repeat of the multi steps cold-working followed by heat treatment, Si crystals and/or intermetallic compounds were broken into some fragments and dispersed in the aluminum matrix. Fine dispersion of the second phase particles exhibited good ductility, since early fracture was overcome. A few large Si crystals or aggregates of compounds, however, gave an origin of fatigue crack generation. Since microcrack linkage generates a larger fetal crack, not only refinement but also random distribution of second particles may be required to improve fatigue strength at and below room temperature. At higher temperature, on the other hand, dynamic recovery may cause apparent strain rate dependence on flow curves.
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  • Masataka Hakamada, Yasuo Yamada, Tatsuho Nomura, Youqing Chen, Hiromu ...
    2005 Volume 46 Issue 12 Pages 2624-2628
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Porous aluminum with a porosity of 78% and pore size of 850–1000 μm was fabricated under various sintering pressure, sintering time and raw Al powder size conditions by the spacer method consisting of spark plasma sintering (SPS) and sodium chloride (NaCl) dissolution. The effects of the fabrication conditions on compressive properties of the porous Al were investigated. The sintering pressure of 20 MPa and sintering time of 10 min were needed to fabricate robust porous Al under the sintering temperature of 843 K and raw Al powder size of 3 μm. Also, the porous Al specimen fabricated from Al powder of 300 μm exhibited much lower flow stress than those fabricated from Al powder of 3 and 20 μm when employing the temperature of 843 K, the pressure of 20 MPa and the duration time of 10 min. This indicates that the raw Al powder size is needed to be much smaller than the spacer size. This is because the Al particle cannot touch with adjacent Al particles when the Al powder size is comparable to the spacer size.
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  • Kazuhiro Mochizuki, Daisuke Hirabayashi, Yoshihiro Kojima, Kenzi Suzuk ...
    2005 Volume 46 Issue 12 Pages 2629-2632
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The catalytic activities of propylene oxidation on different aluminum silicates with the mayenite structure [Ca12Al14−xSixO33+0.5x (x=0,4)] formed at 500, 800 and 1000°C were investigated. The aluminum silicates were prepared by the hydrothermal and solid-state reactions of a stoichiometric mixture of calcium oxide, alumina sol and silica. The XRD results of the aluminum silicates obtained by the solid-state reaction showed that the peak intensities of the mayenite phases became larger as the calcination temperature increased. The aluminum silicates included two kinds of active oxygen species (O22−, O2) related to Raman shifts around 887 and 1092 cm−1, respectively. As a result, the aluminum silicates exhibited oxidation activities based on the easily reducible active oxygen species. Notably, the Ca12Al10Si4O35 calcined at 1000°C without the hydrothermal treatment showed the highest activity of all catalysts, indicating that the crystal structures play an important role in determining the catalytic activity.
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  • Yasuo Yamada, Takumi Banno, Zhenkai Xie, Cui’e Wen
    2005 Volume 46 Issue 12 Pages 2633-2636
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The crushing behaviour and energy absorption of foam filled aluminium tubular structures were investigated using the quasi-static compressive tests. The crushing behaviour of the tubular structures changed due to foam filling. The energy absorption of the foam filled tubular structures was improved significantly. Foam filling caused an interaction effect between the tube and the foam during progressive crushing, leading to an increase in the mean crushing load compared to that of the foam or tube itself. This interaction effect might be affected by several parameters such as the density of the foam, the properties of both the foam material and tube material, and the thickness and outer diameter of the tube. In particular, the interaction effect essentially depended on the ratio of the mean crushing force of the foam to that of the tube.
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  • J. S. Lee, Y. Chino, H. Hosokawa, K. Shimojima, Y. Yamada, M. Mabuchi
    2005 Volume 46 Issue 12 Pages 2637-2640
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Deformation mechanism of the recycled aluminum alloy by solid state recycling at elevated temperature was investigated. Elongation of the recycled specimen did not decrease when deformation mechanism was other than grain boundary sliding. Harmful effect of contaminations is negligible when deformation mechanism is related to dislocation activity in grains.
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  • Hiroshi Nishikawa, Kouhei Seo, Seiji Katayama, Tadashi Takemoto
    2005 Volume 46 Issue 12 Pages 2641-2646
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    It is important to develop an effective sorting system of aluminum to reduce the cascade recycling of aluminum scraps by instead returning the scraps to wrought aluminum. A feasibility study has been conducted to develop a new sorting process of aluminum scraps. In this study, irradiation of an aluminum surface by pulsed Nd:YAG laser and an automatic sorting method by a pattern-matching method were tested to identify the alloy number of aluminum scraps. For sorting test samples, seven aluminum alloys (1050, 2024, 3003, 4343, 5052, 6063, 7075) were selected from seven wrought aluminum alloy series. The surface of the aluminum irradiated and melted by a YAG laser beam. The surface morphology, including the molten area, brightness profile and change in color, was observed after irradiation. There was a difference in the surface morphology among the aluminum alloys after irradiation. The effect of laser irradiation conditions such as the defocus distance, input energy and laser irradiation angle on the surface morphology after irradiation was investigated to establish the appropriate conditions of laser irradiation for sorting aluminum alloys. It was clear that the surface morphology of aluminum seems to depend on physical properties such as thermal conductivity and liquidus temperature. Therefore, it seems possible to establish an automated aluminum sorting method by using the pattern matching method on irradiated aluminum samples.
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  • Minoru Hashiba, Akinobu Harada, Naoki Adachi, Seizo Obata, Osamu Sakur ...
    2005 Volume 46 Issue 12 Pages 2647-2650
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The dispersion and fluidity of aqueous platelet γ-alumina slurries were enhanced by addition of ammonium polyacrylate (PAA) as a dispersant at pH 10. Magnesia powder was mixed with the slurries using a planetary mixer for 150 s after ball milling of the slurries for 24 h. Magnesia was eluted gradually into the aqueous media by formation of a chelate with PAA. The slurries were solidified by PAA deficiency because of reduction of the electrostatic repulsive force between the alumina particles. The degree of shrinkage of the green body on drying was very small, and this was therefore regarded as a near-net-shaping process. A porosity of about 60% and strength of 45 MPa were obtained in bodies fired at 1300°C and the mean pore diameter was 0.6 μm.
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  • Shyamal Kumar Saha, Pusparatu, Kenichi Komura, Yoshihiro Kubota, Yosh ...
    2005 Volume 46 Issue 12 Pages 2651-2658
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The effects of seeding on synthesis of MCM-22 (MWW) have been studied by the dry gel conversion (DGC) method. Highly reproducible crystalline MWW zeolite could be obtained by DGC method, using seeds of calcined sodium MWW with SiO2/Al2O3=31. Crystallization of MWW phase was completed in the presence of seeds (2 mass% against SiO2) at 150°C within two days. The small amount of seed (0.25 mass% against SiO2) was sufficient for the required phase formation of MWW. The MWW with SiO2/Al2O3 ratio from 35 to 66 was obtained as pure phase; however, the crystallinity of MWW decreased with further increase in the ratio: products were contaminated with impurities.
    The catalytic properties of MWW were examined in the skeleton isomerization and the cracking of hexane, and compared to zeolites such as BEA, MFI, and MOR. The catalytic activities were in the order: MFI>BEA>MWW>>MOR; however, the selectivity for the isomerization were in the order: BEA>MWW>MFI. These catalytic properties were due to the differences of structures and acid strength of zeolites.
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  • Shyamal Kumar Saha, Hiroyoshi Maekawa, Suresh B. Waghmode, Shafeek A. ...
    2005 Volume 46 Issue 12 Pages 2659-2667
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Zincoaluminophosphates, ZnAPO-5 and ZnAPO-36 with AFI and ATS topologies, were successfully synthesized by dry-gel conversion (DGC) method: vapor-phase transport (VPT) and steam-assisted conversion (SAC) methods. ZnAPO-5 was synthesized successfully at 175°C by VPT and SAC methods using Et3N as structure directing agent (SDA). ZnAPO-36 was also obtained by VPT and SAC methods using Pr3N as SDA. The heating protocol was a key factor for the crystallization in the synthesis of ZnAPO-36: the best result was obtained by heating at 140°C for 1 d after aging of the gel at 105°C for 2 d. Calcination procedure is important to get microporous molecular sieves. ZnAPO-5 by VPT method calcined at 550°C gave clear XRD with high microporosity. Highly microporous ZnAPO-36 by VPT method was obtained by careful calcination. Characterization of these zincoaluminophosphates was performed by XRD, NH3-TPD, TG, SEM, N2 adsorption, and ICP analysis. ZnAPO-5 and ZnAPO-36 have the Brønsted acidic characters by the substitution of a part of aluminum with zinc.
    The isopropylation of biphenyl (BP) over these molecular sieves gave different level of the selectivities for 4,4′-DIPB: 60–75% for ZnAPO-5 and 35–45% for ZnAPO-36: these selectivities are in the similar level to corresponding magnesioaluminophosphates corresponding magnesioaluminophosphates. These differences of ZnAPO-5 and ZnAPO-36 in the selectivity are due to the pore structure: ZnAPO-5 has one-dimensional straight channel; however, ZnAPO-36 has one-dimensional channel with side pocket. The steric restriction by ZnAPO-5 effectively controls the transition state to differentiate the slim isomers from others; however, pores of ZnAPO-36 cannot differentiate effectively the isomers because of their side pockets.
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  • Naohisa Tamura, Kazuhiro Ban, Shinya Takahashi, Tomoyuki Kasemura
    2005 Volume 46 Issue 12 Pages 2668-2672
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Poly(L-lactic acid) (PLLA) was blended with poly(ε-caprolactone) (PCL) using a single-screw extruder in order to modify poor characteristic of these polymers. When the polymer was blended, the block copolymer that is synthesized by methyl acrylate (MA) and ε-caprolactone (ε-CL) via an atom transfer radical polymerization was used as a novel compatibilizer. The structure of the synthesized compatibilizer is determined by 1H or 13C NMR. From this result, it was found that the ring-opening polymerization of the ε-CL was taken place in the hydroxyl end group of MA. Moreover, the morphologies of the PLLA/PCL solvent-cast blend films were observed by the optical microscope and SEM. From the optical microscopic observation, the morphologies of the solvent-cast blend films with the synthesized compatibilizer were more homogeneous than that of the solvent-cast blend films without the compatibilizer. It was confirmed that the phase structure of the solvent-cast blend films with the compatibilizer was more stable than that of solvent-cast blend films without the compatibilizer.
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  • Riko Ozao, Toshihiro Okabe, Tadashi Arii, Yuko Nishimoto, Yan Cao, Nat ...
    2005 Volume 46 Issue 12 Pages 2673-2678
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Gas adsorption properties of woodceramics prepared from cedar (Cryptomeria japonica, abbreviated as CE), apple waste (AP), and chicken waste (CH) were studied. Depending on the starting material, woodceramics differed in physisorption properties as evaluated by specific surface area (SSA) obtained by BET (Brunauer–Emmett–Teller) method, in pore structure and size, and in chemical adsorption properties for perfumery substances. CH and AP yielded lower SSA as compared with CE, however, they showed higher gas selectivity for oxygen vs nitrogen gas molecules. The adsorption ability of CE on perfumery essential oil components was evaluated for the first time using the rapid measuring method for VOCs; i.e., the adsorption capacity of cedar-based woodceramics for perfumery materials (essential oil extracts: carvone, pulegone, geraniol, citronellol, menthone, nerol, and citral) was examined. CE showed particularly strong affinity with geraniol and citral, in which more than 99.9% of the compounds were adsorbed. About 99.7–99.8% of pulegone and menthone, 99.0% of nerol, 97.9% of carvone, and 94.0% of citronellol were adsorbed by CE. The adsorption affinity was also influenced by the particle size; particles coarser than 4.0 mm in size showed stronger adsorption.
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  • Junichiro Tsuji, Riko Ozao, Toshihiro Okabe, Toshikazu Suda, Ryoichi Y ...
    2005 Volume 46 Issue 12 Pages 2679-2684
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Woodceramics are carbon–carbon composites produced by impregnating plant-origin lignocellulosic materials with phenolic resin and by carbonizing the resulting precursor at temperatures higher than 650°C. Since the electric resistance of the woodceramics changes as a function of the carbonizing temperature, heating elements for use in biological incubator systems can be prepared by controlling the electric resistance to obtain optimal Joule heat. Woodceramic heating blocks carbonized at temperatures lower than 800°C were found preferable from the viewpoint of lower water absorptivity. Then, woodceramic test specimens (310×52×18 mm3) were produced from medium density fiberboard (MDF) at carbonizing temperatures of 650, 700, 750, and 800°C (which are simply denoted as 650, 700, 750, and 800, respectively). The electric resistance of the test specimens 650, 700, 750, and 800 at applied voltage of 10 V was 50, 10, 8, and 4 Ω, respectively. Thus, single test piece of 650, 3 serially connected 700, 7 serially connected 750, and 10 serially connected 800 were used to obtain the temperature profile. Temperature rise of each test specimen was measured under applied voltages of 10, 20, 30, and 40 V. For 650, fair temperature stability was obtained at 22°C (10 V) and 27–31°C (20 V). The advantages of the woodceramic heaters as compared with the conventional ceramic heaters are: (1) quick rise in temperature; (2) high stability at designated temperature; (3) lower power consumption; and (4) free of air convection (heats the sample directly and homogeneously).
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  • Yutaka Sawada, Sachiko Sezaki, Riko Ozao, Yuko Nishimoto, Toshihiro Ok ...
    2005 Volume 46 Issue 12 Pages 2685-2689
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Systematic morphological observations and surface analyses were completed in order to clarify the surface structure of “woodceramics”, i.e., carbon-carbon composite materials consisting of plant-originated carbon reinforced by carbon generated from phenol resin. The woodceramics manufactured from cedar sawdust at various temperatures (650°, 700°, 800°, 1000° and 1200°C) in a nitrogen atmosphere were examined. The microstructure was not affected by the manufacturing temperatures; bundles of the micro-tubes of the original plant (cedar) were preserved. The nanostructure was also unaffected by the manufacturing temperatures except for the one manufactured at the highest temperature (1200°C). Fine needles (fibers) on the surface of the 1000°C-prepared specimen were incorporated into the substrate for the 1200°C-prepared specimen. The oxygen/carbon atomic ratio (0.14) determined by XPS was approximately constant for all specimens manufactured at various temperatures. This value agreed with that of the bulk composition (0.12) except for the one (0.07) manufactured at the highest temperature (1200°C). The binding energy of C1s (284.1 eV) was attributed to elementary carbon. The binding energies of C1s and O1s (532.4 eV) were unchanged by the manufacturing at different temperatures. The specimens manufactured at low temperatures (650°, 700° and 750°C) showed high hydrogen/oxygen atomic ratios (2.6, 2.0 and 1.9, respectively) while those manufactured at high temperatures (1000° and 1200°C) had the lower values (1.3 and 1.4, respectively). The X-ray diffraction analysis indicated an amorphous phase with weak hallos at 23.7° and 43.1° (d-spacing; 0.375 and 0.210 nm, respectively). The weak peaks at 30.41°, 35.30° and 50.84° (d-spacings; 0.2937, 0.2541 and 0.1795 nm, respectively) that appeared eventually were attributed to a minute amount of impurities.
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  • Pinwen Zhu, Yoshio Imai, Yukihiro Isoda, Yoshikazi Shinohara, Xiaopeng ...
    2005 Volume 46 Issue 12 Pages 2690-2693
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The conversion of heat to electricity by thermoelectric (TE) devices may play a key role in the future for energy production and utilization. Lead telluride (PbTe) is one of the best TE materials used for TE generator in the medium temperature. In this report, the transport and TE properties of PbTe doped with antimony telluride (Sb2Te3), which has been used to optimize the carrier concentration for improved TE performance, have been studied. The scattering factor is estimated from the temperature-dependent Hall mobility and the results indicate that the scattering mechanism is changed from an ionized impurity scattering to the interaction between an acoustical and an optical phonon scattering as carrier concentration decreases and the temperature increases. The thermal conductivities for all the samples exhibit linearly dependence with reciprocal temperature and the slope increases with the carrier concentration increasing. The effective maximum power Pmax for PbTe samples increases with an increase of carrier concentration when the temperature gradient is over 400 K and is comparable to the functional gradient materials with the same carrier concentration. This result indicates that high TE performance has been achieved in PbTe with Sb2Te3 as dopants.
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  • Tetsuya Kako, Jinhua Ye
    2005 Volume 46 Issue 12 Pages 2694-2698
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Two types of rubidium bismuth niobate, RbBi2Nb5O16 and RbBiNb2O7, were prepared by a conventional solid state reaction method and characterized by X-ray diffraction analysis, UV–vis spectroscopy and SEM. These oxides can absorb up to approximately 420–440 nm wavelength of visible light. The photocatalytic activity of the two niobates in decomposing gaseous acetaldehyde, an indoor pollutant, was evaluated under visible light irradiation. The results indicated that RbBi2Nb5O16 showed a higher photocatalytic activity than RbBiNb2O7, in accordance with their different absorption properties. Moreover, RbBi2Nb5O16 deposited with 1 mass%–Pd on the surface exhibited approximately three times better photocatalytic activity than the bare material.
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  • Defa Wang, Jinhua Ye
    2005 Volume 46 Issue 12 Pages 2699-2703
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    A new series of visible-light-driven photocatalysts In12NiM2Ti10O42 (M = Al, Cr, Ga) with a pyrochlore-related layered structure were synthesized by the conventional solid-state reaction method. The substitution effects of trivalent cations M3+ on the electronic structure, photophysical and photocatalytic properties were investigated. It was found that although the three materials were all crystallized in a monoclinic symmetry with the same space group P21/a, their photocatalytic activities of H2 evolution were quite different. In comparison with In12NiAl2Ti10O42 and In12NiGa2Ti10O42, In12NiCr2Ti10O42 showed the narrowest band gap and highest activity, which could be ascribed to the formation of broadly dispersed continuous conduction and valence bands due to the involvement of partially filled Cr 3d orbitals in addition to Ni 3d orbitals. The present study suggests a promising method for developing visible-light-driven photocatalysts with tailored properties via transition-metal(s)-mediated band structure engineering.
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  • Chi-Yuan Cho, Kuo-Huang Wang, Jun-Yen Uan
    2005 Volume 46 Issue 12 Pages 2704-2708
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Fuel cells are often seen as a long-term solution to environmental problems such as CO2 emission associated with transportation. To ensure long-term sustainability and the supply of fuel, new renewable of hydrogen (H2) generator have to be introduced. In this study, Ni-rich AZ91D magnesium alloy ingot, which was considered as waste material, was used as a H2 generator in sodium chloride (NaCl) solution with catalyst. The chemical reaction Mg+H2O→H2+Mg(OH)2 occurred in NaCl aqueous solution. The H2 evolution rate depended on the solution’s temperature (25 or 70°C), length of catalyst (0.9 or 1.8 m) and the concentration of NaCl solution (5 or 10 mass%). The H2 evolution rate increased with increasing the solution’s temperature. The catalyst (Pt wire) could significantly improve the H2 generation rate. In addition, the by-product of this method is Mg(OH)2, a non-toxic chemical compound which is usually used as flame retardant.
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  • Shigeyuki Uemiya, Masayuki Uchida, Hiroshi Moritomi, Ryo Yoshiie, Mako ...
    2005 Volume 46 Issue 12 Pages 2709-2712
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    A cheap and disposal catalyst will be required for the decomposition of ammonia in the presence of sulfur compounds. The possibility of iron ore and red mud as the ammonia decomposition catalyst was investigated using pure or diluted ammonia containing hydrogen sulfide as a reactant. Among the catalysts tested, red mud had the highest catalytic activity for the ammonia decomposition in the presence of hydrogen sulfide. On the other hand, a relatively low conversion of ammonia was observed using a nickel-based commercial catalyst for the ammonia decomposition. The deactivation behavior of an iron ore catalyst caused by sulfur poisoning depended on the pretreatment atmosphere before the reaction; namely, the deactivation was observed for the H2 pretreatment, while the high level of ammonia conversion remained constant for the CO pretreatment. From the X-ray diffraction pattern of the catalysts, the used iron ore catalyst pretreated in the CO atmosphere included FeCx, which was also included in the red mud that was active for the ammonia decomposition. FeCx may be responsible to the sulfur poisoning resistance.
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  • Atsushi Nakano, Nurul Taufiqu Rochman, Hidekazu Sueyoshi
    2005 Volume 46 Issue 12 Pages 2713-2718
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    To promote the recycling of copper alloy scrap, we developed a new technique for removing Pb from copper alloy scrap containing 2–6 mass% Pb. However, we must evaluate quantitatively the level of environmental impact reduction that can be obtained using this new technology. In this study, a manufacturing system that produces Pb-free copper alloy products using copper alloy scrap was assessed by means of life cycle assessment (LCA). The superiority of the new manufacturing system that uses Pb-free copper alloy scrap over the conventional one that uses virgin materials was investigated from the viewpoint of environmental impact. LCA software (JEMAI-LCA) was used to assess environmental impacts such as global warming, acidification, energy consumption and resource consumption. We assessed the raw material acquisition and casting process of Pb-free copper alloy products. The subsequent processes such as machining, assembling, transportation, use and recycling/waste processing are not taken into account in the environmental impact assessment. The results show that the conversion of the conventional system that uses virgin materials into the new one that uses Pb-free copper alloy scrap decreases the environmental impact, significantly. This is attributed to the nonutilization of virgin materials and the decrease in energy consumption during the casting process.
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  • Atsushi Nakano, Nurul Taufiqu Rochman, Hidekazu Sueyoshi
    2005 Volume 46 Issue 12 Pages 2719-2724
    Published: 2005
    Released: January 14, 2006
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    Recently, the global scale environmental problem has become a critical issue. In metallic material, not only the cost reduction and improvement of mechanical properties but also the decrease in environmental load is required. In copper alloys, several mass% Pb was added to improve the machinability. However, due to the adverse toxicity of Pb that is harmful to the health, a new regulation to limit the amount of Pb permitted in drinking water supplies has been enforced. A huge amount of copper alloy scraps containing Pb will become industrial waste because the scrap will not be available as the raw materials.
    We developed a new technique for removing Pb from copper alloy scraps in order to promote recycle of copper alloy scraps containing Pb. Pb was removed from brass and bronze using compound-separation method.
    Copper alloys containing 2–6 mass% Pb were molten using a high-frequency induction furnace under nitrogen atmosphere. Ca–Si compound and NaF were added into the molten copper alloys to form large particles of a Pb compound. The large particles of the Pb compound were skimmed off from the molten copper alloys. Liquid metal extractions and castings were characterized by electron probe microanalyser (EPMA) and fluorescence X-ray (XRF) analysis.
    The results show that high percentage (83% in brass and 82% in bronze) of Pb removal can be achieved. Therefore Pb-free copper alloys can be produced from copper alloy scraps, resulting in the solution of environmental problems.
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  • Ikuo Shohji, Hiroki Goto, Kiyotomo Nakamura, Toshikazu Ookubo
    2005 Volume 46 Issue 12 Pages 2725-2729
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Electroless Ni/Au plating is often performed on a surface of a Cu pad to improve the wettability of lead-free solders on such a pad. Generally, electroless Au plating is performed by an immersion plating method. Since a substitution reaction of Ni and Au occurs selectively on the surface of a Ni layer in immersion plating, the Au layer does not uniformly form on the Ni layer and microvoids or microcracks easily form at the Ni/Au interface. Such defects induce void formation at the joint interface in soldering, and consequently degrade the reliability of the lead-free solder joint. In this study, the influences of immersion plating time on microvoid formation at the joint interface and the reliability of a solder ball joint with a Sn–3 mass%Ag–0.5 mass%Cu lead-free solder were investigated.
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  • Kiyotomo Nakamura, Ikuo Shohji, Hiroki Goto, Toshikazu Ookubo
    2005 Volume 46 Issue 12 Pages 2730-2736
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Electroless Ni/Au plating is presently in use with high-density Jisso technology in the manufacture of electrical appliances. Electroless Ni/Au plating is said to be less satisfactory than conventional electrolytic plating with respect to the quality of solder joints and lead-free solder in particular. The reason for this is considered the P-rich layer which forms at the interface of solder bulk and Ni layer but this has yet to be fully confirmed.
    Solder joints made by electroless Ni/Au plating and Sn–3 mass%Ag–0.5 mass%Cu lead-free solder balls were examined here for reliability assessment under high temperature storage, using an electroless Ni/Au layer made by autocatalytical deposition and another made by immersion Au plating. Interfacial structure and solder pull strength data for the two layers were compared as basis for this assessment and confirm if solder joints made by electrolytic plating is actually superior.
    At the interface of both layers, cavity formation was found to have occurred by Ni corrosion during Au plating and the number of which appeared to be a factor determining solder joint reliability. Electrolytic Au plating not accompanied by Ni corrosion should provide solder joints with reliability exceeding that by electroless Au plating.
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  • Ikuo Shohji, Satoshi Tsunoda, Hirohiko Watanabe, Tatsuhiko Asai, Megum ...
    2005 Volume 46 Issue 12 Pages 2737-2744
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The reliability of a solder ball joint with a Sn–Ag–Cu–Ni–Ge lead-free alloy, which is expected to be an advanced lead-free solder, was investigated under heat exposure conditions. Solder ball joints with a eutectic Sn–Ag alloy and a ternary Sn–Ag–Cu alloy were also prepared to compare with that of the Sn–Ag–Cu–Ni–Ge alloy. Microstructual observations of the cross sections of the solder ball joints were conducted to investigate microstructural evolutions in the solders and the growth kinetics of reaction layers formed at joint interfaces. The influence of heat exposure treatment on joint strength was investigated by ball shear test. Moreover, the influence of surface treatment of a Cu pad on the reliability of the solder joint was also investigated.
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  • T. Yamasaki, S. Maeda, Y. Yokoyama, D. Okai, T. Fukami, H. M. Kimura, ...
    2005 Volume 46 Issue 12 Pages 2746-2750
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Viscosity of Zr55Cu30Al10Ni5 and Pd40Cu30Ni10P20 supercooled liquid alloys having bulk metallic glass forming ability has been measured by using a penetration viscometer with a cylindrical probe under high speed heating conditions at heating rates between 20 and 400°C/min in the temperature range from the glass transition temperatures (Tg) up to above the crystallization temperatures. The viscosity of these alloys decreased with increasing the heating rate and tended to saturate at the heating rate of 200°C/min and above. Their viscosity could be well represented by the Arrhenius relation. The activation energies for viscous flow for Zr55Cu30Al10Ni5 and Pd40Cu30Ni10P20 supercooled liquid alloys were about 350 and 250 kJ/mol, respectively. The viscosity was also fitted by a Vogel–Fulcher–Tammann (VFT) relationship over the entire temperature range.
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  • Shinji Muraishi, Hirono Naito, Tatuhiko Aizawa
    2005 Volume 46 Issue 12 Pages 2751-2754
    Published: 2005
    Released: January 14, 2006
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    Ni-implantation has been conducted for sputter deposited Zr alloy films to investigate compositional dependent amorphization behavior in proportion to Ni in Zr alloys. As-deposited Zr and Zr–Cu with thickness of 200 nm shows columnar hcp-Zr and nano-crystalline hcp-Zr(Cu), respectively. Implantation of 150 keV Ni+ with the amount of 1×1017 ions/cm2 induces amorphization of Zr and Zr(Cu) with 100 nm in thick. Critical amorphization concentration of penetrated Ni decreases for Ni-implanted Zr–Cu film to be 10 at%Ni as comparison with that of 20 at%Ni for Zr film. The displacement collision effect has been examined by penetration of 300 keV-Ni+. As increasing the beam energy, penetration depth increases to yield equi-axed crystalline surface and inside amorphization, which corresponding to compositional gradient of penetrated Ni. This compositional dependent amorphization via ion implantation implies that induced amorphization is attributed to chemical reaction between penetrated Ni with constituents.
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  • Yoshihiko Yokoyama, Yasutake Akeno, Toru Yamasaki, Peter K. Liaw, Raym ...
    2005 Volume 46 Issue 12 Pages 2755-2761
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The volume of a quenched glassy alloy is a variable of cooling rates during the amorphization. Hence a change in the volume caused by the structural relaxation can be regarded as a degree of amorphousness. The density of Zr50Cu40Al10 bulk glassy alloys (BGAs) increases linearly with the annealing temperature below the glass-transition temperature (Tg). With increasing the annealing temperature, the tensile strength and Vickers hardness show constant values, whereas the Young’s moduli and Charpy impact values become larger and smaller, respectively. Especially, Charpy impact values of Zr–Cu–Al BGAs have a linear relationship with the relative value of excessive free volume, which correspond to the volume-change ratio caused by the full structural relaxation.
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  • Hideyuki Yasuda, Yuki Tamura, Tomoya Nagira, Itsuo Ohnaka, Yoshihiko Y ...
    2005 Volume 46 Issue 12 Pages 2762-2767
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    A levitation method using alternating and static magnetic fields was used to measure nucleation and growth of the crystalline phases in melts of the bulk-metallic-glass forming Zr60Ni25Al15 alloy. For comparison, Zr66.7Ni33.3 and Zr66.5Ni33.2Al0.3 were also examined. Nucleation undercooling in the bulk-metallic-glass forming Zr60Ni25Al15 alloy did not depend on the cooling rate (<102 K/s), and the maximum undercooling observed was approximately 200 K. Recalescence was not observed in the cooling curves of the Zr60Ni25Al15 and the Zr66.5Ni33.2Al0.3 alloys. The growth velocity of the crystalline phase in the Zr60Ni25Al15 alloy was of the order of 10−4 m/s even at a undercooling of 100 K. In contrast, clear recalescence was always observed in the Zr66.7Ni33.3 alloy. The results showed that the addition of Al into the Zr–Ni alloy significantly reduced growth velocity of the crystalline phases. The extremely low growth rate in the Zr–Ni–Al system can contribute to the high glass forming ability.
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  • Hyung-Seop Shin, Young-Jin Jeong, Ho-Yeon Choi, Hidemi Kato, Akihisa I ...
    2005 Volume 46 Issue 12 Pages 2768-2772
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The friction welding of Zr55Al10Ni5Cu30 bulk metallic glasses (BMG) has been tried. An apparatus for the friction welding of BMGs adopting a pneumatic cylinder and gripper based on a conventional lathe, and a welding process which provides a sufficient cooling rate after welding were devised. Friction time and friction pressure were chosen as the control parameters in the friction welding process. Their influences on the shape and volume of the protrusion formed from the welded interface were investigated. In addition, the temperature distribution around the interface during friction welding was measured using an infrared thermal imager. In order to characterize the friction welded interface, X-ray diffraction (XRD) and micrographic observation of welded sections were carried out. A successful joining of Zr55Al10Ni5Cu30 alloy was accomplished through the precise control of friction time and friction pressure. The condition whether crystallization occurred or not during friction welding could be classified depending upon the volume of the protrusion formed at the welded interface which is also related to the thickness of the protrusion formed at the root part of the welded interface.
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  • Masahiro Akiba, Baolong Shen, Akihisa Inoue
    2005 Volume 46 Issue 12 Pages 2773-2776
    Published: 2005
    Released: January 14, 2006
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    The effect of Mo and Si additions on the glass-forming ability (GFA) of Fe77−xMoxGa3P10C4B4Si2 alloys was investigated. The addition of 2 at%Mo combined with 2 at%Si was found to be effective for the extension of the supercooled liquid region (ΔTx) defined by the difference between glass transition temperature (Tg) and crystallization temperature (Tx). The ΔTx value is 33 K for the Fe77Ga3P12C4B4 alloy, and increases to 60 K for the Fe75Mo2Ga3P10C4B4Si2 glassy alloy. In addition, this glassy alloy exhibits a high reduced glass transition temperature (TgTl) of 0.6. The large ΔTx and high TgTl enabled us to prepare the Fe75Mo2Ga3P10C4B4Si2 bulk glassy alloy successfully with a diameter of 2 mm and high saturation magnetization (Is) of 1.27 T. The Fe75Mo2Ga3P10C4B4Si2 glassy alloy also exhibits good soft magnetic properties, i.e., high effective permeability at 1 kHz of 1.1×104 and low coercive force of 5 A/m.
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  • Takeshi Wada, Kana Takenaka, Nobuyuki Nishiyama, Akihisa Inoue
    2005 Volume 46 Issue 12 Pages 2777-2780
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Porous Pd35Pt15Cu30P20 bulk glassy alloy rods were prepared by holding the alloy melts under 1 MPa hydrogen atmosphere, followed by water quenching in reduced hydrogen pressures of 0.9 or 0.1 MPa. The volume fraction and size of pores were controlled by hydrogen pressure of the atmosphere. No crystalline phase was observed over the whole pore wall regions. The porous alloys show slightly decreased thermal stability as compared with the pore-free one, but still keep a large supercooled liquid region. The porous alloy rods exhibited significant plastic elongations in compression while the pore-free rod fractured instantly after the elastic strain limit. The high plasticity of the porous alloys is presumed to originate from the generation of a high density of shear-bands resulting from the effect of stress concentration around the pores.
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  • Akihiko Hirata, Yoshihiko Hirotsu, Eiichiro Matsubara
    2005 Volume 46 Issue 12 Pages 2781-2784
    Published: 2005
    Released: January 14, 2006
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    Effect of Nb addition on the stabilization of amorphous Fe80B20 alloy was studied by electron diffraction structure analysis with the help of computer simulation. Atomic structure models with dense-random-packing 5000 atoms were constructed to reproduce interference functions obtained experimentally for the amorphous Fe80B20 and Fe70Nb10B20 alloys. In the structure models so obtained, prism-type local atomic arrangements dominated around B atoms in both the alloys, while deformed-bcc and icosahedral-like clusters were frequently found around Fe atoms. The icosahedral-like clusters and short Fe–Fe bondings were more frequently found in Fe70Nb10B20. The difference of glass forming abilities of these alloys is discussed in relation to the local structural differences.
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  • Masashi Hasegawa, Tsuyoshi Taketomi, Hidemi Kato, Tsunehiro Takeuchi, ...
    2005 Volume 46 Issue 12 Pages 2785-2790
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    The phase stabilities of Zr–Co–Al and Zr–Ni–Al metallic glasses have been investigated by the thermal analysis and compared with each other. It is found that the largest ΔTx, TgTl and γ parameters of the former are larger than those of the latter, indicating that the former have higher glassy phase stability than the latter. It is also found that the optimum compositions of the former are Zr-poorer and Al-richer than those of the latter and that their transition metal compositions are almost the same. Since Co and Ni have almost the same atomic radius and mixing enthalpy against Zr which are factors correlated with the glassy phase stability, this composition difference may be attributable to another factor, i.e. their difference of the electronic contribution due to the different electronic structure around the Fermi level.
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  • Tsunehiro Takeuchi, Sakura Nakano, Masashi Hasegawa, Kazuo Soda, Hirok ...
    2005 Volume 46 Issue 12 Pages 2791-2798
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Free-energy of Zr–Ni–Al bulk metallic glass (BMG) was estimated by making full use of coordination clusters in the relevant crystals. The clusters in the BMG were determined by using the BMG’s experimentally determined radial distribution functions. and the electronic structure of the identified clusters was calculated by the DVXα cluster calculation. The local atomic arrangements in the Zr–Ni–Al BMG are found to be characterized by the prism clusters with Zr or Ni atom in their center and the Kasper polyhedrons about Al atoms. It was conclude, as a consequence of the present analysis, that the Zr–Ni–Al BMG are stabilized by the low internal-energy of the constituent local atomic clusters assisted by the large entropy caused by the freedom in the bond-direction between the prism clusters and the Kasper polyhedrons.
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  • Akitoshi Mizuno, Seiichi Matsumura, Masahito Watanabe, Shinji Kohara, ...
    2005 Volume 46 Issue 12 Pages 2799-2802
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    High-energy X-ray diffraction experiments were performed for a metallic glass-forming Zr70Cu30 alloy in the liquid state at a high temperature. Conical nozzle levitation was applied as a containerless method of obtaining accurate structure information of a highly reactive melt. The total structure factor obtained for the liquid alloy above its melting point shows a particular shoulder on the second peak, which is probably an indication of local icosahedral short-range ordering typically observed in deeply undercooled liquids. This implies that short-range ordered clusters already exist even in the equilibrium liquid state of Zr-based metallic glass-forming alloys.
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  • Shinya Hosokawa, Naohisa Happo, Hitoshi Sato, Masaki Taniguchi, Tetsu ...
    2005 Volume 46 Issue 12 Pages 2803-2806
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Incident photon-energy dependence of photoemission spectra of Pd42.5Ni7.5Cu30P20 metallic glass was measured using a synchrotron radiation facility. Compared to the elemental Pd, Ni, or Cu metal, the electronic density of states of this extremely good glass-former is highly suppressed at the Fermi energy, which indicates the existence of covalent bonds in this metallic mixture. From the incident photon-energy dependence of the spectra, partial density of states of the Pd, Ni, and Cu elements can be estimated, which suggests the selective formation of Pd–P bonds using the Pd 4d states.
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  • Nobuyuki Nishiyama, Kana Takenaka, Takeshi Wada, Hisamichi Kimura, Aki ...
    2005 Volume 46 Issue 12 Pages 2807-2810
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    In order to realize biomedical applications of bulk glassy alloys, we have developed new Pd-based glassy alloys with Ni-free composition in Pd–Pt–Cu–P system and it is revealed that the highest glass-forming ability is obtained at a composition of Pd35Pt15Cu30P20. In addition, the alloy can be formed into bulk glassy rods with diameters of up to at least 30 mm by fluxed water quenching. In order to clarify the critical cooling rate for glass-formation, undercooling behavior and crystal growth rate are also discussed. Crystallization of the alloy under continuous cooling is mainly dominated by surface nucleation. Apparent crystal growth rate of the alloy at 0.73 Tm is evaluated to be 5.2×10−6 m·s−1 and this value is four orders of magnitude higher than that of previous Pd40Cu30Ni10P20 at the same degree of undercooling.
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  • Tetsuo Mohri, Yoshitaka Kobayashi
    2005 Volume 46 Issue 12 Pages 2811-2816
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Kinetics of glass transition is simulated within the Path Probability Method (PPM) which is the natural extension of the Cluster Variation Method (CVM) to time domain. Temperature dependences of order parameter during continuous cooling are calculated as a function of cooling rate. When the temperature dependence of viscosity is introduced in the mobility term in the PPM, the order parameter is frozen as approaching the ideal glass transition temperature. Furthermore, a preliminary calculation which incorporates the cooling rate dependence into the viscosity reproduces the experimental tendency of the glass transition temperature. Together with the previous studies of thermodynamic frameworks of glass transition based on the CVM, it is confirmed that the combination of the CVM and PPM provides a unique theoretical tool to study glass transition in a consistent manner covering thermodynamics and kinetics.
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  • Akira Takeuchi, Akihisa Inoue
    2005 Volume 46 Issue 12 Pages 2817-2829
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Bulk metallic glasses (BMGs) have been classified according to the atomic size difference, heat of mixing (ΔHmix) and period of the constituent elements in the periodic table. The BMGs discovered to date are classified into seven groups on the basis of a previous result by Inoue. The seven groups are as follows: (G-I) ETM/Ln-LTM/BM-Al/Ga, (G-II) ETM/Ln-LTM/BM-Metalloid, (G-III) Al/Ga-LTM/BM-Metalloid, (G-IV) IIA-ETM/Ln-LTM/BM, (G-V) LTM/BM-Metalloid, (G-VI) ETM/Ln-LTM/BM and (G-VII) IIA-LTM/BM, where ETM, Ln, LTM, BM and IIA refer to early transition, lanthanide, late transition, group IIIB–IVB and group IIA-group metals, respectively. The main alloying element of ternary G-I, G-V and G-VII, ternary G-II and G-IV, and ternary G-VI BMGs is the largest, intermediate and smallest atomic radius compared to the other alloying elements, respectively. The main alloying element of ternary BMGs belonging to G-I, G-V, G-VI and G-VII is an element in the atomic pair with the largest and negative value of ΔHmix (ΔHL.N.mix), while the main element of ternary BMGs belonging to G-II and G-IV is independent of the atomic pair with ΔHL.N.mix. The characteristics of the main element derived for the ternary BMGs are directly applicable to multicomponent BMGs belonging to G-I, G-II, G-IV (Mg-based BMGs), G-V and G-VII. The main element can be the larger-sized element in the atomic pair with ΔHL.N.mix or in the same group as the other elements for multicomponent BMGs belonging to G-III, G-IV (Be-containing Zr-based BMG) and G-VI. The main element of BMGs belonging to G-VI tends to change from the element with the smallest atomic radius in a ternary system to an element with a relatively large atomic size in a multicomponent system. The change is due to an increase in glass-forming ability through multicomponent alloying of BMGs belonging to G-VI. The results of the classification of BMGs obtained in the present study are important for further development of BMGs, with the results providing a road map for the development of new BMG compositions.
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  • Masato Shimono, Hidehiro Onodera
    2005 Volume 46 Issue 12 Pages 2830-2837
    Published: 2005
    Released: January 14, 2006
    JOURNALS FREE ACCESS
    Relaxation behavior of structural change at the atomic cluster level in supercooled liquids during isothermal annealing processes is investigated for a model alloy system by using molecular dynamics simulations. The simulation results show that the number density of icosahedral clusters increases with the annealing time. Moreover, the number density of icosahedral clusters, the structural relaxation time, and the atomic diffusivity strongly correlate with the packing density of the supercooled liquids for many kinds of systems of alloying components with a variety of atomic size ratios and heats of mixing. This suggests that the packing density would be a good probe to estimate the stability of supercooled liquid phases and the glass-forming ability of the system.
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