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| 1.
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Watanabe, Chihiro ; Monzen, Ryoichi ; Tazaki, Kazue
概要:
金沢大学大学院自然科学研究科機能創成システム<br />The effects of addition of Zr and Ag on the mechanical properties of a Cu-0.5 wt%Cr alloy ha
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ve been investigated. The addition of 0.15 wt%Zr enhances the strength and resistance to stress relaxation of the Cu-Cr alloy. The increase in strength is caused by both the decrease in inter-precipitate spacing of Cr precipitates and the precipitation of Cu5Zr phase. The stress relaxation resistance is improved by the preferentially forming Cu5Zr precipitates on dislocations, in addition to Cr precipitates on dislocations. The addition of 0.1 wt%Ag to the Cu-Cr and Cu-Cr-Zr alloys improves the strength, stress relaxation resistance and bend formability of these alloys. The increase in strength and stress relaxation resistance is ascribed to the decrease in inter-precipitate spacing of Cr precipitates and the suppression of recovery during aging, and to the Ag-atom-drag effect on dislocation motion. The better bend formability of the Ag-added alloys is explained in terms of the larger post-uniform elongation of the alloys. © 2007 Springer Science+Business Media, LLC.
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| 2.
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Watanabe, Chihiro ; Monzen, Ryoichi ; Tazaki, Kazue
概要:
金沢大学大学院自然科学研究科機能創成システム<br />The effects of addition of Zr and Ag on the mechanical properties of a Cu-0.5 wt%Cr alloy ha
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ve been investigated. The addition of 0.15 wt%Zr enhances the strength and resistance to stress relaxation of the Cu-Cr alloy. The increase in strength is caused by both the decrease in inter-precipitate spacing of Cr precipitates and the precipitation of Cu5Zr phase. The stress relaxation resistance is improved by the preferentially forming Cu5Zr precipitates on dislocations, in addition to Cr precipitates on dislocations. The addition of 0.1 wt%Ag to the Cu-Cr and Cu-Cr-Zr alloys improves the strength, stress relaxation resistance and bend formability of these alloys. The increase in strength and stress relaxation resistance is ascribed to the decrease in inter-precipitate spacing of Cr precipitates and the suppression of recovery during aging, and to the Ag-atom-drag effect on dislocation motion. The better bend formability of the Ag-added alloys is explained in terms of the larger post-uniform elongation of the alloys. © 2007 Springer Science+Business Media, LLC.
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| 3.
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Watanabe, Chihiro ; Nishijima, Fumiya ; Monzen, Ryoichi ; Tazaki, Kazue
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金沢大学大学院自然科学研究科機能創成システム<br />The effects of P and Cr addition and two-step aging on the microstructure and mechanical pro
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perties of a Cu-4wt%Ni-0.95wt%Si alloy have been examined. The addition of 0.02wt%P improves both strength and elongation because it suppresses discontinuous precipitation reaction. The Cr addition to the Cu-Ni-Si-P alloy decreases greatly the grain size, resulting in an increase in elongation. Two-step aging, pre-aging at 300 or 350°C and subsequent second-step aging at 450°C, causes an increase in strength without reducing elongation. The increase in strength is attributable to the decrease in inter-precipitate spacing by the two-step aging. The two-step aged Cu-4wt%Ni-0.95wt%Si-0.02wt%P-0.02wt%Cr alloy attains a tensile strength of 830MPa, an elongation of 13% and an electrical conductivity of 35%IACS.
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| 4.
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Tazaki, Kazue ; Asada, Ryuji
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金沢大学大学院自然科学研究科環境動態<br />Mercury is a toxic substance that is widely distributed throughout the hydrosphere, biosphere, a
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nd lithosphere. Mine waste environments and mine waters support a wide diversity of microbial life. The microbial ecology of environments where mine waters are polluted with heavy metals is poorly understood. Here, we describe the features of bacteria in mercury-contaminated gold panning ponds in a small-scale gold mine (Geita) near Lake Victoria, Tanzania using energy filtering transmission electron microscopy (EF-TEM) and scanning transmission electron microscopy equipped with energy dispersive X-ray spectroscopy (STEM-EDX). Most bacteria in the panning pond showed thick exopolysaccharides (EPSs), and many clay minerals attached onto the surface of EPSs. The clay minerals and EPSs might act as protective layers for the bacteria against toxic materials. The clay minerals were composed of smectite, halloysite, and kaolinite associated with calcite and goethite. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy indicated that the bulk soil samples contained abundant Si, Al, K, Ca, and Fe with heavy metals such as Au, Ti, and Ag. The results indicate that Hg pollution from panning ponds is caused by not only volatilization of Hg from Au-Hg amalgams, but Hg is also released into the air as dust mixed with dry fine clays, suggesting high long-term environmental risks. Mercury-resistant bacteria associated with clay minerals may have a significant effect on the weathering processes of the ore during long-term bioremediation. The clay mineral complexes on the surface of bacterial cell walls are a stimulator for Hg-resistant bacterial growth in mud ponds contaminated with the Au-Hg materials. 全文公開200809
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| 5.
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Tazaki, Kazue ; Morikawa, Toshikazu ; Watanabe, Hiroaki ; Asada, Ryuji ; Okuno, Masayuki
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出版者照会後に全文公開<br />Microbial formation, Bio-imogolite, Fibrous network structure, Bacterial cell wall, Cohesion, Electron microscope
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Brandon, Keely ; Tazaki, Kazue ; Okuno, Masayuki
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出版者照会後に全文公開<br />A unique ecosystem composed of liverworts, diatoms, bacteria and argillaceous sediments is able to thri
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ve in spite of acidic, sulfur and heavy metal contaminated water below the abandoned Ogoya Copper Mine in Ishikawa, Japan. Sample analyses by optical microscope, ED-XRF, XRD, SEM, TEM and FE-TEM revealed that Fe and Cu were taken up by benthic organisms and sediments. Metal uptake and precipitation, including adsorption by clay minerals, improves the water quality for surrounding organisms. Liverworts shelter diatoms and bacteria, also trapping sediments and precipitates that would otherwise be washed away. Meanwhile bacteria are involved in metal accumulation and converting toxic aqueous metals to minerals. Liverworts displayed Cu and occasionally Fe and Zn content. Clay sediments were enriched in Fe and sometimes S, with traces of Ti, Mn, Cu, Zn, and occasionally As, Br, Sr and Zr. Based on XRD analyses, chlorite, mica minerals, feldspar, quartz and chloritoid were predominant in the <2μm fraction of the river sediments, along with traces of the sulfate minerals melanterite, chalcanthite and despujolsite. Mine drainage has compromised the health of surrounding communities and damaged river ecosystems. Clarification and optimization of natural metal uptake processes and the fate of mine-related elements could hold keys to sustainable remediation methods for use in the Ogoya mine area.
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| 7.
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Nagase, Takako ; Tazaki, Kazue
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出版者照会後に全文公開<br />Low-silica zeolite samples and smectite were hydrothermally synthesized from Si-Al hydrous oxides. The
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synthesized zeolite phases changed to structures having lower Si/Al ratio with increases in the amount of NaOH in the slurry, and time of hydrothermal treatment. When tetraethyl ammonium hydroxide (TEAOH) was added instead of NaOH, ammonium smectite was produced without zeolite. SEM and TEM images suggested that crystallization occurred at the solid-liquid interface. Upon addition of NaOH (Na/Si<0.2) to the smectite, zeolite nucleation was observed on the surface of the clay film. The zeolite phase changes depended on the dissolution of the solid phase and the resultant change in composition of the liquid phase. The observed phase relationships agreed with the calculated formation free energies and solubilities. Thus, low-silica zeolite formation under hydrothermal conditions was strongly affected by the composition and concentration of the solution. The phase relationships based on solubility curves, can be used to control the synthesis of metastable aluminous silicates and can be applied to the design of some industrial materials such as zeolite membranes and molecular sieves using hydrophilic low-silica zeolites and smectites.
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| 8.
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POLGARI, MARTA ; Tazaki, Kazue ; Watanabe, Hiroaki ; VIGH, TAMAS ; Gucsik, Arnold
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出版者照会後に全文公開<br />The black shale-hosted ÚRKÚT Mn-mineralization is among the 10 largest deposits in the World. In this s
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tudy optical and electron microscopy demonstrated the biological formation of Mn-Fe minerals in Mn-carbonate ores. The ED-XRF elemental content maps and SEM-EDX observation of the ores showed distribution of Mn, Fe, and Si banded layer structure whereas the Mg, Al, and K are randomly distributed, as well as to explain the role of microorganisms associated with Ca and P. In both samples abundant microorganisms were found in the dark brown and white layers. Optical micrographs of thin sections clearly showed various shapes of cellular materials, such as spherule, oval, and filamentous morphologies. SEM-EDX observation revealed Fe-rich and P-Ca components around microorganisms showing spherule, tubular, and filamentous cells. The present investigation strongly suggests that the Mn-Fe and Si minerals were associated with microorganisms as a biological organic product. The identity of the bacteria responsible for Mn mineral formation is unknown, but is tentatively assigned to Mn and Fe bacteria on the basis of morphology. The genesis of rocks and minerals have played a pivotal role in Toarcian age, and they may even have acted as life genetic system.
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| 9.
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Mitsuno, Masumi ; Tazaki, Kazue ; Fyfe, W. S. ; Powell, Michael A. ; Hart, Brian ; Daishng, Sun ; Li, Sheng-Rong
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出版者照会後に全文公開<br />Natural cultivation experiments using coal ash, reservoir sediments and Yellow River sediments were car
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ried out to determine the applicability of using these wastes to remediate desertificated soil in Inner Mongolia, China. In the experiments, the microorganisms multiplied more when coal ash was applied to the desertificated soil. Under optical microscope, abundant bacteria were observed in porous surfaces and inside of coal ash particles thereby indicating that the addition of coal ash to desertificated soil hastens the breeding of bacteria, improves soil quality and could be used in afforestation practices. The effects of ash on soil can be explained in two ways: first, in terms of its chemical characteristics (the coal ash contains C, N, P and K); and second, in terms of its micromorphology (it is porous). In natural cultivation experiments, the mixing of reservoir sediments and/orYellow River sediments with the coal ash helped multiply bacteria. These experiments suggest that coal ash and reservoir sediments can be utilized to help solve some of the most serious environmental issues facing China today.
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| 10.
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Chaerun, S. Khodijah ; Tazaki, Kazue
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出版者照会後に全文公開<br />The effect of kaolinite on the growth of hydrocarbon-utilizing indigenous microorganisms in high concen
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tration of heavy oil (i.e., approximately 150 g/l) was studied. Microorganisms were able to grow well in such an extremely high concentration in the presence of yeast extract as co-substrate in direct contact with kaolinite. The presence of kaolinite was not toxic but stimulant for the microbial growth associated with the formation of biofilms at pH values of 5-6 after 36 days of incubation. Bacterial growth predominated when the pH of solutions was neutral-alkaline condition, while fungal growth was predominant as the pH of solutions decreased to be as low as 5 or lower. TEM observation of the kaolinite-oil-microorganism complexes showed that the microbial cells tended to be primarily bound on the edges of kaolinite, and XRD analysis confirmed that their complexes were the adsorption of the cells and heavy oil to the external surfaces of kaolinite. The results may contribute to what environmental factors having a great influence on the bioremediation process is therefore fundamental to many areas contaminated with oil spills, primarily marine and coastal environments. To our knowledge, there are no previous reports on the use of the clay minerals (i.e., kaolinite) in the bioremediation of the Nakhodka oil spill in combination with biofilm formation.
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