10 results on '"Akiyoshi Nakata"'
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2. Influence of surfactants as additives to electrolyte solutions on zinc electrodeposition and potential oscillation behavior
- Author
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Kohei Miyazaki, Tomokazu Fukutsuka, Takeshi Abe, Akiyoshi Nakata, and You-Shin Lee
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Aqueous solution ,Oscillation ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,Zinc ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Pulmonary surfactant ,Bromide ,Materials Chemistry ,Sodium dodecyl sulfate ,0210 nano-technology - Abstract
The effects of surfactants as organic additives to electrolyte solutions on potential oscillation behavior and Zn electrodeposition were observed. Applying a constant current density (−20 mA cm−2), we induced the potential oscillation of electrochemical Zn deposition in aqueous solutions of KOH, ZnO, and surfactants. Potential oscillation behavior for Zn electrodeposition was strongly affected by the presence of surfactants. While an anionic surfactant (sodium dodecyl sulfate) slightly increased the period of potential oscillation, even small amounts of nonionic (Triton X-100) and cationic surfactants [cetyltrimethylammonium bromide(CTAB)] greatly increased the period of potential oscillation. The presence of CTAB in an electrolyte produced small spherical Zn deposits, which clearly implies that CTAB plays a role in suppressing dendrite formation during Zn deposition. more...
- Published
- 2016
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Catalog
3. Study on the ‘Shape Change’ of Rechargeable Zinc Electrodes in Alkaline Electrolytes
- Author
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Masayuki Morita, Akiyoshi Nakata, Takeshi Abe, and Zempachi Ogumi
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Materials science ,Shape change ,chemistry ,Electrode ,Inorganic chemistry ,chemistry.chemical_element ,Electrolyte ,Zinc - Abstract
Zinc, the most historical material for battery application, is one of the candidates for the high capacity electrodes of the next-generation secondary batteries, and has been applied in Zn/Air, Zn/NiOOH. These zinc-based batteries commonly employ aqueous alkaline electrolytes that have some advantages such as high ionic conductivity for high rate capability and non-flammability for high safety, which are particularly attractive for the mobile and EV applications. However, their insufficient cycle life due to the deterioration modes such as zinc dendrite formation, densification and shape change, has limited the widespread use of the zinc-based secondary batteries. In particular, the shape change is known to be a serious problem, in which the active material is gradually lost at the edge and agglomerates in the center of the electrode in the course of cycling, resulting in the capacity fade. For suppressing this undesirable redistribution of the zinc electrode, it is essential to clarify the growth mechanism of the shape change phenomenon. So far the growth mechanism has been studied and analyzed, especially in the view point of the reaction (current) distribution, by various methods such as direct visual observation, tracing radioisotope, monitoring current distribution with the use of divided electrode, and calculating mathematical model. As the shape change proceeds dynamically with charging-discharging cycles causing electrode composition changes, the detailed observation of the composition change of zinc species during the cycling offer fruitful information on the reaction distribution to understand the growth mechanism of the shape change precisely and key to improve it. In this study, we evaluate the distribution of zinc species in Zn/NiOOH cells to elucidate the way the shape change occurs in the course of cell cycling. References: [1] A. Nakata , H. Arai , H. Murayama , K. Fukuda , T. Yamane , T. Hirai , Y. Uchimoto , J. i. Yamaki , and Z. Ogumi,APL Materials 6, 047703 (2018); https://doi.org/10.1063/1.5011272. more...
- Published
- 2020
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4. A Reversible Conversion Reaction of Metal and BF4−Anions for the Use in Li-Ion Batteries
- Author
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Zempachi Ogumi, Toshiro Hirai, Tooru Matsui, Akiyoshi Nakata, and Junichi Yamaki
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Conversion reaction ,Renewable Energy, Sustainability and the Environment ,Chemistry ,020502 materials ,Inorganic chemistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,Metal ,0205 materials engineering ,visual_art ,Materials Chemistry ,Electrochemistry ,visual_art.visual_art_medium ,0210 nano-technology - Published
- 2016
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5. Preserving Zinc Electrode Morphology in Aqueous Alkaline Electrolytes Mixed with Highly Concentrated Organic Solvent
- Author
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Zempachi Ogumi, Tomokazu Yamane, Toshiro Hirai, Akiyoshi Nakata, and Hajime Arai
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Morphology (linguistics) ,Aqueous solution ,Renewable Energy, Sustainability and the Environment ,Organic solvent ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,Zinc ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Electrode ,Materials Chemistry ,Electrochemistry ,0210 nano-technology - Abstract
Zinc-based secondary batteries are promising power sources with high energy density but their deterioration modes such as dendritic growth and shape changes need to be solved. These drastic morphology changes of the zinc electrode come from the nature of the discharged product that is easily dissolved in the alkaline electrolyte as zincate species. In this study, we attempt to preserve the zinc electrode morphology by employing the zinc oxidation-reduction processes in the vicinity of electrode, which is attained by controlling the electrolyte solvent property with mixing an organic solvent propylene carbonate (PC). The results show that the use of PC-water mixed solvent is effective in restricting the zincates dissolution into the electrolyte and preserving the zinc electrode morphology with no dendrite formation through 500 oxidation-reduction cycles is demonstrated in the electrolyte with high PC concentrations. more...
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- 2015
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6. Transformation of Leaf-like Zinc Dendrite in Oxidation and Reduction Cycle
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Toshiro Hirai, Tomokazu Yamane, Zempachi Ogumi, Haruno Murayama, Katsutoshi Fukuda, Junichi Yamaki, Yoshiharu Uchimoto, Hajime Arai, and Akiyoshi Nakata
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Electrode material ,Aqueous solution ,Scanning electron microscope ,General Chemical Engineering ,Inorganic chemistry ,Oxide ,chemistry.chemical_element ,Zinc ,Redox ,chemistry.chemical_compound ,chemistry ,Electrode ,Electrochemistry ,Current density - Abstract
Zinc is a promising negative electrode material for aqueous battery systems whereas it shows insufficient rechargeability for use in secondary batteries. It has been reported that leaf-like dendrite deposits are often the origin of cell-failure, however, their nature and behavior on discharge (oxidation) - charge (reduction) cycling have been only poorly understood. Here we investigate the transformation of the leaf-like zinc dendrites using ex-situ scanning electron microscopy, X-ray computational tomography and in-situ X-ray diffraction. It is shown that the leaf-like zinc dendrites obtained under diffusion-limited conditions are nearly completely dissolved at a low oxidation current density of 1 mA cm−2 and cause re-evolution of the zinc dendrites. Oxidation at a high current density of 10 mA cm−2 leads to the formation of leaf-like zinc oxide residual products that result in particulate zinc deposits in the following reduction process, enabling good rechargeability. The reaction behavior of this oxide residue is detailed and discussed for the development of long-life zinc electrodes. more...
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- 2015
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7. Oxidation of Nickel in AlCl3-1-Butylpyridinium Chloride at Ambient Temperature
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Katsunori Nakaya, Toshiro Hirai, Akiyoshi Nakata, and Zempachi Ogumi
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Materials science ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,chemistry.chemical_element ,Condensed Matter Physics ,Chloride ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Nickel ,chemistry ,Materials Chemistry ,Electrochemistry ,medicine ,medicine.drug - Published
- 2014
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8. Deposition of Metal Oxide Films at Liquid−Liquid Interface by the Liquid Phase Deposition Method
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Minoru Mizuhata, Shigehito Deki, Akiyoshi Nakata, and Yasuyuki Sakakibara
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Morphology (linguistics) ,Materials science ,Bilayer ,Inorganic chemistry ,Oxide ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Titanium oxide ,Metal ,chemistry.chemical_compound ,symbols.namesake ,General Energy ,chemistry ,Chemical engineering ,visual_art ,visual_art.visual_art_medium ,symbols ,Physical and Theoretical Chemistry ,Raman spectroscopy ,Fluoride ,Deposition (law) - Abstract
The liquid phase deposition (LPD) of metal oxide thin films at the liquid−liquid interface was investigated. Just after the start of the LPD reaction, depositions were observed continually at the liquid−liquid interface. The deposition grew two-dimensionally into a self-standing film with thickness of 1 μm and domain size of up to ca. 1 mm without any solid substrates. The self-standing film was formed with asymmetrical morphology, which consisted of flat surface on the side of the liquid−liquid interface and relatively rough surface on the side of the bulk solution. The structure was characterized by Raman spectroscopy, confirming that metastable ammonium titanium oxide fluoride (NH4TiOF3) was first deposited at the liquid−liquid interface, on which anatase-type titanium oxide (TiO2) was deposited second to forming the asymmetrical bilayer structure. It was suggested that the metal fluoride complex of the precursor was concentrated in the vicinity of the liquid−liquid interface compared with the solid−li... more...
- Published
- 2008
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9. Novel fabrication of highly crystallized nanoparticles in the confined system by the liquid phase deposition (LPD) method
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Minoru Mizuhata, Shigehito Deki, and Akiyoshi Nakata
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Fabrication ,Chemistry ,General Chemical Engineering ,Inorganic chemistry ,Nanoparticle ,Micelle ,symbols.namesake ,Chemical engineering ,Rutile ,Electrochemistry ,symbols ,Deposition (phase transition) ,Orthorhombic crystal system ,Raman spectroscopy ,Monoclinic crystal system - Abstract
In this study, we successfully synthesized monodispersed metal oxide nanoparticles of high-temperature phases such as monoclinic VO 2 , orthorhombic Ta 2 O 5 under an ambient condition without any post-annealing process, applying the liquid phase deposition (LPD) method in the confined system of reverse micelle (RM). It was suggested that the obtained nanoparticles were highly crystallized due to the depression of surface disorder, indicated by Raman spectrum of rutile type SnO 2 nanoparticles. This procedure represents a simple route for the production of highly crystallized nanoparticles with potentially interesting applications. more...
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- 2007
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10. High Quality Monodispersed Oxide Nanoparticles Prepared by the Liquid Phase Deposition Method in Aqueous Polymer Solution
- Author
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Akiyoshi Nakata, Minoru Mizuhata, and Shigehito Deki
- Subjects
Anatase ,Materials science ,Aqueous solution ,Inorganic chemistry ,Oxide ,Nanoparticle ,Electrolyte ,Nanocrystalline material ,Titanium oxide ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Crystallization - Abstract
Nanoscale materials are of great interest scientifically and technologically because of their potential to exhibit interesting properties which cannot be achieved in bulk materials. In particular, nanoparticles have attracted much interest owing to the quantum size effect which causes the peculiar optical and magnetic characters. Especially, nanocrystalline metal oxides have potential or demonstrated application in many technologies, including solar energy conversion, batteries, catalysis and ductile ceramics. It is well-known that the optical, electronic, and chemical properties of the quantum dots are dominated by physical size and the chemistry of their surface and crystal structure. For such materials, various fabrication methods were employed using various chemical and physical techniques. It is especially demanding to make crystalline metal oxide nanopaticles at ambient conditions, as the usual fabrication process performed in water-rich solvent mixtures results in a poor crystallinity which does not possess the desired electronic and relies on a high temperature recrystallization. We have developed and proposed the liquid phase deposition (LPD) method as a novel aqueous solution-based process to prepare various metal oxide thin films and/or nanostructures using ligand-exchange hydrolysis of metal-fluoro complexes and the F consumption reaction with boric acid, aluminum metal and so on[1-3]. The LPD process relies on the chemical equilibrium between the metalfluoro complex and metal oxide by the minute energy difference in the aqueous solution at ambient temperature, which is a typical soft solution process in the homogeneously mixed system. In this study, we investigated the LPD reaction with hydrophilic polymer of polyethyleneglycol known as green materials applied for electrolyte, in order to fabricate monodispersed metal oxide nanoparticles fabricated at ambient condition. For the preparation of nanosized particles of titanium oxide, the guest molecule of PEG were solvated into the metal-fluoro complex aqueous solution of (NH4)2TiF6. After mixing two components, H3BO3 aqueous solution was added into the treatment solution with rapid stirring. The mixed solution was kept in the 303K bath for 20 hours. After the LPD reaction, the solution was centrifuged, and the obtained precipitate was washed in the distilled water by ultrasonic apparatus three times to be separated from the residual PEG and byproducts. It was observed that the transmittance of transparent solution was quickly reduced by dropping boric acid solution into treatment solution and whitened within 10 minutes, although fluoride complex have been stable with only PEG molecules. It was maybe proceeding in boric acid reacted metalfluoro complex under LPD reaction mechanism. The typical TEM images of oxide nanoparticles obtained by the LPD process are shown in Fig.1. The TEM image show so many nanoparticels uniformly distributed without aggregation, whose particle diameter is the average of 3.8nm and standard deviation is 0.4 nm around 10%. The obtained powder was characterized by X-ray diffraction measurement and Raman spectroscopy. It is shown that fluoride complex degraded and generated anatase type of titanium oxide with small size crystallite. In detail investigation with high-resolution TEM, it is shown that the titanium oxide have highly crystallization, reacted under ambient condition as shown in Fig. 2. The particle size distribution was controllable in the degree of from 2-10 nm with PEG concentration. Moreover, the reactivity of metal-fluoride complex was also enlarged with PEG concentration, up to 70% of reactivity. These results may suggest that PEG interact with metal-fluoro complex, which is supported by XPS analysis and Raman spectroscopy study revealing PEG existence on the surface of nanoparticles. Consequently, monodispersed TiO2 nanoparticle was synthesized by the LPD process controlling the size and reactivity of metal-fluoro complex, using polyethyleneglycol. The present method represents a simple route for the production of crystalline metal oxide nanopartciles with potentially interesting applications at ambient condition. more...
- Published
- 2006
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