Y. Uchimoto - Academia.edu (original) (raw)
Papers by Y. Uchimoto
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2013
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2013
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2016
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2013
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2017
J. Chem. Soc., Chem. Commun., 1989
... Zempachi Ogumi," Yoshiharu Uchimoto, and Zen-ichiro Takehara Department of Industrial Ch... more ... Zempachi Ogumi," Yoshiharu Uchimoto, and Zen-ichiro Takehara Department of Industrial Chemistry, Faculty of Engineering, Kyoto University, Yoshida, Kyoto 606, Japan J. CHEM. SOC., CHEM. ... 3 K. Nagaoka, H. Naruse, and I. Shinohara, J. Polym. Sci., Polym. Lett. ...
Solid State Ionics, 2004
Electrochemical behavior and the variation of electronic structure upon lithium insertion into th... more Electrochemical behavior and the variation of electronic structure upon lithium insertion into the A-site-deficient perovskite oxide, Gd 1/3 TaO 3 , have been studied by X-ray absorption spectroscopy (XAS). During electrochemical lithium insertion, Gd L III-edge and Ta L I-edge XAS revealed that Gd ion did not contribute the charge compensation, while Ta ion reduced its oxidation state. Furthermore, the changes in O K-edge spectra with electrochemical lithium insertion were clearly observed, indicating that O ions also contribute to the electron-transfer reaction.
Journal of The Electrochemical Society, 2005
High-Rate-Capable Lithium-Ion Battery Based on Surface-Modified Natural Graphite Anode and Substi... more High-Rate-Capable Lithium-Ion Battery Based on Surface-Modified Natural Graphite Anode and Substituted Spinel Cathode for Hybrid Electric Vehicles. [Journal of The Electrochemical Society 152, A1595 (2005)]. Iresha RM ...
![Research paper thumbnail of Preparation of Perovskite-type LaFexCo1−xO3 by thermal decomposition of heteronuclear complex, La[FexCo1−x(CN)6]·nH2O for electroceramic applications](https://attachments.academia-assets.com/98695312/thumbnails/1.jpg)
](Journal of Alloys and Compounds, 1997
Heteronuclear complex. LalFe Co, ,(CN),,I.nH,O was synthesized and the thermal decomposed product... more Heteronuclear complex. LalFe Co, ,(CN),,I.nH,O was synthesized and the thermal decomposed products were examined. Single phase of perovskite-type LaFe,Co~ ,(), powders were obtained by the thermal decomposition of the complexes even at 600°C. Hexagonal structure is observed for Fe/La<[).5 and orthorhombic ¢pseudo-cubic) for Fe/La>0.5. From a mechanically rnixed and compacted complexes of LalFe(CN),,I'nH,O and LalCo(CN),,I.nH,O. perovskite-type LaFe,Co, (), oxide could not be formed by thermal decomposition/sintering even at II1)0°C. it is concluded that La[Fe,Co~ ,(CN),,I.nH,O complex is a suitable precursor to prepare liner and ht,mogeneous l')erovskitc-type l.aFe Co~ ,O,. @ 1997 Elsevier Science S.A.
International Journal of Quantum Chemistry, 2002
Quantitative analysis of the formation energy of Cr vacancy in MgCr 2 O 4 was made by first princ... more Quantitative analysis of the formation energy of Cr vacancy in MgCr 2 O 4 was made by first principles calculation. A 56-atom supercell was employed and relaxation of atoms within the second-nearest-neighbor shell of the vacancy was taken into account. The formation energy was calculated as a function of the atomic chemical potential of Cr. Theoretical formation energy of Cr vacancy in MgCr 2 O 4 shows negative values in the case of the oxidation limit of MgCr 2 O 4 , in good agreement with experimental results showing abundance of Cr vacancies when annealed in air. On the other hand, the formation energy of the Al vacancy in MgAl 2 O 4 under the same condition is as large as 4.76 eV. This also corresponds well to the experimental fact that Al vacancy does not form alone in MgAl 2 O 4 in air.
Journal of The Electrochemical Society, 2003
We produced a novel Mg 2ϩ conducting polymer electrolyte and added a poly͑ethylene glycol͒ ͑PEG͒-... more We produced a novel Mg 2ϩ conducting polymer electrolyte and added a poly͑ethylene glycol͒ ͑PEG͒-borate ester as a new type plasticizer having a Lewis acidity and investigated the influence of the Lewis acidity of the PEG-borate ester to a solid polymer electrolyte containing Mg(ClO 4) 2 salt. Adding the PEG-borate ester into the electrolyte shows the increase in the ionic conductivity of the polymer electrolyte. By measuring the glass transition temperature (T g) of the polymer electrolytes using differential scanning calorimetry, it became clear that the mobility of the carrier ion increases with increasing the amount of the PEG-borate ester. By investigating the temperature dependence of the ionic conductivity using William-Landel-Ferry type equation and measuring Raman spectra of the polymer electrolytes, it was found that the concentration of the carrier ion increases with increasing the amount of the PEG-borate ester in the polymer electrolyte. Furthermore, by estimating the transference number of the Mg 2ϩ cation and performing the ab initio calculation for the PEG-borate ester, it is suggested that the PEG-borate ester may enhance the degree of dissociation of the Mg salt in the polymer electrolyte to increase the ratio of the free ion, especially Mg 2ϩ , by interacting with and trapping the ClO 4 Ϫ anion of the salt as a Lewis acid.
Journal of the Electrochemical Society, 2013
The electrodeposition of Mg metal from an ionic liquid-glyme mixture was investigated at room tem... more The electrodeposition of Mg metal from an ionic liquid-glyme mixture was investigated at room temperature. The mixture contains a glyme, a simple amide salt Mg(Tf 2 N) 2 (Tf = SO 2 CF 3), and a quaternary-ammonium Tf 2 N ionic liquid. Using the mixture bath, substantial cathodic electrodeposition of Mg at a large current density (∼10 mA cm −2) was observed, suggesting a change in coordination geometry around Mg 2+ cation together with improved conductivity. By mixing diglyme, the conductivity increased by an order of magnitude (2.5-2.6 mS cm −1) compared to the glyme-free ionic liquid (0.35 mS cm −1) and the viscosity became as low as that of pure glyme. Additionally, potentiostatic electrolysis resulted in a non-dendritic thin film of elemental Mg with metallic luster.
We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk ... more We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel LixMn2O4, a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen 2p orbital. Moreover, the manganese 3d states are shown to experience spatial delocalization involving 0.16 electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery.
ECS Proceedings Volumes
Methods for synthesizing solid oxide fuel cell ceramic materials from aqueous solutions at ordina... more Methods for synthesizing solid oxide fuel cell ceramic materials from aqueous solutions at ordinary temperatures and ordinary pressures are ad vantageous because of the applicability to making films with wide areas and/or complicated shapes with no requirement of vacuum or high tem perature, and because of lower cost. Solutions of fluoro-complex ions were obtained by dissolving sodium hexafluorozirconate in distilled water or dissolving LaMeO3 (Me=Cr, Mn, Fe, Co) or (La,Sr)MeO3 perovskite pre pared by usual solid state reaction in hydrofluoric acid. Boric acid was added into the solution, the fluoride ions were consumed by the formation of BF4' complex ion, and then the fluoro-complex ions were hydrolyzed to ZrO2, LaMeO3 or (La,Sr)MeO3 in order to increase the amount of fluoride ions. The high crystallinity of the product was confirmed by sharp and strong X-ray diffraction peaks. Aggregates of synthesized ZrO2, LaMeO3 or (La,Sr)MeO3 were observed on the substrates in scanning electron micro scope images. Deposition of LaMnO3 on yttria stabilized zirconia substrate was performed by using this method.
Heat capacity of spinel LiCr 1/6 Mn 11/6 O 4-d (d=0, 0.0184) was measured between 5 and 300 K. Bo... more Heat capacity of spinel LiCr 1/6 Mn 11/6 O 4-d (d=0, 0.0184) was measured between 5 and 300 K. Both compounds showed no anomaly in the measured temperature range, especially around the room temperature where a structural phase transition is reported for the parent compound LiMn 2 O 4. The non-stoichiometric compound LiCr 1/6 Mn 11/6 O 3.9816 has greater heat capacity than that of the stoichiometric LiCr 1/6 Mn 11/6 O 4. Molecular dynamics study on the vibrational property of LiMn 2 O 4-d revealed that the lattice defects in the non-stoichiometric compound increase the low frequency phonons compared with the stoichiometric compound. It should be related to the greater heat capacity of the non-stoichiometric compound LiCr 1/6 Mn 11/6 O 3.9816 .
Journal of Physics: Conference Series, 2013
In situ two-dimensional (2D) micro-imaging X-ray absorption fine structure (XAFS) measurements we... more In situ two-dimensional (2D) micro-imaging X-ray absorption fine structure (XAFS) measurements were performed in transmission mode using a charge coupled device (CCD) detector, phosphor screen, and magnifying lens. This method makes it possible to display a 2D image with a spatial resolution of around 2 μm at each energy point in a XAFS spectrum. The method was applied to in situ transmission micro-imaging XAFS measurement with a quick scanning technique.
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2013
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2013
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2016
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2013
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2017
J. Chem. Soc., Chem. Commun., 1989
... Zempachi Ogumi," Yoshiharu Uchimoto, and Zen-ichiro Takehara Department of Industrial Ch... more ... Zempachi Ogumi," Yoshiharu Uchimoto, and Zen-ichiro Takehara Department of Industrial Chemistry, Faculty of Engineering, Kyoto University, Yoshida, Kyoto 606, Japan J. CHEM. SOC., CHEM. ... 3 K. Nagaoka, H. Naruse, and I. Shinohara, J. Polym. Sci., Polym. Lett. ...
Solid State Ionics, 2004
Electrochemical behavior and the variation of electronic structure upon lithium insertion into th... more Electrochemical behavior and the variation of electronic structure upon lithium insertion into the A-site-deficient perovskite oxide, Gd 1/3 TaO 3 , have been studied by X-ray absorption spectroscopy (XAS). During electrochemical lithium insertion, Gd L III-edge and Ta L I-edge XAS revealed that Gd ion did not contribute the charge compensation, while Ta ion reduced its oxidation state. Furthermore, the changes in O K-edge spectra with electrochemical lithium insertion were clearly observed, indicating that O ions also contribute to the electron-transfer reaction.
Journal of The Electrochemical Society, 2005
High-Rate-Capable Lithium-Ion Battery Based on Surface-Modified Natural Graphite Anode and Substi... more High-Rate-Capable Lithium-Ion Battery Based on Surface-Modified Natural Graphite Anode and Substituted Spinel Cathode for Hybrid Electric Vehicles. [Journal of The Electrochemical Society 152, A1595 (2005)]. Iresha RM ...
Journal of Alloys and Compounds, 1997
Heteronuclear complex. LalFe Co, ,(CN),,I.nH,O was synthesized and the thermal decomposed product... more Heteronuclear complex. LalFe Co, ,(CN),,I.nH,O was synthesized and the thermal decomposed products were examined. Single phase of perovskite-type LaFe,Co~ ,(), powders were obtained by the thermal decomposition of the complexes even at 600°C. Hexagonal structure is observed for Fe/La<[).5 and orthorhombic ¢pseudo-cubic) for Fe/La>0.5. From a mechanically rnixed and compacted complexes of LalFe(CN),,I'nH,O and LalCo(CN),,I.nH,O. perovskite-type LaFe,Co, (), oxide could not be formed by thermal decomposition/sintering even at II1)0°C. it is concluded that La[Fe,Co~ ,(CN),,I.nH,O complex is a suitable precursor to prepare liner and ht,mogeneous l')erovskitc-type l.aFe Co~ ,O,. @ 1997 Elsevier Science S.A.
International Journal of Quantum Chemistry, 2002
Quantitative analysis of the formation energy of Cr vacancy in MgCr 2 O 4 was made by first princ... more Quantitative analysis of the formation energy of Cr vacancy in MgCr 2 O 4 was made by first principles calculation. A 56-atom supercell was employed and relaxation of atoms within the second-nearest-neighbor shell of the vacancy was taken into account. The formation energy was calculated as a function of the atomic chemical potential of Cr. Theoretical formation energy of Cr vacancy in MgCr 2 O 4 shows negative values in the case of the oxidation limit of MgCr 2 O 4 , in good agreement with experimental results showing abundance of Cr vacancies when annealed in air. On the other hand, the formation energy of the Al vacancy in MgAl 2 O 4 under the same condition is as large as 4.76 eV. This also corresponds well to the experimental fact that Al vacancy does not form alone in MgAl 2 O 4 in air.
Journal of The Electrochemical Society, 2003
We produced a novel Mg 2ϩ conducting polymer electrolyte and added a poly͑ethylene glycol͒ ͑PEG͒-... more We produced a novel Mg 2ϩ conducting polymer electrolyte and added a poly͑ethylene glycol͒ ͑PEG͒-borate ester as a new type plasticizer having a Lewis acidity and investigated the influence of the Lewis acidity of the PEG-borate ester to a solid polymer electrolyte containing Mg(ClO 4) 2 salt. Adding the PEG-borate ester into the electrolyte shows the increase in the ionic conductivity of the polymer electrolyte. By measuring the glass transition temperature (T g) of the polymer electrolytes using differential scanning calorimetry, it became clear that the mobility of the carrier ion increases with increasing the amount of the PEG-borate ester. By investigating the temperature dependence of the ionic conductivity using William-Landel-Ferry type equation and measuring Raman spectra of the polymer electrolytes, it was found that the concentration of the carrier ion increases with increasing the amount of the PEG-borate ester in the polymer electrolyte. Furthermore, by estimating the transference number of the Mg 2ϩ cation and performing the ab initio calculation for the PEG-borate ester, it is suggested that the PEG-borate ester may enhance the degree of dissociation of the Mg salt in the polymer electrolyte to increase the ratio of the free ion, especially Mg 2ϩ , by interacting with and trapping the ClO 4 Ϫ anion of the salt as a Lewis acid.
Journal of the Electrochemical Society, 2013
The electrodeposition of Mg metal from an ionic liquid-glyme mixture was investigated at room tem... more The electrodeposition of Mg metal from an ionic liquid-glyme mixture was investigated at room temperature. The mixture contains a glyme, a simple amide salt Mg(Tf 2 N) 2 (Tf = SO 2 CF 3), and a quaternary-ammonium Tf 2 N ionic liquid. Using the mixture bath, substantial cathodic electrodeposition of Mg at a large current density (∼10 mA cm −2) was observed, suggesting a change in coordination geometry around Mg 2+ cation together with improved conductivity. By mixing diglyme, the conductivity increased by an order of magnitude (2.5-2.6 mS cm −1) compared to the glyme-free ionic liquid (0.35 mS cm −1) and the viscosity became as low as that of pure glyme. Additionally, potentiostatic electrolysis resulted in a non-dendritic thin film of elemental Mg with metallic luster.
We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk ... more We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel LixMn2O4, a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen 2p orbital. Moreover, the manganese 3d states are shown to experience spatial delocalization involving 0.16 electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery.
ECS Proceedings Volumes
Methods for synthesizing solid oxide fuel cell ceramic materials from aqueous solutions at ordina... more Methods for synthesizing solid oxide fuel cell ceramic materials from aqueous solutions at ordinary temperatures and ordinary pressures are ad vantageous because of the applicability to making films with wide areas and/or complicated shapes with no requirement of vacuum or high tem perature, and because of lower cost. Solutions of fluoro-complex ions were obtained by dissolving sodium hexafluorozirconate in distilled water or dissolving LaMeO3 (Me=Cr, Mn, Fe, Co) or (La,Sr)MeO3 perovskite pre pared by usual solid state reaction in hydrofluoric acid. Boric acid was added into the solution, the fluoride ions were consumed by the formation of BF4' complex ion, and then the fluoro-complex ions were hydrolyzed to ZrO2, LaMeO3 or (La,Sr)MeO3 in order to increase the amount of fluoride ions. The high crystallinity of the product was confirmed by sharp and strong X-ray diffraction peaks. Aggregates of synthesized ZrO2, LaMeO3 or (La,Sr)MeO3 were observed on the substrates in scanning electron micro scope images. Deposition of LaMnO3 on yttria stabilized zirconia substrate was performed by using this method.
Heat capacity of spinel LiCr 1/6 Mn 11/6 O 4-d (d=0, 0.0184) was measured between 5 and 300 K. Bo... more Heat capacity of spinel LiCr 1/6 Mn 11/6 O 4-d (d=0, 0.0184) was measured between 5 and 300 K. Both compounds showed no anomaly in the measured temperature range, especially around the room temperature where a structural phase transition is reported for the parent compound LiMn 2 O 4. The non-stoichiometric compound LiCr 1/6 Mn 11/6 O 3.9816 has greater heat capacity than that of the stoichiometric LiCr 1/6 Mn 11/6 O 4. Molecular dynamics study on the vibrational property of LiMn 2 O 4-d revealed that the lattice defects in the non-stoichiometric compound increase the low frequency phonons compared with the stoichiometric compound. It should be related to the greater heat capacity of the non-stoichiometric compound LiCr 1/6 Mn 11/6 O 3.9816 .
Journal of Physics: Conference Series, 2013
In situ two-dimensional (2D) micro-imaging X-ray absorption fine structure (XAFS) measurements we... more In situ two-dimensional (2D) micro-imaging X-ray absorption fine structure (XAFS) measurements were performed in transmission mode using a charge coupled device (CCD) detector, phosphor screen, and magnifying lens. This method makes it possible to display a 2D image with a spatial resolution of around 2 μm at each energy point in a XAFS spectrum. The method was applied to in situ transmission micro-imaging XAFS measurement with a quick scanning technique.