DSpace Collection:
http://hdl.handle.net/2115/54843
2024-03-28T11:06:11ZFormation of Nanostructured Anodic Films on Iron and Their Electrode Applications
http://hdl.handle.net/2115/91388
Title: Formation of Nanostructured Anodic Films on Iron and Their Electrode Applications
Authors: Fadillah, Laras2021-03-24T15:00:00ZFadillah, LarasTheoretical Study on Formation and Reactivity of Coordination Compounds Employing AFIR [an abstract of entire text]
http://hdl.handle.net/2115/91271
Title: Theoretical Study on Formation and Reactivity of Coordination Compounds Employing AFIR [an abstract of entire text]
Authors: Skjelstad, Bastian Bjerkem
Description: この博士論文全文の閲覧方法については、以下のサイトをご参照ください。2023-03-22T15:00:00ZSkjelstad, Bastian Bjerkem炭素材料の細孔構造および表面官能基の精密分析に基づくリチウム空気電池の正極開発 [全文の要約]
http://hdl.handle.net/2115/91267
Title: 炭素材料の細孔構造および表面官能基の精密分析に基づくリチウム空気電池の正極開発 [全文の要約]
Authors: 永石, 新太郎
Description: この博士論文全文の閲覧方法については、以下のサイトをご参照ください。2023-03-22T15:00:00Z永石, 新太郎Characterizations of Ferric Uptake Regulator (Fur) and Development of Antimicrobial Agents Based on Fur-mediated Polymyxin Resistance in Vibrio cholerae [an abstract of entire text]
http://hdl.handle.net/2115/91263
Title: Characterizations of Ferric Uptake Regulator (Fur) and Development of Antimicrobial Agents Based on Fur-mediated Polymyxin Resistance in Vibrio cholerae [an abstract of entire text]
Authors: 村西, 和佳
Description: この博士論文全文の閲覧方法については、以下のサイトをご参照ください。2023-03-22T15:00:00Z村西, 和佳Biosynthetic Studies of Fungal Terpenoids and Meroterpenoids Having Antiinsectant and Antitumor Activity [an abstract of dissertation and a summary of dissertation review]
http://hdl.handle.net/2115/91210
Title: Biosynthetic Studies of Fungal Terpenoids and Meroterpenoids Having Antiinsectant and Antitumor Activity [an abstract of dissertation and a summary of dissertation review]
Authors: Liu, Yaping2023-12-24T15:00:00ZLiu, YapingHigh-Pressure Synthesis, Crystal Structures and Physical Properties of Perovskite-Related 5d Transition Metal Oxides
http://hdl.handle.net/2115/91206
Title: High-Pressure Synthesis, Crystal Structures and Physical Properties of Perovskite-Related 5d Transition Metal Oxides
Authors: KANG, Xun
Abstract: Perovskite-related materials have gained significant popularity in recent years due to their unconventional and outstanding physical and chemical properties, including ferroelectricity, multiferroicity, magnetoresistance, and exchange bias effects. Notably, materials related to perovskites that incorporate 5d elements have emerged as a leading and potentially applicable research area in inorganic and solid-state chemistry. This is attributed to the competition between local and itinerant d electrons, which can yield a range of beneficial characteristics, including frustrated magnetism, metal-insulator transitions, high-Tc superconductivity, and more. In this study, I successfully synthesized several 5d perovskiterelated compounds using the high-pressure high-temperature method and subsequently investigated their crystal structures, as well as their magnetic and electrical transport properties.
Chapter 1 provides an overview of the research background, encompassing the fundamental crystal structure, mechanisms related to magnetism, material conductivity models referenced in this work, and the historical significance of high-pressure technology in materials science.
Chapter 2 predominantly outlines the experimental details and characteristic techniques employed in this study.
Chapter 3 presents the investigation of two double perovskite oxides, Cd2FeOsO6 and Cd2FeReO6, obtained under high-temperature and high-pressure conditions, with a space group of P21/n. Structure and composition determinations were confirmed by synchrotron powder Xray diffraction and electron probe microanalysis. Magnetic and electronic property measurements revealed that Cd2FeReO6 exhibits ferrimagnetic order well above room temperature at ~460 K, with a soft ferrimagnetic feature. Additionally, a tunneling-type magnetoresistance as large as 37% was discovered in Cd2FeOsO6, while first-principles calculations indicated its half-metallic state. In Cd2FeOsO6, significant exchange bias (EB) effects were detected under remarkably small cooling fields, revealing a unique mechanism and providing valuable guidance for the advancement of materials exhibiting significant EB effects. Both materials behave as semiconductors, in accordance with a three-dimensional variable-range hopping transport model. These results not only provide a new platform for enhancing advanced EB-effect materials but also demonstrate that A-site Cd-occupied double perovskites constitute a promising class of oxides for exploring new materials with practical significance, particularly in the realm of soft and hard magnets or in the field of spintronics.
Chapter 4 primarily focuses on the KSbO3-type Fe-doped Bi3Re3O11 and Bi3Os3O11 compounds, synthesized under high-pressure and high-temperature conditions. Doping with Fe up to 29 atomic% was achieved under these conditions. The crystal structures and chemical compositions of Bi3Os2.45Fe0.55O11 and Bi3Re2.13Fe0.87O11 were determined through synchrotron powder X-ray diffraction and electron probe microanalysis. Both crystal structures were elucidated using a KSbO3-type model with the space group Pn-3. Measurements of magnetic and electronic transport properties revealed that Bi3Os2.45Fe0.55O11 exhibited a ferrimagnetic transition at the highest magnetic ordering temperature of 490 K in the KSbO3-type structure, while Bi3Re2.13Fe0.87O11 displayed a spin-glass behavior below 22 K. The magnetoresistance at 5 K and 90 kOe was nearly zero for Bi3Os2.45Fe0.55O11, but -10% for Bi3Re2.13Fe0.87O11. These findings suggest that KSbO3-type 5d oxides, which have thus far exhibited only weak temperature-dependent paramagnetism, represent a class of compounds that can be transformed into spintronic materials through doping with 3d elements, thereby paving the way for the development of new KSbO3-type materials with both theoretical and practical significance.
Chapter 5 introduces ABO3-type perovskite oxides MnV0.5Nb0.5O3 and MnV0.5Ta0.5O3, prepared under high-pressure and high-temperature conditions. Structure analysis using synchrotron XRD patterns revealed that both of them crystallize in GdFeO3-type structure with the space group Pnma. Magnetic measurements confirmed that MnV0.5Nb0.5O3 and MnV0.5Ta0.5O3 order ferrimagnetically at 17 and 18K, respectively. Both phases are semiconductors, with activation energies of 0.13 eV and 0.31 eV.
Chapter 6 presents the overall conclusions and future prospects based on this body of work.2023-12-24T15:00:00ZKANG, XunPerovskite-related materials have gained significant popularity in recent years due to their unconventional and outstanding physical and chemical properties, including ferroelectricity, multiferroicity, magnetoresistance, and exchange bias effects. Notably, materials related to perovskites that incorporate 5d elements have emerged as a leading and potentially applicable research area in inorganic and solid-state chemistry. This is attributed to the competition between local and itinerant d electrons, which can yield a range of beneficial characteristics, including frustrated magnetism, metal-insulator transitions, high-Tc superconductivity, and more. In this study, I successfully synthesized several 5d perovskiterelated compounds using the high-pressure high-temperature method and subsequently investigated their crystal structures, as well as their magnetic and electrical transport properties.
Chapter 1 provides an overview of the research background, encompassing the fundamental crystal structure, mechanisms related to magnetism, material conductivity models referenced in this work, and the historical significance of high-pressure technology in materials science.
Chapter 2 predominantly outlines the experimental details and characteristic techniques employed in this study.
Chapter 3 presents the investigation of two double perovskite oxides, Cd2FeOsO6 and Cd2FeReO6, obtained under high-temperature and high-pressure conditions, with a space group of P21/n. Structure and composition determinations were confirmed by synchrotron powder Xray diffraction and electron probe microanalysis. Magnetic and electronic property measurements revealed that Cd2FeReO6 exhibits ferrimagnetic order well above room temperature at ~460 K, with a soft ferrimagnetic feature. Additionally, a tunneling-type magnetoresistance as large as 37% was discovered in Cd2FeOsO6, while first-principles calculations indicated its half-metallic state. In Cd2FeOsO6, significant exchange bias (EB) effects were detected under remarkably small cooling fields, revealing a unique mechanism and providing valuable guidance for the advancement of materials exhibiting significant EB effects. Both materials behave as semiconductors, in accordance with a three-dimensional variable-range hopping transport model. These results not only provide a new platform for enhancing advanced EB-effect materials but also demonstrate that A-site Cd-occupied double perovskites constitute a promising class of oxides for exploring new materials with practical significance, particularly in the realm of soft and hard magnets or in the field of spintronics.
Chapter 4 primarily focuses on the KSbO3-type Fe-doped Bi3Re3O11 and Bi3Os3O11 compounds, synthesized under high-pressure and high-temperature conditions. Doping with Fe up to 29 atomic% was achieved under these conditions. The crystal structures and chemical compositions of Bi3Os2.45Fe0.55O11 and Bi3Re2.13Fe0.87O11 were determined through synchrotron powder X-ray diffraction and electron probe microanalysis. Both crystal structures were elucidated using a KSbO3-type model with the space group Pn-3. Measurements of magnetic and electronic transport properties revealed that Bi3Os2.45Fe0.55O11 exhibited a ferrimagnetic transition at the highest magnetic ordering temperature of 490 K in the KSbO3-type structure, while Bi3Re2.13Fe0.87O11 displayed a spin-glass behavior below 22 K. The magnetoresistance at 5 K and 90 kOe was nearly zero for Bi3Os2.45Fe0.55O11, but -10% for Bi3Re2.13Fe0.87O11. These findings suggest that KSbO3-type 5d oxides, which have thus far exhibited only weak temperature-dependent paramagnetism, represent a class of compounds that can be transformed into spintronic materials through doping with 3d elements, thereby paving the way for the development of new KSbO3-type materials with both theoretical and practical significance.
Chapter 5 introduces ABO3-type perovskite oxides MnV0.5Nb0.5O3 and MnV0.5Ta0.5O3, prepared under high-pressure and high-temperature conditions. Structure analysis using synchrotron XRD patterns revealed that both of them crystallize in GdFeO3-type structure with the space group Pnma. Magnetic measurements confirmed that MnV0.5Nb0.5O3 and MnV0.5Ta0.5O3 order ferrimagnetically at 17 and 18K, respectively. Both phases are semiconductors, with activation energies of 0.13 eV and 0.31 eV.
Chapter 6 presents the overall conclusions and future prospects based on this body of work.Development of Multimetallic Alloy Catalysts Efficient for CO2 utilization by Dry Reforming of Hydrocarbons
http://hdl.handle.net/2115/91203
Title: Development of Multimetallic Alloy Catalysts Efficient for CO2 utilization by Dry Reforming of Hydrocarbons
Authors: 劉, 可2023-12-24T15:00:00Z劉, 可Development of Multimetallic Alloy Catalysts Efficient for CO2 utilization by Dry Reforming of Hydrocarbons [an abstract of dissertation and a summary of dissertation review]
http://hdl.handle.net/2115/91202
Title: Development of Multimetallic Alloy Catalysts Efficient for CO2 utilization by Dry Reforming of Hydrocarbons [an abstract of dissertation and a summary of dissertation review]
Authors: 劉, 可2023-12-24T15:00:00Z劉, 可Development of Highly Efficient Multimetallic Alloy Catalysts for Alkane Dehydrogenation
http://hdl.handle.net/2115/91193
Title: Development of Highly Efficient Multimetallic Alloy Catalysts for Alkane Dehydrogenation
Authors: 中谷, 勇希2023-12-24T15:00:00Z中谷, 勇希Development of Highly Efficient Multimetallic Alloy Catalysts for Alkane Dehydrogenation [an abstract of dissertation and a summary of dissertation review]
http://hdl.handle.net/2115/91192
Title: Development of Highly Efficient Multimetallic Alloy Catalysts for Alkane Dehydrogenation [an abstract of dissertation and a summary of dissertation review]
Authors: 中谷, 勇希2023-12-24T15:00:00Z中谷, 勇希