The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Nancy R Sottos - One of the best experts on this subject based on the ideXlab platform.
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silicon composite electrodes with dynamic Ionic Bonding
Advanced Energy Materials, 2017Co-Authors: Sen Kang, Ke Yang, Scott R White, Nancy R SottosAbstract:Silicon (Si) composite electrodes are developed with increased cycle lifetimes and reliability through dynamic Ionic Bonding between active Si nanoparticles and a polymer binder. Amine groups are covalently attached to Si nanoparticles via surface functionalization. Si composite electrodes are fabricated by combining the Si nanoparticles with a poly(acrylic acid) (PAA) binder. The formation of Ionic bonds between amine groups on Si particles and carboxylic acid groups on the PAA binder is characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Si composite anodes with Ionic Bonding demonstrate long term cycling stability with capacity retention of 80% at 400 cycles at a current density of 2.1 A g−1 and good rate capability. The dynamic Ionic bonds effectively mitigate the deterioration of electrical interfaces in the composite anodes as suggested by stable impedance over 300 cycles.
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Silicon Composite Electrodes with Dynamic Ionic Bonding
Advanced Energy Materials, 2017Co-Authors: Sen Kang, Ke Yang, Scott R White, Nancy R SottosAbstract:© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Silicon (Si) composite electrodes are developed with increased cycle lifetimes and reliability through dynamic Ionic Bonding between active Si nanoparticles and a polymer binder. Amine groups are covalently attached to Si nanoparticles via surface functionalization. Si composite electrodes are fabricated by combining the Si nanoparticles with a poly(acrylic acid) (PAA) binder. The formation of Ionic bonds between amine groups on Si particles and carboxylic acid groups on the PAA binder is characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Si composite anodes with Ionic Bonding demonstrate long term cycling stability with capacity retention of 80% at 400 cycles at a current density of 2.1 A g −1 and good rate capability. The dynamic Ionic bonds effectively mitigate the deterioration of electrical interfaces in the composite anodes as suggested by stable impedance over 300 cycles.
T. Sakuma - One of the best experts on this subject based on the ideXlab platform.
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Grain boundary electronic structure related to the high-temperature creep resistance in polycrystalline Al2O3
Acta Materialia, 2002Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, T. SakumaAbstract:High-temperature creep deformation in polycrystalline Al2O3 with an average grain size of 1 μm is suppressed by the doping of 0.1 mol% SrO, LuO1.5, SiO2 or ZrO2, while that is accelerated by MgO, CuO or TiO2-doping at 1250°C. The difference in the creep resistance is considered to be originated from change in the grain boundary diffusion in Al2O3 due to the grain boundary segregation of the dopant cation. Change in the chemical Bonding state in the cations-doped Al2O3 is examined by a first-principle molecular orbital calculations using DV-Xα method based on [Al5O21]27- cluster model. A correlation is found between the creep resistance and product of net charges of aluminum and oxygen ions. The dopant effect on the high-temperature creep resistance in polycrystalline Al2O3 is in good agreement with the change in the Ionic Bonding strength between Al and O. The change in the chemical Bonding strength can be explained in terms of both effects of cation-doping, which changes constitutions of molecular orbitals, and vacancy, which decreases the chemical Bonding strength in Al2O3. © 2002 Elsevier Science Ltd. All rights reserved.
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A change in the chemical Bonding strength and high-temperature creep resistance in A12O3with lanthanoid oxide doping
Philosophical Magazine A: Physics of Condensed Matter Structure Defects and Mechanical Properties, 2002Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, T. Yamamoto, T. SakumaAbstract:High-temperature creep resistance in polycrystalline Al2O3 is highly improved by doping with 0.05 mol% lanthanoid (Ln) oxide (Ln = Sm, Eu, Tm or Lu) at 1250degreesC. The improvement in creep resistance probably occurs as a result of retardation of the grain-boundary diffusion in Al2O3 due to grain-boundary segregation of dopant cations. The change in chemical Bonding state in grain boundaries with the segregation of Ln cations is examined by a first-principles molecular orbital calculation using the discrete variational-Xalpha method based on [Al5O21](27-) model cluster. The result of the calculation indicates that the Ionic Bonding between Al and O ions, and the covalent Bonding between Al and the surrounding cation, are strengthened by the presence of Ln ions. A correlation is found between the creep resistance and product of net charges of the constituent ions. The improved creep resistance must be explained in terms of a change in chemical Bonding strength around the Al ion.
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Vacancy effect of dopant cation on the high-temperature creep resistance in polycrystalline Al2O3
Materials Science and Engineering A, 2001Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, T. SakumaAbstract:High-temperature creep resistance in polycrystalline Al2O3 with 0.1 mo1% oxides of YO1.5, ZrO2 or MgO has been examined by uniaxial compression creep testing at 1250 °C. The creep resistance is highly improved by the doping of Y or Zr even in the dopant level of 0.1 mo1%, but is retarded by Mg doping. The dopant effect on the creep resistance cannot be explained in terms of, for example, Ionic radius of the dopant cation or eutectic point in Al2O3-oxide of dopant cation system. Each dopant cation was found to segregate in grain boundaries, and is likely to influence grain boundary diffusion in Al2O3. The Ionic Bonding and the covalent Bonding of Al-O are lowered by the introduction of V″o or V‴Al but the values of the net charge in Al and O are increased by the cations doping. The change in the value of Net Charge is correlated well with the high-temperature creep resistance in Al2O3 with cation doping. It is suggested that the Ionicity in Al and O is an important factor to determine high-temperature creep resistance in polycrystalline Al2O3. © 2001 Elsevier Science B.V. All rights reserved.
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High-temperature creep resistance in lanthanoid ion-doped polycrystalline Al2O3
Philosophical Magazine Letters, 1999Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, T. SakumaAbstract:High-temperature creep resistance in polycrystalline Al2O3 with 0.05mol% lanthanoid oxides of Y, Sm, Eu, Tm or Lu has been examined by uniaxial compression creep testing at 1250ë C. The creep resistance is improved by the doping, and the dopant e? ect is dependent on the type of lanthanoid; the e? ect is in the order Sm < Tm < Eu < Y < Lu. Each dopant cation was found to segregate in grain boundaries and is likely to suppress grain-boundary di? usion. The change in chemical Bonding state with doping was estimated by a ® rst-principlesmolecular orbital calculation using the discrete variational (DV)- Xa method. A good correlation is found between the creep resistance and the net charge of the constituent ions. A change in the Ionic Bonding state in grain boundaries due to lanthanoid segregation must be the origin of the improved creep resistance in polycrystalline Al2O3.
Sen Kang - One of the best experts on this subject based on the ideXlab platform.
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silicon composite electrodes with dynamic Ionic Bonding
Advanced Energy Materials, 2017Co-Authors: Sen Kang, Ke Yang, Scott R White, Nancy R SottosAbstract:Silicon (Si) composite electrodes are developed with increased cycle lifetimes and reliability through dynamic Ionic Bonding between active Si nanoparticles and a polymer binder. Amine groups are covalently attached to Si nanoparticles via surface functionalization. Si composite electrodes are fabricated by combining the Si nanoparticles with a poly(acrylic acid) (PAA) binder. The formation of Ionic bonds between amine groups on Si particles and carboxylic acid groups on the PAA binder is characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Si composite anodes with Ionic Bonding demonstrate long term cycling stability with capacity retention of 80% at 400 cycles at a current density of 2.1 A g−1 and good rate capability. The dynamic Ionic bonds effectively mitigate the deterioration of electrical interfaces in the composite anodes as suggested by stable impedance over 300 cycles.
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Silicon Composite Electrodes with Dynamic Ionic Bonding
Advanced Energy Materials, 2017Co-Authors: Sen Kang, Ke Yang, Scott R White, Nancy R SottosAbstract:© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Silicon (Si) composite electrodes are developed with increased cycle lifetimes and reliability through dynamic Ionic Bonding between active Si nanoparticles and a polymer binder. Amine groups are covalently attached to Si nanoparticles via surface functionalization. Si composite electrodes are fabricated by combining the Si nanoparticles with a poly(acrylic acid) (PAA) binder. The formation of Ionic bonds between amine groups on Si particles and carboxylic acid groups on the PAA binder is characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Si composite anodes with Ionic Bonding demonstrate long term cycling stability with capacity retention of 80% at 400 cycles at a current density of 2.1 A g −1 and good rate capability. The dynamic Ionic bonds effectively mitigate the deterioration of electrical interfaces in the composite anodes as suggested by stable impedance over 300 cycles.
Hidehiro Yoshida - One of the best experts on this subject based on the ideXlab platform.
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Grain boundary electronic structure related to the high-temperature creep resistance in polycrystalline Al2O3
Acta Materialia, 2002Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, T. SakumaAbstract:High-temperature creep deformation in polycrystalline Al2O3 with an average grain size of 1 μm is suppressed by the doping of 0.1 mol% SrO, LuO1.5, SiO2 or ZrO2, while that is accelerated by MgO, CuO or TiO2-doping at 1250°C. The difference in the creep resistance is considered to be originated from change in the grain boundary diffusion in Al2O3 due to the grain boundary segregation of the dopant cation. Change in the chemical Bonding state in the cations-doped Al2O3 is examined by a first-principle molecular orbital calculations using DV-Xα method based on [Al5O21]27- cluster model. A correlation is found between the creep resistance and product of net charges of aluminum and oxygen ions. The dopant effect on the high-temperature creep resistance in polycrystalline Al2O3 is in good agreement with the change in the Ionic Bonding strength between Al and O. The change in the chemical Bonding strength can be explained in terms of both effects of cation-doping, which changes constitutions of molecular orbitals, and vacancy, which decreases the chemical Bonding strength in Al2O3. © 2002 Elsevier Science Ltd. All rights reserved.
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A change in the chemical Bonding strength and high-temperature creep resistance in A12O3with lanthanoid oxide doping
Philosophical Magazine A: Physics of Condensed Matter Structure Defects and Mechanical Properties, 2002Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, T. Yamamoto, T. SakumaAbstract:High-temperature creep resistance in polycrystalline Al2O3 is highly improved by doping with 0.05 mol% lanthanoid (Ln) oxide (Ln = Sm, Eu, Tm or Lu) at 1250degreesC. The improvement in creep resistance probably occurs as a result of retardation of the grain-boundary diffusion in Al2O3 due to grain-boundary segregation of dopant cations. The change in chemical Bonding state in grain boundaries with the segregation of Ln cations is examined by a first-principles molecular orbital calculation using the discrete variational-Xalpha method based on [Al5O21](27-) model cluster. The result of the calculation indicates that the Ionic Bonding between Al and O ions, and the covalent Bonding between Al and the surrounding cation, are strengthened by the presence of Ln ions. A correlation is found between the creep resistance and product of net charges of the constituent ions. The improved creep resistance must be explained in terms of a change in chemical Bonding strength around the Al ion.
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Vacancy effect of dopant cation on the high-temperature creep resistance in polycrystalline Al2O3
Materials Science and Engineering A, 2001Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, T. SakumaAbstract:High-temperature creep resistance in polycrystalline Al2O3 with 0.1 mo1% oxides of YO1.5, ZrO2 or MgO has been examined by uniaxial compression creep testing at 1250 °C. The creep resistance is highly improved by the doping of Y or Zr even in the dopant level of 0.1 mo1%, but is retarded by Mg doping. The dopant effect on the creep resistance cannot be explained in terms of, for example, Ionic radius of the dopant cation or eutectic point in Al2O3-oxide of dopant cation system. Each dopant cation was found to segregate in grain boundaries, and is likely to influence grain boundary diffusion in Al2O3. The Ionic Bonding and the covalent Bonding of Al-O are lowered by the introduction of V″o or V‴Al but the values of the net charge in Al and O are increased by the cations doping. The change in the value of Net Charge is correlated well with the high-temperature creep resistance in Al2O3 with cation doping. It is suggested that the Ionicity in Al and O is an important factor to determine high-temperature creep resistance in polycrystalline Al2O3. © 2001 Elsevier Science B.V. All rights reserved.
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High-temperature creep resistance in lanthanoid ion-doped polycrystalline Al2O3
Philosophical Magazine Letters, 1999Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, T. SakumaAbstract:High-temperature creep resistance in polycrystalline Al2O3 with 0.05mol% lanthanoid oxides of Y, Sm, Eu, Tm or Lu has been examined by uniaxial compression creep testing at 1250ë C. The creep resistance is improved by the doping, and the dopant e? ect is dependent on the type of lanthanoid; the e? ect is in the order Sm < Tm < Eu < Y < Lu. Each dopant cation was found to segregate in grain boundaries and is likely to suppress grain-boundary di? usion. The change in chemical Bonding state with doping was estimated by a ® rst-principlesmolecular orbital calculation using the discrete variational (DV)- Xa method. A good correlation is found between the creep resistance and the net charge of the constituent ions. A change in the Ionic Bonding state in grain boundaries due to lanthanoid segregation must be the origin of the improved creep resistance in polycrystalline Al2O3.
Michel W Barsoum - One of the best experts on this subject based on the ideXlab platform.
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Two-Dimensional Transition Metal Carbides Herein we report on the synthesis of two-dimensional transition metal carbides and
ACS Nano, 2012Co-Authors: Michael Naguib, Joshua Carle, Lars Hultman, Yury Gogotsi, Olha Mashtalir, Volker Presser, Jun Lu, Michel W BarsoumAbstract:T wo-dimensional (2-D) materials, such as graphene, are known to have unique properties 1À4 that, in turn, can potentially lead to some promising applications. 5À12 Over the years, other 2-D materials with different chemistries have been synthesized by exfoliation of layered 3-D precursors such as boron nitride, 13 metal chalcogenides (e.g., MoS 2 , 14,15 WS 2 16,17), oxi-des, and hydroxides. 18À20 In most, if not all, of these cases, the initial Bonding between the layers was relatively weak, making the structure amenable to exfoliation. As far as we are aware, and until our re-cent work, 21 the exfoliation of layered solids with strong primary bonds had not been reported. Very recently, we reported on the exfoliation of the layered transition metal carbide, Ti 3 AlC 2 . 21 A schematic of the exfo-liation process is shown in Figure 1. We note that Ti 3 AlC 2 is a member of a large family of layered hexagonal (space group P6 3 /mmc) ternary metal carbides and nitrides referred to as the MAX phases. The term MAX phases reflects the chemical composition: M nþ1 AX n , where n = 1, 2, or 3 (M 2 AX, M 3 AX 2 , or M 4 AX 3 , etc.), " M " is an early transition metal, " A " is an A group (mostly groups 13 and 14) ele-ment, and " X " is C and/or N. 22 These solids combine unusual and sometimes unique properties, as they are easily machinable and, in addition to being highly damage tolerant, extremely thermal shock resis-tant. 23 Some MAX phases, most notably, Ti 3 AlC 2 , are also quite oxidation resistant, especially when compared to their chemi-cally related binary carbides. 24 In general, the MAX phases are chemi-cally quite stable, but the A layers are chemi-cally more reactive because they are rela-tively weakly bonded when compared to the MÀX bonds. At high temperatures, the MAX phases partially decompose according to the following reaction. 25 M n þ 1 AX n ¼ M n þ 1 X n þ A (1) Such high decomposition temperatures, however, induce recrystallization and the M nþ1 X n layers turn into nonlayered, bulk 3-D cubic carbides and/or nitrides with rock-salt structures with some ordering of the vacancies on the X sites. 25À27 It is important to note that the Bonding in the MAX phases is a combination of metallic, covalent, and Ionic Bonding, and the bond-ing strength is, in most cases, quite strong. 25 Many of these compounds, especially the Al-containing ones, were fabricated at tempera-tures as high as 1600 °C. For example, the Ti 3 AlC 2 powders tested in our previous work were synthesized at 1350 °C, 21 and bulk Ti 2 AlC samples are hot pressed at 1600 °C.
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fundamentals of ceramics
1997Co-Authors: Michel W BarsoumAbstract:INTRODUCTION Introduction Definition of Ceramics Elementary Crystallography Ceramic Microstructures Traditional Versus Advanced Ceramics General Characteristics of Ceramics Applications The Future Bonding IN CERAMICS Introduction Structure of Atoms Ionic versus Covalent Bonding Ionic Bonding Ionically Bonded Solids Covalent Bond Formation Covalently Bonded Solids Band Theory of Solids Summary Appendix 2A: Kinetic Energy of Free Electrons STRUCTURE OF CERAMICS Introduction Ceramic Structures Binary Ionic Compounds Composite Crystal Structures Structure of Covalent Ceramics Structure of Silicates Lattice Parameters and Density Summary Appendix 3A: Ionic Radii EFFECT OF CHEMICAL FORCES ON PHYSICAL PROPERTIES Introduction Melting Points Thermal Expansion Young's Modulus and the Strength of Perfect Solids Surface Energy Summary THERMODYNAMIC AND KINETIC CONSIDERATIONS Introduction Free Energy Chemical Equilibrium and the Mass Action Expression Chemical Stability Domains Electrochemical Potentials Charged Interfaces, Double Layers, and Debye Lengths Gibbs-Duhem Relation for Binary Oxides Kinetic Considerations Summary Appendix 5A: Derivation of Eq. (5.27) DEFECTS IN CERAMICS Introduction Point Defects Linear Defects Planar Defects Summary DIFFUSION AND ELECTRICAL CONDUCTIVITY Introduction Diffusion Electrical Conductivity Ambipolar Diffusion Relationships between Self-, Tracer, Chemical, Ambipolar, and Defect Diffusion Coefficients Summary Appendix 7A: Relationship between Fick's First Law and Eq. (7.30) Appendix 7B: Effective Mass and Density of States Appendix 7C: Derivation of Eq. (7.79) Appendix 7D: Derivation of Eq. (7.92) PHASE EQUILIBRIA Introduction Phase Rule One-Component Systems Binary Systems Ternary Systems Free-Energy Composition and Temperature Diagrams Summary FORMATION, STRUCTURE, AND PROPERTIES OF GLASSES Introduction Glass Formation Glass Structure Glass Properties Glass-Ceramics Summary Appendix 9A: Derivation of Eq. (9.7) SINTERING AND GRAIN GROWTH Introduction Solid-State Sintering Liquid-Phase Sintering Hot Pressing and Hot Isostatic Pressing Summary Appendix 10A: Derivation of the Gibbs-Thompson Equation Appendix 10B: Radii of Curvature Appendix 10C: Derivation of Eq. (10.20) Appendix 10D: Derivation of Eq. (10.22) MECHANICAL PROPERTIES: FAST FRACTURE Introduction Fracture Toughness Strength of Ceramics Toughening Mechanisms Designing with Ceramics Summary CREEP, SUBCRITICAL CRACK GROWTH, AND FATIGUE Introduction Creep Subcritical Crack Growth Fatigue of Ceramics Lifetime Predictions Summary Appendix 12A: Derivation of Eq. (12.24) THERMAL PROPERTIES Introduction Thermal Stresses Thermal Shock Spontaneous Microcracking of Ceramics Thermal Tempering of Glass Thermal Conductivity Summary DIELECTRIC PROPERTIES Introduction Basic Theory Equivalent Circuit Description of Linear Dielectrics Polarization Mechanisms Dielectric Loss Dielectric Breakdown Capacitors and Insulators Summary Appendix 14A: Local Electric Field MAGNETIC AND NONLINEAR DIELECTRIC PROPERTIES Introduction Basic Theory Microscopic Theory Para-, Ferro-, Antiferro-, and Ferrimagnetism Magnetic Domains and the Hysteresis Curve Magnetic Ceramics and their Applications Piezo- and Ferroelectric Ceramics Summary Appendix 15A: Orbital Magnetic Quantum Number OPTICAL PROPERTIES Introduction Basic Principles Absorption and Transmission Scattering and Opacity Fiber Optics and Optical Communication Summary Appendix 16A: Coherence Appendix 16B: Assumptions Made in Deriving Eq. (16.24) INDEX *Each chapter contains Problems and Additional Reading.
