Author: Hui Li
Publisher:
ISBN: 9780438629882
Category :
Languages : en
Pages :
Book Description
Nanocrystalline materials have been attracting wide attention because of their advanced technological application owing to their superior properties such as enhanced mechanical strength and ionic conductivity. The intrinsic presence of excess interfacial areas in nanomaterials causes their properties and functionalities to be strongly dependent on interfacial properties. From a thermodynamics perspective, this suggests both crystallographic stability and microstructural evolution are largely affected by interfacial energies, implying those energies can be used for microstructural control. However, there is still a dearth of understanding on the relationships between interfacial energies and processes such as sintering and coarsening of nanocrystalline ceramics, in particular in what concerns the usage of ionic dopants as sintering aids working on the modification of interfacial energies rather than from the classical kinetic approach (dopants affecting mechanisms of sintering). In this dissertation, nanocrystalline ceramic yttria stabilized zirconia (YSZ) was used as a model system to concomitantly evaluate the quantitative effect of dopants on both kinetics and thermodynamics of densification in order to provide a more comprehensive picture to allow refined control of sintering evolution. Doped and pure YSZ nanoparticles were synthesized using co-precipitation method and used as the starting powders for sintering. By using sophisticated calorimetric approaches, the interfacial energies of the nanoparticles were quantified, while the kinetic analysis was carried out using Kissinger method applied with sintering experiment in differential scanning calorimetry (DSC) with different heating rates. Manganese and lanthanum were the studied dopants, selected based on potential for segregation to interfaces, which would hypothetically cause a more pronounced interfacial energy change. Remarkable decrease in both surface and grain boundary energies, as well as an increase in the calculated dihedral angles, was observed with increasing Mn concentration in YSZ. Mn also caused a decrease in activation energy of densification of this system that could achieve high densities at moderate temperatures albeit with massive grain growth. La-doping, on the other hand, whilst decreasing interfacial energies and increasing dihedral angles in a similar manner as Mn, did not affect the activation energy of the process. Inhibition of both densification and grain growth was observed, implying that the design of favorable thermodynamic states is a necessary but not sufficient condition for densification to take place. Utilizing similar methodologies, studies proceeded on magnesium aluminate spinel with manganese and titanium as dopants to test if the concepts developed for YSZ could be extended to other systems. The results from analyzing Mn-doped spinel were perfectly aligned with the conclusions from the YSZ studies, such that a favorable thermodynamics and kinetics helped improve densification of the spinel. However, Ti-doped spinel showed significant deviations from the predicted behavior, as it had favorable thermodynamic and kinetic conditions but high densification could not be obtained during sintering. This anomalous behavior was attributed to abnormal grain growth that hindered pore elimination due to likely an energetic anisotropy in the grain boundaries.
Kinetic and Thermodynamic Effects of Dopants (Mn/La) on the Microstructure of Yttria-stabilized Zirconia (YSZ)
Author: Hui Li
Publisher:
ISBN: 9780438629882
Category :
Languages : en
Pages :
Book Description
Nanocrystalline materials have been attracting wide attention because of their advanced technological application owing to their superior properties such as enhanced mechanical strength and ionic conductivity. The intrinsic presence of excess interfacial areas in nanomaterials causes their properties and functionalities to be strongly dependent on interfacial properties. From a thermodynamics perspective, this suggests both crystallographic stability and microstructural evolution are largely affected by interfacial energies, implying those energies can be used for microstructural control. However, there is still a dearth of understanding on the relationships between interfacial energies and processes such as sintering and coarsening of nanocrystalline ceramics, in particular in what concerns the usage of ionic dopants as sintering aids working on the modification of interfacial energies rather than from the classical kinetic approach (dopants affecting mechanisms of sintering). In this dissertation, nanocrystalline ceramic yttria stabilized zirconia (YSZ) was used as a model system to concomitantly evaluate the quantitative effect of dopants on both kinetics and thermodynamics of densification in order to provide a more comprehensive picture to allow refined control of sintering evolution. Doped and pure YSZ nanoparticles were synthesized using co-precipitation method and used as the starting powders for sintering. By using sophisticated calorimetric approaches, the interfacial energies of the nanoparticles were quantified, while the kinetic analysis was carried out using Kissinger method applied with sintering experiment in differential scanning calorimetry (DSC) with different heating rates. Manganese and lanthanum were the studied dopants, selected based on potential for segregation to interfaces, which would hypothetically cause a more pronounced interfacial energy change. Remarkable decrease in both surface and grain boundary energies, as well as an increase in the calculated dihedral angles, was observed with increasing Mn concentration in YSZ. Mn also caused a decrease in activation energy of densification of this system that could achieve high densities at moderate temperatures albeit with massive grain growth. La-doping, on the other hand, whilst decreasing interfacial energies and increasing dihedral angles in a similar manner as Mn, did not affect the activation energy of the process. Inhibition of both densification and grain growth was observed, implying that the design of favorable thermodynamic states is a necessary but not sufficient condition for densification to take place. Utilizing similar methodologies, studies proceeded on magnesium aluminate spinel with manganese and titanium as dopants to test if the concepts developed for YSZ could be extended to other systems. The results from analyzing Mn-doped spinel were perfectly aligned with the conclusions from the YSZ studies, such that a favorable thermodynamics and kinetics helped improve densification of the spinel. However, Ti-doped spinel showed significant deviations from the predicted behavior, as it had favorable thermodynamic and kinetic conditions but high densification could not be obtained during sintering. This anomalous behavior was attributed to abnormal grain growth that hindered pore elimination due to likely an energetic anisotropy in the grain boundaries.
Publisher:
ISBN: 9780438629882
Category :
Languages : en
Pages :
Book Description
Nanocrystalline materials have been attracting wide attention because of their advanced technological application owing to their superior properties such as enhanced mechanical strength and ionic conductivity. The intrinsic presence of excess interfacial areas in nanomaterials causes their properties and functionalities to be strongly dependent on interfacial properties. From a thermodynamics perspective, this suggests both crystallographic stability and microstructural evolution are largely affected by interfacial energies, implying those energies can be used for microstructural control. However, there is still a dearth of understanding on the relationships between interfacial energies and processes such as sintering and coarsening of nanocrystalline ceramics, in particular in what concerns the usage of ionic dopants as sintering aids working on the modification of interfacial energies rather than from the classical kinetic approach (dopants affecting mechanisms of sintering). In this dissertation, nanocrystalline ceramic yttria stabilized zirconia (YSZ) was used as a model system to concomitantly evaluate the quantitative effect of dopants on both kinetics and thermodynamics of densification in order to provide a more comprehensive picture to allow refined control of sintering evolution. Doped and pure YSZ nanoparticles were synthesized using co-precipitation method and used as the starting powders for sintering. By using sophisticated calorimetric approaches, the interfacial energies of the nanoparticles were quantified, while the kinetic analysis was carried out using Kissinger method applied with sintering experiment in differential scanning calorimetry (DSC) with different heating rates. Manganese and lanthanum were the studied dopants, selected based on potential for segregation to interfaces, which would hypothetically cause a more pronounced interfacial energy change. Remarkable decrease in both surface and grain boundary energies, as well as an increase in the calculated dihedral angles, was observed with increasing Mn concentration in YSZ. Mn also caused a decrease in activation energy of densification of this system that could achieve high densities at moderate temperatures albeit with massive grain growth. La-doping, on the other hand, whilst decreasing interfacial energies and increasing dihedral angles in a similar manner as Mn, did not affect the activation energy of the process. Inhibition of both densification and grain growth was observed, implying that the design of favorable thermodynamic states is a necessary but not sufficient condition for densification to take place. Utilizing similar methodologies, studies proceeded on magnesium aluminate spinel with manganese and titanium as dopants to test if the concepts developed for YSZ could be extended to other systems. The results from analyzing Mn-doped spinel were perfectly aligned with the conclusions from the YSZ studies, such that a favorable thermodynamics and kinetics helped improve densification of the spinel. However, Ti-doped spinel showed significant deviations from the predicted behavior, as it had favorable thermodynamic and kinetic conditions but high densification could not be obtained during sintering. This anomalous behavior was attributed to abnormal grain growth that hindered pore elimination due to likely an energetic anisotropy in the grain boundaries.
Ceramic Abstracts
Author: American Ceramic Society
Publisher:
ISBN:
Category : Ceramics
Languages : en
Pages : 1150
Book Description
Publisher:
ISBN:
Category : Ceramics
Languages : en
Pages : 1150
Book Description
High-Temperature Solid Oxide Fuel Cells for the 21st Century
Author: Kevin Kendall
Publisher: Elsevier
ISBN: 0124104835
Category : Technology & Engineering
Languages : en
Pages : 522
Book Description
High-temperature Solid Oxide Fuel Cells, Second Edition, explores the growing interest in fuel cells as a sustainable source of energy. The text brings the topic of green energy front and center, illustrating the need for new books that provide comprehensive and practical information on specific types of fuel cells and their applications. This landmark volume on solid oxide fuel cells contains contributions from experts of international repute, and provides a single source of the latest knowledge on this topic. - A single source for all the latest information on solid oxide fuel cells and their applications - Illustrates the need for new, more comprehensive books and study on the topic - Explores the growing interest in fuel cells as viable, sustainable sources of energy
Publisher: Elsevier
ISBN: 0124104835
Category : Technology & Engineering
Languages : en
Pages : 522
Book Description
High-temperature Solid Oxide Fuel Cells, Second Edition, explores the growing interest in fuel cells as a sustainable source of energy. The text brings the topic of green energy front and center, illustrating the need for new books that provide comprehensive and practical information on specific types of fuel cells and their applications. This landmark volume on solid oxide fuel cells contains contributions from experts of international repute, and provides a single source of the latest knowledge on this topic. - A single source for all the latest information on solid oxide fuel cells and their applications - Illustrates the need for new, more comprehensive books and study on the topic - Explores the growing interest in fuel cells as viable, sustainable sources of energy
Surface Segregation
Author: J. du Plessis
Publisher: Trans Tech Publications Ltd
ISBN: 3035706468
Category : Technology & Engineering
Languages : en
Pages : 132
Book Description
The book presents the fundamental aspects of surface segregation theory. The material is presented in a self-contained manner and mathematical procedures are worked through in some cases in order to provide the reader with the necessary opportunity to realize the restrictions under which the expressions are valid.
Publisher: Trans Tech Publications Ltd
ISBN: 3035706468
Category : Technology & Engineering
Languages : en
Pages : 132
Book Description
The book presents the fundamental aspects of surface segregation theory. The material is presented in a self-contained manner and mathematical procedures are worked through in some cases in order to provide the reader with the necessary opportunity to realize the restrictions under which the expressions are valid.
Solid Oxide Fuel Cell Technology
Author: K Huang
Publisher: Elsevier
ISBN: 1845696514
Category : Technology & Engineering
Languages : en
Pages : 341
Book Description
High temperature solid oxide fuel cell (SOFC) technology is a promising power generation option that features high electrical efficiency and low emissions of environmentally polluting gases such as CO2, NOox and SOx. It is ideal for distributed stationary power generation applications where both high-efficiency electricity and high-quality heat are in strong demand. For the past few decades, SOFC technology has attracted intense worldwide R&D effort and, along with polymer electrolyte membrane fuel cell (PEMFC) technology, has undergone extensive commercialization development.This book presents a systematic and in-depth narrative of the technology from the perspective of fundamentals, providing comprehensive theoretical analysis and innovative characterization techniques for SOFC technology. The book initially deals with the basics and development of SOFC technology from cell materials to fundamental thermodynamics, electronic properties of solids and charged particle transport. This coverage is extended with a thorough analysis of such operational features as current flow and energy balance, and on to voltage losses and electrical efficiency. Furthermore, the book also covers the important issues of fuel cell stability and durability with chapters on performance characterization, fuel processing, and electrode poisoning. Finally, the book provides a comprehensive review for SOFC materials and fabrication techniques. A series of useful scientific appendices rounds off the book.Solid oxide fuel cell technology is a standard reference for all those researching this important field as well as those working in the power industry. - Provides a comprehensive review of solid oxide fuel cells from history and design to chemistry and materials development - Presents analysis of operational features including current flow, energy balance, voltage losses and electrical efficiency - Explores fuel cell stability and durability with specific chapters examining performance characterization, fuel processing and electrode poisoning
Publisher: Elsevier
ISBN: 1845696514
Category : Technology & Engineering
Languages : en
Pages : 341
Book Description
High temperature solid oxide fuel cell (SOFC) technology is a promising power generation option that features high electrical efficiency and low emissions of environmentally polluting gases such as CO2, NOox and SOx. It is ideal for distributed stationary power generation applications where both high-efficiency electricity and high-quality heat are in strong demand. For the past few decades, SOFC technology has attracted intense worldwide R&D effort and, along with polymer electrolyte membrane fuel cell (PEMFC) technology, has undergone extensive commercialization development.This book presents a systematic and in-depth narrative of the technology from the perspective of fundamentals, providing comprehensive theoretical analysis and innovative characterization techniques for SOFC technology. The book initially deals with the basics and development of SOFC technology from cell materials to fundamental thermodynamics, electronic properties of solids and charged particle transport. This coverage is extended with a thorough analysis of such operational features as current flow and energy balance, and on to voltage losses and electrical efficiency. Furthermore, the book also covers the important issues of fuel cell stability and durability with chapters on performance characterization, fuel processing, and electrode poisoning. Finally, the book provides a comprehensive review for SOFC materials and fabrication techniques. A series of useful scientific appendices rounds off the book.Solid oxide fuel cell technology is a standard reference for all those researching this important field as well as those working in the power industry. - Provides a comprehensive review of solid oxide fuel cells from history and design to chemistry and materials development - Presents analysis of operational features including current flow, energy balance, voltage losses and electrical efficiency - Explores fuel cell stability and durability with specific chapters examining performance characterization, fuel processing and electrode poisoning
Perovskite Materials
Author: Likun Pan
Publisher: BoD – Books on Demand
ISBN: 9535122452
Category : Technology & Engineering
Languages : en
Pages : 652
Book Description
The book summarizes the current state of the know-how in the field of perovskite materials: synthesis, characterization, properties, and applications. Most chapters include a review on the actual knowledge and cutting-edge research results. Thus, this book is an essential source of reference for scientists with research fields in energy, physics, chemistry and materials. It is also a suitable reading material for graduate students.
Publisher: BoD – Books on Demand
ISBN: 9535122452
Category : Technology & Engineering
Languages : en
Pages : 652
Book Description
The book summarizes the current state of the know-how in the field of perovskite materials: synthesis, characterization, properties, and applications. Most chapters include a review on the actual knowledge and cutting-edge research results. Thus, this book is an essential source of reference for scientists with research fields in energy, physics, chemistry and materials. It is also a suitable reading material for graduate students.
Nonstoichiometric Oxides
Author: O.T. Soerensen
Publisher: Elsevier
ISBN: 0323149804
Category : Science
Languages : en
Pages : 454
Book Description
Nonstoichiometric Oxides discusses the thermodynamic and structural studies of nonstoichiometric oxides. This eight-chapter text also covers the defect-defect interactions in these compounds. The introductory chapters describe the thermodynamic properties of nonstoichiometric oxides in terms of defect complexes using the classical thermodynamic principles and from a statistical thermodynamics point of view. These chapters also include statistical thermodynamic models that indicate the ordered nonstoichiometric phase range in these oxides. The subsequent chapters examine the transport properties, such as diffusion and electrical conductivity. Diffusion theories and experimental diffusion coefficients for several systems, as well as the electrical properties of the highly defective ionic and mixed oxide conductor, are specifically tackled in these chapters. The concluding chapters present the pertinent results obtained in nonstoichiometric oxide structural studies using high-resolution electron microscopy and X-ray and neutron diffraction. Inorganic chemists and inorganic chemistry teachers and students will greatly appreciate this book.
Publisher: Elsevier
ISBN: 0323149804
Category : Science
Languages : en
Pages : 454
Book Description
Nonstoichiometric Oxides discusses the thermodynamic and structural studies of nonstoichiometric oxides. This eight-chapter text also covers the defect-defect interactions in these compounds. The introductory chapters describe the thermodynamic properties of nonstoichiometric oxides in terms of defect complexes using the classical thermodynamic principles and from a statistical thermodynamics point of view. These chapters also include statistical thermodynamic models that indicate the ordered nonstoichiometric phase range in these oxides. The subsequent chapters examine the transport properties, such as diffusion and electrical conductivity. Diffusion theories and experimental diffusion coefficients for several systems, as well as the electrical properties of the highly defective ionic and mixed oxide conductor, are specifically tackled in these chapters. The concluding chapters present the pertinent results obtained in nonstoichiometric oxide structural studies using high-resolution electron microscopy and X-ray and neutron diffraction. Inorganic chemists and inorganic chemistry teachers and students will greatly appreciate this book.
Physics Briefs
Author:
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 1216
Book Description
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 1216
Book Description
Environmental Barrier Coatings
Author: Kang N. Lee
Publisher: MDPI
ISBN: 3039365177
Category : Science
Languages : en
Pages : 168
Book Description
The global increase in air travel will require commercial vehicles to be more efficient than ever before. Advanced engine hot section materials are a key technology required to keep fuel consumption and emission to a minimum in next-generation gas turbines. Ceramic matrix composites (CMCs) are the most promising material to revolutionize gas turbine hot section materials technology because of their excellent high‐temperature properties. Rapid surface recession due to volatilization by water vapor is the Achilles heel of CMCs. Environmental barrier coatings (EBCs) is an enabling technology for CMCs, since it protects CMCs from water vapor. The first CMC component entered into service in 2016 in a commercial engine, and more CMC components are scheduled to follow within the next few years. One of the most difficult challenges to CMC components is EBC durability, because failure of EBC leads to a rapid reduction in CMC component life. Key contributors to EBC failure include recession, oxidation, degradation by calcium‐aluminum‐magnesium silicates (CMAS) deposits, thermal and thermo‐mechanical strains, particle erosion, and foreign object damage (FOD). Novel EBC chemistries, creative EBC designs, and robust processes are required to meet EBC durability challenges. Engine-relevant testing, characterization, and lifing methods need to be developed to improve EBC reliability. The aim of this Special Issue is to present recent advances in EBC technology to address these issues. In particular, topics of interest include but are not limited to the following: • Novel EBC chemistries and designs; • Processing including plasma spray, suspension plasma spray, solution precursor plasma spray, slurry process, PS-PVD, EB-PVD, and CVD; • Testing, characterization, and modeling; • Lifing.
Publisher: MDPI
ISBN: 3039365177
Category : Science
Languages : en
Pages : 168
Book Description
The global increase in air travel will require commercial vehicles to be more efficient than ever before. Advanced engine hot section materials are a key technology required to keep fuel consumption and emission to a minimum in next-generation gas turbines. Ceramic matrix composites (CMCs) are the most promising material to revolutionize gas turbine hot section materials technology because of their excellent high‐temperature properties. Rapid surface recession due to volatilization by water vapor is the Achilles heel of CMCs. Environmental barrier coatings (EBCs) is an enabling technology for CMCs, since it protects CMCs from water vapor. The first CMC component entered into service in 2016 in a commercial engine, and more CMC components are scheduled to follow within the next few years. One of the most difficult challenges to CMC components is EBC durability, because failure of EBC leads to a rapid reduction in CMC component life. Key contributors to EBC failure include recession, oxidation, degradation by calcium‐aluminum‐magnesium silicates (CMAS) deposits, thermal and thermo‐mechanical strains, particle erosion, and foreign object damage (FOD). Novel EBC chemistries, creative EBC designs, and robust processes are required to meet EBC durability challenges. Engine-relevant testing, characterization, and lifing methods need to be developed to improve EBC reliability. The aim of this Special Issue is to present recent advances in EBC technology to address these issues. In particular, topics of interest include but are not limited to the following: • Novel EBC chemistries and designs; • Processing including plasma spray, suspension plasma spray, solution precursor plasma spray, slurry process, PS-PVD, EB-PVD, and CVD; • Testing, characterization, and modeling; • Lifing.
Intermediate Temperature Solid Oxide Fuel Cells
Author: Gurbinder Kaur
Publisher: Elsevier
ISBN: 0128174463
Category : Technology & Engineering
Languages : en
Pages : 516
Book Description
Intermediate Temperature Solid Oxide Fuel Cells: Electrolytes, Electrodes and Interconnects introduces the fundamental principles of intermediate solid oxide fuel cells technology. It provides the reader with a broad understanding and practical knowledge of the electrodes, pyrochlore/perovskite/oxide electrolytes and interconnects which form the backbone of the Solid Oxide Fuel Cell (SOFC) unit. Opening with an introduction to the thermodynamics, physiochemical and electrochemical behavior of Solid Oxide Fuel Cells (SOFC), the book also discusses specific materials, including low temperature brownmillerites and aurivillius electrolytes, as well as pyrochlore interconnects. This book analyzes the basic concepts, providing cutting-edge information for both researchers and students. It is a complete reference for Intermediate Solid Oxide Fuel Cells technology that will be a vital resource for those working in materials science, fuel cells and solid state chemistry. - Provides a single source of information on glass, electrolytes, interconnects, vanadates, pyrochlores and perovskite SOFC - Includes illustrations that provide a clear visual explanation of concepts being discussed - Progresses from a discussion of basic concepts that will enable readers to easily comprehend the subject matter
Publisher: Elsevier
ISBN: 0128174463
Category : Technology & Engineering
Languages : en
Pages : 516
Book Description
Intermediate Temperature Solid Oxide Fuel Cells: Electrolytes, Electrodes and Interconnects introduces the fundamental principles of intermediate solid oxide fuel cells technology. It provides the reader with a broad understanding and practical knowledge of the electrodes, pyrochlore/perovskite/oxide electrolytes and interconnects which form the backbone of the Solid Oxide Fuel Cell (SOFC) unit. Opening with an introduction to the thermodynamics, physiochemical and electrochemical behavior of Solid Oxide Fuel Cells (SOFC), the book also discusses specific materials, including low temperature brownmillerites and aurivillius electrolytes, as well as pyrochlore interconnects. This book analyzes the basic concepts, providing cutting-edge information for both researchers and students. It is a complete reference for Intermediate Solid Oxide Fuel Cells technology that will be a vital resource for those working in materials science, fuel cells and solid state chemistry. - Provides a single source of information on glass, electrolytes, interconnects, vanadates, pyrochlores and perovskite SOFC - Includes illustrations that provide a clear visual explanation of concepts being discussed - Progresses from a discussion of basic concepts that will enable readers to easily comprehend the subject matter