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This book describes spark plasma sintering (SPS) in depth. It addresses fundamentals and material-specific considerations, techniques, and applications across a broad spectrum of materials. The book highlights methods used to consolidate metallic or ceramic particles in very short times. It highlights the production of complex alloys and metal matrix composites with enhanced mechanical and wear properties. Emphasis is placed on the speed of the sintering processes, uniformity in product microstructure and properties, reduced grain growth, the compaction and sintering of materials in one processing step, various materials processing, and high energy efficiency. Current and potential applications in space science and aeronautics, automation, mechanical engineering, and biomedicine are addressed throughout the book.
"Transparent polycrystalline ceramics consist of small crystalline grains densified into bulk materials. Properly sintered ceramics display unique combinations of properties, such as hardness, fracture toughness, elastic modulus, transparency, absorption coefficient, thermal conductivity, dopant absorption, emission characteristics and optical isotropy, that are very close or even better than those of single crystals. Moreover, polycrystalline ceramics offer various advantages over single crystals, such as cost-effectiveness, the possibility for large-scale production, shape control and improved mechanical properties. As such, polycrystalline ceramics have become increasingly attractive for a wide range of applications, both military and civil. The development of transparent polycrystalline ceramics for laser oscillation and armor materials is an important goal of materials technology. In 1995, Ikesue presented efficient laser oscillation the first time, using polycrystalline Nd:YAG. Polycrystalline magnesium aluminate spinel (PMAS) is another attractive transparent ceramic that can be utilized as armor material due to its simple synthesis, excellent mechanical properties and high-level of transparency over a wide range of wavelengths. Extensive investigations have been conducted by various groups around the world, given the economic implications of the possible application of polycrystalline ceramics. Conventional technological approaches for the fabrication of the polycrystalline ceramics are based on prolonged pressureless sintering (PLS) at relatively high temperatures, hot pressing (HP) and hot isostatic pressing (HIP). While these approaches allow for the fabrication of transparent ceramics with adequate functional properties, they are time-consuming and very expensive. In recent decades, Spark Plasma Sintering (SPS) technology has been employed for the fabrication of polycrystalline ceramics. The SPS process involves simultaneous application of an electric field, temperature and pressure and permits rapid powder consolidation at temperatures significantly lower than those used with conventional sintering processes. The aims of this dissertation were to understand and investigate the effect of SPS parameters (i.e., dwell time, temperature, pressure, heating rate) and sintering additives (mainly LiF) on functional properties of polycrystalline transparent ceramics for a wide range of laser and armor applications. The present study addresses both fundamental aspects of functional properties and the fabrication of transparent polycrystalline ceramics with controlled microstructure by high-pressure SPS process. The fundamental aspects of transparent ceramic sintering and the effects of SPS under high pressure were investigated in depth and are discussed. This doctoral research can be divided into two main parts. The first part is related to the fabrication of PMAS by high-pressure SPS (HPSPS) techniques (up to 1.0 GPa) and characterization of the optical and mechanical properties of the material generated. Codoped PMAS suitable for Q-switching applications with an adequate saturable absorption was successfully fabricated using a combined SPS approach followed by HIP treatment. The second part of the work describes the SPS-based fabrication of Nd:YAG specimens and characterization of their mechanical and optical properties, including lasing efficiency and power threshold. HPSPS-processed Nd:YAG displayed laser generation characteristics comparable with commercially available, conventionally sintered specimens. The obtained results point to the ability to fabricate cost-effective nanostructured polycrystalline ceramics with controlled microstructure and unique combinations of optical, thermal and mechanical properties. It was established that the hardness values of these materials followed the well-known Hall-Petch relation down to grain sizes of 30 nm. For grain sizes lower than 30 nm, an inverse Hall-Petch relation was clearly observed. The results of this investigations were published in seven international peer-reviewed journals with high ranking and were presented at more than twenty international conferences."--abstract.
The chapters covered in this book include emerging new techniques on sintering. Major experts in this field contributed to this book and presented their research. Topics covered in this publication include Spark plasma sintering, Magnetic Pulsed compaction, Low Temperature Co-fired Ceramic technology for the preparation of 3-dimesinal circuits, Microwave sintering of thermistor ceramics, Synthesis of Bio-compatible ceramics, Sintering of Rare Earth Doped Bismuth Titanate Ceramics prepared by Soft Combustion, nanostructured ceramics, alternative solid-state reaction routes yielding densified bulk ceramics and nanopowders, Sintering of intermetallic superconductors such as MgB2, impurity doping in luminescence phosphors synthesized using soft techniques, etc. Other advanced sintering techniques such as radiation thermal sintering for the manufacture of thin film solid oxide fuel cells are also described.
Sintering process studies have re-emerged strongly in the past decade due to extensive discussions about the stabilization of nanoparticles and nanostructures, and the development of controlled nanograined bulk materials. This book presents the state-of-art in experiments and theory of novel sintering processes, traditional sintering and grain growth. The scope ranges from powder metallurgy to ceramic and composites processing. The challenges of conventional and novel sintering and grain growth in nanopowders and nanostructures are addressed, being useful for students as well as professionals interested in sintering at the nanoscale.
This book represents the first ever scientific monograph including an in-depth analysis of all major field-assisted sintering techniques. Until now, the electromagnetic field-assisted technologies of materials processing were lacking a systematic and generalized description in one fundamental publication; this work promotes the development of generalized concepts and of comparative analyses in this emerging area of materials fabrication. This book describes modern technologies for the powder processing-based fabrication of advanced materials. New approaches for the development of well-tailored and stable structures are thoroughly discussed. Since the potential of traditional thermo-mechanical methods of material treatment is limited due to inadequate control during processing, the book addresses ways to more accurately control the resultant material's structure and properties by an assisting application of electro-magnetic fields. The book describes resistance sintering, high-voltage consolidation, sintering by low-voltage electric pulses (including spark plasma sintering), flash sintering, microwave sintering, induction heating sintering, magnetic pulse compaction and other field-assisted sintering techniques. Includes an in-depth analysis of all major field-assisted sintering techniques; Explains new techniques and approaches for material treatment; Provides detailed descriptions of spark plasma sintering, microwave sintering, high-voltage consolidation, magnetic pulse compaction, and various other approaches when field-assisted treatment is applied.
The chapters covered in this book include emerging new techniques on sintering. Major experts in this field contributed to this book and presented their research. Topics covered in this publication include Spark plasma sintering, Magnetic Pulsed compaction, Low Temperature Co-fired Ceramic technology for the preparation of 3-dimesinal circuits, Microwave sintering of thermistor ceramics, Synthesis of Bio-compatible ceramics, Sintering of Rare Earth Doped Bismuth Titanate Ceramics prepared by Soft Combustion, nanostructured ceramics, alternative solid-state reaction routes yielding densified bulk ceramics and nanopowders, Sintering of intermetallic superconductors such as MgB2, impurity doping in luminescence phosphors synthesized using soft techniques, etc. Other advanced sintering techniques such as radiation thermal sintering for the manufacture of thin film solid oxide fuel cells are also described.
Ultra High Temperature Ceramics (UHTCs) are the most promising candidates for high temperature applications in extreme environments, such as conditions experienced during re-entry of out space flying objects, for their known high melting points, good chemical and thermal stability and high thermal conductivity. To improve the densification and oxidation resistance of UHTCs, a second phase, such as silicon carbide, is usually added to monolithic UHTCs to form ceramic matrix composites. While UHTCs/composites have many unique advantages for high temperature applications, they are very difficult to densify due to their very strong covalent chemical bonds and very high melting point. Conventional methods for processing UHTCs usually use powders as starting materials. A major issue of the conventional methods is the poor mixing/processing of powders with different densities and sizes, especially for nano-sized powders. Thus more research needs to be focused on improving UHTCs' densification, microstructure and properties.This thesis studies the development of novel sol-gel techniques for preparation of starting materials and spark plasma sintering (SPS) for densification of UHTCs and composites. The thesis is organized into eight chapters. The First Chapter is an introduction to the thesis structure organization. The Second Chapter is the background of the research and literature review. Chapter Three is a description of the experimental procedures and characterization techniques. In the first result chapter, Chapter Four, silicon nitride ceramic and silicon nitride/titanium nitride composite were fabricated by hot pressing and spark plasma sintering (SPS) respectively to study the effect of the SPS DC current on the densification, microstructure and properties of conductive and non-conductive materials. A sol-gel based approach was investigated to improve the UHTC ceramics/composites with fine microstructures in Chapter Five. Although sol-gel techniques may not be suitable for making large bulk materials, they have unique advantages on modifying or improving the microstructures, properties and surfaces of materials through the solution chemistry approach. The sol-gel processing technique was used to synthesize TiC/SiC nanocomposites and followed by SPS sintering. Dense TiC/SiC composites were fabricated successfully to form a microstructure consisted of nano TiC and SiC grains. Work in Chapter Six used a sol-gel infiltration technique to fabricate dense TiC/SiC nanocomposites from porous TiC scaffolds. In Chapter Seven, zirconium diboride/silicon carbide composites of fine microstructures were successfully fabricated by sol-gel coating of ZrB2 powders and SPS sintering. Compared to conventional ceramic processing methods, the sol-gel based wet chemistry process has many unique advantages such as homogeneous mixing of starting materials, infiltration of porous green bodies with complex shapes, avoiding the formation of intermediate transit phase/liquid phase in sintering, restricting grain growth and assisting densification by reaction. Chapter Eight presents the conclusions of the thesis and provides some directions for future work.
Sintering technology is an old and extensive technology in many areas, and it has been used especially in ceramic fabrication. This book covers many fields, for example, the development of different sintering technologies in recent years, such as spark plasma sintering, flash sintering, microwave sintering, reaction and laser sintering, and so on, and also some special ceramic material fabrication methods and applications, such as carbon nanotubes mixed with alumina and zirconia ceramics, pure and doped zirconia, ZnO ceramic varistors, and so on.