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Author: Eric William Neuman Publisher: ISBN: Category : Borides Languages : en Pages : 259
Book Description
"Research presented in this dissertation focused on the mechanical behavior of ZrB2 based ceramic at elevated temperatures. Flexure strength, fracture toughness, and elastic modulus were measured at temperatures up to 2300°C for three compositions: monolithic ZrB2 (Z); ZrB2 - 30 vol% SiC - 2 vol% B4C (ZS); and ZrB2 - 10 vol% ZrC (ZC). In argon, Z, ZS, and ZC had strengths of 210 (at 2300°C), 260 (at 2200°C), and 295 MPa (at 2300°C), the highest temperatures tested for each composition. Fractography was used extensively to characterize the strength limiting flaws as a function of temperature. Strength of ZS in argon was controlled by the SiC cluster size up to 1800°C, and the formation of B-O-C-N phases that bridged SiC clusters above 2000°C. For ZC, surface flaws introduced during specimen preparation were the source of critical flaws in the material up to 1400°C, sub-critical crack growth of surface flaws between 1600 and 2000°C, and microvoid coalescence above 2000°C. It was also shown that thermal annealing at either 1400, 1500, or 1600°C improves the strength and modulus of ZS at temperatures between 800°C and 1600°C. Heat treatment at 1400°C for 10 hours produced the largest improvement in strength, 430 MPa at 1600°C versus 380 MPa for the as processed material. As a whole, the research pointed to several key microstructural features currently limiting the mechanical properties at the highest temperatures. In particular, removal of unfavorable secondary phases, and improved control over microstructure, should be promising methods to improve the elevated temperature properties of ZrB2 ceramics."--Abstract, page iv.
Author: Eric William Neuman Publisher: ISBN: Category : Borides Languages : en Pages : 259
Book Description
"Research presented in this dissertation focused on the mechanical behavior of ZrB2 based ceramic at elevated temperatures. Flexure strength, fracture toughness, and elastic modulus were measured at temperatures up to 2300°C for three compositions: monolithic ZrB2 (Z); ZrB2 - 30 vol% SiC - 2 vol% B4C (ZS); and ZrB2 - 10 vol% ZrC (ZC). In argon, Z, ZS, and ZC had strengths of 210 (at 2300°C), 260 (at 2200°C), and 295 MPa (at 2300°C), the highest temperatures tested for each composition. Fractography was used extensively to characterize the strength limiting flaws as a function of temperature. Strength of ZS in argon was controlled by the SiC cluster size up to 1800°C, and the formation of B-O-C-N phases that bridged SiC clusters above 2000°C. For ZC, surface flaws introduced during specimen preparation were the source of critical flaws in the material up to 1400°C, sub-critical crack growth of surface flaws between 1600 and 2000°C, and microvoid coalescence above 2000°C. It was also shown that thermal annealing at either 1400, 1500, or 1600°C improves the strength and modulus of ZS at temperatures between 800°C and 1600°C. Heat treatment at 1400°C for 10 hours produced the largest improvement in strength, 430 MPa at 1600°C versus 380 MPa for the as processed material. As a whole, the research pointed to several key microstructural features currently limiting the mechanical properties at the highest temperatures. In particular, removal of unfavorable secondary phases, and improved control over microstructure, should be promising methods to improve the elevated temperature properties of ZrB2 ceramics."--Abstract, page iv.
Author: Sumin Zhu Publisher: ISBN: Category : Ceramic materials Languages : en Pages : 360
Book Description
"The first part of this dissertation was aimed at studying the densification of ZrB2 ceramics by pressureless sintering techniques. Various processes have been applied to coat ZrB2 powders with polymer precursors, which were used to produce C after charring. After sintering at 1900°C, relative density increased of ~70% for uncoated ZrB2 to >99% for ZrB2 coated with at least 1.0 wt% C. Thermodynamic analysis suggested that C reacted with and removed oxide impurities (ZrO2 and B2O3) that were present on the ZrB2 particle surfaces, which promoted densification by minimizing grain coarsening"--Abstract, leaf iv.
Author: William G. Fahrenholtz Publisher: John Wiley & Sons ISBN: 111892441X Category : Technology & Engineering Languages : en Pages : 601
Book Description
The first comprehensive book to focus on ultra-high temperature ceramic materials in more than 20 years Ultra-High Temperature Ceramics are a family of compounds that display an unusual combination of properties, including extremely high melting temperatures (>3000°C), high hardness, and good chemical stability and strength at high temperatures. Typical UHTC materials are the carbides, nitrides, and borides of transition metals, but the Group IV compounds (Ti, Zr, Hf) plus TaC are generally considered to be the main focus of research due to the superior melting temperatures and stable high-melting temperature oxide that forms in situ. Rather than focusing on the latest scientific results, Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications broadly and critically combines the historical aspects and the state-of-the-art on the processing, densification, properties, and performance of boride and carbide ceramics. In reviewing the historic studies and recent progress in the field, Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications provides: Original reviews of research conducted in the 1960s and 70s Content on electronic structure, synthesis, powder processing, densification, property measurement, and characterization of boride and carbide ceramics. Emphasis on materials for hypersonic aerospace applications such as wing leading edges and propulsion components for vehicles traveling faster than Mach 5 Information on materials used in the extreme environments associated with high speed cutting tools and nuclear power generation Contributions are based on presentations by leading research groups at the conference "Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications II" held May 13-19, 2012 in Hernstein, Austria. Bringing together disparate researchers from academia, government, and industry in a singular forum, the meeting cultivated didactic discussions and efforts between bench researchers, designers and engineers in assaying results in a broader context and moving the technology forward toward near- and long-term use. This book is useful for furnace manufacturers, aerospace manufacturers that may be pursuing hypersonic technology, researchers studying any aspect of boride and carbide ceramics, and practitioners of high-temperature structural ceramics.
Author: Matthew Joseph Thompson Publisher: ISBN: Category : Borides Languages : en Pages : 430
Book Description
"The research presented in this dissertation focuses on the processing and thermomechanical properties of ZrB2 based ceramics. The overall goal was to improve the understanding of thermal and mechanical properties based on processing conditions and additives to ZrB2. To achieve this, the relationships between the thermal and mechanical properties were analyzed for ZrB2 ceramics that were densified by different methods, varying amounts of carbon, B4C, or TiB2 additions. Four main areas were investigated in this dissertation. The first showed that decreased processing times, regardless of densification method, improved mechanical strength to >500 MPa. This study also revealed that lower oxygen impurity contents led to less grain coarsening. The second study showed that higher heating rates narrowed the grain size distribution, which resulted in strengths above 600 MPa. However, the decreased processing times led to retention of ZrO2, which decreased the thermal conductivity. The third study revealed that carbon additions interacted with ZrO2 and WC impurities introduced during powder processing to form (Zr,W)C, which led to higher thermal conductivity than ZrB2 with no carbon added. The last area examined the effect of solid solution additions on the electron and phonon contributions to thermal conductivity. The formation of solid solutions decreased thermal conductivity to
Author: John B. Wachtman Publisher: John Wiley & Sons ISBN: 9780470451502 Category : Technology & Engineering Languages : en Pages : 496
Book Description
A Comprehensive and Self-Contained Treatment of the Theory and Practical Applications of Ceramic Materials When failure occurs in ceramic materials, it is often catastrophic, instantaneous, and total. Now in its Second Edition, this important book arms readers with a thorough and accurate understanding of the causes of these failures and how to design ceramics for failure avoidance. It systematically covers: Stress and strain Types of mechanical behavior Strength of defect-free solids Linear elastic fracture mechanics Measurements of elasticity, strength, and fracture toughness Subcritical crack propagation Toughening mechanisms in ceramics Effects of microstructure on toughness and strength Cyclic fatigue of ceramics Thermal stress and thermal shock in ceramics Fractography Dislocation and plastic deformation in ceramics Creep and superplasticity of ceramics Creep rupture at high temperatures and safe life design Hardness and wear And more While maintaining the first edition's reputation for being an indispensable professional resource, this new edition has been updated with sketches, explanations, figures, tables, summaries, and problem sets to make it more student-friendly as a textbook in undergraduate and graduate courses on the mechanical properties of ceramics.
Author: Brett Hunter Publisher: ISBN: Category : Languages : en Pages : 100
Book Description
Ultra high temperature ceramics (UHTCs), which typically comprise carbides, nitrides, and borides, are a class of materials associated with high melting temperatures and high hardness. These materials offer a range of mechanical responses, from being very brittle to exhibiting significant plasticity as a function of composition and loading temperature. The purpose of this investigation is to characterize the slip mechanisms in ZrB2, where slip has been inferred but not definitively quantified. This work confirmed prior studies that dense dislocation arrays, with straight dislocation lines, exist under room temperature indents and demonstrates that such networks are highly localized to the load region. For elevated temperature deformation, ZrB2 has been reported to have a drop in flexural strength from 390 MPa at 1200 °C to 110 MPa at 1600 °C. Dynamical electron diffraction and image analysis confirmed basal, pyramidal, and prismatic slip which is rationalized by ZrB2's hexagonal close packed c/a lattice parameter ratio of 1.11, which is less than the ideal ratio of 1.63. The dislocation densities prior to and after this flexural strength drop were 1.3 x 1013 m-2 and 1.0 x 1013 m-2, respectively. This indicates that the reduction in strength was not significantly associated with increased dislocation nucleation but rather stress relaxation.
Author: Dileep Singh Publisher: John Wiley & Sons ISBN: 0470584254 Category : Technology & Engineering Languages : en Pages : 350
Book Description
Gain insight into the mechanical properties and performance of engineering ceramics and composites. This collection of articles illustrates the Mechanical Behavior and Performance of Ceramics & Composites symposium, which included over 100 presentations representing 10 countries. The symposium addressed the cutting-edge topics on mechanical properties and reliability of ceramics and composites and their correlations to processing, microstructure, and environmental effects.
Author: Bikramjit Basu Publisher: John Wiley & Sons ISBN: 1119538831 Category : Technology & Engineering Languages : en Pages : 400
Book Description
This book covers the area of tribology broadly, providing important introductory chapters to fundamentals, processing, and applications of tribology. The book is designed primarily for easy and cohesive understanding for students and practicing scientists pursuing the area of tribology with focus on materials. This book helps students and practicing scientists alike understand that a comprehensive knowledge about the friction and wear properties of advanced materials is essential to further design and development of new materials. The description of the wear micromechanisms of various materials will provide a strong background to the readers as how to design and develop new tribological materials. This book also places importance on the development of new ceramic composites in the context of tribological applications. Some of the key features of the book include: Fundamentals section highlights the salient issues of ceramic processing and mechanical properties of important oxide and non-oxide ceramic systems; State of the art research findings on important ceramic composites are included and an understanding on the behavior of silicon carbide (SiC) based ceramic composites in dry sliding wear conditions is presented as a case study; Erosion wear behavior of ceramics, in which case studies on high temperature erosion behavior of SiC based composites and zirconium diboride (ZrB2) based composites is also covered; Wear behavior of ceramic coatings is rarely discussed in any tribology related books therefore a case study explaining the abrasion wear behavior of WC-Co coating is provided. Finally an appendix chapter is included in which a collection of several types of questions including multiple choice, short answer and long answer are provided.
Author: Low, I. M. Publisher: IGI Global ISBN: 1466640677 Category : Technology & Engineering Languages : en Pages : 679
Book Description
Ceramics are a versatile material, more so than is widely known. They are thermal resistant, poor electrical conductors, insulators against nuclear radiation, and not easily damaged, making ceramics a key component in many industrial processes. MAX Phases and Ultra-High Temperature Ceramics for Extreme Environments investigates a new class of ultra-durable ceramic materials, which exhibit characteristics of both ceramics and metals. Readers will explore recent advances in the manufacturing of ceramic materials that improve their durability and other physical properties, enhancing their overall usability and cost-effectiveness. This book will be of primary use to researchers, academics, and practitioners in chemical, mechanical, and electrical engineering. This book is part of the Research Essentials collection.
Author: Eric William Neuman
Author: Eric William Neuman
Author: Sumin Zhu
Author: Dipankar Ghosh
Author: William G. Fahrenholtz
Author: Matthew Joseph Thompson
Author: John B. Wachtman
Author: Brett Hunter
Author: Dileep Singh
Author: Bikramjit Basu
Author: Low, I. M.