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Author: Kanak Anant Kuwelkar Publisher: ISBN: Category : Boron Languages : en Pages : 186
Book Description
Boron carbide is the material of choice for lightweight armor applications due to its extreme hardness, high Young's modulus and low specific weight. The homogeneity range in boron carbide extends from ~9 to ~20 at% carbon with the solubility limits not uniquely defined in literature. Over the homogeneity range, the exact lattice positions of boron and carbon atoms have not been unambiguously established, and this topic has been the consideration of significant debate over the last 60 years. The atomic configuration and positions of the boron and carbon atoms play a key role in the crystal structure of the boron carbide phases. Depending on the atomic structure, boron carbide exhibits different mechanical properties which may alter its ballistic performance under extreme dynamic conditions. This work focusses on refinement and development of analytical and chemical methods for an accurate determination of the boron carbide stoichiometry. These methods were then utilized to link structural changes of boron carbide across the solubility range to variations in mechanical properties. After an extensive assessment of the currently employed characterization techniques, it was discerned that the largest source of uncertainty in the determination of the boron carbide stoichiometry was found to arise from the method utilized to evaluate the free carbon concentration. To this end, a modified spiking technique was introduced for free carbon determination where curve fitting techniques were employed to model the asymmetry of the 002 free carbon diffraction peak based on the amorphous, disordered and graphitic nature of carbon. A relationship was then established between the relative intensities of the carbon and boron carbide peaks to the percentage of added carbon and the free-carbon content was obtained by extrapolation. Samples with varying chemistry and high purity were synthesized across the solubility range by hot pressing mixtures of amorphous boron and boron carbide. Vibrational mode frequencies and lattice parameter measurements from Rietveld refinement were correlated to the respective B:C ratios calculated using the developed characterization techniques. An expansion of the unit cell and change in slope in the lattice parameter-stoichiometry relationship were observed at more boron rich stoichiometries. These observations were justified through the proposal of a simplified structural model considering preferential substitution of boron atoms for carbon atoms in the icosahedra from 20 at% to 13.3 at% carbon, followed by formation of B-B bonds from 13.3 at % C to ~9 at% C. Hardness measurements uncovered decreased hardness values in boron rich boron carbide which was attributed to the formation of weaker unit cells. Load induced amorphization was also detected in all the indented materials. Finally, experimental observations have shown that failure in boron carbide may be governed by a mechanism other than amorphization and synthesizing boron carbide with a modified microstructure at stoichiometries close to B4C may be the way forward to attain improved ballistic performance.
Author: Kanak Anant Kuwelkar Publisher: ISBN: Category : Boron Languages : en Pages : 186
Book Description
Boron carbide is the material of choice for lightweight armor applications due to its extreme hardness, high Young's modulus and low specific weight. The homogeneity range in boron carbide extends from ~9 to ~20 at% carbon with the solubility limits not uniquely defined in literature. Over the homogeneity range, the exact lattice positions of boron and carbon atoms have not been unambiguously established, and this topic has been the consideration of significant debate over the last 60 years. The atomic configuration and positions of the boron and carbon atoms play a key role in the crystal structure of the boron carbide phases. Depending on the atomic structure, boron carbide exhibits different mechanical properties which may alter its ballistic performance under extreme dynamic conditions. This work focusses on refinement and development of analytical and chemical methods for an accurate determination of the boron carbide stoichiometry. These methods were then utilized to link structural changes of boron carbide across the solubility range to variations in mechanical properties. After an extensive assessment of the currently employed characterization techniques, it was discerned that the largest source of uncertainty in the determination of the boron carbide stoichiometry was found to arise from the method utilized to evaluate the free carbon concentration. To this end, a modified spiking technique was introduced for free carbon determination where curve fitting techniques were employed to model the asymmetry of the 002 free carbon diffraction peak based on the amorphous, disordered and graphitic nature of carbon. A relationship was then established between the relative intensities of the carbon and boron carbide peaks to the percentage of added carbon and the free-carbon content was obtained by extrapolation. Samples with varying chemistry and high purity were synthesized across the solubility range by hot pressing mixtures of amorphous boron and boron carbide. Vibrational mode frequencies and lattice parameter measurements from Rietveld refinement were correlated to the respective B:C ratios calculated using the developed characterization techniques. An expansion of the unit cell and change in slope in the lattice parameter-stoichiometry relationship were observed at more boron rich stoichiometries. These observations were justified through the proposal of a simplified structural model considering preferential substitution of boron atoms for carbon atoms in the icosahedra from 20 at% to 13.3 at% carbon, followed by formation of B-B bonds from 13.3 at % C to ~9 at% C. Hardness measurements uncovered decreased hardness values in boron rich boron carbide which was attributed to the formation of weaker unit cells. Load induced amorphization was also detected in all the indented materials. Finally, experimental observations have shown that failure in boron carbide may be governed by a mechanism other than amorphization and synthesizing boron carbide with a modified microstructure at stoichiometries close to B4C may be the way forward to attain improved ballistic performance.
Author: Yury G. Gogotsi Publisher: Springer Science & Business Media ISBN: 9401145628 Category : Technology & Engineering Languages : en Pages : 371
Book Description
A survey of current research on a wide range of carbide, nitride and boride materials, covering the general issues relevant to the development and characterisation of a variety of advanced materials. Topics include structure and electronic properties, modeling, processing, high-temperature chemistry, oxidation and corrosion, mechanical behaviour, manufacturing and applications. The volume complements more specialised books on specific materials as well as more general texts on ceramics or hard materials, presenting a survey of materials research as a key to technological development. After decades of research, the materials are being used in electronics, wear resistant, refractory and other applications, but numerous new applications are possible. Roughly equal numbers of papers cover theoretical and experimental research in the general field of materials science of refractory materials. Audience: Researchers and graduate students in materials science and engineering.
Author: Kolan Madhav Reddy Publisher: ISBN: 9781536171211 Category : Languages : en Pages : 252
Book Description
Boron carbide is a superhard and lightweight ceramic material. As a result of these characteristics, it used as a protective component in bulletproof vests, tank armour and also has many other industrial applications (eg: tooling, abrasives). Research on boron carbide remains active given a long-standing challenge to understand its complex failure behavior in extreme environments owing to its unique microstructure and mechanical properties, where many current efforts are underway to improve its behavior through microstructure alteration via additives that form secondary phases, chemical doping, and altering the chemical composition of the boron-to-carbon ratio in the crystal structure. This book covers some of the key challenges involving boron carbide that are currently being studied by many materials scientists and ceramists. The authors who are active in this research field have prepared the chapters for this book and specific topics covered highlight the state-of-the art research in structure, processing, properties and applications. The organization of the book is designed to provide an easy understanding for students and professionals interested in advanced material for novel applications.
Author: A.W. Weimer Publisher: Springer Science & Business Media ISBN: 9400900716 Category : Technology & Engineering Languages : en Pages : 675
Book Description
Carbide, Nitride and Boride Materials Synthesis and Processing is a major reference text addressing methods for the synthesis of non-oxides. Each chapter has been written by an expert practising in the subject area, affiliated with industry, academia or government research, thus providing a broad perspective of information for the reader. The subject matter ranges from materials properties and applications to methods of synthesis including pre- and post-synthesis processing. Although most of the text is concerned with the synthesis of powders, chapters are included for other materials such as whiskers, platelets, fibres and coatings. Carbide, Nitride and Boride Materials Synthesis and Processing is a comprehensive overview of the subject and is suitable for practitioners in the industry as well as those looking for an introduction to the field. It will be of interest to chemical, mechanical and ceramic engineers, materials scientists and chemists in both university and industrial environments working on or with refractory carbides, nitrides and borides.
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: R. Freer Publisher: Springer Science & Business Media ISBN: 9400921012 Category : Technology & Engineering Languages : en Pages : 716
Book Description
Carbides, nitrides and borides are families of related refractory materials. Traditionally they have been employed in applications associated with engineering ceramics where either high temperature strength or stability is of primary importance. In recent years there has been a growing awareness of the interesting electrical, thermal and optical properties exhibited by these materials, and the fact that many can be prepared as monolithic ceramics, single crystals and thin films. In practical terms carbides, nitrides and borides offer the prospect of a new generation of semiconductor materials, for example, which can function at very high temperatures in severe environmental conditions. However, as yet, we have only a limited understanding of the detailed physics and chemistry of the materials and how the preparation techniques influence the properties. Under the auspices of the NATO Science Committee an Advanced Research Workshop (ARW) was held on the Physics and Chemistry of Carbides, Nitrides and Borides (University of Manchester, 18-22 September, 1989) in order to assess progress to date and identify the most promising themes and materials for future research. An international group of 38 scientists considered developments in 5 main areas: The preparation of powders, monolithic ceramics, single crystals and thin films; Phase transformations, microstructure, defect structure and mass transport; Materials stability; Theoretical studies; Electrical, thermal and optical properties of bulk materials and thin films.
Author: Nina Orlovskaya Publisher: Springer ISBN: 9048198186 Category : Science Languages : en Pages : 339
Book Description
The objective of this book is to discuss the current status of research and development of boron-rich solids as sensors, ultra-high temperature ceramics, thermoelectrics, and armor. Novel biological and chemical sensors made of stiff and light-weight boron-rich solids are very exciting and efficient for applications in medical diagnoses, environmental surveillance and the detection of pathogen and biological/chemical terrorism agents. Ultra-high temperature ceramic composites exhibit excellent oxidation and corrosion resistance for hypersonic vehicle applications. Boron-rich solids are also promising candidates for high-temperature thermoelectric conversion. Armor is another very important application of boron-rich solids, since most of them exhibit very high hardness, which makes them perfect candidates with high resistance to ballistic impact. The following topical areas are presented: •Boron-rich solids: science and technology •Synthesis and sintering strategies of boron rich solids •Microcantilever sensors •Screening of the possible boron-based thermoelectric conversion materials; •Ultra-high temperature ZrB2 and HfB2 based composites •Magnetic, transport and high-pressure properties of boron-rich solids •Restrictions of the sensor dimensions for chemical detection •Armor
Author: Muhammet Fatih Toksoy Publisher: ISBN: Category : Boron Languages : en Pages : 165
Book Description
Boron carbide is a structural ceramic material with exceptionally good physical and chemical properties. Thus, boron carbide is proposed for applications in extreme conditions. However synthesizing and sintering of boron carbide is extremely difficult due to its high melting point and strong covalent bonding. Secondary phases, non-uniform composition, complex stoichiometry and powder morphology are problems in most commercial powders as a result of synthesis and powder preparation procedures. Achieving more than 90% TD is difficult due to strong covalent bonding structure and low plasticity of boron carbide. Very high sintering temperatures that approach the melting point are needed for densification. This dissertation seeks to establish an improved understanding on Spark Plasma Sintering (SPS) behaviors of boron carbide and effects of powder properties on final products. Rapid carbothermal reduction (RCR) method was utilized to synthesize boron carbide powder. Submicron boron carbide powders with narrow particle size distribution were synthesized. Free carbon was significantly reduced and near B4C stoichiometry was achieved. Commercial boron carbide powders were also modified by processing in the RCR reactor. Free carbon was reduced to trace amounts; powder morphology and stoichiometry was modified. Commercial, synthesized and modified boron carbide powders were analyzed and characterized using X-Ray diffraction (XRD), electron microscopy, particle size analysis and chemical analyses. Synthesized boron carbide powder had smaller particle size, lower free carbon levels and increased concentration of twinning compared to commercial samples. Standard sintering procedure for boron carbide was established for SPS. Powders were sintered to different temperatures with various dwell times to analyze sintering behavior of boron carbide on SPS without any additives. Synthesized boron carbide powders reached +99% TD at lower temperature and shorter dwell times compared to commercial boron carbide samples. Highly dense materials were produced with limited grain growth. Dense samples were analyzed by XRD and electron microscopy. Knoop hardness tests were applied to dense boron carbide samples. Hardness results showed an improvement with RCR synthesized powders. Results were correlated and powder-sintering-final properties relations were established.
Author: Jerry C. LaSalvia Publisher: John Wiley & Sons ISBN: 1119211530 Category : Technology & Engineering Languages : en Pages : 160
Book Description
The Ceramic Engineering and Science Proceeding has been published by The American Ceramic Society since 1980. This series contains a collection of papers dealing with issues in both traditional ceramics (i.e., glass, whitewares, refractories, and porcelain enamel) and advanced ceramics. Topics covered in the area of advanced ceramic include bioceramics, nanomaterials, composites, solid oxide fuel cells, mechanical properties and structural design, advanced ceramic coatings, ceramic armor, porous ceramics, and more.
Author: Minoru Matsui Publisher: John Wiley & Sons ISBN: 1118371496 Category : Technology & Engineering Languages : en Pages : 282
Book Description
This new book presents new ceramic information in two parts. Thefirst section presents state-of-the-art information on newmeasurements and characterization methods in the ceramicmanufacturing process including characterization of mechanicalproperties microstructure, and machining techniques, as well as thestatus on the activity of standards in ceramics. The second part isa selection of peer reviewed research papers in this field. This volume will prove indispensable for academic as well asindustry researchers and for anyone seeking broader knowledge onthe quality improvements through new measurements and processingtechnology.
Author: Kanak Anant Kuwelkar
Author: Kanak Anant Kuwelkar
Author: Yury G. Gogotsi
Author: Kolan Madhav Reddy
Author: A.W. Weimer
Author: William G. Fahrenholtz
Author: R. Freer
Author: Nina Orlovskaya
Author: Muhammet Fatih Toksoy
Author: Jerry C. LaSalvia
Author: Minoru Matsui