Download or read book An Improved Method for the Preparation of Boron Carbide with Some Notes on Its Properties written by Arthur Wayland Dox and published by . This book was released on 1905 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Improved Method for the Preparation of Boron Carbide with Some Notes on Its Properties written by Henry James Wheeler Bliss and published by . This book was released on 1905 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Deposition of Pure Boron written by Hermann Irving Schlesinger and published by . This book was released on 1947 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Densification of Rapid Carbothermal Synthesized and Commercial Boron Carbide by Spark Plasma Sintering written by Muhammet Fatih Toksoy and published by . This book was released on 2014 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Boron Carbide written by Kolan Madhav Reddy and published by . This book was released on 2020-04-04 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Manufacturing Method for Improved Forming of Boron Carbide written by Thomas Vasilos and published by . This book was released on 1973 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: 12 IN. X 12 IN. X 3/8 IN. THICKNESS WAS HOT PRESSED TO A DENSITY OF> 98% of theoretical by alloying additions at a temperature of 1750C and a pressure of 3500 psi. Chemical analysis reveals iron as the principal densification aid remaining in the hot pressed structure. Transverse rupture and elastic modulus tests were conducted on samples 1 3/4 in x 1/4 in. x .100 in. cut from a 12 in. x 12 in. tile. The data show the rupture strength decreasing from an average of 73.4 Ksi at room temperature to an average of 38.4 Ksi at 1400C. The elastic modulus decreases from 55.5 x 10 to the 6th power psi at room temperature to 35.5 x 10 to the 6th power psi at 1200C. Hardness measurements taken with a Knoop indenter (100 gm load) range from 2530 to 2670. (Author) Portions of this document are not fully legible.
Download or read book Carbide Nitride and Boride Materials Synthesis and Processing written by Alan Wesley Weimer and published by Springer Science & Business Media. This book was released on 1997 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many of the advanced ceramics being developed today are boride, carbide and nitride materials. These are targeted for applications in both electronic and structural markets. This book aims to address methods for the synthesis of these materials. This text is intended as an overview of the subject and is suitable for practitioners in the industry as well as those looking for an introduction to the field. The subject matter ranges from introductory material properties and applications to various 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 including whiskers, platelets, fibres and coatings. Specific safety considerations are discussed for each part of the text. The book is split into nine parts covering a wide range of topics under the heading and includes an appendix comprising selcted data for crystallographic, thermodynamic, thermal, mechanical, electrical, magnetic and chemical properties of some boride, carbide and nitride materials.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Improvement of the Mechanical Properties of the Reaction Bonded Boron Carbide Composites by Using Multimodal Boron Carbide Powder Mixtures written by Amir Weizman and published by . This book was released on 2009 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemical and Structural Characterization of Boron Carbide Powders and Ceramics written by Kanak Anant Kuwelkar and published by . This book was released on 2016 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book PEM Water Electrolysis written by Dmitri Bessarabov and published by Academic Press. This book was released on 2018-08-04 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: PEM Water Electrolysis, a volume in the Hydrogen Energy and Fuel Cell Primers series presents the most recent advances in the field. It brings together information that has thus far been scattered in many different sources under one single title, making it a useful reference for industry professionals, researchers and graduate students. Volumes One and Two allow readers to identify technology gaps for commercially viable PEM electrolysis systems for energy applications and examine the fundamentals of PEM electrolysis and selected research topics that are top of mind for the academic and industry community, such as gas cross-over and AST protocols. The book lays the foundation for the exploration of the current industrial trends for PEM electrolysis, such as power to gas application and a strong focus on the current trends in the application of PEM electrolysis associated with energy storage. Presents the fundamentals and most current knowledge in proton exchange membrane water electrolyzers Explores the technology gaps and challenges for commercial deployment of PEM water electrolysis technologies Includes unconventional systems, such as ozone generators Brings together information from many different sources under one single title, making it a useful reference for industry professionals, researchers and graduate students alike
Download or read book Computational Studies of Physical Properties of Boron Carbide written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall goal is to provide valuable insight in to the mechanisms and processes that could lead to better engineering the widely used boron carbide which could play an important role in current plight towards greener energy. Carbon distribution in boron carbide, which has been difficult to retrieve from experimental methods, is critical to our understanding of its structure-properties relation. For modeling disorders in boron carbide, we implemented a first principles method based on supercell approach within our G(P, T) package. The supercell approach was applied to boron carbide to determine its carbon distribution. Our results reveal that carbon prefers to occupy the end sites of the 3-atom chain in boron carbide and further carbon atoms will distribute mainly on the equatorial sites with a small percentage on the 3-atom chains and the apex sites. Supercell approach was also applied to study mechanical properties of boron carbide under uniaxial load. We found that uniaxial load can lead to amorphization. Other physical properties of boron carbide were calculated using the G(P, T) package.
Download or read book Boron Rich Solids written by David Emin and published by AIP Conference Proceedings (Nu. This book was released on 1991 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Evolution and Implication of Boron Carbide Microstructural Variations and Transformations During Powder Processing written by Daniel W. Maiorano and published by . This book was released on 2011 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boron carbide is a material of key interest in structural ceramic applications due to its extremely favorable physical properties including low theoretical density, high hardness, high strength, and excellent wear resistance. However, boron carbide microstructures often exhibit the presence of secondary phases, most typically composed of carbon. Under very high stress and strain rate conditions, boron carbide has been shown to have reduction in compressive strength. It has been postulated that a ~3 nm wide region of amorphous material is the cause of this reduction in properties and appears to be the result of a pressure induced structural transformation. The impact of both carbon inclusions and the amorphous bands on bulk physical properties is not easy to resolve due to the complex crystal structures of the boron carbide solid solution from 8-20 at% carbon. As these variations have only been noted to date following application of high stress upon the boron carbide with no examination of powders prior to high stress, this dissertation attempts to determine whether these variations are inherent to boron carbide powders or introduced during typical powder processing. Most boron carbides are produced by a large scale carbothermic reduction process within an electric arc furnace. While it remains the most cost effective production method at this time, carbothermic reduction suffers from uneven heating rates across the reactive melt which makes it difficult to maintain a chemically uniform product. Boron carbide melted ingots are crushed, followed by comminution and sorting based upon size. To determine the extent of preexisting variations, commercially available powders were compared with segments taken directly from the carbothermic reduction ingot via X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Raman microspectroscopy. All powders were then subjected to various levels of comminution to examine the level of pressure induced by common powder processing. Analyses showed that due to the nature of the carbothermic reduction process, significant stoichiometry variations of over 2 at% carbon are present across the length of segments classified as "good" boron carbide visually. These stoichiometric variations correspond with a large presence of secondary phase carbon, including unreacted precursor material, deposited thin films, and graphite products. The comminution process impacted the relative exposed carbon content of the boron carbides, resulting in powders that were coated with carbonaceous materials. At high comminution energies in a lab scale jet mill, resulting surfaces exhibited evidence of amorphized boron carbide through Raman and FTIR analysis. Attempts at reversing the processing induced variations proved ineffective and suggest inherent difficulties in altering the structure of boron carbide produced via carbothermic reduction.
Download or read book Journal of the American Chemical Society written by American Chemical Society and published by . This book was released on 1906 with total page 1190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the Society are included in v. 1-59, 1879-1937.
Download or read book Journal of the Institute of Metals written by Institute of Metals and published by . This book was released on 1925 with total page 756 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues for Sept. 1951- include the Bulletin.
Download or read book Determination of Structural Changes and Phase Transformations in Boron Carbide by Static and Dynamic Studies written by Varun Gupta and published by . This book was released on 2010 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent transmission electron microscopy results demonstrate that the failure of B4C is commensurate with the segregation of boron icosahedra embedded in amorphous carbon in 2-3 nm wide amorphous bands along the (113) lattice direction, in good agreement with our recent theoretical results. Boron carbide is generally composed of multiple polytypes of B4C which have the same primitive lattice parameters but differ from each other by the location of the boron and carbon atoms in the unit cells. The unit cells are formed by a 12-atom B12-nCn icosahedron and a 3-atom (C3-nBn) chain. Our theoretical results indicate that one polytype, B12(C3), whose formation is responsible for the failure of the entire material. This anomalous and poorly understood glass-like behavior in boron carbide has been the subject of research since its discovery over 70 years ago. The characterization of disorder in hot pressed and powder boron carbide samples is therefore of primary interest. The research work has focused on characterization techniques which can be used at a micrometric sampling size so that individual powder grains of the material can be utilized. Specifically, micro-Raman and electrical conductivity measurements can be used with micrometric gap cells to understand the disorder in B4C. The results also demonstrate that it is possible to induce transformations in boron carbide using electric fields that are comparable with those obtained under shock and nanoindentation. Our calculations present a hypothesis which can provide a solution to prevent the premature failure of B4C. A route to achieve suppression of the B12(CCC) polytype without significantly affecting the elastic constants is via low concentration Silicon (Si) doping of B4C. Suppression of B12(CCC) by Si doping has implications towards development of boron carbide armor with improved properties for protection against high velocity threats. In order to achieve this, nanostructures (nanowires, nanorods, etc.) of Sidoped boron carbide have been synthesized using a Solid-Liquid-Solid (SLS) growth mechanism. The resulting structures have been characterized by SEM, TEM and Raman spectroscopy and consolidated to evaluate their mechanical properties. In addition, the application of nanowires in a transparent and thermally conducting nanocomposite is demonstrated.
