An Improved Method for the Preparation of Boron Carbide with Some Notes on Its Properties PDF Download

Author: Arthur Wayland Dox
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description

Author: Henry James Wheeler Bliss
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description

Author: Hermann Irving Schlesinger
Publisher:
ISBN:
Category : Boron steel
Languages : en
Pages : 32

View

Book Description

Author: Muhammet Fatih Toksoy
Publisher:
ISBN:
Category : Boron
Languages : en
Pages : 165

View

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: Kolan Madhav Reddy
Publisher:
ISBN: 9781536171211
Category :
Languages : en
Pages : 252

View

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: Thomas Vasilos
Publisher:
ISBN:
Category :
Languages : en
Pages : 28

View

Book Description
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.

Author: Alan Wesley Weimer
Publisher: Springer Science & Business Media
ISBN: 9780412540608
Category : Science
Languages : en
Pages : 671

View

Book Description
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.

Author:
Publisher:
ISBN:
Category : Nuclear energy
Languages : en
Pages : 724

View

Book Description

Author: Amir Weizman
Publisher:
ISBN:
Category : Boron compounds
Languages : en
Pages : 138

View

Book Description

Author: Kanak Anant Kuwelkar
Publisher:
ISBN:
Category : Boron
Languages : en
Pages : 186

View

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.