Synthesis of Boron Carbide Las
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Superhard and Superconducting B6C
Superhard and Superconducting B6C Kang Xia a, Mengdong Ma b, Cong Liu a, Hao Gao a, Qun Chen a, Julong He b, Jian Sun a,*, Hui-Tian Wang a, Yongjun Tian b, and Dingyu Xing a a National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructure, Nanjing University, Nanjing 210093, China b State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China ABSTRACT Crystal structure searching and ab initio calculations have been used here to explore low-energy structures of boron carbides under high pressure. Under pressures of 85–110 GPa, a metastable B6C with R3 m symmetry is found to be energetically more stable than the mixture of previous B4C and elemental boron. This B6C is a rhombohedral structure and contains mooncake-like B24 clusters with stuffing of C2 pairs. The mechanical and dynamical stabilities of this structure at ambient pressure are confirmed by its elastic constants and phonon dispersions. The bulk modulus and shear modulus of this newly predicted B6C at ambient pressure reach high values of 291 GPa and 272 GPa, respectively. The Vickers hardness is calculated to be around 48 GPa, and its melting temperature at ambient pressure is estimated to be around 2500 K, indicating that this metastable B6C is a potential superhard material with very good thermal stability. Interestingly, this superhard B6C structure is also found to be superconducting and its superconducting critical temperature (Tc) is evaluated to be around 12.5 K at ambient pressure by electron-phonon coupling. * Corresponding author. E-mail address: [email protected] 1. -
Effect of High Temperature on Wear Behavior of Stir Cast Aluminium
Mechanics and Mechanical Engineering Vol. 22, No. 4 (2018) 1031{1046 c Technical University of Lodz https://doi.org/10.2478/mme-2018-0082 Effect of High Temperature on Wear Behavior of Stir Cast Aluminium/Boron Carbide Composites X. Canute and M. C. Majumder Department of Mechanical Engineering, National Institute of Technology, Durgapur, India Received (9 May 2018) Revised (11 December 2018) Accepted (20 December 2018) The need for development of high temperature wear resistant composite materials with superior mechanical properties and tribological properties is increasing significantly. The high temperature wear properties of aluminium boron carbide composites was evaluated in this investigation. The effect of load, sliding velocity, temperature and reinforcement percentage on wear rate was determined by the pin heating method using pin heating arrangement. The size and structure of base alloy particles change considerably with an increase of boron carbide particles. The wettability and interface bonding between the matrix and reinforcement enhanced by the addition of potassium flurotitanate. ANOVA technique was used to study the effect of input parameters on wear rate. The investi- gation reveals that the load had higher significance than sliding velocity, temperature and weight fraction. The pin surface was studied with a high-resolution scanning elec- tron microscope. Regression analysis revealed an extensive association between control parameters and response. The developed composites can be used in the production of automobile parts requiring high wear, frictional and thermal resistance. Keywords: PCM, enhancement melting, eccentric cylinders, fins, LHS. 1. Introduction Metal matrix composites are widely preferred due to yield strength and wear re- sistance for high temperature applications [1]. -
Experiments on the Oxidation of Boron Carbide at High Temperatures
Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Wissenschaftliche Berichte FZKA 6979 Experiments on the Oxidation of Boron Carbide at High Temperatures M. Steinbrück, A. Meier, U. Stegmaier, L. Steinbock Institut für Materialforschung Programm Nukleare Sicherheitsforschung Mai 2004 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Wissenschaftliche Berichte FZKA 6979 Experiments on the Oxidation of Boron Carbide at High Temperatures M. Steinbrück, A. Meier, U. Stegmaier, L. Steinbock Institut für Materialforschung Programm Nukleare Sicherheitsforschung Forschungszentrum Karlsruhe GmbH, Karlsruhe 2004 Impressum der Print-Ausgabe: Als Manuskript gedruckt Für diesen Bericht behalten wir uns alle Rechte vor Forschungszentrum Karlsruhe GmbH Postfach 3640, 76021 Karlsruhe Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF) ISSN 0947-8620 urn:nbn:de:0005-069792 OXIDATION VON BORKARBID BEI HOHEN TEMPERATUREN ZUSAMMENFASSUNG Borkarbid wird weltweit in verschiedenen Kernreaktoren als Absorbermaterial in Steuer- stäben eingesetzt. Während eines hypothetischen schweren Störfalls führen eutektische Wechselwirkungen zwischen B4C und den umgebenden Hüllrohren aus rostfreiem Stahl schon bei Temperaturen um 1200 °C und somit weit unterhalb der Schmelztemperaturen der einzelnen Komponenten zur Bildung von Schmelzphasen. Das so freigelegte Absorber- material sowie gebildete B4C/Metall-Schmelzen sind dem Dampf im Reaktor ausgesetzt. Die Oxidation von Borkarbid ist stark exotherm und führt zur Bildung von gasförmigen -
Synthesis, Characterization and Energetic Performance
SYNTHESIS, CHARACTERIZATION AND ENERGETIC PERFORMANCE OF METAL BORIDE COMPOUNDS FOR INSENSITIVE ENERGETIC MATERIALS by Michael L. Whittaker A thesis submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of Master of Science Department of Materials Science and Engineering University of Utah May 2012 Copyright © Michael L. Whittaker 2012 All Rights Reserved The University of Utah Graduate School STATEMENT OF THESIS APPROVAL The thesis of Michael L. Whittaker has been approved by the following supervisory committee members: Raymond A. Cutler , Chair 03/09/2012 Date Approved Anil V. Virkar , Member 03/09/2012 Date Approved Gerald B. Stringfellow , Member 03/09/2012 Date Approved and by Feng Liu , Chair of the Department of Materials Science and Engineering and by Charles A. Wight, Dean of The Graduate School. ABSTRACT Six metal boride compounds (AlB2, MgB2, Al0.5Mg0.5B2, AlB12, AlMgB14 and SiB6) with particle sizes between 10-20 m were synthesized for insensitive energetic fuel additives from stoichiometric physical mixtures of elemental powders by high temperature solid state reaction. B4C was also investigated as a lower cost source of boron in AlB2 synthesis and showed promise as a boron substitute. Thermal analysis confirmed that the formation of boride compounds from physical mixtures decreased sensitivity to low temperature oxidation over the aluminum standard. Both Al+2B and AlB2 were much less sensitive to moisture degradation than aluminum in high humidity (10-100% relative humidity) and high temperature (20-80°C) environments. AlB2 was determined to be safe to store for extended periods of time in cool, dry environments. -
Surface Properties and Morphology of Boron Carbide Nanopowders Obtained by Lyophilization of Saccharide Precursors
materials Article Surface Properties and Morphology of Boron Carbide Nanopowders Obtained by Lyophilization of Saccharide Precursors Dawid Kozie ´n 1,* , Piotr Jele ´n 1 , Joanna St˛epie´n 2 , Zbigniew Olejniczak 3 , Maciej Sitarz 1 and Zbigniew P˛edzich 1,* 1 Faculty of Materials Science and Ceramics, AGH University of Science and Technology, 30 Mickiewicz Av., 30-059 Kraków, Poland; [email protected] (P.J.); [email protected] (M.S.) 2 Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, 30 Mickiewicz Av., 30-059 Kraków, Poland; [email protected] 3 Institute of Nuclear Physics, 152 Radzikowskiego St., 31-342 Kraków, Poland; [email protected] * Correspondence: [email protected] (D.K.); [email protected] (Z.P.) Abstract: The powders of boron carbide are usually synthesized by the carbothermal reduction of boron oxide. As an alternative to high-temperature reactions, the development of the carbothermal reduction of organic precursors to produce B4C is receiving considerable interest. The aim of this work was to compare two methods of preparing different saccharide precursors mixed with boric acid with a molar ratio of boron to carbon of 1:9 for the synthesis of B4C. In the first method, aqueous ◦ ◦ solutions of saccharides and boric acid were dried overnight at 90 C and pyrolyzed at 850 C for 1 h under argon flow. In the second method, aqueous solutions of different saccharides and boric acid Citation: Kozie´n,D.; Jele´n,P.; were freeze-dried and prepared in the same way as in the first method. -
Volumetric Determination of Boron in Boron Carbide V
B. A. R. C.-1017 ei GOVERNMENT OF INDIA ATOMIC ENERGY COMMISSION VOLUMETRIC DETERMINATION OF BORON IN BORON CARBIDE V. K. Manchanda and M. S. Subramanian Radiochemistry Division BHABHA ATOMIC RESEARCH CENTRE BOMBAY, INDIA 1979 B. A. R.C.-1017 GOVERNMENT OF INDIA ATOMIC ENERGY COMMISSION U erf < ffl VOLUMETRIC DETERMINATION OF BORON IN BORON CARBIDE by V.K. Manchanda and M. S. Subramantan Radlochernlstry Division BHABHA ATOMIC RESEARCH CENTRE BOMBAY, INDIA 1979 INIS Subject Category : Bll Descriptor a : BORON CARBIDES BORON QUANTITATIVE CHEMICAL ANALYSIS TITRATION ACCURACY ABSTRACT Boron carbide is used for oontrol rods and as a shielding material In nuclear reactors. As such, the boron carbide must conform to rigid chemical specifications. Impurities present have a significant effect on the life time of the control rods under conditions of high temperature and i neutron flux. Therefore, methods for the accurate determination of the various constituents in boron carbide is of utmost importance. This-report discusses p\volumetric procedure for i •_ . •' i : ((.•>;•" ••%. the, determination of boron content In boron carbide/ '•••>',••. A VOLtCIKTRIC DET3SIINATI0N 0? BCRON IN BORON CAR3IDE by V.K. Jfenchanda and M.S. Subramanian IU7R0DVCT10N Boron carbide is an important nuclear material a.3 it is used in nuclear reactors for control rods and as a shielding material « Preparation of boron carbide yields a product often contaminated with either unreacted carbon or boric acid. These impurities affect the physical, chemical and neutron absorption properties of the material, Particularly under conditions of high temperature and neutron flux in a reactor, tlie life time of the control rods depends on its composition. -
Ceramic Carbides: the Tough Guys of the Materials World
Ceramic Carbides: The Tough Guys of the Materials World by Paul Everitt and Ian Doggett, Technical Specialists, Goodfellow Ceramic and Glass Division c/o Goodfellow Corporation, Coraopolis, Pa. Silicon carbide (SiC) and boron carbide (B4C) are among the world’s hardest known materials and are used in a variety of demanding industrial applications, from blasting-equipment nozzles to space-based mirrors. But there is more to these “tough guys” of the materials world than hardness alone—these two ceramic carbides have a profile of properties that are valued in a wide range of applications and are worthy of consideration for new research and product design projects. Silicon Carbide Use of this high-density, high-strength material has evolved from mainly high-temperature applications to a host of engineering applications. Silicon carbide is characterized by: • High thermal conductivity • Low thermal expansion coefficient • Outstanding thermal shock resistance • Extreme hardness FIGURE 1: • Semiconductor properties Typical properties of silicon carbide • A refractive index greater than diamond (hot-pressed sheet) Chemical Resistance Although many people are familiar with the Acids, concentrated Good Acids, dilute Good general attributes of this advanced ceramic Alkalis Good-Poor (see Figure 1), an important and frequently Halogens Good-Poor overlooked consideration is that the properties Metals Fair of silicon carbide can be altered by varying the Electrical Properties final compaction method. These alterations can Dielectric constant 40 provide knowledgeable engineers with small Volume resistivity at 25°C (Ohm-cm) 103-105 adjustments in performance that can potentially make a significant difference in the functionality Mechanical Properties of a finished component. -
The Formation and Reactivity of I BORON CARBIDE and Related
University of Plymouth PEARL https://pearl.plymouth.ac.uk 04 University of Plymouth Research Theses 01 Research Theses Main Collection 1970 The Formation and Reactivity of BORON CARBIDE and related materials JONES, JAMES ALFRED http://hdl.handle.net/10026.1/1880 University of Plymouth All content in PEARL is protected by copyright law. Author manuscripts are made available in accordance with publisher policies. Please cite only the published version using the details provided on the item record or document. In the absence of an open licence (e.g. Creative Commons), permissions for further reuse of content should be sought from the publisher or author. The Formation and Reactivity of I BORON CARBIDE and related materials A Thesis presented for the Research Degree of DOCTOR OF PHILOSOPHY of the COUNCIL FOR NATIONAL ACADEMIC AWARDS London by JAMES ALFRED JONES Department of Chemistry Plymouth Polytechnic Plymouth, Devon- February^ 1970o F'.V flCCH. i'iC. 1 CLASS, T Shi LJl JoH 13' ABSTRACT 1 The formation of boron carbide, (CBC)*B^^0*^(3^0 is re• viewed with special reference to newer production methods and fabrication techniques. Its crystal structure and the nature of its bonding are discussed in relation to those of other borides and carbides. Information so far available on the sintering of this material is summarised in relation to its reactivity. Sintering into monolithic compoaentBcan only be achieved by hot pressing at pressures between 200 and 300 Kgcm'^ and at temperatures above 2000°C preferably at about 2,300^0 for the most rapid achievement of theoretical density, i.e. -
The 5-Th Element a New High Pressure High Temperature Allotrope
The 5-th element A new high pressure high temperature allotrope Von der Fakultät für Chemie und Geowissenschaften Der Universität Bayreuth zur Erlangung der Würde eines Doctors der Naturwissenschaften -Dr. rer. nat.- Dissertation vorgelegt von Evgeniya Zarechnaya aus Moskau (Russland) Bayreuth, April 2010 TABLE OF CONTENTS SUMMARY................................................................................................................................................... 1 ZUSAMMENFASSUNG.............................................................................................................................. 3 1 INTRODUCTION....................................................................................................................... 6 1.1 History of the discovery of boron................................................................................................... 6 1.2 Basic chemistry and crystal-chemistry of boron........................................................................... 7 1.3 Boron in natural systems ................................................................................................................ 9 1.4 Physical properties of boron and its application ........................................................................ 12 1.5 Boron at high pressure.................................................................................................................. 15 1.6 Experimental techniques and sample characterization ............................................................ -
Equations of State of New Boron-Rich Selenides B6se and B12se
Equations of state of new boron-rich selenides B6Se and B12Se Kirill A. Cherednichenko,1,2 Yann Le Godec,3 and Vladimir L. Solozhenko 1,* 1 LSPM–CNRS, Université Sorbonne Paris Nord, 93430 Villetaneuse, France 2 Department of Physical and Colloid Chemistry, Gubkin University, Moscow, 119991, Russia 3 IMPMC–CNRS, UPMC Sorbonne Universités, 75005 Paris, France Abstract Two novel of boron-rich selenides, orthorhombic B6Se and rhombohedral B12Se, have been recently synthesized at high pressure – high temperature conditions. Room-temperature compressibilities of these phases were studied in a diamond anvil cell using synchrotron powder X-ray diffraction. A fit of experimental p-V data by third-order Birch-Murnaghan equation of state yielded the bulk moduli of 155(2) GPa for B12Se and 144(3) GPa for B6Se. No pressure-induced phase transitions have been observed in the studied pressure range, i.e. up to 35 GPa. Keywords : boron-rich selenides; high pressure; equation of state Introduction Boron-rich compounds containing B12-icosahedra have been known since 1960-s [1]. The majority of these compounds are the structural derivatives of elemental α-rhombohedral boron (α-B12) with general stoichiometry: B12Xy (where X is interstitial atom, y ≤ 2). They received a considerable attention due to the high hardness, chemical inertness, thermal conductivity, radiation resistance and unusual electronic properties [2-5]. For instance, boron carbide B12C3 is hard compound widely used as abrasive and armor material [6,7], boron suboxide B12O2 is the hardest known oxide [8,9], and B12As2 was found to be extremely stable under electron bombardment and able to the self-healing [10]. -
Processing of Reaction-Bonded B4C–Sic Composites in a Single-Mode Microwave Cavity
Available online at www.sciencedirect.com CERAMICS INTERNATIONAL Ceramics International 39 (2013) 1215–1219 www.elsevier.com/locate/ceramint Processing of reaction-bonded B4C–SiC composites in a single-mode microwave cavity Anthony Thuaulta,n, Sylvain Marinela,b, Etienne Savarya,c, Romain Heugueta, Se´bastien Saunierc, Dominique Goeuriotc, Dinesh Agrawalb aCRISMAT Laboratory UMR 6508 CNRS-ENSICAEN-UCBN, 6 Boulevard du Mare´chal Juin, 14050 Caen Cedex, France bMaterials Research Institute, Materials Research Laboratory Building, The Pennsylvania State University, University Park, PA 16802, USA cDe´partement Me´canique et Proce´de´s d’e´laboration, Centre des Sciences des Mate´riaux et des Structures, Ecole Nationale Supe´rieure des Mines de Saint- Etienne, 42023 Saint-Etienne Cedex 2, France Received 5 July 2012; received in revised form 16 July 2012; accepted 16 July 2012 Available online 24 July 2012 Abstract In this study, the reaction sintering of boron carbide, which consists in doing reactive infiltration of molten silicon throughout a porous sample made of B4C and carbon graphite was investigated. Thus, it has been shown that a single-mode microwave cavity can be successfully used to produce reaction-bonded B4C–SiC composite. A specific package, consisting of a SiC based susceptor and a boron nitride based insulating container, was used to heat up the B4C–Si system using a single-mode microwaves cavity under an Ar–H2 atmosphere. Pore-free B4C–SiC composite successfully produced consists of a mixture of B4C and polygonal shaped b-SiC within a residual silicon matrix. The indentation technique permits to determine mechanical properties of the samples which are compared to those obtained conventionally. -
Nitrogen Containing Carbon Nanofibers As Non-Noble Metal Cathode Catalysts In
Nitrogen Containing Carbon Nanofibers as Non-Noble Metal Cathode Catalysts in PEM and Direct Methanol Fuel Cells Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Elizabeth Joyce Biddinger, B.S.ChE Graduate Program in Chemical Engineering * * * * The Ohio State University 2010 Dissertation Committee: Professor Umit S. Ozkan, Advisor Professor Jeffrey Chalmers Professor Stuart Cooper Copyright by Elizabeth Joyce Biddinger 2010 ABSTRACT PEM and direct methanol fuel cells (DMFC) have great potential for use as alternative fuel energy conversion devices. Before this potential can be realized, however, performance improvements must be made and material costs need to be reduced. The limiting reaction in the PEMFCs and DMFCs is the oxygen reduction reaction (ORR), which occurs at the cathode. In an attempt to improve the reaction kinetics, substantial loadings of Pt catalysts are required on the cathode. This significantly increases the overall cost of the fuel cell. Also, in DMFCs, methanol crossover from the anode allows for competing reactions at the cathode catalyst to occur, reducing the power output of the fuel cell further. As the demand for fuel cells increase, the demand for Pt will far outpace the supply of Pt. Replacements studied for Pt cathode catalysts include Pt alloys, other noble metals, chalcogenides and nitrogen-containing carbons. Nitrogen-containing carbons made from simple precursors can provide an economical replacement to Pt catalysts. Before this can be realized, improvements in the activity and selectivity of the nitrogen- containing carbons need to occur. ii The work presented here involves the study of nitrogen-containing carbon nanostructures (CNx) as ORR catalysts for PEMFCs and DMFCs.