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THE REACTIVITY of SOME TRANSITION METAL NITRIDES and CARBIDES by JEREMY NEIL CLARK a Thesis Submitted to the University of Plymo

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University of Plymouth PEARL https://pearl.plymouth.ac.uk 04 University of Plymouth Research Theses 01 Research Theses Main Collection 1995 THE REACTIVITY OF SOME TRANSITION METAL NITRIDES AND CARBIDES CLARK, JEREMY NEIL http://hdl.handle.net/10026.1/1891 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 REACTIVITY OF SOME TRANSITION METAL NITRIDES AND CARBIDES by JEREMY NEIL CLARK A thesis submitted to the University of Plymouth in partial fiilfilment for the degree of DOCTOR OF PHILOSOPHY Department of Environmental Sciences Faculty of Science in collaboration with British Steel, Teesside April 1995 i i":/-\f"rd(J REFERENCE ONLY 90 0274095 3 UNIVERSiTY OF PLYMOUTH Item No. I c:^002"/4 0953 Date 7 JUN 18§g Class No. ContlNe, LIBRARY STORE THE REACTIVITY OF SOME TRANSITION METAL NITRIDES AND CARBIDES Jeremy Neil Clark ABSTRACT The formation and oxidation of transition metal nitrides and carbides is reviewed and the crystal structures and types of bonding are discussed. Types of nitrides and carbides are categorized in terms of physical and chemical properties and type of bonding. The principles of sintering are summarised. Tlie theory and applications of thermal analytical techniques are reviewed. Surface area determination and estimation of average crystallite size by the BET method utilizing the adsorption of nitrogen gas at -196 X are explained along with the application of x-ray dififractometry ajid scanning electron microscopy to work in this area. In this present research selected transition metal nitrides and carbides have been oxidised in air and carbon dioxide. Activation energies have been determined for these reactions from isothennal oxidations utilizing the Arrhenius equation and from oxidations at different heating rates utilizing the Kissinger equation. Kinetic schemes for the isothermal oxidations have been proposed based on two models of the reactions, that is half order kinetics in which the rate of reaction is determined by the diffijsion of oxidising gas througli the oxide product and two-thirds order kinetics in which the reaction takes place at the surface of a spherical particle of diminishing size as the reaction pioceeds. Surface area measurements and electron microscopy have been utilized to study the ability of the product formed during the oxidations to sinter. X-ray diffractometry has been used to identify the crystal phases present in the initial nitride or carbide and in the oxidation products. The activation energies of the carbides were found to be lower than that foimd for the respective nitrides. At low temperatures the carbides oxidised more extensively than the respective nitrides, but at high temperatures the situation was reversed. Tliis is explained in terms of the difference in the pre- exponential term of the Arrhenius equation. Tlie kinetics were found to be dependent on whether the oxide produced was structurally compatible with the remaining reactant and whether the oxide produced was able to sinter at the temperature used in the experiment. CONTENTS Page Copyright statement 1 Title page 2 Abstract 3 Contents 4 Tables 7 Figures 8 Plates 11 Acknowledgements 12 Author's declaration 13 Chapter 1 INTRODUCTORY SURVEY AND REVIEW 14 1.1 Introduction 14 1.2 Solid-gas reactions 16 1.2.1 Non-porous solid-gas reactions 17 1.2.2 Porous solid-gas reactions 18 1.2.3 Two-thirds and half order reaction kinetics 19 1.2.4 Sintering 20 1.3 Classification of nitrides and carbides 22 1.3.1 Transition metal nitrides and carbides 25 1.3.2 Hagg rules 26 1.3.3 Pauling-Rundle theory 27 1.3.4 Band theory 28 1.3.5 Ubbelohde - Samsanov theory 29 1.4 Production of refractory nitrides and carbides 31 1.5 Oxidation of carbides and nitrides 35 1.5.1 Titanium nitride and carbide systems 35 1.5.2 Zirconium nitride and carbide systems 38 1.5.3 Vanadium nitride and carbide systems 39 1.5.4 Niobium nitride and carbide systems 40 1.5.5 Tantalum nitride and carbide systems 41 1.5.6 Manganese nitride and carbide systems 42 1.5.7 Chromium nitride and carbide systems 42 1.5.8 Iron nitride and carbide systems 42 1.6 Aims of this research 44 Chapter 2 EXPERIMENTAL TECHNIOUES 45 2.1 Thermal analysis 45 2.1.1 Review and introduction 45 2.1.2 The Massflow thermobalance 49 2.1.3 Procedure 56 2.1.4 The STA 781 thermal analyzer 57 2.1.5 Procedure 61 2.1.6 Tube furnace 62 2.1.7 Procedure 62 2.2 Surface area determination 63 2.2.1 Review and introduction 63 2.2.2 The nitrogen sorption balance 70 2.2.3 Procedure 75 2.3 X-ray diffraction 77 2.3.1 Introduction 77 2.3.2 X-ray generator 80 2.3.3 Procedure 81 2.4 Electron microscopy 82 2.4.1 Introduction 82 2.4.2 The Joel JSM-T20 scanning electron microscope 85 2.4.3 Procedure 86 2.5 Products used 88 Chapter 3 RESULTS OF OXIDATIONS IN AIR 90 3.1 Introduction 90 3.2 Oxidation of titanium nitride and carbide in air 91 3.3 Oxidation of zirconium nitride and carbide in air 114 3.4 Oxidation of vanadium nitride and carbide in air 139 3.5 Oxidation of niobium carbide in air 145 3.6 Oxidation of chromium nitride and carbide in air 153 3.7 Oxidation of iron nitride in air 168 3.8 Oxidation of tantalum carbide in air 177 3.9 Oxidation of manganese carbide in air 183 3.10 Effect of addition of chromium carbide on the oxidation of zirconium carbide in air 189 Chapter 4 RESULTS OF OXIDATIONS IN CARBON DIOXIDE 190 4.1 Introduction 190 4.2 Oxidation of chromium nitride in carbon dioxide 191 4.3 Oxidation of iron nitride in carbon dioxide 195 4.4 Oxidation of titanium nitride in carbon dioxide 202 Chapter 5 COMPARISONS AND CONCLUSIONS 204 5.1 Introduction 204 5.2 Comparison between carbides and nitrides 210 5.3 Comparisons within group IVa 211 5.4 Comparisons within group Va 213 5.5 Comparisons across period 214 5.6 Comparison between oxidation in air and carbon dioxide 215 5.7 Conclusions and future work 216 5 .7 .1 Recent research 216 5.7.2 Conclusions 217 5.7.3 Future work 224 References 227 Appendicies 1 Paper published in Thermochimica Acta, 1986, 103(1\ 193-199 243 2 Paper published in Revue de Chimie Minerale, 1987, 24(6), 654-666 251 TABLES Table Page 1 Classification of crystal systems, based on characteristic symmetry 78 2 Isothermal oxidation of titanium nitride in air 94 3 Effect of heating rate on the oxidation of titanium nitride in air 98 4 Isothermal oxidation of titanium carbide in air 108 5 Variation of surface area during oxidation of titanium carbide in air 110 6 Isothermal oxidation of zirconium nitride in air 119 7 Effect of heating rate on the oxidation of zirconium nitride in air 124 8 Isothermal oxidation of zirconium carbide in air 128 9 Variation of specific surface area during oxidation of zirconium carbide and oxide products with temperature and oxidation period 134 10 Isothermal oxidation of vanadium carbide in air 143 11 Isothermal oxidation of niobium carbide in air 147 12 Effect of heating rate on the oxidation of chromium carbide in air 162 13 Isothennal oxidation of chromium carbide in air 165 14 Isothennal oxidation of iron nitride in air 173 15 Isothennal oxidation of tantalum carbide in air 180 16 Variation of specific surface area during oxidation of manganese carbide and oxide products with temperature and oxidation period 186 17 Isothennal oxidafion of iron nitride in carbon dioxide 200 18 Summary of starting materials and oxidation phases observed 205 19 Activation energies for the oxidation of selected transition metal nitrides and carbides determined by Arrhenius and Kissinger methods 208 FIGURES Figure Page 1 Schematic diagram of Massflow thermobalance 50 2 Schematic diagram of Massflow reaction chamber and gas inlet/outlet ports 51 3A Schematic diagram of DTA sample head showing positioning of thermocouples 53 3B Schematic diagram of TG sample head showing position of thermocouple 53 4 Schematic diagram of thermocouple electrical connections 55 5 Schematic diagram of ST A 781 thermal analyser 58 6 Schematic diagram of DTA hangdown assembly and reaction chamber 60 7 The five types of adsorption isotherm in the BET classiflcation 66 8 Schematic diagram CI Electronics Microforce balance 72 9 Chart recorder interface circuit 72 10 Schematic diagram of light microscope, transmission electron microscope and scanning electron microscope 83 11 DTA curves and TG curves for oxidation of titanium nitride in flowing air 92 12 Isothermal TG curves for the oxidation of titanium nitride in static and flowing air 93 13 Arrhenius plot for the oxidation of titanium nitride in air 95 14 Half order and two-thirds order kinetic plots for the isothermal oxidation of titanium nitride in air 97 15 Kissinger plot for the oxidation of titanium nitride in air 99 16 X-ray diflraction traces for titanium nitride and its oxidation products on heating in air at 10 °C min-' 101 17 Isothential TG curves for the oxidation of titanium carbide in flowing air 105 18 Half order and two-thirds order kinetic plots for the isothermal oxidation of titanium carbide in air 106 19 Arrhenius plot for the oxidation of titanium carbide in air 109 20 Surface area changes for 1 hour oxidations of titanium carbide in air 111 2! X-ray diffraction traces of the oxidation products of zirconium nitride 115 22 Isothermal TG curves for oxidation of zirconium nitride
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  • Crystal Structure of Hexabarium Mononitride Pentaindide,(Ba6n)[In5]

    Crystal Structure of Hexabarium Mononitride Pentaindide,(Ba6n)[In5]

    Z. Kristallogr. NCS 219 (2004) 349-350 349 © by Oldenbourg Wissenschaftsverlag, München Crystal structure of hexabarium mononitride pentaindide, (Ba6N)[In5] A. Schlechte, Yu. Prots and R. Niewa* Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany Received October 1, 2004, accepted and available on-line November 12, 2004; CSD no. 409805 Discussion Indium, when combined with alkaline-earth elements forms a va- riety of ternary nitrides. The compounds known so far may be de- scribed as built from indium clusters and octahedra of alkaline- earth cations surrounding nitride ions. In the latter cationic sub- structure the polyhedra might be isolated, vertex-, and/or edge- sharing. The variety of In arrangements extends from isolated In species in (Ca7N4)Ini.o4 [1], isolated tetrahedral units in (AI9N7)[ID4]2 (A = Ca, Sr, Ba) [2,3], trigonal bipyramidal [Ins] clusters next to [Ins] ions of more complicated geometry in (Ba38Ni8)[In5]2[In8] [4], and infinite chains in (A4N)[In2] (A = Ca, Sr) [5] and (Ca2N)In [6]. None of these metallic compounds follows Zintl-like counting. The new compound (Ba6N)[Ins] is an isotype of (¿6N)[Ga5] (A = Sr, Ba) [7]. The crystal structure of (Ba6N)tIns] is characterized as rocksalt type motif of N-centred octahedra (BaiN) and trigonal bi- pyramidal clusters [Ins]. The trigonal bipyramidal units [Ins] might be described as [Ins]7- ions, quite the same according to Zintl-type electronic counting and using the Wade-rules for closo-cluster. The isotypes (AeN)[Gas] were previously de- scribed by the formula (A2+)6(N3-)[Ga5]7~ • 2e_ based on elec- tronic structure calculations.