[Alexander_Fridman]_Plasma_Chemistry_(Cambridge_20(BookZZ.org).pdf

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Unformatted text preview: P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 This page intentionally left blank ii March 26, 2008 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 PLASMA CHEMISTRY This unique book provides a fundamental introduction to all aspects of modern plasma chemistry. The book describes mechanisms and kinetics of chemical processes in plasma, plasma statistics, thermodynamics, fluid mechanics, and electrodynamics, as well as all major electric discharges applied in plasma chemistry. The book considers most of the major applications of plasma chemistry, from electronics to thermal coatings, from treatment of polymers to fuel conversion and hydrogen production, and from plasma metallurgy to plasma medicine. The book can be helpful to engineers, scientists, and students interested in plasma physics, plasma chemistry, plasma engineering, and combustion, as well as in chemical physics, lasers, energy systems, and environmental control. The book contains an extensive database on plasma kinetics and thermodynamics, as well as many convenient numerical formulas for practical calculations related to specific plasma–chemical processes and applications. The book contains a large number of problems and concept questions that are helpful in university courses related to plasma, lasers, combustion, chemical kinetics, statistics and thermodynamics, and high-temperature and high-energy fluid mechanics. Alexander Fridman is Nyheim Chair Professor of Drexel University and Director of Drexel Plasma Institute. His research focuses on plasma approaches to material treatment, fuel conversion, hydrogen production, biology, medicine, and environmental control. Professor Fridman has more than 35 years of plasma research experience in national laboratories and universities in Russia, France, and the United States. He has published 6 books and 450 papers, chaired several international plasma conferences, and received numerous awards, including the Stanley Kaplan Distinguished Professorship in Chemical Kinetics and Energy Systems, the George Soros Distinguished Professorship in Physics, and the State Prize of the USSR for discovery of selective stimulation of chemical processes in non-thermal plasma. i March 26, 2008 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 ii March 26, 2008 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 Plasma Chemistry Alexander Fridman Drexel University iii March 26, 2008 23:32 CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York Information on this title: © Alexander Fridman 2008 This publication is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published in print format 2008 ISBN-13 978-0-511-39857-5 eBook (EBL) ISBN-13 978-0-521-84735-3 hardback Cambridge University Press has no responsibility for the persistence or accuracy of urls for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 To my wife Irene v March 26, 2008 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 vi March 26, 2008 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 March 26, 2008 Contents Foreword Preface 1 Introduction to Theoretical and Applied Plasma Chemistry 1.1. Plasma as the Fourth State of Matter 1.2. Plasma in Nature and in the Laboratory 1.3. Plasma Temperatures: Thermal and Non-Thermal Plasmas 1.4. Plasma Sources for Plasma Chemistry: Gas Discharges 1.5. Fundamentals of Plasma Chemistry: Major Components of Chemically Active Plasma and Mechanisms of Plasma-Chemical Processes 1.6. Applied Plasma Chemistry 1.7. Plasma as a High-Tech Magic Wand of Modern Technology 2 Elementary Plasma-Chemical Reactions 2.1. Ionization Processes 2.1.1. Elementary Charged Particles in Plasma 2.1.2. Elastic and Inelastic Collisions and Their Fundamental Parameters 2.1.3. Classification of Ionization Processes 2.1.4. Elastic Scattering and Energy Transfer in Collisions of Charged Particles: Coulomb Collisions 2.1.5. Direct Ionization by Electron Impact: Thomson Formula 2.1.6. Specific Features of Ionization of Molecules by Electron Impact: Frank-Condon Principle and Dissociative Ionization 2.1.7. Stepwise Ionization by Electron Impact 2.1.8. Ionization by High-Energy Electrons and Electron Beams: Bethe-Bloch Formula 2.1.9. Photo-Ionization Processes 2.1.10. Ionization in Collisions of Heavy Particles: Adiabatic Principle and Massey Parameter 2.1.11. Penning Ionization Effect and Associative Ionization 2.2. Elementary Plasma-Chemical Reactions of Positive Ions 2.2.1. Different Mechanisms of Electron–Ion Recombination in Plasma page xxxix xli 1 1 2 4 5 8 9 10 12 12 12 13 14 15 16 17 18 20 20 21 21 22 22 vii 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 March 26, 2008 Contents 2.2.2. Dissociative Electron–Ion Recombination and Possible Preliminary Stage of Ion Conversion 2.2.3. Three-Body and Radiative Electron–Ion Recombination Mechanisms 2.2.4. Ion–Molecular Reactions, Ion–Molecular Polarization Collisions, and the Langevin Rate Coefficient 2.2.5. Ion–Atomic Charge Transfer Processes and Resonant Charge Transfer 2.2.6. Non-Resonant Charge Transfer Processes and Ion–Molecular Chemical Reactions of Positive and Negative Ions 2.3. Elementary Plasma-Chemical Reactions Involving Negative Ions 2.3.1. Dissociative Electron Attachment to Molecules as a Major Mechanism of Negative Ion Formation in Electronegative Molecular Gases 2.3.2. Three-Body Electron Attachment and Other Mechanisms of Formation of Negative Ions 2.3.3. Destruction of Negative Ions: Associative Detachment, Electron Impact Detachment, and Detachment in Collisions with Excited Particles 2.3.4. Recombination of Negative and Positive Ions 2.3.5. Ion–Ion Recombination in Binary Collisions 2.3.6. Three-Body Ion–Ion Recombination: Thomson’s Theory and Langevin Model 2.4. Electron Emission and Heterogeneous Ionization Processes 2.4.1. Thermionic Emission: Sommerfeld Formula and Schottky Effect 2.4.2. Field Emission of Electrons in Strong Electric Fields: Fowler-Nordheim Formula and Thermionic Field Emission 2.4.3. Secondary Electron Emission 2.4.4. Photo-Ionization of Aerosols: Monochromatic Radiation 2.4.5. Photo-Ionization of Aerosols: Continuous-Spectrum Radiation 2.4.6. Thermal Ionization of Aerosols: Einbinder Formula 2.4.7. Space Distribution of Electrons and Electric Field Around a Thermally Ionized Macro-Particle 2.4.8. Electric Conductivity of Thermally Ionized Aerosols 2.5. Excitation and Dissociation of Neutral Particles in Ionized Gases 2.5.1. Vibrational Excitation of Molecules by Electron Impact 2.5.2. Rate Coefficients of Vibrational Excitation by Electron Impact: Semi-Empirical Fridman Approximation 2.5.3. Rotational Excitation of Molecules by Electron Impact 2.5.4. Electronic Excitation of Atoms and Molecules by Electron Impact 2.5.5. Dissociation of Molecules by Direct Electron Impact 2.5.6. Distribution of Electron Energy in Non-Thermal Discharges Between Different Channels of Excitation and Ionization viii 23 25 26 28 29 31 31 33 35 37 38 39 42 42 43 45 46 49 51 52 53 54 54 56 58 59 61 63 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 March 26, 2008 Contents 2.6. Elementary Relaxation Processes of Energy Transfer Involving Vibrationally, Rotationally, and Electronically Excited Molecules 2.6.1. Vibrational–Translational (VT) Relaxation: Slow Adiabatic Elementary Process 2.6.2. Landau–Teller Formula for VT-Relaxation Rate Coefficients 2.6.3. Fast Non-Adiabatic Mechanisms of VT Relaxation 2.6.4. Vibrational Energy Transfer Between Molecules: Resonant VV Relaxation 2.6.5. Non-Resonant VV Exchange: Relaxation of Anharmonic Oscillators and Intermolecular VV Relaxation 2.6.6. Rotational Relaxation Processes: Parker Formula 2.6.7. Relaxation of Electronically Excited Atoms and Molecules 2.7. Elementary Chemical Reactions of Excited Molecules: Fridman-Macheret α-Model 2.7.1. Rate Coefficient of Reactions of Excited Molecules 2.7.2. Efficiency α of Vibrational Energy in Overcoming Activation Energy of Chemical Reactions: Numerical Values and Classification Table 2.7.3. Fridman-Macheret α-Model 2.7.4. Efficiency of Vibrational Energy in Elementary Reactions Proceeding Through Intermediate Complexes: Synthesis of Lithium Hydride 2.7.5. Dissociation of Molecules in Non-Equilibrium Conditions with Essential Contribution of Translational Energy: Non-Equilibrium Dissociation Factor Z 2.7.6. Semi-Empirical Models of Non-Equilibrium Dissociation of Molecules Determined by Vibrational and Translational Temperatures Problems and Concept Questions 3 Plasma-Chemical Kinetics, Thermodynamics, and Electrodynamics 3.1. Plasma Statistics and Thermodynamics, Chemical and Ionization Equilibrium, and the Saha Equation 3.1.1. Statistical Distributions: Boltzmann Distribution Function 3.1.2. Equilibrium Statistical Distribution of Diatomic Molecules over Vibrational–Rotational States 3.1.3. Saha Equation for Ionization Equilibrium in Thermal Plasma 3.1.4. Dissociation Equilibrium in Molecular Gases 3.1.5. Complete Thermodynamic Equilibrium (CTE) and Local Thermodynamic Equilibrium (LTE) in Plasma 3.1.6. Thermodynamic Functions of Quasi-Equilibrium Thermal Plasma Systems 3.1.7. Non-Equilibrium Statistics of Thermal and Non-Thermal Plasmas 3.1.8. Non-Equilibrium Statistics of Vibrationally Excited Molecules: Treanor Distribution 3.2. Electron Energy Distribution Functions (EEDFs) in Non-Thermal Plasma 3.2.1. Fokker-Planck Kinetic Equation for Determination of EEDF 67 67 69 71 72 74 76 76 79 79 81 81 83 86 87 89 92 92 92 93 94 94 95 95 97 99 100 100 ix 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 March 26, 2008 Contents 3.3. 3.4. 3.5. 3.6. x 3.2.2. Druyvesteyn Distribution, Margenau Distributions, and Other Specific EEDF 3.2.3. Effect of Electron–Molecular and Electron–Electron Collisions on EEDF 3.2.4. Relation Between Electron Temperature and the Reduced Electric Field 3.2.5. Isotropic and Anisotropic Parts of the Electron Distribution Functions: EEDF and Plasma Conductivity Diffusion, Electric/Thermal Conductivity, and Radiation in Plasma 3.3.1. Electron Mobility, Plasma Conductivity, and Joule Heating 3.3.2. Plasma Conductivity in Crossed Electric and Magnetic Fields 3.3.3. Ion Energy and Ion Drift in Electric Field 3.3.4. Free Diffusion of Electrons and Ions; Continuity Equation; and Einstein Relation Between Diffusion Coefficient, Mobility, and Mean Energy 3.3.5. Ambipolar Diffusion and Debye Radius 3.3.6. Thermal Conductivity in Plasma 3.3.7. Non-Equilibrium Thermal Conductivity and Treanor Effect in Vibrational Energy Transfer 3.3.8. Plasma Emission and Absorption of Radiation in Continuous Spectrum and Unsold-Kramers Formula 3.3.9. Radiation Transfer in Plasma: Optically Thin and Optically Thick Plasmas Kinetics of Vibrationally and Electronically Excited Molecules in Plasma: Effect of Hot Atoms 3.4.1. Fokker-Plank Kinetic Equation for Non-Equilibrium Vibrational Distribution Functions 3.4.2. VT and VV Fluxes of Excited Molecules in Energy Space 3.4.3. Non-Equilibrium Vibrational Distribution Functions: Regime of Strong Excitation 3.4.4. Non-Equilibrium Vibrational Distribution Functions: Regime of Weak Excitation 3.4.5. Kinetics of Population of Electronically Excited States in Plasma 3.4.6. Non-Equilibrium Translational Energy Distribution Functions of Heavy Neutrals: Effect of “Hot” Atoms in Fast VT-Relaxation Processes 3.4.7. Generation of “Hot” Atoms in Chemical Reactions Vibrational Kinetics of Gas Mixtures, Chemical Reactions, and Relaxation Processes 3.5.1. Kinetic Equation and Vibrational Distributions in Gas Mixtures: Treanor Isotopic Effect in Vibrational Kinetics 3.5.2. Reverse Isotopic Effect in Plasma-Chemical Kinetics 3.5.3. Macrokinetics of Chemical Reactions of Vibrationally Excited Molecules 3.5.4. Vibrational Energy Losses Due to VT Relaxation 3.5.5. Vibrational Energy Losses Due to Non-Resonance VV Exchange Energy Balance and Energy Efficiency of Plasma-Chemical Processes 101 103 104 104 106 106 107 109 109 110 111 112 112 113 114 114 115 117 119 120 122 123 124 124 126 129 131 132 132 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 March 26, 2008 Contents 3.6.1. Energy Efficiency of Quasi-Equilibrium and Non-Equilibrium Plasma-Chemical Processes 3.6.2. Energy Efficiency of Plasma-Chemical Processes Stimulated by Vibrational Excitation of Molecules 3.6.3. Energy Efficiency of Plasma-Chemical Processes Stimulated by Electronic Excitation and Dissociative Attachment 3.6.4. Energy Balance and Energy Efficiency of Plasma-Chemical Processes Stimulated by Vibrational Excitation of Molecules 3.6.5. Components of Total Energy Efficiency: Excitation, Relaxation, and Chemical Factors 3.6.6. Energy Efficiency of Quasi-Equilibrium Plasma-Chemical Systems: Absolute, Ideal, and Super-Ideal Quenching 3.6.7. Mass and Energy Transfer Equations in Multi-Component Quasi-Equilibrium Plasma-Chemical Systems 3.6.8. Transfer Phenomena Influence on Energy Efficiency of Plasma-Chemical Processes 3.7. Elements of Plasma Electrodynamics 3.7.1. Ideal and Non-Ideal Plasmas 3.7.2. Plasma Polarization: Debye Shielding of Electric Field in Plasma 3.7.3. Plasmas and Sheaths: Physics of DC Sheaths 3.7.4. High-Voltage Sheaths: Matrix and Child Law Sheath Models 3.7.5. Electrostatic Plasma Oscillations: Langmuir or Plasma Frequency 3.7.6. Penetration of Slow-Changing Fields into Plasma: Skin Effect in Plasma 3.7.7. Magneto-Hydrodynamics: “Diffusion” of Magnetic Field and Magnetic Field Frozen in Plasma 3.7.8. Magnetic Pressure: Plasma Equilibrium in Magnetic Field and Pinch Effect 3.7.9. Two-Fluid Magneto-Hydrodynamics: Generalized Ohm’s Law 3.7.10. Plasma Diffusion Across Magnetic Field 3.7.11. Magneto-Hydrodynamic Behavior of Plasma: Alfven Velocity and Magnetic Reynolds Number 3.7.12. High-Frequency Plasma Conductivity and Dielectric Permittivity 3.7.13. Propagation of Electromagnetic Waves in Plasma 3.7.14. Plasma Absorption and Reflection of Electromagnetic Waves: Bouguer Law: Critical Electron Density Problems and Concept Questions 4 Electric Discharges in Plasma Chemistry 4.1. Fundamentals of Electric Breakdown, Streamer Processes, and Steady-State Regimes of Non-Equilibrium Electrical Discharges 4.1.1. Townsend Mechanism of Electric Breakdown and Paschen Curves 4.1.2. Spark Breakdown Mechanism: Streamer Concept 132 133 134 134 136 137 137 139 140 140 141 142 144 145 146 146 147 149 149 150 151 153 154 155 157 157 157 159 xi 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 March 26, 2008 Contents 4.1.3. Meek Criterion of Streamer Formation: Streamer Propagation Models 4.1.4. Streamers and Microdischarges 4.1.5. Interaction of Streamers and Microdischarges 4.1.6. Monte Carlo Modeling of Interaction of Streamers and Microdischarges 4.1.7. Self-Organized Pattern of DBD Microdischarges due to Streamer Interaction 4.1.8. Steady-State Regimes of Non-Equilibrium Electric Discharges and General Regimes Controlled by Volume and Surface Recombination Processes 4.1.9. Discharge Regime Controlled by Electron–Ion Recombination 4.1.10. Discharge Regime Controlled by Electron Attachment 4.1.11. Non-Thermal Discharge Regime Controlled by Charged-Particle Diffusion to the Walls: The Engel-Steenbeck Relation 4.2. Glow Discharges 4.2.1. General Structure and Configurations of Glow Discharges 4.2.2. Current-Voltage Characteristics of DC Discharges 4.2.3. Dark Discharge and Transition from Townsend Dark to Glow Discharge 4.2.4. Current-Voltage Characteristics of Cathode Layer: Normal Glow Discharge 4.2.5. Abnormal, Subnormal, and Obstructed Regimes of Glow Discharges 4.2.6. Positive Column of Glow Discharge 4.2.7. Hollow Cathode Glow Discharge 4.2.8. Other Specific Glow Discharge Plasma Sources 4.2.9. Energy Efficiency Peculiarities of Glow Discharge Application for Plasma-Chemical Processes 4.3. Arc Discharges 4.3.1. Classification and Current-Voltage Characteristics of Arc Discharges 4.3.2. Cathode and Anode Layers of Arc Discharges 4.3.3. Cathode Spots in Arc Discharges 4.3.4. Positive Column of High-Pressure Arcs: Elenbaas-Heller Equation 4.3.5. Steenbeck-Raizer “Channel” Model of Positive Column 4.3.6. Steenbeck-Raizer Arc “Channel” Modeling of Plasma Temperature, Specific Power, and Electric Field in Positive Column 4.3.7. Configurations of Arc Discharges Applied in Plasma Chemistry and Plasma Processing 4.3.8. Gliding Arc Discharge 4.3.9. Equilibrium Phase of Gliding Arc, Its Critical Parameters, and Fast Equilibrium-to-Non-Equilibrium Transition 4.3.10. Gliding Arc Stability Analysis and Transitional and Non-Equilibrium Phases of the Discharge xii 163 164 166 167 168 170 171 172 172 175 175 177 178 179 181 182 183 184 186 187 187 189 191 193 194 196 197 200 204 205 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 March 26, 2008 Contents 4.3.11. Special Configurations of Gliding Arc Discharges: Gliding Arc Stabilized in Reverse Vortex (Tornado) Flow 4.4. Radiofrequency and Microwave Discharges in Plasma Chemistry 4.4.1. Generation of Thermal Plasma in Radiofrequency Discharges 4.4.2. Thermal Plasma Generation in Microwave and Optical Discharges 4.4.3. Non-Thermal Radiofrequency Discharges: Capacitive and Inductive Coupling of Plasma 4.4.4. Non-Thermal RF-CCP Discharges in Moderate Pressure Regimes 4.4.5. Low-Pressure Capacitively Coupled RF Discharges 4.4.6. RF Magnetron Discharges 4.4.7. Non-Thermal Inductively Coupled RF Discharges in Cylindrical Coil 4.4.8. Planar-Coil and Other Configurations of Non-Thermal Inductively Coupled RF Discharges 4.4.9. Non-Thermal Low-Pressure Microwave and Other Wave-Heated Discharges 4.4.10. Non-Equilibrium Plasma-Chemical Microwave Discharges of Moderate Pressure 4.5. Non-Thermal Atmospheric Pressure Discharges 4.5.1. Corona Discharges 4.5.2. Pulsed Corona Discharges 4.5.3. Dielectric Barrier Discharges 4.5.4. Special Modifications of DBD: Surface, Packed-Bed, and Ferroelectric Discharges 4.5.5. Spark Discharges 4.5.6. Atmospheric Pressure Glow Mode of DBD 4.5.7. APGs: Resistive Barrier Discharge 4.5.8. One-Atmosphere Uniform Glow Discharge Plasma as Another Modification of APG 4.5.9. Electronically Stabilized APG Discharges 4.5.10. Atmospheric-Pressure Plasma Jets 4.6. Microdischarges 4.6.1. General Features of Microdischarges 4.6.2. Micro-Glow Discharge 4.6.3. Micro-Hollow-Cathode Discharge 4.6.4. Arrays of Microdischarges: Microdischarge Self-Organization and Structures 4.6.5. Kilohertz-Frequency-Range Microdischarges 4.6.6. RF Microdischarges 4.6.7. Microwave Microdischarges Problems and Concept Questions 5 Inorganic Gas-Phase Plasma Decomposition Processes 5.1. CO2 : Dissociation in Plasma, Thermal, and Non-Thermal Mechanisms 5.1.1. Fundamental and Applied Aspects of the CO2 Plasma Chemistry 207 209 209 211 215 216 219 222 224 226 229 231 233 233 234 237 239 240 241 242 243 244 245 247 247 248 251 252 254 255 257 257 259 259 259 xiii 23:32 P1: SBT CUUS097-pre CUUS097/Fridman Printer: cupusbw 978 0 521 84735 3 March 26, 2008 Contents 5.1.2. Major Experimental Results on CO2 : Dissociation in Different Plasma Systems and Energy Efficiency of the Process 5.1.3. Mechanisms of CO2 Decomposition in Quasi-Equilibrium Thermal Plasma 5.1.4. CO2 Dissociation in Plasma, Stimulated by Vibrational Excit...
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