Dynamics of Nanoparticles in Stagnation Flames (eBook)

Supervisor’s Foreword 6
Parts of this thesis have been published in the following journal articles: 9
Acknowledgements 10
Contents 11
Nomenclature 15
1 Introduction 18
1.1 Background 18
1.2 Flame Synthesis of Nanoparticles 19
1.3 Coagulation of Nanoparticles in Flames 23
1.4 Sintering of Nanoparticles 25
1.5 Deposition of Nanoparticles and Synthesis of NanoPorous Films 28
1.6 In Situ Optical Diagnostics on NanoAerosol System 29
1.7 Road map of Present Study 31
References 32
2 Synthesis of TiO2 Nanoparticles by Stagnation Swirl Flame 37
2.1 Experimental Methods 37
2.2 Population Balance Modeling of Nanoparticle Coagulation in Stagnation Swirl Flame 40
2.2.1 Comparison of Characteristic Times for Different Steps 40
2.2.2 Modeling of Particle Coagulation in Flames 43
2.2.3 Modeling Results and Comparison with Experiments 47
2.3 Synthesis of TiO2 Nanoporous Films by Stagnation Swirl Flame 49
2.4 Pilot-Scale Experiments of TiO2 Nanoparticle Synthesis by Stagnation Swirl Flame 51
2.5 Summary 53
References 53
3 Laser Diagnostics on Nanoparticles in Flames 55
3.1 Introduction 55
3.2 Measurement of Temperature Profile of the Stagnation Swirl Flame 56
3.2.1 Photon Scattering 56
3.2.2 Measurement of Temperature Field Using Rayleigh Scattering 57
3.2.3 Measurement of Temperature Profile Using Raman Scattering 65
3.3 Diagnostics of TiO2 Nanoparticles in Flames by Phase-Selective Laser-Induced Breakdown Spectroscopy 71
3.3.1 A Brief Review of Laser-Induced Breakdown Spectroscopy (LIBS) 71
3.3.2 Laser Diagnostics of Aerosols and Original Idea of Phase-Selective LIBS 75
3.3.3 Experimental Phenomena of Phase-Selective LIBS 77
3.3.4 Time-Resolved Analysis of Laser-Induced Nanosized Plasmas 80
3.3.5 Effect of Laser Fluence 82
3.3.6 Effect of Particle Size 82
3.3.7 In Situ Measurement of Particle Volume Fraction 84
3.3.8 Two-Dimensional Imaging of Particle Volume Fraction 85
3.3.9 Phase-Selective LIBS Diagnostic on the Simultaneous Formation of Multi-component Metal Oxides 86
3.4 Summary 89
References 90
4 Molecular Dynamics Study on Nanoparticle Collision and Coalescence 93
4.1 Introduction 93
4.2 Brief Introduction of Computational Method 94
4.2.1 Ensemble 94
4.2.2 Fundamental Algorithm 95
4.2.3 Potential 96
4.2.4 Simulation Procedure 97
4.3 Interaction Forces Between TiO2 Nanoparticles 102
4.3.1 Brief Review of Interaction Forces Between Nanoparticles 102
4.3.2 MD Simulation Settings 111
4.3.3 Results and Discussion 112
4.4 Enhancement of Particle Collision Rate by Long-range Interaction Forces 119
4.4.1 Collision Mechanisms in an Aerosol System 119
4.4.2 Collision Frequency Function for Brownian Coagulation 120
4.4.3 Effect of Inter-particle Forces on Collision Rate 121
4.4.4 Simulation Methods and Conditions 124
4.4.5 Results and Discussions 126
4.5 Grain Structure of Single TiO2 Nanoparticles 131
4.5.1 Grain Structure of Nanoparticles and Melting-Point Depression 132
4.5.2 Simulation Settings and Data Extraction 134
4.5.3 Results and Discussions 135
4.6 Coalescence of Two TiO2 Nanoparticles 140
4.6.1 A Brief Introduction to Particle Sintering 140
4.6.2 Particle Coalescence in High-Temperature Nanoaerosols 142
4.6.3 Simulation Settings and Data Extraction 144
4.6.4 Results and Discussions 146
4.7 Summary 155
References 156
5 Deposition of Nanoparticles in Stagnation Flames 161
5.1 Deposition Mechanisms 161
5.2 Experimental Study on Nanoparticle Deposition Flux in Stagnation Flames 164
5.2.1 Experimental System 164
5.2.2 A Typical Radial Distribution of Deposition Flux 165
5.3 Theoretical Analysis on Nanoparticle Transport and Deposition in Boundary Layer of Stagnation Flames 166
5.3.1 Velocity and Temperature Profile in Boundary Layer 166
5.3.2 Simplification of Particle Transport Equation in the Boundary Layer 171
5.3.3 Simplified Approach Within the Stationary Layer 172
5.3.4 Particle Transport Within the Entire Boundary Layer 175
5.3.5 Discussion on Experimental Results of Deposition Flux 179
5.4 The Structure and Morphology of Deposited Nanofilms 181
5.4.1 Experimental Methods 182
5.4.2 The Morphology and Packing Density of Nanofilms 183
5.4.3 Simplified Deposition Model for Particle Packing 186
5.4.4 The Specific Surface Area (SSA) of Nanofilms 190
5.5 Summary 192
References 193
6 Conclusions and Future Work 194
6.1 Conclusions 194
6.1.1 The Phenomenological Laws at Reactor Level 194
6.1.2 Collision and Coalescence at Particle Level 196
6.1.3 In Situ Laser Diagnostics of Nanoparticle Formation and Transport 197
6.2 Future Work 198
7 Erratum to: Dynamics of Nanoparticles in Stagnation Flames 199
Erratum to: Y. Zhang, Dynamics of Nanoparticles in Stagnation Flames, Springer Theses, DOI 10.1007/978-3-662-53615-5 199