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Über dieses Buch

This book studies the collision, coalescence and deposition of nanoparticles in stagnation flames. With the help of synthesis experiments, in-situ laser diagnostics and molecular dynamics simulations, it investigates the growth of nanoparticles in flames and their deposition in boundary layers at a macroscopic flow field scale, as well as particle and molecular scale issues such as the interaction force between particles, how the collision rate is enhanced by attractive forces, and how the nano-scale coalescence process is influenced by the high surface curvature – all of which are crucial to understanding nanoparticle transport phenomena at high temperatures. The book also reports on a novel in-situ laser diagnostics phenomenon called phase-selective laser-induced breakdown spectroscopy and related applications for tracing gas-to-particle transitions and measuring local particle volume fractions in nano-aerosols.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
As a fundamental system of heterogeneous combustion and energy, high-temperature nanoaerosols widely exist in both nature and industry, for example, large-scale gas-phase synthesis of nanoparticles, formation of ultrafine particles in coal combustion, and burning of energetic metal nanoparticles. Arising from the high-temperature environment and ultra small scale, particle dynamics exhibit unique features, especially on the collision, coalescence, and deposition. Understanding the underlying physics of these behaviors is of great importance toward precise control of particle morphology and structure.
Yiyang Zhang

Chapter 2. Synthesis of TiO2 Nanoparticles by Stagnation Swirl Flame

Abstract
The experimental system for the synthesis of TiO2 nanoparticles by stagnation swirl flame (SSF). The system is composed of three main parts, i.e., a delivery system for reactant gases and precursor, a downward stainless steel tube of 18 mm i.d with a vane swirler inside, and a temperature-controlled substrate.
Yiyang Zhang

Chapter 3. Laser Diagnostics on Nanoparticles in Flames

Abstract
As mentioned in the previous chapter, multiple processes occur simultaneously with timescale ranging from picoseconds to microseconds and spatial ranging from nanometer to millimeter. Solely characterizing the final products is not able to explore the underlying physics of the gas-to-particle transition and particle growth. Therefore, in situ diagnostics of gas and particle phases is of great importance for both laboratory research and industrial production.
Yiyang Zhang

Chapter 4. Molecular Dynamics Study on Nanoparticle Collision and Coalescence

Abstract
Chapters 2 and 3 study nanoparticle dynamics at the flow field level. In this chapter, we will go deeper to particle level with the help of molecular dynamics (MD) simulation method. Conventional theories on particle dynamics, for instance collision kinetics from aerosol field and sintering laws from ceramics field, could not be directly extended to nanoparticles without proper consideration of size effects. First, some forces become long-ranged as particle size gets small and thus important for nanoparticle dynamics. Second, as the surface-to-volume ratio increases, the impact of surface forces and energy on the whole system dramatically increases. Third, the high surface curvature largely alters the crystalline properties of nanoparticles, e.g., melting point. All these factors have great influences on particle dynamics and hence drive a lot of attention in both academics and industry.
Yiyang Zhang

Chapter 5. Deposition of Nanoparticles in Stagnation Flames

Abstract
Possible mechanisms of particle deposition include inertia deposition, inception, diffusion, thermophoresis, and external field for instance gravity and electrical field.
Yiyang Zhang

Chapter 6. Conclusions and Future Work

Abstract
This work studies dynamic behaviors of metal oxide nanoparticles in flames, including collision, coalescence, and deposition, with flame synthesis as the background. We focus on effects of high temperature environment and small particle scale. At the scale of flow field, the phenomenological laws that control the morphology and structure of final particles and films are investigated by parametric experiments and theoretical modeling.
Yiyang Zhang

Erratum to: Dynamics of Nanoparticles in Stagnation Flames

Without Abstract
Yiyang Zhang
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