Page 30 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Chapter 1
1.4 Research Aim and Scope
The main objective of this research is to develop and characterize an atmospheric pressure microplasma-assisted process to produce nanoparticles in a simple, flexible and environmental benign manner. The influence of operation conditions on the product properties were studied in details in order to engineer nanoparticles with desired properties. There are three main stages in the PhD project: 1) In the first stage, an atmospheric pressure microplasma setup with wide operational window was developed and built up for the synthesis of nanoparticles. 2) In the second stage, systematic experiments were designed and carried out to produce nanoparticles in the gas phase (iron oxides, TiN, Ni), with micro- reactor optimization for each specific process. 3) In the third stage, the setup was expanded to synthesize nanoparticles in the liquid phase, with the model case of lanthanide (Ln)-doped nanophosphors. The main contributions of this thesis are as follows:
In Chapter 2, the atmospheric pressure microplasma setup built as the modular-design reactor is described. Meanwhile, the involved characterization methodologies and instrumentation techniques applied during the project are briefly introduced and summarized.
To show proof-of-concept of nanoparticles synthesis using the novel microplasma setup, in Chapter 3, iron oxide NPs were firstly synthesized in the gas phase from ferrocene vapors. Moreover, based on a simplified model, experimental and literature data, the underlying mechanisms of ferrocene dissociation in microplasma were discussed.
In Chapter 4, the process was expanded by the setup adjustment for the first demonstration of microplasma-assisted TiN nanoparticles production using TiCl4 as the precursor and N2 as the plasma gas. In addition, the influence of H2 admixture to the process gas on the products properties was explored. Besides, comparisons of the process with preceding techniques for TiN nanoparticles synthesis were carried out to show their advantages and disadvantages.
In order to investigate the possibility of endowing nanoparticles with desired properties by the microplasma process, in Chapter 5 the gas phase synthesis of Ni nanoparticles was investigated. Systematic experiments were designed and carried out to study the relationship between operational conditions and product parameters, aiming to tune the magnetic properties “in-flight” by tuning operational parameters.
For the first-time demonstration of the plasma-assisted rare-earth nanoparticles synthesis in the liquid phase, in Chapter 6 the microplasma process was applied to fabricate Y2O3 nanoparticles via a two-step method: plasma electrodeposition of yttrium hydroxide followed by heat-treatment at various temperatures. Possible mechanisms for plasma-assisted yttrium hydroxide precipitation were discussed by correlating spectroscopic studies, plasma kinetic analysis and the precipitation equilibrium.
In Chapter 7, the microplasma-liquid interaction process was advanced by doping lanthanide (Ln) elements into Y2O3 nanoparticles to fabricate Y2O3:Ln3+ nanophosphors of adjustable luminescent properties. By choosing Y2O3:Eu3+ nanophosphors as a model study, the influence of heat treatment and the dopant concentration on the luminescent efficiency was investigated.
18