Page 159 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Chapter 9
Epilogue
9.1 Conslusions
The presented thesis has demonstrated an atmospheric pressure microplasma-assisted process for the synthesis of nanoparticles both in the gas phase and the liquid phase. A DC-driven microplasma setup with broad operational windows (metallic NPs, nitrides NPs, oxides NPs) and flexible process control (labview-controlled power and gas flow rate adjustment) was built up in the first stage of the PhD project. As a further development, a multiphase operational microplasma reactor with modular design was engineered for carrying out the experiments. Afterwards, systematic experiments were conducted for the gas/liquid phase synthesis of nanoparticles, in a step-to-step manner. The ultimate goal of this study is to demonstrate a simple, flexible and environmental friendly way to produce various nanomaterials, in which their properties can be controlled and tuned by adjusting processing parameters. Table 9.1 gives a summary of the experiment design for this facile microplasma- assisted nanofabrication technique.
In Chapter 3, as a proof-of-concept model study, ferrocene was used as the precursor to produce iron-containing nanoparticles in the gas phase. The influence of the plasma power and the ferrocene concentration on the dissociation process as well as the obtained products were investigated. Based on experimental data, simplified modeling as well as relevant information from literature, possible mechanisms for ferrocene decomposition were discussed. Results show that nanometer-sized and well-dispersed iron oxide nanoparticles with polycrystalline nature can be produced by the atmospheric pressure microplasma setup. The increase of dissipated power and precursor vapor pressure helps to enhance the precursor dissociation rate. However, it also contributes to the production of larger sized nanoparticles with higher agglomeration degree.
In Chapter 4, by the adjustment of the microreactor to use titanium tetrachloride (TiCl4) as the precursor and nitrogen as the N source, TiN nanoparticles, for the first time, were produced at the atmospheric pressure via a single step one pot microplasma enhanced synthesis. It was demonstrated that the introduction of H2 could significantly suppress the generation of TiO2 impurities. This study once again shows the plasma technique can act as an effective and promising tool for process intensification.
In Chapter 5, to demonstrate the feasibility of “in-flight” tuning of product properties by the miroplasma technique, systematic experiments were designed to study nanoparticles synthesis from nockelocene vapors at various conditions, aiming to establish the relationship 147
Epilogue