Page 165 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin
P. 165

Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process
The fabrication of nanomaterials has been of long standing interest, primarily motivated by their unique properties which are highly demanded in various applications and at the same time being fascinating for science. Despite various production methods have been already developed, a number of technological and scientific challenges still exists. For example, the implementation of time/energy consuming procedures, the requirement of large-footprint equipment and considerable operation costs, the production of nanoparticles with wide size distributions, the incorporation of impurities, the involvement of toxic chemicals. In order to address these challenges, the thesis takes an integrated approach to design and develop a technological platform based on atmospheric pressure microplasma for the multiphase synthesis of nanomaterials, aiming to explore a new synthetic method to produce high quality nanoparticles with adjustable properties via a simple, flexible and environmental benign manner. The content of the present PhD research can be partitioned as follow: the design and build up of the microplasma reactor, the detailed study on nanomaterial synthesis first in the gas-phase and then in the liquid-phase.
In the first stage, the possibility of developing a microplasma-based process for the synthesis of nanoparticles with various chemical composition was assessed. Chapter 1 introduced the existing methods for nanomaterials synthesis and their associated pros and cons, allowing readers to have a general idea on the start-of-the-art nanofabrication technique and challenges. This was followed by the review of four main microplasma configurations used for the production of nanomaterials, aiming to provide useful guides for the proper selection of the plasma configuration in light of different conditions. Finally, a brief introduction of related nanomaterials applications as well as the research aim and scope were presented.
Based on the current status of nanofabrication technique and the existing plasma configurations, Chapter 2 introduced the microplasma setup employed for nanomaterial synthesis in the present research. The setup was designed for the preparation of metallic/oxide/nitride nanoparticles by adding and mixing process gases such as argon, hydrogen, nitrogen and ammonia with the possibility to use solid or liquid precursors and to precisely control environment temperature. To endow the process with wide operational space, in addition to various plasma gases, other important parameters such as the gas flow rate, precursor concentration, dissipated plasma power etc. were controlled and adjusted to a large extent. Meanwhile, a multiphase microplasma reactor of modular design was fabricated to carry out experiments both in the gas phase and in the liquid phase. From the safety point of view, complementary safety analysis was conducted. Gas sensors were added to detect the leakage of dangerous gases (H2 and ammonia). The whole reactor was constructed in a way to prevent possible explosion risks. Moreover, the gas flows, plasma voltage and power were remotely controlled and adjusted via LabVIEW-based programs, in which all important experimental parameters were automatically logged.
In the second stage, systematic experiments were designed and carried out to produce nanoparticles in the gas phase using the novel technological platform. The first experimental 153

   163   164   165   166   167