Page 37 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin
P. 37

Multiphase Operational Microplasma Setup and the Involved Instrumentation Techniques
inside an oven. Moreover, a LabVIEW based program was designed to control the oven temperature, the DC power supply and the MFCs. Therefore, the experimental values of the plasma current, voltage, power and gas flow rates can be set ad recorded through the control box.
(2) Easy assembling and dissembling. Dedicated and independent parts (pipe fittings, gas feeder, reaction chamber, etc.) which can be relatively easy assembled and disassembled for each type of experiment/diagnostics were designed and fabricated to allow convenient operation.
(3) Direct product collection. The products are confined within a quartz tube that enclosed the electrodes. Si wafer (or SS mesh) as the substrate was placed downstream the anode mesh to collect aerosol products directly. The distance between the substrate and the mesh is controllable through an adjustable table, allowing investigating the optimal distance for particle collection and plasma coating for further study.
The electrodes are connected to a DC power supply (Matsusada Precision, Model AU- 10R30), while a ballast resistor (500 kΩ) is used to stabilize discharge current. A quartz tube was installed between hollow cathode, employed in reactor, and pipelines for electrical insulation. The whole setup is operated at atmospheric pressure. As a safety measure, gas sensors are installed inside the oven to detect gas leakage. Once any leakage is detected, the whole setup would be shut down automatically by the control system, with automatic closing of MFCs. This allows us to explore hazardous precursors and process gases.
2.1.2 Advanced Concept of the Microplasma Setup for the Gas-phase Nanofabrication
As the project progressed, in order to enable different plasma-chemistries, the microplasma setup has been gradually improved. Figure 2.2 shows the advanced concept of the microplasma setup for the gas-phase nanofabrication process. Based on the initial setup, two extra gas flows (line 3: H2; Line 4: N2) were added to the setup to broaded its operational window. In this manner, the setup can be used to study the influence of H2 and N2 to the products, with the ultimate goal to produce nitrides nanoparticles. In addition, another sub- pipeline from the pipeline 1 was constructed to connect a bubbler vessel, in which liquid precursors can be filled and the vapors transported into the plasma by this gas flow. Therefore, in addition to the solid precursors, liquid chemicals can also be used. Meanwhile, the bubbler vessel was installed on the top of an electronic scale (Sartorius, type R 300 S), so the mass flow rate of the liquid precursor can be quantified.

   35   36   37   38   39