Diagnostic Study of Pulsed Power Solution Plasmas and its Application on the Synthesis of Metal Organic Frameworks
Date Issued
2015
Date
2015
Author(s)
Lin, Shen-Chieh
Abstract
The diagnosis of plasma generated by a pulsed voltage in NaCl electrolytic solution and its potential applications are studied. The pulsed power can offer the solution plasma system a better stability and cycle-to-cycle reproducibility than the performance driven by DC or AC power. The optimum plasma behavior can be represented by regulating the suitable operation parameters, and this advantage gives a potential opportunity of the application for the system diagnosis and material fabrication. The experimental investigations include two parts: Diagnostic study of the effect of the electrode diameter on the behavior of plasmas and Synthesis of metal-organic frameworks by using aqueous solution plasma. In the first part, the effect of the electrode diameter on the discharge behavior of plasmas in saline solution was studied. The measurement of the plasma performance including current and voltage waveforms, discharge emissions, bubble dynamics and power consumptions were detected in the system. The driving electrode was a platinum wire covered by a glass tube to precisely define the area exposed to the solution. Platinum wires of four different diameters, namely 0.1 mm, 0.3 mm, 0.5 mm, and 1 mm, were used. A positive correlation was found between the generating rate of the bubble on the electrode surface and the power density consumption calculated from the IV waveform recorded by the oscilloscope. The result didn’t depended on the working period (Ton). However, a negative correlation existed between the area of the driving electrode exposed to the solution and the power density consumption. The outcome may explain why a higher appearance frequency of the bubbles and the current peaks in the small diameter driving electrode system. The time-resolved bubble dynamics taken by the high speed video show that the vapor formation process in this experiment is the same as the one driven by a DC power supply. The bubble formation mechanism is strong related to the change of the current waveform. The plasma discharges would not form until the vapor layer collapse or shrink in each system. The observations done in the experiment offer an explanation of the general solution plasma behaviors. In the second part, we tried to synthesize metal-organic frameworks by using aqueous solution plasma. The object of this experiment was to develop a fabrication which could synthesize high purity metal-organic frameworks in the conditions of low concentration of the reactants and reduced time. An attempt that the zinc salt microfluidics was introduced to the reaction container and a plasma was ignited in the contact zone between the zinc salt solution and the ligand solution was approached. After the reactants were treated in the aqueous phase, they were dissolved in the methanol for centrifugation and drying. The pure products were confirmed by analyzing the XRD, SEM and FTIR patterns. The experiment results supported that we reach the goal.
Subjects
solution plasma
pulsed power
plasma diagnostics
metal-organic frameworks
ZIF-8
Type
thesis
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