Author: Dante Filice

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

"The world is rapidly transitioning its energy and chemical feedstocks from carbon intensive sources to renewable sources. Many existing and new technologies that utilize renewable electricity will need to come online in order to reduce CO2 emissions and reach carbon neutral goals. Plasma-driven systems for NH3 synthesis and reactions involving CO2 conversion can not only meet the challenges of carbon neutrality, but also have the potential to increase performance and reduce operational costs.Common excitation sources for non-thermal plasma processing include high voltage nanosecond (ns) pulsed plasma sources and radiofrequency (RF) sources. High voltage ns pulsed plasma sources are effective at igniting and sustaining plasmas in atmospheric pressure gases and gas mixtures. These pulses produce large quantities of excited species and highly reactive radicals participating in the desired chemical reaction pathways. When sufficiently separated in time, the power delivery of each pulse is relatively discrete resulting in minimal memory effect. The rapid quenching of the electron and excited species densities causes the discharge to essentially face re-ignition conditions every pulse. This dynamic load impedance leads to low efficiency of power delivery from the electrical mains to the plasma. On the other hand, conventional RF discharges can provide high electrical power-to-plasma chemical energy conversion efficiency, however sustaining a uniform discharge at atmospheric pressure proves to be challenging. Commercially available RF power supplies cannot reach the breakdown voltage thresholds required to ignite electrical discharges at atmospheric pressure in most gas mixtures and useful interelectrode gaps. This Master's thesis focuses on developing a plasma excitation source that combines a high voltage ns pulsed source with a RF source. Each power supply was designed and characterized to determine the electrical performance of the excitation system. Gas mixtures containing increasing amounts of N2 in Ar were introduced into the system to observe the effects on the plasma characteristics. High speed imaging was also used to focus in on the transition period from high voltage ns pulsed excitation to RF excitation.A parameterization sweep was performed to determine the operational characteristics of the RF power supply with varying gas mixture ratios. Observable RF discharge effects were present in reactor conditions with N2 concentrations up to 50% in Ar. The temporal RF discharge evolution was captured with a high-speed camera, providing insight into the mechanisms involved in obtaining RF discharge effects"--