Date of Award

Fall 2005

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Karl Schoenbach

Committee Member

Mounir Laroussi

Committee Member

Linda Vahala

Call Number for Print

Special Collections LD4331.E55 S93 2005

Abstract

A stable micro-plasma jet in air was generated from a direct current discharge between two molybdenum electrodes (0.25 mm thick) that were separated by an alumina insulator of the same thickness. The after-glow plasma jet was generated by blowing air through the space between the electrodes. A change from laminar to turbulent flow was observed at a gas flow rate of 140 ml/min. The length of the plasma jet increased with flow rate in the laminar mode to approximately 15 mm and decreased in the turbulent mode.

Increasing the gas flow rate up to 200 ml/min at a constant discharge current of 15 mA resulted in a considerable decrease of gas temperature from 2000 K to 450 K. The change is due to the transition of plasma jet &om laminar to turbulent mode. As the current was increased &om 13 mA to 25 mA, the gas temperature of the plasma jet increased by up to 25 K, independent of flow rate.

Ozone concentrations in the plasma jet were measured by using iodometric method. Ozone concentrations up to 3.5 µg/ml were obtained in the turbulent mode of the plasma jet. It decreased linearly with flow rate below the transition from laminar to turbulent. The ozone generation efficiency was higher for the plasma jets having smaller hole diameters at the same flow rate, and decreased with the increase of current.

This cold plasma jet offers the opportunities for applications such as fine surface treatment of organic materials, plasma surgery and cleaning of semiconductor chips.

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DOI

10.25777/kbna-2112

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