Date of Award

Spring 2002

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Committee Director

Leposava Vuskovic

Committee Member

Charles I. Sukenik

Committee Member

Gail E. Dodge

Committee Member

Gary E. Copeland

Committee Member

Robert L. Ash

Abstract

Decomposition of CO2 was studied in a capacitively coupled radio frequency discharge using Martian Simulant Gas mixture that contains 95% CO2. The discharge was operated at a gas pressure of 3 to 6 Torr and a discharge power density of less than 2.0 W/cm3. The main mechanism of the CO2 decomposition process is the electron impact dissociation and the rate of the process depends on the electron density, Ne, the concentration of CO2, and the reduced electric field, E/N. A self-consistent model was established to describe the CO2 decomposition process based on these parameters. The model gave the microscopic description of the discharge in terms of the electron energy distribution function (EEDF) and electron mean energy Te, electron density N e, and dissociative rate coefficients. In addition, the CO2 decomposition rate depends on all complex gas reactions during the discharge. A simplified set of major gas reactions was used to describe the rate of CO2 decomposition in the discharge. The validity of the model was successfully verified by comparing the calculated results with the experimental results. The discharge characteristics such as Te, Ne, and E/N, were determined by using the Langmuir probe technique, while the discharge temperature, Tg, was determined by using the CO rotational temperature that was obtained from the CO rotational emission spectrum, and compared with results obtained from the thermocouple measurements. The steady-state gas composition was measured using a quadrupole mass spectrometer. Measurement of gas composition in the discharge condition was within 5% of the prediction from the model. Due to a high power efficiency to decompose CO2 by using an RF discharge, one direct application of the study is to produce oxygen on the planet Mars. In such an experiment, oxygen was extracted and diffused through a silver membrane used as one of the electrodes during discharge. The oxygen flux produced by the present discharge condition was shown to reach about 5.0 × 10−14 cm−2s−1. The study of the CO2 decomposition can be used in developing the optimum RF discharge conditions that yield the maximum oxygen flux production.

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DOI

10.25777/z2jd-mf59

ISBN

9780493713014

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