CAREER: Controlling Low Temperature Plasma Activation

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Low temperature plasmas (LTPs) have been used successfully to excite relatively inert materials into states that promote useful chemical reactions. Applications of LTPs are diverse and include bonding of advanced lightweight structural materials, semiconductor processing, carbon dioxide utilization, wastewater treatment, plasma-assisted wound healing, and agricultural technologies. The discovery and exploration of LTP activation processes has historically proceeded by trial and error, which is expensive and time-consuming. This proposal aims to develop a fundamental understanding of LTPs to accelerate the development of new applications based on them.The research hypothesis of this project is that chemical reactions occurring in LTPs proceed towards a superlocal equilibrium state, which can be derived from first principles. Preliminary data supports the hypothesis, which will be further tested experimentally using gas-phase reactions that are of interest for energy and environmental applications. Under conditions of superlocal equilibrium, different species can have different temperatures at the same location in space. The superlocal equilibrium state in LTPs is expected to be a function of the background gas temperature, electron temperature, total pressure, electron concentration, and mole numbers of different species. Chemical systems containing carbon, hydrogen and oxygen will be studied that are of considerable interest for energy and environmental applications, with carbon dioxide and methane being two key molecules. To characterize the C-H-O system, which is multiphase, a robust and reliable method will be developed to measure plasma parameters over a wide pressure range in LTPs that produce solids. Integration of research and education will be focused on developing active learning modules on chemical equilibria for high school students, in collaboration with a Chemistry Teacher from a local High School, and for undergraduate students taking a Thermodynamics course at Washington University.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.