Microwave atmospheric pressure plasma jet: A review

Considerable interest has emerged in atmospheric pressure discharges within the microwave frequency range over the past decade, driven by the growing potential applications such as material processing, CO2 dissociation, waste treatment, hydrogen production, water treatment, and so forth. This review delves into the diverse types of atmospheric pressure plasma jets (APPJs) operated at microwave frequencies. The analysis integrates insights from an overall review that encapsulates the different types of geometry, characterizations, modeling, and various applications of microwave atmospheric plasma jets (MW-APPJs). This paper will contribute to a comprehensive understanding of microwave plasma generated in the ambient atmosphere. The fundamental insights into these discharges are emerging, but there are still numerous unexplained phenomena in these inherently complex plasmas that need to be studied. The properties of these MW-APPJs encompass a higher range of electron densities (n(e)), gas temperatures (T-g), electron temperatures (T-e), and reactive oxygen and nitrogen species (RONS). This review provides an overview of the key underlying processes crucial for generating and stabilizing MW-APPJs. Additionally, the unique physical and chemical properties of these discharges are summarized. In the initial section, we aim to introduce the primary scientific characterizations of different types of waveguide-based and non-waveguide-based MW-APPJs. The subsequent part focuses on the diverse modeling approaches for different MW-APPJs and the outcomes derived from these models. The final section describes the potential applications of MW-APPJs in various domains.