Abstract
In this work, a two-dimensional fluid model of the needle-plane discharge plasma has been built to numerically investigate the spatio-temporal evolution characteristics of the electric field intensity and electric potential as well as generating and consuming reaction pathways of various oxygen species in a He–O2 atmospheric pressure plasma jet. Simulation results have indicated that the region of high electric field intensity moves in the direction of the plane electrode with the formation and propagation of an ionization wave. The region of low electric field intensity exists between the needle electrode and the head of the ionization wave, and its area increases continuously. The obvious voltage drop and local electric field enhancement occur between the head of the ionization wave and the plane electrode. Electron attachment reactions e + O2 → O + O− and e + 2O2 → O2− + O2 produce negative ions O− and O2−. More than 80% of the positive ions O2+ and H2O+ come from Penning ionizations between He* and molecules O2 and H2O. e + O2 → e + O + O(1D) is the main pathway to generate O and O(1D). O(1D) + H2O → 2OH and O + H + H2O → OH + H2O produce 69.3% and 39.2% of OH, respectively. 2O2 + O → O3 + O2 is the key generating reaction of O3.
Highlights
Plasma is called the fourth state of matter, which consists of electrons, ions, atoms, molecules, radicals, and excited species.1–3 The non-equilibrium discharge plasmas have been applied in such fields as material processing, flow control, environment remediation, and biomedicine.4–10 Jeong et al have developed an atmospheric pressure plasma jet (APPJ) for spraying the non-equilibrium plasma at atmospheric pressure.11 The APPJ has overcome shortcomings of traditional gas discharges, and it can produce non-equilibrium discharge plasma that possesses low gas temperature and high chemical activity and directly transport charged particles and active components, such as reactive oxygen species (ROS) and reactive nitrogen species (RNS), to the surface of the treated material at atmospheric pressure
It is shown that the high radial electric field intensity region in red is located at the area around the needle electrode during 1–3 ns, and it moves toward the plane electrode
The enhanced local electric field can dramatically increase the electron energy and accelerate the electron movement to the ionization waves (IWs) head region, resulting in an obvious electron-ion multiplication effect near the IW head region,36 which promotes the rapid spread of the ionization wave to the plane electrode
Summary
Plasma is called the fourth state of matter, which consists of electrons, ions, atoms, molecules, radicals, and excited species. The non-equilibrium discharge plasmas have been applied in such fields as material processing, flow control, environment remediation, and biomedicine. Jeong et al have developed an atmospheric pressure plasma jet (APPJ) for spraying the non-equilibrium plasma at atmospheric pressure. The APPJ has overcome shortcomings of traditional gas discharges, and it can produce non-equilibrium discharge plasma that possesses low gas temperature and high chemical activity and directly transport charged particles and active components, such as reactive oxygen species (ROS) and reactive nitrogen species (RNS), to the surface of the treated material at atmospheric pressure. The non-equilibrium discharge plasmas have been applied in such fields as material processing, flow control, environment remediation, and biomedicine.. Jeong et al have developed an atmospheric pressure plasma jet (APPJ) for spraying the non-equilibrium plasma at atmospheric pressure.. The APPJ has overcome shortcomings of traditional gas discharges, and it can produce non-equilibrium discharge plasma that possesses low gas temperature and high chemical activity and directly transport charged particles and active components, such as reactive oxygen species (ROS) and reactive nitrogen species (RNS), to the surface of the treated material at atmospheric pressure. Since novel APPJ reactors in combination with new plasma biomedical applications have emerged in recent years, the APPJ has become a hot research topic in the subjects of plasma physics and gas discharge.
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