Search for: All records

Abstract Plasmas interacting with liquid surfaces produce a complex interfacial layer where the local chemistry in the liquid is driven by fluxes from the gas phase of electrons, ions, photons, and neutral radicals. Typically, the liquid surface has at best mild curvature with the fluxes of impinging plasma species and applied electric field being nominally normal to the surface. With liquids such as water having a high dielectric constant, structuring of the liquid surface by producing a wavy surface enables local electric field enhancement due to polarization of the liquid, as well as producing regions of higher and lower advective gas flow across the surface. This structuring (or waviness) can naturally occur or can be achieved by mechanical agitation such as with acoustic transducers. Electric field enhancement at the peaks of the waves of the liquid produces local increases in sources of reactive species and incident plasma fluxes which may be advantageous for plasma driven solution electrochemistry (PDSE) applications. In this paper, results are discussed from a computational investigation of pulsed atmospheric pressure plasma jets onto structured water solutions containing AgNO₃as may be used in PDSE for silver nanoparticle (NP) formation. The solution surface consists of standing wave patterns having wavelength and wave depth of hundreds of microns to 1 mm. The potential for structured liquid surfaces to facilitate spatially differentiated chemical selectivity and enhance NP synthesis in the context of PDSE is discussed. 

Abstract Non-equilibrium inductively coupled plasmas (ICPs) operating in hydrogen are of significant interest for applications including large-area materials processing. Increasing control of spatial gas heating, which drives the formation of neutral species density gradients and the rate of gas-temperature-dependent reactions, is critical. In this study, we use 2D fluid-kinetic simulations with the Hybrid Plasma Equipment Model to investigate the spatially resolved production of atomic hydrogen in a low-pressure planar ICP operating in pure hydrogen (10–20 Pa or 0.075–0.15 Torr, 300 W). The reaction set incorporates self-consistent calculation of the spatially resolved gas temperature and 14 vibrationally excited states. We find that the formation of neutral-gas density gradients, which result from spatially non-uniform electrical power deposition at constant pressure, can drive significant variations in the vibrational distribution function and density of atomic hydrogen when gas heating is spatially resolved. This highlights the significance of spatial gas heating on the production of reactive species in relatively high-power-density plasma processing sources.