Production of Metal Nanoparticles in Asymmetrical Dielectric Barrier Discharge‐Plasma Reactor at Atmospheric Pressure

Abstract

Production of Metal Nanoparticles in Asymmetrical Dielectric Barrier Discharge-Plasma Reactor at Atmospheric PressureThis paper focuses on the production of metal nanoparticles in a dielectric barrier discharge (DBD) reactor at atmospheric pressure. In the developed reactor only one electrode is provided with a dielectric (alumina), while the point-shaped counter electrode is not covered and is accessible to the filamentary discharges (asymmetrical DBD). The metallic particles are formed from the material of the open counter electrode, on which the filamentary discharges lead to the formation of craters. A high number of larger nanoparticles (with diameter of some tens of nanometers) are observed in the cold reactor at the beginning of the discharges. After the achievement of the thermal equilibrium in the reactor mainly very small metallic nanoparticles are produced with constant size and number concentration. The produced metallic particles in thermal equilibrium are crystalline and not agglomerated. The mean diameter of the produced particles is about 4 nm. For given operating conditions of the reactor (fixed electrode gap and gas flow rate) the electrode material has almost no influence on the size of the produced particles, but it determines the number concentration.

Nano-droplet ejection and nucleation of materials submitted to non-thermal plasma filaments

“…Droplet ejection mechanism has recently been proposed [22] to account for the 10 to few hundreds nm solidified metal droplet observed on the electrode of prevented spark discharge as well as in the collected aerosol (cf. Figure 3b).…”

“…Figure 6 : (a) TEM micrograph of craters formed for 1 (upper) and 60min (lower) of prevented spark discharges on silver electrode; (b) Mechanisms of nucleation/agglomeration and droplet ejection from melted craters formed in spots of interaction between prevented spark discharge and electrode [22][23].…”