A Catalytic Sensor for Measurement of Radical Density in CO2 Plasmas

Abstract

A catalytic sensor for the measurement of radical density in weakly ionized CO2 plasmas, created in a low-pressure electrodeless discharge, is presented. The CO2 plasma was created in a 4 cm wide borosilicate glass tube inside a copper coil connected to a radio frequency generator operating at 27.12 MHz with a nominal power of 250 W. The dissociation fraction of the CO2 molecules was measured in the early afterglow at pressures ranging from 10 Pa to 100 Pa, and at distances of up to 35 cm along the gas stream from the glowing plasma. The radical density peaked (2 × 1020 m−3) at 80 Pa. The density quickly decreased with increasing distance from the glowing plasma despite a rather large drift velocity. The dissociation fraction showed similar behavior, except that the maximum was obtained at somewhat lower pressure. The results were explained by rather intense surface recombination of radicals.

Synthesis of Micro- and Nanomaterials in CO2and CO Dielectric Barrier Discharges

“…It is important to mention that gas chromatography allows only the evaluation of the overall reaction products, while within the discharge, a more complex mixture of species contributes to the reactions taking place. For instance, it is known that also atomic oxygen and ozone are formed in the CO 2 plasma, but special techniques are needed to detect and quantify them …”

Exothermic Surface Reactions on Sintered Graphite Upon Exposure to CO₂ Plasma Created in Microwave Discharge

“…CO 2 dissociates to CO and O radicals in MW plasmas. The concentration of these radicals exceeds 10% [3]. The radicals are likely to recombine on thesample surface either to parent CO 2 molecules or O 2 molecules in the ground state since the reaction probabilities are close to 0.1.…”