Naphthalene oxidation by different non-thermal electrical discharges at atmospheric pressure

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Analysis of discharge regimes obtained by microsecond underwater electrical breakdown in regard to energy balance

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n-hexane soot oxidation reactivity in N

This paper discusses some aspects of n-hexane soot reactivity in a multi-pin to plate pulsed corona discharge working in the nanosecond regime at atmospheric pressure. The soot-discharge interaction was quantified by measuring the densities of CO, CO2, O3 and NO2 out-coming from the discharge cell. Results showed that CO2 is the major product of soot oxidation. They also showed a strong enhancement of soot oxidation for O2 percentage greater than 10% and cathode temperatures above 425 K. The soot reactivity is significantly enhanced when the discharge frequency is increased. The results obtained were interpreted in term of the competition between the kinetics of plasma active species adsorption and oxidation product desorption

Cr(VI) Reduction by Microsecond Pin-to-Pin Discharges Generated in an Aqueous Solution

International audienceThe total reduction of Cr(VI) by microsecond pin-to-pin electric discharge generated in aqueous solution has been reported. [Cr(VI)] and [H 2 O 2 ] were measured simultaneously by UV-vis absorption spectroscopy during the process. The kinetics of the Cr(VI) reduction resulting from the discharges is found to be pseudo zero order rate. The influence of the electron properties has been studied by varying the applied voltage and the electrode gap showing a better reduction for a higher electric field. In addition pH and conductivity of the solution have been measured before and after the process. The analysis of the chemical kinetics has been completed by varying the pulse duration of the discharge. The results show that the reduction occurs both during the plasma and the post plasma phases. It is also noted that the increase of the pulse duration involves a better Cr(VI) reduction, a higher [H 2 O 2 ] production and a more important change in conductivity

Time-resolved diagnostics of a pin-to-pin pulsed discharge in water: pre-breakdown and breakdown analysis

International audienceThis paper presents an experimental study of an underwater pulsed plasma discharge in a pin-to-pin electrode configuration. Time resolved refractive index-based techniques and electrical measurements have been performed in order to study the pre-breakdown and breakdown phenomena in water (σ  =  100 µS cm−1). A single high voltage pulse with amplitude of a dozen of kV, rise time of 20 ns and duration of [0.1–1] ms is applied between two 100 µm diameter platinum tips separated by 2 mm. This novel experimental work reports that different cases of electrical discharge in water occurs for a unique set of experimental conditions such as (i) bush-like channels from the cathode that do not span the electrode gap, (ii) bush-like channels from the cathode leading to breakdown and (iii) filamentary structures from the anode leading to a stronger breakdown. Two breakdown mechanisms, anode and cathode regimes, have been clearly identified and related to the two principal schools of thoughts to explain discharge propagation in liquid.Cet article présente une étude expérimentale d'une décharge de plasma pulsé dans l'eau dans une configuration d'électrode de broche à broche. Des techniques basées sur l'indice de réfraction à résolution temporelle et des mesures électriques ont été réalisées afin d'étudier les phénomènes de pré-claquage et de claquage dans l'eau. Une seule impulsion haute tension d'une douzaine de kV et d'une durée de [0,1-1] ms est appliquée entre deux pointes de platine de 100 μm de diamètre séparées de 2 mm. Ce nouveau travail expérimental rapporte que différents cas de décharges électriques dans l'eau se produisent pour un ensemble unique de conditions expérimentales telles que (i) des canaux en forme de buisson de la cathode qui ne couvrent pas l'espace entre les électrodes, (ii) des canaux en forme de buissons cathode conduisant à la dégradation et (iii) des structures filamentaires de l'anode conduisant à une rupture plus forte. Deux mécanismes de décomposition, les régimes d'anode et de cathode, ont été clairement identifiés et reliés aux deux principales écoles de pensée pour expliquer la propagation de décharge dans un liquide