26 research outputs found
Reactivity of fatty acid methyl esters under atmospheric pressure plasma jet exposure: An experimental and theoretical study
Non-equilibrium in low-temperature plasmas
The wide range of applications of cold plasmas originates from their special
characteristic of being a physical system out of thermodynamic equilibrium. This property
enhances its reactivity at low gas temperature and allows to obtain macroscopic effects
with a moderate energy consumption. In this review, the basic concepts of non-equilibrium
in ionized gases are treated by showing why and how non-equilibrium functions of the
degrees of freedom are formed in a variety of natural and man-made plasmas with particular
emphasis on the progress made in the last decade. The modern point of view of a molecular
basis of non-equilibrium and of a state-to-state kinetic approach is adopted.
Computational and diagnostic techniques used to investigate the non-equilibrium conditions
are also surveyed
Un exemple de STSM du COST: Application de la LIF pour la détection du radical OH, à Bari, Italie
National audienc
Corrigendum on ‘OH Density Measurements by Time-Resolved Broad Band Absorption Spectroscopy in a He-H 2
He/O2 Atmospheric Pressure Plasma Jet Treatments of PCL Scaffolds for Tissue Engineering and Regenerative Medicine
Nanosecond pulsed discharge for <tex>CO_{2}$</tex> conversion : kinetic modeling to elucidate the chemistry and improve the performance
Nanosecond pulsed discharge for CO 2 conversion: kinetic modeling to elucidate the chemistry and improve the performance
We study the mechanisms of CO 2 conversion in a nanosecond repetitively pulsed (NRP) discharge, by means of a chemical kinetics model. The calculated conversions and energy efficiencies are in reasonable agreement with experimental results over a wide range of specific energy input values, and the same applies to the evolution of gas temperature and CO 2 conversion as a function of time in the afterglow, indicating that our model provides a realistic picture of the underlying mechanisms in the NRP discharge and can be used to identify its limitations and thus to suggest further improvements. Our model predicts that vibrational excitation is very important in the NRP discharge, explaining why this type of plasma yields energy-efficient CO 2 conversion. A significant part of the CO 2 dissociation occurs by electronic excitation from the lower vibrational levels toward repulsive electronic states, thus resulting in dissociation. However, vibration-translation (VT) relaxation (depopulating the higher vibrational levels) and CO + O recombination (CO + O + M → CO 2 + M), as well as mixing of the converted gas with fresh gas entering the plasma in between the pulses, are limiting factors for the conversion and energy efficiency. Our model predicts that extra cooling, slowing down the rate of VT relaxation and of the above recombination reaction, thus enhancing the contribution of the highest vibrational levels to the overall CO 2 dissociation, can further improve the performance of the NRP discharge for energy-efficient CO 2 conversion
CO2 Reduction by Nanosecond-Plasma Discharges: Revealing the Dissociation’s Time Scale and the Importance of Pulse Sequence
Power-to-chemical technologies with CO2 as feedstock recycle CO2 and store energy into value-added compounds. Plasma discharges fed by renewable electricity are a promising approach to CO2 conversion. However, controlling the mechanisms of plasma dissociation is crucial to improving the efficiency of the technology. We have investigated pulsed nanosecond discharges, showing that while most of the energy is deposited in the breakdown phase, CO2 dissociation only occurs after an order of microsecond delay, leaving the system in a quasi-metastable condition in the intervening time. These findings indicate the presence of delayed dissociation mechanisms mediated by CO2 excited states rather than direct electron impact. This “metastable” condition, favorable for an efficient CO2 dissociation, can be prolonged by depositing more energy in the form of additional pulses and critically depends on a sufficiently short interpulse time