Abstract: Dielectric Barrier Discharges operating in CO and CO2 form solid products at atmospheric pressure. The main differences between both plasmas and their deposits were analyzed, at similar energy input. GC measurements revealed a mixture of CO2, CO, and O2 in the CO2 DBD exhaust, while no O2 was found in the CO plasma. A coating of nanoparticles composed of Fe, O, and C was produced by the CO2 discharge, whereas, a microscopic dendrite-like carbon structure was formed in the CO plasma. Fe3O4 and Fe crystalline phases were found in the CO2 sample. The CO
deposition was characterized as an amorphous structure, close to polymeric CO (p-CO). Interestingly, p-CO is not formed in the CO2 plasma, in spite of the significant amounts of CO produced (up to 30% in the reactor exhaust).

Abstract: An extensive CO2 plasmamodel is presented that is relevant for the production of ‘‘solar fuels.’’ It is based on reaction rate coefficients fromrigorously reviewed literature, and is augmented with reactionrate coefficients that are obtained fromscaling laws.The input data set,which is suitable for usage with the plasma simulation software Plasimo (https://plasimo.phys.tue.nl/), is available via the Plasimo and publisher’s websites.1 The correctness of this model implementation has been established by independent ZDPlasKin implementation (http://www.zdplaskin.
laplace.univ-tlse.fr/), to verify that the results agree. Results of these ‘‘global models’’ are presented for a DBD plasma reactor.

Abstract: The modelling of a gliding arc discharge (GAD) is studied by means of the quasineutral (QN) plasma modelling approach. The model is first evaluated for reliability and proper description of a gliding arc discharge at atmospheric pressure, by comparing with a more elaborate non-quasineutral (NQN) plasma model in two different geometries – a 2D axisymmetric and a Cartesian geometry. The NQN model is considered as a reference, since it provides a continuous self-consistent plasma description, including the near electrode regions. In general, the results of the QN model agree very well with those obtained from the NQN model. The small differences between both models are attributed to the approximations in the derivation of the QN model. The use of the QN model provides a substantial reduction of the computation time compared to the NQN model, which is crucial for the development of more complex models in three dimensions or with complicated chemistries. The latter is illustrated for (i) a reverse vortex flow(RVF) GAD in argon, and (ii) a GAD in CO2. The RVF discharge is modelled in three dimensions and the effect of the turbulent heat transport on the plasma and gas characteristics is
discussed. The GAD model in CO2 is in a 1D geometry with axial symmetry and provides results for the time evolution of the electron, gas and vibrational temperature of CO2, as well as for the molar fractions of the different species.

Abstract: This paper gives an overview of our plasma chemistry modeling for CO2 and CH4 conversion in a dielectric barrier discharge (DBD) and microwave (MW) plasma. We focus on pure CO2 splitting and pure CH4 reforming, as well as mixtures of CO2/CH4, CH4/O2, and CO2/H2O. We show calculation results for the conversion, energy efficiency, and product formation, in comparison with experiments where possible. We also present the underlying chemical reaction pathways, to explain the observed
trends. For pure CO2, a comparison is made between a DBD and MW plasma, illustrating that the higher energy efficiency of the latter is attributed to the more important role of the vibrational levels.

Abstract: The catalytic oxidative dehydrogenation of hydrocarbons is an industrially important process, in which selectivity is a key issue. We here investigate the conversion of methanol to formaldehyde on a vanadia surface employing long timescale simulations, reaching a time scale of seconds. In particular, we compare the thermal process to the case where an additional external electric field is applied, as would be the case in a direct plasma-catalysis setup. We find that the electric field influences the retention time of the molecules at the catalyst surface. These simulations provide an atomic scale insight in the thermal catalytic oxidative dehydrogenation process, and in how an external electric field may affect this process.

Abstract: Cryogenic plasma etching is a promising technique for high-control wafer development with limited plasma induced damage. Cryogenic wafer temperatures effectively reduce surface damage during etching, but the fundamental mechanism is not well understood. In this study, the influences of wafer temperature, gas mixture and substrate bias on the (cryogenic) etch rates of Si with SF6/O2 inductively coupled plasmas are experimentally and computationally investigated. The etch rates are measured in situ with double-point reflectometry and a hybrid computational Monte Carlo – fluid model is applied to calculate plasma properties. This work allows the reader to obtain a better insight in the effects of wafer temperature on the etch rate and to find operating conditions for successful anisotropic (cryo)etching.

Abstract: We perform molecular dynamics simulations to study the flip-flop motion of phosphatidylserine (PS) across the plasma membrane upon increasing oxidation degree of the membrane. Our computational results show that an increase of the oxidation degree in the lipids leads to a decrease of the free energy barrier for translocation of PS through the membrane. In other words, oxidation of the lipids facilitates PS flip-flop motion across the membrane, because in native phospholipid bilayers this is only a “rare event” due to the high energy barriers for the translocation of PS. The present study provides an atomic-scale insight into the mechanisms of the PS flip-flop upon oxidation of lipids, as produced for example by cold atmospheric plasma, in living cells.

Abstract: Over the past decade, graphene oxide (GO) has emerged as a promising membrane material with superior separation performance and intriguing mechanical/chemical stability. However, its practical implementation remains very challenging primarily because of its undesirable swelling in an aqueous environment. Here, we demonstrated that dissociation of water molecules into H3O+ and OH- ions inside the interlayer gallery of a layered GO membrane can strongly affect its stability and performance. We reveal that H3O+ and OH- ions form clusters inside the GO laminates that impede the permeance of water and salt ions through the membrane. Dynamics of those clusters is sensitive to an external ac electric field, which can be used to tailor the membrane performance. The presence of H3O+ and OH- ions also leads to increased stability of the hydrogen bond (H-bond) network among the water molecules and the GO layers, which further reduces water permeance through the membrane, while crucially imparting stability to the layered GO membrane against undesirable swelling. KEYWORDS: layered graphene-oxide membrane, aqueous stability, H3O+ and OH- ions, external electric field, molecular dynamics

Abstract: We present here some of our modeling efforts for PECVD growth of nanostructured carbon materials with focus on amorphous hydrogenated carbon. Experimental data from an expanding thermal plasma setup were used as input for the simulations. Attention was focused both on the film growth mechanism, as well as on the hydrocarbon reaction mechanisms during growth of the films. It is found that the reaction mechanisms and sticking coefficients are dependent on the specific surface sites, and the structural properties of the growth radicals. The film growth results are in correspondence with the experiment. Furthermore, it is found that thin a-C:H films can be densified using an additional H-flux towards the substrate.