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“Plasma-based dry reforming of CH4: Plasma effects vs. thermal conversion”. Slaets J, Loenders B, Bogaerts A, Fuel 360, 130650 (2024). http://doi.org/10.1016/j.fuel.2023.130650
Abstract: In this work we evaluate the chemical kinetics of dry reforming of methane in warm plasmas (1000–4000 K) using modelling with a newly developed chemistry set, for a broad range of parameters (temperature, power density and CO2/CH4 ratio). We compare the model against thermodynamic equilibrium concentrations, serving as validation of the thermal chemical kinetics. Our model reveals that plasma-specific reactions (i.e., electron impact collisions) accelerate the kinetics compared to thermal conversion, rather than altering the overall kinetics pathways and intermediate products, for gas temperatures below 2000 K. For higher temperatures, the kinetics are dominated by heavy species collisions and are strictly thermal, with negligible influence of the electrons and ions on the overall kinetics. When studying the effects of different gas mixtures on the kinetics, we identify important intermediate species, side reactions and side products. The use of excess CO2 leads to H2O formation, at the expense of H2 formation, and the CO2 conversion itself is limited, only approaching full conversion near 4000 K. In contrast, full conversion of both reactants is only kinetically limited for mixtures with excess CH4, which also gives rise to the formation of C2H2, alongside syngas. Within the given parameter space, our model predicts the 30/70 ratio of CO2/CH4 to be the most optimal for syngas formation with a H2/CO ratio of 2.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 7.4
DOI: 10.1016/j.fuel.2023.130650
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“In Situ Plasma Studies Using a Direct Current Microplasma in a Scanning Electron Microscope”. Grünewald L, Chezganov D, De Meyer R, Orekhov A, Van Aert S, Bogaerts A, Bals S, Verbeeck J, Advanced Materials Technologies (2024). http://doi.org/10.1002/admt.202301632
Abstract: Microplasmas can be used for a wide range of technological applications and to improve the understanding of fundamental physics. Scanning electron microscopy, on the other hand, provides insights into the sample morphology and chemistry of materials from the mm‐ down to the nm‐scale. Combining both would provide direct insight into plasma‐sample interactions in real‐time and at high spatial resolution. Up till now, very few attempts in this direction have been made, and significant challenges remain. This work presents a stable direct current glow discharge microplasma setup built inside a scanning electron microscope. The experimental setup is capable of real‐time in situ imaging of the sample evolution during plasma operation and it demonstrates localized sputtering and sample oxidation. Further, the experimental parameters such as varying gas mixtures, electrode polarity, and field strength are explored and experimental<italic>V</italic>–<italic>I</italic>curves under various conditions are provided. These results demonstrate the capabilities of this setup in potential investigations of plasma physics, plasma‐surface interactions, and materials science and its practical applications. The presented setup shows the potential to have several technological applications, for example, to locally modify the sample surface (e.g., local oxidation and ion implantation for nanotechnology applications) on the µm‐scale.
Keywords: A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
Impact Factor: 6.8
DOI: 10.1002/admt.202301632
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“Accurate Reaction Probabilities for Translational Energies on Both Sides of the Barrier of Dissociative Chemisorption on Metal Surfaces”. Gerrits N, Jackson B, Bogaerts A, The Journal of Physical Chemistry Letters 15, 2566 (2024). http://doi.org/10.1021/acs.jpclett.3c03408
Abstract: Molecular dynamics simulations are essential for a better understanding of dissociative chemisorption on metal surfaces, which is often the rate-controlling step in heterogeneous and plasma catalysis. The workhorse quasi-classical trajectory approach ubiquitous in molecular dynamics is able to accurately predict reactivity only for high translational and low vibrational energies. In contrast, catalytically relevant conditions generally involve low translational and elevated vibrational energies. Existing quantum dynamics approaches are intractable or approximate as a result of the large number of degrees of freedom present in molecule−metal surface reactions. Here, we extend a ring polymer molecular dynamics approach to fully include, for the first time, the degrees of freedom of a moving metal surface. With this approach, experimental sticking probabilities for the dissociative chemisorption of methane on Pt(111) are reproduced for a large range of translational and vibrational energies by including nuclear quantum effects and employing full-dimensional simulations.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 5.7
DOI: 10.1021/acs.jpclett.3c03408
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“Importance of plasma discharge characteristics in plasma catalysis: Dry reforming of methane vs. ammonia synthesis”. De Meyer R, Gorbanev Y, Ciocarlan R-G, Cool P, Bals S, Bogaerts A, Chemical Engineering Journal 488, 150838 (2024). http://doi.org/10.1016/j.cej.2024.150838
Abstract: Plasma catalysis is a rapidly growing field, often employing a packed-bed dielectric barrier discharge plasma reactor. Such dielectric barrier discharges are complex, especially when a packing material (e.g., a catalyst) is introduced in the discharge volume. Catalysts are known to affect the plasma discharge, though the underlying mechanisms influencing the plasma physics are not fully understood. Moreover, the effect of the catalysts on the plasma discharge and its subsequent effect on the overall performance is often overlooked. In this work, we deliberately design and synthesize catalysts to affect the plasma discharge in different ways. These Ni or Co alumina-based catalysts are used in plasma-catalytic dry reforming of methane and ammonia synthesis. Our work shows that introducing a metal to the dielectric packing can affect the plasma discharge, and that the distribution of the metal is crucial in this regard. Further, the altered discharge can greatly influence the overall performance. In an atmospheric pressure dielectric barrier discharge reactor, this apparently more uniform plasma yields a significantly better performance for ammonia synthesis compared to the more conventional filamentary discharge, while it underperforms in dry reforming of methane. This study stresses the importance of analyzing the plasma discharge in plasma catalysis experiments. We hope this work encourages a more critical view on the plasma discharge characteristics when studying various catalysts in a plasma reactor.
Keywords: A1 Journal Article; Gas conversion Dry reforming of methane Ammonia Microdischarges Dielectric barrier discharge; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 15.1
DOI: 10.1016/j.cej.2024.150838
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“Plasma catalysis in ammonia production and decomposition: Use it, or lose it?”.Gorbanev Y, Fedirchyk I, Bogaerts A, Current Opinion in Green and Sustainable Chemistry 47, 100916 (2024). http://doi.org/10.1016/j.cogsc.2024.100916
Abstract: The combination of plasma with catalysis for the synthesis and decomposition of NH3 is an attractive route to the production of carbon-neutral fertiliser and energy carriers and its conversion into H2. Recent years have seen fast developments in the field of plasma-catalytic NH3 life cycle. This work summarises the most recent advances in plasma-catalytic and related NH3-focussed processes, identifies some of the most important discoveries, and addresses plausible strategies for future developments in plasma-based NH3 technology.
Keywords: A1 Journal Article; Plasma Nitrogen fixation Ammonia Plasma catalysis Production and decomposition; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 9.3
DOI: 10.1016/j.cogsc.2024.100916
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“Machine learning-driven optimization of plasma-catalytic dry reforming of methane”. Cai Y, Mei D, Chen Y, Bogaerts A, Tu X, Journal of Energy Chemistry 96, 153 (2024). http://doi.org/10.1016/j.jechem.2024.04.022
Abstract: This study investigates the dry reformation of methane (DRM) over Ni/Al2O3 catalysts in a dielectric barrier discharge (DBD) non-thermal plasma reactor. A novel hybrid machine learning (ML) model is developed to optimize the plasma-catalytic DRM reaction with limited experimental data. To address the non-linear and complex nature of the plasma-catalytic DRM process, the hybrid ML model integrates three well-established algorithms: regression trees, support vector regression, and artificial neural networks. A genetic algorithm (GA) is then used to optimize the hyperparameters of each algorithm within the hybrid ML model. The ML model achieved excellent agreement with the experimental data, demonstrating its efficacy in accurately predicting and optimizing the DRM process. The model was subsequently used to investigate the impact of various operating parameters on the plasma-catalytic DRM performance. We found that the optimal discharge power (20 W), CO2/CH4 molar ratio (1.5), and Ni loading (7.8 wt%) resulted in the maximum energy yield at a total flow rate of 51 mL/min. Furthermore, we investigated the relative significance of each operating parameter on the performance of the plasmacatalytic DRM process. The results show that the total flow rate had the greatest influence on the conversion, with a significance exceeding 35% for each output, while the Ni loading had the least impact on the overall reaction performance. This hybrid model demonstrates a remarkable ability to extract valuable insights from limited datasets, enabling the development and optimization of more efficient and selective plasma-catalytic chemical processes.
Keywords: A1 Journal Article; Plasma catalysis Machine learning Process optimization Dry reforming of methane Syngas production; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 13.1
DOI: 10.1016/j.jechem.2024.04.022
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“Investigation of O atom kinetics in O2plasma and its afterglow”. Albrechts M, Tsonev I, Bogaerts A, Plasma Sources Science and Technology 33, 045017 (2024). http://doi.org/10.1088/1361-6595/ad3f4a
Abstract: We have developed a comprehensive kinetic model to study the O atom kinetics in an O<sub>2</sub>plasma and its afterglow. By adopting a pseudo-1D plug-flow formalism within the kinetic model, our aim is to assess how far the O atoms travel in the plasma afterglow, evaluating its potential as a source of O atoms for post-plasma gas conversion applications. Since we could not find experimental data for pure O<sub>2</sub>plasma at atmospheric pressure, we first validated our model at low pressure (1–10 Torr) where very good experimental data are available. Good agreement between our model and experiments was achieved for the reduced electric field, gas temperature and the densities of the dominant neutral species, i.e. O<sub>2</sub>(a), O<sub>2</sub>(b) and O. Subsequently, we confirmed that the chemistry set is consistent with thermodynamic equilibrium calculations at atmospheric pressure. Finally, we investigated the O atom densities in the O<sub>2</sub>plasma and its afterglow, for which we considered a microwave O<sub>2</sub>plasma torch, operating at a pressure between 0.1 and 1 atm, for a flow rate of 20 slm and an specific energy input of 1656 kJ mol<sup>−1</sup>. Our results show that for both pressure conditions, a high dissociation degree of ca. 92% is reached within the discharge. However, the O atoms travel much further in the plasma afterglow for<italic>p</italic>= 0.1 atm (9.7 cm) than for<italic>p</italic>= 1 atm (1.4 cm), attributed to the longer lifetime (3.8 ms at 0.1 atm vs 1.8 ms at 1 atm) resulting from slower three-body recombination kinetics, as well as a higher volumetric flow rate.
Keywords: A1 Journal Article; oxygen plasma, pseudo-1D plug-flow kinetic model, O atoms, low-pressure validation, atmospheric pressure microwave torch; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 3.8
DOI: 10.1088/1361-6595/ad3f4a
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“Effect of Gas Composition on Temperature and CO2Conversion in a Gliding Arc Plasmatron reactor: Insights for Post‐Plasma Catalysis from Experiments and Computation”. Xu W, Van Alphen S, Galvita VV, Meynen V, Bogaerts A, ChemSusChem (2024). http://doi.org/10.1002/cssc.202400169
Abstract: Plasma‐based CO<sub>2</sub>conversion has attracted increasing interest. However, to understand the impact of plasma operation on post‐plasma processes, we studied the effect of adding N<sub>2</sub>, N<sub>2</sub>/CH<sub>4</sub>and N<sub>2</sub>/CH<sub>4</sub>/H<sub>2</sub>O to a CO<sub>2</sub>gliding arc plasmatron (GAP) to obtain valuable insights into their impact on exhaust stream composition and temperature, which will serve as feed gas and heat for post‐plasma catalysis (PPC). Adding N<sub>2</sub>improves the CO<sub>2</sub>conversion from 4 % to 13 %, and CH<sub>4</sub>addition further promotes it to 44 %, and even to 61 % at lower gas flow rate (6 L/min), allowing a higher yield of CO and hydrogen for PPC. The addition of H<sub>2</sub>O, however, reduces the CO<sub>2</sub>conversion from 55 % to 22 %, but it also lowers the energy cost, from 5.8 to 3 kJ/L. Regarding the temperature at 4.9 cm post‐plasma, N<sub>2</sub>addition increases the temperature, while the CO<sub>2</sub>/CH<sub>4</sub>ratio has no significant effect on temperature. We also calculated the temperature distribution with computational fluid dynamics simulations. The obtained temperature profiles (both experimental and calculated) show a decreasing trend with distance to the exhaust and provide insights in where to position a PPC bed.
Keywords: A1 Journal Article; CO2 conversion · Plasma · Gliding arc plasmatron · Temperature profiles · Computational modelling; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 8.4
DOI: 10.1002/cssc.202400169
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“Improving the performance of gliding arc plasma-catalytic dry reforming via a new post-plasma tubular catalyst bed”. Xu W, Buelens LC, Galvita VV, Bogaerts A, Meynen V, Journal of CO2 Utilization 83, 102820 (2024). http://doi.org/10.1016/j.jcou.2024.102820
Abstract: A combination of a gliding arc plasmatron (GAP) reactor and a newly designed tubular catalyst bed (N-bed) was applied to investigate the post-plasma catalytic (PPC) effect for dry reforming of methane (DRM). As comparison, a traditional plasma catalyst bed (T-bed) was also utilized. The post-plasma catalytic effect of a Ni-based mixed oxide (Ni/MO) catalyst with a thermal catalytic performance of 77% CO2 and 86% CH4 conversion at 700 ℃ was studied. Although applying the T-bed had little effect on plasma based CO2 and CH4 conversion, an increase in selectivity to H2 was obtained with a maximum value of 89% at a distance of 2 cm. However, even when only α-Al2O3 packing material was used in the N-bed configuration, compared to the plasma alone and the T-bed, an increase of the CO2 and CH4 conversion from 53% and 53% to 69% and 69% to 83% was achieved. Addition of the Ni/MO catalyst further enhanced the DRM reaction, resulting in conversions of 79% for CO2 and 91% for
CH4. Hence, although no insulation nor external heating was applied to the N-bed post plasma, it provides a slightly better conversion than the thermal catalytic performance with the same catalyst, while being fully electrically driven. In addition, an enhanced CO selectivity to 96% was obtained and the energy cost was reduced from ~ 6 kJ/L (plasma alone) to 4.3 kJ/L. To our knowledge, it is the first time that a post-plasma catalytic system achieves this excellent catalytic performance for DRM without extra external heating or insulation.
Keywords: A1 Journal Article; Dry reforming Gliding arc plasma Plasma catalytic DRM Ni-based mixed oxide Post-plasma catalysis; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 7.7
DOI: 10.1016/j.jcou.2024.102820
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“Coupled multi-dimensional modelling of warm plasmas: Application and validation for an atmospheric pressure glow discharge in CO2/CH4/O2”. Maerivoet S, Tsonev I, Slaets J, Reniers F, Bogaerts A, Chemical Engineering Journal 492, 152006 (2024). http://doi.org/10.1016/j.cej.2024.152006
Abstract: To support experimental research into gas conversion by warm plasmas, models should be developed to explain the experimental observations. These models need to describe all physical and chemical plasma properties in a coupled way. In this paper, we present a modelling approach to solve the complete set of assumed relevant equations, including gas flow, heat balance and species transport, coupled with a rather extensive chemistry set, consisting of 21 species, obtained by reduction of a more detailed chemistry set, consisting of 41 species. We apply this model to study the combined CO2 and CH4 conversion in the presence of O2, in a direct current atmospheric pressure glow discharge. Our model can predict the experimental trends, and can explain why higher O2 fractions result in higher CH4 conversion, namely due to the higher gas temperature, rather than just by additional chemical reactions. Indeed, our model predicts that when more O2 is added, the energy required to reach any set temperature (i.e., the enthalpy) drops, allowing the system to reach higher temperatures with similar amounts of energy. This is in turn related to the higher H2O fraction and lower H2 fraction formed in the plasma, as demonstrated by our model. Altogether, our new self-consistent model can capture the main physics and chemistry occurring in this warm plasma, which is an important step towards predictive modelling for plasma-based gas conversion.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 15.1
DOI: 10.1016/j.cej.2024.152006
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“Improving Molecule–Metal Surface Reaction Networks Using the Meta-Generalized Gradient Approximation: CO2Hydrogenation”. Cai Y, Michiels R, De Luca F, Neyts E, Tu X, Bogaerts A, Gerrits N, The Journal of Physical Chemistry C 128, 8611 (2024). http://doi.org/10.1021/acs.jpcc.4c01110
Abstract: Density functional theory is widely used to gain insights into molecule−metal surface reaction networks, which is important for a better understanding of catalysis. However, it is well-known that generalized gradient approximation (GGA)
density functionals (DFs), most often used for the study of reaction networks, struggle to correctly describe both gas-phase molecules and metal surfaces. Also, GGA DFs typically underestimate reaction barriers due to an underestimation of the selfinteraction energy. Screened hybrid GGA DFs have been shown to reduce this problem but are currently intractable for wide usage. In this work, we use a more affordable meta-GGA (mGGA) DF in combination with a nonlocal correlation DF for the first time to study and gain new insights into a catalytically important surface
reaction network, namely, CO2 hydrogenation on Cu. We show that the mGGA DF used, namely, rMS-RPBEl-rVV10, outperforms typical GGA DFs by providing similar or better predictions for metals and molecules, as well as molecule−metal surface adsorption
and activation energies. Hence, it is a better choice for constructing molecule−metal surface reaction networks.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 3.7
DOI: 10.1021/acs.jpcc.4c01110
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“Catalyzed growth of carbon nanotube with definable chirality by hybrid molecular dynamics-force biased Monte Carlo simulations”. Neyts EC, Shibuta Y, van Duin ACT, Bogaerts A, ACS nano 4, 6665 (2010). http://doi.org/10.1021/nn102095y
Abstract: Metal-catalyzed growth mechanisms of carbon nanotubes (CNTs) were studied by hybrid molecular dynamics−Monte Carlo simulations using a recently developed ReaxFF reactive force field. Using this novel approach, including relaxation effects, a CNT with definable chirality is obtained, and a step-by-step atomistic description of the nucleation process is presented. Both root and tip growth mechanisms are observed. The importance of the relaxation of the network is highlighted by the observed healing of defects.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 13.942
Times cited: 129
DOI: 10.1021/nn102095y
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“Combining molecular dynamics with Monte Carlo simulations : implementations and applications”. Neyts EC, Bogaerts A, Theoretical chemistry accounts : theory, computation, and modeling 132, 1320 (2013). http://doi.org/10.1007/s00214-012-1320-x
Abstract: In this contribution, we present an overview of the various techniques for combining atomistic molecular dynamics with Monte Carlo simulations, mainly in the context of condensed matter systems, as well as a brief summary of the main accelerated dynamics techniques. Special attention is given to the force bias Monte Carlo technique and its combination with molecular dynamics, in view of promising recent developments, including a definable timescale. Various examples of the application of combined molecular dynamics / Monte Carlo simulations are given, in order to demonstrate the enhanced simulation efficiency with respect to either pure molecular dynamics or Monte Carlo.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.89
Times cited: 27
DOI: 10.1007/s00214-012-1320-x
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“Development of a ReaxFF reactive force field for intrinsic point defects in titanium dioxide”. Huygh S, Bogaerts A, van Duin ACT, Neyts EC, Computational materials science 95, 579 (2014). http://doi.org/10.1016/j.commatsci.2014.07.056
Abstract: A reactive ReaxFF force field is developed for studying the influence of intrinsic point defects on the chemistry with TiO2 condensed phases. The force field parameters are optimized to ab initio data for the equations of state, relative phase stabilities for titanium and titanium dioxide, potential energy differences for (TiO2)n-clusters (n = 116). Also data for intrinsic point defects in anatase were added. These data contain formation energies for interstitial titanium and oxygen vacancies, diffusion barriers of the oxygen vacancies and molecular oxygen adsorption on a reduced anatase (101) surface. Employing the resulting force field, we study the influence of concentration of oxygen vacancies and expansion or compression of an anatase surface on the diffusion of the oxygen vacancies. Also the barrier for oxygen diffusion in the subsurface region is evaluated using this force field. This diffusion barrier of 27.7 kcal/mol indicates that the lateral redistribution of oxygen vacancies on the surface and in the subsurface will be dominated by their diffusion in the subsurface, since both this barrier as well as the barriers for diffusion from the surface to the subsurface and vice versa (17.07 kcal/mol and 21.91 kcal/mol, respectively, as calculated with DFT), are significantly lower than for diffusion on the surface (61.12 kcal/mol as calculated with DFT).
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.292
Times cited: 15
DOI: 10.1016/j.commatsci.2014.07.056
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“Differences between ultrananocrystalline and nanocrystalline diamond growth: theoretical investigation of CxHy species at diamond step edges”. Eckert M, Neyts E, Bogaerts A, Crystal growth &, design 10, 4123 (2010). http://doi.org/10.1021/cg100804v
Abstract: The behavior of hydrocarbon species at step edges of diamond terraces is investigated by means of combined molecular dynamics−Metropolis Monte Carlo simulations. The results show that the formation of ballas-like diamond films (like UNCD) and well-faceted diamond films (like NCD) can be related to the gas phase concentrations of CxHy in a new manner: Species that have high concentrations above the growing UNCD films suppress the extension of step edges through defect formation. The species that are present above the growing NCD film, however, enhance the extension of diamond terraces, which is believed to result in well-faceted diamond films. Furthermore, it is shown that, during UNCD growth, CxHy species with x ≥ 2 play an important role, in contrast to the currently adopted CVD diamond growth mechanism. Finally, the probabilities for the extension of the diamond (100) terrace are much higher than those for the diamond (111) terrace, which is in full agreement with the experimental observation that diamond (100) facets are more favored than diamond (111) facets during CVD diamond growth.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.055
Times cited: 11
DOI: 10.1021/cg100804v
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“Dynamic Monte Carlo simulation for reactive sputtering of aluminium”. Chen ZY, Bogaerts A, Depla D, Ignatova V, Nuclear instruments and methods in physics research: B 207, 415 (2003). http://doi.org/10.1016/S0168-583X(03)01120-0
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.109
Times cited: 20
DOI: 10.1016/S0168-583X(03)01120-0
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“Fluid simulation of the bias effect in inductive/capacitive discharges”. Zhang Y-R, Gao F, Li X-C, Bogaerts A, Wang Y-N, Journal of vacuum science and technology: A: vacuum surfaces and films 33, 061303 (2015). http://doi.org/10.1116/1.4928033
Abstract: Computer simulations are performed for an argon inductively coupled plasma (ICP) with a capacitive radio-frequency bias power, to investigate the bias effect on the discharge mode transition and on the plasma characteristics at various ICP currents, bias voltages, and bias frequencies. When the bias frequency is fixed at 13.56 MHz and the ICP current is low, e.g., 6A, the spatiotemporal averaged plasma density increases monotonically with bias voltage, and the bias effect is already prominent at a bias voltage of 90 V. The maximum of the ionization rate moves toward the bottom electrode, which indicates clearly the discharge mode transition in inductive/capacitive discharges. At higher ICP currents, i.e., 11 and 13 A, the plasma density decreases first and then increases with bias voltage, due to the competing mechanisms between the ion acceleration power dissipation and the capacitive power deposition. At 11 A, the bias effect is still important, but it is noticeable only at higher bias voltages. At 13 A, the ionization rate is characterized by a maximum at the reactor center near the dielectric window at all selected bias voltages, which indicates that the ICP power, instead of the bias power, plays a dominant role under this condition, and no mode transition is observed. Indeed, the ratio of the bias power to the total power is lower than 0.4 over a wide range of bias voltages, i.e., 0300V. Besides the effect of ICP current, also the effect of various bias frequencies is investigated. It is found that the modulation of the bias power to the spatiotemporal distributions of the ionization rate at 2MHz is strikingly different from the behavior observed at higher bias frequencies. Furthermore, the minimum of the plasma density appears at different bias voltages, i.e., 120V at 2MHz and 90V at 27.12 MHz.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.374
Times cited: 9
DOI: 10.1116/1.4928033
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“How do plasma-generated OH radicals react with biofilm components? Insights from atomic scale simulations”. Khosravian N, Bogaerts A, Huygh S, Yusupov M, Neyts EC, Biointerphases 10, 029501 (2015). http://doi.org/10.1116/1.4904339
Abstract: The application of nonthermal atmospheric pressure plasma is emerging as an alternative and efficient technique for the inactivation of bacterial biofilms. In this study, reactive molecular dynamics simulations were used to examine the reaction mechanisms of hydroxyl radicals, as key reactive oxygen plasma species in biological systems, with several organic molecules (i.e., alkane, alcohol, carboxylic acid, and amine), as prototypical components of biomolecules in the biofilm. Our results demonstrate that organic molecules containing hydroxyl and carboxyl groups may act as trapping agents for the OH radicals. Moreover, the impact of OH radicals on N-acetyl-glucosamine, as constituent component of staphylococcus epidermidis biofilms, was investigated. The results show how impacts of OH radicals lead to hydrogen abstraction and subsequent molecular damage. This study thus provides new data on the reaction mechanisms of plasma species, and particularly the OH radicals, with fundamental components of bacterial biofilms.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.603
Times cited: 10
DOI: 10.1116/1.4904339
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“Identification of the biologically active liquid chemistry induced by a nonthermal atmospheric pressure plasma jet”. Wende K, Williams P, Dalluge J, Van Gaens W, Aboubakr H, Bischof J, von Woedtke T, Goyal SM, Weltmann KD, Bogaerts A, Masur K, Bruggeman PJ;, Biointerphases 10, 029518 (2015). http://doi.org/10.1116/1.4919710
Abstract: The mechanism of interaction of cold nonequilibrium plasma jets with mammalian cells in physiologic liquid is reported. The major biological active species produced by an argon RF plasma jet responsible for cell viability reduction are analyzed by experimental results obtained through physical, biological, and chemical diagnostics. This is complemented with chemical kinetics modeling of the plasma source to assess the dominant reactive gas phase species. Different plasma chemistries are obtained by changing the feed gas composition of the cold argon based RF plasma jet from argon, humidified argon (0.27%), to argon/oxygen (1%) and argon/air (1%) at constant power. A minimal consensus physiologic liquid was used, providing isotonic and isohydric conditions and nutrients but is devoid of scavengers or serum constituents. While argon and humidified argon plasma led to the creation of hydrogen peroxide dominated action on the mammalian cells, argonoxygen and argonair plasma created a very different biological action and was characterized by trace amounts of hydrogen peroxide only. In particular, for the argonoxygen (1%), the authors observed a strong negative effect on mammalian cell proliferation and metabolism. This effect was distance dependent and showed a half life time of 30 min in a scavenger free physiologic buffer. Neither catalase and mannitol nor superoxide dismutase could rescue the cell proliferation rate. The strong distance dependency of the effect as well as the low water solubility rules out a major role for ozone and singlet oxygen but suggests a dominant role of atomic oxygen. Experimental results suggest that O reacts with chloride, yielding Cl2 − or ClO−. These chlorine species have a limited lifetime under physiologic conditions and therefore show a strong time dependent biological activity. The outcomes are compared with an argon MHz plasma jet (kinpen) to assess the differences between these (at least seemingly) similar plasma sources.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.603
Times cited: 137
DOI: 10.1116/1.4919710
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“Insights into the growth of (ultra)nanocrystalline diamond by combined molecular dynamics and Monte Carlo simulations”. Eckert M, Neyts E, Bogaerts A, Crystal growth &, design 10, 3005 (2010). http://doi.org/10.1021/cg100063c
Abstract: In this paper, we present the results of combined molecular dynamics−Metropolis Monte Carlo (MD-MMC) simulations of hydrocarbon species at flat diamond (100)2 × 1 and (111)1 × 1 surfaces. The investigated species are considered to be the most important growth species for (ultra)nanocrystalline diamond ((U)NCD) growth. When applying the MMC algorithm to stuck species at monoradical sites, bonding changes are only seen for CH2. The sequence of the bond breaking and formation as put forward by the MMC simulations mimics the insertion of CH2 into a surface dimer as proposed in the standard growth model of diamond. For hydrocarbon species attached to two adjacent radical (biradical) sites, the MMC simulations give rise to significant changes in the bonding structure. For UNCD, the combinations of C3 and C3H2, and C3 and C4H2 (at diamond (100)2 × 1) and C and C2H2 (at diamond (111)1 × 1) are the most successful in nucleating new crystal layers. For NCD, the following combinations pursue the diamond structure the best: C2H2 and C3H2 (at diamond (100)2 × 1) and CH2 and C2H2 (at diamond (111)1 × 1). The different behaviors of the hydrocarbon species at the two diamond surfaces are related to the different sterical hindrances at the diamond surfaces.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.055
Times cited: 13
DOI: 10.1021/cg100063c
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“Modeling adatom surface processes during crystal growth: a new implementation of the Metropolis Monte Carlo algorithm”. Eckert M, Neyts E, Bogaerts A, CrystEngComm 11, 1597 (2009). http://doi.org/10.1039/b822973m
Abstract: In this paper, a new implementation of the Metropolis Monte Carlo (MMC) algorithm is presented. When combining the MMC model with a molecular dynamics (MD) code, crystal growth by plasma-enhanced chemical vapor deposition can be simulated. As the MD part simulates impacts of growth species onto the surface on a time scale of picoseconds, the MMC algorithm simulates the slower adatom surface processes. The implementation includes a criterion for the selection of atoms that are allowed to be displaced during the simulation, and a criterion of after how many MMC cycles the simulation is stopped. We performed combined MD-MMC simulations for hydrocarbon species that are important for the growth of ultrananocrystalline diamond (UNCD) films at partially hydrogenated diamond surfaces, since this implementation is part of a study of the growth mechanisms of (ultra)nanocrystalline diamond films. Exemplary for adatom arrangements during the growth of UNCD, the adatom surface behavior of C and C2H2 at diamond (111)1 × 1, C and C4H2 at diamond (111)1 × 1 and C3 at diamond (100)2 × 1 has been investigated. For all cases, the diamond crystal structure is pursued under the influence of MMC simulation. Additional longer time-scale MD simulations put forward very similar structures, verifying the MMC algorithm. Nevertheless, the MMC simulation time is typically one order of magnitude shorter than the MD simulation time.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.474
Times cited: 15
DOI: 10.1039/b822973m
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“Modeling of glow discharge ion sources for mass spectrometry: potentials and limitations”. Gijbels R, Bogaerts A, Spectroscopy 9, 8 (1997)
Keywords: A3 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Modeling of glow discharge sources with flat and pin cathodes and implications for mass spectrometric analysis”. Bogaerts A, Gijbels R, Journal of the American Society of Mass Spectrometry 8, 1021 (1997). http://doi.org/10.1016/S1044-0305(97)00120-7
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.786
Times cited: 15
DOI: 10.1016/S1044-0305(97)00120-7
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“Modeling of glow discharges: what can we learn from it?”.Bogaerts A, Gijbels R, Analytical chemistry A-pages 69, 719 (1997)
Keywords: A3 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Modeling of magnetron and glow discharges”. Bogaerts A, Kolev I, Le vide: science, technique et applications 57, 296 (2002)
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Modeling of radio-frequency and direct current glow discharges in argon”. Bogaerts A, Gijbels R, Journal of technical physics 41, 183 (2000)
Keywords: A3 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Modeling of the synthesis and subsequent growth of nanoparticles in dusty plasmas”. de Bleecker K, Bogaerts A, High temperature material processes 11, 21 (2007). http://doi.org/10.1615/HighTempMatProc.v11.i1.20
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.1615/HighTempMatProc.v11.i1.20
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“Modeling PECVD growth of nanostructured carbon materials”. Neyts E, Bogaerts A, van de Sanden MCM, High temperature material processes 13, 399 (2009). http://doi.org/10.1615/HighTempMatProc.v13.i3-4.120
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.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.1615/HighTempMatProc.v13.i3-4.120
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“Modelleren van plasmas gebruikt voor de afzetting van dunne lagen”. Herrebout D, Bogaerts A, Gijbels R, Chemie magazine , 34 (2004)
Keywords: A2 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Molecular dynamics simulation of temperature effects on CF(3)(+) etching of Si surface”. Jian-Ping N, Xiao-Dan L, Cheng-Li Z, You-Min Q, Ping-Ni H, Bogaerts A, Fu-Jun G, Wuli xuebao 59, 7225 (2010)
Abstract: Molecular dynamics method was employed to investigate the effects of the reaction layer formed near the surface region on CF(3)(+) etching of Si at different temperatures. The simulation results show that the coverages of F and C are sensitive to the surface temperature. With increasing temperature, the physical etching is enhanced, while the chemical etching is weakened. It is found that with increasing surface temperature, the etching rate of Si increases. As to the etching products, the yields of SiF and SiF(2) increase with temperature, whereas the yield of SiF(3) is not sensitive to the surface temperature. And the increase of the etching yield is mainly due to the increased desorption of SiF and SiF(2). The comparison shows that the reactive layer plays an important part in the subsequeat impacting, which enhances the etching rate of Si and weakens the chemical etching intensity.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 0.624
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